EP2087227A1

EP2087227A1 - Delivery pump, in particular for delivering diesel fuel, having improved mounting of the drive shaft

Info

Publication number: EP2087227A1
Application number: EP07803526A
Authority: EP
Inventors: Gerhard Meier; Johannes Muellers
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2006-10-31
Filing date: 2007-09-17
Publication date: 2009-08-12
Also published as: KR20090074068A; US20100068079A1; CN101535628B; WO2008052842A1; CN101535628A; KR101387782B1; DE102006051332A1; US8157548B2

Abstract

The present invention relates to a delivery pump (1), in particular for delivering diesel fuel into a high-pressure accumulator, having a housing (2) and a drive shaft (3) which is accommodated in the latter and is mounted by means of at least one sliding bearing arrangement (4) such that it can rotate about a drive shaft axis (5), wherein the sliding bearing arrangement (4) is formed by a bearing hole (6) and a bearing shaft section (7) which extends through the latter, wherein the sliding bearing arrangement (4) comprises a bearing play (X) which extends in the radial direction between the bearing shaft section (7) and the bearing hole (6) and has a smaller value in the bearing centre (8) than at at least one bearing edge (9a, 9b). A delivery pump (1) for delivering diesel fuel is therefore provided which has a low-wear sliding bearing arrangement (4).

Description

description

title

Feed pump, in particular for the promotion of diesel fuel with improved storage of the drive shaft

The present invention relates to a feed pump for conveying diesel fuel according to the preamble of claim 1. The present invention is directed in particular to an improved embodiment of the slide bearing assembly for supporting the drive shaft in the housing of the feed pump.

State of the art

A generic pump for the promotion of diesel fuel is known from the published patent application DE 101 38 362 Al. The feed pump serves to convey diesel fuel into a so-called common-rail

Fuel injection system. The so-called common rail forms a high-pressure accumulator whose high pressure is maintained by the feed pump. The feed pump has a housing with a drive shaft accommodated therein, which is mounted rotatably about a drive shaft axis by means of two slide bearing arrangements. The slide bearing assembly is formed by a bearing bore and a bearing shaft portion extending therethrough. The bearing shaft section forms part of the drive shaft, wherein the bearing arrangements are preferably arranged adjacent to a cam portion, over which a roller rolls, and thus is operatively connected to a valve assembly. The sliding bearing assembly each comprises a bearing bush in which the bearing bore is formed.

Another embodiment of a generic feed pump is disclosed in the published patent application DE 199 13 804 Al. The feed pump serves to convey diesel fuel into a high-pressure accumulator for an internal combustion engine. Machine, wherein the feed pump with two pumping chambers, which are arranged one behind the other, is executed. The valve assemblies are operated in this embodiment via two adjacent arranged on a drive shaft cam gear, wherein the cam drives are taken on the drive shaft between two Gleitlageranordnun- gene. Thus, an advantageous load case between the forms

Bearing arrangements.

With regard to the generation of the stroke of the extending into the valve assembly in the lifting element, the feed pump may be formed with a cam drive or with an eccentric drive. In both types of such feed pumps, however, there is the problem that due to the very high delivery pressures large forces acting on the drive shaft, which must be absorbed by the sliding bearing assemblies. These forces are introduced via the pressure rollers on the cam sections in the drive shaft and result from the respective valve assemblies. In addition, significant lateral forces can be introduced into the drive shaft, which are also caused by driven via the drive shafts units. The drive shaft extends in at least one direction out of the housing of the feed pump, and receives at least one transmission means for power transmission by means of a traction means, a toothing or the like. If additional units are driven via the drive shaft of the feed pump for the power throughput, considerable forces can be introduced into the drive shaft, which also has to be absorbed by the respective slide bearing arrangement. Deflecting deflections of the drive shaft lead to edge supports in the bearing edges, which cause very high edge pressures between the bearing shaft portion and the bearing bore. The high values of the bearing pressures can cause a bearing lubricating film between the bearing bore and the bearing shaft portion can no longer form, which can lead to significant wear and a premature failure of the feed pump. Conventional bearing arrangements according to the prior art have a cylindrical configuration, so that the bearing shaft section and the bearing bore each form a concentric cylinder section. Plain bearings have a common bearing air, which forms in the radial direction between the bearing shaft portion and the bearing bore as a diameter difference. Such bearing air is provided to form a hydrodynamic lubrication by means of a lubricant such as a grease or a lubricating oil. With a slight tilting of the drive shaft, either by an oblique position, ie by a skew through both sliding bearing assemblies, or by a deflection of the drive shaft, there is a geometric malposition, ie the alignment of the bearing bore is no longer consistent with the alignment of the bearing shaft section.

It is therefore the object of the present invention to provide a delivery pump for the promotion of diesel fuel, which has a low-wear sliding bearing assembly.

Disclosure of the invention

This object is achieved on the basis of a feed pump for the promotion of diesel fuel according to the preamble of claim 1 in conjunction with its characterizing features. Advantageous developments of the invention are specified in the dependent claims.

The invention includes the technical teaching that the slide bearing arrangement comprises a bearing air extending in the radial direction between the bearing shaft section and the bearing bore, which has a smaller value in the bearing center than at least one bearing edge.

The invention is based on the idea that the maximum surface pressures between the bearing bore and the bearing shaft section in the region of the bearing edge can be reduced. If the alignment of the bearing bore does not coincide with the alignment of the bearing shaft section, then the increased bearing clearance in the region of the bearing edges can compensate for the angular error. The slide bearing arrangement thus forms a symmetry, wherein the bearing center forms the plane of symmetry. Due to the increased bearing clearance at the edge of the bearing, the slide bearing arrangement can compensate for alignment errors in the manner of a ball-and-socket joint for very small angular ranges without the need for a corresponding compliant - A -

speed in the bearing bore or in the bearing shaft section is required. Experiments have shown that the surface pressure can be reduced by about 20 ... 25%. This makes it a considerable advantage of the plain bearing arrangement according to the invention for a feed pump to compensate for misalignment, deflections and other discontinuities in the drive shaft, without resorting to an expensive self-aligning bearing arrangement.

With regard to the design of the feed pump, the bearing arrangement according to the invention extends to both types of feed pumps, so that the feed pump can comprise a cam drive or an eccentric drive in order to drive a lifting element extending into at least one valve assembly. Concerning a feed pump according to known Excenterbauart star-shaped valve assemblies may be provided, in each of which a lifting element extends, and the lifting elements are in operative connection with a Excenterschei-. However, the forces acting on the bearing assembly according to the invention forces are equally available, regardless of the design of the feed pump for both a cam drive and for an eccentric drive, so that the bearing assembly according to the proposed embodiment for both types is applicable and provided.

A further advantageous embodiment of the present invention provides that the bearing bore has a cylindrical shape and the bearing shaft portion has a spherical shape, so that it is formed symmetrically in the direction of the drive shaft axis. The spherical shape is formed by a radius contour, which extends from the first bearing edge to the second bearing edge. The crown is thus a kind of thickening with a maximum thickness in the center of the bearing, so that in the center of the bearing clearance is minimal. On the other hand, the bearing clearance is maximum. The transitions of the crowned section into the cylindrical drive shaft at the level of the respective bearing edges may include compensation radii in order to avoid edge formation.

According to a further embodiment of the sliding bearing arrangement can be provided that the bearing shaft portion in the region of the bearing center has a cylindrical portion, and in the direction of the drive shaft axis in each case laterally a spherical section connects. The cylindrical section goes over each Transitional radii in the spherical portion over, wherein the spherical portion each again merges by means of a transition radius in the cylindrical part of the adjacent drive shaft. With an angular error between the alignment of the bearing bore and the alignment of the bearing shaft section, the bearing region can leave the cylindrical section formed in the area of the bearing center and travel along the convex section. The surface pressure between the bearing bore and the bearing shaft portion is only slightly increased at the contact point or in the contact area. The spherical section has a radius, wherein the transition between the cylindrical portion and the convex portion is formed free of edges.

According to yet another embodiment of the invention, a conical section adjoins the cylindrical section in the direction of the drive shaft axis laterally. Instead of a crowned portion, the region formed between the cylindrical portion and the bearing edges may also be provided as a conical portion. The transition between the conical section and the cylindrical section may again have transition radii to smooth the edges formed between the sections.

For design reasons, it may be of particular advantage that the bearing shaft portion is cylindrical and corresponds to a conventional slide bearing assembly. The increased bearing clearance in the edge region of the bearing is achieved, in which the bearing bore itself has a curvature, wherein the bearing bore in the bearing center has a smaller diameter than at the

Bearing edges. According to this structural design of the slide bearing assembly with a crown in the bearing bore misalignment can be compensated in the same way. In an inclined position of the alignment of the bearing shaft section relative to the alignment of the bearing bore, according to this exemplary embodiment, edge beams are avoided, in which the diameter of the bearing shaft is avoided

Bearing bore in the region of the bearing edge is designed to be larger than in the region of the bearing center.

Advantageously, the bearing air in the region of the center of the bearing has a value of from 1 μm to 150 μm, preferably from 10 μm to 50 μm, and particularly preferably 40 microns. Similarly, it can be provided that the difference in diameter of a bearing shaft portion between the bearing center and the bearing edges a value of lμm to 150μm, preferably from lOμm to 50μm and more preferably from 20μm to 30μm comprises. For example, the bearing clearance be sized with 40μm, which results when both the bearing bore and the bearing shaft portion are cylindrical. With a widening of the bearing clearance in the region of the bearing edges to, for example, 60 μm, a reduction of the surface pressure between the bearing shaft section and the bearing bore from 90 MPa to approximately 70 MPa can be achieved.

According to a further advantageous embodiment of the invention, the at least one sliding bearing arrangement comprises a bearing bush, wherein the bearing bore is formed in the bearing bush. The bearing bush is either received in the housing of the feed pump or in a bearing flange, which in turn is connected to the housing. The bearing bush is in each case pressed into the housing or in the bearing flange, glued or otherwise connected axially and rotationally. As a sliding bearing material, the bearing bush may comprise an aluminum material, a bronze material or a plastic material such as PEEK or PPS (polyetheretherketones or polyphenylsulphide). By these materials, an optimal friction pairing is formed between a preferably made of steel drive shaft and the bearing bush. The lubrication of the bearings can be done either by a lubricating oil, a permanent lubrication by a grease filling or by the diesel fuel itself.

Advantageously, the drive shaft comprises a cam portion or a

Excenterabschnitt, and adjacent to this is a sliding bearing assembly. Since the forces are mainly introduced into the cam portion or into the eccentric portion, a slide bearing assembly immediately adjacent to the cam portion is particularly advantageous. Thus, the forces introduced into the cam section or eccentric section can be optimally absorbed by the slide bearing arrangement, whereby the deflection of the drive shaft is minimized. Further, measures improving the invention will be described in more detail below together with the description of a preferred embodiment of the invention with reference to FIGS.

embodiment

It shows:

Figure 1 is a cross-sectional side view of an exemplified formed with a cam drive pump for pumping diesel fuel, which comprises a drive shaft which is rotatably received in two slide bearing assemblies;

FIG. 2 shows a first embodiment of a slide bearing arrangement for a feed pump according to the present invention;

Figure 3 shows a second embodiment of a sliding bearing assembly for a feed pump according to the present invention;

Figure 4 shows a third embodiment of a sliding bearing assembly for a feed pump according to the present invention; and

Figure 5 shows a fourth embodiment of a sliding bearing assembly for a feed pump according to the present invention.

FIG. 1 shows a feed pump 1 in a cross-sectional side view. This serves to promote diesel fuel in a high-pressure accumulator. The feed pump 1 comprises a housing 2, in which a drive shaft 3 is received rotatably mounted. The drive shaft 3 extends along a drive shaft axis 5, and is mounted in two slide bearing arrangements 4a and 4b.

The slide bearing assembly 4a is received in a bearing flange 15, whereas the slide bearing assembly 4b is introduced directly into the housing 2. The slide bearing arrangements 4a and 4b are each formed by a bearing bush 13, which receives the drive shaft 3 via bearing shaft sections 7. Intermediate see the two slide bearing assemblies 4a and 4b includes the drive shaft. 3 a cam portion 14 via the cam portion 14 rolls off a pressure roller 16, so that by the rotation of the drive shaft 3, a lifting movement is generated in a valve assembly 17. Occurring forces are preferably introduced via the pressure roller 16 in the cam portion 14, which are received by the adjacent slide bearing assemblies 4a and 4b. Furthermore, forces can be introduced via the region of the drive shaft 3 projecting out of the housing 2, these forces being absorbed mainly by the slide bearing arrangement 4 a.

FIG. 2 shows a first exemplary embodiment of a geometrical embodiment of a slide bearing arrangement 4 according to the present invention. Shown is the drive shaft 3, which extends through the bearing bush 13 therethrough. The region of the drive shaft 3 forming the sliding bearing arrangement 4 is formed by the bearing shaft section 7. This extends through the bearing bore 6 in the bearing bush 13. The bearing bore 6 is cylindrical, whereas the bearing shaft portion 7 comprises a spherical portion, which is indicated by the radius R. The diameter of the drive shaft 3 is smaller than the diameter of the bearing bore 6. The spherical region, which forms the bearing shaft section 7, extends from the bearing edge 9a to the bearing edge 9b. The bearing edges 9a and 9b are indicated by a dot-dash line, with the central bearing 8 is located centrally between the bearing edges 9a and 9b, which is also indicated by a dashed line. The axis of rotation of the drive shaft 3 is indicated by the drive shaft axis 5, which coincides in their flight with the alignment of the bearing bore 6 as shown in FIG. If now the escape of the drive shaft axis 5 deviates from the alignment of the bearing bore 6, the bearing region of the crowned bearing shaft section 7 moves away from the bearing center 8 and approaches a bearing edge 9a or 9b. By means of the embodiment of the sliding bearing arrangement 4 according to the invention, large pressures between the bearing bore 6 and the bearing shaft section 7 are avoided, so that wear of the sliding bearing arrangement 4 is minimal.

FIG. 3 shows a further exemplary embodiment of the geometric design of the slide bearing arrangement 4. The bearing shaft section of the drive shaft 3 is subdivided into a cylindrical section 10, to which the left-hand side and right-hand side tig each a spherical portion 11 connects and merges into the drive shaft 3. The cylindrical portion 10 has a larger diameter than the drive shaft 3, wherein the transition from the larger diameter of the cylindrical portion 10 to the smaller diameter of the drive shaft 3 is provided by the respective adjacent spherical portion 11. The radii of the crowned sections 11 are indicated by an arrow and an R. Thus, edge formation between the cylindrical portion 10 and the respective crowned portion 11 is avoidable because the cylindrical portion 10 directly merges into the crowned portion.

4 shows a further embodiment of a slide bearing assembly 4 is shown, wherein the bearing shaft portion is in turn formed by a cylindrical portion 10, on both the left side and the right side adjacent a conical portion 12. The cylindrical portion 10 also has, according to this embodiment, a larger diameter than the drive shaft 3, wherein the transition are formed by the respective conical portions 12. In order to minimize the edge formed between the cylindrical portion 10 and the conical portions 12, they can be smoothed by an edge radius.

FIG. 5 shows a further possible slide bearing arrangement 4, which initially comprises a cylindrical bearing shaft section 7. Thus, the drive shaft 3 is uniform, i. with a fixed cross-section in the bearing shaft section 7 via. The spherical contour for generating a bearing air, which is smaller in the bearing center 8 than at the respective bearing edge 9a and 9b, the bearing bush 13 is designed with a spherical bearing bore 6. The bearing bore 6 has a larger diameter in the region of the bearing edges 9a and 9b than in the region of the bearing center 8. According to the illustration in FIG. 5, the transition from the smaller to the larger diameter of the bearing bore 6 is parabolic, with the respective transitions also having a design can, which is created analogously to the stepped contour of the bearing shaft sections 7 according to Figures 2 to 4.

The invention is not limited in its execution to the preferred embodiment given above. Rather, a number of variants conceivable, which makes use of the solution shown even in fundamentally different versions. In particular, the proposed embodiment of the slide bearing arrangement does not extend to the cam drive exemplified in the figures, but the scope of the present invention also extends to feed pumps in the form of an eccentric pump or a crank drive pump.

Claims

claims

1. conveying pump (1), in particular for conveying diesel fuel into a high-pressure accumulator, with a housing (2) and a drive shaft (3) accommodated therein, which is mounted rotatably about a drive shaft axis (5) by means of at least one sliding bearing arrangement (4), the slide bearing arrangement (4) being formed by a bearing bore (6) and a bearing shaft section (7) extending therethrough, characterized in that the slide bearing arrangement (4) projects radially between the bearing shaft section (7) and the bearing bore (7). 6) extending bearing air (X), which in the bearing center (8) has a smaller value than at least one bearing edge (9a, 9b).

2. Feed pump (1) according to claim 1, characterized in that the feed pump (1) comprises a cam drive in order to drive a lifting element which extends into at least one valve assembly (17).

3. Feed pump (1) according to claim 1, characterized in that the feed pump (1) comprises an eccentric drive in order to drive a lifting element which extends into at least one valve assembly (17).

4. Feed pump (1) according to claim 1 to 3, characterized in that the bearing bore (6) has a cylindrical shape and the bearing shaft portion (7) has a spherical shape, wherein the sliding bearing assembly (4) about the bearing center (8) in the direction of Drive shaft axis (5) is symmetrical.

5. Feed pump (1) according to one of the preceding claims, character- ized in that the bearing shaft section (7) in Beriech the bearing center (8) has a cylindrical portion (10) to which in the direction of the drive shaft axis (5) each laterally a spherical portion (11) connects.

6. Feed pump (1) according to claim 4, characterized in that adjoins the cylindrical portion (10) in the direction of the drive shaft axis (5) each laterally a conical section (12).

7. Feed pump (1) according to claim 1 to 3, characterized in that the bearing shaft section (7) is cylindrical and the Lagerboh- tion (6) has a curvature, so that the bearing bore (6) in the bearing center (8) has a smaller Diameter than at the bearing edges (9a, 9b) comprises.

8. Feed pump (1) according to one of the preceding claims, characterized in that the bearing air (X) in the region of the bearing center (8) a

Value of lμm to 150μm, preferably from 10μm to 50μm and particularly preferably 40μm comprises.

9. Feed pump (1) according to one of the preceding claims, character- ized in that the diameter difference of the bearing shaft portion

(7) between the bearing center (8) and the bearing edges (9a, 9b) has a value of lμm to 150μm, preferably from 10μm to 50μm and more preferably from 20μm to 30μm.

10. Feed pump (1) according to any one of the preceding claims, characterized in that the at least one slide bearing assembly (4) comprises a bearing bush (13), and the bearing bore (6) in the bearing bush (13) is formed.

11. Feed pump (1) according to claim 8, characterized in that the bearing bush (13) is made of a sliding bearing material comprising an aluminum material, a bronze material or a plastic material such as a PEEK or PPS.

12. Feed pump (1) according to any one of the preceding claims, characterized in that the drive shaft (3) comprises a cam portion (14) and / or an eccentric portion, and adjacent to each a sliding bearing assembly (4) is provided.