Exhaust gas purification apparatus for internal combustion engine

摘要

Provided is an exhaust gas purification apparatus for an internal combustion engine (10) with an oxidation catalyst (13) wherein a fault diagnosis of the NOx sensor (15, 18) located at the downstream side of the catalyst is carried out with high accuracy. When the temperature of the catalyst (13) is in a predetermined temperature range in which the catalyst (13) exhibits an action of adsorbing NOx in the exhaust gas and an action of using a hydrocarbon in the exhaust gas as a reducing agent to reduce NOx in the exhaust gas, then an adsorption rate and a desorption rate are estimated on the basis of a flow rate of the hydrocarbon in the exhaust gas and the temperature of the catalyst (13), and when the net desorption amount of the NOx is equal to or greater than a predetermined amount, then the fault determination of the NOx sensor (15,18) is halted.