Abstract:
An exhaust gas recirculation system including an intake passage, an exhaust passage joining the intake passage at a junction and in fluid communication with the intake passage, and a closing member having a first position and a second position. When in the first position, the closing member blocks fluid communication between the intake passage and the exhaust passage. When in the second position, the closing member permits fluid communication between the intake passage and the exhaust passage and creates a pressure differential across the junction so that the fluid is either drawn or forced into the intake passage.

Description:
This application claims priority of copending provisional application(s) No. 60/297,111 filed on Jun. 8, 2001 which is hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     One conventional exhaust gas recirculation (EGR) system for compression ignition internal combustion engines uses two actuators. The first actuator creates a pressure differential in the intake passage that draws exhaust gas from the exhaust passage into the intake passage where it mixes with the intake charge. The second actuator regulates the flow rate of exhaust gas in the exhaust passage that is drawn into the intake passage by the first actuator. 
     Another conventional EGR system employs a single actuator to regulate the flow rate of exhaust gas drawn into the intake passage from the exhaust passage. A stationary throttling device is located in the exhaust passage to promote the flow of exhaust gas into the intake passage. The negative pressure pre-existing in the intake passage created during the intake stroke of the engine provides the pressure differential needed to draw the exhaust gas into the intake passage. 
     SUMMARY OF THE INVENTION 
     There is provided an exhaust gas recirculation system including an intake passage, an exhaust passage joining the intake passage at a junction and in fluid communication with the intake passage, and a closing member having a first position and a second position. When in the first position, the closing member blocks fluid communication between the intake passage and the exhaust passage. When in the second position, the closing member permits fluid communication between the intake passage and the exhaust passage and creates a pressure differential across the junction so that the fluid is either drawn or forced into the intake passage. 
     There is also provided an exhaust gas recirculation system including an intake passage, an exhaust passage in fluid communication with the intake passage, and a closing member movably mounted in the exhaust passage and having a first position and a second position. When in the first position, the closing member blocks fluid communication between the intake passage and the exhaust passage and is outside of a fluid stream of the exhaust passage when fluid is flowing through the exhaust passage. When in the second position, the closing member opens fluid communication between the intake passage and the exhaust passage and extends into the fluid stream of the exhaust passage when fluid is flowing through the exhaust passage. 
     There is yet also provided an exhaust gas recirculation system including an intake passage, an exhaust passage in fluid communication with the intake passage, a closing member having a first position and a second position, and a recess receiving the closing member when the closing member is in the first position. When in the first position, the closing member blocks fluid communication between the intake passage and the exhaust passage and is outside of a fluid stream of one of the intake passage and the exhaust passage when fluid is flowing through the one of the intake passage and the exhaust passage. When in the second position, the closing member opens fluid communication between the intake passage and the exhaust passage and extends into the fluid stream of the one of the intake passage and the exhaust passage when fluid is flowing through the one of the intake passage and the exhaust passage. The recess is in an inner wall of the one of the intake passage and the exhaust passage. 
     There is further provided a method for controlling exhaust gas recirculation for an internal combustion engine. The engine includes an exhaust passage in fluid communication with an intake passage and a port fluidly joining the intake passage and the exhaust passage. The method includes simultaneously positioning a closing member to open fluid communication between the intake passage to the exhaust passage and creating, with the closing member, a pressure differential across the port so that the fluid is either drawn or forced into the intake passage. 
     There is yet further provided a method for controlling exhaust gas recirculation for an internal combustion engine. The engine includes an exhaust passage selectively fluidly connected to an intake passage. The method includes forcing exhaust gas from the exhaust passage into the intake passage. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate an embodiment of the invention, and, together with the general description given above and the detailed description given below, serve to explain the features of the invention. 
         FIG. 1  is a schematic in accordance with a first embodiment of an exhaust gas recirculation system of an internal combustion engine according to the present invention. 
         FIG. 2  is a schematic of a valve assembly of the exhaust gas recirculation system of  FIG. 1 , where the valve assembly is in a first operating condition. 
         FIG. 3  is a schematic of the valve assembly of  FIG. 2  in a second operating condition. 
         FIG. 4  is a schematic in accordance with a second embodiment of an exhaust gas recirculation system of according to the invention. 
         FIG. 5  is a schematic of a valve assembly of the exhaust gas recirculation system of  FIG. 4 , where the valve assembly is in a first operating condition. 
         FIG. 6  is a schematic of the valve assembly of  FIG. 5  in a second operating condition. 
         FIG. 7  is a perspective view of an exhaust gas recirculation valve for use in the recirculation systems of FIGS.  1 - 6 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIGS. 1-3 , a first configuration of an exhaust gas recirculation system (EGR)  10  includes an intake passage  12 , an exhaust passage  14  in fluid communication with the intake passage  12  and a valve assembly  16  between the intake passage  12  and the exhaust passage  14  to selectively open and close the fluid communication between the intake passage  12  and the exhaust passage  14 . The EGR  10  can be used with an internal combustion engine  18  to control when and the amount of exhaust gas flowing in the exhaust passage  14  enters the intake passage  12  to mix with an intake charge flowing in the intake passage  12  on route to a combustion chamber (not shown) of the engine  18 . The EGR  10  can be used with a compression-ignition engine or a spark-ignition engine. Preferably, the EGR  10  is used in a compression-ignition engine. 
     Referring to  FIGS. 2 and 3 , the valve assembly  16  includes a closing member  20 , a port  22  fluidly connecting the exhaust passage to the intake passage  12 , and a drive assembly  24  for moving the closing member  20 . The closing member  20  performs two functions. First, it opens and closes the port  22  to selectively open and close the fluid communication between the intake passage  12  and the exhaust passage  14 . Second, after the closing member  20  opens the fluid communication between the intake passage  12  and the exhaust passage  14 , the closing member  20  meters the flow rate of exhaust gas that passes from the exhaust passage  14  to the intake passage  12 . 
     The drive assembly  24  includes a servo assembly  26  drivingly coupled to the closing member  20  and a servo controller  28  electrically connected to the servo assembly  26 , and a return spring  30  (FIG.  3 ). The return spring  30  biases the closing member  20  toward the port  22 . Preferably, the servo assembly  26  includes an electric motor drivingly coupled to a gear train. The servo controller  28  generates a drive signal and sends it to the servo actuator to move the closing member  20  from the first position to the second position. Preferably, the servo controller  28  follows a closed-loop algorithm using an engine performance data input and a door position input. Alternatively, the servo controller  28  can follow an open-loop algorithm and additional inputs can be provided to the servo controller  28 , such as transmission gear selection and vehicle inclination. 
     Comparing  FIGS. 2 and 3 , the closing member  20  is movable between a first position ( FIG. 2 ) where the closing member  20  blocks fluid communication between the intake passage  12  and the exhaust passage  14  and a second position ( FIG. 3 ) where the closing member  20  opens fluid communication between the intake passage  12  and the exhaust passage  14  and selectively meters the flow rate of exhaust gas passing into the intake passage  12 . The exhaust gas flows through the exhaust passage in the direction indicated by arrow EF. 
       FIGS. 2 and 3  schematically represent the closing member  20  as a door pivoting at one end about a rotary shaft  32 . Alternatively, the closing member  20  can be displaced in a different manner between the first position and the second position, such as sliding along a linear path. The servo assembly  26  can include any suitable driving mechanism that imparts the chosen pivoting motion, linear motion or other motion on the closing member, such as, an electric or pneumatic motor with or without and gear train, or a solenoid with or without a linkage. 
     When in the first position, as shown in  FIG. 2 , the closing member  20  sealingly engages a valve seat of the port  22  to seal the port  22  and block the flow of exhaust gas from the exhaust passage  14  into the intake passage  12 . A recess  36  receives the closing member  20  when the closing member  20  is in the first position. When the closing member  20  is in the recess  36 , the closing member  20  is outside of the fluid stream of exhaust gas flowing in the exhaust passage  14  and has a minimum influence on the exhaust gas stream. 
     When in the second position, as shown in  FIG. 3 , the closing member  20  is disengaged from the valve seat  34  to open the port  22  and permit fluid communication between the exhaust passage  14  and the intake passage  12 . In the second position, the closing member  20  extends away from intake passage  12  and extends into the exhaust gas stream flowing in the exhaust passage  14 . By extending into the exhaust gas stream, the closing member  20  creates a high pressure region HPE in the exhaust passage  14  that is upstream of and adjacent to the port  22  and an exhaust low pressure region LPE 1  in the exhaust passage  14  that is positioned downstream of the port  22 . The closing member  20  can vary the pressure value of the high pressure region HPE by the amount to which it extends into the exhaust gas stream. As will be explained below, by varying the pressure value of the high pressure region HPE, the closing member  20  can meter the volume of exhaust gas entering the intake passage  12 . 
     During the intake cycle of the engine, an intake low pressure region LPI 1  exists in the intake passage  12  that is less than the high pressure region HPE. The pressure differential between the high pressure region HPE in the exhaust passage  14  and the intake low pressure region LPI 1  in the intake passage  12  forces exhaust gas into the intake passage by pushing the exhaust gas from the exhaust passage  14  through the open port  22  and into the intake passage  12 . 
     The closing member  20  further includes an operative surface  38  that creates the high pressure region HPE. The extent to which of the operative surface  38  reaches into the exhaust gas stream controls the value of the high pressure region HPE and, thus, the pressure differential between the high pressure region HPE and the intake low pressure region LPI 1  during the intake cycle of the engine. The geometry of the operative surface  38  is, preferably, chosen to provide an optimum value for the high pressure region HPE. The selected geometry must balance with the capacity of the drive assembly  24  and the effect the operative surface has on flow restriction in the exhaust passage  14 . The drive assembly  24  should be of a configuration capable of generating sufficient force to move the closing member  20  between the first position and second position against the resistance created by the exhaust gas stream against the closing member  20  while simultaneously requiring a minimum packaging volume. The flow restriction should minimally affect back pressure exerted on the combustion chamber during the exhaust cycle and, thus, the power production of the engine  18 . 
     The amount of exhaust gas that enters the intake passage  12  is proportional to the pressure differential between the high pressure region HPE and the intake low pressure region LPI 1 . The pressure value of the intake low pressure region LPI 1  remains relatively steady over time. Thus, a change in the flow rate of exhaust gas in the intake passage  12  can be varied by varying the pressure value of the high pressure region HPE. 
     When the closing member  20  first opens, the closing member  20  reaches into a small amount of the exhaust gas stream and the high pressure region HPE has a value only slightly greater than that of the intake low pressure region LPI 1 . Accordingly, the pressure differential is small and the flow rate of exhaust gas through the port  20  and into the intake passage is correspondingly small. The pressure value of the high pressure region HPE, and thus the pressure difference and flow rate of exhaust gas passing through the port  22 , increases as the closing member  20  reaches farther into the exhaust gas stream flowing in the exhaust passage  14 . Therefore, closing member  20  opens fluid communication between the intake passage  12  and the exhaust passage  14  and the closing member  20  also meters the amount of exhaust gas passing into the intake passage  12 . 
     Referring to  FIGS. 4-6 , and similar to the first configuration the EGR  10  of  FIGS. 1-3 , a second configuration of an exhaust gas recirculation system (EGR)  110  includes an intake passage  112 , an exhaust passage  114  in fluid communication with the intake passage  112  and a valve assembly  116  between the intake passage  112  and the exhaust passage  114  to selectively open and close the fluid communication between the intake passage  112  and the exhaust passage  114 . The EGR  110  can be used with an internal combustion engine  118  to control when and the amount of exhaust gas flowing in the exhaust passage  114  enters the intake passage  112  to mix with an intake charge flowing in the intake passage  112  on route to a combustion chamber (not shown) of the engine  118 . The EGR  110  can be used with a compression-ignition engine or a spark-ignition engine. Preferably, the EGR  110  is used in a compression-ignition engine. 
     Referring to  FIGS. 5 and 6 , the valve assembly  116  includes a closing member  120 , a port  122  fluidly connecting the exhaust passage to the intake passage  112 , and a drive assembly  124  for moving the closing member  120 . The closing member  120  performs two functions. First, it opens and closes the port  122  to selectively open and close the fluid communication between the intake passage  112  and the exhaust passage  114 . Second, after the closing member  120  opens the fluid communication between the intake passage  112  and the exhaust passage  114 , the closing member  120  meters the flow rate of exhaust gas that passes from the exhaust passage  114  to the intake passage  112 . 
     The drive assembly  124  includes a servo assembly  126  drivingly coupled to the closing member  120  and a servo controller  128  electrically connected to the servo assembly  126 , and a return spring  130  (FIG.  6 ). The return spring  130  biases the closing member  120  toward the port  122 . Preferably, the servo assembly  126  includes an electric motor drivingly coupled to a gear train. The servo controller  128  generates a drive signal and sends it to the servo actuator  126  to move the closing member  120  from the first position to the second position. Preferably, the servo controller  28  follows a closed-loop algorithm using an engine performance data input and a door position input. Alternatively, the servo controller  128  can follow an open-loop algorithm and additional inputs can be provided to the servo controller  128 , such as transmission gear selection and vehicle inclination. 
     Comparing  FIGS. 5 and 6 , the closing member  120  is movable between a first position ( FIG. 5 ) where the closing member  120  blocks fluid communication between the intake passage  112  and the exhaust passage  114  and a second position ( FIG. 6 ) where the closing member  120  opens fluid communication between the intake passage  112  and the exhaust passage  114  and selectively meters the flow rate of exhaust gas passing into the intake passage  112 . The exhaust gas flows through the exhaust passage  114  in the direction indicated by arrow EF 2  and intake charge gas flows through the intake passage  112  in the direction of arrow IF. 
       FIGS. 5 and 6  schematically represent the closing member  120  as a door pivoting at one end about a rotary shaft  132 . Alternatively, the closing member  120  can be displaced in a different manner between the first position and the second position, such, as sliding along a linear path. The servo assembly  26  can include any suitable driving mechanism that imparts the chosen pivoting motion, linear motion or other motion on the closing member, such as, an electric or pneumatic motor with or without and gear train, or a solenoid with or without a linkage. 
     When in the first position, as shown in  FIG. 5 , the closing member  120  sealingly engages a valve seat  134  of the port  122  to seal the port  122  and block the flow of exhaust gas from the exhaust passage  114  into the intake passage  112 . A recess  136  receives the closing member  120  when the closing member  120  is in the first position. When the closing member  120  is in the recess  136 , the closing member  120  is outside of the fluid stream of intake charge gas flowing in the intake passage  112  and has a minimum influence on the intake charge gas stream. 
     When in the second position, as shown in  FIG. 6 , the closing member  120  is disengaged from the valve seat  134  to open the port  122  and permit fluid communication between the exhaust passage  114  and the intake passage  112 . In the second position, the closing member  120  extends away from the exhaust passage  114  extends into the intake charge gas stream flowing in the exhaust passage  114 . By extending into the intake charge gas stream, the closing member  120  creates a high pressure region HPI in the intake passage  112  that is upstream of the port  122  and intake low pressure region LPI 2  in the intake passage  112  that is positioned downstream of and adjacent to the port  122 . The closing member  120  can vary the pressure value of the intake low pressure region LPI 2  by the amount to which it extends into the intake charge gas stream. As will be explained below, by varying the pressure value of the intake low pressure region LPI 2 , the closing member  120  can meter the volume of exhaust gas entering the intake passage  112 . 
     During the intake cycle of the engine, the exhaust passage  114  has a low pressure region LPE 2  that is approximately equal to ambient atmospheric pressure and a vacuum pressure that is much less than of the ambient atmospheric pressure generated at the junction of the intake passage  112  and the combustion chamber (not shown) of the engine  118 . The closing member  120  further includes an operative surface  138  that creates the intake low pressure region LPI 2 . The extent to which of the operative surface  138  reaches into the exhaust gas stream controls the value of the intake low pressure region LPI 2  and, thus, the pressure differential between the exhaust low pressure region LPE 2  and the intake low pressure region LPI 1  during the intake cycle of the engine. The geometry of the operative surface  138  is, preferably, chosen to provide an optimum value for the intake low pressure region LPI 2 . The selected geometry must balance with the capacity of the drive assembly  124  and the effect the operative surface has on flow restriction in the intake passage  112 . The drive assembly  124  should be of a configuration capable of generating sufficient force to move the closing member  120  between the first position and second position against the resistance created by the intake charge gas stream against the closing member  120  while simultaneously requiring a minimum packaging volume. The flow restriction should minimally affect the flow of intake charge gas to the combustion chamber during the intake cycle and, thus, the power production of the engine  118 . 
     The pressure of the intake charge gas in the intake passage  112  is approximately equal to ambient atmospheric pressure when the closing member  120  is in the first position (FIG.  5 ). As the closing member  120  moves away from the port  122  and toward the second position (FIG.  6 ), the intake low pressure region LPI 2  is created adjacent the port  122  and has a value slightly less than that of the ambient atmospheric pressure. As the closing member  120  moves farther into the intake charge stream toward the second position, the value of the intake low pressure region LPI 2  approaches that of the vacuum pressure. The pressure differential between the intake low pressure region LPI 2  in the intake passage  112  and the exhaust low pressure region LPE 2  in the exhaust passage  114  forces exhaust gas into the intake passage  112  by drawing the exhaust gas from the exhaust passage  114  through the open port  122  and into the intake passage  112 . The amount of exhaust gas that enters the intake passage  112  is proportional to the pressure differential between the intake low pressure region LPI 2  and the exhaust low pressure region LPE 2 . The pressure value of the exhaust low pressure region LPE 2  remains relatively steady over time. Thus, a change in the flow rate of exhaust gas in the intake passage  112  can be varied by varying the pressure value of the intake low pressure region LPI 2 . 
     The extent to which of the closing member  120  reaches into the exhaust gas stream controls the value of the intake low pressure region LPI 2  and, thus, the pressure differential between the intake low pressure region LPI 2  and the exhaust low pressure region LPE 2  during the intake cycle of the engine. When the closing member  120  first opens, the closing member  120  reaches into a small amount of the intake charge gas stream and the intake low pressure region LPI 2  has a value only slightly less than that of the exhaust low pressure region LPE 2 . Accordingly, the pressure differential is small and the flow rate of exhaust gas through the port  122  and into the intake passage  112  is correspondingly small. The pressure value of the intake low pressure region LPI 2 , and thus the pressure difference and flow rate of exhaust gas passing through the port  122 , increases as the closing member  118  reaches farther into the intake charge gas stream flowing in the intake passage  112 . Therefore, closing member  120  opens fluid communication between the intake passage  112  and the exhaust passage  114  and the closing member  120  also meters the amount of exhaust gas passing into the intake passage  112 . 
       FIG. 7  illustrates an embodiment of the valve assembly  200  schematically represented in  FIGS. 1-6 . The valve assembly  200  includes a mounting flange  202  adapted for connection to one of intake passage  12 ,  112  and the exhaust passage  14 ,  114 , a conduit portion  204  extending from the mounting flange  202 , a closing member  206  movably mounted on the mounting flange  202 , and a drive assembly  208  supported on the mounting flange  202  and drivingly engaging the closing member  206 . 
     The mounting flange  202  includes a port  210  in fluid communication with the conduit portion  204 . The port  210  is in fluid communication with the exhaust passage  14 ,  114  and the intake passage when the mounting flange  202  is mounted to the other of the intake passage  12 ,  112  and the exhaust passage  14 ,  114  as described above with reference to  FIGS. 1-6 . The port  210  includes a valve seat  214  located at the periphery of the port  210 . 
     The closing member  206  moves between a first position where the closing member  206  blocks fluid communication between the intake passage  12 ,  112  and the exhaust passage  14 ,  114  and a second position where the closing member  206  opens fluid communication between the intake passage  12 ,  112  and the exhaust passage  14 ,  114  and selectively meters the flow rate exhaust gas passing into the intake passage  12 ,  112 . To better view the details of the valve assembly,  FIG. 7  shows the closing member  206  in the second position represented in  FIGS. 3 and 6 . 
     The closing member  206  includes a flapper door  214 ; a seal  216  on the flapper door, and a rotary shaft  218  pivotally coupling the flapper door  214  to the mounting flange  202 . The flapper door  214  has a rectangular base  215  and a semicircular end  217 . The rectangular base  215  of the flapper door  214  is fixed to the rotary shaft  218 . The seal  216  matingly engages the valve seat  212  when the closing member  206  is in the first position to sealingly block the port  210  and close fluid communication between the intake passage  12 ,  112  and the exhaust passage  14 ,  114  (see FIGS.  2  and  5 ). 
     The mounting flange  202  includes a recess  220  directed toward the fluid stream of one of the intake passage  12 ,  112  and the exhaust passage  14 ,  114 . The recess  220  is recessed from the inner wall of one of the intake passage  12  and the exhaust passage  14  and the closing member  206  is received in the recess  220  when the closing member  206  is in the first position (see FIGS.  2  and  5 ). 
     The conduit portion  204  includes a connecting flange  222  at the end spaced from the mounting flange  202 . The connecting flange  222  is connectable to the other of the intake passage  12 ,  112  and the exhaust passage  14 ,  114 . Preferably, the conduit portion  204  extends from the mounting flange  202  at an oblique angle. 
     Alternatively, the conduit portion  204  can extend from the mounting flange  202  at any angle or the conduit portion  204  can extend from the mounting flange  202  in a curved manner. It is possible to omit the conduit portion  204  as an integral component of the valve assembly  200  and provide a connecting flange directly on the mounting flange  202  on the side opposite to the face  220 . A separate conduit can be secured to this alternate connecting flange. This can provide greater flexibility for packaging and assembling the EGR  10 . 
     A drive housing  224  is attached to the mounting flange  202 . The drive housing  224  contains the servo assembly (e.g.,  26  of  FIG. 2 ) and a servo controller (e.g.,  28  of  FIG. 2 ) electrically connected to the servo assembly. The drive housing  224  includes an electrical connector  226  for attachment to an electrical power supply (not shown) and electrically connected to the servo controller. 
     As described with reference to  FIGS. 2 ,  3 ,  5  and  6 , above, the servo assembly is drivingly coupled to the rotary shaft  218  and pivots the closing member  206  between the first position and the second position based on a drive signal received from the servo controller, as explained above with reference to  FIGS. 1-6 . 
     While the present invention has been disclosed with reference to certain embodiments, numerous modifications, alterations and changes to the described embodiments are possible without departing from the sphere and scope of the present invention, as defined in the appended claims. Accordingly, it is intended that the present invention not be limited to the described embodiments, but that it has the full scope defined by the language of the following claims, and equivalents thereof.