Internal combustion engine

Abstract

An internal combustion engine includes a cylinder head having a pair of upright intake ports formed therein on opposite sides of a plug hole extending along a cylinder axis, and each intake port has an upstream-side upright part extending from the top face of the cylinder head along the cylinder axis and a downstream-side slanting part having an intake opening communicating with a combustion chamber on one side of an imaginary plane containing the cylinder axis. An upper opening of each intake port opening in the top face of the cylinder head has a peripheral edge extending along the peripheral edge of an upper opening of the plug hole, and the peripheral edge of the upstream-side upright part extends along the outer surface of a lash adjuster. When viewed in vertical section along the imaginary plane, the upstream-side upright part extends obliquely downward from the top face of the cylinder head in a direction away from the lash adjuster, and the downstream-side slanting part approaches the plug hole with decrease in distance to the combustion chamber and then extends parallel to the plug hole. The downstream-side slanting part, when viewed in vertical section perpendicular to the imaginary plane, extends away from the cylinder axis with decrease in distance to the intake opening. With the intake ports having the above overall shape and sectional shape, each intake port can be given a required cross-sectional area without increasing the dimensions of the engine, and makes it possible to form a proper intake air flow inside the combustion chamber.