Particle filter and method for the purification of an exhaust-gas flow

Abstract

Particle filters and a method for the purification of an exhaust-gas flow are described. In one example, exhaust gas is directed solely to a first particulate filter until a predetermined condition. Then exhaust gas is directed to a second particulate filter. One particulate filter may surround the other of two particulate filters. The particulate filters may provide filtered exhaust gas even when one filter becomes at least partially loaded.

1 . An exhaust system of a motor vehicle, comprising:
 a first particulate filter;   a second particulate filter; and   a exhaust gas routing system including a first exhaust passage through the first particulate filter and a second exhaust passage through the second particulate filter, an inlet valve biased in a closed position and located upstream of the first and second particulate filters.   
     
     
         2 . The exhaust system of  claim 1 , where exhaust gases are directed substantially solely to the first particulate filter when particulates stored in the first particulate filter are less than a threshold level, and the exhaust gas routing system supplying exhaust gases to the second particulate filter when particulates stored in the first particulate filter are greater than the threshold level. 
     
     
         3 . The exhaust system of  claim 1 , where the second particulate filter surrounds the first particulate filter. 
     
     
         4 . The exhaust system of  claim 1 , further comprising a preload spring biasing the inlet valve in a closed position. 
     
     
         5 . The exhaust system of  claim 1 , further comprising an outlet valve positioned downstream of the second particulate filter and the first particulate filter. 
     
     
         6 . The exhaust system of  claim 5 , further comprising a preload spring biasing the outlet valve in a closed position. 
     
     
         7 . The exhaust system of  claim 1 , further comprising a pressure sensor positioned upstream of the first particulate filter. 
     
     
         8 . The exhaust system of  claim 7 , further comprising a pressure sensor located downstream of the second particulate filter. 
     
     
         9 . The exhaust system of  claim 1 , further comprising an inlet valve position sensor, an outlet valve position sensor, and a temperature sensor positioned upstream of the second particulate filter. 
     
     
         10 . An exhaust purification method, comprising:
 directing exhaust gases from an engine substantially solely to a first particulate filter (PF) when a stored soot amount in the first PF is less than a threshold; and   directing exhaust gases from the engine to a second PF when the stored soot amount in the first PF is greater than the threshold, the second PF adjacent to and surrounding the first PF.   
     
     
         11 . The method of  claim 10 , further comprising combusting an air-fuel mixture in an engine to produce the exhaust gases, and where the amount of soot stored in the first particulate filter is determined from an increased exhaust-gas counterpressure. 
     
     
         12 . The method of  claim 11 , where during a condition where the amount of soot stored in the first particulate filter is greater than a threshold amount, a filtering efficiency of the first particulate filter is decreased from a nominal filtering efficiency and an exhaust-gas counterpressure remains below a threshold level. 
     
     
         13 . The method of  claim 10 , further comprising where the first particulate filter is regenerated when exhaust flow is directed to the second particulate filter, and further comprising opening and closing an inlet valve regulating flow to the second particulate filter during regeneration of the first particulate filter. 
     
     
         14 . The method of  claim 13 , further comprising directing engine exhaust gas solely through the first particulate filter after the first particulate filter is regenerated. 
     
     
         15 . A method for purification of engine exhaust, comprising:
 combusting an air-fuel mixture in an engine;   directing exhaust gases from the engine substantially solely to a first particulate filter when an pressure upstream of the first particulate filter is less than a threshold amount; and   directing exhaust gases from the engine to a second particulate filter when exhaust pressure upstream of the first particulate filter overcomes a spring force, where the second particulate filter surrounds a portion of the first particulate filter.   
     
     
         16 . The method of  claim 15 , where exhaust gases are directed via an inlet valve and an outlet valve. 
     
     
         17 . The method of  claim 16 , further comprising where the first particulate filter is regenerated when exhaust gases are directed to the second particulate filter.