Patent ID: 7703428
Filing Date: 2010-04-27
Classification: H01T

Abstract:
1. A spark plug comprising: a central electrode, an insulator having an axial hole extending in the direction of an axial line and holding the central electrode at the leading end side of the axial hole, a metal housing including: wherein the ratio B/A is 0.2 or greater; B is 2 mm or greater, and C−B is 1.5 mm or greater when A is an axial length from a leading end of the second tapered part to the leading end surface of the cylindrical part, B is an axial length from the leading end of the first tapered part to the leading end surface of the cylindrical part, and C is the maximum axial length from the leading end of the first tapered part to an opening end on the combustion chamber side of the mounting hole when the metal housing is screwed into the mounting hole of the internal combustion engine.