JPH0534856Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electrode structure used in resistance welding such as spot welding, and particularly to an electrode structure for resistance welding suitable for efficiently cooling electrode chips.

[Conventional technology]

Electrodes used for resistance welding, such as spot welding, conduct large currents during welding, so if they are used repeatedly, they accumulate heat and transfer heat from the workpiece contact, and if they continue to be used, the electrode tip may become damaged. becomes soft and the tip becomes deformed due to repeated impact points, reducing its lifespan.

For this reason, conventionally, as shown in FIG. 3, a cooling water pipe 3 is provided in a cylindrical shank 2 into which the flat-bottomed recess 1a of the electrode chip 1 is removably fitted at the tip, and cooling water is supplied from the cooling water pipe 3. After water was supplied into the flat-bottomed recess 1a of the electrode chip 1 to cool the electrode chip 1, it was discharged to the outside through the shank 2.

In addition, as a proposal for a cooling structure for this type of electrode chip, as disclosed in Utility Model Application Publication No. 61-4891, there is a proposal for an outgoing channel, a return channel, and a connection between the outgoing channel and the return channel within the shank. A U-turn waterway is integrally formed for each waterway, and the cross-sectional area of each waterway is large enough to prevent cooling water from accumulating and boiling, and the flow of cooling water is not obstructed. As disclosed in Publication No. 61-195883, a cooling air blowing path is provided in the center of the electrode rod that penetrates in the axial direction, and the air is released to the outside from the opening in the center of the tip of the electrode rod. A device in which the center is cooled by rapid expansion of volume when
As disclosed in Japanese Patent No. 10972, there is a known device in which a deformable soft thermally conductive material is interposed in the gap between the tip of the shank and the recess of the electrode chip to prevent a gap. It is.

[Problem that the invention attempts to solve]

However, according to the prior art disclosed in the above-mentioned publications, although it is effective in lowering the temperature of the electrode chip on average, it is not effective in suppressing the instantaneous temperature rise at each contact point. The problem was that it was not very effective.

Additionally, in order to suppress the instantaneous temperature rise of the electrode tip, it is effective to increase the heat capacity by increasing the diameter of the electrode tip, but this is often not possible due to conditions such as the structure of the welding area. . Furthermore, if the electrode tip is made larger, the side surface of the tip will interfere with the workpiece to be welded, and to avoid this interference, it is necessary to lengthen the overlapping part of the workpiece to be welded, which increases material costs and other parts. There was a problem that interference occurred.

The present invention was developed in view of the above circumstances, and the purpose is to provide a resistance welding electrode structure that has a simple structure, can efficiently cool the electrode tip at each welding point, and can extend its life. shall be.

[Means for solving problems]

In order to achieve the above object, the present invention has a cylindrical shank in which a cooling water flow path is formed, the outer circumference of the opening at the tip of the shank is formed into a tapered shape, and the tip of the shank is provided with an electrode having a U-shaped cross section. In the electrode structure for resistance welding, in which the tips are removably fitted while maintaining an internal cavity, and the cooling water is circulated in the internal cavity, the tip is fitted inside the curved bottom of the electrode tip having a U-shaped cross section. A melting metal having a melting point lower than that of the electrode chip body is buried therein, and the melting metal is further cooled by the cooling water.

[Effect]

According to the above structure, the heat generated during welding causes the portion of the low melting point metal in the electrode chip close to the welded member to melt. As a result, a large amount of heat is removed from the inside of the curved bottom of the electrode tip by the latent heat of fusion, and heat is transferred by convection within the molten low-melting point metal part, so the amount of heat transfer increases and the tip of the electrode tip Temperature rises are also suppressed, making it difficult to soften, preventing deformation of the chip tip and extending life.

〔Example〕

Hereinafter, one embodiment of the resistance welding electrode structure according to the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. In the figure, parts that are the same or equivalent to those of the conventional example shown in FIG. 3 are denoted by the same reference numerals, and explanations thereof will be omitted.

The feature of this embodiment is that a metal 4 having a melting point lower than that of the electrode chip 1, such as lead, lithium, selenium, tin, zinc, etc., is placed at the tip of the recess 1a of the electrode chip 1 made of a copper-based alloy or the like. and the fact that these alloys are buried.

Next, the operation and effects of this embodiment will be explained with reference to FIG. 2.

Two members to be welded 5a and 5b are overlapped and 1
The pair of electrode chips 1 and 1' are clamped and pressed to apply electricity.
A nugget 6 is then formed between the members to be welded 5a and 5b due to resistance heat generation. The heat generated at this time flows in the direction of arrow 7 and is finally carried away by cooling water 8.

In this process, the part 4a of the low melting point metal 4 close to the workpiece 5 melts at around 300°C, and this latent heat of fusion removes a large amount of heat from the inside of the curved bottom of the electrode tip, and reduces the molten state. Heat moves within the melting point metal 4a by convection, so the amount of heat transfer increases, and heat absorption due to latent heat of fusion is also added.
The temperature of the portion of the electrode chip 1 in contact with the low melting point metal 4a does not significantly exceed the melting point of the low melting point metal 4.

Therefore, the temperature rise at the tip of the electrode chip 1 is suppressed, making it difficult to soften. Furthermore, when the member to be welded 5 is a galvanized steel plate or the like, a copper-zinc alloy is less likely to be formed, and the tip of the electrode tip 1 is less likely to be deformed, so that the life of the electrode tip 1 can be extended.

[Effect of idea]

As described above, according to the present invention, a fusible metal having a lower melting point than the electrode tip body is buried inside the curved bottom of the electrode tip having a U-shaped cross section of the resistance welding electrode, so that when electricity is applied at the welding point, A slight temperature rise at the curved bottom of the electrode tip causes the low melting point melting metal to melt, and the latent heat of fusion and convection inside the molten metal remove a large amount of heat from the curved bottom, creating a cooling effect. Furthermore, since the molten metal surface is cooled by cooling water, a large temperature rise at the curved tip of the electrode tip can be reliably suppressed, thereby preventing deformation due to softening of the electrode tip. is possible,
The life of the electrode tip can be extended.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional view showing an embodiment of the resistance welding electrode structure according to the present invention, Fig. 2 is a longitudinal sectional view showing the operation of this embodiment, and Fig. 3 is a longitudinal sectional view showing the conventional resistance welding electrode structure. FIG. DESCRIPTION OF SYMBOLS 1...Electrode chip, 1a...Recessed part, 2...Shank, 3...Cooling water pipe, 4...Low melting point metal.

Claims (1)

[Scope of utility model registration request] The outer periphery of the opening at the tip of a cylindrical shank with a cooling water flow path formed inside is formed into a tapered shape, and an electrode chip with a U-shaped cross section is attached to the tip of the shank so that it can be attached and detached while maintaining an internal space. In a resistance welding electrode structure in which the cooling water is circulated through the internal cavity, a melting metal having a melting point lower than that of the electrode tip body is placed inside the curved bottom of the electrode tip having a U-shaped cross section. 1. An electrode structure for resistance welding, characterized in that the electrode structure is configured such that the meltable metal is buried and further cooled by the cooling water.