| 摘要 |
PURPOSE:To decrease discharge of harmfull components by providing at an intake passage of air, a control means which decreases scavenging quantity of intake air with respect to a combustion chamber according to decrease of engine load at a no-load operation range including idling operation from low- middle load operation to idling operation. CONSTITUTION:When an engine, during operation is judged by a microcomputer 84 to be in low/middle load operation range at which scavenging quantity is decreased, opening of a control valve 26 (a control means) is determined from a map, and it is decreased according to decrease in engine load. Intake air quantity to a crank chamber 13 is decreased accordingly. When a scavenging port 12 is opened, the scavenging quantity flowing into a combustion chamber 8 from the crank chamber 13 is decreased. As a result, combusted gas remains in the combustion chamber 8. Since a large quantity of components of specific heat is included in the combusted gas, highest temperature of combustion is decreased. Furthermore since the combusted gas is also inactive gas, intake air introduced from the crank chamber 13 is diluted, so that O2 concentration is decreased.
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