Abstract:
An Exhaust Gas Recirulation (EGR) valve is integrated onto a turbocharger by providing an EGR outlet in a flange in the volute of the turbine housing and a mating valve assembly extending from a mating flange with an elbow. The outlet direction of the elbow is adjustable to a plurality of directions by positioning the mating flange relative to the EGR outlet flange.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority of copending application Ser. No. 60/186,647 filed on Mar. 03, 2000 having the same title as the present application. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to exhaust gas recirculation (EGR) systems, and more particularly, to an EGR valve integrated into a turbocharger with a valve inlet cast into the turbine housing and an actuation system mounted directly to the turbocharger. 
     2. Description of the Prior Art 
     Commercial Diesel EGR Systems require an EGR valve to control the flow of exhaust gas into the intake manifold. Commercial Diesel EGR Systems are characterized by very challenging packaging constraints of the EGR system, within the existing vehicle envelope, sensitivity to EGR system pressure losses and fuel consumption. 
     Present EGR systems are typically configured using separate components for each element of the system. This approach does not allow optimization of the system to accommodate the challenges described. 
     SUMMARY OF THE INVENTION 
     The present invention addresses the packaging and EGR system pressure loss resulting in a minimized effect on the vehicle fuel consumption. An EGR valve is incorporated onto a turbocharger turbine housing in a more compact manner than a separate EGR valve assembly (which is more typical within the component suppliers). In addition, the EGR valve is located such that the EGR system pressure losses are minimized (relative to the EGR valve). This is accomplished by taking advantage of the dynamic pressure associated with the turbine inlet flow. The design of the EGR valve integration provides “infinite” flexibility in the orientation of the EGR valve outlet relative to the turbocharger centerline. This feature aids significantly in the packaging of the EGR system within the vehicle installation constraints. The design of the EGR valve lends itself to this packaging advantage. The invention employs a “swing valve” design. A EGR port is cast into the turbocharger turbine housing such that the gas dynamics of the engine exhaust entering the turbine housing supplements the flow of exhaust gas into the EGR system therefore reducing the EGR system pressure losses. The EGR valve is attached to the turbine housing such that the exhaust port from the EGR valve may be directed in an infinite number of directions without redesign of the turbocharger, turbine housing, or EGR valve sub-assembly. 
     The EGR valve actuator, and associated actuator mounting bracket are combined as a sub-assembly for mounting to the turbocharger permitting the EGR valve exhaust port to be directed in the best orientation for the EGR System/engine packaging. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features and advantages of the present invention will be appreciated as the same become better understood by reference to the following Detailed Description when considered in connection with the accompanying drawings, wherein: 
     FIG. 1 is a schematic illustration of an internal combustion engine having an EGR system employing a turbocharger with an integrated EGR valve according to the present invention; 
     FIG. 2 is a pictorial view of an embodiment of turbocharger having an integrated EGR valve incorporating the present invention; 
     FIG. 3 is a cutaway view of the valve poppet and actuator for the EGR valve of FIG. 2; 
     FIG. 4 is a top view of the turbocharger disclosed in FIG. 2; 
     FIG. 5 is an end view of the turbocharger disclosed in FIG. 2; and 
     FIG. 6 is a section view of the turbine housing casting of the turbocharger disclosed in FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to FIG. 1, an EGR system is schematically illustrated in an internal combustion engine having a turbocharger and an EGR system. Engine  10  includes an intake manifold  12  and an exhaust manifold  14 . In the illustrated embodiment, the engine includes a turbocharger  16 , generally comprising a turbine contained in a housing  18  and a compressor contained in a housing  20 , for compressing the intake air of engine  10 . The intake air is heated during the turbocharger compression process and must be cooled to satisfy engine durability and performance requirements. That cooling is accomplished by routing the air discharged from the turbocharger  16  to a charger air cooler (CAC)  22  via conventional conduits or ducting  24 . The intake air is then routed from the CAC to the intake manifold of the engine via conventional conduits or ducting  30 . 
     Engine  10  also includes an EGR system. The EGR system includes a control valve  34 , integrated into the turbocharger in accordance with the present invention, that regulates the proportion of exhaust gas that is taken from the exhaust manifold and either returned to the engine induction system for mixing with the intake air that has passed through the CAC, or directed to the turbine of the turbocharger. The control valve  34  routes a portion of the exhaust gas received into the turbine housing from the exhaust manifold through the EGR system. 
     The EGR system also includes an engine mounted EGR cooler  38  or heat exchanger for cooling the exhaust gas passing through the system. By providing a heat exchanger in the EGR conduit or ducting  40 , the efficiency of engine  10  is improved. Other advantages, such as a reduction in NOx and PM emissions and in fuel consumption also result from the presence of the heat exchanger  38 . The exhaust gas passing through the heat exchanger  38  is then combined with the intake air that has passed through the CAC in an EGR mixer  42 . The mixture of the intake air and exhaust gas leaves the mixer  42  and enters the intake manifold of the engine. 
     A variable geometry nozzle  44  in the turbocharger is utilized for back pressure in the turbine housing inlet and exhaust manifold. 
     FIGS. 2,  4  and  5  show the turbocharger  16  incorporating the present invention in greater detail. The turbine housing  18  includes an inlet  50  from the exhaust manifold of the engine. Exhaust gas entering the inlet flows into a torus or volute  52 . An EGR outlet  54  from the volute is cast into the turbine housing as shown in FIG.  6 . The location and orientation of the EGR outlet tangentially to the volute and substantially linearly along the flow stream entering the turbine housing inlet, minimizes the pressure losses for the extracted EGR flow. A flange  56  is provided for mounting the EGR valve assembly shown in detail in FIG.  3 . 
     The EGR valve includes a poppet  58  which is mounted by an arm  60  to an axle  62  for pivoting the poppet from a closed position on a seat  64 , shown in FIG. 6, at the exit of the EGR outlet, to an open position with the poppet rotated into a chamber  66  in the valve casting  68 . The valve casting includes a bored boss  70  receiving the axle and a mating flange  71  for flange  56  on the turbine housing. For the embodiment shown, the valve casting includes an elbow  72 , which terminates in a flange  74  for attachment to the EGR conduit  40 . A pneumatic actuator  76  is mounted by a bracket  78  to the valve casting and incorporates an actuating arm  80  which connects to a crank  82  extending from the axle. 
     The mating flange is connected to flange  56  using bolts  84 . The mating hole pattern on the flange  56  can be adapted to allow any desired orientation of the elbow to accommodate varying engine arrangements for EGR plumbing. 
     For the embodiment shown in the drawings, the turbocharger includes a second actuator  86  for control of the variable geometry turbine inlet nozzle  44  which provides a means for controlling backpressure in the exhaust system and turbine volute to control EGR flow rate in combination with the EGR valve. In the embodiment shown the second actuator is pneumatically actuated and mounted to the turbine housing with a bracket  88 . For the embodiment shown in the drawings, the variable geometry nozzle is constructed as disclosed in U.S. Pat. No. 5, 947,681 entitled PRESSURE BALANCED DUAL AXLE VARIABLE NOZZLE TURBOCHARGER issuing on Sep. 7, 1999 having a common assignee with the present application, the disclosure of which is incorporated herein by reference. 
     Having now described the invention in detail as required by the patent statutes, those skilled in the art will recognize modifications and substitutions to the specific embodiments disclosed herein. Such modifications are within the scope and intent of the present invention as defined in the following claims.