| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To judge whether a three-way catalyst is degraded or not without impairing drivability. <P>SOLUTION: In the device for judging catalyst degradation, the rate CgoutO2(N) of effluent oxygen from a 1st catalyst is estimated on the basis of a catalyst model constructed on the assumption that the 1st catalyst is a fresh one. An air-fuel ratio feedback control is conducted on the basis of an air-fuel-ratio-sensor output Voxs on a downstream side. In the above control, in points in time (times t1-t4, t10-t60) where the output Voxs takes a 1st state (the output is in a state passing while a rich-side specific value Vrich being increased, or while a lean-side specified value Vlean being decreased), if the probability where the rate CgoutO2(N) takes a 2nd state (a state where the value is smaller than a negative threshold Crefmns, or the value is greater than a positive threshold Crefpls) is smaller than a specified value, the catalyst is determined to be degraded. <P>COPYRIGHT: (C)2005,JPO&NCIPI</p> |
