Patent ID: 9306374
Filing Date: 2016-04-05
CPC Classification: H01T

Claim Text:
1. A spark plug, comprising: a cylindrical insulator having an axial hole formed therethrough in an axis direction of the spark plug; a center electrode inserted in a front side of the axial hole; a cylindrical metal shell arranged on an outer circumference of the insulator; a ground electrode comprised of a base material, said ground electrode having a first end joined to a front end portion of the metal shell and a free end forming a gap with the center electrode, said ground electrode having an electrode base portion, a curved bent portion and an electrode distal end portion, the electrode base portion being joined to the front end portion of the metal shell and extending from the front end portion of the metal shell toward a front end of the spark plug in the axis direction; the curved bent portion being connected at one end thereof to the electrode base portion and connected at another end to the electrode distal end portion, said electrode distal end portion extending from the bent portion in a direction different from the direction of the electrode base portion, said distal end portion having a distal end face at the free end of said ground electrode, and forming the gap with the center electrode, a coating layer applied to the base material of said ground electrode, said coating layer made of a material having higher oxidation resistance than that of the base material, said coating layer applied to the face end of the ground electrode so as to cover the distal end face and an outer circumferential surface of said ground electrode except a surface of the electrode distal end portion facing the center electrode; and wherein at least a part of the base material of the electrode base portion of the ground electrode is not covered by said coating layer.