High-pressure pump

Abstract

The invention relates to a high-pressure pump (1), in particular for a motor vehicle, for conveying a fluid, in particular fuel, e.g. diesel fuel, comprising a drive shaft having at least one cam, at least one piston, at least one cylinder (6) for mounting the at least one cam, wherein the at least one piston is supported on the drive shaft by the at least one cam, so that a translational motion can be carried out by the at least one cam as a result of a rotary motion of the drive shaft, at least one cover cap (8), which is attached indirectly or directly to the outside of the cylinder (6), wherein one end (18) of the at least one cover cap (8) rests on a projection (16) of the remaining high-pressure pump (1) for the interlocking attachment of the end (18) of the cover cap (8) to the projection (16).

Claims

1. A high pressure pump (1) for delivering a fluid, the high pressure pump comprising a drive shaft (2) with at least one cam (3), at least one piston (5), at least one cylinder (6) in which the at least one piston (5) is mounted, the at least one piston (5) being supported on the drive shaft (2) with the at least one cam (3), with the result that a translational movement can be carried out by the at least one piston (5) on the basis of a rotational movement of the drive shaft (2), and at least one covering cap (8) which is fastened indirectly to the cylinder (6) on an outer side, wherein an end (18) of the at least one covering cap (8) lies on a projection (16) of the high pressure pump (1) in order to fasten the end (18) of the covering cap (8) to the projection (16) in a positively and non-positively locking manner, and wherein the at least one covering cap (8) lies on the high pressure pump (1) with an elastic prestressing force.

2. The high pressure pump as claimed in claim 1, characterized in that the projection (16) is configured on the high pressure pump (1) on the outer side and/or the projection (16) is configured as an undercut (42) and/or the projection (16) is configured in the radial direction (41) with regard to a longitudinal axis (17) of the cylinder (6), and the end (18) of the at least one covering cap (8) lies on an axial stop (43) of the projection (16).

3. The high pressure pump as claimed in claim 1, characterized in that the projection (16) is configured in the circumferential direction or tangential direction with regard to a longitudinal axis (17) of the cylinder (6) and/or the projection (16) is formed by a ring (44) or a nut (45) on the cylinder (6).

4. The high pressure pump as claimed in claim 1, characterized in that the at least one covering cap (8) has a substantially central opening (48).

5. The high pressure pump as claimed in claim 4, characterized in that the at least one covering cap (8) has a substantially radially configured supporting section (50) and a substantially axially configured supporting section (51).

6. The high pressure pump as claimed in claim 5, characterized in that the opening (48) is configured on the supporting section (50).

7. The high pressure pump as claimed in claim 4, characterized in that the end (18) of the at least one covering cap (8) which lies on the projection (16) of the remaining high pressure pump (1) is an edge (49) of the opening (48).

8. The high pressure pump as claimed in claim 4, characterized in that an electric plug (52) is arranged in the opening (48).

9. The high pressure pump as claimed in claim 1, characterized in that a cutout (55) for a fuel nozzle (54) is configured on the at least one covering cap (8), and/or the cylinder (6) comprises a cylinder head (14) and/or a mounting cylinder (15).

10. The high pressure pump as claimed in claim 1, characterized in that the at least one covering cap (8) is configured at least partially from an elastic plastic, and/or the at least one covering cap (8) is configured at least partially from a material with a modulus of elasticity of less than 5, 1, or 0.2 kN/mm.sup.2.

11. A method for producing a high pressure pump (1) as claimed in claim 1, the method comprising the steps: provision of a drive shaft (2) with at least one cam (3), provision of at least one piston (5), provision of at least one cylinder (6) in which the at least one piston (5) is mounted, provision of at least one covering cap (8), assembling of the at least one drive shaft (2), the at least one piston (5) and the at least one cylinder (6), with the result that the at least one piston (5) is supported on the drive shaft (2) with the at least one cam (3), and a translational movement can be carried out by the at least one piston (5) on the basis of a rotational movement of the drive shaft (2), and fastening of the at least one covering cap (8) indirectly on the cylinder (6) on the outer side, characterized in that the covering cap (8) is first of all stretched elastically for fastening purposes, and an elastic recovery is subsequently carried out, with the result that an end (18) of the at least one covering cap (8) lies on the projection (16) of the remaining high pressure pump (1) on account of the elastic recovery, and the at least one covering cap (8) is fastened to the projection (16) in a positively and non-positively locking manner as a result.

12. The method as claimed in claim 11, characterized in that first of all an electric plug (52) is mounted, and subsequently the at least one covering cap (8) is fastened, and/or the at least one covering cap (8) is stretched in the radial direction (41) with regard to the longitudinal axis (17) of the cylinder (6) and is recovered elastically.

13. The method as claimed in claim 11, characterized in that the at least one covering cap (8) is stretched substantially at an edge (49) of an opening (48) as the end (18) of the at least one covering cap (8), with the result that the size of the opening (48) is increased by way of the stretching, and the elastic recovery is subsequently carried out substantially at the edge (49) of the opening (48), and/or the electric plug (52) which has already been mounted is first of all guided through the opening (48) of the at least one covering cap (8), and the elastic stretching of the at least one covering cap (8) is subsequently carried out, and/or the covering cap (8) is stretched, and the covering cap (8) is subsequently fastened on the remaining high pressure pump (1) with an elastic prestress.

14. The method as claimed in claim 11, characterized in that the at least one covering cap (8) is stretched, by the covering cap (8) being pushed onto the high pressure pump (1) on the outer side in the axial direction (40), and the axial movement of the at least one covering cap (8) bringing about stretching of the at least one covering (8) on account of the outer-side geometry of the high pressure pump (1).

15. A high pressure injection system (36) for an internal combustion engine (39), the high pressure injection system comprising a high pressure pump (1) as claimed in claim 1, and a high pressure rail (30) communicating with the high pressure pump.

16. The high pressure injection system as claimed in claim 15, further comprising a prefeed pump for delivering a fuel from a fuel tank to the high pressure pump.

17. The high pressure pump as claimed in claim 1, characterized in that the projection (16) is configured in the circumferential direction or tangential direction with regard to a longitudinal axis (17) of the cylinder (6) and/or the projection (16) is formed by a ring (44) or a union nut (45) on the cylinder (6).

18. The high pressure pump as claimed in claim 1, characterized in that the at least one covering cap (8) lies on the high pressure pump (1) with an elastic prestressing force and/or the at least one covering cap (8) is configured completely from a thermoplastic elastomer, and/or the at least one covering cap (8) is configured completely from a material with a modulus of elasticity of less than 5, 1, or 0.2 kN/mm.sup.2.

19. The method as claimed in claim 11, characterized in that the at least one covering cap (8) is stretched substantially at an edge (49) of an opening (48) as the end (18) of the at least one covering cap (8), with the result that the size of the opening (48) is increased by way of the stretching, and the elastic recovery is subsequently carried out substantially at the edge (49) of the opening (48), and/or the electric plug (52) which has already been mounted is first of all guided through the opening (48) of the at least one covering cap (8), and the elastic stretching of the at least one covering cap (8) is subsequently carried out, and/or an axial supporting section (51) of the covering cap is stretched in the radial direction (41), and the axial supporting section (51) is subsequently fastened on the remaining high pressure pump (1) with an elastic prestress.

20. The method as claimed in claim 11, characterized in that the at least one covering cap (8) is stretched, by the covering cap (8) being pushed onto the high pressure pump (1) on the outer side in the axial direction (40), and the axial movement of the at least one covering cap (8) bringing about radial stretching of the at least one covering (8) on account of the outer-side geometry of the high pressure pump (1).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following text, exemplary embodiments of the invention will be described in greater detail with reference to the appended drawings, in which:

(2) FIG. 1 shows a cross section of a high pressure pump,

(3) FIG. 2 shows a section A-A in accordance with FIG. 1 of a cam roller with a roller shoe and a drive shaft,

(4) FIG. 3 shows a greatly diagrammatic view of a high pressure injection system, and

(5) FIG. 4 shows a view of a motor vehicle,

(6) FIG. 5 shows a perspective view of a covering cap in a first exemplary embodiment for a cylinder of the high pressure pump,

(7) FIG. 6 shows a longitudinal section through the covering cap in accordance with FIG. 5, a part of the cylinder and a union nut after the fastening of the covering cap to the cylinder,

(8) FIG. 7 shows a first perspective view of a part of the high pressure pump during the fastening of the covering cap in accordance with FIG. 5 to the cylinder,

(9) FIG. 8 shows a second perspective view of a part of the high pressure pump during the fastening of the covering cap in accordance with FIG. 5 to the cylinder,

(10) FIG. 9 shows a first side view of a part of the high pressure pump shortly before the fastening of the covering cap in accordance with FIG. 5 to the cylinder, and a longitudinal section of the covering cap,

(11) FIG. 10 shows a second side view of the part of the high pressure pump after the fastening of the covering cap in accordance with FIG. 5 to the cylinder, and the longitudinal section of the covering cap, and

(12) FIG. 11 shows a second side view of the part of the high pressure pump after the fastening of the covering cap in a second exemplary embodiment to the cylinder, and the longitudinal section of the covering cap.

DETAILED DESCRIPTION

(13) FIG. 1 shows a greatly simplified cross section of a high pressure pump 1 for a high pressure injection system 36. FIG. 1 serves only to illustrate the operating principle and does not show, in particular, the exact geometrical configuration of a cylinder 6. The cylinder 6 comprises a cylinder head 14 and a mounting cylinder 15. The high pressure pump 1 serves to deliver fuel, for example gasoline or diesel, to an internal combustion engine 39 under high pressure. The pressure which can be generated by the high pressure pump 1 lies, for example, in a range of between 1000 and 3000 bar.

(14) The high pressure pump 1 has a drive shaft 2 with two cams 3, which drive shaft 2 carries out a rotational movement about a rotational axis 26. The rotational axis 26 lies in the plane of the drawing of FIG. 1 and lies perpendicularly on the plane of the drawing of FIG. 2. A piston 5 is mounted in a piston guide 7 of the mounting cylinder 15. The cylinder 6 therefore also forms a housing. A working space 29 is delimited by the cylinder 6, in particular the cylinder head 14, and the piston 5. An inlet duct 22 with an inlet valve 19 and an outlet duct 24 with an outlet valve 20 open into the working space 29. The fuel flows through the inlet duct 22 into the working space 29, and the fuel flows at high pressure out of the working space 29 again through the outlet duct 24. The inlet valve 19 (for example, a check valve) is configured in such a way that only fuel can flow into the working space 29, and the outlet valve 20 (for example, a check valve) is configured in such a way that only fuel can flow out of the working space 29. The volume of the working space 29 is changed on the basis of an oscillating stroke movement of the piston 5. The piston 5 is supported indirectly on the drive shaft 2. A roller shoe 9 with a cam roller 10 is fastened to the end of the piston 5 or pump piston 5. Here, the cam roller 10 can carry out a rotational movement, the rotational axis 25 of which lies in the plane of the drawing in accordance with FIG. 1 and lies perpendicularly on the plane of the drawing of FIG. 2. The drive shaft 2 with the at least one cam 3 has a shaft rolling face 4, and the cam roller 10 has a roller rolling face 11.

(15) The roller rolling face 11 of the cam roller 10 rolls on the shaft rolling face 4 of the drive shaft 2 with the two cams 3. The roller shoe 9 is mounted as a plain bearing in a roller shoe bearing system which is formed by the cylinder 6. A spring 27 or spiral spring 27 as an elastic element 28 which is clamped in between the cylinder 6 and the roller shoe 9 applies a pressure force to the roller shoe 9, with the result that the roller rolling face 11 of the cam roller 10 is in constant contact with the shaft rolling face 4 of the drive shaft 2. The roller shoe 9 and the piston 5 therefore jointly carry out an oscillating stroke movement. Substantially no slip occurs on a contact face 12 between the shaft rolling face 4 of the drive shaft 2 and the roller rolling face 11 of the cam roller 10.

(16) An elastic covering cap 8 made from an elastic plastic serves to conceal corrosion on the cylinder 6, in particular the cylinder head 14, with the result that corrosion which possibly occurs is not visible from the outside. The covering cap 8 has a radial supporting section 50 and an axial supporting section 51. The axial supporting section 51 is of substantially cylindrical or cylinder shell-shaped configuration and, moreover, has a cutout 55 for a fuel nozzle 54 of the high pressure pump 1. The inlet duct 22 and/or the outlet duct 24 are/is integrated into or installed in the fuel nozzle 54. An opening 48 for receiving an electric plug 52 is configured on the disk-shaped radial supporting section 50. The cylinder 6 has a longitudinal axis 17, and the longitudinal axis 17 also corresponds to a movement direction of the translational movement of the piston 5. An axial direction 40 is oriented parallel to the longitudinal axis 17, and a radial direction 41 lies perpendicularly on the longitudinal axis 17 of the cylinder 6. FIG. 6 shows the cylinder 6 in a very greatly simplified manner without a distinction in terms of the cylinder head 14 and the mounting cylinder 15. A bore 53 for receiving the electric plug 52 is machined into the cylinder 6. Moreover, an end region of the cylinder 6 has an external thread 47, and a union nut 45 with an internal thread 46 is screwed onto the external thread 47. The union nut 45 also forms a ring 44. The lower end region (shown in FIG. 6) of the union nut 45 has a greater radial spacing from the longitudinal axis 17 than the cylinder 6 in this region, with the result that a lower axial end (shown in FIG. 6) of the union nut 45 forms an axial stop 43 for the covering cap 8 as a result. The axial stop 43 or the lower end region of the union nut 45 in accordance with the illustration in FIG. 6 therefore forms a projection 16 with regard to the cylinder 6 and also an undercut 42 which is completely circumferential in the circumferential direction.

(17) The covering cap 8 has an edge 49 at the opening 48. Before the mounting or fastening of the covering cap 8 to the high pressure pump 1, the electric plug 52 has already been finally fastened to the cylinder 6. In order to mount the covering cap 8, the electric plug 52 is first of all introduced into the opening 48 of the covering cap 8 (FIG. 7), and the covering cap 8 is subsequently placed in the region of the opening 48 or in the region of the edge 49 onto an upper end of the union nut 45. Here, the diameter of the opening 48 is slightly smaller than the external diameter of the union nut 45 on the upper end region of the union nut 45 in accordance with the illustration in FIG. 6. In FIG. 8, the covering cap 8 is placed in the region of the opening 48 on said upper end region of the union nut 45. Subsequently, a force is applied in the axial direction to the covering cap 8 at the edge 49 by way of a tool 56, with the result that the edge 49 is stretched radially to the outside in the region of the opening 48 on account of the geometry of the union nut 45 on the upper end region, with the result that the diameter of the opening 48 of the covering cap 8 is increased as a result and corresponds substantially to the diameter of the union nut 45. On account of said elastic radial stretching of the covering cap 8 at the edge 49, the edge 49 of the covering cap 8 is therefore prestressed elastically. Furthermore, in accordance with the illustration in FIGS. 6, 9 and 10, the covering cap 8 is moved in a downward direction by the tool 56 in the direction of the fuel nozzle 54, until the edge 49 of the covering cap 8 has swept over the union nut 45, with the result that an elastic recovery of the covering cap 8 occurs at the edge 49 as a result, and, as a result, the diameter of the opening 48 of the covering cap 8 is reduced again on account of the elastic recovery in the radial direction 41. In FIGS. 6 and 10, the covering cap 8 has already been fastened to the high pressure pump 1, with the result that the edge 49 lies on the axial stop 43 of the union nut 45 on account of the elastic recovery of the edge 49 of the covering cap 8. As a result, the covering cap 8 is reliably fastened to the remaining high pressure pump 1 in a positively locking manner. Here, the geometry of the axial supporting section 51 can also be configured in such a way that the axial supporting section 51 also optionally additionally lies on the cylinder 6 with an elastic prestress after the fastening in the position in FIGS. 6 and 10. As a result, the covering cap 8 is additionally optionally fastened to the remaining high pressure pump 1 in a non-positive manner.

(18) FIG. 11 shows a further, second exemplary embodiment of the fastened covering cap 8. The covering cap 8 also covers the union nut 45.

(19) FIG. 3 depicts a greatly diagrammatic illustration of the high pressure injection system 36 for a motor vehicle 38 with a high pressure rail 30 or a fuel distributor pipe 31. From the high pressure rail 30, the fuel is injected by means of valves (not shown) into the combustion chamber of the internal combustion engine 39. A prefeed pump 35 delivers fuel from a fuel tank 32 through a fuel line 33 to the high pressure pump 1 in accordance with the above exemplary embodiment. The prefeed pump 35 can also be driven by way of an electric motor (not shown) without a mechanical coupling (not shown) to the drive shaft 2. Here, the high pressure pump 1 and the prefeed pump 35 are driven by the drive shaft 2. The drive shaft 2 is coupled to a crankshaft of the internal combustion engine 39. As has already been described, the high pressure rail 30 serves to inject the fuel into the combustion chamber of the internal combustion engine 39. The fuel which is delivered by the prefeed pump 35 is guided through the fuel line 33 to the high pressure pump 1. Here, the fuel which is not required by the high pressure pump 1 is guided back into the fuel tank 32 again through a fuel return line 34. A metering unit 37 controls and/or regulates the quantity of fuel which is fed to the high pressure pump 1, with the result that the fuel return line 34 can be dispensed with in a further refinement (not shown).

(20) Viewed overall, considerable advantages are associated with the high pressure pump 1 according to the invention and the high pressure injection system 36 according to the invention. The covering cap 8 is configured from an elastic plastic. As a result, the covering cap 8 can be adapted advantageously to different geometries, in particular even during the mounting. This makes the mounting of the covering cap 8 possible after the fastening of the electric plug 52 to the high pressure pump 1, since an elastic deformation of the covering cap 8 is necessary during guiding of the electric plug 52 through the opening 48 of the covering cap 8 on account of the geometry of the high pressure pump 1 including the electric plug 52. On account of said elastic properties of the covering cap 8, said covering cap 8 can also make a sealing function possible with regard to the cylinder 6, in particular in the case of an additional optional prestress of the covering cap 8 after the fastening, with the result that the covering cap 8 lies on the remaining high pressure pump 1 under an elastic prestress at least on part faces between the covering 8 and the remaining high pressure pump 1, and this makes a sealing function possible as a result. As a result, a penetration of moisture and water into the region between the covering cap 8 and the remaining high pressure pump 1 can advantageously be avoided.