JPH0573516B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an electrode for a spot welding machine, and more particularly to a first electrode, a second electrode opposite to the first electrode, and a tip of which is connected to the first electrode. and a third electrode connected to the tip of the electrode.

(Prior art) Conductive wires used in electronic devices that are exposed to high-temperature atmospheres are coated with heat-resistant synthetic resin such as polyesterimide. It is connected to the terminal by a welded joint (spot weld) so that the electrical connection can be maintained for a long period of time even in the atmosphere.
When welding conductive wires to terminals, it is necessary to remove the synthetic resin insulation coating before welding.
To remove this coating film, for example, a chemical removal method in which the film is dissolved using a strong alkaline solvent (for example, Solcoat) or a mechanical removal method has been used.
However, the work of removing the insulating coating film is laborious and time consuming, and is one of the factors that increases manufacturing costs.

Therefore, in order to solve this problem, the applicant 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. Discloses a ``spot welding machine'' (patent application No. 62-6580) that can do this.

This spot welding machine holds a workpiece between a first electrode and a second electrode, and performs spot welding on the workpiece by passing 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, between the first electrode, the third electrode, and the second electrode, for example, a conductive wire coated with a synthetic resin coating film to be melted and removed by heating is inserted. When the workpieces consisting of electrodes to be connected are stacked and held between them and electricity is started, the current is blocked by the synthetic resin coating film and the current flows through the path from the first electrode to the third electrode (or
flows through the opposite route). 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 directly from one electrode to the second electrode, making it possible to weld the workpiece.

(Problem to be Solved by the Invention) By the way, in the spot welding machine described above, the tip of the first electrode and the tip of the third electrode are in good contact with each other, so that a large contact area can be obtained, and the tip of the third electrode is in close contact with the tip of the third electrode during welding. It is necessary to be able to concentrate heat generation at the tip of the electrode, and to improve the durability of the first and third electrodes and to increase the welding strength of the workpiece.

The present invention has been made in view of the above points, and it is possible to bring the first and third electrodes into good contact with each other with a large contact area, and to uniformly concentrate heat generation at the tip of the third electrode when the film is peeled off. It is an object of the present invention to provide an electrode for a spot welder that can improve the durability of each of these electrodes and increase the welding strength of a workpiece.

(Means for Solving the Problems) In order to achieve the above object, according to the present invention, an engagement groove is formed that has a predetermined inclination angle with respect to a plane perpendicular to the axis of the tip and has a substantially semicircular cross section. a second electrode having a tip end face spaced apart from and facing the first electrode; and a second electrode having a tip end face having a radius of curvature smaller than the radius of curvature of the groove of the first electrode. A curved surface having a substantially semicircular cross section is fitted and abutted to the engagement groove for a predetermined length, and a side surface is a plane perpendicular to the axis of the first electrode and serves as a contact surface to the workpiece. This configuration includes three electrodes.

The inclination angle of the engagement groove of the first electrode is 0 to
It is preferable to set it within a range of 30°.

Further, the engagement groove of the first electrode increases the inclination angle from the middle of the groove to restrict the length of the contact surface with the tip of the third electrode.

Furthermore, the end face of either the second or third electrode is inclined at a predetermined angle along the direction of entry and exit of the workpiece.

(Function) When the tip of the third electrode, which has a semicircular cross section, is fitted into the engagement groove of the first electrode, the approximate centers of the curved surfaces of each electrode come into contact with each other. When electricity is applied in the abutting state, the abutting portions of these two electrodes adhere well over substantially the front surface due to electrolytic erosion, and since the adhesion surface is a curved surface, the contact area is larger than that of a flat surface. As a result, the tip of the third electrode generates heat uniformly and is heated.

By setting the inclination angle of the engagement groove of the first electrode to a small angle in the range of 0 to 30 degrees, when the first and third electrodes are pressed against the workpiece during welding, the third electrode Make sure that it does not slip out of the first electrode.

In addition, by increasing the angle of inclination of the engagement groove of the first electrode from the middle of the groove and regulating the length of the contact surface with the tip of the third electrode, heat is generated at the tip of the third electrode. It acts to concentrate the welding current, stabilize the welding current, and prevent the occurrence of cracks due to electrolytic corrosion.

Furthermore, by inclining the end face of either the second or third electrode at a predetermined angle along the direction in which the workpiece enters and exits, the welding part is moved from the proximal end to the distal end when welding wire rods, etc. It is tapered on the side and acts to prevent the strength of the portion connected to the proximal end from decreasing.

(Example) Hereinafter, an example 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 electrode for a spot welding machine 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 includes an upper electrode support arm 4, that is, electrode holders 10 and 12 that support first and third electrodes 7 and 9, which will be described later.
An adjustment screw 5a is provided for regulating the amount of vertical movement of the electrodes 7 and 9, and the workpiece pressing force of the electrodes 7 and 9 is adjusted to a required value by adjusting the adjustment 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 constituted by a water cooling jacket, so that the first electrode 7 is cooled with cooling water. It's getting old. As shown in FIG. 2, the third electrode 9 is arranged such that its tip comes into close contact with the tip of the first electrode 7 (workpiece contact area) from behind and diagonally above the first electrode 7. An electrode holder 12 is supported by the upper electrode support arm 4. This electrode holder 12 is also constituted by a water-cooled 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 the second electrode 8 is also constituted by a water-cooled jacket, and the electrode 8 is cooled by cooling water. In addition, each electrode holder 10 to 12
have respective cooling water supply ports 10a to 12a,
Cooling water discharge ports 10b to 12b are provided, and these cooling water supply ports 10a to 12a and cooling water discharge ports 10b to 12b are connected to a cooling system (not shown) and supplied with cooling water.

The first electrode 7 is formed of a solid round bar as shown in FIGS. 3 to 5, and the end surface of the tip 7a is inclined at a predetermined angle θ with respect to a plane perpendicular to the axis. An engaging groove 7b having a radius _r1 and a substantially semicircular cross section is carved in the center of the end surface. This engagement groove 7b consists of two grooves 7c and 7d which are arranged in _succession as shown in FIG _. ing. Further, the inclination angle of the bottom surface of the groove 7c is set to the above-mentioned inclination angle θ, and the inclination angle of the bottom surface of the groove 7d is set to be larger than the inclination angle θ of the bottom surface of the groove 7c. The groove 7c is a groove for coming into close contact with the third electrode 9, and the groove 7d is a relief part from which the third electrode 9 does not come into close contact. Further, the second electrode 8 is a solid round rod having the same diameter as the first electrode 7.

The third electrode 9 is formed of a solid round rod with a slightly smaller diameter than the first electrode 7, as shown in FIGS. It is cut out diagonally by a plane forming an angle θ, and one side 9b is a curved surface with a radius r ₂ (<r ₁ ),
The other end surface 9c is a flat surface. One side surface 9b forming a curved surface is abutted and fitted into the groove 7c of the engagement groove 7b of the first electrode 7, and the other side surface 9c is used as a contact surface with the workpiece.

The curved surface 9b of the tip 9a of the third electrode 9 fits into the groove 7c of the first electrode 7, and these radii r ₁ and r ₂
The difference Δr (=r ₁ −r ₂ ) is set to a value slightly larger than the processing tolerance for normal fitting. For example, the radius r ₂ of the curved surface 9b of the third electrode 9 is 0.93r ₁ <r _{2 <} with respect to the radius r 1 of the groove 7c of the first electrode 7.
It is preferable to set the value within the range of _0.95r1 .

As shown in FIGS. 9 to 11, the upper limit value of the radius _r2 is determined by the processing error of each of these electrodes when fitting the tip 9a of the third electrode 9 into the groove 7c of the first electrode 7. It is not enough to simply set the value to absorb mounting errors, etc., but also to set the value to a value that allows the inner surface of the groove 7c and the side surface 9b of the electrode 9 to reliably come into contact at the center P of each of these two curved surfaces, Furthermore, the lower limit of the radius _r2 is such that when electricity is applied in such a state that they are in contact with each other, as shown in Fig. 11, both curved surfaces are brought into good contact over almost the entire surface due to electrolytic corrosion between the abutting surfaces. This is to set it to the minimum value that can be achieved. Moreover, the groove 7c of the electrode 7 and the electrode 9 are in close contact with each other.
By forming the side surface 9b of the electrode into a curved surface, the contact area between these two electrodes can be made larger than when the side surface 9b is made into a flat surface.

As a result, the curved surface 9b of the third electrode 9 is biased into the groove 7c of the first electrode 7, so that, for example, only one side of the curved surface 9b comes into contact with the inner surface of the groove 7c, or both sides of the curved surface 9b are in contact with the inner surface of the groove 7c. It is possible to prevent a problem in which the center is not in contact even though it is in contact with the inner surface of 7c.

As shown in FIG. 9, the first electrode 7 and the tip 9a of the third electrode 9 are in close contact and electrically connected in the groove 7c of the first electrode 7, and the groove 7d and the tip 9a of the electrode 9 are are far apart. Therefore, the welding current from the electrode 7 to the electrode 9 flows concentratedly in the groove 7c and the part that is in close contact with the groove 7c, and as a result, heat generation can be concentrated in the vicinity of the end 9a' of the tip 9a of the electrode 9. can.

The first electrode 7 is arranged vertically with its tip facing downward, and the third electrode 9 fits its tip 9a into the groove 7c from behind and obliquely above the first electrode 7. The workpiece is placed in close contact with the workpiece so that the flat surface 9c is in horizontal contact with the workpiece. Therefore, the third
The electrode 9 is arranged at the predetermined angle θ with respect to the horizontal plane. This predetermined angle θ is, for example, 8
It is set in the range of ~30°, and particularly preferably about 13°. By slanting the contact area between the first electrode 7 and the third electrode 9 in this way, the welding current can be stabilized, and the occurrence of cracks due to electrolytic corrosion can be prevented, and these electrodes can be Improves durability.

In addition, the second electrode 8, as shown in FIG.
The end face 8a facing the first and third electrodes 7 and 9 is inclined at a predetermined angle θ' with respect to a plane perpendicular to the axial direction. The direction of inclination of the end surface 8a is set to be inclined along the workpiece loading direction A or the workpiece unloading direction B.
Note that this end surface 8a is preferably set so that the upper end of the inclined surface is flush with the front end side of the workpiece. The inclination angle θ' of the end surface 8a of the electrode 8 is set to about 1 to 3 degrees, but if the workpiece is a wire rod, it is preferably set to an appropriate value depending on the diameter of the wire rod.

By inclining the end surface 8a of the second electrode 8 in this way, the welding strength of the workpiece can be improved, especially when welding wire rods, etc., and the welded portion can be tapered from the base end side to the distal end side. It is possible to prevent the strength of the portion connected to the base end of the welded portion from decreasing.

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

As shown in FIG. 13, the base end of the first electrode 7 is connected to one end of the secondary coil 20a of the welding transformer 20 through a conductive wire 21, and the base end of the third electrode 9 is connected through a conductive wire 22. 2 along with the base end side of the second electrode 22.
It is connected to the other end of the next coil 20a. Also,
The primary coil 20b of the welding transformer 20 is connected to a power supply control circuit 23.

Next, the operating procedure and operation of the spot welding machine 1 configured as described above will be described. As a workpiece, for example, a conductive wire 30 with an outer diameter of 0.31φ, which is coated with polyesterimide on a wire diameter of 0.28φ, is conductive. The case of welding to the terminal member 31 (FIG. 14) 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 FIG. It is placed on the second electrode 8, the actuator 5 is operated to lower the first and third electrodes 7 and 9, and the electrode 9 is placed on the second electrode 8.
The flat surface 9c of is brought into pressure contact with the workpiece, and the workpiece is held between the first and third electrodes 7 and 9 and the second electrode 8.

Next, the power supply control circuit 23 is adjusted so that the AC welding power is a predetermined value, for example, 3 KVA in the primary coil 20b, and a current with a frequency of 50 Hz is caused to flow in the secondary coil 20a. Immediately after applying the welding current, the conductive wire 30 has insulation properties because it is covered with the coating film 30b, and the current flows between the first electrode 7 and the second electrode 8.
There is no direct flow between the conductive wire 22 and the third electrode 9.
through the first electrode 7, the conductive wire 21, and the secondary coil 2.
0a, flows through a closed circuit formed by the conductive wire 22.
At this time, the first and third electrodes 7 and 9 have a higher electrical resistance value than the second electrode 8, and the first electrode 7 and the third electrode 9 simply have their tips touching each other. Since they are connected only in contact with each other, the area near the contact part 9a' where the resistance value is high as the current is applied (Fig. 9)
suddenly heats up and reaches a high temperature.

By heating the first and third electrodes 7 and 9, the coating film 30b of the conductive wire 30 is melted and peeled off, and the wire 30a is exposed, and the first electrode 7 and the terminal member 31
It becomes conductive with respect to. Due to this conduction, the welding current passes through the workpiece to the first electrode 7 and the second electrode 8.
The strands 30a and the terminal member 31 are welded together.

At this time, since the end surface 8a of the second electrode 8 is inclined, the terminal member 31 and the wire 30a are separated by the pressing force of the first and third electrodes 7 and 9 during welding, as shown in FIG. It is inclined along the end surface 8a, and as a result, as shown in FIGS. 15 to 17, the contact surface 30c of the wire 30a with the third electrode 9 is directed from the proximal end to the distal end. It becomes thinner and tapered. This particularly prevents a decrease in the strength of the continuous portion 30d of the welded portion of the wire 30a with the base end. When the end surface 8a of the second electrode 8 is not inclined, the portion of the wire 30a that comes into contact with the third electrode 9, that is, the welded portion is as shown by the two-dot chain line 30c' in FIGS. 16 and 17. As a result, the strength of the continuous portion 30d with the base end of the welded portion is reduced.

In the above embodiment, the end face 8a of the second electrode 8 is inclined at an angle θ' with respect to the horizontal plane, and the third
Although the case has been described in which the surface 9c of the electrode 9 is horizontal, on the contrary, the end surface 8a of the second electrode 8 may be horizontal and the surface 9c of the third electrode 9 may be inclined.

Heating of the first and third electrodes 7 and 9, coating film 30b
Welding separation and welding of the wire 30a and the terminal member 31 can be completed in an extremely short time. For example, the time for applying current to the welding transformer 30 (welding time) is
It is sufficient to set the time to a time equivalent to 22 cycles, that is, about 440 msec. 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 strength of the welded joint will be insufficient. line 3
Since there are disadvantages such as crushing of the wire 0a and annealing of the wire 30a and making it brittle, the welding time may be set to an appropriate value taking these into consideration.

(Effects of the Invention) As explained above, according to the present invention, the first electrode is formed with an engagement groove having a predetermined inclination angle with respect to a plane perpendicular to the axis of the tip and having a substantially semicircular cross section. , a second electrode whose tip end face is spaced apart from and faces the first electrode; and one side of the tip end which has a substantially semicircular cross section with a radius of curvature smaller than the radius of curvature of the groove of the first electrode. a third electrode having a curved surface and fitted into the engagement groove for a predetermined length, and the other side thereof being a flat surface perpendicular to the axis of the first electrode and serving as the contact surface to the workpiece; Because of this configuration, there is no bias caused by the assembly of the contact portions of the first electrode and the third electrode, and these electrodes can be brought into contact approximately at the center of the contact surface. The contact surfaces of these two electrodes are brought into close contact with each other by electrolytic corrosion. Furthermore, by forming the contact surface into a curved surface, the contact area can be increased.

In addition, the inclination angle of the engagement groove of the first electrode is set to 0 to 30°.
By setting the angle to a small value in the range of , it is possible to prevent the third electrode from slipping out from the first electrode when the first and third electrodes are pressed against the work during welding.

In addition, by increasing the angle of inclination of the engagement groove of the first electrode from the middle of the groove and regulating the length of the contact surface with the tip of the third electrode, heat is generated at the tip of the third electrode. This makes it possible to reduce welding time.

Furthermore, by tilting the third electrode with respect to the first electrode, it is possible to stabilize the welding current, and to effectively prevent the occurrence of cracks caused by electrolytic corrosion caused by the welding current of these electrodes. This makes it possible to significantly improve the durability of each electrode.

Furthermore, by slanting the end face of either the second or third electrode at a predetermined angle along the in/out direction of the workpiece, the welding part can be placed on the proximal end side, especially when welding wire rods, etc. It becomes tapered from the tip to the tip side, and as a result, there are excellent effects such as being able to prevent the strength of the portion connected to the proximal end of the workpiece from decreasing.

[Brief explanation of the drawing]

Fig. 1 is a front view showing an embodiment of a spot welding machine to which the electrode for a spot welding machine according to the present invention is applied, Fig. 2 is a side view of the same, and Fig. 3 is a view of the tip of the first electrode in Fig. 2. Fig. 4 is a side view in the direction of the arrow in Fig. 3, Fig. 5 is an end view in the direction of the arrow in Fig. 3, and Fig. 6 is an enlarged view of the tip of the third electrode shown in Fig. 2. 7 is a bottom view of FIG. 6, FIG. 8 is a sectional view taken along the arrow line - in FIG. 6, FIG. 9 is a sectional view of the connecting portion of the tips of the first and third electrodes, 10
The figure is a sectional view taken along the direction of the arrow in Figure 9.
Figure 1 is a diagram showing the adhesion state of the electrodes in Figure 10.
Fig. 2 is an enlarged view of the tip of the second electrode of the spot welding machine shown in Fig. 1, Fig. 13 is a wiring circuit diagram of the spot welding machine shown in Fig. 1, and Fig. 14 is an enlarged view of the tip of the second electrode of the spot welding machine shown in Fig. 1. FIG. 15 is a partial cross-sectional enlarged view of essential parts showing a state in which a workpiece is being held, FIG. 15 is a diagram showing the relationship between the electrode and the workpiece during welding of the workpiece shown in FIG. 14, and FIG.
The figure is a side view of the welded part of the workpiece shown in FIG. 15 after welding, and FIG. 17 is a plan view of FIG. 16. 1...Spot welding machine, 2...Base, 3...Main 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 control circuit, 30...Conducting wire, 30a...Element wire, 30b
...Coating film, 31...Terminal member.

Claims (1)

[Scope of Claims] 1. A first electrode formed with an engagement groove having a predetermined inclination angle with respect to a plane perpendicular to the axis of the tip and having a substantially semicircular cross section; a second electrode disposed facing away from the first electrode, and one side of the tip having a curved surface having a substantially semicircular cross section with a radius of curvature smaller than the radius of curvature of the groove of the first electrode, and a second electrode disposed facing the engagement groove; A third electrode that is fitted and abutted for a predetermined length and whose other side is a plane perpendicular to the axis of the first electrode and serves as a contact surface for the workpiece. Machine electrode. 2 The inclination angle of the engagement groove of the first electrode is 0 to
Claim 1 characterized in that the angle is set within a range of 30°.
Electrodes for spot welding machines as described. 3. The engaging groove of the first electrode has an inclination angle that increases from the middle of the groove to limit the length of the contact surface with the tip of the third electrode. Electrodes for spot welding machines. 4. The electrode for a spot welding machine according to claim 1, wherein an end surface of one of the second and third electrodes is inclined at a predetermined angle along the direction of entry and exit of the workpiece. .