SPARK-IGNITION INTERNAL COMBUSTION ENGINE

摘要

A spark-ignition internal combustion engine is provided with a variable compression ratio mechanism (A) capable of changing a mechanical compression ratio, a variable valve timing mechanism (B) capable of controlling the timing of closing of an intake valve, and a supercharger (15). For low load operation of the engine, the mechanical compression ratio is set to a value higher than that for high load operation of the engine. For medium load operation of the engine, the pressure in an intake pipe is raised by supercharging action of the supercharger to a value higher than that for the low load operation of the engine to increase the amount of suction air supplied into a combustion chamber (5) and reduce the mechanical compression ratio, and this reduces the actual compression ratio.