Patent ID: 8242672
Filing Date: 2012-08-14
Classification: H01T

Abstract:
1. A spark plug comprising: a center electrode, a terminal portion electrically connected to the center electrode so as to apply a voltage from an external power source to the center electrode; a ground electrode disposed on a front end side such that a gap for spark discharge is formed between the ground electrode and the center electrode; a metallic shell which holds the ground electrode, which is electrically connected to the ground electrode, and in which the center electrode is disposed; and an insulator which is held within the metallic shell and in which the center electrode and the terminal portion are held, wherein the insulator is integrally formed and includes a collar portion which is located at an approximate center with respect to a longitudinal direction thereof and has an outer diameter greater than that of the remaining portion, and a tubular fixation assisting member is provided on the rear end side of the collar portion between said insulator and said metallic shell in order to assist a function of the metallic shell of holding the insulator; and the fixation assisting member includes at least a high dielectric constant material which is higher in dielectric constant than alumina.