INTAKE PORT SHAPE OF INTERNAL COMBUSTION ENGINE

摘要

An object of the present invention is to restrict a part of intake flow which is apt to flow in a direction opposite to a counter swirl flow after colliding against a valve stem, and to produce an intense swirl while controlling a worsening of flow coefficient. A valve seat supporting annular stepped surface(14) is formed on an intake port outlet portion of a cylinder head (1), its inner peripheral edge is formed into a shape having an inner peripheral edge (4a) of a valve stem (4)for serving as a base circle, and a extending portion (15) projecting toward a side of a valve stem (11) is provided on a radial intake port inlet side portion. The extending portion (15) is formed into a mountain-like shape which widens from a top portion projecting toward the valve stem side to both peripheral sides and connects to the base circle at its foot ends; or into an arc-like shape; or into a trapezoidal shape. A back wall (16) is formed on a side opposite to the valve seat of the extending portion (15), the back wall decreasing its projecting height toward an upstream side in the intake port to smoothly connect to an inner peripheral wall surface of the intake port 2. <IMAGE>