Annular body, speed reducer, robot, and torque detection device

Abstract

To provide a technique for detecting torque applied to an annular body and for diagnosing a state of a resistance wire.SOLUTION: An annular body comprises a base part, and a resistance wire 412 disposed on the base part. The resistance wire includes a first resistance wire portion W1 and a second resistance wire portion W2. The second resistance wire portion is disposed on an outer side in the radial direction beyond the first resistance wire portion. The first resistance wire portion includes a plurality of first regions Ra, Rb arranged at an interval in the circumferential direction. The plurality of first regions respectively comprises a region where a first site extending in a direction including constituents of both the radial direction and the circumferential direction, is repeatedly arranged in the circumferential direction. The second resistance wire portion includes a plurality of second regions Re, Rf arranged at an interval in the circumferential direction. The plurality of second regions respectively comprises a region where a second site extending in a direction including constituents of both the radial direction and the circumferential direction, is repeatedly arranged in the circumferential direction.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to an annular body, a harmonic reducer, a robot, and a torque detection device.

Background Art

[0002] In recent years, the demand for harmonic reducers mounted on robot joints and the like has been increasing. In a conventional harmonic reducer, a strain gauge is attached to an external gear that rotates at a rotational speed after deceleration. This enables detection of the torque applied to the external gear (Patent Document 1).

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0003] However, in the conventional structure, when the output signal of the strain gauge changes greatly, it is impossible to distinguish whether the change in the output signal is due to the application of a large torque or due to an abnormality occurring in the resistance wire of the strain gauge.

[0004] An object of the present invention is to provide a technique for detecting the torque applied to an annular body by a resistance wire and diagnosing the state of the resistance wire.

Means for Solving the Problems

[0005] The first invention is an annular body that surrounds a central axis and has a base portion that extends in a direction intersecting the central axis and a resistance wire disposed on the base portion. The resistance wire has a first resistance wire portion and a second resistance wire portion disposed radially outside the first resistance wire portion. The first resistance wire portion has an inner first resistance wire portion and an outer first resistance wire portion disposed radially outside the inner first resistance wire portion. The second resistance wire portion has an inner second resistance wire portion and an outer second resistance wire portion disposed radially outside the inner second resistance wire portion. The inner first resistance wire portion and the outer first resistance wire portion each have a plurality of first regions arranged at intervals in the circumferential direction. Each of the plurality of first regions includes a region in which a first portion extending in a direction having components in both the radial direction and the circumferential direction is repeatedly arranged in the circumferential direction. The inner second resistance wire portion and the outer second resistance wire portion each have a plurality of second regions arranged at intervals in the circumferential direction. Each of the plurality of second regions includes a region in which a second portion extending in a direction having components in both the radial direction and the circumferential direction is repeatedly arranged in the circumferential direction.

[0006] The second invention is a torque detection device, comprising a resistance wire arranged in the circumferential direction with respect to a central axis, and a detection circuit electrically connected to the resistance wire. The resistance wire has a first resistance wire portion and a second resistance wire portion arranged radially outside the first resistance wire portion. The first resistance wire portion has an inner first resistance wire portion and an outer first resistance wire portion arranged radially outside the inner first resistance wire portion. The second resistance wire portion has an inner second resistance wire portion and an outer second resistance wire portion arranged radially outside the inner second resistance wire portion. The inner first resistance wire portion and the outer first resistance wire portion each have a plurality of first regions arranged at intervals in the circumferential direction. Each of the plurality of first regions includes a region in which a first part extending in a direction having components in both the radial direction and the circumferential direction is repeatedly arranged in the circumferential direction. The inner second resistance wire portion and the outer second resistance wire portion each have a plurality of second regions arranged at intervals in the circumferential direction. Each of the plurality of second regions includes a region in which a second part extending in a direction having components in both the radial direction and the circumferential direction is repeatedly arranged in the circumferential direction. The first resistance wire portion further has a first connection region connected to the plurality of first regions. A first bridge circuit is formed by connecting the plurality of first regions via the first connection region. The second resistance wire portion further has a second connection region connected to the plurality of second regions. A second bridge circuit is formed by connecting the plurality of second regions via the second connection region. The resistance values of the first part and the second part change according to the torque applied to the region where the resistance wire is arranged. The detection circuit outputs a diagnostic signal indicating the state of the resistance wire by comparing the output signal of the first bridge circuit with the output signal of the second bridge circuit.

Advantages of the Invention

[0007] According to the first and second inventions, the torque applied to the annular body can be detected by the first resistance wire portion and the second resistance wire portion. Further, the state of the resistance wire can be diagnosed by comparing the output signal of the first resistance wire portion with the output signal of the second resistance wire portion.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

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Figure 8

Figure 9

Figure 10

Figure 11

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Figure 15

Embodiments for Carrying Out the Invention

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

[0010] <1. Regarding the robot> FIG. 1 is a schematic diagram of a robot 100 equipped with a harmonic reducer 1 according to an embodiment. The robot 100 is, for example, a so-called industrial robot that performs operations such as part transfer, processing, and assembly in a manufacturing line of industrial products. As shown in FIG. 1, the robot 100 includes a base frame 101, an arm 102, a motor 103, and a harmonic reducer 1.

[0011] The arm 102 is rotatably supported with respect to the base frame 101. The motor 103 and the harmonic reducer 1 are incorporated in a joint portion between the base frame 101 and the arm 102. When a drive current is supplied to the motor 103, a rotational motion is output from the motor 103. Further, the rotational motion output from the motor 103 is decelerated by the harmonic reducer 1 and transmitted to the arm 102. Thereby, the arm 102 rotates with respect to the base frame 101 at the decelerated speed.

[0012] As described above, the robot 100 has a harmonic reducer 1. The harmonic reducer 1 has a function of detecting torque by a resistance wire as described later. Further, the harmonic reducer 1 has a function of diagnosing the state of the resistance wire. Thereby, a highly functional robot 100 can be realized.

[0013] <2. Configuration of Harmonic Reducer> Subsequently, the detailed structure of the harmonic reducer 1 will be described.

[0014] In the following, the direction parallel to the central axis 9 of the harmonic reducer 1 is referred to as the "axial direction", the direction orthogonal to the central axis 9 of the harmonic reducer 1 is referred to as the "radial direction", and the direction along an arc centered on the central axis 9 of the harmonic reducer 1 is referred to as the "circumferential direction", respectively. However, the above "parallel direction" includes a substantially parallel direction. Further, the above "orthogonal direction" includes a substantially orthogonal direction.

[0015] FIG. 2 is a longitudinal sectional view of the harmonic reducer 1 according to an embodiment. FIG. 3 is a cross-sectional view of the harmonic reducer 1 viewed from the A-A position in FIG. 2. To avoid complication of the drawings, the hatching indicating the cross section is omitted in FIG. 3. The harmonic reducer 1 is a device that decelerates the rotational motion at the first rotational speed obtained from the motor 103 to the second rotational speed lower than the first rotational speed. As shown in FIGS. 1 and 2, the harmonic reducer 1 of the present embodiment includes an internal gear 10, an annular body 20, and a wave generator 30. The annular body 20 has a function of detecting torque by a resistance wire as described later. Further, the annular body 20 has a function of diagnosing the state of the resistance wire. Thereby, a highly functional harmonic reducer 1 can be realized.

[0016] That is, in the harmonic reducer 1, the torque applied to the annular body 20 can be detected, and the state of the resistance wire disposed on the annular body 20 can be diagnosed. More specifically, it is possible to diagnose whether the resistance wire is functioning normally. In the present embodiment, the annular body 20 is an external gear having flexibility. However, the annular body may be other members than the external gear.

[0017] The internal gear 10 is an annular gear centered on the central axis 9. The internal gear 10 is fixed to the base frame 101. The internal gear 10 is arranged coaxially with the central axis 9. Further, the internal gear 10 is arranged radially outside the outer teeth 22 described later. The rigidity of the internal gear 10 is sufficiently higher than the rigidity of the body portion 21 of the annular body 20 described later. Therefore, the internal gear 10 can be regarded as a substantially rigid body. The internal gear 10 has a plurality of internal teeth 11. The plurality of internal teeth 11 project radially inward from the radially inner surface of the internal gear 10. The plurality of internal teeth 11 are arranged at a constant pitch in the circumferential direction on the inner peripheral surface of the internal gear 10.

[0018] The annular body 20 is an annular gear that can be elastically deformed. The annular body 20 is fixed to the arm 102. The annular body 20 is rotatably supported about the central axis 9.

[0019] As shown in FIGS. 2 and 3, the annular body 20 has a body portion 21 and a plurality of external teeth 22. The annular body 20 further has an annular plate portion 23.

[0020] The body portion 21 is a cylindrical portion that extends axially from the radial end portion of a base portion 231 described later. In the present embodiment, the body portion 21 extends axially from the radially inner end portion of the base portion 231 toward one axial side. One axial end portion of the body portion 21 is located radially outside the wave generator 30 and radially inside the internal gear 10. Since the body portion 21 has flexibility, it can be deformed radially. In particular, one axial end of the body portion 21 can be displaced more greatly in the radial direction than other portions.

[0021] The plurality of external teeth 22 project radially outward from the radially outer surface of the body portion 21. The plurality of external teeth 22 are arranged on the radially outer surface of one axial end of the body portion 21. The plurality of external teeth 22 are arranged at a constant pitch in the circumferential direction. A part of the plurality of external teeth 22 meshes with a part of the plurality of internal teeth 11 described above. The number of internal teeth 11 of the internal gear 10 and the number of external teeth 22 of the annular body 20 are slightly different.

[0022] The annular plate portion 23 has a base portion 231 and a thick portion 232. That is, the annular body 20 has a base portion 231. The base portion 231 surrounds the central axis 9 and extends in a direction intersecting the central axis 9. The base portion 231 preferably extends along a plane orthogonal to the central axis 9. The base portion 231 extends radially outward from the other axial end portion of the body portion 21. The base portion 231 is annular and surrounds the central axis 9. Since the base portion 231 is thin, it can be slightly bent and deformed.

[0023] The thick portion 232 is an annular portion located radially outside the base portion 231. The thick portion 232 extends further radially outward from the radially outer end portion of the base portion 231. The axial thickness of the thick portion 232 is larger than the axial thickness of the base portion 231. The thick portion 232 is fixed to the arm 102, for example, with bolts.

[0024] The vibration generator 30 is a mechanism that generates periodic flexural deformation in the body portion 21. The vibration generator 30 is disposed radially inward of the external teeth 22. The vibration generator 30 of the present embodiment has a cam 31 and a flexible bearing 32. The cam 31 is rotatably supported about the central axis 9. The radially outer surface of the cam 31 is elliptical when viewed in the axial direction. The flexible bearing 32 is a bearing that can be flexurally deformed. The flexible bearing 32 is disposed between the radially outer surface of the cam 31 and the radially inner surface of the body portion 21 of the annular body 20. Therefore, the cam 31 and the body portion 21 can rotate at different rotational speeds.

[0025] The inner ring of the flexible bearing 32 contacts the radially outer surface of the cam 31. The outer ring of the flexible bearing 32 contacts the radially inner surface of the body portion 21. For this reason, the body portion 21 deforms into an elliptical shape along the radially outer surface of the cam 31. As a result, at two locations corresponding to both ends of the major axis of the ellipse, the external teeth 22 of the annular body 20 and the internal teeth 11 of the internal gear 10 mesh with each other. At other positions in the circumferential direction, the external teeth 22 and the internal teeth 11 do not mesh with each other.

[0026] The cam 31 is connected to the output shaft (not shown) of the motor 103. When the motor 103 is driven, the cam 31 rotates about the central axis 9 at a first rotational speed. As a result, the major axis of the above-described ellipse of the annular body 20 also rotates at the first rotational speed. Then, the meshing position between the external teeth 22 and the internal teeth 11 also changes in the circumferential direction at the first rotational speed. Further, as described above, the number of internal teeth 11 of the internal gear 10 and the number of external teeth 22 of the annular body 20 are slightly different. Due to this difference in the number of teeth, for each rotation of the cam 31, the meshing position between the external teeth 22 and the internal teeth 11 slightly changes in the circumferential direction. As a result, the annular body 20 rotates about the central axis 9 relative to the internal gear 10 at a second rotational speed lower than the first rotational speed.

[0027] <3. First Embodiment> <3-1. About the Torque Detection Device> Next, the torque detection device 40 will be described. The torque detection device 40 is a sensor for detecting the torque applied to the annular body 20. As shown in FIG. 2, the torque detection device 40 includes a substrate 41 and a detection circuit 42. The substrate 41 is disposed on the base portion 231 of the annular body 20. Specifically, the base portion 231 has a surface 234 that intersects the central axis 9 and extends in an annular shape centered on the central axis 9. The surface 234 is the other surface on the axial direction other side of the base portion 231. The substrate 41 is fixed to the surface 234 of the base portion 231.

[0028] FIG. 4 is a partial longitudinal sectional view of the annular body 20 in the vicinity of the substrate 41. FIG. 5 is a plan view of the substrate 41. As shown in FIGS. 4 and 5, the substrate 41 has an insulating layer 411 and a resistance wire 412. That is, the torque detection device 40 includes the resistance wire 412 and the detection circuit 42.

[0029] The insulating layer 411 is deformable flexibly. The insulating layer 411 extends in a direction intersecting the central axis 9. Also, the insulating layer 411 is annular with the central axis 9 as the center. The insulating layer 411 is made of a resin or an inorganic insulating material that is an insulator. The insulating layer 411 is disposed on the surface 234 of the base portion 231.

[0030] The resistance wire 412 is formed on the surface of the insulating layer 411. That is, the resistance wire 412 is disposed on the base portion 231. A metal that is a conductor is used as the material of the resistance wire 412. For example, a copper alloy, a chromium alloy, or copper is used as the material of the resistance wire 412. The resistance wire 412 is disposed in the circumferential direction with respect to the central axis 9. Also, the resistance wire 412 has a first resistance wire portion W1 and a second resistance wire portion W2. The second resistance wire portion W2 is disposed radially outside the first resistance wire portion W1.

[0031] The first resistance wire portion W1 has an inner first resistance wire portion W11 and an outer first resistance wire portion W12. The outer first resistance wire portion W12 is disposed radially outside the inner first resistance wire portion W11.

[0032] The inner first resistance line portion W11 has a plurality of first regions Ra, Rb. The plurality of first regions Ra, Rb are arranged at intervals in the circumferential direction. In the present embodiment, the inner first resistance line portion W11 has two first regions Ra, Rb. The two first regions Ra, Rb are each provided in a semi-circular arc shape within a range of approximately 180° centered on the central axis 9. The two first regions Ra, Rb are arranged concentrically and symmetrically with respect to a line. Also, the radial distance from the central axis 9 to the first region Ra and the radial distance from the central axis 9 to the first region Rb are substantially the same.

[0033] FIG. 6 is a partial plan view of the substrate 41. As shown in FIG. 6, each of the plurality of first regions Ra, Rb includes a region in which first portions r1 extending in a direction having components in both the radial direction and the circumferential direction are repeatedly arranged in the circumferential direction. Specifically, in each of the two first regions Ra, Rb, one conductor extends in the circumferential direction while zigzagging. The plurality of first portions r1 are arranged in the circumferential direction in a posture substantially parallel to each other. Among the two first regions Ra, Rb, the first portion r1 of one first region Ra is inclined to one side in the circumferential direction with respect to the radial direction. The first portion r1 of the other first region Rb is inclined to the other side in the circumferential direction with respect to the radial direction. The inclination angle of the first portion r1 with respect to the radial direction is, for example, 45°. The ends of the first portions r1 adjacent to each other in the circumferential direction are alternately connected on the inner side or the outer side in the radial direction. Thereby, the plurality of first portions r1 are connected in series as a whole.

[0034] The outer first resistance line portion W12 has a plurality of first regions Rc, Rd. The plurality of first regions Rc, Rd are arranged at intervals in the circumferential direction. In the present embodiment, the outer first resistance line portion W12 has two first regions Rc, Rd. The two first regions Rc, Rd are each provided in a semi-circular arc shape within a range of approximately 180° centered on the central axis 9. The two first regions Rc, Rd are arranged concentrically and symmetrically with respect to a line. Also, the radial distance from the central axis 9 to the first region Rc and the radial distance from the central axis 9 to the first region Rd are substantially the same.

[0035] As shown in FIG. 6, each of the plurality of first regions Rc and Rd includes a region in which first portions r1 extending in a direction having components in both the radial direction and the circumferential direction are repeatedly arranged in the circumferential direction. Specifically, in each of the two first regions Rc and Rd, one conducting wire extends in the circumferential direction while zigzagging. The plurality of first portions r1 are arranged in the circumferential direction in a posture substantially parallel to each other. Among the two first regions Rc and Rd, the first portion r1 of one first region Rc is inclined toward the other side in the circumferential direction with respect to the radial direction. The first portion r1 of the other first region Rd is inclined toward one side in the circumferential direction with respect to the radial direction. The inclination angle of the first portion r1 with respect to the radial direction is, for example, 45°. The ends of the first portions r1 adjacent to each other in the circumferential direction are alternately connected inside or outside the radial direction. Thereby, the plurality of first portions r1 are connected in series as a whole.

[0036] The second resistance wire portion W2 has an inner second resistance wire portion W21 and an outer second resistance wire portion W22. The outer second resistance wire portion W22 is arranged on the outer side in the radial direction with respect to the inner second resistance wire portion W21.

[0037] The inner second resistance wire portion W21 has a plurality of second regions Re and Rf. The plurality of second regions Re and Rf are arranged at intervals in the circumferential direction. In the present embodiment, the inner second resistance wire portion W21 has two second regions Re and Rf. The two second regions Re and Rf are each provided in a semicircular arc shape in a range of about 180° centered on the central axis 9. The two second regions Re and Rf are arranged concentrically and symmetrically with respect to a line. Also, the radial distance from the central axis 9 to the second region Re and the radial distance from the central axis 9 to the second region Rf are substantially the same.

[0038] As shown in FIG. 6, each of the plurality of second regions Re and Rf includes a region in which second portions r2 extending in a direction having components in both the radial direction and the circumferential direction are repeatedly arranged in the circumferential direction. Specifically, in each of the two second regions Re and Rf, a single conductor extends in the circumferential direction while zigzagging. The plurality of second portions r2 are arranged in the circumferential direction in a posture substantially parallel to each other. Among the two second regions Re and Rf, the second portion r2 of one second region Re is inclined toward one side in the circumferential direction with respect to the radial direction. The second portion r2 of the other second region Rf is inclined toward the other side in the circumferential direction with respect to the radial direction. The inclination angle of the second portion r2 with respect to the radial direction is, for example, 45°. The ends of the second portions r2 adjacent to each other in the circumferential direction are alternately connected on the inner side or the outer side in the radial direction. Thereby, the plurality of second portions r2 are connected in series as a whole.

[0039] The outer second resistance wire portion W22 has a plurality of second regions Rg and Rh. The plurality of second regions Rg and Rh are arranged at intervals in the circumferential direction. In the present embodiment, the outer second resistance wire portion W22 has two second regions Rg and Rh. The two second regions Rg and Rh are each provided in a semi-circular arc shape within a range of approximately 180° centered on the central axis 9. The two second regions Rg and Rh are arranged concentrically and symmetrically with respect to a line. Also, the radial distance from the central axis 9 to the second region Rg and the radial distance from the central axis 9 to the second region Rh are substantially the same.

[0040] As shown in FIG. 6, each of the plurality of second regions Rg and Rh includes a region in which a second part r2 extending in a direction having components in both the radial direction and the circumferential direction is repeatedly arranged in the circumferential direction. Specifically, in each of the two second regions Rg and Rh, one conducting wire extends in the circumferential direction while zigzagging. The plurality of second parts r2 are arranged in the circumferential direction in a posture substantially parallel to each other. Among the two second regions Rg and Rh, the second part r2 of one second region Rg is inclined to the other side in the circumferential direction with respect to the radial direction. The second part r2 of the other second region Rh is inclined to one side in the circumferential direction with respect to the radial direction. The inclination angle of the second part r2 with respect to the radial direction is, for example, 45°. The ends of the second parts r2 adjacent to each other in the circumferential direction are alternately connected inside or outside the radial direction. Thereby, the plurality of second parts r2 are connected in series as a whole.

[0041] FIG. 7 is a circuit diagram of a first bridge circuit C1 including four first regions Ra, Rb, Rc, and Rd of the first resistance wire part W1. As shown in FIGS. 6 and 7, the first resistance wire part W1 has a first connection region W13 connected to the plurality of first regions Ra, Rb, Rc, and Rd. In the present embodiment, the number of the first regions Ra, Rb, Rc, and Rd is four. The plurality of first regions Ra, Rb, Rc, and Rd are connected via the first connection region W13. Thereby, the first bridge circuit C1 is formed.

[0042] The first region Ra and the first region Rb are connected in series in this order. The first region Rc and the first region Rd are connected in series in this order. Then, between the + pole and the - pole of the power supply voltage, the column of the two first regions Ra and Rb and the column of the two first regions Rc and Rd are connected in parallel. Also, the midpoint M11 between the two first regions Ra and Rb and the midpoint M12 between the two first regions Rc and Rd are connected to the first voltmeter V1.

[0043] The resistance value of each first part r1 changes according to the torque applied to the region where the resistance wire 412 is disposed. That is, in the present embodiment, the resistance values of the first parts r1 in the four first regions Ra, Rb, Rc, and Rd change according to the torque applied to the base part 231. For example, when a torque directed to one side in the circumferential direction is applied to the base part 231 about the central axis 9, the resistance values of the first parts r1 in the two first regions Ra and Rd decrease, and the resistance values of the first parts r1 in the other two first regions Rb and Rc increase. On the other hand, when a torque directed to the other side in the circumferential direction is applied to the base part 231 about the central axis 9, the resistance values of the first parts r1 in the two first regions Ra and Rd increase, and the resistance values of the first parts r1 in the other two first regions Rb and Rc decrease. Thus, the two first regions Ra and Rd and the other two first regions Rb and Rc exhibit resistance value changes opposite to each other with respect to the torque.

[0044] Then, when the resistance values of the four first regions Ra, Rb, Rc, and Rd change, the potential difference between the midpoint M11 between the two first regions Ra and Rb and the midpoint M12 between the two first regions Rc and Rd changes, so the measured value of the first voltmeter V1 also changes. Therefore, based on the measured value of this first voltmeter V1, the direction and magnitude of the torque applied to the base part 231 can be detected.

[0045] FIG. 8 is a circuit diagram of a second bridge circuit C2 including four second regions Re, Rf, Rg, and Rh of the second resistance wire part W2. As shown in FIGS. 6 and 8, the second resistance wire part W2 has a second connection region W23 connected to a plurality of second regions Re, Rf, Rg, and Rh. In the present embodiment, the number of the second regions Re, Rf, Rg, and Rh is four. The plurality of second regions Re, Rf, Rg, and Rh are connected via the second connection region W23. Thereby, the second bridge circuit C2 is formed.

[0046] The second region Re and the second region Rf are connected in series in this order. The second region Rg and the second region Rh are connected in series in this order. Then, between the + pole and the - pole of the power supply voltage, the series of two second regions Re and Rf and the series of two second regions Rg and Rh are connected in parallel. Also, the midpoint M21 between the two second regions Re and Rf and the midpoint M22 between the two second regions Rg and Rh are connected to the second voltmeter V2.

[0047] The resistance value of each second part r2 changes according to the torque applied to the region where the resistance wire 412 is arranged. In this embodiment, the resistance values of the second parts r2 of the four second regions Re, Rf, Rg, and Rh change according to the torque applied to the base part 231. For example, when a torque acting in one circumferential direction is applied to the base part 231 about the central axis 9, the resistance values of the second parts r2 of the two second regions Re and Rh decrease, and the resistance values of the second parts r2 of the other two second regions Rf and Rg increase. On the other hand, when a torque acting in the other circumferential direction is applied to the base part 231 about the central axis 9, the resistance values of the second parts r2 of the two second regions Re and Rh increase, and the resistance values of the second parts r2 of the other two second regions Rf and Rg decrease. Thus, the two second regions Re and Rh and the other two second regions Rf and Rg show resistance value changes in opposite directions with respect to the torque.

[0048] Then, when the resistance values of the four second regions Re, Rf, Rg, and Rh change, the potential difference between the midpoint M21 between the two second regions Re and Rf and the midpoint M22 between the two second regions Rg and Rh changes, so the measured value of the second voltmeter V2 also changes. Therefore, based on the measured value of this second voltmeter V2, the direction and magnitude of the torque applied to the base part 231 can be detected.

[0049] In this way, in this embodiment, two bridge circuits, the first bridge circuit C1 and the second bridge circuit C2, are configured. Thereby, even when an abnormality occurs in one of the bridge circuits, the torque can be detected by the other bridge circuit. Also, when an abnormality occurs in one of the bridge circuits, the abnormality can be detected.

[0050] Note that a part of the first connection region W13 and the second connection region W23 may be connected in parallel to a common power supply voltage or may be connected to different power supply voltages. That is, the power supply voltage may be divided for each bridge circuit. When the power supply voltage is divided for each bridge circuit, even if a part of the power supply voltages fails to function properly, the power supply voltage is supplied from other power supply voltages to at least one bridge circuit, so that torque can be detected by the bridge circuit.

[0051] The detection circuit 42 is electrically connected to the resistance wire 412. The detection circuit 42 may be attached to the annular body 20 or may be provided at a position separated from the annular body 20. The detection circuit 42 outputs a first output signal Tr1 based on the measured value of the first voltmeter V1 and a second output signal Tr2 based on the measured value of the second voltmeter V2, respectively. However, the detection circuit 42 may output a signal based on the sum of the output signals of the first bridge circuit C1 and the second bridge circuit C2. Specifically, the detection circuit 42 may output a detection signal indicating the direction and magnitude of the torque applied to the base portion 231 based on the sum of the first output signal Tr1 based on the measured value of the first voltmeter V1 and the second output signal Tr2 based on the measured value of the second voltmeter V2. Thereby, when the base portion 231 is affected by the cam 31 or the like depending on the angle of the base portion 231, by outputting a detection signal based on the sum of the first output signal Tr1 and the second output signal Tr2 at different angles, a detection signal with the influence depending on the angle reduced can be output. Note that the detection circuit 42 may output a detection signal based on the linear sum of the first output signal Tr1 and the second output signal Tr2. Further, the detection circuit 42 may output a detection signal based on the result obtained by substituting the first output signal Tr1 and the second output signal Tr2 into a predetermined function. Further, the detection circuit 42 may output a detection signal based on either one of the first output signal Tr1 and the second output signal Tr2.

[0052] <3-2. Regarding the diagnostic function> The detection circuit 42 has a diagnostic function for diagnosing the state of the resistance wire 412. Hereinafter, this diagnostic function will be described. FIG. 9 is a flowchart showing the flow of diagnostic processing in the detection circuit 42. As shown in FIG. 9, the detection circuit 42 outputs a diagnostic signal indicating the state of the resistance wire 412 by comparing the output signal of the first bridge circuit C1 and the output signal of the second bridge circuit C2. Thereby, the torque detection device 40 can diagnose and output the state of the resistance wire 412.

[0053] Specifically, the detection circuit 42 first compares a first output signal Tr1 based on the measured value of the first voltmeter V1 and a second output signal Tr2 based on the measured value of the second voltmeter V2. Then, it is determined whether the relationship between the first output signal Tr1 and the second output signal Tr2 is within the normal range (step ST1). For example, the detection circuit 42 determines whether the difference between the first output signal Tr1 and the second output signal Tr2 is less than a predetermined threshold value.

[0054] When there is no abnormality such as a disconnection in both the first resistance wire part W1 and the second resistance wire part W2, the first resistance wire part W1 and the second resistance wire part W2 show approximate resistance value changes with respect to the torque applied to the base part 231. Therefore, the difference between the first output signal Tr1 and the second output signal Tr2 becomes less than a predetermined threshold value (yes in step ST1). In this case, the detection circuit 42 outputs a first signal as a diagnostic signal indicating the state of the resistance wire 412 (step ST2). The first signal is a diagnostic signal indicating that there is no abnormality in the resistance wire 412.

[0055] On the other hand, when there is an abnormality such as a disconnection in either the first resistance wire part W1 or the second resistance wire part W2, the one of the first resistance wire part W1 and the second resistance wire part W2 shows a resistance value different from normal. Therefore, the difference between the first output signal Tr1 and the second output signal Tr2 becomes equal to or greater than a predetermined threshold value (no in step ST1). In this case, the detection circuit 42 outputs a second signal indicating that there is an abnormality in the resistance wire 412 (step ST3).

[0056] In the process of step ST3, the current values of the first bridge circuit C1 and the second bridge circuit C2 may be checked. Thereby, it is possible to determine which bridge circuit, the first bridge circuit C1 or the second bridge circuit C2, has an abnormality. Then, only the second signal and the output signal of the normally functioning bridge circuit may be output. Thereby, it is possible to perform torque detection with the normally functioning bridge circuit.

[0057] Also, when the detection circuit 42 determines that there is an abnormality in the resistance wire 412, if the current values of the first bridge circuit C1 and the second bridge circuit C2 are normal, it can be determined that an abnormality has occurred at a location other than the bridge circuit. As a specific example, when the resistance wire 412 is peeled off from the base portion 231, it is possible to detect that an abnormality has occurred at a location other than the bridge circuit.

[0058] Note that the above-described step ST2 may be omitted. That is, when the difference between the output signal of the first bridge circuit C1 and the output signal of the second bridge circuit C2 is less than a predetermined threshold value, the detection circuit 42 may not output a diagnostic signal. The detection circuit 42 may output a predetermined signal as a diagnostic signal when the difference between the output signal of the first bridge circuit C1 and the output signal of the second bridge circuit C2 is equal to or greater than the predetermined threshold value. Thereby, when an abnormality occurs in either the first bridge circuit C1 or the second bridge circuit C2, the torque detection device 40 can output a diagnostic result.

[0059] Thereafter, the detection circuit 42 displays the diagnostic result (step ST4). Specifically, the detection circuit 42 displays the diagnostic result indicated by the diagnostic signal on a display (not shown). Thereby, the user of the wave decelerator 1 or the robot 100 can know the state of the resistance wire 412. Note that the diagnostic result of the above-described step ST4 may be displayed by a device other than the display or by other means.

[0060] As described above, the annular body 20 has a resistance wire 412 for detecting the torque applied to the base portion 231. Further, the resistance wire 412 has a first resistance wire portion W1 and a second resistance wire portion W2. Therefore, by comparing the output signal of the first resistance wire portion W1 and the output signal of the second resistance wire portion W2, the state of the resistance wire 412 can be diagnosed. That is, a torque detection device 40 can be realized that can detect the torque applied to the base portion 231 and can constantly monitor the state of the resistance wire 412.

[0061] In particular, in the present embodiment, as shown in FIG. 5, the circumferential gap w14 between the first regions Ra, Rb, Rc, Rd adjacent in the circumferential direction and the circumferential gap w24 between the second regions Re, Rf, Rg, Rh adjacent in the circumferential direction are arranged at the same position in the circumferential direction. For this reason, in the first resistance wire portion W1 and the second resistance wire portion W2, the influences depending on the circumferential angle can be approximated. Therefore, by comparing the output signal of the first resistance wire portion W1 and the output signal of the second resistance wire portion W2, the state of the resistance wire 412 can be diagnosed more accurately.

[0062] In the present embodiment, the number of the first regions Ra, Rb included in the inner first resistance wire portion W11, the number of the first regions Rc, Rd included in the outer first resistance wire portion W12, the number of the second regions Re, Rf included in the inner second resistance wire portion W21, and the number of the second regions Rg, Rh included in the outer second resistance wire portion W22 are the same. Specifically, the number of the first regions Ra, Rb included in the inner first resistance wire portion W11, the number of the first regions Rc, Rd included in the outer first resistance wire portion W12, the number of the second regions Re, Rf included in the inner second resistance wire portion W21, and the number of the second regions Rg, Rh included in the outer second resistance wire portion W22 are all two. And, the circumferential gap w14 between the first regions Ra, Rb adjacent in the circumferential direction in the inner first resistance wire portion W11, the circumferential gap w14 between the first regions Rc, Rd adjacent in the circumferential direction in the outer first resistance wire portion W12, the circumferential gap w24 between the second regions Re, Rf adjacent in the circumferential direction in the inner second resistance wire portion W21, and the circumferential gap w24 between the second regions Rg, Rh adjacent in the circumferential direction in the outer second resistance wire portion W22 are arranged at the same position in the circumferential direction.

[0063] In this way, in the first resistance wire portion W1 and the second resistance wire portion W2, effects depending on the circumferential angle occur under substantially the same conditions. Therefore, by comparing the output signal of the first resistance wire portion W1 and the output signal of the second resistance wire portion W2, the state of the resistance wire 412 can be diagnosed with higher accuracy.

[0064] When the wave reducer 1 is driven, periodic flexural deformation occurs in the annular body 20. For this reason, the output signals of the first resistance wire portion W1 and the second resistance wire portion W2 include a component reflecting the torque to be originally measured and an error component (ripple error) caused by the periodic flexural deformation of the annular body 20. The ripple error varies according to the rotation angle of the rotational motion input to the annular body 20.

[0065] FIG. 10 is a graph showing the time changes of the ripple error E1 of the first resistance wire portion W1 and the ripple error E2 of the second resistance wire portion W2. The horizontal axis of the graph in FIG. 10 indicates time. The vertical axis of the graph in FIG. 10 indicates a value obtained by normalizing the voltage representing the ripple error. These ripple errors E1 and E2 correspond to the above-described "effects depending on the circumferential angle". As described above, in the present embodiment, the circumferential gaps w14 between the first regions Ra, Rb, Rc, Rd adjacent in the circumferential direction and the circumferential gaps w24 between the second regions Re, Rf, Rg, Rh adjacent in the circumferential direction are arranged at the same circumferential position. For this reason, the ripple error E1 of the first resistance wire portion W1 and the ripple error E2 of the second resistance wire portion W2 have approximate waveforms. For this reason, even without performing the ripple correction described later, by comparing the difference between the output signal of the first resistance wire portion W1 and the second resistance wire portion W2 with a predetermined threshold value, the state of the resistance wire 412 can be diagnosed accurately. Note that, as described above, the ripple errors E1 and E2 shown in the graph of FIG. 10 are values obtained by normalizing the voltage. As the above-described "effects depending on the circumferential angle", a strain amount may be used instead of the value obtained by normalizing the voltage.

[0066] In addition, in the present embodiment, the first resistance wire portion W1 and the second resistance wire portion W2 are arranged concentrically about the central axis 9. By doing so, the difference between the output signal of the first resistance wire portion W1 and the output signal of the second resistance wire portion W2 can be reduced as compared with the case where the centers of the first resistance wire portion W1 and the second resistance wire portion W2 are displaced. Therefore, by comparing the output signal of the first resistance wire portion W1 and the output signal of the second resistance wire portion W2, the state of the resistance wire 412 can be diagnosed with higher accuracy.

[0067] Also, as shown in FIG. 5, in the present embodiment, the central angle θ of the circumferential gap w14 between the circumferentially adjacent first regions Ra, Rb, Rc, Rd and the central angle θ of the circumferential gap w24 between the circumferentially adjacent second regions Re, Rf, Rg, Rh are equal. By doing so, the difference between the output signal of the first resistance wire portion W1 and the output signal of the second resistance wire portion W2 can be further reduced. Therefore, by comparing the output signal of the first resistance wire portion W1 and the output signal of the second resistance wire portion W2, the state of the resistance wire 412 can be diagnosed with higher accuracy.

[0068] Also, as shown in FIG. 5, in the present embodiment, the radial interval d0 between the first resistance wire portion W1 and the second resistance wire portion W2 is narrower than both the radial width d1 of the first regions Ra, Rb, Rc, Rd and the radial width d2 of the second regions Re, Rf, Rg, Rh. By thus reducing the radial interval d0 between the first resistance wire portion W1 and the second resistance wire portion W2, the difference in the influence depending on the radial position between the output signal of the first resistance wire portion W1 and the output signal of the second resistance wire portion W2 can be reduced as compared with the case where the radial interval d0 between the first resistance wire portion W1 and the second resistance wire portion W2 is large. Therefore, by comparing the output signal of the first resistance wire portion W1 and the output signal of the second resistance wire portion W2, the state of the resistance wire 412 can be diagnosed with higher accuracy.

[0069] Also, as shown in FIG. 5, in the present embodiment, the radial interval d0 between the first resistance wire portion W1 and the second resistance wire portion W2 is narrower than either the interval d3 between the first regions Ra, Rb, Rc, Rd adjacent in the circumferential direction or the interval d4 between the second regions Re, Rf, Rg, Rh adjacent in the circumferential direction. In this way, by reducing the radial interval d0 between the first resistance wire portion W1 and the second resistance wire portion W2, the difference in the influence depending on the radial position between the output signal of the first resistance wire portion W1 and the output signal of the second resistance wire portion W2 can be reduced as compared with the case where the radial interval d0 between the first resistance wire portion W1 and the second resistance wire portion W2 is large. Therefore, by comparing the output signal of the first resistance wire portion W1 and the output signal of the second resistance wire portion W2, the state of the resistance wire 412 can be diagnosed more accurately.

[0070] The resistance values of the plurality of first regions Ra, Rb, Rc, Rd may be equal to each other. Also, the resistance values of the plurality of second regions Re, Rf, Rg, Rh may be equal to each other. By doing so, the difference between the output signal of the first resistance wire portion W1 in the normal state and the output signal of the second resistance wire portion W2 in the normal state can be reduced. Therefore, by comparing the output signal of the first resistance wire portion W1 and the output signal of the second resistance wire portion W2, the state of the resistance wire 412 can be diagnosed more accurately.

[0071] In the present embodiment, the first resistance wire portion W1 had four first regions Ra, Rb, Rc, Rd. And the first bridge circuit C1 was a full-bridge circuit including the four first regions Ra, Rb, Rc, Rd. However, the first resistance wire portion W1 may have only two first regions. In that case, the first bridge circuit C1 may be a half-bridge circuit composed of the two first regions and two fixed resistors.

[0072] Further, in the present embodiment, the second resistance wire portion W2 had four second regions Re, Rf, Rg, and Rh. And the second bridge circuit C2 was a full-bridge circuit including the four second regions Re, Rf, Rg, and Rh. However, the second resistance wire portion W2 may have only two second regions. In that case, the second bridge circuit C2 may be a half-bridge circuit composed of the two second regions and two fixed resistors.

[0073] <3-3. About Ripple Correction> As described above, when the wave reducer 1 is driven, periodic flexural deformation occurs in the annular body 20. For this reason, the output signals of the first resistance wire portion W1 and the second resistance wire portion W2 include a component reflecting the torque to be originally measured and an error component (ripple error) caused by the periodic flexural deformation of the annular body 20. The ripple error changes according to the rotation angle of the rotational motion input to the annular body 20.

[0074] Therefore, the detection circuit 42 of the present embodiment performs a correction process (ripple correction) for canceling the above ripple error. Hereinafter, this ripple correction will be described.

[0075] As shown in FIG. 5, the resistance wire 412 of the present embodiment further has a third resistance wire portion W3. The third resistance wire portion W3 is a resistance wire portion for detecting the rotation angle of the rotational motion input to the annular body 20.

[0076] The third resistance line portion W3 has a plurality of third regions Ri, Rj, Rk, Rl, Rm, Rn, Ro, Rp. In the present embodiment, the third resistance line portion W3 has eight third regions Ri, Rj, Rk, Rl, Rm, Rn, Ro, Rp. The plurality of third regions Ri, Rj, Rk, Rl, Rm, Rn, Ro, Rp are arranged at intervals in the circumferential direction. In the present embodiment, the eight third regions Ri, Rj, Rk, Rl, Rm, Rn, Ro, Rp are arranged at equal intervals in the circumferential direction. The plurality of third regions Ri, Rj, Rk, Rl, Rm, Rn, Ro, Rp are each formed by a single conducting wire. Each of the third regions Ri, Rj, Rk, Rl, Rm, Rn, Ro, Rp extends in an arc shape along the circumferential direction.

[0077] Each of the third regions Ri, Rj, Rk, Rl, Rm, Rn, Ro, Rp includes a region in which the third part r3 is repeatedly arranged. The third part r3 extends in the circumferential direction and is repeatedly arranged in the radial direction. However, the third part r3 may extend in the radial direction and be repeatedly arranged in the circumferential direction.

[0078] Among the eight third regions Ri, Rj, Rk, Rl, Rm, Rn, Ro, Rp, four non-adjacent third regions Ri, Rk, Rm, Ro are connected to each other to form a third bridge circuit C3. FIG. 11 is a circuit diagram of the third bridge circuit C3. As shown in FIG. 11, the third region Ri and the third region Rk are connected in series in this order. The third region Ro and the third region Rm are connected in series in this order. Then, between the + pole and the - pole of the power supply voltage, the column of the two third regions Ri, Rk and the column of the two third regions Ro, Rm are connected in parallel. Also, the midpoint M31 between the two third regions Ri, Rk and the midpoint M32 between the two third regions Ro, Rm are connected to the third voltmeter V3.

[0079] Of the eight third regions Ri, Rj, Rk, Rl, Rm, Rn, Ro, Rp, the remaining four third regions Rj, Rl, Rn, Rp are connected to each other to form a fourth bridge circuit C4. FIG. 12 is a circuit diagram of the fourth bridge circuit C4. As shown in FIG. 12, the third region Rp and the third region Rn are connected in series in this order. The third region Rj and the third region Rl are connected in series in this order. Then, between the + pole and the - pole of the power supply voltage, the column of the two third regions Rp, Rn and the column of the two third regions Rj, Rl are connected in parallel. Also, the midpoint M41 between the two third regions Rp, Rn and the midpoint M42 between the two third regions Rj, Rl are connected to the fourth voltmeter V4.

[0080] When the wave decelerator 1 is driven, a portion extending in the circumferential direction (hereinafter referred to as the "extension portion") and a portion contracting in the circumferential direction (hereinafter referred to as the "contraction portion") are generated in the base portion 231 of the annular body 20. 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 alternately generated at intervals of 90° in the circumferential direction around the central axis 9. And the locations where these extension portions and contraction portions are generated rotate at the first rotational speed described above.

[0081] The resistance values of the eight third regions Ri, Rj, Rk, Rl, Rm, Rn, Ro, Rp change according to the expansion and contraction in the circumferential direction of the base portion 231. For example, when the above-described extension portion overlaps a certain third region, the resistance value of that third region decreases. Also, when the above-described contraction portion overlaps a certain third region, the resistance value of that third region increases.

[0082] In the example of FIG. 5, when the contraction portion overlaps the third regions Ri, Rm, the extension portion overlaps the third regions Rk, Ro. Also, when the extension portion overlaps the third regions Ri, Rm, the contraction portion overlaps the third regions Rk, Ro. Therefore, in the third bridge circuit C3, the third regions Ri, Rm and the third regions Rk, Ro show opposite resistance value changes.

[0083] Also, in the example of Fig. 5, when the contraction part overlaps with the third regions Rp and Rl, the extension part overlaps with the third regions Rn and Rj. Also, when the extension part overlaps with the third regions Rp and Rl, the contraction part overlaps with the third regions Rn and Rj. Therefore, in the fourth bridge circuit C4, the third regions Rp and Rl and the third regions Rn and Rj show reverse resistance value changes.

[0084] Fig. 13 is a graph showing the time changes of the measured value v3 of the third voltmeter V3 of the third bridge circuit C3 and the measured value v4 of the fourth voltmeter V4 of the fourth bridge circuit C4. The horizontal axis of the graph in Fig. 13 indicates time. The vertical axis of the graph in Fig. 13 indicates voltage value. When the wave reducer 1 is driven, as shown in Fig. 13, sinusoidal measured values v3 and v4 that change periodically are output from the third voltmeter V3 and the fourth voltmeter V4, respectively. The period T of these measured values v3 and v4 corresponds to 1 / 2 times the period of the first rotational speed described above. Also, depending on whether the phase of the measured value v4 of the fourth voltmeter V4 is advanced by 1 / 8 of the first rotational speed (1 / 4 of the measured values v3 and v4) or delayed by 1 / 8 of the first rotational speed (1 / 4 of the measured values v3 and v4) with respect to the phase of the measured value v3 of the third voltmeter V3, the direction of the input rotational motion can be determined.

[0085] The detection circuit 42 can detect the rotation angle of the rotational motion input to the annular body 20 based on the measured value v3 of the third voltmeter V3 and the measured value v4 of the fourth voltmeter V4. Specifically, for example, the detection circuit 42 has a storage unit that stores a function table associating combinations of the measured value v3 of the third voltmeter V3 and the measured value v4 of the fourth voltmeter V4 with the rotation angle. The detection circuit 42 outputs the rotation angle by inputting the measured values v3 and v4 to the function table.

[0086] In addition, with respect to the rotation angle of the annular body 20, the ripple error changes in a sine wave shape. The detection circuit 42 calculates the above-described ripple error according to the output rotation angle. Thereafter, the output signal of the first resistance wire portion W1 and the output signal of the second resistance wire portion W2 are corrected using the calculated ripple error. As a result, the detection circuit 42 can output the torque applied to the annular body 20 with higher accuracy.

[0087] As described above, the resistance wire 412 of the present embodiment has the third resistance wire portion W3. Therefore, the rotation angle of the rotational motion input to the annular body 20 can be detected. Accordingly, the output signal of the first resistance wire portion W1 and the output signal of the second resistance wire portion W2 can be corrected according to the rotation angle.

[0088] Note that the detection circuit 42 may multiply the measured values v3 and v4 of the third voltmeter V3 and the fourth voltmeter V4 by a predetermined coefficient without calculating the above-described rotation angle, and synthesize them with the output signal of the first resistance wire portion W1 and the output signal of the second resistance wire portion W2. In this way, the processing load associated with the calculation of the rotation angle is reduced. Therefore, the calculation speed of the detection circuit 42 can be improved.

[0089] Also, in the present embodiment, the circumferential gaps w14 between the circumferentially adjacent first regions Ra, Rb, Rc, Rd and the circumferential gaps w24 between the circumferentially adjacent second regions Re, Rf, Rg, Rh are arranged at the same circumferential position as the circumferential gap w34 between the circumferentially adjacent third regions Ri, Rp. In this way, using these gaps w14, w24, w34, the wiring can be easily drawn out radially outward.

[0090] Note that in the present embodiment, the third resistance wire portion W3 is arranged radially outside the first resistance wire portion W1 and the second resistance wire portion W2. However, the third resistance wire portion W3 may be arranged radially inside the first resistance wire portion W1 and the second resistance wire portion W2. Also, the third resistance wire portion W3 may be arranged radially outside the first resistance wire portion W1 and radially inside the second resistance wire portion W2.

[0091] Of the four third regions Ri, Rk, Rm, and Ro described above, two of the third regions Ri, Rk or two of the third regions Rm, Ro may be omitted. Even in such a case, by using the third bridge circuit C3 as a half-bridge circuit using two fixed resistors, an output value corresponding to the rotation angle can be obtained. Similarly, of the four third regions Rj, Rl, Rn, and Rp described above, two of the third regions Rj, Rl or two of the third regions Rn, Rp may be omitted. Even in such a case, by using the fourth bridge circuit C4 as a half-bridge circuit using two fixed resistors, an output value corresponding to the rotation angle can be obtained.

[0092] That is, the third resistance wire portion W3 only needs to have four or more third regions. Thereby, the rotation angle and the direction of rotation of the rotational motion input to the annular body 20 can be detected.

[0093] <3-4. About Temperature Compensation> The resistance value of the first resistance wire portion W1 and the resistance value of the second resistance wire portion W2 change slightly according to the temperature of the resistance wire 412. Therefore, the output signals of the first resistance wire portion W1 and the second resistance wire portion W2 include an error component (temperature error) caused by temperature. Therefore, the detection circuit 42 of the present embodiment performs a correction process (temperature compensation) for canceling the above temperature error. Hereinafter, this temperature compensation will be described.

[0094] As shown in FIG. 5, the resistance wire 412 of the present embodiment further has a fourth resistance wire portion W4. The fourth resistance wire portion W4 is a resistance wire portion for detecting the temperature of the resistance wire 412. The fourth resistance wire portion W4 includes a fourth part r4. The fourth part r4 extends in the circumferential direction. That is, the fourth part r4 extends in an arc shape around the central axis 9. For this reason, the change in the resistance value of the fourth part r4 due to the circumferential torque is extremely small. In addition, the fourth part r4 extends over substantially the entire circumference around the central axis 9. For this reason, the resistance value of the fourth part r4 is hardly affected by the expansion and contraction caused by the bending deformation of the base portion 231. Therefore, the change in the resistance value of the fourth part r4 is dominated by the change in temperature.

[0095] The detection circuit 42 measures the resistance value of the fourth part r4. The measured resistance value becomes a signal reflecting the temperature of the resistance wire 412. The detection circuit 42 corrects the output signal of the first resistance wire part W1 and the output signal of the second resistance wire part W2 based on the measured resistance value. Specifically, the output signal of the first resistance wire part W1 and the output signal of the second resistance wire part W2 are increased or decreased in a direction to cancel the change due to temperature. As a result, the detection circuit 42 can output the torque applied to the annular body 20 with higher accuracy.

[0096] As described above, the resistance wire 412 of the present embodiment has the fourth resistance wire part W4. Therefore, the temperature of the resistance wire 412 can be detected. Accordingly, the output signal of the first resistance wire part W1 and the output signal of the second resistance wire part W2 can be corrected according to the temperature of the resistance wire 412.

[0097] In the present embodiment, the fourth resistance wire part W4 is arranged on the outer side in the radial direction than the first resistance wire part W1 and the second resistance wire part W2. However, the fourth resistance wire part W4 may be arranged on the inner side in the radial direction than the first resistance wire part W1 and the second resistance wire part W2. Also, the fourth resistance wire part W4 may be arranged on the outer side in the radial direction of the first resistance wire part W1 and on the inner side in the radial direction of the second resistance wire part W2.

[0098] Also, in the present embodiment, the fourth resistance wire part W4 is arranged on the outer side in the radial direction than the third resistance wire part W3. However, the fourth resistance wire part W4 may be arranged on the inner side in the radial direction than the third resistance wire part W3.

[0099] In addition, the fourth resistance wire part may be arranged in a double layer in the radial direction. In that case, the output signal of the first resistance wire part W1 and the output signal of the second resistance wire part W2 can be corrected by each of the two fourth resistance wire parts. In this case, even if an abnormality occurs in either of the two fourth resistance wire parts, the abnormality can be detected immediately. Also, even if an abnormality occurs in either of the two fourth resistance wire parts, the other fourth resistance wire part can play the role of a temperature sensor.

[0100] <4. Second Embodiment> Next, the second embodiment will be described. Hereinafter, in order to facilitate understanding of the correspondence with the above-described first embodiment, the same reference numerals as those in the first embodiment are used. Also, hereinafter, redundant descriptions of points equivalent to those in the first embodiment are omitted, and the description will focus on the differences from the first embodiment.

[0101] FIG. 14 is a plan view of the substrate 41 according to the second embodiment. As shown in FIG. 14, in the second embodiment, the circumferential gap w14 between the first regions Ra, Rb, Rc, Rd adjacent to each other in the circumferential direction of the first resistance wire portion W1 and the circumferential gap w24 between the second regions Re, Rf, Rg, Rh adjacent to each other in the circumferential direction of the second resistance wire portion W2 are arranged with a constant angular shift in the circumferential direction. By doing so, an influence depending on the circumferential angle occurs in a state where there is a constant angular shift between the output signal of the first resistance wire portion W1 and the output signal of the second resistance wire portion W2. Therefore, based on the output signal of the first resistance wire W1 portion and the output signal of the second resistance wire portion W2, an output signal with the influence depending on the circumferential angle reduced can be obtained.

[0102] In this embodiment, the number of the first regions Ra, Rb of the inner first resistance wire portion W11, the number of the first regions Rc, Rd of the outer first resistance wire portion W12, the number of the second regions Re, Rf of the inner second resistance wire portion W21, and the number of the second regions Rg, Rh of the outer second resistance wire portion W22 are the same. Specifically, the number of the first regions Ra, Rb of the inner first resistance wire portion W11, the number of the first regions Rc, Rd of the outer first resistance wire portion W12, the number of the second regions Re, Rf of the inner second resistance wire portion W21, and the number of the second regions Rg, Rh of the outer second resistance wire portion W22 are all two. And the circumferential gap w14 between the first regions Ra, Rb, Rc, Rd adjacent to each other in the circumferential direction in the inner first resistance wire portion W11 and the outer first resistance wire portion W12, and the circumferential gap w24 between the second regions Re, Rf, Rg, Rh adjacent to each other in the circumferential direction in the inner second resistance wire portion W21 and the outer second resistance wire portion W22 are arranged with a constant angular shift in the circumferential direction.

[0103] In this way, the output signals of the first resistance line portion W1 and the second resistance line portion W2 generate an influence depending on the circumferential angle in a state where there is a constant angular deviation. Therefore, for example, when the influence depending on the circumferential angle has a 180° period, an output signal with the influence depending on the circumferential angle reduced can be obtained based on the output signals of the first resistance line portion W1 and the second resistance line portion W2.

[0104] In particular, in this embodiment, the above-mentioned "constant angle" is 90°. In this way, the periods of the influences depending on the circumferential angle deviate by 90° between the output signal of the first resistance line portion W1 and the output signal of the second resistance line portion W2. Therefore, by taking the sum of the output signals of the first resistance line portion W1 and the second resistance line portion W2, the influence depending on the circumferential angle with a 180° period can be canceled.

[0105] FIG. 15 is a graph showing the time changes of the ripple error E1 of the first resistance line portion W1 and the ripple error E2 of the second resistance line portion W2. The horizontal axis of the graph in FIG. 15 indicates time. The vertical axis of the graph in FIG. 15 indicates a value obtained by normalizing the voltage representing the ripple error. These ripple errors E1 and E2 correspond to the above-mentioned "influence depending on the circumferential angle". As described above, in this embodiment, the circumferential gaps w14 between the circumferentially adjacent first regions Ra, Rb, Rc, Rd and the circumferential gaps w24 between the circumferentially adjacent second regions Re, Rf, Rg, Rh are arranged with a 90° deviation in the circumferential direction. For this reason, the ripple error E1 of the first resistance line portion W1 and the ripple error E2 of the second resistance line portion W2 have waveforms shifted by a half cycle. Therefore, the ripple error E1 of the first resistance line portion W1 and the ripple error E2 of the second resistance line portion W2 always have opposite signs and approximately the same absolute value (values with opposite signs reversed).

[0106] In this case, the detection circuit 42 can cancel the ripple errors E1 and E2 by calculating the sum of the output signal of the first resistance wire part W1 and the output signal of the second resistance wire part W2. Therefore, even without performing ripple correction as in the first embodiment, the detected value of the torque applied to the base part 231 can be output with the ripple error reduced. Thus, in this embodiment, since ripple correction is unnecessary, the third resistance wire part W3 can be omitted.

[0107] <5. Modification Example> As described above, the first and second embodiments of the present invention have been explained, but the present invention is not limited to the above embodiments.

[0108] In the above embodiment, the resistance wire 412 was arranged on the surface of the flexible deformable insulating layer 411. However, the resistance wire 412 may be arranged on the surface 234 of the base part 231. For example, an insulating film is formed on the surface 234 of the base part 231, and a conductor layer is formed on the surface of the insulating film by sputtering or the like. Then, the resistance wire 412 may be formed by removing unnecessary portions of the conductor layer by chemical means such as etching or physical means such as a laser. Note that, for example, an inorganic insulating material is used for the insulating film.

[0109] Also, in the above embodiment, the annular body 20 was a so-called "hat-type" flexible external gear in which the base part 231 extends radially outward from the body part 21. The hat-type annular body 20 is excellent in that it can effectively utilize the space inside the body part 21 in the radial direction. However, the annular body 20 may be a so-called "cup-type" flexible external gear in which the base part 231 extends radially inward from the body part 21.

[0110] Also, in the above embodiment, the harmonic reducer 1 mounted on the robot 100 has been described. However, a harmonic reducer 1 having a similar structure may be mounted on other devices such as an assist suit or an automated guided vehicle.

[0111] In addition, regarding the annular body, the wave reducer, and the detailed configuration of the robot, they may be appropriately changed without departing from the spirit of the present invention. Also, the elements appearing in the above-described embodiments and each modification may be appropriately combined within a range where no contradiction occurs.

Industrial Applicability

[0112] The present invention can be used in an annular body, a wave reducer, a robot, and a torque detection device.

Explanation of Reference Numerals

[0113] 1 Wave reducer 9 Central axis 10 Internal gear 11 Internal teeth 20 Annular body 21 Body part 22 External teeth 23 Annular plate part 30 Wave generator 31 Cam 32 Flexible bearing 40 Torque detection device 41 Substrate 42 Detection circuit 100 Robot 101 Base frame 102 Arm 103 Motor 231 Base part 232 Thick part 234 Surface 411 Insulation layer 412 Resistance wire C1 First bridge circuit C2 Second bridge circuit C3 Third bridge circuit C4 Fourth bridge circuit W1 First resistance wire part W11 Inner first resistance wire part W12 Outer first resistance wire part W13 First connection area W2 Second resistance wire part W21 Inner second resistance wire part W22 Outer Second Resistance Line Portion W23 Second Connection Region W3 Third Resistance Line Portion W4 Fourth Resistance Line Portion Ra, Rb, Rc, Rd First Region Re, Rf, Rg, Rh Second Region Ri, Rj, Rk, Rl, Rm, Rn, Ro, Rp Third Region r1 First Site r2 Second Site r3 Third Site r4 Fourth Site

Claims

1. a base portion that surrounds a central axis and extends in a direction intersecting the central axis; a resistance wire disposed on the base portion; and having; the resistance wire is; a first resistance wire portion; a second resistance wire portion disposed radially outside the first resistance wire portion; and having; the first resistance wire portion is; an inner first resistance wire portion; an outer first resistance wire portion disposed radially outside the inner first resistance wire portion; and having; the second resistance wire portion is; an inner second resistance wire portion; an outer second resistance wire portion disposed radially outside the inner second resistance wire portion; and having; the inner first resistance wire portion and the outer first resistance wire portion each have a plurality of first regions arranged at intervals in the circumferential direction; each of the plurality of first regions includes a region in which a first part extending in a direction having both radial and circumferential components is repeatedly arranged in the circumferential direction; the inner second resistance wire portion and the outer second resistance wire portion each have a plurality of second regions arranged at intervals in the circumferential direction; each of the plurality of second regions includes a region in which a second part extending in a direction having both radial and circumferential components is repeatedly arranged in the circumferential direction, an annular body.

2. The annular body according to claim 1, wherein a circumferential gap between the first regions adjacent to each other in the circumferential direction and a circumferential gap between the second regions adjacent to each other in the circumferential direction are arranged at the same circumferential position, an annular body.

3. The annular body according to claim 2, wherein the number of the first regions of the inner first resistance wire portion; the number of the first regions of the outer first resistance wire portion; the number of the second regions of the inner second resistance wire portion; the number of the second regions of the outer second resistance wire portion; are the same number, and a circumferential gap between the first regions adjacent to each other in the circumferential direction in the inner first resistance wire portion; a circumferential gap between the first regions adjacent to each other in the circumferential direction in the outer first resistance wire portion; a circumferential gap between the second regions adjacent to each other in the circumferential direction in the inner second resistance wire portion; a circumferential gap between the second regions adjacent to each other in the circumferential direction in the outer second resistance wire portion; are arranged at the same circumferential position, an annular body.

4. The annular body according to claim 2 or claim 3, wherein the resistance wire further has a third resistance wire portion, the third resistance wire portion has a plurality of third regions arranged at intervals in the circumferential direction, the third region includes a region in which a third part is repeatedly arranged. The third part is an annular body that extends in the radial direction and is repeatedly arranged in the circumferential direction, or extends in the circumferential direction and is repeatedly arranged in the radial direction. **Claim 5** An annular body according to claim 4, wherein the third resistance wire part has four or more of the third regions, and is an annular body. **Claim 6** An annular body according to claim 4 or claim 5, wherein the circumferential gap between the first regions adjacent in the circumferential direction and the circumferential gap between the second regions adjacent in the circumferential direction are arranged at the same circumferential position as the circumferential gap between the third regions adjacent in the circumferential direction, and is an annular body. **Claim 7** An annular body according to claim 1, wherein the circumferential gap between the first regions adjacent in the circumferential direction and the circumferential gap between the second regions adjacent in the circumferential direction are arranged with a constant angular shift in the circumferential direction, and is an annular body. **Claim 8** An annular body according to claim 7, the number of the first regions of the inner first resistance wire part, the number of the first regions of the outer first resistance wire part, the number of the second regions of the inner second resistance wire part, the number of the second regions of the outer second resistance wire part, are the same, and the circumferential gap between the first regions adjacent in the circumferential direction in the inner first resistance wire part and the outer first resistance wire part, and the circumferential gap between the second regions adjacent in the circumferential direction in the inner second resistance wire part and the outer second resistance wire part are arranged with a constant angular shift in the circumferential direction, and is an annular body. **Claim 9** An annular body according to claim 7 or claim 8, wherein the constant angle is 90°, and is an annular body. **Claim 10** An annular body according to any one of claims 1 to 9, wherein the first resistance wire part and the second resistance wire part are arranged concentrically about the central axis, and is an annular body. **Claim 11** An annular body according to claim 10, wherein the central angle of the circumferential gap between the first regions adjacent in the circumferential direction and the central angle of the circumferential gap between the second regions adjacent in the circumferential direction are equal, and is an annular body. **Claim 12** An annular body according to any one of claims 1 to 11, wherein the radial interval between the first resistance wire part and the second resistance wire part is narrower than either the radial width of the first region or the radial width of the second region, and is an annular body. **Claim 13** An annular body according to any one of claims 1 to 12, An annular body in which the radial interval between the first resistance wire portion and the second resistance wire portion is narrower than either the interval between the first regions adjacent in the circumferential direction or the interval between the second regions adjacent in the circumferential direction.

14. An annular body according to any one of Claims 1 to 13, wherein the first resistance wire portion further has a first connection region connected to a plurality of the first regions ; a first bridge circuit is formed by connecting the plurality of the first regions through the first connection region; the second resistance wire portion further has a second connection region connected to a plurality of the second regions ; a second bridge circuit is formed by connecting the plurality of the second regions through the second connection region.

15. An annular body according to any one of Claims 1 to 14, wherein the resistance values of the plurality of the first regions are equal to each other, and the resistance values of the plurality of the second regions are equal to each other.

16. An annular body according to any one of Claims 1 to 15, wherein the resistance wire further has a fourth resistance wire portion, and the fourth resistance wire portion includes a fourth part extending in the circumferential direction.

17. A harmonic reducer having an annular body according to any one of Claims 1 to 16, a wave generator, and an internal gear, wherein the annular body has a cylindrical body portion extending axially from a radially outer end of the base portion, and a plurality of external teeth protruding radially outward from a radially outer surface of the body portion, the wave generator is disposed radially inside the external teeth, the internal gear is disposed radially outside the external teeth, the internal gear has a plurality of internal teeth protruding radially inward from a radially inner surface, and a part of the plurality of external teeth meshes with a part of the plurality of internal teeth.

18. A robot having the harmonic reducer of Claim 17.

19. A torque detection device having a resistance wire disposed circumferentially with respect to a central axis, and a detection circuit electrically connected to the resistance wire, wherein the resistance wire has a first resistance wire portion, a second resistance wire portion disposed radially outside the first resistance wire portion, the first resistance wire portion has an inner first resistance wire portion, and an outer first resistance wire portion disposed radially outside the inner first resistance wire portion, the second resistance wire portion has an inner second resistance wire portion, and an outer second resistance wire portion disposed radially outside the inner second resistance wire portion. ​ ​ ​ ​ ​ ​ The inner first resistance wire portion and the outer first resistance wire portion each have a plurality of first regions arranged at intervals in the circumferential direction. Each of the plurality of first regions includes a region in which first portions extending in a direction having components in both the radial direction and the circumferential direction are repeatedly arranged in the circumferential direction. The inner second resistance wire portion and the outer second resistance wire portion each have a plurality of second regions arranged at intervals in the circumferential direction. Each of the plurality of second regions includes a region in which second portions extending in a direction having components in both the radial direction and the circumferential direction are repeatedly arranged in the circumferential direction. The first resistance wire portion further has a first connection region connected to the plurality of first regions and a first bridge circuit is formed by connecting the plurality of first regions via the first connection region. The second resistance wire portion further has a second connection region connected to the plurality of second regions and a second bridge circuit is formed by connecting the plurality of second regions via the second connection region. The resistance values of the first portion and the second portion change according to the torque applied to the region where the resistance wire is arranged. The detection circuit outputs a diagnostic signal indicating the state of the resistance wire by comparing the output signal of the first bridge circuit and the output signal of the second bridge circuit. A torque detection device.

20. The torque detection device according to claim 19, wherein the detection circuit outputs a predetermined signal as the diagnostic signal when the difference between the output signal of the first bridge circuit and the output signal of the second bridge circuit is equal to or greater than a predetermined threshold value. A torque detection device.

21. The torque detection device according to claim 19 or claim 20, wherein the detection circuit outputs a signal based on the sum of the output signal of the first bridge circuit and the output signal of the second bridge circuit. A torque detection device.

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