Wheel unit

Abstract

To provide a wheel unit for actively controlling a relative position between a wheel and a vehicle body with a simple configuration.SOLUTION: A vehicle unit has: an annular stator mounted on an axle fixed to a vehicle body coaxially with the axle; a first annular rotor which is arranged in the periphery of the stator and is rotated with respect to the stator around a center axis of the axle; and a second annular rotor which is fixed to the axle eccentric to the axle coaxially with the axle, is arranged in the periphery of the first rotor, and is rotated with respect to the first rotor around the center axis of the axle.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a wheel unit.

Background Art

[0002] Vehicles such as autonomous driving robots are becoming widespread. In this type of vehicle, in order to distribute the load to each wheel while ensuring wheel contact with the ground and enable attitude control such as stably maintaining the vehicle body horizontally, a suspension mechanism using a spring or an active suspension device using an actuator may be mounted as a vehicle body attitude control device. This active suspension device generally has, for example, a piston-cylinder type hydraulic actuator or an electromagnetic actuator such as a motor, and is mounted as a unit near the drive wheels of the vehicle (Patent Documents 1 to 3).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] Since the above-described active suspension type attitude control device is separate from the components for driving the vehicle body (components that transmit rotation from a power source such as a motor to the wheels), when this device is mounted on a vehicle, it causes an increase in the number of components and complication of the entire mechanism.

[0005] Therefore, the present invention provides a wheel unit that actively controls the relative position between a wheel and a vehicle body with a simple configuration.

Means for Solving the Problems

[0006] One aspect of the present invention provides a wheel unit. The wheel unit includes an annular stator coaxially attached to an axle fixed to a vehicle body, an annular first rotor disposed around the stator and rotating with respect to the stator about the central axis of the axle, and a wheel eccentric with respect to the axle, coaxially fixed to the wheel, disposed around the first rotor, and rotating with respect to the first rotor about the central axis of the wheel, an annular second rotor.

Advantages of the Invention

[0007] In an aspect of the present invention, by rotating the first rotor disposed around the stator coaxially attached to the axle, the axle eccentric with respect to the wheel is displaced in the vertical direction, and like a suspension, while ensuring the contact of the wheel with the ground, the relative position between the wheel and the vehicle body can be actively controlled. When a plurality of wheels and a plurality of axles are provided, the vehicle body can be maintained in a desired posture, for example, a horizontal posture. Further, by rotating the second rotor disposed around the first rotor, the wheel is rotated to move the vehicle body. That is, the first rotor is used as a stator to rotate the second rotor and thus the wheel. Therefore, compared with a wheel unit provided with a conventional attitude control device, the number of components is small, the entire mechanism can be simplified, and space can be saved. Further, the first rotor can rotate the second rotor in a direct drive manner, and a reduction mechanism that becomes a noise source can be reduced.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Mode for Carrying Out the Invention

[0009] Hereinafter, various embodiments of the present invention will be described with reference to the accompanying drawings. The scales of the drawings are not necessarily accurate, and some features may be exaggerated or omitted.

[0010] Vehicle As shown in FIG. 1, a vehicle 1 having a wheel unit according to each embodiment of the present invention includes a vehicle body 2, a plurality of axles 4, and a plurality of wheels 6. The axles 4 are fixed to the vehicle body 2, and the wheels 6 are rotatably supported on the axles 4 via wheel drive units, respectively. Each wheel 6 is attached to the axle 4 in a state eccentric with respect to the axle 4 by the wheel drive unit.

[0011] Hereinafter, the unit that supports and rotates each wheel 6 is called a "wheel drive unit", and the unit including a plurality of wheel drive units for a plurality of wheels 6 and a control system that controls the plurality of wheel drive units provided in the entire vehicle is called a "wheel unit".

[0012] In FIG. 1, the number of axles 4 is 4 and the number of wheels 6 is also 4. However, the numbers of the axles 4 and the wheels 6 are not limited to the illustration and may be 3 or 5 or more.

[0013] The vehicle 1 may be, for example, an autonomous driving robot, or may be other vehicles such as a cart pushed or operated by a companion, a vehicle that supports a medical stretcher.

[0014] The vehicle 1 is movable in the direction indicated by the arrow FR. Also, the height of the axle 4 with respect to the wheel 6 can be displaced as indicated by the arrow UD by the wheel unit described later.

[0015] First Embodiment FIGS. 2 to 4 show the basic configuration of the wheel drive unit. FIGS. 2 and 3 are cross-sectional views taken along the line A-A of FIG. 4. In FIG. 4 and other side cross-sectional views of the present application, the right side is the vehicle body 2 side, and the left side is the side away from the vehicle body 2.

[0016] As shown in FIGS. 2 to 4, the wheel drive unit 7 has an annular stator 8, an annular first rotor 10, and an annular second rotor 12.

[0017] The annular stator 8 is coaxially attached to the axle 4 fixed to the vehicle body 2. That is, the central axis C1 of the axle 4 is also the central axis of the stator 8. In this embodiment, the stator 8 is fixed to the axle 4 and does not rotate. As the fixing method, for example, interference fit may be used, or connection by a key or spline may be used.

[0018] A plurality of permanent magnets 8a are fixed to the outer peripheral surface of the stator 8. The number of the permanent magnets 8a is not limited to the illustration.

[0019] The annular first rotor 10 is disposed around the stator 8 and rotates relative to the stator 8 about the central axis C1 of the axle 4.

[0020] The annular second rotor 12 is coaxially fixed to the wheel 6 that is eccentric with respect to the axle 4. The second rotor 12 is disposed around the first rotor 10 and rotates relative to the first rotor 10 about the central axis C2 of the second rotor 12 and the wheel 6.

[0021] A plurality of permanent magnets 12a are fixed to the inner peripheral surface of the second rotor 12. The number of the permanent magnets 12a is not limited to the illustration.

[0022] The first rotor 10 has an inner peripheral surface 10a concentric with the stator 8 and an outer peripheral surface 10b concentric with the second rotor 12. A plurality of inner teeth 10c project from the inner peripheral surface 10a, and inner coils 10d are wound around the respective inner teeth 10c. A plurality of outer teeth 10e project from the outer peripheral surface 10b, and outer coils 10f are wound around the respective outer teeth 10e.

[0023] When the inner coil 10d is excited by energization, as shown by the arrow R1, the first rotor 10 rotates around the stator 8 about the central axis C1 of the axle 4. When the outer coil 10f is excited by energization, the first rotor 10 functions as a stator with respect to the second rotor 12, and as shown by the arrow R2, the second rotor 12 rotates around the first rotor 10 about the central axis C2 of the second rotor 12 and the wheel 6.

[0024] As shown in FIG. 4, an outer protruding ring portion 8b concentric with the outer peripheral surface is formed on the stator 8. A bearing 50 is disposed between the outer protruding ring portion 8b and the inner peripheral surface 10a of the first rotor 10 to enable the rotation of the first rotor 10 with respect to the stator 8.

[0025] The stator 8 has a fixed part 34a of the first angle sensor 34 fixed thereto, and the rotating part 34b of the first angle sensor 34 is fixed to the inner peripheral surface 10a of the first rotor 10. The first angle sensor 34 measures the rotation angle of the first rotor 10 with respect to the stator 8. The first angle sensor 34 may be, for example, an optical rotary encoder or a resolver.

[0026] Further, an inner protruding ring portion 12b concentric with the inner peripheral surface is formed on the second rotor 12. A bearing 52 is disposed between the inner protruding ring portion 12b and the outer peripheral surface 10b of the first rotor 10 to enable rotation of the second rotor 12 with respect to the first rotor 10.

[0027] A fixed part 44a of the second angle sensor 44 is fixed to the outer peripheral surface of the first rotor 10, and a rotating part 44b of the second angle sensor 44 is fixed to the inner peripheral surface of the second rotor 12. The second angle sensor 44 measures the rotation angle of the second rotor 12 with respect to the first rotor 10. The second angle sensor 44 may be, for example, an optical rotary encoder or a resolver.

[0028] In the above-described wheel drive unit 7, the second rotor 12 disposed around the first rotor 10 is rotated as shown by an arrow R2 to rotate the wheel 6 and cause the vehicle body 2 to travel. That is, with the first rotor 10 as a stator, the second rotor 12 and thus the wheel 6 are rotated.

[0029] As shown in FIG. 2, when the vehicle 1 travels on a horizontal and flat road surface 18, the first rotor 10 may be stationary with respect to the stator 8 and the second rotor 12 may be rotated with respect to the first rotor 10.

[0030] By rotating the first rotor 10 disposed around the stator 8 coaxially attached to the axle 4, the axle 4 eccentric with respect to the wheel 6 is displaced in the vertical direction, and like a suspension, while ensuring the contact of the wheel 6 with the ground, the relative position between the wheel 6 and the vehicle body 2 can be actively controlled. In the vehicle 1 provided with a plurality of wheels 6 and a plurality of axles 4, the vehicle body 2 can be maintained in a desired posture, for example, a horizontal posture. As shown in FIG. 3, when the vehicle 1 travels on a road surface 18 having an uphill slope, the first rotor 10 is rotated with respect to the stator 8, the axle 4 is displaced upward with respect to the wheel 6, and while ensuring the contact between the wheel 6 and the road surface 18, the second rotor 12 may be rotated with respect to the first rotor 10. Although not shown, when the vehicle 1 travels on a road surface 18 having a downhill slope, the first rotor 10 is rotated with respect to the stator 8, the axle 4 is displaced downward with respect to the wheel 6, and while ensuring the contact between the wheel 6 and the road surface 18, the second rotor 12 may be rotated with respect to the first rotor 10.

[0031] As described above, the wheel drive unit 7 can be called an eccentric two-axis integrated motor. The wheel drive unit 7 has fewer parts than a wheel unit provided with a conventional attitude control device, can simplify the entire mechanism, and can save space. Further, the stator 8 can rotate the first rotor 10 in a direct drive manner, and the first rotor 10 can rotate the second rotor 12 in a direct drive manner, so a speed reduction mechanism that becomes a noise source is not required.

[0032] The first rotor 10 has an inner peripheral surface 10a concentric with the stator 8 and an outer peripheral surface 10b concentric with the second rotor 12. Therefore, the first rotor 10 rotates smoothly with respect to the stator 8, and the second rotor 12 rotates smoothly with respect to the first rotor 10.

[0033] FIG. 5 shows a wheel unit 20 including a plurality of wheel drive units 7 and a control system for controlling the plurality of wheel drive units 7. The wheel unit 20 has a main control unit 21, a memory 22, a RAM (Random Access Memory) 24, a measuring device 26, and a plurality of wheel drive units 7. The main control unit 21, the memory 22, the RAM 24, and the measuring device 26 are mounted on the vehicle body 2.

[0034] Each wheel drive unit 7 has a first rotor control unit 30, a first drive circuit 32, a first rotor 10, a first angle sensor 34, a second rotor control unit 40, a second drive circuit 42, a second rotor 12, and a second angle sensor 44.

[0035] The main control unit 21 is, for example, a CPU, operates according to a computer program stored in the memory 22, and executes control related to the running of the vehicle 1, specifically, commands to the first rotor control unit 30 and the second rotor control unit 40 of each wheel drive unit 7.

[0036] The memory 22 stores a computer program to which the main control unit 21 conforms. The memory 22 is, for example, a ROM, a hard disk, or an SSD.

[0037] The RAM 24 is a work area of the main control unit 21.

[0038] The measuring device 26 is used to monitor or predict the state of the road surface on which the wheel 6 travels. The measuring device 26 may be, for example, a combination of acceleration sensors, or an IMU (Inertial Measurement Unit). In this case, the main control unit 21 calculates a monitoring result of the current state of the road surface on which the wheel 6 travels based on the measurement result of the measuring device 26. Alternatively, the measuring device 26 may be a lidar device using laser light, or an RGB-D (Red Green Blue - Depth) camera. In this case, the main control unit 21 calculates a prediction result of the future state of the road surface on which the wheel 6 travels based on the measurement result of the measuring device 26.

[0039] In the wheel drive unit 7, the first rotor control unit 30 controls a first drive circuit 32 that rotates the first rotor 10 based on a command from the main control unit 21 and the measurement result of the first angle sensor 34. The first drive circuit 32 supplies power to the inner coil 10d for rotating the first rotor 10. The first rotor control unit 30 and the first drive circuit 32 constitute a first rotor drive unit that vertically displaces the axle 4 eccentric with respect to the wheel 6 by rotating the first rotor 10.

[0040] The main control unit 21 controls the first rotor control unit 30, which is the first rotor drive unit of each wheel drive unit 7, according to the monitoring result or prediction result obtained from the measurement result of the measuring device 26. Specifically, based on the monitoring result or prediction result, when the vehicle 1 travels on a horizontal and flat road surface, the main control unit 21 sends a command to the first rotor control unit 30 of each wheel drive unit 7 to stop the rotation of the first rotor 10 with respect to the stator 8 in each wheel drive unit 7. In this case, the first rotor control unit 30 of each wheel drive unit 7 performs feedback control on the first drive circuit 32 so that the rotation angle of the first rotor 10 measured by the first angle sensor 34 becomes zero.

[0041] Based on the monitoring result or prediction result, when the vehicle 1 ascends or descends, the main control unit 21 sends a command to the first rotor control unit 30 of the wheel drive unit 7 that should raise or lower the wheel 6 to rotate the first rotor 10 with respect to the stator 8 of the wheel drive unit 7. In this case, the first rotor control unit 30 of the wheel drive unit 7 performs feedback control on the first drive circuit 32 while monitoring the rotation angle of the first rotor 10 measured by the first angle sensor 34. In this way, according to the monitoring result or prediction result obtained from the measurement result of the measuring device 26, it is possible to rotate the first rotor 10 and actively raise or lower the axle 4 with respect to the wheel 6. Therefore, even when the wheel 6 travels on an inclined road or a stepped road, the relative position between the wheel 6 and the vehicle body 2 can be actively controlled, and a vehicle provided with a plurality of wheels 6 and a plurality of axles 4 can maintain the vehicle body 2 in a desired posture, for example, a horizontal posture.

[0042] Also, when there are irregularities on the road surface, from the monitoring result or prediction result, the main control unit 21 sends a command to the first rotor control unit 30 of each wheel drive unit 7 to frequently raise and lower each wheel 6 so as to appropriately absorb the irregularities. Therefore, like a shock absorber, the wheel drive unit 7 can absorb the impact applied from the road surface to the vehicle body 2.

[0043] In the wheel drive unit 7, the second rotor control unit 40 controls the second drive circuit 42 that rotates the second rotor 12 based on the command from the main control unit 21 and the measurement result of the second angle sensor 44. The second drive circuit 42 supplies power to the outer coil 10f for rotating the second rotor 12. The second rotor control unit 40 and the second drive circuit 42 constitute a second rotor drive unit that rotates the wheel 6 to make the vehicle body 2 travel by rotating the second rotor 12.

[0044] The main control unit 21 controls the second rotor control unit 40, which is the second rotor drive unit of each wheel drive unit 7, according to a computer program. Specifically, when the vehicle 1 is traveling on a straight road, the main control unit 21 sends a command to the second rotor control unit 40 of each wheel drive unit 7 so that the second rotor 12 of each wheel drive unit 7 rotates at a constant speed. When the vehicle 1 is traveling on a curved road, the main control unit 21 sends a command to the second rotor control unit 40 of each wheel drive unit 7 so that the second rotor 12 of each wheel drive unit 7 rotates at a desired speed. The second rotor control unit 40 of each wheel drive unit 7 feedback-controls the second drive circuit 42 so that the rotational speed calculated from the rotational angle of the second rotor 12 measured by the second angle sensor 44 matches the rotational speed commanded by the main control unit 21.

[0045] The wheel unit 20 according to another embodiment described later is a modification of the wheel unit 20 according to the first embodiment, and has the same components as the wheel unit 20 according to the first embodiment unless otherwise specified.

[0046] Second Embodiment As shown in FIGS. 6 and 7, in the wheel drive unit 7 according to the second embodiment of the present invention, metal cover plates 54, 55, 56, 57 for protecting the inside of the wheel drive unit 7 are provided.

[0047] On the left side of FIG. 6 away from the vehicle body 2, the first cover plate 54 is disposed between the end of the stator 8 and the end of the first rotor 10, closing the gap between the end of the stator 8 and the end of the first rotor 10, and protecting the stator 8, the first rotor 10, the first angle sensor 34, and the bearing 50.

[0048] On the right side of FIG. 6 on the vehicle body 2 side, the first cover plate 56 is disposed between the end of the stator 8 and the end of the first rotor 10, closing the gap between the end of the stator 8 and the end of the first rotor 10, and protecting the stator 8 and the first rotor 10.

[0049] The outer peripheral edges of the first cover plates 54 and 56 are fixed to the inner peripheral surface 10a of the first rotor 10. As shown in FIG. 7, the first cover plates 54 and 56 are disks centered on the central axis C1 of the stator 8 and the inner peripheral surface 10a. Although not shown, a rubber seal member that slides against the outer peripheral surface of the stator 8 may be fixed to the inner peripheral edge of the first cover plates 54 and 56.

[0050] However, the inner peripheral edge of the first cover plates 54 and 56 may be fixed to the outer peripheral surface of the stator 8, and a rubber seal member that slides against the inner peripheral surface 10a of the first rotor 10 may be fixed to the outer peripheral edge of the first cover plates 54 and 56.

[0051] On the left side of FIG. 6 away from the vehicle body 2, the second cover plate 55 is disposed between the end of the first rotor 10 and the second rotor 12, closing the gap between the end of the first rotor 10 and the end of the second rotor 12, and protecting the first rotor 10, the second rotor 12, the second angle sensor 44, and the bearing 52.

[0052] On the right side of FIG. 6 which is the vehicle body 2 side, the second cover plate 57 is disposed between the end of the first rotor 10 and the end of the second rotor 12, closing the gap between the end of the first rotor 10 and the end of the second rotor 12, and protecting the first rotor 10 and the second rotor 12.

[0053] The inner peripheral edges of the second cover plates 55 and 57 are fixed to the outer peripheral surface 10b of the first rotor 10. As shown in FIG. 7, the second cover plates 55 and 57 are disks centered on the central axis C2 of the second rotor 12 and the outer peripheral surface 10b. Although not shown, a rubber seal member that slides against the inner peripheral surface of the second rotor 12 may be fixed to the outer peripheral edge of the second cover plates 55 and 57.

[0054] However, the outer peripheral edge of the second cover plates 55 and 57 may be fixed to the inner peripheral surface of the second rotor 12, and a rubber seal member that slides against the outer peripheral surface 10b of the first rotor 10 may be fixed to the inner peripheral edge of the second cover plates 55 and 57.

[0055] In this embodiment, it is possible to protect the interior of the wheel drive unit 7, for example, the teeth 10c, 10e and coils 10d, 10f provided on the first rotor 10, the bearing 50 that supports the first rotor 10, the bearing 52 that supports the second rotor 12, etc. from external foreign matter.

[0056] Third Embodiment As shown in FIG. 8, in the wheel drive unit 7 according to the third embodiment, the first rotor 10 is supported by two bearings 50, 58, and the second rotor 12 is supported by two bearings 52, 60. In this embodiment, the first rotor 10 and the second rotor 12 can be firmly supported.

[0057] On the right side of FIG. 8, which is the vehicle body 2 side, the stator 8 has an outer protruding ring 8c fixed or integrally formed concentric with its outer peripheral surface, and the bearing 58 is disposed between the outer protruding ring 8c and the inner peripheral surface 10a of the first rotor 10 to facilitate the rotation of the first rotor 10 with respect to the stator 8.

[0058] Also, on the right side of FIG. 8, which is the vehicle body 2 side, the second rotor 12 has an inner protruding ring 12c fixed or integrally formed concentric with its inner peripheral surface. The bearing 60 is disposed between the inner protruding ring 12c and the outer peripheral surface 10b of the first rotor 10 to facilitate the rotation of the second rotor 12 with respect to the first rotor 10.

[0059] Fourth Embodiment As shown in FIG. 9, the wheel drive unit 7 according to the fourth embodiment has all the features related to the second embodiment and the features related to the third embodiment.

[0060] On the right side of FIG. 9, which is the side of the vehicle body 2, the first cover plate 56 is disposed between the end of the stator 8 and the end of the first rotor 10, closing the gap between the end of the stator 8 and the end of the first rotor 10 to protect the stator 8, the first rotor 10, and the bearing 58. The second cover plate 57 is disposed between the end of the first rotor 10 and the end of the second rotor 12, closing the gap between the end of the first rotor 10 and the end of the second rotor 12 to protect the first rotor 10, the second rotor 12, and the bearing 60.

[0061] The modifications regarding the second embodiment are also applicable to this embodiment.

[0062] Fifth Embodiment The wheel drive unit 7 according to the fifth embodiment shown in FIG. 10 is a modification of the fourth embodiment. In this embodiment, instead of the first cover plate 56, a permanent magnet type electromagnetic brake 62 is provided. The permanent magnet type electromagnetic brake 62 is disposed on the right side of FIG. 10, which is the side of the vehicle body 2. The permanent magnet type electromagnetic brake 62 has a yoke 64, a boss 65, an armature 66, and a spring 67.

[0063] The yoke 64 is fixed to the first rotor 10 instead of the first cover plate 56. Similar to the first cover plate 56, the yoke 64 is disposed between the end of the stator 8 and the end of the first rotor 10, closing the gap between the end of the stator 8 and the end of the first rotor 10 to protect the stator 8, the first rotor 10, and the bearing 58. Also, a permanent magnet 64a and a coil 64b are provided inside the yoke 64.

[0064] The boss 65 is an annulus and is attached to the end of the axle 4 on the vehicle body 2 side in a slidable and non-rotatable manner with respect to the axle 4. As a mounting method, for example, a spline connection may be used. An armature 66 is fixed to the boss 65. The spring 67 is disposed between the yoke 64 and the armature 66, applying a spring force that separates the armature 66 from the yoke 64 to the armature 66 and the boss 65.

[0065] When the coil 64b is energized, due to the electromagnetic force, the armature 66 and the boss 65 approach the yoke 64 against the spring force of the spring 67. The boss 65 does not rotate with respect to the stator 8, and the yoke 64 is fixed to the first rotor 10. Therefore, the rotation of the first rotor 10 with respect to the stator 8 is restricted.

[0066] When the energization of the coil 64b is stopped, due to the spring force of the spring 67, the armature 66 and the boss 65 move away from the yoke 64. Therefore, the rotation of the first rotor 10 with respect to the stator 8 becomes possible.

[0067] Preferably, a rubber cylindrical seal member 68 is disposed in the gap between the inner peripheral surface of the yoke 64 and the outer peripheral surface of the axle 4 to protect the bearing 58 from external foreign matters. The seal member 68 may be fixed to the yoke 64 and slide with respect to the axle 4, or may be fixed to the axle 4 and slide with respect to the yoke 64.

[0068] FIG. 11 is a block diagram showing the wheel unit 20 according to this embodiment. Each wheel drive unit 7 has a coil 64b of the permanent magnet type electromagnetic brake 62.

[0069] The main control unit 21 controls the energization of the coil 64b of the permanent magnet type electromagnetic brake 62 that restricts the rotation of the first rotor 10 according to the monitoring result or prediction result obtained from the measurement result of the measuring device 26. Specifically, based on the monitoring result or prediction result, when the vehicle 1 travels on a horizontal and flat road surface, the main control unit 21 sends a command to the first rotor control unit 30 of each wheel drive unit 7 so as to stop the rotation of the first rotor 10 with respect to the stator 8 in each wheel drive unit 7. Also, in this case, the main control unit 21 energizes the coil 64b so as to stop the rotation of the first rotor 10 with respect to the stator 8 in each wheel drive unit 7. Therefore, the rotation of the first rotor 10 with respect to the stator 8 is completely stopped by the permanent magnet type electromagnetic brake 62, and the height of the axle 4 with respect to the wheel 6 can be fixed.

[0070] Based on the monitoring result or prediction result, when the vehicle 1 ascends or descends, the main control unit 21 stops the energization of the coil 64b of the permanent magnet electromagnetic brake 62 of the wheel drive unit 7 that should raise or lower the wheel 6, and sends a command to the first rotor control unit 30 to rotate the first rotor 10 with respect to the stator 8 of the wheel drive unit 7. In this case, the first rotor control unit 30 of the wheel drive unit 7 feedback-controls the first drive circuit 32 while monitoring the rotation angle of the first rotor 10 measured by the first angle sensor 34.

[0071] Instead of the permanent magnet electromagnetic brake 62, other brakes such as a friction brake or a meshing brake may be used.

[0072] Sixth Embodiment FIG. 12 shows the wheel drive unit 7 according to the sixth embodiment. In the wheel drive unit 7 according to the first to fifth embodiments, the stator 8 is fixed to the axle 4, but in the wheel drive unit 7 according to the sixth embodiment, the stator 8 is excited by the first rotor 10 and can rotate around the axle 4.

[0073] Also, the wheel drive unit 7 according to the sixth embodiment has a planetary gear mechanism 70 that transmits the rotation of the stator 8 to the first rotor 10. The planetary gear mechanism 70 is arranged on the right side of FIG. 12, which is the vehicle body 2 side. The planetary gear mechanism 70 has a sun gear 72, a plurality of planetary gears 74, a planetary carrier 76, and an internal gear 78.

[0074] The sun gear 72 rotates around the axle 4 together with the stator 8. The sun gear 72 is fixed to an outer protruding ring 8c fixed or integrally formed with the stator 8.

[0075] The plurality of planetary gears 74 are each rotatable around a shaft 74a supported by a planetary carrier 76 fixed to the vehicle body 2 and mesh with the sun gear 72. Since the planetary carrier 76 is fixed, the position of the planetary gear 74 in the wheel drive unit 7 does not change.

[0076] The internal gear 78 meshes with these planetary gears 74. An annular connecting portion 78a is provided at one end of the internal gear 78. The connecting portion 78a connects the internal gear 78 to the first rotor 10, transmits the rotation of the internal gear 78 to the first rotor 10, and rotates the first rotor 10.

[0077] Therefore, when the first rotor 10 is excited and the stator 8 rotates, the sun gear 72 rotates, and its rotation is transmitted from the planetary gear 74 to the internal gear 78, causing the first rotor 10 to rotate. That is, the first rotor 10 is used as a stator for the rotation of the stator 8, and the rotation of the stator 8 is transmitted to the first rotor 10 through the sun gear 72, which is a speed reduction mechanism, and finally the first rotor 10 is rotated. Since the planetary gear mechanism 70, which is a speed reduction mechanism, is utilized, it is necessary to rotate the stator 8 at a high speed. However, even if the torque for driving the stator 8 is small, a large torque can be applied to the first rotor 10 to displace the axle 4 eccentric to the wheel 6 in the vertical direction.

[0078] FIG. 13 shows the wheel unit 20 according to this embodiment. In this wheel unit 20, each wheel drive unit 7 has a stator control unit 80 and a stator drive circuit 82 instead of the first rotor control unit 30 and the first drive circuit 32. However, substantially, the stator control unit 80 and the stator drive circuit 82 are the same as the first rotor control unit 30 and the first drive circuit 32, except that the object to be directly rotated is the stator 8 instead of the first rotor 10.

[0079] The stator control unit 80 controls the stator drive circuit 82 that rotates the stator 8 and thus the first rotor 10 based on the command from the main control unit 21 and the measurement result of the first angle sensor 34. The stator drive circuit 82 supplies power to the inner coil 10d of the first rotor 10 to rotate the stator 8. The stator control unit 80 and the stator drive circuit 82 constitute a stator drive unit that displaces the axle 4 eccentric to the wheel 6 in the vertical direction by rotating the stator 8 and thus the first rotor 10.

[0080] The main control unit 21 controls the stator control unit 80, which is the stator drive unit of each wheel drive unit 7, according to the monitoring result or prediction result obtained from the measurement result of the measuring device 26. Specifically, based on the monitoring result or prediction result, when the vehicle 1 is traveling on a horizontal and flat road surface, the main control unit 21 sends a command to the stator control unit 80 of each wheel drive unit 7 to stop the rotation of the stator 8 with respect to the first rotor 10 (and thus the rotation of the first rotor 10 with respect to the stator 8) in each wheel drive unit 7. In this case, the stator control unit 80 of each wheel drive unit 7 performs feedback control on the stator drive circuit 82 so that the rotation angle of the first rotor 10 measured by the first angle sensor 34 becomes zero.

[0081] Based on the monitoring result or prediction result, when the vehicle 1 is ascending or descending, the main control unit 21 sends a command to the stator control unit 80 of the wheel drive unit 7 whose wheel 6 is to be raised or lowered to cause the rotation of the stator 8 with respect to the first rotor 10 (and thus the rotation of the first rotor 10 with respect to the stator 8) of the wheel drive unit 7. In this case, the stator control unit 80 of that wheel drive unit 7 performs feedback control on the stator drive circuit 82 while monitoring the rotation angle of the first rotor 10 measured by the first angle sensor 34. In this way, according to the monitoring result or prediction result obtained from the measurement result of the measuring device 26, it is possible to rotate the stator 8 and thus the first rotor 10, and actively raise or lower the axle 4 with respect to the wheel 6. Therefore, even when the wheel 6 is traveling on an inclined road or a stepped road, the relative position between the wheel 6 and the vehicle body 2 can be actively controlled, and a vehicle provided with a plurality of wheels 6 and a plurality of axles 4 can maintain the vehicle body 2 in a desired posture, for example, a horizontal posture.

[0082] Also, when there are irregularities on the road surface, from the monitoring results or prediction results, the main control unit 21 sends a command to the stator control unit 80 of each wheel drive unit 7 to frequently raise and lower each wheel 6 so as to appropriately absorb the irregularities. Therefore, like a shock absorber, the wheel drive unit 7 can absorb the impact applied from the road surface to the vehicle body 2.

[0083] Modification example As described above, the present invention has been illustrated and described with reference to the preferred embodiments of the present invention. However, it will be understood by those skilled in the art that changes in form and details can be made without departing from the scope of the invention described in the claims. Such changes, modifications, and corrections should be included in the scope of the present invention.

[0084] For example, in the above embodiment, the magnet 8a is arranged around the stator 8 and the inner coil 10d is arranged on the first rotor 10. However, a coil may be arranged around the stator 8 and a magnet may be arranged on the inner peripheral surface of the first rotor 10.

Explanation of reference numerals

[0085] 1 Vehicle 2 Vehicle body 4 Axle 6 Wheel 7 Wheel drive unit 8 Stator 10 First rotor 10a Inner peripheral surface 10b Outer peripheral surface 12 Second rotor 20 Wheel unit 21 Main control unit 26 Measuring device 30 First rotor control unit (first rotor drive unit) 32 First drive circuit (first rotor drive unit) 40 Second rotor control unit (second rotor drive unit) 42 Second drive circuit (second rotor drive unit) 54, 56 First cover plate 55, 57 Second cover plate 62 Permanent magnet type electromagnetic brake 70 Planetary gear mechanism 72 Sun gear 74 Planet gear 78 Internal gear 80 Stator control unit (stator drive unit) 82 Stator drive circuit (stator drive unit)

Claims

1. An annular stator attached coaxially to an axle fixed to a vehicle body, and An annular first rotor disposed around the stator and rotating with respect to the stator about the central axis of the axle, An annular second rotor fixed coaxially to a wheel eccentric with respect to the axle, disposed around the first rotor, and rotating with respect to the first rotor about the central axis of the wheel, A first rotor driving unit that displaces the axle eccentric with respect to the wheel in the vertical direction by rotating the first rotor, A second rotor driving unit that rotates the wheel to make the vehicle body travel by rotating the second rotor, and The first rotor has an inner peripheral surface concentric with the stator and an outer peripheral surface concentric with the second rotor. A wheel unit characterized by this.

2. A first cover plate disposed between the end of the stator and the end of the first rotor, closing the gap between the end of the stator and the end of the first rotor, and protecting the stator and the first rotor, Further comprising a second cover plate disposed between the end of the first rotor and the end of the second rotor, closing the gap between the end of the stator and the end of the second rotor, and protecting the first rotor and the second rotor The wheel unit according to claim 1, characterized by this.

3. A measuring device used to monitor or predict the state of the road surface on which the wheel travels, Further comprising a control unit that controls the first rotor driving unit according to a monitoring result or a prediction result obtained from the measurement result of the measuring device The wheel unit according to claim 1 or 2, characterized by this.

4. Further comprising a brake that restricts the rotation of the first rotor according to a monitoring result or a prediction result obtained from the measurement result of the measuring device The wheel unit according to claim 3, characterized in that...

5. An annular stator rotatably attached coaxially with an axle fixed to a vehicle body around the axle, and An annular first rotor disposed around the stator, rotating with respect to the stator about the central axis of the axle, and exciting the stator to rotate the stator around the axle, An annular second rotor fixed coaxially with the wheel to a wheel eccentric with respect to the axle, disposed around the first rotor, and rotating with respect to the first rotor about the central axis of the wheel, A stator drive unit that displaces the axle eccentric with respect to the wheel in the vertical direction by rotating the stator, A second rotor drive unit that rotates the wheel to cause the vehicle body to travel by rotating the second rotor, A sun gear that rotates around the axle together with the stator, A plurality of planet gears meshing with the sun gear, An internal gear meshing with the planet gear, And a connecting portion that connects the internal gear to the first rotor and transmits the rotation of the internal gear to the first rotor to rotate the first rotor. The wheel unit characterized in that...

6. A measuring device used to monitor or predict the state of the road surface on which the wheel travels, and A control unit that controls the stator drive unit according to a monitoring result or a prediction result obtained from the measurement result of the measuring device. The wheel unit according to claim 5, characterized in that...

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