Spark ignition type internal combustion engine

摘要

Disclosed is a spark ignition type internal combustion engine, which comprises a variable compression ratio mechanism capable of changing a mechanical compression ratio, and a variable valve timing mechanism capable of controlling the closing timing of an intake valve. The intake air flow to be fed to the inside of a combustion chamber is controlled mainly by changing the closing timing of an intake valve so that the mechanical compression ratio is set higher at an engine low-load running time than that at an engine high-load running time. The mechanical compression ratio at the engine low-load running time before completion of the warm-up of the internal combustion engine is set lower than that at the engine low-load running time after completion of the warm-up of the internal combustion engine. Although the expansion ratio at the engine low-load running time is raised to improve the mileage, it is possible at an engine cold start to heat an exhaust purifying catalyst promptly and to suppress the deterioration of an exhaust emission.