JPS629783A - Device for detecting electrode derailment in seam welding machine - Google Patents

Abstract

PURPOSE:To increase the accuracy in detecting a derailment by providing the constant current device composed of a welding current detecting element and welding current control element, et. and by arranging as well the detecting circuit to output a detecting signal when the control signal reaches the set value. CONSTITUTION:A welding current detecting element 2 and current control element 4 constitute a constant current device 8 together with a control circuit 7. The device 8 outputs the control signal of a phase from the control circuit 7 according to the output signal of the detecting element 2 and performs the phase control of a thyristor of as the current control element 4. The welding current of the circuit 5 is therefore kept constant always. The detecting circuit 9 composed of a setting volume 10, etc. is further arranged. An overcurrent is passed to the circuit 5 when rotary electrodes 1, 1 are derailed but the current is held constant with the actuation of the device 8. In this case, the control signal inputted into the circuit 9 performs the derailment detection by being compared with the set value of the setting volume 10. The derailment detecting accuracy is therefore increased.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a device for detecting detachment of a rotating electrode from a workpiece in a seam welding machine.

(Prior art) As a conventional device of this type, one is known that detects the distance between the upper and lower electrodes by utilizing the fact that the upper and lower electrodes approach each other by the thickness of the object to be welded when the wheels come off. However, there is an inconvenience in that it is necessary to change the mounting position or set value of the detector due to wear of the electrode, and in the case where the radio wave welding object has a shape that envelops the electrode, it is difficult to mount the detector.

An object of the present invention is to provide an electrode derailment detection device that does not have the above-mentioned conventional disadvantages.

(Problems to be Solved by the Invention) The present invention provides a seam welding machine that pressurizes a workpiece with a pair of rotating electrodes and welds the workpiece by applying electricity. A constant current device consisting of a current control element and a control circuit that supplies a control signal 'ft corresponding to the output signal of the detection element to the current control element to control it, and detects when the control signal reaches a set value. The present invention is characterized in that it includes a detection circuit that outputs a signal.

(Example) Embodiments of the invention will now be described with reference to the drawings.

In the drawing, il)+1) is a pair of rotating electrodes of a seam welding machine, and the rotating electrodes+1) (11 are a welding current detection element (2) such as a current transformer, a transformer (3), and a thyristor, etc.). The welding current detecting element (2) is connected to the power source (6) through the welding current circuit (5) in which the current control element (4), etc. ) and the current control element (4) constitute a constant current device (8) together with the control circuit (7). The constant current device (8) outputs a control signal with an amplitude corresponding to the output signal, and thus the constant current device (8) is connected to the welding current detection element (
The current control element (
4) The phase of the thyristor is controlled and the welding current circuit (
5) It was assumed that the welding current flowing in the welding current was always constant.

A control signal having an amplitude corresponding to the output signal of the welding current detection element (2) outputted from the control circuit (7) is sent to a detection circuit (9) that outputs a detection signal when the control signal reaches a set value.
), and the detection signal output from the detection circuit (9) is used to detect the derailment of the rotating pole (1) from the workpiece.

The detection circuit (9) is set at a level corresponding to the excessive current flowing in the welding current circuit (5) when the rotating electrode (1) comes off the workpiece and the rotating electrodes (IHII) are short-circuited. Setting volume (1G and the setting volume α [
and an operational amplifier a connected to the control circuit (7), respectively.
υ, amplifier α2, and relay αJ.

Next, its operation will be explained.

Now, if the rotating electrode (11) comes off the workpiece and the rotating electrodes are short-circuited, an excessive current will flow into the welding current circuit (5), but the constant current device (8) will operate and the circuit (
5) The current flowing through becomes constant. At this time, the control circuit (
)) outputs a control signal with an amplitude corresponding to the excessive current. The control signal is set by the operational amplifier aυ and the set volume α
It is compared with the setting value of [.

Since the set value is set to the same value as the control signal,
An output signal is generated in the operational amplifier aυ, and the output signal operates the relay Qh via the amplifier αzt-.

Since the detection circuit (9) outputs a detection signal, the work drive device and the like and an alarm (not shown) are stopped and activated by this detection signal.

(Effects of the Invention) According to the present invention, an excessive current does not flow in the welding current circuit even when the electrode comes off the workpiece, and the detachment of the electrode from the workpiece is not affected by the wear of the electrode and the mounting condition of the electrode. It has the effect of ensuring reliable detection without any damage.

[Brief explanation of drawings]

The drawing is a circuit diagram of one embodiment of the present invention. (1)...Rotating electrode (2)...Welding current detection element (4)...Current control element (5)...Welding current circuit (7)...control circuit (8)... Constant current device (9)...Detection circuit

Claims (1)

[Claims] In a seam welding machine that welds a workpiece by pressurizing the workpiece with a pair of rotating electrodes and applying electricity, a welding current detection element, a current control element inserted in a welding current circuit, and control according to the output signal of the detection element are used. a constant current device comprising a control circuit that supplies a signal to the current control element to control it;
1. An electrode derailment detection device for a seam welding machine, comprising a detection circuit that outputs a detection signal when the control signal reaches a set value.