| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a technique to accurately detect degradation of a selective reduction type NOx catalyst by accurately calculating a purification ratio of the selective reduction type NOx catalyst. <P>SOLUTION: An ECU 10 uses that if bed temperatures vary in respective areas when an SCR catalyst 3 is divided into a plurality of areas sequentially from an upstream side of an exhaust flow, activation levels of three reactions vary which include a first reaction R1 which consumes both of NO and NO<SB POS="POST">2</SB>, a second reaction R2 of consuming NO<SB POS="POST">2</SB>, and a third reaction R3 of consuming NO, calculates a ratio between NO and NO<SB POS="POST">2</SB>entering/exiting from each area, calculates a purification ratio of the SCR catalyst 3 based on the calculated ratio between NO and NO<SB POS="POST">2</SB>entering/exiting from respective areas, and determines degradation of the SCR catalyst 3 based on the calculated purification ratio of the SCR catalyst 3. <P>COPYRIGHT: (C)2012,JPO&INPIT |
