Exhaust system

Abstract

An exhaust system includes a diesel oxidation catalyst (DOC) device mounted to an exhaust pipe for exhausting an exhaust gas of an engine and purifying hydrocarbon (HC) and carbon monoxide (CO) among the exhaust gas, an urea injector positioned at a rear of the diesel oxidation catalyst device for injecting an urea aqueous solution to an inside of the exhaust pipe, a mixer positioned at the rear of the urea injector, a diesel particulate matter filter (DPF) positioned at the rear of the mixer and coated with a catalyst devoid of a noble metal or a hydrolysis catalyst that does not oxidize ammonia and hydrolyzes the injected urea to reduce a particulate material of the exhaust gas, and a selective catalytic reduction (SCR) device positioned at the rear of the diesel particulate matter filter.

What is claimed is: 
     
         1 . An exhaust system comprising:
 a diesel oxidation catalyst (DOC) device mounted to an exhaust pipe for exhausting an exhaust gas of an engine and purifying hydrocarbon (HC) and carbon monoxide (CO) among the exhaust gas;   an urea injector positioned at a rear of the diesel oxidation catalyst device for injecting an urea aqueous solution to an inside of the exhaust pipe;   a mixer positioned at the rear of the urea injector for enabling a rapid flow diffusion of the exhaust gas passing through the diesel oxidation catalyst device;   a diesel particulate matter filter (DPF) positioned at the rear of the mixer and coated with a catalyst devoid of a noble metal or a hydrolysis catalyst that does not oxidize ammonia and hydrolyzes the injected urea to reduce a particulate material of the exhaust gas; and   a selective catalytic reduction (SCR) device positioned at the rear of the diesel particulate matter filter for reducing the nitrogen oxide of the exhaust gas passing through the diesel particulate matter filter.   
     
     
         2 . The exhaust system of  claim 1 , wherein a low pressure exhaust gas regeneration (LP-EGR) device pipe is connected between the diesel particulate matter filter and the selective catalytic reduction device. 
     
     
         3 . The exhaust system of  claim 1 , further comprising an ammonia oxidation catalyst (AOC) device positioned at the rear of the selective catalytic reduction device for oxidizing ammonia (NH 3 ) of the exhaust gas passing through the selective catalytic reduction device and reducing the nitrogen oxide. 
     
     
         4 . The exhaust system of  claim 1 , wherein a nitrogen oxide sensor is provided at the front and the rear of the selective catalytic reduction device. 
     
     
         5 . The exhaust system of  claim 1 , wherein a nitrogen oxide sensor is provided between the diesel oxidation catalyst device and the urea injector and between the diesel particulate matter filter and the selective catalytic reduction device. 
     
     
         6 . The exhaust system of  claim 1 , wherein the diesel oxidation catalyst device, the urea injector, the mixer, and the diesel particulate matter filter are positioned in an engine compartment CC of the vehicle, and
 the selective catalytic reduction device is positioned at a vehicle lower part uf.   
     
     
         7 . The exhaust system of  claim 1 , further comprising an injection chamber as a part of the exhaust pipe connecting the diesel oxidation catalyst device and the diesel particulate matter filter, and forming a space where the reduction agent is injected by the urea injector. 
     
     
         8 . An exhaust system comprising:
 a nitrogen oxide storage catalyst (lean NOx trap; LNT) device for absorbing and storing a nitrogen oxide generated by a lean combustion of an engine and reducing the nitrogen oxide into nitrogen by a reduction action to be exhausted;   an urea injector positioned at a rear of the nitrogen oxide storage catalyst device for injecting an urea aqueous solution inside the exhaust pipe;   a mixer positioned at the rear of the urea injector for enabling a rapid flow diffusion of the exhaust gas passing through the nitrogen oxide storage catalyst device;   a diesel particulate matter filter (DPF) positioned at the rear of the mixer and coated with a catalyst devoid of noble metal or a hydrolysis catalyst that does not oxidize ammonia and hydrolyzes the injected urea to reduce a particulate material of the exhaust gas; and   a selective catalytic reduction (SCR) device positioned at the rear of the diesel particulate matter filter for reducing the nitrogen oxide of the exhaust gas passing through the diesel particulate matter filter.   
     
     
         9 . The exhaust system of  claim 8 , wherein a low pressure exhaust gas regeneration device pipe is connected between the diesel particulate matter filter and the selective catalytic reduction device. 
     
     
         10 . The exhaust system of  claim 8 , further comprising an ammonia oxidation catalyst device positioned at the rear of the selective catalytic reduction device for oxidizing ammonia of the exhaust gas passing through the selective catalytic reduction device and reducing the nitrogen oxide. 
     
     
         11 . The exhaust system of  claim 8 , wherein a nitrogen oxide sensor is provided at the front and the rear of the selective catalytic reduction device. 
     
     
         12 . The exhaust system of  claim 8 , wherein a nitrogen oxide sensor is provided between the nitrogen oxide storage catalyst device and the urea injector and between the diesel particulate matter filter and the selective catalytic reduction device. 
     
     
         13 . The exhaust system of  claim 8 , wherein the nitrogen oxide storage catalyst device, the urea injector, the mixer, and the diesel particulate matter filter are positioned in an engine compartment of a vehicle, and the selective catalytic reduction device is positioned at a vehicle lower part. 
     
     
         14 . The exhaust system of  claim 8 , further comprising an injection chamber as a part of the exhaust pipe connecting the nitrogen oxide storage catalyst device and the diesel particulate matter filter and forming a space where the reduction agent is injected by the urea injector.