Electric drive device

Abstract

An electric drive device (20) is applied to a vehicle (10) provided with a drive wheel (21), and the vehicle is driven by rotating the drive wheel about a rotation center axis extending in a horizontal direction. An electric drive device is provided with: a drive unit (22) provided below a base part (11) of a vehicle, the drive unit having a motor (30) and transmission mechanisms (50, 60) connected to drive wheels and transmitting rotational power of the motor to the drive wheels; and a steering mechanism (70) provided on the lower side of the base part, the steering mechanism having a steering center axis (74) extending in the vertical direction. The steering mechanism supports the drive unit so that the drive unit can rotate about the steering center axis with respect to the base part while maintaining the rotation center axis of the drive wheel in a horizontal state. The steering mechanism is configured such that, in the horizontal direction, the position of the steering center axis is offset from a ground contact portion of the drive wheel with respect to the travel road surface (GL).

Description

[0001] Cross-reference to related applications

[0002] This application is based on Japanese Patent Application No. 2022-086724 filed on May 27, 2022, and the contents thereof are incorporated herein by reference. Technical Field

[0003] The invention relates to an electric drive device. Background Art

[0004] As such an electric drive device, as described in Patent Document 1, there is known a device which is applied to an unmanned transport vehicle having a driving wheel, and causes the driving wheel to rotate around a rotation center axis extending in a horizontal direction to drive the unmanned transport vehicle. The device includes a driving mechanism for rotating the driving wheel and a steering mechanism for changing the direction of the driving wheel around a steering shaft extending in a vertical direction. The driving mechanism and the steering mechanism are provided on the lower side of the trolley body of the unmanned transport vehicle.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2021-91401

[0008] The steering mechanism described in Patent Document 1 includes a steering motor for changing the direction of the drive wheels. Therefore, there is a concern that the structure of the steering mechanism may become complicated. Summary of the invention

[0009] A main object of the present invention is to provide an electric drive device that can achieve a simplified structure.

[0010] The present invention is an electric drive device, which is applied to a vehicle having a driving wheel, and causes the driving wheel to rotate around a rotation center axis extending in a horizontal direction to drive the vehicle to travel, wherein the electric drive device comprises:

[0011] a drive unit provided on a lower side of a base portion of the vehicle and having a motor and a transmission mechanism that is coupled to the drive wheel and transmits the rotational power of the motor to the drive wheel; and

[0012] a steering mechanism disposed on the lower side of the base portion and having a steering center axis extending in the vertical direction,

[0013] The steering mechanism supports the driving unit relative to the base portion so as to be rotatable around the steering center axis while maintaining the rotation center axis of the driving wheel in a horizontal state.

[0014] The steering mechanism is configured such that the position of the steering center axis is offset from a contact portion of the driving wheel with respect to a travel road surface in a horizontal direction.

[0015] The steering mechanism of the present invention is configured such that, in the horizontal direction, the position of the steering center axis extending in the vertical direction is a position deviated from the ground contact portion of the driving wheel relative to the driving road surface of the vehicle. Therefore, when the rotational power is transmitted from the motor to the driving wheel via the transmission mechanism in a state where the driving wheel is grounded to the driving road surface, a torque that rotates the driving unit around the steering center axis is generated in the steering mechanism. In this case, the driving unit rotates around the steering center axis relative to the base of the vehicle while maintaining the rotation center axis of the driving wheel in a horizontal state. That is, the driving wheel can be steered. In this way, in the present invention, the driving wheel can be steered by the rotational power of the motor used to drive the vehicle. Therefore, a motor for steering the driving wheel that is different from the motor for driving the vehicle is not required. Thus, the structure of the electric drive device having the driving unit and the steering mechanism can be simplified. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and other objects, features and advantages of the present invention will become more apparent with reference to the accompanying drawings and the following detailed description. The accompanying drawings are as follows:

[0017] Figure 1 1 is a diagram showing the overall structure of the unmanned transport vehicle according to the first embodiment.

[0018] Figure 2 This is a side view of the unmanned delivery vehicle.

[0019] Figure 3 is a perspective view showing the overall structure of the electric drive device.

[0020] Figure 4 This is a diagram showing the internal structure of the motor and reduction gear.

[0021] Figure 5 Yes means Figure 4 The 5-5 line cross-sectional view of the motor part,

[0022] Figure 6 This is a diagram showing the electrical structure of an unmanned transport vehicle.

[0023] Figure 7 is a top view of the electric drive device in a state where the steering of the steering mechanism is locked.

[0024] Figure 8 1 is a diagram showing the structure near the housing when the steering mechanism is in a state where the steering is locked.

[0025] Fig. 9is a top view showing the electric drive device in a state where the steering of the steering mechanism is not locked.

[0026] Fig.10 1 is a diagram showing the structure near the housing when the steering mechanism is not locked.

[0027] Fig.11 is a diagram showing an example of the driving mode of an unmanned transport vehicle.

[0028] Fig.12 is a diagram showing an example of the driving mode of an unmanned transport vehicle.

[0029] Fig.13 is a flowchart showing the steps of the driving control process of the unmanned guided vehicle.

[0030] Fig.14 is a top view of the electric drive device of the steering mechanism during turning.

[0031] Fig.15 This is a top view of the electric drive unit when the turn is completed.

[0032] Fig.16 This is a top view of the electric drive unit when the turn is completed and locked.

[0033] Fig.17 is a flowchart showing the steps of a travel control process of an unmanned guided vehicle according to a second embodiment.

[0034] Fig.18 is a top view of an electric drive device according to a third embodiment.

[0035] Fig.19 is a side view of the electric drive unit. DETAILED DESCRIPTION

[0036] <First embodiment>

[0037] Hereinafter, with reference to the accompanying drawings, a first embodiment of an unmanned transport vehicle as a vehicle is described in which the electric drive device according to the present invention is applied. The unmanned transport vehicle of this embodiment is an AGV (Automatic Guided Vehicle) used for transporting articles in a factory production line or warehouse or other workplace. The unmanned transport vehicle is controlled by a computer and automatically travels along a prescribed driving route in the workplace.

[0038] like Figure 1 and Figure 2As shown in FIG. 1 , the unmanned transport vehicle 10 includes a base 11 and driven wheels 12. The base 11 is plate-shaped and rectangular (specifically, a long rectangular shape) when viewed from above. The upper surface of the base 11 is a loading surface 11a for loading the transported object. The loading surface is substantially parallel to the road surface GL on which the unmanned transport vehicle 10 is traveling. Figure 1 In FIG. 1 , the outer peripheral edge of the base portion 11 is depicted by a dotted line, and the structure below the placement surface 11 a of the base portion 11 is depicted by a solid line.

[0039] The driven wheels 12 are provided at four corners of the lower surface of the base 11. That is, in the present embodiment, two rows of driven wheels 12 are provided in the vehicle width direction and two rows of driven wheels 12 are provided in the vehicle length direction of the unmanned guided vehicle 10. Each driven wheel 12 supports the base 11 from below.

[0040] The driven wheel 12 is supported by the driven wheel mounting portion 13. The driven wheel 12 is mounted on the lower end of the driven wheel mounting portion 13 in a manner that allows rotation around a rotation center axis extending in the horizontal direction. The upper end of the driven wheel mounting portion 13 is mounted on the base portion 11 in a manner that allows rotation around a rotation center axis extending in the vertical direction. When the unmanned transport vehicle 10 is traveling forward or backward, the driven wheel 12 rotates in a state where the rotation center axis of the driven wheel 12 extends in the vehicle width direction. On the other hand, when the unmanned transport vehicle 10 is traveling in the vehicle width direction, the driven wheel 12 rotates in a state where the rotation center axis of the driven wheel 12 extends in the vehicle length direction.

[0041] The unmanned transport vehicle 10 includes an electric drive device 20 mounted on the lower surface of the base 11. The electric drive device 20 includes a drive wheel 21, a drive unit 22 that drives the drive wheel 21 to rotate, and a steering mechanism 70 that steers the drive wheel 21. The electric drive device 20 of the present embodiment includes: a plurality of (two) drive wheels 21; a drive unit 22 that is respectively provided corresponding to each drive wheel 21; and a steering mechanism 70 that is respectively provided corresponding to each drive wheel 21. In the present embodiment, each drive unit 22 has the same structure, and each steering mechanism 70 has the same structure. Each drive wheel 21 is provided on a diagonal line of a corner portion of the base 11 when the base 11 is viewed from above. In the present embodiment, the diameter of the drive wheel 21 is the same as the diameter of the driven wheel 12.

[0042] First, use Figure 3 to Figure 5 The drive unit 22 will be described. Figure 5 Yes means Figure 4 The sectional view of the motor 30 in the 5-5 line sectional view. Figure 4 and Figure 5 Some of the structures shown are omitted for convenience. Figure 3 The structure shown is a simplified representation.

[0043] The drive unit 22 is provided on the lower side of the base portion 11. The drive unit 22 includes a motor 30, a first reduction gear 50, and a second reduction gear 60. The rotational power of the rotor 31 constituting the motor 30 is transmitted to the drive wheel 21 only by the reduction gears 50 and 60. In the present embodiment, the reduction gears 50 and 60 correspond to "transmission mechanisms".

[0044] The motor 30 includes a rotor 31 including excitation poles (e.g., permanent magnets); a shaft 32 fixed to the rotor 31; and a stator 33 disposed radially outwardly relative to the rotor 31. The rotation center axis of the shaft 32 extends in the horizontal direction. The stator 33 includes a stator core (not shown) and a stator winding 33a wound around the stator core (see FIG. Figure 6 ).

[0045] The motor 30 includes a motor housing 34. The motor housing 34 includes a tubular portion 35, a first connecting portion 36, a second connecting portion 37, and a cover portion 38. The tubular portion 35 is in the shape of a tube that is longer in the direction in which the shaft 32 extends, and is specifically in the shape of a cylinder. The first connecting portion 36 is provided on the first end side of the two ends in the long side direction of the tubular portion 35, and the second connecting portion 37 is provided on the second end side. The rotor 31 and the stator 33 are accommodated in the cylindrical space surrounded by the tubular portion 35, the first connecting portion 36, and the second connecting portion 37. The stator 33 is provided on the inner circumferential surface of the tubular portion 35. In addition, the motor housing 34 is not limited to a cylindrical cross section, and may also be a rectangular cross section, for example.

[0046] A first opening 36a is formed in the first connection portion 36. A first bearing 39 is provided in the first opening 36a. In addition, a second opening 37a is formed in the second connection portion 37, and a second bearing 40 is provided in the second opening 37a. In the present embodiment, each bearing 39, 40 is a rolling bearing having an inner ring, an outer ring, and a rolling element provided between the inner ring and the outer ring. The first end side of the shaft 32 is rotatably supported by the first bearing 39, and the second end side of the shaft 32 is rotatably supported by the second bearing 40.

[0047] A cover portion 38 is provided on the side of the second connection portion 37 opposite to the tubular portion 35 in the longitudinal direction of the motor housing 34. A control board 41 is disposed in the space surrounded by the second connection portion 37 and the cover portion 38. In the present embodiment, the control board 41 is disposed so that the board surface of the control board 41 is orthogonal to the extending direction of the shaft 32. An inverter 45 (see FIG. 4 ) described later is provided on the control board 41. Figure 6 ).like Figure 5As shown, a connector opening 38a is formed in the cover 38. A connector 42 electrically connected to the control board 41 is inserted through the connector opening 38a. The connector 42 includes a power connector and a communication connector.

[0048] Next, the first reduction gear 50 is described. The first reduction gear 50 amplifies and outputs the input torque from the shaft 32 of the motor 30. The first reduction gear 50 includes a first housing 51 connected to the first connecting portion 36. A planetary gear mechanism 52 is accommodated in the first housing 51. The planetary gear mechanism 52 includes: a sun gear 52S fixed to the shaft 32, a plurality of planetary gears 52P meshing with the sun gear 52S, a ring gear 52R meshing with the planetary gears 52P, and a planetary carrier 52C that supports the planetary gears 52P so that they can rotate freely. The rotation center axis of the sun gear 52S is the same as the rotation center axis of the shaft of the planetary carrier 52C.

[0049] The sun gear 52S is an external gear, and is fixed to the shaft 32 inserted through the first opening 51a of the first housing 51, and rotates integrally with the shaft 32. The ring gear 52R is an annular internal gear, and is fixed to the inner peripheral surface of the first housing 51. The planetary gears 52P are external gears, and are rotatably supported on the shaft of the planetary carrier 52C via rolling bearings.

[0050] A second opening 51b is formed in the first housing 51, and a bearing 53 (rolling bearing) is provided in the second opening 51b. The bearing 53 rotatably supports the shaft of the carrier 52C.

[0051] In addition, the speed reduction mechanism accommodated in the first housing 51 may be, for example, a cycloid gear mechanism.

[0052] Next, the second reduction gear 60 is described. The second reduction gear 60 amplifies and outputs the input torque from the shaft of the planetary carrier 52C. In the present embodiment, in order to suppress the increase in the volume of the drive unit 22 in the vehicle width direction, the second reduction gear 60 is a structure that is longer in the vehicle length direction. The second reduction gear 60 includes a second housing 61 connected to the first housing 51.

[0053] A plurality of spur gears are housed in the second housing 61. Specifically, a first gear 62, a second gear 63, and a third gear 64 are housed in the second housing 61 in a row in the vehicle length direction. The rotation center axis of each gear 62 to 64 extends in the same direction as the direction in which the shaft 32 extends.

[0054] The second housing 61 is formed with a first opening 61a, and the shaft of the planetary carrier 52C is inserted through the first opening 61a. The end of the shaft of the planetary carrier 52C is rotatably supported by a first bearing 66 (rolling bearing) provided in the second housing 61. In addition, a first gear 62 is provided on the shaft. The second gear 63 meshing with the first gear 62 is rotatably supported by a second bearing 67 (rolling bearing) provided in the second housing 61, and the third gear 64 meshing with the second gear 63 is rotatably supported by a third bearing 68 (rolling bearing) provided in the second housing 61.

[0055] The diameter of the second gear 63 is larger than that of the first gear 62, and the diameter of the third gear 64 is larger than that of the second gear 63. That is, the diameters of the gears 62 to 64 accommodated in the second housing 61 increase from the first opening 61a side toward the second opening 61b side in the long side direction of the second housing 61. As a result, the rotation speed of the third gear 64 is reduced relative to the first gear 62, and the input torque of the first gear 62 is amplified and output from the third gear 64.

[0056] A drive shaft 65 extending in the horizontal direction is fixed to the third gear 64. A first end of the drive shaft 65 is rotatably supported by a third bearing 68 provided in the second housing 61. The drive shaft 65 is inserted through the second opening 61b of the second housing 61. A second end of the drive shaft 65 is connected to the drive wheel 21.

[0057] Next, use Figure 6 , the electrical structure of the unmanned transport vehicle 10 is described.

[0058] The unmanned guided vehicle 10 includes a power storage unit 46. The power storage unit 46 is, for example, a secondary battery such as a lithium ion battery.

[0059] An inverter 45 and a control unit 47 are provided on the control substrate 41 of each drive unit 22. The inverter 45 includes three-phase upper and lower arm semiconductor switches. The inverter 45 converts the direct current supplied from the power storage unit 46 of the unmanned guided vehicle 10 into alternating current by switching control of the upper and lower arm semiconductor switches and supplies the alternating current to the stator winding 33a.

[0060] Each drive unit 22 is equipped with a sensor 49. The sensor 49 includes a current sensor and a rotation angle sensor. The current sensor detects the current (phase current) flowing to the stator winding 33a. The rotation angle sensor detects the rotation angle position (electrical angle) of the rotor 31. The detection value of the sensor 49 is input to the control unit 47. In this embodiment, the current sensor and the rotation angle sensor are housed in the motor housing 34.

[0061] The control unit 47 is mainly composed of a microcomputer. The control unit 47 performs switching control of the inverter 45 based on each detection value so as to control the control amount of the motor 30 to a command value. The control amount is, for example, torque.

[0062] The control unit 47 of each drive unit 22 communicates with the upper ECU 48 of the unmanned guided vehicle 10 via the communication connector constituting the connector 42. The upper ECU 48 is mainly composed of a microcomputer. The upper ECU 48 sends a command value to the control unit 47 of each drive unit 22 via the communication connector so that the desired control such as the driving control of the unmanned guided vehicle 10 can be realized. When the upper ECU 48 determines that the unmanned guided vehicle 10 is instructed to drive forward, the upper ECU 48 sends a command value to the control unit 47 of each drive unit 22 so that the driving wheels 21 of each drive unit 22 rotate in the same direction and the rotation speed of each driving wheel 21 is the same.

[0063] Furthermore, in the present embodiment, the control unit 47 and the upper ECU 48 are equivalent to a "control device". The functions provided by the microcomputers of the control unit 47 and the upper ECU 48 may be provided by software recorded in a physical storage device and a computer that executes the software, software only, hardware only, or a combination thereof. For example, in the case where the microcomputer is provided by an electronic circuit as hardware, it may be provided by a digital circuit or an analog circuit including a plurality of logic circuits. For example, the microcomputer executes a program stored in a non-transitory tangible storage medium that is a storage unit possessed by the microcomputer. In the program, for example, Figure 6 The program for the driving control process shown in the example above is executed. The method corresponding to the program is executed by executing the program. The storage unit is, for example, a nonvolatile memory. In addition, the program stored in the storage unit can be updated via a network such as the Internet such as OTA (Over The Air).

[0064] Next, use Figure 2 as well as Figure 7 to Figure 10 , the steering mechanism 70 is described.

[0065] The steering mechanism 70 is a mechanism for supporting the drive unit 22 with respect to the base portion 11 so as to be rotatable about a steering center axis extending in the up-down direction.

[0066] The steering mechanism 70 includes a base portion 71 fixed to the housing of the drive unit 22. The base portion 71 includes a rectangular plate-shaped base plate 72 and a side panel 73. The upper surface of the base plate 72 is parallel to the mounting surface 11a of the base portion 11, and the side panel 73 extends downward from one of the four edges of the base plate 72. The base plate 72 is fixed to the upper part of the drive unit 22, and more specifically, to the upper parts of the first housing 51 and the second housing 61. The side panel 73 is fixed to the side surface of the second housing 61. Figure 4 As shown, a through hole 73a through which the drive shaft 65 is inserted is formed in the side plate 73. The base plate 72 is provided with a steering center shaft 74 extending upward from the base plate 72.

[0067] The steering mechanism 70 includes a housing 75 corresponding to a "fixed portion" and a steering bearing 76. The steering bearing 76 is a rolling bearing having an inner ring 76a, an outer ring 76b, and an intermediate receiving portion 76c for receiving a plurality of rolling elements (specifically, rollers or balls) provided in the inner ring 76a and the outer ring 76b. A through hole 75a extending in the up-down direction is formed in the housing 75, and the housing 75 is cylindrical. The steering bearing 76 is fitted into the through hole 75a, and the outer ring 76b is fixed to the housing 75. The upper portion of the housing 75 is fixed to the lower portion of the base 11. The inner ring 76a is fixed to the upper end portion of the steering center shaft 74. Thus, the steering mechanism 70, the drive unit 22, and the drive wheel 21 can rotate integrally around the steering center shaft 74 relative to the base 11.

[0068] As a structure for allowing and limiting the rotation of the drive unit 22 and the drive wheel 21 relative to the base 11 around the steering center axis 74, the steering mechanism 70 includes a linear actuator 80 as an electric actuator, a locking pin 81 equivalent to a "limiting member", a linkage mechanism 82, a first stop portion 90 and a second stop portion 91.

[0069] The lock pin 81 has an elongated shape extending in a direction perpendicular to the longitudinal direction of the steering center shaft 74. The lock pin 81 is disposed in a state where a first end portion in the longitudinal direction faces the steering center shaft 74.

[0070] The linear actuator 80 is in the shape of an elongated strip and is fixed to the upper surface of the pedestal plate 72. The linear actuator 80 includes an elongated linear motion portion 80a extending in a direction perpendicular to the steering center axis 74 and a driving portion 80b on the base end side of the linear motion portion 80a. The driving portion 80b is fixed to the pedestal plate 72 in a state where it is arranged in a groove portion 77 formed in the pedestal plate 72. The driving portion 80b causes the linear motion portion 80a to reciprocate along the long side direction of the linear motion portion 80a by controlling the power supply by the control portion 47 or the upper ECU 48. The linear motion portion 80a is arranged in parallel with the locking pin 81 in a state where the long side direction of the linear motion portion 80a is in the same direction as the long side direction of the locking pin 81.

[0071] The linear actuator 80 and the lock pin 81 are arranged in parallel, thereby preventing the lengthwise dimension of the lock mechanism including the linear actuator 80 and the lock pin 81 from being large. As a result, the steering mechanism 70 can be miniaturized.

[0072] The linkage mechanism 82 is a mechanism for linking the movement of the linear motion portion 80a with the movement of the locking pin 81, and includes a bushing 83 (specifically a linear bushing), a connecting member 84, and a shaft portion 84a. The bushing 83 is fixed to the base plate 72 in parallel with the driving portion 80b, and supports the locking pin 81 so that the locking pin 81 can move in the longitudinal direction.

[0073] The connecting member 84 is in the shape of a strip extending in a direction perpendicular to the steering center axis 74. The shaft portion 84a extends upward from the base plate 72 and is provided between the linear action portion 80a and the locking pin 81 in the direction in which the linear action portion 80a and the locking pin 81 are arranged. The shaft portion 84a is connected to the middle portion in the longitudinal direction of the connecting member 84 so that the connecting member 84 can rotate around the shaft portion 84a with the middle portion of the connecting member 84 as the rotation center.

[0074] A first through hole is formed at the first end portion in the long side direction of the connecting member 84. In the first through hole, the shaft portion of the first bolt is inserted through the first through hole with the head portion of the first bolt facing upward. The top end portion of the shaft portion of the first bolt is fixed to the top end portion of the linear motion portion 80a. Thus, the top end portion of the linear motion portion 80a is connected to the first end portion of the connecting member 84 so that the first end portion of the connecting member 84 can rotate around the vertical axis relative to the top end portion of the linear motion portion 80a.

[0075] A second through hole is formed at the second end in the long-side direction of the connecting member 84. In the second through hole, the shaft of the second bolt is inserted through the second through hole with the head of the second bolt facing upward. The top end of the shaft of the second bolt is fixed to the second end in the long-side direction of the locking pin 81. Thus, the second end of the locking pin 81 is connected to the second end of the connecting member 84 so that the second end of the connecting member 84 can rotate around the vertical axis relative to the second end of the locking pin 81.

[0076] Since the lock mechanism including the linear actuator 80 , the lock pin 81 , and the interlocking mechanism 82 is located between the base 11 of the automated guided vehicle 10 and the travel road surface GL, the height dimension of the automated guided vehicle 10 can be reduced.

[0077] exist Figure 8 In FIG. 7 , the bushing 83, the housing 75 and the steering center shaft 74 of the steering mechanism 70 are shown in cross-section. Figure 8 As shown in FIG. 1 , a first rotation restricting portion 75b and a second rotation restricting portion 75c are formed on the side surface of the lower portion of the housing 75. The first rotation restricting portion 75b and the second rotation restricting portion 75c restrict the rotation of the housing 75 around the steering center shaft 74 by being fitted into the first end portion of the locking pin 81. The rotation restricting portions 75b and 75c are openings formed on the side surface of the housing 75. When the steering center shaft 74 is viewed from above, the first rotation restricting portion 75b is formed at a position rotated 90 degrees counterclockwise from the second rotation restricting portion 75c.

[0078] The first stopper 90 and the second stopper 91 extend upward from the base plate 72. Figure 7 and Figure 8 As shown, the first stopper 90 is configured to abut against the side surface of the housing 75 when the first end of the locking pin 81 faces the first rotation limiting portion 75b, so as to limit the rotation of the housing 75 relative to the pedestal plate 72 about the steering center axis 74. That is, when the housing 75 abuts against the first stopper 90, the housing 75 is prevented from rotating clockwise about the steering center axis 74 relative to the pedestal plate 72 when the steering center axis 74 is viewed from above.

[0079] exist Fig.15 In, with Figure 8 Similarly, the bushing 83, the housing 75, and the steering center shaft 74 in the steering mechanism 70 are shown in cross-section. Fig.15As shown, the second stopper 91 is configured to abut against the side surface of the housing 75 when the first end of the locking pin 81 faces the second rotation limiting portion 75c, so as to limit the rotation of the housing 75 relative to the base plate 72 about the steering center axis 74. That is, when the housing 75 abuts against the second stopper 91, the housing 75 is prevented from rotating counterclockwise about the steering center axis 74 relative to the base plate 72 when the steering center axis 74 is viewed from above.

[0080] The interlocking action of the linear actuator 80 and the locking pin 81 will be described by taking the case where the first end of the locking pin 81 is opposite to the first rotation restricting portion 75b as an example. Figure 7 and Figure 8 As shown in FIG. 1 , when the linear motion part 80a of the linear actuator 80 is advanced relative to the driving part 80b, the locking pin 81 is moved in the direction opposite to the advancing direction of the linear motion part 80a, and the first end of the locking pin 81 is inserted into the first rotation restricting part 75b. As a result, the rotation of the driving unit 22 and the driving wheel 21 relative to the base part 11 around the steering center axis 74 is prevented. At this time, the locking pin 81 is supported by the bushing 83, so that the rotation of the driving unit 22 and the driving wheel 21 relative to the steering center axis 74 of the base part 11 can be reliably prevented.

[0081] like Fig. 9 and Fig.10 As shown in FIG. 1 , when the linear motion part 80a is moved backward toward the driving part 80b, the locking pin 81 moves in the direction opposite to the backward direction of the linear motion part 80a, and the first end of the locking pin 81 is disengaged from the first rotation restricting part 75b. Thus, the rotation of the driving unit 22 and the driving wheel 21 around the steering center axis 74 relative to the base part 11 is allowed.

[0082] When a force in a direction intersecting the moving direction of the linear motion part 80a acts on the linear motion part 80a, there is a concern that the linear motion part 80a is difficult to move or the linear motion part 80a fails. In this regard, according to the structure including the locking pin 81, the connecting member 84 and the shaft portion 84a, a force in a direction intersecting the moving direction of the linear motion part 80a is difficult to act on the linear motion part 80a.

[0083] Next, an example of driving control of the unmanned transport vehicle 10 is described. Fig.11 and Fig.12 As shown, a travel control will be described for a case where an object to be transported is placed on the placement surface 11 a of the unmanned transport vehicle 10 , the unmanned transport vehicle 10 transports the object to a predetermined station ST, and then the unmanned transport vehicle 10 leaves the station ST.

[0084] like Fig.11As shown, 10A indicates an unmanned transport vehicle that is traveling forward. When the unmanned transport vehicle 10A reaches a predetermined position in the travel route of the work site, it switches from the forward travel mode to the mode of moving in the vehicle width direction. 10B indicates an unmanned transport vehicle that is moving in the vehicle width direction. When the unmanned transport vehicle 10B moves to the right and reaches the station ST, it moves the transported object to the station ST. Thereafter, as shown in FIG. Fig.12 As shown, the unmanned transport vehicle 10C moves to the left to leave the station ST. When the unmanned transport vehicle 10C reaches the predetermined position, the unmanned transport vehicle 10C switches from the vehicle width direction movement mode to the forward travel mode. Thus, the unmanned transport vehicle 10D starts to travel forward.

[0085] Below, use Fig.13 Flow chart of Fig.11 The driving control in the case shown will be described. This control is executed by the host ECU 48.

[0086] In step S10, in each electric drive device 20, the driving portion 80b of the linear actuator 80 is energized and controlled so that the lock pin 81 is inserted into the first rotation restricting portion 75b (see Figure 7 and Figure 8 ). Thus, the long side direction of the drive shaft 65 is fixed in the same direction as the vehicle width direction. In addition, a command is sent to the control unit 47 of each drive unit 22 to rotate the rotor 31 of the motor 30 in the first direction. Thus, in each drive unit 22, the control unit 47 controls the switch of the inverter 45, and the rotor 31 rotates in the first direction. As a result, the unmanned transport vehicle 10 moves forward.

[0087] When the driving wheels 21 are not being steered, the rotation of the housing 75 relative to the base plate 72 is restricted by the lock pin 81. Therefore, the automated guided vehicle 10 can be caused to travel forward in a stable manner.

[0088] In step S11, it is determined whether the position of the unmanned transport vehicle 10 has reached the position for switching from the forward driving mode to the vehicle width direction movement mode. If a positive determination is made in step S11, the process proceeds to step S12, and in each electric drive device 20, the drive unit 80b is energized and controlled so that the locking pin 81 is disengaged from the first rotation limiting unit 75b (equivalent to the "current rotation limiting unit") (refer to Fig. 9 and Fig.10 ). In the horizontal direction, the position of the steering center axis 74 is offset from the contact portion of the driving wheel 21 with respect to the road surface GL on which the unmanned guided vehicle 10 is traveling. Therefore, when the rotor 31 is rotated in the first direction to rotate the driving wheel 21, as shown in FIG. Fig.14As shown, in the steering mechanism 70, a moment is generated to rotate the drive unit 22 around the steering center axis 74. In this case, the drive unit 22 starts turning around the steering center axis 74 relative to the base portion 11 while maintaining the drive shaft 65 of the drive wheel 21 in a horizontal state. When the turning starts, the housing 75 leaves the first stopper 90.

[0089] In step S13, it is determined whether the turning of the drive unit 22 around the steering center axis 74 is completed. In the present embodiment, the turning completion means that the first end of the locking pin 81 is in a state opposite to the second rotation limiting portion 75c (equivalent to the "next rotation limiting portion") (see Fig.15 Whether the turn is completed can be determined by, for example, the following methods (A) to (C).

[0090] (A) The turning is determined to be completed when it is determined that the housing 75 is in contact with the second stopper 91. In this case, for example, based on the detection value of the current sensor, when it is determined that the maximum value of the phase current flowing to the stator winding 33a exceeds the determination current value, it is determined that the housing 75 is in contact with the second stopper 91.

[0091] (B) The sensor 49 includes a steering angle sensor that detects the rotation angle (steering angle) of the housing 75 relative to the pedestal plate 72 about the steering center axis 74. Based on the detection value of the steering angle sensor, it is determined that the turn is completed.

[0092] (C) The elapsed time from when the lock pin 81 is separated from the first rotation restricting portion 75b is counted, and when the counted elapsed time reaches the determination time, it is determined that the turn is completed.

[0093] When the housing 75 is in contact with the second stopper 91, the first end of the locking pin 81 is opposite to the second rotation limiting portion 75c. Therefore, the locking pin 81 can be easily aligned with the second rotation limiting portion 75c, and the locking pin 81 can be easily inserted into the second rotation limiting portion 75c.

[0094] In the subsequent step S14, in each electric drive device 20, the drive unit 80b is energized so that the lock pin 81 is inserted into the second rotation restricting portion 75c (see Fig.16 ). Thus, the long side direction of the drive shaft 65 is the vehicle length direction of the unmanned transport vehicle 10, and the driving mode is switched to the vehicle width direction moving mode. In step S15, the drive wheel 21 is rotated by rotating the rotor 31 in the first direction, thereby, Fig.11 As shown, the automated transport vehicle 10 is moved to the left toward the station ST.

[0095] Incidentally, although not shown in the flowchart, the unmanned transport vehicle 10 moves the transported object to the station ST. Fig.12 The driving control shown is explained.

[0096] The upper ECU 48 sends a command to the control unit 47 of each drive unit 22 to rotate the rotor 31 in a second direction opposite to the first direction. As a result, in each drive unit 22, the control unit 47 performs switch control on the inverter 45, and the rotor 31 rotates in the second direction. As a result, the unmanned guided vehicle 10 moves to the left in the vehicle width direction movement mode.

[0097] The host ECU 48 determines whether the position of the automated guided vehicle 10 has reached a position for switching from the vehicle width direction movement mode to the forward travel mode.

[0098] When it is determined that the position for switching to the forward driving mode has been reached, the upper ECU 48 controls the driving portion 80b in each electric drive device 20 to energize the locking pin 81 so that it is disengaged from the second rotation restricting portion 75c (equivalent to the "current rotation restricting portion"). In this state, when the rotor 31 is rotated in the second direction to rotate the driving wheel 21, the driving wheel 21 turns counterclockwise around the steering center axis 74 when the steering center axis 74 is viewed from above.

[0099] When it is determined that the housing 75 is in contact with the first stopper 90 and the turning of the drive unit 22 around the steering center axis 74 is completed, in each electric drive device 20, the upper ECU 48 controls the power supply of the drive unit 80b so that the locking pin 81 is embedded in the first rotation limiting portion 75b (equivalent to the "next rotation limiting portion"). As a result, the long side direction of the drive shaft 65 is the vehicle width direction of the unmanned transport vehicle 10, and the driving mode is switched to the forward driving mode. The upper ECU 48 switches the rotation direction of the rotor 31 from the second direction to the first direction, causing the rotor 31 to rotate in the first direction and causing the drive wheel 21 to rotate, thereby, as shown in FIG. Fig.12 As shown, the unmanned transport vehicle 10 is driven forward.

[0100] According to the present embodiment described in detail above, the driving wheels 21 can be steered by the rotational power of the motor 30 for driving the unmanned transport vehicle 10. Therefore, it is not necessary to use a motor for steering the driving wheels 21 that is different from the motor 30 for driving the unmanned transport vehicle 10. As a result, the structure of the electric drive device 20 can be simplified, and the unmanned transport vehicle 10 that is miniaturized in the vehicle width direction and the vehicle length direction can be provided.

[0101] <Second embodiment>

[0102] The second embodiment will be described below with reference to the accompanying drawings, centering on the differences from the first embodiment. In this embodiment, when the locking pin 81 is embedded in the rotation limiting portion, the rotation limiting portion is swung about the steering center axis 74 while maintaining the relative state of the first end portion of the locking pin 81.

[0103] Fig.17 is with Fig.13 Corresponding flowchart. In addition, Fig.17 In the previous Fig.13 The same processes are indicated by the same symbols for convenience.

[0104] If the determination in step S13 is positive, in step S16, the control unit 47 of each drive unit 22 is instructed to execute the swing control, and the drive unit 80b is energized so that the first end of the lock pin 81 fits into the second rotation restricting portion 75c. The swing control is a switch control of the inverter 45 that alternately repeats the rotation of the rotor 31 in a first direction and the rotation in a second direction opposite to the first direction.

[0105] According to the swing control, even when the positions of the lock pin 81 and the rotation restricting portion are slightly offset, the lock pin 81 can be inserted into the rotation restricting portion. In addition, the swing control can be performed even when the lock pin 81 is separated from the rotation restricting portion.

[0106] <Third Embodiment>

[0107] Hereinafter, the third embodiment will be described with reference to the accompanying drawings, centering on the differences from the first embodiment. Fig.18 and Fig.19 As shown, the drive unit 22 does not include the second reduction gear 60. Therefore, the drive shaft 65 is connected to the planetary carrier 52C included in the first reduction gear 50. As a result, the rotation center axis of the shaft 32 of the motor 30 is the same as the rotation center axis of the drive shaft 65. Fig.18 and Fig.19 In the drawings, the same structures as those shown in the first embodiment are denoted by the same reference numerals for convenience.

[0108] In the steering mechanism 70, the steering center shaft 74 is provided on the rotation center axis of the drive shaft 65 when the steering center shaft 74 is viewed from above. In addition, the linear actuator 80 is also provided on the rotation center axis of the drive shaft 65 when the steering center shaft 74 is viewed from above.

[0109] The linear action portion 80a of the linear actuator 80 is supported by the bushing 83. The linear action portion 80a is arranged so that the top end can be opposite to the first rotation limiting portion 75b or the second rotation limiting portion 75c of the housing 75. The top end of the linear action portion 80a can be embedded in the first rotation limiting portion 75b or the second rotation limiting portion 75c, and corresponds to a "limiting member". Incidentally, as a structure for limiting the rotation of the housing 75 relative to the pedestal plate 72 around the steering center axis 74, a structure having the linkage mechanism 82 described in the first embodiment may also be used.

[0110] <Other embodiments>

[0111] In addition, each of the above-mentioned embodiments can be implemented with modifications as follows.

[0112] The housing is not limited to the configurations described in the above embodiments, and may be a housing in which the inner ring 76 a of the steering bearing 76 is fixed to the housing 75 and the outer ring 76 b is fixed to the steering center shaft 74 , for example.

[0113] In the above-mentioned embodiments, the steering center shaft 74, the linear actuator 80, and the linkage mechanism 82 are provided on the pedestal plate 72, and the upper end of the housing 75 is fixed to the lower side of the base portion 11, but the present invention is not limited thereto. For example, the steering center shaft 74, the linear actuator 80, and the linkage mechanism 82 may be fixed to the lower side of the base portion 11, and the lower end of the housing 75 may be fixed to the pedestal plate 72.

[0114] The rotation restricting portion provided on the housing 75 is not limited to a structure penetrating the side surface of the housing 75 , and may be, for example, a recessed portion formed on the side surface of the housing 75 .

[0115] Either or both of the first stopper 90 and the second stopper 91 may be omitted.

[0116] The linkage mechanism is not limited to that of the first embodiment. Figure 3The structure shown in the figure may be a structure without the shaft portion 84a, for example. In this case, the top end of the linear motion portion 80a is connected to the first end of the connecting member 84 so that the first end of the connecting member 84 cannot rotate relative to the top end of the linear motion portion 80a around the vertical axis, and the second end of the locking pin 81 is connected to the second end of the connecting member 84 so that the second end of the connecting member 84 cannot rotate relative to the second end of the locking pin 81 around the vertical axis. In this structure, when the linear motion portion 80a is advanced relative to the driving portion 80b, the locking pin 81 moves in the same direction as the advancing direction of the linear motion portion 80a, and the first end of the locking pin 81 is disengaged from the rotation limiting portion. On the other hand, when the linear motion portion 80a is retreated toward the driving portion 80b, the locking pin 81 moves in the same direction as the retreating direction of the linear motion portion 80a, and the first end of the locking pin 81 is embedded in the rotation limiting portion.

[0117] The structure for operating the forward motion unit is not limited to a linear actuator, and may be, for example, a solenoid.

[0118] The motor is not limited to an inner rotor type motor, and may be an outer rotor type motor.

[0119] The unmanned transport vehicle is not limited to a six-wheel vehicle having two driving wheels and four driven wheels, and may be, for example, a four-wheel vehicle having two driving wheels and two driven wheels, or a three-wheel vehicle having two driving wheels and one driven wheel. In addition, the unmanned transport vehicle may have all wheels as driving wheels.

[0120] The unmanned transport vehicle used in the factory is not limited to the AGV, and may be, for example, an autonomous mobile robot (AMR).

[0121] The small mobile body is not limited to an unmanned transport vehicle, and may be, for example, a small electric vehicle such as an electric wheelchair or a walker for the elderly. The small electric vehicle is, for example, a vehicle with a travel speed of 10 km / h or less.

[0122] The control unit and method thereof recorded in the present invention can be implemented by a special-purpose computer, which is provided by constituting a processor and a memory programmed to execute one or more functions embodied by a computer program. Alternatively, the control unit and method thereof recorded in the present invention can also be implemented by a special-purpose computer, which is provided by constituting a processor composed of one or more special-purpose hardware logic circuits. Alternatively, the control unit and method thereof recorded in the present invention can also be implemented by one or more special-purpose computers, which are composed of a combination of a processor and a memory programmed to execute one or more functions and a processor composed of one or more hardware logic circuits. In addition, the computer program can be stored as an instruction executed by a computer in a non-transient tangible storage medium readable by a computer.

[0123] Hereinafter, characteristic structures extracted from the above-mentioned embodiments will be described.

[0124] [Structure 1]

[0125] An electric drive device (20) is applied to a vehicle (10) having a driving wheel (21), and causes the driving wheel to rotate around a rotation center axis extending in a horizontal direction to drive the vehicle to travel, wherein the electric drive device comprises:

[0126] a drive unit (22) disposed on the lower side of a base portion (11) of the vehicle and having a motor (30) and a transmission mechanism (50, 60) connected to the drive wheel and transmitting the rotational power of the motor to the drive wheel; and

[0127] a steering mechanism (70) disposed on the lower side of the base portion and having a steering center axis (74) extending in the vertical direction,

[0128] The steering mechanism supports the driving unit relative to the base portion so as to be rotatable around the steering center axis while maintaining the rotation center axis of the driving wheel in a horizontal state.

[0129] The steering mechanism is configured such that, in the horizontal direction, the position of the steering center axis is offset from a contact portion of the driving wheel with respect to a driving road surface (GL).

[0130] [Structure 2]

[0131] The electric drive device described in structure 1, wherein:

[0132] The steering mechanism comprises:

[0133] a limiting member (81, 80a) capable of moving between a position allowing the drive unit to rotate about the steering center axis and a position limiting the rotation of the drive unit about the steering center axis; and

[0134] An actuator (80) actuates the limiting member.

[0135] [Structure 3]

[0136] The electric drive device described in structure 2, wherein:

[0137] The steering mechanism comprises:

[0138] a fixing portion (75) fixed to the lower side of the base portion;

[0139] a pedestal portion (71), which is disposed on the lower side of the fixing portion and is fixed with the actuator; and

[0140] A bearing (76) comprising an inner ring (76a), an outer ring (76b) and a rolling element arranged between the inner ring and the outer ring.

[0141] The steering center shaft is fixed to the base portion in a manner extending upward from the base portion.

[0142] One of the inner ring and the outer ring is fixed to the steering center shaft, and the other is fixed to the fixing portion.

[0143] The base portion is rotatable relative to the fixing portion around the steering center axis.

[0144] The actuator has:

[0145] a long linear action portion (80a) extending in a direction orthogonal to the steering center axis; and

[0146] A driving unit (80b) is provided on the base end side of the linear motion unit and fixed to the pedestal unit, so as to cause the linear motion unit to reciprocate along the longitudinal direction of the linear motion unit.

[0147] The limiting component (81) is in the shape of an elongated strip.

[0148] The limiting member is arranged in parallel with the linear motion portion in a state where the first end portion faces the steering center axis and the longitudinal direction of the limiting member is in the same direction as the longitudinal direction of the linear motion portion.

[0149] A rotation limiting portion (75b, 75c) is provided on the side surface of the fixing portion, and the rotation limiting portion limits the rotation of the fixing portion around the steering center axis by allowing the first end of the limiting member to be embedded.

[0150] The electric drive device includes a linkage mechanism (82) which is provided on the base portion and links the movement of the linear motion portion with the movement of the restricting member.

[0151] [Structure 4]

[0152] The electric drive device described in structure 3, wherein:

[0153] The linkage mechanism comprises:

[0154] a shaft portion (84a) disposed between the linear action portion and the limiting member in a direction in which the linear action portion and the limiting member are arranged, and extending upward from the pedestal portion; and

[0155] A connecting member (84) is in the shape of an elongated strip.

[0156] The shaft portion is connected to a middle portion in the longitudinal direction of the connecting member so that the connecting member can rotate around the shaft portion with the middle portion as a rotation center.

[0157] The top end of the linear motion portion is connected to the first end of the connection member so that the first end of the connection member can rotate around the vertical axis relative to the top end of the linear motion portion.

[0158] The second end of the limiting member is connected to the second end of the connecting member so that the second end of the connecting member can rotate around the vertical axis relative to the second end of the limiting member.

[0159] When the linear motion part is advanced relative to the driving part, the limiting member moves in a direction opposite to the advancing direction of the linear motion part, and the first end of the limiting member is engaged with the rotation limiting part.

[0160] When the linear motion portion is retracted toward the driving portion, the restriction member is moved in a direction opposite to the retracting direction of the linear motion portion, and the first end portion of the restriction member is separated from the rotation restriction portion.

[0161] [Structure 5]

[0162] The electric drive device described in structure 3 or 4, wherein:

[0163] The rotation restricting portions are respectively provided at different positions in the circumferential direction around the steering center axis on the side surface of the fixing portion.

[0164] The electric drive device includes a stopper (90, 91) provided on the stopper (90, 91) of the pedestal.

[0165] The stopper is configured so as to come into contact with the fixing portion and restrict the rotation of the fixing portion around the steering center axis when the first end portion of the restriction member faces any one of the rotation restriction portions.

[0166] [Structure 6]

[0167] The electric drive device described in structure 5, wherein:

[0168] The electric drive device includes a control device (47, 48) that controls the energization of the motor and the energization of the drive unit for actuating the linear motion unit.

[0169] After the driving unit is driven and controlled so that the first end of the limiting member is disengaged from the current rotation limiting member in which the first end of the limiting member is currently embedded, the control device controls the power supply of the motor to rotate the rotor (31) constituting the motor in a first direction to turn the driving wheel around the steering center axis.

[0170] After the driving wheel starts turning, the control device determines whether the first end of the limiting member is in a state opposite to a next rotation limiting portion, which is a next insertion destination of the first end of the limiting member, among the rotation limiting portions.

[0171] When it is determined that the first end of the limiting member is in a state relative to the next rotation limiting member, the control device controls the power supply of the motor and the driving unit so that the first end of the limiting member is embedded in the next rotation limiting member while maintaining the first end of the limiting member relative to the next rotation limiting member and alternatingly repeating the rotation of the rotor in the first direction and the rotation in the second direction opposite to the first direction.

[0172] [Composition 7]

[0173] The electric drive device according to any one of structures 1 to 6, wherein:

[0174] The vehicle to which the electric drive device is applied is an unmanned transport vehicle used in a work area.

[0175] The present invention is described based on the embodiments. However, it should be understood that the present invention is not limited to the embodiments and structures. The present invention also includes various modifications and modifications within the equivalent range. In addition, various combinations and modes, even other combinations and modes that only include one element, more than one or less than one element, also fall within the scope and thought range of the present invention.

Claims

1. An electric drive device (20) applied to a vehicle (10) having a driving wheel (21), which causes the driving wheel to rotate around a rotation center axis extending in a horizontal direction to drive the vehicle, characterized in that: have: a drive unit (22) disposed on the lower side of a base portion (11) of the vehicle and having a motor (30) and a transmission mechanism (50, 60) connected to the drive wheel and transmitting the rotational power of the motor to the drive wheel; as well as a steering mechanism (70) disposed on the lower side of the base portion and having a steering center axis (74) extending in the vertical direction, The steering mechanism supports the driving unit relative to the base portion so as to be rotatable around the steering center axis while maintaining the rotation center axis of the driving wheel in a horizontal state. The steering mechanism is configured such that, in the horizontal direction, the position of the steering center axis is offset from a contact portion of the driving wheel with respect to a driving road surface (GL).

2. The electric drive device according to claim 1, characterized in that: The steering mechanism comprises: a limiting component (81, 80a) capable of moving between a position allowing the drive unit to rotate around the steering center axis and a position limiting the rotation of the drive unit around the steering center axis; as well as An actuator (80) actuates the limiting member.

3. The electric drive device according to claim 2, characterized in that: The steering mechanism comprises: a fixing portion (75) fixed to the lower side of the base portion; a pedestal portion (71), which is disposed on the lower side of the fixing portion and is fixed with the actuator; and A bearing (76) comprising an inner ring (76a), an outer ring (76b) and a rolling element arranged between the inner ring and the outer ring. The steering center shaft is fixed to the base portion in a manner extending upward from the base portion. One of the inner ring and the outer ring is fixed to the steering center shaft, and the other is fixed to the fixing portion. The base portion is rotatable relative to the fixing portion around the steering center axis. The actuator has: a long linear action portion (80a) extending in a direction orthogonal to the steering center axis; and A driving unit (80b) is provided on the base end side of the linear motion unit and fixed to the pedestal unit, so as to cause the linear motion unit to reciprocate along the longitudinal direction of the linear motion unit. The limiting component (81) is in the shape of an elongated strip. The limiting member is arranged in parallel with the linear motion portion in a state where the first end portion faces the steering center axis and the longitudinal direction of the limiting member is in the same direction as the longitudinal direction of the linear motion portion. A rotation limiting portion (75b, 75c) is provided on the side surface of the fixing portion, and the rotation limiting portion limits the rotation of the fixing portion around the steering center axis by allowing the first end of the limiting member to be embedded. The electric drive device includes a linkage mechanism (82) which is provided on the base portion and links the movement of the linear motion portion with the movement of the restricting member.

4. The electric drive device according to claim 3, characterized in that: The linkage mechanism comprises: a shaft portion (84a) disposed between the linear action portion and the limiting component in a direction in which the linear action portion and the limiting component are arranged, and extending upward from the pedestal portion; as well as A connecting member (84) is in the shape of an elongated strip. The shaft portion is connected to a middle portion in the longitudinal direction of the connecting member so that the connecting member can rotate around the shaft portion with the middle portion as a rotation center. The top end of the linear motion portion is connected to the first end of the connection member so that the first end of the connection member can rotate around the vertical axis relative to the top end of the linear motion portion. The second end of the limiting member is connected to the second end of the connecting member so that the second end of the connecting member can rotate around the vertical axis relative to the second end of the limiting member. When the linear motion part is advanced relative to the driving part, the limiting member moves in a direction opposite to the advancing direction of the linear motion part, and the first end of the limiting member is engaged with the rotation limiting part. When the linear motion portion is retracted toward the driving portion, the restriction member is moved in a direction opposite to the retracting direction of the linear motion portion, and the first end portion of the restriction member is separated from the rotation restriction portion.

5. The electric drive device according to claim 3 or 4, characterized in that: The rotation restricting portions are respectively provided at different positions in the circumferential direction around the steering center axis on the side surface of the fixing portion. The electric drive device includes a stopper (90, 91) provided on the pedestal. The stopper is configured so as to come into contact with the fixing portion and restrict the rotation of the fixing portion around the steering center axis when the first end portion of the restriction member faces any one of the rotation restriction portions.

6. The electric drive device according to claim 5, characterized in that: The electric drive device includes a control device (47, 48) that controls the energization of the motor and the energization of the drive unit for actuating the linear motion unit. After the driving unit is driven and controlled so that the first end of the limiting member is disengaged from the current rotation limiting member in which the first end of the limiting member is currently embedded, the control device controls the power supply of the motor to rotate the rotor (31) constituting the motor in a first direction to turn the driving wheel around the steering center axis. After the driving wheel starts turning, the control device determines whether the first end of the limiting member is in a state opposite to a next rotation limiting portion, which is a next insertion destination of the first end of the limiting member, among the rotation limiting portions. When it is determined that the first end of the limiting member is in a state relative to the next rotation limiting member, the control device controls the power supply of the motor and the driving unit so that the first end of the limiting member is embedded in the next rotation limiting member while maintaining the first end of the limiting member relative to the next rotation limiting member and alternatingly repeating the rotation of the rotor in the first direction and the rotation in the second direction opposite to the first direction.

7. The electric drive device according to claim 6, characterized in that: The vehicle to which the electric drive device is applied is an unmanned transport vehicle used in a work area.

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