| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide an exhaust emission control device capable of accurately determining if a NOx control device has deteriorated, regardless of the degree of deterioration of a catalyst provided upstream of the NOx control device. SOLUTION: A first exhaust parameter GAIRLNCL is calculated which indicates the amount of exhaust that flows into the NOx control device 15 from the time when an output SVO2 of an upstream O2 sensor 18 has reached a first upstream reference voltage value SVREFL, and a second exhaust parameter GAIRLNCH is calculated which indicates the amount of exhaust that flows into the NOx control device 15 from the time when the output value SVO2 of the upstream O2 sensor has reached a second upstream reference voltage SVREFH (> SVREFL). Based on the first and second exhaust parameters GAIRLNCL and GAIRLNCH and an output value TVO2 of a downstream O2 sensor, a determination is made as to whether the NOx control device 15 has deteriorated.</p> |
