Abstract:
A combustion seal for a fuel injector assembly mountable within a cylinder head of an internal combustion engine is provided. The combustion seal is energized by combustion gases within a combustion chamber to effect sealing of an injector tip portion of the fuel injector assembly with respect to the cylinder head, thereby preventing the leakage or escape of combustion gases from the combustion chamber. A cylinder head assembly including the combustion seal is also disclosed.

Description:
TECHNICAL FIELD 
     The present invention relates to a combustion seal for a direct injection internal combustion engine. 
     BACKGROUND OF THE INVENTION 
     Recent advances in fuel delivery and combustion research have allowed direct injection, or DI, fuel delivery systems to increase in popularity. The DI fuel delivery system provides a fuel injector within the cylinder head of the internal combustion engine. The fuel injector operates to inject a predetermined amount of fuel directly into the combustion chamber at a predetermined time. The DI fuel delivery system enables higher power levels, improved fuel economy, and lower emissions. These beneficial aspects of the DI fuel delivery system are a result of the precise metering of the fuel injected into the combustion chamber as well as improved intake airflow into the combustion chamber. 
     SUMMARY OF THE INVENTION 
     A fuel injector assembly mountable within an injector bore defined by a cylinder head of an internal combustion engine is provided. The fuel injector includes a fuel injector body having an injector tip portion configured to be at least partially received within the injector bore. An annular groove is defined by the injector tip and is configured to receive a generally annular combustion seal subject to combustion gas pressures. The annular groove includes a generally tapering portion. The generally annular combustion seal is biased against the generally tapering portion of the annular groove when the generally annular combustion seal is subject to combustion gas pressures. The generally annular combustion seal is biased radially outward to sealingly engage the injector bore when the generally annular combustion seal is biased against the generally tapering portion of the annular groove. A cylinder head assembly incorporating the fuel injector assembly is also disclosed. 
     In another embodiment, a cylinder head assembly for an internal combustion engine is provided. The cylinder head assembly includes a cylinder head at least partially defining a combustion chamber. An injector piloting sleeve is mounted within the cylinder head and defines an injector bore. A fuel injector assembly having an injector body and an injector tip portion is also provided. The injector tip portion is at least partially disposed within the injector bore and is in communication with the combustion chamber. An annular groove, having a generally tapering portion, is defined by the injector piloting sleeve and is configured to receive a generally annular combustion seal subject to combustion gas pressures within the combustion chamber. The generally annular combustion seal is biased against the generally tapering portion of the annular groove when the generally annular combustion seal is subject to combustion gas pressures. Furthermore, the generally annular combustion seal is biased radially inward to sealingly engage the injector tip portion when the generally annular combustion seal is biased against the generally tapering portion of the annular groove. 
     The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view of a portion of a cylinder head assembly with a fuel injector assembly mounted thereto illustrating a combustion seal energized by combustion gases; 
         FIG. 2  is a magnified view of a portion of the cylinder head assembly of  FIG. 1  illustrating aspects of the combustion seal; 
         FIG. 3   a  is a cross sectional view of the combustion seal of  FIGS. 1 and 2 ; 
         FIG. 3   b  is a cross sectional view of an alternate embodiment of the energized combustion seal of  FIG. 3   a;    
         FIG. 4  is a sectional view of an alternate embodiment of the cylinder head assembly of  FIG. 1 ; and 
         FIG. 5  is a magnified view of a portion of the cylinder head assembly of  FIG. 4 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings wherein like reference numbers correspond to like or similar components throughout the several figures, there is shown in  FIG. 1  a portion of a cylinder head assembly  10  for a direct injection internal combustion engine, not shown. The cylinder head assembly  10  includes a cylinder head  12  formed from a cast metal such as aluminum, iron, magnesium, etc. having a fuel injector assembly  14  mounted thereto. The cylinder head  12  defines an injector bore  16  and partially defines a combustion chamber  18 . The injector bore  16  is in communication with the combustion chamber  18 . The fuel injector assembly  14  includes an injector body  20  having an injector tip portion  22  extending therefrom. The injector bore  16  is configured to receive the injector tip portion  22  such that the injector tip portion  22  is in communication with the combustion chamber  18 . 
     A fuel rail  24  is mounted with respect to the fuel injector assembly  14  and is operable to provide a source of pressurized fuel  26  to the fuel injector assembly  14 . The fuel injector assembly  14  is operable to communicate metered and timed amounts of pressurized fuel  26  from the fuel rail  24  directly into the combustion chamber  18  for subsequent combustion therein. As such, the fuel injector assembly  14  may be characterized as a direct injection fuel injector. An isolator member  28  is disposed between the cylinder head  12  and the fuel injector assembly  14  and is operable to provide a measure of compliance such that hard contact or grounding between the fuel injector assembly  14  and the cylinder head  12  is prevented. In so doing, the transmission of noise producing vibrations between the fuel injector assembly  14  and the cylinder head  12  is reduced. A secondary seal  29  is operable to seal the injector body  20  with respect to the cylinder head  12 . 
     The injector bore includes first and second generally cylindrical portions  30  and  32 , respectively, having a generally tapering bore portion  34  therebetween. The generally tapering bore portion  34  is operable to guide or pilot the injector tip portion  22  into the second generally cylindrical portion  32  during insertion of the fuel injector assembly  14 . Since the fuel injector assembly  14  is in direct communication with the combustion chamber  18 , the fuel injector assembly  14  is subject to high pressure loads and temperatures of the combustion process. Therefore, the fuel injector assembly  14  must be sealed with respect to the cylinder head  12 . The injector tip portion  22  defines an annular groove  36  configured to receive a portion of a combustion seal  38 . The annular groove  36  includes a generally tapering portion  37  operable to radially expand the combustion seal  38  as the combustion seal  38  is biased thereon by combustion gases, indicated by arrows  39 , within the combustion chamber  18 . The combustion seal  38  is generally annular and sleeve-like in shape and is operable to sealingly engage the second generally cylindrical portion  32  of the injector bore  16  thereby preventing combustion gases  39  from traversing the injector bore  16  during operation of the internal combustion engine. The combustion seal  38  is preferably formed from glass or carbon filled polytetrafluoroethylene; however, other materials may be employed possessing the requisite temperature and chemical resistance while remaining within the scope of that which is claimed. 
     Referring to  FIG. 2  and with continued reference to  FIG. 1 , there is shown a portion of the cylinder head assembly  10  enlarged to illustrate further aspects of the present embodiment. In operation, the combustion seal  38  is subject to pressure forces exerted thereon by the combustion gases  39 . As a result, the combustion seal  38  is biased upward, as viewed in  FIG. 2 , against the generally tapering portion  37  of the annular groove  36 . As the combustion seal  38  is biased against the generally tapering portion  37 , the generally tapering portion  37  expands the combustion seal  38  radially outward to sealingly engage the second generally cylindrical portion  32  of the injector bore  16 . As such, the combustion seal  38  may be characterized as an “energized” combustion seal. That is, the combustion seal  38  is energized by the pressure forces of the combustion gases  39  to effect sealing of the injector tip portion  22  with respect to the injector bore  16 . Therefore, the sealing effectiveness of the combustion seal  38  is proportional to the pressure forces acting on the combustion seal by the combustion gases  39 . The generally tapering portion  37  of the annular groove  36  has a taper angle Θ, shown in  FIG. 2 . In the preferred embodiment the taper angle Θ is approximately 12 to approximately 20 degrees. This range of taper angles will enable ease of insertion of the injector tip portion  22  within the injector bore  16  during assembly, while maintaining adequate sealing effectiveness of the combustion seal over a range of friction coefficients for the injector bore  16 , injector tip portion  22 , and the combustion seal  38 . 
     In operation, the fuel injector assembly  14  will exhibit small axial movements, as illustrated by arrow  44 , as a result of variations in pressure within the combustion chamber  18  and the pressurized fuel  26  within the fuel rail. The isolation member  28  may tend to increase the magnitude of this movement. Since the combustion seal  38  is energized by pressure forces exerted by the combustion gases  39 , the combustion seal  38  is operable to maintain a seal between the injector tip portion  22  and the second generally cylindrical portion  32  of the injector bore  16  during axial movement of the fuel injector assembly  14 . 
     Referring to  FIG. 3   a  and with continued reference to  FIGS. 1 and 2 , there is shown the combustion seal  38  in an un-deformed state, i.e. prior to installation within the generally annular groove  36 . As shown, the combustion seal  38  has a bore  40  that extends the length of the combustion seal  38 . The bore  40  is shown in  FIG. 3   a  as generally cylindrical; however, the bore  40  may have a generally tapering shape to complement the taper angle Θ of the generally tapering portion  37 . Referring to  FIG. 3   b  and with continued reference to  FIGS. 1 and 2 , an alternate embodiment of the combustion seal  38  is indicated at  38 A. The combustion seal  38 A defines a bore  42  that extends the length of the combustion seal  38 A. The bore  42  includes first and second tapering portions  45  and  46 , respectively, extending from the midline or center of the combustion seal  38 A and tapering outward. The first and second tapering portions  45  and  46  have a taper configured to generally complement the taper angle Θ of the generally tapering portion  37 . The first and second tapering portions  45  and  46  provide a measure of error-proofing for assembly purposes since the orientation of the combustion seal  38 A as the combustion seal  38 A is inserted into the generally annular groove  36  is irrelevant. 
     Referring now to  FIG. 4 , there is shown an alternate embodiment of the cylinder head assembly  10  of  FIG. 1 , generally indicated at  10 A. The cylinder head assembly  10 A includes a fuel injector assembly  14 A. The fuel injector assembly  14 A includes the injector body  20  having an injector tip portion  22 A extending therefrom. The annular groove  36  defined by injector tip portion  22  of  FIG. 1  is lacking in the injector tip portion  22 A of  FIG. 4 . An injector piloting sleeve  48  is mounted with respect to the cylinder head  12  and defines the generally tapering bore portion  34  and the generally cylindrical bore portion  32  of the injector bore  16 . The injector piloting sleeve  48  may be retained within the cylinder head  12  by interference fit, threaded engagement, or other fastening means. The injector piloting sleeve  48  defines an annular groove  50  configured to receive a portion of the combustion seal  38 . The annular groove  50  may be formed by a machining operation. The injector piloting sleeve  48  may be formed by a powdered metal process. 
     The combustion seal  38  sealingly engages the injector tip portion  22 A of the fuel injector assembly  14 A. The annular groove  50  is preferably formed in the second generally cylindrical bore portion  32 . The annular groove  50  includes a generally tapering portion  52  operable to radially compress the combustion seal  38  as the combustion seal  38  is biased thereon by combustion gases  39  within the combustion chamber  18 . The combustion seal  38  is operable to sealingly engage the second injector tip portion  22 A of the fuel injector assembly  14 A thereby preventing combustion gases  39  from traversing the injector bore  16  during operation of the engine. 
     Referring to  FIG. 5  and with continued reference to  FIG. 4 , there is shown a portion of the cylinder head assembly  10 A enlarged to illustrate further aspects of the present embodiment. In operation, the combustion seal  38  is subject to pressure forces exerted thereon by the combustion gases  39 . As a result, the combustion seal  38  is biased upward, as viewed in  FIG. 5 , against the generally tapering portion  52  of the annular groove  50 . As the combustion seal  38  is biased against the generally tapering portion  52 , the generally tapering portion  52  biases or urges the combustion seal  38  radially inward to sealingly engage the injector tip portion  22 A of the fuel injector assembly  14 A. The combustion seal  38  is energized by the pressure forces of the combustion gases  39  to effect sealing of the injector tip portion  22 A with respect to the injector bore  16 . Therefore the sealing effectiveness of the combustion seal  38  is proportional to the pressure forces acting on the combustion seal by the combustion gases  39 . The generally tapering portion  52  of the annular groove  50  has a taper angle Φ, shown in  FIG. 5 . In the preferred embodiment the taper angle Φ is approximately 10 to approximately 20 degrees. This range of taper angles will enable ease of insertion and removal of the injector tip portion  22 A within the injector bore  16 , while maintaining adequate sealing effectiveness of the combustion seal  38  over a range of friction coefficients for the injector bore  16 , injector tip portion  22 A, and the combustion seal  38 . 
     As described hereinabove, the fuel injector assembly  14 A will exhibit small axial movements, as illustrated by arrow  44 , as a result of variations in pressure within the combustion chamber  18  and the pressurized fuel  26  within the fuel rail. The isolation member  28  may tend to increase the magnitude of this movement. Since the combustion seal  38  is energized by pressure forces exerted by the combustion gases  39 , the combustion seal  38  is operable to maintain a seal between the injector tip portion  22 A and the injector bore  16  during the axial movement of the fuel injector assembly  14 A. 
     Additionally, the injector piloting sleeve  48  may be formed from a material having a similar coefficient of thermal expansion as that of the injector tip portion  22 A. In this case, close tolerances may be maintained between the second generally cylindrical bore portion  32  and the injector tip portion  22 A over a wide range of temperatures. Furthermore, the injector piloting sleeve  48  may be formed without the annular groove  50  for use with the fuel injector assembly  14  of  FIG. 1 . 
     While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.