JPS6429726A - Electrode pressurizing force sensor for resistance welding - Google Patents

Abstract

PURPOSE:To improve the set accuracy of the pressurized contact force with which optimum welding quality is obtainable by detecting the mechanical pressurized contact force to a weld zone and the output voltage to the weld zone in a welding stage for resistance welding. CONSTITUTION:After a pressure is set to a fluid pressure apparatus for pressurizing electrodes of a welding machine, a sensor 1 is set between upper and lower electrodes 2 and 3. A solenoid valve is changed over and a welding head is lowered when the welding machine is started. The upper and lower electrodes 2, 3 are then pressed respectively to conductive members 4, 5 of the sensor 1 via insulators 7 and are stopped. A pressure sensitive element 6 outputs the quantity of the electricity suitable for the loaded pressure. The thyristor of a main power supply turns on and the energizing time is started upon lapse of the set squeeze time. Current does not flow between the electrodes but the secondary no-load voltage of a welding transformer is generated between the electrodes. The main thyristor turns off and the voltage between the electrodes is annihilated when the energizing time is completed. The solenoid valve is changed over and the pressurized contact force is gradually decreased upon completion of the holding time after the start of the holding time. The electrodes are then opened and the output of the pressure sensitive element 6 is reset to the state before the pressurization.