| 摘要 |
PURPOSE: To provide a spark plug capable of securing sufficiently high sealing performance, even if the inside diameter of the through-hole of an insulator is small, and also capable of achieving sufficient durability, when applied to an engine having a high output. CONSTITUTION: In this spark plug 100, an insulator 2 is constituted of alumina ceramics and the inner diameter of the through-hole 6 is not more than 4 mm at a position where conductive sealing materials 16, 17 are disposed. The coefficient of linear expansion of the conductive sealing materials 16, 17 is adjusted to be within a range of not more than 6.5x10¬-6/°C.
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