To provide a cylinder direct injection spark ignition engine capable of forming a proper stratified air-fuel mixture in the vicinity of the ignition timing, even in high speed operation of the engine.
This spark ignition engine is constituted so as to strengthen a rising flow turning to a combustion chamber upper surface from a piston, by strengthening a tumble flow or a swirl flow in a high area (a stratified combustion mode (2)) of an engine rotating speed in the stratified combustion mode, and to reduce a fuel spray speed, by increasing cylinder gas density, by bringing the closing timing of an intake valve near to the intake lower dead center. Thus, a combustible air-fuel mixture can be formed around a spark plug, before a fuel spray collides with a piston crown surface, by reducing the fuel spray speed at a high rotating speed, and a fuel sticking quantity onto the piston crown surface can be reduced.
HIRATANI KOJI
KUBO MASAAKI
TSUCHIDA HIROBUMI
TAKAHASHI EIJI
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