| 摘要 |
PROBLEM TO BE SOLVED: To perform proper feedback control of an air-fuel ratio during introduction of purge gas. SOLUTION: Purge of fuel evaporation gas is started from a canister and when purge gas concentration is started to rise, a target air-fuel ratio correction amountλPRG is set to the rich side according to the rise of purge gas concentration and a target air-fuel ratioλTG is corrected to the rich side. Since in a conventional type, even during introduction of purge gas, the target air-fuel ratioλTG is not corrected, during introduction of purge gas, an air fuel ratio of exhaust gas is displaced to the lean side and NOx purification factor is reduced. To cope with this situation, when, during introduction of purge gas, the target air-fuel ratioλTG is corrected to the rich side according to purge gas concentration, displacement of the target air-fuel ratio to the rich side is cancelled through correction of the target air-fuel ratioλTG to the rich side, an air-fuel ratio of exhaust gas during introduction of purge gas is controllable to a catalyst window and even during introduction of purge gas, a high NOx purification factor is maintained.
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