JPH0371982A - Resistance welding method - Google Patents

Abstract

PURPOSE:To stabilize a resistance welding stage by detecting a point of time when a covering layer is molten and peeled off and then, providing the non-weld time in welding of material to be welded having the covering layer using first, second and third electrodes. CONSTITUTION:The material 4 to be welded having the covering layer is abutted on a work 5 and the first and third electrodes whose tips are brought into contact with each other are pressed on the material 4 to be welded and energized and the covering layer of the material to be welded is molten and peeled off. After this point of time when the covering layer is molten and peeled off is detected, energizing is executed between the first electrode and the second electrode for the specified time and after the specified non-weld and cooling time, energizing is again executed between the first and second electrodes. By this method, even if the time when the covering layer is molten and removed is changed by deterioration of the electrodes, variation of a resistance value, variance of the covering layer thickness, etc., satisfactory and stable resistance welding can be performed.

Description

[Detailed Description of the Invention] <Industrial Application Field> When welding a workpiece such as a conductor having an insulating N layer, the present invention applies a method in which the N layer is peeled off (melted and removed) by heating and then welded. This invention relates to a resistance welding method.

<Conventional technology> For example, when connecting conductor wires coated with heat-resistant synthetic resin (esterimide, etc.) to the terminals of electrical equipment, resistance welding (spot Welding) may be used to connect them. In such a case, the heat-resistant coating layer does not easily melt during welding, so if resistance welding is performed as is, welding defects may occur. For this reason, it is necessary to chemically remove carbon from the conductor's coating layer using a solvent before welding, and this removal work is complicated and takes a long time, so it is necessary to remove C from the conductor's coating layer using a solvent. A welding machine capable of welding was requested.

<Problem to be solved by the invention> Therefore, conventionally, the first
In addition to the electrode and the second electrode, a spot welding machine has been developed in which a third electrode is disposed in contact with the tip of the first electrode (see Japanese Patent Laid-Open No. 63-235081).

This spot welding machine makes the electrical resistance of the first electrode and the third electrode higher than that of the second electrode, and when welding, first conducts electricity between the first electrode and the third electrode that contacts at its tip. The tip of the electrode is heated to melt and remove the coating layer of the workpiece, and then, as the coating layer is removed, a current flows between the first and second electrodes through the workpiece, thereby causing a welding current to flow through the workpiece. , operate to weld the workpiece.

However, such three-electrode spot welding machines perform welding under predetermined welding conditions (particularly a constant energization time), so there is a risk of deterioration of the electrodes, fluctuations in resistance, and thickness of the coating layer. If the time required to melt and remove the coating layer varies depending on the workpiece due to variations in There was an issue.

The present invention has been made to solve the above-mentioned problems, and is a resistance welding method capable of welding a workpiece with a coating layer in a good and stable manner regardless of the conditions of the workpiece, the workpiece, and the electrode. The purpose is to provide a method.

Means for Solving the Problems> In order to achieve the above object, the resistance welding method of the present invention brings a workpiece with a coating layer into contact with a workpiece, and first electrodes whose tips are brought into contact with each other. and the third electrode is pressed onto the workpiece, the second electrode is brought into contact with the workpiece, and first, electricity is applied between the first electrode and the third electrode to melt and peel off the coating layer of the workpiece. In a resistance welding method in which the object to be welded is welded to the workpiece by applying current between the first electrode and the second electrode as the object peels off, what is the resistance welding method? & Detect the point in time when the coating layer of the welded object melts and peels off, and from the point of detection, the first electrode and the second electrode
The structure is such that electricity is applied between the electrodes, and after a certain non-current cooling time, electricity is applied again between the first electrode and the second electrode.

<Operation> Welding is started and a voltage is applied between the first electrode and the second electrode and between the first electrode and the third electrode, but since the object to be welded has an insulating coating layer, the first electrode No current flows between the second electrodes, but current flows between the first and third electrodes whose tips are in contact, and the tips of the electrodes rapidly become red-hot. This heat melts and peels off the coating layer of the object to be welded, and the first electrode is attached to the object to be welded.
The object to be welded comes into contact with the workpiece. Then, the first electrode and the third
Since the electrode is made of a material with a relatively high electrical resistance and the second electrode is made of a material with a lower electrical resistance, a current flows between the first electrode and the second electrode, which have a lower resistance, and at this point It is detected by detecting the current flowing through two electrodes.

Then, electricity is applied for a certain period of time from this detection point, and then, after a certain period of de-energization, the first electrode and the second electrode are connected again.
Welding is performed by passing a current between the electrodes to melt the abutting portion of the object to be welded and the workpiece.

<Example> Embodiments of the present invention will be described below based on the drawings.

First, the general structure of the resistance welding machine will be explained with reference to Fig. 1. 1 is the first electrode, 2 is the 2' electrode, 3 is the third electrode, and the tips of the first electrode 8i1 and the third electrode 3 are It has a structure in which the workpiece 4 to be welded is held down by contacting each other. The object to be welded 4 is the workpiece 5
The tip of the second electrode 2 contacts the workpiece 5 . As the object to be welded 4, a conducting wire having an N layer such as enamel or esterimide is used, and as the workpiece 5, a conductive terminal member or the like is used.

The first electrode 1 and the third IT electrode 3 are raised and lowered by a lifting mechanism (not shown), and are lowered to a position as shown in FIG. 1 during welding to press the workpiece 4 to be welded. The second electrode 2 is in contact with the upper part of the workpiece 5, but the second electrode 2 is positioned on the lower side of the workpiece 5 facing the first electrode 8i1, and the second electrode 2 and the first and 31st poles are connected to each other. The workpiece 5 and the object to be welded 4 may be placed between them.

Each electrode is formed of, for example, an alloy containing tungsten as a main component, but the first electrode 1 and the third electrode 3 contain molybdenum or the like to increase their electrical resistance, and the second electrode 2 is made of copper, silver, etc. 6 is a transformer for welding, and the primary side of the transformer 6 is connected to a power supply control circuit 7 for welding, and one of the secondary sides is connected to the first electrode 1. and the other is connected to the third
It is connected to the electrode 3 and the second electrode 2. The power supply control circuit 7 is
For example, the structure is such that the AC power is supplied to the transformer 6 by controlling the firing angle using a thyristor.

Reference numeral 9 denotes a toroidal coil provided for detecting the flowing current of the second electrode 2&, which is connected to the waveform restoration circuit 10. The output side of the waveform restoration circuit 10 is connected to a waveform shaping circuit 11 that integrates the alternating current waveform and shapes it into a rectangular wave, and the output side of the waveform shaping circuit 11 detects the point in time when current begins to flow into the second voltage Vi2. It is connected to the timing detection circuit 12.

The timing detection circuit 12 sends a short one-shot signal to the delay circuit 13 in synchronization with the rise of the rectangular wave sent from the waveform shaping circuit 11, that is, the start of energization of the second electrode.
Output to. The delay circuit 13 inputs the signal sent from the timing detection circuit 12, and the sequencer 8 is configured to output the signal to the sequencer 8 after a certain delay time (for example, 0.1 seconds) from the time of manual input. It is programmed to continuously control the entire operation over time, and controls the actuator for pole elevation (not shown) and the power supply control circuit 7 based on a preset program. That is, regarding the control of the welding power source, a predetermined welding current is started to flow between the electrodes, and when a signal from the delay circuit 13 is input, the welding current is interrupted once, and a certain cooling time (for example, 0.1
The sequence is configured such that the welding current is started again after 5 seconds have elapsed, and the welding current is passed for a certain period of time (for example, 0.16 seconds).

Next, a welding method using the resistance welding machine having the above configuration will be explained.

With the workpiece 5 and the object to be welded 4 placed on top of each other on the table,
The first and third Ti electrodes descend and contact each other in the first electrode 1
The object to be welded 4 is held down by the tip of the third electrode 3. In this state, the power supply control 1J1 circuit 7 operates to start supplying the welding current (point A in the waveform diagram in Figure 2), and the transformer 6
The current generated on the secondary side of the workpiece 4 does not flow between the second electrode 2 and the first electrode 1 due to the coating layer of the workpiece 4;
1 flows between pole 1 and third electrode 3.

At this time, the tips of the first t-pole 1 and the third electrode 3, which have high resistance, rapidly generate heat due to Joule heat, and this heat melts and peels off the coating layer of the workpiece 4 immediately below. Then, the tip of the first pole 1 comes into contact with the wire of the workpiece 4, and the wire comes into contact with the workpiece 5, and a current starts to flow between the first electrode 1 and the M2 electrode 2, which have less resistance ( At this point, the actual welding of the object to be welded 4 and the workpiece 5 begins (point B in FIG. 2), and at this time, the current of the second electrode 2 is detected by the toroidal coil 9 and the waveform restoration circuit 1G. After passing through the waveform shaping circuit 11, a one-shot detection signal is sent from the timing detection circuit 12 to the delay circuit 13 in synchronization with the start of the current flow.
and a certain delay time (e.g. 0.1
seconds) later, a signal is output from the delay circuit 13 to the sequencer 8.

When the sequencer 8 receives the signal from the delay circuit 13,
Immediately, a cutoff signal is output to the power supply control circuit 7 to cut off the welding current (point C in FIG. 2).

Then, the sequencer 8 stops the energization for a preset certain period of time (for example, 0.15 seconds) (C in Fig. 2).
-D), by providing such a non-energizing period, that is, cooling time, the object to be welded 4 and the workpiece 51. 1: It is possible to prevent excessive heating and melting in the metal and to minimize the effect of heat on the metal, thereby achieving good welding results.

After the cooling time has elapsed, welding current is again started to flow between the first electrode 1 and the second electrode 2 for a fixed period of time (for example, 0
．． 16 seconds) Welding current is applied (between DE and E in FIG. 2), and after the current is stopped and a certain work holding period has elapsed, this welding is completed.

In this way, the coating layer of the object to be welded 4 melts! II! 1t
After Lk, energization is carried out for a certain period of time, including a certain non-current cooling period, and a substantial welding current is passed through the workpiece for a certain period of time, so the time it takes for the coating layer to melt and peel off, unlike conventional methods, is longer due to various factors. Even if there are fluctuations, stable welding can be performed.

In the above embodiment, the point at which the coating layer of the welded object 4 peeled off and the second electrode 2 started to be energized was detected by detecting the current of the second electrode 2, but at this point, the first electrode 1 and second
It can also be detected by measuring the resistance value (voltage) between the electrodes 2 and detecting a decrease in the voltage.
When current begins to flow through pole 2, the temperature of the welded object and workpiece rises, and the temperature is measured by an infrared temperature sensor.
It is also possible to detect that point in time.

<Effects of the Invention> As explained above, according to the resistance welding method of the present invention,
The point in time when the coating layer of the workpiece melts and peels off is detected, the first electrode and the second electrode are energized for a certain period of time from the point of detection, and after a certain period of non-energized cooling time, the first electrode and the second electrode are connected again. 2
Since the structure is configured so that current is applied between the electrodes, after the coating layer of the workpiece is melted and peeled off, the current is applied for a certain period of time including a certain non-current cooling period, and the substantial welding current is applied to the workpiece for a certain period of time. Therefore, even if the time required to melt and remove the coating layer varies depending on the workpiece due to electrode deterioration, resistance value fluctuation, or coating layer thickness variation, good and stable welding can be performed. .

In addition, since a certain amount of non-current cooling time is interposed during the current flow between the first electrode and the second electrode, excessive heating and melting of the welded object and workpiece can be prevented, and the thermal effect on the metal can be minimized, resulting in a good condition. Welding results can be obtained.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, Fig. 1 is a block diagram of a resistance welding machine that implements the method of the invention, and Fig. 2 is a current waveform diagram of the first electrode and the second electrode. DESCRIPTION OF SYMBOLS 1... 1st electrode, 2... 2nd electrode, 3... 3rd electrode, 4... Welding object, 5... Workpiece.

Claims (1)

[Claims] A workpiece with a coating layer is brought into contact with the workpiece, a first electrode and a third electrode whose tips are in contact with each other are pressed onto the workpiece, and the second electrode is brought into contact with the workpiece. First, electricity is applied between the first electrode and the third electrode to melt and peel off the coating layer of the welded object, and along with this melting and separation, electricity is applied between the first and second electrodes to remove the welded object. In a resistance welding method for welding an object to a workpiece, a point in time when the coating layer of the object to be welded melts and peels off is detected, and from the point of detection, electricity is applied between the first electrode and the second electrode for a certain period of time, and a certain amount of non-conformity is applied. A resistance welding method characterized in that after an energization cooling time, energization is again performed between the first electrode and the second electrode.