| 摘要 |
<p>PURPOSE:To judge the degradation of a catalyst and a first exhaust sensor correctly, and reduce dispersion in instrumentation so as to improve the accu racy of degradation judgment. CONSTITUTION:At the time of judging degradation, the feedback correction quantity is set larger than that at the normal time. At the same time, dual exhaust sensor feedback control is stopped, and the rich judgment delay time and lean judgment delay time are set according to the ratio at the normal dual sensor feedback control time in order to make the rich-lean judgment delay time constant. The feedback correction quantity is set as the degradation judgment value to correct the second exhaust sensor response delay time by engine load and exhaust temperature and also to correct this value by the cycle of the first exhaust sensor cycle time, and the second exhaust sensor response delay time after correction is compared with the degradation judgment value to judge the degradation of a catalyst. When the rich-lean judgment delay time is made constant, the dispersion characteristic of output performance of a first exhaust sensor is measured by the first exhaust sensor cycle time, and the degradation judgment value is corrected by this dispersion characteristic.</p> |
