JPH06143154A - Control device for motor-operated nut runner - Google Patents

Abstract

PURPOSE:To perform accurate decision of whether normal fastening is executed and to improve reliability by providing a control circuit to monitor the torque value of a nut runner and two loops for an amount of a current to the motor of the nut runner. CONSTITUTION:It is decided by a first control circuit 3 whether a proper torque value is proper and an output for a fact that a torque value is proper or a fact that a torque value is +NG or -NG is transmitted. Further, when a current value exceeds a value preset by a current lower limit value detecting means, an output is transmitted. Further, it is decided by a second control circuit 5 that a fastening force is proper when a torque value is proper and a current value exceeds a set value, and it is decided thereby that a fastening force is improper in other case than the above.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for appropriately performing a tightening force of a nut in an electric nut runner for screwing and tightening a nut onto a bolt protruding from a workpiece.

[0002]

2. Description of the Related Art A conventional controller for an electric nutrunner will be described with reference to FIG. 1 is a nut runner, and the output shaft 1b fitted into the nut is rotated by the driving force of the motor 1a. Further, a torque sensor 1c for detecting the torque applied to the output shaft 1b is provided.

Reference numeral 2 is a torque detection circuit for converting the output from the torque sensor 1c of the nut runner 1 into a digital signal and outputting the digital signal. Reference numeral 3 is a microcomputer to which the output from the torque detection circuit 2 is input. As a circuit, the RAM 3a stores the target torque value and the upper limit value and the lower limit value of the allowable range of the target torque value. In addition,
3b is a ROM.

Reference numeral 4 is a motor control circuit for controlling the voltage applied to the motor 1a of the nut runner 1 by the output from the control circuit 3 to tighten the screw until a predetermined torque is generated. Reference numeral 5 is the first control circuit 3 7a, 7b, 7c for stopping the mechanical device 6 when the output from the first control circuit 3 is NG or displaying the NG output or the OK output from the first control circuit 3.
Is a second control circuit for driving the.

Next, the operation of the above-mentioned first control circuit 3 will be described with reference to the flow chart of FIG. 6. First, the operator sets a target torque value which is the tightening force desired by the bolt (step S1). Further, the upper limit value and the lower limit value of the allowable range of the target torque value are set (step S2).

Next, the first control circuit 3 monitors whether power is supplied to the motor 1a of the nut runner 1 and the motor 1a is started (step S3), and if it is determined that the motor 1a is energized, the torque sensor is detected. The torque value from the torque detection circuit 2 for detecting the output from 1c is stored in the RAM 3a (step S4), and it is monitored whether or not the torque value reaches the preset target torque value (step S5).

When it is judged that the target torque value has been reached, the energization of the motor 1a is cut off (step S6), and the maximum torque peak value from the torque detection circuit 2 is read out (step S7). Next, it is determined whether or not the read peak value is equal to or more than the upper limit set in advance in step S2 (step S8), and if it is determined to be equal to or more than the set value, the torque value determination + NG output is output to the second control circuit 5. (Step S9).

When it is determined that the peak value is equal to or less than the set value in the above determination, it is determined whether or not the read peak value is equal to or more than the lower limit value preset in step S2 (step S10). If it is determined that there is, the torque value-NG output is output to the second control circuit 5 (step S11).

Further, in the above judgment, it is judged that the torque is not less than the set value, that is, the target torque value is reached and the torque is between the upper limit value and the lower limit value, so the tightening force which is the torque value is appropriate. Then, the torque value OK output is output to the second control circuit 5 (step S12).

Then, torque value + NG output and torque value−
The second control circuit 5, which has received the NG output, stops the mechanical device 6 to which the nut runner 1 is attached, performs the -NG display and the + NG display, and confirms that the above has occurred.
When the output is received, the mechanical device 6 is continuously driven,
Moreover, the OK display is performed.

[0011]

By the way, since the above-described control device for the electric nutrunner determines whether the screw tightening force is proper or abnormal only by the output from the torque sensor 1c, a torque feedback loop is constructed. If any one of the parts, cables, etc., which is present, deteriorates or breaks, the reliability of the screw tightening force pass / fail judgment result is significantly reduced, leading to a defective accident.

The present invention is intended to solve the above-mentioned problems, and an object of the present invention is to detect a motor inflow current independently of a signal loop for detecting and returning the torque generated in the output shaft of the motor. It is intended to provide a control device for an electric nutrunner that improves reliability by newly providing a feedback signal loop and performing work determination by integrating both loops.

[0013]

The electric nutrun of the present invention
The control device of the gnar attempts to solve the above-mentioned problems.
The means is to use the motor output of the nutrunner.
A torque detection circuit for detecting the torque generated by the force axis, and the torque
Whether the torque output from the detection circuit is within the preset range
The first control circuit for determining the
The current detection circuit to detect and the output from the current detection circuit
Appropriate output when it is judged to be above the preset lower limit of current
Current lower limit value detection means for transmitting the
Flow output and proper torque output from the first control circuit are input
If it is tightened, it is judged that the tightening is proper, and
When there is no positive current output and when there is no proper torque output
Is a second control circuit that judges that the tightening is not proper
It consists of

Further, a torque detection circuit for detecting the motor output shaft generated torque mounted on the nut runner, a current detection circuit for detecting the current flowing in the motor, and a torque output from the torque detection circuit are in a preset range. And whether or not the current output from the current detection circuit is below a preset current value, the torque value is within an appropriate range, and the current value is above a set value. The first control circuit determines that the tightening is proper, and determines that the tightening is not proper when the torque value is equal to or higher than or equal to the proper torque and the current value is equal to or lower than the set current value. It consists of and.

[0015]

In the control device for the electric nutrunner of the present invention constructed as described above, the first control circuit judges whether the torque value is proper or not, and the torque value is proper, or the torque value is + NG or -NG. To send the output of
An output is sent out when the current lower limit value detecting means exceeds a preset current value, and a proper tightening is performed by the second control circuit when the torque value is proper and the current value exceeds the preset value. It is determined that the force is the force, and in other cases, it is determined that the tightening force is inappropriate.

Further, the first control circuit judges whether the torque value is proper or not to judge whether the torque value is proper or not, and whether the torque value is + NG or -NG, and the current flowing through the motor is preset. It is determined whether it is less than or equal to the lower limit value, and further, when the torque value is appropriate and the current value exceeds the set value, it is determined that the tightening force is appropriate,
In other cases, it is determined that the tightening force is inappropriate.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a first embodiment of a control device for an electric nutrunner according to the present invention will be described with reference to FIG. The same reference numerals as those in FIG. 5 in the above-mentioned conventional example indicate the same parts, and the description thereof will be omitted. 8 is a motor 1 of the electric nut runner 1.
A motor current detection circuit for detecting the amount of current flowing through a is configured to average analog instantaneous values and ignore spike-like large currents due to noise or the like. 9
Is a comparison circuit that outputs when the output from the motor current detection circuit 8 is higher than the output from the preset reference voltage source 9a, and the output from the comparison circuit 9 is input to the second control circuit 5. This is different from the conventional control device.

The second control circuit 5 includes two AND circuits 5
a, 5b, OR circuit 5c, and three inverters 5d-
5f, and the output from the AND circuit 5b is input to the display 7d that displays the overall determination OK, and OR
The output from the circuit 5c is a display 7 that displays a comprehensive judgment NO.
It is input to e.

Next, the operation of the control device for the electric nutrunner having the above-mentioned structure will be described with reference to the flow chart of FIG. The operation up to step S12 is the same as the operation of the conventional example described above, and the + NG output, the -NG output, the OK output, and the output from the comparison circuit 9 are input to the second control circuit 5.

When the output from the comparison circuit 9 is at a low level (the output from the motor current detection circuit 8 does not exceed a preset value), it is inverted by the inverter circuit 5d to become a high level output and the OR circuit. 5c is input. Also, when the output from the first control circuit 3 is the torque value determination OK, it is inverted by the inverter circuit 5e and becomes a high level output, which is input to the OR circuit 5c.

Therefore, since the high level output is sent from the OR circuit 5c, the comprehensive judgment NG display 7d is driven and the driving of the mechanical device 6 is stopped. The output from the comparison circuit 9 and the torque value determination OK output from the first control circuit 3 are input to the OR circuit 5c for some reason (the comparison circuit 9 and the first control circuit 3 are out of order). This is for operating the mechanical device 6 on the safe side when a signal is sent.

When the output from the first control circuit 3 is the torque value judgment + NG or -NG, these outputs are input to the OR circuit 5c.
It is output from c and drives the comprehensive judgment NG display 7d, and stops driving the mechanical device 6.

When the output from the comparison circuit 9 is at a high level (the output from the motor current detection circuit 8 exceeds the preset value), and the output from the first control circuit 3 is the torque value determination. In the case of OK, the output is sent from the AND circuit 5a. Then, this output is input to one input terminal of the AND circuit 5b.

OR is applied to the other input terminal of the AND circuit 5b.
Since the output from the circuit 5c is inverted by the inverter circuit 5f, the output is sent from the AND circuit 5b and the comprehensive judgment OK indicator 7d is displayed when the output from the AND circuit 5c is not present. While driving, the mechanical device 6 is continuously driven.

In the above operation, the OR circuit 5
The inverted output from c is applied to the AND circuit 5f when the OR circuit 5c is at a low level when it should output a high level for some reason.
This is for operating the mechanical device 6 on the safe side.

Next, a second embodiment of the present invention will be described with reference to FIG.
As will be described later, in the first embodiment, the output from the motor current detection circuit 8 is input to the first control circuit 3, and the comprehensive judgment OK or NG output is sent from the first control circuit 3. The difference is that this is done.

The operation will be described below with reference to FIG.
Up to step S12 is the same as the conventional example described above,
In the initial setting, the motor current lower limit value is set (step S13). Then, when the motor 1a of the nut runner 1 starts driving, the current value from the motor current detection circuit 8 is stored in the RAM 3a (step S14).

When it is determined in step S5 that the target torque value has been reached, the current detection circuit 8
The current peak value, which is the maximum output from, is read (step S15). Then, it is determined whether or not the read peak value is equal to or more than the lower limit value preset in step S13 (step S16), and if it is determined to be less than the set value, the output is input to the OR circuit 5c. When it is determined that the value is equal to or larger than the set value, the output is output from the AND circuit 5a.
To enter.

The OR circuit 5c outputs torque value judgment + NG output,
When any of the torque value judgment-NG output, the output of the motor current value lower limit value or less or the inverted output of the torque value judgment OK output is inputted, the comprehensive judgment NG output is sent out, and the AN
The D circuit 5a sends the output when the torque value determination OK output and the output of the motor current lower limit value or more are input, and AND
When the output from the AND circuit 5a and the inverted output from the OR circuit 5c are input to the circuit 5b, the circuit 5b sends out the output of comprehensive determination OK.

Therefore, in the former case, the comprehensive judgment NG indicator 7e is driven and the driving of the mechanical device 6 is stopped,
In the latter case, the comprehensive judgment OK display 7d is driven and the mechanical device 6 is continuously driven.

In the first and second embodiments, in the case of the second embodiment, if the first control circuit 3 fails for some reason, the determination cannot be made. First
This embodiment is different in that the safety side (general judgment NG) is output when the first control circuit 3 becomes defective.

[0032]

As described above, according to the present invention, two loops of the torque value of the nut runner and the amount of current flowing through the motor of the nut runner are monitored. The judgment function can be accurately performed, and the judgment function itself can be distributed in two places to improve reliability, and a small amount of investment can provide equipment with high reliability. is there.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a flowchart of a control circuit of the above.

FIG. 3 is a block diagram showing a second embodiment of the present invention.

FIG. 4 is a flowchart of a control circuit of the above.

FIG. 5 is a block diagram of a conventional example.

FIG. 6 is a flowchart of the control circuit of the above.

[Explanation of symbols]

 1 Nut Runner 1a Motor 1c Torque Sensor 2 Torque Detection Circuit 3 First Control Circuit 4 Motor Control Circuit 5 Second Control Circuit 6 Machinery 8 Motor Current Detection Circuit

Claims (2)

[Claims] 1. A torque detection circuit for detecting a motor output shaft generated torque mounted on a nut runner, and a first control circuit for judging whether or not a torque output from the torque detection circuit is within a preset range. A current detection circuit that detects a current flowing through the motor, a current lower limit value detection unit that outputs an appropriate output when it is determined that the output from the current detection circuit is equal to or more than a preset lower limit value of the current, and an appropriate value from the unit. When the current output and the proper torque output from the first control circuit are input, it is determined that the tightening is proper, and when there is no proper current output or when the torque is not the proper torque, it is determined that the tightening is not proper. A control device for an electric nutrunner, which comprises a second control circuit for 2. A torque detection circuit for detecting a motor output shaft generated torque mounted on a nut runner, a current detection circuit for detecting a current flowing through the motor, and a torque output from the torque detection circuit in a preset range. And whether or not the current output from the current detection circuit is below a preset current value, the torque value is within an appropriate range, and the current value is above a set value. The first control circuit determines that the tightening is proper, and determines that the tightening is not proper when the torque value is equal to or higher than or equal to the proper torque and the current value is equal to or lower than the set current value. Control device for electric nutrunner.