Patent ID: 7650872

Claim:
An internal combustion engine comprising: a cylinder; a piston which reciprocates within said cylinder; a cylinder head which defines a combustion chamber in cooperation with said cylinder and piston; and a spark plug which is provided in said cylinder head, wherein: said engine has a geometric compression ratio of 13.0 or greater; and said combustion chamber is configured to satisfy a condition of S/V 2 ≦0.12 (mm −1 ) when a radius r of a hypothetical sphere with its center at an ignition point of said spark plug is set to satisfy a condition of V 2 =0.15×V 1 , where: S (mm 2 ) is an area of an interference surface between said hypothetical sphere and an inner wall of said combustion chamber in a state when said piston is at its top dead center position; V 1 (mm 3 ) is a volume of said combustion chamber in the state when said piston is at the top dead center position; and V 2 (mm 3 ) is a volume of a non-interference part of said hypothetical sphere which is free of interference with the inner wall of said combustion chamber when said piston is at the top dead center position.