Radial piston pump for generating high pressure for fuel in fuel injection systems of combustion engines

Abstract

The invention relates to a radial piston pump ( 1 ) for high-pressure fuel generation in fuel injection systems of internal combustion engines, in particular in a common rail injection system, having a drive shaft ( 4 ) which is mounted in a pump casing ( 2 ) and has an eccentric shaft section ( 6 ) on which a running roller ( 8 ) is mounted, and having preferably a plurality of pistons ( 16 ), which are arranged in a respective cylinder ( 14 ) radially with respect to the drive shaft ( 4 ) and each have a piston footplate ( 18 ), which makes contact with the circumferential surface ( 10, 12 ) of the running roller ( 8 ), at their ends facing the running roller ( 8 ). The invention provides that at least that surface ( 28 ) of the piston footplate ( 18 ) which is in contact with the circumferential surface ( 10, 12 ) of the running roller ( 8 ) consists of a wear-resistant material, namely hard metal, a ceramic material, a cast carbide material or cermet, and/or that at least part of the running roller ( 8 ), in particular at least part of the circumferential surface ( 10, 12 ) of the running roller ( 8 ), consists of a wear-resistant material, namely of hard metal, a precision-cast material, a cast carbide material, a sintered tool steel or an alloyed nitriding steel and/or that the piston ( 16 ) consists of a ceramic material.

1 - 13 . (canceled)  
     
     
         14 . A radial piston pump ( 1 ) for high-pressure fuel generation in fuel injection systems of internal combustion engines, in particular in a common rail injection system, having a drive shaft ( 4 ) which is mounted in a pump casing ( 2 ) and has an eccentric shaft section ( 6 ) on which a running roller ( 8 ) is mounted, and having preferably a plurality of pistons ( 16 ), which are arranged in a respective cylinder ( 14 ) radially with respect to the drive shaft ( 4 ) and each have a piston footplate ( 18 ), which makes contact with the circumferential surface ( 10 ,  12 ) of the running roller ( 8 ), at their ends facing the running roller ( 8 ), wherein surface ( 28 ,  31 ) of the piston footplate ( 18 ) which is in contact with the circumferential surface ( 10 ,  12 ) of the running roller ( 8 ) has at least one insert ( 30 ) made from a wear-resistant material, namely of hard metal, a ceramic material, a cast carbide material or cermet, and/or in that at least part of the running roller ( 8 ), in particular at least part of the circumferential surface ( 10 ,  12 ) of the running roller ( 8 ), consists of a wear-resistant material, namely of hard metal, a sintered tool steel or an alloyed nitriding steel.  
     
     
         15 . The radial piston pump as claimed in claim wherein the piston ( 16 ) consists of a ceramic material.  
     
     
         16 . The radial piston pump as claimed in  claim 14 , wherein the running roller ( 8 ) consists of a heat-treated steel and has inserts ( 32 ) made from hard metal, such as G20, GC37 or GC20, and in that the piston footplate ( 18 ) has inserts ( 30 ) made from ceramic, such as Si 3 N 4  ceramic, from chilled cast iron, such as SoGGH, or from cermet.  
     
     
         17 . The radial piston pump as claimed in  claim 14 , wherein the running roller ( 8 ) consists of a precision-cast material, such as GX-210WCr13 H, and in that the piston footplate ( 18 ) has inserts ( 30 ) made from ceramic, such as Si 3 N 4  ceramic, from hard metal, such as G20, or from cermet.  
     
     
         18 . The radial piston pump as claimed in  claim 14 , wherein the running roller ( 8 ) consists of a cast carbide material, such as chilled cast iron SoGGH, and in that the piston footplate ( 18 ) has inserts ( 30 ) made from ceramic, such as Si 3 N 4  ceramic, from hard metal, such as G20, or from cermet.  
     
     
         19 . The radial piston pump as claimed in  claim 14 , wherein the running roller ( 8 ) consists of sintered tool steel, such as ASP23, or of an alloyed nitriding steel, and in that the piston footplate ( 18 ) has inserts ( 30 ) made from ceramic, such as Si 3 N 4  ceramic, from hard metal, such as G20, from cermet or from a cast carbide material, such as SoGGH.  
     
     
         20 . The radial piston pump as claimed in  claim 14 , wherein the alloyed nitriding steel contains C and/or Cr and/or V and/or Mo, is gas-nitrided and does not have a compound layer in the region of contact with the piston footplate ( 18 ).  
     
     
         21 . The radial piston pump as claimed in  claim 14 , wherein the running roller ( 8 ), on its circumferential surface ( 10 ,  12 ), has at least one insert ( 32 ) made from the respective wear-resistant material.  
     
     
         22 . The radial piston pump as claimed in  claim 14 , wherein the running roller ( 8 ), on its circumferential surface ( 12 ), has at least one transverse groove ( 36 ) extending transversely to the direction of movement.  
     
     
         23 . The radial piston pump as claimed in  claim 14 , wherein the piston footplate ( 18 ) has at least two grooves ( 50 ) which cross one another on its surface ( 31 ) facing the running roller ( 8 ).  
     
     
         24 . The radial piston pump as claimed in  claim 14 , wherein the surface of the piston footplate ( 18 ) and/or of the running roller ( 8 ) has a surface roughness R z  of between 0.15 μm and 2 μm.  
     
     
         25 . The radial piston pump as claimed in  claim 14 , wherein the piston consists of an Si 3 N 4  ceramic or a ZrO 2  ceramic.  
     
     
         26 . The radial piston pump as claimed in  claim 14 , wherein the piston ( 16 ) is produced by extrusion and has a porosity of less than 5%, the surface being infiltrated with MOS 2 .  
     
     
         27 . The radial piston pump as claimed in  claim 14 , wherein the piston ( 16 ) is isostatically extruded and sintered.