Abstract:
An engine assembly includes an engine structure and an exhaust gas recirculation control valve supported on the engine structure. The engine structure defines a cylinder bore and intake and exhaust ports in communication with the cylinder bore. An internal exhaust gas recirculation passage is defined in the engine structure and extends from the exhaust port to the intake port and may overlie a central region of the cylinder bore. The exhaust gas recirculation control valve is at least partially located within the internal exhaust gas recirculation passage and is displaceable between an open position and a closed position. The open position allows exhaust gas flow from the exhaust port to the intake port through the internal exhaust gas recirculation passage and the closed position obstructs exhaust gas flow from the exhaust port to the intake port through the internal exhaust gas recirculation passage.

Description:
FIELD 
       [0001]    The present disclosure relates to engine exhaust gas recirculation systems. 
       BACKGROUND 
       [0002]    This section provides background information related to the present disclosure which is not necessarily prior art. 
         [0003]    Internal combustion engines may include exhaust gas recirculation systems to provide exhaust gas to the combustion chambers for a subsequent combustion event. In order to provide exhaust gas flow to the combustion chambers a flow path from the exhaust system to the intake system is typically included, resulting in heat loss and additional components requiring packaging space and assembly time. 
       SUMMARY 
       [0004]    An engine cylinder head may include a cylinder head structure defining intake and exhaust ports for communication with a cylinder bore and an internal exhaust gas recirculation passage. The internal exhaust gas recirculation passage may extend from the exhaust port to the intake port in a direction from an exhaust side of the cylinder head to an intake side of the cylinder head and may be configured to overlie a central region of the cylinder bore. 
         [0005]    An engine assembly may include an engine structure and an exhaust gas recirculation control valve supported on the engine structure. The engine structure may define a cylinder bore and intake and exhaust ports in communication with the cylinder bore. An internal exhaust gas recirculation passage may be defined in the engine structure and may extend from the exhaust port to the intake port and may overlie a central region of the cylinder bore. The exhaust gas recirculation control valve may be at least partially located within the internal exhaust gas recirculation passage and may be displaceable between an open position and a closed position. The open position may allow exhaust gas flow from the exhaust port to the intake port through the internal exhaust gas recirculation passage and the closed position may obstruct exhaust gas flow from the exhaust port to the intake port through the internal exhaust gas recirculation passage. 
         [0006]    In another arrangement, an engine assembly may include an engine block defining a cylinder bore, a cylinder head coupled to the engine block, an exhaust gas recirculation control valve supported on the cylinder head, an intake system, an exhaust system and a backpressure control valve. The cylinder head may define intake and exhaust ports in communication with the cylinder bore and an internal exhaust gas recirculation passage extending from the exhaust port to the intake port and overlying a central region of the cylinder bore. The exhaust gas recirculation control valve may be at least partially located within the internal exhaust gas recirculation passage and may be displaceable between an open position and a closed position. The open position may allow exhaust gas flow from the exhaust port to the intake port through the internal exhaust gas recirculation passage and the closed position may obstruct exhaust gas flow from the exhaust port to the intake port through the internal exhaust gas recirculation passage. The intake system may be in communication with the intake port and the exhaust system may be in communication with the exhaust port. The backpressure control valve may be located in the exhaust system and may be configured to adjust a pressure differential between the intake and exhaust ports. 
         [0007]    Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0009]      FIG. 1  is a schematic illustration of an engine assembly according to the present disclosure; 
           [0010]      FIG. 2  is a schematic section view of the engine assembly from  FIG. 1  with an internal EGR valve in a closed position according to the present disclosure; 
           [0011]      FIG. 3  is a schematic section view of the engine assembly from  FIG. 1  with the internal EGR valve in an open position; and 
           [0012]      FIG. 4  is a schematic section view of the cylinder head from the engine assembly shown in  FIGS. 2 and 3 . 
       
    
    
       [0013]    Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
       DETAILED DESCRIPTION 
       [0014]    Examples of the present disclosure will now be described more fully with reference to the accompanying drawings. The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
         [0015]    Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail. As used herein, the term “module” refers to an application specific integrated circuit (ASIC), an electronic circuit, and/or a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs. 
         [0016]    When an element or layer is referred to as being “on,” “engaged to,” “connected to” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
         [0017]    Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments. 
         [0018]    With reference to  FIGS. 1 and 2 , an engine assembly  10  may include an engine structure  12 , an intake system  14 , an exhaust system  16 , a valvetrain assembly  18  and an exhaust gas recirculation (EGR) assembly  20 . The engine structure  12  may define cylinder bores  22  forming combustion chambers. The engine structure  12  may include an engine block  24  defining the cylinder bores  22  and a cylinder head  26  coupled to the engine block  24  and defining intake and exhaust ports  28 ,  30  in communication with the combustion chambers. 
         [0019]    An inline engine configuration having four cylinders ( 22 - 1 ,  22 - 2 ,  22 - 3 ,  22 - 4 ) is schematically shown in  FIG. 1  for illustration purposes only with a single cylinder illustrated in the section view shown in  FIG. 2  for simplicity. It is understood that the features discussed relative to the cylinder shown in  FIG. 2  apply equally to the remaining cylinders of the engine assembly  10 . Additionally, it is understood that the present teachings apply to any number of piston-cylinder arrangements and a variety of reciprocating engine configurations including, but not limited to, V-engines, inline engines, and horizontally opposed engines, as well as both overhead cam and cam-in-block configurations. 
         [0020]    The intake system  14  may include an intake conduit  32 , an intake manifold  36  coupled to the cylinder head  26  and in communication with the intake conduit  32 , a throttle valve  38  in the intake conduit  32  and controlling air flow to intake port  28  through the intake manifold  36 , a turbocharger  40  including an intake side  42  (compressor) located in the intake conduit  32  and an air cleaner  44  located in the intake conduit  32 . The intake conduit  32  may define an air inlet into the intake system  14  and the turbocharger  40  may be in communication with the intake ports  28  via the intake manifold  36 . While a single turbocharger  40  is illustrated, it is understood that the present disclosure applies equally to arrangements including multiple turbochargers. 
         [0021]    The exhaust system  16  may include an exhaust conduit  48 , an exhaust manifold  52  coupled to the cylinder head  26  and in communication with the exhaust conduit  48 , and a diesel particulate filter (DPF)  54  and a selective catalytic reduction (SCR) catalyst  56  located in the exhaust conduit  48 . While illustrated as including an individual DPF  54  and an individual SCR catalyst  56 , it is understood that the present disclosure is not limited to such arrangements. The DPF  54  may alternatively be included in a combined DPF/SCR catalyst. Further, the SCR catalyst  56  may alternatively be located upstream of the DPF  54  or an additional SCR catalyst (not shown) may be included upstream of the DPF  54 . The exhaust side  58  (turbine) of the turbocharger  40  may be located in the exhaust conduit  48  and may include a turbine wheel in communication with and driven by exhaust gas flowing through the exhaust conduit  48 . The exhaust side  58  of the turbocharger  40  may include a variable exhaust gas outlet  60  that controls an exhaust gas flow restriction through the turbocharger  40 . The variable exhaust gas outlet  60  may be in the form of a variable nozzle. 
         [0022]    As seen in  FIGS. 2 and 3 , the valvetrain assembly  18  may include intake valves  62  located in the intake ports  28 , exhaust valves  64  located in the exhaust ports  30 , intake valve lift mechanisms  66  supported on the cylinder head  26  and engaged with the intake valves  62 , exhaust valve lift mechanisms  68  supported on the cylinder head  26  and engaged with the exhaust valves  64 , an intake camshaft  70  supported for rotation on the cylinder head  26  and engaged with the intake valve lift mechanisms  66  and an exhaust camshaft  72  supported for rotation on the cylinder head  26  and engaged with the exhaust valve lift mechanisms  68 . 
         [0023]    The exhaust gas recirculation assembly  20  may include an EGR control valve  74  and an actuation mechanism  76 . With additional reference to  FIG. 4 , the cylinder head  26  may define an internal exhaust gas recirculation passage  78  extending from the exhaust port  30  to the intake port  28  and overlying a central region of the cylinder bore  22 . The internal exhaust gas recirculation passage  78  may extend from an exhaust side to an intake side of the cylinder head  26  and may be completely defined within the cylinder head  26  within an outer perimeter of the cylinder bore  22 . More specifically, the internal exhaust gas recirculation passage  78  may be defined within the cylinder head  26  at a location radially between the intake and exhaust ports  28 ,  30 . The minimal length of the internal exhaust gas recirculation passage  78  defined within the cylinder head  26  may generally minimize heat loss from the exhaust gas being provided for a subsequent combustion event. The intake or exhaust port  28 ,  30  may form an entry location for a machining tool to create the internal exhaust gas recirculation passage  78 . 
         [0024]    The cylinder head  26  may additionally define a bore  80  intersecting the internal exhaust gas recirculation passage  78 . The EGR control valve  74  may be supported on the cylinder head  26  and may include an actuation piston  82  and a biasing member  84 . The actuation piston  82  may be located in the bore  80  and engaged with the actuation mechanism  76  for displacement between a closed position ( FIG. 2 ) and an open position ( FIG. 3 ). The biasing member  84  may take a variety of forms including, but not limited to, a compression spring and may bias the actuation piston  82  to the open position. The actuation mechanism  76  may take a variety of forms including, but not limited to, an electro-mechanical arrangement including the rocker arm illustrated in  FIGS. 2 and 3 . Alternatively, the actuation mechanism  76  may be in the form of a hydraulically-actuated valve. 
         [0025]    The exhaust gas recirculation assembly  20  may additionally include an EGR line  98 , an EGR cooler  100  and cooler bypass  102  located in the EGR line  98 , an EGR control valve  104  and a backpressure control valve  106 . The EGR line  98  may extend from the exhaust conduit  48  at a location between the turbocharger  40  and an outlet of the exhaust conduit  48  to the intake system  14  to provide communication between the intake and exhaust systems  14 ,  16 . 
         [0026]    In the non-limiting example shown in  FIG. 1 , the EGR control valve  104  may be located at the outlet of the EGR line  98  and may control exhaust gas recirculation flow to the intake system  14  from the EGR line  98 . The backpressure control valve  106  may be located in the exhaust conduit  48  at a location between the EGR line  98  and an outlet of the exhaust conduit  48 . In the non-limiting example shown in  FIG. 1 , the backpressure control valve  106  is located at the outlet of the exhaust conduit  48 . The DPF  54  may be located in the exhaust conduit  48  at a location between the exhaust side  58  of the turbocharger  40  and the backpressure control valve  106 . The arrangement discussed above provides an internal EGR system in combination with a low pressure EGR system. 
         [0027]    More specifically, the engine assembly  10  may additionally include a control module  108  in communication with the actuation mechanism  76 , the EGR control valve  104  and the backpressure control valve  106 . The backpressure control valve  106  may be used to control the pressure differential between the intake system  14  and the exhaust system  16  for both the internal EGR system and the low pressure EGR system to adjust recirculation of exhaust gas in the engine assembly  10 . The EGR control valves  74 ,  104  may be adjusted by the control module  108  to provide a desired amount of exhaust gas recirculation during engine operation. The throttle valve  38  and the variable exhaust gas outlet  60  of the turbocharger  40  may also be used to control the pressure differential between the intake system  14  and the exhaust system  16  to further adjust the amount of exhaust gas recirculated in the engine assembly  10 . In some arrangements, the exhaust gas recirculation assembly  20  may additionally include a bypass passage  112  and a bypass valve  114  located in the bypass passage  112  and in communication with the control module  108 . The bypass passage  112  may extend from the exhaust manifold  52  to a region of the intake conduit  32  located between the intake throttle valve  38  and the intake manifold  36  to provide further control of exhaust gas recirculation. 
         [0028]    The internal EGR system may be used as the high pressure EGR system, eliminating the typical high pressure EGR lines and cooler, eliminating the potential for high pressure EGR cooler fouling.