| 摘要 |
PROBLEM TO BE SOLVED: To keep or raise the temperature of a catalytic device without being accompanied by the deterioration of fuel consumption by injecting a fuel directly into a combustion chamber during compression stroke, when the temperature rise of the catalytic device is required, so that the air-fuel ratio of an engine is close to a theoretical air-fuel ratio by a temperature raising means to execute a stratified charge combustion. SOLUTION: A solenoid fuel injection valve 6 is provided every cylinder of an engine 1 so that fuel can be directly injected into a combustion chamber 8. An exhaust emission purifying catalytic device 30 is provided with a selective reduction type NOx catalyst 30a and a three-way catalyst 30b, and an exhaust air temperature sensor 32 is provided in the downstream thereof. On the basis of the information from various sensors, the operation mode is switched to a compression stroke slight lean mode or a compression stroke O2 feedback mode in the state where the temperature of the catalytic device 30 is low. According to this, the CO and O2 discharged to an exhaust passage start the oxidation reaction by the effect of the catalyst, and the reaction heat raises the temperature of the catalytic device 30. Optimum ignition timing and injection end timing capable of minimizing the quantity of smoke and sufficiently providing CO are set.
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