Patent Publication Number: US-11644112-B2

Title: Seal for rotary plug valve

Description:
BACKGROUND 
     A rotary plug valve is a type of directional control valve that may be used in a fluid delivery system to control fluid flow and distribution through the system. For example, rotary plug valves may be used to control the flow of coolant through a vehicle cooling system. The rotary plug valve may include a valve body that defines several ports, a valve plug disposed in the valve body, and a seal disposed between the valve body and the valve plug. The valve plug is shaped to distribute the flow to predetermined ports for certain rotational orientations of the valve plug within the valve body and is rotated relative to the valve body to control flow through the valve. 
     SUMMARY 
     Complex fluid delivery systems may require a rotary plug valve that is capable of controlling fluid flow between three, four, five or more individual ports of the valve body. Depending on the system requirements, it may be desirable to close several flow paths simultaneously. For example, in a five-port rotary plug valve, it may be desirable to close as many as three of five flow paths for a given rotational orientation of the valve plug relative to the valve body. This requires that a large angular portion of the valve plug have no passageway openings. If all the valve ports in the valve body are on the same level along a height dimension of the valve body, the area available for closed ports is limited. In the rotary plug valve disclosed herein, the flow paths of the valve plug are separated into two levels, which provides a larger area on the plug without a passageway opening to meet a valve body port. However, a multi-level valve plug may be complicated to fabricate and require a complicated mold and/or molding process. In one solution, the interface between the valve body and valve plug may have a conical shape, making it possible to mold the valve seal (also referred to as a valve seat) as a single, monolithic structure in a simple two part mold. However the conical shape then makes it difficult to mold the valve plug in a simple two part mold without creating areas with large wall thickness, a configuration that is associated with poor dimensional control of the part. To address this issue, the valve plug is formed in portions, which allows the coring (e.g., removal of material) of the area inside the conical shape defined by the valve plug, and outside the passageways. 
     In some fluid delivery systems having, for example, thermal applications, it may be desirable to close of two or three of the ports in a given valve plug rotational position. For example, a multi-port rotary plug valve may be used in a cooling system of an electric vehicle to control flow of coolant fluid between a radiator, an electric drive motor, a battery, vehicle electronics, and one or more bypass lines. The rotary plug valve may include a valve body that has ports at two or more levels along a height dimension of the valve body. The rotary plug valve may include a plug assembly that is disposed in the valve body and is rotatable relative to the valve body about a rotational axis that is parallel to the height direction of the valve body. In addition, the rotary plug valve may include a seal disposed between the valve plug and the valve body. 
     The plug assembly may be made of two interlocking parts (e.g., first and second plug portions) that cooperate to control fluid flow through the valve body. The plug assembly may have more than two openings to divert fluid to the different levels. The addition of levels and corresponding plug openings makes it possible to provide valve configurations corresponding to certain rotational positions of the valve plug relative to the valve body in which fluid passageways extend between levels, are restricted to a single level, or in which no ports of the valve body are open. This can be compared to some conventional rotary plug valves that only allow for the closing of one port at a time. The plug assembly provides some passageways that can access ports on multiple levels and others that can only access one level. The two-part plug assembly simplifies molding of a valve plug that can service the additional port levels. The valve body and plug assembly may be tapered along the rotational axis in order to simplify manufacture and improve sealing. 
     The seal may have a conical shape when viewed in a direction perpendicular to the rotational axis of the plug assembly. By forming the seal in a conical shape it can be formed as a single-piece or monolithic structure in a simple, two-part mold. Since the seal is a single-piece or monolithic structure, it is free of seams or joints. This is advantageous as compared to some conventional seals that include seams or joints, since such seams or joints may sometimes be a source of fluid leakage. 
     The seal has a cage-like structure that permits the seal to seal a valve body having any number of ports or port levels. In particular, the seal includes a first ring that seals an upper periphery of the plug assembly, a second ring that seals a lower periphery of the valve plug assembly, and ribs that extend between the first and second rings. In particular, a rib is disposed between each pair of adjacent valve ports. The plug assembly-facing surface of each rib includes a channel that extends between the first ring and the second ring. In some embodiments, the two lands that bound the channel may serve to prevent contaminant particles and/or other debris from being trapped in the seal/plug interface, whereby abrasive wear is reduced. In some embodiments, the channel may serve to reduce seal surface area and thus reduce friction between the seal and the plug assembly. 
     In some aspects, a valve seal includes a first ring having a first ring diameter, and a second ring that is parallel to, and spaced apart from, the first ring. The second ring has a second ring diameter that is different than the first ring diameter. In addition, the valve seal includes a first rib that extends between the first ring and the second ring, and a second rib that extends between the first ring and the second ring, the second rib being spaced apart from the first rib along a circumference of the first ring. 
     In some embodiments, the seal is formed integrally as a single unit whereby the seal is free of a seam. 
     In some embodiments, the inward-facing surfaces of each of the first rib and the second rib include a channel that extends between the first ring and the second ring. 
     In some embodiments, the channel has a V shaped profile. 
     In some embodiments, the inward-facing surfaces of the first rib and the second rib include a pair of parallel lands. One land of the pair of lands is disposed on each side of the channel, and the lands provide a sealing contact surface of the seal. 
     In some embodiments, the outward facing surfaces of the first rib and the second rib have a rectangular profile. 
     In some embodiments, the spacing about a circumference of the seal between ribs is irregular. 
     In some embodiments, the seal is formed of an elastic material. 
     In some embodiments, the seal is formed of low friction elastomer. 
     In some embodiments, a portion of the surfaces of the seal include a low-friction coating. 
     In some aspects, a rotary plug valve includes a valve body, a valve plug disposed in the valve body and a seal that is disposed between the valve body and the valve plug. The valve body includes a body sidewall that encircles and is centered on a body axis, a body base that closes one end of the body sidewall, the body sidewall and body base cooperating to define a valve body chamber, and valve ports, each valve port communicating with the valve body chamber. The valve plug is disposed in the valve body chamber so as to be rotatable relative to the valve body about a rotational axis that coincides with the body axis. The valve plug includes a plug first end, a plug second end opposed to the plug first end, a side surface that extends between the first end and the second end, the side surface surrounding the body axis, and passageways that extend through the valve plug and open at the side surface of the valve plug. In addition, the seal includes a first ring having a first ring diameter, and a second ring that is parallel to, and spaced apart from, the first ring. The second ring has a second ring diameter that is different than the first ring diameter. The seal includes a first rib that extends between the first ring and the second ring, and a second rib that extends between the first ring and the second ring. The second rib is spaced apart from the first rib along a circumference of the first ring. 
     In some embodiments, the seal is formed integrally as a single unit whereby the seal is free of a seam. 
     In some embodiments, the inward-facing surfaces of the first rib and the second rib face the valve plug, and the inward-facing surface of each rib includes a channel that extends between the first ring and the second ring. 
     In some embodiments, the channel has a V shaped profile. 
     In some embodiments, the inward-facing surfaces of each of the first rib and the second rib include a pair of parallel lands. One land of the pair of lands is disposed on each side of the channel, and the lands provide a sealing contact surface between the seal and the valve plug. 
     In some embodiments, the outward facing surfaces of each of the first rib and the second rib have a rectangular profile. 
     In some embodiments, the outward-facing portions of the first rib and the second rib are received in grooves provided in the body sidewall. 
     In some embodiments, the shape and dimensions of outward-facing portions of the first rib and the second rib correspond to the shape and dimensions of the grooves. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG.  1    is a schematic of a vehicle cooling system including a multi-level, multi-port rotary plug valve. 
         FIG.  2    is a perspective view of the multi-level, multi-port rotary plug valve of  FIG.  1   . 
         FIG.  3    is an exploded perspective view of the rotary plug valve of  FIG.  2   . 
         FIG.  4    is a perspective view of the valve body of the rotary plug valve of  FIG.  2   . 
         FIG.  5    is a cross-sectional view of the rotary plug valve as seen along line  5 - 5  of  FIG.  2   . 
         FIG.  6    is a perspective view of the plug assembly of the rotary plug valve of  FIG.  2    showing one side of the plug assembly. 
         FIG.  7    is another perspective view of the plug assembly of the rotary plug valve of  FIG.  2    showing another side of the plug assembly. 
         FIG.  8    is a perspective view of the first plug portion of the plug assembly of  FIG.  6    showing one side of the first plug portion. 
         FIG.  9    is perspective view of the first plug portion of the plug assembly of  FIG.  6    showing a top view of the first plug portion. 
         FIG.  10    is perspective view of the first plug portion of the plug assembly of  FIG.  6    showing a bottom view of the first plug portion. 
         FIG.  11    is a cross-sectional view of the first plug portion as seen along line  11 - 11  of  FIG.  9   . 
         FIG.  12    is a cross-sectional view of the rotary plug valve as seen along line  12 - 12  of  FIG.  2   . 
         FIG.  13    is a cross-sectional view of the rotary plug valve as seen along line  13 - 13  of  FIG.  2   . 
         FIG.  14    is a perspective view of the second plug portion of the plug assembly of  FIG.  6    showing one side of the second plug portion. 
         FIG.  15    is perspective view of the second plug portion of the plug assembly of  FIG.  6    showing another side of the second plug portion. 
         FIG.  16    is perspective view of the second plug portion of the plug assembly of  FIG.  6    showing another side of the second plug portion. 
         FIG.  17    is perspective view of the second plug portion of the plug assembly of  FIG.  6    showing another side and bottom of the second plug portion. 
         FIG.  18    is a cross-sectional view of the seal as seen along line  18 - 18  of  FIG.  19   . 
         FIG.  19    is a top plan view of the seal. 
         FIGS.  20 A and  20 B  illustrate fluid flow through the valve plug of the rotary plug valve of  FIG.  2    for one rotational position of the plug assembly relative to the valve body, where solid arrows represent fluid flow through the valve plug, and open arrows represent a blocked flow path. 
         FIGS.  21 A and  21 B  illustrate fluid flow through the valve plug of the rotary plug valve of  FIG.  2    for another rotational position of the plug assembly relative to the valve body, where solid arrows represent fluid flow through the valve plug, and open arrows represent a blocked flow path. 
         FIGS.  22 A and  22 B  illustrate fluid flow through the valve plug of the rotary plug valve of  FIG.  2    for another rotational position of the plug assembly relative to the valve body, where solid arrows represent fluid flow through the valve plug, and open arrows represent a blocked flow path. 
         FIGS.  23 A and  23 B  illustrate fluid flow through the valve plug of the rotary plug valve of  FIG.  2    for another rotational position of the plug assembly relative to the valve body, where solid arrows represent fluid flow through the valve plug, and open arrows represent a blocked flow path. 
         FIG.  24    is an exploded perspective view of an alternative embodiment rotary plug valve. 
         FIG.  25    is a cross-sectional view of the rotary plug valve of  FIG.  24   . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS.  1 - 3   , a fluid delivery system  1  includes a multi-level, multi-port rotary plug valve  18  that is capable of controlling fluid flow driven by a pump  8  between three, four, five or more individual fluid lines  10 ,  11 ,  12 ,  13 ,  14  within the system  1 . The rotary plug valve  18  may be may be used, for example, to control the distribution and flow of coolant in a cooling system  1  of an electric vehicle. In this example, the rotary plug valve  18  may control flow of coolant fluid between the rotary plug valve  18  and a radiator  2  that is part of a vehicle passenger cabin heating and cooling system  7 , where coolant from the radiator  2  may also cools a battery  3  and battery management system  4 . In addition, the rotary plug valve  18  may control fluid flow to heat exchangers  5 ,  6  that support temperature control of other vehicle devices and systems, such as an electric drive motor, vehicle electronics and/or electronic control units and/or the oil supply. The rotary plug valve  18  includes a valve body  20  and a plug assembly  50  that is disposed in, and rotates relative to, the valve body  20  about a rotational axis  52 . In addition, the rotary plug valve  18  has a single, elastomeric valve seal  110  that provides a fluid-tight seal between the valve body  20  and the plug assembly  50 . The valve body  20  includes multiple valve ports  33 ,  34 ,  35 ,  36 ,  37 , the number of ports being determined by the specific application. At least one valve port  33  is positioned at a different level along a height dimension of the valve body  20  than the other valve ports  34 ,  35 ,  36 ,  37 , where the height dimension is measured in a direction parallel to the rotational axis  52 . The rotational orientation of the plug assembly  50  relative to the valve body  20  is set via an actuator (not shown). The rotational orientation of the plug assembly  50  relative to the valve body  20  determines one or more fluid flow paths through corresponding ones of the valve ports  33 ,  34 ,  35 ,  36 ,  37 . The plug assembly  50  may be an assembly of two interlocking plug portions  60 ,  80  that together control fluid flow through the valve body  20 . The plug assembly  50  has multiple openings associated with passageways  72 ,  92 ,  96  that, depending on the rotational orientation of the plug assembly  50  relative to the valve body  20 , divert fluid to certain ones of the valve ports  33 ,  34 ,  35 ,  36 ,  37 , whereby the distribution of coolant fluid in the coolant system  1  is controlled. Details of the rotary plug valve  18 , including the valve body  20 , the plug assembly  50  and the seal  110 , will now be described. 
     Referring to  FIGS.  4  and  5   , the valve body  20  includes a base  26 , and a sidewall  21 . The base  26  has a circular profile when viewed in a direction parallel to the rotational axis  52 . The sidewall  21  is joined at one end (referred to here as the “base end”)  22  to a peripheral edge of the base  26 , and the sidewall  21  surrounds the base  26 . The sidewall  21  and the base  26  together form a generally cup-shaped structure that defines a valve plug chamber  30  therein. An open end  23  of the sidewall  21  (e.g., the end of the sidewall  21  that is spaced apart from the base  26 ) has a diameter that is greater than the diameter of the base end  22 , whereby the sidewall  21  protrudes at an obtuse angle θ 1  ( FIG.  5   ) relative to the base  26 . In the illustrated embodiment, the angle θ 1  is in a range of 95 to 150 degrees, for example 97 degrees. 
     In the illustrated embodiment, the valve body  20  includes five valve ports  33 ,  34 ,  35 ,  36 ,  37 , but is not limited to this number of ports. In particular, the valve body  20  includes a first valve port  33 , a second valve port  34 , a third valve port  35 , a fourth valve port  36  and a fifth valve port  37 . Each of the valve ports  33 ,  34 ,  35 ,  36 ,  37  protrudes outward from the sidewall  21  along a radius of the rotational axis  52 , and communicates with the valve plug chamber  30 . In the illustrated embodiment, the valve ports  33 ,  34 ,  35 ,  36 ,  37  are cylindrical tubes, and each valve port  33 ,  34 ,  35 ,  36 ,  37  forms a circular opening at the intersection with the valve body sidewall  21 . 
     In the illustrated embodiment, the valve ports  33 ,  34 ,  35 ,  36 ,  37  are cylindrical tubes, and each valve port  33 ,  34 ,  35 ,  36 ,  37  forms a circular opening at the intersection with the valve body sidewall  21 . Although, as illustrated, the valve ports  33 ,  34 ,  35 ,  36 ,  37  each have the same length, cross-sectional shape and dimensions, the valve ports  33 ,  34 ,  35 ,  36 ,  37  are not limited to this configuration. Moreover, the valve ports  33 ,  34 ,  35 ,  36 ,  37  are not limited to the illustrated co-planar and radially oriented configuration. For example, in other embodiments, certain ones of the valve ports  33 ,  34 ,  35 ,  36 ,  37  may be non-co-planar with the other valve ports and/or may protrude from the base rather than the sidewall. The valve ports  33 ,  34 ,  35 ,  36 ,  37  may protrude in a direction that is parallel to the rotational axis  16 , in a direction that is perpendicular to the rotational axis  16  or at any angle between perpendicular and parallel to the rotational axis  16 . The valve ports  33 ,  34 ,  35 ,  36 ,  37  may protrude non-radially; an axis of a given valve port is not required to intersect the rotational axis  16 . In many applications, the configuration of the valve ports  33 ,  34 ,  35 ,  36 ,  37  is determined by packaging requirements. 
     The valve ports  33 ,  34 ,  35 ,  36 ,  37 , are provided at spaced-apart locations about a circumference of the sidewall  21 . In the illustrated embodiment, the first and fourth valve ports  33 ,  36  are disposed on opposed sides of the valve body  20 , extend in parallel to a common diameter of the valve body  20 , and are at different levels along a height dimension of the valve body  20 . In particular, the first valve port  33  is closer to the valve body open end  23  than the fourth valve port  36  when the valve body  20  is viewed in a direction perpendicular to the rotational axis  52 . The second and fifth valve ports  34 ,  37  are disposed on opposed sides of the valve body  20 , are coaxial with a common diameter of the valve body, and share a level with the fourth valve port  36 . The third valve port  35  shares a level with the second, fourth and fifth valve ports  34 ,  36 ,  37  and is disposed between the second and fourth valve ports  34 ,  36 . Thus, the first valve port  33  resides in a first plane P 1  that is perpendicular to the rotational axis  52 , and the second, third, fourth and fifth valve ports  34 ,  35 ,  36 ,  37  reside in a second plane P 2  that is perpendicular to the rotational axis  52  and spaced apart from the first plane. In the illustrated embodiment, the plane P 1  is between the plane P 2  and the open end  23  of the valve body  20 , but is not limited to this configuration. 
     The inner surface of the valve body sidewall  21  is provided with grooves  32  that extend between the base end  22  and the open end  23 . The grooves  32  have the same cross-sectional shape as the ribs of the seal  110 , and are dimensioned to receive ribs of the seal  110  in a press-fit configuration, as discussed further below. The number of grooves  32  provided corresponds to the number of ribs of the seal  110 . In the illustrated embodiment, the valve body  20  includes six grooves  32 . At least one groove  32  is disposed between the ports of each adjacent pair of valve ports  33 ,  34 ,  35 ,  36 ,  37 . For example, when viewed in a direction parallel to the rotation axis, the first and second ports  33 ,  34  form a pair of adjacent valve ports, and a groove  32  is disposed between the first and second ports  33 ,  34 . Likewise, a groove  32  is provided between the second and third valve ports  34 ,  35 , between the third and fourth valve ports  35 ,  36 , between the fourth and fifth valve ports  36 ,  37  and between the fifth and first valve ports  37 ,  33 . The spacing of the valve body grooves  32  about the inner circumference of the valve body  20  depends on the spacing of the valve body ports  33 ,  34 ,  35 ,  36 ,  37 , and therefore may be non-uniform. 
     The valve body sidewall  21  has a height dimension that corresponds to the distance between the sidewall open end  23  and the sidewall base end  22  in a direction parallel to the rotational axis. In the illustrated embodiment, the height dimension of the valve body  20  is the same as or slightly less than a diameter of the sidewall base end  22 . 
     In some embodiments, a lid (not shown) is provided that closes an open end  23  of the valve body  20 , whereas in other embodiments, the open end  23  of the valve body  20  may be closed by a housing (not shown) of the actuator or other ancillary structure. A second seal (not shown) may be disposed between the valve body open end  23  and the lid or housing. 
     Referring to  FIGS.  6  and  7   , the plug assembly  50  is disposed in the valve body chamber  30 , and is rotatable within the chamber  30  about the rotational axis  52 . The plug assembly  50  is an assembly of a first plug portion  60  and a second plug portion  80  that are stacked together along the rotational axis  52 . The mating surfaces of the first and second plug portions  60 ,  80  are interlocking, whereby the first and second plug portions  60 ,  80  rotate in unison and cooperate to control fluid flow through the valve body  20 . 
     Referring to  FIGS.  8 - 12   , the first plug portion  60  includes a first base  66 , and a first sidewall  61 . The first base  66  is parallel to the body base  26 , and has a circular profile when viewed in a direction parallel to the rotational axis  52 . The first base  66  has an outer surface  67  that faces the body base  26 , and an opposed, inner surface  68  that faces away from the body base  26 . The first sidewall  61  is joined at one end (referred to here as the “base end”)  62  to a peripheral edge of the first base  66 . The first sidewall  61  encircles the first base  66 , and is centered on the rotational axis  52 . The first sidewall  61  and the first base  66  together form a generally cup-shaped structure. An open end  63  of the first sidewall  61  (e.g., the end of the first sidewall  61  that is spaced apart from the first base  66 ) has a diameter that is greater than the diameter of the base end  62 , whereby the first sidewall  61  protrudes at an obtuse angle θ 2  ( FIG.  5   ) relative to the first base  66 . In the illustrated embodiment, the angle θ 2  is in a range 95 to 150 degrees, for example 97 degrees. 
     The first sidewall  61  includes an alpha opening  70  and a beta opening  71  that are spaced apart along a circumference of the first sidewall  61 . With respect to a reference diameter D 1  ( FIG.  12   ) of the plug assembly  50 , the alpha and beta openings  70 ,  71  reside on the same side of the reference diameter D 1  when the plug assembly  50  is viewed in a direction parallel to the rotational axis  52 . 
     The first plug portion  60  includes a projection  73  that protrudes from the base outer surface  67  and intersects the first sidewall  61  at a location corresponding to the beta opening  71 . The projection  73  is hollow, and has the shape of a right rectangular prism. The projection  73  extends along a radius of the first base  66 , and has a minimum height dimension at a location between a center of the first base  66  and a peripheral edge of the first base  66 . The projection has a maximum height at the first sidewall  61 . The projection  73 , together with the first sidewall  61 , define the beta opening  71 , whereby the beta opening  71  has a height dimension h 1  that is greater than a height dimension h 2  of the first sidewall  61 . 
     The first plug portion  60  includes a first passageway  72  that extends along, and protrudes from, the base inner surface  68 . The first passageway  72  extends between the alpha opening  70  and the beta opening  71 . The first passageway  72  includes a first linear portion  74  that extends along a radius of the first base  66  between the alpha opening  70  and the center of the first base  66 , and a second linear portion  75  that extends along a radius of the first base  66  between the beta opening  71  and the center of the first base  66 . An internal angle θ 3  ( FIG.  9   ) between the first linear portion  74  and the second linear portion  75  is less than 180 degrees. In the illustrated embodiment, the internal angle θ 3  is about 135 degrees. 
     The first plug portion  60  includes a hollow cylindrical stub  76  that protrudes from an outer surface of the first passageway  72 . The stub  76  is coaxial with the longitudinal axis, and has surface features such as flats, axial splines or gear teeth that permit engagement with an output shaft of the actuator, whereby the first plug portion  60  can be driven to rotate about the rotational axis  52  by the actuator. In the illustrated embodiment, the surface features are external. In other embodiments, the surface features may be internal. In the illustrated embodiment, the stub  76  has a low profile in that the sum of the height dimensions of the stub  76  and the first passageway  72  are less than or equal to the height dimension of the first sidewall  61 . In other embodiments, the stub  76  may have a high profile and protrude out of the first plug portion  60 , as required by the specific application. 
     Referring to  FIGS.  13 - 17   , the second plug portion  80  includes a second base  86 , and a second sidewall  81 . The second base  86  has a circular profile when viewed in a direction parallel to the rotational axis  52 . The second base  86  has an outer surface  87  that faces the body base  26 , and an opposed, inner surface  88  that faces away from the body base  26  and toward the first base  66 . The second sidewall  81  is joined at one end (referred to here as the “base end”)  82  to a peripheral edge of the second base  86 . The second sidewall  81  encircles the second base  86 , and is centered on the rotational axis  52 . The second sidewall  81  and the second base  86  together form a generally cup-shaped structure. An open end  83  of the second sidewall  81  (e.g., the end of the second sidewall  81  that is spaced apart from the second base  86 ) has a diameter that is greater than the diameter of the base end  62 , whereby the second sidewall  81  protrudes at an obtuse angle θ 4  ( FIG.  5   ) relative to the second base  86 . In the illustrated embodiment, the angle θ 4  is in a range of 95 to 150 degrees, for example 97 degrees. 
     The second sidewall  81  includes delta opening  90 , a gamma opening  91  and a zeta opening  95  that are spaced apart along a circumference of the second sidewall  81 . With respect to the reference diameter D 1  ( FIG.  13   ) of the plug assembly  50 , the delta and gamma openings  90 ,  91  reside on the same side of the reference diameter D 1  when the plug assembly  50  is viewed in a direction parallel to the rotational axis  52 . In addition, the delta and gamma openings  90 ,  91  reside on the opposed side of the reference diameter D 1  relative to the zeta, alpha and beta openings  95 ,  70 ,  71 . 
     The second plug portion  80  includes a second passageway  92  that extends along, and protrudes from, the base inner surface  88 . The second passageway  92  extends between the delta opening  90  and the gamma opening  91 . The second passageway  92  includes a first linear portion  93  that extends along a radius of the second base  86  between the delta opening  90  and a center of the second base  86 , and a second linear portion  94  that extends along a radius of the second base  86  between the gamma opening  91  and the center of the second base  86 . An internal angle θ 5  ( FIG.  15   ) between the first linear portion  93  and the second linear portion  94  is less than or equal to 180 degrees. In the illustrated embodiment, the internal angle θ 5  of the second passageway  92  is less than the internal angle θ 3  of the first passageway  72 . For example, the internal angle θ 5  is about 112 degrees. 
     The zeta opening  95  is a blind opening that is configured to connect adjacent valve ports in certain rotational orientations of the plug assembly  50  with respect to the valve body  20 . To that end, the zeta opening  95  has a dimension along a circumference of the second sidewall  81  that is at least twice a dimension along a circumference of the second sidewall  81  of the delta and gamma openings  90 ,  91 , whereby the zeta opening  95  has generally a sector shape when the second plug portion  80  is viewed in transverse cross section ( FIG.  13   ). The zeta opening  95  serves as a third fluid passageway  96  extends along, and protrudes from, the base inner surface  88 . 
     The second plug portion  80  includes a recess  98  that is formed in the second sidewall open end  83 . The recess  98  is disposed between the zeta opening  95  and the delta opening  90 . The recess  98  opens facing away from the second base  86 , and is shaped and dimensioned to receive the projection  73  in a tolerance fit. The cooperative engagement between the projection  73  and the recess  98  ensures that the first and second plug portions  60 ,  80  rotate about the rotational axis  52  in concert with each other. 
     Referring again to  FIGS.  5 - 7   , in the plug assembly  50 , the first plug portion  60  is axially aligned with the second plug portion  80  in such a way that the base outer surface  67  of the first plug portion  60  abuts the second sidewall open end  83 , and the projection  73  is disposed in, and engaged with, the recess  98 . In this configuration, the projection  73  serves as a key that engages the recess  98  in such a way that the first plug portion  60  and the second plug portion  80  are fixed relative to each other and are rotatable about the rotational axis  52  together as a single unit. In addition, the beta opening  71  is partially received within the recess  98 , whereby the first passageway  72  can provide fluid communication between the levels of the valve body  20  in certain rotational orientations of the plug assembly  50  with respect to the valve body  20 . In the plug assembly  50 , the second plug portion  80  is disposed between the first plug portion  60  and the body base  26 . The second base  86  is spaced apart from the first base  66  in a direction parallel to the rotational axis  52  with the second sidewall  82  and second and third passageways  92 ,  96  disposed between the first base  66  and the second base  86 . In addition, the first and second sidewalls  61 ,  81  are aligned. 
     Referring to  FIGS.  18 - 19   , the seal  110  is a cage-like structure that includes a first ring  111 , a second ring  112  that is parallel to, and spaced apart from, the first ring  111 , and linear ribs  113  that extend between the first ring  111  and the second ring  112 . The first ring  111  has a first diameter d 1  corresponding to an inner diameter of the valve body  20  at the sidewall open end  23 . The second ring  112  has a second diameter d 2  corresponding to an inner diameter of the valve body  20  at the sidewall base end  22 . Since the valve body has a conical profile in which the sidewall open end  23  has a greater diameter than the sidewall base end  22 , the second diameter d 2  is less than the first diameter d 1 . The seal  110  includes an inner surface  114  that faces the rotational axis  52  and the plug assembly  50 . The first and second plug portions  60 ,  80  of the plug assembly  50  abut the seal  110  at the seal inner surface  114 . 
     The ribs  113  are spaced apart from each other about the circumference of the first and second rings  111 ,  112 . At least one rib  113  is disposed between each valve port. In the illustrated embodiment in which the valve body  20  includes five valve ports  33 ,  34 ,  35 ,  36 ,  37 , the seal includes six ribs  113 . However, in other embodiments, providing two ribs  113  between a pair of adjacent ports may provide a blocked region or closed port. The particular spacing of the ribs  113  along a circumference of the first and second rings  111 ,  112  depends on the spacing of the valve body grooves  32 , which in turn depends on the spacing of the valve body ports  33 ,  34 ,  35 ,  36 ,  37  along a circumference of the valve body sidewall  21 . Moreover, the relation of the ribs  113  and valve body grooves  32  to the valve ports  33 ,  34 ,  35 ,  36 ,  37  defines the timing of opening of the valve ports  33 ,  34 ,  35 ,  36 ,  37 . 
     Each of the first and second rings  111 ,  112  and the ribs  113  have a rectangular cross sectional shape. In addition, the inner surface  114  of each rib  113  includes a channel  115  that extends between the first ring  111  and the second ring  112 . The channel  115  may be shaped and dimensioned to prevent particles or debris carried by the fluid from being retained therein. The channel  115  may also reduce the contact area between each rib  113  and the plug assembly  50 . In the illustrated embodiment, the channel  115  may have a V-shaped profile. As a result, the inner surface  114  of each rib  113  includes a pair of parallel lands  116 , where one land  116  is disposed on each side of the channel  115 . The lands  116  each provide a linear, narrow sealing contact surface between the seal  110  and an outer surface of the plug assembly  50 . In some embodiments, the lands  116  that bound the channel  115  may serve to prevent contaminant particles and/or other debris from being trapped in the seal/plug interface, whereby abrasive wear is reduced. 
     The outer surface (e.g., the valve body-facing surface)  118  of each rib  113  is received within a corresponding one of the axially-extending grooves  32  of the valve body  20 . The shape, or cross-sectional profile, of the outer surface  118  corresponds to the shape of the groove  32 . In the illustrated embodiment, the outer surface  118  has a rectangular shape to correspond to the rectangular shape of the groove  32 . 
     The seal  110  is formed of an elastic material that is compatible with the fluid that flows through the rotary plug valve  18  and meets the requirements for operating temperature and durability. For example, for a fluid valve used to control fluid in a vehicle coolant system, the seal  110  is formed of an elastomer that is compatible with automotive coolant. In some embodiments, the seal  110  is formed as a single unit in a molding process. By forming the seal  110  as a single unit, the seal  110  is formed without seams (e.g., lines along which two pieces of seal material are joined together) or other joints, whereby the reliability and durability of the seal  110  is improved as compared to some other manufacturing methods. 
     In some embodiments, the plug assembly-facing surfaces  114  of the seal  110  may include a low-friction coating, whereby these surfaces may have a lower coefficient of friction than the remainder of the seal  110 . In other embodiments, the entirety of the seal  110  is coated with a coating that is low friction relative to the elastomer used to form the seal  110 . In one non-limiting example, the seal  110  is formed of an elastomer, and the coating is formed of a Polytetrafluoroethylene (PTFE). By providing the seal  110  with a low-friction coating, the torque required to operate the rotary plug valve  18  is reduced. In still other embodiments, the entirety of the seal  110  is formed of a low friction elastomer. 
     In use, the seal  110  is disposed in the valve body  20  with the first ring  111  adjacent the body sidewall open end  23 , the second ring  112  adjacent to the body sidewall base end  22  and with the ribs  113  disposed in the grooves  32 . The grooves  32  retain the seal  110  in a fixed configuration relative to the valve body  20  when the plug assembly  50  rotates about the rotational axis  52 . The plug assembly  50  is disposed in the valve body chamber  30  with the seal  110  disposed between the plug assembly  50  and the body sidewall  21 . In this configuration, the seal first ring  111  surrounds the first plug portion open end  63  and provides a fluid-tight annular seal between the first plug portion  60  and the valve body  20 . In addition, the seal second ring  112  surrounds the second plug portion  80  at the second base  86  and provides a fluid-tight annular seal between the second plug portion and the valve body  20 . Still further, each valve port  33 ,  34 ,  35 ,  36 ,  37  is surrounded by a portion of the seal  110  that includes an adjacent pair of ribs  113  and portions of the first and second rings  111 ,  112  that extend between the adjacent pair of ribs  113 , whereby a fluid-tight seal separates each valve port from the other valve ports. 
     The rotary plug valve  18  includes the valve body  20  having five valve ports  33 ,  34 ,  35 ,  36 ,  37 . The first valve port  33  is disposed at a first level L 1  (e.g., at a first axial position), and remaining valve ports  34 ,  35 ,  36 ,  37  are disposed at a second level L 2  (e.g., at a second axial position). In addition, the valve plug assembly  50  is disposed in the valve body  20  so as to be sealed relative to the valve body  20  by the seal  110 . The valve plug assembly  50 , including the interlocking first and second plug portions  60 ,  80  is rotatable about the rotational axis  52  to control fluid flow through the valve body  20 . For example, in one rotational position of the valve plug assembly  50  relative to the valve body  20  ( FIG.  20 A ,  FIG.  20 B ), the first passageway  72  extends between the first and second levels L 1 , L 2 , permitting fluid flow between the first valve port  33  and the fifth valve port  37 . In this position, the second passageway  92  permits fluid flow between the third and fourth valve ports  35 ,  36 , while the third passageway  96  is not used as it does not align with multiple valve ports. In another rotational position of the valve plug assembly  50  relative to the valve body  20  ( FIG.  21 A ,  FIG.  21 B ), the third passageway  96  is aligned with both the third and fourth valve ports  35 ,  36  and permits fluid flow therebetween. In this position, the first passageway  72  and the second passageway  92  are not used as they do not extend between valve ports. In another rotational position of the valve plug assembly  50  relative to the valve body  20  ( FIG.  22 A ,  FIG.  22 B ), the second passageway  92  permits fluid flow between the second and third valve ports  34 ,  35 , while the third passageway  96  permits fluid flow between the fourth and fifth valve ports  36 ,  37 . In this position, the first passageway  72  is not used as it does not extend between valve ports. In yet another rotational position of the valve plug assembly  50  relative to the valve body  20  ( FIG.  23 A ,  FIG.  23 B ), the third passageway  96  permits fluid flow between the second and third valve ports  34 ,  35 . In this position, the first passageway  72  and the second passageway  92  are not used as they do not extend between valve ports. 
     Referring to  FIGS.  24  and  25   , an alternative embodiment rotary plug valve  218  includes a valve body  220  and a plug assembly  250  that is disposed in, and rotates relative to, the valve body  220  about a rotational axis  52 . In addition, the rotary plug valve  218  includes the valve seal  110  disposed in the valve body  220 . As in the previous embodiment, the seal  110  provides a fluid-tight seal between the valve body  220  and the plug assembly  250 . 
     The valve body  220  is similar to the valve body  20  described above in that the valve body  220  includes multiple valve ports  33 ,  34 ,  35 ,  36 ,  37 , the number of ports being determined by the specific application. However, in the rotary plug valve  218 , the valve ports  33 ,  34 ,  35 ,  36 ,  37  are arranged on a single level (e.g., the valve ports  33 ,  34 ,  35 ,  36 ,  37  reside in a single plane that is transverse to the rotation axis  52 ). The valve body  220  is similar to the valve body  20  described above in that the valve body  220  includes a base  226 , and a sidewall  221 . The base  226  has a circular profile when viewed in a direction parallel to the rotational axis  52 . The sidewall  221  is joined at the sidewall base end  222  to a peripheral edge of the base  226 , and the sidewall  221  surrounds the base  226 . The sidewall  221  and the base  226  together form a generally cup-shaped structure that defines a valve plug chamber  230  therein. The open end  223  of the sidewall  221  has a diameter that is greater than the diameter of the base end  222 , whereby the sidewall  221  protrudes at an obtuse angle θ 1  relative to the base  226 . In the illustrated embodiment, the angle θ 1  is in a range of 95 to 150 degrees, for example 97 degrees. 
     In the valve body  220 , the inner surface of the valve body sidewall  221  is provided with grooves  232  that extend between the base end  222  and the open end  223 . The grooves  232  have the same cross-sectional shape as the ribs of the seal  110 , and are dimensioned to receive ribs of the seal  110  in a press-fit configuration. The number of grooves  232  provided corresponds to the number of ribs of the seal  110 . In the illustrated embodiment, the valve body  220  includes six grooves  232 . At least one groove  232  is disposed between the ports of each adjacent pair of valve ports  33 ,  34 ,  35 ,  36 ,  37 . 
     The rotary plug valve  218  of  FIGS.  24  and  25    differs from the previous embodiment in that it includes a lid  240  that closes the open end of the valve body  220 . An inner surface  241  of the lid  240  may include an annular groove  242  that extends along a periphery of the inner surface  241 . The groove  242  is shaped and dimensioned to receive the open end  223  of the valve body sidewall  221  in, for example, a press fit engagement. The lid inner surface  241  may also include an annular protrusion  243  that engages the seal first ring  111 , whereby the lid  240  is connected to the valve body  220  in a fluid-tight manner. The annular protrusion  243  is disposed between the groove  242  and a center of the lid  240 , at a location adjacent to the groove  242 . 
     The rotary plug valve  218  of  FIGS.  24  and  25    differs from the previous embodiment in that it includes a spring  246  that is disposed in the valve body chamber  30  between the lid  240  and plug assembly  250 . In the illustrated embodiment, a first end  248  of the spring  246  is received in a centrally-located blind hole  244  provided on the lid inner surface  241 . In addition, a second end  249  of the spring  246  encircles the stub  276 . The spring  246  may be a coil spring that is under compression, whereby the spring  246  applies a force to the plug assembly  250 , ensuring a good seal between plug assembly  250  and the seal  110 , and between the seal  110  and the valve body  220 . 
     The rotary plug valve  218  of  FIGS.  24  and  25    differs from the previous embodiment in that the plug assembly  250  is a single-piece structure that defines two fluid passageways  272 ,  292  that permit fluid delivery within a single level. The plug assembly  250  is similar to the plug assembly  50  described above in that the plug assembly  250  includes a first base  266 , and a first sidewall  261 . The first base  266  is parallel to the body base  226 , and has a circular profile when viewed in a direction parallel to the rotational axis  52 . The first base  266  has an outer surface  267  that faces the body base  226 , and an opposed, inner surface  268  that faces away from the body base  226 . The first sidewall  261  is joined at the base end  262  to a peripheral edge of the first base  266 . The first sidewall  261  encircles the first base  266 , and is centered on the rotational axis  52 . The first sidewall  261  and the first base  266  together form a generally cup-shaped structure. An open end  263  of the first sidewall  261  (e.g., the end of the first sidewall  261  that is spaced apart from the first base  266 ) has a diameter that is greater than the diameter of the base end  262 , whereby the first sidewall  261  protrudes at an obtuse angle θ 2  relative to the first base  266 . In the illustrated embodiment, the angle θ 2  is in a range of 95 to 150 degrees, for example 97 degrees. 
     The rotary plug valve  218  of  FIGS.  24  and  25    differs from the previous embodiment in that the base  226  of the valve body  220  includes a central opening  229 , and the plug assembly  250  includes an input shaft  297  that protrudes outward from the base outer surface  267  and extends through the base central opening  229 . An annular seal  299  is disposed between the input shaft  297  and the base  26 . The input shaft  297  may be connected to the actuator via a splined connection or other known connecting structures, whereby the plug assembly  250  may be driven to rotate about the rotational axis  52  by the actuator. 
     Selective illustrative embodiments of the fluid delivery system including the rotary plug valve are described above in some detail. It should be understood that only structures considered necessary for clarifying the fluid delivery system and the rotary plug valve have been described herein. Other conventional structures, and those of ancillary and auxiliary components of the fluid delivery system and the rotary plug valve, are assumed to be known and understood by those skilled in the art. Moreover, while a working example of the fluid delivery system and the rotary plug valve have been described above, the fluid delivery system and the rotary plug valve are not limited to the working example described above, but various design alterations may be carried out without departing from the fluid delivery system and/or the rotary plug valve as set forth in the claims.