Method for producing electrodes for spark plugs and spark plug e

Details Method for producing electrodes for spark plugs and spark plug e Method for producing electrodes for spark plugs and spark plug e

1992-05-08

1994-05-10

Bradley, Paula A.

Electric lamp or space discharge component or device manufacturi

Process

Spark plug or spark gap making

445 49, 313136, 313141, H01T 2102

Patent

active

053103734

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION:

The present invention relates generally to a method for producing spark plug electrodes, and to a spark plug so made. Background: Such a method has already been disclosed by U.S. Pat. No. 2,955,222, in which a composite body which is assembled from three initial parts of different material is formed by impact extrusion into a spark plug centre electrode; the composite body has a rivet-shaped spark section, which consists of noble metal and fills up the throughbore of a round blank made from nickel with its countersunk head and a part of its shank, and there being soldered onto the side of the nickel round blank which accommodates the head of the spark section a copper round blank of the same diameter. After the impact extrusion, the copper initial part then forms the electrode core of high thermal conductivity, and the nickel initial part the corrosion-resistant electrode shell from the floor of which the spark section projects on the combustion-chamber side in the shape of a rod. The spark section of this centre electrode does permit good accessibility of the fuel-vapour/air mixture to the spark gap of the spark plug, but its attachment to the centre electrode is in need of improvement for use in modern high-efficiency internal combustion engines.
Japanese Patent 4,922,989 discloses a spark plug with a centre electrode which has a copper core, a nickel shell and a spark tip made from platinum, gold, palladium or the like, the spark tip material being in direct contact with the core material. This centre electrode was produced by impact extrusion of a composite body consisting of three round blanks, the round blank provided for the spark tip either being of virtually the same diameter as the round blanks for the core and for the shell, or having a smaller diameter, with the result that this round blank can be inserted into a throughhole in the round blank for the shell. The spark section made from the noble metal is not, however, reliably attached to the shell and to the core of this centre electrode, and in the event of the loss of the spark section the spark plug does not have adequate emergency running properties in this region.
German Offenlegungsschrift 3,607,243 discloses a method for producing spark plug centre electrodes by impact extrusion, in which the starting point is, once again, a composite body, which is assembled from three initial parts of different material; the finished electrode in this case has a shell of corrosion-resistant material (for example nickel alloy), a core surrounded by the shell and made from a material of high thermal conductivity, and a spark section which consists of noble metal and is fixed in a blind bore in the floor of the shell on the combustion-chamber side. In this electrode, however, the electrode core, which efficiently conducts the heat, is separated from the spark section by a part of the shell floor, and the heat flow in the electrode is obstructed as a result. The production of the composite body of this electrode is, however, relatively complex from the point of view of mass production, because the rod-shaped initial part for the core has to be inserted into the deep blind bore on the connection side, and the pin-shaped initial part of the spark section has to be inserted into the blind bore, on the combustion-chamber side, of the initial part for the shell.
A method similar to that in the previously described German Offenlegungsschrift 3,607,243 is also disclosed in German Offenlegungsschrift 3,433,683: instead of a pin-shaped initial part for the spark section, use is made here of a disc-shaped initial part.
DE-AS 2,614,274 describes a spark plug with electrodes which have a silver core, which is surrounded by a tubular nickel shell, and in which the silver core is exposed on the end face on the combustion-chamber side. Such electrodes can be used in functional terms, but they have a relatively high fraction of silver which makes these electrodes expensive.
U.S. Pat. No. 2,296,033 exhibits spark plugs with centre and earth electr

REFERENCES:
patent: 2783409 (1957-02-01), McDougal
patent: 2955222 (1960-04-01), Boesch
patent: 3407326 (1968-10-01), Romine
patent: 4540910 (1985-09-01), Kondo et al.
patent: 4695759 (1987-09-01), Podiak
patent: 4904216 (1990-02-01), Kagawa et al.

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