| 摘要 |
PROBLEM TO BE SOLVED: To prevent knocking when an engine is operated at a theoretical air-fuel ratio while operating the engine at the theoretical air-fuel ratio in a wide operating area, and provide a large engine torque beyond a critical torque obtained when the engine is operated at the theoretical air-fuel ratio. SOLUTION: A control valve 26 for increasing an intake flow in a combustion chamber by reducing an opening is installed in an intake passage. A maximum load line when the engine is operated at the theoretical air-fuel ratio is set in such a manner as to be positioned further on the low torque side than the maximum torque line of the engine. A load area equal to or lower than the maximum load line is a theoretical air-fuel ratio area where a cylinder air-fuel ratio is equal to the theoretical air-fuel ratio. The area between the maximum load line and the maximum torque line is an enrich area where the cylinder air-fuel ratio is richer than the theoretical air-fuel ratio, and a torque is increased. In the engine low speed range, the opening of the control valve 26 in a high load area within the theoretical air-fuel ratio area including the maximum load line is smaller than that of the control valve 26 in the enrich area. COPYRIGHT: (C)2010,JPO&INPIT
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