Gas-bearing device and turbocharger

Abstract

Provided is a gas-bearing device that rotatably supports a rotary shaft by using gas as a working fluid, the gas-bearing device comprising: a top foil that surrounds the radially outer side of the rotary shaft; a bump foil which is disposed on the radially outer side of the top foil and in which crests and troughs are alternately and continuously arranged in contact with the top foil in the circumferential direction; and a surrounding member that surrounds the radially outer side of the bump foil and has the inner circumferential surface against which the troughs slidably contact. The inner circumferential surface includes at least one slippage-suppression part that is configured to suppress slippage in the bump foil to a greater extent than in other parts of the inner circumferential surface.

Description

Gas bearing device and turbocharger

[0001] The present disclosure relates to a gas bearing device and a turbocharger including the gas bearing device.

[0002] Among gas bearings, there is known 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 (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2024-`14299

[0004] In a foil bearing, damping is obtained by friction between the foils or between the foil and the housing. In order to obtain damping, it is desirable that the bump foil has low rigidity so that slippage 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 when the central axis of the rotating shaft is greatly displaced by an external disturbance, structures such as the rotating shaft and the impeller attached to the rotating shaft may contact the housing. For this reason, a bearing that has low rigidity for relatively small displacements (loads) during normal operation and high rigidity for relatively large displacements (loads), such as those caused by external disturbances, is desired. Also, those with a complicated uneven shape, such as the bump foil described in Patent Document 1, are not preferable because they are 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, and a turbocharger including the gas bearing device.

[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 bump foil disposed radially outside the top foil and having alternating peaks and valleys that abut the top foil in the circumferential direction; and a surrounding member surrounding the radially outer side of the bump foil, the surrounding member having an inner circumferential surface into which the valleys slidably abut, wherein the inner circumferential surface includes at least one slip suppression portion configured to suppress the sliding of the bump foil more than other portions of the inner circumferential surface.

[0007] A turbocharger according to at least one embodiment of the present disclosure comprises the gas bearing device and the rotating shaft.

[0008] 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, and a turbocharger equipped with the gas bearing device is provided.

[0009] 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 a gas bearing device according to a first embodiment of the present disclosure. This is a schematic cross-sectional view schematically showing a cross section perpendicular to the axial direction of a gas bearing device according to a modified example of the first embodiment of the present disclosure. This is an explanatory diagram for illustrating an example of a slip suppression portion in a gas bearing device according to a first embodiment of the present disclosure. This is an explanatory diagram for illustrating an example of a slip suppression portion in a gas bearing device according to a first embodiment of the present disclosure. This is an explanatory diagram for illustrating an example of a slip suppression portion in a gas bearing device according to a first embodiment of the present disclosure. This is a schematic unfolded view of a plate-shaped member of a gas bearing device according to a first embodiment of the present disclosure. This is an explanatory diagram for illustrating a method for forming a protrusion in a plate-shaped member of a gas bearing device according to a first embodiment of the present disclosure. This is an explanatory diagram for illustrating a method for forming a protrusion in a plate-shaped member of a gas bearing device according to a first embodiment of the present disclosure. This is a schematic cross-sectional view schematically showing a part of a cross section perpendicular to the axial direction of a gas bearing device according to a second embodiment of the present disclosure. This is a schematic cross-sectional view schematically showing a part of a cross section perpendicular to the axial direction of a gas bearing device according to a third embodiment of the present disclosure. This is a schematic cross-sectional view schematically showing a part of a cross section perpendicular to the axial direction of a gas bearing device according to a fourth embodiment of the present disclosure. This is a schematic cross-sectional view showing a portion of a cross-section perpendicular to the axial direction of a gas bearing device according to a fifth embodiment of the present disclosure. This is a schematic unfolded view of a surrounding member in a gas bearing device according to one embodiment of the present disclosure. This is an explanatory diagram for illustrating a method for forming a protrusion in a gas bearing device according to one embodiment of the present disclosure.

[0010] 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.

[0011] (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 (for example, for onshore power generation).

[0012] 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 rotor 102 connected to the other side of the rotating shaft 2.

[0013] The turbine rotor 102 is configured to rotate using exhaust gas discharged from an engine (internal combustion engine) or fuel cell, etc. (not shown). The compressor impeller 101 is connected coaxially to the turbine rotor 102 via a rotating shaft 2, and therefore rotates together with the rotating shaft 2 in conjunction with the rotation of the turbine rotor 102. As the compressor impeller 101 rotates, the gas (for example, air) introduced into the compressor impeller 101 is compressed.

[0014] 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).

[0015] (Gas Bearing Device) Figure 2 is a schematic cross-sectional view schematically showing a cross-section perpendicular to the axial direction of a gas bearing device 1 according to a first embodiment of the present disclosure. Figure 3 is a schematic cross-sectional view schematically showing a cross-section perpendicular to the axial direction of a gas bearing device 1 according to a modified example of the first embodiment of the present disclosure. In some embodiments, the gas bearing device 1 is configured to rotatably support a rotating shaft 2 with 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.

[0016] (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.

[0017] (Bump Foil) As shown in Figures 2 and 3, the bump foil 4 is positioned radially outward from the top foil 3 on the rotating shaft 2. The bump foil 4 has a corrugated shape and is flexible enough to be elastically deformable when the top foil 3 is subjected to a load. The bump foil 4 has alternating peaks 41 and valleys 42 in the circumferential direction of the rotating shaft 2. The inner circumferential surface 411 of each of the multiple peaks 41 is configured to be in contact with the outer circumferential surface 32 of the top foil 3. When the top foil 3 is subjected to a load, or from the initial state when the top foil 3 is not subjected to a load, a portion of the inner circumferential surface 411 of each of the multiple peaks 41 is in contact with the outer circumferential surface 32 of the top foil 3. 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 due to the load transmitted from the top foil 3.

[0018] In the embodiments shown in Figures 2 and 3, each of the multiple peaks 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 412 of each of the multiple peaks 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 412 toward the base 413 connected to the valley 42.

[0019] In the embodiments shown in Figures 2 and 3, each of the multiple valleys 42 connects the bases 413 of two adjacent peaks 41 in the circumferential direction of the rotating shaft 2. In the embodiments shown in Figures 2 and 3, each of the multiple valleys 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. In some other embodiments, each of the multiple valleys 42 may be formed in a concave arc shape that is concave outward in the radial direction of the rotating shaft 2 when viewed from one side in the axial direction of the rotating shaft 2.

[0020] (Enclosing member) The enclosing member 5 surrounds the radially outer side of the bump foil 4. The enclosing member 5 has an inner surface 51 that can contact the outer surface 421 of each of the multiple valleys 42. When the top foil 3 is subjected to a load, or from the initial state when the top foil 3 is not subjected to a load, a portion of the outer surface 421 of each of the multiple valleys 42 is made to slidably contact the inner surface 51 of the enclosing member 5 along the circumferential direction of the rotating shaft 2.

[0021] The surrounding member 5 is the housing 7 when no other member is positioned between the bump foil 4 and the housing 7 (see Figure 2), and is the other member when another member (member 8 in the illustrated example) is positioned between the bump foil 4 and the housing 7 (see Figure 3). In the embodiment shown in Figure 2, the surrounding member 5 is the housing 7 configured to rotatably house the rotating shaft 2. The inner circumferential surface 51 described above is the inner circumferential surface 71 of the housing 7. The top foil 3 and the bump foil 4 are positioned in the annular space formed between the inner circumferential surface 71 of the housing 7 and the outer circumferential surface 21 of the rotating shaft 2.

[0022] In the embodiment shown in Figure 3, the gas bearing device 1 includes a housing 7 having an inner circumferential surface 71. The surrounding member 5 is a separate member 8 housed within the housing 7. In the illustrated example, the surrounding member 5 (member 8) is a plate-shaped member 8A that curves to surround the radially outer side of the bump foil 4. The plate-shaped member 8A 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 described above is the inner circumferential surface 81 of the plate-shaped member 8A. The top foil 3, bump foil 4, and plate-shaped member 8A are arranged in the annular space formed between the inner circumferential surface 71 of the housing 7 and the outer circumferential surface 21 of the rotating shaft 2. The outer circumferential surface 82 of the plate-shaped member 8A faces the inner circumferential surface 71 of the housing 7. The outer circumferential surface 82 of the plate-shaped member 8A is in non-slidable contact with the inner circumferential surface 71 of the housing 7. The plate-shaped member 8A is supported by the housing 7.

[0023] (First Embodiment) In some embodiments of the gas bearing device 1, as shown in Figures 2 and 3, the inner circumferential surface 51 includes at least one slip suppression portion 6 configured to suppress the sliding of the bump foil 4 more than other portions 52 of the inner circumferential surface 51.

[0024] By providing a slip suppression section 6 on a part of the inner circumferential surface 51, the effect of suppressing the sliding of the bump foil 4 can be varied according to the load (load) received by the top foil 3. That is, when the load (load) received by the top foil 3 is small, the amount of circumferential sliding (elongation) of the bump foil 4 is relatively small, and the effect of the slip suppression section 6 in suppressing the sliding of the bump foil 4 is also relatively small, making the bump foil 4 more prone to sliding, resulting in low rigidity of the bump foil 4 against the load received by the top foil 3. Conversely, when the load (load) received by the top foil 3 is large, the amount of circumferential sliding (elongation) of the bump foil 4 is relatively large, and the effect of the slip suppression section 6 in suppressing the sliding of the bump foil 4 is also relatively large, making it more difficult for the bump foil 4 to slide, resulting in high rigidity of the bump foil 4 against the load received by the top foil 3. With this type of gas bearing device 1, the complexity of the bump foil 4 shape is suppressed, while achieving higher rigidity under high load compared to low load.

[0025] In some embodiments, as shown in Figures 2 and 3, the above-described at least one slip suppression portion 6 includes a plurality of slip suppression portions 6 arranged at intervals in the circumferential direction. That is, the above-described inner circumferential surface 51 has a plurality of slip suppression portions 6 arranged in the circumferential direction. The plurality of slip suppression portions 6 may be evenly or unevenly arranged in the circumferential direction. By arranging a plurality of slip suppression portions 6 in the circumferential direction, the slip suppression portion 6 can more reliably exert its effect of suppressing the sliding of the bump foil 4 compared to the case where a single slip suppression portion 6 is arranged.

[0026] In some embodiments, as shown in Figures 2 and 3, the housing 7 described above has a groove 72 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 72. 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.

[0027] The aforementioned peaks 41 are arranged at equal intervals in the circumferential direction. As shown in Figure 3, for each of the multiple slip suppression sections 6 described above, the difference between the circumferential distance CD1 to an adjacent slip suppression section 6 in the circumferential direction and the circumferential distance CD2 to the peak 41 is shorter than the circumferential width GW of the groove 72. The circumferential distance CD2 of the peak 41 is the circumferential distance (maximum circumferential distance) between the hems 413, 413 of a single peak 41. The bump foil 4 may shift circumferentially by about the circumferential width of the groove 72. By making the above difference shorter than the circumferential width GW of the groove 72, even if the bump foil 4 shifts circumferentially, one of the multiple slip suppression sections 6 can exert a sliding suppression effect on the bump foil 4.

[0028] Figures 4 to 6 are explanatory diagrams illustrating an example of a slip suppression portion 6 in a gas bearing device according to the first embodiment of this disclosure. In some embodiments, as shown in Figure 4, each of the plurality of slip suppression portions 6 described above is a friction resistance portion 61 with a higher coefficient of friction than other portions 52 of the inner circumferential surface 51. The friction resistance portion 61 is processed to increase the coefficient of friction compared to other portions 52 of the inner circumferential surface 51.

[0029] In one embodiment, the friction resistance portion 61 is a coating layer laminated on the inner circumferential surface 51 by coating. The coating layer may be, for example, a resin coating made of a resin material. In another embodiment, the friction resistance portion 61 may have a surface roughness (arithmetic mean roughness, maximum height, etc.) that is rougher than other parts 52 of the inner circumferential surface 51 due to surface treatment. In yet another embodiment, the friction resistance portion 61 may be an uneven surface formed on the inner circumferential surface 51 by surface processing such as patterning.

[0030] Each of the figures in Figure 4 shows the bump foil 4, the surrounding member 5 (housing 7 or member 8), and the friction resistance part 61. The upper figure in Figure 4 shows the initial state in which the top foil 3 and bump foil 4 are not subjected to any load. The lower figure in 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.

[0031] As shown in Figure 4, when the bump foil 4 is subjected to a load and slides in the circumferential direction, the outer circumferential surface 421 of the valley portion 42 comes into contact with the friction resistance portion 61. The frictional resistance generated by the friction resistance portion 61 against the outer circumferential surface 421 of the valley portion 42 suppresses the circumferential sliding of the bump foil 4.

[0032] In some embodiments, as shown in Figure 5, each of the above-described slip-suppressing portions 6 is a convex portion 62 that protrudes radially inward from the other portion 52 of the inner circumferential surface 51. Each figure in Figure 5 shows the bump foil 4, the surrounding member 5 (housing 7 or member 8), and the convex portion 62. The upper figure in Figure 5 shows the initial state in which the top foil 3 and bump foil 4 are not subjected to any load. The middle figure in Figure 5 shows the state in which the top foil 3 and bump foil 4 are subjected to a low load L1, causing the bump foil 4 to stretch in the circumferential direction. The lower figure in Figure 5 shows the state in which the top foil 3 and bump foil 4 are subjected to a high load L2, which is higher than the low load L1, causing the bump foil 4 to stretch in the circumferential direction.

[0033] As shown in Figure 5, when the bump foil 4 is subjected to a load and slides in the circumferential direction, the outer circumferential surface 414 of the peak 41 is engaged with the protrusion 62, thereby suppressing the circumferential sliding of the bump foil 4. The larger the load L applied to the bump foil 4, the more the bump foil 4 is pressed outward in the radial direction, making it difficult for the bump foil 4 to overcome the protrusion 62 when it slides in the circumferential direction, and causing it to catch on the protrusion 62.

[0034] In some embodiments, as shown in Figure 6, each of the above-described slip-suppressing portions 6 is a recess 63 that is recessed radially outward from the other portion 52 of the inner circumferential surface 51. Each figure in Figure 6 shows a bump foil 4, a surrounding member 5 (housing 7 or member 8), and a recess 63. The upper figure in Figure 6 shows the initial state in which the top foil 3 and bump foil 4 are not subjected to any load. The middle figure in Figure 6 shows the state in which the top foil 3 and bump foil 4 are subjected to a low load L1, causing the bump foil 4 to stretch in the circumferential direction. The lower figure in Figure 6 shows the state in which the top foil 3 and bump foil 4 are subjected to a high load L2, which is higher than the low load L1, causing the bump foil 4 to stretch in the circumferential direction.

[0035] As shown in Figure 6, when the bump foil 4 is subjected to a load and slides in the circumferential direction, the bottom 413 of the peak 41 is engaged in the recess 63, thereby suppressing the circumferential sliding of the bump foil 4. The larger the load L applied to the bump foil 4, the more the bump foil 4 is pressed radially outward, making it difficult for the bump foil 4 to overcome the recess 63 when it slides in the circumferential direction, and causing it to catch in the recess 63.

[0036] (Method for forming the protrusions) Figure 7 is a schematic unfolded view of the plate-shaped member 8A of the gas bearing device 1 according to the first embodiment of the present disclosure. Figures 8 and 9 are explanatory diagrams for illustrating the method for forming the protrusions 62 in the plate-shaped member 8A of the gas bearing device 1 according to the first embodiment of the present disclosure. As shown in Figure 7, in some embodiments, the plate-shaped member 8A has a plurality of portions 85 that protrude to one side beyond the side 83 in the axial direction. The plurality of protruding portions 85 are provided at intervals in the circumferential direction.

[0037] In some embodiments, as shown in Figures 8 and 9, each of the plurality of protrusions 62 described above is configured such that at least a portion of the part 85 that protrudes to one side of the plate-like member 8A in the axial direction relative to one side 83 is bent to the other side of the one side 83 in the axial direction. Each of the plurality of protruding parts 85 has a bent portion 85A in the middle of its length.

[0038] In some embodiments, each of the multiple protrusions 62 described above may be configured such that at least a portion of the part 86 that protrudes to the other side of the other side 84 in the axial direction of the plate-like member 8A is bent so that it is located to one side in the axial direction of the other side 84. Each of the multiple protruding parts 86 has a bent portion 86A in the middle of its length. In some other embodiments, the multiple protrusions 62 may include both those configured by the parts 85 described above and those configured by the parts 86 described above. In these cases, the multiple protrusions 62 can be easily formed on the plate-like member 8A.

[0039] (Second Embodiment) Figure 10 is a schematic cross-sectional view showing a portion of a cross-section perpendicular to the axial direction of a gas bearing device 1 according to a second embodiment of the present disclosure. The gas bearing device 1 according to several embodiments comprises the top foil 3 described above, a bump foil 4, and a surrounding member 5 (housing 7 or member 8). The surrounding member 5 described above has a plurality of recesses 11 that accommodate one of the valleys 42 described above, as shown in Figure 10. Of the plurality of recesses 11, at least one recess 11 is configured such that the portion of the valley 42 that abuts the recess 11 increases or decreases depending on the load received by the gas bearing device 1.

[0040] In Figure 10, each figure shows a bump foil 4 and a surrounding member 5. The upper figure in Figure 10 shows the top foil 3 and bump foil 4 under a low load L1, with the bump foil 4 stretched in the circumferential direction. The lower figure in Figure 10 shows the top foil 3 and bump foil 4 under a high load L2, which is higher than the low load L1, with the bump foil 4 stretched in the circumferential direction.

[0041] In the embodiment shown in Figure 10, each of the multiple valleys 42 is formed in a concave arc shape that is concave toward the radially outward direction of the rotating shaft 2 when viewed from one side in the axial direction of the rotating shaft 2. The recess 11 has a bottom surface 111, a one-end side wall surface 112 extending radially inward from one end of the bottom surface 111 in the circumferential direction, and a other-end side wall surface 113 extending radially inward from the other end of the bottom surface 111 in the circumferential direction. Preferably, each of the one-end side wall surface 112 and the other-end side wall surface 113 has an inclined surface such that the circumferential distance between them increases as they move away from the bottom surface 111, so that the valleys 42 can easily enter the bottom surface 111 side of the recess 11.

[0042] Of the multiple recesses 11, at least one recess 11 is configured such that when the top foil 3 or bump foil 4 is subjected to a high load L2, the area in contact with the recess 11 of the valley 42 increases compared to the initial state when the top foil 3 or bump foil 4 is not subjected to a load (load) or when it is subjected to a low load L1. For example, in the embodiment shown in Figure 10, the bottom 422 of the valley 42 does not contact the bottom surface 111 of the recess 11 in the initial state, but the bottom 422 of the valley 42 contacts the bottom surface 111 of the recess 11 depending on the load the gas bearing device 1 receives. In the initial state when the top foil 3 or bump foil 4 is not subjected to a load (load) or when it is subjected to a low load L1, the bottom 422 of the valley 42 does not contact the bottom surface 111 of the recess 11. When the top foil 3 or bump foil 4 is subjected to a high load L2, the loaded valley 42 is pushed into the recess 11, causing the bottom 422 of the valley 42 to contact the bottom surface 111 of the recess 11. It is not essential that all of the valleys 42 do not have their bottoms 422 contacting the bottom surface 111 of the recess 11 in the initial state or when subjected to a low load L1; some of the valleys 42 may have their bottoms 422 contacting the bottom surface 111 of the recess 11 in the initial state or when subjected to a low load L1. Furthermore, the increased contact points when the loaded valley 42 is pushed into the recess 11 are not limited to the bottom surface 111.

[0043] In the gas bearing device 1 according to the second embodiment, the support point for the valley portion 42 of the recess 11 can be increased or decreased according to the load received by the gas bearing device 1. That is, when the load received by the top foil 3 is small, the support point for the valley portion 42 of the recess 11 is small, and the valley portion 42 is relatively easily deformed according to the load. Therefore, the bump foil 4 has a low rigidity with respect to the load received by the top foil 3. On the other hand, when the load received by the top foil 3 is large, the number of support points for the valley portion 42 of the recess 11 increases, making it relatively difficult for the valley portion 42 to deform according to the load. Thus, the bump foil 4 has a high rigidity with respect to the load received by the top foil 3. According to such a gas bearing device 1, while suppressing the complication of the shape of the bump foil 4, it has a higher rigidity under high loads than under low loads.

[0044] (Third Embodiment) FIG. 11 is a schematic cross-sectional view schematically showing a part of a cross section orthogonal to the axial direction of the gas bearing device 1 according to the third embodiment of the present disclosure. The gas bearing device 1 according to some embodiments includes the above-described top foil 3, a bump foil 4, and a surrounding member 5 (housing 7 or member 8). The above-described surrounding member 5 is provided outside the peak portion 41 in the radial direction and has a plurality of convex portions 12 that project inward in the radial direction from the other portion 52 of the inner peripheral surface 51. Each of the plurality of convex portions 12 is arranged at intervals in the circumferential direction. Each of the plurality of convex portions 12 is configured such that the outer peripheral surface 414 of the peak portion 41 does not contact each of the plurality of convex portions 12 in the initial state, and the outer peripheral surface 414 of the peak portion 41 contacts each of the plurality of convex portions 12 according to the load received by the gas bearing device 1.

[0045] In each of the diagrams in FIG. 11, the bump foil 4 and the surrounding member 5 are shown. The upper diagram in FIG. 11 shows the initial state in which the top foil 3 and the bump foil 4 are not receiving a load (load). The middle diagram in FIG. 11 shows a state in which the top foil 3 and the bump foil 4 are receiving a low load L1 and the bump foil 4 is extended in the circumferential direction. The lower diagram in FIG. 11 shows a state in which the top foil 3 and the bump foil 4 are receiving a high load L2 that is higher than the low load L1 and the bump foil 4 is extended in the circumferential direction.

[0046] In the gas bearing device 1 according to the third embodiment, the support points on the outer peripheral surface 414 of the mountain portion 41 can be increased or decreased according to the load received by the gas bearing device 1. That is, when the load received by the top foil 3 is small, the outer peripheral surface 414 of the mountain portion 41 does not contact the plurality of convex portions 12 located on the radially outer side, so the mountain portion 41 is relatively easy to deform according to the load. Therefore, the bump foil 4 has a low rigidity with respect to the load received by the top foil 3. On the other hand, when the load received by the top foil 3 is large, the outer peripheral surface 414 of the mountain portion 41 contacts the plurality of convex portions 12 located on the radially outer side. Therefore, the mountain portion 41 is difficult to deform according to the load, and the bump foil 4 has a high rigidity with respect to the load received by the top foil 3. According to such a gas bearing device 1, while suppressing the complication of the shape of the bump foil 4, it has a higher rigidity at high loads than at low loads.

[0047] In some embodiments, as shown in FIGS. 8 and 9, each of the above-described plurality of convex portions is configured by bending at least a part of a protruding portion 85 that protrudes to the above-described one side in the axial direction of the plate-like member 8A so as to be located on the other side in the axial direction than the one side edge 8 and a plurality of protruding portions 85 each have a bent portion 85A in the middle of its length.

[0048] In some embodiments, each of the above-described plurality of convex portions 12 may be configured by bending at least a part of a protruding portion 86 that protrudes to the other side in the axial direction of the plate-like member 8A so as to be located on the one side in the axial direction than the other side edge 84. Each of the plurality of protruding portions 86 has a bent portion 86A in the middle of its length. In some other embodiments, the plurality of convex portions 12 may include both those configured by the above-described portion 85 and those configured by the above-described portion In these cases, the plurality of convex portions 12 can be easily formed on the plate-like member 8A.

[0049] (Fourth Embodiment) Figure 12 is a schematic cross-sectional view showing a portion of a cross-section perpendicular to the axial direction of a gas bearing device 1 according to the fourth embodiment of the present disclosure. The gas bearing device 1 according to several embodiments comprises the top foil 3, bump foil 4, and surrounding member 5 (housing 7 or member 8) described above. Each of the plurality of peaks 41 described above is configured such that the thickness increases from the apex 412 to the base 413, as shown in Figure 12. As shown in Figure 12, the thickness T1 at the apex 412 is the minimum thickness of the peak 41, and the thickness T2 at the base 413 is the maximum thickness of the peak 41. In the embodiment shown in Figure 12, the thickness is configured to increase continuously from the apex 412 to the base 413.

[0050] In this case, the apex 412 side of the relatively thin-walled peak 41 is relatively easy to deform in response to the load, so the bump foil 4 has low rigidity against the load on the top foil 3. The base 413 side of the relatively thick-walled peak 41 is relatively difficult to deform in response to the load, so the bump foil 4 has high rigidity against the load on the top foil 3. With such a gas bearing device 1, the rigidity is higher at high loads compared to low loads.

[0051] (Fifth Embodiment) Figure 13 is a schematic cross-sectional view showing a portion of a cross-section perpendicular to the axial direction of a gas bearing device 1 according to a fifth embodiment of the present disclosure. The gas bearing device 1 according to some embodiments comprises the top foil 3 described above, a bump foil 4, a surrounding member 5 (housing 7 or member 8), and at least one (multiple in the illustrated example) reinforcing plate 13 (see Figure 13). Each of the multiple reinforcing plates 13 is configured to cover a portion of the outer peripheral surface 414, including the base 413 of each of the multiple peaks 41, from the outside in the radial direction.

[0052] In the embodiment shown in Figure 13, each of the multiple reinforcing plates 13 is a thin metal plate. Each of the multiple reinforcing plates 13 is designed not to cover a portion of the outer surface 414, including the vertices 412 of each of the multiple peaks 41. Alternatively, each of the multiple reinforcing plates 13 may cover at least a portion of the outer surface 421 of the valleys 42 from the radial outside.

[0053] In this case, the apex 412 side of the peak 41 that is not covered by the reinforcing plate 13 is relatively easy to deform in response to the load, so the bump foil 4 has low rigidity against the load received by the top foil 3. The base 413 side of the peak 41 that is covered by the reinforcing plate 13 is relatively difficult to deform in response to the load, so the bump foil 4 has high rigidity against the load received by the top foil 3. With such a gas bearing device 1, the rigidity is higher at high loads compared to low loads.

[0054] (Projections) Figure 14 is a schematic unfolded view of the surrounding member 5 in a gas bearing device 1 according to one embodiment of the present disclosure. Figure 15 is an explanatory diagram for illustrating the method of forming the protrusions 62 and 12 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 14 and 15, the surrounding member 5 (housing 7 or member 8) described above includes at least one (multiple in the illustrated example) fitting groove 91 into which each projection 90 can be fitted. In the illustrated embodiment, each of the multiple fitting grooves 91 is formed on the inner circumferential surface 51 of the surrounding member 5. Each of the multiple fitting grooves 91 extends along the axial direction of the surrounding member 5, and at least one (both in the illustrated example) of one end or the other end in the axial direction is open, forming opening edges 92 and 93. In this case, the projection 90 can be fitted into the fitting groove 91 along the axial direction via either the opening edge 92 or the opening edge 93.

[0055] The projection 90 is configured such that a portion of it fits into the corresponding fitting groove 91, and the aforementioned protrusion 62 or protrusion 12 is the portion of the projection 90 that protrudes from the fitting groove 91. In other words, the aforementioned protrusion 62 or protrusion 12 is the portion that protrudes radially inward from the inner circumferential surface 51 of the projection 90 that is partially fitted into the fitting groove 91.

[0056] As shown in Figure 15, each of the multiple fitting grooves 91 has a closing portion in which the groove width narrows towards the inside in the radial direction, thereby preventing the projection 90 fitted into the fitting groove 91 from coming out radially inward. Each of the multiple fitting grooves 91 may be a dovetail groove with a cross-section shaped like an inverted V, or it may be composed of a circular hole with a circular cross-section along the circumferential direction and a communication hole that connects the circular hole to the outside of the fitting groove 91, and has a groove width shorter than the diameter of the circular hole. The circumferential width of the communication hole may be constant, or it may be configured to decrease towards the inside in the radial direction.

[0057] As shown in Figure 15, the projection 90 may have a triangular cross-sectional shape or a square shape (in the illustrated example, a trapezoidal shape with the upper base protruding from the fitting groove 91). The projection 90 may also have a circular cross-sectional shape and include a circular hole fitting portion that can be fitted into the circular hole and a communication hole insertion portion that can be inserted through the communication hole. The circumferential length of the communication hole insertion portion may be constant or may be configured to decrease towards the inside in the radial direction. The fitting groove 91 and the projection 90 are not limited to the shapes shown in Figure 15.

[0058] The protrusions 62 and 12 are formed by fitting the projection 90 into the fitting groove 91 of the surrounding member 5, thus making it easy to form the protrusions 62 and 12.

[0059] Each of the gas bearing devices 1 according to the first to fifth embodiments can be implemented independently of the gas bearing devices 1 according to the other embodiments. Each of the gas bearing devices 1 according to the first to fifth embodiments may be appropriately combined with the configuration of the gas bearing devices 1 according to the other embodiments.

[0060] As shown in Figure 1, some embodiments of the turbocharger 100 include the gas bearing device 1 and a rotating shaft 2 described above. The gas bearing device 1 mounted on the turbocharger 100 suppresses the complexity of the bump foil 4 shape while providing higher rigidity at high loads compared to low loads.

[0061] 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.

[0062] 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.

[0063] The contents described in some of the embodiments above can be understood, for example, as follows:

[0064] 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 bump foil (4) positioned radially outside the top foil (3) and having alternating peaks (41) and valleys (42) that abut the top foil (3) in the circumferential direction; and a surrounding member (5) surrounding the radially outer side of the bump foil (4), the surrounding member (5) having an inner circumferential surface (51) into which the valleys (42) slidably abut, wherein the inner circumferential surface (51) includes at least one slip suppression portion (6) configured to suppress the sliding of the bump foil (4) more than other portions (52) of the inner circumferential surface (51).

[0065] According to the configuration described in 1) above, by providing a slip suppression portion (6) on a part of the inner circumferential surface (51), the effect of suppressing the sliding of the bump foil (4) can be varied depending on the load on the top foil (3). That is, when the load on the top foil (3) is small, the amount of circumferential sliding of the bump foil (4) is relatively small, and the effect of suppressing the sliding of the bump foil (4) exerted by the slip suppression portion (6) is also relatively small, making the bump foil (4) prone to sliding, resulting in low rigidity of the bump foil (4) with respect to the load on the top foil (3). In contrast, when the load on the top foil (3) is large, the amount of circumferential sliding of the bump foil (4) is relatively large, and the effect of suppressing the sliding of the bump foil (4) exerted by the slip suppression portion (6) is also relatively large, making it difficult for the bump foil (4) to slide, resulting in high rigidity of the bump foil (4) 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 under high load compared to low load.

[0066] 2) In some embodiments, the gas bearing device (1) described in 1) above, wherein the at least one slip suppression portion (6) is a friction resistance portion (61) with a higher coefficient of friction than the other portion (52) of the inner circumferential surface (51).

[0067] According to the configuration in 2) above, when the bump foil (4) is subjected to a load and slides in the circumferential direction, the outer surface (421) of the valley (42) comes into contact with the friction resistance portion (61), and the friction resistance generated by the friction resistance portion (61) against the outer surface (421) of the valley (42) suppresses the circumferential sliding of the bump foil (4).

[0068] 3) In some embodiments, the gas bearing device (1) described in 1) above, wherein the at least one slip suppression portion (6) is a convex portion (62) that protrudes radially inward from the other portion (52) of the inner circumferential surface (51).

[0069] According to the configuration described in 3) above, when the bump foil (4) is subjected to a load and slides in the circumferential direction, the outer circumferential surface (414) of the peak (41) is locked onto the convex portion (62), thereby suppressing the circumferential sliding of the bump foil (4).

[0070] 4) In some embodiments, the gas bearing device (1) described in 1) above, wherein the at least one slip suppression portion (6) is a recess (63) that is recessed radially outward from the other portion (52) of the inner circumferential surface (51).

[0071] According to the configuration described in 4) above, when the bump foil (4) is subjected to a load and slides in the circumferential direction, the bottom edge (413) of the peak (41) is locked into the recess (63), thereby suppressing the circumferential sliding of the bump foil (4).

[0072] 5) In some embodiments, the gas bearing device (1) described in any of 1) to 4) above, wherein the at least one slip suppression portion (6) includes a plurality of slip suppression portions (6) arranged at intervals in the circumferential direction.

[0073] According to the configuration in 5) above, by arranging multiple slip suppression parts (6) in the circumferential direction, the slip suppression parts (6) can more reliably exert their effect of suppressing the sliding of the bump foil (4) compared to the case where a single slip suppression part (6) is arranged.

[0074] 6) In some embodiments, the gas bearing device (1) described in any of 1) to 4) above, wherein the surrounding member (5) is either a housing (7) configured to rotatably house the rotating shaft (2), or a member (8) housed in the housing, the housing (7) has a groove (72) formed therein that restricts the circumferential movement of the bump foil (4) by inserting a part of the bump foil (4) in the circumferential direction, the at least one slip suppression portion (6) includes a plurality of slip suppression portions (6) arranged at intervals in the circumferential direction, and each of the plurality of slip suppression portions (6) has an interval such that the difference between the circumferential distance (CD1) to an adjacent slip suppression portion (6) in the circumferential direction and the circumferential distance (CD2) between the hems (413, 413) of the peaks (41) is shorter than the circumferential width (GW) of the groove (72).

[0075] According to the configuration in 6) above, the bump foil (4) may shift circumferentially by an amount approximately equal to the circumferential width (GW) of the groove (71). By making the above difference shorter than the circumferential width of the groove (72), even if the bump foil (4) shifts, one of the multiple slip suppression parts (6) can exert a sliding suppression effect on the bump foil (4).

[0076] 7) In some embodiments, the gas bearing device (1) described in 3) above, wherein the surrounding member (5) is a plate-shaped member (8A) that curves to surround the radially outer side of the bump foil (4), and the at least one slip suppression portion (6) includes a plurality of protrusions (62) that are spaced apart in the circumferential direction, and each of the plurality of protrusions (62) is configured such that at least a portion (85) of the plate-shaped member (8A) that protrudes to one side of the axial side (83) is bent so that it is located to the other side of the axial direction relative to the one side (83).

[0077] According to the configuration described in 7) above, multiple protrusions (62) can be easily formed on the plate-shaped member (8A).

[0078] 8) In some embodiments, the gas bearing device (1) described in 3) above, wherein the at least one slip suppression portion (6) includes at least one protrusion (62), the surrounding member (5) includes at least one fitting groove (91) into which one projection (90) can be fitted, and the at least one protrusion (62) is the portion of the projection (90) that protrudes from the fitting groove (91) when a part of the projection (90) is fitted into the at least one fitting groove (91).

[0079] According to the configuration described in 8) above, a protrusion (62) is formed by fitting the projection (90) into the fitting groove (91) of the surrounding member (5), thus making it easy to form the protrusion (62).

[0080] 9) 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 bump foil (4) positioned radially outside the top foil (3) and having alternating peaks (41) and valleys (42) that abut the top foil (3) in the circumferential direction; and a surrounding member (5) surrounding the radially outer side of the bump foil (4), the surrounding member (5) having an inner circumferential surface (51) into which the valleys (42) slidably abut, wherein the surrounding member (5) is The present invention comprises a plurality of recesses (11) that accommodate each of the valleys (42), wherein the portion of the valley (42) that contacts the recess (11) is configured to increase or decrease in accordance with the load received by the gas bearing device (1).

[0081] According to the configuration in 9) above, the number of support points for the valleys (42) of the recesses (11) 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, there are fewer support points for the valleys (42) of the recesses (11), and the valleys (42) deform relatively easily in response to the load, so 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 number of support points for the valleys (42) of the recesses (11) increases, making it relatively difficult for the valleys (42) 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 bump foil (4) shape is suppressed, while achieving higher rigidity at high loads compared to low loads.

[0082] 10) 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 bump foil (4) positioned radially outside the top foil (3) and having alternating peaks (41) and valleys (42) that abut the top foil (3) in the circumferential direction; and a surrounding member (5) surrounding the radially outer side of the bump foil (4), the surrounding member (5) having an inner circumferential surface (51) into which the valleys (42) slidably abut, wherein the surrounding member (5) is The present invention provides a plurality of protrusions (12) provided on the radially outer side of the mountain portion (41) and projecting radially inward from the other portion (52) of the inner circumferential surface (51), wherein the outer circumferential surface (414) of the mountain portion (41) does not initially contact each of the plurality of protrusions (12), but the outer circumferential surface (414) of the mountain portion (41) contacts each of the plurality of protrusions (12) in accordance with the load received by the gas bearing device (1).

[0083] According to the configuration described in 10) above, the number of support points on the outer circumferential surface (414) of the peak (41) 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 outer circumferential surface (414) of the peak (41) does not come into contact with the multiple protrusions (12) located radially outward, so the peak (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). In contrast, when the load on the top foil (3) is large, the outer circumferential surface (414) of the peak (41) comes into contact with the multiple protrusions (12) located radially outward, so the peak (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 bump foil (4) shape is suppressed, and the rigidity is higher at high loads compared to low loads.

[0084] 11) In some embodiments, the gas bearing device (1) described in 10) above, wherein the surrounding member (5) is a plate-shaped member (8A) that curves to surround the radially outer side of the bump foil (4), and each of the plurality of protrusions (12) is configured such that at least a portion of the portion (84) that protrudes to one side of the axial side (83) of the surrounding member (5) is bent so that it is located to the other side in the axial direction relative to the one side (83).

[0085] According to the configuration described in 11) above, multiple protrusions (12) can be easily formed on the plate-shaped member (8A).

[0086] 12) In some embodiments, the gas bearing device (1) described in 10) above, wherein the surrounding member (5) includes a plurality of fitting grooves (91) into which each projection (90) can be fitted, and the plurality of protrusions (12) are the portions of the projections (90) that protrude from the fitting grooves (91) when a part of the projection (90) is fitted into each of the plurality of fitting grooves (91).

[0087] According to the configuration of 12) above, the protrusion (12) is formed by fitting the projection (90) into the fitting groove (91) of the surrounding member (5), so the protrusion (12) can be easily formed.

[0088] 13) In some embodiments, the gas bearing device (1) described in any of 1) to 12) above is configured such that each of the plurality of peaks (41) is configured such that the thickness increases from the apex (412) to the base (413).

[0089] According to the configuration described in 13) above, the peak (412) side of the relatively thin-walled peak (41) is relatively easy to deform in response to the load, so the bump foil (4) has low rigidity against the load received by the top foil (3). The base (413) side of the relatively thick-walled peak (41) is relatively difficult to deform in response to the load, so the bump foil (4) has high rigidity against the load received by the top foil (3). With such a gas bearing device (1), the rigidity is higher at high loads compared to low loads.

[0090] 14) In some embodiments, the gas bearing device (1) described in any of 1) to 12) above further comprises a reinforcing plate (13) that covers a portion of each of the plurality of peaks (41), including the base (413), from the outside in the radial direction.

[0091] According to the configuration described in 14) above, the peak (412) side of the peak (41) that is not covered by the reinforcing plate (13) is relatively easy to deform in response to the load, so the bump foil (4) has low rigidity against the load received by the top foil (3). The base (413) side of the peak (41) that is covered by the reinforcing plate (13) is relatively difficult to deform in response to the load, so the bump foil (4) has high rigidity against the load received by the top foil (3). With such a gas bearing device (1), the rigidity is higher at high loads compared to low loads.

[0092] 15) A turbocharger (100) according to at least one embodiment of the present disclosure comprises a gas bearing device (1) as described in any of 1) to 14) above, and the rotating shaft (2).

[0093] According to the configuration described in 15) above, the gas bearing device (1) mounted on the turbocharger (100) has higher rigidity under high load conditions compared to low load conditions, while suppressing the complexity of the bump foil (4) shape.

[0094] 1 Gas bearing device 2 Rotating shaft 3 Top foil 4 Bump foil 5 Surrounding member 6 Slip suppression part 7 Housing 8A Plate-shaped member 11 Convex part 12 Recessed part 13 Reinforcement plate 41 Peak part 42 Valley part 51 Inner circumferential surface 61 Friction resistance part 62 Convex part 63 Recessed part 100 Turbocharger

Claims

1. 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 bump foil positioned radially outside the top foil and having alternating peaks and valleys that abut the top foil in the circumferential direction; and a surrounding member surrounding the radially outer side of the bump foil, the surrounding member having an inner circumferential surface into which the valleys slidably abut, wherein the inner circumferential surface includes at least one slip suppression portion configured to suppress the sliding of the bump foil more than other portions of the inner circumferential surface.

2. The gas bearing device according to claim 1, wherein the at least one slip suppressing portion is a friction resistance portion with a higher coefficient of friction than the other portions of the inner circumferential surface.

3. The gas bearing device according to claim 1, wherein the at least one slip-suppressing portion is a convex portion that protrudes radially inward from the other portion of the inner circumferential surface.

4. The gas bearing device according to claim 1, wherein the at least one slip-suppressing portion is a recess that is recessed radially outward from the other portion of the inner circumferential surface.

5. The gas bearing device according to any one of claims 1 to 4, wherein the at least one slip suppression portion includes a plurality of slip suppression portions arranged at intervals in the circumferential direction.

6. The surrounding member is either a housing configured to rotatably accommodate the rotating shaft, or a member housed in the housing, wherein the housing has a groove formed therein that restricts the circumferential movement of the bump foil by allowing a circumferential portion of the bump foil to be inserted, and the at least one slip suppression portion includes a plurality of slip suppression portions arranged at intervals in the circumferential direction, wherein the difference between the circumferential distance of each of the plurality of slip suppression portions to an adjacent slip suppression portion in the circumferential direction and the circumferential distance between the bases of the peaks is shorter than the circumferential width of the groove, the gas bearing device according to any one of claims 1 to 4.

7. The gas bearing device according to claim 3, wherein the surrounding member is a plate-shaped member that curves to surround the outer side of the bump foil in the radial direction, and the at least one slip suppression portion includes a plurality of protrusions arranged at intervals in the circumferential direction, and each of the plurality of protrusions is bent such that at least a portion of the portion that protrudes to one side of the axial side of the plate-shaped member is located to the other side of the axial direction of the one side.

8. The gas bearing device according to claim 3, wherein the at least one slip-suppressing portion includes at least one protrusion, the surrounding member includes at least one fitting groove into which each projection can be fitted, and the at least one protrusion is the portion of the projection that protrudes from the fitting groove when a part of the projection is fitted into the at least one fitting groove.

9. 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 bump foil positioned radially outside the top foil and having alternating peaks and valleys that abut the top foil in the circumferential direction; and a surrounding member surrounding the radially outer side of the bump foil, the surrounding member having an inner circumferential surface into which the valleys slidably abut, wherein the surrounding member has a plurality of recesses that accommodate one of the valleys, and the portion of the valleys that abuts the recesses is configured to increase or decrease in accordance with the load received by the gas bearing device.

10. 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 bump foil positioned radially outside the top foil and having alternating peaks and valleys that abut the top foil in the circumferential direction; and a surrounding member surrounding the radially outer side of the bump foil, the surrounding member having an inner circumferential surface that slidably abuts against the valleys, wherein the surrounding member has a plurality of protrusions provided on the radially outer side of the peaks and projecting radially inward from the other parts of the inner circumferential surface, wherein the outer circumferential surface of the peaks does not initially abut against each of the plurality of protrusions, but is configured to abut against each of the plurality of protrusions depending on the load received by the gas bearing device.

11. The gas bearing device according to claim 10, wherein the surrounding member is a plate-shaped member that curves to surround the outer side of the bump foil in the radial direction, and each of the plurality of protrusions is bent such that at least a portion of the portion that protrudes to one side of the axial side of the surrounding member is located to the other side of the axial direction of the one side.

12. The gas bearing device according to claim 10, wherein the surrounding member includes a plurality of fitting grooves into which each projection can be fitted, and the plurality of protrusions are the portions of the projections that protrude from the fitting grooves when a part of the projection is fitted into each of the plurality of fitting grooves.

13. The gas bearing device according to any one of claims 1 to 4, 7 to 12, wherein each of the plurality of peaks is configured such that the thickness increases from the peak to the base.

14. The gas bearing device according to any one of claims 1 to 4, 7 to 12, further comprising a reinforcing plate that covers a portion of each of the plurality of peaks, including the base, from the outside in the radial direction.

15. A turbocharger comprising a gas bearing device according to any one of claims 1 to 4 or 7 to 12, and the rotating shaft.

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