Apparatus and method for purifying exhaust gas in engine

Abstract

The apparatus improves regeneration efficiency of a diesel particulate filter (DPF) that traps particulate matter, reduces pressure loss caused by the filter, and benefits space of a vehicle. Therefor, the DPF that traps particulate matter having a large diameter is connected to or close to an exhaust manifold in an engine, and the DPF that traps particulate matter having a small diameter is disposed in an exhaust pipe downstream of the exhaust manifold and at a location away (under a vehicle floor) from the exhaust manifold.

What is claimed:  
     
         1 . An apparatus for purifying an exhaust gas in an engine comprising: 
 an exhaust passage in the engine;    a first filter disposed in an upstream side of the exhaust passage, the first filter trapping particulate matter that has at least a first diameter; and    a second filter disposed in a downstream side of the exhaust passage and placed separately from the first filter, the second filter trapping particulate matter that has at least a second diameter, the second diameter smaller than the first diameter.    
     
     
         2 . An apparatus according to  claim 1 , further comprising: 
 a first casing containing the first filter; and    a second casing containing the second filter, the second casing separate from the first casing.    
     
     
         3 . An apparatus according to  claim 1 , wherein the first diameter is in the range of 80-100 nm.  
     
     
         4 . An apparatus according to  claim 1 , wherein the second diameter is in the range of 20-50 nm.  
     
     
         5 . An apparatus according to  claim 1 , wherein 
 the exhaust passage comprises an exhaust manifold connected to a cylinder head of the engine and an exhaust pipe downstream of the exhaust manifold, further comprising: 
 an exhaust turbine in a turbocharger disposed between the exhaust manifold and the exhaust pipe wherein, 
 the first filter is disposed upstream of the exhaust turbine.  
 
   
     
     
         6 . An apparatus according to  claim 1 , further comprising: 
 the exhaust passage comprises an exhaust manifold connected to a cylinder head of the engine and an exhaust pipe downstream of the exhaust manifold, further comprising: 
 an exhaust turbine in a turbocharger disposed between the exhaust manifold and the exhaust pipe wherein, 
 the first filter is disposed downstream of the exhaust turbine.  
 
   
     
     
         7 . An apparatus according to  claim 1 , wherein 
 the first filter is disposed under an engine hood; and    the second filter is disposed under a vehicle body floor.    
     
     
         8 . An apparatus according to  claim 1 , wherein 
 a capacity of the first filter is less than a capacity of the second filter.    
     
     
         9 . An apparatus according to  claim 1 , wherein 
 each of the first and second filters carries a catalyst.    
     
     
         10 . A method for purifying an exhaust gas in an engine comprising: 
 disposing a first filter in an upstream side of an exhaust passage; and    disposing a second filter in a downstream side of the exhaust passage and placed separately from the first filter wherein 
 the first filter traps particulate matter having a larger diameter than the diameter of the particulate matter which the second filter traps.