MOUNTING STRUCTURE OF PROPULSION DEVICE FOR WATER-SURFACE MOVABLE BODY AND PROPULSION UNIT FOR WATER-SURFACE MOVABLE BODY

Description

TECHNICAL FIELD

The present invention relates to a mounting structure of a propulsion device for a water-surface movable body, and a propulsion unit for the water-surface movable body provided with the propulsion device for the water-surface movable body and the mounting structure.

BACKGROUND ART

In recent years, efforts have been actively made to realize a low-carbon or decarbonized society, and research and development of electrification technology is being conducted in a propulsion device for a water-surface movable body, such as an outboard motor, to reduce CO₂ emissions and improve energy efficiency.

For example, JP6327052B2 discloses a propulsion device for a water-surface movable body (an electric outboard motor) that includes an electric motor and a propulsor (a propeller shaft and a propeller) configured to rotate by a driving force of the electric motor. The electric motor is supported by a swivel via a pair of upper and lower mounting members.

In the propulsion device for the water-surface movable body using the electric motor as a driving source, vibrations caused by the driving source are smaller than in the propulsion device for the water-surface movable body using an internal combustion engine as a driving source. However, since the vibrations caused by the driving source are small, the vibrations caused by the propulsor may be perceived as large. Accordingly, there is still a strong demand for reducing vibrations.

SUMMARY OF THE INVENTION

In view of the above background, an object of the present invention is to effectively reduce the vibrations of the propulsion device for the water-surface movable body using the electric motor as a driving source.

To achieve such an object, one aspect of the present invention provides a mounting structure (7, 114, and 134) of a propulsion device (6, 113, and 133) for a water-surface movable body, wherein the propulsion device comprises: a case (11); an electric motor (12) accommodated in the case; and a propulsor (14) supported by the case and configured to rotate by a driving force of the electric motor, the mounting structure comprising: a fixed member (71, 116, and 136) fixed to a hull (4) of the water-surface movable body (3); a support member (72, 118, and 138) attached to the fixed member via an attachment shaft (87, 121, and 139) and supporting the case; and a plurality of mounting members (73, 74, 119, 120, and 144) arranged between the support member and the case, wherein in a plan view or a bottom view, the plurality of mounting members is arranged on an opposite side of the hull with a virtual line interposed therebetween, the virtual line passing through a center of an output shaft (49) of the electric motor and being parallel to the attachment shaft.

According to this aspect, by arranging the plurality of mounting members on the opposite side of the hull with the virtual line (the line passing through the center of the output shaft of the electric motor, which is a heavy object) interposed therebetween, the support member can stably support the case via the plurality of mounting members. Accordingly, it is possible to effectively reduce vibrations of the propulsion device for the water-surface movable body.

In the above aspect, preferably, the case includes: an upper case (21) that accommodates the electric motor; and a lower case (22) rotatably supported by the upper case and supporting the propulsor, the plurality of mounting members includes: at least one upper mounting member (73) attached to an upper surface of the upper case; and at least one lower mounting member (74) attached to a lower end of the upper case, and at least a portion of the upper mounting member overlaps with the electric motor in the plan view.

According to this aspect, by arranging the plurality of mounting members so as to sandwich the upper case from above and below, the support member can more stably support the case via the plurality of mounting members. Accordingly, it is possible to more effectively reduce the vibrations of the propulsion device for the water-surface movable body.

In the above aspect, preferably, the at least one upper mounting member comprises a pair of upper mounting members, the at least one lower mounting member comprises a pair of lower mounting members, and a gap between the pair of lower mounting members is wider than a gap between the pair of upper mounting members.

According to this aspect, by widening the gap between the pair of lower mounting members that receive the load of the upper case, the swing of the propulsion device for the water-surface movable body can be suppressed. Accordingly, it is possible to more effectively reduce the vibrations of the propulsion device for the water-surface movable body.

In the above aspect, preferably, the upper case comprises: a motor case (24) that accommodates the electric motor; and a lower bracket (25) formed separately from the motor case and attached to a lower end of the motor case, the upper mounting member is attached to the motor case, and the lower mounting member is attached to the lower bracket.

According to this aspect, the lower mounting member is attached to the lower bracket, which is formed separately from the motor case. Accordingly, an attachment position of the lower mounting member can be easily adjusted without being restricted by the shape of the motor case.

In the above aspect, preferably, the support member comprises: a base plate (81) that extends in an up-and-down direction; an upper stay (83) that extends from an upper end of the base plate toward the opposite side of the hull; and a lower stay (84) that extends from a lower end of the base plate toward the opposite side of the hull, the upper mounting member is attached to a tip of the upper stay, and the lower mounting member is attached to a tip of the lower stay.

According to this aspect, by using the support member having a simple structure, the upper mounting member and the lower mounting member can be arranged on the opposite side of the hull with the virtual line interposed therebetween.

In the above aspect, preferably, a position and a spring constant of each of the plurality of mounting members are set so that an elastic center of the propulsion device for the water-surface movable body coincides with a center of gravity of the propulsion device for the water-surface movable body.

According to this aspect, resonance in the six degrees of freedom-forward/back, left/right, up/down, yaw, pitch, and roll-occurs independently at each frequency without affecting each other. In other words, resonance in the six degrees of freedom can be unrelated to each other. Accordingly, it is possible to suppress the amplification of vibrations of degrees of freedom that are not related to the input form, and further effectively reduce a couple (a couple that arises according to the distance between the elastic center and the center of gravity) acting on the plurality of mounting members. Accordingly, the vibrations of the propulsion device for the water-surface movable body can be further effectively reduced. Furthermore, when the vibration-proof properties of the mounting structure are designed, characteristics such as the spring constant can be designed separately for each direction, which makes it easier to design the characteristics.

In the above aspect, preferably, the plurality of mounting members comprises: a pair of first side mounting members (119) attached to both side surfaces of the case; and a pair of second side mounting members (120) attached to both the side surfaces of the case and arranged lower than the pair of first side mounting members.

According to this aspect, by arranging the plurality of mounting members so as to sandwich the upper case from both sides, the support member can more stably support the case via the plurality of mounting members. Accordingly, it is possible to more effectively reduce the vibrations of the propulsion device for the water-surface movable body.

In the above aspect, preferably, a center of gravity of the propulsion device for the water-surface movable body is arranged within an area surrounded by the plurality of mounting members.

According to this aspect, the mounting structure with the center of gravity support method can effectively reduce the vibrations of the propulsion device for the water-surface movable body.

In the above aspect, preferably, at least a portion of the plurality of mounting members is arranged on a principal axis of inertia of the propulsion device for the water-surface movable body.

According to this aspect, the mounting structure with the principal axis of inertia support method can effectively reduce the vibrations of the propulsion device for the water-surface movable body.

In the above aspect, preferably, the plurality of mounting members includes a pair of side mounting members (144) attached to both side surfaces of the case, and the pair of side mounting members are arranged on a pitch axis as the principal axis of inertia of the propulsion device for the water-surface movable body.

According to this aspect, the mounting structure with the principal axis of inertia support method can more effectively reduce the vibrations of the propulsion device for the water-surface movable body.

To achieve such an object, another aspect of the present invention provides a propulsion unit (1, 111 and 131) for the water-surface movable body comprising: the propulsion device for the water-surface movable body; and the mounting structure, wherein the propulsion device for the water-surface movable body further comprises a controller (13) configured to control the electric motor, and at least a portion of the controller is arranged behind the electric motor and overlaps with the electric motor in a front view.

According to this aspect, by aligning the electric motor and the controller in the front-and-rear direction, the lateral width of the propulsion device for the water-surface movable body can be reduced. Accordingly, it is possible to make the propulsion device for the water-surface movable body more compact.

Thus, according to the above aspects, it is possible to effectively reduce the vibrations of the propulsion device for the water-surface movable body using the electric motor as a driving source.

BRIEF DESCRIPTION OF THE DRAWING(S)

FIG. 1 is a side view showing a propulsion unit according to the first embodiment;

FIG. 2 is a cross-sectional view showing an outboard motor according to the first embodiment;

FIG. 3 is a perspective view showing a motor case according to the first embodiment;

FIG. 4 is a perspective view showing a lower bracket according to the first embodiment;

FIG. 5 is a front view showing a positional relationship between an electric motor and a controller according to the first embodiment;

FIG. 6 is a perspective view showing a support member according to the first embodiment;

FIG. 7 is a plan view showing the propulsion unit according to the first embodiment;

FIG. 8 is a bottom view showing the propulsion unit according to the first embodiment;

FIG. 9A is a cross-sectional view showing an upper mounting member and the surroundings thereof according to the first embodiment;

FIG. 9B is an IXB-IXB cross-sectional view of FIG. 9A;

FIG. 10A is a side view of a propulsion unit according to the second embodiment;

FIG. 10B is a rear view of the propulsion unit according to the second embodiment;

FIG. 10C is a plan view of the propulsion unit according to the second embodiment;

FIG. 11A is a side view of a propulsion unit according to the third embodiment;

FIG. 11B is a rear view of the propulsion unit according to the third embodiment; and

FIG. 11C is a plan view of the propulsion unit according to the third embodiment.

DETAILED DESCRIPTION OF THE INVENTION

First Embodiment

Hereinafter, with reference to FIGS. 1 to 9, a propulsion unit 1 for a water-surface movable body (hereinafter, abbreviated as “the propulsion unit 1”) according to the first embodiment of the present invention will be described. The arrow Fr in the figures indicates the front of the propulsion unit 1.

With reference to FIG. 1, the propulsion unit 1 is attached to a hull 4 of a ship 3 (an example of a water-surface movable body) such as a boat so as to apply a propulsion force to the ship 3. The propulsion unit 1 includes an outboard motor 6 (an example of a propulsion device for a water-surface movable body) disposed outside the hull 4, and a mounting structure 7 for mounting the outboard motor 6 to the hull 4. In the following, the outboard motor 6 and the mounting structure 7 will be described one by one.

<Outboard Motor 6>

With reference to FIG. 2, the outboard motor 6 comprises a case 11, an electric motor 12 accommodated in the case 11, a controller 13 configured to control the electric motor 12, a propulsor 14 supported by the case 11 and configured to rotate around a propulsion axis X1 by a driving force of the electric motor 12, a drive shaft 15 provided in a driving force transmission path R that leads from the electric motor 12 to the propulsor 14 and extending along a rotation axis X2, a bevel gear mechanism 16 that connects the drive shaft 15 and the propulsor 14, and a deceleration mechanism 17 provided in the driving force transmission path R and configured to decelerate a rotation of the electric motor 12. In the following, a description will be given based on a state where the propulsion axis X1 extends in the front-and-rear direction and the rotation axis X2 extends in a vertical direction (see FIG. 2).

<Case 11>

With reference to FIGS. 1 and 2, the case 11 includes an upper case 21 and a lower case 22 rotatably supported around the rotation axis X2 by the upper case 21.

The upper case 21 includes a motor case 24, a lower bracket 25 fixed to a lower end of the motor case 24, and a control case 26 fixed to the upper rear part of the motor case 24.

With reference to FIG. 3, the motor case 24 includes a cylindrical circumferential wall 28 extending in the up-and-down direction, and a plate-shaped upper wall 29 closing the upper end of the circumferential wall 28. The upper wall 29 is integrally formed with the circumferential wall 28. A pair of upper pedestals 31 protrude upward from the upper surface of the upper wall 29. The pair of upper pedestals 31 are provided at an interval in the lateral direction. The upper surface of each upper pedestal 31 is provided with an upper fitting groove 32 extending in the front-and-rear direction. The upper surface of each upper pedestal 31 is provided with upper engagement holes 33 on both the left and right sides of the upper fitting groove 32.

With reference to FIG. 4, the lower bracket 25 is formed separately from the motor case 24. The lower bracket 25 has an annular shape. A pair of lower pedestals 35 protrude laterally outward from the lower bracket 25. The pair of lower pedestals 35 are provided at an interval in the lateral direction. The lower surface of each lower pedestal 35 is provided with a lower fitting groove 36 extending in the front-and-rear direction. The lower surface of each lower pedestal 35 is provided with lower engagement holes 37 on both the left and right sides of the lower fitting groove 36.

With reference to FIGS. 1 and 2, the control case 26 is formed separately from the motor case 24. The control case 26 is arranged behind the motor case 24. The control case 26 is arranged on the opposite side of the mounting structure 7 with the motor case 24 interposed therebetween.

The lower case 22 is connected to a steering motor (not shown) and is configured to rotate relative to the upper case 21 around the rotation axis X2 by the driving force of the steering motor. The lower case 22 includes a rotation body 41 and a main body 42 arranged below the rotation body 41.

The rotation body 41 has a cylindrical shape centered on the rotation axis X2. The upper part of the rotation body 41 is accommodated in the motor case 24. The rotation body 41 is attached to the motor case 24 via a plurality of the bearings 44.

The main body 42 is fixed to the rotation body 41. A bullet-shaped gear case 45 extending in the front-and-rear direction is provided at the lower part of the main body 42. A shaft hole 46 extending in the up-and-down direction is provided in the upper part of the main body 42, and an internal space of the gear case 45 communicates with an internal space of the rotation body 41 via the shaft hole 46.

<Electric Motor 12>

With reference to FIG. 2, the electric motor 12 is accommodated in the motor case 24. The electric motor 12 includes a motor body 48 and an output shaft 49 extending downward from the motor body 48.

<Controller 13>

With reference to FIG. 2, the controller 13 is accommodated in the control case 26. The controller 13 consists of a power control unit (PCU). The controller 13 is connected to the electric motor 12 and a battery (not shown), and configured to control the power supply from the battery to the electric motor 12.

With reference to FIG. 5, a portion of the controller 13 is arranged behind the electric motor 12 and overlaps with the electric motor 12 in a front view. In another embodiment, the entire controller 13 may be arranged behind the electric motor 12 and overlap with the electric motor 12 in a front view.

<Propulsor 14>

With reference to FIG. 2, the propulsor 14 is rotatable relative to the lower case 22 around the propulsion axis X1, and is also rotatable integrally with the lower case 22 around the rotation axis X2. The propulsor 14 includes a propeller shaft 51 extending along the propulsion axis X1 and a propeller 52 fixed to the rear part of the propeller shaft 51. A front part of the propeller shaft 51 is rotatably supported by the gear case 45.

<Drive Shaft 15>

With reference to FIG. 2, the drive shaft 15 includes an upper shaft 54 and a lower shaft 55 arranged below the upper shaft 54. The upper end of the upper shaft 54 is fixed to the output shaft 49 of the electric motor 12. This allows the upper shaft 54 to rotate integrally with the output shaft 49 of the electric motor 12. The lower shaft 55 is rotatable relative to the upper shaft 54. The lower shaft 55 penetrates through the shaft hole 46 in the main body 42 of the lower case 22. The lower shaft 55 is rotatably supported by the lower case 22 via a plurality of bearings 57.

<Bevel Gear Mechanism 16>

With reference to FIG. 2, the bevel gear mechanism 16 includes a first bevel gear 61 and a second bevel gear 62 that engages with the first bevel gear 61. The first bevel gear 61 is fixed to the lower end of the lower shaft 55. The second bevel gear 62 is fixed to the front end of the propeller shaft 51.

<Deceleration Mechanism 17>

The deceleration mechanism 17 is accommodated in the rotation body 41 of the lower case 22. The deceleration mechanism 17 consists of, for example, a planetary gear mechanism. An input portion of the deceleration mechanism 17 is fixed to the lower end of the upper shaft 54. An output portion of the deceleration mechanism 17 is fixed to the upper end of the lower shaft 55.

<Function of the Outboard Motor 6>

With reference to FIG. 2, when the output shaft 49 of the electric motor 12 rotates, the rotation of the output shaft 49 is transmitted to the input portion of the deceleration mechanism 17 via the upper shaft 54, and the rotation of the output shaft 49 is decelerated by the deceleration mechanism 17. The decelerated rotation of the output shaft 49 is transmitted from the output portion of the deceleration mechanism 17 to the lower shaft 55, causing the lower shaft 55 to rotate. The rotation of the lower shaft 55 is transmitted to the propulsor 14 via the bevel gear mechanism 16, causing the propulsor 14 to rotate around the propulsion axis X1. Accordingly, a propulsion force is applied to the ship 3, causing the ship 3 to be propelled.

When the motor shaft of the steering motor (not shown) rotates, the rotation of the motor shaft is transmitted to the lower case 22, and the lower case 22 and the propulsor 14 rotate around the rotation axis X2. Accordingly, a turning force is applied to the ship 3, causing the ship 3 to turn.

<Mounting Structure 7>

With reference to FIG. 1, the mounting structure 7 comprises a fixed member 71 fixed to the hull 4, a support member 72 attached to the fixed member 71 and supporting the case 11, and a plurality of mounting members 73 and 74 arranged between the support member 72 and the case 11.

<Fixed Member 71>

With reference to FIGS. 1 and 7, the fixed member 71 includes a main wall 76 extending in the up-and-down direction, and a pair of attachment walls 77 extending forward from the upper end of the main wall 76. The main wall 76 is fixed to the rear end (transom) of the hull 4. The pair of attachment walls 77 are provided at an interval in the lateral direction.

<Support Member 72>

With reference to FIGS. 1 and 6, the support member 72 includes a base plate 81 extending in the up-and-down direction, an arm 82 extending forward (towards the hull 4) from the upper end of the base plate 81, an upper stay 83 extending backward (the opposite side of the hull 4) from the upper end of the base plate 81, and the lower stay 84 extending backward (the opposite side of the hull 4) from the lower end of the base plate 81.

With reference to FIG. 7, a pair of attachment pieces 86 are provided on the front end (the tip) of the arm 82. The pair of attachment pieces 86 are arranged inside the pair of attachment walls 77 of the fixed member 71 in the lateral direction. An attachment shaft 87 (the tilt shaft) extending in the lateral direction penetrates through the pair of attachment pieces 86 and the pair of attachment walls 77. Accordingly, the support member 72 is attached to the fixed member 71 via the attachment shaft 87, and the outboard motor 6 and the support member 72 are tiltable relative to the hull 4 and the fixed member 71 around the attachment shaft 87.

With reference to FIG. 6, a pair of upper bosses 88 are provided at the rear end (the tip) of the upper stay 83. The pair of upper bosses 88 are provided at an interval in the lateral direction. An upper bolt hole 89 is provided on the rear surface of each upper boss 88.

A pair of lower bosses 91 are provided at the rear end (the tip) of the lower stay 84. The pair of lower bosses 91 are provided at an interval in the lateral direction. A lower bolt hole 92 is provided on the rear surface of each lower boss 91.

<a Plurality of Mounting Members 73 and 74>

With reference to FIGS. 1, 7 and 8, the plurality of mounting members 73 and 74 include a pair of upper mounting members 73 attached to the upper surface of the upper case 21, and a pair of lower mounting members 74 attached to the lower end of the upper case 21. One-dot chain lines V in FIGS. 7 and 8 indicate a virtual line (hereinafter referred to as “the virtual line V”) extending in the lateral direction and parallel to the attachment shaft 87. In the plan and bottom views, the virtual line V passes through the center C of the output shaft 49 of the electric motor 12.

With reference to FIG. 7, the pair of upper mounting members 73 are provided at an interval in the lateral direction. In the plan view, the pair of upper mounting members 73 are arranged on the opposite side of the hull 4 with the virtual line V interposed therebetween. In the plan view, the entirety of each upper mounting member 73 overlaps with the electric motor 12. In another embodiment, only a portion of each upper mounting member 73 may overlap with the electric motor 12 in the plan view.

With reference to FIGS. 9A and 9B, each upper mounting member 73 includes a mounting bolt 94 extending in the front-and-rear direction, a mounting body 95 arranged on the outer circumference of the mounting bolt 94, a mounting cover 96 covering the mounting body 95, and a pair of mounting washers 97 arranged on both the front and rear sides of the mounting body 95. The pair of mounting washers 97 are omitted except in FIG. 9A.

The front end (one axial end) of the mounting bolt 94 engages with the upper bolt hole 89 provided in each upper boss 88 of the upper stay 83 of the support member 72. Accordingly, each upper mounting member 73 is attached to each upper boss 88. A fastening nut 99 engages with the rear end (the other axial end) of the mounting bolt 94. The mounting body 95 and the pair of mounting washers 97 are sandwiched between the fastening nut 99 and each upper boss 88.

The mounting body 95 is generally cylindrical. The mounting body 95 includes an inner cylinder 100, an outer cylinder 101 arranged on the outer circumference of the inner cylinder 100, and an elastic portion 102 arranged between the inner cylinder 100 and the outer cylinder 101. The inner cylinder 100 is fitted onto the outer circumferential surface of the mounting bolt 94. The lower part of the outer cylinder 101 is fitted into the upper fitting groove 32 provided in each upper pedestal 31 of the motor case 24. The elastic portion 102 is made of an elastic material such as rubber. In another embodiment, the mounting body 95 is not limited to the cylindrical shape used in the present embodiment, but may adopt various shapes such as a rectangular shape or a V-shape.

The laterally central part of the mounting cover 96 covers the outer cylinder 101 of the mounting body 95 from above. Attachment bolts 107 penetrate through both the left and right side parts of the mounting cover 96. The attachment bolts 107 engage with respective upper engagement holes 33 provided in each upper pedestal 31 of the motor case 24. Accordingly, each upper mounting member 73 is attached to each upper pedestal 31.

With reference to FIG. 8, the pair of lower mounting members 74 are provided at an interval in the lateral direction. The gap between the pair of lower mounting members 74 in the lateral direction is wider than the gap between the pair of upper mounting members 73 in the lateral direction. In a bottom view, the pair of lower mounting members 74 are arranged on the opposite side of the hull 4 with the virtual line V interposed therebetween. In the bottom view, each lower mounting member 74 does not overlap with the electric motor 12. In another embodiment, a portion or the entirety of each lower mounting member 74 may overlap with the electric motor 12 in the bottom view.

With reference to FIG. 1, the structure of each lower mounting member 74 is similar to the structure of each upper mounting member 73, except that the structure is inverted upside down. The front end (one axial end) of the mounting bolt 94 of each lower mounting member 74 engages with the lower bolt hole 92 (see FIG. 6) provided in each lower boss 91 of the lower stay 84 of the support member 72. Accordingly, each lower mounting member 74 is attached to each lower boss 91.

With reference to FIG. 8, attachment bolts 108 penetrate through both the left and right side parts of the mounting cover 96 of each lower mounting member 74. The attachment bolts 108 engage with respective lower engagement holes 37 (see FIG. 4) provided in each lower pedestal 35 of the lower bracket 25. Accordingly, each lower mounting member 74 is attached to each lower pedestal 35.

<Setting of Positions and Dynamic Spring Constants K1 and K2 of Mounting Members 73 and 74>

With reference to FIG. 1, the positions of the pair of upper mounting members 73 and the pair of lower mounting members 74 in the front-and-rear direction coincide with the position of the center of gravity G of the outboard motor 6 in the front-and-rear direction. In other words, the elastic center of the outboard motor 6 coincides with the center of gravity G of the outboard motor 6 in the front-and-rear direction.

With reference to FIG. 1, the distance from each upper mounting member 73 (here, from the center of each upper mounting member 73) to the center of gravity G of the outboard motor 6 in the up-and-down direction is defined as D1, and the distance from each lower mounting member 74 (here, from the center of each lower mounting member 74) to the center of gravity G of the outboard motor 6 in the up-and-down direction is defined as D2. Furthermore, the dynamic spring constant of each upper mounting member 73 is defined as K1, and the dynamic spring constant of each lower mounting member 74 is defined as K2. The dynamic spring constants K1 and K2 of the plurality of mounting members 73 and 74 are set so as to satisfy the following relational expression (1).

K ⁢ 1 : K ⁢ 2 = D ⁢ 2 : D ⁢ 1 ( 1 )

Accordingly, the position of the elastic center of the outboard motor 6 in the up-and-down direction coincides with the position of the center of gravity G of the outboard motor 6 in the up-and-down direction.

With reference to FIG. 7, the distance from one upper mounting member 73 to the center of gravity G of the outboard motor 6 in the lateral direction is equal to the distance from the other upper mounting member 73 to the center of gravity G of the outboard motor 6 in the lateral direction. With reference to FIG. 8, the distance from one lower mounting member 74 to the center of gravity G of the outboard motor 6 in the lateral direction is equal to the distance from the other lower mounting member 74 to the center of gravity G of the outboard motor 6 in the lateral direction. Accordingly, the position of the elastic center of the outboard motor 6 coincides with the position of the center of gravity G of the outboard motor 6 in the lateral direction.

As described above, the positions and the dynamic spring constants K1 and K2 of the plurality of mounting members 73 and 74 are set so that the elastic center of the outboard motor 6 coincides with the center of gravity G of the outboard motor 6. Note that, with reference to FIG. 7, in the present embodiment, the pair of upper mounting members 73 are arranged symmetrically in the lateral direction, and the dynamic spring constant of one upper mounting member 73 coincides with the dynamic spring constant of the other upper mounting member 73. On the other hand, in another embodiment, due to constraints imposed by the positional relationship with other components, it may not be possible to arrange the pair of upper mounting members 73 symmetrically in the lateral direction. In such a case, the dynamic spring constant of one upper mounting member 73 may be made different from the dynamic spring constant of the other upper mounting member 73 (i.e., a lateral difference in the dynamic spring constants of the pair of upper mounting members 73 may be made), so that the position of the elastic center of the outboard motor 6 is adjusted to coincide with the center of gravity G of the outboard motor 6. The same applies to the pair of lower mounting members 74.

An area Y1 in FIG. 1 indicates the area surrounded by the plurality of mounting members 73 and 74. The positions of the plurality of mounting members 73 and 74 are set so that the center of gravity G of the outboard motor 6 is arranged within the area Y1. That is, the mounting structure 7 adopts the center of gravity support method.

<Effects>

In the plan view or the bottom view, the plurality of mounting members 73 and 74 is arranged on the opposite side of the hull 4 with the virtual line V interposed therebetween. Accordingly, the support member 72 can stably support the case 11 via the plurality of mounting members 73 and 74. Accordingly, the vibrations of the outboard motor 6 can be suitably reduced.

Furthermore, as mentioned above, the mounting structure 7 adopts the center of gravity support method. By adopting the center of gravity support method in this manner, the moment of inertia of the outboard motor 6 becomes small, so that the outboard motor 6 becomes more likely to swing. Accordingly, in the present embodiment, the gap between the pair of lower mounting members 74 in the lateral direction is made wider than the gap between the pair of upper mounting members 73 in the lateral direction, so that the swing of the outboard motor 6 is suppressed. Accordingly, the vibrations of the outboard motor 6 can be suitably reduced.

Modifications

In the present embodiment, the mounting structure 7 includes only the plurality of mounting members 73 and 74 arranged on the opposite side of the hull 4 with the virtual line V interposed therebetween. In another embodiment, the mounting structure 7 may include the plurality of mounting members 73 and 74 arranged on the opposite side of the hull 4 with the virtual line V interposed therebetween, as well as a plurality of mounting members arranged on the same side of the hull 4 relative to the virtual line V (see the third embodiment).

Second Embodiment

Next, with reference to FIGS. 10A to 10C, a propulsion unit 111 for a water-surface movable body (hereinafter abbreviated as “the propulsion unit 111”) according to the second embodiment of the present invention will be described. Description of the contents similar to those of the first embodiment will be omitted as appropriate. Arrows XB and XC in FIG. 10A indicate the line-of-sight directions in FIGS. 10B and 10C, respectively.

The propulsion unit 111 comprises an outboard motor 113 (an example of a propulsion device for the water-surface movable body) arranged outside the hull 4, and a mounting structure 114 for mounting the outboard motor 113 to the hull 4. The configuration of the outboard motor 113 is similar to the configuration of the outboard motor 6 according to the first embodiment, and therefore a description thereof will be omitted.

<Mounting Structure 114>

The mounting structure 114 comprises a fixed member 116 fixed to the hull 4, a support member 118 attached to the fixed member 116 and supporting the upper case 21, and a plurality of mounting members 119 and 120 arranged between the support member 118 and the upper case 21. It should be noted that the fixed member 116 and the support member 118 are omitted in FIGS. 10B and 10C.

The support member 118 is attached to the fixed member 116 via an attachment shaft 121 (a tilt shaft) extending in the lateral direction. Accordingly, the outboard motor 113 and the support member 118 are tiltable relative to the hull 4 and the fixed member 116 around the attachment shaft 121. A one-dot chain line V in FIG. 10C indicates the virtual line (hereinafter referred to as “the virtual line V”) extending in the lateral direction and parallel to the attachment shaft 121. In the plan view, the virtual line V passes through the center C of the output shaft 49 of the electric motor 12.

The plurality of mounting members 119 and 120 include a pair of first side mounting members 119 attached to the upper part of both left and right side surfaces of the upper case 21, and a pair of second side mounting members 120 attached to the lower part of both the left and right side surfaces of the upper case 21 and arranged lower than the pair of first side mounting members 119. In the plan view, the pair of first side mounting members 119 and the pair of second side mounting members 120 are arranged on the opposite side of the hull 4 with the virtual line V interposed therebetween.

An area Y2 in FIG. 10A indicates the area surrounded by the plurality of mounting members 119 and 120. The positions of the plurality of mounting members 119 and 120 are set so that the center of gravity G of the outboard motor 113 is arranged within the area Y2. That is, the mounting structure 114 adopts the center of gravity support method.

Third Embodiment

Next, with reference to FIGS. 11A to 11C, a propulsion unit 131 for a water-surface movable body (hereinafter abbreviated as “the propulsion unit 131”) according to the third embodiment of the present invention will be described. Description of the contents similar to those of the first embodiment will be omitted as appropriate. Arrows XIB and XIC in FIG. 11A indicate the line-of-sight directions in FIGS. 11B and 11C, respectively.

The propulsion unit 131 comprises an outboard motor 133 (an example of a propulsion device for the water-surface movable body) arranged outside the hull 4, and a mounting structure 134 for mounting the outboard motor 133 to the hull 4.

<Outboard Motor 133>

The outboard motor 133 includes three principal axes of inertia I1 to I3. More specifically, the outboard motor 133 includes a roll axis I1 (X-axis) extending in the front-and-rear direction, a pitch axis I2 (Y-axis) extending in the lateral direction, and a yaw axis I3 (Z-axis) extending in the up-and-down direction. The configuration of the outboard motor 133 is similar to the configuration of the outboard motor 6 according to the first embodiment, except for the fact that the upper case 21 and the lower case 22 are fixed (the upper case 21 and the lower case 22 rotate integrally), and therefore a description thereof will be omitted.

<Mounting Structure 134>

The mounting structure 134 comprises a fixed member 136 fixed to the hull 4, a support member 138 attached to the fixed member 136 and supporting the case 11, and a plurality of mounting members 144 to 146 arranged between the support member 138 and the case 11. It should be noted that the fixed member 136 and the support member 138 are omitted in FIGS. 11B and 11C.

The support member 138 includes an attachment portion 140 attached to the fixed member 136 via an attachment shaft 139 (tilt shaft) extending in the lateral direction, and a support portion 142 attached to the attachment portion 140 via a swivel shaft 141 that extends in the up-and-down direction and supporting the case 11. Accordingly, the outboard motor 133 and the support member 138 are tiltable relative to the hull 4 and the fixed member 136 around the attachment shaft 139. Further, the outboard motor 133 and the support portion 142 are rotatable relative to the hull 4, the fixed member 136, and the attachment portion 140 around the swivel shaft 141. A one-dot chain line V in FIG. 11C indicates the virtual line (hereinafter referred to as “the virtual line V”) extending in the lateral direction and parallel to the attachment shaft 139. In the plan view, the virtual line V passes through the center C of the output shaft 49 of the electric motor 12.

The plurality of mounting members 144 to 146 include a pair of side mounting members 144 attached to the left and right side surfaces of the upper case 21, an upper mounting member 145 attached to the front surface of the upper case 21, and a lower mounting member 146 attached to the front surface of the lower case 22. In the plan view, the pair of side mounting members 144 are arranged on the opposite side of the hull 4 with the virtual line V interposed therebetween. The pair of side mounting members 144 are arranged on the pitch axis 12. That is, the mounting structure 134 adopts the principal axis of inertia support method.

The upper mounting member 145 and the lower mounting member 146 are arranged at an interval in the up-and-down direction. In the plan view, the upper mounting member 145 and the lower mounting member 146 are arranged on the same side of the hull 4 relative to the virtual line V.

Modifications

In the present embodiment, the pair of side mounting members 144 are arranged on the pitch axis I2. In another embodiment, a plurality of mounting members may be arranged on the roll axis I1 or the yaw axis I3.

Concrete embodiments of the present invention have been described in the foregoing, but the present invention should not be limited by the foregoing embodiments and various modifications and alterations are possible within the scope of the present invention.