| 摘要 |
To provide a combustion chamber structure for an internal combustion engine that prevents knocking in a two-valve internal combustion engine. [Solution] In an internal combustion engine having an intake valve opening (42) and an exhaust valve opening (43) disposed at opposite positions to each other across a cylinder axis (C) as a center axis of a cylinder bore (16b), in a ceiling surface (50) of a cylinder head (17) and opening facing a combustion chamber (40), a top surface (60t) of a piston (60) has a piston-side recess (61) formed by recessing the inside of a piston-side squish surface (62) formed along an outer peripheral edge of the top surface (60t), and the piston-side recess (61) is formed inan elliptical shape substantially surrounding an umbrella portion (46p) of an intake valve (46) and an umbrella portion (47p) of an exhaust valve (47) on both sides in a major axis direction as viewed in a cylinder axis direction. |
