Sensor and power transmission device

Abstract

To provide a technique capable of reducing a region occupied by a resistance line in a sensor.SOLUTION: A sensor 40 includes a base, a plurality of first resistance lines R1, and a plurality of second resistance lines R2. The base extends in a direction intersecting with a central axis. The plurality of first resistance lines is arrayed in a circumferential direction on the surface of the base. The plurality of second resistance lines is arranged concentrically with the plurality of first resistance lines and between the first resistance lines in the circumferential direction on the surface of the base. In the first resistance lines, the number of regions of the resistance line along the circumferential direction is one or less, and the number of regions of the resistance line along a radial direction is one or less. Thus, a region occupied by the first resistance line on the surface of the base can be reduced.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a sensor and a power transmission device. [Background technology]

[0002] In recent years, the demand for reducers to be installed in the joints of robots and the like has been rapidly increasing. A conventional reducer is described, for example, in JP 2004-198400 A. In this publication, a strain gauge is attached to a flexible external gear that rotates at a reduced rotation speed. This makes it possible to detect the torque acting on the flexible external gear. [Patent Document 1] JP 2004-198400 A Summary of the Invention [Problem to be solved by the invention]

[0003] However, the flexible external gear used in this type of reducer repeatedly undergoes periodic flexural deformation. As a result, the output value of the strain gauge contains a component caused by the torque that is the intended measurement target, and an error component caused by the periodic deformation of the flexible external gear. This error component changes depending on the rotation angle of the rotational motion input to the flexible external gear.

[0004] Therefore, it is conceivable to provide a resistance wire in the strain gauge for detecting the rotation angle of the rotational motion input to the flexible external gear. In this case, by subtracting an error component corresponding to the rotation angle detected by the resistance wire from the detected torque value, the torque acting on the flexible external gear can be output with high accuracy.

[0005] In that case, however, it is necessary to arrange the resistance wire for detecting the torque and the resistance wire for detecting the rotation angle in a limited space, and therefore it is required to minimize the area occupied by the resistance wire for detecting the rotation angle.

[0006] An object of the present invention is to provide a technique capable of reducing the area occupied by a resistance wire in a sensor. [Means for solving the problem]

[0007] The sensor of the present invention has a base portion extending in a direction intersecting a central axis, a plurality of first resistance wires arranged circumferentially on the surface of the base portion, and a plurality of second resistance wires arranged on the surface of the base portion concentrically with the plurality of first resistance wires and circumferentially between the first resistance wires, and in at least one of the first resistance wires, the number of resistance wire regions along the circumferential direction is one or less and the number of resistance wire regions along the radial direction is one or less. Effect of the Invention

[0008] According to the present invention, the first resistance wire has one or less regions along the circumferential or radial direction, which makes it possible to reduce the region that the first resistance wire occupies on the surface of the base portion. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a vertical cross-sectional view of the power transmission device. [Diagram 2] FIG. 2 is a cross-sectional view of the power transmission device. [Diagram 3] FIG. 3 is a plan view of the sensor. [Figure 4] FIG. 4 is a partial cross-sectional view of the diaphragm portion and the sensor. [Diagram 5] FIG. 5 is a circuit diagram of a first bridge circuit including four first resistance wires. [Figure 6] FIG. 6 is a circuit diagram of a second bridge circuit including four second resistive wires. [Figure 7] FIG. 7 is a graph showing the measurement values ​​of the first voltmeter and the measurement values ​​of the second voltmeter. [Figure 8] FIG. 8 is a partial plan view of the sensor. [Figure 9] FIG. 9 is a circuit diagram of a third bridge circuit including the third to sixth resistance wires. [Figure 10] FIG. 10 is a diagram conceptually showing the correction process. [Figure 11] FIG. 11 is a plan view of a sensor according to a first modified example. [Figure 12] FIG. 12 is a plan view of a sensor according to a first modified example. [Figure 13] FIG. 13 is a plan view of a sensor according to a first modified example. [Figure 14] FIG. 14 is a plan view of the sensor according to the first modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, exemplary embodiments of the present application will be described with reference to the drawings.

[0011] In this application, a direction parallel to the central axis of the power transmission device is referred to as the "axial direction," a direction perpendicular to the central axis of the power transmission device is referred to as the "radial direction," and a direction along an arc centered on the central axis of the power transmission device is referred to as the "circumferential direction." However, the above "parallel direction" also includes a direction that is approximately parallel. Furthermore, the above "orthogonal direction" also includes a direction that is approximately orthogonal.

[0012] In addition, in this application, the "number of rotations" refers to the number of rotations per unit time, that is, the speed of rotation.

[0013] <1. Power transmission device configuration> FIG. 1 is a vertical cross-sectional view of a power transmission device 1 according to an embodiment. FIG. 2 is a horizontal cross-sectional view of the power transmission device 1 as viewed from the position AA in FIG. 1. This power transmission device 1 is a device that transmits rotational motion of a first rotation speed obtained from a motor to a subsequent stage while reducing the rotation speed to a second rotation speed lower than the first rotation speed. The power transmission device 1 is used, for example, by being incorporated into a joint of a robot together with a motor. However, the power transmission device of the present invention may also be used in other devices such as an assisted suit or an unmanned transport vehicle.

[0014] As shown in FIGS. 1 and 2, the power transmission device 1 of this embodiment includes an internal gear 10, a flex gear 20, a wave generator 30, and a sensor 40.

[0015] The internal gear 10 is an annular gear having a plurality of internal teeth 11 on its inner circumferential surface. The internal gear 10 is fixed, for example, by bolts, to a frame of the device on which the power transmission device 1 is mounted. The internal gear 10 is arranged coaxially with the central axis 9. The internal gear 10 is also located radially outside a cylindrical portion 21 (described later) of the flex gear 20. The rigidity of the internal gear 10 is much higher than the rigidity of the cylindrical portion 21 of the flex gear 20. For this reason, the internal gear 10 can be considered as a substantially rigid body. The internal gear 10 has a cylindrical inner circumferential surface. The multiple internal teeth 11 are arranged on the inner circumferential surface at a constant pitch in the circumferential direction. Each internal tooth 11 protrudes radially inward.

[0016] The flex gear 20 is a flexibly deformable annular gear. The flex gear 20 is supported so as to be rotatable about a central axis 9. The flex gear 20 is an example of the "flexible member" in the present invention.

[0017] The flex gear 20 of this embodiment has a cylindrical portion 21 and a flat portion 22. The cylindrical portion 21 extends cylindrically in the axial direction around the central axis 9. The axial tip of the cylindrical portion 21 is located radially outside the wave generator 30 and radially inside the internal gear 10. The cylindrical portion 21 is flexible and can deform in the radial direction. In particular, the tip of the cylindrical portion 21, which is located radially inside the internal gear 10, is a free end and can therefore be displaced more radially than other portions.

[0018] The flex gear 20 has a plurality of external teeth 23. The plurality of external teeth 23 are provided on a radially outer surface near the axial tip of the cylindrical portion 21. The plurality of external teeth 23 are arranged at a constant pitch in the circumferential direction. Each of the external teeth 23 protrudes radially outward. The number of internal teeth 11 of the internal gear 10 described above and the number of external teeth 23 of the flex gear 20 are slightly different.

[0019] The flat plate portion 22 has a diaphragm portion 221 and a thick portion 222. The diaphragm portion 221 spreads outward in the radial direction from the axial base end of the cylindrical portion 21 in a flat plate shape, and spreads in an annular shape around the central axis 9. The diaphragm portion 221 is slightly deformable in the axial direction. The thick portion 222 is an annular portion located radially outward of the diaphragm portion 221. The axial thickness of the thick portion 222 is thicker than the axial thickness of the diaphragm portion 221. The thick portion 222 is fixed, for example, by a bolt, to a component to be driven of an apparatus in which the power transmission device 1 is mounted.

[0020] The wave generator 30 is a mechanism that generates periodic bending deformation in the cylindrical portion 21 of the flex gear 20. The wave generator 30 has a cam 31 and a flexible bearing 32. The cam 31 is supported rotatably about a central axis 9. The radial outer surface of the cam 31 is elliptical when viewed in the axial direction. The flexible bearing 32 is interposed between the radial outer surface of the cam 31 and the radial inner surface of the cylindrical portion 21 of the flex gear 20. Therefore, the cam 31 and the cylindrical portion 21 can rotate at different rotation speeds.

[0021] 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 flex gear 20. As a result, the cylindrical portion 21 of the flex gear 20 is deformed into an elliptical shape that follows the radially outer surface of the cam 31. As a result, the external teeth 23 of the flex gear 20 mesh with the internal teeth 11 of the internal gear 10 at two locations that correspond to both ends of the major axis of the ellipse. The external teeth 23 do not mesh with the internal teeth 11 at other circumferential positions.

[0022] The cam 31 is connected to the motor directly or via another power transmission mechanism. When the motor is driven, the cam 31 rotates around the central axis 9 at a first rotation speed. As a result, the major axis of the ellipse of the flex gear 20 also rotates at the first rotation speed. Then, the meshing position between the external teeth 23 and the internal teeth 11 also changes in the circumferential direction at the first rotation speed. As described above, the number of the internal teeth 11 of the internal gear 10 and the number of the external teeth 23 of the flex gear 20 are slightly different. Due to this difference in the number of teeth, the meshing position between the external teeth 23 and the internal teeth 11 changes slightly in the circumferential direction for each rotation of the cam 31. As a result, the flex gear 20 rotates around the central axis 9 at a second rotation speed lower than the first rotation speed relative to the internal gear 10. Therefore, a rotational motion of the second rotation speed, which is reduced in speed, can be obtained from the flex gear 20.

[0023] <2. About sensors> <2-1. Sensor configuration> Sensor 40 is a detector for detecting circumferential torque applied to flex gear 20. Sensor 40 is fixed to diaphragm portion 221 of flex gear 20. Diaphragm portion 221 has surface 223 that intersects with central axis 9 and extends in an annular shape centered on central axis 9. Surface 223 is a surface facing the axial direction. Sensor 40 is fixed to surface 223 of diaphragm portion 221.

[0024] FIG. 3 is a plan view of the sensor 40. FIG. 4 is a partial cross-sectional view of the diaphragm portion 221 and the sensor 40. As shown in FIGS. 3 and 4, the sensor 40 has a circuit board 41. The circuit board 41 of this embodiment has a conductor formed on the surface of a flexibly deformable insulating layer 42. The circuit board 41 has a main body portion 411 and a flap portion 412. The main body portion 411 is an annular portion centered on the central axis 9. The flap portion 412 is a portion that protrudes radially outward from the main body portion 411.

[0025] As shown in FIG. 4, the circuit board 41 has an insulating layer 42, a first conductor layer 43, and a second conductor layer 44. The insulating layer 42 extends in a direction intersecting with the central axis 9. The insulating layer 42 is made of a resin or an inorganic insulating material, which is an insulator. The insulating layer 42 is an example of the "base portion" in the present invention. The insulating layer 42 is disposed on the surface 223 of the diaphragm portion 221. The first conductor layer 43 and the second conductor layer 44 are made of a metal, which is a conductor. The first conductor layer 43 is formed on the surface of the insulating layer 42. The material of the first conductor layer 43 is, for example, a material containing copper or a material containing chromium. The second conductor layer 44 is laminated on the surface of the first conductor layer 43. The material of the second conductor layer 44 is, for example, copper, silver, or gold.

[0026] When manufacturing the circuit board 41, first, a thin metal film constituting the first conductor layer 43 is formed on the entire surface of the insulating layer 42. Then, the formed thin metal film is partially etched according to the shapes of the first resistance wire R1 to the seventh resistance wire R7 and the connection wires W1 to W3 described later. In this way, the first conductor layer 43 is formed. Then, a thin metal film constituting the second conductor layer 44 is formed on the surfaces of the insulating layer 42 and the first conductor layer 43. Then, the formed thin metal film is partially etched according to the shapes of the connection wires W1 to W3 described later. In this way, the second conductor layer 44 is formed. At this time, since the second conductor layer 44 is formed of a metal material different from that of the first conductor layer 43, the second conductor layer 44 can be etched without etching the first conductor layer 43. However, the manufacturing method of the circuit board 41 is not limited to this example.

[0027] As shown in FIG. 4, the circuit board 41 is fixed to the surface 223 of the diaphragm portion 221 by the double-sided adhesive tape 45. Specifically, the surface 223 of the diaphragm portion 221 and the back surface of the circuit board 41 are fixed via the double-sided adhesive tape 45. The double-sided adhesive tape 45 is made by forming an adhesive material into a tape shape and hardening it to such an extent that it can maintain its shape. By using such a double-sided adhesive tape 45, the work of fixing the sensor 40 to the diaphragm portion 221 becomes easier than when a fluid adhesive is used. In addition, the variation in the fixing work by the worker can be reduced.

[0028] In order to transmit the deformation of the diaphragm portion 221 to the sensor 40 with high accuracy, it is preferable that the double-sided adhesive tape 45 does not have a base film and is made of an adhesive material only.

[0029] 3, the sensor 40 of this embodiment has a signal processing circuit C0. The signal processing circuit C0 is disposed in the flap portion 412. The sensor 40 of this embodiment also includes a rotation angle detection sensor S1, a torque detection sensor S2, and a temperature detection sensor S3. Each detection sensor will be described in detail below.

[0030] <2-2. Rotation angle detection sensor> The rotation angle detection sensor S1 is a sensor that detects the rotation angle of the rotational motion input to the flex gear 20 in order to correct the detection value of the torque detection sensor S2.

[0031] 3, the rotation angle detection sensor S1 has four first resistance wires R1 and four second resistance wires R2. The four first resistance wires R1 and the four second resistance wires R2 are disposed on the surface of the insulating layer 42. The four first resistance wires R1 and the four second resistance wires R2 are formed of the first conductor layer 43 described above.

[0032] The four first resistance wires R1 are arranged at equal intervals in the circumferential direction around the central axis 9. Each of the four first resistance wires R1 is a single conductor. Each of the first resistance wires R1 extends in an arc shape along the circumferential direction. The four second resistance wires R2 are arranged at equal intervals in the circumferential direction around the central axis 9. Each of the four second resistance wires R2 is a single conductor. Each of the second resistance wires R2 extends in an arc shape along the circumferential direction.

[0033] The four first resistance wires R1 and the four second resistance wires R2 are arranged concentrically. Each second resistance wire R2 is arranged between two first resistance wires R1 adjacent to each other in the circumferential direction. The circumferential center portions of the first resistance wires R1 and the circumferential center portions of the second resistance wires R2 are arranged alternately at intervals of 45° around the central axis 9. In this embodiment, the four first resistance wires R1 and the four second resistance wires R2 are arranged in a circular ring shape centered on the central axis 9 as a whole. In this manner, by arranging a plurality of first resistance wires R1 and second resistance wires R2, the rotation angle of the rotational motion input to the flex gear 20 can be detected with high accuracy.

[0034] Fig. 5 is a circuit diagram of a first bridge circuit C1 including four first resistance wires R1. In the example of Fig. 5, the four first resistance wires R1 are distinguished and shown as Ra, Rb, Rc, and Rd. The first resistance wires Ra, Rb, Rc, and Rd are arranged in the order of Ra, Rb, Rc, and Rd in a counterclockwise direction from Ra in Fig. 3.

[0035] As shown in FIG. 5, the four first resistance wires Ra, Rb, Rc, and Rd are incorporated into a first bridge circuit C1. The first resistance wire Ra and the first resistance wire Rb are connected in series in this order. The first resistance wire Rd and the first resistance wire Rc are connected in series in this order. Then, between the positive and negative poles of the power supply voltage, a series of two first resistance wires Ra and Rb and a series of two first resistance wires Rd and Rc are connected in parallel. In addition, a midpoint M11 between the first resistance wires Ra and the first resistance wire Rb and a midpoint M12 between the first resistance wires Rd and the first resistance wire Rc are connected to a first voltmeter V1.

[0036] Fig. 6 is a circuit diagram of a second bridge circuit C2 including four second resistance wires R2. In the example of Fig. 6, the four second resistance wires R2 are distinguished and shown as Re, Rf, Rg, and Rh. The second resistance wire Re is located between the first resistance wire Ra and the first resistance wire Rd in Fig. 3. The second resistance wires Re, Rf, Rg, and Rh are arranged in the order of Re, Rf, Rg, and Rh in a clockwise direction from Re in Fig. 3.

[0037] As shown in FIG. 6, the four second resistance wires Re, Rf, Rg, and Rh are incorporated into a second bridge circuit C2. The second resistance wire Re and the second resistance wire Rf are connected in series in this order. The second resistance wire Rh and the second resistance wire Rg are connected in series in this order. Then, between the positive and negative poles of the power supply voltage, a series of two second resistance wires Re and Rf and a series of two second resistance wires Rh and Rg are connected in parallel. In addition, a midpoint M21 between the second resistance wires Re and the second resistance wire Rf and a midpoint M22 between the second resistance wires Rh and the second resistance wire Rg are connected to a second voltmeter V2.

[0038] When the power transmission device 1 is driven, a portion that expands in the circumferential direction (hereinafter referred to as the "expanded portion") and a portion that contracts in the circumferential direction (hereinafter referred to as the "contracted portion") are generated in the diaphragm portion 221. Specifically, two expanded portions and two contracted portions are generated alternately in the circumferential direction. That is, the expanded portions and contracted portions are generated alternately at intervals of 90° in the circumferential direction around the central axis 9. The locations where these expanded portions and contracted portions are generated rotate at the first rotation speed described above.

[0039] The resistance values ​​of the first resistance wires Ra, Rb, Rc, Rd and the second resistance wires Re, Rf, Rg, Rh change according to the expansion and contraction in the circumferential direction of the diaphragm portion 221. For example, when the above-mentioned expansion portion overlaps with a certain resistance wire, the resistance value of the resistance wire increases. Also, when the above-mentioned contraction portion overlaps with a certain resistance wire, the resistance value of the resistance wire decreases.

[0040] In the example of Fig. 3, when the contracted portion overlaps with the first resistance lines Ra, Rc, the expanded portion overlaps with the first resistance lines Rb, Rd. Also, when the expanded portion overlaps with the first resistance lines Ra, Rc, the contracted portion overlaps with the first resistance lines Rb, Rd. Therefore, in the first bridge circuit C1, the first resistance lines Ra, Rc and the first resistance lines Rb, Rd show resistance value changes in opposite directions.

[0041] 3, when the contracted portion overlaps with the second resistance lines Re, Rg, the expanded portion overlaps with the second resistance lines Rf, Rh. When the expanded portion overlaps with the second resistance lines Re, Rg, the contracted portion overlaps with the second resistance lines Rf, Rh. Therefore, in the second bridge circuit C2, the second resistance lines Re, Rg and the second resistance lines Rf, Rh show opposite resistance value changes.

[0042] FIG. 7 is a graph showing the measurement value v1 of the first voltmeter V1 of the first bridge circuit C1 and the measurement value v2 of the second voltmeter V2 of the second bridge circuit C2. When the power transmission device 1 is driven, as shown in FIG. 7, the first voltmeter V1 and the second voltmeter V2 output periodically changing sinusoidal measurement values ​​v1 and v2, respectively. The period T of the measurement values ​​v1 and v2 corresponds to 1 / 2 the period of the first rotation speed described above. In addition, the direction of the input rotational motion can be determined based on whether the phase of the measurement value v2 of the second voltmeter V2 leads the phase of the measurement value v1 of the first voltmeter V1 by 1 / 8 period of the first rotation speed (1 / 4 period of the measurement values ​​v1 and v2) or lags behind the phase of the measurement value v1 of the first voltmeter V1 by 1 / 8 period of the first rotation speed (1 / 4 period of the measurement values ​​v1 and v2).

[0043] Therefore, based on the measurement value v1 of the first voltmeter V1 and the measurement value v2 of the second voltmeter V2, it is possible to detect the rotation angle of the rotational motion input to the flex gear 20. Specifically, for example, a function table that associates combinations of the measurement value v1 of the first voltmeter V1 and the measurement value v2 of the second voltmeter V2 with the rotation angle may be prepared in advance, and the measurement values ​​v1 and v2 may be input into the function table to output the rotation angle.

[0044] Thus, in this embodiment, the first bridge circuit C1 and the second bridge circuit C2 function as a detection circuit that detects the rotation angle of the rotational motion input to the flex gear 20. That is, in this embodiment, the sensor 40 attached to the flex gear 20 has a detection circuit. Therefore, compared to a case in which the sensor 40 does not have a detection circuit, it is possible to reduce the amount of wiring extending outside the sensor 40. As a result, it is easy to attach the sensor 40 to the flex gear 20. Furthermore, since the detection circuit has the first bridge circuit C1 and the second bridge circuit C2, it is possible to appropriately detect the rotation angle of the rotational motion input to the flex gear 20, which is a flexible member.

[0045] In this embodiment, each of the first resistance wires R1 is an arc extending in the circumferential direction from one end to the other end in the circumferential direction. That is, each of the first resistance wires R1 is composed of one resistance wire region along the circumferential direction. Therefore, the area occupied by the first resistance wires R1 on the surface of the insulating layer 42 can be made smaller than when the first resistance wires R1 have multiple resistance wire regions along the circumferential direction.

[0046] Similarly, in this embodiment, each of the second resistance wires R2 is an arc extending circumferentially from one end to the other end in the circumferential direction. That is, each of the second resistance wires R2 is composed of one resistance wire region along the circumferential direction. Therefore, the area occupied by the second resistance wire R2 on the surface of the insulating layer 42 can be made smaller than when the second resistance wire R2 has multiple resistance wire regions along the circumferential direction.

[0047] FIG. 8 is a partial plan view of the sensor 40. Specifically, FIG. 8 is an enlarged view of the vicinity of the area surrounded by the two-dot chain line in FIG. 3. As shown in FIG. 3 and FIG. 8, the sensor 40 has a plurality of connection wires W1. Some of the connection wires W1 extend from the ends of the first resistance wires R1 to connect the plurality of first resistance wires R1 to each other. This forms the first bridge circuit C1 described above. In addition, other connection wires W1 extend from the ends of the second resistance wires R2 to connect the plurality of second resistance wires R2 to each other. This forms the second bridge circuit C2 described above.

[0048] 8, the first resistance wire R1 and the second resistance wire R2 are formed of a first conductor layer 43. That is, the first conductor layer 43 is exposed on the surfaces of the first resistance wire R1 and the second resistance wire R2. In contrast, the connection wire W1 is formed of the first conductor layer 43 and the second conductor layer 44. That is, the second conductor layer 44 is laminated on the surface of the connection wire W1.

[0049] In this way, when the connecting wire W1 is composed of the first conductor layer 43 and the second conductor layer 44, the resistance value of the connecting wire W1 is lower than when the connecting wire W1 is composed of only the first conductor layer 43. This increases the relative resistance values ​​of the first resistance wire R1 and the second resistance wire R2. Therefore, in the first bridge circuit C1 and the second bridge circuit C2, the influence of the change in the resistance value of the connecting wire W1 on the measured values ​​v1 and v2 can be reduced. That is, the measured value v1 of the first voltmeter V1 reflects the change in the resistance value of the first resistance wire R1 with higher accuracy. Also, the measured value v2 of the second voltmeter V2 reflects the change in the resistance value of the second resistance wire R2 with higher accuracy.

[0050] Therefore, even if the first resistance wire R1 and the second resistance wire R2 do not have multiple resistance wire regions along the circumferential direction, the rotational angle of the rotational motion input to the flex gear 20 can be accurately detected based on the measurement value v1 of the first voltmeter V1 and the measurement value v2 of the second voltmeter V2.

[0051] The resistivity of the material of the second conductor layer 44 is preferably lower than the resistivity of the material of the first conductor layer 43. Alternatively, the gauge factor of the material of the second conductor layer 44 is preferably lower than the gauge factor of the material of the first conductor layer 43. If a material with a low resistivity or gauge factor is used for the second conductor layer 44, the resistance value of the connection wire W1 can be more effectively reduced by stacking the second conductor layer 44. Therefore, the detection accuracy of the rotation angle by the first resistance wire R1 and the second resistance wire R2 can be further improved. Therefore, even if the first resistance wire R1 and the second resistance wire R2 do not have multiple resistance wire regions along the circumferential direction, the rotation angle of the rotational motion input to the flex gear 20 can be accurately detected based on the measurement value v1 of the first voltmeter V1 and the measurement value v2 of the second voltmeter V2.

[0052] For example, the material of the first conductor layer 43 may be a material containing copper, such as a Cu-Ni alloy, and the material of the second conductor layer 44 may be copper. Alternatively, the material of the first conductor layer 43 may be a material containing chromium, and the material of the second conductor layer 44 may be gold. However, the material of the first conductor layer 43 may be chromium, chromium nitride, chromium oxide, or the like.

[0053] As shown in FIG. 8, the width d0 of the connection line W1 is wider than the width d1 of the first resistance line R1 and the width d2 of the second resistance line R2. This can reduce the resistance value of the connection line W1. This can improve the accuracy of detecting the rotation angle by the first resistance line R1 and the second resistance line R2. Therefore, even if the first resistance line R1 and the second resistance line R2 do not have multiple resistance line regions along the circumferential direction, the rotation angle of the rotational motion input to the flex gear 20 can be detected with high accuracy based on the measurement value v1 of the first voltmeter V1 and the measurement value v2 of the second voltmeter V2.

[0054] The line width of the entire connecting line W1 does not necessarily have to be wider than the line width d1 of the first resistance line R1 and the line width d2 of the second resistance line R2. It is sufficient that the line width of at least a part of the connecting line W1 is wider than the line width d1 of the first resistance line R1 and the line width d2 of the second resistance line R2.

[0055] Furthermore, by reducing the axial thickness of the first resistance wire R1 and the second resistance wire R2, the resistance values ​​of the first resistance wire R1 and the second resistance wire R2 can be increased. This can further improve the accuracy of detecting the rotation angle by the first resistance wire R1 and the second resistance wire R2. Therefore, even if the first resistance wire R1 and the second resistance wire R2 do not have multiple resistance wire regions along the circumferential direction, the rotation angle of the rotational motion input to the flex gear 20 can be detected with high accuracy based on the measurement value v1 of the first voltmeter V1 and the measurement value v2 of the second voltmeter V2.

[0056] The axial thickness of the first resistance wire R1 and the axial thickness of the second resistance wire R2 are preferably, for example, 1000 nm or less. That is, as shown in FIG. 4, the axial thickness h of the first conductor layer 43 is preferably 1000 nm or less.

[0057] <2-3. Torque detection sensor> The torque detection sensor S2 is a sensor that detects the torque applied to the flex gear 20 in the circumferential direction.

[0058] 3, the torque detection sensor S2 has a third resistance wire R3 to a sixth resistance wire R6. The third resistance wire R3 to the sixth resistance wire R6 are disposed on the surface of the insulating layer 42. The third resistance wire R3 to the sixth resistance wire R6 are formed of the first conductor layer 43 described above.

[0059] The third resistance wire R3 is an overall arc-shaped pattern in which a single conductor extends in the circumferential direction while being bent in a zigzag pattern. In this embodiment, the third resistance wire R3 is provided in a semicircular shape within a range of approximately 180° centered on the central axis 9. The third resistance wire R3 also includes a plurality of detection wires r3. The plurality of detection wires r3 are arranged in the circumferential direction in a substantially parallel posture to each other. Each detection wire r3 is inclined toward one side in the circumferential direction with respect to the radial direction. The inclination angle of the detection wire r3 with respect to the radial direction is, for example, 45°. The ends of the detection wires r3 adjacent to each other in the circumferential direction are alternately connected to each other on the inside or outside in the radial direction. As a result, the plurality of detection wires r3 are connected in series as a whole.

[0060] The fourth resistance wire R4 is an arc-shaped pattern as a whole, in which a single conductor extends in the circumferential direction while being bent in a zigzag pattern. In this embodiment, the fourth resistance wire R4 is provided in a semicircular shape within a range of about 180° centered on the central axis 9. The fourth resistance wire R4 also includes a plurality of detection wires r4. The plurality of detection wires r4 are arranged in the circumferential direction in a substantially parallel posture to each other. Each detection wire r4 is inclined toward the other circumferential side with respect to the radial direction. The inclination angle of the detection wire r4 with respect to the radial direction is, for example, 45°. The ends of the detection wires r4 adjacent to each other in the circumferential direction are alternately connected on the inside or outside of the radial direction. As a result, the plurality of detection wires r4 are connected in series as a whole.

[0061] The third resistance wire R3 and the fourth resistance wire R4 are arranged concentrically and line-symmetrically. The radial distance from the central axis 9 to the third resistance wire R3 is the same as the radial distance from the central axis 9 to the fourth resistance wire R4.

[0062] The fifth resistance wire R5 is an arc-shaped pattern as a whole, in which a single conductor extends in the circumferential direction while being bent in a zigzag pattern. In this embodiment, the fifth resistance wire R5 is provided in a semicircular shape within a range of about 180° centered on the central axis 9. The fifth resistance wire R5 also includes a plurality of detection wires r5. The plurality of detection wires r5 are arranged in the circumferential direction in a substantially parallel posture to each other. Each detection wire r5 is inclined toward the other circumferential side with respect to the radial direction. The inclination angle of the detection wire r5 with respect to the radial direction is, for example, 45°. The ends of the detection wires r5 adjacent to each other in the circumferential direction are alternately connected to each other on the inside or outside of the radial direction. As a result, the plurality of detection wires r5 are connected in series as a whole.

[0063] The sixth resistance wire R6 is an arc-shaped pattern as a whole, in which a single conductor extends in the circumferential direction while being bent in a zigzag pattern. In this embodiment, the sixth resistance wire R6 is provided in a semicircular shape within a range of about 180° centered on the central axis 9. The sixth resistance wire R6 also includes a plurality of detection wires r6. The plurality of detection wires r6 are arranged in the circumferential direction in a substantially parallel posture to each other. Each detection wire r6 is inclined toward one side in the circumferential direction with respect to the radial direction. The inclination angle of the detection wire r6 with respect to the radial direction is, for example, 45°. The ends of the detection wires r6 adjacent to each other in the circumferential direction are alternately connected to each other on the inside or outside in the radial direction. As a result, the plurality of detection wires r6 are connected in series as a whole.

[0064] The fifth resistance wire R5 and the sixth resistance wire R6 are arranged concentrically and line-symmetrically. The radial distance from the central axis 9 to the fifth resistance wire R5 is the same as the radial distance from the central axis 9 to the sixth resistance wire R6. The fifth resistance wire R5 and the sixth resistance wire R6 are located radially inward of the third resistance wire R3 and the fourth resistance wire R4.

[0065] FIG. 9 is a circuit diagram of a third bridge circuit C3 including the third resistance wire R3 to the sixth resistance wire R6. As shown in FIG. 9, the third resistance wire R3 to the sixth resistance wire R6 are incorporated into the third bridge circuit C3. The third resistance wire R3 and the fourth resistance wire R4 are connected in series in this order. The fifth resistance wire R5 and the sixth resistance wire R6 are connected in series in this order. Then, between the positive and negative poles of the power supply voltage, the series of the third resistance wire R3 and the fourth resistance wire R4 and the series of the fifth resistance wire R5 and the sixth resistance wire R6 are connected in parallel. In addition, the midpoint M31 of the third resistance wire R3 and the fourth resistance wire R4 and the midpoint M32 of the fifth resistance wire R5 and the sixth resistance wire R6 are connected to the third voltmeter V3.

[0066] The resistance values ​​of the detection lines r3 to r6 of the third resistance line R3 to the sixth resistance line R6 change according to the torque applied to the flex gear 20. For example, when a torque is applied to the flex gear 20 in one circumferential direction about the central axis 9, the resistance value of each detection line r3 of the third resistance line R3 and the resistance value of each detection line r6 of the sixth resistance line R6 decreases, and the resistance value of each detection line r4 of the fourth resistance line R4 and the resistance value of each detection line r5 of the fifth resistance line R5 increases. On the other hand, when a torque is applied to the flex gear 20 in the other circumferential direction about the central axis 9, the resistance value of each detection line r3 of the third resistance line R3 and the resistance value of each detection line r6 of the sixth resistance line R6 increases, and the resistance value of each detection line r4 of the fourth resistance line R4 and the resistance value of each detection line r5 of the fifth resistance line R5 decreases. In this way, the third resistance line R3 and the sixth resistance line R6, and the fourth resistance line R4 and the fifth resistance line R5 exhibit resistance value changes in opposite directions relative to the torque.

[0067] When the resistance values ​​of the third resistance wire R3 to the sixth resistance wire R6 change, the potential difference between the midpoint M31 between the third resistance wire R3 and the fourth resistance wire R4 and the midpoint M32 between the fifth resistance wire R5 and the sixth resistance wire R6 changes, and the measurement value v3 of the third voltmeter V3 also changes. Therefore, the direction and magnitude of the torque applied to the flex gear 20 can be detected based on the measurement value v3 of the third voltmeter V3.

[0068] The third resistance wire R3 to the sixth resistance wire R6 are connected to each other by the connection wire W2. This forms the above-mentioned third bridge circuit C3. The third resistance wire R3 to the sixth resistance wire R6 are formed of the first conductor layer 43. That is, the first conductor layer 43 is exposed on the surfaces of the third resistance wire R3 to the sixth resistance wire R6. In contrast, the connection wire W2 is formed of the first conductor layer 43 and the second conductor layer 44. That is, the second conductor layer 44 is laminated on the surface of the connection wire W2.

[0069] In this way, when the connecting wire W2 is configured with the first conductor layer 43 and the second conductor layer 44, the resistance value of the connecting wire W2 is lower than when the connecting wire W2 is configured with only the first conductor layer 43. This increases the relative resistance values ​​of the third resistance wire R3 to the sixth resistance wire R6. Therefore, in the third bridge circuit C3, the influence of the change in the resistance value of the connecting wire W2 on the measurement value v3 can be reduced. That is, the measurement value v3 of the third voltmeter V3 reflects the change in the resistance values ​​of the third resistance wire R3 to the sixth resistance wire R6 with higher accuracy. Therefore, the torque applied to the flex gear 20 can be detected with higher accuracy based on the measurement value v3 of the third voltmeter V3.

[0070] As described above, in the sensor 40, the area occupied by the multiple first resistance wires R1 and multiple second resistance wires R2 constituting the rotation angle detection sensor S1 is small on the surface of the insulating layer 42. Therefore, the multiple first resistance wires R1 and multiple second resistance wires R2 constituting the rotation angle detection sensor S1 and the third resistance wire R3 to the sixth resistance wire R6 constituting the torque detection sensor S2 are arranged on the same surface of the insulating layer 42. In this way, it is not necessary to form a conductor layer on both sides of the insulating layer 42 when manufacturing the sensor 40. Therefore, the manufacturing cost of the sensor 40 can be reduced.

[0071] The first resistance wire R1 of this embodiment is an arc extending from one end to the other end in the circumferential direction. The second resistance wire R2 of this embodiment is an arc extending from one end to the other end in the circumferential direction. Therefore, the first resistance wire R1 and the second resistance wire R2 can be arranged in a narrower radial range than when the first resistance wire R1 and the second resistance wire R2 extend in the radial direction. Therefore, a wide space can be secured for arranging the third resistance wire R3 to the sixth resistance wire R6 on the radial inner side or the radial outer side of the first resistance wire R1 and the second resistance wire R2.

[0072] In this embodiment, the first resistance wires R1 and the second resistance wires R2 constituting the rotation angle detection sensor S1 are located radially outward of the third resistance wire R3 to the sixth resistance wire R6 constituting the torque detection sensor S2. In this way, the connection wire W1 extending from the ends of the first resistance wire R1 and the second resistance wire R2 can be extended to the signal processing circuit C0 on the radially outer side without being blocked by the third resistance wire R3 to the sixth resistance wire R6 constituting the torque detection sensor S2.

[0073] <2-4. Ripple correction> When the power transmission device 1 is driven, periodic flexural deformation occurs in the flex gear 20. Therefore, the measurement value v3 of the third voltmeter V3 contains a component reflecting the torque that is originally to be measured, and an error component (ripple) caused by the periodic flexural deformation of the flex gear 20. The error component changes according to the rotation angle of the rotational motion input to the flex gear 20.

[0074] Therefore, the signal processing circuit C0 performs a correction process to cancel the above-mentioned error component from the measurement value v3 of the third voltmeter V3. FIG. 10 is a diagram conceptually showing the correction process of the signal processing circuit C0. As shown in FIG. 10, the measurement values ​​v1, v2, and v3 of the first voltmeter V1, the second voltmeter V2, and the third voltmeter V3 are input to the signal processing circuit C0. The signal processing circuit C0 first detects the rotation angle of the rotation motion input to the flex gear 20 based on the measurement values ​​v1 and v2 of the first voltmeter V1 and the second voltmeter V2. Then, the signal processing circuit C0 calculates the above-mentioned error component according to the detected rotation angle. After that, the measurement value v3 of the third voltmeter V3 is corrected using the calculated error component. As a result, the torque applied to the flex gear 20 can be output with higher accuracy.

[0075] Alternatively, the signal processing circuit C0 may multiply the measured values ​​v1 and v2 of the first voltmeter V1 and the second voltmeter V2 by a predetermined coefficient and combine them into the measured value v3 of the third voltmeter V3 without calculating the rotation angle. In this way, the processing load for calculating the rotation angle is reduced, and the calculation speed of the signal processing circuit C0 can be improved.

[0076] <2-5. Temperature correction> The sensor 40 of this embodiment includes a temperature detection sensor S3 to compensate for the effect of temperature.

[0077] As shown in FIG. 3, the temperature detection sensor S3 has a seventh resistance wire R7. The seventh resistance wire R7 is disposed on the surface of the insulating layer 42. The seventh resistance wire R7 is composed of the first conductor layer 43 and the second conductor layer 44 described above. The seventh resistance wire R7 extends in an arc shape centered on the central axis 9. Therefore, the change in the resistance value of the seventh resistance wire R7 due to the torque in the circumferential direction is extremely small. In addition, the seventh resistance wire R7 extends over substantially the entire circumference around the central axis 9. Therefore, the resistance value of the seventh resistance wire R7 is not easily affected by the expansion and contraction caused by the bending deformation of the diaphragm portion 221. Therefore, the change in the resistance value of the seventh resistance wire R7 due to the temperature becomes dominant. Therefore, by measuring the resistance value of the seventh resistance wire R7, a signal reflecting the temperature of the flex gear 20 can be obtained.

[0078] The signal processing circuit C0 corrects the measurement value v3 of the third voltmeter V3, taking into account not only the rotation angle but also the resistance value of the seventh resistance wire R7. Specifically, the measurement value v3 of the third voltmeter V3 is increased or decreased in a direction that cancels changes due to temperature. In this way, the effect of temperature changes can be suppressed, and the torque applied to the flex gear 20 can be detected with higher accuracy.

[0079] When a Cu-Ni alloy, whose resistance value changes very little with temperature, is used as the material for the first conductor layer 43, as described above, the seventh resistance wire R7 is composed of the first conductor layer 43 and the second conductor layer 44. However, when a material whose resistance value changes greatly with temperature, such as copper, is used as the material for the first conductor layer 43, the seventh resistance wire R7 may be composed of only the first conductor layer 43.

[0080] The seventh resistance wire R7 and the signal processing circuit C0 are connected to each other by a connection line W3. The connection line W3 is composed of a first conductor layer 43 and a second conductor layer 44. That is, the second conductor layer 44 is laminated on the surface of the connection line W3.

[0081] In this way, when the connecting line W3 is composed of the first conductor layer 43 and the second conductor layer 44, the resistance value of the connecting line W3 is lower than when the connecting line W3 is composed of only the first conductor layer 43. This increases the relative resistance value of the seventh resistance wire R7. This reduces the effect of changes in the resistance value of the connecting line W3 on the detection value of the temperature detection sensor S3. This allows the temperature of the flex gear 20 to be detected with high accuracy based on changes in the resistance value of the seventh resistance wire R7.

[0082] <3. Modifications> Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment.

[0083] <3-1. First modified example> Fig. 11 is a plan view of a sensor 40 according to a first modified example. In Fig. 11, the third resistance wire R3 to the sixth resistance wire R6 constituting the torque detection sensor S2, the seventh resistance wire R7 constituting the temperature detection sensor S3, and the connection wires W1 to W3 are not shown.

[0084] In the above embodiment, the four first resistance wires R1 and the four second resistance wires R2 each extend in a curved shape from one end to the other end in the circumferential direction. In contrast, in the first modified example of FIG. 11, the four first resistance wires R1 and the four second resistance wires R2 each extend in a straight line from one end to the other end in the circumferential direction. Even with such a shape, the resistance values ​​of the four first resistance wires R1 and the four second resistance wires R2 change according to the expansion and contraction of the diaphragm portion 221 in the circumferential direction. Therefore, the rotation angle of the rotational motion input to the flex gear 20 can be detected based on the change in the resistance values ​​of the four first resistance wires R1 and the four second resistance wires R2.

[0085] In this way, at least one of the four first resistance wires R1 may be curved or straight. At least one of the four second resistance wires R2 may be curved or straight. This improves the degree of freedom in arranging the first resistance wire R1 and the second resistance wire R2. For example, the first resistance wire R1 and the second resistance wire R2 can be arranged while avoiding other wiring on the circuit board 41. Alternatively, the first resistance wire R1 and the second resistance wire R2 can be arranged in consideration of the shape of the flex gear 20. In particular, when the first resistance wire R1 and the second resistance wire R2 are straight, the length of the resistance wire can be shortened, making it easy to form the resistance wires.

[0086] <3-2. Second modified example> Fig. 12 is a plan view of a sensor 40 according to a second modified example. In Fig. 12, the third resistance wire R3 to the sixth resistance wire R6 constituting the torque detection sensor S2, the seventh resistance wire R7 constituting the temperature detection sensor S3, and the connection wires W1 to W3 are not shown.

[0087] 12, the four first resistance wires R1 and the four second resistance wires R2 each extend in a broken line shape approximately along the circumferential direction between one end and the other end in the circumferential direction. Even with this shape, the resistance values ​​of the four first resistance wires R1 and the four second resistance wires R2 change according to the expansion and contraction of the diaphragm portion 221 in the circumferential direction. Therefore, the rotation angle of the rotational motion input to the flex gear 20 can be detected based on the change in the resistance values ​​of the four first resistance wires R1 and the four second resistance wires R2.

[0088] In this way, at least one of the four first resistance wires R1 may be a bent line extending substantially along the circumferential direction. At least one of the four second resistance wires R2 may be a bent line extending substantially along the circumferential direction. This improves the degree of freedom in arranging the first resistance wire R1 and the second resistance wire R2. For example, the first resistance wire R1 and the second resistance wire R2 can be arranged while avoiding other wiring on the circuit board 41. Alternatively, the first resistance wire R1 and the second resistance wire R2 can be arranged in consideration of the shape of the flex gear 20. In particular, when the first resistance wire R1 and the second resistance wire R2 are bent lines, a detection result that more accurately reflects the expansion and contraction in the circumferential direction can be obtained than when the first resistance wire R1 and the second resistance wire R2 are linear.

[0089] <3-3.Third modified example> Fig. 13 is a plan view of a sensor 40 according to a third modified example. In Fig. 13, the third resistance wire R3 to the sixth resistance wire R6 constituting the torque detection sensor S2, the seventh resistance wire R7 constituting the temperature detection sensor S3, and the connection wires W1 to W3 are omitted from the illustration.

[0090] 13, the four first resistance wires R1 and the four second resistance wires R2 extend obliquely with respect to the circumferential and radial directions, respectively. Even with this shape, the resistance values ​​of the four first resistance wires R1 and the four second resistance wires R2 change according to the expansion and contraction of the diaphragm portion 221 in the circumferential direction. Therefore, the rotation angle of the rotational motion input to the flex gear 20 can be detected based on the change in the resistance values ​​of the four first resistance wires R1 and the four second resistance wires R2.

[0091] In this manner, at least one of the four first resistance wires R1 may extend obliquely with respect to the circumferential and radial directions. At least one of the four second resistance wires R2 may extend obliquely with respect to the circumferential and radial directions. This improves the degree of freedom in arranging the first resistance wires R1 and the second resistance wires R2. For example, the first resistance wires R1 and the second resistance wires R2 can be arranged while avoiding other wiring on the circuit board 41. Alternatively, the first resistance wires R1 and the second resistance wires R2 can be arranged in consideration of the shape of the flex gear 20.

[0092] When the first resistance wire R1 and the second resistance wire R2 are inclined with respect to the circumferential direction, the resistance values ​​of the first resistance wire R1 and the second resistance wire R2 change according to the torque applied to the flex gear 20. In order to cancel the change in resistance value caused by this torque, it is preferable that, of the four first resistance wires Ra to Rd, two first resistance wires Ra, Rc that are 180° apart from the central axis 9 are inclined in opposite directions with respect to the circumferential direction. It is also preferable that, of the four first resistance wires Ra to Rd, two first resistance wires Rb, Rd that are 180° apart from the central axis 9 are inclined in opposite directions with respect to the circumferential direction. However, the inclination directions with respect to the circumferential direction of the first resistance wires R1 adjacent to each other in the circumferential direction may be the same or opposite.

[0093] Similarly, of the four second resistance wires Re to Rh, it is preferable that the two second resistance wires Re, Rg that are 180° apart from the central axis 9 are inclined in opposite directions with respect to the circumferential direction. Also, of the four second resistance wires Re to Rh, it is preferable that the two second resistance wires Rf, Rh that are 180° apart from the central axis 9 are inclined in opposite directions with respect to the circumferential direction. However, the inclination directions with respect to the circumferential direction of the second resistance wires R2 adjacent to each other in the circumferential direction may be the same or opposite.

[0094] <3-4. Fourth transformation> Fig. 14 is a plan view of a sensor 40 according to a fourth modified example. In Fig. 14, the third resistance wire R3 to the sixth resistance wire R6 constituting the torque detection sensor S2, the seventh resistance wire R7 constituting the temperature detection sensor S3, and the connection wires W1 to W3 are omitted from the illustration.

[0095] In the above embodiment, the four first resistance wires R1 and the four second resistance wires R2 each extend in the circumferential direction. This is to detect the periodic deformation of the diaphragm portion 221 in the circumferential direction. However, when the power transmission device 1 is driven, the diaphragm portion 221 deforms periodically not only in the circumferential direction but also in the radial direction. For this reason, as shown in FIG. 14, the four first resistance wires R1 and the four second resistance wires R2 may each extend in the radial direction. Even in this case, the resistance values ​​of the four first resistance wires R1 and the four second resistance wires R2 change according to the expansion and contraction of the diaphragm portion 221 in the radial direction. Therefore, the rotation angle of the rotational motion input to the flex gear 20 can be detected based on the change in the resistance values ​​of the four first resistance wires R1 and the four second resistance wires R2.

[0096] 14, the multiple first resistance wires R1 each extend linearly in the radial direction from one end to the other end in the radial direction. That is, each first resistance wire R1 is composed of one resistance wire region along the radial direction. Therefore, the area occupied by the first resistance wire R1 on the surface of the insulating layer 42 can be made smaller than when the first resistance wire R1 has multiple resistance wire regions along the radial direction.

[0097] 14, each of the second resistance wires R2 extends linearly from one circumferential end to the other in the radial direction. That is, each of the second resistance wires R2 is composed of one resistance wire region along the radial direction. Therefore, the area occupied by the second resistance wire R2 on the surface of the insulating layer 42 can be made smaller than when the second resistance wire R2 has multiple resistance wire regions along the radial direction.

[0098] <3-5. Other variations> In the above embodiment, the number of resistance wire regions along the circumferential direction is one in each of the four first resistance wires R1. Also, in the above embodiment, the number of resistance wire regions along the circumferential direction is one in each of the four second resistance wires R2. However, the number of resistance wire regions along the circumferential direction may be one in at least one of the four first resistance wires R1. Also, the number of resistance wire regions along the circumferential direction may be one in at least one of the four second resistance wires R2.

[0099] That is, in at least one first resistance wire R1, the number of resistance wire regions along the circumferential direction may be one or less and the number of resistance wire regions along the radial direction may be one or less. This makes it possible to reduce the area occupied by the first resistance wire R1 on the surface of the insulating layer 42. Also, in at least one second resistance wire R2, the number of resistance wire regions along the circumferential direction may be one or less and the number of resistance wire regions along the radial direction may be one or less. This makes it possible to reduce the area occupied by the second resistance wire R2 on the surface of the insulating layer 42.

[0100] In the above embodiment, the radial positions of the four first resistance wires R1 and the radial positions of the four second resistance wires R2 are the same. However, the radial positions of the four first resistance wires R1 and the radial positions of the four second resistance wires R2 may be different. This improves the degree of freedom in arranging the first resistance wires R1 and the second resistance wires R2. For example, the first resistance wires R1 and the second resistance wires R2 can be arranged while avoiding other wiring on the circuit board 41. Alternatively, the first resistance wires R1 and the second resistance wires R2 can be arranged in consideration of the shape of the flex gear 20.

[0101] In the above embodiment, the four first resistance wires R1 and the four second resistance wires R2 are arranged at equal intervals in the circumferential direction. However, the four first resistance wires R1 and the four second resistance wires R2 may be arranged at uneven intervals in the circumferential direction.

[0102] In the above embodiment, the four first resistance wires R1 and the four second resistance wires R2 constituting the rotation angle detection sensor S1 are located radially outward from the third resistance wire R3 to the sixth resistance wire R6 constituting the torque detection sensor S2. However, the four first resistance wires R1 and the four second resistance wires R2 constituting the rotation angle detection sensor S1 may be located radially inward from the third resistance wire R3 to the sixth resistance wire R6 constituting the torque detection sensor S2.

[0103] In the above embodiment, the four first resistance wires R1 and the four second resistance wires R2 constituting the rotation angle detection sensor S1 and the third resistance wire R3 to the sixth resistance wire R6 constituting the torque detection sensor S2 are arranged on the same surface of the insulating layer 42. However, the four first resistance wires R1 and the four second resistance wires R2 constituting the rotation angle detection sensor S1 and the third resistance wire R3 to the sixth resistance wire R6 constituting the torque detection sensor S2 may be arranged on different surfaces of the insulating layer 42. In that case, the first conductor layer 43 and the second conductor layer 44 may be formed on both surfaces of the insulating layer 42.

[0104] Furthermore, the sensor 40 in the above embodiment has four first resistance wires R1 and four second resistance wires R2. However, the number of the first resistance wires R1 and the number of the second resistance wires R2 included in the sensor 40 may be other than four.

[0105] In the above embodiment, the first resistance wire R1 and the second resistance wire R2 are disposed on the surface of the insulating layer 42 of the circuit board 41. However, the first resistance wire R1 and the second resistance wire R2 may be disposed on the surface 223 of the diaphragm portion 221. For example, an insulating film is formed on the surface 223 of the diaphragm portion 221, and a conductor layer is formed on the surface of the insulating film by sputtering or the like. Then, unnecessary parts of the conductor layer may be removed by a scientific means such as etching or a physical means such as a laser. In this case, the insulating film formed on the surface 223 of the diaphragm portion 221 becomes the "base portion" in the present invention. For example, an inorganic insulating material is used for the insulating film.

[0106] Furthermore, the sensor 40 may include sensors other than the rotation angle detection sensor S1, the torque detection sensor S2, and the temperature detection sensor S3. For example, the sensor 40 may include a sensor for detecting distortion of the flex gear 20 in the axial direction.

[0107] In the above embodiment, the torque detection sensor S2 has four resistance wires, the third resistance wire R3 to the sixth resistance wire R6. The third bridge circuit C3 is a full bridge circuit including the four resistance wires, the third resistance wire R3 to the sixth resistance wire R6. However, the torque detection sensor S2 may have only two resistance wires. In that case, the third bridge circuit C3 may be a half bridge circuit configured with the two resistance wires and two fixed resistors.

[0108] In the above embodiment, the signal processing circuit C0 is mounted on the circuit board 41. However, the signal processing circuit C0 may be provided outside the circuit board 41.

[0109] In the flex gear 20 of the above embodiment, the diaphragm portion 221 extends radially outward from the axial end of the cylindrical portion 21. However, the diaphragm portion 221 may extend radially inward from the axial end of the cylindrical portion 21.

[0110] In the above embodiment, the object to be detected by sensor 40 is flex gear 20. However, the object to be detected by sensor 40 is not limited to flex gear 20. Sensor 40 having a structure equivalent to that of the above embodiment may be used to detect the rotation angle of a rotational motion input to a flexible member other than flex gear 20.

[0111] In addition, the detailed configurations of the sensor and the power transmission device may be appropriately modified without departing from the spirit of the present invention. Furthermore, the elements appearing in each of the above-described embodiments and modifications may be appropriately combined without causing any contradiction. [Industrial Applicability]

[0112] The present application can be used in sensors and power transmission devices. [Explanation of symbols]

[0113] 1 Power transmission device 9 Center axis 10 Internal Gear 20 Flex Gear 30 Wave Generator 40 Sensors 41 Circuit Board 42 Insulating layer 43 First conductor layer 44 Second conductor layer 221 Diaphragm part 411 Main body 412 Flap section C0 Signal processing circuit C1 First bridge circuit C2 Second bridge circuit C3 3rd bridge circuit R1, Ra~Rd First resistance line R2,Re~Rh 2nd resistance wire R3 3rd resistance wire R4 Fourth resistance line R5 5th resistance wire R6 6th resistance wire R7 7th resistance wire S1 Rotation angle detection sensor S2 Torque detection sensor S3 Temperature detection sensor W1 Connection wire W2 connection wire W3 Connection wire

Claims

1. A base portion extending in a direction intersecting the central axis; A plurality of first resistance wires arranged in a circumferential direction on a surface of the base portion; a plurality of second resistance wires disposed on a surface of the base portion, concentric with the plurality of first resistance wires and circumferentially between the first resistance wires; having A sensor, wherein in at least one of the first resistance wires, the number of resistance wire regions along the circumferential direction is one or less and the number of resistance wire regions along the radial direction is one or less.

2. 2. The sensor of claim 1, A sensor, wherein in at least one of the second resistance wires, the number of resistance wire regions along the circumferential direction is one or less and the number of resistance wire regions along the radial direction is one or less.

3. The sensor according to claim 1 or 2, At least one of the first resistance wires extends in a straight line, a curved line, or a bent line, The sensor, wherein at least one of the second resistance wires extends in a straight line, a curved line, or a zigzag line.

4. A sensor according to any one of claims 1 to 3, Each of the first resistance wires extends obliquely with respect to the circumferential direction and the radial direction, The sensor, wherein each of the plurality of second resistance wires extends obliquely with respect to the circumferential direction and the radial direction.

5. A sensor according to any one of claims 1 to 4, the base portion is an insulating layer, A first conductor layer formed on a surface of the insulating layer; A second conductor layer laminated on a surface of the first conductor layer; having the first resistance wire and the second resistance wire are formed of the first conductor layer, A sensor, wherein connection lines extending from the ends of the first resistance wire and the second resistance wire are formed by the first conductor layer and the second conductor layer.

6. 6. The sensor of claim 5, A sensor, wherein the resistivity of the material of the second conductor layer is lower than the resistivity of the material of the first conductor layer.

7. 6. The sensor of claim 5, The sensor, wherein the gauge factor of the material of the second conductor layer is lower than the gauge factor of the material of the first conductor layer.

8. A sensor according to any one of claims 5 to 7, the material of the first conductor layer is a material containing copper or a material containing chromium, The material of the second conductor layer is copper, silver, or gold.

9. A sensor according to any one of claims 5 to 8, A sensor, wherein a line width of at least a part of the connection line is wider than a line width of the first resistance line and a line width of the second resistance line.

10. A sensor according to any one of claims 1 to 9, The first resistance wire has an arc shape extending along a circumferential direction from one end to the other end in the circumferential direction, A sensor, wherein the second resistance wire is arc-shaped and extends circumferentially from one end to the other end in the circumferential direction.

11. A sensor according to any one of claims 1 to 10, A sensor, wherein a radial position of the second resistance wire is different from a radial position of the first resistance wire.

12. A sensor according to any one of claims 1 to 11, Four of the first resistance wires; Four of the second resistance wires; having A sensor in which the circumferential central portions of the first resistance wire and the circumferential central portions of the second resistance wire are alternately arranged at 45° intervals around the central axis.

13. 13. The sensor of claim 12, A detection circuit including the first resistance line and the second resistance line. A sensor having

14. 14. The sensor of claim 13, The detection circuit includes: a first bridge circuit including the four first resistance wires; a second bridge circuit including the four second resistance wires; A sensor having

15. A sensor according to claim 13 or claim 14, the base portion extends in a direction intersecting the central axis and is disposed on a surface of a flexible member that is capable of bending and deforming; a rotation angle detection sensor that detects a rotation angle of the rotational motion input to the flexible member by the detection circuit; a torque detection sensor that detects a torque applied to the flexible member; Including a sensor.

16. 16. The sensor of claim 15, a signal processing circuit for correcting a measurement value of the torque detection sensor based on the rotation angle detected by the rotation angle detection sensor; A sensor comprising:

17. 17. The sensor of claim 15 or 16, A sensor in which a resistance wire constituting the torque detection sensor, the plurality of first resistance wires, and the plurality of second resistance wires are arranged on the same surface of the base portion.

18. 18. The sensor of claim 17, The plurality of first resistance wires and the plurality of second resistance wires are located radially outward of a resistance wire constituting the torque detection sensor.

19. A sensor according to any one of claims 15 to 18, A temperature detection sensor that detects the temperature of the flexible member by a resistance wire that extends in an arc shape around the central axis. The sensor further comprises:

20. A sensor according to any one of claims 15 to 19; The flexible member; A power transmission device having the same.

21. 21. The power transmission device of claim 20, The flexible member is A flexible cylindrical portion extending in an axial direction; A plurality of external teeth provided on a radially outer surface of the cylindrical portion; A diaphragm portion that extends from an axial end of the cylindrical portion toward a radially outward or radially inward direction; having A power transmission device, wherein the base portion is disposed on a surface of the diaphragm portion.

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