Life prediction device, speed reducer, robot, and life prediction method

Abstract

The invention provides a life prediction device, a decelerator, a robot, and a life prediction method. The life prediction device calculates a threshold value relating to the life of at least one of the flexible bearing and the flexible external gear on the basis of the input rotational speed and / or the output rotational speed of the speed reducer and the measurement value of the torque sensor. Then, when the driving time of the speed reducer reaches the threshold value, the life prediction device outputs an alarm signal.

Description

Technical Field

[0001] The present invention relates to a life prediction device, a speed reducer, a robot, and a life prediction method. Background Art

[0002] Conventionally, a speed reducer that decelerates the rotational motion output from a motor has been known. Regarding an existing speed reducer, for example, it is described in Patent Document 1.

[0003] Patent Document 1: International Publication No. 2014 / 098008

[0004] In the above document, the rotational drive device has a tooth skipping detection unit and a life prediction unit. The tooth skipping detection unit detects the occurrence of tooth skipping when the difference value between the detection value of the first encoder and the detection value of the second encoder is equal to or greater than a threshold value. The life prediction unit predicts the life of the speed reducer based on the number of detected tooth skippings.

[0005] However, in the method of the above document, the life of the speed reducer cannot be predicted unless tooth skipping occurs. Summary of the Invention

[0006] An object of the present invention is to provide a technique capable of managing the life of a speed reducer regardless of the presence or absence of tooth skipping.

[0007] A first invention is a life prediction device for a speed reducer, the speed reducer having a flexible external gear, an internal gear, a flexible bearing, and a torque sensor disposed on at least one of the flexible external gear and the internal gear, wherein the life prediction device calculates a threshold value related to the life of at least one of the flexible bearing and the flexible external gear based on at least one of the input rotation speed and the output rotation speed of the speed reducer and the measurement value of the torque sensor, and outputs an alarm signal when the driving time of the speed reducer reaches the threshold value.

[0008] A second invention is a life prediction device for a speed reducer, the speed reducer having a flexible external gear, an internal gear, a flexible bearing, and a torque sensor disposed on at least one of the flexible external gear and the internal gear, wherein the life prediction device outputs the remaining time of the life of at least one of the flexible bearing and the flexible external gear based on at least one of the input rotation speed and the output rotation speed of the speed reducer and the measurement value of the torque sensor.

[0009] A third invention is a speed reducer having the life prediction device of the first invention or the second invention.

[0010] A fourth invention is a robot having the life prediction device of the first invention or the second invention or the speed reducer of the third invention.

[0011] The fifth invention is a method for predicting the service life of a speed reducer, which has a flexible external gear, an internal gear, a flexible bearing, and a torque sensor disposed on at least one of the flexible external gear and the internal gear. Among them, a threshold value related to the service life of at least one of the flexible bearing and the flexible external gear is calculated based on at least one of the input speed and the output speed of the speed reducer and the measured value of the torque sensor. When the driving time of the speed reducer reaches the threshold value, an alarm signal is output.

[0012] The sixth invention is a method for predicting the service life of a speed reducer, which has a flexible external gear, an internal gear, a flexible bearing, and a torque sensor disposed on at least one of the flexible external gear and the internal gear. Among them, the remaining time of the service life of at least one of the flexible bearing and the flexible external gear is output based on at least one of the input speed and the output speed of the speed reducer and the measured value of the torque sensor.

[0013] According to the first invention, the second invention, the third invention, the fourth invention, the fifth invention, and the sixth invention, it is possible to manage the service life of at least one of the flexible bearing and the flexible external gear based on the measured value of the torque sensor mounted on the speed reducer. Description of the Drawings

[0014] Figure 1 is a schematic diagram of a robot.

[0015] Figure 2 is a longitudinal sectional view of the speed reducer.

[0016] Figure 3 is a transverse sectional view of the speed reducer.

[0017] Figure 4 is a partial longitudinal sectional view of the flexible external gear near the sensor substrate.

[0018] Figure 5 is a top view of the sensor substrate.

[0019] Figure 6 is a circuit diagram of the first bridge circuit of the first torque sensor.

[0020] Figure 7 is a circuit diagram of the second bridge circuit of the second torque sensor.

[0021] Figure 8 is a circuit diagram of the third bridge circuit of the angle sensor.

[0022] Figure 9 is a circuit diagram of the fourth bridge circuit of the angle sensor.

[0023] Figure 10 It is a graph showing the time variation of the output value of the third voltmeter of the third bridge circuit and the output value of the fourth voltmeter of the fourth bridge circuit.

[0024] Figure 11 It is a block diagram showing the structure related to the life prediction of the speed reducer.

[0025] Figure 12 It is a flowchart showing the operation process of the first embodiment of the life prediction device.

[0026] Figure 13 It is a graph showing the lives of the flexible bearing and the flexible external gear.

[0027] Figure 14 It is a flowchart showing the operation process of the second embodiment of the life prediction device.

[0028] Reference Numeral Explanation

[0029] 1: Speed reducer; 9: Central axis; 10: Input shaft; 20: Internal gear; 30: Flexible external gear; 40: Wave generator; 41: Cam; 42: Flexible bearing; 50: Sensor; 51: Sensor substrate; 52: Signal processing circuit; 60: Torque sensor; 70: Angle sensor; 80: Life prediction device; 81: Encoder; 100: Robot; Al: Alarm signal; Lr: Remaining time. Detailed Embodiment

[0030] Hereinafter, exemplary embodiments of the present application will be described with reference to the drawings.

[0031] <1. Structure of Robot>

[0032] Figure 1 It is a schematic diagram of a robot 100 having a speed reducer 1 of one embodiment. The robot 100 is, for example, a device that performs operations such as transporting, processing, and assembling components on an industrial product production line. As Figure 1 shown, the robot 100 includes a base frame 101, an arm 102, a motor 103, and a speed reducer 1.

[0033] The arm 102 is supported by the base frame 101 so as to be rotatable. The motor 103 and the speed reducer 1 are assembled at the joint portion between the base frame 101 and the arm 102. When a drive current is supplied to the motor 103, a rotational motion is output from the motor 103. The speed reducer 1 decelerates the rotational motion output from the motor 103 and transmits it to the arm 102. Thus, the arm 102 rotates relative to the base frame 101 at a decelerated speed.

[0034] <2. Structure of Speed Reducer>

[0035] Next, the detailed structure of the speed reducer 1 will be described.

[0036] In addition, hereinafter, the direction parallel to the central axis 9 of the speed reducer 1 will be referred to as the "axial direction", the direction perpendicular to the central axis 9 of the speed reducer 1 will be referred to as the "radial direction", and the direction along the arc centered on the central axis 9 of the speed reducer 1 will be referred to as the "circumferential direction". Among them, the above-mentioned "parallel direction" also includes a substantially parallel direction. In addition, the above-mentioned "perpendicular direction" also includes a substantially perpendicular direction.

[0037] Figure 2 It is a longitudinal sectional view of the speed reducer 1 of an embodiment. Figure 3 It is from Figure 2 The transverse sectional view of the speed reducer 1 observed from the A-A position. To avoid complicating the drawing, in Figure 3 The hatching indicating the section is omitted.

[0038] The speed reducer 1 is a device that reduces the rotational motion of the first speed output from the motor 103 to a second speed slower than the first speed. As Figure 2 and Figure 3 shown, the speed reducer 1 includes an input shaft 10, an internal gear 20, a flexible external gear 30, and a wave generator 40.

[0039] The input shaft 10 is a component that rotates at the first speed before deceleration. The input shaft 10 is connected to the output shaft of the motor 103. The input shaft 10 extends axially along the central axis 9. The input shaft 10 of this embodiment is in a cylindrical shape centered on the central axis 9. The input shaft 10 penetrates the speed reducer 1 axially. In addition, the input shaft 10 may also be the same component as the output shaft of the motor 103.

[0040] The internal gear 20 is a gear that rotates at the second speed after deceleration. The internal gear 20 is fixed to the arm 102. The internal gear 20 is in an annular shape centered on the central axis 9. The internal gear 20 has a plurality of internal teeth 21. The plurality of internal teeth 21 protrude radially inward from the inner circumferential surface of the internal gear 20. The plurality of internal teeth 21 are arranged at a constant pitch along the circumferential direction on the inner circumferential surface of the internal gear 20. The rigidity of the internal gear 20 is sufficiently higher than the rigidity of the body portion 31 of the flexible external gear 30 described later.

[0041] The flexible external gear 30 is a gear that undergoes flexural deformation by the rotation of the cam 41 described later. The flexible external gear 30 is fixed to the base frame 101. As Figure 2 and Figure 3 shown, the flexible external gear 30 includes a body portion 31, a plurality of external teeth 32, a diaphragm portion 33, and a wall thickness portion 34.

[0042] The body portion 31 is a cylindrical portion centered on the central axis 9. One axial end of the body portion 31 is connected to the diaphragm portion 33. The other axial end of the body portion 31 is disposed radially outside the vibration generator 40 and radially inside the internal gear 20. The body portion 31 is flexible and thus can be flexed and deformed in the radial direction.

[0043] A plurality of external teeth 32 are disposed on the radially outer surface of the other axial end of the body portion 31. The plurality of external teeth 32 project radially outward from the radially outer surface of the body portion 31. The plurality of external teeth 32 are arranged at a constant pitch in the circumferential direction. A part of the plurality of external teeth 32 meshes with a part of the plurality of internal teeth 21. The number of the internal teeth 21 of the internal gear 20 is slightly different from the number of the external teeth 32 of the flexible external gear 30.

[0044] The diaphragm portion 33 extends radially outward from one axial end of the body portion 31. That is, the diaphragm portion 33 extends in a direction intersecting the central axis 9. The diaphragm portion 33 is in a ring shape surrounding the central axis 9. The diaphragm portion 33 is in a thin-wall shape and thus can be slightly flexed and deformed.

[0045] The wall thickness portion 34 is a ring-shaped portion located radially outside the diaphragm portion 33. The axial thickness of the wall thickness portion 34 is thicker than the axial thickness of the diaphragm portion 33. The wall thickness portion 34 is fixed to the base frame 101 directly or via other components.

[0046] The vibration generator 40 is a mechanism that causes the flexible external gear 30 to undergo periodic flexural deformation. The vibration generator 40 is disposed radially inside the external teeth 32. The vibration generator 40 has a cam 41 and a flexible bearing 42.

[0047] The cam 41 is a component that gives displacement to the flexible external gear 30 at a period of 180°. In the present embodiment, the input shaft 10 and the cam 41 are formed of one component. However, the cam 41 may also be a component different from the input shaft 10. In this case, it is only necessary to fix the cam 41 to the input shaft 10. The cam 41 has a non-circular outer surface. The cam 41 of the present embodiment has an elliptical outer surface centered on the central axis 9.

[0048] The flexible bearing 42 is a bearing that can be flexed and deformed. The flexible bearing 42 is disposed between the radially outer surface of the cam 41 and the radially inner surface of the body portion 31 of the flexible external gear 30. The inner ring of the flexible bearing 42 contacts the radially outer surface of the cam 41. The outer ring of the flexible bearing 42 contacts the radially inner surface of the body portion 31. As a result, the body portion 31 is deformed into an elliptical shape along the radially outer surface of the cam 41. As a result, at two positions corresponding to both ends of the major axis of the ellipse, the external teeth 32 of the flexible external gear 30 mesh with the internal teeth 21 of the internal gear 20. At other positions in the circumferential direction, the external teeth 32 do not mesh with the internal teeth 21.

[0049] When driving the drive motor 103, the cam 41 rotates together with the input shaft 10 about the central axis 9 at a first rotational speed. As a result, the major axis of the ellipse of the flexible external gear 30 also rotates at the first rotational speed. Then, the meshing position of the external teeth 32 and the internal teeth 21 also changes in the circumferential direction at the first rotational speed. In addition, as described above, the number of internal teeth 21 of the internal gear 20 is slightly different from the number of external teeth 32 of the flexible external gear 30. Due to this difference in the number of teeth, every time the cam 41 rotates one week, the meshing position of the external teeth 32 and the internal teeth 21 slightly changes in the circumferential direction. As a result, the internal gear 20 rotates about the central axis 9 relative to the flexible external gear 30 at a second rotational speed slower than the first rotational speed.

[0050] <3. Regarding the sensor>

[0051] <3-1. Structure of the sensor>

[0052] The speed reducer 1 is provided with a sensor 50. As Figure 2 shown, the sensor 50 has a sensor substrate 51. The sensor substrate 51 is fixed on the surface of the diaphragm portion 33.

[0053] Figure 4 is a partial longitudinal sectional view of the flexible external gear 30 near the sensor substrate 51. Figure 5 is a top view of the sensor substrate 51. As Figure 4 shown, the sensor substrate 51 has an insulating layer 511 and a conductor layer 512.

[0054] The insulating layer 511 can be deformed softly. The insulating layer 511 extends in a direction intersecting the central axis 9. In addition, the insulating layer 511 is in a circular ring shape centered on the central axis 9. The insulating layer 511 is made of a resin or an inorganic insulating material as an insulator. The insulating layer 511 is disposed on the surface of the diaphragm portion 33. The conductor layer 512 is formed on the surface of the insulating layer 511. The material of the conductor layer 512 uses a metal as a conductor. For example, the material of the conductor layer 512 uses a copper alloy, a chromium alloy, or copper.

[0055] The conductor layer 512 includes a torque sensor 60 and an angle sensor 70. The torque sensor 60 and the angle sensor 70 are each composed of a strain gauge. In addition, as Figure 2 shown, the sensor 50 has a signal processing circuit 52. The signal processing circuit 52 is electrically connected to the torque sensor 60 and the angle sensor 70.

[0056] <3-2. Torque sensor>

[0057] The torque sensor 60 is a sensor for detecting the torque applied to the flexible external gear 30. That is, the torque sensor 60 is a sensor whose output value changes according to the torque applied to the flexible external gear 30. As Figure 5 shown, the torque sensor 60 of the present embodiment has a first torque sensor 61 and a second torque sensor 62. The second torque sensor 62 is arranged at a position radially outside the first torque sensor 61.

[0058] The first torque sensor 61 has four strain gauges Ra, Rb, Rc, and Rd. Two of the four strain gauges Ra, Rb, Rc, and Rd, namely Ra and Rb, are arranged at intervals in the circumferential direction. The two strain gauges Ra and Rb are each arranged in a semi-circular arc shape within a range of approximately 180° centered on the central axis 9. The radial distance from the central axis 9 to the strain gauge Ra is substantially the same as the radial distance from the central axis 9 to the strain gauge Rb.

[0059] The other two of the four strain gauges Ra, Rb, Rc, and Rd, namely Rc and Rd, are arranged at a position radially outside the above two strain gauges Ra and Rb. The two strain gauges Rc and Rd are arranged at intervals in the circumferential direction. The two strain gauges Rc and Rd are each arranged in a semi-circular arc shape within a range of approximately 180° centered on the central axis 9. The radial distance from the central axis 9 to the strain gauge Rc is substantially the same as the radial distance from the central axis 9 to the strain gauge Rd.

[0060] In addition, the two strain gauges Ra and Rc and the two strain gauges Rb and Rd are arranged concentrically and symmetrically with respect to the line.

[0061] As Figure 5 shown, the strain gauges Ra, Rb, Rc, and Rd are each a pattern that extends circumferentially while being zigzag bent on one side. Each of the strain gauges Ra, Rb, Rc, and Rd has a plurality of resistance wires r1 that are arranged parallel to each other in the circumferential direction. Each resistance wire r1 extends obliquely with respect to the radial direction. That is, each resistance wire r1 extends in a direction having both radial and circumferential components.

[0062] The resistance wires r1 of the strain gauges Ra and Rd are inclined toward the circumferential direction on one side with respect to the radial direction. The resistance wires r1 of the strain gauges Rb and Rc are inclined toward the other side of the circumferential direction with respect to the radial direction. The inclination angle of the resistance wire r1 with respect to the radial direction is, for example, 45°. The ends of the resistance wires r1 adjacent to each other in the circumferential direction are alternately connected to each other inside or outside the radial direction. Thus, the plurality of resistance wires r1 are connected in series as a whole.

[0063] The second torque sensor 62 has four strain gauges Re, Rf, Rg, and Rh. Two of the four strain gauges Re, Rf, Rg, and Rh, namely Re and Rf, are arranged at intervals in the circumferential direction. The two strain gauges Re and Rf are each arranged in a semi-circular arc shape within a range of approximately 180° centered on the central axis 9. The radial distance from the central axis 9 to the strain gauge Re is substantially the same as the radial distance from the central axis 9 to the strain gauge Rf.

[0064] The other two of the four strain gauges Re, Rf, Rg, and Rh, namely Rg and Rh, are arranged at positions radially outside the above two strain gauges Re and Rf. The two strain gauges Rg and Rh are arranged at intervals in the circumferential direction. The two strain gauges Rg and Rh are each arranged in a semi-circular arc shape within a range of approximately 180° centered on the central axis 9. The radial distance from the central axis 9 to the strain gauge Rg is substantially the same as the radial distance from the central axis 9 to the strain gauge Rh.

[0065] In addition, the two strain gauges Re and Rg and the two strain gauges Rf and Rh are arranged concentrically and linearly symmetrically.

[0066] As Figure 5 shown, the strain gauges Re, Rf, Rg, and Rh are each a pattern that extends circumferentially while being zigzag bent on one side. Each of the strain gauges Re, Rf, Rg, and Rh has a plurality of resistance wires r2 that are arranged circumferentially and are substantially parallel to each other. Each resistance wire r2 extends obliquely with respect to the radial direction. That is, each resistance wire r2 extends in a direction having both radial and circumferential components.

[0067] The resistance wires r2 of the strain gauges Re and Rh are inclined toward the circumferential direction on one side with respect to the radial direction. The resistance wires r2 of the strain gauges Rf and Rg are inclined toward the circumferential direction on the other side with respect to the radial direction. The inclination angle of the resistance wire r2 with respect to the radial direction is, for example, 45°. The ends of the resistance wires r2 adjacent to each other in the circumferential direction are alternately connected to each other on the inner side or the outer side in the radial direction. Thereby, the plurality of resistance wires r2 are connected in series as a whole.

[0068] Figure 6 is a circuit diagram of a first bridge circuit C1 including four strain gauges Ra, Rb, Rc, and Rd of the first torque sensor 61. As Figure 6 shown, the four strain gauges Ra, Rb, Rc, and Rd are connected to each other to form a first bridge circuit C1.

[0069] The strain gauges Ra and Rb are connected in series in sequence. The strain gauges Rc and Rd are connected in series in sequence. Moreover, between the + pole and the - pole of the power supply voltage, the columns of the two strain gauges Ra and Rb are connected in parallel with the columns of the two strain gauges Rc and Rd. Additionally, a first voltmeter V1 is connected between the midpoint M11 of the two strain gauges Ra and Rb and the midpoint M12 of the two strain gauges Rc and Rd.

[0070] The resistance value of each resistance wire r1 varies according to the torque applied to the area where the resistance wire r1 is disposed. For example, when a torque toward one side in the circumferential direction with the central axis 9 as the center is applied to the diaphragm portion 33, the resistance values of the resistance wires r1 of the two strain gauges Ra and Rd decrease, and the resistance values of the resistance wires r1 of the other two strain gauges Rb and Rc increase. On the other hand, when a torque toward the other side in the circumferential direction with the central axis 9 as the center is applied to the diaphragm portion 33, the resistance values of the resistance wires r1 of the two strain gauges Ra and Rd increase, and the resistance values of the resistance wires r1 of the other two strain gauges Rb and Rc decrease. In this way, the two strain gauges Ra and Rd and the other two strain gauges Rb and Rc show resistance value changes opposite to each other with respect to the torque.

[0071] Moreover, when the resistance values of the four strain gauges Ra, Rb, Rc, and Rd change, the potential difference between the midpoint M11 of the two strain gauges Ra and Rb and the midpoint M12 of the two strain gauges Rc and Rd changes, and thus the output value of the first voltmeter V1 also changes. The signal processing circuit 52 detects the direction and magnitude of the torque applied to the diaphragm portion 33 based on the output value of the first voltmeter V1.

[0072] Figure 7 It is a circuit diagram of a second bridge circuit C2 including four strain gauges Re, Rf, Rg, and Rh of a second torque sensor 62. As Figure 7 shown, the four strain gauges Re, Rf, Rg, and Rh are connected to form a second bridge circuit C2.

[0073] The strain gauge Re and the strain gauge Rf are connected in series in sequence. The strain gauge Rg and the strain gauge Rh are connected in series in sequence. Moreover, between the + pole and the - pole of the power supply voltage, the columns of the two strain gauges Re and Rf are connected in parallel with the columns of the two strain gauges Rg and Rh. Additionally, a second voltmeter V2 is connected between the midpoint M21 of the two strain gauges Re and Rf and the midpoint M22 of the two strain gauges Rg and Rh.

[0074] The resistance value of each resistance wire r2 varies according to the torque applied to the area where the resistance wire r2 is disposed. For example, when torque is applied to the diaphragm portion 33 toward one side in the circumferential direction with the central axis 9 as the center, the resistance values of the resistance wires r2 of the two strain gauges Re and Rh decrease, and the resistance values of the resistance wires r2 of the other two strain gauges Rf and Rg increase. On the other hand, when torque is applied to the diaphragm portion 33 toward the other side in the circumferential direction with the central axis 9 as the center, the resistance values of the resistance wires r2 of the two strain gauges Re and Rh increase, and the resistance values of the resistance wires r2 of the other two strain gauges Rf and Rg decrease. In this way, the two strain gauges Re and Rh and the other two strain gauges Rf and Rg exhibit resistance value changes opposite to each other with respect to the torque.

[0075] Moreover, when the resistance values of the four strain gauges Re, Rf, Rg, and Rh change, the potential difference between the midpoint M21 of the two strain gauges Re and Rf and the midpoint M22 of the two strain gauges Rg and Rh changes, and thus the output value of the second voltmeter V2 also changes. The signal processing circuit 52 detects the direction and magnitude of the torque applied to the diaphragm portion 33 based on the output value of the second voltmeter V2.

[0076] In addition, the speed reducer 1 of the present embodiment has two torque sensors 61 and 62. The signal processing circuit 52 uses any one of the output signals of the two torque sensors 61 and 62 as the output signal of the torque sensor 60. By having two torque sensors 61 and 62, even when an abnormality occurs in either torque sensor, the torque can be detected by the other torque sensor. In addition, when an abnormality occurs in either torque sensor, it is possible to detect that an abnormality has occurred.

[0077] <3-3. Angle Sensor>

[0078] The angle sensor 70 is a sensor for detecting the rotation angle of the rotational motion input to the speed reducer 1. That is, the angle sensor 70 is a sensor whose output value varies according to the rotation angle of the cam 41. As Figure 5 shown, the angle sensor 70 has eight strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp. The eight strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp are arranged at intervals in the circumferential direction.

[0079] Eight strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, Rp are each formed by one wire. Each of the strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, Rp has a resistance wire extending in an arc shape along the circumferential direction. However, in each of the strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, Rp, the resistance wires extending along the circumferential direction may also be repeatedly arranged in the radial direction. In addition, the resistance wires of each of the strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, Rp may also extend in the radial direction. Further, in each of the strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, Rp, the resistance wires extending in the radial direction may also be repeatedly arranged in the circumferential direction.

[0080] Four non-adjacent strain gauges Ri, Rk, Rm, Ro among the eight strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, Rp are connected to each other to form a third bridge circuit C3. Figure 8 is a circuit diagram of the third bridge circuit C3. As Figure 8 shown, the strain gauge Ri and the strain gauge Rk are connected in series in sequence. The strain gauge Ro and the strain gauge Rm are connected in series in sequence. Moreover, between the + pole and the - pole of the power supply voltage, the columns of the two strain gauges Ri, Rk and the columns of the two strain gauges Ro, Rm are connected in parallel. In addition, a third voltmeter V3 is connected between the midpoint M31 of the two strain gauges Ri, Rk and the midpoint M32 of the two strain gauges Ro, Rm.

[0081] The remaining four strain gauges Rj, Rl, Rn, Rp among the eight strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, Rp are connected to each other to form a fourth bridge circuit C4. Figure 9 is a circuit diagram of the fourth bridge circuit C4. As Figure 9 shown, the strain gauge Rp and the strain gauge Rn are connected in series in sequence. The strain gauge Rj and the strain gauge Rl are connected in series in sequence. Moreover, between the + pole and the - pole of the power supply voltage, the columns of the two strain gauges Rp, Rn and the columns of the two strain gauges Rj, Rl are connected in parallel. In addition, a fourth voltmeter V4 is connected between the midpoint M41 of the two strain gauges Rp, Rn and the midpoint M42 of the two strain gauges Rj, Rl.

[0082] When the reducer 1 is driven, a circumferentially extending portion (hereinafter referred to as "elongated portion") and a circumferentially contracting portion (hereinafter referred to as "contracting portion") are generated in the diaphragm portion 33 of the flexible external gear 30. Specifically, two elongated portions and two contracting portions are alternately generated in the circumferential direction. That is, the elongated portions and the contracting portions are alternately generated at intervals of 90° in the circumferential direction with the central axis 9 as the center. Moreover, the portions where these elongated portions and contracting portions are generated rotate at the above-mentioned first rotational speed.

[0083] The resistance values of the eight strain gauges Ri, Rj, Rk, Rl, Rm, Rn, Ro, and Rp change according to the circumferential expansion and contraction of the diaphragm portion 33. For example, when the above-mentioned elongation portion overlaps with a certain strain gauge, the resistance of that strain gauge increases. Additionally, when the above-mentioned contraction portion overlaps with a certain strain gauge, the resistance value of that strain gauge decreases.

[0084] In Figure 5 's example, when the contraction portion overlaps with the strain gauges Ri and Rm, the elongation portion overlaps with the strain gauges Rk and Ro. Additionally, when the elongation portion overlaps with the strain gauges Ri and Rm, the contraction portion overlaps with the strain gauges Rk and Ro. Therefore, in the third bridge circuit C3, the strain gauges Ri and Rm show reverse resistance value changes compared to the strain gauges Rk and Ro.

[0085] Additionally, in Figure 5 's example, when the contraction portion overlaps with the strain gauges Rp and Rl, the elongation portion overlaps with the strain gauges Rn and Rj. Additionally, when the elongation portion overlaps with the strain gauges Rp and Rl, the contraction portion overlaps with the strain gauges Rn and Rj. Therefore, in the fourth bridge circuit C4, the strain gauges Rp and Rl show reverse resistance value changes compared to the strain gauges Rn and Rj.

[0086] Figure 10 is a graph showing the time variation of the output value v3 of the third voltmeter V3 of the third bridge circuit C3 and the output value v4 of the fourth voltmeter V4 of the fourth bridge circuit C4. Figure 10 The horizontal axis of the graph of Figure 10 represents time. Figure 10 The vertical axis of the graph of

[0087] represents the voltage value. When driving the reduction gear 1, as

[0088] shown, sinusoidal output values v3 and v4 that change periodically are obtained from the third voltmeter V3 and the fourth voltmeter V4 respectively. The period T of the output values v3 and v4 is equivalent to 1 / 2 times the period of the above-mentioned first rotational speed.

[0087] Additionally, the output value v3 of the third voltmeter V3 and the output value v4 of the fourth voltmeter V4 have a phase difference of 1 / 4 cycle. That is, the output values of the two bridge circuits C3 and C4 have a phase difference of 1 / 4 cycle. Then, based on whether the phase of the output value v4 of the fourth voltmeter V4 is ahead of the phase of the output value v3 of the third voltmeter V3 by 1 / 8 cycle amount of the first rotational speed (1 / 4 cycle amount of the output values v3 and v4) or lags behind by 1 / 8 cycle amount of the first rotational speed (1 / 4 cycle amount of the output values v3 and v4), it is possible to determine the direction of the input rotational motion.

[0088] The signal processing circuit 52 detects the rotation angle of the rotational motion input to the speed reducer 1 based on the output values v3 of these third voltmeters V3 and the output values v4 of the fourth voltmeter V4. Specifically, the signal processing circuit 52 stores a function table that correlates combinations of the output value v3 of the third voltmeter V3 and the output value v4 of the fourth voltmeter V4 with the rotation angle. The signal processing circuit 52 outputs the rotation angle by inputting the output values v3 and v4 into this function table.

[0089] When driving the speed reducer 1, the flexible external gear 30 undergoes periodic flexural deformation. Therefore, the output signals of the first torque sensor 61 and the second torque sensor 62 include components that reflect the torque originally intended to be measured and error components (fluctuation errors) caused by the periodic flexural deformation of the flexible external gear 30. This fluctuation error varies sinusoidally according to the rotation angle of the rotational motion input to the speed reducer 1.

[0090] Therefore, the signal processing circuit 52 calculates the above-mentioned fluctuation error based on the rotation angle detected by the angle sensor 70. Then, the calculated fluctuation error is used to correct the output signals of the first torque sensor 61 and the second torque sensor 62. Specifically, the signal processing circuit 52 increases or decreases the output signals of the first torque sensor 61 and the second torque sensor 62 in a direction to eliminate the fluctuation error. As a result, the signal processing circuit 52 can output the torque applied to the flexible external gear 30 with higher accuracy.

[0091] In addition, the signal processing circuit 52 may not calculate the above-mentioned rotation angle, but multiply the respective output values v3 and v4 of the third voltmeter V3 and the fourth voltmeter V4 by a prescribed coefficient and synthesize them into the output signals of the first torque sensor 61 and the second torque sensor 62. In this way, the processing burden involved in the calculation of the rotation angle can be reduced. Therefore, the operation speed of the signal processing circuit 52 can be increased.

[0092] In the above-described embodiment, the torque sensor 60 and the angle sensor 70 are arranged on the flexible external gear 30. However, the torque sensor 60 and the angle sensor 70 may also be arranged on the internal gear 20.

[0093] <4. Regarding life prediction>

[0094] <4-1. First embodiment>

[0095] Next, the life prediction of the speed reducer 1 will be described. Figure 11It is a block diagram showing the structure related to the life prediction of the speed reducer 1. As described above, the life prediction device 80 is a device that predicts the life of the speed reducer 1 having a flexible external gear 30, an internal gear 20, a flexible bearing 42, and a torque sensor 60 disposed in at least any one of the flexible external gear 30 and the internal gear 20.

[0096] Life refers to the service time. That is, the life of the speed reducer 1 is the time during which the speed reducer 1 can operate without failure. Among the components constituting the speed reducer 1, the component with the shortest service time is the flexible bearing 42 or the flexible external gear 30. Therefore, the life prediction device 80 predicts the life of at least any one of the flexible bearing 42 and the flexible external gear 30.

[0097] The life prediction device 80 is composed of a circuit having a processor 801 such as a CPU and a memory 802 such as a RAM. The life prediction device 80 of the present embodiment is disposed in the speed reducer 1. For example, the life prediction device 80 is mounted on the signal processing circuit 52. Thereby, the function of predicting the life can be mounted on the speed reducer 1 itself. However, the life prediction device 80 may also be disposed in the controller that controls the robot 100. In addition, the life prediction device 80 may also be disposed in a computer connected to at least any one of the speed reducer 1 and the robot 100 via a network. The robot 100 has the life prediction device 80 or has a speed reducer 1 in which the life prediction device 80 is disposed, whereby the life of at least any one of the flexible bearing 42 and the flexible external gear 30 can be managed based on the measurement value of the torque sensor 60 mounted on the speed reducer 1.

[0098] As Figure 11 shown, the life prediction device 80 is electrically connected to the torque sensor 60. More specifically, the life prediction device 80 is electrically connected to the torque sensor 60 via the signal processing circuit 52.

[0099] In addition, as Figure 11 shown, the life prediction device 80 is electrically connected to the encoder 81. The encoder 81 is, for example, the encoder of the motor 103. In this case, the encoder 81 measures the input rotational speed of the speed reducer 1 and outputs it. However, the encoder 81 may also be provided on the output side of the speed reducer 1. In this case, the encoder 81 measures the output rotational speed of the speed reducer 1 and outputs it.

[0100] In addition, the encoder 81 may use the above-described angle sensor 70. In this case, the encoder 81 is, for example, mounted on the signal processing circuit 52. Then, the encoder 81 calculates the input rotational speed of the speed reducer 1 based on the measurement value of the angle sensor 70.

[0101] Next, the operation of the life prediction device 80 will be described. Figure 12It is a flowchart showing the operation process of the first embodiment of the life prediction device 80.

[0102] As Figure 12 shown, the life prediction device 80 first obtains the measured value of the torque from the torque sensor 60 (step S1). Specifically, the measured value of the torque sensor 60 is output from the signal processing circuit 52. Then, this measured value is input to the life prediction device 80.

[0103] Next, the life prediction device 80 obtains at least any one of the input speed and the output speed of the speed reducer 1 (step S2). Specifically, at least any one of the input speed and the output speed is output from the encoder 81. Then, this speed is input to the life prediction device 80.

[0104] Next, the life prediction device 80 calculates a threshold related to the life of at least any one of the flexible bearing 42 and the flexible external gear 30 based on at least any one of the input speed and the output speed of the speed reducer 1 and the measured value of the torque sensor 60 (step S3).

[0105] The life of the flexible bearing 42 is represented by the following mathematical formula (1), for example.

[0106] Lhe = 10000×(Tar / Tao) ^ 3×(nar / nai) (1)

[0107] In the mathematical formula (1), Lhe is the life of the flexible bearing 42, and the unit is time. Tar is the rated torque, and the unit is N·m. Tao is the average torque, and the unit is Nm. nar is the rated input speed, and the unit is r / min. nai is the average input speed, and the unit is r / min.

[0108] The rated torque Tar and the rated input speed nar in the above are fixed values. The rated torque Tar and the rated input speed nar are pre-stored in the memory 802 of the life prediction device 80. The life prediction device 80 calculates the average torque Tao based on the measured value of the torque obtained from the torque sensor 60. In addition, the life prediction device 80 calculates the average input speed nai based on at least any one of the input speed and the output speed obtained from the encoder 81.

[0109] The life prediction device 80 substitutes the rated torque Tar and the rated input speed nar read from the memory and the calculated average torque Tao and average input speed nai into the above mathematical formula (1). Therefore, the life prediction device 80 calculates the life Lhe of the flexible bearing 42.

[0110] Figure 13It is a graph showing the service lives of the flexible bearing 42 and the flexible external gear 30. Figure 13 The horizontal axis of [it] represents the total number of revolutions N of the input shaft 10. Figure 13 The vertical axis of [it] represents the average torque Tao.

[0111] As Figure 13 shown, when the average torque Tao is Tao1, the total number of revolutions N of the input shaft 10 representing the service life of the flexible bearing 42 is N1. Additionally, as Figure 13 shown, when the average torque Tao is Tao1, the total number of revolutions N of the input shaft 10 representing the service life of the flexible external gear 30 is N2. Thus, in this speed reducer 1, the total number of revolutions N of the input shaft 10 representing the service lives of the flexible bearing 42 and the flexible external gear 30 can be predicted based on the average torque Tao.

[0112] The service life prediction device 80 stores Figure 13 the graph of [it] in the memory 801 in advance as reference data. The service life prediction device 80 calculates the average torque Tao based on the measured value of the torque acquired from the torque sensor 60. Then, the service life prediction device 80 determines the total number of revolutions N corresponding to the average torque Tao according to the above-mentioned reference data read from the memory. Thereby, the total number of revolutions N of the input shaft 10 representing the service lives of the flexible bearing 42 and the flexible external gear 30 is determined. The service life prediction device 80 calculates the service life of the flexible bearing 42 and the flexible external gear 30 as the durable time by dividing the total number of revolutions N by the average input rotational speed nai.

[0113] As described above, the service life prediction device 80 calculates the service life of at least any one of the flexible bearing 42 and the flexible external gear 30 according to the mathematical formula (1) or the reference data. Then, the service life prediction device 80 calculates the threshold value Lth related to the service life based on the calculated service life. The threshold value Lth is set to a time shorter than the service life. For example, the threshold value Lth is the time obtained by multiplying the service life by a specified coefficient such as 0.9. Additionally, the threshold value Lth can also be the time after subtracting a specified time from the service life.

[0114] The service life prediction device 80 determines whether the total driving time from the start of use of the speed reducer 1 has reached the threshold value Lth (step S4). When the driving time has not reached the threshold value Lth (in step S4, "no"), the service life prediction device 80 repeats the processing from step S1 to step S4.

[0115] Shortly after, when the driving time reaches the threshold value Lth (Yes in step S4), the life prediction device 80 outputs an alarm signal Al (step S5). The alarm signal Al is a signal indicating that the life of the speed reducer 1 is about to end. The life prediction device 80, for example, displays a warning on the display according to the alarm signal Al. In addition, the life prediction device 80 can turn on a warning light or sound an alarm tone according to the alarm signal Al. In addition, the life prediction device 80 can also stop the motor 103 according to the alarm signal Al.

[0116] As described above, the life prediction device 80 calculates the threshold value Lth related to the life of at least any one of the flexible bearing 42 and the flexible external gear 30 based on at least any one of the input rotation speed and the output rotation speed of the speed reducer 1 and the measured value of the torque sensor 60. When the driving time of the speed reducer 1 reaches the threshold value Lth, the alarm signal Al is output. Thereby, it is possible to manage the life of at least any one of the flexible bearing 42 and the flexible external gear 30 based on the measured value of the torque sensor 60 mounted on the speed reducer 1.

[0117] The life predicted by the life prediction device 80 may be only any one of the life of the flexible bearing 42 and the life of the flexible external gear 30. By predicting at least the life of the flexible bearing 42, the life prediction device 80 can manage the life of the flexible bearing 42. In addition, by predicting at least the life of the flexible external gear 30, the life prediction device 80 can manage the life of the flexible external gear 30.

[0118] The life prediction device 80 can also calculate both the first threshold value Lth1 related to the life of the flexible bearing 42 and the second threshold value Lth2 related to the life of the flexible external gear 30 based on at least any one of the input rotation speed and the output rotation speed of the speed reducer 1 and the measured value of the torque sensor 60. Then, the life prediction device 80 can output the alarm signal Al when the driving time of the speed reducer 1 reaches any one of the first threshold value Lth1 and the second threshold value Lth2. In this way, the alarm signal Al can be output at the moment when the driving time of the speed reducer 1 reaches the shorter one of the first threshold value Lth1 and the second threshold value Lth2. Therefore, it is possible to manage the life based on the shorter one of the life of the flexible bearing 42 and the flexible external gear 30.

[0119] <4-2. Second Embodiment>

[0120] Next, a second embodiment of the operation of the life prediction device 80 will be described. Figure 14 It is a flowchart showing the flow of the operation of the second embodiment of the life prediction device 80.

[0121] As Figure 14As shown, the life prediction device 80 first obtains the measured value of the torque from the torque sensor 60 (step S11). Specifically, the measured value of the torque sensor 60 is output from the signal processing circuit 52. Then, this measured value is input to the life prediction device 80.

[0122] Next, the life prediction device 80 obtains at least either the input rotational speed or the output rotational speed of the speed reducer 1 (step S12). Specifically, at least either the input rotational speed or the output rotational speed is output from the encoder 81. Then, this rotational speed is input to the life prediction device 80.

[0123] Next, the life prediction device 80 calculates the remaining life time Lr of at least either the flexible bearing 42 or the flexible external gear 30 based on at least either the input rotational speed or the output rotational speed of the speed reducer 1 and the measured value of the torque sensor 60 (step S13).

[0124] Specifically, in the same manner as in the first embodiment, the life prediction device 80 calculates the life of at least either the flexible bearing 42 or the flexible external gear 30 based on at least either the input rotational speed or the output rotational speed of the speed reducer 1, the measured value of the torque sensor 60, and the mathematical formula (1) or the reference data. After that, the life prediction device 80 calculates the remaining life time Lr by subtracting the total driving time from the calculated life.

[0125] After that, the life prediction device 80 outputs the calculated remaining life time Lr (step S14). For example, the life prediction device 80 displays the remaining life time Lr on the display. In addition, the life prediction device 80 may also output the remaining life time Lr as data to an external information terminal. The life prediction device 80 repeatedly performs the operations of steps S11 to S14, sequentially updates the remaining life time Lr, and outputs it.

[0126] As described above, the life prediction device 80 outputs the remaining life time Lr of at least either the flexible bearing 42 or the flexible external gear 30 based on at least either the input rotational speed or the output rotational speed of the speed reducer 1 and the measured value of the torque sensor 60. Thus, it is possible to manage the life of at least either the flexible bearing 42 or the flexible external gear 30 based on the measured value of the torque sensor 60 mounted on the speed reducer 1.

[0127] The remaining life prediction device 80 can also calculate a first remaining life Lr1 of the remaining life Lr of the flexible bearing 42 and a second remaining life Lr2 of the remaining life Lr of the flexible external gear 30 based on at least any one of the input rotation speed and the output rotation speed of the speed reducer 1 and the measurement value of the torque sensor 60. In this case, it is desirable for the remaining life prediction device 80 to output the shorter one of the first remaining life Lr1 and the second remaining life Lr2. Thereby, the remaining life Lr can be managed based on the shorter one of the flexible bearing 42 and the flexible external gear 30. In addition, in order to calculate the second remaining life Lr2, it is preferable to count the number of times the torque exceeds the threshold value of the stress value exceeding the fatigue limit of the flexible external gear 30.

[0128] <5. Modification example>

[0129] The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments. Hereinafter, various modification examples will be described centering on the differences from the above embodiments.

[0130] In the above embodiment, the speed reducer 1 has a signal processing circuit 52. However, the signal processing circuit 52 can also be provided outside the speed reducer 1. In addition, one signal processing circuit 52 can be connected to the sensors 50 of multiple speed reducers 1.

[0131] In the above embodiment, the torque sensor 60 has a first torque sensor 61 and a second torque sensor 62. However, the torque sensor 60 can be only any one of the first torque sensor 61 and the second torque sensor 62.

[0132] In the speed reducer 1 of the above embodiment, the flexible external gear 30 is fixed to the base frame 101, and the internal gear 20 rotates at the decelerated second rotation speed. However, it can also be that the internal gear 20 is fixed to the base frame 101, and the flexible external gear 30 rotates at the decelerated second rotation speed.

[0133] The flexible external gear 30 of the above embodiment is a so-called "cap type" gear in which the diaphragm portion 33 extends radially outward from the body portion 31. However, the flexible external gear 30 can also be a so-called "cup type" gear in which the diaphragm portion 33 extends radially inward from the body portion 31.

[0134] In the above embodiment, the robot 100 is an industrial robot with an arm. However, the robot 100 can be other devices such as a powered exoskeleton or an automated guided vehicle.

[0135] In addition, the structures of the detailed parts of the speed reducer, the robot, and the life prediction device can be appropriately changed without departing from the gist of the present invention. Additionally, the elements appearing in the above-described embodiments and modification examples can be appropriately combined without causing contradictions.

[0136] <6. Summary>

[0137] The present technology can adopt the following structures.

[0138] (1) A life prediction device, which is a life prediction device for a speed reducer. The speed reducer has a flexible external gear, an internal gear, a flexible bearing, and a torque sensor disposed on at least one of the flexible external gear and the internal gear. The life prediction device calculates a threshold related to the life of at least one of the flexible bearing and the flexible external gear based on at least one of the input speed and the output speed of the speed reducer and the measured value of the torque sensor. When the driving time of the speed reducer reaches the threshold, the life prediction device outputs an alarm signal.

[0139] (2) A life prediction device, which is a life prediction device for a speed reducer. The speed reducer has a flexible external gear, an internal gear, a flexible bearing, and a torque sensor disposed on at least one of the flexible external gear and the internal gear. The life prediction device outputs the remaining time of the life of at least one of the flexible bearing and the flexible external gear based on at least one of the input speed and the output speed of the speed reducer and the measured value of the torque sensor.

[0140] (3) The life prediction device according to (1) or (2), wherein the life at least includes the life of the flexible bearing.

[0141] (4) The life prediction device according to any one of (1) to (3), wherein the life at least includes the life of the flexible external gear.

[0142] (5) The life prediction device according to (1), wherein the life prediction device calculates a first threshold related to the life of the flexible bearing and a second threshold related to the life of the flexible external gear based on at least one of the input speed and the output speed of the speed reducer and the measured value of the torque sensor. When the driving time of the speed reducer reaches any one of the first threshold and the second threshold, the life prediction device outputs an alarm signal.

[0143] (6) The life prediction device according to (2), wherein the life prediction device calculates a first remaining time, which is the remaining time of the life of the flexible bearing, and a second remaining time, which is the remaining time of the life of the flexible external gear, based on at least any one of the input speed and the output speed of the speed reducer and the measured value of the torque sensor, and the life prediction device outputs the shorter one of the first remaining time and the second remaining time.

[0144] (7) A speed reducer having the life prediction device according to any one of (1) to (6).

[0145] (8) A robot having the life prediction device according to (1) or (2) or the speed reducer according to (7).

[0146] (9) A life prediction method, which is a life prediction method of a speed reducer. The speed reducer has a flexible external gear, an internal gear, a flexible bearing, and a torque sensor disposed on at least any one of the flexible external gear and the internal gear. Wherein, a threshold value related to the life of at least any one of the flexible bearing and the flexible external gear is calculated based on at least any one of the input speed and the output speed of the speed reducer and the measured value of the torque sensor, and an alarm signal is output when the driving time of the speed reducer reaches the threshold value.

[0147] (10) A life prediction method, which is a life prediction method of a speed reducer. The speed reducer has a flexible external gear, an internal gear, a flexible bearing, and a torque sensor disposed on at least any one of the flexible external gear and the internal gear. Wherein, the remaining time of the life of at least any one of the flexible bearing and the flexible external gear is output based on at least any one of the input speed and the output speed of the speed reducer and the measured value of the torque sensor.

[0148] (11) The life prediction method according to (9) or (10), wherein the life at least includes the life of the flexible bearing.

[0149] (12) The life prediction method according to any one of (9) to (11), wherein the life at least includes the life of the flexible external gear.

[0150] (13) The life prediction method according to (9), wherein a first threshold related to the life of the flexible bearing and a second threshold related to the life of the flexible external gear are calculated based on at least any one of the input speed and the output speed of the speed reducer and the measured value of the torque sensor, and an alarm signal is output when the driving time of the speed reducer reaches any one of the first threshold and the second threshold.

[0151] (14) The life prediction method according to (10), wherein a first remaining time as the remaining time of the life of the flexible bearing and a second remaining time as the remaining time of the life of the flexible external gear are calculated based on at least any one of the input speed and the output speed of the speed reducer and the measured value of the torque sensor, and the shorter one of the first remaining time and the second remaining time is output.

[0152] Industrial applicability

[0153] The present invention can be used in a life prediction device, a speed reducer, and a life prediction method.

Claims

1. A life prediction device, which is a life prediction device for a reducer, the reducer having a flexible external gear, an internal gear, a flexible bearing, and a torque sensor disposed on at least one of the flexible external gear and the internal gear, wherein: The life prediction device calculates a threshold value related to the life of at least one of the flexible bearing and the flexible external gear based on at least one of the input rotation speed and the output rotation speed of the speed reducer and the measurement value of the torque sensor. The life prediction device outputs an alarm signal when the driving time of the speed reducer reaches the threshold value.

2. A life prediction device, which is a life prediction device for a reducer, the reducer having a flexible external gear, an internal gear, a flexible bearing, and a torque sensor disposed on at least one of the flexible external gear and the internal gear, wherein: The life prediction device outputs a remaining time of the life of at least one of the flexible bearing and the flexible externally toothed gear based on at least one of an input rotation speed and an output rotation speed of the speed reducer and a measurement value of the torque sensor.

3. The life prediction device according to claim 1 or 2, wherein: The lifespan includes at least the lifespan of the flexible bearing.

4. The life prediction device according to claim 1 or 2, wherein: The lifespan includes at least the lifespan of the flexible externally-toothed gear.

5. The life prediction device according to claim 1, wherein: The life prediction device calculates a first threshold value related to the life of the flexible bearing and a second threshold value related to the life of the flexible external gear based on at least one of the input rotation speed and the output rotation speed of the reducer and the measurement value of the torque sensor. The life prediction device outputs an alarm signal when the driving time of the speed reducer reaches any one of the first threshold value and the second threshold value.

6. The life prediction device according to claim 2, wherein: The life prediction device calculates a first remaining time as the remaining time of the life of the flexible bearing and a second remaining time as the remaining time of the life of the flexible external gear based on at least one of the input rotation speed and the output rotation speed of the speed reducer and the measurement value of the torque sensor. The life prediction device outputs the shorter of the first remaining time and the second remaining time.

7. A reducer, wherein: The reducer has the life prediction device according to claim 1 or 2.

8. A robot, wherein: The robot has the life prediction device according to claim 1 or 2 or the reducer according to claim 7.

9. A life prediction method, which is a life prediction method for a reducer, the reducer having a flexible external gear, an internal gear, a flexible bearing, and a torque sensor disposed on at least one of the flexible external gear and the internal gear, wherein: calculating a threshold value related to the life of at least one of the flexible bearing and the flexible externally toothed gear based on at least one of the input rotation speed and the output rotation speed of the speed reducer and the measurement value of the torque sensor, When the driving time of the speed reducer reaches the threshold value, an alarm signal is output.

10. A life prediction method, which is a life prediction method for a reducer, the reducer having a flexible external gear, an internal gear, a flexible bearing, and a torque sensor disposed on at least one of the flexible external gear and the internal gear, wherein: The remaining time of the life of at least one of the flexible bearing and the flexible externally toothed gear is outputted based on at least one of the input rotation speed and the output rotation speed of the speed reducer and the measurement value of the torque sensor.

11. The life prediction method according to claim 9 or 10, wherein: The lifespan includes at least the lifespan of the flexible bearing.

12. The life prediction method according to claim 9 or 10, wherein: The lifespan includes at least the lifespan of the flexible externally-toothed gear.

13. The life prediction method according to claim 9, wherein: calculating a first threshold value related to the life of the flexible bearing and a second threshold value related to the life of the flexible external gear based on at least one of the input rotation speed and the output rotation speed of the speed reducer and the measurement value of the torque sensor, When the driving time of the speed reducer reaches any one of the first threshold value and the second threshold value, an alarm signal is output.

14. The life prediction method according to claim 10, wherein: calculating a first remaining time as a remaining time of the life of the flexible bearing and a second remaining time as a remaining time of the life of the flexible externally toothed gear based on at least one of an input rotation speed and an output rotation speed of the speed reducer and a measurement value of the torque sensor, The shorter one of the first remaining time and the second remaining time is output.

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