Patent ID: 7164225
Filing Date: 2007-01-16
Classification: H01T

Abstract:
1. A spark plug comprising: an insulator having an axial hole in an axial direction of the spark plug; a center electrode disposed in a tip end side of the axial hole of said insulator so as to project a tip end of said center electrode from said tip end side of the insulator, said center electrode including: an electrode base member made of pure Ni or an Ni alloy containing 85 wt% or more of Ni; and a noble metal chip fixed to a tip end of said electrode base member; a metal shell surrounding said insulator; and a ground electrode in which one end is joined to said metal shell, and another end portion opposes said noble metal chip to form a spark discharge gap between said ground electrode and said noble metal chip, wherein when an outer diameter of a tip end of said metal shell is M, an inner diameter of said tip end of said metal shell is D