JPS61214980A - Screw driver - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a device for determining and classifying the quality of screw tightening by an electric screwdriver in an automatic machine.

(Technical Prelude to the Invention and Its Problems) A conventional screw tightening device in an automatic machine is shown in Fig. 5. In the figure, an electric screwdriver 1 having a screw tightening torque detection section rotates and a screwdriver bit attached to the tip thereof rotates. 2
Screw in the screw 3 and screw the parts to a relay (not shown) or the like. In this case, the tightening torque of the screw 3 gradually increases from the beginning of screwing in and reaches its maximum when the screw is closed.

At this time, the tightening generated from the electric screwdriver 1 causes the control device 4 to stop the rotation of the electric screwdriver 1 based on the torque detection signal, and at the same time, the tightening generated from the electric screwdriver 1 is detected by the screw height detector 5 that detects the height position of the flange of the screwdriver bit 2. The screw height is checked to see if the screw has been completely tightened according to the signal, and the tightening work of the screw 3 is completed. Figure 2 shows the torque one-hour curve when screw tightening work is performed normally, and Figures 3 and 4 show the torque curve when screw tightening work is not performed normally due to poor fitting or tapping. The torque hourly curves for each case are not shown. For example, in a screw tightening device that shows a torque one-hour curve as shown in Fig. 3, if the screw tightening is defective, the rotation of the electric screwdriver 1 will stop when the torque reaches the completion torque value a. After stopping, the screw height is checked by the screw height detector 5, and since screw tightening has not reached the completed position, it is determined that the screw tightening is defective. However, the defective screw tightening shown in the torque one-hour curve as shown in Fig. 4 is an example of the screw spinning idly, and the tightening torque is set to 1 to torque value a1. : The screws rotate until they reach the desired level and the screws cannot be detected as being tightened, causing damage to the assembled parts and screws.In addition, unnecessary idling may prolong the work time, and in some cases, the screws may engage in the middle and become screwed in, resulting in defective screws being installed as they are. There was a problem that it would get lost.

[Object of the Invention] In order to solve these problems, it is an object of the present invention to provide a screw tightening device that detects idling in screw tightening and determines whether the screw tightening is good or bad.

[Summary of the Invention] The present invention is a screw tightening device that converts the number of rotations of an electric screwdriver that tightens a screw into a number of pulses, counts the number of pulses within a set time, and compares the counted value with a preset ltp.
It consists of a counting comparator that compares the values and generates different outputs depending on the difference, and is characterized in that the screw tightening condition is determined to be good or bad based on this output signal.

[Embodiment of the Invention] FIG. 1 shows a configuration diagram showing an embodiment of the screw tightening device of the present invention. In the figure, an electric screwdriver 7 with a screw tightening torque detector built into an automatic machine has a driver bit 8 attached to the tip of its rotating shaft, and a screw 9 is fitted to the tip of the driver bit 8. . Reference numeral 10 denotes a screw height detector, which detects the height of a flange provided on the driver bit 8 when the screw 9 is normally tightened to a screw assembly (not shown). .

A signal line 11 that transmits an output signal from a screw tightening torque detection section built into the electric screwdriver 7 and a signal line from the screw height detector 10 are connected to a control device 12. Also? A pulse generator 13 for converting the rotational speed into a pulse number is attached to the dynamic driver 7 on the side opposite to the installation side of the driver bit 8, and the output of this pulse generator 13 is connected to the time limit contact of the timer device 15 by a signal line 14. 16 and enters the pulse counter 17. 18 is a signal line to which a start signal to start counting pulses is sent, and this signal line 18 is connected to the timer device 15 and the pulse counter 17.
connected to. The output signal of the pulse counter 17 is connected to a device for classifying defective products provided on a conveyor (not shown) by a signal line 19, and drives this device.

Next, the operation of this embodiment will be explained. When the screw tightening operation is started, the electric screwdriver 7 rotates, and the screw 9 is screwed into a screw assembly (not shown) by the screwdriver bit 8. For screw tightening, after the start of work, a pulse counting start signal is input to the timer device 15 and pulse counter 17 via the signal line 18, so that the timer device 1-5 is started and the time limit contact 16 is closed.
When the set time 15 has elapsed, the time-limiting contact 16 opens. On the other hand, when the pulse counter 17 receives the signal, the time limit contact 16 closes and starts counting the number of pulses of the pulse generator 13.
Compare the count value obtained by integrating the number of rotations of the electric screwdriver 7 from the number of pulses until the screwdriver 6 opens with the preset value set in advance as the number of pulses that represents a normal screw tightening state, and if the count value ≧ the set value. If the count value is equal to the set value, a “fail” signal is output.

FIGS. 2 to 4 are torque one-hour curves showing the screw tightening state, and the time ts when the pulse counting start signal is output, the timer Si! The time te at which the time set by the device 15 has elapsed and the completion torque value a for tightening are shown, respectively. The second reason is that the screw indicates a normal tightening condition, and the screw rotates at an almost constant low torque value from the start of tightening, and when tightening with the assembled parts begins, the torque gradually increases to the completion torque Ia, and the screw rotates at a constant low torque value. Tightening is completed. Figures 3 and 4 show cases where a tightening failure occurs; the rotational torque for screw tightening increases after the start of screw tightening and then decreases due to poor plating or tapping of the screw or screw hole. Since this increase in rotational torque results in a decrease in the number of rotations of the electric screwdriver 7, the time (t) set by the timer device 15 is
The number of rotations (i.e., the number of pulses) in do.

As explained above, in the screw tightening device, in addition to the screw height detector 10 and the screw tightening device, which determines the quality of screw tightening by detecting the completion torque value a, Since the number of revolutions of the electric screwdriver 7 is detected, integrated, and compared, it is possible to easily detect and classify problems such as galling, idling, breakage of screws, and damage to assembled parts due to poor thread engagement or poor taps. can.

[Effects of the Invention] According to the present invention, by converting the rotation speed of the electric screwdriver into the number of pulses and cumulatively counting the number of pulses within a certain period of time, screw tightening is performed by converting changes in torque into the rotation speed of the electric screwdriver. Since the screw tightening condition is detected as a change and classified as good or bad, it is possible to easily detect screw tightening defects that occur before the screw tightening torque reaches the completion torque, and prevent defective products from getting mixed in. I can do it.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram showing one embodiment of the screw tightening device of the present invention, Figs. 2 to 4 are torque hourly curve diagrams without showing the screw tightening state, and Fig. 5 shows a conventional screw tightening device. FIG. 1.7... Electric screwdriver 13... Pulse generator 15... Timer device 16... Time limit contact 17.・・・・・・・・・Pulse counter agent Patent attorney Noriyuki Chika (1 idiot) Figure 1 Figure 5 I-C 净 Figure 2 Figure 4

Claims (1)

[Claims] An electric screwdriver for tightening screws, a pulse generator for converting the number of revolutions of the electric screwdriver into a number of pulses, a means for setting the time for counting this pulse signal, and a pulse generator for counting the pulse signal within the time set by this means. It consists of a count comparator that counts the number of screws and generates a different output signal depending on the difference between the counted value and a preset reference value, and the screw tightening condition is classified as good or bad based on this output signal. Screw tightening device.