Patent Publication Number: US-6907868-B2

Title: Modular exhaust gas recirculation assembly

Description:
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 conduit that draws exhaust gas from the exhaust conduit into the intake conduit where it mixes with the intake charge. The second actuator regulates the flow rate of exhaust gas in the exhaust conduit that is drawn into the intake conduit by the first actuator. 
     Another conventional EGR system employs a single actuator to regulate the flow rate of exhaust gas drawn into the intake conduit from the exhaust conduit. A stationary throttling device is located in the exhaust conduit to promote the flow of exhaust gas into the intake conduit. The negative pressure pre-existing in the intake conduit created during the intake stroke of the engine provides the pressure differential needed to draw the exhaust gas into the intake conduit. 
     SUMMARY OF THE INVENTION 
     There is provided a modular exhaust gas recirculation assembly includes a flow control body, a closing member movably mounted in the manifold conduit between a first position and a second position, and an actuator assembly coupled to the closing member and driving the closing member between the first position and the second position. The flow control body includes a manifold conduit and an inlet conduit in fluid communication with the manifold conduit. The manifold conduit includes manifold conduit a recirculation opening, a first open end having a first cross-sectional shape, and a second open end having a second cross-sectional shape. The closing member includes a boundary defining an operative surface. The boundary has a configuration that is different from the first cross-sectional shape and the second cross-sectional shape. When in the first position, the closing member closes the recirculation opening and blocks fluid communication between the inlet conduit and the manifold conduit. When in the second position, the closing member opens the recirculation opening and permits fluid communication between the inlet conduit and the manifold conduit such that the operative surface creates a pressure differential across the recirculation opening so that fluid is drawn from the inlet conduit into the manifold conduit. 
     There is also provided a modular exhaust gas recirculation assembly including a flow control body having a manifold conduit and an inlet conduit, an actuator receptacle along at least a portion of one of the manifold conduit and the inlet conduit, a closing member movably mounted in the manifold conduit between a first position and a second position, an actuator assembly contained in the actuator receptacle, and an actuator cover extending over the actuator assembly and connected to the actuator receptacle to enclose the actuator assembly. The manifold conduit includes an inner surface defining a fluid passageway. The inlet conduit is in fluid communication with the manifold conduit and extends perpendicularly from the manifold conduit. The closing member is movably mounted in the manifold conduit between a first position where the closing member lies adjacent to the inner surface the manifold conduit and blocks fluid communication between the manifold conduit and the inlet conduit, and a second position where the closing member extends into the fluid passageway of the manifold conduit and opens fluid communication between the manifold conduit and the inlet conduit such that when fluid is flowing through the manifold conduit fluid flowing in the inlet conduit is drawn into the manifold conduit. The actuator assembly is coupled to the closing member and drives the closing member between the first position and the second position. 
    
    
     
       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 an EGR system of an internal combustion engine according to the present invention. 
         FIG. 2  is a schematic of the EGR system of  FIG. 1  with the closing member in a first operating condition. 
         FIG. 3  is a schematic of the EGR system of  FIG. 1  with the closing member in a second operating condition. 
         FIG. 4  is a perspective view of an embodiment of an exhaust gas recirculation assembly for an EGR according to the invention. 
         FIG. 5  is an end view of the flow control body according to FIG.  4 . 
         FIG. 6  is a bottom view of the flow control body according to FIG.  4 . 
         FIG. 7  is a perspective view of a torque motor for mounting in the flow control body according to FIG.  4 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIGS. 1-3 , a first configuration of an exhaust gas recirculation (EGR) system  10  includes an intake conduit  12 , an exhaust conduit  14  in fluid communication with the intake conduit  12  and a flow control body  16  between the intake conduit  12  and the exhaust conduit  14  to selectively open and close the fluid communication between the intake conduit  12  and the exhaust conduit  14 . The intake conduit  12  can be a manifold in fluid communication with a plurality of combustion chambers (not shown) of an internal combustion engine  18 . The exhaust conduit  14  can include an exhaust manifold  20  in fluid communication with the combustion chambers of the internal combustion engine  18  and a recirculation conduit  22  in fluid communication with the exhaust manifold  18  and the flow control body  16 . 
     The EGR system  10  can be used with the internal combustion engine  18  to control the emissions of the engine  18  when the amount of exhaust gas flowing in the exhaust conduit  14  enters the intake conduit  12  to mix with an intake charge flowing in the intake conduit  12  on route to a combustion chamber (not shown) of the engine  18 . The EGR system  10  can be used with a compression-ignition engine or a spark-ignition engine. Preferably, the EGR system  10  is used in a compression-ignition engine. 
     Referring to  FIGS. 2 and 3 , the flow control body  16  includes a manifold conduit  24  in fluid communication with the intake conduit  12  and an inlet conduit  26  in fluid communication with the manifold conduit  24  and the recirculation conduit  22  of the exhaust conduit  14 . The manifold conduit  24  includes a recirculation opening  28  and an inner surface  30  defining a fluid passageway  32 . 
     A closing member  34  is movably mounted in the manifold conduit  24 . The closing member  34  performs two functions. First, it opens and closes the recirculation opening  28  to selectively open and close the fluid communication between the intake conduit  12  and the exhaust conduit  14 . Second, after the closing member  34  opens the fluid communication between the intake conduit  12  and the exhaust conduit  14 , the closing member  34  meters the flow rate of exhaust gas that passes from the exhaust conduit  14  to the intake conduit  12 . 
     An actuator assembly  36  includes a servo assembly  38  drivingly coupled to the closing member  34  and a servo controller  40  electrically connected to the servo assembly  38  and a return spring  42  biasing the closing member  34  toward the recirculation opening  28 . Preferably, the servo assembly  38  includes an electric motor (not shown) drivingly coupled to a gear train (not shown). The servo controller  40  generates an actuator signal and sends it to the servo assembly  38  to move the closing member  34  from the first position to the second position. Preferably, the servo controller  40  follows a closed-loop algorithm using an engine performance data input and a door position input. Alternatively, the servo controller  40  can follow an open-loop algorithm and additional inputs can be provided to the servo controller  40 , such as transmission gear selection and vehicle inclination. 
     Comparing  FIGS. 2 and 3 , the closing member  34  is movable between a first position ( FIG. 2 ) where the closing member  34  blocks fluid communication between the intake conduit  12  and the exhaust conduit  14  and a second position ( FIG. 3 ) where the closing member  34  opens fluid communication between the intake conduit  12  and the exhaust conduit  14  and selectively meters the flow rate of exhaust gas passing into the intake conduit  12 . The exhaust gas flows through the recirculation conduit  22  in the direction indicated by arrow EF. 
       FIGS. 2 and 3  schematically represent the closing member  34  as a door pivoting at one end about a rotary shaft  44 . Alternatively, the closing member  34  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  38  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 a gear train, or a solenoid with or without a linkage. 
     When in the first position, as shown in  FIG. 2 , the closing member  34  lies adjacent the inner surface  30  of the intake conduit  12  and engages a seat  46  surrounding the recirculation opening  28  to seal the recirculation opening  28  and block the flow of exhaust gas from the recirculation conduit  22  into the intake conduit  12 . Preferably, the closing member  34  is positioned in the fluid passageway  32  to minimize disturbance by the closing member  34  of the fluid flowing in the fluid passageway  32  when the closing member  34  is in the first position. As shown in  FIGS. 2 and 3 , this can be achieved by providing a recess  48  at a location in the inner surface  30  which surrounds the recirculation opening  28 . The recess  48  receives the closing member  34  so that the closing member  34  lies approximately coplanar with the inner surface  30  when the closing member  34  is in the first position. Alternatively, a ramp can be providing on the inner surface  30  that diverts the fluid flowing in the fluid passageway  32  over the closing member  34 . 
     When in the second position, as shown in  FIG. 3 , the closing member  34  is disengaged from the valve seat  46  to open the recirculation opening  28  and permit fluid communication between the recirculation conduit  22  and the intake conduit  12 . In the second position, the closing member  34  extends away from recirculation conduit  22  and extends into the fluid passageway  32  to affect the fluid flowing in the intake conduit  12 . By extending into the fluid passageway  32 , the closing member  22  creates a high pressure region HPI in the intake passage  12  that is upstream of the recirculation opening  28  and an intake low pressure region LPI in the intake conduit  12  that is downstream of and adjacent to the recirculation opening  28 . The closing member  34  can vary the pressure value of the intake low pressure region LPI by the amount to which it extends into the fluid passageway  32 . As will be explained below, by varying the pressure value of the intake low pressure region LPI, the closing member  34  can meter the volume of exhaust gas entering the intake conduit  12  from the recirculation conduit  22 . 
     During the intake cycle of the engine, the exhaust conduit  14  has a low pressure region LPE that is approximately equal to ambient atmospheric pressure. The closing member  34  further includes an operative surface  50  that causes the fluid flowing in the fluid passageway  32  to separate from a portion of the inner surface  30  adjacent the recirculation opening  28 . This separation creates the intake low pressure region LPI. When the closing member  34  initially extends into the fluid passageway  32  (e.g., 10 degrees relative to a plane containing the recirculation opening), partial separation of the fluid occurs and the value of the intake low pressure region LPI is less than a maximum value. When the closing member extends far enough into the fluid passageway  32  to cause full separation (e.g., 35 degrees relative to a plane containing the recirculation opening), then the value of the intake low pressure region LPI reaches a maximum value. Thus, the extent to which of the operative surface  50  reaches into the fluid passageway  32  controls the value of the intake low pressure region LPI and, thus, the pressure differential between the exhaust low pressure region LPE and the intake low pressure region LPI during the intake cycle of the engine  18 . 
     The geometry of the operative surface  50  is, preferably, different in shape than the boundary configuration of the fluid passageway  32  to provide an adequate value for the intake low pressure region LPI and to promote mixing of the exhaust gas from the exhaust conduit  14  with the fluid flowing in the fluid passageway  32 . Preferably, the exhaust gas is mixed with the fluid flowing in the fluid passageway  32  so that each combustion chamber (not shown) of the engine receives at least some of the exhaust gas passing through the recirculation opening  28 . The selected geometry must balance with the capacity of the actuator assembly  36  and the effect the operative surface  50  has on flow restriction in the intake conduit  12 . The actuator assembly  36  should be of a configuration capable of generating sufficient force to move the closing member  34  between the first position and second position against the resistance created by the fluid flowing in the fluid passageway  32  against the closing member  34  while simultaneously requiring a minimum packaging volume. It is preferred that the restriction of the fluid passageway  32  by the closing member  34  minimally affect the fluid flowing through the fluid passageway  32  to the combustion chamber during the intake cycle and, thus, the power production of the engine  18 . 
     The geometry of the operative surface  50  and the relationship between the angle of the closing member  34  and the amount of exhaust gas that enters the fluid passageway  32  are described in the U.S. patent application filed on Nov. 8, 2002, entitled “Apparatus and Method for Exhaust Gas Flow Management of an Exhaust Gas Recirculation system,” U.S. application Ser. No. 10/290,497, which application is hereby incorporated by reference. 
     The pressure of the fluid flowing in the intake conduit  12  is approximately equal to ambient atmospheric pressure if the engine is a normally aspirated engine and is greater than ambient atmospheric pressure if the engine is a turbocharged engine. As the closing member  34  moves away from the recirculation conduit  22  and toward the second position (FIG.  3 ), the intake low pressure region LPI is created adjacent the recirculation opening  28  and has a value slightly less than that of the ambient atmospheric pressure. As the closing member  34  moves farther into the fluid passageway toward the second position, the value of the intake low pressure region LPI approaches vacuum pressure. The pressure differential between the intake low pressure region LPI in the intake conduit  12  and the exhaust low pressure region LPE in the recirculation conduit  22  draws exhaust gas from the exhaust conduit  14  into the intake conduit  12  through the recirculation opening  28 . The amount of exhaust gas that enters the intake conduit  12  is proportional to the pressure differential between the intake low pressure region LPI and the exhaust low pressure region LPE. The pressure value of the exhaust low pressure region LPE remains relatively steady over time. Thus, a change in the flow rate of exhaust gas in the intake conduit  12  can be varied by varying the pressure value of the intake low pressure region LPI. 
     The extent to which of the closing member  34  reaches into the fluid passageway controls the value of the intake low pressure region LPI and, thus, the pressure differential between the intake low pressure region LPI and the exhaust low pressure region LPE during the intake cycle of the engine. When the closing member  34  first opens, the closing member  34  reaches into the fluid passageway  32  by a small amount and the intake low pressure region LPI has a value only slightly less than that of the exhaust low pressure region LPE. Accordingly, the pressure differential is small and the flow rate of exhaust gas through the recirculation opening  28  and into the intake conduit  12  is correspondingly small. The pressure value of the intake low pressure region LPI, and thus the pressure difference and flow rate of exhaust gas passing through the recirculation opening  28 , increases as the closing member  34  reaches farther into the fluid passageway  32  of the manifold conduit  24 . Therefore, closing member  34  opens fluid communication between the intake conduit  12  and the exhaust conduit  14  and the closing member  34  also meters the amount of exhaust gas passing into the intake conduit  12 . 
       FIGS. 4-6  illustrate an embodiment of a modular exhaust gas recirculation assembly  100  according to the EGR system  10  schematically represented in  FIGS. 1-3 . The modular exhaust gas recirculation assembly  100  integrates a flow control body  116 , a closing member  134 , and an actuator assembly  136  into a modular unit. The modular exhaust gas recirculation assembly  100  can be configured as a single component for assembly with the engine  18  (FIG.  1 ). This can reduce the part count for the engine  18  (FIG.  1 ). The modular exhaust gas recirculation assembly  100  is assembled to the engine  18  ( FIG. 1 ) by connecting the modular exhaust gas recirculation assembly  100  to each of the intake conduit  12  and the exhaust conduit  14  (see  FIG. 1 ) and the number of assembly steps can be minimized because the number of components for assembly is reduced. 
     The flow control body  116  includes a manifold conduit  124  and an inlet conduit  126  in fluid communication with the manifold conduit  124 . As described above with reference to  FIGS. 1-3 , the manifold conduit  124  can be placed in fluid communication with an intake conduit (e.g., at  12  in  FIGS. 1-3 ) and the inlet conduit  126  can be placed in fluid communication with a recirculation conduit of the exhaust conduit (e.g.,  22  and  14  in FIGS.  1 - 3 ). 
     Referring to  FIG. 4 , the manifold conduit  124  includes a recirculation opening  128  and an inner surface  130  defining a fluid passageway  132 . The recirculation opening  128  is in fluid communication with the inlet conduit  126 . The inner surface  130  extends from a first open end  152  to a second open end  154 . As shown in  FIGS. 4 and 5 , the first open end  152  and the second open  154  end each include a circular cross-sectional shape. 
     Referring to  FIGS. 4-6 , the inlet conduit  126  extends perpendicular to the manifold conduit  124  from the recirculation opening  128  to a third open end  156 . The third open end  156  is adjacent to and perpendicular to the second open end  154  of the manifold conduit  124  and includes a circular cross-sectional shape. 
     A closing member  134  is movably mounted in the manifold conduit  124  between a first position ( FIG. 6 ) where the closing member  134  seals the recirculation opening  128  and blocks fluid communication between the intake conduit and the exhaust conduit and a second position ( FIG. 4 ) where the closing member  134  opens recirculation opening  128  and permits fluid communication between the intake conduit and the exhaust conduit and selectively meters the flow rate exhaust gas passing into the intake conduit. 
     Referring to  FIGS. 4 and 6 , the closing member  134  includes a flapper door  162 , a seal  164  on the flapper door  162 , and a rotary shaft  144  pivotally coupling the flapper door  162  to the flow control body  116 . The flapper door  162  has a rectangular base  166  (in phantom in  FIG. 6 ) and a semicircular end  168  (in phantom in FIG.  6 ). The rectangular base  166  of the flapper door  162  is fixed to the rotary shaft  144 . Referring to  FIGS. 4 and 6 , a cylindrical projection  170  extends from flapper door  162  adjacent the semicircular end  168 . As shown in  FIG. 4 , the seal  164  is mounted about the periphery of a cylindrical projection  170 . 
     Referring to  FIGS. 4 and 6 , when the flapper door  162  is in the first position (FIG.  6 ), the cylindrical projection  170  extends through the recirculation opening  128  and the seal  164  engages the seat  146  (not shown) to block the recirculation opening  128  and close fluid communication between the intake conduit and the exhaust conduit. The flapper door  162  pivots about the rotary shaft  144  to the second position ( FIG. 4 ) such that the flapper door  162  extends away from the recirculation opening  128  and into the fluid passageway  132 . 
     The flapper door  162  also includes a boundary  167  ( FIG. 6 ) that defines an operative face  150  (FIG.  4 ). Comparing  FIGS. 4 and 6 , the boundary  167  has a configuration that is different than the circular cross-sectional shape of the first open end  152  and the second open end  154 . The fluid flowing in the manifold conduit  124  strikes the operative face  150  when the flapper door  162  is in the second position to create the low pressure region, as described with reference to FIG.  3 . 
     Referring to  FIG. 4 , a recess  148  is located in the fluid passageway  132  of the manifold conduit  124  and surrounds the recirculation opening  128 . The recess  148  is planar and is sized to accommodate the flapper door  162  when the flapper door  162  is in the first position. The planar recess  148  in the cylindrical fluid passageway  132  permits the flapper door  162  to fully engage the seat  146  of the recirculation opening  128  when the closing member is in the first position with only a minimum of disturbance to the flow flowing through the fluid passageway  132 . 
     Other arrangements are possible to minimize disturbance by the closing member  134  of the fluid flowing through the fluid passageway  132  when the closing member  134  is in the first position, such a, providing a ramp in the inner surface  130  adjacent to the rotary shaft  144  to smoothly deflect fluid around the closing member  134 . 
     Referring to  FIGS. 4-6 , the flow control body  116  also can include an actuator receptacle  174  extending from the manifold conduit  124 . The actuator assembly  136  is received in the actuator receptacle  174  and is coupled to the rotary shaft  144 . The actuator assembly  136  drives the rotary shaft  144  and moves the closing member  134  between the first position and the second position against the bias of the return spring  142 . As shown in  FIGS. 5 and 6 , an actuator cover  176  extends over the actuator assembly  136  and connects to the actuator receptacle  174  to enclose the actuator assembly  136 . The actuator cover  176  can include an electrical receptacle  178  electrically connected to the servo controller. The actuator cover  176  and the electrical receptacle  178  are removed from  FIG. 4  to show the details of the actuator assembly  138 . 
     Referring to  FIG. 4 , the actuator assembly  136  includes a servo assembly  138  drivingly coupled to the closing member  134  and a servo controller (not shown) electrically connected to the servo assembly  138 , and a return spring (not shown) connected to the closing member  134 . The return spring is located inside the actuator receptacle  174  and concealed from view if  FIGS. 4-6 . The return spring biases the closing member  134  toward the first position. Preferably, the return spring includes a torsion spring coiled about the rotary shaft  144  with one end secured to the rotary shaft  144  and the other end secured to the flow control body  116 . With reference to  FIGS. 4 and 7 , it is preferred that the servo assembly  138  includes an electric torque motor  180  and a shaft mount  181 . The rotary shaft  144  is received in the shaft mount  182 , which is driven by the electric torque motor  180 . Alternatively, the servo assembly  138  can include other driving arrangements, such as, an electric torque motor with a gear train, a d.c. motor with or without a gear train, a pneumatic actuator, a hydraulic actuator, or a solenoid with or without a linkage. 
     The servo controller generates an actuator signal and sends it to the servo assembly  138  to move the closing member  134  from the first position to the second position. Preferably, the servo controller follows a closed-loop algorithm using an engine performance data input and a door position input. Alternatively, the servo controller can follow an open-loop algorithm and additional inputs can be provided to the servo controller, such as transmission gear selection and vehicle inclination. 
     As shown in  FIGS. 4-6 , it is preferable to include a manifold bolt flange  184  about the perimeter of the second open end  154  and an inlet bolt flange  186  about the perimeter of the third open end  156 . The bolt flanges  184 ,  186  are adapted to receive bolts for securing the flow control body  116  to the intake conduit and the recirculation conduit. Alternatively, other arrangements can be used to secure the flow control body  116  to the intake conduit and the recirculation conduit, such as, clamps, crimped flanges, solder, and flexible conduit. 
     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.