Patent ID: 6470845
Filing Date: 2002-10-29
Classification: H01T

Abstract:
A spark plug for an internal combustion engine, comprising:a center electrode with an end portion; an insulator surrounding a periphery of the center electrode to support the center electrode; a fitting piece that supports the insulator, said fitting piece being provided with an end surface and at a periphery thereof with a fitting screw portion, said end portion of the center electrode projecting from the end surface of the fitting piece, said fitting screw portion having a diameter of M10; a noble metal chip with one end surface and other end surface opposite thereto, said one end surface being mounted on the end portion of the center electrode, said other end surface being arranged so that an axial distance A between the end surface of the fitting piece and the other end surface of the noble metal chip is set within a range of 3 mm to 8 mm, said other end surface having an area S which is set within a range of 0.07 mm2 to 0.55 mm2; and a ground electrode having one end portion and other end portion, said one end portion thereof being fitted to the end surface of the fitting piece, said other end portion being inclined toward the noble metal chip at a slant angle of &thgr; with respect to an axial length of the spark plug so as to provide a discharge gap G between the noble chip and the other end portion, said slant angle &thgr; being set within a range of 40Â° to 70Â°, said discharge gap G being set within a range of 0.7 mm to 0.9 mm.