Gas bearing device

Abstract

This gas bearing device comprises: a top foil; a surrounding member; and a bump foil disposed between the top foil and the surrounding member, in which base parts extending along the circumferential direction and bump parts protruding in the radial direction so as to be separated from the base parts are alternatingly provided in the circumferential direction, said bump foil elastically supporting the top foil by being bent in the radial direction. At least one bump part is configured such that the stiffness ratio RS / CS is such that 0.8≦RS / CS≦3.0, where CS is the circumferential stiffness of the bump part under radial load and RS is the radial stiffness of the bump part when subjected to a radial load.

Description

Gas bearing device

[0001] The present disclosure relates to a gas bearing device.

[0002] It is known that a foil bearing in which a thin plate-shaped top foil and a corrugated bump foil are arranged in an annular gap formed between the outer peripheral surface of a rotating shaft and the inner peripheral surface of a housing is provided in a gas bearing (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2013-053719

[0004] The foil bearing is a bearing for a high-speed rotating body, and it is required to increase the applicable rotational speed. However, the higher the rotational speed, the higher the pressure, and an instability force is also generated depending on the form of the pressure distribution. Vibration is generated by this instability force, but it is desirable to suppress the vibration as much as possible from the viewpoints of noise and strength, and improvement of the damping force of the foil bearing is required. In Patent Document 1, the damping force is improved by reducing the contact angle between the bump foil (back spring) and the housing.

[0005] In view of the above circumstances, an object of at least one embodiment of the present disclosure is to provide a gas bearing device capable of obtaining a high damping effect.

[0006] A gas bearing device according to at least one embodiment of the present disclosure is a gas bearing device configured to rotatably support a rotating shaft with gas as the working fluid, comprising: a top foil surrounding the radially outer side of the rotating shaft; a surrounding member surrounding the radially outer side of the top foil; and a bump foil disposed between the top foil and the surrounding member, having a base portion extending circumferentially and bump portions projecting radially away from the base portion alternately provided in the circumferential direction, and configured to elastically support the top foil by bending radially, Of the plurality of bump portions, at least one bump portion is configured such that, when the circumferential stiffness of the bump portion when it is subjected to a load from the radial direction is defined as CS, and the radial stiffness of the bump portion when it is subjected to a load from the radial direction is defined as RS, the stiffness ratio RS / CS of the radial stiffness RS to the circumferential stiffness CS satisfies the condition 0.8 ≤ RS / CS ≤ 3.0.

[0007] According to at least one embodiment of the present disclosure, a gas bearing device is provided that can achieve a high damping effect.

[0008] This is a schematic cross-sectional view along the axial direction of a turbocharger equipped with a gas bearing device according to one embodiment of the present disclosure. This is a schematic cross-sectional view schematically showing a cross section perpendicular to the axial direction of the gas bearing device according to one embodiment of the present disclosure. This is a schematic cross-sectional view schematically showing a cross section perpendicular to the axial direction of the gas bearing device according to one embodiment of the present disclosure. This is an explanatory diagram for explaining the bump foil in a gas bearing device according to one embodiment of the present disclosure. This is a graph for explaining the relationship between the stiffness and loss coefficient of the gas bearing device according to one embodiment of the present disclosure. This is a graph for explaining the relationship between the stiffness ratio of the bump foil and the loss coefficient of the gas bearing device according to one embodiment of the present disclosure. This is a graph for explaining the relationship between the ratio of the bump height to the bump half width and the stiffness ratio of the bump foil according to one embodiment of the present disclosure. This is an explanatory diagram for explaining the bump foil in a gas bearing device according to one embodiment of the present disclosure. This is an explanatory diagram for explaining the bump foil in a gas bearing device according to one embodiment of the present disclosure. This is an explanatory diagram for explaining the bump foil in a gas bearing device according to one embodiment of the present disclosure. This is a schematic cross-sectional view schematically showing a cross section perpendicular to the axial direction of the This is a schematic cross-sectional view showing a cross-section perpendicular to the axial direction of a modified example of a gas bearing device according to one embodiment of this disclosure. This is a schematic cross-sectional view showing a cross-section perpendicular to the axial direction of a modified example of a gas bearing device according to one embodiment of this disclosure. This is a schematic cross-sectional view showing a cross-section perpendicular to the axial direction of a modified example of a gas bearing device according to one embodiment of this disclosure. This is a flowchart showing an example of a flow of a design method for the bump foil of a gas bearing device according to one embodiment of this disclosure.

[0009] Hereinafter, several embodiments of this disclosure will be described with reference to the attached drawings. However, the dimensions, materials, shapes, relative arrangements, etc., of the components described or shown in the drawings as embodiments are not intended to limit the scope of this disclosure, but are merely illustrative examples.

[0010] (Turbocharger) Figure 1 is a schematic cross-sectional view along the axial direction of a turbocharger 100 equipped with a gas bearing device 1 according to one embodiment of the present disclosure. Several embodiments of the gas bearing device 1 are mounted on a turbocharger 100, as shown in Figure 1. The gas bearing device 1 according to the present disclosure can be mounted on, for example, a turbocharger (supercharger) 100 for automobiles, marine or industrial use (e.g., for onshore power generation). However, the gas bearing device 1 of the present disclosure is not limited to being mounted on a turbocharger 100. The gas bearing device 1 of the present disclosure can be mounted on a rotating machine that includes a rotating shaft 2 and a housing 6 configured to rotatably house the rotating shaft 2.

[0011] As shown in Figure 1, the turbocharger 100 includes a rotating shaft 2, a gas bearing device 1 configured to rotatably support the rotating shaft 2, a compressor impeller 101 connected to one side of the rotating shaft 2, and a turbine wheel 102 connected to the other side of the rotating shaft 2.

[0012] The turbine wheel 102 is configured to rotate using exhaust gas discharged from an engine (internal combustion engine) or the like (not shown). The compressor impeller 101 is connected coaxially to the turbine wheel 102 via a rotating shaft 2, and therefore rotates together with the rotating shaft 2 in conjunction with the rotation of the turbine wheel 102. As the compressor impeller 101 rotates, the gas (for example, air) introduced into the compressor impeller 101 is compressed.

[0013] Hereinafter, the direction in which the central axis CA of the rotating shaft 2 extends will be defined as the axial direction of the rotating shaft 2 (gas bearing device 1), the direction perpendicular to the central axis CA of the rotating shaft 2 will be defined as the radial direction of the rotating shaft 2 (gas bearing device 1), and the circumferential direction around the central axis CA of the rotating shaft 2 will be defined as the circumferential direction of the rotating shaft 2 (gas bearing device 1).

[0014] (Gas Bearing Device) Figures 2 and 3 are schematic cross-sectional views showing a cross-section perpendicular to the axial direction of a gas bearing device 1 according to one embodiment of the present disclosure. In some embodiments, the gas bearing device 1 is configured to rotatably support a rotating shaft 2 using gas (for example, air) as the working fluid. The gas bearing device 1 comprises at least a top foil 3, a bump foil 4, and a surrounding member 5, as shown in Figures 2 and 3.

[0015] (Top Foil) The top foil 3 is a thin metal plate formed in an arc shape (illustrated example) or annular shape, extending along the circumferential direction of the rotating shaft 2, as shown in Figures 2 and 3. The top foil 3 surrounds the outer side of the rotating shaft 2 in the radial direction. The top foil 3 has an inner circumferential surface 31 and an outer circumferential surface 32 that face the outer circumferential surface 21 of the rotating shaft 2 with a radial gap in between.

[0016] (Bump Foil) The bump foil 4 is positioned between the top foil 3 and the surrounding member 5, as shown in Figures 2 and 3. Specifically, the bump foil 4 is positioned radially outward from the top foil 3 and radially inward from the surrounding member 5. The bump foil 4 is a thin metal plate, with bump portions 41 and base portions 42 alternating and continuous in the circumferential direction of the rotating shaft 2.

[0017] The bump foil 4 is flexible and can elastically deform when the top foil 3 is subjected to a load. The bump foil 4 is designed to contract along the radial direction of the rotating shaft 2 and expand along the circumferential direction of the rotating shaft 2 in response to the load transmitted from the top foil 3. The bump foil 4 is configured to elastically support the top foil 3 by bending radially along the rotating shaft 2 in response to the load transmitted from the top foil 3.

[0018] Each of the multiple base portions 42 extends in the circumferential direction of the rotating shaft 2 and connects the hems 412 and 413 of two adjacent bump portions 41 in the circumferential direction of the rotating shaft 2. In the embodiments shown in Figures 2 and 3, each of the multiple base portions 42 is formed in a flat plate shape that extends along the circumferential direction of the rotating shaft 2 when viewed from one side in the axial direction of the rotating shaft 2. Each of the multiple bump portions 41 protrudes radially so as to be separated from the base portions 42.

[0019] In the embodiments shown in Figures 2 and 3, each of the multiple bump portions 41 is formed in a convex arc shape that is convex toward the inside in the radial direction of the rotating shaft 2 when viewed from one side in the axial direction of the rotating shaft 2. At the apex 411 of each of the multiple bump portions 41, the radial distance from the central axis CA of the rotating shaft 2 is minimized, and the radial distance from the central axis CA of the rotating shaft 2 increases as it moves from the apex 411 toward the base 42 and the tail 412, 413 connected thereto.

[0020] In the embodiments shown in Figures 2 and 3, each of the multiple bump portions 41 is configured such that when the top foil 3 is subjected to a load, or from its initial state when the top foil 3 is not subjected to a load, a portion of its inner circumferential surface (outer surface of the bump portion 41) 414 contacts the outer circumferential surface 32 of the top foil 3. Each of the multiple base portions 42 is configured such that when the top foil 3 is subjected to a load, or from its initial state when the top foil 3 is not subjected to a load, a portion of its outer circumferential surface 421 contacts the inner circumferential surface 51 of the surrounding member 5 in a slidable manner along the circumferential direction of the rotating shaft 2.

[0021] (Enclosing Member) The enclosing member 5 is configured to surround the radially outer side of the bump foil 4. When no other member is placed between the bump foil 4 and the housing 6 (see Figure 2), the enclosing member 5 is the housing 6, and when another member (a plate-shaped member 7 in the illustrated example) is placed between the bump foil 4 and the housing 6 (see Figure 3), the enclosing member 5 is that other member.

[0022] In the embodiment shown in Figure 2, the surrounding member 5 is a housing 6 configured to rotatably house the rotating shaft 2. The inner circumferential surface 51 mentioned above is the inner circumferential surface 61 of the housing 6. The top foil 3 and bump foil 4 are arranged in the annular space formed between the inner circumferential surface 61 of the housing 6 and the outer circumferential surface 21 of the rotating shaft 2.

[0023] In the embodiment shown in Figure 3, the gas bearing device 1 includes a housing 6 having an inner circumferential surface 61. The surrounding member 5 is a plate-shaped member 7 separate from the housing 6 and housed within the housing 6. In the illustrated example, the surrounding member 5 (plate-shaped member 7) is curved along the circumferential direction of the rotating shaft 2 so as to surround the radially outer side of the bump foil 4. The plate-shaped member 7 may be a thin metal plate formed in an arc shape (illustrated example) or an annular shape extending along the circumferential direction of the rotating shaft 2. The inner circumferential surface 51 mentioned above is the inner circumferential surface 71 of the plate-shaped member 7. The top foil 3, bump foil 4, and plate-shaped member 7 are arranged in the annular space formed between the inner circumferential surface 61 of the housing 6 and the outer circumferential surface 21 of the rotating shaft 2. The outer circumferential surface 72 of the plate-shaped member 7 faces the inner circumferential surface 61 of the housing 6. The outer circumferential surface 72 of the plate-shaped member 7 is in non-slidable contact with the inner circumferential surface 61 of the housing 6. The plate-shaped member 7 is supported by the housing 6.

[0024] In some embodiments, as shown in Figures 2 and 3, the housing 6 described above has a groove 62 into which a portion of the bump foil 4 in the circumferential direction is inserted, thereby restricting the circumferential movement of the bump foil 4. In the embodiments shown in Figures 2 and 3, one circumferential end 33 of the top foil 3 and one circumferential end 43 of the bump foil 4 are bent radially outward and inserted into the groove 62. In this case, when the top foil 3 or bump foil 4 is subjected to a load (load) directed radially outward, the bump foil 4 is more likely to stretch from the circumferential end 43 to the other end 44.

[0025] (Stiffness Ratio) Figure 4 is an explanatory diagram illustrating the bump foil 4 in a gas bearing device 1 according to one embodiment of the present disclosure. The upper part of Figure 4 shows the initial state in which the top foil 3 and bump foil 4 are not subjected to any load. The lower part of Figure 4 shows the state in which the top foil 3 and bump foil 4 are subjected to a load L, and the bump foil 4 is stretched in the circumferential direction.

[0026] As shown in Figure 4, the circumferential length of the bump portion 41 of the bump foil 4 from one end (hem 412) to the other end (hem 413) in the circumferential direction (maximum circumferential length of the bump portion 41) is defined as the bump width W, and half the length of this bump width W is defined as the bump half width LW. In addition, the radial height at the apex 411 of the bump portion 41 (maximum radial height of the bump portion 41) is defined as the bump height H. In the illustrated example, the radial height means the radial distance between the inner circumferential surface 414 at the circumferential position where the apex 411 of the bump portion 41 is formed and either the hem 412, 413, or the outer circumferential surface 421 of the base portion 42 of the bump portion 41.

[0027] The circumferential stiffness of the bump portion 41 of the bump foil 4 when it receives a load L from the radial direction is defined as CS, and the radial stiffness of the bump portion 41 when it receives a load L from the radial direction is defined as RS. The stiffness ratio of the radial stiffness RS of the bump portion 41 to the circumferential stiffness CS is defined as RS / CS. The circumferential stiffness CS of the bump portion 41 is a parameter that can quantitatively evaluate the degree of deformation of the bump width W (increase in bump width W according to load L) when the bump portion 41 receives a load L from the radial direction, as shown in Figure 4. The radial stiffness RS of the bump portion 41 is a parameter that can quantitatively evaluate the degree of deformation of the bump height H (decrease in bump height H according to load L) when the bump portion 41 receives a load L from the radial direction, as shown in Figure 4.

[0028] Figure 5 is a graph illustrating the relationship between the stiffness and loss coefficient of a gas bearing device 1 according to one embodiment of the present disclosure. In Figure 5, the stiffness of the gas bearing device 1 is shown on the horizontal axis and the loss coefficient of the gas bearing device 1 is shown on the vertical axis. Figure 6 is a graph illustrating the relationship between the stiffness ratio RS / CS of a bump foil 4 according to one embodiment of the present disclosure and the loss coefficient of the gas bearing device 1. In Figure 6, the stiffness ratio RS / CS of the bump foil 4 is shown on the horizontal axis and the loss coefficient of the gas bearing device 1 is shown on the vertical axis. Figure 7 is a graph illustrating the relationship between the ratio H / LW of the bump height H to the bump half width LW of a bump foil 4 according to one embodiment of the present disclosure and the stiffness ratio RS / CS. In Figure 7, the ratio H / LW of the bump foil 4 is shown on the horizontal axis and the stiffness ratio RS / CS is shown on the vertical axis.

[0029] The graphs in Figures 5 to 7 plot the initial design value DV at which the desired rigidity is obtained in the gas bearing device 1, and the optimization calculation results (solution S) for each design parameter related to the shape of the bump foil 4. The design parameters of the bump foil 4 include the bump height H, bump half width LW, plate thickness of the bump section 41, and pitch between the bump sections 41. The above optimization calculation was performed with the aim of making the rigidity value of the gas bearing device 1 as close as possible to the initial design value DV and maximizing the damping effect of the gas bearing device 1 with respect to the design parameters of the bump foil 4. Here, the initial design value DV is a design value based on the shape of a conventional bump foil 4.

[0030] In some embodiments of the gas bearing device 1, at least one (preferably all) of the above-described bump portions 41 is configured such that the stiffness ratio RS / CS satisfies the condition 0.8 ≤ RS / CS ≤ 3.0.

[0031] As shown in Figure 6, the smaller the stiffness ratio RS / CS of the gas bearing device 1, the less the circumferentially adjacent bump portions 41 hinder each other's sliding in the circumferential direction, resulting in a higher loss coefficient and a better damping effect. However, if the stiffness ratio RS / CS is excessively low (less than 0.8), it is highly likely that the dimensions will not be within a realistic range for a real machine. A gas bearing device 1 that satisfies the condition that the stiffness ratio RS / CS of radial stiffness RS to circumferential stiffness CS is 0.8 ≤ RS / CS ≤ 3.0 can obtain a high damping effect within a realistic dimensional range for a real machine.

[0032] The inventors have found that among the design parameters of the bump foil 4, the bump height H, the bump half width LW, and the plate thickness of the bump portion 41 are highly sensitive to the rigidity of the gas bearing device 1, and that changing these design parameters significantly changes the rigidity of the gas bearing device 1. Furthermore, the inventors have also found that among the design parameters of the bump foil 4, the bump height H and the bump half width LW are highly sensitive to the loss coefficient of the gas bearing device 1, and that changing these design parameters significantly changes the loss coefficient of the gas bearing device 1.

[0033] In some embodiments of the gas bearing device 1, at least one (preferably all) of the above-described plurality of bump portions 41 is configured such that the ratio H / LW of the bump height H to the bump half width LW satisfies the condition 0.4 ≤ H / LW ≤ 1.0.

[0034] The bump height H and bump half-width LW are parameters that have a significant impact on the loss coefficient of the gas bearing device 1. The higher the bump height H and the narrower the bump half-width LW, the higher the loss coefficient of the gas bearing device 1. Therefore, the larger the ratio H / LW, the higher the loss coefficient of the gas bearing device 1. However, if the ratio H / LW is excessively high (greater than 1.0), it is highly likely that the dimensions will not be within a realistic range for actual equipment. A gas bearing device 1 that satisfies the condition that the ratio H / LW of bump height H to bump half-width LW is 0.4 ≤ H / LW ≤ 1.0 can obtain a high damping effect within a realistic dimensional range for actual equipment.

[0035] The plate thickness of the bump portion 41 has relatively little sensitivity to the loss coefficient of the gas bearing device 1. Therefore, in order to improve the damping performance of the gas bearing device 1 while keeping the bearing stiffness of the gas bearing device 1 (specifically, the radial stiffness RS) within the design value, it is effective to reduce the plate thickness of the bump portion 41. Furthermore, the radial stiffness RS of each bump portion 41 predominantly affects the bearing stiffness of the gas bearing device 1. To reduce the bearing stiffness of the gas bearing device 1, it is also effective to increase the pitch of the bump portion 41 (the circumferential length of the base portion 42) to reduce the stiffness per unit area.

[0036] (Base plate thickness) Figures 8 to 10 are explanatory diagrams illustrating the bump foil 4 in a gas bearing device 1 according to one embodiment of the present disclosure. In some embodiments of the gas bearing device 1, as shown in Figure 8, the plate thickness T2 of the base 42 is thinner than the plate thickness T1 of the bump portion 41. In the embodiment shown in Figure 8, the plate thickness of the bump portion 41 and the base 42 are constant. If the plate thicknesses of the bump portion 41 and the base 42 are not constant, the minimum values, average values, or intermediate values ​​of their plate thicknesses may be compared.

[0037] By making the plate thickness T2 of the base portion 42 thinner than the plate thickness T1 of the bump portion 41, the base portion 42 becomes more easily deformable. When the base portion 42 is easily deformable, adjacent bump portions 41 in the circumferential direction are less likely to hinder each other's sliding in the circumferential direction, and the hems 412 and 413 of the bump portions 41 become more easily slid in the circumferential direction. As a result, the gas bearing device 1 can increase the amount of sliding of the bump foil 4, and thus obtain a high damping effect.

[0038] (Slits) In some embodiments of the gas bearing device 1, as shown in Figure 9, the base portion 42 has at least one slit 422 extending along the axial direction. In the illustrated embodiment, the base portion 42 has a plurality of slits 422 arranged at intervals in the circumferential direction. In the illustrated embodiment, the plurality of slits 422 have a longitudinal direction along the axial direction and are elongated holes that penetrate the base portion 42. In the embodiment shown in Figure 9, the plurality of slits 422 are formed concentrated in the axial center and circumferential center of the base portion 42.

[0039] By forming the slit 422 in the base portion 42, the base portion 42 becomes more easily deformable. When the base portion 42 is easily deformable, the bump portions 41 adjacent to each other in the circumferential direction are less likely to hinder each other's sliding in the circumferential direction, and the hems 412 and 413 of the bump portions 41 become more easily slid in the circumferential direction. As a result, the gas bearing device 1 can increase the amount of sliding of the bump foil 4, and thus obtain a high damping effect.

[0040] (Bellows structure) In some embodiments of the gas bearing device 1, as shown in Figure 10, at least a portion of the base 42 has a bellows structure 423 that is expandable and contractible in the circumferential direction. In the embodiment shown in Figure 10, the shape of the bellows structure 423 is formed by making the edges of the plate material constituting the base 42 bent radially inward and the edges bent radially outward continuous in the circumferential direction. In the embodiment shown in Figure 10, the bellows structure 423 is formed in the circumferential center of the base 42.

[0041] By making the base portion 42 have a bellows structure 423, the base portion 42 becomes more easily deformable. When the base portion 42 is easily deformable, the bump portions 41 adjacent to each other in the circumferential direction are less likely to hinder each other's sliding in the circumferential direction, and the hems 412 and 413 of the bump portions 41 become more easily circumferentially slidable. As a result, the gas bearing device 1 can increase the amount of sliding of the bump foil 4, and thus obtain a high damping effect.

[0042] Figures 11 and 12 are schematic cross-sectional views showing a cross-section perpendicular to the axial direction of a gas bearing device 1 according to one embodiment of the present disclosure. In some embodiments of the gas bearing device 1, as shown in Figure 11, at least one (or more in the illustrated example) bump portion 41A among the plurality of bump portions 41 described above has a thicker plate than the other bump portions 41B. In the embodiment shown in Figure 11, the bump portion 41A has the same bump height H as the other bump portions 41B.

[0043] In the embodiment shown in FIG. 11, the plurality of bump portions 41 are divided into bump portions 41A belonging to a first group having a predetermined first plate thickness and bump portions 41B belonging to a second group having a predetermined second plate thickness thinner than the first plate thickness. In the gas bearing device 1, the plurality of bump portions 41 are provided such that the first group and the second group are alternately arranged in the circumferential direction. As shown in FIG. 11, in the gas bearing device 1, in the circumferential direction, a plurality of bump portions 41B belonging to the second group may be provided between the bump portions 41A belonging to the first group.

[0044] By adjusting the plate thickness of the plurality of bump portions 41, an arbitrary distribution can be given to the rigidity of the gas bearing device 1. By increasing the bearing rigidity around the bump portions 41 (41A) located in the main load direction, the function as a gas bearing can be exhibited. And by reducing the bearing rigidity around the bump portions 41 (41B) that receive a relatively small load, the sliding amount of the bump foil 4 can be increased.

[0045] [[ID=⑥]]In the gas bearing device 1 according to some embodiments, as shown in FIG. 12, among the plurality of base portions 42 described above, at least one (a plurality in the illustrated example) of the base portions 42A has a longer circumferential length than the other base portions 42B.

[0046] In the embodiment shown in FIG. 12, the plurality of base portions 42 are divided into base portions 42A belonging to a first group having a predetermined first circumferential length P1 and base portions 42B belonging to a second group having a predetermined second circumferential length P2 shorter than the first circumferential length P1. In the gas bearing device 1, the plurality of base portions 42 are provided such that the first group and the second group are alternately arranged in the circumferential direction. As shown in FIG. 12, in the gas bearing device 1, in the circumferential direction, a plurality of base portions 42B belonging to the second group may be provided between the base portions 42A belonging to the first group.

[0047] By adjusting the circumferential lengths of the plurality of base portions 42, an arbitrary distribution can be given to the rigidity of the gas bearing device 1. By making the circumferential length of the base portion 42 (42B) adjacent in the circumferential direction to the bump portion 41 located in the main load direction short, the bearing rigidity around the bump portion 41 can be increased, and the function as a gas bearing can be exhibited. And, by making the circumferential length of the base portion 42 (42A) adjacent in the circumferential direction to the bump portion 41 that receives a relatively small load long, the bearing rigidity around the bump portion 41 can be decreased, and the sliding amount of the bump foil 4 can be obtained.

[0048] Each of FIGS. 13 to 15 is a schematic cross-sectional view schematically showing a cross-section orthogonal to the axial direction of a modified example of the gas bearing device 1 according to an embodiment of the present disclosure. In the embodiment shown in FIG. 13, each of the plurality of bump portions 41 is formed in a convex arc shape that protrudes outward in the radial direction of the rotating shaft 2 when viewed from one side in the axial direction of the rotating shaft 2. In each of the plurality of bump portions 41, the radial distance from the central axis CA of the rotating shaft 2 is maximum at the apex 411, and the radial distance from the central axis CA of the rotating shaft 2 decreases toward the skirts 412 and 413 connected to the base portion 42 from the apex 411.

[0049] In the embodiment shown in FIG. 13, each of the plurality of bump portions 41 is such that, when the top foil 3 receives a load (load), or from the initial state where the top foil 3 is not receiving a load (load), a part of the outer peripheral surface 415 (the outer surface of the bump portion 41) comes into contact with the inner peripheral surface 51 of the surrounding member 5. Each of the plurality of base portions 42 is such that, when the top foil 3 receives a load (load), or from the initial state where the top foil 3 is not receiving a load (load), a part of the inner peripheral surface 424 comes into contact with the outer peripheral surface 32 of the top foil 3 so as to be slidable along the circumferential direction of the rotating shaft 2.

[0050] The gas bearing device 1 according to some of the embodiments described above can achieve a high damping effect whether the bump portion 41 protrudes radially inward and contacts the top foil 3 (see Figure 2) or whether the bump portion 41 protrudes radially outward and contacts the surrounding member 5 (see Figure 13).

[0051] In the gas bearing device 1 according to some embodiments described above, each of the plurality of bump portions 41 described above was formed in an arc shape. However, each of the plurality of bump portions 41 described above may be formed in a triangular shape having two sides 416 and 417, as shown in Figures 14 and 15.

[0052] In the embodiment shown in Figure 14, each of the multiple bump portions 41 described above is connected at the vertex 411 to a first side 416 that slopes to one side in the circumferential direction as it extends radially outward from the vertex 411 of the bump portion 41, and to a second side 417 that slopes to the other side in the circumferential direction as it extends radially outward from the vertex 411 of the bump portion 41.

[0053] In the embodiment shown in Figure 15, each of the multiple bump portions 41 described above is connected at the vertex 411 to a first side 416 that slopes to one side in the circumferential direction as it moves radially inward from the vertex 411 of the bump portion 41, and to a second side 417 that slopes to the other side in the circumferential direction as it moves radially inward from the vertex 411 of the bump portion 41.

[0054] The gas bearing device 1 according to some of the embodiments described above can achieve a high damping effect whether the bump portion 41 is formed in an arc shape or in a triangular shape having two sides 416 and 417.

[0055] Figure 16 is a flowchart showing an example of a design method for a bump foil 4 of a gas bearing device 1 according to one embodiment of the present disclosure. In the design method for the bump foil 4, the design parameters of the bump foil 4 (bump height H, bump half width LW, plate thickness of the bump portion 41, pitch between bump portions 41, etc.) are set (provisional setting) (step S1). In addition, the target characteristics of the gas bearing device 1, specifically the required values ​​for the rigidity of the gas bearing device 1 (e.g., lower threshold) and the required values ​​for the loss coefficient (e.g., lower threshold) are set (step S2).

[0056] In the design method for the bump foil 4, before performing the multi-objective optimization calculation (step S4) described later, an analysis model (association information) for the bump foil 4 is created (step S3). The analysis model (association information) for the bump foil 4 only needs to be an analysis model (association information) that associates the stiffness and loss coefficient of the gas bearing device 1 with the design parameters of the bump foil 4, and it is sufficient that the stiffness and loss coefficient of the gas bearing device 1 can be output as output information by inputting the design parameters of the bump foil 4 as at least part of the input information. The analysis model (association information) for the bump foil 4 may also take the physical properties of the bump foil 4 (e.g., material properties) as input information. The analysis model (association information) for the bump foil 4 may be a finite analysis model, a surrogate model (predictive model) constructed by machine learning, or may employ multiple such models.

[0057] In the bump foil 4 design method, a multi-objective optimization step S4 is performed to simultaneously find a first objective function that takes design parameters related to the shape of the bump foil 4 as input and outputs the stiffness of the gas bearing device 1 as an output variable, and a second objective function that takes design parameters as input and outputs the loss coefficient of the gas bearing device 1 as an output variable, thereby obtaining a Pareto solution that maximizes the loss coefficient of the gas bearing device 1 and minimizes the difference from the target value of the stiffness of the gas bearing device 1. Then, in the bump foil 4 design method, a design parameter determination step S5 is performed to determine the design parameters based on the Pareto solution obtained in the Pareto solution acquisition step S4.

[0058] In the design method for the bump foil 4, the design parameters determined based on the Pareto solution are such that the stiffness of the gas bearing device 1 is close to the target value and the loss coefficient of the gas bearing device 1 is large. Here, a large loss coefficient for the gas bearing device 1 allows for a high damping effect. Therefore, the design method for the bump foil 4 of the gas bearing device 1 allows for obtaining the above design parameters for the gas bearing device 1 that ensure the desired stiffness while also providing a high damping effect.

[0059] In some embodiment of the design method for the bump foil 4, a prototype of the bump foil 4 may be fabricated using the design parameters determined in the design parameter determination step S5. If it is difficult to fabricate a prototype of the bump foil 4 using the design parameters determined in the design parameter determination step S5 (resulting in "No" in step S6), the design parameter determination step S5 is repeated to determine new design parameters.

[0060] In the design method for the bump foil 4 according to several embodiments, the prototype bump foil 4 is mounted on the gas bearing device 1, and the characteristics (rigidity and loss coefficient) of the gas bearing device 1 are obtained by measuring the rigidity and loss coefficient of the gas bearing device 1 (characteristic acquisition step S7). If either the rigidity or loss coefficient of the gas bearing device 1 obtained in characteristic acquisition step S7 does not meet the required value, the design parameter determination step S5 is executed again to determine new design parameters.

[0061] By performing the characteristic acquisition step S7 and the design parameter determination step S5 again, the above design parameters for the gas bearing device 1 that satisfy the required values ​​for stiffness and loss coefficient can be obtained.

[0062] In this specification, expressions describing relative or absolute arrangements such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial" shall not only describe such arrangements strictly, but also describe states of relative displacement with tolerances or angles or distances sufficient to achieve the same function. For example, expressions describing things being in an equal state such as "identical," "equal," and "homogeneous" shall not only describe states of being strictly equal, but also describe states where tolerances or differences exist to the extent that the same function is achieved. Furthermore, in this specification, expressions describing shapes such as quadrilaterals or cylindrical shapes shall not only describe geometrically precise quadrilaterals or cylindrical shapes, but also describe shapes including concave and concave parts, chamfered parts, etc., to the extent that the same effect is achieved. In addition, in this specification, expressions such as "equipment," "includes," or "possesses" a component are not exclusive expressions that exclude the existence of other components.

[0063] This disclosure is not limited to the embodiments described above, but also includes modified forms of the embodiments described above, as well as forms that combine these forms as appropriate.

[0064] The contents described in some of the embodiments above can be understood, for example, as follows:

[0065] 1) A gas bearing device (1) according to at least one embodiment of the present disclosure is a gas bearing device (1) configured to rotatably support a rotating shaft (2) with gas as the working fluid, comprising: a top foil (3) surrounding the radially outer side of the rotating shaft (2); a surrounding member (5) surrounding the radially outer side of the top foil (3); and a bump foil (4) disposed between the top foil (3) and the surrounding member (5), having a base portion (42) extending along the circumferential direction and a bump portion (41) projecting radially away from the base portion (42) alternately provided in the circumferential direction, and configured to elastically support the top foil (3) by bending radially, Of the plurality of bump portions (41), at least one bump portion (41) is configured such that, when the circumferential stiffness of the bump portion (41) when it is subjected to a load from the radial direction is defined as CS, and the radial stiffness of the bump portion (41) when it is subjected to a load from the radial direction is defined as RS, the stiffness ratio RS / CS of the radial stiffness RS to the circumferential stiffness CS satisfies the condition 0.8 ≤ RS / CS ≤ 3.0.

[0066] According to the configuration described in 1) above, the smaller the stiffness ratio RS / CS of the gas bearing device (1), the less the circumferentially adjacent bump portions hinder each other's sliding in the circumferential direction, resulting in a higher loss coefficient and a better damping effect. However, if the stiffness ratio RS / CS is excessively low (less than 0.8), it is highly likely that the dimensions will not be within a realistic range for actual equipment. A gas bearing device (1) that satisfies the condition that the stiffness ratio RS / CS of radial stiffness RS to circumferential stiffness CS is 0.8 ≤ RS / CS ≤ 3.0 can obtain a high damping effect within a realistic dimensional range for actual equipment.

[0067] 2) In some embodiments, the gas bearing device (1) described in 1) above is configured such that, when the length of half of the circumferential length of the bump portion (41) from one end (hem 412) to the other end (hem 413) in the circumferential direction of the bump portion (41) is defined as the bump half width LW, and the radial height at the apex (411) of the bump portion (41) is defined as the bump height H, the ratio of the bump height H to the bump half width LW, H / LW, satisfies the condition 0.4 ≤ H / LW ≤ 1.0.

[0068] According to the configuration described in 2) above, the parameters that have a significant influence on the loss coefficient of the gas bearing device (1) are the bump height H and the bump half width LW. The higher the bump height H and the narrower the bump half width LW, the higher the loss coefficient of the gas bearing device (1). Therefore, the larger the ratio H / LW, the higher the loss coefficient of the gas bearing device (1). However, if the ratio H / LW is excessively high (greater than 1.0), it is highly likely that the dimensions will not be within a realistic range for actual equipment. A gas bearing device (1) that satisfies the condition that the ratio H / LW of the bump height H to the bump half width LW is 0.4 ≤ H / LW ≤ 1.0 can obtain a high damping effect within a realistic dimensional range for actual equipment.

[0069] 3) In some embodiments, the gas bearing device (1) described in 1) or 2) above, wherein the plate thickness of the base portion (42) is thinner than the plate thickness of the bump portion (41).

[0070] According to the configuration described in 3) above, by making the plate thickness of the base portion (42) thinner than the plate thickness of the bump portion (41), the base portion (42) becomes more easily deformable. When the base portion (42) is easily deformable, adjacent bump portions in the circumferential direction are less likely to hinder each other's sliding in the circumferential direction, and the bottom edge of the bump portion (41) becomes more easily circumferentially slidable. As a result, the gas bearing device (1) can increase the amount of sliding of the bump foil (4), and thus obtain a high damping effect.

[0071] 4) In some embodiments, the gas bearing device (1) described in any of 1) to 3) above is provided, wherein the base (42) has at least one slit (422) extending along the axial direction.

[0072] According to the configuration of 4) above, forming the slit (422) in the base (42) makes the base (42) more easily deformable. When the base (42) is easily deformable, adjacent bump portions in the circumferential direction are less likely to hinder each other's sliding in the circumferential direction, and the bottom edge of the bump portion (41) slides more easily in the circumferential direction. As a result, the gas bearing device (1) can increase the amount of sliding of the bump foil (4), and thus obtain a high damping effect.

[0073] 5) In some embodiments, the gas bearing device is as described in any of 1) to 3) above, wherein at least a portion of the base (42) has a bellows structure (423) that is expandable and contractible in the circumferential direction.

[0074] According to the configuration in 5) above, by making the base (42) have a bellows structure (423), the base (42) becomes more easily deformable. When the base (42) is easily deformable, adjacent bump portions in the circumferential direction are less likely to hinder each other's sliding in the circumferential direction, and the bottom edge of the bump portion (41) slides more easily in the circumferential direction. As a result, the gas bearing device (1) can increase the amount of sliding of the bump foil (4), and thus obtain a high damping effect.

[0075] 6) In some embodiments, the gas bearing device (1) described in any of 1) to 5) above, wherein at least one of the plurality of bump portions (41) has a thicker plate thickness than the other bump portions (41).

[0076] According to the configuration described in 6) above, the rigidity of the gas bearing device (1) can be arbitrarily distributed by adjusting the plate thickness of the multiple bump sections (41). By increasing the bearing rigidity around the bump sections (41) located in the main load direction, the gas bearing can perform its function. Conversely, by lowering the bearing rigidity around the bump sections (41) that receive relatively small loads, the amount of sliding of the bump foil (4) can be increased.

[0077] 7) In some embodiments, the gas bearing device (1) described in any of 1) to 6) above, wherein at least one of the plurality of bases (42) has a longer circumferential length than the other bases (42).

[0078] According to the configuration described in 7) above, the rigidity of the gas bearing device (1) can be arbitrarily distributed by adjusting the circumferential lengths of the multiple bases (42). By increasing the bearing rigidity around the bump sections (41) located in the main load direction, the gas bearing can perform its function. Conversely, by lowering the bearing rigidity around the bump sections (41) that receive relatively small loads, the amount of sliding of the bump foil (4) can be increased.

[0079] 8) In some embodiments, the gas bearing device (1) described in any of 1) to 7) above, wherein the bump portion (41) is formed in an arc shape.

[0080] According to the configuration described in 8) above, the gas bearing device (1) can obtain a high damping effect when the bump portion (41) is formed in an arc shape.

[0081] 9) In some embodiments, the gas bearing device (1) described in any of 1) to 7) above, wherein the bump portion (41) is formed in a triangular shape having two sides.

[0082] According to the configuration described in 9) above, the gas bearing device (1) can obtain a high damping effect even when the bump portion (41) is formed in a triangular shape with two sides.

[0083] 10) In some embodiments, the gas bearing device (1) described in any of 1) to 9) above, wherein the bump portion (41) abuts against the top foil (3), and the base portion (42) abuts against the surrounding member (5).

[0084] According to the configuration of 10) above, the gas bearing device (1) can obtain a high damping effect when the bump portion (41) protrudes radially inward and contacts the top foil (3).

[0085] 11) In some embodiments, the gas bearing device (1) described in any of 1) to 9) above, wherein the bump portion (41) abuts against the surrounding member (5), and the base portion (42) abuts against the top foil (3).

[0086] According to the configuration described in 11) above, the gas bearing device (1) can obtain a high damping effect even when the bump portion (41) protrudes radially outward and contacts the surrounding member (5).

[0087] 1 Gas bearing device 2 Rotating shaft 3 Top foil 4 Bump foil 5 Surrounding member 6 Housing 7 Plate-shaped member 31 Inner surface 32 Outer surface 41 Bump section 42 Base 51 Inner surface 411 Apex 412, 413 Skirt 416 First side 417 Second side 422 Slit 423 Bellows structure CA Central axis CS Circumferential stiffness DV Initial design value L Load LW Bump half width RS Radial stiffness S Solution T1, T2 Plate thickness W Bump width

Claims

1. A gas bearing device configured to rotatably support a rotating shaft using gas as the working fluid, comprising: a top foil surrounding the radially outer side of the rotating shaft; a surrounding member surrounding the radially outer side of the top foil; and a bump foil disposed between the top foil and the surrounding member, having a base portion extending circumferentially and bump portions projecting radially away from the base portion alternately provided in the circumferential direction, and configured to elastically support the top foil by bending radially, A gas bearing device in which, of the plurality of bump portions, at least one bump portion is configured such that, when the circumferential stiffness of the bump portion when it is subjected to a load from the radial direction is defined as CS, and the radial stiffness of the bump portion when it is subjected to a load from the radial direction is defined as RS, the stiffness ratio RS / CS of the radial stiffness RS to the circumferential stiffness CS satisfies the condition 0.8 ≤ RS / CS ≤ 3.

0.

2. The gas bearing device according to claim 1, wherein the at least one bump portion is configured such that, when the length of half the circumferential length of the bump portion from one end to the other in the circumferential direction is defined as the bump half width LW, and the radial height at the apex of the bump portion is defined as the bump height H, the ratio of the bump height H to the bump half width LW, H / LW, satisfies the condition 0.4 ≤ H / LW ≤ 1.

0.

3. The gas bearing device according to claim 1 or 2, wherein the plate thickness of the base portion is thinner than the plate thickness of the bump portion.

4. The gas bearing device according to claim 1 or 2, wherein at least one slit extending along the axial direction is formed in the base portion.

5. The gas bearing device according to claim 1 or 2, wherein at least a portion of the base has a bellows structure that is expandable and contractible in the circumferential direction.

6. The gas bearing device according to claim 1 or 2, wherein at least one of the plurality of bump portions has a thicker plate thickness than the other bump portions.

7. The gas bearing device according to claim 1 or 2, wherein at least one of the plurality of bases has a longer circumferential length than the other bases.

8. The gas bearing device according to claim 1 or 2, wherein the bump portion is formed in an arc shape.

9. The gas bearing device according to claim 1 or 2, wherein the bump portion is formed in a triangular shape having two sides.

10. The gas bearing device according to claim 1 or 2, wherein the bump portion abuts against the top foil and the base portion abuts against the surrounding member.

11. The gas bearing device according to claim 1 or 2, wherein the bump portion abuts against the surrounding member, and the base portion abuts against the top foil.

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