| 摘要 |
PROBLEM TO BE SOLVED: To obtain suitable purifying performance across a wide operation region by inhibiting a change of an additive concentration distribution in exhaust caused by a change of an engine operation state, when a mixer 4 for mixing an additive jetted in the exhaust with the exhaust is included on an upstream side of an exhaust emission control device (SCR catalyst 2, for example) located in an exhaust passage 1 of an internal combustion engine.SOLUTION: An exhaust emission control device includes a bypass passage 5 for bypassing a mixer 4 to provide communication between an upstream side of the bypass passage and a downstream side of an exhaust passage 1; and passage area variable means (valve plates 51, 52 and a valve plate motion mechanism 6) for varying a cross-sectional area of the bypass passage 5 so that the cross-sectional area gets larger as a flow rate of exhaust increases in the exhaust passage on the upstream side of the mixer 4 (an upstream-side exhaust pipe 10, for example). |
