EXHAUST EMISSION CONTROL SYSTEM

摘要

PROBLEM TO BE SOLVED: To effectively continue performance of SOx purge even when an internal combustion engine becomes an idle operation state during the SOx purge.SOLUTION: An exhaust emission control system includes: an NOx reduction type catalyst 32 provided in an exhaust passage 13 of an internal combustion engine 10 to reduce NOx in exhaust gas for purification; an idle-time air system control section 52 that performs open loop control of an air flow rate when the internal combustion engine 10 becomes an idle operation state; an SOx purge control section 60 that performs catalyst regeneration processing for removing sulfur oxide adsorbed to the NOx reduction type catalyst 32 by reducing exhaust gas to a predetermined target excess air factor by using both of air system control for performing feedback control of the air flow rate and injection system control for increasing a fuel injection amount; and an air system open loop control prohibition section 70 that prohibits the idle-time air system control section 52 from performing the open loop control even when the internal combustion engine becomes the idle operation state while the catalyst regeneration processing is being performed.SELECTED DRAWING: Figure 1