JPH11147179A - Tip holder in electric resistance welding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sufficiently bulge a joining part at the time of electrically heating and to improve the soundness by arranging a taper hole continued to a holding hole and enlarging the diameter upward at the upper part of the holding hole of a tip holder for holding a tip joined to the lower end surface of a rod-like work so as to be freely attached/detached and placing the lower end of the taper hole at lower level in the tip thickness. SOLUTION: At the time of projection-welding the wear resistant tip 3 to the end part of shaft part 2 of an engine valve 1, the tip holder 16 has the tip holder hole 16a having the larger diameter by a little than the valve shaft part 2 and forms the taper hole 16b enlarging the diameter upward. Further, the lower end position of the taper hole 16b continued to the holding hole 16a is made to the height of almost 1/3 of the tip 3 thickness so as to position to remarkably lower part from the joining surface of the valve shaft 2. By this constitution, the joining part at the time of press-welding can largely be bulged outward along the inclining hole 16 and the development of a little gap on the outer peripheral surface of the shaft appeared at the time of cutting the bulged part can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tip holder used for electric resistance welding of a wear-resistant tip to a shaft end face of an engine valve, for example.

[0002]

2. Description of the Related Art As shown in FIG.
In order to prevent abrasion of the end face of the shaft (2),
There is a shaft end welded with a wear-resistant chip (3) capable of quench hardening such as martensitic steel. (3a) is a conical protrusion for locally increasing the current density and increasing the heating efficiency.

FIG. 3 shows a main part of a resistance welding apparatus for welding the above-mentioned tip (3), that is, a projection welding apparatus. In the figure, (4) shows an engine valve (hereinafter referred to as a work) (1). A support arm vertically grips an intermediate portion of the shaft portion (2) so as to be slidable, and a cylindrical upper electrode (5) is fitted to the center of the support arm. (6) is an electrode holder.

[0004] (7) is a lower electrode device, its cover (8)
Inside, in order from the top, there is a holding hole (9a) having an inner diameter slightly larger than the shaft portion (2) of the work (1), and a tapered hole (9b) whose upper half expands upward in diameter. Tip holder (9)
And the lower electrode (10) and the spacer (11) are connected to the electrode base (1).
2) It is placed on top and housed. Upper and lower electrodes (5) (10)
Is connected to a power supply (14) by a power supply cord (13).

[0005] In the above-mentioned projection welding apparatus, the tip (3) is inserted into the tip holder with the projection facing upward.
After being inserted into (9), the work (1) vertically supported by the upper electrode (15) is lowered by an upper pressing device (not shown), and the lower end is pressed against the projection of the chip (3). Both electrodes
(5) When the power is supplied to (10), the contact surface between the work (1) and the chip (3) is heated by heating and melts, and the entire surface is welded.

[0006]

However, in the above-mentioned conventional chip holder (9), the tapered hole (9a) is shallow, and the lower end thereof is almost at the same position as the upper surface of the chip (3), that is, the work ( Since it is located slightly below the joint surface (17) between the chip (1) and the chip (3), only the work (1) side swells outward during energization heating, and the chip (3) side swells. The amount was extremely small, and the joining area could not be increased.

In this way, in the finishing after joining, when the bulging portion is cut, a slight gap (15) is formed on the outer peripheral surface.
May be formed, and the bonding strength may decrease.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and is intended to increase the bonding area and greatly increase the bonding strength by expanding the joint between the work and the chip. It is an object of the present invention to provide a chip holder which has been manufactured.

[0009]

According to the present invention, there is provided an electric resistance welding apparatus for joining a tip to a lower end of a rod-shaped work, the upper end of a holding hole for holding the lower end of the tip so that it can be inserted and removed. The problem is solved by providing a tapered hole whose diameter is increased upward continuously with the holding hole and whose lower end is lower than the thickness of the chip.

[0010]

FIG. 1 shows a main part of a projection welding apparatus to which the present invention is applied. The same reference numerals are given to the same members as those in the above-mentioned conventional example, and the detailed description thereof is given. Description is omitted.

The tip holder (16) of the present invention has a holding hole (16a) at the lower end for holding the chip (3) in a detachable manner, and a tapered hole (16b) continuous with the holding hole (16a). Has its lower end positioned approximately one-third the thickness of the chip (3), that is, significantly lower than the joint surface with the work (1).

Therefore, when the electric heating is performed, the work (1)
And the chip (3) can largely swell outwardly along the tapered hole (16b), so that the bonding area is large and the bonding is strong.

The present invention can be applied not only to the connection between the engine valve and the chip as in the embodiment but also to the case where another rod-shaped work and the chip are subjected to electric resistance welding.

[0014]

According to the present invention, the joint between the work and the chip can be greatly expanded outward, so that the joint area increases and a strong joint surface can be obtained.

[Brief description of the drawings]

FIG. 1 is a partially cutaway front view of a central longitudinal section of a main part of a projection welding apparatus to which the present invention is applied, at the time of welding.

FIG. 2 is a front view schematically illustrating a step of welding a tip to an end of an engine valve shaft.

FIG. 3 is a front view of a central longitudinal section and a partially cutaway view of a main part of a projection welding apparatus including a conventional tip holder when welding is performed.

[Explanation of symbols]

 (1) Engine valve (work) (2) Shaft (3) Tip (3a) Projection (4) Support arm (5) Upper electrode (6) Electrode holder (7) Lower electrode device (8) Cover (10) Lower Electrode (11) Spacer (12) Electrode base (13) Power cord (14) Power supply (15) Void (16) Tip holder (16a) Holding hole (16b) Tapered hole

Claims (1)

[Claims] In an electric resistance welding apparatus for joining a chip to a lower end of a rod-like work, a diameter of the upper end of a holding hole for holding a lower end of the chip as being insertable and removable is continuously increased with the holding hole. And a taper hole having a lower end lower than the thickness of the chip.