Patent ID: 6414420
Filing Date: 2002-07-02
Classification: H01T

Abstract:
A spark plug comprising:an insulator having a center through-hole formed therein; a center electrode held in the center through-hole; a metallic shell holding the insulator by swaging and having a male-threaded portion formed on an outer circumferential surface of a front end portion of the metallic shell and a tightening portion formed on an outer circumferential surface of the metallic shell, located at a rear side with respect to the male-threaded portion; and a ground electrode electrically connected to the metallic shell and defining a spark discharge gap in cooperation with the center electrode, wherein the distance between two opposed parallel surfaces of the tightening portion is not greater than 14 mm, a cushion material is charged into a cylindrical space defined by an outer surface of the insulator and an inner surface of the metallic shell to thereby form a cushion-material charged portion, and the cushion-material charged portion has an axial length L of from 0.5 mm to 10.0 mm inclusive (0.5 mm&lE;L &lE;10.0 mm) and a thickness M of from 0.5 mm to 1.3 mm inclusive (0.5 mm&lE;M&lE;1.3 mm).