| 摘要 |
PROBLEM TO BE SOLVED: To provide a spark plug in which an igniting part creeping discharge voltage is heightened to prevent an igniting part creeping discharge. SOLUTION: In a spark plug A which has a main metal fitting 1 having a fitting rack 111, an insulator 2 fixed inside the main metal fitting 1 with its seat surface 211 locked to a rear slope 114 via packing 10, and a center electrode 3 fixed inside an axial hole 20, the bore of the packing 10 prior to assembly is 0.4mm or more greater than the minimum boreϕN2 of the fitting rack 111, and clearance between the base of a leg length 21 and the interior wall surface 115 of the fitting rack 111 is 1.1mm or more.
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