Dynamic pressure gas bearing structure and turbo fluid machine

Abstract

The present invention provides a dynamic pressure gas bearing structure and a turbo-type fluid machine that can suppress wear on the bearing surface of a rotating body. [Solution] The dynamic pressure gas bearing structure comprises a rotating body and a dynamic pressure gas bearing that supports the rotating body. The dynamic pressure gas bearing has a bearing surface formed of a coating layer containing at least polyamide-imide. The rotating body has a bearing surface facing the bearing surface and formed of a metallic material. The bearing surface has grooves extending across its entire surface in a direction intersecting the rotational direction of the rotating body.

Description

Technical Field

[0006] , ,

[0007] , ,

[0001] The present invention relates to a hydrodynamic gas bearing structure and a turbo-type fluid machine.

Background Art

[0002] A foil bearing is known as a hydrodynamic gas bearing that supports a rotating body, which is the shaft of a turbo-type fluid machine (for example, Patent Document 1). The foil bearing floats and supports the rotating body by a fluid film such as an air film generated between the bearing surface of the foil bearing and the rotating body. Patent Document 1 discloses forming a coating on the bearing surface in order to improve the wear resistance and durability of the bearing surface of the foil bearing.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to make it easier for the fluid film to float the rotating body, the bearing surface of the foil bearing and the bearing surface of the rotating body may be subjected to a smoothing process. In a general smoothing process of a metal, the wear of the bearing surface of the rotating body cannot be sufficiently suppressed.

[0005] An object of the present invention is to provide a hydrodynamic gas bearing structure and a turbo-type fluid machine that can suppress wear of the bearing surface of a rotating body.

Means for Solving the Problems

[0006] The present invention provides the following hydrodynamic gas bearing structure and turbo-type fluid machine.

[0007] The dynamic pressure gas bearing structure comprises a rotating body and a dynamic pressure gas bearing supporting the rotating body, wherein the dynamic pressure gas bearing has a bearing surface formed of a coating layer containing at least polyamide-imide, and the rotating body has a bearing surface facing the bearing surface and formed of a metallic material, and the bearing surface has grooves extending over its entire surface in a direction intersecting the rotational direction of the rotating body.

[0008] In the aforementioned dynamic pressure gas bearing structure, the height Rvk of the protruding valley portion on the bearing surface is preferably 0.2 μm or more.

[0009] In the aforementioned dynamic pressure gas bearing structure, it is preferable that the load length ratio Mr1 of the bearing surface is 7% or less.

[0010] In the dynamic pressure gas bearing structure described above, the dynamic pressure gas bearing is a radial bearing that supports the rotating body in a direction perpendicular to the axial direction of the rotating body, facing the outer circumferential surface of the rotating body, and has a bearing surface. Preferably, the first bearing surface of the rotating body facing the bearing surface is made of a metallic material and has a linear groove extending across its entire surface in a direction intersecting the rotational direction of the rotating body.

[0011] In the aforementioned dynamic pressure gas bearing structure, it is preferable that the linear grooves include grooves that intersect the rotational direction and the axial direction across the entire surface of the first bearing surface.

[0012] In the dynamic pressure gas bearing structure described above, it is preferable that the first bearing surface has a plurality of linear grooves, and that the plurality of linear grooves intersect each other across the entire surface of the first bearing surface.

[0013] In the hydrodynamic gas bearing structure described above, the hydrodynamic gas bearing is a thrust bearing that supports the rotating body in the axial direction of the rotating body and has a bearing surface, wherein the second bearing surface of the rotating body facing the bearing surface is formed of a metallic material and has grooves extending over its entire surface in a direction intersecting the rotational direction of the rotating body, and preferably the grooves include at least one of grooves extending radially from the position of the axial center of the rotating body on the second bearing surface toward the outer circumference, grooves extending in a direction transverse to the second bearing surface, and grooves extending in a spiral direction.

[0014] In the aforementioned dynamic pressure gas bearing structure, the coating layer preferably further contains polytetrafluoroethylene.

[0015] In the aforementioned dynamic pressure gas bearing structure, the coating layer preferably further contains one or more inorganic additives selected from the group consisting of molybdenum disulfide, titanium oxide, and calcium fluoride.

[0016] In the aforementioned dynamic pressure gas bearing structure, it is preferable that the rotating body is made of the aforementioned metallic material.

[0017] In the aforementioned dynamic pressure gas bearing structure, the metallic material is preferably one or more selected from the group consisting of titanium, titanium alloys, and stainless steel.

[0018] The turbo-type fluid machine comprises a rotating body, an actuator that rotates integrally with the rotating body to pump fluid, a housing that houses the rotating body and the actuator, and a dynamic pressure gas bearing that rotatably supports the rotating body relative to the housing, wherein the dynamic pressure gas bearing has a bearing surface formed of a coating layer containing at least polyamide-imide, and the rotating body has a bearing surface facing the bearing surface and formed of a metallic material, and the bearing surface has grooves extending over its entire surface in a direction intersecting the rotational direction of the rotating body.

[0019] In the turbo-type fluid machine, the protrusion valley height Rvk of the bearing surface is preferably 0.2 μm or more.

[0020] In the turbo-type fluid machine, the load length ratio Mr1 of the bearing surface is preferably 7% or less.

[0021] In the turbo-type fluid machine, the hydrodynamic gas bearing is a radial bearing that faces the outer peripheral surface of the rotating body and supports the rotating body in a direction perpendicular to the axial direction of the rotating body, and has a bearing surface. The first bearing surface of the rotating body facing the bearing surface is formed of a metal-based material, and preferably has linear grooves extending in a direction intersecting the rotation direction of the rotating body over the entire surface.

[0022] In the turbo-type fluid machine, the hydrodynamic gas bearing is a thrust bearing that supports the rotating body in the axial direction of the rotating body and has a bearing surface. The second bearing surface of the rotating body facing the bearing surface is formed of a metal-based material, and has the grooves extending in a direction intersecting the rotation direction of the rotating body over the entire surface. The grooves preferably include at least one of a groove extending radially outward from the position of the axis of the rotating body on the second bearing surface, a groove extending in a direction crossing the second bearing surface, and a groove extending in a spiral direction.

[0023] In the turbo-type fluid machine, the hydrodynamic gas bearing is preferably a foil bearing.

[0024] In the turbo-type fluid machine, the metal-based material is preferably at least one selected from the group consisting of titanium alloys and stainless steels.

Advantages of the Invention

[0025] According to the present invention, a hydrodynamic gas bearing structure and a turbo-type fluid machine capable of suppressing wear of the bearing surface of a rotating body can be provided.

Brief Description of the Drawings

[0026] [Figure 1] It is a cross-sectional view showing a turbo compressor. [Figure 2] It is a cross-sectional view showing an enlarged part of the turbo compressor shown in FIG. 1. [Figure 3] It is a cross-sectional view showing an enlarged other part of the turbo compressor shown in FIG. 1. [Figure 4] It is a schematic diagram explaining an example of a groove on the bearing surface facing the radial foil bearing of the turbo compressor shown in FIG. 1. [Figure 5] It is a schematic diagram explaining an example of a groove on the bearing surface facing the thrust foil bearing of the turbo compressor shown in FIG. 1. [Figure 6] It is a schematic diagram explaining another example of a groove on the bearing surface facing the thrust foil bearing of the turbo compressor shown in FIG. 1. [Figure 7] It is a schematic diagram explaining yet another example of a groove on the bearing surface facing the thrust foil bearing of the turbo compressor shown in FIG. 1. [Figure 8] It is a schematic diagram explaining yet another example of a groove on the bearing surface facing the thrust foil bearing of the turbo compressor shown in FIG. 1. [Figure 9] It is a schematic diagram explaining yet another example of a groove on the bearing surface facing the thrust foil bearing of the turbo compressor shown in FIG. 1. [Figure 10] It is a cross-sectional view schematically showing an enlarged part of the rotating body and foil bearing of the turbo compressor shown in FIG. 1. [Figure 11] It is a cross-sectional view schematically explaining the state in which the coating layer of the foil bearing of the turbo compressor shown in FIG. 1 wears. [Figure 12] It is a perspective view schematically showing the friction and wear test (1). [Figure 13] It is a backscattered electron image obtained by observing the outer peripheral surface of the ring after the friction and wear test (1) of Test Example 1-1 with a scanning electron microscope. [Figure 14]This is a backscattered electron image of the outer surface of the ring after the friction and wear test (1) in Test Example 1-5, observed with a scanning electron microscope. [Figure 15] This is a backscattered electron image of the outer surface of the ring after the friction and wear test (1) in Test Example 1-7, observed with a scanning electron microscope. [Figure 16] This is a schematic perspective view of the friction and wear test (2). [Figure 17] This is a backscattered electron image of the outer surface of the ring after the friction and wear test (1) in Test Example 2-1, observed with a scanning electron microscope. [Figure 18] This is a backscattered electron image of the outer surface of the ring after the friction and wear test (1) in Test Example 2-9, observed with a scanning electron microscope. [Figure 19] This is a backscattered electron image of the outer surface of the ring after the friction and wear test (1) in Test Example 2-11, observed with a scanning electron microscope. [Figure 20] This is a backscattered electron image of the outer surface of the ring after the friction and wear test (1) in Test Example 3-1, observed with a scanning electron microscope. [Figure 21] These are SEM images of the coating layer of the block after the friction and wear test (1) of Test Example 1-1, observed with a scanning electron microscope. (a) is a backscattered electron image, and (b) is a secondary electron image. [Figure 22] These are SEM images of the coating layer of the block after the friction and wear test (1) of Test Example 1-5, observed with a scanning electron microscope. (a) is a backscattered electron image, and (b) is a secondary electron image. [Figure 23] These are SEM images of the coating layer of the block after the friction and wear test (1) of Test Example 1-7, observed with a scanning electron microscope. (a) is a backscattered electron image, and (b) is a secondary electron image. [Figure 24] These are SEM images of the coating layer of the block after the friction and wear test (1) of Test Example 2-1, observed with a scanning electron microscope. (a) is a backscattered electron image, and (b) is a secondary electron image. [Figure 25] These are SEM images of the coating layer of the block after the friction and wear test (1) of Test Example 2-9, observed with a scanning electron microscope. (a) is a backscattered electron image, and (b) is a secondary electron image. [Figure 26] These are SEM images of the coating layer of the block after the friction and wear test (1) of Test Example 2-11, observed with a scanning electron microscope. (a) is a backscattered electron image, and (b) is a secondary electron image. [Figure 27] These are SEM images of the coating layer of the block after the friction and wear test (1) of Test Example 3-1, observed with a scanning electron microscope. (a) is a backscattered electron image and (b) is a secondary electron image. [Figure 28] These are SEM images of the coating layer of the block after the friction and wear test (2) of Test Example 3-2, observed with a scanning electron microscope; (a) is a backscattered electron image and (b) is a secondary electron image. [Figure 29] These are SEM images of the coating layer of the block after the friction and wear test (2) of Test Example 3-3, observed with a scanning electron microscope; (a) is a backscattered electron image and (b) is a secondary electron image. [Figure 30] This is a backscattered electron image of the outer surface of the ring after the friction and wear test (1) in Test Example 1-3, observed with a scanning electron microscope. [Figure 31] This is a backscattered electron image of the outer surface of the ring after the friction and wear test (1) in Test Example 2-8, observed with a scanning electron microscope. [Figure 32] These are SEM images of the coating layer of the block after the friction and wear test (1) of Test Example 1-3, observed with a scanning electron microscope. (a) is a backscattered electron image, and (b) is a secondary electron image. [Figure 33] These are SEM images of the coating layer of the block after the friction and wear test (1) of Test Example 2-8, observed with a scanning electron microscope; (a) is a backscattered electron image and (b) is a secondary electron image. [Modes for carrying out the invention]

[0027] Embodiments of the present invention will be described below with reference to the drawings. In this specification, numerical ranges such as "x~y" include upper and lower limits unless otherwise specified, and represent numerical ranges of "x or greater and y or less".

[0028] In this embodiment, a turbo compressor is used as an example of a turbo-type fluid machine, and the dynamic pressure gas bearing structure is described in an example where it has a rotating body and a foil bearing which is a dynamic pressure gas bearing.

[0029] <Basic configuration of a turbo compressor> Figure 1 is a cross-sectional view showing a turbo compressor. Figures 2 and 3 are enlarged cross-sectional views showing a part of the turbo compressor shown in Figure 1. Figure 4 is a schematic diagram illustrating an example of grooves on the bearing surface facing the radial foil bearing of the turbo compressor shown in Figure 1. Figures 5 to 9 are schematic diagrams illustrating an example of grooves on the bearing surface facing the thrust foil bearing of the turbo compressor shown in Figure 1. Figure 10 is a schematic enlarged cross-sectional view showing a part of the rotating body and foil bearing of the turbo compressor shown in Figure 1. Figure 11 is a schematic cross-sectional view illustrating the wear of the coating layer of the foil bearing of the turbo compressor shown in Figure 1.

[0030] The turbo compressor 10 (turbo fluid machine) is installed in a fuel cell vehicle equipped with a fuel cell system 1. The fuel cell system 1 supplies oxygen and hydrogen to the onboard fuel cell to generate electricity. The turbo compressor 10 compresses the oxygen-containing air supplied to the onboard fuel cell.

[0031] (housing) As shown in Figure 1, the turbo compressor 10 is equipped with a housing 11. The housing 11 is made of metal, for example, an aluminum alloy. The housing 11 is cylindrical. The housing 11 includes a motor housing 12, a compressor housing 13, a turbine housing 14, a first plate 15, a second plate 16, and a third plate 17.

[0032] The motor housing 12 is cylindrical. The motor housing 12 has a plate-shaped end wall 12a and a peripheral wall 12b. The peripheral wall 12b extends cylindrically from the outer circumference of the end wall 12a. The first plate 15 is connected to the open end of the peripheral wall 12b of the motor housing 12, closing the opening of the peripheral wall 12b.

[0033] The motor chamber S1 is partitioned by the inner surface 121a of the end wall 12a of the motor housing 12, the inner circumferential surface 121b of the peripheral wall 12b, and the end surface 15a of the first plate 15 on the motor housing 12 side. An electric motor 18 is housed inside the motor chamber S1.

[0034] The first plate 15 has a first bearing retaining portion 20. The first bearing retaining portion 20 protrudes from the center of the end face 15a of the first plate 15 toward the electric motor 18. The first bearing retaining portion 20 is cylindrical.

[0035] A recess 15c with a bottom surface 15d is formed on the end face 15b of the first plate 15 opposite to the motor housing 12. The recess 15c is circular. The inside of the first bearing retainer 20 penetrates the first plate 15 and opens to the bottom surface 15d of the recess 15c. The axis of the recess 15c and the axis of the first bearing retainer 20 coincide.

[0036] The motor housing 12 has a second bearing retaining portion 22. The second bearing retaining portion 22 protrudes toward the electric motor 18 from the center of the inner surface 121a of the end wall 12a of the motor housing 12. The second bearing retaining portion 22 is cylindrical. The inside of the cylinder of the second bearing retaining portion 22 penetrates the end wall 12a of the motor housing 12 and opens to the outer surface 122a of the end wall 12a. The axis of the first bearing retaining portion 20 and the axis of the second bearing retaining portion 22 coincide.

[0037] As shown in Figure 2, the second plate 16 is connected to the end face 15b of the first plate 15. A shaft insertion hole 16a is formed in the center of the second plate 16. The shaft insertion hole 16a communicates with the recess 15c. The axis of the shaft insertion hole 16a coincides with the axis of the recess 15c and the axis of the first bearing retaining portion 20. The thrust bearing housing chamber S2 is partitioned by the end face 16b of the second plate 16 on the first plate 15 side and the recess 15c of the first plate 15.

[0038] The compressor housing 13 is cylindrical and has a circular air intake port 13a into which air is drawn. The compressor housing 13 is connected to the end face 16c of the second plate 16 opposite to the first plate 15. The axis of the air intake port 13a of the compressor housing 13 coincides with the axis of the shaft insertion hole 16a of the second plate 16 and the axis of the first bearing retaining portion 20. The air intake port 13a opens to the end face of the compressor housing 13 opposite to the second plate 16.

[0039] Between the compressor housing 13 and the end face 16c of the second plate 16, a first impeller chamber 13b, a discharge chamber 13c, and a diffuser passage 13d are formed. The first impeller chamber 13b communicates with the intake port 13a. The discharge chamber 13c extends around the axis of the intake port 13a, surrounding the first impeller chamber 13b. The diffuser passage 13d connects the first impeller chamber 13b and the discharge chamber 13c. The first impeller chamber 13b communicates with the shaft insertion hole 16a of the second plate 16.

[0040] As shown in Figure 3, the third plate 17 is connected to the outer surface 122a of the end wall 12a of the motor housing 12. A shaft insertion hole 17a is formed in the center of the third plate 17. The shaft insertion hole 17a communicates with the inside of the cylinder of the second bearing holder 22. The axis of the shaft insertion hole 17a coincides with the axis of the second bearing holder 22.

[0041] The turbine housing 14 is cylindrical and has a circular discharge port 14a for discharging air. The turbine housing 14 is connected to the end face 17b of the third plate 17 opposite to the motor housing 12. The axis of the discharge port 14a of the turbine housing 14 coincides with the axis of the shaft insertion hole 17a of the third plate 17 and the axis of the second bearing retaining portion 22. The discharge port 14a opens to the end face of the turbine housing 14 opposite to the third plate 17.

[0042] Between the turbine housing 14 and the end face 17b of the third plate 17, a second impeller chamber 14b, an intake chamber 14c, and a communication passage 14d are formed. The second impeller chamber 14b communicates with the discharge port 14a. The intake chamber 14c extends around the axis of the discharge port 14a, surrounding the second impeller chamber 14b. The communication passage 14d connects the second impeller chamber 14b and the intake chamber 14c. The second impeller chamber 14b communicates with the shaft insertion hole 17a of the third plate 17.

[0043] (Electric motor) The electric motor 18 comprises a cylindrical rotor 31 and a cylindrical stator 32. The rotor 31 is fixed to the rotating shaft 24a (described later). The stator 32 is fixed to the housing 11. The rotor 31 is positioned radially inward of the stator 32 and rotates integrally with the rotating body 24 (described later). The rotor 31 has a cylindrical rotor core 31a fixed to the rotating shaft 24a and a plurality of permanent magnets (not shown) provided on the rotor core 31a. The stator 32 surrounds the rotor 31. The stator 32 has a cylindrical stator core 33 fixed to the inner circumferential surface 121b of the peripheral wall 12b of the motor housing 12 and a coil 34 wound around the stator core 33. When current flows from a battery (not shown) to the coil 34, the rotating body 24 rotates integrally with the rotor 31. The electric motor 18 rotates at a speed of 100,000 rpm or more, for example, in the range of 100,000 to 120,000 rpm.

[0044] (Rotating body) As shown in Figure 1, a rotating body 24 is housed inside the housing 11. The rotating body 24 has a rotating shaft 24a as the shaft portion, a first support portion 24b, a second support portion 24c, and a third support portion 24d as a thrust collar. The rotating shaft 24a has a first end portion 24e, which is the end on the compressor housing 13 side, and a second end portion 24f, which is the end on the turbine housing 14 side.

[0045] The first support portion 24b is provided on the outer circumferential surface 240a of the rotating shaft 24a, near the first end portion 24e, and is located inside the cylinder of the first bearing retaining portion 20. The first support portion 24b is integrally formed with the rotating shaft 24a and protrudes annularly from the outer circumferential surface 240a of the rotating shaft 24a.

[0046] The second support portion 24c is provided on the outer circumferential surface 240a of the rotating shaft 24a, near the second end portion 24f, and is positioned inside the cylinder of the second bearing retaining portion 22. The second support portion 24c is cylindrical in shape and is fixed to the outer circumferential surface 240a of the rotating shaft 24a, protruding annularly from the outer circumferential surface 240a of the rotating shaft 24a. The second support portion 24c is rotatable integrally with the rotating shaft 24a.

[0047] The third support portion 24d is located in the thrust bearing housing chamber S2. The third support portion 24d is disc-shaped and is fixed to the outer circumferential surface 240a of the rotating shaft 24a, protruding annularly from the outer circumferential surface 240a of the rotating shaft 24a. The third support portion 24d is rotatable integrally with the rotating shaft 24a. The third support portion 24d is located at a position separated from the electric motor 18 in the axial direction of the rotating body 24 (hereinafter also simply referred to as the "axial direction").

[0048] A first impeller 25 (actuator) is connected to the first end 24e of the rotating shaft 24a. The first impeller 25 is positioned closer to the first end 24e than to the third support portion 24d on the rotating shaft 24a. The first impeller 25 is housed in the first impeller chamber 13b. A second impeller 26 is connected to the second end 24f of the rotating shaft 24a. The second impeller 26 is positioned closer to the second end 24f than to the second support portion 24c on the rotating shaft 24a. The second impeller 26 is housed in the second impeller chamber 14b. The housing 11 houses the first impeller 25, the second impeller 26, and the rotating body 24.

[0049] A first sealing member 27 is provided between the shaft insertion hole 16a of the second plate 16 and the rotating body 24. The first sealing member 27 suppresses air leakage from the first impeller chamber 13b toward the motor chamber S1. A second sealing member 28 is provided between the shaft insertion hole 17a of the third plate 17 and the rotating body 24. The second sealing member 28 suppresses air leakage from the second impeller chamber 14b toward the motor chamber S1. The first sealing member 27 and the second sealing member 28 are, for example, sealing rings.

[0050] The rotating body 24 is supported by a foil bearing 60 (described later) so as to be rotatable relative to the housing 11. The rotating body 24 has a bearing surface 24g (first bearing surface, second bearing surface) facing the bearing surface 60a (described later) and formed of a metallic material. The rotating body 24 may be formed of a material other than the bearing surface 24g, as long as at least the bearing surface 24g is formed of a metallic material, and the parts other than the bearing surface 24g may be formed of a material other than a metallic material, and may be formed of a metallic material different from the metallic material forming the bearing surface 24g. Examples of materials other than metallic materials include ceramics and resins. Alternatively, the entire rotating body 24 may be formed of a metallic material, and the metallic material of the surface that becomes the bearing surface 24g (each surface of the first to third support parts 24b to 24d) may be used as the bearing surface 24g. Examples of metallic materials forming the rotating body 24 or the bearing surface 24g include pure metals such as titanium; metallic alloys such as titanium alloys; nickel alloys; and alloy steels such as stainless steel and chromium-molybdenum steel. Examples of stainless steel include SUS. Since the rotating body 24 is preferably made of a material that is less susceptible to the magnetic field of the electric motor 18, the metallic material is preferably a material other than a ferromagnetic material, for example, an antiferromagnetic material, a paramagnetic material, or a diamagnetic material. Preferably, the metallic material is a metal or alloy containing titanium, and austenitic stainless steel such as austenitic SUS, and more preferably titanium or a titanium alloy.

[0051] The bearing surfaces 24g of the rotating body 24 have a first bearing surface 24g1 (bearing surface) in the first support portion 24b, a first bearing surface 24g1 (bearing surface) in the second support portion 24c, and a second bearing surface 24g2 (bearing surface) in the third support portion 24d (Figures 4 to 9), and all of these bearing surfaces 24g are formed of a metallic material. The first bearing surfaces 24g1 in the first support portion 24b and the second support portion 24c are surfaces that are rotatably supported by a pair of radial foil bearings 40 (described later). The two second bearing surfaces 24g2 in the third support portion 24d are surfaces that are rotatably supported by a pair of thrust foil bearings 30, 30 (described later).

[0052] The bearing surface 24g of the rotating body 24 has grooves extending over its entire surface in a direction intersecting the rotational direction of the rotating body 24. The grooves only need to have a portion extending in a direction intersecting the rotational direction of the rotating body 24; the entire groove may extend in a direction intersecting the rotational direction of the rotating body 24, or a part of the groove may extend in a direction intersecting the rotational direction of the rotating body 24. In a plan view of the bearing surface 24g, the grooves may be linear, curved, a combination of these shapes, or a mixture of linear and curved grooves may be present. The grooves may be continuous over the entire surface of the bearing surface 24g, or intermittently over the entire surface of the bearing surface 24g, or multiple grooves may be formed over the entire surface of the bearing surface 24g, or a mixture of these may be present. The grooves formed on the bearing surface 24g may intersect each other. Having grooves over the entire surface means that grooves are evenly formed over the entire surface of the bearing surface 24g.

[0053] For example, as shown in Figure 4, the first bearing surface 24g1 may have linear grooves 81 extending across its entire surface in a direction intersecting the rotation direction Dr of the rotating body 24. Having linear grooves 81 across the entire surface means that linear grooves 81 are formed evenly across the entire surface of the first bearing surface 24g1. Preferably, the first bearing surface 24g1 has multiple linear grooves 81 formed across its entire surface. The multiple linear grooves 81 do not have to intersect each other, or they may intersect each other. The linear grooves 81 may be formed continuously around the circumferential direction of the rotating body 24, or they may be formed intermittently, or a mixture of these may be present.

[0054] The linear groove 81 only needs to extend so as to intersect the rotational direction Dr, and the smaller of the angles between the linear groove 81 and the rotational direction Dr is, for example, 1° or more, may be 2° or more, may be 5° or more, preferably 10° or more, more preferably 30° or more, may be 40° or more, may be 90°, may be 90° or less, may be 5° or more but less than 90°, may be 10 to 80°, or may be 30 to 60°.

[0055] The linear grooves 81 preferably include grooves that intersect the rotational direction Dr and the axial direction Da across the entire surface of the first bearing surface 24g1. More preferably, the linear grooves 81 include grooves that intersect the rotational direction Dr and the axial direction Da across the entire surface of the first bearing surface 24g1 and intersect each other. Even more preferably, the linear grooves 81 include grooves with a diagonal pattern across the entire surface of the first bearing surface 24g1 (Figure 4).

[0056] The first bearing surface 24g1, in a plan view, may have, in addition to the straight groove 81, at least one of the following: a curved groove, a groove with a shape combining a straight and a curve, and a straight groove parallel to the rotational direction Dr.

[0057] As shown in Figures 5 to 9, since the third support portion 24d is disc-shaped, the second bearing surface 24g2 is circular. The direction of rotation of the rotating body 24 is in the direction of drawing a ring on the plane of the second bearing surface 24g2 (Figures 5 to 9). The second bearing surface 24g2 can have grooves extending across its entire surface in a direction intersecting the direction of rotation of the rotating body 24. Examples of such grooves include, as shown in Figures 5 and 6, grooves 82 extending radially from the axis of the rotating body 24 outward on the second bearing surface 24g2 (hereinafter also referred to as "radial grooves 82"); as shown in Figures 7 and 8, grooves 83 extending in a direction transverse to the second bearing surface 24g2 (hereinafter also referred to as "transverse grooves 83"); as shown in Figure 9, grooves 84 extending in a spiral direction (hereinafter also referred to as "spiral grooves 84"); and grooves extending in a ring-like direction (hereinafter also referred to as "first annular grooves") which are not shown. The second bearing surface 24g2 preferably has at least one of the radial grooves 82, transverse grooves 83, and spiral grooves 84 over its entire surface. Having at least one of the radial grooves 82, transverse grooves 83, and spiral grooves 84 over its entire surface means that grooves are evenly formed over the entire surface of the second bearing surface 24g2.

[0058] When radial grooves 82 are formed on the second bearing surface 24g2 (Figures 5 and 6), it is preferable that multiple radial grooves 82 are formed over the entire surface of the second bearing surface 24g2. The multiple radial grooves 82 do not have to intersect each other, or they may intersect each other. The radial grooves 82 may be straight (Figure 5), curved (Figure 6), or a combination of these. The radial grooves 82 may extend over the entire second bearing surface 24g2 from the axis of the rotating body 24 to the outer circumference, or they may extend over a part of it, or a combination of these. The radial grooves 82 may be formed continuously from the axis of the rotating body 24 to the outer circumference on the second bearing surface 24g2, or they may be formed intermittently, or a combination of these.

[0059] When transverse grooves 83 are formed on the second bearing surface 24g2 (Figures 7 and 8), it is preferable that multiple transverse grooves 83 are formed across the entire surface of the second bearing surface 24g2. The multiple transverse grooves 83 do not have to intersect each other, or they may intersect each other. The transverse grooves 83 may be straight, curved, or a combination of these. The transverse grooves 83 only need to extend along the direction traversing the second bearing surface 24g2, and may or do not traverse the entire second bearing surface 24g2. The transverse grooves 83 may be formed continuously, intermittently, or a mixture of these along the direction traversing the second bearing surface 24g2.

[0060] If a spiral groove 84 is formed on the second bearing surface 24g2, there may be one spiral groove 84 or multiple spiral grooves 84. Multiple spiral grooves 84 may or may not intersect each other. One spiral groove 84 may have a portion that partially intersects with the others. The spiral shape of the spiral groove 84 may be formed only of curves, only of straight lines, or a combination of curves and straight lines. The spiral grooves 84 may be formed continuously, intermittently, or a mixture of both.

[0061] When a first annular groove is formed on the second bearing surface 24g2, it is preferable that a plurality of first annular grooves are formed over the entire surface of the second bearing surface 24g2. The plurality of first annular grooves do not have to intersect each other, or they may intersect each other. The plurality of first annular grooves may be formed concentrically. The first annular grooves may extend partially along at least a part of the ring, may extend continuously along the entire ring, or may extend intermittently along at least a part of the ring. The shape of the ring is not particularly limited and examples include circular and elliptical shapes.

[0062] The second bearing surface 24g2 may have, in addition to at least one of the radial grooves 82, transverse grooves 83, spiral grooves 84, and the first annular groove described above, a groove that does not intersect with the rotational direction of the rotating body 24. This groove may be, for example, a groove 85 (hereinafter also referred to as the "second annular groove 85") that extends along the rotational direction of the rotating body 24, as shown in Figure 8. The second annular groove 85 may extend partially along at least a part of the ring, continuously along the entire ring, or intermittently along at least a part of the ring. The shape of the ring is not particularly limited and examples include circular and elliptical shapes. The second annular groove 85 may be formed to intersect with the transverse groove 83, as shown in Figure 8.

[0063] The height Rvk of the protruding valley portion of the bearing surface 24g is preferably 0.2 μm or more, but may be 0.3 μm or more, 0.5 μm or more, 0.7 μm or more, or 1.0 μm or more. The height Rvk of the protruding valley portion of the bearing surface 24g is preferably 0.2 to 1.9 μm, but may be 0.2 to 1.7 μm, 0.3 to 1.6 μm, 0.4 to 1.6 μm, 0.4 to 1.0 μm, or 0.5 to 0.9 μm.

[0064] The load length ratio Mr1 of the bearing surface 24g is, for example, 10.5% or less, may be 10% or less, 9% or less, 8% or less, preferably 7% or less, may be 6.8% or less, or may be 6.5% or less. The load length ratio Mr1 of the bearing surface 24g is, for example, 2 to 10.5%, may be 2 to 10%, may be 3 to 9%, may be 3 to 8%, preferably 4 to 7%, may be 4 to 6.8%, or may be 4 to 6.5%.

[0065] The load length ratio Mr2 of the bearing surface 24g is, for example, 90% or less, may be 88% or less, may be 86% or less, preferably 84% or less, may be 82% or less, may be 80% or less, or may be 79% or less. The protruding valley height Rvk of the bearing surface 24g is, for example, 70-90%, may be 70-88%, preferably 70-86%, may be 72-84%, may be 73-82%, may be 75-80%, or may be 76-79%.

[0066] The height Rvk of the protruding valley and the load length ratios Mr1 and Mr2 are specified in JIS B 0671-2 (2002) and are defined as follows: A load curve (vertical axis: height, horizontal axis: load length ratio) is obtained from the shape curve measured on the bearing surface 24g, and the equivalent line is defined as the straight line with the gentlest slope of the secant line passing through two points on the load curve where the difference in load length ratio is 40%. The core is defined as the area between the two height positions where the equivalent line intersects the vertical axis at the positions where the horizontal axis is 0% and 100%. In the shape curve, the average depth of the protruding peak above the core is Rpk, and the average depth of the protruding valley below the core is Rvk. The load length ratio at the intersection of the separation line between the peak and the core and the shape curve is Mr1, and the load length ratio at the intersection of the separation line between the valley and the core and the shape curve is Mr2. Therefore, the protruding valley height Rvk represents the average depth of the protruding valleys on the bearing surface 24g, the load length ratio Mr1 is an index representing the proportion of the bearing surface 24g occupied by the protruding peaks, and the load length ratio Mr2 is an index representing the proportion of the bearing surface 24g occupied by the protruding valleys.

[0067] In this specification, the protruding valley height Rvk and the load length ratios Mr1 and Mr2 refer to the values ​​measured by the following procedure. A sample is prepared to measure the protruding valley height Rvk and the load length ratios Mr1 and Mr2, and 3D shape data is measured in a field of view of 290 μm horizontally × 230 μm vertically observed at a magnification of 1000x. In the same sample, 3D shape data is measured in 2 to 5 fields of view using the above procedure, changing the observation location. In each field of view, 60 shape curves are obtained in a direction perpendicular to the direction in which friction occurs. The protruding valley height Rvk and the load length ratios Mr1 and Mr2 are determined for each shape curve. The protruding valley height Rvk and the load length ratios Mr1 and Mr2 obtained from each shape curve in each field of view are averaged, and these average values ​​are taken as the protruding valley height Rvk and load length ratios Mr1 and Mr2 of the bearing surface 24g of the sample. When acquiring the shape curve, no high-pass or low-pass filter correction will be applied.

[0068] The bearing surface 24g is preferably a polished surface. The direction in which the grooves extend on the bearing surface 24g, the height Rvk of the protruding valleys, and the load length ratios Mr1 and Mr2 can be adjusted by the grinding method and grinding conditions when forming the bearing surface 24g.

[0069] For example, the first bearing surface 24g1, which is rotatably supported by a radial foil bearing 40 (described later), is preferably a ground surface obtained by grinding by moving a cylindrical member for forming a rotating body 24 axially while moving a grinding wheel (hereinafter also referred to as the "traverse grinding method"). In the traverse grinding method, the angle of the linear groove 81 can be adjusted by adjusting the ratio of the moving speed of the cylindrical member to the feed speed of the grinding wheel. In the traverse grinding method, the direction in which the groove extends on the first bearing surface 24g1, the protruding valley height Rvk, and the load length ratios Mr1 and Mr2 can be adjusted by adjusting the grit size of the grinding wheel and the pressing pressure of the grinding wheel.

[0070] For example, on the second bearing surface 24g2, which is rotatably supported by thrust foil bearings 30, 30 (described later), a transverse groove 83 (Figure 7) can be formed by grinding a cylindrical member for forming the rotating body 24 with a grinding wheel in one direction without rotating the cylindrical member. A second annular groove 85 (Figure 8) can be formed by grinding a cylindrical member for forming the rotating body 24 with a grinding wheel while rotating the cylindrical member in the rotational direction. When forming the second annular groove 85, a transverse groove 83 (Figure 8) can also be formed by moving the grinding wheel radially from the axis of the rotating body 24 toward the outer circumference on the second bearing surface 24g2. Radial grooves 82 (Figures 5, 6) and spiral grooves 84 (Figure 9) can also be formed by adjusting the rotation of the cylindrical member and the movement of the grinding wheel. In these grinding methods, a tape (film) coated with abrasive grains may be used instead of a grinding wheel. By adjusting the grit size of the grinding wheel, the size of the abrasive grains, and the pressing pressure of the grinding wheel and tape, the direction in which the grooves extend on the first bearing surface 24g1, the height Rvk of the protruding valleys, and the load length ratios Mr1 and Mr2 can be adjusted.

[0071] The grinding method for forming the bearing surface 24g is not particularly limited, but in addition to the traverse grinding method described above, examples include the grinding wheel grinding method, in which a grinding wheel is pressed against the surface to be polished and grinding is performed; the tape polishing method, in which a tape (or film) coated with the above-mentioned abrasive grains is pressed against the surface to be polished and polishing is performed; and combinations thereof. In the grinding wheel grinding method and the tape polishing method, the tape and grinding wheel may be vibrated while polishing so that the above-mentioned grooves are formed, the cylindrical member for forming the rotating body 24 may be vibrated while grinding is performed, or the tape, grinding wheel, and cylindrical member may be polished without vibration.

[0072] The bearing surface 24g having the grooves described above can be manufactured, for example, as follows: Prepare a cylindrical member for forming a rotating body 24, wherein the surface on which the bearing surface 24g of the rotating body 24 is formed is made of a metallic material. Next, using the grinding wheel or tape described above, the surface of the metallic material of the cylindrical member is ground while adjusting the grinding method and grinding conditions as described above to form a bearing surface 24g having grooves of the desired shape.

[0073] The cylindrical member is a cylindrical member made of a metallic material when the entire rotating body 24 is made of a metallic material. When the bearing surface 24g of the rotating body 24 is made of a metallic material, and the parts other than the bearing surface 24g are made of a material other than a metallic material, the cylindrical member only needs to have a surface on which the bearing surface 24g is formed made of a metallic material, and the parts other than said surface may be made of a material other than a metallic material. Examples of metallic materials that constitute the cylindrical member and the surface on which the bearing surface 24g of the cylindrical member is formed include the metallic materials described for the rotating body 24 and the bearing surface 24g.

[0074] The traverse grinding method, grinding wheel grinding method, and tape polishing method described above may be applied to the bearing surface 24g of the cylindrical member, but may also be applied to other surfaces of the cylindrical member.

[0075] (Foil bearing) The turbo compressor 10 has a plurality of foil bearings 60 (dynamic gas bearings) that rotatably support the rotating body 24 relative to the housing 11. Each foil bearing 60 is not a so-called oil-lubricated bearing, but a dynamic air bearing (dynamic gas bearing) in which air is introduced as a fluid (gas) lubricant into the gap between the bearing surface 60a (described later) and the bearing surface 24g, and the load is supported by the dynamic pressure generated in the gap. The rotating body 24 and the foil bearings 60 constitute a dynamic gas bearing structure. The plurality of foil bearings 60 include a pair of thrust foil bearings 30, 30 (thrust bearings) and a pair of radial foil bearings 40, 40 (radial bearings). The pair of thrust foil bearings 30, 30 are bearings that support the rotating body 24 in the axial direction, and support the third support portion 24d of the rotating body 24 in the axial direction of the rotating body 24. The pair of radial foil bearings 40, 40 are bearings that support the rotating body 24 in a direction perpendicular to the axial direction, and support the first support portion 24b and the second support portion 24c of the rotating body 24 so that they can rotate relative to the housing 11 in a direction perpendicular to the axial direction of the rotating body 24.

[0076] A pair of thrust foil bearings 30, 30 are arranged in a thrust bearing housing chamber S2. The pair of thrust foil bearings 30, 30 are positioned to sandwich a third support portion 24d, which acts as a thrust collar. The pair of thrust foil bearings 30, 30 face the third support portion 24d in the axial direction of the rotating body 24. One thrust foil bearing 30 is positioned on the first end 24e side of the rotating shaft 24a relative to the third support portion 24d. The other thrust foil bearing 30 is positioned on the second end 24f side of the rotating shaft 24a relative to the third support portion 24d.

[0077] As shown in Figure 2, the end face of the rotating shaft 24a on the first end 24e side of the third support portion 24d is the bearing surface 24g that is axially supported by one of the thrust foil bearings 30. The thrust foil bearing 30 has a bearing surface 60a that faces this bearing surface 24g. Similarly, the end face of the rotating shaft 24a on the second end 24f side of the third support portion 24d is the bearing surface 24g that is axially supported by the other thrust foil bearing 30. The other thrust foil bearing 30 has a bearing surface 60a that faces this bearing surface 24g.

[0078] As shown in Figures 2 and 3, one radial foil bearing 40 is located within a first bearing holder 20, and the other radial foil bearing 40 is located within a second bearing holder 22. Within the first bearing holder 20, the first support portion 24b of the rotating body 24 is rotatably supported by one of the radial foil bearings 40. The outer circumferential surface of the first support portion 24b is the bearing surface 24g supported by one of the radial foil bearings 40 in a direction perpendicular to the axial direction. One of the radial foil bearings 40 has a bearing surface 60a facing this bearing surface 24g. Similarly, within the second bearing holder 22, the second support portion 24c of the rotating body 24 is rotatably supported by the other radial foil bearing 40. The outer circumferential surface of the second support portion 24c is the bearing surface 24g supported by the other radial foil bearing 40 in a direction perpendicular to the axial direction. The other radial foil bearing 40 has a bearing surface 60a that faces the bearing surface 24g.

[0079] As shown in Figure 10, the bearing surfaces 60a of each foil bearing 60, i.e., the bearing surfaces 60a of each thrust foil bearing 30, 30 and the bearing surfaces 60a of each radial foil bearing 40, 40, are each formed with a coating layer 61. The coating layer 61 is formed to improve the wear resistance and durability of the bearing surfaces 60a. The coating layer 61 contains at least polyamide-imide (PAI). PAI is used as a resin binder 61a. Preferably, the coating layer 61 further contains polytetrafluoroethylene (PTFE). In addition to PAI, or in addition to PAI and PTFE, the coating layer 61 may contain one or more inorganic additives 61b selected from the group consisting of molybdenum disulfide (MoS2), titanium oxide (TiO2), and calcium fluoride (CaF2). PTFE and MoS2 are used as solid lubricants, and TiO2 and CaF2 are used as reinforcing agents.

[0080] The PTFE content in each coating layer 61 may be 1 to 150 parts by mass, 20 to 120 parts by mass, or 40 to 80 parts by mass per 100 parts by mass of PAI. The MoS2 content in the coating layer 61 may be 1 to 200 parts by mass, 20 to 150 parts by mass, or 40 to 120 parts by mass per 100 parts by mass of PAI.

[0081] The coating layer 61 can be formed by known methods such as application using a spray, brush, knife, or applicator, or by screen printing. The coating layer 61 may be formed before or after the molding process of the foil bearing 60. Furthermore, the coating layer 61 may or may not be polished after formation.

[0082] The foil bearing 60 can employ the basic configuration of a so-called dynamic pressure gas bearing. For example, the foil bearing 60 may have a top foil having a bearing surface 60a, and a bump foil having a corrugated shape that elastically supports the top foil. When the rotating body 24 is rotating at a low speed until its rotational speed reaches the levitation speed, the foil bearing 60 supports the rotating body 24 as it rotates relative to the bearing surface 24g with the bearing surface 60a in contact with the bearing surface 24g. When the rotating body 24 rotates at high speed and reaches the levitation speed, the bearing surface 60a and the bearing surface 24g are not in contact, and the rotating body 24 is supported by the air film generated in the bearing gap 60b between the bearing surface 60a and the bearing surface 24g. In this specification, the state in which the bearing surface 60a and the bearing surface 24g are in contact means the state in which the coating layer 61 of the bearing surface 60a and the bearing surface 24g are in contact.

[0083] (cooling passage) As shown in Figures 1 to 3, a cooling passage 50 is formed in the housing 11. Air flows as a fluid through the cooling passage 50. The cooling passage 50 is formed across the second plate 16, the first plate 15, the motor housing 12, and the third plate 17. The cooling passage 50 has a first passage 51 and a second passage 52.

[0084] The first passage 51 is provided in the second plate 16. The first passage 51 has an inlet 51a provided on the side wall surface of the second plate 16. The branch passage L3 connects the supply passage L1 and the inlet 51a of the first passage 51. The first passage 51 is in communication with the motor chamber S1 via the thrust bearing housing chamber S2 and one of the radial foil bearings 40.

[0085] The second passage 52 is provided in the third plate 17. The second passage 52 has an outlet 52a provided on the side end face of the third plate 17. The second passage 52 is in communication with the motor chamber S1 via the other radial foil bearing 40.

[0086] (Fuel cell system) As described above, the turbo compressor 10 constitutes part of the fuel cell system 1. In addition to the turbo compressor 10, the fuel cell system 1 includes a fuel cell stack 100 as an on-board fuel cell, a supply channel L1, a discharge channel L2, and a branch channel L3. The fuel cell stack 100 is composed of multiple fuel cells. The supply channel L1 connects the discharge chamber 13c to the fuel cell stack 100. The discharge channel L2 connects the fuel cell stack 100 to the intake chamber 14c. An intercooler 110 is provided in the middle of the branch channel L3, which branches off from the supply channel L1. The intercooler 110 cools the air flowing through the branch channel L3.

[0087] <Operation of Turbo Compressors and Fuel Cell Systems> The turbo compressor 10 and fuel cell system 1 configured as described above operate as follows.

[0088] As the rotating body 24 rotates integrally with the rotor 31, the first impeller 25 and the second impeller 26 rotate integrally with the rotating body 24. As a result, air drawn in from the intake port 13a is compressed by the first impeller 25 in the first impeller chamber 13b, passes through the diffuser passage 13d, and is discharged from the discharge chamber 13c. The air discharged from the discharge chamber 13c is supplied to the fuel cell stack 100 via the supply passage L1. The air supplied to the fuel cell stack 100 is used to generate electricity in the fuel cell stack 100, and then discharged to the discharge passage L2 as exhaust from the fuel cell stack 100. The exhaust from the fuel cell stack 100 is drawn into the intake chamber 14c via the discharge passage L2. The exhaust from the fuel cell stack 100 drawn into the intake chamber 14c is discharged to the second impeller chamber 14b via the communication passage 14d. The exhaust from the fuel cell stack 100 discharged into the second impeller chamber 14b causes the second impeller 26 to rotate. The rotating body 24 rotates not only due to the drive of the electric motor 18, but also due to the rotation of the second impeller 26, which is rotated by the exhaust from the fuel cell stack 100. Therefore, the first impeller 25 (actuator) rotates integrally with the rotating body 24 and also pumps air as an external fluid. The exhaust from the fuel cell stack 100 discharged into the second impeller chamber 14b is discharged to the outside from the discharge port 14a.

[0089] While the turbo compressor 10 is operating, a portion of the air flowing through the supply channel L1 toward the fuel cell stack 100 flows into the first passage 51 via the branch channel L3. The air flowing into the first passage 51 is cooled air that has been cooled by the intercooler 110 while flowing through the branch channel L3. The cooled air that has flowed into the first passage 51 flows into the thrust bearing housing chamber S2.

[0090] The cooling air that flows into the thrust bearing housing chamber S2 flows mainly from the inner circumference to the outer circumference through one of the thrust foil bearings 30. Subsequently, the cooling air that has passed radially outside the third support portion 24d flows mainly from the outer circumference to the inner circumference through the other thrust foil bearing 30.

[0091] The cooling air that has passed through the thrust bearing housing chamber S2 flows into the motor chamber S1 via one of the radial foil bearings 40. The air that has flowed into the motor chamber S1 passes, for example, between the rotor 31 and the stator 32, flows into the second passage 52 via the other radial foil bearing 40, and is discharged from the outlet 52a.

[0092] In this way, the electric motor 18, the pair of thrust foil bearings 30, 30, and the pair of radial foil bearings 40, 40 are directly cooled by the cooling air as it flows through the cooling passage 50.

[0093] In the turbo compressor 10, the rotating body 24 rotates integrally with the rotor 31. At this time, during low-speed rotation until an air film is formed in the bearing gap between the bearing surface 60a and the bearing surface 24g, that is, until the rotational speed of the rotating body 24 reaches the levitation speed, the bearing surface 60a and the bearing surface 24g slide in contact with each other. During high-speed rotation when the rotational speed of the rotating body 24 reaches the levitation speed, the air film that forms in the bearing gap 60b between the bearing surface 60a and the bearing surface 24g causes the bearing surface 60a and the bearing surface 24g to be in a non-contact state, and the rotating body 24 is supported by this air film.

[0094] When the rotating body 24 rotates at a low speed, a portion of the coating layer 61 on the bearing surface 60a is scraped off due to the initial wear caused by the sliding, and the PAI in the coating layer 61 is transferred to the bearing surface 24g (Figure 11). It is presumed that a film of transferred particles 61c is formed on the bearing surface 24g by the PAI transferred to the bearing surface 24g (hereinafter also referred to as "transferred particles 61c"). This film reduces the frictional force when the bearing surface 60a and the bearing surface 24g slide against each other after the initial wear, thereby suppressing wear of the metallic material forming the bearing surface 24g. In addition, it is possible to suppress damage to the coating layer 61 and increase the surface roughness caused by wear particles from the metallic material, thus improving the durability of the coating layer 61.

[0095] As described above, the bearing surface 24g of the rotating body 24 has grooves extending in a direction intersecting the rotational direction of the rotating body 24 over its entire surface. Therefore, the transferred particles 61c are easily transferred to the bearing surface 24g. Furthermore, even if the transferred particles 61c move in the rotational direction due to the high-speed rotation of the rotating body 24, they are likely to get caught in the grooves extending in a direction intersecting the rotational direction, and it is presumed that a coating is easily formed on the bearing surface 24g. This coating reduces the frictional force when the bearing surface 60a and the bearing surface 24g slide against each other after initial wear, thereby suppressing wear of the metallic material forming the bearing surface 24g. In addition, it is possible to suppress damage to the coating layer 61 and increase the surface roughness caused by wear particles of the metallic material, thus improving the durability of the coating layer 61.

[0096] When the first bearing surface 24g1 includes linear grooves 81, a coating is more easily formed on the first bearing surface 24g1. When the entire surface of the first bearing surface 24g1 includes grooves that intersect with each other in the rotational direction Dr and the axial direction Da, or grooves with a diagonal pattern, the transferred particles 61c become more easily caught, which makes it easier to suppress wear on the first bearing surface 24g1 and improves the durability of the coating layer 61.

[0097] As described above, the second bearing surface 24g2 also has grooves extending across its entire surface in a direction intersecting the rotational direction of the rotating body 24. Therefore, even if the transferred particles 61c move in the rotational direction of the second bearing surface 24g2 as the rotating body 24 rotates at high speed, they are likely to get caught in these grooves, and a coating is likely to form on the second bearing surface 24g2. This makes it easier to suppress wear on the second bearing surface 24g2 and improve the durability of the coating layer 61.

[0098] By keeping the height Rvk of the protruding valleys of the bearing surface 24g, and the load length ratios Mr1 and Mr2 within the above-mentioned range, wear of the metallic material forming the bearing surface 24g is easily suppressed, and wear of the coating layer 61 is also suppressed, thereby improving durability.

[0099] The coating layer 61 may contain PTFE as described above. When PTFE is present in the coating layer 61, the PTFE particles transferred due to initial wear can also adhere to the bearing surface 24g and form a film. Since the PTFE film is slippery and easily achieves low friction, the frictional force when the bearing surface 60a and the bearing surface 24g slide against each other after initial wear is reduced. This suppresses wear of the metallic material forming the bearing surface 24g, and also suppresses wear of the coating layer 61.

[0100] As described above, the coating layer 61 may contain one or more inorganic additives selected from the group consisting of MoS2, TiO2, and CaF2. The inorganic additives have lower toughness and are harder than the PAI contained in the coating layer 61. When the bearing surface 60a and the bearing surface 24g slide against each other, the PAI (transferred particles 61c) that are scraped off from the coating layer 61 are broken up by the inorganic additive, thus reducing the size of the transferred particles 61c. This suppresses the increase in surface roughness of the coating layer 61 due to initial wear and suppresses the limit thickness of the air film when levitating the rotating body.

[0101] In particular, when the coating layer 61 contains MoS2 as an inorganic additive, MoS2 has a layered crystalline structure in which S layers are stacked, so slippage occurs between the S layers, making it easier to achieve low friction. This suppresses the sliding resistance when the bearing surface 60a and the bearing surface 24g slide against each other.

[0102] [Differentiation] The above embodiments are not limited to those embodiments, and can be implemented with modifications as follows, for example.

[0103] The above description describes a case where all bearing surfaces 24g of the turbo compressor 10 are made of a metallic material, and grooves extending in a direction intersecting the rotation direction of the rotating body 24 are present on the entire surface of the first bearing surface 24g1 and the entire surface of the second bearing surface 24g2. However, the description is not limited to this. As long as at least one of the bearing surfaces 24g supported by the bearing surface 60a formed of the coating layer 61 is made of a metallic material and has the grooves described above, the other bearing surfaces 24g do not have to be made of a metallic material and may have grooves of a shape other than those described above. For example, the grooves may be formed on the first bearing surfaces 24g1 of the first support portion 24b and the second support portion 24c facing a pair of radial foil bearings 40, 40, but the grooves may not be formed on the second bearing surface 24g2 of the third support portion 24d facing a pair of thrust foil bearings 30, 30. Alternatively, the groove may not be formed on the first bearing surface 24g1, but rather on the second bearing surface 24g2.

[0104] When the height Rvk of the protruding valleys Rvk and the load length ratios Mr1 and Mr2 of the multiple bearing surfaces 24g are within the above range, these values ​​forming each bearing surface 24g may be the same as or different from each other, but are preferably the same as each other.

[0105] The above describes the case where all bearing surfaces 60a of the turbo compressor 10 are coated with a coating layer 61. However, if the bearing surfaces 60a supporting the bearing surface 24g, which is made of a metallic material and has grooves extending across its entire surface in a direction intersecting the rotational direction of the rotating body 24, are formed with a coating layer 61, then bearing surfaces 60a that are not coated with a coating layer 61 may also be included. For example, the bearing surfaces 60a of a pair of thrust foil bearings 30, 30 may be made of a metallic material, and the bearing surfaces 60a of a pair of radial foil bearings 40, 40 may be made of a material other than a metallic material, or vice versa. When multiple bearing surfaces 60a are formed with a coating layer 61, it is sufficient if any of the bearing surfaces 60a have a coating layer 61 containing at least PAI, but preferably all bearing surfaces 60a have a coating layer 61 containing at least PAI. In this case, the composition of each coating layer 61 may be the same as or different from each other, but preferably they are the same.

[0106] Although Figure 1 describes the case of compressing air with the turbo compressor 10, the fluid to be compressed may be a fluid other than air (gas or liquid). For example, when the turbo compressor 10 is used in an air conditioning system, a refrigerant may be compressed. The refrigerant may change its state from gas to liquid depending on the pressure and temperature. The turbo compressor may be applied to air conditioning systems such as cabin air conditioning systems for vehicles and cooling circuits for battery temperature control.

[0107] In the turbo compressor 10 shown in Figure 1, the case in which the rotating body 24 is supported by an air film formed in the bearing gap 60b between the bearing surface 60a and the bearing surface 24g has been described. However, a gaseous film other than an air film may also be formed in the bearing gap 60b. Examples of gaseous films include refrigerant films and fluid films formed by the fluid compressed by the turbo compressor 10.

[0108] In the turbo compressor 10 shown in Figure 1, a pair of thrust foil bearings 30, 30 are provided on the first end 24e side of the rotating shaft 24a, but they may also be provided on the second end 24f side of the rotating shaft 24a, between the second impeller 26 and the second support portion 24c. [Examples]

[0109] The present invention will be described in more detail below with reference to test examples.

[0110] [Determination of protruding valley height Rvk, and load length ratios Mr1 and Mr2] The height Rvk of the protruding valleys on the outer surface of the ring used in the test example, as well as the load length ratios Mr1 and Mr2, were measured using the following procedure. First, using a shape analysis laser microscope (VK-X250, manufactured by Keyence Corporation), 3D shape data was measured at a height pitch of 0.1 μm in a field of view of 290 μm horizontally × 230 μm vertically, observed at a magnification of 1000x, on the outer surface of the ring. Next, 3D shape data was measured for 2 to 5 fields of view on the same outer surface of the ring, changing the observation location and using the above procedure. For each field of view, 60 shape curves were obtained in the direction perpendicular to the direction in which friction occurs, using analysis software (VK-H1XM, manufactured by Keyence Corporation) that measures in accordance with JIS B 0671-2 (2002). The height Rvk of the protruding valleys, as well as the load length ratios Mr1 and Mr2, were determined for each shape curve. The protruding valley height Rvk and load length ratios Mr1 and Mr2 obtained from each shape curve in each field of view were averaged and defined as the protruding valley height Rvk and load length ratios Mr1 and Mr2 on the outer surface of the ring.

[0111] [Test Examples 1-1 to 1-7 (Grinding Method using abrasive wheels)] To evaluate the frictional wear properties when the bearing surface of a dynamic pressure gas bearing slides against the bearing surface of a rotating body, a frictional wear test (1) was conducted according to the following procedure. Figure 12 is a schematic perspective view of the frictional wear test (1).

[0112] As shown in Figure 12, a block 74 simulating a hydrodynamic gas bearing was prepared by forming a 40 μm thick coating layer 74a on the top surface (16.5 mm wide x 6.2 mm high) of a raw material block measuring 16.5 mm wide x 6.2 mm long x 10.2 mm high, which was entirely made of stainless steel. The coating layer 74a is modeled after the coating layer on the bearing surface of a hydrodynamic gas bearing, and both the top surface of the block and the surface of the coating layer 74a are flat. The coating layer 74a was formed by spraying a coating solution containing 100 parts by mass of polyamide-imide (PAI), 78 parts by mass of polytetrafluoroethylene (PTFE), and 114 parts by mass of molybdenum disulfide (MoS2) onto the top surface of the raw material block, firing it, and then polishing it.

[0113] A ring 73 simulating a rotating body was prepared by grinding the outer circumferential surface of a raw material ring, which was entirely made of 64 titanium alloy, by pressing a grinding wheel against it. The grinding conditions were adjusted so that an outer circumferential surface 73a with grooves of the shape shown in Table 1, load length ratios Mr1 and Mr2, and protruding valley height Rvk was formed. The ring diameter φ of the ring 73 was 35 mm, and the width of the outer circumferential surface 73a of the ring was 8.77 mm. In Table 1, the angles shown in parentheses for the groove shapes are the target values ​​in the grinding process, and are the smaller of the angles that the direction of extension of the linear groove makes with the rotation direction of the ring 73.

[0114] With the coating layer 74a of the block 74 prepared above and the outer circumferential surface 73a of the ring 73 in contact (Figure 12), a friction and wear test (1) was performed under the following conditions. The test time was set to 30 seconds for test examples 1-1, 1-4, 1-6, and 1-7, 150 seconds for test example 1-2, 30 minutes for test example 1-3, and 90 seconds for test example 1-5. Testing machine: UMT-TriboLab (manufactured by Bruker) Load: 50gf Ring 73 rotation speed: 3000 rpm (steady state) Lubricated environment: no lubrication Test start temperature: Room temperature (natural temperature)

[0115] After the friction and wear test (1), a scanning electron microscope (SEM) was used to obtain backscattered electron images at 100x magnification of the central part in the width direction of the outer surface 73a of the rings 73 in test examples 1-1 to 1-7. The backscattered electron images of test examples 1-1, 1-5, 1-7, and 1-3 are shown in Figures 13 to 15 and 30, respectively. Energy-dispersive X-ray spectroscopy (EDS) analysis of the substance adhering to the grooves of the outer surface 73a of the rings 73 in test examples 1-1 to 1-7 detected carbon, oxygen, fluorine, sulfur, and molybdenum, indicating the presence of resin transferred from the coating layer 74a.

[0116] After the friction and wear test (1), a scanning electron microscope (SEM) was used to observe the sliding marks across an area of ​​8.3 mm horizontally and 1.3 mm vertically in the central part of the surface of the coating layer 74a of block 74. Titanium was detected by EDS analysis of the deposits adhering to the sliding marks. If titanium was detected, it was determined that a titanium alloy was adhering, and it was evaluated according to the following criteria. The results are shown in Table 1. (Evaluation Criteria) A: No titanium alloy deposits were found in any of the observed areas. B: No titanium alloy adhesion was observed in the observed range of 90% to less than 100% (although titanium alloy adhesion was observed, the area in which titanium alloy adhesion was observed was less than 10% of the observed range). C: No titanium alloy adhesion was observed in the range of 0% to less than 90% of the observed area (the range in which titanium alloy adhesion was observed was 10% or more of the observed area).

[0117] Furthermore, after the friction and wear test (1), backscattered electron images and secondary electron images at a magnification of 30x were obtained for the coating layer 74a of block 74 in test examples 1-1, 1-5, 1-7, and 1-3, and the results are shown in Figures 21 to 23 and 32, respectively.

[0118] [Test Examples 1-8 to 1-11 (Grinding Method using abrasive wheels)] To evaluate the frictional wear properties when the bearing surface of a dynamic pressure gas bearing slides against the bearing surface of a rotating body, a frictional wear test (2) was conducted according to the following procedure. Figure 16 is a schematic perspective view of the frictional wear test (2).

[0119] As shown in Figure 16, a block 76 was prepared with the same structure as block 75 described in Test Examples 1-1 to 1-7, except that the top surface of block 76 and the surface of the coating layer 76a were concave.

[0120] As described in Test Examples 1-1 to 1-7, the polishing conditions were adjusted to prepare a ring 73 with an outer surface 73a having grooves of the shape shown in Table 1, protruding valley height Rvk, and load length ratios Mr1 and Mr2.

[0121] With the coating layer 76a of the block 76 prepared above in contact with the outer surface 73a of the ring 73 (Figure 16), a friction and wear test (2) was conducted under the following conditions. The test time was set to 5 minutes in all cases. Testing machine: UMT-TriboLab (manufactured by Bruker) Load: 14N Ring 73 rotation speed: Repeated starting and stopping at 2900 rpm. Lubricated environment: no lubrication Test start temperature: Room temperature (natural temperature)

[0122] After the friction and wear test (2), a scanning electron microscope (SEM) was used to obtain a backscattered electron image at 100x magnification of the central part in the width direction of the outer surface 73a of the rings 73 in test examples 1-8 to 1-11. EDS analysis of the substance adhering to the grooves of the outer surface 73a of the rings 73 in test examples 1-8 to 1-11 detected carbon, oxygen, fluorine, sulfur, and molybdenum, indicating the presence of resin transferred from the coating layer 76a.

[0123] After the friction and wear test (2), a scanning electron microscope (SEM) was used to observe the sliding marks across an area of ​​8.3 mm horizontally and 1.3 mm vertically in the central part of the lateral direction of the surface of the coating layer 76a of block 76. Titanium was detected by EDS analysis of the deposits adhering to the sliding marks. If titanium was detected, it was determined that a titanium alloy was adhering, and it was evaluated according to the criteria described in Test Examples 1-1 to 1-7. The results are shown in Table 1.

[0124] [Table 1]

[0125] [Test Examples 2-1 to 2-11 (Tape Polishing Method)] To evaluate the frictional wear properties when the bearing surface of a dynamic pressure gas bearing slides against the bearing surface of a rotating body, a frictional wear test (1) was conducted using the following procedure.

[0126] A block 74, as described in Test Examples 1-1 to 1-7, was prepared. A ring 73, simulating a rotating body, was prepared using the procedure described in Test Examples 1-1 to 1-7, except that a tape coated with abrasive grains was used instead of a grinding wheel, and the tape was pressed against the outer surface of the raw material ring to polish it, adjusting the polishing conditions so that an outer surface 73a with grooves of the shape shown in Table 2, a protruding valley height Rvk, and load length ratios Mr1 and Mr2 was formed. The angles shown in parentheses for the groove shapes in Table 2 are as described in Table 1.

[0127] With the coating layer 74a of the block 74 prepared above in contact with the outer circumferential surface 73a of the ring 73 (Figure 12), friction and wear tests (1) were conducted under the conditions described in Test Examples 1-1 to 1-7, except that the test time was 30 seconds for Test Example 2-1, 15 minutes for Test Examples 2-2 to 2-7 and 2-10, 30 minutes for Test Example 2-8, and 150 seconds for Test Examples 2-9 and 2-11. After friction and wear tests (1), a scanning electron microscope (SEM) was used to obtain backscattered electron images at a magnification of 100x for the central part in the width direction of the outer circumferential surface 73a of the ring 73 in Test Examples 2-1 to 2-11. The backscattered electron images for Test Examples 2-1, 2-9, 2-11, and 2-8 are shown in Figures 17 to 19 and 31, respectively. EDS analysis of the substances adhering to the grooves in test examples 2-1 to 2-11 detected carbon, oxygen, fluorine, sulfur, and molybdenum, indicating the presence of resin transferred from coating layer 74a.

[0128] After the friction and wear test (1), a scanning electron microscope (SEM) was used to check whether titanium alloy was adhering to the surface of the coating layer 74a of block 74, following the procedure described in Test Examples 1-1 to 1-7, and the results were evaluated according to the criteria described in Test Examples 1-1 to 1-7. The results are shown in Table 2.

[0129] Furthermore, the backscattered electron images and secondary electron images obtained at a magnification of 30x for the coating layer 74a of block 74 in test examples 2-1, 2-9, 2-11, and 2-8 are shown in Figures 24 to 26 and 33, respectively.

[0130] [Test Examples 2-12 to 2-14 (Tape Polishing Method)] To evaluate the frictional wear properties when the bearing surface of a dynamic pressure gas bearing slides against the bearing surface of a rotating body, a frictional wear test (2) was conducted using the following procedure.

[0131] A block 76, as described in Test Examples 1-8 to 1-11, was prepared (Figure 16). By adjusting the polishing conditions as described in Test Examples 2-1 to 2-11, a ring 73 was prepared in which an outer surface 73a had grooves of the shape shown in Table 2, a protruding valley height Rvk, and load length ratios Mr1 and Mr2.

[0132] With the coating layer 76a of block 76 and the outer surface 73a of ring 73 in contact (Figure 16), a friction and wear test (2) was conducted under the conditions described in Test Examples 1-8 to 1-11. After the friction and wear test (2), backscattered electron images were obtained using a scanning electron microscope (SEM) following the procedure described in Test Examples 1-8 to 1-11. EDS analysis of the substances adhering to the grooves in Test Examples 2-12 to 2-14 detected carbon, oxygen, fluorine, sulfur, and molybdenum, indicating the presence of resin transferred from the coating layer 76a.

[0133] After the friction and wear test (2), a scanning electron microscope (SEM) was used to confirm whether or not titanium alloy was adhering, following the procedure described in Test Examples 1-8 to 1-11, and the results were evaluated according to the criteria described in Test Examples 1-1 to 1-7. The results are shown in Table 2.

[0134] [Table 2]

[0135] [Test Example 3-1 (Lapping Polishing Method)] To evaluate the frictional wear properties when the bearing surface of a dynamic pressure gas bearing slides against the bearing surface of a rotating body, a frictional wear test (1) was conducted using the following procedure.

[0136] A block 74, as described in Test Examples 1-1 to 1-7, was prepared. A ring 73, which simulates a rotating body, was prepared using the procedure described in Test Examples 1-1 to 1-7, except that the polishing conditions were adjusted so that the outer surface of the raw material ring was polished using a liquid abrasive instead of a grinding wheel, and an outer surface 73a was formed having grooves extending in a direction parallel to the rotation direction of the ring 73, and having the protruding valley height Rvk and load length ratios Mr1 and Mr2 shown in Table 3. The angles shown in parentheses for the groove shapes in Table 3 are as described in Table 1.

[0137] With the coating layer 74a of block 74 prepared above in contact with the outer surface 73a of ring 73 (Figure 12), friction and wear test (1) was performed under the conditions described in Test Examples 1-1 to 1-7, except that the test time was set to 30 seconds. After friction and wear test (1), a backscattered electron image at a magnification of 100x was obtained from the center of the width direction of the outer surface 73a of ring 73 in Test Example 3-1 using a scanning electron microscope (SEM). The backscattered electron image of Test Example 3-1 is shown in Figure 20. It was found that there was almost no material adhering to the groove in Test Example 3-1.

[0138] After the friction and wear test (1), a scanning electron microscope (SEM) was used to check whether titanium alloy was adhering to the surface of the coating layer 74a of block 74, following the procedure described in Test Examples 1-1 to 1-7, and the results were evaluated according to the criteria described in Test Examples 1-1 to 1-7. The results are shown in Table 3.

[0139] Furthermore, Figure 27 shows the results of obtaining backscattered electron images and secondary electron images at a magnification of 30x for the coating layer 74a of block 74 in Test Example 3-1.

[0140] [Test Examples 3-2 and 3-3 (Lapping Polishing Method)] To evaluate the frictional wear properties when the bearing surface of a dynamic pressure gas bearing slides against the bearing surface of a rotating body, a frictional wear test (2) was conducted using the following procedure.

[0141] A block 76, as described in Test Examples 1-8 to 1-11, was prepared. By adjusting the polishing conditions as described in Test Example 3-1, a ring 73 was prepared in which an outer circumferential surface 73a was formed having grooves extending in a direction parallel to the rotational direction of the ring 73, and having the protruding valley height Rvk and load length ratios Mr1 and Mr2 shown in Table 3.

[0142] With the coating layer 76a of block 76 prepared above in contact with the outer surface 73a of ring 73 (Figure 16), friction and wear test (2) was performed under the conditions described in Test Examples 1-8 to 1-11. After friction and wear test (2), backscattered electron images were obtained using a scanning electron microscope (SEM) following the procedure described in Test Examples 1-8 to 1-11. It was found that there was almost no material adhering to the grooves in Test Examples 3-2 and 3-3.

[0143] After the friction and wear test (2), a scanning electron microscope (SEM) was used to confirm whether or not titanium alloy was adhering, following the procedure described in Test Examples 1-8 to 1-11, and the results were evaluated according to the criteria described in Test Examples 1-1 to 1-7. The results are shown in Table 3.

[0144] Furthermore, Figures 28 and 29 show the results of obtaining backscattered electron images and secondary electron images at a magnification of 30x for the coating layer 76a of block 76 in test examples 3-2 and 3-3.

[0145] [Table 3]

[0146] [Note] Those skilled in the art will understand that the exemplary embodiments described above are specific examples of the following embodiments. (Aspect 1) A dynamic pressure gas bearing structure comprising a rotating body and a dynamic pressure gas bearing supporting the rotating body, The aforementioned dynamic pressure gas bearing has a bearing surface formed with a coating layer containing at least polyamide-imide, The rotating body has a bearing surface that faces the bearing surface and is made of a metallic material. The bearing surface has grooves extending across its entire surface in a direction intersecting the rotational direction of the rotating body, thus forming a dynamic pressure gas bearing structure. (Aspect 2) The dynamic pressure gas bearing structure according to embodiment 1, wherein the height Rvk of the protruding valley portion of the bearing surface is 0.2 μm or more. (Aspect 3) The dynamic pressure gas bearing structure according to embodiment 1 or 2, wherein the load length ratio Mr1 of the bearing surface is 7% or less. (Aspect 4) The aforementioned dynamic pressure gas bearing is a radial bearing that supports the rotating body in a direction perpendicular to the axial direction of the rotating body, facing the outer circumferential surface of the rotating body, and has the bearing surface. The dynamic pressure gas bearing structure according to any one of embodiments 1 to 3, wherein the first bearing surface of the rotating body facing the bearing surface is made of a metallic material and has a linear groove extending across its entire surface in a direction intersecting the rotational direction of the rotating body. (Aspect 5) The dynamic pressure gas bearing structure according to embodiment 4, wherein the linear groove includes grooves that intersect the rotational direction and the axial direction across the entire surface of the first bearing surface. (Aspect 6) The first bearing surface has a plurality of linear grooves, The dynamic pressure gas bearing structure according to embodiment 4 or 5, wherein the plurality of linear grooves intersect each other across the entire surface of the first bearing surface. (Aspect 7) The aforementioned dynamic pressure gas bearing is a thrust bearing that supports the rotating body in the axial direction of the rotating body and has the bearing surface, The second bearing surface of the rotating body facing the bearing surface is made of a metallic material and has the groove extending across its entire surface in a direction intersecting the rotational direction of the rotating body. The dynamic pressure gas bearing structure according to any one of embodiments 1 to 6, wherein the groove includes at least one of a groove extending radially outward from the position of the axis of the rotating body on the second bearing surface, a groove extending in a direction transverse to the second bearing surface, and a groove extending in a spiral direction. (Pattern 8) The hydrodynamic gas bearing structure according to any one of embodiments 1 to 7, wherein the coating layer further comprises polytetrafluoroethylene. (Aspect 9) The hydrodynamic gas bearing structure according to any one of embodiments 1 to 8, wherein the coating layer further comprises one or more inorganic additives selected from the group consisting of molybdenum disulfide, titanium oxide, and calcium fluoride. (Aspect 10) The rotating body is formed of the metallic material, a dynamic pressure gas bearing structure according to any one of embodiments 1 to 9. (Aspect 11) The dynamic pressure gas bearing structure according to any one of embodiments 1 to 10, wherein the metallic material is one or more selected from the group consisting of titanium, titanium alloys, and stainless steel. (Aspect 12) A rotating body and An actuator that rotates integrally with the aforementioned rotating body to pump fluid, A housing that accommodates the rotating body and the operating body, The rotating body is rotatably supported by a dynamic pressure gas bearing relative to the housing, The aforementioned dynamic pressure gas bearing has a bearing surface formed with a coating layer containing at least polyamide-imide, The rotating body has a bearing surface that faces the bearing surface and is made of a metallic material. The bearing surface has grooves extending across its entire surface in a direction intersecting the rotational direction of the rotating body, in a turbo-type fluid machine. (Aspect 13) The turbo-type fluid machine according to embodiment 12, wherein the height Rvk of the protruding valley portion of the bearing surface is 0.2 μm or more. (Aspect 14) The turbo-type fluid machine according to embodiment 12 or 13, wherein the load length ratio Mr1 of the bearing surface is 7% or less. (Aspect 15) The aforementioned dynamic pressure gas bearing is a radial bearing that supports the rotating body in a direction perpendicular to the axial direction of the rotating body, facing the outer circumferential surface of the rotating body, and has the bearing surface. The turbo-type fluid machine according to any one of embodiments 12 to 14, wherein the first bearing surface of the rotating body facing the bearing surface is made of a metallic material and has a linear groove extending across its entire surface in a direction intersecting the rotational direction of the rotating body. (Aspect 16) The aforementioned dynamic pressure gas bearing is a thrust bearing that supports the rotating body in the axial direction of the rotating body and has the bearing surface, The second bearing surface of the rotating body facing the bearing surface is made of a metallic material and has the groove extending across its entire surface in a direction intersecting the rotational direction of the rotating body. The turbo fluid machine according to any one of embodiments 12 to 15, wherein the groove includes at least one of the following: a groove extending radially outward from the position of the axis of the rotating body on the second bearing surface; a groove extending in a direction transverse to the second bearing surface; and a groove extending in a spiral direction. (Aspect 17) The turbo-type fluid machine according to any one of embodiments 12 to 16, wherein the dynamic pressure gas bearing is a foil bearing. (Aspect 18) The turbo-type fluid machine according to any one of embodiments 12 to 17, wherein the metallic material is one or more selected from the group consisting of titanium alloys and stainless steel.

[0147] The embodiments and examples disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of this disclosure is indicated by the claims rather than the foregoing description, and all modifications are intended to be in the sense and scope equivalent to the claims. [Industrial applicability]

[0148] The dynamic pressure gas bearing structure of the present invention can be used, for example, in turbo-type fluid machinery. The turbo-type fluid machinery of the present invention can be used in air compressors used in fuel cell systems, air conditioning compressors, turbines, generators, blowers, and the like. [Explanation of symbols]

[0149] 1 Fuel cell system, 10 Turbo compressor (turbo fluid machine), 11 Housing, 24 Rotating body, 24b First support, 24c Second support, 24d Third support, 24g Bearing surface (First bearing surface, Second bearing surface), 24g1 First bearing surface (Bearing surface), 24g2 Second bearing surface (Bearing surface), 25 First impeller (Actuator), 30 Thrust foil bearing (Thrust bearing), 40 Radial foil bearing (Radial bearing), 60 Foil bearing (Hydrographic gas bearing), 60a Bearing surface, 61 Coating layer, 61a Resin binder, 61b Inorganic additive, 61c Transfer particles, 81 Linear groove, 82 Groove (Radial groove), 83 Groove (Transverse groove), 84 Groove (Spiral groove), 85 Groove (second annular groove), Da axial direction, Dr rotational direction.

Claims

1. A dynamic pressure gas bearing structure comprising a rotating body and a dynamic pressure gas bearing supporting the rotating body, The aforementioned dynamic pressure gas bearing has a bearing surface formed with a coating layer containing at least polyamide-imide, The rotating body has a bearing surface that faces the bearing surface and is made of a metallic material. The bearing surface has grooves extending across its entire surface in a direction intersecting the rotational direction of the rotating body, thus forming a dynamic pressure gas bearing structure.

2. The dynamic pressure gas bearing structure according to claim 1, wherein the height Rvk of the protruding valley portion of the bearing surface is 0.2 μm or more.

3. The dynamic pressure gas bearing structure according to claim 1 or 2, wherein the load length ratio Mr1 of the bearing surface is 7% or less.

4. The aforementioned dynamic pressure gas bearing is a radial bearing that supports the rotating body in a direction perpendicular to the axial direction of the rotating body, facing the outer circumferential surface of the rotating body, and has the bearing surface. The dynamic pressure gas bearing structure according to claim 1 or 2, wherein the first bearing surface of the rotating body facing the bearing surface is made of a metallic material and has a linear groove extending across its entire surface in a direction intersecting the rotational direction of the rotating body.

5. The dynamic pressure gas bearing structure according to claim 4, wherein the linear groove includes grooves that intersect the rotational direction and the axial direction across the entire surface of the first bearing surface.

6. The first bearing surface has a plurality of linear grooves, The dynamic pressure gas bearing structure according to claim 4, wherein the plurality of linear grooves intersect each other across the entire surface of the first bearing surface.

7. The aforementioned dynamic pressure gas bearing is a thrust bearing that supports the rotating body in the axial direction of the rotating body and has the bearing surface, The second bearing surface of the rotating body facing the bearing surface is made of a metallic material and has the groove extending across its entire surface in a direction intersecting the rotational direction of the rotating body. The dynamic pressure gas bearing structure according to claim 1 or 2, wherein the groove includes at least one of the following: a groove extending radially outward from the position of the axis of the rotating body on the second bearing surface; a groove extending in a direction transverse to the second bearing surface; and a groove extending in a spiral direction.

8. The dynamic pressure gas bearing structure according to claim 1 or 2, wherein the coating layer further comprises polytetrafluoroethylene.

9. The dynamic pressure gas bearing structure according to claim 1 or 2, wherein the coating layer further comprises one or more inorganic additives selected from the group consisting of molybdenum disulfide, titanium oxide, and calcium fluoride.

10. The dynamic pressure gas bearing structure according to claim 1 or 2, wherein the rotating body is formed of the metallic material.

11. The dynamic pressure gas bearing structure according to claim 1 or 2, wherein the metallic material is one or more selected from the group consisting of titanium, titanium alloys, and stainless steel.

12. A solid of rotation and An actuator that rotates integrally with the aforementioned rotating body to pump fluid, A housing that accommodates the rotating body and the operating body, The rotating body is rotatably supported by a dynamic pressure gas bearing relative to the housing, The aforementioned dynamic pressure gas bearing has a bearing surface formed with a coating layer containing at least polyamide-imide, The rotating body has a bearing surface that faces the bearing surface and is made of a metallic material. The bearing surface has grooves extending across its entire surface in a direction intersecting the rotational direction of the rotating body, in a turbo-type fluid machine.

13. The turbo-type fluid machine according to claim 12, wherein the height Rvk of the protruding valley portion of the bearing surface is 0.2 μm or more.

14. The turbo-type fluid machine according to claim 12, wherein the load length ratio Mr1 of the bearing surface is 7% or less.

15. The aforementioned dynamic pressure gas bearing is a radial bearing that supports the rotating body in a direction perpendicular to the axial direction of the rotating body, facing the outer circumferential surface of the rotating body, and has the bearing surface. The turbo-type fluid machine according to claim 12 or 13, wherein the first bearing surface of the rotating body facing the bearing surface is made of a metallic material and has a linear groove extending across its entire surface in a direction intersecting the rotational direction of the rotating body.

16. The aforementioned dynamic pressure gas bearing is a thrust bearing that supports the rotating body in the axial direction of the rotating body and has the bearing surface, The second bearing surface of the rotating body facing the bearing surface is made of a metallic material and has the groove extending across its entire surface in a direction intersecting the rotational direction of the rotating body. The turbo-type fluid machine according to claim 12 or 13, wherein the groove includes at least one of a groove extending radially outward from the position of the axis of the rotating body on the second bearing surface, a groove extending in a direction transverse to the second bearing surface, and a groove extending in a spiral direction.

17. The turbo-type fluid machine according to claim 12 or 13, wherein the dynamic pressure gas bearing is a foil bearing.

18. The turbo-type fluid machine according to claim 12 or 13, wherein the metallic material is one or more selected from the group consisting of titanium alloys and stainless steel.

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