Patent ID: 7997068

Claim:
A control device for an internal combustion engine provided with a NOx catalytic converter in an exhaust passage thereof, comprising: a control unit that estimates an extent of deposition of undesired substance in the NOx catalytic converter and changes operating parameters of the engine so as to produce a reducing agent in exhaust gas and thereby carry out a removal process of the undesired substance from the NOx catalytic converter; an upstream detector for detecting a value corresponding to an air fuel ratio in an upstream part of the NOx catalytic converter; a space velocity detector for detecting a space velocity of exhaust gas that enters the NOx catalytic convert; means for estimating an amount of supply of a reducing agent to the NOx catalytic converter according to an output of the upstream detector; and first correcting means for correcting an estimated amount of supply of a reducing agent into a corrected amount of supply of a reducing agent which increases with an increase in the space velocity detected by the space velocity detector; wherein an end of the undesired substance removal process is determined according to the corrected amount of supply of a reducing agent to the NOx catalytic converter.