| 摘要 |
PROBLEM TO BE SOLVED: To prevent lowering of air-fuel ratio control accuracy and wrong judgement of abnormality diagnosis due to oxidation phenomenon of an oxygen sensor (or an air-fuel ratio sensor) installed for an exhaust gas pipe of an engine. SOLUTION: An intake air quantity integration value is calculated as information correlating with an oxidation degree of the oxygen sensor 26 of a downstream side of a catalyst 24 and, in the case that this intake air quantity integration value does not exceed an oxidation aging judgement value, it is judged that rich deviation due to the oxidation phenomenon of the oxygen sensor 26 occurs and the abnormality diagnosis using output of the oxygen sensor 26 is inhibited and an oxygen aging correction value according to difference between an oxidation aging judgement value and the intake air quantity integration value is calculated and a target air-fuel ratio of an upstream side of the catalyst 24 is corrected by this oxidation aging correction value and thus the target air-fuel ratio of the upstream side is corrected according to a deviation quantity in a rich direction due to the oxidation phenomenon of the oxygen sensor 26. COPYRIGHT: (C)2009,JPO&INPIT
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