Exhaust emission control device for an internal combustion engine

摘要

A NOx catalyst in the exhaust passage of an internal combustion engine is capable of lean burn and adapted to release and reduce absorbed NOx by a reducing agent. Reducing agent supplier is provided in the exhaust passage on the upstream side of the NOx catalyst. A load detector detects the load of an internal combustion engine. Reducing agent addition controller controls the reducing agent addition period and the reducing agent addition interval based on the load of the internal combustion engine, whereby sufficient reducing agent is supplied to the NOx catalyst side independently of the operating condition.