Purification device for decreasing particulate matter and nitrogen oxides in diesel engine

Abstract

A diesel exhaust purification device for decreasing the amount of particulate matter and nitrogen oxides includes a Catalyzed Diesel Particulate Filter (CDPF) disposed in an exhaust conduit to capture particulate matter (PM). A differential pressure sensor detects the amount of PM contained in the CDPF. A post-injection injector is in the exhaust conduit. A Diesel Fuel Decomposition Catalyst (DFC) forms a reducing agent by decomposing the fuel injected from the post-injection injector. A nitrogen oxide adsorbing catalyst reduces nitrogen oxides accumulated therein and removes them using the reducing agent. A nitrogen oxide sensor in the exhaust conduit detects the amount of nitrogen oxides in exhaust gases. A control unit determines the regeneration time of the CDPF from signals detected by the differential pressure sensor, controls the amount of the fuel post-injected, determines the regeneration time of the nitrogen oxide adsorbing catalyst from signals detected by the nitrogen oxide sensor, controls the fuel post-injected through the post-injection injector.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]The present application is based on, and claims priority from, Korean Application Serial Number 10-2006-0115167, filed on Nov. 21, 2006, the disclosure of which is hereby incorporated by reference herein in its entirety.FIELD OF THE INVENTION[0002]The present invention relates to a purification device for diesel engine exhaust and, more particularly, for decreasing particulate matter and nitrogen oxides contained in exhaust gases of diesel engines.BACKGROUND OF THE INVENTION[0003]Generally, in a conventional purification device for decreasing both particulate matter and nitrogen oxides contained in exhaust gases of diesel engines, a Catalyzed Diesel Particulate Filter (CDPF), a nitrogen oxide adsorbing catalyst (de-NOx catalyst) and a Diesel Oxidation Catalyst (DOC) are disposed in sequence in an exhaust conduit, a subsidiary exhaust conduit branched from the exhaust conduit is disposed in the exhaust conduit at a position located in fron...

AI Technical Summary

Benefits of technology

[0008]Embodiments of the present invention provide a purification device which can reliably realize the purification for nitrogen oxides (NOx) by forming a reducing agent from fuel post-injected at the time of the regeneration of a nitrogen oxide adsorbing catalyst and regenerating the nitrogen oxide adsorbing catalyst using the reducing agent.

Problems solved by technology

However, there has been a problem in that the Diesel Fuel Decomposition Catalyst (DFC) is rapidly oxidized depending on the condition of exhaust gases, with the result that a phenomenon of purifying exhaust gases by oxidizing fuel, rather than by decomposing fuel injected from the secondary injection system, thus forming a reducing agent, occurs.

Moreover, there has been a problem in that the conventional purification device has a complicated structure, in which an additional bypass conduit, which is branched from the exhaust conduit in front of the Catalyzed Diesel Particulate Filter (CDPF) and includes an outlet in front of the nitrogen oxide adsorbing catalyst (de-NOx catalyst), is provided, and the Diesel Fuel Decomposition Catalyst (DFC) is contained in the bypass conduit.

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