Radial foil bearing and gas supply device

Abstract

The invention relates to a radial foil bearing having a bearing foil arrangement which is arranged and designed in a radial direction between a housing inner contour and a rotor outer contour of a rotor in such a manner that the rotor is mounted so as to be rotatable about an axis of rotation via the radial foil bearing, thereby forming a gas film within the housing inner contour. In order to improve the function of the radial foil bearing, the bearing foil arrangement comprises a one-piece cover foil which is formed from a piece of a flexible sheet-metal material which is configured in terms of its thickness and geometry in such a way that the one-piece cover foil is sufficiently rigid to ensure solely by itself the formation and maintenance of the gas film in the radial foil bearing, wherein the one-piece cover foil is fixed at ends facing away from one another in a manner secured against rotation at one point of the housing inner contour.

Description

[0001] Description

[0002] title

[0003] The invention relates to a radial foil bearing with a bearing foil arrangement that is arranged and configured in a radial direction between an inner housing contour and an outer rotor contour such that the rotor is rotatably mounted about an axis of rotation by the radial foil bearing, forming a gas film within the inner housing contour. The invention further relates to a gas supply device, for example, an electrically driven turbomachine, with a rotor mounted by at least one such radial foil bearing.

[0004] State of the art

[0005] Foil bearings, in particular radial foil bearings, are known, for example, from German patent applications DE 10 2018 222 572 A1 and DE 10 2018 222 603 A1. Such foil bearings are used, for example, in an air compressor of a fuel cell system for the radial support of a rotor shaft of an electric motor drive of the air compressor. Spring foils of such radial foil bearings are disclosed, for example, in American patent US 5,427,455, wherein a spring foil is equipped, for example, with a plurality of spring elements that form a cantilevered beam spring pattern in the radial foil bearing.

[0006] Disclosure of the invention

[0007] The object of the invention is to improve a radial foil bearing according to the preamble of claim 1 with regard to its manufacturability and / or its function in operation in a gas conveying device, in particular in an air compressor, where very high rotational speeds of, for example, one hundred thousand revolutions per minute can occur.

[0008] The problem is solved in a radial foil bearing with a bearing foil arrangement that is arranged and designed in a radial direction between an inner housing contour and an outer rotor contour of a rotor such that the rotor is rotatably mounted about an axis of rotation by the radial foil bearing while forming a gas film within the inner housing contour, by the bearing foil arrangement comprising a one-piece cover foil formed from a single piece of flexible sheet material, the thickness and geometry of which are designed such that the one-piece cover foil is sufficiently stiff to ensure the formation and maintenance of the gas film in the radial foil bearing on its own, wherein the one-piece cover foil is fixed at a point on the inner housing contour with its ends facing away from each other in a rotationally secure manner.The top foil, also known as the top foil, is, according to a particularly preferred embodiment, the only bearing foil in the bearing foil arrangement. This means, in particular, that the one-piece top foil also performs a spring function, which in conventional radial foil bearings is performed by at least one spring foil or beam foil. The rotor, with its outer contour, is, for example, a shaft section with a cross-section that is as ideally circular as technically possible. A gas, such as air, serves as the lubricant in the radial foil bearing. Therefore, the radial foil bearing is also referred to as a gas bearing, and especially as an air bearing. Once a lift-off speed is reached, the rotor can thus be supported with virtually no wear, even at extremely high speeds.The thickness and geometry of the one-piece cover film are designed such that the cover film provides both the necessary stiffness and damping in the radial foil bearing and a suitable gap profile for gas film build-up. The gap profile comprises, for example, two bearing gaps, ideally three or five, in which the gas film builds up during operation of the radial foil bearing. By using only one cover film in the bearing foil assembly, the number of individual parts to be manufactured and assembled can be advantageously reduced. A conventional spring foil is advantageously not required. Depending on the design, a spring foil or at least one spring element, and optionally an elastomer element, can be used in the bearing foil assembly if necessary. However, this is not the preferred embodiment of the radial foil bearing claimed.The design of the radial foil bearing is significantly simplified by using only a single bearing foil, i.e., the single-piece cover foil. Furthermore, a shorter tolerance chain improves the performance of the radial foil bearing during operation. In addition, the service life of the radial foil bearing can be extended.

[0009] A preferred embodiment of the radial foil bearing is characterized in that the one-piece cover film is designed and configured such that it forms a non-circular, i.e., not ideally circular, bearing contour within a housing inner contour that is circular in cross-section. This significantly simplifies the manufacturing of the radial foil bearing. The housing inner contour that is circular in cross-section is much easier to produce than a non-circular, i.e., not ideally circular, housing inner contour. A perceived disadvantage is deliberately accepted in this design: the one-piece cover film is more difficult to design, engineer, and manufacture.

[0010] Another preferred embodiment of the radial foil bearing is characterized in that the one-piece cover foil comprises at least one predetermined curvature region extending in an axial direction, in which the stiffness of the one-piece cover foil is selectively reduced. The predetermined curvature region in the cover foil is advantageously designed and arranged in such a way that the one-piece cover foil bends in a desired manner when installed in the inner contour of the housing. This eliminates the need for pre-bending of the cover foil, which would otherwise be required.

[0011] Another preferred embodiment of the radial foil bearing is characterized in that the desired curvature area includes at least one material weakening. This accepts the perceived disadvantage of an additional manufacturing step. The material weakening comprises, for example, simple through-holes in the flexible sheet metal from which the cover foil is made. The through-holes can be produced relatively easily by punching the sheet metal. Depending on the manufacturing process, the material weakening can also include recesses in the sheet metal, which can be easily created, for example, by etching. The material weakening is advantageously designed such that the cover foil assumes its desired shape during assembly, i.e., when inserted into the inner contour of the housing, preferably automatically.

[0012] Another preferred embodiment of the radial foil bearing is characterized in that the opposite ends of the one-piece cover foil are designed with an interlocking retaining geometry. The interlocking retaining geometry comprises, for example, finger-like interlocking retaining fingers, which are formed for this purpose at the opposite ends of the one-piece cover foil. With the aid of the interlocking retaining geometry, the opposite ends can be interlocked within the one-piece cover foil.

[0013] Another preferred embodiment of the radial foil bearing is characterized in that the opposite ends of the one-piece cover foil are fixed in an axially extending groove in the inner contour of the housing. The axially extending groove is relatively easy to manufacture in the inner contour of the housing. Depending on the design of the opposite ends of the one-piece cover foil, the fixing to the inner contour of the housing can also be achieved by a suitable fastening device and / or other means.

[0014] Another preferred embodiment of the radial foil bearing is characterized in that the inner housing contour is non-circular, i.e., not perfectly circular. Here, the additional effort required to manufacture the inner housing contour is deliberately accepted because it simplifies the production of the cover film. Due to the non-circular, i.e., not perfectly circular, inner housing contour, the at least one desired curvature area in the one-piece cover film can optionally be omitted. Another preferred embodiment of the radial foil bearing is characterized in that the inner housing contour has at least one circumferentially raised area against which the one-piece cover film is supported. Depending on the desired number of bearing gaps for gas film formation, two or more support points are formed in the inner housing contour.

[0015] The above-mentioned problem is solved alternatively or additionally by a gas supply device with a rotor which is supported by at least one radial foil bearing as described above.

[0016] The radial foil bearing is particularly advantageous in an air compressor, also known as a turbomachine, for supporting a shaft to which at least one impeller, for example a compressor impeller, is attached at either end. The shaft with the impeller is also called the rotor.

[0017] The invention may also relate to a preferably electrically driven air compressor with a previously described rotor, which is supported by at least one previously described radial foil bearing.

[0018] The invention further relates to a bearing film, in particular a cover film, and / or a housing body with an inner housing contour for a radial film bearing as described above. The aforementioned parts are available separately.

[0019] Further advantages, features and details of the invention will become apparent from the following description, in which various embodiments are described in detail with reference to the drawing.

[0020] Brief description of the drawing

[0021] They show:

[0022] Figure 1 shows an electric machine with a multi-part rotor shaft in longitudinal section; Figure 2 shows a radial foil bearing with a bearing foil arrangement comprising only a one-piece cover foil between a rotor outer contour of a rotor and a housing inner contour;

[0023] Figure 3 shows a highly exaggerated depiction of the non-circular inner bearing contour on the inside of the one-piece cover film; and

[0024] Figure 4 shows an embodiment of the one-piece cover film before its installation in the radial film bearing in a top view.

[0025] Description of the exemplary implementations

[0026] Figure 1 shows a longitudinal section of an electrically driven turbomachine 1 comprising a compressor wheel 2 and a turbine wheel 4. The compressor wheel 2 is located on a compressor side 3 of the turbomachine 1. The turbine wheel 4 is located on a turbine side 5 of the turbomachine 1.

[0027] The turbine wheel 4 is driven by the compressor wheel 2. The two wheels 2 and 4 belong to a rotating assembly 6. The rotating assembly 6 includes a motor shaft 7 to provide a rotationally fixed connection between the compressor wheel 2 and the turbine wheel 4. The motor shaft 7 is partially designed as a hollow shaft and is rotatable about a pivot axis 8.

[0028] For electric drive, the turbomachine 1 comprises an electric machine 9. The electric machine 9 is designed as an electric motor with a motor housing 10 and a motor winding 11. A magnet 12, designed as a permanent magnet, is arranged in the motor shaft 7, which is designed as a hollow shaft.

[0029] The compressor wheel 2 of the turbomachine 1 is driven in a fuel cell system by two means: firstly, by the turbine wheel 4, and secondly, by the electric motor 9. The impeller 6 with the motor shaft 7 is rotatably mounted in the motor housing 10 of the electric machine 9 by means of two radial bearings 13 and 14. The radial bearings 13 and 14 are advantageously designed as foil air bearings.

[0030] On compressor side 3, a compressor spiral casing 15 is attached to the motor housing 10. The compressor spiral casing 15 includes a compressor inlet 16, through which air to be compressed is supplied to the turbomachine 1.

[0031] On turbine side 5, a turbine spiral casing 17 is attached to the motor housing 10. The turbine spiral casing 17 includes a turbine outlet 18 through which expanded air exits. The energy generated during the expansion of the air is used to drive the compressor wheel 2.

[0032] The motor shaft 7 can also be called a rotor shaft because it serves to represent a rotor 19 in the electric machine 9. The rotor 19 comprises a magnetic section 20 in which the magnet 12 is arranged. Two shaft sections 21, 22 are attached to the opposite ends of the magnetic section 20. The magnet 12 is surrounded in the magnetic section 20 by a bandage 23, which can also be called a sleeve.

[0033] Figure 2 shows a cross-sectional view of a radial foil bearing 30 with a rotor 31. The rotor 31 is, for example, a rotor 19 as shown in detail in Figure 1 in the turbomachine 1. The radial foil bearing 30 is, for example, the radial bearing 13 or the radial bearing 14 in Figure 1.

[0034] The rotor 31 is radially mounted about an axis of rotation 32 within a bearing cartridge 33 by means of the radial foil bearing 30. An arrow in Figure 2 indicates the direction of rotor rotation 37. The bearing cartridge 33 is, for example, installed in a housing body 36.

[0035] The housing body 36 is, for example, made of a softer material than the bearing cartridge 33. Depending on the design and the type of materials used, the bearing cartridge 33 may also be omitted. The housing body 36, or the bearing cartridge 33, comprises an inner housing contour 35. In the illustrated embodiment, the inner housing contour 35 is non-circular, i.e., not perfectly circular. In contrast, the outer rotor contour 38 has a circular cross-section, i.e., is ideally circular to the extent that this is feasible within the cost constraints of manufacturing.

[0036] For the bearing of the rotor 31, the radial foil bearing 30 comprises a bearing foil arrangement 40 with only a single bearing foil 34. The bearing foil 34 is designed as a cover foil 85. Unlike conventional cover foils, the cover foil 85 also performs a spring function. In the cover foil 85, a conventional cover foil is, in effect, combined with a spring foil. This offers the advantage, among others, that a conventional spring foil can be omitted.

[0037] Figure 4 shows a top view of the cover film 85 before its installation in the inner housing contour 35 of the radial foil bearing 30 in Figure 2. The cover film 85 is made of a flexible sheet metal material 45.

[0038] At opposite ends 51, 52, the cover sheet 85 has two fastening fingers 41, 42; 43, 44. The fastening fingers 41, 42; 43, 44 at the opposite ends 51, 52 of the cover sheet 85 serve to form a retaining geometry for the cover sheet 85 in its installed state, as shown in Figure 2.

[0039] In the installed state, the opposite ends 51 , 52 of the cover film 85 are interlocked in an axial groove 97.

[0040] The retaining geometry 46, in combination with the axial groove 97, serves to represent an anti-rotation device 95 at a point 96 of the housing inner contour 35.

[0041] The non-circular inner housing contour 35 has radially inwardly raised areas.

[0042] 61, 62. The raised areas 61, 62, in combination with the anti-rotation device 95 at point 96 of the housing inner contour 35, serve to represent a non-circular, i.e., non-circular, bearing inner contour 47 radially inside the cover film 85.

[0043] The targeted out-of-roundness of the bearing inner contour 47 advantageously creates three narrowing bearing gaps for a gas film that builds up between the rotor outer contour 38 and the bearing inner contour 47 during operation of the radial foil bearing 30.

[0044] Figure 4 shows that the cover sheet 85, which forms the non-circular inner contour 47, includes predetermined curvature areas 53, 54. These predetermined curvature areas 53, 54 comprise material weakenings 55, 56, which are intentionally introduced into the flexible sheet material 45 to selectively reduce the stiffness of the cover sheet 85 in these predetermined curvature areas 53, 54. In the illustrated embodiment, the material weakenings 55, 56 are designed as through holes, which are easy to create in manufacturing, for example, by punching.

[0045] The cover film 85 can be flat, as shown in Figure 4, and only acquire its curved shape during installation. However, the cover film 85 can also be pre-formed by additional forming steps, for example by rolling it around its entire circumference or parts of it.

[0046] In Figure 3, the non-circular inner contour 86 of the cover sheet 85 is greatly exaggerated to illustrate the non-circularity. Arrows indicate a maximum radius 88 and a minimum radius 89. The different radii serve to represent non-circularities 91, 92, 93 on the non-circular inner contour 86. The non-circular inner contour essentially has the shape of a triangle with rounded corners 81 to 83.

[0047] In the radial foil bearing 30, air is advantageously used to support the rotor 31. Therefore, the radial foil bearing 30 is also referred to as an air bearing. A resulting bearing gap or lubrication gap, or several, ideally three, resulting bearing gaps or lubrication gaps, between the rotor 31 and the non-circular inner contour 86 of the cover foil 85 is / are crucial both for the rotor-dynamic behavior of the turbomachine 1 shown in Figure 1, which is also referred to as a turbomachine, and for its service life, in particular for the number of start-stop cycles achievable with the turbomachine 1.

Claims

Claims 1. Radial foil bearing (30) with a bearing foil arrangement (40) arranged and configured in a radial direction between an inner housing contour (36) and an outer rotor contour (38) of a rotor (31) such that the rotor (31) is rotatably mounted about an axis of rotation (32) by the radial foil bearing (30) while forming a gas film within the inner housing contour (36), characterized in that the bearing foil arrangement (40) comprises a one-piece cover foil (85) formed from a single piece of flexible sheet material (45) designed in its thickness and geometry such that the one-piece cover foil (85) is sufficiently stiff to ensure the formation and maintenance of the gas film in the radial foil bearing (30) on its own, wherein the one-piece cover foil (85) is fixed in a rotationally secure manner at a location (96) of the inner housing contour (36) with its ends (51, 52) facing away from each other.

2. Radial foil bearing (30) according to claim 1, characterized in that the one-piece cover foil (85) is designed and configured such that it forms a non-circular, i.e., not ideally circular, bearing inner contour (47) within a housing inner contour (36) that is circular in cross-section.

3. Radial foil bearing (30) according to one of the preceding claims, characterized in that the one-piece cover foil (85) comprises at least one predetermined curvature region (53, 54) extending in an axial direction, in which the stiffness of the one-piece cover foil (85) is selectively reduced.

4. Radial foil bearing (30) according to claim 3, characterized in that the desired curvature area (53, 54) comprises at least one material weakening (55, 56).

5. Radial foil bearing (30) according to one of the preceding claims, characterized in that the opposite ends (51, 52) of the are designed as a one-piece cover film (85) with an interlocking retaining geometry (46).

6. Radial foil bearing (30) according to one of the preceding claims, characterized in that the opposite ends (51, 52) of the one-piece cover foil (85) are fixed in an axially extending groove (97) in the housing inner contour (36).

7. Radial foil bearing (30) according to one of the preceding claims, characterized in that the housing inner contour (36) is non-circular, i.e. not ideally circular.

8. Radial foil bearing (30) according to claim 7, characterized in that the housing inner contour (36) has at least one circumferentially raised area (61, 62) on which the one-piece cover foil (85) is supported.

9. Gas supply device with a rotor (31) which is supported by at least one radial foil bearing (30) according to one of the preceding claims.

10. Bearing film (34), in particular cover film (85), and / or housing body (36) with an inner housing contour (35) for a radial film bearing (30) according to one of claims 1 to 8.

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