An apparatus for detecting deterioration of a three-way catalytic converter for an engine

摘要

The object of the present invention is to provide an apparatus for detecting the deterioration of a converter enabled to avoid a misjudgement even though the balance between the oxygen absorbing power and the oxygen releasing power disappears. The present apparatus is furnished with an upstream air-fuel ratio sensor installed at the upstream side of the converter and a downstream air-fuel ratio sensor installed at the downstream side of the converter. The deterioration of the converter is detected in accordance with the trajectory lengths of these sensors, and a parameter which denotes the oxygen balance of the converter is calculated in accordance with the outputs of these sensors. When the value of the parameter is outside a fixed lower limit or a fixed upper limit, the detection for deterioration is inhibited in order to prevent a misjudgement occuring.