Bearing bush of a turbocharger and turbocharger

Abstract

A bearing bush of a turbocharger for radially mounting a shaft of the turbocharger. The bearing bush on an inner surface facing the shaft to be mounted, which forms a running surface of the bearing bush, has a microstructuring of multiple cup-shaped recesses at least in sections. The recesses have a maximum depth.

Claims

1. A bearing bush of a turbocharger configured to radially mount a shaft of the turbocharger, comprising: an inner surface of the bearing bush facing the shaft to be mounted, which forms a running surface of the bearing bush; at least one lubricating pocket arranged in the running surface of the bearing bush; a radially extending lubricating passage configured to supply a lubricant; a microstructuring arranged in the running surface of the bearing bush outside lubricating pockets configured as multiple cup-shaped recesses at least in sections of the inner surface of the bearing bush, wherein the cup-shaped recesses have a maximum depth, such that:
s.sub.LW/t.sub.MAX≥0.1 and/or
(h.sub.SS+t.sub.MAX)*v.sub.MAX/v.sub.SM≤1800, wherein: s.sub.LW is an absolute clearance between the bearing bush and the shaft, t.sub.MAX is a maximum depth of the cup-shaped recesses, h.sub.SS is a minimum bearing clearance between the bearing bush and the shaft during operation, v.sub.MAX is a maximum circumferential speed of the shaft, and v.sub.SM is a kinematic viscosity of the lubricant utilised for lubrication.

2. The bearing bush according to claim 1, wherein the microstructuring is provided at least into sections of the running surface of the bearing bush that are positioned in a region of a converging lubricating gap section between the bearing bush and the shaft.

3. The bearing bush according to claim 1, wherein the depth of the cup-shaped recesses varies between respective cup-shaped recesses.

4. The bearing bush according to claim 1, wherein in a radial viewing direction in plan view of the cup-shaped recesses a contour of a respective cup-shaped recesses varies.

5. The bearing bush according to claim 1, wherein each of the cup-shaped recesses are contoured one of: rectangularly, triangularly, trapezoidally, and round.

6. The bearing bush according to claim 1, wherein in an axial viewing direction a cross-sectional surface of the cup-shaped recesses varies.

7. The bearing bush according to claim 1, wherein seen in a direction of rotation of the shaft, wherein at each respective point along a groove base of the cup-shaped recesses extends, linearly and/or curved with a constant and/or increasing and/or decreasing depth.

8. The bearing bush according to claim 1, wherein the cup-shaped recesses of the microstructuring forms at least one cluster of equidistant or non-equidistant recesses, wherein the recesses in the respective cluster are linearly offset relative to one another.

9. The bearing bush according to claim 1, wherein the at least one lubricating pocket comprises at least a lead in region a center region and a lead out region, wherein the center region has a greater redial depth than the lead in region and the lead out region.

10. The bearing bush according to claim 9, wherein the lead in region and the lead out region have radially increasing depths that increase circumferentially towards the center region.

11. The bearing bush according to claim 1, wherein the cup-shaped recesses of the microstructuring forms at least one cluster of equidistant or non-equidistant recesses, wherein the recesses in the respective cluster are twisted relative to one another.

12. A turbocharger, comprising: a shaft; a turbine for expanding a first medium comprising: a turbine rotor; a compressor for compressing a second medium utilising energy extracted in the turbine during the expansion, comprising: a compressor rotor that is coupled to the turbine rotor via the shaft; and at least one bearing bush configured to radially mount the shaft, wherein an inner surface of the bearing bush facing the shaft to be mounted, which forms a running surface of the bearing bush; at least one lubricating pocket arranged in the running surface of the bearing bush; a radially extending lubricating passage configured to supply a lubricant; a microstructuring arranged in the running surface of the bearing bush outside lubricating pockets configured as multiple cup-shaped recesses at least in sections of the inner surface of the bearing bush, wherein the cup-shaped recesses have a maximum depth, such that:
s.sub.LW/t.sub.MAX≥0.1 and/or
(h.sub.SS+t.sub.MAX)*v.sub.MAX/v.sub.SM≤1800, wherein: s.sub.LW is an absolute clearance between the bearing bush and the shaft, t.sub.MAX is a maximum depth of the cup-shaped recesses, h.sub.SS is a minimum bearing clearance between the bearing bush and the shaft during operation, v.sub.MAX is a maximum circumferential speed of the shaft, and v.sub.SM is a kinematic viscosity of the lubricant utilised for lubrication.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Preferred further developments of the invention are obtained from the subclaims and the following description. Exemplary embodiments of the invention are explained in more detail by way of the drawing without being restricted to this. There it shows:

(2) FIG. 1 is an axial section through a bearing bush;

(3) FIG. 2 is a radial section through a bearing bush together with a mounted shaft;

(4) FIG. 3a-3d are different types of microstructuring of multiple cup-shaped recesses in plan view;

(5) FIG. 4a-4h are each a cross section through a cup-shaped recess; and

(6) FIG. 5a-b are cross sections through multiple cup-shaped recesses each.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

(7) The invention relates to a bearing bush of a turbocharger for the radial mounting of a shaft of the turbocharger. The fundamental construction of such a bearing bush is shown in FIG. 1. Accordingly, FIG. 1 shows a bearing bush 1 in cross section, which comprises a recess 2 for guiding and mounting a shaft 3. FIG. 2 shows a cross section rotated by 90° through the bearing bush 1 together with the shaft 3.

(8) The recess 2 of the bearing bush 1, which serves for guiding and mounting the shaft 3, is bounded by an inner surface 4 seen in the axial section of FIG. 1, which in the middle comprises a cylindrically contoured section 4a and at axial ends sections 4b-4c that are contoured conically or truncated-cone like. The cylindrically contoured section 4a of the inner surface 4 of the running bush 1 defines a running surface 56 of the bearing bush 1.

(9) As is evident from FIG. 1, lubricating passages 9 extending in the radial direction are introduced into the bearing bush 1, which serve for supplying the bearing bush 1 with a lubricant. Accordingly, a lubricating gap 7 is formed between the running surface 5 of the bearing bush 1 and the shaft to be mounted, which is to be supplied with the lubricant. The lubricating passage 6 extend in the radial direction through the bearing bush 1 and lead into the lubricating pockets 8 in the region of the running surface 5. In the exemplary embodiment, three such lubricating pockets 8 are distributed over the circumference of the bearing bush 1, which serve for supplying the lubricating gap 7 with lubricant.

(10) FIG. 2 shows a possible relative position between shaft 3 and running surface 5 of the bearing bush 1 that can form during the operation. Accordingly, it is evident from FIG. 2, that the lubricating gap 7 seen in the circumferential direction does not have a uniform dimension but that the radial thickness of the lubricating gap 7 changes. In FIG. 2, the dimension h.sub.SS characterises the so-called minimum bearing clearance between the running surface 5 of the bearing bush 1 and the shaft 3. Seen in the direction of rotation and thus in the movement direction 9 of the shaft 3, the lubricating gap 7 has a lubricating gap section 7a, which converges in the direction of this minimum bearing clearance h.sub.SS, and a lubricating gap section 7b, that seen in the movement direction 9 diverges away from this minimum bearing clearance h.sub.SS.

(11) In the case of the bearing bush 1 according to one aspect of the invention, the running surface 5 of the bearing bush 1 comprises a microstructuring of multiple cup-shaped recesses 10 at least in sections. The recesses 10 have a maximum depth so that the following applies:
V=s.sub.LW/t.sub.MAX≥0.1
and/or
Re=(h.sub.SS+t.sub.MAX)*v.sub.MAX/v.sub.SM≤1:800,
wherein
s.sub.LW is the absolute clearance between bearing bush 1 and shaft 3,
T.sub.MAX is the maximum depth of the cup-shaped recesses 10,
h.sub.SS is the minimum load clearance between bearing bush 1 and shaft 3,
v.sub.MAX is the maximum circumferential speed of the shaft 3,
v.sub.SM is the kinematic viscosity of a lubricant utilised for the lubrication.

(12) The absolute clearance between bearing bush 1 and shaft 3 is the difference between an inner diameter of the running surface 5 of the bearing bush 1 and an outer diameter of the section of the shaft 3 mounted in the bearing bush 1.

(13) Preferentially, the following applies:
0.1≤V≤
and/or
Re=(h.sub.SS+t.sub.MAX)*v.sub.MAX/v.sub.SM≤1800.

(14) The bearing bush 1 is less susceptible to wear in particular when the cup-shaped recesses 10 of the microstructuring fulfil at least one, preferentially both of the above conditions.

(15) As already explained, the microstructuring is introduced into the running surface of the bearing bush 1 at least in sections.

(16) Here, the microstructuring is introduced at least into such sections of the running surface 5 of the bearing bush 1 as are positioned in the region of the converging lubricating gap section 7a between bearing bush 1 and shaft 3 or bound the converging lubricating gap section 7a on the outside.

(17) The microstructuring, seen in the circumferential direction, can also be introduced into the running surface over the entire region of the running surface 5 except for the lubricating pockets 8.

(18) FIGS. 3a, 3b, 3c and 3d each show in radial viewing direction a plan view of a section of the running surface 5 of the bearing bush 1, which comprises cup-shaped recesses 10 for providing the microstructuring.

(19) In FIG. 3a, these cup-shaped recesses 10 are arranged in the form of columns and rows forming a cluster 11, wherein in FIG. 3a in each column or each row the recesses 10 are arranged equidistantly relative to one another and wherein seen in the plan view, the cup-shaped recesses 10 are all rectangularly contoured identically. In FIG. 3b, a modification is shown in which all recesses are rectangularly contoured in the plan view but the recesses 10, based on directly adjacent rows, are linearly offset relative to one another. In FIG. 3c, all cup-shaped recesses 10 in turn are contoured rectangularly, but have contours in the plan view that deviate from one another in their size. In FIG. 3d, not only rectangular, cup-shaped recesses are shown but additionally cup-shaped recesses which are contoured trapezoidally, namely both convergingly and divergingly seen in the movement direction 9 of the shaft 3. The invention is not limited to rectangularly or trapezoidally contoured cup-shaped recesses 10, but the cup-shaped recesses can rather also be contoured triangularly, round, circularly, elliptically, or the like. The cup-shaped recesses 10 cannot only be linearly offset relative to one another seen in the movement direction 9 of the rotating shaft 3 and seen transversely to the movement direction 9 of the shaft 3 but the cup-shaped recesses can also be twisted relative to one another.

(20) FIGS. 4a, 4b, 4c, 4d, 4e, 4f, 4g and 4h each show possible cross section through a cup-shaped recess 10 of the microstructuring on the running surface 5 of the bearing bush 1.

(21) In FIG. 4a, the cup-shaped recess 10 is contoured rectangularly, namely with a groove base 10a that is constant seen in the movement direction 9 and thus a constant depth of the cup-shaped recess 10 seen in the movement direction 9. The groove base 10a and thus the depth of the cup-shaped recess 10 is also constant in the movement direction 9 in FIG. 4d, likewise in FIG. 4f, wherein however in FIGS. 4d and 4f boundaries adjoining the groove base 10a do not run perpendicularly to the groove base 10a but are inclined relative to the same. In FIGS. 4b and 4c as well as in FIG. 4e, the groove base 10 is inclined in the movement direction 9 at least in sections, so that in FIG. 4b the depth of the cup-shaped recess 10 seen in the movement direction 9 changes convergingly and in FIGS. 4c and 4e divergingly. In FIGS. 4g and 4h, the groove base 10a of the respective cup-shaped recess 10, in contrast with the exemplary embodiments of FIGS. 4a to 4f, is not contoured linearly but rather curved, namely in FIG. 4g curved towards the outside in the direction of the shaft 3 and in FIG. 4b curved towards the inside away from the shaft 3.

(22) FIG. 5a, 5b show a cross section through the bearing bush 4a and shaft 3 analogously to the FIGS. 4a to 4h, however not through a cup-shaped recess 10, but in each case through multiple cup-shaped recesses 10 which seen in the movement direction 9 of the shaft 3 are positioned one behind the other. In FIG. 5a, all cup-shaped recesses 10 have an identical depth while in FIG. 5b the depth of the cup-shaped recesses 10 varies.

(23) Accordingly, the invention relates to a bearing bush 1 for a turbocharger having a defined microstructuring in the region of its running surface 5. A shaft section of the shaft 3 mounted in the bearing bush 1 can be embodied smooth or likewise have a microstructuring.

(24) With the microstructuring of the running surface 5 of the bearing bush 1, the susceptibility to wear of the bearing bush 1 is reduced in particular during the start-stop operation.

(25) The cup-shaped recesses 10 form a type of lubricant reservoir for the start-stop operation. Furthermore, the cup-shaped recesses 10 improve the rotor-dynamic support behaviour. On the whole, the rotor-dynamic behaviour of the bearing bush 1 can be improved. The susceptibility to wear of the bearing bush 1 is reduced.

(26) The bearing bush 1 can be secured against rotation or alternatively rotate relative to the shaft 3.

(27) Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.