EXHAUST PURIFICATION APPARATUS

摘要

Not only is a reduction catalyst capable of reduction purification of NOx disposed in an engine exhaust pipe but also in two pipes branched from the exhaust pipe positioned in the exhaust upstream, there are respectively disposed plural oxidation catalysts differing from each other in the capacity of oxidation of NO to NO₂. A control unit appropriately controls a flow rate control valve capable of independent and multistaged control of exhaust flow rates to the branched pipes on the basis of exhaust volume flow rate and oxidation catalyst temperature so that the ratio between NO and NO₂ in the exhaust led to the reduction catalyst approaches a given ratio.