Capacitive welding method and welding device

Abstract

[Problem] To prevent, with a simple circuit configuration, an after-flash from occurring and a large surge voltage from occurring in a primary winding when opening between welding electrodes between which excitation current is flowing. [Solution] In a capacitor type welding method according to the present invention, electric charges charged on a welding capacitor are discharged and when the discharge current is brought into a state in which the discharge current does not substantially flow through a discharge switch, excitation current that has been flowing through the primary winding of a welding transformer is transferred to the secondary winding thereof. When opening between a first welding electrode and a second welding electrode while the transferred excitation current is flowing through the secondary winding, the discharge switch is brought into a state in which the discharge switch can be turned on by applying a drive signal thereto. Surge voltage occurring in the primary winding of the welding transformer when opening between the first and second welding electrodes is thereby flowed through the discharge switch to the welding capacitor as surge current.

Description

technical field [0001] The present invention relates to a capacitive welding method and welding device for welding a workpiece by discharging energy accumulated in a welding capacitor by a charging circuit in a short time between welding electrodes via a welding transformer. Background technique [0002] Capacitive welding devices take longer than the discharge time to accumulate welding power in the welding capacitor, and discharge it all at once in a short time. Therefore, compared with general alternating-current welding apparatuses, there is an advantage in that it does not increase the capacity of power receiving equipment. There are also advantages in that since the degree of heating of the object to be welded is small, there are almost no welding traces (burn marks) at the welding place, and deformation and the like are also small. Capacitive welding devices are widely used in small to large industrial equipment. [0003] Capacitive welding devices generally use a c...

AI Technical Summary

Problems solved by technology

[0005] In this case, there is a problem that if the secondary coils are opened when the wave tail part of the welding current flows through the secondary coils of the welding transformer, a large voltage is induced between the primary coils and at the same time, the welding electrode Sparks called afterflash are generated between the object to be welded, causing damage to the object to be welded

Therefore, it is difficult to obtain high-quality welded items that are not easily scarred by after-flash

In addition, because a discharge switch such as a thyristor with a high withstand voltage must be used, it becomes a cause of cost increase.

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