| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a catalyst degradation diagnosis device capable of accurately diagnosing degradation of a storage reduction type NOx catalyst, and inhibiting deterioration of fuel economy and emission, and harmful effect of torque shock. <P>SOLUTION: Input NOx quantity which is total quantity of NOx flowing into the NOx catalyst during a period from completion of previous rich spike to start of present rich spike is acquired. Total storage quantity which is sum of NOx storage quantity and oxygen storage quantity of the NOx catalyst before rich spike is calculated based on quantity of reducer flowing in the NOx catalyst during execution of rich spike. A value corresponding to total storage quantity under a condition where the input NOx quantity is zero is calculated by extrapolating relation between the input NOx quantity and total storage quantity in rich spike executed under a condition where input NOx quantity is below at least two levels, and the value is defined as oxygen storage quantity of the NOx catalyst. <P>COPYRIGHT: (C)2008,JPO&INPIT |
