CN116476123A - Detection device, speed reducer, robot, and diagnosis method - Google Patents

Abstract

The invention provides a detection device, a speed reducer, a robot and a diagnosis method. The speed reducer has a ring gear, a strain gauge disposed on the gear, and a detection device. The detection device includes a diagnostic value output unit, a storage unit, a comparison unit, and a signal output unit. The diagnostic value output unit outputs a diagnostic value based on the output signal of the strain gauge. The storage unit stores a first reference value. The comparing unit compares the diagnosis value with the first reference value. The signal output unit outputs a first signal when the diagnostic value reaches the first reference value.

Description

Detection device, speed reducer, robot, and diagnosis method

Technical Field

The present invention relates to a detection device, a speed reducer, a robot, and a diagnosis method.

Background

In recent years, the need for a speed reducer mounted on a joint or the like of a robot has been increasing. The state of the speed reducer may change due to long-term use. Therefore, it is required to detect abnormality of the speed reducer. As a technique for detecting an abnormality of a speed reducer, for example, there is a technique including: a first encoder that detects rotation of a motor-side rotary shaft of the speed reducer; a second encoder that detects rotation of a rotary shaft on a load side of the speed reducer; a difference detection unit that obtains a difference value between a first detection value obtained by dividing the output of the first encoder by the reduction ratio of the speed reducer and a second detection value obtained from the output of the second encoder; and a tooth skip detection unit that detects occurrence of a tooth skip of the speed reducer based on the differential value, wherein the tooth skip detection unit compares the differential value with a predetermined threshold value, and detects occurrence of a tooth skip of the speed reducer when the differential value is greater than or equal to the threshold value (International publication No. 2014/098008).

However, the technique described in japanese unexamined patent publication No. 2014/098008 uses a first encoder that detects rotation of a rotary shaft on a motor side and a second encoder that detects rotation of a rotary shaft on a load side of a speed reducer, and detects when a tooth skip occurs in the speed reducer. In the related art, a first encoder for detecting rotation of a rotary shaft on a motor side and a second encoder for detecting rotation of a rotary shaft on a load side of a speed reducer are required, and a change in the state of the speed reducer cannot be detected before an abnormality such as tooth jump occurs in the speed reducer.

Disclosure of Invention

The present invention aims to provide a technology capable of detecting the change of the state of a speed reducer before the speed reducer is abnormal.

A first aspect of the present invention provides a detection device for diagnosing a state of a speed reducer based on an output signal of a strain gauge disposed on a ring gear provided in the speed reducer, the detection device including: a diagnostic value output unit that outputs a diagnostic value based on the output signal; a storage unit that stores a first reference value; a comparison unit that compares the diagnostic value with the first reference value; and a signal output unit that outputs a first signal based on a comparison result of the comparison unit, the signal output unit outputting the first signal when the diagnostic value reaches the first reference value.

A second aspect of the present invention provides a detection device for diagnosing a state of a speed reducer based on an output signal of a strain gauge disposed on a ring gear provided in the speed reducer, wherein the speed reducer includes two sets of bridge circuits each including a plurality of strain gauges, the strain gauge includes a pattern in which a resistance wire extending in a radial direction is disposed or a pattern in which a resistance wire extending in a circumferential direction is disposed, the output signal is an output signal of the bridge circuit, and a first signal is output when a phase difference between the output signals of the two sets of bridge circuits reaches a first reference value.

A third aspect of the present invention provides a diagnostic method for diagnosing a state of a speed reducer based on an output signal of a strain gauge disposed on a ring gear provided in the speed reducer, the diagnostic method including: a step of outputting a diagnostic value based on the output signal; a step of comparing the diagnosis value with a first reference value; and outputting a first signal based on a result of the comparison, the first signal being output when the diagnostic value reaches the first reference value.

A fourth aspect of the present invention is a speed reducer including the detection device, the gear, and the strain gauge.

A fifth aspect of the present invention is a robot including the above-described speed reducer.

According to the first to fifth aspects of the present invention, when the diagnostic value based on the output signal of the strain gauge disposed on the gear reaches the first reference value, the first signal is outputted. This makes it possible to detect a change in the state of the speed reducer before an abnormality occurs in the speed reducer.

The above and other features, elements, steps, features and advantages of the present invention will be more clearly understood from the following detailed description of the preferred embodiments of the present invention with reference to the accompanying drawings.

Drawings

Fig. 1 is a schematic view of a robot.

Fig. 2 is a longitudinal sectional view of the speed reducer.

Fig. 3 is a cross-sectional view of the speed reducer.

Fig. 4 is a partial longitudinal cross-sectional view of a flexible externally toothed gear.

Fig. 5 is a top view of a substrate.

Fig. 6 is a partial top view of a substrate.

Fig. 7 is a circuit diagram of a bridge circuit.

Fig. 8 is a circuit diagram of a bridge circuit.

Fig. 9 is a circuit diagram of a bridge circuit.

Fig. 10 is a graph showing the time variation of the output signals of two sets of bridge circuits.

Fig. 11 is a block diagram conceptually showing functions related to the diagnostic processing of the detection device.

Fig. 12 is a flowchart showing a flow of the first diagnostic process.

Fig. 13 is a graph showing an example of the change with time of the diagnostic value in the first diagnostic process.

Fig. 14 is a block diagram conceptually showing functions related to the second diagnostic process of the detection device.

Fig. 15 is a flowchart showing a flow of the second diagnosis process.

Fig. 16 is a graph showing an example of the change with time of the diagnostic value in the second diagnostic process.

Fig. 17 is a block diagram conceptually showing functions related to the third diagnostic process of the detection device.

Fig. 18 is a flowchart showing a flow of the third diagnostic process.

In the figure:

1-speed reducer, 9-central shaft, 10-internal gear, 20-flexible external gear, 40-torque sensor, 41-base plate, 42-detection device, 100-robot, 231-base, 421-diagnostic value output unit, 422-storage unit, 423-comparison unit, 424-signal output unit, 425-control unit, C1-C3-bridge circuit, ra-Rl-strain gauge, th1, th3, th 5-first reference value, th2, th4, th 6-second reference value, V1-V3-voltmeter.

Detailed Description

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

< 1 concerning robot >)

Fig. 1 is a schematic view of a robot 100 equipped with a speed reducer 1 according to an embodiment. The robot 100 is, for example, a so-called industrial robot that performs operations such as transportation, machining, and assembling of parts on a production line of industrial products. As shown in fig. 1, a robot 100 includes a base frame 101, an arm 102, a motor 103, and a speed reducer 1.

The arm 102 is rotatable relative to the base frame 101 by a support position. The motor 103 and the speed reducer 1 are assembled to the joint between the base frame 101 and the arm 102. When a driving current is supplied to the motor 103, a rotational motion is output from the motor 103. The rotational motion output from the motor 103 is decelerated by the speed reducer 1 and transmitted to the arm 102. Thereby, the arm 102 rotates at a speed reduced with respect to the base frame 101.

As described above, the robot 100 includes the speed reducer 1. The speed reducer 1 has a function of diagnosing the state of the speed reducer 1 by a detection device 42 described later. Thereby, the robot 100 having advanced functions can be realized.

< 2. Structure of speed reducer >)

Next, a detailed structure of the speed reducer 1 will be described.

Hereinafter, a direction parallel to the center axis 9 of the speed reducer 1 is referred to as an "axial direction", a direction orthogonal to the center axis 9 of the speed reducer 1 is referred to as a "radial direction", and a direction along an arc centered on the center axis 9 of the speed reducer 1 is referred to as a "circumferential direction". However, the above-described "parallel direction" also includes a substantially parallel direction. The "orthogonal direction" described above also includes a substantially orthogonal direction.

Fig. 2 is a longitudinal sectional view of the speed reducer 1 according to the embodiment. Fig. 3 is a cross-sectional view of the speed reducer 1 as seen from the A-A position of fig. 2. To avoid complicating the drawing, cross-section lines representing cross-sections are omitted from fig. 3. The speed reducer 1 is a device that reduces the rotational motion at a first rotational speed obtained from the motor 103 to a second rotational speed lower than the first rotational speed. The speed reducer 1 includes a flexible externally toothed gear 20, strain gauges Ra to Rl (see fig. 5), and a detection device 42. The speed reducer 1 of the present embodiment further includes an internal gear 10 and a wave generator 30.

As will be described later, the speed reducer 1 has a function of diagnosing the state of the speed reducer 1 by the detection device 42. This enables the reduction gear 1 to realize advanced functions.

The internal gear 10 is an annular gear centered on the center axis 9. The internal gear 10 is fixed relative to the base frame 101. The internal gear 10 meshes with the flexible external gear 20. The internal gear 10 is disposed radially outward of external teeth 22 described later. The rigidity of the internal gear 10 is sufficiently higher than that of a main body 21 of the flexible external gear 20, which will be 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 protrude radially inward from the radially inner side 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 tooth gear 10.

The flexible externally toothed gear 20 is a flexible annular gear. Flexible externally toothed gear 20 is fixed relative to arm 102. The flexible externally toothed gear 20 is supported rotatably about the central axis 9. As shown in fig. 2 and 3, the flexible externally toothed gear 20 includes a main body portion 21, a plurality of external teeth 22, and an annular plate portion 23.

The body 21 is a cylindrical portion extending in the axial direction from a radial end of the base 231 described later. In the present embodiment, the body portion 21 extends from the radially inner end portion of the base portion 231 toward one axial side. One axial end of the body 21 is located radially outward of the wave generator 30 and radially inward of the internal gear 10. The body portion 21 is flexible and therefore can be deformed in the radial direction. In particular, one axial end of the main body 21 can be displaced radially more than the other.

The plurality of external teeth 22 protrude radially outward from the radially outer side surface of the main body 21. The plurality of external teeth 22 are arranged on the radially outer side surface of one axial end of the body 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 and a part of the plurality of internal teeth 11 are meshed with each other. The number of internal teeth 11 provided by the internal gear 10 and the number of external teeth 22 provided by the flexible externally toothed gear 20 are slightly different.

The annular plate portion 23 has a base portion 231 and a thick portion 232. That is, flexible externally toothed gear 20 has base 231. The base 231 surrounds the central axis 9 and expands in a direction intersecting the central axis 9. The base 231 preferably extends along a plane orthogonal to the central axis 9. The base 231 extends radially outward from the end on the other axial side of the main body 21. The base 231 is annular and surrounds the central axis 9. The base 231 is thin-walled, and therefore can be slightly deformed by bending.

The thick portion 232 is an annular portion located radially outward of the base 231. The thick portion 232 further expands radially outward from the radially outer end of the base 231. The thickness of the thick portion 232 in the axial direction is larger than the thickness of the base portion 231 in the axial direction. The thick portion 232 is fixed to the arm 102 by, for example, a bolt.

Wave generator 30 is a mechanism for generating flexural deformation of flexible externally toothed gear 20. The wave generator 30 is disposed radially inward of the external teeth 22. The wave generator 30 of the present embodiment has a cam 31 and a flexible bearing 32. The cam 31 is supported rotatably about the center axis 9. The radially outer side surface of the cam 31 is elliptical when viewed in the axial direction. The flexible bearing 32 is a flexible deformable bearing. The flexible bearing 32 is disposed between the radially outer surface of the cam 31 and the radially inner surface of the main body 21 of the flexible externally toothed gear 20. Therefore, the cam 31 and the main body 21 can rotate at different rotational speeds.

The inner wheel of the flexible bearing 32 is in contact with the radially outer side surface of the cam 31. The outer ring of the flexible bearing 32 contacts the radially inner surface of the main body 21. Therefore, the body portion 21 is deformed into an elliptical shape along the radially outer side surface of the cam 31. As a result, the external teeth 22 of the flexible externally toothed gear 20 and the internal teeth 11 of the internally toothed gear 10 mesh at two positions corresponding to both ends of the major axis of the ellipse. In other circumferential positions, the external teeth 22 and the internal teeth 11 are not meshed.

The cam 31 is connected to an output shaft (not shown) of the motor 103. When the motor 103 is driven, the cam 31 rotates at a first rotational speed centering on the center shaft 9. Thereby, the major axis of the ellipse of flexible externally toothed gear 20 also rotates at the first rotational speed. Then, the meshing position of the external teeth 22 and the internal teeth 11 also varies in the circumferential direction at the first rotational speed. In addition, as described above, the number of internal teeth 11 of the internal gear 10 and the number of external teeth 22 of the flexible externally toothed gear 20 are slightly different. Due to the difference in the number of teeth, the meshing position of the external teeth 22 with the internal teeth 11 slightly varies in the circumferential direction every one revolution of the cam 31. As a result, the flexible externally toothed gear 20 rotates about the central axis 9 with respect to the internally toothed gear 10 at a second rotational speed lower than the first rotational speed.

< 3 regarding Torque sensor >)

Next, the torque sensor 40 will be described. Torque sensor 40 is a sensor for detecting torque applied to flexible externally toothed gear 20. As shown in fig. 2, the torque sensor 40 has a substrate 41 and a detection device 42. The base plate 41 is disposed on the base 231 of the flexible externally toothed gear 20.

Fig. 4 is a partial longitudinal sectional view of flexible externally toothed gear 20 in the vicinity of base plate 41. As shown in fig. 4, the base 231 of the flexible externally toothed gear 20 has a surface 234 intersecting the central axis 9 and extending in a circular ring shape centering around the central axis 9. The surface 234 is a surface on the other axial side of the base 231. The substrate 41 is secured to the surface 234 of the base 231.

As shown in fig. 4, the substrate 41 has an insulating layer 411 and a conductor layer 412. The insulating layer 411 can be flexibly deformed. The insulating layer 411 expands in a direction intersecting with the central axis 9. The insulating layer 411 is annular and centered on the central axis 9. The insulating layer 411 is made of a resin or an inorganic insulating material as an insulator. The insulating layer 411 is disposed on the surface 234 of the base 231.

The conductor layer 412 is formed on the surface of the insulating layer 411. That is, the conductor layer 412 is disposed on the base 231. The material of the conductor layer 412 uses, for example, copper alloy, chromium alloy, or copper.

Fig. 5 is a plan view of the substrate 41. As shown in fig. 5, the conductor layer 412 has a plurality of strain gauges Ra to Rd. The plurality of strain gauges Ra to Rd are resistors for detecting the torque of the flexible externally toothed gear 20. In the present embodiment, the conductor layer 412 includes four strain gauges Ra to Rd.

The strain gauges Ra and Rb are circumferentially arranged at intervals. The strain gauges Ra and Rb are each provided in a semicircular arc shape within a range of about 180 ° around the central axis 9. The strain gauges Ra and Rb are arranged concentrically and line symmetrically. In addition, the distance from the central axis 9 to the radial direction of the strain gauge Ra is substantially the same as the distance from the central axis 9 to the radial direction of the strain gauge Rb.

The strain gauges Rc and Rd are arranged radially outward of the strain gauges Ra and Rb. More specifically, the strain gauge Rc is disposed radially outward of the strain gauge Ra, and the strain gauge Rd is disposed radially outward of the strain gauge Rb.

The strain gauges Rc and Rd are circumferentially arranged at intervals. The strain gauges Rc and Rd are each provided in a semicircular arc shape within a range of about 180 ° around the central axis 9. The strain gauges Rc and Rd are concentrically and line symmetrically arranged. The distance from the center axis 9 to the strain gauge Rc in the radial direction is substantially the same as the distance from the center axis 9 to the strain gauge Rd in the radial direction.

Fig. 6 is a partial plan view of the substrate 41. As shown in fig. 6, the strain gauge Ra, rb, rc, rd includes a pattern in which resistance lines r1 inclined with respect to the radial direction and the circumferential direction are repeatedly arranged in the circumferential direction. Specifically, the four strain gauges Ra, rb, rc, rd each extend circumferentially along one side of one wire bent in a zigzag manner. The plurality of resistance lines r1 are arranged in a circumferential direction in a posture substantially parallel to each other.

The resistance line r1 of the strain gauge Ra is inclined to one side in the circumferential direction with respect to the radial direction. The resistance line r1 of the strain gauge Rb is inclined to the other side in the circumferential direction with respect to the radial direction. The resistance line r1 of the strain gauge Rc is inclined to the other side in the circumferential direction with respect to the radial direction. The resistance line r1 of the strain gauge Rd is inclined to one side in the circumferential direction with respect to the radial direction.

The inclination angle of the resistance line r1 with respect to the radial direction is, for example, 45 °. The ends of the resistance wires r1 adjacent in the circumferential direction are alternately connected to each other on the radially inner side or the radially outer side. Thereby, the plurality of resistance lines r1 are connected in series as a whole.

Four strain gauges Ra, rb, rc, rd are connected to each other to constitute a bridge circuit C1. That is, the speed reducer 1 has a bridge circuit C1 composed of a plurality of strain gauges Ra to Rd.

Fig. 7 is a circuit diagram of the bridge circuit C1. As shown in fig. 7, the strain gauges Ra and Rb are connected in series in this order. The strain gauges Rc and Rd are connected in series in this order. Further, between the +pole and the-pole of the power supply voltage, the columns of the two strain gauges Ra, rb and the columns of the two strain gauges Rc, rd are connected in parallel. The intermediate point M11 of the two strain gauges Ra and Rb and the intermediate point M12 of the two strain gauges Rc and Rd are connected to the voltmeter V1.

The resistance values of the strain gauges Ra to Rd vary according to the torque applied to the base 231. That is, in the present embodiment, the resistance value of each resistance wire r1 of the four strain gauges Ra to Rd changes according to the torque applied to the base 231. For example, when a torque is applied to the base 231 toward one side in the circumferential direction about the center axis 9, the resistance value of each resistance wire r1 of the strain gauges Ra and Rd decreases, and the resistance value of each resistance wire r1 of the strain gauges Rb and Rc increases. On the other hand, when a torque is applied to the base 231 toward the other side in the circumferential direction about the center axis 9, the resistance value of each resistance wire r1 of the strain gauges Ra and Rd increases, and the resistance value of each resistance wire r1 of the strain gauges Rb and Rc decreases. In this way, the strain gauges Ra, rd and the strain gauges Rb, rc show resistance values that are opposite to each other with respect to the torque.

When the resistance values of the four strain gauges Ra, rb, rc, rd change, the potential difference between the intermediate point M11 of the two strain gauges Ra and Rb and the intermediate point M12 of the two strain gauges Rc and Rd changes, and thus the output signal of the voltmeter V1 also changes. Accordingly, the direction and magnitude of the torque applied to the base 231 can be detected based on the output signal of the voltmeter V1.

The detection device 42 is electrically connected to the plurality of strain gauges Ra to Rd and the voltmeter V1. The detection device 42 diagnoses the state of the speed reducer 1 based on the output signal of the strain gauge disposed on the ring gear included in the speed reducer 1. The detection device 42 may be attached to the flexible externally toothed gear 20 or may be provided at a position separate from the flexible externally toothed gear 20. The output signal of the voltmeter V1 is input to the detection device 42. The detection device 42 outputs a detection signal indicating the direction and magnitude of the torque applied to the base 231 based on the output signal of the voltmeter V1.

< 4 > regarding ripple correction

As described above, when the speed reducer 1 is driven, the flexible externally toothed gear 20 is periodically deformed. Thus, the output signal of voltmeter V1 contains a component reflecting the torque that would otherwise be desired to be measured and an error component (ripple error) caused by the periodic flexural deformation of flexible externally toothed gear 20. The ripple error varies periodically according to the rotation angle of the rotational motion input to the flexible externally toothed gear 20.

Therefore, the detection device 42 of the present embodiment performs correction processing (ripple correction) for canceling the ripple error described above. Hereinafter, this ripple correction will be described.

As shown in fig. 5, the conductor layer 412 of the present embodiment has a plurality of strain gauges Re to Rl. The plurality of strain gauges Re to Rl are resistors for detecting the rotation angle of the rotational motion input to the flexible externally toothed gear 20. In the present embodiment, the conductor layer 412 includes eight strain gauges Re to Rl.

The eight strain gauges Re to Rl are arranged at intervals in the circumferential direction. The eight strain gauges Re to Rl are each formed of one wire. Each strain gauge Re, rf, rg, rh, ri, rj, rk, rl extends in an arc shape along the circumferential direction.

The strain gauges Re to Rl include a pattern in which resistance wires extending in the radial direction are arranged or a pattern in which resistance wires extending in the circumferential direction are arranged. In the present embodiment, each of the eight strain gauges Re to Rl includes a pattern in which a resistance wire r2 extending in the circumferential direction is arranged. However, each of the eight strain gauges Re to Rl may be a pattern in which the resistance lines r2 extending in the circumferential direction are repeatedly arranged in the radial direction. The eight strain gauges Re to Rl may each include a pattern in which a resistance wire extending in the radial direction is arranged. The eight strain gauges Re to Rl may be arranged in a pattern in which resistance wires extending in the radial direction are arranged repeatedly in the circumferential direction.

Four strain gauges Re, rg, ri, rk out of eight strain gauges Re to Rl, which are not adjacent to each other, are connected to each other to constitute a bridge circuit C2. The remaining four strain gauges Rf, rh, rj, rl out of the eight strain gauges Re to Rl are connected to each other to form a bridge circuit C3. In this way, the speed reducer 1 has the bridge circuit C2 composed of the plurality of strain gauges Re, rg, ri, rk. In the present embodiment, the speed reducer 1 further includes a bridge circuit C3 including a plurality of strain gauges Rf, rh, rj, rl. That is, the speed reducer 1 of the present embodiment has two sets of bridge circuits each including a plurality of strain gauges.

Fig. 8 is a circuit diagram of the bridge circuit C2. As shown in fig. 8, strain gauges Re and Rg are connected in series in this order. The strain gauges Rk and Ri are connected in series in this order. Further, between the positive and negative poles of the power supply voltage, the columns of the two strain gauges Re, rg and the columns of the two strain gauges Rk, ri are connected in parallel. The intermediate point M21 of the two strain gauges Re and Rg and the intermediate point M22 of the two strain gauges Rk and Ri are connected to the voltmeter V2.

Fig. 9 is a circuit diagram of the bridge circuit C3. As shown in fig. 9, the strain gauges Rl and Rj are connected in series in this order. Strain gauges Rf and Rh are connected in series in this order. Between the positive and negative poles of the power supply voltage, the columns of the two strain gauges Rl and Rj and the columns of the two strain gauges Rf and Rh are connected in parallel. The intermediate point M31 of the two strain gauges Rl, rj and the intermediate point M32 of the two strain gauges Rf, rh are connected to the voltmeter V3.

When the speed reducer 1 is driven, a portion extending in the circumferential direction (hereinafter referred to as an "extension portion") and a portion contracting in the circumferential direction (hereinafter referred to as a "contraction portion") are generated at the base 231 of the flexible externally toothed gear 20. Specifically, two elongated portions and two contracted portions are alternately generated 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 center axis 9. The portions where these extension and contraction portions occur are rotated at the first rotational speed described above.

The resistance values of the eight strain gauges Re to Rl change according to the expansion and contraction in the circumferential direction of the base 231. For example, when the extension portion overlaps a certain strain gauge, the resistance value of the strain gauge increases. When the above-described constricted portion overlaps a certain strain gauge, the resistance value of the strain gauge decreases.

In the example of fig. 5, when the contraction portion overlaps with the strain gauges Re, ri, the extension portion overlaps with the strain gauges Rg, rk. When the extension portion overlaps with the strain gauges Re and Ri, the contraction portion overlaps with the strain gauges Rg and Rk. Therefore, in the bridge circuit C2, the strain gauges Re, ri and the strain gauges Rg, rk show resistance value changes in opposite directions.

In the example of fig. 5, when the contraction portion overlaps with the strain gauges Rl and Rh, the extension portion overlaps with the strain gauges Rj and Rf. When the extension portion overlaps with the strain gauges Rl and Rh, the contraction portion overlaps with the strain gauges Rj and Rf. Therefore, in the bridge circuit C3, the strain gauges Rl, rh and the strain gauges Rj, rf show resistance value changes in opposite directions.

Fig. 10 is a graph showing time changes of the output signal V2 of the voltmeter V2 of the bridge circuit C2 and the output signal V3 of the voltmeter V3 of the bridge circuit C3. The horizontal axis of the graph of fig. 10 represents time. The vertical axis of the graph of fig. 10 represents the voltage value. When the speed reducer 1 is driven, as shown in fig. 10, sinusoidal output signals V2 and V3 that periodically vary are output from the voltmeter V2 and the voltmeter V3, respectively. The period T of the output signals v2 and v3 corresponds to 1/2 times the period of the first rotation speed. The direction of the rotational movement to be input can be determined by advancing the phase of the output signal V3 of the voltmeter V3 by 1/8 cycle of the first rotational speed (1/4 cycle of the output signals V2 and V3) or by delaying the phase of the output signal V2 of the voltmeter V2 by 1/8 cycle of the first rotational speed (1/4 cycle of the output signals V2 and V3).

The detection device 42 detects the rotation angle of the rotational motion input to the flexible externally toothed gear 20 based on the output signals V2, V3 of the voltmeters V2, V3. Specifically, for example, the detection device 42 includes a storage unit in which a function table is stored in which a combination of the output signal V2 of the voltmeter V2 and the output signal V3 of the voltmeter V3 and the rotation angle are associated. The detection device 42 can output the rotation angle by inputting the output signals v2 and v3 into the function table.

In addition, the ripple error varies in a sine wave manner with respect to the rotation angle of the flexible externally toothed gear 20. The detection device 42 calculates the ripple error described above from the output rotation angle. Then, the detection device 42 corrects the output signal of the voltmeter V1 using the calculated ripple error. As a result, the detection device 42 can output the torque applied to the flexible externally toothed gear 20 with higher accuracy.

The detection device 42 may directly calculate the ripple error based on the output signals V2 and V3 of the two voltmeters V2 and V3, instead of calculating the rotation angle. In this way, the processing load of the calculation of the rotation angle can be reduced. Therefore, the operation speed of the detection device 42 can be increased.

In the present embodiment, strain gauges Re to Rl for detecting rotation angles are arranged radially outward of strain gauges Ra to Rd for detecting torque. However, the strain gauges Re to Rl for detecting the rotation angle may be disposed radially inward of the strain gauges Ra to Rd for detecting the torque.

Two strain gauges Re, rg or two strain gauges Ri, rk out of the four strain gauges Re, rg, ri, rk described above may also be omitted. Even in this case, by using the bridge circuit C2 as a half bridge circuit using two fixed resistors, an output signal according to the rotation angle can be obtained. Likewise, two strain gauges Rf, rh or two strain gauges Rj, rl out of the four strain gauges Rf, rh, rj, rl described above may be omitted. Even in this case, by using the bridge circuit C3 as a half bridge circuit using two fixed resistors, an output signal according to the rotation angle can be obtained.

< 5 > concerning diagnostic function

The detection device 42 can diagnose the state of the speed reducer 1 based on the output signals of the strain gauges Ra to Rd or the strain gauges Re to Rl. The diagnosis process will be described below. Fig. 11 is a block diagram conceptually showing functions of the detection device 42 related to the diagnosis process. As shown in fig. 11, the detection device 42 includes a diagnostic value output unit 421, a storage unit 422, a comparison unit 423, a signal output unit 424, and a control unit 425. The diagnostic value output unit 421, the comparison unit 423, the signal output unit 424, and the control unit 425 are realized by, for example, a microcomputer included in the detection device 42 operating in accordance with a program. The storage unit 422 is implemented by, for example, a memory provided in the detection device 42.

It is desirable that the comparing unit 423 and the signal output unit 424 be a single component. For example, the comparing unit 423 and the signal output unit 424 are desirably implemented by the same microcomputer. This makes it possible to simplify the structure of the detection device 42, compared with a case where the comparison unit 423 and the signal output unit 424 are different components.

< 5-1. First diagnostic treatment: case of using angle sensor

First, a first diagnosis process for diagnosing the state of the speed reducer 1 using output signals of the strain gauges Re to Rl for detecting the rotation angle will be described. Fig. 12 is a flowchart showing a flow of the first diagnostic process.

When the speed reducer 1 is driven, the diagnostic value output unit 421 outputs a diagnostic value based on the output signals from the strain gauges Re to Rl (step S11). In the first diagnostic process, the diagnostic value output unit 421 outputs a diagnostic value based on the output signals of the bridge circuits C2, C3. More specifically, the diagnostic value output unit 421 outputs, as a diagnostic value, a difference between the maximum value and the minimum value of the output signal V2 of the voltmeter V2 or a difference between the maximum value and the minimum value of the output signal V3 of the voltmeter V3. That is, the diagnostic value is a difference between the maximum value and the minimum value of the output signal v2 or a difference between the maximum value and the minimum value of the output signal v 3. The "maximum value" is the maximum value of the output signals v2 and v3 during the half rotation of the cam 31. The "minimum value" is the minimum value of the output signals v2 and v3 during half a revolution of the cam 31.

As shown in fig. 11, the first reference value Th1 is stored in the storage unit 422. The comparison unit 423 reads the first reference value Th1 from the storage unit 422. Then, the comparison unit 423 compares the diagnostic value output from the diagnostic value output unit 421 with the first reference value Th1 (step S12).

Fig. 13 is a graph showing an example of the change with time of the diagnostic value. The horizontal axis of fig. 13 shows the number of days elapsed from the start of use of the speed reducer 1. The vertical axis of fig. 13 represents the value of the diagnostic value. The vertical axis of fig. 13 represents a value obtained by scaling the diagnostic value at the start of use of the speed reducer 1 to 1. As shown in fig. 13, the first reference value Th1 is smaller than the diagnostic value output from the diagnostic value output unit 421 at the time of normal driving of the speed reducer 1, for example, at the time of starting the use of the speed reducer 1.

The diagnostic value may gradually decrease due to the change with time of the use of the speed reducer 1. In step S12, it is determined whether the diagnostic value has reached the first reference value Th1. When the diagnostic value is greater than the first reference value Th1 (step S12: no), the detection device 42 returns to step S11, and the diagnostic value output process is executed again. That is, when the diagnostic value does not reach the first reference value Th1, the detection device 42 returns to step S11, and the diagnostic value output process is executed again.

On the other hand, when the diagnostic value is equal to or less than the first reference value Th1 (yes in step S12), the signal output unit 424 outputs the first signal (step S13). That is, when the diagnostic value reaches the first reference value Th1, the signal output unit 424 outputs the first signal. In this way, the signal output unit 424 outputs the first signal based on the comparison result of the comparison unit 423. This makes it possible to detect a change in the state of the speed reducer 1 before an abnormality occurs in the speed reducer 1. In the present embodiment, if strain gauges Re to Rl are provided on the ring gear 20, even when the motor 103 does not have a sensor or the like, for example, a change in the state of the speed reducer 1 can be detected.

As described above, in the first diagnosis process, the change in the state of the speed reducer 1 can be detected by using the difference between the maximum value and the minimum value of the output signal V2 of the voltmeter V2 and the difference between the maximum value and the minimum value of the output signal V3 of the voltmeter V3, which decrease due to the change with time.

The first reference value Th1 is, for example, a value based on a diagnostic value obtained in advance by driving the speed reducer 1 in advance. In this way, the first reference value Th1 can be appropriately set according to the mechanical difference of the speed reducer 1. For example, the first reference value Th1 is desirably set to a value that deviates from the average value of diagnostic values obtained in advance by driving the speed reducer 1 in advance by three times the standard deviation. For example, when the average value of the diagnostic values obtained in advance is 1.00 and the standard deviation is 0.005, the first reference value Th1 may be 1.00 to 0.005×3=0.985. Thereby, the first reference value Th1 can be appropriately set. Therefore, the first signal can be output at an appropriate timing. By setting the first reference value Th1 to the above value, it is possible to suppress statistical fluctuations due to various causes when the speed reducer 1 is driven, and to output the first signal.

The first reference value Th1 is stored in the storage unit 422 in advance as a fixed value. However, the first reference value Th1 may be determined based on the diagnostic value output from the diagnostic value output unit 421 and stored in the storage unit 422 while the speed reducer 1 is driven.

In this case, the first reference value Th1 is a value smaller than a difference between a maximum value and a minimum value of the output signals v2 and v3 preceding the output of the first signal. This enables the first signal to be output at an appropriate timing. Further, the first reference value Th1 is desirably a value of 97% or less of the average value of the differences between the maximum value and the minimum value of the output signals v2 and v3 preceding the output of the first signal. This enables the first signal to be output at a more appropriate timing. By setting the first reference value Th1 to the above value, it is possible to suppress statistical fluctuations due to various causes when the speed reducer 1 is driven, and to output the first signal.

The speed reducer 1 may be driven after the first signal is output. Therefore, the detection device 42 can detect a change in the state of the speed reducer 1 while continuing the driving of the speed reducer 1. In the present embodiment, the control unit 425 does not stop the speed reducer 1 even when the first signal is output. Specifically, the control unit 425 does not output a signal for stopping the motor 103. In other words, in the present embodiment, even in a state where the speed reducer 1 can be driven sufficiently, the occurrence of a sign of a change in the speed reducer 1 can be diagnosed based on the outputs of the strain gauges Re to Rl.

As shown in fig. 11, the second reference value Th2 is stored in the storage unit 422. After the signal output unit 424 outputs the first signal, the comparison unit 423 reads the second reference value Th2 from the storage unit 422. Then, the comparison unit 423 compares the diagnostic value output from the diagnostic value output unit 421 with the second reference value Th2 (step S14).

As shown in fig. 13, the second reference value Th2 is smaller than the first reference value Th 1. That is, the second reference value Th2 is a value far from the first reference value Th1 with respect to the diagnostic value before the first signal is output. In step S14, it is determined whether the diagnostic value has reached the second reference value Th2.

When the diagnostic value is greater than the second reference value Th2 (step S14: no), the detection device 42 executes the processing of step S14 again. That is, when the diagnostic value does not reach the second reference value Th2, the detection device 42 executes the processing of step S14 again. On the other hand, when the diagnostic value is equal to or less than the second reference value Th2 (step S14: yes), the signal output unit 424 outputs the second signal (step S15). That is, when the diagnostic value reaches the second reference value Th2, the signal output unit 424 outputs the second signal. That is, the signal output unit 424 outputs the second signal when the diagnostic value reaches the second reference value Th2 which is far from the diagnostic value before the output of the first signal, compared with the first reference value Th1, after the first signal is output. Thereby, the detection device 42 can detect a further development of the change in the state of the speed reducer 1. For example, the detection device 42 can detect that the driving of the speed reducer 1 is difficult to continue.

When the second signal is output from the signal output unit 424, the control unit 425 stops the speed reducer 1 (step S16). Specifically, the control unit 425 outputs a signal for stopping the motor 103. In this way, when the change in the state of the speed reducer 1 is further advanced than the output of the first signal, the speed reducer 1 can be stopped.

The control unit 425 may stop the speed reducer 1 at the time when the first signal is output from the signal output unit 424.

< 5-2. Second diagnostic treatment: case of using torque sensor

Next, a second diagnosis process for diagnosing the state of the speed reducer 1 using the output signals of the strain gauges Ra to Rd for detecting torque will be described. Fig. 14 is a block diagram conceptually showing the functions of the detection device 42 related to the second diagnostic process. Fig. 15 is a flowchart showing a flow of the second diagnosis process.

When the speed reducer 1 is driven, the diagnostic value output unit 421 outputs a diagnostic value based on the output signals from the strain gauges Ra to Rd (step S21). In the second diagnostic process, the diagnostic value output section 421 outputs a diagnostic value based on the output signal of the bridge circuit C1. That is, the output signal is the output signal of the bridge circuit C1. More specifically, the diagnostic value output unit 421 outputs the maximum value of the output signal of the voltmeter V1 as the diagnostic value. The "maximum value" is the maximum value of the output signal of the voltmeter V1 when a torque of a specific magnitude is applied to the flexible externally toothed gear 20.

As shown in fig. 14, the first reference value Th3 is stored in the storage unit 422. The comparison unit 423 reads the first reference value Th3 from the storage unit 422. Then, the comparison unit 423 compares the diagnostic value output from the diagnostic value output unit 421 with the first reference value Th3 (step S22).

Fig. 16 is a graph showing an example of the change with time of the diagnostic value. The horizontal axis of fig. 16 shows the number of days elapsed from the start of use of the speed reducer 1. The vertical axis of fig. 16 represents the value of the diagnostic value. The vertical axis of fig. 16 represents a value converted so that the diagnostic value at the start of use of the speed reducer 1 is 1. As shown in fig. 16, the first reference value Th3 is larger than the diagnostic value output from the diagnostic value output unit 421 when the speed reducer 1 is normally driven, for example, when the speed reducer 1 starts to be used.

The diagnostic value may become gradually larger as the speed reducer 1 is used with time. In step S22, it is determined whether the diagnostic value has reached the first reference value Th3. When the diagnostic value is smaller than the first reference value Th3 (step S22: no), the detection device 42 returns to step S21, and the diagnostic value output process is executed again. That is, when the diagnostic value does not reach the first reference value Th3, the detection device 42 returns to step S21, and the diagnostic value output process is executed again.

On the other hand, when the diagnostic value is equal to or greater than the first reference value Th3 (step S22: yes), the signal output unit 424 outputs the first signal (step S23). That is, when the diagnostic value reaches the first reference value Th3, the signal output unit 424 outputs the first signal. In this way, the signal output unit 424 outputs the first signal based on the comparison result of the comparison unit 423. This makes it possible to detect a change in the state of the speed reducer 1 before an abnormality occurs in the speed reducer 1.

As described above, in the second diagnosis process, the maximum value of the output signal of the voltmeter V1 increases due to the change with time, and the change in the state of the speed reducer 1 can be detected. I.e. the diagnostic value is the maximum value of the output signal.

The first reference value Th3 is, for example, a value based on a diagnostic value obtained in advance by driving the speed reducer 1 in advance. In this way, the first reference value Th3 can be appropriately set according to the mechanical difference of the speed reducer 1. For example, the first reference value Th3 is desirably a value that deviates 3 times from the standard with respect to the average value of diagnostic values obtained in advance by driving the speed reducer 1 in advance. For example, when the average value of the diagnostic values obtained in advance is 1.00 and the standard deviation is 0.02, the first reference value Th3 may be 1.00+0.02x3=1.06. Thereby, the first reference value Th3 can be appropriately set. Therefore, the first signal can be output at an appropriate timing. By setting the first reference value Th3 to the above value, it is possible to suppress statistical fluctuations due to various causes when the speed reducer 1 is driven, and to output the first signal.

The first reference value Th3 is stored in the storage unit 422 in advance as a fixed value. However, the first reference value Th3 may be determined based on the diagnostic value output from the diagnostic value output unit 421 while the speed reducer 1 is driven, and stored in the storage unit 422.

In this case, the first reference value Th3 is larger than the maximum value of the output signal preceding the output of the first signal. That is, the first reference value Th3 is a value larger than the maximum value of the output signal of the voltmeter V1 preceding the output of the first signal. This enables the first signal to be output at an appropriate timing. The first reference value Th3 is 103% or more of the average value of the maximum values of the output signals before the output of the first signal. The first reference value Th3 is desirably a value of 103% or more of the average value of the maximum value of the output signal of the voltmeter V1 preceding the output of the first signal. This enables the first signal to be output at a more appropriate timing. Further, by setting the first reference value Th3 to the above value, it is possible to suppress statistical fluctuations due to various causes when the speed reducer 1 is driven, and to output the first signal.

The speed reducer 1 can be driven after the first signal is output. Therefore, the detection device 42 can detect a change in the state of the speed reducer 1 while continuing the driving of the speed reducer 1. In the present embodiment, the control unit 425 does not stop the speed reducer 1 even when the first signal is output. Specifically, the control unit 425 does not output a signal for stopping the motor 103.

As shown in fig. 14, the second reference value Th4 is stored in the storage unit 422. After the signal output unit 424 outputs the first signal, the comparison unit 423 reads the second reference value Th4 from the storage unit 422. Then, the comparison unit 423 compares the diagnostic value output from the diagnostic value output unit 421 with the second reference value Th4 (step S24).

As shown in fig. 16, the second reference value Th4 is a value larger than the first reference value Th 3. That is, the second reference value Th4 is a value far from the first reference value Th3 with respect to the diagnostic value before the output of the first signal. In step S24, it is determined whether the diagnostic value has reached the second reference value Th4.

When the diagnostic value is smaller than the second reference value Th4 (step S24: no), the detection device 42 executes the processing of step S24 again. That is, when the diagnostic value does not reach the second reference value Th4, the detection device 42 executes the processing of step S24 again. On the other hand, when the diagnostic value is equal to or greater than the second reference value Th4 (step S24: yes), the signal output unit 424 outputs the second signal (step S25). That is, when the diagnostic value reaches the second reference value Th4, the signal output unit 424 outputs the second signal. Thereby, the detection device 42 can detect a further development of the change in the state of the speed reducer 1. For example, the detection device 42 can detect that the driving of the speed reducer 1 is difficult to continue.

When the second signal is output from the signal output unit 424, the control unit 425 stops the speed reducer 1 (step S26). Specifically, the control unit 425 outputs a signal for stopping the motor 103. In this way, when the change in the state of the speed reducer 1 is more gradual than the output of the first signal, the speed reducer 1 can be stopped.

The control unit 425 may stop the speed reducer 1 at the time when the first signal is output from the signal output unit 424.

< 5-3. Third diagnostic treatment: eccentric detection case

Next, a third diagnosis process for diagnosing whether the speed reducer 1 is not in an eccentric state by using the output signals of the strain gauges Re to Rl for detecting the rotation angle will be described. The eccentric state is a state in which the center line of the flexible externally toothed gear 20 is offset from the center line of the internally toothed gear 10. Fig. 17 is a block diagram conceptually showing the functions of the detection device 42 related to the third diagnostic process. Fig. 18 is a flowchart showing a flow of the third diagnostic process.

When the speed reducer 1 is driven, the diagnostic value output unit 421 outputs a diagnostic value based on the output signals from the strain gauges Re to Rl (step S31). In the third diagnostic process, the diagnostic value output unit 421 outputs a diagnostic value based on the output signals of the bridge circuits C2, C3. That is, the output signals are output signals of the bridge circuits C2, C3. More specifically, the diagnostic value output unit 421 outputs the phase difference between the output signal V2 of the voltmeter V2 and the output signal V3 of the voltmeter V3 as the diagnostic value. For example, as shown in fig. 10, the diagnostic value output unit 421 may calculate a value Δt/T obtained by dividing a time difference Δt between the zero-crossing time of the output signal v2 and the zero-crossing time of the output signal v3 by the period T as the phase difference.

As shown in fig. 17, the first reference value Th5 is stored in the storage unit 422. The comparison unit 423 reads the first reference value Th5 from the storage unit 422. Then, the comparison unit 423 compares the diagnostic value output from the diagnostic value output unit 421 with the first reference value Th5 (step S32).

In the case where the speed reducer 1 is driven normally, the diagnostic value output from the diagnostic value output section 421 hardly changes. However, when the speed reducer 1 is in the eccentric state, the diagnostic value output from the diagnostic value output unit 421 changes.

In step S32, it is determined whether the diagnostic value has reached the first reference value Th5. When the diagnostic value does not reach the first reference value Th5 (step S32: no), the detection device 42 returns to step S31, and the diagnostic value output process is executed again.

On the other hand, when the diagnostic value reaches the first reference value Th5 (step S32: yes), the signal output unit 424 outputs the first signal (step S33). That is, when the phase difference between the output signals of the two sets of bridge circuits C2 and C3 reaches the first reference value Th5, the signal output unit 424 outputs the first signal. In this way, the signal output unit 424 outputs the first signal based on the comparison result of the comparison unit 423. This makes it possible to detect a change in the state of the speed reducer 1 before an abnormality occurs in the speed reducer 1.

As described above, in the third diagnostic process, when the speed reducer 1 changes to the eccentric state, the speed reducer 1 can be detected to gradually become the eccentric state by using the change in the phase difference between the output signal V2 of the voltmeter V2 and the output signal V3 of the voltmeter V3.

The first reference value Th5 is, for example, a value based on a diagnostic value obtained in advance by driving the speed reducer 1 in advance. In this way, the first reference value Th5 can be appropriately set according to the mechanical difference of the speed reducer 1. For example, the first reference value Th5 is desirably a value that deviates from the average value of diagnostic values obtained in advance by driving the speed reducer 1 in advance by three times the standard deviation. Thereby, the first reference value Th5 can be appropriately set. Therefore, the first signal can be output at an appropriate timing.

The first reference value Th5 is stored in the storage unit 422 in advance as a fixed value. However, the first reference value Th5 may be determined based on the diagnostic value output from the diagnostic value output unit 421 and stored in the storage unit 422 while the speed reducer 1 is driven.

The speed reducer 1 can be driven after the first signal is output. Therefore, the detection device 42 can detect a change in the state of the speed reducer 1 while continuing the driving of the speed reducer 1. In the present embodiment, the control unit 425 does not stop the speed reducer 1 even when the first signal is output. Specifically, the control unit 425 does not output a signal for stopping the motor 103.

As shown in fig. 17, the second reference value Th6 is stored in the storage unit 422. After the signal output unit 424 outputs the first signal, the comparison unit 423 reads the second reference value Th6 from the storage unit 422. Then, the comparison unit 423 compares the diagnostic value output from the diagnostic value output unit 421 with the second reference value Th6 (step S34).

The second reference value Th6 is a value far from the first reference value Th5 with respect to the diagnostic value before the output of the first signal. In step S34, it is determined whether the diagnostic value has reached the second reference value Th6.

When the diagnostic value does not reach the second reference value Th6 (step S34: no), the detection device 42 executes the processing of step S34 again. On the other hand, when the diagnostic value reaches the second reference value Th6 (step S34: yes), the signal output unit 424 outputs the second signal (step S35). Thereby, the detection device 42 can detect that the speed reducer 1 is closer to the eccentric state. For example, the detection device 42 can detect that the driving of the speed reducer 1 is difficult to continue.

When the second signal is output from the signal output unit 424, the control unit 425 stops the speed reducer 1 (step S36). Specifically, the control unit 425 outputs a signal for stopping the motor 103. In this way, the speed reducer 1 can be stopped when the speed reducer 1 is closer to the eccentric state than when the first signal is output.

The control unit 425 may stop the speed reducer 1 at the time when the first signal is output from the signal output unit 424.

< 6. Modification >

The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments.

In the above embodiment, the strain gauges Ra to Rl are disposed on the surface of the insulating layer 411 that can be flexibly deformed. However, the strain gauges Ra to Rl may be disposed on the surface 234 of the base 231. For example, an insulating film may be formed on the surface 234 of the base 231, and a conductor layer may be formed on the surface of the insulating film by sputtering or the like. Then, unnecessary portions of the conductor layer are removed by chemical means such as etching or physical means such as laser, thereby forming strain gauges Ra to Rl. The insulating film is made of, for example, an inorganic insulating material.

The flexible externally toothed gear 20 of the above-described embodiment is a so-called "hat-shaped" flexible externally toothed gear in which the base 231 extends radially outward from the main body 21. The cap-shaped flexible externally toothed gear 20 is excellent in that it can effectively use the space on the inner side in the radial direction of the main body 21. However, the flexible externally toothed gear 20 may be a so-called "cup-shaped" flexible externally toothed gear in which the base 231 extends radially inward from the main body 21.

In the above embodiment, the speed reducer 1 mounted on the robot 100 is described. However, the speed reducer 1 having the same structure may be mounted on other devices such as an auxiliary suit and an unmanned conveyance carriage.

The details of the detection device, the speed reducer, and the robot may be appropriately changed within the scope of the present invention. The elements appearing in the above-described embodiments and modifications may be appropriately combined within a range where no contradiction occurs.

The present invention can be used for, for example, a detection device, a speed reducer, a robot, and a diagnostic method.

Claims (18)

1. A detection device for diagnosing the state of a speed reducer based on the output signal of a strain gauge arranged on a ring gear provided in the speed reducer,

the detection device comprises:

a diagnostic value output unit that outputs a diagnostic value based on the output signal;

a storage unit that stores a first reference value;

a comparison unit that compares the diagnostic value with the first reference value; and

a signal output unit that outputs a first signal based on a comparison result of the comparison unit,

the detection device is characterized in that,

the signal output unit outputs the first signal when the diagnostic value reaches the first reference value.

2. The detecting device according to claim 1, wherein,

after the first signal is output, the speed reducer can also be driven.

3. The detecting device according to claim 1 or 2, wherein,

the comparing unit and the signal output unit are a single component.

4. The detecting device according to any one of claims 1 to 3, wherein,

the first reference value is a value based on the diagnostic value obtained in advance by driving the speed reducer in advance.

5. The detecting device according to claim 4, wherein,

the first reference value is a value that deviates from an average value of the diagnostic values, which are obtained in advance by driving the speed reducer, by three times a standard deviation.

6. The detecting device according to any one of claims 1 to 5, wherein,

the signal output unit outputs a second signal when the diagnostic value reaches a second reference value which is far from the diagnostic value before the output of the first signal after the output of the first signal.

7. The detecting device according to claim 6, wherein,

The control unit stops the speed reducer when the second signal is output.

8. The detecting device according to any one of claims 1 to 7, wherein,

the speed reducer is provided with a bridge circuit formed by a plurality of strain gauges,

the strain gauge comprises a pattern provided with radially extending resistance wires or a pattern provided with circumferentially extending resistance wires,

the output signal is the output signal of the bridge circuit,

the diagnostic value is the difference between the maximum and minimum values of the output signal,

the signal output unit outputs the first signal when the diagnostic value is equal to or less than the first reference value.

9. The detecting device according to claim 8, wherein,

the first reference value is smaller than a difference between a maximum value and a minimum value of the output signal preceding an output of the first signal.

10. The detecting device according to claim 8 or 9, wherein,

the first reference value is a value of 97% or less of an average value of differences between a maximum value and a minimum value of the output signal before the output of the first signal.

11. The detecting device according to any one of claims 1 to 7, wherein,

The speed reducer is provided with a bridge circuit formed by a plurality of strain gauges,

the strain gauge includes a pattern of circumferentially repeated arrangements of resistance wires inclined relative to the radial and circumferential directions,

the output signal is the output signal of the bridge circuit,

the diagnostic value is the maximum value of the output signal,

the signal output unit outputs the first signal when the diagnostic value is equal to or greater than the first reference value.

12. The apparatus of claim 11, wherein the sensor is configured to detect,

the first reference value is larger than a maximum value of the output signal preceding an output of the first signal.

13. The device according to claim 11 or 12, wherein,

the first reference value is a value of 103% or more of an average value of maximum values of the output signals before the output of the first signal.

14. A detection device for diagnosing the state of a speed reducer based on the output signal of a strain gauge arranged on a ring gear provided in the speed reducer,

the detection device is characterized in that,

the speed reducer is provided with two groups of bridge circuits formed by a plurality of strain gauges,

the strain gauge comprises a pattern provided with radially extending resistance wires or a pattern provided with circumferentially extending resistance wires,

The output signal is the output signal of the bridge circuit,

and outputting a first signal when the phase difference of the output signals of the two groups of bridge circuits reaches a first reference value.

15. A speed reducer is characterized by comprising:

the detection device of any one of claims 1 to 14;

the gear; and

the strain gauge.

16. The speed reducer according to claim 15, wherein,

the gear is a flexible externally toothed gear,

the device further comprises:

an internal gear meshed with the flexible external gear; and

and a wave generator for generating flexural deformation of the flexible externally toothed gear.

17. A robot is characterized in that,

a speed reducer according to claim 15 or 16.

18. A diagnostic method for diagnosing the state of a speed reducer based on the output signal of a strain gauge arranged on a ring gear provided in the speed reducer,

the diagnostic method is characterized by comprising:

a step of outputting a diagnostic value based on the output signal;

a step of comparing the diagnosis value with a first reference value; and

a step of outputting a first signal based on a result of the comparison,

outputting the first signal when the diagnostic value reaches the first reference value.