| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control system and an exhaust emission control method capable of preventing the CO poisoning of an NOx adsorption reduction catalyst in a wide temperature zone, in particular, in a low temperature zone where an ordinary exhaust gas temperature is 200°C or less, and to keep the activity of the NOx adsorption reduction catalyst in a good condition. <P>SOLUTION: An upstream side exhaust gas component concentration adjusting means reduces the CO concentration in an exhaust gas when an air-fuel ratio is rich or stoichiometric, and a downstream side NOx adsorption reduction catalyst adsorbs NOx, when the air-fuel ratio is lean, and reduces the adsorbed NOx, when the air-fuel ratio is rich or stoichiometric. A temperature of the NOx adsorption reduction catalyst is determined to be more than T<SB>NOx</SB>°C, when a temperature of the exhaust gas flowing in the NOx adsorption reduction catalyst is T<SB>NOx</SB>°C or less, the CO concentration is increased in rich or stoichiometric operation, and the NOx concentration near an inlet of the NOx adsorption reduction catalyst is C<SB>NOx</SB>ppm or more in lean operation after rich spike. <P>COPYRIGHT: (C)2004,JPO |
