High pressure pump

Abstract

A piston ( 6 ) of a piston pump unit ( 2 ), which can be displaced in a translatory manner, is guided in a cylinder bore ( 7 ). The piston ( 6 ) is driven by a crank drive ( 13 ) comprising an eccentric element ( 15 ) which is arranged on a drive shaft ( 14 ). A stroke ring ( 12 ) is rotationally mounted on the eccentric element ( 15 ) but does not rotate therewith. A sliding surface ( 10 ) of the piston ( 6 ) is arranged on a sliding bearing surface ( 11 ) on the stroke ring ( 12 ). A discharge chamber ( 22 ) is embodied inside the piston ( 6 ) on an end opposite the stroke ring ( 12 ). Said discharge chamber is open towards the sliding bearing surface ( 11 ). The discharge chamber ( 22 ) is connected in a pressure-wise manner to a working chamber ( 8 ) by means of a passage ( 23 ) in the piston ( 6 ). A displaceable control piston ( 25 ) is guided in a longitudinal bore ( 24 ) pertaining to said passage ( 23 ). Said control piston ( 25 ) is impinged upon on one side by a medium in the working chamber ( 8 ) and on the other front side by a pressure medium in the discharge chamber ( 22 ). The control piston ( 25 ) separates the medium which is to be transported from the pressure medium in the discharge chamber ( 22 ) and ensures that the pressure in the discharge chamber ( 22 ) increases if the pressure increases in the working chamber ( 8 ). This results in decompression of the sliding bearing between the piston ( 6 ) and the stroke ring ( 12 ).

1 . A high pressure pump, in particular for a fuel injection system for internal combustion engines, having at least one piston pump unit ( 2 ,  2 ′) which has a piston ( 6 ) guided in a cylinder bore ( 7 ) and delimiting a working chamber ( 8 ), having a crank drive ( 13 ) for driving the piston ( 6 ), having a stroke ring ( 12 ) which is arranged between the crank drive ( 13 ) and the piston ( 6 ) and which is mounted such that it is driven rotatably with respect to the crank drive ( 13 ) but does not rotate and which has a flat sliding bearing surface ( 11 ), on which the piston ( 6 ) is supported with a sliding surface ( 10 ), wherein a connecting duct ( 34 ,  35 ) is formed in the stroke ring ( 12 ), said connecting duct ( 34 ,  35 ) opens at one, first end into the sliding bearing surface ( 11 ) and is connected to a fluid source by means of a fluid feed conduit ( 31 ,  32 ,  33 ) provided in the crank drive ( 13 ).  
   
   
       2 . The high pressure pump as claimed in  claim 1 , wherein the fluid is a lubricant and the fluid feed conduct is a lubricant feed conduct.  
   
   
       3 . The high pressure pump as claimed in  claim 2 , wherein the crank drive ( 13 ) has an eccentric element ( 15 ) and wherein the connecting duct ( 34 ,  35 ) opens at the other, second end into the inner surface ( 12   a ) of the stroke ring ( 12 ) which is in contact with the eccentric element ( 15 ), and wherein a lubricating groove ( 31 ) is provided on the circumference of the eccentric element ( 15 ), said lubricating groove ( 31 ) is open toward the outside and is connected to the lubricant source via a connecting line ( 32 ,  33 ) running in the eccentric element ( 15 ) and in the drive shaft ( 14 ).  
   
   
       4 . The high pressure pump as claimed in  claim 3 , wherein the lubricating groove ( 31 ) extends over part of the circumference of the eccentric element ( 15 ).  
   
   
       5 . The high pressure pump as claimed in  claim 2 , further comprising a relief chamber ( 22 ) which is arranged in the region of the sliding surface ( 10 ), is open toward the sliding bearing surface ( 11 ) and is fluidically separated from the working chamber ( 8 ).  
   
   
       6 . The high pressure pump as claimed in  claim 5 , wherein an annular groove ( 36 ) is formed in the piston ( 6 ), said annular groove ( 36 ) surrounds the relief chamber ( 22 ) and is open toward the sliding bearing surface ( 11 ).  
   
   
       7 . The high pressure pump as claimed in  claim 6 , wherein the annular groove ( 36 ) is connected to a chamber ( 5 ) in which the crank drive ( 13 ) and the stroke ring ( 12 ) are accommodated.  
   
   
       8 . The high pressure pump as claimed in  claim 5 , wherein the opening of the relief chamber ( 22 ) is completely surrounded by the sliding surface ( 10 ) of the piston, said sliding surface ( 10 ) acting together with the sliding bearing surface ( 11 ) of the stroke ring ( 12 ).  
   
   
       9 . The high pressure pump as claimed in  claim 7 , wherein a longitudinal groove ( 37 ) is formed in the stroke ring ( 12 ) in the region of the sliding bearing surface ( 11 ), said longitudinal groove ( 37 ) is open toward the sliding surface ( 10 ) and opens into said chamber ( 5 ), is offset with respect to the relief chamber ( 22 ) in the direction of the axis of rotation ( 14   a ) of the drive shaft ( 14 ) and communicates with the annular groove ( 36 ).  
   
   
       10 . The high pressure pump as claimed in  claim 5 , wherein the pressure medium in the relief chamber ( 22 ) is a lubricant, preferably lubricating oil.  
   
   
       11 . The high pressure pump as claimed in  claim 2 , wherein said connecting duct ( 34 ,  35 ) opens into the sliding bearing surface ( 11 ) at a point such that it is connected to the relief chamber ( 22 ) only in specific positions of the stroke ring ( 12 ) with respect to the piston ( 6 ) and is connected periodically to said lubricant feed conduit ( 31 ,  32 ,  33 ).  
   
   
       12 . The high pressure pump as claimed in  claim 11 , wherein the lubricating groove ( 15 ) is arranged such that it is connected to the connecting duct ( 34 ,  35 ) in the stroke ring ( 12 ) when this connecting duct ( 34 ,  35 ) is connected to the relief chamber ( 22 ).  
   
   
       13 . The high pressure pump as claimed in  claim 5 , wherein the relief chamber ( 22 ) is fluidically separated from the working chamber ( 8 ) by a pressure transmission element ( 25 ,  41 ) arranged in a passage ( 23 ) in the piston ( 6 ), said pressure transmission element ( 25 ,  41 ) is pressurized on one side by the medium to be delivered and on the opposite side by a pressure medium in the relief chamber ( 22 ) and can be displaced in the direction of the application of pressure under the action of pressure.  
   
   
       14 . The high pressure pump as claimed in  claim 13 , wherein the pressure transmission element is a control piston ( 25 ) which can be displaced in a longitudinal bore ( 24 ) belonging to said passage ( 23 ) and is guided closely in a sliding manner.  
   
   
       15 . The high pressure pump as claimed in  claim 14 , wherein the control piston ( 6 ) on its first end facing the relief chamber ( 22 ) is supported on a compression spring ( 26 ) which rests on an abutment at the other end.  
   
   
       16 . The high pressure pump as claimed in  claim 15 , wherein said abutment is formed by a supporting element retained in the control piston ( 25 ).  
   
   
       17 . The high pressure pump as claimed in  claim 16 , wherein said supporting element is a spring ring ( 27 ).  
   
   
       18 . The high pressure pump as claimed in  claim 13 , wherein the pressure transmission element is a diaphragm ( 41 ) which can be deflected elastically, covers the passage ( 23 ) and is fixed in a sealing manner in its edge region.  
   
   
       19 . The high pressure pump as claimed in  claim 18 , wherein the piston ( 6 ) has a piston element ( 38 ) guided in the cylinder bore ( 7 ) and a ring ( 39 ) which is connected to the piston element ( 38 ) at the end of the latter facing away from the working chamber ( 8 ).  
   
   
       20 . The high pressure pump as claimed in  claim 19 , wherein the diaphragm ( 41 ) is held firmly in its edge region between the piston element ( 38 ) and the ring ( 39 ).  
   
   
       21 . The high pressure pump as claimed in  claim 2 , wherein the crank drive ( 13 ) has an eccentric element ( 15 ) which is arranged on a rotatably driven drive shaft ( 14 ) with an eccentricity (e) and on which the stroke ring ( 12 ) is mounted such that it does not rotate with the eccentric element ( 15 ).  
   
   
       22 . The high pressure pump as claimed in  claim 2 , wherein an annular collecting groove ( 28 ) is formed in the wall of the cylinder bore ( 7 ), said annular collecting groove ( 28 ) is open toward the piston ( 6 ), is used to collect seepage which passes through the gap between the wall of the cylinder bore ( 7 ) and the piston ( 6 ) and to which a discharge conduit ( 30 ) is connected.  
   
   
       23 . The high pressure pump as claimed in  claim 2 , wherein the high pressure pump ( 1 ,  1 ′) is designed to deliver fuel.  
   
   
       24 . The high pressure pump as claimed in  claim 23 , wherein the high pressure pump ( 1 ,  1 ′) is designed to deliver diesel fuel.