| 摘要 |
PROBLEM TO BE SOLVED: To provide an air-fuel ratio control device of an internal combustion engine suitably performing feedback control of an air-fuel ratio without using an output value itself of an upstream side air-fuel ratio sensor upstream of a catalyst. SOLUTION: The device performs the feedback control of the air-fuel ratio based on an estimation of the air-fuel ratio of gas discharged from a combustion chamber 25 to an exhaust passage (upstream side estimation air fuel ratio) and on an output value of an air-fuel ratio sensor 68 downstream of the catalyst 53. The upstream side estimation air fuel ratio is accurately estimated based on an engine operation state and on an engine combustion state (an extent of misfire in the combustion chamber). As a result, the upstream side air-fuel ratio sensor 67 upstream of the catalyst 53 can be omitted from a construction of the device and a manufacturing cost of the entire device can be reduced. Since the air-fuel ratio feedback control is not performed with use of the output value itself of the upstream side air-fuel ratio sensor 67, which may cause an error in the output value under the influence of gas collision or gas composition, the suitable air-fuel ratio feedback control can be maintained. COPYRIGHT: (C)2007,JPO&INPIT
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