JPH0994672A - Method for detecting energized state in flash welding electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for detecting an energized state between an electrode and a holding part of a member to be welded before flash welding. SOLUTION: Electrodes 3A, 3B, 4A, 4B for holding two members 1, 2 to be welded are prepared at least for two sets; before allowing a flash current to flow after abutting the end faces of the two members 1, 2 on each other, a voltage lower than that of the flash current is applied to each feeding transformer 5, 6; and comparison is made between a current value under the normal contact condition of the electrode with the holding part and the current value of each feeding transformer 5, 6, or among themselves between the current values of these feeding transformers 5, 6, so that the energized state is detected in each holding part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a current-carrying state of a flash-welding electrode, which can detect a current-carrying state between a power feeding electrode and a gripped portion of a member to be welded during flash welding. Is.

[0002]

2. Description of the Related Art As is well known, in flash welding, two members to be welded are held by their respective electrodes and the end faces of the members to be welded are brought into pressure contact with each other, and the applied voltage is as low as 7 to 13 V. A large current is passed between the electrodes to generate heat intensively at local contact points on the end faces to melt and disperse a spark, and one electrode is moved toward the other electrode to bring the end faces into close contact with each other. While repeating, contact and sparks are repeated. After the end face is sufficiently heated, it is pressed and thus the entire end face is welded.

The surface of a member to be welded in ordinary flash welding is covered with a scale, an oxide film or the like (hereinafter, simply referred to as scale). These films have a very large resistance value (impedance) as compared with the member to be welded, and if such a member to be welded is held by the electrode as it is and a current of a normal flash current of several thousand A to tens of thousands A is passed, Compared with the case where the scale is removed, a large voltage drop occurs at the contact portion (holding portion) between the electrode and the member to be welded. For this,
When the impedance becomes larger than usual, current does not flow even if a predetermined voltage is applied, and if current is allowed to flow even in such a state, not only the size of the power equipment is increased but also the power loss is increased, It is desirable that the voltage drop be as small as possible.

Further, if a large current is continuously applied to the above-mentioned member to be welded through the scale on the surface, the film is heated by resistance heating, which eventually leads to fusing and arcing. This arc not only causes arc marks or product damage, but also damages the electrodes (often chrome copper and beryllium copper) that supply current from the power supply transformer to the member. Therefore, in any case, it is necessary to suppress the generation of arc in the electrode.

Therefore, conventionally, the state of flash generated at the initial stage of flash welding was observed, and if stable flash could not be obtained, the welding was stopped and the electrode was gripped again. .

[0006]

However, in order to observe the flash, it is necessary to generate the flash.
If a flash is generated even once, a large amount of resistance heat will be generated at the contact part between the electrode and the gripped part that are not energized, and in an extreme case, an arc will be generated at the electrode and the gripped part, causing arcing on the welded member. Not only the marks are left, but also the electrodes may be damaged.

Therefore, it is important to measure the voltage drop at the contact portion between the electrode and the gripped portion before the flash occurs. However, this contact resistance was so small that it could not be measured by an ordinary tester or the like.

The present invention provides a method for simply and inexpensively detecting the electrical connection between an electrode and a grasped portion without requiring a special device.

[0009]

Two members to be welded to be flash-welded are respectively held by two electrodes, which are connected to both output terminals on the secondary side of a power supply transformer and form a pair, The present invention has at least two sets of such electrodes. The electrodes of each set are connected to the respective separate power supply transformers as described above.

In the present invention, the end faces of the two members to be welded are brought into contact with each other, and a flash current is supplied to the primary side of the power supply transformer to which the electrodes of each set are connected before the flash current is passed for the test. A detection voltage lower than the current is applied. The secondary side of each power supply transformer forms an electric circuit through the electrode and the member to be welded. Then, the current value on the primary side or the secondary side of each power feeding transformer at that time is measured.

Before such a test, when the contact between the electrode and the member to be welded is in a normal state, the same voltage as the voltage for detection is applied to the electric circuit and the secondary side at that time is applied. Measure the current value of. The current value in the normal contact state is compared with the current value detected before welding for each power feeding transformer, and when a decrease in the current value is observed, it is determined that the electrodes are not energized. Moreover, even if the current value in the normal state is not measured, the current values are compared between the primary side current or the secondary side current of each power feeding transformer, and if there is a difference between these values, the power feeding transformer with the smaller value is selected. It is possible to judge that the contact surface of the gripped part with the electrode is worse than the other.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS. 1 and 2 of the accompanying drawings.

In FIG. 1, reference numerals 1 and 2 denote members to be welded, the ends of which are held by two sets of electrodes 3A, 3B and 4A, 4B. The electrodes 3A and 3B of one set are connected to the secondary side of the first power supply transformer 5, and the other electrodes 4A and 4B are connected to the secondary side of the second power supply transformer 6.
In the two sets of electrodes, the opposing electrodes 3A, 4A and the electrodes 3B, 4B can be respectively brought into and out of contact with the members to be welded 1 and 2 by a clamp mechanism (not shown), and hold the members to be welded 1 and 2 at a predetermined time. It is like this. Further, one counter electrode, for example, the electrodes 3A, 4A, can be moved to a position where it is held in contact with the member to be welded 2 shown in FIG. 1 while holding the member to be welded 1 during flash welding.

The first and second power feeding transformers 5 and 6 are both constructed in the same manner, and the secondary sides 7 and 8 have electrodes 3 respectively.
A, 4B and 4A, 4B connected to the primary side 9,10
Voltage detectors 11 and 12 and current detectors 13 and 1
4 are connected. Furthermore, on the primary side, an SCR circuit 15 for turning on and off the power feeding transformers 5 and 6,
16 are provided.

Next, the procedure for detecting the energization state between the electrode and the gripped portion of the member to be welded in the apparatus of FIG. 1 will be described.

First, as shown in FIG. 1, the members 3 to be welded 1 and 2 are operated by operating a clamp mechanism (not shown).
The member 1 to be welded is held by 4A and the member 2 to be welded is held by the electrodes 3B and 4B, and the end surfaces of the members 1 and 2 to be welded are brought into contact with each other.

Next, the SCR circuits 15 and 16 of the first power feeding transformer 5 and the second power feeding transformer 6 are turned on. At that time, in order to make the secondary side voltage of the first power supply transformer 5 and the second power supply transformer 6 lower than that at the time of flash welding, the SCR
The primary side voltage is lowered by controlling the phases of the circuits 15 and 16 or switching taps (not shown).

When the SCR circuits 15 and 16 are turned on, the members to be welded 1 and 2 are in contact with each other, so that the secondary sides 7 and 8 of the first power feeding transformer 5 and the second power feeding transformer 6 are
Electrodes 3A, 3B, electrodes 4A, 4B and welded members 1,
Each of the electric circuits is formed via 2, and a current flows through them.

If the primary voltage is kept constant by monitoring the voltage detectors 11 and 12 of the first feeding transformer 5 and the second feeding transformer 6, the current value I ₅ , flowing through the respective secondary side, that is, the above electric circuit, Since I ₆ is proportional to the reciprocal of the impedance of the electric circuit, if the primary currents are measured by the current detectors 13 and 14, the currents of the respective electric circuits are calculated based on the turns ratio of the primary side and the secondary side. Get the value. In each of the above electric circuits, the impedance of the member to be welded, the electrode, and the winding on the secondary side is considered to be constant at all times. It is the contact resistance at the grip. That is, if there is a scale or the like on the surface of the gripped portion, this contact resistance becomes large and it becomes difficult for current to flow.

Thus, the detection voltage is applied to the primary side of each of the power feeding transformers 5 and 6, the secondary currents I ₅ and I ₆ are calculated from the detected primary currents, and the contact between the gripped part and the electrodes is made. It can be determined whether or not the energization is defective by comparing with the current value in the normal state.

Further, the current values of the secondary currents of the first power feeding transformer 5 and the second power feeding transformer 6 can be compared with each other without previously measuring the current value when the contact between the gripped portion and the electrode is in the normal state. It is possible to judge that the one with a lower current value is defective due to the energization only by making a comparison.

In the case of FIG. 1, one member to be welded is gripped by two electrodes opposed to each other on the diameter line, but it is also possible to grip by more electrodes. FIG. 2 shows a case of gripping with three electrodes arranged at equal intervals in the circumferential direction.

In FIG. 2, electrodes 21A, 22A, 23A and 21B, 22B, 23B are arranged around the members 1 and 2 to be welded at equal intervals in the circumferential direction. The secondary sides of the power supply transformers P, Q, R are electrodes 21A, 21B; 2
2A, 22B, and 23A, 23B, respectively. Each of these power feeding transformers P, Q, and R itself has exactly the same configuration as that of the power feeding transformer 5 or 6 in FIG. 1, and the description thereof will be omitted here. When three or more power supply transformers are used in this way, it is possible to detect a conduction failure by evaluating the difference between the maximum value and the minimum value between the secondary current values.

In the cases of FIG. 1 and FIG. 2, the secondary current value was calculated from the primary current value to determine the conduction failure, but since the primary current value and the secondary current value are always in a proportional relationship, the primary current value is You may evaluate by a value.

[0025]

As described above, according to the present invention, two or more sets of electrodes connected to the power feeding transformer are provided to grip the members to be welded, and the two members to be welded are brought into contact with each other before flash welding. To detect the energization state before flash welding by passing a detection current through the transformer and comparing the primary side current value or the secondary side current value for each power supply transformer with that in the normal contact state between the electrode and the gripped part. Because you can
This has the effect of preventing product scratches and device damage before they occur.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing another embodiment of the present invention.

[Explanation of symbols]

 1, 2 Members to be welded 3A, 3B Electrodes 4A, 4B Electrodes 5 First feeding transformer 6 Second feeding transformers 21A, 21B Electrodes 22A, 22B Electrodes 23A, 23B Electrodes P, Q, R Feeding transformers

Claims (1)

[Claims] 1. The two electrodes to be welded are respectively held by two electrodes which are respectively connected to both output terminals on the secondary side of the power feeding transformer to form a pair, and the end faces of the members to be welded are brought into contact with each other. In order to perform flash welding in which a current is passed between both electrodes, in the method of detecting the energization state between the electrode and the gripped portion of the member to be welded, at least two sets of electrodes for gripping the two members to be welded are used, and the two Before the flash current is applied after the end faces of the two members to be welded are brought into contact with each other, a voltage lower than the flash current is applied to each power supply transformer, and the current value under the normal contact state between the electrode and the gripped part A method for detecting the energization state of a flash welding electrode, characterized by detecting the energization state of each gripped portion by comparing the current values of the power supply transformers or the current values of the power supply transformers.