JPH03149789A - Manufacture of spark plug outside electrode surrounding good-heat conductivity metal - Google Patents

Abstract

PURPOSE:To obtain good welding strength and allow production at a low cost by machining the rear end of an extension body so that the exposed face of a good-heat conductivity metal is withdrawn from the rear end face of a corrosion-resistant metal. CONSTITUTION:A corrosion-resistant metal 200 such as a nickel alloy is molded into a cup shape, a good-heat conductivity metal 2 such as copper is inserted into a cup-shaped mold 1 to obtain a coupling body 3, the coupling body 3 is inserted into a molding die 4 having a circular inlet 41 and the rectangular hole cross section of a molding section 42 with the closed portion of the cup inserted first, and forward extrusion molding is performed to obtain an extension body 5. The extension body 5 is extracted from the molding die 4, and the rear end of the extension body 5 is machined so that the exposed face of a good-heat conductivity metal 200 is withdrawn from the rear end face of the corrosion-resistant metal 100. When an outside electrode is welded to a main body metal, the welding property between the rear end face of the corrosion-resistant metal and the tip face of the main body metal is improved, the connection strength between the outside electrode and the main body metal is improved, the good-heat conductivity metal 2 is not covered by the corrosion-resistant metal 100, thus the production process is simple, and this device can be manufactured at a low cost.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a spark plug in which a metal with good thermal conductivity such as copper, silver, a copper alloy, or a silver alloy is wrapped in a corrosion-resistant metal such as a nickel alloy. The present invention relates to a method of manufacturing an outer electrode.

[Conventional technology] If a heat-resistant nickel alloy is used for the outer shell material and copper or silver, which has good thermal conductivity, is inserted into the core material and used as the outer electrode, it is possible to improve the heat dissipation of the spark plug. It is known that it can be done.

For this reason, JP-A-5-163051 (U.S. Pat. No. 4,575,343) - JP-A-5-5
No. 7480 (U.S. Pat. No. 4,526,551)
JP-A No. 58-140985 (U.S. Pat. No. 4,695,759), etc., disclose a method for manufacturing a composite electrode in which the core material is exposed, and a method for manufacturing a composite electrode in which the core material is completely covered with an outer shell material. A method of manufacturing an electrode is described.

[Problems to be solved by the invention] However, the manufacturing method in which the core material is exposed is inferior in welding strength to the metal shell, and the manufacturing method in which the core material is completely covered with the outer shell material significantly increases manufacturing costs. It has the disadvantage of inviting

The purpose of the present invention is to obtain good welding strength, and
To provide a method for manufacturing a spark plug outer electrode wrapped in a metal with good thermal conductivity, which can be manufactured at low cost.

[Means for Solving the Problems 1] In order to achieve the above object, the present invention employs the following configuration.

A process in which a corrosion-resistant metal such as a nickel alloy is formed into a cup shape.

A process of charging a metal with good thermal conductivity such as copper into the cup-shaped molded body to form a fitted body.

A step of inserting the fitted body into a mold having a circular inlet and a rectangular hole cross section in the molding part from the closed side of the cup first, and performing forward extrusion molding to form an extension body.

The extension body is removed from the molding die, and the rear end of the extension body is processed so that the exposed surface of the good heat conductive metal is recessed from the rear end surface of the corrosion-resistant metal.

[Actions and Effects of the Invention] The method for manufacturing a spark plug outer electrode wrapped in a metal with good thermal conductivity according to the present invention has the following actions and effects.

Ah, the rear end of the extension body is processed so that the exposed surface of the good heat conductive metal is recessed from the rear end surface of the corrosion-resistant metal, and the outer electrode is M
is being built. Therefore, when welding the outer electrode to the metal shell by butting the rear end of the extension body against the front end surface of the metal shell, welding begins between the rear end surface of the corrosion-resistant metal and the front end surface of the metal shell. .

Since the weldability between both metals is good, the bonding strength between the outer electrode and the metal shell is excellent.

However, since the structure excludes the rear end of a metal with good thermal conductivity, and the structure does not cover the metal with good thermal conductivity with a corrosion-resistant metal, the manufacturing process is simple and does not cause a significant increase in manufacturing costs. .

[Example] Next, a first example of the present invention will be described with reference to FIG.

The outer electrode A of the spark plug has a substantially rectangular parallelepiped shape,
Copper 200, which is a metal with good thermal conductivity, is wrapped in nickel alloy 100, which is a corrosion-resistant metal.

The rear end of the outer electrode A is cut into a V-shaped cross section so that the exposed surface of the copper 200 is recessed from the rear end surface of the nickel alloy 100.

The outer electrode A of this spark plug is manufactured through the steps (a) to (d).

A. A nickel alloy with excellent corrosion resistance is produced by adding chromium, iron, silicon, aluminum, etc. to the main component, nickel.

This nickel alloy round bar is cut to the desired length.

This round bar is placed in a mold and the cut surface is flattened with a punch.

Next, a shallow guide hole is punched in the molded product with a flattened cut surface.

When the hole formed by the punch is further punched, a hollow bullet-shaped cup molded body 1 is completed.

First, the bullet-shaped body 2 is manufactured from copper, which is a metal with good thermal conductivity. As shown in FIG. 1-1, this bullet-shaped body 2 is inserted into the cup molded body 1 to produce a fitted body 3.

C. As shown in FIG. 1-1, the fitting body 3 is placed in the mold 4 having a circular inlet 41 and a rectangular hole cross section in the molding part 42, with the cup closed first, and punched. Front extrusion molding is performed in step 43. Due to this forward extrusion molding, the axial dimension of the fitted body 3 is expanded to become an extension body 5.

2. As shown in the 11th M-mV, the extension body 5 is taken out from the molding die 4 by the take-out rod 44, and the remaining part 51 located at the rear end of the extension body 5 is cut into a V-shaped cross section. Thus, the outer electrode A as shown in FIG. 1-V is completed.

The outer electrode B shown in FIG. 2 is a second embodiment of the present invention, and the copper 200 at the rear end is cut into a V-shape.

The outer electrode C shown in FIG. 3 is a third embodiment of the present invention, and has the copper 200 at the rear end cut away.

Next, the functions and effects of the above embodiment will be described together with a simple welding strength test.

Each outer electrode (each l
After joining the pieces (O pieces) by resistance welding, the pieces were bent back and forth and the number of times it took to come off (one round trip was counted as one round trip) was examined. The results are shown in Table 1.

In addition, comparative crystal 1 is an outer electrode manufactured by cutting the unpressed portion 51 of extension body 5 into rings, and comparative crystal 2 is manufactured by cutting the core material (copper) into the outer shell material (
The outer electrode is completely encapsulated with a nickel alloy.

(Leaving space below) Table 1 Number of times it was achieved (times) Comparison product 1 Less than 1 time Outer electrode A 3 times Front and back outer electrode B 2 times - 3 times Outer electrode 0 3 times or more Comparison product 2 3 times or more From this table As can be seen, the outer electrode A=
In B=C, a welding strength comparable to that of the outer electrode of Comparative Product 2, which was manufactured by completely covering the core material with the outer shell material, was obtained. This is because, during resistance welding, current flows through the portion of the nickel alloy 100 that comes into contact with the metal shell, and welding is mainly performed between the nickel alloy 100 and the metal shell.

Note that since the void space 300 is filled with the melted nickel alloy 100, the welded outer electrode has the copper 200 almost completely wrapped in the nickel alloy 100.

In addition to the above embodiments, the present invention includes the following embodiments.

3. Only the rear end of the metal with good thermal conductivity or the rear end of the extension body may be processed into an arc shape.

b. The rear end of the extension body may be processed by grinding, punching, etc. in addition to cutting so that the exposed surface of the heat-conductive metal is recessed from the rear end surface of the corrosion-resistant metal.

C. When welding the outer gI4 electrode, the same material as the corrosion-resistant metal used for the outer electrode may be previously welded to the tip surface of the metal shell in order to improve weldability.

[Brief explanation of the drawing]

FIG. 1 is a manufacturing process diagram of a spark plug external Ill electrode wrapped in a metal with good thermal conductivity according to a first embodiment of the present invention;
FIG. 2 is a structural diagram of an outer electrode manufactured according to a second embodiment of the present invention, and FIG. 3 is a structural diagram of an outer electrode manufactured according to a third embodiment of the present invention.

Claims (1)

[Claims] 1) A method for manufacturing a spark plug outer electrode wrapped in a metal with good thermal conductivity, which comprises the following steps. B. The process of forming a cup shape from corrosion-resistant metal such as nickel alloy. B. A step of charging a metal with good thermal conductivity such as copper into the cup-shaped molded body to form a fitted body. c. Inserting the fitted body into a molding mold having a circular entrance and a rectangular hole cross section in the molding part, with the cup closed first;
This process involves front extrusion molding to create an extension. D. Taking out the extension from the mold and processing the rear end of the extension so that the exposed surface of the good heat conductive metal is recessed from the rear end of the corrosion-resistant metal.