Abstract:
A fuel injector assembly sufficiently configured to be mountable within an injector bore defined by a cylinder head assembly is provided. The fuel injector assembly includes an injector body having an injector tip portion and a generally annular combustion seal mounted with respect to the injector tip portion. A secondary combustion seal is mounted with respect to the injector tip portion and is substantially adjacent to the generally annular combustion seal. A cylinder head assembly incorporating the disclosed fuel injector assembly is also provided.

Description:
TECHNICAL FIELD 
     The present invention relates to a fuel injector having a secondary combustion seal. 
     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 a cylinder head of an internal combustion engine. The fuel injector operates to inject a predetermined amount of fuel directly into the combustion chamber. 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. 
     Since the fuel injector assembly is in direct communication with the combustion chamber, the fuel injector is subject to high pressure loads and temperatures of the combustion process. Therefore, the fuel injector must be sealed with respect to the cylinder head to prevent combustion gases from leaking past the fuel injector. 
     SUMMARY OF THE INVENTION 
     A fuel injector assembly sufficiently configured to be mountable within an injector bore defined by a cylinder head assembly is provided. The fuel injector assembly includes an injector body having an injector tip portion and a generally annular combustion seal mounted with respect to the injector tip portion. A secondary combustion seal is mounted with respect to the injector tip portion and is substantially adjacent to the generally annular combustion seal. The secondary combustion seal is preferably an o-ring type seal. The injector bore may include a tapering portion and a generally cylindrical portion. The generally annular combustion seal and the secondary combustion seal are preferably configured to sealingly engage the generally cylindrical portion. A cylinder head assembly incorporating the disclosed fuel injector assembly is also provided. 
     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 and illustrating a secondary combustion seal; and 
         FIG. 2  is a sectional view of a portion of a cylinder head assembly with a fuel injector assembly mounted thereto and illustrating an alternate embodiment of the secondary combustion seal of  FIG. 1 . 
     
    
    
     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., and a fuel injector assembly  14  mounted thereto. The cylinder head  12  defines an injector bore  16  and a 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 . 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 assembly. 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 to reduce or eliminate hard contact or grounding between the fuel injector assembly  14  and the cylinder head  12 . In so doing, the transmission of noise producing vibrations between the fuel injector assembly  14  and the cylinder head  12  is reduced. 
     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 . The injector tip portion  22  defines an annular groove  36  configured to receive a portion of a combustion seal  38 . 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 from within the combustion chamber  18  from traversing the injector bore  16  during operation of the engine. The combustion seal  38  is preferably formed from a glass or carbon filled polytetrafluoroethylene material, however, those skilled in the art will recognize that other materials may be employed possessing the requisite thermal and chemical resistance while remaining within the scope of that which is claimed. 
     An annular groove  40  is defined by the injector tip portion  22  and is configured to contain a portion of a secondary combustion seal  42 . The secondary combustion seal  42  is mounted substantially adjacent to the combustion seal  38  and is operable to sealingly engage the second generally cylindrical portion  32  of the injector bore  16 . The secondary combustion seal  42  is operable to prevent combustion gases that may traverse the combustion seal  38  from flowing further into the injector bore  16 . The secondary combustion seal  42  is preferably an o-ring type seal formed from a rubber. In a preferred embodiment the secondary combustion seal  42  is formed from a fluoropolymer elastomer material. 
     In operation, the fuel injector assembly  14  will exhibit small axial displacements or 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  24 . The isolation member  28  may tend to increase the magnitude of this movement. The axial movements of the fuel injector assembly  14  may tend to destabilize the combustion seal  38  thereby causing a reduction in the sealing effectiveness of the combustion seal  38 . The secondary combustion seal  42  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 the axial movement of the fuel injector assembly since the o-ring shape of the secondary combustion seal  42  will allow the secondary combustion seal  42  to “roll” within the annular groove  40  while maintaining engagement with the injector bore  16 . 
     Referring now to  FIG. 2 , 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. The annular groove  40  defined by injector tip portion  22  of  FIG. 1  is absent in the injector tip portion  22 A of  FIG. 2 . An injector piloting sleeve  46  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  46  may be retained within the cylinder head  12  by interference fit, threaded engagement, or other fastening means known to those skilled in the art. The injector piloting sleeve  46  defines an annular groove  48  configured to receive a portion of the secondary combustion seal  42 . In this configuration, the secondary combustion seal  42  sealingly engages the injector tip portion  22 A of the fuel injector assembly  14 A. The annular groove  48  is preferably formed in the second generally cylindrical bore portion  32  such that when the fuel injector assembly  14 A is mounted with respect to the cylinder head  12 , the secondary combustion seal  42  is substantially adjacent to the combustion seal  38 . The secondary combustion seal  42  operates in substantially the same fashion as described hereinabove with reference to  FIG. 1 . Additionally, the injector piloting sleeve  46  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 piloting sleeve  46  may be formed without the annular groove  48  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.