Bearing structure and fluid machinery

Abstract

This bearing structure includes a rotation axis, a thrust collar, and a first thrust bearing. The rotation axis has a central axis. The thrust collar is attached to the rotation axis. The first thrust bearing includes a first dynamic pressure generation mechanism. The first dynamic pressure generation mechanism is opposed to the thrust collar. When the length from the central axis to a peripheral edge of the thrust collar is defined as Rt and the length from the central axis to a peripheral edge of the first dynamic pressure generation mechanism is defined as Rf1, the relation Rt > Rf1 is satisfied.

Description

[Technical field]

[0001] The present disclosure relates to a bearing structure and a fluid machine. [Background technology]

[0002] In a rotating body, a load is generated in the axial direction of the rotating shaft. A thrust bearing is known as a bearing that supports the axial load. Patent Document 1 discloses a bearing structure including a thrust bearing. FIG. 1 shows the bearing structure of Patent Document 1.

[0003] 1 includes a rotating shaft 101, a thrust collar 104, a first thrust bearing 103A, and a second thrust bearing 103B. The thrust collar 104 is attached to the rotating shaft 101. The thrust collar 104 is disposed between the thrust bearings 103A and 103B.

[0004] When the rotating shaft 101 rotates at high speed, an axial load is generated on the rotating shaft 101. On the other hand, when the rotating shaft 101 rotates at high speed, the thrust collar 104 also rotates at high speed. This generates dynamic pressure between the thrust collar 104 and the thrust bearing 103A. Dynamic pressure is also generated between the thrust collar 104 and the thrust bearing 103B.

[0005] The axial load acts to move the thrust collar 104 closer to the first thrust bearing 103A or the second thrust bearing 103B. However, a repulsive force against this force is generated by the dynamic pressure. In this way, the rotating shaft is supported without contact in a bearing structure that utilizes dynamic pressure. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2014 / 061698 Summary of the Invention [Problem to be solved by the invention]

[0007] The axial load that a thrust bearing can support is sometimes called its load capacity. If an axial load is applied that exceeds the load capacity, the thrust collar may come into physical contact with the thrust bearing, causing the thrust bearing to fail.

[0008] The present disclosure provides techniques suitable for obtaining high load capacities. [Means for solving the problem]

[0009] The present disclosure relates to A rotating shaft having a central axis; A thrust collar attached to the rotating shaft; a first thrust bearing including a first dynamic pressure generating mechanism facing the thrust collar; Equipped with a length from the central axis to an outer circumferential end of the thrust collar is defined as Rt, and a length from the central axis to an outer circumferential end of the first dynamic pressure generating mechanism is defined as Rf1, the relationship of Rt>Rf1 is satisfied. A bearing structure is provided. Effect of the Invention

[0010] The techniques disclosed herein are suitable for achieving high load capacities. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional view of a prior art bearing structure. [Diagram 2] FIG. 2 is a configuration diagram of a fluid machine. [Diagram 3] FIG. 3 is a cross-sectional view of the bearing structure. [Figure 4] FIG. 4 is a cross-sectional view of the bearing structure. [Diagram 5] FIG. 5 is a cross-sectional view of the bearing structure. [Figure 6] FIG. 6 is a cross-sectional view of the bearing structure. [Figure 7] FIG. 7 is a cross-sectional view of the bearing structure. [Figure 8] FIG. 8 is a plan view of the bearing structure. [Figure 9] FIG. 9 is an enlarged cross-sectional view of the bearing structure. [Figure 10] FIG. 10 is a cross-sectional view of the bearing structure. [Figure 11A] FIG. 11A is an explanatory diagram of the mechanism. [Figure 11B] FIG. 11B is an explanatory diagram of the mechanism. [Figure 11C] FIG. 11C is an explanatory diagram of the mechanism. [Figure 12] FIG. 12 is a diagram showing the simulation results. [Figure 13] FIG. 13 is a diagram showing the simulation results. [Figure 14] FIG. 14 is a diagram showing the simulation results. [Figure 15] FIG. 15 is a diagram showing the simulation results. [Figure 16] FIG. 16 is a diagram showing the simulation results. [Figure 17] FIG. 17 is a diagram showing the simulation results. [Figure 18] FIG. 18 is an explanatory diagram of the dynamic pressure generating mechanism. [Figure 19A] FIG. 19A is a plan view of the dynamic pressure generating mechanism. [Figure 19B] FIG. 19B is a cross-sectional view of the dynamic pressure generating mechanism. [Figure 20] FIG. 20 is a plan view of the dynamic pressure generating mechanism. [Figure 21] FIG. 21 is a cross-sectional view of a thrust collar. [Figure 22] FIG. 22 is a cross-sectional view of the bearing structure. [Diagram 23] FIG. 23 is a cross-sectional view of the bearing structure. [Figure 24] FIG. 24 is a cross-sectional view of the bearing structure. [Diagram 25] FIG. 25 is a cross-sectional view of the bearing structure. [Figure 26] FIG. 26 is an explanatory diagram of the flow of the working fluid. [Figure 27] FIG. 27 is an explanatory diagram of the flow of the working fluid. [Figure 28] FIG. 28 is an explanatory diagram of the flow of the working fluid. [Figure 29] FIG. 29 is an explanatory diagram of the flow of the working fluid. [Diagram 30] FIG. 30 is an explanatory diagram of the flow of the working fluid. [Diagram 31] FIG. 31 is an explanatory diagram of the flow of the working fluid. [Diagram 32] FIG. 32 is an explanatory diagram of the axial displacement of the compressor. [Diagram 33] FIG. 33 is an enlarged cross-sectional view of the bearing structure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] (Summary of one aspect of the present disclosure) The bearing structure according to the first aspect of the present disclosure includes: A rotating shaft having a central axis; A thrust collar attached to the rotating shaft; a first thrust bearing including a first dynamic pressure generating mechanism facing the thrust collar; Equipped with When the length from the central axis to the outer circumferential end of the thrust collar is defined as Rt, and the length from the central axis to the outer circumferential end of the first dynamic pressure generating mechanism is defined as Rf1, the relationship Rt>Rf1 is satisfied.

[0013] The first embodiment is suitable for obtaining a large load capacity.

[0014] In a second aspect of the present disclosure, for example, in the bearing structure according to the first aspect, The first thrust bearing may include a first stage and a first base, The first stage may extend from the first base toward the thrust collar. The first dynamic pressure generating mechanism may be provided in the first stage, When defining the length from the central axis to the outer peripheral end of the first stage as Rs1 and the length from the central axis to the outer peripheral end of the first base as Rb1, the relationship Rs1 < Rb1 may be satisfied.

[0015] The first stage of the second aspect can contribute to obtaining a large load capacity.

[0016] In the third aspect of the present disclosure, for example, in the bearing structure according to the first aspect or the second aspect, the first thrust bearing may include the first stage, the first hydrodynamic generation mechanism may be provided on the first stage, When defining the length from the central axis to the outer peripheral end of the first stage as Rs1, the relationship Rs1 < Rt may be satisfied.

[0017] The third aspect is suitable for obtaining a large load capacity.

[0018] In the fourth aspect of the present disclosure, for example, in the bearing structure according to any one of the first to third aspects, the thrust collar may have a first opposing plane that faces the first hydrodynamic generation mechanism and extends in a direction orthogonal to the central axis, When defining the length from the central axis to the outer peripheral end of the first opposing plane as Ro1, the relationship Ro1 > Rf1 may be satisfied.

[0019] The fourth aspect is suitable for obtaining a large load capacity.

[0020] In the fifth aspect of the present disclosure, for example, in the bearing structure according to any one of the first to fourth aspects, the first thrust bearing may include the first stage, the first hydrodynamic generation mechanism may be provided on the first stage, When defining the length from the central axis to the outer peripheral end of the first stage as Rs1, the relationship Rs1 > Rf1 may be satisfied.

[0021] The fifth aspect is suitable for obtaining a large load capacity.

[0022] In the sixth aspect of the present disclosure, for example, in the bearing structure according to any one of the first to fifth aspects, the first thrust bearing may include a first stage, the first hydrodynamic generation mechanism may be provided on the first stage, when the direction in which the central axis extends is defined as the axial direction, the dimension of the first hydrodynamic generation mechanism in the axial direction is defined as Tf1, and the dimension of the first stage in the axial direction is defined as Ts1, the relationship of Tf1 < Ts1 may be satisfied.

[0023] The sixth aspect is suitable for obtaining a large load capacity.

[0024] In the seventh aspect of the present disclosure, for example, in the bearing structure according to any one of the first to sixth aspects, the first thrust bearing may include a first stage and a first convex portion, the first hydrodynamic generation mechanism may be provided on the first stage, the first convex portion may extend from the first stage toward the thrust collar, when observed along the central axis, the first convex portion may be on the outer peripheral side of the first hydrodynamic generation mechanism.

[0025] The seventh aspect is suitable for obtaining a large load capacity.

[0026] In the eighth aspect of the present disclosure, for example, the bearing structure according to the seventh aspect, when the direction in which the central axis extends is defined as the axial direction, the dimension of the first convex portion in the axial direction is defined as Tp1, and the dimension of the first hydrodynamic generation mechanism in the axial direction is defined as Tf1, the relationship of Tf1 > Tp1 may be satisfied.

[0027] According to the eighth aspect, it is difficult for the first convex portion to contact the thrust collar.

[0028] In a ninth aspect of the present disclosure, for example, in the bearing structure according to any one of the first to sixth aspects, The first thrust bearing may have a first recess. The first dynamic pressure generating mechanism may be provided in the first recess.

[0029] The ninth embodiment is suitable for obtaining a large load capacity.

[0030] In a tenth aspect of the present disclosure, for example, the bearing structure according to the ninth aspect is When the direction in which the central axis extends is defined as the axial direction, the dimension of the first recess in the axial direction is defined as Tg1, and the dimension of the first dynamic pressure generating mechanism in the axial direction is defined as Tf1, the relationship Tf1>Tg1 may be satisfied.

[0031] According to the tenth aspect, the portion surrounding the first recess is less likely to come into contact with the thrust collar.

[0032] In an eleventh aspect of the present disclosure, for example, in the bearing structure according to any one of the first to tenth aspects, The first dynamic pressure generating mechanism may include a plurality of foil pieces, The plurality of foil pieces may be arranged in an annular shape so as to surround the rotation shaft, Adjacent foil pieces of the plurality of foil pieces may partially overlap each other.

[0033] The first dynamic pressure generating mechanism of the eleventh aspect is a specific example of the first dynamic pressure generating mechanism.

[0034] In a twelfth aspect of the present disclosure, for example, in the bearing structure according to any one of the first to eleventh aspects, The thrust collar may be plane-symmetric with respect to a reference plane perpendicular to the central axis.

[0035] The twelfth aspect is suitable for preventing the thrust collar from flexing during rotation.

[0036] In a thirteenth aspect of the present disclosure, for example, the bearing structure according to the twelfth aspect is The thrust collar may include a disk portion, a first hub portion, and a second hub portion, The first hub portion and the second hub portion may sandwich the disk portion in an axial direction along which the central axis extends, The first hub portion and the second hub portion may be plane-symmetric with respect to the reference plane.

[0037] The thirteenth aspect is suitable for preventing the thrust collar from flexing during rotation.

[0038] In a fourteenth aspect of the present disclosure, for example, the bearing structure according to any one of the first to thirteenth aspects may include:

[0023] The device may include a casing, An enclosure may be provided that includes the casing and the first thrust bearing; The enclosure may have an interior space; In the internal space, the first dynamic pressure generating mechanism may face the thrust collar, The enclosure may have a first through hole and a second through hole communicating with the interior space.

[0039] According to the fourteenth aspect, the working fluid can be made to flow into the internal space through the first through hole, and the working fluid can be made to flow out from the internal space through the second through hole, thereby making it possible to prevent the temperature of the thrust collar, etc. from becoming excessively high.

[0040] In a fifteenth aspect of the present disclosure, for example, the bearing structure according to the fourteenth aspect is It may include a heat exchanger, The heat exchanger may divide the internal space into a first space and a second space, In the first space, the first dynamic pressure generating mechanism may face the thrust collar, The first through hole and the second through hole may communicate with the second space.

[0041] In the fifteenth aspect, it is possible to prevent foreign matter from entering the gap between the first dynamic pressure generating mechanism and the thrust collar, while preventing the temperature of the thrust collar and the like from becoming excessively high.

[0042] A fluid machine according to a sixteenth aspect of the present disclosure includes: A bearing structure according to any one of the first to fifteenth aspects; A compressor; and an expander, The compressor and the expander may be attached to the rotating shaft.

[0043] According to the sixteenth aspect, a fluid machine making use of the bearing structure according to any one of the first to fifteenth aspects is obtained.

[0044] A fluid machine according to a seventeenth aspect of the present disclosure includes: A bearing structure according to the fourteenth or fifteenth aspect; A compressor; and an expander, The compressor and the expander may be attached to the rotating shaft, A working fluid discharged from the compressor may flow into the internal space through the first through hole.

[0045] According to the seventeenth aspect, it is possible to prevent the temperature of the thrust collar and the like from becoming excessively high due to the working fluid discharged from the compressor and flowing into the internal space through the first through hole.

[0046] In an eighteenth aspect of the present disclosure, for example, in the fluid machine according to the seventeenth aspect, The compressor may be a centrifugal compressor; The centrifugal compressor may include a compressor impeller attached to the rotating shaft, When observed along the central axis, the first through hole may be located on the outer circumferential side relative to an outer circumferential end of the compressor impeller.

[0047] According to the 18th aspect, it is easy to increase the flow rate of the working fluid flowing into the internal space from the first through hole.

[0048] In the 19th aspect of the present disclosure, for example, in the fluid machine according to any one of the 16th to 18th aspects, when the direction in which the central axis extends is defined as the axial direction, the compressor, the thrust collar, and the expander may be provided in this order in the axial direction. When the separation distance between the compressor and the thrust collar in the axial direction is defined as Lct, and the separation distance between the thrust collar and the expander in the axial direction is defined as Lte, the relationship Lct < Lte may be satisfied.

[0049] According to the 19th aspect, it is easy to suppress the displacement of the compressor in the axial direction as the temperature of the rotating shaft changes.

[0050] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments. In particular, unless there is a contradiction, the technologies shown in each drawing can be combined as appropriate. In the following, there may be cases where common descriptions are established for a certain example, embodiment, etc. and subsequent examples, embodiments, etc. In such cases, the common descriptions may be omitted in the subsequent examples, embodiments, etc.

[0051] (Embodiment 1) FIG. 2 shows a bearing structure 50 according to Embodiment 1. The bearing structure 50 includes a rotating shaft 51, a thrust collar 52, and a pair of thrust bearings 10 and 20.

[0052] The bearing structure 50 can be adopted in a fluid machine that uses a working fluid. The working fluid is typically a compressible fluid. Also, the working fluid is typically a gas. Specific examples of the working fluid are air, fluorine-based refrigerant, nitrogen (N), neon (Ne), argon (Ar), helium (He), and the like. Here, the fluorine-based refrigerant refers to a refrigerant containing a component containing a fluorine atom.

[0053] The bearing structure 50 can be applied to various systems. In the example of Fig. 2, the bearing structure 50 is applied to a fluid machine 80. The fluid machine 80 to which the bearing structure 50 is applied will be described in detail later.

[0054] (Configuration of bearing structure 50) Fig. 3 is a schematic diagram for explaining a bearing structure 50. The bearing structure 50 may include elements not shown in Fig. 3. For example, the bearing structure 50 may include a first seal portion that prevents the working fluid from passing through a gap between the rotating shaft 51 and the thrust bearing 10. The bearing structure 50 may also include a second seal portion that prevents the working fluid from passing through a gap between the rotating shaft 51 and the thrust bearing 20.

[0055] 3, the rotating shaft 51 has a central axis 51c. Components such as a compressor impeller, a turbine wheel, and the like can be attached to the rotating shaft 51. In this way, a compressor and / or an expander can be realized in the fluid machinery in which the bearing structure 50 is adopted.

[0056] The thrust collar 52 is attached to the rotating shaft 51. The thrust collar 52 rotates together with the rotating shaft 51.

[0057] In the present embodiment, thrust collar 52 extends in radial direction 42. Thrust collar 52 is disk-shaped. Specifically, when observed along axial direction 41, thrust collar 52 has a circular shape. Thrust collar 52 is disposed coaxially with rotation shaft 51.

[0058] Here, the axial direction 41 is the direction in which the central axis 51c extends. The radial direction 42 is the radial direction of the rotation shaft 51. The axial direction 41 and the radial direction 42 are perpendicular to each other. Hereinafter, the outside of the radial direction 42 may be referred to as the outer circumferential side, and the inside of the radial direction 42 may be referred to as the inner circumferential side. In addition, below, the term circumferential direction 43 may be used. The circumferential direction 43 is the direction surrounding the central axis 51c.

[0059] The thrust collar 52 has a first opposing flat surface 52x and a second opposing flat surface 52y. The flat surfaces 52x and 52y are provided on opposite sides of the thrust collar 52 in the axial direction 41.

[0060] The first opposing flat surface 52x faces the first dynamic pressure generating mechanism 11. The first opposing flat surface 52x extends in a direction perpendicular to the central axis 51c of the rotation shaft 51.

[0061] The second opposing flat surface 52y faces the second dynamic pressure generating mechanism 21. The second opposing flat surface 52y extends in a direction perpendicular to the central axis 51c of the rotation shaft 51.

[0062] In reality, the dimensions, angles, etc. of the elements in the bearing structure 50 may have errors within the tolerance range with respect to the design values. Dimensions, angles, etc. that deviate within the tolerance range from the dimensions, angles, etc. described in this embodiment are considered to be the same as the dimensions, angles, etc. described in this embodiment. For example, a plane that extends in a direction substantially perpendicular to the rotation axis but deviates from the perpendicular direction within the tolerance range may correspond to the first opposing plane 52x. Also, such a plane may correspond to the second opposing plane 52y.

[0063] The pair of thrust bearings 10 and 20 are arranged on both sides of the thrust collar 52 in the axial direction 41 of the rotating shaft 51. The pair of thrust bearings 10 and 20 includes a first thrust bearing 10 and a second thrust bearing 20. In this embodiment, the thrust bearings 10 and 20 are gas bearings. Specifically, the thrust bearings 10 and 20 are dynamic pressure gas bearings.

[0064] The first thrust bearing 10 includes a first dynamic pressure generating mechanism 11 and a first base 14. The second thrust bearing 20 includes a second dynamic pressure generating mechanism 21 and a second base 24.

[0065] The first base body 14 includes a first stage 14a and a first base 14b. The first stage 14a extends from the first base 14b toward the thrust collar 52.

[0066] The second base body 24 includes a second stage 24a and a second base 24b. The second stage 24a extends from the second base 24b toward the thrust collar 52.

[0067] The first dynamic pressure generating mechanism 11 faces the thrust collar 52. The first dynamic pressure generating mechanism 11 is provided on the first base 14. Specifically, the first dynamic pressure generating mechanism 11 is provided on the first stage 14a.

[0068] The second dynamic pressure generating mechanism 21 faces the thrust collar 52. The second dynamic pressure generating mechanism 21 is provided on the second base 24. Specifically, the second dynamic pressure generating mechanism 21 is provided on the second stage 24a.

[0069] The dynamic pressure generating mechanisms 11 and 21 generate dynamic pressure. In the bearing structure 50, the dynamic pressure generated by the dynamic pressure generating mechanisms 11 and 21 is used to support the rotating shaft 51 in a non-contact manner.

[0070] Specifically, the rotating shaft 51 rotates at high speed in a state in which a gap 19 is formed between the first dynamic pressure generating mechanism 11 and the thrust collar 52. When the rotating shaft 51 rotates at high speed, the thrust collar 52 also rotates at high speed. As a result, dynamic pressure is generated in the gap 19.

[0071] Furthermore, the rotating shaft 51 rotates at high speed with a gap 29 formed between the second dynamic pressure generating mechanism 21 and the thrust collar 52. When the rotating shaft 51 rotates at high speed, the thrust collar 52 also rotates at high speed. This generates dynamic pressure in the gap 29.

[0072] The following provides a further description of the bearing structure 50. In the following description, the terms length Rt, length Ro1, length Ro2, length Rf1, length Rf2, length Rs1, length Rs2, length Rb1, length Rb2, dimension Tf1, dimension Tf2, dimension Ts1, and dimension Ts2 may be used.

[0073] The length Rt is the length from the central axis 51c of the rotating shaft 51 to the outer circumferential end of the thrust collar 52. The length Ro1 is the length from the central axis 51c to the outer circumferential end of the first opposing flat surface 52x. The length Ro2 is the length from the central axis 51c to the outer circumferential end of the second opposing flat surface 52y.

[0074] The length Rf1 is the length from the central axis 51c of the rotating shaft 51 to the outer circumferential end of the first dynamic pressure generating mechanism 11. The length Rf2 is the length from the central axis 51c to the outer circumferential end of the second dynamic pressure generating mechanism .

[0075] The length Rs1 is the length from the central axis 51c of the rotating shaft 51 to the outer circumferential end of the first stage 14a. The length Rs2 is the length from the central axis 51c to the outer circumferential end of the second stage 24a.

[0076] The length Rb1 is the length from the central axis 51c of the rotating shaft 51 to the outer circumferential end of the first base 14b. The length Rb2 is the length from the central axis 51c to the outer circumferential end of the second base 24b.

[0077] The dimension Tf1 is the dimension of the first dynamic pressure generating mechanism 11 in the axial direction 41. The dimension Tf2 is the dimension of the second dynamic pressure generating mechanism 21 in the axial direction 41.

[0078] Dimension Ts1 is the dimension of the first stage 14a in the axial direction 41. Dimension Ts2 is the dimension of the second stage 24a in the axial direction 41. Hereinafter, dimension Ts1 may be referred to as height Ts1. Dimension Ts2 may be referred to as height Ts2.

[0079] As can be seen from Fig. 3, in the bearing structure 50, the relationship Rt>Rf1 is satisfied. Also, the relationship Rt>Rf2 is satisfied. Satisfying these relationships is suitable for obtaining a large load capacity. In this context, the load capacity refers to the axial load that the thrust bearing can support.

[0080] For example, 0 < Rt - Rf1 < 1000 μm. Also, 0 < Rt - Rf2 < 1000 μm. In one specific example, 250 μm < Rt - Rf1 < 750 μm. Also, 250 μm < Rt - Rf2 < 750 μm.

[0081] In the present embodiment, the relationship Rs1 < Rb1 is satisfied. When this relationship holds, the presence of the first stage 14a can contribute to obtaining a large load capacity. Also, in the present embodiment, the relationship Rs2 < Rb2 is satisfied.

[0082] In the present embodiment, the relationship Rs1 < Rt is satisfied. Also, the relationship Rs2 < Rt is satisfied. The satisfaction of these relationships is suitable for obtaining a large load capacity.

[0083] However, Rt may be equal to Rs1. Rt may be equal to Rs2.

[0084] Specifically, Rt - 600 μm < Rs1 ≤ Rt may be satisfied. Rt - 600 μm < Rs2 ≤ Rt may be satisfied. More specifically, Rt - 300 μm < Rs1 ≤ Rt may be satisfied. Rt - 300 μm < Rs2 ≤ Rt may be satisfied.

[0085] In the present embodiment, the relationship Ro1 > Rf1 is satisfied. Also, the relationship Ro2 > Rf2 is satisfied. The satisfaction of these relationships is suitable for obtaining a large load capacity.

[0086] Ro1 > Rf1 and Ro2 > Rf2 will be further described with reference to FIGS. 4 to 6. The examples in FIGS. 4 to 6 are included in the present disclosure.

[0087] Figure 4 shows the same bearing structure 50 as in Figure 3. In the example of Figure 4, the surface of the thrust collar 52 facing the first hydrodynamic generation mechanism 11 is perpendicular to the central axis 51c up to its outer peripheral end. Therefore, Ro1 = Rt. Also, the surface of the thrust collar 52 facing the second hydrodynamic generation mechanism 21 is perpendicular to the central axis 51c up to its outer peripheral end. Therefore, Ro2 = Rt. In the example of Figure 4, Rt > Rf1, Rt > Rf2, Ro1 > Rf1, and Ro2 > Rf2 hold.

[0088] The example of Figure 5 is a modification of the thrust collar 52 in the example of Figure 4. Specifically, in the example of Figure 5, the outer peripheral end of the thrust collar 52 is chamfered. Therefore, Ro1 ≠ Rt and Ro2 ≠ Rt. In the example of Figure 5, the chamfered area is large. Therefore, Rt > Rf1 and Rt > Rf2 hold, but neither Ro1 > Rf1 nor Ro2 > Rf2 holds.

[0089] The example of Figure 6 is a modification of the thrust collar 52 in the example of Figure 4. Also in the example of Figure 6, the outer peripheral end of the thrust collar 52 is chamfered. Therefore, Ro1 ≠ Rt and Ro2 ≠ Rt. However, in the example of Figure 6, the chamfered area is small. Therefore, although the outer peripheral end of the thrust collar 52 is chamfered, Rt > Rf1, Rt > Rf2, Ro1 > Rf1, and Ro2 > Rf2 hold.

[0090] According to the chamfering as in Figures 5 and 6, it becomes difficult for the thrust collar 52 to contact the thrust bearings 10 and 20. Further, if it is as in Figure 6, while obtaining this effect by chamfering, Rt > Rf1, Rt > Rf2, Ro1 > Rf1, and Ro2 > Rf2 can be made to hold.

[0091] In the examples of Figure 4 and Figure 6, any of the relationships Rs1 < Rt, Rs2 < Rt, Rs1 < Ro1, and Rs2 < Ro2 are satisfied. In the example of Figure 5, the relationships Rs1 < Rt and Rs2 < Rt are both satisfied, but neither of the relationships Rs1 < Ro1 and Rs2 < Ro2 are satisfied.

[0092] Returning to FIG. 3, in the present embodiment, the relationship Rs1 > Rf1 is satisfied. Also, the relationship Rs2 > Rf2 is satisfied. By doing so, it is easy to suppress the decrease in the static pressure between the first stage 14a and the thrust collar 52. Also, it is easy to suppress the decrease in the static pressure between the second stage 24a and the thrust collar 52. This is suitable for obtaining a large load capacity.

[0093] In the present embodiment, the relationship Tf1 < Ts1 is satisfied. Also, the relationship Tf2 < Ts2 is satisfied. By doing so, it is easy to secure Ts1 and Ts2. Therefore, it is easy to suppress the flow of the working fluid between the gap 19 and the space on the first base 14b, and it is easy to suppress the decrease in the static pressure between the first stage 14a and the thrust collar 52. Also, it is easy to suppress the flow of the working fluid between the gap 29 and the space on the second base 24b, and it is easy to suppress the decrease in the static pressure between the second stage 24a and the thrust collar 52. This is suitable for obtaining a large load capacity. Note that the space on the first base 14b in this context corresponds to the free space FS described later.

[0094] For example, Ts1 > 500 μm. Also, Ts2 > 500 μm. For example, Ts1 < 2000 μm. Also, Ts2 < 2000 μm.

[0095] In the present embodiment, in the supporting state where the thrust bearing 10 supports the rotating shaft 51 that rotates, at the outer peripheral end of the first stage 14a, the dimension Ts1 is larger than the separation width between the first stage 14a and the thrust collar 52 in the axial direction 41. Similarly, in the supporting state where the thrust bearing 20 supports the rotating shaft 51 that rotates, at the outer peripheral end of the second stage 14b, the dimension Ts2 is larger than the separation width between the second stage 14b and the thrust collar 52 in the axial direction 41.

[0096] Examples shown in Figures 7 to 9 may also be employed. The examples in Figures 7 to 9 are obtained by adding a first convex portion 17 and a second convex portion 27 to the example in Figure 4. Note that Figure 8 is used to explain the first convex portion 17 and the second convex portion 27, but this does not necessarily mean that the first convex portion 17 and the second convex portion 27 have the same dimensions, shape, etc.

[0097] In the examples of Figs. 7 to 9, the first thrust bearing 10 includes a first protruding portion 17. The first protruding portion 17 protrudes from the first stage 14a toward the thrust collar 52. When observed along the central axis 51c, the first protruding portion 17 is located on the outer periphery side of the first dynamic pressure generating mechanism 11. This narrows the path of the working fluid between the gap 19 and the space above the first base 14b. This makes it easier to suppress the flow from the gap 19 to the space above the first base 14b and to suppress the drop in static pressure between the first stage 14a and the thrust collar 52. This is suitable for obtaining a large load capacity.

[0098] Here, the dimension of the first convex portion 17 in the axial direction 41 is defined as Tp1. In this case, in a typical example, the relationship Tf1>Tp1 is satisfied, as shown in Figs. 7 and 9. Therefore, the first convex portion 17 is farther away from the thrust collar 52 in the axial direction 41 than the first dynamic pressure generating mechanism 11. In this way, the first convex portion 17 is less likely to come into contact with the thrust collar 52. Note that hereinafter, the dimension Tp1 may be referred to as height Tp1.

[0099] In a typical example, when observed along the central axis 51c, the first protrusion 17 is spaced apart from the first dynamic pressure generating mechanism 11. This makes it easy to install the first dynamic pressure generating mechanism 11. The width of this space is, for example, not less than 100 μm and not more than 500 μm.

[0100] However, when observed along the central axis 51c, the first protrusion 17 may be in contact with the first dynamic pressure generating mechanism 11. In this way, a large load capacity is easily obtained.

[0101] 8, when observed along the central axis 51c, the first convex portion 17 has a frame shape surrounding the first dynamic pressure generating mechanism 11. Specifically, this frame shape is annular.

[0102] 9, the first convex portion 17 has a first inner circumferential surface 17i. The first inner circumferential surface 17i extends in the axial direction 41. In this manner, the first convex portion 17 can satisfactorily suppress the static pressure drop. In the example of FIG. 9, when observed along the central axis 51c, the first inner circumferential surface 17i is located on the outer circumferential side of the outer circumferential end of the first dynamic pressure generating mechanism 11 and on the inner circumferential side of the outer circumferential end of the thrust collar 52.

[0103] The height Tp1 is, for example, 10 μm or more. The height Tp1 is, for example, ⅓ or more of the dimension Tf1. The height Tp1 is, for example, ⅔ or less of the dimension Tf1.

[0104] 7 to 9, the second thrust bearing 20 includes a second convex portion 27. The second convex portion 27 protrudes from the second stage 24a toward the thrust collar 52. When observed along the central axis 51c, the second convex portion 27 is located on the outer circumferential side of the second dynamic pressure generating mechanism 21.

[0105] Here, the dimension of the second convex portion 27 in the axial direction 41 is defined as Tp2. In this case, in a typical example, the relationship Tp2>Tp2 is satisfied, as shown in Figs. 7 and 9. Therefore, the second convex portion 27 is farther away from the thrust collar 52 in the axial direction 41 than the second dynamic pressure generating mechanism 21. Hereinafter, the dimension Tp2 may be referred to as height Tp2.

[0106] In a typical example, when observed along the central axis 51c, the second convex portion 27 is spaced apart from the second dynamic pressure generating mechanism 21. The width of this space is, for example, not less than 100 μm and not more than 500 μm.

[0107] However, the second protrusion 27 may be in contact with the second dynamic pressure generating mechanism 21 when observed along the central axis 51c.

[0108] 8, when observed along the central axis 51c, the second convex portion 27 has a frame shape surrounding the second dynamic pressure generating mechanism 21. Specifically, this frame shape is annular.

[0109] 9, the second protrusion 27 has a second inner circumferential surface 27i. The second inner circumferential surface 27i expands in the axial direction 41. In the example of FIG. 9, when observed along the central axis 51c, the second inner circumferential surface 27i is located on the outer circumferential side of the outer circumferential end of the second dynamic pressure generating mechanism 21 and on the inner circumferential side of the outer circumferential end of the thrust collar 52.

[0110] The height Tp2 is, for example, 10 μm or more. The height Tp2 is, for example, ⅓ or more of the dimension Tf2. The height Tp2 is, for example, ⅔ or less of the dimension Tf2.

[0111] An example shown in Fig. 10 may also be adopted. In the example of Fig. 10, a first recess 15 and a second recess 25 are formed in the example of Fig. 4 .

[0112] In the example of Fig. 10, the first thrust bearing 10 has a first recess 15. Specifically, the first stage 14a has the first recess 15. The first dynamic pressure generating mechanism 11 is provided in the first recess 15. In this way, the amount of working fluid that flows out in the outer circumferential direction from the gap 19 between the first dynamic pressure generating mechanism 11 and the thrust collar 52 can be suppressed. Therefore, this is suitable for obtaining a large load capacity.

[0113] Here, the dimension of the first recess 15 in the axial direction 41 is defined as Tg1. In this case, in a typical example, the relationship Tf1>Tg1 is satisfied, as shown in FIG. 10. Therefore, the first dynamic pressure generating mechanism 11 protrudes from the first recess 15. In this way, the portion around the first recess 15 is unlikely to come into contact with the thrust collar 52. Note that hereinafter, the dimension Tg1 may be referred to as the depth Tg1.

[0114] The depth Tg1 is, for example, 10 μm or more. The depth Tg1 is, for example, ⅓ or more of the dimension Tf1. The depth Tg1 is, for example, ⅔ or less of the dimension Tf1.

[0115] 10, the second thrust bearing 20 has a second recess 25. Specifically, the second stage 24a has the second recess 25. The second dynamic pressure generating mechanism 21 is provided in the second recess 25.

[0116] Here, the dimension of the second recess 25 in the axial direction 41 is defined as Tg2. In a typical example, the relationship Tg2>Tg2 is satisfied as shown in FIG. 10. Therefore, the second dynamic pressure generating mechanism 21 protrudes from the second recess 25. Note that hereinafter, the dimension Tg2 may be referred to as the depth Tg2.

[0117] The depth Tg2 is, for example, 10 μm or more. The depth Tg2 is, for example, ⅓ or more of the dimension Tf1. The depth Tg2 is, for example, ⅔ or less of the dimension Tf2.

[0118] The present inventors conducted a study focusing on the structure on the outer periphery side of the dynamic pressure generating mechanisms 11 and 21 in order to increase the load capacity of the bearing structure 50. The present inventors considered that the pressure in the gaps 19 and 29 between the dynamic pressure generating mechanisms 11 and 21 and the thrust collar 52 depends on the structure on the outer periphery side of the dynamic pressure generating mechanisms 11 and 21, and actually fabricated the bearing structure 50 having the configuration shown in FIG. 3. The present inventors measured the load capacity of the fabricated bearing structure 50 and confirmed that the load capacity of the bearing structure 50 is increased by adopting the configuration of FIG. 3. The present inventors further verified the mechanism by which the load capacity is increased by using a simulation. This simulation will be described later with reference to FIGS. 12 to 17.

[0119] (Mechanism M) The inventors examined the reason why a large load capacity can be obtained by setting Rt > Rf1 and Rs1 < Rt. Specifically, the inventors assumed that in the bearing structure 50, the following mechanism M works and as a result, a large load capacity can be obtained, and verified it. Hereinafter, the mechanism M will be described with reference to FIGS. 11A to 11C. Note that the description of the mechanism M should not be used for a restrictive interpretation of the present disclosure.

[0120] FIGS. 11A to 11C are schematic diagrams for explaining the mechanism M. In the following description, it is assumed that the working fluid is a gas.

[0121] In FIG. 11A, the boundary portion BP refers to the portion immediately outside the dynamic pressure generation mechanism DPGM. The outer peripheral portion OCP refers to the portion immediately outside the thrust collar TC. The end portion EP refers to the end portion on the thrust bearing TB side in the outer peripheral portion OCP. The gap GP refers to the gap between the dynamic pressure generation mechanism DPGM and the thrust collar TC.

[0122] The mechanism M is such that a decrease in the load capacity due to the suction of gas by the end portion EP is suppressed. Hereinafter, the mechanism M will be further described while comparing FIGS. 11B and 11C. In FIGS. 11B and 11C, it is assumed that the outer peripheral end of the thrust collar TC rotates in the direction toward the front of the paper surface.

[0123] In FIG. 11B, the length from the central axis of the rotating shaft to the outer peripheral end of the thrust collar TC is equal to the length from the central axis of the rotating shaft to the outer peripheral end of the dynamic pressure generation mechanism DPGM. The length from the central axis of the rotating shaft to the outer peripheral end of the base BS is longer than the length from the central axis of the rotating shaft to the outer peripheral end of the thrust collar TC. The dynamic pressure generation mechanism DPGM is provided on the base BS.

[0124] In the situation of Figure 11B, the following phenomena are considered to occur: The thrust collar TC rotates at high speed; the gas in the outer peripheral portion OCP rotates at high speed in the same direction as the thrust collar TC, generating an airflow in the outer peripheral portion OCP; the static pressure at the end portion EP decreases; (b1) gas is sucked from the boundary portion BP to the end portion EP, decreasing the static pressure at the boundary portion BP; and (b2) gas is sucked directly from the gap GP to the end portion EP.

[0125] In contrast, in Fig. 11C, the length from the central axis of the rotating shaft to the outer circumferential end of the thrust collar TC is longer than the length from the central axis of the rotating shaft to the outer circumferential end of the dynamic pressure generating mechanism DPGM. A stage ST is interposed between the base BS and the dynamic pressure generating mechanism DPGM. The length from the central axis of the rotating shaft to the outer circumferential end of the stage ST is shorter than the length from the central axis of the rotating shaft to the outer circumferential end of the thrust collar TC. The dynamic pressure generating mechanism DPGM is provided on the stage ST.

[0126] In the situation of Fig. 11C, the following phenomena are considered to occur: The thrust collar TC rotates at high speed; the gas present in the outer peripheral portion OCP rotates at high speed in the same direction as the thrust collar TC, generating an airflow in the outer peripheral portion OCP; the static pressure of the end portion EP decreases; however, in the case of Fig. 11C, (c1) the end portion EP is away from the dynamic pressure generating mechanism DPGM, so the end portion EP does not directly decrease the static pressure in the boundary portion BP; and (c2) the end portion EP is located on the outer peripheral side of the stage ST, so gas is sucked from the free space FS around the boundary portion BP to the end portion EP, so that the static pressure decreased in the end portion EP is unlikely to propagate to the boundary portion BP.

[0127] The above (b1) and (b2) in the case of FIG. 11B are disadvantageous in terms of obtaining a large load capacity. On the other hand, the above (c1) and (c2) in the case of FIG. 11C are advantageous in terms of obtaining a large load capacity. Note that it is not essential to interpose the stage ST as in FIG. 11C. It is believed that a large load capacity can be obtained based on the above (c1) even without the stage ST.

[0128] In addition, in Fig. 11C, the free space FS functions as a supply source of gas to the end portion EP. For this reason, in Fig. 11C, a decrease in the static pressure of the end portion EP is easily suppressed.

[0129] (simulation) Figures 12 to 17 show the results of two-dimensional simulations using Flowsquare, a thermal fluid simulation software by NORA Scientific. In the simulations of Figures 12 to 17, a constant flow boundary CFB, where the gas flow rate is constant, and an open boundary OB, where the reference pressure P0 is set and gas can pass back and forth, are given. In the simulations of Figures 12 to 17, the components of the bearing structure, including the thrust collar, are stationary, which is different from reality. However, by giving a constant flow boundary CFB, the flow of the working fluid that occurs when the thrust collar is rotating is simulated.

[0130] 12 to 17, the curves show a schematic representation of the change in the static pressure level. In Fig. 12 to 17, the rightward direction may be referred to as the x-direction, and the upward direction may be referred to as the y-direction. The x-direction corresponds to the radial direction 42 toward the outer periphery. The y-direction corresponds to one side of the axial direction 41.

[0131] (Rt>Rf1; Figures 12 and 13) From the simulation results of FIG. 12 and FIG. 13, it can be seen that Rt>Rf1 is suitable for obtaining a large load capacity.

[0132] 12 simulates a situation where Rt=Rf1. More specifically, the x coordinate representing the outer circumferential end of the thrust collar TC is the same as the x coordinate representing the outer circumferential end of the dynamic pressure generating mechanism DPGM.

[0133] In the simulation of FIG. 12, a stationary thrust collar TC, a stationary dynamic pressure generating mechanism DPGM, and a stationary base BS were given in the simulation space. The dynamic pressure generating mechanism DPGM was provided in the base BS. Then, by making the working fluid flow out of the simulation space from the constant flow boundary CFB, a situation was simulated in which the working fluid is sucked from the base BS side to the outer periphery OCP of the thrust collar TC, and the distribution of static pressure in this situation was calculated. The "High" part in FIG. 12 is the part where the calculation result showed that the static pressure was high. The "Low" part is the part where the calculation result showed that the static pressure was low. From such a distribution of static pressure and the action of the constant flow boundary CFB, it can be understood that the flow of the working fluid occurs as shown by the arrows in FIG. 12.

[0134] The simulation in Fig. 13 is different from the simulation in Fig. 12 in that it simulates a situation where Rt>Rf1. Specifically, the x coordinate representing the outer circumferential end of the thrust collar TC is larger than the x coordinate representing the outer circumferential end of the dynamic pressure generating mechanism DPGM.

[0135] In the simulations of Figures 12 and 13, a first reference point RP1 was set on the same coordinates near the outer circumferential end of the dynamic pressure generating mechanism DPGM. In the simulations of Figures 12 and 13, a second reference point RP2 was set on the dynamic pressure generating mechanism DPGM at a position on the inner circumferential side of the first reference point RP1. In terms of the coordinates of the simulation space, the x coordinate of the first reference point RP1 is greater than the x coordinate of the second reference point RP2.

[0136] In the simulations of FIGS. 12 and 13, the static pressure P1 at the first reference point RP1, the static pressure P2 at the second reference point RP2, the difference ΔP1 = P0 - P1 between the reference pressure P0 and the first pressure P1, and the difference ΔP2 = P0 - P2 between the reference pressure P0 and the second pressure P2 were calculated. When ΔP1 in the simulation of FIG. 12 was normalized to 100, ΔP1 in the simulation of FIG. 13 was 70.3. When ΔP2 in the simulation of FIG. 12 was normalized to 100, ΔP2 in the simulation of FIG. 13 was 68.6. This result indicates that when Rt > Rf1, compared with the case of Rt = Rf1, it is easier to suppress the decrease in the static pressure of the portion immediately outside the dynamic pressure generation mechanism, and it is easier to suppress the decrease in the static pressure of the gap between the dynamic pressure generation mechanism and the thrust collar. Therefore, it is easy to obtain a large load capacity.

[0137] (Rs1 < Rb1: FIG. 14) From the simulation results of FIG. 14, it is understood that interposing the first stage 14a between the first base 14b and the first dynamic pressure generation mechanism 11, setting Rs1 < Rb1, and providing the first dynamic pressure generation mechanism 11 in the first stage 14a are suitable for obtaining a large load capacity. Here, as described above, the length Rb1 is the length from the central axis 51c to the outer peripheral end of the first base 14b. The length Rs1 is the length from the central axis 51c to the outer peripheral end of the first stage 14a.

[0138] Specifically, the simulation of FIG. 14 is different from the simulation of FIG. 13 in that a stage ST is interposed between the base BS and the dynamic pressure generation mechanism DPGM. The simulation of FIG. 14 simulates the situation where Rs1 < Rb1. Specifically, the x - coordinate representing the outer peripheral end of the stage ST is smaller than the x - coordinate representing the outer peripheral end of the base BS. Also, the simulation of FIG. 14 simulates the situation where Rt = Rs1. Specifically, the x - coordinate representing the outer peripheral end of the thrust collar TC is the same as the x - coordinate representing the outer peripheral end of the stage ST.

[0139] In the simulation of FIG. 14, the first reference point RP1 and the second reference point RP2 were set on the same coordinates as those in the simulations of FIGS. 12 and 13. Also in the simulation of FIG. 14, the static pressure P1 of the first reference point RP1, the static pressure P2 of the second reference point RP2, the difference ΔP1 = P0 - P1 between the reference pressure P0 and the first pressure P1, and the difference ΔP2 = P0 - P2 between the reference pressure P0 and the second pressure P2 were calculated. When ΔP1 in the simulation of FIG. 12 was normalized to 100, ΔP1 in the simulation of FIG. 14 was 23.6. When ΔP2 in the simulation of FIG. 12 was normalized to 100, ΔP2 in the simulation of FIG. 14 was 21.6. Compared with the simulation of FIG. 13, in the simulation of FIG. 14, ΔP1 and ΔP2 are small. This indicates that interposing the first stage 14a between the first base 14b and the first dynamic pressure generating mechanism 11 and setting Rs1 < Rb1 and providing the first dynamic pressure generating mechanism 11 in the first stage 14a are suitable for suppressing the decrease in the static pressure of the portion immediately outside the dynamic pressure generating mechanism and suppressing the decrease in the static pressure of the gap between the dynamic pressure generating mechanism and the thrust collar, and obtaining a large load capacity.

[0140] From the static pressure distribution shown by the simulation results of FIG. 14, it is understood that the flow of the working fluid indicated by the arrow occurs. By comparing FIGS. 13 and 14, it is understood that due to the presence of the stage ST, the fluid path flowing into the gap GP between the dynamic pressure generating mechanism DPGM and the thrust collar TC expands in the direction of decreasing the x coordinate and increasing the y coordinate. This expansion is presumed to contribute to reducing ΔP1 and ΔP2. Note that the direction of decreasing the x coordinate and increasing the y coordinate corresponds to the direction from the outer peripheral side to the inner peripheral side and from the base BS side to the gap GP.

[0141] (Rs1 < Rt: FIGS. 15 and 16) From the simulation results of FIG. 15, it is understood that setting Rs1 < Rt is suitable for obtaining a large load capacity.

[0142] Specifically, the simulation in FIG. 15 is different from the simulation in FIG. 14 in that the situation where Rs1 < Rt is simulated. More specifically, the simulation in FIG. 15 is different from the simulation in FIG. 14 in that the x - coordinate representing the outer peripheral end of the stage ST is smaller than the x - coordinate representing the outer peripheral end of the thrust collar TC.

[0143] In the simulation of FIG. 15, the first reference point RP1 and the second reference point RP2 were set on the same coordinates as those in the simulations of FIGS. 12 to 14. Also in the simulation of FIG. 15, the static pressure P1 of the first reference point RP1, the static pressure P2 of the second reference point RP2, the difference ΔP1 = P0 - P1 between the reference pressure P0 and the first pressure P1, and the difference ΔP2 = P0 - P2 between the reference pressure P0 and the second pressure P2 were calculated. When ΔP1 in the simulation of FIG. 12 was normalized to 100, ΔP1 in the simulation of FIG. 15 was 22.2. When ΔP2 in the simulation of FIG. 12 was normalized to 100, ΔP2 in the simulation of FIG. 15 was 19.6. Compared with the simulation of FIG. 14, in the simulation of FIG. 15, ΔP1 and ΔP2 are smaller. This result indicates that when Rs1 < Rt, compared with the case of Rt = Rs1, it is easier to suppress the decrease in the static pressure of the portion immediately outside the dynamic pressure generation mechanism, and it is easier to suppress the decrease in the static pressure of the gap between the dynamic pressure generation mechanism and the thrust collar. Therefore, it is easier to obtain a large load capacity.

[0144] When Rs1 < Rt, the following phenomena may occur. Fig. 16 is Fig. 15 with additional notes for explaining the phenomena. As shown in Fig. 16, the explanations in the order of (1), (2), (3), and (4) may hold. Specifically, (1) a static pressure distribution is formed in which the static pressure of the outer peripheral part OCP of the thrust collar TC decreases, making it easy for the flow of the working fluid to the outer peripheral part OCP; (2) accordingly, a flow of the working fluid from the base BS side toward the outer peripheral part OCP, that is, a flow of the working fluid in the substantially y direction, occurs; (3) a part of the working fluid flowing in the substantially y direction collides with the thrust collar TC, increasing the static pressure in the vicinity of the collision part; (4) a part of the outlet of the working fluid from the gap GP between the thrust collar TC and the stage ST to its outer periphery is occupied by the high-pressure part formed in (3) above, preventing the outflow of the working fluid.

[0145] (First convex part 17: Fig. 17) The simulation in Fig. 17 is different from the simulation in Fig. 14 in that the first convex part 17 is simulated. More specifically, the simulation in Fig. 17 has a convex part PP provided.

[0146] In the simulation of FIG. 17, the first reference point RP1 and the second reference point RP2 were set on the same coordinates as those in the simulations of FIG. 12 to FIG. 15. In the simulation of FIG. 17, the static pressure P1 at the first reference point RP1, the static pressure P2 at the second reference point RP2, the difference ΔP1=P0-P1 between the reference pressure P0 and the first pressure P1, and the difference ΔP2=P0-P2 between the reference pressure P0 and the second pressure P2 were also calculated. When ΔP1 in the simulation of FIG. 12 was normalized to 100, ΔP1 in the simulation of FIG. 17 was 17.9. When ΔP2 in the simulation of FIG. 12 was normalized to 100, ΔP2 in the simulation of FIG. 17 was 17.6. Compared to the simulation of FIG. 14, ΔP1 and ΔP2 are smaller in the simulation of FIG. 17. This result shows that when the first convex portion 17 is present, it is easier to suppress the drop in static pressure in the portion immediately outside the dynamic pressure generating mechanism and it is easier to suppress the drop in static pressure in the gap between the dynamic pressure generating mechanism and the thrust collar compared to when the first convex portion 17 is not present, and therefore it is easier to obtain a larger load capacity.

[0147] (Configuration of dynamic pressure generating mechanism) As the dynamic pressure generating mechanisms 11 and 21, various dynamic pressure generating mechanisms can be adopted.

[0148] 4 to 17 will be described with reference to Fig. 18. In the example of Fig. 18, the first dynamic pressure generating mechanism 11 includes a plurality of foil pieces 11f. The plurality of foil pieces 11f are arranged in an annular shape so as to surround the rotation shaft 51. Among the plurality of foil pieces 11f, adjacent foil pieces 11f partially overlap each other.

[0149] In the example of Fig. 18, the foil pieces 11f have protruding portions 11fp. The protruding portions 11fp of one foil piece 11f overlap one another. This overlap is repeated for the multiple foil pieces 11f.

[0150] 18, one end of the foil piece 11f on the protruding portion 11fp side is a free end in the circumferential direction 43. The foil piece 11f is fixed by the attachment portion 11t.

[0151] The thickness of each foil piece 11f is, for example, within the range of 40 μm to 200 μm.

[0152] The operation of the first dynamic pressure generating mechanism 11 in FIG. 18 will now be described.

[0153] When the thrust collar 52 rotates in the rotation direction 52R, the working fluid in the gap 19 between the first dynamic pressure generating mechanism 11 and the thrust collar 52 rotates as if being dragged by this rotation. The working fluid thus dragged is guided to the protrusion 11fp. The protrusion 11fp overlaps with the other foil pieces 11f and is relatively close to the thrust collar 52. Therefore, narrowed portions are intermittently formed between the protrusion 11fp and the thrust collar 52, and the pressure increases when the working fluid passes through the narrowed portions. As the working fluid intermittently passes through the narrowed portions along the circumferential direction 43, the pressure increases intermittently, and the rotating shaft 51 is supported.

[0154] Specifically, as shown in Fig. 18, a region 11fph of high static pressure is formed on the protruding portion 11fp. The region 11fph supports the thrust load. A linear arrow AR1 and a block arrow AR2 are drawn near the region 11fph in Fig. 18. These arrows AR1 and AR2 are also drawn in the cross-sectional view in the lower left of the figure.

[0155] The linear arrow AR1 shows a schematic diagram of the working fluid accelerating due to the rotation of the thrust collar 52. In the region where such acceleration occurs, the gradient of the foil pieces 11f generates dynamic pressure, which supports the gradient of the static pressure. The block arrow AR2 shows a schematic diagram of the working fluid flowing out due to the difference between the total pressure of the high pressure region 11fph in a certain foil piece 11f and the static pressure of the low pressure region of the adjacent foil piece 11f. Here, the total pressure of the high pressure region 11fph refers to the sum of the static pressure and dynamic pressure in the high pressure region 11fph.

[0156] 18 shows a cross-sectional view parallel to the radial direction 42. In this cross-sectional view, the overlapping of the foil pieces 11f1, 11f2, and 11f3, which are three foil pieces 11f adjacent to each other, is shown.

[0157] 18, the outer circumferential end of the first dynamic pressure generating mechanism 11 is the outer circumferential end of the foil piece 11f. Therefore, the length Rf1 from the central axis 51c of the rotating shaft 51 to the outer circumferential end of the first dynamic pressure generating mechanism 11 is defined as shown in FIG.

[0158] In the example of FIG. 18, the dimension Tf1 of the first dynamic pressure generating mechanism 11 in the axial direction 41 is the maximum height of the protruding portion 11fp from the base 14, and depends on the thickness of the multiple foil pieces 11f.

[0159] A bearing in which the dynamic pressure generating mechanism of the example in FIG. 18 is adopted is sometimes called a leaf-type foil bearing.

[0160] 19A and 19B show another example of the first dynamic pressure generating mechanism 11. In the example of FIG. 19A and FIG. 19B, the first dynamic pressure generating mechanism 11 includes a top foil 11tf and a bump foil 11bf. The top foil 11tf faces the thrust collar 52. The bump foil 11bf has a continuous arch shape. The bump foil 11bf elastically supports the top foil 11tf. With respect to the circumferential direction 43, one end of the top foil 11tf is a fixed end fixed to the base body 14, and the other end is a free end. A part of the bump foil 11bf is fixed to the base body 14.

[0161] 19B is a cross-sectional view parallel to the circumferential direction 43 of the first dynamic pressure generating mechanism 11. When the thrust collar 52 rotates, the rotating shaft 51 is supported by the pressure of the working fluid in the gap 19.

[0162] 19A and 19B, the outer circumferential end of the first dynamic pressure generating mechanism 11 is the outer circumferential end of the top foil 11tf. Therefore, the length Rf1 from the central axis 51c of the rotating shaft 51 to the outer circumferential end of the first dynamic pressure generating mechanism 11 is defined as shown in FIG. 19A.

[0163] In the example of Figures 19A and 19B, the dimension Tf1 of the first dynamic pressure generating mechanism 11 in the axial direction 41 is the maximum height of the top foil 11tf from the base 14, and depends on the shape of the bump foil 11bf and the thicknesses of the bump foil 11bf and the top foil 11tf.

[0164] Fig. 20 shows another example of the first dynamic pressure generating mechanism 11. In the example of Fig. 20, the first dynamic pressure generating mechanism 11 includes a plurality of spiral grooves 11g. The plurality of grooves 11g extend radially from the rotation axis 51. The plurality of grooves 11g are provided in the base body 14.

[0165] In the first dynamic pressure generating mechanism 11 in FIG. 20, the rotating shaft 51 is supported by the pressure of the working fluid in the gap 19 when the thrust collar 52 rotates.

[0166] 20, the outer circumferential end of the first dynamic pressure generating mechanism 11 is the outer circumferential end of the groove 11g. Therefore, the length Rf1 from the central axis 51c of the rotating shaft 51 to the outer circumferential end of the first dynamic pressure generating mechanism 11 is defined as shown in FIG.

[0167] In the example of FIG. 20, the dimension Tf1 of the first dynamic pressure generating mechanism 11 in the axial direction 41 is the depth of the groove 11g.

[0168] A bearing in which the dynamic pressure generating mechanism of the example in FIG. 20 is adopted is sometimes called a spiral groove bearing.

[0169] 18 to 20 can also be applied to the second dynamic pressure generating mechanism 21. When applying in this manner, the terminology can be changed as appropriate, such as changing "first" to "second."

[0170] (Thrust collar configuration) As described above, in this embodiment, the thrust collar 52 is disk-shaped. In a typical example, the thrust collar 52 is made of metal.

[0171] 21 shows thrust collar 52 of the present embodiment. Thrust collar 52 of FIG. 21 is symmetrical with respect to a reference plane 52p perpendicular to central axis 51c of rotation shaft 51.

[0172] Specifically, the thrust collar 52 in FIG. 21 includes a disk portion 52d, a first hub portion 52j, and a second hub portion 52k. The first hub portion 52j and the second hub portion 52k sandwich the disk portion 52d with respect to the axial direction 41 in which the central axis 51c extends. The first hub portion 52j and the second hub portion 52k are plane-symmetric with respect to a reference plane 52p. In a typical example, the disk portion 52d, the first hub portion 52j, and the second hub portion 52k are a single member. Such a single member can be produced, for example, by integral molding.

[0173] If thrust collar 52 is not plane-symmetrical with respect to reference plane 52p, thrust collar 52 will tend to flex toward the thicker side due to centrifugal force during rotation. This tendency becomes more pronounced when the diameter of thrust collar 52 is increased. In this regard, the plane symmetry of thrust collar 52 in FIG. 21 makes it possible to suppress flexing of thrust collar 52 during rotation.

[0174] Even when thrust collar 52 is composed only of disk portion 52d, it is possible for thrust collar 52 to be plane-symmetrical with respect to reference plane 52p. However, by providing first hub portion 52j and second hub portion 52k and then making thrust collar 52 plane-symmetrical with respect to reference plane 52p, further advantages can be achieved.

[0175] Specifically, when the thrust collar 52 is composed of only the disk portion 52d, it is possible to thicken the disk portion 52d so that the thrust collar 52 can withstand the stress generated by high-speed rotation. However, doing so increases the mass of the disk portion 52d, and the mass of the rotating system is likely to increase. When the mass of the rotating system increases, the bending resonance eigenvalue of the rotating system is likely to decrease. A lower bending resonance eigenvalue means that the rotation speed at which the vibration of the rotating system becomes noticeable is lowered. Therefore, if the bending resonance eigenvalue is low, it is difficult to rotate the rotating system at high speed. In contrast, when the thrust collar 52 has the hub portions 52j and 52k, it is easy to reduce the thickness of the disk portion 52d. Therefore, the bending resonance eigenvalue of the rotating system is likely to increase, and it is easy to rotate the rotating system at high speed. In this context, the "rotating system" refers to a combination of the rotating shaft 51 and an element that rotates together with the rotating shaft 51. Elements that rotate with the rotating shaft 51 may include a thrust collar 52, a compressor impeller, a turbine wheel, etc.

[0176] The flexural resonance eigenvalue is a parameter that may also be called the flexural critical resonance frequency, the flexural critical velocity, the flexural resonance frequency, or the like.

[0177] [Casing] In the example shown in Fig. 22, the bearing structure 50 includes a casing 70. An enclosure 75 is provided that includes the casing 70, a first thrust bearing 10, and a second thrust bearing 20. The enclosure 75 has an internal space 77. In the internal space 77, the first dynamic pressure generating mechanism 11 faces the thrust collar 52. In the internal space 77, the second dynamic pressure generating mechanism 21 faces the thrust collar 52. The enclosure 75 has a first through hole 71i and a second through hole 71о that communicate with the internal space 77.

[0178] When the thrust collar 52 rotates, a flow of the working fluid is generated, and the working fluid has kinetic energy. When the working fluid loses kinetic energy, thermal energy is generated.

[0179] In this regard, the first through hole 71i and the second through hole 71о as described above can prevent the temperature of the thrust collar 52 and the like from rising excessively. Specifically, in the example of FIG. 22, the working fluid can be made to flow into the internal space 77 through the first through hole 71i, and the working fluid can be made to flow out from the internal space 77 through the second through hole 71о. In this way, the temperature of the thrust collar 52 and the like can be prevented from rising excessively. In the example of FIG. 22, the first through hole 71i is an inlet for the working fluid. The second through hole 71о is an outlet for the working fluid.

[0180] Generally, the pressure that supports the thrust collar, which is generated by the dynamic pressure generating mechanism, is roughly proportional to the density ρ of the working fluid. When the temperature of the working fluid increases, the density ρ decreases. In this regard, in the example of FIG. 22, a first through hole 71i is provided in the thrust bearing 24, and a second through hole 71о is provided in the thrust bearing 14. In this way, it is easy to lower the temperature of the working fluid in the gaps 29 and 19, increase the density ρ, and ensure the pressure that supports the thrust collar, which is generated by the dynamic pressure generating mechanism. This is advantageous from the viewpoint of obtaining a large load capacity.

[0181] 22, a first through hole 71i is provided on the outer periphery side of the second stage 24a of the thrust bearing 24. A second through hole 71о is provided on the outer periphery side of the first stage 14a of the thrust bearing 14. More specifically, the first through hole 71i is provided in the second base 24b. The second through hole 71о is provided in the first base 14b.

[0182] However, as shown in Fig. 23, a configuration in which the enclosure 75 does not have the first through-hole 71i and the second through-hole 71о may be adopted. Even in such a case, it is possible to take measures against heat, for example, by using a material with excellent thermal conductivity as the casing 70.

[0183] 24, the bearing structure 50 includes a heat exchanger 76. The heat exchanger 76 divides an internal space 77 into a first space 78 and a second space 79. In the first space 78, the first dynamic pressure generating mechanism 11 faces the thrust collar 52. In the first space 78, the second dynamic pressure generating mechanism 21 faces the thrust collar 52. A first through hole 71i and a second through hole 71о communicate with the second space 79.

[0184] The heat exchanger 76 as described above can prevent foreign matter such as dust from entering the gap between the dynamic pressure generating mechanism and the thrust collar, while also preventing the temperature of the thrust collar and other components from becoming excessively high.

[0185] The heat exchanger 76 is not particularly limited. In the example of Fig. 24, the heat exchanger 76 has fins. Specifically, in the example of Fig. 24, the heat exchanger 76 has corrugated fins. Other examples of the heat exchanger 76 include a plate type heat exchanger, a shell-and-tube type heat exchanger, a fin tube type heat exchanger 76, and the like.

[0186] 24, the heat exchanger 76 separates the first space 78 and the second space 79 without any gap. This is suitable for preventing foreign matter from entering the gap between the dynamic pressure generating mechanism and the thrust collar in the first space 78.

[0187] In the example of FIG. 24, the first through hole 71i penetrates both the second base 24b and the casing 70. However, as shown in FIG. 25, the first through hole 71i may penetrate the casing 70 without penetrating the second base 24b. Also, in the example of FIG. 24, the second through hole 71о penetrates both the first base 14b and the casing 70. However, as shown in FIG. 25, the second through hole 71о may penetrate the casing 70 without penetrating the first base 14b. This point is similar to the example of FIG. 22.

[0188] [Fluid machinery] The bearing structure 50 described with reference to Fig. 3 to Fig. 25 can be applied to a fluid machine 80. Fig. 2 illustrates an example of the fluid machine 80. In Fig. 2, the flow of a fluid is represented by arrows.

[0189] 2, the fluid machine 80 includes a compressor 61 and an expander 62. The compressor 61 and the expander 62 are attached to the rotating shaft 51. Specifically, the compressor 61 and the expander 62 are mechanically attached to the rotating shaft 51. The fluid machine 80 also includes a regenerative heat exchanger 63 and a combustor 64.

[0190] In the example of FIG. 2, the compressor 61 is a centrifugal compressor. The centrifugal compressor 61 includes a compressor impeller 61i and a diffuser. The compressor impeller 61i of the centrifugal compressor 61 is attached (mechanically in the specific example) to the rotating shaft 51. The diffuser is located on the outer periphery side of the compressor impeller 61i. The working fluid may pass through the compressor impeller 61i and the diffuser in this order. Note that the diffuser is not illustrated in FIG. 2. This also applies to FIGS. 22 to 25.

[0191] 2, the fluid machine 80 is a turbine system, and the expander 62 is an expansion turbine.

[0192] Specifically, in the example of Fig. 2, the expander 62 is a radial expansion turbine. The radial expansion turbine 62 includes a turbine wheel 62w and a nozzle. The turbine wheel 62w is attached (mechanically in the specific example) to the rotating shaft 51. The nozzle is located on the outer periphery side of the turbine wheel 62w. The combustion gas from the combustor 64 may pass through the nozzle and the turbine wheel 62w in this order. Note that the nozzle is not shown in Fig. 2.

[0193] 2, the compressor 61, the thrust collar 52, and the expander 62 are provided in this order with respect to the axial direction 41. Specifically, the compressor impeller 61i, the thrust collar 52, and the turbine wheel 62w are provided in this order with respect to the axial direction 41.

[0194] 2, the working fluid discharged from the compressor 61 flows from the first through-hole 71i into the internal space 77. In this way, it is possible to prevent the temperature of the thrust collar 52 and the like from becoming excessively high.

[0195] Specifically, in the example of FIG. 2, a first flow path 81 and a second flow path 82 are provided.

[0196] The first flow path 81 connects the compressor 61, the combustor 64, and the expander 62 in this order. Specifically, the first flow path 81 connects the compressor 61, the regenerative heat exchanger 63, the combustor 64, the expander 62, and the regenerative heat exchanger 63 in this order.

[0197] The second flow path 82 bypasses the combustor 64. Specifically, the second flow path 82 bypasses the regenerative heat exchanger 63 and the combustor 64. The second flow path 82 connects the compressor 61, the first through-hole 71i, the internal space 77, the second through-hole 71о, and the expander 62 in this order.

[0198] In the first flow path 81, the compressor 61 compresses the working fluid. Next, the regenerative heat exchanger 63 exchanges heat between the working fluid and the turbine exhaust fluid. This increases the temperature of the working fluid. Next, the combustor 64 injects fuel into the working fluid and burns it. This generates combustion gas. Next, the expander 62 expands the combustion gas. In the expander 62, torque is generated by the combustion gas passing through it. This torque can be used for compressing the working fluid by the compressor 61. In addition, a generator can be connected to the expander 62, and this torque can be used for generating electricity in the generator. Next, the turbine exhaust fluid flowing out of the expander 62 flows into the regenerative heat exchanger 63.

[0199] As can be understood from the above description, a portion of the working fluid that flows into the compressor 61 flows to the regenerative heat exchanger 63 and the combustor 64. Another portion of the working fluid that flows into the compressor 61 flows into the second flow path 82.

[0200] In the second flow path 82, the working fluid flows into the internal space 77 through the first through hole 71i. In the internal space 77, the working fluid cools the internal space 77. Next, the working fluid flows out of the internal space 77 through the second through hole 71о. Next, the working fluid flows into the expander 62. The working fluid thus flowing into the expander 62 can also contribute to torque generation in the expander 62. In addition, the working fluid thus flowing into the expander 62 can cool the expander 62.

[0201] In one specific example, in the first flow passage 81, the combustion gas is supplied to the turbine wheel 62w via a nozzle, while in the second flow passage 82, the working fluid is supplied to the expander 62.

[0202] Generally, in order to increase the torque generated by the expander, it is desirable for the heat quantity and mass of the working fluid flowing into the expander to be large. On the other hand, from the viewpoint of heat-resistant design, it is not desirable for the inlet temperature of the expander to be too high.

[0203] For example, by dissipating the heat of the nozzle and the turbine wheel to the outside, the heat resistance of the nozzle and the turbine wheel can be ensured even when the inlet temperature of the expander is high. However, doing so may cause a risk of a decrease in the torque generated by the expander due to the heat of the combustion gas dissipating to the outside through the nozzle and the turbine wheel.

[0204] Therefore, the inventors have considered using a working fluid to cool the nozzle and the turbine wheel, and further supplying the working fluid to the intake side of the expander. In this way, the expander can generate torque by utilizing the heat absorbed from the nozzle and the turbine wheel. Furthermore, by mixing the working fluid, which is at a lower temperature than the combustion gas, with the combustion gas, the intake temperature of the expander can be lowered without reducing the heat of the intake air of the expander.

[0205] Furthermore, the present inventors have considered supplying the working fluid that has passed through the bearing mechanism 50 to the expander 62. The working fluid that has passed through the bearing mechanism 50 is at a lower temperature than the nozzle and the turbine wheel, and may have a heat quantity that contributes to the generation of torque in the expander. Therefore, the working fluid that has passed through the bearing mechanism 50 may contribute to cooling the nozzle and / or the turbine wheel and / or to generating the torque in the expander.

[0206] An example of the flow of the working fluid supplied from the bearing mechanism 50 to the expander 62 through the second flow path 82 will be described below with reference to Figures 26, 27, 28, 29, 30, and 31. Specifically, the flow of the working fluid discharged from the second through-hole 71о of the bearing mechanism 50 in the expander 62 will be described below.

[0207] 26, the working fluid is supplied to the intake side of the expander 62 to rotate the turbine wheel 62w. According to the example of FIG. 26, the heat generated in the bearing mechanism 50 can be used to generate torque in the expander 62.

[0208] 27, in the expander 62, the working fluid cools the turbine wheel 62w and is then supplied to the intake side to rotate the turbine wheel 62w. According to the example of Fig. 27, the heat generated in the bearing mechanism 50 and the heat absorbed from the turbine wheel 62w can be used to generate torque in the expander 62.

[0209] 28, in the expander 62, the working fluid cools the nozzle 62n and is then supplied to the intake side to rotate the turbine wheel 62w. According to the example of Fig. 28, the heat generated in the bearing mechanism 50 and the heat absorbed from the nozzle 62n can be used to generate torque in the expander 62.

[0210] In the example of FIG. 29, a part of the working fluid cools the nozzle 62n in the expander 62. Another part (specifically, the remainder) of the working fluid cools the turbine wheel 62w. The working fluid that has cooled the nozzle 62n and the working fluid that has cooled the turbine wheel 62w are supplied to the intake side to rotate the turbine wheel 62w. According to the example of FIG. 29, the amount of heat generated in the bearing mechanism, the amount of heat absorbed from the nozzle 62n, and the amount of heat absorbed from the turbine wheel can be used to generate torque in the expander 62.

[0211] 30, in the expander 62, the working fluid cools the nozzle 62n, then cools the turbine wheel 62w, and is then supplied to the intake side to rotate the turbine wheel 62w. According to the example of Fig. 30, the amount of heat generated in the bearing mechanism 50, the amount of heat absorbed from the nozzle 62n, and the amount of heat absorbed from the turbine wheel 61w can be used to generate torque in the expander 62.

[0212] In the example of FIG. 31, in the expander 62, the working fluid cools the nozzle 62n. A portion of the working fluid that has cooled the nozzle 62n is directly supplied to the intake side. Another portion (specifically, the remainder) of the working fluid that has cooled the nozzle 62n cools the turbine wheel 62w and is then supplied to the intake side. Both of the working fluids supplied to the intake side rotate the turbine wheel 62w. According to the example of FIG. 31, the amount of heat generated in the bearing mechanism 50, the amount of heat absorbed from the nozzle 62n, and the amount of heat absorbed from the turbine wheel 61w can be used to generate torque in the expander 62.

[0213] Here, the pressure of the working fluid according to one specific example will be described. The pressure of the working fluid discharged from the compressor 61 is Pc. The pressure loss of the working fluid in the regenerative heat exchanger 63 is ΔP1. The difference obtained by subtracting the outlet pressure from the inlet pressure of the combustor 64 is ΔP2. At this time, the pressure Ptin1 of the combustion gas flowing into the expander 62 by the first flow path 81 is given by Ptin1=Pc-ΔP1-ΔP2. On the other hand, the pressure loss of the working fluid in the bearing structure 50 is ΔPtb. At this time, the pressure Ptin2 of the working fluid flowing into the expander 62 by the second flow path 82 is given by Ptin2=Pc-ΔP1. In the example of FIG. 2, Ptin2>Ptin1. In this way, it is easy to supply the working fluid to the bearing structure 50 and the expander 62 via the second flow path 82. Also, in the example of FIG. 2, the pressure of the turbine exhaust fluid is higher than the atmospheric pressure. Therefore, it is easy to discharge the turbine exhaust fluid from the expander 62.

[0214] Next, the temperature of the working fluid according to one specific example will be described. The temperature of the working fluid discharged from the compressor 61 is Tc. The temperature of the working fluid immediately after it flows out of the regenerative heat exchanger 63 is Trh. The temperature of the combustion gas flowing out of the combustor 64 is Tb. The temperature of the working fluid flowing out of the bearing structure 50 is Ttb. Due to the heat exchange in the regenerative heat exchanger 63, Trh>Tc, and the temperature of the working fluid flowing into the combustor 64 increases, making it possible to save the fuel supplied to the combustor 64. Although Ttb>Tc, Ttb is sufficiently lower than Tb, so that the expander 62 can be cooled by the working fluid flowing out of the bearing structure 50.

[0215] 22 to 25 exemplify the position of the compressor 61 when the bearing structure 50 is applied to a fluid machine 80. Specifically, a centrifugal compressor 61 is shown in Fig. 22 to 25.

[0216] 22, 24, and 25, when observed along the central axis 51c, the first through hole 71i may be located on the outer circumferential side of the outer circumferential end of the compressor impeller 61i. In this way, it is easy to increase the flow rate of the working fluid flowing into the internal space 77 from the first through hole 71i.

[0217] In one specific example, the working fluid that has passed through the compressor impeller 61i and the diffuser of the centrifugal compressor 61 flows from the first through hole 71i into the internal space 77. For example, when observed along the central axis 51c, the first through hole 71i is located at a position overlapping with the diffuser or at a position on the outer circumferential side of the diffuser.

[0218] However, when observed along the central axis 51c, the first through-hole 71i may be located at a position overlapping with the compressor impeller 61i.

[0219] In the present embodiment, the bearing mechanism 50 supports a rotating part of the compressor 61. The rotating part includes a compressor impeller 61i. The rotating part rotates together with the rotating shaft 51. Specifically, like the rotating shaft 51, the rotating part rotates substantially about the central axis 51c.

[0220] When the temperature changes, the rotating shaft 51 expands and the length in the axial direction 41 may change. Therefore, even if the position of the thrust collar 52 is held by the bearing mechanism 50, the position of the rotating part may change. In this embodiment, the axial direction 41 is the thrust direction.

[0221] On the other hand, by precisely maintaining the position of the rotating part in the axial direction 41, it is possible to reduce the loss of the compressor 61. In this embodiment, as shown in FIG. 32, the compressor 61 has a shroud 61s whose position is fixed. In this case, by precisely maintaining the position of the compressor impeller 61i in the axial direction 41, it is possible to maintain a state in which a small gap 61g is formed between the compressor impeller 61i and the shroud 61s while avoiding contact between the rotating impeller 61i and the fixed shroud 61s. This makes it possible to reduce the loss in the compressor 61 while avoiding breakdown of the compressor 61.

[0222] In this regard, in the present embodiment, the relationship Lct < Lte is satisfied. Here, Lct is the separation distance between the compressor 61 and the thrust collar 52 with respect to the axial direction 41. Lte is the separation distance between the thrust collar 52 and the expander 62 with respect to the axial direction 41. In the present embodiment, since Lct < Lte, it is easy to reduce the separation distance Lct. Therefore, it is easy to suppress the displacement of the compressor 61 in the axial direction 41 as the temperature of the rotating shaft 51 changes.

[0223] Specifically, Lct is the separation distance between the rotating part of the compressor 61 and the thrust collar 52 with respect to the axial direction 41. Lte is the separation distance between the thrust collar 52 and the rotating part of the expander 62 with respect to the axial direction 41. Here, the rotating part of the expander 62 includes the turbine wheel 62w.

[0224] More specifically, Lct is the separation distance between the compressor impeller 61i and the thrust collar 52 with respect to the axial direction 41. Lte is the separation distance between the thrust collar 52 and the turbine wheel 62w with respect to the axial direction 41.

[0225] Regarding Lct < Lte, further explanation is as follows. In the present embodiment, since the separation distance Lte is relatively large, it is difficult for the heat of the high-temperature expander 62 to be transmitted to the thrust collar 52. Therefore, the temperature change of the expander 62 hardly affects the temperature of the portion of the rotating shaft 51 between the thrust collar 52 and the compressor 61. Therefore, it is easy to suppress the displacement of the compressor 61 in the axial direction 41 due to the variation of the separation distance Lct as the temperature of the expander 62 changes. For the above reasons, Lct < Lte is appropriate as the design of the fluid machine 80.

[0226] Further, in this embodiment, the bearing structure 50 is provided with the through holes 71i and 71o. Therefore, the temperature of the working fluid around the thrust collar 52 can be lowered, the temperature of the thrust collar 52 can be lowered, and the temperature of the rotating shaft 51 can be lowered. Specifically, the temperature of the portion of the rotating shaft 51 between the compressor 61 and the thrust collar 52 can be lowered. This can suppress the displacement of the compressor 61 in the axial direction 41 caused by the temperature change of the rotating shaft 51. As for the expander 62, since the through holes 71i and 71o are provided, the heat propagated from the expander 62 to the thrust collar 52 can be easily released from the thrust collar 52 to the working fluid. Therefore, the temperature change of the expander 62 is unlikely to affect the temperature of the portion of the rotating shaft 51 between the thrust collar 52 and the compressor 61. This is advantageous from the viewpoint of suppressing the fluctuation of the separation distance Lct and suppressing the displacement of the compressor 61 in the axial direction 41.

[0227] As described above, according to the fluid machine 80 of the present embodiment, the position of the compressor 61 in the axial direction 41 can be precisely maintained. This is expected to reduce losses in the compressor 61.

[0228] (Another mechanism) 11A to 11C, a description has been given based on mechanism M. However, in reality, a mechanism other than mechanism M may also act. For example, centrifugal force may also act on the bearing structure 50.

[0229] The advantage of the first convex portion 17 described with reference to Figs. 7 to 9 can be explained not only by mechanism M but also by centrifugal force. Specifically, it can be explained that the first convex portion 17 acts to hold back the working fluid that attempts to flow outward in the radial direction 42 from the gap 19 due to centrifugal force, toward the inner periphery side of the first convex portion 17. This action can contribute to obtaining a large load capacity. The same applies to the second convex portion. In Fig. 33, the above-mentioned holding back action is diagrammatically represented by arrows.

[0230] Various modifications may be made to the present disclosure.

[0231] For example, the application of the technology according to the present disclosure is not limited to turbine systems, and may be applied to other systems besides turbine systems, such as electric compressors, rotating shafts of hard disk drives (HDDs), and processing equipment in factories.

[0232] In the example of Fig. 2, the first thrust bearing of the first and second thrust bearings is closer to the compressor. However, the term "first thrust bearing" should not be interpreted as referring to the first thrust bearing closer to the compressor.

[0233] In the above description, the case where both the first thrust bearing and the second thrust bearing are present has been described. However, the present disclosure also includes a configuration where only one of the first thrust bearing and the second thrust bearing is present.

[0234] It is also possible to omit some of the elements shown in the figures. For example, the regenerative heat exchanger can be omitted. Some of the elements of the bearing structure can also be omitted. [Industrial Applicability]

[0235] The bearing structure described in the above embodiment can be applied to a turbine system or the like. [Explanation of symbols]

[0236] 10,20 Thrust bearing 11,21 Dynamic pressure generation mechanism 11f, 11f1, 11f2, 11f3 foil pieces 11fp protrusion 11fph High static pressure area 11t Mounting part 11bf Bump Foil 11tf top foil 11g groove 14,24 Base Stages 14a and 24a 14b,24b bass 15,25 Recess 17,27 Convex 19,29 Gap 41 Axial 42 Radial 43 Circumferential direction 50 Bearing structure 51 Rotation axis 51c center axis 52 Thrust collar 52d Disc Section 52j, 52k hub section 52p reference plane 52R Rotation direction 52x,52y opposing planes 61 Compressor 61g gap 61i Compressor Impeller 61s Shroud 62 Expander 62n Nozzle 62w turbine wheel 63 Regenerative heat exchanger 64 Combustor 70 Casing 71i,71o Through hole 75 Enclosure 76 Heat exchanger 77,78,79 space 80 Fluid machinery 81,82 Flow path 101 Rotation axis 103A, 103B Thrust bearing 104 Thrust collar

Claims

1. A bearing structure; A compressor; and an expander, The bearing structure includes: A rotating shaft having a central axis; A thrust collar attached to the rotating shaft; a first thrust bearing including a first dynamic pressure generating mechanism facing the thrust collar; a length from the central axis to an outer circumferential end of the thrust collar is defined as Rt, and a length from the central axis to an outer circumferential end of the first dynamic pressure generating mechanism is defined as Rf1, the relationship Rt>Rf1 is satisfied, the first dynamic pressure generating mechanism includes a plurality of foil pieces, The plurality of foil pieces are arranged in an annular shape so as to surround the rotation shaft, In the plurality of foil pieces, adjacent foil pieces are partially overlapped with each other such that a protruding portion of one of the adjacent foil pieces overlaps on top of the other foil piece, The bearing structure includes a casing, an enclosure including the casing and the first thrust bearing is provided; the enclosure has an interior space; In the internal space, the first dynamic pressure generating mechanism faces the thrust collar, the enclosure has a first through hole and a second through hole communicating with the internal space, The compressor and the expander are attached to the rotating shaft, A working fluid discharged from the compressor flows into the internal space through the first through hole, The compressor is a centrifugal compressor, The centrifugal compressor includes a compressor impeller attached to the rotating shaft, When observed along the central axis, the first through hole is located on the outer circumferential side of the outer circumferential end of the compressor impeller. Fluid machinery.

2. A bearing structure; A compressor; and an expander, The bearing structure includes: A rotating shaft having a central axis; A thrust collar attached to the rotating shaft; a first thrust bearing including a first dynamic pressure generating mechanism facing the thrust collar; a length from the central axis to an outer circumferential end of the thrust collar is defined as Rt, and a length from the central axis to an outer circumferential end of the first dynamic pressure generating mechanism is defined as Rf1, the relationship Rt>Rf1 is satisfied, the first dynamic pressure generating mechanism includes a plurality of foil pieces, The plurality of foil pieces are arranged in an annular shape so as to surround the rotation shaft, In the plurality of foil pieces, adjacent foil pieces are partially overlapped with each other such that a protruding portion of one of the adjacent foil pieces overlaps on top of the other foil piece, The compressor and the expander are attached to the rotating shaft, When a direction in which the central axis extends is defined as an axial direction, the compressor, the thrust collar, and the expander are provided in this order in the axial direction, When a distance between the compressor and the thrust collar in the axial direction is defined as Lct, and a distance between the thrust collar and the expander in the axial direction is defined as Lte, a relationship of Lct<Lte is satisfied. Fluid machinery.

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