Abstract: Intake ports are arranged independently from each other between an injector and each combustion chamber and are formed in an inverted triangular cross-sectional shape, whereby intake fluids flow along upper walls of the corresponding ports and become a stratified tumble flow in the combustion chamber 10. One of the three ports, said one port being centrally located and opposing a spark plug, is used as an air-fuel intake port, while the remaining ports arranged on both sides of the port are employed as air intake ports. A fuel injector is provided to feed fuel only to the port. An air-fuel mixture drawn into the combustion chamber through the port flows as a tumble flow. This tumble flow is flanked by tumble flows of air drawn into the combustion chamber through the ports respectively, whereby tumble flows flow in the form of a three-layer tumble swirl as a whole.