Foil bearing

Abstract

A foil bearing stably supports a rotating shaft in a radial direction. A foil bearing is provided with: a bearing housing having a through hole through which a rotating shaft is inserted; a top foil sheet in the shape of a thin plate; and a thin-plate-shaped bump foil. The top foil has a substantially cylindrical top foil body, a trailing edge sheet, and a leading edge sheet. The trailing edge sheet and the leading edge sheet are inserted into the grooves of the bearing housing. The groove dividing wall of the dividing groove has a leading wall which is a wall located on the leading side in the rotation direction of the rotating shaft. The trailing edge piece passes through a position closer to the radial outer side than the leading edge piece in the groove. The trailing edge piece has a tip portion that comes into contact with the leading wall at least when the rotating shaft rotates. The leading edge piece is separated from the leading wall and the trailing edge piece in the circumferential direction of the rotating shaft at least when the rotating shaft rotates.

Description

TECHNICAL FIELD

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

[0002] A foil bearing that supports a rotating shaft in a radial direction has a bearing housing, a top foil, and a wave foil. The bearing housing has a through-hole through which the rotating shaft is inserted. The top foil is thin plate-like. The top foil is disposed between the rotating shaft and the bearing housing. The wave foil is thin plate-like. The wave foil is disposed between the bearing housing and the top foil. Also, the wave foil elastically supports the top foil.

[0003] Such a foil bearing supports the rotating shaft in a state where the rotating shaft is in contact with the top foil until the rotating shaft reaches a lift-off rotational speed. Also, when the rotational speed of the rotating shaft reaches the lift-off rotational speed, the rotating shaft is lifted off with respect to the top foil by dynamic pressure of a fluid film generated between the top foil and the rotating shaft. Thus, the foil bearing supports the rotating shaft without being in contact with the rotating shaft.

[0004] For example, as in Japanese Patent No. 5449553, a groove extending in an axial direction of the bearing housing is formed in an inner peripheral surface of the bearing housing. The top foil has a top foil main body, a trailing edge piece, and a leading edge piece. The top foil main body is substantially cylindrical. The top foil main body forms a bearing surface that supports the rotating shaft, and surrounds an outer peripheral surface of the rotating shaft. The trailing edge piece is formed by bending an end portion of the top foil main body on a trailing side in a rotational direction of the rotating shaft to an outer side in a radial direction of the rotating shaft. The leading edge piece is formed by bending an end portion of the top foil main body on a leading side in the rotational direction of the rotating shaft to the outer side in the radial direction of the rotating shaft. Also, the trailing edge piece and the leading edge piece are inserted into the groove. SUMMARY

[0005] PROBLEMS TO BE SOLVED BY THE INVENTION

[0006] However, in such a foil bearing, there is a case where a trailing portion of the trailing edge piece of the top foil main body on the trailing side in the rotational direction is dragged toward the rotating shaft due to flow of fluid between the top foil and the rotating shaft accompanying rotation of the rotating shaft. If the trailing portion of the top foil main body on the trailing side in the rotational direction is dragged toward the rotating shaft, the trailing portion of the top foil main body on the trailing side in the rotational direction can be caught in the rotating shaft. If the trailing portion of the top foil main body on the trailing side in the rotational direction is caught in the rotating shaft, the rotating shaft can not be lifted off with respect to the top foil by dynamic pressure of a fluid film generated between the top foil and the rotating shaft. Thus, it can not be possible to stably support the rotating shaft.

[0007] On the other hand, if the movement of the leading edge piece is obstructed, when the dynamic pressure of the fluid film generated between the top foil piece and the rotating shaft, the leading portion of the front edge piece of the top foil piece body on the leading side in the direction of rotation is difficult to deform in a manner of flexing in a direction away from the rotating shaft. Then, the gap between the leading portion of the top foil piece body in the direction of rotation and the rotating shaft is difficult to become large, and thus it is difficult to take in fluid from the gap between the leading portion of the top foil piece body in the direction of rotation and the rotating shaft. As a result, the rotating shaft is difficult to float with respect to the top foil piece due to the dynamic pressure of the fluid film generated between the top foil piece and the rotating shaft, and thus it can be impossible to stably support the rotating shaft.

[0008] Means for solving the problem

[0009] According to an aspect of the present disclosure, there is provided a foil bearing that supports a rotating shaft in a radial direction. The foil bearing includes 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 wave foil disposed between the bearing housing and the top foil, which elastically supports the top foil. A groove extending in an axial direction of the bearing housing is formed in an inner peripheral surface of the bearing housing. The top foil has a substantially cylindrical top foil body that forms a bearing surface that supports the rotating shaft and surrounds an outer peripheral surface of the rotating shaft; a trailing edge piece that is formed by bending an end portion of the top foil body on a trailing side in a direction of rotation of the rotating shaft outward in a radial direction; and a leading edge piece that is formed by bending an end portion of the top foil body on a leading side in the direction of rotation outward in the radial direction. The trailing edge piece and the leading edge piece are inserted into the groove. A groove division wall that divides the groove has a wall on the leading side in the direction of rotation, i.e., a leading wall. The trailing edge piece is positioned outward in the radial direction than the leading edge piece in the groove. The trailing edge piece has a front end portion that abuts against the leading wall at least when the rotating shaft rotates. The leading edge piece is separated from the leading wall and the trailing edge piece, respectively, in a circumferential direction of the rotating shaft at least when the rotating shaft rotates. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 is a schematic configuration view of a centrifugal compressor that is provided with a radial bearing in an embodiment.

[0011] Figure 2 is an enlarged view of a part of the centrifugal compressor of Figure 1 .

[0012] Figure 3 is a cross-sectional view for explaining the radial bearing of Figure 1 .

[0013] Figure 4 is a cross-sectional view for explainingFigure 1 is an exploded perspective view of the radial bearing of

[0014] Figure 5 is an enlarged view showing a portion of the radial bearing of Figure 1

[0015] Figure 6 is a cross-sectional view showing a state in which the rotating shaft is radially moved in the axial direction, which is supported by the radial bearing of Figure 1

[0016] Figure 7 is a cross-sectional view showing a state in which the rotating shaft is radially moved in the axial direction, which is supported by the radial bearing of Figure 1

[0017] Figure 8 is an enlarged view showing a portion of the radial bearing of Figure 1

[0018] Figure 9 is an enlarged view showing a portion of the radial bearing in the modification. DETAILED DESCRIPTION

[0019] Hereinafter, an embodiment in which the foil bearing is embodied will be described with reference to Figures 1-8 The foil bearing of the present embodiment is applied to a centrifugal compressor mounted on a fuel cell vehicle. In the fuel cell vehicle, a fuel cell system that supplies oxygen and hydrogen to a fuel cell to generate electricity is mounted. Also, the centrifugal compressor compresses air, which is a fluid containing oxygen, supplied to the fuel cell.

[0020] <Outline of Centrifugal Compressor>

[0021] 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 motor 14 rotates the rotating shaft 12. The housing 11 is a cylindrical shape. The housing 11 houses the rotating shaft 12, the impeller 13, and the motor 14. The rotating shaft 12 is rotated by driving of the motor 14. The impeller 13 is connected to a first end of the rotating shaft 12. The impeller 13 rotates integrally with the rotating shaft 12 in order to compress air. Figure 1

[0022] The centrifugal compressor 10 includes two radial bearings 15. Each radial bearing 15 is disposed in the housing 11. The two radial bearings 15 are disposed on both sides of the motor 14. The two radial bearings 15 support portions of the rotating shaft 12 on both sides of the motor 14 so as to be rotatable. Each radial bearing 15 is a foil bearing that supports the rotating shaft 12 so as to be rotatable in a radial direction. Note that the "radial direction" refers to a direction orthogonal to an axial direction of the rotating shaft 12. Thus, the "radial direction" refers to a radial direction of the rotating shaft 12.

[0023] ​​​​​The housing 11 has a compressor housing member 16 and a housing plate 17. The compressor housing member 16 is cylindrical with an intake 18. Air purified by an air filter (not shown) flows into the intake 18. The housing plate 17 is joined to the compressor housing member 16. The housing plate 17 and the compressor housing member 16 together define an impeller chamber 19. The impeller chamber 19 communicates with the intake 18. The impeller chamber 19 houses an impeller 13. The first end of a rotating shaft 12 passes through the housing plate 17 and protrudes into the impeller chamber 19.

[0024] The casing 11 has a diffusion path 20 and a discharge chamber 21. The diffusion path 20 and the discharge chamber 21 are divided by the compressor casing member 16 and the casing plate 17. The diffusion path 20 is located radially outward of the impeller chamber 19 relative to the rotation axis 12. The diffusion path 20 extends annularly around the impeller chamber 19. The discharge chamber 21 is located radially outward of the diffusion path 20 relative to the rotation axis 12. The discharge chamber 21 extends annularly around the impeller chamber 19. The diffusion path 20 connects the impeller chamber 19 and the discharge chamber 21.

[0025] Air drawn into the impeller chamber 19 from the intake 18 flows toward the diffuser path 20 due to the rotation of the impeller 13. As the air passes through the diffuser path 20, it is pressurized and discharged toward the exhaust chamber 21. The air discharged into the exhaust chamber 21 is supplied to the fuel cell. Therefore, the impeller 13 rotates together with the rotating shaft 12 to compress the air supplied to the fuel cell. In the following description, the direction of rotation of the rotating shaft 12 when the impeller 13 compresses the air is sometimes referred to as the "rotation direction R1". Thus, the rotating shaft 12 is used for applications where it rotates only in one direction.

[0026] like Figure 2 As shown, the impeller 13 has a hub 22 and a plurality of blades 23. The hub 22 rotates integrally with the rotating shaft 12. The hub 22 is mounted on the first end of the rotating shaft 12. The hub 22 has a front end portion positioned near the suction port 18 and a rear end portion on the opposite side of the front end portion. The hub 22 is a generally conical shape whose outer diameter increases from the front end portion toward the rear end portion. The hub 22 has a curved surface recessed toward the axis L1 of the rotating shaft 12.

[0027] Multiple blades 23 are arranged circumferentially along the hub 22. The multiple blades 23 are arranged at equal intervals circumferentially on the surface of the hub 22. The outer diameter of the hub 22 increases from the front end to the rear end, so the spacing between adjacent blades 23 in the circumferential direction of the hub 22 gradually widens from the front end to the rear end of the hub 22.

[0028] The compressor housing component 16 has a shroud 24. The shroud 24 divides the impeller chamber 19. The shroud 24 is positioned opposite the hub 22 and extends along the surface of the hub 22. The shroud 24 surrounds a plurality of blades 23. A head clearance 25 is formed between the plurality of blades 23 and the shroud 24. Thus, a head clearance 25 is formed between the impeller 13 and the shroud 24. The amount of head clearance between the impeller 13 and the shroud 24 is predetermined such that even if the impeller 13 moves within the impeller chamber 19 as the rotating shaft 12 moves radially along the rotating shaft 12, the blades 23 will not contact the shroud 24. This head clearance amount is determined in advance through experiments, etc.

[0029] Radial bearings

[0030] like Figure 3 and Figure 4 As shown, the radial bearing 15 includes a bearing retaining portion 26, a top foil 27, and a corrugated foil 28. The bearing retaining portion 26 is cylindrical. The bearing retaining portion 26 is part of the housing 11. The bearing retaining portion 26 has a first end face in the axial direction and a second end face opposite to the first end face. The bearing retaining portion 26 has a through hole 29 for the insertion of a rotating shaft 12. The through hole 29 opens at both the first and second end faces of the bearing retaining portion 26. Therefore, the bearing retaining portion 26 functions as a bearing housing having a through hole 29 for the insertion of a rotating shaft 12.

[0031] like Figure 3 As shown, the top foil 27 is radially opposed to the rotating shaft 12. The top foil 27 is disposed between the rotating shaft 12 and the bearing retainer 26. The corrugated foil 28 is disposed on the side opposite to the rotating shaft 12 relative to the top foil 27. The corrugated foil 28 is disposed between the bearing retainer 26 and the top foil 27. The corrugated foil 28 elastically supports the top foil 27.

[0032] <groove>

[0033] A groove 30 is formed on the inner circumferential surface of the bearing retaining portion 26, i.e., the inner circumferential surface of the through hole 29. The groove 30 extends axially along the bearing retaining portion 26. The first end of the groove 30 opens at the first end face of the bearing retaining portion 26. The second end of the groove 30 is closed by a portion of the bearing retaining portion 26.

[0034] like Figure 5As shown, the bearing retaining portion 26 has a groove dividing wall 31 for dividing the groove 30. The groove dividing wall 31 has a leading wall 32, a trailing wall 33, and a connecting wall 34. The leading wall 32 is a wall located on the leading side in the rotation direction R1 of the rotating shaft 12. The leading wall 32 extends radially outward from the inner circumference of the bearing retaining portion 26 towards the rotating shaft 12. The trailing wall 33 is a wall located on the trailing side in the rotation direction R1 of the rotating shaft 12. The trailing wall 33 extends radially outward from the inner circumference of the bearing retaining portion 26 towards the rotating shaft 12. The leading wall 32 and the trailing wall 33 extend parallel to each other. The leading wall 32 and the trailing wall 33 are opposite each other in the circumferential direction of the bearing retaining portion 26. The connecting wall 34 connects the radially outward end of the leading wall 32 to the radially outward end of the trailing wall 33.

[0035] like Figure 3 and Figure 4 As shown, two secondary grooves 35 are formed separately from the groove 30 on the inner circumferential surface of the bearing retaining portion 26. The two secondary grooves 35 extend axially along the bearing retaining portion 26. The first end of each secondary groove 35 opens at the first end face of the bearing retaining portion 26 in the axial direction. The second end of each secondary groove 35 is closed by a portion of the bearing retaining portion 26.

[0036] The slot 30 and two sub-slots 35 are arranged at equal intervals around the bearing retaining portion 26. The circumferential width of the bearing retaining portion 26 in the slot 30 is larger than the circumferential width of the bearing retaining portion 26 in each sub-slot 35. It should be noted that the circumferential direction of the bearing retaining portion 26 is consistent with the circumferential direction of the rotating shaft 12.

[0037] <Top Foil>

[0038] The top foil 27 is made of a flexible metal material. The top foil 27 is formed of stainless steel or Inconel (registered trademark). The top foil 27 is in the form of a thin sheet.

[0039] The top foil 27 has a top foil body 36, a trailing edge 37, and a leading edge 38. The top foil body 36 is generally cylindrical. The top foil body 36 surrounds the outer peripheral surface of the rotation shaft 12. The top foil body 36 forms a bearing surface 39 that supports the rotation shaft 12. The bearing surface 39 is the inner peripheral surface of the top foil body 36. The bearing surface 39 faces the outer peripheral surface of the rotation shaft 12.

[0040] like Figure 5 As shown, the first end of the top foil body 36 located on the rearward side of the rotation direction R1 of the rotation axis 12 is positioned opposite the second end of the top foil body 36 on the leading side of the rotation direction R1 of the rotation axis 12, in a state of being separated in the circumferential direction of the top foil body 36. Therefore, the top foil body 36 is a non-annular shape with a portion cut off.

[0041] <The Trailing Edge>

[0042] The trailing edge piece 37 is formed by bending it radially outward from the first end of the top foil body 36 toward the rotation shaft 12. The leading edge piece 38 is formed by bending it radially outward from the second end of the top foil body 36 toward the rotation shaft 12. The trailing edge piece 37 and the leading edge piece 38 are inserted into the groove 30.

[0043] The trailing edge plate 37 has a first extension 41 and a second extension 42. The first extension 41 extends radially outward from the top foil body 36 toward the rotation shaft 12. The first extension 41 bends radially outward from a first end in the top foil body 36 toward the rotation shaft 12. The first extension 41 is elongated and flat. The end of the first extension 41 on the side opposite to the top foil body 36 is inserted into the groove 30.

[0044] The first extension 41 has a counter portion 41a that faces the front end 38e of the leading edge plate 38 in the circumferential direction of the rotation axis 12. The second extension 42 extends from the end of the first extension 41 on the side opposite to the top foil body 36 toward the leading wall 32. The second extension 42 is an elongated flat plate. The second extension 42 passes within the groove 30 at a position radially outward of the rotation axis 12 than the leading edge plate 38.

[0045] The trailing edge plate 37 has a bent portion 43. The bent portion 43 is the front end of the trailing edge plate 37. The bent portion 43 is formed by bending the front end of the trailing edge plate 37. Specifically, the bent portion 43 is formed by bending the front end of the trailing edge plate 37 radially outward toward the rotation axis 12. The bent portion 43 is an elongated flat plate. The side surface 43a of the bent portion 43 abuts against the leading wall 32. The side surface 43a of the bent portion 43 abuts against the leading wall 32 when the rotation axis 12 rotates, and also abuts against the leading wall 32 when the rotation axis 12 is not rotating. In this way, the trailing edge plate 37 passes within the groove 30 at a position radially outward of the rotation axis 12 than the leading edge plate 38, and the front end of the trailing edge plate 37 abuts against the leading wall 32 at least when the rotation axis 12 rotates.

[0046] <Wave Foil>

[0047] like Figure 3 and Figure 4 As shown, the radial bearing 15 has three corrugated foils 28. Therefore, the radial bearing 15 has corrugated foils 28 divided into multiple sections circumferentially. Each corrugated foil 28 is in the shape of a curved plate. Each corrugated foil 28 is made of a flexible metal material. Each corrugated foil 28 is formed of stainless steel or Inconel (registered trademark). Each corrugated foil 28 is in the shape of a thin plate. The three corrugated foils 28 are arranged at equal intervals circumferentially between the bearing retainer 26 and the top foil 27 on the rotating shaft 12. The circumferential lengths of the rotating shaft 12 in the three corrugated foils 28 are the same.

[0048] Each foil 28 has an elastic plate portion 45 and a fixing piece 46. The elastic plate portion 45 is disposed between the bearing retaining portion 26 and the top foil 27. Specifically, the elastic plate portion 45 is disposed between the inner peripheral surface of the bearing retaining portion 26 and the outer peripheral surface of the top foil body 36. The elastic plate portion 45 is in the shape of a curved plate. The bending direction of the elastic plate portion 45 is consistent with the circumferential direction of the rotating shaft 12.

[0049] The fixing plate 46 is formed by bending one end of the elastic plate portion 45 in the circumferential direction towards the radially outward side of the rotation shaft 12. The fixing plate 46 is elongated and plate-shaped. The fixing plate 46 of one of the three corrugated foils 28 is inserted into the groove 30. The fixing plates 46 of the remaining two of the three corrugated foils 28 are respectively inserted into the sub-grooves 35.

[0050] like Figure 5 As shown, the retaining piece 46 is inserted into the groove 30 between the rear edge piece 37 and the rear wall 33. The front end of the retaining piece 46 is bent in such a way that it separates from the rear edge piece 37 and approaches the rear wall 33 in the circumferential direction of the rotation axis 12. Therefore, the retaining piece 46 extends from the elastic plate portion 45 toward the rear wall 33. In other words, the retaining piece 46 includes a portion in the circumferential direction of the rotation axis 12 that is closer to the rear wall 33 than the end of the elastic plate portion 45 located on one side of the circumferential direction of the rotation axis 12. The cross-sectional shape of the retaining piece 46 is hook-shaped.

[0051] like Figure 3 As shown, the elastic plate portion 45 has multiple peaks 47 and multiple valleys 48. Therefore, each corrugated foil 28 has multiple peaks 47 and multiple valleys 48. Each peak 47 is convex and contacts the top foil 27. Each peak 47 contacts the outer peripheral surface of the top foil body 36. Each peak 47 extends circumferentially along the elastic plate portion 45. Each valley 48 contacts the inner peripheral surface of the bearing retaining portion 26. The elastic plate portion 45 has a corrugated shape in which peaks 47 and valleys 48 are alternately arranged in the circumferential direction of the elastic plate portion 45. Each peak 47 connects to adjacent valleys 48 in the circumferential direction of the rotating shaft 12.

[0052] As the rotating shaft 12 rotates, air enters between the top foil 27 and the rotating shaft 12, forming an air film between them. Before the rotating shaft 12 reaches its levitation speed, it rotates in contact with the top foil 27. When the rotating shaft 12 reaches its levitation speed, the dynamic pressure of the air film causes the rotating shaft 12 to levitate relative to the top foil 27. The top foil 27 supports the rotating shaft 12 radially via the air film. Thus, the top foil 27 supports the rotating shaft 12 radially.

[0053] The top foil 27 is elastically deformed by the dynamic pressure of the air film between the top foil 27 and the rotating shaft 12, and displaces toward the elastic plate portion 45 of each corrugated foil 28. Thus, the top foil 27 presses the peaks 47 of the elastic plate portion 45 toward the bearing retaining portion 26. Consequently, the elastic plate portion 45 elastically deforms. Furthermore, the elastic plate portion 45, together with the top foil 27, displaces toward the bearing retaining portion 26. The elastic plate portion 45 elastically supports the top foil 27. In this way, each corrugated foil 28 elastically supports the top foil 27 by elastic deformation, allowing it to displace radially along the rotating shaft 12.

[0054] <Anti-detachment components>

[0055] like Figure 3 and Figure 4 As shown, the radial bearing 15 includes an anti-detachment member 49. The anti-detachment member 49 is annular. The anti-detachment member 49 is made of, for example, stainless steel. The hardness of the anti-detachment member 49 is lower than that of the top foil 27 and the corrugated foil 28. The inner diameter of the anti-detachment member 49 is slightly larger than the inner diameter of the through hole 29. The anti-detachment member 49 is fixed to the first end face of the bearing retaining portion 26 with the first end of the groove 30 and the first ends of each sub-groove 35 closed. The anti-detachment member 49 is axially opposed to the retaining pieces 46 of the trailing edge piece 37, the leading edge piece 38, and each corrugated foil 28 in the bearing retaining portion 26.

[0056] Furthermore, the bearing retaining portion 26 in the top foil 27 is prevented from detaching from the first end face by abutting the trailing edge 37 and the leading edge 38 against the anti-detachment member 49. In addition, the bearing retaining portion 26 in each wave foil 28 is prevented from detaching from the first end face by abutting the fixing piece 46 against the anti-detachment member 49.

[0057] <Prelude>

[0058] like Figure 6 and Figure 7 As shown, the rotating shaft 12 can move radially. The rotating shaft 12 can move until the peak 47 of the elastic plate portion 45 is completely flattened by the top foil 27. The maximum displacement of the corrugated foil 28 is the displacement of the peak 47 from its original shape to when it is completely flattened. Here, the maximum displacement of the corrugated foil 28 is smaller than the top clearance between the impeller 13 and the shroud 24.

[0059] The amount of travel that the rotating shaft 12 can move from the state where the axis L1 of the rotating shaft 12 is aligned with the axis of the through hole 29 until the peak 47 of the elastic plate portion 45 is completely flattened by the top foil 27 is the maximum radial travel of the rotating shaft 12 from the state where the axis L1 of the rotating shaft 12 is aligned with the axis of the through hole 29. Thus, the maximum radial travel of the rotating shaft 12 from the state where the axis L1 of the rotating shaft 12 is aligned with the axis of the through hole 29 is determined based on the smaller of the top clearance and the maximum displacement of the corrugated foil 28. It should be noted that in the following description, sometimes "the maximum radial travel of the rotating shaft 12 from the state where the axis L1 of the rotating shaft 12 is aligned with the axis of the through hole 29" will be simply referred to as "maximum travel".

[0060] like Figure 5 As shown, the width Larm between the opposing portion 41a and the leading wall 32 in the circumferential direction of the rotating shaft 12 is set to be larger than the value obtained by adding twice the maximum stroke amount to the plate thickness Ttab of the leading edge plate 38. The gap Lgap1 between the front end 38e of the leading edge plate 38 and the second extension 42 in the radial direction of the rotating shaft 12 is larger than the maximum stroke amount. In addition, the width Lgap2 between the front end 38e of the leading edge plate 38 and the leading wall 32 in the circumferential direction of the rotating shaft 12 is larger than the maximum stroke amount.

[0061] like Figure 8 As shown, during the manufacturing of the top foil 27, there is a tolerance issue regarding the angle between the leading edge piece 38 and the main body 36 of the top foil. It should be noted that... Figure 8 The tolerance of angle θ1, resulting from the angle between the leading edge sheet 38 and the top foil body 36, is exaggeratedly illustrated using a double-dotted line. Additionally, during the manufacturing of the top foil 27, tolerances sometimes occur along the entire circumferential length of the top foil 27.

[0062] The width Larm is set to a value larger than that obtained by adding twice the maximum stroke amount, the thickness Ttab of the leading edge plate 38, the tolerance of the circumferential length of the top foil 27, and twice the tolerance of the angle of the leading edge plate 38 relative to the top foil body 36. Therefore, the width Larm between the opposing portion 41a and the leading wall 32 in the circumferential direction of the rotation shaft 12 is set by further taking into account the tolerance of the circumferential length of the top foil 27 and the tolerance of the angle of the leading edge plate 38 relative to the top foil body 36.

[0063] By thus setting the width Larm, the gap Lgapi, and the width Lgap2, the leading edge piece 38 is separated from the preceding wall 32 and the trailing edge piece 37, respectively, when the rotating shaft 12 rotates. In addition, the leading edge piece 38 is separated from the preceding wall 32 and the trailing edge piece 37, respectively, when the rotating shaft 12 does not rotate. In this way, the leading edge piece 38 is separated from the preceding wall 32 and the trailing edge piece 37, respectively, in the circumferential direction of the rotating shaft 12 at least when the rotating shaft 12 rotates.

[0064] [Effects of the Embodiment]

[0065] Next, the effects of the embodiment will be described.

[0066] However, in such a radial bearing 15, due to the flow of air between the top foil piece 27 and the rotating shaft 12 accompanying the rotation of the rotating shaft 12, there is a case where the trailing portion of the trailing edge piece 37 in the trailing side of the rotation direction R1 in the top foil body 36 is to be dragged toward the rotating shaft 12. Specifically, the trailing portion of the top foil body 36 in the rotation direction R1 is to be dragged toward the rotating shaft 12 as indicated by the double-dotted line in FIG. 6. Figure 5

[0067] In the present embodiment, the leading end portion of the trailing edge piece 37 is in abutment with the preceding wall 32 at least when the rotating shaft 12 rotates. Specifically, the side surface 43a of the bent portion 43 is in abutment with the preceding wall 32. Therefore, by the flow of air between the top foil piece 27 and the rotating shaft 12 accompanying the rotation of the rotating shaft 12, the trailing portion of the top foil body 36 in the rotation direction R1 is prevented from being dragged toward the rotating shaft 12. Therefore, the trailing portion of the top foil body 36 in the rotation direction R1 is prevented from being entangled in the rotating shaft 12, and thus the rotating shaft 12 is stably floated with respect to the top foil piece 27 by the dynamic pressure of the air film generated between the top foil piece 27 and the rotating shaft 12.

[0068] In addition, the leading edge piece 38 is separated from the preceding wall 32 and the trailing edge piece 37, respectively, in the circumferential direction of the rotating shaft 12 at least when the rotating shaft 12 rotates. Therefore, the movement of the leading edge piece 38 is prevented from being hindered, and thus the leading portion of the leading edge piece 38 in the leading side of the rotation direction R1 in the top foil body 36 is easily deformed in a manner of being deflected in a direction away from the rotating shaft 12 as indicated by the double-dotted line in FIG. 6. Thereby, the gap between the leading portion of the top foil body 36 in the leading side of the rotation direction R1 and the rotating shaft 12 is increased. Therefore, air is easily taken in from the gap between the leading portion of the top foil body 36 in the leading side of the rotation direction R1 and the rotating shaft 12. Thus, the rotating shaft 12 is stably floated with respect to the top foil piece 27 by the dynamic pressure of the air film generated between the top foil piece 27 and the rotating shaft 12. Figure 5

[0069] [Effects of the Embodiment] ​​

[0070] In the above-described embodiment, the following effects can be obtained.

[0071] (1) The leading end portion of the trailing edge piece 37 abuts against the preceding wall 32 at least when the rotation shaft 12 rotates. Therefore, by the flow of air between the top foil piece 27 and the rotation shaft 12 accompanying the rotation of the rotation shaft 12, the trailing portion of the rotation direction Rl of the top foil body 36 can be prevented from being dragged toward the rotation shaft 12. Therefore, the trailing portion of the rotation direction Rl of the top foil body 36 is prevented from being wrapped around the rotation shaft 12, and thus the rotation shaft 12 is stably floated with respect to the top foil piece 27 by the dynamic pressure of the air film generated between the top foil piece 27 and the rotation shaft 12.

[0072] In addition, the leading edge piece 38 is separated from the preceding wall 32 and the trailing edge piece 37 in the circumferential direction of the rotation shaft 12 at least when the rotation shaft 12 rotates. Therefore, the movement of the leading edge piece 38 can be prevented from being hindered, and thus the preceding portion of the rotation direction Rl in the top foil body 36 is easily deformed in a manner of being flexed in a direction away from the rotation shaft 12. Thereby, the gap between the preceding portion of the rotation direction Rl in the top foil body 36 and the rotation shaft 12 becomes large. Therefore, air is easily taken in from the gap between the preceding portion of the rotation direction Rl in the top foil body 36 and the rotation shaft 12. Thus, the rotation shaft 12 is stably floated with respect to the top foil piece 27 by the dynamic pressure of the air film generated between the top foil piece 27 and the rotation shaft 12. According to the above, the rotation shaft 12 can be stably supported in the radial direction by the radial bearing 15.

[0073] (2) The side surface 43a of the bent portion 43 abuts against the preceding wall 32, and thus the contact area of the leading end portion of the trailing edge piece 37 and the preceding wall 32 can be greatly increased. Therefore, the frictional force between the leading end portion of the trailing edge piece 37 and the preceding wall 32 can be reduced, and the aging resistance can be improved.

[0074] (3) The trailing edge piece 37 inserted into the slot 30 between the fixed piece 46 and the trailing wall 33, and extends from the elastic plate portion 45 toward the trailing wall 33. Thereby, the fixed piece 46 easily abuts against the trailing wall 33. By the fixed piece 46 abutting against the trailing wall 33, the trailing edge piece 37 is easily positioned in the slot 30 between the fixed piece 46 and the preceding wall 32 in the circumferential direction of the rotation shaft 12. As a result, the leading end portion of the trailing edge piece 37 can be stably abutted against the preceding wall 32 at least when the rotation shaft 12 rotates.

[0075] (4) The width Larm between the opposing portion 41a and the leading wall 32 in the circumferential direction of the rotating shaft 12 is set to be larger than the value obtained by adding twice the maximum stroke amount to the plate thickness Ttab of the leading edge plate 38. This easily prevents the leading edge plate 38 from contacting the leading wall 32 and the trailing edge plate 37, at least when the rotating shaft 12 rotates. Therefore, it is possible to avoid obstruction of the movement of the leading edge plate 38.

[0076] (5) The width Larm between the opposing portion 41a and the leading wall 32 in the circumferential direction of the rotation shaft 12 is set with further consideration of the tolerance of the total circumferential length of the top foil 27 and the tolerance of the angle of the leading edge piece 38 relative to the top foil body 36. As a result, it is easier to avoid the leading edge piece 38 contacting the leading wall 32 and the trailing edge piece 37 at least when the rotation shaft 12 rotates. Therefore, it is possible to avoid the movement of the leading edge piece 38 being hindered.

[0077] (6) The gap Lgap1 between the front end 38e of the leading edge plate 38 and the second extension 42 in the radial direction of the rotating shaft 12 is larger than the maximum stroke. As a result, it is possible to avoid the leading edge plate 38 contacting the second extension 42 of the trailing edge plate 37 at least when the rotating shaft 12 rotates. Therefore, it is possible to further avoid the situation where the movement of the leading edge plate 38 is hindered.

[0078] (7) The width Lgap2 between the front end 38e of the leading edge plate 38 in the circumferential direction of the rotation shaft 12 and the leading wall 32 is larger than the maximum stroke. As a result, it is easier to avoid the leading edge plate 38 contacting the leading wall 32 at least when the rotation shaft 12 rotates. Therefore, it is possible to further avoid the situation where the movement of the leading edge plate 38 is hindered.

[0079] [Example of Change]

[0080] It should be noted that the above embodiments can be implemented by modification as follows. The above embodiments and the following modifications can be combined with each other within the scope of technical inconsistency.

[0081] ○ For example Figure 9 As shown, the bent portion 43 can also be formed by bending the front end of the trailing edge piece 37 radially inward toward the rotating shaft 12. Therefore, for example, compared to the case where the front end of the trailing edge piece 37 is bent radially outward toward the rotating shaft 12, the depth of the groove 30 from the inner circumferential surface of the bearing retaining portion 26 can be reduced. As a result, the radial size of the rotating shaft 12 of the radial bearing 15 can be miniaturized.

[0082] In the embodiment, the side surface 43a of the bent portion 43 can also not abut against the preceding wall 32 when the rotary shaft 12 is not rotating. In any case, the trailing edge piece 37 is only required to abut against the preceding wall 32 at least when the rotary shaft 12 is rotating.

[0083] In the embodiment, the leading edge piece 38 can also not be separated from the preceding wall 32 and the trailing edge piece 37 when the rotary shaft 12 is not rotating. In any case, the leading edge piece 38 is only required to be separated from the preceding wall 32 and the trailing edge piece 37 in the circumferential direction of the rotary shaft 12 at least when the rotary shaft 12 is rotating.

[0084] In the embodiment, the bent portion 43 is an elongated flat plate, but is not limited thereto and can be a curved plate, for example.

[0085] In the embodiment, the trailing edge piece 37 can also not have the bent portion 43, and the front end of the second extension portion 42 can also abut against the preceding wall 32, for example. In this case, the front end portion of the second extension portion 42 is the front end portion of the trailing edge piece 37. In any case, the trailing edge piece 37 is only required to abut against the preceding wall 32.

[0086] In the embodiment, the fixed piece 46 can also gradually incline toward the trailing wall 33 as it separates from the elastic plate portion 45. In any case, the fixed piece 46 is only required to extend from the elastic plate portion 45 toward the trailing wall 33.

[0087] In the embodiment, the tip clearance amount between the impeller 13 and the shroud 24 can also be smaller than the maximum displacement amount of the wave foil 28. In this case, the tip clearance amount between the impeller 13 and the shroud 24 is the maximum travel amount of the rotary shaft 12 in the radial direction of the rotary shaft 12 from the state in which the axis Ll of the rotary shaft 12 coincides with the axis of the through hole 29. In this way, the maximum travel amount is determined based on the smaller one of the tip clearance amount and the maximum displacement amount of the wave foil 28.

[0088] In the embodiment, the width Larm between the opposing portion 41a in the circumferential direction of the rotary shaft 12 and the preceding wall 32 can also be set without considering the tolerance of the overall length in the circumferential direction of the tip foil 27 and the tolerance of the angle of the leading edge piece 38 with respect to the tip foil body 36.

[0089] In the embodiment, the gap Lgapl between the front end 38e of the leading edge piece 38 and the second extension portion 42 in the radial direction of the rotary shaft 12 can also be below the maximum travel amount.

[0090] In the embodiment, the width Lgap2 between the front end 38e of the leading edge piece 38 and the preceding wall 32 in the circumferential direction of the rotary shaft 12 can also be below the maximum travel amount.

[0091] In the embodiment, the wave foil 28 can also not be divided into a plurality in the circumferential direction. In this case, the sub-groove 35 formed in the inner circumferential surface of the bearing holding portion 26 can also be deleted.

[0092] In the embodiment, a groove can also be formed in the inner circumferential surface of the bearing holding portion 26, and the foil member extends along the inner surface of the groove. Also, the groove dividing wall 31 that divides the groove 30 can also be formed by the foil member.

[0093] In the embodiment, the radial bearing 15 can also additionally have a bearing housing as a member different from the housing 11. In this case, for example, both end portions of the groove 30 can also be respectively opened at both end surfaces of the bearing housing. Also, the falling of the top foil 27 and the wave foil 28 toward both end surface sides of the bearing housing can be prevented by fixing the anti-falling member 49 to both end surfaces of the bearing housing.

[0094] In the embodiment, the centrifugal compressor 10 can also not be mounted on a fuel cell vehicle. In any case, the centrifugal compressor 10 is not limited to being mounted on a vehicle.

[0095] In the embodiment, the centrifugal compressor 10 is not limited to being used for compressing air supplied to a fuel cell. In any case, the centrifugal compressor 10 compresses a fluid.

Claims

1. A foil bearing that supports a rotating shaft in the radial direction, wherein, The foil bearing comprises: A bearing housing having a through hole through which the rotating shaft is inserted; A thin, plate-like top foil is disposed between the rotating shaft and the bearing housing; and A thin, plate-shaped corrugated foil is disposed between the bearing housing and the top foil, elastically supporting the top foil. A groove extending axially along the bearing housing is formed on the inner circumferential surface of the bearing housing. The top foil has: The main body of the top foil is generally cylindrical, forming a bearing surface that supports the rotating shaft and surrounding the outer circumferential surface of the rotating shaft; The trailing edge sheet is formed by bending the end of the top foil body on the rearward side in the rotational direction of the rotation axis toward the radially outward side of the rotation axis; as well as The leading edge sheet is formed by bending from the leading end of the top foil body on the leading side in the direction of rotation toward the radially outward side. The trailing edge plate and the leading edge plate are inserted into the groove. The groove dividing wall has a wall located on the leading side in the direction of rotation, i.e., a leading wall. The trailing edge plate passes within the groove at a position that is radially outer compared to the leading edge plate. The trailing edge plate has at least a front end that abuts against the leading wall when the rotation axis rotates. The leading edge plate separates from the leading wall and the trailing edge plate respectively in the circumferential direction of the rotation axis at least when the rotation axis rotates.

2. The foil bearing according to claim 1, wherein, The trailing edge piece has a bent portion formed by bending the front end of the trailing edge piece. The side of the bent portion abuts against the preceding wall.

3. The foil bearing according to claim 2, wherein, The bending portion is formed by bending the front end of the trailing edge piece toward the radially inward side.

4. The foil bearing according to any one of claims 1 to 3, wherein, The foil has the following characteristics: The elastic plate portion is disposed between the bearing housing and the top foil; and A fixing piece is formed by bending from one end of the elastic plate in the circumferential direction toward the radially outward side. The groove dividing wall also has a wall located on the rearward side in the direction of rotation, namely the rearward wall. The fixing piece is inserted between the rear edge piece and the rear wall in the groove, and extends from the elastic plate portion toward the rear wall.

5. The foil bearing according to any one of claims 1 to 3, wherein, An impeller is connected to the rotating shaft, and the impeller is housed in an impeller chamber divided by a shroud. The trailing edge plate has: A first extension extends from the top foil body toward the radially outward side; as well as The second extension extends from the end of the first extension on the side opposite to the top foil body toward the leading wall, and passes within the groove at a position radially outward than the leading edge sheet. The first extension has an opposing portion that faces the front end of the leading edge piece in the circumferential direction. The maximum radial stroke of the rotating shaft, starting from the state where the axis of the rotating shaft is aligned with the axis of the through hole, is determined based on the smaller of the head clearance between the impeller and the shroud (24) and the maximum displacement of the corrugated foil. The width between the opposing portion and the leading wall in the circumferential direction is set to a width greater than the value obtained by adding twice the maximum stroke amount to the thickness of the leading edge plate.

6. The foil bearing according to claim 5, wherein, The width between the opposing portion and the leading wall in the circumferential direction is further set taking into account the tolerance of the total length of the top foil in the circumferential direction and the tolerance of the angle of the leading edge relative to the main body of the top foil.

7. The foil bearing according to any one of claims 1 to 3, wherein, An impeller is connected to the rotating shaft, and the impeller is housed in an impeller chamber divided by a shroud. The trailing edge plate has: A first extension extends from the top foil body toward the radially outward side; as well as The second extension extends from the end of the first extension on the side opposite to the top foil body toward the leading wall, and passes within the groove at a position radially outward than the leading edge sheet. The maximum radial travel of the rotating shaft, starting from the state where the axis of the rotating shaft is aligned with the axis of the through hole, is determined based on the smaller of the head clearance between the impeller and the shroud, and the maximum displacement of the corrugated foil. The gap between the front end of the radially extending leading edge plate and the second extension is larger than the maximum stroke.

8. The foil bearing according to any one of claims 1 to 3, wherein, An impeller is connected to the rotating shaft, and the impeller is housed in an impeller chamber divided by a shroud. The trailing edge plate has: A first extension extends from the top foil body toward the radially outward side; as well as The second extension extends from the end of the first extension on the side opposite to the top foil body toward the leading wall, and passes within the groove at a position radially outward than the leading edge sheet. The maximum radial travel of the rotating shaft, starting from the state where the axis of the rotating shaft is aligned with the axis of the through hole, is determined based on the smaller of the head clearance between the impeller and the shroud, and the maximum displacement of the corrugated foil. The width between the front end of the leading edge piece in the circumferential direction and the leading wall is greater than the maximum stroke.

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