| 摘要 |
PROBLEM TO BE SOLVED: To provide an engine wherein while EGR in the valve-opening initial-range is being efficiently conducted, hunting in the engine revolution occurring in the valve-opening intermediate-range is restricted. SOLUTION: An EGR valve is energized by force of a valve spring 9b in the valve-closing direction. The EGR valve 9 is linked up to a pneumatic valve-actuator. An intake-pressure chamber of the valve actuator is allowed to communicate with an intake path. Supercharging is conducted to the intake path by a supercharger driven by exhaust-gas energy. If the totally closed position in the EGR valve 9 is taken as a 0% stroke position, the full-open position thereof is taken as a 100% stroke position, a 0-9% stroke range is taken as a valve-opening initial-range 9c, and a 10-50% stroke range is taken as a valve-opening initial-range-following range 9d, control is contrived as follows. In a specified spring-constant increasing range 9f which is close to the 100% stroke position starting from a specified spring-constant-changing position 9e in the valve-opening initial-range-following range 9d, a spring constant of the valve spring 9b is made larger than the spring constant in the valve-opening initial range 9c. COPYRIGHT: (C)2008,JPO&INPIT
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