| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a fuel injection device capable of obtaining a precise air-fuel ratio imbalance index value using an output value of an upstream side air-fuel ratio sensor. <P>SOLUTION: An upstream air-fuel ratio sensor 56 is provided which is disposed at a position between an exhaust assembly part HK and a three-way catalyst 43. A control device corrects the amount of fuel injected from an fuel injection valve 33 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. The control device performs a high-pass filtering operation on the output value of the upstream air-fuel ratio sensor, so as to obtain a post-high-pass-filtering output value VHPF by removing a component that varies with variations in the center air-fuel ratio of the engine, included in the output value of the upstream air-fuel ratio sensor. The control device 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 post-high-pass-filtering output value VHPF. <P>COPYRIGHT: (C)2012,JPO&INPIT |
