Patent ID: 6741015
Filing Date: 2004-05-25
Classification: H01T

Abstract:
A spark plug comprising a cylindrical metallic shell having a tool engagement portion for mounting said spark plug on an engine fixedly attached to an axially extending insulator inserted into said metallic shell, by crimping a protrusion formed at one opening portion of said metallic shell toward a crimp rest portion formed on an outer circumferential surface of said insulator to thereby form said protrusion into a crimped portion of said metallic shell, andwherein a distance between opposed sides of said tool engagement portion is not greater than 14 mm; and said crimped portion as projected orthogonally on a virtual plane in parallel with an axis of said insulator is curved such that an end-side part of said crimped portion approaches said insulator, such that an exterior outline of said crimped portion has an outwardly convex crimped curve portion at the end-side part, and such that a tangent to said exterior outline at a base point of said crimped curve portion and a line perpendicular to the axis projected on the virtual plane form an angle of 50Â° to less than 90Â°.