| 摘要 |
PROBLEM TO BE SOLVED: To provide an exhaust gas purifying apparatus for purifying NOx using a selective reduction catalyst, which can accurately determine the deterioration in the reducing agent supply accuracy due to changes in the concentration of a reducing agent contained in a reactant for generating the reducing agent or characteristic changes in a reducing agent supply device, with a comparatively simple configuration. SOLUTION: Storage amount change control is performed so that the storage amount NH3ACT indicative of the amount of the reducing agent (NH3, urea) stored in the selective reduction catalyst is temporarily reduced from the state where the storage amount is at the maximum, and the storage amount NH3ACT is subsequently increased to time (t3, t4, t5) at which the occurrence of reducing-agent slip is detected. The concentration of the reducing agent (urea) in the reactant (urea water) is determined according to the state where the reducing-agent slip occurs during execution of the storage amount change control. Therefore, it is possible to determine the deterioration in the reducing agent supply accuracy due to a change in the concentration of the reducing agent by a comparatively simple method. COPYRIGHT: (C)2011,JPO&INPIT
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