| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an emission gas concentration detecting device using a gas sensor capable of accurately measuring a gas concentration for a long period of time. <P>SOLUTION: This device is provided with a NOx occlusion catalyst or a NOx selection reduction catalyst arranged in an exhaust pipe of an internal combustion engine, a NOx sensor attached in the downstream of the NOx occlusion catalyst or the NOx selection reduction catalyst in the exhaust pipe and detecting the concentration of NOx in emission gas, an operating condition establishing means temporarily making an air fuel ratio rich for purifying NOx occluded by the NOx occlusion catalyst, and a means detecting the deterioration condition of the NOx occlusion catalyst based on the change of the detection output of the NOx sensor before and after making the air fuel ratio rich. <P>COPYRIGHT: (C)2004,JPO |
