| 摘要 |
PROBLEM TO BE SOLVED: To provide an internal combustion engine capable of operating under a uniform A/F value condition even if combination of a plug assembly and/or cylinder head is different, a spark plug assembly for an internal combustion engine, a cylinder head, a spark plug, and a plug fixture suitable for the same. SOLUTION: A tip side main body part 14 of a main body metal fitting 11 of this spark plug 10 includes a key groove 36 formed on the tip side main body corresponding part 34 corresponding to a tip side main body part of a plug mounting hole 32, and a projection part 14t fitting at only one section when the spark plug 10 is rotated around an axis O with being inserted in the plug mounting hole 32 formed on a cylinder head 30. Circumference direction angle relation of the projection part 14t and an outer electrode fixing part 16a around the axis is roughly same 180 degrees for any spark plug if spark plugs of same part number are investigated. COPYRIGHT: (C)2008,JPO&INPIT
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