Electric lamp and discharge devices – Spark plugs – With specific joint structure
Patent
1993-08-11
1995-11-07
O'Shea, Sandra L.
Electric lamp and discharge devices
Spark plugs
With specific joint structure
313144, 313142, H01T 1320, H01T 1332
Patent
active
054650224
ABSTRACT:
A composite chip formed by joining a discharging layer and a heat stress relieving layer at a joint interface therebetween beforehand is provided on at least one of a central electrode and a ground electrode in its discharge portion made of an electrode material. The discharging layer is made of a precious metal or a precious metal alloy having superior spark- and wear-resistance, and the heat stress relieving layer is made of a metal or an alloy having a linear expansion coefficient between those of the discharging layer and the electrode material. Formed at the joint interface between both the discharging layer and the heat stress relieving layer through mutual diffusion of those materials developed when the two layers are joined to each other is a diffusion layer, in which concentrations of materials of both the layers are continuously changed. A thickness of the diffusion layer is not less than 3 .mu.m in a state that the composite chip is welded to the discharge portion.
REFERENCES:
patent: 3673452 (1972-06-01), Brennen
patent: 3868530 (1975-02-01), Eaton et al.
patent: 4122366 (1978-10-01), Von Stutterheim et al.
patent: 4540910 (1985-09-01), Kondo et al.
patent: 4581558 (1986-04-01), Takamura et al.
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patent: 4853582 (1989-08-01), Sato et al.
Abe Nobuo
Hanai Takeshi
Horibe Kenji
Katoh Akio
Nippondenso Co. Ltd.
O'Shea Sandra L.
Patel Ashok
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