Patent ID: 8256206

Claim:
An exhaust emission control device for an internal combustion engine, comprising: a NOx catalyst that is disposed in an exhaust system of the engine, for trapping NOx in exhaust gases; exhaust-gas reducing condition-detecting means for detecting a reducing condition of exhaust gases flowing into said NOx catalyst; main fuel supply means for supplying main fuel for obtaining an output of the engine; auxiliary fuel supply means for supplying auxiliary fuel for regenerating said NOx catalyst; first feedback control means for feedback-controlling the detected reducing condition of exhaust gases to a predetermined reducing condition, by controlling only an amount of the main fuel supplied from said main fuel supply means, as a regeneration operation for regenerating said NOx catalyst; second feedback control means for feedback-controlling the reducing condition of exhaust gases to the predetermined reducing condition, by feedback-controlling an amount of the auxiliary fuel supplied from said auxiliary fuel supply means and preventing the amount of the main fuel from being feedback-controlled, as the regeneration operation; regeneration operation mode-determining means for determining whether or not the regeneration operation should be executed in a catalyst temperature control mode for controlling a temperature of said NOx catalyst; and selection means operable when the regeneration operation should be executed in the catalyst temperature control mode as a result of determination by said regeneration operation mode-determining means, to select said first feedback control means, and when the regeneration operation should be executed not in the catalyst temperature control mode, as the result of the determination, to select said second feedback control means.