JPH1055874A - Manufacturing method of multi-pole spark plug - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a multipolar spark plug in which a noble metal is provided on an outer electrode, wherein the noble metal can be accurately provided on a front end face of an outer electrode. A multi-polar spark plug includes a welding step of welding outer electrode base materials (401, 401) to a metal tip surface (11) of a metal shell (1), a bending step of plastically deforming the outer electrode into a substantially L-shape, and a noble metal tip. Is manufactured through a noble metal welding step of welding the precious metal tip to the front end face 42 and a punching step of punching out the center of the welded noble metal tip.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multipolar spark plug in which a noble metal is disposed on an outer electrode.

[0002]

2. Description of the Related Art A multipolar spark plug having a noble metal disposed on an outer electrode has been conventionally manufactured by the following method (see FIG. 10). The outer electrode base material is welded to the front end surface of the cylindrical metal shell. Plastic deformation of each outer electrode substrate {Step (a)}. Step (b): punching out the tip of each outer electrode substrate to form the outer electrode. Step (c) of welding a plate-shaped noble metal to the tip of each outer electrode.

[0003]

The above prior art has the following problems. (1) When welding a noble metal, it is necessary to accurately position the noble metal. When the noble metal is displaced during welding, the spark gap length varies. (2) It is necessary to weld noble metals by the number of outer electrodes, which is troublesome.

An object of the present invention is to provide a method for manufacturing a multipolar spark plug in which a noble metal is disposed on an outer electrode, which can accurately position the noble metal on the front end face of the outer electrode.

[0005]

In order to solve the above-mentioned problems,
The present invention employs the following configuration. (1) A method of manufacturing a multipolar spark plug includes an electrode welding step of welding a plurality of outer electrode base materials to a tip end surface of a cylindrical metal shell, and a bending mold having a forming surface corresponding to a bent shape of the outer electrode. A bending step of pressing each outer electrode substrate against the molding surface to plastically deform inward, and a precious metal such that one end surface is joined to the front end surfaces of all the outer electrode substrates, straddling a gap formed by each end surface. And a punching step of punching out the center of the noble metal and the tip of each outer electrode base material.

(2) A method for manufacturing a multipolar spark plug is as follows.
An electrode welding step of welding a plurality of outer electrode base materials to the metal tip end surface of the cylindrical metal shell, and pressing each outer electrode base material onto the forming surface of a bending mold having a forming surface corresponding to the bending shape of the outer electrode. A bending step of inwardly deforming plastically inward, an electrode punching step of punching the front end of each outer electrode base material, and a step of straddling the gap formed by the punching, and applying one to the front end faces of all the punched outer electrode base materials. The method includes a noble metal welding step of welding a noble metal so that end faces are joined, and a noble metal punching step of punching a central portion of the noble metal.

(3) The structure of (1) or (2) above, wherein the number of the outer electrode base material is two, and the outer electrode base material is welded to the front end face of the metal fitting in a facing state, and the noble metal is in a belt shape , Resistance welding is performed on the front end face of the outer electrode base material before punching or on the front end face of the outer electrode base material after punching.

[0008]

[Action and effect of the invention]

[Claim 1] A plurality of outer electrode bases are welded to the front end surface of a cylindrical metal shell. Each outer electrode base material is pressed against a forming surface of a bending die having a forming surface corresponding to the bending shape of the outer electrode, and is plastically deformed inward. The noble metal is welded so as to straddle the gap between the respective front end surfaces and join one end surface of the noble metal to the front end surfaces of all the outer electrode base materials. The center of the noble metal and the tip of each outer electrode substrate are punched. As a result, the noble metal and the front end surface (ignition surface) of the outer electrode base material become flush, and the noble metal is accurately positioned on the outer electrode. The work of welding the noble metal to the front end surface of the outer electrode base material can be performed only once, and high positioning accuracy is not required when welding the noble metal.

[Claim 2] A plurality of outer electrode base materials are welded to the front end surface of the cylindrical metal shell. Each outer electrode base material is pressed against a forming surface of a bending die having a forming surface corresponding to the bending shape of the outer electrode, and is plastically deformed inward. Punch out the tip of each outer electrode substrate. A noble metal is welded across the gap formed by punching so that one end face is joined to the front end faces of all the outer electrode base materials.

A central portion of the noble metal is punched. This allows
The dimension of the portion where the noble metal protrudes from the tip surface (firing surface) of the outer electrode is accurately determined, and the leading surface (firing surface) of the noble metal is accurately positioned on the outer electrode. The work of welding the noble metal to the front end face of the punched outer electrode base material can be performed only once, and high positioning accuracy is not required when welding the noble metal. Since the noble metal protrudes from the tip surface (ignition surface) of the outer electrode, the ignitability is improved.

[Claim 3] The two outer electrode bases are welded to the front end face of the metal fitting in an opposed state. The strip-shaped noble metal is resistance-welded to the front end face of the outer electrode base material before punching or to the front end face of the outer electrode base material after punching. Since the noble metal is strip-shaped, the amount of the noble metal formed on the outer electrode can be reduced.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention (Claim 2,
3) will be described with reference to FIGS. As shown in FIG. 1, the bipolar spark plug A is a cylindrical metal shell 1.
An insulator 2 having a shaft hole 21 fitted and fixed in the metal shell 1, a center electrode 3 fixed in the shaft hole 21 so that an electrode tip 31 protrudes from the insulator tip surface 22, Outer electrodes (4, 4) that are bent and project from the metal fitting tip surface (11) so that the surface (41) (discharge surface) faces the tip outer peripheral surface (311) of the center electrode (3).

The metal shell 1 is made of low carbon steel, and the outer electrodes 4 are 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 outer electrode 4 is a composite electrode in which the tip is bent in an L shape and a nickel alloy material or copper having good thermal conductivity is sealed inside the nickel alloy material. Tip surface 41 of outer electrode 4
Is an outer peripheral surface 311 of the center electrode 3 which is formed in a circular arc shape.
(See FIG. 1). A noble metal 40 such as Pt, Pt-Ir alloy, Ir alloy or the like is welded to a front end face (outer face) 42 of the outer electrodes 4, 4, and the noble metal 40 is separated from a tip face 41 (firing surface) of the outer electrodes 4, 4. It slightly protrudes in the direction of the center electrode 3.

The insulator 2 is made of a ceramic mainly composed of alumina, and has a seating surface fixed to a step (not shown) of the metal shell 1 via a packing (not shown).
By caulking the upper end (not shown) of the metal shell 1
Is fixed in the metal shell 1 so that the insulator tip 23 projects from the opening.

The center electrode 3 is a composite electrode in which copper having good thermal conductivity is sealed in a nickel alloy material, and has an outer diameter of φ2.0 in this embodiment.

Next, a method of manufacturing the bipolar spark plug A will be described with reference to manufacturing process diagrams {(α) to (ε)} in FIGS. 2 to 4 and shape change diagrams (a) to (d) in FIG. It is described based on｝.

(1) A low carbon steel material (carbon content: several percent) is subjected to a process such as cold extrusion to produce a metal shell (without screws). The metal shell may be manufactured by performing a cutting process from a cylindrical or polygonal bar without performing the cold extrusion. Next, a round die or a flat die (neither is shown) having a mountain shape corresponding to the screw 12 is pressed against the outer periphery of the metal shell (without a screw) and rolled to perform thread rolling.

(2) Next, the outer electrode base materials 401, 401
(Electrode welding process; (α) in FIG. 2) by resistance welding or the like in a state facing the metal fitting end surface 11 of the metal shell 1. The outer electrode substrate 401 is a nickel alloy (such as Inconel) obtained by adding Cr, Mn, and Si to nickel as a base material.

After washing with hydrochloric acid and washing with water, the inner and outer peripheries of the metal shell 1 and the outer electrode substrates 401, 401
Is subjected to zinc plating and chromate treatment. Furthermore,
Lubricating oil is applied to the tip surfaces of the outer electrode base materials 401 and 401.

(3) Outer electrode base material 40 by press molding machine
Forming steps 1 and 401 {bending step; (β) in FIG. 2}.
The press forming machine includes a bending die 500 having a forming surface 501 having a shape opposite to the bending shape of the outer electrodes 4 and 4 (see FIG. 1), a guide 502 for guiding the metal shell 1 to the bending die 500, and a bending punch 503. It is configured.

The bending punch penetrates through the communication hole 13 of the metal shell 1 and presses the outer electrode bases 401, 401 against the forming surface 501 of the bending mold 500 to press the outer electrode bases 401, 401.
Is plastically deformed. The bending punch 503 includes a shoulder portion 504 that abuts on the locking portion 14 of the through hole 13 of the metal shell 1, and a leg portion 505 that determines a bending height (electrode height) of the outer electrode base materials 401 and 401. Have.

The tip surfaces of the outer electrode substrates 401 and 401 (to which lubricating oil is applied) are connected to the forming surface 50 of the bending mold 500.
By inserting the metal shell 1 into the guide 502 so as to make contact with the outer electrode substrate 40,
1 and 401 are bent into a substantially L-shape. The state where the bending is completed is shown in FIGS.

(4) Next, the tip portions of the outer electrode base materials 401, 401 are punched out by a press molding machine (electrode punching step; (γ) in FIG. 2). Outer electrode base material 40 of metal shell 1
1, 401 are inserted into the guide 512 so as to contact the upper end surface of the punching die 510, and the outer diameter (φ2.
The tip of the punch 513 punches out the outer electrode base materials 401 from the inside of the through hole 13 so that the gap diameter s becomes 0.2 mm or more larger than 0). FIG. 6B shows a state in which the punching is completed.

The press forming machine is composed of outer electrode base materials 401, 4
01, punched chips 402, 40
A punching die 510 having a discharge hole 511 for discharging
Guide 51 for guiding metal shell 1 to punching die 510
2, and a punch 513 that moves from the inside to the outside of the metal shell 1.

(5) Next, the gap 400 formed by punching is straddled, and one end face 404 of the noble metal 40 is placed on the front end faces of the outer electrodes 4, 4 (the front end faces 42 of the punched outer electrode bases 401, 401). So that they are joined together.
Resistance welding of the belt-shaped noble metal tip 40a according to {noble metal welding process; (δ) in FIG. 3}.

[0027] As shown in FIG.
And a positive electrode 62 and the like, which are fitted into the communication holes 13 of the outer electrodes 4 and 4, and the noble metal 40 is placed on the front end surfaces 42 of the outer electrodes 4, 4. -With the direct current applied between the plus electrodes 62, the plus electrode 62 is pressed down from above in the figure to perform resistance welding. FIG. 6C shows a state in which the welding of the noble metal tip 40a is completed.

(6) The outer electrodes 4 and 4 of the metal shell 1 are inserted into the guide 711 such that the outer electrodes 4 and 4 come into contact with the upper end surface of the punching die 710, and the punched portion 712 a having a length d is inserted into the noble metal tip 4.
Punching the central portion of No. 0a (precious metal punching step; (ε) in FIG. 4). The state where the punching is completed is shown in FIGS.

The punching machine 7 has a punching die 710 having a discharge hole 713 for discharging the punching chips 403 of the noble metal tip 40 a, a guide 711 for guiding the metal shell 1 to the punching die 710, and from the inside to the outside of the metal shell 1. And a punch 712 having a rectangular column shape having a punching portion 712a that moves.

When the insulator 2 in which the center electrode 3 is inserted by a glass seal is fitted and fixed in the through hole 13 of the metal shell 1 shown in FIG. 7, the spark plug A shown in FIG. 1 is completed.

The spark plug A of this embodiment has a gap 40
In this configuration, the noble metal tip 40a is resistance-welded to the front end surfaces 42 of the outer electrodes 4 and 4 across 0, and the center of the noble metal tip 40a is punched by a punch 712. Therefore, it has the following advantages.

The dimension of the portion where the noble metal 40 protrudes from the tip surface 41 (firing surface) of the outer electrodes 4, 4 is accurately determined. Thereby, a gap k between the tip surface 41 (ignition surface) of the noble metal 40 and the tip outer peripheral surface 311 of the center electrode 3 can be accurately formed.

Further, the noble metal 4
Since the dimension up to the front end face of 0 is accurately defined, the dimension between the center electrode 3 protruding from the insulator 2 and the tip end face of the electrode tip 31 is constant, and the ignitability is stabilized.

The work of welding the noble metal tip 40a to the outer electrode 4 only needs to be performed once, and high positioning accuracy is not required when welding the noble metal tip 40a. Since the noble metal 40 protrudes from the front end surface 41 (firing surface) of the outer electrode 4, ignitability is improved. Since the noble metal tip 40a to be welded has a band shape, the amount of the noble metal for forming the noble metal 40 on the outer electrode 4 can be reduced.

Next, a second embodiment of the present invention will be described.
2) will be described with reference to FIGS. The bipolar spark plug B differs from the bipolar spark plug A in the following points.

The front end face of the noble metal 40 to be welded to the front end faces 42 of the outer electrodes 4 and 4 is formed in an arc shape, is punched flush with the front end face 41 (discharge surface) of the outer electrode 4, and has a front end outer peripheral face 311. (See FIG. 8).

Next, a method of manufacturing the spark plug B will be described with reference to FIGS. 9A to 9C. As in the production of the two-pole spark plug A, the above (1) to
Step (3) is performed. FIG. 9A shows a state in which the bending of the outer electrode base materials 401 is completed.

Next, a band-shaped noble metal is welded according to FIG. 3 so as to straddle the gap 400 between the respective front end surfaces and join the one end surface 404 of the noble metal tip 40a to the front end surfaces of the outer electrode base materials 401 and 401. The tip 40a is resistance-welded. The state where the noble metal tip 40a is welded is shown in FIG.

The central part of the noble metal tip 40a and the front parts of the outer electrode bases 401, 401 are punched by a punching machine according to FIG. The punching portion of the punching machine of the punching machine used for the punching has an arc-shaped cross section. FIG. 9C shows a state in which the punching is completed.

The spark plug B of this embodiment has a gap 40
The precious metal tip 40a is resistance-welded to the front end surfaces 42 of the outer electrodes 4 and 4 across 0, and the central part of the precious metal tip 40a and the front parts of the side electrode base materials 401 and 401 are punched by a punch. Therefore, it has the following advantages.

The tip surface of the noble metal 40 and the outer electrodes 4, 4
, The noble metal 40 is accurately positioned on the outer electrodes 4, 4. Outer electrode substrate 4
The welding operation of the noble metal tip 40a to the front end surface 42 of No. 01 only needs to be performed once, and a high positioning accuracy is not required when welding the noble metal tip 40a.

The present invention includes the following embodiments in addition to the above embodiments. a. The number of the outer electrodes 4 protruding from the metal fitting end surface 11 may be two or more. b. The tip surface 41 of the noble metal 40, the outer electrode substrate 401,
The cut shape of the distal end surface of 401 may be V-shaped, U-shaped, corrugated, or flat. c. The cross section of the outer electrode may be square, circular, trapezoidal, or polygonal.

[Brief description of the drawings]

FIG. 1 is a front view (top) and a top view (bottom) of a two-pole spark plug according to a first embodiment of the present invention.

FIG. 2 is a manufacturing process diagram ((α) to (γ)) showing a manufacturing process of the two-pole spark plug.

FIG. 3 is a manufacturing process diagram (δ) showing a manufacturing process of the bipolar spark plug.

FIG. 4 is a manufacturing process diagram (ε) showing a manufacturing process of the bipolar spark plug.

FIG. 5 is a cross-sectional view of the metal shell at the end of the bending step in the manufacture of the bipolar spark plug.

FIG. 6 is a shape change diagram showing a change in shape during the manufacturing process of the bipolar spark plug.

FIG. 7 is a perspective view of the metal shell at the completion of the noble metal punching step in the manufacture of the bipolar spark plug.

FIG. 8 is a front view (top) and a top view (bottom) of a two-pole spark plug according to a second embodiment of the present invention.

FIG. 9 is a shape change diagram showing a shape change during the manufacturing process of the two-pole spark plug.

FIG. 10 is a shape change diagram showing a change in shape during a manufacturing process of a bipolar spark plug according to the related art.

[Explanation of symbols]

 Reference Signs List 1 metal shell (cylindrical metal shell) 2 insulator 3 center electrode 4 outer electrode 11 metal fitting tip surface 40 noble metal 40a noble metal tip (noble metal) 42 front end face 400 gap 401 outer electrode base material 404 one end face 500 bending mold 501 forming surface A , B Two-pole spark plug (multi-pole spark plug)

Claims (3)

[Claims] An electrode welding step of welding a plurality of outer electrode bases to a tip end surface of a cylindrical metal shell, and each of said forming surfaces of a bending mold having a forming surface corresponding to a bent shape of an outer electrode. A bending process in which the electrode base material is pressed and plastically deformed inward, and a noble metal welding process in which a precious metal is welded so as to straddle the gap between the end surfaces and join one end surface to the front end surfaces of all the outer electrode base materials. And a punching step of punching a central portion of the noble metal and a tip portion of each outer electrode base material. 2. An electrode welding step of welding a plurality of outer electrode bases to a front end surface of a metal shell of a cylindrical metal shell, and forming each outer surface on a bending surface of a bending mold having a forming surface corresponding to a bending shape of the outer electrode. A bending process in which the electrode base material is pressed and plastically deformed inward, an electrode punching process in which the tip of each outer electrode base material is punched out, and all the outer electrode base materials that are punched out across the gap formed by the punching A method for manufacturing a multipolar spark plug, comprising: a precious metal welding step of welding a precious metal so that one end face is joined to a front end face of the precious metal; and a precious metal punching step of punching a central portion of the noble metal. 3. The outer electrode base material is two, and is welded to the front end face of the metal fitting in an opposed state, and the noble metal is strip-shaped, and the front end face of the outer electrode base material before punching or after punching. 3. The method for manufacturing a multipolar spark plug according to claim 1, wherein the outer electrode substrate is resistance-welded to a front end surface of the outer electrode substrate.