Dynamic pressure gas bearing structure and turbo fluid machine

Abstract

According to the present invention, a dynamic pressure gas bearing structure has a rotating body (24) and a dynamic pressure gas bearing that supports the rotating body (24). More specifically, this dynamic pressure gas bearing has a bearing surface formed of a coating layer containing at least a polyamide-imide. The rotating body (24) has a supported surface (24g, 24g1) formed of a metal material and facing the bearing surface. The supported surface (24g, 24g 1) has grooves (81) extending in a direction (Da) intersecting the rotation direction (Dr) of the rotating body (24) on the entire surfaces thereof.

Description

Dynamic pressure gas bearing structure and turbo fluid machine

[0001] The present invention relates to a dynamic pressure gas bearing structure and a turbo fluid machine.

[0002] Foil bearings are known as hydrodynamic gas bearings that support a rotating body, which is the shaft of a turbo-type fluid machine (see, for example, Patent Document 1). Foil bearings support the rotating body by levitating it using a fluid film, such as an air film, that forms between the bearing surface of the foil bearing and the rotating body. Patent Document 1 discloses forming a coating on the bearing surface of the foil bearing to improve the wear resistance and durability of the bearing surface.

[0003] Japanese Patent Application Laid-Open No. 2019-82195

[0004] To facilitate the floating of the rotor by the fluid film, the bearing surfaces of the foil bearing and the bearing surfaces of the rotor are sometimes smoothed. However, typical smoothing processes for metals do not sufficiently suppress wear on the bearing surfaces of the rotor.

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

[0006] The present invention provides the following dynamic pressure gas bearing structure and turbo fluid machine.

[0007] The dynamic pressure gas bearing structure has a rotating body and a dynamic pressure gas bearing that supports the rotating body, wherein the dynamic pressure gas bearing has a bearing surface formed with a coating layer that contains at least polyamideimide, and the rotating body has a bearing surface that faces the bearing surface and is formed of a metallic material, and the bearing surface has grooves on its entire surface that extend in a direction that intersects the rotational direction of the rotating body.

[0008] In the dynamic pressure gas bearing structure, it is preferable that the height Rvk of the protruding valley of the bearing surface is 0.2 μm or more.

[0009] In the 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 above-mentioned dynamic pressure gas bearing structure, the dynamic pressure gas bearing is a radial bearing having a bearing surface 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 it is preferable that the first bearing surface of the rotating body that faces the bearing surface is formed of a metallic material and has linear grooves on its entire surface that extend in a direction intersecting the rotational direction of the rotating body.

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

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

[0013] In the dynamic pressure gas bearing structure, the 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, and the second bearing surface of the rotating body that faces the bearing surface is formed of a metallic material and has the grooves over its entire surface extending in a direction intersecting the rotational direction of the rotating body, and it is preferable that the grooves include at least one of grooves that extend in a direction that spreads radially from the position of the axial center of the rotating body on the second bearing surface toward the outer periphery, grooves that extend in a direction that crosses the second bearing surface, and grooves that extend in a spiral direction.

[0014] In the dynamic pressure gas bearing structure, it is preferable that the coating layer further contains polytetrafluoroethylene.

[0015] In the above-described dynamic pressure gas bearing structure, it is preferable that the coating layer further contains one or more inorganic additives selected from the group consisting of molybdenum disulfide, titanium oxide, and calcium fluoride.

[0016] In the dynamic pressure gas bearing structure, the rotating body is preferably made of the metallic material.

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

[0018] The turbo fluid machine comprises a rotating body, an actuating body that rotates integrally with the rotating body to pump a fluid, a housing that accommodates the rotating body and the actuating body, 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 with a coating layer that contains at least polyamideimide, the rotating body has a bearing surface facing the bearing surface and formed of a metal-based material, and the bearing surface has grooves on its entire surface that extend in a direction that intersects the rotational direction of the rotating body.

[0019] In the turbo fluid machine, it is preferable that the height Rvk of the protruding valley portion of the bearing surface is 0.2 μm or more.

[0020] In the turbo fluid machine, it is preferable that the load length ratio Mr1 of the bearing surface is 7% or less.

[0021] In the turbo-type fluid machine, the dynamic pressure gas bearing is a radial bearing that faces the outer peripheral surface of the rotating body, supports the rotating body in a direction perpendicular to the axial direction of the rotating body, and has the bearing surface, and it is preferable that the first bearing surface of the rotating body that faces the bearing surface is formed of a metallic material and has linear grooves on its entire surface that extend in a direction intersecting the rotational direction of the rotating body.

[0022] In the turbo-type fluid machine, the dynamic pressure gas bearing is a thrust bearing that supports the rotor in the axial direction of the rotor and has the bearing surface, and the second bearing surface of the rotor that faces the bearing surface is formed of a metallic material and has grooves on its entire surface that extend in a direction intersecting the rotational direction of the rotor, and the grooves preferably include at least one of grooves that extend in a direction that spreads radially from the position of the rotor's axis on the second bearing surface toward the outer periphery, grooves that extend in a direction that crosses the second bearing surface, and grooves that extend in a spiral direction.

[0023] In the turbo fluid machine, the dynamic pressure gas bearing is preferably a foil bearing.

[0024] In the turbo fluid machine, the metallic material is preferably at least one selected from the group consisting of titanium alloys and stainless steel.

[0025] According to the present invention, it is possible to provide a dynamic pressure gas bearing structure and a turbo fluid machine that can suppress wear on the bearing surface of a rotating body.

[0026] 1 is a cross-sectional view showing a turbo compressor. FIG. 1 is a cross-sectional view showing an enlarged view of a portion of the turbo compressor shown in FIG. 1. FIG. 2 is a cross-sectional view showing an enlarged view of another portion of the turbo compressor shown in FIG. 1. FIG. 3 is a schematic view illustrating an example of a groove provided on a bearing surface facing a radial foil bearing of the turbo compressor shown in FIG. 1. FIG. 4 is a schematic view illustrating an example of a groove provided on a bearing surface facing a thrust foil bearing of the turbo compressor shown in FIG. 1. FIG. 5 is a schematic view illustrating another example of a groove provided on a bearing surface facing a thrust foil bearing of the turbo compressor shown in FIG. 1. FIG. 6 is a schematic view illustrating yet another example of a groove provided on a bearing surface facing a thrust foil bearing of the turbo compressor shown in FIG. 1. FIG. 7 is a schematic view illustrating yet another example of a groove provided on a bearing surface facing a thrust foil bearing of the turbo compressor shown in FIG. 1. 1 is a cross-sectional view schematically illustrating the wear of a coating layer of a foil bearing of the turbo compressor shown in FIG. 1 . FIG. 2 is a perspective view schematically illustrating a frictional wear test (1). FIG. 3 is a backscattered electron image of the outer peripheral surface of a ring observed with a scanning electron microscope after a frictional wear test (1) of Test Example 1-1. FIG. 4 is a backscattered electron image of the outer peripheral surface of a ring observed with a scanning electron microscope after a frictional wear test (1) of Test Example 1-5. FIG. 5 is a backscattered electron image of the outer peripheral surface of a ring observed with a scanning electron microscope after a frictional wear test (1) of Test Example 1-7. FIG. 6 is a perspective view schematically illustrating a frictional wear test (2). FIG. 7 is a backscattered electron image of the outer peripheral surface of a ring observed with a scanning electron microscope after a frictional wear test (1) of Test Example 2-1. FIG. 8 is a backscattered electron image of the outer peripheral surface of a ring observed with a scanning electron microscope after a frictional wear test (1) of Test Example 2-9. FIG. 9 is a backscattered electron image of the outer peripheral surface of a ring observed with a scanning electron microscope after a frictional wear test (1) of Test Example 2-11. 1A and 1B are backscattered electron images of the outer peripheral surface of the ring after the friction and wear test (1) in Test Example 3-1, observed with a scanning electron microscope. 1C are SEM images of the coating layer of the block after the friction and wear test (1) in Test Example 1-1, observed with a scanning electron microscope, where (a) is a backscattered electron image and (b) is a secondary electron image.1 shows SEM images of the coating layer of the block of Test Example 1-5 after friction and wear test (1) observed with a scanning electron microscope, where (a) is a backscattered electron image and (b) is a secondary electron image. 2 shows SEM images of the coating layer of the block of Test Example 1-7 after friction and wear test (1) observed with a scanning electron microscope, where (a) is a backscattered electron image and (b) is a secondary electron image. 3 shows SEM images of the coating layer of the block of Test Example 2-1 after friction and wear test (1) observed with a scanning electron microscope, where (a) is a backscattered electron image and (b) is a secondary electron image. 4 shows SEM images of the coating layer of the block of Test Example 2-9 after friction and wear test (1) observed with a scanning electron microscope, where (a) is a backscattered electron image and (b) is a secondary electron image. 1 shows SEM images of the coating layer of the block after friction and wear test (1) of Test Example 2-11, observed with a scanning electron microscope, where (a) is a backscattered electron image and (b) is a secondary electron image. 2 shows SEM images of the coating layer of the block after friction and wear test (1) of Test Example 3-1, observed with a scanning electron microscope, where (a) is a backscattered electron image and (b) is a secondary electron image. 3 shows SEM images of the coating layer of the block after friction and wear test (2) of Test Example 3-2, observed with a scanning electron microscope, where (a) is a backscattered electron image and (b) is a secondary electron image. 4 shows SEM images of the coating layer of the block after friction and wear test (2) of Test Example 3-3, observed with a scanning electron microscope, where (a) is a backscattered electron image and (b) is a secondary electron image. 5 shows backscattered electron images of the outer peripheral surface of the ring after friction and wear test (1) of Test Example 1-3, observed with a scanning electron microscope. 1A and 1B are backscattered electron images of the outer peripheral surface of the ring after the friction and wear test (1) of Test Example 2-8, observed with a scanning electron microscope. 1B 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, where (a) is a backscattered electron image and (b) is a secondary electron image. 1C 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, where (a) is a backscattered electron image and (b) is a secondary electron image.

[0027] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this specification, a numerical range such as "x to y" includes an upper limit and a lower limit unless otherwise specified, and represents a numerical range of "x or more and y or less."

[0028] In this embodiment, a turbo compressor is taken as an example of a turbo fluid machine, and a dynamic pressure gas bearing structure having a rotating body and a foil bearing which is a dynamic pressure gas bearing will be described.

[0029] <Basic Configuration of Turbo Compressor> Fig. 1 is a cross-sectional view showing a turbo compressor. Figs. 2 and 3 are cross-sectional views showing enlarged portions of the turbo compressor shown in Fig. 1. Fig. 4 is a schematic view illustrating an example of a groove provided on a bearing surface facing a radial foil bearing of the turbo compressor shown in Fig. 1. Figs. 5 to 9 are schematic views illustrating an example of a groove provided on a bearing surface facing a thrust foil bearing of the turbo compressor shown in Fig. 1. Fig. 10 is a cross-sectional view showing an enlarged schematic portion of a rotating body and a foil bearing of the turbo compressor shown in Fig. 1. Fig. 11 is a cross-sectional view showing a schematic view illustrating wear of a coating layer of a foil bearing of the turbo compressor shown in Fig. 1.

[0030] The turbo compressor 10 (turbo fluid machinery) is mounted on a fuel cell vehicle equipped with a fuel cell system 1. The fuel cell system 1 supplies oxygen and hydrogen to an on-board fuel cell to generate electricity. The turbo compressor 10 compresses the oxygen-containing air that is supplied to the on-board fuel cell.

[0031] (Housing) As shown in Fig. 1 , the turbo compressor 10 includes 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 periphery of the end wall 12a. The first plate 15 is connected to the end of the peripheral wall 12b on the opening side of the motor housing 12 and closes the opening of the peripheral wall 12b.

[0033] A motor chamber S1 is defined by an inner surface 121a of the end wall 12a of the motor housing 12, an inner peripheral surface 121b of the peripheral wall 12b, and an end surface 15a of the first plate 15 facing the motor housing 12. An electric motor 18 is accommodated in the motor chamber S1.

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

[0035] A recess 15c having a bottom surface 15d is formed in an end surface 15b of the first plate 15 opposite the motor housing 12. The recess 15c is a circular hole. The cylindrical interior of the first bearing holder 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 holder 20 coincide with each other.

[0036] The motor housing 12 has a second bearing retaining portion 22. The second bearing retaining portion 22 protrudes from the center of the inner surface 121a of the end wall 12a of the motor housing 12 toward the electric motor 18. The second bearing retaining portion 22 is cylindrical. The interior of the second bearing retaining portion 22 passes through 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 with each other.

[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 is connected to the inside of 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 holder 20. A thrust bearing accommodating chamber S2 is defined 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 suction port 13a through which air is drawn in. The compressor housing 13 is connected to an end face 16c of the second plate 16 opposite the first plate 15. The axial centers of the suction port 13a of the compressor housing 13, the shaft insertion hole 16a of the second plate 16, and the first bearing holder 20 are aligned. The suction port 13a opens at the end face of the compressor housing 13 opposite the second plate 16.

[0039] A first impeller chamber 13b, a discharge chamber 13c, and a diffuser passage 13d are formed between the compressor housing 13 and an end face 16c of the second plate 16. The first impeller chamber 13b is in communication with the suction port 13a. The discharge chamber 13c extends around the axis of the suction port 13a around the periphery of 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 is in communication 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 cylindrical interior 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 through which air is discharged. The turbine housing 14 is connected to an end face 17b of the third plate 17 opposite the motor housing 12. The axis of the discharge port 14a of the turbine housing 14, the axis of the shaft insertion hole 17a of the third plate 17, and the axis of the second bearing holder 22 are aligned. The discharge port 14a opens into the end face of the turbine housing 14 opposite the third plate 17.

[0042] A second impeller chamber 14b, a suction chamber 14c, and a communication passage 14d are formed between the turbine housing 14 and an end face 17b of the third plate 17. The second impeller chamber 14b is in communication with the discharge port 14a. The suction chamber 14c extends around the axis of the discharge port 14a around the periphery of the second impeller chamber 14b. The communication passage 14d connects the second impeller chamber 14b and the suction chamber 14c. The second impeller chamber 14b is in communication with the shaft insertion hole 17a of the third plate 17.

[0043] (Electric Motor) The electric motor 18 includes a cylindrical rotor 31 and a cylindrical stator 32. The rotor 31 is fixed to a rotating shaft 24a (described later). The stator 32 is fixed to the housing 11. The rotor 31 is disposed radially inward of the stator 32 and rotates integrally with the rotating body 24 (described later). The rotor 31 includes 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 includes 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 a current flows through the coil 34 from a battery (not shown), the rotating body 24 rotates integrally with the rotor 31. The electric motor 18 rotates at 100,000 rpm or more, for example, in the range of 100,000 to 120,000 rpm.

[0044] 1, a rotor 24 is accommodated within the housing 11. The rotor 24 has a rotating shaft 24a as a 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 that is the end portion on the compressor housing 13 side and a second end portion 24f that is the end portion on the turbine housing 14 side.

[0045] The first support portion 24b is provided on an outer peripheral surface 240a of the rotating shaft 24a at a position closer to the first end 24e, and is disposed inside the cylinder of the first bearing holder 20. The first support portion 24b is formed integrally with the rotating shaft 24a, and protrudes in an annular shape from the outer peripheral surface 240a of the rotating shaft 24a.

[0046] The second support portion 24c is provided on the outer peripheral surface 240a of the rotating shaft 24a at a position closer to the second end 24f and is disposed within the cylinder of the second bearing holder 22. The second support portion 24c is cylindrical and fixed to the outer peripheral surface 240a of the rotating shaft 24a in a state where it protrudes in an annular shape from the outer peripheral 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 disposed in the thrust bearing accommodating chamber S2. The third support portion 24d is disk-shaped and fixed to the outer peripheral surface 240a of the rotating shaft 24a in a state where it protrudes annularly from the outer peripheral surface 240a of the rotating shaft 24a. The third support portion 24d can rotate integrally with the rotating shaft 24a. The third support portion 24d is disposed at a position spaced apart from the electric motor 18 in the axial direction of the rotating body 24 (hereinafter simply referred to as the "axial direction").

[0048] A first impeller 25 (actuator) is connected to a first end 24e of the rotary shaft 24a. The first impeller 25 is disposed closer to the first end 24e than the third support portion 24d of the rotary shaft 24a. The first impeller 25 is housed in the first impeller chamber 13b. A second impeller 26 is connected to a second end 24f of the rotary shaft 24a. The second impeller 26 is disposed closer to the second end 24f than the second support portion 24c of the rotary 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 rotor 24.

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

[0050] The rotating body 24 is supported by a foil bearing 60 (described below) so as to be rotatable relative to the housing 11. The rotating body 24 faces a bearing surface 60a (described below) and has bearing surfaces 24g (first bearing surface, second bearing surface) formed of a metallic material. As long as at least the bearing surfaces 24g of the rotating body 24 are formed of a metallic material, portions of the rotating body 24 other than the bearing surfaces 24g may be formed of a material other than the metallic material, or may be formed of a metallic material different from the metallic material forming the bearing surfaces 24g. Examples of materials other than metallic materials include ceramics and resin. Alternatively, the entire rotating body 24 may be formed of a metallic material, and the metallic material of the surfaces that become the bearing surfaces 24g (the surfaces of the first to third support portions 24b to 24d) may serve as the bearing surfaces 24g. Examples of metallic materials forming the rotating body 24 or the bearing surface 24g include simple metals such as titanium; metal alloys such as titanium alloys; nickel alloys; and alloy steels such as stainless steel and chrome-molybdenum steel. Stainless steel is an example of stainless steel. Since the rotating body 24 is preferably made of a material that is not easily affected by the magnetic field of the electric motor 18, the metallic material is preferably a material other than a ferromagnetic material, such as an antiferromagnetic material, a paramagnetic material, or a diamagnetic material. The metallic material is preferably a metal or alloy containing titanium, or an austenitic stainless steel such as austenitic SUS, and more preferably titanium or a titanium alloy.

[0051] The bearing surface 24g of the rotating body 24 is the first bearing surface 24g of the first support portion 24b. １ (bearing surface), the first bearing surface 24g in the second support portion 24c １ (bearing surface), and the second bearing surface 24g of the third support portion 24d ２ The first support portion 24b and the second support portion 24c have respective bearing surfaces 24g (see FIGS. 4 to 9), and the bearing surfaces 24g are all made of a metal material. １ are surfaces that are rotatably supported by a pair of radial foil bearings 40 (described later). ２ is a surface that is 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 over its entire surface that extend in a direction intersecting the rotational direction of the rotating body 24. The grooves may have a portion that extends 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 only a portion 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, or a combination of these, or a mixture of linear and curved grooves. The grooves may be grooves that are continuously continuous over the entire bearing surface 24g, or grooves that are intermittently continuous over the entire bearing surface 24g. Multiple grooves may be formed over the entire bearing surface 24g, or a mixture of these. The grooves formed in the bearing surface 24g may intersect each other. "Having grooves over the entire surface" means that the grooves are evenly formed over the entire bearing surface 24g.

[0053] For example, as shown in FIG. 4, the first bearing surface 24g １ The first bearing surface 24g can have linear grooves 81 extending in a direction intersecting the rotation direction Dr of the rotating body 24 on the entire surface. １ The first bearing surface 24g has linear grooves 81 formed evenly over the entire surface. １ Preferably, a plurality of linear grooves 81 are formed over the entire surface of the rotor 24. The linear grooves 81 may or may not intersect with one another. The linear grooves 81 may be formed continuously around the circumference of the rotor 24, or may be formed intermittently, or a mixture of these may be used.

[0054] The linear groove 81 may extend so as to intersect with the rotation direction Dr, and the smaller of the angles formed by the linear groove 81 and the rotation direction Dr may be, 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, for example, 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 groove 81 is preferably formed on the first bearing surface 24g. １ The linear grooves 81 preferably include grooves that intersect with the rotational direction Dr and the axial direction Da on the entire surface of the first bearing surface 24g. １ The grooves 81 are preferably grooves that intersect with each other in the rotational direction Dr and the axial direction Da on the entire surface of the first bearing surface 24g. １ The entire surface of the surface contains grooves in a twill pattern (Figure 4).

[0056] 1st bearing surface 24g １ In plan view, in addition to the linear grooves 81, the grooves 81 may have at least one of curved grooves, grooves having a shape that combines straight and curved lines, and linear grooves that are parallel to the rotation direction Dr.

[0057] As shown in FIGS. 5 to 9, the third support portion 24d is disk-shaped, and therefore the second bearing surface 24g ２ The rotation direction of the rotor 24 is the second bearing surface 24g. ２ 5 to 9. ２ The second bearing surface 24g may have a groove extending in a direction intersecting the rotation direction of the rotor 24. For example, as shown in FIGS. ２ 7 and 8, grooves 82 (hereinafter also referred to as "radial grooves 82") extending in a direction spreading radially from the position of the axis of the rotor 24 toward the outer periphery of the rotor 24; ２grooves 83 extending in a direction transverse to the second bearing surface 24g (hereinafter also referred to as "transverse grooves 83"); grooves 84 extending in a spiral direction as shown in FIG. 9 (hereinafter also referred to as "spiral grooves 84"); and grooves extending in a direction drawing a ring (not shown) (hereinafter also referred to as "first annular grooves"). ２ It is preferable that the second bearing surface 24g has at least one of radial grooves 82, transverse grooves 83, and spiral grooves 84 on the entire surface. ２ This means that grooves are formed evenly over the entire surface.

[0058] 2nd bearing surface 24g ２ When the radial grooves 82 are formed in the second bearing surface 24g (FIGS. 5 and 6), ２ It is preferable that a plurality of radial grooves 82 are formed over the entire surface of the second bearing surface 24g. The plurality of radial grooves 82 may not intersect with each other, or may intersect with each other. The radial grooves 82 may be linear (FIG. 5), curved (FIG. 6), or a combination thereof. The radial grooves 82 are formed in the second bearing surface 24g. ２ The radial grooves 82 may extend over the entire surface of the rotor 24 from the axis to the outer periphery, or may extend over a portion of the entire surface, or may be a mixture of both. ２ The grooves may be formed continuously from the position of the axis of the rotor 24 to the outer periphery, or may be formed intermittently, or may be a mixture of these.

[0059] 2nd bearing surface 24g ２ When the transverse grooves 83 are formed in the second bearing surface 24g (FIGS. 7 and 8), ２ It is preferable that a plurality of transverse grooves 83 are formed over the entire surface of the second bearing surface 24g. The plurality of transverse grooves 83 may not intersect with each other, or may intersect with each other. The transverse grooves 83 may be linear, curved, or a combination thereof. The transverse grooves 83 are formed so that the second bearing surface 24g ２The second bearing surface 24g may extend in a direction crossing the ２ It may cross the entire second bearing surface 24g ２ The grooves 83 in the transverse direction do not have to cross the entire second bearing surface 24g. ２ The grooves may be formed continuously or intermittently along the direction crossing the groove, or may be formed in a mixture of these.

[0060] 2nd bearing surface 24g ２ When a spiral groove 84 is formed in the surface of the roller, the number of spiral grooves 84 may be one or more. The multiple spiral grooves 84 may not intersect with each other, or may intersect with each other. One spiral groove 84 may have a partially intersecting portion. The spiral shape of the spiral groove 84 may be a shape formed only with curved lines, a shape formed only with straight lines, or a shape formed by a combination of curved lines and straight lines. The spiral groove 84 may be formed continuously, intermittently, or a mixture of these.

[0061] 2nd bearing surface 24g ２ When the first annular groove is formed in the second bearing surface 24g, ２ It is preferable that a plurality of first annular grooves are formed over the entire surface of the ring. The plurality of first annular grooves may not intersect with each other, or may intersect with each other. The plurality of first annular grooves may be formed concentrically. The first annular grooves may extend partially along at least a portion of the ring, may extend continuously along the entire ring, or may extend intermittently along at least a portion of the ring. The shape of the ring is not particularly limited, and examples thereof include a circular shape and an elliptical shape.

[0062] 2nd bearing surface 24g ２The ring 24 may have a groove that does not intersect with the rotation direction of the rotor 24, in addition to at least one of the radial grooves 82, the transverse grooves 83, the spiral grooves 84, and the first annular groove. For example, the groove may be a groove 85 (hereinafter also referred to as a "second annular groove 85") that extends along the rotation direction of the rotor 24, as shown in FIG. 8. The second annular groove 85 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 thereof include a circular shape and an elliptical shape. The second annular groove 85 may be formed so as to intersect with the transverse groove 83, as shown in FIG. 8, for example.

[0063] The protruding valley height Rvk of the bearing surface 24g is preferably 0.2 μm or more, and may be 0.3 μm or more, 0.5 μm or more, 0.7 μm or more, or 1.0 μm or more. The protruding valley height Rvk of the bearing surface 24g is preferably 0.2 to 1.9 μm, and 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, and may be 10% or less, 9% or less, or 8% or less, preferably 7% or less, 6.8% or less, or 6.5% or less. The load length ratio Mr1 of the bearing surface 24g is, for example, 2 to 10.5%, 2 to 10%, 3 to 9%, or 3 to 8%, preferably 4 to 7%, 4 to 6.8%, or 4 to 6.5%.

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

[0066] The protruding valley height Rvk, as well as 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 determined from the profile curve obtained by measuring the bearing surface 24g, and the equivalent line is the straight line with the gentlest slope, where the secant passing through two points on the load curve where the difference in load length ratio is 40% is taken as the equivalent line. The core portion is defined as the area between two height positions where the equivalent line intersects with the vertical axis at 0% and 100% of the horizontal axis. In the profile curve, the average depth of the protruding peaks above the core portion is Rpk, and the average depth of the protruding valleys below the core portion is Rvk. The load length ratio at the intersection of the separation line between the peaks and core portion and the profile curve is Mr1, and the load length ratio at the intersection of the separation line between the valleys and core portion and the profile curve is Mr2. Therefore, the protruding valley height Rvk represents the average depth of the protruding valley of the bearing surface 24g, the load length ratio Mr1 is an index representing the proportion of the bearing surface 24g occupied by the protruding peak, and the load length ratio Mr2 can be said to be an index representing the proportion of the bearing surface 24g occupied by the protruding valley.

[0067] In this specification, the protruding valley height Rvk and the load length ratios Mr1 and Mr2 refer to values ​​measured using the following procedure. A sample for measuring the protruding valley height Rvk and the load length ratios Mr1 and Mr2 is prepared, and 3D shape data is measured in a field of view measuring 290 μm wide x 230 μm long, observed at 1000x magnification. The same sample is observed at different locations, and 3D shape data is measured in two to five fields of view using the above procedure. Sixty shape curves are obtained in each field of view, perpendicular to the direction in which friction occurs. The protruding valley height Rvk and the load length ratios Mr1 and Mr2 of each shape curve are determined. 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 the respective average values ​​are used as the protruding valley height Rvk and the load length ratios Mr1 and Mr2 of the bearing surface 24g of the sample. When obtaining the shape curve, high-pass and low-pass correction processes are not performed.

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

[0069] For example, the first bearing surface 24g rotatably supported by a radial foil bearing 40 (described later) １ is preferably a ground surface obtained by grinding by moving a cylindrical member for forming the rotor 24 back and forth in the axial direction while moving the grindstone (hereinafter also referred to as "traverse grinding method"). In the traverse grinding method, the angle of the linear grooves 81 can be adjusted by adjusting the ratio between the moving speed of the cylindrical member and the feed speed of the grindstone. In the traverse grinding method, the first bearing surface 24g can be adjusted by adjusting the grit size of the grindstone, the pressing pressure of the grindstone, etc. １ The groove extending direction, the protruding valley height Rvk, and the load length ratios Mr1 and Mr2 can be adjusted.

[0070] For example, the second bearing surface 24g rotatably supported by the thrust foil bearings 30, 30 (described later) ２Among these, for example, the transverse groove 83 (FIG. 7) can be formed by grinding the cylindrical member for forming the rotor 24 with a grindstone in one direction without rotating the cylindrical member. The second annular groove 85 (FIG. 8) can be formed by grinding the cylindrical member for forming the rotor 24 with a grindstone while rotating the cylindrical member in the rotational direction. When forming the second annular groove 85, the second bearing surface 24g ２ Transverse grooves 83 (FIG. 8) can also be formed by moving the grindstone radially from the axial position of the rotor 24 toward the outer periphery. Radial grooves 82 (FIGS. 5 and 6) and spiral grooves 84 (FIG. 9) can also be formed by adjusting the rotation of the cylindrical member and the movement of the grindstone. In these grinding methods, a tape (film) coated with abrasive grains may be used instead of the grindstone. By adjusting the grit size of the grindstone, the size of the abrasive grains, the pressing pressure of the grindstone and tape, etc., the first bearing surface 24g can be formed. １ The groove extending direction, the protruding valley height Rvk, 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, and examples thereof include, in addition to the traverse grinding method described above, a grindstone grinding method in which a grindstone is pressed against the surface to be polished, a 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 a combination of these. In the grindstone grinding method and the tape polishing method, polishing may be performed while vibrating the tape and grindstone so as to form the grooves described above, grinding may be performed while vibrating the cylindrical member that forms the rotating body 24, or grinding may be performed without vibrating the tape, grindstone, and cylindrical member.

[0072] The bearing surface 24g having the grooves described above can be manufactured, for example, as follows: A cylindrical member for forming the rotating body 24 is prepared, the cylindrical member having a surface made of a metallic material on which the bearing surface 24g of the rotating body 24 is formed. Next, the metallic material surface of the cylindrical member is ground using the grinding stone or tape described above while adjusting the grinding method, grinding conditions, etc. as described above, thereby forming the 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 portion other than the bearing surface 24g is made of a material other than a metallic material, it is sufficient that at least the surface of the cylindrical member on which the bearing surface 24g is formed is made of a metallic material, and the portion other than this surface may be made of a material other than a metallic material. Examples of metallic materials that constitute the cylindrical member and the surface of the cylindrical member on which the bearing surface 24g is formed include the metallic materials described for the rotating body 24 and the bearing surface 24g.

[0074] The above-mentioned traverse grinding method, grindstone grinding method, and tape polishing method may be applied to the surface of the cylindrical member that will become the bearing surface 24g, but may also be applied to surfaces of the cylindrical member other than this surface.

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

[0076] The pair of thrust foil bearings 30 are disposed in the thrust bearing accommodating chamber S2. The pair of thrust foil bearings 30 are disposed so as to sandwich the third support portion 24d, which serves as a thrust collar. The pair of thrust foil bearings 30 face the third support portion 24d in the axial direction of the rotating body 24. One thrust foil bearing 30 is disposed 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 disposed on the second end 24f side of the rotating shaft 24a relative to the third support portion 24d.

[0077] 2, the end face of third support portion 24d on the side of first end 24e of rotating shaft 24a serves as bearing surface 24g that is axially supported by one thrust foil bearing 30. One thrust foil bearing 30 has a bearing surface 60a that faces this bearing surface 24g. Similarly, the end face of third support portion 24d on the side of second end 24f of rotating shaft 24a serves as 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 disposed in the first bearing holder 20, and the other radial foil bearing 40 is disposed in the 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 radial foil bearing 40. The outer peripheral surface of the first support portion 24b serves as a bearing surface 24g that is supported by one radial foil bearing 40 in a direction perpendicular to the axial direction. One radial foil bearing 40 has a bearing surface 60a that faces 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 peripheral surface of the second support portion 24c serves as a bearing surface 24g that is 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 FIG. 10 , the bearing surface 60 a of each foil bearing 60, i.e., the bearing surface 60 a of each thrust foil bearing 30, 30 and the bearing surface 60 a of each radial foil bearing 40, 40, is formed with a coating layer 61. The coating layer 61 is formed to improve the wear resistance and durability of the bearing surface 60 a. The coating layer 61 contains at least polyamideimide (PAI). The PAI is used as a resin binder 61 a. The coating layer 61 preferably further contains polytetrafluoroethylene (PTFE). The coating layer 61 contains molybdenum disulfide (MoS) in addition to PAI or in addition to PAI and PTFE. ２ ), titanium oxide (TiO ２ ), and calcium fluoride (CaF ２ ) may contain one or more inorganic additives 61b selected from the group consisting of PTFE and MoS ２ is used as a solid lubricant, and TiO ２ and CaF ２ is used as a strengthening agent.

[0080] The content of PTFE 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 relative to 100 parts by mass of PAI. ２ The content of may be 1 to 200 parts by mass, 20 to 150 parts by mass, or 40 to 120 parts by mass relative to 100 parts by mass of PAI.

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

[0082] The foil bearing 60 may have the basic configuration of a hydrodynamic gas bearing. For example, the foil bearing 60 may have a top foil having a bearing surface 60a and a corrugated bump foil that elastically supports the top foil. The foil bearing 60 supports the rotating body 24, which rotates relative to the bearing surface 60a while the bearing surface 60a and the bearing surface 24g are in contact with each other, during low-speed rotation of the rotating body 24 until the rotation speed of the rotating body 24 reaches the floating rotation speed. Once the rotating body 24 rotates at high speed and reaches the floating rotation speed, the bearing surface 60a and the bearing surface 24g are no longer in contact with each other, and the foil bearing 60 supports the rotating body 24 by an air film formed in a 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 with each other refers to the state in which the coating layer 61 of the bearing surface 60a is in contact with the bearing surface 24g.

[0083] 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 in a side wall surface of the second plate 16. The branch passage L3 connects the supply passage L1 to the inlet 51a of the first passage 51. The first passage 51 communicates with the motor chamber S1 via the thrust bearing accommodation 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 a discharge port 52a provided in a side end surface of the third plate 17. The second passage 52 communicates 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 also includes a fuel cell stack 100 as an on-board fuel cell, a supply flow path L1, a discharge flow path L2, and a branch flow path L3. The fuel cell stack 100 is made up of a plurality of fuel cells. The supply flow path L1 connects the discharge chamber 13c to the fuel cell stack 100. The discharge flow path L2 connects the fuel cell stack 100 to the suction chamber 14c. An intercooler 110 is provided midway along the branch flow path L3 that branches off from the supply flow path L1. The intercooler 110 cools the air flowing through the branch flow path L3.

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

[0088] When 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. Air drawn in through the suction 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 is then discharged to the discharge passage L2 as exhaust gas from the fuel cell stack 100. The exhaust gas from the fuel cell stack 100 is drawn into the suction chamber 14c via the discharge passage L2. The exhaust gas from the fuel cell stack 100 drawn into the suction chamber 14c is discharged to the second impeller chamber 14b via the communication passage 14d. The second impeller 26 is rotated by the exhaust gas from the fuel cell stack 100 that is discharged into the second impeller chamber 14b. The rotor 24 is rotated not only by the drive of the electric motor 18 but also by the rotation of the second impeller 26, which is rotated by the exhaust gas from the fuel cell stack 100. Therefore, the first impeller 25 (actuator) rotates integrally with the rotor 24 and pressurizes and delivers air as an external fluid. The exhaust gas from the fuel cell stack 100 that is discharged into the second impeller chamber 14b is discharged to the outside from the discharge port 14a.

[0089] During operation of the turbo compressor 10, a portion of the air flowing through the supply passage L1 toward the fuel cell stack 100 flows into the first passage 51 via the branch passage 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 passage L3. The cooled air that has flowed into the first passage 51 flows into the thrust bearing accommodation chamber S2.

[0090] The cooling air that flows into the thrust bearing accommodation chamber S2 flows from the inner periphery toward the outer periphery mainly via one of the thrust foil bearings 30. After that, the cooling air that passes radially outside the third support portion 24d flows from the outer periphery toward the inner periphery mainly via 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 discharge port 52a.

[0092] In this way, the cooling air flows through the cooling passage 50, whereby 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.

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

[0094] During low-speed rotation of the rotating body 24, initial wear caused by the sliding causes a portion of the coating layer 61 on the bearing surface 60a to be torn off, and the PAI in the coating layer 61 is transferred to the bearing surface 24g ( FIG. 11 ). It is presumed that the PAI transferred to the bearing surface 24g (hereinafter also referred to as "transferred particles 61c") forms a coating of the transferred particles 61c on the bearing surface 24g. This coating reduces the frictional force when the bearing surface 60a and the bearing surface 24g slide together after initial wear, thereby suppressing wear of the metallic material forming the bearing surface 24g. Furthermore, damage to the coating layer 61 caused by wear particles from the metallic material, which would otherwise increase surface roughness, can be prevented, thereby improving the durability of the coating layer 61.

[0095] As described above, the bearing surface 24g of the rotating body 24 has grooves extending across the entire surface in a direction intersecting the rotational direction of the rotating body 24. 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 as the rotating body 24 rotates at high speed, they are likely to be caught in the grooves extending across the rotational direction, and a coating is likely to be formed on the bearing surface 24g. This coating reduces the frictional force when the bearing surface 60a and the bearing surface 24g slide together after initial wear, thereby suppressing wear of the metallic material forming the bearing surface 24g. Furthermore, damage to the coating layer 61 caused by wear powder from the metallic material, which would otherwise increase surface roughness, is also suppressed, thereby improving the durability of the coating layer 61.

[0096] 1st bearing surface 24g １ When the first bearing surface 24g includes a linear groove 81, １ A coating is easily formed on the first bearing surface 24g. １ If the first bearing surface 24g includes grooves that intersect with each other in the rotational direction Dr and the axial direction Da, or grooves with a twill pattern, the transferred particles 61c are more likely to be caught. １ This makes it easier to suppress wear, and makes it easier to improve the durability of the coating layer 61.

[0097] 2nd bearing surface 24g ２As described above, the second bearing surface 24g also has grooves on the entire surface extending in a direction intersecting the rotation direction of the rotor 24. Therefore, as the rotor 24 rotates at high speed, the transferred particles 61c are transferred to the second bearing surface 24g. ２ Even if the second bearing surface 24g moves in the rotation direction, it is likely to be caught in this groove. ２ It is assumed that a coating is easily formed on the second bearing surface 24g. ２ This makes it easier to suppress wear, and makes it easier to improve the durability of the coating layer 61.

[0098] By having the protruding valley height Rvk of the bearing surface 24g and the load length ratios Mr1 and Mr2 within the above-mentioned ranges, wear of the metallic material forming the bearing surface 24g is easily suppressed, and wear of the coating layer 61 is also suppressed, making it easier to improve durability.

[0099] As described above, the coating layer 61 may contain PTFE. If PTFE is present in the coating layer 61, the transferred particles of PTFE can adhere to the bearing surface 24g and form a coating upon initial wear. Because the PTFE coating is slippery and tends to achieve low friction, the frictional force when the bearing surface 60a and the bearing surface 24g slide together after initial wear is reduced. This suppresses wear of the metallic material that forms the bearing surface 24g, and also suppresses wear of the coating layer 61.

[0100] As described above, the coating layer 61 is made of MoS ２ , TiO ２ , and CaF ２ The coating layer 61 may contain one or more inorganic additives selected from the group consisting of: The inorganic additives are harder and less tough than the PAI contained in the coating layer 61. If the inorganic additive is present in the coating layer, when the bearing surface 60a and the bearing surface 24g slide against each other, the PAI (transferred particles 61c) that is ripped off from the coating layer 61 is broken up by the inorganic additive, thereby reducing the size of the transferred particles 61c. This makes it possible to prevent the surface roughness of the coating layer 61 from increasing due to initial wear, and to suppress the critical thickness of the air film when levitating the rotating body.

[0101] In particular, the coating layer 61 contains MoS as an inorganic additive.２ If it contains MoS ２ has a layered crystalline structure in which S layers are stacked, which allows for sliding between the S layers and facilitates low friction, thereby reducing the sliding resistance when the bearing surface 60a and the bearing surface 24g slide against each other.

[0102] [Modifications] The above embodiment is not limited to the above embodiment, and can be modified as follows, for example.

[0103] In the above description, all bearing surfaces 24g of the turbo compressor 10 are made of a metal material, and the first bearing surface 24g １ and the second bearing surface 24g ２ In the above description, the entire surface of the bearing surface 60a formed by the coating layer 61 has grooves extending in a direction intersecting the rotation direction of the rotor 24, but this is not limited to this. As long as at least one of the bearing surfaces 24g supported by the bearing surface 60a formed by the coating layer 61 is formed of a metallic material and has the grooves described above, the other bearing surfaces 24g do not have to be formed of a metallic material and may have grooves of a shape other than the above. For example, the first bearing surface 24g of the first support portion 24b and the second support portion 24c facing the pair of radial foil bearings 40, 40 １ The grooves are formed in the second bearing surface 24g of the third support portion 24d, which faces the pair of thrust foil bearings 30, 30. ２ The groove may not be formed on the first bearing surface 24g. １ The groove is not formed on the second bearing surface 24g. ２ The groove may be formed in the groove.

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

[0105] In the above description, all bearing surfaces 60 a of the turbo compressor 10 are coated with the coating layer 61. However, as long as the bearing surfaces 60 a that are formed of a metallic material and support the bearing surface 24 g having grooves extending across the entire surface in a direction intersecting the rotational direction of the rotor 24 are formed with the coating layer 61, some bearing surfaces 60 a may not be formed with the coating layer 61. For example, the bearing surfaces 60 a of the pair of thrust foil bearings 30 may be formed with a metallic material, and the bearing surfaces 60 a of the pair of radial foil bearings 40 may be formed with a material other than a metallic material, or vice versa. When multiple bearing surfaces 60 a are formed with the coating layer 61, it is sufficient that any one of the bearing surfaces 60 a has the coating layer 61 containing at least PAI. Preferably, all bearing surfaces 60 a have the coating layer 61 containing at least PAI. In this case, the compositions of the coating layers 61 may be the same or different, but are preferably the same.

[0106] Although the turbo compressor 10 shown in FIG. 1 has been described as compressing air, 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, it may compress a refrigerant. The refrigerant may change state between gas and liquid depending on pressure and temperature. The turbo compressor may be applied to air conditioning systems such as an automotive cabin air conditioner, a cooling circuit for battery temperature control, and the like.

[0107] 1, the rotating body 24 is supported by an air film generated in the bearing gap 60b between the bearing surface 60a and the bearing surface 24g, but a gas film other than an air film may be generated in the bearing gap 60b. Examples of the gas film include a refrigerant film and a fluid film formed by the fluid compressed by the turbo compressor 10.

[0108] In the turbo compressor 10 shown in FIG. 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 between the second impeller 26 and the second support portion 24c on the second end 24f side of the rotating shaft 24a.

[0109] The present invention will be explained in more detail below by showing test examples.

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

[0111] Test Examples 1-1 to 1-7 (Grinding Stone Method) In order to evaluate the friction and wear properties when the bearing surface of a hydrodynamic gas bearing was caused to slide against the bearing surface of a rotating body, a friction and wear test (1) was carried out according to the following procedure. Fig. 12 is a perspective view showing the friction and wear test (1) in a simplified manner.

[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 (the 16.5 mm wide x 6.2 mm long surface) of a raw material block made entirely of stainless steel and measuring 16.5 mm wide x 6.2 mm long x 10.2 mm high. The coating layer 74a imitates the coating layer on the bearing surface of a hydrodynamic gas bearing, and the top surface of the block and the surface of the coating layer 74a are also flat. The coating layer 74a is made of 100 parts by mass of polyamideimide (PAI), 78 parts by mass of polytetrafluoroethylene (PTFE), and molybdenum disulfide (MoS ２The upper surface of the raw material block was sprayed with a coating solution containing 114 parts by mass of hydroxybenzoates, followed by firing and polishing.

[0113] A grinding wheel was pressed against the outer peripheral surface of a raw material ring entirely formed with 64 titanium alloy, and the polishing conditions were adjusted to form an outer peripheral surface 73a having grooves, load length ratios Mr1 and Mr2, and protruding valley heights Rvk, as shown in Table 1, to prepare a ring 73 simulating a rotating body. The ring 73 had a ring diameter φ of 35 mm and a width of the outer peripheral surface 73a of the ring of 8.77 mm. In Table 1, the angle shown in parentheses next to the groove shape is the target value for the grinding process, and is the smaller angle between the extension direction of the linear groove and the rotation direction of the ring 73.

[0114] With the coating layer 74a of the block 74 prepared above and the outer peripheral surface 73a of the ring 73 in contact (FIG. 12), a friction and wear test (1) was conducted 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: 50 gf Ring 73 rotation speed: 3000 rpm (steady state) Lubrication environment: no lubrication Test start temperature: room temperature (as it happened)

[0115] After the friction and wear test (1), a scanning electron microscope (SEM) was used to obtain backscattered electron images at a magnification of 100x for the widthwise center portion of the outer circumferential surface 73a of the rings 73 of Test Examples 1-1 to 1-7. The backscattered electron images for Test Examples 1-1, 1-5, 1-7, and 1-3 are shown in Figures 13 to 15 and 30, respectively. EDS (energy dispersive X-ray spectroscopy) analysis of the substances adhering to the grooves on the outer circumferential surface 73a of the rings 73 of Test Examples 1-1 to 1-7 detected carbon, oxygen, fluorine, sulfur, and molybdenum, indicating the presence of resin that had migrated 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 wide x 1.3 mm long in the horizontal center of the surface of the coating layer 74a of the block 74. Titanium was detected by EDS analysis of the deposits on the sliding marks. If titanium was detected, it was determined that a titanium alloy had adhered, and the results were evaluated according to the following criteria. The results are shown in Table 1. (Evaluation criteria) A: No titanium alloy adhesion was observed in the entire observed area. B: No titanium alloy adhesion was observed in 90% or more but less than 100% of the observed area (titanium alloy adhesion was observed, but the area in which titanium alloy adhesion was confirmed was less than 10% of the observed area). C: No titanium alloy adhesion was observed in 0% or more but less than 90% of the observed area (titanium alloy adhesion was confirmed in 10% or more of the observed area).

[0117] After the friction and wear test (1), backscattered electron images and secondary electron images were taken at a magnification of 30 times for the coating layer 74a of the blocks 74 of Test Examples 1-1, 1-5, 1-7, and 1-3. The results are shown in Figures 21 to 23 and Figure 32, respectively.

[0118] [Test Examples 1-8 to 1-11 (Grinding Stone Method)] In order to evaluate the friction and wear properties when the bearing surface of a hydrodynamic gas bearing was caused to slide against the bearing surface of a rotating body, a friction and wear test (2) was carried out in the following manner. Fig. 16 is a perspective view showing a schematic diagram of the friction and wear test (2).

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

[0120] The polishing conditions were adjusted as described in Test Examples 1-1 to 1-7, and a ring 73 was prepared having an outer peripheral surface 73a formed thereon with grooves having the shapes shown in Table 1, protruding valley heights Rvk, and load length ratios Mr1 and Mr2.

[0121] With the coating layer 76a of the block 76 prepared above and the outer circumferential surface 73a of the ring 73 in contact (FIG. 16), a friction and wear test (2) was carried out 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: 2900 rpm with repeated start and stop Lubrication environment: No lubrication Test start temperature: Room temperature (as it happened)

[0122] After the friction and wear test (2), a scanning electron microscope (SEM) was used to obtain backscattered electron images at a magnification of 100x for the widthwise center portion of the outer circumferential surface 73a of the ring 73 of Test Examples 1-8 to 1-11. EDS analysis of the substances adhering to the grooves on the outer circumferential surface 73a of the ring 73 of Test Examples 1-8 to 1-11 detected carbon, oxygen, fluorine, sulfur, and molybdenum, indicating the presence of resin that had migrated from the coating layer 76a.

[0123] After the friction and wear test (2), the sliding marks were observed using a scanning electron microscope (SEM) over an area of ​​8.3 mm wide x 1.3 mm long in the horizontal center of the surface of the coating layer 76a of the block 76. Titanium was detected by EDS analysis of the deposits adhering to the sliding marks, and if titanium was detected, it was determined that a titanium alloy had adhered, and the results were evaluated according to the criteria described in Test Examples 1-1 to 1-7. The results are shown in Table 1.

[0124]

[0125] [Test Examples 2-1 to 2-11 (Tape Polishing Method)] In order to evaluate the friction and wear properties when the bearing surface of a hydrodynamic gas bearing and the bearing surface of a rotating body were caused to slide, a friction and wear test (1) was carried out according to the following procedure.

[0126] A block 74 was prepared as described in Test Examples 1-1 to 1-7. A ring 73 simulating a rotating body was prepared in the same manner as in Test Examples 1-1 to 1-7, except that a tape coated with abrasive grains was used instead of a grindstone, and the tape was pressed against the outer peripheral surface of the raw material ring for grinding, and the grinding conditions were adjusted so as to form an outer peripheral surface 73a having grooves with the shapes shown in Table 2, protruding valley heights Rvk, and load length ratios Mr1 and Mr2. 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 and the outer peripheral surface 73a of the ring 73 in contact (FIG. 12), a friction and wear test (1) was conducted under the conditions described for 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 the friction and wear test (1), a scanning electron microscope (SEM) was used to obtain backscattered electron images at a magnification of 100x for the widthwise center portions of the outer peripheral surface 73a of the ring 73 of Test Examples 2-1 to 2-11. The backscattered electron images of Test Examples 2-1, 2-9, 2-11, and 2-8 are shown in FIGS. 17 to 19 and 31, respectively. EDS analysis of the substances adhering to the grooves of Test Examples 2-1 to 2-11 detected carbon, oxygen, fluorine, sulfur, and molybdenum, indicating the presence of resin that had migrated from the coating layer 74a.

[0128] After the friction and wear test (1), a scanning electron microscope (SEM) was used to confirm whether or not a titanium alloy had adhered to the surface of the coating layer 74a of the 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] 24 to 26 and 33 show the results of backscattered electron images and secondary electron images taken at 30x magnification for the coating layers 74a of the blocks 74 of Test Examples 2-1, 2-9, 2-11, and 2-8, respectively.

[0130] [Test Examples 2-12 to 2-14 (Tape Polishing Method)] In order to evaluate the friction and wear properties when the bearing surface of a hydrodynamic gas bearing and the bearing surface of a rotating body were caused to slide, a friction and wear test (2) was carried out according to the following procedure.

[0131] A block 76 as described in Test Examples 1-8 to 1-11 was prepared ( FIG. 16 ). The polishing conditions were adjusted as described in Test Examples 2-1 to 2-11, and a ring 73 was prepared, on which an outer circumferential surface 73 a having grooves, protruding valley heights Rvk, and load length ratios Mr1 and Mr2 as shown in Table 2 was formed.

[0132] With the coating layer 76a of the block 76 prepared above and the outer peripheral surface 73a of the ring 73 in contact (FIG. 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), a backscattered electron image was obtained using a scanning electron microscope (SEM) according to the procedure described in Test Examples 1-8 to 1-11. EDS analysis of the material adhering to the grooves of Test Examples 2-12 to 2-14 detected carbon, oxygen, fluorine, sulfur, and molybdenum, indicating the presence of resin that had migrated from the coating layer 76a.

[0133] After the friction and wear test (2), a scanning electron microscope (SEM) was used to check whether or not the titanium alloy had adhered, using the procedures 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]

[0135] Test Example 3-1 (Lapping Method) In order to evaluate the friction and wear properties when the bearing surface of a hydrodynamic gas bearing and the bearing surface of a rotating body were caused to slide, a friction and wear test (1) was carried out according to the following procedure.

[0136] A block 74 was prepared as described in Test Examples 1-1 to 1-7. A ring 73 simulating a rotating body was prepared according to the procedure described in Test Examples 1-1 to 1-7, except that the outer peripheral surface of the raw material ring was polished using a liquid abrasive instead of a grinding stone, and the polishing conditions were adjusted so as to form an outer peripheral surface 73a 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. A ring 73 was prepared. 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 the block 74 prepared above and the outer peripheral surface 73a of the ring 73 in contact (FIG. 12), a friction and wear test (1) was conducted under the conditions described for Test Examples 1-1 to 1-7, except that the test time was 30 seconds. After the friction and wear test (1), a backscattered electron image was obtained at a magnification of 100x using a scanning electron microscope (SEM) for the widthwise center portion of the outer peripheral surface 73a of the ring 73 of Test Example 3-1. The backscattered electron image of Test Example 3-1 is shown in FIG. 20. It was found that there was almost no material adhering to the grooves of Test Example 3-1.

[0138] After the friction and wear test (1), a scanning electron microscope (SEM) was used to confirm whether or not a titanium alloy had adhered to the surface of the coating layer 74a of the 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] FIG. 27 shows the results of acquiring a backscattered electron image and a secondary electron image at a magnification of 30 times for the coating layer 74a of the block 74 of Test Example 3-1.

[0140] [Test Examples 3-2 and 3-3 (Lapping Method)] In order to evaluate the friction and wear properties when the bearing surface of a hydrodynamic gas bearing and the bearing surface of a rotating body were caused to slide, a friction and wear test (2) was carried out according to the following procedure.

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

[0142] With the coating layer 76a of the block 76 prepared above and the outer peripheral surface 73a of the ring 73 in contact (FIG. 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), a backscattered electron image was obtained using a scanning electron microscope (SEM) according to the procedure described in Test Examples 1-8 to 1-11. It was found that almost no material was adhering to the grooves of Test Examples 3-2 and 3-3.

[0143] After the friction and wear test (2), a scanning electron microscope (SEM) was used to check whether or not the titanium alloy had adhered, using the procedures 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] 28 and 29 show the results of acquiring backscattered electron images and secondary electron images at a magnification of 30 times for the coating layer 76a of the block 76 of Test Examples 3-2 and 3-3.

[0145]

[0146] [Additional Notes] It will be understood by those skilled in the art that the exemplary embodiments described above are specific examples of the following embodiments. (Aspect 1) A dynamic pressure gas bearing structure having a rotating body and a dynamic pressure gas bearing supporting the rotating body, wherein the dynamic pressure gas bearing has a bearing surface formed with a coating layer containing at least polyamideimide, the rotating body has a bearing surface facing the bearing surface and formed of a metallic material, and the bearing surface has grooves on its entire surface extending in a direction intersecting the rotational direction of the rotating body. (Aspect 2) The dynamic pressure gas bearing structure according to Aspect 1, wherein a protruding valley height Rvk of the bearing surface is 0.2 μm or more. (Aspect 3) The dynamic pressure gas bearing structure according to Aspect 1 or 2, wherein a load length ratio Mr1 of the bearing surface is 7% or less. (Aspect 4) The dynamic pressure gas bearing structure according to any one of Aspects 1 to 3, wherein the dynamic pressure gas bearing is a radial bearing that faces the outer peripheral surface of the rotating body, supports the rotating body in a direction perpendicular to the axial direction of the rotating body, and has the bearing surface, and a first bearing surface of the rotating body that faces the bearing surface is made of a metallic material and has linear grooves over its entire surface that extend in a direction intersecting the rotational direction of the rotating body. (Aspect 5) The dynamic pressure gas bearing structure according to Aspect 4, wherein the linear grooves include grooves that intersect the rotational direction and the axial direction over the entire surface of the first bearing surface. (Aspect 6) The dynamic pressure gas bearing structure according to Aspect 4 or 5, wherein the first bearing surface has a plurality of the linear grooves, and the plurality of linear grooves intersect each other over the entire surface of the first bearing surface. (Aspect 7) A dynamic pressure gas bearing structure according to any one of Aspects 1 to 6, wherein the 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, wherein a second bearing surface of the rotating body facing the bearing surface is formed of a metallic material and has the grooves over the entire surface extending in a direction intersecting the rotational direction of the rotating body, and wherein the grooves include at least one of grooves that extend in a direction that spreads radially from the position of the axial center of the rotating body on the second bearing surface towards the outer periphery, grooves that extend in a direction that crosses the second bearing surface, and grooves that extend in a spiral direction.(Aspect 8) The hydrodynamic gas bearing structure according to any one of Aspects 1 to 7, wherein the coating layer further contains polytetrafluoroethylene. (Aspect 9) The hydrodynamic gas bearing structure according to any one of Aspects 1 to 8, wherein the coating layer further contains one or more inorganic additives selected from the group consisting of molybdenum disulfide, titanium oxide, and calcium fluoride. (Aspect 10) The hydrodynamic gas bearing structure according to any one of Aspects 1 to 9, wherein the rotating body is formed of the metallic material. (Aspect 11) The hydrodynamic gas bearing structure according to any one of Aspects 1 to 10, wherein the metallic material is one or more selected from the group consisting of titanium, a titanium alloy, and stainless steel. (Aspect 12) A turbo fluid machine comprising: a rotating body; an actuating body that rotates integrally with the rotating body to pump a fluid; a housing that accommodates the rotating body and the actuating body; 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 with a coating layer containing at least polyamideimide, the rotating body has a bearing surface facing the bearing surface and formed of a metal-based material, the bearing surface having grooves on its entire surface extending in a direction intersecting the rotational direction of the rotating body. (Aspect 13) The turbo fluid machine according to Aspect 12, wherein a protruding valley height Rvk of the bearing surface is 0.2 μm or more. (Aspect 14) The turbo fluid machine according to Aspect 12 or 13, wherein a load length ratio Mr1 of the bearing surface is 7% or less. (Aspect 15) A turbo fluid machine according to any one of Aspects 12 to 14, wherein the dynamic pressure gas bearing is a radial bearing that faces an outer peripheral surface of the rotating body, supports the rotating body in a direction perpendicular to the axial direction of the rotating body, and has the bearing surface, and a first bearing surface of the rotating body that faces the bearing surface is formed of a metallic material and has linear grooves on its entire surface that extend in a direction intersecting the rotational direction of the rotating body.(Aspect 16) The turbo fluid machine according to any one of Aspects 12 to 15, wherein the dynamic pressure gas bearing is a thrust bearing that supports the rotor in an axial direction of the rotor and has the bearing surface, a second bearing surface of the rotor facing the bearing surface is formed of a metallic material and has the grooves extending over the entire surface thereof, the grooves including at least one of grooves extending in a direction radially expanding from the position of the rotor's axis on the second bearing surface toward the outer periphery, grooves extending in a direction transverse to the second bearing surface, and grooves extending in a spiral direction. (Aspect 17) The turbo fluid machine according to any one of Aspects 12 to 16, wherein the dynamic pressure gas bearing is a foil bearing. (Aspect 18) The turbo fluid machine according to any one of Aspects 12 to 17, wherein the metallic material is one or more selected from the group consisting of a titanium alloy and stainless steel.

[0147] The embodiments and examples disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0148] The dynamic pressure gas bearing structure of the present invention can be used, for example, in turbo fluid machines, such as air compressors used in fuel cell systems, air conditioning compressors, turbines, generators, and blowers.

[0149] 1 Fuel Cell System 10 Turbo Compressor (Turbo Fluid Machine) 11 Housing 24 Rotating Body 24b First Support Part 24c Second Support Part 24d Third Support Part 24g Bearing Surface (First Bearing Surface, Second Bearing Surface) 24g １ First bearing surface (bearing surface) 24g ２DESCRIPTION OF SYMBOLS Second bearing surface (bearing surface) 25 First impeller (working body) 30 Thrust foil bearing (thrust bearing) 40 Radial foil bearing (radial bearing) 60 Foil bearing (hydrodynamic gas bearing) 60a Bearing surface 61 Coating layer 61a Resin binder 61b Inorganic additive 61c Transferred 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 having a rotating body and a dynamic pressure gas bearing that supports the rotating body, wherein the dynamic pressure gas bearing has a bearing surface formed with a coating layer that contains at least polyamideimide, the rotating body has a bearing surface that faces the bearing surface and is formed of a metallic material, and the bearing surface has grooves on its entire surface that extend in a direction that intersects with the rotational direction of the rotating body.

2. A hydrodynamic gas bearing structure according to claim 1, wherein the height Rvk of the protruding valley of the bearing surface is 0.2 μm or more.

3. A 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. A dynamic pressure gas bearing structure as described in claim 1 or 2, wherein the dynamic pressure gas bearing is a radial bearing having a bearing surface 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 the first bearing surface of the rotating body that faces the bearing surface is made of a metallic material and has linear grooves on its entire surface that extend in a direction intersecting the rotational direction of the rotating body.

5. A dynamic pressure gas bearing structure according to claim 4, wherein the linear grooves include grooves that intersect the rotational direction and the axial direction over the entire surface of the first bearing surface.

6. A hydrodynamic gas bearing structure according to claim 4, wherein the first bearing surface has a plurality of linear grooves, and the plurality of linear grooves intersect with each other over the entire surface of the first bearing surface.

7. A dynamic pressure gas bearing structure as described in claim 1 or 2, wherein the 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, and a second bearing surface of the rotating body facing the bearing surface is formed of a metallic material and has the grooves over the entire surface extending in a direction intersecting the rotational direction of the rotating body, and the grooves include at least one of grooves that extend in a direction that spreads radially from the position of the axial center of the rotating body on the second bearing surface towards the outer periphery, grooves that extend in a direction that crosses the second bearing surface, and grooves that extend in a spiral direction.

8. The hydrodynamic gas bearing structure according to claim 1 or 2, wherein the coating layer further contains polytetrafluoroethylene.

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

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

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

12. A turbo fluid machine comprising: a rotating body; an actuator that rotates integrally with the rotating body to pump a fluid; a housing that accommodates 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 with a coating layer that contains at least polyamideimide, the rotating body has a bearing surface facing the bearing surface and formed of a metallic material, and the bearing surface has grooves on its entire surface that extend in a direction intersecting the rotational direction of the rotating body.

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

15. A turbo fluid machine as described in claim 12 or 13, wherein the dynamic pressure gas bearing is a radial bearing that faces the outer peripheral surface of the rotating body, supports the rotating body in a direction perpendicular to the axial direction of the rotating body, and has the bearing surface, and the first bearing surface of the rotating body that faces the bearing surface is made of a metallic material and has linear grooves on its entire surface that extend in a direction intersecting the rotational direction of the rotating body.

16. A turbo fluid machine as described in claim 12 or 13, wherein the hydrodynamic gas bearing is a thrust bearing that supports the rotor in the axial direction of the rotor and has the bearing surface, and the second bearing surface of the rotor facing the bearing surface is formed of a metallic material and has the grooves extending over the entire surface in a direction intersecting the rotational direction of the rotor, and the grooves include at least one of grooves that extend in a direction that spreads radially from the position of the rotor's axis on the second bearing surface towards the outer periphery, grooves that extend in a direction that crosses the second bearing surface, and grooves that extend in a spiral direction.

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

18. A turbo-fluid machine according to claim 12 or 13, wherein the metallic material is at least one material selected from the group consisting of titanium alloys and stainless steels.

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