Patent Publication Number: US-2023140167-A1

Title: Compact egr valve

Description:
BACKGROUND 
     Aspects of the disclosure relate to a compact exhaust gas recirculation (EGR) valve. 
     It is well known in the field of automotive engineering and in particular in connection with emissions and fuel efficiency improvements in internal combustion engines to provide an exhaust-gas recirculation system. An EGR valve regulates the flow of exhaust gases to the engine intake system, resulting in increased engine efficiency, reduced fuel consumption and lower nitrogen oxide pollutant emissions. EGR valves operate in a high heat environment and are exposed to exhaust gasses that can accumulate carbon deposits on the valve, resulting in failure. 
     SUMMARY OF THE INVENTION 
     A compact EGR valve uses a BLDC motor to drive a valve member between a closed position blocking flow of exhaust gases and an open position where exhaust gasses flow through the valve. A drive mechanism includes a nut in a fixed position and a screw arranged to rotate within the nut so that rotation of the screw causes the screw to move axially relative to the nut. The screw is coupled to a valve member so that the valve member moves axially and rotationally with the screw. The shaft of the motor has at least one flat or non-round feature that applies rotational force to the screw, and the cross-sectional configuration of the shaft is constant, allowing the screw to slide along the length of the shaft as the screw moves axially relative to the nut and motor. The valve member has a cylindrical side surface that is guided within a cylindrical portion of a valve chamber. Rotation of the valve member within the valve chamber during axial movement aids in removal of deposits that may accumulate within the valve housing. 
     According to a preferred embodiment, the inlet to the valve chamber is rectangular and laterally offset from a longitudinal axis of the valve chamber. The valve chamber includes a hemispherical portion extending from the cylindrical portion and the outlet opening of the valve is at least partially defined in the hemispherical portion of the valve chamber. 
     A disclosed valve comprises a valve housing defining a valve chamber with an inlet opening communicating with a cylindrical portion of the valve chamber and an outlet opening communicating with the cylindrical portion of the valve chamber. A valve member having a cylindrical side wall and an annular leading edge is arranged in the cylindrical portion of the valve chamber. The valve member is moveable between a closed position where the cylindrical side wall covers the inlet opening and a range of open positions where the cylindrical side wall does not cover the inlet opening. 
     An embodiment of the disclosed valve includes a drive mechanism including a screw coupled to the valve member for axial and rotational movement with the valve member, said screw having a first thread on an outside surface and defining an axial bore. A nut secured in a fixed position and having a second thread engaged with the first thread so that rotation of the screw moves the screw and the valve member axially relative to the nut while rotating the valve member within the cylindrical portion of the valve chamber. 
     A motor has a shaft received within the screw, the shaft having a constant non-round configuration along its length, said motor shaft received in the bore defined by the screw. Rotation of the motor shaft rotates the screw relative to the nut to move the screw and valve member axially relative to the nut and motor. The screw sliding along the shaft as the valve member moves axially between the closed position and the open position, said valve member rotating with the motor shaft and screw during axial movement. 
     The disclosure also includes a method of regulating gas flow through a valve comprising simultaneously rotating and moving a valve member having a cylindrical side wall in a cylindrical valve chamber between a closed position wherein the cylindrical side wall covers a radial opening in the cylindrical valve chamber and a range of open positions wherein the cylindrical side wall uncovers at least a portion of the radial opening in the cylindrical valve chamber. The cylindrical valve member includes an annular leading edge that removes deposits from an inside surface of the cylindrical valve chamber as the valve member rotates and moves axially from the range of open positions to the closed position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee. 
       The application contains three drawings,  FIGS.  10 - 12   , executed in color. Copies of this patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee. 
         FIG.  1    is an exterior perspective view of an embodiment of a compact EGR valve according to aspects of the disclosure; 
         FIG.  2    is an exterior perspective view of the compact EGR valve of  FIG.  1    with the valve body removed, showing the valve member in a retracted position; 
         FIG.  3    is an exterior perspective view of the compact EGR valve of  FIG.  2    with the valve member and mechanism for controlling movement of the valve member removed showing the motor shaft with two longitudinally extending flat surfaces; 
         FIG.  4    is an exterior perspective view of the compact EGR valve of  FIG.  3    showing a screw arranged to slide axially on the motor shaft; 
         FIG.  5    is an exterior perspective view of the compact EGR valve of  FIG.  4    showing a nut fixed to the motor and surrounding the screw so that rotation of the screw by the motor shaft generates rotational and axial movement of the screw relative to the nut; 
         FIG.  6    is a longitudinal sectional view through a compact EGR valve according to aspects of the disclosure; 
         FIG.  7    is an exploded perspective view of the compact EGR valve of  FIG.  6   ; 
         FIG.  8    is a longitudinal sectional view of an embodiment of a compact EGR valve illustrating a second opening to the valve chamber where the second opening is aligned with an axis of rotation of the valve member; 
         FIG.  9    is a longitudinal sectional view of an embodiment of a compact EGR valve illustrating a second opening to the valve chamber where the second opening has a radial orientation relative to the rotational axis of the valve member; 
         FIG.  10    is a longitudinal sectional view through the compact EGR valve of  FIG.  9    showing the velocity of gas flow through the valve housing; 
         FIG.  11    is a model of a non-preferred valve housing configuration showing pressure drop from the inlet to the outlet of the valve housing; 
         FIG.  12    is a model of a preferred valve housing configuration according to aspects of the disclosure showing reduced pressure drop from the inlet to the outlet of the valve housing; and 
         FIG.  13    is a model of the interior of a valve housing having the configuration and flow characteristics of the valve housing model shown in  FIG.  12   . 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of a compact EGR valve will be described with reference to  FIGS.  1 - 13   .  FIG.  1    is an exterior perspective view of an embodiment of a compact EGR valve  10  according to aspects of the disclosure. The compact EGR valve  10  includes a motor assembly  12  and a valve housing  14  configured to attach the compact EGR valve  10  to exhaust flow passages in an internal combustion engine (not shown). The motor assembly  12  includes a brushless direct current (BLDC) motor  32  surrounded by a cooling jacket  16  through which engine coolant is circulated to cool the BLDC motor  32 . An end cap  18  covers a torsion spring  50  connected to one end of a shaft  34  of the BLDC motor to counterrotate the rotor  33  of the BLDC motor  32  to return the valve member to a closed position when power is removed from the BLCD motor. Cooling fittings  20  connect the cooling jacket  16  to the coolant circulation system of the internal combustion engine (not shown). The motor assembly  12  includes the BLDC motor, cooling jacket  16 , end cap  18 , torsion spring  50 , and cooling fittings  20 . The construction and function of a BLDC motor is well-understood and need not be explained in detail here. For the purposes of this disclosure, the BLDC motor has a stator  35  arranged in a fixed position with respect to a motor housing. The stator  35  includes a plurality of coils arranged in groups (phases) around a cylindrical central space occupied by the rotor  33 . The rotor  33  is supported for rotation within the stator  35  on a motor shaft  34  that projects from both ends of the rotor  33 . The rotor  33  includes permanent magnets  37  arranged on an outer periphery of the rotor and radially adjacent to the stator coils. A motor control circuit  41  sequentially applies electrical power to the groups of coils in the stator to produce a rotating magnetic field that acts on the magnets in the rotor to produce torque that rotates the rotor within the stator. An electrical connector  39  connects the motor control circuit  41  to the BLDC motor  32 . The motor control circuit  41  is also connected to an engine control unit (ECU) or emissions control system to receive signals to actuate the BLDC motor  32  to position the valve member  22  to provide a desired flow of exhaust gasses between the inlet  62  and outlet  54  openings in the valve chamber  56 . 
     At one end, the motor shaft  34  is coupled to the torsion spring  50  so that powered rotation of the rotor  33  winds the torsion spring  50 . The other end of the motor shaft  34  is coupled to the valve member drive mechanism  24  so that powered rotation of the rotor  22  causes the valve actuation mechanism  24  to move the valve member  22  from a closed position toward an open position within the valve housing  14 . When power is removed from the stator coils, the torsion spring  50  unwinds to return the valve member  22  to the closed position. In one embodiment, the valve  10  is configured to recirculate exhaust gasses produced by an internal combustion engine back to the intake of the engine, which can reduce emissions produced by the engine. In the closed position of the valve  22 , no exhaust gasses are recirculated to the intake and in the open position, a predetermined maximum flow of exhaust gasses are recirculated to the intake. The disclosed BLDC motor  32  is selected to produce torque to position the valve member  22  at any position between the closed and fully open position and maintain the valve member  22  in that position according to commands to the motor control circuit  41  from an engine control unit (ECU) or other engine management or emissions control system. BLDC motors of this type may be described as stepper motors. The motor control circuit  41  may be arranged in a separate protective enclosure and connected to the BLDC motor  32  by conductors extending into the motor housing from an electrical connector  39 . 
       FIG.  2    illustrates the compact EGR valve of  FIG.  1    with the valve housing  14  removed to show the valve member  22  and valve member drive mechanism  24  connected to the motor assembly  12 . The valve member  22  is rotationally symmetrical and in a disclosed embodiment has a cylindrical side surface  26  and an annular leading edge  28 . The valve member  22  rotates as it moves axially from a closed (extended) position to an open (retracted) position when power is applied to the stator coils.  FIG.  2    illustrates the valve member  22  in the open (retracted) position. An adaptor plate  30  connects the valve member drive mechanism  24  to the motor assembly  12 .  FIG.  3    shows the motor assembly  12  with the adaptor plate  30  and valve member drive mechanism  24  removed to show one end of the BLDC motor  32  and the motor shaft  34 . The motor shaft  34  extends through the BLDC motor  32  and protrudes from both ends of the BLDC motor  32 . One end of the shaft  34  extends into a chamber defined by the end cap  18  and is coupled to a torsion spring  50  contained within the end cap  18  to tighten (wind) the torsion spring  50  when the power is applied to the BLDC motor  32  to rotate the rotor  33  and shaft  34 , and when power is removed from the BLDC motor  32 , the torsion spring  50  releases its tension (unwinds) to counterrotate the rotor  33 , shaft  34  and valve member  22 . As shown in  FIGS.  3 - 5   , the motor shaft  34  has flats  36  on opposite sides.  FIG.  4    illustrates a screw  38  having a longitudinally extending bore  40  configured to receive the motor shaft  34 . The complementary configuration of the bore  40  and the motor shaft  34  allow the motor  32  to deliver rotational torque to the screw  38  while allowing the screw  38  to move axially along the shaft  34 . An axial end portion  42  of the screw  38  has a polygonal configuration that mates with a complementary opening on the valve member  22  so that the valve member  22  and the screw  38  rotate together. The illustrated end portion  42  has a hexagonal configuration but any coupling capable of connecting the valve member  22  to the screw  38  so they rotate and move axially together is compatible with he disclosed compact EGR valve  10 . The screw  38  has a threaded exterior surface  44 .  FIG.  5    illustrates the adaptor plate  30  supporting a nut  46  in a fixed position relative to the motor assembly  12 . The nut  46  has a thread on its inside diameter complementary to the threaded exterior surface  44  of the screw  38 . In the illustrated drive mechanism  24 , the screw  38  is rotated by the motor shaft  34  and the threaded engagement of the screw  38  with the nut  46  cause the screw  38  to move axially along the motor shaft  34  rotating the valve member  22  and moving the valve member  22  axially with the screw  38 . Although a threaded engagement of the screw  38  and nut  36  is disclosed, a ramp or other engagement that produces rotation and axial movement of the screw  38  relative to the nut  46  may also be used.  FIG.  5    illustrates the screw  38  in a retracted position relative to the nut  46 . The retracted position of the screw  38  illustrated in  FIG.  5    requires powered rotation of the rotor  33  and motor shaft  34  against the force of the torsion spring  50  and friction of the valve actuation mechanism  24  and valve  22  in the valve chamber  56 . The retracted position of the screw  38  corresponds to an open position of the valve member  22  in the valve chamber  56 . The pitch of the threaded or ramp connection between the screw  38  and nut  46  determines the amount of axial movement of the nut  38  (and coupled valve member  22 ) relative to the nut  46  for each rotation of the motor shaft  34 . The predetermined relationship of valve axial movement to motor rotation can be used to control the BLDC motor  32  to move the valve member  22  from the closed position to the fully open position or any position between the closed and fully open position. The disclosed compact EGR valve  10  is a “normally closed” valve that is returned to the closed position by the torsion spring  50  when power is not applied to the BLDC motor  32 . 
       FIG.  6    shows the motor assembly  12  including the valve actuation mechanism  24  in functional conjunction with the valve member  22  and valve housing  14 .  FIG.  7    is an exploded perspective view of an embodiment of a compact EGR valve according to aspects of the disclosure. The adaptor plate  30  supports the BLDC motor  32  within an inner cooling jacket  48 . The inner cooling jacket  48  is surrounded by and sealed to the cooling jacket  16  so that coolant can be circulated through openings defined by the cooling jacket  16  to cool the BLDC motor  32 . A torsion spring  50  is contained in the end cap  18  and coupled to the motor shaft  34  to rotate the motor shaft  34  in a direction to move the valve member  22  to the closed (extended) position when power is removed from the BLDC motor  32 . The torque of the BLDC motor  32  must be sufficient to overcome the rotational bias of the torsion spring  50  and the friction of the drive mechanism  24  and valve member  22 . The nut  46  is secured in a fixed rotational and axial position relative to the adaptor plate  30 , while the screw  38  rotates with the motor shaft  34  and is moved axially along the motor shaft  34  by threaded engagement with the nut  46 .  FIG.  6    illustrates the screw  38  and valve member  22  in the closed (extended) position. The disclosed valve actuation mechanism  24  produces simultaneous axial and rotational movement of the valve member  22 . 
       FIGS.  6  and  7    illustrate one manner of connecting the valve member  22  to the screw  38 . An end portion  42  of the screw  38  has a polygonal shape that fits with a complementary opening in a rear end of the valve member  22  to that the screw  38  and valve member  22  rotate and move axially together. In a disclosed configuration, the outer end of the screw  38  includes a protrusion  43  and a retainer  45 . The protrusion  43  may be threaded and the retainer  45  may be a nut with a thread complementary to the protrusion  43 . A thread  45  in the retainer may be distorted to lock the retainer  45  to the protrusion and prevent loosening of the retainer  45  from the protraction  43 . The valve member  22  may be configured to allow for limited movement relative to the screw  38  to allow the valve member to self-center relative to the valve chamber inside surface and the shoulder  60 . Alternative configurations of a protrusion  43  and retainer  45  may be used to permanently couple the valve member  22  to the screw  38 . As shown in  FIGS.  6  and  7   , the center of the valve member  22  is occupied by a domed heat shield  63  and insulation  64 . After the valve member  22  is joined to the screw  38 , the insulation  64  is placed in the heat shield  63  and the heat shield  63  is coupled to the valve member  22  by inserting tabs  65  through corresponding slots in the valve member  22 . The tabs  65  may be bent radially inwardly to secure the heat shield  63  to the valve member  22  with the insulation  64  filling the heat shield  63 . The insulation  63  may be preformed mineral wool, fibrous mineral wool, or other suitable heat resistant insulating material. The assembled valve member  22 , screw  38 , heat shield  63  and insulation  64  can then be engaged with the nut  46  as shown in  FIG.  2    before connection of the valve housing to the motor assembly  12 . 
     The valve housing  14  defines a valve chamber  56 , an exhaust gas inlet  52 , an exhaust gas outlet  54 , and an annular shoulder  60  that defines the closed (extended) position of the valve member  22  and can also be described as a valve seat. The valve chamber  56  includes a cylindrical portion  58  within which the valve member  22  moves between the closed (extended) position and the open (retracted) position. An inlet opening  62  to the valve chamber  56  has a rectangular configuration in the illustrated embodiment, but other inlet opening configurations may be used. An advantage of a rectangular inlet opening is that the long sides of the rectangular opening can be arranged parallel to the annular leading edge  28  of the valve member  22 . In this configuration, axial movement of the valve member  22  from the closed position to the open position produces a linear opening of the inlet opening  62 . The linear opening of the inlet opening  62  and the known axial movement of the valve member per rotation of the motor shaft  34  allows for a relatively simple control algorithm for the disclosed compact EGR valve  10 . In the closed (extended position) where the annular leading edge  28  of the valve member  22  abuts the annular shoulder  60 , the side wall  26  of the valve member  22  completely covers the inlet opening  62 . One significant advantage of a valve member  22  that rotates as it moves axially is that the annular leading edge will clean deposits off the side surfaces of the cylindrical portion  58  of the valve chamber  56  and the annular shoulder  60 . This cleaning action of the rotating valve member  22  prevents the accumulation of excess deposits of carbon from the exhaust gasses passing through the valve chamber  56  and ensures reliable operation of the disclosed compact EGR valve  10 . Any deposits removed from the valve chamber  56  by the valve member  22  are allowed to leave the valve chamber  56  via the outlet  54 . 
     As shown in  FIG.  6   , the adaptor plate  30  supports the nut  46  and separates the motor  32  from the heat present in the exhaust gasses passing through the valve housing  14 . The center of the valve member  22  is occupied by a domed heat shield  63  containing insulation fiber  64  such as mineral wool. The adaptor plate  30  has a sealed connection with the valve housing  14 , which prevents escape of exhaust gasses from the compact EGR valve  10 . The disclosed configuration of the compact EGR valve  10  protects the BLDC motor  32  from the exhaust gasses and cools the BLDC motor  32  to ensure reliable operation in the harsh environment immediately adjacent an internal combustion engine. 
       FIG.  8    is a longitudinal sectional view of the motor assembly  12  and drive mechanism  24  with the valve member  22  in the open (retracted) position. In this position, the screw  38  abuts a shoulder on the motor shaft  34  adjacent the end of the BLDC motor  32 , as also shown in  FIG.  6   .  FIG.  9    is a longitudinal sectional view of the motor assembly  12  and drive mechanism  24  with the valve member  22  in the closed (extended position). In this position, the screw  38  projects axially from the nut  46  and the annular leading edge  28  of the valve member  22  abuts the annular shoulder  60  within the valve chamber  56 . Even though the screw  38  extends out of the nut  46  and only a small portion of the motor shaft  34  is within the screw  38 , movement of the screw  38  and coupled valve member  22  are guided by sliding contact between the cylindrical outside surface  26  of the valve member  22  on the inside surface of the cylindrical portion  58  of the valve chamber  56 .  FIGS.  8  and  9    illustrate the rotationally coupled relationship between the screw  38  and the valve member  22 . The torsion spring  50  coupled to the shaft  34  is wound up as the BLDC motor is energized to move the valve member  22  from the closed (extended) position of  FIG.  9    to the open (retracted) position shown in  FIG.  8   . When power is removed from the BLDC motor  32 , the torsion spring  50  unwinds to rotate the motor shaft  34  and return the valve member to the closed (extended) position. This valve configuration ensures that if power to the BLDC motor  32  is lost, the disclosed compact EGR valve  10  returns to the closed position. 
     The configuration of the valve chamber  56  and the position of the inlet opening  62  within the cylindrical portion  58  of the valve chamber  56  ensure the smooth flow of exhaust gasses through the disclosed compact EGR valve  10 . As shown in  FIGS.  11  and  12   , the inlet opening  62  is rectangular with the long sides of the rectangular opening  62  oriented parallel to the annular leading edge  28  of the valve member  22  and perpendicular to an axis of rotation of the valve member  22 . One of the short sides of the rectangular opening  62  is coincident with an inner wall of the cylindrical valve chamber  56  as best seen in  FIG.  12   . The long sides of the rectangular opening  62  extend across a majority of the diameter of the cylindrical valve chamber  56 . This configuration of the rectangular inlet opening  62  is offset from a central axis of the cylindrical valve chamber  56 , with one short side joining an inside surface of the cylindrical valve chamber  56 . This inlet opening configuration causes gas passing through the inlet opening  62  to form a vortex as shown in  FIGS.  11  and  12   . The rotation of the gas passing through the valve chamber  56  reduces a pressure drop through the disclosed compact EGR valve  10 .  FIG.  11    illustrates gas flow through one embodiment of a valve chamber having a flat end  57 , while  FIGS.  12  and  13    illustrate an embodiment of a valve chamber having a hemispherical end adjacent the outlet  54 . The pressure drops shown in  FIGS.  11  and  12    show that the hemispherical end of  FIGS.  12  and  13    result in smoother flow and reduced pressure drop through the valve than the flat end valve chamber of  FIG.  11   . 
     The rectangular opening  62  has a length in the axial direction of movement of the valve member  22  corresponding to the short sides of the rectangular opening. As shown in  FIG.  6   , the axial length of the cylindrical side wall  26  of the valve member  22  is sufficient to span the axial dimension of the rectangular inlet opening  62  and overlap with the inside wall of the valve chamber  56  at both ends of the inlet opening  62  in the axial direction. The inlet opening  62 .  FIGS.  6  and  10    illustrate the domed heat shield  63  inward of the annular leading edge  28  of the valve member  22 . The dome of the heat shield  63  is arranged to direct gas flow toward the outlet  56  as shown in  FIG.  10   . The disclosed domed shape of the heat shield  63  and its axial position relative to the annular leading edge  28  of the valve member  22  reduce turbulence of gas passing the annular leading edge  28  and promote smooth flow of gas through the disclosed compact EGR valve  10 .  FIG.  11    illustrates gas flow through one embodiment of a valve chamber having a flat end  57   FIG.  10    is a longitudinal sectional view through the compact EGR valve  10  with the valve member  22  at a position partially opening the inlet opening  62 . The velocity of gas passing through the valve chamber  56  is illustrated, with red indicating high velocity and blue indicating low velocity. Gas passing through the valve chamber  56  has its highest velocity as it passes the annular leading edge  28  of the valve member  22 . This high velocity facilitates the removal of deposits from the annular leading edge  28  of the valve member  22  and helps to ensure reliable operation of the compact EGR valve  10 . 
       FIGS.  11  and  12    compare gas flow through two differently configured valve chambers. In  FIG.  11   , the inlet  52  and inlet opening  62  are arranged at the center of the cylindrical portion  58  of the valve chamber  56 . Further, the cylindrical portion  58  of the valve chamber  56  ends in a flat end face  57 . In this configuration, gas flow is turbulent and results in relatively high pressure drop across the valve chamber  56 . Flow analysis shows that the flat end face  57  results in a valve chamber  56  with dead volume in the corners that hinder gas flow through the valve chamber  56  to the outlet  54 . In  FIG.  12   , the inlet  52  and inlet opening  62  are offset to one side of the cylindrical portion  58  so that one edge of the inlet opening  62  is tangent to a side of the cylindrical potion  58  of the valve chamber  56 . In this configuration, the offset flow of gas into the valve chamber  56  initiates a swirling motion of the gas that reduces turbulence and promotes gas flow. The end of the valve chamber  56  communicating with the outlet  54  is hemispherical, reducing the volume of the valve chamber  56  and promoting smooth flow of gases from the inlet opening  62  to the outlet  54 . The swirling motion of the gas initiated by the offset inlet opening  62  continues as the gas passes through the hemispherical end portion of the valve chamber  56  to the outlet  54 . The valve chamber configuration illustrated in  FIGS.  12  and  13    results in improved gas flow through the disclosed EGR valve  10  and reduced pressure drop across the valve relative to the valve chamber configuration of  FIG.  11   .