DIE GRINDER

Description

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to Japanese patent application Nos. 2024-044580 filed on Mar. 21, 2024 and 2025-005915 filed on Jan. 16, 2025. The contents of the foregoing applications are hereby fully incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a die grinder.

BACKGROUND

A rotary tool (such as a die grinder and a disc grinder) is known that is configured to perform an operation such as grinding and polishing a workpiece by rotationally driving a tool accessory coupled to a spindle. For example, Japanese Unexamined Patent Application Publication No. 2024-076277 discloses a disc grinder that has a grip part to be held by a user and is configured to rotate a spindle by a motor being rotated by power supplied from a battery.

SUMMARY

A rotary tool can be improved in workability if a grip part can be suitably held by a user. If, for example, the length of the grip part in a front-rear direction is increased, however, the whole length of the rotary tool may be increased and thus the size of the rotary tool may be increased. It is therefore desired to provide a rotary tool configured such that a grip part can be suitably held by a user, while suppressing increase in size of the rotary tool. A die grinder is generally more often used in a narrow place than a disc grinder. It is therefore more strongly desired to solve the above-described problem in a die grinder.

It is accordingly a non-limiting object of the present disclosure to provide a die grinder configured such that a grip part can be suitably held by a user, while suppressing increase in size of the die grinder.

According to a non-limiting aspect of the present disclosure, a die grinder is provided. The die grinder includes a motor, a spindle and a main housing. The motor is driven by power supplied from a battery. The spindle is rotated by power of the motor around a drive axis that defines a front-rear direction of the die grinder. The main housing includes a motor housing, a handle housing and a battery housing. The motor housing houses the motor. The handle housing is connected to a rear end of the motor housing and has an elongate grip part configured to be held by a user. The battery housing is connected to a rear end of the handle housing and has a battery mounting part configured such that the battery is mounted thereto. The battery mounting part is arranged in a position through which the drive axis passes and configured such that the battery is mounted in a direction orthogonal to the drive axis. A center axis of the grip part is arranged outward of the drive axis in a radial direction.

In the die grinder according to this aspect, compared with a structure in which the battery is obliquely mounted to the battery mounting part, the length of the battery housing in the front-rear direction can be shortened to secure the length of the grip part easy to hold. Thus, the die grinder is provided and configured such that the grip part can be suitably held by a user, while suppressing increase in size of the die grinder.

According to another non-limiting aspect of the present disclosure, a die grinder is provided. The die grinder includes a motor, a spindle and a main housing. The motor is driven by power supplied from a battery. The spindle is rotationally driven by power of the motor around a drive axis that defines a front-rear direction of the die grinder. The main housing includes a motor housing, a handle housing, a tool housing and a battery housing. The motor housing houses the motor. The handle housing is connected to a rear end of the motor housing and has an elongate grip part configured to be held by a user. The tool housing is connected to a front end of the motor housing, and the spindle is arranged in the tool housing. The battery housing is connected to a rear end of the handle housing and has a battery mounting part that is configured such that the battery is mounted thereto. The length of the main housing from a rear end of the battery housing to a front end of the tool housing in the front-rear direction is 400 mm or less.

In the die grinder according to this aspect, the length of the main housing in the front-rear direction is 400 mm or less and is shorter than that of a main housing of a general die grinder. Thus, the die grinder is provided that can be suitably used for operation even in a narrow place.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view for showing the structure of elements forming the outer appearance of a die grinder according to a first embodiment of the present disclosure.

FIG. 2 is a sectional view for showing the structure of elements disposed within the die grinder of the first embodiment.

FIG. 3 is a sectional view for showing the structure of elements disposed within a handle housing and a battery housing.

FIG. 4 is a sectional view for showing the structure of elements disposed within a motor housing and a tool housing.

FIG. 5 is a sectional view for showing the structure of a shaft lock mechanism.

FIG. 6 is an explanatory view for showing the length of the die grinder in a front-rear direction.

FIG. 7 is a sectional view taken at a position shown by arrow VII-VII in FIG. 6.

FIG. 8 is a sectional view for showing the structure of a die grinder according to a second embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Representative, non-limiting examples of the present invention are described in detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. Furthermore, each of the additional features and teachings disclosed below may be utilized separately or in conjunction with other features and teachings to provide improved tools and manufacturing and using methods of the tools.

Moreover, combinations of features and steps disclosed within the following detailed description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe representative examples of the invention. Furthermore, various features of the representative examples described above and below, as well as the various independent and dependent claims below, may be combined in ways that are not specifically and explicitly enumerated in order to provide additional useful embodiments of the present teachings.

All features disclosed in the description and/or the claims are intended to be disclosed separately and independently from each other for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter, independent of the compositions of the features in the embodiments and/or the claims. In addition, all value ranges or indications of groups of entities are intended to disclose every possible intermediate value or intermediate entity for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter.

In at least one non-limiting embodiment according to the present disclosure, when a direction in which the battery is mounted to the battery mounting part is defined as an up-down direction of the die grinder, the drive axis may be arranged to pass a middle point between an upper end and a lower end of the battery mounted to the battery mounting part when the die grinder is viewed from the side.

According to this embodiment, a user can easily move the die grinder along the drive axis and operate the die grinder in a well-balanced manner. Therefore, the workability of the die grinder is improved.

In addition or in the alternative to the preceding embodiment, the die grinder may further have a controller configured to control driving of the motor. The controller may be arranged in a position through which the drive axis passes. The controller may extend in a direction orthogonal to the drive axis when the die grinder is viewed from the side.

According to this embodiment, the arrangement of the controller on the drive axis suppresses or restricts increase in size of the main housing in the radial direction. Further, the length of the main housing in the front-rear direction can be shortened compared with a structure in which the controller is arranged obliquely to the drive axis.

In addition or in the alternative to the preceding embodiments, the controller may be housed behind the grip part within the main housing.

According to this embodiment, by housing the controller in the battery housing in which a space is more easily formed inside than in the motor housing and the handle housing, the controller is efficiently arranged in the main housing, and increase in size of the main housing is suppressed or prevented.

In addition or in the alternative to the preceding embodiments, the main housing may have an air inlet from which outside air is led into the main housing. The controller may be arranged to overlap at least part of the air inlet when the die grinder is viewed from the side.

According to this embodiment, the length of the main housing in the front-rear direction can be shortened, compared with a structure in which the controller is arranged in a different position through the air inlet in the front-rear direction, while the controller is cooled by air.

In addition or in the alternative to the preceding embodiments, the motor may include a stator having a stator core, a rotor and a motor shaft that rotates together with the rotor. The motor may be housed in the motor housing such that a rotation axis of the motor shaft extends in parallel to the front-rear direction. A length of the stator core in the front-rear direction may be 30 mm or less.

According to this embodiment, the length of the motor in the front-rear direction is relatively short. Therefore, the length of the grip part in the front-rear direction can be increased, while increase in length of the die grinder in the front-rear direction is suppressed.

In addition or in the alternative to the preceding embodiments, the die grinder may further have a shaft locking mechanism that locks the spindle while the spindle is stopped rotating.

According to this embodiment, the die grinder is provided that is convenient in replacement of the tool accessory.

In addition or in the alternative to the preceding embodiments, the die grinder may further have a coupling that connects a motor shaft of the motor and the spindle such that a rotation axis of the motor shaft coincides with the drive axis. The shaft locking mechanism may be configured to lock the spindle by engagement between the shaft locking mechanism and the coupling.

According to this embodiment, by utilizing the coupling, increase of the number of parts of the die grinder is prevented, and increase in length of the die grinder in the front-rear direction is prevented.

In addition or in the alternative to the preceding embodiments, the die grinder may further have a switch that turns on and off the motor according to user's operation of a first operation part. The switch may be housed in the grip part.

According to this embodiment, compared with a structure in which the switch is housed in the motor housing or the battery housing, increase in length of the die grinder in the front-rear direction is prevented.

In addition or in the alternative to the preceding embodiments, the die grinder may have a second operation part that adjusts the rotation speed of the motor. The second operation part may be arranged behind the grip part

According to this embodiment, by housing the dial in the battery housing in which a space is more easily formed inside than in the motor housing and the handle housing, the dial is efficiently arranged in the main housing, and increase in size of the main housing is suppressed or prevented.

In addition or in the alternative to the preceding embodiments, a length from a rear end to a front end of the grip part in the front-rear direction may be 60 mm or more.

According to this embodiment, the grip part is longer than a grip part of a general die grinder. Therefore, a user can suitably hold the grip part, so that the die grinder is improved in usability.

In addition or in the alternative to the preceding embodiments, a circumferential length of the grip part in a cross section orthogonal to the drive axis may be 150 mm or less.

According to this embodiment, the grip part is thinner than a grip part of a general die grinder. Therefore, a user can suitably hold the grip part, so that the die grinder is improved in usability.

In addition or in the alternative to the preceding embodiments, a length of the main housing from the rear end of the battery housing to a front end of the motor housing in the front-rear direction may be 260 mm or less.

According to this embodiment, the length from the rear end of the battery housing to the front end of the motor housing in the front-rear direction is shorter than that of a general die grinder. A rear half of the main housing is relatively short, so that a user can operate the die grinder in a well-balanced manner by holding the grip part.

A. First Embodiment

A1. The structure of elements forming the outer appearance of a die grinder 100:

A die grinder 100 according to a first embodiment of the present disclosure is now described with reference to FIG. 1. The die grinder 100 is a representative example of a rotary tool that rotationally drives a tool accessory that is removably held on a front end. The die grinder 100 rotates a spindle 90 around a drive axis TX with rotational power generated by driving a motor. A tool accessory TA is mounted to a front end of the spindle 90 and rotated by rotation of the spindle 90. The die grinder 100 is also referred to as a hand grinder or a straight grinder.

In the example shown in FIG. 1, the tool accessory TA is a generally cylindrical grinding stone with a shank. A side face TS of the tool accessory TA functions as a grinding face. A user can perform an operation such as grinding and polishing by operating the die grinder 100 to rotate the tool accessory TA while pressing the side face TS of the tool accessory TA onto a workpiece. The shape of the tool accessory TA is not limited to a cylindrical shape, and it may be appropriately changed to other various shapes, such as a pyramid shape including a cone shape, according to the kind of a workpiece or the purpose of the operation. The tool accessory TA is not limited to a grinding stone, and it may be other tool accessories such as a flap wheel with sanding paper adhered thereon.

The die grinder 100 has a generally cylindrical main housing 10 extending in an extending direction of the drive axis TX. The main housing 10 includes a battery housing 80, a handle housing 40, a motor housing 30 and a tool housing 50.

A2. The structure of the battery housing 80:

As shown in FIG. 1, the battery housing 80 is arranged in a rear end part of the main housing 10. An air inlet 82 is formed in a side of the battery housing 80. Air for cooling a motor 20 is led into the main housing 10 through the air inlet 82.

As shown in FIG. 2, the battery housing 80 has a battery mounting part 86 configured such that a rechargeable battery BT is removably mounted thereto. The battery BT is, for example, a known secondary battery such as a lithium-ion battery including cells.

The battery mounting part 86 is arranged in a position through which the drive axis TX passes in a rear end part of the handle housing 40. In FIG. 2, for the sake of convenience of illustration, the battery BT is not shown. The battery mounting part 86 has a pair of rails and a terminal that can be electrically connected to a terminal of the battery BT. The pair of rails of the battery mounting part 86 are physically engaged with a pair of grooves of the battery BT, so that the battery BT is guided in a direction orthogonal to the drive axis TX and removably mounted to the battery mounting part 86.

In this specification, for the sake of convenience of explanation, the extending direction of the drive axis TX is defined as a front-rear direction of the die grinder 100. In the front-rear direction, a side on which the spindle 90 is disposed is defined as a front side of the die grinder 100, and the opposite side is defined as a rear side of the die grinder 100. A direction orthogonal to the front-rear direction and in which the battery BT is mounted on and removed from the battery mounting part 86 is defined as an up-down direction. A direction orthogonal to the front-rear direction and the up-down direction is defined as a left-right direction of the die grinder 100. Further, any direction orthogonal to the drive axis TX is defined as a radial direction of the die grinder 100, and in the radial direction, a direction away from the drive axis TX and a direction toward the drive axis TX are defined as a radially outward direction and a radially inward direction, respectively.

As shown in FIG. 3, a mounting/removing direction of the battery BT is a direction orthogonal to the drive axis TX and is defined as the up-down direction of the die grinder 100. A user can remove the battery BT from the battery mounting part 86 by pulling out the battery BT upward. Further, the user can mount the battery BT to the battery mounting part 86 by pushing in the battery BT downward. The battery BT mounted to the battery mounting part 86 can supply power to the motor 20 and a controller 84.

In this embodiment, the mounting/removing direction of the battery BT is set orthogonal to the drive axis TX. This prevents the battery mounting part 86 and the battery BT from protruding rearward compared with a structure in which the mounting/removing direction of the battery BT is set oblique to the drive axis TX. Thus, the length of the battery housing 80 in the front-rear direction can be shortened compared with the structure in which the battery BT is obliquely mounted to the battery mounting part 86. Therefore, the length of the grip part 42 can be increased by the shortened length of the battery housing 80, while suppressing increase in length of the die grinder 100 in the front-rear direction. Thus, the die grinder 100 is provided and configured such that the grip part 42 can be suitably held by a user. If the length of the grip part 42 is sufficiently secured, the length of the die grinder 100 may be shortened.

In the die grinder 100 of this embodiment, as shown in FIG. 3, the drive axis TX is arranged to pass a middle point BC between an upper end BU and a lower end BD of the battery BT mounted to the battery mounting part 86 when viewed from the side. With this arrangement, a user can easily move the die grinder 100 along the drive axis TX and operate the die grinder 100 in a well-balanced manner. Further, compared with a structure in which the middle point BC of the battery BT is offset radially outward from the drive axis TX, the battery BT is prevented from protruding radially outward from the main housing 10. Thus, the die grinder 100 is suppressed or restricted from being increased in size radially outward around the drive axis TX. Further, in this embodiment, although not specifically shown, the drive axis TX is also arranged to pass a middle point between a left end and a right end of the battery BT.

As shown in FIG. 3, a dial 88 and the controller 84 are further arranged in the battery housing 80. As shown in FIG. 1, the dial 88 is exposed to the outside from the battery housing 80 and configured to be rotated by user's manual operation. The dial 88 outputs a signal for setting the rotation speed of the motor to the controller 84 according to the rotation position.

As shown in FIG. 3, the controller 84 comprises a computer having a central processing unit CPU and memories such as a RAM and a ROM. The controller 84 is a plate-like member including a circuit substrate. The controller 84 controls driving of the motor 20 and other various operations in the die grinder 100.

The controller 84 is arranged in a position through which the drive axis TX passes. This suppresses or restricts increase in size of the main housing 10 in the radial direction compared with a structure in which the controller 84 is arranged radially outward of the drive axis TX.

The controller 84 is arranged in the battery housing 80 behind the handle housing 40. By housing the controller 84 in the battery housing 80 in which a space is more easily formed inside than in the motor housing 30 and the handle housing 40, the controller 84 is efficiently arranged within the main housing 10, and increase in size of the main housing 10 is suppressed or restricted.

The controller 84 is arranged to extend in a direction orthogonal to the drive axis TX. Specifically, a circuit substrate forming the controller 84 is arranged to extend in the up-down direction and the left-right direction. By this arrangement, compared with a structure in which the controller 84 is arranged obliquely to the drive axis TX, the length of the main housing 10 in the front-rear direction can be shortened.

The controller 84 is arranged substantially in the same position as the air inlet 82 in the front-rear direction. Specifically, the controller 84 is arranged to overlap at least part of the air inlet 82 in the front-rear direction when the die grinder 100 is viewed from the side. By this arrangement, the length of the main housing 10 in the front-rear direction can be shortened compared with a structure in which the controller 84 is arranged in a different position from the air inlet 82 in the front-rear direction, while the controller 84 is cooled by utilizing air led in through the air inlet 82.

A3. The structure of the handle housing 40:

As shown in FIG. 2, the handle housing 40 is arranged between the motor housing 30 and the battery housing 80. The handle housing 40 includes the grip part 42. A boundary between the handle housing 40 and the battery housing 80 in the front-rear direction is the position of front ends of the controller 84, the dial 88 and other members disposed within the battery housing 80. In this embodiment, the position of the front end of the dial 88 is the boundary between the handle housing 40 and the battery housing 80.

The grip part 42 has an elongate cylindrical shape extending in the front-rear direction. The grip part 42 is thinner than the motor housing 30 and the battery housing 80 and configured to be held by a user. The grip part 42 is configured to have a thickness (outer diameter), length and sectional shape easy to hold. The detailed structure of the grip part 42 will be described below.

A4. The structure of the motor housing 30:

As shown in FIG. 2, the motor housing 30 is arranged between the handle housing 40 and the tool housing 50. The motor housing 30 has an elongate cylindrical shape extending in the front-rear direction and houses the motor 20. A boundary between the motor housing 30 and the handle housing 40 in the front-rear direction is, for example, the position of a rear end of the motor 20.

As shown in FIG. 2, a switch knob 34 is provided on the upper side of the motor housing 30. The switch knob 34 is moved between an off position and an on position according to user's manual operation. The switch knob 34 is operably connected to a switch 14. The switch 14 is disposed in the grip part 42. The switch 14 is turned on and off according to user's operation of the switch knob 34 to switch ON and OFF of the motor 20. The motor 20 is driven while the switch 14 is ON.

As shown in FIG. 4, the motor 20 is a brushless DC motor that is driven under control of the controller 84. The motor 20 has a motor body 21, a motor shaft 22 and a fan 26 mounted onto the motor shaft 22.

The motor body 21 includes a stator 212 having a stator core 212C, and a rotor 214. The stator core 212C is formed by a lamination of electromagnetic steel sheets. The stator 212 rotates the rotor 214 by utilizing a magnetic field generated by the DC current supplied from the battery. The motor shaft 22 is rotated around a motor rotation axis MX by rotation of the rotor 214. The volume of the stator core 212C affects the output (rotation speed and torque) of the motor 20.

In the die grinder 100 of this embodiment, considering the use, the output of the motor 20 can be designed smaller than that of a hand-held electric disc grinder. The electric disc grinder is an example of a rotary tool that performs grinding, polishing, cutting and other similar operations by using, for example, a grinding wheel or stone, a cutting grinding wheel or stone, a blade or a brush as a tool accessory. The electric disc grinder is also referred to as an angle grinder.

In the die grinder 100 of this embodiment, as shown in FIG. 4, a length LC of the stator core 212C in the front-rear direction, or the thickness of the stator core 212C is designed relatively small. Specifically, in a motor for a general electric disc grinder, the thickness of a stator core is, for example, more than 30 mm and less than 80 mm. In the motor 20 of the die grinder 100 of this embodiment, the thickness of the stator core 212C is 24.15 mm, which is less than 30 mm. Thus, the length of the motor housing 30 in the front-rear direction is made shorter than that of the electric disc grinder. Thus, the die grinder 100 of this embodiment is configured such that the motor 20 is relatively short in the front-rear direction while ensuring an output required for the die grinder 100.

As shown in FIG. 4, the motor shaft 22 is supported to be rotatable relative to the motor housing 30 by a front bearing 201 and a rear bearing 202 that are disposed within the motor housing 30. The front bearing 201 is supported within the motor housing 30 while being restricted from moving by a motor bearing retainer 32. The motor bearing retainer 32 has openings 322 that communicate with air outlets 58 (see FIG. 1) formed in the tool housing 50.

The motor shaft 22 rotates around the motor rotation axis MX together with the rotor 214. In this embodiment, the motor shaft 22 is connected to the spindle 90 via a coupling 204 such that the motor rotation axis MX coincides with the drive axis TX. The arrangement that the motor rotation axis MX coincides with the drive axis TX suppresses or restricts increase in size of the die grinder 100 in the radial direction. The motor rotation axis MX and the drive axis TX may however be not coincident, but, for example, may be close and parallel to each other.

The fan 26 rotates together with the motor shaft 22. The fan 26 generates an air flow for cooling the motor 20. More specifically, as shown in FIG. 2, outside air is led into the inside of the battery housing 80 through the air inlet 82 formed in the battery housing 80, by rotation of the fan 26. The air led into the battery housing 80 flows forward through the handle housing 40 and is led into the motor housing 30. Then the air passes through the openings 322 and is discharged to the outside through the air outlets 58 (see FIG. 1) formed in the tool housing 50.

Thus, a space within the grip part 42 serves as a passage of air flow for cooling the motor 20 and the controller 84. Therefore, the thickness of the grip part 42, or more specifically, the outer contour of the grip part 42 in a cross section orthogonal to the drive axis TX affects the size of the air flow passage. In the die grinder 100 of this embodiment, as described above, the output of the motor 20 is smaller than that of a general electric disc grinder, so that temperature rise of the motor 20 is smaller than that of the motor of the electric disc grinder. Accordingly, the cooling performance of cooling the motor 20 and the controller 84 by air utilizing the fan 26 can be set lower than that of the electric disc grinder. In this embodiment, this allows the grip part 42 to be designed thinner than that of an electric disc grinder so as to be suitably held by a user. The grip part 42 may however have a thickness equal to that of the grip part of the electric disc grinder. Further, the die grinder 100 may have the same level of air cooling performance as the electric disc grinder.

A5. The structure of the tool housing 50:

As shown in FIG. 2, the tool housing 50 is arranged in a front end part of the main housing 10. The tool housing 50 is connected to a front end of the motor housing 30 and houses the spindle 90. The tool housing 50 is configured to have a thickness (outer diameter), length and sectional shape easy to hold.

As shown in FIG. 4, a barrel 60 is housed in the tool housing 50. The barrel 60 houses the spindle 90. The spindle 90 is supported to be rotatable relative to the barrel 60 by a front bearing 601 and a rear bearing 602 that are held within the barrel 60. The front bearing 601 is fixed by a bearing retainer 66 and restricted from moving in the front-rear direction.

A collet cone 92 and a collet nut 94 are provided on a front end of the spindle 90 to fix the tool accessory TA to the spindle 90. The tool accessory TA is inserted into the collet cone 92, and mounted unrotatably to the spindle 90 by tightening the collet nut 94.

When the switch knob 34 is manually operated by a user and the motor 20 is turned on, the motor shaft 22 is driven. The spindle 90 and the tool accessory TA then rotate together with the motor shaft 22 via the coupling 204.

A6. The structure of the shaft locking mechanism:

As shown FIG. 5, the die grinder 100 of this embodiment has a shaft locking mechanism 70. The shaft locking mechanism 70 is configured to lock the spindle 90 while the spindle 90 is stopped rotating. The shaft locking mechanism 70 restricts the spindle 90 from rotating together with the collet nut 94 relative to the main housing 10 in replacement of the tool accessory TA. As shown FIG. 5, the shaft locking mechanism 70 has a button 72, a pin 74, a biasing member 76 and a fitting part 78.

The button 72 serves as an operation part for turning on and off the shaft locking mechanism 70. An outer surface of the button 72 is exposed to the outside of the tool housing 50. An inner surface of the button 72 faces an outer surface of the barrel 60. A recess 724 is formed in the inner surface of the button 72 and configured to receive the biasing member 76.

The biasing member 76 is a metal coil spring. The biasing member 76 is arranged in a recess 604 formed in an outer surface of the barrel 60. The biasing member 76 biases the recess 724 of the button 72 and the recess 604 in a direction away from each other.

The pin 74 has an elongate and generally cylindrical shape. The pin 74 is inserted through a through hole 606 formed in the barrel 60. In the example shown in FIG. 5, the through hole 606 extends in the up-down direction, but it may extend in the left-right direction or any other direction orthogonal to the drive axis TX. The pin 74 is arranged in the through hole 606 such that a tip end 746 of the pin 74 faces the coupling 204.

The pin 74 has a second coupling part 742 and a restricting part 744. The second coupling part 742 is a groove formed in the pin 74. The pin 74 is integrally connected to the button 72 by the second coupling part 742 of the pin 74 being engaged with a projecting first coupling part 721 of the button 72.

The restricting part 744 is a diameter enlarged part of the pin 74. The restricting part 744 cannot enter the through hole 606 and thus restricts the pin 74 from moving upward from a prescribed position. As shown FIG. 5, when the button 72 is not depressed, the pin 74 is placed in an initial position in which the restricting part 744 abuts on the inner surface of the barrel 60 by a biasing force of the biasing member 76.

The fitting part 78 is configured to be fitted with the tip end 746 of the pin 74. In this embodiment, the fitting part 78 is formed in the coupling 204. The fitting part 78 is a recess formed in a surface of the coupling 204. The shaft locking mechanism 70 is configured to lock the spindle 90 by engagement between the pin 74 and the coupling 204. In the die grinder 100 of this embodiment, the coupling 204 is utilized as part of the shaft locking mechanism 70, thereby avoiding the need to additionally provide a new member and suppressing or preventing increase of the number of parts of the die grinder 100. Further, compared with a structure in which components of the shaft locking mechanism 70 are formed on the spindle 90, the die grinder 100 is restricted from increasing in length in the front-rear direction.

As shown FIG. 5, the pin 74 is placed in the initial position while the button 72 is not depressed. In the initial position, the tip end 746 of the pin 74 is not fitted in the fitting part 78. When a user depresses the button 72 against the biasing force of the biasing member 76, the pin 74 is moved to a position (hereinafter also referred to as a “fitting position”) in which the tip end 746 is fitted in the fitting part 78 formed on the coupling 204.

Rotation of the coupling 204 around the drive axis TX, or rotation of the spindle 90 around the drive axis TX is restricted by engagement between the pin 74 and the fitting part 78 while the button 72 is depressed. Therefore, the spindle 90 is restricted from rotating together with the collet nut 94 while the button 72 is depressed. A user can stop rotation of the spindle 90 by a simple operation of depressing the button 72 and thus easily replace the tool accessory TA.

A7: The length of the die grinder 100 in the front-rear direction:

As shown in FIG. 6, in this embodiment, with the above-described structures of the components, the die grinder 100 is configured to have a relatively short length in the front-rear direction. The length of a main housing of a general die grinder in the front-rear direction is more than 400 mm. The “length of the main housing 10” means the length from a rear end of the battery housing 80 to a front end of the tool housing 50 in the front-rear direction. The front end of the tool housing 50 does not include the collet cone 92, the collet nut 94 and the tool accessory TA. The rear end of the battery housing 80 does not include the battery BT.

In the die grinder 100 of this embodiment, a length LA of the main housing 10 in the front-rear direction is 382.1 mm, which is less than 385 mm. Thus, the length of the die grinder 100 of this embodiment is shorter than the length of a main housing of a general die grinder. The die grinder 100 of this embodiment, having a relatively short length in the front-rear direction, can be suitably used for operation even in a narrow place.

Further, in this embodiment, the die grinder 100 is configured such that a length LB from a rear end of the battery housing 80 to a front end of the motor housing 30 in the main housing 10 in the front-rear direction is relatively short. In a general die grinder, the length from the rear end of the battery housing 80 to the front end of the motor housing 30 in the front-rear direction is more than 260 mm. In this embodiment, the “front end of the motor housing 30” means a front end of a part of contact of the motor housing 30 with the motor bearing retainer 32. Where the die grinder 100 does not have the motor bearing retainer 32, however, the front end of the motor housing 30 may be, for example, a front end of the motor shaft 22, or a front end of a part of contact of the motor housing 30 with the tool housing 50.

In the die grinder 100 of this embodiment, the length LB from the rear end of the battery housing 80 to the front end of the motor housing 30 in the front-rear direction is 246.5 mm and is shorter than that of a general die grinder. A rear half of the main housing 10 in the front-rear direction tends to be increased in load due to the presence of the motor 20 and the battery BT mounted to the battery mounting part 86. In the die grinder 100 of this embodiment, a rear half of the main hosing 10 that tends to be increased in load is relatively short, so that a user can carry the die grinder 100 in a well-balanced manner by holding the grip part 42. Further, the user can easily operate a front half of the main housing 10 by holding the grip part 42, and thus can suitably perform an operation by the tool accessory TA.

A8. The structure of the grip part 42:

In the die grinder 100 of this embodiment, the grip part 42 has the following structure.

• • (1) As shown in FIG. 3, in the die grinder 100 of this embodiment, a center axis HX of the grip part 42 is arranged outward in the radial direction around the drive axis TX. In this embodiment, the center axis HX is arranged above the drive axis TX. In the die grinder 100 of this embodiment, the center axis HX is substantially parallel to the drive axis TX and is arranged above the drive axis TX in any position of the grip part 42 in the front-rear direction. As shown in FIG. 7, the center axis HX of the grip part 42 is arranged right above the drive axis TX.

The “center axis HX of the grip part 42” means a straight line passing through the center of the cross-sectional shape of the grip part 42. The “cross-sectional shape of the grip part 42” means an outer contour of the grip part 42 in a cross section orthogonal to the drive axis TX. The “center of the cross-sectional shape” includes a centroid or a center of gravity of the cross-sectional shape. In this embodiment, the center of gravity of a cross section of the grip part 42 is defined as a center of the cross-sectional shape of the grip part 42. Further, in this embodiment, a straight line connecting a center of the cross-sectional shape of a rear end of the grip part 42 and a center of the cross-sectional shape of a front end of the grip part 42 is defined as the center axis HX of the grip part 42. A straight line derived by linear regression analysis based on the centers of the cross-sectional shape that are extracted at a plurality of positions of the grip part 42 may be defined as the center axis HX of the grip part 42.

As described above, an operation such as grinding and polishing by the die grinder 100 can be performed with the side face TS of the tool accessory TA pressed onto a workpiece. Therefore, in such an operation, a user inclines the die grinder 100 forward and downward with a front end of the die grinder 100 set below the motor housing 30 in the vertical direction, or specifically, with the front end of the die grinder 100 set below a rear end of the die grinder 100. Alternatively, the user moves the whole die grinder 100 downward toward the workpiece. In the die grinder 100 of this embodiment, the center axis HX of the grip part 42 is arranged above the drive axis TX. With this arrangement, when performing an operation while holding the grip part 42 with one hand and holding the tool housing 50 with the other hand, the user can easily incline the die grinder 100 forward and downward with the front end set below the rear end of the die grinder 100. Therefore, the workability of the die grinder 100 is improved.

• • (2) An upper end of the grip part 42 is substantially flush with an upper end of the motor housing 30. With this configuration, the user can suitably hold the grip part 42. Further, the user can easily operate the switch knob 34 provided on the motor housing 30 while holding the grip part 42.
  • (3) The circumferential length of the grip part 42 is shorter than that of a general die grinder. The “circumferential length of the grip part 42” means the contour length of the grip part 42 in the cross section orthogonal to the drive axis TX. In FIG. 7, the circumferential length of the grip part 42 is schematically shown by a broken line. In this disclosure, the circumferential length of the grip part 42 is also referred to as the “thickness of the grip part 42”. A portion of the grip part 42 that does not get into contact with the user holding the grip part 42, and local irregularities of the grip part 42 that do not affect the function of the grip part 42, such as a through hole, a screw hole, a groove and a decoration are not considered in measurement of the circumferential length of the grip part 42.

In the die grinder 100 of this embodiment, the mean value of the circumferential length of the grip part 42 is 150 mm or less. Thus, the grip part 42 is thinner than that of a general die grinder. Therefore, the user can suitably hold the grip part 42. In the die grinder 100 of this embodiment, the mean value of the circumferential length of the grip part 42 is approximately 146 mm.

• • (4) The length of the grip part 42 in the front-rear direction is longer than that of a general die grinder, or more specifically, approximately 80 mm in the die grinder 100 of this embodiment.

The “length of the grip part 42 in the front-rear direction” means the length from the front end of the grip part 42 to the rear end of the grip part 42. In this disclosure, the “front end of the grip part 42” means a part of the grip part 42 in which the circumferential length of the grip part 42 is longer than the mean value of the circumferential length of the grip part 42 by a prescribed value or more in the front end part of the handle housing 40. The “rear end of the grip part 42” means a part of the grip part 42 in which the circumferential length of the grip part 42 is longer than the mean value of the circumferential length of the grip part 42 by a prescribed value or more in the rear end part of the handle housing 40.

In this embodiment, the front end of the grip part 42 is defined as a part of the grip part 42 in which the circumferential length of the grip part 42 exceeds 150 mm in the front end part of the handle housing 40. In other words, the front end of the grip part 42 is set at a part in which the circumferential length of the grip part 42 is longer than the mean value of the circumferential length of the grip part 42 by about 3%. Similarly, the rear end of the grip part 42 is also defined as a part of the grip part 42 in which the circumferential length of the grip part 42 exceeds 150 mm in the rear end part of the handle housing 40. In other words, the rear end of the grip part 42 is set at a part in which the circumferential length of the grip part 42 is longer than the mean value of the circumferential length of the grip part 42 by about 3%.

In a general die grinder, the length of the grip part in the front-rear direction is less than 60 mm. In the die grinder 100 of this embodiment, the length of the grip part 42 in the front-rear direction is 80 mm and is sufficiently secured. Therefore, a user can operate the die grinder 100 while holding only the grip part 42 without holding any other part of the main housing 10 such as the motor housing 30 and the battery housing 80. Thus, the user can suitably hold the grip part 42, so that the die grinder 100 is improved in usability. Further, the length of the grip part 42 is about 20% or more of the length LA of the main housing 10 in the front-rear direction. Thus, the grip part 42 occupies a relatively large area of the main housing 10. In a general die grinder, the length of the grip part is about 15% of the length LA of the main housing 10. In the die grinder 100 of this embodiment, the grip part 42 occupying a relatively large area of the main housing 10 is easy to hold, and the user can carry the die grinder 100 in a well-balanced manner by holding the grip part 42.

• • (5) The circumferential length of the grip part 42 is substantially uniform in the front-rear direction. More specifically, a dimensional error of the circumferential length of the grip part 42 from the front end to the rear end of the grip part 42 is less than 3%. The grip part 42 having a uniform thickness can be suitably held by a user.

As described above, in the die grinder 100 according to this embodiment, the battery mounting part 86 is arranged in a position through which the drive axis TX passes and configured such that the battery BT can be mounted in a direction orthogonal to the drive axis TX. The center axis HX of the grip part 42 is arranged radially outward of the drive axis TX. Compared with a structure in which the battery BT is obliquely mounted to the battery mounting part 86, the length of the battery housing 80 in the front-rear direction can be shortened. Therefore, the length of the grip part 42 in the front-rear direction can be increased by the shortened length of the battery housing 80, while increase in length of the die grinder 100 in the front-rear direction is suppressed. Thus, the die grinder 100 is provided and configured such that the grip part 42 can be suitably held, while suppressing increase in size of the die grinder 100. Further, with the configuration that the center axis HX of the grip part 42 is arranged radially outward of the drive axis TX, when operating the die grinder 100, the user can easily incline the attitude of the die grinder 100 forward and downward with the front end set below the rear end of the die grinder 100 in the vertical direction. Therefore, the workability of the die grinder 100 is improved.

In the die grinder 100 of this embodiment, the drive axis TX is arranged to pass the middle point BC between the upper end BU and the lower end BD of the battery BT mounted to the battery mounting part 86 when viewed from the side. With this arrangement, a user can easily move the die grinder 100 along the drive axis TX and operate the die grinder 100 in a well-balanced manner. Therefore, the workability of the die grinder 100 is improved. Further, the die grinder 100 is suppressed or restricted from being increased in size radially outward around the drive axis TX.

In the die grinder 100 of this embodiment, the controller 84 is arranged in a position through which the drive axis TX passes, and extends in the up-down direction when the die grinder 100 is viewed from the side. The arrangement of the controller 84 on the drive axis TX suppresses or restricts increase in size of the main housing 10 in the radial direction. Further, the length of the main housing 10 in the front-rear direction can be shortened compared with a structure in which the controller 84 is arranged obliquely to the drive axis TX.

In the die grinder 100 of this embodiment, the controller 84 is housed behind the grip part 42 within the main housing 10. By housing the controller 84 in the battery housing 80 in which a space is more easily formed inside than in the motor housing 30 and the handle housing 40, the controller 84 is efficiently arranged within the main housing 10, and increase in size of the main housing 10 is suppressed or restricted.

In the die grinder 100 of this embodiment, the controller 84 is arranged to overlap at least part of the air inlet 82 in the front-rear direction when the die grinder 100 is viewed from the side. By this arrangement, the length of the main housing 10 in the front-rear direction can be shortened compared with a structure in which the controller 84 is arranged in a different position through the air inlet 82 in the front-rear direction, while the controller 84 is cooled by air.

In the die grinder 100 of this embodiment, the length LC of the stator core 212C of the motor 20 in the front-rear direction is 30 mm or less. The length of the motor 20 in the front-rear direction is designed relatively short, so that the length of the grip part 42 in the front-rear direction can be increased while increase in length of the die grinder 100 in the front-rear direction is suppressed.

In this embodiment, the die grinder 100 has the shaft locking mechanism 70 utilizing the coupling 204. The use of the coupling 204 as part of the shaft locking mechanism 70 avoids the need to additionally provide a new member for the shaft locking mechanism 70, thus restricting increase of the number of parts of the die grinder 100 and restricting increase in length of the die grinder 100 in the front-rear direction.

In the die grinder 100 of this embodiment, the switch 14 is housed in the grip part 42. This restricts increase in length of the die grinder 100 in the front-rear direction, compared with a structure in which the switch 14 is housed in the motor housing 30 or the battery housing 80.

In the die grinder 100 of this embodiment, the dial 88 is arranged in the battery housing 80 behind the grip part 42. By arranging the dial 88 in the battery housing 80 in which a space is more easily formed inside than in the motor housing 30 and the handle housing 40, the dial 88 is efficiently arranged within the main housing 10, and increase in size of the main housing 10 is suppressed or restricted.

In the die grinder 100 of this embodiment, the length of the grip part 42 in the front-rear direction is 80 mm, and is sufficiently secured compared with the length of the grip part of a general die grinder. Therefore, the user can suitably hold the grip part 42, so that the die grinder 100 is improved in usability.

In the die grinder 100 of this embodiment, the circumferential length of the grip part 42 is 146 mm and is thinner than a grip part of a general die grinder. Therefore, the user can suitably hold the grip part 42, so that the die grinder 100 is improved in usability.

In the die grinder 100 of this embodiment, the length LA of the main housing 10 in the front-rear direction is 382.1 mm and is shorter than a main housing of a general die grinder. Therefore, having a relatively short length in the front-rear direction, the die grinder 100 can be suitably used for operation even in a narrow place.

In the die grinder 100 of this embodiment, the length LB from the rear end of the battery housing 80 to the front end of the motor housing 30 in the front-rear direction is 246.5 mm and is shorter than that of a general die grinder. A rear half of the main housing 10 is relatively short, so that a user can operate the die grinder 100 in a well-balanced manner by holding the grip part 42

B. Second Embodiment

As shown in FIG. 8, a die grinder 100b according to a second embodiment is different from the die grinder 100 of the first embodiment in that a paddle switch 34b is provided in place of the switch knob 34, and in the other points, it has the same structure as the first embodiment. Even with such a structure, the same effect as the first embodiment can be obtained.

The paddle switch 34b is provided on a lower end of the grip part 42. The paddle switch 34b is biased outward of the grip part 42 by a coil spring 342, and is normally placed in a stop position for stopping the motor 20. When a user depresses the paddle switch 34b into the grip part 42 against the biasing force of the coil spring 342, the paddle switch 34b is moved to a start position for starting the motor 20. In FIG. 8, the paddle switch 34b in the stop position is shown.

In FIG. 8, an outer surface 34S of the paddle switch 34b placed in the start position is schematically shown by broken line. The outer surface 34S in the start position is substantially flush with the lower end of the grip part 42. In the die grinder 100b having such a structure, the outer surface 34S of the paddle switch 34b in the start position may be considered as a part of the grip part 42 in defining the circumferential length of the grip part 42.

Correspondences between the features of the above-described embodiments and the features of the present disclosure or invention are as follows. However, the features of the above-described embodiments are merely exemplary and do not limit the features of the present disclosure or invention.

The die grinder 100 and the die grinder 100b are examples of the “die grinder”. The motor 20 is an example of the “motor”. The stator core 212C is an example of the “stator core”. The stator 212, the rotor 214 and the motor shaft 22 are examples of the “stator”, the “rotor” and the “motor shaft”, respectively. The motor rotation axis MX is an example of the “rotation axis of the motor shaft”. The drive axis TX is an example of the “drive axis”. The spindle 90 is an example of the “spindle”. The main housing 10 is an example of the “main housing”. The motor housing 30 is an example of the “motor housing”. The handle housing 40 is an example of the “handle housing”. The battery mounting part 86 is an example of the “battery mounting part”. The battery housing 80 is an example of the “battery housing”. The grip part 42 is an example of the “grip part”. The controller 84 is an example of the “controller”. The air inlet 82 is an example of the “air inlet”. The shaft locking mechanism 70 is an example of the “shaft locking mechanism”. The coupling 204 is an example of the “coupling”. The switch knob 34 and the paddle switch 34b are examples of the “first operation part”. The switch 14 is an example of the “switch”. The dial 88 is an example of the “second operation part”.

The die grinder according to the present disclosure is not limited to the die grinders 100, 100b of the above-described embodiments. For example, the following non-limiting modifications may be made. At least one of these modifications can be adopted in combination with at least one of the features of the die grinders 100, 100b of the above-described embodiments and the claimed invention.

(C1) In the first embodiment, the die grinder 100 is provided with the switch knob 34, and in the second embodiment, the die grinder 100b is provided with the paddle switch 34b. In place of the switch knob 34 and the paddle switch 34b, however, a trigger switch may be provided for starting the motor 20 by user's depressing operation. The trigger switch is arranged, for example, in the lower end of the grip part 42.

(C2) In the first embodiment, the drive axis TX is arranged to pass the middle point BC between the upper end BU and the lower end BD of the battery BT mounted to the battery mounting part 86 when the die grinder 100 is viewed from the side. The drive axis TX may however be arranged to pass the center of gravity of the battery BT mounted to the battery mounting part 86. Alternatively, the drive axis TX may be arranged to pass the center (centroid) of the outer contour of the battery BT in a cross section orthogonal to the drive axis TX. Even with this configuration, a user can easily move the die grinder 100 along the drive axis TX and operate the die grinder 100 in a well-balanced manner.

The present disclosure is not limited to any of the above-described embodiments but may be implemented by a diversity of configurations without departing from the scope of the disclosure. For example, the technical features of any of the above embodiments may be replaced or combined appropriately, in order to solve part or all of the problems described above or in order to achieve part or all of the advantageous effects described above. Any of the technical features may be omitted appropriately unless the technical feature is described as essential in the description hereof.

DESCRIPTION OF THE REFERENCE NUMERALS

• • 10: main housing, 14: switch, 20: motor, 21: motor body, 22: motor shaft, 26: fan, 30: motor housing, 32: motor bearing retainer, 34: switch knob, 34S: outer surface, 34b: paddle switch, 40: handle housing, 42: grip part, 50: tool housing, 58: air outlet, 60: barrel, 66: bearing retainer, 70: shaft locking mechanism, 72: button, 74: pin, 76: biasing member, 78: fitting part, 80: battery housing, 82: air inlet, 84: controller, 86: battery mounting part, 88: dial, 90: spindle, 92: collet cone, 94: collet nut, 100, 100b: die grinder, 201: front bearing, 202: rear bearing, 204: coupling, 212: stator, 212C: stator core, 214: rotor, 322: opening, 342: coil spring, 601: front bearing, 602: rear bearing, 604: recess, 606: through hole, 721: first coupling part, 724: recess, 742: second coupling part, 744: restricting part, 746: tip end, BT: battery, HX: center axis, MX: motor rotation axis, TA: tool accessory, TS: side face, TX: drive axis