ENGINE EXHAUST EMISSION CONTROL DEVICE

摘要

PROBLEM TO BE SOLVED: To prevent erroneous determination on the performance of NOx catalyst by determining whether the condition affecting the performance evaluation on NOx catalyst is established or not, and stopping the performance evaluation on NOx catalyst when it is established. SOLUTION: Determination on an engine system is performed (S1501) to determine whether the condition of exhaust emission inputted to a capture agent, such as air-fuel ratio, exhaust emission quantity, components is suitable for diagnosis or not. When it is determined that abnormality is caused in the engine system (S1502), the performance evaluation on the capture agent is by- passed. Further, it is determined from the temperature of the capture agent whether the capture agent itself is put in the condition suitable for performance evaluation or not (S1503). When the capture agent itself is not suitable for performance evaluation or not (S1504), the performance evaluation on the capture agent is by-passed. Lastly, it is determined that a diagnosing means for the capture agent is suitable for diagnosis or not (S1505), and when it is detected that it is in the unsuitable condition (S1506), the performance evaluation on the capture agent is by-passed.