Flexible foil air radial bearing

Abstract

A flexible foil air radial bearing comprises a bearing sleeve, a gas foil and a spring foil, the spring foil and the gas foil are sequentially installed on the inner wall of the bearing sleeve, the thickness of the spring foil is gradually increased in the circumferential direction, cantilever beams are arranged on the spring foil in the transverse direction and the longitudinal direction, and the cantilever beams are arranged on the bearing sleeve. The cantilever beam is erected between the gas foil and the bearing sleeve, and a contraction circumferential airflow channel for compressing and pressurizing gas can be formed between the inner side of the gas foil and the outer side of the cylindrical rotor. The thickness of the spring foil is gradually increased along the circumferential direction, so that a gap between the outer diameter of the rotor and the inner diameter of the bearing sleeve is gradually reduced, namely, the thickness of a bearing gas film is narrowed, pneumatic pressure is generated, meanwhile, the rigidity of the cantilever beam is correspondingly improved along the circumferential direction, and the cantilever beam is enabled to cope with the gradually increased pneumatic pressure and keep stable dynamic rigidity balance.

Description

Technical Field

[0001] The invention belongs to the technical field of gas bearings and relates to a flexible foil air radial bearing. Background Art

[0002] Compliant foil gas film journal bearings are currently being used in various high speed rotor applications such as air compressors, hydrogen compressors, small turbine generators, etc. These bearings consist of an inner rotating cylindrical rotor, a non-rotating flexible gas foil surrounding the rotating cylindrical rotor, a non-rotating flexible spring foil surrounding the gas foil, and a non-rotating cylindrical rotor sleeve surrounding and providing fixation for the foil. The space between the outer diameter of the smooth rotating cylindrical rotor and the gas foil is divided into one or more gas dynamic wedge channel sections. These wedge channels are formed by overlapping gas and spring foils to form a slope on the inner surface of the gas foil. The motion of the rotating cylindrical rotor generates viscous drag, and the spring foil bending and sliding generates Coulomb damping. At low speeds of starting and stopping, the rotating cylindrical rotor of the bearing comes into physical contact with the gas foil, causing bearing wear. Only when the rotor speed is above takeoff speed, the gas dynamic forces generated in the wedge channels can ensure that the gap between the cylindrical rotor and the gas foil is larger than the surface roughness. Conventional flexible foil gas dynamic gas film bearings rely on the spring properties of the support spring and the curved gas foil to preload the gas foil onto the relatively rotating cylindrical rotor to control the foil positioning within the bearing sleeve and the dynamic stability of the foil. This preload will significantly increase the wedge channel effect, thereby reducing the speed at which the rotating cylindrical rotor breaks away from physical contact with the non-rotating element of the bearing. This preload and takeoff speed result in less bearing wear each time the rotor is started or stopped. Most conventional flexible foil gas dynamic pressure gas film bearings use multiple gas foils and multiple spring foils. However, the traditional structure is prone to excessive deformation of the spring when the load is too large, resulting in preload failure. Summary of the invention

[0003] The present invention provides a flexible foil air radial bearing, which can significantly reduce the bearing take-off speed and the contact time between the cylindrical rotor and the gas foil, and has the advantages of high load-bearing capacity, high damping, low torque, low take-off speed, small swing space, small number of parts and low manufacturing cost.

[0004] The technical solution adopted by the present invention is:

[0005] A flexible foil air radial bearing comprises a bearing sleeve, a gas foil and a spring foil. The spring foil and the gas foil are sequentially mounted on the inner wall of the bearing sleeve. The thickness of the spring foil gradually increases along the circumferential direction. Cantilever beams are arranged transversely and longitudinally on the spring foil. The cantilever beams stand upright between the gas foil and the bearing sleeve. A contraction circumferential airflow channel for compressing and pressurizing the gas can be formed between the inner side of the gas foil and the outer side of a cylindrical rotor.

[0006] Furthermore, the thickness of the spring foil increases stepwise along the rotation direction of the cylindrical rotor, and the thickness increase of each step is consistent.

[0007] Furthermore, the length of the cantilever beam gradually increases along the rotation direction of the cylindrical rotor.

[0008] Furthermore, the upright height of the cantilever beam gradually increases along the rotation direction of the cylindrical rotor.

[0009] Furthermore, the spring foil is processed by multiple chemical etching methods, and the surface is etched by 15% to 50%.

[0010] Furthermore, the thickness of the gas foil is consistent.

[0011] Furthermore, the bearing sleeve is provided with an annular gas foil and an annular spring foil, or an annular structure formed by assembling a plurality of gas foils and an annular structure formed by assembling a plurality of spring foils.

[0012] Furthermore, the bearing sleeve comprises a bearing sleeve shell, the inner wall of the bearing sleeve shell is provided with a plurality of foil positioning pins, and the gas foil and the spring foil are installed in the bearing sleeve shell through the foil positioning pins.

[0013] Furthermore, the inner wall of the bearing sleeve housing is provided with straight line segments on both sides of the foil positioning pins, the straight line segments between the two foil positioning pins are connected by an arc segment, and the straight line segment is tangent to the arc segment.

[0014] Furthermore, both sides of the protruding portion of the foil locating pin protruding from the inner wall of the bearing sleeve housing are provided with snap-fit ​​sockets for clamping the ends of the gas foil and the spring foil.

[0015] Beneficial effects of the present invention:

[0016] 1. The thickness of the spring foil gradually increases along the circumferential direction, so that the gap between the outer diameter of the rotor and the inner diameter of the bearing sleeve gradually decreases, that is, the thickness of the bearing air film is narrowed, thereby generating aerodynamic pressure. At the same time, the stiffness of the cantilever beam is correspondingly increased along the circumferential direction, so that it can cope with the gradually increasing aerodynamic pressure and maintain a stable dynamic stiffness balance.

[0017] 2. The step-wise change in spring foil thickness can be produced by multiple etching processes. The step-wise change in spring thickness along the circumferential direction has greater flexibility in controlling the spring stiffness, bearing air film thickness and pneumatic pressure.

[0018] 3. The bearing sleeve is composed of a bearing housing and a number of locating pins. The height of the locating pins can be adjusted according to the thickness of the bearing spring and the foil. This design improves the flexibility of the bearing sleeve design and reduces the production cost.

[0019] 4. The inner diameter of the bearing is divided into two parts, consisting of a straight line segment and a circular arc segment, and is set tangently. This design makes the inner diameter easier to process and also facilitates dimensional detection after processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the structure of the present invention.

[0021] Figure 2 It is a structural schematic diagram of the bearing sleeve of the present invention.

[0022] Figure 3 It is a structural schematic diagram of the bearing housing of the present invention.

[0023] Figure 4 It is a schematic diagram of the main structure of the bearing housing of the present invention.

[0024] Figure 5 It is a schematic structural diagram of the foil positioning pin of the present invention.

[0025] Figure 6 It is a schematic side view of the structure of the foil positioning pin of the present invention.

[0026] Figure 7 It is a schematic diagram of the structure of the gas foil of the present invention.

[0027] Figure 8 It is a schematic structural diagram of the spring foil of the present invention.

[0028] Fig. 9 It is a schematic diagram of the main structure of the spring foil of the present invention.

[0029] Fig.10 for Fig. 9 AA section view.

[0030] Fig.11 It is a schematic diagram of the shrinking circumferential airflow channel of the present invention. DETAILED DESCRIPTION

[0031] The present invention is further described below in conjunction with specific embodiments, but the present invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all possible alternatives, improvements and equivalents within the scope of the claims.

[0032] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "clockwise", "counterclockwise" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, the meaning of "multiple" is two or more, unless otherwise clearly defined.

[0033] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0034] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0035] See also Figure 1-11 The present embodiment provides a flexible foil air radial bearing, comprising a bearing sleeve 1, a gas foil 2 and a spring foil 3, wherein the spring foil 2 and the gas foil 3 are sequentially mounted on the inner wall of the bearing sleeve 1, the thickness of the spring foil 3 gradually increases along the circumferential direction, and cantilever beams 31 are arranged transversely and longitudinally on the spring foil 3, wherein the cantilever beams 31 stand upright between the gas foil 2 and the bearing sleeve 1, and a contraction circumferential airflow channel 5 for compressing and pressurizing the gas can be formed between the inner side of the gas foil 2 and the outer side of the cylindrical rotor 4.

[0036] The thickness of the spring foil 3 described in this embodiment increases stepwise along the rotation direction of the cylindrical rotor, and the thickness increase of each step is consistent. The thickness difference between the front section and the rear section of the airflow of the spring foil 3 is 100 to 200 microns, and the thickness increase T of each step is determined by the total number of circumferential cantilever beams 31. The cantilever beams 31 are arranged on the spring foil 3 through beam supports 32. The length L of the cantilever beam 31 gradually increases along the rotation direction of the cylindrical rotor 4. The upright height of the cantilever beam 31 gradually increases along the rotation direction of the cylindrical rotor 4. The upright height of the cantilever beam 31 is proportional to its length. As the height increases, a contracting circumferential airflow channel 5 is formed between the gas foil 2 and the cylindrical rotor 4, thereby achieving the effect of compressing the gas. When the load is too large and the spring is excessively deformed, the cantilever beam 31 is severely bent, so that the corresponding vertical height almost disappears. In that case, the spring foil 3 gradually increases in thickness to form a contracting pneumatic wedge-shaped channel between the gas foil 2 and the cylindrical rotor 4, thereby achieving the effect of compressing the gas. The step-by-step increase in the thickness of the spring foil 3 combined with the increase in the length of the cantilever beam 31 can significantly reduce the bearing takeoff speed and reduce the contact time between the cylindrical rotor 4 and the gas foil 2.

[0037] The spring foil 3 of this embodiment is processed by multiple chemical etching methods, and the surface is etched by 15% to 50%. The step-wise change in thickness of the spring foil 3 can be produced by multiple etching methods. The step-wise change in spring thickness along the circumferential direction has greater flexibility in controlling the spring stiffness, bearing air film thickness and pneumatic pressure. The thickness of the gas foil 2 is consistent.

[0038] In the bearing sleeve 1 of the present embodiment, an annular gas foil 2 and an annular spring foil 3 are arranged, or an annular structure formed by assembling multiple gas foils 2 and an annular structure formed by assembling multiple spring foils 3 are arranged. Thus, the bearing sleeve 1 can be divided into one or more gas foil 2 and spring foil 3 sections along the circumferential direction, forming one or more corresponding gas contraction channels, and pressurizing the gas to generate bearing capacity.

[0039] The bearing sleeve 1 described in this embodiment includes a bearing sleeve housing 11, and the inner wall of the bearing sleeve housing 11 is provided with a plurality of foil positioning pins 12, and the gas foil 2 and the spring foil 3 are installed in the bearing sleeve housing 11 through the foil positioning pins 12. The inner wall of the bearing sleeve housing 11 is provided with straight line segments on both sides of the foil positioning pins 12, that is, from point i to the foil positioning pin 12, and from the foil positioning pin 12 to point j is a straight line segment, and the straight line segments between the two foil positioning pins 12 are connected by a circular arc segment (j to point i), and the straight line segment is tangent to the circular arc segment. The protruding part of the foil positioning pin 12 protruding from the inner wall of the bearing sleeve housing is provided with a bayonet 13 for clamping the ends of the gas foil 2 and the spring foil 3. The height h of the foil positioning pin 12 can be adjusted according to the thickness of the bearing spring and the foil.

[0040] The bearing sleeve 1 of this embodiment is usually machined from bar stock, and all aspects except its aperture are machined from bar stock. The finished size of the aperture is usually formed by broaching or wire cutting machining (EDM). The gas foil 2 is etched from a nickel alloy and has been rolled to the final thickness. The spring foil 3 is etched from a chromium-nickel-iron alloy that has been fully heat-treated. The etched gas foil is coated with a low-friction coating to reduce the starting torque and avoid damage to the metal foil caused by accidental contact during high-speed operation. The gas foil 2 can be bent into a nearly circular arc by a tooling to facilitate installation in the bearing sleeve 1. The inner wall of the bearing sleeve 1 is circumferentially provided with one or more foil locating pins 12 evenly distributed along the circumference, and the bayonet 13 on the side of the foil locating pin 12 provides contact positioning for the spring foil 3 and the gas foil 2 to prevent the foil from falling off, while generating the necessary preload force.

[0041] The thickness of the spring foil of the present invention gradually increases along the circumferential direction, so that the gap between the outer diameter of the rotor and the inner diameter of the bearing sleeve gradually decreases, that is, the thickness of the bearing air film is narrowed, thereby generating pneumatic pressure, and at the same time, the stiffness of the cantilever beam is correspondingly improved along the circumferential direction, so that it can cope with the gradually increasing pneumatic pressure and maintain a stable dynamic stiffness balance. The step-by-step change in the thickness of the spring foil can be produced by multiple etching methods, and the step-by-step change in the spring thickness along the circumferential direction has greater flexibility in controlling the spring stiffness, the thickness of the bearing air film and the pneumatic pressure. The bearing sleeve is composed of a bearing housing and a plurality of locating pins. The height of the locating pins can be adjusted according to the bearing spring and the thickness of the foil. This design improves the flexibility of the bearing sleeve design and reduces the production cost. The inner diameter of the bearing is divided into two parts, which are composed of a straight line segment and a circular arc segment, and are arranged tangently. This design makes the inner diameter easier to process and also facilitates the size detection after processing.

Claims

1. A flexible foil air radial bearing, comprising a bearing sleeve, a gas foil and a spring foil, wherein the spring foil and the gas foil are sequentially mounted on the inner wall of the bearing sleeve, characterized in that: The thickness of the spring foil gradually increases along the circumferential direction. Cantilever beams are arranged horizontally and vertically on the spring foil. The cantilever beams stand upright between the gas foil and the bearing sleeve. A contraction circumferential airflow channel for compressing and pressurizing the gas can be formed between the inner side of the gas foil and the outer side of the cylindrical rotor.

2. A flexible foil air radial bearing according to claim 1, characterized in that: The thickness of the spring foil increases step by step along the rotation direction of the cylindrical rotor, and the thickness increase of each step is consistent.

3. A flexible foil air radial bearing according to claim 2, characterized in that: The length of the cantilever beam gradually increases along the rotation direction of the cylindrical rotor.

4. A flexible foil air radial bearing according to claim 3, characterized in that: The vertical height of the cantilever beam gradually increases along the rotation direction of the cylindrical rotor.

5. The flexible foil air radial bearing according to claim 1, characterized in that: The spring foil is processed by multiple chemical etching methods, and the surface is etched by 15% to 50%.

6. The flexible foil air radial bearing according to claim 1, characterized in that: The thickness of the gas foil is consistent.

7. The flexible foil air radial bearing according to claim 1, characterized in that: The bearing sleeve is provided with an annular gas foil and an annular spring foil, or an annular structure formed by assembling a plurality of gas foils and an annular structure formed by assembling a plurality of spring foils.

8. The flexible foil air radial bearing according to claim 1, characterized in that: The bearing sleeve comprises a bearing sleeve shell, the inner wall of which is provided with a plurality of foil positioning pins, and the gas foil and the spring foil are installed in the bearing sleeve shell through the foil positioning pins.

9. A flexible foil air radial bearing according to claim 8, characterized in that: The inner wall of the bearing sleeve housing is provided with straight line segments on both sides of the foil positioning pins, the straight line segments between the two foil positioning pins are connected by an arc segment, and the straight line segment is tangent to the arc segment.

10. A flexible foil air radial bearing according to claim 9, characterized in that: The protruding part of the foil locating pin protruding from the inner wall of the bearing sleeve housing is provided with bayonet holes for clamping the ends of the gas foil and the spring foil on both sides.

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