APPARATUS FOR DETECTING DETERIORATION OF A NOX SELECTIVE REDUCTION CATALYST

摘要

An object of the invention is to detect deterioration of an NOx selective reduction catalyst provided in an exhaust passage of an internal combustion engine with improved accuracy. An apparatus for detecting deterioration of NOx selective reduction catalyst according to the invention has an NOx purification rate calculation unit. A determination as to whether the NOx selective reduction catalyst is deteriorated is made if the temperature of said NOx selective reduction catalyst (Tc) at which the NOx purification rate starts to decrease with a rise in the temperature of said NOx selective reduction catalyst is lower than a predetermined criterion temperature (Tc0).