JPS57149073A - Method and device for controlling resistance welding machine - Google Patents

Abstract

PURPOSE:To improve welding quality with an inexpensive device by detecting interelectrode voltage at every cycle of electricity conduction during the process of welding, comparing the same with the value in the stage of a test mode and executing prescribed feedback controlling in accordance with the difference thereof. CONSTITUTION:A test mode is selected with a keyboard circuit 7, and a timer circuit 9 is kept operated with a starting circuit 8 until satisfactory weldig can be executed. The voltage detected with an interelectrode detecting circuit 4 is converted with an A/D circuit 5 to digital quantity which is inputted, integrated and stored in a microcomputer 6. Then, the circuit 7 is changed over to an automatic controlling mode and the interelectrode voltage during welding electricity conduction cycle is detected. This voltage is inputted with the circuit 5 to the computer 6, which compares the same with the value stored in the test mode. When the value in the test mode is higher, the computer conducts electricity by increasing the conduction angle of the thyristor in the next electricity conduction to the thyristor. In a reverse case, it operates oppositely, thereby controlling the value so as to approach to the values stored in the respective modes. The above- mentioned circuit is simple and inexpensive.