| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a NOx cleaning device for cleaning NOx by selectively adding urea water or ammonia as a reducer to a selective reduction NOx catalyst contained in an exhaust passage of an internal combustion engine, wherein the deterioration of the selective reduction NOx catalyst itself is diagnosed from a vehicle-mounted state or the like. <P>SOLUTION: The diagnostic method is composed of a step for determining whether or not the temperature of an NOx catalyst 44 is a temperature in a prescribed temperature region which is lower than a NOx cleaning temperature region and is included in an ammonia adsorbing temperature region, a step for adding a reducer until ammonia leaks to an exhaust passage on the NOx catalyst 44 downstream side when it is determined affirmative in the determining step, and a step for determining that the NOx catalyst 44 is deteriorated when an actual addition amount or a value equivalent thereto as a total amount of the reducer added to the NOx catalyst 44 by the step for adding a reducer is not higher than a threshold γ1 for the determination of the deterioration of the NOx catalyst 44. <P>COPYRIGHT: (C)2009,JPO&INPIT |
