Patent ID: 6619035
Filing Date: 2003-09-16
Classification: F01N,F02B,F02M,Y02T

Abstract:
An exhaust emission control device for an internal combustion engine, comprising:an NOx catalyst provided in an exhaust passage of an internal combustion engine capable of lean burn and adapted to release absorbed NOx by a reducing agent for reduction; a reducing agent supplying means provided in the exhaust passage on an upstream side of the NOx catalyst for adding an amount of the reducing agent; a load detecting means for detecting a load of the internal combustion engine; a reducing agent addition control means for controlling a reducing agent addition period and a reducing agent addition interval based on the load of the internal combustion engine; and an addition determining means for determining whether or not the reducing agent is to be added according to an operating condition of the vehicle, wherein the addition amount of the reducing agent and the reducing agent addition interval are controlled based on the load detected by the load detecting means when the addition determining means determines that adding the reducing agent is possible, and the amount of the reducing agent to be added is increased and the reducing agent addition interval is elongated when the load of the internal combustion engine is small, as compared to when the load of the internal combustion engine is large.