Emission control system of internal combustion engine

摘要

An emission control system of an lean-burn internal combustion engine (1) includes a NOx catalyst (17), and a reductant supply device (12, 19, 20, 21, 22) disposed upstream of the NOx catalyst for adding a reducing agent so as to release and reduce NOx absorbed in the NOx catalyst. The emission control system detects an engine load, and calculates an amount of the reducing agent that is added in one NOx reducing process, based on the engine load. The system then executes a plurality of reductant adding operations in a controlled manner so as to provide the calculated amount of the reducing agent.