Abstract:
A fuel injector-engine component assembly includes an engine component with a stepped bore defined along an axis and having a stepped bore stop surface facing axially upward. A fuel injector extending along the axis is disposed in the stepped bore and includes a fuel injector stop surface facing axially downward and axially opposing the stepped bore stop surface. An isolation ring is disposed between the engine component and fuel injector stop surfaces for axially isolating the fuel injector from the engine component. The isolation ring includes a rigid support member for limiting the axial motion of the engine component and fuel injector stop surfaces together. The isolation ring also includes a resilient and compliant isolation member located axially between the engine component and fuel injector stop surfaces to provide acoustic and thermal isolation between the fuel injector and the engine component below a predetermined pressure of the fuel injector.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. provisional patent application Ser. No. 61/330,629 filed May 3, 2010, the disclosure of which is hereby incorporated by reference in its entirety. 
     
    
     TECHNICAL FIELD OF INVENTION 
       [0002]    The present invention relates to fuel injection systems of internal combustion engines; more particularly, to fuel injectors for direct injection; and most particularly to a device for acoustic and thermal isolation of a fuel injector from a cylinder head. 
       BACKGROUND OF INVENTION 
       [0003]    Fuel injector systems that deliver fuel to the combustion chamber of an internal combustion engine have been known for many years. The typical fuel injection system draws fuel from a fuel tank to a fuel rail mounted adjacent to the cylinder bank of the engine. The fuel injectors are electro-mechanical devices that deliver fuel in precise amounts and times to the respective cylinder. 
         [0004]    While the engine is running, the valve within each fuel injector is constantly being operationally cycled from an opened to a closed position. Vibration is generated by the mechanical movement of the injector valves and pressure waves are generated by the movement of the fuel flowing through the injectors. Additionally, a substantial amount of heat generated in the combustion chambers of the cylinder heads may be transferred from the engine to the fuel injector. 
         [0005]    In an engine having a direct injection fuel injector, atomized fuel is sprayed by the injector directly into the combustion chamber of the engine. The fuel injector tip portion of the direct injection fuel injector typically fits through a stepped bore defined in the cylinder head that has a peripheral bottom shoulder whose top surface provides a positive stop to the bottom surface of the body of the direct injection fuel injector. However, direct metal-to-metal contact between the bottom surface of the direct injection fuel injector body and the top surface of the shoulder allows for unmitigated transfer of the vibration from the direct injection fuel injector to the cylinder head and allows for the transfer of heat by thermal conduction from the cylinder head to the direct injection fuel injector. Noise created thereby can be particularly objectionable at engine idling and low load operation. Additionally, allowing the vibration from the direct injection fuel injector to propagate into the combustion chamber can adversely effect the placement of the highly precise fuel spray pattern into the combustion chamber. Moreover, allowing thermal conduction of heat from the cylinder head to the direct injection fuel injector can lead to injector tip plugging thereby affecting fuel metering and injector spray pattern. 
         [0006]    Prior attempts to isolate vibration and heat transfer between the direct injection fuel injector and the cylinder head have included, for example, the installation of a full-fitting isolation spacer between the bottom surface of the body of the direct injection fuel injector and the shoulder in the cylinder head bore such as a plastic ring on top of a metal ring or a rubber encapsulated metal ring. However, the high downward compressive pressure exerted on these existing rings and their plastic or rubber isolation materials during normal engine operation causes the materials to creep around the engaging surfaces, effectively reducing the isolation materials between the direct injection fuel injector and the cylinder head. The use of compliant materials may also result in excessive axial movement between the direct injection fuel injector and the cylinder head which can adversely effect the placement of the highly precise fuel spray pattern into the combustion chamber thereby causing combustion problems. Excessive axial movement between the direct injection fuel injector and the cylinder head can also cause detrimental wear to the seal member between the direct injection fuel injector and the cylinder head which seals the combustion chamber from the atmosphere. 
         [0007]    What is needed in the art is a method for effectively thermally and acoustically isolating the fuel injector from the cylinder head of an internal combustion engine. What is also needed is method for limiting compression of a compliant isolation member used to isolate the fuel injector from the cylinder head. 
       SUMMARY OF THE INVENTION 
       [0008]    A fuel injector-engine component assembly for an internal combustion engine is provided. The fuel injector-engine component assembly includes an engine component with a stepped bore defined along an axis. The stepped bore includes a stepped bore stop surface facing axially upward. A fuel injector is disposed in the stepped bore and extends along the axis. The fuel injector includes a fuel injector stop surface facing axially downward and axially opposing the stepped bore stop surface to define a predetermined annular space. In operation, the fuel injector is subjected to axial pulses that tend to drive the fuel injector stop surface and the stepped bore stop surface together. An isolation ring is disposed in the predetermined annular space and axially between the stepped bore stop surface and the fuel injector stop surface for axially isolating the fuel injector from the engine component. The isolation ring includes a rigid support member for limiting the axial motion of the stepped bore stop surface and the fuel injector stop surface together to a predetermined, limited degree. The isolation ring also includes a resilient and compliant isolation member located axially between the stepped bore stop surface and the fuel injector stop surface. The isolation member has sufficient resilience, compressibility, and insulative potential to provide at least one of acoustic and thermal isolation between the fuel injector and the cylinder head below a predetermined pressure of the fuel injector. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0009]    This invention will be further described with reference to the accompanying drawings in which: 
           [0010]      FIG. 1  is a cross section of an isolation ring in accordance with the present invention installed in a cylinder head-fuel injector assembly; 
           [0011]      FIG. 2A  is an elevation view of a first embodiment of an isolation ring in accordance with the present invention; 
           [0012]      FIG. 2B  is a cross section of the first embodiment of an isolation ring in accordance with the present invention; 
           [0013]      FIG. 2C  is an isometric view of the first embodiment of an isolation ring in accordance with the present invention; 
           [0014]      FIG. 2D  is a second isometric view of the first embodiment of an isolation ring in accordance with the present invention; 
           [0015]      FIG. 3A  is an isometric view of a second embodiment of an isolation ring in accordance with the present invention; 
           [0016]      FIG. 3B  is a cross section of the second embodiment of an isolation ring in accordance with the present invention; 
           [0017]      FIG. 4  is a cross section of a third embodiment of an isolation ring in accordance with the present invention; 
           [0018]      FIG. 5  is a cross section of a fourth embodiment of an isolation ring in accordance with the present invention; 
           [0019]      FIG. 6  is a cross section of a fifth embodiment of an isolation ring in accordance with the present invention; 
           [0020]      FIG. 7  is a cross section of a sixth embodiment of an isolation ring in accordance with the present invention; 
           [0021]      FIG. 8  is a cross section of a seventh embodiment of an isolation ring in accordance with the present invention installed in a cylinder head-fuel injector assembly; 
           [0022]      FIG. 9  is a cross section of an eighth embodiment of an isolation ring in accordance with the present invention installed in a cylinder head-fuel injector assembly; and 
           [0023]      FIG. 10  is a cross section of a ninth embodiment of an isolation ring in accordance with the present invention installed in a cylinder head-fuel injector assembly. 
       
    
    
     DETAILED DESCRIPTION OF INVENTION 
       [0024]    Referring to  FIG. 1 , a fuel-injector-engine component assembly illustrated as fuel injector-cylinder head assembly  20  of internal combustion engine  22  includes fuel injector  24 , an engine component illustrated as cylinder head  26 , and isolation ring  28  assembled therebetween. Fuel injector-cylinder head assembly  20  extends along an axis  30 . 
         [0025]    Fuel injector  24  extends along axis  30  and includes solenoid housing  32  and injector tip  34  axially extending from solenoid housing  32 . Solenoid housing  32  includes fuel injector stop surface  35  facing axially downwardly. Cylinder head  26  includes stepped bore  36  defined along axis  30  and having stepped bore stop surface  37  facing axially upwardly and center opening  38 . Fuel injector  24  is assembled in stepped bore  36  of cylinder head  26  such that stepped bore  36  of cylinder head  26  accommodates solenoid housing  32  of fuel injector  24  and such that injector tip  34  extends through center opening  38  of cylinder head  26 . When fuel injector  24  is assembled within stepped bore  36 , fuel injector stop surface  35  and stepped bore stop surface  37  axially oppose each other and define predetermined annular space  39 . In operation, fuel injector  24  is subject to high frequency vibrations or axial pulses that tend to drive fuel injector stop surface  35  and stepped bore stop surface  37  axially together. Fuel injector  24  may be, but is not limited to, a fuel injector for direct injection as shown in  FIG. 1 . 
         [0026]    Isolation ring  28  is positioned within stepped bore  36  such that isolation ring  28  is positioned adjacent to solenoid housing  32  and encircling fuel injector  24  within predetermined annular space  39 . Accordingly, isolation ring  28  has outer circumference  40  that fits into stepped bore  36  and that is wider than center opening  38 . Isolation ring  28  further includes center aperture  42  adapted to receive fuel injector  24  therethrough. Isolation ring  28  includes rigid support member  44  and isolation member  46 . Support member  44  may be made of any material that is capable of withstanding the axial loads provided by fuel injector  24  while in operation and is preferably made of metal. Isolation member  46  is a compliant, resilient material and may be a rubber material such as fluorocarbon. Although not shown, it should now be understood that support member  44  may be formed integrally with fuel injector  24  or formed separately and attached to fuel injector  24 . 
         [0027]    Support member  44  includes recess  48  extending axially into support member  44  from first surface  50 . Before isolation ring  28  is assembled into fuel injector-head assembly  20 , isolation member  46  is in an uncompressed or free state. In the uncompressed state, isolation member  46  extends axially outward from first surface  50 . For example, isolation member  46  may extend axially outward from first surface  50  a distance of about 1 millimeter. When isolation ring  28  is installed into fuel injector-head assembly  20 , but not yet subjected to fuel pressure load from fuel injector  24 , isolation member  46  may be compressed slightly. For example, isolation member  46  may now be compressed such that isolation member  46  may extend axially outward from first surface  50  a distance of about 0.4 millimeters. Isolation member  46  may be compressed further when internal combustion engine  22  is running at low to moderate loads, thereby requiring lower fuel pressure than the maximum fuel pressure it is capable of realizing. For example, isolation member  46  may now be compressed such that isolation member  46  may extend axially outward from first surface  50  a distance of about 0.1-0.2 millimeters. When internal combustion engine  22  is running at higher loads, thereby requiring higher fuel pressure than at lower loads, isolation member  46  may now be compressed such that isolation member  46  no longer extends axially outward from first surface  50 . In other words, first surface  50  is now in contact with stepped bore stop surface  37  of cylinder head  26 . Isolation ring  28  may therefore be designed to allow support member  44  to contact cylinder head  26  at a predetermined fuel pressure. It is now understood that isolation member  46  is the only portion of isolation ring  28  in contact with cylinder head  26  except in instances when fuel pressure applied to fuel injector  24  is at or above the predetermined fuel pressure. Therefore, the material characteristics of isolation member  46  reduce noise at lower to moderate engine loads, which is when noise reduction is most critical. Additionally, the material characteristics of isolation member  46  include insulative potential to isolate heat from being transmitted from cylinder head  26  to fuel injector  24  at lower to moderate engine loads which is the loading internal combustion engine  22  predominantly experiences. When fuel pressure is at its highest levels, support member  44  prevents isolation member  46  from being over compressed. 
         [0028]    Recess  48  may be arranged to allow isolation member  46  to deform in order allow for axial compression of isolation member  46  as the axial load applied thereto increases. Isolation member  46  may also be arranged to deform in order to allow for axial compression thereof as the axial load applied thereto increases. This will be described in more detail with the description of the embodiments that follow. 
         [0029]    Now referring to  FIGS. 2A-2D , a first embodiment of isolation ring  128  is shown in an uncompressed state. Isolation member  146  may include a plurality of protrusions  152  that extend radially inward therefrom. Protrusions  152  serve to form an interference fit with fuel injector  24  in order to retain isolation ring  128  to fuel injector  24  before isolation ring  128  and fuel injector  24  are assembled into cylinder head  26 . 
         [0030]    Still referring to  FIGS. 2A-2D , recess  148  is arranged to allow isolation member  146  to expand radially inward and radially outward when isolation member  146  is compressed axially. This is accomplished by allowing isolation member  146  to expand radially outward because radial clearance is provided between support member  144  and isolation member  146 . This is also accomplished by allowing isolation member  146  to expand radially inward because recess  148  extends to center aperture  142 , thereby bounding isolation member  146  only radially outward by support member  144 . 
         [0031]    Now referring to  FIGS. 3A and 3B , a second embodiment of isolation ring  228  is shown in an uncompressed state. Isolation ring  228  is different from isolation ring  128  of the first embodiment in that the height of isolation member  246  is substantially increased. Isolation member  246  may include a plurality of protrusions  252  that extend radially inward therefrom. Protrusions  252  serve to form an interference fit with fuel injector  24  in order to retain isolation ring  228  to fuel injector  24  before isolation ring  228  and fuel injector  24  are assembled into cylinder head  26 . In addition to, or in alternative to protrusions  252 , support member  244  may include a plurality of fingers  254  that extend radially inward therefrom. Fingers  254  serve to form an interference fit with fuel injector  24  in order to retain isolation ring  228  to fuel injector  24  before isolation ring  228  and fuel injector  24  are assembled into cylinder head  26 . 
         [0032]    In the second embodiment, support member  244  may be made of stamped sheet metal. This may result in hollow cavity  256  being formed at the end of support member  244  opposite recess  248 . Isolation member  246  may then be injection molded to support member  244 . In this way, isolation member  246  may be retained to support member  244 . 
         [0033]    Still referring to  FIGS. 3A and 3B , recess  248  is arranged to allow isolation member  246  to expand radially inward when isolation member  246  is compressed axially. This is accomplished by allowing isolation member  246  to expand radially inward because recess  248  extends to center aperture  242 , thereby bounding isolation member  246  only radially outward by support member  244 . 
         [0034]    Now referring to  FIG. 4 , a third embodiment is shown in an uncompressed state in which isolation ring  328  is shown at only a single radial location. In this embodiment, recess  348  bounds isolation member  346  both radially outward and radially inward over most of the axial length of isolation member  346 . Recess  348  is arranged to allow isolation member  346  to expand radially outward and radially inward when isolation member  346  is compressed axially. This is accomplished by providing expansion cavities  358  at the open end of support member  344 . 
         [0035]    Now referring to  FIG. 5 , a fourth embodiment is shown in an uncompressed state in which isolation ring  428  is shown at only a single radial location. In this embodiment, recess  448  bounds isolation member  446  both radially outward and radially inward over only a small portion of the axial length of isolation member  446 . Recess  448  is arranged to allow isolation member  446  to expand radially outward and radially inward when isolation member  446  is compressed axially. This is accomplished by providing expansion cavities  458  at the open end of support member  444 . 
         [0036]    Now referring to  FIG. 6 , a fifth embodiment is shown in which isolation ring  528  is shown in an uncompressed state at only a single radial location. In this embodiment, recess  548  bounds isolation member  546  both radially outward and radially inward over a portion of the axial length of isolation member  546 . Recess  548  and isolation member  546  are arranged to allow isolation member  546  to expand radially outward, radially inward, and axially upward when isolation member  546  is compressed axially. This is accomplished by providing expansion cavities  558 . The barrel-shape cross sectional of isolation member  546  in combination with the straight sides and domed top of support member  544  form expansion cavities  558 . 
         [0037]    Now referring to  FIG. 7 , a sixth embodiment is shown in which isolation ring  628  is shown in an uncompressed state at only a single radial location. In this embodiment, recess  648  bounds isolation member  646  both radially outward and radially inward over a portion of the axial length of isolation member  646 . Recess  648  and isolation member  646  are arranged to allow isolation member  646  to expand radially outward and radially inward when isolation member  646  is compressed axially. This is accomplished by providing expansion cavities  658 . Grooves  664  and chamfers  666  formed in isolation member  646  in combination with the straight sides of support member  644  form expansion cavities  658 . 
         [0038]    Now referring to  FIG. 8 , a seventh embodiment is shown in which isolation ring  728  is inverted from the embodiments previously shown. That is, isolation member  746  contacts fuel injector  24  rather than cylinder head  26 . 
         [0039]    Now referring to  FIG. 9 , an eighth embodiment is shown in which isolation ring  828  allows isolation member  846  to contact both fuel injector  24  and cylinder head  26 . This is accomplished by the support member comprising inner ring  860  and outer ring  862  with isolation member  846  contained therebetween. In the uncompressed state, isolation member  846  extends axially outward from both ends of inner and outer rings  860 ,  862 . Alternatively, but not shown, isolation ring  828  may include only one of the inner and outer rings  860 ,  862 . Also alternatively, but not shown, one or more of inner and outer rings  862  may be integrally formed with fuel injector  24  or affixed thereto in order to form an annular recess for receiving isolation member  846  therewithin. 
         [0040]    Now referring to  FIG. 10 , a ninth embodiment is shown in which the isolation ring does not include a support member attached thereto. In this embodiment, the support member is integral with fuel injector  24 . In this way, the interaction between features of fuel injector  24  and cylinder head  26  limit the amount of axial compression applied to isolation member  946 . Specifically, surface  968  of fuel injector  24  is allowed to come into contact with corner  970  of cylinder head  26  when fuel pressure compress isolation member  946  sufficiently. 
         [0041]    While stepped bore  36  has been described as being formed in cylinder head  26  of internal combustion engine  22 , it should be now understood that the stepped bore could be located in other elements of the internal combustion which may receive a fuel injector therein. For example, the stepped bore could be formed in the intake manifold of a port injection fuel injection engine. Accordingly, fuel injector-cylinder head assembly  20  may be generically referred to as a fuel injector-engine component assembly where the engine component is any element of the engine with a stepped bore in which the fuel injector is installed. 
         [0042]    While the isolation ring has been described as having one isolation member, it should now be understood that multiple isolation members may be used. One example may be a first isolation member for interfacing with the fuel injector and a second isolation member for interfacing with the cylinder head. 
         [0043]    While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but rather only to the extent set forth in the claims that follow.