JPH07106462B2 - Energizing the spot welder - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for energizing a spot welding machine, and particularly to a third method for melting and peeling off the coating of a wire coated with a coating film of synthetic resin or the like. The present invention relates to a method for energizing a spot welding machine equipped with the above electrodes.

(Prior Art) Conductive wires used in electronic devices exposed to high temperature atmosphere are
For example, it is coated with heat-resistant synthetic resin such as polyester imide, and when connecting this type of conductive wire to the terminal, a welded joint (spot) is used so that the electrical connection is maintained for a long period of time even in a high temperature atmosphere. It is connected to the terminal by welding. When welding a conductive wire to a terminal, it is necessary to remove the insulating coating film of synthetic resin before welding.
For removing the coating film, for example, a chemical removal method or a mechanical removal method in which a strong alkaline solvent (for example, Solcoat) is used for dissolution has been used. However, the work of removing the insulating coating film takes time and labor, and is one of the factors that increase the manufacturing cost.

Therefore, in order to solve such a problem, the applicant of the present application has previously connected a conductive wire coated with a heat-resistant synthetic resin such as polyesterimide to a terminal or the like without performing a special pretreatment. Possible "spot welder"
(Japanese Patent Application No. 62-65802) is proposed.

In this spot welding machine, a work is sandwiched between a first electrode and a second electrode, and the work is spot-welded by energizing the work between these electrodes. One end of the third electrode is brought into close contact with the contact portion, and the other end of the third electrode is electrically connected to the second electrode side, and the first and third electrodes are the second electrode. The electrode has a higher electric resistance value than the electrode.

According to this spot welding machine, for example, a conductive wire coated with a synthetic resin coating film to be melted and removed by heating is connected between the first and third electrodes and the second electrode. When a work consisting of power terminals is overlapped and sandwiched, and then an alternating current for welding is applied, first, the current is blocked by the synthetic resin coating film and the current flows in the paths of the first electrode and the third electrode. Flowing. At this time, the first and third electrodes having a high electric resistance value generate heat to instantly reach a high temperature, and the synthetic resin coating film is melted. It flows in the path of the first electrode and the second electrode, and the work can be welded. A unique feature of this spot welding machine is that the coating film can be peeled off and welded at once by continuing the energization period for melting the coating film and the energization period for workpiece welding. The structure of the electrodes of this spot welding machine and the connection of these electrodes and the power supply circuit are unconventional, and the total current is always the first during the coating film peeling energization period and the work welding energization period.
It is possible to generate a stable heat generation on this surface by passing through the contact surface between the electrode and the third electrode.

(Problem to be Solved by the Invention) By the way, in the case of continuously performing melt peeling and welding of a coating film by the spot welding machine, a current for peeling the coating film and a welding current among welding currents are used. When the electric current and the electric current are set to the same electric current value, for example, the electric current value necessary for melting and peeling of the coating film, a part of the welding current is generated when the welding is performed subsequent to the peeling of the coating film. The welding current is insufficient due to the increase in the resistance value due to heat generation, electrolytic corrosion, oxidation, etc. of the electrode during welding, resulting in insufficient welding and poor welding. . Therefore, it is necessary to set the current value to a large current value required for welding. However, when a large welding current is applied during melting and peeling of the coating film, the third electrode is overheated, and the coating film is rapidly melted, causing local peeling and welding from the previously peeled portion. Since it is started, there is a problem that not only welding defects are likely to occur, but also the welded surface becomes dirty, the reproducibility is deteriorated, and the welding strength varies among products.

The present invention has been made in view of the above points, and an object of the present invention is to provide a method for energizing a spot welding machine capable of melting and peeling a coating film in a favorable manner and also performing welding in a favorable manner.

(Means for Solving the Problems) In order to achieve the above object, according to the present invention, one end of the first electrode, the second electrode, and the other end of the first electrode are brought into close contact with the workpiece contact portion. A third electrode electrically connected to the second electrode
Of the first electrode and the second electrode and a power supply control circuit connected to the first electrode and the second electrode for supplying an alternating current for welding for a predetermined period, and the first and third electrodes and the second electrode. The work is sandwiched between them, and the third electrode is heated by the current flowing in the paths of the first and third electrodes to melt and peel the coating film of the work, and the first and second electrodes are accompanied by the peeling. A method for energizing a spot welding machine that performs welding with a current flowing in a path, wherein a predetermined value of the AC current for welding is set so that the current value in the latter half of the period is larger than the current value in the first half. It is the one.

(Operation) When the welding current starts to be supplied, first, in the first half of the predetermined current supply period, the current necessary for melting and peeling the coating film of the work is supplied through the paths of the first and third electrodes. As a result, the third electrode is prevented from overheating, whereby the coating film is melted and peeled off well. Subsequent to the melting and peeling of the coating film, a large welding current required for welding is applied in the paths of the first electrode, the work, and the second electrode to weld the work, and the work is welded during the predetermined period. The peeling of the coating film and the welding are continuously performed.

(Embodiment) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a front view of a spot welding machine to which the energization method according to the present invention is applied, and FIG. 2 is a side view thereof. A main body frame 3 is mounted and fixed on a base 2 of the spot welding machine 1, and an upper electrode support arm 4 is attached to an upper front portion of the main body frame 3 so as to be vertically movable. The upper electrode support arm 4 is vertically driven by an actuator 5 such as an air cylinder. The actuator 5 is provided with an adjusting screw 5a for regulating the vertical movement amount of the upper electrode supporting arm 4, that is, the electrode holders 10 and 12 for supporting the first and third electrodes 7 and 9 which will be described later. The work pressure contact force of the electrodes 7 and 9 is adjusted to a required value by adjusting the screw 5a.

The electrode holder 10 is supported by the upper electrode support arm 4 with the tip of the first electrode 7 facing downward, and the electrode holder 10 is composed of a water cooling jacket so that the first electrode 7 is cooled by cooling water. It has become. The third electrode 9 is
As shown in FIG. 2, an electrode is attached to the upper electrode support arm 4 so that the tip of the first electrode 7 comes into close contact with the tip (workpiece contact portion) of the first electrode 7 from behind and obliquely above. The holder 12 is supported. This electrode holder 12 is also composed of a water cooling jacket, and the electrode 9 is cooled by cooling water.

A lower electrode support arm 6 is fixedly provided on the upper surface of the base 2 at a position facing the upper electrode support arm 4 below, and a second electrode (fixed electrode) 8 is supported on the lower electrode support arm 6. The electrode holder 11 is supported. The second electrode 8 is fixed with its tip end face facing upward and facing the end face of the first electrode 7 and the oblique end face of the third electrode 9.
The electrode holder 11 of the second electrode 8 is also constituted by a water cooling jacket, and the electrode 8 is cooled by cooling water. The electrode holders 10 to 12 are provided with respective cooling water supply ports 10a to 12a and cooling water discharge ports 10b to 12b, and these cooling water supply ports 10a to 12a and cooling water discharge port 10b to 12b is connected to a cooling system (not shown) to supply cooling water.

The first electrode 7 is formed of a round bar as shown in FIGS. 3 and 4, and the end surface 7a is formed with a groove 7b having a semicircular cross section in diameter and the depth of which changes in a taper shape. Has been done. The third electrode 9 is formed by a round bar that fits into the groove 7b of the electrode 7, and the tip 9a is obliquely cut to form a flat surface 9b. The electrode 9 is arranged with its tip 9a fitted in the groove 7b of the electrode 7, and the flat surface 9b is horizontal in the fitted state. The electrodes 7 and 9 are closely contacted and electrically connected in the groove 7b of the electrode 7.

The electrode 7 is disposed vertically with its tip face downward, the electrode 9 is fitted to the groove 7c at the tip 9a from the rear and obliquely above the first electrode 7, and the plane 9b is horizontal. It is arranged so as to come into contact with the work in such a state.

The first and third electrodes 7 and 9 have a higher electric resistance value than the second electrode 8, and as the electrode material of the first and third electrodes 7 and 9, for example, molybdenum and tungsten are preferably used. To be done. The electrode material of the second electrode 8 is, for example, 35 wt% tungsten (W) containing Cu, silver (Ag).
Tungsten (W) containing, tungsten (W) containing zirconium (Zr), etc. are preferably used. In addition, first to
As a material for the third electrodes 7 to 9, a tungsten alloy having the same electric characteristics may be used in addition to the above members.

As shown in FIG. 5, the base end side of the first electrode 7 is connected to one end of the secondary coil 20a of the welding transformer 20 via the conductive wire 21,
The base end side of the electrode 9 is connected to the other end of the secondary coil 20a together with the base end side of the second electrode 8 via a conductive wire 22. The primary coil 20b of the welding transformer 20 is connected to the power control circuit 23.
It is connected to the.

The power supply control circuit 23 supplies, for example, 50 Hz commercial AC power to the primary coil 20b of the transformer 20 to supply 50H to the secondary coil 20a.
The welding AC current of z is supplied for a predetermined period T to continuously perform the melt separation of the coating film of the work and the welding. This power supply control circuit 23, as shown in FIG. 6, has the energization period T necessary for melting and peeling the coating film of the work and welding.
Is divided into two periods, that is, a period required for melt peeling of the coating film (hereinafter referred to as peeling period) Ta and a period required for actual welding (hereinafter referred to as welding period) Tb, and the first half is the peeling period Ta and the second half. Is the welding period Tb, and the energizing current I is divided into a current required for melting and peeling the coating film (hereinafter referred to as peeling current) Ia and a current required for actual welding (hereinafter referred to as welding current) Ib, and peeling is performed. The peeling current Ia during the period Ta and the welding current Ib during the welding period Tb
To the secondary coil 20a of the transformer 20.

For example, when a 0.34φ copper wire coated with polyesterimide is used as the work, the peeling period Ta and the welding period Tb are set to about 0.3 sec (about 15 cycles), respectively, and the peeling current Ia is set to about 600 A. The welding current Ib is set to about 800A. Then, the welding current Ib is set to a value (Ib> Ia) larger than the peeling current Ia. Of course, these peeling periods
It goes without saying that Ta, the welding period Tb, the peeling current Ia, the welding current Ib, etc. are set to optimum values depending on the wire diameter of the wire rod, the thickness of the coating film, and the like. Even in this case, the welding current Ib
Of course, is set to a value larger than the peeling current Ia.

In this way, by making the welding current Ib larger than the peeling current Ia, as will be described later, a part of the welding current is bypassed by the path of the third electrode during welding which is performed subsequent to the peeling of the coating film. Furthermore, even if the resistance value increases due to heat generation, electrolytic corrosion, oxidation, etc. of the electrode, it becomes possible to supply a sufficient welding current necessary for welding.

It should be noted that the peeling period Ta and the welding period Tb are made continuous so that the peeling current Ia
And welding current Ib may be continuously applied, or
A cool period (pause period) of about one cycle may be provided between the peeling period Ta and the welding period Tb.

Next, the operation procedure and action of the spot welding machine 1 configured as described above will be described as a work, for example, a conductive wire obtained by coating a copper wire having a wire diameter of 0.34φ with polyesterimide
The case of welding 30 to the conductive terminal member 31 (FIG. 7) will be described as an example.

First, cooling water is supplied to the water cooling jackets of the electrode holders 10 to 12, and the conductive wire 30 is placed on the upper surface of the terminal member 31 at a required position as shown in FIGS. 1, 2, and 7. Then, the overlapped work is placed on the second electrode 8, the actuator 5 is operated to lower the first and third electrodes 7 and 9, and the flat surface 9b of the electrode 9 is pressed against the work, The work is held between the first and third electrodes 7 and 9 and the second electrode 8.

Then, switch on the power supply control circuit 23 to turn on the transformer.
A current is applied to the 20 secondary coils 20a. Power control circuit 23
Is the peeling current Ia (6th
(Fig.) Is energized to the secondary coil 20a. At the time when the peeling current Ia is started to flow, the conductive wire 30 is covered with the coating film 30b and thus has an insulating property. Therefore, the current flows between the first electrode 7 and the second electrode 8. No direct flow, conductive wire
It flows through a closed circuit formed by the electrode 7, the conductive wire 21, the secondary coil 20 a, and the conductive wire 22 via the 22 and the third electrode 9. At this time, the electrodes 7 and 9 have a higher electric resistance value than the electrode 8,
In addition, since the tips of the electrodes 7 and 9 are simply contacted to each other and connected to each other, the vicinity of the contact portion (FIG. 3) having a high resistance value rapidly heats up due to the energization, and the temperature becomes high. become.

The coating film 30b of the conductive wire 30 is melted and peeled by the heating of the first and third electrodes 7 and 9, and the wire 30a is exposed in the latter half of the peeling period Ta to the electrode 7 and the terminal member 31. It becomes conductive. As a result, the coating film 30b is satisfactorily melted and peeled from the wire 30a. This conduction allows the welding current to directly flow between the first electrode 7 and the second electrode 8 through the work. During the welding period Tb following the peeling period Ta, the power supply control circuit 23 causes the welding current Ib larger than the peeling current Ia to flow through the secondary coil 20a during the welding period Tb.

As described above, a part of the welding current Ib flows in the path from the first electrode 7 to the third electrode 9 to bypass it, and the resistance value caused by heating, electrolytic corrosion, oxidation, etc. of the electrode. It decreases with the increase of. However, the welding current Ib is set to the large current value in consideration of the decrease due to these, and therefore the power supply control circuit 23 can supply a sufficient welding current for welding the workpiece during the welding period Tb. Then, the wire 30a and the terminal member 31 are welded during the welding period Tb.

Thereby, the heating of the electrodes 7 and 9, the melting and peeling of the coating film 30b, and the welding of the wire 30a and the terminal member 31 can be completed in an extremely short time. The welding time varies depending on the work such as the wire diameter of the conductive wire 30 to be welded and the plate thickness of the terminal member 31, but if the welding time is too short, the strength of the welded joint will be insufficient, and if it is too long, the wire 30a will be used. Since there is a problem that the crushing of the wire occurs or the wire 30a is annealed and becomes brittle,
The welding time may be set to an appropriate value in consideration of these.

(Effects of the Invention) As described above, according to the present invention, one end of the first electrode, the second electrode, and the work contact portion of the first electrode are brought into close contact with the other end of the second electrode. A third power supply circuit electrically connected to the first electrode, a power supply control circuit connected to the first electrode and the second electrode for supplying an alternating current for welding for a predetermined period,
And sandwiching the work between the third electrode and the second electrode,
The third electrode is heated by the current flowing through the first and third electrodes to melt and peel off the coating film of the work, and welding is performed by the current flowing through the first and second electrodes along with the peeling. In the spot welding machine energizing method for performing, in a predetermined period of the AC current for welding, the current value in the latter half period is made larger than the current value in the first half period, so that The coating film can be satisfactorily melt-peeled, and the workpiece can be satisfactorily welded after the coating film is peeled. As a result, it is possible to significantly reduce the occurrence of welding defects, to finish the welded surface satisfactorily, and to reduce the variation in welding strength among products.

[Brief description of drawings]

FIG. 1 is a front view showing an embodiment of a spot welding machine to which the energization method of the spot welding machine according to the present invention is applied, FIG. 2 is a side view of the same, and FIG. 3 is a first and a third of FIG. FIG. 4 is an enlarged cross-sectional view of the contact portion of the tip of the electrode of FIG.
FIG. 5 is a graph showing an example of the energizing current waveform in the energizing method of the spot welding machine according to the present invention, and FIG. 7 is a sectional view of the spot welding machine of FIG. It is sectional drawing which shows the state which clamped the workpiece | work between the electrode of FIG. 1 ... Spot welder, 2 ... Base, 3 ... Main body frame, 4 ... Upper electrode support arm, 5 ... Actuator (air cylinder), 6 ... Lower electrode support arm, 7 ...
1st electrode, 8 ... 2nd electrode, 9 ... 3rd electrode, 10
〜12 …… Electrode holder, 20 …… Welding transformer, 23 …… Power control circuit, 30 …… Conducting wire, 30a …… Element wire, 30b …… Coating film, 31 …… Terminal member.

Claims (1)

[Claims] 1. A first electrode, a second electrode, and a third electrode, one end of which is in close contact with a work contact portion of the first electrode and the other end of which is electrically connected to the second electrode. , A power supply control circuit connected to the first electrode and the second electrode for supplying an alternating current for welding for a predetermined period, and a work between the first and third electrodes and the second electrode. Sandwiching, and heating the third electrode by the current flowing in the paths of the first and third electrodes to melt and peel off the coating film of the work, and along with the peeling, in the paths of the first and second electrodes. A method of energizing a spot welding machine for welding by flowing current, characterized in that, in a predetermined period of the alternating current for welding, the current value in the latter half period is larger than the current value in the first half period. How to energize the spot welder.