| 摘要 |
PROBLEM TO BE SOLVED: To always supply proper quantity of a reducing agent to a NOX catalyst, even if an operating state of an internal combustion engine is changed. SOLUTION: This device is provided with the NOX catalyst 17 provided on an exhaust passage of the internal combustion engine 1 capable of performing lean combustion to discharge and reduce absorbed NOX by the reducing agent, a reducing agent supply means 19 provided in the exhaust passage on an upstream side of the NOX catalyst 17, a load detection means for detecting load of the internal combustion engine 1, a particle size control means for controlling a particle size of the added reducing agent according to load of the internal combustion engine 1. The reducing agent controlled in particle size is added to the NOX catalyst 17 based on the load detected by the load detection means. When the internal combustion engine 1 has low load, adhesion of particle on a wall surface within the exhaust passage can be reduced by reducing the particle size since an exhaust temperature is low and flow speed of exhaust is slow. |
