| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide the air-fuel ratio diagnostic device of an internal combustion engine capable of reducing the frequency not acquiring appropriate determination results about variation among cylinders. <P>SOLUTION: The air-fuel ratio diagnostic device of the internal combustion engine 1 includes an air-fuel ratio sensor 45 for detecting oxygen concentration in the exhaust of the collection part 33 of an exhaust tube 31 where the exhaust gases discharged from a plurality of cylinders 11 are combined to flow, and makes determination about variation among the cylinders on the basis of a detection value from the air-fuel ratio sensor 45. A change amount per unit time when the detection value from the air-fuel ratio sensor 45 changes from the peak value of a lean side to the peak value of a rich side is set as a rich change rate R, a change amount per unit time when the detection value changes from the peak value of the rich side to the peak value of the lean side is set as a lean change rate L, and a variation rate IR that is the level of variation among the cylinders is determined on the basis of the rich change rate R and the lean change rate L. <P>COPYRIGHT: (C)2012,JPO&INPIT |
