| 摘要 |
PROBLEM TO BE SOLVED: To improve thermal efficiency of an engine while suppressing combustion noise due to steep combustion by appropriately changing combustion gravity center and combustion period according to the engine load. SOLUTION: Two fuel injection valves are disposed at an upper part center of a combustion chamber. Air fuel mixtures having different octane numbers are distributed in a cylinder by dividing injection timing into twice, and octane numbers of individual air fuel mixtures are adjusted by adjusting injection ratio at each injection timing. In a light-middle load zone lighter than prescribed load SL, combustion gravity center is maintained roughly constant to inhibit drop of thermal efficiency by expanding octane number widthΔRON while keeping average octane number aveRON high as engine load increases. In a middle-heavy load zone not lighter than the prescribed load SL, combustion period is maintained roughly constant to inhibit drop of thermal efficiency by reducing octane number widthΔRON while keeping average octane number aveRON high as engine load increases. COPYRIGHT: (C)2010,JPO&INPIT
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