| 摘要 |
A sparkplug includes an insulator having an axial hole, a center electrode of which a front end is placed further forwards than a front end of the insulator, and a shell. The center electrode has a shoulder portion and a main body portion and is made up of an outer layer and an inner layer. A front end face, which is connected to an outer circumferential surface of the insulator and the axial hole and slopes towards the rear end side, is formed at a front end portion of the insulator, and the front end of the insulator is placed further forwards than a boundary between the shoulder portion and the main body portion. A front end portion of the inner layer is placed further forwards than the boundary between the shoulder portion and the main body portion.
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