Radial foil bearing and method for producing radial foil bearing

Abstract

The invention relates to a radial foil bearing, comprising a rotor, a cover foil and a spring foil, which rotor is mounted such that it can rotate about an axis of rotation in a bearing cylinder by means of the radial foil bearing after a lifting rotational speed has been reached, forming a gas film. In order to improve the manufacturability of the radial foil bearing and / or the functionality of the radial foil bearing during operation in a gas delivery system, the bearing cylinder is equipped with only one groove extending in the axial direction, in which groove the radial foil bearing is arranged, at least one first foil end section having an outlet edge rests on the long groove edge of the groove in a planar manner, at least one second foil end section having an inlet edge is spaced apart from the first foil end section in the groove by the inlet edge thereof, the first foil end section is spaced apart from the short groove edge by the outlet edge thereof, and at least one second foil end section having an outlet edge is spaced apart from the short groove edge by the outlet edge thereof. And the short groove edge is bent from the long groove edge.

Description

Field of the Invention

[0001] The present invention relates to a radial foil bearing having a rotor, a cover foil, and a spring foil, the rotor being supported rotatably about a rotational axis in a bearing housing in the presence of a formed gas film by the radial foil bearing after reaching a lift-off speed. In addition, the present invention relates to a method for manufacturing a radial foil bearing of this type. Background Art

[0002] For example, foil bearings, in particular radial foil bearings, are known from German published documents DE 10 2018 222 572 A1 and DE 10 2018 222 603 A1. A foil bearing of this type is used, for example, in an air compressor of a fuel cell system to radially support a rotor shaft of an electric motor drive of the air compressor. The spring foil of a radial foil bearing of this type is disclosed, for example, in US Patent US 5,427,455, where the spring foil is equipped with a plurality of spring elements, which form a cantilever spring pattern in the radial foil bearing. Summary of the Invention

[0003] The object of the present invention is to improve the radial foil bearing with respect to the manufacturability of the radial foil bearing and / or the function of the radial foil bearing during operation in a gas delivery device, in particular in an air compressor, where very high speeds, for example, one hundred thousand revolutions per minute, can occur.

[0004] The radial foil bearing has a rotor, a covering foil, and a spring foil. The rotor is supported in a bearing housing in a rotatable manner about a rotational axis by means of the radial foil bearing in the case of a constructed gas film after reaching the lift-off speed. In the case of this radial foil bearing, this task is solved in the following way: The bearing housing is equipped with only one axially extending groove. In this groove, at least one first foil end section having an outlet edge lies against the long groove side of the groove in a planar manner. Here, at least one second foil end section having an inlet edge is spaced apart from the first foil end section in the groove by its inlet edge. Here, the first foil end section is spaced apart from the short groove side by its outlet edge, and the short groove side bends out from the long groove side. The term "axial" refers to the rotational axis of the rotor. Axial means in the direction of the rotational axis or parallel to the rotational axis. Similarly, radial means transverse to the rotational axis. Compared with a conventional radial foil bearing having grooves, the bearing foils advantageously do not need to cross according to the finger principle as disclosed in German published document DE 10 2019 210 456 A1 because their ends are spaced apart from each other in the groove. Thereby, the assembly is significantly simplified. The thermally induced and material-induced thermal expansion of the bearing foils in the circumferential direction can occur particularly advantageously without the bearing foils colliding with each other or with the short groove side. The desired spacing of the foil end sections can be designed based on empirical values. The covering foil and the spring foil are also referred to as bearing foils. For example, if the spring foil is also arranged between the covering foil and the bearing housing in the region of the groove in the installed state, the planar contact of the first foil end section against the long groove side of the groove relates to the spring foil. For the case where the spring foil is not arranged or not completely arranged between the covering foil and the bearing housing in the groove, the first groove section lying against the long groove side relates to the covering foil. Advantageously, it is not necessary to pre-bend the bearing foils. Thereby, the manufacture of the radial foil bearing is simplified. In addition, it is thus ensured in a simple manner that the bearing foils lie against the long groove side or against each other in a planar manner with their first foil end sections after assembly. The long groove side of the groove extends substantially tangentially. Advantageously, a converging lubrication gap is produced at the inlet edge of the groove. Advantageously, the course of the long groove side of the groove is based on the of course predictable course of the bearing foils after assembly. Advantageously, the edge between the short groove side and the inner contour of the bearing housing is rounded, for example by machining or deburring. The long groove side of the groove extends substantially tangentially with respect to the inner contour of the bearing housing. However, the long groove side does not need to extend precisely tangentially with respect to the inner contour of the bearing housing. A small angle with respect to the tangent, for example a small angle of less than twenty degrees, is possible and may also be advantageous. The groove angle between the long groove side and the short groove side is, for example, approximately ninety degrees. Preferably, the inner contour of the bearing housing is provided with at least one non-circular portion for forming a bearing gap between the covering foil and the rotor.

[0005] One preferred embodiment of a radial foil bearing is characterized in that the groove has a triangular or quadrilateral groove cross-section. It is accepted here that the anti-twist portion formed by the groove only functions properly in the rotor rotation direction. A groove having a triangular groove cross-section is also referred to as a triangular groove. A geometrically simple embodiment of the triangular groove allows cost-effective cutting production with a broaching tool. With this triangular groove, the amount of contact and force acting on the bearing foil and the rotor required to form the holding function can be kept to a minimum.

[0006] Another preferred embodiment of a radial foil bearing is characterized in that the cover foil and the spring foil are formed from flat and not pre-bent foil material, and the cover foil and the spring foil are also referred to as bearing foils. By consciously omitting clamping or similar fixing types during the preparation of the bearing foils, adverse deformations and prestresses acting on the rotor are minimized, and the clamping moments at the contact points and / or fixing points are also minimized. However, if necessary, the bearing foils can also be pre-bent. However, especially in the region of the outlet edge, a tangentially finishing end is advantageous.

[0007] Another preferred embodiment of a radial foil bearing is characterized in that the cover foil and the spring foil each have a rectangular configuration. In this way, the bearing foils can be manufactured cost-effectively and with simple tools, such as by stamping. The cover foil is implemented in a closed manner, that is, without notches or voids.

[0008] Another preferred embodiment of a radial foil bearing is characterized in that the spring foil is equipped with spring elements that resiliently abut against the inner contour of the bearing cylinder, and the spring foil does not have spring elements in the groove. For example, the spring foil is implemented like a conventional spring foil or similarly to a conventional spring foil. To form the spring function of the spring foil, the spring foil has, for example, spring elements that can be implemented as spring tabs.

[0009] Another preferred embodiment of a radial foil bearing is characterized in that the spring foil abuts against the long groove side of the groove in a planar manner in the groove, and the cover foil abuts against the spring foil in a planar manner in the groove. The planar or nearly planar contact on the long groove side prevents the foil from bending undesirably when the rotor starts in its driving rotation direction.

[0010] Another preferred embodiment of the radial foil bearing is characterized in that the grooves occupy less than one tenth, preferably less than one fifteenth, of the inner circumference of the bearing sleeve in the circumferential direction. The minimum extension scale of the grooves on the inner circumference of the bearing sleeve in the circumferential direction, for example, close to twenty degrees out of a total of three hundred and sixty degrees of an arc, can most efficiently allow a large bearing surface for constructing at least one load-bearing lubricating film from the gas used. This is beneficial for the rotor to be lifted earlier as desired during start-up and shutdown processes, and thus beneficial for the high service life of the radial foil bearing with a rotor.

[0011] Another preferred embodiment of the radial foil bearing is characterized in that the bearing foils are fixed to each other and / or in the grooves, especially on the long groove sides of the grooves, in a material-locking, force-locking and / or material-locking manner. Material-locking fixation is achieved, for example, by laser spot welding. Advantageously, the arching caused by welding is sufficiently far from the load-bearing air gap of the radial foil bearing. In a special embodiment, the grooves can also have a substantially rectangular groove cross-section. However, advantageously, the substantially rectangular groove cross-section is configured such that the surface contact of the first foil end section on the long groove side described above is ensured.

[0012] Another preferred embodiment of the radial foil bearing is characterized in that the two bearing foils are fixed to each other and / or surface-to-surface in a material-locking manner on the long groove sides of the grooves. Preferably, the material-locking fixation is achieved by welding, for example, by laser welding. In this way, the two bearing foils can be stably fixed not only to each other but also to the long groove sides of the grooves in a simple manner.

[0013] Another preferred embodiment of the radial foil bearing is characterized in that the two bearing foils are fixed to the long groove sides of the grooves by fixing devices. The fixing devices are, for example, clamping plates or flat head screws. For this purpose, the bearing sleeve has, for example, holes, which are advantageously provided with threads.

[0014] Another preferred embodiment of the radial foil bearing is characterized in that the fixing part is combined with a gap that starts from the groove and extends in the extension of the long groove side. Advantageously, a fixing tab engages into the gap, and the fixing tab is preferably provided on the covering foil for this purpose.

[0015] In the method for manufacturing the radial foil bearing described above, the above task is alternatively or additionally solved by the following means: the bearing foils are axially pushed into the bearing sleeve by means of an insertion tool. By omitting clamping or similar fixation during assembly, adverse deformations and prestresses acting on the rotor are minimized.

[0016] In addition, the present invention relates to a bearing sleeve, a covering foil, a spring foil and / or a rotor for the radial foil bearing described above. The mentioned components can be handled individually.

[0017] Particularly advantageously, a radial foil bearing is used in an air compressor to support a shaft to which at least one rotating wheel, such as a compressor rotating wheel, is fastened at an end thereof. The air compressor is also referred to as a fluid machine. The shaft with the rotating wheel is also referred to as a rotor.

[0018] The invention may also relate to an air compressor preferably driven by an electric motor, which has a rotor as described above and is supported by at least one radial foil bearing as described above.

[0019] Other advantages, features and details of the invention result from the following description, in which different embodiments are described in detail with reference to the drawings. Description of the Drawings

[0020] The drawings show:

[0021] Figure 1 a motor in a longitudinal sectional view, which has a multi-piece rotor shaft;

[0022] Figure 2 a radial foil bearing according to a first embodiment in a cross-sectional view, which has triangular grooves;

[0023] Figure 3 shows Figure 2 a strongly exaggerated non-circular inner contour of the radial foil bearing in ; and

[0024] Figures 4 to 7 shows enlarged segments according to three different embodiments, Figure 2 in. Detailed Description

[0025] In Figure 1 a longitudinally sectioned view shows an electrically driven fluid machine 1, which has a compressor wheel 2 and a turbine 4. The compressor wheel 2 is arranged on the compressor side 3 of the fluid machine 1. The turbine 4 is arranged on the turbine side 5 of the fluid machine 1.

[0026] The turbine 4 is drivingly connected to the compressor wheel 2. The two wheels 2 and 4 belong to a working wheel 6. For a torsion-resistant connection between the compressor wheel 2 and the turbine 4, the working wheel 6 includes a motor shaft 7. The motor shaft 7 is implemented as a hollow shaft and is rotatable about a rotational axis 8.

[0027] For electric drive, the fluid machine 1 includes an electric motor 9. The electric motor 9 is implemented as an electric motor, which has a motor housing 10 and a motor winding 11. A magnet 12 implemented as a permanent magnet is arranged in the motor shaft 7 implemented as a hollow shaft.

[0028] The compressor wheel 2 of the fluid machine 1 is driven on the one hand via a turbine 4 when operating in a fuel cell system. In addition, the compressor wheel 2 is driven via an electric motor 9.

[0029] The impeller 6 with the motor shaft 7 is rotatably supported in the motor housing 10 of the electric motor 9 by means of two radial bearings 13, 14. Advantageously, the radial bearings 13, 14 are designed as foil air bearings.

[0030] On the compressor side 3, the compressor volute 15 is mounted on the motor housing 10. The compressor volute 15 includes a compressor inlet 16 through which air to be compressed is supplied to the fluid machine 1.

[0031] On the turbine side 5, the turbine volute 17 is mounted on the motor housing 10. The turbine volute 17 includes a turbine outlet 18 through which the decompressed air is discharged. The energy generated during the decompression of the air is used to drive the compressor wheel 2.

[0032] The motor shaft 7 can also be referred to as the rotor shaft because it serves to form the rotor 19 in the electric motor 9. The rotor 19 includes a magnet section 20 in which magnets 12 are arranged. Two shaft sections 21, 22 are fastened to opposite ends of the magnet section 20. The magnets 12 are surrounded in the magnet section 20 by a retaining ring 23, which is also referred to as a sleeve.

[0033] In Figure 2 a radial foil bearing 30 with a bearing sleeve 33 is shown. The radial foil bearing 30 serves to radially support the rotor 31. The rotor 31 is, for example, the rotor 19 shown in the Figure 1 fluid machine 1. The radial foil bearing 30 is, for example, Figure 1 the radial bearing 13 or the radial bearing 14 in

[0034] The rotor 31 is radially supported in the bearing sleeve 33 about the axis of rotation 32 by means of the radial foil bearing 30. The radial foil bearing 30 includes a spring foil 34 which is only designated by reference numerals in the Figure 2 and which is clamped in the radial direction between a cover foil 35 and the bearing sleeve 33. For this purpose, the spring foil 34 is provided with spring elements or is elastically embossed In a preferred variant, the spring foil 34 is designed with radially outwardly protruding tabs, as disclosed, for example, in European patent document EP 0756 672B1. The cover foil 35 serves to form an eccentric inner contour 86. The eccentric inner contour 86 can be achieved only by the cover foil 35. However, the eccentric inner contour 86 can also be achieved by a corresponding eccentric inner contour in the bearing sleeve 33 or by the spring foil 34.

[0035] InFigure 3 The non-circular inner contour 86 of the covering foil 35 or the bearing cylinder 33 is strongly exaggerated in Figure 3 to illustrate the non-circular portion. The maximum radius 88 and the minimum radius 89 are marked by arrows. Different-sized radii are used to form the non-circular portions 91, 92, 93 on the non-circular inner contour 86. The non-circular inner contour 86 basically has a triangular configuration with rounded corners 81 to 83.

[0036] Advantageously, in the radial foil bearing 30, air is used to support the rotor 31. Therefore, the radial foil bearing 30 is also referred to as an air bearing. One bearing gap or lubrication gap that appears between the rotor 31 and the non-circular inner contour 86, or multiple, for example three, bearing gaps or lubrication gaps that appear, are crucial not only for the rotor dynamics characteristics of the fluid machine 1 (also referred to as a turbomachine) shown in Figure 3 , but also for its service life, especially for the number of start-stop processes that can be achieved by means of the fluid machine 1. Figure 1 Figure 1

[0037] In Figure 3 Figures 4 to 6 an enlarged segment with a groove 121 is shown in cross-section in Figure 3 . The same reference numerals are used to denote the same or similar components. First, the commonalities of the different embodiments are described. Then, the differences between the three embodiments are explored. Figure 2 Figure 2

[0038] In Figure 3 Figures 4 to 6 the rotor rotation direction 122 is marked by an arrow. The rotor 31 rotates in this rotor rotation direction during operation. With reference to the rotor rotation direction 122, the groove 121 has a groove start 123 and a groove end 124. The groove 121 includes a long groove side 133 from which a short groove side 134 bends.

[0039] The bearing foils 34 and 35 are surface-adhered to the long groove side 133 by means of the first foil end sections 131, 141. More precisely, the first foil end section 131 of the bearing foil 34 is adhered to the long groove side 133. The first foil end section 141 of the covering foil 35 is surface-adhered to the first foil end section 131 of the spring foil 34.

[0040] The second foil end sections 132, 142 of the spring foil 34 and the covering foil 35 extend into the groove 121, but are spaced apart from the first foil end sections 131, 141 of the bearing foils 34, 35. The ends of the two bearing foils 34, 35 that extend into the groove 121 are the inlet edges 125. The ends of the two first foil end sections 131, 141 of the bearing foils 34, 35 are the outlet edges 126.

[0041] The spacing between the inlet edges 125 and the foil end sections 131, 141 is for the thermal expansion of the two bearing foils 34, 35 during operation, so that these bearing foils do not collide with each other.

[0042] The end angle of the long slot edge 133 of the slot 121 matches the naturally expected run of the bearing foils 34, 35 during assembly. For this purpose, the long slot edge 133 extends, for example, substantially tangentially. However, here, the run of the long slot edge 133 of the slot 121 can deviate from the tangential direction by up to twenty degrees, for example.

[0043] In Figure 4 the illustrated embodiment, the slot 121 is embodied as a triangular slot 103. In Figure 5 the illustrated embodiment, the slot 121 is substantially embodied as a rectangular slot 102. However, Figure 5 the slot 121 in

[0044] Figure 5 is embodied such that the first foil end sections 131, 141 of the bearing foils 34, 35 are surface - abutted against the long slot edge 133.

[0045] In addition, Figure 4 and 5 the fixing locations 127 are symbolically indicated, at which the two bearing foils 34, 35 can be fixed relative to each other and, if necessary, surface - fixed on the long slot edge 133 of the slot 121. This fixing can be achieved form - fit, force - fit or material - fit.

[0046] By fixing the outlet edges 126 of the bearing foils 34, 35 on the long slot edge 133 of the slot 121, an undesired tightening (Einschnüren) of the covering foil 35 during start - up and shut - down is prevented. In this way, it is ensured that the rotor 31 is lifted earlier during the operation of the radial foil bearing 30, thereby extending the service life. In addition, an unintentional slipping of the bearing foils 34, 35 is prevented. Furthermore, the surface contact of the bearing foils 34, 35 on the long slot edge 133 of the slot 121 prevents an undesired bending of the bearing foils 34, 35 during the start - up of the rotor 31.

[0047] In Figure 6 and 7 the illustrated embodiments, further possibilities are shown of how the bearing foils 34, 35 can be fixed in the slot 121. The two bearing foils 34, 35 are fixed, for example, on the fixing location 147 on the first bearing foil end 101 and / or on the fixing location 148 on the bearing cylinder 33.

[0048] The fixing of the first bearing foil end 101 to the fixing part 147 is achieved by means of a fixing device 149. The fixing device 149 is, for example, a clamping plate or a flat head screw. For this purpose, the bearing cylinder 33 has, for example, a hole which is provided with a thread for this purpose.

[0049] Advantageously, the fixing part 148 is combined with a gap 151 which starts from the groove 121 and extends in the extension 150 of the slot edge 133. Fixing tabs 152, 153 engage into the gap 151, as Figure 7 shown, the fixing tabs being provided for this purpose on the covering foil 35. In the gap 151, the fixing tabs 152, 153 can be fixed, for example, by bolts which are clamped or screwed into corresponding holes in the fixing part 148.

Claims

1. A radial foil bearing (30) comprising a rotor (31), a cover foil (35) and a spring foil (34), wherein the rotor is supported by the radial foil bearing (30) in a bearing cartridge (33) in a manner rotatable about a rotation axis (32) after reaching a lifting speed while forming a gas film, characterized in that: The bearing sleeve (33) is provided with only one groove (121) extending in the axial direction, in which at least one first foil end section (131; 141) having an outlet edge (126) is flatly abutted against a long groove side (133) of the groove (121), wherein at least one second foil end section (132; 142) having an inlet edge (125) is spaced apart from the first foil end section (131; 141) by its inlet edge (125) in the groove (121), wherein the first foil end section (131; 141) is spaced apart from a short groove side (134) by its outlet edge (126), and the short groove side is bent out from the long groove side (133).

2. The radial foil bearing according to claim 1, characterized in that The groove (121) has a triangular or quadrilateral groove cross section.

3. A radial foil bearing according to any one of the preceding claims, characterised in that The cover foil (35) and the spring foil (34) are formed from a flat and non-prebent foil material, which is also referred to as bearing foil.

4. A radial foil bearing according to any one of the preceding claims, characterised in that The cover foil (35) and the spring foil (34) each have a rectangular configuration.

5. A radial foil bearing according to any one of the preceding claims, characterised in that The spring foil (34) is equipped with a spring element (84) which bears resiliently against the inner contour of the bearing cartridge (33), wherein the spring foil (34) has no spring element (84) in the groove (121).

6. A radial foil bearing according to any one of the preceding claims, characterised in that The spring foil (34) lies in the groove (121) over its entirety on a long groove edge (133) of the groove (121), wherein the cover foil (35) lies in the groove (121) over its entirety on the spring foil (34).

7. A radial foil bearing according to any one of the preceding claims, characterised in that The groove (121) occupies less than one tenth, preferably less than one fifteenth, of the inner circumference of the bearing sleeve (133) in the circumferential direction.

8. A radial foil bearing according to any one of the preceding claims, characterised in that The bearing foils (34, 35) are fixed in a materially bonded manner relative to one another and / or in a planar manner on the longitudinal groove sides (133) of the groove (121).

9. A radial foil bearing according to any one of the preceding claims, characterised in that The two bearing foils (34, 35) are fixed to the long groove sides (133) of the groove (121) by means of fixing means (149).

10. A radial foil bearing according to any one of the preceding claims, characterised in that The fastening point (148) is combined with a slot (151) which starts from the groove (121) and extends in the extension (150) of the long groove leg (133).

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