Active Caster

Abstract

To provide an active caster that facilitates wheel replacement. [Solution] The active caster 10 according to this disclosure enables steering of a single wheel 6 by interference drive. The active caster 10 comprises a vertically extending steering axis T, a horizontally extending axle 5, and a wheel 6 connected to the axle 5. The active caster 10 has both an offset s of the axle 5 from the steering axis T in the horizontal direction perpendicular to the direction in which the axle 5 extends, and an offset d of the wheel 6 from the steering axis T in the direction in which the axle 5 extends.

Description

[Technical Field]

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

[0002] Patent Document 1 discloses an active caster capable of movement in all directions. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2016-049921 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Conventional interference-driven active single-wheel casters transmit rotational force to both sides of the axle, which presents a problem in that wheel replacement is not easy.

[0005] This disclosure is made in view of the above background and aims to provide an active caster that facilitates wheel replacement. [Means for solving the problem]

[0006] The active caster according to this disclosure is an active caster that enables steering of a single wheel by interference drive, comprising a vertically extending steering shaft, a horizontally extending axle, and a wheel that rotates around the axle, and having both an offset s of the axle from the steering shaft in a horizontal direction perpendicular to the direction in which the axle extends, and an offset d of the wheel from the steering shaft in the direction in which the axle extends. [Effects of the Invention]

[0007] According to this disclosure, an active caster that facilitates wheel replacement can be provided. [Brief explanation of the drawing]

[0008] [Figure 1] This is a perspective cross-sectional view illustrating an active caster according to Embodiment 1. [Figure 2] This is a schematic cross-sectional view illustrating an active caster according to Embodiment 1. [Figure 3] This diagram shows an active caster according to Embodiment 1, illustrated with graphic symbols. [Figure 4] This is a diagram illustrating the configuration of a vehicle equipped with an active caster according to Embodiment 1. [Modes for carrying out the invention]

[0009] Embodiment 1 Figure 1 is a perspective cross-sectional view illustrating an active caster 10 according to Embodiment 1. Figure 2 is a diagram illustrating the configuration of the active caster 10. The active caster 10 comprises a main body 11, motors M1 to M2, timing belts 21 to 22, rotating cylinders 31 to 32, intermediate shaft 4, axle 5, wheel 6, and control unit 7.

[0010] Motors M1 and M2 may be supported by the main body 11. Motors M1 and M2 may be motors of the same performance.

[0011] Timing belt 21 is stretched between the output shaft of motor M1 and the rotating cylinder 31. Timing belt 22 is stretched between the output shaft of motor M2 and the rotating cylinder 32. When motor M1 rotates, the rotating cylinder 31 is able to rotate around the vertically extending steering shaft T. When motor M2 rotates, the rotating cylinder 32 is able to rotate around the steering shaft T.

[0012] The intermediate shaft 4 has a basic form of a cylinder extending in the horizontal direction. At one end of the intermediate shaft 4, a second spur gear that meshes with a first spur gear fixed to the wheel 6 is fixed. At the other end of the intermediate shaft 4, a third bevel gear that meshes with a first bevel gear fixed to the lower part of the rotating cylinder 31 is fixed. On the intermediate shaft 4, a fourth bevel gear that meshes with a second bevel gear fixed to the lower part of the rotating cylinder 32 is fixed. The fourth bevel gear is arranged between the second spur gear and the third spur gear. The wheel 6 is rotatable around the axle 5. The axle 5 extends horizontally. It is also possible to consider the shaft to which the above-mentioned first spur gear is fixed as the axle 5.

[0013] Let the rotational speed transmission ratio of the first rotational transmission mechanism including the timing belt 21 be G1. Let the rotational speed transmission ratio of the second rotational transmission mechanism including the timing belt 22 be G2. Let the rotational speed transmission ratio of the third rotational transmission mechanism including the first bevel gear of the rotating cylinder 31 and the third bevel gear of the intermediate shaft 4 be G3. Let the rotational speed transmission ratio of the fourth rotational transmission mechanism including the second bevel gear of the rotating cylinder 32 and the fourth bevel gear of the intermediate shaft 4 be G4. Let the rotational speed transmission ratio by the fifth rotational transmission mechanism including the second spur gear of the intermediate shaft 4 and the first spur gear of the wheel 6 be G5.

[0014] The active caster 10 may include a support member that rotatably supports the intermediate shaft 4 and the axle 5 around the turning axis T. It is also possible to consider this support member as the steering axis T.

[0015] For example, when the rotating cylinders 31 and 32 rotate in opposite directions, the direction in which the rotating cylinder 31 rotates the intermediate shaft 4 is opposite to the direction in which the rotating cylinder 32 rotates the intermediate shaft 4. Therefore, the wheel 6 does not rotate around the axle 5 but rotates around the steering axis T. When the rotating cylinders 31 and 32 rotate in the same direction, the wheel 6 rotates around the axle 5.

[0016] Let the rotational speed of the output shaft of the motor M1 be ω1, and the rotational speed of the output shaft of the motor M2 be ω2. Let the rotational speed of the wheel 6 around the axle 5 be ω w and the rotational speed of the wheel 6 around the steering axis T be ω sLet it be so. The arc-shaped arrow represents the positive direction of rotation. G1 to G4 can be positive or negative real numbers.

[0017] The active caster enables the steering of the wheel 6 by interference drive. The rotational speed ω1 of the motor M1 is transmitted to the rotation of the wheel 6 around the steering shaft T via the first rotational transmission mechanism, and the rotational speed ω2 of the motor M2 is transmitted to the rotation of the wheel 6 around the steering shaft T via the second rotational transmission mechanism. The rotational speed ω1 of the motor M1 is transmitted to the rotation of the intermediate shaft 4 via the first rotational transmission mechanism and the third rotational transmission mechanism, and the rotational speed ω2 of the motor M2 is transmitted to the rotation of the intermediate shaft 4 via the second rotational transmission mechanism and the fourth rotational transmission mechanism. The rotational speed of the intermediate shaft 4 is transmitted to the rotation of the wheel 6 around the axle 5 via the fifth transmission mechanism.

[0018] Figure 3 is a diagram showing the active caster 10 by graphical symbols. The active caster 10 includes the steering shaft T and the axle 5 as already described. Let the offset of the axle 5 from the steering shaft T in the direction orthogonal to the extending direction of the axle 5 be s. Let the offset of the wheel 6 from the steering shaft T in the extending direction of the axle 5 be d. Let the x component and the y component of the speed of the wheel 6 in the xy coordinate system rotating around the steering shaft T be v x and v y respectively. The x direction corresponds to the direction orthogonal to the extending direction of the axle 5. The y direction corresponds to the extending direction of the axle 5. Let l = √(s 2 + r 2 ), cosα = s / l, and sinα = d / l. Then, the following equations are obtained.

Equation

[0019] v x and v y respectively. Let the vector with v

Equation

[0020] In the vehicle coordinate system XY of a vehicle equipped with the active caster 10, the X and Y components of the speed of the wheel 6 are respectively V x and V y Let them be. Let the rotation angle of the wheel 6 around the steering axis T be θ, and let the vector with V x and V y as components be V (boldface). Then the following equation can be obtained.

Equation

[0021] Referring to FIG. 2, ω1 and ω2 are represented by the following equations.

Equation

Equation

[0022] From equations (4) and (5), the following equation can be obtained. ω (boldface) represents the vector with ω1 and ω2 as components.

Equation

[0023] From equations (2) and (6), the following equation can be obtained.

Equation

[0024] From equation (3) and equation (7), the following equation can be obtained.

Equation

[0025] From equation (8), the rotational speed ω1 of the motor M1 and the rotational speed ω2 of the motor M2 for an arbitrary speed vector V (boldface) can be obtained.

[0026] For the active caster 10 to operate, the rank of the matrix on the right-hand side of equation (6) must be 2. i If we set ≠0 (i=1~5), we obtain the following equation.

number

[0027] Similarly, for the active caster 10 to function, the rank of the matrix on the right-hand side of equation (7) must be 2. i If we set ≠0 (i=1~5), we obtain the following equation.

number

[0028] Referring to Figure 2, the control unit 7 is hardware-based, centered around a microcomputer consisting of, for example, a CPU (Central Processing Unit), memory, and an interface unit (I / F). The CPU performs control processing, arithmetic processing, etc. The memory consists of ROM (Read Only Memory) that stores control programs, arithmetic programs, etc., executed by the CPU. The interface unit performs signal input and output with the outside. The CPU, memory, and interface unit are interconnected via a data bus.

[0029] The control unit 7 controls the rotation of the wheels 6 around the steering axis T and the rotation of the wheels 6 around the axle 5 by transmitting control signals to the motors M1 and M2. The control unit 7 controls the motors M1 and M2 based on equation (8). In other words, the control unit 7 uses equation (8) to calculate the rotational speed ω1 of motor M1 and the rotational speed ω2 of motor M2 from the speed V (bold) of the vehicle equipped with the active caster 10. The control unit 7 transmits control signals corresponding to the calculated rotational speeds ω1 and ω2 to motors M1 and M2.

[0030] The upper left diagram in Figure 4 is a schematic perspective view showing the configuration of a vehicle 200 equipped with a conventional active caster 20. The upper right diagram in Figure 4 is a schematic bottom view of the conventional vehicle 200. In the conventional active caster 20, rotational force needs to be transmitted to both sides of the wheel 6, so the wheel 6 is positioned inward from the side of the vehicle 200. Replacing the wheel 6 requires disassembling the active caster 20, and since the wheel 6 is positioned far from the side of the vehicle 200, replacing the wheel 6 is not easy.

[0031] The lower left diagram of Figure 4 is a schematic perspective view showing the configuration of a vehicle 100 equipped with an active caster 10 according to Embodiment 1. The lower right diagram of Figure 4 is a schematic bottom view showing the vehicle 100 according to Embodiment 1. The distance between the side of the vehicle 100 and the wheel 6 is smaller than the distance between the side of the vehicle 100 and the steering shaft T. The wheel 6 of the active caster 10 is positioned close to the side of the vehicle 100. There is no need to disassemble the active caster 10, and since the wheel 6 is positioned close to the side of the vehicle 100, the wheel 6 is easy to replace.

[0032] The active caster according to Embodiment 1 facilitates the replacement of the wheels 6 and improves the aesthetic design of the vehicle equipped with the wheels 6.

[0033] This disclosure is not limited to the embodiments described above, and may be modified as appropriate without departing from its spirit. [Explanation of Symbols]

[0034] 10, 20 Active Casters T Steering axis M1, M2 motors 21, 22 Timing belt 31, 32 Rotating cylinder 4 Intermediate axis 5 axles 6 wheels 7 Control Unit 100, 200 vehicles

Claims

1. An active caster that enables steering of a single wheel through interference drive, It comprises a steering shaft extending vertically, an axle extending horizontally, and wheels that rotate around the axle, The axle has an offset s from the steering axis in a horizontal direction perpendicular to the direction in which the axle extends, and the wheel has an offset d from the steering axis in the direction in which the axle extends. Active caster.

2. The active caster comprises a first motor, a second motor, first to fifth rotation transmission mechanisms, a horizontally extending intermediate shaft, and a control unit. The first rotational speed ω of the first motor １ However, the rotation of the wheel around the steering shaft is transmitted via the first rotation transmission mechanism, and the second rotational speed ω of the second motor ２ However, this is transmitted to the rotation of the wheel around the steering shaft via the second rotation transmission mechanism. The first rotational speed ω １ However, the rotation of the intermediate shaft is transmitted via the first rotation transmission mechanism and the third rotation transmission mechanism, and the second rotation speed ω ２ However, the rotation is transmitted to the intermediate shaft via the second rotation transmission mechanism and the fourth rotation transmission mechanism. The rotational speed of the intermediate shaft is transmitted to the rotation of the wheel around the axle via the fifth rotation transmission mechanism. The control unit sets the rotational speed transmission ratio in the first to fifth rotational transmission mechanisms to G １ ~G ５ Let V (bold) be the velocity vector of the vehicle equipped with the active caster, and let θ be the rotation angle of the wheel around the steering axis, ω １ and ω ２ Let ω (in bold) be a vector whose components are , and control the first motor and the second motor based on the following equation. [Math 1] The active caster according to claim 1.

3. 2d - rG ５ (G ３ + G ４ ) ≠ 0 holds The active caster according to claim 2.

4. G ４ -G ３ ≠ 0 The active caster according to claim 2 or 3.

5. The distance between the side of the vehicle on which the wheel is installed and the wheel is smaller than the distance between the side of the vehicle and the steering shaft. The active caster according to claim 1 or 2.

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