Shaft bearing assembly for a shaft of a turbomachine and turbomachine

Abstract

A shaft bearing assembly (10) for a shaft (11) of a turbomachine is described. The shaft bearing assembly (10) includes the shaft (11) having a radial step (111) provided by the shaft or by a separate element fixed to the shaft. Further, the shaft bearing assembly (10) includes a bearing bush (12) supporting the shaft (11). At least one of an axial surface (121) of the bearing bush (12) facing the radial step (111) and an axial segment of the bearing bush (12) has at least one groove (122) opening into a hole (123), wherein a radial outer side of the at least one groove (122) is delimited by a radial side wall (124), wherein a radial inner side of the groove (122) is open, and wherein a radial cross-sectional area of the at least one groove (122) increases towards the hole (123).

Description

SHAFT BEARING ASSEMBLY FOR A SHAFT OF A TURBOMACHINE AND TURBOMACHINETECHNICAL FIELD

[0001] Embodiments of the present disclosure relate to shaft bearing assemblies for shafts of turbomachines, such as turbochargers, turbo-compounds and electrified turbomachines.BACKGROUND

[0002] Charging systems such as exhaust gas turbochargers are known to be used for increasing the power demand of an internal combustion engine or fuel cell system. In such an exhaust gas turbocharger, a turbine is provided in the exhaust gas path of the internal combustion engine or fuel cell, and a compressor is arranged upstream of the internal combustion engine or fuel cell, which is connected to the turbine via a common shaft. The shaft is typically supported by a shaft bearing supported in a bearing housing. Thus, an exhaust gas turbocharger is generally constituted by a rotor, a bearing assembly for the shaft, flow-guiding housing sections (compressor housing and turbine housing) and a bearing housing. The rotor includes a shaft and both a compressor and turbine wheel.

[0003] With charging of an internal combustion engine or fuel cell by means of an exhaust gas turbocharger, the capacity and therefore the fuel mixture in the cylinders or fuel cell are increased and a noticeable power increase for the engine or fuel cell is thereby gained. Optionally, the energy which is stored within the exhaust gas of an internal combustion engine or fuel cell can be converted into electrical or mechanical energy by means of a power turbine. In this case, instead of a compressor, as in the case of the exhaust gas turbocharger, a generator or a mechanical consumer is connected to the turbine shaft.

[0004] Because of the high process pressure in the turbine-side and in the compressor-side flow region, the shaft of the exhaust gas turbocharger is sealed with a suitable sealing concept in relation to the cavity of the bearing housing. The internal pressure in the cavity of the bearing housing usually corresponds to the atmospheric pressure. The gas pressure in the flow passage of the compressor side and turbine side depends, however, upon the current operating point of the exhaust gas turbocharger and at most operating points lies above the pressure in the cavity of the bearing housing. In certain cases, however, a negative pressure has also to be taken into consideration, for example, in partial load operation or at rest.

[0005] Rotating shafts of exhaust gas turbochargers are usually supported in hydrodynamic fluid film bearings, whereas the oil needed is taken from the oil supply of the internal combustion engine or in case of the fuel cell from an external oil supply. In addition to the oil supply of the bearings, dependent on the application, oil can additionally be used for cooling purposes of the charging system or power turbine. The lube oil supplied to the bearings and cooling holes (typically splash oil bores) accumulates inside the bearing housing, from where it via a drain flows off out of the bearing housing.

[0006] A shaft seal between bearing housing and turbine or compressor is used to avoid oil leakage into the gas paths of these components. Especially idling or part load conditions of internal combustion engines are critical in terms of oil tightness behavior as within these operating conditions, slight overpressures of only few millibars can occur inside the bearing housing. These overpressures are often sufficient enough for a positive pressure gradient across the shaft seal, which means that the pressure inside the bearing housing is higher than the one on the compressor or turbine side. The positive pressure gradient is often the main driver for oil leakage as air and oil are sucked through the seal from the bearing housing into the gas paths of these components. Oil in the sealing area bears the risk of coking which in turn can lead to increased wear and in the worst case to failure of the seal and thus thewhole charging system or power turbine. For this reason, care must always be taken to ensure that shaft seals work properly and seal highly efficiently.

[0007] Accordingly, in view of the above, there is a demand for an improved shaft bearing assembly for a shaft of a turbomachine which at least partially overcome the problems of the state of the art.SUMMARY

[0008] In light of the above, a shaft bearing assembly according to independent claim 1 is provided. Further aspects, advantages, and features are apparent from the dependent claims, the description, and the accompanying drawings.

[0009] More specifically, according to an aspect of the present disclosure, a shaft bearing assembly for a shaft of a turbomachine is provided. The shaft bearing assembly includes the shaft having a radial step provided by the shaft or by a separate element fixed to the shaft. Further, the shaft bearing assembly includes a bearing bush supporting the shaft. At least one of an axial surface of the bearing bush facing the radial step and an axial segment of the bearing bush has at least one groove opening into a hole. A radial outer side of the at least one groove is delimited by a radial side wall, a radial inner side of the at least one groove is open, and a radial cross-sectional area of the at least one groove increases towards the hole.

[0010] Accordingly, compared to the state of the art, an improved shaft bearing assembly is provided. In particular, the shaft bearing assembly beneficially provides for an improved oil tightness. Further, embodiments of the shaft bearing assembly as described herein provide for a redirection of the oil flows emerging from the bearings which in turn helps to reduce the internal oil load of a shaft sealing in the bearing housing of the charging system. Additionally, compared to the state of the art, the shaft bearing assembly as described herein provides for a more compact design, particularly in the axial direction.

[0011] According to another aspect of the present disclosure a turbomachine including a shaft bearing assembly according to any embodiments described herein is provided. In particular, the turbomachine can be a turbocharger, a turbo-compound or an electrified turbomachine.BRIEF DESCRIPTION OF THE DRAWINGS

[0012] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments. The accompanying drawings relate to embodiments of the disclosure and are described in the following:Fig. 1 shows a schematic cross-sectional view of a shaft bearing assembly according to embodiments described herein;Fig. 2 shows a schematic cross-sectional view of a shaft bearing assembly according to further embodiments described herein;Fig. 3 shows a schematic perspective view of a bearing bush according to embodiments described herein;Fig. 4 shows an enlarged portion of Fig. 3;Fig. 5 shows a schematic cross-sectional view of a bearing bush illustrating an axial segment of the bearing bush having at least one groove opening into a hole according to embodiments described herein, andFig. 6 shows a sectional front view along line A-A indicated in Fig. 5.DETAILED DESCRIPTION OF EMBODIMENTS

[0013] Reference will now be made in detail to the various embodiments of the disclosure, one or more examples of which are illustrated in the figures. Within the following description of the drawings, the same reference numbers refer to same components. Generally, only the differences with respect to individual embodiments are described. Each example is provided by way of explanation of the disclosure and is not meant as a limitation of the disclosure. Further, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield yet a further embodiment. It is intended that the description includes such modifications and variations.

[0014] Within the following description of the drawings, the same reference numbers refer to the same or similar components. Generally, only the differences with respect to the individual embodiments are described. Unless specified otherwise, the description of a part or aspect in one applies to a corresponding part or aspect in another embodiment as well.

[0015] With reference to Figs. 1 to 6 a shaft bearing assembly 10 for a shaft 11 of a turbomachine according to embodiments of the present disclosure are described.

[0016] According to embodiments which can be combined with other embodiments described herein, the shaft bearing assembly 10 includes the shaft 11 having a radial step 111. The radial step 111 can be provided by the shaft or by a separate element fixed to the shaft. In particular, the radial step 111 can be an integral part of the shaft or the radial step may be provided by a separate element which is attached to the shaft such during operation the separate element rotates with the shaft. For instance, the separate element fixed to the shaft can be a sleeve. Figs. 1 and 2 show an example in which the radial step 111 is an integral part of the shaft 11. As shown in Figs. 1 and 2, typically the radial step I l l is provided by a step from a first radius R1 to a second radius R2, the second radius R2 being larger than the first radius Rl.Typically, the second radius R2 is R2 > 1.22xRl, particularly R2 > 1.4*R1, more particularly R2 > 1.6xRl.

[0017] Further, as exemplarily shown in Figs. 1 and 2, the shaft bearing assembly 10 includes a bearing bush 12 supporting the shaft 11. At least one of an axial surface 121 of the bearing bush 12 facing the radial step 111 and an axial segment 16 of the bearing bush 12 has at least one groove 122 opening into a hole 123. In other words, the axial surface 121 of the bearing bush 12 facing the radial step 111 and / or the axial segment 16 of the bearing bush 12 have at least one groove 122 opening into a hole 123. Accordingly, it is to be understood that only the axial surface 121 of the bearing bush 12 facing the radial step 111 can have at least one groove 122 opening into a hole 123, only the axial segment 16 of the bearing bush 12 can have at least one groove 122 opening into a hole 123, or both the axial surface 121 of the bearing bush 12 facing the radial step 111 and the axial segment 16 of the bearing bush 12 each can have at least one groove 122 opening into a hole 123. Figures 1 and 2 show exemplary embodiments in which the least one groove 122 is provided in an axial surface 121 facing the radial step 111. Figures 5 and 6 show an exemplary embodiment in which the least one groove 122 is provided in an axial segment 16 of the bearing bush 12. The description of the least one groove 122 and the hole 123 with reference to Figures 3 and 4 can be applied to each of the embodiments described with reference to Figs. 1, 2, 5 and 6. It is to be understood, that although not explicitly shown, two or more axial segments of the bearing bush may be provided with the least one groove 122 as described herein with respect to the axial segment 16.

[0018] Typically, the bearing bush 12 has an aspect ratio AR of radial height Hrof the bearing bush 12 to axial width Wxof the bearing bush 12 of AR < 1. The radial height Hrof the bearing bush can be understood as the difference between an outer radius of the bearing bush and an inner radius of the bearing bush. The axial width Wxof the bearing bush can be understood as the extension of the bearing bush in the axial direction, as for example apparent from Fig. 3. Accordingly, typically the radialheight Hrof the bearing bush corresponds to the radial extension of axial surface 121 as exemplarily shown in FIG. 3. Accordingly, the radial height Hrtypically corresponds to the thickness of the radial wall of the bearing bush.

[0019] In the present disclosure, the least one groove 122 may also be referred to as conveyor groove. Further, the hole 123 may be referred to as drainage hole or drainage bore hole. Accordingly, the expression “at least one groove 122 opening into a hole 123” may be rephrased by “at least one conveyor groove opening in a drainage hole”. In this regard, it is to be noted that a “conveyor groove” is configured for conveying oil towards the drainage hole. The drainage hole is configured for providing a drainage of oil away from the conveyor groove, particularly towards an opposite axial surface of the bearing bush. Further, it is to be understood that during operation the shaft 11 is rotated in direction from the start of the at least one conveyor groove towards the drainage hole of the least one conveyor groove. For better understanding, for the exemplary bearing bush 12 shown in Fig. 3 a shaft (not shown in Fig. 3) extending through the central opening of the bearing bush would be rotated clockwise during operation.

[0020] In the present disclosure, an “axial segment of the bearing bush” can be understood as portion of the bearing bush along the axial direction x. It is to be understood that the axial direction x is in the direction extending along a central axis 17, as exemplarily shown in Figs. 1, 2, 3 and 5. Typically, the central longitudinal axis of the shaft 11 and the central longitudinal axis of the bearing bush 12 coincide and correspond to the central axis 17 shown in the figures.

[0021] With exemplary reference to Figs. 3 and 4, according to embodiments which can be combined with other embodiments described herein, a radial outer side of the at least one groove 122 is delimited by a radial side wall 124. Typically, the radial side wall 124 extends in the circumferential direction along the length of the at least one groove 122. Typically, a radial inner side of the groove 122 is open. In particular, the radial inner open side of the groove 122 extends in the circumferential directionalong the length of the at least one groove 122. In other words, as indicated in Fig. 4, the radial outer side of the bottom 122B of the groove 122 is delimited by the radial side wall 124, whereas the radial inner side of the bottom 122B of the groove 122 is not delimited.

[0022] According to embodiments which can be combined with other embodiments described herein, a radial cross-sectional area of the at least one groove 122 increases towards the hole 123. It is to be understood that the radial cross-sectional area of the at least one groove 122 at a selected angular position about the central axis 17 of the bearing bush 12 is given by the radial width W of the at least one groove 122 times the depth D of the at least one groove 122 at the selected angular position. Accordingly, the radial cross-sectional area of the at least one groove 122 can be changed by changing the radial width W of the at least one groove 122 and / or changing the depth D of the at least one groove 122.

[0023] According to embodiments which can be combined with other embodiments described herein, a width W of the at least one groove 122 increases towards the hole 123. It is to be understood that the width W of the at least one groove 122 may at least partially increase in circumferential direction towards the hole 123. In other words, at least a circumferential segment of the at least one groove 122 may have an increasing width W in a direction towards the hole 123. Alternatively, the width W of the at least one groove 122 may increase in circumferential direction towards the hole 123 over the complete circumferential extension of the at least one groove 122.

[0024] According to embodiments which can be combined with other embodiments described herein, a depth D of the at least one groove 122 increases towards the hole 123. It is to be understood that the depth D of the at least one groove 122 may at least partially increase in circumferential direction towards the hole 123. In other words, at least a circumferential segment of the at least one groove 122 may have an increasing depth D in a direction towards the hole 123. Alternatively, the depth D of the at least one groove 122 may increase in circumferential direction towards the hole123 over the complete circumferential extension of the at least one groove 122. It is to be understood, that according to an alternative implementation the depth D of the at least one groove 122 can be constant in circumferential direction towards the hole 123, particularly over the complete circumferential extension of the at least one groove 122.

[0025] According to embodiments which can be combined with other embodiments described herein, the hole 123 extends from the bottom 122B of the at least one groove 122 through the bearing bush 12 to an opposite axial surface of the bearing bush 12. Typically, the hole 123 extends in an axial direction x of the shaft 11. Accordingly, it is to be understood that the hole 123 may extend parallel to the central axis 17 of the bearing bush 12.

[0026] According to embodiments which can be combined with other embodiments described herein, the at least one groove 122 extends in a circumferential direction over at least 10%, particularly over at least 20%, of at least one of the axial surface 121 and the axial segment 16. In other words, the axial surface 121 facing the radial step 111 may include at least one groove 122 which extends in a circumferential direction about the central axis 17 of the bearing bush 12 over at least 10%, particularly over at least 20%, of the axial surface 121. Additionally or alternatively, the axial segment 16 may include at least one groove 122 which extends in a circumferential direction about the central axis 17 of the bearing bush 12 over at least 10%, particularly over at least 20%, of the axial segment 16.

[0027] According to embodiments which can be combined with other embodiments described herein, the at least one groove 122 includes two or more grooves, particularly three or more grooves, more particularly four or more grooves. Typically, the grooves are circumferentially evenly distributed within at least one of the axial surface 121 of the bearing bush 12 facing the radial step 111 and the axial segment 16 of the bearing bush 12. It is to be understood that each of the features described with respect to the at least one groove 122 can also be applied toembodiments with two or more grooves. Accordingly, each of the two or more grooves may open into a respective drainage hole.

[0028] With exemplary reference to Fig. 3, according to embodiments which can be combined with other embodiments described herein, the bearing bush 12 comprises at least one radial oil supply hole 126. Typically, the at least one radial oil supply hole 126 includes two or more radial oil supply holes, particularly three or more radial oil supply holes. Typically, the two or more radial oil supply holes are circumferentially evenly distributed.

[0029] With exemplar reference to Fig. 3, it is to be understood that typically the angular positions of radial oil supply holes 126 are located between the angular positions of the drainage holes 123. It is to be understood, that the angular position refers to an angular position about the central axis 17. In particular, the angular positions of radial oil supply holes 126 can be located between a drainage hole 123 of a first conveyor groove and beginning of a neighboring second conveyor groove.

[0030] According to embodiments which can be combined with other embodiments described herein, the bearing bush 12 is a full-floating bearing bush. Alternatively, the bearing bush 12 can be a semi-floating bearing bush. In particular, as exemplarily shown in Fig. 3, the semi-floating bearing bush may have a reception 127 on a radial outer surface of the bearing bush 12 for receiving a blocking element for blocking a rotation of the bearing bush 12 with respect to a bearing flange 13. Typically, two or more receptions 127, e.g. three or more receptions, may be provided on the radial outer surface of the bearing bush 12 for receiving blocking elements, respectively. The two or more receptions 127 may be circumferentially evenly distributed about the central axis 17 of the bearing bush 12.

[0031] Accordingly, it is to be understood depending on the rotordynamic requirements of the turbomachine, the radial bearing bush can be designed as so- called full-floating bearing or semi-floating bearing. The difference is that a fullfloating bearing bush rotates likewise the shaft at approximately half of the shaftspeed. A semi-floating bearing bush is fixed in position and the lubricating gap between bearing support and bearing bush purely acts as squeeze film damper with non-rotation of the oil film. Therefore, full-floating bearings exhibit an oil share between inner and outer lubricating gap which is roughly equal. In contrast, semifloating bearings show a significantly uneven oil share at which up to ninety percent of the overall oil consumption of the radial bearing is conveyed by the inner lubricating gap.

[0032] With exemplary reference to Fig. 1, according to embodiments which can be combined with other embodiments described herein, a radial inner side of the axial surface 121 may include a chamfer 128. Typically, the chamfer 128 is provided over the complete circumference of the radial inner side. Providing a chamfer as described herein can be beneficial for improving oil conveyance, particularly away from the radial step 111.

[0033] According to embodiments which can be combined with other embodiments described herein, the shaft bearing assembly 10 includes a radial gap G1 between a bearing flange 13 supporting the bearing bush 12 and the shaft 11. Alternatively, the radial gap G1 may be provided between a separate element 14 attached to the bearing flange 13 and the shaft 11. Typically, the gap G1 provides a throttle gap between a shaft sealing side 101 and a shaft bearing side 102 of the shaft bearing assembly 10. As exemplarily shown in Figs. 1 and 2, the axial position of the radial step 111 may represent the boundary between the shaft sealing side 101 and the shaft bearing side 102. As schematically shown in Figs. 1 and 2, a shaft sealing 15 can be provided at the shaft sealing side 101.

[0034] According to embodiments which can be combined with other embodiments described herein, the radial gap G1 has a radial width WGI of 0.05 mm < WGI < 0.5 mm.

[0035] According to embodiments which can be combined with other embodiments described herein a ratio L1 / WG1of an axial length LI of the gap G1 to the radial width Woi is 10 < L1 / WGI < 20, particularly L1 / WGI = 15±2.5.

[0036] With exemplary reference to Fig. 2, according to embodiments which can be combined with other embodiments described herein, the bearing bush 12 has a radial outer, axially extending protrusion 129 which at least partially extends over the radial step 111 for providing a radial gap G2 between the axially extending protrusion 129 and the shaft 11 or the separate element (not shown) fixed to the shaft providing the radial step 111. Typically, an axial gap G4 between the protrusion 129 of bearing bush and the bearing flange (not shown configuration) or a separate element 14 attached to the bearing flange 13 (shown configuration of Figs. 1 and 2) is provided. However, it is to be understood that in the case that the axially extending protrusion 129 is implemented, the radial gap G1 and the axial gap G4 may be omitted.

[0037] According to embodiments which can be combined with other embodiments described herein a ratio L2 / WG2 of an axial length L2 of the gap G2 to the radial width WG2 is 45 < L2 / WG2 < 105, particularly L1 / WG2 = 70±15.

[0038] According to embodiments which can be combined with other embodiments described herein a ratio (R1-R2) / WG3 is 20 < (R1-R2) / WG3 < 40, particularly (Rl- R2) / W G3 = 30 ±6, wherein R1-R2 is the radial length of the axial gap G3 between the surface 121 of the bearing bush 12 facing the radial step 111 and the radial step 111, and wherein WG3 is the axial width of the gap G3.

[0039] According to embodiments which can be combined with other embodiments described herein, the radial gap G2 between the axially extending protrusion 129 and the shaft 11 has a radial width WG2 of 0.025 mm < WG2 < 0.5 mm.

[0040] Providing one or more of the gaps Gl, G2, G3 and G4 according to configurations as described herein is beneficial for improving oil tightness at the interface between the bearing bush 12 and the shaft 111.

[0041] It is to be understood that embodiments of the shaft bearing assembly as described herein may be applied to any kind of turbomachines, for example turbochargers, turbo-compounds or electrified turbomachines.

[0042] Accordingly, according to another aspect of the present disclosure a turbomachine, particularly at least one of a turbocharger, a turbo-compound and electrified turbomachine, including a shaft bearing assembly according to any embodiments described herein is provided. For example, the electrified turbomachine may be connected to a fuel cell.

[0043] Accordingly, in view of the above it is to be understood that embodiments described herein beneficially provide for an improved shaft bearing assembly and an improved turbomachine. In particular, embodiments of the present disclosure beneficially provide for an improved oil tightness. Further, embodiments as described herein provide for a redirection of the oil flows emerging from the bearings which in turn helps to reduce the internal oil load of a shaft sealing in the bearing housing of the charging system. Additionally, compared to the state of the art, embodiments of the present disclosure provide for a more compact design, particularly in the axial direction.

[0044] While the foregoing is directed to embodiments of the disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.REFERENCE NUMBERS10 shaft bearing assembly101 shaft sealing side102 shaft bearing side11 shaft111 radial step12 bearing bush121 axial surface of bearing bush122 groove / convey or groove122B bottom of the groove123 hole / drainage hole124 radial side wall of the groove126 oil supply hole127 reception128 chamfer129 protrusion13 bearing flange14 separate element15 shaft sealing16 axial segment17 central axis18 entrance hole x axial direction r radial directionR1 first radiusR2 second radiusG1 radial gap between oil catch plate and shaftG2 radial gap between protrusion of bearing bush and shaftG3 axial gap between axial surface of the bearing bush facing the radial step of the shaft and the axial step surfaceG4 axial gap between protrusion of bearing bush and bearing flange or between protrusion of bearing bush and a separate element attached to the bearing flangeLI length of G1L2 length of G2 W width of grooveD depth of groove

Claims

CLAIMS1. A shaft bearing assembly (10) for a shaft (11) of a turbomachine, comprising:- the shaft (11) having a radial step (111) provided by the shaft or by a separate element fixed to the shaft,- a bearing bush (12) supporting the shaft (11), wherein at least one of an axial surface (121) of the bearing bush (12) facing the radial step (111) and an axial segment (16) of the bearing bush (12) has at least one groove (122) opening into a hole (123), wherein a radial outer side of the at least one groove (122) is delimited by a radial side wall (124), wherein a radial inner side of the at least one groove (122) is open, and wherein a radial cross-sectional area of the at least one groove (122) increases towards the hole (123).

2. The shaft bearing assembly (10) of claim 1, wherein a width W of the at least one groove (122) increases towards the hole (123).

3. The shaft bearing assembly (10) of claim 1 or 2, wherein the hole (123) extends from a bottom of the at least one groove through the bearing bush (12) to an opposite axial surface of the bearing bush (12), particularly the hole (123) extending in an axial direction x of the shaft (11).

4. The shaft bearing assembly (10) of any of claims 1 to 3, wherein the at least one groove (122) extends in a circumferential direction over at least 10%, particularly over at least 20%, of at least one of the axial surface (121) and the axial segment.

5. The shaft bearing assembly (10) of any of claims 1 to 4, wherein the at least one groove (122) comprises two or more grooves, particularly three or more grooves, more particularly four or more grooves, wherein the grooves are circumferentially evenly distributed within at least one of the axial surfacesegment of the bearing bush (12).

6. The shaft bearing assembly (10) of any of claims 1 to 5, wherein the bearing bush (12) comprises at least one radial oil supply hole (126).

7. The shaft bearing assembly (10) of any of claims 1 to 6, wherein the bearing bush (12) is a full-floating bearing bush or a semi-floating bearing bush, particularly the semi-floating bearing bush having a reception (127) on a radial outer surface of the bearing bush (12) for receiving a blocking element for blocking a rotation of the bearing bush (12) with respect to a bearing flange (13).

8. The shaft bearing assembly (10) of any of claims 1 to 7, wherein a radial inner side of the axial surface (121) comprises a chamfer (128).

9. The shaft bearing assembly (10) of any of claims 1 to 8, further comprising a radial gap (Gl) between a bearing flange (13) supporting the bearing bush (12) or a separate element (14) attached to the bearing flange (13) and the shaft (11), particularly wherein the gap (Gl) provides a throttle gap between a shaft sealing side (101) and a shaft bearing side (102) of the shaft bearing assembly (10).

10. The shaft bearing assembly (10) of claim 9, wherein the radial gap (Gl) has a radial width WGI of 0.05 mm < WGI < 0.5 mm.

11. The shaft bearing assembly (10) of any of claims 1 to 10, wherein the bearing bush (12) has a radial outer, axially extending protrusion (129) which at least partially extends over the radial step (111) for providing a radial gap (G2) between the axially extending protrusion (129) and the shaft (11).

12. The shaft bearing assembly (10) of claim 11, wherein the radial gap (G2) between the axially extending protrusion (129) and the shaft (11) has a radial width WG2 of 0.025 mm < WG2 < 0.5 mm.

13. The shaft bearing assembly (10) of any of claims 1 to 12, wherein the bearing bush (12) has an aspect ratio AR of a radial height Hrof the bearing bush (12) to an axial width Wxof the bearing bush (12) of AR < 1, wherein the radial height Hrof the bearing bush (12) is the difference between an outer radius of the bearing bush and an inner radius of the bearing bush.

14. A turbomachine, particularly at least one of a turbocharger, a turbo-compound and electrified turbomachine, comprising a shaft bearing assembly (10) according to any of claims 1 to 13.

Images