Foil bearing

Abstract

To stably support a rotary shaft in the radial direction by a foil bearing.SOLUTION: At least when the rotating shaft 12 is rotating, the leading end of the trailing edge tab 37 is in contact with the leading wall 32. Accordingly, it is possible to prevent a portion of the top foil main body 36 on the trailing edge tab 37 side from being dragged toward the rotary shaft 12 due to the flow of air between the top foil 27 and the rotary shaft 12 caused by the rotation of the rotary shaft 12. The leading edge tab 38 is separated from each of the preceding wall 32 and the trailing edge tab 37 in the circumferential direction of the rotary shaft 12 at least when the rotary shaft 12 is rotating. Therefore, since the movement of the leading edge tab 38 is prevented from being hindered, a portion of the top foil main body 36 on the leading edge tab 38 side is easily deformed so as to be bent in a direction away from the rotary shaft 12.SELECTED DRAWING: Figure 5

Description

[Technical Field]

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

[0002] 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 thin and arranged between the rotating shaft and the bearing housing. The bump foil is thin and arranged between the bearing housing and the top foil. The bump foil elastically supports the top foil.

[0003] Such a foil bearing supports a rotating shaft with the top foil in contact with the rotating shaft until the rotating shaft reaches the floating rotation speed. Once the rotating shaft reaches the floating rotation speed, the dynamic pressure of the fluid film generated between the top foil and the rotating shaft causes the rotating shaft to float relative to the top foil. As a result, the foil bearing supports the rotating shaft without contacting it.

[0004] For example, as disclosed in Patent Document 1, a slot extending in the axial direction of the bearing housing is formed on the inner peripheral surface of the bearing housing. The top foil has a top foil body, a trailing edge tab, and a leading edge tab. The top foil body is approximately cylindrical. The top foil body forms a bearing surface that supports the rotating shaft and surrounds the outer peripheral surface of the rotating shaft. The trailing edge tab is formed by bending an end of the top foil body located on the trailing side in the rotation direction of the rotating shaft outward in the radial direction of the rotating shaft. The leading edge tab is formed by bending an end of the top foil body located on the leading side in the rotation direction of the rotating shaft outward in the radial direction of the rotating shaft. The trailing edge tab and the leading edge tab are inserted into the slots. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5449553 Summary of the Invention [Problem to be solved by the invention]

[0006] In such a foil bearing, the flow of fluid between the top foil and the rotating shaft as the rotating shaft rotates can sometimes cause the trailing-edge tab side of the top foil body to be pulled toward the rotating shaft. If the trailing-edge tab side of the top foil body is pulled toward the rotating shaft, the trailing-edge tab side of the top foil body may become wrapped around the rotating shaft. If the trailing-edge tab side of the top foil body becomes wrapped around the rotating shaft, it becomes difficult for the rotating shaft to lift off the top foil due to the dynamic pressure of the fluid film generated between the top foil and the rotating shaft. Therefore, there is a risk that the rotating shaft may no longer be stably supported.

[0007] On the other hand, if the movement of the leading edge tab is hindered, when dynamic pressure of the fluid film is generated between the top foil and the rotating shaft, the portion of the top foil main body on the leading edge tab side is less likely to deform so as to bend away from the rotating shaft. This makes it difficult for the gap between the portion of the top foil main body on the leading edge tab side and the rotating shaft to become large, making it difficult for fluid to be taken in through the gap between the portion of the top foil main body on the leading edge tab side and the rotating shaft. As a result, it becomes difficult for the rotating shaft to lift off the top foil due to the dynamic pressure of the fluid film generated between the top foil and the rotating shaft, which may result in an inability to stably support the rotating shaft. [Means for solving the problem]

[0008] A foil bearing that solves the above-mentioned problems is a foil bearing that supports a rotating shaft in a radial direction, and includes: a bearing housing having a through hole through which the rotating shaft is inserted; a thin plate-like top foil that is arranged between the rotating shaft and the bearing housing; and a thin plate-like bump foil that is arranged between the bearing housing and the top foil and elastically supports the top foil, wherein an inner peripheral surface of the bearing housing is formed with slots that extend in the axial direction of the bearing housing, and the top foil forms a bearing surface that supports the rotating shaft and includes a substantially cylindrical top foil body that surrounds the outer peripheral surface of the rotating shaft, and a top foil body that extends from an end of the top foil body that is located on the trailing side in the rotation direction of the rotating shaft to an outer peripheral surface of the rotating shaft in the radial direction. a trailing-edge tab formed by bending an end of the top foil body located on a leading side in the rotation direction toward the outside in the radial direction, and a leading-edge tab formed by bending an end of the top foil body located on a leading side in the rotation direction toward the outside in the radial direction, the trailing-edge tab and the leading-edge tab being inserted into the slot, a slot partition wall that partitions the slot has a leading wall that is a wall located on the leading side in the rotation direction, the trailing-edge tab passing outside in the slot in the radial direction more than the leading-edge tab, a tip end of the trailing-edge tab abutting against the leading wall at least when the rotation shaft is rotating, and the leading-edge tab being spaced apart from the leading wall and the trailing-edge tab in the circumferential direction of the rotation shaft at least when the rotation shaft is rotating.

[0009] According to this, the tip end of the trailing-edge tab abuts against the leading wall at least when the rotating shaft is rotating. Therefore, it is possible to prevent the portion of the top foil main body on the trailing-edge tab side from being dragged toward the rotating shaft due to the flow of fluid between the top foil and the rotating shaft as the rotating shaft rotates. Therefore, since the portion of the top foil main body on the trailing-edge tab side is prevented from being caught in the rotating shaft, the floating of the rotating shaft relative to the top foil due to the dynamic pressure of the fluid film generated between the top foil and the rotating shaft is stably performed.

[0010] Furthermore, the leading edge tab is spaced apart from the leading wall and the trailing edge tab in the circumferential direction of the rotating shaft, at least when the rotating shaft is rotating. Therefore, it is possible to avoid obstruction of the movement of the leading edge tab, and the portion of the top foil main body on the leading edge tab side is more likely to deform so as to bend in a direction away from the rotating shaft. This increases the gap between the portion of the top foil main body on the leading edge tab side and the rotating shaft. Therefore, fluid is more likely to be taken in through the gap between the portion of the top foil main body on the leading edge tab side and the rotating shaft, and the floating of the rotating shaft relative to the top foil due to the dynamic pressure of the fluid film generated between the top foil and the rotating shaft is stably achieved. As described above, the foil bearing can stably support the rotating shaft in the radial direction.

[0011] In the above foil bearing, the trailing edge tab may have a bent portion formed by bending a tip end of the trailing edge tab, and a side surface of the bent portion may abut against the leading wall.

[0012] With this, the side surface of the bent portion abuts against the leading wall, which maximizes the contact area between the tip of the trailing edge tab and the leading wall, thereby reducing the frictional force between the tip of the trailing edge tab and the leading wall and improving durability.

[0013] In the above foil bearing, the bent portion may be formed by bending a tip end portion of the trailing edge tab inward in the radial direction. This allows the depth of the slot from the inner peripheral surface of the bearing housing to be shallower than when the tip of the trailing edge tab is formed by bending it outward in the radial direction of the rotating shaft, thereby making it possible to reduce the size of the foil bearing in the radial direction of the rotating shaft.

[0014] In the above foil bearing, the bump foil has an elastic plate portion arranged between the bearing housing and the top foil, and a fixing tab formed by bending an end portion of the elastic plate portion located on one side in the circumferential direction radially outward from the rotating shaft, the slot partition wall has a trailing wall that is a wall located on the trailing side in the rotational direction, and the fixing tab is inserted between the trailing edge tab and the trailing wall within the slot and extends from the elastic plate portion toward the trailing wall.

[0015] This makes it easier for the fixed tab to abut against the trailing wall. The abutment of the fixed tab against the trailing wall makes it easier for the trailing edge tab to be positioned within the slot between the fixed tab and the leading wall in the circumferential direction of the rotation shaft. As a result, the tip of the trailing edge tab can be stably abutted against the leading wall at least while the rotation shaft is rotating.

[0016] In the above foil bearing, the trailing edge tab may have a first extension portion extending radially outward from the top foil body, and a second extension portion extending from an end of the first extension portion opposite the top foil body toward the leading wall and passing radially outward of the leading edge tab within the slot, the first extension portion having an opposing portion opposing a tip of the leading edge tab in the circumferential direction, a maximum stroke amount of the rotating shaft in the radial direction from a state in which an axis of the rotating shaft and an axis of the through hole are aligned is determined based on the smaller of a tip clearance amount between an impeller connected to the rotating shaft and a shroud that defines an impeller chamber that houses the impeller, and a maximum displacement amount of the bump foil, and a width between the opposing portion and the leading wall in the circumferential direction is set to a width greater than a value obtained by adding twice the maximum stroke amount to a plate thickness of the leading edge tab.

[0017] This makes it easier to prevent the leading edge tab from coming into contact with the leading wall and the trailing edge tab at least while the rotation shaft is rotating, thereby preventing the movement of the leading edge tab from being hindered.

[0018] In the above foil bearing, the width between the opposing portion and the leading wall in the circumferential direction may be set by further taking into account the tolerance of the overall circumferential length of the top foil and the tolerance of the angle of the leading edge tab relative to the top foil body.

[0019] This makes it easier to prevent the leading edge tab from coming into contact with the leading wall and the trailing edge tab at least while the rotation shaft is rotating, thereby preventing the movement of the leading edge tab from being hindered.

[0020] In the above foil bearing, the trailing edge tab has a first extension portion extending radially outward from the top foil body, and a second extension portion extending from an end of the first extension portion opposite the top foil body toward the leading wall and passing radially outward of the leading edge tab within the slot, wherein a maximum stroke amount of the rotating shaft in the radial direction from a state in which an axis of the rotating shaft and an axis of the through hole are aligned is determined based on the smaller of a tip clearance amount between an impeller connected to the rotating shaft and a shroud that defines an impeller chamber that houses the impeller, and a maximum displacement amount of the bump foil, and a gap in the radial direction between the tip of the leading edge tab and the second extension portion is larger than the maximum stroke amount.

[0021] This prevents the leading edge tab from coming into contact with the second extension portion of the trailing edge tab at least while the rotation shaft is rotating, thereby further preventing the movement of the leading edge tab from being hindered.

[0022] In the above foil bearing, the trailing edge tab may have a first extension portion extending radially outward from the top foil body, and a second extension portion extending from an end of the first extension portion opposite the top foil body toward the leading wall and passing radially outward of the leading edge tab within the slot, wherein a maximum stroke amount of the rotating shaft in the radial direction from a state in which an axis of the rotating shaft and an axis of the through hole are aligned is determined based on the smaller of a tip clearance amount between an impeller connected to the rotating shaft and a shroud that defines an impeller chamber that houses the impeller, and a maximum displacement amount of the bump foil, and a width in the circumferential direction between the tip of the leading edge tab and the leading wall is greater than the maximum stroke amount.

[0023] This makes it easier to prevent the leading edge tab from coming into contact with the leading wall at least when the rotation shaft is rotating, thereby further preventing the movement of the leading edge tab from being hindered. [Effects of the Invention]

[0024] According to this invention, the rotating shaft can be stably supported in the radial direction by the foil bearing. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 is a schematic configuration diagram showing a centrifugal compressor according to an embodiment. [Figure 2] FIG. 2 is an enlarged cross-sectional view of a portion of the centrifugal compressor. [Figure 3] FIG. 3 is a cross-sectional view for explaining a radial bearing. [Figure 4] FIG. 4 is an exploded perspective view for explaining the radial bearing. [Figure 5] FIG. 5 is an enlarged cross-sectional view of a portion of the radial bearing. [Figure 6] FIG. 6 is a cross-sectional view showing a state in which the rotating shaft is moving in the radial direction. [Figure 7] FIG. 7 is a cross-sectional view showing a state in which the rotating shaft is moving in the radial direction. [Figure 8] FIG. 8 is an enlarged cross-sectional view of a portion of the radial bearing. [Figure 9] FIG. 9 is an enlarged cross-sectional view showing a part of a radial bearing according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0026] An embodiment of a foil bearing will be described below with reference to Figs. 1 to 8. The foil bearing of this embodiment is applied to a centrifugal compressor mounted on a fuel cell vehicle. The fuel cell vehicle is equipped with a fuel cell system that supplies oxygen and hydrogen to a fuel cell to generate electricity. The centrifugal compressor compresses air, which serves as an oxygen-containing fluid, to be supplied to the fuel cell.

[0027] <Outline of centrifugal compressor> As shown in FIG. 1, a 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 cylindrical. The housing 11 accommodates the rotating shaft 12, the impeller 13, and the motor 14. The rotating shaft 12 is rotated by being driven by 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 to compress air.

[0028] The centrifugal compressor 10 includes two radial bearings 15. Each radial bearing 15 is disposed within the housing 11. The two radial bearings 15 are disposed on either side of the motor 14. The two radial bearings 15 rotatably support portions of the rotating shaft 12 on either side of the motor 14. Each radial bearing 15 is a foil bearing that rotatably supports the rotating shaft 12 in the radial direction. The "radial direction" is a direction perpendicular to the axial direction of the rotating shaft 12. Therefore, the "radial direction" is the radial direction of the rotating shaft 12.

[0029] The housing 11 has a compressor housing 16 and a housing plate 17. The compressor housing 16 is cylindrical and has an intake port 18. Air that has been purified by an air cleaner (not shown) flows through the intake port 18. The housing plate 17 is joined to the compressor housing 16. The housing plate 17, together with the compressor housing 16, defines an impeller chamber 19. The impeller chamber 19 communicates with the intake port 18. The impeller chamber 19 houses the impeller 13. A first end of the rotating shaft 12 penetrates the housing plate 17 and protrudes into the impeller chamber 19.

[0030] The housing 11 has a diffuser passage 20 and a discharge chamber 21. The diffuser passage 20 and the discharge chamber 21 are partitioned by the compressor housing 16 and the housing plate 17. The diffuser passage 20 is arranged radially outward of the impeller chamber 19 from the rotary shaft 12. The diffuser passage 20 extends annularly around the impeller 13. The discharge chamber 21 is arranged radially outward of the impeller chamber 19 from the diffuser passage 20 from the rotary shaft 12. The discharge chamber 21 extends annularly around the impeller chamber 19. The diffuser passage 20 connects the impeller chamber 19 and the discharge chamber 21.

[0031] Air drawn into the impeller chamber 19 from the intake port 18 flows toward the diffuser passage 20 due to the rotation of the impeller 13. The air is then pressurized as it passes through the diffuser passage 20 and is discharged into the discharge chamber 21. The air discharged into the discharge chamber 21 is supplied to the fuel cell. Therefore, the impeller 13 rotates together with the rotary shaft 12 to compress the air to be supplied to the fuel cell.

[0032] As shown in Figure 2, the impeller 13 has a hub 22 and a plurality of blades 23. The hub 22 rotates integrally with the rotary shaft 12. The hub 22 is attached to a first end of the rotary shaft 12. The hub 22 has a generally conical shape whose outer diameter increases from the front end located on the suction port 18 side toward the rear end. The hub 22 has a curved surface that is concave toward the axis L1 of the rotary shaft 12.

[0033] The multiple blades 23 are arranged in the circumferential direction of the hub 22. The multiple blades 23 are arranged at equal intervals in the circumferential direction on the surface of the hub 22. Because the outer diameter of the hub 22 increases from the front end to the rear end, the intervals between adjacent blades 23 in the circumferential direction of the hub 22 gradually increase from the front end to the rear end of the hub 22.

[0034] The compressor housing 16 has a shroud 24. The shroud 24 defines an impeller chamber 19. The shroud 24 is disposed opposite the hub 22 and extends along the surface of the hub 22. The shroud 24 surrounds a plurality of blades 23. A tip clearance 25 is formed between the plurality of blades 23 and the shroud 24. In this manner, the tip clearance 25 is formed between the impeller 13 and the shroud 24. The amount of tip clearance between the impeller 13 and the shroud 24 is set in advance so that the blades 23 do not come into contact with the shroud 24 even if the impeller 13 moves within the impeller chamber 19 as the rotating shaft 12 moves in the radial direction of the rotating shaft 12. This amount of tip clearance is determined in advance by experiment or the like.

[0035] <Radial bearing> 3 and 4, the radial bearing 15 includes a bearing holder 26, a top foil 27, and a bump foil 28. The bearing holder 26 is cylindrical. The bearing holder 26 is part of the housing 11. The bearing holder 26 has a through hole 29 through which the rotating shaft 12 is inserted. Therefore, the bearing holder 26 functions as a bearing housing having the through hole 29 through which the rotating shaft 12 is inserted.

[0036] As shown in Fig. 3, the top foil 27 faces the rotating shaft 12 in the radial direction. The top foil 27 is disposed between the rotating shaft 12 and the bearing holder 26. The bump foil 28 is disposed on the opposite side of the rotating shaft 12 with the top foil 27 in between. The bump foil 28 is disposed between the bearing holder 26 and the top foil 27. The bump foil 28 elastically supports the top foil 27.

[0037] <slot> A slot 30 is formed in the inner peripheral surface of the bearing holder 26. The slot 30 extends in the axial direction of the bearing holder 26. A first end of the slot 30 opens to a first axial end face of the bearing holder 26. A second end of the slot 30 is closed by a part of the bearing holder 26.

[0038] As shown in FIG. 5 , the bearing holder 26 has a slot partition wall 31 that partitions the slot 30. The slot partition 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 from the inner circumferential surface of the bearing holder 26 to the outside in the radial direction of 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 from the inner circumferential surface of the bearing holder 26 to the outside in the radial direction of 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 face each other in the circumferential direction of the bearing holder 26. The connecting wall 34 connects the end of the leading wall 32 located radially outward from the rotary shaft 12 to the end of the trailing wall 33 located radially outward from the rotary shaft 12 .

[0039] 3 and 4, two sub-slots 35 are formed in addition to the slots 30 on the inner peripheral surface of the bearing holder 26. The two sub-slots 35 extend in the axial direction of the bearing holder 26. A first end of each sub-slot 35 opens to a first axial end of the bearing holder 26. A second end of each sub-slot 35 is closed by a part of the bearing holder 26.

[0040] The slot 30 and the two sub-slots 35 are arranged at equal intervals in the circumferential direction of the bearing holder 26. The circumferential width of the bearing holder 26 in the slot 30 is greater than the circumferential width of the bearing holder 26 in the two sub-slots 35. The circumferential direction of the bearing holder 26 coincides with the circumferential direction of the rotating shaft 12.

[0041] <Top foil> The top foil 27 is made of a flexible metal material such as stainless steel or Inconel (registered trademark). The top foil 27 is in the form of a thin plate.

[0042] The top foil 27 has a top foil body 36, a trailing edge tab 37, and a leading edge tab 38. The top foil body 36 is substantially cylindrical. The top foil body 36 surrounds the outer peripheral surface of the rotating shaft 12. The top foil body 36 forms a bearing surface 39 that supports the rotating 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 rotating shaft 12.

[0043] 5, the end of the top foil body 36 located on the trailing side in the rotation direction R1 of the rotating shaft 12 faces, but is spaced apart from, the end of the top foil body 36 located on the leading side in the rotation direction R1 of the rotating shaft 12 in the circumferential direction of the top foil body 36. Therefore, the top foil body 36 has a non-annular shape with a portion cut out.

[0044] <Trailing edge tab> The trailing edge tab 37 is formed by bending an end of the top foil body 36 located on the trailing side in the rotation direction R1 of the rotary shaft 12 outward in the radial direction of the rotary shaft 12. The leading edge tab 38 is formed by bending an end of the top foil body 36 located on the leading side in the rotation direction R1 of the rotary shaft 12 outward in the radial direction of the rotary shaft 12. The trailing edge tab 37 and the leading edge tab 38 are inserted into the slots 30.

[0045] The trailing edge tab 37 has a first extension portion 41 and a second extension portion 42. The first extension portion 41 extends from the top foil main body 36 outward in the radial direction of the rotating shaft 12. The first extension portion 41 is bent from an end of the top foil main body 36 located on the trailing side in the rotation direction R1 of the rotating shaft 12 outward in the radial direction of the rotating shaft 12. The first extension portion 41 has a narrow, elongated flat plate shape. An end of the first extension portion 41 opposite the top foil main body 36 is inserted into the slot 30.

[0046] The first extension portion 41 has an opposing portion 41a that faces the tip 38e of the leading edge tab 38 in the circumferential direction of the rotary shaft 12. The second extension portion 42 extends from an end of the first extension portion 41 opposite the top foil main body 36 toward the leading wall 32. The second extension portion 42 has a narrow, elongated flat plate shape. The second extension portion 42 passes inside the slot 30 on the outer side of the leading edge tab 38 in the radial direction of the rotary shaft 12.

[0047] The trailing edge tab 37 has a bent portion 43. The bent portion 43 is a tip portion of the trailing edge tab 37. The bent portion 43 is formed by bending the tip portion of the trailing edge tab 37. Specifically, the bent portion 43 is formed by bending the tip portion of the trailing edge tab 37 radially outward from the rotary shaft 12. The bent portion 43 has a shape of an elongated flat plate. A 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 rotary shaft 12 is rotating, and also abuts against the leading wall 32 when the rotary shaft 12 is not rotating. In this way, the trailing edge tab 37 passes outside the leading edge tab 38 in the slot 30 in the radial direction of the rotary shaft 12, and the tip portion of the trailing edge tab 37 abuts against the leading wall 32 at least when the rotary shaft 12 is rotating.

[0048] <Bump foil> As shown in Figures 3 and 4, the radial bearing 15 has three bump foils 28. Therefore, the radial bearing 15 has bump foils 28 that are divided into multiple parts in the circumferential direction. Each bump foil 28 is in the shape of a curved plate. Each bump foil 28 is made of a flexible metal material. Each bump foil 28 is made of stainless steel or Inconel (registered trademark). Each bump foil 28 is in the shape of a thin plate. The three bump foils 28 are arranged at equal intervals in the circumferential direction of the rotating shaft 12 between the bearing holder 26 and the top foil 27. The length of each bump foil 28 in the circumferential direction of the rotating shaft 12 is the same.

[0049] Each bump foil 28 has an elastic plate portion 45 and a fixing tab 46. The elastic plate portion 45 is disposed between the bearing holder 26 and the top foil 27. Specifically, the elastic plate portion 45 is disposed between the inner peripheral surface of the bearing holder 26 and the outer peripheral surface of the top foil main body 36. The elastic plate portion 45 has a curved plate shape. The curved direction of the elastic plate portion 45 coincides with the circumferential direction of the rotation shaft 12.

[0050] The fixing tab 46 is formed by bending an end of the elastic plate portion 45 located on one side in the circumferential direction of the rotary shaft 12 outward in the radial direction of the rotary shaft 12. The fixing tab 46 has a long, thin plate shape. The fixing tab 46 of one of the three bump foils 28 is inserted into the slot 30. The fixing tabs 46 of the remaining two of the three bump foils 28 are inserted into each of the sub-slots 35.

[0051] 5, the fixing tab 46 inserted into the slot 30 is inserted between the trailing edge tab 37 and the trailing wall 33 in the slot 30. The tip of the fixing tab 46 is bent so as to be spaced apart from the trailing edge tab 37 in the circumferential direction of the rotation shaft 12 and approach the trailing wall 33. Therefore, the fixing tab 46 extends from the elastic plate portion 45 toward the trailing wall 33. The fixing tab 46 has a hook-shaped cross section.

[0052] As shown in FIG. 3 , the elastic plate portion 45 has a plurality of peaks 47 and a plurality of valleys 48. Therefore, each bump foil 28 has a plurality of peaks 47 and a plurality of 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 main body 36. Each peak 47 extends in the circumferential direction of the elastic plate portion 45. Each valley 48 contacts the inner peripheral surface of the bearing holder 26. The elastic plate portion 45 has a wave shape in which the peaks 47 and valleys 48 are alternately arranged in the circumferential direction of the elastic plate portion 45. Each peak 47 connects adjacent valleys 48 in the circumferential direction of the rotating shaft 12.

[0053] When the rotating shaft 12 rotates, air enters between the top foil 27 and the rotating shaft 12, and an air film is formed between the top foil 27 and the rotating shaft 12. Until the rotation speed of the rotating shaft 12 reaches the lift-off rotation speed, the rotating shaft 12 rotates while in contact with the top foil 27. Then, when the rotation speed of the rotating shaft 12 reaches the lift-off rotation speed, the dynamic pressure of the air film causes the rotating shaft 12 to lift off relative to the top foil 27. The top foil 27 supports the rotating shaft 12 in the radial direction via the air film. In this way, the top foil 27 supports the rotating shaft 12 in the radial direction.

[0054] 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 is displaced toward the elastic plate portion 45 of each bump foil 28. As a result, the top foil 27 presses each ridge portion 47 of the elastic plate portion 45 toward the bearing holder 26. This causes the elastic plate portion 45 to elastically deform. The elastic plate portion 45 is then displaced toward the bearing holder 26 together with the top foil 27. The elastic plate portion 45 elastically supports the top foil 27. In this way, each bump foil 28 elastically deforms to elastically support the top foil 27 in a state in which it can be displaced radially around the rotating shaft 12.

[0055] <Prevention member> As shown in FIGS. 3 and 4 , the radial bearing 15 includes a retaining member 49. The retaining member 49 is annular. The retaining member 49 is formed of, for example, stainless steel. The hardness of the retaining member 49 is lower than that of the top foil 27 and the bump foil 28. The inner diameter of the retaining member 49 is slightly larger than that of the through hole 29. The retaining member 49 is fixed to the first end face of the bearing holder 26 while closing the first end of the slot 30 and the first ends of each sub-slot 35. The retaining member 49 faces the trailing edge tab 37, the leading edge tab 38, and the fixing tabs 46 of each bump foil 28 in the axial direction of the bearing holder 26.

[0056] The trailing edge tab 37 and the leading edge tab 38 come into contact with the retaining member 49, thereby preventing the bearing holding portion 26 of the top foil 27 from coming off toward the first end face side. Furthermore, the fixing tab 46 of each bump foil 28 comes into contact with the retaining member 49, thereby preventing the bearing holding portion 26 of each bump foil 28 from coming off toward the first end face side.

[0057] <Leading edge tab> 6 and 7, the rotating shaft 12 can move in the radial direction of the rotating shaft 12. The rotating shaft 12 can move until the peaks 47 of the elastic plate portion 45 are completely crushed by the top foil 27. The maximum displacement of the bump foil 28 is the amount of displacement of the peaks 47 from their original shape until they are completely crushed. Here, the maximum displacement of the bump foil 28 is smaller than the tip clearance between the impeller 13 and the shroud 24.

[0058] The stroke amount by which the rotating shaft 12 can move from a state in which the axis L1 of the rotating shaft 12 and the axis of the through hole 29 are aligned until the peak portions 47 of the elastic plate portion 45 are completely crushed by the top foil 27 is the maximum stroke amount of the rotating shaft 12 in the radial direction from a state in which the axis L1 of the rotating shaft 12 and the axis of the through hole 29 are aligned. In this way, the maximum stroke amount of the rotating shaft 12 in the radial direction from a state in which the axis L1 of the rotating shaft 12 and the axis of the through hole 29 are aligned is determined based on the smaller of the tip clearance amount and the maximum displacement amount of the bump foil 28. In the following description, "the maximum stroke amount of the rotating shaft 12 in the radial direction from a state in which the axis L1 of the rotating shaft 12 and the axis of the through hole 29 are aligned" may also be simply referred to as "maximum stroke amount."

[0059] 5, 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 sum of twice the maximum stroke amount and the plate thickness Ttab of the leading edge tab 38. The gap Lgap1 between the tip 38e of the leading edge tab 38 and the second extension portion 42 in the radial direction of the rotating shaft 12 is larger than the maximum stroke amount. In addition, the width Lgap2 between the tip 38e of the leading edge tab 38 and the leading wall 32 in the circumferential direction of the rotating shaft 12 is larger than the maximum stroke amount.

[0060] As shown in Fig. 8, when manufacturing the top foil 27, a tolerance may occur in the angle θ1 of the leading edge tab 38 relative to the top foil main body 36. Note that in Fig. 8, the tolerance of the angle θ1 of the leading edge tab 38 relative to the top foil main body 36 is exaggerated by a two-dot chain line. Furthermore, when manufacturing the top foil 27, a tolerance may occur in the overall length of the top foil 27 in the circumferential direction.

[0061] The width Larm is set to a value greater than the sum of twice the maximum stroke amount, the thickness Ttab of the leading edge tab 38, the tolerance of the overall circumferential length of the top foil 27, and twice the angle θ1 of the leading edge tab 38 with respect to the top foil main body 36. Therefore, the width Larm between the opposing portion 41a and the leading wall 32 in the circumferential direction of the rotating shaft 12 is set by further taking into account the tolerance of the overall circumferential length of the top foil 27 and the tolerance of the angle θ1 of the leading edge tab 38 with respect to the top foil main body 36.

[0062] By setting the width Larm, the gap Lgap1, and the width Lgap2 in this manner, the leading edge tab 38 is spaced apart from the leading wall 32 and the trailing edge tab 37 when the rotary shaft 12 is rotating. The leading edge tab 38 is also spaced apart from the leading wall 32 and the trailing edge tab 37 when the rotary shaft 12 is not rotating. In this way, the leading edge tab 38 is spaced apart from the leading wall 32 and the trailing edge tab 37 in the circumferential direction of the rotary shaft 12 at least when the rotary shaft 12 is rotating.

[0063] [Operation of the embodiment] Next, the operation of the embodiment will be described. In such a radial bearing 15, the air flow between the top foil 27 and the rotating shaft 12 caused by the rotation of the rotating shaft 12 may cause the portion of the top foil main body 36 on the trailing edge tab 37 side to be dragged toward the rotating shaft 12. Specifically, the portion of the top foil main body 36 on the trailing edge tab 37 side tends to be dragged toward the rotating shaft 12 as shown by arrow A1 in FIG.

[0064] At this time, the tip end of the trailing edge tab 37 abuts against the leading wall 32 at least while the rotating shaft 12 is rotating. Specifically, the side surface 43a of the bent portion 43 abuts against the leading wall 32. Therefore, the portion of the top foil main body 36 on the trailing edge tab 37 side is prevented from being dragged toward the rotating shaft 12 by the air flow between the top foil 27 and the rotating shaft 12 as the rotating shaft 12 rotates. Therefore, the portion of the top foil main body 36 on the trailing edge tab 37 side is prevented from being caught in the rotating shaft 12, and therefore, the floating of the rotating shaft 12 relative to the top foil 27 due to the dynamic pressure of the air film generated between the top foil 27 and the rotating shaft 12 is stably performed.

[0065] Furthermore, the leading edge tab 38 is spaced apart from the leading wall 32 and the trailing edge tab 37 in the circumferential direction of the rotary shaft 12, at least when the rotary shaft 12 is rotating. Therefore, the movement of the leading edge tab 38 is not hindered, and the portion of the top foil main body 36 on the leading edge tab 38 side is easily deformed so as to bend in a direction away from the rotary shaft 12, as shown by the two-dot chain line in FIG. 5 . This increases the gap between the portion of the top foil main body 36 on the leading edge tab 38 side and the rotary shaft 12. Therefore, air is easily taken in through the gap between the portion of the top foil main body 36 on the leading edge tab 38 side and the rotary shaft 12. Therefore, the floating of the rotary shaft 12 relative to the top foil 27 due to the dynamic pressure of the air film generated between the top foil 27 and the rotary shaft 12 is stably performed.

[0066] [Effects of the embodiment] The above embodiment can provide the following effects. (1) At least when the rotating shaft 12 is rotating, the tip end of the trailing edge tab 37 abuts against the leading wall 32. Therefore, it is possible to prevent the portion of the top foil main body 36 on the trailing edge tab 37 side from being dragged toward the rotating shaft 12 due to the air flow between the top foil 27 and the rotating shaft 12 as the rotating shaft 12 rotates. Therefore, since it is possible to prevent the portion of the top foil main body 36 on the trailing edge tab 37 side from being caught in the rotating shaft 12, the floating of the rotating shaft 12 relative to the top foil 27 due to the dynamic pressure of the air film generated between the top foil 27 and the rotating shaft 12 is stably performed.

[0067] Furthermore, the leading edge tab 38 is spaced apart from the leading wall 32 and the trailing edge tab 37 in the circumferential direction of the rotary shaft 12, at least when the rotary shaft 12 is rotating. Therefore, it is possible to avoid obstruction of the movement of the leading edge tab 38, and the portion of the top foil main body 36 on the leading edge tab 38 side is more likely to deform so as to bend in a direction away from the rotary shaft 12. This increases the gap between the portion of the top foil main body 36 on the leading edge tab 38 side and the rotary shaft 12. Therefore, air is more likely to be taken in through the gap between the portion of the top foil main body 36 on the leading edge tab 38 side and the rotary shaft 12. Therefore, the floating of the rotary shaft 12 relative to the top foil 27 due to the dynamic pressure of the air film generated between the top foil 27 and the rotary shaft 12 is stably performed. As described above, the radial bearing 15 can stably support the rotary shaft 12 in the radial direction.

[0068] (2) Because the side surface 43a of the bent portion 43 abuts against the leading wall 32, it is possible to maximize the contact area between the tip of the trailing edge tab 37 and the leading wall 32. This reduces the frictional force between the tip of the trailing edge tab 37 and the leading wall 32, thereby improving durability.

[0069] (3) The fixed tab 46 is inserted between the trailing edge tab 37 and the trailing wall 33 in the slot 30 and extends from the elastic plate portion 45 toward the trailing wall 33. This makes it easier for the fixed tab 46 to abut against the trailing wall 33. When the fixed tab 46 abuts against the trailing wall 33, the trailing edge tab 37 is more easily positioned between the fixed tab 46 and the leading wall 32 in the circumferential direction of the rotary shaft 12 within the slot 30. As a result, the tip of the trailing edge tab 37 can stably abut against the leading wall 32 at least while the rotary shaft 12 is rotating.

[0070] (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 a width greater than the sum of twice the maximum stroke amount and the thickness Ttab of the leading edge tab 38. This makes it easier to prevent the leading edge tab 38 from coming into contact with the leading wall 32 and the trailing edge tab 37, at least while the rotating shaft 12 is rotating. This makes it possible to prevent the movement of the leading edge tab 38 from being hindered.

[0071] (5) The width Larm between the opposing portion 41a and the leading wall 32 in the circumferential direction of the rotating shaft 12 is set by further taking into consideration the tolerance of the overall circumferential length of the top foil 27 and the tolerance of the angle θ1 of the leading edge tab 38 relative to the top foil main body 36. This makes it easier to prevent the leading edge tab 38 from coming into contact with the leading wall 32 and the trailing edge tab 37, at least while the rotating shaft 12 is rotating. Therefore, it is possible to prevent the movement of the leading edge tab 38 from being hindered.

[0072] (6) The gap Lgap1 between the tip 38e of the leading edge tab 38 and the second extension 42 in the radial direction of the rotary shaft 12 is larger than the maximum stroke amount. This prevents the leading edge tab 38 from coming into contact with the second extension 42 of the trailing edge tab 37, at least while the rotary shaft 12 is rotating. This further prevents the movement of the leading edge tab 38 from being hindered.

[0073] (7) The width Lgap2 between the tip 38e of the leading edge tab 38 and the leading wall 32 in the circumferential direction of the rotary shaft 12 is greater than the maximum stroke amount. This makes it easier to prevent the leading edge tab 38 from coming into contact with the leading wall 32, at least while the rotary shaft 12 is rotating. This further prevents the movement of the leading edge tab 38 from being hindered.

[0074] [Example of change] The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0075] 9, the bent portion 43 may be formed by bending the tip of the trailing edge tab 37 radially inward of the rotary shaft 12. This allows the depth of the slot 30 from the inner circumferential surface of the bearing holder 26 to be shallower than when the tip of the trailing edge tab 37 is formed by bending it radially outward of the rotary shaft 12. As a result, the size of the radial bearing 15 in the radial direction of the rotary shaft 12 can be reduced.

[0076] In the embodiment, the side surface 43 a of the bent portion 43 does not need to abut against the leading wall 32 when the rotary shaft 12 is not rotating. In short, it is sufficient that the tip of the trailing edge tab 37 abuts against the leading wall 32 at least when the rotary shaft 12 is rotating.

[0077] In the embodiment, the leading edge tab 38 does not have to be spaced apart from the leading wall 32 and the trailing edge tab 37 when the rotary shaft 12 is not rotating. In short, it is sufficient that the leading edge tab 38 is spaced apart from the leading wall 32 and the trailing edge tab 37 in the circumferential direction of the rotary shaft 12 at least when the rotary shaft 12 is rotating.

[0078] In the above embodiment, the bent portion 43 is in the shape of a long, narrow flat plate. However, the bent portion 43 is not limited to this and may be in the shape of a curved plate, for example. In the embodiment, the trailing edge tab 37 does not have to have the bent portion 43. For example, the tip of the second extension portion 42 may abut against the leading wall 32. In this case, the tip of the second extension portion 42 is the tip of the trailing edge tab 37. In short, it is sufficient that the tip of the trailing edge tab 37 abuts against the leading wall 32.

[0079] In the above embodiment, the fixing tab 46 may be gradually inclined toward the trailing wall 33 as it moves away from the elastic plate portion 45. In short, it is sufficient that the fixing tab 46 extends from the elastic plate portion 45 toward the trailing wall 33.

[0080] In the embodiment, the tip clearance between the impeller 13 and the shroud 24 may be smaller than the maximum displacement of the bump foil 28. In this case, the tip clearance between the impeller 13 and the shroud 24 is the maximum stroke of the rotary shaft 12 in the radial direction of the rotary shaft 12 from a state in which the axis L1 of the rotary shaft 12 and the axis of the through hole 29 are aligned. In this way, the maximum stroke is determined based on the smaller of the tip clearance and the maximum displacement of the bump foil 28.

[0081] In the embodiment, the width Larm between the opposing portion 41a and the leading wall 32 in the circumferential direction of the rotating shaft 12 may be set without taking into account the tolerance of the overall circumferential length of the top foil 27 and the tolerance of the angle θ1 of the leading edge tab 38 relative to the top foil main body 36.

[0082] In the above embodiment, the gap Lgap1 between the tip 38e of the leading edge tab 38 and the second extension portion 42 in the radial direction of the rotary shaft 12 may be equal to or less than the maximum stroke amount. In an embodiment, the width Lgap2 between the tip 38e of the leading edge tab 38 and the leading wall 32 in the circumferential direction of the rotary shaft 12 may be equal to or less than the maximum stroke amount.

[0083] In the above embodiment, the bump foil 28 does not have to be divided into a plurality of parts in the circumferential direction. In this case, the sub-slots 35 formed on the inner circumferential surface of the bearing holder 26 may be omitted.

[0084] In the above embodiment, a groove may be formed on the inner circumferential surface of the bearing holder 26, and a foil member may extend along the inner surface of the groove. The foil member may then form a slot partition wall 31 that partitions the slot 30.

[0085] In the embodiment, the radial bearing 15 may include a separate bearing housing that is a component separate from the housing 11. In this case, for example, both ends of the slot 30 may open to both end surfaces of the bearing housing. Then, by fixing anti-slip members 49 to both end surfaces of the bearing housing, it is possible to prevent the top foil 27 and the bump foil 28 from slipping out toward both end surfaces of the bearing housing.

[0086] In the above-described embodiment, the centrifugal compressor 10 does not necessarily have to be mounted on a fuel cell vehicle. In other words, the centrifugal compressor 10 is not limited to being mounted on a vehicle. In the above-described embodiment, the centrifugal compressor 10 is not limited to a compressor used to compress air supplied to a fuel cell. The key is that the centrifugal compressor 10 may be any compressor that compresses a fluid.

[0087] [Note] The technical ideas that can be understood from the above-described embodiment and modifications will be described below. <Appendix 1> A foil bearing that supports a rotating shaft in the radial direction, a bearing housing having a through hole through which the rotating shaft is inserted; a thin top foil disposed between the rotating shaft and the bearing housing; a thin-plate-shaped bump foil disposed between the bearing housing and the top foil, and elastically supporting the top foil; A slot extending in the axial direction of the bearing housing is formed in the inner peripheral surface of the bearing housing, The top foil is a substantially cylindrical top foil body that forms a bearing surface that supports the rotating shaft and surrounds an outer circumferential surface of the rotating shaft; a trailing edge tab formed by bending an end portion of the top foil body located on a trailing side in a rotation direction of the rotation shaft toward an outer side in a radial direction of the rotation shaft; a leading edge tab formed by bending an end portion of the top foil body located on a leading side in the rotation direction outward in the radial direction, the trailing edge tab and the leading edge tab are inserted into the slot; a slot partition wall that partitions the slot has a leading wall that is a wall located on the leading side in the rotation direction, the trailing edge tab passes within the slot radially outward of the leading edge tab, and a tip end of the trailing edge tab abuts against the leading wall at least when the rotation shaft is rotating, The foil bearing, characterized in that the leading edge tab is spaced apart from the leading wall and the trailing edge tab in the circumferential direction of the rotation shaft at least when the rotation shaft is rotating.

[0088] <Appendix 2> the trailing edge tab has a bent portion formed by bending a tip end portion of the trailing edge tab, The foil bearing described in <Appendix 1>, characterized in that the side of the bent portion abuts against the leading wall.

[0089] <Appendix 3> The foil bearing described in <Appendix 2>, characterized in that the bent portion is formed by bending the tip end of the trailing edge tab radially inward.

[0090] <Appendix 4> The bump foil is an elastic plate portion disposed between the bearing housing and the top foil; a fixing tab formed by bending an end portion of the elastic plate portion located on one side in the circumferential direction outward in the radial direction of the rotation shaft, The slot partition wall has a trailing wall that is a wall located on the trailing side in the rotation direction, A foil bearing described in any one of <Appendix 1> to <Appendix 3>, characterized in that the fixing tab is inserted between the trailing edge tab and the trailing wall in the slot and extends from the elastic plate portion toward the trailing wall.

[0091] <Appendix 5> The trailing edge tab a first extension portion extending radially outward from the top foil body; a second extension portion that extends from an end of the first extension portion opposite to the top foil body toward the leading wall and passes in the slot radially outward of the leading edge tab, the first extension portion has an opposing portion that faces a tip end of the leading edge tab in the circumferential direction, a maximum stroke amount of the rotating shaft in the radial direction from a state in which the axis of the rotating shaft and the axis of the through hole are aligned is determined based on the smaller of a tip clearance amount between an impeller connected to the rotating shaft and a shroud that defines an impeller chamber that houses the impeller, and a maximum displacement amount of the bump foil, A foil bearing described in any one of <Appendix 1> to <Appendix 4>, characterized in that the width between the opposing portion and the leading wall in the circumferential direction is set to a width greater than the sum of twice the maximum stroke amount and the plate thickness of the leading edge tab.

[0092] <Appendix 6> The foil bearing described in <Appendix 5>, characterized in that the width between the opposing portion and the leading wall in the circumferential direction is set by further taking into account the tolerance of the overall length of the top foil in the circumferential direction and the tolerance of the angle of the leading edge tab relative to the top foil body.

[0093] <Appendix 7> The trailing edge tab a first extension portion extending radially outward from the top foil body; a second extension portion that extends from an end of the first extension portion opposite to the top foil body toward the leading wall and passes in the slot radially outward of the leading edge tab, a maximum stroke amount of the rotating shaft in the radial direction from a state in which the axis of the rotating shaft and the axis of the through hole are aligned is determined based on the smaller of a tip clearance amount between an impeller connected to the rotating shaft and a shroud that defines an impeller chamber that houses the impeller, and a maximum displacement amount of the bump foil, A foil bearing described in any one of <Appendix 1> to <Appendix 4>, characterized in that a gap between the tip of the leading edge tab and the second extension portion in the radial direction is larger than the maximum stroke amount.

[0094] <Appendix 8> The trailing edge tab a first extension portion extending radially outward from the top foil body; a second extension portion that extends from an end of the first extension portion opposite to the top foil body toward the leading wall and passes in the slot radially outward of the leading edge tab, a maximum stroke amount of the rotating shaft in the radial direction from a state in which the axis of the rotating shaft and the axis of the through hole are aligned is determined based on the smaller of a tip clearance amount between an impeller connected to the rotating shaft and a shroud that defines an impeller chamber that houses the impeller, and a maximum displacement amount of the bump foil, A foil bearing described in any one of <Appendix 1> to <Appendix 4>, characterized in that the width between the tip of the leading edge tab and the leading wall in the circumferential direction is greater than the maximum stroke amount. [Explanation of symbols]

[0095] 12...rotating shaft, 13...impeller, 15...radial bearing which is a foil bearing, 19...impeller chamber, 24...shroud, 26...bearing retaining portion which functions as a bearing housing, 27...top foil, 28...bump foil, 29...through hole, 30...slot, 31...slot partition wall, 32...leading wall, 33...trailing wall, 36...top foil body, 37...trailing edge tab, 38...leading edge tab, 38e...tip, 39...bearing surface, 41...first extension portion, 41a...opposing portion, 42...second extension portion, 43...bent portion, 43a...side surface, 45...elastic plate portion, 46...fixing tab.

Claims

1. A foil bearing that supports a rotating shaft in the radial direction, a bearing housing having a through hole through which the rotating shaft is inserted; a thin top foil disposed between the rotating shaft and the bearing housing; a thin-plate-shaped bump foil disposed between the bearing housing and the top foil, and elastically supporting the top foil; A slot extending in the axial direction of the bearing housing is formed in the inner peripheral surface of the bearing housing, The top foil is a substantially cylindrical top foil body that forms a bearing surface that supports the rotating shaft and surrounds an outer circumferential surface of the rotating shaft; a trailing edge tab formed by bending an end portion of the top foil body located on a trailing side in a rotation direction of the rotation shaft outward in a radial direction of the rotation shaft; a leading edge tab formed by bending an end portion of the top foil body located on a leading side in the rotation direction outward in the radial direction, the trailing edge tab and the leading edge tab are inserted into the slot; a slot partition wall that partitions the slot has a leading wall that is a wall located on the leading side in the rotation direction, the trailing edge tab passes within the slot radially outward of the leading edge tab, and a tip end of the trailing edge tab abuts against the leading wall at least when the rotation shaft is rotating, The foil bearing, characterized in that the leading edge tab is spaced apart from the leading wall and the trailing edge tab in the circumferential direction of the rotating shaft at least when the rotating shaft is rotating.

2. the trailing edge tab has a bent portion formed by bending a tip end portion of the trailing edge tab, The foil bearing according to claim 1 , wherein a side surface of the bent portion abuts against the leading wall.

3. The foil bearing according to claim 2 , wherein the bent portion is formed by bending a tip end portion of the trailing edge tab inward in the radial direction.

4. The bump foil is an elastic plate portion disposed between the bearing housing and the top foil; a fixing tab formed by bending an end portion of the elastic plate portion located on one side in the circumferential direction outward in the radial direction of the rotation shaft, The slot partition wall has a trailing wall that is a wall located on the trailing side in the rotation direction, The foil bearing according to any one of claims 1 to 3, characterized in that the fixing tab is inserted between the trailing edge tab and the trailing wall in the slot and extends from the elastic plate portion toward the trailing wall.

5. The trailing edge tab a first extension portion extending radially outward from the top foil body; a second extension portion that extends from an end of the first extension portion opposite to the top foil body toward the leading wall and passes radially outward of the leading edge tab within the slot, the first extension portion has an opposing portion that faces a tip end of the leading edge tab in the circumferential direction, a maximum stroke amount of the rotating shaft in the radial direction from a state in which the axis of the rotating shaft and the axis of the through hole are aligned is determined based on the smaller of a tip clearance amount between an impeller connected to the rotating shaft and a shroud that defines an impeller chamber that houses the impeller, and a maximum displacement amount of the bump foil, A foil bearing according to any one of claims 1 to 3, characterized in that the width between the opposing portion and the leading wall in the circumferential direction is set to a width greater than the sum of twice the maximum stroke amount and the plate thickness of the leading edge tab.

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

7. The trailing edge tab a first extension portion extending radially outward from the top foil body; a second extension portion that extends from an end of the first extension portion opposite to the top foil body toward the leading wall and passes radially outward of the leading edge tab within the slot, a maximum stroke amount of the rotating shaft in the radial direction from a state in which the axis of the rotating shaft and the axis of the through hole are aligned is determined based on the smaller of a tip clearance amount between an impeller connected to the rotating shaft and a shroud that defines an impeller chamber that houses the impeller, and a maximum displacement amount of the bump foil, The foil bearing according to any one of claims 1 to 3, characterized in that a gap between the tip of the leading edge tab and the second extension portion in the radial direction is larger than the maximum stroke amount.

8. The trailing edge tab a first extension portion extending radially outward from the top foil body; a second extension portion that extends from an end of the first extension portion opposite to the top foil body toward the leading wall and passes radially outward of the leading edge tab within the slot, a maximum stroke amount of the rotating shaft in the radial direction from a state in which the axis of the rotating shaft and the axis of the through hole are aligned is determined based on the smaller of a tip clearance amount between an impeller connected to the rotating shaft and a shroud that defines an impeller chamber that houses the impeller, and a maximum displacement amount of the bump foil, The foil bearing according to any one of claims 1 to 3, characterized in that the width between the tip of the leading edge tab and the leading wall in the circumferential direction is larger than the maximum stroke amount.

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