Abstract:
A leakage arresting system comprising a novel gas arrestor for installation on an interrupted pintle shaft in a pintle-type valve, such as an exhaust gas recirculation valve for an internal combustion engine, for preventing leakage of gas and moisture along the pintle shaft into the actuator, to prevent corrosion and failure of the actuator. The system comprises two elements: a pintle shaft which is interrupted outside the actuator, and a positive vapor block in the form of a cup-shaped arrestor disposed across the pintle interruption. The invention is applicable to both unbalanced and force-balanced valves.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application Serial No. 60/184,513, filed February 24, 2000 and U.S. Provisional Application Serial No. 60/184,533, filed February 24, 2000. 
    
    
     TECHNICAL FIELD 
     The present invention relates to pintle-type valves; more particularly to solenoid-actuated 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 system including an interrupted pintle and gas arrestor for preventing entrance of corrosive gases and moisture into the valve actuator. 
     BACKGROUND OF THE INVENTION 
     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. 
     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 pintle shaft having a valve head fitted to the valve seat and 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 having an armature into which the outer end of the valve pintle extends. 
     A problem inherent to EGR valve applications is that the managed fluid (exhaust gas) is moisture-laden, corrosive, and dirty. If this gas enters the actuator, for example, by leaking along the pintle shaft, then internal corrosion, malfunction, and ultimate failure of the actuator can result. Such failure can lead to emission non-compliance and can incur significant cost to a vehicle manufacturer if a recall is required. Two known solutions to this problem are a sealed, impermeable actuator, or, alternatively, an actuator having working components which are unaffected by exhaust gas. Either of such actuators is currently impractical for cost and performance reasons. Further, a sealed actuator would be even more vulnerable to damage from trapped moisture if a leak should develop in the seal; and a corrosion-resistant actuator would require materials of construction which are less magnetically efficient than the currently used soft iron and powder metals, thus dictating a substantially larger solenoid. 
     What is needed is a gas arrestor between an EGR valve and actuator that prevents gas and moisture intrusion into the actuator without impairing efficiency, size, and performance of the valve and actuator. Preferably, such an arrestor is simple and inexpensive to fabricate and install. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a leakage arresting system comprising a novel gas arrestor for installation on an interrupted pintle shaft in a pintle-type valve, such as an exhaust gas recirculation valve for an internal combustion engine, for preventing leakage of gas and moisture along the pintle shaft into the actuator to prevent corrosion and failure of the actuator. The system comprises two elements: a pintle shaft which is interrupted outside the actuator, and a positive vapor block in the form of a cup-shaped arrestor disposed across the pintle interruption. The invention is applicable to both unbalanced and force-balanced valves. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     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: 
     FIG. 1 is an elevational cross-sectional view of a prior art EGR valve; 
     FIG. 2 is an elevational cross-sectional view of a valve like that shown in FIG. 1 equipped with an interrupted pintle shaft and a gas arrestor in accordance with the invention; 
     FIG. 3 is a view like that shown in FIG. 2, showing the invention adapted to a force-balanced valve; and 
     FIG. 4 is an elevational cross-sectional view of the valve shown in FIG. 2 mounted onto an actuator modified for an interrupted pintle shaft. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     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  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 pintle shaft  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 shaft  22  in reciprocating motion to open and close the valve when actuator  30  is energized and de-energized, respectively. 
     Bearing  26  is provided with a circumferential flange  32  having an 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 shaft  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 pintle shaft  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 inhibit dust intrusion into the actuator. 
     A second spring  54  disposed in compression within actuator  30  between armature  28  and polepiece  51  keeps valve  10  in the normally-closed position shown in FIG. 1 when the solenoid is de-energized, pintle shaft  22  thus being under tension. When the valve is opened, by energizing of the actuator, pintle shaft  22  is subjected to compressive force, an important consideration in providing an interrupted pintle shaft and gas arrestor in accordance with the invention. 
     Referring to FIG. 2, an improved valve  10 ′ in accordance with the invention is shown, for clarity without an actuator. Like prior art valve  10 , valve  10 ′ has a valve body  12 ′ having a valve seat  14 ′ separating a first chamber  16  (outside of the valve body in this embodiment but analogous to chamber  16  in FIG. 1) from a second chamber  18 . Valve head  20 ′ having a mating element  21  attached thereto as by any conventional means is disposed adjacent to seat  14 ′ for selectively mating therewith to open or to lose communication between chambers  16  and  18 . Pintle shaft  22 ′ extends from head  20 ′ through an axial bore  24 ′ in bearing  26 ′. Bearing  26 ′ is disposed in a port  27 ′ in a all of valve body  12 ′ and guides pintle shaft  22 ′ bin reciprocating motion to open and close the valve when the actuator (not shown) is energized and de-energized, respectively. 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. Preferably, the diameter of port  27 ′ is slightly greater than the diameter of the corresponding portion of bearing  26 ′, providing a gap  29  therebetween, such that the bearing may be radially compliant to accommodate axial misalignments of other valve components. 
     For ease of assembly, pintle shaft  22 ′ may be provided in upper and lower sections  22 ′ a , 22 ′ b  which are threaded appropriately to screw together to form pintle shaft  22 ′. Alternatively, pintle shaft  22 ′ may be provided as a one-piece element, and the metering head may be attached conventionally. Pintle shaft  22 ′ terminates in a flared portion  39  having a flat outer surface  41 . 
     A gas arrestor  43 , cup-shaped and inverted downwards, has a central aperture for receiving portion  39 . Arrestor  43  is readily and inexpensively formed as by stamping from sheet metal. A coil spring  50 ′ is disposed in compression around pintle shaft  22   a ′ between bearing flange  32 ′ and the underside of arrestor  43 , urging the arrestor into sealing contact with the underside of flared portion  39 . Actuator standoffs  45  are attached to valve body  12 ′ and are provided with one or more vents  47 . 
     Gases which may leak from chamber  18  along pintle shaft  22   a ′ through bore  24 ′ are thus positively precluded from migrating past arrestor  43  and instead are directed by arrestor  43  back toward valve body  12 ′ and are allowed to escape through vents  47 . 
     Referring to FIG. 4, the valve  10 ′ just described and shown in FIG. 2 is here shown fully attached to an actuator  30 ′ modified as necessary to interface with the shortened pintle shaft  22 ′. Valve  10 ′ is shown mounted for use as an exhaust gas recirculation (EGR) valve on an internal combustion engine  104 , exhaust manifold  100  and intake manifold  102  being attached to valve  10 ′ adjacent chambers  16  and  18 , respectively. With respect to actuator  30 ′, second spring  54  is eliminated. The outer portion of pintle shaft  22  extending into and captured by armature  28  is replaced by a stub shaft, or pintle lifter,  22 ′ c  which makes contact with but is not connected to surface  41 . Thus, the combination of pintle shaft elements  22 ′ a ,  22 ′ b , and  22 ′ c  may be thought of as an “interrupted” pintle shaft having a positive gas-arresting break between elements  22 ′ b  and  22 ′ c . Pintle lifter  22 ′c is radially supported and guided by a new flanged bearing  62 , similar to bearing  26 ′, disposed preferably as a press fit in a new axial bore  64  in modified polepiece  51 ′. Preferably, the length of lifter  22 ′ c  in the bearing is at least 1.5 times the diameter of lifter  22 ′ c  to inhibit potential ingress of gas and moisture into actuator  30 ′ through bearing  62 . 
     Because valve head  20 ′ is urged towards the closed valve position by spring  50 ′, armature  28  and pintle lifter  22 ′ c  act on pintle shaft  22 ′ only under compression. 
     Because surface  41  presents a relatively broad contact surface for pintle lifter  22 ′ c , the axial alignment of actuator  30 ′ with valve  10 ′ is significantly relaxed over the tight tolerance required in prior art valve  10 . 
     Referring to FIG. 3, a second embodiment  10 ″ of a valve with a gas arrestor in accordance with the invention is configured as a force-balanced valve. Valve  10 ′ is not force-balanced in that pressure or vacuum in chamber  18  exerts an opening or closing force on the back side of valve head  20 ′ which must be overcome by spring  50 ′ for the valve to remain closed or by actuator  30 ′ for the valve to open. Thus, the operating range of valve  10 ′ is limited to pressures below the spring force of the closing spring and the solenoid force of the actuator. In valve  10 ″, however, a piston  53  having a cross-sectional area substantially equivalent to the area of valve head  20 ′ is disposed on pintle shaft  22   a ″ in opposition to head  20 ′ such that the opening or closing force exerted on head  20 ′ is balanced by an equal closing or opening force exerted on piston  53 . Thus valve  10 ″ may be used over a broader range of internal pressures than valve  10 ′. 
     In valve  10 ″, piston  53  effectively takes the place of bearing  26 ′ in guiding the pintle shaft in the valve. A piston cylinder  55  is disposed in a bore  27 ″ in valve body  12 ″ to be radially-compliant as described above for bearing  26 ′ in valve body  12 ′. Cylinder  55  is provided with a flange  32 ″ for supporting and sealing against surface  36 ″. Piston  53  is slidingly disposed within cylinder  55 , the diametral tolerance between piston  53  and cylinder  55  being as small as possible without causing significant drag therebetween. Pintle shaft  22   a ″ extends beyond piston  53  and is terminated in a broad, flat cap  56  having an upper surface  41 . A second embodiment  43 ′ of a gas arrestor is disposed on shaft  22   a ″ and a coil spring  50 ″ in compression is captured between arrestor  43 ′ and flange  32 ″, again for urging arrestor  43 ′ sealingly against cap  56  and for urging head  20 ″ into closed relationship with seat  14 ″. Because the cylindrical surface area of piston  53  is substantially greater than the surface area of shaft  22   a ′ in valve  10 ′, the potential for leakage along the piston surface is also substantial. Therefore, cylinder  55  preferably is provided with an inwardly curved flange  58  for receiving a shaft seal  60  which may be formed from an appropriate material, for example, an elastomer, metal, or polymer, and disposed with minimal radial pressure on shaft  22 a″. 
     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.