| 摘要 |
PROBLEM TO BE SOLVED: To simultaneously join a plurality of parts to be welded to the uniform welding strength in series welding. SOLUTION: In the first energization period, a control part 56 continuously switches switching elements 32, 36 of the first set (positive pole side) through the PWM control for the prescribed period. The welding current I2 of the positive polarity having the trapezoidal current waveform flows in the route of a first welding electrode 48→a work W1 to be welded→a first part to be welded→a work W2 to be welded→a second part to be welded→a work W1 to be welded→a second welding electrode 50. In the second energization period, the control part switches switching elements 34, 38 of the second set (negative pole side) for the period longer than the first energization period by the prescribed time. The welding current of the negative polarity having the trapezoidal current waveform flows in the reverse route to that in the first energization time. As a reust, a nugget in each part to be welded is grown to the same size when the total energization time is completed.
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