SPARK-IGNITED INTERNAL COMBUSTION ENGINE

摘要

An internal combustion engine comprises a variable compression ratio mechanism (A) capable of varying the mechanical compression ratio and a variable valve timing mechanism (B) capable of controlling the closing timing of an intake valve (7). In an engine low-load operation, the mechanical compression ratio is so maximized that the expansion ratio is 20 or more. In the engine low-load operation, the actual compression ratio is lower in part or all of the operating range than that in an engine high-load operation. In the engine low-load operation, a throttle valve (17) is closed when at least the actual compression ratio is lower than thatin the engine high-load operation.