Centrifugal compressor

Abstract

The present invention provides a centrifugal compressor having a seal member (100) provided at an axial end of a radial foil bearing (20) to suppress fluid leakage from an impeller chamber to a motor chamber. The seal member (100) has: an annular plate part (101) into which a rotating shaft (40) is inserted and which covers an area from the radially outer periphery of a top foil (72) to a more radially outer peripheral position than a radially inner peripheral position on a bearing housing part (18); and a locking part (102) that protrudes from the annular plate part (101) toward the radial foil bearing (20) in an axial direction (X) and is locked to the radially outer periphery of the top foil (72).

Description

centrifugal compressor

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

[0002] The centrifugal compressor includes a rotating shaft, a motor that rotates the rotating shaft, an impeller that rotates integrally with the rotating shaft to compress a fluid, and a housing that accommodates the rotating shaft and the impeller. The housing defines an impeller chamber that accommodates the impeller and a motor chamber that accommodates the motor. The centrifugal compressor also includes a radial foil bearing. The radial foil bearing is disposed between the impeller chamber and the motor chamber within the housing and rotatably supports the rotating shaft without contacting it. The radial foil bearing is fixed to a bearing housing portion provided in the housing. The bearing housing portion is disposed in the housing at a position between the impeller chamber and the motor chamber.

[0003] The radial foil bearing has a top foil and a bump foil. The top foil is disposed between the bearing housing and the rotating shaft, and rotatably supports the rotating shaft in a non-contact state when the rotating shaft rotates. The bump foil is disposed between the bearing housing and the top foil, and elastically supports the top foil.

[0004] Centrifugal compressors have a sealing function that prevents fluid leakage from the impeller chamber, which is a high-pressure chamber that has a higher pressure than the motor chamber, to the motor chamber. For example, in an electric turbo compressor described in Patent Document 1, a seal portion that performs the sealing function is provided on the top foil. The seal portion is integrally formed with the top foil so as to extend radially outward from the top foil in a flange-like shape. The seal portion is fitted into a recess formed in the housing. The seal portion is located between the high-pressure chamber and the motor chamber.

[0005] In the electric turbo compressor described in Patent Document 1, the pressure inside the high-pressure chamber is applied to the seal portion, which is then urged to seat in the recess, thereby sealing the gap between the motor chamber and the high-pressure chamber.

[0006] JP 2017-89384 A

[0007] However, in the seal portion described in Patent Document 1, there is a risk that the shape of the top foil may change when the seal portion is provided on the top foil, which is undesirable because it may affect the radial foil bearing's ability to rotatably support the rotating shaft in a non-contact state.

[0008] A centrifugal compressor that solves the above problem includes a rotating shaft driven by a motor, an impeller that rotates integrally with the rotating shaft to compress a fluid, a housing that accommodates the rotating shaft and has formed therein a motor chamber that accommodates the motor and an impeller chamber that accommodates the impeller, a radial foil bearing that 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, and a seal member that is provided at an end of the radial foil bearing in the axial direction and that suppresses leakage of fluid from the impeller chamber to the motor chamber, The radial foil bearing has a bearing housing portion to which a foil bearing is fixed, and the radial foil bearing comprises a top foil arranged between the bearing housing portion and the rotating shaft, and a bump foil arranged between the bearing housing portion and the top foil and elastically supporting the top foil, and the sealing member has an annular plate portion through which the rotating shaft is inserted and which covers from the radial outer periphery of the top foil to the radial inner peripheral position of the bearing housing portion to the radial outer peripheral position, and a locking portion which protrudes from the annular plate portion in the axial direction of the rotating shaft toward the radial foil bearing and is locked to the radial outer periphery of the top foil.

[0009] According to this, the annular plate portion of the seal member can cover the gap from the radial outer periphery of the top foil to the radial inner periphery of the bearing housing, thereby preventing leakage of high-pressure fluid from the impeller chamber to the motor chamber. Furthermore, because the seal member is locked to the radial outer periphery of the top foil by the locking portion, when the rotating shaft is displaced in the radial direction, the seal member also displaces in the same direction along with the top foil. As a result, even when the rotating shaft is displaced in the radial direction due to external vibration or the like, the gap from the radial outer periphery of the top foil to the radial inner periphery of the bearing housing can be covered, preventing leakage of high-pressure fluid from the impeller chamber to the motor chamber.

[0010] Furthermore, the top foil and the seal member are configured as separate bodies. This eliminates the risk of the shape of the top foil changing when a gap-covering structure is provided, as would be the case if the top foil were bent and the gap-covering structure were integrally formed with the top foil. As a result, the impact on the radial foil bearing's ability to rotatably support the rotating shaft in a non-contact state can be reduced.

[0011] In the centrifugal compressor, the bearing housing portion may be open toward the impeller chamber and the motor chamber and have a slit into which a fixed end of at least one of the top foil and the bump foil is inserted, and the annular plate portion may cover an outer peripheral position of the slit along the radial direction of the bearing housing portion.

[0012] According to this, the annular plate portion can suppress leakage of fluid from the impeller chamber to the motor chamber through the slit. In the centrifugal compressor, the locking portion may be formed as a plurality of locking pieces provided at intervals in a circumferential direction of the annular plate portion.

[0013] In the centrifugal compressor, the bump foil may have a plurality of bump foil portions arranged in a circumferential direction of the bearing housing portion, each of the plurality of bump foil portions having a fixed end fixed to the bearing housing portion at one end of the bump foil portion in the circumferential direction and an open end at the other end of the bump foil portion in the circumferential direction, and the locking portion may be inserted between the fixed end and the open end of the bump foil portions adjacent to each other in the circumferential direction.

[0014] According to this, for example, if the locking portion is cylindrical and extends over the entire circumferential direction of the bearing housing, in order to lock the locking portion to the radial outer periphery of the top foil, the cylindrical locking portion needs to be provided with a structure to avoid interference with the bump foil. However, by forming the locking portion as a locking piece, the locking portion can be locked to the radial outer periphery of the top foil by utilizing the gap between the fixed end and the open end. Therefore, unlike when the locking portion is cylindrical and extends over the entire circumferential direction of the bearing housing, the locking portion can be locked to the radial outer periphery of the top foil without requiring a structure to avoid interference between the locking portion and the bump foil.

[0015] In the centrifugal compressor, the sealing member may have a top foil abutment portion that abuts against the axial end face of the top foil, located radially inward of the locking portion of the sealing member, and the top foil abutment portion may extend between a radial outer peripheral position and a radial inner peripheral position of the top foil.

[0016] According to this, the top foil abutment portion can suppress leakage of fluid along the outer peripheral surface of the top foil, thereby improving the function of suppressing leakage of high-pressure fluid from the impeller chamber to the motor chamber.

[0017] The locking portion may be cylindrical, and may have a fitting groove formed therein into which an end of the top foil fixed to the bearing housing portion fits. This allows the locking area of ​​the locking portion relative to the radial outer periphery of the top foil to be increased compared to when the locking portions are spaced apart circumferentially. This allows the seal member to more easily conform to the top foil. Furthermore, the fitting groove prevents interference between the locking portion and the end of the top foil fixed to the bearing housing portion.

[0018] In the above-mentioned centrifugal compressor, the axial length of the top foil may be longer than the axial length of the bump foil, and the engaging portion may extend between the axial end face of the bump foil and the axial end face of the top foil and be engaged with the radial outer periphery of the top foil.

[0019] According to this, by adjusting the axial length of the bump foil, the locking portion can be locked to the radial outer periphery of the top foil.

[0020] This can reduce the influence on the radial foil bearing's ability to rotatably support the rotating shaft in a non-contact state.

[0021] FIG. 1 is a cross-sectional view showing a centrifugal compressor. FIG. 2 is an exploded perspective view of a radial foil bearing and a seal member of a first embodiment. FIG. 3 is a cross-sectional view showing a radial foil bearing of the first embodiment. FIG. 4 is a front view showing a seal member and a radial foil bearing of the first embodiment. FIG. 5 is a cross-sectional view taken along line 5-5 in FIG. 4 showing a seal member and a radial foil bearing. FIG. 6 is a front cross-sectional view showing an eccentric state of a rotating shaft in the first embodiment. FIG. 7 is a side cross-sectional view showing an eccentric state of a rotating shaft in the first embodiment. FIG. 8 is an exploded perspective view of a seal member and a radial foil bearing of a second embodiment. FIG. 9 is a side cross-sectional view of a radial foil bearing and a seal member of the second embodiment. FIG. 10 is a perspective view showing another example of a bearing housing portion.

[0022] (First embodiment) A first embodiment of a centrifugal compressor will be described below with reference to Fig. 1 to Fig. 7. <Basic configuration of centrifugal compressor 10> As shown in Fig. 1, the centrifugal compressor 10 includes a housing 11, a rotating shaft 40, two radial foil bearings 20, a first impeller 34 as an impeller, a second impeller 35 as an impeller, and a motor 39. The centrifugal compressor 10 also includes a seal member 100 provided on each radial foil bearing 20.

[0023] The centrifugal compressor 10 of this embodiment is used as a centrifugal compressor that compresses air as an oxygen-containing fluid to be supplied to a fuel cell of a fuel cell vehicle. The housing 11 is made of a metal material. An example of the material for the housing 11 is aluminum. The housing 11 has 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.

[0024] The motor housing 12 has a cylindrical peripheral wall 12a and a flat end wall 12b located at a first end of the peripheral wall 12a. A first plate 15 closes a second end of the motor housing 12. A motor chamber 51 is defined by the inner surface of the motor housing 12 and the first plate 15. The motor 39 is accommodated in the motor chamber 51. Therefore, the motor chamber 51 that accommodates the motor 39 is formed in the housing 11.

[0025] The first plate 15 has a bearing housing portion 18. A recess 15c is formed in an end face 15b of the first plate 15 opposite the motor housing 12. The bearing housing portion 18 provided on the first plate 15 extends cylindrically from the first plate 15 toward the motor 39. A first bearing recess 15d is formed in the first plate 15. The first bearing recess 15d is recessed from the recess 15c toward the bearing housing portion 18.

[0026] The end wall 12b of the motor housing 12 also has a bearing housing portion 18. The bearing housing portion 18 provided on the end wall 12b extends cylindrically from the end wall 12b toward the motor 39. A second bearing recess 12c is formed in the end wall 12b of the motor housing 12. The second bearing recess 12c is recessed from the end surface of the end wall 12b toward the bearing housing portion 18.

[0027] The second plate 16 is connected to the first plate 15. A first shaft insertion hole 16a is formed in the center of the second plate 16. A thrust bearing accommodating chamber 52 is defined by the inner surface that defines the recess 15c in the first plate 15 and the second plate 16.

[0028] The first impeller housing 13 is cylindrical and has a circular suction port 13a through which air is drawn in. The first impeller housing 13 is connected to a second plate 16. A first impeller chamber 13b, a discharge chamber 13c, and a first diffuser passage 13d are formed between the first impeller housing 13 and the second plate 16.

[0029] The first impeller chamber 13b is formed in the housing 11. The first impeller chamber 13b is in communication with the suction port 13a. The discharge chamber 13c extends around the axis of the suction port 13a around the periphery of the first impeller chamber 13b. The first diffuser passage 13d connects the first impeller chamber 13b and the discharge chamber 13c. The first impeller chamber 13b is in communication with a first shaft insertion hole 16a of the second plate 16.

[0030] The first impeller housing 13 has a first shroud surface 53a. The first shroud surface 53a defines a first impeller chamber 13b in cooperation with the second plate 16. The first shroud surface 53a has a truncated cone shape.

[0031] The third plate 17 is connected to the end wall 12b of the motor housing 12. A second shaft insertion hole 17a is formed in the center of the third plate 17. The second impeller housing 14 is cylindrical and has a circular discharge port 14a through which air is drawn. The second impeller housing 14 is connected to the end face of the third plate 17 opposite to the motor housing 12. The discharge port 14a opens to the end face of the second impeller housing 14 opposite to the third plate 17. A second impeller chamber 14b, a suction chamber 14c, and a second diffuser passage 14d are formed between the second impeller housing 14 and the third plate 17.

[0032] The second impeller chamber 14b is formed in the housing 11. The second impeller chamber 14b is in communication with the discharge port 14a. The suction chamber 14c extends around the axis of the discharge port 14a around the periphery of the second impeller chamber 14b. The second diffuser passage 14d connects the second impeller chamber 14b and the suction chamber 14c. The second impeller chamber 14b is in communication with the second shaft insertion hole 17a.

[0033] The second impeller housing 14 includes a second shroud surface 53b. The second shroud surface 53b defines a second impeller chamber 14b in cooperation with the third plate 17. The second shroud surface 53b has a truncated cone shape.

[0034] <Rotating shaft 40> The rotating shaft 40 is accommodated in the housing 11. The rotating shaft 40 is driven by the motor 39. A portion of the rotating shaft 40 is located in the first impeller chamber 13b and the second impeller chamber 14b. As a result, the rotating shaft 40 is accommodated in the first impeller housing 13 and the second impeller housing 14.

[0035] The rotating shaft 40 passes through the first impeller chamber 13b, the first shaft insertion hole 16a, the recess 15c of the first plate 15, the first bearing recess 15d, the inside of the bearing housing portion 18 provided in the first plate 15, the motor chamber 51, the inside of the bearing housing portion 18 provided in the motor housing 12, the second bearing recess 12c, the second shaft insertion hole 17a, and the second impeller chamber 14b in that order.

[0036] In the following description, the direction in which the axis SL of the rotating shaft 40 extends will be referred to as the "axial direction of the rotating shaft 40." The direction in which the diameter of the rotating shaft 40 extends will be referred to as the "radial direction of the rotating shaft 40." The axial direction of the rotating shaft 40 will also be referred to as the axial direction X. The radial direction of the rotating shaft 40 will also be referred to as the radial direction Y.

[0037] The rotating shaft 40 is provided with a disk-shaped support plate 33. The support plate 33 protrudes from the outer circumferential surface of the rotating shaft 40. The support plate 33 is press-fitted onto the outer circumferential surface of the rotating shaft 40. The support plate 33 rotates integrally with the rotating shaft 40. The support plate 33 is disposed in a thrust bearing accommodating chamber 52.

[0038] The support plate 33 is supported by a thrust bearing 80. <First impeller 34> The first impeller 34 is made of metal. An example of the material of the first impeller 34 is aluminum. The first impeller 34 is connected to the first end 30a of the rotary shaft 40. The first impeller 34 is an impeller that rotates integrally with the rotary shaft 40. The first impeller 34 is housed in the first impeller chamber 13b.

[0039] The first impeller 34 has a truncated cone shape. The diameter of the first impeller 34 gradually decreases from a first back surface 34a, which is the back surface of the first impeller 34, to a first tip surface 34b, which is the tip surface of the first impeller 34. The first back surface 34a faces the second plate 16 in the axial direction X. A first shroud surface 53a extends along the outer periphery of the first impeller 34 from the first back surface 34a to the first tip surface 34b. As a result, the first shroud surface 53a covers the outer periphery of the first impeller 34. The first back surface 34a faces the second plate 16 in the axial direction X. The first impeller 34 compresses air as a fluid by rotating integrally with the rotary shaft 40.

[0040] <Second impeller 35> The second impeller 35 is made of metal. An example of the material of the second impeller 35 is aluminum. The second impeller 35 is connected to the second end 30b of the rotary shaft 40. The second impeller 35 is an impeller that rotates integrally with the rotary shaft 40. The second impeller 35 is housed in the second impeller chamber 14b.

[0041] The second impeller 35 has a truncated cone shape. The diameter of the second impeller 35 gradually decreases from a second back surface 35a, which is the back surface of the second impeller 35, to a second tip surface 35b, which is the tip surface of the second impeller 35. The second back surface 35a faces the third plate 17 in the axial direction X. A second shroud surface 53b extends along the outer periphery of the second impeller 35 from the second back surface 35a to the second tip surface 35b. As a result, the second shroud surface 53b covers the outer periphery of the second impeller 35. The second impeller 35 compresses air as a fluid by rotating integrally with the rotary shaft 40.

[0042] <First High-Pressure Passage 90 and Second High-Pressure Passage 91> The first high-pressure passage 90 is formed between the first back surface 34a and the first impeller-side end face 16b of the second plate 16, and is in communication with the first shaft insertion hole 16a. The second high-pressure passage 91 is formed between the second back surface 35a and the second impeller-side end face 17b of the third plate 17, and is in communication with the second shaft insertion hole 17a. Thus, the first high-pressure passage 90 communicates between the first diffuser passage 13d and the first shaft insertion hole 16a. Furthermore, the second high-pressure passage 91 communicates between the second diffuser passage 14d and the second shaft insertion hole 17a.

[0043] <Configuration of Radial Foil Bearings 20> The radial foil bearings 20 are fixed to the respective bearing housing portions 18. Therefore, the two radial foil bearings 20 are disposed inside the housing 11. 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, and the other of the two radial foil bearings 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.

[0044] The radial foil bearing 20 supports the rotating shaft 40 in a state of contact with the rotating shaft 40 until the rotation speed of the rotating shaft 40 reaches a floating rotation speed at which the rotating shaft 40 is floated by the radial foil bearing 20. When the rotating shaft 40 rotates, dynamic pressure is generated between the rotating shaft 40 and the radial foil bearing 20. When the rotation speed of the rotating shaft 40 reaches the floating rotation speed, the generated dynamic pressure causes the rotating shaft 40 to float relative to the radial foil bearing 20. In this way, the radial foil bearing 20 rotatably supports the rotating shaft 40 in a state of not contacting the rotating shaft 40.

[0045] Next, a specific configuration of the radial foil bearing 20 will be described. As shown in Figures 2 and 3, the radial foil bearing 20 has a top foil 72 and a bump foil 73. Each of the two radial foil bearings 20 is fixed inside a bearing housing portion 18. Therefore, the housing 11 has the bearing housing portion 18 to which the radial foil bearings 20 are fixed.

[0046] <Bearing Housing Portion 18> The bearing housing portion 18 provided on the first plate 15 and the bearing housing portion 18 provided on the motor housing 12 have the same configuration, so one of the bearing housing portions 18 will be described as an example.

[0047] The bearing housing portion 18 is cylindrical. The circumferential direction of the bearing housing portion 18 coincides with the circumferential direction of the radial foil bearing 20. In the following description, the circumferential direction of the radial foil bearing 20 and the bearing housing portion 18 will be referred to as circumferential direction B.

[0048] The axis of the bearing housing portion 18 coincides with the axis SL of the rotating shaft 40. Therefore, the axial direction X is also the axial direction of the bearing housing portion 18. The radial direction Y is also the radial direction of the bearing housing portion 18. An insertion hole 18h through which the rotating shaft 40 is inserted is formed in the bearing housing portion 18.

[0049] As shown in FIG. 1 , the bearing housing portion 18 has a first end face 18A and a second end face 18B. The first end face 18A and the second end face 18B are end faces of the bearing housing portion 18 in the axial direction X. The first end face 18A is an end face located at one end of the bearing housing portion 18 in the axial direction X, and the second end face 18B is an end face located at the other end of the bearing housing portion 18 in the axial direction X. The first end face 18A of the bearing housing portion 18 of the first plate 15 is an end face exposed to the first bearing recess 15 d, and the first end face 18A of the bearing housing portion 18 of the motor housing 12 is an end face exposed to the second bearing recess 12 c. The second end face 18B of each bearing housing portion 18 is an end face exposed to the motor chamber 51.

[0050] As shown in Figures 2 and 3, the inner circumferential surface 18g of the bearing housing portion 18 is a cylindrical surface that defines an insertion hole 18h. A first slit 18a, a second slit 18b, a third slit 18c, and a fourth slit 18d are formed in 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 aligned in this order in the circumferential direction B of the bearing housing portion 18. The distance between the first slit 18a and the second slit 18b in the circumferential direction B, the distance between the second slit 18b and the third slit 18c in the circumferential direction B, and the distance between the third slit 18c and the first slit 18a in the circumferential direction B are equal. Furthermore, these distances are larger than the distance between the fourth slit 18d and the third slit 18c in the circumferential direction B. Each of the first to fourth slits 18a to 18d is provided over the entire length of the bearing housing portion 18 in the axial direction X. Each of the first to fourth slits 18a to 18d opens toward the first impeller chamber 13b or the second impeller chamber 14b at a first end surface 18A of the bearing housing portion 18. Each of the first to fourth slits 18a to 18d opens toward the motor chamber 51 at a second end surface 18B of the bearing housing portion 18.

[0051] <Top foil 72> The top foil 72 is tubular. The top foil 72 in this embodiment is approximately cylindrical. The top foil 72 is located inside the bearing housing portion 18. The top foil 72 extends in the circumferential direction B inside the bearing housing portion 18. The top foil 72 is thin plate-shaped. In detail, the top foil 72 is made of a strip-shaped metal plate made of a flexible metal such as stainless steel. The top foil 72 is formed by curving this metal plate into a cylindrical shape so that the longitudinal direction extends in the circumferential direction B of the bearing housing portion 18 and the lateral direction extends in the axial direction X.

[0052] Top foil fixing ends 72a are provided on both ends of the top foil 72 in the circumferential direction B. Each top foil fixing end 72a is formed by bending a metal plate material outward from the top foil 72 in the radial direction Y. Each top foil fixing end 72a has a rectangular flat plate shape extending perpendicular to the circumferential direction B. The dimension of each top foil fixing end 72a in the axial direction X is the same as the dimension of the top foil 72 in the axial direction X. One top foil fixing end 72a is inserted into the first slit 18a, and the other top foil fixing end 72a is inserted into the fourth slit 18d. By inserting each top foil fixing end 72a into each slit 18a, 18d, movement of the top foil 72 in the circumferential direction B is suppressed.

[0053] The top foil 72 is disposed outward of the rotating shaft 40 in the radial direction Y. Therefore, the top foil 72 is disposed between the bearing housing portion 18 and the rotating shaft 40 in the radial direction Y. The top foil 72 faces the rotating shaft 40 in the radial direction Y. The top foil 72 has a bearing surface 72s and a bump foil surface 72t. The bearing surface 72s is an inner surface in the radial direction Y, and the bump foil surface 72t is an outer surface in the radial direction Y. The bearing surface 72s faces the circumferential surface of the rotating shaft 40, and the bump foil surface 72t faces a bump foil 73, which will be described later.

[0054] <Bump foil 73> The bump foil 73 has three bump foil portions 73c divided in the circumferential direction B of the bearing housing portion 18. The three bump foil portions 73c constituting the bump foil 73 are hereinafter also referred to as multiple bump foil portions 73c. ​​The multiple bump foil portions 73c may have approximately the same circumferential dimension, or some or all of them may have different dimensions. The dimension of each bump foil portion 73c in the axial direction X is the same as the dimension of the top foil 72 in the axial direction X.

[0055] Each bump foil portion 73c has a plurality of peaks 81 and a plurality of valleys 82. Each peak 81 contacts the bump foil surface 72t. Each valley 82 contacts the inner circumferential surface 18g of the bearing housing portion 18. The peaks 81 and valleys 82 are alternately arranged in the circumferential direction B of the bearing housing portion 18.

[0056] The valley portions 82 protrude away from the bump foil surface 72t in the radial direction Y and are curved in an arc so as to bulge toward the bearing housing portion 18. The peak portions 81 protrude from the ends of the valley portions 82 in the circumferential direction B toward the bump foil surface 72t and are curved in an arc so as to bulge toward the top foil 72. Each bump foil portion 73c elastically supports the top foil 72 as the peak portions 81 and valley portions 82 extend in the circumferential direction B. The multiple bump foil portions 73c may have the same number of peak portions 81, or the number of peak portions 81 included in some or all of the bump foil portions 73c may differ from one another. The multiple bump foil portions 73c may have the same number of valley portions 82, or the number of valley portions 82 included in some or all of the bump foil portions 73c may differ from one another.

[0057] Each of the multiple bump foil portions 73c has a fixed end 73d fixed to the bearing housing portion 18 at one end of the bump foil portion 73c in the circumferential direction B, and an open end 73e at the other end of the bump foil portion 73c in the circumferential direction B. In each bump foil portion 73c, the end opposite the fixed end 73d in the circumferential direction B is the open end 73e.

[0058] As shown in FIG. 3 , the fixed end 73d of one of the three bump foil portions 73c is inserted into the first slit 18a along with one of the top foil fixed ends 72a. The fixed end 73d of the second bump foil portion 73c adjacent to the first bump foil portion 73c in the counterclockwise direction is inserted into the second slit 18b. The fixed end 73d of the third bump foil portion 73c adjacent to the second bump foil portion 73c in the counterclockwise direction is inserted into the third slit 18c. Therefore, the bearing housing portion 18 has first to third slits 18a to 18c as slits into which the fixed ends 73d of the bump foil portions 73c that form the bump foil 73 are inserted. The fixed end 73d of the bump foil portion 73c is not inserted into the fourth slit 18d.

[0059] In the circumferential direction B, of two adjacent bump foil portions 73c, the fixed end 73d of one bump foil portion 73c and the open end 73e of the other bump foil portion 73c are adjacent to each other while being spaced apart in the circumferential direction B.

[0060] Of two bump foil portions 73c adjacent to each other in the circumferential direction B, a gap 83 is formed between the fixed end 73d of one bump foil portion 73c and the open end 73e of the other bump foil portion 73c. ​​The gap 83 is formed regardless of the extension of the multiple bump foil portions 73c. ​​The gap 83 is a gap that penetrates the bump foil 73 in the radial direction Y, which is the direction from the top foil 72 toward the bearing housing portion 18. The gaps 83 are formed in three locations spaced apart from each other in the circumferential direction B.

[0061] Each bump foil portion 73c is interposed between the inner circumferential surface 18g of the bearing housing portion 18 and the bump foil surface 72t of the top foil 72. Therefore, the bump foil 73, which is composed of multiple bump foil portions 73c, is disposed between the inner circumferential surface 18g of the bearing housing portion 18 and the bump foil surface 72t of the top foil 72. Due to the presence of the bump foil portions 73c, an annular gap S is formed between the inner circumferential surface 18g of the bearing housing portion 18 and the bump foil surface 72t of the top foil 72. Both ends of the gap S in the axial direction X are open in areas other than the bump foil portions 73c. ​​The opening width W of this gap S in the radial direction Y changes depending on the expansion and contraction of the bump foil portions 73c in the circumferential direction B and the eccentricity of the rotating shaft 40.

[0062] Next, the radial foil bearing 20 will be described in a state where no load is acting on the bearing surface 72s from the rotating shaft 40. As shown in Figure 3, the state where no load is acting on the bearing surface 72s from the rotating shaft 40 refers to a state where 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 where no load is acting on the bearing surface 72s from the rotating shaft 40 will be referred to as a no-load state below.

[0063] <No-load state> As shown in Figure 3, in the no-load state, each of the peaks 81 of each bump foil portion 73c locally contacts the bump foil surface 72t of the top foil 72. In the no-load state, the tip portions of the peaks 81 in the direction of protrusion toward the top foil 72 contact the bump foil surface 72t of the top foil 72. In the no-load state, each of the valleys 82 of the bump foil portion 73c locally contacts the inner circumferential surface 18g of the bearing housing portion 18. In the no-load state, the tip portions of the valleys 82 in the direction of protrusion toward the bearing housing portion 18 contact the inner circumferential surface 18g of the bearing housing portion 18.

[0064] <First State> 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 above the bearing surface 72s.

[0065] 4 and 5 , in the first state, as the rotating shaft 40 rotates, the top foil 72 elastically deforms outward in the radial direction Y. This causes an air film to form 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 rotatably supports the rotating shaft 40 without the rotating shaft 40 coming into contact with the top foil 72.

[0066] When 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, the top foil 72 presses the peaks 81 of the bump foil portion 73c, which are in contact with the bump foil surface 72t of 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. As the top foil 72 displaces outward in the radial direction Y, the peaks 81 and valleys 82 elastically deform. In the first state, a load is applied evenly from the rotating shaft 40 to the entire bearing surface 72s via the air film. Therefore, the peaks 81 and valleys 82 elastically deform uniformly. In the first state, the opening width W of the gap S in the radial direction Y becomes narrower than in the no-load state due to the elastic deformation of the bump foil portion 73c. The distance in the radial direction Y between the inner circumferential surface 18g of the bearing housing portion 18 and the bump foil surface 72t is defined as a first distance.

[0067] <Second State> Next, the second state will be described. As shown in Figures 6 and 7 , the second state refers to a state of the radial foil bearing 20 in which the rotating shaft 40 is closer to a portion 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 can be when 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. The position at which the rotating shaft 40 is closest to the bearing housing portion 18 is defined as a close position P1. The side of the bearing housing portion 18 opposite the close position P1 in the radial direction Y is defined as a separated position P2. The separated position P2 is the position at which the rotating shaft 40 is farthest from the inner circumferential surface 18g of the bearing housing portion 18.

[0068] In the second state, at the approaching position P1, the peaks 81 and valleys 82 elastically deform more than in the first state. As a result, the contact area of ​​the bump foil portion 73c with the top foil 72 and the bearing housing portion 18 is expanded compared to the first state. Furthermore, in accordance with the elastic deformation of the peaks 81 and valleys 82, the bump foil portion 73c deforms near the approaching position P1 such that the fixed end 73d and the released end 73e, which are adjacent in the circumferential direction B, approach each other. As a result, at the approaching position P1, the bump foil surface 72t of the top foil 72 approaches the inner circumferential surface 18g of the bearing housing portion 18.

[0069] Conversely, in the second state, at the separated position P2, the peaks 81 and valleys 82 elastically deform less than in the first state. As a result, the contact area of ​​the bump foil portion 73c with the top foil 72 and the bearing housing portion 18 is reduced compared to the first state. As the peaks 81 and valleys 82 elastically deform, the bump foil portion 73c deforms near the separated position P2 such that the fixed end 73d and the released end 73e, which are adjacent in the circumferential direction B, move away from each other. As a result, at the separated position P2, the bump foil surface 72t of the top foil 72 is separated from the inner circumferential surface 18g of the bearing housing portion 18.

[0070] In the second state, the opening width W in the radial direction Y of the gap S at the close position P1 is narrower than in the first state. On the other hand, in the second state, the opening width W in the radial direction Y of the gap S at the separated position P2 is wider than in the first state.

[0071] <Sealing member 100> As shown in FIG. 1, the centrifugal compressor 10 has sealing members 100 that are provided at the axial ends of the radial foil bearings 20 and that suppress leakage of high-pressure air from each impeller chamber 13 b, 14 b through each radial foil bearing 20 to the motor chamber 51.

[0072] The seal member 100 is formed by shaping a flexible metal plate, such as stainless steel. A shaft insertion hole 100a is formed in the center of the seal member 100. The shaft insertion hole 100a penetrates the seal member 100 in the axial direction X. The seal member 100 is provided adjacent to each radial foil bearing 20 in the axial direction X. The rotating shaft 40 is inserted through the seal member 100.

[0073] The seal member 100 adjacent 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. The seal member 100 adjacent 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. The two seal members 100 have the same shape.

[0074] As shown in FIG. 4 , the seal member 100 includes an annular plate portion 101, three locking portions 102, and a top foil abutment portion 103. The annular plate portion 101 is thin. The annular plate portion 101 is a portion of the seal member 100 that is closer to the outer periphery in the radial direction Y than the locking surfaces 102a of the locking portions 102. The locking surfaces 102a of the locking portions 102 will be described later. The outer diameter of the annular plate portion 101 in the seal member 100 is also the outer diameter of the seal member 100. The outer diameter of the annular plate portion 101 is smaller than the outer diameter of the bearing housing portion 18. Here, among the inner surfaces of the first to fourth slits 18a to 18d in the bearing housing portion 18, the inner surface located furthest outward in the radial direction Y of the bearing housing portion 18 is referred to as an inner bottom surface 181. The inner bottom surface 181 of the bearing housing portion 18 provided in the motor housing 12 is located more inward in the radial direction Y than the inner circumferential surface of the second bearing recess 12c. Also, the inner bottom surface 181 of the bearing housing portion 18 provided in the first plate 15 is located more inward in the radial direction Y than the inner circumferential surface of the first bearing recess 15d.

[0075] A first imaginary circle C1 is a circle formed by connecting the inner bottom surfaces 181 of the first to fourth slits 18a to 18d in the circumferential direction B of the bearing housing portion 18. The diameter of the first imaginary circle C1 is smaller than the outer diameter of the annular plate portion 101. Therefore, in the no-load state, the annular plate portion 101 covers the openings of the first to fourth slits 18a to 18d on the first end face 18A side.

[0076] The dimension in the radial direction Y from the inner peripheral surface 18g of the bearing housing portion 18 to the inner bottom surface 181 is defined as the depth D of the first to fourth slits 18a to 18d. The dimension in the radial direction Y of the annular plate portion 101 is greater than the sum of the opening width W and the depth D of the gap S at the separated position P2 when the rotating shaft 40 approaches any of the first to fourth slits 18a to 18d to enter the second state.

[0077] 6, the annular plate portion 101 is large enough to cover the outer peripheral positions of the first to fourth slits 18a to 18d along the radial direction Y of the bearing housing portion 18. Therefore, the annular plate portion 101 is large enough to cover all of the first to fourth slits 18a to 18d in any of the no-load state, the first state, and the second state. The annular plate portion 101 covers from the radial outer periphery of the top foil 72 to the radial inner peripheral position of the bearing housing portion 18 to the radial outer peripheral position. In other words, the annular plate portion 101 covers the gap S over the entire circumferential direction B in any of the no-load state, the first state, and the second state.

[0078] As shown in Figures 4 and 5, each locking portion 102 is a protrusion that protrudes in the axial direction X from the annular plate portion 101 toward the radial foil bearing 20. Each locking portion 102 is formed by cutting out a portion of the inner periphery of a metal plate. The seal member 100 has grooves 103a formed by cutting out the locking portions 102 from the metal plate. The three locking portions 102 are formed at equal intervals in the circumferential direction B. Therefore, the three locking portions 102 are formed as a plurality of locking pieces that are spaced apart in the circumferential direction of the annular plate portion 101.

[0079] The thickness of each locking portion 102 is the same as the thickness of the metal plate forming the seal member 100. Each locking portion 102 has a locking surface 102a on the inner circumferential side of the seal member 100, among the two surfaces of the locking portion 102 in the thickness direction. A circle connecting the locking surfaces 102a in the circumferential direction B is defined as a second imaginary circle C2. Note that while the second imaginary circle C2 is shown in FIG. 4 , the second imaginary circle C2 coincides with the bump foil surface 72t of the top foil 72, and therefore is indicated by a dashed line in FIG. 4 . The diameter of this second imaginary circle C2 is greater than the sum of the diameter of the rotating shaft 40 and twice the thickness of the top foil 72. The locking surface 102a of each of the three locking portions 102 is locked to the bump foil surface 72t, which is the radial outer periphery of the top foil 72.

[0080] As shown in Figure 3, each locking portion 102 is inserted into a gap 83 between a fixed end 73d and an open end 73e adjacent to each other in the circumferential direction B, and is locked to the bump foil surface 72t located in the gap 83.

[0081] As shown in FIGS. 4 and 5 , the top foil abutment portion 103 is provided on the inner circumferential side of the seal member 100 in the radial direction Y relative to the locking surface 102a of the locking portion 102. The inner diameter of the seal member 100 at the radially inner circumferential end of the top foil abutment portion 103 is larger than the diameter of the rotating shaft 40. The top foil abutment portion 103 is partially divided in the circumferential direction B by three grooves 103a. In the top foil abutment portion 103, the dimension in the radial direction Y from the locking surface 102a of the locking portion 102 to the tip of the top foil abutment portion 103 is less than the plate thickness of the top foil 72. In any of the no-load state, the first state, and the second state, when the locking surface 102a of the locking portion 102 is locked to the bump foil surface 72t, the top foil abutment portion 103 is positioned so as to be able to abut against the axial end surface 72c of the top foil 72. The top foil abutment portion 103 abuts against the axial end surface 72 c of the top foil 72 , and the top foil abutment portion 103 extends from the radially outer peripheral position to the radially inner peripheral position of the top foil 72 .

[0082] [Operation of First Embodiment] The operation of the first embodiment will be described. When the centrifugal compressor 10 is in operation, the first impeller 34 rotates together with the rotation of the rotary shaft 40, and air is taken into the first impeller chamber 13b from the suction port 13a. The air is then compressed in the first diffuser passage 13d and flows into the discharge chamber 13c and the first high-pressure passage 90.

[0083] The air discharged from the discharge chamber 13c is supplied to a fuel cell stack (not shown). The exhaust air from the fuel cell stack is drawn into the suction chamber 14c. The exhaust air from the fuel cell stack drawn into the suction 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 air from the fuel cell stack discharged into the second impeller chamber 14b. The rotation of the rotating shaft 40 is assisted by the rotation of the second impeller 35 caused by the exhaust air from the fuel cell stack. The exhaust air from the fuel cell stack discharged into the suction chamber 14c is discharged to the outside from the discharge port 14a.

[0084] During operation of the centrifugal compressor 10, the radial foil bearing 20 supports the rotating shaft 40 in a non-contact state in the first state. The seal member 100 is biased toward the radial foil bearing 20 in the axial direction X by the high pressure of the first high-pressure passage 90 and the second high-pressure passage 91. As shown in Fig. 5, the annular plate portion 101 of the seal member 100 is pressed against the first end face 18A of the bearing housing portion 18 by this biasing force. As a result, the annular plate portion 101 seals between the radial foil bearing 20 and each of the high-pressure passages 90, 91, and the first to fourth slits 18a to 18d formed in the bearing housing portion 18, and the gap S.

[0085] The biasing force also biases the top foil abutment portion 103 toward the radial foil bearing 20. The top foil abutment portion 103 abuts against the axial end face 72c of the top foil 72, sealing the gap between the locking surface 102a of the locking portion 102 and the bump foil surface 72t.

[0086] 6 and 7 , when the centrifugal compressor 10 is subjected to an external force due to external vibration or the like during operation, the rotating shaft 40 may become eccentric, resulting in the second state. When the rotating shaft 40 is displaced in the radial direction Y, the top foil 72 is also displaced following the rotating shaft 40. At this time, because the locking portion 102 is locked to the top foil 72, the seal member 100 is also displaced in the same manner as the rotating shaft 40. By displacing the seal member 100 in the same manner as the rotating shaft 40, the sealed state provided by the annular plate portion 101 and the top foil abutment portion 103 can be maintained.

[0087] [Effects of the First Embodiment] The effects of the first embodiment will be described. (1-1) The seal member 100 is engaged with the bump foil surface 72t of the top foil 72 by the engaging portion 102. When the centrifugal compressor 10 is subjected to an external force, such as external vibration, the seal member 100 displaces in response to the displacement of the rotating shaft 40 in the radial direction Y, so that the annular plate portion 101 can maintain a state in which the gap S is covered. As a result, the seal member 100 can suppress leakage of high-pressure air from the first impeller chamber 13b to the motor chamber 51 via the first high-pressure passage 90 and the radial foil bearing 20, and from the second impeller chamber 14b to the motor chamber 51 via the second high-pressure passage 91 and the radial foil bearing 20. As a result, the centrifugal compressor 10 does not need to provide a complex structure such as a labyrinth seal in the housing 11 to prevent leakage of high-pressure air from each impeller chamber 13b, 14b to the motor chamber 51. Furthermore, since leakage of high-pressure and high-temperature air can be prevented, heat damage to the motor 39 can be reduced, and an increase in power consumption due to a decrease in output of the motor 39 caused by heat damage can be suppressed.

[0088] (1-2) The seal member 100 is formed as a separate body from the radial foil bearing 20. This eliminates the risk of the shape of the top foil 72 changing when the seal member is provided, as occurs when the seal member is integrally formed by bending the top foil 72. As a result, it is possible to reduce the impact on the radial foil bearing 20 of rotatably supporting the rotating shaft 40 in a non-contact state.

[0089] (1-3) Each of the three locking portions 102 is inserted into the gap 83 between the bump foil portions 73c adjacent to each other in the circumferential direction B. This allows the locking portion 102 to be locked to the top foil 72 without changing the lengths of the three bump foil portions 73c in the axial direction X. That is, the locking portion 102 can be locked to the bump foil surface 72t of the top foil 72 by utilizing the gap 83 between the fixed end 73d and the open end 73e adjacent to each other in the circumferential direction B. Therefore, unlike a case in which the locking portion 102 is cylindrical and extends over the entire circumferential direction B of the bearing housing portion 18, the centrifugal compressor 10 can lock the locking portion 102 to the bump foil surface 72t of the top foil 72 without requiring a configuration to avoid interference between the locking portion 102 and the bump foil 73. Furthermore, the locking portion 102 can be locked to the bump foil surface 72t of the top foil 72 without causing the seal member 100 to interfere with the top foil fixed end 72a and the fixed end 73d of the bump foil portion 73c.

[0090] (1-4) The locking portions 102 are three locking pieces formed at intervals in the circumferential direction of the annular plate portion 101. This makes it easy to create the locking portions 102 in the seal member 100. (1-5) The top foil abutment portion 103 of the seal member 100 is positioned facing the axial end surface 72c of the top foil 72 while being located radially inner than the bump foil surface 72t of the top foil 72. This allows the top foil abutment portion 103 to prevent compressed air from leaking along the bump foil surface 72t of the top foil 72. This further prevents high-pressure air from leaking from each impeller chamber 13b, 14b to the motor chamber 51.

[0091] (1-6) The annular plate portion 101 is large enough to cover all of the first to fourth slits 18a to 18d in any of the no-load state, the first state, and the second state. Therefore, even in the radial foil bearing 20 in which the bearing housing portion 18 is provided with the first to fourth slits 18a to 18d to suppress movement of the top foil 72 and the bump foil portion 73c in the circumferential direction B, the annular plate portion 101 can suppress leakage of high-pressure air from each of the impeller chambers 13b, 14b to the motor chamber 51 via the first to fourth slits 18a to 18d.

[0092] [Second Embodiment] A second embodiment of a centrifugal compressor will now be described with reference to Figures 8 and 9. The main differences from the first embodiment are the number of slits in the bearing housing, the shape of the bump foil, the shape of the locking portion, and the presence or absence of a top foil abutment portion. Therefore, detailed descriptions of the same components as those in the first embodiment will be omitted.

[0093] 8, the radial foil bearing 20 of the second embodiment includes a top foil 72 and a bump foil 110. The centrifugal compressor 10 also includes a seal member 111.

[0094] Two slits 114 are formed in the inner peripheral surface 18g of the bearing housing portion 18. The two slits 114 are provided over the entire length of the bearing housing portion 18 in the axial direction X. The two slits 114 are also provided adjacent to each other in the circumferential direction B. The two slits 114 open toward the first impeller chamber 13b or the second impeller chamber 14b at the first end surface 18A of the bearing housing portion 18. The two slits 114 also open toward the motor chamber 51 at the second end surface 18B of the bearing housing portion 18.

[0095] The bump foil 110 is not divided like the three bump foil portions 73c of the first embodiment. The bump foil 110 has one fixed end 110d and one open end 110e. The bump foil 110 is annular, with only the fixed end 110d and the open end 110e being disconnected. The length of the bump foil 110 in the axial direction X is shorter than the length of the top foil 72 in the axial direction X. The difference between the length of the bump foil 110 in the axial direction X and the length of the top foil 72 in the axial direction X is referred to as "difference L."

[0096] One top foil fixed end 72a is inserted into one slit 114, and the other top foil fixed end 72a is inserted into the other slit 114. In addition, the fixed end 110d of the bump foil 110 is also inserted into one of the slits 114.

[0097] The seal member 111 has an annular plate portion 101 and a locking portion 112. The locking portion 112 is formed by bending the inner periphery of an annular metal plate. Specifically, the locking portion 112 is formed by drawing the metal plate. The locking portion 112 is cylindrical. The locking portion 112 protrudes in the thickness direction of the annular plate portion 101, i.e., in the axial direction X. The length of the locking portion 112 in the axial direction X is formed to be shorter than the difference L.

[0098] The inner diameter of the locking portion 112 is greater than the sum of the diameter of the rotating shaft 40 and twice the thickness of the top foil 72. A pair of fitting grooves 113 is formed in part of the locking portion 112 in the circumferential direction B. One of the fitting grooves 113 is fitted with one of the top foil fixed ends 72a and the fixed end 110d of the bump foil 110, and the other top foil fixed end 72a is fitted with the other fitting groove 113. The locking portion 112 extends between the end face of the top foil 72 in the axial direction X and the end face of the bump foil 110 in the axial direction X, and is locked to the bump foil surface 72t of the top foil 72.

[0099] [Effects of Second Embodiment] The effects of the second embodiment will be described. The second embodiment has the same effects as those of the first embodiment (1-1), (1-2), and (1-6), as well as the following effects.

[0100] (2-1) The locking portion 112 of the seal member 111 is cylindrical, and is formed with a fitting groove 113 to avoid interference with the top foil fixed end 72a. For example, compared to when the locking portions 112 are arranged at intervals in the circumferential direction B, the locking area of ​​the locking portion 112 with respect to the bump foil surface 72t of the top foil 72 can be increased. This makes it easier for the seal member 111 to follow the top foil 72. Furthermore, the fitting groove 113 can avoid interference between the locking portion 112 and the top foil fixed end 72a.

[0101] [Modifications] The above-described embodiments can be modified as follows: The above-described embodiments and the following modifications can be combined with each other within the scope of technical compatibility.

[0102] As shown in FIG. 10 , in the first and second embodiments, the bearing housing portion 18 may be formed from a cylindrical retaining portion 182 and a bearing housing component 183 fixed to the inner circumferential surface of the retaining portion 182. The bearing housing component 183 is cylindrical. The inner circumferential surface of the bearing housing component 183 forms the inner circumferential surface 18g of the bearing housing portion 18. In the first embodiment, first to fourth slits 18a to 18d are formed in the inner circumferential surface of the bearing housing component 183, and in the second embodiment, a slit 114 is formed in the inner circumferential surface of the bearing housing component 183. In addition, one axial end face of the bearing housing component 183 forms the first end face 18A, and the other axial end face of the bearing housing component 183 forms the second end face 18B.

[0103] In the second embodiment, the seal member 111 may have the top foil abutment portion located more inner than the locking portion 112. In the first embodiment, the seal member 100 does not have to have the top foil abutment portion 103.

[0104] In the first embodiment, the number of the locking portions 102 may be two or four or more. That is, the number of the locking portions 102 may be changed as appropriate, and the dimension of each of the locking portions 102 in the circumferential direction B may be adjusted depending on the number of the locking portions 102.

[0105] In the first embodiment, the length of the bump foil portion 73c in the axial direction X may be shorter than the length of the top foil 72 in the axial direction X. In this case, the locking portion 102 does not have to be inserted into the gap 83 between the bump foil portions 73c adjacent to each other in the circumferential direction B, and the position at which the locking portion 102 is locked may be arbitrary.

[0106] In the first embodiment, the annular plate portion 101 does not have to be large enough to cover the first to fourth slits 18a to 18d, and in the second embodiment, the annular plate portion 101 does not have to be large enough to cover the slit 114.

[0107] In the first embodiment, the first to fourth slits 18a to 18d may not be formed in the bearing housing portion 18. In this case, the top foil 72 does not have the top foil fixed end 72a, and the bump foil portion 73c does not have the fixed end 73d. Also, in the second embodiment, the slit 114 may not be formed in the bearing housing portion 18. In this case, the top foil 72 does not have the top foil fixed end 72a, and the bump foil 110 does not have the fixed end 110d. The top foil 72, the bump foil portion 73c, and the bump foil 110 are each fixed to the inner circumferential surface 18g of the bearing housing portion 18 by welding or the like. In this case, the outer diameters of the seal members 100 and 111 are smaller than those in the embodiment.

[0108] The centrifugal compressor 10 may not include, for example, the second impeller 35. 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 chlorofluorocarbon (CFC) that exists in both a gaseous and liquid state. Therefore, the centrifugal compressor 10 may compress any fluid. 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 centrifugal compressor 10 may be installed in any device, not limited to a vehicle.

[0109] REFERENCE SIGNS LIST 10 Centrifugal compressor 11 Housing 13b First impeller chamber as impeller chamber 14b Second impeller chamber 18 Bearing housing portion 18a First slit 18b Second slit 18c Third slit 18d Fourth slit 20 Radial foil bearing 34 First impeller as impeller 35 Second impeller 39 Motor 40 Rotating shaft 51 Motor chamber 72 Top foil 72c Axial end surface 73, 110 Bump foil 73c Multiple bump foil portions 73d Fixed end 73e Open end 100, 111 Seal member 101 Annular plate portion 102, 112 Locking portion 103 Top foil abutment portion 113 Fitting groove 114 Slit

Claims

1. 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 forms a motor chamber for housing the motor and an impeller chamber for housing the impeller, a radial foil bearing disposed inside the housing and rotatably supporting the rotating shaft between the impeller chamber and the motor chamber in the axial direction of the rotating shaft, and a seal member provided at an axial end of the radial foil bearing to suppress leakage of fluid from the impeller chamber to the motor chamber. The housing has a bearing housing portion to which the radial foil bearing is fixed. The radial foil bearing includes 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 and elastically supporting the top foil. The seal member has an annular plate portion through which the rotating shaft is inserted and that covers a radially outer peripheral position from a radially outer periphery of the top foil to a radially inner peripheral position of the bearing housing portion, and a locking portion that protrudes in the axial direction of the rotating shaft from the annular plate portion toward the radial foil bearing and is locked to the radially outer periphery of the top foil. The centrifugal compressor is characterized by this structure.

2. The bearing housing portion opens toward the impeller chamber and the motor chamber and has a slit into which a fixed end of at least one of the top foil and the bump foil is inserted. The annular plate portion covers an outer peripheral position of the slit along the radial direction of the bearing housing portion. The centrifugal compressor according to claim 1 is characterized by this structure.

3. The locking portion is formed as a plurality of locking pieces spaced apart in the circumferential direction of the annular plate portion. The centrifugal compressor according to claim 1 or claim 2 is characterized by this structure.

4. The bump foil has a plurality of bump foil portions arranged in the circumferential direction of the bearing housing portion. Each of the plurality of bump foil portions has a fixed end fixed to the bearing housing portion at one end in the circumferential direction of the bump foil portion, and a free end at the other end in the circumferential direction of the bump foil portion. The locking portion is inserted between the fixed end and the free end of the bump foil portions adjacent to each other in the circumferential direction. The centrifugal compressor according to claim 3, characterized in that.

5. The seal member includes a top foil contact portion that contacts the axial end surface of the top foil on the inner circumferential side of the locking portion in the radial direction of the seal member. The top foil contact portion extends between the radially outer peripheral position and the radially inner peripheral position of the top foil. The centrifugal compressor according to claim 1 or claim 2, characterized in that.

6. The locking portion is cylindrical, and a fitting groove into which the fixed end of the top foil to the bearing housing portion is fitted is formed in the locking portion. The centrifugal compressor according to claim 1, characterized in that.

7. The length of the top foil in the axial direction is longer than the length of the bump foil in the axial direction. The locking portion extends between the end surface of the bump foil in the axial direction and the end surface of the top foil in the axial direction and is locked to the radially outer periphery of the top foil. The centrifugal compressor according to claim 6, characterized in that.

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