Axial foil bearing

Abstract

The invention relates to an axial foil bearing (61) having at least one spring foil and at least one top foil (44) which is provided with a stepped structure (8) in the circumferential direction for forming a loadable fluid film in a bearing gap, said stepped structure having at least three segment transitions (21, 22; 22, 23; 23, 24; 24, 25; 25, 26; 25, 21). In order to improve the axial foil bearing (61) with respect to maximum bearing capacity and / or reduction of friction loss during operation, the axial foil bearing (61) is formed in a section transition (21, 22; 22, 23; 23, 24; 24, 25; 25, 26; a step (31-36) having a logarithmic spiral step line (13) is formed on the top foil (44) in each case between two circumferentially adjacent sections of the first, second, third, fourth, fifth, sixth, seventh, seventh, seventh, seventh, seventh, seventh, seventh, seventh, seventh, seventh, seventh, seventh, seventh, seventh, seventh, seventh, seventh, seventh, seventh, seventh, seventh, seventh,

Description

Technical Field

[0001] The invention relates to an axial foil bearing having at least one spring foil and at least one top foil, wherein the top foil is provided with a stepped structure in the circumferential direction for forming a load-bearing fluid film in the bearing gap, the stepped structure having at least three segment transitions repeated in the circumferential direction. Background Art

[0002] US Patent Publication US2012 / 0207414 A1 discloses an axial bearing implemented as an air bearing, which includes a spring foil and a top foil. Due to the foil used, this type of air bearing is also called a foil bearing. German Patent Publication DE 102019 200 330 A1 discloses a rotor bearing system for a turbine, wherein the rotor bearing system includes at least an axial foil air bearing having at least one top foil and at least one spring foil, the top foil being axially spaced apart from a support element, the spring foil being arranged between the top foil and the support element; and a rotor that rests on the top foil of the axial foil air bearing and is rotatable relative to the axial foil air bearing. German Patent Publication DE 10 2019 200 331 A1 discloses a foil axial bearing for a fuel cell system, wherein the foil axial bearing includes a pressure plate having at least one top foil and a spring foil, the top foil being arranged circumferentially on the pressure plate, and the spring foil being arranged between the pressure plate and the top foil. Summary of the Invention

[0003] The object of the present invention is to improve an axial foil bearing according to the preamble of claim 1 with regard to the maximum load-bearing capacity and / or friction losses during operation.

[0004] In the case of an axial foil bearing having at least one spring foil and at least one top foil, the top foil being provided with a stepped structure in the circumferential direction for forming a load-bearing fluid film in the bearing gap, the stepped structure having at least three circumferentially repeating segment transitions, this object is achieved by forming a step having a logarithmic spiral-shaped step line on the top foil between two circumferentially adjacent segments of a segment transition. The axial foil bearing is preferably used to support a shaft having an axial bearing disk. In the at least one bearing gap, a load-bearing fluid film is formed between the axial bearing disk and the top foil during operation of the axial foil bearing. The fluid is preferably a gas, particularly air. Therefore, the axial foil bearing is also referred to as a gas bearing, particularly an air bearing. The rotational movement of the axial bearing disk generates a gas flow extending substantially in the circumferential direction during operation of the axial foil bearing, which forms a load-bearing gas film between the axial bearing disk and the top foil. Adjacent segments of a segment transition have opposite slopes in the circumferential direction. The first segment has a positive slope, while the second segment has a negative slope at the segment transition. According to an important aspect of the present invention, the resulting step is configured as a logarithmic spiral. Logarithmic spirals are known, for example, from spiral groove bearings. Spiral groove bearings are known, for example, from German laid-open patent DE 26 35 416 A1 and German patent DE 26 35 416 C3. By configuring the top foil of the axial foil bearing with the known logarithmic spiral, the load-bearing capacity of the axial foil bearing can be effectively increased, particularly at very high rotational speeds.

[0005] A preferred embodiment of the axial foil bearing is characterized in that the steps with the logarithmic spiral step line have a step height of 10 to 300 micrometers. When studying the claimed structure, it was found that a significant improvement can be achieved with these values ​​compared to conventional axial foil bearings.

[0006] Another preferred embodiment of the axial foil bearing is characterized in that the steps with logarithmic spiral steps comprise logarithmic spiral grooves, which extend from the outer diameter of the top foil. The logarithmic spiral grooves can also be approximated by circular arcs or elliptical curves, or, if necessary, by a combination of circular arcs and elliptical curves. In extreme cases, the logarithmic spiral grooves can also be approximated by a straight line. The optimal winding degree, or inclination, of the spiral grooves depends on the fluid used and the circumferential speeds encountered during operation of the axial foil bearing.

[0007] Another preferred embodiment of the axial foil bearing is characterized in that the logarithmic spiral grooves are connected by a rounded transition region to a straight terminal edge that extends to the inner diameter of the top foil. This has also proven to be advantageous during studies of the claimed structure. The straight terminal edge stabilizes the load-bearing fluid film in the bearing gap.

[0008] Another preferred embodiment of the axial foil bearing is characterized by straight terminal edges extending radially. This minimizes wear during operation of the axial foil bearing. The terminal edges of the at least three segment transitions at the step preferably intersect at the center of the top foil.

[0009] Another preferred embodiment of the axial foil bearing is characterized in that the spring foil and the top foil are designed and arranged so as to produce a contact line that runs parallel to the terminal edge. The contact line is arranged at the segment transition in each segment with a positive slope. This ensures that the top foil is sufficiently stably supported in this area by the spring foil. The arrangement of the contact line parallel to the respective terminal edge has proven advantageous with regard to the desired supporting effect in conjunction with the spring foil.

[0010] Another preferred embodiment of the axial foil bearing is characterized in that the top foil has the configuration of a circular ring disk with an average bearing diameter, which is obtained by half the sum of the inner diameter and the outer diameter of the top foil, wherein the logarithmic spiral groove does not exceed the average bearing diameter. This further stabilizes the load-bearing fluid film between the top foil and the axial bearing disk. A preferably rounded transition area is formed on a step between the logarithmic spiral groove and the terminal edge. This has also proven to be a stable measure with respect to the flow between the top foil and the axial bearing disk. The circular ring disk is additionally provided with a retaining structure, which is used to connect the top foil to the housing part in a rotationally fixed manner relative to the axial bearing disk that rotates during operation of the axial bearing disk when the axial foil bearing is installed. The retaining structure is preferably arranged radially outside the top foil.

[0011] Another preferred embodiment of the axial foil bearing is characterized in that the top foil has a retaining arm extending from its outer diameter. By means of the retaining arm, the top foil is arranged in a rotationally fixed manner in the housing.

[0012] Another preferred embodiment of the axial foil bearing is characterized in that the top foil is designed as a single piece. This single-piece top foil can also be referred to as a monolithic top foil. "One-piece" or "monolithic" in the context of the top foil means that the segments of the segment transitions and the retaining arms are integrally connected to one another. The monolithic top foil (also called "top foil") is produced, for example, by a forming process from a suitable sheet material. This forming process can be combined with a heat treatment.

[0013] The present invention also relates to a top foil and / or spring foil for the above-mentioned axial foil bearing. The top foil and the spring foil can be sold separately.

[0014] The invention further relates to a gas supply device having a rotor supported by the above-mentioned foil axial bearing. The gas supply device is preferably an electrically driven air compressor, by means of which air is provided in the fuel cell system. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Further advantages, features and details of the invention emerge from the following description, in which various exemplary embodiments are described in detail with reference to the drawings.

[0016] The accompanying drawings show:

[0017] Figure 1 : A top view of a top foil having a stepped structure in the circumferential direction;

[0018] Figure 2 : A schematic diagram of a compressor having a rotor which is rotatably supported in radial and axial directions by three bearings;

[0019] Figure 3 : An exploded view of a foil axial bearing (also called an axial foil bearing) having different bearing foils; and

[0020] Figure 4 : Figure 1 The portion having an additional gap in the top foil. DETAILED DESCRIPTION

[0021] exist Figure 2 Schematically, a compressor 100 of a fuel cell system is shown in FIG. The compressor 100 includes a housing 101 in which an electric motor 102 is arranged. The electric motor 102 is used to drive a rotor 103 of the compressor 100 .

[0022] The rotor 103 of the compressor 100 is radially supported in the housing 101 by means of two radial gas bearings 104 and 105 . The axial gas bearing 106 is used for axial support of the rotor 103 .

[0023] In the rotor 103 Figure 2 A compressor wheel 107 is mounted on the left end portion thereof. When the compressor wheel 107 is driven by the motor 102 via the rotor 103, the compressor wheel 107 is used to compress air provided in the fuel cell system.

[0024] The radial gas bearings 104 , 105 and 106 each include a housing body 108 , 109 and 110 . The rotor 103 includes two rotor segments (also referred to as rotor bodies 111 and 112 ), by means of which the rotor 103 is radially supported in the radial gas bearings 104 and 105 .

[0025] The rotor 103 further comprises a rotor ring (also referred to as a rotor body 113). The rotor 103 is axially supported in the housing 101 by the rotor body 113 via the axial gas bearing 106. The rotor body 113 is also referred to as an axial bearing disk.

[0026] Figure 3An exploded view of a foil axial bearing 61 (also referred to as an axial foil bearing) is shown. The foil axial bearing 61 comprises two foil packs 70 and 80. Each foil pack 70 and 80 comprises a spring foil 71 and 81, a stop disc 72 and 82, a spacer disc 73 and 83, and a top foil 74 and 84. The structure and function of this type of foil axial bearing 61 are known per se.

[0027] Ten adjusting disks and an intermediate ring 90 are arranged in the axial gap 68 between the two foil packages 70 and 80. The adjusting disks serve to form a defined distance between the two foil packages 70, 80.

[0028] When the foil axial bearing 61 is installed, an axial bearing disk (not shown) is arranged radially inside the adjusting disk. This axial bearing disk is arranged, for example, on the rotor of a compressor and serves to axially support the rotor by means of the foil axial bearing 61. The axial bearing disk can be connected integrally to the shaft and can also be referred to as a disk-shaped region of the rotor.

[0029] In the mounted state, the foil axial bearing 61 comprises a disk-shaped region of the rotor radially inside the adjusting disk and the intermediate ring 90 in the axial gap 68 , specifically on both sides, i.e. Figure 3 In the mounted state of the foil axial bearing 61, the disc-shaped area of ​​the rotor or the axial bearing disk can stop on the left and right sides respectively. Between the disc-shaped area and the adjacent components there is a foil package 70, 80 of the foil axial bearing 61.

[0030] For example, during installation, first install the spring foil 81 (also called spring leaf or "bump foil") on the left. The spring foil 81 is oriented by three pins, which are arranged 120 degrees offset from each other in the circumferential direction in conventional foil axial bearings and are received in the bearing plate.

[0031] Then, the stop disc 82 (also called overtravel stop disc) is installed. Next, the spacer disc 83 and the top foil 84 (also called "top foil") are installed. When installed in the correct position, the top foil (or "top foil" 84) serves to form an air gap with the axial bearing disc of the rotor (also called rotor disc) during rotation during operation of the rotor.

[0032] The bearing arrangement on the right side is installed in a similar manner. The gap 68 formed and measured is bridged by a suitable number of adjusting disks. This ensures that all the different bearing foils or bearing disks of the foil packs 70, 80 are stably and correctly clamped between the two bearing plates. The aforementioned intermediate ring 90 is also arranged between the top foil 84 and the adjusting disks.

[0033] exist Figure 3It can be vaguely seen that the top foil 74; 84 (also called the top foil) is provided with a stepped structure in the circumferential direction. When the axial foil bearing or the foil axial bearing 61 is in operation, the stepped structure is used to form a load-bearing fluid film in the axial bearing gap.

[0034] exist Figure 1 FIG. 4 shows a top view of the top foil 44. Figure 3 The top foil 74; 84 in the embodiment is slightly different. In order to form a load-bearing fluid film, Figure 1 The top foil 44 in FIG. 4 is provided with a stepped structure 8 .

[0035] The top foil 10 is essentially in the form of a circular disk with an inner diameter 11 and an outer diameter 12. From the outer diameter 12 of the top foil 10 extend holding arms 1 to 6 for connecting the top foil 10 to a housing part (not shown) in a rotationally fixed manner in the assembled state.

[0036] The top foil 10 comprises six sections 21 to 26. Steps 31 to 36 are formed between two circumferentially consecutive sections 21, 22; 22, 23; 23, 24; 24, 25; 25, 26 and 26, 21, respectively. Figure 1 Viewed clockwise in FIG, the top foil 10 has, for example, a positive or increasing slope before the steps 31 to 36. After the steps 31 to 36, the top foil has a negative or decreasing slope in the circumferential direction.

[0037] exist Figure 3 It can be seen that the step lines of the stepped structure, which are only vaguely shown there, extend essentially radially. Figure 1 In the embodiment, the steps 31 to 36 each include a step line 13 having a logarithmic spiral shape. The logarithmic spiral shape of the step line 13 in the top foil 44 is implemented identically or similarly to the logarithmic spiral shape in a conventional spiral groove bearing.

[0038] The step line 13, starting from the outer diameter 12 of the top foil 10, comprises a logarithmic spiral groove 14. The logarithmic spiral groove 14 can transition from the outer diameter 12 to the inner diameter 11. However, in the embodiment shown, the logarithmic spiral groove 14 does not exceed the average bearing diameter. The average bearing diameter is half the sum of the inner diameter 11 and the outer diameter 12.

[0039] The logarithmic spiral groove 14 is connected to the terminal edge 16 via a rounded transition area 15. The terminal edge 16 extends straight in the radial direction. The extension line of the terminal edge 16 ideally passes through the bearing center point (corresponding to the center of the top foil 10).

[0040] The top foil 44 is supported on the underlying spring foil in its raised region, ie, in the sections 21 to 26 before the steps 31 to 36 , in the region of the contact lines 17 , 18 , 19 . The contact lines 17 to 19 extend parallel to the end edge 16 .

[0041] Figure 1 The top foil 44 shown is designed as a single piece or monolithic structure. Unlike the illustration, the rotationally fixed attachment to the housing can also be achieved by connection techniques such as clamping, screwing or spot welding. The retaining arms 1 to 6 can also be connected radially outside the outer diameter 12 via a common retaining ring.

[0042] In equipped with Figure 1 When the top foil 44 of the axial foil bearing is operated, a negative pressure may occur when overflowing the steps 31 to 36, thereby reducing the load-bearing capacity in an undesirable manner. Figure 1 The terminal edge marked 16 passes through Figure 4 The slots marked 56 in the figure can be advantageous instead. The slots 56 have the shape of an elongated rectangle 57, which is arranged radially with its longitudinal extension. The slots 56 can reduce the above-mentioned undesirable negative pressure.

[0043] It has proven to be advantageous to arrange the contact lines 17, 18 as close as possible to the gap 56, which can be attributed to the omission of the terminal edge. Figure 4 The arrows 58 in FIG. 5 indicate that the contact lines 17 , 18 of the elastic stepped structure 8 are guided as close as possible to the gap 56 .

[0044] Different from the illustration, the gap 56 can also be arranged behind the step 31 in the circumferential direction, that is, Figure 4 , and offset in clockwise direction. Figure 4 Instead of the one slot 56 shown, it may also be sensible to provide a plurality of slots in the radial or tangential direction on the top foil 10 to reduce undesired negative pressure. Instead of the slot 56, other notches or cutouts may also be provided in the top foil.

Claims

1. An axial foil bearing (61) comprising at least one spring foil (71, 81) and at least one top foil (74; 84; 44), the top foil being provided with a stepped structure (8) in the circumferential direction for forming a load-bearing fluid film in the bearing gap, the stepped structure having at least three segment transitions (21, 22; 22, 23; 23, 24; 24, 25; 25, 26; 25, 21), characterized in that In a section transition (21, 22; 22, 23; Between two circumferentially adjacent sections of the top foil (74, 84; 44), steps (31-36) having a logarithmic spiral step line (13) are formed in each case.

2. The axial foil bearing according to claim 1, characterized in that The steps (8) having the logarithmic spiral step lines (13) have a step height of 10 micrometers to 300 micrometers.

3. Axial foil bearing according to any one of the preceding claims, characterized in that The step (8) with the logarithmic spiral step line (13) comprises a logarithmic spiral groove (14) which originates from the outer diameter (12) of the top foil (74, 84; 44).

4. The axial foil bearing according to claim 3, characterized in that The logarithmic spiral groove (14) is connected to a straight terminal edge (16) via a rounded transition region (15), which extends to the inner diameter (11) of the top foil (74, 84; 44).

5. The axial foil bearing according to claim 3 or 4, characterized in that The straight terminal edge (16) extends radially.

6. The axial foil bearing according to any one of claims 3 to 5, characterized in that The spring foil (71, 81) and the top foil (74, 84; 44) are designed and arranged such that a contact line (17-19) is produced which extends parallel to the terminal edge (16).

7. The axial foil bearing according to any one of claims 3 to 6, characterized in that The top foil (44) has the configuration of a circular ring disk with a mean bearing diameter which is half the sum of the inner diameter (11) and the outer diameter (12) of the top foil (44), wherein the logarithmic spiral grooves (14) do not exceed the mean bearing diameter.

8. The axial foil bearing according to any one of claims 3 to 7, characterized in that The top foil (44) has retaining arms (1-6) extending from an outer diameter (12) of the top foil.

9. Axial foil bearing according to any one of the preceding claims, characterized in that The top foil (44) is embodied in one piece.

10. A top foil (74, 84; 44) and / or a spring foil (71, 81) for an axial foil bearing (61) according to any one of the preceding claims.

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