Foil bearing

Abstract

Peaks (80) of elastically deforming portions (77) adjacent to each other in the direction in which a rotation axis of a rotating shaft (41) extends are offset from each other with respect to the rotation direction of the rotating shaft (41). The same is true for valleys (81) of the elastically deforming portions. Air warmed by heat from a top foil (70) when flowing between the peaks (80) and the top foil (70) is cooled by merging with air flowing between the peaks (80) and a housing (11). Air warmed by heat from the top foil (70) when flowing between the valleys (81) and the top foil (70) is cooled by merging with air flowing between the valleys (81) and the housing (11).

Description

Foil bearings

[0001] The present invention relates to a foil bearing that supports a rotating body in the radial direction.

[0002] For example, as described in Patent Document 1, a foil bearing that supports a rotating body in the radial direction includes a top foil, a bump foil, and a housing. The top foil faces the rotating body in the radial direction. The bump foil is disposed on the opposite side of the rotating body with the top foil sandwiched therebetween. The bump foil elastically supports the top foil. The housing is disposed on the opposite side of the top foil with the bump foil sandwiched therebetween. The housing supports the top foil and the bump foil. Such a foil bearing supports the rotating body with the rotating body and the top foil in contact with each other until the rotating body reaches a levitation rotation speed. Then, when the rotation speed of the rotating body reaches the levitation rotation speed, the dynamic pressure of the gas film generated between the top foil and the rotating body causes the rotating body to levitate relative to the top foil. As a result, the foil bearing supports the rotating body without contacting the rotating body.

[0003] JP 2013-53719 A

[0004] In such foil bearings, heat is generated in the top foil due to the dynamic pressure of the gas film generated between the top foil and the rotor, so it is desirable to efficiently cool the top foil.

[0005] A foil bearing that solves the above problem comprises a top foil that faces a rotating body in the radial direction, a bump foil that is arranged on the opposite side of the rotating body with the top foil in between and elastically supports the top foil, and a housing that is arranged on the opposite side of the top foil with the bump foil in between and supports the top foil and the bump foil, wherein the bump foil has a fixed end that is fixed to the housing and an elastically deforming portion that extends from the fixed end and is formed so that peaks that contact the top foil and valleys that contact the housing are arranged alternately in the rotational direction of the rotating body, and a plurality of the elastically deforming portions are arranged side by side in the direction in which the rotational axis of the rotating body extends, and at least one of the peaks and valleys of elastically deforming portions that are adjacent in the direction in which the rotational axis of the rotating body extends is offset with respect to the rotational direction.

[0006] Consider, for example, a case where adjacent peaks of an elastically deforming portion in the direction of the rotation axis of the rotor are offset from each other relative to the rotation direction of the rotor. In this case, the gas heated by the heat from the top foil as it flows between the peaks and the top foil merges with the gas flowing between the peaks and the housing, thereby being cooled. Also consider, for example, a case where adjacent valleys of an elastically deforming portion in the direction of the rotation axis of the rotor are offset from each other relative to the rotation direction of the rotor. In this case, the gas heated by the heat from the top foil as it flows between the valleys and the top foil merges with the gas flowing between the valleys and the housing, thereby being cooled. As a result, even if the heat of the top foil is dissipated into the gas, the temperature of the gas can be prevented from rising. This makes it easier to avoid problems such as poor cooling of the portion of the top foil located downstream of the gas. Therefore, the top foil can be efficiently cooled.

[0007] In the above foil bearing, the housing has a built-in cooling fluid path that extends so as to overlap the elastic deformation portion in the radial direction and through which a cooling fluid flows, and the gas flow path that flows between the rotating body and the housing that overlap in the radial direction has a first flow path that extends between the valley portion of one of the plurality of elastic deformation portions and the top foil, and a second flow path that extends between the housing and the peak portion of an adjacent elastic deformation portion among the plurality of elastic deformation portions that is downstream in the gas flow direction from the first flow path, and the gas that has flowed through the first flow path may flow through the second flow path.

[0008] According to this, the housing is cooled by the cooling fluid flowing through the cooling fluid path. Therefore, the gas flowing between the peaks and the housing and the gas flowing between the valleys and the housing are efficiently cooled by the housing. The gas that has flowed through the first flow path is efficiently cooled by the housing by flowing through the second flow path. As a result, even if heat from the top foil is dissipated to the gas, the increase in the gas temperature can be more easily suppressed, making it easier to avoid problems such as a deterioration in the cooling ability of the portion of the top foil located downstream of the gas. Therefore, the top foil can be cooled more efficiently.

[0009] In the above foil bearing, the gas flow path may further have a third flow path extending between the top foil and the valley portion of an adjacent elastic deformation portion among the plurality of elastic deformation portions that is downstream in the gas flow direction relative to the second flow path, and the gas that has flowed through the second flow path may flow through the third flow path.

[0010] With this, the gas that has been cooled by the housing by flowing through the second flow passage flows into the third flow passage, and therefore the top foil can be cooled more efficiently by the gas flowing through the third flow passage.

[0011] In the above foil bearing, the housing has a built-in cooling fluid path that extends so as to overlap the elastic deformation portion in the radial direction and through which a cooling fluid flows, and the gas flow path that flows between the rotating body and the housing that overlap in the radial direction has a fourth flow path that extends between the peak portion of one of the multiple elastic deformation portions and the housing, and a fifth flow path that extends between the valley portion of an adjacent elastic deformation portion among the multiple elastic deformation portions that is downstream of the fourth flow path in the gas flow direction and the top foil, and the gas that has flowed through the fourth flow path may flow through the fifth flow path.

[0012] According to this, the housing is cooled by the cooling fluid flowing through the cooling fluid passage. Therefore, the gas flowing between the peaks and the housing and the gas flowing between the valleys and the housing are efficiently cooled by the housing. The gas cooled by the housing by flowing through the fourth passage flows through the fifth passage. Therefore, the top foil can be cooled even more efficiently by the gas flowing through the fifth passage.

[0013] In the above foil bearing, the gas flow path may further have a sixth flow path extending between the housing and the peak portion of an adjacent elastic deformation portion among the plurality of elastic deformation portions that is downstream in the gas flow direction relative to the fifth flow path, and the gas that has flowed through the fifth flow path may then flow through the sixth flow path.

[0014] According to this, the gas that has flowed through the fifth flow path flows through the sixth flow path and is thereby efficiently cooled by the housing. As a result, even if heat from the top foil is dissipated into the gas, the temperature of the gas can be more easily prevented from rising, making it easier to avoid the problem of the cooling ability of the portion of the top foil located downstream of the gas being deteriorated. Therefore, the top foil can be cooled more efficiently.

[0015] In the above foil bearing, at least one of the phase between the centers of adjacent peaks in one of the elastic deformation sections adjacent in the direction in which the rotation axis of the rotating body extends relative to the phase between the centers of adjacent peaks in the other of the elastic deformation sections adjacent in the direction in which the rotation axis of the rotating body extends, and the phase between the centers of adjacent valleys in one of the elastic deformation sections adjacent in the direction in which the rotation axis of the rotating body extends relative to the phase between the centers of adjacent valleys in the other of the elastic deformation sections adjacent in the direction in which the rotation axis of the rotating body extends, may be shifted by 1 / 2.

[0016] This makes it possible to easily prevent uneven temperatures between the bump foil and the top foil, thereby enabling the top foil to be cooled more efficiently.

[0017] In the above foil bearing, the elastic deformation portion has a connection portion connecting the peak portion and the valley portion, the peak portion and the valley portion are arranged alternately with the connection portion sandwiched between them, the peak portion is protruded from the connection portion toward the top foil, and the valley portion is recessed from the connection portion toward the housing, and the connection portions of adjacent elastic deformation portions in the direction in which the rotation axis of the rotating body extends are offset with respect to the rotation direction.

[0018] According to this configuration, the elastic deformation portion has a connection portion connecting the peak portion and the valley portion, thereby improving the durability of the bump foil. Furthermore, in this configuration, the connection portions of adjacent elastic deformation portions in the direction of the rotation axis of the rotating body are offset relative to the rotation direction of the rotating body. According to this configuration, the gas heated by the heat from the top foil when flowing between the peak portion and the top foil merges with the gas flowing between the peak portion and the housing, thereby being cooled. Furthermore, the gas heated by the heat from the top foil when flowing between the valley portion and the top foil merges with the gas flowing between the valley portion and the housing, thereby being cooled. As a result, even if the heat of the top foil is dissipated to the gas, the temperature of the gas can be prevented from rising, thereby making it easier to avoid problems such as poor cooling performance of the portion of the top foil located downstream of the gas. Therefore, the top foil can be efficiently cooled.

[0019] In the above foil bearing, the phase between the centers of adjacent peaks in one of the elastic deformation sections adjacent to each other in the direction in which the rotation axis of the rotating body extends is shifted by 1 / 4 relative to the phase between the centers of adjacent peaks in the other of the elastic deformation sections adjacent to each other in the direction in which the rotation axis of the rotating body extends, and the phase between the centers of adjacent valleys in the other of the elastic deformation sections adjacent to each other in the direction in which the rotation axis of the rotating body extends is shifted by 1 / 4 relative to the phase between the centers of adjacent valleys in one of the elastic deformation sections adjacent to each other in the direction in which the rotation axis of the rotating body extends.

[0020] This makes it possible to easily prevent uneven temperatures between the bump foil and the top foil, thereby enabling the top foil to be cooled more efficiently.

[0021] In the above foil bearing, the bump foil is provided on the opposite side of the fixed end in the rotational direction and has a free end that is not fixed to the housing, and the bump foil may have a slit extending in the rotational direction from the free end toward the fixed end between adjacent elastic deformation portions in the direction in which the rotation axis of the rotating body extends.

[0022] Thus, the configuration in which the bump foil has slits is suitable for allowing gas heated by heat from the top foil as it flows between the peaks and the top foil to merge with gas flowing between the peaks and the housing.Furthermore, the configuration in which the bump foil has slits is suitable for allowing gas heated by heat from the top foil as it flows between the valleys and the top foil to merge with gas flowing between the valleys and the housing.

[0023] In the above foil bearing, the top foil may have a resin coating layer on a portion facing the rotating body, and the resin coating layer may have lower heat resistance than the top foil.

[0024] In this way, even if the top foil has a resin coating layer on the portion facing the rotating body, the durability of the resin coating layer can be improved by efficiently cooling the top foil.

[0025] In the foil bearing, the housing may be made of a material having a higher thermal conductivity than the top foil and the bump foil. This allows the gas flowing between the ridges and the housing and the gas flowing between the valleys and the housing to be efficiently cooled by the housing. As a result, the top foil can be cooled even more efficiently by the gas.

[0026] According to the present invention, the top foil can be cooled efficiently.

[0027] FIG. 1 is a cross-sectional view showing a centrifugal compressor in an embodiment. FIG. 2 is an exploded perspective view for explaining a radial bearing. FIG. 3 is a cross-sectional view for explaining a radial bearing. FIG. 4 is a perspective view showing a portion of the radial bearing. FIG. 5 is a cross-sectional view taken along line 5-5 in FIG. 4. FIG. 6 is a cross-sectional view taken along line 6-6 in FIG. 4. FIG. 7 is a cross-sectional view for explaining a radial bearing in a modified example. FIG. 8 is a cross-sectional view for explaining a radial bearing in a modified example. FIG. 9 is a cross-sectional view for explaining a radial bearing in a modified example. FIG. 10 is a cross-sectional view for explaining a radial bearing in a modified example.

[0028] An embodiment of a foil bearing will be described below with reference to Figures 1 to 6. The foil bearing of this embodiment is applied to a centrifugal compressor mounted on a fuel cell vehicle. The fuel cell vehicle is equipped with a fuel cell system that supplies oxygen and hydrogen to a fuel cell to generate electricity. The centrifugal compressor compresses air, which is an oxygen-containing gas, to be supplied to the fuel cell.

[0029] <Overview of Centrifugal Compressor> As shown in Fig. 1, a centrifugal compressor 10 includes a housing 11. The housing 11 is made of a metal material, such as aluminum. The housing 11 includes a motor housing 12, a compressor housing 13, a first plate 15, and a second plate 16.

[0030] The motor housing 12 has an end wall 12a and a peripheral wall 12b. The end wall 12a is plate-shaped. 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 of the motor housing 12 on the opening side. The first plate 15 closes the opening of the peripheral wall 12b of the motor housing 12. The motor housing 12 and the first plate 15 define a motor chamber 18. Therefore, the housing 11 has the motor chamber 18.

[0031] The centrifugal compressor 10 includes a motor 20. The motor 20 is housed in a motor chamber 18. Therefore, the motor chamber 18 houses the motor 20. The motor housing 12 surrounds the motor 20.

[0032] The centrifugal compressor 10 includes a first bearing holder 21. The first bearing holder 21 protrudes from the center of the first plate 15 into the motor chamber 18. Therefore, the first plate 15 has the first bearing holder 21. The first bearing holder 21 is cylindrical. The inside of the first bearing holder 21 communicates with the inside of the motor chamber 18.

[0033] The first plate 15 has a chamber-forming recess 22. The chamber-forming recess 22 is formed on the end face of the first plate 15 opposite the motor housing 12. The chamber-forming recess 22 is a circular hole. The inside of the first bearing holder 21 penetrates the first plate 15 and opens to the bottom face of the chamber-forming recess 22. The axis of the chamber-forming recess 22 and the axis of the first bearing holder 21 are aligned.

[0034] The second plate 16 is connected to the end face of the first plate 15 opposite the motor housing 12. The second plate 16 is attached to the first plate 15 with the thickness direction of the second plate 16 aligned with the thickness direction of the first plate 15. The second plate 16 has a first insertion hole 23. The first insertion hole 23 is formed in the center of the second plate 16. The axis of the first insertion hole 23 is aligned with the axis of the chamber-forming recess 22 and the axis of the first bearing holder 21. The chamber-forming recess 22 and the second plate 16 define an accommodating chamber 24. The housing 11 therefore defines the accommodating chamber 24. The accommodating chamber 24 is in communication with the inside of the first bearing holder 21. The accommodating chamber 24 is also in communication with the first insertion hole 23. The inside of the first bearing holder 21 is in communication with the first insertion hole 23 via the accommodating chamber 24.

[0035] A cooling fluid path 17 is built into the housing 11. A portion of the cooling fluid path 17 extends through the peripheral wall 12b of the motor housing 12, the first plate 15, and the second plate 16. Furthermore, a portion of the cooling fluid path 17 extends through the first plate 15 in a direction perpendicular to the thickness direction of the first plate 15, and also extends annularly through the first bearing holder 21. Cooling water from a cooling water circuit (not shown) flows through the cooling fluid path 17. The cooling water flowing through the cooling fluid path 17 cools the motor housing 12, the first plate 15, and the second plate 16. Heat generated by the motor 20 is dissipated to the motor housing 12, thereby cooling the motor 20. Therefore, the cooling water flowing through the cooling fluid path 17 cools the motor 20.

[0036] The centrifugal compressor 10 includes a second bearing holder 25. The second bearing holder 25 protrudes from the center of the end wall 12a of the motor housing 12 into the motor chamber 18. Therefore, the motor housing 12 has the second bearing holder 25. The second bearing holder 25 is cylindrical. The inside of the second bearing holder 25 communicates with the inside of the motor chamber 18. A portion of the cooling fluid path 17 extends inside the end wall 12a of the motor housing 12 in a direction perpendicular to the thickness direction of the end wall 12a, and also extends annularly inside the second bearing holder 25.

[0037] The housing 11 has a second insertion hole 26. The second insertion hole 26 is formed in the center of the end wall 12a of the motor housing 12. The axis of the second insertion hole 26 coincides with the axis of the second bearing holder 25. The second insertion hole 26 communicates with the inside of the second bearing holder 25.

[0038] The compressor housing 13 is cylindrical and has a circular suction port 27 through which air is drawn. The compressor housing 13 is connected to the end face of the second plate 16 opposite to the first plate 15, with the axis of the suction port 27 coinciding with the axis of the first insertion hole 23. The suction port 27 opens to the end face of the compressor housing 13 opposite to the second plate 16. Air that has been purified by an air cleaner (not shown) flows through the suction port 27.

[0039] The centrifugal compressor 10 includes an impeller chamber 28, a discharge chamber 29, and a diffuser passage 30. The impeller chamber 28, the discharge chamber 29, and the diffuser passage 30 are formed between the compressor housing 13 and the second plate 16. Therefore, the housing 11 defines the impeller chamber 28. The second plate 16 is a partition wall that separates the impeller chamber 28 from the accommodating chamber 24. The impeller chamber 28 communicates with the suction port 27. The discharge chamber 29 extends around the axis of the suction port 27 around the periphery of the impeller chamber 28. The diffuser passage 30 communicates between the impeller chamber 28 and the discharge chamber 29. The impeller chamber 28 communicates with the first insertion hole 23.

[0040] The centrifugal compressor 10 has a discharge passage 31. A first end of the discharge passage 31 communicates with the discharge chamber 29. A second end of the discharge passage 31 opens to the outer peripheral surface of the compressor housing 13.

[0041] The centrifugal compressor 10 includes a rotating shaft 41, an impeller 42, and a thrust collar 44. The rotating shaft 41 is accommodated in the housing 11. The rotating shaft 41 crosses the motor chamber 18 while extending along the axis of the motor housing 12. The axial direction of the rotating shaft 41 coincides with the axial direction of the motor housing 12. A first end of the rotating shaft 41 passes from the motor chamber 18 through the inside of the first bearing holder 21, the accommodation chamber 24, and the first insertion hole 23, and protrudes into the impeller chamber 28. A second end of the rotating shaft 41 is inserted from the motor chamber 18 into the inside of the second bearing holder 25.

[0042] The impeller 42 is connected to a first end of the rotary shaft 41. The impeller 42 is housed in the impeller chamber 28. Therefore, the impeller chamber 28 houses the impeller 42. The impeller 42 rotates integrally with the rotary shaft 41 to compress the air drawn into the impeller chamber 28.

[0043] The thrust collar 44 is disk-shaped. The thrust collar 44 protrudes from the outer circumferential surface of the rotary shaft 41 into the accommodation chamber 24. Therefore, the thrust collar 44 is disposed within the accommodation chamber 24. The thrust collar 44 is fixed to the rotary shaft 41 in a state where it protrudes radially outward from the outer circumferential surface of the rotary shaft 41 in an annular shape. The thrust collar 44 is a separate body from the rotary shaft 41. The thrust collar 44 rotates integrally with the rotary shaft 41.

[0044] The motor 20 has a cylindrical motor rotor 47 and a cylindrical motor stator 48. The motor chamber 18 accommodates the motor rotor 47. The motor rotor 47 is fixed to the rotating shaft 41. The motor stator 48 is fixed to the housing 11. The motor rotor 47 is disposed radially inside the motor stator 48. The motor rotor 47 rotates integrally with the rotating shaft 41. The motor rotor 47 has a cylindrical rotor core 49 fixed to the rotating shaft 41 and a plurality of permanent magnets (not shown) provided on the rotor core 49. The motor stator 48 surrounds the motor rotor 47. The motor stator 48 has a cylindrical stator core 50 and a motor coil 51. The stator core 50 is fixed to the inner circumferential surface of the motor housing 12. The motor coil 51 is wound around the stator core 50. The rotating shaft 41 rotates integrally with the motor rotor 47 when a current flows from a battery (not shown) to the motor coil 51. Therefore, the motor 20 rotates the rotating shaft 41.

[0045] The centrifugal compressor 10 includes two radial bearings 52. The radial bearings 52 are cylindrical. One of the two radial bearings 52 is held by the first bearing holder 21. One of the two radial bearings 52 rotatably supports a portion of the rotating shaft 41 that is closer to the first end of the rotating shaft 41 than the motor 20. The other of the two radial bearings 52 is held by the second bearing holder 25. The other of the two radial bearings 52 rotatably supports a portion of the rotating shaft 41 that is closer to the second end of the rotating shaft 41 than the motor 20. The rotating shaft 41 is a rotating body.

[0046] The two radial bearings 52 support the rotating shaft 41 rotatably in the radial direction at positions on either side of the motor 20 sandwiched in the axial direction of the rotating shaft 41. Note that the "radial direction" is a direction perpendicular to the axial direction of the rotating shaft 41. In this way, the radial bearings 52 are foil bearings that support the rotating shaft 41 in the radial direction.

[0047] The centrifugal compressor 10 includes a thrust bearing 54. The thrust bearing 54 is accommodated in the accommodation chamber 24. Therefore, the accommodation chamber 24 accommodates the thrust bearing 54. The thrust bearing 54 supports the thrust collar 44 rotatably in the thrust direction. Therefore, the thrust bearing 54 supports the rotating shaft 41 in the thrust direction via the thrust collar 44. Note that the "thrust direction" is a direction parallel to the axial direction of the rotating shaft 41.

[0048] The thrust bearing 54 has a first thrust bearing portion 54a and a second thrust bearing portion 54b. The first thrust bearing portion 54a is disposed between the thrust collar 44 and the second plate 16. The second thrust bearing portion 54b is disposed between the thrust collar 44 and the first plate 15.

[0049] The centrifugal compressor 10 includes a seal portion 55. The seal portion 55 is a labyrinth seal formed by a plurality of grooves formed on the inner circumferential surface of the first insertion hole 23. The seal portion 55 provides a seal between the first insertion hole 23 and the rotating shaft 41.

[0050] The centrifugal compressor 10 includes an introduction passage 58. The introduction passage 58 is formed in the first plate 15. A first end of the introduction passage 58 opens to the outer circumferential surface of the first plate 15. A second end of the introduction passage 58 communicates with the accommodation chamber 24.

[0051] The centrifugal compressor 10 includes a discharge passage 59. The discharge passage 59 is formed in the end wall 12a of the motor housing 12. A first end of the discharge passage 59 communicates with a portion of the second insertion hole 26 that is located on the opposite side of the radial bearing 52 from the motor chamber 18. A second end of the discharge passage 59 opens to the outer circumferential surface of the end wall 12a of the motor housing 12. Therefore, the discharge passage 59 communicates with the outside of the housing 11.

[0052] <Fuel Cell System> The centrifugal compressor 10 configured as described above constitutes part of a fuel cell system 60 mounted on a fuel cell vehicle. In addition to the centrifugal compressor 10, the fuel cell system 60 includes a fuel cell stack 61, a supply pipe 62, branch pipes 64, and an intercooler 65. The fuel cell stack 61 is made up of a plurality of battery cells (not shown). The supply pipe 62 connects the discharge passage 31 and the fuel cell stack 61.

[0053] The branch pipe 64 branches off from the middle of the supply pipe 62. A first end of the branch pipe 64 is connected to the supply pipe 62. A second end of the branch pipe 64 is connected to the first end of the introduction passage 58. The intercooler 65 is provided in the middle of the branch pipe 64. The intercooler 65 cools the air flowing through the branch pipe 64.

[0054] When the impeller 42 rotates, air is drawn into the impeller chamber 28 through the intake port 27. The air drawn into the impeller chamber 28 is accelerated by the rotation of the impeller 42 and sent into the diffuser passage 30, where it is pressurized as it passes through the diffuser passage 30. The air that has passed through the diffuser passage 30 is then discharged into the discharge chamber 29.

[0055] The air discharged into the discharge chamber 29 is discharged into a discharge passage 31. The air discharged into the discharge passage 31 is supplied to the fuel cell stack 61 via a supply pipe 62. The oxygen contained in the air supplied to the fuel cell stack 61 contributes to the power generation of the fuel cell stack 61. The air that passes through the fuel cell stack 61 is then discharged to the outside as exhaust gas from the fuel cell stack 61.

[0056] Furthermore, a portion of the air flowing through the supply pipe 62 flows into the branch pipe 64. The air flowing through the branch pipe 64 is cooled by the intercooler 65. As a result, the air passing through the intercooler 65 has a lower temperature than the air discharged into the discharge chamber 29. The air cooled by the intercooler 65 then passes through the introduction passage 58, the accommodation chamber 24, and the inside of the first bearing holder 21 and is introduced into the motor chamber 18. Therefore, the introduction passage 58 introduces a portion of the air compressed by the rotation of the impeller 42 into the motor chamber 18 at a temperature lower than the temperature of the air discharged into the discharge chamber 29. The air in the motor chamber 18 is then discharged to the outside of the housing 11 via the inside of the second bearing holder 25, the second insertion hole 26, and the discharge passage 59.

[0057] 2 and subsequent figures, a detailed description will be given of the configuration of the radial bearing 52 held by the first bearing holder 21, of the two radial bearings 52. Note that the configuration of the radial bearing 52 held by the second bearing holder 25 is the same as the configuration of the radial bearing 52 held by the first bearing holder 21, and therefore a detailed description of the configuration of the radial bearing 52 held by the second bearing holder 25 will be omitted.

[0058] 2 and 3, the radial bearing 52 includes a top foil 70 and a bump foil 71. Therefore, the radial bearing 52 includes the top foil 70 and the bump foil 71.

[0059] The top foil 70 faces the rotating shaft 41 in the radial direction. The bump foil 71 is arranged on the opposite side of the rotating shaft 41 with the top foil 70 sandwiched therebetween. The bump foil 71 elastically supports the top foil 70. The first bearing holder 21 is arranged on the opposite side of the top foil 70 with the bump foil 71 sandwiched therebetween. Therefore, the housing 11 is arranged on the opposite side of the top foil 70 with the bump foil 71 sandwiched therebetween. The first bearing holder 21 supports the top foil 70 and the bump foil 71. Therefore, the radial bearing 52 includes the housing 11 which is arranged on the opposite side of the top foil 70 with the bump foil 71 sandwiched therebetween and supports the top foil 70 and the bump foil 71.

[0060] A retaining groove 72a is formed on the inner peripheral surface of the first bearing retaining portion 21. The retaining groove 72a extends in the axial direction of the first bearing retaining portion 21. The retaining groove 72a opens to a first end face of the first bearing retaining portion 21 in the axial direction.

[0061] <Top Foil> The top foil 70 has a substantially cylindrical shape. The top foil 70 is made of a flexible metal material. The top foil 70 is formed of stainless steel or Inconel (registered trademark). The top foil 70 has a thin plate shape.

[0062] A fixed end 701, which is a first circumferential end of the top foil 70, is bent radially outward of the top foil 70. A free end 702, which is a second circumferential end of the top foil 70, faces the base end of the fixed end 701 while being spaced apart in the circumferential direction. Therefore, the top foil 70 is non-annular with a portion cut out.

[0063] The top foil 70 is disposed inside the first bearing holder 21 with the fixed end 701 inserted into the retaining groove 72a. The top foil 70 is disposed inside the first bearing holder 21 with the fixed end 701 held in the retaining groove 72a by inserting the fixed end 701 into the retaining groove 72a. The fixed end 701 is fixed to the first bearing holder 21 by, for example, welding.

[0064] As shown in Fig. 3, the top foil 70 has a resin coating layer 70a. The resin coating layer 70a is provided on the surface of the top foil 70 facing the rotation shaft 41. The resin coating layer 70a is provided on the portion of the top foil 70 facing the rotation shaft 41. In this way, the top foil 70 has the resin coating layer 70a on the portion facing the rotation shaft 41. The resin coating layer 70a has lower heat resistance than the top foil 70.

[0065] 2 and 3, the bump foil 71 is substantially cylindrical. The bump foil 71 is made of a flexible metal material. The bump foil 71 is made of stainless steel or Inconel (registered trademark). Therefore, the housing 11 is made of a material with a higher thermal conductivity than the top foil 70 and the bump foil 71.

[0066] The bump foil 71 has a fixed end 78 and a free end 79. The fixed end 78 is formed by bending a first circumferential end of the bump foil 71 radially outward. The fixed end 78 has a long, narrow plate shape. The free end 79 faces the base end of the fixed end 78 while being spaced apart in the circumferential direction. Therefore, the bump foil 71 has a non-annular shape with a portion cut out. The free end 79 is located on the opposite side of the fixed end 78 with respect to the rotation direction of the rotary shaft 41.

[0067] 3 , the bump foil 71 is disposed inside the first bearing holder 21 with the fixed end 78 inserted into the retaining groove 72a. The bump foil 71 is disposed inside the first bearing holder 21 with the fixed end 78 inserted into the retaining groove 72a and thereby held in the retaining groove 72a. The fixed end 78 is fixed to the first bearing holder 21 by, for example, welding. Therefore, the fixed end 78 is fixed to the housing 11. The free end 79 is not fixed to the first bearing holder 21. Therefore, the free end 79 is not fixed to the housing 11.

[0068] As shown in FIG. 2 , the bump foil 71 has slits 82. Two slits 82 are formed in the bump foil 71. Each slit 82 extends in the rotational direction of the rotary shaft 41 from the free end 79 toward the fixed end 78. Each slit 82 extends in the rotational direction of the rotary shaft 41 from the free end 79 to the fixed end 78. The bump foil 71 has a plurality of elastic deformation portions 77 arranged side by side in the axial direction of the rotary shaft 41 with the slits 82 interposed therebetween. In this manner, the bump foil 71 has the elastic deformation portions 77. The elastic deformation portions 77 are arranged side by side in the direction of the rotational axis L1 of the rotary shaft 41. The slits 82 extend in the rotational direction of the rotary shaft 41 from the free end 79 toward the fixed end 78 between adjacent elastic deformation portions 77 in the direction of the rotational axis L1 of the rotary shaft 41.

[0069] Each elastic deformation portion 77 has a long, narrow plate shape. Each elastic deformation portion 77 is disposed relative to the first bearing holder 21 with the longitudinal direction of the elastic deformation portion 77 aligned with the rotation direction of the rotary shaft 41. The end of each elastic deformation portion 77 on the fixed end 78 side is connected to the fixed end 78. Each elastic deformation portion 77 extends from the fixed end 78.

[0070] As shown in FIG. 4 , each elastically deforming portion 77 has a plurality of peaks 80 and a plurality of valleys 81. Therefore, the bump foil 71 has a plurality of peaks 80 and valleys 81. As shown in FIG. 3 , each peak 80 contacts the top foil 70. Each peak 80 extends in the circumferential direction of the elastically deforming portion 77. Each valley 81 connects adjacent peaks 80 in the rotational direction of the rotating shaft 41. Each valley 81 contacts the first bearing holder 21. Each valley 81 is in the form of a long, narrow plate extending along the inner circumferential surface of the first bearing holder 21. Each peak 80 is in the form of a curved plate that is convex toward the top foil 70 relative to the valleys 81. Each elastically deforming portion 77 has a wave shape in which peaks 80 and valleys 81 are alternately arranged in the circumferential direction of the elastically deforming portion 77. Each peak 80 and each valley 81 is a portion of the bump foil 71 located between the fixed end 78 and the free end 79. The peaks 80 and valleys 81 are alternately arranged in the circumferential direction of the bump foil 71 from the fixed end 78 to the free end 79. In this way, the elastic deformation portion 77 is formed so that the peaks 80 and valleys 81 are alternately arranged in the rotational direction of the rotating shaft 41.

[0071] 3 and 4 , the peaks 80 and valleys 81 of adjacent elastic deformation portions 77 sandwiching a slit 82 therebetween are alternately out of phase with each other. The peaks 80 of each elastic deformation portion 77 are adjacent to the valleys 81 of the adjacent elastic deformation portion 77 sandwiching the slit 82 therebetween. In this manner, the peaks 80 and valleys 81 are alternately arranged with the slits 82 sandwiched therebetween in the rotational direction of the rotating shaft 41. Therefore, the peaks 80 and valleys 81 of adjacent elastic deformation portions 77 in the direction in which the rotation axis L1 of the rotating shaft 41 extends are offset from each other in the rotational direction of the rotating shaft 41. As shown in FIG. 3 , the cooling fluid paths 17 extend radially so as to overlap with the elastic deformation portions 77.

[0072] Each valley portion 81 of the elastic deformation portion 77 contacts the first bearing holder 21, and each peak portion 80 of the elastic deformation portion 77 contacts the top foil 70. When the rotating shaft 41 rotates, air enters between the top foil 70 and the rotating shaft 41, and an air film is formed between the top foil 70 and the rotating shaft 41. The rotating shaft 41 rotates while in contact with the top foil 70 until the rotation speed of the rotating shaft 41 reaches the lift-off rotation speed. When the rotation speed of the rotating shaft 41 reaches the lift-off rotation speed, the dynamic pressure of the air film causes the rotating shaft 41 to lift off relative to the top foil 70. The top foil 70 supports the rotating shaft 41 in the radial direction via the air film. In this way, the top foil 70 supports the rotating shaft 41 in the radial direction.

[0073] The top foil 70 is elastically deformed by the dynamic pressure of the air film between the top foil 70 and the rotating shaft 41, and is displaced toward each elastic deformation portion 77 of the bump foil 71. As a result, the top foil 70 presses each ridge portion 80 of the elastic deformation portion 77 toward the first bearing holder 21. This causes the elastic deformation portion 77 to elastically deform. The elastic deformation portion 77 is then displaced toward the first bearing holder 21 together with the top foil 70. The elastic deformation portion 77 elastically supports the top foil 70. In this way, the bump foil 71 elastically deforms to elastically support the top foil 70 in a state in which the top foil 70 can be displaced in the axial direction of the rotating shaft 41.

[0074] <First Flow Passage, Second Flow Passage, Third Flow Passage> In Figure 5, the air flow is indicated by arrows. As shown in Figure 5, the air flow passage 90 that flows between the rotating shaft 41 and the first bearing holder 21, which overlap in the radial direction, includes a first flow passage 91 and a second flow passage 92. The first flow passage 91 extends between the top foil 70 and a valley portion 81 of one of the multiple elastic deformation portions 77. The elastic deformation portion 77 that forms the first flow passage 91 is the elastic deformation portion 77 that is located most upstream in the air flow direction among the multiple elastic deformation portions 77. The second flow passage 92 extends between the first bearing holder 21 and a peak portion 80 of the elastic deformation portion 77 that is adjacent to the first flow passage 91 downstream in the air flow direction. The air that flows through the first flow passage 91 then flows through the second flow passage 92.

[0075] The air flow path 90 further includes a third flow path 93. The third flow path 93 extends between the top foil 70 and the valley portion 81 of an adjacent elastic deformation portion 77, among the multiple elastic deformation portions 77, that is located downstream in the air flow direction with respect to the second flow path 92. The air that has flowed through the second flow path 92 then flows through the third flow path 93.

[0076] <Fourth Flow Passage, Fifth Flow Passage, and Sixth Flow Passage> In FIG. 6 , the air flow is indicated by arrows. As shown in FIG. 6 , the air flow passage 90 includes a fourth flow passage 94 and a fifth flow passage 95. The fourth flow passage 94 extends between a peak portion 80 of one of the plurality of elastic deformation portions 77 and the first bearing holder 21. The elastic deformation portion 77 forming the fourth flow passage 94 is the elastic deformation portion 77 located furthest upstream in the air flow direction among the plurality of elastic deformation portions 77. The fifth flow passage 95 extends between the valley portion 81 of the elastic deformation portion 77 adjacent to the fourth flow passage 94 on the downstream side in the air flow direction and the top foil 70. The air flowing through the fourth flow passage 94 then flows through the fifth flow passage 95.

[0077] The air flow path 90 further includes a sixth flow path 96. The sixth flow path 96 extends between the first bearing holder 21 and the peak portion 80 of one of the plurality of elastic deformation portions 77 that is adjacent to the fifth flow path 95 on the downstream side in the air flow direction with respect to the fifth flow path 95. The air that has flowed through the fifth flow path 95 then flows through the sixth flow path 96.

[0078] [Operation of the Embodiment] Next, the operation of the embodiment will be described. As shown in FIG. 1 , air is introduced from the introduction passage 58 as gas to cool the thrust bearing 54, the two radial bearings 52, and the motor 20. The thrust bearing 54 is cooled by the air introduced from the introduction passage 58 into the accommodation chamber 24. The air in the accommodation chamber 24 passes inside the first bearing holder 21. One of the two radial bearings 52 is cooled by the air passing inside the first bearing holder 21. The air that has passed inside the first bearing holder 21 is introduced into the motor chamber 18. The motor 20 is cooled by the air introduced into the motor chamber 18. The air introduced into the motor chamber 18 passes inside the second bearing holder 25. The other of the two radial bearings 52 is cooled by the air passing inside the second bearing holder 25. The air that has passed through the inside of the second bearing holder 25 is discharged to the outside of the housing 11 via the second insertion hole 26 and the discharge passage 59 .

[0079] 5 and 6 , part of the air flowing through the flow passage 90 flows in the axial direction of the rotating shaft 41 between the valley portions 81 and the top foil 70. Part of the air flowing through the flow passage 90 also flows in the axial direction of the rotating shaft 41 between the valley portions 81 and the first bearing holder 21. Part of the air flowing through the flow passage 90 also flows in the axial direction of the rotating shaft 41 between the ridge portions 80 and the top foil 70. Part of the air flowing through the flow passage 90 also flows in the axial direction of the rotating shaft 41 between the ridge portions 80 and the first bearing holder 21.

[0080] The first bearing holder 21 is cooled by the cooling water flowing through the cooling fluid path 17. Therefore, the air flowing between the ridge portion 80 and the first bearing holder 21, and the air flowing between the valley portion 81 and the first bearing holder 21, are efficiently cooled by the first bearing holder 21. Therefore, the cooling water flowing through the cooling fluid path 17 is a cooling fluid that cools the air. Therefore, the cooling fluid that cools the air flows through the cooling fluid path 17.

[0081] In the radial bearing 52, heat is generated in the top foil 70 due to the dynamic pressure of the air film generated between the top foil 70 and the rotating shaft 41. At this time, as shown in FIG. 5 , the air flowing through the first flow passage 91 cools the top foil 70. The air that has flowed through the first flow passage 91 flows through the second flow passage 92 via the slits 82, and is thereby efficiently cooled by the first bearing holder 21. Then, the air that has been cooled by the first bearing holder 21 by flowing through the second flow passage 92 flows into the third flow passage 93 via the slits 82. As a result, the top foil 70 is further cooled by the air flowing through the third flow passage 93.

[0082] As shown in FIG. 6 , the air flowing through the fourth flow path 94 is cooled by the first bearing holder 21. Then, the air that has been cooled by the first bearing holder 21 by flowing through the fourth flow path 94 flows into the fifth flow path 95 via the slit 82. Therefore, the top foil 70 is cooled by the air flowing through the fifth flow path 95. Furthermore, the air that has flowed through the fifth flow path 95 flows through the sixth flow path 96 via the slit 82, and is thereby cooled by the first bearing holder 21. As a result, even if heat from the top foil 70 is dissipated into the air, an increase in the temperature of the air is suppressed. This makes it easier to avoid problems such as a deterioration in the cooling performance of the portion of the top foil 70 that is located downstream of the air.

[0083] 5 , the air heated by the heat from the top foil 70 while flowing through the first flow passage 91 merges with the air flowing between the valley portions 81 of the elastic deformation portions 77 that form the first flow passage 91 and the first bearing holder 21 through the slits 82 in the second flow passage 92, where it is cooled. Furthermore, the air flowing between the peak portions 80 of the elastic deformation portions 77 that form the second flow passage 92 and the top foil 70 cools the top foil 70. The air heated by the heat from the top foil 70 while flowing between the peak portions 80 of the elastic deformation portions 77 that form the second flow passage 92 and the top foil 70 merges with the air flowing through the second flow passage 92 through the slits 82 in the third flow passage 93, where it is cooled.

[0084] 6 , air flowing between the top foil 70 and the peaks 80 of the elastically deforming portion 77 that form the fourth flow passage 94 cools the top foil 70. The air is heated by heat from the top foil 70 while flowing between the peaks 80 of the elastically deforming portion 77 that form the fourth flow passage 94, and is cooled by merging with the air flowing through the fourth flow passage 94 in a fifth flow passage 95 via the slits 82. The air is heated by heat from the top foil 70 while flowing through the fifth flow passage 95, and is cooled by merging with the air flowing between the valleys 81 of the elastically deforming portion 77 that form the fifth flow passage 95 and the first bearing retainer 21 in a sixth flow passage 96 via the slits 82.

[0085] In this way, the peaks 80 and the valleys 81 of the elastic deformation portions 77 that are adjacent in the direction in which the rotation axis L1 of the rotating shaft 41 extends are offset with respect to the rotation direction of the rotating shaft 41. Therefore, the air that is warmed by the heat from the top foil 70 when flowing between the peaks 80 and the top foil 70 is cooled by merging with the air flowing between the peaks 80 and the first bearing holder 21. In addition, the air that is warmed by the heat from the top foil 70 when flowing between the valleys 81 and the top foil 70 is cooled by merging with the air flowing between the valleys 81 and the first bearing holder 21.

[0086] Effects of the Embodiment The above embodiment can achieve the following effects. (1) The peaks 80 and valleys 81 of the elastic deformation portions 77 that are adjacent to each other in the direction in which the rotation axis L1 of the rotating shaft 41 extends are offset from each other with respect to the rotation direction of the rotating shaft 41. Here, for example, consider a case in which the peaks 80 of the elastic deformation portions 77 that are adjacent to each other in the direction in which the rotation axis L1 of the rotating shaft 41 extends are offset from each other with respect to the rotation direction of the rotating shaft 41. In this case, air that is heated by heat from the top foil 70 while flowing between the peaks 80 and the top foil 70 is cooled by merging with air flowing between the peaks 80 and the housing 11. Furthermore, for example, consider a case in which the valleys 81 of the elastic deformation portions 77 that are adjacent to each other in the direction in which the rotation axis L1 of the rotating shaft 41 extends are offset from each other with respect to the rotation direction of the rotating shaft 41. In this case, the air that is warmed by heat from the top foil 70 as it flows between the valley portions 81 and the top foil 70 merges with the air flowing between the valley portions 81 and the housing 11 and is cooled. As a result, even if the heat of the top foil 70 is dissipated into the air, the air temperature can be prevented from rising, which makes it easier to avoid problems such as a deterioration in the cooling performance of the portion of the top foil 70 that is located downstream of the air. Therefore, the top foil 70 can be cooled efficiently.

[0087] (2) The air flow path 90, which flows between the rotating shaft 41 and the housing 11, which are overlapping in the radial direction, includes a first flow path 91 and a second flow path 92. The first flow path 91 extends between the top foil 70 and a valley portion 81 of one of the elastic deformation portions 77. The second flow path 92 extends between the housing 11 and a peak portion 80 of an adjacent elastic deformation portion 77 downstream of the first flow path 91 in the air flow direction. The air that flows through the first flow path 91 then flows through the second flow path 92. This allows the air that flows through the first flow path 91 to be efficiently cooled by the housing 11 by flowing through the second flow path 92. As a result, even if heat from the top foil 70 is dissipated to the air, it is possible to further easily suppress an increase in the air temperature. This makes it easier to avoid problems such as a deterioration in the cooling performance of the portion of the top foil 70 located downstream of the air. Therefore, the top foil 70 can be cooled more efficiently.

[0088] (3) The air flow path 90 further includes a third flow path 93 extending between the top foil 70 and the valley portion 81 of an adjacent elastic deformation portion 77, among the multiple elastic deformation portions 77, downstream in the air flow direction with respect to the second flow path 92. The air that has flowed through the second flow path 92 then flows through the third flow path 93. As a result, the air that has been cooled by the housing 11 by flowing through the second flow path 92 flows into the third flow path 93. Therefore, the top foil 70 can be cooled more efficiently by the air flowing through the third flow path 93.

[0089] (4) The air flow path 90 has a fourth flow path 94 and a fifth flow path 95. The fourth flow path 94 extends between the housing 11 and one of the peak portions 80 of the multiple elastic deformation portions 77. The fifth flow path 95 extends between the top foil 70 and a valley portion 81 of an adjacent elastic deformation portion 77 downstream of the fourth flow path 94 in the air flow direction. The air that has flowed through the fourth flow path 94 then flows through the fifth flow path 95. As a result, the air that has flowed through the fourth flow path 94 and been cooled by the housing 11 then flows through the fifth flow path 95. Therefore, the top foil 70 can be cooled more efficiently by the air flowing through the fifth flow path 95.

[0090] (5) The air flow path 90 further includes a sixth flow path 96 extending between the housing 11 and the peak portion 80 of the adjacent elastic deformation portion 77 downstream of the fifth flow path 95 in the air flow direction. The air that has flowed through the fifth flow path 95 then flows through the sixth flow path 96. This allows the air that has flowed through the fifth flow path 95 to be efficiently cooled by the housing 11 by flowing through the sixth flow path 96. As a result, even if heat from the top foil 70 is dissipated into the air, it is possible to further suppress an increase in the air temperature. This further facilitates avoiding a problem such as a deterioration in the cooling performance of the portion of the top foil 70 located downstream of the air. Therefore, the top foil 70 can be cooled more efficiently.

[0091] (6) The configuration in which the slits 82 are provided in the bump foil 71 is suitable for allowing the air heated by the heat from the top foil 70 when flowing between the peak portions 80 and the top foil 70 to merge with the air flowing between the peak portions 80 and the housing 11. In addition, the configuration in which the slits 82 are provided in the bump foil 71 is suitable for allowing the air heated by the heat from the top foil 70 when flowing between the valley portions 81 and the top foil 70 to merge with the air flowing between the valley portions 81 and the housing 11.

[0092] (7) The resin coating layer 70a has lower heat resistance than the top foil 70. Even if the top foil 70 has the resin coating layer 70a on the portion facing the rotating shaft 41, the durability of the resin coating layer 70a can be improved by efficiently cooling the top foil 70.

[0093] (8) The housing 11 is formed of a material with a higher thermal conductivity than the top foil 70 and the bump foil 71. As a result, the air flowing between the peaks 80 and the housing 11 and the air flowing between the valleys 81 and the housing 11 is efficiently cooled by the housing 11. As a result, the top foil 70 can be cooled even more efficiently by the air.

[0094] [Modifications] The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0095] 7 , the phase between the centers C1 of adjacent peaks 80 in one of the elastic deformation portions 77 adjacent to each other in the direction of extension of the rotation axis L1 of the rotation shaft 41 may be shifted by half relative to the phase between the centers C1 of adjacent peaks 80 in the other of the elastic deformation portions 77 adjacent to each other in the direction of extension of the rotation axis L1 of the rotation shaft 41. Furthermore, the phase between the centers C2 of adjacent valleys 81 in one of the elastic deformation portions 77 adjacent to each other in the direction of extension of the rotation axis L1 of the rotation shaft 41 may be shifted by half relative to the phase between the centers C2 of adjacent valleys 81 in the other of the elastic deformation portions 77 adjacent to each other in the direction of extension of the rotation axis L1 of the rotation shaft 41.

[0096] The center C1 of the peak portion 80 is the portion of the peak portion 80 that is located in the center in the rotation direction of the rotating shaft 41. The center C1 of the peak portion 80 is the highest point of the peak portion 80. The center C2 of the valley portion 81 is the portion of the valley portion 81 that is located in the center in the rotation direction of the rotating shaft 41.

[0097] This makes it possible to easily prevent uneven temperatures from occurring between the bump foil 71 and the top foil 70. As a result, the top foil 70 can be cooled more efficiently.

[0098] Fig. 8 shows a modification of the embodiment shown in Fig. 7. As shown in Fig. 8, each peak 80 may be an elongated plate extending along the outer surface of the top foil 70. Each valley 81 may be a curved plate recessed from the peak 80 toward the first bearing holder 21.

[0099] Fig. 9 shows a modification of the embodiment shown in Fig. 7. As shown in Fig. 9, each peak 80 may be a curved plate-like member that is convex relative to the valley 81 toward the top foil 70, and each valley 81 may be a curved plate-like member that is concave and curved from the peak 80 toward the first bearing holder 21.

[0100] As shown in FIG. 10 , the elastic deformation portion 77 may have a connection portion 83 that connects the peak portion 80 and the valley portion 81. The connection portion 83 is in the form of an elongated plate. The connection portion 83 extends along the outer surface of the top foil 70 and the inner circumferential surface of the first bearing holder 21. The peak portions 80 and the valley portions 81 are alternately arranged with the connection portion 83 sandwiched therebetween. The peak portions 80 are protruding from the connection portion 83 toward the top foil 70. The peak portions 80 connect adjacent connection portions 83 in the rotation direction of the rotating shaft 41. The valley portions 81 are recessed from the connection portion 83 toward the first plate 15. The valley portions 81 connect adjacent connection portions 83 in the rotation direction of the rotating shaft 41. The peak portions 80 are in the form of a curved plate that is convex from the connection portion 83 toward the top foil 70. The valley portion 81 is a curved plate-like recess that is curved from the connection portion 83 toward the first plate 15 .

[0101] The connection portions 83 of the elastic deformation portions 77 that are adjacent in the direction in which the rotation axis L1 of the rotating shaft 41 extends are offset from each other in the rotation direction of the rotating shaft 41. The phase between the centers C1 of the adjacent peak portions 80 of one of the elastic deformation portions 77 that are adjacent in the direction in which the rotation axis L1 of the rotating shaft 41 extends is shifted by ¼ from the phase between the centers C1 of the adjacent peak portions 80 of the other of the elastic deformation portions 77 that are adjacent in the direction in which the rotation axis L1 of the rotating shaft 41 extends. The phase between the centers C2 of the adjacent valley portions 81 of the other of the elastic deformation portions 77 that are adjacent in the direction in which the rotation axis L1 of the rotating shaft 41 extends is shifted by ¼ from the phase between the centers C2 of the adjacent valley portions 81 of the other of the elastic deformation portions 77 that are adjacent in the direction in which the rotation axis L1 of the rotating shaft 41 extends.

[0102] The center C1 of the peak portion 80 is the portion of the peak portion 80 that is located in the center in the rotation direction of the rotating shaft 41. The center C1 of the peak portion 80 is the highest point of the peak portion 80. The center C2 of the valley portion 81 is the portion of the valley portion 81 that is located in the center in the rotation direction of the rotating shaft 41. The center C2 of the valley portion 81 is the lowest point of the valley portion 81.

[0103] This makes it possible to easily prevent uneven temperatures from occurring between the bump foil 71 and the top foil 70. As a result, the top foil 70 can be cooled more efficiently.

[0104] Furthermore, since the elastic deformation portions 77 have connection portions 83 that connect the peak portions 80 and the valley portions 81, the durability of the bump foil 71 can be improved. In this configuration, the connection portions 83 of the elastic deformation portions 77 that are adjacent to each other in the direction in which the rotation axis L1 of the rotating shaft 41 extends are offset from each other in the rotation direction of the rotating shaft 41. This allows air that is heated by heat from the top foil 70 when flowing between the peak portions 80 and the top foil 70 to merge with air flowing between the peak portions 80 and the housing 11 and be cooled. Furthermore, air that is heated by heat from the top foil 70 when flowing between the valley portions 81 and the top foil 70 to merge with air flowing between the valley portions 81 and the housing 11 and be cooled. As a result, even if heat from the top foil 70 is dissipated into the air, the temperature of the air can be prevented from rising, which makes it easier to avoid problems such as a deterioration in the cooling performance of a portion of the top foil 70 that is located downstream of the air. Therefore, the top foil 70 can be cooled efficiently.

[0105] In the embodiment shown in Figure 7, the phase between the centers C1 of adjacent peaks 80 on one of the elastic deformation portions 77 adjacent to each other in the direction in which the rotation axis L1 of the rotation shaft 41 extends does not have to be shifted by 1 / 2 relative to the phase between the centers C1 of adjacent peaks 80 on the other of the elastic deformation portions 77 adjacent to each other in the direction in which the rotation axis L1 of the rotation shaft 41 extends.

[0106] In the embodiment shown in Figure 7, the phase between the centers C2 of adjacent valley portions 81 in one of the elastic deformation portions 77 adjacent to each other in the direction in which the rotation axis L1 of the rotation shaft 41 extends does not have to be shifted by 1 / 2 relative to the phase between the centers C2 of adjacent valley portions 81 in the other of the elastic deformation portions 77 adjacent to each other in the direction in which the rotation axis L1 of the rotation shaft 41 extends. In short, it is sufficient if at least one of the following is shifted by 1 / 2: the phase between the centers C1 of adjacent peak portions 80 on one of the elastic deformation portions 77 adjacent to each other in the direction in which the rotation axis L1 of the rotation shaft 41 extends relative to the phase between the centers C1 of adjacent peak portions 80 on the other of the elastic deformation portions 77 adjacent to each other in the direction in which the rotation axis L1 of the rotation shaft 41 extends; and the phase between the centers C2 of adjacent valley portions 81 on one of the elastic deformation portions 77 adjacent to each other in the direction in which the rotation axis L1 of the rotation shaft 41 extends relative to the phase between the centers C2 of adjacent valley portions 81 on the other of the elastic deformation portions 77 adjacent to each other in the direction in which the rotation axis L1 of the rotation shaft 41 extends.

[0107] In the embodiment, the peaks 80 of the elastic deformation portions 77 that are adjacent to each other in the extension direction of the rotation axis L1 of the rotation shaft 41 do not have to be offset from each other. In the embodiment, the valleys 81 of the elastic deformation portions 77 that are adjacent to each other in the extension direction of the rotation axis L1 of the rotation shaft 41 do not have to be offset from each other. In short, it is sufficient that at least one of the peaks 80 and the valleys 81 of the elastic deformation portions 77 that are adjacent to each other in the extension direction of the rotation axis L1 of the rotation shaft 41 are offset from each other with respect to the rotation direction of the rotation shaft 41.

[0108] In the embodiment, instead of the slits 82, the bump foil 71 may be provided with, for example, through holes extending in the rotational direction of the rotary shaft 41. In the embodiment, the ends of the elastic deformation portions 77 on the fixed end 78 side may not be connected to each other by the fixed end 78, and each elastic deformation portion 77 may be independent. In this case, the bump foil 71 is made up of a plurality of elastic deformation portions 77. One longitudinal end of each elastic deformation portion 77 constitutes the fixed end of the bump foil 71. The other longitudinal end of each elastic deformation portion 77 constitutes the free end of the bump foil 71.

[0109] In the embodiment, there is no particular limitation on the number of slits 82. In the embodiment, the top foil 70 does not have to have the resin coating layer 70a.

[0110] In the above-mentioned embodiment, for example, air may flow as the cooling fluid through the cooling fluid path 17. In the above-mentioned embodiment, the cooling fluid path 17 may not be built into the housing 11.

[0111] In the embodiment, the housing 11 does not have to be made of a material having a higher thermal conductivity than the top foil 70 and the bump foil 71. In the embodiment, the bump foil 71 may be divided into multiple parts in the circumferential direction. In this case, for example, the inner circumferential surface of the first bearing holder 21 is formed with multiple retaining grooves 72 a in which the fixed ends 78 of the bump foils 71 are respectively held.

[0112] In the embodiment, the centrifugal compressor 10 does not have to be mounted on a fuel cell vehicle. In other words, the centrifugal compressor 10 is not limited to being mounted on a vehicle. In the embodiment, the centrifugal compressor 10 is not limited to being used for compressing air supplied to the fuel cell stack 61. In other words, the centrifugal compressor 10 may be any compressor that compresses gas.

[0113] [Notes] The technical ideas that can be understood from the above-described embodiments and modified examples are described below. <Note 1> A foil bearing comprising: a top foil that faces a rotating body in the radial direction; a bump foil that is arranged on the opposite side of the rotating body with the top foil sandwiched therebetween and elastically supports the top foil; and a housing that is arranged on the opposite side of the top foil with the bump foil sandwiched therebetween and supports the top foil and the bump foil, wherein the bump foil has a fixed end fixed to the housing and an elastically deforming portion that extends from the fixed end and is formed so that peaks that contact the top foil and valleys that contact the housing are arranged alternately in a rotational direction of the rotating body, wherein a plurality of the elastically deforming portions are arranged side by side in a direction extending along a rotation axis of the rotating body, and at least one of the peaks and valleys of elastically deforming portions that are adjacent in the direction extending along the rotation axis of the rotating body are offset with respect to the rotational direction.

[0114] <Appendix 2> The foil bearing described in <Appendix 1>, characterized in that the housing has a built-in cooling fluid path that extends to overlap the elastic deformation portion in the radial direction and through which a cooling fluid flows, and the gas flow path that flows between the rotating body and the housing that overlap in the radial direction has: a first flow path that extends between the valley portion of one of the plurality of elastic deformation portions and the top foil, and a second flow path that extends between the housing and the peak portion of an adjacent elastic deformation portion of the plurality of elastic deformation portions that is downstream in the gas flow direction with respect to the first flow path,

[0115] <Appendix 3> The foil bearing described in <Appendix 2>, characterized in that the gas flow path further has a third flow path extending between the top foil and the valley portion of an adjacent elastic deformation portion among the plurality of elastic deformation portions that is downstream in the gas flow direction with respect to the second flow path, and the gas that has flowed through the second flow path flows through the third flow path.

[0116] <Appendix 4> The foil bearing according to <Appendix 1>, characterized in that the housing incorporates a cooling fluid path that extends to overlap the elastic deformation portion in the radial direction and through which a cooling fluid flows, and the gas flow path that flows between the rotating body and the housing that overlap in the radial direction includes: a fourth flow path that extends between the housing and the peak portion of one of the plurality of elastic deformation portions; and a fifth flow path that extends between the top foil and the valley portion of an adjacent elastic deformation portion among the plurality of elastic deformation portions that is downstream of the fourth flow path in the gas flow direction, and the gas that has flowed through the fourth flow path flows through the fifth flow path.

[0117] <Appendix 5> The foil bearing described in <Appendix 4>, characterized in that the gas flow path further has a sixth flow path extending between the housing and the peak portion of an adjacent elastic deformation portion among the plurality of elastic deformation portions that is downstream in the gas flow direction with respect to the fifth flow path, and the gas that has flowed through the fifth flow path flows through the sixth flow path.

[0118] <Appendix 6> The foil bearing according to any one of <Appendix 1> to <Appendix 5>, wherein at least one of the phase between the centers of adjacent peaks in one of the elastic deformation portions adjacent in the direction of extension of the rotation axis of the rotating body relative to the phase between the centers of adjacent peaks in the other of the elastic deformation portions adjacent in the direction of extension of the rotation axis of the rotating body, and the phase between the centers of adjacent valleys in one of the elastic deformation portions adjacent in the direction of extension of the rotation axis of the rotating body relative to the phase between the centers of adjacent valleys in the other of the elastic deformation portions adjacent in the direction of extension of the rotation axis of the rotating body, is shifted by ½.

[0119] <Appendix 7> The foil bearing according to any one of <Appendix 1> to <Appendix 5>, characterized in that the elastically deforming portions have connection portions that connect the peak portions and the valley portions, the peak portions and the valley portions are arranged alternately with the connection portions sandwiched therebetween, the peak portions are provided in a protruding manner from the connection portions toward the top foil, and the valley portions are provided in a recessed manner from the connection portions toward the housing, and the connection portions of the elastically deforming portions that are adjacent to each other in a direction in which the rotation axis of the rotating body extends are offset from each other in the rotation direction.

[0120] <Appendix 8> The foil bearing according to <Appendix 7>, characterized in that the phase between the centers of adjacent peaks in one of the elastic deformation portions adjacent in the direction of extension of the rotation axis of the rotating body is shifted by ¼ with respect to the phase between the centers of adjacent peaks in the other of the elastic deformation portions adjacent in the direction of extension of the rotation axis of the rotating body, and the phase between the centers of adjacent valleys in one of the elastic deformation portions adjacent in the direction of extension of the rotation axis of the rotating body is shifted by ¼ with respect to the phase between the centers of adjacent valleys in the other of the elastic deformation portions adjacent in the direction of extension of the rotation axis of the rotating body.

[0121] <Appendix 9> The foil bearing according to any one of <Appendix 1> to <Appendix 8>, wherein the bump foil is provided on the opposite side of the fixed end with respect to the rotation direction, and has a free end that is not fixed to the housing, and the bump foil is provided with a slit that extends in the rotation direction from the free end toward the fixed end between elastic deformation portions that are adjacent in the direction in which the rotation axis of the rotating body extends.

[0122] <Appendix 10> The foil bearing according to any one of <Appendix 1> to <Appendix 9>, wherein the top foil has a resin coating layer on a portion facing the rotating body, and the resin coating layer has lower heat resistance than the top foil.

[0123] <Appendix 11> The foil bearing according to any one of <Appendix 1> to <Appendix 10>, wherein the housing is formed of a material having a higher thermal conductivity than the top foil and the bump foil.

[0124] REFERENCE SIGNS LIST 11 Housing 17 Cooling fluid path 41 Rotating shaft as a rotating body 52 Radial bearing as a foil bearing 70 Top foil 70a Resin coating layer 71 Bump foil 77 Elastically deformable portion 78 Fixed end 79 Free end 80 Peak portion 81 Valley portion 82 Slit 83 Connection portion 90 Flow path 91 First flow path 92 Second flow path 93 Third flow path 94 Fourth flow path 95 Fifth flow path 96 Sixth flow path

Claims

1. A foil bearing comprising: a top foil radially opposed to a rotating body; a bump foil arranged on the opposite side of the rotating body with the top foil sandwiched therebetween and elastically supporting the top foil; and a housing arranged on the opposite side of the top foil with the bump foil sandwiched therebetween and supporting the top foil and the bump foil, wherein the bump foil has a fixed end fixed to the housing and an elastically deforming portion extending from the fixed end and formed so that peaks contacting the top foil and valleys contacting the housing are arranged alternately in the rotational direction of the rotating body, wherein a plurality of the elastically deforming portions are arranged side by side in the direction of extension of the rotational axis of the rotating body, and at least one of the peaks and valleys of elastically deforming portions adjacent in the direction of extension of the rotational axis of the rotating body are offset with respect to the rotational direction.

2. A foil bearing as described in claim 1, characterized in that the housing incorporates a cooling fluid path through which a cooling fluid flows, the cooling fluid path extending to overlap the elastically deforming portion in the radial direction, and the gas flow path flowing between the rotating body and the housing overlapping in the radial direction includes a first flow path extending between the valley portion of one of the plurality of elastically deforming portions and the top foil, and a second flow path extending between the housing and the peak portion of an adjacent elastically deforming portion among the plurality of elastically deforming portions downstream in the gas flow direction with respect to the first flow path, and the gas that has flowed through the first flow path flows through the second flow path.

3. A foil bearing as described in claim 2, characterized in that the gas flow path further has a third flow path extending between the top foil and the valley portion of an adjacent elastic deformation portion among the plurality of elastic deformation portions that is downstream in the gas flow direction relative to the second flow path, and the gas that has flowed through the second flow path flows through the third flow path.

4. A foil bearing as described in claim 1, characterized in that the housing incorporates a cooling fluid path through which a cooling fluid flows, the cooling fluid path extending to overlap the elastic deformation portion in the radial direction, and the gas flow path flowing between the rotating body and the housing overlapping in the radial direction includes: a fourth flow path extending between the housing and the peak portion of one of the plurality of elastic deformation portions; and a fifth flow path extending between the top foil and the valley portion of an adjacent elastic deformation portion among the plurality of elastic deformation portions downstream of the fourth flow path in the gas flow direction, the gas having flowed through the fourth flow path then flows through the fifth flow path.

5. A foil bearing as described in claim 4, characterized in that the gas flow path further has a sixth flow path extending between the housing and the peak of an adjacent elastic deformation portion among the plurality of elastic deformation portions that is downstream in the gas flow direction relative to the fifth flow path, and the gas that has flowed through the fifth flow path flows through the sixth flow path.

6. A foil bearing as claimed in any one of claims 1 to 5, characterized in that at least one of the phase between the centers of adjacent peaks in one of the elastically deforming sections adjacent in the direction of extension of the rotation axis of the rotating body relative to the phase between the centers of adjacent peaks in the other of the elastically deforming sections adjacent in the direction of extension of the rotation axis of the rotating body, and the phase between the centers of adjacent valleys in one of the elastically deforming sections adjacent in the direction of extension of the rotation axis of the rotating body relative to the phase between the centers of adjacent valleys in the other of the elastically deforming sections adjacent in the direction of extension of the rotation axis of the rotating body, is shifted by 1 / 2.

7. A foil bearing as described in any one of claims 1 to 5, characterized in that the elastically deforming portion has a connection portion connecting the crest portion and the valley portion, the crest portion and the valley portion are arranged alternately with the connection portion sandwiched therebetween, the crest portion is provided protruding from the connection portion toward the top foil, and the valley portion is provided recessed from the connection portion toward the housing, and the connection portions of elastically deforming portions adjacent to each other in the direction in which the rotation axis of the rotating body extends are offset from each other in the rotation direction.

8. A foil bearing as described in claim 7, characterized in that the phase between the centers of adjacent peaks in one of the elastically deforming sections adjacent to each other in the direction of extension of the rotation axis of the rotating body is shifted by 1 / 4 compared to the phase between the centers of adjacent peaks in the other of the elastically deforming sections adjacent to each other in the direction of extension of the rotation axis of the rotating body, and the phase between the centers of adjacent valleys in the other of the elastically deforming sections adjacent to each other in the direction of extension of the rotation axis of the rotating body is shifted by 1 / 4 compared to the phase between the centers of adjacent valleys in one of the elastically deforming sections adjacent to each other in the direction of extension of the rotation axis of the rotating body.

9. A foil bearing as claimed in any one of claims 1 to 5, characterized in that the bump foil is provided on the opposite side of the fixed end in the direction of rotation and has a free end that is not fixed to the housing, and the bump foil is provided with a slit extending in the direction of rotation from the free end to the fixed end between adjacent elastic deformation portions in the direction in which the rotation axis of the rotating body extends.

10. A foil bearing as described in any one of claims 1 to 5, characterized in that the top foil has a resin coating layer on the portion facing the rotating body, and the resin coating layer has lower heat resistance than the top foil.

11. A foil bearing according to any one of claims 1 to 5, characterized in that the housing is formed from a material having a higher thermal conductivity than the top foil and the bump foil.

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