Method and apparatus for measuring NOx gas concentration

摘要

The present invention relate to an apparatus for detecting the concentration of exhaust gases comprising: an NOx occlusion catalyst disposed in an exhaust pipe of an internal combustion engine, an NOx sensor mounted downstream of said NOx occlusion catalyst in the exhaust pipe to detect the NOx concentration in the exhaust gases, driving condition setting means for transiently providing a rich air-to-fuel ratio for cleaning NOx occluded in said NOx occlusion catalyst, and means for detecting a state of deterioration of said NOx occlusion catalyst based on changes in a detection output of said NOx sensor before and after setting the rich air-to-fuel ratio.