EXHAUST EMISSION CONTROL DEVICE OF INTERNAL COMBUSTION ENGINE

摘要

PROBLEM TO BE SOLVED: To estimate the total quantity of NOx absorbed in NOx catalyst more accurately from the concentration of NOx in the exhaust gas flowing out of the NOx catalyst. SOLUTION: The exhaust emission control device has the NOx catalyst 23 for purifying the exhaust gas discharged from an internal combustion engine and a NOx sensor 29 for detecting the concentration of NOx in the exhaust gas flowing out of the NOx catalyst. The internal combustion engine and the exhaust emission control device are mounted on a vehicle. The total quantity of NOx flowing out of the NOx catalyst while the vehicle is running for a prescribed travel distance is calculated based on the concentration of NOx detected by the NOx sensor, and the quantity of NOx flowing out by unit travel distance is calculated based on the total quantity of NOx . When the calculated quantity of NOx flowing out by unit travel distance is larger than a previously determined value, the exhaust gas with a rich air-fuel ratio is fed to the NOx catalyst.