JPH0249190B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a spot welding method for welding a covered electric wire and a base metal.

Conventionally, when spot welding an electric wire made of a conductor coated with a thermoplastic coating material such as vinyl chloride to a base material, the coating material at the welded portion of the wire has been peeled off in advance. However, this method requires a step of peeling off the covering material before the welding step, resulting in a large number of work steps and a problem of poor efficiency.

Therefore, a spot welding method has been proposed in which one of the pair of electrodes is heated before welding, and the coating material is melted and automatically peeled off. In other words, the wire is placed on a base metal while being covered, held under pressure with a pair of electrodes, the electrode on the wire side is heated, and then a large current is passed between both electrodes to weld the wire and base metal. I have to.

However, in this method, since the coating material is melted by heating only one electrode, there is a problem that the coating material is not completely melted. In particular, the coating material on the base metal side is difficult to melt, and the remaining coating material has a negative effect on welding.
Forcibly applying a large current may cause an explosion,
The welding surface was dirty and the finish was poor, making perfect welding difficult.

This invention was made in view of this point, and by heating one electrode, passing a small current, and then passing a large current, it is possible to completely melt the coating material and perform reliable welding. The object of the present invention is to provide a spot welding method that achieves the following.

That is, in order to achieve the above object, the present invention includes an electric wire in which the conductor is coated with a thermoplastic insulating coating material, which is placed on a base material while being coated, and interposed between a pair of electrodes. The electric wire and the base material are held under pressure in close proximity, the electrode on the electric wire side is energized to heat this electrode, the insulating coating is melted and a part of the conductive wire is exposed, and then this A first current is passed between the two electrodes via the conductor exposed part and the base material to further melt the insulation coating and enlarge the conductor exposed part, and then the conductor exposed part and the base material are A second current, which is larger than the first current, is caused to flow between the two electrodes via the electric wire to weld the electric wire and the base metal.

Hereinafter, one embodiment of the present invention will be described in detail based on the drawings.

As shown in FIG. 1, numeral 1 is a spot welding device for spot welding an electric wire 2 and a base material 3, and is comprised of a fixed electrode 4 and a movable electrode 5.

The electric wire 2 consists of a conducting wire 2a covered with a covering material 2b, and the covering material 2b is made of a thermoplastic material such as vinyl chloride or enamel. This electric wire 2 is placed on the base material 3 while being covered.

The fixed electrode 4 is arranged below, and the movable electrode 5 is arranged above, with their tip surfaces facing each other. The movable electrode 5 has conductive plates 5 on both sides of the insulating plate 5a.
5b and 5b are bonded together, and a chip 5c made of tungsten or the like having a suitable electric resistance is fixed to the lower end, and is supported by a holder 5d so as to be movable up and down.

Further, a heating control circuit 6 is connected to the movable electrode 5, and this heating control circuit 6 is constructed by connecting a switch 6a and an AC power source 6b in series between two terminals 5e, 5e provided on the holder 5d. There is. This heating control circuit 6 applies alternating current to the chip 5c via both conductive plates 5b, 5b, and
It is designed to directly heat c.

Furthermore, a welding control circuit 7 is connected between both electrodes 4 and 5, and this welding control circuit 7 is connected from the fixed electrode 4 to the movable electrode 5 via a current detection section 7a, a DC power supply section 7b, and a switch 7c in this order. has been configured. This welding control circuit 7 includes both electrodes 4 and 5.
Current is applied twice in between, and the first
The current for the first time is small and the current for the second time is large. After the first energization, the current detection section 7a outputs a detection signal to the power supply section 7b, and the second energization is performed. .

Next, a spot welding method using this spot welding apparatus 1 will be explained based on FIGS. 2 and 3.

As shown by the solid line in FIG. 1, first, with the movable electrode 5 raised, the base material 3 is placed on the fixed electrode 4, and the electric wire 2 is placed on this base material 3 while being covered. It is interposed between electrodes 4 and 5.

Subsequently, the movable electrode 5 is lowered, and the electric wire 2 and base material 3 are
is held under pressure between it and the fixed electrode 4. On this occasion,
As shown in FIG. 3a, the electric wire 2 and the base material 3 are positioned on the base material 3 in a substantially perfect circle state.

Subsequently, the switch 6a of the heating control circuit 6 is turned on, and the alternating current shown in FIG. 2A is applied to the chip 5c to heat the chip 5c. By this heating, as shown in FIG. 3b, the upper and lower portions of the covering material 2b are slightly melted, and the upper and lower portions of the conducting wire 2a are slightly exposed.

Thereafter, the switch 6a of the heating control circuit 6 is opened, and the switch 7c of the melting control circuit 7 is turned on.
By this application, a first relatively small direct current (see FIG. 2B) is first applied between the electrodes 4 and 5 via the exposed portion of the conductor 2a and the base material 3. Due to this energization, Joule heat is generated in the conductor 2a and the base material 3,
Since this heat has a small current, it does not melt the conductor 2a etc., but only the covering material 2b further melts, and the exposed portion of the conductor 2a expands (see FIG. 3c).

When this first energization is performed, the detection unit 7a
A detection signal is output to the power supply section 7b, and a second DC current is applied following the first one. This second current is larger than the first current as shown in FIG.
Electricity is applied between both electrodes 4 and 5 via. Due to this energization, Joule heat is generated again in the conducting wire 2a and the base material 3, and since this heat has a large current, the conducting wire 2a and the base material 3 melt, and as shown in FIG. 3 will be welded.

Finally, the switch 7c is opened and the movable electrode 5 is raised to complete the spot welding.

In this embodiment, the welding control circuit 7 is configured to flow a direct current, but an alternating current may be used.

As described above, according to the spot welding method of the present invention, one of the electrodes is heated to melt the insulating coating of the wire and expose a part of the conductor, thereby creating a small area between the two electrodes while ensuring a conductive path. The insulation coating is completely melted by the heat generated when the current is applied, so
By passing a second large current between the electrodes, the electric wire and the base metal are reliably welded.

Furthermore, since the work of peeling off the covering material is omitted, work efficiency is significantly improved.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, in which Fig. 1 is a schematic cross-sectional view of a spot welding device, Fig. 2 is a waveform diagram of the current flowing through the electrode, and Fig. 3 a, b, c, and d are diagrams showing electric wires and FIG. 3 is an end view showing the state with the base material. 1: Spot welding device, 2: Electric wire, 2a: Conductive wire, 2b: Covering material, 3: Base material, 4: Fixed electrode,
5: Movable electrode, 6: Heating control circuit, 7: Welding control circuit.

Claims (1)

[Claims] 1. An electric wire in which a conducting wire is coated with a thermoplastic insulating coating material is placed on a base material while being covered, interposed between a pair of electrodes, and the electric wire and base material are processed by bringing both electrodes close together. The pressure is maintained, and electricity is applied to the electrode on the wire side to heat this electrode, melting the insulating coating material and exposing a part of the conductor, and then connecting both the electrodes through the exposed portion of the conductor and the base material. A first current is applied in between to further melt the insulating coating material and enlarge the exposed conductor part, and then a first current is applied between the electrodes via the exposed conductor part and the base material. A spot welding method characterized in that a second current larger than the current is passed to weld the electric wire and the base metal.