| 摘要 |
<p>PURPOSE: To improve accuracy of catalyst deterioration detection by stopping detection of deterioration in a catalytic means when phase difference between output of an upstream side oxygen concentration detecting means and output of a downstream side oxygen concentration detecting means is a prescribed value or more. CONSTITUTION: A three way catalyst (C) for purifying exhaust gas is arranged in an exhaust pipe 12, an upstream side O2 sensor (FS) and a downstream side O2 sensor (RS) are arranged upstream and downstream of the catalyst (C), and each electric signal according to each detecting value is supplied to an ECU 5. When output of the upstream side O2 sensor (FS) is inverted and the output of the downstream side O2 sensor (RS) is not inverted within a prescribed time corresponding to a second prescribed value, namely, when a phase difference between output of the upstream side O2 sensor (FS) and output of the downstream side O2 sensor (RS) is in a prescribed value or more, it is judged that oxygen storage capacity of the catalyst (C) is large, and normal condition in a system is judged, and then a deterioration monitor is completed. It is thus possible to judge rapidly that condition of the catalyst (C) is in a normal condition.</p> |
