| 摘要 |
PROBLEM TO BE SOLVED: To provide a control device of an engine that can prevent exhaust emission characteristics from significantly degrading within all operating ranges including a range with a high air amount and a high exhaust temperature even if a low noble metal catalyst is used and the catalyst degrades to some degree. SOLUTION: The control device includes a means for setting a target air-fuel ratio for an air-fuel ratio before the catalyst, an air-fuel ratio control means for performing a feedback control of a fuel injection amount based on outputs from an upstream air-fuel ratio sensor 51 and a downstream O<SB POS="POST">2</SB>sensor 52 so as to converge the air-fuel ratio before the catalyst to the target air-fuel ratio, a degradation level learning means for detecting a degradation level of the catalyst by using the output from the downstream O<SB POS="POST">2</SB>sensor 52 and a degradation degree detection threshold S3 that is set to be within or near a stoichiometric range, and for storing and updating the detected degradation level as a learning value for every operating range, and a learning value reflecting means for correcting the target air-fuel ratio by using the learning value stored in the learning means. COPYRIGHT: (C)2012,JPO&INPIT
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