A dual conical foil hydrostatic and aerostatic radial gas bearing

Abstract

The application discloses a double-cone foil dynamic and static pressure radial gas bearing, which comprises a bearing outer ring, a bearing inner ring and foils; the bearing outer ring is provided with air inlet throttling structures; the bearing inner ring is composed of smooth surface structures in the middle and conical structures at two ends; the smooth surface structures are cylindrical; the conical structures are circular truncated cone-shaped; the small-diameter one ends of the two conical structures are connected with the two end portions of the smooth surface structures respectively; the foils comprise bottom foils, wave foils and top foils; the bottom foils are fixed on the outer walls of the conical structures; the wave foils are multiple in number and are distributed in the circumferential direction between the bottom foils and the top foils; the first ends of the wave foils are connected with the outer walls of the bottom foils; the second ends of the wave foils are free ends; one end of the top foils is connected with the outer wall of the bottom foils; the other end of the top foils is a free end; and the welded end of the top foils corresponds to the free end of the wave foils. The application can improve the stability of the gas bearing from low speed to high speed, increase the bearing carrying capacity and the anti-interference capacity.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of gas bearings, and particularly relates to a double-tapered foil dynamic and static pressure radial gas bearing, which is mainly used for the radial support of a rotor system with high stability, high rotating speed, low load and large external disturbance, is a key part in the related field, and can be used for high-speed rotor systems in the fields of aviation, aerospace, energy, and chemical industry. BACKGROUND

[0002] Because the gas medium has a lower viscosity, a gas-lubricated radial sliding bearing must form a complete gas film at a higher rotating speed, and thus has a smaller load and a poorer stability. Therefore, researchers try to enhance the dynamic and static pressure effect of the gas bearing by surface modification or introduction of a new additional structure, and thus different types of dynamic and static pressure radial gas bearings are proposed. The dynamic and static pressure radial gas bearing has the advantages of both the static pressure and dynamic pressure gas bearings. At a low speed, the bearing has a high load-carrying capacity and stability due to the addition of high-pressure gas. At a high speed, the bearing has a stable gas film due to the dynamic pressure effect of the bearing structure, and thus has a high stability.

[0003] However, the gas dynamic and static pressure bearing still has some deficiencies. The low viscosity of the lubricating medium leads to a low load-carrying capacity and limited damping of the gas bearing. To solve this problem, a foil structure can be introduced into the gas bearing. The elastic properties and dissipation structure of the foil structure can effectively improve the load-carrying capacity and damping of the gas bearing, and improve the anti-interference ability of the gas bearing.

[0004] For example, the patent with the application publication number CN 110242671 A (a conical foil dynamic pressure air bearing) proposes a conical foil dynamic pressure air bearing that can simultaneously bear radial force and axial force. The foil bearing proposed in the patent is provided with different numbers of foil arches inside the bearing outer ring, and the foil has spiral grooves and herringbone grooves. However, the foil in the foil bearing is relatively thin, and the installation inside the bearing outer ring may cause damage to the foil. Moreover, the machining of grooves on the foil may cause damage to the structure of the foil itself during the dynamic pressure effect, thereby affecting the stability of the foil gas bearing itself.

[0005] The patent CN 102151852 A (a dynamic and static pressure ceramic spindle device) proposes a spindle device that can simultaneously bear radial pressure and axial thrust function. The structure for realizing this function in the patent is the tapered structure at the left and right ends of the spindle, that is, a special shaft part is provided. The large-diameter end of the tapered structure in the invention patent is the inside of the spindle, and the small-diameter end is the outside of the spindle, forming a convex structure as a whole, which does not form a converging dynamic pressure effect area. Moreover, the invention realizes the axial and radial bearing through a liquid film, and the vibration of the spindle is easy to cause wear and failure of the tapered structure.

[0006] Patent CN 104685183 B (a kind of suitable for supporting rotatable shaft gas dynamic pressure foil bearing assembly) discloses a conical rotor and gas dynamic pressure foil bearing combination structure that can be installed on a rotating shaft, the gas dynamic pressure foil bearing of the conical rotor is matched with the conical rotor, the number of the gas dynamic pressure bearing corresponds to the number of the conical rotor, the wedge formed by the gas dynamic pressure foil bearing and the rotor forms a dynamic pressure effect at high speed; Therefore, such bearing only meets the established performance at high speed; At low speed, it cannot play its dynamic pressure effect, so the radial bearing capacity is weak; Affected by its large taper, although it has good axial bearing characteristics, it further reduces its radial bearing capacity. In addition, the foil of the bearing is installed on the inner side of the bearing, which is more troublesome.

[0007] Patent CN 206495901 U (a kind of radial foil dynamic pressure air bearing) proposes a separate radial foil dynamic pressure air bearing, the radial deformation of the foil structure can promote the bearing to produce dynamic pressure effect; But the whole foil is installed on the inner side of the bearing outer ring, which makes it difficult to process and install the foil on the inner side of the bearing outer ring, and the composition of the foil is a wave-shaped elastic support foil and a top foil, which makes the wave-shaped elastic support foil directly contact with the bearing outer ring. Greater pressure can easily damage the wave-shaped foil.

[0008] Patent CN 213598404 U (a kind of thrust bearing assembly) proposes a stacked foil structure, the support structure between the top foil and the elastic foil of the stacked foil structure can change the bearing support stiffness, realizing the elastic support of the variable stiffness bearing; But the support structure between the top foil and the elastic foil is a plurality of separate structures, when one support structure is damaged, the whole foil needs to be replaced, which costs more. SUMMARY

[0009] In order to overcome the shortcomings of the prior art, the purpose of the present application is to provide a double-tapered foil dynamic and static pressure radial gas bearing, which aims to at least one of the purposes of improving the stability of the gas bearing from low speed to high speed, increasing the bearing capacity and anti-interference ability.

[0010] In order to achieve the above purpose, the technical scheme adopted by the present application is:

[0011] A double-tapered foil dynamic and static pressure radial gas bearing, comprising a bearing outer ring, a bearing inner ring and a foil; The bearing outer ring is provided with an air inlet throttling structure;

[0012] The bearing inner ring is composed of a smooth surface structure in the middle and two tapered structures at both ends, the smooth surface structure is cylindrical, and the tapered structure is a circular truncated cone, and the small diameter end of each tapered structure is connected with the end of the smooth surface structure;

[0013] The foil comprises a bottom foil, a wave-shaped foil and a top foil, the bottom foil is fixed on the outer wall of the conical structure, the number of the wave-shaped foil is N, which is distributed between the bottom foil and the top foil in the circumferential direction, N>1, the first end of each wave-shaped foil is connected with the outer wall of the bottom foil, and the second end is a free end, the number of the top foil is 1, one end of which is connected with the outer wall of the bottom foil, and the other end is a free end, and the welded end of the top foil corresponds to the free end of the wave-shaped foil.

[0014] In one embodiment, the bearing outer ring is in a cylindrical shape, and a deep groove is opened in the circumferential direction at the axially symmetrical center of the outer side, a plurality of short capillary restrictors are uniformly distributed in the deep groove, the short capillary restrictors correspond to the outer wall of the smooth surface structure, each restrictor structure is the same, and the length to diameter ratio is in the range of 1-20.

[0015] In one embodiment, the depth of the deep groove is 1 / 4-1 / 3 of the difference between the inner and outer diameters of the bearing outer ring, and the axial width is 1 / 5-1 / 2 of the bearing width.

[0016] In one embodiment, the conical structure at both ends is symmetrical about the smooth surface structure, the inclination angle of the conical inclined surface of the conical structure is in the range of 0.01°-5°, and the outer diameter of the small diameter end is 1-10 mm smaller than the outer diameter of the smooth surface structure.

[0017] In one embodiment, the number of the bottom foil is N, which is sequentially fixed on the outer wall of the conical structure in the circumferential direction; each wave-shaped foil is correspondingly located between a bottom foil and a top foil.

[0018] In one embodiment, the outer wall of the bottom foil is provided with at least one elastic gasket foil, the gasket foil does not completely cover the bottom foil, and the wave-shaped foil completely covers the gasket foil.

[0019] In one embodiment, the thickness of the bottom foil, gasket foil, wave-shaped foil and top foil is 0.2-1 mm; the wave height of the wave-shaped foil is 0.2-0.8 mm; the number of wave shapes of a single wave-shaped foil is 5-30, and the overall deformation of the foil in the radial direction is controllable in the range of 0.05-3 mm.

[0020] In one embodiment, the top foil covers all wave-shaped foils in the circumferential direction.

[0021] In one embodiment, N installation grooves are opened in the axial direction on the conical structure, the cross section of the installation groove is L-shaped or J-shaped, and the two ends of each bottom foil are respectively fixed in the adjacent two installation grooves.

[0022] In one embodiment, the bearing outer ring and the bearing inner ring form three gaps, respectively, the converging region gap between the tapered structure at both ends and the bearing outer ring and the static pressure region gap between the smooth surface structure and the bearing outer ring; the converging region gap promotes the formation of dynamic pressure effect in the bearing inner ring rotation process, and the static pressure region gap forms static pressure effect under the inlet throttling structure; the cooperation design of the top foil and the bearing outer ring is gap fit, which is micron level, ranging from 1 to 100 microns; to ensure the realization of dynamic and static pressure effect between the top foil and the bearing outer ring in the high-speed operation process.

[0023] Compared with the prior art, the beneficial effects of the present application are:

[0024] 1. The bearing inner ring tapered surface added foil in the present application has smaller processing difficulty, lower processing cost and higher processing precision.

[0025] 2. The short capillary throttling device used in the present application introduces a short capillary throttling device into the bearing outer ring processing, which makes the gas bearing have larger stiffness and carrying capacity of the gas film at medium and low speed rotation.

[0026] 3. The large gap short capillary throttling tapered foil structure used in the present application forms a large gap between the bearing outer ring and the tapered bearing inner ring, so that the bearing generates static pressure effect at low speed, and the bearing has larger carrying capacity and stability, the tapered foil structure increases the dynamic characteristics of the bearing at high speed, and increases the carrying capacity and anti-interference ability of the bearing. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 It is a schematic diagram of the overall structure of the radial gas bearing of the present application.

[0028] Figure 2 It is an appearance view along the axial center of the radial gas bearing of the present application.

[0029] Figure 3 It is Figure 2 B-B sectional view, that is, radial section view.

[0030] Figure 4 It is an overall view of the bearing inner ring of the radial gas bearing of the present application.

[0031] Figure 5 It is an overall view of the tapered structure of the bearing inner ring of the radial gas bearing of the present application.

[0032] Figure 6 It is a foil structure diagram of the radial gas bearing of the present application.

[0033] Figure 7 It is a cooperation diagram of the foil and the tapered structure of the bearing inner ring of the radial gas bearing of the present application. DETAILED DESCRIPTION

[0034] The embodiments of the present application will be described in detail below with reference to the accompanying drawings and examples.

[0035] As Figures 1 to 7 shown in the drawings, the present application is a double-tapered foil dynamic and static pressure radial gas bearing, comprising a bearing outer ring 1, a bearing inner ring 2 and a foil 3, wherein the bearing outer ring 1 is provided with an air inlet throttling structure.

[0036] Referring to Figure 4 , the bearing inner ring 2 is composed of a smooth surface structure 2-2 in the middle and two tapered structures 2-1 at both ends, wherein the two tapered structures 2-1 are the "double taper" of the present application. The smooth surface structure 2-2 is cylindrical with a central hole for mounting a shaft, and the outer wall of the smooth surface structure 2-2 is a smooth surface corresponding to the air inlet throttling structure. The tapered structure 2-1 is a circular truncated cone, and the small diameter end of each tapered structure 2-1 is connected to the two ends of the smooth surface structure 2-2 respectively to form an integral concave outer surface structure, which together constitutes the bearing inner ring 2.

[0037] Referring to Figure 6 and Figure 7 , the foil 3 mainly includes a bottom layer foil 3-1, a wave-shaped foil 3-3 and a top layer foil 3-4. The bottom layer foil 3-1 is fixed to the outer wall of the tapered structure 2-1, the number of wave-shaped foils 3-3 is N, which are distributed between the bottom layer foil 3-1 and the top layer foil 3-4 in the circumferential direction, N>1, the first end of each wave-shaped foil 3-3 is connected to the outer wall of the bottom layer foil 3-1, and the second end is a free end. The number of top layer foils 3-4 is 1, one end of which is connected to the outer wall of the bottom layer foil 3-1, and the other end is a free end, and the welded end of the top layer foil 3-4 corresponds to the free end of the wave-shaped foil 3-3.

[0038] In the present application, the bottom layer foil 3-1 is a tapered ring structure (i.e. the cross section is arc-shaped and the circumference increases linearly in the axial direction towards both ends) or a tapered arc structure (i.e. the cross section is arc-shaped and the arc length increases linearly in the axial direction towards both ends) covering the tapered structure 2-1, and both sides are smooth, i.e. flat foils. The wave-shaped foil 3-3 is also a tapered arc structure, which is a wave-shaped plate that undulates in the circumferential direction, and the "end" refers to the "beginning and end in the undulating direction". The top layer foil 3-4 is an incomplete tapered ring structure with a notch, and both sides are smooth, i.e. flat foils.

[0039] In the present application, the "first end and second end" of each wave-shaped foil 3-3 can be defined in the counterclockwise or clockwise direction, and for ease of description, the counterclockwise direction is taken as the standard. For a wave-shaped foil 3-3, the counterclockwise beginning is the "first end" and the end is the "second end".

[0040] According to the above structure, three gaps are formed between the bearing outer ring 1 and the bearing inner ring 2, which are two converging region gaps between the converging region of the outer wall of the tapered structure 2-1 and the inner wall of the bearing outer ring 1, and one static pressure region gap between the static pressure bearing region of the outer wall of the smooth surface structure 2-2 and the inner wall of the bearing outer ring 1. The converging region gap promotes the formation of dynamic pressure effect during the rotation of the bearing inner ring 2, and the static pressure region gap forms static pressure effect under the intake throttling structure.

[0041] In the above structure, the bottom foil 3-1 is the base layer of the foil 3, which mainly fixes the corrugated foil 3-3 on the bearing inner ring 2 and prevents the corrugated foil 3-3 from directly contacting the bearing inner ring 2 and being squeezed and damaged. The main function of the corrugated foil 3-3 is to increase the overall damping and dynamic characteristics of the bearing, and the foil 3 can be deformed radially to change the converging region gap, so as to realize self-adjustment when the bearing is subjected to axial impact. The top foil 3-4 is the top layer of the foil 3, which mainly protects the corrugated foil 3-3 and prevents the corrugated foil 3-3 from being squeezed and damaged due to impact on the bearing.

[0042] For example, the top foil 3-4 and the bearing outer ring 1 are designed as a gap fit, which is in the micron level, and the preferred range is 1-100 μm; to ensure the realization of dynamic and static pressure effect between the top foil 3-4 and the bearing outer ring 1 during high-speed operation.

[0043] Therefore, the bearing will fully enhance the dynamic pressure of the high-speed gas bearing and the static pressure effect under low-speed working condition, and combine the elastic properties of the foil 3 to realize the generation of static pressure and elastic support effect at low speed and dynamic pressure effect at high speed, thereby ensuring the stable operation of the bearing from low speed to high speed, and the way of fixing the foil outside the bearing inner ring will also increase the dynamic pressure effect and damping of the bearing, so that the bearing has larger carrying capacity and anti-interference ability.

[0044] In some embodiments of the present application, reference is made to Figure 2 and Figure 3, the bearing outer ring 1 is cylindrical, and a deep groove 1-1 is formed on the outer side of the bearing outer ring 1 in the circumferential direction, the deep groove 1-1 is used as an oil guide groove, a plurality of short capillary flow restrictors 1-2 are uniformly distributed, the short capillary flow restrictors 1-2 correspond to the outer wall of the smooth surface structure 2-2, each flow restrictor structure is the same, is a radial circular hole, and the length-to-diameter ratio is in the range of 1-20, which meets the short capillary flow restrictor structure parameter range, and is different from the small hole or capillary flow in structure; the outer end of the short capillary flow restrictor 1-2 is connected with the oil guide groove, and the inner end tail can be further provided with a rectangular, square or circular oil cavity, so as to further enhance the static pressure effect of the tail of the flow restrictor. For example, each inlet flow restrictor 1-2 is arranged in a single row in the axial direction, the number of the inlet flow restrictors 1-2 is an even number, and the number is preferably in the range of 2-24, the inlet flow restrictors 1-2 are uniformly distributed along the deep groove 1-1 in the circumferential direction, and the number is designed according to the bearing working condition and the structure parameter, that is, the number is related to the bearing capacity required by the bearing.

[0045] In some embodiments of the present application, the width-to-inner diameter ratio of the bearing outer ring 1 is 0.5-2, and the wall thickness of the bearing outer ring 1 is 1 / 8-1 / 6 of the inner diameter; the depth of the deep groove 1-1 is 1 / 4-1 / 3 of the difference between the inner and outer diameters of the bearing outer ring 1, and the axial width is 1 / 5-1 / 2 of the bearing width.

[0046] In some embodiments of the present application, referring to Figure 4 , the two end tapered structures 2-1 are symmetrical about the smooth surface structure 2-2, and the length ratio of the two end tapered structures 2-1 and the smooth surface structure 2-2 in the axial length direction is preferably 1:1:1. The outer surface of the tapered structure 2-1 is tapered, and the inner surface is cylindrical for mounting the shaft. The tapering angle of the tapered structure 2-1 is in the range of 0.01°-5°, which is designed according to the external axial force borne by the tapered structure 2-1, and the outer diameter of the small-diameter end of the tapered structure 2-1 is 1-10 mm smaller than the outer diameter of the smooth surface structure 2-2; the radial wall thickness of the smooth surface structure 2-2 is 1 / 6-1 / 4 of the inner diameter of the bearing outer ring 1.

[0047] The selection of the above-mentioned tapering angle range can ensure that the gap in the converging area is in the micron level. According to the thickness of the foil 3, the outer diameter of the small-diameter end of the tapered structure 2-1 plus the thickness of the foil 3 is consistent with the outer diameter of the smooth surface structure 2-2.

[0048] In some embodiments of the present application, the number of the bottom foils 3-1 is N, referring to Figure 6 and Figure 7 , N=4. In the circumferential direction, each bottom foil 3-1 is fixed to the outer wall of the tapered structure 2-1 in turn; each wave-shaped foil 3-3 is correspondingly located between a bottom foil 3-1 and a top foil 3-4.

[0049] In this embodiment, the bottom foil 3-1 and the wave foil 3-3 are each 4, in the counterclockwise direction, the first end of the i-th wave foil 3-3 is fixed to the outer wall of the i-th bottom foil 3-1 near the first end, the second end of the i-th wave foil 3-3 is a free end, and is located on the outside of the i-th bottom foil 3-1 near the first end, i = 1, 2, 3 or 4. Thus, it is sequentially arranged along the circumference to form a kind of component structure of the foil 3.

[0050] The foil 3 forms a converging area with the bearing outer ring 1, and the dynamic pressure effect is formed in the converging area when the bearing rotates at high speed. When the bearing is subjected to axial or radial impact, the bearing will lose its balance state, at this time the converging area of the bearing is no longer uniform in the circumferential direction, forming a small converging area on one side and a large converging area on the other side, the pressure distribution of the converging area changes, the pressure distribution of the converging area becomes larger when the converging area becomes smaller, and the pressure distribution of the converging area becomes smaller when the converging area becomes larger, thereby causing the foil 3 to deform differently, so that the bearing can adjust itself to return to the balance state after being impacted.

[0051] In some embodiments of the present application, the outer wall of the bottom foil 3-1 is further provided with at least one elastic gasket foil 3-2, and the gasket foil 3-2 can be fixed to the bottom foil 3-1 by bonding (or welding, riveting, etc.). The gasket foil 3-2 fixed on one bottom foil 3-1 does not completely cover the bottom foil 3-1, but the wave foil 3-3 on one bottom foil 3-1 completely covers the gasket foil 3-2 fixed on the bottom foil 3-1.

[0052] In this embodiment, the number of gasket foils 3-2 provided on the outer wall of a single bottom foil 3-1 is preferably 1, and obviously the gasket foil 3-2 is arranged at the center position of the bottom foil 3-1. The gasket foil 3-2 is also a conical arc structure, and its two surfaces are smooth, i.e. a flat foil, which is arranged in contact with the corresponding bottom foil 3-1. The gasket foil 3-2 has a certain elasticity, which functions to slow down the deformation of the wave foil 3-3 and increase the overall damping of the bearing.

[0053] Similarly, the bottom foil 3-1 can fix the gasket foil 3-2 and prevent it from directly contacting the bearing inner ring and being squeezed and damaged. If the gasket foil 3-2 completely covers the bottom foil 3-1, it will cause the overall deformation of the foil 3 to increase, and slow down the recovery of the overall deformation of the foil, thereby reducing the self-adjusting function of the bearing as a whole, thus reducing its coverage. The wave foil 3-3 completely covering the gasket foil 3-2 can slow down the deformation of the wave foil 3-3 and protect the wave foil 3-3.

[0054] The number of the wave-shaped foils 3-3 is consistent with the number of the bottom foils 3-1, which can prevent the wave-shaped foils 3-3 from coinciding with the mounting slots 2-1-1, thereby causing the wave-shaped foils 3-3 to be pressed and damaged. However, if the number of the wave-shaped foils 3-3 is 1 and the number of the bottom foils 3-1 is also 1, the bottom foil 3-1 is only fixed in one mounting slot 2-1-1, and the overall stability of the foil 3 is low, which can easily cause the foil 3 to contact the inner side of the bearing outer ring. Therefore, in the present application, N > 1 is selected.

[0055] In some embodiments of the present application, the thickness of the bottom foil 3-1, the spacer foil 3-2, the wave-shaped foil 3-3 and the top foil 3-4 is 0.2-1 mm; the wave height of the wave-shaped foil 3-3 is 0.2-0.8 mm; the number of the wave shapes of a single wave-shaped foil 3-3 is 5-30; and the overall deformation of the foil 3 in the radial direction is controllable in the range of 0.05-3 mm. The stiffness of the foil is reasonably designed according to the load borne by the bearing and the working condition of the environment, which can prevent the foil from being damaged due to excessive deformation and from generating severe friction due to excessive stiffness and inability to deform. The foil can be replaced as a whole after being damaged, which will not cause the structural adjustment of the inner ring and the outer ring.

[0056] In some embodiments of the present application, the top foil 3-4 covers all the wave-shaped foils 3-3 in the circumferential direction. The top foil 3-4 covering all the wave-shaped foils 3-3 in the circumferential direction makes the foil 3 a whole. When the bearing loses the balance state due to impact, the foil 3 will deform, and the deformation of one side of the foil 3 will cause the deformation of the whole foil 3, thereby accelerating the self-adjustment of the bearing and quickly returning to the balance position.

[0057] In some embodiments of the present application, referring to Figure 4 and Figure 5 , the conical structure 2-1 is provided with N mounting slots 2-1-1 in the axial direction. The mounting slots 2-1-1 are machined on the outer wall of the conical structure 2-1, and the cross section thereof is L-shaped or J-shaped. The number of the mounting slots 2-1-1 is selected in combination with the actual working condition and the number of the wave-shaped foils 3-3, and the preferred number is 1-8. The two ends of each bottom foil 3-1 are respectively fixed in two adjacent mounting slots 2-1-1.

[0058] The present application will be described in further detail below in combination with the drawings and specific embodiments:

[0059] A conical foil dynamic and static pressure radial gas bearing lubricated by air is designed. It is known that n max = 30000 rpm; the air supply pressure of the air supply source is 70 N / cm 2 ; the working environment pressure is 10 N / cm 2 ; the environment temperature is 25℃; and the radial bearing capacity of the bearing is greater than 500 N.

[0060] Referring to Figure 1The embodiment includes a radial bearing outer ring 1, a bearing inner ring 2 and a foil 3, wherein:

[0061] The bearing outer ring 1 is cylindrical in shape, and has a structure as shown in Figure 2 and Figure 3 The outer side has a circumferential deep groove 1-1 and a short capillary restrictor 1-2. The bearing outer ring 1 has a width of 60 mm, an inner diameter of 60 mm, a width-to-diameter ratio of 1, and a wall thickness of 7.5 mm, which is 1 / 8 of the bearing inner diameter;

[0062] The deep groove 1-1 is machined along the circumferential direction of the axial center of the outer side of the bearing outer ring 1, and serves as a radial gas bearing gas inlet hole. The depth of the deep groove 1-1 is 2.5 mm, which is 1 / 3 of the difference between the inner and outer diameters of the bearing outer ring (i.e., the wall thickness of the bearing outer ring 1), and the axial width is 12 mm, which is 1 / 5 of the bearing width. The deep groove 1-1 uniformly distributes 6 short capillary restrictors 1-2.

[0063] The short capillary restrictor 1-2 is installed at the axial center of the bearing outer ring, uniformly distributed along the circumferential direction of the deep groove 1-2, and penetrates the bearing outer ring 2, so that the external high-pressure gas acts on the bearing inner ring 2 through the deep groove 1-1 and the short capillary restrictor 1-2. The length of the short capillary restrictor 1-2 is 5 mm, and the diameter is 0.266 mm. The short capillary restrictor 1-2 is uniformly distributed along the circumferential direction of the deep groove 1-1, and the size and number of the short capillary restrictor 1-2 are related to the bearing capacity required by the bearing (the radial load range is greater than 500 N). The specific design is as follows: the pressure ratio P0 is defined as follows:

[0064]

[0065] Wherein, P1 is the environmental pressure, P2 is the restrictor outlet pressure, and P3 is the gas supply pressure. According to the maximum bearing design, P0 is 0.4. Under the condition of known gas supply pressure and environmental pressure, the restrictor outlet pressure P2 can be calculated as 24 N / cm 2 . At the same time, the pressure ratio P0 can also be calculated by the following formula:

[0066]

[0067] Y=Y P Y η Y d

[0068]

[0069]

[0070]

[0071]

[0072]

[0073] wherein Y P is a pressure coefficient; Y η is a gas medium coefficient; Y d is a size coefficient; A j is a throttling area of the capillary flow restrictor; R is a gas constant; T is an ambient temperature; η is a gas viscosity; b is a distance from a center of the throttling hole to a bearing end surface; α is a flow coefficient, equal to 0.8; Z is a number of the throttling holes; D is an inner diameter of the bearing outer ring; d j is a diameter of the short capillary flow restrictor; and h0 is a gap between a smooth surface of the bearing inner ring and the bearing outer ring.

[0074] According to the calculation of the above formula, h0 is 30 μm, and the relationship between the diameter of the short capillary flow restrictor and the number of the throttling holes is shown in the following formula:

[0075]

[0076] According to the parameter setting of the length-diameter ratio of the short capillary flow restrictor as 1-20, the diameter of the restrictor is 0.25-5 mm, the number of the restrictors is 6, and the diameter d j of the restrictor is calculated as 0.266 mm, at this time, the length-diameter ratio of the restrictor is 18.8, which meets the design requirement.

[0077] The formula for verifying the bearing capacity is as follows:

[0078] F = 2 (P3 - P1) BDF0

[0079] wherein B is a bearing width; D is an inner diameter of the bearing outer ring; and F0 is a bearing load coefficient, when B / D = 1 and b / B = 1 / 2, F0 = 0.29. The calculated bearing capacity meets the requirement.

[0080] The bearing inner ring 2 has a structure as shown in Figure 4 , which is integrally machined; comprising two tapered structures 2-1 and one smooth surface structure 2-2; the left and right axial lengths of the tapered structure 2-1 are respectively 20 mm, and the axial length of the smooth surface structure 2-2 is 20 mm.

[0081] The tapered structure 2-1 has a structure as shown in Figure 5 , the outer surface is tapered, and the inner surface is a column with a diameter of 40 mm. The tapered structure 2-1 is divided into a large-diameter end and a small-diameter end, and the wall thickness of the small-diameter end is 7.47 mm. The difference between the outer diameters of the two ends and the tapered width determine the taper angle of the tapered structure 2-1, which is designed to be 0.069° according to the design requirement. The gap between the foil 3 matched with the outer surface of the tapered structure 2-1 and the bearing outer ring 1 is wedge-shaped, and the gas medium forms a dynamic pressure effect through the wedge-shaped gap. The taper angle is specifically designed as follows:

[0082] The radial dynamic pressure gas bearing, the gap definition adopts the following formula:

[0083]

[0084] Wherein, c is the gap; r is the bearing radius. So the gap c is 6 μm. The taper at this time is 0.069 °.

[0085] The taper structure 2-1 is a structure symmetrical along the axial direction of the bearing, the inner diameter of the small diameter end of each side structure is consistent with the inner diameter of the smooth surface structure 2-2, the outer diameter of the small diameter end is 5mm smaller than the outer diameter of the smooth surface structure 2-2, and the small diameter end of the taper structure 2-1 is welded with the smooth surface to form the bearing inner ring 2; the taper structure 2-1 and the smooth surface structure 2-2 are welded to form a concave structure, so that the static pressure effect can be formed without machining a deep cavity structure on the inner side of the bearing outer ring 1, and the bearing structure is simplified.

[0086] The taper structure 2-1 is uniformly distributed with mounting grooves 2-1-1 along the circumferential direction of the taper structure 2-1, the number of the mounting grooves 2-1-1 is 4, and the cross section is J-shaped, which is used for fixing the foil 3.

[0087] The mounting groove 2-1-1 has a width of 1mm, a length consistent with the axial length of the taper surface of the taper structure 2-1, and a depth of 3mm. The length of the bottom of the mounting groove 2-1-1 in the circumferential direction is 1mm.

[0088] The smooth surface structure 2-2 is a cylindrical structure, and the outer surface of the cylinder is a smooth surface; the inner diameter of the smooth surface structure 2-2 is 40mm, and the radial wall thickness is 9.97mm.

[0089] The bearing outer ring 1 and the bearing inner ring 2 form three gap sections, which are the convergent region gap formed between the left and right taper outer side convergent gap regions of the inner ring and the inner diameter of the outer ring, i.e. the cooperation of the flat foil and the bearing outer ring, designed as a gap fit, combined with the designed taper of 0.069 °, the gap converges from the maximum value of 30 μm to 6 μm, and the convergent region gap promotes the formation of dynamic pressure effect during the rotation of the inner ring. The static pressure region gap between the static pressure bearing region of the outer diameter of the middle part of the inner ring and the inner diameter of the outer ring, the design value is 30 μm, and the static pressure region gap forms the static pressure effect through the air inlet throttling device.

[0090] The structure of the foil 3 is as follows Figure 6, the bottom foil 3-1 is fixedly installed on the outer surface of the conical structure 2-1, a gasket foil 3-2 is arranged on the top of the bottom foil 3-1, the gasket foil 3-2 is bonded to the top foil 3-1, and the gasket foil 3-2 functions to slow down the deformation of the wave-shaped foil 3-3. The wave-shaped foil 3-3 is arranged on the top of the gasket foil 3-2, one end of the wave-shaped foil 3-3 is welded to one end of the bottom foil 3-1, and the other end of the wave-shaped foil 3-3 is a free end, the wave-shaped foil 3-3 functions to increase the damping and the bearing dynamics of the whole bearing. The top foil 3-4 is arranged on the top of the wave-shaped foil 3-3, one end of the top foil 3-4 is welded to one end of the bottom foil 3-1, the welded end of the top foil 3-4 is the free end of the wave-shaped foil 3-3, and the other end of the top foil 3-4 is a free end, the top foil 3-4 functions to protect the wave-shaped foil 3-3 from being damaged by extrusion. The thicknesses of the bottom foil 3-1, the gasket foil 3-2, the wave-shaped foil 3-3 and the top foil 3-4 are each 0.5 mm, the wave height of the wave-shaped foil 3-3 is 0.5 mm, and the number of waves is 20.

[0091] The number of the bottom foil 3-1, the gasket foil 3-2 and the wave-shaped foil 3-3 of the foil 3 is 4, and the number of the top foil 4 is 1.

[0092] The foil 3 cooperates with the conical structure 2-1, and the cooperation structure is as shown in Figure 7 The two ends of the bottom foil 3-1 are fixed in the mounting groove 2-1-1, and the bearing capacity and the damping are increased.

[0093] The overall deformation of the foil 3 in the radial direction is controllable within a range of 0.5 mm, the rigidity of the foil is reasonably designed to be 1.0*10 6 N / m (calculated under the condition of bearing 500 N and maximum deformation 0.5 mm), so as to prevent damage of the foil due to excessive deformation and serious friction caused by excessive rigidity and unable to deform. The foil can be replaced as a whole after being damaged, and the structure adjustment of the inner ring and the outer ring is not caused.

[0094] The cooperation between the flat foil 3-4 and the bearing outer ring 2 is designed as a clearance fit, which is in the micron level and ranges from 6 to 30 microns, so as to ensure the realization of the dynamic and static pressure effect between the bearing outer ring and the flat foil during high-speed operation.

Claims

1. A dual conical foil hydrostatic-radial gas bearing, characterized by, The bearing outer ring (1), the bearing inner ring (2) and the foil (3) are included; the bearing outer ring (1) is provided with air inlet throttling structure; The bearing inner ring (2) is composed of a smooth surface structure (2-2) in the middle and two tapered structures (2-1) at both ends, the smooth surface structure (2-2) is cylindrical, and the tapered structures (2-1) are frustoconical, and the small-diameter ends of the two tapered structures (2-1) are respectively connected with the both ends of the smooth surface structure (2-2); The foil (3) includes a bottom foil (3-1), a wave-shaped foil (3-3) and a top foil (3-4), the bottom foil (3-1) is fixed to the outer wall of the tapered structure (2-1), the wave-shaped foil (3-3) is N in number, is distributed between the bottom foil (3-1) and the top foil (3-4) in the circumferential direction, N>1, the first end of each wave-shaped foil (3-3) is connected with the outer wall of the bottom foil (3-1), and the second end is a free end, the top foil (3-4) is one in number, one end of which is connected with the outer wall of the bottom foil (3-1), and the other end is a free end, and the welded end of the top foil (3-4) corresponds to the free end of the wave-shaped foil (3-3).

2. The dual conical foil hydrostatic-radial gas bearing of claim 1 wherein, The bearing outer ring (1) is cylindrical, a deep groove (1-1) is formed in the circumferential direction at the axial symmetry center of the outer side of the bearing outer ring (1), a plurality of short capillary throttling devices (1-2) are uniformly distributed in the deep groove (1-1), the short capillary throttling devices (1-2) correspond to the outer wall of the smooth surface structure (2-2), each throttling hole structure of the short capillary throttling devices (1-2) is the same, and the length-diameter ratio range is 1-20.

3. The dual conical foil hydrostatic-radial gas bearing of claim 2 wherein, The depth of the deep groove (1-1) is 1 / 4-1 / 3 of the difference between the inner diameter and the outer diameter of the bearing outer ring (1), and the axial width is 1 / 5-1 / 2 of the bearing width.

4. The dual conical foil hydrostatic-radial gas bearing of claim 1 wherein, The two tapered structures (2-1) are symmetrical about the smooth surface structure (2-2), the inclination angle of the tapered inclined surface of the tapered structure (2-1) is 0.01°-5°, and the outer diameter of the small-diameter end of the tapered structure (2-1) is 1-10 mm smaller than the outer diameter of the smooth surface structure (2-2).

5. The dual conical foil hydrostatic-radial gas bearing of claim 1 wherein, The bottom foils (3-1) are N in number, are fixed to the outer wall of the tapered structure (2-1) in the circumferential direction, and are sequentially arranged; each wave-shaped foil (3-3) is correspondingly located between a bottom foil (3-1) and a top foil (3-4).

6. The dual conical foil hydrostatic-radial gas bearing of claim 5 wherein, The outer wall of the bottom foil (3-1) is provided with at least one elastic gasket foil (3-2), the gasket foil (3-2) does not completely cover the bottom foil (3-1), and the wave-shaped foil (3-3) completely covers the gasket foil (3-2).

7. The dual conical foil hydrostatic-radial gas bearing of claim 6 wherein, The thicknesses of the bottom foil (3-1), the gasket foil (3-2), the wave-shaped foil (3-3) and the top foil (3-4) are 0.2-1 mm, the wave height of the wave-shaped foil (3-3) is 0.2-0.8 mm, the number of wave shapes of a single wave-shaped foil (3-3) is 5-30, and the overall deformation of the foil (3) in the radial direction is controllable in the range of 0.05-3 mm.

8. The dual conical foil hydrostatic radial gas bearing of claim 1 or 5 or 6, wherein, The top foil (3-4) covers all the wave-shaped foils (3-3) in the circumferential direction.

9. The dual conical foil hydrostatic radial gas bearing of claim 5 wherein, The conical structure (2-1) is provided with N mounting grooves (2-1-1) in the axial direction, the cross section of the mounting grooves (2-1-1) is L-shaped or J-shaped, and the two ends of each bottom foil (3-1) are fixed in two adjacent mounting grooves (2-1-1) respectively.

10. The dual conical foil hydrostatic radial gas bearing of claim 1 wherein, The bearing outer ring (1) and the bearing inner ring (2) form three gaps, which are the converging area gap between the conical structure (2-1) at both ends and the bearing outer ring (1) and the static pressure area gap between the smooth surface structure (2-2) and the bearing outer ring (1); the converging area gap promotes the formation of dynamic pressure effect in the rotating process of the bearing inner ring (2), and the static pressure area gap forms static pressure effect under the inlet throttling structure; the top foil (3-4) and the bearing outer ring (1) are designed as a gap fit, which is micron level, to ensure the realization of dynamic and static pressure effect between the top foil (3-4) and the bearing outer ring (1) in the high-speed operation process.

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