Exhaust gas purifying apparatus for internal combustion engine

An exhaust gas purifying apparatus for an internal combustion engine having a lean NOx catalyst in an exhaust system, said lean NOx catalyst trapping NOx in exhaust gases when the exhaust gases are in an oxidizing state, and discharging the trapped NOx when the exhaust gases are in an reducing state, said exhaust gas purifying apparatus comprising:

• trapped NOx amount estimating means for calculating an estimated trapped NOx amount which is an estimated value of an amount of NOx trapped in the lean NOx catalyst using a neural network to which engine operating parameters indicative of an operating condition of said engine are input, wherein said neural network outputs at least one control parameter which is relevant to said lean NOx catalyst;
• and
• reducing process means for performing a reducing process of the NOx trapped in said lean NOx catalyst, according to the estimated trapped NOx amount.