| 摘要 |
PROBLEM TO BE SOLVED: To enable operation at low nitrogen oxide emission rate by combining the long time remaining stage of burnt gas in a combustion chamber and the intake period stage of fresh gas following the remaining period of the burnt gas, and executing the control method during partial load. SOLUTION: In the case of an engine having a mechanical cam operation type exhaust valve, the opening period of the exhaust valve is very (as compared with the opening time at the time of high load) delayed in its cycle, and slowly ended during the next lowering stroke (during intake start) of a piston. This delay can be accomplished by delaying all of the exhaust port opening time or increasing the exhaust port opening time. In the case of mechanical supply, in order to increase internal EGR effect, a variable throttle device 10 is provided downstream from the exhaust valve. Thus, after the end of exhaust, intake can be started as later as possible, so that the possibility of mixture of fresh gas and burnt gas can be delayed, in other words, stratification can be proceeded. |
