Patent ID: 8701605

Claim:
A spark ignition type internal combustion engine comprising: a variable compression ratio mechanism able to change a mechanical compression ratio, a variable valve timing mechanism able to control a closing timing of an intake valve, and a supercharger, wherein: at a time of engine low load operation at which a pressure inside an intake pipe is less than atmospheric pressure, the mechanical compression ratio is made higher compared with at a time of engine high load operation at which a pressure inside the intake pipe is at a limit pressure, at a time of engine medium load operation at which the pressure inside the intake pipe is at or above atmospheric pressure and below the limit pressure: the supercharging action of the supercharger is used to raise a pressure inside the intake pipe so that an amount of intake air fed into a combustion chamber is made to rise, compared with at the time of engine low load operation, and the mechanical compression ratio is made to fall so that the actual compression ratio is made to fall, and until the pressure inside the intake pipe reaches the limit pressure where the pressure cannot be raised further due to the structure of the intake pipe or the ability of the supercharger, the higher the engine load becomes, the lower the actual compression ratio is made.