Bearing foil assembly, bearing assembly, and air compressor

Abstract

The present disclosure provides a bearing foil assembly, a bearing assembly, and an air compressor. The bearing foil assembly consists of a flat foil layer and a bump foil layer, the bump foil is located on the outer periphery of the flat foil, and the inner periphery of the flat foil is of a flat structure and the flat foil has a center O; an upper half curve segment of the inner periphery of the flat foil and a lower half curve segment opposite thereto are smoothly connected by means of a first dashed curve segment, and the upper half curve segment and the lower half curve segment opposite thereto are smoothly connected by means of a second dashed curve segment; and the distance between the intersection point of the X-axis and the first dashed curve segment and the intersection point of the X-axis and the second dashed curve segment is x, the distance between the intersection point of the Y-axis and the upper half curve segment and the intersection point of the Y-axis and the lower half curve segment is y, and x>y. The present disclosure can effectively increase the wedge ratio, and can increase the lift force of an air bearing; and a single-layer bump foil and a single-layer flat foil are used, a smooth, continuous and flat curve internally tangent to troughs can be formed, and when the bump foil is attached to the flat foil, a rotor can be uniformly and continuously supported, thereby improving the load-bearing performance.

Description

Bearing foil assembly, bearing assembly and air compressor

[0001] The present disclosure claims priority to the Chinese patent application No. 202410736802.2, filed on June 7, 2024, and entitled "Bearing foil assembly, bearing assembly and air compressor", the entire content of which is incorporated herein by reference. TECHNICAL FIELD

[0002] The present disclosure relates to the technical field of bearings, in particular to a bearing foil assembly, a bearing assembly and an air compressor. BACKGROUND

[0003] High-speed permanent magnet synchronous motors have the advantages of small size, high power density and high motor efficiency, and are widely used in the field of centrifuges. Small power high-speed centrifuges generally use air suspension bearings to support the rotor, and the motor speed exceeds 100,000 rpm. The gas that floats the motor rotor is the same as the gas pumped by the centrifuge, so there is no pollution. The dynamic pressure gas suspension bearing forms a dynamic pressure gas film through a wedge-shaped gap. The current air suspension bearing is generally made of special metal foil punched and combined, mainly in a circular structure.

[0004] Such a structure has the main defect that the ratio of the front and rear end cross-sectional areas (or size cross-sectional areas) of the wedge-shaped gap is limited, and this ratio determines the air suspension pressure. If the gap between the motor shaft diameter and the bearing inner foil diameter is large, although the wedge ratio can be increased, the shaft and bearing coaxiality is poor, the shaft vibration is large, and the running stability is poor. If the gap between the motor shaft diameter and the bearing inner foil diameter is small, the air suspension pressure is limited, and the rotor weight must be light, which limits the motor structure and performance.

[0005] Since the air suspension bearing in the related art has the technical problems of low wedge ratio, low air suspension pressure, poor support effect, and poor transition smoothness between two or more wave foils, which cannot uniformly and continuously support the rotor, the present disclosure designs a bearing foil assembly, a bearing assembly and an air compressor. SUMMARY

[0006] Therefore, the technical problem to be solved by the present disclosure is to overcome the defects of the air suspension bearing in the related art, such as poor support effect and the inability of two or more wave foils to uniformly and continuously support the rotor, so as to provide a bearing foil assembly, a bearing assembly and an air compressor.

[0007] To solve the above problems, the present disclosure provides a bearing foil assembly:

[0008] It is composed of one layer of flat foil and one layer of wave foil, the wave foil is located at the outer periphery of the flat foil, in the projection plane of the vertical plane, the inner periphery of the flat foil is a flat structure with center O, and the horizontal straight line through the O point is the X axis, and the vertical straight line through the O point is the Y axis, the inner periphery of the flat foil includes an upper half curve segment above the X axis and a lower half curve segment below the X axis, the first lower end of the upper half curve segment and the first upper end of the lower half curve segment opposite to it are spaced apart, and the two are smoothly connected by a first virtual curve segment, the second lower end of the upper half curve segment and the second upper end of the lower half curve segment opposite to it are spaced apart, and the two are smoothly connected by a second virtual curve segment, the first virtual curve segment and the second virtual curve segment are both virtual non-solid line segments;

[0009] The distance between the intersection point of the X axis and the first virtual curve segment and the intersection point of the X axis and the second virtual curve segment is the length x of the inner periphery of the flat foil along the X direction, and the distance between the intersection point of the Y axis and the upper half curve segment and the intersection point of the Y axis and the lower half curve segment is the length y of the inner periphery of the flat foil along the Y direction, and x>y.

[0010] In some embodiments,

[0011] The wave foil includes a plurality of wave crests protruding radially outward, two adjacent wave crests are spaced apart, and a wave valley is formed between the two adjacent wave crests, the inner periphery of a plurality of wave valleys is arranged in close contact with the outer periphery of the flat foil; a plurality of wave crests circumscribe a continuous annular curve, the center of the annular curve is also the O point, and the distance between the two intersection points of the annular curve and the X axis is the length x' of the outer periphery of the wave foil along the X direction, and the distance between the two intersection points of the annular curve and the Y axis is the length y' of the outer periphery of the wave foil along the Y direction, and x'>y'.

[0012] In some embodiments,

[0013] The upper half curve segment of the flat foil is a partial curve segment of an elliptical curve, a parabola or an involute, the lower half curve segment of the flat foil is a partial curve segment of an elliptical curve, a parabola or an involute, when the upper half curve segment and the lower half curve segment are both elliptical curves, the upper half curve segment, the first virtual curve segment, the lower half curve segment and the second virtual curve segment are connected to form an elliptical whole circle, and the radially inner convex surfaces of a plurality of wave valleys are tangent to the elliptical whole circle; when the upper half curve segment and the lower half curve segment are both parabolas, the radially inner convex surfaces of a plurality of wave valleys are tangent to the parabolas; when the upper half curve segment and the lower half curve segment are both involutes, the radially inner convex surfaces of a plurality of wave valleys are tangent to the involutes;

[0014] The wave foil is provided with a plurality of wave crests, and the wave crests closer to the Y axis are higher in height, and the wave crests farther from the Y axis are lower in height, the radially outer convex surfaces of the wave crests are located on a same first circumscribed circle, that is, the annular curve is a circle, so that x' = y', and the center of the first circumscribed circle is located at the O point.

[0015] In some embodiments,

[0016] The wave foil comprises an upper half wave foil above the X axis and a lower half wave foil below the X axis, the radially outer convex surfaces of all the wave crests of the upper half wave foil are in contact with the first circumscribed circle, the radially inner convex surfaces of all the wave troughs of the upper half wave foil are tangent to the outer circumferential surface of the upper half curve segment of the flat foil, the radially outer convex surfaces of all the wave crests of the lower half wave foil are in contact with the first circumscribed circle, and the radially inner convex surfaces of all the wave troughs of the lower half wave foil are tangent to the outer circumferential surface of the lower half curve segment of the flat foil.

[0017] In some embodiments,

[0018] The upper half curve segment and the lower half curve segment of the flat foil are symmetrically arranged with respect to the X axis, the upper half curve segment of the flat foil is symmetrically arranged with respect to the Y axis, and the lower half curve segment of the flat foil is symmetrically arranged with respect to the Y axis.

[0019] The upper half wave foil and the lower half wave foil are symmetric with respect to the X axis, the upper half wave foil is symmetrically arranged with respect to the Y axis, and the lower half wave foil is symmetrically arranged with respect to the Y axis.

[0020] In some embodiments,

[0021] The upper half curve segment of the flat foil is a circular partial arc segment, and the lower half curve segment of the flat foil is a circular partial arc segment,

[0022] The upper half curve segment and the lower half curve segment are formed by first manufacturing a circular flat foil in a projection plane of a vertical plane, the circular flat foil has the O point as a center, the X axis as a horizontal symmetry axis, and the Y axis as a vertical symmetry axis, then cutting off arc segments of partial lengths at two positions where the circular flat foil intersects the X axis, and connecting the upper half curve segment and the lower half curve segment together.

[0023] In some embodiments,

[0024] After cutting, the first lower end of the upper half curve segment is connected with the first upper end of the opposite lower half curve segment by the first dotted curve segment, and the second lower end of the upper half curve segment is connected with the second upper end of the opposite lower half curve segment by the second dotted curve segment, the lengths of the arc segments of the cut parts are equal, and the lengths of the first dotted curve segment and the second dotted curve segment are equal and symmetrically arranged relative to the O point.

[0025] In some embodiments,

[0026] The wave foil includes a plurality of wave crests protruding radially outward, adjacent two wave crests are arranged at intervals, and a wave trough is formed between adjacent two wave crests, the inner periphery of a plurality of the wave troughs is arranged in close contact with the outer periphery of the flat foil, the wave foil is also cut at a position radially opposite to the cut part of the flat foil, and the two cut parts of the wave foil are spliced together; a plurality of wave crests are circumscribed by a continuous annular curve, the center of the annular curve is also the O point, and the distance between the two intersection points of the annular curve and the X axis is the length x' of the outer periphery of the wave foil in the X direction, the distance between the two intersection points of the annular curve and the Y axis is the length y' of the outer periphery of the wave foil in the Y direction, and x'≥y'.

[0027] In some embodiments,

[0028] After cutting and before cutting, the radially inner convex surfaces of a plurality of the wave troughs are tangent to the outer surface of the flat foil; the heights of a plurality of the wave crests in the wave foil are equal;

[0029] Before cutting, the radially outer convex surfaces of a plurality of the wave crests are located on the same second circumscribed circle, the center of the second circumscribed circle is located at the O point, so that after cutting, x'>y'.

[0030] In some embodiments,

[0031] Further comprising a rotor shaft, the rotor shaft is located at the inner periphery of the flat foil, and in the projection plane in the vertical plane, the minimum distance between the rotor shaft and the ellipse, parabola or involute of the inner periphery of the flat foil on the X axis is the side gap, the minimum distance between the rotor shaft and the ellipse, parabola or involute of the inner periphery of the flat foil on the Y axis is the top gap, the side gap is greater than the top gap, and the ratio between the side gap and the top gap is the wedge ratio.

[0032] In some embodiments,

[0033] The rotor shaft is located at the inner periphery of the flat foil, and in a projection plane of a vertical plane, the minimum distance between the rotor shaft and the first broken curve segment or the second broken curve segment of the inner periphery of the flat foil on the X-axis is a side gap, the minimum distance between the rotor shaft and the inner periphery of the flat foil on the Y-axis is a top gap, the side gap is greater than the top gap, and the ratio between the side gap and the top gap is a wedge ratio.

[0034] The present disclosure also provides a bearing assembly, which comprises the aforementioned bearing foil assembly, and further comprises a bearing seat having a shaft hole, wherein the bearing foil assembly is arranged in the shaft hole to support a rotor shaft.

[0035] In some embodiments,

[0036] In a projection plane of a vertical plane, the inner periphery of the bearing seat is provided with a first accommodating groove at the junction with the axial side of the X-axis, and is provided with a second accommodating groove at the junction with the other axial side of the X-axis, the first lower end of the upper half of the flat foil is connected to the first upper end of the lower half of the flat foil opposite thereto through a first connecting portion, the first connecting portion is a convex structure protruding towards the first accommodating groove, and the first connecting portion is inserted into the first accommodating groove to form a fixed end; the second lower end of the upper half of the flat foil is connected to the second upper end of the lower half of the flat foil opposite thereto through a second connecting portion, the second connecting portion is a convex structure protruding towards the second accommodating groove, and the second connecting portion is inserted into the second accommodating groove to form a free end.

[0037] In some embodiments,

[0038] The third lower end of the upper half of the wave foil is connected to the third upper end of the lower half of the wave foil opposite thereto through a third connecting portion, the third connecting portion is a convex structure protruding towards the first accommodating groove, and the third connecting portion is inserted into the first accommodating groove to form a fixed end of the wave foil; the fourth lower end of the upper half of the wave foil is connected to the fourth upper end of the lower half of the wave foil opposite thereto through a fourth connecting portion, the fourth connecting portion is a convex structure protruding towards the second accommodating groove, and the fourth connecting portion is inserted into the second accommodating groove to form a free end of the wave foil.

[0039] In some embodiments,

[0040] When the free end of the flat foil, the fixed end of the flat foil, the free end of the wave foil and the fixed end of the wave foil are included, the rotation direction of the rotor shaft is such that the lower half of the flat foil structure rotates from the free end of the flat foil to the fixed end of the flat foil,

[0041] The rotation direction of the rotor shaft is such that the lower half of the wave foil structure rotates from the free end of the wave foil to the fixed end of the wave foil.

[0042] The air compressor provided by the present disclosure also includes a rotor shaft, and the bearing assembly supports the rotor shaft.

[0043] The bearing foil assembly, the bearing assembly and the air compressor provided by the present disclosure have the following beneficial effects:

[0044] 1. The present disclosure can make the inner circle of the aerostatic bearing flat and elliptical or quasi-elliptical by setting the inner periphery of the bearing foil assembly, especially the flat foil, to be flat, that is, the length x of the inner periphery of the flat foil along the X direction is greater than the length y of the inner periphery of the flat foil along the Y direction, so that the side gap is greater than the top gap, the front end cross-sectional area can be further increased, and the ratio of the front end cross-sectional area to the rear end cross-sectional area is increased, the wedge ratio is increased, the buoyancy of the aerostatic bearing is effectively increased, and therefore a heavier rotor can be suspended. Compared with the scheme of at least two layers of wave foils and / or at least two layers of flat foils in the related art, the present disclosure adopts a single layer of wave foils and a single layer of flat foils, can form a very smooth and continuous flat continuous curve (such as an elliptical curve or a quasi-elliptical curve, and the quasi-elliptical curve includes a parabola and an involute) by parameter adjustment, and can uniformly and continuously support the rotor after being attached to the flat foil, improve the support performance, and reduce the resistance of the rotating airflow in the bearing inner diameter.

[0045] 2. The present disclosure optimizes the structure of the aerostatic bearing inner diameter of the ultra-high-speed motor, adopts an elliptical or quasi-elliptical flat foil structure with a large transverse size and a small longitudinal size, forms an elliptical or quasi-elliptical aerostatic bearing, has a larger wedge ratio than a circular aerostatic bearing, and therefore has a larger air pressure, can increase the buoyancy of the aerostatic bearing, and can support a heavier rotor. Under the premise that the rotor weight remains unchanged, after increasing the ratio of the front end cross-sectional area to the rear end cross-sectional area, the aerostatic pressure is increased at the same speed, and if the speed is reduced, the aerostatic pressure can be the same as that of the circular inner diameter, the adjustable speed range of the motor can be effectively increased. Since the center of gravity of the rotor is downward and deviates from the center of the aerostatic bearing, the larger the bearing buoyancy of the present disclosure, the smaller the deviation between the center line of the rotor and the center line of the bearing, which can further reduce the whirling and vibration of the rotor, further reduce the collision caused by the whirling, and further reduce the motor noise caused by the vibration.

[0046] 3. The elliptical gas suspension bearing of the first aspect of the present disclosure is realized by a structure with smooth stepless gradual change of corrugation amplitude, variable or invariable corrugation width, i.e. the corrugation amplitude is large in the middle (close to the y-axis) and low on both sides (far from the y-axis), the height and width of the corrugation are accurately adjusted through simulation calculation, the crest envelope of the inner diameter of the corrugated foil (or the inscribed curve of the inner diameter) is formed, i.e. the inner foil, which becomes a standard ellipse, parabola or involute, i.e. a continuous curve, and the outer diameter envelope of the corrugated foil is a standard circle, so that the gas bearing has only one layer of corrugated foil, realizing a new structure with circular outer diameter and elliptical, parabolic or involute inner diameter. In this way, a circular bearing seat can realize the shape of an elliptical, parabolic or involute inner ring. Compared with the related art which adopts a two-layer corrugated foil with different lengths, the present disclosure has one less layer of corrugated foil, can realize a continuous curve, is simpler and has lower cost. Therefore, the present disclosure has structural advantages and cost advantages over the related art which uses a single layer of corrugated foil to increase dynamic pressure.

[0047] 4. The approximate elliptical gas suspension bearing of the second aspect of the present disclosure is designed as an approximate elliptical shape, and the foil with equal corrugation height is made into the same shape as the bearing seat, the outer diameter is fitted to the inner diameter of the bearing seat, and the flat foil is made into the same size and shape as the inner diameter of the corrugated foil. In this way, the approximate elliptical gas suspension bearing of the second aspect is formed. The two aspects of the present disclosure are two pieces combined together, one side must be fixed with the bearing seat to form a fixed end, the other side is free to form a free end, and the long axis direction of the elliptical inner circumference is the fixed position of the foil. When the motor rotates clockwise, the left side is the fixed end and the right side is the free end. When the motor rotates counterclockwise, the right side is the fixed end and the left side is the free end. That is, the motor rotor should rotate from the free end to the fixed end. Through such a setting form, the starting process of the motor can be more gentle and stable. BRIEF DESCRIPTION OF DRAWINGS

[0048] FIG. 1a is a structural diagram of a bearing foil assembly in the related art;

[0049] FIG. 1b is a cooperation structural diagram of a bearing assembly (including a bearing foil assembly and a bearing seat) and a rotor shaft in the related art;

[0050] FIG. 2a is a structural diagram of a bearing foil assembly of the first aspect of the present disclosure;

[0051] FIG. 2b is a structural diagram of a first circumscribed circle drawn by a wave crest of the wave foil of FIG. 2a;

[0052] FIG. 2c is a top view of FIG. 2a;

[0053] FIG. 3a is a structural diagram of the upper half of a flat foil in the bearing foil assembly of the first aspect of the present disclosure;

[0054] FIG. 3b is a top view of FIG. 3a;

[0055] Fig. 4a is a structural view of the upper half of a wave foil in a bearing foil assembly according to the first aspect of the present disclosure;

[0056] Fig. 4b is a plan view of Fig. 4a;

[0057] Fig. 5 is a structural view of a bearing assembly (including a bearing foil assembly and a bearing housing) and a rotor shaft according to the first aspect of the present disclosure;

[0058] Fig. 6a is a structural view of a bearing foil assembly according to the second aspect of the present disclosure (after cutting off a partial arc segment);

[0059] Fig. 6b is a structural view of Fig. 6a (before cutting off a partial arc segment) (including a second circumscribed circle drawn for a wave crest of a wave foil);

[0060] Fig. 6c is a plan view of Fig. 6a;

[0061] Fig. 7a is a structural view of the upper half of a flat foil in a bearing foil assembly according to the second aspect of the present disclosure;

[0062] Fig. 7b is a plan view of Fig. 7a;

[0063] Fig. 8a is a structural view of the upper half of a wave foil in a bearing foil assembly according to the second aspect of the present disclosure;

[0064] Fig. 8b is a plan view of Fig. 8a;

[0065] Fig. 9 is a structural view of a bearing assembly (including a bearing foil assembly and a bearing housing) and a rotor shaft according to the second aspect of the present disclosure.

[0066] Reference signs are indicated as follows: 1, flat foil; 2, wave foil; 3, upper half curve segment; 4, lower half curve segment; 5, first lower end; 6, first upper end; 7, first dotted curve segment; 8, second lower end; 9, second upper end; 10, second dotted curve segment; 11, wave crest; 12, wave trough; 13, upper half wave foil; 14, lower half wave foil; 15, first circumscribed circle; 16, second circumscribed circle; 17, rotor shaft; 18, side gap; 19, top gap; 20, bearing housing; 21, first accommodating groove; 22, second accommodating groove; 23, first connecting portion; 24, second connecting portion; 25, third connecting portion; 26, fourth connecting portion; 27, first cut-off portion; 28, second cut-off portion. DETAILED DESCRIPTION

[0067] In the following, the technical solutions in the embodiments of the present disclosure will be described clearly and completely with the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, rather than all the embodiments. The following description of at least one example embodiment is merely illustrative in nature and not intended to limit the present disclosure, its application or uses in any way. Based on the embodiments in the present disclosure, all other embodiments obtained by those of ordinary skill in the art without creative effort fall within the scope of the present disclosure.

[0068] It should be noted that the terms used herein are only intended to describe specific embodiments and are not intended to limit exemplary embodiments according to the present disclosure. As used herein, the singular forms are intended to include the plural forms unless the context clearly indicates otherwise, and it should be further understood that the terms "comprise" and / or "include" as used herein specify the presence of stated features, steps, operations, devices, components and / or combinations thereof.

[0069] Unless specifically stated otherwise, the relative arrangements of components and steps, numerical expressions, and numerical values set forth in the various embodiments described herein are not limiting. It should be understood that the various parts shown in the drawings are not necessarily drawn to scale in proportion. Techniques, methods, and devices known to those of ordinary skill in the relevant art can not be discussed in detail, but should be considered as part of the authorized description. In all examples shown and discussed herein, any specific value should be interpreted as merely exemplary, not as a limitation. Therefore, other examples of exemplary embodiments can have different values. It should be noted that similar reference numbers and letters represent similar items in the following drawings, and therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0070] In the description of the present disclosure, it should be understood that the orientation words such as "front, back, up, down, left, right", "horizontal, vertical, perpendicular, horizontal" and "top, bottom" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present disclosure and simplifying the description, and does not indicate and imply that the indicated device or element must have a particular orientation or be constructed and operated in a particular orientation, therefore, it cannot be understood as a limitation on the scope of protection of the present disclosure; the orientation words "inner, outer" refer to the inner and outer relative to the contour of each component.

[0071] For purposes of the description hereinafter, spatially relative terms, such as "above", "below", "up", "down", "right", "left", "vertical", "horizontal", "top", "bottom", "lateral", "longitudinal", "transverse", "forward", "rearward", "radial", "peripheral" and the like, can be used herein for ease of description to describe one element's or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientations depicted in the figures. For example, if a device in the figures is inverted, elements described as "above" or "up" other elements or features would then be oriented "below" or "down" the other elements or features. Thus, the exemplary term "above" can encompass both an orientation of above and below. The device can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. It will also be understood that the terms "first", "second", "third", etc. are used herein, merely for purposes of nomenclature, and are not intended to limit the scope of the disclosure.

[0072] In addition, it should be noted that the use of "first", "second", etc. words to define parts is merely for the convenience of distinguishing the corresponding parts, and the above words have no special meaning unless otherwise stated, and therefore cannot be understood as limiting the protection scope of the present disclosure.

[0073] As shown in FIG. 2a-9, the present disclosure provides a bearing foil assembly:

[0074] It is composed of 1 layer of flat foil 1 and 1 layer of wave foil 2, which is located at the outer periphery of the flat foil 1. In the projection plane of the vertical plane, the inner periphery of the flat foil 1 is a flat structure with a center O, and a horizontal straight line through the O point is the X axis, and a vertical straight line through the O point is the Y axis. The inner periphery of the flat foil 1 includes an upper half curve segment 3 above the X axis and a lower half curve segment 4 below the X axis. The first lower end 5 of the upper half curve segment 3 and the first upper end 6 of the lower half curve segment 4 opposite to it are spaced apart, and the two are smoothly connected by a first dashed curve segment 7. The second lower end 8 of the upper half curve segment 3 and the second upper end 9 of the lower half curve segment 4 opposite to it are spaced apart, and the two are smoothly connected by a second dashed curve segment 10. The first dashed curve segment 7 and the second dashed curve segment 10 are both virtual non-solid line segments.

[0075] The distance between the intersection point of the X axis and the first dashed curve segment 7 and the intersection point of the X axis and the second dashed curve segment 10 is the length x of the inner periphery of the flat foil 1 along the X direction. The distance between the intersection point of the Y axis and the upper half curve segment 3 and the intersection point of the Y axis and the lower half curve segment 4 is the length y of the inner periphery of the flat foil 1 along the Y direction, and x>y.

[0076] The present disclosure can make the inner circle of the aerostatic bearing flat and elliptical or similar to an ellipse, and the length in the horizontal direction is greater than the length in the vertical direction, so as to effectively make the side gap greater than the top gap, further increase the front end cross-sectional area, and then increase the ratio of the front end cross-sectional area to the rear end cross-sectional area, improve the wedge ratio, effectively increase the aerostatic pressure, and thus suspend a heavier rotor. Compared with the scheme of at least two layers of wave foils and / or at least two layers of flat foils in the related art (the related art adopts a circular flat foil, but the wedge ratio is small, and the aerostatic force is limited; in order to increase the side gap, the related art adopts double-layer wave foils with different lengths to improve the wedge ratio), the present disclosure adopts a single-layer wave foil plus a single-layer flat foil, can form a very smooth and continuous wave valley inscribed flat continuous curve (such as an elliptical curve or a similar elliptical curve, and the similar elliptical curve includes a parabola and an involute) through parameter adjustment, and can support the rotor more uniformly and continuously after being combined with the flat foil, improve the support performance, and reduce the resistance of the rotating airflow in the bearing inner diameter.

[0077] The present disclosure optimizes the structure of the aerostatic bearing inner diameter of the ultra-high-speed motor, adopts an elliptical or approximately elliptical flat foil structure with a large transverse size and a small longitudinal size, forms an elliptical or approximately elliptical aerostatic bearing, has a greater wedge ratio than a circular aerostatic bearing, and thus has a greater air pressure, can increase the aerostatic force of the aerostatic bearing, and can support a heavier rotor; under the premise that the rotor weight is unchanged, after increasing the ratio of the front end cross-sectional area to the rear end cross-sectional area, the aerostatic pressure is increased at the same speed, and if the speed is reduced, the aerostatic pressure can be the same as that of the circular inner diameter, can effectively increase the adjustable speed range of the motor; since the gravity center of the rotor is downward and deviates from the center of the aerostatic bearing, the greater the bearing floating force of the present disclosure, the smaller the deviation between the center line of the rotor and the center line of the bearing, which can further reduce the vortex and vibration of the rotor and further reduce the collision of the vortex and the noise of the motor caused by the vibration.

[0078] The present disclosure optimizes the design of the aerostatic bearing of the ultra-high-speed motor, mainly expands the wedge ratio (or wedge slope) to improve the pressure bearing capacity of the bearing and float a larger rotor. The present disclosure can make the inner diameter of the aerostatic bearing elliptical or approximately elliptical through two different structure optimization schemes, and the horizontal direction must be the major axis and the vertical direction (the direction of gravity) must be the minor axis, so as to increase the inlet cross-sectional area of the aerostatic bearing and thus increase the wedge ratio and the pressure bearing capacity of the bearing.

[0079] In some embodiments,

[0080] The upper half curve segment 3 and the lower half curve segment 4 of the flat foil 1 are symmetrically arranged relative to the X axis, the upper half curve segment 3 of the flat foil 1 is symmetrically arranged relative to the Y axis, and the lower half curve segment 4 of the flat foil 1 is symmetrically arranged relative to the Y axis.

[0081] This is a preferred structure of the flat foil of the present disclosure, and by symmetrically arranging the upper and lower half curve segments of the flat foil relative to the X axis, symmetrically arranging the upper half curve segment relative to the Y axis, and symmetrically arranging the lower half curve segment relative to the Y axis, the gas in the inner periphery of the flat foil can uniformly support the bearing area of the inner rotor shaft, thereby improving the bearing force and bearing effect.

[0082] As shown in FIGS. 2a-5, in some embodiments,

[0083] The wave foil 2 comprises a plurality of wave crests 11 protruding radially outward, and adjacent two wave crests 11 are arranged at intervals, and a wave trough 12 is formed between adjacent two wave crests 11. The inner periphery of the plurality of wave troughs 12 is arranged in abutment with the outer periphery of the flat foil 1 (that is, the inner periphery of the wave foil is also a flat structure with a horizontal direction length greater than a vertical direction length x>y); a plurality of wave crests 11 circumscribe a continuous annular curve, the center of the annular curve is also the O point, and the distance between the two intersection points of the annular curve and the X axis is the length x' of the outer periphery of the wave foil 2 along the X direction, the distance between the two intersection points of the annular curve and the Y axis is the length y' of the outer periphery of the wave foil 2 along the Y direction, and x'>y'.

[0084] The outer periphery of the wave crest of the wave foil of the present disclosure circumscribes an annular curve, which can or can not be a circle. The preferred solution of the present disclosure is a circle, which needs to be matched with the shape of the bearing seat hole, but can all form an elliptical or approximately elliptical flat structure of the inner periphery of the flat foil, thereby improving the wedge ratio and improving the bearing performance.

[0085] In some embodiments,

[0086] The upper half curve segment 3 of the flat foil 1 is a partial curve segment of an elliptical curve, a parabola or an involute, the lower half curve segment 4 of the flat foil 1 is a partial curve segment of an elliptical curve, a parabola or an involute, when the upper half curve segment 3 and the lower half curve segment 4 are both elliptical curves, the upper half curve segment 3, the first dashed curve segment 7, the lower half curve segment 4 and the second dashed curve segment 10 are connected to form an elliptical whole circle, and the radial inner convex surfaces of the plurality of wave troughs 12 are tangent to the elliptical whole circle; when the upper half curve segment 3 and the lower half curve segment 4 are both parabolas, the radial inner convex surfaces of the plurality of wave troughs 12 are tangent to the parabolas; when the upper half curve segment 3 and the lower half curve segment 4 are both involutes, the radial inner convex surfaces of the plurality of wave troughs 12 are tangent to the involutes;

[0087] The wave foil 2 has a higher wave crest height closer to the Y axis and a lower wave crest height farther from the Y axis, the radially outer convex surfaces of the plurality of wave crests 11 are located on the same first circumscribed circle 15, that is, the annular curve is a circle, so that x' = y', and the center of the first circumscribed circle 15 is located at the O point.

[0088] This is a specific structural form of the present disclosure scheme one, and the elliptical, parabolic or involute gas suspension bearing of the present disclosure scheme one is realized through a structure with a smooth stepless gradual change in wave amplitude, a variable or invariable wave width, that is, the wave amplitude is large in the middle (close to the y axis) and low on both sides (far from the y axis). Through simulation calculation, the height and width of the wave are accurately adjusted to form the wave crest envelope (or the inscribed curve of the inner diameter) of the wave foil inner diameter, that is, the inner foil, which becomes a standard ellipse, parabola or involute, that is, a continuous curve, and the outer diameter envelope of the wave foil is a standard circle, so that the gas bearing has only one layer of wave foil, realizing a new structure with a circular outer diameter and an elliptical, parabolic or involute inner diameter. In this way, a circular bearing seat can realize an elliptical, parabolic or involute inner ring shape. Compared with the related art scheme of two layers of wave foils with different lengths, one layer of wave foils is saved, a continuous curve can be realized, it is simpler, and the cost is lower. Therefore, the present disclosure has structural advantages and cost advantages over the related art double-layer or multi-layer wave foils in increasing dynamic pressure through a single-layer wave foil.

[0089] In some embodiments,

[0090] The wave foil 2 includes an upper half wave foil 13 located above the X axis and a lower half wave foil 14 located below the X axis, the radially outer convex surfaces of all the wave crests 11 of the upper half wave foil 13 are connected with the first circumscribed circle 15, the radially inner convex surfaces of all the wave troughs of the upper half wave foil 13 are tangent to the outer circumferential surface of the elliptical, parabolic or involute of the upper half curve segment 3 of the flat foil 1, the radially outer convex surfaces of all the wave crests 11 of the lower half wave foil 14 are connected with the first circumscribed circle 15, and the radially inner convex surfaces of all the wave troughs 12 of the lower half wave foil 14 are tangent to the outer circumferential surface of the elliptical, parabolic or involute of the lower half curve segment 4 of the flat foil 1.

[0091] This is a specific structural form of the wave foil of the present disclosure, that is, a wave foil structure including upper and lower halves, and the upper and lower half wave foils are symmetrical relative to the X axis. The radially inner convex surfaces of the wave troughs of the upper half wave foil are connected with the inner circumferential flat foil to form a uniform supporting action on the inner circumferential flat foil and improve the supporting performance. The wave crests of the upper and lower half wave foils form a circular outer circumferential surface and are connected with the first circumscribed circle, so that the structure surrounded by the wave crests is circular and can be adapted to the circular shaft hole of the bearing seat to improve the universal performance.

[0092] In some embodiments,

[0093] The upper half-wave foil 13 is symmetrical to the lower half-wave foil 14 with respect to the X axis, the upper half-wave foil 13 is symmetrically arranged with respect to the Y axis, and the lower half-wave foil 14 is symmetrically arranged with respect to the Y axis.

[0094] This is a further preferred structure of the wave foil of the present disclosure, i.e., the upper half and lower half wave foils are symmetrical with respect to the X axis, the upper half wave foil is symmetrical with respect to the Y axis, and the lower half wave foil is symmetrical with respect to the Y axis, which can enable the wave foil inner circumference to provide uniform support to the flat foil, further enabling the gas of the flat foil inner circumference to uniformly support the internal rotor shaft support area, improving the support force and support effect.

[0095] The first scheme of the present disclosure is to design wave amplitudes with different wave amplitudes on a wave foil, adopt a structure with low edges and high middle, and bend by mold pressing to make the wave peak contour line of the outer diameter of the wave foil on the same circumscribed circle, as shown by the dotted line circle in FIG. 2b, i.e., the outer diameter circumscribed circle of the formed wave foil should coincide with the inner diameter of the bearing seat, so that the wave valley inscribed curve automatically forms an ellipse, a parabola or an involute, rather than a circular arc (which belongs to an elliptical arc, a parabolic arc or an involute arc), which coincides with the outer diameter curve of the flat foil, thereby forming an elliptical, parabolic or involute gas suspension bearing of the first scheme. The flat foil and the wave foil described above can be realized by die cutting and cold pressing of a mold.

[0096] As shown in FIGS. 6a-9, in some embodiments,

[0097] The upper half curve segment 3 of the flat foil 1 is a circular partial arc segment, and the lower half curve segment 4 of the flat foil 1 is a circular partial arc segment,

[0098] The flat foil is first made into a circular flat foil in a vertical plane projection surface, the circular flat foil takes the O point as the center, the X axis is the horizontal symmetry axis, and the Y axis is the vertical symmetry axis, then partial length arc segments are cut off at two positions where the circular flat foil intersects with the X axis to form the upper half curve segment 3 and the lower half curve segment 4, and the upper half curve segment 3 and the lower half curve segment 4 are connected together.

[0099] This is the preferred structure of the second scheme of the present disclosure, the approximate elliptical gas suspension bearing of the second scheme of the present disclosure is obtained by first designing the inner curve of the circular flat foil, then cutting off the positions where the two sides are connected with the X axis, then splicing the upper and lower arc segments after cutting, which can design the bearing seat into an approximate elliptical shape, and the foil with equal corrugation height is made into the same shape as the bearing seat, the outer diameter is fitted with the inner diameter of the bearing seat (the inner hole of the bearing seat is also approximately elliptical), and the flat foil is made with the same size and shape as the inner diameter of the corrugated foil, so that the approximate elliptical gas suspension bearing of the second scheme is formed, which has only one layer of corrugated foil and can realize continuous curve, which is simpler and has lower cost; compared with the double or multi-layer corrugated foil of the related technology, the single-layer corrugated foil has structural advantages and cost advantages.

[0100] In some embodiments,

[0101] After cutting, the first lower end 5 of the upper half curve segment 3 and the first upper end 6 of the lower half curve segment 4 opposite to it are connected by the first virtual curve segment 7, and the second lower end 8 of the upper half curve segment 3 and the second upper end 9 of the lower half curve segment 4 opposite to it are connected by the second virtual curve segment 10. The lengths of the arc segments of the two cut parts are equal (including the first cut part 27 on the left and the second cut part 28 on the right), and the lengths of the first virtual curve segment 7 and the second virtual curve segment 10 are equal and symmetrically arranged relative to the O point.

[0102] This is the preferred structure of the flat foil of the present disclosure, which can make the gas support area of the inner circumference of the flat foil uniform, improve the support force and support effect, by the upper and lower half curve segments of the flat foil being symmetrical relative to the X axis, the upper half curve segment being symmetrical relative to the Y axis, and the lower half curve segment being symmetrical relative to the Y axis.

[0103] In some embodiments,

[0104] The wave foil 2 includes a plurality of wave crests 11 protruding radially outward, and adjacent two wave crests 11 are arranged with a spacing therebetween, and a wave trough 12 is formed between adjacent two wave crests 11. The inner circumferences of a plurality of wave troughs 12 are arranged in abutment with the outer circumference of the flat foil 1. The wave foil 2 is also cut at a position radially opposite to the cut part of the flat foil 1, and the two cut parts of the wave foil are spliced together. A plurality of wave crests 11 are circumscribed by a continuous annular curve, the center of the annular curve is also the O point, and the distance between the two intersection points of the annular curve and the X axis is the length x' of the outer circumference of the wave foil 2 along the X direction, the distance between the two intersection points of the annular curve and the Y axis is the length y' of the outer circumference of the wave foil 2 along the Y direction, and x'≥y' is satisfied.

[0105] The wave crest of the wave foil of the present disclosure circumscribes a circular curve, which can or can not be a circle. The second scheme of the present disclosure preferably is not a circle, but a flat structure formed by cutting off the middle part and splicing, which matches the shape of the bearing seat hole (flat), can form an elliptical or approximately elliptical flat structure in the inner periphery of the flat foil, improve the wedge ratio, and improve the bearing capacity.

[0106] In some embodiments,

[0107] The radial inner convex surface of each of the plurality of wave troughs 12 is tangent to the outer peripheral surface of the flat foil 1 before and after cutting; and the height of each of the plurality of wave crests 11 in the wave foil 2 is equal.

[0108] Before cutting, the radial outer convex surface of the plurality of wave crests 11 is located on the same second circumscribed circle 16, and the center of the second circumscribed circle 16 is located at the O point, so that x' > y' after cutting.

[0109] This is the preferred structure of the second scheme of the present disclosure, that is, by equalizing the height of the wave crest, the inner periphery of the wave trough is tangent to the flat foil before and after cutting, which can provide uniform support to the flat foil. Before cutting, the radial outer convex surface of the plurality of wave crests is located on the same second circumscribed circle, which can facilitate the integrated machining and manufacturing of the wave foil and the flat foil.

[0110] The second scheme of the present disclosure is to design the bearing seat into an approximately elliptical structure. This approximately elliptical structure is preferably composed of two segments of less than a semicircle. The wave amplitude of the corrugated foil is equal. The circumscribed circle of the wave crest and the inscribed circle of the wave trough are both standard circles after forming. See FIG. 6b for details. The circumscribed circle of the wave crest is shown by a dotted line in the figure, which is a complete circle. FIG. 6a shows that after folding, it becomes a two-segment circular arc joint, and the inner diameter forms an approximately elliptical shape. The inner diameter of the bearing seat of the second scheme can be machined first, and then a portion of the horizontal diameter is cut off within a certain range. Then, the upper and lower two circular arcs are folded and fastened with bolts (not shown in the figure). The corrugated foil and the inner diameter flat foil of the present disclosure are also completed by molding.

[0111] In some embodiments,

[0112] The rotor shaft 17 is located in the inner periphery of the flat foil 1, and in the projection plane in the vertical plane, the minimum distance between the rotor shaft 17 and the ellipse, parabola or involute of the inner periphery of the flat foil 1 in the X axis is the side gap 18, and the minimum distance between the rotor shaft 17 and the ellipse, parabola or involute of the inner periphery of the flat foil 1 in the Y axis is the top gap 19. The side gap 18 is greater than the top gap 19, and the ratio between the side gap 18 and the top gap 19 is the wedge ratio.

[0113] This is the preferred structure of the first aspect of the present disclosure. The present disclosure can increase the wedge ratio by making the minimum gap (side gap) between the rotor shaft and the inner periphery of the flat foil on the X-axis larger than the top gap in the Y-axis direction (achieved by the flat structure or the elliptical or approximately elliptical structure described above), thereby increasing the pressure of the gas suspension, and thus suspending a heavier rotor.

[0114] In some embodiments,

[0115] The rotor shaft 17 is located at the inner periphery of the flat foil 1, and in the projection plane of the vertical plane, the minimum distance between the rotor shaft 17 and the first dashed curve segment 7 or the second dashed curve segment 10 of the inner periphery of the flat foil 1 on the X-axis is the side gap 18, and the minimum distance between the rotor shaft 17 and the inner periphery of the flat foil 1 on the Y-axis is the top gap 19, the side gap 18 is larger than the top gap 19, and the ratio between the side gap 18 and the top gap 19 is the wedge ratio.

[0116] This is the preferred structure of the second aspect of the present disclosure. The present disclosure can increase the wedge ratio by making the minimum gap (side gap) between the rotor shaft and the first or second dashed curve segment of the inner periphery of the flat foil on the X-axis larger than the top gap in the Y-axis direction (achieved by the flat structure or the elliptical or approximately elliptical structure described above), thereby increasing the pressure of the gas suspension, and thus suspending a heavier rotor.

[0117] The present disclosure also provides a bearing assembly, which comprises the bearing foil assembly described above, and further comprises a bearing housing 20 having a shaft hole, and the bearing foil assembly is arranged in the shaft hole to support the rotor shaft 17.

[0118] In some embodiments,

[0119] In the projection plane of the vertical plane, the inner periphery of the bearing housing 20 is provided with a first accommodating groove 21 at the side connected to the axial side of the X-axis, and a second accommodating groove 22 at the side connected to the other axial side of the X-axis. The first lower end of the upper half of the flat foil 1 and the first upper end of the lower half of the flat foil 1 opposite to it are connected by a first connecting part 23, which is a convex structure protruding towards the first accommodating groove 21, and the first connecting part 23 is inserted into the first accommodating groove 21 to form a fixed end. The second lower end of the upper half of the flat foil 1 and the second upper end of the lower half of the flat foil 1 opposite to it are connected by a second connecting part 24, which is a convex structure protruding towards the second accommodating groove 22, and the second connecting part 24 is inserted into the second accommodating groove 22 to form a free end.

[0120] This is the preferred structure of the bearing seat of the present disclosure, the first connecting part of the flat foil is inserted into the first accommodating groove to form the fixed end, and the second connecting part of the flat foil is inserted into the second accommodating groove to form the free end, so as to relatively fix the flat foil and enable it to move to a certain extent to support the rotor shaft at its inner periphery.

[0121] In some embodiments,

[0122] The third connecting part 25 is a convex structure protruding towards the first accommodating groove 21, and the fourth connecting part 26 is a convex structure protruding towards the second accommodating groove 22.

[0123] This is the preferred structure of the bearing seat of the present disclosure, the first connecting part of the flat foil is inserted into the first accommodating groove to form the fixed end, and the second connecting part of the flat foil is inserted into the second accommodating groove to form the free end, so as to relatively fix the flat foil and enable it to move to a certain extent to support the rotor shaft at its inner periphery.

[0124] The present disclosure also provides an air compressor, which comprises the aforementioned bearing assembly and further comprises a rotor shaft 17, wherein the bearing assembly supports the rotor shaft 17.

[0125] In some embodiments,

[0126] When the free end of the flat foil, the fixed end of the flat foil, the free end of the wave foil and the fixed end of the wave foil are included, the rotation direction of the rotor shaft 17 is such that the lower half structure of the flat foil 1 rotates from the free end of the flat foil to the fixed end of the flat foil,

[0127] The rotation direction of the rotor shaft 17 is such that the lower half structure of the wave foil 2 rotates from the free end of the wave foil to the fixed end of the wave foil.

[0128] The two schemes of the first and second schemes of the present disclosure are combined together, one side must be fixed with the bearing seat to form a fixed end, the other side is free to form a free end, and the long axis direction of the inner circle of the ellipse, parabola or involute is the fixed position of the foil. When the motor rotates clockwise, the left side is the fixed end and the right side is the free end. When the motor rotates counterclockwise, the right side is the fixed end and the left side is the free end. That is, the motor rotor should be rotated from the free end to the fixed end. Through such a setting form, the impact force and vortex during starting can be reduced, and the motor starting process is more gentle and stable.

[0129] The first scheme of the present disclosure is a two-segment curve composed of an elliptical, parabolic or involute inner diameter, and the core of the claim is a wave-shaped foil with a high middle and a low two ends and its curved characteristics. The second scheme of the present disclosure is a two-segment arc composed of an elliptical, parabolic or involute inner diameter, and the claim is an arc of the bearing seat that forms an elliptical structure and corresponds to the same shape of the foil bearing assembly

[0130] The first scheme of the present disclosure is a single-layer wave-shaped foil, which adjusts the ellipticity of the inner diameter ellipse, parabola or involute, and the cross-sectional area of the bearing inlet by adjusting the wave height, and must be high in the middle and low at both ends. The unequal height wave-shaped foil of the present disclosure can form a very smooth and continuous wave valley inscribed ellipse curve, parabola or involute through parameter adjustment. After being fitted with the inner foil, the rotor can be supported more uniformly and continuously, and the resistance of the rotating airflow in the bearing inner diameter can be reduced.

[0131] The second scheme of the present disclosure is a two-segment arc composed of an elliptical bearing inner diameter, wherein the intersection position of the two-segment arc is provided with a notch, which is arranged as a fixed foil bearing, and at the same time eliminates the intersection point of the circular arc, achieving an approximate elliptical effect. This can improve the flow of the inner diameter rotating airflow and reduce airflow resistance.

[0132] The first scheme of the present disclosure is simple and practical, the bearing seat inner diameter is circular, the foil bearing inner diameter is elliptical, parabolic or involute, and the wave-shaped foils with different heights are formed by molding. At the same time, the outer diameter circumscribed circle can also be formed by molding. The process difficulty of the second scheme of the present disclosure is the bearing seat inner diameter, which has one more process than the whole circle in terms of processing cost. The processing method of the foil bearing assembly is basically the same as the first scheme.

[0133] The above only describes the preferred embodiments of the present disclosure and does not limit the present disclosure. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present disclosure shall be included in the protection scope of the present disclosure. The above only describes the preferred embodiments of the present disclosure, and it should be pointed out that for ordinary skilled persons in the technical field, without departing from the technical principles of the present disclosure, a number of improvements and modifications can be made, which should also be considered as the protection scope of the present disclosure.

Claims

1. A bearing foil assembly, consisting of 1 layer of flat foil (1) and 1 layer of wave foil (2), the wave foil (2) is located at the outer periphery of the flat foil (1), in the projection plane of the vertical plane, the inner periphery of the flat foil (1) is a flat structure with center O, and the horizontal straight line through the O point is the X axis, and the vertical straight line through the O point is the Y axis, the inner periphery of the flat foil (1) includes an upper half curve segment (3) located above the X axis and a lower half curve segment (4) located below the X axis, the first lower end (5) of the upper half curve segment (3) is spaced apart from the first upper end (6) of the lower half curve segment (4) opposite to it, and the two are smoothly connected by a first dotted curve segment (7), the second lower end (8) of the upper half curve segment (3) is spaced apart from the second upper end (9) of the lower half curve segment (4) opposite to it, and the two are smoothly connected by a second dotted curve segment (10), the first dotted curve segment (7) and the second dotted curve segment (10) are both virtual non-solid line segments; The distance between the intersection point of the X axis and the first dotted curve segment (7) and the intersection point of the X axis and the second dotted curve segment (10) is the length x of the inner periphery of the flat foil (1) in the X direction, and the distance between the intersection point of the Y axis and the upper half curve segment (3) and the intersection point of the Y axis and the lower half curve segment (4) is the length y of the inner periphery of the flat foil (1) in the Y direction, and x>y.

2. The bearing foil assembly according to claim 1, wherein: The wave foil (2) includes a plurality of wave crests (11) protruding radially outward, adjacent two wave crests (11) are spaced apart, and a wave trough (12) is formed between adjacent two wave crests (11), and the inner periphery of a plurality of wave troughs (12) is fitted with the outer periphery of the flat foil (1); a plurality of wave crests (11) circumscribe a continuous annular curve, the center of the annular curve is also O point, and the distance between the two intersection points of the annular curve and the X axis is the length x' of the outer periphery of the wave foil (2) in the X direction, and the distance between the two intersection points of the annular curve and the Y axis is the length y' of the outer periphery of the wave foil (2) in the Y direction, and x'>y'.

3. The bearing foil assembly according to claim 2, wherein: The upper half curve segment (3) of the flat foil (1) is a partial curve segment of an elliptic curve, a parabola or an involute, the lower half curve segment (4) of the flat foil (1) is a partial curve segment of an elliptic curve, a parabola or an involute, when the upper half curve segment (3) and the lower half curve segment (4) are both elliptic curves, the upper half curve segment (3), the first dotted curve segment (7), the lower half curve segment (4) and the second dotted curve segment (10) are connected to form an elliptic whole circle, and the radially inner convex surfaces of the plurality of wave troughs (12) are all tangent to the elliptic whole circle; when the upper half curve segment (3) and the lower half curve segment (4) are both parabolas, the radially inner convex surfaces of the plurality of wave troughs (12) are all tangent to the parabolas; when the upper half curve segment (3) and the lower half curve segment (4) are both involutes, the radially inner convex surfaces of the plurality of wave troughs (12) are all tangent to the involutes; The wave foil (2) is higher in height of the wave crest closer to the Y axis and lower in height of the wave crest farther from the Y axis, the radially outer convex surfaces of the plurality of wave crests (11) are located on a same first circumscribed circle (15), that is, the annular curve is a circle, so that x' = y', and the center of the first circumscribed circle (15) is located at the O point.

4. The bearing foil assembly of claim 3, wherein: The wave foil (2) comprises an upper half wave foil (13) located above the X axis and a lower half wave foil (14) located below the X axis, the radially outer convex surfaces of all the wave crests (11) of the upper half wave foil (13) are tangent to the first circumscribed circle (15), the radially inner convex surfaces of all the wave troughs of the upper half wave foil (13) are tangent to the outer circumferential surface of the upper half curve segment (3) of the flat foil (1), the radially outer convex surfaces of all the wave crests (11) of the lower half wave foil (14) are tangent to the first circumscribed circle (15), and the radially inner convex surfaces of all the wave troughs (12) of the lower half wave foil (14) are tangent to the outer circumferential surface of the lower half curve segment (4) of the flat foil (1).

5. The bearing foil assembly of claim 4, wherein: The upper half curve segment (3) and the lower half curve segment (4) of the flat foil (1) are symmetrically arranged relative to the X axis, the upper half curve segment (3) of the flat foil (1) is symmetrically arranged relative to the Y axis, and the lower half curve segment (4) of the flat foil (1) is symmetrically arranged relative to the Y axis; The upper half wave foil (13) is symmetric relative to the X axis with the lower half wave foil (14), the upper half wave foil (13) is symmetrically arranged relative to the Y axis, and the lower half wave foil (14) is symmetrically arranged relative to the Y axis.

6. The bearing foil assembly of any one of claims 1-5, wherein: The upper half curve segment (3) of the flat foil (1) is a partial arc segment of a circle, and the lower half curve segment (4) of the flat foil (1) is a partial arc segment of a circle, By first making a circular flat foil in the projection plane of the vertical plane, the circular flat foil takes the O point as the center, the X axis as the horizontal symmetry axis, and the Y axis as the vertical symmetry axis, then cutting off arc segments of partial length at two positions where the circular flat foil intersects with the X axis respectively to form the upper half curved segment (3) and the lower half curved segment (4), and connecting the upper half curved segment (3) and the lower half curved segment (4) together.

7. The bearing foil assembly of claim 6, wherein: After cutting off, the first lower end (5) of the upper half curved segment (3) and the first upper end (6) of the opposite lower half curved segment (4) are connected by the first virtual curved segment (7), and the second lower end (8) of the upper half curved segment (3) and the second upper end (9) of the opposite lower half curved segment (4) are connected by the second virtual curved segment (10), the lengths of the two cut-off arc segments of partial length are equal, and the lengths of the first virtual curved segment (7) and the second virtual curved segment (10) are equal and symmetrically arranged relative to the O point.

8. The bearing foil assembly of claim 6 or 7, wherein: The wave foil (2) includes a plurality of wave crests (11) protruding radially outward, and adjacent two wave crests (11) are arranged with a spacing therebetween, and a wave trough (12) is formed between adjacent two wave crests (11), the inner periphery of a plurality of wave troughs (12) is arranged in abutment with the outer periphery of the flat foil (1), the wave foil (2) is also cut off at a position radially opposite to the cut-off portion of the flat foil (1), and the two cut-off portions of the wave foil are spliced together; a plurality of wave crests (11) are circumscribed by a continuous annular curve, the center of the annular curve is also the O point, the distance between the two intersection points of the annular curve and the X axis is the length x' of the outer periphery of the wave foil (2) in the X direction, the distance between the two intersection points of the annular curve and the Y axis is the length y' of the outer periphery of the wave foil (2) in the Y direction, and x' ≥ y'.

9. The bearing foil assembly of claim 8, wherein: After cutting off and before cutting off, the radially inner convex surfaces of a plurality of wave troughs (12) are tangent to the outer periphery of the flat foil (1); the heights of a plurality of wave crests (11) in the wave foil (2) are equal; Before cutting off, the radially outer convex surfaces of a plurality of wave crests (11) are located on a same second circumscribed circle (16), the center of the second circumscribed circle (16) is located at the O point, so that after cutting off, x' > y'.

10. The bearing foil assembly of claim 3, wherein: The rotor shaft (17) is located at the inner periphery of the flat foil (1), and in the projection plane of the vertical plane, the minimum distance between the rotor shaft (17) and the ellipse, parabola or involute of the inner periphery of the flat foil (1) on the X-axis is the side gap (18), and the minimum distance between the rotor shaft (17) and the ellipse, parabola or involute of the inner periphery of the flat foil (1) on the Y-axis is the top gap (19), the side gap (18) is greater than the top gap (19), and the ratio between the side gap (18) and the top gap (19) is the wedge ratio.

11. The bearing foil assembly of claim 7, wherein: The rotor shaft (17) is located at the inner periphery of the flat foil (1), and in the projection plane of the vertical plane, the minimum distance between the rotor shaft (17) and the first broken curve segment (7) or the second broken curve segment (10) of the inner periphery of the flat foil (1) on the X-axis is the side gap (18), and the minimum distance between the rotor shaft (17) and the inner periphery of the flat foil (1) on the Y-axis is the top gap (19), the side gap (18) is greater than the top gap (19), and the ratio between the side gap (18) and the top gap (19) is the wedge ratio.

12. A bearing assembly comprising the bearing foil assembly of any one of claims 1-11, further comprising a bearing housing (20) having a shaft hole, the bearing foil assembly being disposed in the shaft hole to support a rotor shaft (17).

13. The bearing assembly of claim 12, wherein: In the projection plane of the vertical plane, the inner periphery of the bearing housing (20) is provided with a first accommodating groove (21) at the joint with the axial side of the X-axis, the inner periphery of the bearing housing (20) is provided with a second accommodating groove (22) at the joint with the axial side of the X-axis, the first lower end of the upper half of the flat foil (1) and the first upper end of the lower half of the flat foil (1) opposite thereto are connected by a first connecting portion (23), the first connecting portion (23) is a convex structure protruding towards the first accommodating groove (21), the first connecting portion (23) is inserted into the first accommodating groove (21) to form a fixed end; the second lower end of the upper half of the flat foil (1) and the second upper end of the lower half of the flat foil (1) opposite thereto are connected by a second connecting portion (24), the second connecting portion (24) is a convex structure protruding towards the second accommodating groove (22), the second connecting portion (24) is inserted into the second accommodating groove (22) to form a free end.

14. The bearing assembly of claim 13, wherein: The third connecting part (25) is a convex structure protruding towards the first accommodating groove (21), and the third connecting part (25) is inserted into the first accommodating groove (21) to form a fixed end of the wave foil; the fourth connecting part (26) is a convex structure protruding towards the second accommodating groove (22), and the fourth connecting part (26) is inserted into the second accommodating groove (22) to form a free end of the wave foil.

15. An air compressor comprising the bearing assembly according to any one of claims 12-14, further comprising a rotor shaft (17), wherein the bearing assembly supports the rotor shaft (17).

16. The air compressor according to claim 15, wherein: when including a free end of the flat foil, a fixed end of the flat foil, a free end of the wave foil and a fixed end of the wave foil, a rotation direction of the rotor shaft (17) is such that the lower half portion structure of the flat foil (1) rotates from the free end of the flat foil to the fixed end of the flat foil, the rotation direction of the rotor shaft (17) is such that the lower half portion structure of the wave foil (2) rotates from the free end of the wave foil to the fixed end of the wave foil.

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