| 摘要 |
PURPOSE:To stop welding simultaneously with generation of expulsion and surface flash from materials to be welded and to form weld zones having high tensile strength by stopping welding current on detecting of a sharp increase in the welding current during lap resistance welding after lapse of a prescribed time. CONSTITUTION:In lap resistance welding wherein welding is executed by the electric power supplied with a welding transformer 4, the current signal detected with a current transformer 5 of the welding current on a primary side is rectified with a current detector 6. Further, the current levels are successively compared with an operator 7 for increments of current, by which a sharp increase in the current conforming to the generation of expulsion and surface flash is discriminated, and a signal is fed to a controller 2 for conduction of electricity, whereby the conduction of a contactor 3 is stopped. A controller 1 for weld time in the control mechanism for welding current regulates the start for conduction of electricity and the longest current conducting time, and a controller 9 for blind time stops the control function during the prescribed transient time. A voltage detector 8 is provided in order to exclude the factors for fluctuation of the voltage of the power source, and an alarm device 10 transmits an alarm signal for the uncompletion of welding when the conduction of electricity is stopped after lapse of the longest current conducting time. |
