Patent Publication Number: US-2015068503-A1

Title: Compressor cover with integrated egr valve

Description:
TECHNICAL FIELD 
     The present disclosure relates to a compressor cover having an integrated EGR valve. 
     BACKGROUND 
     In internal combustion engines (ICE), exhaust gas recirculation (EGR) is a nitrogen oxide (NOx) emissions reduction technique used in gasoline and diesel engines. EGR works by recirculating a portion of an engine&#39;s exhaust as an inert gas back to the engine&#39;s cylinders. 
     In a gasoline engine, this inert exhaust gas displaces some portion of combustible fuel-air mixture in the cylinder. In a diesel engine, the inert exhaust gas replaces some of the excess oxygen in pre-combustion fuel-air mixture. Because NOx forms primarily when a mixture of nitrogen and oxygen is subjected to high temperature, the lower combustion temperatures caused by EGR reduces the amount of NOx the combustion generates. 
     Frequently, such engines are also called upon to generate considerable levels of power for prolonged periods of time on a dependable basis while maintaining respectable fuel efficiency. To meet such demands, many gasoline and diesel engines employ a supercharging device, such as an exhaust gas turbine driven turbocharger, to compress the airflow before it enters the intake manifold of the engine. 
     Specifically, a turbocharger is a centrifugal gas compressor that forces more air and, thus, more oxygen into the combustion chambers of the ICE than is otherwise achievable with ambient atmospheric pressure. The additional mass of oxygen-containing air that is forced into the ICE improves the engine&#39;s volumetric efficiency, allowing it to burn more fuel in a given cycle, and thereby produce more power. 
     SUMMARY 
     One embodiment of the disclosure is directed to a compressor assembly for pressurizing an airflow for delivery to an internal combustion engine having a cylinder block section and a cylinder head section. The cylinder head section is configured to supply an air-fuel mixture to the cylinder for combustion therein and exhaust post-combustion gases therefrom. The compressor assembly includes a compressor cover configured to receive the airflow from the ambient and a compressor wheel disposed inside the compressor cover and configured to pressurize the airflow. The compressor assembly also includes an exhaust gas recirculation (EGR) valve that is incorporated, i.e., structurally integrated, into the compressor cover and is in fluid communication with each of the cylinder head section and the compressor wheel. The EGR valve is configured to control delivery of the exhaust post-combustion gases from the cylinder head into the compressor cover. 
     The compressor cover may include an inlet for the airflow being received from the ambient and an outlet for the pressurized airflow. In such a case, the EGR valve may be incorporated at the inlet and configured to control reintroduction of the exhaust post-combustion gases into the airflow received from the ambient, i.e., the unpressurized airflow. Additionally, the compressor cover may include a fluid flow mixer arranged at the inlet. Accordingly, the fluid flow mixer may be configured to mix the exhaust post-combustion gases with the unpressurized airflow. 
     The compressor cover may include an inlet for the airflow being received from the ambient and an outlet for the pressurized airflow. In such a case, the EGR valve may be incorporated at the outlet and configured to control reintroduction of the exhaust post-combustion gases into the pressurized airflow. Additionally, the compressor cover may include a fluid flow mixer arranged at the outlet. Accordingly, the fluid flow mixer may be configured to mix the exhaust post-combustion gases with the pressurized airflow. 
     The compressor cover may include a coolant passage configured to route a coolant proximate to the EGR valve such that the coolant removes heat generated by the reintroduced exhaust post-combustion gases. 
     The EGR valve may be configured as one of a poppet-, butterfly-, and swing-type valve. 
     The compressor cover may include a sealable opening configured to provide a service access to the EGR valve. 
     The compressor cover may include a removable cover configured to selectively open and close the opening to control service access to the EGR valve. 
     Furthermore, the engine may include an electronic controller. In such a case, the EGR valve may be in electric communication with the controller, such that the EGR valve is regulated by the controller. 
     Another embodiment of the present disclosure is directed to an internal combustion engine having the compressor assembly as described above. 
     The above features and advantages, and other features and advantages of the present disclosure, will be readily apparent from the following detailed description of the embodiment(s) and best mode(s) for carrying out the described invention when taken in connection with the accompanying drawings and appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top view of an engine with a compressor assembly having a compressor cover and an exhaust gas recirculation (EGR) valve incorporated into the compressor cover according to the disclosure. 
         FIG. 2  is a partial cross-sectional view of the compressor assembly shown in  FIG. 1 . 
         FIG. 3  is a close up perspective view of the compressor assembly shown in  FIG. 1  showing the EGR valve incorporated at an inlet of the compressor cover according to an embodiment of the disclosure. 
         FIG. 4  is a close up perspective view of the compressor assembly shown in  FIG. 1  showing the EGR valve incorporated at an outlet of the compressor cover according to another embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings wherein like reference numbers correspond to like or similar components throughout the several figures,  FIG. 1  illustrates an internal combustion (IC) engine  10 . The engine  10  may be configured as either a spark-ignition (gasoline) or a compression-ignition (diesel) engine. The engine  10  also includes a cylinder block section  12  with a plurality of cylinders  14  arranged therein. The engine  10  also includes a cylinder head section  16 . The cylinder head section  16  may be mounted to the cylinder block section  12  or be structurally integrated therewith. Each cylinder  14  includes a piston  18  configured to reciprocate therein. Combustion chambers  20  are formed within the cylinders  14  between the bottom surface of the cylinder head section  16  and the tops of the pistons  18 . As known by those skilled in the art, each of the combustion chambers  20  receives fuel and air via the cylinder head section  16 , wherein the fuel and air form a fuel-air mixture for subsequent combustion inside the subject combustion chamber. The cylinder head section  16  is also configured to exhaust post-combustion gases from the combustion chambers  20 . 
     The engine  10  also includes a crankshaft  22  configured to rotate within the cylinder block section  12 . The crankshaft  22  is rotated by the pistons  18  as a result of an appropriately proportioned fuel-air mixture being burned in the combustion chambers  20 . After the air-fuel mixture is burned inside a specific combustion chamber  20 , the reciprocating motion of a particular piston  18  serves to exhaust post-combustion gases  24  from the respective cylinder  14 . From the cylinder  14 , the post-combustion gases  24  are channeled via an exhaust manifold  26  to a compressor assembly  36  that will be described in detail below. After the compressor assembly  36 , the post-combustion gases  24  are channeled via an exhaust passage  28 . 
     The engine  10  additionally includes an induction system  30  configured to channel an airflow  32  from the ambient to the compressor assembly  36  and a pressurized airflow  32 A from the compressor assembly to the cylinders  14 . The induction system  30  includes an intake air duct  33 , an intake manifold  31  for distributing the airflow between the cylinders  14 , an intercooler  35  for reducing temperature of the pressurized airflow  32 A, and the compressor assembly  36 . Although not shown, the induction system  30  may additionally include an air filter upstream of the compressor assembly  36  for removing foreign particles and other airborne debris from the airflow  32 . The compressor assembly  36  is configured to pressurize the airflow  32  received from the ambient, while the intake air duct  33  is configured to channel the pressurized airflow  32 A from the compressor assembly  36  to the intake manifold  31  for delivery via the cylinder head section  16  to the respective cylinders  14 . The intake manifold  31  additionally distributes the pressurized airflow  32 A to the cylinders  14  for mixing with an appropriate amount of fuel and subsequent combustion of the resultant fuel-air mixture. 
     In the case of an exhaust driven compressor assembly (shown in  FIG. 2 ), the compressor assembly  36  may include a rotating assembly  37 . The rotating assembly includes a shaft  38  and a turbine wheel  40  mounted thereon. The turbine wheel  40  is configured to be rotated along with the shaft  38  about an axis  42  by the post-combustion gases  24  emitted from the cylinders  14 . The turbine wheel  40  is typically formed from a temperature and oxidation resistant material, such as a nickel-chromium-based “inconel” super-alloy to reliably withstand temperatures of the post-combustion gases  24 , which in some engines may approach  2 , 000  degrees Fahrenheit. The turbine wheel  40  is disposed inside a turbine housing  44  that includes a turbine volute or scroll  46 . The turbine scroll  46  receives the post-combustion exhaust gases  24  and directs the exhaust gases to the turbine wheel  40 . The turbine scroll  46  is typically formed from a high strength material, such as a cast iron, and configured to achieve specific performance characteristics, such as efficiency and response, of the compressor assembly  36 . 
     The rotating assembly also includes a compressor wheel  48  that is mounted on the shaft  38 . As the shaft  38  is rotated via the turbine wheel  40  by the post-combustion gases  24 , the shaft imparts rotation to the compressor wheel  48 . As a consequence, the rotating compressor wheel  48  pressurizes the airflow  32  being received from the ambient for eventual delivery to the cylinders  14 . The compressor wheel  48  is disposed inside a compressor cover  50  that includes a compressor volute or scroll  52 . The compressor scroll  52  receives unpressurized airflow  32  at an inlet  50 A and directs the airflow to the compressor wheel  48  for pressurization. Pressurized airflow  32 A is emitted from the compressor cover  50  aft of the compressor wheel  48  via an outlet  50 B. The scroll  52  is configured to achieve specific performance characteristics, such as peak airflow and efficiency of the compressor assembly  36 . As understood by those skilled in the art, the variable flow and force of the post-combustion exhaust gases  24  influences the amount of boost pressure that may be generated by the compressor wheel  48  throughout the operating range of the engine  10 . The compressor wheel  48  is typically formed from a high-strength aluminum alloy that provides the compressor wheel with reduced rotating inertia and quicker spin-up response. 
     With continued reference to  FIG. 2 , the rotating assembly  37  is supported for rotation about the axis  42  via journal bearings  54  and also includes thrust bearings  56  configured to absorb thrust forces generated by the rotating assembly  37  as the compressor assembly  36  is pressurizing the airflow  32 , to generate the pressurized airflow  32 A. In addition to the compressor assembly  36  being configured as a conventional type that is driven by the post-combustion gases  24 , a.k.a., a turbocharger, as described above, the compressor assembly may also be configured as an electrically driven unit. In the case of an electrically driven compressor assembly, in place of the turbine wheel  40 , the rotating assembly  37  typically employs an actuator (not shown), such as an electric motor configured to drive the shaft  38 . In the case of a conventional exhaust energy driven compressor assembly  36 , the post-combustion gases  24  are routed to the compressor assembly to energize the rotating assembly  37  and also provide exhaust gas recirculation (EGR) by reintroducing the post-combustion gases into the airflow  32  prior to combustion. In the case of an electrically driven compressor assembly, the post-combustion gases  24  are not used to energize the compressor assembly, but are still routed to the compressor assembly to provide EGR. 
     As shown in  FIGS. 1-3 , an EGR valve actuator  60  is incorporated, i.e., structurally integrated into the compressor cover  50 . The EGR valve actuator  60  is configured to control operation of an EGR valve  60 A. The EGR valve  60 A is configured to variably restrict delivery of the post-combustion gases  24  from the cylinder head section into the compressor cover  50  via an EGR valve  60 A at an EGR inlet  50 C. Accordingly, the EGR valve  60 A is in fluid communication with both, the cylinder head section  16  and the compressor wheel  48 . Additionally, the compressor cover  50  defines a seat  62  (shown in  FIG. 3 ) configured to accept and locate the EGR valve  60 A with respect to the compressor wheel  48 . The EGR valve  60 A and the EGR inlet  50 C may be positioned either upstream or downstream of the compressor wheel  48  such that the post-combustion gases  24  are directed from the cylinder head section  16  into the compressor cover  50  by being respectively mixed in with the unpressurized airflow  32  or pressurized airflow  32 A. Accordingly, the EGR valve  60 A may be incorporated at the inlet  50 A to control reintroduction of the exhaust post-combustion gases  24  into the unpressurized airflow  32  (as shown in  FIG. 3 ). In the alternative, the EGR valve  60 A and the EGR inlet  50 C may be incorporated at the outlet  50 B to control reintroduction of the exhaust post-combustion gases  24  into the pressurized airflow  32 A (as shown in  FIG. 4 ). 
     As shown in  FIGS. 3-4 , the compressor cover  50  may also include a fluid flow mixer  64 . The fluid flow mixer  64  is configured to mix the exhaust post-combustion gases  24  with the airflow  32 . In the case where the EGR valve  60 A is incorporated at the inlet  50 A, the mixer  64  is arranged at the inlet  50 A, downstream of the EGR valve ( FIG. 3 ). On the other hand, in the case where the EGR valve  60 A is incorporated at the outlet  50 B, the mixer  64  is arranged proximately to and downstream of the EGR valve at the outlet  50 B ( FIG. 4 ). The engine  10  may additionally include an electronic controller  66 . The controller  66  may be configured to control operation of the engine  10  and also programmed to regulate operation of the EGR valve  60 A via the EGR valve actuator  60 . 
     In general, atmospheric nitrogen begins to react with oxygen at elevated combustion temperatures, which can exceed  2500  degrees Fahrenheit. The result is emissions of various compounds called nitrogen oxides (NOx) as part of the exhaust stream. Generally, to reduce the formation of NOx, combustion temperatures are reduced to slow down the NOx formation kinetics. Typically, combustion temperatures are reduced below such a threshold by recirculating a small amount of post-combustion gases through the EGR valve. Typically, around 5-15% of the post-combustion gases in gasoline engines and up to 50% of the post-combustion gases in diesel engines is routed back to the combustion chambers as EGR. The EGR process may be used to reduce formation of NOx emissions in both gasoline and diesel engines. 
     In gasoline engines, use of EGR may additionally increase engine efficiency through such factors as reduction in throttling losses and reduced heat rejection. EGR dilutes the incoming air/fuel mixture and has a quenching effect on combustion temperatures which keeps NOx within acceptable limits. As an added benefit, EGR also reduces a gasoline engine&#39;s octane requirements, which lessens the danger of premature ignition and spark knock. Since the EGR system recirculates a portion of exhaust gases, in both gasoline and diesel engines, over time the EGR valve can become clogged with carbon deposits that may cause the valve to stick or prevent the valve from closing properly. However, a clogged EGR valve can be cleaned and returned to proper operation. 
     As shown, the compressor cover  50  may also include a coolant supply passage  68 . The coolant supply passage  68  is configured to route a coolant proximate to the EGR valve  60 A and near the seat  62  such that the coolant removes heat generated by the reintroduced exhaust post-combustion gases  24  from the compressor cover  50 . Coolant flow within the coolant supply passage  68  may be provided by a fluid pump (not shown) that is also used to circulate coolant throughout the engine  10 . Additionally, the coolant in the coolant supply passage  68  may be circulated through a dedicated radiator or cooler  70  (shown in  FIG. 1 ) that is configured to reject heat that the coolant was able to remove from the compressor cover  50  near the seat  62 . 
     The EGR valve  60 A may be configured as one of a swing-, poppet-, and butterfly-type valve, shown in  FIGS. 2 ,  3 , and  4 , respectively. As shown in  FIG. 3 , the compressor cover  50  may include a sealable opening  72  configured to provide a service access to the EGR valve  60 A. The opening  72  is configured to facilitate removal of soot that may collect due to the flow of post-combustion gases  24 . Such cleaning of the EGR valve  60 A may be necessary to minimize possible sticking of the valve and restore proper operation thereof. The compressor cover  50  may also include a removable cover  74 . The cover  74  may be configured to selectively open and close the opening  72  to control the service access to the EGR valve  60 A. The cover  74  may be attached to the compressor cover  50  via appropriate fasteners  76  (shown in  FIGS. 2 and 3 ). 
     The detailed description and the drawings or figures are supportive and descriptive of the invention, but the scope of the invention is defined solely by the claims. While some of the best modes and other embodiments for carrying out the claimed invention have been described in detail, various alternative designs and embodiments exist for practicing the invention defined in the appended claims. Furthermore, the embodiments shown in the drawings or the characteristics of various embodiments mentioned in the present description are not necessarily to be understood as embodiments independent of each other. Rather, it is possible that each of the characteristics described in one of the examples of an embodiment can be combined with one or a plurality of other desired characteristics from other embodiments, resulting in other embodiments not described in words or by reference to the drawings. Accordingly, such other embodiments fall within the framework of the scope of the appended claims.