| 摘要 |
PROBLEM TO BE SOLVED: To provide an air-fuel ratio control device capable of properly setting the oscillation amplitude of an air-fuel ratio in air-fuel ratio oscillation control and carrying out accurate determination of imbalance failure despite the imbalance grade of the air-fuel ratio. SOLUTION: Air-fuel ratio oscillation control to oscillate the air-fuel ratio with a set frequency f1 which is different from a 0.5th-order frequency fIMB (half of the frequency corresponding to a rotational speed of the engine) is executed, the intensity MIMB of a 0.5th-order frequency component included in a LAF sensor output signal and the intensity MPTf1 of a frequency component f1 are calculated, a determining parameter RSRC is calculated according to the 0.5th-order frequency component intensity MIMB and the frequency f1 component intensity MPTf1, and an imbalance failure is determined using the determining parameter RSRC. The determining parameter RSRC is used as a predicting value of the imbalance grade of the air-fuel ratio and an oscillation control amplitude DAF is set according to the determining parameter RSRC. COPYRIGHT: (C)2013,JPO&INPIT
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