| 摘要 |
PROBLEM TO BE SOLVED: To provide a spark plug which allows for enhancement of combustion efficiency by spreading a flame significantly, thereby stabilizing ignition (firing) of a fuel-air mixture even under incombustible conditions, and to provide an ignition device and an engine.SOLUTION: The following relation is satisfied; L+R>L+R+R, where Ris the distance in the radial direction from the side face of a center electrode 14 to the inner surface of a body metal fitting 18, Lis the distance in the axial direction from the inner surface of the body metal fitting 18 to the tip of an insulator 12, Ris the distance in the radial direction from the inner surface of the body metal fitting 18 to the tip of a ground electrode 16, and Lis the distance in the axial direction from the tip of the ground electrode 16 to the tip of the center electrode 14. |
