EXHAUST EMISSION CONTROL SYSTEM FOR INTERNAL COMBUSTION ENGINE

摘要

PROBLEM TO BE SOLVED: To provide an exhaust emission control system for an internal combustion engine capable of improving a trouble detection accuracy of an exhaust gas purification filter while a reduction of purification performance being restricted.SOLUTION: This invention relates to an exhaust emission control system 10 for an engine 1 comprising an exhaust flow rate incremental part 51 for increasing a flow rate of exhaust gas flowing into DPF 32; a front/rear pressure parameter acquisition part 56 for acquiring the front/rear pressure parameter of the DPF 32; a failure detection part 52 for detecting failure of the DPF 32 on the basis of the front/rear pressure parameter taken when the exhaust gas flow rate is increased by the exhaust flow rate incremental part 51; a purification performance estimating part 53 for estimating a purification performance of LNT 31 when the exhaust gas flow rate is increased by the exhaust flow rate incremental part 51; and a restriction part 54 for prohibiting an increasing of the exhaust gas flow rate by the exhaust flow rate incremental part 51 when a purifying performance estimated by the purification performance estimating part 53 is lower than the predetermined allowable purification performance or the purification performance of the LNT 31 may become more than the allowable purification performance so as to restrict increasing amount of exhaust gas flow rate by the exhaust flow rate incremental part 51.SELECTED DRAWING: Figure 2