| 摘要 |
PROBLEM TO BE SOLVED: To provide an air-fuel ratio control device for reducing excess or deficiency in fuel supply amount during controlling an alcohol concentration correction learning in a flexible fuel vehicle. SOLUTION: The air-fuel ratio control device for the internal combustion engine includes an air-fuel ratio sensor 23 and an oxygen sensor 24 respectively arranged in an exhaust passage upstream of a three-way catalyst 20 and in an exhaust passage downstream of the three-way catalyst 20. The control device performs main feedback control for correcting a fuel supply amount based on an output value of the air-fuel ratio sensor, a sub feedback control for correcting the fuel supply amount based on an output value of the oxygen sensor, an alcohol concentration correction learning control for learning an alcohol concentration correction learning value, and a sub feedback learning control for learning a learning value calculated based on the correction value in the sub feedback control. During the learning in which the alcohol concentration correction learning value increases, the sub feedback control is performed to make an exhaust air-fuel ratio rich. During the learning in which the alcohol concentration correction learning value decreases, the sub feedback control is performed to make the exhaust air-fuel ratio lean. COPYRIGHT: (C)2009,JPO&INPIT
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