| 摘要 |
<P>PROBLEM TO BE SOLVED: To prevent the deterioration of fuel economy by efficiently utilizing fuel injected as a reducing agent. <P>SOLUTION: An exhaust emission control device for an internal combustion engine comprises an NOx storage/reduction catalyst 15 arranged in an engine exhaust passage, an oxidation catalyst 13 arranged in the engine exhaust passage upstream of the NOx storage/reduction catalyst, and a fuel supply valve 24 arranged in the engine exhaust passage upstream of the oxidation catalyst. When NOx is released from the NOx storage/reduction catalyst, the fuel supply valve performs exhaust system injection for injecting fuel into the exhaust passage to set the air-fuel ratio of exhaust gas flowing into the NOx storage/reduction catalyst to be temporarily theoretical or rich. When the catalyst temperature of the oxidation catalyst with the NOx released from the NOx storage/reduction catalyst is lower than a predetermined temperature, an engine cycle for post injection is started. A time for starting the engine cycle for post injection is set a predetermined preceding time earlier than a time for starting the exhaust system injection, and the preceding time is set longer as the temperature of the oxidation catalyst is lower. <P>COPYRIGHT: (C)2010,JPO&INPIT |
