Radial foil bearing

Abstract

This paper describes a radial foil bearing that can stably support a rotating shaft during high-speed rotation. [Solution] The radial foil bearing 20 comprises a bearing housing 45 having a shaft hole Sh, a top foil 22 disposed inside the shaft hole Sh, a back foil 23 disposed between the top foil 22 and the bearing housing 45, and an intermediate foil 24 disposed between the top foil 22 and the back foil 23, wherein the intermediate foil 24 is provided with claws 8 that lock the back foil 23 to the bearing housing 45, the back foil 23 is provided with a claw insertion portion 23x through which the claws 8 are inserted, the bearing housing 45 is provided with a positioning groove 9 that accommodates the claws 8 that have passed through the claw insertion portion 23x, the positioning groove 9 is provided with an opening A1 facing the shaft hole Sh, and the claws 8 are provided with a main body portion 82 that extends in the circumferential direction D2 of the shaft hole Sh within the positioning groove 9, the width W of the opening A1 in the circumferential direction D2 is greater than the length L of the claws 8 in the circumferential direction D2.

Description

Technical Field

[0001] This disclosure relates to a radial foil bearing.

Background Art

[0002] For example, Patent Document 1 discloses a foil bearing that supports a rotating shaft in a bearing housing via an upper foil supported by an under foil. Patent Document 2 discloses a gas bearing structure that combines a plurality of elastic foils to support a rotating shaft. Patent Document 3 discloses a radial foil bearing that supports a rotating shaft by a top foil and a bump foil.

[0003] Different from the above bearing structures, Patent Document 4 discloses a radial foil bearing in which an intermediate foil is disposed between a top foil and a back foil facing a rotating shaft. The intermediate foil is provided with a bent portion that protrudes in the radial direction of the rotating shaft and is inserted into a shaft hole of the back foil. The bent portion that has passed through the shaft hole is fitted into a fitting groove of the bearing housing to lock the back foil to the bearing housing. A pair of bent portions standing upright so as to face each other in the circumferential direction are fitted into one fitting groove. The pair of bent portions are in contact with each other so as to be pressed against both side surfaces in the circumferential direction of the fitting groove.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0005] In a structure where the back foil is secured to the bearing housing by the intermediate foil, it is necessary to fit a pair of bent sections into a single fitting groove, and this fitting process is time-consuming and requires ingenuity during assembly. In particular, both of the pair of bent sections that face each other in the circumferential direction must be inserted into the fitting groove, and both must be fitted so that they abut against the sides of the fitting groove, which presents challenges from the standpoint of ease of assembly.

[0006] This disclosure describes a radial foil bearing that can improve the ease of assembly when the back foil is locked to the bearing housing with the intermediate foil. [Means for solving the problem]

[0007] A radial foil bearing according to one embodiment of the present disclosure comprises a bearing housing having a shaft bore, a top foil disposed inside the shaft bore, a back foil disposed between the top foil and the bearing housing, and an intermediate foil disposed between the top foil and the back foil, wherein the intermediate foil has claws for locking the back foil to the bearing housing, the back foil has a claw insertion portion through which the claws are inserted, the bearing housing has a positioning groove that accommodates the claws after they have passed through the claw insertion portion, the positioning groove has an opening facing the shaft bore, and the claws have a body portion that extends in the circumferential direction of the shaft bore within the positioning groove, the circumferential width of the opening is greater than the circumferential length of the claws.

[0008] The intermediate foil is equipped with claws housed within a positioning groove, and the movement of the claws is restricted by interference with the inner surface of the positioning groove. The claws lock onto the back foil, and thus the movement of the back foil is restricted by the restricted movement of the claws. The claws have a main body that extends circumferentially around the shaft hole. Therefore, the claws can be positioned to match the circumferential width of the positioning groove. Furthermore, during the assembly of the radial foil bearing, the claws of the intermediate foil are inserted into the claw insertion portion of the back foil and then fitted into the positioning groove through its opening in that state. Here, the circumferential width of the shaft hole at the opening of the positioning groove is greater than the circumferential length of the shaft hole of the claw. Therefore, insertion of the claws into the positioning groove is easy, and as a result, assembly is improved.

[0009] In some embodiments, the positioning groove has an inner surface, the intermediate foil has a base portion facing the top foil, and the claws may project outward from the base portion away from the top foil and have a root portion that is inserted into a claw insertion portion and faces the inner surface of the positioning groove. The root portion locks the back foil by being inserted into the claw insertion portion. Also, since the root portion faces the inner surface of the positioning groove, it can restrict the movement of the claws by interfering with the inner surface.

[0010] In some embodiments, the positioning groove has an inner surface facing the claw. The claw may have a tip that is positioned opposite the body to the root and facing the inner surface. The circumferential movement of the claw's axial hole is restricted by the tip interfering with the inner surface of the positioning groove. The tip and the inner surface come into contact. As a result, the claw is subjected to interference from the inner surface, and the movement of the backfoil is restricted by the interference between the claw and the inner surface.

[0011] In some embodiments, the inner surface comprises a first surface facing the base, a second surface facing the first surface in the circumferential direction of the shaft hole, and a curved surface connecting the first and second surfaces and curving in a concave shape, and the tip can be curved to follow the curved surface. By forming a concave curved surface connecting the first and second surfaces, depth for receiving the tip can be secured, while the circumferential movement of the tip can be restricted by the curved surface. Furthermore, since the tip is positioned to face the curved surface, when the tip moves in the circumferential direction, it will interfere with the curved surface earlier than the second surface, thereby reducing the range of motion of the tip.

[0012] In some embodiments, multiple claws are provided circumferentially around the shaft hole, and at least one of the multiple claws may have a tip portion positioned spaced apart from its base portion on the side of the rotational direction of the rotating shaft inserted into the shaft hole. The movement of the claw in the rotational direction of the rotating shaft is restricted by the tip portion interfering with the inner surface of the positioning groove. As a result, the rotational movement of the back foil locked to the claw is restricted.

[0013] In some embodiments, multiple claws are provided circumferentially around the shaft hole, and at least one of the multiple claws may have a tip portion positioned spaced apart from its base portion in the direction opposite to the direction of rotation of the rotating shaft inserted into the shaft hole. Movement of the claw in the direction opposite to the direction of rotation of the rotating shaft is restricted by the tip portion interfering with the inner surface of the positioning groove. As a result, movement of the back foil locked to the claw in the direction opposite to the direction of rotation is restricted.

[0014] In some embodiments, multiple claws are provided circumferentially around the shaft hole, and at least one claw may have a tip portion spaced apart from its base portion on the side of the rotational direction of the rotating shaft inserted into the shaft hole, and at least one claw may have a tip portion spaced apart from its base portion on the side opposite to the rotational direction of the rotating shaft. Movement of the claws in the direction of rotation of the rotating shaft and in the direction opposite to the rotational direction is restricted by the tip portion interfering with the inner surface of the positioning groove. As a result, movement of the back foil locked to the claws in the direction of rotation and in the direction opposite to the rotational direction is restricted.

[0015] In some embodiments, the tip and the curved surface may be spaced apart, and the base and the first surface of the inner surface may be spaced apart. Even if the claw moves in the circumferential direction of the axial hole, the movement of the claw is restricted by contact between the tip and the curved surface, or by contact between the base and the first surface, and the movement of the back foil locked to the claw is restricted.

[0016] In some embodiments, the distance between the tip and the curved surface can be smaller than the distance between the base and the first surface. The movement dependent on the distance between the tip and the curved surface can be set to be smaller than the movement dependent on the distance between the base and the first surface.

[0017] In some embodiments, the positioning groove may comprise a claw introduction portion having an opening and a claw housing portion having an inner surface. The inner surface may comprise a first surface, a second surface opposite the first surface, and a curved surface connecting the first and second surfaces. The tip may be in contact with the curved surface, and the base may be in contact with the first surface. The circumferential width of the axial hole in the opening may be greater than the circumferential width of the axial hole between the first and second surfaces. The contact between the tip and the curved surface, and the contact between the base and the first surface, restricts the movement of the claw and restricts the movement of the back foil locked to the claw. Furthermore, the circumferential width of the opening is greater than the circumferential width between the first and second surfaces. Therefore, the circumferential width of the opening of the positioning groove is greater than the circumferential length of the claw, improving ease of assembly. [Effects of the Invention]

[0018] According to some aspects of the present disclosure, it is possible to improve the assemblability when locking the back foil to the bearing housing with an intermediate foil.

Brief Description of the Drawings

[0019] [Figure 1] FIG. 1 is a cross-sectional view showing an example of a rotating machine. [Figure 2] FIG. 2 shows an embodiment of a radial foil bearing and is a schematic cross-sectional view taken along line II-II of FIG. 1, for example, a cross-sectional view cut along a plane perpendicular to the rotation axis. [Figure 3] FIG. 3 is a perspective view showing an example of a top foil. [Figure 4] FIG. 4 shows an example of a back foil piece and is a plan view showing the back foil piece in a developed state. [Figure 5] FIG. 5 shows an example of an intermediate foil piece. FIG. 5(a) is a plan view showing the intermediate foil piece in a developed state, and FIG. 5(b) is a cross-sectional view taken along line b-b of FIG. 5(a). [Figure 6] FIG. 6 shows an example of a radial foil bearing and is a perspective view showing the back foil partially broken away. [Figure 7] FIG. 7 is an enlarged cross-sectional view showing a part of a radial foil bearing. FIG. 7(a) is a cross-sectional view showing one claw accommodated in a positioning groove, and FIG. 7(b) is a cross-sectional view showing another claw accommodated in the positioning groove. [Figure 8] FIG. 8 shows an example of a radial foil bearing and is a cross-sectional view showing a radial foil bearing in which all the claws are facing the rotation direction side. [Figure 9] FIG. 9 shows an example of a radial foil bearing and is a cross-sectional view showing a radial foil bearing in which all the claws are facing the side opposite to the rotation direction. [Figure 10] FIG. 10 shows modified examples of claws. FIG. 10(a) is a cross-sectional view showing a first modified example, and FIG. 10(b) is a cross-sectional view showing a second modified example. [Figure 11]Figure 11 is a cross-sectional view of a radial foil bearing according to another embodiment. [Figure 12] Figure 12 is a cross-sectional view showing an enlarged portion of a radial foil bearing according to another embodiment. [Modes for carrying out the invention]

[0020] Embodiments of this disclosure will be described below with reference to the drawings. In the description of the drawings, the same elements will be denoted by the same reference numerals, and redundant descriptions will be omitted.

[0021] Figure 1 shows a rotating machine 1. The rotating machine 1 is, for example, an electric-assisted turbocharger. The rotating machine 1 comprises a turbine 2, a compressor 3, an electric motor 10, and a rotating shaft 15. The turbine 2 has a turbine impeller 4 provided at one end of the rotating shaft 15 and a turbine housing 6 that houses the turbine impeller 4. The compressor 3 has a compressor impeller 5 provided at the other end of the rotating shaft 15 and a compressor housing 7 that houses the compressor impeller 5.

[0022] The rotor 11 of the electric motor 10 is positioned, for example, in the center of the rotating shaft 15. The rotor 11 is fixed to the rotating shaft 15 and can rotate together with the rotating shaft 15. The stator 12 of the electric motor 10 is positioned to surround the rotor 11. The stator 12 is fixed to a motor housing 13 located between the turbine housing 6 and the compressor housing 7. The stator 12 can rotate the rotor 11 by generating a magnetic field around the rotating shaft 15. This cooperation between the rotor 11 and the stator 12 assists in the rotation of the rotating shaft 15.

[0023] In the rotating machine 1, exhaust gas discharged from the internal combustion engine flows into the turbine housing 6 through the scroll passage 6a, causing the turbine impeller 4 to rotate around the rotation axis H. The exhaust gas that has rotated the turbine impeller 4 is discharged through the discharge port 6b of the turbine housing 6. As the turbine impeller 4 rotates as described above, the compressor impeller 5 rotates via the rotating shaft 15. At this time, torque is applied to the rotating shaft 15 by the electric motor 10, which assists in the rotation of the rotating shaft 15 and the compressor impeller 5. The rotating compressor impeller 5 draws in outside air through the intake port 7b of the compressor housing 7. This air is compressed as it passes through the compressor impeller 5 and the scroll passage 7a. The compressed air is discharged from the discharge port of the compressor housing 7 and supplied to the internal combustion engine mentioned above.

[0024] The rotating shaft 15 is rotatably supported around the axis of rotation H via a plurality of bearings. At least one of the plurality of bearings is a radial foil bearing 20 of the present disclosure. In the example shown in Figure 1, a pair of radial foil bearings 20 are provided at each end of the rotating shaft 15. The radial foil bearings 20 are pneumatic bearings that support the rotating shaft 15 in the radial direction (i.e., in a direction perpendicular to the axis of rotation H).

[0025] In the rotating machine 1 of this disclosure, a thrust collar 17 and a pair of thrust air bearings 18 are provided between the radial foil bearing 20 closer to the compressor impeller 5 and the compressor impeller 5. The thrust collar 17 and the pair of thrust air bearings 18 support the rotating shaft 15 in the thrust direction (i.e., in a direction parallel to the rotation axis H).

[0026] <Radial foil bearing> An example of a radial foil bearing 20 will be described in detail with reference to Figure 2. The radial foil bearing 20 is a bearing that is externally fitted to the rotating shaft 15 and supports the rotating shaft 15. The radial foil bearing 20 comprises a foil assembly 21 and a bearing housing 45 that houses the foil assembly 21. The bearing housing 45 has a shaft hole Sh through which the rotating shaft 15 is inserted.

[0027] The foil assembly 21 comprises a top foil 22, a back foil 23, and an intermediate foil 24. The top foil 22 is positioned inside the shaft hole Sh of the bearing housing 45 and faces the rotating shaft 15, surrounding it. The back foil 23 is positioned between the top foil 22 and the bearing housing 45, surrounding the top foil 22. The intermediate foil 24 is positioned between the top foil 22 and the back foil 23. When the rotating shaft 15 rotates, an air film is formed between the rotating shaft 15 and the top foil 22. The radial foil bearing 20 rotatably supports the rotating shaft 15 by the formation of this air film.

[0028] <Bearing Housing> The bearing housing 45 is a cylindrical casing having a shaft hole Sh. The shaft hole Sh penetrates the bearing housing 45 in the direction in which the rotation axis H extends. In the following description, "axial direction D1" means the direction along the rotation axis H passing through the center of the shaft hole Sh. For example, assuming the rotation shaft 15 is inserted, it substantially means the axial direction D1 (rotation axis direction) of the rotation shaft 15. "Circumferential direction D2" means the circumferential direction D2 of the shaft hole Sh with respect to the rotation axis H. For example, assuming the rotation shaft 15 is inserted, it substantially means the circumferential direction of the rotation shaft 15. "Radial direction D3" means the direction perpendicular to the rotation axis H or the direction along the diameter of the shaft hole Sh. For example, assuming the rotation shaft 15 is inserted, it substantially means the radial direction of the rotation shaft 15. Furthermore, "radial outward" refers to the direction from the axis of rotation H toward the inner circumferential surface 45a of the bearing housing 45 (outward direction), while "radial inward" refers to the opposite direction from the outward direction, meaning the direction from the inner circumferential surface 45a of the bearing housing 45 toward the axis of rotation H (inward direction).

[0029] The bearing housing 45 is positioned to surround the foil assembly 21, with the foil assembly 21 housed within the shaft hole Sh. The bearing housing 45 includes an inner cylindrical circumferential surface 45a. This inner circumferential surface 45a can be considered as the inner circumferential surface 45a of the shaft hole Sh. The cylindrically wound foil assembly 21 is positioned between the inner circumferential surface 45a of the shaft hole Sh and the rotating shaft 15.

[0030] A locking groove 45b is provided on the inner circumferential surface 45a of the shaft hole Sh, which accommodates the locking structure 31 of the foil assembly 21. The locking structure 31 is provided so as to extend in the axial direction D1. The locking groove 45b is a vertically elongated groove that extends in the axial direction D1 so as to accommodate the locking structure 31. The width of the locking groove 45b in the circumferential direction D2 corresponds to the width of the locking structure 31 in the circumferential direction D2, and the locking groove 45b can abut against the locking structure 31 in the circumferential direction D2. The movement of the top foil 22 in the circumferential direction D2 is restricted by the locking structure 31 interfering with the locking groove 45b. As a result, the rotation of the top foil 22 is suppressed.

[0031] <Foil Assembly> The foil assembly 21 comprises a top foil 22, a back foil 23, and an intermediate foil 24. Figure 3 is a perspective view showing the top foil 22 wound into a cylindrical shape. Assuming the top foil 22 is in an unfolded state, the top foil 22 is a rectangular metal foil with the circumferential direction D2 as the longer side and the axial direction D1 as the shorter side. When the foil assembly 21 is formed, the top foil 22 is wound into a cylindrical shape and positioned to face the circumferential surface of the rotation axis 15.

[0032] A protruding convex portion 31a is provided on one of the short sides of the top foil 22 in the direction of its long side, and a recessed portion 31b, which has a notched shape, is formed on the other short side. When the top foil 22 is rolled into a cylindrical shape, the one short side and the other short side overlap, and the convex portion 31a is inserted into the recessed portion 31b and they intersect. The interlocking structure 31 is formed when the convex portion 31a and the recessed portion 31b combine and the one short side and the other short side overlap so that they intersect.

[0033] Figure 2 is a schematic cross-sectional view of the radial foil bearing 20. Figure 6 is a schematic perspective view of the radial foil bearing 20. In Figure 6, the top foil is omitted, the shape of the back foil is simplified, and a portion of the back foil is shown in a cutaway view. As shown in Figures 2 and 6, the back foil 23 is positioned between the bearing housing 45 and the top foil 22. The back foil 23 is also positioned between the bearing housing 45 and the intermediate foil 24. The back foil 23 is a foil (thin plate) that elastically supports the intermediate foil 24 and the top foil 22. A bump foil is an example of a back foil 23, but a spring foil or the like may also be used.

[0034] The back foil 23 comprises three (or more) back foil pieces 23a arranged inside the shaft hole Sh. The back foil pieces 23a are foils (thin sheets) that are corrugated in the circumferential direction D2. The three back foil pieces 23a are aligned in the circumferential direction D2 and are curved so that they are substantially cylindrical when viewed from the axial direction D1. The back foil pieces 23a are arranged along the inner circumferential surface 45a of the shaft hole Sh. For example, all of the multiple back foil pieces 23a are formed to be the same shape and dimensions. For example, the back foil pieces 23a are arranged so as to divide the inner circumferential surface 45a of the shaft hole Sh substantially equally in the circumferential direction D2.

[0035] The back foil 23 (see Figure 7(a)) has a peak 23b that protrudes radially inward and a valley 23c that protrudes radially outward when viewed from the peak 23b. The peaks 23b and valleys 23c are formed alternately in the circumferential direction D2, with the valleys 23c positioned between adjacent peaks 23b in the circumferential direction D2. The valleys 23c contact the inner circumferential surface 45a of the bearing housing 45 directly or indirectly. The peaks 23d of the peaks 23b contact the intermediate foil 24 directly or indirectly. Indirect contact refers to cases where another foil or other component is positioned between the valley 23c and the inner circumferential surface 45a of the bearing housing 45, or between the peaks 23b and the intermediate foil 24. The back foil 23 elastically supports the top foil 22 via the intermediate foil 24 by changing the curvature (flex) of the peaks 23b. Both ends of the back foil piece 23a in the circumferential direction D2 are valleys 23c.

[0036] Figure 4 is a plan view showing an example of a back foil piece 23a in an unfolded state without curving. The back foil piece 23a has two edges (hereinafter referred to as the "first edge portion 23e") which are opposing end portions in the axial direction D1. The first edge portion 23e is positioned to extend in the circumferential direction D2 in a curved state when mounted on the inner circumferential surface 45a of the axial hole Sh. The back foil piece 23a also has two edges (hereinafter referred to as the "second edge portion 23f") which are opposing end portions in the axial direction D1. The second edge portion 23f is positioned to extend in the axial direction D1 in a curved state when mounted on the inner circumferential surface 45a of the axial hole Sh.

[0037] One or more claw insertion portions 23x are formed on the first edge portion 23e. The claw insertion portion 23x is, for example, a slit formed along the valley portion 23c, with a part of its outer edge open. The claw insertion portion 23x may also be a slit or opening with the entire circumference of the outer edge closed. Claw insertion portions 23x are formed on both opposing first sides. The claw insertion portion 23x formed on one first side and the claw insertion portion 23x formed on the other first side are arranged opposite each other in the axial direction D1. For example, the claw insertion portion 23x formed on one first side and the claw insertion portion 23x formed on the other first side are arranged to be aligned on the same straight line in the axial direction D1 (see Figure 6).

[0038] As shown in Figures 2 and 6, the intermediate foil 24 is positioned between the top foil 22 and the back foil 23. The intermediate foil 24 comprises three (or more) intermediate foil pieces 24a arranged side by side in the circumferential direction D2. The three intermediate foil pieces 24a are arranged side by side in the circumferential direction D2 and are curved so that, when viewed from the axial direction D1, they form a substantially cylindrical shape as a whole. In other words, the intermediate foil pieces 24a are positioned along the back foil 23, which is positioned along the inner circumferential surface 45a of the axial hole Sh. The multiple intermediate foil pieces 24a are arranged, for example, to divide the inner circumferential surface 45a of the axial hole Sh into substantially equal parts in the circumferential direction D2.

[0039] The thickness of the intermediate foil piece 24a is thinner than that of the back foil piece 23a. The outer shape of the intermediate foil piece 24a is approximately the same as that of the back foil piece 23a. The intermediate foil piece 24a is in contact with the top portion 23d of the peak portion 23b of the back foil 23 (see Figure 7(a)). The intermediate foil piece 24a is provided with a claw 8 that is inserted into the claw insertion portion 23x of the back foil piece 23a. The claw 8 locks the back foil piece 23a to the bearing housing 45.

[0040] Figure 5(a) is a plan view showing an example of an intermediate foil piece 24a in an unfolded state without curvature, and Figure 5(b) is a cross-sectional view along line bb in Figure 5(a). As shown in Figure 5(a), the intermediate foil piece 24a has two opposing end portions in the axial direction D1 (hereinafter referred to as "circumferential edge portions 24e"). The circumferential edge portions 24e are arranged to extend in the circumferential direction D2 in a curved state when mounted on the inner circumferential surface 45a of the shaft hole Sh. The intermediate foil piece 24a also has two opposing end portions in the axial direction D1 (hereinafter referred to as "axial edge portions 24f"). The axial edge portions 24f are arranged to extend in the axial direction D1 in a curved state when mounted on the inner circumferential surface 45a of the shaft hole Sh.

[0041] As shown in Figure 5(b), the intermediate foil piece 24a has a base portion 24b. The base portion 24b is the portion facing the top foil 22 (see Figure 2). The circumferential edge 24e of the intermediate foil piece 24a has a notch formed to form a separate portion that is folded away from the base portion 24b. This separate portion is folded away from the base portion 24b to form a claw 8. The claw 8 is inserted into the claw insertion portion 23x of the back foil piece 23a (see Figure 6). After passing through the claw insertion portion 23x of the back foil piece 23a, the claw 8 is housed in a positioning groove 9 provided in the bearing housing 45.

[0042] (Positioning groove and claw) Figure 6 is a perspective view showing a radial foil bearing 20, with the top foil 22 omitted for convenience. The foil assembly 21 comprises one end and the other end in the axial direction D1. One end of the foil assembly 21 is provided with three (or more) claws 8 along the circumferential direction D2, and the other end is also provided with three (or more) claws 8 along the circumferential direction D2. The claws 8 formed at one end and the claws 8 formed at the other end are arranged to face each other in the axial direction D1. For example, the claws 8 at the other end are arranged on a straight line extending in the axial direction D1 through the claws 8 provided at one end. Note that the claws 8 formed at one end and the claws 8 formed at the other end may be offset in the circumferential direction D2.

[0043] The multiple claws 8 provided at one end of the foil assembly 21 and the multiple claws 8 provided at the other end have essentially the same arrangement and shape. Therefore, although the explanation will be given using the multiple claws 8 provided at one end as an example, the arrangement and shape of the multiple claws 8 provided at the other end may be different from those of the multiple claws 8 provided at one end.

[0044] For the sake of explanation, the three claws 8 provided at one end of the foil assembly 21 will be described as the first claw 8A, the second claw 8B, and the third claw 8C. Figure 7(a) is a cross-sectional view showing the first claw 8A, and Figure 7(b) is a cross-sectional view showing the second claw 8B. The first claw 8A and the third claw 8C have the same orientation of their tip portions 83, while the second claw 8B has the opposite orientation of its tip portion 83 compared to the first claw 8A. However, since the first claw 8A, the second claw 8B, and the third claw 8C have the same basic structure, the first claw 8A will be used as an example for explanation, and the common structure of the second claw 8B and the third claw 8C will be given the same reference numerals and their explanation will be omitted. Furthermore, in the following explanation, a cross-sectional view refers to a cross-section perpendicular to the axis of rotation H. For example, Figures 7(a) and 7(b) are cross-sectional views perpendicular to the axis of rotation H.

[0045] As shown in Figure 7(a), the first claw 8A is housed in a positioning groove 9 provided in the bearing housing 45. The first claw 8A comprises a root portion 81, a body portion 82, and a tip portion 83, which are integrally formed by bending.

[0046] The root portion 81 is erected so as to protrude radially outward from the base portion 24b. Radially outward is an example of an outward direction that is opposite to the top foil 22 with respect to the base portion 24b. The root portion 81 is positioned to face the inner surface 90 of the positioning groove 9. The root portion 81 is also positioned to be spaced apart from the inner surface 90.

[0047] In cross-sectional view, the root portion 81 is, for example, a plate-like shape extending along the radial direction D3. Furthermore, the root portion 81 is a plate-like shape with a constant thickness and a continuous identical shape along the axial direction D1. The root portion 81 may have holes, uneven surfaces, or a structure with partially different thicknesses, as long as its placement in the positioning groove 9 is not impaired and at least a portion of it faces the inner surface 90 of the positioning groove 9.

[0048] The main body portion 82 is connected to the base portion 81 in a curved state and is positioned to extend in the circumferential direction D2 of the shaft hole Sh within the positioning groove 9. "Extending in the circumferential direction D2 of the shaft hole Sh" broadly includes examples of extending in a direction intersecting the radial direction D3. In cross-sectional view, the main body portion 82 is, for example, a flat plate shape extending linearly along the circumferential direction D2. Alternatively, the main body portion 82 is a plate shape of constant thickness with the same shape continuing in the axial direction D1. The main body portion 82 may have holes or uneven shapes, or a structure with partially different thicknesses, as long as its housing in the positioning groove 9 is not impaired. For example, the main body portion 82 may be a plate shape curved along the circumferential direction D2.

[0049] The tip portion 83 is connected to the main body portion 82 in a curved manner. The tip portion 83 is positioned on the opposite side of the main body portion 82 from the base portion 81 and is positioned to face the inner surface 90 of the positioning groove 9. The tip portion 83 is positioned away from the top foil 22 relative to the main body portion 82 and has a shape that is, for example, bent radially outward relative to the main body portion 82. The tip portion 83 is also positioned away from the inner surface 90.

[0050] In cross-sectional view, the tip portion 83 is, for example, a curved plate shape that is curved to face the curvature of the inner surface 90. The tip portion 83 is also a plate shape of constant thickness with the same shape continuing in the axial direction D1. The tip portion 83 may have holes or uneven shapes, or a structure with partially different thicknesses, as long as its placement in the positioning groove 9 is not impaired and at least a portion of it is positioned to face the inner surface 90 of the positioning groove 9.

[0051] The second claw 8B has a base portion 81, a main body portion 82, and a tip portion 83 which are integrally formed by bending (see Figure 7(b)). The third claw 8C has a base portion 81, a main body portion 82, and a tip portion 83 which are integrally formed by bending (see Figure 2).

[0052] As shown in Figures 2 and 6, the positioning grooves 9 are provided at multiple locations corresponding to the multiple claws 8. The bearing housing 45 has a cylindrical inner circumferential surface 45a facing the shaft hole Sh. Three (or more) positioning grooves 9 are formed along the circumferential direction D2 at one end of the inner circumferential surface 45a, and three (or more) positioning grooves 9 are formed along the circumferential direction D2 at the other end. Since the shapes of the multiple positioning grooves 9 are substantially the same, the following explanation will use one positioning groove 9 as an example, but they may have different shapes as long as they can accommodate the claws 8.

[0053] As shown in Figure 7(b), the positioning groove 9 has an inverted U-shaped (dome-shaped) cross-section and includes a claw housing portion 95 and a claw introduction portion 96. The claw housing portion 95 has an inner surface 90 that faces the claw 8 housed in the positioning groove 9. The inner surface 90 has a first surface 91 and a second surface 92 that face each other in the circumferential direction D2 of the shaft hole Sh. The first surface 91 is the portion that faces the root portion 81. The inner surface 90 also has a curved surface 93 that connects the first surface 91 and the second surface 92 on the radially outward side. The curved surface 93 is curved in a concave shape and faces the tip portion 83. The positioning groove 9 also has a depth in the axial direction D1. The depth of the positioning groove 9 is greater than the width of the claw 8 in the axial direction D1, and the claw 8 can be housed in the axial direction D1.

[0054] The claw introduction section 96 is provided with an opening A1 facing the shaft hole Sh. The claws 8 of the intermediate foil 24 are inserted through the opening A1 and housed in the positioning groove 9. The width W of the opening A1 in the circumferential direction D2 of the shaft hole Sh is greater than the length L of the claws 8 in the circumferential direction D2 of the shaft hole Sh, making it easier to insert the claws 8 into the positioning groove 9. The relationship between the width W of the opening A1 and the length L of the claws 8 will now be explained in detail.

[0055] The opening A1 is positioned to face the shaft hole Sh, and in cross-sectional view, it is curved to conform to the shape of the shaft hole Sh. For example, the width W of the opening A1 in the circumferential direction D2 is constant in the axial direction D1. The width W of the opening A1 in the circumferential direction D2 refers to the distance between the first point Pa on one side and the second point Pb on the other side of the opening A1 in the circumferential direction D2 when viewed in cross-section. Note that if the width W of the opening A1 is not constant in the axial direction D1, the width W of the opening A1 in the circumferential direction D2 of the shaft hole Sh refers to the smallest width among the different widths in the axial direction D1.

[0056] The length L of the claw 8 in the circumferential direction D2 is, for example, constant in the axial direction D1. The length L of the claw 8 in the circumferential direction D2 refers to the distance between the first part Pc, which is one end of the axial hole Sh in the circumferential direction D2, and the second part Pd, which is the other end, when viewed in cross-section. For example, the length L of the claw 8 in the circumferential direction D2 refers to the straight-line distance between the first part Pc and the second part Pd when the first part Pc and the second part Pd are projected onto a reference plane including the surface of the base part 24b. Note that if the length L of the claw 8 is not constant in the axial direction D1, the length L of the claw 8 in the circumferential direction D2 refers to the longest length among the different lengths in the axial direction D1.

[0057] As shown in Figure 7(b), for example, the tip 83 of the claw 8 and the curved surface 93 (inner surface 90) are spaced apart, and the root 81 and the first surface 91 (inner surface 90) are spaced apart. Even if the claw 8 moves in the circumferential direction D2 of the shaft hole Sh, the movement of the claw 8 is restricted by contact between the tip 83 and the curved surface 93, or by contact between the root 81 and the first surface 91, and the movement of the back foil 23 locked to the claw 8 is restricted. Also, the distance G1 between the tip 83 and the curved surface 93 is smaller than the distance G2 between the root 81 and the first surface 91. As a result, the movement of the claw 8 dependent on the distance G1 between the tip 83 and the curved surface 93 can be set to be smaller than the movement of the claw 8 dependent on the distance G2 between the root 81 and the first surface 91.

[0058] When assembling the radial foil bearing 20, the claws 8 of the intermediate foil 24 are inserted into the claw insertion portion 23x of the back foil 23, and in that state, are inserted into the positioning groove 9 through the opening A1 of the positioning groove 9. Here, the width W in the circumferential direction D2 of the opening A1 of the positioning groove 9 is greater than the length L in the circumferential direction D2 of the claw 8. In other words, when fitting the claw 8 into the positioning groove 9, there is no need to bend or change the claw 8 and push it in. Therefore, insertion of the claw 8 into the positioning groove 9 is easy, and as a result, assembly is improved.

[0059] Furthermore, since there is no need for procedures or processes such as bending or deforming the claws 8 when inserting them into the positioning groove 9, it becomes easier to apply this method to automatically assembling radial foil bearings 20 using industrial robots.

[0060] For example, when considering the automated assembly of a radial foil bearing 20 that supports a rotating shaft 15 with a length of 10 mm or more and 70 mm or less, the positioning accuracy of the industrial robot is assumed to be ±0.3 mm. The dimensional tolerance of the positioning groove 9 is approximately ±0.1 mm, the positional accuracy of the positioning groove 9 is approximately ±0.1 mm, and the dimensional tolerance of the jaw insertion portion 23x of the back foil 23 is approximately ±0.2 mm. Under these conditions, for automated assembly, the dimensional difference between the length L of the jaw 8 and the opening A1, that is, the dimension required to avoid interference between the jaw 8 and the bearing housing 45, taking into account the positioning accuracy of the industrial robot, is 0.2 mm or more and 2.0 mm or less. The jaw 8 must avoid interference with the bearing housing 45 on both sides in the circumferential direction D2, and the dimension required on one side to avoid interference between the jaw 8 and the bearing housing 45 is 0.1 mm or more and 1.0 mm or less.

[0061] Furthermore, in the radial foil bearing 20, when the claws 8 are housed in the positioning groove 9, the root portion 81 and the inner surface 90 of the positioning groove 9 are spaced apart, and the tip portion 83 and the inner surface 90 are spaced apart. By designing the claws 8 and the inner surface 90 to be spaced apart, the claws 8 are less likely to interfere with the bearing housing 45 when inserted into the positioning groove 9. The distance between the tip portion 83 and the inner surface 90 can be, for example, 0.05 mm or more and 0.5 mm or less, and preferably 0.05 mm or more and 0.25 mm or less. Also, the distance between the root portion 81 and the inner surface 90 can be, for example, 0.05 mm or more and 0.5 mm or less, and preferably 0.05 mm or more and 0.25 mm or less.

[0062] In the radial foil bearing 20, the tip portion 83 of the claw 8 is positioned spaced apart from the inner surface 90, so the claw 8 can effectively move in the circumferential direction D2. However, since the concave curved surface 93 of the inner surface 90 faces and overlaps the tip portion 83, it is possible to reduce the gap between the tip portion 83 and the curved surface 93 (inner surface 90) while ensuring sufficient depth to accommodate the tip portion 83.

[0063] As shown in Figure 2, the foil assembly 21 comprises a first claw 8A, a second claw 8B, and a third claw 8C arranged in the circumferential direction D2 of the shaft hole Sh. In the cross-sectional view of Figure 2, the rotational direction Da of the rotating shaft 15 is counterclockwise. In the radial foil bearing 20 shown in Figure 2, the orientation of the tip 83 of any one of the claws 8 is different from the orientation of the tip 83 of the other claws 8. The orientation of the tip 83 refers to the direction in which the tip 83 is positioned relative to the root 81.

[0064] For example, the tip 83 of the first claw 8A and the tip 83 of the third claw 8C are oriented in the opposite direction (clockwise) to the rotation direction Da of the rotation axis 15. In contrast, the tip 83 of the second claw 8B is oriented in the rotation direction Da of the rotation axis 15. Also, for example, the tip 83 of the first claw 8A and the tip 83 of the third claw 8C are spaced apart from the base 81 in the direction opposite to the rotation direction Da of the rotation axis 15. In contrast, the tip 83 of the second claw 8B is spaced apart towards the rotation direction Da of the rotation axis 15.

[0065] Figure 8 shows another example of a radial foil bearing 20A. In the radial foil bearing 20A shown in Figure 8, the tips 83 of each of the multiple claws 8 are arranged to face the same direction. For example, the tips 83 of the first claw 8A, the second claw 8B, and the third claw 8C are all arranged to face the rotation direction Da of the rotation axis 15. However, as shown in Figure 9, the radial foil bearing 20B may also be one in which the tips 83 of the first claw 8A, the second claw 8B, and the third claw 8C are all arranged to face the opposite direction to the rotation direction Da of the rotation axis 15.

[0066] Next, with reference to Figure 10, modified versions of the claws will be described. Figure 10(a) shows claw 8X relating to the first modified version, and Figure 10(b) shows claw 8Y relating to the second modified version. Claws 8X and 8Y can be applied to radial foil bearing 20 and radial foil bearing 20A, respectively. Hereafter, elements and structures common to radial foil bearings 20, 20A, and 20B will be denoted by the same reference numerals, and detailed explanations will be omitted.

[0067] As shown in Figure 10(a), the claw 8X comprises a root portion 81X, a body portion 82X, and a tip portion 83X, which are integrally formed by bending. The root portion 81X protrudes outward from the base portion 24b, on the opposite side from the top foil 22. The root portion 81X is inserted into the claw insertion portion 23x of the back foil 23 and locks the back foil 23. The body portion 82X is connected to the root portion 81X and extends in the circumferential direction D2. The tip portion 83X is connected to the body portion 82X and is positioned on the opposite side of the body portion 82X from the root portion 81X. In cross-sectional view, the root portion 81X, the body portion 82X, and the tip portion 83X are each linear and flat. The root portion 81X extends so as to face the first surface 91 of the inner surface 90. The tip portion 83X extends in the circumferential direction D2 so as to face the second surface 92 and the curved surface 93, which are opposite the first surface 91. The main body portion 82X is inclined such that the portion connected to the base portion 81X is positioned radially outward, and the portion connected to the tip portion 83 is positioned closer to the top foil 22 than the portion connected to the base portion 81.

[0068] As shown in Figure 10(b), the claw 8Y comprises a root portion 81Y, a body portion 82Y, and a tip portion 83Y, which are integrally formed by bending. The root portion 81Y protrudes outward from the base portion 24b, on the opposite side from the top foil 22. The root portion 81 is inserted into the claw insertion portion 23x of the back foil 23, and locks the back foil 23. The body portion 82Y is connected to the root portion 81Y and extends in the circumferential direction D2. The tip portion 83 is connected to the body portion 82Y and is positioned on the opposite side of the body portion 82Y from the root portion 81Y. In cross-sectional view, the root portion 81Y, the body portion 82Y, and the tip portion 83Y are each linear and flat. The root portion 81Y extends so as to face the first surface 91 of the inner surface 90, and the body portion 82Y extends so as to face the curved surface 93. Furthermore, the tip portion 83Y is curved to follow the curved surface 93 and connected to the main body portion 82Y, and extends in the circumferential direction D2 to face the second surface 92 which faces the first surface 91.

[0069] Next, with reference to Figures 11 and 12, a radial foil bearing 20C according to another embodiment will be described. The radial foil bearing 20C shown in Figure 11 has substantially the same structure and elements as the radial foil bearings 20, 20A, and 20B shown in Figure 2, etc. Therefore, the structures and elements common to the radial foil bearings 20, 20A, and 20B shown in Figure 2, etc. will be denoted by the same reference numerals and detailed explanations will be omitted.

[0070] As shown in Figure 11, the radial foil bearing 20C is equipped with a plurality of claws 8 positioned in the circumferential direction D2 of the shaft bore Sh. The claws 8 have substantially the same shape and structure as, for example, the claws 8 shown in Figure 7(a) or (b). Alternatively, claws 8X or 8Y may be used instead of claws 8 as appropriate.

[0071] Of the multiple claws 8, the tips 83 of some claws 8 are positioned to face in different directions from the tips 83 of the other claws 8. For example, the tips 83 of some claws 8 are positioned to face in the opposite direction to the rotation direction Da of the rotation axis 15, while the tips 83 of the other claws 8 are positioned to face the rotation direction Da of the rotation axis 15. The tips 83 of the multiple claws 8 may also be positioned to face the same direction; for example, the tips 83 of all claws 8 may be positioned to face the rotation direction Da of the rotation axis 15, or they may be positioned to face in the opposite direction to the rotation direction Da of the rotation axis 15.

[0072] As shown in Figure 12, the claw 8 is housed in a positioning groove 9A provided in the bearing housing 45. The claw 8 has a root portion 81 that extends radially outward from the base portion 24b. The root portion 81 is positioned to face the inner surface 90A of the positioning groove 9A. The root portion 81 is in contact with the inner surface 90A (first surface 91A) and its movement in the circumferential direction D2 is restricted. The main body portion 82 is connected to the root portion 81 in a curved manner and is positioned to extend in the circumferential direction D2 within the positioning groove 9A. The tip portion 83 is connected to the main body portion 82 in a curved manner. The tip portion 83 is positioned on the opposite side of the main body portion 82 from the root portion 81. The tip portion 83 is positioned to face the inner surface 90A of the positioning groove 9A. The tip portion 83 is curved to follow the curved surface 93A, and its movement in the circumferential direction D2 is restricted by contact with the inner surface 90A (curved surface 93).

[0073] The positioning groove 9A comprises a claw introduction portion 96A and a claw housing portion 95A. The claw introduction portion 96A has an opening A2 facing the shaft hole Sh. The inner surface 90A facing the claw 8 is provided in the claw housing portion 95A. The inner surface 90A comprises a first surface 91A and a second surface 92A that face each other in the circumferential direction D2. The inner surface 90A has a curved surface 93A connecting the first surface 91A and the second surface 92A. The claw introduction portion 96A has a chamfered portion 96a (introduction passage) that connects the inside of the claw housing portion 95A and the opening A2. The width of the chamfered portion 96a in the circumferential direction D2 gradually widens from the claw housing portion 95A to the opening A2. For example, in a cross-sectional view, the chamfered portion 96a widens in a tapered shape from the claw housing portion 95A to the opening A2.

[0074] The claws 8 of the intermediate foil 24 are inserted through the opening A2 of the positioning groove 9A and housed within the positioning groove 9A. The width W of the opening A2 in the circumferential direction D2 is greater than the width Wa of the circumferential direction D2 between the first surface 91A and the second surface 92A. Also, the width W of the opening A2 is greater than the length L of the claw 8 in the circumferential direction D2. As a result, the claws 8 are easily inserted into the positioning groove 9A. Furthermore, the root portion 81 of the claw 8 abuts against the first surface 91A, and the tip portion 83 abuts against the curved surface 93A. Therefore, the movement of the claws 8 in the circumferential direction D2 is completely constrained. In other words, the claws 8 of the intermediate foil 24 are inserted through the opening A2 of the positioning groove 9A and housed within the positioning groove 9A. The width W of the opening A2 in the circumferential direction D2 is greater than the width Wa of the circumferential direction D2 between the first surface 91A and the second surface 92A. Furthermore, the width W of the opening A2 is greater than the length L of the claw 8 in the circumferential direction D2. As a result, the radial foil bearing 20C can completely restrain the movement of the claw 8 in the circumferential direction D2 while improving the ease of assembly when inserting the claw 8 into the positioning groove 9A.

[0075] Furthermore, in the radial foil bearing 20C equipped with a chamfered portion 96a, a modified form may be created in which the claw 8 and the inner surface 90A of the positioning groove 9A are separated to form a gap. Also, in the radial foil bearing 20C, claws 8X or 8Y may be applied instead of claw 8. In addition, the orientation of the tips 83 of the multiple claws 8 of the radial foil bearing 20C may all be the same, or some may be in different orientations. Furthermore, the orientation of the tips 83 may all be in the direction of rotation Da of the rotating shaft 15, or in the opposite direction to the rotation direction Da, or the orientation of the tips 83 of some claws 8 may be in the direction of rotation Da, and the orientation of the tips 83 of the other tips 83 may be in the opposite direction to the rotation direction Da.

[0076] (The function and effects of radial foil bearings) The foil assembly 21 of the radial foil bearings 20, 20A, 20B, and 20C includes an intermediate foil 24 that locks the back foil 23 to the bearing housing 45. The movement of the claws 8, 8X, and 8Y is restricted by interference with the inner surfaces 90 and 90A of the positioning grooves 9 and 9A. Since the claws 8, 8X, and 8Y lock the back foil 23, the movement of the back foil 23 is restricted by the restriction of the movement of the claws 8, 8X, and 8Y. The claws 8, 8X, and 8Y include main body portions 82, 82X, and 82Y that extend in the circumferential direction D2. Therefore, it is possible to arrange the claws 8, 8X, and 8Y to match the width of the positioning grooves 9 and 9A in the circumferential direction D2.

[0077] During the assembly of radial foil bearings 20, 20A to 20C, the claws 8, 8X, and 8Y of the intermediate foil 24 are inserted into the claw insertion portion 32x of the back foil 23, and then, in that state, are fitted into the positioning grooves 9, 9A by inserting them into the positioning grooves 9, 9A through the openings A1, A2. The width W in the circumferential direction D2 of the openings A1, A2 of the positioning grooves 9, 9A is greater than the length L in the circumferential direction D2 of the claws 8, 8X, and 8Y. In other words, when fitting the claws 8, 8X, and 8Y into the positioning grooves 9, 9A, it is not necessary to bend or change the claws 8, 8X, and 8Y to force them in. Therefore, insertion of the claws 8, 8X, and 8Y into the positioning grooves 9, 9A is easy, and as a result, assembly efficiency is improved. Furthermore, since it is possible to avoid the claws 8, 8X, and 8Y protruding from the positioning grooves 9, 9A and interfering with the bearing housing 45 during assembly, it becomes easier to apply to automated assembly processes.

[0078] In the case of radial foil bearings 20, 20A to 20C, during assembly, the claws 8, 8X, 8Y of the intermediate foil 24 are inserted into the claw insertion section of the back foil 23, and then fitted into the positioning grooves 9, 9A through the openings A1, A2 of the positioning grooves 9, 9A. The width W of the circumferential direction D2 of the openings A1, A2 of the positioning grooves 9, 9A is greater than the length L of the circumferential direction D2 of the claws 8, 8X, 8Y. In other words, when fitting the claws 8, 8X, 8Y into the positioning grooves 9, 9A, it is not necessary to bend or change the claws 8, 8X, 8Y to force them in. Therefore, insertion of the claws 8, 8X, 8Y into the positioning grooves 9, 9A is easy, and as a result, assembly is improved.

[0079] Furthermore, when the claws 8,8X,8Y are housed within the positioning grooves 9,9A, the root portions 81,81X,81Y face the inner surfaces 90,90A of the positioning grooves 9,9A. When the claws 8,8X,8Y of the back foil 23 or intermediate foil 24 move in the circumferential direction D2, the claws 8,8X,8Y also move in accordance with that movement. However, this movement is restricted by the interference between the root portions 81,81X,81Y and the inner surfaces 90,90A. In the case of the radial foil bearing 20, there is a gap between the root portions 81,81X,81Y and the inner surface 90. However, this gap is specified as a dimension within the range in which movement of the claws 8,8X,8Y in the circumferential direction D2 is permitted.

[0080] Furthermore, the movement of the claws 8,8X,8Y in the circumferential direction D2 is restricted by the interference of the tip portions 83,83X,83Y with the inner surfaces 90,90A of the positioning grooves 9,9A. The tip portions 83,83X,83Y face the inner surfaces 90,90A, resulting in surface-to-surface contact. As a result, the claws 8,8X,8Y are subjected to interference from the inner surfaces 90,90A, and the movement of the back foil 23 is restricted by the interference between the claws 8,8X,8Y and the inner surfaces 90,90A. In the case of the radial foil bearing 20, there is a gap between the tip portions 83,83X,83Y and the inner surface 90. However, this gap is specified as a dimension within the range in which the movement of the claws 8,8X,8Y in the circumferential direction D2 is permitted.

[0081] Furthermore, the inner surfaces 90, 90A include a first surface 91, 91A, a second surface 92, 92A, and concave curved surfaces 93, 93A connecting the first surface 91, 91A and the second surface 92, 92A. The tips 83, 83X, 83Y of the claws 8, 8X, 8Y are curved to follow the curved surfaces 93, 93A. By forming the concave curved surfaces 93, 93A, depth is secured to receive the tips 83, 83X, 83Y, while the movement of the tips 83, 83X, 83Y in the circumferential direction D2 can be restricted by the curved surfaces 93, 93A. In the radial foil bearing 20, the tips 83, 83X, 83Y are positioned spaced apart from the curved surface 93. When the tip portions 83, 83X, and 83Y are positioned spaced apart from the inner surfaces 90 and 90A, positioning the tip portions 83, 83X, and 83Y so that they face the curved surface 93 reduces the spacing distance compared to positioning the tip portions 83, 83X, and 83Y so that they face the second surface 92, making it easier to restrict the movement of the claws 8, 8X, and 8Y.

[0082] Furthermore, the radial foil bearings 20, 20A to 20C are equipped with multiple claws 8, 8X, 8Y in the circumferential direction D2, and at least one of the multiple claws 8, 8X, 8Y has a tip portion 83, 83X, 83Y positioned spaced apart from the root portion 81, 81X, 81Y toward the rotation direction Da of the rotating shaft 15. The movement of the claws 8, 8X, 8Y toward the rotation direction Da of the rotating shaft 15 is restricted by the interference of the tip portion 83, 83X, 83Y with the inner surfaces 90, 90A of the positioning grooves 9, 9A. As a result, the movement of the back foil 23, which is locked to the claws 8, 8X, 8Y toward the rotation direction Da is restricted.

[0083] Furthermore, the radial foil bearings 20, 20A to 20C are equipped with multiple claws 8, 8X, 8Y in the circumferential direction D2, and at least one of the multiple claws 8, 8X, 8Y has a tip portion 83, 83X, 83Y positioned spaced apart from the root portion 81, 81X, 81Y on the side opposite to the rotation direction Da of the rotating shaft 15. The movement of the claws 8, 8X, 8Y in the direction opposite to the rotation direction Da of the rotating shaft 15 is restricted by the tip portion 83, 83X, 83Y interfering with the inner surfaces 90, 90A of the positioning grooves 9, 9A. As a result, the back foil 23, which is locked to the claws 8, 8X, 8Y, is restricted from moving in the direction opposite to the rotation direction Da.

[0084] Furthermore, the radial foil bearings 20, 20A to 20C are equipped with multiple claws 8, 8X, 8Y in the circumferential direction D2. Of the multiple claws 8, 8X, 8Y, at least one claw 8, 8X, 8Y has a tip portion 83, 83X, 83Y positioned spaced apart from the root portion 81, 81X, 81Y toward the rotation direction Da, and at least one claw 8, 8X, 8Y has a tip portion 83, 83X, 83Y positioned spaced apart from the root portion 81, 81X, 81Y toward the direction opposite to the rotation direction Da. The movement of the claws 8, 8X, 8Y in the rotation direction Da and the direction opposite to the rotation direction Da of the rotating shaft 15 is restricted by the interference of the tip portions 83, 83X, 83Y with the inner surfaces 90, 90A of the positioning grooves 9, 9A. As a result, the back foil 23, which is locked to the claws 8, 8X, and 8Y, is restricted from moving in the rotational direction Da and in the direction opposite to the rotational direction Da.

[0085] Furthermore, in the radial foil bearing 20, the tip portions 83, 83X, 83Y are spaced apart from the curved surface 93, and the root portions 81, 81X, 81Y are spaced apart from the first surface 91. Even if the claws 8, 8X, 8Y move in the circumferential direction D2 of the shaft hole Sh, the movement of the claws 8, 8X, 8Y is restricted by contact between the tip portions 83, 83X, 83Y and the curved surface 93, 93A, or by contact between the root portions 81, 81X, 81Y and the first surface 91, 91A, and the movement of the back foil 23, which is locked to the claws 8, 8X, 8Y, is restricted. In addition, the distance G1 between the tip portion 83 and the curved surface 93 is smaller than the distance G2 between the root portion 81 and the first surface 91. As a result, the movement of the claw 8, which depends on the distance G1 between the tip portion 83 and the curved surface 93, can be set to be smaller than the movement of the claw 8, which depends on the distance G2 between the base portion 81 and the first surface 91.

[0086] Furthermore, the positioning groove 9A of the radial foil bearing 20C includes a claw introduction portion 96A with an opening A2 and a claw housing portion 95A with an inner surface 90A. The tip portions 83, 83X, 83Y of the claws 8, 8X, 8Y are in contact with the curved surface 93A, and the root portions 81, 81X, 81Y are in contact with the first surface 91A. Therefore, the movement of the claws 8, 8X, 8Y in the circumferential direction D2 within the positioning groove 9A is constrained. Also, the width W of the circumferential direction D2 of the opening A2 of the positioning groove 9A is greater than the width W of the circumferential direction D2 between the first surface 91A and the second surface 92A. Therefore, the width W of the circumferential direction D2 of the opening A2 of the positioning groove 9A is greater than the length L of the circumferential direction D2 of the claws 8, 8X, 8Y, making it easier to insert the claws 8, 8X, 8Y into the positioning groove 9A. As a result, it is possible to achieve both constraint on the movement of claws 8, 8X, and 8Y in the circumferential direction D2 and improved ease of assembly.

[0087] The radial foil bearings according to this disclosure are not limited to the examples described above, and various other modifications are possible. For example, the examples described above may be combined with each other depending on the required purpose and effect. Furthermore, multiple claws may have different shapes and dimensions, and the positioning grooves may have shapes and dimensions corresponding to those claws. In addition, either the tip or the root of a claw may be shaped to abut the inner surface of the positioning groove. Furthermore, the claws may not have a tip, and the end portion of the main body opposite the root may face the inner surface (second surface or curved surface) of the positioning groove in the circumferential direction. [Explanation of symbols]

[0088] 8,8X,8Y claws 9,9A Positioning groove 15 Rotation axis 20, 20A, 20B, 20C Radial Foil Bearings 22 Top Foil 23 Backfoil 23x Nail insertion section 24 Intermediate foil 24b Base section 45 Bearing housing 81, 81X, 81Y Root part 82, 82X, 82Y Main Unit 83,83X,83Y Tip 90,90A Inner surface 91,91A 1st page 92,92A 2nd side 93,93A Curved surface 95,95A Claw housing 96,96A Claw introduction section A1,A2 opening Da rotation direction D2 Circumferential direction Sh shaft hole W: Width of opening Wa Width between the first and second surfaces L Nail length

Claims

1. A bearing housing having a shaft hole, The top foil is positioned inside the aforementioned shaft hole, The back foil is positioned between the top foil and the bearing housing, The system comprises an intermediate foil positioned between the top foil and the back foil, The intermediate foil is provided with claws that engage the back foil with the bearing housing. The back foil is provided with a claw insertion portion through which the claw is inserted, The bearing housing is provided with a positioning groove that accommodates the claw that has passed through the claw insertion portion, The positioning groove has an opening facing the shaft hole, The claw comprises a main body portion that extends in the circumferential direction of the shaft hole within the positioning groove, A radial foil bearing in which the circumferential width of the opening is greater than the circumferential length of the claw.

2. The positioning groove has an inner surface facing the claw, The intermediate foil comprises a base portion facing the top foil, The radial foil bearing according to claim 1, wherein the claw protrudes outward from the base portion on the opposite side from the top foil and is inserted through the claw insertion portion and has a root portion facing the inner surface.

3. The radial foil bearing according to claim 2, wherein the claw is positioned on the opposite side of the main body from the base and has a tip facing the inner surface.

4. The inner surface comprises a first surface facing the root portion, a second surface facing the first surface in the circumferential direction, and a curved surface that connects the first surface and the second surface and curves in a concave shape. The radial foil bearing according to claim 3, wherein the tip portion is curved to conform to the curved surface.

5. Multiple claws are provided in the circumferential direction, The radial foil bearing according to claim 3, wherein at least one of the plurality of claws has a tip portion that is spaced apart from the base portion on the side of the rotational direction of the rotating shaft that is inserted into the shaft hole.

6. Multiple claws are provided in the circumferential direction, The radial foil bearing according to claim 3, wherein at least one of the plurality of claws has a tip portion that is spaced apart from the base portion in the direction opposite to the direction of rotation of the rotating shaft that is inserted into the shaft hole.

7. Multiple claws are provided in the circumferential direction, At least one of the claws has a tip portion that is spaced apart from the base portion on the side of the rotational direction of the rotating shaft that is inserted into the shaft hole, The radial foil bearing according to claim 3, wherein at least one of the claws has a tip portion that is spaced apart from the root portion in the direction opposite to the direction of rotation.

8. The radial foil bearing according to claim 4, wherein the tip portion and the curved surface are spaced apart, and the root portion and the first surface are spaced apart.

9. The radial foil bearing according to claim 8, wherein the distance between the tip and the curved surface is smaller than the distance between the root and the first surface.

10. The positioning groove comprises a claw introduction portion having the opening and a claw housing portion having the inner surface, The tip portion and the curved surface are in contact with each other. The base portion and the first surface are in contact with each other. The radial foil bearing according to claim 4, wherein the circumferential width of the opening is greater than the circumferential width between the first surface and the second surface.

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