SPARK PLUG

摘要

A spark plug having a metal shell, center electrode and a ground electrode. The ground electrode includes an electrode base portion extending from a front end portion of the metal shell toward the front, a bent portion connected at one end thereof to a front end of the electrode base portion and an electrode distal end portion extending from the other end of the bent portion and forming a spark discharge gap with a center electrode. The ground electrode has a base material and a coating layer applied to the base material. The coating layer is formed on at least a front end face and an outer circumferential surface other than a center-electrode-side surface of the electrode distal end portion of the ground electrode. The base material of the ground electrode is exposed at least at a part of the electrode base portion.

主权项

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 an front side of the axial hole; a cylindrical metal shell arranged on an outer circumference of the insulator; and a ground electrode joined to a front end portion of the metal shell so as to form a gap between the ground electrode and the center electrode, the ground electrode including an electrode base portion extending from the front end portion of the metal shell toward the front in the axis direction; a curved bent portion connected at one end thereof to a front end of the electrode base portion; and an electrode distal end portion extending from the other end of the bent portion in a direction different from the direction of extension of the electrode base portion and forming the gap with the center electrode, wherein the ground electrode comprises a base material and a coating layer applied to the base material and made of a material having higher oxidation resistance than that of the base material so as to cover at least a distal end face and an outer circumferential surface other than a center-electrode-side surface of the electrode distal end portion; and wherein the base material of the ground electrode is exposed at least at a part of the electrode base portion.