| 摘要 |
PROBLEM TO BE SOLVED: To provide a spark plug having improved anti-preignition characteristic, without impairing its anti smolder-stain characteristics. SOLUTION: In a spark plug 1, a center electrode 5 is fitted inside a shaft hole 4 provided in an insulating body 2; a shaft core P2 of the center electrode 5 is slanted, with respect to a shaft core P1 of the insulating body 2; and the inner diameter t of the shaft hole and the tip-end diameter s of the center electrode is set as described by the expression: 0.05 mm≤t-s≤0.140 mm. The minimum width x and the maximum width y of a gap formed between an outer peripheral surface of the center electrode and an inner peripheral surface of the shaft hole formed in the insulating body satisfy the relationship defined by the following expression: 0≤x/y≤0.43. COPYRIGHT: (C)2011,JPO&INPIT
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