JPH10180573A - Automatic parts fastener - Google Patents

Abstract

PROBLEM TO BE SOLVED: To complete fastening by final fastening torque by providing a control part outputting a command value in response to a target torque at every moment obtained from torque increasing acceleration to a driving part, and outputting a motor stopping command signal to the driving part after the lapse of a set time. SOLUTION: Even when target torque and detected torque are conformed to each other so as to make zero in difference of both torque until a measured time reaches a set time, target torque in a fastening process is only output to a driver bit 2b, hence even thereafter a command value is output from a control part 4 to a driving part 8, a motor 2a is continuously rotated, and fastening is continued along a torque-time characteristic curve. Further, when the target torque and the detected torque are conformed to each other after the measured time exceeds the set time, torque increasing acceleration is selected so that the detected torque reaches the final fastening torque at the point of time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic component fastening machine for fastening fasteners such as screws, bolts and nuts, and more particularly to a final tightening torque which is not affected by rotation of a motor immediately before reaching a final tightening torque. As described above, the present invention relates to an automatic component fastening machine that controls a motor to tighten components.

[0002]

2. Description of the Related Art Recently, a servomotor has been used as a rotary drive source of a fastening machine for fastening fastening parts such as screws, bolts, nuts and the like with a desired fastening torque because of its easy speed control. In this type of tightening machine, when the tightening torque approaches the final tightening torque, the speed of the servo motor is controlled and gradually reduced, and the tightening torque control is performed so that the torque does not exceed the final tightening torque due to the inertia of the motor. Has been made.

[0003]

For this reason, the fastening accuracy of this fastening machine has been considerably improved. However, since the speed of the servomotor is controlled while controlling the tightening torque, the control is responsive. And accurate tightening torque control was not possible. In addition, in this fastening machine, the detection of the completion of the tightening is performed by comparing the detected torque detected by the torque detecting means with the final tightening torque. Since the tightening torque is larger than the final tightening torque, accurate tightening torque control cannot be performed, and a tightening torque control method capable of eliminating these problems and performing more accurate tightening is desired.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned demands, and it is only necessary to set a final tightening torque and a set time to reach the final tightening torque, irrespective of the torque detected by the torque detecting means. It is an object of the present invention to provide an automatic component fastening machine capable of arbitrarily selecting a rising curve and completing tightening with a final tightening torque.

[0005]

A driving tool that rotates in response to rotation of a motor, torque detecting means for detecting a torque applied to the driving tool, a driving unit for supplying power to the motor, and a command value for the driving unit In the automatic component fastening machine provided with a control unit that sends a final tightening torque and a setting unit that sets a set time from the start of torque control to the final tightening torque is provided, the control unit determines from the set time and the final tightening torque A torque increase acceleration that reaches the final tightening torque is calculated, and a command value corresponding to a momentary target torque obtained from the torque increase acceleration is output to the drive unit, and a motor stop command signal is output after the lapse of the set time. Output.

[0006] The control section may have a configuration for integrating and compensating for the difference between the target torque and the torque detected by the torque detecting means.

Further, the control unit is configured to calculate a torque increase acceleration that reaches a tightening torque larger than the final tightening torque in a set time and output a command value corresponding to the acceleration to the drive unit. When the torque detected by the means reaches the final tightening torque, a tightening completion signal may be output to the drive unit.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 denotes a screw tightening machine as an example of an automatic component tightening machine, which has a tightening unit 2 which can be moved up and down by operation of an elevating means (not shown). The tightening unit 2 includes a motor 2a, a driver bit 2b as an example of a driving tool that rotates by receiving the rotation, and a torque detecting unit 2c that detects a torque applied thereto. The motor 2a is driven by power supplied from the control device 3, and is configured to tighten a screw supplied to the tip of the driver bit 2b to a predetermined counterpart (not shown).

The control device 3 includes a control section 4, an operation section 5 for outputting various command signals such as a work start signal, and a setting for setting a final tightening torque and a set time from the start of torque control to the final tightening torque. Section 6, a storage section 7 for storing various data, a drive section 8 for supplying power to the motor 2a in accordance with a command value from the control section 4, and a conversion of the detected value of the torque detecting means 2c into a digital value. It comprises an A / D converter 9 for sending this to an input port of the controller 4, and a display 10 for performing various displays.

When the control unit 4 receives the work start command signal, it activates the elevating means to lower the tightening unit 2 with respect to the counterpart material, and also issues a command value for rotating the motor 2a at a predetermined speed and the motor 2a. And a motor stop command signal for stopping the driving is output to the drive unit 8. When the control unit 4 detects that the screw is seated on the mating member by some means, the control unit 4 starts 1) time measurement as shown in FIG. 2) calls the final tightening torque τ _d. 3) Setting time to reach the final tightening torque tau _d t _d
Call. 4) reads the detected torque detected by the torque detecting means as the offset torque tau _off. 5) the set time _{t d} at a constant torque increase acceleration reaching the final tightening torque tau _d from the offset torque tau _off a =
Calculating a _{-2 (τ d -τ off) /} t d 2. 6) Set the previous integral compensation amount S = 0. 7) Read the measurement time. 8) An instantaneous target torque τ obtained from the torque increase acceleration a and the measurement time is calculated from the following equation, and a command value corresponding to the total torque of the target torque τ and the previous integral compensation amount S is output to the drive unit. I do. reads the detected torque detected by ^{τ = a · t 2/2} -a · t d · t + τ off 9) torque detecting means. 10) Calculate the difference e between the target torque τ and the detected torque. 11) It is determined whether the difference e is within a predetermined range from 0, and when the difference e is within the predetermined range, jump to 13). 12) The integral compensation amount S is calculated from the difference e between the target torque τ and the detected torque (S = S + K · e, where K is an integral gain), and the process returns to 7). 13) Read the measurement time. 14) Determine whether the measurement time is longer than the set time, and if this is short, return to 12). 15) Output a motor stop command signal (reset the measurement time). 16) Return. It is configured so that

It should be noted that the time set in step 14 may be compared with a time slightly longer than the set time. Further, the target torque τ is multiplied by a feedforward gain G, so that the control amount of the control target P can be arbitrarily controlled (see FIG. 3).

In the above screw tightening machine, when the final tightening torque τ _d and the set time t _d to reach the final torque are input from the setting unit 6 and the operation start command signal is output from the operation unit 5, the lifting and lowering is performed. Means, a command value for rotating the motor 2a at a predetermined speed is output to the drive unit 8, and the tightening unit 2 is driven by the driver bit 2b.
Descend while rotating.

When the screw at the tip of the driver bit 2b is tightened to the mating member and the seating of the screw is detected by some means, torque control is started and time measurement is started, and the final tightening torque τ _d and the set time are set. t _d and is called. The torque detected by the torque detecting means 2c for detecting the torque applied to the driver bit 2b is A
Read rare via -D converter 9, the torque at the time of the screw seating is stored as an offset torque tau _off.

The final tightening torque τ _d and the set time t
and _d, from the offset torque tau _off, a constant torque increase acceleration a to reach a final tightening torque tau _d time set from the start of torque control _{t d, a = -2 (τ} d -τ off) It is calculated as / _t ^{d 2.} From the torque increase acceleration a and the measurement time, the instantaneous target torque τ becomes τ = a. is calculated from _{^{t 2/2-a · t}} d · t + τ off, the target torque tau and the previous integral compensation amount S
A command value corresponding to the sum torque with (initial value = 0) is supplied to the drive unit 8.

Thereafter, the detected torque is read, and a difference e between the detected torque and the target torque τ is calculated. From the difference e, an integral compensation amount S is calculated as S = S + K · e (K is an integral gain), and a command value corresponding to a sum torque of the integral compensation amount S and the next target torque τ is repeatedly outputted to the driving unit 8.
Is output to

While this torque control is repeated, the target torque .tau.
Even if the difference is not transmitted to b, the difference is integrated and compensated at the next control. Also, before the measurement time reaches the set time,
Even if the target torque τ and the detected torque coincide with each other and the difference between the two torques becomes almost zero, it is merely that the target torque in the tightening process has been output to the driver bit 2b. Output to the motor 8a
Continuously rotates, and the tightening continues along the torque-hour characteristic curve shown in FIG. Further, when the target torque τ and the detected torque match after the measurement time has elapsed after the set time, the torque increase acceleration a is selected so that the detected torque reaches the final tightening torque at that time. When it is determined that the tightening is completed, a motor stop command signal is output to the drive unit 8, and the rotation of the motor 2a is stopped, whereby the tightening can be completed.

In the embodiment, the torque increase acceleration a that reaches the final tightening torque in the set time is calculated. However, the torque increase acceleration that reaches the tightening torque that is larger than the final tightening torque in the set time is calculated, and this is calculated. A corresponding command value is output to the drive unit 8, and the torque detecting means 2c is used together with the control of the target torque τ every moment.
When the detected torque reaches the final tightening torque, a tightening completion signal may be output to the drive unit 8.

[0018]

As described above, according to the present invention, the final tightening torque and the set time from the start of torque control to the final tightening torque are set, and the torque increase acceleration that reaches the final tightening torque is calculated in the set time. With
Even if the target torque momentarily matches the detected torque before the set time elapses, the motor is continuously rotated, and after the set time elapses, the motor is stopped when the target torque matches the detected torque. As a result, the tightening torque can be directly controlled, there is no control delay, and extremely accurate torque control can be performed. In addition, the tightening torque after the fastening parts such as screws are seated regardless of the hardness of the mating material In this case, there is an advantage that the ascending curve with the lapse of time can be made constant, the tightening can be performed without impact, and the tightening torque can be controlled without being affected by the speed of the motor immediately before the completion of the tightening. In addition, the present invention is configured such that the instantaneous target torque supplied to the motor in the tightening process is not transmitted to the driver bit, but is integrated during the next control, so that the final torque is accurately set after the set time. The tightening torque is transmitted to the driver bit, and extremely accurate tightening torque control can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic view of a screw tightening machine according to the present invention.

FIG. 2 is a flowchart illustrating an operation of the control unit according to the present invention during tightening torque control.

FIG. 3 is a block diagram of a control system of a control unit according to the present invention.

FIG. 4 is a torque-hour characteristic diagram according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Screw tightener 2 Tightening unit 2a Motor 2b Driver bit 2c Torque detection means 3 Control device 4 Control unit 5 Operation unit 6 Setting unit 7 Storage unit 8 Drive unit 9 A / D conversion unit 10 Display unit P Control target

Claims (3)

[Claims] 1. A driving tool that rotates by receiving rotation of a motor, a torque detecting unit that detects a torque applied to the driving tool, a driving unit that supplies power to the motor, and a control unit that sends a command value to the driving unit. In the automatic parts tightening machine provided with the above, a setting unit for setting the final tightening torque and the set time from the start of the torque control to reaching the final tightening torque is provided, and the control unit determines the final tightening torque from the set time and the final tightening torque. A torque increase acceleration to be reached is calculated, and a command value corresponding to a momentary target torque obtained from the torque increase acceleration is output to the drive unit, and a motor stop instruction signal is output to the drive unit after the lapse of the set time. An automatic parts fastening machine characterized in that: 2. The automatic component fastening machine according to claim 1, wherein the control section integrates and compensates for a difference between the target torque and the torque detected by the torque detecting means. 3. A driving tool which rotates in response to rotation of a motor, a torque detecting means for detecting a torque applied to the driving tool, a driving unit for supplying power to the motor, and a control unit for sending a command value to the driving unit. In the automatic component fastening machine provided with, a setting unit for setting a tightening torque larger than the final tightening torque and a set time from the start of the torque control to reaching the tightening torque is provided, and the control unit sets the set time, the tightening torque and From the torque increase acceleration to reach the tightening torque, and outputs a command value corresponding to the instantaneous target torque obtained from the torque increase acceleration to the drive unit, and the torque detected by the torque detecting means becomes the final tightening torque. The automatic component fastening machine is configured to output a motor stop command signal to a drive unit when the automatic stop is performed.