Patent ID: 6265816
Filing Date: 2001-07-24
Classification: H01T

Abstract:
A spark plug comprising:a center electrode;a metallic shell placed outside the center electrode;a ground electrode which has one end coupled to the metallic shell and which is placed opposite to the center electrode; andan insulator placed between the center electrode and the metallic shell so as to cover exterior of the center electrode, whereinthe insulator is made of an insulating material which is composed mainly of alumina, which contains Al component within a range of 95 to 99.7 wt % in Al.sub.2 O.sub.3 -converted weight, and in which an area ratio occupied by alumina base principal-phase particles with particle size not less than 20 .mu.m is not less than 50% as a cross-sectional structure of the insulator is observed.