| 摘要 |
PROBLEM TO BE SOLVED: To provide an internal combustion engine that does not cause abnormal combustion, matched in characteristics, can be driven even with a lean mixture, and has good fuel consumption, and an ignition plug and a cylinder head which are adequate to it and are easily assembled. SOLUTION: This ignition plug 20 is provided with a plug body 10, having a central electrode 1 extending in an axis O-direction, an insulator 2, and a main fitting 3, and an annular tip side fitting 8 which surrounds the radial circumference of a tip side portion 2F of the insulator. This fitting 8 has an outside electrode 11, that extends from an outside electrode extending portion 8e of a tip side surface 8d and forms a gap between it and the central electrode, and can rotate around the axis O-in with respect to the main fitting by the engagement of a punch portion 8c with an engagement groove 6c. In addition, an engagement portion 8A of the tip side fitting has a key projection 8g, and the relation between a circumferential angle of the outside electrode extending portion and the key projection is substantially the same for any ignition plug 20 with the same stock number. Therefore, the plug can be easily assembled to a cylinder head in which a plug mounting hole having a key groove, and the outside electrodes are matched in position.
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