Foil bearing

Abstract

To provide a foil bearing capable of suppressing an inclination of a bump foil with respect to a top foil.SOLUTION: A foil bearing 10 includes a cylindrical bearing housing 12, and a plurality of thin plate-like bump foils 14 arranged in a circumferential direction Z of the bearing housing 12. Each of the bump foils 14 includes a first locking portion 43 extending toward the bearing housing 12 from a first end 40a of a body 40 in the circumferential direction Z of the bearing housing 12 and inserted into a first locking groove 20a of the bearing housing 12, and a second locking portion 44 extending toward the bearing housing 12 from a second end 40b of the body 40 in the circumferential direction Z of the bearing housing 12 and inserted into a second locking groove 20b of the bearing housing 12. A pair of regulating members 15 separate from the bearing housing 12 is provided on both sides of the first locking portion 43 and the second locking portion 44 in an axial direction X of the bearing housing 12.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a foil bearing. [Background technology]

[0002] Patent Document 1 discloses a foil bearing that rotatably supports a rotating shaft. The foil bearing includes a cylindrical bearing housing, a thin top foil, and a thin bump foil. The rotating shaft is inserted through the bearing housing. The axial direction of the rotating shaft coincides with the axial direction of the bearing housing. The top foil is disposed between the rotating shaft and the bearing housing. The bump foil is disposed between the bearing housing and the top foil.

[0003] The bump foil has a main body portion and a locking portion. The main body portion extends in the circumferential direction of the bearing housing. The main body portion elastically supports the top foil. The locking portion extends from a first end of the main body portion in the circumferential direction of the bearing housing toward the bearing housing. A groove is provided on the inner peripheral surface of the bearing housing into which the locking portion of the bump foil is inserted. The groove opens at one end face of the bearing housing in the axial direction. Therefore, the bearing housing is located on one side of the locking portion in the axial direction of the bearing housing. In addition, a restricting member is provided on the other side of the locking portion in the axial direction of the bearing housing. This restricts movement of the locking portion in the axial direction of the bearing housing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2022-57207 Summary of the Invention [Problem to be solved by the invention]

[0005] FIG. 6 is a development view of the top foil 60 and the bump foil 70. The up-down direction in FIG. 6 corresponds to the axial direction of the bearing housing. The left-right direction in FIG. 6 corresponds to the circumferential direction of the bearing housing. As described above, the first end 71a of the main body 71 in the circumferential direction of the bearing housing is provided with the locking portion 72. The movement of the locking portion 72 in the axial direction of the bearing housing is restricted by the bearing housing and a restricting member (not shown). Therefore, at the first end 71a of the main body 71 in the circumferential direction of the bearing housing, the bump foil 70 is unlikely to move in the axial direction of the bearing housing. On the other hand, at the second end 71b of the main body 71 in the circumferential direction of the bearing housing, the movement of the bump foil 70 in the axial direction of the bearing housing is not restricted. Therefore, when the foil bearing is assembled, as shown by the two-dot chain line in FIG. 6, the bump foil 70 may be tilted relative to the top foil 60 due to the movement of the bump foil 70 in the axial direction of the bearing housing.

[0006] 7, the distance from the main body 71 of the bump foil 70 to the top foil 60 changes in the axial direction of the bearing housing. Where the distance from the main body 71 to the top foil 60 is short, the top foil 60 is less likely to deform in a direction away from the rotating shaft 80 compared to where the distance from the main body 71 to the top foil 60 is long. For this reason, where the distance from the main body 71 to the top foil 60 is short, the top foil 60 is more likely to come into contact with the rotating shaft 80 compared to where the distance from the main body 71 to the top foil 60 is long. In other words, if the bump foil 70 is inclined with respect to the top foil 60, uneven wear occurs in the top foil 60 in the axial direction of the bearing housing. [Means for solving the problem]

[0007] A foil bearing for solving the above problems includes a cylindrical bearing housing through which a rotating shaft is inserted, a thin plate-like top foil arranged between the rotating shaft and the bearing housing, and a plurality of thin plate-like bump foils arranged between the bearing housing and the top foil and arranged in a circumferential direction of the bearing housing, each of the plurality of bump foils having a main body portion that extends in the circumferential direction of the bearing housing and elastically supports the top foil, a first engaging portion that extends from a first end of the main body portion in the circumferential direction of the bearing housing toward the bearing housing, and a second engaging portion that engages with the main body portion from a second end of the main body portion in the circumferential direction of the bearing housing toward the bearing housing. The bearing housing has a second locking portion extending toward the bump foil, and an inner peripheral surface of the bearing housing is provided with first locking grooves that open at both axial end faces of the bearing housing and into which the first locking portion is inserted, and second locking grooves that open at both axial end faces of the bearing housing and into which the second locking portion is inserted, the number of grooves being the same as the number of bump foils, and the first locking portions are individually inserted into the first locking grooves, and the second locking portions are individually inserted into the second locking grooves, and a pair of regulating members separate from the bearing housing are provided on both sides of the first locking portion and the second locking portion in the axial direction of the bearing housing.

[0008] According to the above configuration, the first locking portion of each bump foil is inserted into a first locking groove that opens at both axial end faces of the bearing housing. The second locking portion of each bump foil is inserted into a second locking groove that opens at both axial end faces of the bearing housing. A pair of restricting members is provided on both sides of the first locking portion and the second locking portion in the axial direction of the bearing housing. This restricts the movement of each bump foil in the axial direction of the bearing housing at both ends of each bump foil in the circumferential direction of the bearing housing. Therefore, each bump foil is less likely to tilt relative to the top foil. As a result, uneven wear of the top foil is suppressed, and the life of the foil bearing can be extended.

[0009] In addition, multiple bump foils are arranged in the circumferential direction of the bearing housing. Therefore, the distance from the center of the main body to each locking portion in the circumferential direction of the bearing housing is shorter than when, for example, one bump foil is arranged over almost the entire circumferential direction of the bearing housing. Therefore, twisting of the bump foil caused by the center of the main body in the circumferential direction of the bearing housing being shifted in the axial direction of the bearing housing can be suppressed.

[0010] For example, when the locking portions of two bump foils are inserted into one locking groove, i.e., when two bump foils share one locking groove, the locking portions may interfere with each other within the locking groove. In contrast, according to the above configuration, the bearing housing is provided with the same number of first locking grooves as the number of bump foils, and the same number of second locking grooves as the number of bump foils. The first locking portions are individually inserted into the first locking grooves, and the second locking portions are individually inserted into the second locking grooves. In other words, the first locking portion of one bump foil is inserted into one first locking groove, and the second locking portion of one bump foil is inserted into one second locking groove. This makes it possible to avoid interference between the locking portions.

[0011] Furthermore, the pair of regulating members are separate from the bearing housing, and therefore the material of the bearing housing and the material of the pair of regulating members can be different, so that the material of the bearing housing can be made of a material with excellent heat dissipation properties, and the material of the pair of regulating members can be made of a material with excellent wear resistance.

[0012] In the above foil bearing, the first locking groove and the second locking groove may each extend over the entire axial direction of the bearing housing. A refrigerant gas for cooling the foil bearing is sometimes passed through the inside of the bearing housing. According to the above configuration, the first locking groove and the second locking groove are each provided over the entire axial direction of the bearing housing. Therefore, the amount of refrigerant gas passing through the inside of the bearing housing can be increased compared to a case where the first locking groove and the second locking groove are each provided only at both ends of the bearing housing in the axial direction. Therefore, the cooling effect of the foil bearing can be increased.

[0013] In the above foil bearing, the first engagement portion may extend over the entire first engagement groove in the axial direction of the bearing housing, and the second engagement portion may extend over the entire second engagement groove in the axial direction of the bearing housing.

[0014] The bump foil is positioned in the circumferential direction of the bearing housing by inserting the first locking portion into the first locking groove and inserting the second locking portion into the second locking groove. According to the above configuration, the first locking portion extends over the entire first locking groove in the axial direction of the bearing housing. Therefore, compared to a case where the first locking portion is provided only at both ends of the first locking groove in the axial direction of the bearing housing, the area where the first locking portion faces the surface that defines the first locking groove in the circumferential direction of the bearing housing is larger. Similarly, the second locking portion extends over the entire second locking groove in the axial direction of the bearing housing. Therefore, compared to a case where the second locking portion is provided only at both ends of the second locking groove in the axial direction of the bearing housing, the area where the second locking portion faces the surface that defines the second locking groove in the circumferential direction of the bearing housing is larger. Therefore, the reliability of the positioning of the bump foil in the circumferential direction of the bearing housing is improved. Effect of the Invention

[0015] According to the present invention, the inclination of the bump foil with respect to the top foil can be suppressed. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic diagram of a centrifugal compressor. [Diagram 2] FIG. 2 is a cross-sectional view of a foil bearing according to an embodiment. [Diagram 3] FIG. 3 is an exploded perspective view of the foil bearing according to the embodiment. [Figure 4] FIG. 4 is a development view of the top foil and the bump foil according to the embodiment. [Diagram 5] FIG. 5 is a cross-sectional view taken along line 5-5 in FIG. [Figure 6] FIG. 6 is a development view of a top foil and a bump foil according to the prior art. [Figure 7] FIG. 7 is a cross-sectional view of a prior art foil bearing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] An embodiment of a foil bearing will now be described with reference to Figures 1 to 5. The foil bearing of this embodiment is used in a centrifugal compressor. As shown in FIG. 1, the centrifugal compressor 100 includes two foil bearings 10, a housing 101, an electric motor 102, a rotating shaft 103, and an impeller 104.

[0018] The electric motor 102, the rotating shaft 103, and the impeller 104 are accommodated in a housing 101. The electric motor 102 is accommodated in a motor chamber 101a formed in the housing 101. The impeller 104 is accommodated in an impeller chamber 101b formed in the housing 101. The rotating shaft 103 extends from the motor chamber 101a to the impeller chamber 101b. The electric motor 102 is attached to the rotating shaft 103. The impeller 104 is attached to one end of the rotating shaft 103 in the axial direction X.

[0019] The electric motor 102 is driven to rotate the rotating shaft 103. When the rotating shaft 103 rotates, the impeller 104 rotates. When the impeller 104 rotates, fluid is drawn into the impeller chamber 101b from outside the housing 101, and the drawn fluid is compressed in the impeller chamber 101b. The fluid compressed in the impeller chamber 101b is discharged to the outside of the housing 101.

[0020] Each foil bearing 10 is a radial bearing that supports the rotating shaft 103 in the radial direction Y of the rotating shaft 103. Each foil bearing 10 is fixed to the housing 101. The two foil bearings 10 are provided in positions in the axial direction X of the rotating shaft 103 such that the electric motor 102 is sandwiched between them.

[0021] <Configuration of foil bearing> 2 and 3, the foil bearing 10 includes a cylindrical bearing housing 12, a thin-plate-shaped top foil 13, a plurality of thin-plate-shaped bump foils 14, and a pair of restricting members 15, 16. The foil bearing 10 of this embodiment includes three bump foils 14.

[0022] <Bearing housing> The bearing housing 12 is made of a material with excellent heat dissipation properties. The bearing housing 12 of this embodiment is made of aluminum. The bearing housing 12 of this embodiment is cylindrical. The inner peripheral surface 12a of the bearing housing 12 is a curved surface extending cylindrically. The rotating shaft 103 is inserted into the bearing housing 12. The axial direction X, radial direction Y, and circumferential direction Z of the rotating shaft 103 respectively coincide with the axial direction, radial direction, and circumferential direction of the bearing housing 12. Therefore, the axial direction X, radial direction Y, and circumferential direction Z of the rotating shaft 103 are also the axial direction X, radial direction Y, and circumferential direction Z of the bearing housing 12, respectively.

[0023] The bearing housing 12 has a first end face 12b and a second end face 12c. The first end face 12b is one end face in the axial direction X of the bearing housing 12. The second end face 12c is the other end face in the axial direction X of the bearing housing 12. In this embodiment, the first end face 12b is located on one side X1 in the axial direction X of the bearing housing 12. The second end face 12c is located on the other side X2 in the axial direction X of the bearing housing 12.

[0024] The bearing housing 12 is provided with first to sixth grooves 21 to 26. The first to sixth grooves 21 to 26 are recessed from the inner circumferential surface 12a of the bearing housing 12. The first to sixth grooves 21 to 26 each have a first opening 201 that opens at the first end surface 12b of the bearing housing 12 and a second opening 202 that opens at the second end surface 12c of the bearing housing 12. That is, the first to sixth grooves 21 to 26 each open at both end surfaces 12b, 12c of the bearing housing 12 in the axial direction X. In this embodiment, the first to sixth grooves 21 to 26 are each provided over the entire axial direction X of the bearing housing 12. That is, the dimensions of the first to sixth grooves 21 to 26 in the axial direction X of the bearing housing 12 are the same as the dimensions of the bearing housing 12 in the axial direction X. In this embodiment, the widths of the first to sixth grooves 21 to 26 in the circumferential direction Z of the bearing housing 12 are the same.

[0025] The first to sixth grooves 21 to 26 are arranged in this order in the circumferential direction Z of the bearing housing 12. The interval between the first groove 21 and the second groove 22, the interval between the third groove 23 and the fourth groove 24, and the interval between the fifth groove 25 and the sixth groove 26 in the circumferential direction Z of the bearing housing 12 are all the same. The interval between the sixth groove 26 and the first groove 21, the interval between the second groove 22 and the third groove 23, and the interval between the fourth groove 24 and the fifth groove 25 in the circumferential direction Z of the bearing housing 12 are all the same. The interval between the first groove 21 and the second groove 22, the interval between the third groove 23 and the fourth groove 24, and the interval between the fifth groove 25 and the sixth groove 26 are each wider than the interval between the sixth groove 26 and the first groove 21, the interval between the second groove 22 and the third groove 23, and the interval between the fourth groove 24 and the fifth groove 25, respectively. In this embodiment, the distance between the sixth groove 26 and the first groove 21, the distance between the second groove 22 and the third groove 23, and the distance between the fourth groove 24 and the fifth groove 25 are each set as narrow as possible within the range in which the strength of the bearing housing 12 is ensured.

[0026] <Top foil> The top foil 13 has a tubular portion 30. The tubular portion 30 is cylindrical with a portion of the circumferential direction interrupted. A coating (not shown) is applied to the inner peripheral surface of the tubular portion 30. The top foil 13 has a free end 31 and a fixed end 32. The free end 31 protrudes from one end of the tubular portion 30 in the circumferential direction toward the radial outside of the tubular portion 30. The fixed end 32 protrudes from the other end of the tubular portion 30 in the circumferential direction toward the radial outside of the tubular portion 30. In this embodiment, the dimension of the tubular portion 30 in the axial direction of the tubular portion 30 is the same as the dimensions of the free end 31 and the fixed end 32 in the axial direction of the tubular portion 30. In this embodiment, the dimension of the top foil 13 in the axial direction of the tubular portion 30 is the same as the dimension of the bearing housing 12 in the axial direction X.

[0027] The top foil 13 is formed by bending a band-shaped metal plate having flexibility. The metal plate forming the top foil 13 is, for example, a plate made of stainless steel such as SUS301 or SUS304. The tube portion 30 is formed by bending a part of the band-shaped metal plate into a cylindrical shape. In this embodiment, the longitudinal direction of the metal plate forming the top foil 13 coincides with the circumferential direction of the tube portion 30. The short side direction of the metal plate forming the top foil 13 coincides with the axial direction of the tube portion 30. The free end 31 and the fixed end 32 are formed by bending both ends of the metal plate in the longitudinal direction toward the radial outside of the tube portion 30.

[0028] 2, the top foil 13 is disposed inside the bearing housing 12. The top foil 13 is disposed between the rotating shaft 103 and the bearing housing 12.

[0029] The cylindrical portion 30 is disposed between the outer peripheral surface of the rotating shaft 103 and the inner peripheral surface 12a of the bearing housing 12. The cylindrical portion 30 extends in the axial direction X and the circumferential direction Z of the bearing housing 12. The inner peripheral surface of the cylindrical portion 30 faces the rotating shaft 103. As described above, the inner peripheral surface of the cylindrical portion 30 is coated. Therefore, even if the rotating shaft 103 comes into contact with the inner peripheral surface of the cylindrical portion 30, friction generated between the rotating shaft 103 and the cylindrical portion 30 is suppressed.

[0030] The free end 31 and the fixed end 32 extend from both ends of the cylindrical portion 30 in the circumferential direction Z of the bearing housing 12 toward the bearing housing 12. The free end 31 is inserted into the sixth groove 26. The fixed end 32 is inserted into the first groove 21. This positions the top foil 13 in the circumferential direction Z of the bearing housing 12.

[0031] <Bump foil> Each bump foil 14 is disposed inside the bearing housing 12. Each bump foil 14 is disposed between the top foil 13 and the bearing housing 12. The three bump foils 14 are disposed at intervals in the circumferential direction Z of the bearing housing 12. Hereinafter, when distinguishing between the three bump foils 14, they will be referred to as a first bump foil 14a, a second bump foil 14b, and a third bump foil 14c.

[0032] Each bump foil 14 has a main body 40. The main body 40 extends in the circumferential direction Z of the bearing housing 12. The main body 40 has a corrugated shape that corrugates in the radial direction Y of the bearing housing 12. More specifically, the main body 40 has a plurality of peaks 41 and a plurality of valleys 42. The peaks 41 and the valleys 42 are alternately arranged in the circumferential direction Z of the bearing housing 12. Each valley 42 is curved so as to follow the inner peripheral surface 12a of the bearing housing 12. Each valley 42 is in contact with the inner peripheral surface 12a of the bearing housing 12. Each peak 41 bulges from the valley 42 toward the outer peripheral surface of the tubular portion 30. Each peak 41 is curved in an arc shape. Each peak 41 is in contact with the outer peripheral surface of the tubular portion 30. The main body 40 elastically supports the top foil 13 by elastically deforming the peaks 41 so as to extend in the circumferential direction Z of the bearing housing 12.

[0033] Each bump foil 14 has a first locking portion 43 and a second locking portion 44. The first locking portion 43 extends from a first end portion 40a of the main body portion 40 in the circumferential direction Z of the bearing housing 12 toward the bearing housing 12. The second locking portion 44 extends from a second end portion 40b of the main body portion 40 in the circumferential direction Z of the bearing housing 12 toward the bearing housing 12.

[0034] Fig. 4 is a development view of the top foil 13 and the bump foil 14. The up-down direction in Fig. 4 corresponds to the axial direction X of the bearing housing 12. The left-right direction in Fig. 4 corresponds to the circumferential direction Z of the bearing housing 12. As shown in Fig. 4, in this embodiment, the dimensions of each of the first locking portion 43 and the second locking portion 44 in the axial direction X of the bearing housing 12 are the same as the dimensions of the main body portion 40 in the axial direction X of the bearing housing 12. The dimensions of each bump foil 14 in the axial direction X of the bearing housing 12 are the same as the dimensions of the top foil 13 in the axial direction X of the bearing housing 12.

[0035] The bump foil 14 is formed by bending a band-shaped metal plate having flexibility. The metal plate forming the bump foil 14 is a plate made of stainless steel such as SUS301 or SUS304. The main body 40 is formed by forming a part of the band-shaped metal plate into a corrugated shape. In this embodiment, the longitudinal direction of the metal plate forming the bump foil 14 coincides with the circumferential direction Z of the bearing housing 12. The lateral direction of the metal plate forming the bump foil 14 coincides with the axial direction X of the bearing housing 12. The first locking portion 43 and the second locking portion 44 are formed by bending both ends of the metal plate in the circumferential direction Z of the bearing housing 12 radially outward.

[0036] As shown in FIG. 2 and FIG. 5, the first locking portion 43 of the first bump foil 14a is inserted into the first groove 21. The first groove 21 is the first locking groove 20a into which the first locking portion 43 of the bump foil 14 is inserted. In this embodiment, the first locking portion 43 of the first bump foil 14a extends over the entire first groove 21 in the axial direction X of the bearing housing 12. The second locking portion 44 of the first bump foil 14a is inserted into the second groove 22. The second groove 22 is the second locking groove 20b into which the second locking portion 44 of the bump foil 14 is inserted. In this embodiment, the second locking portion 44 of the first bump foil 14a extends over the entire second groove 22 in the axial direction X of the bearing housing 12. The first engaging portion 43 is inserted into the first groove 21 and the second engaging portion 44 is inserted into the second groove 22, so that the first bump foil 14a is positioned in the circumferential direction Z of the bearing housing 12.

[0037] The first locking portion 43 of the second bump foil 14b is inserted into the third groove 23. The third groove 23 is the first locking groove 20a into which the first locking portion 43 of the bump foil 14 is inserted. In this embodiment, the first locking portion 43 of the second bump foil 14b extends over the entire third groove 23 in the axial direction X of the bearing housing 12. The second locking portion 44 of the second bump foil 14b is inserted into the fourth groove 24. The fourth groove 24 is the second locking groove 20b into which the second locking portion 44 of the bump foil 14 is inserted. In this embodiment, the second locking portion 44 of the second bump foil 14b extends over the entire fourth groove 24 in the axial direction X of the bearing housing 12. The first locking portion 43 is inserted into the third groove 23 and the second locking portion 44 is inserted into the fourth groove 24, so that the second bump foil 14b is positioned in the circumferential direction Z of the bearing housing 12.

[0038] The first locking portion 43 of the third bump foil 14c is inserted into the fifth groove 25. The fifth groove 25 is the first locking groove 20a into which the first locking portion 43 of the bump foil 14 is inserted. In this embodiment, the first locking portion 43 of the third bump foil 14c extends over the entire fifth groove 25 in the axial direction X of the bearing housing 12. The second locking portion 44 of the third bump foil 14c is inserted into the sixth groove 26. The sixth groove 26 is the second locking groove 20b into which the second locking portion 44 of the bump foil 14 is inserted. In this embodiment, the second locking portion 44 of the third bump foil 14c extends over the entire sixth groove 26 in the axial direction X of the bearing housing 12. The first locking portion 43 is inserted into the fifth groove 25 and the second locking portion 44 is inserted into the sixth groove 26, so that the third bump foil 14c is positioned in the circumferential direction Z of the bearing housing 12.

[0039] In this way, the bearing housing 12 is provided with the same number of first locking grooves 20a as the bump foils 14, and the same number of second locking grooves 20b as the bump foils 14. The first locking grooves 20a and the second locking grooves 20b are arranged alternately in the circumferential direction Z of the bearing housing 12. The first locking portions 43 are individually inserted into the first locking grooves 20a. That is, the first locking portion 43 of one bump foil 14 is inserted into one first locking groove 20a. The second locking portions 44 are individually inserted into the second locking grooves 20b. That is, the second locking portion 44 of one bump foil 14 is inserted into one second locking groove 20b.

[0040] The width of the first locking groove 20a in the circumferential direction Z of the bearing housing 12 is set to a width such that the first locking portion 43 does not come into contact with the surface defining the first locking groove 20a even if the main body portion 40 elastically deforms to extend in the circumferential direction Z of the bearing housing 12. Moreover, the width of the second locking groove 20b in the circumferential direction Z of the bearing housing 12 is set to a width such that the second locking portion 44 does not come into contact with the surface defining the second locking groove 20b even if the main body portion 40 elastically deforms to extend in the circumferential direction Z of the bearing housing 12.

[0041] As shown in FIG. 3, the pair of regulating members 15, 16 are separate from the bearing housing 12. The pair of regulating members 15, 16 are each made of a material having excellent wear resistance. In this embodiment, the pair of regulating members 15, 16 are each made of stainless steel such as SUS301 or SUS304. In this embodiment, the pair of regulating members 15, 16 are each annular. When distinguishing between the pair of regulating members 15, 16, one regulating member 15 is referred to as a first regulating member 15 and the other regulating member 16 is referred to as a second regulating member 16.

[0042] 5, the pair of restricting members 15, 16 are each provided on the bearing housing 12. In this embodiment, the first restricting member 15 is provided on the first end face 12b of the bearing housing 12. The second restricting member 16 is provided on the second end face 12c of the bearing housing 12. In this embodiment, the pair of restricting members 15, 16 are each fixed to the bearing housing 12 by fixing means such as bolts (not shown).

[0043] The first restricting member 15 covers a portion of the first openings 201 of the first to sixth grooves 21 to 26. The first restricting member 15 is located on one side X1 in the axial direction X of the bearing housing 12 with respect to the free end 31 and the fixed end 32 of the top foil 13 and the first locking portions 43 and second locking portions 44 of each bump foil 14. The first restricting member 15 restricts movement of the free end 31 and the fixed end 32 of the top foil 13 and the first locking portions 43 and second locking portions 44 of each bump foil 14 toward the one side X1 in the axial direction X of the bearing housing 12.

[0044] The second restricting member 16 covers a portion of the second openings 202 of the first to sixth grooves 21 to 26. The second restricting member 16 is located on the other side X2 in the axial direction X of the bearing housing 12 with respect to the free end 31 and the fixed end 32 of the top foil 13 and the first locking portions 43 and second locking portions 44 of each bump foil 14. The second restricting member 16 restricts movement of the free end 31 and the fixed end 32 of the top foil 13 and the first locking portions 43 and second locking portions 44 of each bump foil 14 toward the other side X2 in the axial direction X of the bearing housing 12.

[0045] In this way, a pair of restricting members 15, 16 are provided on both sides of the first locking portion 43 and the second locking portion 44 in the axial direction X of the bearing housing 12. This restricts movement of the bump foil 14 in the axial direction X of the bearing housing 12 at both ends of the bump foil 14 in the circumferential direction Z of the bearing housing 12.

[0046] <Foil bearing operation> 2, when the rotating shaft 103 rotates in the rotation direction R, air is drawn between the outer circumferential surface of the rotating shaft 103 and the inner circumferential surface of the tubular portion 30 of the top foil 13. The air flows between the rotating shaft 103 and the tubular portion 30 in the rotation direction R of the rotating shaft 103. The fixed end 32 of the top foil 13 is pressed against a surface that precedes the rotation direction R of the rotating shaft 103, that is, a surface that is closer to the sixth groove 26, among the surfaces that define the first groove 21, by the air flow that flows between the rotating shaft 103 and the tubular portion 30.

[0047] Then, when the rotation speed of the rotating shaft 103 reaches a predetermined rotation speed, a fluid film 17 is formed by the air drawn between the rotating shaft 103 and the tubular portion 30. The rotating shaft 103 floats relative to the top foil 13 due to the dynamic pressure of the fluid film 17. The rotating shaft 103 is supported in the radial direction Y by the fluid film 17 without contacting the top foil 13. When the fluid film 17 is formed, the top foil 13 elastically deforms such that the tubular portion 30 bulges outward in the radial direction Y. At this time, the free end 31 of the top foil 13 moves in the rotation direction R within the sixth groove 26.

[0048] When the tubular portion 30 elastically deforms so as to bulge outward in the radial direction Y, a load is input from the tubular portion 30 to each peak portion 41 of the bump foil 14. Each peak portion 41 elastically deforms so as to extend in the circumferential direction Z due to the load input from the tubular portion 30. As a result, the top foil 13 is elastically supported by the main body portion 40 of the bump foil 14. When the main body portion 40 elastically deforms so as to extend in the circumferential direction Z, the first locking portion 43 and the second locking portion 44 move in directions away from each other within the first locking groove 20a and the second locking groove 20b.

[0049] Specifically, the first engagement portion 43 of the first bump foil 14a moves to approach the surface that is closer to the sixth groove 26 among the surfaces that define the first groove 21. The second engagement portion 44 of the first bump foil 14a moves to approach the surface that is closer to the third groove 23 among the surfaces that define the second groove 22. The first engagement portion 43 of the second bump foil 14b moves to approach the surface that is closer to the second groove 22 among the surfaces that define the third groove 23. The second engagement portion 44 of the second bump foil 14b moves to approach the surface that is closer to the fifth groove 25 among the surfaces that define the fourth groove 24. The first engagement portion 43 of the third bump foil 14c moves to approach the surface that is closer to the fourth groove 24 among the surfaces that define the fifth groove 25. The second engagement portion 44 of the third bump foil 14c moves to approach the surface that is closer to the first groove 21 among the surfaces that define the sixth groove 26.

[0050] As described above, the width of the first locking groove 20a in the circumferential direction Z of the bearing housing 12 is set to a width such that the first locking portion 43 does not come into contact with the surface defining the first locking groove 20a even if the main body portion 40 is elastically deformed. This allows the movement of the first locking portion 43 in the first locking groove 20a to be unrestricted. In addition, the width of the second locking groove 20b in the circumferential direction Z of the bearing housing 12 is set to a width such that the second locking portion 44 does not come into contact with the surface defining the second locking groove 20b even if the main body portion 40 is elastically deformed. This allows the movement of the second locking portion 44 in the second locking groove 20b to be unrestricted. Therefore, the elastic deformation of the main body portion 40 is permitted.

[0051] [Actions and Effects of the Present Embodiment] The operation and effects of this embodiment will be described. (1) The first locking portion 43 of each bump foil 14 is inserted into the first locking groove 20a that opens at both end faces 12b, 12c in the axial direction X of the bearing housing 12. The second locking portion 44 of each bump foil 14 is inserted into the second locking groove 20b that opens at both end faces 12b, 12c in the axial direction X of the bearing housing 12. A pair of regulating members 15, 16 are provided on both sides of the first locking portion 43 and the second locking portion 44 in the axial direction X of the bearing housing 12. This restricts the movement of each bump foil 14 in the axial direction X of the bearing housing 12 at both ends of each bump foil 14 in the circumferential direction Z of the bearing housing 12. Therefore, each bump foil 14 is less likely to tilt with respect to the top foil 13. As a result, uneven wear of the top foil 13 is suppressed, and the life of the foil bearing 10 can be extended.

[0052] (2) A plurality of bump foils 14 are arranged in the circumferential direction Z of the bearing housing 12. In this embodiment, three bump foils 14 are arranged in the circumferential direction Z of the bearing housing 12. Therefore, compared to a case where, for example, one bump foil 14 is arranged over substantially the entire circumferential direction Z of the bearing housing 12, the distance from the center of the main body portion 40 in the circumferential direction Z of the bearing housing 12 to each of the locking portions 43, 44 is shorter. Therefore, twisting of the bump foils 14 caused by the center of the main body portion 40 in the circumferential direction Z of the bearing housing 12 being shifted in the axial direction X of the bearing housing 12 can be suppressed.

[0053] (3) For example, when the locking portions 43, 44 of two bump foils 14 are inserted into one locking groove 20a, 20b, i.e., when two bump foils 14 share one locking groove 20a, 20b, the locking portions 43, 44 may interfere with each other.

[0054] For example, consider a case where the third groove 23 is not provided in the bearing housing 12, and the second locking portion 44 of the first bump foil 14a and the first locking portion 43 of the second bump foil 14b are inserted into the second groove 22. In this case, if the main body portion 40 of the second bump foil 14b elastically deforms so as to extend in the circumferential direction Z of the bearing housing 12, there is a risk that the first locking portion 43 of the second bump foil 14b will interfere with the second locking portion 44 of the first bump foil 14a. This will prevent the main body portion 40 of the second bump foil 14b from elastically deforming, and the second bump foil 14b will no longer be able to properly support the top foil 13. Furthermore, when the first locking portion 43 of the second bump foil 14b presses the second locking portion 44 of the first bump foil 14a, the main body portion 40 of the first bump foil 14a may be deformed so as to rise up from the inner circumferential surface 12a of the bearing housing 12. Then, the first bump foil 14a will no longer be able to properly support the top foil 13.

[0055] In contrast, in this embodiment, the bearing housing 12 is provided with the same number of first locking grooves 20a and second locking grooves 20b as the bump foils 14. The first locking portions 43 are individually inserted into the first locking grooves 20a. The second locking portions 44 are individually inserted into the second locking grooves 20b. In other words, the first locking portion 43 of one bump foil 14 is inserted into one first locking groove 20a, and the second locking portion 44 of one bump foil 14 is inserted into one second locking groove 20b. This makes it possible to avoid interference between the locking portions 43, 44.

[0056] (4) For example, when the movement of the bump foil 14 in the axial direction X of the bearing housing 12 is restricted by the bearing housing 12, that is, when the bearing housing 12 functions as a restricting member, the following problem occurs. If the bearing housing 12 is made of aluminum as in this embodiment, the bump foil 14 comes into contact with the bearing housing 12 as it tries to move in the axial direction X of the bearing housing 12, causing wear to the bearing housing 12. However, if the bearing housing 12 is made of, for example, stainless steel in order to improve the wear resistance of the bearing housing 12, the heat dissipation performance of the foil bearing 10 will decrease and the weight of the foil bearing 10 will increase.

[0057] In contrast, in this embodiment, the pair of regulating members 15, 16 are separate from the bearing housing 12. This allows the bearing housing 12 to be made of a different material from the pair of regulating members 15, 16. This allows the bearing housing 12 to be made of a material with excellent heat dissipation properties, and the pair of regulating members 15, 16 to be made of a material with excellent wear resistance.

[0058] (5) A refrigerant gas for cooling the foil bearing 10 may be flowed inside the bearing housing 12. The refrigerant gas is, for example, air. In this embodiment, the first locking groove 20a and the second locking groove 20b are each provided over the entire axial direction X of the bearing housing 12. Therefore, the amount of refrigerant gas passing through the inside of the bearing housing 12 can be increased compared to a case in which the first locking groove 20a and the second locking groove 20b are each provided only at both ends of the bearing housing 12 in the axial direction X. Therefore, the cooling effect of the foil bearing 10 can be increased.

[0059] In addition, when two foil bearings 10 are arranged in positions sandwiching the electric motor 102 in the axial direction X of the rotating shaft 103 as in this embodiment, the amount of refrigerant gas passing through the inside of the bearing housing 12 increases, thereby improving the cooling effect of the electric motor 102.

[0060] (6) The bump foil 14 is positioned in the circumferential direction Z of the bearing housing 12 by inserting the first locking portion 43 into the first locking groove 20a and inserting the second locking portion 44 into the second locking groove 20b. In this embodiment, the first locking portion 43 extends over the entire first locking groove 20a in the axial direction X of the bearing housing 12. Therefore, compared to a case where the first locking portion 43 is provided only at both ends of the first locking groove 20a in the axial direction X of the bearing housing 12, the area of ​​the first locking portion 43 facing the surface defining the first locking groove 20a in the circumferential direction Z of the bearing housing 12 is larger. Similarly, the second locking portion 44 extends over the entire second locking groove 20b in the axial direction X of the bearing housing 12. Therefore, compared to a case where the second locking portions 44 are provided only at both ends of the second locking groove 20b in the axial direction X of the bearing housing 12, the area where the second locking portions 44 face the surfaces defining the second locking groove 20b in the circumferential direction Z of the bearing housing 12 is larger. This improves the reliability of positioning the bump foil 14 in the circumferential direction Z of the bearing housing 12.

[0061] (7) In the present embodiment, the first to sixth grooves 21-26 have the same width in the circumferential direction Z of the bearing housing 12. This reduces the cost of forming the first to sixth grooves 21-26 compared to when the first to sixth grooves 21-26 have different widths.

[0062] (8) In this embodiment, the distance between the sixth groove 26 and the first groove 21, the distance between the second groove 22 and the third groove 23, and the distance between the fourth groove 24 and the fifth groove 25 in the circumferential direction Z of the bearing housing 12 are each set as narrow as possible while still ensuring the strength of the bearing housing 12. This makes it possible to minimize the area in the circumferential direction Z of the bearing housing 12 where the bump foil 14 is not provided.

[0063] (9) In this embodiment, the fixed end 32 of the top foil 13 and the first locking portion 43 of the first bump foil 14a are inserted into the first groove 21. That is, the first groove 21 is shared by the fixed end 32 of the top foil 13 and the first locking portion 43 of the first bump foil 14a. In addition, the free end 31 of the top foil 13 and the second locking portion 44 of the third bump foil 14c are inserted into the second groove 22. That is, the second groove 22 is shared by the free end 31 of the top foil 13 and the second locking portion 44 of the third bump foil 14c. This allows the number of grooves formed in the bearing housing 12 to be reduced, thereby reducing the cost of manufacturing the bearing housing 12.

[0064] [Example of change] The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

[0065] The number of bump foils 14 included in the foil bearing 10 is not limited to three, as long as there is more than one. The foil bearing 10 may include two bump foils 14, or four or more bump foils 14.

[0066] The number of the first locking grooves 20a and the second locking grooves 20b provided in the bearing housing 12 is changed according to the number of the bump foils 14. Specifically, the number of the first locking grooves 20a and the number of the second locking grooves 20b provided in the bearing housing 12 are set to the same number as the number of the bump foils 14.

[0067] The top foil 13 does not have to have a free end 31. In the top foil 13, the dimension of the cylindrical portion 30 in the axial direction X of the bearing housing 12 may be different from the dimensions of each of the free end 31 and the fixed end 32 in the axial direction X of the bearing housing 12.

[0068] In each bump foil 14, the dimension of the main body 40 in the axial direction X of the bearing housing 12 may be different from the dimensions of each of the first and second locking portions 43 and 44 in the axial direction X of the bearing housing 12.

[0069] Although both the fixed end 32 of the top foil 13 and the first locking portion 43 of the first bump foil 14a are inserted into the first groove 21, this is not limiting. The groove into which the fixed end 32 of the top foil 13 is inserted and the first locking groove 20a into which the first locking portion 43 of the first bump foil 14a is inserted may be provided separately.

[0070] Although both the free end 31 of the top foil 13 and the second locking portion 44 of the third bump foil 14c are inserted into the sixth groove 26, this is not limiting. The groove into which the free end 31 of the top foil 13 is inserted and the second locking groove 20b into which the second locking portion 44 of the third bump foil 14c is inserted may be provided separately.

[0071] As long as the first to sixth grooves 21 to 26 are open at both end faces 12b, 12c in the axial direction X of the bearing housing 12, respectively, they do not have to be provided throughout the entire axial direction X of the bearing housing 12. For example, the first to sixth grooves 21 to 26 may not be provided in the central portion of the bearing housing 12 in the axial direction X, but may be provided only at both end portions of the bearing housing 12 in the axial direction X.

[0072] The first locking portion 43 of each bump foil 14 does not have to extend over the entire first locking groove 20a in the axial direction X of the bearing housing 12. For example, the first locking portions 43 may be provided only on both ends of the main body portion 40 in the axial direction X of the bearing housing 12 so as to be located only on both ends of the first locking groove 20a in the axial direction X of the bearing housing 12.

[0073] Similarly, the second locking portion 44 of each bump foil 14 does not have to extend over the entire second locking groove 20b in the axial direction X of the bearing housing 12. For example, the second locking portions 44 may be provided only on both ends of the main body portion 40 in the axial direction X of the bearing housing 12 so as to be located only on both ends of the second locking groove 20b in the axial direction X of the bearing housing 12.

[0074] The material of the bearing housing 12 is not limited to aluminum and may be other materials that have excellent heat dissipation properties. The material of the pair of restriction members 15 and 16 is not limited to stainless steel. The material of the pair of restriction members 15 and 16 may be other materials having excellent wear resistance.

[0075] Each of the pair of regulating members 15 and 16 may be plated to improve wear resistance. The first to sixth grooves 21 to 26 may have different widths.

[0076] The distance between the sixth groove 26 and the first groove 21, the distance between the second groove 22 and the third groove 23, and the distance between the fourth groove 24 and the fifth groove 25 in the circumferential direction Z of the bearing housing 12 may each be changed as appropriate within the range in which the strength of the bearing housing 12 is ensured.

[0077] The method of fixing the restriction members 15, 16 to the bearing housing 12 may be changed as appropriate. For example, each of the regulating members 15, 16 may be fixed to the bearing housing 12 by being fitted into the inner circumferential surface 12a of the bearing housing 12. In this case, each of the regulating members 15, 16 is configured to have a convex portion that protrudes radially outward and is inserted into the first to sixth grooves 21-26.

[0078] For example, the restriction members 15, 16 may be fixed to the bearing housing 12 by being fitted into annular grooves provided in both end faces 12b, 12c of the bearing housing 12.

[0079] The regulating members 15, 16 do not have to be annular. For example, the regulating members 15, 16 may be divided in the circumferential direction Z of the bearing housing 12 so that the regulating members 15, 16 are provided only at positions corresponding to the first to sixth grooves 21-26 in the circumferential direction Z of the bearing housing 12.

[0080] The application of the foil bearing 10 is not limited to the centrifugal compressor 100 . [Explanation of symbols]

[0081] 10...foil bearing, 12...bearing housing, 12a...inner surface, 12b...first end face as end face, 12c...second end face as end face, 13...top foil, 14...bump foil, 15...regulating member, 16...regulating member, 20a...first locking groove, 20b...second locking groove, 40...main body, 40a...first end, 40b...second end, 43...first locking portion, 44...second locking portion, 103...rotation axis, X...axial direction, Z...circumferential direction.

Claims

1. a cylindrical bearing housing through which a rotating shaft is inserted; A thin top foil disposed between the rotating shaft and the bearing housing; a plurality of thin-plate-shaped bump foils disposed between the bearing housing and the top foil in a circumferential direction of the bearing housing; Equipped with Each of the plurality of bump foils comprises: a main body portion extending in a circumferential direction of the bearing housing and elastically supporting the top foil; a first engaging portion extending from a first end of the main body portion in a circumferential direction of the bearing housing toward the bearing housing; a second engaging portion extending from a second end of the main body portion in a circumferential direction of the bearing housing toward the bearing housing; having an inner peripheral surface of the bearing housing is provided with first locking grooves, the first locking portions being inserted into the first locking portions and second locking grooves, the second locking grooves being inserted into the second locking portions and opening at both axial end faces of the bearing housing, the second locking grooves being inserted into the second locking portions and opening at both axial end faces of the bearing housing, the first locking grooves being inserted into the second locking portions and the second locking grooves being inserted into the second locking portions, the first locking portions are individually inserted into the first locking grooves, and the second locking portions are individually inserted into the second locking grooves; A foil bearing, characterized in that a pair of regulating members separate from the bearing housing are provided on both sides of the first engagement portion and the second engagement portion in the axial direction of the bearing housing.

2. The foil bearing according to claim 1 , wherein the first locking groove and the second locking groove are each provided over the entire axial direction of the bearing housing.

3. 3. The foil bearing according to claim 2, wherein the first engagement portion extends over the entire first engagement groove in the axial direction of the bearing housing, and the second engagement portion extends over the entire second engagement groove in the axial direction of the bearing housing.

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