| 摘要 |
PROBLEM TO BE SOLVED: To provide a technique capable of suppressing oxidation near a tip of a main body metal fitting.SOLUTION: A spark plug comprises: an insulator having a shaft hole extending in an axial line direction; a center electrode inserted in the shaft hole; a main body metal fitting arranged on an outer periphery of the insulator; and a ground electrode fixed to a tip of the main body metal fitting. A screw part is formed on the outer periphery of the main body metal fitting, and length from a tip of the screw part of the main body metal fitting to the tip of the main body metal fitting is 3 mm or more. A film layer with more excellent oxidation resistance than that of a plating layer on a surface of the main body metal fitting or a surface of the main body metal fitting is formed on the main body metal fitting at least on an outer periphery positioned nearer an axial line direction tip than the screw part, an inner periphery positioned nearer the axial line direction tip than the screw part, and a tip face positioned at the tip of the main body metal fitting. |
