JP2010107361A - Abrasion detection device of gear - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect abrasion of a gear more accurately by utilizing a control system of a motor. <P>SOLUTION: In this abrasion detection device of a gear, when a motor connected directly to either gear of a pair of mutually-mating gears is driven rotatively as much as a command angle by a control means, an actual rotation angle of the motor is detected by a rotation sensor, and the command angle is compared with the detected angle, and if the command angle is larger than the detected angle and the detected angle is smaller than a threshold angle determined beforehand, it is determined that the gear is not abraded, and if the command angle is larger than the detected angle and the detected angle is larger than the threshold angle determined beforehand, it is determined that the gear is abraded. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a gear wear detection apparatus configured to detect gear wear by slightly rotating a motor that drives the gear.

  As a method for detecting wear of a pair of gears meshing with each other, there are methods disclosed in Patent Documents 1 and 2. In the method of Patent Document 1, the current value of the motor that drives the gear is integrated, and the maximum load amount is selected from the integrated value. The maximum load amount, the number of meshing of the gear in one cycle, and a predetermined time. The amount of wear is calculated by substituting the number of cycles in the equation for determining the amount of gear wear.

The method of Patent Document 2 calculates a gear angle function, an angular acceleration function, and the like from the position coordinate data of the tool at the tip of the arm, the posture data of the arm, and the weight data of the tool and the arm, and the tooth surface of the gear in one cycle. The number of times of meshing. Also, based on data input from the data input unit, a load torque function and a load moment of inertia function using the cycle time as parameters are calculated, and the load variation of the gear during one cycle is derived from the angular acceleration sensor. Then, the maximum load is calculated from the number of meshes and the load variation, and the gear wear amount is calculated.
Japanese Patent Application Laid-Open No. 7-100782 JP-A-9-136287

  In the wear amount detection methods of Patent Documents 1 and 2, the wear amount of the gear can be detected using a control system for controlling the motor without adding a new sense. However, these methods are methods for calculating the wear of the gear from the load amount and the number of meshing of the tooth surfaces, and do not directly detect the wear amount.

  The present invention has been made in view of the above circumstances, and its object is to wear gears that can more accurately detect gear wear using a motor control system without adding a new sensor. It is to provide a detection device.

  In claim 1, when a motor directly connected to one of a pair of gears meshing with each other is driven to rotate by a command angle by the control means, an actual rotation angle of the motor is detected by a rotation sensor, and the command When the command angle is greater than the detection angle and the detection angle is less than or equal to a predetermined threshold angle, it is determined that there is no wear, and the command angle is greater than the detection angle. And, when the detected angle exceeds a predetermined threshold angle, it is determined that there is wear, so there is no wear of gears using the motor control system without adding a new sensor. Can be detected.

  According to a second aspect of the present invention, the output of the forward rotation command signal and the reverse rotation command signal for rotating the motor in the forward direction and the reverse direction by the same angle means that the detected angle of the rotation sensor with respect to the forward rotation command signal and the rotation with respect to the reverse rotation command signal. Since it repeats until the difference with the detection angle of the sensor is within a predetermined value, the other gear is set so that one tooth of one gear is located at the center between the two teeth of the other gear. Can move. Therefore, the measurement with and without wear according to claim 1 can be performed in a state where there is no bias in the teeth, so that the accuracy of the measurement is increased.

  In claim 3, for each of the forward rotation and reverse rotation of the motor, it is determined whether or not the rotation sensor continuously detects the same angle for a predetermined time, and when the same angle is not detected for a predetermined time continuously, Since the motor is rotated forward and backward by an angle larger than the previous time, even if there is wear or the wear amount is large, one tooth of one gear is between two teeth of the other gear. The other gear can be moved to be centered.

  In claim 4, when the rotation sensor detects the same angle continuously for a predetermined time with respect to the normal rotation command signal or the reverse rotation command signal, the command angle and the normal rotation according to the normal rotation command signal and the reverse rotation command signal Since the detection angle of the rotation sensor with respect to the command signal and the reverse rotation command signal is compared, from the state where one tooth of one gear is located at the center between the two teeth of the other gear, the rotation command signal A reverse rotating state is obtained, and the presence or absence of wear can be detected more accurately. Furthermore, in claim 4, it becomes possible to detect the amount of wear quantitatively by angle.

  According to the fifth aspect, when the determination means determines that there is wear, the wear amount is calculated from the detection angle of the rotation sensor, so that it is possible to specifically know how much wear has occurred.

Hereinafter, an embodiment in which the present invention is applied to a gear reduction device in an arm drive device of a robot will be described with reference to the drawings. For example, in a vertical articulated robot, the arms are connected to each other by a rotating joint. Each arm is rotationally driven by an arm driving device.
FIG. 2 shows an example of the arm drive device 1, which is disposed, for example, in the arm 2 at the front stage of the arm to be driven. The arm drive device 1 is mainly composed of a gear reduction device 4 having a motor 3 as a drive source, and includes a rotation shaft 5, an intermediate shaft 6 and an output shaft 7 of the motor 3 as input shafts. The small gear 8 is attached, the large gear 9 is attached to the intermediate shaft 6, the small gear 10 is attached to the intermediate shaft 6, and the large gear 11 is attached to the output shaft 7.

  Among these gears 8 to 11, the small gear 8 of the rotary shaft 5 and the large gear 9 of the intermediate shaft 6 are engaged, and the small gear 10 of the intermediate shaft 6 and the large gear 11 of the output shaft 7 are engaged. Accordingly, the rotation of the rotary shaft 5 is decelerated by the pair of small gears 8 and the large gear 9 and transmitted to the intermediate shaft 6, and the rotation of the intermediate shaft 6 is further separated into another set of the small gear 10 and the large gear 11. And is transmitted to the output shaft 7. The next stage arm (not shown) is rotationally driven by the rotation of the output shaft 7.

  FIG. 1 is a block diagram showing a control system of the motor 3. As shown in FIG. 1, the control device 12 includes a CPU 13, a drive circuit (drive means) 14, and a position detection circuit (position detection means) 15. The CPU 13 is connected to an interface 20 for connecting a ROM 16, a RAM 17, an operation panel 18, and a personal computer 19 that store system programs for the entire robot.

  The position detection circuit 15 is for detecting the rotational position of the motor 3, and a rotary encoder 21 as a rotation sensor for detecting the rotation of the rotary shaft 5 of the motor 3 is connected to the position detection circuit 15. Has been. In FIG. 2, only one motor 3 and one rotary encoder 21 are illustrated, but in reality, a plurality of motors 3 and rotary encoders 21 are provided in a one-to-one relationship with each joint.

  When the motor 3 is driven to rotate, the CPU 13 outputs a rotation command signal to the drive circuit 14. On the other hand, the position detection circuit 15 detects the rotation angle of the motor 3 based on the detection signal of the rotary encoder 21 and supplies the detected angle signal to the CPU 13 and the drive circuit 14 as a feedback signal, as in the conventional control configuration. The drive circuit 14 compares the command angle according to the rotation command signal from the CPU 13 with the detection angle according to the feedback signal from the position detection circuit 15 and controls the rotation of the motor 3 according to the comparison result. Specifically, the drive circuit 14 compares the command angle and the detected angle, and supplies a drive current corresponding to the difference to the motor 3. Thereby, the motor 3 rotates the rotating shaft 5 so that it may become the same rotation angle as the command angle of CPU13. Therefore, the CPU 13 functions as a control unit that controls the motor 3 to rotate by the command angle, together with an addition / subtraction unit that compares the command angle of the position detection circuit 15 and the drive circuit 14 with the detection angle and outputs a difference.

  On the other hand, as is well known, the personal computer 19 includes a control unit having a CPU, a ROM, a RAM, an operation unit including a keyboard and a mouse, and a display unit (none of which is shown) including a liquid crystal display. Have The personal computer 19 stores a program (wear measurement program) for calculating the wear amount of a pair of gears meshing with each other.

  Next, the control contents when the gear wear is detected using the wear measurement program of the personal computer 19 will be described with reference to the flowchart of FIG. The gear reduction device 4 has two sets of a pair of gears that mesh with each other. The pair of gears that are subject to wear measurement are a small gear 8 that is directly connected to the motor 3 and a large gear that meshes with the small gear 8. Gear 9. Here, the direct connection to the motor 3 includes that in which the input shaft is composed of a shaft different from the rotation shaft 5 of the motor 3 and the rotation shaft 5 of the motor 3 is coupled to the input shaft via a joint.

  In the present embodiment, a rotation command signal is output from the CPU 13, and the actual rotation angle of the rotating shaft 5 of the motor 3 at that time is detected by the rotary encoder 21. Then, the presence / absence of wear is determined by comparing the command angle corresponding to the rotation command signal with the detected angle of the rotary encoder 21, and the wear amount is further calculated. As the rotation command signal, the rotation shaft 5 of the motor 3 is rotated at the stop position (reference position) by the angle 0, and is rotated from the reference position at this angle 0 by the positive angle + θn to return to the original reference position. A signal and a reverse rotation command signal for rotating the reference position by an angle −θn in the reverse direction and returning to the original reference position are output as one set. The command angle + θn of the pair of forward rotation command signals and the command angle −θn of the reverse rotation command signal are the same in the magnitude of the angles except that the rotation directions are opposite to each other.

  The magnitudes of the absolute values of the command angle + θn of the pair of forward rotation command signals and the command angle −θn of the reverse rotation command signal are represented by numbers (n = 1, 2, 3,...) Indicated by the subscript n. It is assumed that the larger the value is, the larger the angle is, such as | θ1 | <| θ2 | <| θ3 | <. It is assumed that | θ1 |, | θ2 |, | θ3 |,... Are stored in advance in a ROM (command angle storage means) of the personal computer 19. Among the absolute values of the command angle, the smallest | θ1 | is a predetermined amount larger than half the rotation angle of the small gear 8 within the backlash when the teeth of the pair of gears 8 and 9 have a wear amount of 0. The value is set larger by β.

  Here, in the following description, the command angle θ1 indicates the absolute value, and + θ1 and −θ1 indicate the command angle of the forward rotation command signal, It shall represent the command signal of a rotation command signal. In addition, when the rotation command signal includes, for example, command angles of + θ1 and −θ1, the CPU 13 does not output the command angles of + θ1 and −θ1 suddenly but until + θ1 and −θ1. Alternatively, a command angle that gradually increases or decreases at a constant rate from the position of + θ1 or −θ1 to the reference position is output at a very short time interval. Therefore, the command angle waveforms of the forward rotation command signal and the reverse rotation command signal are triangular.

  Now, in order to detect the presence or absence of wear of the small gear 8 directly connected to the motor 3 and the large gear 9 meshing with the small gear 8, a personal computer 19 is connected to the interface 20 of the robot controller 12, and a wear measurement program is connected. Start up. Then, first, the personal computer 19 sets a numerical value n indicating the magnitude of the command signal to 1 (step S1 in FIG. 3), sets the magnitude of the commanded rotation angle to θ1, and instructs the CPU 13 of the control device 12 to A command is transmitted so as to output a forward rotation command signal with a command angle of + θ1 and a reverse rotation command signal with −θ1 (step S2).

  When the CPU 13 of the robot control device 12 receives the above command, it outputs a forward rotation command signal of command angle + θ1 and a reverse rotation command signal of command angle −θ1 to the drive circuit 14 in order (step S3, step S5). . As a result, the drive circuit 14 rotates the motor 3 in the forward direction from the stop position (reference position) by θ1, and when it rotates θ1, the motor 3 rotates in the reverse direction and returns to the original reference position. It is driven to rotate further by θ1 in the opposite direction from the reference position.

  At this time, the rotary encoder 21 detects the actual rotation angle of the rotating shaft 5 every predetermined short time and gives a detection signal to the position detection circuit 15. The position detection circuit 15 determines the detection angle by the rotary encoder 21. It gives to CPU13 (step S4, step S6). Then, the CPU 13 stores the command angle of the forward rotation command signal and the reverse rotation command signal and the detected angle by the rotary encoder 21 in the RAM 17 (command value / detected value storage means), and the command angle and detected angle are stored in the personal computer 19. Send to.

  The personal computer 1 generates a change in the command angle (command angle waveform) and a waveform indicating the change in the detection angle (detection angle waveform) based on the command angle and the detection angle transmitted from the CPU 13 of the control device 12 (step S7). : Waveform generating means). Next, the personal computer 1 detects the detected angle waveform from the time when the command value + θn (here, + θ1) is reached until the time t1 elapses, and the time when the command value −θn (here, −θ1) is reached. It is determined whether or not the detected angle waveform until t1 has elapsed (step S8: waveform shape determining means). The symmetry in this case includes not only complete symmetry but also a case where both detected waveforms are within a predetermined error range. Therefore, in step S8, when the command value becomes + θn within the predetermined time t1 from the time when the command value becomes + θn and within the predetermined time t1 from the time when the command value becomes −θn, This is equivalent to determining whether or not the difference in detection angle at the time when an arbitrary time has passed is within a predetermined value.

  By the way, when the forward rotation command signal and the reverse rotation command signal of θ1 are outputted from the CPU 13, the meshing states of the teeth of the small gear 8 and the large gear 9 are various. Ideally, as shown in FIG. 4, one tooth 8a of the small gear 8 is located in the center between the two adjacent teeth 9a, 9b of the large gear 9 (the state where there is no tooth bias). That is, a state where the gaps G1, G2 on both sides of one tooth 8a are equal to each other appears, and in this state, it is preferable that the forward rotation command signal and the reverse rotation command signal are output.

As a typical example of this ideal state, a straight line C connecting the rotation center points of the small gear 8 and the large gear 9 passes through the center between the two teeth 9a and 9b (tooth groove) of the large gear 9, FIG. 5A shows the case where one tooth 8a of the small gear 8 is located at the center of the tooth groove. When the tooth wear is 0, in FIG. 5A, the gaps G1 and G2 on both sides of the tooth 8a are ½ of the initially set backlash.
The state of FIG. 4A and the state of FIG. 5A are not completely the same as the conditions when the wear detection of the present invention is applied, but are considered to be substantially equivalent. The straight line C connecting the rotation center of the large gear 9 and the large gear 9 will be described as passing through the center of the tooth 8a of the small gear 8.

When a forward rotation command signal having a command angle + θ1 and a reverse rotation command signal having a command angle −θ1 are sequentially output, when the small gear 8 and the large gear 9 are in the ideal state, the command angle is + θ1. At the time of -θ1, the tooth 8a hits the tooth 9a or the tooth 9b when it is rotated by the same angle (θ1-β) from the position of the angle 0 (position where the tooth 8a exists). And since the small gear 8 receives rotational resistance from the large gear 9 in the rotation position, the rotating shaft 5 does not rotate any more.
Therefore, a waveform (positive detection angle waveform) indicating a change in the detection angle of the rotary encoder 21 from when the command value + θ1 is reached until the predetermined time t1 elapses, and from when the command value −θ1 is reached. The waveform indicating the change in the detection angle of the rotary encoder 21 until the predetermined time t1 elapses (reverse detection angle waveform) is symmetric as shown in FIG.

  On the other hand, for example, as shown in FIG. 6A, when the large gear 9 deviates from the ideal state with respect to the small gear 8, the sizes of the gaps G1 and G2 on both sides of the tooth 8a are different. The rotation angle until the tooth 8a of the small gear 8 hits one tooth 9a of the large gear 9 and the other tooth depending on whether the rotating shaft 5 rotates in the forward direction from the position of the angle 0 The rotation angle until it hits 9b will be different. Therefore, as shown in FIG. 6B, the positive side detection angle waveform and the reverse side detection angle waveform are not symmetric.

  When the positive side detection angle waveform and the reverse side detection angle waveform are asymmetric as described above ("NO" in step S8), the personal computer 19 again sends the forward rotation command signal of the command angle + θ1 and the command angle -θ1. Is transmitted to the CPU 13 of the control device 12 so as to output a reverse rotation command signal, and a command angle waveform and a detected angle waveform are generated from the command angle and the detected angle transmitted from the CPU 13, and the positive detection angle is detected. It is determined whether or not the waveform and the reverse detection angle waveform are targets (steps S3 to S8).

If the positive side detection angle waveform and the reverse side detection angle waveform are not symmetric, the personal computer 19 performs steps S3 to S8 until the positive side detection angle waveform and the reverse side detection angle waveform are targeted. Run repeatedly. In this way, by repeating the operation of outputting the forward rotation command signal and the reverse rotation command signal while keeping the command angle constant, the tooth 8a of the small gear 8 is changed to the two teeth of the large gear 9. It reciprocates (rotates) between 9a and 9b. As a result, the smaller gap side tooth of the gaps G1 and G2, that is, the tooth 9a in the example of FIG. 6, receives a larger abutting force from the tooth 8a of the small gear 8 than the large gap side tooth 9b.
For this reason, as shown in FIG. 7A, the large gear 9 rotates little by little in the direction from the tooth 9b having a large gap toward the tooth 9a having a small gap, and finally, as shown in FIG. As shown, the gaps G1 and G2 on both sides of the tooth 8a have the same size. Then, the positive side detection angle waveform and the reverse side detection angle waveform are symmetric.

  As described above, when the symmetry between the positive side detection angle waveform and the reverse side detection angle waveform is detected (“YES” in step S8), the personal computer 19 then determines when the command value becomes + θ1. From a predetermined time t2, it is determined whether or not the state in which the detected angle of the rotary encoder 21 is the same angle continues (step S9). Note that t2 is set within a time corresponding to a time when the magnitude of the command angle changes by the angle β.

  The significance of this step S9 is as follows. That is, the symmetry of the positive side detection angle waveform and the reverse side detection angle waveform was confirmed, and that the tooth 8a of the small gear 8 was in contact with both of the two teeth 9a and 9b of the large gear 9 equally. Does not necessarily match. For example, as shown in FIG. 8A, when the amount of wear of the teeth is large, at the command angles of + θ1 and −θ1, the teeth 8a do not hit the two teeth 9a and 9b and reciprocate in the tooth groove. It may be just there. The detected angle waveform in this case is as shown in FIG. 8B, and the positive side detected angle waveform and the reverse side detected angle waveform are symmetric. However, this cannot detect the wear amount. In order to detect the amount of wear, the tooth 8a must hit both the two teeth 9a and 9b evenly.

  If the tooth 8a hits both the two teeth 9a and 9b evenly, a state where the detection angle is constant appears. In step S9, it is detected that the detected angle is constant, in other words, that the tooth 8a is in contact with both the teeth 9a and 9b evenly. When the tooth 8a hits both of the two teeth 9a and 9b, the large gear 9 is slightly rotated. However, since the rotation angle is extremely small, the detection angle is substantially constant. .

  Now, even if the positive side detection angle waveform and the reverse side detection angle waveform are symmetric, the state where the detection angle of the rotary encoder 21 within the predetermined time t2 is the same angle from the time when the command value becomes + θ1 continues for t2 time. If not (“NO” in step S9), the personal computer 19 increments a numerical value n indicating the magnitude of the command signal (step S10). Here, since n is “1”, it is changed to “2” in step S10. After that, the personal computer 19 returns to the above-described step S2, sets the commanded angle to θ2, which is one step larger than θ1, and reverses the forward rotation command signal with the command angles of + θ2 and −θ2 to the CPU 13 of the control device 12. A command is transmitted so as to output a rotation command signal.

  Then, the CPU 13 of the robot control device 12 sequentially outputs a forward rotation command signal with a command angle + θ2 and a reverse rotation command signal with a command angle −θ2, and transmits the detected angle by the rotary encoder 21 to the personal computer 19. When the symmetry between the positive detection angle waveform and the reverse detection angle waveform is confirmed, it is determined whether or not the same angle is maintained within a predetermined time t2 from the command value + θ2. If the same angle is not maintained for t2 time, the personal computer 19 further increases the numerical value indicating the magnitude of the command angle (step S10), and outputs a normal rotation command signal and a reverse rotation command signal for the command angle. Are transmitted to the control device 12 of the robot, the detection angle information sent from the control device 12 is symmetrical in the positive detection angle waveform and the reverse detection angle waveform, and the command value peak of the forward rotation command signal After that, until it is confirmed that a state where the detection angle is constant only for a predetermined time t2 is confirmed, the command angle is increased step by step, the motor 3 is driven in the forward and reverse directions, and the actual rotation angle of the rotary shaft 5 is detected. Repeat the operation.

  If it is confirmed that a state where the detection angle is constant for a predetermined time t2 exists after the peak of the command value of the forward rotation command signal (“YES” in step S9), the personal computer 19 predetermines the command angle θn at that time. The commanded threshold angle θy is compared to determine whether the command angle θn exceeds the threshold angle θy (θ1-β) (step S11: comparison means). If the command angle θn does not exceed the threshold angle θy, the personal computer 19 determines that there is no wear (step S12: determination means) and ends. Note that “no wear” in this case means that the wear is not in a state that is within the allowable range of wear set by the user and causes a problem.

If the command angle θn exceeds the threshold angle θy, the personal computer 19 determines that there is wear and sets the maximum detected angle as the wear angle θx (step S13: determination means, wear angle detection means). The wear amount is obtained by substituting the angle θx (step S14: wear amount calculation means), and the end.
Amount of wear = reference pitch circle diameter of gear × π × 2θx ÷ 360
The reference pitch circle diameter of the gear in the above equation is the reference pitch circle diameter D0 (see FIG. 4) of the gear directly connected to the rotating shaft 5, that is, the small gear 8 in this embodiment.

  Thus, according to this embodiment, the presence or absence of gear wear can be detected using the control system of the motor 3. In addition, the amount of wear of the gear is detected based on the rotation angle of the rotating shaft 5 of the motor 3 when the tooth 8a of the small gear 8 on the driving side hits the two teeth 9a and 9b of the large gear 9 on the driven side. Wear can be detected.

The present invention is not limited to the embodiment described above and shown in the drawings, and the following modifications or expansions are possible.
Step S8 determines whether or not the difference between the detected angles when the command value is + θn or −θn, or the difference between the detected angles after a predetermined time from when the command value becomes + θn or −θn is within the predetermined value. It may be changed to judge.
You may stop only in the function which detects the presence or absence of wear.
If a rotation command signal is output in a state where one tooth 8a is set at the center between the two teeth 9a and 9b, the rotation command signal can be used to determine whether or not there is wear and the amount of wear only in one of the positive and reverse directions. Detection can be performed.
The function of the personal computer 19 may be performed by the CPU 13 of the control device 12 so that gear wear can be detected without using the personal computer 19.
The present invention is not limited to the case of gears of robot arm drive devices, and can be widely applied to the detection of gear wear.

The block diagram which shows the structure of the control system of the motor in one Embodiment of this invention. Sectional drawing which shows the outline of a gear reduction device Flow chart for wear detection Partial plan view showing an example of an ideal state of a gear for wear inspection (A) is a partial plan view showing another example of an ideal state of a gear for wear inspection, (b) is a waveform diagram of command angle and detection angle (A) is a plan view showing an example in which one tooth is biased in the tooth groove, (b) is a waveform diagram of command angle and detection angle (A) is a plan view showing the way in which the deviation of one tooth in the tooth groove is corrected, (b) is a waveform diagram of command angle and detection angle (A) is a partial plan view of a gear when the amount of wear is large, and (b) is a waveform diagram of command angle and detection angle.

Explanation of symbols

  In the drawings, 4 is a gear reduction device, 5 is a rotation shaft, 6 is an intermediate shaft, 7 is an output shaft, 8 is a small gear, 9 is a large gear, 12 is a control device, and 13 is a CPU (control means, comparison means, determination) Means, wear amount calculating means), 14 a drive circuit, 15 a position detection circuit, 19 a personal computer, and 21 a rotary encoder (rotation sensor).

Claims (5)

A device for detecting wear of a pair of gears meshing with each other,
A motor directly connected to one of the pair of gears;
Control means for outputting a rotation command signal and controlling the motor so that the motor rotates by a command angle corresponding to the rotation command signal using a detection signal from a rotation sensor for detecting a rotation angle of the motor as a feedback signal; ,
A comparison means for comparing the command angle according to the rotation command signal with a detection angle of the rotation sensor;
When the command angle is larger than the detection angle and the detection angle is equal to or smaller than a predetermined threshold angle by comparison of the comparison means, it is determined that there is no wear, and the command angle is greater than the detection angle. And when the detected angle exceeds the predetermined threshold angle, a determination unit that determines that there is wear,
A gear wear detection device comprising: The control means outputs, as the rotation command signal, a normal rotation command signal and a reverse rotation command signal for rotating the motor by the same angle in the forward direction and the reverse direction. The gear wear detection device according to claim 1, wherein the gear wear detection device is repeated until a difference between a detection angle and a detection angle of the rotation sensor with respect to the reverse rotation command signal falls within a predetermined value. When the difference between the detected angle of the rotation sensor with respect to the forward rotation command signal and the detected angle of the rotation sensor with respect to the reverse rotation command signal is within the predetermined value, the control means In response to the reverse rotation command signal, the rotation sensor determines whether or not the same angle is detected continuously for a predetermined time. When the same angle is not detected continuously for a predetermined time, the forward rotation command signal and the reverse rotation are determined. The output of the command signal at a command angle larger than the previous command is repeated until the rotation sensor detects the same angle continuously for a predetermined time with respect to the forward rotation command signal or the reverse rotation command signal. The gear wear detecting device according to claim 2. When the rotation sensor detects the same angle continuously for a predetermined time with respect to the normal rotation command signal or the reverse rotation command signal, the comparison unit responds to the normal rotation command signal and the reverse rotation command signal. 4. The gear wear detection device according to claim 3, wherein the rotation angle of the rotation sensor with respect to the command angle is compared with the normal rotation command signal and the reverse rotation command signal. 5. The gear according to claim 1, further comprising: a wear amount calculation unit that calculates a wear amount from the detection angle of the rotation sensor when the determination unit determines that there is wear. Wear detection device.

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