Gas bearing device

Abstract

Provided is a gas bearing device that rotatably supports a rotary shaft using gas as a working fluid, the gas bearing device comprising: a top foil that surrounds a radially outer side of the rotary shaft; a surrounding member that surrounds a radially outer side of the top foil; and a bump foil that is disposed between the top foil and the surrounding member and has base portions and radially protruding bump portions alternately provided in the circumferential direction. At least one of the bump portions is formed with at least one notch and is configured such that a top portion with a radial height from the base portion that is equal to or greater than a predetermined height has a greater proportion of the area of the notch in a unit circumferential length than that of a skirt portion with a radial height from the base portion that is less than the predetermined height.

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 used for a gas bearing (see, for example, Patent Document 1).

[0003] Japanese Unexamined Patent Application Publication No. 2024-14299

[0004] In a foil bearing, attenuation is obtained by friction between the foils or between the foil and the housing. In order to obtain attenuation, it is desirable that the bump foil has low rigidity so that sliding due to deformation of the bump foil is likely to occur. However, if the rigidity of the bump foil is too low, there is a risk that a structure such as a rotating shaft or an impeller attached to the rotating shaft may contact the housing when the central axis of the rotating shaft is greatly displaced due to a disturbance. Therefore, a bearing that has low rigidity for relatively small displacements (loads) during normal operation and high rigidity for relatively large displacements (loads) due to disturbances or the like is desired. In addition, a bump foil having a complicated concavo-convex shape like the one described in Patent Document 1 is not preferable because it is difficult to form.

[0005] In view of the above circumstances, at least one embodiment of the present disclosure aims to provide a gas bearing device that suppresses complication of the shape of the bump foil and has higher rigidity at high loads than at low loads.

[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 using gas as a 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 along the circumferential direction 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 spreading in the circumferential direction, wherein at least one of the plurality of bump portions has at least one notch formed therein, and the top portion, whose radial height from the base portion is above a predetermined value, is configured such that the ratio of the area of ​​the notch per unit circumferential length is greater than that of the bottom portion, whose radial height from the base portion is less than a predetermined value.

[0007] According to at least one embodiment of the present disclosure, a gas bearing device is provided that has higher rigidity under high load conditions compared to low load conditions, while suppressing the complexity of the bump foil shape.

[0008] This is a schematic cross-sectional view along the axial direction of an electric compressor 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 illustrating a bump foil in a gas bearing device according to one embodiment of the present disclosure. This is an explanatory diagram for illustrating a bump foil having a plurality of slit holes extending along the circumferential direction in a gas bearing device according to one embodiment of the present disclosure. This is an explanatory diagram for illustrating a bump foil having a plurality of slit holes extending along the circumferential direction in a gas bearing device according to one embodiment of the present disclosure. This is an explanatory diagram for illustrating a bump foil having a plurality of slit holes extending along the axial direction in a gas bearing device according to one embodiment of the present disclosure. This is an explanatory diagram for illustrating a bump foil having a plurality of circular slit holes in a gas bearing device according to one embodiment of the present disclosure. This is an explanatory diagram for illustrating a bump foil having a notch extending along the circumferential direction in a gas bearing device according to one embodiment of the present disclosure. This is an explanatory diagram for illustrating one-sided contact of the rotating shaft with respect to the gas bearing device. This is an explanatory diagram illustrating a bump foil having a plurality of slit holes extending circumferentially in a gas bearing device according to one embodiment of the present disclosure. This is an explanatory diagram illustrating a bump foil having a plurality of slit holes extending circumferentially in a gas bearing device according to one embodiment of the present disclosure. This is an explanatory diagram illustrating a gas film formed between a rotating shaft and a gas bearing device in a gas bearing device according to one embodiment of the present disclosure. This is a schematic perspective view of the bump portion and the base portion adjacent to the bump portion of a bump foil in one embodiment of the present disclosure. This is an explanatory diagram illustrating a bump foil in a gas bearing device according to one embodiment of the present disclosure. This is an explanatory diagram illustrating a bump foil in a gas bearing device according to one embodiment of the present 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 the present 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] (Electric Compressor) Figure 1 is a schematic cross-sectional view along the axial direction of an electric compressor 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 an electric compressor 100, as shown in Figure 1. The gas bearing device 1 according to the present disclosure can be mounted on, for example, an electric compressor 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 an electric compressor 100. The gas bearing device 1 of the present disclosure can be mounted on a rotating machine (e.g., a supercharger) 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 electric compressor 100 comprises a rotating shaft 2, a gas bearing device 1 configured to rotatably support the rotating shaft 2, and compressor impellers 101 and 102 connected to both sides of the rotating shaft 2, respectively.

[0012] The rotating shaft 2 is configured to rotate by a motor mounted on its outer circumference. Each of the compressor impellers 101 and 102 is connected to the rotating shaft 2 and therefore rotates together with the rotating shaft 2. As the compressor impellers 101 and 102 rotate, the gas (for example, air) introduced into the compressor impellers 101 and 102 is compressed. The electric compressor 100 shown in Figure 1 is a two-stage compression type electric compressor, in which the gas compressed by one of the compressor impellers 101 and 102 is guided to the other compressor impeller 101 and 102 and compressed by the other compressor impeller 101 and 102.

[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 expanding along the circumferential direction of 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 circumferential ends 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 portion 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 circumferential ends 412 and 413 connected to the base 42.

[0020] In the embodiments shown in Figures 2 and 3, the bump portion 41 is provided radially inward from the base portion 42. 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 the outer surface 414 of the bump portion 41 contacts the outer peripheral 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 the outer peripheral surface 421 contacts the inner peripheral 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] (Top and bottom portions) Figure 4 is an explanatory diagram for illustrating a 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 a 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 extended in the circumferential direction. As shown in the upper part of Figure 4, the portion of the bump portion 41 in the initial state in which the radial height from the base 42 of the bump portion 41 is greater than or equal to a predetermined (reference height) is defined as the top portion 45, and the portion of the bump portion 41 in the initial state in which the radial height from the base 42 of the bump portion 41 is less than a predetermined (reference height) is defined as the bottom portion 46. The boundary between the top portion 45 and the bottom portion 46 of the bump portion 41 is denoted as B. In one embodiment, when the radial height positions of the circumferential ends 412 and 413, which are the connection points between the bump portion 41 and the base portion 42, are defined as 0%, and the radial height position of the apex 411 of the bump portion 41 is defined as 100%, the reference height is the 50% radial height position.

[0026] When the load L (load) on the top foil 3 is small, the amount of radial contraction of the bump foil 4 is relatively small, and the top 45 of the bump section 41 deforms. In contrast, when the load L (load) on the top foil 3 is large, the amount of radial contraction of the bump foil 4 is relatively large, and not only the top 45 of the bump section 41 but also the bottom 46 deforms.

[0027] Figures 5 to 10 are explanatory diagrams illustrating a 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, at least one of the plurality of bump portions 41 described above has at least one notch 8 formed therein, and the top portion 45 is configured such that the ratio of the area of ​​the notch 8 to the unit circumferential length is larger than that of the bottom portion 46.

[0028] The notch 8 may be at least one (multiple in the illustrated example) slit hole 81 penetrating the bump portion 41 as shown in Figures 5 to 9, or it may be a notch 82 formed at the axial end of the bump portion 41 as shown in Figure 10. The notch 8 may be formed only on the top portion 45 and not on the bottom portion 46, as shown in Figures 5 to 9. Alternatively, the notch 8 may be formed on both the top portion 45 and the bottom portion 46, as shown in Figure 10. As shown in Figure 10, the notch 8 may be formed to straddle the boundary B.

[0029] When a notch 8 is formed in the bump portion 41, the axial length of the bump portion 41 is substantially shortened in the circumferential range where the notch 8 is formed, and the area of ​​the bump portion 41 per unit circumferential length (excluding the notch 8) becomes smaller. The portion of the bump portion 41 where the area of ​​the notch 8 per unit circumferential length is large receives the radial load L over a relatively smaller area compared to the portion where the ratio is small, and is therefore more prone to deformation.

[0030] In the gas bearing device 1, the top portion 45 of the bump portion 41 has a larger proportion of the notch 8 than the bottom portion 46, so the top portion 45 is more easily deformed in response to radial loads than the bottom portion 46. When the load on the top foil 3 is small, the top portion 45 deforms in response to the load, so the bump foil 4 has low rigidity with respect to the load on the top foil 3. When the load on the top foil 3 is large, not only the top portion 45 but also the bottom portion 46 deforms, but the bottom portion 46 is less easily deformed in response to the load. For this reason, when the load on the top foil 3 is large, the bump foil 4 has high rigidity with respect to the load on the top foil 3. With such a gas bearing device 1, the complexity of the shape of the bump foil 4 is suppressed, while the rigidity is higher at high loads compared to low loads.

[0031] As shown in Figures 5 to 10, it is preferable that in each of two or more bump portions 41 spaced apart in the circumferential direction, the top portion 45 of the bump portion 41 is configured such that the ratio of its area to that of the notch 8 per unit circumferential length is larger than that of the bottom portion 46 of the bump portion 41. It is also possible that in all of the bump portions 41 of the bump foil 4, the top portion 45 is configured such that the ratio of its area to that of the notch 8 per unit circumferential length is larger than that of the bottom portion 46.

[0032] In some embodiments of the gas bearing device 1, as shown in Figures 5 to 9, the above-mentioned at least one notch 8 includes a plurality of slit holes 81 (81A to 81E) that penetrate the bump portion 41. By providing a plurality of slit holes 81 in the bump portion 41, it is possible to easily change the above-mentioned ratio of the notch 8 between the top portion 45 and the bottom portion 46 of the bump portion 41. When the notch 8 is a plurality of slit holes 81 (81A to 81E), the molding of the bump foil 4 is easy, and the complexity of the shape of the bump foil 4 can be suppressed.

[0033] In the embodiments shown in Figures 5 and 6, the multiple slit holes 81 (81A, 81B) of the bump foil 4 have a longitudinal direction along the circumferential direction of the bump foil 4 and are formed at intervals in the axial direction of the bump foil 4. In the embodiment shown in Figure 5, the multiple slit holes 81A are formed in a line in the axial direction. In the embodiment shown in Figure 6, the multiple slit holes 81B are arranged in a staggered pattern. Specifically, the multiple slit holes 81B are formed at positions offset in the circumferential direction from other slit holes 81B adjacent in the axial direction, and a portion of them overlaps in the circumferential direction with respect to these other slit holes 81B. Here, overlapping in the circumferential direction means that a portion of the slit hole 81B is formed in the circumferential range where other slit holes 81B are formed.

[0034] Figure 11 is an explanatory diagram illustrating the uneven contact of the rotating shaft 2 with respect to the gas bearing device 1. As shown in Figure 11, during rotation of the rotating shaft 2, the central axis CA of the rotating shaft 2 may be inclined with respect to the central axis CA2 of the gas bearing device 1, causing the rotating shaft 2 to make uneven contact with one end of the top foil 3 in the axial direction. When the multiple slit holes 81 (81A, 81B) of the bump portion 41 have a longitudinal direction along the circumferential direction, the axial end of the bump portion 41 is easily deformed in response to radial load. For this reason, a gas bearing device 1 equipped with a bump foil 4 having multiple slit holes 81 (81A, 81B) formed in the bump portion 41 can easily deform the axial end of the bump portion 41 when the rotating shaft 2 makes uneven contact with the top foil 3, thereby suppressing wear of the gas bearing device 1 due to uneven contact.

[0035] In the embodiments shown in Figures 7 and 8, the multiple slit holes 81 (81C, 81D) of the bump foil 4 have a longitudinal direction along the axial direction of the bump foil 4 and are formed at intervals in the circumferential direction of the bump foil 4. In the embodiment shown in Figure 7, the multiple slit holes 81C are formed in a line in the circumferential direction. In the embodiment shown in Figure 8, the multiple slit holes 81D are arranged in a staggered pattern. Specifically, the multiple slit holes 81D are formed at positions offset in the axial direction from other slit holes 81D adjacent to them in the circumferential direction, and a portion of their axial direction overlaps with that of the other slit holes 81D. Here, overlapping in the axial direction means that a portion of the slit hole 81D is formed in the axial range where the other slit holes 81D are formed.

[0036] In the embodiment shown in Figure 9, the multiple slit holes 81 (81E) of the bump foil 4 are formed in a circular shape. The multiple slit holes 81 (81E) of the bump foil 4 may also be formed in an elliptical shape.

[0037] In some of the embodiments described above, the rigidity (resistance to deformation) against radial loads between the top 45 and bottom 46 of the bump portion 41 is changed by changing the distribution of the notches 8 in the circumferential direction. Alternatively, the rigidity (resistance to deformation) against radial loads between the axial ends 47, 48 and the central portion 49 of the bump portion 41 may be changed by changing the distribution of the notches 8 in the axial direction.

[0038] Figures 12 and 13 are explanatory diagrams illustrating a bump foil 4 having a plurality of circumferentially extending slit holes 81 in a gas bearing device 1 according to one embodiment of the present disclosure. Figure 14 is an explanatory diagram illustrating a gas film AM formed between a rotating shaft 2 and a gas bearing device 1 in a gas bearing device 1 according to one embodiment of the present disclosure.

[0039] As shown in Figures 12 and 13, the bump portion 41 includes an axial end 47 containing side 471, an axial end 48 containing side 481, and a central portion 49 provided between these ends 47 and 48. The central portion 49 includes the axial center position CP (50% axial position) of the bump portion 41. In one embodiment, when the axial position of one side 471 of the bump portion 41 is defined as 0% and the axial position of the other side 481 of the bump portion 41 is defined as 100%, the end 47 has an axial position in the range of 0% to 30%, the end 48 has an axial position in the range of 70% to 100%, and the central portion 49 has an axial position in the range of more than 30% and less than 70%.

[0040] In some embodiments of the gas bearing device 1, as shown in Figures 12 and 13, the axial ends 47 and 48 of the bump portion 41 have a larger proportion occupied by the notches 8 (multiple slit holes 81 in the illustrated example) compared to the axial central portion 49 of the bump portion 41. In such a gas bearing device 1, because the axial ends 47 and 48 of the bump portion 41 have a relatively large proportion occupied by the notches 8, they are more susceptible to deformation in response to radial loads than the axial central portion 49 of the bump portion 41, and have lower rigidity against radial loads. As shown in Figure 14, during the rotation of the rotating shaft 2, the gas film AM formed between the rotating shaft 2 and the gas bearing device 1 creates a pressure distribution in which the pressure is high in the axial central portion 49 of the gas bearing device 1 and low in the axial ends 47 and 48. The left side of Figure 14 shows the case where the axial ends 47 and 48 of the bump portion 41 and the central portion 49 have the same rigidity (resistance to deformation) against radial load, while the right side of Figure 14 shows the case where the axial ends 47 and 48 of the bump portion 41 have lower rigidity (resistance to deformation) against radial load compared to the central portion 49. By making the axial ends 47 and 48 of the bump portion 41 more easily deformable in response to radial load, the radial distance between the axial ends of the gas bearing device 1 and the rotating shaft 2 can be made relatively large, as shown in Figure 14. This allows for a relatively large gas film AM to be secured between the gas bearing device 1 and the rotating shaft 2, thereby improving the load capacity of the gas bearing device 1.

[0041] In some embodiments of the gas bearing device 1, as shown in Figures 12 and 13, the multiple slit holes 81 (81A) of the bump foil 4 have a longitudinal direction along the circumferential direction of the bump foil 4 and are formed at intervals in the axial direction of the bump foil 4. Multiple slit holes 81 (81A) are formed at one end 47, the other end 48, and the central part 49 in the axial direction of the bump portion 41.

[0042] As shown in Figure 12, the above-mentioned multiple slit holes 81 (81A) have a distance S1 between two axially adjacent slit holes 81 in the central part 49 of the bump portion 41 that is greater than the distance S2 between two axially adjacent slit holes 81 in the axial ends 47 and 48 of the bump portion 41. When the distance between two axially adjacent slit holes 81 is short, the material is more easily deformed by a radial load L compared to when the distance between two axially adjacent slit holes 81 is long. In the embodiment shown in Figure 12, the hole width (axial length) W1 of the multiple slit holes 81 formed in the central part 49 of the bump portion 41 is the same as the hole width (axial length) W2 of the multiple slit holes 81 formed in the axial ends 47 and 48 of the bump portion 41. In some other embodiments, the width of the multiple slit holes 81 formed in the central portion 49 of the bump portion 41 (axial length of the bump portion 41) W1 may be made larger or smaller than the width of the multiple slit holes 81 formed in the axial ends 47 and 48 of the bump portion 41 (axial length of the bump portion 41) W2.

[0043] The axial ends 47 and 48 of the bump portion 41 have a relatively small distance S2 between two adjacent slit holes 81 in the axial direction, making them more susceptible to deformation in response to radial loads than the axial central portion 49 of the bump portion 41, and thus exhibiting lower rigidity against radial loads. By making the axial ends 47 and 48 of the bump portion 41 more susceptible to deformation in response to radial loads, the radial distance between the axial ends of the gas bearing device 1 and the rotating shaft 2 can be made relatively large, as shown in Figure 14. This allows for the securing of a relatively large gas film AM between the gas bearing device 1 and the rotating shaft 2, thereby improving the load capacity of the gas bearing device 1.

[0044] As shown in FIG. 13, the plurality of slit holes 81 described above include at least one (a plurality in the illustrated example) of slit holes 81 formed in the central portion 49 in the axial direction of the bump portion 41 and at least one (a plurality in the illustrated example) of slit holes 81 formed in the end portions 47 and 48 in the axial direction of the bump portion 41. The hole width (the length in the axial direction of the bump portion 41) W1 of each of the plurality of slit holes 81 formed in the central portion 49 in the axial direction of the bump portion 41 is smaller than the hole width (the length in the axial direction of the bump portion 41) W2 of each of the plurality of slit holes 81 formed in the end portions 47 and 48 in the axial direction of the bump portion 41.

[0045] Since the hole width W2 of the slit holes 81 in the end portions 47 and 48 in the axial direction of the bump portion 41 is relatively large, the end portions 47 and 48 in the axial direction of the bump portion 41 are more likely to deform in response to a radial load than the central portion 49 in the axial direction of the bump portion 41, and have low rigidity with respect to the radial load. By making the end portions 47 and 48 in the axial direction of the bump portion 41 more likely to deform in response to a radial load, as shown in FIG. 14, the radial distance between the end portion in the axial direction of the gas bearing device 1 and the rotating shaft 2 can be made relatively large. As a result, a relatively large gas film AM can be ensured between the gas bearing device 1 and the rotating shaft 2, so that the load capacity of the gas bearing device 1 can be improved.

[0046] In the embodiment shown in FIG. 13, the interval S1 between two axially adjacent slit holes 81 in the central portion 49 of the bump portion 41 is the same as the interval S2 between two axially adjacent slit holes 81 in the end portions 47 and 48 in the axial direction of the bump portion 41. In some other embodiments, the above-described interval S1 may be made larger or smaller than the above-described interval S2. In the gas bearing device 1 according to some embodiments, the interval S1 between two axially adjacent slit holes 81 in the central portion 49 of the bump portion 41 may be larger than the interval S2 between two axially adjacent slit holes 81 in the end portions 47 and 48 in the axial direction of the bump portion 41 (see FIG. 12), and the hole width W1 of each of the plurality of slit holes 81 formed in the central portion 49 of the bump portion 41 may be smaller than the hole width W2 of each of the plurality of slit holes 81 formed in the end portions 47 and 48 in the axial direction of the bump portion 41 (see FIG. 13).

[0047] (Notch) In the gas bearing device 1 according to some embodiments, as shown in FIG. 10, at least one of the above-described notches 8 is formed on one side 471 in the axial direction of the bump portion 41 and includes a one-sided notch portion 82A that is notched toward the other side in the axial direction. The one-sided notch portion 82A has a notch width larger than the notch depth.

[0048] By providing the one-sided notch portion 82A in the bump portion 41, it is possible to easily change the above ratio of the notch 8 between the top portion 45 and the bottom portion 46 of the bump portion 41. When the notch 8 includes the one-sided notch portion 82A, the forming of the bump foil 4 is easy, and the complication of the shape of the bump foil 4 can be suppressed. Further, by providing the one-sided notch portion 82A in the bump portion 41, one end portion 47 on one side in the axial direction of the bump portion 41 is likely to deform according to the load. Since the gas bearing device 1 can deform one end portion 47 on one side in the axial direction of the bump portion 41 when the rotating shaft 2 hits one side in the axial direction of the top foil 3, the wear due to the single contact of the gas bearing device 1 can be suppressed.

[0049] In the gas bearing device 1 according to some embodiments, as shown in FIG. 10, the above-described one-sided notch portion 82A is configured such that the notch depth increases as it goes toward the apex 411 in the circumferential direction of the bump portion 41. In the embodiment shown in FIG. 10, the one-sided notch portion 82A is formed in a concave arc shape that is concave toward the other side in the axial direction on one side 471 when viewed from one side in the radial direction of the rotating shaft 2.

[0050] By configuring the one-sided notch portion 82A such that the notch depth increases as it goes toward the apex 411 in the circumferential direction of the bump portion 41, the change in the above ratio of the notch 8 in the circumferential direction can be moderated, and the occurrence of a local stress concentration portion due to the one-sided notch portion 82A in the bump portion 41 can be suppressed.

[0051] Furthermore, by configuring the notch 82A on one side such that the notch depth increases towards the apex 411 in the circumferential direction of the bump portion 41, the axial end 47 of the bump portion 41 is more easily deformed in response to radial loads than the axial central portion 49 of the bump portion 41. As explained using Figure 14 as an example, by making the axial end 47 of the bump portion 41 more easily deformed in response to radial loads, the radial distance between the axial end of the gas bearing device 1 and the rotating shaft 2 can be made relatively large. As a result, a relatively large gas film AM can be secured between the gas bearing device 1 and the rotating shaft 2, thereby improving the load capacity of the gas bearing device 1.

[0052] In some embodiments of the gas bearing device 1, as shown in Figure 10, the at least one notch 8 described above further includes a other-side notch 82B formed on the other axial side 481 of the bump portion 41 and cut toward the one axial side. The other-side notch 82B has a notch width greater than the notch depth.

[0053] By providing the other-side notch 82B in the bump portion 41, it is easy to change the above ratio of the notch 8 between the top portion 45 and the bottom portion 46 of the bump portion 41. When the notch 8 includes the other-side notch 82B, the molding of the bump foil 4 is easy, and complexity of the shape of the bump foil 4 can be suppressed. In addition, by providing the other-side notch 82B in the bump portion 41, the other-side end 48 in the axial direction of the bump portion 41 is easily deformed in response to the load. The gas bearing device 1 can deform the other-side end 48 in the axial direction of the bump portion 41 when the rotating shaft 2 makes uneven contact with the top foil 3, thereby suppressing wear of the gas bearing device 1 due to uneven contact.

[0054] In some embodiments of the gas bearing device 1, as shown in Figure 10, the other-side notch 82B described above is configured such that the notch depth increases as it approaches the apex 411 in the circumferential direction of the bump portion 41. In the embodiment shown in Figure 10, the other-side notch 82B is formed in a concave arc shape that is concave toward one side in the axial direction on the other side 481 when viewed from one side in the radial direction of the rotating shaft 2.

[0055] By configuring the other side notch 82B such that the notch depth increases as it approaches the apex 411 in the circumferential direction of the bump portion 41, the change in the above ratio of notches 8 in the circumferential direction can be made gradual, and the occurrence of localized stress concentration areas in the bump portion 41 due to the other side notch 82B can be suppressed.

[0056] Furthermore, by configuring the other side notch 82B such that the notch depth increases towards the apex 411 in the circumferential direction of the bump portion 41, the other axial end 48 of the bump portion 41 is more easily deformed in response to radial loads than the central part 49 of the bump portion 41 in the axial direction. As explained using Figure 14 as an example, by making the other axial end 48 of the bump portion 41 more easily deformed in response to radial loads, the radial distance between the other axial end of the gas bearing device 1 and the rotating shaft 2 can be made relatively large. As a result, a relatively large gas film AM can be secured between the gas bearing device 1 and the rotating shaft 2, thereby improving the load capacity of the gas bearing device 1.

[0057] (Protrusions) Figures 15 and 16 are schematic perspective views of a bump portion 41 and a base portion 42 adjacent to the bump portion 41 of a bump foil 4 in one embodiment of the present disclosure. Figures 17 and 18 are explanatory diagrams for illustrating a 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 Figures 15 to 17, the bump portion 41 has at least one slit hole 83 having a longitudinal direction along the circumferential direction. In the illustrated embodiment, the at least one slit hole 83 described above includes, as shown in Figure 17, a one-side slit hole 83A formed on one side in the axial direction of the axial center position CP (50% axial position) of the bump portion 41, and a other-side slit hole 83B formed on the other side in the axial direction of the axial center position CP of the bump portion 41. The one-side slit hole 83A and the other-side slit hole 83B are formed in a line in the axial direction.

[0058] The at least one notch 8 described above includes a projection 84 formed by making at least one of the multiple regions divided axially by the at least one slit hole 83 of the bump portion 41 protrude in the opposite direction to the protruding direction of the bump portion 41. The projection 84 is formed in a convex arc shape that is convex in the opposite direction to the protruding direction of the bump portion 41.

[0059] In this embodiment, the gas bearing device 1 can increase or decrease the support points for the bump portion 41 depending on the load the gas bearing device 1 receives. That is, as shown in Figure 18, when the load on the top foil 3 is small, the projection 84 does not contact the surrounding member 5, so the bump portion 41 deforms relatively easily in response to the load, and the bump foil 4 has low rigidity against the load on the top foil 3. On the other hand, when the load on the top foil 3 is large, the projection 84 contacts the surrounding member 5, so the bump portion 41 deforms relatively slowly in response to the load, and the bump foil 4 has high rigidity against the load on the top foil 3. With such a gas bearing device 1, the complexity of the shape of the bump foil 4 is suppressed, while achieving higher rigidity at high loads compared to low loads.

[0060] In the embodiment shown in Figure 15, the projection 84 described above includes a central projection 84C formed between one slit hole 83A and the other slit hole 83B in the axial direction of the bump portion 41. In this case, when the load on the top foil 3 is large, the central projection 84C comes into contact with the surrounding member 5, so that the bump portion 41 is relatively less likely to deform in response to the load, and the bump foil 4 becomes highly rigid against the load on the top foil 3.

[0061] In the embodiment shown in Figure 16, the projection 84 includes a one-sided projection 84A formed on one side in the axial direction of the one-sided slit hole 83A of the bump portion 41, and a other-sided projection 84B formed on the other side in the axial direction of the other-sided slit hole 83B of the bump portion 41. In this case, when the load on the top foil 3 is large, the one-sided projection 84A and the other-sided projection 84B come into contact with the surrounding member 5, so that the bump portion 41 is relatively less likely to deform in response to the load, and the bump foil 4 becomes highly rigid against the load on the top foil 3.

[0062] Figure 19 is a schematic cross-sectional view schematically showing a cross-section perpendicular to the axial direction of a modified example of a gas bearing device 1 according to one embodiment of the present disclosure. In the embodiment shown in Figure 19, each of the plurality of bump portions 41 is formed in a convex arc shape that is convex outward 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 plurality of bump portions 41, the radial distance from the central axis CA of the rotating shaft 2 is maximum, and the radial distance from the central axis CA of the rotating shaft 2 decreases as it moves from the apex 411 toward the circumferential ends 412 and 413 connected to the base 42.

[0063] In the embodiment shown in Figure 19, the bump portion 41 is provided radially outward from the base portion 42. 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 the outer surface 414 of the bump portion 41 contacts the inner circumferential surface 51 of the surrounding member 5. 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 the inner circumferential surface 424 contacts the outer circumferential surface 32 of the top foil 3 in a slidable manner along the circumferential direction of the rotating shaft 2.

[0064] In the gas bearing device 1 according to some embodiments described above, whether the bump portion 41 is provided radially inward from the base portion 42 (see Figures 2 and 3) or radially outward from the base portion 42 (see Figure 19), the device becomes more rigid under high load conditions compared to low load conditions, and a high damping effect can be obtained. Here, when the bump portion 41 is provided radially inward from the base portion 42, the axial ends 47 and 48 of the bump portion 41 are more easily deformed than when the bump portion 41 is provided radially outward from the base portion 42. For this reason, the gas bearing device 1 can suppress wear due to uneven contact and improve the load capacity of the gas bearing device 1.

[0065] 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.

[0066] 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.

[0067] The contents described in some of the embodiments above can be understood, for example, as follows:

[0068] 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 spreading in the circumferential direction, wherein at least one of the plurality of bump portions (41) is At least one notch (8) is formed, and the top portion (45), whose radial height from the base portion (42) is greater than or equal to a predetermined value, is configured such that the ratio of the area of ​​the notch (8) to the unit circumferential length is greater than that of the bottom portion (46), whose radial height from the base portion (42) is less than a predetermined value.

[0069] According to the configuration described in 1) above, the top portion (45) of the bump portion (41) has a larger proportion of the notch (8) than the bottom portion (46), so the top portion (45) is more easily deformed in response to radial loads than the bottom portion (46). When the load on the top foil (3) is small, the top portion (45) deforms in response to the load, resulting in low rigidity of the bump foil (4) with respect to the load on the top foil (3). When the load on the top foil (3) is large, not only the top portion (45) but also the bottom portion (46) deforms, but the bottom portion (46) is less easily deformed in response to the load. For this reason, when the load on the top foil (3) is large, the bump foil (4) has high rigidity with respect to the load on the top foil (3). With such a gas bearing device (1), the complexity of the bump foil (4) shape is suppressed, while achieving higher rigidity at high loads compared to low loads.

[0070] 2) In some embodiments, the gas bearing device (1) described in 1) above, wherein the at least one notch (8) includes a plurality of slit holes (81) that penetrate the bump portion (41).

[0071] According to the configuration in 2) above, by providing a plurality of slit holes (81) in the bump portion (41), the above ratio of the notches (8) between the top (45) and bottom (46) of the bump portion (41) can be easily changed. When the notches (8) are a plurality of slit holes, the molding of the bump foil (4) is easy, and the complexity of the shape of the bump foil (4) can be suppressed.

[0072] 3) In some embodiments, the gas bearing device (1) described in 2) above, wherein the plurality of slit holes (81) have a longitudinal direction along the circumferential direction and are formed at intervals in the axial direction.

[0073] According to the configuration described in 3) above, when the multiple slit holes (81) of the bump portion (41) have a longitudinal direction along the circumferential direction, the axial end of the bump portion (41) is easily deformed in response to the load. The gas bearing device (1) can easily deform the axial end of the bump portion (41) when the rotating shaft (2) makes uneven contact with the top foil (3), thereby suppressing wear of the gas bearing device (1) due to uneven contact.

[0074] 4) In some embodiments, the gas bearing device (1) described in 2) above, wherein the plurality of slit holes (81) have a longitudinal direction along the axial direction and are formed with spacing in the circumferential direction.

[0075] According to the configuration in 4) above, by providing the bump portion (41) with a plurality of slit holes having a longitudinal direction along the axial direction, the above ratio of the notches (8) between the top (45) and bottom (46) of the bump portion (41) can be easily changed.

[0076] 5) In some embodiments, the gas bearing device (1) described in 3) above, wherein the plurality of slit holes (81) have a distance (S1) between two adjacent slit holes (81) in the axial direction at the axial central portion (49) that is greater than the distance (S2) between two adjacent slit holes (81) in the axial direction at the axial ends (47, 48).

[0077] According to the configuration in 5) above, the axial ends (47, 48) of the bump portion (41) have a relatively small gap (S2) between two axially adjacent slit holes (81), so they are more easily deformed in response to radial loads than the axial central portion (49) of the bump portion (41), and have lower rigidity against radial loads. During rotation of the rotating shaft (2), the gas film (AM) formed between the rotating shaft (2) and the gas bearing device (1) creates a pressure distribution in which the pressure is high at the axial central portion (49) of the gas bearing device (1) and low at the axial ends (47, 48). By making the axial ends (47, 48) of the bump portion (41) more easily deformed in response to radial loads, the radial distance between the axial ends of the gas bearing device (1) and the rotating shaft (2) can be made relatively large. This allows for the securing of a relatively large gas film (AM) between the gas bearing device (1) and the rotating shaft (2), thereby improving the load capacity of the gas bearing device (1).

[0078] 6) In some embodiments, the gas bearing device (1) described in 3) or 5) above, wherein the plurality of slit holes (81) include at least one slit hole (81) formed in the axial central portion (49) and at least one slit hole (81) formed in the axial end portions (47, 48), wherein the slit hole (81) formed in the axial central portion (49) has a smaller hole width than the slit hole (81) formed in the axial end portions (47, 48).

[0079] According to the configuration in 6) above, the axial ends (47, 48) of the bump portion (41) have relatively large slit holes (81), so they are more easily deformed in response to radial loads than the axial central portion (49) of the bump portion (41), and have lower rigidity against radial loads. During rotation of the rotating shaft (2), the gas film (AM) formed between the rotating shaft (2) and the gas bearing device (1) creates a pressure distribution in which the pressure is high at the axial central portion (49) of the gas bearing device (1) and low at the axial ends (47, 48). By making the axial ends (47, 48) of the bump portion (41) more easily deformed in response to radial loads, the radial distance between the axial ends of the gas bearing device (1) and the rotating shaft (2) can be made relatively large. As a result, a relatively large gas film (AM) can be secured between the gas bearing device (1) and the rotating shaft (2), and the load capacity of the gas bearing device (1) can be improved.

[0080] 7) In some embodiments, the gas bearing device (1) described in 1) above, wherein the at least one notch (8) is a one-sided notch (82A) formed on one axial side (471) of the bump portion (41) and cut toward the other axial side, the one-sided notch (82A) having a notch width greater than the notch depth.

[0081] According to the configuration of 7) above, by providing a one-sided notch (82A) in the bump portion (41), it is possible to easily change the above ratio of the notch (8) between the top (45) and bottom (46) of the bump portion (41). When the notch (8) includes a one-sided notch (82A), the molding of the bump foil (4) is easy, and complexity of the shape of the bump foil (4) can be suppressed. In addition, by providing a one-sided notch (82A) in the bump portion (41), the axial end (47) of the bump portion (41) is easily deformed in response to the load. The gas bearing device (1) can deform the axial end (47) of the bump portion (41) when the rotating shaft (2) makes contact with one side of the top foil (3) in the axial direction, thus suppressing wear of the gas bearing device (1) due to contact with one side.

[0082] 8) In some embodiments, the gas bearing device (1) described in 7) above, wherein the at least one notch (8) further includes a other notch (82B) formed on the other side (481) of the bump portion (41) in the axial direction and cut toward the one side in the axial direction, wherein the width of the other notch (82B) is greater than the depth of the notch.

[0083] According to the configuration of 8) above, by providing a notch (82B) on the other side of the bump portion (41), it is possible to easily change the above ratio of the notch (8) between the top (45) and bottom (46) of the bump portion (41). When the notch (8) includes the notch (82B) on the other side, the molding of the bump foil (4) is easy, and complexity of the shape of the bump foil (4) can be suppressed. In addition, by providing a notch (82B) on the other side of the bump portion (41), the other end (48) on the axial side of the bump portion (41) is easily deformed in response to the load. The gas bearing device (1) can deform the other end (48) on the axial side of the bump portion (41) when the rotating shaft (2) makes uneven contact with the top foil (3), thereby suppressing wear of the gas bearing device (1) due to uneven contact.

[0084] 9) In some embodiments, the gas bearing device (1) described in 7) or 8) above is configured such that the depth of the notch (82A) increases in the circumferential direction of the bump portion (41) toward the apex (411).

[0085] According to the configuration in 9) above, by configuring the one-sided notch (82A) such that the notch depth increases towards the apex (411) in the circumferential direction of the bump portion (41), the change in the above ratio of notches (8) in the circumferential direction can be made gradual, and the occurrence of localized stress concentration areas in the bump portion (41) due to the one-sided notch (82A) can be suppressed.

[0086] 10) In some embodiments, the gas bearing device (1) described in 7) above is configured such that the other side notch (82B) has a notch depth that increases in the circumferential direction of the bump (41) toward the apex (411).

[0087] According to the configuration in 10) above, by configuring the other side notch (82B) such that the notch depth increases as it approaches the apex (411) in the circumferential direction of the bump portion (41), the change in the above ratio of notches (8) in the circumferential direction can be made gradual, and the occurrence of localized stress concentration areas in the bump portion (41) due to the other side notch (82B) can be suppressed.

[0088] 11) In some embodiments, the gas bearing device (1) described in 1) above, wherein the bump portion (41) has at least one slit hole (83) having a longitudinal direction along the circumferential direction, and the at least one notch (8) includes a projection (84) formed by causing at least one region from among a plurality of regions divided axially by the at least one slit hole (83) of the bump portion (41) to protrude in the opposite direction to the protruding direction of the bump portion (41).

[0089] According to the configuration described in 11) above, the support points for the bump portion can be increased or decreased depending on the load on the gas bearing device (1). That is, when the load on the top foil (3) is small, the projection (84) does not come into contact with the surrounding member (5), so the bump portion (41) is relatively easy to deform in response to the load, and the bump foil (4) has low rigidity with respect to the load on the top foil (3). On the other hand, when the load on the top foil (3) is large, the projection (84) comes into contact with the surrounding member (5), so the bump portion (41) is relatively difficult to deform in response to the load, and the bump foil (4) has high rigidity with respect to the load on the top foil (3). With such a gas bearing device (1), the complexity of the shape of the bump foil (4) is suppressed, while the rigidity is higher at high loads compared to low loads.

[0090] 12) In some embodiments, the gas bearing device (1) described in 11) above, wherein the at least one slit hole (83) includes a one-side slit hole (83A) formed on one side in the axial direction from the axial center position and a other-side slit hole (83B) formed on the other side in the axial direction from the axial center position, and the projection (84) includes a central projection (84C) formed between the one-side slit hole (83A) and the other-side slit hole (83B) in the axial direction.

[0091] According to the configuration described in 12) above, when the load on the top foil (3) is large, the central projection (84C) comes into contact with the surrounding member (5), so the bump portion (41) is relatively less likely to deform in response to the load, and the bump foil (4) becomes highly rigid against the load on the top foil (3).

[0092] 13) In some embodiments, the gas bearing device (1) described in 11) above, wherein the at least one slit hole (83) includes a one-side slit hole (83A) formed on one side in the axial direction from the axial center position and a other-side slit hole (83B) formed on the other side in the axial direction from the axial center position, and the projection (84) includes a one-side projection (84A) formed on the one side in the axial direction from the one-side slit hole (83A) and a other-side projection (84B) formed on the other side in the axial direction from the other-side slit hole (83B).

[0093] According to the configuration described in 13) above, when the load on the top foil (3) is large, the projection on one side (84A) and the projection on the other side (84B) come into contact with the surrounding member (5), so that the bump portion (41) is relatively less likely to deform in response to the load, and the bump foil (4) becomes highly rigid against the load on the top foil (3).

[0094] 14) In some embodiments, the gas bearing device (1) described in any of 1) to 13) above, wherein the bump portion (41) is provided radially inward from the base portion (42).

[0095] According to the configuration described in 14) above, even when the bump portion (41) of the gas bearing device (1) is located radially inward from the base portion (42), the rigidity is higher at high loads compared to low loads, and a high damping effect can be obtained. When the bump portion (41) is located radially inward from the base portion (42), the axial ends (47, 48) of the bump portion (41) are more prone to deformation compared to when the bump portion (41) is located radially outward from the base portion (42). Therefore, the gas bearing device (1) can suppress wear due to uneven contact and improve the load capacity of the gas bearing device (1).

[0096] 15) In some embodiments, the gas bearing device (1) described in any of 1) to 13) above, wherein the bump portion (41) is provided radially outward from the base portion (42).

[0097] According to the configuration described in 15) above, even when the bump portion (41) is located radially outward from the base portion (42), the gas bearing device (1) becomes more rigid under high load conditions compared to low load conditions, and a high damping effect can be obtained.

[0098] 1 Gas bearing device 2 Rotating shaft 3 Top foil 4 Bump foil 5 Surrounding member 6 Housing 7 Plate-shaped member 8 Notch 31 Inner surface 32 Outer surface 41 Bump portion 42 Base portion 45 Top portion 46 Bottom portion 47, 48 Axial end portion 49 Center portion 51 Inner surface 81, 81A to 81E, 83, 83A, 83B Slit hole 82, 82A, 82B Notch portion 84, 84A to 84C Projection portion B Boundary CA, CA2 Central axis CP Center position L Load S1, S2 Spacing W1, W2 Hole 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 spreading in the circumferential direction, wherein at least one of the plurality of bump portions has at least one notch formed therein, and the top portion, whose radial height from the base portion is above a predetermined value, is configured such that the ratio of the area of ​​the notch per unit circumferential length is greater than that of the bottom portion, whose radial height from the base portion is less than a predetermined value.

2. The gas bearing device according to claim 1, wherein the at least one notch includes a plurality of slit holes that penetrate the bump portion.

3. The gas bearing device according to claim 2, wherein the plurality of slit holes have a longitudinal direction along the circumferential direction and are formed at intervals in the axial direction.

4. The gas bearing device according to claim 2, wherein the plurality of slit holes have a longitudinal direction along the axial direction and are formed at intervals in the circumferential direction.

5. The gas bearing device according to claim 3, wherein the distance between two adjacent slit holes in the axial direction at the axial central portion of the plurality of slit holes is greater than the distance between two adjacent slit holes in the axial direction at the axial ends.

6. The gas bearing device according to claim 3, wherein the plurality of slit holes include at least one slit hole formed in the axial central portion and at least one slit hole formed at the axial end, the slit hole formed in the axial central portion having a smaller hole width than the slit hole formed at the axial end.

7. The gas bearing device according to claim 1, wherein the at least one notch is a one-sided notch formed on one axial side of the bump portion and cut toward the other axial side, the one-sided notch having a notch width greater than the notch depth.

8. The gas bearing device according to claim 7, wherein the at least one notch further comprises a other-side notch formed on the other side of the bump portion in the axial direction and cut toward the one side in the axial direction, wherein the width of the notch is greater than the depth of the notch.

9. The gas bearing device according to claim 7, wherein the one-sided notch is configured such that the notch depth increases towards the apex in the circumferential direction of the bump portion.

10. The gas bearing device according to claim 8, wherein the other side notch is configured such that the notch depth increases towards the apex in the circumferential direction of the bump portion.

11. The gas bearing device according to claim 1, wherein the bump portion has at least one slit hole having a longitudinal direction along the circumferential direction, and the at least one notch includes a projection formed by causing at least one region of a plurality of regions divided axially by the at least one slit hole in the bump portion to protrude in the opposite direction to the protruding direction of the bump portion.

12. The gas bearing device according to claim 11, wherein the at least one slit hole includes a one-side slit hole formed on one side in the axial direction from the axial center position and a other-side slit hole formed on the other side in the axial direction from the axial center position, and the projection includes a central projection formed between the one-side slit hole and the other-side slit hole in the axial direction.

13. The gas bearing device according to claim 11, wherein the at least one slit hole includes a one-side slit hole formed on one side in the axial direction from the axial center position and a other-side slit hole formed on the other side in the axial direction from the axial center position, and the projection includes a one-side projection formed on one side in the axial direction from the one-side slit hole and a other-side projection formed on the other side in the axial direction from the other-side slit hole.

14. The gas bearing device according to any one of claims 1 to 13, wherein the bump portion is provided radially inward from the base portion.

15. The gas bearing device according to any one of claims 1 to 13, wherein the bump portion is provided radially outward from the base portion.

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