Fluid machine

Abstract

To provide a fluid machine which enables a thrust foil bearing to support a thrust load occurring during operation preferably even if an allowance set during manufacturing exists.SOLUTION: In a fluid machine 10 of the invention, a thrust foil bearing 30 includes: a base 31; top foils 33a to 33f; and bump foils 32a to 32f. Each of top foils 33a to 33f has a first top foil 61 and a second top foil 63. A first body part 61c is formed at the first top foil 61, and a second body part 63c is formed at the second top foil 63. The first body part 61c and the second body part 63c separate from each other when a drive shaft 24a does not rotate and a thrust load F1 acting on the first body 61c through an air film 80 is a predetermined value or lower and contact with each other when the thrust load F1 exceeds the predetermined value.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a fluid machine. [Background technology]

[0002] Patent Document 1 discloses a conventional fluid machine. This fluid machine includes a drive shaft, an actuator, a thrust foil bearing, and a housing. The drive shaft is rotatable about its axis. The drive shaft is provided with a thrust collar. The thrust collar is rotatable integrally with the drive shaft. The actuator compresses a fluid while being rotated by the drive shaft. The housing accommodates the drive shaft, the actuator, and the thrust foil bearing.

[0003] The thrust foil bearing has a base, a plurality of top foils, and a plurality of bump foils. A drive shaft is inserted through the base. Each top foil is arranged in the circumferential direction of the drive shaft and fixed to the base. Each top foil has a restricting portion and a main body portion. The restricting portion is fixed to the base. This restricts the circumferential rotation of the restricting portion relative to the base. The main body portion is connected to the restricting portion and extends toward the thrust collar. Each bump foil is arranged in the circumferential direction of the drive shaft and fixed to the base, and is arranged between the top foils and the base in the drive axial direction.

[0004] The thrust foil bearing supports the thrust load generated by the operation of the actuating body. Specifically, in the thrust foil bearing, as the drive shaft rotates, an air film is formed between the thrust collar and each main body of each top foil. As a result, the thrust foil bearing supports the thrust load without contact between the thrust collar and each top foil. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-115021 A Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, in a thrust foil bearing, the air film supports the thrust load without contact between the thrust collar and each top foil. In the above-mentioned conventional fluid machine, if the height to which the main body of each top foil extends toward the thrust collar, i.e., the height of the apex of the main body that is closest to the thrust collar, is uniform for all the main bodies of the top foils, the thickness of the air film formed between the thrust collar and each main body will be uniform. Therefore, the thrust load acts uniformly from each air film to each main body and, ultimately, to each top foil.

[0007] However, due to manufacturing tolerances, there is unavoidable variation in the height at which each body portion extends toward the thrust collar. As a result, the top foil having the body portion that extends the longest toward the thrust collar receives a thrust load preferentially over the other top foils. In other words, the thrust load does not act uniformly on all the top foils. This results in a decrease in the thrust load that the thrust foil bearing can support, compared to a case in which the thrust load acts uniformly on all the top foils.

[0008] Therefore, for example, it is conceivable to design each top foil to have a low rigidity. This makes the main body easily deformed even when the thrust load acting through each air film is relatively small, i.e., when the load is low. Therefore, it is possible to reduce the state in which the thrust load acts preferentially on the top foil having the main body that extends the highest toward the thrust collar. As a result, when the load is low, each top foil can favorably support the thrust load. However, when the rigidity of each top foil is low, when the thrust load acting through each air film is large, i.e., when the load is high, each top foil is supported by the bump foil from the side opposite the air layer. However, when the rigidity of each top foil is low, the main body easily deforms along the shape of the bump foil. Therefore, when the rigidity of each top foil is designed to be low, each top foil cannot favorably support the thrust load when the load is high.

[0009] On the other hand, if the rigidity of each top foil is designed to be high, the main body portion is less likely to deform along the shape of the bump foil even under high load, so that each top foil can favorably support the thrust load under high load. However, in this case, the main body portion is less likely to deform under low load, so that the thrust load is more likely to act preferentially on the top foil having the main body portion that extends the longest toward the thrust collar. This makes it difficult for each top foil to favorably support the thrust load under low load.

[0010] Incidentally, in addition to thrust foil bearings, radial foil bearings also exist as foil bearings. Here, even in radial foil bearings, an air film is formed between the drive shaft and the top foil due to the rotation of the drive shaft, but in radial foil bearings, the thin part of the air film always moves in the rotation direction of the drive shaft as the drive shaft rotates. Therefore, the above-mentioned problem is unique to thrust foil bearings.

[0011] The present invention has been made in consideration of the above-mentioned conventional situation, and has as its object to provide a fluid machinery in which the thrust foil bearing can suitably support the thrust load generated during operation, even if there are manufacturing tolerances. [Means for solving the problem]

[0012] A fluid machine according to the present invention is a fluid machine including a drive shaft rotatable about a drive axis, a working body that compresses a fluid while being rotated by the drive shaft, a thrust foil bearing that supports a thrust load generated by the operation of the working body, and a housing that accommodates the drive shaft, the working body, and the thrust foil bearing, The drive shaft is provided with a thrust collar that is rotatable integrally with the drive shaft, the thrust foil bearing includes a base through which the drive shaft is inserted, a plurality of top foils whose circumferential rotation with respect to the base is restricted, and a plurality of bump foils each disposed between the top foils and the base in the drive shaft direction while being restricted in the circumferential rotation with respect to the base, Each of the top foils includes a first top foil facing the thrust collar in the drive shaft direction; a second top foil disposed between the first top foil and the bump foil in the drive axial direction; The first top foil is provided with a first restricting portion that restricts rotation in the circumferential direction relative to the base, and a first main body portion that is connected to the first restricting portion and forms an air film between the first restricting portion and the thrust collar by rotation of the drive shaft. The second top foil is formed with a second restricting portion that restricts rotation in the circumferential direction relative to the base, and a second main body portion that is connected to the second restricting portion, the second body portion extends from a position closest to the first body portion toward the first body portion at a height lower than that of the first body portion; The first body portion and the second body portion are separated from each other when the drive shaft is not rotating and when the thrust load acting on the first body portion through the air film is equal to or less than a predetermined value, but are brought into contact with each other when the thrust load exceeds the predetermined value.

[0013] In the fluid machine of the present invention, the thrust foil bearing has a plurality of top foils. Each top foil has a first top foil and a second top foil. The first body portion of the first top foil and the second body portion of the second top foil are separated from each other when a thrust load acting on the first body portion is equal to or smaller than a predetermined value.

[0014] Therefore, in this fluid machine, when the thrust load acting on the first body portion through the air film is equal to or lower than a predetermined value, i.e., when the load is low, including when the drive shaft is not rotating, the first body portion alone supports the thrust load in the top foil. This makes it easy for each first body portion and therefore each first top foil to deform. Thus, in this fluid machine, even if the height at which the first body portion extends toward the thrust collar varies due to manufacturing tolerances, it is possible to reduce as much as possible the state in which the thrust load acts preferentially on the top foil having the first body portion with the highest height. In other words, in this fluid machine, even if there is variation in the height at which the first body portion extends toward the thrust collar, the variation in height is easily corrected by the action of the thrust load. As a result, in this fluid machine, it is easy to uniform the thrust load acting on each first top foil and therefore on the top foil when the load is low.

[0015] On the other hand, in this fluid machine, the first body portion and the second body portion come into contact with each other when the thrust load acting on the first body portion through the air film exceeds a predetermined value, i.e., when the load is high. This allows the first top foil and the second top foil to cooperate to ensure the rigidity of the top foil. Therefore, even when the load is high, the top foil is less likely to deform in accordance with the shape of each bump foil.

[0016] Thus, in this fluid machine, the thrust foil bearing can suitably support the thrust load both under low load and under high load.

[0017] Therefore, in the fluid machine of the present invention, even if there is a manufacturing tolerance, the thrust foil bearing can suitably support the thrust load generated during operation.

[0018] In the fluid machine of the present invention, the second top foil preferably has a rigidity higher than that of the first top foil.

[0019] In this case, there is no need to make the rigidity of the first top foil excessively high in order to ensure the rigidity of the top foil, so that the first main body portion, and therefore the first top foil, can be easily deformed under low loads.

[0020] The second top foil and the first top foil may be made of the same metal plate. The thickness of the second top foil is preferably greater than the thickness of the first top foil. In this case, the rigidity of the second top foil can be suitably made greater than the rigidity of the first top foil while facilitating manufacture. Effect of the Invention

[0021] In the fluid machine of the present invention, even if there is a manufacturing tolerance, the thrust foil bearing can suitably support the thrust load generated during operation. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is a cross-sectional view of a fluid machine according to a first embodiment. [Diagram 2] FIG. 2 is an enlarged cross-sectional view of a main part of the fluid machine according to the first embodiment. [Diagram 3] FIG. 3 is a cross-sectional view of the fluid machine of the first embodiment taken along line AA of FIG. [Figure 4] FIG. 4 is a cross-sectional view of the fluid machine of the first embodiment taken along line BB of FIG. [Diagram 5] FIG. 5 is a cross-sectional view of the fluid machine of the first embodiment taken along line CC of FIG. [Figure 6] FIG. 6 is a schematic diagram showing variations in height from the top foils to the thrust plate in the fluid machine of the first embodiment. [Figure 7] FIG. 7 is a schematic view similar to FIG. 6 showing deformation of each top foil when a low load is applied to the fluid machine of the first embodiment. [Figure 8] FIG. 8 is a cross-sectional view similar to FIG. 5 of the fluid machine of the first embodiment under a high load. [Figure 9] Second Embodiment FIG. 9 is a cross-sectional view similar to FIG. 4, showing a thrust foil bearing in a fluid machine according to a second embodiment. [Figure 10] FIG. 10 is a cross-sectional view showing a thrust foil bearing in a fluid machine according to a second embodiment, with a first top foil plate removed. [Figure 11] FIG. 11 is a cross-sectional view showing a cross section taken along line DD of FIG. 9, relating to a fluid machine according to a second embodiment. [Figure 12] FIG. 12 is a cross-sectional view similar to FIG. 11, showing the fluid machine of the second embodiment under a high load. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, first and second embodiments of the present invention will be described with reference to the drawings.

[0024] Example 1 As shown in Fig. 1, a turbo compressor 10 of the first embodiment is mounted on a fuel cell vehicle (not shown) equipped with a fuel cell system 1. The turbo compressor 10 is an example of a "fluid machine" in the present invention. The fuel cell system 1 supplies oxygen and hydrogen to an on-board fuel cell to generate power. The turbo compressor 10 compresses air containing oxygen that is supplied to the on-board fuel cell.

[0025] In this embodiment, the front-rear direction of the turbo compressor 10 is defined by the arrow shown in Fig. 1. Then, in Fig. 2 and subsequent figures, the front-rear direction of the turbo compressor 10 is defined in accordance with Fig. 1. Note that the front-rear direction is for convenience of explanation, and the attitude of the turbo compressor 10 can be changed as appropriate depending on the vehicle in which it is installed.

[0026] As shown in Fig. 1, the turbo compressor 10 includes a housing 11. The housing 11 is made of a metal material, for example, an aluminum alloy. The housing 11 includes a motor housing 12, a compressor housing 13, a turbine housing 14, a first top foil plate 15, a second top foil plate 16, and a third plate 17.

[0027] The motor housing 12 has a front end wall 12a, a rear end wall 12b, and a peripheral wall 12c. The front end wall 12a and the rear end wall 12b are formed in a plate shape. The front end wall 12a is located at the front end of the motor housing 12, and the rear end wall 12b is located at the rear end of the motor housing 12. The peripheral wall 12c is located between the front end wall 12a and the rear end wall 12b, and extends in a cylindrical shape in the front-rear direction. The peripheral wall 12c is connected to the front end wall 12a at its front end and to the rear end wall 12b at its rear end.

[0028] The first top foil plate 15 is connected to the front end of the motor housing 12 with its rear end surface 15a abutting against the front end wall 12a of the motor housing 12. As a result, the first top foil plate 15 closes the front opening of the peripheral wall 12c. The first top foil plate 15 has a first bearing retaining portion 20. The first bearing retaining portion 20 protrudes rearward from the center of the rear end surface 15a toward the electric motor 18. The first bearing retaining portion 20 is cylindrical.

[0029] As shown in FIG. 2, a recess 15c having a bottom surface 15d is formed on the end surface of the first top foil plate 15 opposite the motor housing 12, i.e., the front end surface 15b. The recess 15c is a circular hole. The inside of the cylinder of the first bearing retaining portion 20 penetrates the first top foil plate 15 and opens to the bottom surface 15d of the recess 15c. The axis of the recess 15c and the axis of the first bearing retaining portion 20 coincide with each other. An inner peripheral surface 15e of the recess 15c connects the front end surface 15b and the bottom surface 15d.

[0030] As shown in Fig. 1, the motor housing 12 has a second bearing retaining portion 22. The second bearing retaining portion 22 protrudes forward from the center of an inner surface 121a of a rear end wall 12b of the motor housing 12 toward the electric motor 18. The second bearing retaining portion 22 is cylindrical. The inside of the cylinder of the second bearing retaining portion 22 penetrates the rear end wall 12b and opens to an outer surface 122a of the rear end wall 12b. The axis of the first bearing retaining portion 20 and the axis of the second bearing retaining portion 22 coincide with each other.

[0031] As shown in FIG. 2, the second top foil plate 16 is connected to a front end surface 15b of the first top foil plate 15. A shaft insertion hole 16a is formed in the center of the second top foil plate 16. The shaft insertion hole 16a communicates with the inside of the recess 15c. The axis of the shaft insertion hole 16a coincides with the axis of the recess 15c and the axis of the first bearing retaining portion 20. A thrust bearing accommodating chamber S2 is defined by a rear end surface 16b, which is the end surface of the second top foil plate 16 on the first top foil plate 15 side, and the recess 15c of the first top foil plate 15.

[0032] The compressor housing 13 is cylindrical and has a circular suction port 13a through which air is drawn. The compressor housing 13 is connected to a front end surface 16c, which is the end surface of the second top foil plate 16 opposite to the first top foil plate 15. The axis of the suction port 13a of the compressor housing 13, the axis of the shaft insertion hole 16a of the second top foil plate 16, and the axis of the first bearing holder 20 are aligned. The suction port 13a opens at the end surface of the compressor housing 13 opposite to the second top foil plate 16. A pipe (not shown) is connected to the suction port 13a.

[0033] Between the compressor housing 13 and the front end surface 16c of the second top foil plate 16, a first impeller chamber 13b, a discharge chamber 13c, and a first diffuser passage 13d are formed. The first impeller chamber 13b communicates with the suction port 13a. The discharge chamber 13c extends around the axis of the suction port 13a around the first impeller chamber 13b. The first diffuser passage 13d communicates with the first impeller chamber 13b and the discharge chamber 13c. The first impeller chamber 13b communicates with the shaft insertion hole 16a of the second top foil plate 16.

[0034] As shown in Fig. 1, the third plate 17 is connected to an outer surface 122a of the rear end wall 12b of the motor housing 12. A shaft insertion hole 17a is formed in the center of the third plate 17. The shaft insertion hole 17a communicates with the cylindrical interior of the second bearing holder 22. The axis of the shaft insertion hole 17a coincides with the axis of the second bearing holder 22.

[0035] The turbine housing 14 is cylindrical and has a circular discharge port 14a through which air is discharged. The turbine housing 14 is connected to a rear end face 17b, which is the end face of the third plate 17 opposite the motor housing 12. The axis of the discharge port 14a of the turbine housing 14, the axis of the shaft insertion hole 17a of the third plate 17, and the axis of the second bearing holder 22 are aligned. The discharge port 14a opens at the rear end face of the turbine housing 14. A pipe (not shown) is connected to the discharge port 14a.

[0036] Between the turbine housing 14 and the rear end surface 17b of the third plate 17, a second impeller chamber 14b, a suction chamber 14c, and a second diffuser passage 14d are formed. The second impeller chamber 14b is in communication with the discharge port 14a. The suction chamber 14c extends around the axis of the discharge port 14a around the periphery of the second impeller chamber 14b. The second diffuser passage 14d is in communication with the second impeller chamber 14b and the suction chamber 14c. The second impeller chamber 14b is in communication with the shaft insertion hole 17a of the third plate 17.

[0037] A rotating body 24 is accommodated within the housing 11. The rotating body 24 has a drive shaft 24a, a first support portion 24b, a second support portion 24c, and a thrust collar 24d.

[0038] The drive shaft 24a extends in the front-rear direction. The drive shaft 24a has a first end 24e which is an end on the compressor housing 13 side, and a second end 24f which is an end on the turbine housing 14 side. The first support portion 24b is provided on an outer circumferential surface 240a of the drive shaft 24a at a position close to the first end 24e, and is disposed within the cylinder of the first bearing holder 20. The first support portion 24b is formed integrally with the drive shaft 24a, and protrudes in an annular shape from the outer circumferential surface 240a of the drive shaft 24a in the radial direction of the drive shaft 24a.

[0039] The second support portion 24c is provided on the outer peripheral surface 240a of the drive shaft 24a at a position close to the second end 24f and is disposed inside the cylinder of the second bearing holder 22. The second support portion 24c is formed separately from the drive shaft 24a and has a cylindrical shape. The second support portion 24c is fixed to the drive shaft 24a with the drive shaft 24a inserted therethrough. As a result, the second support portion 24c protrudes in an annular shape from the outer peripheral surface 240a of the drive shaft 24a in the radial direction of the drive shaft 24a. The second support portion 24c can rotate integrally with the drive shaft 24a.

[0040] The thrust collar 24d is disposed in the thrust bearing accommodating chamber S2. The thrust collar 24d is disk-shaped. The thrust collar 24d is fixed to the outer circumferential surface 240a of the drive shaft 24a in a state in which it extends radially from the outer circumferential surface 240a of the drive shaft 24a and protrudes in an annular shape. The thrust collar 24d can rotate integrally with the drive shaft 24a. The thrust collar 24d is disposed at a position spaced forward from the electric motor 18.

[0041] A first impeller 25 is connected to a first end 24e of the drive shaft 24a. The first impeller 25 is an example of the "actuator" in the present invention. The first impeller 25 is disposed closer to the first end 24e than the thrust collar 24d of the drive shaft 24a. The first impeller 25 is housed in the first impeller chamber 13b. A second impeller 26 is connected to a second end 24f of the drive shaft 24a. The second impeller 26 is disposed closer to the second end 24f than the second support portion 24c of the drive shaft 24a. The second impeller 26 is housed in the second impeller chamber 14b.

[0042] A first seal member 27 is provided between the shaft insertion hole 16a of the second top foil plate 16 and the rotor 24. The first seal member 27 seals the gap between the first impeller chamber 13b and the motor chamber S1. A second seal member 28 is provided between the shaft insertion hole 17a of the third plate 17 and the rotor 24. The second seal member 28 seals the gap between the second impeller chamber 14b and the motor chamber S1. The first seal member 27 and the second seal member 28 are, for example, seal rings.

[0043] The electric motor 18 includes a cylindrical rotor 3 and a cylindrical stator 5. The rotor 3 is fixed to the drive shaft 24a. The stator 5 is fixed to the housing 11. The stator 5 includes a cylindrical stator core 5a fixed to the inner circumferential surface 121b of the peripheral wall 12c of the motor housing 12, and a coil 5b wound around the stator core 5a.

[0044] The rotor 3 is disposed within the stator 5. The rotor 3 has a cylindrical rotor body 3a to which a drive shaft 24a is attached, and a plurality of permanent magnets (not shown) provided on the rotor body 3a. When power is supplied to the coil 5b from a battery (not shown), the rotor 3 rotates around a drive axis O together with the drive shaft 24a and thus the rotating body 24. This drive axis O is parallel to the front-rear direction. That is, in this embodiment, the "direction of the drive axis O" and the "front-rear direction" are synonymous.

[0045] The turbo compressor 10 also includes a pair of thrust foil bearings 30, 30 and a pair of radial foil bearings 40, 40. Both thrust foil bearings 30, 30 support the drive shaft 24a in the direction of the drive axis O so as to be rotatable relative to the housing 11. Both radial foil bearings 40, 40 support the drive shaft 24a in a direction perpendicular to the direction of the drive axis O so as to be rotatable relative to the housing 11.

[0046] Both thrust foil bearings 30, 30 are disposed in the thrust bearing accommodating chamber S2, and sandwich the thrust collar 24d in the front-rear direction. That is, the thrust foil bearing 30 located in front of the thrust collar 24d in the thrust bearing accommodating chamber S2 is disposed on the first end 24e side of the drive shaft 24a. The thrust foil bearing 30 located behind the thrust collar 24d in the thrust bearing accommodating chamber S2 is disposed on the second end 24f side of the drive shaft 24a.

[0047] The thrust foil bearings 30, 30 are basically symmetrical in the front-rear direction. Therefore, in the following description, the configuration of the thrust foil bearing 30 located in front of the thrust collar 24d will be described in detail, and a description of the configuration of the thrust foil bearing 30 located behind the thrust collar 24d will be omitted as appropriate.

[0048] 3 and 4, the thrust foil bearing 30 includes a base 31, six bump foils 32a to 32f, and six top foils 33a to 33f. The bump foils 32a to 32f and the top foils 33a to 33f each have an approximately fan-shaped outer shape in a plan view. For ease of explanation, the thrust collar 24d is shown by imaginary lines in FIG. 4.

[0049] The base 31 is formed by a part of the second top foil plate 16. That is, as shown in Figures 1 and 2, the base 31 is formed by a part of the rear end surface 16b of the second top foil plate 16 that defines the thrust bearing accommodating chamber S2. The base 31 of the thrust foil bearing 30 located behind the thrust collar 24d is formed by a part of the bottom surface 15d of the recess 15c.

[0050] The base 31 is opposed to the thrust collar 24d in the direction of the drive axis O while being spaced apart from the thrust collar 24d in the direction of the drive axis O. As shown in Figures 3 and 4, the base 31 is formed with an insertion hole 31a through which the drive shaft 24a is inserted.

[0051] As shown in Figure 3 Each of the bump foils 32a to 32f is formed by pressing a stainless steel plate. Each of the bump foils 32a to 32f is disposed at equal intervals in the circumferential direction of the drive shaft 24a on the end face of the base 31 on the thrust collar 24d side, i.e., on the rear face of the base 31. In this way, each of the bump foils 32a to 32f surrounds the drive shaft 24a in the rotation direction R1 of the rotor 24.

[0052] Each of the bump foils 32a to 32f is fixed to the base 31 by welding at an end portion on one side in the rotation direction R1 of the rotor 24, i.e., an end portion on the trailing side in the rotation direction R1. Thus, each of the bump foils 32a to 32f has an end portion on one side in the rotation direction R1 of the rotor 24 as a fixed end 321, and an end portion on the other side in the rotation direction R1 of the rotor 24, i.e., an end portion on the leading side in the rotation direction R1, as a free end 322. Note that each of the bump foils 32a to 32f may have an end portion on the other side in the rotation direction R1 of the rotor 24 as the fixed end 321, and an end portion on one side in the rotation direction R1 of the rotor 24 as the free end 322.

[0053] 5, each of the bump foils 32a to 32f is formed with a plurality of peaks 323 and a plurality of valleys 324. Each peak 323 protrudes toward the thrust collar 24d in the direction of the drive shaft center O. Each valley 324 is located between the peaks 323 and protrudes toward the base 31. Thus, each of the bump foils 32a to 32f has a corrugated shape in which the plurality of peaks 323 and the plurality of valleys 324 are alternately arranged in the circumferential direction of the drive shaft 24a.

[0054] As shown in Fig. 4, the top foils 33a to 33f are disposed at equal intervals in the circumferential direction of the drive shaft 24a so as to correspond to the bump foils 32a to 32f on the rear surface of the base 31. That is, the top foil 33a is disposed between the thrust collar 24d and the bump foil 32a in the direction of the drive shaft center O. Similarly, the top foils 33b to 33f are disposed between the thrust collar 24d and the bump foils 32b to 32f in the direction of the drive shaft center O. In other words, the six bump foils 32a to 32f are disposed between the six top foils 33a to 33f and the base 31 in the direction of the drive shaft center O.

[0055] As shown in Figs. 5 to 8, each of the top foils 33a to 33f includes a first top foil 61 and a second top foil 63. The first top foil 61 and the second top foil 63 are both formed by pressing a stainless steel plate material. Here, as shown in Figs. 5 and 8, the second top foil 63 is formed to have a greater plate thickness than the first top foil 61. As a result, the second top foil 63 has a higher rigidity than the first top foil 61. Note that in Figs. 6 and 7, for ease of explanation, the shapes of the top foils 33a to 33f, i.e., the first top foil 61 and the second top foil 63, are exaggerated, and the first top foil 61 is illustrated by a solid line and the second top foil 63 is illustrated by a broken line. Also, in Figs. 6 and 7, the bump foils 32a to 32f are omitted from illustration.

[0056] 5 and 8, the first top foil 61 is formed with a first restricting portion 61a, a first connecting portion 61b, and a first main body portion 61c. The first restricting portion 61a is located at an end portion on one side of the first top foil 61 in the rotation direction R1 of the rotor 24. The first connecting portion 61b is located on the other side of the rotation direction R1 of the rotor 24 from the first restricting portion 61a, and is connected to the first restricting portion 61a. The first connecting portion 61b extends at an incline toward the thrust collar 24d in the direction of the drive shaft center O as it moves away from the first restricting portion 61a.

[0057] The first main body portion 61c is located on the other side of the first connecting portion 61b in the rotation direction R1 of the rotor 24, and is connected to the first connecting portion 61b. Thus, the first main body portion 61c is connected to the first restricting portion 61a through the first connecting portion 61b. As the first main body portion 61c moves away from the first connecting portion 61b and therefore the first restricting portion 61a, it extends at an incline toward the thrust collar 24d in the direction of the drive axis O. Here, the first main body portion 61c is inclined more gently than the first connecting portion 61b.

[0058] The second top foil 63 is located on the back side of the first top foil 61. That is, in the case of the top foil 33b as an example, the second top foil 63 is located between the first top foil 61 and the bump foil 32b. The second top foil 63 is formed with a second restricting portion 63a, a second connecting portion 63b, and a second main body portion 63c.

[0059] The second restricting portion 63a is located at one end of the second top foil 63 in the rotation direction R1 of the rotor 24. The second connecting portion 63b is located on the other side of the second restricting portion 63a in the rotation direction R1 of the rotor 24, and is connected to the second restricting portion 63a. The second connecting portion 63b extends at an incline toward the first top foil 61 and the thrust collar 24d in the direction of the drive shaft center O as it moves away from the second restricting portion 63a. Here, the second connecting portion 63b is inclined more gently than the first connecting portion 61b.

[0060] The second body portion 63c is located on the other side of the rotation direction R1 of the rotor 24 from the second connection portion 63b, and is connected to the second connection portion 63b. Thus, the second body portion 63c is connected to the second regulating portion 63a through the second connection portion 63b. As the second body portion 63c moves away from the second connection portion 63b and thus the second regulating portion 63a, it extends at an incline toward the first top foil 61 and the thrust collar 24d in the direction of the drive axis O. Here, the second body portion 63c is inclined more gently than the second connection portion 63b. Also, the inclination angle of the second body portion 63c is approximately equal to the inclination angle of the first body portion 61c. That is, the second body portion 62c is closest to the first body portion 61c on the second connection portion 63b side in the direction of the drive axis O. The second main body portion 62c extends from a position closest to the first main body portion 61c toward the first main body portion 61c at a height lower than that of the first main body portion 61c. The second main body portion 63c may be inclined more gently than the first main body portion 61c, and the inclination angle of the second main body portion 63c may be completely the same as that of the first main body portion 61c.

[0061] In each of the top foils 33a to 33f, the first restricting portion 61a of the first top foil 61 and the second restricting portion 63a of the second top foil 63 are abutted against each other, and the first restricting portion 61a and the second restricting portion 63a are fixed to the base 31 by welding. This restricts the first restricting portion 61a and the second restricting portion 63a, and therefore the first top foil 61 and the second top foil 63, from rotating in the circumferential direction relative to the base 31. In each of the top foils 33a to 33f, one side in the rotation direction R1 of the rotating body 24 is a fixed end 331, and the other side in the rotation direction R1 of the rotating body 24 is a free end 332. That is, in each of the top foils 33a to 33f, the first restricting portion 61a and the second restricting portion 63a are fixed ends 331, and the first and second connecting portions 61b, 63b and the first and second main portions 61c, 63c are free ends 332.

[0062] In this manner, the six top foils 33a to 33f are fixed to the base 31, so that in the thrust foil bearing 30, the six first main body portions 61c face the thrust collars 24d in the direction of the drive axis O, respectively.

[0063] As shown in FIG. 1, one of the two radial foil bearings 40 is disposed in the first bearing holder 20. The other radial foil bearing 40 is disposed in the second bearing holder 22. In the first bearing holder 20, the first support portion 24b of the rotating body 24 is rotatably supported by one radial foil bearing 40. As a result, the outer circumferential surface of the first support portion 24b is made into the radial bearing surface 24g supported by one radial foil bearing 40. In the second bearing holder 22, the second support portion 24c of the rotating body 24 is rotatably supported by the other radial foil bearing 40. As a result, the outer circumferential surface of the second support portion 24c is made into the radial bearing surface 24g.

[0064] Since both radial foil bearings 40, 40 basically have the same configuration, we will explain the configuration of the radial foil bearing 40 arranged in the first bearing retaining portion 20, and omit the explanation of the configuration of the radial foil bearing 40 arranged in the second bearing retaining portion 22 as appropriate.

[0065] 2, the radial foil bearing 40 includes a radial bearing housing 41, a radial bump foil 42, and a radial top foil 43. Here, in the radial foil bearing 40 disposed in the first bearing retaining portion 20, the first bearing retaining portion 20 constitutes the radial bearing housing 41. In addition, in the radial foil bearing 40 disposed in the second bearing retaining portion 22, the second bearing retaining portion 22 constitutes the radial bearing housing 41 (see FIG. 1).

[0066] The radial bump foil 42 and the radial top foil 43 shown in Fig. 2 are both substantially cylindrical and are formed by pressing a stainless steel plate. The radial bump foil 42 and the radial top foil 43 have the other circumferential end bent radially outward and fixed to the radial bearing housing 41. That is, the radial bump foil 42 and the radial top foil 43 have the other circumferential end as a fixed end and the one circumferential end as a free end.

[0067] Although detailed illustration is omitted, the radial bump foil 42 has a corrugated shape in which the ridges of the peaks protruding toward the radial top foil 43 are aligned in the circumferential direction of the drive shaft 24a. The radial bump foil 42 elastically supports the radial top foil 43 by each peak, with each valley located between adjacent peaks being supported by the radial bearing housing 41. As shown in Fig. 2, the surface of the radial top foil 43 opposite the surface elastically supported by the radial bump foil 42 is a radial bearing surface 43a that faces the radially-bearing surface 24g in the radial direction.

[0068] As shown in FIG. 1, the fuel cell system 1 includes a turbo compressor 10, a fuel cell stack 100 as an on-vehicle fuel cell, a supply flow path L1, a discharge flow path L2, a branch flow path L3, and an intercooler 110.

[0069] The fuel cell stack 100 is composed of a plurality of fuel cell units (not shown). The supply flow path L1 connects the discharge chamber 13c and the fuel cell stack 100. The discharge flow path L2 connects the fuel cell stack 100 and the suction chamber 14c. The branch flow path L3 branches off from the supply flow path L1. The intercooler 110 is provided in the branch flow path L3 and cools the air flowing through the branch flow path L3.

[0070] 1 and 2, a cooling passage 50 is formed in the housing 11. Air flows through the cooling passage 50. The cooling passage 50 is formed across the second top foil plate 16, the first top foil plate 15, the motor housing 12, and the third plate 17. The cooling passage 50 has a first passage 51 and a second passage 52.

[0071] As shown in Fig. 2, the first passage 51 is provided in the second top foil plate 16. The first passage 51 has an inlet 51a provided in a side wall surface of the second top foil plate 16. A branch passage L3 is connected to the inlet 51a. As a result, the branch passage L3 connects the supply passage L1 and the inlet 51a of the first passage 51. The first passage 51 communicates with the motor chamber S1 via the thrust bearing accommodating chamber S2 and the radial foil bearing 40 arranged in the first bearing retaining portion 20.

[0072] 1, the second passage 52 is provided in the third plate 17. The second passage 52 has an outlet 52a provided in a side end surface of the third plate 17. The second passage 52 communicates with the motor chamber S1 via the radial foil bearing 40 arranged in the second bearing holder 22.

[0073] In the turbo compressor 10 configured as above, when the drive shaft 24a rotates integrally with the rotor 3 about the drive shaft center O, the first impeller 25 and the second impeller 26 rotate integrally with the drive shaft 24a about the drive shaft center O. As a result, in the turbo compressor 10, air is compressed by the first impeller 25. Specifically, in the turbo compressor 10, air sucked in from the suction port 13a is compressed by the first impeller 25 in the first impeller chamber 13b, passes through the first diffuser passage 13d, and is discharged from the discharge chamber 13c. Air is an example of the "fluid" in the present invention.

[0074] The air discharged from the discharge chamber 13c is supplied to the fuel cell stack 100 through the supply flow path L1. The air supplied to the fuel cell stack 100 is used to generate power in the fuel cell stack 100, and then discharged to the discharge flow path L2 as the exhaust gas of the fuel cell stack 100. The exhaust gas of the fuel cell stack 100 is drawn into the suction chamber 14c through the discharge flow path L2. The exhaust gas of the fuel cell stack 100 drawn into the suction chamber 14c is discharged into the second impeller chamber 14b through the second diffuser flow path 14d. The second impeller 26 is also rotated by the exhaust gas of the fuel cell stack 100 discharged into the second impeller chamber 14b in this manner. That is, the drive shaft 24a rotates around the drive axis O not only by the rotation caused by the drive of the electric motor 18, but also by the rotation of the second impeller 26 rotated by the exhaust gas of the fuel cell stack 100. In this way, the exhaust gas from the fuel cell stack 100 discharged into the second impeller chamber 14b is discharged to the outside from the discharge port 14a.

[0075] In addition, in the process of pumping air by the first impeller 25, a thrust load F1 acts on the drive shaft 24a and, ultimately, on the rotor 24. Here, in both thrust foil bearings 30, 30, the first main body portions 61c of each of the top foils 33a to 33f are in contact with the thrust collar 24d until the rotation speed of the drive shaft 24a rotating around the drive axis O reaches a floating rotation speed at which the thrust collar 24d floats relative to the thrust foil bearing 30. In this way, both thrust foil bearings 30, 30 support the thrust load F1 acting on the drive shaft 24a.

[0076] When the rotation speed of the drive shaft 24a reaches the floating rotation speed, as shown in Figs. 5 to 8, an air film 80 formed between the thrust collar 24d and each of the top foils 33a to 33f causes the thrust collar 24d to float in the direction of the drive axis O relative to both thrust foil bearings 30. As a result, both thrust foil bearings 30 support the thrust load F1 acting on the rotor 24 without contacting the thrust collar 24d. The support of the thrust load F1 by the thrust foil bearings 30 will be described in detail later.

[0077] Similarly, in both radial foil bearings 40, 40 shown in Fig. 1 and Fig. 2, the radial bearing surface 43a of the radial top foil 43 and the radial bearing surface 24g are in contact with each other to support the drive shaft 24a until the rotation speed of the drive shaft 24a reaches a floating rotation speed at which the first support portion 24b and the second support portion 24c float. Then, when the rotation speed of the drive shaft 24a reaches the floating rotation speed, the first support portion 24b and the second support portion 24c float relative to the radial foil bearing 40 due to an air film (not shown) generated between the radial top foil 43 and the first support portion 24b and the second support portion 24c. As a result, both radial foil bearings 40 support the drive shaft 24a in a non-contact state with the first support portion 24b and the second support portion 24c.

[0078] Furthermore, in this turbo compressor 10, a portion of the air flowing through the supply passage L1 toward the fuel cell stack 100 flows into the first passage 51 via the branch passage L3. At this time, the air flowing into the first passage 51 becomes cooled air that has been cooled by the intercooler 110 while flowing through the branch passage L3. The cooled air that has flowed into the first passage 51 then flows into the thrust bearing accommodation chamber S2.

[0079] The cooling air that has thus flowed into the thrust bearing accommodating chamber S2 cools both thrust foil bearings 30. Then, the cooling air that has cooled both thrust foil bearings 30 passes through the thrust bearing accommodating chamber S2 and reaches the motor chamber S1. As a result, the rotor 3, the stator 5, and both radial foil bearings 40, 40 are cooled by the cooling air. The cooling air then reaches the second passage 52 and is discharged to the outside of the turbo compressor 10 from the discharge port 52a.

[0080] As described above, the thrust foil bearing 30 supports the thrust load F1 acting on the drive shaft 24a when the turbo compressor 10 is in operation. However, the thrust foil bearing 30, and in turn the turbo compressor 10, have manufacturing tolerances. As a result, there is unavoidable variation in the height to which the first main body portion 61c of the first top foil 61 extends toward the thrust collar 24d among the six top foils 33a to 33f. In this regard, even if such variation in height occurs, in the turbo compressor 10, both thrust foil bearings 30 can favorably support the thrust load F1. This operation will be specifically described below.

[0081] Here, for convenience of explanation, among the six top foils 33a to 33f, the top foil 33b is appropriately referred to as the "specific top foil 33b". In this embodiment, as shown in Fig. 6, in the specific top foil 33b among the six top foils 33a to 33f, the height of the first main body portion 61c of the first top foil 61 at the position where the height of the first main body portion 61c extending toward the thrust collar 24d is maximum, that is, the height of the top of the first main body portion 61c is a first height H1, and in the remaining five top foils 33a, 33c to 33f, the height of the top of the first main body portion 61c of the first top foil 61 (the first main body portion 61c of the other first top foils 61) is a second height H2 lower than the first height H1.

[0082] Since the height to the top of the first main body portion 61c is the first height H1 in this manner, the thickness of the air film 80 formed between the thrust collar 24d and the specific top foil 33b is the first thickness t1. Meanwhile, since the height to the top of the first main body portion 61c of the other first top foils 61 is the second height H2, the thickness of the air film 80 formed between the thrust collar 24d and the five top foils 33a, 33c to 33f is the second thickness t2. The first thickness t1 is thinner than the second thickness t2. As a result, the thrust load F1 acts preferentially on the specific top foil 33b compared to the other five top foils 33a, 33c to 33f.

[0083] In this regard, in the turbo compressor 10, each of the top foils 33a to 33f is composed of a first top foil 61 and a second top foil 63. As shown in Fig. 5, the first connection portion 61b and the first main body portion 61c of each first top foil 61 and the second connection portion 63b and the second main body portion 63c of each second top foil 63 are separated from each other when the thrust load F1 acting on the first main body portion 61c of the first top foil 61 via the air film 80 is equal to or less than a predetermined value. Here, this predetermined value can be appropriately set according to, for example, the amount of air compressed by the first impeller 25, the maximum value of the thrust load F1 acting on the rotor 24 during operation, and the like.

[0084] For this reason, in this turbo compressor 10, even when the thrust collar 24d is raised relative to the thrust foil bearing 30 due to the rotation of the drive shaft 24a, including when the drive shaft 24a is not rotating, when the thrust load F1 acting on the first main body portion 61c via the air film 80 is below a predetermined value, i.e., at a low load, in each of the top foils 33a to 33f, the first main body portion 61c will alone support the thrust load F1 (see Figure 5).

[0085] Furthermore, in the turbo compressor 10, the first top foil 61 including the first main body portion 61c is formed to have a thinner plate thickness than the second top foil 63, and is therefore less rigid than the second top foil 63.

[0086] As a result, the first main body portion 61c, and therefore the first top foil 61, are easily elastically deformed by the thrust load F1. Thus, in the turbo compressor 10, as described above, even if the height of the top foil 33b, i.e., the first main body portion 61c of the first top foil 61 in the specific top foil 33b, extending toward the thrust collar 24d is higher than the height of the first main body portion 61c of the other first top foils 61, it is possible to minimize the state in which the thrust load F1 acts preferentially on the first top foil 61 in the specific top foil 33b.

[0087] That is, in the turbo compressor 10, the thrust load F1 acts preferentially on the first main body portion 61c of the specific top foil 33b, but since the first top foil 61 is easily elastically deformed, the height to the top of the first main body portion 61c tends to approach the second height H2 due to the action of the thrust load F1. Therefore, as shown in Fig. 7, although the thrust load F1 acts preferentially on the first main body portion 61c of the specific top foil 33b momentarily, the height of the first main body portion 61c extending toward the thrust collar 24d of all the first top foils 61 tends to be aligned with the second height H2.

[0088] In this way, in the turbo compressor 10, even if there is variation in the height of the first main body portion 61c of the first top foil 61 extending toward the thrust collar 24d, the thrust load F1 acts on the first main body portion 61c, so that the variation in height can be easily corrected. In other words, in the turbo compressor 10, the state in which the thrust load F1 acts preferentially on the first main body portion 61c of the specific top foil 33b can be reduced as much as possible. As a result, in the turbo compressor 10, the thrust load F1 acting on each of the top foils 33a to 33f at the time of low load can be easily uniformed. This allows the six top foils 33a to 33f to support the thrust load F1 as a whole.

[0089] On the other hand, as shown in FIG. 8, in this turbo compressor 10, the first connection portion 61b and the first main body portion 61c of the first top foil 61 and the second connection portion 63b and the second main body portion 63c of the second top foil 63 abut against each other when the thrust load F1 acting on the first main body portion 61c via the air film 80 exceeds a predetermined value, i.e., at the time of high load.

[0090] Taking the specific top foil 33b as an example, under high load, the bump foil 32b abuts against the back side of the specific top foil 33b, i.e., from the side of the second top foil 63, so that the bump foil 32b elastically supports the specific top foil 33b from the back side. Here, as described above, the first connection portion 61b and the first main body portion 61c of the first top foil 61 abut against the second connection portion 63b and the second main body portion 63c of the second top foil 63, so that in the turbo compressor 10, the first top foil 61 and the second top foil 63 constituting the specific top foil 33b cooperate to ensure the rigidity of the specific top foil 33b.

[0091] For this reason, in the turbo compressor 10, the specific top foil 33b is less likely to deform into a corrugated shape that matches the shape of the second bump foil 32b even under a high load. The same is true for the other five top foils 33a, 33c to 33f.

[0092] As a result, in the turbo compressor 10, both thrust foil bearings 30, 30 can favorably support the thrust load F1 both under low load and under high load.

[0093] Therefore, in the turbo compressor 10 of the first embodiment, even if there is a manufacturing tolerance, the thrust foil bearings 30, 30 can suitably support the thrust load F1 generated during operation.

[0094] In particular, in the turbo compressor 10, the rigidity of each of the second top foils 63 is higher than that of each of the first top foils 61. Therefore, in the turbo compressor 10, it is not necessary to excessively increase the rigidity of each of the first top foils 61 in order to ensure the rigidity of each of the top foils 33a to 33f. Therefore, in the turbo compressor 10, while each of the first top foils 61 is made easy to deform under low load, the second top foils 63 can suitably ensure the rigidity of each of the top foils 33a to 33f under high load.

[0095] Moreover, while both the first top foils 61 and the second top foils 63 are formed from stainless steel plate material, the plate thickness of each of the second top foils 63 is made thicker than the plate thickness of each of the first top foils 61. As a result, in order to ensure the rigidity of each of the second top foils 63, the turbo compressor 10 does not need to form each of the second top foils 63 from a material that is difficult to process. Furthermore, the rigidity required of each of the second top foils 63 can be suitably adjusted by the plate thickness of each of the second top foils 63. For these reasons, the turbo compressor 10 can be easily manufactured while achieving the above-mentioned functions.

[0096] Example 2 The turbo compressor 10 of the second embodiment includes thrust foil bearings 70, 70 shown in Fig. 9, instead of the pair of thrust foil bearings 30, 30 in the first embodiment. The thrust foil bearings 70, 70 are also disposed in the thrust bearing accommodation chamber S2 (see Fig. 1), and sandwich the thrust collar 24d in the front-rear direction. As with the thrust foil bearings 30, 30 in the first embodiment, these thrust foil bearings 70, 70 are basically symmetrical in shape in the front-rear direction, so in the following description, the configuration of the thrust foil bearing 70 located in front of the thrust collar 24d will be described in detail, and a description of the configuration of the thrust foil bearing 70 located behind the thrust collar 24d will be omitted.

[0097] Although detailed illustration is omitted, in the thrust foil bearing 70, six bump foils 32a to 32f are fixed to the base 31 in the same manner as in the thrust foil bearing 30 (see FIG. 3). The thrust foil bearing 70 has a first top foil plate 81 shown in FIG. 9, a second top foil plate 82 shown in FIG. 10, and six fixing pins 83. The first top foil plate 81 is an example of the "first top foil" in the present invention. The second top foil plate 82 is an example of the "second top foil" in the present invention. The number of fixing pins 83 can be designed as appropriate.

[0098] The first top foil plate 81 shown in Fig. 9 and the second top foil plate 82 shown in Fig. 10 are both formed by pressing a stainless steel plate material. Here, the plate material forming the second top foil plate 82 is formed to have a greater plate thickness than the plate material forming the first top foil plate 81. Thus, the first top foil plate 81 and the second top foil plate 82 have the same shape except for the plate thickness.

[0099] 9, one first frame portion 811, six first main body portions 812a to 812f, and six first bridge portions 813a to 813f are integrally formed on the first top foil plate 81. The first frame portion 811 is an example of a "first restricting portion" in the present invention.

[0100] The first frame portion 811 is disposed on the outer periphery side of each of the first main body portions 812a to 812f in the first top foil plate 81. The first frame portion 811 has an annular shape in a plan view. In the first top foil plate 81, each of the first main body portions 812a to 812f is disposed on the inner periphery side of the first frame portion 811. In this case, the first frame portion 811 and each of the first main body portions 812a to 812f are disposed to be spaced apart in the radial direction of the first top foil plate 81.

[0101] Each of the first bridge portions 813a to 813f extends linearly in the radial direction of the first top foil plate 81 from each of the first main body portions 812a to 812f toward the first frame portion 811. Each of the first bridge portions 813a to 813f is connected to the first frame portion 811 on the radially outer side of the first top foil plate 81 than each of the first main body portions 812a to 812f.

[0102] Each of the first main body portions 812a to 812f is substantially fan-shaped in a plan view. The first main body portions 812a to 812f are disposed at equal intervals in the circumferential direction of the drive shaft 24a. The first main body portion 812a is connected to the first frame portion 811 by the first bridge portion 813a. Similarly, the first main body portions 812b to 812f are connected to the first frame portion 811 by the first bridge portions 813b to 813f. In addition, taking the first main body portion 812b as an example, the first main body portion 812b extends at an angle toward the thrust collar 24d in the direction of the drive axis O as it moves away from the first bridge portion 813b in the rotation direction R1 of the rotor 24 (see FIG. 11). That is, the first main body portion 812b is inclined so that the height toward the thrust collar 24d in the direction of the drive axis O increases as the first main body portion 812b moves away from the first bridge portion 813b in the rotational direction R1. The first main body portions 812a, 812c to 812f also have a similar configuration.

[0103] 10, one second frame portion 814, six second main body portions 815a to 815f, and six second bridge portions 816a to 816f are integrally formed on the second top foil plate 82. The second frame portion 814 is an example of a "second restricting portion" in the present invention.

[0104] The second frame portion 814 and the second bridge portions 816a to 816f have the same shapes as the above-mentioned first frame portion 811 and the first bridge portions 813a to 813f, respectively. As a result, in the second top foil plate 82, the second main body portions 815a to 815f are disposed on the inner circumferential side of the second frame portion 814.

[0105] Each of the second main body parts 815a-815f is substantially fan-shaped in a plan view, similar to each of the first main body parts 812a-812f. Each of the second main body parts 815a-815f is disposed at equal intervals in the circumferential direction of the drive shaft 24a, and is connected to the second frame part 814 by each of the second bridge parts 816a-816f. Each of the second main body parts 815a-815f extends at an incline toward the thrust collar 24d in the direction of the drive axis O as it moves away from the second bridge parts 816a-816f in the rotation direction R1 of the rotor 24 (see FIG. 11). At this time, each of the second main body parts 815a-815f is inclined so that the height toward the thrust collar 24d in the direction of the drive axis O is lower than that of each of the first main body parts 812a-812f.

[0106] As shown in FIG. 9, in the thrust foil bearing 70, the first top foil plate 81 and the second top foil plate 82 are arranged in a state of being overlapped in the direction of the drive axis O, and the first top foil plate 81 and the second top foil plate 82 are fixed to the base 31 by each fixing pin 83. At this time, in the thrust foil bearing 70, the first top foil plate 81 and the second top foil plate 82 are overlapped in the direction of the drive axis O so that the first top foil plate 81 is closer to the thrust collar 24d in the direction of the drive axis O than the second top foil plate 82. As a result, the first top foil plate 82 is arranged between the thrust collar 24d and the second top foil plate 82 in the direction of the drive axis O. And the second top foil plate 82 is arranged between the first top foil plate 81 and each of the bump foils 32a to 32f in the direction of the drive axis O (see FIGS. 11 and 12).

[0107] More specifically, the first frame portion 811 and the second frame portion 814 overlap in the direction of the drive axis O. Furthermore, the first main body portion 812a and the second main body portion 815a overlap in the direction of the drive axis O, and the first bridge portion 813a and the second bridge portion 816a overlap in the direction of the drive axis O. Similarly, the first main body portions 812b to 812f and the second main body portions 815b to 815f also overlap in the direction of the drive axis O, and the first bridge portions 813b to 813f and the second bridge portions 816b to 816f also overlap in the direction of the drive axis O.

[0108] Moreover, the first top foil plate 81 and the second top foil plate 82 are fixed to the base 31 by the fixing pins 83, so that the first frame portion 811 is restricted from rotating in the circumferential direction relative to the base 31. Similarly, the second frame portion 814 is restricted from rotating in the circumferential direction relative to the base 31.

[0109] Thus, in the thrust foil bearing 70, six top foils 91a to 91f are formed by the first top foil plate 81 and the second top foil plate 82. That is, the top foil 91a is composed of the first and second frame parts 811 and 814, the first and second main body parts 812a and 815a, and the first and second bridge parts 813a and 816a. The top foil 91b is composed of the first and second frame parts 811 and 814, the first and second main body parts 812b and 815b, and the first and second bridge parts 813b and 816b. The top foil 91c is composed of the first and second frame parts 811 and 814, the first and second main body parts 812c and 815c, and the first and second bridge parts 813c and 816c. The top foil 91d is composed of the first and second frame parts 811 and 814, the first and second main body parts 812d and 815d, and the first and second bridge parts 813d and 816d. The top foil 91e is composed of the first and second frame parts 811 and 814, the first and second main body parts 812e and 815e, and the first and second bridge parts 813e and 816e. The top foil 91f is composed of the first and second frame parts 811 and 814, the first and second main body parts 812f and 815f, and the first and second bridge parts 813f and 816f. In other words, the first and second frame parts 811 and 814 are common to the six top foils 91a to 91f.

[0110] In addition, in each of the top foils 91a to 91f, the first and second bridge portions 813a to 813f, 816a to 816f, which are one end side in the rotational direction R1 of the rotating body 24, are fixed ends, and the other end side in the rotational direction R1 of the rotating body 24 is a free end.

[0111] Although not shown in detail, the first and second top foil plates 81 and 82 are fixed to the base 31, so that in the thrust foil bearing 70, the bump foil 32a is located on the back side of the top foil 91a, i.e., on the opposite side of the top foil 91a from the thrust collar 24d. Similarly, the bump foil 32b is located on the back side of the top foil 91b, the bump foil 32c is located on the back side of the top foil 91c, the bump foil 32d is located on the back side of the top foil 91d, the bump foil 32e is located on the back side of the top foil 91e, and the bump foil 32f is located on the back side of the top foil 91f. The other configurations of the turbo compressor 10 of the second embodiment, including the other configurations of the thrust foil bearing 70, are the same as those of the turbo compressor 10 of the first embodiment, and the same configurations are denoted by the same reference numerals, and detailed description of the configurations will be omitted.

[0112] In this thrust foil bearing 70, the first top foil plate 81 and the second top foil plate 82 are overlapped in the direction of the drive axis O. For this reason, in the case of the top foil 91b as an example, the second main body portion 815b is closest to the first main body portion 812b in the direction of the drive axis O at the portion where the second main body portion 815b is connected to the second bridge portion 816b. The second main body portion 815b extends from the position closest to the first main body portion 812b toward the first main body portion 812b at a height lower than that of the first main body portion 812b (see FIG. 11). The same is true for the second main body portions 815a, 815c to 815f in the top foils 91a, 91c to 91f.

[0113] Similarly to the top foils 33a-33f in the first embodiment, in each of the top foils 91a-91f, when the thrust load F1 acting on the first body portions 812a-812f through the air film 80 is equal to or less than a predetermined value, the first body portions 812a-812f and the second body portions 815a-815f are separated from each other. Therefore, in the case of a low load in which the thrust load F1 acting on the first body portions 812a-812f through the air film 80 is equal to or less than a predetermined value, in each of the top foils 91a-91f, the first body portions 812a-812f each support the thrust load F1 independently.

[0114] On the other hand, when the thrust load F1 acting on the first main body portion 61c through the air film 80 exceeds a predetermined value, the first main body portions 812a-812f come into contact with the second main body portions 815a-815f, respectively, as shown in Fig. 12. Furthermore, the bump foils 32a-32f come into contact with the second main body portions 815a-815f from the side opposite to the first main body portions 812a-812f. Thus, in this thrust foil bearing 70 as well, the bump foils 32a-32f elastically support the top foils 91a-91f from their back surfaces.

[0115] Also, the second top foil plate 82 is formed to have a greater thickness than the first top foil plate 81. In other words, the thickness of the first top foil plate 81, including the first main body portions 812a-812f, is reduced, and the first main body portions 812a-812f are more likely to elastically deform. For this reason, in the thrust foil bearing 70, even if the first main body portion 812b extends higher toward the thrust collar 24d than the other first main body portions 812a, 812c-812f, the state in which the thrust load F1 acts preferentially on the first main body portion 812b and, by extension, the top foil 91b during low load can be reduced as much as possible.

[0116] Then, under high load, the second main body portions 815a-815f come into contact with the first main body portions 812a-812f, thereby ensuring the rigidity of each of the top foils 91a-91f. Thus, the turbo compressor 10 of the second embodiment including the thrust foil bearing 70 can achieve the same effect as the turbo compressor 10 of the first embodiment including the thrust foil bearing 30.

[0117] In particular, in the thrust foil bearing 70, the first frame portion 811, the first main body portions 812a to 812f, and the first bridge portions 813a to 813f are integrally formed with the first top foil plate 81. Also, the second frame portion 814, the second main body portions 815a to 815f, and the second bridge portions 816a to 816f are integrally formed with the second top foil plate 82. Therefore, by overlapping the first top foil plate 81 and the second top foil plate 82 in the direction of the drive axis O, it is easy to position the first frame portion 811 and the second frame portion 814, the first main body portions 812a to 812f and the second main body portions 815a to 815f, and the first bridge portions 813a to 813f and the second bridge portions 816a to 816f. This makes it easier to manufacture the thrust foil bearing 70.

[0118] In the above, the present invention has been described based on Examples 1 and 2. However, the present invention is not limited to the above Examples 1 and 2, and it goes without saying that the present invention can be modified as appropriate without departing from the spirit of the present invention.

[0119] For example, in the turbo compressor 10 of the first embodiment, the thrust foil bearing 30 has the first to sixth top foils 33a to 33f and the first to sixth bump foils 32a to 32f. However, this is not limited thereto, and the thrust foil bearing 30 may be formed by omitting the third to sixth top foils 33c to 33f and the third to sixth bump foils 32c to 32f. Also, the thrust foil bearing 30 may further have a top foil in addition to the first to sixth top foils 33a to 33f. In this case, the thrust foil bearing 30 may have a bump foil in addition to the first to sixth bump foils 32a to 32f. The same applies to the thrust foil bearing 70 in the turbo compressor 10 of the second embodiment.

[0120] In addition, in the thrust foil bearing 70 of the turbo compressor 10 of Example 2, a single bump foil plate on which each of the bump foils 32a to 32f is formed may be adopted, and the first and second top foil plates 81, 82 and the bump foil plate may be stacked in the direction of the drive shaft center O and fixed to the base 31 by a fixing pin 83.

[0121] In the turbo compressor 10 of the first and second embodiments, a part of the second top foil plate 16 serves as the base 31 of the thrust foil bearing 30 located in front of the thrust collar 24d, and a part of the bottom surface 15d of the recess 15c serves as the base 31 of the thrust foil bearing 30 located behind the thrust collar 24d. However, this is not limiting, and both bases 31 may be formed of dedicated members.

[0122] In the turbo compressor 10 of the first embodiment, each first top foil 61 is formed with a first restricting portion 61a, a first connecting portion 61b, and a first main body portion 61c. However, this is not limited thereto, and the first connecting portion 61b may be omitted, and the first main body portion 61c may be directly connected to the first restricting portion 61a. Similarly, each second top foil 63 may be formed with the second connecting portion 63b omitted, and the second main body portion 63c may be directly connected to the second restricting portion 63a.

[0123] Furthermore, in the turbo compressor 10 of the first embodiment, the first connection portion 61b and the first main body portion 61c of the first top foil 61, and the second connection portion 63b and the second main body portion 63c of the second top foil 63 are separated from each other when the thrust load F1 acting on each first main body portion 61c via the air film 80 is equal to or less than a predetermined value. However, this is not limiting, and a configuration may be used in which only the first main body portion 61c and the second main body portion 63c are separated from each other when the thrust load F1 is equal to or less than a predetermined value, including when the drive shaft 24a is not rotating.

[0124] In the turbo compressor 10 of the first embodiment, both the first top foil 61 and the second top foil 63 are made of stainless steel plate material, and the plate thickness of the second top foil 63 is made thicker than the plate thickness of the first top foil 61. However, this is not limited thereto, and the plate thickness of the first top foil 61 and the plate thickness of the second top foil 63 may be made equal to each other, and the first top foil 61 may be made of a material having a lower rigidity than the second top foil 63. In addition to forming the first top foil 61 from a material having a lower rigidity than the second top foil 63, the plate thickness of the second top foil 63 may be made thicker than the plate thickness of the first top foil 61. The same applies to the first top foil plate 81 and the second top foil plate 82 in the turbo compressor 10 of the second embodiment.

[0125] In the first and second embodiments, the turbo compressor 10 is defined as the "fluid machine" of the present invention. However, the present invention is not limited to this and any compressor that compresses a refrigerant may be defined as the "fluid machine" of the present invention. [Industrial Applicability]

[0126] The present invention can be used in an air compressor or the like used in a fuel cell system. [Explanation of symbols]

[0127] 10...Turbo compressor (fluid machinery) 11. Housing 24a…Drive shaft 24d…Thrust collar 25…First impeller (actuator) 30, 70...Thrust foil bearing 31...Bass 32a~32f…Bump foil 33a~33f…Top foil 61…1st Top Foil 61a…First Regulatory Section 61c…First body part 63…2nd Top Foil 63a…Second Regulatory Section 63c…Second body part 80...Air membrane 81…First top foil plate (First top foil) 82…Second top foil plate (Second top foil) 811...First frame portion (first restriction portion) 812a to 812f: First main body part 814...Second frame portion (second restriction portion) 815a to 815f: Second main body part F1: Thrust load O…Drive shaft center

Claims

1. A fluid machine comprising: a drive shaft rotatable about a drive axis; a working body that compresses a fluid while being rotated by the drive shaft; a thrust foil bearing that supports a thrust load generated by operation of the working body; and a housing that accommodates the drive shaft, the working body, and the thrust foil bearing, The drive shaft is provided with a thrust collar that is rotatable integrally with the drive shaft, the thrust foil bearing includes a base through which the drive shaft is inserted, a plurality of top foils whose circumferential rotation with respect to the base is restricted, and a plurality of bump foils each disposed between the top foils and the base in the drive shaft direction while being restricted in the circumferential rotation with respect to the base, Each of the top foils includes a first top foil facing the thrust collar in the drive shaft direction; a second top foil disposed between the first top foil and the bump foil in the drive axial direction; The first top foil is provided with a first restricting portion that restricts rotation in the circumferential direction relative to the base, and a first main body portion that is connected to the first restricting portion and forms an air film between the first main body portion and the thrust collar by rotation of the drive shaft. The second top foil is formed with a second restricting portion that restricts rotation in the circumferential direction relative to the base, and a second main body portion that is connected to the second restricting portion, the second body portion extends from a position closest to the first body portion toward the first body portion at a height lower than that of the first body portion; The first body portion and the second body portion are separated from each other when the drive shaft is not rotating and when the thrust load acting on the first body portion through the air film is equal to or less than a predetermined value, and abut each other when the thrust load exceeds the predetermined value.

2. The fluid machine according to claim 1 , wherein the second top foil has a rigidity higher than that of the first top foil.

3. the second top foil and the first top foil are made of the same metal plate, The fluid machine according to claim 2 , wherein the second top foil has a thickness greater than a thickness of the first top foil.

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