Patent ID: 8091404
Filing Date: 2012-01-10
Classification: B01D,F01N,F02D,Y02T

Abstract:
1. An abnormality diagnosis apparatus for an NOx sensor comprising: an NOx catalyst of storage reduction type provided in an exhaust passage in an internal combustion engine; an after-catalyst NOx sensor detecting NOx concentration of exhaust gas on a downstream side of the NOx catalyst, before-catalyst NOx concentration acquiring means for detecting or estimating the NOx concentration of the exhaust gas on an upstream side of the NOx catalyst; catalyst temperature acquiring means for detecting or estimating temperature of the NOx catalyst; abnormality determining means for determining possible abnormality of the after-catalyst NOx sensor by comparing the NOx concentration detected by the after-catalyst NOx sensor and the NOx concentration detected or estimated by the before-catalyst NOx concentration acquiring means, under a condition that the catalyst temperature detected or estimated by the catalyst temperature acquiring means is such that at the temperature, the NOx catalyst does not substantially absorb the NOx in the exhaust gas; and rich spike control means for performing rich spike control for allowing NOx absorbed by the NOx catalyst to be released, and performing the rich spike control before the after-catalyst NOx sensor detects the NOx concentration.