| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device for an internal combustion engine in which selective reduction type NOx catalysts 3, 4 are provided in series to each other for preventing the desorption exhaust of adsorbed ammonia resulting from the temperature rise of the rear stage side NOx catalyst 4. <P>SOLUTION: The exhaust emission control device includes a bypass line 8 for bypassing the rear stage NOx catalyst 4, and a bypass valve 9 changed over between a first position where exhaust gas flows to the side of the rear stage NOx catalyst 4 and a second position where the gas flows to the side of the bypass line 8. The device detects the temperature of the rear stage NOx catalyst or its relative temperature and estimates the amount of ammonia adsorbed on the rear stage NOx catalyst. In accordance with the estimated amount of the adsorbed ammonia, the device sets a temperature threshold for suppressing the discharge of the adsorbed ammonia from the rear stage NOx catalyst 4, and controls the bypass valve 9 depending on the result of the comparison of the detected temperature with the temperature threshold value. <P>COPYRIGHT: (C)2010,JPO&INPIT |
