| 摘要 |
PROBLEM TO BE SOLVED: To realize characteristics of a gasket for a spark plug which can secure adhesiveness through deformation due to clamping at an initial mounting stage and which does not suffer plastic deformation even with a larger action force than before when an engine is operating. SOLUTION: Of a spark plug provided with a center electrode 30 retaining a screw part 10a to be screwed with an engine with inside a cylindrical main metal fitting 10 through an insulator 20, a grounding electrode 40 set in opposition to the center electrode 30 through a discharge gap 70, and a circular gasket fitted at an outer periphery of the main metal fitting 10 for maintaining a sealing property in screwing the main metal fitting 10 with an engine head 100, and the gasket 80 is to be provided with two bent parts of nearly an S-shape in cross section in a radial direction bent so as to have a smaller curvature due to an axial force generated by screwing with the engine, and is to be of a Vickers hardness of 200 or more and 400 or less. COPYRIGHT: (C)2004,JPO
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