Exhaust gas purifying device for internal combustion engine

Abstract

An exhaust gas purifying device which can sufficiently perform HC purification even if a lean NOx catalyst included in a metal substrate is used. The exhaust gas purifying device comprises, in an exhaust passage in an internal combustion engine along a flowing direction of the exhaust gas, a lean NOx catalyst including a catalyst layer which purifies nitrogen oxide contained in the exhaust gas under a hyperoxia atmosphere and a metal honeycomb, the lean NOx catalyst having the catalyst layer supported within the metal honeycomb; and a reaction catalyst for subjecting to an oxidation reaction at least hydrocarbon contained in the exhaust gas.

What is claimed is:  
     
         1 . An exhaust gas purifying device for an internal combustion engine used for purifying exhaust gas exhausted from the internal combustion engine through an exhaust passage, comprising: 
 a lean NOx catalyst including a catalyst layer which purifies nitrogen oxide contained in the exhaust gas under a hyperoxia atmosphere and a metal honeycomb, said lean NOx catalyst having the catalyst layer supported within the metal honeycomb; and    a reaction catalyst for subjecting to an oxidation reaction at least hydrocarbon contained in the exhaust gas;    said lean NOx catalyst and said reaction catalyst being disposed in the exhaust passage along a flowing direction of the exhaust gas.    
     
     
         2 . An exhaust gas purifying device for an internal combustion engine used for purifying exhaust gas exhausted from the internal combustion engine through an exhaust passage, comprising: 
 a lean NOx catalyst including a catalyst layer which purifies nitrogen oxide contained in the exhaust gas under a hyperoxia atmosphere and a metal honeycomb, said lean NOx catalyst having the catalyst layer supported within the metal honeycomb; and    a reaction catalyst for subjecting to an oxidation reaction hydrocarbon and carbon monoxide contained in the exhaust gas downstream of said lean NOx catalyst;    said lean NOx catalyst and said reaction catalyst being disposed in the exhaust passage.    
     
     
         3 . An exhaust gas purifying device for an internal combustion engine used for purifying exhaust gas exhausted from the internal combustion engine through an exhaust passage, comprising: 
 a lean NOx catalyst including a catalyst layer which traps nitrogen oxide contained in the exhaust gas with a trapping material so that the trapped nitrogen oxide is purified by reduction and a metal honeycomb, said lean NOx catalyst having the catalyst layer supported within the metal honeycomb; and    a reaction catalyst including a catalyst layer for subjecting to an oxidation reaction at least hydrocarbon contained in the exhaust gas and a cordierite substrate, said reaction catalyst having the catalyst layer supported within the cordierite substrate;    said lean NOx catalyst and said reaction catalyst being disposed in the exhaust passage along a flowing direction of the exhaust gas.    
     
     
         4 . An exhaust gas purifying device for an internal combustion engine used for purifying exhaust gas exhausted from the internal combustion engine through an exhaust passage, comprising: 
 a lean NOx catalyst including a catalyst layer which purifies nitrogen oxide contained in the exhaust gas under a hyperoxia atmosphere and a metal honeycomb, said lean NOx catalyst having the catalyst layer supported within the metal honeycomb; and    a three-way catalyst for purifying nitrogen oxide, hydrocarbon, and carbon monoxide contained in the exhaust gas;    said lean NOx catalyst and said three-way catalyst being disposed in the exhaust passage along a flowing direction of the exhaust gas.    
     
     
         5 . An exhaust gas purifying device for an internal combustion engine used for purifying exhaust gas exhausted from the internal combustion engine through an exhaust passage, comprising: 
 a three-way catalyst;    a lean NOx catalyst including a catalyst layer which purifies nitrogen oxide contained in the exhaust gas under a hyperoxia atmosphere and a metal honeycomb, said lean NOx catalyst having the catalyst layer supported within the metal honeycomb; and    a reaction catalyst for subjecting to an oxidation reaction at least hydrocarbon contained in the exhaust gas;    said three-way catalyst, said lean NOx catalyst, and said reaction catalyst being disposed in the exhaust passage along a flowing direction of the exhaust gas.    
     
     
         6 . An exhaust gas purifying device for an internal combustion engine used for purifying exhaust gas exhausted from the internal combustion engine through an exhaust passage, comprising: 
 a filter for eliminating carbon particles contained in the exhaust gas;    a lean NOx catalyst including a catalyst layer which purifies nitrogen oxide contained in the exhaust gas under a hyperoxia atmosphere and a metal substrate, said lean NOx catalyst having the catalyst layer supported within the metal substrate; and    a reaction catalyst for subjecting to an oxidation reaction at least hydrocarbon contained in the exhaust gas;    said filter, said lean NOx catalyst, and said reaction catalyst being disposed in the exhaust passage along a flowing direction of the exhaust gas.    
     
     
         7 . An exhaust gas purifying device for an internal combustion engine used for purifying exhaust gas exhausted from the internal combustion engine through an exhaust passage, comprising: 
 a lean NOx catalyst including a catalyst layer which purifies nitrogen oxide contained in the exhaust gas under a hyperoxia atmosphere and a metal honeycomb, said lean NOx catalyst having the catalyst layer supported within the metal honeycomb to eliminate carbon particles contained in the exhaust gas; and    a reaction catalyst for subjecting to an oxidation reaction at least hydrocarbon contained in the exhaust gas;    said lean NOx catalyst and said reaction catalyst being disposed in the exhaust passage along a flowing direction of the exhaust gas.