INTERNAL COMBUSTION ENGINE EXHAUST EMISSION CONTROL DEVICE

摘要

PROBLEM TO BE SOLVED: To appropriately remove predetermined components contained in exhaust gas while suppressing degradation in fuel economy.SOLUTION: An internal combustion engine exhaust emission control device comprises: an upstream catalyst 31 and a downstream catalyst 33 sequentially provided from an upstream side of an exhaust passage 16 of an internal combustion engine 1. The upstream catalyst 31 and the downstream catalyst 33 occlude predetermined components in exhaust gas in an oxidation atmosphere and release the predetermined components in a reduction atmosphere. The exhaust emission control device comprises control means 40 executing a first purge control to supply a reducing agent to release the predetermined components from the first catalyst 31 if an occlusion quantity of the predetermined components occluded by the upstream catalyst 31 is equal to or greater than a first threshold, and executing a second purge control to supply the reducing agent to release the predetermined components from the second catalyst 33 if an occlusion quantity of the predetermined components occluded by the downstream catalyst 33 is equal to or greater than a second threshold. The control means 40 executes the first purge control and the second purge control simultaneously and continuously if the occlusion quantity of the predetermined components occluded by the upstream catalyst (upstream NOx trap catalyst) 31 exceeds a third threshold smaller than the first threshold and the occlusion quantity of the predetermined components occluded by the downstream catalyst (downstream NOx trap catalyst) 33 exceeds a fourth threshold smaller than the second threshold.