JPH05290952A - Manufacture of center electrode for multi-electrode spark plug - Google Patents

Abstract

PURPOSE:To improve the durability of a multi-electrode spark plug by forming a center electrode with a core material of copper or copper alloy inserted in a base material of nickel alloy, making a slit directed from the center of the electrode toward an outer electrode, and coupling an ignition electrode of platinum, iridium, gold or the like to the slit. CONSTITUTION:A center electrode 4 held with an insulator 2 comprises a core material 10 as a good heat conductor of copper or a copper alloy inserted in a cup-shaped base material of nickel alloy, thereby forming a center electrode composite material. At the same time, a straight slit 13 directed from a center to an outer electrode is formed on the forward edge 12 of the composite material. Then, an ignition electrode 6 of alloy material mainly composed of platinum, iridium, gold or a combination thereof is coupled to the slit 13 and welded. Thereafter, the forward end of the center electrode composite material is extrusion molded, thereby forming an electrode of fine diameter. According to this construction, an amount of precious metal itself used as the electrode 6 can be reduced. Also, excellent durability and resistance against abrasion due to ignition, pertaining to the electrode 6 of precious metal, can be displayed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spark plug mounted on an internal combustion engine, and more particularly to a structure of a center electrode having a plurality of outer electrodes at the tip of a metal shell holding an insulator.

[0002]

2. Description of the Related Art Conventionally, the tip of the center electrode of a spark plug is liable to be consumed for a long period of time due to ignition by a spark discharge to a mixture in a combustion chamber of an internal combustion engine. It is common practice to join a noble metal member made of Pt, Ir, Au or an alloy mainly containing them, which is excellent in spark consumption resistance, to improve durability as a spark plug and enable long-term use. However, especially in a multi-pole spark plug that has multiple outer electrodes at the end of the metal shell that holds the insulator, there are multiple parts where spark discharge occurs, and the amount of precious metal members used increases. Since this causes an increase in cost, a recess is provided at the tip of the center electrode in order to reduce the amount of precious metal member used. That the noble metal member of the annular body fitted welding, comprising a small-diameter portion by extruding the leading end of the center electrode for has been proposed (JP 61-135
87).

[0003]

However, in the case of the above-mentioned Japanese Patent Laid-Open No. 61-13587, in the multipolar spark plug having a plurality of outer electrodes, an effect of reducing the amount of the noble metal member used is recognized to some extent. However, since the noble metal member is disposed between the outer electrode and the portion that causes the spark discharge, there is a drawback that a drastic cost reduction cannot be ensured.

Therefore, the present invention is intended to improve the drawbacks of the above-mentioned conventional ones, and while ensuring effective corrosion resistance and spark wear resistance, it is possible to reduce the cost only to the site where the noble metal member is required to be used. It is something to try.

[0005]

To this end, a core material, which is a good heat conductor made of Cu or Cu alloy, is inserted into a cup-shaped base material made of Ni alloy to form a center electrode composite material. A slit is provided from the center toward each outer electrode on the tip surface of the center electrode composite material, and an ignition part electrode material made of Pt, Ir, Au or an alloy material mainly containing these is fitted and welded to the slit. After that, this center electrode composite material is extruded to form a center electrode having a small diameter.

[0006]

With the above-described structure, the outer electrode disposed at the tip of the metal shell that holds the insulator and the ignition part electrode made of the noble metal of the center electrode that generates spark discharge are attached to the outer end of the center electrode composite material. Since it is fitted and welded to the slits arranged toward the electrode direction, Pt, Ir, Au or an alloy material mainly composed of them is always present only at the position where the spark discharge is generated. The amount used can be greatly reduced.

In addition, Pt, Ir, Au, or an alloy material mainly composed of Pt, Ir, Au is ignited at the center electrode tip where a spark discharge is generated between a plurality of outer electrodes arranged at the tip of the metal shell holding the insulator. Since it exists as a partial electrode,
Excellent corrosion resistance and spark wear resistance can be exhibited, and durability as a spark plug can be improved.

[0008]

The present invention will be further described with reference to the embodiments shown in the drawings. (1) is a multipolar spark plug comprising an embodiment of the present invention, the multipolar spark plug (1),
A center electrode (4) having a firing part electrode (6) made of Pt, Ir, Au or an alloy material mainly containing these is held at the tip of the shaft hole (3), and the rear end of the shaft hole (3) is held. An insulator (2) for encapsulating and holding a resistor and a terminal electrode (5) therein, and an insulator (2) for holding the insulator (2) and facing the ignition part electrode (6) of the center electrode (4) at the tip. A plurality of (preferably 2 to 3) outer electrodes (8) are arranged at positions where the metal shell (7) is formed.

The center electrode (4) held by the insulator (2) is a cup-shaped base material (9) made of Ni alloy.
A core material (10), which is a good heat conductor made of Cu or a Cu alloy, is inserted therein to form a center electrode composite material (11), and a tip surface (12) of the center electrode composite material (11) is
A linear slit (13) or a Y-shaped slit (14) is arranged from the center toward the outer electrode (8) of the metal shell (7), and P is provided for these slits (13) and (14).
After fitting and welding the ignition part electrode material (15) made of t, Ir, Au or an alloy material mainly containing these, the tip end side of this center electrode composite material (11) is extruded to have a small diameter. It serves as the center electrode (4) (FIG. 3).

Since the present invention has the above structure, the plurality of outer electrodes (8) arranged at the tip of the metal shell (7) for holding the insulator (2) and the center electrode (4) for generating spark discharge. ), Which is made of Pt, Ir, Au, or an alloy material mainly composed of Pt, Ir, and Au, is the center electrode composite material (1).
1) At the tip, since it is fitted and welded to the slits (13) and (14) arranged toward the outer electrodes (8) arranged in plural at the tip of the metal shell (7), Pt,
The ignition part electrode (6) made of Ir, Au or an alloy material mainly containing these is always the ground electrode (8) of the metal shell (7).
Since it exists only at a position where a spark discharge is generated between and, the amount of the noble metal itself used as the ignition part electrode (6) can be significantly reduced.

The spark discharge between a plurality of outer electrodes (8) arranged at the tip of the metal shell (7) causes the tip of the center electrode (4) at a position opposite to the outer electrode (8). In P., Ir, Au, or an alloy material composed mainly of Pt, Ir, Au, or the like, the ignition portion electrode (6) made of a noble metal or the like has excellent corrosion resistance and fire resistance. Flower exhaustion can be exhibited, and durability as a spark plug can be improved.

In the above embodiment, a multi-pole spark plug having a plurality of outer electrodes opposed to the tip side of the center electrode is shown. However, the multi-pole spark plug of this embodiment has a multi-pole spark plug. Without being limited thereto, a multipolar spark plug having a plurality of inwardly inclined outer electrodes arranged opposite to the tip peripheral edge of the center electrode, or a center electrode (4) protruding from the tip surface of the insulator (2) The tip of the center electrode of the present invention is also advantageous for a semi-creeping discharge multi-pole spark plug in which a plurality of outer electrodes (8) are provided to face the tip peripheral side (16) of the insulator (2). Some ignition electrode materials can be applied.

[0013]

As described above, in a multipolar spark plug having a plurality of outer electrodes, by arranging a firing part electrode made of a noble metal or the like only at a position where the outer electrodes face each other, it is used as a firing part electrode. The cost can be reduced because the amount of precious metal used can be greatly reduced.
Since the noble metal is present at the position where the spark discharge occurs, it has an excellent effect of exhibiting corrosion resistance and spark consumption resistance and remarkably improving the durability of the spark plug itself.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of this multipolar spark plug.

FIG. 2 is an enlarged cross-sectional view of the main part, (a) is a side view,
(B) shows a plan view.

FIG. 3 is a diagram showing a method of manufacturing a center electrode.

FIG. 4A is an enlarged perspective view of a main part showing a tip of a center electrode having a linear slit and FIG. 4B a Y-shaped slit.

[Explanation of symbols]

1 Multipolar Spark Plug 2 Insulator 3 Shaft Hole 4 Center Electrode 5 Terminal Electrode 6 Ignition Part Electrode 7 Metal Shell 8 Outer Electrode 9 Base Material (Cup Shape Made of Ni Alloy) 10 (Good Heat Made of Cu or Cu Alloy) It is a conductor)
Core material 11 Center electrode composite material 12 Tip surface 13 Linear slit 14 Y-shaped slit 15 Ignition part electrode material 16 Tip peripheral side of insulator

Claims (1)

[Claims] 1. A tip of a center electrode is provided with a plurality of tips of outer electrodes, and the center electrode is made of Cu or a Cu alloy in a cup-shaped base material made of Ni alloy. A core material, which is a conductor, is inserted to form a center electrode composite material, and slits are provided on the tip surface of the center electrode composite material from the center toward each outer electrode, and Pt, I
Manufacture of the center electrode of a multi-pole type spark plug, which is used as a center electrode of a small diameter by extruding this center electrode composite material after fitting and welding the ignition part electrode material composed of r, Au or an alloy material mainly containing them. Method.