| 摘要 |
PURPOSE:To enhance the scavenging effect by controlling a valve timing to retard a closing timing of an exhaust valve in a supercharging operational region wherein a suction air is supercharged by pressure pulsation to be generated in a suction passage at least at a low engine speed under a high load. CONSTITUTION:A mechanical supercharger 10 is provided in a suction passage 5 at a position upstream of a fuel injector 7, and a bypass passage 11 bypassing the supercharger 10 is connected to the suction passage 5. A control valve 12 is provided in the bypass passage 11. Suction and exhaust valves 3 and 4 are formed to open into a combustion chamber 1, and an exhaust valve 9 for opening and closing the exhaust port 4 is adjusted in its valve timing by rotating a worm gear 18 by means of an exhaust valve driving motor 17. The driving motor 17 is controlled by a control unit 16 receiving output signals from an air flow meter 14 and a crank angle sensor to retard a closing timing of an exhaust valve 9 in an engine operational region (at a low engine speed under a high load, for example) wherein a suction air is supercharged by pressure pulsation.
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