Patent Publication Number: US-7900609-B2

Title: Dual exhaust gas recirculation valve

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The application claims priority to U.S. Provisional Application No. 60/912,532 all filed on Apr. 18, 2007. 
    
    
     BACKGROUND OF THE INVENTION 
     This disclosure generally relates to an exhaust gas recirculation (EGR) system for controlling the flow of exhaust gases. 
     Current EGR systems include an EGR valve for modulating and controlling exhaust gas flow and a bypass valve for flow path control disposed in series with the EGR valve. The bypass valve can cause internal leakage problems and complicates exhaust passage configuration and packaging. 
     Accordingly, it is desirable to design and develop an improved EGR system to improve performance, simplify manufacture, assembly and operation. 
     SUMMARY OF THE INVENTION 
     An example exhaust gas recirculation (EGR) system communicates hot exhaust gases from an exhaust manifold to an intake manifold through a first passage and a second passage parallel with the first passage. 
     A first EGR valve assembly controls exhaust gas flow through the first passage and a second EGR valve assembly controls exhaust gas flow through the second passage. The second exhaust passage directs exhaust gases through a cooler. The cooler reduces the temperature of exhaust gases being communicated to the intake manifold. The first and second EGR valves are independently actuateable to provide a desired flow and temperature of exhaust gas to the intake manifold. Exhaust gas is selectively flowed through one or both of the first and second passages to provide the desired temperature and flow through the intake manifold to the engine. Accordingly, the example EGR system provides control of exhaust gas flow and temperature by selectively controlling gas flow through parallel cooled and un-cooled passages. 
     These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of an example exhaust gas recirculation system. 
         FIG. 2  is another schematic view of an example exhaust gas recirculation system. 
         FIG. 3  is an exploded view of the example exhaust gas recirculation valve assembly. 
         FIG. 4  is a perspective view of the example EGR valve assembly. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIG. 1 , an exhaust gas recirculation (EGR) system  10  communicates hot exhaust gases produced by an engine  16  through an exhaust manifold  12  to an intake manifold  14 . The flow of exhaust gas is communicated through a first passage  24  and a second passage  26  that is parallel with the first passage  24 . A first EGR valve assembly  18  controls exhaust gas flow through the first passage  24  and a second EGR valve assembly  20  controls exhaust gas flow through the second passage  26 . A controller  15  is utilized to control actuation of the first and second EGR valves  18 , 20  responsive to a desired engine operating parameter. The second exhaust passage  26  directs exhaust gases through a cooler  22 . The cooler  22  reduces the temperature of exhaust gases being communicated to the intake manifold  14 . 
     The first and second EGR valves  18 ,  26  are independently actuateble to provide a desired flow and temperature of exhaust gas to the intake manifold  14 . The temperature of exhaust gas is controlled to provide the desired operational characteristics of the engine  16 . Exhaust gas is selectively flowed through one or both of the first and second passages to provide the desired temperature and flow through the intake manifold  14  to the engine  16 . 
     Referring to  FIG. 2 , the example system  10  includes the first and second EGR valves  18 ,  20  mounted within a common housing  28 . The housing  28  defines inlets and outlets required to route and control the flow of exhaust gases. The example first and second EGR valves  18 ,  20  are of a common configuration and operation to simplify assembly, manufacture and operation. Further, although the example housing  28  illustrates a common mounting location for both the first and second EGR valves  18 ,  20 , other mounting configurations and placements are within the contemplation of this invention. For example, the first EGR valve  18  could be mounted in a location separate from the second EGR valve as is required for application specific requirements. 
     The example housing  28  defines only a portion of the first and second passages  24 ,  26 . Other connections such as hoses, pipes or other cavities for directing and communicating exhaust gases between the source of the exhaust gases and the intake manifold  14  are within the contemplation of this invention. 
     Referring to  FIGS. 3 and 4 , with continued reference to  FIG. 2 , the example EGR valves  18 ,  20  are mounted into separate bores  30 ,  32  of the housing  28 . The bores  30 ,  32  are similar in that each is configured to receive one of the EGR valves  18 ,  20 . The housing  28  includes inlet  34  for exhaust gases from the example exhaust manifold  12 . A first outlet  38  communicates exhaust gases directly to the intake manifold  14  to bypass the cooler  22 . A second outlet  36  A communicates exhaust gases out to a cooler  22 . The cooled exhaust gases then flow back through inlet  36 B into the housing and then through the outlet  38  to the intake manifold  14 . The example cooler  22  provides for the control and reduction of a temperature of the exhaust gases. 
     The example EGR valves  18 ,  20  include a metering housing  44  that is received within a corresponding bore  30 ,  32  in the housing  28 . A rotary flap valve  42  rotates within the metering housing  44  to selectively block exhaust gas flow and thereby control exhaust gas flow. The rotary flap valve  42  is driven through a drive mechanism  46  by a motor  40 . The example motor  40  comprises an electric motor that is separated from the meter housing  44 . The motor  40  is separate from the rotary flap valve  42  to isolate the motor  40  from temperatures encountered upon exposure to hot exhaust gases. Although a rotary flap valve is illustrated and described as a disclosed example, other EGR valve configurations such as poppet or spool type valves are also within the contemplation of this invention. 
     Because the example EGR system  10  includes two parallel exhaust gas paths, greater ranges of operational capabilities are possible. Exhaust gases can flow through one or some proportion of both the first passage  24  and the second passage  26 . Cooled exhaust gas directed through the second passage  26  can be combined with un-cooled bypassed exhaust gas flow through the first passage  24  to obtain a desired temperature of exhaust gas at the intake manifold  12 . Further, a switch between un-cooled bypassed exhaust gases is made possible by the parallel flow passages without interruption exhaust gas flow. 
     Operation of the system  10  includes providing the first and second  24 ,  26  parallel passages for exhaust gases. The example second flow passage  26  directs hot exhaust gases to a cooler  22 . The example cooler  22  can be any heat exchange device as is known that provides for the reduction in temperature of exhaust gases. The controller  15  controls actuation of the EGR valves  18 , 20  to communicate exhaust gases from the source, in this example the exhaust manifold  12  to the intake manifold  14  and then to the engine  16 . The example controller  15  is as know and can be a separate microcontroller or a part of a vehicle electronic control unit. 
     Each of the EGR valves  18 ,  20  is independently actuatable to provide a desired proportion of exhaust gas flow through each of the first and second passages  24 ,  26 . As appreciated, any proportion from completely closed to fully open can be utilized to provide a desired mixture of cooled and un-cooled exhaust gas to obtain a desired temperature of exhaust gas to the intake manifold  14 . Further, the EGR valves  18 ,  20  can simply be operated as on/off valves to provide cooled or un-cooled gas flow. 
     Accordingly, the example EGR system  10  provides control of exhaust gas flow and temperature by selectively controlling gas flow through parallel cooled and un-cooled passages. 
     Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.