| 摘要 |
<P>PROBLEM TO BE SOLVED: To accurately determine abnormality of NOx purifying catalyst. <P>SOLUTION: In this emission control device for an internal combustion engine, an upstream side O<SB>2</SB>sensor and a downstream side O<SB>2</SB>sensor are arranged on the upstream side and the downstream side of the NOx purifying catalyst. In the emission control device, during rich spike control (S1), from the time when an output value VO2_F of the upstream side O<SB>2</SB>sensor becomes a predetermined value VO2_SF# (S2) to the time when an output value VO2_R of the downstream side O<SB>2</SB>sensor becomes a predetermined value VO2_SR# (S6), an integrated value of differences between the output value VO2_R of the downstream side O<SB>2</SB>sensor and the output value VO2_F of the upstream side O<SB>2</SB>sensor is calculated (S5). The calculated integrated value is defined as a diagnostic value KOBDF1 for determination (S8), and the abnormality is determined by comparing this diagnostic value KOBDF1 with an abnormality determination threshold KOBDFSL1# (S10-S12). <P>COPYRIGHT: (C)2004,JPO&NCIPI |
