Power transmission mechanism and drive system

Abstract

To accurately calculate load torque applied to an output shaft 20.SOLUTION: A power transmission mechanism 100 transmits power from an actuator 10 to an output shaft 20, and comprises: a drive pulley 110; a driven pulley 120; a timing belt 130 that is stretched between the drive pulley 110 and the driven pulley 120, and transmits power from the actuator 10 to the driven pulley 120; a biasing pulley 151 that is supported movably in a direction intersecting a driving direction of the timing belt 130, and biases the timing belt 130; an elastic spring 50 that elastically biases the biasing pulley 151 against the timing belt 130; an additional pulley 152 that is bridged across the timing belt 130 between the biasing pulley 151 and the drive pulley 110; and an additional pulley 153 that is bridged across the timing belt 130 between the biasing pulley 151 and the driven pulley 120.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a power transmission mechanism and a drive system.

Background Art

[0002] Patent Document 1 discloses a so-called series elastic actuator (SEA) using an elastic element.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The inventors of the present application have considered accurately calculating the load torque applied to the output shaft in a power transmission mechanism using an elastic element.

[0005] An object of the present disclosure is to provide a power transmission mechanism and a drive system capable of accurately calculating the load torque applied to the output shaft.

Means for Solving the Problems

[0006] The power transmission mechanism according to the present disclosure is a power transmission mechanism that transmits the power from the actuator to the output shaft, and includes a drive pulley that rotates by the power, a driven pulley that transmits the power to the output shaft, a transmission belt that is stretched between the drive pulley and the driven pulley and transmits the power to the driven pulley, a biasing pulley that is supported so as to be movable in a direction intersecting the direction in which the drive belt drives and is biased with respect to the transmission belt, a first elastic member that elastically biases the biasing pulley with respect to the transmission belt, a first additional pulley that is stretched over the transmission belt between the biasing pulley and the drive pulley, and a second additional pulley that is stretched over the transmission belt between the biasing pulley and the driven pulley.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4A

Figure 4B

Embodiments for Carrying Out the Invention

[0008] Hereinafter, an example of an embodiment of a drive system S according to the present disclosure will be described with reference to the drawings. FIG. 1 is a block diagram showing an outline of the overall configuration of the drive system according to the present embodiment. FIG. 2 is a diagram showing an outline of the power transmission mechanism of the present embodiment.

[0009] The drive system S includes a power transmission mechanism 100 and a torque calculation device 200.

[0010] The power transmission mechanism 100 includes an actuator 10, an output shaft 20, an angle detection sensor 30, and an angle detection sensor 40. The power transmission mechanism 100 is used, for example, in an arm robot. In that case, the output shaft 20 may be a shaft that drives an end effector.

[0011] The angle detection sensor 30 is a sensor that detects the rotation angle of the actuator 10. The angle detection sensor 40 is a sensor that detects the rotation angle of the output shaft 20. The angle detection sensors 30 and 40 may be, for example, encoders.

[0012] The power transmission mechanism 100 further includes an elastic element TS that generates an elastic force when the actuator 10 drives the output shaft 20. An actuator that transmits power with such an elastic element interposed therebetween is sometimes called a SEA (series elastic actuator).

[0013] In the power transmission mechanism 100, the actuator 10 and the output shaft 20 are arranged separately. As shown in FIG. 2, the power transmission mechanism 100 further includes a drive pulley 110, a driven pulley 120, and a timing belt 130 that is a transmission belt. The drive pulley 110 is rotatably supported by the actuator 10 with the rotation center O1 of the actuator 10 as the rotation center. The driven pulley 120 is rotatably supported by the output shaft 20 with the rotation center O2 of the output shaft 20 as the rotation center. Note that the drive pulley 110 preferably rotates as the actuator 10 rotates, but is not limited to having its rotation center coincide with the rotation center O1 of the actuator 10. Similarly, the driven pulley 120 only needs to transmit power to the output shaft 20, and is not limited to having its rotation center coincide with the rotation center O2 of the output shaft 20.

[0014] The timing belt 130 is an annular belt that is stretched between the drive pulley 110 and the driven pulley 120 and transmits the power from the actuator 10 to the driven pulley 120. That is, the timing belt 130 is driven as the drive pulley 110 rotates and rotates the driven pulley 120. Gears are formed on the inner peripheral surface of the timing belt 130 and the outer peripheral surfaces of the drive pulley 110 and the driven pulley 120, and they may be interlocked by meshing with each other.

[0015] The torque calculation device 200 is a computer for calculating the load torque applied to the output shaft 20 based on the detection values of the angle detection sensor 30 and the angle detection sensor 40. The torque calculation device 200 may be composed of one or more computers. The torque calculation device 200 includes at least one processor, at least one of a volatile memory or a non-volatile memory, and a communication interface for wired communication or a communication interface for wireless communication. Further, the program stored in the torque calculation device 200 may be supplied via a network. For example, a reading unit (for example, a memory card slot) for reading a computer-readable information storage medium or an input / output unit (for example, a USB terminal) for connecting to an external device may be included. In this case, the program stored in the information storage medium may be supplied via the reading unit or the input / output unit.

[0016] Conventionally, in a power transmission mechanism using a timing belt, a tensioner including an elastic spring has been adopted to suppress the deflection and vibration of the belt. The applicants of the present application are considering calculating the load torque applied to the output shaft by using the deformation amount of the elastic spring in the tensioner. The deformation amount of the elastic spring corresponds to the difference between the rotation angle of the actuator and the rotation angle of the output shaft, and the load torque applied to the output shaft can be obtained by multiplying the deformation amount by a known spring constant. Note that the rotation angle of the actuator and the rotation angle of the output shaft may be displaced, for example, when the end effector contacts some obstacle.

[0017] Here, referring to FIG. 3, the calculation of the load torque applied to the output shaft (driven pulley) in the conventional power transmission mechanism and its problems will be described. FIG. 3 is a diagram for explaining the load torque applied to the output shaft when using a conventional tensioner. In FIG. 3, the illustration of the tensioner (including the elastic spring) is omitted.

[0018] In FIG. 3, F represents the elastic force by the tensioner, θ represents the angle of the timing belt bent when the tensioner abuts at the tension position T, and f represents the load applied to the timing belt at the tension position T. Here, for simplicity of explanation, an example where the tensioner makes point contact at the tension position T will be described, but actually the tension position T may be a region having a predetermined width. Also, for simplicity of explanation, an example where the tension position T is in the middle of the driven pulley and the driving pulley of the timing belt will be described.

[0019] Hereinafter, an example of calculating the load torque applied to the driven pulley when the driven pulley is non-rotating and the driving pulley is rotated clockwise in FIG. 3 will be described. When the driven pulley is fixed so as not to rotate and the driving pulley is rotated clockwise, the timing belt is wound around the driving pulley. As a result, while eliminating the deflection, the tension position T rises, and the elastic spring of the tensioner is compressed. That is, the elastic spring of the tensioner deforms according to the difference in the rotation angles of the driving pulley and the driven pulley. Also, as the tension position T rises, θ in FIG. 3 gradually increases.

[0020] In the mechanism shown in FIG. 3, as described above, the amount of deformation (compression amount) of the elastic spring is determined from the difference between the rotation angle of the actuator and the rotation angle of the output shaft. Therefore, based on the difference between the rotation angle of the actuator and the rotation angle of the output shaft and the known spring constant of the elastic spring, the load torque applied to the output shaft (driven pulley) can be obtained.

[0021] However, when adopting a conventional tensioner, since the load torque applied to the output shaft changes non-linearly according to the deformation amount of the elastic spring, it has been difficult to accurately calculate the load torque.

[0022] When the spring constant of the elastic spring of the tensioner is k and the compression amount of the elastic spring is x, the elastic force F by the tensioner is expressed as F = kx according to Hooke's law. Also, the load f applied to the timing belt corresponds to the load torque applied to the driven pulley and is expressed as f = F / (2cos(θ / 2)). From this, the load torque f is expressed as f = kx / (2cos(θ / 2)).

[0023] That is, the load torque f changes with θ and x as variables. θ changes, for example, between 90° and 180° at most. That is, θ / 2 changes between 45° and 90° at most. For example, when θ changes from 120° to 150° as the driving pulley rotates, cos(θ / 2) decreases from 0.5 to about 0.26. Therefore, the value of 1 / cos(θ / 2) increases. Also, as θ increases, the compression amount x of the elastic spring also increases. Therefore, the load torque f applied to the driven pulley increases in a quadratic curve as θ increases. In particular, even when the increase amount of θ is minute in a state where θ is close to 180°, the change amount of the load torque f becomes rapidly large. Thus, since the load torque f increases in a quadratic curve (non-linearly) according to θ, the calculation of the load torque f becomes complicated, and it is difficult to accurately calculate the load torque f because the load torque f changes greatly even when θ changes slightly.

[0024] Therefore, in the present embodiment, a configuration is adopted in which the load torque f is proportional to the compression amount of the elastic spring 50. Specifically, a configuration is adopted in which θ in the load torque f = kx / (2cos(θ / 2)) is always 0°. When θ = 0°, cos(θ / 2) = 1, and the load torque f can be expressed as f = kx / 2. That is, the load torque f is proportional to the compression amount of the elastic spring 50 (changes linearly).

[0025] Referring to FIG. 2, a specific configuration for realizing θ = 0° will be described. The power transmission mechanism 100 includes tensioners TS1 and TS2 which are elastic elements TS in addition to the above-described drive pulley 110, driven pulley 120, and timing belt 130.

[0026] Tensioner TS1 is a mechanism that applies tension to the timing belt 130 so as to suppress the deflection and vibration of the timing belt 130 when the drive pulley 110 rotates in the R1 direction (clockwise direction) in FIG. 3. Tensioner T1 includes an elastic spring 50, a biasing pulley 151, and additional pulleys 152 and 153.

[0027] The elastic spring 50 elastically biases the biasing pulley 151 with respect to the timing belt 130. One end (the upper end in FIG. 2) of the elastic spring 50 is fixed, and the other end (the lower end in FIG. 2) is connected to the biasing pulley 151.

[0028] The biasing pulley 151 is supported so as to be movable in a direction intersecting (orthogonal) to the direction in which the timing belt 130 is driven, and is in contact with the outer peripheral surface of the timing belt 130. In the example shown in FIG. 2, when the drive pulley 110 rotates in the R1 direction, the biasing pulley 151 rises while maintaining the state of being in contact with the timing belt 130. When the biasing pulley 151 rises, the elastic spring 50 is compressed.

[0029] The additional pulley 152 has a gear formed on its outer peripheral surface and is arranged so as to be spanned over the timing belt 130 between the biasing pulley 151 and the drive pulley 110. The additional pulley 152 is supported so as to be rotatable along with the drive of the timing belt 130. Also, the position of the additional pulley 152 is fixed.

[0030] The additional pulley 153 has a gear formed on its outer peripheral surface and is arranged to be spanned over the timing belt 130 between the biasing pulley 151 and the driven pulley 120. The additional pulley 153 is rotatably supported as the timing belt 130 is driven. Also, the position of the additional pulley 153 is fixed.

[0031] Here, among the timing belt 130, the portion between the biasing pulley 151 and the additional pulley 152 is defined as the first belt portion 130a1, the portion between the biasing pulley 151 and the additional pulley 153 is defined as the second belt portion 130a2, the portion between the additional pulley 152 and the driving pulley 110 is defined as the third belt portion 130b1, and the portion between the additional pulley 153 and the driven pulley 120 is defined as the fourth belt portion 130b2.

[0032] The additional pulley 152 and the additional pulley 153 are arranged so as to keep the angle between the direction in which the first belt portion 130a1 is driven and the direction in which the second belt portion 130a2 is driven constant. Specifically, the additional pulley 152 and the additional pulley 153 are arranged so that the angle between the direction in which the first belt portion 130a1 is driven and the direction in which the second belt portion 130a2 is driven becomes 0°. In other words, the additional pulleys 152 and 153 are arranged so that the first belt portion 130a1 and the second belt portion 130a2 are parallel to each other.

[0033] Also, the additional pulley 152 is arranged so that the direction in which the first belt portion 130a1 is driven and the direction in which the third belt portion 130b1 is driven are orthogonal to each other. Similarly, the additional pulley 153 is arranged so that the direction in which the second belt portion 130a2 is driven and the direction in which the fourth belt portion 130b2 is driven are orthogonal to each other.

[0034] The tensioner T2 is a mechanism that applies tension to the timing belt 130 so as to suppress the deflection of the timing belt 130 when the driving pulley 110 rotates in the direction opposite to the R1 direction (counterclockwise direction) in FIG. 3. Since the tensioner T2 has the same mechanism as the tensioner T1, a detailed description thereof is omitted.

[0035] In the power transmission mechanism 100 of the present embodiment, since θ = 0°, the load torque f represented by f = kx / (2cos(θ / 2)) and the compression amount x of the elastic spring 50 are in a proportional (linear) relationship. Therefore, it is possible to easily and accurately calculate the load torque f by the torque calculation device 200.

[0036] In the present embodiment, the configuration in which the additional pulleys 152 and 153 are arranged so that θ = 0° has been described, but the present invention is not limited to this. That is, by arranging the additional pulleys 152 and 153, the configuration may be such that θ changes in a range close to 0°.

[0037] In the present embodiment, an example in which the tensioners T1 and T2 include the elastic spring 50 as an elastic member has been described, but the present invention is not limited to a spring as long as it elastically biases the timing belt 130.

[0038] Next, with reference to FIGS. 4A and 4B, a power transmission mechanism according to a modification of the present embodiment will be described. FIG. 4A is a diagram showing the power transmission mechanism of the modification. FIG. 4B is a perspective view showing the power transmission mechanism of the modification. In FIG. 4B, the illustration of the elastic spring 50A and the elastic spring 50B is omitted.

[0039] In the configuration shown in FIG. 2, in order to suppress the deflection of the timing belt 130 when the drive pulley 110 rotates in either the clockwise or counterclockwise direction, a configuration in which two tensioners TS1 and TS2 are provided is adopted, and a space for arranging these tensioners is required. Therefore, the power transmission mechanism becomes large-sized, and the applicable range of the mechanism is limited. Therefore, in the modification, a configuration for improving space efficiency is adopted. Specifically, a configuration using one biasing pulley 1510 is adopted.

[0040] The power transmission mechanism 500 according to the modified example includes two timing belts. Specifically, the power transmission mechanism 500 includes a timing belt 130A and a timing belt 130B. The timing belt 130A and the timing belt 130B are separate bodies and are arranged side by side in the axial direction of the drive pulley 110 so as not to overlap each other. The timing belt 130A is provided on the back side of the paper surface in FIG. 4A compared to the timing belt 130B.

[0041] One end of the timing belt 130A is fixed to the drive pulley 110, and the other end is fixed to the driven pulley 120. One end of the timing belt 130B is fixed to the drive pulley 110, and the other end is fixed to the driven pulley 120.

[0042] In addition, the urging pulley 1510 is provided so as to elastically urge the timing belt 130A by the elastic spring 50A. Further, the urging pulley 1510 is provided so as to elastically urge the timing belt 130B in the direction opposite to the direction in which the elastic spring 50A urges the timing belt 130A by the elastic spring 50B.

[0043] In addition, the power transmission mechanism 500 includes an additional pulley 1520 spanned over the timing belt 130A between the urging pulley 1510 and the drive pulley 110, and an additional pulley 1530 spanned over the timing belt 130A between the urging pulley 1510 and the driven pulley 120. In addition, the power transmission mechanism 500 includes an additional pulley 1540 spanned over the timing belt 130B between the urging pulley 1510 and the drive pulley 110, and an additional pulley 1550 spanned over the timing belt 130B between the urging pulley 1510 and the driven pulley 120.

[0044] With the above configuration, in the power transmission mechanism 500, similar to the power transmission mechanism 100 shown in FIG. 2, the load torque and the compression amounts of the elastic springs 50A and 50B can be made to have a proportional (linear) relationship. Therefore, it becomes possible to easily and accurately calculate the load torque by the torque calculation device 200. Also, in the power transmission mechanism 500, miniaturization can be achieved as compared with the configuration in which two biasing pulleys shown in FIG. 2 are provided. The power transmission mechanism 500 is particularly useful when the distance between the drive pulley 110 and the driven pulley 120 is short, for example.

[0045] [Appendix] For example, the power transmission mechanism can also have the following configuration. (1) A power transmission mechanism that transmits the power from the actuator to the output shaft, a drive pulley that rotates by the power, a driven pulley that transmits the power to the output shaft, a transmission belt that is stretched between the drive pulley and the driven pulley and transmits the power to the driven pulley, a biasing pulley that is supported so as to be movable in a direction intersecting the direction in which the drive belt drives and is biased with respect to the transmission belt, a first elastic member that elastically biases the biasing pulley with respect to the transmission belt, a first additional pulley that is stretched over the transmission belt between the biasing pulley and the drive pulley, a second additional pulley that is stretched over the transmission belt between the biasing pulley and the driven pulley, and a power transmission mechanism. (2) The first additional pulley and the second additional pulley are arranged so as to keep constant the angle between the direction in which the first belt portion between the first biasing pulley and the first additional pulley of the transmission belt drives and the direction in which the second belt portion between the biasing pulley and the second additional pulley of the transmission belt drives. The power transmission mechanism according to (1). (3) The first additional pulley and the second additional pulley are arranged such that the first belt portion and the second belt portion are parallel to each other. The power transmission mechanism according to (2). (4) The first additional pulley is arranged such that the driving direction of the first belt portion is orthogonal to the driving direction of the third belt portion between the first additional pulley and the driving pulley in the transmission belt. The second additional pulley is arranged such that the driving direction of the second belt portion is orthogonal to the driving direction of the fourth belt portion between the second additional pulley and the driven pulley in the transmission belt. The power transmission mechanism according to (2) or (3). (5) The transmission belt includes a first transmission belt having one end fixed to the driving pulley and the other end fixed to the driven pulley, and a second transmission belt having one end fixed to the driving pulley and the other end fixed to the driven pulley and arranged side by side with the first driving belt in the axial direction of the driving pulley. The first elastic member is arranged to elastically bias the biasing pulley with respect to the first driving belt. The first additional pulley is spanned over the first driving belt between the biasing pulley and the driving pulley. The second additional pulley is spanned over the first driving belt between the biasing pulley and the driven pulley. A second elastic member that elastically biases the biasing pulley with respect to the second driving belt in a direction opposite to the direction in which the first elastic member elastically biases the biasing pulley. A third additional pulley spanned over the second driving belt between the biasing pulley and the driving pulley. A fourth additional pulley spanned over the second driving belt between the biasing pulley and the driven pulley. Including The power transmission mechanism according to any one of (1) to (4).

Explanation of reference numerals

[0046] 10 Actuator, 20 Output shaft, 30 Angle detection sensor, 40 Angle detection sensor, 50, 50A, 50B Elastic spring, 100, 500 Power transmission mechanism, 110 Driving pulley, 120 Driven pulley, 130 Timing belt, 151, 1510 Biasing pulley, 152, 153, 1520, 1530, 1540, 1550, 200 Torque calculation device, S Drive system.

Claims

1. A power transmission mechanism that transmits power from an actuator to an output shaft, comprising: a drive pulley that rotates by the power; a driven pulley that transmits the power to the output shaft; a transmission belt that is stretched between the drive pulley and the driven pulley and transmits the power to the driven pulley; a biasing pulley that is supported so as to be movable in a direction intersecting the direction in which the drive belt drives and is biased with respect to the transmission belt; a first elastic member that elastically biases the biasing pulley with respect to the transmission belt; a first additional pulley that is stretched over the transmission belt between the biasing pulley and the drive pulley; a second additional pulley that is stretched over the transmission belt between the biasing pulley and the driven pulley; and a power transmission mechanism.

2. The first additional pulley and the second additional pulley are arranged so as to keep constant an angle between a driving direction of a first belt portion of the transmission belt between the first biasing pulley and the first additional pulley and a driving direction of a second belt portion of the transmission belt between the biasing pulley and the second additional pulley. The power transmission mechanism according to claim 1. The power transmission mechanism according to claim 1.

3. The first additional pulley and the second additional pulley are arranged so that the first belt portion and the second belt portion are parallel to each other. The power transmission mechanism according to claim 2. The power transmission mechanism according to claim 2.

4. The first additional pulley is arranged so that a driving direction of the first belt portion and a driving direction of a third belt portion of the transmission belt between the first additional pulley and the drive pulley are orthogonal to each other. The second additional pulley is arranged so that a driving direction of the second belt portion and a driving direction of a fourth belt portion of the transmission belt between the second additional pulley and the driven pulley are orthogonal to each other. The power transmission mechanism according to claim 2. The power transmission mechanism according to claim 2.

5. The transmission belt includes a first transmission belt having one end fixed to the drive pulley and the other end fixed to the driven pulley, and a second transmission belt having one end fixed to the drive pulley, the other end fixed to the driven pulley, and arranged side by side with the first drive belt in the axial direction of the drive pulley. The first elastic member is arranged to elastically bias the biasing pulley with respect to the first drive belt. The first additional pulley is stretched over the first drive belt between the biasing pulley and the drive pulley. The first additional pulley is stretched over the first drive belt between the biasing pulley and the drive pulley. The first elastic member is arranged to elastically bias the biasing pulley with respect to the first drive belt. The first additional pulley is stretched over the first drive belt between the biasing pulley and the drive pulley. The second additional pulley is spanned by the first drive belt between the biasing pulley and the driven pulley. A second elastic member that elastically biases the biasing pulley with respect to the second drive belt in a direction opposite to the direction in which the first elastic member elastically biases the biasing pulley. A third additional pulley spanned by the second drive belt between the biasing pulley and the drive pulley. A fourth additional pulley spanned by the second drive belt between the biasing pulley and the driven pulley. comprising The power transmission mechanism according to claim 1.

6. The power transmission mechanism according to any one of claims 1 to 5, A torque calculation device that calculates a load torque applied to the output shaft based on the rotation angle of the actuator, the rotation angle of the output shaft, and the spring constant of the elastic spring included in the first elastic member. comprising A drive system.

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