JPH01233074A - Inverter type resistance welding machine - Google Patents

Abstract

PURPOSE:To obtain an optimum AC-DC waveform for welding by providing PWM control circuit to the title inverter type resistance welding machine and selecting arbitrarily a waveform generation function of a function generator. CONSTITUTION:When an AC current is necessary as a welding current, a diode 8 is not necessary and when a DC current is necessary, the diode 8 is used. The output current is then detected by a current detector 9 provided to the inverter output. This output current is compared with a signal wave from the function generator 10 and the compared signal wave and a carrier wave of a carrier wave generation circuit 11 are inputted to the PWM control circuit 12 and its output is inputted to a gate amplifier 13 and the gate amplifier output switches a switching element 14 of a main circuit and generates the welding current via a filter 17. Further, marks 15 and 16 are a rectifier and a capacitor respectively to convert three-phase AC into DC.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to improvements in inverter type resistance welding machines.

(Prior art) In general sub-I welding, as shown in the main component circuit of the figure, a pair of electrode tips 3.4 connected to the secondary conductor 2 of the welding transformer 1 5 from both sides, and the pressure device 6 applies the necessary pressure for welding to the electrode prong 3.
At the same time, an electronic control element such as a Zyristor inserted between the welding transformer and the welding power source is used to open and close the main current by controlling the ignition circuit included in the control device. A necessary current is passed between the electrodes for a certain period of time to form a nugget 7 at the welding part and join the parts.

Recently, inverter type spot welding machines, which are capable of making welding transformers smaller and lighter and can be precisely controlled, have become popular in place of the SIRIS type spot welding machines.

An inverter-type resistance welding machine converts commercial frequency alternating current into direct current, converts the direct current into high-frequency current via an inverter, and converts the high-frequency current into alternating current necessary for welding via a welding transformer. A rectifier is inserted into the secondary side of the welding transformer and direct current is supplied to the electrodes to pressure weld the workpiece.

(Problems to be Solved by the Invention) However, in the conventional inverter type resistance welding machine, only a rectangular wave can be obtained as the inverter output waveform due to mere pulse width control.

(Means for Solving the Problems) The present invention was developed to solve the above problems, and its gist is to convert commercial frequency alternating current into direct current, and to convert the direct current into direct current using a pulse width modulation circuit. In an inverter-type resistance welding machine that switches an inverter to convert the high-frequency current into a high-frequency current, and supplies the current necessary for welding to the electrodes through a welding transformer to pressure-weld the workpiece, the pulse Compares the carrier wave of the carrier wave generation circuit and the signal wave of the function generator through the width modulation circuit, switches the inverter, and generates a welding current waveform faithful to the optimal setting signal waveform for resistance welding through the filter. This is an inverter-type resistance welding machine configured to allow this.

(Example) Embodiments of the present invention will be described below based on the drawings.

The figure shows an embodiment of an inverter type resistance welding machine according to the present invention.

In this embodiment, groove welding is performed, and the welding current, which is an inverter output, is constant current controlled with a waveform faithful to a signal wave by pulse width modulation. When alternating current is required as the welding current, diode 8 is not required, but when direct current is required, diode 8 is used.

The output current is detected by a current detector 9 provided at the inverter output, this output current is compared with the signal wave from the function generator 10, and this comparison signal wave and the carrier wave of the carrier wave generation circuit 11 are input to the PWM control circuit 12. The output is input to the gate amplifier 13, and the output is input to the gate amplifier 13.
The amplifier output is the switching element (MOSFET) of the main circuit.
etc.) 14 to generate a welding current faithful to the signal wave via the filter 17.

Note that numerals 15 and 16 are a rectifier and a capacitor that convert three-phase alternating current to direct current.

(Effect of the invention) With the above configuration, the inverter-type resistance welding machine is equipped with a full-fledged PWM control circuit for the first time, so the waveform generation function of the function generator can be arbitrarily selected to determine the optimum current waveform for welding. By doing so, ideal waveforms of AC and DC can be obtained.

[Brief explanation of the drawing]

The figure is an electrical block diagram showing an embodiment of the present invention.

Claims (1)

[Claims] Converts commercial frequency alternating current to direct current, converts the direct current into high-frequency current by switching an inverter using a pulse width modulation circuit, and supplies the current necessary for welding to the electrodes with the high-frequency current via a welding transformer. In an inverter-type resistance welding machine that pressurizes and welds objects to be welded, the carrier wave of the carrier wave generation circuit is compared with the signal wave of the function generator via the pulse width modulation circuit, and the inverter is switched to weld the resistance via the filter. An inverter-type resistance welding machine configured to generate a welding current waveform faithful to the optimal setting signal waveform for welding.