To prevent misfire when emitting NOx from NOx absorbent in a stratified charge combustion type internal combustion engine.
Fuel/air mixture is stratified in a state that the average air-fuel ratio is lean when an engine is operated under a low load, and NOx generated in this state is absorbed by NOx absorbent 26 disposed in an exhaust passage. When NOx is emitted from the NOx absorbent in a lean fuel/air mixture combustion operating state in which fuel is supplied only in a combustion chamber, the fuel injection timing into the combustion chamber is accelerated, the fuel injection into the combustion chamber is increased, and the average air-fuel ratio in the combustion chamber is dropped from a lean state to the theoretical air-fuel ratio or a rich state. When NOx is emitted from the NOx absorbent in a lean fuel/air mixture combustion operating state in which fuel is supplied in an intake port, the amount of fuel injection in the intake port is increased, and the average air-fuel ratio in the combustion chamber is reduced from a lean state to the theoretical air-fuel ratio or a rich state.
MASUKI ZENICHIRO
Jun Tsuruta
Masaya Nishiyama
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