Importance

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Abstract

An improved intake system in an internal combustion engine of a high compression ratio capable of producing a swirl of air-fuel mixture so as to increase the combustion speed thereof for improved combustion efficiency and hence fuel economy during light-load operation of the engine, and at the same time of effectively suppressing the generation of a swirl so as to reduce the level of combustion noises to a substantial extent during heavy-load operation of the engine at full-open throttle. The engine has a combustion chamber defined in a recess in the cylinder head above the top of a piston, slidably received in a cylinder bore in the cylinder block, at its top dead-center, with a squish area of a limited clearance formed adjacent the combustion chamber in the cylinder bore between the cylinder head and the piston. An intake passage in the cylinder head leading to the combustion chamber for supply of air-fuel mixture comprises a light-load intake passage for admitting the mixture into the combustion chamber or the squish area in the circumferential direction of the cylinder bore so as to produce a swirl under light-load operation of the engine, and a heavy-load intake passage having a valve adapted to be closed during light-load operation of the engine and opened during heavy-load operation of the engine for admitting the mixture into the combustion chamber or the squish area in the direction parallel to the central axis of the cylinder bore so as to suppress the generation of a swirl.

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First Claim