JPH01186283A - Method for electrifying spot welding machine - Google Patents

Abstract

PURPOSE:To peel off a coating film well by melting and to execute welding well by making the current value in welding larger than that in peeling off the coating film in the specified period of the AC current for welding. CONSTITUTION:In case of using the wire rod coating a polyesterimide on a copper wire as a work, for instance, the peeling period Ta and welding period Tb are respectively set at about 15 cycles, the peeling current Ia is set about 600A, the welding period Tb about 800A and the welding current Ib is set at the larger value than the peeling current Ia. The coating film 30b of an electric wire 30 is peeled off by its melting with the heating of 1st and 2nd electrode 7 and 9, an element wire 30a is exposed, a continuity state is attained for the electrode 7 and terminal member 31 and the direct flow is attained between 1st and 2nd electrode 7 and 8. In continuation to this peeling period Ta the welding period Tb comes in, meanwhile the welding current Ib larger than the peeling current Ia is passed to a secondary coil 20a.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for energizing a spot welder, and in particular to a method for energizing a spot welding machine, particularly for melting and peeling off a wire coated with a coating film such as a synthetic resin. The present invention relates to a method for energizing a spot welding machine equipped with an electrode.

(Prior art) Conductive wires used in electronic devices exposed to high temperature atmospheres are
For example, it is coated with a heat-resistant synthetic resin such as polyesterimide, and when connecting this type of conductive wire to a terminal, welded joints (spot (welding) to the terminals.

When welding conductive wires to terminals, it is necessary to remove the synthetic resin insulation coating before welding. Conventionally, this coating has been removed by dissolving it with a strong alkaline solvent (for example, Turucoat). Chemical removal methods or mechanical removal methods have been used.

However, the work of removing the insulating coating film is laborious and time consuming, which is one of the factors that increases manufacturing costs.

Therefore, in order to solve this problem, the applicant of the present application has previously developed a method for connecting conductive wires coated with a heat-resistant synthetic resin such as polyesterimide to terminals without any special pretreatment. "Spot welding machine J" that can
(Japanese Patent Application No. 62-6580).

This spot welding machine holds a workpiece between a first electrode and a second electrode, and performs spot welding on the workpiece by supplying current between these electrodes. One end of a third electrode is brought into close contact with the contact portion, the other end of the third electrode is electrically connected to the second electrode side, and the first and third electrodes are connected to the second electrode. This electrode is constructed to have a higher electrical resistance value than that of 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 welding alternating current is applied after stacking and sandwiching workpieces consisting of terminals, the synthetic resin coating first blocks the current and the current flows through the path between the first and third electrodes. flows. At this time, the first and third electrodes, which have a high electrical resistance value, generate heat and reach a high temperature instantaneously, melting the synthetic resin coating film, and the melting of the coating film breaks down the electrical insulation and the current flows to the second electrode. It flows through the path between the first electrode and the second electrode, making it possible to weld the workpiece.

(Problem to be Solved by the Invention) By the way, when melting and peeling the coating film and welding are performed continuously using the spot welding machine, the welding current is divided into a current for peeling the coating film and a current for welding. If the current is set to the same current value, for example, to the current value necessary for melting and peeling off the coating film, a part of the welding current will be transferred to the third electrode during welding that is performed subsequent to peeling off the coating film. The welding current is insufficient due to the increase in resistance due to heat generation, electrolytic corrosion, oxidation, etc. of the electrode during welding, and as a result, welding is not performed sufficiently and welding defects occur. Therefore, it is necessary to set the current value to a large current value necessary for welding. However, when a large welding current is applied when the coating is melted and peeled off, the third electrode becomes overheated and the coating is rapidly melted, causing local peeling and welding from the previously peeled off area. As a result, not only are welding defects likely to occur, but the welding surface becomes dirty, and furthermore, there are problems such as a decrease in reproducibility and variations in welding strength from product to product.

The present invention has been made in view of the above-mentioned points, and it is an object of the present invention to provide a method for energizing a spot welder that can melt and peel a coating film well and also perform welding well.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a first electrode, a second electrode, one end of which is in close contact with a workpiece contacting portion of the first electrode, and the other end of which is in close contact with a workpiece contacting portion of the first electrode. a third electrode electrically connected to the second electrode.
electrode and the power supply side that supplies alternating current for welding for a predetermined period of time? n circuit, a workpiece is sandwiched between the first and third electrodes and the second electrode, and the third electrode is heated by the current flowing in the path between the first and third electrodes. In a method for energizing a spot welder, which melts and peels off a coating film on a workpiece, and performs welding with a current flowing through the path of the first and second electrodes as the coating film is peeled off, during a predetermined period of the alternating current for welding, , the current value in the second half period is made larger than the current value in the first half period.

(Function) At the start of energization, the third electrode is prevented from overheating by first applying a current necessary for melting and peeling off the coating film of the workpiece, so that the coating film can be melted and peeled off well. Following this melting and peeling of the coating film, a large welding current necessary for welding the workpieces is applied to weld the workpieces.

(Example) Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a front view of a spot welding machine to which the current application 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 a spot welding machine 1, and an upper electrode support arm 4 is attached to the front upper part of the main body frame 3 so as to be movable up and down. This upper electrode support arm 4 is driven in the vertical direction by an actuator 5 such as an air cylinder. The actuator 5 is provided with an adjustment screw 5a for regulating the amount of vertical movement of the upper electrode support arm 4, that is, the electrode holder 10.12 that supports the first and third electrodes 7.9, which will be described later. By adjusting the adjustment screw 5a, the workpiece pressing force of the electrode 7.9 is adjusted to a required value.

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 constituted by a water cooling jacket, so that the first electrode 7 is cooled by cooling water. It has become. Third electrode 9
As shown in FIG. 2, the upper electrode support is placed so that its tip comes into close contact with the tip of the electrode 7 of the tube 1 (work contact area) from the rear and diagonally above the first electrode. An electrode holder 12 is supported by the arm 4. This electrode holder 12 is also constituted by a water cooling jacket, and the electrode 9 is cooled by cooling water.

A lower electrode support arm 6 is fixedly installed on the upper surface of the base 2 at a position below the upper electrode support arm 4, and a second electrode (fixed electrode) 8 is supported on the lower electrode support arm 6. An electrode holder 11 is supported. The second electrode 8 is fixed with its distal 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 this second electrode 8 is also constituted by a water cooling jacket, and the electrode 8 is cooled by cooling water. In addition, each electrode holder 10 to 12 has a respective cooling water supply port) LOa to 12a and a cooling water discharge port) 1.
0b to 12b are provided, and these cooling water supply ports) 10a to 12a and cooling water discharge boats 10b to 12
b is connected to a cooling system (not shown) and supplied with cooling water.

The first electrode 7 is formed of a round bar as shown in FIGS. 3 and 4, and has a semicircular cross section on the diameter at the end surface 7a.
A hole 7b whose depth changes in a tapered manner is formed. Further, the third electrode 9 is formed of a round rod that fits into the groove 7b of the electrode 7, and the tip 9a is obliquely crimped to form a flat surface 9.
b. This electrode 9 is disposed with its tip 9a fitted into the groove 7b of the electrode 7, and in the fitted state, the plane 9b becomes horizontal. These electrodes 7
and the electrode 9 are in close contact with each other in the groove 7bg of the electrode 7 and are electrically connected.

The electrode 7 is arranged vertically with the tip surface facing downward, and the tip 9a of the electrode 9 is fitted into the groove 7c from behind and diagonally above the electrode 7 of the tube 1, so that the plane 9b is horizontal. It is arranged so that it comes into contact with the workpiece in a stable state.

The first and third electrodes 7 and 9 have a higher electrical resistance value than the second electrode 8, and as electrode materials for the first and third electrodes 7 and 9, molybdenum, tungsten, etc. are preferably used. be done. Further, as the electrode material of the second electrode 8, for example, Cu containing 35 wt% of tungsten (W),
tJ! Tungsten (W) containing (Ag), tungsten (W) containing zirconium (Zr), etc. are preferably used. In addition to the above-mentioned materials, a tungsten alloy having the same electrical properties may be used as the material for the first to third electrodes 7 to 9.

The base end side of the first electrode 7 is connected to a conductive wire 21 as shown in FIG.
The base end of the third electrode 9 is connected to one end of the secondary coil 20a of the welding transformer 20 via a conductive wire 22, and the base end of the second electrode 22 is connected to the other end of the secondary coil 20a. has been done. In addition, the primary coil 20b of the welding transformer 20
is connected to the power supply control circuit 23.

The power supply control circuit 23 supplies, for example, 50 Hz commercial AC power to the primary coil 20b of the transformer 20, and applies a 50 Hz welding AC current to the secondary coil 20a for a predetermined period T, thereby removing the coating film of the workpiece. The melting and peeling and welding are performed continuously. As shown in FIG. 6, this power supply control circuit 23 converts the energization period T necessary for melting and peeling off the coating film of the workpiece and welding to a period Ta necessary for melting and peeling off the coating film (hereinafter referred to as the peeling period). and a period Tb necessary for actual welding (hereinafter referred to as the welding period), the first half is the peeling period Ta, and the second half is the welding period Tb, and the current I is applied to melt and peel the coating film. The peeling current 1a is divided into a necessary current (hereinafter referred to as peeling current) Ia and a current necessary for actual welding (hereinafter referred to as welding current) Ib, and the peeling current 1a is maintained during the peeling period Ta.
, welding current 1b during welding period Tb0 is 2 of transformer 20.
Next, the coil 20a is energized.

For example, when using a 0.34φ copper wire coated with polyesterimide as the workpiece, the peeling period Ta
, the welding period Tb is set to approximately 0.3 sec (approximately 15 cycles), and the peeling current 1a is approximately 600 A.
Welding current 1b is set to approximately 800A. The welding current [b is a value larger than the peeling current 1a (Ib>
Ia). Of course, it goes without saying that these peeling period Ta, welding period Tb, peeling current Ia, welding current 1b, etc. are set to optimal values depending on the diameter of the wire material, the thickness of the coating film, etc. In addition, even in this case, the welding current 1
Of course, b is set to a value larger than the peeling current 1a.

In this way, by making the welding current 1b larger than the peeling current 1a, a part of the welding current is bypassed through the third electrode path during welding that is performed subsequent to peeling off the coating, as will be described later. Further, even if the resistance value increases due to heat generation, electrolytic corrosion, oxidation, etc. of the electrode, it is possible to supply a sufficient welding current necessary for welding.

Note that the peeling period Ta and the welding period Tb may be continuous, and the peeling current 1a and the welding current 1b may be applied continuously.
Alternatively, a cool period (rest period) of about one cycle may be provided between the peeling period Ta and the welding period Tb.

Next, we will explain the operating procedure and function of the spot welding machine 1 configured as described above. The case of welding to the terminal member 31 (FIG. 7) will be explained as an example.

First, cooling water is supplied to the water cooling jacket of each electrode holder 10 to 12, and as shown in FIGS. The superimposed 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 9c of the electrode 9 is pressed against the work.
A workpiece is held between the first and third electrodes 7 and 9 and the second electrode 8.

Next, the switch of the power supply control circuit 23 is turned on to supply current to the secondary coil 20a of the transformer 20. The power supply control circuit 23 energizes the secondary coil 20a with a peeling current Xa (FIG. 6) for a peeling period Ta0 from the time when energization is started. At the time when the application of the peeling current 1a is started, the conductive wire 30 is covered with the coating film 30b and therefore has insulating properties. Therefore, the current flows between the first electrode 7 and the second electrode 8. It does not flow directly, but flows through a closed circuit formed by the electrode 7, the conductive wire 21, the secondary coil 20a, and the conductive wire 22 via the conductive wire 22 and the third electrode 9. At this time, electrodes 7 and 9 have a higher electrical resistance value than electrode 8, and since electrodes 7 and 9 are simply connected with their tips touching each other, resistance increases as electricity is applied. The area near the abutting part where the value is high (Fig. 3) rapidly generates heat and becomes high temperature.

The coating #30b of the conductive wire 30 is melted and peeled off by heating the first and third electrodes 7 and 9, and in the latter half of the peeling period Ta, the strand 30a is exposed and the electrode 7 and the terminal member 31
It becomes conductive with respect to.

Thereby, the coating film 30b is melted and peeled off from the wire 30a in a good manner. Due to this conduction, the welding current flows directly between the first electrode 7 and the second electric FIi8 through the workpiece. The welding period Tb that follows this peeling period Ta begins, and the power supply control circuit 23 operates the secondary coil 20 during the welding period Tb.
A welding current [b larger than the peeling current 1a] is applied to a.

As mentioned above, this welding current 1b has a negative part in the first
flows from the electrode 7 to the third electrode 9 and bypasses it,
It also decreases due to an increase in resistance value caused by heating, electrolytic corrosion, oxidation, etc. of the electrode. However, the welding current 1b is set to the above-mentioned large current value in consideration of the decrease due to these factors, and therefore, the power supply control circuit 23 can supply a sufficient welding current to weld the workpiece during the welding period Tb0. Then, during the welding period Tb, the wire 30a and the terminal member 3
1 are welded.

Thereby, the heating of the electrode 7.9, 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 workpiece, 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 The welding time may be set to an appropriate value in consideration of these problems.

(Effects of the Invention) As explained above, according to the present invention, there is a first electrode, a second electrode, and one end of the first electrode is in close contact with the work contacting part, and the other end is in contact with the second electrode. It has a third electrode electrically connected to it and a power supply control circuit that supplies an alternating current for welding for a predetermined period, and a workpiece is held between the first and third electrodes and the second electrode. Then, the third electrode is heated by the current flowing in the path between the first and third electrodes, melting and peeling off the coating film of the workpiece, and the current flowing in the path between the first and second electrodes as a result of the peeling. In the energization method of a spot welding machine that performs welding, the current value in the second half of the predetermined period of the welding alternating current is made larger than the current value in the first half, so that It becomes possible to melt and peel off the coating film in a good manner, and it also becomes possible to weld the workpiece in a good manner after peeling off the coating film. As a result,
This method has excellent effects in that it is possible to significantly reduce the occurrence of welding defects, the welded surface can be finished satisfactorily, and the variation in welding strength from product to product can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a front view showing an embodiment of a spot welding machine to which the current supply method for a spot welding machine according to the present invention is applied, FIG. 2 is a side view of the same, and FIG. FIG. 4 is an enlarged cross-sectional view of the abutting part of the tip of the electrode.
5 is a wiring circuit diagram of the spot welding machine shown in FIG. 1, FIG. 6 is a graph showing an example of the current waveform in the energization method of the spot welding machine according to the present invention, and FIG. 7 is a sectional view in the IV direction. 2 is a sectional view showing a state in which a workpiece is held between the electrodes of FIG. 1; FIG. DESCRIPTION OF SYMBOLS 1... Spot welding machine, 2... Base, 3... Main body frame, 4... Upper electrode support arm, 5... Actuator (air cylinder), 6... Lower electrode support arm, 7... First electrode, 8... Second electrode, 9...
...Third electrode, 10-12... Electrode holder, 20.
... Welding transformer, 23... Power supply control circuit, 30...
・Conducting wire, 30a... Element wire, 30b... Coating film, 3
1...Terminal member.

Claims (1)

[Claims] Welding a first electrode, a second electrode, and a third electrode whose one end is in close contact with the workpiece contacting part of the first electrode and whose other end is electrically connected to the second electrode for a predetermined period of time. The workpiece is sandwiched between the first and third electrodes and the second electrode, and the current flowing in the path between the first and third electrodes causes the workpiece to be The third electrode is heated to melt and peel off the coating film on the workpiece, and along with the peeling off, the first and second
In a method of energizing a spot welding machine that performs welding with a current flowing through an electrode path, the current value in the second half of the predetermined period of the welding alternating current is made larger than the current value in the first half. A method for energizing a spot welding machine characterized by: