Harmonic gear reducer

Abstract

This harmonic gear reducer comprises a wave generator, an external gear, an internal gear, a first detection unit, and a second detection unit. The first detection unit and the second detection unit are capable of detecting torque about a central axis that acts on an output member which is capable of rotation at an output rotational speed along with one of the external gear and the internal gear. The first detection unit has a plurality of strain gauges, the output of which changes due to torque about the central axis acting on the external gear. The second detection unit has an input-side angle detection unit, an output-side angle detection unit, and a torque calculation unit. The input-side angle detection unit detects the rotation angle of the input member about the central axis. The output-side angle detection unit detects the rotation angle of the output member about the central axis. The torque calculation unit can calculate the torque about the central axis acting on the output member, on the basis of the difference between a theoretical value of the rotation angle of the output member about the central axis, which is the result of dividing by the detection result of the input-side angle detection unit by a reduction ratio, and the actual value of the rotation angle of the output member about the central axis, which is the detection result by the output-side angle detection unit.

Description

Harmonic drive reducer

[0001] The present invention relates to a harmonic drive reducer. This application claims priority based on Japanese Patent Application No. 2024-198939 filed in Japan on November 14, 2024, the content of which is incorporated herein by reference.

[0002] In recent years, the demand for harmonic reducers installed in robot joints and the like has been increasing. Some conventional harmonic reducers have strain gauges. The strain gauge is adhesively fixed to an external gear that meshes with a member rotating at the rotational speed after deceleration. Thereby, it is possible to detect the torque applied to the external gear (Patent Document 1). Japanese Patent Application Laid-Open No. 2000-131160

[0003] In order to improve the reliability of torque detection, it is conceivable to form a film sensor in which two sets of resistance wire portions including strain gauges are arranged on the external gear. However, in this case, since the two sets of resistance wire portions are arranged in a single film sensor, if the film peels off or breaks, there is a risk that neither resistance wire portion can appropriately detect the strain generated in the external gear or that the wire breaks. In this case, there is a risk that torque cannot be detected normally.

[0004] An object of the present invention is to provide a technique that can further enhance the redundancy of torque detection.

[0005] The first invention is a wave gear reducer that reduces the input rotational speed of an input member rotatable together with the rotating part of a motor, thereby rotating an output member at an output rotational speed smaller than the input rotational speed, comprising: a wave generator having a non-circular cross-section perpendicular to the central axis and rotatable together with the input member around the central axis at the input rotational speed; an external gear having at least a portion arranged radially outward from the wave generator and having a plurality of external teeth protruding radially outward; an internal gear having at least a portion arranged radially outward from the external gear, spreading in an annular shape around the central axis and having a plurality of internal teeth protruding radially inward and partially meshing with the plurality of external teeth; and a first detection unit and a second detection unit, respectively, capable of detecting the torque acting on the output member around the central axis, wherein the output member is the external gear The gear and one of the internal gears are rotatable together at the output rotational speed, and the first detection unit has a plurality of strain gauges arranged on the external gear whose output changes with respect to the torque around the central axis acting on the external gear, and the second detection unit has an input-side angle detection unit capable of detecting the rotation angle of the input member around the central axis, an output-side angle detection unit capable of detecting the rotation angle of the output member around the central axis, and a torque calculation unit capable of calculating the torque around the central axis acting on the output member based on the difference between a theoretical value of the rotation angle of the output member around the central axis obtained by dividing the detection result by the input-side angle detection unit by the reduction ratio of the wave gear reducer and a measured value of the rotation angle of the output member around the central axis which is the detection result by the output-side angle detection unit.

[0006] The second invention is a wave gear reducer that reduces the input rotational speed of an input member rotatable together with the rotating part of a motor, thereby rotating an output member at an output rotational speed smaller than the input rotational speed, comprising: a wave generator having a non-circular cross-section perpendicular to the central axis and rotatable together with the input member around the central axis at the input rotational speed; an external gear having at least a portion arranged radially outward from the wave generator and having a plurality of external teeth protruding radially outward; an internal gear having at least a portion arranged radially outward from the external gear, spreading in an annular shape around the central axis and having a plurality of internal teeth protruding radially inward and partially meshing with the plurality of external teeth; and a first detection unit and a second detection unit, respectively, capable of detecting the torque acting on the output member around the central axis, wherein the output member rotates together with one of the external gear and the internal gear at the output speed The first detection unit is rotatable at rolling speed and has a plurality of first strain gauges arranged on the external gear whose output changes according to the torque around the central axis acting on the external gear; the second detection unit has a plurality of second strain gauges arranged on the external gear whose output changes according to the rotation angle of the input member around the central axis; an output-side angle detection unit capable of detecting the rotation angle of the output member around the central axis; and a torque calculation unit capable of calculating the torque around the central axis acting on the output member based on the difference between a second theoretical value of the rotation angle of the output member around the central axis, obtained by dividing the rotation angle of the input member around the central axis, which is obtained based on the outputs of the plurality of second strain gauges, by the reduction ratio of the wave gear reducer, and a second measured value of the rotation angle of the output member around the central axis, which is the result of detection by the output-side angle detection unit.

[0007] According to the first and second inventions, the first detection unit and the second detection unit can obtain two values ​​as torque around the central axis acting on the output member. Furthermore, since the first detection unit and the second detection unit are different mechanical parts, the possibility of both failing simultaneously is reduced compared to when the first and second detection units are the same mechanical part. This further enhances the redundancy of torque detection.

[0008] Figure 1 is a schematic diagram of the robot according to the first embodiment. Figure 2 is a longitudinal cross-sectional view of the harmonic drive gear reducer according to the first embodiment. Figure 3 is a transverse cross-sectional view of the harmonic drive gear reducer according to the first embodiment. Figure 4 is a partial longitudinal cross-sectional view of the external gear according to the first embodiment. Figure 5 is a plan view of the first detection substrate according to the first embodiment. Figure 6 is a partial plan view of the first detection substrate according to the first embodiment. Figure 7 is a partial plan view of the first detection substrate according to the first embodiment. Figure 8 is a circuit diagram of the first bridge circuit of the first detection substrate according to the first embodiment. Figure 9 is a longitudinal cross-sectional view of the harmonic drive gear reducer according to the first modified example. Figure 10 is a longitudinal cross-sectional view of the harmonic drive gear reducer according to the second modified example. Figure 11 is a longitudinal cross-sectional view of the harmonic drive gear reducer according to the third modified example. Figure 12 is a longitudinal cross-sectional view of the harmonic drive gear reducer according to the second embodiment. Figure 13 is a plan view of the first detection substrate according to the second embodiment. Figure 14 is a partial plan view of the first detection substrate according to the second embodiment. Figure 15 is a circuit diagram of the third bridge circuit. Figure 16 is a circuit diagram of the fourth bridge circuit. Figure 17 is a graph showing the time evolution of the measured value from the third voltmeter of the third bridge circuit and the measured value from the fourth voltmeter of the fourth bridge circuit.

[0009] Hereinafter, exemplary embodiments of the present application will be described with reference to the drawings.

[0010] <1. First Embodiment> <1-1. Robot Configuration> Figure 1 is a schematic diagram of a robot 100 equipped with a harmonic drive gear reducer 1 according to the first embodiment. The robot 100 is a so-called industrial robot that performs tasks such as transporting, processing, and assembling parts in, for example, an industrial product manufacturing line. As shown in Figure 1, the robot 100 comprises a base frame 101, an arm 102, a motor 103, a harmonic drive gear reducer 1, and a control unit 105. The arm 102 is rotatably supported with respect to the base frame 101. The motor 103 and the harmonic drive gear reducer 1 are incorporated into the joint between the base frame 101 and the arm 102. However, the robot 100 may be provided with multiple joints, and the motor 103 and the harmonic drive gear reducer 1 may be incorporated into each joint.

[0011] The motor 103 is a drive source that generates rotational motion in response to the drive current. The motor 103 has a stationary part with a stator and a rotating part with a magnet. The stationary part is fixed directly or indirectly to the base frame 101. The rotating part is rotatable around a rotation axis 91 (see Figure 2, described later) that is parallel to the central axis 9 of the wave drive gear reducer 1, relative to the stationary part.

[0012] The stator, included in the stationary part of the motor 103, has a configuration in which coils are wound around a stator core made of laminated electromagnetic steel sheets. When a drive current is supplied to the coils, magnetic flux is generated in multiple teeth of the stator core around which the coils are wound. Then, due to the action of the magnetic flux between each tooth and the magnets included in the rotating part facing each tooth, a circumferential torque is generated between the stationary part and the rotating part, causing the rotating part to rotate around the rotation axis 91 relative to the stationary part. As a result, rotational motion about the rotation axis 91 is output from the motor 103. The motor output shaft 110 (see Figure 2, described later), included in the rotating part of the motor 103, extends columnarly along the rotation axis 91. The motor output shaft 110 rotates around the rotation axis 91 due to this rotational motion. Furthermore, the rotational motion output from the motor 103 is reduced by the wave drive gear reducer 1 and transmitted to the arm 102. As a result, the arm 102 rotates relative to the base frame 101 at the reduced speed.

[0013] The control unit 105 is configured, for example, by a computer. As described later, the harmonic drive gear reducer 1 has a first detection unit 70 and a second detection unit 80. The first detection unit 70 and the second detection unit 80 are each capable of detecting the torque around the central axis 9 acting on the output member 300. The control unit 105 is electrically connected to the first detection unit 70 and the second detection unit 80, respectively. The control unit 105 controls the drive of the motor 103 based on the values ​​detected by the first detection unit 70 and the second detection unit 80.

[0014] <1-2. Configuration of the Harmonic Drive Gear Reducer> Next, the detailed configuration of the Harmonic Drive Gear Reducer 1 will be explained.

[0015] In the following, the direction parallel to the central axis 9 will be referred to as the "axial direction," the direction perpendicular to the central axis 9 will be referred to as the "radial direction," and the direction along the arc centered on the central axis 9 will be referred to as the "circumferential direction." Furthermore, in the following, in Figures 2, 4, 9, 10, 11, and 12, the direction of the central axis 9 of the wave drive gear reducer 1 will be defined as the left-right direction, with the right side being referred to as the "axial side" and the left side as the "other axial side," and the shapes and positional relationships of each part will be explained accordingly. Also, in Figures 2, 4, 9, 10, 11, and 12, the "axial side" will be indicated as "a1" and the "other axial side" as "a2." Furthermore, in Figures 2, 5, 6, 7, 9, 10, 11, 12, and 13, described later, the "radial direction" is indicated as "r0," and in Figures 3, 5, 6, 7, 13, and 14, the "circumferential direction" is indicated as "c0."

[0016] However, this definition of left-right direction is not intended to limit the orientation of the harmonic drive gear reducer 1 during manufacturing and use according to the present invention. Furthermore, in this application, "parallel directions" are not limited to cases where they are strictly parallel geometrically. In other words, it is sufficient that a direction that is substantially parallel to a certain direction is substantially parallel to a degree that produces the effects of the invention. Furthermore, in this application, "orthogonal directions" are not limited to cases where they are strictly orthogonal geometrically. In other words, it is sufficient that a direction that is substantially orthogonal to a certain direction is substantially orthogonal to a degree that produces the effects of the invention.

[0017] Figure 2 is a longitudinal cross-sectional view of the harmonic drive gear reducer 1 according to the first embodiment. Figure 3 is a transverse cross-sectional view of the harmonic drive gear reducer 1 viewed from position A-A in Figure 2. To avoid cluttering the diagram, hatching indicating the cross-section is omitted in Figure 3. The harmonic drive gear reducer 1 is a device that reduces the rotational motion of the input rotational speed obtained from the motor 103 to an output rotational speed smaller than the input rotational speed. As shown in Figure 2, the harmonic drive gear reducer 1 includes an input member 10, an internal gear 20, an external gear 30, a wave generator 40, an output side housing 50, an output transmission member 55, a cover member 60, an input side housing 61, a circuit board 65, a first detection unit 70, and a second detection unit 80.

[0018] The input member 10 is a member that extends axially and cylindrically along the central axis 9 around the central axis 9. A first transmission gear 111 is fixed to the outer circumferential surface of the other axial end of the input member 10. A second transmission gear 115 is fixed to the outer circumferential surface of the motor output shaft 110 of the motor 103. The second transmission gear 115 meshes with the first transmission gear 111 from the radially outside in a portion of the circumferential direction around the central axis 9. As a result, when the rotating part of the motor 103, including the motor output shaft 110, rotates, the input member 10 can be rotated via the second transmission gear 115 and the first transmission gear 111. This allows the input member 10 to rotate at the input rotational speed before deceleration in conjunction with the rotation of the rotating part of the motor 103. Alternatively, instead of providing the first transmission gear 111 and the second transmission gear 115, a first pulley 121 may be attached to the outer circumferential surface of the input member 10 (see Figure 10, described later). Furthermore, a second pulley 125 may be attached to the outer circumferential surface of the motor output shaft 110. A transmission belt 104 may be provided that wraps around the outer circumferential surfaces of the first pulley 121 and the second pulley 125. This allows the input member 10 to be rotated at the input rotational speed before deceleration in conjunction with the rotation of the motor 103's rotating part. In this case, by changing the diameters of the first pulley 121 and the second pulley 125, the input member 10 can be rotated at a rotational speed different from that of the motor output shaft 110. Furthermore, the input member 10 may be directly connected to the rotating part of the motor 103. Alternatively, the input member 10 may be the same component as the rotating part of the motor 103.

[0019] The internal gear 20 is an annular gear with a central axis 9 as its center. That is, the internal gear 20 extends in an annular shape around the central axis 9. In this embodiment, the internal gear 20 is fixed to the arm 102. The internal gear 20 is positioned radially outward of the external teeth 32 of the external gear 30, which will be described later. That is, at least a portion of the internal gear 20 is positioned radially outward of the external gear 30. The rigidity of the internal gear 20 is sufficiently higher than the rigidity of the body 31 of the external gear 30, which will be described later.

[0020] The internal gear 20 has a plurality of internal teeth 21. The plurality of internal teeth 21 protrude radially inward from the inner circumferential surface of the internal gear 20. The plurality of internal teeth 21 are also arranged at a constant pitch in the circumferential direction on the inner circumferential surface of the internal gear 20. Some of the plurality of internal teeth 21 mesh with some of the plurality of external teeth 32 of the external gear 30, which will be described later. That is, the internal gear 20 has a plurality of internal teeth 21 that protrude radially inward and partially mesh with the plurality of external teeth 32. The internal gear 20 is provided with a through hole 200. The through hole 200 penetrates the internal gear 20 in the axial direction.

[0021] The external gear 30 is a flexible annular gear. In this embodiment, the external gear 30 is fixed to the base frame 101. As shown in Figures 2 and 3, the external gear 30 has a cylindrical body 31, a plurality of external teeth 32, a diaphragm portion 33, and a thickened portion 34. That is, the external gear 30 has a cylindrical body 31, a plurality of external teeth 32, and a diaphragm portion 33. However, the structure of the external gear 30 described below is just one example and may differ from this structure.

[0022] The body portion 31 is a part that extends in an axial direction parallel to the central axis 9. The other axial end of the body portion 31 is connected to the diaphragm portion 33. The body portion 31 extends from the radially inner end of the diaphragm portion 33 toward one axial side. The axial end of the body portion 31 is located radially outward of the wave generator 40 and radially inward of the internal gear 20. That is, at least a portion of the external gear 30 is positioned radially outward of the wave generator 40. Because the body portion 31 is flexible, it can bend and deform in the radial direction. In particular, the axial end of the body portion 31 can be displaced radially more than other parts.

[0023] Multiple external teeth 32 protrude radially outward from the radially outer surface of the body 31. That is, the external gear 30 has multiple external teeth 32 that protrude radially outward. Furthermore, the multiple external teeth 32 are arranged on the radially outer surface of one axial end of the body 31. That is, the multiple external teeth 32 are arranged on one axial side of the body 31 and protrude radially outward. The multiple external teeth 32 are arranged at a constant pitch in the circumferential direction. As described above, some of the multiple external teeth 32 and some of the multiple internal teeth 21 of the internal gear 20 mesh with each other. The number of internal teeth 21 of the internal gear 20 and the number of external teeth 32 of the external gear 30 are slightly different.

[0024] The diaphragm portion 33 surrounds the central axis 9 and extends in a direction intersecting the central axis 9. Preferably, the diaphragm portion 33 extends along a plane perpendicular to the central axis 9. The diaphragm portion 33 also extends radially outward from the other axial end of the body portion 31. That is, the diaphragm portion 33 extends radially on the other axial side of the body portion 31. Furthermore, the diaphragm portion 33 is annular in shape, surrounding the central axis 9. Because the diaphragm portion 33 is thin-walled, it is slightly flexible and deformable.

[0025] The thickened portion 34 is an annular portion located radially outward from the diaphragm portion 33, with the central axis 9 as the center. The thickened portion 34 extends radially outward from the radially outer end of the diaphragm portion 33. The axial thickness of the thickened portion 34 is greater than the axial thickness of the diaphragm portion 33. The thickened portion 34 is fixed to the base frame 101, for example, with bolts.

[0026] Furthermore, the external gear 30, including the thickened portion 34, rotatably supports the internal gear 20 by a cross roller bearing 150. The cross roller bearing 150 has an outer ring 152, an inner ring 151, and rollers 161. In this embodiment, the outer ring 152 is fixed to one axial side of the thickened portion 34. The outer ring 152 rotatably supports the inner ring 151 via the rollers 161.

[0027] Furthermore, the inner ring 151 is provided with a screw hole 153. The screw hole 153 is formed from one axial end face of the inner ring 151 toward the other axial side. In this embodiment, the inner ring 151 can be fixed to the internal gear 20, the output side housing 50, and the output transmission member 55 by fastening a screw 155, which passes through the through hole 200 of the internal gear 20, the through hole 500 of the output side housing 50 (described later), and the through hole 550 of the output transmission member 55 (described later), into the screw hole 153. This allows the inner ring 151 to be fixed to the internal gear 20, the output side housing 50, and the output transmission member 55, which are fixed to the arm 102. As a result, the inner ring 151, the internal gear 20, the output side housing 50, and the output transmission member 55 are rotatably supported by the outer ring 152 via the rollers 161.

[0028] The wave generator 40 is a mechanism that generates periodic deflection deformation in the external gear 30. The wave generator 40 is positioned radially inward of the external gear 32. The wave generator 40 includes a cam 41 and a flexible bearing 42. In this embodiment, the input member 10 and the cam 41 are formed from a single part. However, the cam 41 may be a separate part from the input member 10. In that case, it is sufficient that the cam 41 is fixed to the input member 10. As a result, the input member 10 and the cam 41 can rotate at the input rotational speed before deceleration in conjunction with the rotation of the rotating part of the motor 103. That is, the wave generator 40 can rotate together with the input member 10 around the central axis 9 at the input rotational speed.

[0029] The cam 41 is a component that imparts displacement to the external gear 30 with a period of 180°. The radial outer surface of the cam 41 is elliptical when viewed in the axial direction. In other words, the wave generator 40 has a non-circular cross-section perpendicular to the central axis 9.

[0030] The flexible bearing 42 is a bearing that can be deformed by bending. The flexible bearing 42 is positioned between the radially outer surface of the cam 41 and the radially inner surface of the body 31 of the external gear 30. Therefore, the cam 41 and the body 31 can rotate at different rotational speeds. The inner ring of the flexible bearing 42 contacts the radially outer surface of the cam 41. The outer ring of the flexible bearing 42 contacts the radially inner surface of the body 31. As a result, the body 31 is pushed from the radially inward by the cam 41 via the flexible bearing 42, causing it to deform into an elliptical shape along the radially outer surface of the cam 41. As a result, the external teeth 32 of the external gear 30 and the internal teeth 21 of the internal gear 20 mesh at two locations corresponding to the ends of the major axis of the ellipse. At other locations in the circumferential direction, the external teeth 32 and the internal teeth 21 do not mesh.

[0031] The output housing 50 is a member that extends in an annular shape around a central axis 9. In this embodiment, the output housing 50 is fixed to the arm 102. The output housing 50 is located radially outward from the input member 10. Furthermore, the output housing 50 is located axially to one side of the internal gear 20, external gear 30, and wave generator 40. A bearing 51 is positioned radially between the output housing 50 and the input member 10. For example, a ball bearing is used for the bearing 51. The inner ring of the bearing 51 is fixed to the outer circumferential surface of the input member 10. The outer ring of the bearing 51 is fixed to the inner circumferential surface of the output housing 50. As a result, the output housing 50 and the input member 10 are able to rotate relative to each other around the central axis 9. The output housing 50 is also provided with a through hole 500. The through hole 500 penetrates the output housing 50 in the axial direction. As described above, the output housing 50 is fixed to the internal gear 20, the inner ring 151, and the output transmission member 55.

[0032] When the motor 103 is driven, the cam 41 rotates together with the input member 10 around the central axis 9 at the input rotational speed. As a result, the major axis of the ellipse of the external gear 30 also rotates at the input rotational speed. Consequently, the meshing position between the external teeth 32 and the internal teeth 21 also changes in the circumferential direction at the input rotational speed. Furthermore, as described above, the number of internal teeth 21 of the internal gear 20 and the number of external teeth 32 of the external gear 30 are slightly different. Due to this difference in the number of teeth, the meshing position between the external teeth 32 and the internal teeth 21 changes slightly in the circumferential direction with each rotation of the cam 41.

[0033] Here, as described above, the external gear 30 having external teeth 32 is fixed to the base frame 101 at the thickened portion 34 and does not rotate. On the other hand, as described above, the internal gear 20 having internal teeth 21 is supported together with the output side housing 50 and the arm 102 so as to be rotatable around the central axis 9. As a result, in this embodiment, the internal gear 20, the output side housing 50 and the arm 102 rotate around the central axis 9 at an output rotational speed that is smaller (slower) than the input rotational speed, relative to the external gear 30 and the base frame 101.

[0034] The output housing 50 corresponds to the "output member 300" in this embodiment. That is, the harmonic drive gear reducer 1 in this embodiment reduces the input rotational speed of the input member 10, which is rotatable in conjunction with the rotation of the motor 103, and rotates the output member 300 at an output rotational speed smaller than the input rotational speed. However, at least two or more of the internal gear 20, output housing 50, inner ring 151, and arm 102 may be formed from a single material.

[0035] As an alternative, the internal gear 20, output housing 50, and inner ring 151 may be fixed to the base frame 101, while the external gear 30 and the input housing 61 (described later) may be fixed to the arm 102. In other words, the internal gear 20 may be kept stationary while the external gear 30 rotates. In this case, for example, the input housing 61 corresponds to the "output member 300". That is, the output member 300 only needs to be able to rotate at the output rotational speed together with either the external gear 30 or the internal gear 20.

[0036] The output transmission member 55 has an axially extended portion 551 and a connecting portion 552. The axially extended portion 551 extends in a cylindrical shape along the central axis 9, radially outward from the central axis 9 and radially inward from the input member 10. However, the output transmission member 55 is not in contact with the input member 10. One axial end of the axially extended portion 551 is located one axial side further to the right than one axial end of the input member 10. The connecting portion 552 extends radially outward from one axial end of the axially extended portion 551. The connecting portion 552 extends in an annular shape around the central axis 9. A through hole 550 is provided in the radially outward portion of the connecting portion 552. The through hole 550 penetrates the connecting portion 552 in the axial direction. The connecting portion 552 is fixed to the output-side housing 50 by a screw 155 inserted into the through hole 550 provided in the radially outward portion, the through hole 500 in the output-side housing 50, and the through hole 200 in the internal gear 20. In other words, the connecting portion 552 of the output transmission member 55 is fixed to the output member 300. As a result, the output transmission member 55, including the connecting portion 552, rotates at the output rotational speed around the central axis 9 together with the internal gear 20, the output-side housing 50, and the arm 102.

[0037] Furthermore, the output transmission member 55 extends from one axial side to the other axial side, passing through the radially inner side of the input member 10. The other axial end of the output transmission member 55 is located further axially than the other axial end of the input member 10. However, the structure of the output transmission member 55 is not limited to this. For example, the axial extension portion 551 may extend cylindrically along the central axis 9. That is, the output transmission member 55 only needs to be fixed to the output member 300 and extend along the central axis 9. Also, the input member 10 only needs to extend cylindrically along the central axis 9 on the radially outer side of at least a portion of the output transmission member 55.

[0038] The cover member 60 extends in a cylindrical shape along the central axis 9, radially outward from the central axis 9. The cover member 60 forms part of the housing of the wave drive gear reducer 1. The cover member 60 is formed from a single material, along with the input side housing 61. The cover member 60 is radially connected to the input side housing 61 in a portion of its circumferential direction. As described later, the external gear 30 is fixed to the input side housing 61 by bolts (not shown). In this way, the cover member 60 is fixed to the external gear 30 and the base frame 101. The cover member 60 houses at least a portion of the wave generator 40, the external gear 30, the internal gear 20, the first detection unit 70, the second detection unit 80, and the output transmission member 55 radially inward.

[0039] The input-side housing 61 is a member that extends in an annular shape around the central axis 9. The input-side housing 61 is fixed to the other axial side of the thickened portion 34 of the external gear 30 by bolts (not shown). The input-side housing 61 is fixed to the base frame 101 together with the external gear 30 and the cover member 60. The input-side housing 61 also covers the external gear 30 from the other axial side. The input-side housing 61 is located radially outside the input member 10. A bearing 52 is positioned radially between the input-side housing 61 and the input member 10. For example, a ball bearing is used for the bearing 52. The inner ring of the bearing 52 is fixed to the outer circumferential surface of the input member 10. The outer ring of the bearing 52 is fixed to the inner circumferential surface of the input-side housing 61. As a result, the input-side housing 61 and the input member 10 can rotate relative to each other around the central axis 9. In this embodiment, the input member 10 is supported so as to be rotatable around a central axis 9 relative to the stationary input-side housing 61.

[0040] The circuit board 65 is a plate-shaped member that extends in an annular shape around the central axis 9, radially outward from the output transmission member 55 and the input member 10. The circuit board 65 extends in a direction intersecting the central axis 9. In this embodiment, the circuit board 65 is directly fixed to the radially inner surface of the cover member 60 by screws or the like. However, the circuit board 65 may also be indirectly fixed to the radially inner surface of the cover member 60 via another member such as a connector. That is, the circuit board 65 only needs to be fixed directly or indirectly to the radially inner surface of the cover member 60. A support base 66 is also fixed to the circuit board 65. The support base 66 is positioned on the other axial side of the circuit board 65, in a position that does not overlap with the first transmission gear 111 and the second transmission gear 115. The support base 66 has a support surface 661 that extends in a direction intersecting the central axis 9. The support surface 661 is the end face on the other axial side of the support base 66. The support base 66 is included in the "circuit board" of the present invention.

[0041] The first detection unit 70 and the second detection unit 80 are devices capable of detecting torque around the central axis 9 acting on the output member 300. The detailed configurations of the circuit board 65, the first detection unit 70, and the second detection unit 80 will be described later.

[0042] <1-3. Detailed Configuration of the First Detection Unit> Next, the detailed configuration of the first detection unit 70 will be explained.

[0043] As shown in Figure 2, the first detection unit 70 includes a first detection substrate 71 and a first torque calculation unit 72. Figure 4 is a partial longitudinal cross-sectional view of the external gear 30 near the first detection substrate 71 according to the first embodiment. Figure 5 is a plan view of the first detection substrate 71 according to the first embodiment. The diaphragm portion 33 has a surface 331 that intersects the central axis 9 and extends in an annular shape around the central axis 9. The surface 331 is the surface on the other axial side of the diaphragm portion 33. The first detection substrate 71 is bonded and fixed to the surface 331 of the diaphragm portion 33. Also, as shown in Figures 4 and 5, the first detection substrate 71 has an insulating layer 711 and a conductive layer 712.

[0044] The insulating layer 711 is a portion that can be deformed flexibly. The insulating layer 711 is made of a resin or an inorganic insulating material that is an insulator such as polyimide. The insulating layer 711 extends in a direction intersecting with the central axis 9. Also, the insulating layer 711 is in an annular shape centered on the central axis 9. The insulating layer 711 is disposed on the surface 331 of the diaphragm portion 33 facing the other side in the axial direction.

[0045] The conductor layer 712 is a portion formed on the surface of the insulating layer 711 facing the other side in the axial direction. A metal that is a conductor is used as the material of the conductor layer 712. Specifically, for example, a copper alloy, a chromium alloy, or copper is used as the material of the conductor layer 712. The conductor layer 712 has a plurality of strain gauges. That is, the first detection unit 70 has a plurality of strain gauges. Also, the plurality of strain gauges are disposed on the diaphragm portion 33. That is, the plurality of strain gauges are disposed on the external gear 30. Thus, by disposing the plurality of strain gauges on the diaphragm portion 33, a wider arrangement space for the plurality of strain gauges can be provided. The function of the first detection unit 70 is mainly realized by using the plurality of strain gauges.

[0046] The first detection unit 70 can detect the torque applied to the output member 300 fixed to the internal gear 20 meshing with the external gear 30 by detecting the torque applied to the diaphragm portion 33 by using the plurality of strain gauges. Specifically, the output signals from the plurality of strain gauges change according to the strain of the diaphragm portion 33 distorted by the torque applied to the diaphragm portion 33. That is, the output from the plurality of strain gauges changes due to the torque around the central axis 9 acting on the external gear 30. Thereby, based on the output signal from the first detection unit 70, the torque around the central axis 9 acting on the output member 300 fixed to the internal gear 20 partially meshing with the external gear 30 having the diaphragm portion 33 can be detected. This will be described in more detail below.

[0047] As shown in FIG. 5, in the present embodiment, the first detection unit 70 has four strain gauges Ra, Rb, Rc, and Rd. That is, the plurality of strain gauges includes the four strain gauges Ra, Rb, Rc, and Rd. Among the four strain gauges Ra, Rb, Rc, and Rd, two strain gauges Ra and Rb are arranged at intervals in the circumferential direction. In the present embodiment, the two strain gauges Ra and Rb are each provided in a semi-arc shape within a range of approximately 180° centered on the central axis 9. The radial distance from the central axis 9 to the strain gauge Ra and the radial distance from the central axis 9 to the strain gauge Rb are substantially the same.

[0048] Among the four strain gauges Ra, Rb, Rc, and Rd, the other two strain gauges Rc and Rd are arranged radially outward of the above two strain gauges Ra and Rb. The two strain gauges Rc and Rd are arranged at intervals in the circumferential direction. In the present embodiment, the two strain gauges Rc and Rd are each provided in a semi-arc shape within a range of approximately 180° centered on the central axis 9. The radial distance from the central axis 9 to the strain gauge Rc and the radial distance from the central axis 9 to the strain gauge Rd are substantially the same.

[0049] As described above, the two strain gauges Rc and Rd are arranged radially outward of the two strain gauges Ra and Rb. Therefore, the two strain gauges Ra and Rb can be respectively referred to as "inner strain gauges", and the two strain gauges Rc and Rd can be respectively referred to as "outer strain gauges". The two inner strain gauges Ra and Rb are arranged in the circumferential direction. Also, the two outer strain gauges Rc and Rd are arranged in the circumferential direction radially outward of the two inner strain gauges Ra and Rb.

[0050] Furthermore, two inner gap regions Gi are positioned between two adjacent inner strain gauges Ra and Rb in the circumferential direction. When viewed from the axial direction, the two inner gap regions Gi are positioned at an angle of 180° around the central axis 9. Similarly, two outer gap regions Go are positioned between two adjacent outer strain gauges Rc and Rd in the circumferential direction. When viewed from the axial direction, the two outer gap regions Go are positioned at an angle of 180° around the central axis 9. The inner gap regions Gi and outer gap regions Go are adjacent in the radial direction. The two strain gauges Ra and Rc, and the two strain gauges Rb and Rd, are positioned concentrically and symmetrically.

[0051] The strain gauges Ra, Rb, Rc, and Rd each have a pattern that extends circumferentially while bending in a zigzag pattern. Figures 6 and 7 are partial plan views of the first detection substrate 71, respectively. As shown in Figures 6 and 7, each strain gauge Ra, Rb, Rc, and Rd has a plurality of resistance wires r1 that are arranged circumferentially and are substantially parallel to each other. Each resistance wire r1 extends in a direction having both radial and circumferential components.

[0052] The resistance wires r1 of strain gauges Ra and Rd are inclined to one side in the circumferential direction relative to the radial direction. The resistance wires r1 of strain gauges Rb and Rc are inclined to the other side in the circumferential direction relative to the radial direction. The angle of inclination of the resistance wires r1 relative to the radial direction is, for example, 45°. The ends of adjacent resistance wires r1 in the circumferential direction are alternately connected radially inward or radially outward. As a result, multiple resistance wires r1 are connected in series as a whole.

[0053] Figure 8 is a circuit diagram of the first bridge circuit C1, which includes four strain gauges Ra, Rb, Rc, and Rd. As shown in Figure 8, the four strain gauges Ra, Rb, Rc, and Rd are connected to each other to form the first bridge circuit C1.

[0054] Strain gauges Ra and Rb are connected in series in this order. Strain gauges Rc and Rd are connected in series in this order. Then, between the positive and negative terminals of the power supply voltage that applies voltage to the four strain gauges Ra, Rb, Rc, and Rd, two rows of strain gauges Ra and Rb and two rows of strain gauges Rc and Rd are connected in parallel. In addition, the first voltmeter V1 is connected between the midpoint M11 of the two strain gauges Ra and Rb and the midpoint M12 of the two strain gauges Rc and Rd.

[0055] The resistance value of each resistance wire r1 changes according to the torque applied to the region where the resistance wire r1 is located. For example, when a torque is applied to the diaphragm portion 33 in one direction circumferentially around the central axis 9, the resistance values ​​of the resistance wires r1 of the two strain gauges Ra and Rd increase, while the resistance values ​​of the resistance wires r1 of the other two strain gauges Rb and Rc decrease. On the other hand, when a torque is applied to the diaphragm portion 33 in the other direction circumferentially around the central axis 9, the resistance values ​​of the resistance wires r1 of the two strain gauges Ra and Rd decrease, while the resistance values ​​of the resistance wires r1 of the other two strain gauges Rb and Rc increase. Thus, the resistance values ​​of the two strain gauges Ra and Rd and the other two strain gauges Rb and Rc show changes in opposite directions with respect to torque.

[0056] When the resistance values ​​of the four strain gauges Ra, Rb, Rc, and Rd change, the potential difference between the midpoint M11 of the two strain gauges Ra and Rb and the midpoint M12 of the two strain gauges Rc and Rd changes, and therefore the measured value of the first voltmeter V1 also changes.

[0057] As described above, the first detection unit 70 has a first torque calculation unit 72. The first torque calculation unit 72 is composed of an electrical circuit equipped with a microprocessor. The first torque calculation unit 72 is formed on a circuit board 65. The first torque calculation unit 72 is electrically connected to the first bridge circuit C1 via wiring. The first torque calculation unit 72 is also provided with an amplifier circuit (not shown) that amplifies the electrical signal output from the first bridge circuit C1. Based on the measurement value of the first voltmeter V1, the first torque calculation unit 72 detects the direction and magnitude of the torque applied to the diaphragm unit 33. Here, the torque applied to the diaphragm unit 33 and the torque applied to the output member 300 are opposite in direction and the same in magnitude due to the action-reaction relationship. Therefore, based on the detection result of the direction and magnitude of the torque applied to the diaphragm unit 33, the first torque calculation unit 72 calculates the direction and magnitude of the torque applied to the output member 300.

[0058] As described above, the first detection unit 70 of this embodiment is provided with a plurality of internal strain gauges Ra, Rb arranged circumferentially in the radially inward direction, and a plurality of external strain gauges Rc, Rd arranged circumferentially outward in the radially outward direction. Furthermore, the plurality of internal strain gauges Ra, Rb and the plurality of external strain gauges Rc, Rd form a first bridge circuit C1. As a result, even when the angular position of the long axis of the cam 41 of the wave generator 40 changes around the central axis 9, the influence on the torque measurement result applied to the diaphragm 33 is suppressed, and the torque can be measured more accurately.

[0059] Furthermore, the first torque calculation unit 72 outputs the calculated values ​​of the direction and magnitude of the torque applied to the calculated output member 300 to the torque diagnosis unit 75 and the control unit 105. The torque diagnosis unit 75 is composed of an electrical circuit equipped with a microprocessor. The torque diagnosis unit 75 is formed on a circuit board 65.

[0060] As described above, the control unit 105 controls the drive of the motor 103 based on the calculated values ​​of the direction and magnitude of the torque applied to the output member 300, which are input from the first torque calculation unit 72 and the second torque calculation unit 83, which will be described later. For example, if the direction and magnitude of the torque applied to the output member 300 exceed predetermined values, the control unit 105 determines that an excessive rotational driving force is being applied to the output member 300. In this case, the control unit 105 determines that the robot 100 is performing an unexpected operation and temporarily stops the drive of the motor 103. This prevents wear or damage to various parts of the robot 100.

[0061] <1-4. Detailed Configuration of the Second Detection Unit> Next, the detailed configuration of the second detection unit 80 will be explained.

[0062] As shown in Figure 2, the second detection unit 80 includes an input-side angle detection unit 81, an output-side angle detection unit 82, and a second torque calculation unit 83. The second torque calculation unit 83 corresponds to the "torque calculation unit" of the present invention.

[0063] The input-side angle detection unit 81 includes an input-side encoder disk 811, a first light source (not shown), and an input-side encoder detection unit 812. The input-side encoder disk 811 is annular in shape with a central axis 9. The input-side encoder disk 811 is fixed to the outer circumferential surface of the input member 10, on one axial side of the circuit board 65 and on the other axial side of the input-side housing 61, either directly by press-fitting or adhesive, or indirectly via a mounting member (not shown). This allows the input-side encoder disk 811 to rotate together with the input member 10 at the input rotational speed. In other words, the input-side encoder disk 811 is fixed to the input member 10 and can rotate together with the input member 10 at the input rotational speed.

[0064] Multiple first slits 810 are formed at equal intervals in the circumferential direction on the outer periphery of the other axial side surface of the input-side encoder disk 811. A first light source is also positioned on the one axial side surface of the circuit board 65. Each of the multiple first slits 810 reflects light emitted from the first light source.

[0065] The input-side encoder detection unit 812 is composed of an electrical circuit equipped with a microprocessor. The input-side encoder detection unit 812 is formed on one axial side surface of the circuit board 65. That is, the input-side encoder detection unit 812 is formed on the circuit board 65. The input-side encoder detection unit 812 receives light reflected from a plurality of first slits 810 of the input-side encoder disk 811 and outputs an electrical signal corresponding to the intensity of the received light. As a result, the input-side encoder detection unit 812 can detect the rotation angle of the input-side encoder disk 811 around the central axis 9 based on the change in the amount of received light.

[0066] In other words, the input-side angle detection unit 81 is an optical encoder capable of detecting the rotation angle of the input-side encoder disk 811 around its central axis 9 by detecting changes in the amount of light received from the input-side encoder disk 811 using the input-side encoder detection unit 812. Furthermore, because the input-side angle detection unit 81 has such a configuration, it can accurately detect the rotation angle of the input-side encoder disk 811 around its central axis 9. As a result, the input-side angle detection unit 81 can detect the rotation angle of the input member 10 fixed to the inner circumferential surface of the input-side encoder disk 811 around its central axis 9. In addition, since the optical encoder is not affected by magnetism, it can detect the rotation angle without any problems even if the harmonic drive gear reducer 1 is installed in a magnetic environment. Moreover, if the input-side angle detection unit 81 were a magnetic encoder, it would be necessary to adopt a magnetic shielding structure to avoid the influence of magnetism from the surroundings, but such a structure is not necessary for an optical encoder. This reduces the number of parts in the harmonic drive gear reducer 1.

[0067] However, the configuration of the input-side angle detection unit 81 is not limited to this. For example, the plurality of first slits 810 of the input-side encoder disk 811 may transmit light emitted from the first light source. The first light source may also be positioned on one side of the axial direction relative to the input-side encoder disk 811. The input-side encoder detection unit 812 may receive the light transmitted through the plurality of first slits 810 and output an electrical signal corresponding to the intensity of the received light. The input-side encoder disk 811 may also be positioned on the other side of the axial direction relative to the circuit board 65. The input-side encoder detection unit 812 and the first light source may also be positioned on the other side of the axial direction relative to the input-side encoder disk 811.

[0068] Furthermore, as shown in the first modified example in Figure 9, the input-side encoder disk 811 may be provided on one axial side surface of the first transmission gear 111. Also, the input-side encoder detection unit 812 may be formed on the other axial side surface of the circuit board 65 so as to face the input-side encoder disk 811. The input-side encoder detection unit 812 may receive light from a plurality of first slits 810 (not shown) of the input-side encoder disk 811 and output an electrical signal corresponding to the intensity of the received light. Even in this case, the input-side encoder detection unit 812 can detect the rotation angle of the input-side encoder disk 811 and the input member 10 around the central axis 9 based on the change in the amount of received light.

[0069] Furthermore, as described above, in the wave drive gear reducer 1, instead of providing the first transmission gear 111 and the second transmission gear 115, a first pulley 121 may be attached to the outer circumferential surface of the input member 10, a second pulley 125 may be attached to the outer circumferential surface of the motor output shaft 110, and a transmission belt 104 may be provided that wraps around the outer circumferential surfaces of the first pulley 121 and the second pulley 125. In this case, as shown in the second modified example in Figure 10, the input-side encoder disk 811 may be provided on one axial side of the first pulley 121. Also, the input-side encoder detection unit 812 may be formed on the other axial side of the circuit board 65 so as to face the input-side encoder disk 811. The input-side encoder detection unit 812 may receive light from a plurality of first slits 810 (not shown) of the input-side encoder disk 811 and output an electrical signal corresponding to the intensity of the received light. Even in this case, the input-side encoder detection unit 812 can detect the rotation angle of the input-side encoder disk 811 and the input member 10 around the central axis 9 based on the change in the amount of light received.

[0070] Furthermore, in the embodiment shown in Figure 2, instead of forming a plurality of first slits 810 on the other axial side surface of the input-side encoder disk 811, an annular magnet centered on the central axis 9 may be provided. Also, the outer circumference of the annular magnet may be alternately magnetized with north and south poles. The input-side encoder detection unit 812 may also detect the magnetic field generated by the magnet and output an electrical signal corresponding to the detected magnetic field. The input-side encoder detection unit 812 may then detect the rotation angle of the input-side encoder disk 811 around the central axis 9 based on the detected change in the magnetic field. In other words, the input-side angle detection unit 81 may be a magnetic encoder capable of detecting the rotation angle of the input-side encoder disk 811 around the central axis 9 by detecting the change in the magnetic field accompanying the rotation of the input-side encoder disk 811 using the input-side encoder detection unit 812. In a magnetic encoder, even if impurities adhere to the input-side angle detection unit 81 or the input-side encoder disk 811, the rotation angle can be detected without any problems as long as they do not have a magnetic effect. For example, in the harmonic drive gear reducer 1, the grease applied to the meshing portion between the external gear 30 and the internal gear 20, or the lubricant filled in the flexible bearing 42, may flow to locations other than the original location. Therefore, in some cases, this grease or lubricant may reach the input-side angle detection unit 81 or the input-side encoder disk 811, but even in such cases, the rotation angle can be detected without any problems.

[0071] The output-side angle detection unit 82 includes an output-side encoder disk 821, a second light source (not shown), and an output-side encoder detection unit 822. The output-side encoder disk 821 is annular in shape with a central axis 9. The output-side encoder disk 821 is fixed to the outer circumferential surface of the output transmission member 55 on the other axial side of the input member 10 and the circuit board 65, either directly by press-fitting or adhesive, or indirectly via a mounting member (not shown). As a result, the output-side encoder disk 821 can rotate at the output rotational speed together with the output transmission member 55. That is, the output-side encoder disk 821 is fixed to the output transmission member 55 on the other axial side of the input member 10, and can rotate at the output rotational speed together with the output transmission member 55 and the output member 300 to which the output transmission member 55 is fixed.

[0072] Multiple second slits 820 are formed at equal intervals in the circumferential direction on the outer periphery of one axial side surface of the output-side encoder disk 821. A second light source is positioned on the support surface 661 of the support base 66 fixed to the circuit board 65. Each of the multiple second slits 820 reflects light emitted from the second light source.

[0073] The output-side encoder detection unit 822 is composed of an electrical circuit equipped with a microprocessor. The output-side encoder detection unit 822 is formed on the support surface 661 of the support base 66. That is, the output-side encoder detection unit 822 is formed on the "circuit board" of the present invention. The output-side encoder detection unit 822 receives light reflected from a plurality of second slits 820 of the output-side encoder disk 821 and outputs an electrical signal corresponding to the intensity of the received light. As a result, the output-side encoder detection unit 822 can detect the rotation angle of the output-side encoder disk 821 around the central axis 9 based on the change in the amount of light received.

[0074] In other words, the output-side angle detection unit 82 is an optical encoder capable of detecting the rotation angle of the output-side encoder disk 821 around its central axis 9 by detecting changes in the amount of light received from the output-side encoder disk 821 using the output-side encoder detection unit 822. Furthermore, because the output-side angle detection unit 82 has such a configuration, it can accurately detect the rotation angle of the output-side encoder disk 821 around its central axis 9. As a result, the output-side angle detection unit 82 can accurately detect the rotation angles of the output transmission member 55 and the output member 300 fixed to the inner circumferential surface of the output-side encoder disk 821 around its central axis 9. In addition, since optical encoders are not affected by magnetism, they can detect the rotation angle without any problems even if the harmonic drive gear reducer 1 is installed in a magnetic environment. Moreover, if the output-side angle detection unit 82 were a magnetic encoder, it would be necessary to adopt a magnetic shielding structure to avoid the influence of magnetism from the surroundings, but such a structure is not necessary for an optical encoder. This reduces the number of parts in the harmonic drive gear reducer 1.

[0075] However, the configuration of the output-side angle detection unit 82 is not limited to this. For example, the plurality of second slits 820 of the output-side encoder disk 821 may transmit light emitted from the second light source. The second light source may also be positioned on the other axial side of the output-side encoder disk 821. The output-side encoder detection unit 822 may receive the light transmitted through the plurality of second slits 820 and output an electrical signal corresponding to the intensity of the received light. The output-side encoder detection unit 822 and the second light source may also be positioned on the other axial side of the output-side encoder disk 821. Furthermore, the plurality of second slits 820 of the output-side encoder disk 821 may be provided facing the output-side encoder detection unit 822 and the second light source.

[0076] Alternatively, instead of forming multiple second slits 820 on one axial side of the output encoder disk 821, an annular magnet centered on the central axis 9 may be provided. Furthermore, the outer circumference of the annular magnet may be alternately magnetized with north and south poles. The output encoder detection unit 822 may also detect the magnetic field generated by the magnet and output an electrical signal corresponding to the detected magnetic field. The output encoder detection unit 822 may then detect the rotation angle of the output encoder disk 821 around the central axis 9 based on the detected change in the magnetic field. In other words, the output angle detection unit 82 may be a magnetic encoder capable of detecting the rotation angle of the output encoder disk 821 around the central axis 9 by detecting the change in the magnetic field accompanying the rotation of the output encoder disk 821 using the output encoder detection unit 822. In a magnetic encoder, even if impurities adhere to the output angle detection unit 82 or the output encoder disk 821, the rotation angle can be detected without any problems as long as they do not have a magnetic effect. For example, in the harmonic drive gear reducer 1, the grease applied to the meshing portion between the external gear 30 and the internal gear 20, or the lubricant filled in the flexible bearing 42, may flow to locations other than their original positions. Therefore, in some cases, this grease or lubricant may reach the output-side angle detection unit 82 or the output-side encoder disk 821, but even in such cases, the rotation angle can be detected without any problems.

[0077] As described above, the second detection unit 80 has a second torque calculation unit 83. The second torque calculation unit 83 is composed of an electrical circuit equipped with a microprocessor. The second torque calculation unit 83 is formed on a circuit board 65. The second torque calculation unit 83 is electrically connected to the input-side encoder detection unit 812 and the output-side encoder detection unit 822, respectively, via wiring that is not shown. The second torque calculation unit 83 receives the electrical signals corresponding to the detection results of the input-side encoder detection unit 812 and the output-side encoder detection unit 822, respectively.

[0078] First, when the second torque calculation unit 83 receives a detection result from the input-side encoder detection unit 812, it divides the detection result by the reduction ratio of the harmonic drive gear reducer 1. Here, as described above, the detection result from the input-side encoder detection unit 812 is the rotation angle around the central axis 9 of the input member 10. By dividing the rotation angle around the central axis 9 of the input member 10 by the reduction ratio of the harmonic drive gear reducer 1, a theoretical value of the rotation angle around the central axis 9 of the output member 300 is obtained. Next, when the second torque calculation unit 83 receives a detection result from the output-side encoder detection unit 822, it compares the detection result with the theoretical value of the rotation angle around the central axis 9 of the output member 300 that has already been calculated. Here, the detection result from the output-side encoder detection unit 822 is the measured value of the rotation angle around the central axis 9 of the output member 300.

[0079] The second torque calculation unit 83 then calculates the difference between the theoretical value of the rotation angle of the output member 300 around the central axis 9 and the measured value of the rotation angle of the output member 300 around the central axis 9. This difference is what is known as the "torsion angle of the harmonic drive reducer 1". Furthermore, the second torque calculation unit 83 multiplies this difference by the "torsional rigidity (spring characteristics)", which is the rigidity value of the harmonic drive reducer 1. As a result, the second torque calculation unit 83 can calculate the direction and magnitude of the torque acting on the output member 300 around the central axis 9. In other words, the second torque calculation unit 83 can calculate the torque acting on the output member 300 around the central axis 9 based on the difference between the theoretical value of the rotation angle of the output member 300 around the central axis 9, which is obtained by dividing the detection result of the input-side angle detection unit 81 by the reduction ratio of the wave gear reducer 1, and the actual measured value of the rotation angle of the output member 300 around the central axis 9, which is the detection result of the output-side angle detection unit 82.

[0080] Furthermore, the second torque calculation unit 83 outputs the calculated values ​​of the direction and magnitude of the torque applied to the output member 300 to the torque diagnosis unit 75 and the control unit 105. As described above, the control unit 105 controls the drive of the motor 103 based on the calculated values ​​of the direction and magnitude of the torque applied to the output member 300, which are input from the first torque calculation unit 72 and the second torque calculation unit 83, respectively.

[0081] <1-5. Configuration of the Torque Diagnostic Unit> Next, the configuration of the torque diagnostic unit 75 will be explained.

[0082] As described above, the circuit board 65 includes the first torque calculation unit 72 of the first detection unit 70, the input-side encoder detection unit 812, the output-side encoder detection unit 822, and the second torque calculation unit 83 of the second detection unit 80, and the torque diagnosis unit 75. The torque diagnosis unit 75 is composed of an electrical circuit equipped with a microprocessor. The torque diagnosis unit 75 is electrically connected to the first torque calculation unit 72 and the second torque calculation unit 83, respectively, via wiring that is not shown in the diagram.

[0083] The torque diagnostic unit 75 compares the calculated values ​​of the direction and magnitude of the torque applied to the output member 300, which are input from the first torque calculation unit 72, with the calculated values ​​of the direction and magnitude of the torque applied to the output member 300, which are input from the second torque calculation unit 83. If the torque diagnostic unit 75 determines that the difference between the calculated value from the first torque calculation unit 72 and the calculated value from the second torque calculation unit 83 is greater than or equal to a predetermined value, it outputs an abnormality signal to the control unit 105.

[0084] Furthermore, when the torque diagnostic unit 75 outputs the abnormal signal, it may alert the operator by visual or auditory means. In other words, the torque diagnostic unit 75 only needs to output an abnormal signal if the difference between the detection result from the first detection unit 70 and the detection result from the second detection unit 80 is greater than or equal to a predetermined value. This allows the operator managing the robot 100 to easily understand that an abnormality has occurred in either the first detection unit 70 or the second detection unit 80.

[0085] Furthermore, when the control unit 105 receives an abnormal signal from the torque diagnostic unit 75, it temporarily stops the motor 103 from running. This allows the operator to take measures such as performing maintenance on the harmonic drive gear reducer 1 while the motor 103 is stopped. As a result, the robot 100 can resume operation in a safe state. However, the function of the torque diagnostic unit 75 may also be provided in the control unit 105.

[0086] As described above, in this embodiment, the first detection unit 70 and the second detection unit 80 can obtain two values ​​as the torque around the central axis 9 acting on the output member 300. Furthermore, the first detection unit 70 has a configuration that includes multiple strain gauges Ra, Rb, Rc, and Rd, while the second detection unit 80 has a configuration that includes encoder disks 811 and 821. These are different mechanical parts and are located in different places. Therefore, compared to the case where the first detection unit 70 and the second detection unit 80 are the same mechanical part or are located in the same place, the possibility of both failing simultaneously can be reduced. This further enhances the redundancy of torque detection.

[0087] Furthermore, as described above, the output-side angle detection unit 82 of the second detection unit 80 detects the rotation angle of the output-side encoder disk 821 and the output member 300 around the central axis 9 by detecting the change in the amount of light received from the output-side encoder disk 821 using the output-side encoder detection unit 822. In other words, the rotation angle of the output member 300 around the central axis 9 obtained from the output-side angle detection unit 82 is an actual measured value. For this reason, for example, when the harmonic drive reducer 1 is applied to a multi-joint robot 100, the position control of the robot 100 can be made more precise based on the highly accurate value of the rotation angle of the output member 300 around the central axis 9 in the harmonic drive reducer 1 arranged at each joint.

[0088] Furthermore, in order to further enhance the redundancy of torque detection, if two sets of conductive layers 712 (torque detection sensors) consisting of multiple strain gauges Ra, Rb, Rc, and Rd are provided in the first detection unit 70, then two amplifier circuits would be required to amplify the output from the multiple strain gauges in each set. In contrast, with the configuration of this embodiment, only one amplifier circuit is required, thus simplifying the circuit configuration.

[0089] Furthermore, in this embodiment, the output transmission member 55 fixed to the output member 300 is extended toward the input side (the other axial side) while passing radially inside the input member 10, and the output side encoder disk 821 is fixed to the input side (the other axial side) portion of the output transmission member 55. With this structure, both the input side encoder disk 811 and the output side encoder disk 821 can be placed on the input side (the other axial side) of the harmonic drive gear reducer 1. As a result, the input side encoder detection unit 812 that detects the rotation angle of the input side encoder disk 811 and the output side encoder detection unit 822 that detects the rotation angle of the output side encoder disk 821 can be placed on a single circuit board 65. In particular, in this embodiment, the first torque calculation unit 72 of the first detection unit 70, the input side encoder detection unit 812 of the second detection unit 80, and the output side encoder detection unit 822 of the second detection unit 80 are formed on a single circuit board 65. This further reduces the number of parts in the harmonic drive gear reducer 1.

[0090] However, the circuit board on which the first torque calculation unit 72 of the first detection unit 70 is formed and the circuit board on which the input-side encoder detection unit 812 and the output-side encoder detection unit 822 are formed may be provided separately. Furthermore, the circuit board on which the input-side encoder detection unit 812 is formed and the circuit board on which the output-side encoder detection unit 822 is formed may be provided separately. In this case, since the input-side encoder detection unit 812 and the output-side encoder detection unit 822 are not dependent on each other, for example, the input-side encoder detection unit 812 can be positioned even closer to the input-side encoder disk 811, and the output-side encoder detection unit 822 can be positioned even closer to the output-side encoder disk 821. As a result, the detection accuracy of the input-side encoder detection unit 812 and the output-side encoder detection unit 822 can be further improved. In addition, more space can be secured for arranging the transmission belt 104 or gears 111, 115, etc., for transmitting the rotation of the rotating part of the motor 103 to the input member 10.

[0091] Furthermore, as shown in the third modified example in Figure 11, the input-side angle detection unit 81 may be a resolver. As shown in Figure 11, the input-side angle detection unit 81 of the third modified example includes an input-side resolver rotor 813, an input-side resolver stator 814, and an input-side voltage signal processing unit 815. The input-side resolver rotor 813 is mounted on the outer circumferential surface of the input member 10 and is rotatable around the central axis 9 at the input rotational speed. The input-side resolver stator 814 is mounted on the circuit board 65 and surrounds the input-side resolver rotor 813. The input-side resolver stator 814 is also positioned radially opposite the input-side resolver rotor 813. An excitation winding and a detection winding are wound around the input-side resolver stator 814.

[0092] The input-side voltage signal processing unit 815 is formed on one axial side of the circuit board 65. That is, the input-side voltage signal processing unit 815 is formed on the circuit board 65. The input-side voltage signal processing unit 815 is composed of an electrical circuit equipped with a microprocessor. The input-side voltage signal processing unit 815 is also electrically connected to the detection winding of the input-side resolver stator 814 via wiring that is not shown. When the input member 10 to which the input-side resolver rotor 813 is attached rotates while an excitation voltage is applied to the excitation winding of the input-side resolver stator 814, the distance between the input-side resolver rotor 813 and the input-side resolver stator 814 changes. As a result of this change in distance, a voltage is induced in the detection winding of the input-side resolver stator 814.

[0093] The induced voltage reflects the rotation angle of the input-side resolver rotor 813. As a result, the input-side voltage signal processing unit 815 can detect the rotation angle of the input member 10 to which the input-side resolver rotor 813 is attached, based on the value of the induced voltage. In other words, the input-side voltage signal processing unit 815 can detect the rotation angle of the input-side resolver rotor 813 around its central axis 9 based on the voltage generated in the detection winding of the input-side resolver stator 814. Thus, in this third modification, durability can be improved by using a highly robust resolver as the input-side angle detection unit 81.

[0094] Similarly, the output-side angle detection unit 82 may be a resolver. As shown in Figure 11, the output-side angle detection unit 82 of the third modified example includes an output-side resolver rotor 823, an output-side resolver stator 824, and an output-side voltage signal processing unit 825. The output-side resolver rotor 823 is mounted on the outer circumferential surface of the output transmission member 55 and is rotatable around the central axis 9 at the output rotational speed. The output-side resolver stator 824 is mounted on the circuit board 65 and surrounds the output-side resolver rotor 823. The output-side resolver stator 824 is also positioned radially opposite the output-side resolver rotor 823. An excitation winding and a detection winding are wound around the output-side resolver stator 824.

[0095] The output-side voltage signal processing unit 825 is formed on the other axial side of the circuit board 65. That is, the output-side voltage signal processing unit 825 is formed on the circuit board 65. The output-side voltage signal processing unit 825 is composed of an electrical circuit equipped with a microprocessor. The output-side voltage signal processing unit 825 is also electrically connected to the detection winding of the output-side resolver stator 824 via wiring that is not shown. When an excitation voltage is applied to the excitation winding of the output-side resolver stator 824, and the output transmission member 55 to which the output-side resolver rotor 823 is attached rotates, the distance between the output-side resolver rotor 823 and the output-side resolver stator 824 changes. As a result of this change in distance, a voltage is induced in the detection winding of the output-side resolver stator 824.

[0096] The induced voltage reflects the rotation angle of the output resolver rotor 823. As a result, the output voltage signal processing unit 825 can detect the rotation angle of the output transmission member 55 to which the output resolver rotor 823 is attached, based on the value of the induced voltage. In other words, the output voltage signal processing unit 825 can detect the rotation angle of the output resolver rotor 823 around the central axis 9 based on the voltage generated in the detection winding of the output resolver stator 824.

[0097] <2. Second Embodiment> Next, the configuration of the harmonic drive gear reducer 1B according to the second embodiment of the present invention will be described. Figure 12 is a longitudinal cross-sectional view of the harmonic drive gear reducer 1B according to the second embodiment. In the following description, the differences from the harmonic drive gear reducer 1 of the first embodiment will be the main focus, and parts equivalent to those in the first embodiment will be denoted by the same reference numerals as the corresponding parts in the harmonic drive gear reducer 1 of the first embodiment, and redundant explanations will be omitted.

[0098] As shown in Figure 12, the wave drive gear reducer 1B includes an input member 10, an internal gear 20, an external gear 30, a wave generator 40, an output side housing 50, an output transmission member 55, a cover member 60, an input side housing 61, a circuit board 65, a first detection unit 70B, and a second detection unit 80B.

[0099] <2-1. Configuration of the First Detection Unit> The first detection unit 70B of this embodiment has substantially the same configuration as the first detection unit 70 of the first embodiment. As shown in Figure 12, the first detection unit 70B includes a first detection substrate 71B and a first torque calculation unit 72B. Figure 13 is a plan view of the first detection substrate 71B according to the second embodiment. Figure 14 is a partial plan view of the first detection substrate 71B. In this embodiment, the "multiple strain gauges Ra, Rb, Rc, Rd" in the first detection unit 70 of the first embodiment will be referred to as "multiple first strain gauges Ra, Rb, Rc, Rd". That is, the first detection unit 70B of this embodiment has multiple first strain gauges Ra, Rb, Rc, Rd arranged on the external gear 30, the output of which changes depending on the torque around the central axis 9 acting on the external gear 30. Furthermore, the multiple first strain gauges Ra, Rb, Rc, and Rd are arranged on the diaphragm portion 33 of the external gear 30. This allows for a wider arrangement space for the multiple first strain gauges Ra, Rb, Rc, and Rd.

[0100] The first torque calculation unit 72B is formed on the circuit board 65. The first torque calculation unit 72B is electrically connected via wiring to a first bridge circuit C1 (see Figure 8) formed by a plurality of first strain gauges Ra, Rb, Rc, and Rd. The first torque calculation unit 72B detects the direction and magnitude of the torque applied to the diaphragm 33 based on the measurement value of a first voltmeter V1 connected between the midpoint M11 of two first strain gauges Ra and Rb and the midpoint M12 of two first strain gauges Rc and Rd. Here, the torque applied to the diaphragm 33 and the torque applied to the output member 300 are opposite in direction and the same in magnitude due to the action-reaction relationship. Therefore, the first torque calculation unit 72B calculates the direction and magnitude of the torque applied to the output member 300 based on the detection result of the direction and magnitude of the torque applied to the diaphragm 33. Furthermore, the first torque calculation unit 72B outputs the calculated torque direction and magnitude values ​​applied to the output member 300 to the torque diagnosis unit 75 and the control unit 105.

[0101] <2-2. Configuration of the Second Detection Unit> The second detection unit 80B of this embodiment includes an input-side angle detection unit 81B, an output-side angle detection unit 82B, and a second torque calculation unit 83B. The second torque calculation unit 83B corresponds to the "torque calculation unit" of the present invention. The input-side angle detection unit 81B has a plurality of second strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp as a resistance wire section 816B for detecting the rotation angle of the internal gear 20 that partially meshes with the external gear 30. In this embodiment, the input-side angle detection unit 81B has eight second strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp.

[0102] Multiple second strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, Rp are positioned in the diaphragm portion 33 of the external gear 30 at different positions from the multiple first strain gauges Ra, Rb, Rc, Rd. This allows for a wider arrangement space for the multiple second strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, Rp. Also, as shown in Figure 13, the multiple second strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, Rp are spaced apart in the circumferential direction. Each of the multiple second strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, Rp is formed by a single wire. Furthermore, each of the multiple second strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, Rp spreads out in an arc shape along the circumferential direction.

[0103] In this embodiment, the multiple second strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp are arranged radially outward from the multiple first strain gauges Ra, Rb, Rc, and Rd. However, the multiple second strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp may be arranged radially inward from the multiple first strain gauges Ra, Rb, Rc, and Rd.

[0104] As shown in Figure 14, each of the multiple second strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp includes a portion r3. The portion r3 extends in the circumferential direction. However, portions r3 extending in the circumferential direction may be repeatedly arranged in the radial direction. Furthermore, portions r3 may extend in the radial direction. Furthermore, portions r3 extending in the radial direction may be repeatedly arranged in the circumferential direction.

[0105] Of the eight second strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp, four second strain gauges Ri, Rk, Rm, and Ro that are not adjacent to each other are connected to each other to form a third bridge circuit C3. Figure 15 is a circuit diagram of the third bridge circuit C3. As shown in Figure 15, the second strain gauge Ri and the second strain gauge Rk are connected in series in this order. The second strain gauge Ro and the second strain gauge Rm are connected in series in this order. Then, between the positive and negative terminals of the power supply voltage (not shown) that applies voltage to the four second strain gauges Ri, Rk, Rm, and Ro, two rows of second strain gauges Ri, Rk and two rows of second strain gauges Ro, Rm are connected in parallel. Furthermore, the midpoint M31 of the two second strain gauges Ri and Rk, and the midpoint M32 of the two second strain gauges Ro and Rm, are connected to the third voltmeter V3.

[0106] Of the eight second strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp, the remaining four second strain gauges Rj, Rl, Rn, and Rp are connected to each other to form a fourth bridge circuit C4. Figure 16 is a circuit diagram of the fourth bridge circuit C4. As shown in Figure 16, the second strain gauge Rp and the second strain gauge Rn are connected in series in this order. The second strain gauge Rj and the second strain gauge Rl are connected in series in this order. Then, between the positive and negative terminals of the power supply voltage (not shown) that applies voltage to the four second strain gauges Rj, Rl, Rn, and Rp, two rows of second strain gauges Rp, Rn and two rows of second strain gauges Rj, Rl are connected in parallel. Furthermore, the midpoint M41 of the two second strain gauges Rp and Rn, and the midpoint M42 of the two second strain gauges Rj and Rl, are connected to the fourth voltmeter V4.

[0107] When the harmonic drive gear reducer 1B is driven, the diaphragm portion 33 of the external gear 30, which partially meshes with the internal gear 20 that rotates at the output rotational speed together with the output member 300, generates portions that expand in the circumferential direction and portions that contract in the circumferential direction. Specifically, two expanded portions and two contracted portions alternately occur in the circumferential direction. That is, the expanded portions and contracted portions alternately occur at 90° intervals in the circumferential direction with respect to the central axis 9. The locations where these expanded and contracted portions occur rotate at the input rotational speed of the harmonic drive gear reducer 1B.

[0108] The resistance values ​​of the eight second strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp change according to the circumferential expansion and contraction of the diaphragm portion 33 of the external gear 30 that partially meshes with the internal gear 20. For example, when the expanded portion overlaps with a certain second strain gauge, the resistance value of that second strain gauge increases. Conversely, when the contracted portion overlaps with a certain second strain gauge, the resistance value of that second strain gauge decreases.

[0109] In this embodiment, when the contracted portion overlaps with the second strain gauges Ri and Rm, the extended portion overlaps with the second strain gauges Rk and Ro. Conversely, when the extended portion overlaps with the second strain gauges Ri and Rm, the contracted portion overlaps with the second strain gauges Rk and Ro. Therefore, in the third bridge circuit C3, the second strain gauges Ri and Rm and the second strain gauges Rk and Ro exhibit resistance changes in opposite directions.

[0110] Furthermore, in this embodiment, when the contracted portion overlaps with the second strain gauges Rp and Rl, the extended portion overlaps with the second strain gauges Rn and Rj. Conversely, when the extended portion overlaps with the second strain gauges Rp and Rl, the contracted portion overlaps with the second strain gauges Rn and Rj. Therefore, in the fourth bridge circuit C4, the second strain gauges Rp and Rl and the second strain gauges Rn and Rj exhibit resistance changes in opposite directions.

[0111] Figure 17 is a graph showing the time variation of the measured value v3 from the third voltmeter V3 of the third bridge circuit C3 and the measured value v4 from the fourth voltmeter V4 of the fourth bridge circuit C4. The horizontal axis of the graph in Figure 17 represents time. The vertical axis of the graph in Figure 17 represents voltage value. When the harmonic drive gear reducer 1B is driven, as shown in Figure 17, periodically changing sinusoidal measured values ​​v3 and v4 are output from the third voltmeter V3 and the fourth voltmeter V4, respectively. That is, the output of the multiple second strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, Rp changes according to the rotation angle around the central axis 9 of the input member 10. The period T of these measured values ​​v3 and v4 corresponds to half the period of the input rotation speed mentioned above. Furthermore, the direction of the input rotational motion can be determined by whether the phase of the measured value v4 of the fourth voltmeter V4 is ahead of the phase of the measured value v3 of the third voltmeter V3 by 1 / 8 of a period of the input rotational speed (1 / 4 of a period of the measured values ​​v3 and v4) or behind by 1 / 8 of a period of the input rotational speed (1 / 4 of a period of the measured values ​​v3 and v4).

[0112] Furthermore, the input-side angle detection unit 81B also includes an input-side angle calculation unit 817B. The input-side angle calculation unit 817B is composed of an electrical circuit equipped with a microprocessor. The input-side angle calculation unit 817B is formed on a circuit board 65. The input-side angle calculation unit 817B can detect the rotation angle of the input member 10 around the central axis 9 based on the measured value v3 of the third voltmeter V3 and the measured value v4 of the fourth voltmeter V4. Specifically, for example, the input-side angle calculation unit 817B has a storage unit that stores a function table that associates the combination of the measured value v3 of the third voltmeter V3 and the measured value v4 of the fourth voltmeter V4 with the rotation angle. The input-side angle calculation unit 817B outputs the input rotation angle by inputting the measured values ​​v3 and v4 into the function table.

[0113] The output-side angle detection unit 82B of this embodiment has substantially the same configuration as the output-side angle detection unit 82 of the first embodiment. The output-side angle detection unit 82B includes an output-side encoder disk 821B, a second light source (not shown), and an output-side encoder detection unit 822B. The output-side encoder disk 821B is fixed to the outer circumferential surface of the output transmission member 55 on the axial side of the other end of the input member 10, and is rotatable at the output rotational speed together with the output transmission member 55 and the output member 300. The output-side encoder detection unit 822B is formed on the circuit board 65.

[0114] The output-side angle detection unit 82B is an optical encoder capable of detecting the rotation angle of the output-side encoder disk 821B around its central axis 9 by detecting changes in the amount of light received from the output-side encoder disk 821B using the output-side encoder detection unit 822B. Furthermore, the output-side angle detection unit 82B has such a configuration, enabling accurate detection of the rotation angle of the output-side encoder disk 821B around its central axis 9. As a result, the output-side angle detection unit 82B can detect the rotation angles of the output transmission member 55 and the output member 300, which are fixed to the inner circumferential surface of the output-side encoder disk 821B, around their central axes 9.

[0115] However, the output-side angle detection unit 82B may be a magnetic encoder capable of detecting the rotation angle of the output-side encoder disk 821B around its central axis 9 by detecting the change in the magnetic field accompanying the rotation of the output-side encoder disk 821B using the output-side encoder detection unit 822B.

[0116] The second torque calculation unit 83B is electrically connected to the input-side angle calculation unit 817B and the output-side encoder detection unit 822B, respectively, via wiring that is not shown in the diagram. The second torque calculation unit 83B receives the rotation angle of the input member 10 around the central axis 9, calculated by the input-side angle calculation unit 817B, and the rotation angle of the output member 300 around the central axis 9 (hereinafter referred to as the "second measured value"), detected by the output-side encoder detection unit 822B.

[0117] Similar to the first embodiment, when the second torque calculation unit 83B receives the calculation result from the input-side angle calculation unit 817B, it divides the calculation result by the reduction ratio of the harmonic drive gear reducer 1B. Here, as described above, the calculation result from the input-side angle calculation unit 817B is the rotation angle around the central axis 9 of the input member 10. By dividing the rotation angle around the central axis 9 of the input member 10 by the reduction ratio of the harmonic drive gear reducer 1B, a theoretical value of the rotation angle around the central axis 9 of the output member 300 (hereinafter referred to as the "second theoretical value") is obtained. Next, when the second torque calculation unit 83B receives the detection result from the output-side encoder detection unit 822B, it compares the detection result with the second theoretical value of the rotation angle around the central axis 9 of the output member 300 that has already been calculated. Here, the detection result from the output-side encoder detection unit 822B is the second measured value of the rotation angle around the central axis 9 of the output member 300.

[0118] The second torque calculation unit 83B then calculates the difference between the second theoretical value of the rotation angle of the output member 300 around the central axis 9 and the second measured value of the rotation angle of the output member 300 around the central axis 9. This difference is what is known as the "torsion angle of the harmonic drive reducer 1B". Furthermore, the second torque calculation unit 83B multiplies this difference by the "torsional stiffness (spring characteristics)", which is the stiffness value of the harmonic drive reducer 1B. As a result, the second torque calculation unit 83B can calculate the direction and magnitude of the torque acting on the output member 300 around the central axis 9. In other words, the second torque calculation unit 83B can calculate the torque acting on the output member 300 around the central axis 9 based on the difference between a second theoretical value of the rotation angle of the output member 300 around the central axis 9, which is obtained by dividing the rotation angle of the input member 10 around the central axis 9, obtained based on the outputs of multiple second strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, Rp of the input-side angle detection unit 81B, by the reduction ratio of the harmonic drive gear reducer 1B, and a second measured value of the rotation angle of the output member 300 around the central axis 9, which is the result of detection by the output-side angle detection unit 82B.

[0119] Furthermore, the second torque calculation unit 83B outputs the calculated values ​​of the direction and magnitude of the torque applied to the output member 300 to the torque diagnosis unit 75 and the control unit 105. The control unit 105 controls the drive of the motor 103 based on the calculated values ​​of the direction and magnitude of the torque applied to the output member 300, which are input from the first torque calculation unit 72B and the second torque calculation unit 83B, respectively.

[0120] The torque diagnostic unit 75 compares the calculated values ​​of the direction and magnitude of the torque applied to the output member 300, which are input from the first torque calculation unit 72B, with the calculated values ​​of the direction and magnitude of the torque applied to the output member 300, which are input from the second torque calculation unit 83B. If the torque diagnostic unit 75 determines that the difference between the calculated value from the first torque calculation unit 72B and the calculated value from the second torque calculation unit 83B is greater than or equal to a predetermined value, it outputs an abnormality signal to the control unit 105.

[0121] Furthermore, when the torque diagnostic unit 75 outputs the abnormal signal, it may alert the operator by visual or auditory means. That is, the torque diagnostic unit 75 only needs to output an abnormal signal if the difference between the detection result from the first detection unit 70B and the detection result from the second detection unit 80B is greater than or equal to a predetermined value. This allows the operator managing the robot 100 to easily understand that an abnormality has occurred in either the first detection unit 70B or the second detection unit 80B. In addition, when the control unit 105 receives an abnormal signal from the torque diagnostic unit 75, it temporarily stops the drive of the motor 103. This allows the operator to take measures such as performing maintenance on the harmonic drive gear reducer 1B while the motor 103 is stopped. As a result, the robot 100 can resume operation in a safe state.

[0122] As described above, in this embodiment, the first detection unit 70B and the second detection unit 80B can obtain two values ​​as the torque around the central axis 9 acting on the output member 300. Furthermore, the first detection unit 70B has a configuration that includes a plurality of first strain gauges Ra, Rb, Rc, and Rd, while the second detection unit 80B has a configuration that includes a plurality of second strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, Rp and an output-side encoder disk 821B, and these are all different mechanical parts. Therefore, compared to the case where the first detection unit 70B and the second detection unit 80B are the same mechanical part, the possibility of both failing simultaneously can be reduced. This makes it possible to further increase the redundancy of torque detection.

[0123] Furthermore, as described above, the output-side angle detection unit 82B of the second detection unit 80B detects the rotation angle of the output-side encoder disk 821B and the output member 300 around the central axis 9 by detecting the change in the amount of light received from the output-side encoder disk 821B using the output-side encoder detection unit 822B. In other words, the rotation angle of the output member 300 around the central axis 9 obtained from the output-side angle detection unit 82B is an actual measured value. For this reason, for example, when the harmonic drive reducer 1B is applied to a multi-joint robot 100, the position control of the robot 100 can be made more precise based on the highly accurate value of the rotation angle of the output member 300 around the central axis 9 in the harmonic drive reducer 1B arranged at each joint.

[0124] Furthermore, in order to further enhance the redundancy of torque detection, if two sets of conductive layers 712 (see Figure 5) consisting of multiple first strain gauges Ra, Rb, Rc, and Rd are provided in the first detection unit 70B, then two amplifier circuits would be required to amplify the output from the multiple first strain gauges in each set. In contrast, with the configuration of this embodiment, only one amplifier circuit is required, thus simplifying the circuit configuration.

[0125] <3. Modifications> Although embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. For example, in the above harmonic drive gear reducer, the torque value obtained from either the first detection unit or the second detection unit may be output as priority, and if one of the detection units fails, it may be switched manually or automatically to output the torque value obtained from the other detection unit.

[0126] The detailed configuration of the harmonic drive gear reducer may be modified as appropriate without departing from the spirit of the present invention. Furthermore, the elements that appeared in the above embodiments may be combined as appropriate without creating any inconsistencies.

[0127] <4. Summary> This technology can take the following configuration:

[0128] (1): A wave gear reducer that reduces the input rotational speed of an input member rotatable together with the rotating part of a motor, thereby rotating an output member at an output rotational speed smaller than the input rotational speed, comprising: a wave generator having a non-circular cross-section perpendicular to the central axis and rotatable together with the input member around the central axis at the input rotational speed; an external gear having at least a portion positioned radially outward of the wave generator and having a plurality of external teeth protruding radially outward; an internal gear having at least a portion positioned radially outward of the external gear, spreading in an annular shape around the central axis and having a plurality of internal teeth protruding radially inward and partially meshing with the plurality of external teeth; and a first detection unit and a second detection unit, respectively, capable of detecting the torque acting on the output member around the central axis, wherein the output member is rotatable together with one of the external gear and the internal gear at the output rotational speed, and the first detection unit is A wave drive gear reducer having a plurality of strain gauges arranged on the external gear whose output changes with respect to the torque around the central axis acting on the external gear, the second detection unit comprising: an input-side angle detection unit capable of detecting the rotation angle of the input member around the central axis; an output-side angle detection unit capable of detecting the rotation angle of the output member around the central axis; and a torque calculation unit capable of calculating the torque around the central axis acting on the output member based on the difference between a theoretical value of the rotation angle of the output member around the central axis obtained by dividing the detection result by the input-side angle detection unit by the reduction ratio of the wave drive gear reducer, and an actual measured value of the rotation angle of the output member around the central axis which is the detection result by the output-side angle detection unit.

[0129] (2): A harmonic drive gear reducer as described in (1), wherein the external gear comprises: a cylindrical body portion extending in an axial direction parallel to the central axis; a plurality of external teeth arranged on one axial side of the body portion and projecting radially outward; and a diaphragm portion extending radially on the other axial side of the body portion, and a plurality of strain gauges arranged on the diaphragm portion.

[0130] (3): A wave drive gear reducer according to (1) or (2), further comprising: an output transmission member fixed to the output member and extending along the central axis; a cover member that expands cylindrically along the central axis on the radially outer side of the central axis and houses the wave generator, the external gear, the internal gear, the first detection unit, the second detection unit, and at least a part of the output transmission member radially inward; and a circuit board directly or indirectly fixed to the radially inner surface of the cover member and extending in a direction intersecting the central axis, wherein the input member extends cylindrically along the central axis on the radially outer side of at least a part of the output transmission member; the output transmission member extends from one axial side to the other axial side, passing through the radially inner side of the input member; the other axial end of the output transmission member is located on the other axial side of the input member than the other axial end of the input member; and the input side angle detection unit comprises an input side encoder disk fixed to the input member and rotatable together with the input member at the input rotational speed, A harmonic drive gear reducer having: an input-side encoder detection unit capable of detecting the rotation angle of the input-side encoder disk about the central axis; an output-side encoder disk fixed to the output transmission member on the other axial side of the other axial end of the input member and capable of rotating together with the output transmission member and the output member at the output rotation speed; and an output-side encoder detection unit capable of detecting the rotation angle of the output-side encoder disk about the central axis; the input-side encoder detection unit and the output-side encoder detection unit are formed on the circuit board.

[0131] (4) A harmonic drive gear reducer as described in (3), wherein the input-side angle detection unit is an optical encoder capable of detecting the rotation angle of the input-side encoder disk around its central axis by detecting a change in the amount of light received from the input-side encoder disk using the input-side encoder detection unit, or the output-side angle detection unit is an optical encoder capable of detecting the rotation angle of the output-side encoder disk around its central axis by detecting a change in the amount of light received from the output-side encoder disk using the output-side encoder detection unit.

[0132] (5) A harmonic drive gear reducer as described in (3), wherein the input-side angle detection unit is a magnetic encoder capable of detecting the rotation angle of the input-side encoder disk around its central axis by detecting a change in the magnetic field accompanying the rotation of the input-side encoder disk using the input-side encoder detection unit, or the output-side angle detection unit is a magnetic encoder capable of detecting the rotation angle of the output-side encoder disk around its central axis by detecting a change in the magnetic field accompanying the rotation of the output-side encoder disk using the output-side encoder detection unit.

[0133] (6): A wave drive gear reducer according to (1) or (2), further comprising: an output transmission member fixed to the output member and extending along the central axis; a cover member that expands cylindrically along the central axis on the radially outer side of the central axis and houses the wave generator, the external gear, the internal gear, the first detection unit, the second detection unit, and at least a part of the output transmission member radially inward; and a circuit board directly or indirectly fixed to the radially inner surface of the cover member and extending in a direction intersecting the central axis, wherein the input member extends cylindrically along the central axis on the radially outer side of at least a part of the output transmission member; the output transmission member extends from one axial side to the other axial side, passing through the radially inner side of the input member; the other axial end of the output transmission member is located on the other axial side of the input member; and the input side angle detection unit is a resolver. A harmonic drive gear reducer comprising: a resolver rotor attached to the input member and rotatable around the central axis at the input rotational speed; a resolver stator attached to the circuit board and surrounding the resolver rotor; a voltage signal processing unit electrically connected to the resolver stator and capable of detecting the rotation angle of the resolver rotor around the central axis based on the voltage generated in the detection winding of the resolver stator; the output side angle detection unit comprising: an output side encoder disk fixed to the output transmission member on the other axial side of the other axial end of the input member and rotatable together with the output transmission member and the output member at the output rotational speed; and an output side encoder detection unit capable of detecting the rotation angle of the output side encoder disk around the central axis; the voltage signal processing unit and the output side encoder detection unit are formed on the circuit board.

[0134] (7): A wave gear reducer that reduces the input rotational speed of an input member rotatable together with the rotating part of a motor, thereby rotating an output member at an output rotational speed smaller than the input rotational speed, comprising: a wave generator having a non-circular cross-section perpendicular to the central axis and rotatable together with the input member around the central axis at the input rotational speed; an external gear having at least a portion arranged radially outward of the wave generator and having a plurality of external teeth protruding radially outward; an internal gear having at least a portion arranged radially outward of the external gear, spreading in an annular shape around the central axis and having a plurality of internal teeth protruding radially inward and partially meshing with the plurality of external teeth; and a first detection unit and a second detection unit, respectively, capable of detecting the torque acting on the output member around the central axis, wherein the output member is rotatable together with one of the external gear and the internal gear at the output rotational speed, and the first detection unit is A harmonic drive gear reducer having a plurality of first strain gauges arranged on the external gear, the output of which changes with respect to the torque acting on the external gear around the central axis, the second detection unit having a plurality of second strain gauges arranged on the external gear, the output of which changes with respect to the rotation angle of the input member around the central axis, an output-side angle detection unit capable of detecting the rotation angle of the output member around the central axis, and a torque calculation unit capable of calculating the torque acting on the output member around the central axis based on the difference between a second theoretical value of the rotation angle of the output member around the central axis, obtained by dividing the rotation angle of the input member around the central axis, which is obtained based on the outputs of the plurality of second strain gauges, by the reduction ratio of the harmonic drive gear reducer, and a second measured value of the rotation angle of the output member around the central axis, which is the result of detection by the output-side angle detection unit.

[0135] (8) A harmonic drive gear reducer as described in (7), wherein the external gear comprises: a cylindrical body portion extending in an axial direction parallel to the central axis; a plurality of external teeth arranged on one axial side of the body portion and projecting radially outward; and a diaphragm portion extending radially on the other axial side of the body portion, wherein a plurality of first strain gauges and a plurality of second strain gauges are arranged on the diaphragm portion.

[0136] (9): A wave drive gear reducer according to (7) or (8), further comprising: an output transmission member fixed to the output member and extending along the central axis; a cover member that expands cylindrically along the central axis on the radially outer side of the central axis and houses the wave generator, the external gear, the internal gear, the first detection unit, the second detection unit, and at least a part of the output transmission member radially inward; and a circuit board directly or indirectly fixed to the radially inner surface of the cover member and extending in a direction intersecting the central axis, wherein the input member extends cylindrically along the central axis on the radially outer side of at least a part of the output transmission member; the output transmission member extends from one axial side to the other axial side, passing through the radially inner side of the input member; the other axial end of the output transmission member is located on the other axial side of the input member; and the output side angle detection unit is A harmonic drive gear reducer comprising: an output-side encoder disk fixed to the output transmission member at a position on the other axial side of the other axial end of the input member and rotatable together with the output transmission member and the output member at the output rotational speed; and an output-side encoder detection unit capable of detecting the rotational angle of the output-side encoder disk about the central axis, wherein the output-side encoder detection unit is formed on the circuit board.

[0137] (10): A harmonic drive gear reducer as described in (9), wherein the output-side angle detection unit is an optical encoder capable of detecting the rotation angle of the output-side encoder disk around its central axis by detecting a change in the amount of light received from the output-side encoder disk using the output-side encoder detection unit.

[0138] (11): A harmonic drive gear reducer as described in (9), wherein the output-side angle detection unit is a magnetic encoder capable of detecting the rotation angle of the output-side encoder disk around its central axis by detecting a change in the magnetic field accompanying the rotation of the output-side encoder disk using the output-side encoder detection unit.

[0139] (12): A harmonic drive gear reducer according to any one of (1) to (11), further comprising a torque diagnostic unit that outputs an abnormal signal when the difference between the detection result by the first detection unit and the detection result by the second detection unit is greater than or equal to a predetermined value.

[0140] This invention can be used in harmonic drive gear reducers.

[0141] 1,1B Harmonic drive gear reducer 9 Central shaft 10 Input member 20 Internal gear 30 External gear 33 Diaphragm section 40 Wave generator 41 Cam 42 Flexible bearing 55 Output transmission member 65 Circuit board 66 Support base 70,70B First detection unit 72,72B First torque calculation unit 75 Torque diagnosis unit 80,80B Second detection unit 81,81B Input side angle detection unit 82,82B Output side angle detection unit 83,83B Second torque calculation unit 100 Robot 101 Base frame 102 Arm 103 Motor 104 Transmission belt 105 Control unit 300 Output member 811 Input side encoder disk 812 Input side encoder detection unit 813 Input side resolver rotor 814 Input side resolver stator 821, 821B Output side encoder disk 822, 822B Output side encoder detection unit Ri, Rj, Rk Second strain gauge Rl, Rm, Rn Second strain gauge Ro, Rp Second strain gauge

Claims

1. A wave drive gear reducer that reduces the input rotational speed of an input member rotatable together with the rotating part of a motor, thereby rotating an output member at an output rotational speed lower than the input rotational speed, comprising: a wave generator having a non-circular cross-section perpendicular to the central axis and rotatable together with the input member around the central axis at the input rotational speed; an external gear having at least a portion positioned radially outward of the wave generator and having a plurality of external teeth protruding radially outward; an internal gear having at least a portion positioned radially outward of the external gear, spreading in an annular shape around the central axis and having a plurality of internal teeth protruding radially inward and partially meshing with the plurality of external teeth; and a first detection unit and a second detection unit, respectively, capable of detecting the torque acting on the output member around the central axis, wherein the output member is rotatable together with one of the external gear and the internal gear at the output rotational speed, and the first detection unit is A wave drive gear reducer having a plurality of strain gauges arranged on the external gear whose output changes with respect to the torque around the central axis acting on the external gear, the second detection unit comprising: an input-side angle detection unit capable of detecting the rotation angle of the input member around the central axis; an output-side angle detection unit capable of detecting the rotation angle of the output member around the central axis; and a torque calculation unit capable of calculating the torque around the central axis acting on the output member based on the difference between a theoretical value of the rotation angle of the output member around the central axis obtained by dividing the detection result by the input-side angle detection unit by the reduction ratio of the wave drive gear reducer, and an actual measured value of the rotation angle of the output member around the central axis which is the detection result by the output-side angle detection unit.

2. A harmonic drive gear reducer according to claim 1, wherein the external gear comprises: a cylindrical body portion extending in an axial direction parallel to the central axis; a plurality of external teeth arranged on one axial side of the body portion and projecting radially outward; and a diaphragm portion extending radially on the other axial side of the body portion, and a plurality of strain gauges arranged on the diaphragm portion.

3. A wave drive gear reducer according to claim 1 or claim 2, further comprising: an output transmission member fixed to the output member and extending along the central axis; a cover member that expands cylindrically along the central axis on the radially outer side of the central axis and houses the wave generator, the external gear, the internal gear, the first detection unit, the second detection unit, and at least a portion of the output transmission member radially inward; and a circuit board directly or indirectly fixed to the radially inner surface of the cover member and extending in a direction intersecting the central axis, wherein the input member extends cylindrically along the central axis on the radially outer side of at least a portion of the output transmission member; the output transmission member extends from one axial side to the other axial side, passing through the radially inner side of the input member; the end of the output transmission member on the other axial side is located on the other axial side of the end of the input member on the other axial side; and the input side angle detection unit comprises an input side encoder disk fixed to the input member and rotatable together with the input member at the input rotational speed. A harmonic drive gear reducer having: an input-side encoder detection unit capable of detecting the rotation angle of the input-side encoder disk about the central axis; an output-side encoder disk fixed to the output transmission member on the other axial side of the other axial end of the input member and capable of rotating together with the output transmission member and the output member at the output rotation speed; and an output-side encoder detection unit capable of detecting the rotation angle of the output-side encoder disk about the central axis; the input-side encoder detection unit and the output-side encoder detection unit are formed on the circuit board.

4. A harmonic drive gear reducer according to claim 3, wherein the input-side angle detection unit is an optical encoder capable of detecting the rotation angle of the input-side encoder disk around its central axis by detecting a change in the amount of light received from the input-side encoder disk using the input-side encoder detection unit, or the output-side angle detection unit is an optical encoder capable of detecting the rotation angle of the output-side encoder disk around its central axis by detecting a change in the amount of light received from the output-side encoder disk using the output-side encoder detection unit.

5. A harmonic drive gear reducer according to claim 3, wherein the input-side angle detection unit is a magnetic encoder capable of detecting the rotation angle of the input-side encoder disk around its central axis by detecting a change in the magnetic field accompanying the rotation of the input-side encoder disk using the input-side encoder detection unit, or the output-side angle detection unit is a magnetic encoder capable of detecting the rotation angle of the output-side encoder disk around its central axis by detecting a change in the magnetic field accompanying the rotation of the output-side encoder disk using the output-side encoder detection unit.

6. A wave drive gear reducer according to claim 1 or claim 2, further comprising: an output transmission member fixed to the output member and extending along the central axis; a cover member that expands cylindrically along the central axis on the radially outer side of the central axis and houses the wave generator, the external gear, the internal gear, the first detection unit, the second detection unit, and at least a part of the output transmission member radially inward; a circuit board directly or indirectly fixed to the radially inner surface of the cover member and extending in a direction intersecting the central axis, wherein the input member extends cylindrically along the central axis on the radially outer side of at least a part of the output transmission member; the output transmission member extends from one axial side to the other axial side, passing through the radially inner side of the input member; the other axial end of the output transmission member is located on the other axial side of the input member than the other axial end of the input member; the input side angle detection unit is a resolver; and a resolver rotor attached to the input member and rotatable around the central axis at the input rotational speed, A harmonic drive gear reducer comprising: a resolver stator mounted on the circuit board and surrounding the resolver rotor; a voltage signal processing unit electrically connected to the resolver stator and capable of detecting the rotation angle of the resolver rotor about the central axis based on the voltage generated in the detection winding of the resolver stator; an output-side angle detection unit comprising: an output-side encoder disk fixed to the output transmission member on the other axial side of the other axial end of the input member and capable of rotating together with the output transmission member and the output member at the output rotation speed; and an output-side encoder detection unit capable of detecting the rotation angle of the output-side encoder disk about the central axis; the voltage signal processing unit and the output-side encoder detection unit are formed on the circuit board.

7. A wave drive gear reducer that reduces the input rotational speed of an input member rotatable together with the rotating part of a motor, thereby rotating an output member at an output rotational speed lower than the input rotational speed, comprising: a wave generator having a non-circular cross-section perpendicular to the central axis and rotatable together with the input member around the central axis at the input rotational speed; an external gear having at least a portion positioned radially outward of the wave generator and having a plurality of external teeth protruding radially outward; an internal gear having at least a portion positioned radially outward of the external gear, spreading in an annular shape around the central axis and having a plurality of internal teeth protruding radially inward and partially meshing with the plurality of external teeth; and a first detection unit and a second detection unit, respectively, capable of detecting the torque acting on the output member around the central axis, wherein the output member is rotatable together with one of the external gear and the internal gear at the output rotational speed, and the first detection unit is A harmonic drive gear reducer having a plurality of first strain gauges arranged on the external gear, the output of which changes with respect to the torque acting on the external gear around the central axis, the second detection unit having a plurality of second strain gauges arranged on the external gear, the output of which changes with respect to the rotation angle of the input member around the central axis, an output-side angle detection unit capable of detecting the rotation angle of the output member around the central axis, and a torque calculation unit capable of calculating the torque acting on the output member around the central axis based on the difference between a second theoretical value of the rotation angle of the output member around the central axis, obtained by dividing the rotation angle of the input member around the central axis, which is obtained based on the outputs of the plurality of second strain gauges, by the reduction ratio of the harmonic drive gear reducer, and a second measured value of the rotation angle of the output member around the central axis, which is the result of detection by the output-side angle detection unit.

8. A harmonic drive gear reducer according to claim 7, wherein the external gear comprises: a cylindrical body portion extending in an axial direction parallel to the central axis; a plurality of external teeth arranged on one axial side of the body portion and projecting radially outward; and a diaphragm portion extending radially on the other axial side of the body portion, wherein a plurality of first strain gauges and a plurality of second strain gauges are arranged on the diaphragm portion.

9. A wave drive gear reducer according to claim 7 or claim 8, further comprising: an output transmission member fixed to the output member and extending along the central axis; a cover member that expands cylindrically along the central axis on the radially outer side of the central axis and houses the wave generator, the external gear, the internal gear, the first detection unit, the second detection unit, and at least a portion of the output transmission member radially inward; and a circuit board directly or indirectly fixed to the radially inner surface of the cover member and extending in a direction intersecting the central axis, wherein the input member extends cylindrically along the central axis on the radially outer side of at least a portion of the output transmission member; the output transmission member extends from one axial side to the other axial side, passing through the radially inner side of the input member; the other axial end of the output transmission member is located on the other axial side of the input member; and the output side angle detection unit is A harmonic drive gear reducer comprising: an output-side encoder disk fixed to the output transmission member at a position on the other axial side of the other axial end of the input member and rotatable together with the output transmission member and the output member at the output rotational speed; and an output-side encoder detection unit capable of detecting the rotational angle of the output-side encoder disk about the central axis, wherein the output-side encoder detection unit is formed on the circuit board.

10. A harmonic drive gear reducer according to claim 9, wherein the output-side angle detection unit is an optical encoder capable of detecting the rotation angle of the output-side encoder disk around its central axis by detecting a change in the amount of light received from the output-side encoder disk using the output-side encoder detection unit.

11. A harmonic drive gear reducer according to claim 9, wherein the output-side angle detection unit is a magnetic encoder capable of detecting the rotation angle of the output-side encoder disk around its central axis by detecting a change in the magnetic field accompanying the rotation of the output-side encoder disk using the output-side encoder detection unit.

12. A harmonic drive gear reducer according to claim 1 or claim 7, further comprising a torque diagnostic unit that outputs an abnormal signal when the difference between the detection result by the first detection unit and the detection result by the second detection unit is greater than or equal to a predetermined value.

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