JPH09262778A - Fastening device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fastening device capable of judging device breakdown. SOLUTION: A fastening device is provided with a driving shaft 1 with a socket 11 fixed to its end, a torque sensor 2 for detecting tightening torque of the drive shaft 1, a speed reducer 3 to which an output shaft of the drive shaft 1 is connected through the torque sensor 2, an AC motor 4 having an output shaft 12 connected to an input shaft of the speed reducer 3, and an encoder 5 for detecting the turning angle of the output shaft 12 of the AC motor 4. When the AC motor 4 is started, turning output of the AC motor 4 is decelerated and energized through the speed reducer 3 and tightens a nut fitted to the socket 11. Turning angle of the output shaft 12 of the AC motor 4 is detected by the encoder 5 and a magnet switch 14. Whether it is a device breakdown or not is judged on the basis of the difference of respective turning angles detected by the encoder 5 and the magnet switch 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tightening device for tightening bolts, nuts and the like with a drive shaft driven by a motor.

[0002]

2. Description of the Related Art Conventionally, as a tightening device, a nut is fitted in a socket fixed to the tip of a drive shaft, and the drive shaft is driven by an output shaft of an AC servomotor through a speed reducer.
Some tighten the nuts. This tightening device controls the rotation angle of the output shaft of the AC servo motor based on the rotation angle of the output shaft of the AC servomotor detected by the encoder, while monitoring the tightening torque of the drive shaft with a torque sensor to tighten the torque. When tightening torque reaches the target value, tightening is completed.

FIG. 6 shows a flowchart of the tightening process of the above-mentioned tightening device, and FIG. 7 shows changes in the tightening torque during the tightening. The tightening process will be described below with reference to FIGS.

First, after the AC servomotor (referred to as a motor in FIG. 6) is started, the tightening torque T is input from the torque sensor to determine whether the tightening torque T exceeds the seating torque T _ST. Yes (steps S31, S32, S3
3). Then, the tightening torque T gradually increases until the nut is seated and rapidly increases immediately before the seating, and when the tightening torque T exceeds the seating torque T _ST , the motor is stopped (step S34). When tightening more than one of the above nuts, restart the motor after all the nuts are seated
(Step S35). When the motor is restarted, the tightening torque T rapidly increases, and when the tightening torque T exceeds the angle start torque T _A , the reading of the rotation angle θ _A of the motor output shaft from the encoder is started (step S36, S37, S38). When the tightening torque T becomes equal to or greater than the stop torque T _E , it is determined that the tightening torque T has reached the target value, and the rotation angle θ _A from the encoder is determined.
After the reading of is stopped, the motor is stopped (steps S42 and S43). Next, it is determined whether or not the tightening torque T is within the allowable range, and when it is determined that the tightening torque T is within the allowable range, the tightening torque T is determined to be normal (step S45). On the other hand, if it is determined that the tightening torque T is not within the allowable range, it is determined that the tightening torque T is abnormal (step S46). After that, if it is determined whether the rotation angle θ _A is within the allowable range and it is determined that the rotation angle θ _A is within the allowable range, it is determined that the rotation angle θ _A is normal, and this processing is ended (step S47). , S48). On the other hand, the rotation angle θ _A
If it is determined that is not within the allowable range, it is determined that the rotation angle θ _A is abnormal, and this processing ends (steps S47, S
49).

As described above, the tightening device performs tightening control and normal tightening of the nut based on the tightening torque T detected by the torque sensor and the rotation angle θ _A detected by the encoder. It is determined whether or not.

[0006]

In the tightening device, the encoder for detecting the rotation angle of the output shaft of the AC servomotor has low mechanical strength and the number of signal lines output from the encoder is small. Since there are many, the encoder breaks down due to vibrations and shocks during tightening, or the signal line is broken, and the rotation angle of the output shaft of the AC servo motor cannot be detected correctly. Stops. In this case, there is a drawback that it is not possible to easily determine whether the nut is not properly attached or the tightening device itself is out of order.

Further, when the tightening device is used in a production line, it is possible to use two torque sensors together so that the production line does not stop due to a failure of the torque sensor. However, in a torque sensor having a similar life, if one torque sensor fails, the other torque sensor may also fail before the production line stops, and the production line may be stopped.

SUMMARY OF THE INVENTION An object of the present invention is to provide a tightening device which can easily determine a failure of the device and can prevent the production line or the like from stopping as much as possible.

[0009]

In order to achieve the above object, the tightening device of claim 1 is connected to a motor, a speed reducer for reducing the rotational output of the motor, and an output shaft of the speed reducer. A drive shaft that drives an object to be fastened, a torque sensor that detects the tightening torque of the drive shaft, an encoder that detects the rotation angle of the rotation shaft of the motor, and a rotation angle of the output shaft of the motor. The motor is driven based on the output of the proximity switch and the torque sensor and the output of the encoder to control the tightening of the object to be fastened, and the device malfunctions based on the output of the encoder and the output of the proximity switch. It is characterized by comprising a control means for determining whether or not.

According to the tightening device of the first aspect, when the motor is started by the control means, the drive shaft is rotated by the rotational output of the motor which is decelerated by the speed reducer, and the object to be tightened such as a nut is removed. While tightening, the encoder and the proximity switch detect substantially the same rotation angle. The proximity switch has a simple structure and is resistant to vibration and impact at the time of tightening, and when a proximity switch such as a magnetic switch is used, the number of connected signal lines is small and there is almost no risk of disconnection. Therefore, even if the encoder fails, the proximity switch accurately detects the rotation angle, so that the angular difference between the rotation angles detected by the encoder and the proximity switch becomes large, and it can be determined that the device is malfunctioning. Therefore, the abnormality of the tightening device can be easily determined.

A tightening device according to a second aspect of the present invention is the tightening device according to the first aspect, wherein the control means sets a rotation angle detected by the encoder and a rotation angle detected by the proximity switch. An angle difference calculating means for calculating an angle difference, and an angle difference determining means for determining whether or not the angle difference calculated by the angle difference calculating means is within a predetermined angle,
When the angle difference determination means determines that the angle difference is not within the predetermined angle, it has a notification means for reporting the determination result.

According to the tightening device of the second aspect, the rotation angle of the motor is detected by the encoder, and the rotation angle of the output shaft of the motor is detected by the proximity switch.
When the angle difference between the rotation angle detected by the encoder by the angle difference calculation means and the rotation angle detected by the proximity switch is calculated, and the angle difference determination means determines that the angle difference is not within the predetermined angle, The judgment result is notified to the operator by the notification means. Therefore, the failure of the encoder can be reliably determined, the operator can easily recognize the determination result, the fastening work can be stopped quickly, and the failure location of the fastening device can be known. Can be shortened.

A tightening device according to a third aspect is the tightening device according to the first or second aspect, wherein the torque sensor has a first torque sensor and a second torque sensor having different sensitivities for detecting a tightening torque. It is characterized by being.

According to the tightening device of the third aspect, for example, when the first torque sensor is lower in sensitivity than the second torque sensor, the outputs of the first and second torque sensors are at substantially the same level. So that the first torque sensor is attached to the torque detection location where the strain amount is larger than that of the second torque sensor, the second torque sensor is attached to the torque detection location where the strain amount is smaller than that of the second torque sensor. Detect the tightening torque. In this case, the failure rate of the first torque sensor having a large amount of strain is higher than that of the second torque sensor, so that the first and second torque sensors do not fail at the same time. Therefore, by using the first and second torque sensors having different lifespans, even if one of them fails, the other torque sensor can be used to continue the tightening work without stopping the production line. .

A tightening device according to a fourth aspect is the tightening device according to the third aspect, wherein the control means detects the tightening torque detected by the first torque sensor and the second torque sensor. A torque difference calculating means for calculating a torque difference from the tightened torque, and a torque difference determining means for determining whether or not the torque difference calculated by the torque difference calculating means is within a predetermined torque. When the torque difference determination means determines that the torque difference is not within the predetermined torque, the determination result is notified by the notification means.

According to the tightening device of the fourth aspect, the first torque sensor detects the tightening torque of the drive shaft, and the second torque sensor detects the tightening torque of the drive shaft. The first torque difference calculating means
Calculating a torque difference between the tightening torque detected by the torque sensor and the tightening torque detected by the second torque sensor, and determining that the torque difference is not within the predetermined torque by the torque difference determining means, The judgment result is notified to the operator by the notification means. Therefore, the failure of the first and second torque sensors can be reliably determined, the operator can easily recognize the result of the determination, and the fastening work can be stopped promptly. Since the location is known, the recovery time can be shortened.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The tightening device of the present invention will be described in detail below with reference to the embodiments shown in the drawings.

(First Embodiment) FIG. 1 is a schematic view of a tightening device according to a first embodiment of the present invention, in which 1 is a drive shaft having a socket 11 fixed to a tip thereof, and 2 is one end fixed to a casing 30. Strain gauge type torque sensor, 3 is a speed reducer whose drive shaft 1 is connected to an output shaft (not shown) via the torque sensor 2, and 4 is an input shaft (not shown) of the speed reducer 3.
An AC (alternating current) motor 5 connected to the output shaft 12 is a rotation angle θ of the output shaft 12 as a rotation shaft of the AC motor 4.
It is an encoder that detects _A. The AC motor 4 and the encoder 5 constitute an AC servo motor. Also,
The torque sensor 2 has one end fixed to the casing 30 and the other end fixed to the speed reducer 3, and the strain gauge is distorted by the reaction force caused by the rotation of the drive shaft 1 to detect the tightening torque of the drive shaft 1. To do.

The tightening device is fixed to the output shaft 12 of the AC motor 4 and has a circular plate 13 having a plurality of slits (not shown) formed at predetermined intervals in the circumferential direction, and the circular plate. A U-shaped magnetic switch 14 sandwiching the outer peripheral side of the plate 13.
And When the output shaft 12 of the AC motor 4 rotates and the disk 13 rotates, the magnetic circuit of the magnetic switch 14 is intermittently cut off as the disk 13 rotates, and the rotation angle of the disk 13 from the magnetic switch 14 increases. That is, a pulse representing the rotation angle θ _B of the output shaft 12 is output. In addition,
Drive shaft 1, torque sensor 2, speed reducer 3, AC motor 4,
When the tightening portion 20 is configured by the encoder 5, the disc 13 and the magnetic switch 14 and a plurality of nuts are tightened in parallel, the tightening portion 20 is provided in the casing 30 for each nut. The resolution of the rotation angle detected using the disc 13 and the magnetic switch 14 is smaller than the resolution of the encoder 5.

Further, the tightening device outputs a signal indicating the tightening torque from the torque sensor 2, a signal indicating the rotation angle θ _A from the encoder 5 and a pulse indicating the rotation angle θ _B from the magnetic switch 14. A control unit 10 that receives and controls the AC motor 4 is provided. The control unit 10 includes a microcomputer, an input / output circuit, and the like, and is an angle difference calculation unit as an angle difference calculation unit that calculates an angle difference (θ _A −θ _B ) between the rotation angle θ _A and the rotation angle θ _B. 10a and an angle difference determination unit 10b as an angle difference determination means for determining the angle difference (θ _A −θ _B ) calculated by the angle difference calculation unit 10a.
And a display unit 10c as a notification means for displaying the determination result of the angle difference determination unit 10b. The display section 10c uses, for example, a CRT (cathode ray tube), LCD (liquid crystal display), or the like.

In the tightening device having the above structure, when the socket 11 is fitted into the nut (not shown) as the object to be tightened and the AC motor 4 is started by the control unit 10, the AC motor 4
The rotation output of is reduced and increased by the speed reducer 3 to drive the drive shaft 1. Then, the control unit 10 controls the tightening of the nut based on the output of the torque sensor 2 and the output of the encoder 5. After the nut is tightened, it is determined whether the nut is normally tightened based on the output of the torque sensor 2 and the output of the encoder 5, and the output of the torque sensor 2 and the output of the encoder 5 are determined. Then, based on the output of the magnetic switch 14, it is determined whether or not the tightening device is normal.

The process of tightening the control unit 10 will be described below with reference to the flow charts of FIGS.

First, when the process starts, step S
1 starts the AC motor 4. Next, the tightening torque T from the torque sensor 2 is input in step S2, and step S
At 3, it is determined whether the tightening torque T exceeds the seating torque T _ST . Then, if it is determined in step S3 that the tightening torque T exceeds the seating torque T _ST , the process proceeds to step S4, while if it is determined that the tightening torque T is less than or equal to the seating torque T _ST , the process returns to step S2 and the tightening torque T Steps S2 and S3 are repeated until T exceeds the seating torque T _ST .

Next, in step S4, the AC motor 4 is stopped. Then, when there are a plurality of tightening portions 20, a predetermined time is waited until all of the tightening portions 20 are seated, and then the process proceeds to step S5 to restart the AC motor 4.

Next, in step S6, the tightening torque T from the torque sensor 2 is input, and in step S7 it is determined whether or not the tightening torque T exceeds the angle start torque T _A. The angle start torque T _A is
The encoder 5 and the magnetic switch 14 are used to rotate the rotation angles θ _A and θ.
The tightening torque T at the start of reading _B , which is the rotation angle θ of the rotating shaft 12 of the AC motor 4 after the nut is seated.
_It is set near the lower limit of the range in which _A and the tightening torque T have a substantially constant proportional relationship (see FIG. 7). Then, if it is determined in step S7 that the tightening torque T exceeds the angle start torque T _A , the process proceeds to step S8, while if it is determined that the tightening torque T is less than or equal to the angle start torque T _A ,
Returning to step S6, steps S6 and S7 are repeated until the tightening torque T exceeds the angle start torque T _A.

Next, in step S8, the rotation angle θ _A from the encoder 5 and the rotation angle θ _B from the magnetic switch 14 are set.
Start reading. Next, in step S9, the tightening torque T is input from the torque sensor 2, and in step S10, the tightening torque T is the stop torque T _E.
It is determined whether or not this is the case. When it is determined in step S10 that the tightening torque T is equal to or larger than the stop torque T _E , the process proceeds to step S11, while the tightening torque T is the stop torque T _E.
If it is determined that it is less than _E , the process returns to step S9, and step S is continued until the tightening torque T becomes equal to or more than the stop torque T _E.
9. Repeat S10.

Next, in step S11, the tightening torque T is input from the torque sensor 2, and in step S12, the reading of the rotation angle θ _A from the encoder 5 and the rotation angle θ _B from the magnetic switch 14 is stopped. And step S
13 and the AC motor 4 is stopped.

Next, the process proceeds to step S14 and step S
When it is determined whether the tightening torque T input in 11 is within the allowable range and it is determined that the tightening torque T is within the allowable range, the process proceeds to step S15, and it is determined that the tightening torque T is normal. It proceeds to step S17. On the other hand, step S14
When it is determined that the tightening torque T is not within the allowable range in step S16, the process proceeds to step S16, and it is determined that the tightening torque T is abnormal.
Proceed to step S17. Note that steps S15 and S16
The normality / abnormality of the tightening torque T is displayed on the display unit 10c.

Next, the rotation angle theta _A is determined whether the allowable range in step S17, the rotation angle theta _A is determined to be within the allowable range, the process proceeds to step S18, the normal rotation angle theta _A is If it is determined that the rotation angle θ _A is not within the allowable range, the process proceeds to step S19, and it is determined that the rotation angle θ _A is abnormal, and the process proceeds to step S20 shown in FIG. . The normality / abnormality of the rotation angle θ _A is displayed on the display unit 10c in steps S18 and S19.

Next, in step S20, it is determined whether the rotation angle θ _B is within the allowable range, and if it is determined that the rotation angle θ _B is within the allowable range, the process proceeds to step S21, and the rotation angle θ _B is normal. , While proceeding to step S23,
If it is determined that the rotation angle θ _B is not within the allowable range, the process proceeds to step S22, and it is determined that the rotation angle θ _B is abnormal, and the process proceeds to step S23. The normality / abnormality of the rotation angle θ _B in steps S21 and S22 is displayed on the display unit 10c.

Next, in step S23, the absolute value of the angular difference (θ _A −θ _B ) between the rotation angle θ _A and the rotation angle θ _B is the predetermined angle Δ.
If it is determined that the absolute value of the angle difference (θ _A −θ _B ) is less than the predetermined angle Δθ, it is determined in step S24.
Then, the process ends, assuming that the device is normal.
On the other hand, if it is determined in step S23 that the absolute value of the angle difference (θ _A −θ _B ) is greater than or equal to the predetermined angle Δθ, the process proceeds to step S25, and this process is terminated because the device is abnormal. The normality / abnormality of the device in steps S24 and S25 is displayed on the display unit 10c.

As described above, when the control unit 10 starts the AC motor 4, the drive shaft 1 is rotated by the rotation output of the AC motor 4 decelerated by the speed reducer 3 to tighten the nut. Then, the output shaft 12 of the AC motor 4
Encoder 5 and magnetic switch 14 for detecting the rotation angle of
Detects substantially the same rotation angles θ _A and θ _B from when the tightening torque T exceeds the angle start torque T _A to when the tightening is completed. The magnetic switch 14 has a simple structure and is resistant to vibration and impact during tightening, and since there are few signal lines to be connected and there is almost no risk of disconnection, even if the encoder 5 fails, the magnetic switch 14 Since the rotation angle θ _B is accurately detected, the angular difference (θ _A −θ _B ) between the rotation angles detected by the encoder 5 and the magnetic switch 14 becomes large, and it can be determined that the device is in failure. Therefore, the abnormality of the tightening device can be easily determined.

The encoder 5 and the magnetic switch 1 are also provided.
4, the rotation angles θ _A and θ _B of the output shaft 12 of the AC motor 4
And the angle difference (θ) between the rotation angle θ _A detected by the encoder 5 and the rotation angle θ _B detected by the magnetic switch 14 by the angle difference calculation unit 10a.
_A− θ _B ), and the angle difference determination unit 10b calculates the angle difference.
If it is determined that the absolute value of (θ _A −θ _B ) is not less than or equal to the predetermined angle Δθ, the display unit 10c notifies the operator of the determination result. Therefore, the failure of the encoder 5 can be reliably determined by the angle difference calculation unit 10a and the angle difference determination unit 10b, the determination result can be easily recognized by the operator, and the tightening work can be stopped promptly. It is possible to reduce the risk of sending defective products. Further, since the failure location of this tightening device is known, the recovery time can be shortened.

(Second Embodiment) FIG. 4 is a schematic view of a tightening device according to a second embodiment of the present invention. This tightening device has the same configuration as the tightening device of the first embodiment shown in FIG. 1 except for the torque sensor and the control unit, and the same components are designated by the same reference numerals and their description is omitted. To do. As shown in FIG.
The tightening device includes a torque sensor portion 70 having one end fixed to the casing 30, and the drive shaft 1 is connected to the speed reducer 3 via the torque sensor portion 70. Then, the tightening device receives the signal indicating the rotation angle θ _A from the encoder 5, the signal indicating the rotation angle θ _B from the magnetic switch 14 and the signal indicating the tightening torque from the torque sensor unit 70, and receives the AC A control unit 60 that controls the motor 4 is provided.

As shown in FIG. 5, the torque sensor portion 70 is provided with a cylindrical member 73 through which the drive shaft 1 penetrates. One end of the cylindrical member 73 is a bolt 75 on the casing 30.
And a large diameter portion 73b connected to the flange 73a, and a small diameter portion 73c connected to the large diameter portion 73b and having one end fixed to the speed reducer 3. The torque sensor section 70 includes a strain gauge type first torque sensor 71 provided on the outer periphery of a small diameter section 73c of the cylindrical member 73, and a large diameter section 73b of the cylindrical member 73.
And a strain gauge type second torque sensor 72 provided on the outer periphery of the. In addition, when the cylindrical member 73 is twisted by a reaction force caused by the rotation of the drive shaft 1 during tightening,
Since the small-diameter portion 73c having a thin wall thickness has a larger strain amount than the large-diameter portion 73b having a large wall thickness in the radial direction, the sensitivity for detecting the tightening torque of the first torque sensor 71 is determined by the second torque sensor. The output levels of the first and second torque sensors 71 and 72 are set to be substantially equal to each other.

The control unit 60 is composed of a microcomputer, an input / output circuit, etc., and, as shown in FIG. 4, the angle difference (θ _A −θ _B ) between the rotation angle θ _A and the rotation angle θ _B is calculated. An angle difference calculation unit 60a as an angle difference calculation means for calculating,
The angle difference calculated by the angle difference calculation unit 60a (θ _A −
The angle difference determination unit 6 as an angle difference determination means for determining θ _B ).
0b and a display unit 60c as a notification means for displaying the determination result of the angle difference determination unit 60b, and the torque difference (T _A -T _B ) between the tightening torque T _A and the tightening torque T _B. Torque difference calculation unit 60d as a torque difference calculation means for calculating
When, and a torque difference determining unit 60e of the torque difference determining means for determining the torque difference calculated by the torque difference calculation section 60d to (T _A -T _B).

In the tightening device having the above structure, the socket 11 is fitted into the nut (not shown) as the object to be tightened, and the AC motor 4 is started by the control unit 60.
The rotation output of is reduced and increased by the speed reducer 3 to drive the drive shaft 1. Then, similarly to the tightening device of the first embodiment, the control unit 60 controls to tighten the nut,
After tightening the nut, the torque sensor 71,
Based on the output of 72 and the output of the encoder 5, it is determined whether or not the nut is normally tightened, and based on the outputs of the torque sensors 71 and 72, the output of the encoder 5, and the output of the magnetic switch 14, It is determined whether or not this tightening device is normal. In this case, the output of either one of the first and second torque sensors 71 and 72 is selected.

The tightening device has the same effect as the tightening device of the first embodiment, and at the time of tightening,
The first torque sensor 71 having a low detection sensitivity is attached to the outer peripheral side of the small diameter portion 73c of the cylindrical member 73 having a large amount of strain so that the outputs of the second torque sensors 71 and 72 are substantially at the same level, and the detection is performed. The second torque sensor 72 on the high sensitivity side is provided with a large diameter portion 73b of the cylindrical member 73 with a small amount of strain.
Since the first torque sensor 71 having a large amount of strain has a higher failure rate than the second torque sensor 72, the first torque sensor 71 having a large amount of strain has a higher failure rate. Therefore, the second torque sensors 71 and 72 do not simultaneously fail. Therefore, even if one of the first and second torque sensors 71 and 72 fails, the other torque sensor can be used to continue the tightening work.
You can avoid stopping the production line.

The first torque sensor 71 detects the tightening torque of the drive shaft 1 and the second torque sensor 7 detects the tightening torque.
2 detects the tightening torque of the drive shaft 1, and the torque difference calculator 60d detects the tightening torque of the first torque sensor 71.
Torque difference between the tightening torque T _A detected by the second torque sensor 72 and the tightening torque T _B detected by the second torque sensor 72 (T _A
-T _B ), and when the torque difference determination unit 60d determines that the absolute value of the torque difference (T _A −T _B ) is not less than or equal to the predetermined torque, the display unit 60c notifies the operator of the determination result. . Therefore, the first and second torque sensors 71,
The failure of 72 can be surely judged, the judgment result can be easily recognized by the operator, the tightening work can be stopped promptly, and the failure point of this tightening device can be known, so that the recovery time is shortened. be able to.

In the first and second embodiments described above, the magnetic switch 14 is used as the proximity switch for detecting the rotation angle θ _B of the output shaft 12 of the AC motor 4, but a proximity switch or encoder using a photo sensor or the like may be used. You may use.

Further, in the first and second embodiments, the tightening of the nut as the object to be tightened has been described, but the object to be tightened is not limited to the nut, and the object to be tightened according to the present invention is not limited to the nut. Can be widely applied.

Although the AC motor 4 is used as the motor in the first and second embodiments, an air motor or the like may be used.

Further, in the first and second embodiments, the resolution of the encoder 5 and the resolution of the magnetic switch 14 as the proximity switch may be set to appropriate values.

[0044]

As is apparent from the above, the tightening device according to the first aspect of the present invention tightens the object to be tightened such as the nut by rotating the drive shaft by the rotation output of the motor that is decelerated by the speed reducer. The encoder detects the rotation angle of the rotation axis of the motor and the proximity switch detects the rotation angle of the output shaft of the motor, and determines whether or not the device is defective based on the output of the encoder and the output of the proximity switch. Therefore, even if the encoder fails, the proximity switch, which is resistant to vibration and shock during tightening, and has few signal lines and little risk of disconnection, accurately detects the rotation angle, so the encoder and proximity switch can detect each It is possible to determine that there is a device failure because the angle difference between the rotation angles thus obtained becomes large. Therefore, the abnormality of the tightening device can be easily determined.

According to a second aspect of the present invention, there is provided a tightening device according to the first aspect, wherein the angle difference calculating means of the control means detects the rotation angle detected by the encoder and the rotation angle detected by the proximity switch. If the angle difference with the angle is calculated and the angle difference determination means of the control means determines that the angle difference is not within the predetermined angle, the notification means notifies the operator of the determination result, so that the encoder failure is surely performed. The tightening work can be stopped promptly by notifying the operator of the result of the judgment, and the failure location of the tightening device can be known, so that the recovery time can be shortened.

A tightening device according to a third aspect of the present invention is the tightening device according to the first or second aspect, wherein the torque sensor has a first torque sensor and a second torque sensor having different sensitivities for detecting the tightening torque. Since it is a torque sensor, the first and second torque sensors are attached to torque detection points with different strain amounts so that the outputs of the first and second torque sensors are at substantially the same level, and the above-mentioned drive shaft tightening is performed. When the applied torque is detected, the failure rate of the torque sensor having a large amount of strain becomes higher, and the first and second torque sensors do not fail at the same time. Therefore, when this tightening device is used in a production line, even if either one of the first and second torque sensors having different lifespans fails, the other torque sensor must be used to continue the tightening work. It does not stop the production line.

The tightening device of the invention of claim 4 is the tightening device of claim 3, wherein the tightening torque detected by the first torque sensor by the torque difference calculating means of the control means and the second tightening torque The torque difference with the tightening torque detected by the torque sensor is calculated, and when the torque difference determination means of the control means determines that the torque difference is not within the predetermined torque, the notification means notifies the operator of the determination result. Since a notification is sent, the encoder failure can be reliably determined, the operator can be notified of the result of the determination, and the tightening work can be stopped promptly. It can be shortened.

[Brief description of drawings]

FIG. 1 is a schematic view of a tightening device according to a first embodiment of the present invention.

FIG. 2 is a flow chart for explaining the operation of the control unit of the tightening device.

FIG. 3 is a flow chart for explaining the operation of the control unit of the tightening device.

FIG. 4 is a schematic view of a tightening device according to a second embodiment of the present invention.

FIG. 5 is an enlarged view of a main part of the tightening device.

FIG. 6 is a flowchart for explaining the operation of the control unit of the conventional tightening device.

FIG. 7 is a diagram showing changes in tightening torque when tightening using the tightening device.

[Explanation of symbols]

1 ... Drive shaft, 2 ... Torque sensor, 3 ... Reducer, 4 ... AC
Motor, 5 ... Encoder, 10 ... Control unit, 10a ... Angle difference calculation unit, 10b ... Angle difference determination unit, 10c ... Display unit, 11
... socket, 12 ... output shaft, 13 ... disk, 14 ... magnetic switch, 20 ... tightening portion, 30 ... casing.

Claims (4)

[Claims] 1. A motor, a speed reducer that reduces the rotational output of the motor, a drive shaft that is connected to the output shaft of the speed reducer and drives an object to be fastened, and a tightening torque of the drive shaft is detected. Torque sensor, an encoder that detects the rotation angle of the rotation shaft of the motor, a proximity switch that detects the rotation angle of the output shaft of the motor, and the motor based on the output of the torque sensor and the output of the encoder. The tightening device is characterized by being driven to perform the tightening control of the object to be tightened and provided with control means for judging whether or not there is a device failure based on the output of the encoder and the output of the proximity switch. . 2. The tightening device according to claim 1, wherein the control means calculates an angle difference between a rotation angle detected by the encoder and a rotation angle detected by the proximity switch. And an angle difference determination means for determining whether the angle difference calculated by the angle difference calculation means is within a predetermined angle, and the angle difference determination means determines that the angle difference is not within the predetermined angle, A fastening device comprising: a reporting means for reporting a determination result. 3. The tightening device according to claim 1 or 2, wherein the torque sensor is a first torque sensor and a second torque sensor having different sensitivities for detecting a tightening torque. Tightening device. 4. The tightening device according to claim 3, wherein the control unit controls the tightening torque detected by the first torque sensor and the tightening torque detected by the second torque sensor. The torque difference calculating means for calculating the torque difference and the torque difference determining means for determining whether or not the torque difference calculated by the torque difference calculating means is within a predetermined torque, wherein the torque difference determining means is the torque A fastening device characterized in that when it is determined that the difference is not within the predetermined torque, the determination result is reported by the reporting means.