| 摘要 |
PROBLEM TO BE SOLVED: To provide an exhaust emission control device capable of improving the reduction purification ratio of nitrogen oxides. SOLUTION: When an actual exhaust gas flow rate Ga is less than a target exhaust gas flow rate Gat, supercharging pressure is increased by driving a motor 11a of a turbocharger 11, and an EGR valve 28 is driven to the valve opening side. Thus, boosted intake air is supplied to the upstream side of an NOx reducing catalyst 23 from an intake passage 5 via an EGR passage 27, and an exhaust gas flow rate flowing in the NOx reducing catalyst 23 is increased. A reducing agent is added from a reducing agent supply nozzle 25 in response to an adding quantity and an adding interval set based on the increased actual exhaust gas flow rate Ga and the NOx reducing catalyst bed temperature. As a result of it, the NOx reduction purification ratio can be improved. COPYRIGHT: (C)2008,JPO&INPIT
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