Wheel device device

Abstract

To provide a wheel drive device which can be formed in a small size.SOLUTION: A wheel drive device 10 includes: a motor 30 which rotates a motor shaft 31; a speed reducer 40 which has an input shaft 41 and an output shaft 42 arranged parallel to the motor shaft 31 and decelerates rotation of the input shaft 41; an axle 52 which is arranged parallel to the motor shaft 31 and rotates in conjunction with rotation of the output shaft 42 of the speed reducer 40; and a frame 20 which holds the motor 30, the speed reducer 40, and the axle 52. In a first direction perpendicular to the motor shaft 31, the motor 30, the speed reducer 40, and the axle 52 are lined up. The structure can achieve downsizing of the wheel drive device.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] This invention relates to a wheel drive device used for a moving body or the like.

Background Art

[0002] In a moving body or the like traveling on a road surface, a wheel drive device in which a motor and a speed reducer are unitized may be used (for example, see Patent Document 1 below).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in an object such as a moving body to which a wheel drive device is attached, there are various needs, for example, a need to miniaturize the object as a whole, or a need to arrange the wheel drive device in a specific limited space. In order to meet such various needs, various wheel drive devices with a layout of each component devised are required.

[0005] An object of this invention is to provide a wheel drive device that can be configured to be small.

Means for Solving the Problems

[0006] The wheel drive device of this first invention includes a motor that rotates a motor shaft, a speed reducer having an input shaft and an output shaft parallel to the motor shaft and that decelerates the rotation of the input shaft, an axle that is parallel to the motor shaft and rotates with the rotation of the output shaft of the speed reducer, and a frame that holds the motor, the speed reducer, and the axle so that the motor, the speed reducer, and the axle are arranged in a first direction perpendicular to the motor shaft.

[0007] With such a configuration, the wheel drive device can be made compact.

[0008] Further, the wheel drive device of the second invention includes, with respect to the first invention, a first transmission structure that transmits rotational force from the motor shaft to the input shaft by an endless flexible member, and a second transmission structure that transmits rotational force from the output shaft to the axle by an endless flexible member.

[0009] With such a configuration, a speed reducer with a relatively small load-bearing capacity in a direction perpendicular to the output shaft can be used, and a wheel drive device with a large load-bearing capacity can be made compact.

[0010] Further, the wheel drive device of the third invention includes, with respect to the second invention, an input shaft that protrudes from the main body of the speed reducer in a second direction parallel to the motor shaft, and an output shaft that protrudes from the main body of the speed reducer in a direction opposite to the direction in which the input shaft protrudes in the second direction.

[0011] With such a configuration, the maintainability of the wheel drive device can be improved.

[0012] Further, the wheel drive device of the fourth invention includes, with respect to any one of the first to third inventions, a base portion located farther from the motor than the axle in the first direction, and a suspension device configured to support the base portion with respect to the frame in the first direction. The suspension device has a spring disposed at a position farther from the base portion than the axle in the first direction.

[0013] With such a configuration, the center of gravity of the object to which the wheel drive device is applied can be made relatively low, and vibrations from the road surface can be buffered so as not to be directly transmitted to the base portion side.

[0014] Further, the wheel drive device of the fifth invention is a wheel drive device in which, with respect to the fourth invention, two or more suspension devices are provided, and when viewed from the first direction, an axle is disposed between at least one suspension device and at least one other suspension device among the two or more suspension devices.

[0015] With such a configuration, the base portion side can be supported in a well-balanced manner with respect to the frame.

[0016] Further, the wheel drive device of the sixth invention is a wheel drive device including a linear guide structure that guides the frame and the base portion so as to approach or separate from each other in the first direction, with respect to the fourth or fifth invention.

[0017] With such a configuration, the base portion side can be firmly supported with respect to the frame.

[0018] Further, the wheel drive device of the seventh invention is a wheel drive device in which, with respect to any one of the fourth to sixth inventions, the suspension device has a first contact portion fixed to the base portion and located at a position away from the base portion in the first direction, and a second contact portion provided on the frame and located closer to the base portion than the first contact portion in the first direction, and the spring is disposed so as to be sandwiched between the first contact portion and the second contact portion, and is configured to be compressed as the base portion moves away from the frame in the first direction.

[0019] With such a configuration, while reliably obtaining a vibration damping effect, the center of gravity of the object to which the wheel drive device is applied can be made relatively low.

Advantages of the Invention

[0020] According to the present invention, a wheel drive device that can be configured to be small can be provided.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0022] Hereinafter, embodiments of the wheel drive device will be described with reference to the drawings. In the following description, the coordinates shown in the drawings are common to each drawing. The Z direction of the coordinates is a direction perpendicular to the horizontal plane. The X direction is a direction perpendicular to the Z direction and is a direction perpendicular to each rotation axis described later. The Y direction is a direction perpendicular to the Z direction and is a direction perpendicular to the X direction. That is, the Y direction is a direction perpendicular to each rotation axis described later. Note that the Z direction may be referred to as the "vertical direction" (the direction that is positive on the Z axis when viewed from the origin is up) or the first direction, the X direction may be referred to as the "front-rear direction" (the direction that is positive on the X axis when viewed from the origin is rear), and the Y direction may be referred to as the "left-right direction" (the direction that is positive on the Y axis when viewed from the origin is left) or the second direction. Also, for each rotation axis, the direction along the rotation axis may be referred to as the "axial direction", and the direction perpendicular to the rotation axis may be referred to as the "radial direction". In the following, the shapes and positional relationships of each part may be described by indicating each direction in this way, but these are defined only for the convenience of explanation and do not limit the orientation and posture of the wheel drive device according to the present invention during use. Also, the expressions indicating directions and the expressions indicating states such as horizontal, vertical, and orthogonal only indicate that they can be roughly understood in that way, and it is not always necessary to be strictly interpreted as being exactly as the expression.

[0023] (Embodiment)

[0024] First, a moving body 1 which is an example of an object to which the wheel drive device 10 according to the present embodiment is applied will be described.

[0025] FIG. 1 is a perspective view showing a schematic configuration of a moving body 1 having a wheel drive device 10 according to one embodiment of the present invention.

[0026] In FIG. 1, detailed shapes of the wheel drive device 10 and other components are not shown.

[0027] The moving body 1 is, for example, capable of traveling on a floor and is used for transporting an object to be transported. The moving body 1 transporting the object to be transported may, for example, transport the object to be transported loaded on the moving body 1 itself, or the moving body 1 may tow a transport cart on which the object to be transported is loaded. The moving body 1 may move following a target to be followed. Note that the moving body 1 may be used for other purposes. The moving body 1 may be, for example, a moving body for guidance, guarding, monitoring, entertainment, etc. That is, the moving body 1 may be a transport robot, a guiding robot, a guarding robot, a monitoring robot, an entertainment robot, etc. The moving body 1 may move, for example, indoors, outdoors, or both.

[0028] As shown in the figure, the moving body 1 includes, for example, a vehicle body 2, four wheels 5, two steering devices 8, and two wheel drive devices 10. The vehicle body 2 is, for example, substantially rectangular in plan view. Two steering devices 8 are arranged on the left and right of the front side of the vehicle body 2. Two wheel drive devices 10 are arranged on the left and right of the rear side of the vehicle body 2. Wheels 5 are attached to the steering device 8 and the wheel drive device 10, respectively, and the four wheels 5 are in contact with the ground, enabling the moving body 1 to travel on the ground surface. The moving body 1 can move forward and backward by the wheel drive device 10 rotating the two wheels 5. Also, the moving direction of the moving body 1 can be changed by the steering device 8 changing the directions of the two wheels 5. Note that the moving body 1 may be configured to turn by causing a rotational difference in the driven wheels 5. Also, the number, arrangement, steerability, and drivability of the wheels 5 are not limited to this. Three or more wheels may be drivable by the wheel drive device 10.

[0029] Although details will be described later, in the present embodiment, the wheel drive device 10 has a suspension device 80 (shown in FIG. 2). It can be said that the wheel drive device 10 is divided into a base portion 11 on the side attached to the vehicle body 2 and a spring lower portion 12 on the side to which the wheel 5 is attached, with the suspension device 80 as a boundary. The base portion 11 is suspended from the spring lower portion 12 via the suspension device 80. That is, the vehicle body 2 can travel in a state of being suspended with respect to the two wheel drive devices 10 at the rear portion of the moving body 1. Note that the suspension device 80 may not be provided.

[0030] As will be described later, the wheel drive device 10 is configured in a vertically long shape in which main components are arranged in the vertical direction (first direction). Therefore, in a plan view, the area occupied by the wheel drive device 10 in the moving body 1 is relatively small. In other words, in a plan view, a wide area where the wheel drive device 10 is not arranged can be secured in the vehicle body 2.

[0031] Next, details of the wheel drive device 10 will be described. In the following description, one of the configurations of the wheel drive devices 10 provided on the left and right in the above-described moving body 1 will be described. As the other wheel drive device 10, one having a symmetric configuration may be used, or one having the same configuration may be used with its orientation changed.

[0032] FIG. 2 is a perspective view of the wheel drive device 10. FIG. 3 is a front view of the wheel drive device 10. FIG. 4 is a right side view of the wheel drive device 10. FIG. 5 is a left side view of the wheel drive device 10. FIG. 6 is a plan view of the wheel drive device 10.

[0033] The wheel drive device 10 has a base portion 11, a spring lower portion 12, and a suspension device 80. The base portion 11 and the spring lower portion 12 are connected via the suspension device 80. The spring lower portion 12 may be said to be a support portion that supports the vehicle body 2. Note that in the present embodiment, a linear motion guide structure 90 is provided between the base portion 11 and the spring lower portion 12.

[0034] In the present embodiment, the lower part of the spring 12 includes a frame 20, a motor 30, a speed reducer 40, an axle portion 50, a first transmission structure 60, and a second transmission structure 70.

[0035] The motor 30 is, for example, an inner rotor type servo motor, but may be another type of motor such as a brushless DC motor. The motor 30 is driven by, for example, a drive circuit (not shown) to rotate the motor shaft 31. The motor 30 is used as a power source for rotating the axle 52.

[0036] The speed reducer 40 is provided at the subsequent stage of the motor 30, and decelerates the rotation of the motor 30 and outputs it to the subsequent stage. The type of the speed reducer 40 is not limited. The reduction ratio of the speed reducer 40 can be set as appropriate. The speed reducer 40 may be capable of changing the reduction ratio to perform speed change.

[0037] The speed reducer 40 has an input shaft 41 and an output shaft 42. The input shaft 41 and the output shaft 42 are parallel to each other. The input shaft 41 and the output shaft 42 are provided so as to protrude from a speed reducer main body 45 having a built-in speed reduction mechanism. In the present embodiment, the tip of the input shaft 41 and the tip of the output shaft 42 are located on opposite sides in the axial direction when viewed from the speed reducer main body 45. In other words, the speed reducer main body 45 is located between the tip of the input shaft 41 and the tip of the output shaft 42 in the axial direction. It may be said that the input shaft 41 and the output shaft 42 protrude from the speed reducer main body 45 in different directions from each other.

[0038] In the present embodiment, the input shaft 41 and the output shaft 42 are arranged coaxially. As the speed reducer 40, for example, a planetary speed reducer can be used.

[0039] The axle portion 50 is provided at the subsequent stage of the speed reducer 40. The axle portion 50 has an axle 52 and a bearing portion 55 that holds the axle 52. The axle 52 rotates by the rotational force transmitted from the output shaft 42 of the speed reducer 40 as will be described later. That is, the axle 52 rotates as the output shaft 42 of the speed reducer 40 rotates.

[0040] The wheel 5 is attached to the axle 52. The wheel 5 usually has a tire that contacts the ground surface, but is not limited thereto. For example, a sprocket that rotates an endless track may be attached to the axle 52 as the wheel 5.

[0041] The frame 20 holds the motor 30, the speed reducer 40, and the axle 52. In the present embodiment, the motor shaft 31, the input shaft 41, the output shaft 42, and the axle 52 are parallel to each other. Each of the rotating shafts 31, 41, 42, 52 is parallel in the left - right direction (second direction).

[0042] Also, in the present embodiment, the frame 20 is configured to hold the motor 30, the speed reducer 40, and the axle 52 such that the motor 30, the speed reducer 40, and the axle 52 are arranged in the vertical direction. Specifically, for example, from above to below, the motor 30, the speed reducer 40, and the axle 52 are arranged in this order. The speed reducer 40 is located below the motor 30, and the axle 52 is located below the speed reducer 40.

[0043] In the present embodiment, the tip of the motor shaft 31 and the tip of the input shaft 41 are located on the left - hand side surface, and the tip of the output shaft 42 and the tip of the axle 52 are located on the right - hand side surface.

[0044] The frame 20 is configured, for example, by combining a lower first frame 21, an upper second frame 22, and a pillar portion 23 that connects the first frame 21 and the second frame 22. Note that the configuration of the frame 20 is not limited thereto, and for example, a monocoque - structured housing may be called a frame.

[0045] In the present embodiment, the first frame 21 is, for example, a plate - shaped member substantially parallel to the horizontal plane. A bearing portion 55 is fixed to the lower side of the first frame 21. That is, the axle 52 is held by the first frame 21.

[0046] Further, the second frame 22 is, for example, a plate-shaped member. The second frame 22 is held above the first frame 21 by a column portion 23 erected on the first frame 21. A motor 30 is fixed to the upper portion of the second frame 22. Further, a speed reducer 40 is fixed to the lower surface of the second frame 22.

[0047] Due to the frame 20 having such a two-layer structure, the motor 30, the speed reducer 40, and the axle 52 are arranged side by side at a distance from each other in the vertical direction.

[0048] The first transmission structure 60 transmits the rotational force from the motor shaft 31 to the input shaft 41. In the present embodiment, the first transmission structure 60 has a first sprocket 61, a second sprocket 62, and an endless flexible member 65.

[0049] In the present embodiment, the first transmission structure 60 is configured using a chain as the endless flexible member 65. That is, the first sprocket 61 is fixed to the motor shaft 31. The second sprocket 62 is fixed to the input shaft 41. The endless flexible member 65 is hung on the first sprocket 61 and the second sprocket 62. Thereby, the rotational force of the motor 30 is transmitted to the input shaft 41. The first transmission structure 60 is arranged on the left side surface side.

[0050] Note that the first transmission structure 60 has a first idler 63. The first idler 63 is arranged to maintain the tension of the endless flexible member 65. The first idler 63 may be a tensioner biased by a spring or the like, or may be fixed at an adjusted position during normal times. The first idler 63 may not be provided.

[0051] The second transmission structure 70 transmits the rotational force from the output shaft 42 to the axle 52. In the present embodiment, the second transmission structure 70 has a third sprocket 71, a fourth sprocket 72, and an endless flexible member 75.

[0052] In this embodiment, the second transmission structure 70 is configured using a chain as the endless flexible member 75. That is, the third sprocket 71 is fixed to the output shaft 42. The fourth sprocket 72 is fixed to the axle 52. The endless flexible member 75 is wound around the third sprocket 71 and the fourth sprocket 72. Thereby, the rotational force of the output shaft 42 is transmitted to the axle 52. The second transmission structure 70 is disposed on the right side surface side.

[0053] Note that the second transmission structure 70 has a second idler 73. The second idler 73 is disposed to maintain the tension of the endless flexible member 75. The second idler 73 may be a tensioner biased by a spring or the like, or may be fixed at an adjusted position during normal times. The second idler 73 may not be provided.

[0054] Note that the transmission structures 60 and 70 are not limited to those including sprockets 61, 62, 71, and 72 fixed to rotating shafts and endless flexible members 65 and 75 that are chains. For example, as the endless flexible members 65 and 75, belts made of rubber or synthetic resin may be used. In this case, pulleys around which the belts are wound may be attached to the respective rotating shafts.

[0055] The base portion 11 is disposed below the spring lower portion 12 including each part held by the frame 20 as described above. The base portion 11 is, for example, a plate-like member and is disposed substantially parallel to the horizontal plane. The base portion 11 is disposed below the axle 52. That is, the base portion 11 is located farther from the motor 30 than the axle 52 in the vertical direction. Note that the shape and configuration of the base portion 11 are not limited to this. For example, a base portion 11 having a shape in which a part of the spring lower portion 12 such as the axle 52 can be located is chipped or recessed due to a change in the relative position between the spring lower portion 12 and the base portion 11 may be used.

[0056] The suspension device 80 is arranged such that at least a part thereof is positioned between the base portion 11 and the lower spring portion 12 in the vertical direction. The suspension device 80 is configured to support the base portion 11 with respect to the frame 20 in the vertical direction. In the present embodiment, the suspension device 80 holds the base portion 11 in a suspended state with respect to the frame 20 so that the base portion 11 does not move too far away from the frame 20 in the vertical direction.

[0057] Two suspension devices 80 are provided. When viewed from above, an axle 52 is arranged between the two suspension devices 80. It can also be said that the axle 52 is arranged between the two springs 81. Thereby, the load from the base portion 11 can be supported in a well-balanced manner with respect to the axle 52 to which the wheel 5 in contact with the ground is attached. Note that three or more suspension devices 80 may be provided. In this case, it is sufficient that the axle 52 is arranged between at least one suspension device 80 and another suspension device 80. Note that only one suspension device 80 may be provided.

[0058] In the present embodiment, the suspension device 80 is configured using a spring 81 which is, for example, a compression coil spring. That is, the suspension device 80 includes the spring 81, a first contact portion 82, and a second contact portion 86.

[0059] The first contact portion 82 is fixed to the base portion 11. The first contact portion 82 is located at a position away from the base portion 11 upward. In the present embodiment, the first contact portion 82 is located above the first frame 21. The first contact portion 82 is above the axle 52. The first contact portion 82 has, for example, a rod 85 extending upward from the base portion 11, and is configured to be able to contact the upper end portion of the spring 81 by a dish-shaped member fixed to the rod 85.

[0060] The second abutting portion 86 is provided on the frame 20. The second abutting portion 86 is located closer to the base portion 11 than the first abutting portion 82 in the vertical direction, that is, below the first abutting portion 82. In the present embodiment, the second abutting portion 86 is a part of the upper surface of the first frame 21, but is not limited thereto. For example, a dish-shaped member may be fixed to the first frame 21 to form the second abutting portion 86. The second abutting portion 86 can contact the lower end portion of the spring 81.

[0061] The spring 81 is disposed sandwiched between the first abutting portion 82 and the second abutting portion 86 in the vertical direction. The spring 81 is disposed at a position farther from the base portion 11 than the axle 52 in the vertical direction, that is, above the axle 52. The spring 81 is disposed above the first frame 21.

[0062] The suspension device 80 configured as described above is configured such that the spring 81 is compressed as the base portion 11 moves away from the frame 20 in the vertical direction. That is, as the base portion 11 is displaced downward with respect to the spring lower portion 12 that contacts the ground surface, the spring 81 is compressed and the repulsive force of the spring 81 increases. Therefore, the base portion 11 is held so that the base portion 11 does not displace downward too much with respect to the spring lower portion 12. Since the base portion 11 is held via the suspension device 80 in this way, it is possible to prevent vibrations applied to the spring lower portion 12 from being directly transmitted to the base portion 11.

[0063] In the present embodiment, the suspension device 80 has a damper (shock absorber) 84. The damper 84 is fixed to the first frame 21, for example, such that the rod 85 penetrates therethrough. A piston is provided on the rod 85, and is configured to absorb shocks and attenuate vibrations by the resistance force generated when the piston moves inside the damper 84. That is, the damper 84 and the rod 85 constitute a through-rod type shock absorber. By using the wheel drive device 10 using such a damper 84, it becomes possible to attenuate vibrations and travel smoothly. Note that the damper 84 may not be provided.

[0064] Further, the suspension device 80 may use other types of springs as the spring 81. For example, a structure that supports a load using a disc spring may be used.

[0065] The linear guide structure 90 guides the frame 20 and the base portion 11 so that they approach and separate from each other in the vertical direction. The linear guide structure 90 includes, for example, a shaft 91 fixed to the base portion 11 and a linear bearing 92 fixed to the frame 20. In the present embodiment, the linear bearing 92 is, for example, a linear bushing or a non-lubricating bushing and is fixed to the first frame 21. The shaft 91 is arranged such that its longitudinal direction is the vertical direction. The linear bearing 92 is movable along the shaft 91 while holding the shaft 91. By providing, for example, two sets of such linear guide structures 90, the base portion 11 can be displaced only in the vertical direction with respect to the frame 20.

[0066] By using such a linear guide structure 90 together with the suspension device 80, a wheel drive device 10 can be configured to reliably suppress the transmission of impacts in the vertical direction.

[0067] Note that the shaft 91 may be attached to the frame 20 and the linear bearing 92 may be attached to the base portion 11. Further, as the linear guide structure 90, a structure using a linear guide having a rail arranged along the vertical direction may be used. Further, the linear guide structure 90 may not be used.

[0068] As described above, in the present embodiment, in the vertical direction, the motor 30, the speed reducer 40, and the axle 52 are arranged side by side, so that the wheel drive device 10 is configured to be vertically long as a whole. The area occupied by the wheel drive device 10 in a top view can be made relatively small.

[0069] A small-sized speed reducer 40 that does not require a bulky gear such as a bevel gear and has a small radial dimension centered on the input shaft 41 and the output shaft 42 can obtain the required reduction ratio. Therefore, the wheel drive device 10 can be configured to be relatively small-sized.

[0070] Since the transmission structures 60 and 70 are configured using endless flexible members 65 and 75, maintenance work can be easily performed. Even if an impact is applied to the axle 52 during traveling or the like, the impact is less likely to be transmitted to the upper speed reducer 40 and the motor 30, so the durability of the wheel drive device 10 can be improved.

[0071] The input shaft 41 protrudes leftward from the speed reducer main body 45, and the output shaft 42 protrudes rightward from the speed reducer main body 45, that is, in a direction opposite to the direction in which the input shaft 41 protrudes in the left-right direction. Since the first transmission structure 60 is arranged on the left side surface and the second transmission structure 70 is arranged on the right side surface, the height of the wheel drive device 10 can be kept low. In addition, since the first transmission structure 60 and the second transmission structure 70 can be independently adjusted, the workability during maintenance work can be improved.

[0072] (Others) The present invention is not limited to the above embodiments, and various modifications are possible, and they are also included in the scope of the present invention.

[0073] Among the above-described embodiments, some components may be omitted. For example, the wheel drive device may not have a suspension device and a base portion. Further, a part of the object to which the wheel drive device is attached may be regarded as a base portion, and in this case, it is preferable that the object is supported by the frame side by the suspension device.

Industrial Applicability

[0074] As described above, the wheel drive device according to the present invention has an effect that it can be configured to be small-sized and is useful as a wheel drive device or the like.

Explanation of Reference Numerals

[0075] 1 Moving body 5 Wheels 10 Wheel drive device 11 Base part 20 Frame 30 Motor 31 Motor shaft 40 Reducer 41 Input shaft 42 Output shaft 45 Body of the reducer 52 Axle 60 First transmission structure 65, 75 Endless flexible member 70 Second transmission structure 80 Suspension device 81 Spring 82 First contact part 86 Second contact part 90 Linear guide structure 91 Shaft 92 Linear bearing

Claims

1. A motor that rotates a motor shaft, A speed reducer having an input shaft and an output shaft parallel to the motor shaft, and reducing the rotation of the input shaft, An axle that is parallel to the motor shaft and rotates with the rotation of the output shaft of the speed reducer, A wheel drive device comprising: a frame that holds the motor, the speed reducer, and the axle such that the motor, the speed reducer, and the axle are arranged in a first direction perpendicular to the motor shaft.

2. A first transmission structure that transmits a rotational force from the motor shaft to the input shaft by an endless flexible member, The wheel drive device according to claim 1, further comprising a second transmission structure that transmits a rotational force from the output shaft to the axle by an endless flexible member.

3. The input shaft protrudes from the main body of the speed reducer in a second direction parallel to the motor shaft, The wheel drive device according to claim 2, wherein the output shaft protrudes from the main body of the speed reducer in a direction opposite to the direction in which the input shaft protrudes in the second direction.

4. A base portion located farther from the motor than the axle in the first direction, A suspension device configured to support the base portion with respect to the frame in the first direction, The wheel drive device according to claim 1, wherein the suspension device has a spring disposed at a position farther from the base portion than the axle in the first direction.

5. Two or more of the suspension devices are provided, The wheel drive device according to claim 4, wherein the axle is disposed between at least one of the two or more suspension devices and at least one other of the two or more suspension devices when viewed from the first direction.

6. The wheel drive device according to claim 4, further comprising a linear guide structure that guides the frame and the base portion to approach and separate from each other in the first direction.

7. The suspension device, A first contact portion fixed to the base portion and located away from the base portion in the first direction, A second contact portion provided on the frame and located closer to the base portion than the first contact portion in the first direction, The wheel drive device according to claim 4, wherein the spring is disposed between the first contact portion and the second contact portion and is configured to be compressed as the base portion moves away from the frame in the first direction.

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