EXHAUST EMISSION CONTROL SYSTEM FOR INTERNAL COMBUSTION ENGINE

摘要

PROBLEM TO BE SOLVED: To change direction of flow of exhaust gas flowing in a NOx selective reduction catalyst and a particulate filter according to demand.

SOLUTION: An oxidation catalyst 12 is provided in an engine exhaust gas passage and a change over valve device 13 is provided on an outlet of the oxidation catalyst 12. Flow direction of exhaust gas can be changed over to first flow I flowing into the particulate filter 1 after flowing out of the NOx selective reduction catalyst 15 and second flow II flowing in the NOx selective reduction catalyst 15 after flowing out of the particulate filter 16 by changing over action of the change over valve device 13. Flow is changed over to either of the first flow I or the second flow II according to demand on the NOx selective reduction catalyst 15 and the particulate filter 16.

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