Method of electrode current control in welding apparatus having a plurality of electrodes

• US 4,396,823 A
• Filed: 10/22/1981
• Issued: 08/02/1983
• Est. Priority Date: 12/08/1978
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Kozono, Yuzo, Onuma, Akira, Nihei, Masayasu, Kokura, Satoshi, Ashida, Eiji
• Primary Examiner(s): Shaw, C. C.
• Application Number:
  US06/313,832
• Time in Patent Office: 649 Days
• Field of Search: 219/130.51, 219/137 PS
• US Class Current: 219/137.0PS
• CPC Class Codes: B23K 9/1068 Electric circuits for the supply of power to two or more arcs from a single source

Abstract

In a welding apparatus having a plurality of electrodes and adapted for carrying out welding operation on a workpiece by alternately supplying currents to the individual electrodes through switching elements, an apparatus and method of controlling the currents supplied to the electrodes, comprising selecting the values of the currents supplied to the individual electrodes depending on the material of the workpiece, and carrying out the welding operation on the workpiece by alternately supplying the currents of the selected values to the individual electrodes respectively through the switching elements. The method is featured by the fact that the ratio between the individual currents is selected under the condition that the sum of the values of all the currents is maintained at a predetermined value. It is also featured by the fact that, depending on the welding condition, the values of the individual currents can be freely selected without the limitation of maintaining the sum of all the currents at the predetermined value. Therefore, the apparatus and method are applicable to welding of a variety of materials by selecting the values of the individual currents depending on whether the workpiece has a high or low melting point and also whether the workpiece has a high or low heat conductivity.

Claims

1. A method of controlling currents supplied to a plurality of electrodes of a welding apparatus having at least a leading electrode and a trailing electrode extending in the weld direction, and an electric power source for supplying welding currents to the welding apparatus for carrying out a welding operation on a workpiece by alternately supplying the currents to the individual electrodes, respectively, the method comprising the steps of selecting a sum of the values of the currents supplied to the individual electrodes in accordance with the material of the workpiece, setting each current supplied to each of the electrodes so that a sum of the values of each current equals the selected sum of the values and that a lower current is supplied to the leading electrode and a higher current is supplied to the trailing electrode with such current combination being selected to prevent molten metal from being driven away from the weld area, and carrying out the welding operation on the workpiece by alternately supplying the set current for each electrode to the individual electrodes, respectively.

2. An electrode current control method as claimed in claim 1, wherein the at least leading and trailing electrodes are in substantial alignment in the weld direction, in said setting step, the ratio between the currents supplied to the individual electrodes is set so that the sum of the values of the currents supplied to the individual electrodes is maintained at a predetermined value, and, in said carrying out step, the currents of the values set at said selected ratio are supplied to the individual electrodes respectively to carry out the welding operation.

3. An electrode current control method as claimed in claim 2, wherein said step of setting said selected ratio between the individual currents includes varying the durations of the currents supplied to the individual electrodes under the conditions that the sum of the values of the currents supplied to the individual electrodes is maintained at the predetermined value and all the currents have the same amplitude, and in said carrying out step, the currents havng the durations set at said selected ratio are supplied to the individual electrodes respectively to carry out the welding operation.

4. An electrode current control method as claimed in claim 2, wherein said step of setting said selected ratio between the individual currents includes varying the amplitudes of the currents supplied to the individual electrodes under the conditions that the sum of the values of the currents supplied to the individual electrodes is maintained at the predetermined value and all the currents have the same duration, and in said carrying out step, the currents having the amplitudes set at said selected ratio are supplied to the individual electrodes respectively to carry out the welding operation.

5. An electrode current control method as claimed in claim 2, wherein said selected ratio between the individual currents is set under the condition that the sum of the mean values of the currents supplied to the individual electrodes is maintained at the predetermined value.

6. An electrode current control method as claimed in claim 2, wherein said selected ratio between the individual currents is set under the condition that the sum of the effective values of the currents supplied to the individual electrodes is maintained at the predetermined value.

7. An electrode current control method as claimed in claim 1, wherein the step of setting includes setting the current supplied to the leading electrode to be substantially equal to the current supplied to the trailing electrode.

8. A welding apparatus comprising a plurality of electrodes including at least a leading electrode and a trailing electrode extending in the weld direction, the trailing electrode being inclined with respect to the leading electrode in the weld direction, electric power source means for supplying welding currents to the welding apparatus, and control means for enabling a welding operation on a workpiece by alternately supplying the currents to the individual electrodes, respectively, the control means including selecting means for selecting a sum of the values of the currents supplied to the individual electrodes in accordance with the material of the workpiece, setting means for setting each current supplied to each of the electrodes so that a sum of the values of each current equals the selected sum of the values, and switching means for alternately supplying the set current for each electrode to the individual electrodes, respectively, to enable carrying out of the welding operation.

9. A welding apparatus as claimed in claim 8, wherein the at least leading and trailing electrodes are in substantial alignment in the weld direction, said setting means includes means for setting a ratio between the currents supplied to the individual electrodes so that the sum of the values of the currents supplied to the individual electrodes is maintained at a predetermined value.

10. A welding apparatus as claimed in claim 9, wherein the means for setting the ratio between the individual currents includes means for varying the durations of the currents supplied to the individual electrodes under the conditions that the sum of the duration values of the currents supplied to the individual electrodes is maintained at the predetermined value with all the currents having the same amplitude.

11. A welding apparatus as claimed in claim 9, wherein said means for setting the ratio between the individual currents includes means for varying the amplitudes of the currents supplied to the individual electrodes under the conditions that the sum of the amplitude values of the currents supplied to the individual electrodes is maintained at a predetermined value with all the currents having the same duration.

12. A welding apparatus as claimed in claim 9, wherein said means for setting the ratio between the individual currents includes means for enabling the sum of one of the mean and effective values of the currents supplied to the individual electrodes to be maintained at the predetermined value.

13. A welding apparatus as claimed in claim 8, wherein the at least leading and trailing electrodes are in substantial alignment in the weld direction, said selecting means includes means for selecting one of a predetermined total time duration for the sum of the duration of the individual currents supplied to the individual electrodes and a total predetermined amplitude value for the sum of the amplitude values of the individual currents supplied to the individual electrodes, said setting means including potentiometer means for varying at least one of the time duration and amplitude value for the individual currents supplied to the individual electrodes, said switching means including transistor means connected between said power source means and said individual electrodes for controlling the operation thereof in response to the selecting means and setting means for enabling the carrying out of the welding operation.

14. A welding apparatus comprising a plurality of electrodes, electric power source means for supplying welding currents to the welding apparatus, and control means for enabling a welding operation on a workpiece by alternately supplying the currents to the individual electrodes, respectively, the control means including a plurality of first switching means connected, respectively, to the individual electrodes for enabling welding current to be supplied to the individual electrodes in accordance with the operation thereof, transistor means coupled between the electric power source means and the plurality of first switching means for controlling welding current to the individual electrodes pulse generator means for providing at least a plurality of pulse outputs corresponding to the number of individual electrodes, the pulse generator means including means for controlling the frequency and duty ratio of the pulse outputs, a plurality of potentiometer means corresponding to the number of individual electrodes, differential amplifier means for providing an output for controlling the transistor means, a plurality of second switching means connected between respective ones of the potentiometer means and one input terminal of the differential amplifier means, respective ones of the second switching means being responsive to different pulse outputs from the pulse generator means for controlling the operation thereof to supply a signal in accordance with the associated potentiometer means to the one input terminal of the differential amplifier means, means for detecting the welding current and for supplying the one input terminal of the differential amplifier with a signal indicative of the welding current so that the one input terminal of the differential amplifier means receives a signal of the difference of the signal applied through a respective one of the second switching means and the welding current detecting means, respective ones of the first switching means receiving output pulse signals from the pulse generator means for operation thereof corresponding with the output pulses received by corresponding respective ones of the second switching means, whereby the control means enables operation of the first and second switching means and the transistor means to provide a selected sum of values of currents to the individual electrodes in accordance with the material of the workpiece with each current supplied to each of the electrodes being applied alternately and the sum of the values of each current equaling the selected sum of the values.

15. A method of controlling currents supplied to a plurality of electrodes of a welding apparatus having at least a leading electrode and a trailing electrode extending in the weld direction, and an electric power source for supplying welding currents to the welding apparatus for carrying out a welding operation on a workpiece by alternately supplying the currents to the individual electrodes, respectively, the method comprising the steps of selecting the sum of the values of the currents supplied to the individual electrodes in accordance with the material of the workpiece, setting each current supplied to each of the electrodes so that a sum of the values of each current equals the selected sum of the values and that a higher current is supplied to the leading electrode and a lower current is supplied to the trailing electrode with such current combination being selected to prevent humping in high speed welding, and carrying out the welding operation on the workpiece by alternately supplying the set current for each electrode to the individual electrodes, respectively.

16. An electrode current control method as claimed in claim 15, wherein the at least leading and trailing electrodes are in substantial alignment in the weld direction, in said setting step, the ratio between the currents supplied to the individual electrodes is set so that the sum of the values of the currents supplied to the individual electrodes is maintained at a predetermined value, and, in said carrying out step, the currents of the values set at said selected ratio are supplied to the individual electrodes, respectively, to carry out the welding operation.

17. An electrode current control method as claimed in claim 16, wherein said first step of setting said selected ratio between the individual currents includes varying the durations of the currents supplied to the individual electrodes under the conditions that the sum of the values of the currents supplied to the individual electrodes is maintained at the predetermined value and all the currents have the same amplitude, and in said second step, the currents having the durations set at said selected ratio are supplied to the individual electrodes, respectively, to carry out the welding operation.

18. An electrode current control method as claimed in claim 16, wherein said first step of setting said selected ratio between the individual currents includes varying the amplitudes of the currents supplied to the individual electrodes under the conditions that the sum of the values of the currents supplied to the individual electrodes is maintained at the predetermined value and all the currents have the same duration, and in said second step, the currents having the amplitudes set at said selected ratio are supplied to the individual electrodes, respectively, to carry out the welding operation.

19. An electrode current control method as claimed in claim 16, wherein said selected ratio between the individual currents is set under the condition that the sum of the means values of the currents supplied to the individual electrodes is maintained at the predetermined value.

20. An electrode current control method as claimed in claim 16, wherein said selected ratio between the individual currents is set under the condition that the sum of the effective values of the currents supplied to the individual electrodes is maintained at the predetermined value.

21. An electrode current control method as claimed in claim 15, wherein the step of setting includes setting the current supplied to the leading electrode to be substantially equal to the current supplied to the trailing electrode.