| 摘要 |
PROBLEM TO BE SOLVED: To provide a control device for spark ignition type direct injection engine equipped in its exhaust passage with a catalyst to absorb NOx in an excessive oxygen atmosphere and release NOx at a lowered oxygen concentration and controlling the air-fuel ratio in the combustion chamber to the prescribed lean state, when the engine is in the low-load range after warming of the catalyst, capable of sufficiently heightening the refreshing effect of the catalyst, while minimizing deterioration of the fuel consumption. SOLUTION: When refreshing a catalyst, (SA2-SA6), the air-fuel ratio in the engine combustion chamber is dither controlled (SA16 and SA17), so that it varies periodically between rich and lean, with respect to the target value of A/F=15 to 16. The fuel is injected from an injector by splitting into two from the suction stroke of cylinder to the compression stroke (SA15) to cause it to burn in a weak stratified condition. The degree of opening of an EGR valve is controlled, and a large quantity of exhaust gas is circulated back to the suction passage so that the EGR rate becomes approx. 40% (SA18).
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