PURPOSE: To achieve stratification without damping a swirl by a method wherein the valve seat angle of an intake valve arranged in each of intake ports for introduction of fresh air and the feed of fuel-air mixture is set to a proper value.
CONSTITUTION: An intake port for introduction of fresh air and an intake port for the feed of fuel-air mixture are provided for each cylinder. One intake port for introduction of fresh air forms a swirl generating port and a swirl is generated in a combustion chamber during low load running. The opening timing of an intake valve to open and close the intake port for the feed of fuel-air mixture is delayed from that of an intake valve to open and close the intake port for introduction of fresh air, and the valve seat angle θ2, of the intake valve on the fuel-air mixture feed side to the valve seat angle 9. of the intake valve on the fresh air introduction side is set to θ1>θ2. Thus stratification is promoted without damping a swirl through prevention of the occurrence of interference between fuel-air mixture and fresh air and lean combustion limit is improved.
NOOI YOSHIHISA
YAMAMOTO TOSHIHIDE
