Patent Publication Number: US-8534055-B2

Title: Filter arrangement for exhaust aftertreatment system

Description:
BACKGROUND 
     The present invention relates to exhaust aftertreatment systems for use with internal combustion diesel engines. 
     Exhaust aftertreatment systems, such as a diesel particulate filter (DPF) system, are commonly used to treat exhaust gases emitted from an internal combustion diesel engine.  FIG. 1  schematically illustrates a conventional DPF system  10 . The DPF  14  is positioned in-line with the exhaust line  18  for receiving the flow of exhaust gases. Particulate or soot traveling with the exhaust gases in the exhaust line  18  is trapped by the DPF  14  to clean the exhaust gases. As the particulate is collected by the DPF  14 , a pressure sensor  22  in communication with the exhaust line  18  monitors the back pressure in the exhaust line  18 . When a predetermined backpressure is reached, indicative of a sufficient quantity of particulate in the DPF  14 , a controller  26  activates a heater  30  adjacent the DPF  14  and an air supply system (including a blower  34  and a control valve  38 ) to oxidize the particulate. The oxidation is commonly referred to as regeneration of the DPF  14 . 
     SUMMARY 
     Operation of conventional DPF systems can be hindered by buildup of particulate or soot in the auxiliary lines or tubes that connect the air supply and the pressure sensor to the exhaust line. The present invention provides an auxiliary filter arrangement for an exhaust aftertreatment system, such as a DPF system. The DPF communicates with the exhaust line to receive the flow of exhaust gases therethrough. An auxiliary filter is positioned in an auxiliary line or tube that connects the air supply, the pressure sensor, and/or any other aftertreatment system component to the exhaust line. The auxiliary filter can be wire mesh, silicon-carbide wall-flow type media, or other effectively similar material operable to trap particulate or soot, thereby preventing the soot from traveling further up the auxiliary line toward the components of the air supply system, the pressure sensor, and/or the components of any other aftertreatment system communicating with the exhaust line through the auxiliary line. 
     In one embodiment, the air supply system and the pressure sensor are integrated into a single auxiliary line communicating with the exhaust line. The auxiliary filter is positioned proximate the intersection of the auxiliary line and the exhaust line to trap particulate or soot and prevent it from traveling up the auxiliary line toward the components of the air supply system and the pressure sensor. The auxiliary filter is also located proximate the heater of the DPF system so that activation of the heater and the air supply system to regenerate the DPF also results in the regeneration of the auxiliary filter. In other words, the particulate collected by the auxiliary filter is oxidized during the regeneration of the DPF, thereby simultaneously regenerating the auxiliary filter. 
     In another embodiment, the air supply system and the pressure sensor are positioned into separate auxiliary lines, each communicating with the exhaust line. 
     Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  schematically illustrates a prior art diesel particulate filter system. 
         FIG. 2  schematically illustrates a diesel particulate filter system embodying the invention according to one embodiment. 
         FIG. 3  schematically illustrates a diesel particulate filter system embodying the invention according to another embodiment. 
         FIG. 4  is a perspective view of an auxiliary filter used in the system of  FIGS. 2 and 3 . 
     
    
    
     DETAILED DESCRIPTION 
     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. 
       FIG. 2  illustrates an exhaust aftertreatment system in the form of a diesel particulate filter (DPF) system  50  of the present invention, according to one embodiment. The DPF  54  is positioned in-line with the exhaust line  58  for receiving the flow of exhaust gases (represented by the arrow  60 ) from an internal combustion engine (not shown). In some embodiments, the engine is used to drive a vehicle, such as a truck or tractor, to drive a refrigeration system on a trailer or container refrigeration unit, to drive a generator on a shipping container, or to drive an auxiliary power unit of a tractor/trailer combination. Particulate or soot traveling with the exhaust gases in the exhaust line  58  is trapped by the DPF  54  to clean the exhaust gases  60 . An auxiliary line  62  communicates with the exhaust line  58  and includes components associated with the regeneration of the DPF  54 . Specifically, an air supply system  66  communicates with the exhaust line  58  via the auxiliary line  62 . The air supply system  66  includes a blower  70  and a control valve  74  for regulating the airflow from the blower  70  through the auxiliary line  62 . A back pressure sensor  78  also communicates with the exhaust line  58  via the auxiliary line  62 . 
     An auxiliary filter  82  is positioned proximate the intersection of the auxiliary line  62  and the exhaust line  58  to trap particulate or soot and prevent it from traveling up the auxiliary line  62  toward the blower  70 , the valve  74 , and the pressure sensor  78 . In the illustrated embodiment, the auxiliary filter  82  is a wire mesh pad or plug (see  FIG. 4 ) that can be fitted within the inner diameter of the tube, hose, or pipe defining the auxiliary line  62 . Auxiliary filters of this construction are available in any desired shapes and sizes from Heraeus GmbH in Hanau, Germany. In other embodiments, the auxiliary filter  82  need not be positioned directly in the inner diameter of the auxiliary line  62 , but instead can be positioned within the exhaust line  58  at the opening to the auxiliary line  62 , or within a junction or fitting interconnecting the auxiliary line  62  and the exhaust line  58 . 
     The auxiliary filter  82  is positioned to also be located proximate the heater  86  of the DPF system  50  so that activation of the heater  86  and the air supply system  66  to regenerate the DPF  54  also results in the regeneration of the auxiliary filter  82 . In other words, the particulate collected by the auxiliary filter  82  is oxidized during the regeneration of the DPF  54 , thereby simultaneously regenerating the auxiliary filter  82 . The proximity of the auxiliary filter  82  to the heater  86  can vary in different systems depending upon the intensity of the regeneration at the DPF  54 . This arrangement provides a more robust DPF system  50  because it improves the monitoring of the backpressure and the ability to supply air to the system for regeneration. Soot that might otherwise clog auxiliary lines communicating with the exhaust line  58 , and hinder the regeneration operation, is trapped in the auxiliary filter  82  and periodically oxidized. 
     In the illustrated embodiment, a thermal isolator  90  is positioned in the auxiliary line  62  at a location between the auxiliary filter  82  and the sensor  78 , the valve  74 , and the blower  70 . The thermal isolator  90  provides thermal protection to the sensor  78 , the valve  74 , and the blower  70  from the heat generated by the heater  86  and the regeneration of the filters  54  and  82 . In particular, the thermal isolator  90  protects the pressure sensor  78  from the high temperatures that might damage the sensor  78  or affect its rated accuracy. 
     While the embodiment illustrated in  FIG. 2  integrates the air supply system  66  and the back pressure sensor  78  in a single auxiliary line  62 , it should be understood that other embodiments, in which each of the air supply system  66  and the back pressure sensor  78  communicate with the exhaust line  58  via distinct auxiliary lines  62 ,  94  (similar to the arrangement shown in  FIG. 1 ), are also contemplated by the invention, see  FIG. 3 . In such embodiments, there can be an auxiliary filter in each auxiliary line, and each auxiliary filter can be positioned proximate the heater for regeneration simultaneously with the regeneration of the DPF. The invention can also be used in auxiliary lines that communicate other aftertreatment system components with the exhaust line  58 . 
     Various features and advantages of the invention are set forth in the following claims.