EXHAUST EMISSION CONTROL SYSTEM

摘要

PROBLEM TO BE SOLVED: To effectively prevent combustion of an engine from becoming unstable at start and completion of catalyst regeneration.SOLUTION: An exhaust emission control system includes: an NOx reduction type catalyst 32 provided in an exhaust passage of an internal combustion engine 10; an intake air amount sensor 40; and a control section 50 for executing regeneration processing of the NOx reduction type catalyst 32 by switching exhaust gas from a lean state to a rich state by using both of air system control for reducing intake air amount and injection system control for increasing fuel injection amount. When switching the lean state where the regeneration processing is started to the rich state, the control section 50 reduces the intake air amount toward target intake air amount over a transition period determined in accordance with a difference between a detection value obtained by the intake air amount sensor 40 and the target intake air amount in the rich state.SELECTED DRAWING: Figure 1