Abstract:
A rotary arm-actuated pintle valve assembly having a pintle valve seat, a pintle shaft, and a valve head forming a pintle valve for regulating flow of gas through a valve body. The shaft extends through a port in a wall of the body. A rotary-arm actuator mounted to the body includes an oscillating motor and shaft. An arm mounted on the motor shaft engages the outer end of the pintle shaft and causes the pintle shaft to reciprocate to open and close the valve. The port permits the pintle to move back and forth radially during actuation of the valve. A floating bearing assembly at the port receives the pintle and slides back and forth as directed by the pintle, all the while maintaining a pneumatic seal around the pintle. A centering element is provided within the valve body to guide the pintle in mating the head with the seat.

Description:
TECHNICAL FIELD 
   The present invention relates to pintle valves; more particularly, to exhaust gas recirculation (EGR) pintle valves for internal combustion engines; and most particularly, to an EGR valve having a rotary actuator wherein a compliant seal/bushing reduces hysteresis and shaft or bearing wear from parasitic radial forces. 
   BACKGROUND OF THE INVENTION 
   Pintle valves are well known for use in controlling flow of fluids, and especially gases. For example, the recirculation of a portion of the exhaust stream of an internal combustion engine into the intake manifold thereof is typically accomplished via a pintle valve. Such pintle valves are known to be actuated by linearly-acting solenoids, linear stepper motors, or motor-driven rotary arms. In the past, solenoid-driven and stepper motor-driven valves have predominated in the automotive art. However, motor-driven rotary arm valves are becoming more common at present because of inherently higher force capabilities. 
   In a solenoid-driven or linear stepper motor-driven valve, the pintle is subjected to actuating forces which are exclusively axial. In a rotary arm-driven valve, however, the pintle is subjected to both axial and radial force vectors over most of the travel path of the arm. It is known that radial vectors can cause unwanted wear of a pintle shaft and/or a seal/bearing, also referred to herein as a seal/bushing. The resultant wear can lead eventually to excessive leakage and non-compliant performance. The condition also robs the valve of efficiency and overall performance and durability. 
   The condition results primarily because a fixed guiding bearing is typically employed to guide the pintle and facilitate proper seating of the valve head on the valve seat. Typically, the engaged length of contact between the bearing and the shaft is several times the diameter of the shaft. Because radial forces are proportional to such length of engagement, in such an arrangement high radial forces are inevitable. The driving mechanism for radial force generation is the necessary variable offset between the centerlines of the actuator and the pintle shaft, which varies as a function of the angular position of the actuator arm. Such offset is necessary to produce working force and is, therefore, unavoidable. 
   What is needed in the art is an improved mechanism for rotary arm-actuation of a pintle valve wherein the bearing/shaft wear known in prior art valves is eliminated. 
   It is a principal object of the present invention to eliminate bearing/shaft wear in arm-actuated pintle valves resulting from parasitic radial forces. 
   SUMMARY OF THE INVENTION 
   Briefly described, a rotary arm-actuated pintle valve assembly in accordance with the invention comprises a valve body having a chamber and a pintle valve seat formed in a first port in a wall of the chamber. A pintle shaft includes a valve head for mating with the valve seat to form a pintle valve for regulating flow of gas through the first port. The pintle shaft extends through a second port in a second wall of the chamber opposite the first wall. A rotary-arm actuating mechanism is mounted to the valve body outside the second port. The mechanism includes an oscillating motor mounted such that the motor shaft is substantially orthogonal to the axis of the valve through the first and second ports, and preferably is offset therefrom. The motor shaft is provided with an arm extending radially from the motor axis, the arm including a stub shaft or pin for receiving an eye on the outer end of the pintle shaft. Rotation of the motor thus causes the pintle shaft to reciprocate like an engine connecting rod, causing the valve head to move onto and away from the valve seat. The second port is large enough to permit the valve pintle to move back and forth radially within the port during actuation of the valve. The port is sealed, and an intermediate bearing provided, by a floating bearing having a double-tapered opening for receiving the pintle shaft. The floating bearing is adapted to slide back and forth in a recess in the valve body as directed by the position of the pintle shaft, all the while maintaining a pneumatic seal around the shaft. Although oscillation of the floating bearing is driven by parasitic radial forces of the shaft, the positional compliance of the bearing prevents those forces from causing bearing and/or shaft wear as in a prior art arm-actuated pintle valve. Preferably, a strut-supported radial spider element is also provided within the chamber adjacent the seat to guide the pintle shaft in mating the valve head with the valve seat. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
       FIG. 1  is an elevational cross-sectional view of a prior art rotary arm-actuated pintle valve; 
       FIG. 2  is an elevational cross-sectional view of a first embodiment of an improved rotary arm-actuated pintle valve in accordance with the invention, showing the valve in a closed position, and showing a first embodiment of a floating seal/bearing; 
       FIG. 3  is a view like that shown in  FIG. 2 , showing the valve in a open position; 
       FIG. 4  is an isometric view of the first embodiment of a floating seal/bearing assembly shown in  FIGS. 2 and 3 ; 
       FIG. 5  is an elevational cross-sectional view of the floating seal/bearing assembly shown in  FIG. 4 ; 
       FIG. 6  is an elevational cross-sectional view of a second embodiment of an improved rotary arm-actuated pintle valve in accordance with the invention, showing the valve in a closed position, and showing a second embodiment of a floating seal/bearing; 
       FIG. 7  is a view like that shown in  FIG. 6 , showing the valve in a open position; 
       FIG. 8  is an isometric view of the second embodiment of a floating seal/bearing assembly shown in  FIGS. 6 and 7 ; 
       FIG. 9  is an elevational cross-sectional view of the floating seal/bearing assembly shown in  FIG. 8 ; 
       FIG. 10  is an elevational cross-sectional view of a third embodiment of an improved rotary arm-actuated pintle valve in accordance with the invention, showing the valve in a closed position, and showing a third embodiment of a floating seal/bearing; 
       FIG. 11  is an a view like that shown in  FIG. 10 , showing the valve in a open position; 
       FIG. 12  is an isometric view of the third embodiment of a floating seal/bearing assembly shown in  FIGS. 10 and 11 ; and 
       FIG. 13  is an elevational cross-sectional view of the floating seal/bearing assembly shown in FIG.  12 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIG. 1 , a prior art rotary arm-actuated pintle valve  10  comprises a valve body  12  having a first chamber  14  and a second chamber  16  separated by an internal port  18  through a first valve wall  17  defined by a valve seat insert  20  having a beveled seat  22  with a face for mating with a similarly-beveled face  24  on a valve head  26 . A second port is defined by an axial bore  28  in valve body  12  coaxial with valve seat face  22 . An elongate bushing  30  is mounted in bore  28  and has an axial bore  32  for slidingly receiving a pintle shaft  34  for actuating valve head  26 . Seat  22 , head  26 , and pintle shaft  34  define a pintle valve  25  for regulating flow through port  18  to or from a third port  19 . 
   Mounted on valve body  12  is a rotary-arm actuator  36  comprising a motor  38  having a shaft  40  having an axis  42  disposed substantially orthogonal to, but not intersecting, the axis  44  of shaft  34 . An arm  46  is mounted on motor shaft  40  for rotation thereby about axis  42 . Arm  46  includes a cam slot  48  for receiving a cam roller follower  50  mounted on pintle shaft  34 . Cam slot  48  has first and second surfaces  52 , 54  for follower  50  to follow during rotation of arm  46  to open and close valve  25 . Surfaces  52 , 54  have varying radii from axis  42 , thereby defining cam surfaces such that rotation of arm  46  causes pintle shaft  34  to move reciprocally within bushing  32 , thereby adjusting the position of face  24  with respect to seat face  22  to control flow of material through port  18 . As previously noted, actuation of follower  50  by cam slot  48  creates not only an axial force vector for reciprocating pintle shaft  34  but also a parasitic radial vector that causes wear of seal/bushing  30  and shaft  34 . 
   Referring to  FIGS. 2 and 3 , a first embodiment  10 ′ of an improved rotary arm-actuated pintle valve in accordance with the invention, showing the valve  25 ′ in the closed ( FIG. 2 ) and open ( FIG. 3 ) positions, comprises a valve body  12 ′ similar to valve body  12  and has first and second chambers  14 ′, 16 ′ separated by a seat  20 ′. Pintle valve  25 ′, analogous to prior art pintle valve  25 , includes seat  20 ′, valve head  26 ′, and pintle shaft  34 ′, for regulating flow between chamber  16 ′ and port  19 ′ through port  18 ′ and chamber  14 ′. 
   Mounted on valve body  12 ′ is a rotary-arm actuator means  36 ′ comprising a motor  38 ′ having a shaft  40 ′ having an axis  42 ′ disposed substantially orthogonal to the axis  44 ′ of shaft  34 ′. An arm  46 ′ is mounted at a first end  47 ′ on motor shaft  40 ′ for rotation thereby as a crank about axis  42 ′. Arm  46 ′ includes a pin  60  disposed at a second end  49 ′ at a radial distance from motor axis  40 ′ for receiving an eye  62  on pintle shaft  34 ′ such that rotation of arm  46 ′ causes pintle shaft  34 ′ to move reciprocally in the fashion of an engine connecting rod, thereby opening and closing pintle valve  25 ′ to control flow of material through port  18 ′. 
   In operation, when valve embodiment  10 ′ is fully closed, axis  44 ′ of pintle shaft  34 ′ is coaxial with the axis (coincident) of seat  20 ′ and port  18 ′ as shown in  FIG. 2  such that valve head  26 ′ is fully seated against seat  20 ′ with seat face  22 ′ in full contact with valve face  24 ′. In this position, pin  60  is at nearly, although preferably not exactly, the 12 o&#39;clock position with respect to motor shaft  40 ′. Thus, motor  38 ′ has maximum closing force of head  26 ′ against seat  20 ′. To open the valve to controllably regulate the position of head  26 ′ with respect to seat  20 ′, motor shaft  40 ′, and arm  46 ′ are rotated clockwise through a desired angle to a new clock position, preferably about 2:30 o&#39;clock when valve  25 ′ is fully open. Further rotation of arm  46 ′ does not generate additional flow through the valve. 
   Preferably, pintle shaft  34 ′ is guided in sealing and unsealing head  26 ′ from seat  20 ′ by a centering element such as spider  70  disposed in a groove  72  in the wall of chamber  14 ′. Spider  70  includes a central opening defined by a flexible bearing  74 , for example, a coil spring  76  surrounding shaft  34 ′, and shaft  34 ′ pivots in the spider central opening in such opening and closing of pintle valve  25 ′. 
   Because the motion of pintle shaft  34 ′ has both x- and y-direction components in passing through second port  28 ′, provision must be made to seal shaft  34 ′ to prevent escape of material from chamber  14 ′ into actuator  36 ′. This requires a seal capable of floating in the x direction in response to x-direction forces and may be accomplished in any of several ways, within the scope of the invention. 
   For the remaining disclosure and discussion, valve body  12 ′, pintle valve  25 ′, and actuator assembly  36 ′ are identical, and valve body  12 ′ is provided with a transverse channel  80  intersecting port  28 ′ for receiving a floating seal/bearing assembly as described below. 
   Referring to  FIGS. 2 through 5 , in a first embodiment of a floating seal/bearing assembly  82  for first pintle valve assembly embodiment  10 ′, a seal/bearing housing  84  is stepped and formed to fit snugly within port  28 ′ and channel  80 . A seal/bearing element  86  is slidable within housing  84  in the x direction as directed by x-direction forces on pintle shaft  34 ′. A cover plate  88  retains element  86  within housing  84 , and the cover plate and housing are bolted to valve body  12 ′ by bolts  90  through bolt holes  92 . Cover plate  88  and housing  84  are each provided with an elongate slot  94   a , 94   b , respectively, for receiving shaft  34 ′. 
   Element  86  is formed to slide easily between cover plate  88  and housing  84 , and to overlap both the left and right sides  84   a , 84   b  of housing  84  at all times. Element  86  includes a central aperture  96  for receiving shaft  34 ′ snugly but slidably. Preferably, aperture  96  comprises opposed conic portions  96   a , 96   b  that meet at a central annular juncture  96   c . Thus, the walls of aperture  96  are in surrounding and sealing contact with shaft  34 ′ at all operating positions of shaft  34 ′. 
   Referring to  FIGS. 6 through 9 , in a second embodiment  82 ′ of a floating seal/bearing assembly for a second embodiment  10 ″ of a pintle valve assembly in accordance with the invention, a seal/bearing housing  84 ′ is formed to fit snugly across port  28 ′ and within channel  80 . A seal/bearing element  86 ′ is slidable within housing  84 ′ in the x direction as directed by x-direction forces on pintle shaft  34 ′. A cover plate  88 ′ similar to cover plate  88  retains element  86 ′ within housing  84 ′. A spring housing  100  has a central opening  102  including an inrolled rim  104  that defines an outer seat for a tapered coil spring  106 . An annular groove  108  formed in the upper surface of element  86 ′ defines an inner seat for spring  106 . Spring housing  100 , cover plate  88 ′, and housing  84 ′ are bolted to valve body  12 ′ by bolts  90  through bolt holes  92 . Cover plate  88 ′ and housing  84 ′ are each provided with an elongate slot  94   a ′, 94   b ′, respectively, for receiving shaft  34 ′. 
   Element  86 ′ includes a central aperture  96 ′ for receiving shaft  34 ′ snugly but slidably. Preferably, aperture  96 ′ comprises conic portion  96   b . Thus, the walls of aperture  96 ′ are in surrounding and sealing contact with shaft  34 ′ at all operating positions of shaft  34 ′. 
   Element  86 ′ is formed to slide easily between cover plate  88 ′ and housing  84 ′. Spring  106  urges the lower surface  110  of element  86 ′ into sealing contact with the inner surface  112  of housing  84 ′ and is sufficiently flexible to permit element  86 ′ to sealingly slide along surface  112  in response to urging in the x direction by shaft  34 ′. 
   Referring to  FIGS. 10 through 13 , in a third embodiment  82 ″ of a floating seal/bearing assembly for a third embodiment  10 ′″ of a pintle valve assembly in accordance with the invention, a seal/bearing housing  84 ″, which may be identical with housing  84 ′, is formed to fit snugly across port  28 ′ and within channel  80 . A seal/bearing element  86 ″, which may be substantially identical with element  86 ′ minus groove  108 , is slidable within housing  84 ″ in the x direction as directed by x-direction forces on pintle shaft  34 ′. A cover plate  88 ″ which may be identical with cover plate  88 ′ retains element  86 ″ within housing  84 ″. A spring housing  100 ′ has a central opening  102 ′ including first and second formed spring tabs defining first and second springs  106 ′. Springs  106 ′ extend through opening  94   a ′ in cover plate  88 ″ to bear directly on element  86 ″. Spring housing  100 ′, cover plate  88 ″, and housing  84 ″ are bolted to valve body  12 ′ by bolts  90  through bolt holes  92 . 
   Element  86 ″ includes a central aperture  96 ″ for receiving shaft  34 ′ snugly but slidably. Preferably, aperture  96 ″ comprises conic portion  96   b ′. Thus, the walls of aperture  96 ″ are in surrounding and sealing contact with shaft  34 ′ at all operating positions of shaft  34 ′. 
   Element  86 ″ is formed to slide easily between cover plate  88 ″ and housing  84 ″. Springs  106 ′ urge the lower surface  110 ′ of element  86 ″ into sealing contact with the inner surface  112 ′ of housing  84 ″, permitting element  86 ″ to sealingly slide along surface  112 ′ in response to urging in the x direction by shaft  34 ′. 
   Pintle valve assemblies  10 ′, 10 ″, and  10 ′″ are especially suited to use in motor vehicles  115  as an exhaust gas recirculation (EGR) valve for an internal combustion engine  120  in known fashion. 
   While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims.