Exhaust gas purifying system for internal combustion engine

摘要

An ECU controls a rich purge in the internal combustion engine by temporarily changing an air/fuel ratio of the exhaust gas into a rich range to deoxidize and remove absorbed NOx, which is absorbed by an NOx storage and reduction catalyst of an NOx catalytic converter. The ECU changes a degree of richness of the air/fuel ratio at a time of performing the rich purge based on a state of the NOx catalytic converter.