| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a deterioration detecting device for a NOx catalyst which can accurately detect the deterioration of a NOx catalyst without deteriorating an emission characteristic. <P>SOLUTION: When a NOx supply amount to a NOx catalyst is a first reference amount NOx1, a reducing agent amount Grd1(Grd1A, Grd1B) used for NOx reduction is calculated through the utilization of air-fuel ratio sensor output before/after the NOx catalyst. Even when the NOx supply amount is a second reference amount NOx2, a reducing agent amount Grd2(Grd2A, Grd2B) is calculated. The difference ΔGrd(ΔGrdA, ΔGrdB) between these reducing agent amounts is then calculated. When the difference ΔGrd is smaller than the reference value, the NOx catalyst detects the deterioration. <P>COPYRIGHT: (C)2008,JPO&INPIT |
