Radial foil bearing

Abstract

The invention relates to a radial foil bearing comprising a rotor which is rotatably mounted about an axis of rotation, thus forming a fluid film between the rotor and a top foil, and comprising a spring foil which is clamped between the top foil and the bearing sleeve, wherein the spring foil has an axial dimension and a dimension in a circumferential direction, wherein the spring foil has multiple spring elements (11, 12) which are connected to a foil body (50) in connection regions via spring connecting pieces, in which foil body the spring elements are arranged and incorporated into the foil body (50) in such a way that they form a self-supporting bar spring pattern (60). The aim of the invention is to improve the radial foil bearing. This aim is achieved in that the spring elements are arranged and incorporated into the foil body (50) in such a way that ends of the spring elements that have various lengths and face away from one another in the circumferential direction come to rest against the inside of the bearing sleeve in at least two stages, according to the load and / or the rotational speed, so that the spring elements form a multi-stage flexible bar spring pattern (60).

Description

[0001] Description

[0002] title

[0003] Radial-

[0004] The invention relates to a radial foil bearing with a rotor which is mounted so as to be rotatable about an axis of rotation while forming a fluid film between the rotor and a cover foil, and with a spring foil which is clamped between the cover foil and the bearing sleeve, wherein the spring foil has an axial dimension and a dimension in a circumferential direction, wherein the spring foil has a plurality of spring elements which are connected in connecting regions via spring webs to a foil body in which the spring elements are arranged and integrated into the foil body in such a way that they represent a self-supporting bar spring pattern.

[0005] State of the art

[0006] Foil bearings, in particular radial foil bearings, are known, for example, from German Offenlegungsschriften 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 the 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.

[0007] Disclosure of the invention

[0008] The object of the invention is to improve a radial foil bearing according to the preamble of patent claim 1 with regard to its manufacturability and / or its function during operation in a gas conveying device, in particular in an air compressor, where very high speeds of, for example, one hundred thousand revolutions per minute can occur.

[0009] The object is achieved in a radial foil bearing with a rotor which is mounted so as to be rotatable about a rotational axis, forming a fluid film between the rotor and a cover foil, and with a spring foil which is clamped between the cover foil and the bearing sleeve, wherein the spring foil has an axial dimension and a dimension in a circumferential direction, wherein the spring foil has a plurality of spring elements which are connected in connecting regions via spring webs to a foil body, in which the spring elements are arranged and integrated into the foil body such that they form a self-supporting bar spring pattern, in that the spring elements are arranged and integrated into the foil body such that ends of the spring elements of different lengths and facing away from one another in the circumferential direction come into contact with the inside of the bearing sleeve in at least two stages, depending on the load and / or speed,so that the spring elements represent a multi-stage bending beam spring pattern. The spring elements are preferably integrally connected to the foil body via the spring bars. The foil body is preferably a sheet material, for example, a steel sheet material, in which the spring elements are produced by a forming process such as punching or embossing. However, the spring elements can also be produced cost-effectively by etching from a suitable steel material, for example, a chromium-nickel steel. Due to the multi-stage bending beam spring pattern, a multi-stage spring can be realized with the spring foil.which enables better adaptation of the spring characteristic of the spring foil in the radial foil bearing to different operating conditions. For example, a spring characteristic optimized for tolerance compensation can ensure robust operation of the radial foil bearing over a long service life. Furthermore, manufacturing costs can be reduced, as the spring characteristic, which can be adjusted via the multi-stage bending beam spring pattern, advantageously allows the radial foil bearing to be mounted directly into an aluminum housing with a high thermal expansion. A preferred embodiment of the radial foil bearing is characterized in that the spring elements are arranged offset in pairs in the circumferential direction. Two axially adjacent spring elements of a pair are preferably arranged offset from one another in the circumferential direction such thatthat only one of the two opposite ends of the spring elements rests against the inside of the bearing sleeve to represent a first stage of the multi-stage bending beam spring pattern. This allows the multi-stage bending beam spring pattern to be created using simple manufacturing techniques.

[0010] A further preferred embodiment of the radial foil bearing is characterized in that the spring elements are each connected to the foil body by at least two spring bars. The spring elements are advantageously each integrally connected to the foil body by at least two, three, or four spring bars. Particularly advantageously, two parallel bars are arranged on each side of the spring elements. These can be arranged at different angles to each other. The spring stiffness in the multi-stage bending beam spring pattern can be highly effectively adjusted and / or adjusted via the at least two spring bars, for example, via the width of the spring bars.

[0011] Another preferred embodiment of the radial foil bearing is characterized in that the spring elements each have a short spring tongue and a long spring tongue, which extend in opposite directions in the circumferential direction on the paired spring elements arranged offset in pairs. Each of the spring elements has a short spring tongue and a long spring tongue. The spring elements are advantageously connected to the foil body in such a way that, during operation of the radial foil bearing, initially only the long spring tongues of a pair of spring elements contribute to the spring effect in the multi-stage bending beam spring pattern.

[0012] Another preferred embodiment of the radial foil bearing is characterized in that the spring bars of the paired, offset spring elements in the connecting areas each run along a common line in the axial direction. This significantly simplifies the setting or adjustment of a desired spring characteristic with the multi-stage bending beam spring pattern in the spring foil.

[0013] A further preferred embodiment of the radial foil bearing is characterized in that the spring elements are designed as spring tabs, each having a tab shape elongated in the circumferential direction. The spring tabs are advantageously connected to one another in one piece by a rectangular connecting body. With the rectangular connecting body, the spring elements between the spring tabs are preferably connected in one piece to the foil body by the spring bars. The spring tabs and also the spring bars on the spring elements are relatively simple and cost-effective to implement in terms of design and manufacturing.

[0014] Another preferred embodiment of the radial foil bearing is characterized in that all spring elements have the same tab shape. This further simplifies the production of the spring foil. However, it is not absolutely necessary for all spring elements to have the same tab shape. The spring elements can, of course, also have a tab shape that varies across the surface. The influence of the tab shape on manufacturability is largely negligible with appropriate automation.

[0015] Another preferred embodiment of the radial foil bearing is characterized in that all spring elements have the shape of an elongated hole. In a plan view, the spring elements preferably have the shape of a circumferentially elongated rectangle with semicircular ends. This allows the desired spring action of the spring elements for the multi-stage bending beam spring pattern in the spring foil to be easily realized both in terms of design and manufacturing technology. In principle, the spring elements can have almost any shape or form, as long as this is appropriate for a bending beam represented by the respective spring elements.

[0016] In a method for operating a previously described radial foil bearing in a gas conveying device, in particular in an air compressor of a fuel cell system, the above-mentioned object is achieved alternatively or additionally in that, in an installed state and at a low rotor speed or at a low rotor deflection, only long ends of the spring elements come into contact with the bearing sleeve, wherein during operation at a high rotor speed or at a greater rotor deflection, in addition to the long ends, short ends of the spring elements also come into contact with the bearing sleeve.As long as only the long ends of the spring elements come into contact with the bearing sleeve, the spring stiffness of the spring foil is mainly determined by the total spring length and the spring webs. If, in addition to the long ends, the short ends of the spring elements also come into contact with the bearing sleeve, the then higher spring stiffness is determined by the length of the individual spring elements in the circumferential direction. Thus, a multi-stage bending beam spring pattern can only be realized in the radial foil bearing through design measures during production of the spring foil.

[0017] The invention further relates to a spring foil for a radial foil bearing as described above. The spring foil is available separately.

[0018] The invention also relates to a method for producing such a spring foil, for example by forming or etching.

[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] Short description of the drawing

[0021] They show:

[0022] Figure 1 shows a spring foil with a plurality of spring elements which represent a multi-stage bending beam spring pattern in a radial foil bearing equipped with the spring foil;

[0023] Figure 2 shows an enlarged section of Figure 1; Figure 3 shows a schematic representation of a gas conveying device with a housing and a bearing sleeve of a radial foil bearing equipped with the spring foil shown in Figures 1 and 2 in an installed state and with a slight movement or deflection of a shaft;

[0024] Figure 4 shows the same representation as in Figure 3 with a larger deflection of the shaft; and

[0025] Figure 5 shows the same representation as in Figures 3 and 4 with an even larger deflection of the shaft.

[0026] Description of the embodiments

[0027] In Figures 3 to 5, a gas delivery device 1 designed as an air compressor in a fuel cell system is indicated only by its reference numeral. The gas delivery device 1 comprises a housing 2 with a bearing sleeve 3, which is only indicated by a circular arc. The bearing sleeve 3 can also be referred to as a bearing cartridge.

[0028] A rotor 4 with a shaft and a cover foil 5 is mounted in the bearing sleeve 3 for rotation about a rotation axis 6. A radial foil bearing 9 serves to rotatably support the shaft. The bearing sleeve 3 is pressed, for example, into the housing 2 of the gas conveying device 1. In Figures 3 to 5, the rotor is designated by the reference numeral 4. The shaft has no reference numeral of its own. The cover foil has the reference numeral 5.

[0029] The bearing cartridge or bearing sleeve 3 is also referred to as a bearing ring and essentially has the shape of a straight, hollow circular cylinder. Several foils of the radial foil bearing 9 are preferably arranged inside the bearing sleeve 3.

[0030] A foil arranged between the radially inner cover foil 5 and the bearing sleeve 3 is also referred to as a beam, bump, or bottom foil. The radially inner cover foil 5 is also referred to as the upper foil and defines an interior space in the bearing sleeve 3 of the radial foil bearing 9, which serves to rotatably support the shaft.

[0031] In Figures 3 to 5, a spring foil 10 without the shaft is shown in a significantly enlarged annular space between the cover foil 5 and the bearing sleeve 3, because in the claimed radial foil bearing 9 only the function and design of the spring foil 10 is important. The spring foil 10 is shown in Figures 1 and 2 in plan view. In the plan view, it can be seen that the spring foil 10 comprises a plurality of spring elements 11 to 20; 21 to 30.

[0032] The spring foil 10 itself has the shape of an elongated rectangle with flattened corners. A lower end of the spring foil 10 in Figure 1 has been cut off. The top of Figure 1 shows that the spring elements 11 to 20 are arranged in a horizontal row. Below them, the spring elements 21 to 30 are also arranged in a horizontal row. Two axially adjacent spring elements 11 and 12 or 21 and 22 are arranged offset from one another in the circumferential direction, i.e., in the vertical direction in Figure 1.

[0033] Furthermore, the spring elements 11, 21, 12, 22, 13, 23 to 20, 30 are arranged in a total of ten columns 31 to 40, each continuing downwards in Figure 1. The spring elements are integrally connected to a film body 50 by a plurality of spring bars 70.

[0034] In Figure 2, a section of the spring foil 10 from Figure 1 is shown enlarged in order to illustrate, in conjunction with Figures 3 to 5, using the example of the spring elements 11 and 12, how a multi-stage bending beam spring pattern 60 is represented with the spring foil 10 in the radial foil bearing 9.

[0035] Figure 2 shows how the spring element 11 is integrally connected to the foil body 50 via a total of four spring bars 41, 42 and 45, 46. The foil body 50 is, for example, a stamped steel sheet.

[0036] The spring element 12 is also connected by a total of four spring bars 43, 44 and

[0037] 47, 48 are integrally connected to the foil body 50. The spring bars 41 to 44 extend in a horizontal line, as can be seen in Figure 2. The spring bars 45 to 48 are also arranged along a horizontal line in Figure 2.

[0038] The spring bars 45, 46 and 43, 44 each engage approximately centrally on the corresponding spring element 11, 12. However, the spring bars 41, 42 on the spring element 11 are arranged offset upward relative to the spring bars 45, 46 in Figure 2. In contrast, the spring bars 47, 48 on the spring element 12 in Figure 2 are arranged offset downward relative to the spring bars 43, 44.

[0039] Due to the offset arrangement of the spring bars on the spring elements 11 and 12, the spring element 11 has a long end 51 and a short end 53 relative to the connecting area 49. The long end 51 of the spring element 11 is directed downward in Figure 2. The short end 53 of the spring element 11 is directed upward in Figure 2.

[0040] In contrast, a long end 52 of the spring element 12 in Figure 2 is directed upwards, while a short end 54 of the spring element 12 in Figure 2 is directed downwards.

[0041] Due to the arrangement of the spring bars 41 to 48 relative to the spring elements 11 and 12, long spring tongues 55 and 56 and short spring tongues 57 and 58 are formed on the spring elements 11 and 12. As can be seen in Figure 2, the long spring tongues 55, 56 and the short spring tongues 57, 58 are each oriented in opposite directions.

[0042] This results in a desired multi-stage bending beam spring pattern 60, as illustrated in Figures 3 to 5 using the spring elements 11 and 12. In Figures 3 to 5, movements or deflections of the shaft with the cover foil 5 in the upward direction are indicated with varying degrees.

[0043] The deflection 61 is the smallest and corresponds, for example, to a

[0044] Installation state of the radial foil bearing 9. The deflection 63 of the shaft with the cover foil 5 facing upwards in Figure 5 is the greatest. The deflection 62 in Figure 4 represents a medium deflection or movement.

[0045] Figure 3 shows that, in the installed state and with slight movement or deflection 61 of the shaft with the cover foil 5, only the long ends 51, 52 of the spring elements 11 and 12 come into contact with the housing 2 or the bearing sleeve 3. The spring stiffness of the spring foil, represented by the multi-stage bending beam spring pattern 60, is primarily determined by the total spring length 65, indicated in Figure 1 by a double arrow, and the spring webs 41 to 48, which can also be referred to as connecting webs.

[0046] With a greater deflection of the shaft with the cover foil 5, as can be seen in Figure 5, the short spring ends 53 and 54 of the spring elements 11 and 12 also come into contact with the housing 2 and the bearing sleeve 3, respectively. The resulting higher spring stiffness of the multi-stage bending beam spring pattern 60 is then determined by the individual spring length 66, indicated in Figure 1 by a double arrow, of the individual spring elements 11 and 12.

Claims

Claims 1. Radial foil bearing (9) with a rotor (4) which is mounted rotatably about a rotational axis (6) with the formation of a fluid film between the rotor (4) and a cover foil (5), and with a spring foil (10) which is clamped between the cover foil (5) and the bearing sleeve (3), wherein the spring foil (10) has an axial dimension and a dimension in a circumferential direction, wherein the spring foil (10) has a plurality of spring elements (11, 12) which are connected in connecting regions (49) via spring webs (41-48) to a foil body (50), in which the spring elements (11, 12) are arranged and incorporated into the film body (50) in such a way that they represent a self-supporting beam spring pattern (60), characterized in that the spring elements (11, 12) are arranged and incorporated into the film body (50) in such a way that ends (51 - 54) of the spring elements of different lengths and facing away from each other in the circumferential direction (11,12) depending on the load and / or speed in at least two stages inside the bearing sleeve (3) come into contact, so that the spring elements (11,12) represent a multi-stage bending beam spring pattern (60).

2. Radial foil bearing according to claim 1, characterized in that the spring elements (11, 12) are arranged offset in pairs in the circumferential direction.

3. Radial foil bearing according to one of the preceding claims, characterized in that the spring elements (11, 12) are each connected to the foil body (50) by at least two spring webs (41-48).

4. Radial foil bearing according to one of the preceding claims, characterized in that the spring elements (11, 12) each have a short spring tongue (57, 58) and a long spring tongue (55, 56) which extend in opposite directions in the circumferential direction on the spring elements (11, 12) arranged offset in pairs.

5. Radial foil bearing according to one of the preceding claims, characterized in that the spring webs (41 - 48) of the paired offset spring elements (11, 12) in the connecting regions (49) each run along a common line in the axial direction.

6. Radial foil bearing according to one of the preceding claims, characterized in that the spring elements (11, 12) are designed as spring tabs, each of which has a tab shape that is elongated in the circumferential direction.

7. Radial foil bearing according to one of the preceding claims, characterized in that all spring elements (11, 12) have the same tab shape.

8. Radial foil bearing according to one of the preceding claims, characterized in that all spring elements (11, 12) have the shape of an elongated hole.

9. Method for operating a radial foil bearing (9) in a gas conveying device (1), in particular in an air compressor of a fuel cell system, characterized in that in an installed state and at a low rotor speed or at a low rotor deflection only long ends (51, 52) of the spring elements (11, 12) come into contact with the bearing sleeve (3), wherein in operation at a high rotor speed or at a greater rotor deflection in addition to the long ends (51, 52) also short ends (53, 54) of the spring elements (11, 12) come into contact with the bearing sleeve (3).

10. Spring foil (10) for a radial foil bearing (9) according to one of claims 1 to 8.

Images