Patent ID: 7298070
Filing Date: 2007-11-20
Classification: H01T

Abstract:
1. A spark plug for an internal combustion engine comprising: a plug mounting shell equipped with a thread which is formed on an outer periphery thereof and has a diameter of M a porcelain insulator disposed inside said mounting shell so as to have a tip end protruding from said mounting shell, said porcelain insulator having a mount portion bearing on the insulator mount portion of said mounting shell; a ground electrode; and a center electrode defining a spark gap between itself and said ground electrode, said center electrode being retained inside said porcelain insulator so as to have a top portion exposed outside said porcelain insulator and including an oxidation resistant alloy-made portion and a thermal conductive metal-made portion, the oxidation resistant alloy-made portion being made from material containing a main component of Ni and an additive of at least one of Cr and Al, the oxidation resistant alloy-made portion occupying at least the top portion of said center electrode, the thermal conductive metal-made portion being made of one of Cu, Cu alloy, Ni, and a composite material containing at least two of Cu, Cu alloy, and Ni, the thermal conductive metal-made portion defining a portion of an outer periphery of said center electrode which faces the insulator mount portion of said mounting shell through said porcelain insulator in a directoion perpendicular to an axial direction of said center electrode.