JP3046613B2 - Method for manufacturing center electrode of spark plug - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a center electrode of a spark plug in which a noble metal is brazed at a tip portion.

[Prior Art] Generally, as the center electrode of a spark plug becomes thinner, the discharge voltage decreases, and the quenching effect of the electrode decreases, thereby improving the ignitability. Since the effect is also worsened, the electrode temperature is increased, and the electrode material such as a normal nickel alloy causes greater electrode wear. Therefore, in order to achieve both ignitability and durability, a noble metal material having excellent corrosion resistance and spark erosion resistance is used for the discharge part of the center electrode. In addition, in order to achieve both ignitability and durability and economy, the use of precious metal materials
It is desirable to limit to the discharge portion (portion requiring characteristics) and reduce it as much as possible.

Spark plugs include multi-pole plugs with multiple outer electrodes around the center electrode, semi-surface discharge plugs or full surface discharge plugs with outer electrodes around the center electrode to use the surface discharge effect of the insulator. There is. In order to be compatible with these types of spark plugs and to achieve both ignitability, durability and economy, the center electrode of the spark plug is welded to a noble metal at the discharge part (the part requiring characteristics) on the outer periphery of the tip of the center electrode. As a method, Japanese Patent Application No. 58-2347
There is No. 87.

The conventional method for manufacturing a center electrode of a conventional spark plug, a hole is formed in a rear end of a cylindrical body of a heat-resistant and corrosion-resistant metal mainly composed of nickel by a predetermined press working to form a metal cup. Manufacture copper studs with legs that fit into the holes and heads equivalent to the cup outer diameter.Fit the legs of the cup's copper studs and combine them by pressing and combining. Before or after the pressure integration, a coaxial annular groove is formed on the tip end face of the installment, and a noble metal annular plate fitted into the annular groove is fitted and subjected to electric resistance welding,
Forming a combination with a noble metal, further extending the combination with a noble metal by extrusion molding to the cup side, reducing the outer diameter of the combination with the annular plate made of noble metal on the tip side surface of the combination. It was formed in a long cylindrical shape.

[Problems to be Solved by the Invention] However, the noble metal welding center electrode manufactured by this conventional method for manufacturing a center electrode of a spark plug may be broken by breaking a noble metal long cylindrical plate due to thermal expansion.
There was a problem with durability.

An object of the present invention is to provide a method for manufacturing a center electrode of a spark plug, which can prevent a noble metal long cylindrical plate attached to a spark discharge portion of a center electrode from being cracked due to thermal expansion and therefore has excellent durability. is there.

Means for Solving the Problems In order to solve the above-mentioned problems, a method of manufacturing a center electrode for a spark plug according to the present invention makes a cup by drilling a bottomed hole from one end surface of a cylindrical body of a heat-resistant and corrosion-resistant metal. And a step of forming a coaxial annular groove on the other end face of the closing, a step of brazing and joining a noble metal annular plate fitted in the annular groove with a brazing material interposed, and the bottomed hole of the cup Fitting a copper stud having a fitting portion into the bottomed hole, press-integrating to form a combined body, and extruding the combined body from the side where the noble metal annular plate is brazed. Elongating by molding, reducing the outer diameter of the combined body and forming the annular plate made of noble metal into a long cylindrical shape on the side surface of the front end portion of the combined body, or , One end of cylindrical body of heat and corrosion resistant metal A step of making a cup by drilling a bottomed hole from; and fitting a copper stud having a fitting portion to be fitted into the bottomed hole of the cup into the bottomed hole, press-integrating and integrating the cup. A step of forming a coaxial annular groove on the other end surface of the closed end; a step of brazing and joining a noble metal annular plate fitted to the annular groove with a brazing material interposed to form a combined body; Is extended by extruding from the side where the noble metal annular plate is brazed to reduce the outer diameter of the combined body, and the noble metal annular plate is formed into a long cylindrical shape on the side of the tip end of the combined body. Forming a
Further, the brazing material used for the brazing had a solidus temperature of 950 ° C. or higher.

[Action and Effect of the Invention] According to the method for manufacturing a center electrode of a spark plug of the present invention, according to claim 1 or claim 2, (action) a noble metal long cylindrical plate attached to a spark discharge portion and a center electrode body ( (Made of a heat-resistant and corrosion-resistant metal mainly composed of nickel), a brazing material layer having a large buffer effect against thermal expansion is formed. (Effect) It is possible to prevent a long cylindrical plate made of noble metal from breaking due to thermal expansion, Therefore, the durability is excellent.

Claim 3 (Effect) The brazing material layer exhibits sufficient heat resistance even when exposed to the combustion gas in the engine for a long time.

Example Next, a method for manufacturing a center electrode of a spark plug according to the present invention will be described based on a first example shown in FIG.

(Step 1) Cut a round bar made of base metal (Inconel 600: Fe8%, Cr16%, Cu0.2%, residual Ni) excellent in heat resistance and corrosion resistance into a predetermined length (4.7mm), and then press. Ends 1
1 and 12 are parallelized to form a metal body 1a (illustration a). (Step 2) Then, the center of one end face 11 is deeply punched with a punch.
An annular groove 13b having a coaxial center is formed at the outer peripheral edge of the other end face 12b (FIG. B). (Step 3) Then, a noble metal (platinum: P) corresponding to the annular groove 13b is formed.
t) Insert the annular plate 87c with the palladium brazing material in between and braze it 88c to form a metal cup 1c (illustrated c), and anneal the cup 1c. (FIG. 5D) to produce a copper stud 6d having good thermal conductivity having a leg portion 61d fitted into the hole 34c of the above and a head portion 62d having an outer diameter equal to the outer diameter of the cup 1c. Insert the leg 61d of the copper stud 6d into 1c,
(Step e) Diffusion treatment is performed for 1 hour in a 930 ° C. atmosphere to reduce the outer diameter. As described above, the combination body 8e is extended by extrusion molding of the cup 1f,
The extruded body 8f and the platinum annular plate 87c
(Step f) Next, a flange 64f is formed on the tip end side surface 86f of the extruded body 8f to remove the flange 64f that has protruded at the end of the extruded body 8f. Shooting body 8g (shown in g), (Step 8) Next, the rear end (shown in the upper end) 81h and the flange 82h
(Step 9) Next, a cross-shaped slit 84i is formed above the flange 82i.
And a center electrode 9 of a spark plug having a long cylindrical plate 87i made of a noble metal (platinum) firmly joined to a tip side surface 86i by brazing 88i (illustration i).

Next, the formation position of the annular groove 13b formed on the other end surface 12b,
The relationship with the shape of the extruded platinum long cylindrical plate 87i will be described with reference to FIG. 2 (first embodiment) and FIG. 3 (modification).

In the first embodiment, as shown in FIG.
The annular groove 13b formed in 12b is formed on the outer peripheral edge of the other end surface 12b, and the extruded platinum long cylindrical plate 87i has a uniform thickness.

On the other hand, as shown in FIG. 3, the annular groove 13b '
In this case, the intermediate portion of the extruded platinum long cylindrical annular plate 87m is formed to be thick.

4 and 5 are a cross-sectional view of a plug incorporating a center electrode 9 manufactured by the spark plug center electrode manufacturing method of the present invention, and an enlarged view of a tip side portion.

The plug 91 has a multi-pole outer electrode 93 at a tip 92a, a hollow metal shell 92 having a mounting screw 92b on the outer periphery, a cylindrical insulator 94 fitted into the metal shell 92, and the cylindrical insulator 94.
The hole 94 has a rod-shaped center electrode 9 protruding from the front end portion 86 at the front end thereof, and a terminal electrode 95 inserted at the rear end side of the hole protruding from the rear end. A long platinum plate 87 made of platinum joined to a protruding tip side surface 86i of the center electrode 9 by brazing 88i.
i forms a spark discharge gap with the multipolar outer electrode 93.

Next, the present invention will be described based on a second embodiment shown in FIG. Also, the same components as those in the first embodiment are denoted by the same reference numerals.

(Step 1) Cut a round bar made of base metal (Inconel 600: Fe8%, Cr16%, Cu0.2%, residual Ni) excellent in heat resistance and corrosion resistance into a predetermined length (4.7mm), and then press. Ends 1
1 and 12 are parallelized to form a metal body 1a (illustration a). (Step 2) Then, the center of one end face 11 is deeply punched with a punch.
34b is formed to produce a metal cup 1b (shown in b), and the cup 1b is annealed. (Step 3) The leg 61c separately fitted in the hole 34b of the cup and the outer diameter of the cup 1b A copper stud 6c having good thermal conductivity having an outer diameter equal to that of the head 62c is manufactured (illustrated c), and (Step 4) the leg 61c of the copper stud 6c is fitted into the cup 1b.
An annular groove 13d having a coaxial center on the outer peripheral edge of the other end surface 12d by being pressed by a press 7 with a pressure of about 2 tons to be integrated.
(Step d), and (Step 5) a noble metal (platinum: P) corresponding to the annular groove 13d
t) Insert the annular plate 87e with a palladium brazing material in between and braze it 88e (illustrated e). (Step 6) Diffusion the integrated combined body 8e in a 930 ° C atmosphere for 1 hour. Extending the combined body 8e by extrusion molding the cup 1f to make the diameter smaller,
The extruded body 8f and the platinum ring plate 87e
(Step f) Next, a flange 64f is formed on the tip end side surface 86f of the extruded body 8f so as to remove the flange 64f protruding at the end of the extruded body 8f. Shooting body 8g (illustrated g), (Step 8) Next, the rear end (the upper end in the illustration) 81h and the collar 82h
(Step 9) Next, a cross-shaped slit 84i is formed above the flange 82i.
And a center electrode 9 of a spark plug having a long cylindrical plate 87i made of a noble metal (platinum) firmly joined to a tip side surface 86i by brazing 88i (illustration i).

(Effect) 1. A brazing material layer with a large buffering effect against thermal expansion is formed between the long cylindrical plate made of noble metal attached to the spark discharge part and the center electrode body (made of heat-resistant and corrosion-resistant metal mainly composed of nickel). Therefore, it is possible to prevent the cylindrical noble metal from being cracked due to thermal expansion, and thus it is excellent in durability.

2. Since the noble metal is formed thinly in the spark discharge portion, the use of the noble metal material can be limited to a portion requiring characteristics, and the amount of the noble metal material used is small and can be manufactured at low cost.

 The present invention includes the following modifications.

As the brazing material, other than the palladium brazing material, a brazing material having a solidus temperature of 950 ° C. or higher, such as a nickel brazing material or a gold brazing material, may be used.

[Brief description of the drawings]

FIG. 1 is a process diagram showing a first embodiment of a method for manufacturing a center electrode of a spark plug according to the present invention, FIG. 2 is a diagram showing a position where an annular groove for brazing a noble metal annular plate in the first embodiment is formed, FIG. 3 is a cross-sectional view for comparing the shape change of the platinum ring plate after extrusion with the modification, and FIG. 3 compares the modification with the annular groove forming position and the shape change after extrusion with the first embodiment. FIG. FIG. 4 is a cross-sectional view of a spark plug incorporating a center electrode manufactured according to the present invention, FIG. 5 is an enlarged view of the tip, and FIG. 6 is a process diagram showing a second embodiment. In the figure, 1b, 1c …… Metal cup, 6c, 6d …… Copper stud, 8e…
… Combination body, 13b, 13d …… Circular groove, 87c, 87e …… Precious metal annular plate, 87i …… Precious metal long cylindrical plate, 88i ……

Continuation of the front page (56) References JP-A-63-133476 (JP, A) JP-A-60-62084 (JP, A) JP-A-57-163976 (JP, A) JP-A-61-13587 (JP) JP-A-62-268080 (JP, A) JP-A-57-154780 (JP, A) JP-A-59-94391 (JP, A) JP-B-49-22989 (JP, B1) (58) Field surveyed (Int.Cl. ⁷ , DB name) H01H 13/00-21/06

Claims (3)

(57) [Claims] 1. A step of forming a cup by drilling a bottomed hole from one end surface of a cylindrical body made of a heat-resistant and corrosion-resistant metal, and forming a coaxial annular groove on the other end surface of the closed end, and a noble metal fitted into the annular groove. A step of brazing and joining the annular plate, with a brazing material interposed, a copper stud having a fitting portion fitted into the bottomed hole of the cup is fitted into the bottomed hole, and pressurized and integrated; Forming a combined body, extending the combined body by extruding the noble metal annular plate from the brazed side, reducing the outer diameter of the combined body, and removing the noble metal annular plate. Forming a long cylindrical shape on the side surface of the front end portion of the combination body. 2. A step of forming a cup by drilling a bottomed hole from one end surface of a cylindrical body made of a heat-resistant and corrosion-resistant metal, and forming a copper stud having a fitting portion fitted into the bottomed hole of the cup. A step of fitting into the hole, press-integrating and forming a coaxial annular groove on the other end face of the cup, and a noble metal annular plate fitted in the annular groove with a brazing material interposed therebetween. Attaching and joining to form a combination, extending the combination by extruding the noble metal annular plate from the brazed side, reducing the outer diameter of the combination and reducing the noble metal Forming an annular plate in the shape of a long cylinder on the side surface of the distal end portion of the combination body. 3. The method according to claim 1, wherein the brazing material used for said brazing has a solidus temperature of 950 ° C. or higher.