Variable stiffness multi-pad foil gas dynamic pressure bearing

Abstract

The application discloses a variable stiffness multi-piece foil gas dynamic pressure bearing, which comprises a bearing sleeve and a plurality of elastic foils arranged in the bearing sleeve. The elastic foils are arranged in a circumferential direction, and the cross section of the elastic foils is in a non-closed triangular structure and has a first side, a second side and a third side. The first side has a fixed end directly or indirectly fixed to the inner surface of the bearing sleeve, and the third side has a free end in contact with the inner surface of the bearing sleeve or a bottom foil. A top foil is arranged on the radially inner side of the elastic foil and supported on the first side. The application realizes multi-stage self-adaptive variable stiffness through the deformation of the elastic foils and the mutual contact of the circumferentially adjacent foils after being pressed, and the sliding of the free end generates dry friction damping. The application has low manufacturing cost and significantly improves the adaptability and running stability of the bearing under wide load working conditions.

Description

Technical Field

[0001] This invention relates to the field of hydrodynamic bearing technology, specifically a variable stiffness multi-plate foil gas hydrodynamic bearing. It has a wide range of applications and can be used in high-speed rotating mechanical equipment such as air compressors, air circulators, blowers, and micro gas turbines. Background Technology

[0002] Foil-type gas hydrodynamic bearings are advanced bearings that use ambient gas as the lubricating medium and achieve non-contact rotor support based on the gas hydrodynamic effect. They typically consist of a smooth top foil, a corrugated foil providing elastic support, and a bearing housing. During operation, the high-speed rotating rotor draws gas into the converging wedge-shaped gap formed between the foil and the top foil, generating a hydrodynamic gas film to support the rotor. Compared to traditional oil-lubricated bearings, these bearings offer significant advantages such as no need for lubrication, low frictional power consumption, no pollution, and adaptability to high-speed and high-temperature environments, making them promising for applications in aerospace, energy and power, and precision machinery.

[0003] However, traditional foil bearings generally use integrally stamped corrugated foil as the elastic element, which presents the following major technical bottlenecks in practical applications: First, the corrugated foil forming relies on complex and expensive special molds; once key parameters such as wave height and wave pitch need to be adjusted to optimize performance, the mold must be redesigned and manufactured, resulting in long R&D cycles and high trial-and-error costs. Second, the arch height (i.e., stiffness) of traditional corrugated foil is fixed, resulting in high initial stiffness of the bearing during startup, no-load, or light-load conditions. This is not conducive to vibration isolation and damping absorption of the rotor system at low speeds, and it is difficult to maintain the optimal wedge-shaped air film over a wide range of operating conditions, reducing the bearing's adaptability and operational stability. Third, the corrugated foil is usually fixed to the bearing sleeve at only one end, with most of the area in a free cantilever state. Under continuous alternating loads and high operating temperatures, the free end is prone to plastic deformation and creep, leading to irreversible changes in the bearing's inner diameter, stiffness, and damping characteristics, severely affecting its load-bearing capacity, vibration level, and service life.

[0004] Therefore, there is an urgent need in this field for a new type of foil gas dynamic bearing that has low manufacturing cost, easy and flexible stiffness parameters, and can provide variable stiffness and high stability damping according to load changes. Summary of the Invention

[0005] To address the aforementioned technical shortcomings, this invention provides a variable stiffness multi-plate foil gas hydrodynamic bearing, which aims to solve the problems of high manufacturing cost, fixed stiffness, and poor long-term stability of traditional corrugated foil bearings through a modular and adjustable elastic support structure.

[0006] To achieve the above-mentioned technical objectives, the present invention provides the following technical solutions: The present invention provides a variable stiffness multi-plate foil gas hydrodynamic bearing, including a bearing sleeve and a plurality of elastic foils disposed within the bearing sleeve.

[0007] The elastic foil is arranged circumferentially, and its cross-section is a non-closed triangular structure with a first side, a second side and a third side; wherein, the first side has a fixed end, which is directly or indirectly fixed to the inner surface of the bearing sleeve, and the third side has a free end, which contacts the inner surface of the bearing sleeve or the bottom foil disposed on the inner surface.

[0008] A top foil is provided on the radial inner side of the elastic foil, and the top foil is supported on the first side; through this arrangement of non-closed triangles, the modularity of the elastic support is realized.

[0009] Furthermore, the first side and the second side are connected to form a first bend, and the second side and the third side are connected to form a second bend; under no-load conditions, the fixed end and the free end abut against each other or overlap, and the second bend contacts the inner surface or bottom foil of the bearing sleeve; in order to optimize stiffness characteristics, the included angle between the second side and the third side is greater than 90°, and the first side is the long side of a triangular structure.

[0010] Furthermore, the elastic foil is configured to have two levels of support stiffness: the triangular structural deformation of the elastic foil itself provides the first level of support stiffness; a preset gap (c) is provided between two circumferentially adjacent elastic foils; when the load increases to a set value, causing the two adjacent elastic foils to contact each other, a second level of support stiffness greater than the first level of support stiffness is provided; specifically, the second level of support stiffness is generated by the contact between the first bend of the preceding elastic foil and the first edge of the following elastic foil; the size of the preset gap (c) is configured to determine the load threshold at which the second level of support stiffness is activated.

[0011] Furthermore, the elastic foil can be formed by integral bending; or the first side and the second side can be connected by welding to form a split structure to reduce the processing difficulty.

[0012] Furthermore, when the bearing includes a bottom foil, the bottom foil is fixed to the inner surface of the bearing sleeve; the fixed end is fixed to the bottom foil, while the free end and the second bend remain in contact with the bottom foil and can generate relative sliding when subjected to compression deformation, thereby providing system damping through dry friction; one end of the bottom foil is provided with a bottom foil fixed end, which is bent outward radially and engaged with the bearing sleeve to ensure the stability of the assembly; one end of the top foil is fixed to the bottom foil or the bearing sleeve, and the top foil includes a top foil arc segment and a foil flat segment, the foil flat segment being attached to the first edge of one of the elastic foils, achieving a tight fit between the top foil and the elastic assembly.

[0013] Furthermore, the elastic foil can be divided into at least two groups in the axial direction, each group consisting of multiple elastic foils arranged in the circumferential direction; the adjacent two groups of elastic foils are staggered by a preset angle (θ) in the circumferential direction, thereby optimizing the bearing load uniformity in the axial direction and smoothing the circumferential stiffness fluctuation.

[0014] The beneficial effects of this invention are as follows: 1. The core elastic unit is an elastic foil with a non-closed triangular cross-section that can be formed by simple bending or welding, which eliminates the need for complex stamping dies and significantly reduces manufacturing costs and production preparation cycle; 2. By using the preset gap (c) and the phased contact mechanism between the first bend (25) and the first edge (21) of the adjacent foil, the "variable stiffness" characteristic of the support stiffness adaptively increases with the increase of load is realized; the stiffness is low under light load, which is conducive to vibration isolation; the stiffness increases stepwise under heavy load, which ensures the support strength under high load and significantly expands the high-efficiency working range. 3. During the deformation process, the free end of the non-closed triangular structure generates a controllable micro-sliding between the free end and the bottom foil or the inner wall of the bearing sleeve, which is transformed into stable dry friction damping. At the same time, after bearing the load, the free end of the elastic foil contacts the fixed end (24), which effectively suppresses the creep and plastic deformation of the traditional cantilever corrugated foil under high temperature alternating load and extends its service life. When the secondary contact is formed, the adjacent foils support each other and construct a collaborative bearing network, which greatly improves the overall bearing capacity and operational stability of the bearing. 4. By arranging multiple groups axially and staggering the circumferential angle (θ), a collaborative bearing network is constructed, eliminating the stiffness dead angle that may be caused by a single foil arrangement, and greatly improving the overall operating stability of the bearing. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 An exploded view of the bearing provided by this invention.

[0017] Figure 2 A front view of the bearing provided by the present invention.

[0018] Figure 3 This is a schematic diagram of the structure of the elastic foil provided by the present invention.

[0019] Figure 4 An enlarged view of the elastic foil provided by the present invention.

[0020] Figure 5 This is a schematic diagram of the bottomless foil solution provided by the present invention.

[0021] Figure 6 This is a schematic diagram of the welding connection method for the elastic foil provided by the present invention.

[0022] Figure 7 This is a schematic diagram of the axial distribution of the elastic foil provided by the present invention.

[0023] The labels in the attached figures are as follows: 1-Top foil, 2-Elastic foil, 3-Bottom foil, 4-Bearing sleeve, 5-Bearing elastic component; 11 - Top foil arc segment; 12 - Foil sheet straight segment; 21-First side, 22-Second side, 23-Third side, 24-Fixed end, 25-First bend, 26-Second bend, 27-Welded part; 32- Bottom foil fixing end; c - Preset gap of foil, d - circumferential distance of fixed end, L - circumferential length of third side, θ - circumferential stagger angle. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0025] In the description of this invention, it should be noted that, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "top," "bottom," "inner," "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0026] In the following, the terms “comprising,” “having,” and their cognates, which may be used in various embodiments of the invention, are intended only to indicate a particular feature, number, step, operation, element, component, or combination thereof, and should not be construed as excluding, firstly, the presence of one or more other features, numbers, steps, operations, elements, components, or combinations thereof, or adding the possibility of one or more features, numbers, steps, operations, elements, components, or combinations thereof.

[0027] Unless otherwise specified, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which the various embodiments of the invention pertain. Terms (such as those defined in commonly used dictionaries) shall be interpreted as having the same meaning as in their contextual meaning in the relevant technical field and shall not be interpreted as having an idealized or overly formal meaning, unless clearly defined in the various embodiments of the invention.

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] The variable stiffness multi-plate foil gas hydrodynamic bearing provided in this application's implementation case will now be described.

[0030] Example 1: Variable stiffness multi-plate foil gas hydrodynamic bearing including a bottom foil, refer to... Figures 1 to 4 As shown, it includes a bearing sleeve (4) and a bearing elastic component (5) installed therein; for ease of manufacturing and assembly, the bearing elastic component (5) is an independent module. The bearing elastic component (5) is composed of a top foil (1), multiple elastic foils (2) and a bottom foil (3) stacked from the inside to the outside. The elastic foils (2) are the core elastic support units. The above three are preferably made of metal foil materials (such as Inconel alloy, stainless steel, etc.) with excellent elasticity and high temperature resistance.

[0031] like Figure 3 As shown, each elastic foil (2) is integrally bent from a single metal foil, and its cross-section is a non-closed triangular structure. Specifically, the triangular structure includes a first side (21), a second side (22), and a third side (23). The first side (21) and the second side (22) are smoothly connected by a first bend (25), and the second side (22) and the third side (23) are smoothly connected by a second bend (26). The first side (21) is the long side of its triangular structure, and its end is a fixed end (24). The end of the third side (23) is a free end. In order to obtain excellent deformation and sliding characteristics, the included angle between the second side (22) and the third side (23) is configured as an obtuse angle greater than 90°.

[0032] In the unloaded (i.e. initial assembly) state, the fixed end (24) of the first side (21) and the free end of the third side (23) collide or overlap in space to form a non-closed force transmission loop; at the same time, a set gap (c) is reserved between the two adjacent elastic foils (2).

[0033] To reduce manufacturing difficulty, the first bending part (25) can be directly bent into shape using a bending tool; or, at multiple positions along the bearing axis, some material can be removed by laser cutting, wire cutting or stamping (such as making rectangular or circular holes to reduce the bending stiffness locally, thereby achieving precise bending).

[0034] like Figure 1 , Figure 2 and Figure 4 As shown, in a preferred assembly process, the components are first pre-assembled in a flat state: multiple elastic foils (2) are arranged circumferentially at intervals, and the fixed ends (24) of each foil are fixed to the inner surface of the bottom foil (3) by spot welding, laser welding or brazing; the top foil (1) and the bottom foil (3) are both planar foils or arc-shaped foils in the initial state; wherein, the top foil (1) includes a smooth top foil arc segment (11) for forming the bearing working surface and a foil straight segment (12) for fixing; during assembly, the foil straight segment (12) is attached to the first side (21) of an elastic foil (2), and the top foil arc segment (11) covers and supports the first side (21) of each of the other elastic foils (2); one end of the top foil (1), the fixed end (24) of the elastic foil (2) and the bottom foil fixed end (32) of the bottom foil (3) are welded and fixed in the same area.

[0035] Subsequently, the pre-assembled, flat bearing elastic component (5) is rolled into a cylindrical shape along the circumference and placed into the bearing sleeve (4); the bottom foil fixing end (32) is preferably bent outward along the radial direction and fixed to the inner surface of the bearing sleeve (4) by means of slots, welding or pins, so that the top foil (1), elastic foil (2) and bottom foil (3) maintain a stable stacked state in the bearing sleeve (4) (e.g. Figure 4 (As shown).

[0036] Under no load or light load (e.g., during rotor start-up or low-speed operation), the load is transmitted to the first side (21) through the dynamic pressure air film and the top foil (1). The elastic foil (2) undergoes elastic deformation after being compressed, resulting in its overall flattening. The free end of the third side (23) and the second bend (26) are squeezed and undergo slight circumferential slip relative to the bottom foil (3). This relative sliding between interfaces effectively consumes the vibration energy of the system and provides excellent dry friction damping. At this time, the circumferential length L of the third side (23) is less than the circumferential distance (d) between adjacent elastic foils. The free end of the third side (23) will gradually approach and eventually abut against the fixed end (24) of the first side (21), forming a "first-level contact". At this stage, the support stiffness of the system mainly comes from the bending deformation of the individual elastic foil (2), which is a low first-level support stiffness, which is very beneficial to the vibration isolation of the rotor system.

[0037] When the rotor load continues to increase and exceeds the preset load threshold, the deformation of the elastic foil (2) increases until the gap (c) between adjacent foils is consumed. The first bend (25) of the previous elastic foil (2) will press down and support the upper surface of the first side (21) of the next elastic foil (2), forming a "secondary contact". Once the secondary contact is triggered, the isolated elastic foils are connected to each other, and the force transmission path is expanded from single-point support to a circumferential cooperative bearing network, which makes the bearing support stiffness significantly improved in a step-like manner (i.e., secondary support stiffness), thereby providing extremely high load-bearing capacity and operational stability for high-speed heavy-load rotors.

[0038] The load threshold for secondary contact can be flexibly controlled by precisely designing the size of the circumferential distance (d); the smaller the gap, the earlier the secondary contact occurs, and the earlier the bearing enters the high stiffness state; the larger the gap, the wider the range of low stiffness under light load; in addition, geometric parameters such as the length of the third side (23) and the angle between the first side (21) and the second side (22) also directly affect the magnitude and variation curve of the primary stiffness, thereby realizing the customized design of the bearing stiffness characteristics. The length of the third side (23) not only determines the number of circumferentially arranged elastic foils (2).

[0039] Example 2: Variable stiffness multi-plate foil gas dynamic bearing without bottom foil.

[0040] Reference Figure 5 As shown, the present invention also provides another more compact embodiment, which omits the bottom foil (3).

[0041] In this embodiment, multiple elastic foils (2) are still arranged circumferentially along the bearing sleeve (4), but their fixed ends (24) are directly (e.g., by laser penetration welding) fixed to the inner surface of the bearing sleeve (4); correspondingly, the free end of the third side (23) directly contacts the inner surface of the bearing sleeve (4) and generates sliding friction when pressed; the top foil (1) is set on the radial inner side of all elastic foils (2), one end of which is directly fixed to the area on the bearing sleeve (4) corresponding to a certain fixed end (24), and the other end is free; this scheme reduces the number of parts, greatly simplifies the structure, and is particularly suitable for applications with extremely high restrictions on manufacturing costs and radial space; its variable stiffness mechanism and damping generation principle are completely consistent with those of Embodiment 1.

[0042] Other preferred implementation schemes: like Figure 6As shown, the forming of the elastic foil (2) is not limited to bending a single piece of material; in an alternative embodiment, it can be formed by welding multiple foil segments: the first side (21) and the second side (22) are independent foils, and their ends are connected together by a welding part (27); while the second side (22) and the third side (23) are still connected by a second bending part (26); this split design allows the use of metal foils of different thicknesses or different materials (e.g., using a high elastic material on the first side and a high wear-resistant material on the third side) in the same elastic component, providing greater design freedom for the local stiffness adjustment and life improvement of the bearing.

[0043] like Figure 7 As shown, in order to further improve the bearing load uniformity and eliminate the fluctuation of circumferential stiffness distribution, multiple elastic foils (2) can be distributed in at least two groups along the bearing axis; in the axial direction, the two adjacent groups of elastic foils (2) are staggered by a preset staggered angle (θ) (for example, staggered by half a pitch) in the circumferential direction; this axially staggered array arrangement constructs a more uniform three-dimensional support network, effectively avoids local stress concentration, and significantly enhances the bearing's anti-disturbance capability under complex working conditions.

[0044] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention, such as changing the specific angle, size, material, or fixing method of the triangular elastic foil, should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A variable stiffness multi-plate foil gas hydrodynamic bearing, characterized in that: Includes a bearing sleeve (4) and a plurality of elastic foils (2) disposed within the bearing sleeve (4); The elastic foil (2) is arranged circumferentially, and its cross-section is a non-closed triangular structure with a first side (21), a second side (22) and a third side (23). The first side (21) has a fixed end (24), which is directly or indirectly fixed to the inner surface of the bearing sleeve (4), and the third side (23) has a free end, which is in contact with the inner surface of the bearing sleeve (4) or the bottom foil (3) disposed on the inner surface of the bearing sleeve (4). The elastic foil (2) has a top foil (1) on its radial inner side, and the top foil (1) is supported on the first side (21).

2. The variable stiffness multi-plate foil gas hydrodynamic bearing according to claim 1, characterized in that: The first side (21) is connected to the second side (22) to form a first bend (25), and the second side (22) is connected to the third side (23) to form a second bend (26). Under no load, the fixed end (24) is in contact with the free end, and the second bend (26) is in contact with the inner surface of the bearing sleeve (4) or the bottom foil (3).

3. The variable stiffness multi-plate foil gas hydrodynamic bearing according to claim 2, characterized in that: The elastic foil (2) is configured to have two levels of support stiffness: The triangular structural deformation of the elastic foil (2) itself provides the first-level support stiffness; A preset gap (c) is provided between two circumferentially adjacent elastic foils (2) to provide a second level of support stiffness when the load increases to the point that the two adjacent elastic foils (2) come into contact with each other; there is a circumferential distance (d) between the fixed ends (24) of the two circumferentially adjacent elastic foils (2) and a gap is left between the bodies of the two adjacent elastic foils (2) in the unloaded state; the size of the circumferential distance (d) is configured to determine the load threshold for enabling the second level of support stiffness.

4. The variable stiffness multi-plate foil gas hydrodynamic bearing according to claim 3, characterized in that: The second-level support stiffness is generated by the contact between the first bend (25) of the previous elastic foil (2) and the first edge (21) of the next elastic foil (2).

5. The variable stiffness multi-plate foil gas hydrodynamic bearing according to claim 2, characterized in that: The angle between the second side (22) and the third side (23) is greater than 90°, and the first side (21) is the long side of the triangle structure.

6. The variable stiffness multi-plate foil gas hydrodynamic bearing according to claim 1, characterized in that: The elastic foil (2) is an integrally formed structure; or, the first side (21) and the second side (22) are connected by a welding part (27) to form a split structure.

7. The variable stiffness multi-plate foil gas hydrodynamic bearing according to claim 1, characterized in that: One end of the top foil (1) is fixed to the bottom foil (3) or the bearing sleeve (4). The top foil (1) includes a top foil arc segment (11) and a foil straight segment (12). The foil straight segment (12) is attached to the first side (21) of one of the elastic foils (2).

8. The variable stiffness multi-plate foil gas hydrodynamic bearing according to claim 1, characterized in that: The elastic foil (2) is divided into at least two groups in the axial direction, and the adjacent groups of elastic foil (2) are staggered at a predetermined angle (θ) in the circumferential direction.

9. The variable stiffness multi-plate foil gas hydrodynamic bearing according to claim 1, characterized in that: The bearing also includes a bottom foil (3), which is fixed to the inner surface of the bearing sleeve (4); the fixed end (24) is fixed to the bottom foil (3), and the free end and the second bent portion (26) are in contact with the bottom foil (3) and can slide relative to each other.

10. The variable stiffness multi-plate foil gas hydrodynamic bearing according to claim 9, characterized in that: One end of the bottom foil (3) is provided with a bottom foil fixing end (32), which is bent outward along the radial direction and engaged with the bearing sleeve (4).

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