| 摘要 |
PROBLEM TO BE SOLVED: To enable large amount of internal EGR, without using an external EGR system in a spark ignition type cylinder direct injection internal combustion engine. SOLUTION: A sub injection 5 is executed in the cylinder, in response to a command of a controller for mixing with a combustion gas of a high oxygen concentration near top dead center from the final stage of an exhaust stroke to the initial stage of an intake stroke in a stratified-charge combustion run or a uniform lean run. A sub ignition 6 is executed by a spark ignition plug for generating such an amount of EGR gas in the cylinder that satisfies the sub injection so as to be held in the cylinder. Accordingly, even if the next cycle is a stratified-charge combustion, the temperature in the cylinder is maintained at a high level, so that carburetion of fuel by a main injection 1 on compression stroke is accelerated. Also, the maximum combustion temperature is lowered by the quantity of heat of an inert gas contained in the cylinder gas and the NOx can be reduced sufficiently. It is preferred to control the valve overlap period of intake/exhaust valves with a variable valve timing mechanism.
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