JPS6110931Y2 - - Google Patents

Description

[Detailed description of the invention] This invention allows automatic tightening by operating a selection circuit to select one of several maximum tightening torques preset in the device when tightening conditions change. This invention relates to a screw tightening device.

When tightening a screw using a screw tightening device that automatically performs tightening until a set maximum tightening torque is reached, conventionally, the maximum tightening torque can only be set in one way. In this case, if there is only one type of nut to be tightened on the work being transported on the assembly line, and the tightening conditions are the same, the tightening torque can be set once and then readjusted about once a month. Just that is enough. However, normally, many types of workpieces are often transported on one assembly line, and to accommodate this, the maximum tightening torque must be reset each time the tightening conditions change.
The tightening torque is reset using a setting switch and a setting dial on a display panel of a control section connected by a cord to the drive section of the screw tightening device. However, it is a troublesome operation for the operator to reset the settings each time the tightening conditions change, resulting in a large loss of time, and there is a risk that the tightening torque may fluctuate due to setting errors.

In view of the above-mentioned drawbacks, the present invention has been improved and will be described in detail below with reference to the drawings.

In the figure, 1 is a DC motor that generates tightening force, 2 is a reducer that decelerates the rotation of DC motor 1 and generates a large torque, and 3 is a reducer that detects the tightening torque generated by the main shaft of the reducer and converts it into an electrical signal. 4 is a nut tightening socket fixedly installed at the tip of the main shaft of the reducer, 5 is an amplifier that amplifies the output signal of the torque transducer, and 6 is a plurality of settings for setting different maximum tightening torques. _A maximum tightening _torque setting section consisting of devices _{6 1 , 6 2 .} For example, it is constituted by a rotary switch or an electronic circuit that performs automatic switching by inputting an external signal a. 8 is a seating torque setting section for setting a seating torque which is a target value for seating the nut, that is, detecting that the gap between the nut and the workpiece has disappeared; 9 is a maximum tightening torque output from the maximum tightening torque setting section 6; , a maximum tightening torque comparison unit that compares the output of the amplifier 5, 10 a seating torque comparison unit that compares the seating torque with the output of the amplifier 5, and 11 based on the outputs of the maximum tightening torque comparison unit 9 and the seating torque comparison unit 10. 12 is a power supply unit that supplies power for driving the DC motor 1 to the control circuit 11; 13 is a motor current detector that detects the motor current output from the control circuit 11 to the DC motor 1; When the motor current detected by the motor current detection section 13 exceeds the set overcurrent limit,
Overcurrent display section that displays overcurrent, 15 is amplifier 5
16 is an upper limit torque setting section for setting the upper limit of tightening torque; 17 is a lower limit torque setting section for setting the lower limit torque for tightening. , 18 is an upper limit torque comparison unit that compares the upper limit torque digitally set in the upper limit torque setting unit 16 and the maximum value output from the peak hold circuit 15 when one tightening is completed;
9 is a lower limit torque comparison unit that compares the lower limit torque set in the lower limit torque setting unit 17 and the output of the peak hold circuit 15 when one tightening is completed;
20 is an upper limit NG output section that indicates a defect when the output of the peak hold circuit 15 exceeds the upper limit torque, and 21 indicates that the output of the peak hold circuit 15 is between the upper limit torque and the lower limit torque and has been properly tightened. 22 is a lower limit NG output section that displays a failure when the output of the peak hold circuit 15 falls below the lower limit torque; 23
24 is an abnormal torque value setting section in which an abnormal torque value is set as a reference for detecting abnormal torque applied to a screw tightening device or workpiece; 24 is an abnormal torque comparison section that compares the output of the amplifier 5 with the abnormal torque value; and 25 is an abnormal torque value for some reason. A tightening time setting section 26 is a tightening time setting section in which a reference tightening time is set to detect when tightening is not completed within a predetermined time. A tightening time comparing section 27 detects an excess of the tightening time by comparing the tightening time with the tightening time, and 27 is an abnormal output that generates an abnormal signal when the abnormal torque comparing section 24 or the tightening time comparing section 26 detects an abnormality. Department.

The operation of this device is as follows.

First, each setting device 6 of the maximum tightening torque setting section 6
Maximum tightening torques corresponding to different tightening conditions are set in ₁ , 6, ₂ , . . . 6 _o , respectively, and a seating torque for detecting seating is set in the seating torque setting section 8. Then, the selection circuit 7 is operated to select one of the setters 6 ₁ , 6 ₂ . . . 6 _o corresponding to the object to be tightened, and output the maximum tightening torque. Start tightening in this state. The control unit 11 controls the rotation of the DC motor 1 and gradually tightens the nut. Initially, the tightening torque detected by the torque transducer 3 hardly increases, but when the nut is seated, that is, when the gap between the nut, the workpiece, and the washer disappears, the tightening torque starts to increase rapidly. This is detected by the seating torque comparison section 10 that compares the output of the amplifier 5 and the seating torque.
A seating detection signal is given to the control circuit 11.
After the seating is detected, the control circuit 11 decelerates the DC motor 1 and slowly tightens the motor 1 with a large force. As the tightening increases, the tightening torque increases. The maximum tightening torque comparator 9 compares the output of the amplifier 5 with the maximum tightening torque output by the selected setting device 6 ₁ , 6 ₂ . . . 6 _o , and when the output of the amplifier 5 reaches the maximum tightening torque, the control This is output to the circuit 11. Then, the control circuit 11 immediately stops the DC motor 1 and the tightening is completed. At this time, the peak hold circuit 15
The maximum value of the detected tightening torque output from the amplifier 5 is stored and held. Then, the upper limit torque comparing section 18 and the lower limit torque comparing section 19 compare this maximum value with the upper limit torque and the lower limit torque, and determine whether the tightening has been properly performed. That is, when the maximum value exceeds the upper limit torque, the upper limit NG output section 20 is made to display that the upper limit is exceeded, and when this maximum value falls below the lower limit torque, the lower limit NG output section 22 is made to display that it is below the lower limit. Further, when this maximum value is between the upper limit torque and the lower limit torque, the torque OK output section 21 displays that the tightening has been performed with the appropriate torque. Based on these displays, the operator can judge whether the tightening is good or bad.

If the tightening torque increases to the extent that it damages the workpiece or the screw tightening device for some reason during screw tightening, the abnormal torque comparison section 24
detects this. That is, when the tightening torque exceeds the set abnormal torque value, it is determined that there is an abnormality, and the abnormality output section 27 displays the abnormality detection. Further, the tightening time comparison section 26 compares the elapsed operation time output from the control section 1 with the set time, and if the tightening operation does not end even after the set time elapses, it is determined to be abnormal and displayed on the abnormality output section 27. let Further, an overcurrent display section 14 receiving the output of the motor current detection section 13 inserted between the control circuit 11 and the DC motor 11 displays an overcurrent state when the motor current increases significantly. The tightening work can be performed one after another while looking at these displays and checking whether the tightening is being performed properly.

When changing the tightening conditions, a different maximum tightening torque is set by sending a switching signal a from the drive section A to the selection circuit 7, or by directly operating the selection circuit 7 from the display panel of the control section B. By selecting the setting device 6 ₁ , 6 _{2 .} . . 6 _o that corresponds to the tightening condition, the nut can be tightened in the same manner as described above for the selected maximum tightening torque.

Furthermore, the screw tightening device of the present invention can also be used as follows.

For example, as shown in FIG.
When tightening and fixing with 6 bolts and nuts,
Nuts 29 ₁ , 29 ₂ ...29 ₆ are close together and 6
If the screw tightening device of the table cannot be placed in the six screw tightening positions, every other three nuts 29 ₁ ,
Tighten 29 ₃ , 29 ₅ with three screw tightening devices, then tighten the remaining three nuts 29 ₂ , 29 ₄ , 2
9 ₆ may be tightened. At this time, if you set the same maximum tightening torque for the first three nuts and the last three nuts, the nut you tightened first will loosen when you tighten the three nuts later, and each nut will be tightened uniformly. It becomes impossible to provide sufficient tightening force. In such a case, the tightening force of the nut that is tightened first
F ₁ and the maximum tightening force F ₂ of the nut to be tightened later.
By setting the setting devices 6 ₁ and 6 ₂ of the present invention in accordance with the relationship F ₁ >F ₂ , the final tightening force of each nut can be made constant. Switching between the first tightening and the later tightening can be performed only by operating the selection circuit 7.

As explained above, the present invention has a torque transducer that detects tightening torque, and when the tightening torque increases to a set maximum tightening torque, the screw tightening device stops tightening the screw. A screw tightening device that is equipped with multiple setting devices that respectively set the corresponding maximum tightening torque and a selection circuit that selects the setting device that corresponds to the tightening conditions, and performs tightening by switching the selection circuit according to the tightening conditions. Since we have provided the device, the maximum tightening torque can be changed simply by switching the selection circuit, and even if the object to be tightened changes frequently, the corresponding maximum tightening torque can be easily changed, and it can be easily changed for each different type of object to be tightened. Quick tightening can be performed without having to take measures such as installing a screw tightening device for each machine. Further, since all types of tightening torques can be set in advance, reliability can be improved by eliminating setting errors caused by resetting the maximum tightening torque by turning the setting dial each time.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a front view of a workpiece illustrating an example of screw tightening using the device of the present invention. 1...DC motor, 2...Reducer, 3...Torque transducer, 4...Socket, 5...Amplifier, 6...Maximum tightening torque setting section, 6 ₁ , 6
₂ ...6 _o ... Setting device, 7... Selection circuit, 8... Seating torque setting section, 9... Maximum tightening torque comparison section, 10... Seating torque comparison section, 11... Control circuit, 12... Power supply Section, 13... Motor current detection section, 14... Overcurrent display section, 15... Peak hold circuit, 16... Upper limit torque setting section, 1
7... Lower limit torque setting section, 18... Upper limit torque comparison section, 19... Lower limit torque comparison section, 20... Upper limit
NG output section, 21...Torque OK output section, 22...
Lower limit NG output section, 23...abnormal torque value setting section,
24... Abnormal torque comparison section, 25... Tightening time setting section, 26... Tightening time comparison section, 27... Abnormal output section, A... Drive section, B... Control section.

Claims (1)

[Scope of utility model registration request] In a screw tightening device that has a torque transducer that detects tightening torque and stops tightening the screw when the tightening torque increases to the set maximum tightening torque, the maximum tightening torque corresponding to different tightening conditions is set respectively. A screw tightening device comprising a plurality of setting devices and a selection circuit for selecting a setting device corresponding to tightening conditions, and tightening is performed by switching the selection circuit according to the tightening conditions.