Active caster wheel

Abstract

The present disclosure provides an active caster that makes wheel replacement easy. The active caster according to the present disclosure is capable of single-wheel steering by interference driving. The active caster has a vertically extending steering shaft, a horizontally extending axle, and a wheel coupled to the axle. The active caster has both an offset of the axle with respect to the steering shaft in a horizontal direction orthogonal to a direction in which the axle extends and an offset of the wheel with respect to the steering shaft in a direction in which the axle extends.

Description

Technical Field

[0001] This disclosure relates to an active caster. Background Technology

[0002] Patent document 1 discloses an active caster that can move in all directions.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2016-049921

[0004] Existing interference-driven active single-wheel casters transmit rotational force to both sides of the axle, which makes it difficult to replace the wheels. Summary of the Invention

[0005] This disclosure was made in view of the above background, and its purpose is to provide an active caster that facilitates wheel replacement.

[0006] The active caster disclosed herein is an active caster capable of steering a single wheel via interference drive, comprising: a vertically extending steering control shaft, a horizontally extending axle, and a wheel that rotates about the axle, and having both an offset s of the axle relative to the steering control shaft in a horizontal direction orthogonal to the direction in which the axle extends, and an offset d of the wheel relative to the steering control shaft in the direction in which the axle extends.

[0007] According to this disclosure, it is possible to provide an active caster that facilitates wheel replacement.

[0008] The above and other objects, features and advantages of this disclosure will be more fully understood from the detailed description and accompanying drawings given below. Attached Figure Description

[0009] Figure 1 This is a perspective sectional view illustrating the active caster according to Embodiment 1.

[0010] Figure 2 This is a schematic cross-sectional view illustrating the drive caster according to Embodiment 1.

[0011] Figure 3 This is a diagram that uses symbols to represent the drive caster involved in Embodiment 1.

[0012] Figure 4 This is a diagram used to illustrate the structure of a vehicle equipped with the active casters according to Embodiment 1. Detailed Implementation

[0013] Implementation Method 1

[0014] Figure 1 This is a perspective sectional view illustrating the active caster 10 according to Embodiment 1. Figure 2 This is a diagram used to explain the structure of the drive caster 10. The drive caster 10 includes a main body 11, motors M1 to M2, timing belts 21 to 22, swivel cylinders 31 to 32, intermediate shaft 4, axle 5, wheel 6, and control unit 7.

[0015] Motors M1 and M2 can be supported on the main body 11. Motors M1 and M2 can be motors with the same performance.

[0016] Synchronous belt 21 is wound around the output shaft of motor M1 and rotating drum 31. Synchronous belt 22 is wound around the output shaft of motor M2 and rotating drum 32. If motor M1 rotates, rotating drum 31 can rotate about a vertically extending steering control axis T. If motor M2 rotates, rotating drum 32 can rotate about the steering control axis T.

[0017] The intermediate shaft 4 is basically a cylinder extending horizontally. A second spur gear, meshing with a first spur gear fixed to the wheel 6, is fixed to one end of the intermediate shaft 4. A third bevel gear, meshing with a first bevel gear fixed to the lower part of the rotating cylinder 31, is fixed to the other end of the intermediate shaft 4. A fourth bevel gear, meshing with a second bevel gear fixed to the lower part of the rotating cylinder 32, is fixed to the intermediate shaft 4. The fourth bevel gear is positioned between the second and third spur gears. The wheel 6 can rotate around the axle 5. The axle 5 extends horizontally. The shaft on which the first spur gear is fixed can be considered as the axle 5.

[0018] The rotational speed transmission ratio of the first rotary transmission mechanism, including the timing belt 21, is set as G1. The rotational speed transmission ratio of the second rotary transmission mechanism, including the timing belt 22, is set as G2. The rotational speed transmission ratio of the third rotary transmission mechanism, including the first bevel gear of the rotating cylinder 31 and the third bevel gear of the intermediate shaft 4, is set as G3. The rotational speed transmission ratio of the fourth rotary transmission mechanism, including the second bevel gear of the rotating cylinder 32 and the fourth bevel gear of the intermediate shaft 4, is set as G4. The rotational speed transmission ratio of the fifth rotary transmission mechanism, including the second spur gear of the intermediate shaft 4 and the first spur gear of the wheel 6, is set as G5.

[0019] The drive caster 10 may include a support member that supports the intermediate shaft 4 and the axle 5 so that they can rotate about the rotation axis T. This support member can be considered as the steering control axis T.

[0020] For example, if rotating cylinders 31 and 32 rotate in opposite directions, the direction in which rotating cylinder 31 rotates the intermediate shaft 4 and the direction in which rotating cylinder 32 rotates the intermediate shaft 4 become opposite, so wheel 6 does not rotate around axle 5, but rotates around steering control axis T. If rotating cylinders 31 and 32 rotate in the same direction, wheel 6 rotates around axle 5.

[0021] Let the rotational speed of the output shaft of motor M1 be ω1, and the rotational speed of the output shaft of motor M2 be ω2. Let the rotational speed of wheel 6 around axle 5 be ω. w Let the rotational speed of wheel 6 about the steering control axis T be ω. s The curved arrow indicates the positive direction of rotation. G1 to G4 can be positive or negative real numbers.

[0022] The active caster wheel can control the steering of wheel 6 via interference drive. The rotational speed ω1 of motor M1 is transmitted to the rotation of wheel 6 around steering shaft T via the first rotational transmission mechanism, and the rotational speed ω2 of motor M2 is transmitted to the rotation of wheel 6 around steering shaft T via the second rotational transmission mechanism. The rotational speed ω1 of motor M1 is transmitted to the rotation of intermediate shaft 4 via the first and third rotational transmission mechanisms, and the rotational speed ω2 of motor M2 is transmitted to the rotation of intermediate shaft 4 via the second and fourth rotational transmission mechanisms. The rotational speed of intermediate shaft 4 is transmitted to the rotation of wheel 6 around axle 5 via a fifth transmission mechanism.

[0023] Figure 3 This diagram represents the drive caster 10 using symbols. As explained, the drive caster 10 includes a steering axis T and an axle 5. Let s be the offset of the axle 5 relative to the steering axis T in a direction orthogonal to the direction in which the axle 5 extends. Let d be the offset of the wheel 6 relative to the steering axis T in the direction in which the axle 5 extends. Let v be the x and y components of the velocity of the wheel 6 in an xy coordinate system rotating about the steering axis T. x and v y The x-direction corresponds to the direction orthogonal to the extension direction of axle 5. The y-direction corresponds to the extension direction of axle 5. If we set l = √(s) 2 +r 2 Given cosα = s / l and sinα = d / l, we can obtain the following formula.

[0024]

Formula 1

[0025]

[0026] If we take v x and v y If we denote the vector of the component as v (in bold), then we can obtain the following formula.

[0027]

Formula 2

[0028]

[0029] Let the X and Y components of the velocity of wheel 6 in the vehicle coordinate system XY of the vehicle equipped with active casters 10 be V respectively. x and V yIf the rotation angle of wheel 6 about the steering axis T is set as θ, then V x and V y If we denote the vector of the components as V (in bold), then we can obtain the following formula.

[0030]

Formula 3

[0031]

[0032] Reference Figure 2 ω1 and ω2 are expressed by the following formula.

[0033]

Formula 4

[0034]

[0035]

Formula 5

[0036]

[0037] From equations (4) and (5), we can obtain the following equation. ω (bold) represents a vector with ω1 and ω2 as components.

[0038]

Formula 6

[0039]

[0040] The following equation can be obtained from equations (2) and (6).

[0041]

Formula 7

[0042]

[0043] The following equation can be obtained from equations (3) and (7).

[0044]

Formula 8

[0045]

[0046] From equation (8), we can obtain the rotational speed ω1 of motor M1 and the rotational speed ω2 of motor M2 relative to any velocity vector V (bold).

[0047] For the active caster 10 to operate, the rank of the matrix on the right side of equation (6) needs to be 2. If we set it to G... i ≠0 (i = 1~5), we can get the following formula.

[0048]

Number 9

[0049]

[0050] Similarly, in order for the active caster 10 to move, the rank of the matrix on the right side of equation (7) needs to be 2. Let G be... i ≠0 (i = 1~5), we can get the following formula.

[0051]

Number 10

[0052]

[0053] Reference Figure 2 The hardware of the control unit 7 is centered around a microcomputer consisting of a CPU (Central Processing Unit), memory, and an interface unit (I / F). The CPU performs control processing and arithmetic processing. The memory consists of ROM (Read Only Memory) storing control programs, arithmetic programs, etc., executed by the CPU. The interface unit inputs and outputs signals to the outside world. The CPU, memory, and interface unit are interconnected via a data bus.

[0054] Control unit 7 controls the rotation of wheel 6 around steering shaft T and the rotation of wheel 6 around axle 5 by sending control signals to motors M1 and M2. Control unit 7 controls motors M1 and M2 based on equation (8). That is, control unit 7 uses equation (8) to calculate the rotational speed ω1 of motor M1 and the rotational speed ω2 of motor M2 based on the speed V (bold) of the vehicle equipped with drive caster 10. Control unit 7 sends control signals corresponding to the calculated rotational speeds ω1 and ω2 to motors M1 and M2.

[0055] Figure 4 The upper left figure is a schematic perspective view showing the structure of a vehicle 200 equipped with existing active casters 20. Figure 4 The upper right figure is a schematic bottom view of the existing vehicle 200. In the existing drive caster 20, rotational force needs to be transmitted to both sides of the wheel 6, so the wheel 6 is positioned further inside the side surface of the vehicle 200. To replace the wheel 6, the drive caster 20 needs to be disassembled, and since the wheel 6 is positioned far from the side surface of the vehicle 200, replacing the wheel 6 is not easy.

[0056] Figure 4 The lower left figure is a schematic perspective view showing the structure of a vehicle 100 equipped with the active caster 10 according to Embodiment 1. Figure 4The lower right figure is a schematic bottom view of the vehicle 100 according to Embodiment 1. The distance between the side surface of the vehicle 100 and the wheel 6 is smaller than the distance between the side surface of the vehicle 100 and the steering shaft T. The wheel 6 of the drive caster 10 is positioned close to the side surface of the vehicle 100. Since the drive caster 10 does not need to be disassembled, and the wheel 6 is positioned close to the side surface of the vehicle 100, replacement of the wheel 6 is easy.

[0057] The active caster described in Embodiment 1 facilitates the replacement of the wheel 6 and improves the appearance design of the vehicle equipped with the wheel 6.

[0058] Furthermore, this disclosure is not limited to the above-described embodiments, and appropriate modifications can be made without departing from the spirit of the subject.

[0059] As will be apparent from the described disclosure, the embodiments of this disclosure can be implemented in a variety of ways. These implementations should not be considered as a departure from the spirit and scope of this disclosure, and all such modifications will be apparent to those skilled in the art as being included within the scope of the claims.

Claims

1. An active caster capable of steering a single wheel via interference drive, wherein, The drive caster includes: a vertically extending steering shaft, a horizontally extending axle, and a wheel that rotates about the axle. It also has both the offset s of the axle relative to the steering axis in a horizontal direction orthogonal to the direction in which the axle extends, and the offset d of the wheel relative to the steering axis in the direction in which the axle extends.

2. The drive caster according to claim 1, wherein, The drive caster includes: a first motor, a second motor, a first rotary transmission mechanism, a second rotary transmission mechanism, a third rotary transmission mechanism, a fourth rotary transmission mechanism, a fifth rotary transmission mechanism, a horizontally extending intermediate shaft, and a control unit. The first rotational speed ω1 of the first motor is transmitted to the rotation of the wheel about the steering axis via the first rotational transmission mechanism, and the second rotational speed ω2 of the second motor is transmitted to the rotation of the wheel about the steering axis via the second rotational transmission mechanism. The first rotational speed ω1 is transmitted to the intermediate shaft via the first and third rotational transmission mechanisms, and the second rotational speed ω2 is transmitted to the intermediate shaft via the second and fourth rotational transmission mechanisms. The rotational speed of the intermediate shaft is transmitted to the rotation of the wheel around the axle via the fifth rotational transmission mechanism. The control unit sets the rotational speed transmission ratios of the first to the fifth rotational transmission mechanisms to be G1 to G5, respectively. It sets the velocity vector of the vehicle equipped with the active caster wheel as V (in bold), the rotation angle of the wheel around the steering axis as θ, and the vector with components ω1 and ω2 as ω (in bold). Based on the following formula, it controls the first and second motors. 【Formula 1】 。 3. The drive caster according to claim 2, wherein, 2d-rG5(G3+G4)≠0.

4. The drive caster according to claim 2 or 3, wherein, G4-G3≠0.

5. The drive caster according to claim 1 or 2, wherein, The distance between the side surface of the vehicle equipped with the wheel and the wheel is smaller than the distance between the side surface of the vehicle and the steering axis.

Images