Patent ID: 7617672

Claim:
An engine exhaust emission control device comprising: an addition device configured to add a NOx reducing agent to exhaust gas of an engine; a first controller configured to control the addition device; and a second controller configured to set an engine control factor that influences the composition of exhaust gas at the point in time of emission from a cylinder of the engine, and output a command signal that corresponds to the set engine control factor, wherein the second controller is further configured to detect an abnormality that occurs in an exhaust gas recirculation device or a supercharger arranged in the engine as an engine part for realizing the engine control factor, if the abnormality is detected, outputs to the first controller, an addition device control signal for making a reducing agent addition amount by the addition device vary from that at normal addition control times, other than at the time of the abnormality occurrence, and the abnormality occurs when a detected voltage of the command signal output to the exhaust gas recirculation device is greater than a predetermined value, or when a detected value of intake air compressed by the supercharger deviates from a predetermined pressure range.