Centrifugal compressor

Abstract

To provide a centrifugal compressor that can cool the radial foil bearing while suppressing the wasteful consumption of compressed fluid. [Solution] The centrifugal compressor includes an intervening member 100. The intervening member 100 has a rotating shaft 40 inserted through it, faces the radial foil bearing 20 in the axial direction X, and is interposed between the first impeller chamber, the second impeller chamber and the motor chamber. The intervening member 100 has a first extending portion 102 that overlaps the outer peripheral gap S1 in the axial direction X, and a communicating recess 108 that opens the inner peripheral gap S2 in the axial direction X.

Description

Technical Field

[0001] The present invention relates to a centrifugal compressor.

Background Art

[0002] A centrifugal compressor includes a rotating shaft, a motor that rotates the rotating shaft, an impeller that compresses a fluid by rotating integrally with the rotating shaft, and a housing that houses the rotating shaft and the impeller. An impeller chamber that houses the impeller and a motor chamber that houses the motor are formed in the housing. Further, the centrifugal compressor includes a radial foil bearing. The radial foil bearing is disposed between the impeller chamber and the motor chamber in the housing and supports the rotating shaft rotatably in a non-contact manner.

[0003] For example, as disclosed in Patent Document 1, a radial foil bearing has a bearing housing, a top foil, and a bump foil. The bump foil is disposed between the top foil and the bearing housing. The bump foil is formed by alternately arranging ridges that contact the outer peripheral surface of the top foil and valleys that contact the inner peripheral surface of the bearing housing along the rotation direction of the rotating shaft.

[0004] When the rotational speed of the rotating shaft reaches a predetermined rotational speed, a fluid film is formed by the air drawn between the rotating shaft and the top foil in the radial foil bearing. The rotating shaft floats with respect to the top foil by the dynamic pressure of the fluid film. The rotating shaft is supported in the radial direction in a state of not contacting the top foil by the fluid film.

[0005] As a centrifugal compressor, there is one in which the fluid compressed by the centrifugal compressor flows to the radial foil bearing to cool the radial foil bearing. In such a centrifugal compressor, the radial foil bearing is cooled by flowing the compressed fluid between the inner peripheral surface of the bearing housing and the outer peripheral surface of the top foil.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Patent Publication No. 2024-092677 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] However, in a centrifugal compressor that uses compressed fluid to cool radial foil bearings, the more fluid that flows toward the radial foil bearings for cooling, the more compressed fluid is wasted. [Means for solving the problem]

[0008] A centrifugal compressor for solving the above problems comprises a rotating shaft driven by a motor, an impeller that compresses fluid by rotating integrally with the rotating shaft, a housing that houses the rotating shaft and has a motor chamber for housing the motor and an impeller chamber for housing the impeller, and a radial foil bearing disposed inside the housing that rotatably supports the rotating shaft between the impeller chamber and the motor chamber in the axial direction of the rotating shaft, wherein the housing includes a bearing housing portion to which the radial foil bearing is fixed, and the radial foil bearing comprises a top foil disposed between the bearing housing portion and the rotating shaft, and a bump foil disposed between the bearing housing portion and the top foil. The centrifugal compressor comprises a bump foil having a plurality of peaks that contact the outer circumferential surface of the top foil and a plurality of valleys that contact the inner circumferential surface of the bearing housing, wherein the peaks and valleys are arranged alternately in the circumferential direction of the rotating shaft, wherein the rotating shaft is inserted through an intervening member that faces the radial foil bearing in the axial direction and is interposed between the impeller chamber and the motor chamber, the intervening member having a covering portion that overlaps in the axial direction with respect to the gap defined between the inner circumferential surface of the bearing housing and the opposing surface of the bump foil to the inner circumferential surface, and having a communicating recess that opens in the axial direction with respect to the gap defined between the outer circumferential surface of the top foil and the opposing surface of the bump foil to the outer circumferential surface.

[0009] According to this, the fluid compressed in the impeller chamber flows through the radial foil bearing towards the motor chamber, where the pressure is lower than in the impeller chamber. Due to dynamic pressure generated between the circumferential surface of the rotating shaft and the inner circumferential surface of the top foil, the temperature rise in the radial foil bearing is greater closer to the top foil in the radial direction of the rotating shaft than closer to the bearing housing. The gap between the outer circumferential surface of the top foil and the opposite side of the bump foil, located closer to the top foil, is opened by a communicating recess in the intervening member, and does not suppress the flow of fluid into the gap closer to the top foil. As a result, the centrifugal compressor can cool the portion of the radial foil bearing closer to the top foil, and furthermore, the rotating shaft located on the inner circumferential side of the top foil, with fluid. On the other hand, closer to the bearing housing, where the temperature rise is smaller than closer to the top foil, the covering portion overlaps axially with the gap between the inner circumferential surface of the bearing housing and the opposite side of the bump foil, thus suppressing the flow of fluid into that gap. As a result, the centrifugal compressor can reduce the amount of fluid flowing into the gap near the bearing housing compared to a compressor without a covering. Therefore, the centrifugal compressor can cool the radial foil bearing while suppressing the wasteful consumption of compressed fluid.

[0010] In the case of a centrifugal compressor, the intervening member may be provided with a plurality of locking portions that engage with the outer circumferential surface of the top foil. According to this, when the rotating shaft is displaced radially, the intervening member also displaces in the same direction along with the top foil. As a result, even when the rotating shaft is displaced radially due to external vibration or the like, the covering portion can maintain a state in which it overlaps the gap near the bearing housing, while the communicating recess maintains an open state in the gap near the top foil.

[0011] In the centrifugal compressor, the intervening member faces the end face of the bearing housing portion closer to the impeller chamber, the end face of the bump foil facing the intervening member is located further away from the intervening member than the end face of the top foil facing the intervening member, and the locking portion protrudes axially from the intervening member toward the end face of the bump foil and is located closer to the end face of the bump foil than the end face of the bearing housing portion.

[0012] According to this, in a centrifugal compressor, fluid that flows into the gap near the top foil passes between the opposing end faces of the bump foil and the intervening member and flows in the circumferential direction of the rotating shaft. Since the locking portion protrudes toward the end face of the bump foil, the locking portion can stop further flow of fluid that has flowed into the gap near the top foil and flowed in the circumferential direction. As a result, the amount of fluid flowing into the motor chamber through the radial foil bearing can be reduced compared to the case where the locking portion does not protrude from the intervening member toward the end face of the bump foil.

[0013] With respect to the centrifugal compressor, the covering portion preferably overlaps in the axial direction with respect to all of the multiple gaps defined between the inner circumferential surface of the bearing housing portion and the opposing side of the bump foil to the inner circumferential surface.

[0014] According to this, centrifugal compressors can efficiently suppress the wasteful consumption of compressed fluid while cooling the radial foil bearings. In the centrifugal compressor, the top foil is provided with top foil fixed ends located at both ends of the top foil in the circumferential direction of the rotating shaft, and a pair of the top foil fixed ends are each inserted into slits recessed from the inner circumferential surface of the bearing housing, and the intervening member may be provided with a rotation suppression piece inserted between the pair of top foil fixed ends facing each other in the circumferential direction.

[0015] According to this, by inserting the top foil fixed end into the recess, rotation of the top foil in the circumferential direction of the rotation axis can be suppressed. And the rotation suppression piece is inserted between the top foil fixed ends of the top foil whose rotation is suppressed. As a result, the intervening member is suppressed from rotating in the circumferential direction of the rotation axis.

Effect of the Invention

[0016] The present invention can suppress wasteful consumption of compressed fluid while cooling a radial foil bearing.

Brief Description of the Drawings

[0017] [Figure 1] FIG. 1 is a cross-sectional view showing a centrifugal compressor. [Figure 2] FIG. 2 is an exploded perspective view of a radial foil bearing and an intervening member. [Figure 3] FIG. 3 is a cross-sectional view showing a radial foil bearing. [Figure 4] FIG. 4 is a front view showing an intervening member and a radial foil bearing. [Figure 5] FIG. 5 is a cross-sectional view showing an intervening member and a radial foil bearing. [Figure 6] FIG. 6 is a cross-sectional view showing a rotation suppression piece. [Figure 7] FIG. 7 is a cross-sectional view showing a rotation suppression piece between top foil fixed ends. [Figure 8] FIG. 8 is a cross-sectional view showing an intervening member and a radial foil bearing.

Mode for Carrying Out the Invention

[0018] Hereinafter, an embodiment in which a centrifugal compressor is embodied will be described. <Centrifugal Compressor> The centrifugal compressor is used as a centrifugal compressor that compresses air as a fluid containing oxygen supplied to a fuel cell of a fuel cell vehicle.

[0019] As shown in Figure 1, the centrifugal compressor 10 comprises a housing 11, a rotating shaft 40, two radial foil bearings 20, a first impeller 34 and a second impeller 35 as impellers, a motor 39, and intervening members 100 provided according to each radial foil bearing 20.

[0020] The housing 11 is made of a metal material. For example, aluminum can be used as the material for the housing 11. The housing 11 comprises a motor housing 12, a first impeller housing 13, a second impeller housing 14, a first plate 15, a second plate 16, and a third plate 17. The direction in which the central axis L of the housing 11 extends is defined as the axial direction X of the centrifugal compressor 10. Since the central axis L coincides with the axis SL of the rotating shaft 40, the axial direction of the rotating shaft 40 is also described as the axial direction X. Furthermore, the radial direction of the rotating shaft 40 is described as the radial direction Y, and the circumferential direction of the rotating shaft 40 is described as the circumferential direction B, as shown in Figure 3.

[0021] As shown in Figure 1, the housing 11 is formed by arranging the first impeller housing 13, the third plate 17, the first plate 15, the motor housing 12, the second plate 16, and the second impeller housing 14 in this order along the axial direction X, and connecting them to one another.

[0022] The motor housing 12 comprises a cylindrical circumferential wall 12a, a first flange 12b extending from the outer surface of the first end of the circumferential wall 12a in the axial direction X, a second flange 12c extending from the outer surface of the second end of the circumferential wall 12a in the axial direction X, and an extended portion 12d extending from the inner surface of the second end of the circumferential wall 12a. Inside the housing 11, the circumferential wall 12a, the extended portion 12d, and the first plate 15 form a motor chamber 51. A motor 39 is housed inside the motor chamber 51.

[0023] The first plate 15 is connected to the first flange 12b of the motor housing 12, and the third plate 17 is connected in the axial direction X to the opposite side of the first plate 15 from the surface connecting to the first flange 12b. On the end face of the first plate 15 on the side facing the third plate 17, a circular recess 15c is formed. Also on the first plate 15, a first bearing recess 15d is formed in the center of the inner bottom surface of the recess 15c, which is smaller in diameter than the recess 15c and recesses in the axial direction X in a circular shape. A first shaft insertion hole 17a is formed in the center of the third plate 17. The first shaft insertion hole 17a penetrates the third plate 17 in the axial direction X. The recess 15c on the first plate 15 and the third plate 17 define a thrust bearing housing chamber 52. A thrust bearing 80 is housed in the thrust bearing housing chamber 52. Furthermore, the recess 15d for the first bearing houses the intervening member 100, which will be described later. On the first plate 15, the bearing housing portion 18 protrudes from the end face on the motor housing 12 side in the axial direction X. The bearing housing portion 18 extends cylindrically into the motor chamber 51 in the axial direction X.

[0024] The first impeller housing 13 is connected in the axial direction X to the opposite side of the third plate 17 from the surface connecting to the first plate 15. Between the first impeller housing 13 and the third plate 17, a first impeller chamber 13b, a discharge chamber 13c, and a first diffuser flow path 13d are formed. Therefore, the housing 11 has a first impeller chamber 13b. The first impeller chamber 13b houses the first impeller 34. When the first impeller 34 rotates, air is drawn into the first impeller chamber 13b. The air is compressed in the first diffuser flow path 13d and then flows into the discharge chamber 13c.

[0025] Furthermore, the air compressed in the first impeller chamber 13b flows from the first impeller chamber 13b through the first shaft insertion hole 17a, the thrust bearing housing chamber 52, and the first bearing recess 15d, through the inside of the bearing housing 18, and into the motor chamber 51. As the air compressed in the first impeller chamber 13b passes through the inside of the bearing housing 18, it cools the radial foil bearing 20 fixed to the inside of the bearing housing 18.

[0026] In the motor housing 12, another bearing housing portion 18 protrudes cylindrically into the motor chamber 51 from the end face of the extended portion 12d on the motor chamber 51 side, similar to the bearing housing portion 18 extending from the first plate 15. Therefore, the centrifugal compressor 10 is equipped with two bearing housing portions 18 inside the housing 11.

[0027] The second plate 16 is connected to the second flange 12c and the extended portion 12d of the motor housing 12. In the extended portion 12d, a second bearing recess 12e is formed in the center of the end face opposite to the protruding end face of the bearing housing portion 18, recessed in the axial direction X in a circular shape. The intervening member 100, which will be described later, is housed in the second bearing recess 12e. A second shaft insertion hole 16a is formed in the center of the second plate 16, penetrating the second plate 16 in the axial direction X. The second shaft insertion hole 16a communicates with the inside of the bearing housing portion 18 that extends from the extended portion 12d.

[0028] The second impeller housing 14 is connected in the axial direction X to the opposite side of the second plate 16 from the surface connecting to the motor housing 12. Between the second impeller housing 14 and the second plate 16, a second impeller chamber 14b, an intake chamber 14c, and a second diffuser passage 14d are formed. Therefore, the housing 11 has a second impeller chamber 14b. The second impeller chamber 14b houses the second impeller 35. The second impeller chamber 14b communicates with the second shaft insertion hole 16a.

[0029] When exhaust gas from the fuel cell stack is drawn into the intake chamber 14c, it is discharged into the second impeller chamber 14b through the second diffuser passage 14d. The second impeller 35 is rotated by the exhaust gas from the fuel cell stack discharged into the second impeller chamber 14b. The exhaust gas from the fuel cell stack is then compressed in the second impeller chamber 14b before being discharged to the outside.

[0030] The air compressed in the second impeller chamber 14b flows from the second impeller chamber 14b through the second shaft insertion hole 16a and the second bearing recess 12e, through the inside of the bearing housing 18, and into the motor chamber 51. As the compressed air in the second impeller chamber 14b passes through the inside of the bearing housing 18, it cools the radial foil bearing 20 fixed inside the bearing housing 18.

[0031] <Rotation axis> The rotating shaft 40 is housed within the housing 11. The rotating shaft 40 is driven by the motor 39. The rotating shaft 40 passes through the following in order: the first impeller chamber 13b, the first shaft insertion hole 17a, the recess 15c of the first plate 15, the first bearing recess 15d, the inside of the bearing housing portion 18 extending from the first plate 15, the motor chamber 51, the inside of the bearing housing portion 18 extending from the extension portion 12d, the second bearing recess 12e, the second shaft insertion hole 16a, and the second impeller chamber 14b.

[0032] The rotating shaft 40 is supported by a thrust bearing 80 housed in a thrust bearing housing chamber 52. The first impeller 34 is connected to the first end of the rotating shaft 40. The second impeller 35 is connected to the second end of the rotating shaft 40. The first impeller 34 and the second impeller 35 compress the air by rotating integrally with the rotating shaft 40 in conjunction with the drive of the motor 39.

[0033] <Radial foil bearing> The radial foil bearings 20 are fixed inside each of the two bearing housings 18. Thus, the two radial foil bearings 20 are located inside the housing 11, and the housing 11 comprises the bearing housings 18 to which the radial foil bearings 20 are fixed. One of the two radial foil bearings 20 rotatably supports the rotating shaft 40 between the first impeller chamber 13b and the motor chamber 51, while the other radial foil bearing 20 rotatably supports the rotating shaft 40 between the second impeller chamber 14b and the motor chamber 51. The two radial foil bearings 20 have the same configuration.

[0034] The radial foil bearing 20 supports the rotating shaft 40 in contact with it until the rotational speed of the rotating shaft 40 reaches the levitation speed at which the rotating shaft 40 is lifted by the radial foil bearing 20. As the rotating shaft 40 rotates, dynamic pressure is generated between the rotating shaft 40 and the radial foil bearing 20. When the rotational speed of the rotating shaft 40 reaches the levitation speed, the generated dynamic pressure causes the rotating shaft 40 to levitate relative to the radial foil bearing 20. As a result, the radial foil bearing 20 supports the rotating shaft 40 in a non-contact state, allowing it to rotate freely.

[0035] Next, the specific configuration of the radial foil bearing 20 will be described. As shown in Figures 2 and 3, the radial foil bearing 20 comprises a bearing housing 18, a top foil 72, and a bump foil 73.

[0036] <Bearing housing section> The circumferential direction of the bearing housing 18 and the radial foil bearing 20 coincides with the circumferential direction B of the rotating shaft 40. In the following description, the circumferential direction of the radial foil bearing 20 and the bearing housing 18 will be referred to as circumferential direction B. The axis of the bearing housing 18 coincides with the axis SL of the rotating shaft 40. Therefore, the axial direction of the bearing housing 18 will be referred to as axial direction X, and the radial direction of the bearing housing 18 will be referred to as radial direction Y.

[0037] As shown in Figure 1, the bearing housing portion 18 includes a first end face 18A located on one side in the axial direction X and a second end face 18B located on the other side in the axial direction X. The first end face 18A of the bearing housing portion 18 formed on the first plate 15 is the end face exposed to the first bearing recess 15d, and the first end face 18A of the bearing housing portion 18 formed on the motor housing 12 is the end face exposed to the second bearing recess 12e. The second end face 18B of each bearing housing portion 18 is the end face exposed to the motor chamber 51.

[0038] As shown in Figures 2 and 3, the inner circumferential surface 18g of the bearing housing portion 18 is a cylindrical surface. A first slit 18a, a second slit 18b, a third slit 18c, and a fourth slit 18d are formed on the inner circumferential surface 18g of the bearing housing portion 18. The first slit 18a, the second slit 18b, the third slit 18c, and the fourth slit 18d are arranged in this order in the circumferential direction B of the bearing housing portion 18. The distances in the circumferential direction B between the first slit 18a and the second slit 18b, the distances in the circumferential direction B between the second slit 18b and the third slit 18c, and the distances in the circumferential direction B between the third slit 18c and the fourth slit 18d are equal. Furthermore, these distances are greater than the distance in the circumferential direction B between the first slit 18a and the fourth slit 18d. Each of the first slits 18a to the fourth slit 18d is provided along the entire length of the bearing housing portion 18 in the axial direction X. Each of the first slits 18a to the fourth slit 18d opens toward the first impeller chamber 13b or the second impeller chamber 14b at the first end face 18A of the bearing housing portion 18. Each of the first slits 18a to the fourth slit 18d opens toward the motor chamber 51 at the second end face 18B of the bearing housing portion 18.

[0039] <Top Foil> The top foil 72 is cylindrical. In this embodiment, the top foil 72 is substantially cylindrical. The top foil 72 is positioned between the bearing housing portion 18 and the rotating shaft 40 in the radial direction Y. The top foil 72 extends in the circumferential direction B inside the bearing housing portion 18. The top foil 72 is plate-like. In detail, the top foil 72 is made of a strip of metal material that is flexible, such as stainless steel. The top foil 72 is formed by curving this metal material into a cylindrical shape such that its longitudinal direction extends in the circumferential direction B of the bearing housing portion 18 and its short direction extends in the axial direction X.

[0040] Top foil fixed ends 72a are provided at both ends of the top foil 72 in the circumferential direction B. Therefore, the top foil 72 has top foil fixed ends 72a located at both ends of the top foil 72 in the circumferential direction B of the rotation axis 40. Each top foil fixed end 72a is formed by bending a metal plate material outward from the top foil 72 in the radial direction Y. Each top foil fixed end 72a is a rectangular flat plate that extends perpendicular to the circumferential direction B.

[0041] The dimension of the top foil 72 in the axial direction X is the same as or approximately the same as the dimension of the bearing housing portion 18 in the axial direction X. Therefore, as shown in Figure 5, one of the top foil end faces 72c, which are both ends of the top foil 72 in the axial direction X, is located on the same virtual plane as the first end face 18A of the bearing housing portion 18, and although not shown, the other end face 72c is located on the same virtual plane as the second end face 18B of the bearing housing portion 18.

[0042] As shown in Figure 3, one top foil fixed end 72a is inserted into the first slit 18a, and the other top foil fixed end 72a is inserted into the fourth slit 18d. By inserting each top foil fixed end 72a into the respective slits 18a and 18d, the movement of the top foil 72 in the circumferential direction B is suppressed. Therefore, in the centrifugal compressor 10, the pair of top foil fixed ends 72a are inserted into the first slit 18a and the fourth slit 18d, respectively, which are recessed from the inner circumferential surface 18g of the bearing housing portion 18.

[0043] The top foil 72 faces the rotation axis 40 in the radial direction Y. The top foil 72 has a bearing surface 72s as its inner circumferential surface and a bump foil surface 72t as its outer circumferential surface. The bearing surface 72s is the inner surface in the radial direction Y, and the bump foil surface 72t is the outer surface in the radial direction Y. The bearing surface 72s faces the circumferential surface of the rotation axis 40, and the bump foil surface 72t faces the bump foil 73, which will be described later.

[0044] <Bump Foil> The bump foil 73 has three bump foil sections 73c divided in the circumferential direction B of the bearing housing section 18. Each bump foil section 73c is interposed between the inner circumferential surface 18g of the bearing housing section 18 and the bump foil surface 72t of the top foil 72. Therefore, the bump foil 73, which is composed of multiple bump foil sections 73c, is positioned between the inner circumferential surface 18g of the bearing housing section 18 and the bump foil surface 72t of the top foil 72. The three bump foil sections 73c that constitute the bump foil 73 will also be referred to as multiple bump foil sections 73c below.

[0045] The circumferential dimensions B of the multiple bump foil sections 73c may be approximately the same as each other, or they may differ in some or all respects. The axial dimension X of each bump foil section 73c is smaller than the axial dimension X of the top foil 72. Therefore, as shown in Figure 5, the top foil end face 72c is located closer to the center of the bearing housing section 18 in the axial direction X than the bump foil end faces 73f, which are the end faces of each bump foil section 73c in the axial direction X. In other words, the bump foil end face 73f is spaced apart from the first end face 18A in the axial direction X. Furthermore, as shown in Figures 3 and 4, the bump foil section 73c is arc-shaped, aligned with the circumferential direction B of the rotation axis 40 when viewed in the axial direction X. In the following description, the circumferential direction of the bump foil section 73c will be referred to as the circumferential direction B.

[0046] Each of the multiple bump foil sections 73c has a fixed end 73d at one end in the circumferential direction B of the bump foil section 73c, and an open end 73e at the other end in the circumferential direction B of the bump foil section 73c. ​​In each bump foil section 73c, the end opposite to the fixed end 73d in the circumferential direction B is the open end 73e.

[0047] Each bump foil section 73c has multiple peaks 81 that contact the bump foil surface 72t and multiple valleys 82 that contact the inner circumferential surface 18g, and these peaks 81 and valleys 82 are arranged alternately in the circumferential direction B of the rotation axis 40, forming a wave shape. In detail, each bump foil section 73c is formed by arranging multiple peaks 81 and valleys 82 alternately in the circumferential direction B. When viewing the bump foil section 73c in the axial direction X, the protruding directions of the peaks 81 and valleys 82 are opposite. Each bump foil section 73c has an inner surface 731 on the side where the valleys 82 are concave and the peaks 81 are bulging, and an outer surface 732 on the side where the peaks 81 are concave and the valleys 82 are bulging.

[0048] As shown in Figure 3, the fixed end 73d of one of the three bump foil sections 73c is inserted into the first slit 18a along with the top foil fixed end 72a. Counterclockwise, the fixed end 73d of the second bump foil section 73c, adjacent to the first bump foil section 73c, is inserted into the second slit 18b. Counterclockwise, the fixed end 73d of the third bump foil section 73c, adjacent to the second bump foil section 73c, is inserted into the third slit 18c. The fixed end 73d of the bump foil section 73c is not inserted into the fourth slit 18d.

[0049] In the circumferential direction B, of the two adjacent bump foil sections 73c, the fixed end 73d of one bump foil section 73c and the open end 73e of the other bump foil section 73c are adjacent to each other while being spaced apart in the circumferential direction B.

[0050] In two adjacent bump foil sections 73c in the circumferential direction B, a gap 83 is formed between the fixed end 73d of one bump foil section 73c and the open end 73e of the other bump foil section 73c. ​​The gap 83 is formed regardless of the extension of the multiple bump foil sections 73c. ​​The gap 83 is formed at three locations in the circumferential direction B that are separated from each other.

[0051] Each bump foil portion 73c contacts the bump foil surface 72t at its inner surface 731 in each peak portion 81, and contacts the inner circumferential surface 18g of the bearing housing portion 18 at its outer surface 732 in each valley portion 82.

[0052] An outer circumferential gap S1 is defined between the inner circumferential surface 18g of the bearing housing portion 18 and the outer surface 732 that is opposite the bump foil 73 to the inner circumferential surface 18g. In addition, an inner circumferential gap S2 is defined between the bump foil surface 72t of the top foil 72 and the inner surface 731 that is opposite the bump foil surface 72t to the bump foil surface 72t. The outer circumferential gap S1 and the inner circumferential gap S2 are formed alternately in the circumferential direction B in each bump foil portion 73c. ​​The outer circumferential gap S1 and the inner circumferential gap S2 are adjacent in the circumferential direction B and the radial direction Y via the bump foil portion 73c.

[0053] Each bump foil section 73c elastically supports the top foil 72 by the extension of its peaks 81 and valleys 82 in the circumferential direction B. Multiple bump foil sections 73c may have the same number of peaks 81, or some or all of them may have different numbers of peaks 81. Multiple bump foil sections 73c may have the same number of valleys 82, or some or all of them may have different numbers of valleys 82.

[0054] <Radial foil bearing under no-load conditions> Next, we will describe the radial foil bearing 20 in a state where no load is applied from the rotating shaft 40 to the bearing surface 72s.

[0055] As shown in Figure 3, the state in which no load acts on the bearing surface 72s from the rotating shaft 40 is the state in which the rotating shaft 40 is not rotating and the entire bearing surface 72s in the circumferential direction B is in contact with the circumferential surface of the rotating shaft 40. This state in which no load acts on the bearing surface 72s from the rotating shaft 40 will be referred to as the unloaded state below.

[0056] In the unloaded state, the tip portion of the peak 81 in the direction of projection toward the top foil 72 is in contact with the bump foil surface 72t. In the unloaded state, the tip portion of the valley 82 in the direction of projection toward the bearing housing portion 18 is in contact with the inner circumferential surface 18g of the bearing housing portion 18.

[0057] <First state of radial foil bearing> Next, the first state will be described. The first state refers to the state of the radial foil bearing 20 when the rotating shaft 40 rotates and floats away from the bearing surface 72s.

[0058] As shown in Figures 4 and 5, in the first state, the top foil 72 elastically deforms outward in the radial direction Y as the rotating shaft 40 rotates. This creates an air film between the circumferential surface of the rotating shaft 40 and the bearing surface 72s of the top foil 72, generating dynamic pressure. As a result, the radial foil bearing 20 supports the rotating shaft 40 in a non-contact state with respect to the top foil 72. Due to the generation of dynamic pressure associated with the formation of this air film, the temperature of the top foil 72 and the rotating shaft 40 rises.

[0059] As the top foil 72 elastically deforms outward in the radial direction Y due to the air film between the rotating shaft 40 and the top foil 72, each peak 81 of the bump foil portion 73c that is in contact with the bump foil surface 72t of the top foil 72 is pressed by the top foil 72. As a result, the bump foil 73 elastically deforms outward in the radial direction Y together with the top foil 72. In this way, the top foil 72 is elastically supported by the bump foil 73. Each peak 81 and each valley 82 elastically deforms with respect to the outward displacement of the top foil 72 in the radial direction Y. In the first state, the load acts evenly across the entire bearing surface 72s from the rotating shaft 40 through the air film. Therefore, each peak 81 and each valley 82 elastically deforms uniformly.

[0060] <Second state of radial foil bearing> Next, we will explain the second state. The second state refers to a state of the radial foil bearing 20 in which the rotating shaft 40 is closer to a part of the inner circumferential surface 18g of the bearing housing portion 18 in the circumferential direction B than in the first state. In the second state, the state in which the rotating shaft 40 is closer to the bearing housing portion 18 than in the first state refers to cases in which the rotating shaft 40 is eccentric in the radial direction Y due to external vibration or the like, for example, when the rotating shaft 40 is displaced in the radial direction Y.

[0061] In the second state, as shown in the upper left of Figure 8, when the rotation axis 40 is close, the peaks 81 and valleys 82 undergo greater elastic deformation than in the first state. As a result, the contact area between the bump foil portion 73c and the top foil 72 and the bearing housing portion 18 is expanded compared to the first state. In addition, as each peak 81 and each valley 82 undergoes elastic deformation, the bump foil portion 73c deforms so that adjacent fixed ends 73d and open ends 73e in the circumferential direction B move closer together. As a result, the bump foil surface 72t of the top foil 72 approaches the inner circumferential surface 18g of the bearing housing portion 18.

[0062] Conversely, in the second state, as shown in the lower right of Figure 8, the peaks 81 and valleys 82 undergo smaller elastic deformation on the opposite side of the close position of the rotating shaft 40 than in the first state. As a result, the contact area between the bump foil portion 73c and the top foil 72 and the bearing housing portion 18 is reduced compared to the first state. Along with the elastic deformation of each peak 81 and each valley 82, the bump foil portion 73c deforms such that the fixed end 73d and the open end 73e adjacent to each other in the circumferential direction B move further apart near the spaced-out position of the rotating shaft 40.

[0063] <Intervening member> The intervening member 100 is formed by shaping a flexible metal sheet material, such as stainless steel.

[0064] As shown in Figures 2 and 4, a shaft insertion hole 100a is formed in the center of the intervening member 100. The shaft insertion hole 100a penetrates the intervening member 100 in the thickness direction. The intervening member 100 is provided adjacent to each radial foil bearing 20 in the axial direction X. The rotating shaft 40 is inserted through the shaft insertion hole 100a of the intervening member 100. The circumferential direction of the intervening member 100 coincides with the circumferential direction B of the bearing housing portion 18, and is therefore referred to as the circumferential direction B of the intervening member 100.

[0065] As shown in Figure 1, the intervening member 100, which corresponds to the radial foil bearing 20 fixed to the bearing housing portion 18 of the first plate 15, is provided on the first impeller chamber 13b side in the axial direction X relative to the radial foil bearing 20. Therefore, the intervening member 100 faces the radial foil bearing 20 in the axial direction X and is interposed between the first impeller chamber 13b and the motor chamber 51.

[0066] Furthermore, the intervening member 100 corresponding to the radial foil bearing 20 fixed to the bearing housing portion 18 of the motor housing 12 is provided on the second impeller chamber 14b side in the axial direction X relative to the radial foil bearing 20. Therefore, the intervening member 100 faces the radial foil bearing 20 in the axial direction X and is interposed between the second impeller chamber 14b and the motor chamber 51. The two intervening members 100 have the same shape.

[0067] As shown in Figures 2 and 4, the intervening member 100 comprises an annular plate portion 101, a first extending portion 102, a second extending portion 103, a third extending portion 104, and a fourth extending portion 105 extending from the annular plate portion 101. The first extending portion 102 is a portion that protrudes in an arc shape from the annular plate portion 101, while the second extending portion 103, the third extending portion 104, and the fourth extending portion 105 each protrude in an elongated plate shape from the annular plate portion 101 and have their longitudinal side extending in the circumferential direction B. The intervening member 100 comprises multiple first extending portions 102, as well as one each of the second extending portion 103, the third extending portion 104, and the fourth extending portion 105.

[0068] The annular plate portion 101 is a portion that extends in an annular shape along the outer edge of the intervening member 100. Furthermore, the annular plate portion 101 is located on the outer peripheral side in the radial direction Y than each of the first to fourth extending portions 102 to 105.

[0069] Boundaries K are defined as the boundaries between adjacent first extensions 102 and second extensions 103, between first extensions 102 and third extensions 104, between first extensions 102 and fourth extensions 105, and between adjacent first extensions 102, all along the circumferential direction B of the intervening member 100. Boundaries K exist on the inner periphery of the intervening member 100 at the locations where the base ends of each first extension 102 and the second to fourth extensions 103 to 105 are located. The imaginary line C connecting all boundaries K along the circumferential direction B of the intervening member 100 is circular in shape. The annular plate portion 101 is the annular part of the intervening member 100 that exists between the imaginary line C and the outer periphery of the intervening member 100. The dimension of the straight line connecting the imaginary line C and the outer edge of the annular plate portion 101 in the radial direction Y is the width H of the annular plate portion 101. The width H will be explained later.

[0070] The outer diameter of the intervening member 100 is the outer diameter of the annular plate portion 101. The outer diameter of the annular plate portion 101 is smaller than the outer diameter of the bearing housing portion 18. Here, in the bearing housing portion 18, among the inner surfaces of the first slit 18a to the fourth slit 18d, the inner surface located on the outermost circumference in the radial direction Y of the bearing housing portion 18 is defined as the inner bottom surface 181.

[0071] The circle formed by connecting the inner bottom surfaces 181 of the first slit 18a to the fourth slit 18d in the circumferential direction B of the bearing housing portion 18 is defined as the first virtual circle C1. The diameter of the first virtual circle C1 is smaller than the outer diameter of the annular plate portion 101 and larger than the diameter of the circle formed by connecting the virtual lines C.

[0072] As shown in Figure 7, the dimension in the radial direction Y from the inner circumferential surface 18g to the inner bottom surface 181 of the bearing housing portion 18 is defined as the depth D of the first slit 18a to the fourth slit 18d. The dimension in the thickness direction of each bump foil portion 73c is defined as the thickness G of the bump foil portion 73c. ​​The thickness G is the same for the peak portion 81 and the valley portion 82. Furthermore, the width H of the annular plate portion 101 is sufficiently larger than the value of the depth D. Moreover, the width H of the annular plate portion 101 is greater than the sum of the depth D and the thickness G.

[0073] The width H of the annular plate portion 101 is large enough to cover the outer circumference of the first slit 18a to the fourth slit 18d along the radial direction Y of the bearing housing portion 18 in the first state of the radial foil bearing 20. Therefore, the annular plate portion 101 is large enough to cover all of the first slit 18a to the fourth slit 18d in any of the positions of the unloaded state, the first state, and the second state.

[0074] As shown in Figure 4, the first extension portion 102 extends radially Y toward the rotation axis 40 from between adjacent boundaries K in the circumferential direction B. The first extension portion 102 has a shape in which the dimension toward the circumferential direction B gradually decreases as it extends from the annular plate portion 101. The tip of the first extension portion 102 is arc-shaped. When the intervening member 100 is viewed in the thickness direction under no load, the first extension portion 102 extends along the inner surface 731 of the peak portion 81.

[0075] When the intervening member 100 is viewed in the thickness direction, the second extending portion 103 has its longitudinal side extending in the circumferential direction B. The intervening member 100 is equipped with a rotation-suppressing piece 106 that extends from the second extending portion 103. As shown in Figure 7, the dimensions of the rotation-suppressing piece 106 in the circumferential direction B are slightly smaller than the distance between the opposing faces in the circumferential direction B at the pair of top foil fixed ends 72a. Also, as shown in Figure 6, the rotation-suppressing piece 106 is curved away from the intervening member 100 in the thickness direction of the intervening member 100, from the inner circumferential edge of the intervening member 100 located at the second extension portion 103.

[0076] As shown in Figure 4, the third extension portion 104 and the fourth extension portion 105 each have their longitudinal sides extending in the circumferential direction B. Furthermore, the dimensions of the third extension portion 104 and the fourth extension portion 105 in the circumferential direction B are smaller than the dimensions of the second extension portion 103 in the circumferential direction B.

[0077] The intervening member 100 has three locking portions 107 formed at the tip of each first extending portion 102. Since one locking portion 107 is formed on each first extending portion 102, the intervening member 100 has three first extending portions 102 on which the locking portions 107 are formed. Each locking portion 107 is a ridge projecting in the axial direction X toward the bump foil 73. The three locking portions 107 are spaced apart in the circumferential direction B.

[0078] As shown in Figure 5, each locking portion 107 has a locking surface 107a on the inner peripheral edge side of the intervening member 100, on one of the two sides of the locking portion 107 in the thickness direction. As shown in Figure 4, the circle formed by connecting the locking surfaces 107a in the circumferential direction B is defined as the second virtual circle C2. Since the second virtual circle C2 coincides with the bump foil surface 72t of the top foil 72, in Figure 4 the second virtual circle C2 is located on the bump foil surface 72t. Therefore, the three locking portions 107 can be locked to the bump foil surface 72t of the top foil 72.

[0079] Communication recesses 108 are defined between adjacent first extensions 102 in the circumferential direction B, between adjacent first extensions 102 and second extensions 103 in the circumferential direction B, between adjacent first extensions 102 and third extensions 104 in the circumferential direction B, and between adjacent first extensions 102 and fourth extensions 105 in the circumferential direction B. When the intervening member 100 is viewed in the thickness direction, the communication recesses 108 are curved inward from the tips of the first extensions 102 and the second to fourth extensions 103 to 105 toward the annular plate portion 101.

[0080] The projection dimension of each of the first extension portion 102, second extension portion 103, third extension portion 104, and fourth extension portion 105 from the annular plate portion 101 in the radial direction Y is the same as the dimension in the radial direction Y between the imaginary line C and the second imaginary circle C2.

[0081] <Arrangement of intervening members> The intervening member 100 faces the first end face 18A on the side closer to the first impeller chamber 13b, among the end faces in the axial direction X of the bearing housing portion 18 formed on the first plate 15, and also faces the first end face 18A on the side closer to the second impeller chamber 14b, among the end faces in the axial direction X of the bearing housing portion 18 formed on the extended portion 12d.

[0082] As shown in Figure 5, of the two end faces of the bump foil portion 73c in the axial direction X, the bump foil end face 73f facing the intervening member 100 is located further away from the intervening member 100 than the two end faces of the top foil 72 in the axial direction X that face the intervening member 100.

[0083] Each of the three locking surfaces 107a of the locking portion 107 engages with the bump foil surface 72t, which is the radial outer circumference of the top foil 72. The engagement of the three locking surfaces 107a with the bump foil surface 72t positions the intervening member 100 on the radial outer circumference side of the top foil 72. Therefore, the intervening member 100 comprises multiple locking portions 107 that engage with the bump foil surface 72t of the top foil 72. Furthermore, each locking portion 107 protrudes from the first extended portion 102 of the intervening member 100 toward the bump foil portion 73c, and from the first end surface 18A toward the bump foil portion 73c. ​​In the axial direction X, the bump foil portion 73c and the locking portion 107 may be in contact or slightly separated. Furthermore, the locking portion 107 is located closer to the bump foil end face 73f than to the first end face 18A of the bearing housing portion 18.

[0084] As shown in Figures 6 and 7, the rotation-inhibiting piece 106 is inserted between a pair of top foil fixed ends 72a. The rotation-inhibiting piece 106 is inclined to approach the inner circumferential surface 18g of the bearing housing 18 as it moves from the inner circumferential edge of the second extension 103 toward the pair of top foil fixed ends 72a. In other words, the rotation-inhibiting piece 106 is inclined to move away from the bump foil surface 72t as it moves from the inner circumferential edge of the second extension 103 toward the pair of top foil fixed ends 72a. The tip of the rotation-inhibiting piece 106 is located closer to the inner circumferential surface 18g of the bearing housing 18 than the bent portion of the top foil fixed end 72a on the top foil 72.

[0085] As shown in Figure 4, the second extension portion 103 overlaps the gap 83 adjacent to the fourth slit 18d, the space between the first slit 18a, the fourth slit 18d, and the pair of top foil fixed ends 72a, and the outer peripheral gap S1 adjacent to the first slit 18a in the axial direction X, and covers all of them from the outside in the axial direction X.

[0086] The third extension portion 104 overlaps the gap 83 adjacent to the second slit 18b, the second slit 18b, and the outer peripheral gap S1 adjacent to the second slit 18b in the axial direction X, and covers all of them from the outside in the axial direction X. The fourth extension portion 105 overlaps the gap 83 adjacent to the third slit 18c, the third slit 18c, and the outer peripheral gap S1 adjacent to the third slit 18c in the axial direction X, and covers all of them from the outside in the axial direction X.

[0087] In the first state, each first extension portion 102 has a shape that follows the inner surface 731 of the other peaks 81, excluding the peaks 81 connected to the fixed end 73d and open end 73e of each bump foil portion 73c. ​​In the first state, the portion of the inner periphery of the intervening member 100 that follows the communication recess 108 follows the corrugated shape of the bump foil 73. In the first state, each first extension portion 102 overlaps the outer peripheral gap S1 opposite in the axial direction X, and covers the entire overlapping outer peripheral gap S1 from the outside in the axial direction X. Therefore, the first extension portion 102 is a covering portion that overlaps in the axial direction X with respect to the outer peripheral gap S1 defined between the inner circumferential surface 18g and the outer surface 732 which is opposite the bump foil portion 73c to the inner circumferential surface 18g. In addition, each communication recess 108 opens the inner circumferential gap S2 in the axial direction X. In other words, the communication recess 108 does not overlap with respect to the inner circumferential gap S2 in the axial direction X. Therefore, the intervening member 100 has a first extending portion 102 that overlaps with respect to the outer circumferential gap S1 defined between the inner circumferential surface 18g of the bearing housing portion 18 and the outer surface 732 which is the opposing surface of the bump foil 73 to the inner circumferential surface 18g, in the axial direction X, and also has a communication recess 108 that opens the inner circumferential gap S2 defined between the bump foil surface 72t of the top foil 72 and the inner surface 731 which is the opposing surface of the bump foil 73 to the bump foil surface 72t in the axial direction X.

[0088] [Effect of the Embodiment] The operation of the embodiment will now be described. When the centrifugal compressor 10 is in operation, the first impeller 34 rotates along with the rotation of the rotating shaft 40, and air is drawn into the first impeller chamber 13b. The air is then compressed in the first diffuser passage 13d and flows into the discharge chamber 13c.

[0089] The air discharged from the discharge chamber 13c is supplied to a fuel cell stack (not shown). The exhaust from the fuel cell stack is drawn into the intake chamber 14c. The exhaust from the fuel cell stack drawn into the intake chamber 14c is discharged into the second impeller chamber 14b through the second diffuser passage 14d. The second impeller 35 is rotated by the exhaust from the fuel cell stack discharged into the second impeller chamber 14b. The rotation of the second impeller 35 due to the exhaust from the fuel cell stack assists the rotation of the rotating shaft 40. The exhaust from the fuel cell stack discharged into the intake chamber 14c is discharged to the outside of the second impeller chamber 14b.

[0090] During the operation of the centrifugal compressor 10, the radial foil bearing 20 supports the rotating shaft 40 in a non-contact manner in the first state. The intervening member 100 is biased toward the radial foil bearing 20 in the axial direction X by the high pressure from the first impeller chamber 13b and the second impeller chamber 14b. Due to this biasing force, as shown in Figure 5, the annular plate portion 101 of the intervening member 100 is pressed against the first end face 18A of the bearing housing portion 18. As a result, the annular plate portion 101 and the first extension portion 102 cover the outer peripheral gap S1 facing the axial direction X from the outside in the axial direction X. The second extension portion 103 also covers the gap 83 adjacent to the fourth slit 18d, the space between the first slit 18a, the fourth slit 18d, the pair of top foil fixed ends 72a, and the outer peripheral gap S1 adjacent to the first slit 18a from the outside in the axial direction X. The third extension portion 104 covers the gap 83 adjacent to the second slit 18b, the second slit 18b, and the outer peripheral gap S1 adjacent to the second slit 18b from the outside in the axial direction X. The fourth extension portion 105 covers the gap 83 adjacent to the third slit 18c, the third slit 18c, and the outer peripheral gap S1 adjacent to the third slit 18c from the outside in the axial direction X.

[0091] These features prevent compressed air from flowing into the outer surface 732 of the bump foil 73 in the first state. Meanwhile, the communication recess 108 opens the inner circumferential gap S2 outwards. As a result, compressed air from the first impeller chamber 13b and the second impeller chamber 14b flows into the inner circumferential gap S2 through the communication recess 108. Consequently, the air flowing through the inner circumferential gap S2 cools the bump foil surface 72t of the top foil 72, and the rotating shaft 40 is cooled through the top foil 72.

[0092] Furthermore, as shown in Figure 8, if the centrifugal compressor 10 is subjected to an external force such as external vibration, the rotating shaft 40 may become eccentric, resulting in a second state. When the rotating shaft 40 is displaced in the radial direction Y, the top foil 72 also displaces in accordance with the rotating shaft 40. At this time, since the locking portion 107 is locked to the top foil 72, the intervening member 100 also displaces in the same way as the rotating shaft 40. As the intervening member 100 displaces in the same way as the rotating shaft 40, the covering state by the annular plate portion 101, the first extended portion 102, the second extended portion 103, the third extended portion 104, and the fourth extended portion 105 can be maintained, and the state in which the inner circumferential gap S2 is opened by the communicating recess 108 can be maintained.

[0093] [Effects of the Embodiment] According to this embodiment, the following effects can be obtained. (1) The intervening member 100 of the centrifugal compressor 10 has a first extending portion 102 that overlaps the outer peripheral gap S1 in the axial direction X, and a communicating recess 108 that opens the inner peripheral gap S2 in the axial direction X. The communicating recess 108 opens the inner peripheral gap S2 of the radial foil bearing 20 closer to the top foil 72, which experiences a large temperature rise, and does not suppress the flow of air into the inner peripheral gap S2. As a result, the centrifugal compressor 10 can cool the top foil 72 and the rotating shaft 40 with air.

[0094] On the other hand, the first extended portion 102 overlaps with the outer peripheral gap S1 closer to the bearing housing portion 18, where the temperature rise is smaller compared to the top foil portion 72, thus suppressing the inflow of air into the outer peripheral gap S1. As a result, the centrifugal compressor 10 can reduce the amount of air flowing into the outer peripheral gap S1 closer to the bearing housing portion 18 compared to when the first extended portion 102 is absent. Therefore, the centrifugal compressor 10 can cool the radial foil bearing 20 while suppressing the wasteful consumption of compressed air.

[0095] (2) The second to fourth extensions 103 to 105 overlap the outer peripheral gap S1 and the gap 83 in the axial direction X, thereby suppressing the flow of air into the outer peripheral gap S1 and the gap 83. Compared to the case where the second to fourth extensions 103 to 105 are absent, the centrifugal compressor 10 can reduce the amount of air consumed for cooling the radial foil bearing 20.

[0096] (3) The intervening member 100 is equipped with three locking portions 107. In the centrifugal compressor 10, the locking portions 107 are locked to the bump foil surface 72t of the top foil 72, so when the rotating shaft 40 is displaced radially in the Y direction, the intervening member 100 is displaced in the same direction along with the top foil 72. As a result, even when the rotating shaft 40 is displaced radially in the Y direction due to external vibration or the like, the first to fourth extending portions 102 to 105 maintain a state in which the outer peripheral gap S1 and the gap 83 are covered, while the communicating recess 108 maintains a state in which the inner peripheral gap S2 is open.

[0097] (4) In the centrifugal compressor 10, the air that flows into the inner circumferential gap S2 passes between the bump foil end face 73f and the end faces of the first extension 102 and flows in the circumferential direction B of the rotating shaft 40. Since the locking portion 107 protrudes from the first extension 102 toward the bump foil end face 73f, the locking portion 107 can stop the further flow of air that has flowed into the inner circumferential gap S2 and flowed in the circumferential direction B. As a result, the amount of air that flows to the motor chamber 51 through the radial foil bearing 20 can be reduced compared to the case where the locking portion 107 does not protrude from the first extension 102 toward the bump foil end face 73f.

[0098] (5) The first to fourth extensions 102 to 105 cover all of the multiple outer peripheral gaps S1. As a result, the centrifugal compressor 10 can cool the radial foil bearing 20 while efficiently suppressing the wasteful consumption of compressed air.

[0099] (6) One of the pair of top foil fixed ends 72a is inserted into the first slit 18a, and the other is inserted into the fourth slit 18d. This prevents the top foil 72 from rotating in the circumferential direction B of the rotation axis 40. The rotation-suppressing piece 106 of the intervening member 100 is inserted between the opposing sides of the pair of top foil fixed ends 72a whose rotation is suppressed. Therefore, even if the intervening member 100 tries to rotate in the circumferential direction B of the rotation axis 40, the rotation of the intervening member 100 can be suppressed by the contact between the rotation-suppressing piece 106 and the top foil fixed ends 72a. As a result, it is possible to prevent the rotation of the intervening member 100 from releasing the state in which the outer peripheral gap S1 is covered and the inner peripheral gap S2 is opened.

[0100] (7) In the first state, the first extended portion 102 follows the normal shape of the other peaks 81, excluding the peaks 81 connected to the fixed end 73d and the open end 73e of the bump foil portion 73c. ​​Therefore, in the first state, the first extended portion 102 can suitably cover the outer peripheral gap S1.

[0101] [Example of changes] Furthermore, each of the above embodiments can be implemented with the following modifications. The above embodiments and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0102] ○The intervening member 100 does not necessarily have to be equipped with a rotation suppression piece 106. ○An insertion recess may be formed in the first end face 18A of the bearing housing portion 18, recessing from the first end face 18A, and a rotation suppression piece 106 may be inserted into the insertion recess to suppress the rotation of the intervening member 100.

[0103] ○ The intervening member 100 does not need to have a number of first extending portions 102 corresponding to all of the outer peripheral gaps S1, in order to overlap all of the outer peripheral gaps S1. The intervening member 100 may have a number of first extending portions 102 that overlap with only some of the outer peripheral gaps S1 in the axial direction X.

[0104] ○In the first state, each first extending portion 102 may overlap only a portion of the opening of the outer peripheral gap S1 facing the axial direction X, rather than overlapping the entire opening. Furthermore, as long as each first extending portion 102 overlaps at least a portion of the outer peripheral gap S1 facing the axial direction X in the first state, the shape as seen in the axial direction X is not limited to the shape of the embodiment and may be changed as appropriate. For example, the first extending portion 102 may protrude rectangularly from the annular plate portion 101, with the tip in the protruding direction formed in a straight line.

[0105] Furthermore, in the first state, each communication recess 108 may not open the entire inner circumferential gap S2, but only a portion of the inner circumferential gap S2. In the first state, as long as each communication recess 108 is shaped to open at least a portion of the inner circumferential gap S2, the shape as viewed in the axial direction X is not limited to the shape of the embodiment and may be changed as appropriate.

[0106] Therefore, the shape of the first extended portion 102 protruding from the annular plate portion 101 and the shape of the communicating recess 108 defined between adjacent first extended portions 102 in the circumferential direction B of the intervening member 100 may be changed as appropriate.

[0107] ○In the first state, at least one of the second to fourth extending portions 103 to 105 may overlap only a portion of the gap opposite the axial direction X, rather than overlapping the entire gap. ○The number of locking parts 107 may be two or four or more. In other words, the number of locking parts 107 may be changed as appropriate.

[0108] ○The top foil 72 and the bump foil 73 may have the same dimension in the axial direction X. In this case, the bump foil end face 73f, together with the top foil end face 72c, is located on the same virtual plane as the first end face 18A. That is, the bump foil end face 73f is not further away from the intervening member 100 than the top foil end face 72c. Furthermore, in order to engage the locking portion 107 with the bump foil surface 72t of the top foil 72, an insertion groove is formed in the bump foil portion 73c for inserting the locking portion 107 from the outside in the circumferential direction B.

[0109] ○The intervening member 100 does not necessarily have a locking portion 107. In this case, the intervening member 100 is integrated with the bearing housing portion 18 by bonding or welding to the first end face 18A. Also in this case, the intervening member 100 will no longer follow the displacement of the rotating shaft 40 in the radial direction Y.

[0110] ○The annular plate portion 101 does not need to be large enough to cover the first slit 18a to the fourth slit 18d. ○The bearing housing portion 18 does not necessarily have to have the first slit 18a to the fourth slit 18d formed therein. In this case, the top foil 72 does not have a top foil fixed end 72a, and the bump foil portion 73c does not have a fixed end 73d. The top foil 72 and the bump foil portion 73c are then fixed to the inner circumferential surface 18g of the bearing housing portion 18 by welding or the like.

[0111] ○The bump foil 73 may not be divided into three bump foil sections 73c as in the embodiment, but may be provided as a single component. ○The centrifugal compressor 10 may, for example, be configured without a second impeller 35.

[0112] ○The fluid compressed by the first impeller 34 and the second impeller 35 is not limited to air. The fluid may be, for example, a refrigerant or a mixture of gaseous and liquid fluorocarbons (CFCs). Therefore, the fluid to be compressed by the centrifugal compressor 10 is arbitrary. For example, the centrifugal compressor 10 may be used in an air conditioning system. In this case, the centrifugal compressor 10 may compress a refrigerant. The mounting target of the centrifugal compressor 10 is not limited to vehicles and is arbitrary.

[0113] ○The intervening member 100 corresponding to the radial foil bearing 20 fixed to the bearing housing portion 18 of the motor housing 12 on the first impeller chamber 13b side is provided on the first impeller chamber 13b side in the axial direction X than the radial foil bearing 20, but it may also be provided on the motor chamber 51 side in the axial direction X than the radial foil bearing 20. Similarly, the intervening member 100 corresponding to the radial foil bearing 20 fixed to the bearing housing portion 18 of the motor housing 12 on the second impeller chamber 14b side is provided on the second impeller chamber 14b side in the axial direction X than the radial foil bearing 20, but it may also be provided on the motor chamber 51 side in the axial direction X than the radial foil bearing 20. In these cases, a restricting member is required to restrict the movement of the intervening member 100 in the axial direction X in order to prevent the intervening member 100 from moving away from the radial foil bearing 20. [Explanation of Symbols]

[0114] B...Circumferential direction, X...Axial direction, Y...Radial direction, S1...Outer circumference clearance, S2...Inner circumference clearance, 10...Centrifugal compressor, 11...Housing, 13b...First impeller chamber, 14b...Second impeller chamber, 18...Bearing housing section, 18A...First end face, 18a...First slit, 18d...Fourth slit, 18g...Inner circumference surface, 20...Radial foil bearing, 34...First impeller, 35...Second impeller, 39...Motor, 40...Rotating shaft, 51...Motor chamber, 72...Top foil 72a... Top foil fixed end, 72c... Top foil end face as end face, 72t... Bump foil surface as outer peripheral surface, 73... Bump foil, 73f... Bump foil end face as end face, 81... Peak portion, 82... Valley portion, 100... Intervening member, 102... First extending portion as covering portion, 106... Rotation suppression piece, 107... Locking portion, 108... Communicating recess, 731... Inner surface as opposite to the bump foil, 732... Outer surface as opposite to the bump foil.

Claims

1. A rotating shaft driven by a motor, An impeller that compresses the fluid by rotating integrally with the aforementioned rotating shaft, A housing that accommodates the rotating shaft and has a motor chamber for housing the motor and an impeller chamber for housing the impeller, The housing includes a radial foil bearing which is disposed inside the housing and rotatably supports the rotating shaft between the impeller chamber and the motor chamber in the axial direction of the rotating shaft, The housing includes a bearing housing portion to which the radial foil bearing is fixed, The aforementioned radial foil bearing is A top foil is positioned between the bearing housing and the rotating shaft, A centrifugal compressor comprising: a bump foil disposed between the bearing housing and the top foil, the bump foil having a plurality of peaks that contact the outer circumferential surface of the top foil and a plurality of valleys that contact the inner circumferential surface of the bearing housing, wherein the peaks and valleys are alternately arranged in the circumferential direction of the rotating shaft; The rotating shaft is inserted through an intervening member that faces the radial foil bearing in the axial direction and is interposed between the impeller chamber and the motor chamber. The intervening member has a covering portion that overlaps in the axial direction with respect to the gap defined between the inner circumferential surface of the bearing housing portion and the opposing side of the bump foil to the inner circumferential surface, A centrifugal compressor characterized by having a communication recess that opens in the axial direction a gap defined between the outer circumferential surface of the top foil and the opposite side of the bump foil to the outer circumferential surface.

2. The centrifugal compressor according to claim 1, wherein the intervening member comprises a plurality of locking portions that engage with the outer peripheral surface of the top foil.

3. The intervening member faces the end face closer to the impeller chamber among the axial end faces of the bearing housing portion. The end face of the bump foil facing the intervening member is located further away from the intervening member than the end face of the top foil facing the intervening member. The centrifugal compressor according to claim 2, wherein the locking portion protrudes axially from the intervening member toward the end face of the bump foil and is located closer to the end face of the bump foil than the end face of the bearing housing portion.

4. The centrifugal compressor according to any one of claims 1 to 3, wherein the covering portion overlaps in the axial direction with respect to all of the plurality of gaps defined between the inner circumferential surface of the bearing housing portion and the opposing side of the bump foil to the inner circumferential surface.

5. The top foil is provided with fixed top foil ends located at both ends of the top foil in the circumferential direction of the rotation axis, and each of the pair of fixed top foil ends is inserted into a slit recessed from the inner circumferential surface of the bearing housing portion. The centrifugal compressor according to claim 1 or 2, wherein the intervening member comprises a rotation-suppressing piece inserted between the pair of top foil fixed ends facing each other in the circumferential direction.

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