Welding-Current Control Method of the Resistance Welding Machine and Welding-Current Control Device

摘要

In spot welding, the condition tolerance for applying a large current in a short time into an aluminum alloy plate or the like is narrow, and also nugget crack sometimes occurs in spot welding. In the case of a mild steel plate, the expulsion sometimes occurs, and thereby a poor weld portion is formed. Due to a pickup removal operation from an electrode tip, the operating ratio is reduced. Here, a PAM control method is employed for raising or dropping a rectified and smoothed voltage EDC output to an inverter circuit, according to a certain set-up ratio in a predetermined time, instead of a conventional PWM control method. By this control method, the nugget can be formed in condition of low heat dissipation and high thermal efficiency. In addition, energy saving and power saving are achieved by using the PAM control method.

主权项

1. A welding-current control method of a resistance welding machine which welds connected materials by applying the welding-current into the materials by the welding transformer under applying pressure to the connected materials by holding the connected materials between upper and lower electrode tips, wherein
the resistance welding machine comprises a rectifying and smoothing circuit rectifying and smoothing the alternating voltage of primary commercial power, and outputting a rectified and smoothed voltage EDC (hereinafter referred to as “voltage EDC”) which is a variable output, and an inverter circuit driving the welding transformer in response to the voltage EDC, and wherein the method comprises a step of varying the welding-current by applying the voltage EDC, which is raised or dropped according to a certain set-up ratio in a predetermined time after a set-up time has passed after a power-on, into the inverter circuit driving the welding transformer.