Gas bearing

Abstract

To provide a gas bearing which is easy to design, and does not require a special mechanism for adjusting a shape and a dimension of a bearing surface.　This gas bearing is provided with: a sleeve having the rigid bearing surface; and a support structure that elastically supports the sleeve from the outside in the radial direction thereof, and is provided over the entire region in the circumferential direction of the sleeve. The preferable support structure is composed of an aggregate of a plurality of beams. The preferred beam is composed of a cantilever beam or a both-end support beam.　The preferable support structure is composed of an aggregate of a plurality of beams.　The preferred beam is composed of a cantilever beam or a both-end support beam.

Description

Gas bearings

[0001] The present disclosure relates to gas bearings that use a gas such as air as a lubricating medium.

[0002] Foil bearings are one example of gas bearings. Foil bearings have a bearing surface made of a flexible thin film, such as a metal foil, tape, or film, which has low bending stiffness. Because the load from the supported shaft is received by the deflection of the foil, they offer high-speed stability, although they have poor axial positioning accuracy.

[0003] Patent Document 1 discloses a gas bearing in which the shape and dimensions of the bearing surface can be adjusted even after the bearing is assembled. The gas bearing in Patent Document 1 includes a housing with a tapered inner surface, a sleeve with a tapered outer surface that fits into the tapered inner surface, and an axial position adjustment means for adjusting the relative axial positional relationship between the housing and the sleeve.

[0004] Japanese Unexamined Patent Publication No. 7-119746

[0005] The design of foil bearings requires coupling of a fluid lubrication analysis that focuses on the gas film with a structural analysis that focuses on the deformation of the foil, making the design complicated. The gas bearing of Patent Document 1 requires a mechanism for adjusting the bearing surface in addition to the bearing elements. In view of the above, the present disclosure aims to provide a gas bearing that is easy to design and does not require a special mechanism for adjusting the shape and dimensions of the bearing surface.

[0006] The gas bearing according to the present disclosure comprises a sleeve (11) having a rigid bearing surface (12), and a support structure (15) that elastically supports the sleeve (11) from its radially outer side and is provided over the entire circumferential area of ​​the sleeve (11).

[0007] According to the present disclosure, a gas bearing is provided that is easy to design and does not require any special mechanism for adjusting the shape and dimensions of the bearing surface.

[0008] FIG. 1 is a diagram showing a basic configuration of an embodiment of a gas bearing according to the present disclosure. FIG. 2 is a diagram explaining a gas bearing according to the basic configuration. FIG. 3 is a diagram showing a gas bearing according to a first embodiment. FIG. 4 is a diagram explaining the rigidity of the gas bearing according to the first embodiment. FIG. 5 is a diagram showing a gas bearing according to a second embodiment. FIG. 6 is a diagram showing another gas bearing according to the second embodiment. FIG. 7 is a diagram showing a gas bearing according to a third embodiment. FIG. 8 is a diagram showing a gas bearing according to a fourth embodiment. FIG. 9 is a diagram showing a gas bearing on which a rotating shaft is supported. FIG. 10 is a diagram showing examples of the configuration of a bearing surface that can be employed in the air bearing according to the present disclosure.

[0009] Hereinafter, embodiments will be described with reference to the accompanying drawings. Although the present disclosure includes multiple embodiments, a basic configuration common to the multiple embodiments will be described first, and then multiple more specific embodiments will be described in order.

[0010] 1 includes a sleeve 11 that houses a rotating shaft 100 therein, and a support structure 15 that elastically supports sleeve 11 from the outside in the radial direction. In gas bearing 1, support structure 15 is elastically deformable, while sleeve 11 includes a rigid bearing surface 12. Support structure 15 is disposed over the entire circumferential area of ​​sleeve 11.

[0011] [Function of Rigid Bearing Surface 12] In a gas bearing, a thin film (hereinafter referred to as an air film) of gas, typically air, is drawn in by the rotation of the shaft and is generated between the bearing surface and the shaft. In the case of a foil bearing, the top foil that provides the bearing surface is formed to be very thin, and is therefore deformed by the pressure of this air film. When the top foil deforms, the circumferential distribution (shape) of the air film changes, and the pressure distribution in the air film also changes. In this way, the pressure distribution in the air film and the deformation of the top foil influence each other. Therefore, when designing a foil bearing, it is necessary to couple a hydrodynamic lubrication analysis that focuses on the air film with a structural analysis that focuses on the deformation of the foil.

[0012] If the bearing surface 12 is rigid, as in the gas bearing 1 of the present disclosure, the bearing surface 12 will not deform regardless of the presence or shape of the gas film, and the shape of the bearing surface 12 will be maintained. Therefore, the bearing surface 12 and the gas film do not affect each other and can be said to be independent. Although the bearing surface 12 has been described as rigid here, hereinafter it is assumed that the entire sleeve 11, including the bearing surface 12, is rigid.

[0013] [Role of the Flexible Support Structure 15] While the sleeve 11 is rigid, the support structure 15 is configured to be elastically deformable and elastically supports the sleeve 11. Although the sleeve 11 is rigid and does not elastically deform, it may be displaced in the radial direction RD while supporting the rotating shaft 100. The support structure 15 absorbs this displacement of the sleeve 11 by elastically deforming. Here, the term "rigid" does not mean that the sleeve 11 is made of a completely rigid body, but rather that the sleeve 11 has a degree of rigidity that prevents it from being elastically deformed by the rotating shaft 100 it supports. Even if the sleeve 11 is made of the same material, it may or may not be considered rigid depending on the rotating shaft 100 it supports. The elastic deformation of the support structure 15 is similar to the rigidity of the sleeve 11, and is not determined solely by the material, but is assumed to be used as a gas bearing 1.

[0014] [Manufacturing Process] It is desirable to adopt a manufacturing process for the gas bearing 1 that takes into account the fact that the mechanical precision of the components of a foil bearing affects bearing performance. For example, to achieve dimensional precision for the sleeve 11 and support structure 15 of the gas bearing 1, methods such as cutting, electrical discharge machining, additive manufacturing (AM), and injection molding can be used. Therefore, the gas bearing 1 can be manufactured with high mechanical precision, including dimensions and shape, and minimize variations in bearing characteristics. The gas bearing 1 can be made of any material, and metal materials are typically used, although resin materials may also be used. In rolling bearings, where the inner and outer rings and rolling elements constantly slide against each other, bearing steel (JIS SUJ) is used to prevent sliding wear. However, in the case of the gas bearing 1, even if sliding occurs between components, it is less frequent than in rolling bearings. Therefore, the gas bearing 1 offers a wide range of material options.

[0015] [Examples of support structure 15: see Fig. 2] Several configurations of the support structure 15 will be described. In the example shown in Fig. 2, a housing 17 is provided around the support structure 15. In this example, the support structure 15 is provided between the housing 17 and the sleeve 11. However, depending on the type of mechanical device in which a gas bearing is used, a member corresponding to the housing 17 may be provided in the mechanical device. Therefore, the housing 17 is an optional feature in the present disclosure.

[0016] Here, three examples are shown: Cmp.1, Emb.1, and Emb.2. Cmp.1, Emb.1, and Emb.2 differ in the configuration of the support structure 15 in the circumferential direction CD. The horizontal direction H and vertical direction V when the gas bearing is in use are defined as shown in Figure 2.

[0017] Cmp.1 is a part of the circumferential direction CD, and has support structures 15 provided only in the direction of the shaft's own weight. These support structures 15 are provided with the sole consideration of supporting only the load of the shaft (not shown). However, in reality, loads are applied to the gas bearing 1 in directions other than the direction of the shaft's own weight due to shaft whirling or external vibrations. Therefore, as shown in Emb.1 and Emb.2, if the support structures 15 are arranged over the entire circumferential direction CD, the shaft can be supported against loads in directions other than the direction of its own weight. The support structure 15 of Emb.1 not only extends over the entire circumferential direction CD, but also has a periodic structure. The support structure 15 of Emb.2 also extends over the entire circumferential direction CD, but does not have a periodic structure but has a non-periodic structure.

[0018] Gas bearings having the above basic configuration are easy to design because the rigidity of bearing surface 12 means that deformation of bearing surface 12 and the pressure distribution of the gas film are independent. Furthermore, gas bearings having the basic configuration have a support structure in directions other than the direction of the rotating shaft's own weight, so they can also accommodate loads other than the rotating shaft's own weight, such as vibrations of the rotating shaft, thereby achieving stable high-speed rotation. Gas bearings having the basic configuration can be manufactured using cutting, AM, and injection molding, allowing for high-precision bearing manufacturing and reducing variation in bearing characteristics.

[0019] The basic configuration and effects of the gas bearing 1 according to the present disclosure have been described above, and more specific examples of the gas bearing 1 will now be described in order.

[0020] [First embodiment: see FIG. 3] Gas bearings 1A to 1F according to a first embodiment will be described with reference to FIG. 3. Gas bearings 1A to 1F have a common configuration in that they include a sleeve 11, a support structure 15, and a housing 17, but the specific structure of support structure 15 differs. Support structure 15 is composed of multiple beams 16 between sleeve 11 and housing 17 that generate mainly bending stress due to the load received from the shaft about which sleeve 11 rotates and transmit this stress to housing 17. In other words, support structure 15 is an assembly of multiple beams 16 provided between sleeve 11 and housing 17. Gas bearings 1A to 1F differ in the shape and arrangement of the beams.

[0021] [Gas Bearing 1A] In the gas bearing 1A, the support structure 15 is formed by multiple cantilever beams 16A that are curved in an arc. The fixed end 16A1 of each cantilever beam 16A is connected to the housing 17, and the free end 16A2 is located between the sleeve 11 and the housing 17. In other words, the cantilever beams 16A of the gas bearing 1A are curved in the radial direction RD. The cantilever beams 16A are connected to the sleeve 11 at a contact point 16A3 between the fixed end 16A1 and the free end 16A2, which is the apex of the arc as viewed from the housing 17 side. The gas bearing 1A has eight cantilever beams 16A arranged at equal intervals in the circumferential direction CD. The multiple contact points 16A3 are joined to the sleeve 11, thereby forming the entire gas bearing 1A as a single unit. The gas bearings 1B to 1F are also similarly formed as a single unit. The shape of the cantilever beams 16A is the shape of the gas bearing 1A when viewed from the front. Also, cantilever beam 16A is connected to gas bearing 1A in the direction of axis C. The same applies to the other gas bearings.

[0022] [Gas bearing 1B] In gas bearing 1B, support structure 15 is formed by multiple diagonal beams 16B1, 16B2 that are inclined with respect to the radial direction RD. Diagonal beam 16B1 is connected to both sleeve 11 and housing 17 and is inclined clockwise in the figure. Diagonal beam 16B2 is connected to both sleeve 11 and housing 17 and is inclined counterclockwise in the figure. One end of the pair of diagonal beams 16B1 and 16B2 is rigidly connected to sleeve 11 and the other end is rigidly connected to housing 17. In other words, support structure 15 in gas bearing 1B forms a rigid frame structure consisting of the combination of triangular diagonal beams 16B1, 16B2, sleeve 11, and housing 17.

[0023] [Gas bearing 1C] Like gas bearing 1B, gas bearing 1C has a rigid frame structure for support structure 15. In the rigid frame structure of gas bearing 1B, one end (the side of sleeve 11) and the other end (the side of housing 17) of a pair of diagonal beams 16B1, 16B2 are rigidly connected together, whereas in gas bearing 1C, one end (the side of sleeve 11) of the pair of diagonal beams 16B1, 16B2 are rigidly connected together, but the other ends (the side of housing 17) are each independently rigidly connected to housing 17. In other words, gas bearing 1C can support housing 17 at more points than gas bearing 1B.

[0024] In gas bearing 1B and gas bearing 1C, diagonal beam units each consisting of a pair of diagonal beams 16B1, 16B2 are provided continuously in the circumferential direction CD, but for example, the diagonal beam units may be provided intermittently in the circumferential direction CD. More specifically, in gas bearing 1B, eight diagonal beam units may be provided without gaps at 45° intervals, or four diagonal beam units may be provided at 90° intervals. In this case, too, support structure 15 is provided over the entire circumferential area.

[0025] [Gas bearing 1D] In gas bearing 1D, support structure 15 is formed of a plurality of double-supported beams 16D that are curved in an arc shape. One end of each double-supported beam 16D is fixed to sleeve 11, and the other end is fixed to housing 17. The plurality of double-supported beams 16D are arranged at equal intervals or intervals in circumferential direction CD. All double-supported beams 16D are curved in the same direction in circumferential direction CD.

[0026] [Gas bearing 1E] In gas bearing 1E, support structure 15 is formed of double-supported beams 16E made of a plurality of thin plates that resemble an involute curve. One end of double-supported beam 16E is fixed to sleeve 11, and the other end is fixed to housing 17. A plurality of double-supported beams 16E, three in this case, are arranged at equal intervals or periods over the entire circumferential direction CD.

[0027] [Gas bearing 1F] In gas bearing 1F, support structure 15 is formed by a plurality of straight cantilever beams 16F. One end 16F1 of cantilever beam 16F is fixed to housing 17, and the other end 16F2 forms a free end. Cantilever beam 16F is connected to sleeve 11 at a contact point 16F3 midway between one end and the other end. A plurality of, here three, both-end supported beams 16E are arranged at equal intervals or intervals in the circumferential direction CD.

[0028] [Adjusting the Stiffness of the Gas Bearing 1A: See FIG. 4 ] In the gas bearing 1A, when the sleeve 11 and the support structure 15 are joined, the sleeve 11 is supported by all of the cantilevers 16A, including not only the cantilevers (1) and (3) arranged above and below the load L, but also the cantilevers (2) and (4). Therefore, as with the design of a foil bearing, if the cantilever 16A is designed with a focus only on the stiffness RV in the load direction (vertical direction V), the stiffness will be greater than necessary. Therefore, the cantilever 16A must be designed taking into account both the stiffness RV and the stiffness RH perpendicular to the stiffness RV. In this case, if the stiffness RV can be made larger than the stiffness RH, the increase in bearing stiffness due to the stiffness RH can be relatively ignored, making the design of the cantilever 16A easier.

[0029] In gas bearings 1B to 1F, the rigidity in the load direction and the direction perpendicular thereto can be adjusted by devising the shape and dimensions of the beams and other components that make up support structure 15. For example, both-end supported beam 16E of gas bearing 1E and cantilever beam 16F of gas bearing 1F have the relationship: vertical rigidity RV<horizontal rigidity RH. Also, both-end supported beam 16D of gas bearing 1D has the relationship: vertical rigidity RV>horizontal rigidity RH.

[0030] [Effects of the First Embodiment] Gas bearings 1A-1F have an integrated structure and do not require the assembly of multiple components, so there is no assembly error. Therefore, gas bearings 1A-1F can reduce manufacturing errors. Next, with gas bearings 1A-1F, by adjusting the rigidity of support structure 15, any rigidity can be imparted in any direction, thereby achieving the desired bearing performance. Furthermore, if radial rigidity >> circumferential rigidity, it is only necessary to consider radial rigidity, making it easier to consider support structure 15 using theoretical formulas.

[0031] [Second embodiment: Figures 5 and 6] Next, gas bearings 2A to 2D according to a second embodiment will be described with reference to Figures 5 and 6. The second embodiment discloses gas bearings 2A to 2D that, in addition to the elements included in the first embodiment, include a friction damping element in the space of support structure 15. Gas bearings 2A to 2D differ in the content of the friction damping element included in support structure 15.

[0032] [Gas bearing 2A: see FIG. 5] The gas bearing 2A uses cantilever beams 16G made of thin plates similar to those of the gas bearing 1E of the first embodiment. The gas bearing 2A divides the multiple cantilever beams 16G into three groups G1, G2, and G3. In each of the groups G1, G2, and G3, the cantilever beams 16G overlap with adjacent cantilever beams 16G. A specific cantilever beam 16G has a fixed end on the housing 17 side and a fixed end on the sleeve 11 side. In each of the groups G1, G2, and G3, the specific cantilever beam 16GI located at the innermost position in the radial direction RD has its other end integrated with the sleeve 11. This allows the sleeve 11 to be elastically supported by the support structure 15. In each of the groups G1, G2, and G3, adjacent cantilever beams 16G are in slidable contact with each other.

[0033] When the gas bearing 2A supports the rotating shaft and a load W is applied in the vertical direction V, the sleeve 11 supported by the cantilever 16GI is displaced in the vertical direction V. When the displaced sleeve 11 presses down on the other cantilever 16G, the overlapping surfaces of the other cantilever 16G slide against each other, generating friction, since the other cantilever 16G is supported in a cantilevered manner. As a result of vibration damping by this friction, particularly stable high-speed rotation can be achieved. The gas bearing 2A is equipped with the first friction damping element of the present disclosure.

[0034] [Gas bearing 2B: see Figure 5] In gas bearing 2B, support structure 15 is formed by a plurality of cantilever beams 16H curved in an arc. Cantilever beam 16H is similar to cantilever beam 16A of the first embodiment, but its free end extends closer to housing 17 than cantilever beam 16A. The portion that contacts housing 17 is folded back toward sleeve 11. This folded back curved surface 16H1 slidably contacts inner circumferential surface 17I of housing 17. Note that the same parts as cantilever beam 16A are given the same reference numerals and descriptions thereof will be omitted.

[0035] When gas bearing 2B supports the rotating shaft and load L is applied in the vertical direction V, friction occurs between multiple curved surfaces 16H1 and inner circumferential surface 17I of housing 17, and vibration is damped by this friction, resulting in particularly stable high-speed rotation. Note that gas bearing 2B is provided with the third friction damping element of the present disclosure.

[0036] Gas bearing 2C: see FIG. 6 In gas bearing 2C, support structure 15 is formed by a plurality of arc-shaped cantilever beams 16I. Cantilever beams 16I are provided with sliding plates 16I1 on the free end side, and sliding surfaces 16I2 of sliding plates 16I1 facing outward in radial direction RD are in slidable contact with inner circumferential surface 17I of housing 17.

[0037] When gas bearing 2C supports a rotating shaft and a load W is applied in the vertical direction V, friction occurs between multiple sliding surfaces 16I2 and inner circumferential surface 17I of housing 17, thereby providing a vibration damping effect. Note that gas bearing 2C includes the third friction damping element of the present disclosure.

[0038] [Gas bearing 2D: see Figure 6] The support structure 15 in the gas bearing 2D includes diagonal beams 16J1, 16J2 and diagonal beams 16J3, 16J4 that are inclined relative to the radial direction RD. The diagonal beams 16J1 and 16J2 intersect with each other, with the diagonal beam 16J1 located further back in the drawing (Figure 6) than the diagonal beam 16J2. The diagonal beams 16J3 and 16J4 intersect with each other, with the diagonal beam 16J3 located further back in the drawing (Figure 6) than the diagonal beam 16J4. The diagonal beams 16J1 and 16J2 form cantilevers with a fixed end on the sleeve 11 side and a free end 16J5 on the housing 17 side. While the example shown is such that the free end 16J5 is a small distance away from the inner circumferential surface 17I of the housing 17, it may also be in contact with the inner circumferential surface 17I. The diagonal beams 16J3 and 16J4 have fixed ends on the sleeve 11 side and also on the housing 17 side, and constitute beams supported at both ends.

[0039] When gas bearing 2D supports a rotating shaft and a load W is applied in the vertical direction V, friction occurs between free ends 16J5 and inner circumferential surface 17I of housing 17, and vibration is damped by this friction, resulting in particularly stable high-speed rotation. Gas bearing 2D also includes the third friction damping element of the present disclosure.

[0040] [Advantages of the Second Embodiment] Gas bearings 2A to 2D are provided with a friction damping element, which provides a vibration damping effect. This reduces contact of the rotating shaft during rotation and improves the stability of the shaft diameter, thereby achieving particularly stable high-speed rotation.

[0041] Third Embodiment: See FIG. 7 Next, gas bearings 3A and 3B according to a third embodiment will be described with reference to FIG. 7. In the third embodiment, friction is generated by including a sliding portion between part or all of sleeve 11 and support structure 15, thereby obtaining a damping effect. Gas bearings 3A and 3B are equipped with the second friction damping element of the present disclosure.

[0042] The gas bearings 3A and 3B have the same basic configuration as the gas bearing 1A. However, in the gas bearing 3A, of the multiple arc-shaped cantilever beams 16K1 and 16K2, the cantilever beam 16K1 is in slidable contact with the outer peripheral surface 11O of the sleeve 11 at the contact surface 16K3, while the cantilever beam 16K2 is joined to the outer peripheral surface 11O of the sleeve 11. Thus, in the gas bearing 3A, the sleeve 11 is supported by the cantilever beams 16K1 and 16K2. In the gas bearing 3B, all of the multiple arc-shaped cantilever beams 16K1 are in slidable contact with the outer peripheral surface 11O of the sleeve 11 at the contact surface 16K3, so that the sleeve 11 is supported by the support structure 15. The gas bearing 3B is constructed by assembling two members: the sleeve 11 and a housing 17 with which the cantilever beams 16K1 are integrally formed.

[0043] Although an example in which sliding is provided over part or all of the space between sleeve 11 and support structure 15 has been illustrated here, in other embodiments, a slidably separated part can be provided over part or all of the space between housing 17 and support structure 15. Furthermore, in cases where gas bearings 3A, 3B do not include housing 17, a slidably separated part can be provided over part or all of the space between a housing that serves as a substitute for housing 17 and support structure 15.

[0044] [Effects of the Third Embodiment] In the third embodiment, as in the second embodiment, the provision of a friction damping element provides a vibration damping effect. This reduces the rotation of the rotating shaft during rotation, improving the stability of the shaft diameter during rotation. If the entire cantilever beam 16K1 is in contact with the sleeve 11 at the contact surface 16K3, as in the gas bearing 3B, and the support structure 15 and the sleeve 11 are separated, only the rigidity in the radial direction RD acts, making it easier to consider the support structure 15 using theoretical formulas.

[0045] [Fourth embodiment: see Fig. 8] Next, gas bearings 4A, 4B, 4C according to a fourth embodiment will be described with reference to Fig. 8. In the fourth embodiment, a viscoelastic body is interposed at the sliding location, thereby achieving vibration damping due to material damping of the viscoelastic body.

[0046] Gas bearing 4A has the same basic configuration as gas bearing 3B, but in addition to providing damping cylinder 18 made of a viscoelastic material between sleeve 11 and cantilever beam 16K1, a damping sheet 19 made of a viscoelastic material is provided between inner circumferential surface 17I of housing 17 and the tip of cantilever beam 16K1. It can be said that gas bearing 4A replaces the frictional damping in gas bearing 3B with material damping made of a viscoelastic material.

[0047] Gas bearing 4B has the same basic configuration as gas bearing 4A, but has a damping body 21 made of a rod-shaped viscoelastic body provided between housing 17 and free end 16A2 of cantilever beam 16A.

[0048] Gas bearing 4C has the same basic configuration as gas bearing 1C, but has a damping body 23 made of a rod-shaped viscoelastic body provided between sleeve 11 and housing 17.

[0049] [Effects of the Fourth Embodiment] According to the gas bearings 4A, 4B, and 4C of the fourth embodiment, a viscoelastic material is interposed between the sleeve 11 and the beam 16, and / or between the housing 17 and the beam 16, thereby achieving a higher damping effect against vibrations.

[0050] [Notes] The gas bearing according to the present disclosure can be understood as follows: [Note 1] A gas bearing comprising: a sleeve (11) having a rigid bearing surface (12), and a support structure (15) that elastically supports the sleeve (11) from the outside in a radial direction (RD) and is provided over the entire circumferential area of ​​the sleeve (11).

[0051] [Supplementary Note 2] In Supplementary Note 1, the preferred support structure (15) is made up of a group of multiple beams (16).

[0052] [Supplementary Note 3] In Supplementary Note 2, the preferred beam (16) is a cantilever beam (16A) or a double-supported beam (16D).

[0053] [Supplementary Note 4] In Supplementary Note 1, the preferred support structure (15) is a rigid frame structure.

[0054] [Supplementary Note 5] In Supplementary Note 3, preferably, a housing (17) is provided surrounding the support structure (15), and the support structure (15) is provided with any of: a first friction damping element formed by a plurality of cantilever beams (16G) that can slide relative to each other; a second friction damping element formed by sliding between the plurality of cantilever beams (16G) and the sleeve (11); and a third friction damping element formed by sliding between the plurality of cantilever beams (16G) and the housing (17).

[0055] [Supplementary Note 6] In Supplementary Note 5, a housing (17) is provided that surrounds the periphery of the support structure, and a viscoelastic material is interposed between the sleeve (11) and the beam (16) and / or between the housing (17) and the beam (16).

[0056] [Supplementary Note 7] In Supplementary Note 1, preferably, a housing (17) surrounding the periphery of the support structure is provided, and the sleeve (11), the support structure (15), and the housing (17) are integrally formed. [Supplementary Note 8] In any of Supplementary Notes 1 to 7, preferably, the bearing surface is either a perfect circle or one having multiple offset arcs.

[0057] In addition to the above, the configurations described in the above embodiments can be selected or modified as appropriate. For example, the support structure 15 is not limited to a collection of beams. For example, instead of the beam 16, a member that is easily elastically deformable, such as rubber, can be disposed between the sleeve 11 and the housing 17. Furthermore, the bearing surface 12 in the present disclosure is not limited to the perfect circular shape shown in FIG. 10 (a). It can also have a shape with multiple offset arcs, such as two arcs AR, three arcs AR, or four arcs AR, as shown in FIGS. 10 (b), 10 (c), and 10 (d) in order. Adopting a bearing surface with multiple offset arcs reduces the destabilizing force compared to a perfect circular bearing surface, thereby improving vibration stability. For example, vibration analysis has shown that adopting a bearing surface with two offset arcs improves vibration stability by approximately 25% compared to a perfect circular shape. Note that the offset amount is exaggerated in FIGS. 10 (b), 10 (c), and 10 (d) to clearly illustrate the offset.

[0058] 1, 1A, 1B, 1C, 1D, 1E, 1F Gas bearing 2A, 2B, 2C, 2D Gas bearing 3A, 3B Gas bearing 4A, 4B, 4C Gas bearing 11 Sleeve 11O Outer surface 12 Bearing surface 15 Support structure 16 Beam 16A Cantilever 16A1 Fixed end 16A2 Free end 16A3 Contact 16B1, 16B2 Diagonal beam 16D, 16E Support beam at both ends 16F, 16G, 16GI, 16H, 16I Cantilever 16F1 One end 16F2 Other end 16F3 Contact 16H1 Curved surface 16I1 Sliding plate 16I2 Sliding surface 16J1, 16J2, 16J3, 16J4 Diagonal beam 16K1, 16K2 Cantilever beam 16K3 Contact surface 16K5 Tip 17 Housing 17I Inner peripheral surface 18 Damping tube 19 Damping sheet 21, 23 Damping body

Claims

1. A gas bearing comprising: a sleeve having a rigid bearing surface; and a support structure that elastically supports the sleeve from its radial outside, the support structure being provided over the entire circumferential area of ​​the sleeve.

2. The gas bearing according to claim 1, wherein the support structure comprises an assembly of a plurality of beams.

3. The gas bearing according to claim 2, wherein the beam comprises a cantilever beam or a beam supported at both ends.

4. The gas bearing according to claim 1, wherein the support structure comprises a rigid frame structure.

5. A gas bearing as described in claim 3, further comprising a housing surrounding the support structure, the support structure comprising either a first friction damping element formed by a plurality of the cantilever beams slidable against each other, a second friction damping element formed by sliding between the plurality of the cantilever beams and the sleeve, and a third friction damping element formed by sliding between the plurality of the cantilever beams and the housing.

6. The gas bearing according to claim 5, further comprising a housing surrounding the support structure, and a viscoelastic material is interposed between the sleeve and the beam, or between the housing and the beam, or both.

7. The gas bearing of claim 1, further comprising a housing surrounding said support structure, said sleeve, said support structure and said housing being integrally formed.

8. The gas bearing of claim 1, wherein the bearing surface is either a perfect circle or a plurality of offset circular arcs.

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