Patent Publication Number: US-7210463-B2

Title: Pump, especially for a fuel injection device for an internal combustion engine

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a 35 USC 371 application of PCT/DE 03/00383 filed on Feb. 11, 2003. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention is directed to an improved pump for a fuel injection apparatus for an internal combustion engine. 
   2. Description of the Prior Art 
   A pump of the kind with which this invention is concerned, known from DE 198 48 035 A1, has at least one pump element with a pump piston that is guided in a sealed fashion in a cylinder bore of a housing part and delimits a pump working chamber in the cylinder bore with its end surface. The pump piston is driven into a stroke motion. The pump working chamber is connected to an inlet conduit via a connection controlled by an inlet valve opening into the pump working chamber and is connected to an outlet conduit via a connection controlled by an outlet valve opening out from the pump working chamber. The inlet valve has a valve element that cooperates with a valve seat and a valve spring acts on this valve element in the direction of the valve seat. The part of the inlet conduit feeding into the pump working chamber is comprised of a separate component that also contains the valve seat; this component is inserted into a bore of the housing part. The bore of the housing part is closed with a screw plug. The production and assembly of the known pump are complex and costly due to the large number of individual parts. 
   SUMMARY OF THE INVENTION 
   The pump according to the invention has the advantage over the prior art that it is simple and inexpensive to produce and assemble since the number of its individual parts has been reduced. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     An exemplary embodiment of the invention is described herein below, with reference to the drawings, in which: 
       FIG. 1  shows a longitudinal section through a pump embodying the invention, and 
       FIG. 2  shows an enlarged detail of the pump, which is labeled II in  FIG. 1 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 1 and 2  show a pump that is particularly provided for a fuel injection apparatus for an internal combustion engine, for example of a motor vehicle. The pump delivers fuel at a high pressure of up to 2000 bar, for example to an accumulator. The pump has a housing that has, for example, a housing part  10  and a flange part  11  connected to it. The housing has a drive shaft  12  disposed in it, which drives one or more pump elements  14  disposed in the housing. Preferably, a number of pump elements  14  are disposed distributed around the circumference of the drive shaft  12 . A bearing  16  in the housing part  10  and a bearing  18  in the flange part  11  support the drive shaft  12  so that it can rotate around an axis  13 ; it is driven by the engine in a manner that is not shown. The drive shaft  12  has a cam section  20  that supports a stroke ring  22 . The pump element  14  has a pump piston  24  that is guided so that it can slide in a sealed fashion in a cylinder bore  26  of the housing part  10  extending at least approximately radially in relation to the drive shaft  12 . The pump piston  24  is supported with its piston base  25  against the stroke ring  22 ; the piston base  25  is kept in contact with the stroke ring  22  by a spring  28 , which is supported at one end against the housing part  10  and at the other end, against the piston base  25 . 
   The end surface of the pump piston  24  delimits a pump working chamber  30  in the cylinder bore  26 , which bore  26  has a reduced diameter portion  27  at its end which reduces the idle volume of the bore  26 . An inlet valve  32  that opens into the pump working chamber  30  can connect the pump working chamber  30  to a fuel inlet conduit  34  in which low pressure prevails. In addition, an outlet valve  36  that opens toward the accumulator can connect the pump working chamber  30  to the accumulator via a fuel outlet conduit  38  extending in the housing part  10 . When the drive shaft  12  rotates, it drives the pump piston  24  in a stroke motion by means of the cam section  20  and the stroke ring  22 . When the pump piston  24  moves radially inward, it executes an intake stroke during which the inlet valve  32  is opened so that fuel flows into the pump working chamber  30  via the fuel inlet conduit  34  while the outlet valve  36  is closed. When the pump piston  24  moves radially outward, it executes a delivery stroke during which the inlet valve  32  is closed and the fuel compressed by the pump piston  24  flows at high pressure through the open outlet valve  36 , the fuel outlet conduit  36 , and into the accumulator. 
   In the housing part  12 , a first blind bore  42  that constitutes a part of the fuel inlet conduit  34  adjoins the pump working chamber  30  disposed in the end region of the cylinder bore  26  oriented radially away from the drive shaft  12 . The first blind bore  42  has a smaller diameter than the cylinder bore  26  and preferably extends at least approximately coaxial to the cylinder bore  26 . The first blind bore  42  ends inside the housing part  10 . The transition from the cylinder bore  26  to the first blind bore  42  is embodied, for example, as at least approximately conical and constitutes a valve seat  44  for the inlet valve  32 . The inlet valve  32  has a valve element  46 , which is embodied, for example, as a ball, and cooperates with the valve seat  44  in order to control the connection of the pump working chamber  30  to the fuel inlet conduit  34 . A prestressed valve spring  48 , for example in the form of a helical compression spring, acts on the valve element  46  in the direction of the valve seat  44 . A support element in the form of a spring plate can be disposed between the valve spring  48  and the valve element  46 . As can be seen in  FIG. 2 , the reduced diameter portion  27  of the bore  26  can be just slightly larger than valve element  46  so as to reduce the idle volume of bore  26 . The valve spring  48  can be supported in stationary fashion either against the housing part  10  or, as shown in the figure, against the end surface of the pump piston  24 . 
   A second blind bore  50 , which is let into the housing part  10  and also ends in the housing part  10 , feeds into the first blind bore  42  as another part of the fuel inlet conduit  34 . The second blind bore  50  extends inclined in relation to the first blind bore  42 , preferably at least approximately perpendicular to the first blind bore  42  and at least approximately parallel to the rotation axis  13  of the drive shaft  12 . The second blind bore  50  is let into the housing part  10  from a side surface  52  oriented toward the flange part  11 . The fuel inlet conduit  34  continues in the flange part  11 , starting from a side surface  54  of the flange part  11 ; the flange part  11  can be provided with a connection  56  for an inlet line via which fuel is supplied from a fuel tank, for example by means of a fuel-supply pump. A sealing element  58  can be clamped in place at the transition of the fuel conduit  34  between the flange part  11  and the housing part  10 . The sides surfaces  52  and  54  of the housing part  10  and the flange part  11  facing each other extend, for example, at least approximately perpendicular to the rotation axis  13  of the drive shaft  12  and can be embodied as flat. The housing part  10  and the flange part  11  are attached to each other in a manner that is not shown, for example by means of a number of screws. 
   The blind bores  42  and  50  that make up the fuel conduit  34  in the housing part  10  can be simply let into the housing part  10  respectively from the cylinder bore  26  and from the side surface  52 . The housing part  10  does not have any openings on its outside for the fuel conduit  34 . The only additional components required for the inlet valve  32  are the valve element  46 , the valve spring  48 , and the support element possibly provided between them. It is possible for a number of pump elements  14  to be provided with a single shared housing part  10  that contains a corresponding number of cylinder bores  26  and blind bores  42  and  50 . Alternatively, it is also possible for each pump element  14  to be provided with a separate housing part  10  that contains only one cylinder bore and one pair of blind bores  42 ,  50 . The housing parts  10  of the pump elements  14  are then attached to one another in a suitable fashion. 
   As part of the fuel outlet conduit  38 , a bore  60  that extends at least approximately perpendicular to the longitudinal axis of the cylinder bore  26  feeds into the pump working chamber  30  in the cylinder bore  26 . The bore  60  is embodied with a multiply stepped diameter, its end section with a small diameter feeding into the pump working chamber  30 . The end section is adjoined at its end oriented away from the pump working chamber  30  by a middle section of the bore  60 ; the transition between the end section of the and the middle section can be embodied, for example, as approximately conical and constitutes a valve seat  62  for the outlet valve  36 . A valve element  64  of the outlet valve  36 , for example in the form of a ball, cooperates with the valve seat  62  in order to control the connection of the pump working chamber  30  to the fuel outlet conduit  38 . A screw plug  66  is screwed into an outer section of the bore  60  that has a diameter larger than that of the middle section and is provided with an internal thread. A prestressed valve spring  68 , for example in the form of a helical compression spring, is clamped between the screw plug  66  and the valve element  64  and acts on the valve element  64  in the direction of the valve seat  62 . 
   The foregoing relates to preferred exemplary embodiments of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.