To solve a problem that NOx might not be efficiently purified in a conventional exhaust emission control device, and unreacted reducing agent is exhausted into the air.
The exhaust emission control device of an internal combustion engine includes an NOx catalyst 14 incorporated in an exhaust passage 11 of the internal combustion engine, and a reducing agent supply means for supplying the reducing agent for reducing NOx in exhaust gas into the exhaust passage 11 on the upstream side of the NOx catalyst 14. The exhaust emission control device further includes a target NOx purification rate setting part 29 for setting a target NOx purification rate according to a state of the exhaust emission control device, an actual NOx purification rate calculation part 30 for obtaining an NOx purification rate in the exhaust gas having passed through the NOx catalyst 14, and an exhaust control means for changing a cross-sectional area of the exhaust passage 11 based on difference between the target NOx purification rate and the actual NOx purification rate and changing an inflow angle of the exhaust gas to the NOx catalyst 14.
ODA TOMIHISA
TOSHIOKA TOSHISUKE
SATO MASAAKI
Kazuo Abe
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