HIGH-PRESSURE FUEL PUMP FOR A FUEL INJECTIN SYSTEM

Abstract

The invention relates to a high-pressure fuel pump having a pump piston and having a piston rotation inducing device which induces a rotation of the pump piston about a movement axis, along which the pump piston moves in translational fashion, during the operation of the pump piston

Claims

1. A high-pressure fuel pump for applying high pressure to a fuel in a fuel injection system comprising: a housing defining a housing bore and a guide bore; a pressure chamber formed at one end region of the housing bore in which high pressure is applied to the fuel, and wherein the guile bore adjoins the end region; a pump piston, guided by the guide bore, wherein the pump piston is translatable in the guide bore along a movement axis during the operation of the high-pressure fuel pump; and a piston rotation inducing device which a rotation of the pump piston about the movement axis during the operation of the pump piston.

2. The high-pressure fuel pump of claim 1, wherein a piston clearance is defined between a guide wall of the guide bore and a piston shell surface of the pump piston, and through which leakage fuel flows out of the pressure chamber parallel to the movement axis during the operation of the pump piston.

3. The high-pressure fuel pump of claim 2, wherein the piston shell surface has a surface structure which interacts with the flowing leakage fuel such that the pump piston rotates about the movement axis

4. The high-pressure fuel pump of claim 3, wherein the surface structure extends over the piston shell surface parallel to the movement axis of the pump piston.

5. The high-pressure fuel pump of claim 4, wherein the surface structure extends over a full length the piston shell surface parallel to the movement axis.

6. The high-pressure fuel pump of claim 3, wherein the surface structure is arranged helically on the piston shell surface.

7. The high-pressure fuel pump of claim 6, wherein a helix gradient of the surface structure is of a magnitude such that said structure winds at most once around a circumference of the pump piston.

8. The high-pressure fuel pump of claim 6, wherein multiple helical surface structures are arranged parallel on the piston shell surface.

9. The high-pressure fuel pump of claim 6, wherein the helical surface structure is formed by one of a continuous helix and a discontinuous helix.

10. The high-pressure fuel pump of claim 3, wherein the surface structure is a relief recessed into the piston shell surface.

11. The high-pressure fuel pump of claim 11, wherein the relief is formed into the piston shell surface by laser removal.

12. The high-pressure fuel pump of claim 10, wherein a depth of the recessed relief lies in a range between 2 m and 5 m.

13. The high-pressure fuel pump of claim 2, wherein a piston clearance between a guide wall of the guide bore and a piston shell surface of the pump piston is smaller than 4 m.

14. The high-pressure fuel pump of claim 13, wherein the piston clearance is smaller than 3.5 m.

15. The high-pressure fuel pump of claim 13, wherein the piston clearance between lies between 2 m and 3 m.

16. The high-pressure fuel pump of claim 1, wherein the guide bore is formed as an optimum cylinder with a cylindrical shape deviation.

17. The high-pressure fuel pump of claim 1, wherein a surface roughness of a guide wall of the guide bore is in the m range.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein

[0029] FIG. 1 shows a schematic sectional illustration of a housing of a high-pressure fuel pump having a pump piston in a first embodiment guided in a guide bore;

[0030] FIG. 2 shows a perspective illustration of the pump piston from FIG. 1 in a second embodiment; and

[0031] FIG. 3 shows a perspective illustration of the pump piston from FIG. 1 in a third embodiment.

DETAILED DESCRIPTION

[0032] FIG. 1 shows a schematic sectional illustration of a high-pressure fuel pump 10 with which high pressure is applied to a fuel, in particular gasoline. The high-pressure fuel pump 10 has a housing 12 in which there is formed a housing bore 14 which, at one end region 16, forms a pressure chamber 18. Adjoining the end region 16, the housing bore 14 forms a guide bore 20, in which a pump piston 22 is arranged. During operation, fuel is supplied to the pressure chamber 18 via a feed bore 24. The pump piston 22 moves upward and, downward in the guide bore 20 along a movement axis 26 and thereby reduces the volume of the pressure chamber 10. In this way, the fuel situated in the pressure chamber 18 is compressed, and thus has high pressure applied thereto.

[0033] In the present embodiment, the guide bore 20 is formed directly in the housing 12. It is however also conceivable for an additional sleeve to be inserted into the housing bore 14, in which sleeve the guide bore 20 for the pump piston 22 is formed.

[0034] A piston clearance 32 is prodded between a piston shell surface 28 of the pump piston 22 and a guide wall 30 of the guide bore 20. Owing to the piston clearance 32, the pump piston 22 can easily move upward and downward in translational fashion in the guide bore 20. The piston clearance 32 additionally serves for the lubrication and cooling of the pump piston 22 during operation, wherein leakage fuel can flow out of the pressure chamber 18 along the piston shell surface 28 in the piston clearance 32.

[0035] The piston shell surface 28 has a surface structure 34 which, in the embodiment shown in FIG. 1, is formed as a helical surface structure 34helix 35in the form of a recessed relief 36.

[0036] If the leakage fuel now flows down along the piston shell surface 28 on the pump piston 22 in the piston clearance 32, said leakage fuel also enters the relief 36 and flows along the helix 35 that is formed. Here, the flowing leakage fuel exerts a movement force on the pump piston 22, which has the effect that the pump piston 22 begins to rotate about the movement axis 26. The combination of the surface structure 34 with the flowing leakage fuel from the pressure chamber 18 thus forms a piston rotation inducing device 38.

[0037] To effect an expedient rotation of the pump piston 22 about the movement axis 26, a depth T of the relief 36, that is to say of the surface structure 34, lies a range of the magnitude of the piston clearance 32, though may also be greater depending on the usage situation. For example, a piston clearance 32 is reduced by 30% in relation to known high-pressure fuel pumps 10, and lies in a size range below 4 m, in particular below 3.5 m, and lies approximately in a range between 2 m and 3 m. Correspondingly the depth T of the relief 36 may lie in a size range between 2 m and 5 m. The recessed relief 36 may for example be formed into the piston shell surface 28 by laser.

[0038] In order that substantially the surface structure 34 effects the rotation of the pump piston 22 about the movement axis 26, guide bore 20 may be formed as an optimum cylinder, that is to say as a cylinder which has only a very slight cylindrical shape deviation and also only a very low surface roughness. Thus, the cylindrical shape deviation and surface roughness of the guide wall 30 may lie at most in the m range.

[0039] To achieve that the rotation of the pump piston 22 about the movement axis 26 is influenced over an entire length L of the piston shell surface 28 parallel to the movement axis 26, the surface structure 34 may extend on the piston shell surface 28 over the full length L parallel to the movement axis 26.

[0040] Depending on the rotation of the pump piston 22 about the movement axis 26, different surface structures 34 may be used.

[0041] FIG. 1 show, in a first embodiment, the use of a single helix 35 which winds around the entire piston shell surface 28.

[0042] FIG. 2 shows a second embodiment of the pump piston 22, wherein multiple helical surface structures 34 which extend parallel to one another are arranged on the piston shell surface 28. In the present embodiment, four parallel helices 35 are arranged on the piston shell surface 28. A helix gradient 40 of said four helices 35 is in each case of such a magnitude that said helices wind in each case only once around a circumference U of the pump piston 22. In FIG. 2, the helices 35 are formed as continuous helices, that is to say are formed continuously over the full extent. FIG. 3 shows an alternative third embodiment, in which the helices 35 are formed as discontinuous helices 35.

[0043] The foregoing preferred embodiments have been shown and described for the purposes of illustrating the structural and functional principles of the present invention, as well as illustrating the methods of employing the preferred embodiments and are subject to change without departing from such principles. Therefore, this invention includes all modifications encompassed within the scope of the following claims.