Foil bearing

Abstract

To improve reliability of a foil bearing.SOLUTION: A radial bump foil 32 is provided so as to be wider than a radial top foil 31 in a rotation axis direction X1. An edge part 35 of the radial bump foil 32 forming the width directly faces a rotating body. Thus, the edge part 35 of the radial bump foil 32 does not contact with the radial top foil 31 directly, and therefore heat is not easily transmitted from the radial top foil 31 to the edge part. The edge part 35 of the radial bump foil 32 is cooled by air more easily than a portion, which does not protrude from the radial top foil 31, of the radial bump foil 32.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to foil bearings.

Background Art

[0002] A foil bearing has a top foil, a bump foil, and a bearing housing. The top foil faces the rotating body. The top foil has a bearing surface. The bump foil is in a thin plate shape. The bump foil is disposed on the side opposite to the rotating body with the top foil sandwiched therebetween. The bump foil elastically supports the top foil by extending. The bearing housing supports the top foil and the bump foil.

[0003] Such a foil bearing supports the rotating body in a state where the rotating body is in contact with the top foil until the rotating speed of the rotating body reaches the floating rotational speed. Then, when the rotational speed of the rotating body reaches the floating rotational speed, the rotating body floats with respect to the top foil due to the hydrodynamic pressure of the air film generated between the top foil and the rotating body. As a result, the foil bearing supports the rotating body without contacting the rotating body. At this time, heat is generated in the top foil due to the hydrodynamic pressure of the air film generated between the top foil and the rotating body. The heat generated in the top foil is transmitted to the bump foil. Since the bump foil is in a thin plate shape, when heat is transmitted from the top foil to the bump foil, the temperature of the bump foil rises, resulting in sagging of the bump foil.

[0004] Therefore, for example, in the foil bearing described in Patent Document 1, a through hole is formed in the bearing housing. Then, by introducing air from the through hole into the inside of the bearing housing, the bump foil is cooled.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In such a foil bearing, there is a desire to improve the reliability of the foil bearing by further improving the cooling performance of the bump foil.

Means for Solving the Problems

[0007] The foil bearing for solving the above problems includes a top foil facing a rotating body and having a bearing surface, a thin plate-shaped bump foil disposed on the opposite side of the rotating body with the top foil interposed therebetween and elastically supporting the top foil by extending, and a bearing housing supporting the top foil and the bump foil. The bump foil is provided wider than the top foil in a direction different from the extending direction of the bump foil, and an edge portion of the bump foil constituting the wider portion directly faces the rotating body.

[0008] According to this, since the edge portion of the bump foil directly faces the rotating body, it protrudes from the top foil. Therefore, since the edge portion of the bump foil does not directly contact the top foil, it is difficult for heat to be transferred from the top foil. And when the rotating body rotates, air flows into the space between the bump foil and the top foil.

[0009] Here, when air receives heat from the surface of the bump foil, a temperature boundary layer, which is a temperature transition region, is formed on the surface of the bump foil. In the temperature boundary layer, the temperature becomes higher as it approaches the surface of the bump foil. And as the temperature boundary layer thickens, the thermal resistance generated between the air flowing outside the temperature boundary layer and the surface of the bump foil increases. Therefore, as the temperature boundary layer thickens, the heat transfer rate between the air flowing outside the temperature boundary layer and the surface of the bump foil decreases, so the cooling performance of the bump foil deteriorates.

[0010] Since the edges of the bump foil protrude from the top foil, air easily flows in the vicinity of the edges of the bump foil. Therefore, the flow velocity of the air flowing in the vicinity of the edges of the bump foil is greater than the flow velocity of the air flowing in the vicinity of the portion of the bump foil that does not protrude from the top foil. For this reason, the thickness of the thermal boundary layer of the air flowing in the vicinity of the edges of the bump foil is thinner than the thickness of the thermal boundary layer of the air flowing in the vicinity of the portion of the bump foil that does not protrude from the top foil. Thus, the heat transfer coefficient between the air flowing outside the thermal boundary layer and the edges of the bump foil is greater than the heat transfer coefficient between the air flowing outside the thermal boundary layer and the portion of the bump foil that does not protrude from the top foil. Therefore, the edges of the bump foil are more easily cooled by air than the portion of the bump foil that does not protrude from the top foil. Thus, the heat transferred from the top foil to the bump foil can be efficiently dissipated from the edges of the bump foil. As a result, the cooling performance of the bump foil can be improved, so that the reliability of the foil bearing can be improved.

[0011] In the foil bearing, the bump foil includes a plurality of peak portions that can contact the top foil and a plurality of valley portions that can contact the bearing housing, the peak portions and the valley portions are arranged alternately with respect to the rotation direction of the rotating body, and the edge portions may include the peak portions and the valley portions that are arranged alternately with respect to the rotation direction.

[0012] In this way, the edges of the bump foil are also provided with peak portions and valley portions that are arranged alternately with respect to the rotation direction of the rotating body. According to this, it is not necessary to manufacture the bump foil so that peak portions and valley portions are not formed at the edges of the bump foil. Therefore, the bump foil can be easily manufactured.

[0013] In the above foil bearing, the top foil is a radial top foil that supports the rotating body in the radial direction, the bump foil is a radial bump foil that elastically supports the radial top foil, and the radial bump foil may be wider than the radial top foil with respect to the rotational axis direction of the rotating body.

[0014] According to this, the heat transmitted from the radial top foil to the radial bump foil can be efficiently dissipated from the edge portion of the radial bump foil. As a result, the cooling performance of the radial bump foil can be improved, and thus the reliability of the foil bearing can be improved.

[0015] In the above foil bearing, the edge portion may protrude evenly from both ends in the rotational axis direction of the radial top foil. According to this, since the heat dissipation areas of the edge portions of the radial bump foils protruding from both ends of the radial top foil are equal, the heat of the entire radial bump foil can be efficiently dissipated from the edge portion of the radial bump foil. Therefore, the cooling performance of the radial bump foil can be further improved, and thus the reliability of the foil bearing can be further improved.

[0016] In the above foil bearing, the top foil is a radial top foil that supports the rotating body in the radial direction, the bump foil is a radial bump foil that elastically supports the radial top foil, the radial bump foil has a fixed end fixed to the bearing housing and a free end not fixed to the bearing housing, the radial top foil has a fixed end fixed to the bearing housing and a free end not fixed to the bearing housing, and the edge portion may protrude in the rotational axis direction from both ends in the rotational axis direction of the rotating body connecting the fixed end and the free end in the radial top foil.

[0017] According to this, since the heat dissipation area of the radial bump foil increases, it becomes easier to further cool the heat of the radial bump foil. Therefore, the cooling performance of the radial bump foil can be further improved.

[0018] In the above foil bearing, in the direction in which the cooling fluid flows from one end to the other end of the radial bump foil in the direction of the rotation axis, the peak portion of the radial bump foil extends in the rotational direction of the rotating body so as to draw in the cooling fluid from the one end to the other end, and the valley portion of the radial bump foil extends in the rotational direction so as to draw in the cooling fluid from the one end to the other end.

[0019] According to this, compared with the case where the peak portion of the radial bump foil and the valley portion of the radial bump foil extend in the direction of the rotation axis, when the rotating body rotates, the cooling fluid is more easily drawn between the radial top foil and the radial bump foil. And the cooling fluid flowing between the radial top foil and the radial bump foil easily flows from one end to the other end in the direction of the rotation axis of the radial bump foil along the peak portion of the radial bump foil and the valley portion of the radial bump foil. For this reason, the radial bump foil is easily cooled by the cooling fluid flowing between the radial bump foil and the radial top foil. Therefore, the cooling performance of the radial bump foil can be further improved.

[0020] In the above foil bearing, the top foil is a thrust top foil that supports the rotating body in the thrust direction, the bump foil is a thrust bump foil that elastically supports the thrust top foil, and the thrust bump foil is wider than the thrust top foil in a direction orthogonal to the direction of the rotation axis of the rotating body.

[0021] According to this, the heat transferred from the thrust top foil to the thrust bump foil can be efficiently dissipated from the edge of the thrust bump foil. As a result, the cooling performance of the thrust bump foil can be improved, so that the reliability of the foil bearing can be improved.

[0022] In the above foil bearing, it is preferable that the edge portion projects evenly from both ends in a direction orthogonal to the axial direction of rotation in the thrust top foil. According to this, since the heat dissipation areas of the edges of the thrust bump foils protruding from both ends of the thrust top foil are equal, the heat of the entire thrust bump foil can be efficiently dissipated from the edges of the thrust bump foil. Therefore, the cooling performance of the thrust bump foil can be further improved, so that the reliability of the foil bearing can be further improved.

[0023] In the above foil bearing, the top foil is a thrust top foil that supports the rotating body in the thrust direction, the bump foil is a thrust bump foil that elastically supports the thrust top foil, the thrust bump foil has a fixed end fixed to the bearing housing and a free end not fixed to the bearing housing, the thrust top foil has a fixed end fixed to the bearing housing and a free end not fixed to the bearing housing, and it is preferable that the edge portion projects in the rotational direction of the rotating body from the edge of the free end in the thrust top foil.

[0024] According to this, since the heat dissipation area of the thrust bump foil increases, the heat of the thrust bump foil can be made easier to cool. Therefore, the cooling performance of the thrust bump foil can be further improved.

[0025] In the foil bearing described above, among both ends in the direction orthogonal to the rotational axis direction of the rotating body in the thrust bump foil, in the direction in which the cooling fluid flows from the inner edge toward the outer edge, the peak portion of the thrust bump foil extends in the rotational direction of the rotating body so as to draw in the cooling fluid from the inner edge toward the outer edge, and the valley portion of the thrust bump foil extends in the rotational direction so as to draw in the cooling fluid from the inner edge toward the outer edge.

[0026] According to this, compared with the case where the peak portion of the thrust bump foil and the valley portion of the thrust bump foil extend in the direction orthogonal to the rotational axis direction, when the rotating body rotates, the cooling fluid is more easily drawn between the thrust top foil and the thrust bump foil. And the cooling fluid flowing between the thrust top foil and the thrust bump foil easily flows from the inner edge toward the outer edge among both ends in the direction orthogonal to the rotational axis direction in the thrust bump foil, along the peak portion of the thrust bump foil and the valley portion of the thrust bump foil. For this reason, the thrust bump foil is easily cooled by the cooling fluid flowing between the thrust bump foil and the thrust top foil. Therefore, the cooling performance of the thrust bump foil can be further improved.

[0027] In the foil bearing described above, it is preferable that a slit for avoiding contact between the peak portion of the edge portion and the rotating body is provided in the peak portion of the edge portion, and the slit is not provided in the valley portion of the edge portion.

[0028] According to this, since the peak portion of the edge portion and the rotating body do not come into contact with each other, generation of frictional heat between the peak portion of the edge portion and the rotating body can be avoided.

Effect of the Invention

[0029] According to this invention, the reliability of the foil bearing can be improved.

Brief Description of the Drawings

[0030]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

BEST MODE FOR CARRYING OUT THE INVENTION

[0031] Hereinafter, an embodiment in which a foil bearing is embodied will be described with reference to FIGS. 1 to 6. The foil bearing of this embodiment is applied to a turbomachine mounted on a fuel cell vehicle. The fuel cell vehicle is equipped with a fuel cell system that supplies oxygen and hydrogen to a fuel cell to generate electricity. And the turbomachine compresses air as a fluid containing oxygen supplied to the fuel cell.

[0032] <Turbo machine 10> As shown in FIG. 1, the turbomachine 10 includes two radial foil bearings 30 as foil bearings and a thrust foil bearing 40. The turbomachine 10 includes a rotating body 12. The rotating body 12 is housed in a housing 11. The rotating body 12 is rotatably supported by the housing 11. The axial direction of the housing 11 coincides with the rotational axis direction X1, which is the direction in which the rotational axis of the rotating body 12 extends. In the following description, the "rotational axis direction X1 of the rotating body 12" may be simply described as the "rotational axis direction X1".

[0033] The housing 11 has a motor chamber S1, a turbine chamber S2, and an impeller chamber S3. The motor chamber S1, the turbine chamber S2, and the impeller chamber S3 are arranged in the rotational axis direction X1 in the order of the impeller chamber S3, the motor chamber S1, and the turbine chamber S2 from one side to the other side in the rotational axis direction X1.

[0034] The housing 11 has a first partition wall 13 and a second partition wall 14. The first partition wall 13 divides the inside of the housing 11 into the motor chamber S1 and the impeller chamber S3. The second partition wall 14 divides the inside of the housing 11 into the motor chamber S1 and the turbine chamber S2. An electric motor 20 is housed in the motor chamber S1. A turbine wheel 15 is housed in the turbine chamber S2. A compressor impeller 16 is housed in the impeller chamber S3.

[0035] The rotating body 12 has a rotating shaft 12a, a first support portion 12b, a second support portion 12c, and a third support portion 12d. The rotating shaft 12a is cylindrical. The rotating shaft 12a penetrates through the turbine chamber S2, the motor chamber S1, and the impeller chamber S3 in this order. A turbine wheel 15 is attached to the first end of the rotating shaft 12a. A compressor impeller 16 is attached to the second end of the rotating shaft 12a.

[0036] The electric motor 20 has a rotor 21 and a stator 22. The rotor 21 is disposed inside the stator 22. The rotor 21 rotates synchronously with the rotating body 12. The stator 22 is fixed to the housing 11. The stator 22 has a cylindrical stator core 23 and a coil 24. The stator core 23 is fixed to the housing 11. The coil 24 is wound around the stator core 23. When a current flows from a battery (not shown) to the coil 24, the rotor 21 rotates synchronously with the rotating body 12. As a result, the turbine wheel 15 and the compressor impeller 16 rotate integrally with the rotating body 12.

[0037] The first support portion 12b is disposed in the motor chamber S1. The first support portion 12b has a cylindrical shape with an outer diameter larger than the outer diameter of the rotary shaft 12a. The first support portion 12b is provided at a portion of the outer peripheral surface of the rotary shaft 12a closer to the compressor impeller 16 than the electric motor 20. The radial direction of the first support portion 12b coincides with the radial direction of the rotary shaft 12a. The axis of the first support portion 12b coincides with the axis of the rotary shaft 12a.

[0038] The second support portion 12c is disposed in the motor chamber S1. The second support portion 12c has a cylindrical shape with an outer diameter larger than the outer diameter of the rotary shaft 12a. The second support portion 12c is provided at a portion of the outer peripheral surface of the rotary shaft 12a closer to the turbine wheel 15 than the electric motor 20. The radial direction of the second support portion 12c coincides with the radial direction of the rotary shaft 12a. The axis of the second support portion 12c coincides with the axis of the rotary shaft 12a.

[0039] The third support portion 12d is disposed in the motor chamber S1. The third support portion 12d has a disk shape extending in the radial direction from the outer peripheral surface of the rotary shaft 12a. The third support portion 12d is provided at a portion of the outer peripheral surface of the rotary shaft 12a closer to the compressor impeller 16 than the first support portion 12b. The radial direction of the third support portion 12d coincides with the radial direction of the rotary shaft 12a. The axis of the third support portion 12d coincides with the axis of the rotary shaft 12a.

[0040] In the motor chamber S1, a first cooling pipe F1 and a second cooling pipe F2 are connected. The first cooling pipe F1 is connected to a portion near the impeller chamber S3 in the motor chamber S1. The second cooling pipe F2 is connected to a portion near the turbine chamber S2 in the motor chamber S1. And air as a cooling fluid is introduced into the motor chamber S1 from the first cooling pipe F1. The air introduced into the motor chamber S1 flows through the motor chamber S1 and is discharged from the second cooling pipe F2. When passing through the motor chamber S1, the air cools the radial foil bearing 30 and the thrust foil bearing 40.

[0041] <radial foil bearing 30> As shown in FIG. 2, each radial foil bearing 30 supports the rotating body 12 in the radial direction. Note that the "radial direction" is a direction orthogonal to the rotational axis direction X1. The radial direction of the rotating shaft 12a coincides with the direction orthogonal to the rotational axis direction X1. Therefore, the radial direction coincides with the radial direction of the rotating shaft 12a. Let the direction in which the rotating body 12 rotates be the rotation direction X2.

[0042] Each radial foil bearing 30 has a radial top foil 31 as a top foil, a radial bump foil 32 as a thin plate-shaped bump foil, and a base portion 33 as a bearing housing, respectively. The base portion 33 is cylindrical. The base portion 33 is made of, for example, metal. The radial top foil 31 is disposed inside the base portion 33.

[0043] As shown in FIGS. 2 and 3, the radial top foil 31 is substantially cylindrical. The radial top foil 31 is formed, for example, by bending a strip-shaped plate material made of a flexible metal material into a cylindrical shape.

[0044] The radial top foil 31 has a bearing surface 310 facing the first support portion 12b. Therefore, the radial top foil 31 faces the rotating body 12 and has the bearing surface 310. The radial top foil 31 has a fixed end 31a located at the first circumferential end of the radial top foil 31 and a free end 31b located at the second circumferential end of the radial top foil 31.

[0045] The fixed end 31a is formed by bending the first circumferential end of the radial top foil 31 outward in the radial direction of the radial top foil 31. The free end 31b faces the fixed end 31a in a circumferentially spaced state of the radial top foil 31.

[0046] The radial bump foil 32 is substantially cylindrical. The radial bump foil 32 has a fixed end 32a located at the first circumferential end of the radial bump foil 32 and a free end 32b located at the second circumferential end of the radial bump foil 32. The fixed end 32a is fixed to the base portion 33. The fixed end 32a is fixed to the base portion 33, for example, by welding, in a state where the fixed end 31a of the radial top foil 31 overlaps in the radial direction of the rotation axis 12a. The free end 32b is not fixed to the base portion 33. The fixed end 31a of the radial top foil 31 is fixed to the fixed end 32a of the radial bump foil 32, for example, by welding. The free end 31b faces the fixed end 31a in a circumferentially spaced state of the radial bump foil 32. Therefore, the free end 31b is not fixed to the base portion 33.

[0047] The radial bump foil 32 is disposed between the inner circumferential surface of the base portion 33 and the radial top foil 31. The radial bump foil 32 sandwiches the radial top foil 31 together with the rotating body 12. Therefore, the radial bump foil 32 is disposed at a position on the opposite side of the rotating body 12 with the radial top foil 31 sandwiched therebetween. The radial bump foil 32 is disposed radially outside the rotation axis 12a than the radial top foil 31. The radial bump foil 32 extends in the circumferential direction of the radial bump foil 32. By extending, the radial bump foil 32 elastically supports the radial top foil 31.

[0048] The dimension L1 of the radial bump foil 32 in the rotation axis direction X1 is larger than the dimension L2 of the radial top foil 31 in the rotation axis direction X1. Therefore, the radial bump foil 32 is wider than the radial top foil 31 with respect to the rotation axis direction X1. That is, the radial bump foil 32 is provided wider than the radial top foil 31 in a direction different from the extending direction of the radial bump foil 32. In the present embodiment, the axis of the radial bump foil 32 coincides with the axis of the radial top foil 31 and the axis of the base portion 33.

[0049] <Edge portion 35> As shown in FIG. 4, the radial bump foil 32 has a main body portion 34 and an edge portion 35. The main body portion 34 is a portion of the radial bump foil 32 that does not protrude from the radial top foil 31. The edge portion 35 is a portion of the radial bump foil 32 that protrudes from the radial top foil 31. Therefore, the edge portion 35 constitutes the wide portion of the radial bump foil 32. The edge portion 35 protrudes evenly from both ends in the rotational axis direction X1 of the radial top foil 31. Therefore, each edge portion 35 has the same length protruding from both ends in the rotational axis direction X1 of the radial top foil 31. Each edge portion 35 directly faces the first support portion 12b. Therefore, the edge portion 35 directly faces the rotating body 12. Each edge portion 35 protrudes in the rotational axis direction X1 from both ends in the rotational axis direction X1 connecting the fixed end 31a and the free end 31b of the radial top foil 31.

[0050] <Mountain portion 36 and valley portion 37> As shown in FIG. 3, the radial bump foil 32 has a plurality of mountain portions 36 that can contact the radial top foil 31 and a plurality of valley portions 37 that can contact the base portion 33. Each valley portion 37 extends along the inner peripheral surface of the base portion 33 while being in contact with the inner peripheral surface of the base portion 33. Each mountain portion 36 protrudes in a direction away from the inner peripheral surface of the base portion 33 and is curved in an arc shape so as to bulge toward the outer peripheral surface of the radial top foil 31. As shown in FIG. 4, in the present embodiment, the mountain portion 36 and the valley portion 37 each extend from the first end to the second end in the rotational axis direction X1 of the radial bump foil 32. The mountain portion 36 and the valley portion 37 are arranged alternately with respect to the rotational direction X2. Therefore, the edge portion 35 includes the mountain portion 36 and the valley portion 37 that are arranged alternately with respect to the rotational direction X2.

[0051] The radial foil bearing 30 supports the rotating body 12 in a state of contact with the first support portion 12b until the rotational speed of the rotating body 12 reaches the floating rotational speed at which the rotating body 12 floats by the radial foil bearing 30. Then, when the rotational speed of the rotating body 12 reaches the floating rotational speed, the first support portion 12b floats with respect to the radial foil bearing 30 due to the dynamic pressure of the air film generated between the first support portion 12b and the radial foil bearing 30. Thereby, the radial foil bearing 30 supports the rotating body 12 in a non-contact state with the first support portion 12b.

[0052] <Thrust foil bearing 40> As shown in FIG. 5, the thrust foil bearing 40 supports the rotating body 12 in the thrust direction. Note that the "thrust direction" is the rotational axis direction X1. The thrust foil bearing 40 has a pair of thrust top foils 41 as top foils, a pair of thin plate-like thrust bump foils 42 as bump foils, and a pair of base portions 43 as bearing housings, respectively. Each base portion 43 is disc-shaped. Each base portion 43 is arranged so as to sandwich the third support portion 12d in the thrust direction. The circumferential direction of the base portion 43 coincides with the circumferential direction of the rotating shaft 12a. In FIG. 5, for convenience of illustration, only one thrust top foil 41, thrust bump foil 42, and base portion 43 are shown.

[0053] The thrust top foil 41 has a plurality of thrust top foil pieces 44. Each thrust top foil piece 44 is fan-shaped in plan view. Each thrust top foil piece 44 is arranged around the rotating shaft 12a. Each thrust top foil piece 44 is arranged at equal intervals in the circumferential direction of the rotating shaft 12a.

[0054] As shown in FIGS. 5 and 6, each thrust top foil piece 44 has a bearing surface 410 facing the third support portion 12d. Each thrust top foil piece 44 has a fixed end 44a located at one end in the circumferential direction and a free end 44b located at the other end. Each thrust top foil piece 44 extends in the circumferential direction. The fixed end 44a extends in the radial direction of the rotation axis 12a. The fixed end 44a is formed by bending the first end in the circumferential direction of the thrust top foil piece 44 toward the base portion 43. The fixed end 44a is fixed to the base portion 43 by welding, for example. The free end 44b is not fixed to the base portion 43. Therefore, the thrust top foil 41 has a fixed end 44a fixed to the base portion 43 and a free end 44b not fixed to the base portion 43. The fixed end 44a of the thrust top foil piece 44 and the free end 44b of the thrust top foil piece 44 adjacent thereto are arranged in a spaced-apart state.

[0055] <Thrust bump foil piece 45> The thrust bump foil 42 has a plurality of thrust bump foil pieces 45. Each thrust bump foil piece 45 is substantially fan-shaped in plan view. Each thrust bump foil piece 45 is made of a flexible metal material, for example. Each thrust bump foil piece 45 is formed by bending a strip-shaped plate material made of a flexible metal material into a wave shape, for example.

[0056] Each thrust bump foil piece 45 has a fixed end 45a located at the first end in the circumferential direction of the thrust bump foil piece 45 and a free end 45b located at the second end in the circumferential direction of the thrust bump foil piece 45. The fixed end 45a is fixed to the base portion 43. The free end 45b is not fixed to the base portion 43. Therefore, the thrust bump foil 42 has a fixed end 44a fixed to the base portion 43 and a free end 44b not fixed to the base portion 43.

[0057] The radial dimension L3 of the rotation axis 12a of the thrust bump foil piece 45 is larger than the radial dimension L4 of the rotation axis 12a of the thrust top foil piece 44. Therefore, the thrust bump foil 42 is wider than the thrust top foil 41 in the direction orthogonal to the rotation axis direction X1 of the rotating body 12.

[0058] <Edge portion 47> The thrust bump foil piece 45 has a main body portion 46 and an edge portion 47. The main body portion 46 is a portion of the thrust bump foil piece 45 that does not protrude from the thrust top foil piece 44. The edge portion 47 is a portion of the thrust bump foil piece 45 that protrudes from the thrust top foil piece 44. The edge portion 47 protrudes evenly from both ends in the radial direction of the rotation axis 12a in the thrust top foil piece 44. Therefore, the length of each edge portion 47 protruding from both ends in the radial direction of the rotation axis 12a in the thrust top foil piece 44 is the same. Also, the edge portion 47 protrudes in the rotation direction X2 from the edge of the free end 44b in the thrust top foil 41. The edge portion 47 faces the third support portion 12d. Therefore, the edge portion 47 faces the rotating body 12 directly.

[0059] <Peak portion 48 and valley portion 49> Each thrust bump foil piece 45 has a plurality of peak portions 48 and a plurality of valley portions 49. Each valley portion 49 is a portion of the thrust bump foil piece 45 that protrudes toward the base portion 43. Each peak portion 48 is a portion of the thrust bump foil piece 45 that protrudes to the side opposite to the valley portion 49. Each peak portion 48 and each valley portion 49 extend in the circumferential direction of the thrust bump foil piece 45 respectively. The circumferential direction of each thrust bump foil piece 45 coincides with the circumferential direction of the base portion 43.

[0060] Each thrust bump foil piece 45 is disposed between the base portion 43 and each thrust top foil piece 44. Each thrust bump foil piece 45 elastically supports each thrust top foil piece 44. Each thrust top foil piece 44 and each thrust bump foil piece 45 are arranged such that most of them overlap in the rotational axis direction X1 of the rotating body 12. Each thrust bump foil piece 45 extends in the circumferential direction of the thrust bump foil piece 45. By extending, each thrust bump foil piece 45 elastically supports each thrust top foil piece 44. Therefore, the thrust bump foil 42 elastically supports the thrust top foil 41 by extending. Further, the base portion 43 supports the thrust top foil 41 and the thrust bump foil 42.

[0061] The thrust foil bearing 40 supports the rotating body 12 in a state of being in contact with the third support portion 12d until the rotational speed of the rotating body 12 reaches the floating rotational speed at which the rotating body 12 floats by the thrust foil bearing 40. When the rotational speed of the rotating body 12 reaches the floating rotational speed, the third support portion 12d floats with respect to the thrust foil bearing 40 due to the dynamic pressure of the air film generated between the third support portion 12d and the thrust foil bearing 40. Thereby, the thrust foil bearing 40 supports the rotating body 12 in a non-contact state with the third support portion 12d.

[0062] <Operation of the Embodiment> Next, the operation of this embodiment will be described. Due to the dynamic pressure of the air film generated between the radial top foil 31 and the first support portion 12b, heat is generated in the radial top foil 31. The heat generated in the radial top foil 31 is transmitted to the radial bump foil 32. Since the edge portion 35 of the radial bump foil 32 directly faces the first support portion 12b, it protrudes from the radial top foil 31. Therefore, since the edge portion 35 of the radial bump foil 32 does not directly contact the radial top foil 31, it is difficult for heat to be transmitted from the radial top foil 31. When the rotating body 12 rotates, air flows into the space between the radial bump foil 32 and the radial top foil 31.

[0063] Here, when the air receives heat from the surface of the radial bump foil 32, a temperature boundary layer, which is a temperature transition region, is formed on the surface of the radial bump foil 32. In the temperature boundary layer, the temperature becomes higher as it approaches the surface of the radial bump foil 32. And the thicker the temperature boundary layer becomes, the greater the thermal resistance generated between the air flowing outside the temperature boundary layer and the surface of the radial bump foil 32. Therefore, the thicker the temperature boundary layer becomes, the smaller the heat transfer rate between the air flowing outside the temperature boundary layer and the surface of the radial bump foil 32, and thus the cooling performance of the radial bump foil 32 deteriorates.

[0064] Since the edge 35 of the radial bump foil 32 protrudes from the radial top foil 31, air flows more easily in the vicinity of the edge 35 of the radial bump foil 32 than in the vicinity of the main body 34 of the radial bump foil 32. Therefore, the flow velocity of the air flowing in the vicinity of the edge 35 of the radial bump foil 32 is greater than the flow velocity of the air flowing in the vicinity of the main body 34 of the radial bump foil 32. For this reason, the thickness of the thermal boundary layer of the air flowing in the vicinity of the edge 35 of the radial bump foil 32 is thinner than the thickness of the thermal boundary layer of the air flowing in the vicinity of the main body 34 of the radial bump foil 32. Thus, the heat transfer coefficient between the air flowing outside the thermal boundary layer and the edge 35 of the radial bump foil 32 is greater than the heat transfer coefficient between the air flowing outside the thermal boundary layer and the main body 34 of the radial top foil 31. Therefore, the edge 35 of the radial bump foil 32 is more easily cooled than the main body 34 of the radial bump foil 32. Thus, the heat transferred from the radial top foil 31 to the radial bump foil 32 is efficiently radiated from the edge 35 of the radial bump foil 32.

[0065] Heat is generated in the thrust top foil piece 44 by the dynamic pressure of the air film generated between the thrust top foil piece 44 and the third support portion 12d. The heat generated in the thrust top foil piece 44 is transferred to the thrust bump foil piece 45. Since the edge 47 of the thrust bump foil piece 45 directly faces the third support portion 12d, it protrudes from the thrust top foil piece 44. Therefore, since the edge 47 of the thrust bump foil piece 45 is not in direct contact with the thrust top foil piece 44, it is difficult for heat to be transferred from the thrust top foil piece 44. Then, when the rotating body 12 rotates, air flows into the space between the thrust bump foil piece 45 and the thrust top foil piece 44.

[0066] Here, as air receives heat from the surface of the thrust bump foil piece 45, a temperature boundary layer, which is a temperature transition region, is formed on the surface of the thrust bump foil piece 45. In the temperature boundary layer, the temperature becomes higher as it approaches the surface of the thrust bump foil piece 45. And as the temperature boundary layer thickens, the thermal resistance generated between the air flowing outside the temperature boundary layer and the surface of the thrust bump foil piece 45 increases. Therefore, as the temperature boundary layer thickens, the heat transfer rate between the air flowing outside the temperature boundary layer and the surface of the thrust bump foil piece 45 decreases, so the cooling performance of the thrust bump foil piece 45 deteriorates.

[0067] Since the edge 47 of the thrust bump foil piece 45 protrudes from the thrust top foil piece 44, air flows more easily in the vicinity of the edge 47 of the thrust bump foil piece 45 than in the vicinity of the main body 46 of the thrust bump foil piece 45. Therefore, the flow velocity of the air flowing in the vicinity of the edge 47 of the thrust bump foil piece 45 is greater than the flow velocity of the air flowing in the vicinity of the main body 46 of the thrust bump foil piece 45. For this reason, the thickness of the temperature boundary layer of the air flowing in the vicinity of the edge 47 of the thrust bump foil piece 45 is thinner than the thickness of the temperature boundary layer of the air flowing in the vicinity of the main body 46 of the thrust bump foil piece 45. Thus, the heat transfer rate between the air flowing outside the temperature boundary layer and the edge 47 of the thrust bump foil piece 45 is greater than the heat transfer rate between the air flowing outside the temperature boundary layer and the main body 46 of the thrust bump foil piece 45. Therefore, the edge 47 of the thrust bump foil piece 45 is more easily cooled than the main body 46 of the thrust bump foil piece 45. Thus, the heat transferred from the thrust top foil piece 44 to the thrust bump foil piece 45 is efficiently radiated from the edge 47 of the thrust bump foil piece 45.

[0068] In the above embodiment, the following effects can be obtained. (1) The heat transferred from the radial top foil 31 to the radial bump foil 32 can be efficiently dissipated from the edge 35 of the radial bump foil 32. As a result, the cooling performance of the radial bump foil 32 can be improved, so that the reliability of the radial foil bearing 30 can be improved. The heat transferred from the thrust top foil 41 to the thrust bump foil 42 can be efficiently dissipated from the edge 47 of the thrust bump foil 42. As a result, the cooling performance of the thrust bump foil 42 can be improved, so that the reliability of the thrust foil bearing 40 can be improved.

[0069] (2) The radial bump foil 32 includes a plurality of peak portions 36 and a plurality of valley portions 37. The peak portions 36 and the valley portions 37 are alternately arranged with respect to the rotation direction X2, and the edge 35 includes the peak portions 36 and the valley portions 37 that are alternately arranged with respect to the rotation direction X2. Thus, the edge 35 of the radial bump foil 32 also includes the peak portions 36 and the valley portions 37 that are alternately arranged with respect to the rotation direction X2. According to this, there is no need to manufacture the radial bump foil 32 so that the peak portions 36 and the valley portions 37 are not formed on the edge 35 of the radial bump foil 32. Therefore, the radial bump foil 32 can be easily manufactured.

[0070] The thrust bump foil 42 includes a plurality of peak portions 48 and a plurality of valley portions 49. The peak portions 48 and the valley portions 49 are alternately arranged with respect to the rotation direction X2, and the edge 47 includes the peak portions 48 and the valley portions 49 that are alternately arranged with respect to the rotation direction X2. Thus, the edge 47 of the thrust bump foil 42 also includes the peak portions 48 and the valley portions 49 that are alternately arranged with respect to the rotation direction X2. According to this, there is no need to manufacture the thrust bump foil 42 so that the peak portions 48 and the valley portions 49 are not formed on the edge 47 of the thrust bump foil 42. Therefore, the thrust bump foil 42 can be easily manufactured.

[0071] (3) The edge portion 35 protrudes evenly from both ends of the radial top foil 31 in the rotational axis direction X1. According to this, since the heat dissipation areas of the edge portions 35 protruding from both ends of the radial top foil 31 are equal, the heat of the entire radial bump foil 32 can be efficiently dissipated from the edge portion 35. Therefore, since the cooling performance of the radial bump foil 32 can be further improved, the reliability of the radial foil bearing 30 can be further improved.

[0072] (4) The edge portion 47 protrudes evenly from both ends in the radial direction of the rotational axis 12a in the thrust top foil 41. According to this, since the heat dissipation areas of the edge portions 47 protruding from both ends of the thrust top foil 41 are equal, the heat of the entire thrust bump foil 42 can be efficiently dissipated from the edge portion 47. Therefore, since the cooling performance of the thrust bump foil 42 can be further improved, the reliability of the thrust foil bearing 40 can be further improved.

[0073] (5) The edge portion 35 protrudes in the rotational axis direction X1 from the edge of the free end 31b in the radial top foil 31. According to this, since the heat dissipation area of the radial bump foil 32 increases, the heat of the radial bump foil 32 can be made easier to cool further. Therefore, the cooling performance of the radial bump foil 32 can be further improved.

[0074] (6) The edge portion 47 protrudes in the rotational direction X2 from the edge of the free end 44b in the thrust top foil piece 44. According to this, since the heat dissipation area of the thrust bump foil 42 increases, the heat of the thrust bump foil 42 can be made easier to cool further. Therefore, the cooling performance of the thrust bump foil 42 can be further improved.

[0075] <Modification Example> Note that the above-described embodiment can be modified and implemented as follows. The above-described embodiment and the following modification examples can be implemented in combination with each other within a technically non-conflicting range.

[0076] ○ As shown in FIG. 7, the radial bump foil 32 may be configured such that slits 60 are provided in the peak portions 36 of the edge portion 35, and no slits 60 are provided in the valley portions 37 of the edge portion 35.

[0077] According to this, since the peak portion 36 of the edge portion 35 and the rotating body 12 do not come into contact with each other, generation of frictional heat between the peak portion 36 of the edge portion 35 and the rotating body 12 can be avoided. ○ As shown in FIG. 8, in the direction in which the cooling fluid flows from one end to the other end of the radial bump foil 32 in the rotational axis direction X1, the peak portion 36 of the radial bump foil 32 extends in the rotational direction X2 so as to draw in the cooling fluid from one end to the other end in the rotational axis direction X1, and the valley portion 37 of the radial bump foil 32 may extend in the rotational direction X2 so as to draw in the cooling fluid from one end to the other end in the rotational axis direction X1. That is, the peak portion 36 of the radial bump foil 32 and the valley portion 37 of the radial bump foil 32 may extend so as to be inclined with respect to the rotational axis direction X1.

[0078] According to this, compared with the case where the peak portion 36 of the radial bump foil 32 and the valley portion 37 of the radial bump foil 32 extend in the rotational axis direction X1, air is more easily drawn in between the radial top foil 31 and the radial bump foil 32 when the rotating body 12 rotates. And the air flowing between the radial top foil 31 and the radial bump foil 32 easily flows from one end to the other end in the rotational axis direction X1 of the radial bump foil 32 along the peak portion 36 of the radial bump foil 32 and the valley portion 37 of the radial bump foil 32. For this reason, the radial bump foil 32 is easily cooled by the air flowing between the radial bump foil 32 and the radial top foil 31. Therefore, the cooling performance of the radial bump foil 32 can be further improved.

[0079] ○ As shown in FIG. 9, the peak portion 36 of the radial bump foil 32 and the valley portion 37 of the radial bump foil 32 may not extend linearly and may extend in a curved manner. ○ As shown in FIG. 10, the edge portion 35 may have different lengths protruding from both ends in the rotational axis direction X1 of the radial top foil 31.

[0080] ○ As shown in FIG. 11, the edge portion 35 may protrude from only one of both ends in the rotational axis direction X1 of the radial top foil 31. ○ As shown in FIG. 12, the peak portion 48 may extend in the rotational direction X2 so as to draw in the cooling fluid from the inner edge 70 toward the outer edge 71, and the valley portion 49 may also extend in the rotational direction X2 so as to draw in the cooling fluid from the inner edge 70 toward the outer edge 71.

[0081] According to this, compared with the case where the peak portion 48 and the valley portion 49 extend in the radial direction of the rotary shaft 12a, air is likely to be drawn between the thrust top foil 41 and the thrust bump foil 42 when the rotating body 12 rotates. And the air flowing between the thrust top foil 41 and the thrust bump foil 42 is likely to flow along the peak portion 48 and the valley portion 49 toward the outer edge 71 from the inner edge 70 of the two ends in the radial direction of the rotary shaft 12a of the thrust bump foil 42. For this reason, the thrust bump foil 42 is likely to be cooled by the air flowing between the thrust bump foil 42 and the thrust top foil 41. Therefore, the cooling performance of the thrust bump foil 42 can be further improved.

[0082] ○ In the embodiment, the edge portion 47 may have different lengths protruding from both ends in the radial direction of the rotary shaft 12a of the thrust top foil piece 44. ○ In the embodiment, the edge portion 47 may protrude from only one of both ends in the radial direction of the rotary shaft 12a of the thrust top foil piece 44.

[0083] ○ In the embodiment, the edge portion 47 may not protrude in the rotational direction X2 from the edge of the free end 44b of the thrust top foil piece 44.

Explanation of Signs

[0084] 12... rotating body, 30... radial foil bearing as a foil bearing, 31... radial top foil as a top foil, 31a... fixed end, 31b... free end, 32... radial bump foil as a bump foil, 32a... fixed end, 32b... free end, 33... base portion as a bearing housing, 35... edge portion, 36... peak portion, 37... valley portion, 40... thrust foil bearing as a foil bearing, 41... thrust top foil as a top foil, 41a... fixed end, 41b... free end, 42... thrust bump foil as a bump foil, 42a... fixed end, 42b... free end, 43... base portion as a bearing housing, 44a... fixed end, 44b... free end, 47... edge portion, 48... peak portion, 49... valley portion, 60... slit, 70... inner edge, 71... outer edge, 310... bearing surface, 410... bearing surface, X1... rotational axis direction, X2... rotational direction.

Claims

1. A top foil having a bearing surface and facing a rotating body, A thin plate-shaped bump foil disposed on the side opposite to the rotating body with the top foil interposed therebetween and elastically supporting the top foil by extending, A foil bearing having a bearing housing that supports the top foil and the bump foil, wherein The bump foil is provided wider than the top foil in a direction different from the extending direction of the bump foil, The edge of the bump foil that constitutes the wider portion directly faces the rotating body. The foil bearing is characterized by this.

2. The bump foil Includes a plurality of peak portions capable of contacting the top foil, And a plurality of valley portions capable of contacting the bearing housing, The peak portions and the valley portions are arranged alternately with respect to the rotation direction of the rotating body, The foil bearing according to claim 1, wherein the edge portion includes the peak portions and the valley portions that are arranged alternately with respect to the rotation direction.

3. The top foil is a radial top foil that supports the rotating body in the radial direction, The bump foil is a radial bump foil that elastically supports the radial top foil, The foil bearing according to claim 1 or claim 2, wherein the radial bump foil is wider than the radial top foil with respect to the rotation axis direction of the rotating body.

4. The foil bearing according to claim 3, wherein the edge portion protrudes evenly from both ends in the rotation axis direction of the radial top foil.

5. The top foil is a radial top foil that supports the rotating body in the radial direction, The bump foil is a radial bump foil that elastically supports the radial top foil, The radial bump foil Has a fixed end fixed to the bearing housing, And a free end not fixed to the bearing housing, The radial top foil Has a fixed end fixed to the bearing housing, And a free end not fixed to the bearing housing, The foil bearing according to any one of claims 1 to 4, wherein the edge portion protrudes in the rotation axis direction from both ends in the rotation axis direction of the rotating body that connect the fixed end and the free end in the radial top foil.

6. In the direction in which the cooling fluid flows from one end to the other end of the radial bump foil in the direction of the rotation axis, the crest portion of the radial bump foil extends in the rotational direction of the rotating body so as to draw in the cooling fluid from the one end to the other end, the trough portion of the radial bump foil extends in the rotational direction so as to draw in the cooling fluid from the one end to the other end, the foil bearing according to any one of claims 3 to 5.

7. The top foil is a thrust top foil that supports the rotating body in the thrust direction, the bump foil is a thrust bump foil that elastically supports the thrust top foil, the thrust bump foil is wider than the thrust top foil in a direction orthogonal to the direction of the rotation axis of the rotating body, the foil bearing according to claim 1 or claim 2.

8. The edge portion projects evenly from both ends in the direction orthogonal to the direction of the rotation axis in the thrust top foil, the foil bearing according to claim 7.

9. The top foil is a thrust top foil that supports the rotating body in the thrust direction, the bump foil is a thrust bump foil that elastically supports the thrust top foil, the thrust bump foil has a fixed end fixed to the bearing housing, and a free end not fixed to the bearing housing, the thrust top foil has a fixed end fixed to the bearing housing, and a free end not fixed to the bearing housing, the edge portion projects from the edge of the free end in the thrust top foil in the rotational direction of the rotating body, the foil bearing according to claim 1 or claim 2.

10. Among both ends in the direction orthogonal to the direction of the rotation axis of the rotating body in the thrust bump foil, in the direction in which the cooling fluid flows from the inner edge to the outer edge, the crest portion of the thrust bump foil extends in the rotational direction of the rotating body so as to draw in the cooling fluid from the inner edge to the outer edge, the trough portion of the thrust bump foil extends in the rotational direction so as to draw in the cooling fluid from the inner edge to the outer edge, the foil bearing according to any one of claims 7 to 9.

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