Foil bearing

Abstract

To improve the reliability of foil bearings. [Solution] Spacer peaks 51 are provided in the space between adjacent valleys 44 in the circumferential direction of the rotating shaft 12, and are more rigid than the bump foil 40, acting as deformation restricting parts that restrict the deformation of the peaks 43. The spacer peaks 51 protrude toward the peaks 43 in the radial direction of the rotating shaft 12 so as to form a gap 55 between them, and when the rotating shaft 12 rotates, the peaks 43 deform toward the spacer peaks 51 so as to reduce the gap 55 between them. Even if the rotating shaft 12 vibrates or moves radially, and the rotating shaft 12 moves in such a way that the top foil 30 crushes the peaks 43 of the bump foil 40, the deformation of the peaks 43 is restricted by the spacer peaks 51. Therefore, the peaks 43 are not completely crushed, and the decrease in the fatigue strength of the bump foil 40 is suppressed.

Description

Technical Field

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

Background Art

[0002] For example, as disclosed in Patent Document 1, a foil bearing that supports a rotating shaft in the radial direction includes a bearing housing, a top foil, and a bump foil. The bearing housing has a through-hole through which the rotating shaft is inserted. The top foil is in the form of a thin plate. The top foil is disposed between the rotating shaft and the bearing housing. The bump foil is in the form of a thin plate. The bump foil is disposed between the bearing housing and the top foil. The bump foil has a plurality of ridges and a plurality of valleys. The ridges contact the top foil. The valleys are supported by the bearing housing. The ridges and valleys are arranged alternately in the circumferential direction of the rotating shaft. And the bump foil elastically supports the top foil.

[0003] Such a foil bearing supports the rotating shaft in a state where the rotating shaft and the top foil are in contact until the rotating speed of the rotating shaft reaches the floating rotational speed. Then, when the rotational speed of the rotating shaft reaches the floating rotational speed, the rotating shaft floats with respect to the top foil due to the dynamic pressure of the fluid film generated between the top foil and the rotating shaft. Thereby, the foil bearing supports the rotating shaft without contacting the rotating shaft.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] For example, if the rotating shaft vibrates and moves radially, the rotating shaft may move until the bump foil's peaks are completely crushed by the top foil. If this complete crushing of the peaks occurs repeatedly, the fatigue strength of the bump foil decreases. A decrease in the fatigue strength of the bump foil reduces the reliability of the foil bearing. [Means for solving the problem]

[0006] A foil bearing that solves the above problems is a foil bearing that supports a rotating shaft in the radial direction, comprising: a bearing housing having a through hole through which the rotating shaft is inserted; a thin plate-shaped top foil disposed between the rotating shaft and the bearing housing; and a thin plate-shaped bump foil disposed between the bearing housing and the top foil and elastically supporting the top foil, wherein the bump foil has a plurality of peaks that contact the top foil and a plurality of valleys that are supported by the bearing housing, the peaks and valleys are arranged alternately in the circumferential direction of the rotating shaft, and a deformation restricting portion is provided in the space between adjacent valleys in the circumferential direction of the rotating shaft, which has higher rigidity than the bump foil and restricts the deformation of the peaks, the deformation restricting portion protrudes toward the peaks in the radial direction of the rotating shaft such that a gap is formed between the peaks and the deformation restricting portion, and when the rotating shaft rotates, the peaks deform toward the deformation restricting portion such that the gap becomes smaller.

[0007] According to this design, a deformation restricting section, which is more rigid than the bump foil and restricts the deformation of the peaks, is provided in the space between adjacent valleys in the circumferential direction of the rotating shaft. The deformation restricting section protrudes toward the peaks in the radial direction of the rotating shaft so as to form a gap between it and the peaks. When the rotating shaft rotates, the peaks deform toward the deformation restricting section so as to reduce the gap between them. Therefore, even if the rotating shaft vibrates and moves radially, causing the rotating shaft to move in a way that crushes the peaks of the bump foil with the top foil, the deformation of the peaks is restricted by the deformation restricting section. Thus, complete crushing of the peaks is avoided, and a decrease in the fatigue strength of the bump foil can be suppressed. As a result, the reliability of the foil bearing can be improved.

[0008] In the foil bearing described above, a corrugated spacer is provided between the bearing housing and the bump foil, and is thicker than the thickness of the bump foil. The spacer has a spacer peak that protrudes toward the peak and a spacer trough that contacts the bearing housing and supports the trough. The pitch between adjacent peaks in the circumferential direction of the rotating shaft is equal to the pitch between adjacent spacer peaks in the circumferential direction of the rotating shaft, and the spacer peak is the deformation restricting portion.

[0009] According to this design, the spacer valleys contact the bearing housing and support the valleys of the bump foil. Therefore, even if a corrugated spacer is placed between the bearing housing and the bump foil, the valleys of the bump foil are suitably supported by the bearing housing via the spacer valleys. The spacer peaks protrude toward the peaks. The pitch between adjacent peaks in the circumferential direction of the rotating shaft is equal to the pitch between adjacent spacer peaks in the circumferential direction of the rotating shaft. Therefore, the spacer peaks act as deformation restrictors. In this case, the spacer is thicker than the bump foil and thus has higher rigidity than the bump foil. Therefore, even if the rotating shaft vibrates and moves radially, causing the rotating shaft to move in a way that crushes the peaks of the bump foil with the top foil, the deformation of the peaks is suitably restricted by the spacer peaks. Thus, complete crushing of the peaks is avoided, and a decrease in the fatigue strength of the bump foil can be suppressed. As a result, the reliability of the foil bearing can be improved.

[0010] In the foil bearing described above, a cylindrical spacer is provided between the bearing housing and the bump foil, the outer circumferential surface of the spacer is in contact with the inner circumferential surface of the bearing housing, the inner circumferential surface of the spacer has spacer protrusions projecting toward the peaks and spacer recesses supporting the valleys, the pitch between adjacent peaks in the circumferential direction of the rotating shaft is equal to the pitch between adjacent spacer protrusions in the circumferential direction of the rotating shaft, and the spacer protrusions are preferably the deformation restricting portions.

[0011] According to this, the outer surface of the spacer is in contact with the inner surface of the bearing housing, and the recess of the spacer supports the valleys of the bump foil. Therefore, even if a cylindrical spacer is placed between the bearing housing and the bump foil, the valleys of the bump foil are suitably supported by the bearing housing via the recess of the spacer. Furthermore, the convex portion of the spacer protrudes toward the peaks. The pitch between adjacent peaks in the circumferential direction of the rotating shaft is equal to the pitch between adjacent spacer convex portions in the circumferential direction of the rotating shaft. Therefore, the spacer convex portion is a deformation restricting portion. In this case, since the outer surface of the spacer is in contact with the inner surface of the bearing housing, movement in the direction that crushes the peaks of the spacer is restricted. Therefore, for example, even if the rotating shaft vibrates and moves radially, and the rotating shaft moves in such a way that the top foil crushes the peaks of the bump foil, the deformation of the peaks is suitably restricted by the spacer convex portion. Thus, complete crushing of the peaks is avoided, and a decrease in the fatigue strength of the bump foil can be suppressed. As a result, the reliability of foil bearings can be improved.

[0012] In the foil bearing described above, the inner circumferential surface of the bearing housing has housing protrusions projecting toward the peaks and housing recesses supporting the valleys, and the pitch between adjacent peaks in the circumferential direction of the rotating shaft is equal to the pitch between adjacent housing protrusions in the circumferential direction of the rotating shaft, and the housing protrusions are preferably the deformation restricting portions.

[0013] According to this design, the valleys of the bump foil are suitably supported by the recesses in the housing. The convex portions of the housing protrude toward the peaks. The pitch between adjacent peaks in the circumferential direction of the rotating shaft is equal to the pitch between adjacent housing convex portions in the circumferential direction of the rotating shaft. Therefore, the housing convex portions act as deformation restrictors. Consequently, even if the rotating shaft vibrates and moves radially, causing the rotating shaft to move in a way that crushes the peaks of the bump foil with the top foil, the deformation of the peaks is suitably restricted by the housing convex portions. Thus, complete crushing of the peaks is avoided, and a decrease in the fatigue strength of the bump foil can be suppressed. As a result, the reliability of the foil bearing can be improved. [Effects of the Invention]

[0014] This invention makes it possible to improve the reliability of foil bearings. [Brief explanation of the drawing]

[0015] [Figure 1] Figure 1 is a schematic diagram showing a centrifugal compressor in an embodiment. [Figure 2] Figure 2 is an exploded perspective view illustrating the foil bearing. [Figure 3] Figure 3 is a cross-sectional view illustrating a foil bearing. [Figure 4] Figure 4 is a cross-sectional view showing a magnified portion of the foil bearing. [Figure 5] Figure 5 is a cross-sectional view showing a magnified portion of the foil bearing in the modified example. [Figure 6] Figure 6 is a cross-sectional view showing a magnified portion of the foil bearing in the modified example. [Modes for carrying out the invention]

[0016] Hereinafter, an embodiment in which the foil bearing is embodied will be described according to FIGS. 1 to 4. 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. And the centrifugal compressor compresses air as a fluid containing oxygen supplied to the fuel cell.

[0017] <Centrifugal compressor> As shown in FIG. 1, the centrifugal compressor 10 includes a housing 11, a rotating shaft 12, an impeller 13, and a motor 14. The housing 11 is cylindrical. The housing 11 is made of metal. The rotating shaft 12 is accommodated in the housing 11 in a state where the axis of the rotating shaft 12 coincides with the axis of the housing 11. The housing 11 has an impeller chamber 15 and a motor chamber 16. The impeller chamber 15 and the motor chamber 16 are arranged side by side in the axial direction of the rotating shaft 12. The housing 11 has a partition wall 17. The partition wall 17 separates the impeller chamber 15 and the motor chamber 16. The first end of the rotating shaft 12 protrudes into the impeller chamber 15 through the partition wall 17 from the motor chamber 16.

[0018] The impeller 13 is accommodated in the impeller chamber 15. The impeller 13 is connected to the first end of the rotating shaft 12. The impeller 13 rotates integrally with the rotating shaft 12 to compress air, which is a fluid. The motor 14 is accommodated in the motor chamber 16. The motor 14 rotates the rotating shaft 12.

[0019] The centrifugal compressor 10 includes two foil bearings 20. Each foil bearing 20 is arranged in the housing 11. The two foil bearings 20 are respectively arranged on both sides sandwiching the motor 14. The two foil bearings 20 respectively support the parts on both sides of the motor 14 on the rotating shaft 12 rotatably. Each foil bearing 20 supports the rotating shaft 12 rotatably in the radial direction. Therefore, the foil bearing 20 is a radial bearing. Note that the "radial direction" is a direction orthogonal to the axial direction of the rotating shaft 12. Therefore, the "radial direction" is the radial direction of the rotating shaft 12.

[0020] In the motor chamber 16, a first pipe 18 and a second pipe 19 are connected. The first pipe 18 is connected to a portion of the motor chamber 16 near the impeller chamber 15. The second pipe 19 is connected to a portion of the motor chamber 16 located on the side opposite to the impeller chamber 15. And, air as a cooling fluid is introduced into the motor chamber 16 from the first pipe 18. The air introduced into the motor chamber 16 flows through the motor chamber 16 and is discharged from the second pipe 19. When passing through the motor chamber 16, the air cools two foil bearings 20. Note that the air introduced into the motor chamber 16 from the first pipe 18 is a part of the air compressed and discharged by the rotation of the impeller 13. The air is cooled by an intercooler (not shown) and then introduced into the motor chamber 16 from the first pipe 18.

[0021] <Foil bearing> As shown in FIGS. 2 and 3, the foil bearing 20 includes a bearing housing 21, a top foil 30, and a bump foil 40. The bearing housing 21 has a through hole 22. The through hole 22 is circular. The rotating shaft 12 is inserted through the through hole 22. The bearing housing 21 is a part of the housing 11. Therefore, the bearing housing 21 is made of metal.

[0022] The top foil 30 is in a thin plate shape. The top foil 30 is substantially cylindrical. The top foil 30 is formed, for example, by bending a strip-shaped plate material made of a flexible metal into a cylindrical shape. The top foil 30 is formed of stainless steel or Inconel (registered trademark). The top foil 30 is disposed between the rotating shaft 12 and the bearing housing 21.

[0023] The top foil 30 surrounds the outer peripheral surface of the rotating shaft 12. The top foil 30 has a bearing surface 31. The bearing surface 31 is the inner peripheral surface of the top foil 30. The bearing surface 31 faces the outer peripheral surface of the rotating shaft 12. The bearing surface 31 supports the rotating shaft 12.

[0024] The top foil 30 has a fixed end 32 and a free end 33. The fixed end 32 is located at the first end of the top foil 30. The free end 33 is located at the second end of the top foil 30. The fixed end 32 is formed by bending the first circumferential end of the top foil 30 radially outward. The free end 33 is opposite the fixed end 32, spaced apart in the circumferential direction of the top foil 30. Therefore, the top foil 30 is non-annular with a portion cut out.

[0025] The bump foil 40 is in the form of a thin plate. The bump foil 40 is substantially cylindrical. The bump foil 40 is formed, for example, by curving a flexible metal strip into a wavy shape. The top foil 30 is made of stainless steel or Inconel®. The bump foil 40 is positioned on the opposite side of the rotation axis 12, with the top foil 30 in between. The bump foil 40 is positioned between the bearing housing 21 and the top foil 30. The bump foil 40 elastically supports the top foil 30.

[0026] The bump foil 40 has a fixed end 41 and a free end 42. The fixed end 41 is located at the first end of the bump foil 40. The free end 42 is located at the second end of the bump foil 40. The free end 42 faces the fixed end 41 at a distance from it in the circumferential direction of the bump foil 40. Therefore, the bump foil 40 is non-annular with a portion cut out.

[0027] The fixed end 41 is fixed to the fixed end 32 of the top foil 30, overlapping with the fixed end 32 of the top foil 30 in the radial direction of the rotation axis 12. The free end 42 is not fixed to the top foil 30.

[0028] The bump foil 40 has a plurality of peaks 43 and a plurality of valleys 44. Each peak 43 is convex and in contact with the top foil 30. Each peak 43 is curved in an arc so as to be convex inward in the radial direction of the rotation shaft 12. Each peak 43 is in contact with the outer circumferential surface of the top foil 30. Each valley 44 is curved in an arc so as to be concave outward in the radial direction of the rotation shaft 12 relative to each peak 43. Each valley 44 is supported by the bearing housing 21. Each peak 43 and each valley 44 are arranged alternately in the circumferential direction of the rotation shaft 12. The bump foil 40 is corrugated in shape with each peak 43 and each valley 44 arranged alternately in the circumferential direction of the rotation shaft 12. Each peak 43 connects adjacent valleys 44 in the circumferential direction of the rotation shaft 12. Multiple peaks 43 are arranged such that the pitch between adjacent peaks 43 is constant in the circumferential direction of the rotation axis 12. Multiple valleys 44 are arranged such that the pitch between adjacent valleys 44 is constant in the circumferential direction of the rotation axis 12.

[0029] <Spacer> The foil bearing 20 is equipped with a spacer 50. The spacer 50 is in the shape of a thin plate. The spacer 50 is in the shape of a corrugated plate that is thicker than the thickness of the bump foil 40. The spacer 50 is substantially cylindrical. The spacer 50 is formed, for example, by curving a flexible metal strip into a corrugated shape. The spacer 50 is made of stainless steel or Inconel®. The spacer 50 is more rigid than the bump foil 40. The spacer 50 is positioned between the bearing housing 21 and the bump foil 40.

[0030] The spacer 50 has spacer peaks 51 and spacer valleys 52. The spacer 50 has multiple spacer peaks 51. The spacer 50 has multiple spacer valleys 52. Each spacer peak 51 and each spacer valley 52 are arranged alternately in the circumferential direction of the rotating shaft 12. The spacer 50 is corrugated in shape with each spacer peak 51 and each spacer valley 52 arranged alternately in the circumferential direction of the rotating shaft 12. Each spacer peak 51 connects adjacent spacer valleys 52 in the circumferential direction of the rotating shaft 12. Multiple spacer peaks 51 are arranged such that the pitch between adjacent spacer peaks 51 in the circumferential direction of the rotating shaft 12 is constant. Multiple spacer valleys 52 are arranged such that the pitch between adjacent spacer valleys 52 in the circumferential direction of the rotating shaft 12 is constant. The pitch between adjacent peaks 43 in the circumferential direction of the rotating shaft 12 is equal to the pitch between adjacent spacer peaks 51 in the circumferential direction of the rotating shaft 12. Also, the pitch between adjacent valleys 44 in the circumferential direction of the rotating shaft 12 is equal to the pitch between adjacent spacer valleys 52 in the circumferential direction of the rotating shaft 12.

[0031] As shown in Figure 4, each spacer peak 51 protrudes toward the peak 43 in the space between adjacent valleys 44 in the circumferential direction of the rotating shaft 12. Each spacer valley 52 is in contact with the bearing housing 21. Each spacer valley 52 supports each valley 44. Each spacer peak 51 is a deformation restricting part that is provided in the space between adjacent valleys 44 in the circumferential direction of the rotating shaft 12 and restricts the deformation of each peak 43. In this way, spacer peaks 51 are provided in the space between adjacent valleys 44 in the circumferential direction of the rotating shaft 12, and are deformation restricting parts that have higher rigidity than the bump foil 40 and restrict the deformation of the peaks 43.

[0032] Before the bump foil 40 undergoes elastic deformation, each spacer peak 51 is spaced apart from each peak 43. Therefore, before the bump foil 40 undergoes elastic deformation, a gap 55 is formed between each spacer peak 51 and each peak 43. In this way, each spacer peak 51 protrudes toward each peak 43 in the radial direction of the rotation axis 12 such that a gap 55 is formed between it and each peak 43. Then, as the rotation axis 12 rotates, the elastic deformation of the bump foil 40 is permitted until each peak 43 contacts each spacer peak 51. Therefore, the elastic deformation of the bump foil 40 is permitted by the amount of the gap 55. In this way, as the rotation axis 12 rotates, the peaks 43 deform toward the spacer peaks 51 such that the gap 55 between them and the peaks 43 becomes smaller. Before the bump foil 40 undergoes elastic deformation, each valley 44 is in contact with each spacer valley 52. Therefore, each valley 44 is supported by the bearing housing 21 via each spacer valley 52.

[0033] As shown in Figures 2 and 3, both axial ends 53 of the spacer 50 with respect to the rotating shaft 12 are bent toward the inner circumferential surface of the bearing housing 21. The outer edges of both ends 53 of the spacer 50 are arc-shaped and extend along the inner circumferential surface of the bearing housing 21. The both ends 53 of the spacer 50 are in contact with the inner circumferential surface of the bearing housing 21.

[0034] As shown in Figure 3, one circumferential end of the spacer 50 is fixed to the bearing housing 21, overlapping the fixed end 41 of the bump foil 40 and the fixed end 32 of the top foil 30. The fixed end 32 of the top foil 30 and the fixed end 41 of the bump foil 40 are fixed to the bearing housing 21 via one circumferential end of the spacer 50. The other circumferential end of the spacer 50 is not fixed to the bearing housing 21.

[0035] [Effect of the Embodiment] Next, the operation of the embodiment will be described. As the rotating shaft 12 rotates, air enters between the top foil 30 and the rotating shaft 12, and a fluid film, an air film, is formed between the top foil 30 and the rotating shaft 12. The rotating shaft 12 rotates in contact with the top foil 30 until its rotational speed reaches the levitation speed. When the rotational speed of the rotating shaft 12 reaches the levitation speed, the dynamic pressure of the air film formed between the top foil 30 and the rotating shaft 12 causes the rotating shaft 12 to levitate relative to the top foil 30. The top foil 30 supports the rotating shaft 12 in the radial direction via the air film. In this way, the top foil 30 supports the rotating shaft 12 in the radial direction.

[0036] The top foil 30 is elastically deformed by the dynamic pressure of the air film between the top foil 30 and the rotating shaft 12, and displaced toward each bump foil 40. As a result, the top foil 30 presses each peak 43 of the bump foil 40 toward the bearing housing 21. This causes the bump foil 40 to elastically deform. The bump foil 40 then displaces toward the bearing housing 21 together with the top foil 30. The spacer valleys 52 contact the bearing housing 21 and support the valleys 44 of the bump foil 40. Therefore, the valleys 44 of the bump foil 40 are supported by the bearing housing 21 via the spacer valleys 52. The bump foil 40 then elastically supports the top foil 30. In this way, the bump foil 40 elastically supports the top foil 30 in a state where it can be displaced radially toward the rotating shaft 12 by elastically deforming.

[0037] Incidentally, when the rotating shaft 12 rotates, for example, the rotating shaft 12 may vibrate, causing it to move radially. At this time, a spacer peak 51, which is more rigid than the bump foil 40 and restricts the deformation of the peak 43, is provided in the space between adjacent valleys 44 in the circumferential direction of the rotating shaft 12. The spacer peak 51 protrudes toward the peak 43 in the radial direction of the rotating shaft 12 so as to form a gap 55 between it and the peak 43. When the rotating shaft 12 rotates, the peak 43 deforms toward the spacer peak 51 so as to reduce the gap 55 between it and the peak 43. Therefore, for example, even if the rotating shaft 12 vibrates, causing it to move radially and the rotating shaft 12 moves in such a way that the top foil 30 crushes the peak 43 of the bump foil 40, the deformation of the peak 43 is restricted by the spacer peak 51. Thus, the peak 43 is not completely crushed.

[0038] Furthermore, in the foil bearing 20, heat is generated in the top foil 30 due to the dynamic pressure of the air film created between the top foil 30 and the rotating shaft 12. Here, the heat generated from the top foil 30 is introduced into the motor chamber 16 and dissipated into the air passing between the top foil 30 and the bump foil 40. This cools the top foil 30.

[0039] Furthermore, both ends 53 of the spacer 50 are bent toward the inner circumferential surface of the bearing housing 21 and are in contact with the inner circumferential surface of the bearing housing 21. Therefore, air introduced into the motor chamber 16 is prevented from passing between the spacer 50 and the bearing housing 21.

[0040] [Effects of the Embodiment] The above embodiment can be achieved to obtain the following effects. (1) Spacer peaks 51 are provided in the space between adjacent valleys 44 in the circumferential direction of the rotating shaft 12, and these spacer peaks 51 have higher rigidity than the bump foil 40 and act as deformation restricting parts that restrict the deformation of the peaks 43. The spacer peaks 51 protrude toward the peaks 43 in the radial direction of the rotating shaft 12 so as to form a gap 55 between them, and when the rotating shaft 12 rotates, the peaks 43 deform toward the spacer peaks 51 so as to reduce the gap 55 between them. Therefore, for example, even if the rotating shaft 12 vibrates and moves radially, causing the rotating shaft 12 to move in such a way that the top foil 30 crushes the peaks 43 of the bump foil 40, the deformation of the peaks 43 is restricted by the spacer peaks 51. Thus, the peaks 43 are not completely crushed, and a decrease in the fatigue strength of the bump foil 40 can be suppressed. As a result, the reliability of the foil bearing 20 can be improved.

[0041] (2) The spacer valleys 52 contact the bearing housing 21 and support the valleys 44 of the bump foil 40. Therefore, even if a corrugated spacer 50 is placed between the bearing housing 21 and the bump foil 40, the valleys 44 of the bump foil 40 are suitably supported by the bearing housing 21 via the spacer valleys 52. The spacer peaks 51 protrude toward the peaks 43. The pitch between adjacent peaks 43 in the circumferential direction of the rotating shaft 12 is equal to the pitch between adjacent spacer peaks 51 in the circumferential direction of the rotating shaft 12. Therefore, the spacer peaks 51 are deformation restricting portions. In this case, the spacer 50 is thicker than the bump foil 40, and therefore has higher rigidity than the bump foil 40. Therefore, even if the rotating shaft 12 vibrates, causing it to move radially and the rotating shaft 12 to move in such a way that the top foil 30 crushes the peaks 43 of the bump foil 40, the deformation of the peaks 43 is suitably restricted by the spacer peaks 51. Thus, complete crushing of the peaks 43 is avoided, and a decrease in the fatigue strength of the bump foil 40 can be suppressed. As a result, the reliability of the foil bearing 20 can be improved.

[0042] (3) Both ends 53 of the spacer 50 are bent toward the inner circumferential surface of the bearing housing 21 and are in contact with the inner circumferential surface of the bearing housing 21. Therefore, the air introduced into the motor chamber 16 is prevented from passing between the spacer 50 and the bearing housing 21. As a result, the air introduced into the motor chamber 16 flows efficiently between the top foil 30 and the bump foil 40. Therefore, the heat generated from the top foil 30 can be efficiently dissipated to the air passing between the top foil 30 and the bump foil 40. Thus, the top foil 30 can be efficiently cooled. Furthermore, because the top foil 30 can be efficiently cooled, the amount of air introduced into the motor chamber 16 can be reduced. As a result, the amount of air supplied to the fuel cell can be increased.

[0043] [Example of changes] The above embodiment can be implemented with the following modifications. The above embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0044] ○ As shown in Figure 5, the foil bearing 20 includes a cylindrical spacer 60 positioned between the bearing housing 21 and the bump foil 40, and the spacer 60 may be configured such that its outer circumferential surface contacts the inner circumferential surface of the bearing housing 21. The outer circumferential surface of the spacer 60 is arc-shaped and extends along the inner circumferential surface of the bearing housing 21. The inner circumferential surface of the spacer 60 has spacer protrusions 61 and spacer recesses 62. The inner circumferential surface of the spacer 60 has multiple spacer protrusions 61. The inner circumferential surface of the spacer 60 has multiple spacer recesses 62. Each spacer protrusion 61 is an arc-shaped curved surface that protrudes inward in the radial direction of the rotation shaft 12. Each spacer recess 62 is an arc-shaped curved surface that recesses outward in the radial direction of the rotation shaft 12 relative to each spacer protrusion 61. Each spacer protrusion 61 and each spacer recess 62 are arranged alternately in the circumferential direction of the rotation shaft 12. The inner circumferential surface of the spacer 60 has a wave-like shape in which each spacer protrusion 61 and each spacer recess 62 are alternately arranged in the circumferential direction of the rotation axis 12. Each spacer protrusion 61 connects adjacent spacer recesses 62 in the circumferential direction of the rotation axis 12. The pitch between adjacent peaks 43 in the circumferential direction of the rotation axis 12 is equal to the pitch between adjacent spacer protrusions 61 in the circumferential direction of the rotation axis 12. Also, the pitch between adjacent valleys 44 in the circumferential direction of the rotation axis 12 is equal to the pitch between adjacent spacer recesses 62 in the circumferential direction of the rotation axis 12.

[0045] Each spacer protrusion 61 projects toward the peak 43 in the space between adjacent valleys 44 in the circumferential direction of the rotation axis 12. Each spacer recess 62 supports each valley 44. Each spacer protrusion 61 is a deformation restricting part that is provided in the space between adjacent valleys 44 in the circumferential direction of the rotation axis 12 and restricts the deformation of each peak 43. In this way, spacer protrusions 61 are provided in the space between adjacent valleys 44 in the circumferential direction of the rotation axis 12, and are deformation restricting parts that have higher rigidity than the bump foil 40 and restrict the deformation of the peaks 43.

[0046] Before the bump foil 40 undergoes elastic deformation, each spacer protrusion 61 is spaced apart from each peak 43. Therefore, before the bump foil 40 undergoes elastic deformation, a gap 55 is formed between each spacer protrusion 61 and each peak 43. In this way, each spacer protrusion 61 protrudes toward each peak 43 in the radial direction of the rotation axis 12 such that a gap 55 is formed between it and each peak 43. Then, as the rotation axis 12 rotates, the elastic deformation of the bump foil 40 is permitted until each peak 43 contacts each spacer protrusion 61. Therefore, the elastic deformation of the bump foil 40 is permitted by the amount of the gap 55. In this way, as the rotation axis 12 rotates, the peaks 43 deform toward the spacer protrusion 61 such that the gap 55 between them and the protrusions 43 becomes smaller. Before the bump foil 40 undergoes elastic deformation, each valley 44 is in contact with each spacer recess 62. Therefore, each valley 44 is supported by the bearing housing 21 via each spacer recess 62.

[0047] According to this, the outer circumferential surface of the spacer 60 is in contact with the inner circumferential surface of the bearing housing 21, and the spacer recess 62 supports the valleys 44 of the bump foil 40. Therefore, even if a cylindrical spacer 60 is placed between the bearing housing 21 and the bump foil 40, the valleys 44 of the bump foil 40 are suitably supported by the bearing housing 21 via the spacer recess 62. Also, the spacer protrusion 61 protrudes toward the peaks 43. The pitch between adjacent peaks 43 in the circumferential direction of the rotating shaft 12 is equal to the pitch between adjacent spacer protrusions 61 in the circumferential direction of the rotating shaft 12. Therefore, the spacer protrusion 61 is a deformation restricting portion. At this time, since the outer circumferential surface of the spacer 60 is in contact with the inner circumferential surface of the bearing housing 21, movement in the direction that would crush the peaks 43 of the spacer 60 is restricted. Therefore, even if the rotating shaft 12 vibrates, causing it to move radially and the rotating shaft 12 to move in such a way that the top foil 30 crushes the peaks 43 of the bump foil 40, the deformation of the peaks 43 is suitably restricted by the spacer protrusions 61. Thus, complete crushing of the peaks 43 is avoided, and a decrease in the fatigue strength of the bump foil 40 can be suppressed. As a result, the reliability of the foil bearing 20 can be improved.

[0048] Furthermore, since the outer surface of the spacer 60 is in contact with the inner surface of the bearing housing 21, the air introduced into the motor chamber 16 is prevented from passing between the spacer 60 and the bearing housing 21. As a result, the air introduced into the motor chamber 16 flows efficiently between the top foil 30 and the bump foil 40. Therefore, the heat generated from the top foil 30 can be efficiently dissipated into the air passing between the top foil 30 and the bump foil 40. Thus, the top foil 30 can be cooled efficiently. In addition, because the top foil 30 can be cooled efficiently, the amount of air introduced into the motor chamber 16 can be reduced. As a result, the amount of air supplied to the fuel cell can be increased.

[0049] ○ As shown in Figure 6, the bearing housing 21 may have an inner circumferential surface having housing protrusions 71 that project toward the peaks 43 and housing recesses 72 that support the valleys 44. The inner circumferential surface of the bearing housing 21 has multiple housing protrusions 71. The inner circumferential surface of the bearing housing 21 has multiple housing recesses 72. Each housing protrusion 71 is an arc-shaped curved surface that protrudes inward in the radial direction of the rotating shaft 12. Each housing recess 72 is an arc-shaped curved surface that recesses outward in the radial direction of the rotating shaft 12 relative to each housing protrusion 71. Each housing protrusion 71 and each housing recess 72 are arranged alternately in the circumferential direction of the rotating shaft 12. The inner circumferential surface of the bearing housing 21 has a wave shape in which each housing protrusion 71 and each housing recess 72 are arranged alternately in the circumferential direction of the rotating shaft 12. Each housing protrusion 71 connects adjacent housing recesses 72 in the circumferential direction of the rotating shaft 12. The pitch between adjacent peaks 43 in the circumferential direction of the rotating shaft 12 is equal to the pitch between adjacent housing protrusions 71 in the circumferential direction of the rotating shaft 12. Also, the pitch between adjacent valleys 44 in the circumferential direction of the rotating shaft 12 is equal to the pitch between adjacent housing recesses 72 in the circumferential direction of the rotating shaft 12.

[0050] Each housing protrusion 71 projects toward the peak 43 in the space between adjacent valleys 44 in the circumferential direction of the rotation axis 12. Each housing recess 72 supports each valley 44. Each housing protrusion 71 is a deformation restricting part that is provided in the space between adjacent valleys 44 in the circumferential direction of the rotation axis 12 and restricts the deformation of each peak 43. In this way, housing protrusions 71 are provided in the space between adjacent valleys 44 in the circumferential direction of the rotation axis 12, and are deformation restricting parts that have higher rigidity than the bump foil 40 and restrict the deformation of the peaks 43.

[0051] Before the bump foil 40 undergoes elastic deformation, each housing protrusion 71 is spaced apart from each peak 43. Therefore, before the bump foil 40 undergoes elastic deformation, a gap 55 is formed between each housing protrusion 71 and each peak 43. In this way, each housing protrusion 71 protrudes toward each peak 43 in the radial direction of the rotation axis 12 such that a gap 55 is formed between it and each peak 43. Then, as the rotation axis 12 rotates, the elastic deformation of the bump foil 40 is permitted until each peak 43 contacts each housing protrusion 71. Therefore, the elastic deformation of the bump foil 40 is permitted by the amount of the gap 55. In this way, as the rotation axis 12 rotates, the peaks 43 deform toward the housing protrusion 71 such that the gap 55 between them and the protrusion 43 becomes smaller. Before the bump foil 40 undergoes elastic deformation, each valley 44 is in contact with each housing recess 72. Therefore, each valley 44 is supported by each housing recess 72.

[0052] According to this, the valleys 44 of the bump foil 40 are suitably supported by the housing recesses 72. The housing protrusions 71 also protrude toward the peaks 43. The pitch between adjacent peaks 43 in the circumferential direction of the rotating shaft 12 is equal to the pitch between adjacent housing protrusions 71 in the circumferential direction of the rotating shaft 12. Therefore, the housing protrusions 71 are deformation restricting parts. Consequently, even if the rotating shaft 12 vibrates, causing it to move radially and the rotating shaft 12 to move in such a way that the top foil 30 crushes the peaks 43 of the bump foil 40, the deformation of the peaks 43 is suitably restricted by the housing protrusions 71. Therefore, complete crushing of the peaks 43 is avoided, and a decrease in the fatigue strength of the bump foil 40 can be suppressed. As a result, the reliability of the foil bearing 20 can be improved.

[0053] ○ In this embodiment, the spacer 50 may not have spacer valleys 52 and may consist only of spacer peaks 51. In this case, the valleys 44 of the bump foil 40 are supported by the bearing housing 21 by contacting the bearing housing 21. In short, it is sufficient that deformation restricting portions are provided between adjacent valleys 44 in the circumferential direction of the rotating shaft 12 to restrict the deformation of the peaks 43.

[0054] ○ In this embodiment, the pitch between adjacent peaks 43 in the circumferential direction of the rotating shaft 12 does not have to be equal to the pitch between adjacent spacer peaks 51 in the circumferential direction of the rotating shaft 12. Also, the pitch between adjacent valleys 44 in the circumferential direction of the rotating shaft 12 does not have to be equal to the pitch between adjacent spacer valleys 52 in the circumferential direction of the rotating shaft 12.

[0055] ○ In the embodiment shown in Figure 5, the pitch between adjacent peaks 43 in the circumferential direction of the rotating shaft 12 does not have to be equal to the pitch between adjacent spacer protrusions 61 in the circumferential direction of the rotating shaft 12. Also, the pitch between adjacent valleys 44 in the circumferential direction of the rotating shaft 12 does not have to be equal to the pitch between adjacent spacer recesses 62 in the circumferential direction of the rotating shaft 12.

[0056] ○ In the embodiment shown in Figure 6, the pitch between adjacent peaks 43 in the circumferential direction of the rotating shaft 12 does not have to be equal to the pitch between adjacent housing protrusions 71 in the circumferential direction of the rotating shaft 12. Also, the pitch between adjacent valleys 44 in the circumferential direction of the rotating shaft 12 does not have to be equal to the pitch between adjacent housing recesses 72 in the circumferential direction of the rotating shaft 12.

[0057] ○ In this embodiment, both ends 53 of the spacer 50 do not need to be bent toward the inner circumferential surface of the bearing housing 21. ○ In this embodiment, the bearing housing 21 may be a separate component from the housing 11.

[0058] ○ In this embodiment, the foil bearing 20 may include, for example, a plurality of bump foils 40 divided in the circumferential direction. In this case, each bump foil 40 is arranged at equal intervals in the circumferential direction of the rotation axis 12 between the bearing housing 21 and the top foil 30. The circumferential length of each bump foil 40 on the rotation axis 12 is the same.

[0059] ○ In this embodiment, the centrifugal compressor 10 does not have to be installed in the fuel cell vehicle. In short, the centrifugal compressor 10 is not limited to being installed in a vehicle. ○ In this embodiment, the centrifugal compressor 10 is not limited to one used to compress air supplied to a fuel cell. In short, the centrifugal compressor 10 can be any compressor that compresses a fluid. [Explanation of symbols]

[0060] 12...rotating shaft, 20...foil bearing, 21...bearing housing, 22...through hole, 30...top foil, 40...bump foil, 43...peak, 44...valley, 50,60...spacer, 51...spacer peak which is a deformation restricting part, 52...spacer valley, 55...gap, 61...spacer convex part which is a deformation restricting part, 62...spacer concave, 71...housing convex part which is a deformation restricting part, 72...housing concave.

Claims

1. A foil bearing that supports the rotating shaft in the radial direction, A bearing housing having a through hole through which the rotating shaft is inserted, A thin plate-shaped top foil is disposed between the rotating shaft and the bearing housing, The bearing housing and the top foil are positioned between them, and a thin, plate-shaped bump foil is provided to elastically support the top foil. The aforementioned bump foil is, Multiple ridges that contact the top foil, The bearing housing has a plurality of valleys supported by the bearing housing, The aforementioned peaks and valleys are arranged alternately in the circumferential direction of the rotation axis. In the space between adjacent valleys in the circumferential direction of the rotation axis, a deformation restricting portion is provided, which has higher rigidity than the bump foil and restricts the deformation of the peak portion. The deformation restricting portion protrudes toward the peak in the radial direction of the rotation axis such that a gap is formed between it and the peak. A foil bearing characterized in that, when the rotating shaft rotates, the peaks deform toward the deformation restricting portion so that the gap becomes smaller.

2. A corrugated spacer is provided between the bearing housing and the bump foil, and is thicker than the thickness of the bump foil. The spacer has a spacer peak that protrudes toward the peak and a spacer valley that contacts the bearing housing and supports the valley. The pitch between adjacent peaks in the circumferential direction of the rotating shaft and the pitch between adjacent spacer peaks in the circumferential direction of the rotating shaft are equal, The foil bearing according to claim 1, characterized in that the spacer ridge is the deformation restricting portion.

3. The bearing housing and the bump foil are provided with a cylindrical spacer, The outer circumferential surface of the spacer is in contact with the inner circumferential surface of the bearing housing. The inner circumferential surface of the spacer has a spacer convex portion that protrudes toward the peak portion and a spacer recess that supports the valley portion. The pitch between adjacent peaks in the circumferential direction of the rotating shaft and the pitch between adjacent spacer protrusions in the circumferential direction of the rotating shaft are equal, The foil bearing according to claim 1, characterized in that the spacer protrusion is the deformation restricting portion.

4. The inner circumferential surface of the bearing housing has a housing convex portion that protrudes toward the peak portion and a housing recess that supports the valley portion. The pitch between adjacent peaks in the circumferential direction of the rotating shaft and the pitch between adjacent housing protrusions in the circumferential direction of the rotating shaft are equal, The foil bearing according to claim 1, characterized in that the housing protrusion is the deformation restricting portion.

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