Electric power conversion systems – Current conversion – With condition responsive means to control the output...
Reexamination Certificate
2000-04-12
2001-01-09
Berhane, Adolf Deneke (Department: 2838)
Electric power conversion systems
Current conversion
With condition responsive means to control the output...
Reexamination Certificate
active
06172888
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a transistor or inverter resistance welding power supply apparatus.
2. Description of the Related Arts
Transistor or inverter resistance welding power supply apparatuses have hitherto often be used for precision resistance welding of materials such as metal foils or small-gage wires.
The transistor power supply is a method substantially allowing only transistors to intervene between a capacitor storing welding energies and welding electrodes without interposition of any welding transformer therebetween, the transistors serving to control a welding current discharged from the capacitor, previous to the supply to the materials to be welded together. In the inverter power supply a commercial-frequency power is converted by an inverter into a high-frequency power which in turn is fed via the transformer to the materials to be welded together. Both the power supply methods are able to flow a DC welding current with rapid rise of the welding current and provide a minute constant-current control or constant-voltage control.
In the transistor or inverter resistance welding power supply apparatus, as described above, the constant-current control and the constant-voltage control are both often employed as welding current control modes. Such a conventional resistance welding power supply apparatus is arranged to make an alternative selection of either of the constant-current control and the constant-voltage control for a single welding current supply. Thus, in case of selection of the constant-current control, a desired current value is set and entered without entry of any voltage set value for the constant-voltage control. On the contrary, in case of selection of the constant-voltage control, a desired voltage value is set and entered without entry of any current set value.
However, even though the desired welding current flows as a result of selection of the constant-current control, too high a voltage applied to the materials to be welded together may bring about any spatters, possibly resulting in defective welding. As opposed to this, even though the desired welding voltage is applied as a result of selection of the constant-voltage control, an excessive welding current may also result in defective welding or may cause faults in the power supply circuit.
In addition, the conventional power supply apparatus has merely provided a feedback control for the purpose of execution of current supply in a given welding current control method during the welding current supply, but has by no means provided a feature to detect any abnormal phenomena associated with parameters out of selection as described above or a feature to ensure a quick transition to proper processing upon the occurrence of any abnormality.
SUMMARY OF THE INVENTION
The present invention was conceived with the aim of overcoming the above prior art deficiencies. It is therefore an object of the present invention to provide a transistor or inverter resistance welding power supply apparatus capable of simultaneous setting of both constant-current control and constant-voltage control, allowing flexible adaptations to a diversity of welding requirements or to variations in welding situations.
Another object of the present invention is to provide a transistor or inverter resistance welding power supply apparatus allowing both current monitor and voltage monitor to be set at the same time as well as capable of simultaneous setting of both the constant-current control and constant-voltage control so as to ensure an acquisition of beneficial monitoring information in accordance with the welding current control mode selected.
According to an aspect of the present invention, in order to achieve the above objects, there is provided a transistor or an inverter resistance welding power supply apparatus comprising set value input means for the input of a desired current set value and a desired voltage set value; constant-current control means for allowing a value of current fed to materials to be welded together to coincide with the current set value; constant-voltage control means for allowing a value of voltage between a pair of welding electrodes to coincide with the voltage set value; welding current control mode selecting means for selecting either of a first welding current control mode provided by the constant-current control means and a second welding current control mode provided by the constant-voltage control means, the selecting means making a switchover from the first welding current control mode to the second welding current control mode when the value of interelectrode voltage reaches a predetermined critical voltage value, the selecting means making a switchover from the second welding current control mode to the first welding current control mode when the value of current fed to the materials to be welded together reaches a predetermined critical current value; and current supply sequence control means for executing a welding current supply in a welding current control mode selected by the welding current control mode selecting means.
In the present invention, switchover of the welding current control modes is automatically carried out and no limitations are imposed on the directions of switchover (from first mode to second, and vice versa) and on the number of times of switchover.
The welding current control mode selecting means may include priority mode selection means for selecting either of the first welding current control mode and the second welding current control mode in accordance with a previously set priority when the value of current fed to the materials to be welded together has not yet reached the critical current value and when the value of interelectrode voltage has not yet reached the critical voltage value.
In addition to the above features, the resistance welding power supply apparatus of the present invention may further comprise current monitoring means for monitoring a current fed to the materials to be welded together; voltage monitoring means for monitoring a voltage between the pair of welding electrodes; and monitor mode selecting means for selecting a first monitor mode provided by the voltage monitoring means when the first welding current control mode is in selection, and for selecting a second monitor mode provided by the current monitoring means when the second welding current control mode is in selection. It may further comprise welding current control mode history recording means for recording a history of welding current control modes selected during the welding current supply.
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Berhane Adolf Deneke
Miyachi Technos Corporation
Wenderoth , Lind & Ponack, L.L.P.
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