CN114051472A

CN114051472A - Wheel drive device and maintenance method for wheel drive device

Info

Publication number: CN114051472A
Application number: CN202080048418.3A
Authority: CN
Inventors: 德田贵司; 栗本直彰
Original assignee: Sumitomo Heavy Industries Ltd
Current assignee: Sumitomo Heavy Industries Ltd
Priority date: 2019-07-11
Filing date: 2020-07-06
Publication date: 2022-02-15
Also published as: WO2021006246A1; JP2021014168A; DE112020003320T5; JP7348764B2

Abstract

A wheel driving device (100) according to an embodiment of the present invention includes: a motor (20); a speed reducer (30) that reduces the rotation of the motor (20); and a wheel (40) driven by the output rotation of the speed reducer (30), wherein the motor (20) and the speed reducer (30) are arranged so as to overlap each other when viewed in a direction orthogonal to the axial direction, the motor (20) is arranged so that the rear portion (20b) side thereof faces the outside of the vehicle body, and a replacement member (50) that can be detached from the motor (20) is attached to the rear portion (20b) of the motor (20).

Description

Wheel drive device and maintenance method for wheel drive device

Technical Field

The present invention relates to a wheel drive device and a maintenance method for the wheel drive device.

Background

There is known a wheel driving device for driving wheels of a transport carriage or the like. The present applicant discloses a wheel driving device in patent document 1. The wheel driving device includes a speed reduction mechanism for reducing the speed of rotation transmitted from a driving source, a rotating body to which the rotation reduced by the speed reduction mechanism is transmitted, and a wheel integrated with the rotating body. In this wheel drive device, the output shaft of the drive source is directly coupled to the input shaft of the reduction mechanism.

Prior art documents

Patent document

Patent document 1: japanese patent laid-open publication No. 2018-144778

Disclosure of Invention

Technical problem to be solved by the invention

The present inventors have obtained the following knowledge about a wheel drive apparatus.

In the wheel driving device, the structure of directly coupling the motor for rotationally driving the input shaft of the speed reduction mechanism and the input shaft of the speed reduction mechanism has the following disadvantages: the axial length is not good for miniaturization. Further, since the rear portion of the motor is disposed toward the inside of the vehicle body, there is a problem in that the maintainability of the replacement member attached to the rear portion of the motor is poor.

As a result, the present inventors have recognized that the conventional wheel drive device has room for improvement in terms of downsizing and improvement in maintainability.

The present invention has been made in view of the above problems, and an object thereof is to provide a wheel driving device that can be downsized and can ensure maintainability.

Means for solving the technical problem

In order to solve the above problem, one embodiment of the present invention provides a wheel driving device including: a motor; a speed reducer for reducing the rotation of the motor; and a wheel driven by the output rotation of the reduction gear, wherein the motor and the reduction gear are arranged to overlap each other when viewed in a direction orthogonal to the axial direction, the rear portion of the motor is arranged to face the vehicle body outer side, and a replacement member detachable from the motor is attached to the rear portion of the motor.

Any combination of the above-described constituent elements or a mode in which constituent elements or expressions of the present invention are substituted for each other in a method, a system, or the like is also effective as an embodiment of the present invention.

Effects of the invention

According to the present invention, a wheel driving device that can be miniaturized and can ensure maintainability is provided.

Drawings

Fig. 1 is a perspective view showing a carriage including a wheel driving device according to an embodiment.

Fig. 2 is a plan view schematically showing the wheel drive apparatus of fig. 1.

Fig. 3 is a plan view of the wheel drive apparatus of fig. 1 with a portion of the housing cut away.

Fig. 4 is a front view schematically showing the wheel drive apparatus of fig. 1.

Fig. 5 is a front view showing a state in which a cover is removed in the wheel drive apparatus of fig. 1.

Fig. 6 is a plan view showing a state where the replacement component is removed from the wheel driving apparatus of fig. 1.

Fig. 7 is a perspective view schematically showing a wheel drive device according to a modification 1.

Fig. 8 is a perspective view showing a state in which a housing is removed from the wheel drive apparatus of fig. 7.

Detailed Description

Preferred embodiments of the present invention will be described below with reference to the drawings. In the embodiment and the modifications, the same or equivalent constituent elements and components are denoted by the same reference numerals, and overlapping description is appropriately omitted. In the drawings, the dimensions of the components are shown enlarged or reduced as appropriate for the convenience of understanding. In the drawings, parts that are not essential to the description of the embodiments are omitted.

Further, although the terms including the numbers 1, 2, and the like are used to describe a plurality of constituent elements, the terms are used only for the purpose of distinguishing one constituent element from other constituent elements, and the terms are not used to limit the constituent elements.

In the following description, "parallel" and "perpendicular (orthogonal)" include not only completely parallel and completely perpendicular (orthogonal), but also the case where the deviation from parallel and the deviation from perpendicular (orthogonal) are included within an error range.

[ embodiment ]

Hereinafter, the structure of the wheel driving device 100 according to the embodiment will be described with reference to the drawings. Fig. 1 is a perspective view schematically showing a carriage 10 provided with a wheel drive device 100 according to the present embodiment. This view is a view of the carriage 10 viewed obliquely from below. The truck 10 includes a flat plate-like loading platform 10b on which a load is loaded, and two wheel driving devices 100 fixed to the rear portion of the lower surface of the loading platform (vehicle body) 10b so as to be spaced from each other in the left-right direction. Further, the cart 10 is provided with: a handle 10h provided on the upper surface of the loading table 10 b; and two casters 10e provided on the front part of the lower surface of the loading platform 10b so as to be spaced from each other in the left-right direction. The carriage 10 can advance, retreat, stop, and turn by performing control such as remote control, tracking control, and autonomous control on the wheel drive device 100.

For example, the carriage 10 may include a battery for supplying power to the wheel driving device 100 and an automatic tracking module for automatic tracking. The auto-tracking module can control the wheel driving apparatus 100 in such a manner as to track a target according to image information acquired by the camera. Further, for example, instead of automatic tracking, the vehicle may travel on a production line or travel while measuring the distance to a surrounding object.

Fig. 2 is a plan view schematically showing the wheel drive device 100. Fig. 2 shows the left wheel drive device of the two wheel drive devices 100 provided on the bogie 10. Since the left and right wheel drive devices 100 have a bilaterally symmetrical structure in a plan view, the following description is also applicable to the right wheel drive device 100.

Fig. 3 is a plan view of the wheel drive device 100 with a part of the housing 60 cut away. For convenience of explanation, as shown in the drawing, an XYZ orthogonal coordinate system is defined in which a horizontal direction is an X-axis direction, a horizontal direction orthogonal to the X-axis direction is a Y-axis direction, and a direction orthogonal to both (i.e., a vertical direction) is a Z-axis direction. The positive direction of each of the X, Y, and Z axes is the direction of the arrow in each drawing, and the negative direction is the direction opposite to the arrow. Such a direction mark is not intended to limit the use posture of the wheel drive apparatus 100, and the wheel drive apparatus 100 may be used in any posture according to the use.

As shown in fig. 3, the wheel drive device 100 includes a motor 20, a transmission mechanism 28, a speed reducer 30, wheels 40, an exchange member 50, and a housing 60. Hereinafter, a direction along the rotation axis La of the motor shaft 20s of the motor 20 is referred to as "axial direction of the motor" or "axial direction".

The motor 20 functions as a prime mover for rotationally driving the wheels 40. The transmission mechanism 28 transmits the rotation of the motor 20 to the reduction gear 30. The speed reducer 30 reduces the rotation of the motor 20. The wheels 40 are driven by the output rotation of the reduction gear 30. An exchange member 50 is attached to the rear portion of the motor 20 so as to be detachable from the motor main body 20 d. The replacement part 50 of the present embodiment includes an electromagnetic brake 52 and an encoder 54. The case 60 functions as a housing covering the motor 20, the reduction gear 30, and the replacement component 50. The housing 70 of the wheel drive device 100 includes a mounting base 72 for supporting the motor 20 and the reduction gear unit 30, and a casing 60. These will be described in detail below.

The motor 20 may be any motor based on various principles as long as it can drive the wheel 40. The motor 20 of the present embodiment is a servomotor. In this case, a servo motor is preferably used because of its advantages of small size, large output, relatively long life, and almost no need for maintenance. The motor 20 includes a motor main body 20d and a motor shaft 20s, and the motor shaft 20s extends toward both front and rear sides of the motor main body 20 d. The control circuit of the motor 20 may be provided inside the casing 60 or may be provided outside the casing 60.

If the motor 20 and the reduction gear 30 are arranged in the axial direction, the axial length of the wheel drive device 100 becomes excessively large. Therefore, in the wheel drive device 100, the motor 20 and the reduction gear 30 are arranged so as to overlap each other when viewed from a direction orthogonal to the axial direction along the rotation axis La of the motor 20. Specifically, the motor 20 and the reduction gear 30 overlap each other when viewed from the direction of the arrow a (X-axis direction) in fig. 3. At this time, miniaturization in the axial direction is facilitated. The rotation axis La of the motor 20 and the rotation axis Lb of the output shaft 30k of the reduction gear 30 extend in parallel, and particularly, the rotation axis La of the motor 20 and the rotation axis Lb of the output shaft 30k of the reduction gear 30 extend on the same horizontal plane.

In the present embodiment, when the wheel drive device 100 is mounted on the truck 10, the motor 20 and the reduction gear 30 are disposed so as to overlap each other when viewed from the front-rear direction of the truck 10. However, the present invention is not limited to this, and the motor 20 and the reduction gear 30 may be disposed so as to overlap each other when viewed from a direction orthogonal to the axial direction, and may be disposed so as to overlap each other when viewed from the vertical direction when mounted on the carriage 10, for example. The motor 20 and the reduction gear 30 need not be entirely overlapped, but may be arranged so that at least a part thereof overlaps with each other when viewed from a direction orthogonal to the axial direction.

The motor 20 is provided with a first pulley 28p, an electromagnetic brake 52, and an encoder 54. In particular, the first pulley 28p and the electromagnetic brake 52 are mounted on the motor shaft 20 s. For convenience of description, a side of the motor main body 20d along the rotation axis La on which the first pulley 28p is provided is referred to as a front portion 20f, and a side on which the electromagnetic brake 52 and the encoder 54 are provided is referred to as a rear portion 20 b. The front portion 20f of the motor main body 20d is fixed to the mounting base 72. The first pulley 28p is mounted to a portion of the motor shaft 20s protruding from the mounting base 72.

The replacement part 50 may be a part having a relatively high frequency of replacement or adjustment among the parts constituting the wheel drive apparatus 100. By replacing or adjusting the replacement member 50, the wheel drive apparatus 100 can be used for a long period of time. From the viewpoint of facilitating replacement or adjustment of the replacement member 50, the motor 20 is disposed such that the rear portion 20b side thereof faces the outside of the cart 10, and the replacement member 50 is attached to the rear portion 20b of the motor 20. That is, when the wheel driving device 100 is mounted on a vehicle body (the bogie 10) to be driven, the rear portion 20b of the motor 20 is configured to face the outside of the vehicle body. In the present embodiment, the rear portion 20b of the motor 20 is disposed toward the wheel 40 attachment side.

In order to restrict an unexpected operation, the wheel driving device 100 is preferably provided with a brake. Further, by providing the brake, the wheel drive apparatus 100 is easy to comply with the safety regulations. Therefore, the wheel drive device 100 includes the non-excitation operation type electromagnetic brake 52 in which the brake is operated when the brake is not energized and the brake is released when the brake is energized. For example, the non-excited operation type electromagnetic brake may be configured by a rotating body such as a disk, a pad, and a coil. In this brake, when the coil is not excited, the spring presses the pad against the rotating body to generate braking force, and when the coil is excited, the pad is released from the rotating body to release the braking.

In the present embodiment, the electromagnetic brake 52 is attached so as to surround the portion of the motor shaft 20s extending from the rear portion 20 b. The electromagnetic brake 52 is fixed to the rear portion 20b by a fixing member 52s such as a screw. The electromagnetic brake 52 restricts the rotation of the motor shaft 20s when not energized, and releases the restriction when energized.

In the electromagnetic brake 52, the rotating body and the pad are in contact for a long time, and they are easily worn, so the frequency of replacement or adjustment is higher than that of other parts of the wheel drive apparatus 100. Therefore, the electromagnetic brake 52 can be easily replaced, and the maintainability of the wheel drive apparatus 100 can be improved.

The encoder 54 detects a rotation angle of the motor shaft 20s in order to control the rotation of the motor 20. The encoder 54 of the present embodiment is configured by, for example, a magnet 54m and a magnetic rotation angle sensor 54c for detecting a rotation angle from a magnetic pole of the magnet 54m, but the configuration of the encoder 54 is not limited thereto. The magnet 54m is attached to an end surface of a portion of the motor shaft 20s extending from the electromagnetic brake 52. The rotation angle sensor 54c is provided on the sensor holder 54h so as to face the magnet 54m, and the sensor holder 54h is fixed to the rear portion 52b of the electromagnetic brake 52 by a fixing member 54s such as a screw.

If the encoder 54 fails, the operation of the wheel drive device 100 becomes unstable. Therefore, when a failure occurs, it is preferable to replace or adjust the encoder 54. By making the encoder 54 easily replaceable, the maintainability of the wheel drive apparatus 100 can be improved.

The transmission mechanism 28 may be any mechanism capable of transmitting the rotation of the motor 20 to the reduction gear 30, and may be a transmission mechanism based on various principles such as a gear train or a power transmission chain. The transmission mechanism 28 of the present embodiment includes a first pulley 28p, a second pulley 28s, and a belt 28 b. The first pulley 28p is provided on the motor shaft 20s of the motor 20, and the second pulley 28s is provided on the input shaft 30j of the reduction gear 30. The belt 28b is bridged between the first pulley 28p and the second pulley 28 s. The belt 28b may be a synchronous belt (e.g., timing belt) or a flat belt, or may be another type of belt. If the structure of the pulley and the belt is used, the number of parts is reduced compared to other structures, which is advantageous for weight reduction.

The bogie can be preferably used for various purposes such as a purpose of quickly conveying light loads and a purpose of conveying heavy loads. However, the preferred speed and torque characteristics vary depending on the application of the truck. However, the preparation of a plurality of types of trucks having different speed and torque characteristics according to the use is disadvantageous for manufacturing and sales management. Further, there is a problem that it is difficult for the user to change the application to a new application because the speed and torque characteristics of the conventional carriage do not match.

Therefore, the transmission mechanism 28 of the present embodiment is configured as follows: the reduction ratio can be changed by selecting at least one of the first pulley 28p and the second pulley 28s from a plurality of pulleys having different outer diameters. By changing the reduction ratio, the speed and torque characteristics of the wheel drive apparatus 100 can be easily changed. Therefore, by preparing a plurality of pulleys having different outer diameters, it is possible to cope with various speed and torque characteristics. And, at the time of manufacturing and selling, the speed reduction ratio can be set according to the speed and torque characteristics desired by the user and then provided. That is, the types of the wheel driving devices 100 that need to be manufactured can be reduced. And when changing uses, the user can easily switch to a new use by replacing the pulley.

The reduction gear 30 may be an eccentric oscillating reduction gear, a flexural wave reduction gear, a simple planetary reduction gear, or other reduction gears based on various principles. The reduction gear 30 of the present embodiment is an eccentric oscillating reduction gear. The speed reducer 30 is a gear device that reduces the rotation input to the input shaft 30j and outputs the reduced rotation to the output shaft 30 k. The input shaft 30j may be disposed at a position offset from the output shaft 30k, but in the present embodiment, the input shaft 30j is disposed on the rotation axis Lb of the output shaft 30 k. The reducer main body 30m of the reducer 30 is fixed to the mounting base 72. The input shaft 30j extends from the front portion 30f of the reducer body 30 m. The second pulley 28s is mounted to a portion of the input shaft 30j that protrudes from the mounting base 72.

The wheel 40 has a wheel body 40m and a rim 40h provided at the center of the wheel body 40 m. The wheel main body 40m may be a rubber tire made of resin such as synthetic rubber. The center of the rim 40h is fixed to the output shaft 30k of the speed reducer 30. The output shaft 30k extends from the housing 70 toward the outside side. The rim 40h is attached to a portion of the output shaft 30k extending outward from the frame 70. Therefore, the rim 40h and the wheel body 40m rotate integrally with the output shaft 30k outside the housing 70.

Referring also to fig. 4 and 5, the housing 60 will be described. Fig. 4 is a front view schematically showing the wheel drive device 100. Fig. 5 is a front view showing the wheel drive apparatus 100 with the cover 62 removed. The housing 60 may have any shape as long as it can cover the motor 20 and the reduction gear 30. The housing 60 of the present embodiment is a substantially rectangular box in an outer shape in side view, and is a substantially rectangular parallelepiped box having a longitudinal direction extending in the X-axis direction.

Reference is also made to fig. 6. Fig. 6 is a plan view showing a state where the replacement component 50 is removed from the wheel drive device 100. In order to facilitate replacement of the replacement member 50, the housing 60 is preferably provided with a working opening. Therefore, as shown in fig. 5, the housing 60 of the present embodiment is provided with a window 60w having a rectangular shape in front view, and the replacement member 50 can be detached from the window 60 w. At this time, as shown in fig. 6, the replacement member 50 can be attached and detached by only opening the window 60w, and therefore, maintenance can be performed in a short time.

Specifically, the window 60w has a size in which a predetermined margin is added to the outer shape of the replacement part 50 so that the replacement part 50 can pass through. In the present embodiment, the X-axis dimension and the Z-axis dimension of the window 60w in the front view are larger than the X-axis dimension and the Z-axis dimension of the electromagnetic brake 52 in the front view, respectively.

From the viewpoint of preventing foreign matter or the like from entering the replacement member 50, it is preferable to close the window 60w except at the time of maintenance. Therefore, the present embodiment has a cover 62 that covers the replacement part 50. As shown in fig. 4, the front cover 62 is substantially rectangular and has a size capable of closing the window 60 w. The cover 62 has a size obtained by adding a predetermined margin to the size of the window 60 w. The cover 62 may be fixed to the housing 60 by a plurality of (e.g., four) fasteners 62s such as screws. At this time, the cover 62 can be easily attached and detached by attaching and detaching the fastener 62 s.

The cover 62 of the present embodiment is attached to the side of the housing 60 where the wheel 40 is provided. Therefore, if the cover 62 interferes with the wheel 40, it takes time to attach and detach the cover 62. Therefore, in the present embodiment, the cover 62 and the wheel 40 are configured not to overlap when viewed in the axial direction of the motor shaft 20 s. In this case, the cover 62 can be detached in a short time. Further, if the cover 62 can be removed without interfering with the wheel by sliding the cover 62 laterally after the anchor 62s is removed, the cover 62 and the wheel 40 may be overlapped when viewed from the axial direction.

Next, an example of a maintenance method of the wheel drive device 100 configured as described above will be described. The maintenance work described below can be performed in a state where the wheel drive device 100 is mounted on the bogie (vehicle body) 10.

(1) First, at least a portion of the rear portion 20b of the motor 20 is exposed to the outside. Specifically, the fastener 62s is removed, and the cover 62 is removed from the housing 60, so that the replacement part 50 is exposed from the window 60 w.

(2) Next, replacement of the replacement part 50 is performed from the rear portion 20b side of the motor 20 exposed to the outside. When the encoder 54 is replaced, the fixing member 54s is removed, and the encoder 54 is removed together with the sensor holder 54h from the rear portion 52b of the electromagnetic brake 52. Then, the encoder 54 for replacement and the sensor holder 54h are attached to the rear portion 52b of the electromagnetic brake 52 by the fixing member 54 s.

(3) When the electromagnetic brake 52 is replaced, the fixing member 52s is detached, and the electromagnetic brake 52 is detached from the rear portion 20b of the motor 20. Then, the electromagnetic brake 52 for replacement is attached to the rear portion 20b of the motor 20 via the fixing member 52 s.

(4) Next, the cover 62 is attached to the housing 60 by the fastener 62 s. When the cover 62 is attached, the maintenance of the wheel drive device 100 is completed. This step is only an example, and the order of the steps may be changed, another step may be added, or a part of the steps may be omitted.

As described above, according to the wheel drive device 100 of the present embodiment, when the wheel drive device 100 is mounted on the bogie 10 to be driven, the rear portion of the motor 20 is disposed toward the vehicle body outer side of the bogie 10, and therefore, the replacement member 50 can be removed from the rear portion of the motor 20 and maintained in a state where the wheel drive device 100 is mounted on the vehicle body of the bogie 10 (in a state where the wheel drive device 100 is not removed from the vehicle body), and therefore, the maintainability is improved.

Further, since the wheel drive device 100 of the present embodiment is configured as a wheel drive module accommodated in the housing 60, the independent travel function can be provided by mounting the wheel drive module to an existing carriage that does not have the independent travel function.

The embodiments of the present invention have been described above. These embodiments are merely illustrative, and those skilled in the art will understand that various modifications and changes can be made within the scope of the present invention, and that such modifications and changes are also within the scope of the present invention. Accordingly, the description and drawings in this specification are to be regarded in an illustrative rather than a restrictive sense.

Hereinafter, a modified example will be described. In the drawings and the description of the modified examples, the same or equivalent constituent elements and components as those of the embodiments are denoted by the same reference numerals. The description overlapping with the embodiment is appropriately omitted, and the description is focused on the structure different from the embodiment.

[ 1 st modification ]

The configuration of a wheel driving device 100 according to modification 1 will be described with reference to fig. 7 and 8. Fig. 7 is a perspective view schematically showing a wheel driving device 100 according to a modification 1. Fig. 8 is a perspective view showing a state in which the housing 60 is removed from the wheel drive device 100 according to the present modification. As shown in these drawings, the present modification differs from the embodiment in that the housing 60 can be removed to the lower side (in the direction of arrow B) of the vehicle body of the bogie 10 in a state where the wheel drive device 100 is attached to the vehicle body of the bogie 10, and the window 60w is not provided, but the other configurations are the same. By removing the case 60, as shown in fig. 8, the replacement member 50 such as the electromagnetic brake 52 and the encoder 54 can be replaced more easily.

According to the present modification, since the housing 60 can be removed to the lower side of the truck 10 with the wheel drive device 100 attached to the body of the truck 10 and the rear portion of the motor 20 faces the outside of the truck 10, the wheel drive device 100 can be maintained with the wheel drive device 100 attached to the truck 10. Further, the housing 60 of the present modification may be provided with a window 60 w. If the wheels 40 are sufficiently large, the wheel drive device 100 can be attached to the upper surface of the loading platform 10b of the truck 10, and at this time, the housing 60 can be detached above the vehicle body of the truck 10.

In the description of the embodiment, the example in which the transmission mechanism 28 transmits the rotation at the same speed is shown, but the present invention is not limited to this, and the transmission mechanism 28 may be configured to transmit the rotation after the deceleration or acceleration from the motor 20 to the reduction gear 30.

In the description of the embodiment, the example in which the replacement member 50 is the electromagnetic brake 52 and the encoder 54 is shown, but the present invention is not limited to this, and the replacement member 50 may be a component (for example, various sensors) other than the electromagnetic brake 52 and the encoder 54.

In the description of the embodiment, the wheel drive device 100 is used for a truck on which a load is mounted, but the present invention is not limited to this, and the wheel drive device 100 may be applied to a vehicle or a mobile body other than a truck.

In the description of the embodiment, the example in which two wheel drive devices 100 are used for one mobile body is shown, but the present invention is not limited to this, and one or three or more wheel drive devices 100 may be used for one mobile body.

In the description of the embodiment, the electromagnetic brake 52 is exemplified as the non-excited operation type electromagnetic brake, but the electromagnetic brake 52 may be a brake based on a principle different from that of the non-excited operation type electromagnetic brake, and may be, for example, an excited operation type electromagnetic brake.

The above-described modifications exhibit the same operational effects as the embodiment.

Any combination of the above-described embodiments and modifications is also effective as an embodiment of the present invention. The new embodiment which is created by the combination has the effects of each of the combined embodiments and modifications.

Industrial applicability

The present invention can be used in a wheel drive device and a maintenance method for the wheel drive device.

Description of the symbols

20-motor, 20 b-rear, 20 s-motor shaft, 28 b-belt, 28 p-first pulley, 28 s-second pulley, 30-reducer, 30 j-input shaft, 40-wheel, 50-replacement part, 52 b-rear, 58-cover, 60-shell, 60 w-window, 62-cover, 70-frame, 100-wheel drive.

Claims

1. A wheel driving device is provided with: a motor; a speed reducer that reduces rotation of the motor; and wheels driven by the output rotation of the speed reducer,

the motor and the reduction gear are arranged so as to overlap each other when viewed from a direction orthogonal to the axial direction,

the motor is disposed with its rear side directed toward the vehicle body outer side,

a replacement part is mounted to a rear portion of the motor and is detachable from the motor.

2. The wheel drive apparatus according to claim 1,

a cover covering the replacement component, wherein the cover and the wheel do not overlap when viewed in an axial direction of a motor shaft of the motor.

3. The wheel drive apparatus according to claim 1 or 2, characterized by having:

a first pulley provided to a motor shaft of the motor; a second belt pulley provided on the input shaft of the speed reducer; and a belt erected between the first belt pulley and the second belt pulley.

4. The wheel drive apparatus according to claim 3,

the reduction ratio can be changed by selecting at least one of the first pulley and the second pulley from a plurality of pulleys having different outer diameters.

5. The wheel drive apparatus according to any one of claims 1 to 4,

the vehicle body structure is provided with a housing for covering the motor and the speed reducer, and the housing is configured to be detachable toward the lower side of the vehicle body.

6. The wheel drive apparatus according to any one of claims 1 to 5,

the motor and the reducer are covered by a housing, and the housing is provided with a window and is configured such that the replacement member can be detached from the window.

7. A maintenance method for maintaining the wheel drive apparatus according to any one of claims 1 to 6,

the replacement member is removed from a rear portion of the motor in a state where the wheel drive device is mounted on a vehicle body.