ENGINE EXHAUST EMISSION CONTROL DEVICE

摘要

PROBLEM TO BE SOLVED: To provide an engine exhaust emission control device to precisely judge whether there is enough room in NOx capturing quantity of a NOx capturing agent, optimize timing of NOx purge control and diagnose deterioration of the NOx capturing agent. SOLUTION: This device is furnished with a driving control parameter changing means to change a driving parameter to change NOx capturing quantity of a NOx capturing agent, a concentration detection means to detect specific component concentration in exhaust gas in the downstream of the NOx capturing agent, an air-fuel ratio changing means to temporarily change the air-fuel ratio of exhaust gas to a stoichiometric air-fuel ratio or rich and an NOx capturing quantity change detection means to detect change of the NOx capturing quantity of the NOx capturing agent from change of a detection result of the concentration detection means at the time of changing the air-fuel ratio after changing the driving parameter.