Power transmission mechanism, drive system, and output unit

Abstract

To provide a power transmission mechanism 100 that has a simple configuration and uses an elastic element.SOLUTION: There is provided a power transmission mechanism 100 including a drive unit 10 that includes a power source 11, and an output unit 20 driven by power from the power source 11, in which the output unit 20 includes an output shaft 222, and a coil spring 23 including a power-side end part 232 that rotates according to the power from the power source 11, an output-side end part 233 that rotates in keeping with rotation of the power-side end part 232 so as to rotate the output shaft 222, and an extension / contraction part 231 that generates elastic force around a rotation center of the power-side end part 232 and the output-side end part 233.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to powertrains, drive systems, and output units. [Background technology]

[0002] Patent Document 1 discloses a so-called series elastic actuator (SEA) that uses elastic elements. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-59235 Summary of the Invention [Problem to be solved by the invention]

[0004] The inventors of the present application are studying how to realize a power transmission mechanism that uses elastic elements with a simple configuration.

[0005] An object of the present disclosure is to provide a power transmission mechanism, a drive system, and an output unit that use elastic elements and have a simple configuration. [Means for solving the problem]

[0006] The power transmission mechanism according to the present disclosure is a power transmission mechanism having a drive unit including a power source, and an output unit driven by power from the power source, wherein the output unit has an output shaft, a power side end that rotates in response to power from the power source, an output side end that rotates together with the rotation of the power side end to rotate the output shaft, and an elastic member including an expandable portion that generates an elastic force around the center of rotation of the power side end and the output side end. [Brief explanation of the drawings]

[0007] [Figure 1]1 is a block diagram showing an outline of the overall configuration of a drive system according to an embodiment of the present invention; [Figure 2] FIG. [Figure 3] FIG. 2 is a plan view showing the power transmission mechanism as viewed from the direction of the rotation axis. [Figure 4] FIG. 4 is a cross-sectional view of the power transmission mechanism taken along the line IV-IV in FIG. 3. [Figure 5] FIG. 2 is a perspective view showing an output unit. [Figure 6] FIG. 2 is an exploded perspective view showing an output unit. [Figure 7] FIG. 2 is a plan view showing the output unit as viewed from a direction perpendicular to the rotation axis. [Figure 8] FIG. 2 is a plan view showing the coil spring as viewed from a direction perpendicular to the rotation axis. [Figure 9A] FIG. 2 is a schematic diagram for explaining the arrangement of a power-side end portion and an output-side end portion. [Figure 9B] FIG. 2 is a schematic diagram for explaining the arrangement of a power-side end portion and an output-side end portion. DETAILED DESCRIPTION OF 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.

[0009] [Overview of the overall configuration of the drive system S] 1 is a block diagram showing an outline of the overall configuration of a drive system according to this embodiment. The drive system S includes a power transmission mechanism 100 and a torque calculation device 200.

[0010] The power transmission mechanism 100 may include a drive unit 10, an output unit 20, an angle detection sensor 30, and an angle detection sensor 40. The drive unit 10 may include a power source 11 such as an actuator, and a drive shaft 12 that rotates by the power of the power source 11. The output unit 20 may include an output shaft 222 that rotates in response to the rotation of the drive shaft 12. The drive shaft 12 may be rotatable in a positive direction and a negative direction. Similarly, the output shaft 222 may be rotatable in a positive direction and a negative direction in response to the rotation of the drive shaft 12. The power transmission mechanism 100 may be used in, for example, an arm robot, in which case the output shaft 222 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 drive shaft 12. The angle detection sensor 40 is a sensor that detects the rotation angle of the output shaft 222. The angle detection sensors 30 and 40 may be, for example, TMR (Tunnel Magneto Resistance) sensors.

[0012] The power transmission mechanism 100 preferably includes a coil spring 23 as an elastic element that is interposed between the drive shaft 12 and the output shaft 222 and generates an elastic force when the output shaft 222 is rotated by the power from the drive unit 10. An actuator that transmits power using an elastic element in this way is sometimes called an SEA (series elastic actuator).

[0013] Here, the rotation angle of the drive shaft 12 and the rotation angle of the output shaft 222 may become misaligned due to an external impact, such as the end effector coming into contact with an obstacle, which may result in a load being applied to the output shaft 222. The torque calculation device 200 is a computer for calculating the load torque applied to the output shaft 222 based on the detection values ​​of the angle detection sensors 30 and 40.

[0014] The torque calculation device 200 may be configured with one or more computers. The torque calculation device 200 includes at least one processor, at least one memory such as a volatile memory or a nonvolatile memory, and a communication interface for wired communication or a communication interface for wireless communication. The programs stored in the torque calculation device 200 may be supplied via a network. For example, the torque calculation device 200 may include a reading unit (e.g., a memory card slot) that reads a computer-readable information storage medium, or an input / output unit (e.g., a USB terminal) for connecting to an external device. In this case, the programs stored in the information storage medium may be supplied via the reading unit or the input / output unit.

[0015] In this embodiment, the torque calculation device 200 calculates the load torque acting on the output shaft 222 due to an external impact or the like, using the amount of expansion and contraction of the coil spring 23. The amount of expansion and contraction of the coil spring 23 corresponds to the difference between the rotation angle of the drive shaft 12 and the rotation angle of the output shaft 222, and the load torque acting on the output shaft 222 can be obtained by multiplying the amount of expansion and contraction by the spring constant of the coil spring 23.

[0016] [Power transmission mechanism 100] Next, the power transmission mechanism of this embodiment will be described with reference to Figures 2 to 4. Figure 2 is a perspective view showing the power transmission mechanism. Figure 3 is a plan view showing the power transmission mechanism as seen from the direction of the rotation axis. Figure 4 is a cross-sectional view of the power transmission mechanism taken along the IV-IV cutting line in Figure 3.

[0017] The power transmission mechanism 100 has a drive pulley 110, an output unit 20 including a driven pulley member 21, and a timing belt 130, which is a transmission belt. The drive pulley 110 is preferably provided to rotate coaxially with the center of rotation of a drive shaft 12 that rotates by power from a power source 11. The power source 11 and the drive shaft 12 constitute a part of the drive unit 10, but are not shown in FIGS. 2 to 4. The driven pulley member 21 is preferably provided to rotate coaxially with a rotation axis O of the output shaft 222, for example.

[0018] The timing belt 130 is a circular belt that is stretched over the drive pulley 110 and the driven pulley member 21 and transmits power from the drive unit 10 to the driven pulley member 21. The timing belt 130 is driven in conjunction with the rotation of the drive pulley 110, and rotates the driven pulley member 21. Gears are formed on the inner peripheral surface of the timing belt 130, the outer peripheral surface of the drive pulley 110, and the outer peripheral surface of the driven pulley member 21, and these gears mesh with each other to interlock.

[0019] Furthermore, the power transmission mechanism 100 may include a tensioner 140 to suppress sagging and vibration of the timing belt 130.

[0020] [Output unit 20] The configuration of the output unit 20 will be described in detail mainly with reference to Fig. 5 to Fig. 7. Fig. 5 is a perspective view showing the output unit. Fig. 6 is an exploded perspective view showing the output unit. Fig. 7 is a plan view showing the output unit as seen from a direction perpendicular to the rotation axis.

[0021] As shown in FIG. 6, the output unit 20 includes the driven pulley member 21 described above, the output shaft member 22 including the output shaft 222 described above, and the coil spring 23 described above.

[0022] The coil spring 23 may include a coil-shaped expansion / contraction portion 231, a power-side end portion 232 provided on one end of the expansion / contraction portion 231, and an output-side end portion 233 provided on the other end of the expansion / contraction portion 231. The coil spring 23 may be, for example, a torsion coil spring that generates a torsion moment.

[0023] The expansion and contraction portion 231 expands and contracts as the power side end portion 232 and the output side end portion 233 rotate, generating an elastic force around the rotation axis O (rotation center) of the output shaft 222.

[0024] The power-side end 232 may have a shape that extends in the same direction as the output shaft 222. The output-side end 233 may have a shape that extends in the opposite direction to the power-side end 232.

[0025] The driven pulley member 21 may include a gear portion 211, a first accommodating portion 212, and a bearing portion 213. The gear portion 211, the first accommodating portion 212, and the bearing portion 213 may be formed integrally with one another.

[0026] The gear portion 211 may be cylindrical with a gear formed on its outer circumferential surface. The first accommodating portion 212 may be shaped to accommodate and hold the power-side end portion 232 of the coil spring 23. As shown in FIG. 6, the first accommodating portion 212 may be provided on the driven pulley member 21 so as to protrude from the side opposite the gear portion 211. The bearing portion 213 may be cylindrical and have a center hole 213h through which the output shaft 222 is inserted, and which, together with the gear portion 211, forms a region for accommodating the expansion / contraction portion 231 of the coil spring 23. Furthermore, as shown in FIGS. 4 and 6, bearings 25 and 26 may be provided between the bearing portion 213 and the output shaft 222.

[0027] The output shaft member 22 may include a flange portion 221, an output shaft 222, and a second accommodating portion 223. The flange portion 221, the output shaft 222, and the second accommodating portion 223 may be formed integrally with one another.

[0028] The flange portion 221 may be a disk having a larger diameter than the output shaft 222 and fixed to the end portion of the output shaft 222. The second accommodating portion 223 may be shaped to accommodate and hold the output side end portion 233 of the coil spring 23. The second accommodating portion 223 may be provided on the flange portion 221, protruding from the output shaft member 22 on the side opposite to the output shaft 222.

[0029] The power-side end 232 of the coil spring 23 is preferably accommodated in the first accommodating portion 212 and fixed to the driven pulley member 21 using a fastener F1 such as a screw. Specifically, as shown in Fig. 7, the fastener F1 is inserted into a screw hole 212h formed in the first accommodating portion 212, and the fastener F1 presses the outer peripheral surface of the power-side end 232, thereby fixing the power-side end 232 to the driven pulley member 21. Note that the fastener F1 is not shown in Fig. 5.

[0030] Similarly, the output side end 233 of the coil spring 23 may be accommodated in the second accommodating portion 223 and fixed to the output shaft member 22 using a fastener F2 such as a screw. Specifically, as shown in Fig. 7, the fastener F2 is inserted into a screw hole 223h formed in the second accommodating portion 223, and the fastener F2 presses the outer circumferential surface of the output side end 233, thereby fixing the output side end 233 to the output shaft member 22. The fastener F2 restricts the coil spring 23 from rotating around the output side end 233.

[0031] As described above, by fixing the power-side end 232 and the output-side end 233 of the coil spring 23, it is possible to prevent these ends from spinning freely. As a result, it is possible to stably transmit power from the drive unit 10 to the output shaft 222 via the coil spring 23.

[0032] [Coil spring 23] Further, the coil spring 23 will be described in detail with reference to Figs. 8, 9A, and 9B. Fig. 8 is a plan view showing the coil spring as viewed from a direction perpendicular to the rotation axis. Figs. 9A and 9B are schematic diagrams for explaining the arrangement of the power-side end portion and the output-side end portion. Fig. 9A schematically shows the arrangement of the power-side end portion 232 and the output-side end portion 233 when the coil spring 23 shown in Fig. 8 is viewed from the direction of the rotation axis O. Fig. 9B schematically shows another example of the coil spring 23. Also, Figs. 9A and 9B show the arrangement of the power-side end portion 232 and the output-side end portion 233 when the expansion / contraction portion 231 of the coil spring 23 is not expanded or contracted.

[0033] As shown in FIG. 8, the expandable portion 231 has a plurality of windings, and thus includes a plurality of annular portions 231a. The plurality of annular portions 231a are preferably spaced apart from one another in the direction in which the rotation axis O (the central axis of the expandable portion 231) extends. This suppresses friction between the plurality of annular portions 231a when the expandable portion 231 expands and contracts to generate elastic force around the rotation axis O. As a result, the linearity of the relationship between the deformation amount of the coil spring 23 and the torque applied to the output shaft 222 can be maintained, and the torque calculation device 200 can accurately calculate the load torque applied to the output shaft 222. Note that the expandable portion 231 is preferably shaped so that the plurality of annular portions 231a are spaced apart from one another both in a state in which torque is applied and a state in which torque is not applied.

[0034] 9A, when the coil spring 23 is viewed from the direction of the rotation axis O, the angle θ formed by an auxiliary line connecting the rotation axis O and the power-side end 232 and an auxiliary line connecting the rotation axis O and the output-side end 233 is preferably 90° or less. More preferably, the angle θ is 45° or less.

[0035] 9A and 9B show an example in which the end faces of the power side end 232 and the output side end 233 have circular shapes, and the auxiliary line forming the angle θ is a straight line passing through the center of the end faces of the power side end 232 and the output side end 233. However, the auxiliary line forming the angle θ may be a straight line passing through at least a portion of the end faces of the power side end 232 and the output side end 233.

[0036] 9B, if the angle θ formed by the auxiliary line connecting the rotation axis O and the power-side end 232 and the auxiliary line connecting the rotation axis O and the output-side end 233 is greater than 90°, the entire coil spring 23 will rotate around the power-side end 232, which may result in inefficient transmission of rotational force to the output shaft 222. In FIGS. 9A and 9B, R1 indicates the direction of rotational torque acting on the output-side end 233 when rotational force is normally transmitted, and R2 indicates the direction in which the entire coil spring 23 rotates.

[0037] In the arrangement shown in FIG. 9B, direction R1 and direction R2 are substantially aligned. In this configuration, if a large rotational force is applied to power end 232, causing the rotational torque applied to output end 233 to exceed the fixing torque of output end 233 by fixture F2, power end 232 will rotate in direction R2 around output end 233. That is, output end 233 will not change position, and coil spring 23 will spin freely. In contrast, in the arrangement shown in FIG. 9A, direction R1 and direction R2 are oriented in different directions. Therefore, even if a large rotational force is applied to power end 232, output end 233 will rotate in direction R1, and coil spring 23 will not spin freely.

[0038] When the arrangement of FIG. 9B is adopted, the output side end 233 should be firmly fixed to the output shaft member 22 so that the coil spring 23 does not rotate freely around the output side end 233 as the center of rotation.

[0039] [summary] In the present embodiment described above, the load torque applied to the output shaft 222 can be calculated using a simple configuration using the coil spring 23. Furthermore, by interposing the coil spring 23 between the drive shaft 12 and the output shaft 222, when an external impact is applied to the output shaft 222, the coil spring 23 absorbs the impact. This improves the durability of the power transmission mechanism 100. Furthermore, the simple configuration makes it easy to assemble the output unit 20. Furthermore, because the coil spring 23 is inexpensive, the cost required to manufacture the power transmission mechanism 100 can be reduced.

[0040] Furthermore, due to the linearity characteristics of the spring constant of the coil spring 23, the load torque acting on the output shaft 222 can be calculated with high precision when the output shaft 222 rotates in either the positive or negative direction.

[0041] The elastic member interposed between the drive shaft 12 and the output shaft 222 is not limited to the coil spring 23, but may be any member that includes an expansion and contraction section that expands and contracts to generate an elastic force around the center of rotation in accordance with the difference in the rotational angle between the drive shaft 12 and the output shaft 222.

[0042] [Note] For example, the power transmission mechanism 100 may have the following configuration. (1) A power transmission mechanism having a drive unit including a power source and an output unit driven by power from the power source, The output unit An output shaft; an elastic member including a power-side end portion that rotates in response to power from the power source, an output-side end portion that rotates together with the power-side end portion to rotate the output shaft, and an expandable portion that generates elastic force around the rotation center of the power-side end portion and the output-side end portion; A power transmission mechanism having the above structure. (2) The stretchable portion is a coil including a plurality of annular portions, The plurality of annular portions are spaced apart from each other in the axial direction of the rotation center of the elastic member. (1) The power transmission mechanism described above. (3) The stretchable portion is coil-shaped, When viewed from the direction in which the central axis of the extension / contraction section extends, the angle formed by an auxiliary line connecting the central axis and the power-side end and an auxiliary line connecting the central axis and the output-side end is 90° or less. The power transmission mechanism according to (1) or (2). (4) The elastic member is a torsion coil spring. The power transmission mechanism according to any one of (1) to (3). (5) the drive unit includes a drive pulley; the output unit includes a driven pulley member and a flange portion formed integrally with the output shaft, The drive pulley further includes a timing belt wound around the drive pulley and the driven pulley member, The power side end is held by the driven pulley member, The output side end is held by the flange portion. The power transmission mechanism according to any one of (1) to (4). (6) the driven pulley member includes a first housing portion in which the power-side end portion is housed, the flange portion includes a second housing portion in which the output side end portion is housed, a fixing member for fixing the output end portion accommodated in the second accommodating portion so as to restrict the elastic member from rotating around the output end portion; (5) The power transmission mechanism described in (5). [Explanation of symbols]

[0043] 10 drive unit, 11 power source, 12 drive shaft, 20 output unit, 21 driven pulley member, 211 gear portion, 212 first housing portion, 213 bearing portion, 22 output shaft member, 221 flange portion, 222 output shaft, 223 second housing portion, 23 coil spring, 231 expansion / contraction portion, 232 drive side end portion, 233 output side end portion, 30 angle detection sensor, 40 angle detection sensor, 100 power transmission mechanism, 110 drive pulley, 130 timing belt, 140 tensioner, 200 torque calculation device, S drive system.

Claims

1. A power transmission mechanism having a drive unit including a power source and an output unit driven by power from the power source, The output unit An output shaft; an elastic member including a power-side end portion that rotates in response to power from the power source, an output-side end portion that rotates together with the power-side end portion to rotate the output shaft, and an expandable portion that generates elastic force around the rotation center of the power-side end portion and the output-side end portion; A power transmission mechanism having the above structure.

2. The stretchable portion is a coil including a plurality of annular portions, The plurality of annular portions are spaced apart from each other in the direction in which the central axis of the stretchable portion extends. The power transmission mechanism according to claim 1 .

3. The stretchable portion is coil-shaped, When viewed from the direction in which the central axis of the extension portion extends, an angle formed by an auxiliary line connecting the central axis and the power side end portion and an auxiliary line connecting the central axis and the output side end portion is 90° or less. The power transmission mechanism according to claim 1 .

4. The elastic member is a torsion coil spring. The power transmission mechanism according to claim 1 .

5. the drive unit includes a drive pulley; the output unit includes a driven pulley member and a flange portion formed integrally with the output shaft, The drive pulley further includes a transmission belt that is stretched over the drive pulley and the driven pulley member, The power side end is held by the driven pulley member, The output side end is held by the flange portion. The power transmission mechanism according to claim 1 .

6. the driven pulley member includes a first housing portion in which the power-side end portion is housed, the flange portion includes a second housing portion in which the output side end portion is housed, a fixing member that fixes the output-side end portion accommodated in the second accommodating portion so as to restrict the elastic member from rotating around the output-side end portion; 6. The power transmission mechanism according to claim 5.

7. a power transmission mechanism according to any one of claims 1 to 6; a torque calculation device that calculates a load torque applied to the output shaft based on an amount of expansion and contraction of the elastic member according to a rotation angle of a drive shaft and a rotation angle of the output shaft of the power unit; The drive system includes:

8. An output unit driven by power from a power source, An output shaft; an elastic member including a power-side end portion that rotates in response to power from the power source, an output-side end portion that rotates together with the power-side end portion to rotate the output shaft, and an expandable portion that generates elastic force around the rotation center of the power-side end portion and the output-side end portion; An output unit having:

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