Active Caster

Abstract

To provide an active caster that can confirm that the encoder is correctly detecting the steering angle of the drive wheels. [Solution] The active caster 110 includes a drive wheel 15 that is steered in accordance with the rotational drive of a first drive unit 23A and a second drive unit 23B, a steering shaft member 35 that rotates in conjunction with the steering of the drive wheel 15, a detection member 410 that extends outward from the steering shaft member 35, an encoder 107 that detects the rotation angle of the steering shaft member 35, and a sensor 400 that determines whether the output of the encoder 107 matches the rotation angle of the steering shaft member 35.

Description

Technical Field

[0001] The present invention relates to an active caster.

Background Art

[0002] For example, Patent Document 1 discloses a transport device having a vehicle body, a plurality of drive wheels supported by the vehicle body, and a plurality of driven wheels supported by the vehicle body. Such drive wheels are connected to an electric motor and rotationally driven to run the transport device.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Patent Document 1 does not consider steering the drive wheels when changing the direction of travel of a conveying device, and assumes the use of Mecanum wheels or Omni wheels as drive wheels. These wheels are usually used in sets of four, and if three or more wheels are not in contact with the ground, there is a risk of slippage against the floor surface. In addition, such wheels can be a source of vibration. Therefore, when using these wheels, stable travel may be difficult. For these reasons, an active caster equipped with drive wheels that can change the direction of travel by steering is advantageous for achieving more stable travel. On the other hand, steering the drive wheels requires that the steering angle of the drive wheels be correctly controlled. When an encoder is used to detect the steering angle of the drive wheels for the purpose of such control, if a mechanical problem occurs in the coupling mechanism between the encoder's detection shaft and the drive wheel's steering shaft, the encoder may not be able to correctly detect the steering angle of the drive wheels. In this case, the conveying device cannot be correctly moved toward the target point. Therefore, there was a need for a mechanism that could confirm that the encoder was correctly detecting the steering angle of the drive wheels.

[0005] This disclosure has been made in view of the above-mentioned problems and aims to provide an active caster that can confirm that the encoder is able to correctly detect the steering angle of the drive wheel. [Means for solving the problem]

[0006] An active caster according to one aspect of the present disclosure for achieving the above objectives includes: a drive wheel connected to at least one electric motor and steered in accordance with the rotational drive of the electric motor; a first member positioned on either side of the drive wheel and facing the ground surface of the drive wheel, functioning as a steering shaft for the drive wheel and rotating in conjunction with the steering of the drive wheel; a second member extending radially outward from the first member around the steering shaft; an encoder for detecting the rotation angle of the first member; and a sensor for determining whether the output of the encoder matches the rotation angle of the steering shaft.

[0007] A preferred embodiment of the active caster described above includes a drive wheel base that rotatably supports the first member, and the sensor is fixed to the drive wheel base.

[0008] In a preferred configuration of the active caster described above, the second member and the sensor are provided on the drive wheel side relative to the first member.

[0009] In a preferred embodiment of the above-described active caster, the encoder detects the rotation angle of the detection shaft, and the detection shaft is connected to the first member via a first toothed pulley fixed to the first member and rotating together with the first member, a second toothed pulley rotating around the detection shaft as the axis of rotation, and a toothed belt connecting the first toothed pulley and the second toothed pulley, and the encoder output indicates that the rotation angle of the first member is not the predetermined rotation angle, and the sensor output indicates that the rotation angle of the first member is not the predetermined rotation angle, the encoder includes a control circuit that determines that tooth skipping has occurred between the first toothed pulley or the second toothed pulley and the toothed belt.

[0010] In a preferred configuration of the active caster described above, the control circuit, when it is determined that tooth skipping has occurred, operates the electric motor to set the steering angle of the drive wheel to such an angle that the sensor output indicating the rotation angle of the first member is the predetermined rotation angle, and sets the output of the encoder when the steering angle is set to the output of the encoder indicating the rotation angle of the first member is the predetermined rotation angle.

[0011] In a preferred embodiment of the above-mentioned active caster, the sensor is a photocoupler.

[0012] In a preferred embodiment of the above-mentioned active caster, the sensor is a magnetic sensor.

[0013] In a preferred embodiment of the above-mentioned active caster, the sensor is a capacitive sensor.

Advantages of the Invention

[0014] According to the present disclosure, it can be verified that the encoder can correctly detect the steering angle of the drive wheel.

Brief Description of the Drawings

[0015] [Figure 1] FIG. 1 is a perspective view of the transport device according to the embodiment as viewed from above. [Figure 2] FIG. 2 is a perspective view of the transport device according to the embodiment as viewed from below. [Figure 3] FIG. 3 is a bottom view of the transport device according to the embodiment. [Figure 4] FIG. 4 is a bottom view of another example of the transport device according to the embodiment. [Figure 5] FIG. 5 is a bottom view of another example of the transport device according to the embodiment. [Figure 6] FIG. 6 is a bottom view of another example of the transport device according to the embodiment. [Figure 7] FIG. 7 is a perspective view of the drive wheel according to the embodiment. [Figure 8] FIG. 8 is a side view of the drive wheel according to the embodiment. [Figure 9] FIG. 9 is a perspective view showing the drive wheel body of the drive wheel according to the embodiment. [Figure 10] FIG. 10 is a perspective view showing the drive system of the drive wheel body of the drive wheel according to the embodiment. [Figure 11] FIG. 11 is an exploded perspective view of the drive wheel according to the embodiment. [Figure 12] FIG. 12 is a schematic diagram showing the driving force transmission path of the drive wheel body of the drive wheel according to the embodiment. [Figure 13] FIG. 13 is a schematic plan view of the active caster 110 as viewed from the Z2 side in the sixth direction. [Figure 14] FIG. 14 is a perspective view showing the configuration near the sensor 400 when the sensor 400 and the detected member 410 are in the positional relationship shown in FIGS. 13 and FIG. 17 described later. [Figure 15]FIG. 15 is a schematic plan view of the active caster 110 as viewed from the fifth direction Z1 side. [Figure 16] FIG. 16 is a perspective view showing the configuration near the toothed pulley 25C and the encoder 107 shown in FIG. 15. [Figure 17] FIG. 17 is a plan view showing an example of the active caster 110 when the rotation angle of the steering shaft member 35 is such that the extending portion 411 and the sensor 400 overlap in a plan view. [Figure 18] FIG. 18 is a plan view showing an example where a deviation from the predefined correspondence relationship between the rotation angles of the steering shaft member 35 and the detection shaft 107C occurs, as viewed from each of the upper side and the lower side. [Figure 19] FIG. 19 is a perspective view showing an enlarged view of the vicinity of the sensor 400 and the detected member 410 in the configuration on the lower side shown in FIG. 18. [Figure 20] FIG. 20 is a block diagram showing the main configuration related to the control of the active caster 110. [Figure 21] FIG. 21 is a flowchart showing the processing flow by the control circuit 420 having the reset function of the output of the encoder 107 treated as 0°. [Figure 22] FIG. 22 is a schematic view showing a configuration example in which a plurality of sensors are provided. [Figure 23] FIG. 23 is a schematic view showing a configuration example in which a plurality of detected members 410 are provided.

Embodiments for Carrying out the Invention

[0016] Hereinafter, with reference to the drawings, preferred embodiments of the drive wheel and the carriage according to the present disclosure will be described in detail. Note that the present invention is not limited by this embodiment, and when there are a plurality of embodiments, those configured by combining each embodiment are also included. In addition, the components in the embodiments include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those within the so-called equivalent range.

[0017] The transport device 1 of this embodiment is applied as a transport trolley that carries transported objects and travels on the floor. Although not explicitly shown in the figure, the transport device 1 can be used as a transport assistance device such as an automated guided vehicle (AGV), an autonomous mobile robot (AMR), or a transport assistance drive device. Transported objects can include a variety of items such as hand lifters, forklifts, picking robots, and medical equipment.

[0018] As shown in Figures 1 to 3, the transport device 1 includes a trolley body 100, active casters 110, driven wheels 210, and a lifting mechanism 310.

[0019] The trolley body 100 is the base on which the active casters 110, the driven wheels 210, and the lifting mechanism 310 are arranged, and it is also the case that houses the active casters 110, the driven wheels 210, and the lifting mechanism 310.

[0020] The trolley body 100 includes a trolley base 102 and a case portion 101 that surrounds the upper part of the trolley base 102. The trolley base 102 constitutes the base of the transport device 1 and is formed in a plate shape, for example, forming the bottom plate of the transport device 1. Active casters 110, driven wheels 210, and a lifting mechanism 310 are arranged on the plate-shaped upper surface of the trolley base 102. The case portion 101 consists of a wall portion that rises upward from the plate-shaped perimeter of the trolley base 102 and a top plate (not shown) that faces the plate shape of the trolley base 102 and covers the upper part of the wall portion. Therefore, the active casters 110, driven wheels 210, and lifting mechanism 310 arranged on the trolley base 102 are housed inside the trolley body 100, which consists of the trolley base 102 and the case portion 101.

[0021] The active casters 110 are provided in at least two locations on the bogie body 100, as shown in Figures 1 to 6, although this will be described in detail later. The driven wheels 210 are provided in at least one location on the bogie body 100, as shown in Figures 1 to 6, although this will be described in detail later.

[0022] The active casters 110 are positioned symmetrically with respect to the center O (or any position in the center) of the bogie base 102 of the bogie body 100. In Figure 3, the active casters 110 are positioned at the front and rear in the direction of travel indicated by arrow R, with respect to the center O of the bogie base 102. In this case, two driven wheels 210 are provided and are positioned on the left and right in the direction of travel indicated by arrow R, with respect to the center O of the bogie base 102.

[0023] Furthermore, in Figure 4, the active casters 110 are positioned diagonally in the front and rear directions of travel indicated by arrow R, with the center O of the bogie base 102 as the reference point. In this case, two driven wheels 210 are provided and are positioned diagonally opposite to the active casters 110, in the front and rear directions of travel indicated by arrow R, with the center O of the bogie base 102 as the reference point.

[0024] Furthermore, in Figure 5, the active casters 110 are positioned to the left and right in the direction of travel indicated by arrow R, with the center O of the bogie base 102 as the reference point. In this case, two driven wheels 210 are provided and are positioned in front of and behind the center O of the bogie base 102 in the direction of travel indicated by arrow R.

[0025] Furthermore, in Figure 6, the active casters 110 are positioned on the left and right sides, either at the rear or front in the direction of travel indicated by arrow R, with respect to the center O of the bogie base 102. In this case, one driven wheel 210 is provided and positioned either at the front or rear in the direction of travel indicated by arrow R, with respect to the center O of the bogie base 102.

[0026] As shown in Figure 1, the lifting mechanism 310 is positioned in the center of the plate-shaped upper surface O of the trolley base 102 of the trolley body 100, surrounded by the active casters 110 and the driven wheels 210. The lifting mechanism 310 includes a link mechanism 311, a connecting module 312, and a drive unit 313. The link mechanism 311 is composed of, for example, a pantograph or an X-link, and is provided between the trolley base 102 and the connecting module 312. The connecting module 312 is fitted into the fixed part of the transported object (not shown). The drive unit 313 is composed of an actuator or the like, and drives the link mechanism 311. The lifting mechanism 310 then drives the link mechanism 311 with the drive unit 313, causing the connecting module 312 to move vertically. The connecting module 312 moving downward is housed in the trolley body 100. The upward-moving connection module 312 engages with the fixed part of the transported object, connecting the trolley body 100 to the transported object. The transport device 1, with the trolley body 100 connected to the transported object, transports the object by moving.

[0027] The details of the active caster 110 are described below. As shown in Figures 7 to 9, the active caster 110 includes a drive wheel base 103, a drive wheel body 105, and a drive wheel side suspension mechanism 106. In the following description, the side of the encoder 107 is referred to as the first direction X1, with the steering shaft member 35 as the reference. The side opposite the encoder 107 is referred to as the second direction X2, with the steering shaft member 35 as the reference. The side of the first drive unit 23A is referred to as the third direction Y1, with the steering shaft member 35 as the reference. The side of the second drive unit 23B is referred to as the fourth direction Y2, with the steering shaft member 35 as the reference. Furthermore, the side of the first drive wheel side elastic member 54A is referred to as the fifth direction Z1, with the drive wheel base 103 as the reference. When the drive wheel base 103 is the reference, the fifth direction Z1 is substantially synonymous with the upward direction. Furthermore, with the drive wheel base 103 as the reference, the side of the second drive wheel elastic member 54B is designated as the sixth direction Z2 side. When the drive wheel base 103 is used as the reference, the sixth direction Z2 side is substantially synonymous with the downward side. Also, the first direction X1 and the second direction X2 are aligned with the X direction. The third direction Y1 and the fourth direction Y2 are aligned with the Y direction. The fifth direction Z1 and the sixth direction Z2 are aligned with the Z direction. The X and Y directions are aligned with the plate surface of the drive wheel base 103. The Z direction is perpendicular to the plate surface of the drive wheel base 103. Furthermore, when "planar viewpoint" is mentioned in the following description, it refers to a viewpoint that looks straight ahead at the plane aligned with the X and Y directions. Furthermore, when "plan view" is mentioned in the following explanation, it refers to a view from a planar viewpoint.

[0028] The drive wheel base 103 constitutes the base of the active caster 110. The drive wheel base 103 is formed in a plate shape. The drive wheel base 103 is positioned above the bogie base 102, with its plate surfaces facing each other vertically. By positioning the drive wheel base 103, which forms the base of the active caster 110, above the bogie base 102, the overall height of the active caster 110 can be reduced compared to positioning the drive wheel base 103 below the bogie base 102, thereby enabling a lower floor profile.

[0029] The drive wheel body 105 is positioned on the drive wheel base 103 and includes a drive mechanism 11 shown in Figure 9, a swivel section 12 shown in Figure 8, a transmission mechanism 13 shown in Figure 10, a power conversion mechanism 14, and a drive wheel 15. The drive mechanism 11 inputs rotational force to the drive wheel body 105. The swivel section 12 is positioned on the drive wheel base 103. The transmission mechanism 13 transmits the rotational force input by the drive mechanism 11. The power conversion mechanism 14 transmits the rotational force of the transmission mechanism 13 to the drive wheel 15. The drive wheel 15 is rotatable by the rotational force input from the drive mechanism 11 via the transmission mechanism 13 and the power conversion mechanism 14, and is also steerable by the swivel section 12.

[0030] The drive mechanism 11 includes a first drive mechanism 22A and a second drive mechanism 22B.

[0031] The first drive mechanism 22A includes a first drive unit 23A, a first drive pulley 24A, a first input shaft 25A, a first driven pulley 26A, and a first drive belt 27A. The first drive unit 23A is composed of an electric motor that functions as a motor. The first drive unit 23A is fixed to the drive wheel base 103. The first drive unit 23A has a drive shaft 23Aa that protrudes above the upper surface of the drive wheel base 103 and extends vertically. The first drive pulley 24A is fixed to the drive shaft 23Aa. The first input shaft 25A is provided extending vertically parallel to the drive shaft 23Aa and is rotatably supported about the axis O1. The first driven pulley 26A is fixed to the upper end of the first input shaft 25A. The first driven pulley 26A and the first drive pulley 24A are provided side by side in directions perpendicular to the first input shaft 25A and the drive shaft 23Aa. The first drive belt 27A is formed in an annular shape and is wrapped around the first driven pulley 26A and the first drive pulley 24A. Therefore, the first drive mechanism 22A is driven by the first drive unit 23A, which causes the first drive pulley 24A to rotate, and this rotation is transmitted from the first drive pulley 24A to the first driven pulley 26A via the first drive belt 27A, causing the first input shaft 25A to rotate.

[0032] The second drive mechanism 22B includes a second drive unit 23B, a second drive pulley 24B, a second input shaft 25B, a second driven pulley 26B, and a second drive belt 27B. The second drive unit 23B is composed of an electric motor that functions as a motor. The second drive unit 23B is fixed to the drive wheel base 103. The second drive unit 23B has a drive shaft 23Ba that protrudes above the upper surface of the drive wheel base 103 and extends vertically. The second drive pulley 24B is fixed to the drive shaft 23Ba. The second drive pulley 24B is formed to have the same diameter as the first drive pulley 24A. The second input shaft 25B is provided extending vertically parallel to the drive shaft 23Ba and is rotatably supported about the axis O1. The second input shaft 25B is cylindrical in shape and passes through the first input shaft 25A. It is positioned to rotate relative to the first input shaft 25A, but independently of the first input shaft 25A. The second driven pulley 26B is fixed to the upper end of the second input shaft 25B. The second driven pulley 26B is formed to the same diameter as the first driven pulley 26A and is located below the first driven pulley 26A. The second driven pulley 26B and the second drive pulley 24B are arranged side by side in a direction perpendicular to the second input shaft 25B and the drive shaft 23Ba. The second drive belt 27B is annular in shape and is wrapped around the second driven pulley 26B and the second drive pulley 24B. Therefore, the second drive mechanism 22B drives the second drive unit 23B, causing the second drive pulley 24B to rotate. This rotation is transmitted from the second drive pulley 24B to the second driven pulley 26B via the second drive belt 27B, causing the second input shaft 25B to rotate.

[0033] As shown in Figure 8, the swivel section 12 is composed of a steering shaft member 35 and a support member 36.

[0034] The steering shaft member 35 is formed in a disc shape, with its center being the axis O1, and is rotatably supported by a through-hole formed vertically through the projection 103A of the drive wheel base 103. Thus, the steering shaft member 35 is supported so as to be rotatable relative to the drive wheel base 103 about the axis O1. In other words, the drive wheel base 103 rotatably supports the steering shaft member 35. Furthermore, the steering shaft member 35 rotatably supports the first input shaft 25A of the first drive mechanism 22A. Therefore, the first input shaft 25A is supported so as to be rotatable relative to the steering shaft member 35 about the axis O1, and also so as to be rotatable relative to the drive wheel base 103 about the axis O1. That is, the steering shaft member 35 is rotatably mounted relative to the drive wheel base 103 regardless of the rotation of the first input shaft 25A. Furthermore, the steering shaft member 35 rotatably supports the second input shaft 25B of the second drive mechanism 22B. Therefore, the second input shaft 25B is supported so as to be rotatable relative to the steering shaft member 35 about the axis O1 via the first input shaft 25A, and is also supported so as to be rotatable relative to the drive wheel base 103 about the axis O1. In other words, the steering shaft member 35 is rotatable relative to the drive wheel base 103 regardless of the rotation of the second input shaft 25B. Thus, the first input shaft 25A, the second input shaft 25B, and the steering shaft member 35 are rotatably arranged coaxially along the axis O1.

[0035] The support members 36 are provided at the lower part of the steering shaft member 35 and are positioned on both sides of the drive wheel 15 in the horizontal direction. The drive wheel 15 is integrally provided with an axle 37 (see Figure 10) that extends along an axis O2 perpendicular to the direction in which the axis O1 extends (vertical direction). Each end of the axle 37 along the axis O2 is rotatably supported with respect to the support members 36. Furthermore, as shown in Figure 8, the rotation axis O5 of the drive wheel 15, which is aligned in the vertical direction intersecting the axis O2 of the axle 37, is positioned offset from the axis O1 of the steering shaft member 35 in the horizontal direction perpendicular to the axis O2 of the axle 37.

[0036] As shown in Figure 10, the transmission mechanism 13 includes a first transmission mechanism 13A and a second transmission mechanism 13B. The first transmission mechanism 13A comprises a first transmission drive gear 38A, a first transmission driven gear 39A, and a first output shaft 40A. The second transmission mechanism 13B comprises a second transmission drive gear 38B, a second transmission driven gear 39B, and a second output shaft 40B. In this embodiment, the first transmission drive gear 38A, the first transmission driven gear 39A, the second transmission drive gear 38B, and the second transmission driven gear 39B are helical gears.

[0037] In the first transmission mechanism 13A, the first transmission drive gear 38A, the first transmission driven gear 39A, and the first output shaft 40A are arranged on the support member 36 of the swivel section 12. The first transmission drive gear 38A is fixed to the lower end of the first input shaft 25A, which passes through the second input shaft 25B. The first transmission driven gear 39A meshes with the first transmission drive gear 38A. The first transmission driven gear 39A is fixed to the first output shaft 40A. The first output shaft 40A is supported by the support member 36 so as to be rotatable about its axis O3. When viewed in the axial direction of the axle 37, that is, in a side view (see Figure 8) where the axis O2 of the axle 37 is viewed as a point, the axis O3 of the first output shaft 40A is set to be inclined with respect to the axis O1 of the first input shaft 25A. The axial directions of the first output shaft 40A and the axle 37 are 90 degrees apart. Furthermore, in a side view (see Figure 8), the axis O3 of the first output shaft 40A intersects with the axis O2.

[0038] In the second transmission mechanism 13B, the second transmission drive gear 38B, the second transmission driven gear 39B, and the second output shaft 40B are arranged on the support member 36 of the swivel section 12. The second transmission drive gear 38B is fixed to the lower end of the second input shaft 25B. The second transmission driven gear 39B meshes with the second transmission drive gear 38B. The second transmission driven gear 39B is fixed to the second output shaft 40B. The second input shaft 25B is supported by the support member 36 so as to be rotatable about its axis O4. When viewed in the axial direction of the axle 37, that is, in a side view (see Figure 8) where the axis O2 of the axle 37 is viewed as a point, the axis O4 of the second input shaft 25B is set to be inclined with respect to the axis O1 of the second input shaft 25B. The axial directions of the second output shaft 40B and the axle 37 are 90 degrees apart. Furthermore, in a side view (see Figure 8), the axis O4 of the second output shaft 40B intersects the axis O2.

[0039] As shown in Figure 10, the power conversion mechanism 14 includes a first power conversion mechanism 14A and a second power conversion mechanism 14B. The first power conversion mechanism 14A is composed of a first conversion drive gear 41A and a first conversion driven gear 42A. The second power conversion mechanism 14B is composed of a second conversion drive gear 41B and a second conversion driven gear 42B. In this embodiment, the first conversion drive gear 41A, the first conversion driven gear 42A, the second conversion drive gear 41B, and the second conversion driven gear 42B are composed of bevel gears.

[0040] In the first power conversion mechanism 14A, the first conversion drive gear 41A is fixed to the lower end of the first output shaft 40A. The first conversion driven gear 42A is fixed to one end of the axle 37. The first conversion drive gear 41A meshes with the first conversion driven gear 42A. Therefore, the first power conversion mechanism 14A converts the rotation of the first output shaft 40A around its axis O3 into rotation of the axle 37 around its axis O2.

[0041] In the second power conversion mechanism 14B, the second conversion drive gear 41B is fixed to the lower end of the second output shaft 40B. The second conversion driven gear 42B is fixed to the other end of the axle 37. The second conversion drive gear 41B meshes with the second conversion driven gear 42B. Therefore, the second power conversion mechanism 14B converts the rotation of the second output shaft 40B around its axis O4 into rotation of the axle 37 around its axis O2.

[0042] The drive wheel body 105 can rotate and steer the drive wheel 15 by rotating the first input shaft 25A and the second input shaft 25B by the drive mechanism 11. For example, by rotating the first input shaft 25A and rotating the second input shaft 25B in the opposite direction to the first input shaft 25A, and making the rotational speeds of the first input shaft 25A and the second input shaft 25B the same, the drive wheel 15 can rotate without steering. At this time, by making the rotational speeds of the first input shaft 25A and the second input shaft 25B different, the drive wheel 15 can be steered while rotating or stationary. In this way, the drive wheel 15 functions as a wheel that is connected to an electric motor (first drive unit 23A, second drive unit 23B) and steers in accordance with the rotational drive of the electric motor.

[0043] Now, let's explain the operation of the drive wheel body 105. As shown in Figure 12, when the first input shaft 25A of the drive wheel body 105 is rotated in the A1 direction, the first transmission drive gear 38A rotates in the same direction, the first transmission driven gear 39A rotates in the A2 direction along with the first output shaft 40A, and the first conversion drive gear 41A rotates in the same direction. Then, the first conversion driven gear 42A rotates in the A3 direction, causing the axle 37 to rotate in the same direction. On the other hand, when the second input shaft 25B of the drive wheel body 105 is rotated in the B1 direction, which is opposite to the A1 direction, the second transmission drive gear 38B rotates in the same direction, the second transmission driven gear 39B rotates in the B2 direction along with the second output shaft 40B, and the second conversion drive gear 41B rotates in the same direction. Then, the second conversion driven gear 42B rotates in the B3 direction, causing the axle 37 to rotate in the same direction. Since directions A3 and B3 are the same direction of rotation, if the first input shaft 25A and the second input shaft 25B are rotating at the same speed, the drive wheel 15 will rotate without turning.

[0044] At this time, when the drive wheel body 105 reduces the rotational speed of the second input shaft 25B relative to the rotational speed of the first input shaft 25A, the rotational speed input from the second conversion drive gear 41B to the axle 37 via the second conversion driven gear 42B becomes lower than the rotational speed input from the first conversion drive gear 41A to the axle 37 via the first conversion driven gear 42A. As a result, the steering shaft member 35 rotates by the difference in rotational speed, causing the drive wheel 15 to turn and steer. Also, when the drive wheel body 105 stops the rotation of the second input shaft 25B, the rotational speed input from the second conversion drive gear 41B to the axle 37 via the second conversion driven gear 42B becomes 0, and the drive wheel 15 turns without rotating and steers.

[0045] The drive wheel body 105 has an encoder 107, as shown in Figure 9. The encoder 107 is mounted on the projection 103A of the drive wheel base 103. Details of the encoder 107 will be described later.

[0046] The drive wheel body 105 has a differential omnidirectional movement mechanism. Specifically, the rotational force of the first input shaft 25A and the second input shaft 25B is transmitted to the first output shaft 40A and the second output shaft 40B via the first transmission mechanism 13A and the second transmission mechanism 13B, and then transmitted from the first output shaft 40A and the second output shaft 40B to each end of the axle 37 via the first power conversion mechanism 14A and the second power conversion mechanism 14B. The drive wheel body 105 can switch between the rotation and steering of the drive wheel 15 by adjusting the rotational speed of the first input shaft 25A and the second input shaft 25B. Therefore, the transport device 1 equipped with the active caster 110 is capable of omnidirectional movement.

[0047] Furthermore, the drive wheel body 105 is positioned such that the rotation axis O5 of the drive wheel 15, which is aligned vertically with the axis O2 of the axle 37, is offset horizontally from the axis O1 of the steering shaft member 35, perpendicular to the axis O2 of the axle 37. Therefore, when the drive wheel body 105 is not being driven, the drive wheel 15 can be passively rotated by external forces acting from the horizontal. In other words, the drive wheel body 105 can be driven and steered automatically, as well as driven and steered manually by an operator.

[0048] As shown in Figure 11, the drive wheel side suspension mechanism 106 includes a sliding support member 51, a drive wheel side suspension shaft 52, a retaining member 53, a drive wheel side elastic member 54, and a drive wheel side connecting member 55.

[0049] The sliding support member 51 is fixed to the drive wheel base 103. The sliding support member 51 has a cylindrical body 51A with a through hole, and a flange 51B integrally provided on the outer circumference of the cylindrical body 51A. The cylindrical body 51A is inserted into the through hole 103B (see Figure 9) of the drive wheel base 103. The flange 51B is fixed to the drive wheel base 103 with screws.

[0050] The drive wheel-side suspension shaft 52 is formed in a rod shape and is inserted through a through hole in the cylindrical body 51A of the sliding support member 51. By being inserted through the through hole in the cylindrical body 51A, the drive wheel-side suspension shaft 52 is supported so as to be able to slide along the axis O6 that extends in the vertical direction. The axis O6 is parallel to the axis O1, which is the center of rotation of the drive wheel body 105 relative to the drive wheel base 103. The drive wheel-side suspension shaft 52 is provided with a flange-shaped head 52A at one end in the direction of sliding. The head 52A has an engaging portion into which a tool engages. In the active caster 110 of this embodiment, the engaging portion of the head 52A is configured as a hexagonal hole. The drive wheel-side suspension shaft 52 is also provided with a male threaded portion 52B at the other end in the direction of sliding. The male threaded portion 52B of the drive wheel-side suspension shaft 52 is screwed into the bogie base 102. Therefore, the drive wheel side suspension shaft 52 has the bogie base 102 fixed to the other end in the direction of sliding.

[0051] The retaining member 53 is configured as a cylindrical member that is inserted into and tightly fitted onto the drive wheel side suspension shaft 52. The retaining member 53 is provided between the cylindrical body 51A of the sliding support member 51 via the second drive wheel side elastic member 54B described later, and functions to define the lower limit of the movement range of the drive wheel base 103. Alternatively, the retaining member 53 may be configured as a nut member that is screwed onto the male threaded portion 52B of the drive wheel side suspension shaft 52. In this case, the retaining member 53 can prevent the component inserted into the drive wheel side suspension shaft 52 (the second drive wheel side elastic member 54B described later) from falling out during assembly, etc.

[0052] The drive wheel side elastic member 54 comprises a first drive wheel side elastic member 54A and a second drive wheel side elastic member 54B. The first drive wheel side elastic member 54A is configured as a compression coil spring and is provided by inserting it through the drive wheel side suspension shaft 52 and winding it around the drive wheel side suspension shaft 52. As shown in Figure 8, the first drive wheel side elastic member 54A is positioned between the head 52A of the drive wheel side suspension shaft 52 and the flange 51B of the sliding support member 51. The second drive wheel side elastic member 54B is configured as a compression coil spring and is provided by inserting it through the drive wheel side suspension shaft 52 and winding it around the drive wheel side suspension shaft 52. As shown in Figure 8, the second drive wheel side elastic member 54B is positioned between the retaining member 53 and the cylindrical body 51A of the sliding support member 51. Note that the second drive wheel side elastic member 54B is optional.

[0053] The drive wheel side connecting member 55 connects a plurality of drive wheel side suspension shafts 52. In the active caster 110 of this embodiment, the drive wheel side suspension mechanism 106 is provided in four sets, with the sliding support member 51, drive wheel side suspension shaft 52, retaining member 53, and drive wheel side elastic member 54 forming one set. The active caster 110 is provided with at least two sets of the drive wheel side suspension mechanism 106. The drive wheel side connecting member 55 is formed by bending sheet metal and has a support plate 55A and a connecting plate 55B. The support plate 55A is provided corresponding to each set of the drive wheel side suspension mechanism 106 and each has a through hole 55Aa through which the drive wheel side suspension shaft 52 is inserted. The head 52A of the drive wheel side suspension shaft 52 does not pass through the through hole 55Aa. Accordingly, the support plate 55A is positioned between the head portion 52A and the first drive wheel side elastic member 54A, with the drive wheel side suspension shaft 52 inserted through it. The connecting plate 55B has a plurality of rising portions 55Ba and a base plate 55Bb connecting each rising portion 55Ba, and is positioned above the drive wheel body 105 and is bent into a downward U-shape to cover the drive mechanism 11. The connecting plate 55B is integrally provided with the support plate 55A by bending it at the lower end of the rising portion 55Ba. Therefore, the connecting plate 55B integrally provides each support plate 55A. For this reason, the drive wheel side connecting member 55 connects each drive wheel side suspension shaft 52 inserted through each support plate 55A. Furthermore, the drive wheel side connecting member 55 is positioned so that the support plate 55A faces the projection 103A of the drive wheel base 103 in the vertical direction.

[0054] As shown in Figure 8, the drive wheel side suspension mechanism 106 configured in this way has a drive wheel side suspension shaft 52 positioned along an axis O6 that extends vertically parallel to the pivot axis O1. The drive wheel side suspension shaft 52 has its central part inserted through a sliding support member 51 fixed to the drive wheel base 103, and its lower end fixed to the trolley base 102. Multiple drive wheel side suspension shafts 52 are provided on the drive wheel base 103 and the trolley base 102. It is desirable that the drive wheel side suspension shafts 52 be positioned symmetrically with the axis O1, which is the pivot center of the drive wheel body 105 provided on the drive wheel base 103, in between. In the active caster 110 of this embodiment, the drive wheel side suspension shafts 52 are provided in a total of four locations at symmetrical positions with the axis O1, which is the pivot center of the drive wheel body 105 provided on the drive wheel base 103, in between. Furthermore, the bogie base 102 has a through hole 102A (see Figures 2 to 6) through which the drive wheel 15 of the drive wheel body 105 passes. For this reason, the drive wheel side suspension mechanism 106 is provided so that the drive wheel base 103 and the bogie base 102 can move relative to each other in the vertical direction via the drive wheel side suspension shaft 52, as shown by arrow A in Figure 8. In addition, the drive wheel side suspension mechanism 106 has a first drive wheel side elastic member 54A provided between the head 52A of the drive wheel side suspension shaft 52 (support plate 55A of the drive wheel side connecting member 55) and the drive wheel base 103 (flange 51B of the sliding support member 51). The first drive wheel side elastic member 54A is compressed by the movement of the drive wheel base 103 and the bogie base 102 moving relative to each other. Therefore, the drive wheel side suspension mechanism 106 applies an elastic force to the drive wheel base 103 and the bogie base 102 as they move apart relative to each other. In addition, the drive wheel side suspension mechanism 106 has a second drive wheel side elastic member 54B provided between the drive wheel base 103 (the cylindrical body 51A of the sliding support member 51) and the bogie base 102 (the retaining member 53). The second drive wheel side elastic member 54B is compressed by the movement of the drive wheel base 103 and the bogie base 102 as they move closer to each other. Therefore, the drive wheel side suspension mechanism 106 applies an elastic force to the drive wheel base 103 and the bogie base 102 as they move closer to each other. In this way, the drive wheel side suspension mechanism 106 connects the drive wheel base 103 and the bogie base 102 so that they can move relative to each other via the drive wheel side elastic member 54.

[0055] Next, the configuration for detecting the steering direction of the drive wheel 15 of the active caster 110 will be explained with reference to Figures 13 to 23.

[0056] Figure 13 is a schematic plan view of the active caster 110 as seen from the sixth direction Z2. The active caster 110 comprises a sensor 400 and a detected member 410. The sensor 400 and the detected member 410 are provided on the sixth direction Z2 side relative to the drive wheel base 103.

[0057] Figure 14 is a perspective view showing the configuration near the sensor 400 when the sensor 400 and the detected member 410 are in the positional relationship shown in Figure 13 and Figure 17, which will be described later. The steering shaft member 35 is a circular member in a plan view. The steering shaft member 35 is rotatably supported by a guide portion 103C provided on the drive wheel base 103. The guide portion 103C is fixed to the drive wheel base 103 so as to surround the steering shaft member 35 in a plan view. The guide portion 103C is, for example, an annular member with a guide rail-shaped recess formed on its inner circumference. The ring of the guide portion 103C is a circle centered on the axis O1. The steering shaft member 35 has an annular protrusion that extends radially outward from the axis O1, corresponding to the recess provided on the guide portion 103C. The steering shaft member 35 is rotatably supported by the engagement of the recess of the guide portion 103C and the protrusion of the steering shaft member 35. The relationship between the concave portion of the guide portion 103C and the convex portion of the steering shaft member 35 may be reversed. That is, the convex portion may be formed on the guide portion 103C and the concave portion on the steering shaft member 35. Furthermore, the guide portion 103C only needs to be configured to rotatably support the steering shaft member 35, and the specific form of the engagement point between the steering shaft member 35 and the guide portion 103C is not limited to these examples and can be changed as appropriate. The steering shaft member 35 is positioned so as to face the ground contact surface FL (see Figure 8) of the drive wheel 15, with the drive wheel 15 in between, and functions as a first member that rotates in conjunction with the steering of the drive wheel 15. The steering shaft of the first member is the rotation axis of the steering shaft member 35, and in this embodiment, it coincides with the axis O1.

[0058] Sensor 400 is a sensor whose one side is adhesively fixed to the drive wheel base 103 and the guide portion 103C. Sensor 400 is positioned so as not to contact the outer edge of the steering shaft member 35. The outer edge of the steering shaft member 35 referred to here is the outer edge of the steering shaft member 35 that can be seen from the sixth direction Z2 side. The outer edge of the steering shaft member 35 that can be seen from the sixth direction Z2 side is the outer edge of the portion of the steering shaft member 35 that protrudes toward the sixth direction Z2 side relative to the drive wheel base 103. In other words, the description of the outer edge of the steering shaft member 35 does not include the outer edge of the portion of the steering shaft member 35 that is on the fifth direction Z1 side of the one side of the drive wheel base 103 toward the sixth direction Z2 side. In this embodiment, sensor 400 is positioned toward the first direction X1 side relative to the steering shaft member 35.

[0059] The detected member 410 is a member in which a portion is fixed to the steering shaft member 35, and the other portion, the extended portion 411, extends outward from the outer peripheral edge of the steering shaft member 35.

[0060] The detected member 410 in this embodiment is a slender member. One longitudinal end of the detected member 410 in this embodiment is adhesively fixed to the surface of the steering shaft member 35 on the sixth direction Z2 side. The other longitudinal end of the detected member 410 in this embodiment extends outward from the outer peripheral edge of the steering shaft member 35. This other end of the detected member 410 that extends outward from the outer peripheral edge of the steering shaft member 35 is the extension portion 411. The detected member 410 in this embodiment is fixed to the steering shaft member 35 such that its longitudinal direction is aligned with the radial direction centered on the axis O1. The detected member 410 functions as a second member that extends radially outward from the steering shaft member 35 centered on the steering shaft (axis O1).

[0061] The detected member 410 in the embodiment has light-shielding properties. The sensor 400 in the embodiment is a photocoupler fixed to the drive wheel base 103 and the guide part 103C such that the light-emitting part 401 and the light-receiving part 402 (see Figure 20) face each other in the Z direction. The light-emitting part 401 emits light that is irradiated towards the light-receiving part 402. The light-receiving part 402 switches between outputting a signal depending on whether or not it detects light emitted from the light-emitting part 401.

[0062] More specifically, as shown in Figures 13 and 14, the sensor 400 of the embodiment has a rectangular U-shaped (concave) housing that does not hinder the rotation of the extension portion 411 of the detected member 410, whose position changes in accordance with the change in the rotation angle of the steering shaft member 35. To describe the concave housing in more detail, it can be described as a frame-shaped housing made up of three sides remaining after removing one side of the four sides that make up a typical picture frame. Of the three sides that make up the concave housing, a light-emitting portion 401 is arranged on one of the two opposing sides, and a light-receiving portion 402 is arranged on the other side, so that the light-emitting portion 401 and the light-receiving portion 402 face each other in the Z direction. That is, in the sensor 400 of the embodiment, one side of the two opposing sides that make up the three sides that make up the concave housing is adhesively fixed to the drive wheel base 103 and the guide portion 103C. In Figure 14, one of the two sides is designated as part 405, and the other side of the two sides where the light-receiving unit 402 is located is designated as part 406. Also in Figure 14, of the three sides that constitute the concave housing, the remaining side after excluding the two opposing sides (parts 405 and 406) is designated as part 407. This remaining side is provided so as to connect the ends of parts 405 and 406 that are furthest from the steering shaft member 35 in the Z direction. Note that the shape of the housing of the sensor 400 is merely an example and is not limited to this, and can be changed as appropriate. For example, the shape of the housing of the sensor 400 may be U-shaped.

[0063] In the following explanation, when referring to the output of sensor 400, it means the output of the signal from the light-receiving unit 402, which switches depending on whether or not light emitted from the light-emitting unit 401 is detected. Furthermore, the output of sensor 400 is considered ON when the light-receiving unit 402 does not detect light emitted from the light-emitting unit 401, and OFF when the light-receiving unit 402 detects light emitted from the light-emitting unit 401.

[0064] As shown in Figure 13, when the extension portion 411 and the sensor 400 overlap in a planar view, the light rays between the light-emitting portion 401 and the light-receiving portion 402 are blocked by the extension portion 411. In other words, in this case, the light-receiving portion 402 does not detect the light emitted from the light-emitting portion 401. Therefore, in this case, the output of the sensor 400 becomes ON.

[0065] On the other hand, as shown in Figure 18 later, when the extension portion 411 and the sensor 400 do not overlap in a planar view, there is no configuration that obstructs the light rays between the light-emitting portion 401 and the light-receiving portion 402. In other words, in this case, the light-receiving portion 402 detects the light emitted from the light-emitting portion 401. Therefore, in this case, the output of the sensor 400 is turned off.

[0066] As described above, the steering shaft member 35 is rotatably supported relative to the drive wheel base 103. The detected member 410 is fixed to the steering shaft member 35 at one end. On the other hand, the sensor 400 is fixed to the drive wheel base 103 and the guide portion 103C. Therefore, when the rotation angle of the steering shaft member 35 relative to the drive wheel base 103 changes, the position of the detected member 410 relative to the sensor 400 changes. That is, the rotation angle of the steering shaft member 35 at which the extension portion 411 and the sensor 400 overlap in a planar view is limited to a predetermined rotation angle. This predetermined rotation angle is, for example, the rotation angle of the steering shaft member 35 at which the encoder 107 detects 0°. Thus, the sensor 400 switches its output according to the change in the position of the detected member 410 between the position of the detected member 410 when the rotation angle of the steering shaft member 35 is a predetermined rotation angle and the position of the detected member 410 when the rotation angle of the steering shaft member 35 is not a predetermined rotation angle. Also, as shown in Figure 13, the detected member 410 and the sensor 400 are provided on the drive wheel 15 side with respect to the steering shaft member 35. The encoder 107 will be described below with reference to Figures 15 to 17.

[0067] Figure 15 is a schematic plan view of the active caster 110 as seen from the fifth direction Z1. Figure 16 is a perspective view showing the configuration around the toothed pulley 25C and encoder 107 shown in Figure 15. In Figures 15 and 16, the first driven pulley 26A, second driven pulley 26B, first drive belt 27A, and second drive belt 27B shown in Figure 9 are omitted in order to illustrate the configuration related to the encoder 107. Also, in Figures 15 and 16, the internal configuration of the cover member 107D is illustrated in order to explain the configuration of the encoder 107 on the fifth direction Z1 side. In addition, Figure 15 can be said to be a front view of the active caster 110 shown in Figure 13, rotated 180° around the X direction.

[0068] The encoder 107 is connected to the steering shaft member 35 via a toothed belt 107A, a toothed pulley 107B, and a toothed pulley 25C. The toothed belt 107A is an annular toothed belt that connects the toothed pulley 25C and the toothed pulley 107B. The inside of the toothed belt 107A has protrusions and indentations that mesh with the gears formed on the outer circumference of the toothed pulleys 25C and 107B.

[0069] The toothed pulley 25C is a toothed pulley fixed to the steering shaft member 35. That is, the toothed pulley 25C rotates passively in conjunction with the rotation of the steering shaft member 35 caused by the operation of the first drive unit 23A and the second drive unit 23B.

[0070] The toothed pulley 107B is a toothed pulley that is mounted so as to rotate on the detection shaft 107C. The toothed pulley 107B is fixed to the detection shaft 107C.

[0071] The detection shaft 107C is an axial member provided parallel to the first input shaft 25A and the second input shaft 25B. The axis of rotation of the detection shaft 107C is parallel to the axis of rotation of the first input shaft 25A and the second input shaft 25B, i.e., the axis O1. Hereinafter, when one end of the detection shaft 107C is referred to, it refers to the end on the sixth direction Z2 side of the detection shaft 107C. When the other end of the detection shaft 107C is referred to, it refers to the end on the fifth direction Z1 side of the detection shaft 107C. One end of the detection shaft 107C is rotatably supported with respect to the drive wheel base 103. Specifically, a recessed hole or hole is formed in the drive wheel base 103 to accommodate one end of the detection shaft 107C, and one end of the detection shaft 107C is housed inside the recessed hole or hole.

[0072] The cover member 107D is fixed to one side of the drive wheel base 103 on the fifth direction Z1 side and is a cover-like member that covers the toothed pulley 107B from the fifth direction Z1 side. The encoder 107 is fixed to the cover member 107D on the fifth direction Z1 side. The detection shaft 107C passes through the cover member 107D and is rotatable relative to the cover member 107D.

[0073] The other end of the detection shaft 107C extends to the encoder 107. The encoder 107 is an encoder that detects the rotation angle of the detection shaft 107C.

[0074] As the steering shaft member 35 rotates due to the operation of the first drive unit 23A and the second drive unit 23B, the toothed pulley 25C rotates, and the toothed pulley 107B, which is connected to the toothed pulley 25C via the toothed belt 107A, rotates in conjunction with it. The rotation of the toothed pulley 107B causes the detection shaft 107C to rotate. In this way, the rotation angle of the detection shaft 107C is linked to the rotation angle of the steering shaft member 35.

[0075] The rotation angle of the detection shaft 107C is detected by the encoder 107. By detecting the rotation angle of the detection shaft 107C, the encoder 107 can detect the rotation angle of the steering shaft member 35, that is, the direction of travel of the active caster 110 driven by the drive wheels 15. In this way, the encoder 107 detects the rotation angle of the steering shaft member 35. The detection shaft 107C of the encoder 107 is connected to the steering shaft member 35 via a toothed pulley 25C, a toothed pulley 107B, and a toothed belt 107A. The toothed pulley 25C functions as a first toothed pulley that rotates together with the steering shaft member 35. The toothed pulley 107B functions as a second toothed pulley that rotates around the detection shaft 107C as its axis of rotation. The toothed belt 107A connects the toothed pulley 25C and the toothed pulley 107B.

[0076] In this embodiment, the toothed pulley 25C and the toothed pulley 107B have the same diameter and the same number of teeth. Therefore, the change in the rotation angle of the steering shaft member 35 corresponds to the change in the rotation angle of the detection shaft 107C in a 1:1 ratio. However, it is not essential that the change in the rotation angle of the steering shaft member 35 and the change in the rotation angle of the detection shaft 107C are in a 1:1 ratio. As long as a mechanism is provided that allows the encoder 107 to detect the rotation angle of the steering shaft member 35 according to the ratio of the change in the rotation angle of the steering shaft member 35 and the change in the rotation angle of the detection shaft 107C, the 1:1 ratio may be replaced with any ratio.

[0077] Figure 17 is a plan view showing an example of the active caster 110 as viewed from above and below, when the rotation angle of the steering shaft member 35 is such that the extension portion 411 and the sensor 400 overlap in a plan view. In Figure 17 and Figure 18, which will be described later, the active caster 110 shown as "above" is rotated 180° around the Y direction and shown as "below".

[0078] The encoder 107 in this embodiment is a so-called absolute encoder that detects the absolute rotation angle of the detection shaft 107C, and the rotation angle of the detection shaft 107C that is treated as 0° is predetermined. In this embodiment, the output of the sensor 400 is pre-adjusted to turn ON when the rotation angle of the detection shaft 107C is detected as 0°. More specifically, as shown in the "lower side" of Figure 17, the rotation angle of the steering shaft member 35 at which the detected member 410 is located on the reference line BL and the extension portion 411 and the detected member 410 overlap in a planar view corresponds to the rotation angle of the detection shaft 107C that is treated as 0°. The reference line BL is a line that runs along the X direction and divides the sensor 400 in the Y direction. In the example shown in Figure 17, when the encoder 107 detects 0°, the reference line BL is perpendicular to the rotation axis of the drive wheel 15 and divides the drive wheel 15 in two. Furthermore, when the drive wheel 15 is rotated while the encoder 107 detects 0°, the active caster 110 and the transport device 1 equipped with the active caster 110 move along the X direction, with the first direction X1 as the forward direction.

[0079] When the encoder detects 0°, the forward direction of the transport device 1 is preferably the direction assumed to be the main direction of travel of the transport device 1, as indicated by arrow R in Figures 3 to 6. In Figures 3 to 6, the sensor 400 is positioned on the side of the active caster 110 in the direction indicated by arrow R, and the detected member 410 is located on the side of the direction indicated by arrow R. Also, in the example shown in Figure 17, when the encoder detects 0°, the drive wheel 15 is driven along the X direction, with the first direction X1 as the forward direction, so the direction indicated by arrow R corresponds to the forward direction of the transport device 1. Hereafter, when simply referred to as the direction of travel, unless otherwise specified, it refers to the direction of travel of the active caster 110 and the transport device 1 equipped with the active caster 110, which is caused by the driving of the drive wheel 15.

[0080] The angle of the direction of travel is detected by the detection of the rotation angle of the detection axis 107C by the encoder 107. That is, as explained with reference to Figure 17, when the encoder 107 detects 0°, the direction of travel is the direction indicated by arrow R. When the encoder 107 detects an angle other than 0°, the direction of travel is the direction tilted by the angle detected by the encoder 107 relative to the direction indicated by arrow R. Also, as explained with reference to Figure 17, when the encoder 107 detects 0°, the output of the sensor 400 is ON.

[0081] In order to establish the correspondence between the detection angle of the encoder 107 and the direction of travel as described above, the rotation angle of the steering shaft member 35, the position of the detected member 410 corresponding to the rotation angle of the steering shaft member 35, the arrangement of the sensor 400, the rotation angle of the detection shaft 107C which is linked to the steering shaft member 35, and the output of the encoder 107 are predetermined to correspond. As explained with reference to Figures 15 and 16, the connection between the steering shaft member 35 and the detection shaft 107C is made by toothed pulleys, namely toothed pulley 25C and toothed pulley 107B, and toothed belt, namely toothed belt 107A. Therefore, if tooth skipping occurs between toothed pulley 25C or toothed pulley 107B and toothed belt 107A, a deviation from the predetermined correspondence between the rotation angles of the steering shaft member 35 and the detection shaft 107C will occur. In the following, when tooth skipping is mentioned, it refers to a skip between tooth pulley 25C or tooth pulley 107B and tooth belt 107A.

[0082] Figure 18 is a plan view showing an example of a deviation from the predetermined correspondence between the rotation angles of the steering shaft member 35 and the detection shaft 107C, viewed from above and below. Figure 19 is a perspective view showing a more enlarged view of the lower configuration shown in Figure 18, near the sensor 400 and the detected member 410. If tooth skipping occurs between the toothed pulley 25C or toothed pulley 107B and the toothed belt 107A, the relationship between the rotation angle of the steering shaft member 35, the position of the detected member 410 corresponding to the rotation angle of the steering shaft member 35, the rotation angle of the detection shaft 107C which is linked to the steering shaft member 35, and the output of the encoder 107, as explained with reference to Figure 17, will no longer hold. In this case, for example, as shown in Figures 18 and 19, the encoder 107 may detect 0° even though the rotation angle of the steering shaft member 35 is such that the extension portion 411 does not overlap with the sensor 400 in a plan view. If this condition were to be overlooked, the direction of travel would be different from the direction indicated by arrow R, even though encoder 107 has detected 0°. In other words, the control related to controlling the direction of travel based on the angle detection by encoder 107 would not function correctly.

[0083] On the other hand, in the states shown in Figures 18 and 19, the output of sensor 400 is turned off. In the explanation with reference to Figure 17, when encoder 107 detects 0°, the output of sensor 400 is turned on. Therefore, even if a deviation occurs due to tooth skipping from the predetermined correspondence between the rotation angles of the steering shaft member 35 and the detection shaft 107C, and encoder 107 detects 0° despite the steering shaft member 35 having a rotation angle where the extension portion 411 does not overlap with sensor 400 in a planar view, as shown in Figure 18, the fact that the output of sensor 400 is turned off allows detection of such a deviation. In other words, according to the embodiment, based on the output of sensor 400, it is possible to detect an abnormality in which encoder 107 detects 0° despite the steering shaft member 35 having a rotation angle where the extension portion 411 does not overlap with sensor 400 in a planar view. Thus, in this embodiment, it is determined whether or not the output of encoder 107 matches the rotation angle of the steering shaft member 35 based on the output of sensor 400. Therefore, the sensor 400 functions as a sensor that determines whether the output of the encoder 107 matches the rotation angle of the steering shaft (steering shaft member 35). The main configuration related to the control of the active caster 110, including the detection of such abnormalities, will be described below with reference to Figure 20.

[0084] Figure 20 is a block diagram showing the main configuration related to the control of the active caster 110. The sensor 400 includes a light-emitting unit 401 and a light-receiving unit 402. The light-emitting unit 401 is connected to the control circuit 420 via terminal 403. In Figure 14, terminal 403 is shown as an exposed terminal, but in reality, wiring is connected to terminal 403, and terminal 403 and the control circuit 420 are connected via this wiring. Terminal 404 is connected to the control circuit 420 via terminal 404. In Figures 13, 14, 17, and 18, terminal 404 is shown as an exposed terminal, but in reality, wiring is connected to terminal 404, and terminal 404 and the control circuit 420 are connected via this wiring.

[0085] The control circuit 420 controls the operation of the first drive unit 23A and the second drive unit 23B based on the output of the encoder 107. The operation control of the first drive unit 23A and the second drive unit 23B by the control circuit 420 controls the driving and direction of travel of the drive wheels 15. The output of the encoder 107 refers to the output indicating the rotation angle of the detection shaft 107C detected by the encoder 107. The control circuit 420 may be a circuit provided as a single package, or it may be a configuration realized by a combination of multiple circuits.

[0086] As an example of the control circuit 420's control of the operation of the first drive unit 23A and the second drive unit 23B, when the transport device 1 is traveling by the rotational drive of the drive wheels 15, the control circuit 420 controls the operation of the first drive unit 23A and the second drive unit 23B so that the rotation direction of the first conversion driven gear 42A and the rotation direction of the second conversion driven gear 42B (see Figure 10) are the same around the axis O2, and the rotation speed of the first conversion driven gear 42A and the rotation speed of the second conversion driven gear 42B are equal. Furthermore, when steering, which changes the direction of the drive wheels 15 around the axis O1, the control circuit 420 stops (locks) the rotation of one of the first drive unit 23A or the second drive unit 23B, for example, and allows the other to rotate. This changes the direction of the drive wheels 15 and the rotation angle of the steering shaft member 35 around the axis O1. In other words, steering of the drive wheels 15 is sufficient with the rotational drive of one electric motor, which is either the first drive unit 23A or the second drive unit 23B. The swaying motion described later is achieved, for example, by controlling the operation of the first drive unit 23A and the second drive unit 23B. When the transport device 1 is traveling in a direction that changes, the control circuit 420 applies control to make the rotational speed of the first drive unit 23A and the rotational speed of the second drive unit 23B different.

[0087] Furthermore, the control circuit 420 detects abnormalities caused by tooth skipping based on the correspondence between the output of the encoder 107 and the output of the sensor 400. An abnormality caused by tooth skipping refers to a state in which the encoder 107 detects 0° even though the rotation angle of the steering shaft member 35 is such that the extension portion 411 does not overlap with the sensor 400 in a plan view, due to tooth skipping. Specifically, when tooth skipping occurs, as explained with reference to Figure 18, the encoder 107 may detect 0° even though the rotation angle of the steering shaft member 35 is such that the extension portion 411 does not overlap with the sensor 400 in a plan view. When an abnormality caused by tooth skipping occurs, the encoder 107 shows a state of 0° and the sensor 400 shows an off state, both of which coexist. On the other hand, as explained with reference to Figure 17, when tooth skipping does not occur, the encoder 107 shows a state of 0° and the sensor 400 shows an on state, both of which coexist. In this way, the control circuit 420 can detect whether an abnormality due to tooth skipping has occurred based on the combination of the output of the encoder 107 indicating 0° and the output of the sensor 400. Thus, the control circuit 420 determines that tooth skipping has occurred between the toothed pulley 25C or toothed pulley 107B and the toothed belt 107A when the rotation angle of the steering shaft member 35 indicated by the output of the encoder 107 is a predetermined rotation angle, and the output of the sensor 400 indicates that the rotation angle of the steering shaft member 35 is not a predetermined rotation angle.

[0088] The above describes the detection of abnormalities due to tooth skipping. The control circuit 420 may further have a function to reset the relationship between the output of the encoder 107 and the angle indicated by the output of the encoder 107 when an abnormality due to tooth skipping occurs. Specifically, when an abnormality due to tooth skipping occurs, the operation of the first drive unit 23A and the second drive unit 23B is controlled so that the drive wheel 15 is driven in the direction of travel of the drive wheel 15 in which the output of the encoder 107 indicates 0°, and the output of the sensor 400 is turned off even though the output of the encoder 107 now indicates 0°. In this case, the control circuit 420 may adjust the first drive unit 23A and the second drive unit 23B so that the output of the sensor 400 is turned on. Such adjustment operation is the operation of the first drive unit 23A and the second drive unit 23B to change the direction of travel of the drive wheel 15 (for example, to swivel). Such adjustment operation is completed when the output of the sensor 400 is turned on. If an abnormality occurs due to tooth skipping, the output of encoder 107 at the time the output of sensor 400 turns ON will be an output indicating an angle other than 0°. From the time the output of sensor 400 turns ON onward, the control circuit 420 considers the output of encoder 107 indicating an angle other than 0° as the output of encoder 107 indicating 0° from that point onward. In other words, the control circuit 420 resets the output of encoder 107 that is treated as 0°. In this way, when the control circuit 420 determines that tooth skipping has occurred, it operates the first drive unit 23A and the second drive unit 23B to set the steering angle of the drive wheel 15 to an output from sensor 400 indicating that the rotation angle of the steering shaft member 35 is a predetermined rotation angle, and sets the output of encoder 107 when this steering angle is achieved as the output of encoder 107 indicating that the rotation angle of the steering shaft member 35 is a predetermined rotation angle.

[0089] Figure 21 is a flowchart showing the processing flow by the control circuit 420, which has a function to reset the output of the encoder 107, which is treated as 0°. First, the control circuit 420 controls the operation of the first drive unit 23A and the second drive unit 23B so that the drive wheels 15 are driven in the direction of travel of the drive wheels 15, where the output of the encoder 107 indicates 0° (step S1). The timing of the processing in step S1 is arbitrary. For example, it may be performed as the initial operation of the active caster 110, or it may be performed when the transport device 1 equipped with the active caster 110 moves in the direction indicated by the arrow R during operation, or it may be performed periodically as a check operation during the operation of the transport device 1.

[0090] After the processing of step S1, that is, after the output of encoder 107 indicates 0°, the control circuit 420 checks whether the output of sensor 400 is ON (step S2). If the output of sensor 400 is ON in the processing of step S2 (step S2; Yes), there is no abnormality due to tooth skipping, so the processing related to the encoder 107 output reset function is terminated. On the other hand, if the output of sensor 400 is OFF in the processing of step S2 (step S2; No), the control circuit 420 controls the operation of the first drive unit 23A and the second drive unit 23B to change the direction of travel of the drive wheel 15 until the output of sensor 400 is ON (step S3). After the processing of step S3, that is, after the output of sensor 400 is ON, the control circuit 420 resets the output of encoder 107 to the output of encoder 107 indicating 0° when the output of sensor 400 was ON (step S4), and terminates the processing related to the encoder 107 output reset function.

[0091] The above explanation has described the detection of abnormalities due to tooth skipping and the resetting of the encoder 107 output based on the relationship between the sensor 400 shown in Figures 13, 14, 17, 18, 19, and 20 and the detected member 410 shown in Figures 13, 14, 17, 18, and 19. However, similar functionality may be achieved by replacing at least one of the sensor 400 and the detected member 410 with other components. For example, the sensor 400 may be a magnetic sensor or a capacitive sensor.

[0092] If the sensor 400 is a magnetic sensor, a magnet is provided on the extension 411. In this case, as shown in Figure 17, when the sensor 400 and the extension 411 overlap in a planar view, the magnetism of the magnet provided on the extension 411 is detected by the sensor 400, and the output of the sensor 400 turns ON. Also, as shown in Figure 18, when the sensor 400 and the extension 411 do not overlap in a planar view, the magnetism of the magnet provided on the extension 411 is not detected by the sensor 400, and the output of the sensor 400 turns OFF.

[0093] When sensor 400 is replaced with a capacitive sensor, the capacitive sensor includes an oscillation circuit that generates an electric field and a detection circuit that detects the oscillation frequency of the electric field. In this case, the extension portion 411 is provided to enter the electric field when it overlaps with the capacitive sensor in a plan view. In this case, as shown in Figure 17, when sensor 400 and extension portion 411 overlap in a plan view, the change in oscillation frequency caused by the extension portion 411 entering the electric field is detected by the detection circuit, causing the output of sensor 400 to turn ON. On the other hand, as shown in Figure 18, when sensor 400 and extension portion 411 do not overlap in a plan view, no change in oscillation frequency occurs, and the output of sensor 400 turns OFF.

[0094] Since the sensor 400 is either a magnetic sensor or a capacitive sensor, it becomes easier to suppress false detections caused by foreign objects such as dust adhering to the sensor 400.

[0095] Furthermore, in the embodiment described above, there was one sensor 400 per active caster 110, but there may be multiple sensors like sensor 400 per active caster 110.

[0096] Figure 22 is a schematic diagram showing an example configuration in which multiple sensors are provided. Figure 22 and Figure 23, which will be described later, show schematic diagrams from a plan view that specifically illustrate the relationship between the steering shaft member 35, the detected member 410 provided on the steering shaft member 35, and the sensors. The specific form of the steering shaft member 35 and the detected member 410 provided on the steering shaft member 35 is the same as that described with reference to Figures 13, 14, etc.

[0097] According to the configuration shown in Figure 22, when an abnormality occurs due to tooth skipping, it is possible to more quickly determine whether the direction of the discrepancy between the rotation angle indicated by the output of the encoder 107 and the actual rotation angle of the steering shaft member 35 is clockwise or counterclockwise around the axis O1. Therefore, in relation to resetting the output of the encoder 107 which is treated as 0° as described above, it is possible to determine the direction of rotation of the steering shaft member 35 in order to make the rotation angle of the steering shaft member 35 the rotation angle corresponding to the "output of the encoder 107 which is treated as 0°". In other words, it becomes unnecessary to attempt to adjust the rotation angle of the steering shaft member 35 in an unspecified direction, such as so-called swaying, and the operation control of the first drive unit 23A and the second drive unit 23B to make the rotation angle of the steering shaft member 35 the rotation angle corresponding to the "output of the encoder 107 which is treated as 0°" can be completed with a simpler process.

[0098] Instead of the sensor 400 shown in Figures 13, 17, and 18, sensors 400A and 400B may be provided as shown in Figure 22. Sensors 400A and 400B are the same type of sensors as sensor 400. Sensors 400A and 400B are positioned so as not to overlap with the extension 411 in a plan view when the output of the encoder 107 indicates 0°, which is the rotation angle of the steering shaft member 35. Sensors 400A and 400B have the same configuration as sensor 400, except for this feature regarding their arrangement in a plan view. That is, in the configuration shown in Figure 22, the outputs of sensors 400A and 400B are turned off in this case. On the other hand, in the configuration shown in Figure 22, if the output of sensor 400A or sensor 400B is turned on even though the output of the encoder 107 indicates 0°, it means that an abnormality has occurred due to tooth skipping. In other words, in the configuration shown in Figure 22, the relationship between the abnormality caused by tooth skipping and the ON / OFF state of the outputs of sensors 400A and 400B is the opposite of the relationship between the abnormality caused by tooth skipping and the ON / OFF state of the output of sensor 400 described above. Except for the points specifically noted above, the configuration shown in Figure 22 is the same as the configuration of the embodiment described with reference to Figures 1 to 21.

[0099] Furthermore, in the embodiment described with reference to Figures 1 to 21, there was one detectable member 410 for each active caster 110, but multiple detectable members 410 may be provided for each active caster 110.

[0100] Figure 23 is a schematic diagram showing an example configuration in which multiple detectable members 410 are provided. The sensor 400 shown in Figure 23 is the same as the sensor 400 shown in Figures 13, 14, 17, 18, 19, and 20.

[0101] As shown in Figure 23, a plurality of detectable members 410 may be provided on the steering shaft member 35. In Figure 23, four detectable members 410 are arranged. The center line CL that divides each of the four detectable members 410 in a direction perpendicular to the longitudinal direction of the detectable member 410 passes through the axis O1. Of the four detectable members 410, the center lines CL of two detectable members 410 that are adjacent in the circumferential direction of the outer edge of the steering shaft member 35 intersect at a 90° angle.

[0102] According to the configuration shown in Figure 23, the consistency check of the correspondence between the output of encoder 107 and the rotation angle of the steering shaft member 35 can be performed not only for one predetermined rotation angle (for example, the "output of encoder 107 treated as 0°" as described above), but also for multiple predetermined rotation angles (for example, 0°, 90°, 180°, and 270° in 90° increments).

[0103] In the example shown in Figure 23, there are four detected members 410, but the number of detected members 410 is not limited to this, and may be increased or decreased as appropriate, as long as the sensor 400 can ensure the ability to detect abnormalities caused by tooth skipping.

[0104] In the configurations shown in Figures 22 and 23, the sensor 400 may be a magnetic sensor or a capacitive sensor.

[0105] As described above, according to the embodiment, the active caster (active caster 110) includes a drive wheel (drive wheel 15) connected to at least one electric motor (at least one of the first drive unit 23A and the second drive unit 23B) and steered in accordance with the rotational drive of the electric motor; a first member (steering shaft member 35) positioned on either side of the drive wheel and facing the ground surface (ground surface FL) of the drive wheel, functioning as the steering shaft of the drive wheel and rotating in conjunction with the steering of the drive wheel; a second member (detected member 410) extending radially outward from the first member around the steering shaft; an encoder (encoder 107) for detecting the rotation angle of the first member; and a sensor (sensor 400) for determining whether the output of the encoder matches the rotation angle of the steering shaft.

[0106] According to the active caster (active caster 110) of this embodiment, when the output of the encoder (encoder 107) indicates that the rotation angle of the first member (steering shaft member 35), which rotates in conjunction with the steering of the drive wheel (drive wheel 15), is a predetermined rotation angle, the sensor (sensor 400) produces an output indicating that the rotation angle of the first member is a predetermined rotation angle, thereby confirming that the encoder is correctly detecting the steering angle of the drive wheel.

[0107] Furthermore, based on the output of the sensor (sensor 400), it is determined whether the output of the encoder (encoder 107) matches the rotation angle of the first member (steering shaft member 35). This allows it to determine, based on the output of the sensor (sensor 400), whether the encoder (encoder 107) is correctly detecting the steering angle of the drive wheel (drive wheel 15).

[0108] Furthermore, the system includes a drive wheel base (drive wheel base 103) that rotatably supports the first member (steering shaft member 35), and the sensor is fixed to the drive wheel base. This allows the drive wheel base to maintain the relationship between the rotatable first member and the sensor (sensor 400) whose output switches in accordance with the position change of the second member (detected member 410) extending from the first member.

[0109] Furthermore, the second member (detected member 410) and the sensor (sensor 400) are provided on the drive wheel (drive wheel 15) side relative to the first member (steering shaft member 35). This allows the positional relationship between the second member and the sensor to be easily confirmed from the drive wheel side.

[0110] Furthermore, the encoder (encoder 107) detects the rotation angle of the detection shaft (detection shaft 107C), and the detection shaft is fixed to the first member (steering shaft member 35) and connected to the first member via a first toothed pulley (toothed pulley 25C) that rotates together with the first member, a second toothed pulley (toothed pulley 107B) that rotates with the detection shaft as its axis of rotation, and a toothed belt (toothed belt 107A) that connects the first toothed pulley and the second toothed pulley. The encoder output indicates that the rotation angle of the first member is a predetermined rotation angle, and the sensor (sensor 400) output indicates that the rotation angle of the first member is not a predetermined rotation angle, in which case the encoder includes a control circuit (control circuit 420) that determines that a tooth skip has occurred between the first toothed pulley or the second toothed pulley and the toothed belt. This makes it possible to detect the discrepancy between the rotation angle of the steering shaft member 35 and the rotation angle indicated by the output of the encoder 107, which occurs due to tooth skipping.

[0111] Furthermore, if the control circuit determines that tooth skipping has occurred, it operates two electric motors (first drive unit 23A, second drive unit 23B) to set the steering angle of the drive wheel (drive wheel 15) to the point where the output of the sensor (sensor 400) indicating that the rotation angle of the first member (steering shaft member 35) is a predetermined rotation angle is obtained. The output of the encoder (encoder 107) when this steering angle is obtained is set as the output of the encoder indicating that the rotation angle of the first member is a predetermined rotation angle. In this way, even if tooth skipping occurs, the rotation angle of the first member (steering shaft member 35) and the rotation angle indicated by the output of the encoder 107 can be matched.

[0112] Furthermore, the fact that the sensor (sensor 400) is a photocoupler confirms that the encoder (encoder 107) can correctly detect the steering angle of the drive wheels using a simple mechanism.

[0113] Furthermore, the fact that the sensor (sensor 400) is a magnetic sensor or a capacitive sensor confirms that the encoder (encoder 107) can correctly detect the steering angle of the drive wheels with a simple mechanism. In addition, it becomes easier to suppress false detections caused by foreign objects such as dust adhering to the sensor.

[0114] Furthermore, according to the active caster 110 of this embodiment, since it is an active caster 110 that can confirm that the encoder (encoder 107) is correctly detecting the steering angle of the drive wheel, even if the possibility of tooth skipping due to impact is relatively higher when traveling on a floor surface G with protrusions G1 and recesses G2 compared to traveling on a flat contact surface FL without protrusions G1 and recesses G2, it is possible to detect the discrepancy between the rotation angle of the first member (steering shaft member 35) and the rotation angle indicated by the output of the encoder 107 due to such tooth skipping, and to set a correction for the discrepancy.

[0115] The material of the detected member 410 is, for example, a dark-colored (e.g., black) synthetic resin (e.g., polystyrene) that exhibits light-shielding properties, but is not limited to this and may be appropriately changed depending on the sensing method of the sensor 400. For example, if the sensor 400 is a photocoupler, the material of the detected member 410 may be, for example, a metal, alloy, or compound that exhibits light-shielding properties. Also, if the sensor 400 is a magnetic sensor or a capacitive sensor, the material of the detected member 410 is not particularly limited.

[0116] Furthermore, it is not essential that the encoder 107 be an absolute encoder; for example, it may be a so-called incremental encoder that detects the rotation angle in relative terms. In this case, for example, the control circuit 420 calculates the rotation angle of the steering shaft member 35 based on the output of the encoder 107.

[0117] Furthermore, the sensor 400 and the detected member 410 may be provided on the fifth direction Z1 side with respect to the drive wheel base 103. In this case, it is desirable that the arrangement of the components on the fifth direction Z1 side of the drive wheel base 103 be adjusted so that the detected member 410 does not collide with the components on the fifth direction Z1 side of the drive wheel base 103.

[0118] Furthermore, it is not essential that the rotation angle of the steering shaft member 35, which is set to a predetermined rotation angle, is treated as 0°, and the degree (°) output of the encoder for the predetermined rotation angle is arbitrary. Also, it is not essential that the rotation angle of the steering shaft member 35, which is set to a predetermined rotation angle, corresponds to the main direction of movement of the conveying device 1, such as the direction indicated by arrow R, and the correspondence between the rotation angle of the steering shaft member 35, which is set to a predetermined rotation angle, and the direction of movement of the configuration equipped with the active caster 110 is arbitrary.

[0119] Furthermore, in the active caster 110 of this embodiment, two electric motors, the first drive unit 23A and the second drive unit 23B, are connected to the drive wheel 15 and used for rotational drive and steering of the drive wheel 15. However, as mentioned above, one electric motor is sufficient for steering. Alternatively, an active caster may be provided in which one electric motor is used for rotational drive of the drive wheel and the other electric motor is used for steering of the drive wheel. [Explanation of Symbols]

[0120] 1. Conveying device 15 drive wheels 23A First drive unit 23B Second drive unit 25C, 107B Toothed pulley 35 Steering shaft member 103 Drive wheel base 107 encoders 107A Toothed belt 107C detection axis 110 Active Caster 400 sensors 410 Detected Member

Claims

1. A drive wheel connected to at least one electric motor, which is steered in accordance with the rotational drive of the electric motor, A first member is positioned on either side of the drive wheel, facing the ground surface of the drive wheel, and functions as the steering shaft of the drive wheel, rotating in conjunction with the steering of the drive wheel. A second member extending radially outward from the first member, centered on the steering axis, An encoder for detecting the rotation angle of the first member, The system includes a sensor that determines whether the output of the encoder matches the rotation angle of the steering shaft. Active caster.

2. The system includes a drive wheel base that rotatably supports the first member, The sensor is fixed to the drive wheel base. The active caster according to claim 1.

3. The second member and the sensor are provided on the drive wheel side relative to the first member. The active caster according to claim 1 or 2.

4. The encoder detects the rotation angle of the detection axis, The aforementioned detection axis is A first toothed pulley is fixed to the first member and rotates together with the first member, A second toothed pulley rotates with the aforementioned detection axis as its axis of rotation, A toothed belt connecting the first toothed pulley and the second toothed pulley, It is connected to the first member via the first member, The circuit includes a control circuit that determines that tooth skipping has occurred between the first toothed pulley or the second toothed pulley and the toothed belt when the output of the sensor indicates that the rotation angle of the first member is not the predetermined rotation angle, while the output of the encoder indicates that the rotation angle of the first member is not the predetermined rotation angle. The active caster according to claim 1 or 2.

5. When the control circuit determines that tooth skipping has occurred, it operates the electric motor to set the steering angle of the drive wheel to such an angle that the output of the sensor indicating that the rotation angle of the first member is the predetermined rotation angle is obtained. The output of the encoder when the steering angle is as described above is set as the output of the encoder indicating that the rotation angle of the first member is the predetermined rotation angle. The active caster according to claim 4.

6. The aforementioned sensor is a photocoupler. The active caster according to claim 1 or 2.

7. The aforementioned sensor is a magnetic sensor. The active caster according to claim 1 or 2.

8. The aforementioned sensor is a capacitive sensor. The active caster according to claim 1 or 2.

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