| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To desorb and purify adsorbed nitrogen oxide NOx without increasing emission quantity of hydrocarbon HC and carbon monoxide CO. <P>SOLUTION: This device determine whether current air fuel ratio control is lean operation or rich operation(S1), and whether quantity of NOx adsorbed by NOx trap catalyst exceeds threshold vale established beforehand (S3). If the device determines that the current air fuel ratio control is lean operation (S1:YES) and quantity of NOx adsorbed by the NOx trap catalyst exceeds the threshold value established beforehand (S3:YES), the device controls air fuel ratio and period of time to maintain the air fuel ratio (S6, S8, S10, S11) based on temperature of the NOx trap catalyst (S5), concentration of CO flowing in the NOx trap catalyst and quantity of reducing agent (S7) and make NOx adsorbed by the NOx trap catalyst desorb from the same and purifies the same. <P>COPYRIGHT: (C)2005,JPO&NCIPI</p> |
