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

Abstract

The invention provides a wave speed reducer, an industrial machine, a drive system, and a correction method. The wave speed reducer has a cam, a flexible gear, an internal gear, an angle sensor, a thrust sensor, and a circuit. The angle sensor is disposed on the flexible gear, and the output value of the angle sensor changes according to the rotation angle of the cam. The thrust sensor is disposed on the flexible gear, and the output value of the thrust sensor changes according to the thrust applied to the cam. And the circuit is electrically connected with the angle sensor and the thrust sensor. The circuit corrects the output value of the angle sensor according to the output value of the thrust sensor.

Description

Technical Field

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

[0002] Conventionally, there is known a speed reducer including a detection device having a plurality of strain gauges (for example, Patent Document 1).

[0003] Patent Document 1: Japanese Patent Application Publication No. 2004-198400

[0004] In this reducer, an angle sensor can be formed by using a plurality of strain gauges. In this case, two sets of bridge circuits are formed by a plurality of strain gauges. The output values ​​of the two sets of bridge circuits are sinusoidal. The two sets of bridge circuits are configured in a manner that has a phase difference of 1 / 4 cycle with each other. The angle sensor detects the rotation angle of the rotational motion input to the reducer based on the output values ​​of the two sets of bridge circuits.

[0005] The amplitude of the output value of the above-mentioned bridge circuit is approximately constant. However, when a force acts from the input side of the reducer or an external force acts from the output side of the reducer, such as when the motor is accelerated, the amplitude of the output value of the bridge circuit changes slightly due to the thrust of the cam applied to 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. In addition, when a force acts from the output side of the reducer, the amplitude of the output value of the bridge circuit becomes slightly larger. As a result, an error occurs in the detection value of the angle sensor. Summary of the invention

[0006] An object of the present invention is to provide a technology capable of suppressing a change in an output value of an angle sensor due to a thrust force applied to a cam of a speed reducer.

[0007] The first exemplary invention of the present application is a wave reducer, which comprises: a cam having an outer surface that is not a perfect circle; a flexible gear that generates flexural deformation through the rotation of the cam; an internal gear that meshes with the flexible gear; an angle sensor arranged on the flexible gear, the output value of which varies according to the rotation angle of the cam; a thrust sensor arranged on the flexible gear, the output value of which varies according to the thrust 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 according to the output value of the thrust sensor.

[0008] The second exemplary invention of the present application is a drive system having a wave reducer and a circuit, wherein the wave reducer has: a cam having a non-circular outer surface; a flexible gear that generates flexural deformation through the rotation of the cam; an internal gear that meshes with the flexible gear; an angle sensor disposed on the flexible gear, the output value of which varies according to the rotation angle of the cam; and a thrust sensor disposed on the flexible gear, the output value of which varies according to the thrust applied to the cam, and the circuit corrects the output value of the angle sensor according to the output value of the thrust sensor.

[0009] The third exemplary invention of the present application is a correction method, which corrects the output value of an angle sensor in a wave reducer, wherein the wave reducer has: a cam having a non-circular outer surface; a flexible gear that generates flexural deformation through the rotation of the cam; an internal gear that meshes with the flexible gear; the angle sensor, which is arranged on the flexible gear, and the output value of the angle sensor varies according to the rotation angle of the cam; and a thrust sensor, which is arranged on the flexible gear, and the output value of the thrust sensor varies according to the thrust applied to the cam, wherein the output value of the angle sensor is corrected according to the output value of the thrust sensor.

[0010] The exemplary fourth invention of the present application is a wave reducer, which comprises: a cam having an outer surface that is not a perfect circle; a flexible gear that generates flexural deformation through the rotation of the cam; an internal gear that meshes with the flexible gear; an angle sensor that is arranged on the flexible gear, and the output value of the angle sensor changes according to the rotation angle of the cam; and a circuit that is electrically connected to the angle sensor, wherein the angle sensor has two sets of bridge circuits composed of multiple strain gauges, the output values ​​of the two sets of bridge circuits have a phase difference of 1 / 4 cycle, and the circuit corrects the output values ​​of the two sets of bridge circuits so that the sum of the squares of the output values ​​of the two sets of bridge circuits is close to a constant value.

[0011] The exemplary fifth invention of the present application is a drive system having a wave reducer and a circuit, wherein the wave reducer has: a cam having an outer surface that is not a perfect circle; a flexible gear that generates flexural deformation through the rotation of the cam; an internal gear that meshes with the flexible gear; and an angle sensor disposed on the flexible gear, wherein the output value of the angle sensor varies according to the rotation angle of the cam, the angle sensor having two sets of bridge circuits composed of a plurality of strain gauges, the output values ​​of the two sets of bridge circuits having a phase difference of 1 / 4 cycle, and the circuit correcting the output values ​​of the two sets of bridge circuits so that the sum of the squares of the output values ​​of the two sets of bridge circuits approaches a constant value.

[0012] The exemplary sixth invention of the present application is a correction method, which corrects the output value of an angle sensor in a wave reducer, wherein the wave reducer has: a cam having an outer surface that is not a perfect circle; a flexible gear that generates flexural deformation through the rotation of the cam; an internal gear that meshes with the flexible gear; and the angle sensor, which is arranged on the flexible gear, and the output value of the angle sensor changes according to the rotation angle of the cam, wherein the angle sensor has two groups of bridge circuits composed of multiple strain gauges, and the output values ​​of the two groups of bridge circuits have a phase difference of 1 / 4 cycle, and the correction method corrects the output values ​​of the two groups of bridge circuits so that the sum of the squares of the output values ​​of the two groups of bridge circuits is close to a constant value.

[0013] According to the exemplary first, second, third, fourth, fifth and sixth inventions of the present application, it is possible to suppress the output value of the angle sensor from changing due to the thrust applied to the cam, thereby enabling the rotation angle to be detected with high accuracy.

[0014] The above and other features, elements, steps, characteristics and advantages of the present invention will be more clearly understood from the following detailed description of preferred embodiments of the present invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of industrial machinery.

[0016] Figure 2 It is a longitudinal section view of the reducer.

[0017] Figure 3 It is a cross-sectional view of the reducer.

[0018] Figure 4 It is a partial longitudinal sectional view of the flexible gear near the sensor substrate.

[0019] Figure 5 is a top view of the sensor substrate.

[0020] Figure 6 This is a circuit diagram of a first bridge circuit of a first torque sensor.

[0021] Figure 7 This is a circuit diagram of a second bridge circuit of the second torque sensor.

[0022] Figure 8 This is a circuit diagram of the third bridge circuit of the angle sensor.

[0023] Fig. 9 This is a circuit diagram of the 4th bridge circuit of the angle sensor.

[0024] Fig.10It is a graph showing the time change of 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.

[0025] Fig.11 This is the circuit diagram of the fifth bridge circuit of the thrust sensor. DETAILED DESCRIPTION

[0026] Hereinafter, exemplary embodiments of the present application will be described with reference to the drawings.

[0027] <1. Structure of industrial machinery>

[0028] Figure 1 1 is a schematic diagram of an industrial machine 100 having a wave speed reducer 1 according to an embodiment. The industrial machine 100 is, for example, a so-called industrial robot that performs operations such as transporting, processing, and assembling parts in a production line of industrial products. Figure 1 As shown, the industrial machine 100 has a base frame 101 , an arm 102 , a motor 103 , and a ripple speed reducer 1 .

[0029] The arm 102 is supported so as to be rotatable relative to the base frame 101. The motor 103 and the wave speed reducer 1 are assembled at the 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 speed reducer 1 decelerates the rotational motion output from the motor 103 and transmits it to the arm 102. As a result, the arm 102 rotates relative to the base frame 101 at a decelerated speed.

[0030] <2. Structure of the wave reducer>

[0031] Next, the detailed structure of the wave speed reducer 1 will be described.

[0032] In addition, hereinafter, 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-mentioned "parallel direction" also includes a substantially parallel direction. In addition, the above-mentioned "vertical direction" also includes a substantially perpendicular direction.

[0033] Figure 2 It is a longitudinal sectional view of the wave speed reducer 1 of one embodiment. Figure 3 is from Figure 2 The cross-sectional view of the wave reducer 1 observed from the AA position of FIG. Figure 3 In the figure, hatching indicating cross sections is omitted.

[0034] The wave speed reducer 1 is a device that reduces the rotational motion of a first rotation speed output from the motor 103 to a second rotation speed that is slower than the first rotation speed. Figure 2 and Figure 3 As shown, the wave speed reducer 1 has an input shaft 10 , an internal gear 20 , a flexible gear 30 , and a wave generator 40 .

[0035] The input shaft 10 is a component that rotates at a first speed before deceleration. The input shaft 10 is connected to the output shaft of the motor 103. The input shaft 10 extends axially along the central axis 9. The input shaft 10 of the present embodiment is cylindrical with the central axis 9 as the center. The input shaft 10 penetrates the wave reducer 1 in the axial direction. In addition, the input shaft 10 may also be the same component as the output shaft of the motor 103.

[0036] The internal gear 20 is a gear meshing with the flexible gear 30. The internal gear 20 rotates at a second speed slower than the first speed as the input shaft 10 rotates. The internal gear 20 is fixed to the arm 102. The internal gear 20 is arranged radially outside the external teeth 32 described later. The rigidity of the internal gear 20 is sufficiently higher than the rigidity of the body 31 of the flexible gear 30 described later.

[0037] The internal gear 20 is annular centered on 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.

[0038] The flexible gear 30 is a gear that is deformed by the rotation of the cam 41 described later. The flexible gear 30 is fixed to the base frame 101. Figure 2 and Figure 3 As shown, the flexible gear 30 has a body portion 31 , a plurality of external teeth 32 , a diaphragm portion 33 , and a thick wall portion 34 .

[0039] The body 31 is a cylindrical portion centered on the central axis 9. One axial end of the body 31 is connected to the diaphragm 33. The body 31 extends from the radial inner end of the diaphragm 33 toward the other axial side. The end of the body 31 on the other axial side is located radially outside the wave generator 40 and radially inside the internal gear 20. The body 31 has flexibility and can be bent and deformed in the radial direction.

[0040] The plurality of external teeth 32 protrude radially outward from the radial outer side of the body 31. The plurality of external teeth 32 are arranged on the radial outer side of the other axial end of the body 31. The plurality of external teeth 32 are arranged at a constant pitch in the circumferential direction. A portion of the plurality of external teeth 32 meshes with a portion of the plurality of internal teeth 21 mentioned above. The number of internal teeth 21 of the internal gear 20 is slightly different from the number of external teeth 32 of the flexible gear 30.

[0041] 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 from one axial end of the body portion 31 toward the radial outer side. In addition, the diaphragm portion 33 is annular and surrounds the central axis 9. The diaphragm portion 33 is thin-walled and can be slightly deformed.

[0042] The thick portion 34 is an annular portion located radially outside the diaphragm portion 33. The axial thickness of the thick portion 34 is thicker 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.

[0043] The wave generator 40 is a mechanism that causes the flexible gear 30 to generate periodic flexural deformation. The wave generator 40 is arranged on the radial inner side of the external tooth 32. The wave generator 40 has a cam 41 and a flexible bearing 42. In the present embodiment, the input shaft 10 and the cam 41 are formed by one component. However, the cam 41 can also be a component different from the input shaft 10. In this case, it is sufficient to fix the cam 41 relative to the input shaft 10. The cam 41 is a component that imparts displacement to the flexible gear 30 with a period of 180°. The cam 41 has an outer surface that is not a perfect circle. The cam 41 of the present embodiment has an elliptical outer surface centered on the central axis 9.

[0044] The flexible bearing 42 is a bearing capable of flexural deformation and is disposed between the radially outer side surface of the cam 41 and the radially inner side surface of the body portion 31 of the flexible gear 30 .

[0045] The inner ring of the flexible bearing 42 contacts the radial outer side of the cam 41. The outer ring of the flexible bearing 42 contacts the radial inner side of the body 31. Therefore, the body 31 is deformed into an elliptical shape along the radial outer side of the cam 41. As a result, the outer teeth 32 of the flexible gear 30 mesh with the inner teeth 21 of the internal gear 20 at two locations corresponding to the ends of the major axis of the ellipse. At other locations in the circumferential direction, the outer teeth 32 and the inner teeth 21 do not mesh.

[0046] When the motor 103 is driven, the cam 41 rotates together with the input shaft 10 at the first speed around the central axis 9. As a result, the major axis of the above-mentioned ellipse of the flexible gear 30 also rotates at the first speed. As a result, the meshing position of the external teeth 32 and the internal teeth 21 also changes in the circumferential direction at the first speed. In addition, as described above, the number of internal teeth 21 of the internal gear 20 is slightly different from the number of external teeth 32 of the flexible gear 30. Due to the difference in the number of teeth, the meshing position of the external teeth 32 and the internal teeth 21 changes slightly in the circumferential direction every time the cam 41 rotates one circle. As a result, the internal gear 20 rotates at a second speed that is slower than the first speed around the central axis 9 relative to the flexible gear 30.

[0047] <3. About sensors>

[0048] <3-1. Sensor structure>

[0049] The wave speed reducer 1 has a sensor 50. Figure 2 As shown, the sensor 50 includes a sensor substrate 51 . The sensor substrate 51 is fixed to the surface of the diaphragm portion 33 .

[0050] Figure 4 It is a partial longitudinal sectional view of the flexible spline 30 in the vicinity of the sensor substrate 51 . Figure 5 is a top view of the sensor substrate 51. Figure 4 As shown, the sensor substrate 51 has an insulating layer 511 and a conductive layer 512 .

[0051] The insulating layer 511 is flexibly deformable. The insulating layer 511 extends in a direction intersecting the central axis 9. In addition, the insulating layer 511 is in a ring shape centered on the central axis 9. The insulating layer 511 is composed of a resin or an inorganic insulating material as an insulator. The insulating layer 511 is arranged on the surface of the diaphragm portion 33. The conductor layer 512 is formed on the surface of the insulating layer 511. A metal serving as a conductor is used as a material of the conductor layer 512. For example, a copper alloy, a chromium alloy, or copper is used as a material of the conductor layer 512.

[0052] 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 respectively formed of strain gauges. Figure 2 As shown, 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.

[0053] <3-2. Torque sensor>

[0054] The torque sensor 60 is a sensor for detecting the torque applied to the diaphragm portion 33 of the flexible gear 30. That is, the torque sensor 60 is a sensor whose output value changes according to the torque applied to the flexible gear 30. Figure 5 As shown in FIG. 1 , the torque sensor 60 of the present embodiment includes a first torque sensor 61 and a second torque sensor 62 . The second torque sensor 62 is arranged radially outward of the first torque sensor 61 .

[0055] The first torque sensor 61 has four strain gauges Ra, Rb, Rc, and Rd. Two strain gauges Ra and Rb of the four strain gauges Ra, Rb, Rc, and Rd are arranged at intervals in the circumferential direction. The two strain gauges Ra and Rb are respectively arranged in a semicircular arc shape within a range of about 180° centered on the central axis 9. The radial distance from the central axis 9 to the strain gauge Ra is substantially the same as the radial distance from the central axis 9 to the strain gauge Rb.

[0056] The other two strain gauges Rc and Rd of the four strain gauges Ra, Rb, Rc, and Rd are arranged radially outward from the above two strain gauges Ra and Rb. The two strain gauges Rc and Rd are arranged at intervals in the circumferential direction. The two strain gauges Rc and Rd are respectively arranged in a semicircular arc shape within a range of about 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.

[0057] Furthermore, the two strain gauges Ra and Rc are arranged concentrically and line-symmetrically with the two strain gauges Rb and Rd.

[0058] like Figure 5 As shown, the strain gauges Ra, Rb, Rc, and Rd are patterns extending in the circumferential direction while being bent in a zigzag shape. Each strain gauge Ra, Rb, Rc, and Rd has a plurality of resistance lines r1 arranged in the circumferential direction and substantially parallel to each other. Each resistance line r1 extends in a direction having both radial and circumferential components.

[0059] The resistance wire r1 of the strain gauges Ra and Rd is inclined toward one side of the circumferential direction relative to the radial direction. The resistance wire r1 of the strain gauges Rb and Rc is inclined toward the other side of the circumferential direction relative to the radial direction. The inclination angle of the resistance wire r1 relative 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 to each other on the radial inner side or the radial outer side. Thus, the plurality of resistance wires r1 are connected in series as a whole.

[0060] The second torque sensor 62 has four strain gauges Re, Rf, Rg, and Rh. Two of the four strain gauges Re, Rf, Rg, and Rh are arranged at intervals in the circumferential direction. The two strain gauges Re and Rf are respectively arranged in a semicircular arc shape within a range of about 180° centered on the central axis 9. The radial distance from the central axis 9 to the strain gauge Re is substantially the same as the radial distance from the central axis 9 to the strain gauge Rf.

[0061] The other two strain gauges Rg and Rh of the four strain gauges Re, Rf, Rg and Rh are arranged radially outwardly of the two strain gauges Re and Rf. The two strain gauges Rg and Rh are arranged at intervals in the circumferential direction. The two strain gauges Rg and Rh are respectively arranged in a semicircular arc shape within a range of about 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.

[0062] Furthermore, the two strain gauges Re and Rg are arranged concentrically and line-symmetrically with the two strain gauges Rf and Rh.

[0063] like Figure 5 As shown, the strain gauges Re, Rf, Rg, and Rh are patterns that are bent in a zigzag shape while extending in the circumferential direction. Each strain gauge Re, Rf, Rg, and Rh has a plurality of resistance lines r2 that are arranged in the circumferential direction and are substantially parallel to each other. Each resistance line r2 extends in a direction having both radial and circumferential components.

[0064] The resistance wire r2 of the strain gauges Re and Rh is inclined toward one side of the circumferential direction relative to the radial direction. The resistance wire r2 of the strain gauges Rf and Rg is inclined toward the other side of the circumferential direction relative to the radial direction. The inclination angle of the resistance wire r2 relative to the radial direction is, for example, 45°. The ends of the resistance wires r2 adjacent to each other in the circumferential direction are alternately connected to each other on the radial inner side or the radial outer side. Thus, the plurality of resistance wires r2 are connected in series as a whole.

[0065] Figure 6 is a circuit diagram of the first bridge circuit C1 including the four strain gauges Ra, Rb, Rc, and Rd of the first torque sensor 61. Figure 6 As shown, the four strain gauges Ra, Rb, Rc, and Rd are connected to each other to form a first bridge circuit C1.

[0066] The strain gauge Ra and the strain gauge Rb are connected in series. The strain gauge Rc and the strain gauge Rd are connected in series. Moreover, between the + pole and the - pole of the power supply voltage, the column of the two strain gauges Ra and Rb is connected in parallel with the column of the two strain gauges Rc and Rd. In addition, the first voltmeter V1 is connected between the middle point M11 of the two strain gauges Ra and Rb and the middle point M12 of the two strain gauges Rc and Rd.

[0067] The resistance value of each resistance wire r1 changes according to the torque applied to the area where the resistance wire r1 is configured. For example, when a torque is applied to the diaphragm portion 33 toward one side in the circumferential direction with the central axis 9 as the center, the resistance value of each resistance wire r1 of the two strain gauges Ra and Rd decreases, and the resistance value of each resistance wire r1 of the other two strain gauges Rb and Rc increases. On the other hand, when a torque is applied to the diaphragm portion 33 toward the other side in the circumferential direction with the central axis 9 as the center, the resistance value of each resistance wire r1 of the two strain gauges Ra and Rd increases, and the resistance value of each resistance wire r1 of the other two strain gauges Rb and Rc decreases. In this way, the two strain gauges Ra and Rd and the other two strain gauges Rb and Rc show resistance value changes in opposite directions to each other with respect to the torque.

[0068] When the resistance values ​​of the four strain gauges Ra, Rb, Rc, and Rd change, the potential difference between the middle point M11 of the two strain gauges Ra and Rb and the middle point M12 of the two strain gauges Rc and Rd changes, so 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.

[0069] Figure 7 : is a circuit diagram of the second bridge circuit C2 including the four strain gauges Re, Rf, Rg, and Rh of the second torque sensor 62. Figure 7 As shown, the four strain gauges Re, Rf, Rg, and Rh are connected to each other to form a second bridge circuit C2.

[0070] The strain gauges Re and Rf are connected in series. The strain gauges Rg and Rh are connected in series. Moreover, between the + pole and the - pole of the power supply voltage, the column of the two strain gauges Re and Rf is connected in parallel with the column of the two strain gauges Rg and Rh. In addition, the second voltmeter V2 is connected between the middle point M21 of the two strain gauges Re and Rf and the middle point M22 of the two strain gauges Rg and Rh.

[0071] The resistance value of each resistance wire r2 changes according to the torque applied to the area where the resistance wire r2 is configured. For example, when a torque is applied to the diaphragm portion 33 toward one side of the circumference with the central axis 9 as the center, the resistance value of each resistance wire r2 of the two strain gauges Re and Rh decreases, and the resistance value of each resistance wire r2 of the other two strain gauges Rf and Rg increases. On the other hand, when a torque is applied to the diaphragm portion 33 toward the other side of the circumference with the central axis 9 as the center, the resistance value of each resistance wire r2 of the two strain gauges Re and Rh increases, and the resistance value of each resistance wire r2 of the other two strain gauges Rf and Rg decreases. In this way, the two strain gauges Re and Rh and the other two strain gauges Rf and Rg show resistance value changes in opposite directions relative to the torque.

[0072] When the resistance values ​​of the four strain gauges Re, Rf, Rg, and Rh change, the potential difference between the middle point M21 of the two strain gauges Re and Rf and the middle point M22 of the two strain gauges Rg and Rh changes, so 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.

[0073] In addition, the wave speed reducer 1 of the present embodiment has two torque sensors 61 and 62. The circuit 52 uses any one of the output signals of the two torque sensors 61 and 62 as the output signal of the torque sensor 60. By having two torque sensors 61 and 62, even if an abnormality occurs in one of the torque sensors, the torque can be detected by the other torque sensor. In addition, when an abnormality occurs in one of the torque sensors, the abnormality can be detected.

[0074] <3-3. Angle sensor>

[0075] The angle sensor 70 is a sensor for detecting the rotation angle of the rotational motion input to the wave speed reducer 1. That is, the angle sensor 70 is a sensor whose output value changes according to the rotation angle of the cam 41. Figure 5 As shown, the angle sensor 70 includes 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.

[0076] The eight strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp are each formed by one conductive wire. Each strain gauge 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 strain gauge 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. In addition, the resistance wire of each strain gauge Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp may also extend in the radial direction. In addition, in each strain gauge 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.

[0077] Four strain gauges Ri, Rk, Rm, and Ro that are not adjacent to each other among the eight strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp are connected to each other to form a third bridge circuit C3. Figure 8 This is the circuit diagram of the third bridge circuit C3. Figure 8As shown, the strain gauge Ri and the strain gauge Rk are connected in series in sequence. The strain gauge Ro and the strain gauge Rm are connected in series in sequence. Moreover, between the + pole and the - pole of the power supply voltage, the column of the two strain gauges Ri and Rk is connected in parallel with the column of the two strain gauges Ro and Rm. In addition, a third voltmeter V3 is connected between the middle point M31 of the two strain gauges Ri and Rk and the middle point M32 of the two strain gauges Ro and Rm.

[0078] The remaining four strain gauges Rj, Rl, Rn, and Rp of the eight strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp are connected to each other to form a fourth bridge circuit C4. Fig. 9 This is the circuit diagram of the 4th bridge circuit C4. Fig. 9 As shown, the strain gauge Rp and the strain gauge Rn are connected in series in sequence. The strain gauge Rj and the strain gauge Rl are connected in series in sequence. Moreover, between the + pole and the - pole of the power supply voltage, the column of the two strain gauges Rp and Rn is connected in parallel with the column of the two strain gauges Rj and Rl. In addition, the fourth voltmeter V4 is connected between the middle point M41 of the two strain gauges Rp and Rn and the middle point M42 of the two strain gauges Rj and Rl.

[0079] When the reducer 1 is driven, a portion extending in the circumferential direction (hereinafter referred to as an "extension portion") and a portion contracting in the circumferential direction (hereinafter referred to as a "contraction portion") are generated in the diaphragm portion 33 of the flexible gear 30. Specifically, two extension portions and two contraction portions are generated alternately in the circumferential direction. That is, the extension portion and the contraction portion are generated alternately at intervals of 90° in the circumferential direction with the central axis 9 as the center. Moreover, the portion where these extension portions and contraction portions are generated rotates at the above-mentioned first rotation speed.

[0080] The resistance values ​​of the eight strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp change according to the expansion and contraction of the diaphragm 33 in the circumferential direction. For example, when the above-mentioned extension portion overlaps with a certain strain gauge, the resistance value of the strain gauge increases. On the other hand, when the above-mentioned contraction portion overlaps with a certain strain gauge, the resistance value of the strain gauge decreases.

[0081] exist Figure 5 In the example of , when the contraction portion overlaps with the strain gauges Ri and Rm, the extension portion overlaps with the strain gauges Rk and Ro. In addition, when the extension portion overlaps with the strain gauges Ri and Rm, the contraction portion overlaps with the strain gauges Rk and Ro. Therefore, in the third bridge circuit C3, the strain gauges Ri and Rm and the strain gauges Rk and Ro show opposite resistance value changes.

[0082] In addition, Figure 5In the example of , when the contraction portion overlaps with the strain gauges Rp and Rl, the extension portion overlaps with the strain gauges Rn and Rj. In addition, when the extension portion overlaps with the strain gauges Rp and Rl, the contraction portion overlaps with the strain gauges Rn and Rj. Therefore, in the fourth bridge circuit C4, the strain gauges Rp and Rl and the strain gauges Rn and Rj show opposite resistance value changes.

[0083] In this way, the angle sensor 70 has two sets of bridge circuits C3 and C4 composed of a plurality of strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp.

[0084] Fig.10 It is a graph showing the time changes 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. Fig.10 The horizontal axis of the graph represents time. Fig.10 The vertical axis of the curve graph represents the voltage value. When the wave reducer 1 is driven, Fig.10 As shown, the third voltmeter V3 and the fourth voltmeter V4 respectively obtain periodically changing sinusoidal output values ​​v3 and v4. The period T of the output values ​​v3 and v4 corresponds to 1 / 2 of the period of the first rotation speed.

[0085] In addition, 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 cycle. That is, the output values ​​of the two bridge circuits C3 and C4 have a phase difference of 1 / 4 cycle. Moreover, 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 is ahead of the phase of the output value v3 of the third voltmeter V3 by 1 / 8 cycle of the first rotation speed (1 / 4 cycle of the output values ​​v3 and v4) or is behind the phase of the output value v3 of the third voltmeter V3 by 1 / 8 cycle of the first rotation speed (1 / 4 cycle of the output values ​​v3 and v4).

[0086] The circuit 52 detects the rotation angle of the rotational 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 the combination 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.

[0087] When the wave reducer 1 is driven, the flexible spline 30 is periodically flexed and deformed. Therefore, the output signal of the first torque sensor 61 and the output signal of the second torque sensor 62 include a component reflecting the torque to be measured and an error component (fluctuation error) caused by the periodic flexure deformation of the flexible spline 30. The fluctuation error changes in a sinusoidal shape according to the rotation angle of the rotational motion input to the wave reducer 1.

[0088] Therefore, the circuit 52 calculates the above-mentioned fluctuation error based on the rotation angle detected by the angle sensor 70. Then, the calculated fluctuation error is used to correct the output signals of the first torque sensor 61 and the second torque sensor 62. Specifically, the circuit 52 increases or decreases the output signals of the first torque sensor 61 and the second torque sensor 62 in the direction of eliminating the fluctuation error. As a result, the circuit 52 can output the torque applied to the flexible gear 30 with higher accuracy.

[0089] In addition, the circuit 52 may not calculate the above-mentioned rotation angle, but may multiply the output values ​​v3 and v4 of the third voltmeter V3 and the fourth voltmeter V4 by a predetermined coefficient to synthesize the output signals of the first torque sensor 61 and the second torque sensor 62. In this way, the processing load caused by the calculation of the rotation angle can be reduced. Therefore, the calculation speed of the circuit 52 can be improved.

[0090] <3-4. Thrust sensor>

[0091] The thrust sensor 80 is a sensor for detecting the thrust applied to the cam 41. That is, the thrust sensor 80 is a sensor whose output value changes according to the thrust applied to the cam 41. The thrust refers to the axial force. Figure 5 As shown, the thrust sensor 80 includes two outer strain gauges Rq and Rr and two inner strain gauges Rs and Rt. The two inner strain gauges Rs and Rt are arranged radially inward of the two outer strain gauges Rq and Rr.

[0092] In the present embodiment, the two outer strain gauges Rq and Rr are arranged radially outside the torque sensor 60. In addition, the two outer strain gauges Rq and Rr are arranged at intervals in the circumferential direction. The two outer strain gauges Rq and Rr are respectively arranged in a semicircular arc shape within a range of about 180° centered on the central axis 9. The radial distance from the central axis 9 to the outer strain gauge Rq is substantially the same as the radial distance from the central axis 9 to the outer strain gauge Rr.

[0093] In the present embodiment, the two inner strain gauges Rs and Rt are arranged radially inward of the torque sensor 60. In addition, the two inner strain gauges Rs and Rt are arranged at intervals in the circumferential direction. The two inner strain gauges Rs and Rt are respectively arranged in a semicircular arc shape within a range of about 180° centered on the central axis 9. The radial distance from the central axis 9 to the inner strain gauge Rs is substantially the same as the radial distance from the central axis 9 to the inner strain gauge Rt.

[0094] That is, the two outer strain gauges Rq and Rr and the two inner strain gauges Rs and Rt are arranged at intervals in the radial direction.

[0095] like Figure 5 As shown, the outer strain gauges Rq, Rr and the inner strain gauges Rs, Rt are patterns extending in the circumferential direction while being bent in a zigzag shape. Each strain gauge 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 flexible gear 30. The ends of the resistance wires r3 adjacent to each other in the circumferential direction are alternately connected to each other radially inward or radially outward. Thus, the plurality of resistance wires r3 are connected in series as a whole.

[0096] Fig.11 is a circuit diagram of a fifth bridge circuit C5 including the outer strain gauges Rq, Rr and the inner strain gauges Rs, Rt of the thrust sensor 80. Fig.11 As shown, the two outer strain gauges Rq and Rr and the two inner strain gauges Rs and Rt are connected to each other to form a fifth bridge circuit C5.

[0097] The strain gauges Rq and Rs are connected in series. The strain gauges Rt and Rr are connected in series. Moreover, between the + pole and the - pole of the power supply voltage, the column of the two strain gauges Rq and Rs is connected in parallel with the column of the two strain gauges Rt and Rr. In addition, the fifth voltmeter V5 is connected between the middle point M51 of the two strain gauges Rq and Rs and the middle point M52 of the two strain gauges Rt and Rr.

[0098] The plurality of 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 caused by the circumferential torque is extremely small. However, when the diaphragm portion 33 of the flexible gear 30 is displaced in the axial direction, the resistance value of the strain gauges Rq, Rr, Rs, and Rt changes.

[0099] Specifically, when the radial inner end of the diaphragm portion 33 is displaced in a direction approaching the internal gear 20, the resistance values ​​of the two outer strain gauges Rq and Rr among the four strain gauges Rq, Rr, Rs, and Rt increase, and the resistance values ​​of the two inner strain gauges Rs and Rt decrease. On the other hand, when the radial 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 and Rr among the four strain gauges Rq, Rr, Rs, and Rt decrease, and the resistance values ​​of the two inner strain gauges Rs and Rt increase. In this way, the two outer strain gauges Rq and Rr and the two inner strain gauges Rs and Rt show resistance value changes in opposite directions to each other with respect to the axial displacement of the diaphragm portion 33.

[0100] When the resistance values ​​of the four strain gauges Rq, Rr, Rs, and Rt change, the potential difference between the middle point M51 of the two strain gauges Rq and Rs and the middle point M52 of the two strain gauges Rt and Rr changes, so the output value of the fifth voltmeter V5 also changes. The circuit 52 detects the direction and magnitude of the thrust applied to the flexible gear 30 based on the output value of the fifth voltmeter V5.

[0101] <3-5. About angle sensor calibration>

[0102] <3-5-1. First embodiment>

[0103] As described above, the angle sensor 70 has two sets of 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 is accelerated, or when an external force acts from the output side of the wave reducer 1 due to the inertia force of the arm 102, the amplitude of the output values ​​v3 and v4 of the two sets of bridge circuits C3 and C4 slightly changes due to the thrust applied to the cam 41.

[0104] Specifically, when a force acts from the input side of the ripple reducer 1, the amplitudes of the output values ​​v3 and v4 of the two bridge circuits C3 and C4 become slightly smaller. Also, when a force acts from the output side of the ripple reducer 1, the amplitudes of the output values ​​v3 and v4 of the two bridge circuits C3 and C4 become slightly larger.

[0105] Therefore, the circuit 52 corrects the output value of the angle sensor 70 according to 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 eliminates the influence of the thrust. In this way, it is possible to suppress the output value of the angle sensor 70 from changing due to the thrust applied to the cam 41. Therefore, the rotation angle of the cam 41 can be detected with high accuracy by the corrected output values ​​v3 and v4 of the angle sensor 70.

[0106] In addition, the circuit 52 corrects the output value of the torque sensor 60 based on the output values ​​v3 and v4 of the angle sensor 70 corrected based on the output value of the thrust sensor 80. Specifically, the circuit 52 calculates the above-mentioned fluctuation error based on the corrected output values ​​v3 and v4 of the angle sensor 70, and corrects the output value of the torque sensor 60 in a manner that eliminates the fluctuation error. As a result, the torque applied to the flexible gear 30 can be detected with higher accuracy.

[0107] <3-5-2. Second embodiment>

[0108] Next, a method of correcting the output value of the angle sensor 70 due to the thrust without using the output value of the thrust sensor 80 will be described.

[0109] The output values ​​v3 and v4 of the two bridge circuits C3 and C4 of the angle sensor 70 have a relationship between a sine wave and a cosine wave. Therefore, the sum v3^2+v4^2 of the squares of these output values ​​v3 and v4 is always a constant value in an ideal state. However, when a force acts from the input side or the output side of the wave reducer 1, the amplitude of the output values ​​v3 and v4 generates an error due to the thrust applied to the cam 41, so the sum v3^2+v4^2 of the squares of the output values ​​v3 and v4 deviates from the constant value.

[0110] Therefore, the circuit 52 corrects the output values ​​v3 and v4 of the two groups of bridge circuits C3 and C4 so that the sum v3^2+v4^2 of the squares of the output values ​​v3 and v4 of the two groups of bridge circuits C3 and C4 approaches a constant value. For example, the circuit 52 normalizes the output values ​​v3 and v4 so that the sum v3^2+v4^2 of the squares of the output values ​​v3 and v4 is always 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 and v4 of the bridge circuits C3 and C4 from changing due to the thrust applied to the cam 41. Therefore, the rotation angle of the cam 41 can be detected with high accuracy by the corrected output values ​​v3 and v4 of the angle sensor 70.

[0111] In addition, the circuit 52 corrects the output value of the torque sensor 60 based on the output values ​​v3 and v4 of the angle sensor 70 after the normalization correction. Specifically, the circuit 52 calculates the above-mentioned fluctuation error based on the corrected output values ​​v3 and v4 of the angle sensor 70, and corrects the output value of the torque sensor 60 in a manner that eliminates the fluctuation error. As a result, the torque applied to the flexible gear 30 can be detected with higher accuracy.

[0112] In addition, the circuit 52 may output the correction amount based on the normalized output values ​​v3 and v4 as the detection value indicating the thrust applied to the cam 41 .

[0113] In addition, the circuit 52 may also output an alarm signal when the sum of the squares of the output values ​​v3 and v4 of the two bridge circuits C3 and C4 is outside a predetermined range. The alarm signal is a signal indicating that at least one of the output values ​​v3 and 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 and v4 of the angle sensor 70 may be abnormal based on the alarm signal. Therefore, the operation of the industrial machine 100 can be stopped, and the angle sensor 70 can be checked.

[0114] <4. Modifications>

[0115] 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, centering on the differences from the above embodiment.

[0116] <4-1. First Modification>

[0117] In the above-described embodiment, the ripple 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 ripple reducer 1. That is, the ripple reducer 1 and the circuit 52 may constitute a drive system.

[0118] In this case, the angle sensor 70 and the thrust sensor 80 of the wave speed reducer 1 are electrically connected to a circuit 52 provided outside the wave speed reducer 1 , and the circuit 52 only needs to correct the output value of the angle sensor 70 based on the output value of the thrust sensor 80 .

[0119] Alternatively, the angle sensor 70 of the oscillating reducer 1 may be electrically connected to a circuit 52 disposed outside the oscillating reducer 1, and the circuit 52 may correct the output values ​​v3 and v4 of the two groups of bridge circuits C3 and C4 of the angle sensor 70 in such a manner that the sum v3^2+v4^2 of the squares of the output values ​​v3 and v4 of the two groups of bridge circuits C3 and C4 approaches a constant value.

[0120] Alternatively, one circuit 52 may correct the output values ​​of the angle sensors 70 of a plurality of wave reducers 1 .

[0121] <4-2. Other Modifications>

[0122] 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 be only one of the first torque sensor 61 and the second torque sensor 62.

[0123] In the above-mentioned embodiment, the thrust sensor 80 has only one set of the fifth bridge circuit C5 composed of the outer strain gauges Rq, Rr and the inner strain gauges Rs, Rt. However, the thrust sensor 80 may also have two sets of the fifth bridge circuit C5 composed of 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 can be detected by the other fifth bridge circuit C5. In addition, if an abnormality occurs in one of the fifth bridge circuits C5, the abnormality can be detected.

[0124] In the wave speed reducer 1 of the above embodiment, the flexible gear 30 is fixed to the base frame 101 and the internal gear 20 rotates at the reduced second speed. However, the internal gear 20 may be fixed to the base frame 101 and the flexible gear 30 may rotate at the reduced second speed.

[0125] The flexible gear 30 of the above embodiment is a so-called "hat-shaped" gear in which the diaphragm portion 33 extends radially outward from the body portion 31. However, the flexible gear 30 may be a so-called "cup-shaped" gear in which the diaphragm portion 33 extends radially inward from the body portion 31.

[0126] In the above embodiment, the industrial machine 100 is an industrial robot having an arm, but the industrial machine 100 may be another device such as an assistive suit or an unmanned transport vehicle.

[0127] In addition, the structures of the details of the wave reducer, industrial machinery and drive system may be appropriately changed without departing from the gist of the present invention. In addition, the elements in the above-mentioned embodiments and modified examples may be appropriately combined without causing contradictions.

[0128] <5. Conclusion>

[0129] The present technology can adopt the following structures.

[0130] (1) A wave reducer, comprising: a cam having a non-circular outer surface; a flexible gear that generates flexural deformation through the rotation of the cam; an internal gear that meshes with the flexible gear; an angle sensor disposed on the flexible gear, the output value of which varies according to the rotation angle of the cam; a thrust sensor disposed on the flexible gear, the output value of which varies according to the thrust 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 according to the output value of the thrust sensor.

[0131] (2) A wave reducer according to (1), wherein the angle sensor has two groups of bridge circuits composed of multiple strain gauges, the output values ​​of the two groups of bridge circuits have a phase difference of 1 / 4 cycle, and the circuit corrects the output values ​​of the two groups of bridge circuits respectively.

[0132] (3) A wave reducer according to (1) or (2), wherein the wave reducer also has a torque sensor, the output value of which varies according to the torque applied to the flexible gear, and the circuit corrects the output value of the torque sensor according to the output value of the angle sensor corrected based on the output value of the thrust sensor.

[0133] (4) A wave reducer according to any one of (1) to (3), wherein the thrust sensor has a bridge circuit including an outer strain gauge and an inner strain gauge, the outer strain gauge having a resistance wire extending radially with the central axis of the flexible gear as the center, the inner strain gauge having a resistance wire extending radially with the central axis of the flexible gear as the center, and the inner strain gauge is arranged at a radially inner side than the outer strain gauge.

[0134] (5) An industrial machine comprising the wave speed reducer described in any one of (1) to (4).

[0135] (6) A drive system comprising a wave reducer and a circuit, wherein the wave reducer comprises: a cam having an outer surface that is not a perfect circle; a flexible gear that generates flexural deformation through the rotation of the cam; an internal gear that meshes with the flexible gear; an angle sensor disposed on the flexible gear, the output value of which varies according to the rotation angle of the cam; and a thrust sensor disposed on the flexible gear, the output value of which varies according to the thrust applied to the cam, and the circuit corrects the output value of the angle sensor according to the output value of the thrust sensor.

[0136] (7) A correction method for correcting the output value of an angle sensor in a wave reducer, wherein the wave reducer comprises: a cam having an outer surface that is not a perfect circle; a flexible gear that generates flexural deformation through the rotation of the cam; an internal gear that meshes with the flexible gear; the angle sensor disposed on the flexible gear, the output value of the angle sensor varying according to the rotation angle of the cam; and a thrust sensor disposed on the flexible gear, the output value of the thrust sensor varying according to the thrust applied to the cam, wherein the output value of the angle sensor is corrected according to the output value of the thrust sensor.

[0137] (8) A wave reducer, comprising: a cam having an outer surface that is not a perfect circle; a flexible gear that generates flexural deformation through the rotation of the cam; an internal gear that meshes with the flexible gear; an angle sensor that is arranged on the flexible gear, the output value of the angle sensor changes according to the rotation angle of the cam; and a circuit that is electrically connected to the angle sensor, wherein the angle sensor has two groups of bridge circuits composed of multiple strain gauges, the output values ​​of the two groups of bridge circuits have a phase difference of 1 / 4 cycle, and the circuit corrects the output values ​​of the two groups of bridge circuits so that the sum of the squares of the output values ​​of the two groups of bridge circuits is close to a constant value.

[0138] (9) The wave speed reducer according to (8), wherein the circuit outputs a correction amount of an output value of the bridge circuit as a detection value representing a thrust force applied to the cam.

[0139] (10) The wave speed reducer according to (8) or (9), wherein when the sum of the squares of the output values ​​of the two groups of bridge circuits is outside a prescribed range, the circuit outputs an alarm signal.

[0140] (11) A drive system having a wave reducer and a circuit, wherein the wave reducer has: a cam having an outer surface that is not a perfect circle; a flexible gear that generates flexural deformation through the rotation of the cam; an internal gear that meshes with the flexible gear; and an angle sensor disposed on the flexible gear, wherein the output value of the angle sensor varies according to the rotation angle of the cam, the angle sensor having two sets of bridge circuits composed of a plurality of strain gauges, the output values ​​of the two sets of bridge circuits having a phase difference of 1 / 4 cycle, and the circuit correcting the output values ​​of the two sets of bridge circuits so that the sum of the squares of the output values ​​of the two sets of bridge circuits approaches a constant value.

[0141] (12) A correction method for correcting the output value of an angle sensor in a wave reducer, wherein the wave reducer comprises: a cam having an outer surface that is not a perfect circle; a flexible gear that generates flexural deformation through the rotation of the cam; an internal gear that meshes with the flexible gear; and the angle sensor disposed on the flexible gear, wherein the output value of the angle sensor varies according to the rotation angle of the cam, wherein the angle sensor has two groups of bridge circuits composed of a plurality of strain gauges, the output values ​​of the two groups of bridge circuits have a phase difference of 1 / 4 cycle, and the correction method corrects the output values ​​of the two groups of bridge circuits so that the sum of the squares of the output values ​​of the two groups of bridge circuits approaches a constant value.

[0142] The present invention can be utilized in, for example, a wave reducer, an industrial machine, a drive system, and a calibration method.

Claims

1. A wave reducer, comprising: A cam having an outer side surface which is not a perfect circle; a flexible gear which is deformed by the rotation of the cam; an internal gear meshing with the flexible gear; an angle sensor disposed on the flexible gear, wherein an output value of the angle sensor changes according to a rotation angle of the cam; a thrust sensor disposed on the flexible gear, wherein an output value of the thrust sensor changes according to a thrust applied to the cam; and a circuit electrically connected to the angle sensor and the thrust sensor, It is characterized in that The circuit corrects the output value of the angle sensor according to the output value of the thrust sensor.

2. The wave reducer according to claim 1, characterized in that: The angle sensor has two sets of bridge circuits composed of multiple strain gauges. The output values ​​of the two groups of bridge circuits have a phase difference of 1 / 4 cycle. The circuit corrects the output values ​​of the two groups of bridge circuits respectively.

3. The wave reducer according to claim 1 or 2, characterized in that: The wave reducer further includes a torque sensor, the output value of which changes according to the torque applied to the flexible gear. The circuit corrects the output value of the torque sensor according to the output value of the angle sensor corrected based on the output value of the thrust sensor.

4. The wave reducer according to claim 1 or 2, characterized in that: The thrust sensor has a bridge circuit including an outer strain gauge and an inner strain gauge, the outer strain gauge has a resistance wire extending radially with the central axis of the flexible gear as the center, the inner strain gauge has a resistance wire extending radially with the central axis of the flexible gear as the center, and the inner strain gauge is arranged at a radially inner position than the outer strain gauge.

5. An industrial machine, characterized in that: This industrial machine has the wave speed reducer according to claim 1 or 2.

6. A drive system having a wave reducer and a circuit, The wave reducer has: A cam having an outer side surface which is not a perfect circle; a flexible gear which is deformed by the rotation of the cam; an internal gear meshing with the flexible gear; an angle sensor disposed on the flexible gear, wherein an output value of the angle sensor changes according to a rotation angle of the cam; as well as a thrust sensor disposed on the flexible gear, wherein an output value of the thrust sensor changes according to a thrust applied to the cam, It is characterized in that The circuit corrects the output value of the angle sensor according to the output value of the thrust sensor.

7. A correction method, the correction method correcting the output value of an angle sensor in a wave reducer, the wave reducer having: A cam having an outer side surface which is not a perfect circle; a flexible gear which is deformed by the rotation of the cam; an internal gear meshing with the flexible gear; The angle sensor is disposed on the flexible gear, and an output value of the angle sensor changes according to a rotation angle of the cam; and a thrust sensor disposed on the flexible gear, wherein an output value of the thrust sensor changes according to a thrust applied to the cam, It is characterized in that The output value of the angle sensor is corrected according to the output value of the thrust sensor.

8. A wave reducer, comprising: A cam having an outer side surface which is not a perfect circle; a flexible gear which is deformed by the rotation of the cam; an internal gear meshing with the flexible gear; an angle sensor disposed on the flexible gear, wherein an output value of the angle sensor changes according to a rotation angle of the cam; as well as A circuit electrically connected to the angle sensor, The angle sensor has two sets of bridge circuits composed of multiple strain gauges. The output values ​​of the two groups of bridge circuits have a phase difference of 1 / 4 cycle. It is characterized in that The circuit corrects the output values ​​of the two groups of bridge circuits so that the sum of the squares of the output values ​​of the two groups of bridge circuits approaches a constant value.

9. The wave reducer according to claim 8, characterized in that: The circuit outputs a correction amount of an output value of the bridge circuit as a detection value indicating a thrust force applied to the cam.

10. The wave reducer according to claim 8 or 9, characterized in that: When the sum of the squares of the output values ​​of the two bridge circuits is outside a prescribed range, the circuit outputs an alarm signal.

11. A drive system having a wave reducer and a circuit, The wave reducer has: A cam having an outer side surface which is not a perfect circle; a flexible gear which is deformed by the rotation of the cam; an internal gear meshing with the flexible gear; as well as an angle sensor disposed on the flexible gear, wherein an output value of the angle sensor changes according to a rotation angle of the cam, The angle sensor has two sets of bridge circuits composed of multiple strain gauges. The output values ​​of the two groups of bridge circuits have a phase difference of 1 / 4 cycle. It is characterized in that The circuit corrects the output values ​​of the two groups of bridge circuits so that the sum of the squares of the output values ​​of the two groups of bridge circuits approaches a constant value.

12. A correction method, the correction method correcting the output value of an angle sensor in a wave reducer, the wave reducer having: A cam having an outer side surface which is not a perfect circle; a flexible gear which is deformed by the rotation of the cam; an internal gear meshing with the flexible gear; as well as The angle sensor is disposed on the flexible gear, and the output value of the angle sensor changes according to the rotation angle of the cam. The angle sensor has two sets of bridge circuits composed of multiple strain gauges. The output values ​​of the two groups of bridge circuits have a phase difference of 1 / 4 cycle. It is characterized in that The output values ​​of the two groups of bridge circuits are corrected so that the sum of the squares of the output values ​​of the two groups of bridge circuits approaches a constant value.

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