Gas bearing device and turbocharger

Abstract

A gas bearing device supports a rotating shaft rotatably with gas as a working fluid, wherein: a housing through which the rotating shaft penetrates; a ring-shaped top foil provided inside the housing and surrounding an outer periphery of the rotating shaft; a return spring provided between the top foil and the housing, and provided with a plurality of peaks that abut against the top foil and a plurality of valleys that abut against the housing; and a pair of clamping rings that are inserted into a shaft hole of the housing through which the rotating shaft penetrates, restrict movement of the return spring in an axial direction of the rotating shaft, and have a self-lubricating inner peripheral surface.

Description

Technical Field

[0001] This disclosure relates to gas bearing assemblies and turbochargers.

[0002] This application claims priority based on Japan Patent Application No. 2020-030469 filed with the Japan Patent Office on February 26, 2021, the contents of which are incorporated herein by reference. Background Technology

[0003] Patent Document 1 discloses a gas bearing device comprising: an annular top foil through which a freely rotatable cylindrical rotating shaft passes, and the inner circumferential surface of the top foil is spaced apart from the outer circumferential surface of the rotating shaft; a damping member disposed on the outer circumference of the top foil, which dampens vibrations in a direction intersecting the axis of the rotating shaft; and an annular outer shell disposed on the outer circumference of the damping member.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2020-122555

[0007] Summary of the Invention The problem to be solved by the invention

[0008] However, in the gas bearing device disclosed in Patent Document 1, if the rigidity of the damping component (return spring) is high, an air film cannot be formed between the rotating shaft and the top foil when the rotating shaft rotates at high speed, and mechanical losses may increase. On the other hand, if the rigidity of the damping component (return spring) is low, the rotating shaft cannot be supported to rotate at low speed.

[0009] This disclosure was created in view of the aforementioned problems, and its purpose is to provide a gas bearing device and a turbocharger that can reliably form a gas film between the rotating shaft and the top foil when the rotating shaft rotates at high speed and reliably support the rotating shaft as a rotatable component when the rotating shaft rotates at low speed.

[0010] Technical solutions for solving the problem

[0011] To achieve the above objectives, this disclosure provides a gas bearing device.

[0012] It uses gas as the working fluid to support the rotating shaft so that it can rotate, and includes:

[0013] A housing through which the rotating shaft passes;

[0014] An annular top foil is disposed inside the housing and around the outer periphery of the rotation axis;

[0015] A return spring is disposed between the top foil and the outer shell, and is provided with a plurality of peaks that abut against the top foil and valleys that abut against the outer shell;

[0016] A pair of retaining rings, which are inserted into a through-hole in the rotating shaft of the housing, restrict the movement of the return spring in the axial direction of the rotating shaft.

[0017] The inner circumferential surfaces of each pair of retaining rings are self-lubricating.

[0018] Invention Effects

[0019] According to the gas bearing device disclosed herein, because the inner circumferential surfaces of each pair of retaining rings are self-lubricating, the load on the rotating shaft does not need to be supported solely by the return spring during low-speed rotation of the rotating shaft, thus reducing the support stiffness of the return spring. Therefore, a gas film can be reliably formed between the rotating shaft and the top foil during high-speed rotation of the rotating shaft. Furthermore, by reducing the support stiffness of the return spring, during low-speed rotation of the rotating shaft, while the pair of retaining rings support the rotating shaft, the self-lubricating nature of the inner circumferential surfaces of the rotating shaft on each of the retaining rings allows the pair of retaining rings to reliably support the rotating shaft for rotation. Attached Figure Description

[0020] Figure 1 This is a longitudinal sectional view that schematically represents the structure of a turbocharger with a built-in gas bearing device.

[0021] Figure 2 It is a general representation Figure 1 The diagram shows a longitudinal sectional view of the structure of the gas bearing assembly.

[0022] Figure 3 It is a general representation Figure 2 The diagram shows a cross-sectional view of the structure of the gas bearing assembly.

[0023] Figure 4-1 is Figure 2 The front view of the circlip shown.

[0024] Figure 4-2 is a transverse sectional view (A-A sectional view) of the retaining ring shown in Figure 4-1.

[0025] Figure 5-1 is a schematic diagram (sectional view) showing the relationship between the retaining ring and the return spring, and it shows the state before the rotating shaft is set.

[0026] Figure 5-2 is a schematic diagram (sectional view) showing the relationship between the retaining ring and the return spring, and it is a diagram showing the state of the rotating shaft at low speed.

[0027] Figure 5-3 is a schematic diagram (sectional view) showing the relationship between the retaining ring and the return spring, and it is a diagram showing the state of the rotating shaft at medium speed.

[0028] Figure 6 This is a diagram used to illustrate the support stiffness of the return spring.

[0029] Figure 7-1 is a schematic diagram showing an example of a bimetallic return spring positioned between the top foil and the outer casing, representing the state at low temperature.

[0030] Figure 7-2 is a schematic diagram showing an example of a bimetallic return spring positioned between the top foil and the outer casing, representing the state at high temperatures. Detailed Implementation

[0031] Hereinafter, the gas bearing device and turbocharger of the embodiments will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, and relative arrangements of the constituent parts described in the embodiments or shown in the drawings are not intended to limit the scope of the invention, but are merely illustrative examples.

[0032] Figure 1 This is a longitudinal sectional view that schematically shows the structure of the turbocharger 1 incorporating the gas bearing device 10 of the embodiment.

[0033] The turbocharger 1, which incorporates the gas bearing assembly 10 of the embodiment, is mounted, for example, in an automotive engine. The turbocharger 1 is configured to include a turbine 3 that rotates in response to the flow of exhaust gas and a compressor 5 that compresses air by drawing in air through the rotation of the turbine 3. The turbine 3 has a turbine housing 31 and turbine blades 33 (turbine impellers) rotatably housed within the turbine housing 31, and the compressor 5 has a compressor housing 51 and an impeller 53 (compressor impeller) rotatably housed within the compressor housing 51.

[0034] The turbine housing 31 and the compressor housing 51 are respectively fixed to the bearing housing 71, which houses the gas bearing assembly 10, using fastening components (e.g., bolts). The turbine blades 33 and the impeller 53 are connected to each other by a rotating shaft 91 that passes through the bearing housing 71 (gas bearing assembly 10). Therefore, the turbine blades 33, the impeller 53, and the rotating shaft 91 are arranged on the same axis AXL. Moreover, the turbine blades 33 rotate, for example, by the exhaust gas discharged from the automobile engine, thereby rotating the impeller 53 via the rotating shaft 91 and compressing the gas supplied to the automobile engine.

[0035] For example, the turbine housing 31 is composed of a cylindrical portion 31a (shroud portion) that houses the turbine blades 33 and a vortex portion 31b that surrounds the portion of the cylindrical portion 31a on the side of the bearing housing 71. The vortex portion 31b has an exhaust gas inlet (not shown) and communicates with the cylindrical portion 31a via a throat portion 31c. An opening on the opposite side of the cylindrical portion 31a from the bearing housing 71 forms an exhaust gas outlet 31d.

[0036] An end wall 75 (turbine-side end wall) of the bearing housing 71 is fitted into the opening on the bearing housing 71 side of the turbine housing 31. The end wall 75 of the bearing housing 71 is fastened to one end of a cylindrical peripheral wall 73 (bearing housing body) by means of fastening components (e.g., bolts), forming a part (end wall 75) of the bearing housing 71. A sealing portion 751 is provided on the end wall 75, and a sealing hole is formed in the sealing portion 751 that passes through the center of the end wall 75. The rotating shaft 91 is disposed in the sealing portion 751.

[0037] For example, the compressor housing 51 is composed of a cylindrical portion 51a (shroud portion) that houses the impeller 53 and a vortex portion 51b that surrounds the bearing housing 71 side of the cylindrical portion 51a. The vortex portion 51b has an air supply outlet (not shown) and communicates with the cylindrical portion 51a via a diffuser portion 51c. An opening on the side of the cylindrical portion 51a opposite to the bearing housing 71 forms an air supply inlet 51d.

[0038] An end wall 77 (compressor-side end wall) of the bearing housing 71 is fitted into the opening on the bearing housing 71 side of the compressor housing 51. The end wall 77 of the bearing housing 71 is fastened to the other end of the peripheral wall 73 (bearing housing body) by means of fastening components (e.g., bolts), forming a part of the bearing housing 71 (end wall 77). An annular sealing portion 771 is fitted into the end wall 77. A through-center sealing hole is formed in the sealing portion 771, and the rotating shaft 91 is disposed within the sealing portion 771.

[0039] Inside the bearing housing 71, bearing portions 76 and 78 are respectively provided on the turbine-side end wall 75 and the compressor-side end wall 77, and bearing holes 761 and 781 are formed in each bearing portion 76 and 78. A gas bearing device 10 of this embodiment is disposed as a radial bearing in each bearing hole 761 and 781, and a rotating shaft 91 is disposed in each bearing hole 761 and 781 of each bearing portion 76 and 78 with the gas bearing device 10 passing through it.

[0040] The rotating shaft 91 has a pair of shaft portions 91a and 91b, an intermediate portion 91c, a turbine blade mounting portion 91d, and a compressor impeller mounting portion 91e. The pair of shaft portions 91a and 91b are disposed within the shaft holes of each bearing portion 76 and 78, respectively, while passing through each gas bearing assembly 10, and extend within the sealing portions 751 and 771. The intermediate portion 91c is located between the pair of shaft portions 91a and 91b, has a larger diameter than the pair of shaft portions 91a and 91b, and has a step at its boundary with the pair of shaft portions 91a and 91b. The turbine blade mounting portion 91d is located at the end of the turbine 3 side, has a smaller diameter than the shaft portion 91a, and has a step between it and the shaft portion 91a. The compressor impeller mounting portion 91e is located at the end of the compressor 5 side, is the same as the turbine blade mounting portion 91d, has a smaller diameter than the shaft portion 91b, and has a step between it and the shaft portion 91b.

[0041] The turbine blade 33 consists of a hub 33a and multiple blades 33b. The hub 33a has a rotationally symmetrical shape about an axis AXL. In the direction along the axis AXL, one end of the hub 33a is located on the exhaust gas outlet side, and the other end of the hub 33a is located on the bearing housing 71 side. The outer peripheral surface of the hub 33a has a flared shape that expands from one end to the other end, and the hub 33a has a back side on the other end that faces the bearing housing 71.

[0042] A mounting hole 33a1 is provided on the hub 33a, extending through the hub 33a along the axis AXL, and the mounting hole 33a1 is open at both ends of the hub 33a. Multiple blades 33b are integrally mounted on the outer circumferential surface of the hub 33a and are arranged at predetermined intervals in the circumferential direction of the hub 33a.

[0043] The impeller 53 consists of a hub 53a and multiple blades 53b. The hub 53a has a shape that is rotationally symmetrical about an axis AXL. In the direction along the axis AXL, one end of the hub 53a is located on the side of the air inlet 51d, and the other end of the hub 53a is located on the side of the bearing housing 71. The outer peripheral surface of the hub 53a has a flared shape that expands from one end to the other end, and the hub 53a has a back side on the other end that faces the bearing housing 71 (end wall 75).

[0044] A mounting hole 53a1 is provided on the hub 53a, extending through the hub 53a along the axis AXL, and the mounting hole 53a1 is open at both ends of the hub 53a. Multiple blades 53b are integrally mounted on the outer circumferential surface of the hub 53a and arranged at predetermined intervals in the circumferential direction of the hub 53a.

[0045] Figure 2 It is a general representation Figure 1 The longitudinal sectional view of the structure of the gas bearing device 10 shown is shown. Figure 3It is a general representation Figure 2 The diagram shows a transverse sectional view of the structure of the gas bearing device 10. Figure 4-1 is... Figure 2 The front view of the retaining rings 17 and 19 shown in Figure 4-2 is a transverse sectional view (A-A sectional view) of the retaining rings 17 and 19 shown in Figure 4-1.

[0046] like Figure 2 and Figure 3 As shown, the gas bearing device 10 is a bearing device that supports the rotating shaft 9 as a rotating part using gas as the working fluid. It includes a housing 11, a top foil 13, a return spring 15, and a pair of retaining rings 17 and 19.

[0047] The rotating shaft 9 passes through the outer casing 11. For example, the outer casing 11 is composed of the bearing portion 76 (78) described above, and the rotating shaft 9 is composed of the rotating shaft 91 described above.

[0048] The top foil 13 is an annular structure located inside the housing 11 and surrounding the outer periphery of the rotation axis 9.

[0049] The return spring 15 is disposed between the top foil 13 and the outer shell 11 (shaft hole), and is provided with a plurality of hills 15a that abut against the top foil 13 and valleys 15b that abut against the outer shell 11.

[0050] A pair of retaining rings 17 and 19 are embedded in the through-hole of the rotating shaft 9 of the housing 11, restricting the movement of the return spring 15 in the axial direction of the rotating shaft 9. The pair of retaining rings 17 and 19 are retaining rings for holes, embedded in the annular groove (circumferential groove) of the through-hole of the rotating shaft 9 of the housing 11, and are fixed by the elastic restoring force of the retaining rings 17 and 19. As shown in Figure 4, the pair of retaining rings 17 and 19 are partially cut-out annular rings, formed such that the outer and inner circumferences are at the same center, and tool holes 17a and 19a are provided at both ends of the cut. The inner circumferential surfaces 17b and 19b of each of the pair of retaining rings 17 and 19 are self-lubricating, for example, formed by a smooth surface.

[0051] Figure 5 is a schematic diagram (sectional view) showing the relationship between retaining rings 17 and 19 and return spring 15. Figure 5-1 shows the state before the rotating shaft 9 is installed. Figure 5-2 shows the state when the rotating shaft 9 rotates at low speed. Figure 5-3 shows the state when the rotating shaft 9 rotates at medium speed. Additionally, Figure 6 This is a diagram used to illustrate the support rigidity of the return spring 15. It should be noted that the top foil 13 is omitted in Figure 5, but the top foil 13 is a necessary structure, which does not mean that the top foil 13 is not a necessary structure.

[0052] As mentioned above, when the inner circumferential surfaces of the pair of retaining rings 17 and 19 are self-lubricating, as shown in Figure 5-2, it is not necessary to support the load of the rotating shaft 9 solely through the return spring 15, thus reducing the support stiffness of the return spring 15. Figure 6 As shown, the support stiffness of the return spring 15 is the ease with which the return spring 15 deforms, and is the reaction force (R) obtained by the rotating shaft 9 from the return spring 15.

[0053] In the gas bearing device 10 with reduced support rigidity of the return spring 15, as shown in Figure 5-1, before the rotating shaft 9 is installed, the height of the return spring 15's apex 15a is its natural length, and the height of the return spring 15's apex 15a is located inside the inner circumference of the retaining rings 17 and 19. As shown in Figure 5-2, with the rotating shaft 9 installed, the rotating shaft 9 is supported by the return spring 15 and the retaining rings 17 and 19, and the height of the return spring 15's apex 15a is at the same height as the inner circumference of the retaining rings 17 and 19. Even when the rotating shaft 9 rotates at low speed, the height of the return spring 15's apex 15a is at the same height as the inner circumference of the retaining rings 17 and 19, and the rotating shaft 9 is supported by the return spring 15 and the retaining rings 17 and 19. As shown in Figure 5-3, when the rotating shaft 9 rotates at medium speed, the rotating shaft 9 floats up from the inner circumference of the retaining rings 17 and 19, and the rotating shaft 9 is supported by the return spring 15. At this time, the height of the return spring 15 (mounta 15a) is located on the inner side of the inner circumference of the bi-rings 17 and 19.

[0054] According to this structure, an air film can be reliably formed between the rotating shaft 9 and the top foil 13 when the rotating shaft 9 rotates at high speed. In addition, by reducing the support stiffness of the return spring 15, when the rotating shaft 9 rotates at low speed, a pair of retaining rings 17 and 19 support the rotating shaft 9, but because the inner circumferential surfaces of the pair of retaining rings 17 and 19 are self-lubricating, the pair of retaining rings 17 and 19 can reliably support the rotating shaft 9 so that it can rotate.

[0055] For example, a pair of retaining rings 17 and 19 are made of self-lubricating materials.

[0056] Because the pair of retaining rings 17 and 19 are made of self-lubricating material, their inner circumferential surfaces are self-lubricating. Therefore, the support stiffness of the return spring 15 can be reduced.

[0057] For example, a pair of retaining rings 17 and 19 are made of synthetic resin. For example, synthetic resin is a high-performance resin known as engineering plastic, such as MC nylon, polyacetal (POM), etc.

[0058] According to this structure, a pair of retaining rings 17 and 19 are each made of synthetic resin.

[0059] For example, the return spring 15 is made of a spring whose support stiffness at high temperature is less than that at low temperature.

[0060] According to this structure, when the return spring 15 rotates at low speed (start-up) with the rotating shaft 9 at a low temperature, the supporting stiffness of the return spring 15 increases; when the return spring 15 rotates at high temperature with the rotating shaft 9 at a high temperature, the supporting stiffness of the return spring 15 decreases. Therefore, when the rotating shaft 9 rotates at low speed (start-up), the rotating shaft 9 is supported by the return spring 15, and when the rotating shaft 9 rotates at high speed, an air film is formed between the rotating shaft 9 and the top foil 13. Thus, an air film can be reliably formed when the rotating shaft 9 rotates at high speed, and the rotating shaft 9 can be reliably supported when rotating at low speed.

[0061] Figure 7 is a schematic diagram showing an example of a bimetallic return spring 15 disposed between the top foil 13 and the outer casing 11. Figure 7-1 shows the state at low temperature, and Figure 7-2 shows the state at high temperature.

[0062] As shown in Figure 7, the return spring 15 disposed between the top foil 13 and the outer casing 11 is, for example, a bimetallic structure formed by bonding two metal plates 151 and 153 with different coefficients of thermal expansion. In the example shown in Figure 7, the coefficient of thermal expansion of the metal plate 153 on the outer casing 11 side is greater than that of the metal plate 151 on the top foil 13 side, and the supporting stiffness of the return spring 15 is greater at high temperatures than at low temperatures.

[0063] This structure allows the support stiffness of the return spring 15 to be smaller at high temperatures than at low temperatures.

[0064] The present invention is not limited to the above-described embodiments, but also includes modifications to the above-described embodiments and appropriate combinations of these modifications.

[0065] The contents described in the above embodiments are as follows.

[0066] [1] provides a gas bearing device (10) in a manner that allows for the provision of a gas bearing device.

[0067] It uses gas as the working fluid to support the rotating shaft (9) so that it can rotate, wherein it has:

[0068] The outer casing (11) through which the aforementioned rotating shaft (9) passes;

[0069] An annular top foil (13) is disposed inside the outer casing (11) and surrounds the outer periphery of the rotation axis (9);

[0070] A return spring (15) is provided between the top foil (13) and the outer shell (11), and is provided with a plurality of hills (15a) that abut against the top foil (13) and valleys (15b) that abut against the outer shell (11);

[0071] A pair of retaining rings (17, 19) are inserted into the through-hole of the rotating shaft (9) of the housing (11), thereby restricting the movement of the return spring (15) in the axial direction of the rotating shaft (9).

[0072] The inner circumferential surfaces of the pair of retaining rings (17, 19) are self-lubricating.

[0073] According to this structure, because the inner circumferential surfaces of each pair of retaining rings (17, 19) are self-lubricating, the load on the rotating shaft (9) does not need to be supported solely by the return spring (15) when the rotating shaft (9) rotates at low speeds, thus reducing the support stiffness of the return spring (15). As a result, an air film can be reliably formed between the rotating shaft (9) and the top foil (13) when the rotating shaft (9) rotates at high speeds. In addition, by reducing the support stiffness of the return spring (15), when the rotating shaft (9) rotates at low speeds, the pair of retaining rings (17, 19) support the rotating shaft (9), but because the inner circumferential surfaces of each pair of retaining rings (17, 19) are self-lubricating, the pair of retaining rings (17, 19) can reliably support the rotating shaft (9) so that it can rotate.

[0074] [2] Another type of gas bearing device (10) is based on the gas bearing device (10) described in [1], wherein,

[0075] The pair of retaining rings (17, 19) mentioned above are made of self-lubricating materials.

[0076] According to this structure, since the pair of retaining rings (17, 19) are each made of a self-lubricating material, the inner circumferential surfaces of each pair of retaining rings (17, 19) are self-lubricating. Therefore, the support stiffness of the return spring (15) can be reduced.

[0077] [3] Another type of gas bearing device (10) is based on the gas bearing device (10) described in [1] or [2], wherein,

[0078] The aforementioned self-lubricating material is a synthetic resin.

[0079] According to this structure, a pair of retaining rings (17, 19) are each made of synthetic resin.

[0080] [4] Another type of gas bearing device (10) is the gas bearing device (10) described in any one of [1] to [3], wherein,

[0081] The aforementioned return spring (15) is composed of a spring whose support stiffness at high temperature is less than that at low temperature.

[0082] According to this structure, when the return spring (15) rotates at low speed (at startup) as the low-temperature rotating shaft (9), the supporting stiffness of the return spring (15) increases, and when the return spring (15) rotates at high speed as the high-temperature rotating shaft (9), the supporting stiffness of the return spring (15) decreases. Therefore, when the rotating shaft (9) rotates at low speed, the return spring (15) supports the rotating shaft (9), and when the rotating shaft (9) rotates at high speed, an air film is formed between the rotating shaft (9) and the top foil (13). Thus, an air film can be reliably formed between the rotating shaft (9) and the top foil (13) when the rotating shaft (9) rotates at high speed, and the rotating shaft (9) can be reliably supported when the rotating shaft (9) rotates at low speed.

[0083] [5] Another type of gas bearing device (10) is based on the gas bearing device (10) described in [4], wherein,

[0084] The aforementioned return spring (15) is a bimetallic structure made of two metal plates (151, 153) with different thermal expansion rates bonded together.

[0085] According to this structure, the support stiffness of the return spring (15) is smaller at high temperatures than at low temperatures.

[0086] [6] provides a turbocharger (1) in a manner that allows for the application of a turbocharger.

[0087] The gas bearing device (10) described in any one of [1] to [5] above is provided.

[0088] According to this structure, because the inner circumferential surfaces of each pair of retaining rings (17, 19) are self-lubricating, the supporting stiffness of the return spring (15) can be reduced. As a result, an air film can be reliably formed between the rotating shaft (9) and the top foil (13) when the rotating shaft (9) rotates at high speed. In addition, by reducing the supporting stiffness of the return spring (15), when the rotating shaft (9) rotates at low speed, the pair of retaining rings (17, 19) support the rotating shaft (9), but because the inner circumferential surfaces of each pair of retaining rings (17, 19) are self-lubricating, the pair of retaining rings (17, 19) can reliably support the rotating shaft (9) so that it can rotate.

[0089] Explanation of reference numerals in the attached figures

[0090] 1 turbocharger

[0091] 3 turbo

[0092] 31 Turbine Housing

[0093] 31a Cylinder Section (Protective Cover Section)

[0094] 31b Vortex section

[0095] 31c Throat

[0096] 31d exhaust gas outlet

[0097] 33 Turbine moving blades (turbine impeller)

[0098] 33a wheels

[0099] 33a1 mounting hole

[0100] 33b blade

[0101] 5 compressors

[0102] 51 Compressor Housing

[0103] 51a cylindrical section (protective cover section)

[0104] 51b vortex section

[0105] 51c diffuser section

[0106] 51d gas supply inlet

[0107] 53 Impeller (Compressor Impeller)

[0108] 53a wheels

[0109] 53a1 mounting hole

[0110] 53b blade

[0111] 71 Bearing Housing

[0112] 73. Peripheral wall (bearing housing body)

[0113] 75 End Wall (Turbine Side End Wall)

[0114] 751 Sealing Section

[0115] 76 bearing section

[0116] 761 bearing bore

[0117] 77 End Wall (Compressor Side End Wall)

[0118] 771 Sealing Section

[0119] 78 Bearing Section

[0120] 781 bearing bore

[0121] 9 rotating axes

[0122] 91 rotating axis

[0123] 91a and 91b shaft sections

[0124] 91c middle section

[0125] 91d turbine moving blade mounting section

[0126] 91e compressor impeller mounting section

[0127] 10 Gas Bearing Assembly

[0128] 11. Shell

[0129] 13 top foil

[0130] 15 Return Spring

[0131] 15a Mountain

[0132] 15b Valley

[0133] 151 and 153 metal plates

[0134] 17, 19 clasps

[0135] Holes for tools 17a and 19a

[0136] 17b, 19b inner circumferential surfaces

[0137] AXL axis

Claims

1. A gas bearing device that uses gas as the working fluid to support a rotating shaft so that it can rotate, wherein, have: A housing through which the rotating shaft passes; An annular top foil is disposed inside the housing and around the outer periphery of the rotation axis; A return spring is disposed between the top foil and the outer shell, and is provided with a plurality of peaks that abut against the top foil and valleys that abut against the outer shell; A pair of retaining rings, which are inserted into a through-hole in the rotating shaft of the housing, restrict the movement of the return spring in the axial direction of the rotating shaft. The pair of retaining rings are each a partially cut circular ring, with the outer and inner circumferences aligned at the same center, and tool holes are provided at both ends. The pair of retaining rings are each made of a self-lubricating synthetic resin. The inner circumferential surfaces of each pair of retaining rings are composed of smooth surfaces. When the rotating shaft rotates at low speed, the pair of retaining rings support the rotating shaft. When the rotating shaft rotates at high speed, an air film is formed in the circumferential direction of the rotating shaft between the inner circumferential surfaces of each of the pair of retaining rings and the outer circumferential surface of the rotating shaft.

2. The gas bearing device according to claim 1, wherein, The return spring is composed of a spring whose supporting stiffness at high temperature is less than that at low temperature.

3. The gas bearing device according to claim 2, wherein, The return spring is made of a bimetallic structure consisting of two metal plates with different coefficients of thermal expansion bonded together.

4. A turbocharger comprising a gas bearing device according to any one of claims 1 to 3.

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