Spark plug

Details Spark plug Spark plug

1998-11-13

2000-04-04

Patel, NimeshKumar D.

Electric lamp and discharge devices

Spark plugs

Particular electrode structure or spacing

313142, H01T 1320

Patent

active

060465328

ABSTRACT:
A spark plug includes a center electrode, an insulator provided outside the center electrode, a metallic shell provided outside the insulator, a ground electrode disposed to oppose the center electrode, and a spark discharge portion fixed on at least one of the center electrode and the ground electrode for defining a spark discharge gap. The spark discharge portion of the spark plug is formed of a metallic material containing Ir as a main component, and a region where the Vickers hardness is not greater than Hv 400 extends from the surface of the spark discharge portion to a depth of 0.05 mm or more. The average value of d.sub.min /d.sub.max ratios of grains on an arbitrary cross-section is preferably equal to or greater than 0.7 where d.sub.min represents the minimum diameter of each grain on the cross-section and d.sub.max represents the maximum diameter of the grain. The ratio of hS/hB is preferably not greater than 0.9, where hS represents an average Vickers hardness measured in a surface layer region extending to a depth of 0.05 mm from the surface that faces the spark discharge gap, and hB represents an average Vickers hardness measured in the remaining region. The spark discharge portion is formed of a chip that is formed from a metallic material that contains Ir as a main component and is annealed at a temperature of 900.degree. to 1700.degree. C.

REFERENCES:
patent: 5017826 (1991-05-01), Oshima et al.
patent: 5461275 (1995-10-01), Oshima
patent: 5488262 (1996-01-01), Takamura

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