| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a technology capable of improving a voltage resistance performance of a spark plug.SOLUTION: The spark plug includes: an insulator including a shaft hole extending along an axial line; a center electrode inserted into the shaft hole; a main metal fitting disposed in an outer circumference of the insulator; and a ground electrode disposed in a distal end of the main metal fitting. In an inner circumference of the main metal fitting, a shelf part is formed that protrudes radially inside. The center electrode includes: a flange that protrudes radially outside; a first shank formed closer to a distal end than the flange; and a small diameter part which is formed between the flange and the first shank and at a position opposing at least the shelf part of the main metal fitting and has a diameter smaller than that of the first shank.</p> |
