CONSTRUCTION MACHINE, DRIVE DEVICE FOR CONSTRUCTION MACHINE, AND DRIVE UNIT FOR CONSTRUCTION MACHINE

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims the benefit of priority from Japanese Patent Application Serial No. 2024-155082 (filed on Sep. 9, 2024), the contents of which are hereby incorporated by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to a construction machine, a drive device for the construction machine, and a drive unit for the construction machine.

BACKGROUND

Japanese Patent Application Publication No. 2001-254395 (“the '395 Publication”) discloses an excavator including a vehicle body, a boom, an arm, and a bucket. The boom is coupled to the front end of the vehicle body. The boom can rotate up and down relative to the vehicle body. The arm is coupled to the distal end of the boom. The arm can rotate up and down relative to the boom. The bucket is coupled to the distal end of the arm. The bucket can rotate up and down relative to the arm. In the technical field described in the '395 Publication, it is desirable to increase an area in which a machine can work using a series of work mechanisms, including a boom.

SUMMARY

One aspect of the disclosure provides a construction machine. The construction machine includes: a drive device outputting torque centered on a rotational axis perpendicular to a reference axis extending in upper and lower directions of a travelable vehicle body; and a boom having a first end portion coupled to the vehicle body, the boom being rotated around the rotational axis by the torque from the drive device. When viewed in a first direction parallel to the rotational axis, the boom is rotatable to both one side and other side with respect to the reference axis.

Another aspect provides a construction machine. A construction machine includes: a first slewing device outputting torque centered on a first slewing axis extending in upper and lower directions of a travelable vehicle body; a boom having a first end portion coupled to the vehicle body, the boom being rotated around the first slewing axis by the torque from the first slewing device; a second slewing device outputting torque centered on a second slewing axis, the second slewing axis being parallel to the first rotational axis and passing through a second end portion of the boom opposite to the first end portion of the boom; an arm having a first end portion coupled to the second end portion of the boom and a second end portion opposite the first end portion, the arm rotating around the second slewing axis by the torque from the second slewing device; an attachment coupled to the second end portion of the arm.

Yet another aspect provides a construction machine. A construction machine includes two work mechanisms. Each work mechanism includes: a first drive device outputting torque centered on a first rotational axis orthogonal to a reference axis extending in upper and lower directions of a travelable vehicle body; a boom having a first end portion coupled to the vehicle body, the boom being rotated around the first rotational axis by the torque from the first drive device; a second drive device outputting torque centered on a second rotational axis, the second rotational axis being parallel to the first rotational axis and passing through a second end portion of the boom opposite to the first end portion of the boom; an arm having a first end portion coupled to the second end portion of the boom and a second end portion opposite the first end portion, the arm rotating around the second rotational axis by the torque from the second drive device; and an attachment coupled to the second end portion of the arm. When viewed in a direction parallel to the first rotation axis of a first work mechanism of the two work mechanisms, the two work mechanisms are disposed on one side and other side respectively with respect to a center of the vehicle body in a direction orthogonal to both the first rotational axis and the reference axis of the first work mechanism.

Still yet another aspect provides a drive device for a construction machine. The drive device is capable of outputting torque centered on a rotational axis to a boom rotatably coupled to a travelable vehicle body around the rotational axis, the rotational axis being orthogonal to a reference axis extending in upper and lower directions of the vehicle body. When viewed in a direction parallel to the rotational axis, the boom is rotatable to both one side and other side with respect to the reference axis.

Yet another aspect provides a drive unit for a construction machine. The drive unit includes: a first drive device capable of outputting torque centered on a first rotational axis to a boom, the boom being rotatably coupled to a travelable vehicle body around the rotational axis orthogonal to a reference axis extending in upper and lower directions of the vehicle body; a second drive device capable of outputting torque centered on a second rotational axis to an arm, the arm having a first end portion coupled to a second end portion of the boom opposite the first end portion of the boom and a second end portion opposite the first end portion, the arm being rotatable around the second rotational axis, the second rotational axis extending parallel to the first rotational axis and passing through the second end portion of the boom; and a third drive device capable of outputting torque centered on a third rotational axis to an attachment, the attachment having a first end portion coupled to the second end portion of the arm, the attachment being rotatable around the third rotational axis, the third rotational axis extending parallel to the first rotational axis and passing through the second end portion of the arm, When viewed in a direction parallel to the first rotational axis, the first drive device is capable of driving and rotating the arm to both one side and other side with respect to the reference axis, the second drive device is capable of driving and rotating the arm to both one side and other side with respect to an imaginary straight line connecting the first rotational axis and the second rotational axis, and the third drive device is capable of driving and rotating the attachment to both one side and other side with respect to an imaginary straight line connecting the second rotational axis and the third rotational axis.

Still yet another aspect provides a drive unit for a construction machine. The drive unit includes: a drive device capable of outputting torque centered on a rotational axis to a boom rotatably coupled to a travelable vehicle body around the rotational axis, the rotational axis being orthogonal to a reference axis extending in upper and lower directions of the vehicle body, the drive device being capable of driving and rotating the boom to both one side and other side with respect to the reference axis when viewed in a direction parallel to the rotational axis; and a slewing device capable of outputting, to a connecting member, torque centered on a slewing axis parallel to the reference axis, the connecting member being interposed between the vehicle body and the boom and rotatable about the slewing axis, the slewing device being capable of driving and rotating the connecting member through 360 degrees about the slewing axis.

Still yet another aspect provides a drive unit for a construction machine that can solve the above mentioned drawback. The drive unit includes: a first slewing device outputting torque centered on a first slewing axis to a boom, the boom being rotatably coupled to a travelable vehicle body around the first slewing axis, the first slewing axis extending in upper and lower directions of the vehicle body; and a second slewing device outputting torque centered on a second slewing axis to an arm, the arm being coupled to a second end portion of the boom opposite the first end portion of the boom, the arm being rotatable around the second slewing axis, the second slewing axis extending parallel to the first slewing axis and passing through the second end portion of the boom.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic top view of an excavator showing its configuration.

FIG. 2 is a schematic side view of the excavator showing its configuration.

FIG. 3 is a schematic side view of the excavator showing its configuration.

FIG. 4 shows a rotation path of first and second buckets.

FIG. 5 schematically illustrates a second work tool.

FIG. 6 is a side view of the excavator, schematically representing an example of the excavator in use.

FIG. 7 is a side view of the excavator, schematically representing an example of the excavator in use.

FIG. 8 is a side view schematically illustrates a modification example of the excavator.

FIG. 9 is a side view schematically illustrating an example of the excavator of FIG. 8 in use.

FIG. 10 is a top view of the excavator of FIG. 9 in use.

FIG. 11 schematically illustrates a modified example of a first mechanism in the excavator of FIG. 8.

FIG. 12 is a side view schematically illustrates a modification example of the excavator.

FIG. 13 is a side view schematically illustrating an example of the excavator of FIG. 12 in use.

FIG. 14 is a top view schematically illustrating an example of arrangement of a first work mechanism and a second work mechanism.

FIG. 15 is a side view schematically illustrates a modification example of the excavator.

DESCRIPTION OF THE EMBODIMENTS

<Overall Configuration>

A construction machine, a drive device and a drive unit for the construction machine according to one embodiment will be described with reference to the appended drawings. The drawings may show the components in an enlarged manner for the sake of better intelligibility. The dimensions of the components and the ratios thereof may be different from those of the actual components, and among the drawings. In the following description of the embodiment, the term “parallel” encompasses both cases where two lines extend without intersecting at different positions and where two lines are perfectly coincident.

As shown in FIG. 1, an excavator 10, serving as a construction machine, includes a vehicle body 12 and a pair of traveling units 16. As shown in FIG. 2, the vehicle body 12 includes a lower body 14 and an upper body 20. The upper body 20 is located on the opposite side to the ground surface G with respect to the lower body 14. In the embodiment, the vehicle body 12 is used as a reference to define the top (high, upper, upward), bottom (low, downward), left, right, front (forward), and rear (backward) of the excavator 10. Specifically, when viewed from the lower body 14, the upper body 20 is located in the upper direction, and the opposite direction is the lower direction. A specific one of the directions orthogonal to the upper direction is the front direction, and the opposite direction is the rear direction. Furthermore, the direction that is orthogonal to both of the upper and front directions faces the left and right directions, which are opposite to each other. In the following description, the front and rear directions may be collectively referred to as X direction. The left and right directions may be collectively referred to as Y direction. The upper and lower directions may be collectively referred to as Z direction.

The pair of traveling units 16 are provided at the left and right sides across the lower body 14. The traveling units 16 each include a traveling crawler and an operating mechanism that circles the crawler. As expressed in the two dotted line labeled with 16 in FIG. 2, the crawler is in the form of an endless belt. The crawler extends in the X direction and is open on both the left and right sides. The lower surface of the crawler is in contact with the ground surface G. As the crawler rotates, the excavator 10, and thus the vehicle body 12, travels. In other words, the vehicle body 12 is capable of traveling.

As shown in FIG. 2, the lower body 14 is, for example, rectangular. The lower body 14 houses various mechanisms, devices, and parts necessary to operate the excavator 10. The upper body 20 is shaped like a truncated cone. The central axis of the upper body 20 is referred to as a reference axis K. The reference axis K extends substantially in the Z-direction. In other words, the reference axis K coincides with a vertical axis of the excavator 10 and thus the vehicle body 12, and extends in the upper and lower direction of the vehicle body 12. The reference axis K in the embodiment passes through the geometric center of the lower body 14 when the lower body 14 is viewed in plan from the upper body 20 side. Furthermore, the reference axis K is perpendicular to a horizontal plane that is an imaginary extension of the ground surface G with which the lower surface of the crawler of the traveling unit 16 is in contact. In accordance with the shape of the upper body 20, the cross-sectional area of the upper body orthogonal to the reference axis K decreases as it extends upward. The upper body 20 is hollow. In other words, the interior of the upper body 20 is a housing space.

The upper body 20 has a top surface 23, a bottom surface 21, and side surfaces 22. A bottom surface 21 is the downward side surface of the upper body 20. The bottom surface 21 is circular. The bottom surface 21 is substantially orthogonal to the reference axis K. A side surface 22 rises from the bottom surface 21. A particular axis orthogonal to the reference axis K is referred to as a first rotational axis 51J. A plan view of the excavator 10 as seen in a direction parallel to the first rotational axis 51J is referred to as a specified plan view. As shown in FIG. 2, in the specified plan view, the side surface 22 is inclined such that it approaches the reference axis K toward the upward direction. In other words, the side surface 22 is an inclined surface. A top surface 23 is an upper surface of the upper body 20. The top surface 23 is circular. The top surface 23 is connected to the entire uppermost edge of the side surface 22. The top surface 23 is substantially orthogonal to the reference axis K. In the specified plan view, the minor angle θ formed by the top surface 23 and the side surface 22 is about 120 degrees. The minor angle θ is an angle that is smaller than 180 degrees of the angles formed by the top surface 23 and the side surface 22. It should be noted that the value of the minor angle θ shown in FIG. 2 is given for illustrative purposes only. Although not shown in the figure, an opening is formed about the center of the top surface 23 to establish communication between the interior and exterior of the upper body 20.

<Main Slewing Device>

As shown in FIG. 2, the excavator 10 includes a main slewing device 30. The main slewing device 30 is disposed inside the upper body 20. The main slewing device 30 is cylindrical in shape as a whole. The central axis of the main slewing device 30 extends substantially in the Z direction. The main slewing device 30 includes a main body 30A and an output member 30B. In FIG. 2, the main body 30A and the output member 30B are separated by the dotted line for convenience. This is the same for the other slewing device described below.

An outer casing of the main body 30A is fixed to an inner wall of the upper body 20. The main body 30A includes an electric motor and a speed reducer. The electric motor serves as a drive source for the main slewing device 30. The electric motor receives power supply from a battery that is not shown. Depending on the power supplied to the electric motor, an output shaft of the electric motor can generate torque in both forward and reverse directions. The speed reducer multiplies the torque output from the output shaft of the electric motor with a predetermined ratio and outputs the resulting torque to the output member 30B. The speed reducer may be of, for example, an eccentric oscillation gear type or planetary gear type. The speed reducer can be of any type as long as it is capable of multiplying the torque from the electric motor and outputting the resulting torque. The output member 30B is rotatable relative to the outer casing of the motor body 30A.

When acted upon by the torque from the speed reducer, the output member 30B rotates on a main slewing axis 30J. The main slewing axis 30J extends substantially in the Z direction. In this embodiment, the main slewing axis 30J substantially coincides with the reference axis K. The output member 30B and the main slewing axis 30J output torque centered on this main slewing axis 30J. The output member 30B is rotatable through 360 degrees in both forward and reverse directions in accordance with the rotational direction of the electric motor. Furthermore, an upper portion of the output member 30B protrudes upward from the top surface 23 of the upper body 20 through the opening in the top surface 23.

<Connecting Member>

As shown in FIG. 2, the excavator 10 includes a connecting member 25. The connecting member 25 is positioned on the upper side of the top surface 23 of the upper body 20. As shown in FIG. 1, the connecting member 25 is circular disc-shaped. The diameter of the circle of the connecting member 25 is slightly smaller than the diameter of the top surface 23. The center of the circle of connecting member 25 is disposed on the reference axis K. As shown in FIG. 2, a lower surface of the connecting member 25 faces the top surface 23. The lower surface of the connecting member 25 is fixed to the output member 30B in the main slewing device 30. The connecting member 25 rotates integrally with the output member 30B of the main slewing device 30. That is, the connecting member 25 receives torque from the main slewing device 30 and rotates around the main slewing axis 30J. In accordance with the rotational range of the output member 30B about the main slewing axis 30J, the connecting member 25 is rotatable through 360 degrees about the main slewing axis 30J. In other words, the main slewing device 30 is capable of outputting torque centered on the main slewing axis 30J to the connecting member 25. Furthermore, the main slewing device 30 is capable of driving and rotating the connecting member 25 through 360 degrees about the main slewing axis 30J. Although not shown in the figure, on the lower surface of the connecting member 25, a bearing is provided between the exposed area of the lower surface, which is outside the output member 30B of the main slewing device 30, and the top surface 23 of the upper body 20. The bearing supports the connecting member 25 so that the connecting member can rotate relative to the top surface 23.

<Support Wall>

As shown in FIG. 2, the excavator 10 includes a support wall 27. The support wall 27 protrudes upward from the upper surface of the connecting member 25. The support wall 27 has a rectangular parallelepiped shape. The support wall 27 is fixed to the upper surface of the connecting member 25. The support wall 27 extends over the central portion of the upper body 20 in the direction orthogonal to both the reference axis K and the first rotational axis 51J.

<First Mechanism>

As shown in FIGS. 1 and 2, the excavator 10 includes a first mechanism 41. The first mechanism 41 includes a first drive device 51, a second drive device 52, a third drive device 53, a first boom 61, a first arm 62, and a first attachment 63. Note that FIG. 2 omits the illustration of a second mechanism 42 described later. Furthermore, FIG. 2 shows an operating state in which both the first boom 61 and the first arm 62 extend straight upward, which is different from the operating state shown in FIG. 1.

<First Drive Device>

As shown in FIG. 1, the first drive device 51 is provided next to the support wall 27. The first drive device 51 includes a main body 51A and a first output member 51B. In FIG. 2, the main body 51A and the first output member 51B are separated by the dotted line for convenience. This is the same for the other drive device.

An outer casing of the main body 51A is fixed to a side surface of the support wall 27. The main body 51A includes an electric motor and a speed reducer. The electric motor is the drive source for the first drive device 51. The electric motor receives power supply from a battery that is not shown. Depending on the power supplied to the electric motor, an output shaft of the electric motor can generate torque in both forward and reverse directions. The speed reducer multiplies the torque output from the output shaft of the electric motor with a predetermined ratio and outputs the resulting torque to the first output member 51B. The speed reducer may be of, for example, an eccentric oscillation gear type or planetary gear type. The speed reducer can be of any type as long as it is capable of multiplying the torque from the electric motor and outputting the resulting torque.

The first output member 51B is rotatable relative to the outer casing of the main body 51A. When acted upon by the torque from the speed reducer, the first output member 51B rotates about the first rotational axis 51J. As described above, the first rotational axis 51J is a specific axis that is approximately orthogonal to the reference axis K. The first output member 51B and the first drive device 51 output torque centered on this first rotational axis 51J. The first output member 51B is rotatable through 360 degrees in both forward and reverse directions in accordance with the rotational direction of the electric motor. The first drive device 51 and the main slewing device 30 together constitute a specific drive unit.

<First Boom>

As shown in FIG. 1, the first boom 61 is disposed on the opposite side of the first drive device 51 from the support wall 27. The first boom 61 is shaped like an elongated plate or column. In the embodiment, the first boom 61 extends in a straight line. A first end portion 61A of the first boom 61 in the longitudinal direction is disposed at a position where the first rotational axis 51J passes. Furthermore, the first output member 51B of the first drive device 51 is fixed to the first end portion 61A of the first boom 61. The first boom 61 rotates integrally with the first output member 51B. That is, when acted upon by the torque from the first drive device 51, the first boom 61 swings around the first rotational axis 51J. In other words, the first drive device 51 outputs the torque centered on the first rotational axis 51J to the first boom 61.

As described above, the first end portion 61A of the first boom 61 is connected to the support wall 27 via the first drive device 51. As shown in FIG. 2, the support wall 27 is coupled to the top surface 23 of the upper body 20 via the connecting member 25 and the main slewing device 30. In other words, the first end portion 61A of the first boom 61 is coupled to the top surface 23 of the upper body 20 via the first drive device 51, the support wall 27, the connecting member 25, and the main slewing device 30. Therefore, the first end portion 61A of the first boom 61 corresponds to the coupling point between the first boom 61 and the upper body 20. In accordance with the arrangement of the support wall 27 relative to the upper body 20 as described above, the first end portion 61A of the first boom 61 is positioned approximately at the center of the upper body 20 in the direction orthogonal to both the reference axis K and the first rotational axis 51J. Furthermore, as a result of the aforementioned coupling configuration, the support wall 27 and the connecting member 25 are interposed between the first boom 61 and the top surface 23 of the upper body 20.

As described above, the first boom 61 rotates around the first rotational axis 51J. The angular range of this rotation will now be explained with reference to FIG. 2. As mentioned above, the minor angle θ formed between the top surface 23 and the side surface 22 of the upper body 20 is approximately 120 degrees. Furthermore, the first output member 51B of the first drive device 51 is rotatable through 360 degrees in both forward and reverse directions about the first rotational axis 51J, which is substantially orthogonal to the reference axis K. The first rotational axis 51J passes in the vicinity of the top surface 23. Due to the positional relationship between this first rotational axis 51J and the top surface 23 and to the magnitude of the minor angle θ between the top surface 23 and the side surface 22, the first boom 61 is rotatable within the following rotational range in the specified plan view. The first boom 61 is rotatable in both directions with respect to the reference axis K. Specifically, in the specified plan view, the first boom 61 can swing across a reference half-line, which extends from the first rotational axis 51J along the reference axis K in the direction opposite the top surface 23, to one side and the other side with respect to the reference half-line. More specifically, the first boom 61 is rotatable to one side with respect to the reference half-line within a range not exceeding a first rotation angle, and is rotatable to the other side with respect to the reference half-line within a range not exceeding the first rotation angle. The first rotation angle is approximately 150°. In other words, in the specified plan view, the first drive device 51 is capable of rotationally driving the first boom 61 within the range not exceeding the first rotation angle to both the one side and the other side with respect to the reference half-line. More specifically, the first drive device 51 is capable of rotationally driving the first boom 61 to one side with respect to the reference half-line, up to the first rotation angle. Similarly, the first drive device 51 is capable of rotationally driving the first boom 61 to the other side with respect to the reference half-line, up to the first rotation angle. Note that the “half-line” is defined as a straight line that extends in only one direction from a specific starting point.

In the specified plan view, the following can be said regarding the rotation of the first boom 61. An imaginary straight line connecting the first end portion 61A of the first boom 61 and a second end portion 61B, which is the opposite end of the first boom 61, is referred to as a first imaginary line 41E. In the embodiment, the first imaginary line 41E corresponds to an imaginary straight line connecting the first rotational axis 51J and a second rotational axis 52J, which will be described later. Rotation of the first boom 61 to one side with respect to the reference axis K means that the first imaginary line 41E swings around the first rotational axis 51J to one side with respect to the reference axis K. Similarly, rotation of the first boom 61 to the other side with respect to the reference axis K means that the first imaginary line 41E swings around the first rotational axis 51J to the other side with respect to the reference axis K.

<Second Drive Device>

As shown in FIG. 1, the second drive device 52 is disposed in the vicinity of the second end portion 61B of the first boom 61. In a direction parallel to the first rotational axis 51J, the second drive device 52 is disposed on the side of the first boom 61 facing away from the first drive device 51. The second drive device 52 is configured similarly to the first drive device 51. That is, the second drive device 52 includes a main body 52A having a speed reducer in addition to an electric motor as a drive source, and a second output member 52B that is rotated with torque from the main body 52A. An outer casing of the main body 52A is fixed to the second end portion 61B of the first boom 61. When acted upon by the torque from the speed reducer in the main body 52A, the second output member 52B rotates about the second rotational axis 52J. The second rotational axis 52J extends substantially parallel to the first rotational axis 51J at a position different from that of the first rotational axis 51J. The second rotational axis 52J passes through the second end portion 61B of the first boom 61. The second output member 52B and the second drive device 52 output torque centered on this second rotational axis 52J. The second output member 52B is rotatable through 360 degrees in both forward and reverse directions in accordance with the rotational direction of the electric motor.

<First Arm>

As shown in FIG. 1, the first arm 62 is disposed next to the second drive device 52. In a direction parallel to the first rotational axis 51J, the first arm 62 is disposed on the side of the second drive device 52 facing away from the first boom 61. The first arm 62 is shaped like an elongated plate or column. In the embodiment, the first arm 62 extends in a straight line. A first end portion 62A of the first arm 62 in the longitudinal direction is disposed at a position where the second rotational axis 52J passes. Furthermore, the first end portion 62A of the first arm 62 is fixed to the second output member 52B of the second drive device 52. The first end portion 62A of the first arm 62 rotates integrally with the second output member 52B. That is, when acted upon by the torque from the second drive device 52, the first arm 62 rotates around the second rotational axis 52J. In other words, the second drive device 52 outputs the torque centered on the second rotational axis 52J to the first arm 62. In this way, the first end portion 62A of the first arm 62 is coupled to the second drive device 52. At the same time, the first end portion 62A of the first arm 62 is coupled to the second end portion 61B of the first boom 61 via the second drive device 52. In other words, the first end portion 62A of the first arm 62 corresponds to the coupling point with the first boom 61.

As described above, the first arm 62 is rotated by the torque from the second drive device 52. The second output member 52B of the second drive device 52 is rotatable through 360 degrees in both forward and reverse directions about the second rotational axis 52J. Thus, in the specified plan view of FIG. 2, the first arm 62 is rotatable to both sides with respect to the first imaginary line 41E connecting the first rotational axis 51J and the second rotational axis 52J. Specifically, in consideration of the arrangement of the first attachment 63 described below, the first arm 62 of the embodiment can swing across a first imaginary half-line, which extends from the second rotational axis 52J along the first imaginary line 41E in the direction opposite the first rotational axis 51J, to one side and the other side with respect to the first imaginary half-line. More specifically, the first arm 62 is rotatable to one side with respect to the first imaginary half-line within a range not exceeding a second rotation angle, and rotatable to the other side with respect to the first imaginary half-line within a range not exceeding the second rotation angle. The second rotation angle is approximately 180°. In other words, in the specified plan view, the second drive device 52 is capable of rotationally driving the first arm 62 to both the one side and the other side with respect to the first imaginary half-line. More specifically, the second drive device 52 is capable of rotationally driving the first arm 62 to one side with respect to the first imaginary half-line up to the second rotation angle. Similarly, the second drive device 52 is capable of rotationally driving the first arm 62 to the other side with respect to the first imaginary half-line, up to the second rotation angle.

Similarly to the first boom 61, in the specified plan view, the following can be said regarding the rotation of the first arm 62. An imaginary straight line connecting the first end portion 62A of the first arm 62 and a second end portion 62B, which is the opposite end of the first arm 62, is referred to as a second imaginary line 41F. In the embodiment, the second imaginary line 41F corresponds to an imaginary straight line connecting the second rotational axis 52J and a third rotational axis 53J, which will be described later. Rotation of the first arm 62 to one side with respect to the first imaginary line 41E means that the second imaginary line 41F swings around the second rotational axis 52J to one side with respect to the reference axis K. Similarly, rotation to the other side means that the second imaginary line 41F swings around the second rotational axis 52J to the other side with respect to the first imaginary line 41E.

<Third Drive Device>

As shown in FIG. 1, the third drive device 53 is disposed in the vicinity of the second end portion 62B of the first arm 62. In the direction parallel to the first rotational axis 51J, the third drive device 53 is disposed at substantially the same position as the second drive device 52. The third drive device 53 is configured similarly to the first and second drive device 51 and 52. That is, the third drive device 53 includes a main body 53A having a speed reducer in addition to an electric motor as the drive source, and a third output member 53B that is rotated with torque from the main body 53A. An outer casing of the main body 53A is fixed to the second end portion 61B of the first arm 62. When acted upon by the torque from the speed reducer in the main body 53A, the third output member 53B rotates about the third rotational axis 53J. The third rotational axis 53J extends substantially parallel to the first rotational axis 51J at a position different from that of the first rotational axis 51J and the second rotational axis 52J. The third rotational axis 53J passes through the second end portion 61B of the first arm 62. The third output member 53B and the third drive device 53 output torque centered on this third rotational axis 53J. The third output member 53B is rotatable through 360 degrees in both forward and reverse directions in accordance with the rotational direction of the electric motor. The third drive device 53 forms a first drive unit together with the first and second drive device 51 and 52.

<First Attachment>

As shown in FIG. 1, the first attachment 63 is disposed in the vicinity of the second end portion 62B of the first arm 62. The first attachment 63 includes a first work tool 65 and a connecting piece 64.

As shown in FIGS. 1 and 2, the connecting piece 64 has a substantially rectangular plate shape. As shown in FIG. 1, the connecting piece 64 is disposed at the position where the third rotational axis 53J passes through. In a direction parallel to the first rotational axis 51J, the connecting piece 64 is disposed on the side opposite the second end portion 62B of the first arm 62 relative to the third drive device 53. A principal surface of the connecting piece 64 faces the third output member 53B of the third drive device 53. The principal surface of the connecting piece 64 is fixed to the third output member 53B. The principal surfaces of a plate-shaped object are the surfaces with the largest area. The connecting piece 64 rotates integrally with the third output member 53B. That is, when acted upon by the torque from the third drive device 53, the connecting piece 64 and thus the first attachment 63 rotate about the third rotational axis 53J. In other words, the third drive device 53 outputs the torque centered on the third rotational axis 53J to the first attachment 63. In this way, the first attachment 63 is coupled to the third drive device 53. At the same time, the first attachment 63 is coupled to the second end portion 62B of the first arm 62 via the third drive device 53.

As described above, the connecting piece 64 is rotated by the torque from the third drive device 53. The third output member 53B of the third drive device 53 is rotatable through 360 degrees in both forward and reverse directions about the third rotational axis 53J. Thus, in the specified plan view of FIG. 2, the first attachment 63 is rotatable to both sides with respect to the second imaginary line 41F connecting the second rotational axis 52J and the third rotational axis 53J. The first attachment 63 of the embodiment is rotatable approximately 360 degrees to one side with respect to the second imaginary line 41F, and also rotatable approximately 360 degrees to the other side with respect to the second imaginary line 41F. In other words, the first attachment 63 of the embodiment can perform the following rotational movements. In the specified plan view, the first attachment 63 is rotatable across a first half-line, which extends from the third rotational axis 53J along the second imaginary line 41F in the direction opposite the second rotational axis 52J, to one side and the other side with respect to the first half-line. In the specified plan view, the first attachment 63 is also rotatable across a second half-line, which extends from the third rotational axis 53J along the second imaginary line 41F in the direction toward the second rotational axis 52J, to one side and the other side with respect to the second half-line. In other words, in the specified plan view, the third drive device 53 is capable of rotationally driving the first attachment 63 to both the one side and the other side with respect to the first half-line. Furthermore, in the specified plan view, the third drive device 53 is capable of rotationally driving the first attachment 63 to both the one side and the other side with respect to the second half-line.

In the specified plan view, the following can be said regarding the rotation of the first attachment 63. As shown in FIG. 2, an imaginary straight line that connects a specific portion of the first work tool 65 and the coupling point between the connecting piece 64 and the first arm 62 is referred to as an attachment line 41H. In the embodiment, the coupling point between the connecting piece 64 and the first arm 62 is the point where the third drive device 53 is fixed in the connecting piece 64, and corresponds to the third rotational axis 53J. In the embodiment, the specific portion of the first work tool 65 is a corner between a first side wall 67B and a bottom wall 67D of a first bucket 65A described below. Rotation of the first attachment 63 to one side with respect to the second imaginary line 41F means that the attachment line 41H rotates around the third rotational axis 53J to one side with respect to the second imaginary line 41F. Similarly, rotation of the first attachment to the other side means that the attachment line 41H rotates around the third rotational axis 53J to the other side with respect to the second imaginary line 41F.

As shown in FIG. 2, the first work tool 65 includes a first bucket 65A and a second bucket 65B. The first bucket 65A and the second bucket 65B have the same configuration. Therefore, the following description will focus on the first bucket 65A, omitting redundant explanations regarding the second bucket 65B.

As shown in FIGS. 1 and 2, the first bucket 65A includes a bucket body 67 and a plurality of teeth 68. The bucket body 67 is box-shaped. That is, the bucket body 67 includes a rectangular bottom wall 67D, side walls rising from each of the four edges of the bottom wall 67D, and an opening 67A enclosed by the edges of the side walls opposite the bottom wall 67D. In other words, the edges of the side walls opposite the bottom wall 67D define a rectangular opening. An outer surface of a first side wall 67B, one of the four side walls, is fixed to a surface of the connecting piece 64 that extends in its thickness direction.

As shown in FIG. 1, there are four teeth 68 in the embodiment. However, the number of the teeth 68 is not limited to four. The teeth 68 protrude from a specified edge 67C of the four edges defining the rectangular opening. The specified edge 67C corresponds to the edge of the side wall that faces the first side wall 67B. Since the first side wall 67B is fixed to the connecting piece 64, as shown in FIG. 2, in the specified plan view, the specified edge 67C is located at the position farthest from the third rotational axis 53J among the opening edges of the bucket body 67. The teeth 68 protrude from this specified edge 67C toward the opposite side of the opening 67A from the bottom wall 67D. As shown in FIG. 1, the multiple teeth 68 are arranged along the specified edge 67C.

The positional relationship between the first bucket 65A and the second bucket 65B. In the specified plan view shown in FIG. 2, the first bucket 65A and the second bucket 65B are arranged symmetrically with respect to an attachment reference line 41H, which is a specific imaginary straight line. Specifically, the outer surfaces of the bottom walls 67D of the first bucket 65A and the second bucket 65B face each other. The bottom walls 67D of both the first bucket 65A and second bucket 65B are fixed to one another. As a result, the opening 67A of the first bucket 65A and the opening 67A of the second bucket 65B face away from each other. In this configuration, the first bucket 65A and the second bucket 65B are arranged in the circumferential direction about the third rotational axis 53J. Furthermore, the first bucket 65A and the second bucket 65B are arranged to satisfy the following first condition in the specified plan view. The first condition is that a distance from the third rotational axis 53J to a distal end of the tooth 68 of the first bucket 65A is equal to a distance from the third rotational axis 53J to a distal end of the tooth 68 of the second bucket 65B. As a result of satisfying this first condition, the first attachment 63 has the following configuration in the specified plan view. Assuming that the first arm 62 is held in a given rotational position, and the first attachment 63 rotates 360 degrees about the third rotational axis 53J relative to the first arm 62. As indicated by the alternate long and short dash line 68Q in FIG. 4, a rotational trajectory of the distal end of the tooth 68 of the first bucket 65A overlaps or coincides with a rotational trajectory of the distal end of the tooth 68 of the second bucket 65B.

<Second Mechanism>

As shown in FIGS. 1 and 3, the excavator 10 includes a second mechanism 42. The second mechanism 42 includes a first slewing device 31, a second slewing device 52, a second boom 71, a second arm 72, and a second attachment 73. Note that the first mechanism 41 and the support wall 27 are not shown in FIG. 3.

<First Slewing Device>

As shown in FIG. 3, the first slewing device 31 is disposed on the upper surface of the connecting member 25. As shown in FIG. 1, the first slewing device 31 is disposed on the opposite side of the support wall 27 from the first drive device 51. The first slewing device 31 is disposed approximately at the center of the upper body 20 in a direction orthogonal to both the first rotational axis 51J and the reference axis K. In this embodiment, in consideration of the position of the first rotational axis 51J, when viewing the excavator 10 in plan view in a direction parallel to the reference axis K, the first slewing device 31 is disposed such that it overlaps with the first rotational axis 51J.

As shown in FIG. 3, the first slewing device 31 is cylindrical in shape as a whole. The first slewing device 31 includes a main body 31A and a first slewing member 31B. An outer casing of the main body 31A is fixed to the upper surface of the connecting member 25. The main body 31A includes an electric motor and a speed reducer. The electric motor is the drive source for the first slewing device 31. The electric motor receives power supply from a battery that is not shown. Depending on the power supplied to the electric motor, an output shaft of the electric motor can generate torque in both forward and reverse directions. The speed reducer multiplies the torque output from the output shaft of the electric motor with a predetermined ratio and outputs the resulting torque to the first slewing member 31B. The first slewing member 31B is rotatable relative to the outer casing of the main body 31A. When acted upon by the torque from the speed reducer, the first slewing member 31B rotates about a first slewing axis 31J. The first slewing axis 31J extends substantially parallel to the reference axis K at a position different from that of the reference axis K. In other words, the first slewing axis 31J extends in the upper and lower directions of the vehicle body 12. The first slewing member 31B and the first slewing device 31 output torque centered on the first slewing axis 31J. The first slewing member 31B is rotatable through 360 degrees in both forward and reverse directions in accordance with the rotational direction of the electric motor. As shown in FIG. 1, due to the position of the first slewing device 31, when viewing the excavator 10 in plan view in the direction parallel to the reference axis K, the first slewing axis 31J is situated on the first rotational axis 51J.

<Second Boom>

As shown in FIG. 3, the second boom 71 is disposed over the first slewing device 31. The second boom 71 is shaped like an elongated plate or column. In this embodiment, the second boom 71 extends in a straight line. A first end portion 71A of the second boom 71 in the longitudinal direction is disposed at a position where the first slewing axis 31J passes. Furthermore, the first slewing member 31B of the first slewing device 31 is fixed to the first end portion 71A of the second boom 71. The second boom 71 rotates integrally with the first slewing member 31B. That is, when acted upon by the torque from the first slewing device 31, the second boom 71 rotates around the first slewing axis 31J. In other words, the first slewing device 31 outputs the torque centered on the first slewing axis 31J to the second boom 71.

As described above, the first end portion 71A of the second boom 71 is coupled to the connecting member 25 via the first slewing device 31. In other words, the first end portion 71A of the second boom 71 is coupled to the top surface 23 of the upper body 20 via the first slewing device 31, the connecting member 25, and the main slewing device 30. Therefore, the first end portion 71A of the second boom 71 corresponds to the coupling point between the second boom 71 and the upper body 20.

As described above, the second arm 71 is rotated by the torque from the first slewing device 31. The first slewing member 31B of the first slewing device 31 is rotatable through 360 degrees in both forward and reverse directions about the first slewing axis 31B. Thus, as shown in FIG. 1, the second boom 71 is rotatable widely in the range where the second boom does not interfere with the support wall 27 disposed next to the first slewing device 31. When viewing the excavator 10 in plan from the direction parallel to the reference axis K, the second boom 71 is rotatable to one side and the other side with respect to the first rotational axis 51J. Specifically, when viewed in plane from the direction parallel to the reference axis K, the second boom 71 can swing across a half-line, which extends from the first slewing axis 31J along the first rotational axis 51J in the direction opposite to the support wall 27 to one side and the other side with respect to the half-line. This half-line is referred to as a boom half-line. More specifically, the second boom 71 is rotatable to one side with respect to the boom half-line within a range not exceeding a first slewing angle, and to be rotatable to the other side with respect to the boom half-line within a range not exceeding the first slewing angle. The first slewing angle is approximately 90°. In other words, when viewing the excavator 10 in plan from the direction parallel to the reference axis K, the first slewing device 31 is capable of rotationally driving the second boom 71 to both the one side and the other side with respect to the boom half-line. More specifically, the first slewing device 31 is capable of rotationally driving the second boom 71 to one side relative to the half-line, up to the first slewing angle. Furthermore, the first slewing device 31 is capable of rotationally driving the second boom 71 to the other side with respect to the half-line, up to the first slewing angle.

As shown in FIG. 1, when the excavator 10 is viewed in plan from the direction parallel to the reference axis K, the following can be said regarding the rotation of the first second boom 71. An imaginary straight line connecting the first end portion 71A of the second boom 71 and a second end portion 71B, which is the opposite end of the second boom 71, is referred to as a third imaginary line 42E. In the embodiment, the third imaginary line 42E corresponds to an imaginary straight line connecting the first slewing axis 31J and a second slewing axis 32J, which will be described later. Rotation of the second boom 71 to one side with respect to the first slewing axis 51J means that the third imaginary line 42E swings around the first slewing axis 31J to one side with respect to the first rotational axis 51J. Similarly, rotation to the other side means that the third imaginary line 42E swings around the first slewing axis 31J to the other side with respect to the first rotational axis 51J.

<Second Slewing Device>

As shown in FIG. 3, the second slewing device 32 is disposed in the vicinity of the second end portion 71B of the second boom 71. The second slewing device 32 is disposed below the second boom 71. The second slewing device 32 is configured similarly to the first slewing device 31. That is, the second slewing device 32 includes a main body 32A having a speed reducer in addition to an electric motor as a drive source, and a second slewing member 32B that is rotated with torque from the main body 32A. An outer casing of the main body 32A is fixed to the second end portion 71B of the second boom 71. When acted upon by the torque from the main body 32A, the second slewing member 32B rotates about the second slewing axis 32J. The second slewing axis 32J extends substantially parallel to the reference axis Kat a position different from that of the first slewing axis 31J and the reference axis K. The second rotational axis 52J passes through the second end portion 71B of the second boom 71. The second slewing member 32B and thus the second slewing device 32 output torque centered on the second slewing axis 32J. The second slewing member 32B is rotatable through 360 degrees in both forward and reverse directions in accordance with the rotational direction of the electric motor. The second slewing device 32 and the first slewing device 31 together constitute a second drive unit.

<Second Arm>

As shown in FIG. 3, the second arm 72 is disposed below the second slewing device 32. The second arm 72 is shaped like an elongated plate or column. In the embodiment, the second arm 72 extends in a straight line. A second end portion 72A of the second boom 72 in the longitudinal direction is disposed at a position where the second slewing axis 32J passes. Furthermore, the second slewing member 32B of the second slewing device 32 is fixed to the first end portion 72A of the second boom 71. The second boom 71 rotates integrally with the second slewing member 32B. That is, when acted upon by the torque from the second slewing device 32, the second arm 72 rotates around the second slewing axis 32J. In other words, the second slewing device 32 outputs the torque centered on the second slewing axis 32J to the second arm 72. In this way, the first end portion 72A of the second arm 72 is coupled to the second slewing device 32. At the same time, the first end portion 72A of the second arm 72 is coupled to the second end portion 71B of the second boom 71 via the second slewing device 32. In other words, the first end portion 72A of the second arm 72 corresponds to the coupling point with the second boom 71.

As described above, the second arm 72 is rotated by the torque from the second slewing device 32. The second slewing member 32B of the second slewing device 32 is rotatable through 360 degrees in both forward and reverse directions about the second slewing axis 32J. As shown in FIG. 1. when viewing the excavator 10 in plan from the direction parallel to the reference axis K, the second arm 72 is rotatable to both one side and the other side with respect to the third imaginary line 42E connecting the first slewing axis 31J and the second slewing axis 32J. Specifically, in consideration of the arrangement of a second attachment 73 described below, the second arm 72 of the embodiment can swing across a third imaginary half-line 42, which extends from the second slewing axis 32J along the third imaginary line 42E in the direction opposite the first slewing axis 31J, to one side and the other side with respect to the third imaginary half-line. More specifically, the second arm 72 is slewable to one side with respect to the third imaginary half-line within a range not exceeding a second slewing angle, and slewable to the other side with respect to the third imaginary half-line within a range not exceeding the second slewing angle. The second slewing angle is approximately 180°. In other words, when viewing the excavator 10 in plan from the direction parallel to the reference axis K, the second slewing device 32 is capable of rotationally driving the second arm 72 to both the one side and the other side with respect to the third imaginary half-line. More specifically, the second slewing device 32 is capable of rotationally driving the second boom 71 to one side with respect to the third imaginary half-line, up to the second slewing angle. Similarly, the second slewing device 32 is capable of rotationally driving the second boom 72 to one side with respect to the third imaginary half-line, up to the second slewing angle.

As shown in FIG. 1, when the excavator 10 is viewed in plan from the direction parallel to the reference axis K, the following can be said regarding the rotation of the second arm 72. An imaginary straight line connecting the first end portion 72A of the second arm 72 and a second end portion 72B, which is the opposite end of the second arm 72, is referred to as a fourth imaginary line 42F. In the embodiment, the fourth imaginary line 42F corresponds to an imaginary straight line connecting the second slewing axis 32J and an operation axis 74J, which will be described later. Rotation of the second arm 72 to one side with respect to the third imaginary line 42E means that the fourth imaginary line 42F swings around the second rotational axis 32J to one side with respect to the third imaginary line 42E. Similarly, rotation to the other side means that the fourth imaginary line 41F swings around the second rotational axis 32J to the other side with respect to the third imaginary line 42E.

<Second Attachment>

As shown in FIG. 3, the second attachment 73 is disposed in the vicinity of the second end portion 72B of the second arm 72. The second attachment 73 is an electric extendable device. Specifically, the second attachment 73 is equipped with a power generating device 74 and a second work tool 75.

The power generating device 74 includes a main body 74A and a rod, which is an example of an operating member 74B. The main body 74A includes a cylinder, an electric motor, and a conversion mechanism. The cylinder forms an outer casing of the main body 74A. The cylinder is cylindrical in shape. The cylinder is fixed to the second end portion 72B of the second arm 72. The cylinder is disposed above the second arm 72. The operation axis 74J, which is the central axis of the cylinder, extends approximately parallel to the first slewing axis 31J at a position different from the first slewing axis 31J and the second slewing axis 32J. The operating axis 74J passes through the second end portion 72B of the second arm 72. The electric motor serves as the drive source for the power generating device 74. The electric motor receives power fed from a battery, which is not shown. Depending on the power supplied to the electric motor, an output shaft of the electric motor can generate torque in both forward and reverse directions. The conversion mechanism converts the rotation of the output shaft of the electric motor into linear motion of the operating member 74B. Examples of the conversion mechanism include ball screw mechanisms and rack-and-pinion mechanisms. The operating member 74B protrudes from the inside of the cylinder to the outside. The operating member 74B penetrates the second end portion 72B of the second arm 72 in the upper and lower directions. The operating member 74B reciprocates along the operating axis 74J in response to the drive of the electric motor. In response to the reciprocating motion of the operating member 74B, the protrusion amount of the operating member 74B relative to the cylinder changes. In this way, the power generating device 74 extends and retracts in the direction along the operating axis 74J.

The second work tool 75 is fixed to a lower end of the operating member 74B. The second work tool 75 has a bifurcated portion including a first portion and a second portion. The first portion and the second portion have the same configuration. Therefore, the first portion will be described here, and the description of the second portion will be omitted. As shown in FIG. 5, when the first portion is viewed in plan from the opposite side to the second portion, the first portion includes a rectangular connecting plate 75A and two or more teeth 75B. An edge corresponding to an upper edge of the connecting plate 75A is fixed to a lower end of the operating member 74B. The two or more teeth 75B protrude from a lower edge of the connecting plate 75A. The two or more teeth 75B are arranged along the lower edge of the connecting plate 75A. In this embodiment, there are three teeth 75B provided. However, the number of the teeth 75B is not limited to three.

<Control Device>

As shown in FIG. 1, the excavator 10 includes a control device 45. The control device 45 is disposed inside, for example, the upper body 20. The position of the control device 45 in each drawing is for convenience only. The control device 45 may include processing circuitry including one or more processors that perform various processes in accordance with computer programs (software). The control device 45 may include processing circuitry including one or more dedicated hardware circuits such as application-specific integrated circuits (ASICs) that perform at least some of the various processes, or processing circuitry including a combination of the above processors and dedicated hardware circuits. The processors include a CPU and a memory such as a RAM or ROM. The memory stores program codes or instructions configured to cause the CPU to perform processes. The memory, or a computer-readable medium, encompasses any kind of available medium accessible to a general-purpose or dedicated computer. The memory includes an electrically rewritable nonvolatile memory. The control device 45 is equipped with a communication circuit. The communication circuit is a circuit for wireless communication with a controller 46 held by the user outside of the excavator 10. The excavator 10 and the controller 46 constitute an excavator system 47.

The control device 45 controls various parts of the excavator 10. The control targets of the control device 45 include the following devices: the first drive device 51, the second drive device 52, the third drive device 53, the first slewing device 31, the second slewing device 32, the power generating device 74 of the second attachment 73, the main slewing device 30, and the traveling unit 16. The control device 45 controls the control targets in response to command signals transmitted from the controller 46. For example, the control device 45 outputs a control signal to the first drive device 51 in response to a command signal. Thus, the control device 45 rotates the first boom 61.

<Operation and Effects of Embodiment>

(1) As shown by the arrow 61P in FIG. 6, the first boom 61 of the embodiment is rotatable to one side with respect to the reference axis K in the specified plan view. Furthermore, as shown by arrow 61Q in FIG. 6, the first boom 61 is also rotatable to the other side with respect to the reference axis K in the specified plan view. In other words, in the excavator 10 of the embodiment, the first boom 61 and the first arm 62 connected to the first boom 61 can be moved to both sides with respect to the reference axis K. Therefore, in the excavator 10 of the embodiment, a large range of movement of the first mechanism 41 can be obtained. As a result, the working envelope of the excavator 10 can be increased.

(2) In the specified plan view, the first boom 61 indicated by the solid line in FIG. 6 is rotatable to an angle exceeding 90 degrees with respect to the reference axis K. Thus, the second end portion 61B of the first boom 61 can reach a position lower than the top surface 23 of the upper body 20. Accordingly, the first boom 61 and the first arm 62 coupled thereto can reach close to the ground surface G. Thus, the excavator 10 of the embodiment is capable of operating over a wide range in the upper and lower directions on both the one side and the other side with reference to the reference axis K.

(3) The first arm 62 of the embodiment can swing to one side and the other side with respect to the first imaginary half-line, which extends from the second rotational axis 52J along the first imaginary line 41E in the direction opposite the first rotational axis 51J. Therefore, as shown by the arrow 62P in FIG. 6, the first arm 62 is rotatable upward and downward relative to the first boom 61 when the first boom 61 is situated on one side with the reference axis K in the specified plan view. Therefore, as shown by the arrow 62Q in FIG. 6, the first arm 62 is also rotatable upward and downward relative to the first boom 61 when the first boom 61 is situated on the other side with the reference axis K in the specified plan view. Moreover, the first attachment 63 is rotatable to both sides with respect to the second imaginary line 41F connecting the second rotational axis 52J and the third rotational axis 53J. Therefore, as shown by the arrow 65P in FIG. 6, the first attachment 63 is rotatable upward and downward relative to the first arm 62 when the first boom 62 is situated on one side with the reference axis K in the specified plan view. As shown by the arrow 65P in FIG. 6, the first attachment 63 is rotatable upward and downward relative to the first arm 62 when the first boom 62 is situated on the other side with the reference axis K in the specified plan view. With these configurations of the embodiment, regardless of the rotational position of the first boom 61, the first arm 62 and the first attachment 63 can be brought to a position appropriate for work.

As shown in FIG. 6, the side surface 22 of the upper body 20 is the inclined surface slanted with respect to the reference axis K. Therefore, even when the first boom 61 is inclined relative to the top surface 23 of the upper body 20, the first boom 61 does not interfere with the side surface 22 of the upper body 20. In other words, because the side surface 22 of the upper body 20 is inclined with respect to the reference axis K, the first boom 61 is allowed to incline downward relative to the top surface 23 of the upper body 20.

To make the first boom 61 incline downward relative to the top surface 23 of the upper body 20, it may be conceivable, for example, to place the first drive unit 51 and consequently the first end 61A of the first boom 61 at a sufficiently elevated location relative to the top surface 23 of the upper body 20. However, adopting such a structure would require, for instance, enlarging the support wall 27 in the upper direction and shifting the mounting position of the first boom 61 on the support wall 27 further upward. In this case, since the position of the first mechanism 41 as a whole would shift upward, there is a concern that the entire excavator 10 may become larger in size.

In this regard, as in the present embodiment, by configuring the side surface 22 of the upper body 20 as the inclined surface, it is possible to secure a wide range of motion for the first mechanism 41, including the first boom 61, without increasing the overall size of the excavator 10.

(6) As shown in FIG. 6, the first boom 61 is connected to the main slewing device 30 via the support wall 27 and the connecting member 25. Furthermore, the output member 30B of the main slewing device 30 is capable of slewing 360 degrees about the main slewing axis 30J. With the slew of the output member 30B, the excavator 10 of the embodiment can move the first boom 61 and consequently the first arm 62 and other components connected to the first boom 61 to any position in the front, rear, left, or right directions. For example, as indicated by the arrow 30P in FIG. 7, the first boom 61, the first arm 62, and the first attachment 63 can slew 90 degrees clockwise in FIG. 7 from the respective positions shown in FIG. 1.

To implement a configuration in which the first boom 61 is capable of slewing through 360 degrees around the reference axis K, one conceivable approach is to make the entire upper body 20 slewable relative to the lower body 14. However, enabling the entire upper body 20 to slew requires the following structural considerations. That is, it is necessary to support the upper body 20 in a manner that allows rotation while supporting the total weight of the upper body 20 and all components attached to it. To achieve this, it is necessary to provide a considerably large bearing. Furthermore, in relation to the above-mentioned weight, the torque necessary to rotationally drive the upper body 20 would also be significantly high. As a result, the drive unit responsible for this slew may need to be substantially larger in size.

In this regard, in the configuration of the embodiment, the bearing that rotatably supports the connecting member 25 only needs to bear the total weight of the components attached to the connecting member 25. Therefore, this bearing can be significantly smaller than one that would be required to support the upper body 20. Moreover, due to the relatively lighter weight involved, the torque required to drive the slew of the connecting member 25 is substantially smaller than that required to slew the entire upper body 20. Accordingly, it is possible to avoid adopting a large sized main slewing device 30, thereby suppressing the increase in size of the main slewing device 30.

(6) As shown in FIG. 6, the upper body 20 has the truncated conical shape. Thus, the side surface 22 of the upper body 20 is inclined relative to the reference axis K over the entire circumferential range around the reference axis K. As described in section (5) above, the first boom 61 is slewable through 360 degrees around the reference axis K. When the side surface 22 of the upper body 20 is inclined over the full circumference, then at any circumferential position around the reference axis K, the first boom 61 can be inclined downward relative to the top surface 23. Moreover, by utilizing the configuration in which the side surface 22 of the upper body 20 is inclined, similarly to the consideration in section (4), it is possible to suppress an increase in the overall size of the excavator 10.

As shown in FIG. 6, the first end portion 61A of the first boom 61, which serves as the center of the rotation in the upper and lower directions, is positioned approximately at the center of the upper body 20 in a direction orthogonal to both the first rotational axis 51J and the reference axis K. In this configuration, the range of motion of the first boom 61 and the components such as the first arm 62 connected to the first boom 61 is balanced on both sides relative to the center of the upper body 20. That is, in the excavator 10 of the embodiment, a wide range of motion for the first mechanism 41 can be secured on both sides of the center of the upper body 20.

(8) As shown in FIG. 6, the first work tool 65 of the first attachment 63 includes the first bucket 65A and the second bucket 65B which are connected to each other via their respective bottom walls 67D. When such a first work tool 65 is employed, the following becomes possible. As indicated by the solid line representation of the first work tool 65 in FIG. 6, when the first boom 61 is situated on one side with respect to the reference axis K in the specified plan view, scraping operations can be performed by pulling the first bucket 65A or by pushing the second bucket 65B. Conversely, as indicated by the alternate long and short dashed line representation of the first work tool 65 in FIG. 6, when the first boom 61 is situated on the other side with respect to the reference axis K in the specified plan view, scraping operations can be performed by pulling the second bucket 65B or by pushing the first bucket 65A.

(9) As indicated by the alternate long and short dashed line 68Q in FIG. 4, in the embodiment, when the first attachment 63 is rotated once, the rotational trajectory of the distal end of the tooth 68 of the first bucket 65A overlaps the rotational trajectory of the distal end of the tooth 68 of the second bucket 65B. That is, at a given rotational position, the distal end of the tooth 68 is placed at the same location between the first bucket 65A and the second bucket 65B. In this case, since the tooth 68 moves along the same positions during both the pulling and scraping operation and the pushing and scraping operation, the user does not need to adjust the position of the first attachment 63, nor the positions of the first arm 62 and the first boom 61 connected thereto, for each respective task. Therefore, the user experiences reduced operational burden when performing the pulling and scraping operation and the pushing and scraping operation.

(10) As shown in FIG. 1, when the excavator 10 is viewed in plan from the direction parallel to the reference axis K, the second boom 71 of the second mechanism 42 is capable of slewing approximately 90 degrees in both forward and reverse directions around the first slewing axis 31J, with respect to the first rotational axis 51J. Furthermore, the second arm 72 is capable of slewing through substantially 360 degrees around the second slewing axis 32J. Accordingly, when an imaginary plane orthogonal to the reference axis K is assumed to be a horizontal plane, the second mechanism 42, including the second boom 71 and the second arm 72, can operate over a wide area on the horizontal plane. For example, as indicated by the arrow 71P in FIG. 7, the second boom 71 can reach a position rotated approximately 30 degrees clockwise from the first rotational axis 51J. Also, as indicated by the arrow 72P in FIG. 7, the second arm 72 can reach a position rotated approximately 30 degrees clockwise from the third imaginary line 42E. In this manner, the excavator 10 of the embodiment can secure a wide range of motion for the second mechanism 42. As a result, the working envelope of the excavator 10 can be increased.

(11) As indicated by the arrow 74P in FIG. 3, the second attachment 73 of the second mechanism 42 extends and retracts in the upper and lower directions. Accordingly, the second mechanism 42 is capable of performing upward and downward operations while also maintaining the wide range of motion on the horizontal plane, as described in section (10) above.

Modification Examples

The above embodiment can be modified as described below. The above embodiment and the following modification examples can be implemented in combination to the extent where they are technically consistent to each other.

• • Either the first mechanism 41 or the second mechanism 42 may be omitted.
  • The overall configuration of the second mechanism 42 is not limited to the above embodiment. The second mechanism 42 is configured such that the second arm 72 is connected to the second boom 71, and the second attachment 73 is connected to the second arm 72 on the opposite side of the connection point between the second arm 72 and the second boom 71. Provided that such a configuration can be realized, the various configurations of the second mechanism 42 may be possible. For example, the relative positions of the second boom 71, the second arm 72, and the second attachment 73 in the direction parallel to the reference axis K may be changed from the example of the above embodiment. Specifically, it is conceivable to arrange the second arm 72 on the upper side relative to the second boom 71.
  • The manner in which the second arm 72 is connected to the second attachment 73 is not limited to the example of the above embodiment. For example, the upper end of the second attachment 73 may be fixed to a lower surface of the second end portion 72B of the second arm 72. As long as the second attachment 73 can be connected to the second arm 72, the manner of connection is not limited.
  • The configuration of the second attachment 73 is not limited to the example of the above embodiment. The second attachment is not limited to the extendable device but may be any device, mechanism, or apparatus that is effective in various operations using the excavator 10.
  • The configuration of the second arm 72 is not limited to the example of the above embodiment. The second arm 72 may be curved or bent along its length. It is preferable that the second arm 72 be an elongated member as a whole. This expands the movable range of the second mechanism 42.
  • The second slewing angle associated with the second arm 72, and thus the rotational range of the second arm 72, is not limited to the example of the above embodiment. The second slewing angle may differ between one side and the other side with respect to the third imaginary line 42E connecting the first slewing axis 31J and the second slewing axis 32J. The second arm 72 may be rotatable 360 degrees to both sides with respect to the third imaginary line 42E. The second arm 72 may be rotatable only to either the one side or the other side with respect to the third imaginary line 42E. It is sufficient that the second arm 72 is rotatable relative to the second boom 71.
  • It is not essential for the second arm 72 to be rotatable relative to the second boom 71. If the second arm 72 is configured to be non-rotatable relative to the second boom 71, the second slewing device 32 may be omitted.
  • The configuration of the second boom 71 is not limited to the example of the above embodiment. Similar to the second arm 72, it is preferable that the second boom 71 be an elongated member as a whole. This expands the movable range of the second mechanism 42.
  • The first slewing angle associated with the second boom 71, and thus the rotational range of the second boom 71, is not limited to the example of the above embodiment. The first slewing angle may differ between one side and the other side with respect to the first rotational axis 51J. Depending on the arrangement of the second boom 71 and the like, the imaginary line that serves as the reference line for the rotation of the second boom 71 may differ from the first rotational axis 51J. The second boom 71 only needs to be connected to the vehicle body 12 such that it is rotatable in at least one of the directions, toward one side or the other with reference to a specified reference line. The second boom 71 may be rotatable through 360 degrees in both forward and reverse directions around the first slewing axis 31J.
  • The arrangement of the first slewing device 31 on the connecting member 25 is not limited to the example of the above embodiment. For example, the first slewing device 31 may be disposed at the center of the circle of the connecting member 25.
  • The object on which the first rotating device 31 is mounted not limited to the connecting member 25. The first slewing device 31 may be mounted anywhere on the upper body 20 or the vehicle body 12, either directly or indirectly. In this case, where to install the first slewing device 31 on the vehicle body 12 may be designed appropriately, taking into consideration the range of motion of the second boom 71 and the configuration of the vehicle body 12. That is, the arrangement of the first slewing device 31 is not limited to the example of the above embodiment.
  • The configuration of the first slewing device 31 and the manner in which the upper body 20 and the second boom 71 are coupled by the first slewing device 31 are not limited to the above embodiment. For example, in the first slewing device 31, the electric motor and the speed reducer may be arranged such that the electric motor is disposed on the upper side relative to the second boom 71, while the speed reducer is disposed between the upper body 20 and the second boom 71. Additionally, the output shaft of the electric motor may be passed through the second boom 71 and connected to the speed reducer. Furthermore, the output side configuration of the speed reducer may be designed to transmit the torque output by the speed reducer to the second boom 71. As long as the torque output by the first slewing device 31 can rotate the second boom 71 relative to the vehicle body 12, the configuration of the connection between the vehicle body 12 and the second boom 71 via the first slewing device 31 is not limited. Furthermore, the first slewing device 31 may be configured in any manner provided that it includes an electric motor and be configured to output torque centered on the first slewing axis 31J extending in the upper and lower directions of the vehicle body 12. The speed reducer may be omitted from the first slewing device 31.
  • It is not essential for the second boom 71 to be coupled to the upper body 20 and thus to the vehicle body 12 via the first slewing device 31. In other words, the manner in which the second boom 71 is connected to the vehicle body 12 is not limited to the above embodiment. As long as the second boom 71 can be connected to the vehicle body 12 in a rotatable manner, the second boom 71 can be connected in any manner. Furthermore, depending on changes or modification to the manner of connecting the second boom 71 to the vehicle body 12 from the example of the above embodiment, the connection point between the second boom 71 and the vehicle body 12 may be located elsewhere than the top surface 23 of the upper body 20. In other words, the connection point of the second boom 71 and the vehicle body 12 is not limited to the example of the above embodiment. The second boom 71 may be connected to any part of the vehicle body 12. Furthermore, the connection point of the second boom 71 to the vehicle body 12 may be displaced from the approximate center of the vehicle body 12 in the direction orthogonal to both the first rotational axis 51J and the reference axis K. In other words, the position of the connection point of the second boom 71 and the vehicle body 12 is not limited to the example of the above embodiment.
  • Similar to the above modification example related to the first slewing device 31, the configuration of the second slewing device 32 and the configuration of the coupling between the second boom 71 and the second arm 72 by the second slewing device 32 are not limited to the example of the above embodiment. As long as the second arm 72 can be rotated relative to the second boom 71 by the torque output by the second slewing device 32, the manner of coupling between the second boom 71 and the second arm 72 by the second slewing device 32 is not limited. Furthermore, the second drive device 32 can be configured in any manner provided that it includes the electric motor and is configured to output torque centered on the second slewing axis 32J parallel to the first slewing axis 31J. The speed reducer may be omitted from the second slewing device 32.
  • It is not essential for the second arm 72 to be coupled to the second boom 71 via the second slewing device 32. As described above, the second slewing device 32 may be omitted. Regardless of whether or not the second slewing device 32 is present, as long as the second arm 72 can be coupled to the second boom 71, they can be coupled to each other in any manner.
  • The overall configuration of the first mechanism 41 is not limited to the above embodiment. The first mechanism 41 is configured such that the first arm 62 is connected to the first boom 61, and the first attachment 63 is connected to the first arm 62 on the opposite side of the connection point between the first arm 62 and the first boom 61. Provided that such a configuration can be realized, the various configurations of the first mechanism 41 may be possible. For example, the relative positions of the first boom 61, the first arm 62, and the first attachment 63 in the direction parallel to the first rotational axis 51) may be changed from the example of the above embodiment. Specifically, the first attachment 63 may be positioned on the opposite side of the first arm 62 from the first boom 61.
  • The configuration of the first attachment 63 is not limited to the example of the above embodiment. For example, the first bucket 65A and the second bucket 65B may be arranged asymmetrically in the specified plan view. Furthermore, the first bucket 65A and the second bucket 65B may have different shapes from each other. Even when the arrangement of the first bucket 65A and the second bucket 65B is asymmetrical, or when the shapes of the first bucket 65A and the second bucket 65B are different from each other, the first bucket 65A and the second bucket 65B can still achieve the advantageous effect described in (9) as long as they are configured to satisfy the first condition.
  • In the first attachment 63, it is not essential for the first bucket 65A and the second bucket 65B to satisfy the first condition. Even if the first bucket 65A and the second bucket 65B do not satisfy the first condition, adopting the first attachment 63 with the first bucket 65A and the second bucket 65B connected facing away from each other allows to obtain the advantageous effect described in (8). Furthermore, it is not essential for the first attachment 63 to have both the first bucket 65A and the second bucket 65B. In other words, in the first attachment 63, either the first bucket 65A or the second bucket 65B may be omitted.
  • As the first attachment 63, it is also possible to use something other than a box-shaped bucket. For example, an extendable device such as the second attachment 73 may be adopted as the first attachment 63. In other words, the first attachment 63 is not limited to ones that rotate relative to the first arm 62. When adopting the first attachment 63 that does not require rotation relative to the first arm 62, the third drive device 53 may be omitted. Similar to the second attachment 73, the first attachment 63 may any device, mechanism, or apparatus that is effective in various operations using the excavator 10.
  • When adopting a type that rotates relative to the first arm 62 as the first attachment 63, the rotational range of the first attachment 63 is not limited to the example of the above embodiment. The first attachment 63 may be rotatable with different ranges of rotation on one side and the other side with respect to the second imaginary line 41F connecting the second rotational axis 52J and the third rotational axis 53J. The first attachment 63 may be rotatable only to the one side or the other with reference to the second imaginary line 41F. It is sufficient that the first attachment 63 is rotatable relative to the first arm 62.
  • The configuration of the first arm 62 is not limited to the example of the above embodiment. The first arm 62 may be curved or bent along its length. It is preferable that the first arm 62 be an elongated member as a whole. This expands the movable range of the first mechanism 41.
  • The second rotation angle associated with the first arm 62, and thus the rotational range of the first arm 62, is not limited to the example of the above embodiment. The second rotation angle may differ between the one side and the other side with respect to the third imaginary line 41E connecting the first rotational axis 51J and the second rotational axis 52J. The first arm 62 may be rotatable 360 degrees to both sides with respect to the first imaginary line 41E. The first arm 62 may be rotatable only to either the one side or the other side with respect to the first imaginary line 41E. It is sufficient that the first arm 62 is rotatable relative to the first boom 61.
  • It is not essential for the first arm 62 to be rotatable relative to the first boom 61. If the first arm 62 is configured to be non-rotatable relative to the first boom 61, the second drive device 52 may be omitted.
  • The configuration of the first boom 61 is not limited to the example of the above embodiment. Similar to the first arm 62, it is preferable that the first boom 61 be an elongated member as a whole. This expands the movable range of the first mechanism 41.
  • The first rotation angle associated with the first boom 61, and thus the rotational range of the first boom 61, is not limited to the example of the above embodiment. The first rotation angle may differ between the one side and the other side with respect to the reference axis K. It is sufficient that the first boom 61 is rotatable in both directions with respect to the reference axis K. In order to ensure a wide range of motion of the first mechanism 41, the first boom 61 is preferably rotatable by 90 degrees or more to the one side and by 90 degrees or more to the other side with reference to the reference axis K.
  • The configuration of the first drive device 51 and the manner in which the support wall 27 and the first boom 61 are coupled by the first drive device 51 are not limited to the above embodiment. For example, the electric motor in the first drive device 51 may be arranged on the opposite side of the support wall 27 from the first boom 61, while the speed reducer may be disposed between the support wall 27 and the first boom 61. Additionally, the output shaft of the electric motor may be passed through the support wall 27 and connected to the speed reducer. Furthermore, the output side configuration of the speed reducer may be designed to transmit the torque output by the speed reducer to the first boom 61. Furthermore, for example, the electric motor may be disposed on the opposite side of the first boom 61 from the support wall 27, while the speed reducer may be disposed between the support wall 27 and the first boom 61. In this case as well, by passing the output shaft of the electric motor through the first boom 61 and connecting it to the speed reducer, the torque of the electric motor can be transmitted to the speed reducer. Furthermore, the first end portion 61A of the first boom 61 may be bifurcated, for example, and the support wall 27 may be disposed between the bifurcated first end portion 61A. With such a configuration, the first end portion 61A of the first boom 61 and the support wall 27 may be coupled by an appropriate method using the first drive device 51. As long as the first boom 61 can be rotated relative to the support wall 27 and the vehicle body 12 by the torque output by the first drive device 51, the manner of coupling between the support wall 27 and the first boom 61 by the first drive device 51 is not limited. Furthermore, the first drive device 51 can be configured in any manner as long as it includes the electric motor and is configured to be capable of outputting torque centered on a rotational axis orthogonal to the reference axis K. The speed reducer may be omitted from the first drive device 51.
  • It is not essential for the first boom 61 to be coupled to the upper body 20 and thus to the vehicle body 12 via the first drive device 51. In other words, the manner in which the first boom 61 is connected to the vehicle body 12 is not limited to the above embodiment. As long as the first boom 61 can be connected to the vehicle body 12 in a rotatable manner, the first boom 61 can be connected in any manner. Furthermore, depending on changes or modification to the manner of connecting the first boom 61 to the vehicle body 12 from the example of the above embodiment, the connection point between the first boom 61 and the vehicle body 12 may be located elsewhere than the top surface 23 of the upper body 20. In other words, the connection point of the first boom 61 and the vehicle body 12 is not limited to the example of the above embodiment. The first boom 61 may be connected to any part of the vehicle body 12. Furthermore, the connection point of the first boom 61 to the vehicle body 12 may be displaced from the approximate center of the vehicle body 12 in the direction orthogonal to both the first rotational axis 51J and the reference axis K. In other words, the position of the connection point of the first boom 61 and the vehicle body 12 is not limited to the example of the above embodiment.
  • Similar to the above modification example related to the first drive device 51, the configuration of the second drive device 52 and the configuration of the coupling between the first boom 61 and the first arm 62 by the second drive device 52 are not limited to the above example of the embodiment. As long as the first arm 62 can be rotated relative to the first boom 61 by the torque output by the second drive device 52, the manner of coupling between the first boom 61 and the first arm 62 by the second drive device 52 is not limited. Furthermore, the second drive device 52 can be configured in any manner as long as it includes the electric motor and is configured to output torque centered on the second rotational axis 52J parallel to the first rotational axis 51J. The speed reducer may be omitted from the second drive device 52.
  • It is not essential for the first arm 62 to be coupled to the first boom 61 via the second drive device 52. As described above, the second drive device 52 may be omitted. Regardless of whether or not the second drive device 52 is present, as long as the second arm 72 can be coupled to the second boom 71, they can be coupled to each other in any manner.
  • Similar to the above modification example related to the first drive device 51 and the second drive device 52, the configuration of the third drive device 53 and the configuration of the coupling between the first arm 62 and the first attachment 63 by the third drive device 53 are not limited to the example of the above embodiment. As long as the first arm 63 can be rotated relative to the first attachment 63 by the torque output by the third drive device 53, the manner of coupling between the first arm 62 and the first attachment 63 by the third drive device 53 is not limited. Furthermore, the third drive device 53 can be configured in any manner as long as it includes the electric motor and is configured to output torque centered on the third rotational axis 53J parallel to the first rotational axis 51J. The speed reducer may be omitted from the third drive device 53.
  • It is not essential for the first attachment 63 to be coupled to the first arm 62 via the third drive device 53. As described above, the third drive device 53 may be omitted. Regardless of whether or not the third drive device 53 is present, as long as the first attachment 63 can be coupled to the first arm 62, they can be coupled to each other in any manner.
  • The arrangement and configuration of the support wall 27 are not limited to the example of the above embodiment. The support wall 27 may be configured and arranged in any appropriate manner from the perspective of coupling the first boom 61 thereto.

The support wall 27 is not an essential component. If the first boom 61 can be connected to the vehicle body 12 using a configuration other than a wall such as a support wall 27, the support wall 27 may be omitted.

• • The configuration and arrangement of the connection member 25 are not limited to the example of the above embodiment. The connecting member 25 can be configured in any manner provided that it transmits the torque output by the main slewing device 30 to the first boom 61. As long as this can be achieved, the configuration and arrangement of the connecting member 25 can be changed as appropriate.
  • The configuration and arrangement of the main slewing device 30 for slewing the connecting member 25 are not limited to the example of the above embodiment. The main slewing device 30 can be configured in any manner provided that it can output torque centered on the main slewing axis 30J parallel to the reference axis K. The rotational range of the output member 30B in the main slewing device 30 is not limited to 360 degrees. The speed reducer may be omitted from the main slewing device 30. The main slewing axis 30J and the reference axis K may be offset from each other.
  • The main slewing device 30 may be omitted. In this case, the connecting member 25 may also be omitted along with the main slewing device 30. When the main slewing device 30 and the connecting member 25 are omitted, it is conceivable, for example, to attach the support wall 27 directly onto the upper body 20.
  • It is not essential for the center axis of the upper body 20 to be considered as the reference axis K. The reference axis K can be any axis extending in the upper and lower direction of the vehicle body 12. The upper and lower directions of the vehicle body 12 may be defined based on the relative positions of the lower body 14 and the upper body 20, as in the above embodiment, or based on the relative positions of the ground surface G and the vehicle body 12. In this case, the ground surface G may be defined as a horizontal plane extending virtually from the undersides of the crawlers of both left and right traveling unit 16.
  • The configuration of the upper body 20 is not limited to the example of the above embodiment. For example, the minor angle θ formed between the top surface 23 and the side surface 22 of the upper structure 20 may be modified from 120 degrees. Furthermore, as in the above modification example, if the main slewing device 30 is omitted, the upper structure 20 may be formed in a shape other than a truncated cone. Even when the upper structure 20 is shaped other than the truncated cone, it is effective for ensuring a wide range of motion of the first boom 61 if the upper structure 20 has the following configuration. That is, in the specified plan view, it is preferable that the upper structure 20 has: an inclined surface that is sloped such that it approaches the reference axis K toward the upward direction; and a top surface that is connected to the uppermost edge of the inclined surface and is orthogonal to the reference axis K. By connecting the first boom 61 to the top surface of such an upper structure 20, the first boom 61 can be inclined downward relative to the top surface along the inclined surface. However, it is not essential for the upper structure 20 to include both the inclined surface and the top surface. As described in section (4) above, for example, by appropriately adopting a configuration such as enlarging the support wall 27 upward, the range of motion of the first boom 61 can be increased even without employing the inclined surface.
  • The upper body 20 and lower body 14 may be coupled so that the upper body 20 can rotate relative to the lower body 14 with respect to the reference axis K. For example, when the main slewing device 30 is omitted, adopting such a connection configuration allows the first mechanism 41 to be rotatably moved to a position favorable for the work.
  • The overall configuration of the vehicle body 12 is not limited to the example of the above embodiment. For example, the vehicle body 12 may be composed of a single piece of material without any separation between the lower body 14 and the upper body 20. The vehicle body 12 may be equipped with a user seat as well as input devices such as switches and levers for operating the first mechanism 41 and the second mechanism 42.
  • The construction machine to which the configuration of the first mechanism 41, the second mechanism 42, and the vehicle body 12 connecting them, as described in the above embodiment and each modification example are applied, is not limited to the excavator 10. Regardless of the type of construction machine, by adopting at least one of the first mechanism 41 or the second mechanism 42, it is possible to obtain a wide working envelope for the construction machine.

The foregoing embodiment describes a plurality of physically separate constituent parts. They may be combined into a single part, and any one of them may be divided into a plurality of physically separate constituent parts. Irrespective of whether or not the constituent parts are integrated, they are acceptable as long as they are configured to solve the problems.

• • An example of modifications made to the shape of the vehicle body 12, the mounting configuration of the first drive device 51 relative to the vehicle body 12, and the arrangement of the connection point between the first boom 61 and the vehicle body 12 from the above embodiment will be now described with reference to FIGS. 8 to 10. In the following description of an excavator 110 shown in FIGS. 8 to 10, redundant description of the same features as in the above embodiment may be omitted or simplified to focus on the differences from the above embodiment. In FIGS. 8 to 10, the same reference labels as in FIGS. 1 to 7 are used for the components that function the same or substantially the same as the corresponding components shown in FIGS. 1 to 7.

As shown in FIG. 8, the excavator 110 includes the vehicle body 12 and the pair of traveling units 16. The vehicle body 12 includes the lower body 14 and an upper body 114. The upper body 114 is located on the opposite side to the ground surface G with respect to the lower body 14. The upper body 114 has a rectangular parallelepiped shape. Both an upper surface and lower surface of the upper body 114 are approximately parallel to the ground surface G and the lower surfaces of the left and right crawlers. The upper body 114 is hollow. The lower body 14 is configured in the same manner as in the above embodiment. The pair of traveling units 16 are provided at the left and right sides of the lower body 14. The traveling units 16 are configured in the same manner as in the above embodiment. The method of specifying the front, rear, left, right, upper, and lower directions of the excavator 110 is the same as that described in the above embodiment.

As shown in FIG. 8, the excavator 110 includes the main slewing device 30. The main slewing device 30 is disposed inside the upper body 20. The main slewing device 30 is disposed at the front end of the upper body 20. As shown in FIG. 10, the main slewing device 30 is disposed in the left end portion of the upper body 20. As shown in FIG. 8, the central axis of the main slewing device 30 extends substantially in the Z direction. The outer casing of the main body 30A of the main slewing device 30 is fixed to the inner wall of the upper body 20. The output member 30B of the main slewing device 30 outputs torque centered on the main slewing axis 30J extending substantially in the Z direction. The main slewing axis 30J is approximately perpendicular to both the upper surface and the lower surface of the upper body 20. In other words, the first slewing axis 30J extends in the upper and lower directions of the upper body 114. The main slewing axis 30J serves as the reference axis K. The output member 30B is rotatable through 360 degrees in both forward and reverse directions in accordance with the rotational direction of the electric motor in the main body 30A. Detailed illustrations are omitted, but the upper end of the output member 30B penetrates the upper surface of the upper body 20 and protrudes upward from the upper surface.

As shown in FIG. 8, the excavator 110 includes the connecting member 25 and the support wall 27. The connecting member 25 is positioned on the upper side of the upper surface of the upper body 114. The connecting member 25 is fixed to the output member 30B in the main slewing device 30. The connecting member 25 rotates integrally with the output member 30B of the main slewing device 30. Although not shown in the drawings, a bearing that rotatably supports the connecting member 25 is disposed between the connecting member 25 and the upper surface of the upper body 114. The support wall 27 protrudes upward from the upper surface of the connecting member 25.

The excavator 110 includes the first mechanism 41. As in the above embodiment, the first mechanism 41 includes the first drive device 51, the second drive device 52, the third drive device 53, the first boom 61, the first arm 62, and the first attachment 63. The following is a simplified explanation of the first mechanism 41, focusing on the parts that differ from the above embodiment. In the following description, it is assumed that the slewing angle of the connecting member 25 connected to the first mechanism 41 is zero degrees. That is, the connecting member 25 is in its default slewing position.

As shown in FIG. 10, the first drive device 51 is disposed on the right side of the support wall 27. The outer casing of the main body 51A of the first drive device 51 is fixed to the support wall 27. The first output member 51B of the first drive device 51 outputs torque centered on the first rotational axis 51J substantially orthogonal to the reference axis K. The first rotational axis 51J extends substantially in the Y direction.

The first boom 61 is located on the right side of the first drive device 51. As shown in FIG. 8, the first boom 61 is a long plate in shape as a whole. The first boom 61 is bent in the middle of its longitudinal direction. That is, in the specified plan view, the first boom 61 is V-shaped. The specified plane view is the same as in the above embodiment, i.e., a plan view of the excavator 110 as seen in a direction parallel to the first rotational axis 51J. The first end portion 61A of the first boom 61 is disposed on the first rotational axis 51J. The first end portion 61A of the first boom 61 is connected to the first output member 51B of the first drive device 51. That is, when acted upon by the torque from the first output member 51B of the first drive device 51, the first boom 61 swings around the first rotational axis 51J. In the specified plan view, the first boom 61 is rotatable to the forward and rearward directions with respect to the reference axis K. Specifically, in the specified plan view, the first boom 61 can swing across the reference half-line, which extends from the first rotational axis 51J along the reference axis K in the direction opposite the connecting member 25, to the front side and the rear side with respect to the reference half-line. The first boom 61 is rotatable 90 degrees or more to the front side with respect to the reference half-line. As shown in FIG. 9, the first boom 61 is also rotatable in the rearward direction up to the upper limit angle with respect to the reference half-line in the specified plan view. The upper limit angle is slightly greater than 90 degrees. When the first boom 61 is rotated rearward to the upper limit angle with respect to the reference half-line, a bent corner portion of the first boom 61 comes into contact with the upper surface of the upper body 114.

As described above, the first end portion 61A of the first boom 61 is connected to the support wall 27 via the first drive device 51. As shown in FIG. 10, the support wall 27 is disposed in the front end portion of the upper body 114. Due to the position of the support wall 27, the first end portion 61A of the first boom 61 or the connection point of the first boom 61 with the upper body 114 is situated on the front side relative to the center of the upper body 114 in the X direction. In other words, the first end portion 61A of the first boom 61 is situated on one side with respect to the center of the upper body 114 in the direction orthogonal to both the reference axis K and the first rotational axis 51J.

As shown in FIG. 10, the second drive device 52 is disposed on the right side of the first boom 61. The outer casing of the main body 52A of the second drive device 52 is fixed to the second end portion 61B of the first boom 61, which is opposite to the first end portion 61A. The second output member 52B of the second drive device 52 outputs the torque centered on the second rotational axis 52J. The second rotational axis 52J extends substantially parallel to the first rotational axis 51J at a position different from that of the first rotational axis 51J. As shown in FIG. 8, the second rotational axis 52J passes through the second end portion 61B of the first boom 61.

As shown in FIG. 10, the first arm 62 is disposed on the right side of the second drive device 52. The first arm 62 is shaped like an elongated plate. As shown in FIG. 8, the first arm 62 extends linearly. As shown in FIG. 10, the first end portion 62A of the first arm 62 is fixed to the second output member 52B of the second drive device 52. Specifically, the first end portion 62A of the first arm 62 is coupled to the second end portion 61B of the first boom 61 via the second drive device 52. When acted upon by the torque from the second output member 52 of the second drive device 52, the first arm 62 rotates around the second rotational axis 52J. Thus, in the specified plan view as shown in FIG. 8, the first arm 62 is rotatable 360 degrees to both sides with respect to the first imaginary line 41E connecting the first rotational axis 51J and the second rotational axis 52J. In other words, in the specified plane view, the first arm 62 can perform the following rotational movements. The first arm 62 is rotatable across a half-line, which extends from the second rotational axis 52J along the first imaginary line 41E in the direction opposite the first rotational axis 51J, to one side and the other side with respect to the half-line. The first arm 62 is also rotatable across a specified half-line 41V, which extends from the second rotational axis 52J along the first imaginary line 41E in the direction toward the first rotational axis 51J, to one side and the other side with respect to the specified half-line 41V. As shown in FIG. 9, the specified half-line 41V is a half-line that extends from the second rotational axis 52J and intersects the first rotational axis 51J in the specified plane view.

As shown in FIG. 10, the third drive device 53 is disposed on the right side of the first arm 62. The main body 53A of the third drive device 53 is fixed to the second end portion 62B of the first arm 62, which is opposite to the first end portion 62A. The third output member 53B of the third drive device 53 outputs the torque centered on the third rotational axis 53J. The third rotational axis 53J extends substantially parallel to the first rotational axis 51J at a position different from that of the first rotational axis 51J and the second rotational axis 52J. As shown in FIG. 8, the third rotational axis 53J passes through the second end portion 62B of the first arm 62.

As shown in FIG. 10, the first attachment 63 is disposed on the right side of the third drive device 53. As shown in FIG. 8, the first attachment 63 has a configuration in which one of the two buckets in the above embodiment is removed. That is, the first attachment 63 includes the connecting piece 64 and a single bucket 66. As shown in FIG. 10, the bucket 66 includes a bucket body 67 having an opening 67A and a plurality of teeth 68 protruding from the opening edge of the bucket body 67. In the Y direction, the bucket body 67 is located within the range of the upper body 114.

The connecting piece 64 of the first attachment 63 is fixed to the third output member 53B of the third drive device 53. In other words, the connecting piece 64 is coupled to the second end portion 62B of the first arm 62 via the third drive device 53. When acted upon by the torque from the third drive device 53, the connecting piece 64 and thus the first attachment 63 rotate about the third rotational axis 53J. Thus, in the specified plan view of FIG. 8, the first attachment 63 is rotatable through 360 degrees to both sides with respect to the second imaginary line 41F connecting the second rotational axis 52J and the third rotational axis 53J.

In the first mechanism 41, the first boom 61 and the first arm 62 are designed to satisfy a following first dimensional relationship in the specified plan view. The first dimensional relationship is defined that the distance from the first rotational axis 51J to the second rotational axis 52J is longer than the distance from the second rotational axis 52J to the third rotational axis 53J.

The first mechanism 41 can have a stowed posture shown in FIGS. 9 and 10, in consideration of the respective rotational ranges of the first boom 61, the first arm 62, and the first attachment 63. As shown in FIG. 9, in the stowed posture, the bent corner portion of the first boom 61 is in contact with the upper surface of the upper body 114. The first arm 62 is arranged in a folded-back configuration relative to the first boom 61, in which the first arm 62 has been rotated approximately 180 degrees around the second rotational axis 52J. In the specified plan view, the third rotational axis 53J is disposed on the specified half-line 41V. In the embodiment, the third rotational axis 53J is situated between the second rotational axis 52J and the first rotational axis 51J in the specified plan view. That is, when the first mechanism 41 is in the stowed posture, the first boom 61, the first arm 62, and the first attachment 63 are arranged so as to overlap one another in the specified plan view. It can also be said that the first boom 61, the first arm 62, and the first attachment 63 are arranged in parallel in the direction parallel to the first rotational axis 51J. By enabling such a stowed posture, the space required for storing the first mechanism 41 in the excavator 110 can be reduced.

As shown in FIG. 10, the excavator 110 includes a control device 45. The control device 45 controls the first mechanism 41 and other components. The control device 45 controls first drive device 51, second drive device 52, third drive device 53, and other components in response to command signals transmitted from the controller 46. The excavator system 47 includes the controller 46 and excavator 110.

The control device 45 is capable of executing a stowing process. The stowing process is a process that causes the first mechanism 41 to transition into a stowed posture. A memory stores, in advance, a program for executing the stowing process. By executing this program by the CPU, the control device 45 performs the stowing process.

In the specified plan view, a state in which the first arm 62 has rotated to a position relative to the first boom 61 where the third rotational axis 53J is situated on the specified half-line 41V is referred to as a first mode. In designing the first mechanism 41 to enable realization of such a first mode, configurations other than the examples shown in FIGS. 8 to 10 may be adopted. For example, in the embodiment shown in FIG. 11, the relative positions of the first boom 61, the first arm 62, and the first attachment 63 in the direction parallel to the first rotational axis 51J are modified from the examples shown in FIGS. 8 to 10. Specifically, in the first mechanism 41 shown in FIG. 11, both the first boom 61 and the first attachment 63 are disposed on the same side of the first arm 62 in the direction parallel to the first rotational axis 51J. In addition, the first boom 61 and the first arm 62 are designed to satisfy the following second dimensional relationship in the specified plan view. The second dimensional relationship is defined that the distance from the first rotational axis 51J to the second rotational axis 52J is shorter than the distance from the second rotational axis 52J to the third rotational axis 53J. When such a configuration is adopted, and the first mechanism 41 is in the first mode, the third rotational axis 53J is disposed on the specified half-line 41V on the side opposite the second rotational axis 52J with respect to the first rotational axis 51J. It should be noted that, as shown in FIG. 11, the first mechanism 41 may be brought into the first mode after being slewed to an appropriate slewing position by the main slewing device 30.

• • An example of modifications made to the shape of the vehicle body 12, the mounting configuration of the first drive device 51 relative to the vehicle body 12, and the arrangement of the connection point between the first boom 61 and the vehicle body 12 from the above embodiment will be now described with reference to FIGS. 8 to 10. In the following description of an excavator 150 shown in FIGS. 12 to 13, redundant description of the same features as in the above embodiment may be omitted or simplified to focus on the differences from the above embodiment. In FIGS. 12 and 13, the same reference labels as in FIGS. 1 to 11 are used for the components that function the same or substantially the same as the corresponding components shown in FIGS. 1 to 11.

As shown in FIG. 12, the excavator 150 includes the pair of traveling units 16. The vehicle body 12 includes a lower body 14 and an upper body 154. The upper body 154 is located on the opposite side to the ground surface G with respect to the lower body 14. The upper body 154 is slewable about an axis extending substantially in the Z direction to the left and right sides relative to the lower body 14. In the following description, it is assumed that the slewing angle of the upper body 154 is zero degrees. The pair of traveling units 16 are provided at the left and right sides of the lower body 14. The lower body 14 and traveling units 16 are configured in the same manner as in the above embodiment and thus those descriptions will not be repeated. The method of specifying the front, rear, left, right, upper, and lower directions of the excavator 150 is the same as that described in the above embodiment.

The upper body 154 includes a main portion 154A and a support wall portion 154B. In FIG. 12, a dotted line is used to indicate a notional boundary between the main portion 154A and the support wall portion 154B for convenience. However, the main portion 154A and the support wall portion 154B are integrally formed, and no actual boundary exists between them. The main portion 154A is generally rectangular parallelepiped in shape. However, a front part of the upper surface of the main portion 154A is inclined downward. The support wall portion 154B is disposed on the front side of the main portion 154A. The support wall portion 154B is situated at a lower part of the main portion 154A. The support wall portion 154B has a rectangular parallelepiped shape. Both the upper and lower surfaces of the support wall portion 154B are substantially parallel to the ground surface G. As the support wall portion 154B is located at the lower part of the main portion 154A, the upper surface of the support wall portion 154B is positioned below the upper surface of the main portion 154A.

The main portion 154A includes a housing portion 154C. In FIG. 12, the housing portion 154C is indicated by a bold solid line. The housing portion 154C is located at a rear part of the upper surface of the main portion 154A. The housing portion 154C is a structure configured to accommodate a battery 98 mounted on the excavator 150. The housing portion 154C is, for example, a recess conforming to the shape of the battery 98.

The excavator 150 includes the first mechanism 41. As in the above embodiment, the first mechanism 41 includes the first drive device 51, the second drive device 52, the third drive device 53, the first boom 61, the first arm 62, and the first attachment 63. The following is a simplified explanation of the first mechanism 41, focusing on the parts that differ from the above embodiment.

The first drive device 51 is disposed on the upper side of the support wall portion 154B. Although detailed illustrations are omitted, the first drive device 51 is coupled to the upper surface of the support wall portion 154B. The first drive device 51 outputs torque centered on the first rotational axis 51J, which is approximately orthogonal to the reference axis K. The reference axis K extends in the Z direction, passing through the upper and lower surfaces of the support wall portion 154B. In other words, the reference axis K extends in the upper and lower directions of the vehicle body 12. The first rotational axis 51J extends substantially in the Y direction.

The first boom 61 extends from the first drive device 51. The first boom 61 is bent in the middle. The first end portion 61A of the first boom 61 is disposed on the first rotational axis 51J. The first end portion 61A of the first boom 61 is coupled to the first drive device 51. That is, when acted upon by the torque from the first drive device 51, the first boom 61 swings around the first rotational axis 51J. Similar to the above embodiment, a plan view of the excavator 150 as seen in a direction parallel to the first rotational axis 51J is referred to as the specified plan view. In the specified plan view, the first boom 61 is rotatable to the front and rear sides with respect to the reference axis K. Specifically, in the specified plan view, the first boom 61 can swing across a reference half-line, which extends upward from the first rotational axis 51J along the reference axis K, to the front side and the rear side with respect to the reference half-line. For example, in the specified plan view, the first boom 61 is rotatable 90 degrees or more to the front side with respect to the reference half-line. For example, in the specified plan view, the first boom 61 is rotatable up to 45 degrees to the rear side with respect to the reference half-line. The rearward rotational range of the first boom 61 is defined from the standpoint of avoiding interference between the first boom 61 and the main portion 154A of the upper body 154 when the first boom 61 rotates to the rear side.

As described above, the first end portion 61A of the first boom 61 is coupled to the support wall 27 via the first drive device 51. The first drive device 51 is disposed on the upper surface of the support wall portion 154B. Due to the position of the first drive device 51, the first end portion 61A of the first boom 61 or the connection point of the first boom 61 with the upper body 154 is situated on the front side relative to the center of the upper body 154 in the X direction. In other words, the first end portion 61A of the first boom 61 is situated at a position shifted from the center of the upper body 154 to one side in the direction orthogonal to both the reference axis K and the first rotational axis 51J.

The second drive device 52 is coupled to the second end portion 61B of the first boom 61, which is opposite to the first end portion 61A. The second drive device 52 outputs the torque centered on the second rotational axis 52J. The second rotational axis 52J extends substantially parallel to the first rotational axis 51J at a position different from that of the first rotational axis 51J. The second rotational axis 52J passes through the second end portion 61B of the first boom 61.

The first boom 62 linearly extends from the second drive device 52. The first end portion 62A of the first arm 62 is coupled to the second drive device 52. Specifically, the first end portion 62A of the first arm 62 is coupled to the second end portion 61B of the first boom 61 via the second drive device 52. When acted upon by the torque from the second drive device 52, the first arm 62 rotates around the second rotational axis 52J. In the specified plan view as shown in FIG. 8, the first arm 62 is rotatable 360 degrees to both sides with respect to the first imaginary line 41E connecting the first rotational axis 51J and the second rotational axis 52J. In other words, in the specified plane view, the first arm 62 can perform the following rotational movements. The first arm 62 is rotatable across a half-line, which extends from the second rotational axis 52J along the first imaginary line 41E in the direction opposite the first rotational axis 51J, to one side and the other side with respect to the half-line. The first arm 62 is also rotatable across a specified half-line 41V, which extends from the second rotational axis 52J along the first imaginary line 41E in the direction toward the first rotational axis 51J, to one side and the other side with respect to the specified half-line 41V.

The third drive device 53 is coupled to the second end portion 62B of the first arm 62, which is opposite to the first end portion 62A. The third drive device 53 outputs the torque centered on the third rotational axis 53J. The third rotational axis 53J extends substantially parallel to the first rotational axis 51J at a position different from that of the first rotational axis 51J and the second rotational axis 52J. The third rotational axis 53J passes through the second end portion 62B of the first arm 62.

The first attachment 63 is coupled to the third drive device 53. In other words, the first attachment 63 is coupled to the second end portion 62B of the first arm 62 via the third drive device 53. Similar to the excavator 110 shown in FIGS. 8 to 10, in the direction parallel to the first rotational axis 51J, the attachment 63 is disposed on the side of the first arm 62 facing away from the first boom 61. The first attachment 63 has a configuration in which one of the two buckets in the above embodiment is removed. That is, the first attachment 63 is a bucket that includes the bucket body 67 having the opening 67A, and the teeth 68 protruding from the edge of the opening of the bucket body 67. The bucket body 67 is configured such that the opening 67A is directed for the pulling and scraping operation. When acted upon by the torque from the third drive device 53, the first attachment 63 rotates about the third rotational axis 53J. The first attachment 63 is rotatable through 360 degrees to both sides with respect to the second imaginary line 41F connecting the second rotational axis 52J and the third rotational axis 53J.

The excavator 150 includes the control device 45. The control device 45 controls the first mechanism 41 and other components. The control device 45 controls first drive device 51, second drive device 52, third drive device 53, and other components in response to command signals transmitted from the controller 46. The excavator system 47 includes the controller 46 and excavator 150.

The control device 45 is capable of executing an installation process. The installation process is a process for installing a battery 98, which is not yet mounted on the excavator 150, onto the excavator 150. A memory stores, in advance, a program for executing the installation process. By executing this program by the CPU, the control device 45 performs the installation process. Furthermore, the excavator 150 is pre-equipped with multiple batteries 98. During the installation process, the control device 45 operates each drive device of the first mechanism 41 using power supplied from the batteries 98 installed in the excavator 150.

Assumption for describing the installation process, and a preparation state of the first mechanism 41, which represents the condition before initiation of the installation process, will be now described. In the preparation state, the first boom 61 is situated on the front side with respect to the reference axis K. In other words, the second end portion 61B of the first boom 61 is situated on the front side relative to the first end portion 61A. At the same time, the second end portion 61B of the first boom 61 is situated on the upper side relative to the first end portion 61A. The first arm 62 is situated on the lower side relative to the second end 61B of the first boom 61. The second end portion 62B of the first arm 62 is situated on the lower side and front side relative to the first end portion 62A. Furthermore, the first attachment 63 is located near the ground surface G. The battery 98 is attached to the tooth (teeth) 68 of the first attachment 63.

Now, it is assumed that, while the first mechanism 41 is in the preparation state, a start signal for the installation process is transmitted from the controller 46 to the control device 45. In response to this start signal, the control device 45 initiates the installation process. Upon initiating the installation process, the control device 45 operates the first mechanism 41 as follows. The operation of the first mechanism 41 will be described below based on the specified plan view. As indicated by the arrow 61M in FIG. 13, the control device 45 rotates the first boom 61 rearward with reference to the reference axis K. Accordingly, the second end 61B of the first boom 61 moves upward compared to its position in the preparation state. In coordination with the rotation of the first boom 61, the control device 45 rotates the first arm 62 from the front side to the rear side across the specified half-line 41V, as indicated by the arrow 62M in FIG. 13. Furthermore, the control device 45 moves the second end portion 62B of the first arm 62 rearward relative to the first end portion 62A. At this time, the second end portion 62B of the first arm 62 is situated below the first end 61A. Simultaneously, the first attachment 63 is situated substantially directly above the housing portion 154C of the upper body 154. Thereafter, the control device 45 finely adjusts the rotational positions of the first boom 61, the first arm 62, and the first attachment 63 to place the battery 98 onto the housing portion 154C. Subsequently, the connection between the battery 98 and the tooth (teeth) 68 of the first attachment 63 is released either automatically or manually.

The control device 45 is capable of executing a removal process. The removal process is a process for detaching the battery 98 from the excavator 150. A memory stores, in advance, a program for executing the removal process. By executing this program, the CPU enables the control device 45 to perform the removal process. During execution of the removal process, the control device 45 operates each drive device in the first mechanism 41 using electric power supplied from another battery 98 already mounted on the excavator 150.

Now, it is assumed that the battery 98 to be removed is disposed on the housing portion 154C. It is also assumed that, as shown in FIG. 13, the battery 98 is connected to the tooth (teeth) 68 of the first attachment 63. In this state, a start signal for the removal process is transmitted from the controller 46 to the control device 45. In response to this start signal, the control device 45 initiates the removal process. Upon initiation of the removal process, the control device 45 causes the first mechanism 41 to perform steps reverse to those of the installation process. That is, the control device 45 rotates the first arm 62 to the front side with reference to the specified half-line 41V. At the same time, the control device 45 rotates the first boom 61 to the front side with reference to the reference axis K. Then, the control device 45 moves the first boom 61, the first arm 62, and the first attachment 63 so as to return them to the respective postures in the preparation state. Once the first mechanism 41 has returned to the posture of the preparation state, the control device 45 terminates the removal process.

As described above, the control device 45 is capable of switching the posture of the first mechanism 41 through the installation process and the removal process. Specifically, the control device 45 can switch the posture of the first mechanism 41, in the specified plan view, between a first posture corresponding to the preparation state and a second posture in which the battery 98 is installed on the housing portion 154C. As shown in FIG. 12, in the first posture, the first boom 61 is rotated to the front side with respect to the reference axis K in the specified planar view, and the third rotational axis 53J is situated on the front and lower side relative to the second rotational axis 52J. That is, in the first posture, in the direction orthogonal to both the first rotational axis 51J and the reference axis K, the third rotational axis 53J is situated opposite to the first rotational axis 51J with respect to the second rotational axis 52J. Whereas in the second posture, as shown in FIG. 13, the first boom 61 is rotated to the rear side with respect to the reference axis K in the specified plan view, and the third rotational axis 53J is situated on the rear and lower side relative to the second rotational axis 52J. That is, in the second posture, in the direction orthogonal to both the first rotational axis 51J and the reference axis K, the third rotational axis 53J is situated opposite to the first rotational axis 51J with respect to the second rotational axis 52J. By enabling such posture switching, the first mechanism 41 can operate over a wide range on both the front side and the rear side with respect to the reference axis K. As a result, in the excavator 150, the installation and removal of the battery 98 can be achieved.

It should be noted that, when switching between the first posture and the second posture, the control device 45 rotates the first arm 62 such that the first arm 62 moves forward and rearward across the specified half-line 41V. As a comparative example to this configuration, suppose the first arm 62 were moved forward and rearward across a half-line extending from the second rotational axis 52J in a direction opposite to the first rotational axis 51J. In such a case, during movement of the first arm 62, the second end portion 62B of the first arm 62 and consequently the first attachment 63 would pass above the first end 61A of the first arm 62 and thus above the first boom 61. As a result, the battery 98 mounted to the first attachment 63 would be transported at a significantly elevated position relative to the upper surface of the upper body 154. In this case, if the battery 98 were to become detached from the first attachment 63 and fall, there is a risk that a large impact load would be exerted on both the battery 98 and the upper body 154. In contrast, as described above, by moving the first arm 62 forward and rearward across the specified half-line 41V, the battery 98 can be transported at a level close to the upper surface of the upper body 154. Therefore, even if the battery 98 were to become detached from the first attachment 63 and fall, the impact load exerted on the battery 98 and the upper body 154 would be very small.

• • Another example of modifications made to the shape of the vehicle body 12, the mounting configuration of the first drive device 51 relative to the vehicle body 12, and the arrangement of the connection point between the first boom 61 and the vehicle body 12 from the above embodiment will be now described with reference to FIG. 15. In the following description of an excavator 170 shown in FIG. 15, redundant description of the same features as in the above embodiment may be omitted or simplified to focus on the differences from the above embodiment. In FIG. 15, the same reference labels as in FIGS. 1 to 13 are used for the components that function the same or substantially the same as the corresponding components shown in FIGS. 1 to 13.

As shown in FIG. 15, the excavator 170 includes the vehicle body 12 and the pair of traveling units 16. The vehicle body 12 includes the lower body 14 and an upper body 172. The upper body 172 is located on the opposite side to the ground surface G with respect to the lower body 14. The pair of traveling units 16 are provided at the left and right sides of the lower body 14. The lower body 14 and traveling units 16 are configured in the same manner as in the above embodiment and thus those descriptions will not be repeated. The method of specifying the front, rear, left, right, upper, and lower directions of the excavator 170 is the same as that described in the above embodiment.

The upper body 172 includes a main portion 174, a first support wall portion 176, and a second support wall portion 178. The upper body 174 is slewable about an axis extending substantially in the Z direction to the left and right sides relative to the lower body 14. In the following description, it is assumed that the slewing angle of the main body 174 is zero degrees. The first support wall portion 176 and the second support wall portion 178 are arranged symmetrically in the front and rear directions with respect to the main portion 174. The first support wall portion 176 is disposed on the front side of the main portion 174. The support wall 176 protrudes frontward from the main portion 174. The first support wall portion 176 is shaped like a rectangular parallelepiped, for example. Both the upper and lower surfaces of the first support wall portion 176 are substantially parallel to the ground surface G. The second support wall portion 178 is disposed on the rear side of the main portion 174. The second support wall 178 protrudes rearward from the main portion 174. The shape of the second support wall portion 178 and the orientations of the respective wall surfaces thereof are substantially the same as those of the first support wall portion 176. Additionally, in the Y direction and Z direction, the second support wall portion 178 is disposed at substantially the same position as the first support wall portion 176.

The excavator 170 includes a first work mechanism 181. The first work mechanism 181 is situated on the front side of the main portion 174 of the upper body 172. The basic configuration of the first work mechanism 181 is the same as that of the first mechanism 41 in the above embodiment. Specifically, the first work mechanism 181 includes the first drive device 51, the second drive device 52, the third drive device 53, the first boom 61, the first arm 62, and the first attachment 63. The following is a simplified explanation of the first work mechanism 181, focusing on the parts that differ from the first mechanism 41 of above embodiment.

The first drive device 51 is coupled to the first support wall portion 176. The first drive device 51 outputs torque centered on the first rotational axis 51J, which is approximately orthogonal to a first reference axis K1. The first reference axis K1 extends substantially in the Z direction, passing through the upper and lower surfaces of the first support wall portion 176. In other words, the first reference axis K1 extends in the upper and lower directions of the vehicle body 12. The first rotational axis 51J extends substantially in the Y direction.

The first boom 61 linearly extends from the first drive device 51 to the front side. The first end portion 61A of the first boom 61 is disposed on the first rotational axis 51J. The first end portion 61A of the first boom 61 is coupled to the first drive device 51. As described above, the first end portion 61A of the first boom 61 is coupled to the first support wall portion 176 via the first drive device 51. That is, when acted upon by the torque from the first drive device 51, the first boom 61 swings around the first rotational axis 51J. Similar to the above embodiment, a plan view of the excavator 170 as seen in a direction parallel to the first rotational axis 51J is referred to as the specified plan view. In the specified plan view, the first boom 61 is rotatable to the front and rear sides with respect to the first reference axis K1. Specifically, in the specified plan view, the first boom 61 can swing across a first reference half-line, which extends upward from the first rotational axis 51J along the first reference axis K1, to the front side and the rear side with respect to the first reference half-line. For example, in the specified plan view, the first boom 61 is rotatable 90 degrees or more to the front side with respect to the first reference half-line.

The second drive device 52 is coupled to the second end portion 61B of the first boom 61, which is opposite to the first end portion 61A. The second drive device 52 outputs the torque centered on the second rotational axis 52J. The second rotational axis 52J extends substantially parallel to the first rotational axis 51J at a position different from that of the first rotational axis 51J. The second rotational axis 52J passes through the second end portion 61B of the first boom 61.

The first arm 62 linearly extends from the second drive device 52 to the front side. The first end portion 62A of the first arm 62 is coupled to the second drive device 52. Specifically, the first end portion 62A of the first arm 62 is coupled to the second end portion 61B of the first boom 61 via the second drive device 52. When acted upon by the torque from the second drive device 52, the first arm 62 rotates around the second rotational axis 52J. In the specified plan view as shown in FIG. 8, the first arm 62 is rotatable to both sides with respect to the first imaginary line 41E connecting the first rotational axis 51J and the second rotational axis 52J. For example, the first arm 62 may be rotatable 360 degrees to both sides with respect to the first imaginary line 41E.

The third drive device 53 is coupled to the second end portion 62B of the first arm 62, which is opposite to the first end portion 62A. The third drive device 53 outputs the torque centered on the third rotational axis 53J. The third rotational axis 53J extends substantially parallel to the first rotational axis 51J at a position different from that of the first rotational axis 51J and the second rotational axis 52J. The third rotational axis 53J passes through the second end portion 62B of the first arm 62.

The first attachment 63 is coupled to the third drive device 53. In other words, the first attachment 63 is coupled to the second end portion 62B of the first arm 62 via the third drive device 53. The first attachment 63 is the same as that described in relation to the excavator 150 of FIG. 12. That is, the first attachment 63 is a box-shaped bucket. When acted upon by the torque from the third drive device 53, the first attachment 63 rotates about the third rotational axis 53J. The first attachment 63 is rotatable to both sides with respect to the second imaginary line 41F connecting the second rotational axis 52J and the third rotational axis 53J. For example, the first attachment 63 may be rotatable 360 degrees to both sides with respect to the second imaginary line 41F. The first attachment 63 is not limited to the bucket. Depending on the nature of the work, any suitable device, mechanism, or tool may be employed as the first attachment 63. When a non-rotational component is adopted as the first attachment 63, the third drive device 53 may be omitted, and the first attachment 63 may be directly connected to the first arm 62.

The excavator 170 includes a second work mechanism 182. The second work mechanism 182 is situated on the rear side of the main portion 174 of the upper body 172. That is, in a specified plan view related to the first work mechanism 181, the first work mechanism 181 and the second work mechanism 182 are disposed on opposite sides with respect to the center of the main portion 174 of the upper body 172 in the X direction. The X direction is a direction orthogonal to both the first rotational axis 51J of the first work mechanism 181 and the first reference axis K1. It should be noted that, in both the Y and Z directions, the second work mechanism 182 is disposed at approximately the same position as the first work mechanism 181.

The second work mechanism 182 is configured as a front-rear reversal of the first work mechanism 181. Specifically, the second mechanism 182 includes the first drive device 51, the second drive device 52, the third drive device 53, the first boom 61, the first arm 62, and the first attachment 63. The first drive device 51 of the second work mechanism 182 is coupled to the second support wall portion 178. The first drive device 51 outputs torque centered on the first rotational axis 51J, which is approximately orthogonal to a second reference axis K2. The second reference axis K2 extends substantially in the Z direction, passing through the upper and lower surfaces of the second support wall portion 178. The second reference axis K2 extends substantially parallel to the first reference axis K1 at a position different from that of the first reference axis K1. Similar to the first work mechanism 181, the first rotational axis 51J extends substantially in the Y direction. In the specified plan view, when acted upon by the torque from the first drive device 51, the first boom 61 can swing across a second reference half-line, which extends upward from the first rotational axis 51J along the second reference axis K2, to the front side and the rear side with respect to the second reference half-line. For example, in the specified plan view, the first boom 61 is rotatable 90 degrees or more to the rear side with respect to the second reference half-line. The manner in which each component is coupled in the second work mechanism 182 is the same as that in the first work mechanism 181. Therefore, further description of the second work mechanism 182 is omitted.

The excavator 170 includes the control device 45. The control device 45 controls both the drive devices in the first work mechanism 181 and the drive devices in the second work mechanism 182. The control device 45 is capable of individually controlling each drive device in the first work mechanism 181 and the second work mechanism 182. That is, the control device 45 can operate the drive devices in the first work mechanism 181 and the drive devices in the second work mechanism 182 either in synchronization or independently. The control device 45 controls the first work mechanism 181 and the second work mechanism 182 in accordance with command signals transmitted from the controller 46. The excavator system 47 includes the controller 46 and excavator 170.

In the excavator 170, the work mechanisms are provided on both the front and rear sides of the upper structure 172. In this case, the excavator 170 is capable of performing work on the front side of the upper body 172 by using the first work mechanism 181. Furthermore, the excavator 170 is capable of performing work on the rear side of the upper structure 172 by using the second work mechanism 182. Accordingly, since the excavator 170 can perform work on both the front and rear sides of the upper body 172, the working envelope of the excavator 170 is broadened.

Here, regarding the excavator 170, a comparative example is considered in which the second work mechanism 182 is omitted from among the first work mechanism 181 and the second work mechanism 182. In this comparative example, due to the omission of the second working mechanism 182, the weight of the rear portion of the excavator 170 is smaller than the weight of the front portion. In such a case, since the weight distribution between the front and rear portions of the excavator 170 becomes uneven, it becomes necessary to provide a counterweight at the rear portion of the excavator 170. The counterweight is a weight provided to balance the excavator 170.

In contrast, in the configuration of this embodiment, since the work mechanism is provided on both the front and rear sides of the excavator 170, the front and rear weights of the excavator 170 become substantially uniform due to these two work mechanisms. Therefore, it is not necessary to equip with a counterweight.

With respect to the excavator 170 shown in FIG. 15, it is not essential that the first work mechanism 181 and the second work mechanism 182 have identical configurations. For example, the first attachment 63 employed in the first work mechanism 181 and the second work mechanism 182 may differ, or the respective first booms 61 may differ in shape or length. Even in such cases, as long as the work mechanisms are provided on both the front and rear sides of the upper body 172, the working envelope of the excavator 170 can be broadened. Furthermore, even in the cases where the configurations of the first work mechanism 181 and the second work mechanism 182 differ, the first work mechanism 181 and the second work mechanism 182 can be configured such that the respective weights thereof are approximately equal, thereby a counterweight becomes unnecessary.

It is also possible to adopt the following configuration in the cases where, for example, the weights of the first work mechanism 181 and the second work mechanism 182 differ. Specifically, a vertical movement mechanism for adjusting the position of the first drive device 51 in the upper and lower directions may be provided between the first support wall portion 176 and the first drive device 51 of the first work mechanism 181. Similarly, a vertical movement mechanism for adjusting the position of the first drive device 51 in the upper and lower directions may be provided between the second support wall portion 178 and the first drive device 51 of the second work mechanism 182. By utilizing such vertical movement mechanisms, the overall height of the first work mechanism 181 and the overall height of the second work mechanism 182 may be made different from each other. For example, in addition to making the heights different, the balance of the excavator 170 may be achieved without the use of a counterweight by varying the lengths of the respective first booms 61 or the respective first arms 62 between the first work mechanism 181 and the second work mechanism 182.

Furthermore, the arrangement of the first work mechanism 181 and the second work mechanism 182 is not limited to the example shown in FIG. 15. For instance, the positions of the first work mechanism 181 and the second work mechanism 182 may differ in at least one of the Z direction or the Y direction. As illustrated in FIG. 14, for example, when the excavator 170 is viewed in the Z direction, the first work mechanism 181 and the second work mechanism 182 may be arranged such that the first rotational axis 51J associated with the first drive device 51 of the first work mechanism 181 intersects with the first rotational axis 51J associated with the first drive device 51 of the second work mechanism 182. The two work mechanisms may be arranged so as to satisfy the following positional condition when the excavator 170 is viewed in plan from a direction parallel to the first rotational axis 51J of a given one of the two work mechanisms. The positional condition is that, in a direction orthogonal to both the first rotational axis 51J and the reference axis of the given work mechanism, the two work mechanisms are disposed on opposite sides of the vehicle body 12, with respect to the center of the vehicle body 12. It is also possible that the direction orthogonal to both the first rotational axis 51J and the reference axis of the given work mechanism is not the X direction.

When the two work mechanisms are provided, the first booms 61, the first arms 62, and the first attachments 63 may be operated hydraulically.

The following clauses set out features of the disclosure which may serve as basis for future amendments or divisional applications:

1. A construction machine comprising:

• • a drive device outputting torque centered on a rotational axis orthogonal to a reference axis extending in upper and lower directions of a travelable vehicle body; and
    • a boom having a first end portion coupled to the vehicle body, the boom being rotated around the rotational axis by the torque from the drive device,
    • wherein, when viewed in a first direction parallel to the rotational axis, the boom is rotatable to both one side and other side with respect to the reference axis.
      2. The construction machine of clause 1, wherein, when viewed in the first direction, the boom is rotatable by 90 degrees or more to the one side and the other side with respect to the reference axis.
      3. The construction machine of clause 1, wherein the drive device is a first drive device, and the rotational axis is a first rotational axis,
  • the construction machine further comprising:
    • a second drive device outputting torque centered on a second rotational axis, the second rotational axis being parallel to the first rotational axis and passing through a second end portion of the boom opposite to the first end portion of the boom;
    • an arm having a first end portion coupled to the second end portion of the boom, the arm rotating around the second rotational axis by the torque from the second drive device;
    • a third drive device outputting torque centered on a third rotational axis, the third rotational axis being parallel to the first rotational axis and passing through a second end portion of the arm opposite to the first end portion of the arm; and
    • an attachment having a first end portion coupled to the second end portion of the arm, the attachment rotating around the third rotational axis by the torque from the third drive device,
    • wherein, when viewed in the first direction, the arm is rotatable to both one side and other side with respect to an imaginary straight line connecting the first rotational axis and the second rotational axis, and the attachment is rotatable to both one side and other side with respect to an imaginary straight line connecting the second rotational axis and the third rotational axis.
      4. The construction machine of clause 2, wherein, when viewed in the first direction, the vehicle body has an inclined surface that is sloped such that it approaches the reference axis toward an upward direction, and a top surface that is connected to an uppermost edge of the inclined surface and is orthogonal to the reference axis, and
  • wherein the first end portion of the boom is coupled to the vehicle body at the top surface.
    5. The construction machine of clause 1, further comprising:
  • a slewing device outputting torque centered on a slewing axis parallel to the reference axis; and
    • a connecting member interposed between the vehicle body and the boom, the connecting member being rotated about the slewing axis by the torque from the slewing device,
    • wherein the connecting member is rotatable through 360 degrees about the slewing axis.
      6. The construction machine of clause 5, wherein the vehicle body is formed in a truncated conical shape such that its cross-sectional area orthogonal to the reference axis decreases toward an upward direction, and
  • wherein the first end portion of the boom is coupled to a top surface of the vehicle body, the top surface being a surface on the upper side.
    7. The construction machine of clause 1, wherein the first end portion of the boom is disposed at a central of the vehicle body in a direction orthogonal to both the rotation axis and the reference axis.
    8. The construction machine of clause 1, wherein the drive device is a first drive device, and the rotational axis is a first rotational axis,
  • the construction machine further comprising:
    • a second drive device outputting torque centered on a second rotational axis, the second rotational axis being parallel to the first rotational axis and passing through a second end portion of the boom opposite to the first end portion of the boom;
    • an arm having a first end portion coupled to the second end portion of the boom, the arm rotating around the second rotation axis by the torque from the second drive device;
    • a third drive device outputting torque centered on a third rotational axis, the third rotational axis being parallel to the first rotational axis and passing through a second end portion of the arm opposite to the first end portion of the arm; and
    • an attachment having a first end portion coupled to the second end portion of the arm, the attachment rotating around the third rotational axis by the torque from the third drive device,
    • wherein the attachment is two buckets having openings respectively, and
    • wherein the openings of the two buckets face away from each other and are arranged in a circumferential direction about the third rotational axis.
      9. The construction machine of clause 8, wherein each bucket includes a box-shaped bucket body having the opening and a tooth protruding from an edge of the opening of the bucket body,
  • wherein, when viewed in a direction parallel to the third rotational axis, the tooth of each bucket protrudes from the edge that is farthest from the third rotational axis among edges of the opening, and
  • wherein, when the attachment is rotated once around the third rotational axis with the arm being in a fixed position, a rotational trajectory of a distal end of the tooth of one of the two buckets overlaps a rotational trajectory of a distal end of the tooth of the other of the two buckets when viewed in the direction parallel to the third rotation axis.
    10. The construction machine of clause 1, wherein the drive device is a first drive device, and the rotational axis is a first rotation axis,
  • the construction machine further comprising:
    • a second drive device outputting torque centered on a second rotational axis, the second rotational axis being parallel to the first rotational axis and passing through a second end portion of the boom opposite to the first end portion of the boom;
    • an arm having a first end portion coupled to the second end portion of the boom, the arm rotating around the second rotation axis by the torque from the second drive device;
    • a third drive device outputting torque centered on a third rotational axis, the third rotational axis being parallel to the first rotational axis and passing through a second end portion of the arm opposite to the first end portion of the arm; and
    • an attachment having a first end portion coupled to the second end portion of the arm, the attachment rotating around the third rotational axis by the torque from the third drive device,
    • the arm is rotatable to a position in which the third rotational axis is placed on a half-straight line extending from the second rotational axis and intersecting the first rotational axis.
      11. The construction machine of clause 1, wherein the drive device is a first drive device, and the rotational axis is a first rotation axis,
  • the construction machine further comprising:
    • a second drive device outputting torque centered on a second rotational axis, the second rotational axis being parallel to the first rotational axis and passing through a second end portion of the boom opposite to the first end portion of the boom;
    • an arm having a first end portion coupled to the second end portion of the boom, the arm rotating around the second rotation axis by the torque from the second drive device;
    • a third drive device outputting torque centered on a third rotational axis, the third rotational axis being parallel to the first rotational axis and passing through a second end portion of the arm opposite to the first end portion of the arm;
    • an attachment having a first end portion coupled to the second end portion of the arm, the attachment rotating around the third rotational axis by the torque from the third drive device; and
    • a control device controlling the first drive device, the second drive device, and the third drive device,
    • wherein the control device is capable of executing a process of switching between: a first posture in which, the boom is rotated to the one side with respect to the reference axis when viewed in the first direction and the third rotational axis is situated opposite to the first rotational axis with respect to the second rotational axis in a direction orthogonal to both the first rotational axis and the reference axis; and
  • a second posture in which, the boom is rotated to the other side with respect to the reference axis when viewed in the first direction and the third rotational axis is situated opposite to the first rotational axis with respect to the second rotational axis in the direction orthogonal to both the first rotational axis and the reference axis, and
    • wherein, during the switching between the first posture and the second posture, the control device causes the arm to rotate across a half-line extending from the second rotational axis and intersecting the first rotational axis, when viewed in the first direction.
      12. A construction machine comprising:
  • a first slewing device outputting torque centered on a first slewing axis extending in upper and lower directions of a travelable vehicle body;
  • a boom having a first end portion coupled to the vehicle body, the boom being rotated around the first slewing axis by the torque from the first slewing device;
  • a second slewing device outputting torque centered on a second slewing axis, the second slewing axis being parallel to the first slewing axis and passing through a second end portion of the boom opposite to the first end portion of the boom;
  • an arm having a first end portion coupled to the second end portion of the boom and a second end portion opposite the first end portion, the arm rotating around the second slewing axis by the torque from the second slewing device; and an attachment coupled to the second end portion of the arm.
    13. The construction machine of clause 12, wherein the attachment is an electric extendable device that is extendable and retractable along an operating axis parallel to the first slewing axis.
    14. A construction machine comprising two work mechanisms, wherein each work mechanism includes:
  • a first drive device outputting torque centered on a first rotational axis orthogonal to a reference axis extending in upper and lower directions of a travelable vehicle body;
  • a boom having a first end portion coupled to the vehicle body, the boom being rotated around the first rotational axis by the torque from the first drive device;
  • a second drive device outputting torque centered on a second rotational axis, the second rotational axis being parallel to the first rotational axis and passing through a second end portion of the boom opposite to the first end portion of the boom;
  • an arm having a first end portion coupled to the second end portion of the boom and a second end portion opposite the first end portion, the arm rotating around the second rotational axis by the torque from the second drive device; and
  • an attachment coupled to the second end portion of the arm,
  • wherein, when viewed in a direction parallel to the first rotation axis of a first work mechanism of the two work mechanisms, the two work mechanisms are disposed on one side and other side respectively with respect to a center of the vehicle body in a direction orthogonal to both the first rotational axis and the reference axis of the first work mechanism.
    15. A drive device for a construction machine, the drive device being capable of outputting torque centered on a rotational axis to a boom rotatably coupled to a travelable vehicle body around the rotational axis, the rotational axis being orthogonal to a reference axis extending in upper and lower directions of the vehicle body,
  • wherein, when viewed in a direction parallel to the rotational axis, the boom is rotatable to both one side and other side with respect to the reference axis.
    16. The drive device of clause 15, wherein, when viewed in a direction parallel to the rotational axis, the drive device is capable of driving and rotating the boom by 90 degrees or more to the one side and by 90 degrees or more to the other side with respect to the reference axis.
    17. A drive unit for a construction machine, comprising:
  • a first drive device capable of outputting torque centered on a first rotational axis to a boom, the boom being rotatably coupled to a travelable vehicle body around the first rotational axis orthogonal to a reference axis extending in upper and lower directions of the vehicle body;
  • a second drive device capable of outputting torque centered on a second rotational axis to an arm, the arm having a first end portion coupled to a second end portion of the boom opposite the first end portion of the boom and a second end portion opposite the first end portion, the arm being rotatable around the second rotational axis, the second rotational axis extending parallel to the first rotational axis and passing through the second end portion of the boom; and
  • a third drive device capable of outputting torque centered on a third rotational axis to an attachment, the attachment having a first end portion coupled to the second end portion of the arm, the attachment being rotatable around the third rotational axis, the third rotational axis extending parallel to the first rotational axis and passing through the second end portion of the arm,
  • wherein, when viewed in a direction parallel to the first rotational axis, the first drive device is capable of driving and rotating the arm to both one side and other side with respect to the reference axis,
  • wherein the second drive device is capable of driving and rotating the arm to both one side and other side with respect to an imaginary straight line connecting the first rotational axis and the second rotational axis, and
  • wherein the third drive device is capable of driving and rotating the attachment to both one side and other side with respect to an imaginary straight line connecting the second rotational axis and the third rotational axis.
    18. A drive unit for a construction machine, comprising:
  • a drive device capable of outputting torque centered on a rotational axis to a boom rotatably coupled to a travelable vehicle body around the rotational axis, the rotational axis being orthogonal to a reference axis extending in upper and lower directions of the vehicle body, the drive device being capable of driving and rotating the boom to both one side and other side with respect to the reference axis when viewed in a direction parallel to the rotational axis; and
  • a slewing device capable of outputting, to a connecting member, torque centered on a slewing axis parallel to the reference axis, the connecting member being interposed between the vehicle body and the boom and rotatable about the slewing axis, the slewing device being capable of driving and rotating the connecting member through 360 degrees about the slewing axis.
    19. A drive unit for a construction machine, comprising:
  • a first slewing device outputting torque centered on a first slewing axis to a boom, the boom being rotatably coupled to a travelable vehicle body around the first slewing axis, the first slewing axis extending in upper and lower directions of the vehicle body; and
  • a second slewing device outputting torque centered on a second slewing axis to an arm, the arm being coupled to a second end portion of the boom opposite the first end portion of the boom, the arm being rotatable around the second slewing axis, the second slewing axis extending parallel to the first slewing axis and passing through the second end portion of the boom.