Abstract:
A coupling for suspending a fuel injector from a fuel rail assembly of an internal combustion engine includes a collar that mates with the fuel injector and a retainer clip that engages with the collar thereby mechanically connecting the fuel injector to the fuel rail assembly. The retainer clip includes windows to enable even load distribution upon the socket flange when assembled. Features are integrated in the collar to facilitate correct alignment of the injector relative to the fuel rail. Paired together, the retainer clip and the collar enable a secure, and a keyed fuel injector-to-fuel rail connection that is able to withstand high pressure separating loads.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to fuel injection systems of internal combustion engines; more particularly to fuel rail assemblies for supplying pressurized fuel to fuel injectors for direct injection into engine cylinders; and most particularly, to an apparatus and method for coupling a fuel injector to a fuel rail for direct injection. 
       BACKGROUND OF THE INVENTION 
       [0002]    Fuel rail assemblies for supplying fuel to fuel injectors of internal combustion engines are well known. A fuel rail assembly, also referred to herein simply as a fuel rail, is essentially an elongated tubular fuel manifold connected at an inlet end to a fuel supply system and having a plurality of ports for mating in any of various arrangements with a plurality of fuel injectors to be supplied. Typically, a fuel rail assembly includes a plurality of fuel injector sockets in communication with a manifold supply tube, the injectors being inserted into the sockets. 
         [0003]    Fuel injectors may be divided generally into multi-port fuel injectors (MPFI), wherein fuel is injected into a runner of an air intake manifold ahead of a cylinder intake valve, and direct injectors (DI), wherein fuel is injected directly into the combustion chamber of an engine cylinder, typically near the end of the compression stroke of the piston. Since a direct injector is exposed to the pressures within a cylinder, a DI fuel rail assembly must handle significantly higher fuel pressures than a MPFI fuel rail assembly in order to provide precisely metered fuel into a cylinder&#39;s combustion chamber. 
         [0004]    Because of the higher operating pressures, typically, DI fuel systems employ fuel injectors that are rigidly supported on the engine&#39;s cylinder head. The rigid connection between the cylinder head and injector provides enough structural support to withstand the higher operational pressures. However, such a rigid connection has a drawback in that the metal-to-metal contact of the rigid connection provides a direct path for transmitting injector noise. Current MPFI technology includes a hanging injector system that avoids the rigid connection between the cylinder head and the injector by suspending the injectors from the fuel rail via a mechanical coupling. However, while such a coupling solves the noise transmission problem of a rigid connection, the hanging injector connection employed by MPFIs cannot withstand the operating pressures of a DI system. 
         [0005]    What is needed in the art is a fuel injector to fuel rail connection that is able to mechanically support loads originating from relatively high fuel pressures and from combustion pressure of direct injection fuel injection systems. 
         [0006]    It is a principal object of the present invention to provide a high-pressure fuel injector coupling that easily connects a DI fuel injector to a fuel rail and that is able to manage relatively high separating loads between the fuel rail and the fuel injector due to relatively high DI fuel pressure levels. 
       SUMMARY OF THE INVENTION 
       [0007]    Briefly described, a fuel injector coupling in accordance with the invention includes a retainer clip and a collar, which, when paired together, enable a simple, secure, and keyed fuel injector-to-fuel rail connection that is able to withstand separating loads originating from the relatively high fuel pressure of a direct injection fuel system. Moreover, the coupling provides for a centralized load path along the longitudinal axis of the fuel injector and fuel rail socket. 
         [0008]    In one aspect of the invention, the retainer clip is U-shaped to capture an end face of the fuel rail socket and includes diametrically opposed windows for receiving features in a fuel injector collar to positively secure the injector in the socket via the clip and collar. Mating features between the clip and injector collar and between the retaining clip and fuel rail socket rotationally locate the injector to the cup to facilitate correct alignment of the injector relative to its associated combustion chamber in the cylinder head. The retainer clip is shaped to provide ease of assembly and disassembly. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
           [0010]      FIG. 1   a  shows a fuel injector/fuel rail system, in accordance with the invention, with one of the injectors and sockets removed; 
           [0011]      FIG. 1   b  is an isometric exploded view of a section of the fuel injector/fuel rail system shown in  FIG. 1   a;    
           [0012]      FIG. 2   a  is an isometric exploded view of one injector coupling, in accordance with the invention; 
           [0013]      FIG. 2   b  is an isometric view of an assembled coupling, in accordance with the invention; 
           [0014]      FIGS. 3   a  and  3   b  are views of the retaining clip, in accordance with the invention; and 
           [0015]      FIG. 4  is a sectioned view of the collar and injector, in accordance with the invention, the sectioned view taken at the top surface of the collar looking down toward the discharge end of the injector. 
       
    
    
       [0016]    Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates one preferred embodiment of the invention, in one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner. 
       DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0017]    Referring to  FIGS. 1   a,    1   b,    2   a  and  2   b,  an injector fuel system  100 , in accordance with the invention, includes a fuel rail assembly  110 , at least one fuel injector  130  and, for each fuel injector, a coupling  150 . Fuel rail assembly  110  includes a fuel distribution conduit  112  that may be, for example, an elongated tube as shown in  FIG. 1  or may be a non-round conduit. At least one injector socket  120  is assembled to conduit  112  to be in fluid communication with the interior of conduit  112  via an opening  114 , shown in a right-most position on the fuel rail in  FIG. 1  before socket  120  is attached to conduit  112 . Fuel rail assembly  110  is connected to a typical fuel supply system (not shown). Fuel rail assembly  110  is secured to cylinder head  116  by, for example, bolts  118  such that, through coupling  150 , each fuel injector  130  is precisely aligned with its associated cylinder/combustion chamber (not shown). 
         [0018]    Injector socket  120  may include a cylindrical body  121  that is closed at one end  122  and that is open at an opposite end  123  for receiving fuel injector  130 . Accordingly, injector socket  120  may have, but is not limited to, the shape of a cup as shown in  FIG. 1 . Injector socket  120  may be straight sided as shown, or may include a flange (not shown) proximate to open end  123 . In one aspect of the invention, socket  120  includes a mating feature  126 , such as for example, opposing flatted sections  127 , disposed substantially 180° from one another, for rotationally positioning the injector relative to the cylinder head, which will be later described. 
         [0019]    Fuel injector  130  includes a fuel inlet end  132 , a fuel discharge end  134 , and an overmold  136  surrounding a fuel tube  138 . Fuel tube  138  communicates fuel through the injector from fuel inlet end  132  to discharge end  134 . Overmold  136  is positioned such that fuel inlet end  132  of fuel tube  138  extends beyond an upper end  140  of overmold  136  for assembly into injector socket  120 . Fuel tube  138  includes a circumferential groove  141 , having a width  142 , that is positioned adjacent the upper end  140  of overmold  136 . In one aspect of the invention, overmold  136  includes anti-rotation feature  144  extending from proximate circumferential groove  141  to beyond an outer surface  139  of overmold  136 . The width  145  of anti-rotation feature  144  is approximately equal to twice the radius  146  of the root surface  143  of circumferential groove  142 . During manufacture of the injector, anti-rotation feature  144  is indexed to features of the injector, for precisely orienting the injector, rotationally, to the cylinder head. While fuel injector  130  is illustrated as a fuel injector for gasoline direct injection, it may be any other type fuel injector. 
         [0020]    Coupling  150  includes a retainer clip  152  and a collar  172 . Retainer clip  152  paired with collar  172  enables a positive mechanical retention of fuel injector  130  to socket  120  even under relatively high separating loads. Accordingly, fuel injector  130  is suspended from fuel rail assembly  110  via mechanical coupling  150  such that no hard, metal-to metal contact is necessary between fuel injector  130  and the cylinder head itself to secure the injector to the cylinder head. 
         [0021]    Retainer clip  152  may take a shape generally of a boxed-U having leg portions  154 , substantially parallel to each other, and bridge portion  156  joining the leg portions  154  to form the boxed-U shape. Referring to  FIGS. 3   a  and  3   b,  leg portions  154  include lower sections  158  and upper sections  160  intermediate the lower sections and bridge portion  156 . 
         [0022]    In one aspect of the invention, lower sections  158  of retainer clip  152  each include a window  160  sized and positioned for close-fittingly receiving locating features in collar  172  to be described below. Lower edge  168  of each window may include a slight curvature ( FIG. 3   b ) for making point contact with the locating features. Lower sections  158  are flat on their inside surfaces to snuggly engage mating features  126  of socket  120 , such as flats  127 , while, at the same time, bridge portion  156  engages closed end  122  of socket  120 , when the clip is assembled to collar  172  and socket  120 . Upper sections  160  may depart from the planar surfaces of lower sections  158 , on an angle α as shown in  FIG. 3   a,  in order to provide clearances  161  ( FIG. 1   a ) between the section of socket  120  shown as  125  and clip  152  to assure that the clip is firmly in contact with the socket at flats  127  and closed end  122 . Lower sections  158  may include chamfered or outwardly flanged ends (not shown) to facilitate assembly of the clip onto the socket and collar  172 . Retainer clip  152  may be formed from sheet spring steel, such as by stamping. In its free state before assembly, width  162  across the lower sections  158  of retainer clip  152  may be slightly less than width  128  across socket flats  127  ( FIG. 1   b ). In one aspect of the invention, bridge portion  156  may be slightly concaved (not shown), in the retainer clip&#39;s free state. 
         [0023]    Referring to  FIG. 4 , collar  172  is generally circular in shape on its periphery  174 . Slot  176  of collar  172  defines central opening  178  having parallel edges  180  and radial inner end  182  for being received in circumferential groove  141  of fuel injector  130 . Radius  184  of inner end  182  is equal to or slightly larger than radius  146  of the groove&#39;s root surface  143 . Width  186  of slot  176  is equal to or slightly larger than width  145  of anti-rotation feature  144 . Thickness  188  of collar  172  is slightly less than width  142  of circumferential groove  141 . As such, referring to  FIG. 2   a,  collar  172  fits snuggly into circumferential groove  141  of the fuel injector. When assembled into the groove, parallel edges  180  abut anti-rotation feature  144  of the injector thereby preventing the collar from rotating about the longitudinal axis  148  of the injector. In one aspect of the invention, one or more collar locating features such as tabs  190  project from periphery  174  and are indexed relative to slot  176  for precisely positioning fuel injector  130  axially and rotationally about its longitudinal axis  148  relative to its associated combustion chamber. In the embodiment shown, tabs  190  are located approximately 90° clockwise and counterclockwise (as shown in  FIG. 4 ) relative to the center of slot  176 . Collar  172  may be formed from a non-resilient cold-formable material, such as by stamping, and may be plated for corrosion protection. 
         [0024]    Next, a sequence for assembling coupling  150  will be described. 
         [0025]    First, collar  172  is inserted into circumferential groove  141  of fuel injector  130  so that parallel edges  180  of slot  176  abut anti-rotation feature  144  and radial inner end  182  of slot  176  fits snuggly against root surface  143  of the circumferential groove. Next, with tabs  190  aligned generally with socket flats  127 , the inlet end  132  of injector  130  is inserted into open end  123  of socket  120  until collar  172  abuts the open end  123  of the socket. Finally, retainer clip  152  is slipped over the closed end  122  of socket  120  so that bridge portion  156  of the retainer clip contacts closed end  122  of the socket, lower sections  158  of the retainer clip firmly engage flats  127  of socket  120  and tabs  190  of collar  172  snap into windows  160  of the retainer clip. In one aspect of the invention, before retainer clip  152  is slipped over closed end  122 , the distance  164  between point  166  of bridge portion  156  of the retainer clip and edges  168  of windows  160  is slightly less than the dimension measured between the closed end  122  of socket  120  and a lower surface  192  of tabs  190  when collar  172  is abutted against the open end  123  of the socket. As such, when tabs  190  of collar  172  snap into windows  160  of the retainer clip after the retainer clip is in place, injector  130  is held firmly in place in its associated socket to withstand the separating loads originating from the relatively high fuel pressures of a direct injection fuel system. The coupling also provides for a load path centralized by bridge portion  156  and windows  160  of the retainer clip along the longitudinal axis  148  of the fuel injector and fuel rail socket. Moreover, since the injector is precisely positioned axially and rotationally relative to its associated socket via anti-rotation feature  144 , tabs  190 , windows  160  and flats  127 , correct alignment of the injector relative to its associated combustion chamber in the cylinder head is readily maintained. 
         [0026]    As shown in  FIG. 4 , complementary mating features  194  may be incorporated in the collar and in the anti-rotation feature so that the collar may be installed to the injector and held in place by the mating features during injector shipment and prior to assembly of the injector to the fuel rail/engine. 
         [0027]    As can be seen in  FIG. 1   a,  one coupling  150  is needed per fuel injector  130 . Accordingly, coupling  150  may be utilized in an internal combustion engine employing two, four, six, eight, or any other number of cylinders. 
         [0028]    While coupling  150  may be especially useful for applications in fuel injection systems for direct injection, applications in fuel injection systems for port injection may be possible. 
         [0029]    While the locating feature in the collar and retention clip are shown as tabs and windows, respectively, it is understood that the mating features, in accordance with the invention, are not limited as such. 
         [0030]    While the mating feature on the socket is shown as a pair of flats located 180° from each other, it is understood that the mating features can be other types of indexing features and need not be 180° apart and, moreover, can be more or less than two. 
         [0031]    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 will have full scope defined by the language of the following claims.