JPH10106716A - Manufacture of spark plug electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a spark plug electrode having high resistance to electrode consumption so that a precious metal can be welded to a tip of the electrode so as to bring the rear of the precious metal into contact with a core material made of good thermal conduction metal. SOLUTION: A manufacturing method of a spark plug electrode includes a cup forming step, a drilling step of boring a communicating hole 507 in a cup, and a core material forming step of forming a shaft having a small diametric part. Moreover, in a fitting step, a composite 510 is manufactured where a front end face 703 of a chip 700 is exposed on a tip face. In this method, an extrusion molding step of elongating the composite 510 is also included, and finally, in a precious metal welding step, a laser weld 312 of a precious metal 33 is produced on the tip face of an extrusion molding so as to bring a back face 332 of the precious metal into contact with the front end face 703 of the chip 700.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing an outer electrode or a center electrode of a spark plug mounted on an internal combustion engine.

[0002]

2. Description of the Related Art A technique for attaching a noble metal (or noble metal alloy) to the tip of an electrode of a spark plug by the following method has been known in order to improve the wear resistance of a spark plug electrode. A heat-resistant metal cup is manufactured, a core made of a good heat-conductive metal is fitted into the cup to manufacture a composite, and the composite is extruded to a desired shape by extrusion. Weld precious metal.

[0003]

However, the above prior art has the following problems. The core material is not exposed at the tip of the extruded product, and the rear part of the welded noble metal does not contact the core material, resulting in poor heat drawing. As a result, the temperature of the noble metal increases and the electrode wears quickly, and the heat resistance is poor.

An object of the present invention is to provide a method for manufacturing an electrode for a spark plug, which is excellent in electrode wear resistance, in which a noble metal can be welded to the tip of an electrode such that the rear portion abuts a core material made of a good heat conductive metal. .

[0005]

In order to solve the above-mentioned problems,
The present invention employs the following configuration. (1) A method for manufacturing a spark plug electrode includes a cup forming step of manufacturing a cup made of a heat-resistant metal, a drilling step of forming a communication hole having a small diameter in the bottom of the cup, and a good heat conductive metal.
A core material forming step of forming the shaft into a shaft shape having a small diameter portion corresponding to the communication hole, and a fitting step of fitting the core material in a cup and manufacturing a composite in which the front end face of the core material is exposed at the front end face And extruding the composite by extrusion molding to produce an extruded body in which the front end face of the core material is exposed at the front end face, and the extrusion forming step such that the rear face is in contact with the front end face of the core material. A noble metal welding step of welding the noble metal to the tip end surface of the body.

(2) A method for manufacturing a spark plug electrode includes a cup forming step of manufacturing a heat-resistant metal cup,
A drilling step of forming a communication hole in the bottom of the cup, a chip forming step of forming a good heat conductive metal into a chip shape corresponding to the communication hole, and inserting the chip into the communication hole from inside the cup; A chip inserting step, a core material forming step of forming a good heat conductive metal into a shaft shape, and a fitting in which the core material is fitted in a cup, and a front end face of the chip is exposed at a front end face. Extruding the composite by extrusion molding to produce an extruded body in which the front end face of the chip is exposed at the front end face, and the extrusion forming so that the rear face is in contact with the front end face of the chip. A noble metal welding step of welding the noble metal to the tip end surface of the body.

(3) In the method for manufacturing an electrode for a spark plug according to the above (2), the tip has a small-diameter portion fitted into the communication hole and a large-diameter portion larger than the communication hole.

(4) In the method for producing an electrode for a spark plug according to any one of the above (1) to (3), the precious metal is welded after cutting the tip of the extruded body into a small diameter.

[0009]

[Action and effect of the invention]

[Claim 1] A core material (made of a good heat conductive metal) having a small diameter communication hole formed in the inner bottom of a cup made of a heat-resistant metal and formed into a shaft shape having a small diameter portion corresponding to the communication hole. Is inserted into a cup, and the composite is extruded and extended to produce an extruded body in which the front end surface of the core material is exposed at the front end surface. Then, a noble metal is welded to the tip surface of the extruded body. Thereby, the rear surface of the noble metal comes into contact with the front end surface of the core material. Further, when a flange portion is formed at the rear end or bent in an L-shape, it becomes a center electrode or an outer electrode of the spark plug.

[0010] Since the rear surface of the noble metal to be welded to the tip of the electrode is in contact with the core made of a good heat conductive metal, the heat is effectively removed. Thereby, the electrode wear is slow (because the temperature of the noble metal does not increase), and the heat resistance is improved.

[Claim 2] A communication hole having a small diameter is formed in the inner bottom of a cup made of a heat-resistant metal, and a chip formed into a chip shape corresponding to the communication hole is inserted into the communication hole from inside the cup. Then, a good heat conductive metal is formed into a shaft shape, fitted into a cup, and then extruded by extruding the composite, whereby an extruded body having a front end face exposed at the front end face of the core material is manufactured. Then, a noble metal is welded to the tip surface of the extruded body. Thereby, the rear surface of the noble metal comes into contact with the front end surface of the core material. Furthermore, a flange is formed at the rear end, or
When bent in an L-shape, it becomes the center electrode and the outer electrode of the spark plug.

Since the rear surface of the noble metal to be welded to the tip of the electrode is in contact with the core made of a good heat conductive metal, the heat is effectively removed. Thereby, the electrode wear is slow (because the temperature of the noble metal does not increase), and the heat resistance is improved.

[Claim 3] When a noble metal is inserted into the communication hole of the cup from the inside of the cup, the large diameter portion of the chip is engaged with the bottom of the cup, so that the chip does not fall off during extrusion molding or use. At the same time, the chip comes into firm contact with the core material (advantageous in heat reduction).

[Claim 4] A noble metal is welded after the tip of the extruded body is cut into a small diameter. Thereby, most of the spark discharge is performed by the noble metal, and the effect of improving the durability by the noble metal can be effectively used. In addition, the ignitability is improved because the ignited portion becomes thinner and the quenching action of the electrode is reduced.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention (Claim 1,
4) will be described with reference to FIGS. As shown in FIG. 1, the spark plug A includes a cylindrical metal shell 1,
An insulator 2 with a shaft hole 21 fitted and fixed in the metal shell 1, a center electrode 3 fixed in the shaft hole 21, and an outer electrode 4 protruding from the metal tip surface 11.

The metal shell 1 is made of low carbon steel, and the outer electrode 4 is welded to the metal tip surface 11. A screw 12 is threaded on the outer periphery of the distal end of the metallic shell 1, and is mounted on a cylinder head (not shown) of the internal combustion engine via a gasket (not shown).

The insulator 2 is made of a ceramic mainly composed of alumina, has a seating surface fixed to a step of the metal shell 1 via a packing (not shown), and has an upper end of a hexagonal head of the metal shell 1. By crimping a portion (not shown), the insulator distal end portion 22 is fixed in the metallic shell 1 so that the insulator distal end portion 22 protrudes from the metal fitting distal end surface 11.

The center electrode 3 has a tip portion formed by an insulator tip surface 20.
Is fixed in the shaft hole 21 so as to protrude several mm from the shaft hole 21.
The center electrode 3 is formed of a composite material in which a copper material 32 such as copper or a copper alloy having good thermal conductivity is enclosed in a nickel alloy material 31 (Inconel 600 in this embodiment). Noble metal 33 is laser welded 31 on surface 311
2 has been done.

The outer electrode 4 has a substantially L-shaped cross section in the axial direction and is formed of a nickel alloy material 40 (for example, Inconel 600 in this embodiment) having a rectangular cross section. The distal inner surface 41 of the outer electrode 4 is opposed to the distal end surface (the distal end surface 311, the front surface 331) of the center electrode 3 in parallel, and air discharge is performed. The rear surface 332 of the noble metal 33 and the front end surface 321 of the copper material 32 are in contact with each other.

The center electrode 3 is manufactured through the following manufacturing steps (see FIGS. 2 and 3). (1) Cup forming process A cylindrical nickel alloy material is diced into a die D1, a punch P0,
An intermediate body 503 having a shallow depression 501 on the upper surface and a roundness 502 on the outer periphery of the lower surface is cold forged by a forging device made of P1.
(See FIG. 2 (a)). Further, cold forging is performed by a forging device including a die D2, a punch P2, and an extrusion pin p. Thereby, the concave portion 504 having a conical bottom is provided.
Is formed (see FIG. 2B).

(2) Drilling Step A small diameter communication hole 507 is drilled in the inner bottom of the cup 506 (see FIG. 2C). The communication hole 507 at the inner bottom of the cup 506 may be formed by pressing a punch.

(3) Core material forming process The copper material is formed by cold forging, cutting, or the like (not shown) into a small diameter portion 601 corresponding to the communication hole 507, a shaft portion 602 corresponding to the concave portion 504, and a large diameter. (D) of FIG. 2 (see the upper part of FIG. 2).

(4) Fitting process A substantially bullet-shaped core material 600 is fitted into the cup 506, and is fitted into a die D3 of a fitting device comprising a die D3, a plunger P3, and an extrusion pin p. Lumber 60
0 is pressed into the cup 506 with the plunger P3 to produce the composite 510 (see (d), lower part of FIG. 2, (e)). The composite 510 is formed by the front end face 604 of the core 600.
Is exposed.

(5) Extrusion Forming Step The composite 510 is extruded using a die D4 having a small diameter hole and a punch P4 to reduce the diameter and elongate (see FIG. 3 (f)). This extruded body 511 is
The front end surface 604 of the core 600 is exposed. Cut the unformed portion 512 at the rear end {see FIG. 3 (g)}.

(6) Flange Forming Step A flange 514 is formed at the rear end of the molded body 513 from which the unformed part 512 is cut, and a cross-shaped slit 515 is formed on the upper surface of the flange 514 {(FIG. h) Reference｝.

(7) Tip Cutting Step The tip of the compact 513 is cut to a small diameter (see FIG. 3 (i)). The small diameter of the tip of the molded body 513 may be formed by extrusion molding.

(8) Noble Metal Welding Step The noble metal 33 is laser-welded 312 to the front end surface 516 (= the front end surface 311) of the molded body 513. At this time, the core material 6
00 (= copper material 32) front end surface 604 (= front end surface 321)
Is exposed, the rear surface 332 of the noble metal 33 is
3 is in contact with the front end face 604 (= front end face 321) of FIG.
See (j) of｝.

Then, the molded body 513 is disposed so that its tip protrudes into the shaft hole 21 of the insulator 2, and is heat-sealed with a known glass seal material made of conductive glass or a resistor to form the center electrode 3. Becomes

Next, the advantages of this embodiment will be described. [A] The center electrode 3 manufactured through the above steps (1) to (8)
In the spark plug A adopting the above, since the rear surface 332 of the noble metal 33 that is laser-welded 312 to the front end surface 311 of the nickel alloy material 31 is in contact with the front end surface 321 of the copper material 32, the center electrode 3 has good heat dissipation. For this reason, the spark plug A is superior in the wear resistance of the center electrode 3 (because the temperature of the noble metal 33 does not increase) and the heat resistance of the center electrode 3 is better than that of the conventional spark plug in which the noble metal is provided. is there.

[A] In the spark plug A, in the tip cutting step (7), most of the spark discharge is performed between the noble metal 33 and the tip of the molded body 513 because the tip of the compact 513 is formed to have a small diameter. The effect of improving the durability of the noble metal 33 can be effectively used. In addition, since the ignition portion becomes thinner and the quenching action of the electrode is reduced, the ignition performance is excellent.

[C] Small diameter portion 60 corresponding to communication hole 507
1 is pressed into the cup 506 to produce the composite 510. Therefore, the number of parts can be reduced.

Next, a second embodiment of the present invention (Claim 2,
3) will be described with reference to FIGS. The bipolar spark plug B is, as shown in FIG.
An insulator 2 having a shaft hole 21 fitted and fixed in the metal shell 1, and a center electrode 3 fixed in the shaft hole 21.
And an outer electrode 4 bent in a substantially L-shape to protrude from the metal fitting end surface 11.
Is the same as

The center electrode 3 has a tip portion formed by an insulator tip surface 20.
And is fixed in the shaft hole 21 so as to protrude therefrom. The center electrode 3 is made of a nickel alloy material (Inconel in this embodiment).
600) is made of a composite material in which copper with good thermal conductivity is enclosed.

The outer electrodes 4, 4 have a nickel alloy material 31, a copper material 32 such as copper or copper alloy, and a copper material chip 34 such as copper or copper alloy (all of which have good thermal conductivity) sealed therein. A noble metal 33 is laser-welded 312 to a tip surface 311 of the nickel alloy material 31 which is formed of a composite material. The distal end surface (the distal end surface 311, the front surface 331) of the outer electrode 4 and the distal end outer peripheral surface 30 of the center electrode 3 are opposed to each other, and an air discharge is performed. The rear surface 332 of the noble metal 33 is in contact with the front end surface 341 of the copper chip 34.

The outer electrode 4 is manufactured through the following manufacturing steps (see FIGS. 5 and 6). Incidentally, (1) and (2) are the same as in the first embodiment. (1) Cup molding process (see FIGS. 5A and 5B). (2) Drilling process {see lower part of FIG. 5 (c)}.

(3) Chip forming process The copper material is formed by cold forging or cutting (not shown) into a small-diameter portion 701 corresponding to the communication hole 507 and a large-diameter portion corresponding to the bottom surface (conical shape) of the recess 504. (See FIG. 5 (c)).

(4) Core Material Forming Step The copper material is put into the recess 5 by cold forging or cutting (not shown).
Mold into a cylindrical shape (shaft shape) corresponding to 04.
(d) See｝.

(5) Fitting Step, Chip Inserting Step The chip 700 and the core member 600 are fitted into the cup 506, and the chip 700 and the core material 600 are placed in the die D3 of a fitting device including a die D3, a plunger P3, and an extrusion pin p. The composite member 510 is manufactured by mounting the core member 600 and press-fitting the core member 600 into the cup 506 with the plunger P3 (see FIGS. 5D and 5E). The composite 510 is provided on the front end face 70 of the chip 700.
3 is exposed.

(6) Extrusion Molding Step The composite 510 is placed in a die D4 having a small rectangular hole.
Extrusion molding is performed using the punch and the punch P4 to reduce and extend {see FIG. 6 (f)}. This extruded body 51
In No. 1, the front end face 703 of the chip 700 is exposed. Cut the unformed portion 512 at the rear end {see FIG. 6 (g)}.

(7) Noble Metal Welding Step The noble metal 33 is laser-welded 312 to the tip surface (= tip surface 311) of the molded body 513. At this time, chip 700
Because the front end face 703 (= front face 331) of the is exposed,
The rear surface 332 of the noble metal 33 is the front end surface 703 of the chip 700.
(= Front end face 341) {see FIG. 6 (h)}. Then, the formed body 513 is bent into a substantially L-shape and is welded to the distal end surface 11 of the metal shell 1 to form the outer electrode 4.

The two-pole spark plug B of this embodiment has the following advantages. [D] The bipolar spark plug B employing the outer electrode 4 manufactured through the above steps (1) to (7) is a rear surface 332 of the noble metal 33 which is laser welded 312 to the front end surface 311 of the nickel alloy material 31. However, since the front end surface 341 of the copper material chip 34 is in contact with the outer electrode 4, the heat of the outer electrode 4 is good. For this reason, the bipolar spark plug B is superior in the wear resistance of the outer electrode 4 (because the temperature of the noble metal 33 does not increase) as compared with the conventional spark plug in which the noble metal is disposed.

[E] Since the conical portion 702 is locked to the inner bottom of the cup, the chip 700 does not fall off at the time of extrusion molding or use, and the chip 700 is firmly in contact with the copper material 32 so that the heat is drawn. Is good.

The present invention includes the following embodiments in addition to the above embodiment. a. Noble metals, Pt-Ir alloy, Pt-Ir- Ni alloy, Au- Pd alloy, Ir, an Ir- Y ₂ O ₃ alloy and the like can be used. b. The number of poles of the outer electrode may be three or more.

C. The welding of the noble metal 33 may be electric resistance welding or arc welding other than the laser welding of the above embodiment. d. Copper material 32 and copper material chip 34 are made of Cu-Cr alloy, C
A u-Zr alloy, a Cu-Cr-Zr alloy or the like can be used.

[Brief description of the drawings]

FIG. 1 is a partial sectional view of a spark plug according to a first embodiment of the present invention.

FIG. 2 is a process chart showing a method for manufacturing a center electrode of a spark plug according to a first embodiment of the present invention.

FIG. 3 is a process diagram showing a method for manufacturing a center electrode of a spark plug according to a first embodiment of the present invention.

FIG. 4 is a partial cross-sectional view of a two-pole spark plug according to a second embodiment of the present invention.

FIG. 5 is a process diagram illustrating a method for manufacturing a center electrode of a bipolar spark plug according to a second embodiment of the present invention.

FIG. 6 is a process diagram illustrating a method of manufacturing a center electrode of a bipolar spark plug according to a second embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List A spark plug B bipolar spark plug 3 center electrode 4 outer electrode 32 copper (core material) 33 noble metal 321 front end face 506 cup 507 communication hole 510 composite 511 extruded body 600 core material 601 small diameter section 604 front end face

Claims (4)

[Claims] 1. A cup forming step of manufacturing a cup made of a heat-resistant metal, a drilling step of forming a small-diameter communication hole in a bottom of the cup, and a step of forming a good heat conductive metal into a small diameter hole corresponding to the communication hole. A core material forming step of molding into a shaft shape having a portion, a fitting step of fitting the core material in a cup, and manufacturing a composite in which a front end face of the core material is exposed at a front end face, and extruding the composite body An extruding step of manufacturing an extruded body in which the front end face of the core material is exposed at the front end face, and welding a noble metal to the front end face of the extruded body so that the rear face is in contact with the front end face of the core material. A method for producing an electrode for a spark plug, comprising: 2. A cup forming step of manufacturing a cup made of a heat-resistant metal, a drilling step of forming a communication hole in a bottom of the cup, and forming a good heat conductive metal into a chip shape corresponding to the communication hole. A chip forming step, a chip inserting step of inserting the chip into the communication hole from inside the cup, a core material forming step of forming a good heat conductive metal into a shaft shape, and fitting the core material into the cup, A fitting step of manufacturing a composite in which the front end face of the chip is exposed on the front end face; and an extrusion forming method of expanding the composite body by extrusion and manufacturing an extruded body in which the front end face of the chip is exposed on the front end face. A method for manufacturing an electrode for a spark plug, comprising: a step of welding a noble metal to a front end face of the extruded body such that a rear face is in contact with a front end face of the tip. 3. The chip has a small-diameter portion that fits into the communication hole, and a large-diameter portion that is larger than the communication hole.
A method for producing an electrode for a spark plug as described above. 4. The method for manufacturing an electrode for a spark plug according to claim 1, wherein the noble metal is welded after a tip of the extruded body is cut into a small diameter.