Importance

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Abstract

A spark ignition type internal combustion engine comprises 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 an air flow control valve controlling an air flow in a cylinder and able to control the amount of intake air fed into a combustion chamber. The mechanical compression ratio is made maximum so as to obtain the maximum expansion ratio at the time of engine low load operation and the actual compression ratio at the time of engine low load operation is made an actual compression ratio substantially the same as that at the time of engine medium and high load operation. When the engine load is in an extremely low load region, the air flow control valve is used to control an amount of intake air fed into the combustion chamber. Due to this, a high heat efficiency can be realized even in a region where the amount of intake air is difficult to control by changing the closing timing of the intake valve.

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First Claim