Wave motion speed reducer, industrial machine, drive system, and correction method

Abstract

To provide an art which can inhibit change of an output value of an angle sensor by a thrust force applied to a cam of a speed reducer.SOLUTION: A wave motion speed reducer includes a cam, a flex gear, an internal gear, an angle sensor, a thrust sensor, and a circuit. The angle sensor is a sensor which is disposed at the flex gear and whose output value changes according to a rotation angle of the cam. The thrust sensor is a sensor which is disposed at the flex gear and whose output value changes according to a thrust force applied to the cam. The circuit is electrically connected to the angle sensor and the thrust sensor. The circuit corrects the output value of the angle sensor based on the output value of the thrust sensor.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a wave reducer, an industrial machine, a drive system, and a correction method. [Background technology]

[0002] 2. Description of the Related Art Conventionally, a reducer equipped with a detection device having a plurality of strain gauges is known (for example, see Patent Document 1). [Patent Document 1] JP 2004-198400 A Summary of the Invention [Problem to be solved by the invention]

[0003] In this type of reducer, it is possible to configure an angle sensor using multiple strain gauges. In this case, two bridge circuits are configured using the multiple strain gauges. The output values ​​of the two bridge circuits are sinusoidal. The two bridge circuits are arranged so that they have a phase difference of 1 / 4 period. The angle sensor detects the rotation angle of the rotary motion input to the reducer based on the output values ​​of the two bridge circuits.

[0004] The amplitude of the output value of the bridge circuit is approximately constant. However, when a force acts from the input side of the reducer, such as when the motor accelerates, or when an external force acts from the output side of the reducer, the amplitude of the output value of the bridge circuit changes slightly due to the thrust force acting on the cam of the reducer. Specifically, when a force acts from the input side of the reducer, the amplitude of the output value of the bridge circuit becomes slightly smaller. On the other hand, when a force acts from the output side of the reducer, the amplitude of the output value of the bridge circuit becomes slightly larger. This causes an error in the detection value of the angle sensor.

[0005] An object of the present invention is to provide a technique capable of suppressing a change in the output value of an angle sensor due to a thrust force acting on a cam of a reducer. [Means for solving the problem]

[0006] The first invention is a wave reducer comprising a cam having a non-circular outer surface, a flex gear that undergoes bending deformation due to rotation of the cam, an internal gear that meshes with the flex gear, an angle sensor arranged on the flex gear and whose output value changes according to the rotation angle of the cam, a thrust sensor arranged on the flex gear and whose output value changes according to the thrust force applied to the cam, and a circuit electrically connected to the angle sensor and the thrust sensor, wherein the circuit corrects the output value of the angle sensor based on the output value of the thrust sensor.

[0007] A second invention is a drive system comprising a wave reducer and a circuit, wherein the wave reducer comprises a cam having a non-circular outer surface, a flex gear that undergoes bending deformation due to rotation of the cam, an internal gear that meshes with the flex gear, an angle sensor disposed on the flex gear and whose output value changes according to the rotation angle of the cam, and a thrust sensor disposed on the flex gear and whose output value changes according to the thrust force applied to the cam, and the circuit corrects the output value of the angle sensor based on the output value of the thrust sensor.

[0008] The third invention relates to a wave reducer including a cam having a non-circular outer surface, a flex gear that undergoes bending deformation due to rotation of the cam, an internal gear that meshes with the flex gear, an angle sensor arranged on the flex gear and whose output value changes according to the rotation angle of the cam, and a thrust sensor arranged on the flex gear and whose output value changes according to the thrust force acting on the cam. The method of correcting an output value of the angle sensor is to correct the output value of the angle sensor based on the output value of the thrust sensor.

[0009] A fourth invention is a wave reducer comprising a cam having a non-circular outer surface, a flex gear that undergoes a bending deformation due to rotation of the cam, an internal gear that meshes with the flex gear, an angle sensor arranged on the flex gear and whose output value changes according to the rotation angle of the cam, and a circuit electrically connected to the angle sensor, wherein the angle sensor has two bridge circuits composed of a plurality of strain gauges, the output values ​​of the two bridge circuits have a phase difference of 1 / 4 period, and the circuit corrects the output values ​​of the two bridge circuits so that the sum of the squares of the output values ​​of the two bridge circuits approaches a constant value.

[0010] A fifth invention is a drive system comprising a wave reducer and a circuit, the wave reducer comprising a cam having a non-circular outer surface, a flex gear that undergoes bending deformation due to rotation of the cam, an internal gear that meshes with the flex gear, and an angle sensor arranged on the flex gear and whose output value changes according to the rotation angle of the cam, the angle sensor having two bridge circuits composed of a plurality of strain gauges, the output values ​​of the two bridge circuits having a phase difference of 1 / 4 period, and the circuit correcting the output values ​​of the two bridge circuits so that the sum of the squares of the output values ​​of the two bridge circuits approaches a constant value.

[0011] A sixth invention is a correction method for correcting an output value of an angle sensor in a wave reducer including a cam having a non-circular outer surface, a flex gear that undergoes a flexural deformation due to rotation of the cam, an internal gear that meshes with the flex gear, and an angle sensor that is arranged on the flex gear and whose output value changes according to the rotation angle of the cam, wherein the angle sensor has two bridge circuits formed by a plurality of strain gauges, and the output values ​​of the two bridge circuits have a phase difference of 1 / 4 period, and the output values ​​of the two bridge circuits are corrected so that the sum of the squares of the output values ​​of the two bridge circuits approaches a constant value. Effect of the Invention

[0012] According to the first, second, third, fourth, fifth and sixth aspects of the invention, it is possible to suppress a change in the output value of the angle sensor due to a thrust force acting on the cam, thereby enabling the rotation angle to be detected with high accuracy. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram of an industrial machine. [Diagram 2] FIG. 2 is a vertical cross-sectional view of the reducer. [Diagram 3] FIG. 3 is a cross-sectional view of the reducer. [Figure 4] FIG. 4 is a partial vertical cross-sectional view of the flex gear in the vicinity of the sensor board. [Diagram 5] FIG. 5 is a plan view of the sensor substrate. [Figure 6] FIG. 6 is a circuit diagram of the first bridge circuit of the first torque sensor. [Figure 7] FIG. 7 is a circuit diagram of the second bridge circuit of the second torque sensor. [Figure 8] FIG. 8 is a circuit diagram of a third bridge circuit of the angle sensor. [Figure 9] FIG. 9 is a circuit diagram of the fourth bridge circuit of the angle sensor. [Figure 10] FIG. 10 is a graph showing changes over time in the output value of the third voltmeter of the third bridge circuit and the output value of the fourth voltmeter of the fourth bridge circuit. [Figure 11] FIG. 11 is a circuit diagram of a fifth bridge circuit of the thrust sensor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, exemplary embodiments of the present application will be described with reference to the drawings.

[0015] <1. Industrial machinery configuration> 1 is a schematic diagram of an industrial machine 100 equipped with a wave reducer 1 according to one embodiment. The industrial machine 100 is, for example, a so-called industrial robot that performs tasks such as transporting, processing, and assembling parts in a manufacturing line for industrial products. As shown in FIG. 1, the industrial machine 100 includes a base frame 101, an arm 102, a motor 103, and the wave reducer 1.

[0016] The arm 102 is rotatably supported with respect to the base frame 101. The motor 103 and the wave motion reducer 1 are incorporated in a joint between the base frame 101 and the arm 102. When a driving current is supplied to the motor 103, a rotational motion is output from the motor 103. The wave motion reducer 1 reduces the speed of the rotational motion output from the motor 103 and transmits it to the arm 102. As a result, the arm 102 rotates with respect to the base frame 101 at a reduced speed.

[0017] <2. Structure of the wave reducer> Next, the detailed structure of the wave reducer 1 will be described.

[0018] In the following, the direction parallel to the central axis 9 of the wave reducer 1 is referred to as the "axial direction", the direction perpendicular to the central axis 9 of the wave reducer 1 is referred to as the "radial direction", and the direction along the arc centered on the central axis 9 of the wave reducer 1 is referred to as the "circumferential direction". However, the above "parallel direction" also includes a substantially parallel direction. Furthermore, the above "perpendicular direction" also includes a substantially perpendicu- lar direction.

[0019] Fig. 2 is a vertical cross-sectional view of a wave reducer 1 according to one embodiment. Fig. 3 is a horizontal cross-sectional view of the wave reducer 1 as seen from position AA in Fig. 2. To avoid complicating the drawing, hatching indicating a cross section is omitted in Fig. 3.

[0020] The wave reducer 1 is a device that reduces the speed of rotational motion at a first rotation speed output from a motor 103 to a second rotation speed that is slower than the first rotation speed. As shown in Figures 2 and 3, the wave reducer 1 includes an input shaft 10, an internal gear 20, a flex gear 30, and a wave generator 40.

[0021] The input shaft 10 is a member that rotates at a first rotational speed before reduction. The input shaft 10 is connected to the output shaft of the motor 103. The input shaft 10 extends in the axial direction along the central axis 9. The input shaft 10 of this embodiment is cylindrical with the central axis 9 as its center. The input shaft 10 passes through the wave reducer 1 in the axial direction. Note that the input shaft 10 may be the same member as the output shaft of the motor 103.

[0022] The internal gear 20 is a gear that meshes with the flex gear 30. The internal gear 20 rotates at a second rotational speed slower than the first rotational speed in association with the rotation of the input shaft 10. The internal gear 20 is fixed to the arm 102. The internal gear 20 is disposed radially outside external teeth 32, which will be described later. The rigidity of the internal gear 20 is sufficiently higher than the rigidity of a body portion 31 of the flex gear 30, which will be described later.

[0023] The internal gear 20 is annular about the central axis 9. 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 arranged on the inner circumferential surface of the internal gear 20 at a constant pitch in the circumferential direction.

[0024] Flex gear 30 is a gear that undergoes flexural deformation due to rotation of cam 41, which will be described later. Flex gear 30 is fixed to base frame 101. As shown in FIGS. 2 and 3 , flex gear 30 has a body portion 31, a plurality of external teeth 32, a diaphragm portion 33, and a thick portion 34.

[0025] The body portion 31 is a cylindrical portion centered on the central axis 9. One axial end of the body portion 31 is connected to the diaphragm portion 33. The body portion 31 extends from a radially inner end of the diaphragm portion 33 toward the other axial side. The other axial end of the body portion 31 is located radially outside the wave generator 40 and radially inside the internal gear 20. The body portion 31 is flexible and therefore capable of bending and deforming in the radial direction.

[0026] The multiple external teeth 32 protrude radially outward from the radially outer surface of the body 31. The multiple external teeth 32 are arranged on the radially outer surface of the other axial end of the body 31. The multiple external teeth 32 are arranged at a constant pitch in the circumferential direction. Some of the multiple external teeth 32 and some of the multiple internal teeth 21 mesh with each other. The number of internal teeth 21 that the internal gear 20 has and the number of external teeth 32 that the flex gear 30 has are slightly different.

[0027] The diaphragm portion 33 surrounds the central axis 9 and extends in a direction intersecting the central axis 9. The diaphragm portion 33 preferably extends along a plane perpendicular to the central axis 9. The diaphragm portion 33 extends radially outward from one axial end of the body portion 31. The diaphragm portion 33 is annular and surrounds the central axis 9. The diaphragm portion 33 is thin-walled and therefore capable of slight flexural deformation.

[0028] The thick portion 34 is an annular portion located radially outward of the diaphragm portion 33. The axial thickness of the thick portion 34 is greater than the axial thickness of the diaphragm portion 33. The thick portion 34 is fixed to the base frame 101 directly or via another member.

[0029] The wave generator 40 is a mechanism that generates periodic bending deformation in the flex gear 30. The wave generator 40 is disposed radially inside the external teeth 32. The wave generator 40 has a cam 41 and a flexible bearing 42. In this embodiment, the input shaft 10 and the cam 41 are formed as a single part. However, the cam 41 may be a part separate from the input shaft 10. In that case, it is sufficient that the cam 41 is fixed to the input shaft 10. The cam 41 is a part that gives a displacement to the flex gear 30 at a period of 180°. The cam 41 has a non-circular outer surface. The cam 41 in this embodiment has an elliptical outer surface centered on the central axis 9.

[0030] The flexible bearing 42 is a bearing that is capable of flexibly deforming. The flexible bearing 42 is disposed between the radially outer surface of the cam 41 and the radially inner surface of the body portion 31 of the flex gear 30.

[0031] 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 deforms into an elliptical shape that follows the radially outer surface of the cam 41. As a result, the external teeth 32 of the flex gear 30 mesh with the internal teeth 21 of the internal gear 20 at two locations that correspond to both ends of the major axis of the ellipse. The external teeth 32 do not mesh with the internal teeth 21 at other circumferential positions.

[0032] When the motor 103 is driven, the cam 41 rotates together with the input shaft 10 at a first rotation speed around the central axis 9. As a result, the major axis of the ellipse of the flex gear 30 also rotates at the first rotation speed. Then, the meshing position between the external teeth 32 and the internal teeth 21 also changes in the circumferential direction at the first rotation speed. Also, as described above, the number of the internal teeth 21 of the internal gear 20 and the number of the external teeth 32 of the flex 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 for each rotation of the cam 41. As a result, the internal gear 20 rotates relative to the flex gear 30 at a second rotation speed slower than the first rotation speed around the central axis 9.

[0033] <3. About sensors> <3-1.Sensor structure> The wave reducer 1 has a sensor 50. As shown in Fig. 2, the sensor 50 has a sensor substrate 51. The sensor substrate 51 is fixed to the surface of the diaphragm portion 33.

[0034] Fig. 4 is a partial vertical cross-sectional view of flex gear 30 in the vicinity of sensor substrate 51. Fig. 5 is a plan view of sensor substrate 51. As shown in Fig. 4, sensor substrate 51 has insulating layer 511 and conductor layer 512.

[0035] The insulating layer 511 is flexibly deformable. The insulating layer 511 spreads in a direction intersecting the central axis 9. The insulating layer 511 is annular about the central axis 9. The insulating layer 511 is made of an insulating resin or an inorganic insulating material. The insulating layer 511 is disposed on the surface of the diaphragm portion 33. The conductor layer 512 is formed on the surface of the insulating layer 511. The conductor layer 512 is made of a metal that is a conductor. The conductor layer 512 is made of a material such as a copper alloy, a chromium alloy, or copper.

[0036] The conductor layer 512 includes a torque sensor 60, an angle sensor 70, and a thrust sensor 80. The torque sensor 60, the angle sensor 70, and the thrust sensor 80 are each configured with a strain gauge. As shown in FIG. 2, the sensor 50 has a circuit 52. The circuit 52 is electrically connected to the torque sensor 60, the angle sensor 70, and the thrust sensor 80.

[0037] <3-2. Torque sensor> The torque sensor 60 is a sensor for detecting the torque applied to the diaphragm portion 33 of the flex gear 30. In other words, the torque sensor 60 is a sensor whose output value changes according to the torque applied to the flex gear 30. As shown in Fig. 5, the torque sensor 60 of this embodiment has a first torque sensor 61 and a second torque sensor 62. The second torque sensor 62 is disposed radially outward of the first torque sensor 61.

[0038] The first torque sensor 61 has four strain gauges Ra, Rb, Rc, and Rd. Of the four strain gauges Ra, Rb, Rc, and Rd, two strain gauges Ra and Rb are arranged at intervals in the circumferential direction. The two strain gauges Ra and Rb are each provided in a semicircular 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 is approximately the same as the radial distance from the central axis 9 to the strain gauge Rb.

[0039] Of 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 an interval in the circumferential direction. The two strain gauges Rc and Rd are each provided in a semicircular 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 is approximately the same as the radial distance from the central axis 9 to the strain gauge Rd.

[0040] Moreover, the two strain gauges Ra, Rc and the two strain gauges Rb, Rd are arranged concentrically and line-symmetrically.

[0041] As shown in Fig. 5, the strain gauges Ra, Rb, Rc, and Rd each have a zigzag pattern extending in the circumferential direction. Each of the strain gauges Ra, Rb, Rc, and Rd has a plurality of resistance wires r1 arranged in the circumferential direction and substantially parallel to each other. Each resistance wire r1 extends in a direction having both radial and circumferential components.

[0042] The resistance wires r1 of the strain gauges Ra and Rd are inclined toward one circumferential side with respect to the radial direction. The resistance wires r1 of the strain gauges Rb and Rc are inclined toward the other circumferential side with respect to the radial direction. The inclination angle of the resistance wires r1 with respect to the radial direction is, for example, 45°. The ends of the resistance wires r1 adjacent to each other in the circumferential direction are alternately connected on the radial inside or the radial outside. As a result, the multiple resistance wires r1 are connected in series as a whole.

[0043] The second torque sensor 62 has four strain gauges Re, Rf, Rg, and Rh. Of the four strain gauges Re, Rf, Rg, and Rh, two strain gauges Re and Rf are arranged at intervals in the circumferential direction. The two strain gauges Re and Rf are each provided in a semicircular 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 Re is approximately the same as the radial distance from the central axis 9 to the strain gauge Rf.

[0044] Of the four strain gauges Re, Rf, Rg, and Rh, the other two strain gauges Rg and Rh are arranged radially outward of the above two strain gauges Re and Rf. The two strain gauges Rg and Rh are arranged at an interval in the circumferential direction. The two strain gauges Rg and Rh are each provided in a semicircular 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 Rg is approximately the same as the radial distance from the central axis 9 to the strain gauge Rh.

[0045] Moreover, the two strain gauges Re, Rg and the two strain gauges Rf, Rh are arranged concentrically and line-symmetrically.

[0046] As shown in Fig. 5, the strain gauges Re, Rf, Rg, and Rh each have a zigzag pattern extending in the circumferential direction. Each of the strain gauges Re, Rf, Rg, and Rh has a plurality of resistance wires r2 arranged in the circumferential direction and substantially parallel to each other. Each resistance wire r2 extends in a direction having both radial and circumferential components.

[0047] The resistance wires r2 of the strain gauges Re and Rh are inclined toward one circumferential side with respect to the radial direction. The resistance wires r2 of the strain gauges Rf and Rg are inclined toward the other circumferential side with respect to the radial direction. The inclination angle of the resistance wires r2 with respect to the radial direction is, for example, 45°. The ends of the resistance wires r2 adjacent in the circumferential direction are alternately connected on the radial inside or the radial outside. As a result, the multiple resistance wires r2 are connected in series as a whole.

[0048] Fig. 6 is a circuit diagram of a first bridge circuit C1 including four strain gauges Ra, Rb, Rc, and Rd of the first torque sensor 61. As shown in Fig. 6, the four strain gauges Ra, Rb, Rc, and Rd are connected to each other to form the first bridge circuit C1.

[0049] The strain gauges Ra and Rb are connected in series in this order. The strain gauges Rc and Rd are connected in series in this order. Then, between the positive and negative poles of the power supply voltage, a row of two strain gauges Ra, Rb and a row of two strain gauges Rc, Rd are connected in parallel. In addition, a first voltmeter V1 is connected between a midpoint M11 of the two strain gauges Ra, Rb and a midpoint M12 of the two strain gauges Rc, Rd.

[0050] The resistance value of each resistance wire r1 changes according to the torque applied to the area in which the resistance wire r1 is disposed. For example, when a torque is applied to the diaphragm portion 33 in one circumferential direction around the central axis 9, the resistance value of each resistance wire r1 of the two strain gauges Ra, Rd decreases, and the resistance value of each resistance wire r1 of the other two strain gauges Rb, Rc increases. On the other hand, when a torque is applied to the diaphragm portion 33 in the other circumferential direction around the central axis 9, the resistance value of each resistance wire r1 of the two strain gauges Ra, Rd increases, and the resistance value of each resistance wire r1 of the other two strain gauges Rb, Rc decreases. In this way, the two strain gauges Ra, Rd and the other two strain gauges Rb, Rc show resistance value changes in opposite directions with respect to torque.

[0051] 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, Rb and the midpoint M12 of the two strain gauges Rc, Rd changes, and the output value of the first voltmeter V1 also changes. The circuit 52 detects the direction and magnitude of the torque applied to the diaphragm portion 33 based on the output value of the first voltmeter V1.

[0052] Fig. 7 is a circuit diagram of a second bridge circuit C2 including four strain gauges Re, Rf, Rg, and Rh of the second torque sensor 62. As shown in Fig. 7, the four strain gauges Re, Rf, Rg, and Rh are connected to each other to form the second bridge circuit C2.

[0053] The strain gauges Re and Rf are connected in series in this order. The strain gauges Rg and Rh are connected in series in this order. Then, between the positive and negative poles of the power supply voltage, a row of two strain gauges Re, Rf and a row of two strain gauges Rg, Rh are connected in parallel. In addition, a second voltmeter V2 is connected between a midpoint M21 of the two strain gauges Re, Rf and a midpoint M22 of the two strain gauges Rg, Rh.

[0054] The resistance value of each resistance wire r2 changes according to the torque applied to the area in which the resistance wire r2 is disposed. For example, when a torque is applied to the diaphragm portion 33 in one circumferential direction around the central axis 9, the resistance value of each resistance wire r2 of the two strain gauges Re, Rh decreases, and the resistance value of each resistance wire r2 of the other two strain gauges Rf, Rg increases. On the other hand, when a torque is applied to the diaphragm portion 33 in the other circumferential direction around the central axis 9, the resistance value of each resistance wire r2 of the two strain gauges Re, Rh increases, and the resistance value of each resistance wire r2 of the other two strain gauges Rf, Rg decreases. In this way, the two strain gauges Re, Rh and the other two strain gauges Rf, Rg show resistance value changes in opposite directions with respect to torque.

[0055] When the resistance values ​​of the four strain gauges Re, Rf, Rg, and Rh change, the potential difference between the midpoint M21 of the two strain gauges Re and Rf and the midpoint M22 of the two strain gauges Rg and Rh changes, and the output value of the second voltmeter V2 also changes. The circuit 52 detects the direction and magnitude of the torque applied to the diaphragm portion 33 based on the output value of the second voltmeter V2.

[0056] Moreover, the wave reducer 1 of this embodiment has two torque sensors 61, 62. The circuit 52 uses one of the output signals of the two torque sensors 61, 62 as the output signal of the torque sensor 60. By having the two torque sensors 61, 62, even if an abnormality occurs in one of the torque sensors, the torque can be detected by the other torque sensor. Furthermore, if an abnormality occurs in one of the torque sensors, the abnormality can be detected.

[0057] <3-3.Angle sensor> The angle sensor 70 is a sensor for detecting the rotation angle of the rotational motion input to the wave reducer 1. In other words, the angle sensor 70 is a sensor whose output value changes according to the rotation angle of the cam 41. As shown in Fig. 5, the angle sensor 70 has eight strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp. The eight strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp are arranged at intervals in the circumferential direction.

[0058] Each of the eight strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp is formed by one conducting wire. Each of the strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp has a resistance wire extending in an arc shape along the circumferential direction. However, in each of the strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp, the resistance wire extending in the circumferential direction may be repeatedly arranged in the radial direction. Also, the resistance wire of each of the strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp may extend in the radial direction. Also, in each of the strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp, the resistance wire extending in the radial direction may be repeatedly arranged in the circumferential direction.

[0059] Of the eight strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp, the four 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. FIG. 8 is a circuit diagram of the third bridge circuit C3. As shown in FIG. 8, the strain gauge Ri and the strain gauge Rk are connected in series in this order. The strain gauge Ro and the strain gauge Rm are connected in series in this order. Then, between the positive and negative poles of the power supply voltage, a row of two strain gauges Ri and Rk and a row of two strain gauges Ro and Rm are connected in parallel. In addition, a third voltmeter V3 is connected between a midpoint M31 of the two strain gauges Ri and Rk and a midpoint M32 of the two strain gauges Ro and Rm.

[0060] Of the eight strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp, the remaining four strain gauges Rj, Rl, Rn, and Rp are connected to each other to form a fourth bridge circuit C4. FIG. 9 is a circuit diagram of the fourth bridge circuit C4. As shown in FIG. 9, the strain gauges Rp and Rn are connected in series in this order. The strain gauges Rj and Rl are connected in series in this order. Then, between the positive and negative poles of the power supply voltage, a row of two strain gauges Rp and Rn and a row of two strain gauges Rj and Rl are connected in parallel. In addition, a fourth voltmeter V4 is connected between a midpoint M41 of the two strain gauges Rp and Rn and a midpoint M42 of the two strain gauges Rj and Rl.

[0061] When the wave reducer 1 is driven, a portion that expands in the circumferential direction (hereinafter referred to as an "expanded portion") and a portion that contracts in the circumferential direction (hereinafter referred to as a "contracted portion") are generated in the diaphragm portion 33 of the flex gear 30. Specifically, two expanded portions and two contracted portions are generated alternately in the circumferential direction. That is, the expanded portions and contracted portions are generated alternately at intervals of 90° in the circumferential direction around the central axis 9. The locations where these expanded portions and contracted portions are generated rotate at the first rotation speed described above.

[0062] The resistance value of each of the eight strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp changes according to the circumferential expansion and contraction of the diaphragm portion 33. For example, when the above-mentioned expansion portion overlaps with a certain strain gauge, the resistance value of that strain gauge increases. Also, when the above-mentioned contraction portion overlaps with a certain strain gauge, the resistance value of that strain gauge decreases.

[0063] In the example of Fig. 5, when the contraction portion overlaps with the strain gauges Ri, Rm, the expansion portion overlaps with the strain gauges Rk, Ro. Also, when the expansion portion overlaps with the strain gauges Ri, Rm, the contraction portion overlaps with the strain gauges Rk, Ro. Therefore, in the third bridge circuit C3, the strain gauges Ri, Rm and the strain gauges Rk, Ro show resistance value changes in opposite directions.

[0064] 5, when the contraction portion overlaps with the strain gauges Rp, Rl, the expansion portion overlaps with the strain gauges Rn, Rj. When the expansion portion overlaps with the strain gauges Rp, Rl, the contraction portion overlaps with the strain gauges Rn, Rj. Therefore, in the fourth bridge circuit C4, the strain gauges Rp, Rl and the strain gauges Rn, Rj show opposite resistance value changes.

[0065] Thus, the angle sensor 70 has two bridge circuits C3, C4 configured with a plurality of strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp.

[0066] Fig. 10 is a graph showing the time change of the output value v3 of the third voltmeter V3 of the third bridge circuit C3 and the output value v4 of the fourth voltmeter V4 of the fourth bridge circuit C4. The horizontal axis of the graph in Fig. 10 represents time. The vertical axis of the graph in Fig. 10 represents voltage value. When the wave reducer 1 is driven, as shown in Fig. 10, periodically changing sinusoidal output values ​​v3 and v4 are obtained from the third voltmeter V3 and the fourth voltmeter V4, respectively. The period T of these output values ​​v3 and v4 corresponds to 1 / 2 the period of the first rotation speed described above.

[0067] Furthermore, the output value v3 of the third voltmeter V3 and the output value v4 of the fourth voltmeter V4 have a phase difference of 1 / 4 period. That is, the output values ​​of the two bridge circuits C3, C4 have a phase difference of 1 / 4 period. The direction of the input rotational motion can be determined based on whether the phase of the output value v4 of the fourth voltmeter V4 leads the phase of the output value v3 of the third voltmeter V3 by 1 / 8 period of the first rotation speed (1 / 4 period of the output values ​​v3, v4) or lags behind the phase of the output value v3 of the third voltmeter V3 by 1 / 8 period of the first rotation speed (1 / 4 period of the output values ​​v3, v4).

[0068] The circuit 52 detects the rotation angle of the rotary motion input to the wave reducer 1 based on the output value v3 of the third voltmeter V3 and the output value v4 of the fourth voltmeter V4. Specifically, the circuit 52 stores a function table that associates combinations of the output value v3 of the third voltmeter V3 and the output value v4 of the fourth voltmeter V4 with the rotation angle. The circuit 52 outputs the rotation angle by inputting the output values ​​v3 and v4 into the function table.

[0069] When the wave reducer 1 is driven, periodic flexural deformation occurs in the flex gear 30. For this reason, the output signal of the first torque sensor 61 and the output signal of the second torque sensor 62 described above contain a component reflecting the torque that is originally to be measured, and an error component (ripple error) caused by the periodic flexural deformation of the flex gear 30. The ripple error changes in a sinusoidal shape according to the rotation angle of the rotational motion input to the wave reducer 1.

[0070] Therefore, the circuit 52 calculates the above-mentioned ripple error according to the rotation angle detected by the angle sensor 70. Then, the output signals of the first torque sensor 61 and the second torque sensor 62 are corrected using the calculated ripple error. Specifically, the circuit 52 increases or decreases the output signals of the first torque sensor 61 and the second torque sensor 62 in a direction that cancels the ripple error. As a result, the circuit 52 can output the torque applied to the flex gear 30 with higher accuracy.

[0071] Alternatively, the circuit 52 may multiply the output values ​​v3 and v4 of the third voltmeter V3 and the fourth voltmeter V4 by a predetermined coefficient and combine the results with the output signals of the first torque sensor 61 and the second torque sensor 62, without calculating the rotation angle. In this way, the processing load for calculating the rotation angle can be reduced. Therefore, the calculation speed of the circuit 52 can be improved.

[0072] <3-4. Thrust sensor> The thrust sensor 80 is a sensor for detecting the thrust force acting on the cam 41. That is, the thrust sensor 80 is a sensor whose output value changes according to the thrust force acting on the cam 41. The thrust force is an axial force. As shown in FIG. 5, the thrust sensor 80 has two outer strain gauges Rq, Rr and two inner strain gauges Rs, Rt. The two inner strain gauges Rs, Rt are disposed radially inward of the two outer strain gauges Rq, Rr.

[0073] In this embodiment, the two outer strain gauges Rq, Rr are disposed radially outside the torque sensor 60. The two outer strain gauges Rq, Rr are also disposed at an interval in the circumferential direction. The two outer strain gauges Rq, Rr are each provided in a semicircular arc shape within a range of approximately 180° centered on the central axis 9. The radial distance from the central axis 9 to the outer strain gauge Rq is approximately the same as the radial distance from the central axis 9 to the outer strain gauge Rr.

[0074] In this embodiment, the two inner strain gauges Rs, Rt are disposed radially inside the torque sensor 60. The two inner strain gauges Rs, Rt are disposed at an interval in the circumferential direction. The two inner strain gauges Rs, Rt are each provided in a semicircular arc shape within a range of approximately 180° centered on the central axis 9. The radial distance from the central axis 9 to the inner strain gauge Rs is approximately the same as the radial distance from the central axis 9 to the inner strain gauge Rt.

[0075] That is, the two outer strain gauges Rq, Rr and the two inner strain gauges Rs, Rt are arranged at intervals in the radial direction.

[0076] As shown in FIG. 5, the outer strain gauges Rq, Rr and the inner strain gauges Rs, Rt each have a pattern that extends in the circumferential direction while winding in a zigzag pattern. Each of the strain gauges Rq, Rr, Rs, Rt has a plurality of resistance wires r3 arranged in the circumferential direction and substantially parallel to each other. Each resistance wire r3 extends in a radial direction centered on the central axis 9 of the flex gear 30. The ends of the resistance wires r3 adjacent in the circumferential direction are alternately connected to each other on the radially inner side or the radially outer side. As a result, the plurality of resistance wires r3 are connected in series as a whole.

[0077] 11 is a circuit diagram of a fifth bridge circuit C5 including outer strain gauges Rq, Rr and inner strain gauges Rs, Rt of the thrust sensor 80. As shown in FIG 11, the two outer strain gauges Rq, Rr and the two inner strain gauges Rs, Rt are connected together to form the fifth bridge circuit C5.

[0078] The strain gauges Rq and Rs are connected in series in this order. The strain gauges Rt and Rr are connected in series in this order. Then, between the positive and negative poles of the power supply voltage, a row of two strain gauges Rq, Rs and a row of two strain gauges Rt, Rr are connected in parallel. In addition, a fifth voltmeter V5 is connected between a midpoint M51 of the two strain gauges Rq, Rs and a midpoint M52 of the two strain gauges Rt, Rr.

[0079] The resistance wires r3 included in the four strain gauges Rq, Rr, Rs, and Rt of the thrust sensor 80 all extend in the radial direction. Therefore, the change in the resistance value of the strain gauges Rq, Rr, Rs, and Rt due to the torque in the circumferential direction is extremely small. However, when the diaphragm portion 33 of the flex gear 30 is displaced in the axial direction, the resistance value of the strain gauges Rq, Rr, Rs, and Rt changes.

[0080] Specifically, when the radially inner end of the diaphragm portion 33 is displaced in a direction toward the internal gear 20, the resistance values ​​of the two outer strain gauges Rq, Rr among the four strain gauges Rq, Rr, Rs, and Rt increase, and the resistance values ​​of the two inner strain gauges Rs, Rt decrease. On the other hand, when the radially inner end of the diaphragm portion 33 is displaced in a direction away from the internal gear 20, the resistance values ​​of the two outer strain gauges Rq, Rr among the four strain gauges Rq, Rr, Rs, and Rt decrease, and the resistance values ​​of the two inner strain gauges Rs, Rt increase. In this way, the two outer strain gauges Rq, Rr and the two inner strain gauges Rs, Rt show resistance value changes in opposite directions to each other with respect to the axial displacement of the diaphragm portion 33.

[0081] When the resistance values ​​of the four strain gauges Rq, Rr, Rs, and Rt change, the potential difference between the midpoint M51 of the two strain gauges Rq, Rs and the midpoint M52 of the two strain gauges Rt, Rr changes, and the output value of the fifth voltmeter V5 also changes. Based on the output value of the fifth voltmeter V5, the circuit 52 detects the direction and magnitude of the thrust force acting on the flex gear 30.

[0082] <3-5. Angle sensor correction> <3-5-1. First embodiment> As described above, the angle sensor 70 has two bridge circuits C3 and C4. The output values ​​v3 and v4 of these bridge circuits C3 and C4 are sinusoidal and have a phase difference of 1 / 4 period. The amplitude of the output values ​​v3 and v4 is approximately constant. However, when a force acts from the input side of the wave reducer 1, such as when the motor 103 accelerates, or when an external force acts from the output side of the wave reducer 1 due to the inertial force of the arm 102, the thrust force applied to the cam 41 causes the amplitude of the output values ​​v3 and v4 of the two bridge circuits C3 and C4 to change slightly.

[0083] Specifically, when a force acts from the input side of the wave reducer 1, the amplitudes of the output values ​​v3, v4 of the two bridge circuits C3, C4 become slightly smaller. On the other hand, when a force acts from the output side of the wave reducer 1, the amplitudes of the output values ​​v3, v4 of the two bridge circuits C3, C4 become slightly larger.

[0084] Therefore, the circuit 52 corrects the output value of the angle sensor 70 based on the output value of the thrust sensor 80. Specifically, the circuit 52 corrects the output values ​​v3 and v4 of the two bridge circuits C3 and C4, respectively. More specifically, the circuit 52 increases or decreases the output values ​​v3 and v4 of the two bridge circuits C3 and C4 in a direction that cancels the influence of the thrust force. In this way, it is possible to suppress the output value of the angle sensor 70 from being changed due to the thrust force acting on the cam 41. Therefore, the rotation angle of the cam 41 can be detected with high accuracy based on the corrected output values ​​v3 and v4 of the angle sensor 70.

[0085] Furthermore, the circuit 52 corrects the output value of the torque sensor 60 based on the output values ​​v3, v4 of the angle sensor 70 after correction based on the output value of the thrust sensor 80. Specifically, the circuit 52 calculates the above-mentioned ripple error based on the corrected output values ​​v3, v4 of the angle sensor 70, and corrects the output value of the torque sensor 60 to cancel the ripple error. This makes it possible to detect the torque applied to the flex gear 30 with greater accuracy.

[0086] <3-5-2. Second embodiment> Next, a method for correcting the output value of the angle sensor 70 caused by the thrust force without using the output value of the thrust sensor 80 will be described.

[0087] The output values ​​v3 and v4 of the two bridge circuits C3 and C4 of the angle sensor 70 have a sine wave and cosine wave relationship. Therefore, the sum of the squares of these output values ​​v3 and v4, v3^2+v4^2, is always a constant value in an ideal state. However, when a force acts from the input side or output side of the wave reducer 1, an error occurs in the amplitude of the output values ​​v3 and v4 due to the thrust force acting on the cam 41, so that the sum of the squares of the output values ​​v3 and v4, v3^2+v4^2, deviates from a constant value.

[0088] Therefore, the circuit 52 corrects the output values ​​v3, v4 of the two bridge circuits C3, C4 so that the sum of the squares of the output values ​​v3, v4 of the two bridge circuits C3, C4, v3^2+v4^2, approaches a constant value. For example, the circuit 52 normalizes the output values ​​v3, v4 so that the sum of the squares of the output values ​​v3, v4, v3^2+v4^2, always becomes a constant value. In this way, even when a force acts from the input side or the output side of the wave reducer 1, it is possible to suppress the output values ​​v3, v4 of the bridge circuits C3, C4 from changing due to the thrust force acting on the cam 41. Therefore, the rotation angle of the cam 41 can be detected with high accuracy by the corrected output values ​​v3, v4 of the angle sensor 70.

[0089] Furthermore, the circuit 52 corrects the output value of the torque sensor 60 based on the output values ​​v3, v4 of the angle sensor 70 after correction by the above-mentioned normalization. Specifically, the circuit 52 calculates the above-mentioned ripple error based on the corrected output values ​​v3, v4 of the angle sensor 70, and corrects the output value of the torque sensor 60 so as to cancel the ripple error. This makes it possible to detect the torque applied to the flex gear 30 with higher accuracy.

[0090] Furthermore, the circuit 52 may output the correction amount of the output values ​​v3 and v4 due to the above-mentioned normalization as a detection value representing the thrust force acting on the cam 41.

[0091] Furthermore, the circuit 52 may output an alert signal when the sum of the squares of the output values ​​v3, v4 of the two bridge circuits C3, C4 is outside a predetermined range. The alert signal is a signal indicating that at least one of the output values ​​v3, v4 of the angle sensor 70 may be abnormal. In this way, the control unit or the user of the industrial machine 100 can recognize that at least one of the output values ​​v3, v4 of the angle sensor 70 may be abnormal based on the alert signal. Therefore, the operation of the industrial machine 100 can be stopped and measures such as inspection of the angle sensor 70 can be taken.

[0092] <4. Modifications> Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. Various modifications will be described below, focusing on the differences from the above embodiment.

[0093] <4-1. First modified example> In the above embodiment, the wave reducer 1 includes the circuit 52 for correcting the output value of the angle sensor 70. However, the circuit 52 may be provided outside the wave reducer 1. In other words, the wave reducer 1 and the circuit 52 may form a drive system.

[0094] In this case, the angle sensor 70 and thrust sensor 80 of the wave reducer 1 are electrically connected to a circuit 52 provided outside the wave reducer 1, and the circuit 52 corrects the output value of the angle sensor 70 based on the output value of the thrust sensor 80.

[0095] Alternatively, the angle sensor 70 of the wave motion reducer 1 and a circuit 52 provided outside the wave motion reducer 1 may be electrically connected, and the circuit 52 may correct the output values ​​v3, v4 of the two bridge circuits C3, C4 of the angle sensor 70 so that the sum v3^2+v4^2 of the squares of the output values ​​v3, v4 of the two bridge circuits C3, C4 may approach a constant value.

[0096] Furthermore, one circuit 52 may correct the output values ​​of the angle sensors 70 of multiple wave reducers 1.

[0097] <4-2. Other variations> In the above embodiment, the torque sensor 60 includes the first torque sensor 61 and the second torque sensor 62. However, the torque sensor 60 may include only one of the first torque sensor 61 and the second torque sensor 62.

[0098] In the above embodiment, the thrust sensor 80 has only one fifth bridge circuit C5 configured by the outer strain gauges Rq, Rr and the inner strain gauges Rs, Rt. However, the thrust sensor 80 may have two fifth bridge circuits C5 configured by the outer strain gauges Rq, Rr and the inner strain gauges Rs, Rt. In this way, even if an abnormality occurs in one of the fifth bridge circuits C5, the thrust force can be detected by the other fifth bridge circuit C5. Furthermore, if an abnormality occurs in one of the fifth bridge circuits C5, the abnormality can be detected.

[0099] In the wave reducer 1 of the above embodiment, the flex gear 30 is fixed to the base frame 101, and the internal gear 20 rotates at the second rotation speed after deceleration. However, the internal gear 20 may be fixed to the base frame 101, and the flex gear 30 may rotate at the second rotation speed after deceleration.

[0100] The flex gear 30 in the above embodiment is a so-called "hat-shaped" gear in which the diaphragm portion 33 spreads outward in the radial direction from the body portion 31. However, the flex gear 30 may be a so-called "cup-shaped" gear in which the diaphragm portion 33 spreads inward in the radial direction from the body portion 31.

[0101] In the above embodiment, the industrial machine 100 is an industrial robot having an arm. However, the industrial machine 100 may be another device such as an assist suit or an unmanned transport vehicle.

[0102] In addition, the detailed configurations of the wave reducer, the industrial machine, and the drive system may be modified as appropriate without departing from the spirit of the present invention. Furthermore, the elements appearing in the above-described embodiment and modified examples may be combined as appropriate without causing any contradiction.

[0103] <5. Summary> The present technology can have the following configurations.

[0104] (1) A wave reducer comprising a cam having a non-circular outer surface, a flex gear that undergoes a bending deformation due to rotation of the cam, an internal gear that meshes with the flex gear, an angle sensor disposed on the flex gear and whose output value changes according to the rotation angle of the cam, a thrust sensor disposed on the flex gear and whose output value changes according to the thrust force acting on the cam, and a circuit electrically connected to the angle sensor and the thrust sensor, wherein the circuit corrects the output value of the angle sensor based on the output value of the thrust sensor.

[0105] (2) A wave reducer as described in (1), wherein the angle sensor has two sets of bridge circuits formed by a plurality of strain gauges, the output values ​​of the two sets of bridge circuits have a phase difference of 1 / 4 period, and the circuit corrects the output values ​​of the two sets of bridge circuits, respectively.

[0106] (3) A wave reducer as described in (1) or (2), further comprising a torque sensor whose output value changes depending on the torque applied to the flex gear, and the circuit corrects the output value of the torque sensor based on the output value of the angle sensor after being corrected based on the output value of the thrust sensor.

[0107] (4) A wave reducer described in any one of (1) to (3), wherein the thrust sensor has a bridge circuit including an outer strain gauge having a resistance wire extending radially around the central axis of the flex gear, and an inner strain gauge having a resistance wire extending radially around the central axis of the flex gear and positioned radially inward of the outer strain gauge.

[0108] (5) An industrial machine equipped with a wave reducer according to any one of (1) to (4).

[0109] (6) A drive system comprising a wave reducer and a circuit, wherein the wave reducer comprises a cam having a non-circular outer surface, a flex gear that undergoes bending deformation due to rotation of the cam, an internal gear that meshes with the flex gear, an angle sensor disposed on the flex gear and whose output value changes according to the rotation angle of the cam, and a thrust sensor disposed on the flex gear and whose output value changes according to the thrust force applied to the cam, and the circuit corrects the output value of the angle sensor based on the output value of the thrust sensor.

[0110] (7) A method for correcting an output value of an angle sensor in a wave reducer including a cam having a non-circular outer surface, a flex gear that undergoes a bending deformation due to rotation of the cam, an internal gear that meshes with the flex gear, an angle sensor arranged on the flex gear and whose output value changes according to the rotation angle of the cam, and a thrust sensor arranged on the flex gear and whose output value changes according to the thrust force acting on the cam, the method comprising the steps of: correcting an output value of the angle sensor based on an output value of the thrust sensor.

[0111] (8) A wave reducer comprising a cam having a non-circular outer surface, a flex gear that undergoes bending deformation due to rotation of the cam, an internal gear that meshes with the flex gear, an angle sensor arranged on the flex gear and whose output value changes according to the rotation angle of the cam, and a circuit electrically connected to the angle sensor, wherein the angle sensor has two bridge circuits constituted by a plurality of strain gauges, the output values ​​of the two bridge circuits have a phase difference of 1 / 4 period, and the circuit corrects the output values ​​of the two bridge circuits so that the sum of the squares of the output values ​​of the two bridge circuits approaches a constant value.

[0112] (9) A wave reducer according to (8), The circuit outputs a correction amount of the output value of the bridge circuit as a detection value representing the thrust force acting on the cam.

[0113] (10) A wave reducer as described in (8) or (9), wherein the circuit outputs an alert signal when the sum of the squares of the output values ​​of the two bridge circuits is outside a predetermined range.

[0114] (11) A drive system including a wave reducer and a circuit, wherein the wave reducer includes a cam having a non-circular outer surface, a flex gear that undergoes bending deformation due to rotation of the cam, an internal gear that meshes with the flex gear, and an angle sensor that is disposed on the flex gear and whose output value changes according to the rotation angle of the cam, wherein the angle sensor has two bridge circuits formed by a plurality of strain gauges, and the output values ​​of the two bridge circuits have a phase difference of 1 / 4 period, and the circuit corrects the output values ​​of the two bridge circuits so that the sum of the squares of the output values ​​of the two bridge circuits approaches a constant value.

[0115] (12) A method for correcting an output value of an angle sensor in a wave reducer including a cam having a non-circular outer surface, a flex gear that undergoes a flexural deformation due to rotation of the cam, an internal gear that meshes with the flex gear, and an angle sensor that is arranged on the flex gear and whose output value changes according to the rotation angle of the cam, the method comprising the steps of: correcting an output value of the angle sensor; the angle sensor having two bridge circuits formed by a plurality of strain gauges; output values ​​of the two bridge circuits having a phase difference of 1 / 4 period; and correcting the output values ​​of the two bridge circuits so that a sum of the squares of the output values ​​of the two bridge circuits approaches a constant value. [Industrial Applicability]

[0116] INDUSTRIAL APPLICABILITY The present invention can be used in a wave reducer, an industrial machine, a drive system, and a correction method. [Explanation of symbols]

[0117] 1 Wave reducer 9 Center axis 10 Input shaft 20 Internal Gear 30 Flex Gear 40 Wave Generator 41 Cam 50 Sensors 52 Circuit 60,61,62 Torque sensor 70 Angle Sensor 80 Thrust Sensor 100 Industrial Machinery C1-C5 bridge circuit Ra-Rt strain gauge V1-V5 Voltmeter r1-r3 resistance wire

Claims

1. a cam having a non-circular outer surface; a flex gear that undergoes bending deformation due to rotation of the cam; an internal gear that meshes with the flex gear; an angle sensor disposed on the flex gear, the output value of which changes in response to a rotation angle of the cam; a thrust sensor disposed on the flex gear, the output value of which changes in response to a thrust force applied to the cam; a circuit electrically connected to the angle sensor and the thrust sensor; A wave reducer comprising: The circuit corrects the output value of the angle sensor based on the output value of the thrust sensor.

2. The wave reducer according to claim 1, The angle sensor is Two bridge circuits consisting of multiple strain gauges having The output values ​​of the two bridge circuits have a phase difference of 1 / 4 period, The circuit corrects the output values ​​of the two sets of bridge circuits, respectively.

3. The wave reducer according to claim 1 or 2, A torque sensor whose output value changes according to the torque applied to the flex gear Further equipped with The circuit corrects the output value of the torque sensor based on the output value of the angle sensor after being corrected based on the output value of the thrust sensor.

4. The wave reducer according to claim 1 or 2, The thrust sensor includes: an outer strain gauge having a resistance wire extending in a radial direction centered on a central axis of the flex gear; an inner strain gauge having a resistance wire extending in a radial direction centered on a central axis of the flex gear and disposed radially inward of the outer strain gauge; A wave reducer having a bridge circuit including:

5. An industrial machine comprising the wave reducer according to claim 1 or 2.

6. A drive system including a wave reducer and a circuit, The wave reducer includes: a cam having a non-circular outer surface; a flex gear that undergoes bending deformation due to rotation of the cam; an internal gear that meshes with the flex gear; an angle sensor disposed on the flex gear, the output value of which changes in response to a rotation angle of the cam; a thrust sensor disposed on the flex gear, the output value of which changes in response to a thrust force applied to the cam; Equipped with The circuit corrects the output value of the angle sensor based on the output value of the thrust sensor.

7. a cam having a non-circular outer surface; a flex gear that undergoes bending deformation due to rotation of the cam; an internal gear that meshes with the flex gear; an angle sensor disposed on the flex gear, the output value of which changes in response to a rotation angle of the cam; a thrust sensor disposed on the flex gear, the output value of which changes in response to a thrust force applied to the cam; A method for correcting an output value of the angle sensor in a wave reducer comprising the steps of: A correction method for correcting an output value of the angle sensor based on an output value of the thrust sensor.

8. a cam having a non-circular outer surface; a flex gear that undergoes bending deformation due to rotation of the cam; an internal gear that meshes with the flex gear; an angle sensor disposed on the flex gear, the output value of which changes in response to a rotation angle of the cam; A circuit electrically connected to the angle sensor; A wave reducer comprising: The angle sensor is Two bridge circuits consisting of multiple strain gauges having The output values ​​of the two bridge circuits have a phase difference of 1 / 4 period, The circuit corrects the output values ​​of the two bridge circuits so that the sum of the squares of the output values ​​of the two bridge circuits approaches a constant value.

9. The wave reducer according to claim 8, The circuit outputs a correction amount of the output value of the bridge circuit as a detection value representing the thrust force acting on the cam.

10. The wave reducer according to claim 8 or 9, The circuit outputs an alert signal when the sum of the squares of the output values ​​of the two bridge circuits is outside a predetermined range.

11. A drive system including a wave reducer and a circuit, The wave reducer includes: a cam having a non-circular outer surface; a flex gear that undergoes bending deformation due to rotation of the cam; an internal gear that meshes with the flex gear; an angle sensor disposed on the flex gear, the output value of which changes in response to a rotation angle of the cam; Equipped with The angle sensor is Two bridge circuits consisting of multiple strain gauges having The output values ​​of the two bridge circuits have a phase difference of 1 / 4 period, The circuit corrects the output values ​​of the two bridge circuits so that a sum of the squares of the output values ​​of the two bridge circuits approaches a constant value.

12. a cam having a non-circular outer surface; a flex gear that undergoes bending deformation due to rotation of the cam; an internal gear that meshes with the flex gear; an angle sensor disposed on the flex gear, the output value of which changes in response to a rotation angle of the cam; A method for correcting an output value of the angle sensor in a wave reducer comprising the steps of: The angle sensor is Two bridge circuits consisting of multiple strain gauges having The output values ​​of the two bridge circuits have a phase difference of 1 / 4 period, a correction method for correcting output values ​​of the two bridge circuits so that a sum of squares of output values ​​of the two bridge circuits approaches a constant value.

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