Inverter seam resistance welding electric power supply apparatus
First Claim
1. An inverter-type resistance welding electric power supply apparatus for supplying a welding current, through a welding transformer and a pair of seam welding electrodes, to a pair of workpieces in which the welding electrodes are contacted with and moved relative to the workpieces so that a seam-welded portion is formed in the workpieces, wherein the welding transformer includes a primary circuit with a primary coil and a secondary circuit, said power supply apparatus comprising:
- a rectifier means for rectifying a commercial AC voltage into a DC voltage;
an inverter means for converting said DC voltage into a pulse-shaped voltage having a predetermined high frequency, and for supplying said pulse-shaped high frequency voltage to the primary coil of the welding transformer to supply the welding current;
a monitor time interval preselecting means for subdividing a seam weld time of a seam weld operation into a plurality of preselected time intervals such that each of said plurality of preselected time intervals consists of a plurality of inverter switching cycles, and for preselecting each of said plurality of preselected time intervals as a respective current monitor time interval;
a current measuring means for measuring a value of a current flowing in the primary or secondary circuit of the welding transformer during each current monitor time interval;
a first determining means for comparing the current value measured by said current measuring means for each current monitor time interval with a preselected monitoring value to determine, for each current monitor time interval, whether a resulting weld corresponding to the respective current monitor time interval is conforming or defective;
a second determining means for determining that a resulting seam weld is defective when said first determining means has successively determined that a defective weld has occurred for a predetermined number of successive current monitor time intervals.
1 Assignment
0 Petitions
Accused Products
Abstract
In order to improve the quality of seam welding, an inverter seam resistance welding electric power supply apparatus reliably determines local weldability (conforming/defective) of seam welding by simply monitoring welding current. In a seam welding operation, when a current monitor time interval has elapsed, a CPU reads, from storage, measured current values I1 !, I2 !, etc., of each inverter cycle obtained during the current monitor time interval and computes an average current value IM1 ! thereof, according to an averaging method such as an arithmetic mean method. Then the CPU compares the average current value IM1 ! with a preselected monitoring value or range. If the average current value IM1 ! falls within the monitoring range, the CPU determines the occurrence of a conforming local welding whereas it determines the occurrence of a defective local welding if the average current value goes out of the monitoring range. For successive determinations of defective local welding for a preselected number of times, for instance, three, the CPU determines that a defective seam welding has occurred, and takes appropriate action immediately, for instance, by stopping the seam welding operation.
-
Citations
4 Claims
-
1. An inverter-type resistance welding electric power supply apparatus for supplying a welding current, through a welding transformer and a pair of seam welding electrodes, to a pair of workpieces in which the welding electrodes are contacted with and moved relative to the workpieces so that a seam-welded portion is formed in the workpieces, wherein the welding transformer includes a primary circuit with a primary coil and a secondary circuit, said power supply apparatus comprising:
-
a rectifier means for rectifying a commercial AC voltage into a DC voltage; an inverter means for converting said DC voltage into a pulse-shaped voltage having a predetermined high frequency, and for supplying said pulse-shaped high frequency voltage to the primary coil of the welding transformer to supply the welding current; a monitor time interval preselecting means for subdividing a seam weld time of a seam weld operation into a plurality of preselected time intervals such that each of said plurality of preselected time intervals consists of a plurality of inverter switching cycles, and for preselecting each of said plurality of preselected time intervals as a respective current monitor time interval; a current measuring means for measuring a value of a current flowing in the primary or secondary circuit of the welding transformer during each current monitor time interval; a first determining means for comparing the current value measured by said current measuring means for each current monitor time interval with a preselected monitoring value to determine, for each current monitor time interval, whether a resulting weld corresponding to the respective current monitor time interval is conforming or defective; a second determining means for determining that a resulting seam weld is defective when said first determining means has successively determined that a defective weld has occurred for a predetermined number of successive current monitor time intervals. - View Dependent Claims (2, 3, 4)
-
Specification