| 摘要 |
PURPOSE:To improve and uniform the quality of spot welding by increasing a welding current gradually after a specific time limit from the starting of feeding and detecting nugget formation on the basis of the accumulated value of the integral values of an interchip voltage for every half cycle. CONSTITUTION:The voltage between chips 1 and 1 which clamp a work 2 is passed through a filter circuit 3 and integrated by an AC integrating circuit 4, whose output is supplied to a rectifying circuit 5. Once a welding current of each half cycle flows, an A/D converting circuit 6 generates a conversion starting pulse to perform conversion. By a conversion ending signal, the circuit 4 is reset and a microcomputer 8 accumulates and stores the interchip voltage of every half cycle. Then this accumulated value is compared with the value of a feeding cut set value circuit 7 and when the former is greater than the latter, an input voltage variation compensating timer 9 cuts the feeding by a feeding cut signal from the computer 8. The welding current setting of the timer 9 is carried out by a welding current setting circuit 10. |
