JPH0732973B2 - Tightening quality judgment device of automatic screw tightener - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention switches the motor from high speed to low speed at the time when the tightening torque reaches the temporary tightening torque value, and at the same time, the time until the predetermined tightening torque value is reached. The present invention relates to a tightening quality judgment device for an automatic screw tightening machine, which is configured to judge whether the tightening is good or bad depending on whether or not the value is within a predetermined time.

[Prior Art] Recently, strict control of tightening torque has been required, and a stock detection mechanism configured to detect a load torque of a driver bit at the time of tightening and match it with a predetermined tightening torque is provided. Many automatic screw tighteners are used. In this type of automatic screw tightening machine, in order to perform more accurate tightening, the tightening torque at the time when the seat surface of the screw is seated on the workpiece is taken as the temporary tightening torque value, and at this time the motor is switched from high speed to low speed to complete tightening. It is configured to reduce the influence of the inertia of the motor. In addition, this automatic screw tightener statistically calculates the time from the temporary tightening torque value to the predetermined tightening torque value so that abnormalities such as oblique biting of the screw can be detected, and from this, the time range for judging the quality of tightening is determined. A fastening quality determination device that determines whether or not the fastening quality is good is based on whether or not the time point at which the detected torque reaches a predetermined fastening torque value is within the determination time width.

[Problems to be Solved by the Invention] In this tightening quality determination device, although the influence of inertia upon completion of tightening is reduced, the motor is temporarily stopped when the temporary tightening torque value is reached, and the motor is changed from high speed to low speed. Therefore, due to the inertia of the motor when the temporary tightening torque value is reached, the tightening torque during low-speed motor start exceeds the temporary tightening torque value, and this tightening torque is different for each tightening work. There is. for that reason,
The tightening torque value at the start of tightening during low-speed driving varies, and there is a drawback in that even if the tightening quality is judged from the time when the temporary tightening torque value is reached, the correct tightening quality cannot be determined.

The present invention aims to eliminate the above-mentioned drawbacks, and corrects the determination time width for determining the quality of tightening as the tightening torque at the time of switching the motor speed changes due to the influence of the inertia of the motor at that time. An object of the present invention is to provide a tightening quality determination device for an automatic screw tightening machine configured as described above.

[Means for Solving the Problems] In order to solve the above problems, a motor is fixed to a driver body that moves up and down by the operation of a lifting drive source, and a driver bit that rotates by receiving the rotation of its drive shaft is arranged. The load torque related to the bit is detected by the torque detection mechanism, and when the detected torque reaches the tightening torque value, the motor is temporarily stopped, then the motor is rotated at a low speed, and when the detected torque reaches the predetermined tightening torque value, the torque is increased. While the signal is transmitted, the automatic screw tightener configured to determine whether the tightening is good or not depending on whether or not the torque-up signal is transmitted within the determination time defined by the lower limit determination time and the upper limit determination time from the time point. In the tightening quality judgment device, the lower limit that defines the judgment time from the time when the detected torque reaches the temporary tightening torque value. Storage means for storing constant time and upper limit determination time, means for measuring the stop time from when the detected torque reaches the temporary tightening torque value until the motor stops, and this stop time and the lower limit determination time, upper limit determination time respectively And the difference between the lower limit determination time and the upper limit determination time previously calculated, and the subtracted values are added to the lower limit determination time and the upper limit determination time stored in the storage unit. A means for calculating the lower limit determination time and the upper limit determination time is provided.

Further, instead of the means for measuring the stop time, a decrease time until the motor decreases to a predetermined low speed is measured, and based on this decrease time, a similar new lower limit judgment time and upper limit judgment time are calculated. Good.

[Operation] In the above automatic screw tightening machine, the load torque related to the driver bit is detected by the torque detection mechanism as the tightening is started. When the detected torque reaches the temporary tightening torque value, the motor is switched from high speed to low speed.
The power supply to the motor is reduced for low speed,
Clock counting starts. At the same time, the time from this point until the motor stops or drops to a predetermined low speed and the time until the detected torque reaches the predetermined tightening torque are measured. When the motor is stopped or lowered to a predetermined low speed, the motor is held and driven at the predetermined low speed. At this time, the difference between the time required for the motor to stop or decrease to a predetermined speed after reaching the temporary tightening torque value and the preset determination time is calculated. This difference and the previously calculated lower and upper limit determination times are subtracted,
That is, the stop time or decrease time at this time and the previous stop time or decrease time are subtracted, and the subtracted value is added to the lower limit and upper limit judgment times stored in the storage unit to calculate a new judgment time.

After that, the load torque related to the driver bit is continuously detected by the torque detection mechanism, and when the detected torque reaches the predetermined tightening torque value, the torque-up signal is transmitted and this time is the newly calculated determination time. It is determined whether or not In this case, there is a variation in the tightening torque value due to the inertia of the motor at the start of the low speed drive, but this is detected as a variation in the motor stop or decrease time and the determination time is corrected accordingly. The quality of tightening can be determined based on the new determination time after correction, and the quality of tightening can be accurately determined.

Embodiments Embodiments will be described below with reference to the drawings. In FIG. 1, reference numeral 1 is an automatic screw tightening machine, which has a motor 2 and a driver bit 4 that receives rotation of the motor 2 via a connecting shaft 3 and integrally rotates. The motor 2 is held by a driver base 7 that is moved up and down by the operation of the elevation drive source 6 via a strain tube 5a forming a part of the torque detection mechanism 5, and the motor 2 and the elevation drive source 6 operate to drive the driver. When the bit 4 tightens a screw (not shown) to a work (not shown), the reaction force generated in the driver bit 4 according to the load torque rotates the strain tube 5a. A detection resistor composed of four strain gauges 5b is attached to the outer periphery of the strain tube 5a so as to form a bridge circuit.
A reference voltage supply unit (not shown) is connected to the input end of this bridge circuit, and the amplification unit 5c from the output end of the bridge circuit,
Torque detection mechanism 5 via filter 5d and A / D converter 5e
The detection torque is obtained.

Further, the control unit 8 of the automatic screw tightening machine 1 is composed of a microcomputer, and the work starting unit 10 through the input side of the I / O interface 9 and the temporary tightening torque value indicating the time when the screw is seated on the work. A first setting unit 11, which stores
A second setting unit 12 that stores a desired tightening torque value, a motor stop detection unit 13 that detects the stop of the motor 2 by detecting the stop of the driver bit 4, and an original position confirmation unit 14 are connected. Also, the control unit 8 theoretically ignores the influence of the inertia of the motor 2 from the temporary tightening torque value, the predetermined tightening torque value, and the speed of the motor 2 at a low speed, and theoretically changes the temporary tightening torque value to the predetermined tightening torque value. Is calculated, the lower limit determination time and the upper limit determination time are calculated based on this time, and these are stored in a storage unit (not shown).

To the control unit 8, a command value is sent to the elevation drive source 6 for raising and lowering the driver base 7 via the output side of the I / O interface 9 and the motor 2 to supply power from the power supply unit 15a. A motor drive unit 15 for controlling the rotation of the motor and a display unit 16 for displaying the detected torque of the torque detection mechanism 5 and the presence / absence of tightening abnormality are connected. This control unit 8
It is configured to send a conversion command signal to the AD converter 5e via the output side of the I / O interface 9. The control unit 8 has a first timer (not shown) having a lower limit determination time stored in the storage unit as a first timer time, and a second timer having an upper limit determination time stored in the storage unit as a second timer time. It has a timer (not shown) and a third timer (not shown) that measures the stop time from when the power supply stop command signal is transmitted to the motor 2 until the motor 2 stops. The signal and the time measurement value are read out at any time.

Further, as shown in FIG. 2, the control unit 8: 1) When receiving the work start signal from the work start unit 10, resets the ideograph.

2) A high speed rotation command signal is sent to the motor drive unit 15 and a descending command signal is sent to the lifting drive source 6.

3) Send an A-D conversion command signal to the A-D converter 5e.

4) The output signal of the AD converter 5e is compared with the first set value stored in the first setting section 11 as the temporary tightening torque value, and when they do not match, the process returns to 3).

5) A power supply stop command signal is sent to the motor 2 and the timer times of the first timer and the second timer are set as the lower limit determination time and the upper limit determination time stored in the storage unit, respectively, and these first timer, second timer and The third timer is activated and time counting is started.

6) Wait for a stop detection signal from the motor stop detection unit 13.

7) A low speed rotation command signal is sent to the motor drive unit 15, the time measurement value of the third timer is stored as a stop time, and the difference between the lower limit judgment time and the upper limit judgment time and the stop time is calculated. The lower limit and upper limit determination times calculated last time are subtracted from this, and the subtracted values are added to the lower limit and upper limit determination times stored in the storage unit to calculate a new determination time. Reset the time.

8) It is determined whether or not there is a time-up signal from the first timer that is newly set as the timer time, the newly calculated lower limit determination time, and when the time-up signal is not transmitted,
16) Jump to.

9) The presence / absence of a time-up signal from the second timer, which has been reset as the timer time, which is newly calculated as the upper limit determination time, is determined, and when the time-up signal is transmitted, an abnormality display command is sent to the display unit 16. , 14) jump to.

10) Detected torque is the second tightening torque value
When the second set value stored in 12 is not reached, the process returns to 9).

11) Reset the second timer.

12) Display the torque display command signal that displays the detected torque
Send to 16.

13) Send a normal display command signal to the display section 16.

14) Send a lift command signal to the lifting drive source 6.

It has an original position confirmation signal from the original position confirmation unit 14.

15) End 16) When the detected torque has not reached the second set value,
Return to 8).

17) Send an error display command to the display section 16.

18) Reset the first timer and return to 14).

It is configured to operate in the above operation sequence.

In the above automatic screw tightener, when the temporary tightening torque value, the predetermined tightening torque value, and the speed of the motor 2 at a low speed are input before the work start signal is transmitted, the temporary tightening torque value is changed to the predetermined tightening torque. The time required to reach it is calculated, and based on this time, the lower limit judgment time and the upper limit judgment time of the tightening quality judgment time are calculated. The lower limit determination time and the upper limit determination time are stored in the storage unit. The lower limit determination time and the upper limit determination time may be calculated and stored in advance.

After that, when a work start signal is transmitted, the previous display is reset, the elevating drive source 6 is activated, and a high-speed rotation command signal is sent to the motor drive unit 15 so that the power supply unit
Power is supplied to the motor 2 from 15a, and the motor 2 rotates at high speed. As the tightening work progresses, the load torque detection mechanism 5 related to the driver bit 4 detects the torque, and the detected torque is compared with the first set value which is the temporary tightening torque value. When the detected torque reaches the temporary tightening torque value, the motor stop command signal is sent, and the first timer and the second timer that set the timer time as the lower limit determination time and the upper limit determination time stored in the storage unit, respectively, and the motor 2 The 3rd timer which measures the stop time until it stops starts time counting. At the same time, it waits for a stop detection signal from the motor stop detection unit 13, and when this signal is transmitted, it sends a low speed rotation command signal to the motor 2 as well as a first timer and a second timer.
Whether or not there is a time-up signal from the timer is determined.

At the same time, the time measured value of the third timer at this time is read as the stop time, and each time the read is performed, the difference between the stop time and the lower limit determination time and the upper limit determination time stored in the storage unit is calculated. Furthermore, this difference and the first calculated last time
A timer, a lower limit determination time that forms the timer time of the second timer,
The upper limit determination time is subtracted from each other, that is, the stop time at this time and the previous stop time are subtracted, and the subtracted value is added to the lower limit determination time and the upper limit determination time stored in the storage unit to obtain a new lower limit. The determination time and the upper limit determination time are calculated. The new lower limit determination time and the new upper limit determination time are reset as the timer times of the first timer and the second timer.
It should be noted that this resetting is performed in a short time only by changing the timer time because each timer is configured inside the control unit. Further, it goes without saying that the torque does not increase when the motor 22 is switched.

In this state, the presence or absence of the time-up signal of the first timer is determined. When the time-up signal is not transmitted from the first timer, the detected torque of the torque detection mechanism 5 is compared with the second setting section of the second setting section 12 having the predetermined tightening torque value. When the detected torque does not reach the second set value, the presence / absence of the time-up signal of the first timer is determined again. Further, when the detected torque reaches the second set value and the torque-up signal is transmitted, since it is before the lower limit determination time has elapsed, it is determined that abnormal tightening such as diagonal biting occurs, and the abnormality display command signal is displayed. It is sent to the part 16 and the abnormal tightening is displayed on the display part 16.

Further, when the time-up signal is transmitted from the first timer, it is determined whether or not there is a time-up signal from the second timer. When the time-up signal is transmitted from the second timer, the abnormality display command is sent to the display unit 16 and the abnormality is displayed. Further, when the time-up signal is not transmitted from the second timer, the second detected torque of the torque detection mechanism 5 and the predetermined tightening torque value are obtained.
The set value is compared. When the detected torque does not reach the second set value and the torque-up signal is not transmitted, the presence / absence of the time-up signal of the second timer is determined again.
On the other hand, when the torque-up signal is transmitted, since the upper limit determination time has not yet elapsed, it is determined that the tightening is normal, and the normal display command signal is displayed together with the detected torque value on the display unit 16.
Will be sent to and the normal tightening will be displayed.

After that, when a lift command signal is transmitted to the lifting drive source 6 and the lifting drive source 6 returns and returns to the original position, the original position confirmation unit
Confirmed at 14, all work can be completed.

[Effects of the Invention] As described above, according to the present invention, the rotation of the motor is switched from the high speed to the low speed to perform the tightening work, and the switching time is the time when the temporary tightening torque value lower than the predetermined tightening torque value is reached. At the same time, whether or not the tightening is good is judged by whether or not the torque-up signal is transmitted within the predetermined time width from this point, and when the temporary tightening torque value is reached, the variation in the tightening torque value due to the inertia of the motor is Since it is configured to detect a stop time or a decrease time to a predetermined low speed, subtract these times from the previous time, and add the subtracted value to the predetermined judgment time to calculate a new judgment time. Even if the tightening torque value at the start of low-speed tightening varies due to the inertia of the motor when switching the motor speed, the judgment time is corrected according to this variation. Therefore, it is possible to accurately judge the quality of tightening at the time of low speed driving. Further, since the present invention is configured such that the judgment of the quality of tightening is performed at the time when the timer that counts the judgment time is up, if the upper limit judgment time is reached even if the tightening is not completed due to a defective screw. There is an advantage that it can be processed as an abnormality and no special defect detection is required.

In the embodiment, when the motor speed is switched, the motor is temporarily stopped and then the motor is driven at a low speed.However, when the speed is reduced to a predetermined speed, the motor is driven so as to maintain the speed. However, the same effect can be obtained.

[Brief description of drawings]

FIG. 1 is an overall explanatory block diagram of the present invention, and FIG. 2 is a flowchart explaining the operation of the present invention. 1 ... Automatic screw tightener, 2 ... motor, 3 ... connecting shaft,
4 …… Driver bit, 5 …… Torque detection mechanism, 5a ……
Strain tube, 5b ... Strain gauge, 5c ... Amplifying section, 5d ... Filter, 5e ... A-D converting section, 6 ... Lifting drive source, 7 ...
Driver stand, 8 ... control unit, 9 ... I / O interface, 10 ... work start unit, 11 ... first setting unit, 12 ...
2nd setting part, 13 ... Motor stop detection part, 14 ... Original position confirmation part, 15 ... Motor drive part, 15a ... Power supply part, 16
...... Display,

Claims (2)

[Claims] Claim: What is claimed is: 1. A motor is fixed to a driver main body that is moved up and down by the operation of an up-and-down drive source, and a driver bit that rotates by receiving the rotation of its drive shaft is arranged. Then, when the detected torque reaches the tightening torque value, the motor is temporarily stopped, then the motor is rotated at a low speed, and when the detected torque reaches the predetermined tightening torque value, a torque up signal is transmitted while the torque up signal is In the tightening pass / fail judgment device of the automatic screw tightener configured to judge whether the tightening is good or bad by transmitting within the judgment time defined by the lower limit judgment time and the upper limit judgment time from the time point, the detected torque is Storage means for storing a lower limit determination time and an upper limit determination time that define the determination time from the time when the temporary tightening torque value is reached , Means for measuring the stop time from when the detected torque reaches the temporary tightening torque value to when the motor stops, and the difference between this stop time and the lower limit judgment time and upper limit judgment time, and these A means for calculating new lower limit determination time and upper limit determination time by subtracting from the calculated lower limit determination time and upper limit determination time and adding the subtracted values to the lower limit determination time and upper limit determination time stored in the storage unit, respectively. An automatic screw tightener tightening quality determination device characterized by being provided. 2. A motor is fixed to a driver main body that moves up and down by the operation of a vertical drive source, and a driver bit that rotates by receiving the rotation of its drive shaft is arranged, and a load torque related to this driver bit is detected by a torque detection mechanism. Then, when the detected torque reaches the tightening torque value, the motor is rotated at a low speed, and when the detected torque reaches the predetermined tightening torque value, a torque up signal is transmitted, while this torque up signal is the lower limit judgment time from the time point. In the tightening quality judgment device of the automatic screw tightener configured to judge whether the tightening is good or bad depending on whether the signal is transmitted within the judgment time specified by the upper limit judgment time and from the time when the detected torque reaches the temporary tightening torque value. The storage means for storing the lower limit judgment time and the upper limit judgment time that specify the judgment time of Means for measuring the decrease time for the motor to decrease to a predetermined low speed after reaching, and the difference between the decrease time and the lower limit determination time, the upper limit determination time, and further calculate the lower limit determination time calculated previously, respectively. It is characterized by comprising means for subtracting from the upper limit determination time and adding the subtracted values to the lower limit determination time and upper limit determination time stored in the storage unit to calculate new lower limit determination time and new upper limit determination time. Tightening quality judgment device for automatic screw tighteners.