Abstract:
An exhaust gas recirculation (EGR) assembly ( 23 ) for an internal combustion engine, including an EGR valve ( 54 ) having a valve stem ( 55 ) reciprocating within a housing ( 61 ), between open (FIG.  3 ) and closed positions. Preferably, the EGR assembly is mounted on the exhaust manifold ( 15 ), and the EGR valve can communicate exhaust gas back to the intake manifold ( 13 ) in a known manner. The EGR assembly includes an electric motor ( 41 ), and a gear train ( 65 ) to move the EGR valve ( 54 ) in response to changes in an electrical input signal. A plurality of power electronic components ( 97 ) are disposed within a controls housing ( 91 ), which defines a slot ( 99 ) in face-to-face relation to a cooling chamber ( 81 ) defined by the housing ( 61 ) surrounding the valve stem ( 55 ). The cooling chamber ( 81 ) and the slot ( 99 ) cooperate to define a coolant passage, and the valve stem ( 55 ) and the power components ( 97 ) are in close proximity to the coolant passage, thus permitting the use of less expensive electrical components, rated for relatively lower temperatures.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     MICROFICHE APPENDIX 
     Not Applicable 
     BACKGROUND OF THE DISCLOSURE 
     The present invention relates to an exhaust gas recirculation system for controlling the flow of exhaust gas from an exhaust manifold to an intake manifold of an internal combustion engine, and more particularly, to an improved actuator and control assembly for such an exhaust gas recirculation system. 
     Although the use of the present invention is not limited to any particular type or configuration of engine, its use is especially advantageous in connection with a heavy duty diesel engine, for reasons which will become apparent subsequently, and the invention will be described in connection therewith. 
     Typically, exhaust gas recirculation (EGR) valves have been disposed between the engine exhaust manifold and the engine intake manifold, and have been operable, when in the open position, to permit the recirculation of exhaust gas from the exhaust side of the engine back to the intake side. As is well known to those skilled in the art, such recirculation of exhaust gasses is helpful in reducing various engine emissions. 
     An EGR system including an electrically operated type actuator is illustrated and described in U.S. Pat. No. 5,606,957. The actuator for the valve stem in the cited patent is a stepper motor, which is generally satisfactory in performing the basic function of opening and closing the EGR valve, but does have a number of performance limitations. Another type of electrically operated actuator is illustrated and described in copending application U.S. Ser. No. 09/249,715, filed Feb. 12, 1999 in the names of Michael J. Sitar, David W. Deppe and Bill D. Wood, for an “EGR SYSTEM AND IMPROVED ACTUATOR THEREFOR”, which is assigned to the assignee of the present invention and incorporated herein by reference. In the device of the above-incorporated application, the actuator includes an electric motor of the relatively high-speed, continuously rotating type, such as a permanent magnet DC commutator motor. The actuator also includes a reduction gear train, suitable to convert the output of the motor into a motion of the valve member which satisfies the operating requirements, in terms of the speed of movement of the valve member versus the force applied to the valve member, at any given position of the valve member during its opening and closing cycle. 
     In the case of either of the devices referred to above, there is a need for electrical/electronic controls, to control the opening and closing of the EGR valve, in response to variations in any one of a number of different engine operating conditions. Those skilled in the vehicle and engine arts understand that, at least in general, it is desirable for such controls to be integrated with the EGR valve and actuator assembly. If the controls are integrated into the actuator assembly, the required wiring harness is simplified, and the connection to the actuator motor and the position sensor can be internal to the actuator housing, thus protecting these connections from environmental problems. In some vehicle applications, there is simply not enough room available in the vehicle engine control module (ECU) to add the necessary control circuitry. 
     As is also well known to those skilled in the art, when dealing with a heavy duty diesel engine, and its various auxiliary components, temperature and the effects of various corrosive materials which are present must also be taken into account in designing and locating the various auxiliary components. Excessive temperatures can negatively effect performance of many components, and corrosive materials can negatively impact the life of the components. 
     It has been determined that when an EGR valve is located on the intake manifold side of a diesel engine, various pollutants in the exhaust gas have the opportunity to condense out of the stream of exhaust gas, because the intake manifold side of the engine is relatively cooler than the exhaust manifold side. The pollutants which condense out of the exhaust gas are of a type which tend to corrode the EGR valve and valve seat combination, as well as other system elements, such as the EGR cooler and associated pipes and plumbing. Thus, it has been determined that the EGR valve itself has better durability if it is located on the exhaust manifold side of the engine. 
     As was noted previously, it is desirable for the electronic controls associated with the EGR valve actuator to be integral with the EGR valve assembly. Unfortunately, if the EGR valve assembly is located on the exhaust manifold side of the engine, for the reasons discussed above, the electronic controls associated with the EGR valve actuator can no longer use the relatively inexpensive, commonly available electronic components which are typically rated for continuous operation at 125° Centigrade. Instead, having the EGR valve assembly on the exhaust manifold side of the engine would require electronic components which are rated for continuous operation at up to 400° Centigrade. Such components are either not yet readily available commercially, or if available, are extremely expensive. 
     BRIEF SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide an improved EGR valve assembly, including the actuator and electronic controls, which make it possible to mount the EGR valve assembly on the exhaust manifold side of the engine. 
     It is a more specific object of the present invention to provide an improved EGR valve assembly which accomplishes the above-stated object, without the need for relatively expensive, high temperature electronic components. 
     It is an even more specific object of the present invention to provide an improved EGR valve assembly which includes a means for cooling the electronic components, in which the cooling means does not add any substantial size or packaging or cost to the assembly. 
     The above and other objects of the invention are accomplished by the provision of an improved exhaust gas recirculation assembly for an internal combustion engine, the assembly having a valve including a valve stem, the valve being moveable between a closed position, blocking communication from an engine exhaust gas passage to an engine intake passage, and an open position. The assembly comprises housing means, and the valve stem is disposed within the housing means for reciprocable movement therein. The assembly includes an electromagnetic actuator operably associated with the housing means, and having an actuator output. The assembly further includes a gear train operably associated with the actuator output and with the valve stem, to move the valve between the closed and open positions in response to changes in an electrical input signal. The gear train is disposed within the housing means. The assembly includes a plurality of power electrical components operable to generate the electrical input signal in response to a signal from the vehicle engine control module. 
     The improved exhaust gas recirculation assembly is characterized by the plurality of power electrical components being disposed within the housing means. The housing means defines a coolant passage including an inlet port for connection to a source of coolant. The coolant passage is configured to be in close proximity to the valve stem and to the plurality of power electrical components. 
     In accordance with a more specific aspect of the present invention, the exhaust gas recirculation assembly is characterized by the housing means including an exhaust manifold portion disposed in heat transmitting relationship to the vehicle engine exhaust manifold, and an intake manifold portion in only indirect communication with the vehicle engine intake manifold. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic view of a diesel engine including the exhaust gas recirculation assembly made in accordance with the present invention. 
     FIG. 2 is a perspective view of the exhaust gas recirculation assembly, made in accordance with the present invention, and as is shown schematically in FIG.  1 . 
     FIG. 3 is a front plan view, with the electronics portion removed, of the EGR valve actuator assembly, looking in a direction opposite that of FIG.  2 . 
     FIG. 4 is a perspective view, on approximately the same scale as FIG. 2, with the cover of the electronics portion, removed, illustrating one aspect of the present invention. 
     FIG. 5 is a plan view of the housing of the electronics module, with the cover removed, as well as the electronic components themselves, as viewed from the right in FIG.  4 . 
     FIG. 6 is a transverse cross-section taken on lines  6 — 6  of FIG. 5, and illustrating one important aspect of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings, which are not intended to limit the invention, FIG. 1 is a schematic of a vehicle internal combustion engine, and more specifically, of a heavy duty diesel engine. As is shown schematically in FIG. 1, the diesel engine includes an engine block  11  including an intake manifold  13  and an exhaust manifold  15 . Disposed forwardly of the engine block  11  is an engine radiator  17 , by means of which engine coolant flowing through the engine block  11  may be cooled as the coolant passes through the radiator  17 . As is well known to those skilled in the art, the radiator  17  would typically be connected to the engine block  11  by means of a pair of hoses or conduits, one hose  19  communicating relatively hot engine coolant to the “top tank” portion of the radiator  17 , and another hose  21  communicating relatively cooler engine coolant from the downstream end of the radiator  17  back to the engine block  11 . 
     In accordance with one important aspect of the present invention, associated with the exhaust manifold  15  is an EGR valve assembly generally designated  23 . The assembly  23  includes an EGR valve portion  25 , an EGR valve actuator portion  27 , and an actuator electronic control portion  29 . Associated with the engine block  11  is an EGR cooler  31 , the function of which is to cool the relatively hot exhaust gasses which are communicated from the EGR valve assembly  23  to the intake manifold  13 . In order to accomplish this cooling of the exhaust gasses, the EGR valve portion  25  is connected by means of a duct or pipe  33  to the cooler  31 , and exhaust gasses passing through the cooler  31  then flow through a duct or pipe  35  to the intake manifold  13 . 
     The vehicle includes a battery  37  which is connected by means of a pair of electrical leads  39  to the actuator electronics portion  29 , thus providing the electrical power for an electric motor  41  which comprises part of the EGR valve actuator portion  27 . It should be understood that the present invention is not limited to any particular type or configuration of electric motor, for reasons which will become apparent subsequently, and within the scope of the present invention, various other forms of electromagnetic actuator could be utilized. The vehicle also is provided with a fairly conventional engine control module (ECM) generally designated  43 . The ECM  43  receives input from the electronic control portion  29  (such as the instantaneous EGR valve position), and provides appropriate command signals to the electronic control portion  29  (such as the desired EGR valve position), by means of a data link  45 , the command signal from the ECM  43  also being referred to hereinafter by the designation “ 45 ”. The data link  45  is also used to send/receive information for diagnostic purposes, for example, to comply with various OBD (on-board diagnostics) regulations. 
     Referring now primarily to FIGS. 2 and 3, the EGR valve assembly  23  will be described in some detail, it being understood that the EGR valve portion  25  and actuator portion  27  are described in great detail in the above-incorporated U.S. Ser. No. 09/249,715. The EGR valve portion  25  includes a manifold housing  47  including a mounting flange  49  adapted to be attached to the exhaust manifold  15 , and a mounting flange  51  adapted to be connected to the duct  33 . The mounting flange  49  is preferably disposed in a heat transmitting relationship with the exhaust manifold  15 , i.e., such that heat is transmitted from the hot exhaust manifold  15  to the mounting flange  49 , for reasons which were explained previously. The EGR valve portion includes a valve seat (not shown herein) against which is seated the poppet valve portion  53  of an EGR valve  54 , which also includes a valve stem  55 . As may best be seen in FIG. 3, the valve stem  55  extends upwardly into the EGR valve actuator portion  27 . 
     The EGR valve  54  is shown in FIG. 3 in its open position, wherein exhaust gasses would be permitted to flow from the exhaust manifold  15  past the poppet portion  53  and then through a passage  56  (see FIG. 2) to the duct  33 . In the subject embodiment, the manifold housing  47  is attached, such as by means of a plurality of bolts  57 , to the undersurface of a heat transfer (cooling) portion  59 . In the subject embodiment, the heat transfer portion  59  is actually formed integrally with an actuator housing  61  which encloses the EGR valve actuator portion  27 . 
     Referring still primarily to FIGS. 2 and 3, the electric motor  41  has, as its output, a motor pinion gear  63  which comprises the input to a gear train, generally designated  65 . In the subject embodiment, and by way of example only, the gear train  65  includes a pivotable sector gear  67 , the pivotal movement of which is translated by means of a linkage member  69  into movement (vertically in FIG. 3) of the EGR valve  54  between its open position (shown in FIG. 3) and its closed position. The sector gear  67  pivots about a mounting shaft  71 , and surrounding the mounting shaft  71  is a torsional spring  73  which serves as the return spring for the EGR valve  54 , tending to bias the valve  54  toward its closed position (upward from the open position shown in FIG.  3 ). 
     The actuator housing  61  includes a portion  75  which is preferably internally-threaded and is therefore adapted to receive a threaded fitting associated with an engine coolant line  77  (see FIG.  1 ). Thus, the portion  75  serves as a coolant inlet port, such that engine coolant flows from the radiator  17  through the coolant line  77  and enters the actuator housing  61 . As may best be seen in FIG. 3, the heat transfer portion  59  includes a valve stem support portion  79 , which surrounds and supports the valve stem  55 . The support portion  79  is surrounded by a cored cooling chamber  81  which is in open communication with the coolant inlet port  75  by means of a coolant passage defined by a portion  83  (see FIG. 2) of the actuator housing  61 . Although not visible in any of the drawing figures, the coolant passage may also bear the reference numeral “ 83 ” hereinafter. The cooling chamber  81  opens at a surface  85  of the heat transfer portion  59 , the surface  85  being co-planar with a surface  87  of the actuator housing  61 . Preferably, both of the surfaces  85  and  87  are in engagement with a rearward surface  89  (see FIGS. 2 and 6) of a housing  91  which encloses the actuator electronic control portion  29 . 
     Referring now primarily to FIGS. 4-6, another important aspect of the invention will be described. The housing  91  for the electronic control portion  29  includes a relatively thicker bottom wall  93 , the reason for the wall  93  being thicker to be described subsequently. Within the housing  91 , and disposed on an inside surface  95 , is a plurality of power electronic components, generally designated  97  (shown only in FIG.  4 ). Although in FIG. 4 the power electronic components  97  appear to be nearly identical, those skilled in the art will understand that the components  97  are shown that way for ease of illustration only. In actual practice, the electronic components  97  may include a variety of different power components, such as power transistors, diodes, voltage regulators, high power resistors, and others. In accordance with good design practice, and as one aspect of the invention, all or as many as possible of the power electronic components within the housing  91  which are relatively high heat generators would be included on the inside surface  95  as shown in FIG.  4 . Those skilled in the art will understand that the electronic control portion  29  would typically also include various “low power” components, such as microprocessor logic gates, etc., which do not generate substantial heat. Therefore, such low power components would also be mounted within the housing  91 , but aren&#39;t necessarily mounted on the inside surface  95 . Instead, the low power components could be mounted anywhere within the housing  91 , and references hereinafter, and in the appended claims, to “power electronic components” will be understand to refer primarily to those components which generate substantial heat, and have the greatest need for cooling. 
     In view of the presence of the various power electronic components  97 , the thicker bottom wall  93  tends to become the hottest part of the housing  91 . In order to dissipate the generated heat, the rearward surface  89  defines an elongated slot or recess  99 , shown best in FIG.  6 . The recess  99  is in open fluid communication with a coolant outlet port  101 , from which engine coolant is communicated back to the radiator  17  by a suitable coolant line, not shown herein. Although the port  75  has been referred to as the inlet and the port  101  has been referred to as the outlet, those skilled in the art will understand that, within the scope of the invention, the ports  75  and  101  could be reversed, such that the direction of coolant flow would be reversed, and the overall operation of the invention would be substantially the same. 
     The shape of the recess  99 , in a transverse direction, may best be seen in FIG. 5, and preferably, the recess  99  has approximately the same overall size and shape as does the opening of the cooling chamber  81  at the surface  85 . Furthermore, it is greatly preferred that the opening of the cooling chamber  81  and the recess  99  are substantially co-extensive, i.e., they overlap and mate with each other. As a result, engine coolant enters the inlet port  75 , flows through the passage  83 , then enters the cooling chamber  81 , at the left end thereof in FIG. 3, also flowing into the left end (in FIG. 5) of the recess  99 . The coolant then flows generally to the right in both FIGS. 3 and 5, cooling both the valves stem support portion  79  and the portion of the bottom wall  93  containing the power electronic components  97 . Then the coolant flows out the right end of the recess  99  through the coolant outlet port  101 . 
     Thus, it may be seen that the present invention provides an improved EGR valve assembly  23  which makes it possible and feasible to mount the assembly on, or in close proximity to, the exhaust manifold  15 . Furthermore, the invention includes an arrangement for cooling the power electronic components  97 , and makes it possible to use relatively lower temperature components, wherein the cooling arrangement does not add any substantial structure, size, packaging or cost to the overall assembly  23 . 
     The invention has been described in great detail in the foregoing specification, and it is believed that various alterations and modifications of the invention will become apparent to those skilled in the art from a reading and understanding of the specification. It is intended that all such alterations and modifications are included in the invention, insofar as they come within the scope of the appended claims.