Abstract:
An integral heat sink for transferring heat from combustion exhaust gas produced by a vehicular internal combustion engine is disclosed. The heat sink includes a body providing an integral base configured for support by a manifold. The heat sink also includes a hollow elongate member providing a first portion contained in the body. The first portion has an exhaust gas intake. The member also includes a second portion extending from the body. The second portion is configured for insertion into the manifold and provides at least one discharge for the exhaust gas. The heat sink also includes a cavity disposed between the body and the member. The cavity is configured for conveying combustion air from the manifold around at least a portion of the member.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to a combustion system for engines. More particularly, the present invention relates to an exhaust gas recirculation system for combustion of recycled exhaust gas in a vehicular internal combustion engine. Most particularly, it relates to heat sinks for mounting exhaust gas recirculation (EGR) valves on intake manifolds. 
     BACKGROUND OF THE INVENTION 
     It is well known to recycle exhaust gas from a combustion chamber of a vehicular internal combustion engine for re-combustion in the chamber. Such recycling of exhaust gas assists in reducing motor vehicle emissions of particular pollutants, such as nitrogen oxides, and may conserve fuel. 
     Typically, the exhaust gas is conveyed directly from an exhaust gas source to an intake manifold that is constructed of metal. However, such metal manifolds are disadvantageous because they are costly to fabricate and subject to deterioration (e.g., rust). Intake manifolds constructed of plastic or plastic composites may be less expensive than metallic intake manifolds, however such plastic manifolds are disadvantageous because they may be easily degraded (e.g., melted, charred, etc.) by the high temperature of EGR valves mounted on the intake manifold. 
     What is needed, therefore, is a heat sink for dissipating the heat of recycled exhaust gas without significantly damaging the intake manifold. Accordingly, it would be advantageous to have a heat sink coupled between the EGR valve and the intake manifold for dissipating enough exhaust gas heat. It would also be advantageous to have a heat sink capable of rapid installation in an engine system. It would further be advantageous to have a heat sink that is readily accessible for rapid service, repair or replacement. It would further be advantageous to have a heat sink that operates for the durable life of a vehicle. 
     SUMMARY OF THE INVENTION 
     The present invention relates to an integral heat sink for transferring heat from combustion exhaust gas produced by a vehicular internal combustion engine. The heat sink includes a body providing an integral base configured for support by a manifold. The heat sink also includes a hollow elongate member with a first portion contained in the body. The first portion has an exhaust gas intake. The member also includes a second portion extending from the body. The second portion is configured for insertion into the manifold and provides at least one discharge for the exhaust gas. The heat sink also includes a cavity disposed between the body and the member. The cavity is configured for conveying combustion air from the manifold around at least a portion of the member. 
     The present invention also relates to an integral heat sink for transferring heat from combustion exhaust gas produced by an internal combustion engine of a vehicle. The heat sink includes a body providing an integral base configured for support by a manifold. The heat sink also includes a hollow elongate member providing a first portion contained in the body. The first portion has an exhaust gas intake. The member also includes a second portion extending from the body. The second portion is configured for insertion into the manifold and provides at least one discharge for the exhaust gas. The heat sink also includes a first cavity disposed between the body and the member. The first cavity is configured for conveying combustion gas from the manifold around the member. The heat sink also includes a second cavity disposed between the body and the first cavity. The second cavity is configured for conveying ambient gas from the atmosphere around the first portion of the member. 
     The present invention also relates to an exhaust gas recirculation system for transferring heat from exhaust gas having a temperature to the atmosphere. The system includes an intake manifold coupled to the internal combustion engine of a vehicle for communicating exhaust gas to the intake manifold and thence to the combustion chamber of the engine. The system also includes a passage for conveying the exhaust gas from the combustion chamber to an EGR valve. The EGR valve outlet is coupled to the inlet of a heat sink. The heat sink has an integral base supported by the manifold and in fluid flow communication with the passage. The system also includes a hollow elongate member with a first portion contained in the heat sink, the first portion having an exhaust gas intake. The member also has a second portion that extends from the body, is disposed in the manifold and provides at least one discharge for the exhaust gas into the manifold. The system also includes a first cavity for conveying combustion air from the manifold around at least a portion of the member disposed between the heat sink and the member. The system also includes a second cavity for conveying ambient air from the atmosphere around at least a portion of the first portion of the member disposed between the body and the first cavity. The temperature of the exhaust gas is substantially reduced by conveying the exhaust gas from the combustion chamber, through the passage, through the intake of the member and through the discharge. 
     It is an object of this invention to provide a heat sink for dissipating enough heat to achieve operating temperatures at the heat sink/manifold interface. It is also an object of this invention to provide a heat sink capable of rapid installation in an engine system. It is also an object of this invention to provide a heat sink that is readily accessible for rapid service, repair or replacement. It is also an object of this invention to provide a heat sink that operates for the durable life of a vehicle. 
     Other principal objects, features and advantages of the invention will become apparent to those skilled in the art upon review of the following FIGURES, the detailed description and the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES 
     FIG. 1 is a fragmentary perspective view of an exhaust gas recirculation system according to a preferred embodiment of the present invention; 
     FIG. 2 is a perspective view of a heat sink of the exhaust gas recirculation system of FIG. 1; 
     FIG. 3 is a fragmentary cross-sectional view of the exhaust gas recirculation system of FIG. 1 along line  3 — 3  of FIG. 1; 
     FIG. 4 is a perspective view of a heat sink according to an alternative embodiment of the present invention; 
     FIG. 5 is a fragmentary cross-sectional view of the heat sink of FIG. 4 coupled to a manifold; and 
     FIG. 6 is a cross-sectional view of the exhaust gas system shown in FIG. 5 along line  6 — 6  of FIG.  5 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1, an engine system  10  providing an exhaust gas recirculation system  12  shown. System  12  includes an EGR valve  13  coupled to a heat sink  14  that is adapted to transfer the heat from exhaust gas, fluid or gas to the atmosphere and to convey exhaust gas from the EGR valve into an intake manifold  16 . 
     During operation of engine system  10 , purified air, fluid or gas from an air filter (not shown) is conveyed to intake manifold  16 . The purified air through intake manifold  16  conveyed from an upstream end  20 , past recirculation system  12  at which point exhaust gas is introduced into the flow of air, to a downstream end  18 . The air/exhaust mixture is subsequently conveyed to a combustion chamber of an internal combustion engine  11  where it is mixed with fuel and burned. A portion of the exhaust gas resulting from this burning is recycled through system  12  back into the intake manifold for mixture with purified air. 
     An exhaust gas induction tube  24  is fluidly coupled to an inlet of system  12  and conveys a portion of the exhaust gas from the combustion chamber to system  12 . A fastener (shown as a crimped connector  22 ) attaches tube  24  to EGR valve  13 . EGR valve  13  includes a valve member (not shown) connected to valve pintle  32  for regulating the flow of exhaust gas through the EGR valve. The valve member is disposed in a generally triangular shaped valve body  28  of EGR valve  13 . Valve body  28  has an exhaust gas inlet  26  to which induction tube  24  is fluidly coupled and an exhaust gas outlet  31  disposed in a base  30 . Base  30  is generally planar and is coupled to heat sink  14  to convey exhaust gas that passes through EGR valve  13  into heat sink  14 . 
     The valve member is controlled by moving pintle  32  into and out of valve body  28  to throttle the flow of exhaust gas. For example, when pintle  32  is in its closed position, substantially no exhaust gas passes through EGR valve  13  and therefore substantially no exhaust gas is recycled through system  12 . When pintle  32  is in its open position, exhaust gas is permitted to pass through EGR valve  13  is recycled through system  12 . 
     FIG. 2 illustrates a preferred embodiment of heat sink  14 . Heat sink  14  includes an exhaust gas tube  34  and a body  36  to which tube  34  is mounted. 
     Exhaust gas tube  34  is generally circular in cross-section and has a first portion  44  disposed within and surrounded by body  36 . A second (or stem) portion  38  of tube  34  extends coaxially from the first portion and is disposed within intake manifold  16 . 
     Stem portion  38  of exhaust gas tube  34  is disposed between a top wall  40  and a bottom wall  42  of manifold  16 . Stem  38  includes a downstream sidewall  46  facing substantially downstream in the manifold and an upstream sidewall  48  facing substantially upstream in the manifold. The free end of stem portion  38  disposed in the intake manifold is enclosed by a stem cap  50  (see FIG.  3 ). 
     An opening  52  in downstream sidewall  46  is spaced apart from top wall  40  and directs exhaust gas passing through the heat sink in a substantially downstream direction. Two openings  54  and  56  are provided in upstream sidewall  48  spaced away from top wall  40  and direct exhaust gas passing through the heat sink in a substantially upstream direction. The combined areas of openings  52 ,  54  and  56  are preferably substantially equal to the area of stem cap  50  so as to allow the rapid release of the exhaust gas through the openings while minimizing the area of stem  38  that blocks the passage of air through the intake manifold. The ratio of the length of the stem to the length of the first portion  44  of the flow tube is preferably at least 1:1. More preferably it is at least 1.5:1, and most preferably it is at least 2:1. 
     First portion  44  of exhaust gas tube  34  extends into body  36  and extends integrally from stem portion  38 . Portion  44  is spaced apart from body  36  and defines a generally cylindrically-shaped cavity  58  between it and body  36 . When exhaust gas passes through exhaust gas tube  34 , this spacing reduces the heat that is transferred to body  36  and thus the heat that is transferred to the intake manifold. In addition, cavity  58  and thus the outer surface of portion  44  is in fluid communication with combustion air passing through the intake manifold. This permits air in cavity  58  that is heated by the outer surface of first portion  44  to be flushed into the combustion air stream, thus additionally reducing the heat transfer from tube  34  to body  36 . 
     Body  36  includes a base  60  and a flange extension  62 , both of which are supported by top wall  40  of manifold  16 . Fasteners (shown as threaded bolts  64 ) inserted through apertures  66  of valve body  28 , apertures  68  of body  36 , are attached to apertures  74  of manifold  16 . These fasteners thereby secure EGR  13  and heat sink  14  to manifold  16 . 
     A generally circular gasket  70  encircles the upper end of first portion  44  of tube  34  to substantially seal the interface between valve body  28  and heat sink body  36  thereby reducing or eliminating the escape of exhaust gases from between the EGR valve and the heat sink. 
     Another generally circular gasket encircles stem  38  of tube  34  and substantially seals the interface between base  60  of body  36  and top wall  40  of manifold  16 . This gasket is disposed between body  36  and the intake manifold, and is spaced away from cavity  58  to permit cavity  58  to be in fluid communication with the interior of the intake manifold. 
     FIG. 3 illustrates the flow of exhaust gas through system  12 . Exhaust gas enters system  12  through inlet  26  at a rate of about 20 cubic feet/minute and a temperature of about 500 degrees Celsius. The exhaust gas passes through EGR valve  13  and thence into first portion  44  of tube  34  to stem  38 . The exhaust gas exits stem  38  through opening  52  in the downstream direction, and through openings  54  and  56  in the upstream direction. 
     Without intending to be limited by theory, it is believed that discharging the exhaust gas in this manner substantially reduces the temperature of top and bottom walls  40  and  42 , and sidewalls  46  and  48  of stem  38 . In addition, this discharge of exhaust gas through stem  38  provides rapid mixing of the exhaust gas with the purified air in manifold  16  and thus rapid reduction in temperature of the mixture, since the combustion air is generally at a temperature of about 40 degrees C. Such rapid mixing assists in channeling the exhaust gas in the downstream direction such that the exhaust gas is directed away from top wall  40  and bottom wall  42  of manifold  16 . The channeling of the exhaust gas in the downstream direction assists in reducing the possibility for degradation of sidewalls  46  and/or  48  due to the temperature of the exhaust gas. 
     Referring further to FIG. 3, the circulation of the purified air (contained in manifold  16 ) into cavity  58  of body  36  is shown. The temperature of the purified air is generally lower than the temperature of the exhaust gas, as the purified air has not yet undergone combustion in the combustion chamber. Such circulation of the lower temperature purified air in cavity  58  tends to act as a heat transfer mechanism to reduce the temperature of the exhaust gas in tube  34 . As the gas travels through tube  34 , the movement of combustion air across the outer surface of tube  34  cools it, and hence reduces the temperature of the exhaust gas traveling through tube  34  toward openings  52 ,  54  and  56 . 
     Without intending to be limited by theory, it is believed that other heat transfer mechanisms include: the transfer of heat from the exhaust gas in first portion  44  of tube  34  to cavity  58 , to body  36  and into the atmosphere; the transfer of heat from the exhaust gas entering inlet  26  directly to body  36  and subsequently to the atmosphere; and/or the transfer of heat between the broad, generally planar interface between heat sink  14  and base  30  of valve body  28 , and the broad interface between base  60  of heat sink  14  and top wall  40  of manifold  16 . Such heat transfer mechanisms are intended to substantially reduce the temperature of the exhaust gas. For example, exhaust gas having a temperature of about 500 degrees Celsius may be processed by heat sink  14  to have a resulting temperature of less than about 200 degrees Celsius, more preferably to a temperature of less than about 175 degrees Celsius. 
     FIGS. 4-6 illustrate heat sink  114 , an alternative embodiment of heat sink  14 . Heat sink  114  differs from heat sink  14  in two respects: a second substantially circular cavity is formed in body  136  of heat sink  114  substantially coaxial with tube  34  and cavity  58 , and the flanges of the body  36  of the first embodiment have recesses. Other than the changes wrought by these two modifications (discussed below), the construction and performance of the second embodiment is identical to that of the first embodiment. (An engine, identical to engine  11  shown in FIG. 1, is coupled to the EGR valve and the intake manifold shown in FIGS. 4-6, but has been removed from FIGS. 4-6 for clarity and convenience.) 
     Two recesses  166  are provided in the flanges extending from opposing sides of body  136  thus dividing the single flanges of body  36  into a base flange  160  that is coupled to the intake manifold and a top flange  162  that is coupled to EGR valve  13 . By providing these recesses, heat that is transferred from tube  34  to body  136  has a limited thermal conduction path downward toward intake manifold  16 , as compared to body  36  of the first embodiment. 
     Cavity  164  similarly provides an additional thermal barrier to heat traveling outward from exhaust gas tube  34  toward body  136 . Cavity  164  is formed in body  136  concentric with and extending around cavity  58 . Unlike cavity  58 , cavity  164  is open to the atmosphere surrounding heat sink  114 —the atmosphere outside of intake manifold  16 —and permits heat transfer to the outside atmosphere. Two openings  170 ,  172  are provided on either side of cavity  164  to permit outside air to enter cavity  164  and carry heated air away from body  136 . 
     Without intending to be limited by theory, it is believed that the following heat transfer mechanisms exist in heat sink  114 : recess  166  and flanges  160  and  162  provide additional surface area for heat transfer from body  136  to the atmosphere; internal cavity  58  provides a space for outside air to transfer exhaust gas heat from first portion  44  of tube  34  to body; and/or external cavity  164  provides a space for atmospheric or ambient air to transfer heat from body  136  to the atmosphere. 
     According to a particularly preferred embodiment, the manifold is constructed of a sulfur containing thermoplastic or thermosetting resin, such as PPS® resin commercially available from Phillips Petroleum Company of Bartlesville, Okla., having a heat transfer property of about k=0.166 W/M/C. The heat sink is preferably constructed of a low carbon steel, such as 1010 or 1020 carbon steel, having a heat transfer property of about k=50.1 W/M/C. The manifold is preferably a cylindrical shaped having a diameter of about 70-mm and a wall thickness of about 1.5-mm. The stem of the heat sink preferably has a diameter of about 19-mm and extends beyond the top wall of the manifold about 36 mm toward the bottom wall of the manifold. 
     According to an alternative embodiment, the engine system may be controlled by a control system. The control system may include a controller, a general purpose computer having a central processing unit (CPU), control circuits activated by input devices, power sources, memory storage modules, display systems and/or instrumentation (e.g., regulators, sensors for monitoring temperature, volume, pressure and/or other variables, heating and/or cooling systems, etc.) and the like. The control system may be implemented in a stand-alone digital processor, or integrated with a microprocessor of the like used to monitor and/or control engine systems and engine functions. (According to other alternative embodiments, the controller and an associated control program may be implemented in hardware, software or a combination thereof, or in a central program implemented in any of a variety of forms.) A differential pressure feedback element (e.g., DPFE sensor) may provide feedback to the controller signaling when the exhaust gas recirculation system is operating at an acceptable pressure drop. In response, the controller may signal an electric vacuum regulator to increase or decrease the vacuum level in the engine recycling system by positioning the pintle to the opened or the closed position, or some combination thereof. 
     The foregoing description has been presented for purposes of explanation and illustration only, and is neither exhaustive nor restrictive. Although only a few exemplary embodiments have been described, the present invention is not limited to one particular embodiment. Indeed, to practice the invention in a given context, those skilled in the art may conceive of variations to the embodiments described herein without materially departing from the true spirit and scope of the invention. For example, variations may be made in sizes, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, and/or use of materials. Any suitable fastening device (e.g., welding, ultrasonic welding, vibration welding, molding, glue, screws, rivets, clamps or other conventional methods) may attach the heat sink to the manifold. The gaskets may be constructed of any rigid or flexible material such as urethane rubber, Viton® rubber, Teflon® polymers, etc. The manifold may be constructed of any plastic, such as polyphenylensulfide, thermoplastic or a synthetic resin such as Minlon® 10B40 commercially available from E. I. Du Pont de Nemours and Company of Wilmington, Delaware. The heat sink may be constructed of any metal, such as stainless steel or magnesium, or any metal alloy. A baffle having any of a variety of shapes (e.g., star-shaped) may be provided in the stem to further increase the heat transfer properties of the heat sink. 
     It should be noted that the use of the term “tube” is not meant as a term of limitation, insofar as any valve, hose, conduit, or like structure providing a channel or passage through which air may flow is intended to be included in the term. It should also be noted that the use of the term “conveyed” is not meant as a term of limitation, insofar as any routing, direction or leading of fluid, gas or air through the engine system and the exhaust gas recirculation system is intended to be included in the term. It should also be noted that the use of the term “engine” is not meant as a term of limitation, insofar as any “engine” or like machine for using fuel to produce motion is intended to be included in the term. 
     Thus, it should be apparent that there has been provided in accordance with the present invention an exhaust gas recirculation system that fully satisfies the objectives and advantages as set forth above. Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the invention is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the preferred embodiments without departing from the spirit of the invention as expressed in the appended claims. 
     For example, while flanges are shown as the method for mounting bodies  36  and  136  to the EGR valve and the manifold, other structures may be employed such as screws, bolts, nuts rivets, welding and the like. Furthermore, bodies  36  and  136  may have external or internal structures, such as threads, to permit them to be fastened directly to the intake manifold or EGR valve. In addition, while in the preferred embodiment an EGR valve is attached to the heat sink, the EGR valve may be disposed away from the intake manifold and communicate with the heat sink via a tube or similar conduit that fluidly couples the EGR valve to the heat sink. Even further, while the various cavities are shown as complete cylinders surrounding tube  34 , there may nonetheless be rods, struts, or ribs extending between the body to tube  34  to help support tube  34  within the cavities.