| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an imbalance index value after filtering precisely representing the degree of ununiformity in the air-fuel ratio among cylinders. <P>SOLUTION: A control device corrects the amount of fuel injected from an fuel injection valve in a feedback manner, based on an output value of an upstream air-fuel ratio sensor, so that the air-fuel ratio of exhaust gas flowing into a three-way catalyst coincides with a target air-fuel ratio, acquires an air-fuel ratio imbalance index value that increases as the degree of ununiformity in the air-fuel ratio among cylinders is larger, based on the output value of the upstream side air-fuel ratio sensor, and acquires an imbalance index learned value by performing a first-order lag filtering operation for removing noise, on the air-fuel ratio imbalance index value to increase the fuel injection amount based on the imbalance index learning value. Furthermore, the control device, when it performs the first-order lag filtering operation, sets the time constant of the filter to a smaller value if a magnitude of a difference between the current value and the last value of the air-fuel ratio imbalance index value is equal to or larger than a threshold value. <P>COPYRIGHT: (C)2012,JPO&INPIT |
