Abstract:
A novel spatial arrangement of valve ports and hold-down bolt holes in the body of an exhaust gas recirculation valve, wherein the centers of the ports are between and aligned with the centers of the bolt holes, thereby producing maximum sealing force around the ports against the surface to which the valve is bolted, such as the exhaust and intake manifolds of an internal combustion engine.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims the benefit of U.S. Provisional Application, Ser. No. 60/184,584, filed Feb. 24, 2000. 
     
    
     
       TECHNICAL FIELD  
         [0002]    The present invention relates to pintle-type valves; more particularly to pintle valves for permitting the controlled admission of exhaust gases into the fuel intake manifold of an internal combustion engine; and most particularly to a pintle valve having optimal sealability of the valve body to an attached substrate.  
         BACKGROUND OF THE INVENTION  
         [0003]    It is well known in the automotive art to provide a variable valve connecting the exhaust manifold with the intake manifold of an internal combustion engine to permit selective and controlled recirculation of a portion of an engine&#39;s exhaust gas into the fuel intake stream. Such recirculation is beneficial for reducing the burn temperature of the fuel mix in the engine to reduce formation of nitrogen and sulfur oxides which are significant components of smog. Such a valve is known in the art as an exhaust gas recirculation (EGR) valve.  
           [0004]    Typically, an EGR valve has a valve body enclosing a chamber disposed between a first port in the exhaust manifold and a second port in the intake manifold; a valve seat dividing the chamber between the two ports; a valve pintle having a valve head fitted to the valve seat and a valve stem extending from the valve head through a bearing mounted in a third port in a sidewall of the valve body; a spring-retained bearing splash shield; and a solenoid actuator mounted on the exterior of the valve body and operationally connected to the outer end of the valve pintle.  
           [0005]    A problem inherent to known EGR valves is that leakage can develop along the interface between the valve body and the exhaust and intake manifolds. Leakage between the connecting ports on the manifolds is, by definition, not metered flow and therefore not controlled. Such unintended flow can cause the engine to run rough or to ultimately stall. Additionally, unmetered external air can be ingested by the engine, thereby causing surges that can result in dangerous driving conditions, particularly in inclement weather. Such undesirable conditions can have the further effects of increasing wear on brakes and other components and of causing customer dissatisfaction.  
           [0006]    It has been found that known EGR valves typically have ports for connecting to manifold ports which are significantly out of line with the force hold-down line generated by the pattern of bolt holes in the valve body. Thus, the sealing force exerted around the ports is not maximized for the degree of torque on the sealing bolts. A further shortcoming of some known EGR valves is that more than two bolts are required to attach the valve, which increases the cost of manufacture. Further, in assembly, it can be quite difficult to tighten three or more bolts equally. In sequential tightening, the tightening of each bolt influences the degree of tightening of all previous bolts, thus requiring tightening iteration. Tightening of all bolts simultaneously is expensive and difficult to perform and does not guarantee uniform torque. With uneven tightening, the valve is susceptible to distortion and outright fracture. Thus a valve attachable at no more than two points is optimal.  
           [0007]    What is needed is an improved spatial relationship between the valve ports and the valve hold-down bolts wherein the sealing force on the ports is maximized and the number of hold-down bolts is limited to two.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention is directed to a novel spatial arrangement of valve ports and hold-down bolt holes in the body of an exhaust gas recirculation valve, wherein the centers of the ports are between and aligned with the centers of the bolt holes, thereby producing maximum sealing force around the ports against the surface to which the valve is bolted, such as the exhaust and intake manifolds of an internal combustion engine. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    The foregoing and other objects, features, and advantages of the invention, as well as presently preferred embodiments thereof, will become more apparent from a reading of the following description in connection with the accompanying drawings, in which:  
         [0010]    [0010]FIG. 1 is a cross-sectional elevational view of a prior art ECR valve;  
         [0011]    [0011]FIG. 2 is an isometric view of the prior art EGR valve shown in FIG. 1;  
         [0012]    [0012]FIG. 3 is a plan view of the mating surface of the valve body of the prior art EGR valve shown in FIGS. 1 and 2, showing non-aligned relationship of the valve ports with the bolt holes in the valve body;  
         [0013]    [0013]FIG. 4 is a plan view like that shown in FIG. 3, showing an improved EGR valve body arranged in accordance with the invention; and  
         [0014]    [0014]FIG. 5 is an elevational cross-sectional view of an EGR valve assembly comprising the view taken along line  5 - 5  in the improved valve body shown in FIG. 4. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0015]    The benefits afforded by the present invention will become more readily apparent by first considering a prior art pintle valve. Referring to FIG. 1, a prior art EGR valve assembly  10  includes a valve body  12  having a valve seat  14  separating a first chamber  16  from a second chamber  18 , which chambers may communicate with the exhaust and intake systems, respectively, of an internal combustion engine (not shown) or the reverse. Valve head  20  is disposed adjacent to seat  14  for selectively mating therewith to open or to close communication between chambers  16  and  18 . Valve stem, or pintle,  22  extends from head  20  through an axial bore  24  in bearing  26  and is captured within armature  28  of solenoid actuator  30 . Bearing  26  is disposed in a port  27  in a wall of valve body  12  and guides stem  22  in reciprocating motion to open and close the valve when actuator  30  is energized and de-energized, respectively.  
         [0016]    Bearing  26  is provided with a circumferential flange  32  having a first axial face  34  for sealing against axial outer surface  36  of valve body  12  to prevent leakage of gases therebetween. A cup-shaped bearing splash shield  38  has an inward-extending flange  40  with a central aperture for passage of stem  22 , preferably without contact therebetween, and a cylindrical skirt  44  extending axially to shield a substantial portion of bearing  26  from external contaminants. Shield  38  is open in a downwards direction to permit venting of any gases which may leak along bore  24  during operation of the valve. Actuator  30  is connected to valve body  12  via a plurality of bolts  46  extending through a plurality of standoffs  48 . A coil spring  50  surrounding stem  22  is disposed within shield  38 , being compressed between actuator  30  and a second surface  52  on flange  32  for urging flange  32  to seal against surface  36  under all operating conditions. Spring  50  also serves to urge shield  38  against surface  49  of primary polepiece  51  of actuator  30  to prevent dust intrusion into the actuator. Valve assembly  10  may be attached along sealing surface  55  to a substrate, such as the exhaust and intake manifolds of an internal combustion engine (not shown), by extending bolts (not shown) through bolt holes  53  in valve body  12 . A conventional fiber, composite, or preferably metal gasket (not shown) may be installed between the valve body and the substrate.  
         [0017]    Referring to FIGS. 2 and 3, the operational axis  57  of valve assembly  12  is offset from the line of bolt holes  53 ; that is, any plane containing axis  57  is not coincident with a plane  58  containing the axes  59  (FIG. 1) of bolt holes  53 . Plane  58  contains the maximum force vectors normal to surface  55 . The sealing force exerted on the valve body by bolts in holes  53  is greatest immediately around holes  53  and in the line directly between holes  53 . The sealing force decays in proportion to vector and distance from that line. Thus, the normal force to seal surfaces  61  and  63  surrounding ports  16  and  18 , respectively, against a substrate must be less than the maximum possible for any given bolt torque in holes  53 .  
         [0018]    Referring to FIGS. 4 and 5, a preferred embodiment  65  of an improved valve body  12 ′ provides the maximum normal force possible on the sealing surfaces with minimum distortion and deformation of valve body  12 ′ under angular or wrenching loads on the valve. Relative to prior art valve body  12 , the operational axis  57 ′ is moved into the plane  58  containing bolt hole axes  59  (coincident with the section along line  5 - 5 ). Further, port  18  is rotated 90° such that it and port  16  are bisected symmetrically by plane  58 . Further, valve body  12 ′ is relieved by cutouts  64  which favorably reduce both the mass of the valve and the area for sealing, thereby increasing the unit sealing force on the remaining lands  66 . Body  12 ′ is shown attached to actuator  30  in FIG. 5 to form an improved valve assembly  10 ′. Preferably, the circular portion  68  of valve body  12 ′ is substantially of the same diameter as actuator  30  to provide stability without excessive mass and volume in body  12 ′.  
         [0019]    Valve assembly  10 ′ in accordance with the invention is especially useful as an exhaust gas recirculation valve disposed in known fashion between the exhaust manifold  70  and the intake manifold  72  of an internal combustion engine  70 .  
         [0020]    The foregoing description of the preferred embodiment of the invention has been presented for the purpose of illustration and description. It is not intended to be exhaustive nor is it intended to limit the invention to the precise form disclosed. It will be apparent to those skilled in the art that the disclosed embodiments may be modified in light of the above teachings. The embodiments described are chosen to provide an illustration of principles of the invention and its practical application to enable thereby one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Therefore, the foregoing description is to be considered exemplary, rather than limiting, and the true scope of the invention is that described in the following claims.