US20050084389A1

US20050084389A1 - Radial piston pump with flat seal between flange and housing

Info

Publication number: US20050084389A1
Application number: US10/503,446
Authority: US
Inventors: Burkhard Boos; Alfons Schoetz; Matthias Distel
Original assignee: Individual
Current assignee: Robert Bosch GmbH
Priority date: 2002-11-15
Filing date: 2003-08-11
Publication date: 2005-04-21
Also published as: CN1695008A; WO2004046547A1; CN100429398C; EP1576288A1; DE10253189A1; JP2006506572A

Abstract

A radial piston pump, having a flange and a housing, a pump element in the housing, and an eccentric drive shaft that actuates a piston in the pump element radial to the drive shaft, which piston seals a pump volume which upon expansion, delivers fuel from an inlet chamber into the pump volume and upon contraction, exerts pressure on the fuel in the pump volume and conveys it out at a high pressure, having an inner chamber that contains the eccentricity, and having a parting plane that extends between the housing part and flange part and intersects the inner chamber and the inlet chamber. A one-piece flat seal is disposed in the parting plane and seals the inlet chamber, the inner chamber, and the environment of the radial piston pump in relation to one another.

Description

PRIOR ART

The invention relates to a radial piston pump, having

- a flange part, a housing part, an inner chamber, and an inlet chamber,
- at least one pump volume disposed in the housing part and sealed by a moving piston,
- an eccentric drive shaft that extends in the axial direction through the inner chamber and actuates the piston in the radial direction so that the piston delivers fuel from the inlet chamber into the pump volume, exerts pressure on the fuel in the pump volume, and conveys the fuel out of the pump volume at a high pressure, and
- a parting plane that extends between the housing part and the flange part and intersects the inlet chamber.

Radial piston pumps of this type are used in injection systems for combustion processes, in particular to generate injection pressures of over 1000 bar in common rail direct injection systems for combustion processes.
A radial piston pump of this type is described in DE 1 98 48 035.
In the known radial piston pump, a low-pressure pump supplies the inlet chamber with fuel by means of a controllable metering unit via bores and conduits that extend inside the flange and housing. As a rule, a radial piston pump has a number of pump elements that are disposed radial to a central drive shaft. The fuel supply of pump volumes of the pump elements occurs on the side oriented away from the drive mechanism and therefore, viewed in the radial direction, away from the middle of the pump, in outer regions of the radial piston pump.
Fuel is often supplied to the individual pump elements by means of radially arranged conduits that extend through the flange, parallel to the parting plane and feed into a central supply line that is shared by all of the pump elements. The central supply line is supplied with fuel via a supply conduit that extends axially through the radial piston pump and passes through the parting plane between the flange and housing.
In a similar fashion, the pump volumes of the pump elements, which are disposed at the outermost radial periphery, are each connected to their respectively associated radially outward extending supply bores by means of axially disposed conduits. In the known radial piston pump, these conduits also pass through the parting plane between the flange and housing. In addition, depending on the design of the radial piston pump, the parting plane has still other conduits passing through it, for example a conduit that is used to ventilate the inner chamber and an inlet line for a low-pressure fuel delivery pump flange-mounted to the radial piston pump.
Another opening in the flange and housing comprises the guide of the axially and centrally disposed drive shaft. In the known radial piston pump, the openings mentioned above are rotationally symmetrical. As a rule, the inner chamber of the radial piston pump in which the drive shaft rotates is filled with fuel. But the fuel pressure in the inner chamber is not the same as the fuel pressure in the inlet chamber.
In order to prevent undesirable fuel flows between the inner chamber and the inlet chambers and associated supply conduits, which could impair the supply of fuel to the pump volumes, the inlet chambers must be sealed in relation to the inner chamber. Furthermore, the fuel-carrying inlet chambers and supply conduits disposed on the radial periphery must be sealed in relation to the environment so that the pump as a whole is sealed. For this reason, all of the fuel-carrying conduits and/or chambers that are intersected by the parting plane are sealed in the parting plane. In the known radial piston pump, these seals are produced by a large number of O-rings made of elastomer material.
In the manufacture of a radial piston pump, this type of seal is relatively expensive. Each one of the large number of O-rings must be inserted exactly into a recess provided to accommodate it in the surface of the flange and/or housing. Such a recess must be produced for each O-ring through a corresponding removal of material, for example by milling, drilling, cutting, or turning.
Furthermore, O-rings achieve a reliable sealing action only when installed in the form of a ring, which inevitably involves structural and production engineering disadvantages in the manufacture of the radial piston pump. Thus, for example, the radially extending connecting conduit between a supply line disposed centrally in the radial piston pump and the connection on the radial periphery to a pump volume must be routed on the inside of the flange or housing and be connected by means of a bore in the parting plane.
As a rule, the radially extending bore is produced by drilling radially inward from the outside. The intrinsically undesirable drilled holes that remain in the outer wall of the radial piston pump are closed, for example, by means of press-fitted sealing balls made of metal. This closing of the bores represents an additional work cycle in the manufacturing process and complicates production. In principle, the press-fitted balls also represent a deviation from the ideal of a pump housing that is sealed to the greatest degree possible.
In principle, the O-rings used in the dividing plane itself are also susceptible to aging and thus represent a possible leak source during subsequent operation of the radial piston pump.
The object of the invention, therefore, is to disclose a seal between a flange part and a housing part in a radial piston pump that does not have the above-mentioned disadvantages.
This object is attained in a radial piston pump of the kind mentioned at the beginning by means of a one-piece flat seal that is disposed in the parting plane and seals the inlet chamber in relation to the environment of the radial piston pump.

ADVANTAGES OF THE INVENTION

This embodiment has the advantage that a one-piece flat seal can be installed with particular ease and reliability since a correct positioning of just two points of the flat seal results in the correct positioning of all of the remaining points. This prevents sealing structures from slipping unnoticed into central regions of the radial piston pump during assembly, particularly at the moment that the flange and housing are fitted together.
It is also no longer necessary to maintain a supply of different sized O-rings since all of the different sizes of sealing contours can be taken into account in the design of the flat seal.
Another advantage is that a flat seal permits the embodiment of sealing contours other than the circular form of O-rings. This advantageously permits additional latitudes in the construction of the parts that are to be sealed, as explained in detail further below.
It is preferable for the parting plane to intersect the inlet chamber and the inner chamber and for the one-piece flat seal to seal the inner chamber from the inlet chamber and the inlet chamber from the environment.
This embodiment has the advantage that a tight separation of the inlet chamber, both from the inner chamber and from the environment, can be achieved by a single component, i.e. the flat seal.
It is also preferable for the flat seal to have a sheet metal layer.
Sheet metal seals withstand aging and exposure to fuel and are also dimensionally stable and inexpensive.
It is also preferable for the sheet metal seal to have a coating.
A coating can further improve the sealing action of the sheet metal seal, particularly if it contains a flexible, elastic material.
It is therefore also preferable for the coating to contain an elastic plastic material.
It is also preferable for the flat seal to have a bead that extends between the inner chamber and the inlet chamber in the installed position.
The bead further improves the sealing action of the flat seal so that a particularly good seal is produced between the inner chamber and the inlet chamber.
It is also preferable for the flat seal to have a bead that extends between the inlet chamber and the environment in the installed position.
This bead also further improves the sealing action of the flat seal so that a particularly good seal is produced between the inlet chamber and the environment.
It is also preferable for the sheet metal to be 0.1 to 0.3 mm thick.
It is also preferable for the bead to be 0.2 to 0.4 mm high.
These dimensions have produced particularly reliable seals.
It is also preferable for the inlet chamber to be supplied with fuel at least in part by means of grooves that are disposed in the housing or flange and are open toward the parting plane.
This embodiment relates to the above-mentioned possibility of using the flat seal to also produce sealing contours that deviate from the circular shape of O-rings. It is therefore no longer necessary to route the above-mentioned radially extending fuel conduit inside the flange material or housing material and then to connect the conduit by means of bores that pass through the parting plane.
When a flat seal is used, it is instead possible to place conduits, in particular even radially aligned conduits, in the parting plane, thus producing e.g. rectangular edges to be sealed. The sealing action can then be achieved, for example, by beads of an adapted form, which extend around the open conduits disposed in the parting plane.
Other advantages ensue from the specification and the accompanying figures.
It should be understood that the features mentioned above and those that will be explained below can be used not only in the respectively indicated combinations, but can also be used in other combinations or individually without going beyond the scope of the current invention.
Exemplary embodiments of the invention are shown in the drawings and will be explained in detail in the subsequent description.

DRAWINGS

FIG. 1 is a schematic sectional view of a radial piston pump according to the prior art, when assembled;
FIG. 2 is a schematic top view of the flange from FIG. 1;
FIG. 3 is a schematic sectional view of a radial piston pump as an exemplary embodiment of the invention;
FIG. 4 is a schematic top view of a flange of the radial piston pump from FIG. 3;
FIG. 5 is a top view of an embodiment of a flat seal for placement in the parting plane between a housing part and a flange part of a radial piston pump;
FIG. 6 shows a section through the flat seal according to FIG. 5.
The reference numeral 10 in FIG. 1 indicates a radial piston pump with a housing 12 and a flange 14. The housing 12 and flange 14 are attached to each other in a parting plane 16; for the sake of clarity, the connecting elements, e.g. screws, are not shown. A drive shaft 18 is guided through the radial piston pump 10 in a central position and is supported in bearings 20, 22. The drive shaft 18 has an eccentric region 24, which actuates a piston 28 via a slide element 26. The piston is disposed radially in a bore of the housing 12 and seals a pump volume 30 in the housing 12 in a mobile fashion. The pump volume 30 is coupled via a valve 32 to an inlet chamber 34 by means of which fuel is supplied to the pump volume 30. In addition, the pump volume 30 is connected via a valve 36 to a high-pressure conduit 38 that conveys high-pressure fuel from the pump volume 30.
The drive shaft 18 rotating in the bearings 20, 22 periodically actuates the piston 28 so that the pump volume 30 periodically contracts and expands. With an expansion of the pump volume 30, the valve 32 opens and fuel flows out of the inlet chamber 34 into the pump volume 30. A contraction of the pump volume 30 causes the valve 32 to close and, assuming there is a sufficiently high pressure, causes the valve 36 to open, allowing fuel to be ejected at high pressure from the pump volume 30.
The radial piston pump 10 is integrated into a low-pressure circuit, not shown, in which a low-pressure delivery pump, also not shown, feeds fuel into a supply conduit 40 in the housing 12. Fuel from the supply conduit 40 is conveyed through the parting plane 16 into the first connecting bore 42 in the flange 14. From there, the fuel flows through a first radial bore 44 that extends inside the flange 14 and through a second connecting bore 48 into an annular conduit or annular groove 50.
During manufacture, the first radial bore 44 is drilled radially inward from the outside and after the bore is produced, the undesirable opening remaining in the housing 12 is tightly sealed with a first sealing ball 46. The annular groove 50 leads around the central region of the radial piston pump 10 in which the drive shaft 18 is supported in rotary fashion. Fuel travels out of the annular groove 50 and into a second radial bore 54 through a third connecting bore. The second radial bore 54 has been produced in a manner analogous to the production of the first radial bore 44, by being drilled in from the outside. Here, too, the remaining undesirable opening is sealed from the outside by means of a sealing ball, in this case the second sealing ball 56. The fuel travels from the second radial bore 54 into the inlet chamber 34 through a fourth connecting bore 58 that intersects the parting plane 16.
The radial piston pump according to FIG. 1 thus has a number of fuel paths that are intersected by the parting plane 16 between the flange 14 and housing 12. In addition, the parting plane 16 between the housing 12 and flange 14 also intersects the inner chamber 60 inside the housing 12, in which the eccentric section 24 of the drive shaft 18 rotates and actuates the piston 28. The fuel paths (40, 42, 50, 54, 58) intersected by the parting plane 16 are subjected to a high pressure that prevails in the inlet chamber 34. The inner chamber 60 is usually filled with fuel and/or has fuel flowing through it. However, a different pressure usually prevails in the inner chamber 60 than in the inlet chamber 34 and the fuel paths (40, 42, 50, 54, 58) that communicate with the inlet chamber 34.
In order to prevent unwanted fuel flows between the inner chamber 60 and the fuel paths (40, 42, 50, 54, 58), in particular the annular groove 50, an O-ring 62 is provided, which is disposed in a recess in the flange 14 concentric to the drive shaft. Another O-ring 64 seals the annular groove 50 in the parting plane 16 in relation to the environment. Another O-ring 66 seals the first connecting bore 42 in the parting plane 16. In an analogous fashion, an additional O-ring 68 seals the fourth connecting bore 58 in the parting plane 16.
FIG. 3 schematically depicts a radial piston pump 10 in the context of an embodiment of the invention. By contrast with the subject of FIGS. 1 and 2, which depict a known radial piston pump, the embodiment according to FIG. 3 does not have any O- rings 62, 64, 66, and 68 in the parting plane 16 between the housing 12 and flange 14 of the radial piston pump 10. For the sake of completeness, it should be noted that features that are the same in the different figures are labeled with the same reference numerals.
The O-rings, which are provided in the subject of FIGS. 1 and 2, are replaced in the embodiment according to FIGS. 3 and 4 by a flat seal 70, which is disposed in the parting plane 16 between the housing 12 and flange 14. The design of this flat seal 70 will be explained in more detail below in conjunction with FIGS. 5 and 6. A significant advantage of using a flat seal 70 is that the flat seal 70 permits a modified routing of fuel. Thus in the subject of FIG. 3, the supply conduit 40 feeds into a radial groove 72, which can be open toward the parting plane 16. The radial groove 72 connects the supply conduit 40 to the annular groove 50 and thus replaces the first connecting bore 42, the first radial bore 44 with the sealing ball 46 and the second connecting bore 48 from FIG. 1. In the same manner, the radial groove 74 in FIG. 3 replaces the third connecting bore 52, the second radial bore 54 with the sealing ball 56, and the fourth connecting bore 58 from FIG. 1. The radial groove 74 is also open in relation to the parting plane 16.
The top view of the flange 14 shown in FIG. 4 without the flat seal 70 shows the open path of the radial grooves 72 and 74, the absence of O- rings 62, 64, 66, and 68, and the absence of the corresponding recesses for accommodating these O-rings in the flange 14.
FIG. 5 is a top view of an embodiment of a flexible seal 70 for a radial piston pump. This embodiment corresponds to the radial piston pumps actually in use better than the schematic depictions in FIGS. 1 to 4. The flat seal 70 shown in FIG. 5 is likewise intended for placement in a parting plane 16 between a housing 12 and a flange 14 of a radial piston pump 10. The flat seal 70 has three regions 76, 78, and 80 arranged in a star pattern, each of which contains an opening 77, 79, and 81. When installed, each of the regions 76, 78, and 80 arranged radially in a star pattern covers over a radial groove in the flange of a radial piston pump.
The associated radial piston pump correspondingly has three pump elements that are arranged radially in a star pattern. The radial grooves are embodied, for example, like the radial groove 74 in the depiction in FIGS. 3 and 4. The openings 77, 79, and 81 respectively permit a flow of fuel from the radial groove, through the flat seal 70, and into the associated pump volumes.
In the embodiment in FIG. 3, the opening in the seal 70 that permits a flow from the radial groove 74 into the inlet chamber 34 corresponds to one of the openings 77, 79, and 81. Therefore the inlet chamber pressure prevails in the region of these openings 77, 79, and 81. This inlet chamber pressure is sealed in relation to the inner chamber of the radial piston pump by an inner bead 82. This inner chamber corresponds to the inner chamber 60 in FIGS. 1 and 3. Toward the outside, the inlet chamber is sealed by another bead 84, which extends in a closed line around all three regions 76, 78, and 80 arranged in a star pattern.
The flat seal 70 has additional openings 86, 88, 90, and 92 that are each encompassed by an associated, concentrically disposed bead 87, 89, 91, and 93.
These openings are provided because the parting plane 16 intersects other conduits and/or pressure chambers. Thus, for example, the opening 92 can be associated with a metering unit that controls the supply of fuel to the radial piston pump. The openings 86, 88, and 90 can, for example, represent inlet conduits and outlet conduits for a low-pressure gear delivery pump that is flange-mounted to the radial piston pump, while the opening 90, for example, can be associated with a ventilation bore for the inner chamber 60 of the radial piston pump. Openings 95 permit fastening elements such as screws to pass through.
FIG. 5 already shows particularly well the possibility, in a flat seal, of producing sealing contours in the form of beads that deviate from the concentric form of the O-rings that are usually used. This makes it possible for the fuel conduits extending radially outward to be placed in the parting plane, as represented by a radial groove 74 in FIGS. 3 and 4. This makes it easier, for example, to produce the flange 14 that contains the radially extending fuel supply conduit. This allows a radial groove, for example, which corresponds to the radial groove 74 in FIGS. 3 and 4, to be produced in a largely preformed fashion in a cast flange 14, thus to a large extent eliminating the need for additional machining steps. The same is true for a forged flange 14.
FIG. 6 is a sectional depiction of the seal 70 according to FIG. 5. The seal 70 has a sheet metal layer 94 that lends the flat seal 70 structure and strength. In the embodiment shown, the sheet metal layer 94 is coated with a layer of flexible, elastic plastic 96, which improves the sealing action. The beads 84 and 82 are depicted as raised areas in the sectional view in FIG. 6.

Claims

1-10. (canceled)

11. A radial piston pump (10) comprising a flange part (14), a housing part (12), an inner chamber (60), and an inlet chamber (34),

at least one pump volume (30) disposed in the housing part (12) and sealed by a moving piston (28),

an eccentric drive shaft (18) that extends in the axial direction through the inner chamber (60) and actuates the piston (28) in the radial direction so that the piston (28) delivers fuel from the inlet chamber (34) into the pump volume (30), exerts pressure on the fuel in the pump volume (30), and conveys it out of the pump volume (30) at a high pressure,

a parting plane (16) that extends between the housing part (12) and flange part (14) and intersects the inlet chamber (34), and

a one-piece flat seal (70) disposed in the parting plane (16) and sealing the inlet chamber (34) in relation to the environment of the radial piston pump (10).

12. The radial piston pump (10) according to claim 11, wherein the parting plane (16) intersects the inlet chamber (34) and inner chamber (60), with the one-piece flat seal (70) sealing the inner chamber (60) in relation to the inlet chamber (34) and sealing the inlet chamber (34) in relation to the environment.

13. The radial piston pump (10) according to claim 11, wherein the flat seal (70) has a sheet metal layer (94).

14. The radial piston pump (10) according to claim 12, wherein the flat seal (70) has a sheet metal layer (94).

15. The radial piston pump (10) according to claim 13, wherein the sheet metal layer (94) has a coating (96).

16. The radial piston pump (10) according to claim 14, wherein the sheet metal layer (94) has a coating (96).

17. The radial piston pump (10) according to claim 15, wherein the coating (96) contains elastic plastic material.

18. The radial piston pump (10) according to claim 16, wherein the coating (96) contains elastic plastic material.

19. The radial piston pump (10) according to claim 11, wherein the flat seal (70) has a bead (82) that extends between the inner chamber (60) and the inlet chamber (34) in the installed position.

20. The radial piston pump (10) according to claim 11, wherein the flat seal (70) has a bead (84) that extends between the inlet chamber (34) and the environment in the installed position.

21. The radial piston pump (10) according to claim 19, wherein the flat seal (70) has a bead (84) that extends between the inlet chamber (34) and the environment in the installed position.

22. The radial piston pump (10) according to claim 13, wherein the sheet metal layer (94) is 0.1 to 0.3 mm thick.

23. The radial piston pump (10) according to claim 15, wherein the sheet metal layer (94) is 0.1 to 0.3 mm thick.

24. The radial piston pump (10) according to claim 17, wherein the sheet metal layer (94) is 0.1 to 0.3 mm thick.

25. The radial piston pump (10) according to claim 19, wherein the sheet metal layer (94) is 0.1 to 0.3 mm thick.

26. The radial piston pump (10) according to claim 19, wherein the bead is 0.2 to 0.4 mm high.

27. The radial piston pump (10) according to claim 20, wherein the bead is 0.2 to 0.4 mm high.

28. The radial piston pump (10) according to claim 11, wherein the inlet chamber (34) is supplied with fuel at least in part by means of grooves (74) that are disposed in the housing (12) or flange (14) and are open toward the parting plane (16).

29. The radial piston pump (10) according to claim 12, wherein the inlet chamber (34) is supplied with fuel at least in part by means of grooves (74) that are disposed in the housing (12) or flange (14) and are open toward the parting plane (16).

30. The radial piston pump (10) according to claim 13, wherein the inlet chamber (34) is supplied with fuel at least in part by means of grooves (74) that are disposed in the housing (12) or flange (14) and are open toward the parting plane (16).