| 摘要 |
PROBLEM TO BE SOLVED: To accurately compensate an error of an intake/exhaust system even if a disturbance occurs when an integral processing value is significantly deviated from a convergent value in an air-fuel ratio control device for feedback controlling an air-fuel ratio based on the integral processing value calculated from an output value of an air-fuel ratio sensor arranged downstream of a catalyst. SOLUTION: This device sets a change speed of an integral processing value SDVoxs with three steps when it is judged that deviation of the integral processing value SDVoxs from a convergent value (SDVoxs1) is large. In a step 1, the change speed is set to a large value, and the integral processing value SDVoxs is lean-deviated by a disturbance of a rich control and the like after FC, but can quickly approach to a value near the convergent value at a certain value. In a step 2, the change speed is changed to a moderate value, so that the integral processing value SDVoxs can further approach to the convergent value while restraining influences of the disturbance. In a step 3, the change speed is changed to a small value, so that the integral processing value SDVoxs can stably be shifted to a value near the convergent value. Accordingly, the integral processing value SDVoxs can quickly and accurately approach to the convergent value. COPYRIGHT: (C)2009,JPO&INPIT
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