Abstract:
A fuel pump comprises a cam assembly having a lobe, and a body assembly including a cavity for receiving the cam assembly. The body assembly includes both a body portion and a cover portion that cooperatively form the cavity. The body portion includes a lobe cavity, an engagement surface and an opening at the cavity, with the cover portion including a respective engagement surface and opening. The engagement surfaces are mated together with the cam assembly disposed in the cavity and extending through the openings, and is configured to rotate in the cavity with the lobe disposed in the lobe cavity. A groove is formed in one of the engagement surfaces of the body portion or cover portion for receiving a seal cap at least partially therein adjacent the lobe cavity.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims priority of U.S. provisional application, Ser. No. 61/803,964 filed Mar. 21, 2013, which is hereby incorporated herein by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention is directed to a fuel injection pump, and in particular to a pump for a common rail fuel system. 
         [0003]    A common rail fuel pump operates to supply pressurized fuel to a fuel rail that is in turn connected with individual injectors, such as solenoid operated injectors, that deliver fuel to the individual cylinders of an engine. Common rail fuel injection pumps are known, such as the Bosch CP3 fuel injection pump. The fuel output of this pump is limited by the geometry of the pump body, and in particular maximum plunger lift is constrained by the diameter of the pump body bore. 
       SUMMARY OF THE INVENTION 
       [0004]    The present invention provides a common rail fuel pump that provides increased fuel supply. In particular, the fuel pump of the present invention enables the stroke of the pump plungers to be increased to thereby provide a higher volume common rail fuel injection pump. 
         [0005]    According to an aspect of the present invention a fuel pump comprises a cam assembly that includes a lobe, and a body assembly including a cavity for receiving the cam assembly. The body assembly includes both a body portion and a cover portion with the body portion and said cover portion cooperatively forming the cavity. The body portion includes a lobe cavity, an engagement surface and an opening at the cavity, with the cover portion including a respective engagement surface and opening. The engagement surfaces are mated together with the cam assembly disposed in the cavity and extending through the openings, and is configured to rotate in the cavity with the lobe disposed in the lobe cavity. A groove is formed in one of the engagement surfaces of the body portion or cover portion for receiving a seal cap at least partially therein adjacent the lobe cavity, where the seal cap is a separate component from the body and cover portions. 
         [0006]    In a particular embodiment the groove is formed in the engagement surface of the cover portion and the body portion further includes a flange disposed about the opening of the body portion with the seal cap being disposed on the flange and the flange and seal cap being at least partially disposed in the groove. Still further, the seal cap may include an internal wall, an external wall, and a radially outwardly projecting shoulder extending from the external wall, with the shoulder being disposed on an end of the flange when the seal cap engages with the flange. The groove further includes an inner wall and an outer wall with the inner wall including a seal ring groove, and wherein a seal ring disposed within the seal ring groove contacts the seal cap. 
         [0007]    According to another aspect of the present invention, a fuel pump comprises a cam assembly having a lobe and a body including a cavity for receiving the lobe with the cavity defining an opening in the body. The fuel pump further includes a cover having a channel defined in an engagement surface of the cover, with a seal cap being disposed within the channel when the cover and body are assembled together. In a particular embodiment the body includes a flange disposed about the opening in the body and the seal cap engages with the flange and both the flange and seal cap are disposed within the channel when the cover and body are assembled together. 
         [0008]    According to still another aspect of the present invention, a fuel pump includes an inlet valve assembly and an inlet valve retainer, with the fuel pump including a body having a threaded bore. The inlet valve retainer includes external threads for engagement with the threaded bore for retaining the inlet valve assembly, and includes an internal cavity defining a receptacle. The inlet valve assembly includes a valve body with the valve body being received within the receptacle for axially aligning the inlet valve assembly relative to the threaded bore. 
         [0009]    The fuel pump of the present invention enables a cam assembly having a greater stroke to be utilized for higher performance applications, with the opening of the body portion of the fuel pump being sized to enable a larger cam lobe to be installed. When so installed, the seal cap engages with the flange on the body portion and extends into the groove or channel on the cover portion, with the seal cap providing a sealing surface at its inner wall against which an o-ring can contact. 
         [0010]    These and other objects, advantages, purposes and features of this invention will become apparent upon review of the following specification in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a side elevation view of a fuel pump assembly in accordance with the present invention; 
           [0012]      FIG. 2  is a top plan view of the fuel pump assembly of  FIG. 1 ; 
           [0013]      FIG. 3  is an exploded perspective view of the fuel pump assembly of  FIG. 1 ; 
           [0014]      FIG. 4  is a cross sectional view of the fuel pump assembly of  FIG. 1  taken along the line A-A of  FIG. 2 ; 
           [0015]      FIGS. 5A and 5B  are partial close up views of portions of  FIG. 4  showing a seal cap in accordance with an aspect of the present invention; 
           [0016]      FIG. 6A  is a top plan view of an inlet valve retainer of the fuel pump assembly of  FIG. 1 ; and 
           [0017]      FIG. 6B  is a partial cross sectional view of the fuel pump assembly of  FIG. 1  taken through the inlet valve retainer along the line A-A of  FIG. 6A . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0018]    The present invention will now be described with reference to the accompanying figures, wherein the numbered elements in the following written description correspond to like-numbered elements in the figures. A fuel pump or fuel pump assembly is shown at  30  in the various views, where fuel pump  30  comprises a common rail fuel pump for supplying high pressure fuel to a rail (not shown) to which are connected various injectors (not shown) for providing fuel to the cylinders of an engine. Fuel pump  30  includes a body assembly  32  comprising a body or first body portion  34  and a cover or second body portion  36 , with body assembly  32  housing a cam assembly  38  that rotates within body assembly  32  for providing high pressure fuel to the rail. Cam assembly  38  includes a rotating cam  40  having an eccentric lobe  41  ( FIG. 4 ) over which is disposed a polygon shaped lobe  42  having cam surfaces  43  that drive plungers  44  within bores  45  of body  34  (one shown in  FIG. 4 ) to generate the high pressure fuel supply. Fuel is delivered into body  34  through three inlet valve assemblies  46  that are held within body  34  by inlet valve retainers  48 . In the illustrated embodiment, fuel pump  30  comprises a modified Bosch CP3 common rail injection pump. 
         [0019]    Body assembly  32  defines a cavity  50  within which cam assembly  38  is disposed, with body  34  including a cavity or bore  52  within which lobe  42  is located, where cavity  52  defines a portion of cavity  50 . Body  34  further includes a mounting face or surface  54  and a circumferential upstanding ridge or flange  56  disposed about an opening  58  to cavity  50 , where body  34  includes a radial surface or wall  59  at flange  56  that extends circumferentially about opening  58 . Body  34  additionally includes threaded bores  60  for receiving retainers  48 , as discussed in more detail below. 
         [0020]    As understood from  FIGS. 4 ,  5 A and  5 B, cover  36  includes a mounting face or surface  62  that mates with surface  54  of body  34  when assembled together. Cover  36  further includes a circumferential groove or channel  64  disposed on surface  62 , where channel  64  extends into cover  36  perpendicularly relative to surface  62  and includes an inner wall  63  and an outer wall  65 . Channel  64  is located about a cavity  66  that defines a portion of cavity  50  and defines an opening  67  in cover  36 , where cavity  66  receives a section  68  of cam  40  for rotational support of the cam  40 . Cover  36  further includes a pair of seal ring grooves  70 ,  72 , for receiving seal rings  74 ,  76 , respectively, where groove  70  is disposed radially inwardly relative to channel  64  and groove  72  is disposed radially outwardly relative to channel  64 . When cover  36  and body  34  are assembled together, flange  56  is received within channel  64  along with a seal cap  80 , as discussed in more detail below. 
         [0021]    With reference now to  FIGS. 3 ,  4 ,  5 A and  5 B, seal cap  80  is positioned between body  34  and cover  36  when assembled. Seal cap  80  comprises a circumferential ring member and includes a top or head portion  82  and a wall portion  84  extending axially relative to head portion  82 , where head portion  82  extends radially outwardly relative to wall portion  84  to define a radially extending shoulder or lip  86 . Seal cap  80  further defines an internal radial surface or wall  88  and an external radial surface or wall  90 , with head portion  82  including an angled radial surface or wall  92  (see  FIG. 5B ). Seal cap  80  is a rigid member, and in the illustrated embodiment is a metallic member. 
         [0022]    Seal cap  80  is assembled to flange  56  by placing shoulder  86  on a top end  57  of flange  56 , whereby axial location is maintained by light interference between external radial wall  90  and opening  58 . Shoulder  86  is also seated against top end  57  of flange  56  through a zero to positive pressure differential of cavity  52  over cavity  50  acting on the projected area between radial wall  59  and radial wall  88 . As understood from  FIGS. 5A and 5B , flange  56  and seal cap  80  thereby fit within channel  64 , with flange  56  and wall portion  84  having a cross-sectional width sized to slip fit within channel  64 . When so assembled, seal ring  74  within ring groove  70  presses against internal radial wall  88  of seal cap  80  to inhibit or seal against fuel leaking there past. Correspondingly, seal ring  76  located within groove  72  on cover  36  likewise inhibits or seals against fuel leaking past the joint between cover  36  and body  34  to a location exterior of body assembly  32 . 
         [0023]    As noted, cam  40  includes an eccentric lobe  41  such that when cam  40  is rotated polygon lobe  42  is driven in an eccentric manner whereby cam surfaces  43  will undergo radial movement relative to the rotational axis  94  of cam  40  to drive plungers  44 . In the illustrated embodiment, lobe  42  of cam  40  is sized to provide greater pumping stroke to plungers  44  relative to a conventional pump, with lobe  42  being sized such that it cannot be installed in the opening of a conventional pump. Accordingly, opening  58  of body  34  is sized to enable installation of lobe  42  such that positions about polygon lobe  42  that are at the maximum radial distance from axis  94  are located axially beneath seal cap  80  when cap  80  is installed, whereby the polygon lobe  42  is able to drive the plungers  44  with a greater stroke. That is, as best understood from  FIG. 5B , in order to install and/or remove cam assembly  38  into or from body  34 , seal cap  80  must be removed, with opening  58  providing sufficient clearance for polygon lobe  42  to be installed into and/or removed from cavity  52 . When seal cap  80  is installed on flange  56  with lobe  42  located within lobe cavity  52 , the radial distance from axis  94  to the inner wall  88  of seal cap  80  is less than the radial distance from axis  94  to portions of the outer periphery of cam lobe  42 . 
         [0024]    In an alternative arrangement, rather than engage seal cap  80  with flange  56 , body  34  can be machined such that flange  56  is removed whereby a larger opening is formed relative to opening  58 . Still further, in this alternative embodiment a circumferential groove or channel or pocket is located on body  34  relative to surface  54 . An alternative seal cap is correspondingly then provided that is located by or within the pocket formed in surface  54  of body  34 . The alternative seal cap includes a portion extending upward relative to surface  54  for receipt in groove  64 , including an axially extending wall defining or including an internal radial surface or wall against which seal ring  74  engages. 
         [0025]    Referring now to  FIGS. 4 ,  6 A and  6 B, inlet valve assembly  46  is shown to include a valve body  100  having a fuel passage  102  there through, and includes a valve  104  having a valve stem  106  and a valve head  108 , where valve head  108  selectively seals against valve body  100 . Valve assembly  46  further includes a biasing member comprising a spring  110  and a seat  112  affixed to stem  106  such that spring  110  normally biases valve head  108  into the closed or sealed position relative to body  100  shown in  FIG. 6A . Valve  104  is opened to allow fuel supplied to fuel passage  102  to fill bores  45  when plungers  44  draw back within bores  45  relative to valve assemblies  46 . 
         [0026]    Inlet valve retainer  48  comprises a retainer body  114  having external threads  116  and an internal cavity  118 . Cavity  118  includes a first portion  120  and a second portion  122 , with first and second portions  120 ,  122  being generally cylindrical in the illustrated embodiment and with first portion  120  having a smaller internal diameter relative to second portion  122  such that a shoulder  124  is formed there between. Still further, valve body  100  is sized to be received within second portion  122  such that shoulder  124  is able to contact body  100 . Second portion  122  of cavity  118  thus defines a receptacle for receiving valve body  100 . Moreover, as understood from  FIG. 6A , threaded bores  60  of body  34  have a greater diameter than bores  45  to define a valve seat  126 . Thus, when assembled together, valve retainer  48  axially locates or pilots valve assembly  46  relative to bore  45  by way of receiving valve assembly  46  within second portion  122  of cavity  118  and contacting valve assembly  46  at shoulder  124  between valve seat  126  of body  34 . 
         [0027]    Changes and modifications in the specifically described embodiments can be carried out without departing from the principles of the present invention which is intended to be limited only by the scope of the appended claims, as interpreted according to the principles of patent law including the doctrine of equivalents.