Centrifugal compressor

Abstract

Provided is a centrifugal compressor capable of reducing pressure loss of a cooling fluid. The centrifugal compressor includes a metal casing having a flow path (R) through which a cooling fluid flows. The flow path (R) includes a motor cooling flow path (R2), a bearing cooling flow path (R3), a split flow path (R5), and a merged flow path (R6). The casing includes an inner casing that is a cylindrical member that houses a stator, and an outer casing that houses the inner casing. The motor cooling flow path (R2) is partitioned by an outer peripheral surface of the inner casing and an inner peripheral surface of the outer casing. The motor cooling flow path (R2) includes a guide wall provided to at least one of the inner casing and the outer casing and guiding the cooling fluid in the motor cooling flow path (R2) to flow in a circumferential direction of the stator. The split flow path (R5) splits the cooling fluid to the motor cooling flow path (R2) and the bearing cooling flow path (R3). The merged flow path (R6) merges the cooling fluid flowing in the bearing cooling flow path (R3) to the motor cooling flow path (R2).

Description

Technical Field

[0001] This invention relates to centrifugal compressors. Background Technology

[0002] A centrifugal compressor comprises a rotating shaft, an electric motor, an impeller, a thrust bearing, and a metal housing. The electric motor has a rotor and a stator. The electric motor rotates the rotating shaft. The impeller compresses the fluid by rotating integrally with the rotating shaft. The thrust bearing supports the rotating shaft for rotation.

[0003] The housing of the electric compressor in Patent Document 1 has a flow path for the flow of cooling fluid. The flow path includes a motor cooling flow path for cooling the electric motor through the flow of cooling fluid, and a bearing cooling flow path for cooling the bearings through the flow of cooling fluid. The motor cooling flow path and the bearing cooling flow path are connected in series. After flowing in the motor cooling flow path, the cooling fluid flows in the bearing cooling flow path.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: International Publication No. 2018 / 139497 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] In the case where the motor cooling flow path and the bearing cooling flow path are connected in series, as in Patent Document 1, all the cooling fluid introduced into the flow path flows in both the motor cooling flow path and the bearing cooling flow path. Therefore, the flow rate of the cooling fluid flowing in the motor cooling flow path and the bearing cooling flow path increases, thereby increasing the pressure loss of the cooling fluid.

[0009] Solution for solving the problem

[0010] A centrifugal compressor for addressing the aforementioned problems comprises: a rotating shaft; an electric motor having a cylindrical stator that rotates the rotating shaft; an impeller that compresses a fluid by rotating integrally with the rotating shaft; a thrust bearing that supports the rotating shaft for rotation; and a metal housing having flow paths for cooling fluid, the flow paths including a motor cooling flow path for cooling the electric motor by the flow of the cooling fluid and a bearing cooling flow path for cooling the thrust bearing by the flow of the cooling fluid. The essence of the centrifugal compressor is that the housing has a cylindrical shape that houses the stator. The device comprises an inner housing and a cylindrical outer housing that houses the inner housing. The motor cooling flow path is divided by the outer peripheral surface of the inner housing and the inner peripheral surface of the outer housing. The flow path has a splitting flow path that separates the cooling fluid into the motor cooling flow path and the bearing cooling flow path, and a merging flow path that merges the cooling fluid flowing in the bearing cooling flow path into the motor cooling flow path. The motor cooling flow path has a guide wall disposed on at least one of the inner housing and the outer housing, and guides the cooling fluid in the motor cooling flow path to flow circumferentially along the stator.

[0011] The cooling fluid is diverted into the motor cooling path and the bearing cooling path by a branch flow path. Therefore, compared to a series flow path where the motor cooling path and the bearing cooling path are connected in series, the flow rate of the cooling fluid flowing separately in the motor cooling path and the bearing cooling path is reduced. As a result, the pressure loss of the cooling fluid can be reduced.

[0012] It should be noted that, as a method to reduce the pressure loss of the cooling fluid, one could consider designing parallel flow paths that completely separate the motor cooling flow path from the bearing cooling flow path. In this case, the flow rates of the cooling fluid flowing separately in the motor cooling flow path and the bearing cooling flow path are also reduced, thus reducing the pressure loss of the cooling fluid. However, electric motors tend to reach higher temperatures than thrust bearings, so when the flow rate of the cooling fluid flowing in the motor cooling flow path is reduced, insufficient cooling of the electric motor may occur. In contrast, in the above structure, the cooling fluid flowing in the bearing cooling flow path merges with the motor cooling flow path through a confluence flow path. Therefore, although the flow rate of the cooling fluid flowing in the motor cooling flow path decreases when the cooling fluid is split between the motor cooling flow path and the bearing cooling flow path, it recovers to the pre-splitting flow rate when the cooling fluid that flowed in the bearing cooling flow path merges back into the motor cooling flow path. Thus, insufficient cooling of the electric motor is less likely to occur.

[0013] In the centrifugal compressor described above, the motor cooling flow path may be a spiral flow path that surrounds the stator multiple times, the bearing cooling flow path may be a flow path that surrounds the thrust bearing, and the confluence flow path may be a location where the cooling fluid flowing in the bearing cooling flow path merges with the motor cooling flow path at a point where the motor cooling flow path surrounds the stator.

[0014] In the above structure, the bearing cooling flow path surrounds the thrust bearing. Therefore, compared to the case where the bearing cooling flow path does not surround the thrust bearing, the thrust bearing is cooled in a balanced and well-proportioned manner in the circumferential direction. Furthermore, the merging flow path causes the cooling fluid flowing in the bearing cooling flow path to merge into the motor cooling flow path at a point around the stator. Therefore, for example, compared to the case where the cooling fluid flowing in the bearing cooling flow path merges into the motor cooling flow path at two points around the stator, the flow rate of the cooling fluid flowing in the motor cooling flow path can be restored to its pre-diversion flow rate earlier. Therefore, the electric motor can be cooled more effectively.

[0015] In the centrifugal compressor described above, the inner housing may have an inner end wall connected to one end of the inner peripheral wall of the inner housing in the axial direction, and the outer housing may have an outer end wall connected to one end of the outer peripheral wall of the outer housing in the axial direction. The inner end wall is located between the stator and the outer end wall in the axial direction of the rotating shaft. The flow path has a downstream cooling flow path that is divided by the inner end wall and the outer end wall and allows the cooling fluid flowing through the motor cooling flow path to flow into it. The stator is located between the bearing cooling flow path and the downstream cooling flow path in the axial direction of the rotating shaft.

[0016] In the above structure, the stator is also cooled by cooling fluid flowing through the bearing cooling path and the downstream cooling path. Therefore, the electric motor can be cooled more effectively.

[0017] Invention Effects

[0018] According to the present invention, the pressure loss of the cooling fluid can be reduced. Attached Figure Description

[0019] Figure 1 This is a cross-sectional view of a centrifugal compressor illustrating an embodiment.

[0020] Figure 2 This is a perspective view showing the inner casing of the embodiment.

[0021] Figure 3 This is a perspective view showing the inner casing of the embodiment.

[0022] Figure 4 This is a cross-sectional view showing the housing of an embodiment.

[0023] Figure 5 This is a cross-sectional view showing the housing of an embodiment.

[0024] Figure 6 This is a partial front view of a centrifugal compressor illustrating an embodiment.

[0025] Figure 7 It is an illustrative diagram used to explain the flow of cooling fluid in a flow path.

[0026] Explanation of reference numerals in the attached figures

[0027] 10: Centrifugal compressor; 11: Housing; 12: Electric motor; 13: Rotating shaft; 14: First impeller (as impeller); 18: Thrust bearing; 30: Inner housing; 31: Inner peripheral wall; 32: Inner end wall; 33: Guide wall; 40: Outer housing; 41: Outer peripheral wall; 42: Outer end wall; 51: Stator; R: Flow path; R2: Motor cooling flow path; R3: Bearing cooling flow path; R4: Downstream cooling flow path; R5: Dividing flow path; R6: Merging flow path. Detailed Implementation

[0028] The following is in accordance with Figures 1 to 7 This section describes one embodiment of a centrifugal compressor. The centrifugal compressor of this embodiment is mounted in a fuel cell vehicle. The fuel cell vehicle has a fuel cell stack that generates electricity through the chemical reaction of hydrogen and oxygen. The centrifugal compressor of this embodiment is used as a supply device to supply oxygen-containing air to the fuel cell stack.

[0029] <Structure of a centrifugal compressor>

[0030] like Figure 1 As shown, the centrifugal compressor 10 includes a metal housing 11, an electric motor 12, a rotating shaft 13, a first impeller 14, a second impeller 15, a first radial bearing 16, a second radial bearing 17, a thrust bearing 18, and an inverter (not shown). In this embodiment, the housing 11 is made of aluminum.

[0031] <Shell>

[0032] The housing 11 has a motor housing 20, an outer plate 21, an inner plate 22, a first compressor housing 23, and a second compressor housing 24. The motor housing 20 has a cylindrical inner housing 30 and a cylindrical outer housing 40.

[0033] like Figure 2 as well as Figure 3 As shown, the inner housing 30 has a cylindrical inner peripheral wall 31 and an annular inner end wall 32 connected to one axial end of the inner peripheral wall 31. The inner end wall 32 extends radially inward from one axial end of the inner peripheral wall 31.

[0034] like Figure 2 As shown, the inner housing 30 has a guide wall 33 protruding from the outer peripheral surface of the inner peripheral wall 31. In this embodiment, the guide wall 33 extends in a generally spiral shape.

[0035] The guide wall 33 of this embodiment has a first peripheral wall portion 33a, a second peripheral wall portion 33b, a third peripheral wall portion 33c, and a fourth peripheral wall portion 33d. The first to fourth peripheral wall portions 33a to 33d extend circumferentially along the inner peripheral wall 31. The first to fourth peripheral wall portions 33a to 33d are arranged sequentially in the axial direction of the inner peripheral wall 31 from the end opposite to the inner end wall 32 toward the end of the inner end wall 32. The first peripheral wall portion 33a is annular.

[0036] Furthermore, the guide wall 33 has a first connecting wall portion 33e, a second connecting wall portion 33f, and a third connecting wall portion 33g. The first to third connecting wall portions 33e to 33g extend obliquely relative to the inner peripheral wall 31 in the circumferential direction. The first to third connecting wall portions 33e to 33g are arranged sequentially in the axial direction of the inner peripheral wall 31 from the end opposite to the inner end wall 32 toward the end of the inner end wall 32. The first connecting wall portion 33e connects the first end of the first peripheral wall portion 33a to the first end of the second peripheral wall portion 33b. The second connecting wall portion 33f connects the second end of the second peripheral wall portion 33b (opposite to the first end) to the first end of the third peripheral wall portion 33c. The third connecting wall portion 33g connects the second end of the third peripheral wall portion 33c (opposite to the first end) to the first end of the fourth peripheral wall portion 33d.

[0037] The inner shell 30 of this embodiment has a first fin 34 protruding from the outer peripheral surface of the inner peripheral wall 31. The amount by which the first fin 34 protrudes from the outer peripheral surface of the inner peripheral wall 31 is less than the amount by which the guide wall 33 protrudes from the outer peripheral surface of the inner peripheral wall 31. The first fin 34 is arranged in three rows along the axial direction of the inner peripheral wall 31 between the first peripheral wall portion 33a and the second peripheral wall portion 33b, between the second peripheral wall portion 33b and the third peripheral wall portion 33c, and between the third peripheral wall portion 33c and the fourth peripheral wall portion 33d.

[0038] like Figure 3 As shown, the inner housing 30 has a first rib 35 and a second rib 36. The first rib 35 and the second rib 36 protrude from the inner end wall 32 in a direction opposite to that of the inner peripheral wall 31. The first rib 35 and the second rib 36 extend radially along the inner end wall 32. The position of the first rib 35 in the circumferential direction of the inner end wall 32 coincides with the position of the portion of the inner peripheral wall 31 in the circumferential direction where the fourth peripheral wall portion 33d is not provided. The second rib 36 is positioned in the circumferential direction of the inner end wall 32 at a position offset by 180 degrees relative to the first rib 35.

[0039] The inner shell 30 of this embodiment has a second fin 37. The second fin 37 protrudes from the inner end wall 32 in a direction opposite to that of the inner peripheral wall 31. The second fin 37 extends in an arc shape along the circumference of the inner end wall 32. Two rows of the second fin 37 are arranged radially along the inner end wall 32 between the first rib 35 and the second rib 36.

[0040] like Figure 1 As shown, the outer casing 40 is a bottomed cylindrical structure with a cylindrical outer peripheral wall 41 and a circular plate-shaped outer end wall 42 connected to one axial end of the outer peripheral wall 41. The outer end wall 42 has a through hole 42a. The through hole 42a passes through the outer end wall 42 along the axial direction of the outer peripheral wall 41. The outer casing 40 has a cylindrical first bearing retainer 43. The first bearing retainer 43 extends from the inner surface of the outer end wall 42 along the axial direction of the outer peripheral wall 41. The axis of the first bearing retainer 43 is aligned with the axis of the outer peripheral wall 41. The inner side of the first bearing retainer 43 communicates with the through hole 42a. The first bearing retainer 43 holds a cylindrical second radial bearing 17.

[0041] like Figure 4 As shown, the outer casing 40 has a first flow path configuration portion 44. The first flow path configuration portion 44 is provided at the end of the outer peripheral wall 41 on the opening side. In this embodiment, the first flow path configuration portion 44 is T-shaped. The first flow path configuration portion 44 has a path 44a extending radially along the outer peripheral wall 41 and an axial path 44b extending axially along the outer peripheral wall 41. The path 44a penetrates the outer peripheral wall 41 radially. The first end of the path 44a communicates with the outside of the outer casing 40. The end of the path 44a opposite to the first end, i.e., the second end, opens on the inner peripheral surface of the outer peripheral wall 41. The first end of the axial path 44b is connected to the middle of the path 44a. The end of the axial path 44b opposite to the first end, i.e., the second end, opens on the front end surface 41a of the outer peripheral wall 41.

[0042] like Figure 5 As shown, the outer casing 40 has a first merging flow path configuration portion 45. The first merging flow path configuration portion 45 is provided at the end of the outer peripheral wall 41 on the opening side. The first merging flow path configuration portion 45 is located at a different position in the circumferential direction of the outer peripheral wall 41 than the first branching flow path configuration portion 44. In this embodiment, the first merging flow path configuration portion 45 is L-shaped. The first end of the first merging flow path configuration portion 45 opens at the front end face 41a of the outer peripheral wall 41. The second end, the end opposite to the first end, opens at the inner circumferential surface of the outer peripheral wall 41.

[0043] like Figure 1As shown, the outer casing 40 houses the inner casing 30. The outer peripheral wall 41 is located on the outer periphery of the inner peripheral wall 31. The axis of the outer peripheral wall 41 is aligned with the axis of the inner peripheral wall 31. The direction in which the axes of the outer peripheral wall 41 and the inner peripheral wall 31 extend is defined as the axial direction of the motor housing 20. The inner peripheral surface of the outer peripheral wall 41 faces the outer peripheral surface of the inner peripheral wall 31. The front end face of the guide wall 33 abuts against the inner peripheral surface of the outer peripheral wall 41. The first bearing retaining portion 43 passes through the inner side of the inner end wall 32. The inner surface of the outer end wall 42 faces the inner end wall 32.

[0044] The outer plate 21 is an annular plate. The outer plate 21 has a first surface 21a and a second surface 21b. The first surface 21a and the second surface 21b are perpendicular to the thickness direction of the outer plate 21. The second surface 21b is located on the opposite side of the first surface 21a in the thickness direction of the outer plate 21.

[0045] The outer plate 21 has a first recess 21c and a second recess 21d. The first recess 21c and the second recess 21d are recessed from the first surface 21a of the outer plate 21. The first recess 21c is disposed on the inner periphery of the outer plate 21. The first recess 21c is annular.

[0046] like Figure 6 As shown, the second recess 21d extends circumferentially along the outer plate 21. The second recess 21d surrounds the first recess 21c. The second recess 21d has a C-shaped shape that is partially interrupted in the circumferential direction of the outer plate 21.

[0047] like Figure 4 As shown, the outer plate 21 has a second flow path configuration portion 27. In this embodiment, the second flow path configuration portion 27 is L-shaped. The first end of the second flow path configuration portion 27 opens at the first surface 21a of the outer plate 21. The end of the second flow path configuration portion 27 opposite to the first end, i.e., the second end, communicates with the first end of the second recess 21d in the circumferential direction of the outer plate 21.

[0048] like Figure 5 As shown, the outer plate 21 has a second confluence flow path configuration portion 28. The second confluence flow path configuration portion 28 is located circumferentially on the outer plate 21 at a different position than the second branch flow path configuration portion 27. In this embodiment, the second confluence flow path configuration portion 28 is L-shaped. The first end of the second confluence flow path configuration portion 28 communicates with the second end of the second recess 21d, which is the end opposite to the first end. The second end of the second confluence flow path configuration portion 28, which is the end opposite to the first end, opens on the first surface 21a of the outer plate 21.

[0049] like Figure 1As shown, the outer plate 21 is connected to the end of the outer casing 40 at the opening side. The outer plate 21 closes the opening of the outer casing 40. The motor chamber S1 is divided by the inner surface of the outer casing 40 and the outer plate 21. The motor chamber S1 houses the inner casing 30, the inner plate 22, and the electric motor 12.

[0050] like Figure 4 As shown, the first surface 21a of the outer plate 21 abuts against the front end surface 41a of the outer peripheral wall 41 of the outer casing 40. The first end of the second diversion flow path component 27 is connected to the second end of the axial path 44b of the first diversion flow path component 44. Therefore, the second diversion flow path component 27 is connected to the first diversion flow path component 44.

[0051] like Figure 5 As shown, the second end of the second merging flow path configuration 28 is connected to the first end of the first merging flow path configuration 45. Therefore, the second merging flow path configuration 28 is connected to the first merging flow path configuration 45.

[0052] like Figure 1 As shown, the inner plate 22 is an annular plate. The inner plate 22 is axially positioned between the outer plate 21 and the inner housing 30 of the motor housing 20. The inner plate 22 abuts against the first surface 21a of the outer plate 21. A bearing housing S2 is defined by the inner plate 22 and the first recess 21c of the outer plate 21. The bearing housing S2 houses an annular thrust bearing 18.

[0053] The inner plate 22 has a cylindrical second bearing retainer 25. The second bearing retainer 25 is erected from the inner periphery of the inner plate 22 in a direction opposite to that of the outer plate 21. The axis of the second bearing retainer 25 is aligned with the axis of the first bearing retainer 43. The inner side of the second bearing retainer 25 communicates with the inner side of the outer plate 21 via the bearing housing S2. The second bearing retainer 25 holds a cylindrical first radial bearing 16.

[0054] The first compressor housing 23 is cylindrical. The first compressor housing 23 has a first vortex flow path 23a. The first vortex flow path 23a is swirling in a vortex shape. The first compressor housing 23 is connected to the second surface 21b of the outer plate 21.

[0055] The first impeller chamber S3 is defined by the inner circumferential surface of the first compressor housing 23 and the outer plate 21. Furthermore, a first diffusion flow path S4 is provided between the first compressor housing 23 and the second surface 21b of the outer plate 21. The first diffusion flow path S4 connects the first impeller chamber S3 with the first vortex flow path 23a.

[0056] The second compressor housing 24 is cylindrical. The second compressor housing 24 has a second vortex flow path 24a. The second vortex flow path 24a is swirling in a vortex shape. The second compressor housing 24 is connected to the outer surface of the outer end wall 42 of the outer casing 40.

[0057] The second impeller chamber S5 is defined by the inner circumferential surface of the second compressor housing 24 and the outer end wall 42 of the outer casing 40. Furthermore, a second diffusion flow path S6 is provided between the second compressor housing 24 and the outer end wall 42 of the outer casing 40. The second diffusion flow path S6 connects the second impeller chamber S5 with the second vortex flow path 24a.

[0058] <Electric Motor>

[0059] like Figure 1 As shown, the electric motor 12 has a cylindrical stator 51 and a rotor 52 disposed inside the stator 51.

[0060] The stator 51 has a cylindrical stator core 53 and a coil 54. The stator core 53 is fixed to the inner circumferential surface of the inner peripheral wall 31 of the inner housing 30. The axis of the stator core 53 is aligned with the axis of the inner peripheral wall 31. The coil 54 is wound around the stator core 53. The inner housing 30 houses the stator 51. The inner end wall 32 of the inner housing 30 is located axially between the stator 51 and the outer end wall 42 of the outer housing 40. The stator 51 is located axially between the inner plate 22 and the inner end wall 32 of the inner housing 30. The rotor 52 has a cylindrical rotor core 55 and a permanent magnet (not shown) disposed on the rotor core 55. The axis of the rotor core 55 is aligned with the axis of the stator core 53.

[0061] <Rotating shaft, first impeller, second impeller>

[0062] The rotating shaft 13 has a shaft body portion 13a, a first support portion 13b, a second support portion 13c, and a third support portion 13d. The rotating shaft 13 is housed within the housing 11. The direction in which the shaft body portion 13a extends is defined as the axial direction of the rotating shaft 13. The axial direction of the rotating shaft 13 coincides with the axial direction of the motor housing 20.

[0063] The shaft body 13a passes through the rotor core 55 within the motor chamber S1. The shaft body 13a is fixed to the rotor core 55. The shaft body 13a is capable of rotating integrally with the rotor 52.

[0064] The first end of the shaft body 13a protrudes from the motor chamber S1 through the inside of the second bearing retaining part 25, the bearing receiving chamber S2, and the outer plate 21 into the first impeller chamber S3. The first impeller 14 is connected to the first end of the shaft body 13a. The first impeller 14 is housed in the first impeller chamber S3. The first impeller 14 is capable of rotating integrally with the shaft body 13a.

[0065] The second end, the side opposite to the first end of the shaft body 13a, protrudes from the motor chamber S1 through the inside of the first bearing retaining part 43 and the inside of the shaft through hole 42a into the second impeller chamber S5. The second impeller 15 is connected to the second end of the shaft body 13a. The second impeller 15 is housed in the second impeller chamber S5. The second impeller 15 is capable of rotating integrally with the shaft body 13a.

[0066] The first support portion 13b is provided on the outer peripheral surface of the shaft body portion 13a at a position closer to the first end than the center portion of the shaft body portion 13a. The first support portion 13b is disposed inside the second bearing retaining portion 25. The first support portion 13b is integrally formed with the shaft body portion 13a. The first support portion 13b protrudes from the outer peripheral surface of the shaft body portion 13a.

[0067] The second support portion 13c is located on the outer peripheral surface of the shaft body portion 13a at a position closer to the second end than the center of the shaft body portion 13a. The second support portion 13c is disposed inside the first bearing retaining portion 43. The second support portion 13c is fixed to the outer peripheral surface of the shaft body portion 13a in a ring-shaped protrusion. The second support portion 13c is rotatable integrally with the shaft body portion 13a.

[0068] The third support portion 13d is provided on the outer peripheral surface of the shaft body portion 13a at a position closer to the first end than the first support portion 13b. The third support portion 13d is disposed in the bearing housing S2. The third support portion 13d is fixed to the outer peripheral surface of the shaft body portion 13a in a ring-shaped protrusion. The third support portion 13d is rotatable integrally with the shaft body portion 13a.

[0069] <First radial bearing, second radial bearing, thrust bearing>

[0070] The first radial bearing 16, the second radial bearing 17, and the thrust bearing 18 support the rotating shaft 13 so that it can rotate. The first radial bearing 16 supports the first support portion 13b of the rotating shaft 13 in the radial direction so that it can rotate. The second radial bearing 17 supports the second support portion 13c of the rotating shaft 13 in the radial direction so that it can rotate. It should be noted that the "radial direction" is a direction orthogonal to the axial direction of the rotating shaft 13. Therefore, the "radial direction" is the radial direction of the rotating shaft 13. The thrust bearing 18 is arranged on both sides of the third support portion 13d in the axial direction of the rotating shaft 13. The thrust bearing 18 supports the third support portion 13d of the rotating shaft 13 in the thrust direction so that it can rotate. It should be noted that the "thrust direction" is a direction parallel to the axial direction of the rotating shaft 13.

[0071] The first radial bearing 16, the second radial bearing 17, and the thrust bearing 18 are all gas bearings. Each bearing 16, 17, and 18 supports the rotating shaft 13 in contact with it until the rotational speed of the rotating shaft 13 reaches the levitation speed at which it floats under the action of each bearing 16, 17, and 18. Furthermore, when the rotational speed of the rotating shaft 13 reaches the levitation speed, under the action of the dynamic pressure generated by the fluid film between the rotating shaft 13 and each bearing 16, 17, and 18, the rotating shaft 13 floats relative to the bearings 16, 17, and 18. Thus, each bearing 16, 17, and 18 supports the rotating shaft 13 in a non-contact state.

[0072] <Flow path>

[0073] The housing 11 has a flow path R for cooling water (LLC) to flow as a cooling fluid. For example... Figure 7 As shown, the flow path R has an external cooling flow path R1, a motor cooling flow path R2, a bearing cooling flow path R3, a downstream cooling flow path R4, a branching flow path R5, and a converging flow path R6. The branching flow path R5 is used to separate the cooling fluid into the motor cooling flow path R2 and the bearing cooling flow path R3. The converging flow path R6 is used to merge the cooling fluid flowing in the bearing cooling flow path R3 into the motor cooling flow path R2.

[0074] like Figure 4 as well as Figure 5 As shown, the motor cooling flow path R2 is divided by the outer peripheral surface of the inner peripheral wall 31 of the inner housing 30 and the inner peripheral surface of the outer peripheral wall 41 of the outer housing 40. The motor cooling flow path R2 is disposed around the stator 51. As described above, a guide wall 33 is provided on the outer peripheral surface of the inner peripheral wall 31 of the inner housing 30. Therefore, the motor cooling flow path R2 has a guide wall 33. The guide wall 33 guides the cooling water flowing in the motor cooling flow path R2 in a manner that allows it to flow circumferentially along the stator 51. In this embodiment, the motor cooling flow path R2 is divided in a spiral shape by the guide wall 33. That is, the motor cooling flow path R2 is a spiral flow path.

[0075] In this embodiment, the motor cooling flow path R2 surrounds the stator 51 three times. The motor cooling flow path R2 has a first flow path R21, a second flow path R22, and a third flow path R23. The first flow path R21 is defined by the outer peripheral surface of the inner peripheral wall 31, the inner peripheral surface of the outer peripheral wall 41, the first peripheral wall portion 33a, and the second peripheral wall portion 33b. The second flow path R22 is defined by the outer peripheral surface of the inner peripheral wall 31, the inner peripheral surface of the outer peripheral wall 41, the second peripheral wall portion 33b, the third peripheral wall portion 33c, the first connecting wall portion 33e, and the second connecting wall portion 33f. The third flow path R23 is defined by the outer peripheral surface of the inner peripheral wall 31, the inner peripheral surface of the outer peripheral wall 41, the third peripheral wall portion 33c, the fourth peripheral wall portion 33d, the second connecting wall portion 33f, and the third connecting wall portion 33g.

[0076] The bearing cooling flow path R3 is defined by the second recess 21d of the inner plate 22 and the outer plate 21. In this embodiment, the bearing cooling flow path R3 surrounds the bearing housing chamber S2. Therefore, the bearing cooling flow path R3 surrounds the thrust bearing 18.

[0077] The downstream cooling flow path R4 is defined by the inner end wall 32 of the inner housing 30 and the inner surface of the outer end wall 42 of the outer housing 40. The downstream cooling flow path R4 is an annular flow path extending circumferentially along the stator 51. The stator 51 is located axially between the bearing cooling flow path R3 and the downstream cooling flow path R4 on the rotating shaft 13.

[0078] like Figure 4 As shown, the branch flow path R5 is composed of a first branch flow path component 44 and a second branch flow path component 27. The inlet of the branch flow path R5 is the first end of path 44a of the first branch flow path component 44. The inlet of the branch flow path R5 is connected to the external cooling flow path R1. The branch flow path R5 branches into a flow path connected to the motor cooling flow path R2 and a flow path connected to the bearing cooling flow path R3. The flow path connected to the motor cooling flow path R2 is the portion of path 44a located on the inner circumferential surface side of the outer peripheral wall 41 compared to the shaft path 44b. The flow path connected to the bearing cooling flow path R3 consists of shaft path 44b and the second branch flow path component 27. The outlet of the flow path connected to the motor cooling flow path R2 is the second end of path 44a. The outlet of the flow path connected to the bearing cooling flow path R3 is the second end of the second branch flow path component 27.

[0079] The second end of path 44a of the first diverting flow path component 44 is located axially between the first peripheral wall portion 33a and the second peripheral wall portion 33b of the motor housing 20. Therefore, the outlet of the flow path in the diverting flow path R5 that is connected to the motor cooling flow path R2 is connected to the first peripheral flow path R21 of the motor cooling flow path R2. As described above, the second end of the second diverting flow path component 27 is connected to the first end of the second recess 21d. Therefore, the outlet of the flow path in the diverting flow path R5 that is connected to the bearing cooling flow path R3 is connected to the bearing cooling flow path R3. That is, the diverting flow path R5 is connected to both the motor cooling flow path R2 and the bearing cooling flow path R3.

[0080] like Figure 5 As shown, the merging flow path R6 is composed of a first merging flow path component 45 and a second merging flow path component 28. The inlet of the merging flow path R6 is the first end of the second merging flow path component 28. The outlet of the merging flow path R6 is the second end of the first merging flow path component 45.

[0081] As described above, the first end of the second confluence flow path configuration 28 is connected to the second end of the second recess 21d. Therefore, the inlet of the confluence flow path R6 is connected to the bearing cooling flow path R3. The second end of the first confluence flow path configuration 45 is located axially between the first peripheral wall portion 33a and the second connecting wall portion 33f of the motor housing 20. Therefore, the outlet of the confluence flow path R6 is connected to the motor cooling flow path R2. In this embodiment, the outlet of the confluence flow path R6 is connected to the motor cooling flow path R2 at the inlet of the second peripheral flow path R22, that is, at the location where the motor cooling flow path R2 surrounds the stator 51. That is, the confluence flow path R6 connects the bearing cooling flow path R3 and the motor cooling flow path R2.

[0082] <Operation of a centrifugal compressor>

[0083] When the inverter supplies power to coil 54, the rotor 52 rotates by generating a rotating magnetic field in stator 51. As rotor 52 rotates, rotating shaft 13 rotates integrally with rotor 52. That is, the inverter drives electric motor 12. Electric motor 12 causes rotating shaft 13 to rotate.

[0084] When the rotating shaft 13 rotates, the first impeller 14 and the second impeller 15 rotate integrally with the rotating shaft 13. This draws in air, which is a fluid, from the outside into the first impeller chamber S3. The drawn-in air is compressed by the first impeller 14. Therefore, the first impeller 14 is a compressor impeller that compresses air by rotating integrally with the rotating shaft 13. The air compressed in the first impeller chamber S3 is slowed down as it passes through the first diffuser flow path S4, thereby converting the air's velocity energy into pressure energy. The high-pressure air is then discharged to the outside of the casing 11 after being expelled through the first vortex flow path 23a.

[0085] In this embodiment, air discharged from the first vortex flow path 23a to the outside of the housing 11 is drawn into the second impeller chamber S5 via a pipe (not shown). The air drawn into the second impeller chamber S5 is compressed by the second impeller 15. Therefore, the second impeller 15 is a compressor impeller that compresses air by rotating integrally with the rotating shaft 13. The air compressed in the second impeller chamber S5 is decelerated when passing through the second diffuser flow path S6, thereby converting the velocity energy of the air into pressure energy. That is, the centrifugal compressor 10 of this embodiment is a two-stage compression centrifugal compressor that uses the second impeller 15 to further compress the air compressed by the first impeller 14. Furthermore, the high-pressure air is discharged into the second vortex flow path 24a and then supplied to the fuel cell stack. The oxygen contained in the air supplied to the fuel cell stack contributes to the power generation of the fuel cell stack. It should be noted that the oxygen that contributes to the power generation of the fuel cell stack is only about 20% present in the air. Therefore, about 80% of the air supplied to the fuel cell stack does not contribute to the power generation of the fuel cell stack but is discharged from the fuel cell stack as exhaust gas.

[0086] <Flow of cooling water in the flow path>

[0087] like Figure 7 As shown, cooling water flows through the external cooling path R1. For example, the inverter dissipates heat to the cooling water flowing through the external cooling path R1. That is, the external cooling path R1 cools the inverter by the flow of cooling water. After flowing through the external cooling path R1, the cooling water flows into the branch path R5.

[0088] like Figure 4 As shown, the cooling water is diverted by the diversion flow path R5 to the first peripheral flow path R21 of the motor cooling flow path R2 and the bearing cooling flow path R3. Therefore, the flow rate of the cooling water flowing in the motor cooling flow path R2 and the flow rate of the cooling water flowing in the bearing cooling flow path R3 are respectively reduced relative to the flow rate of the cooling water flowing in the external cooling flow path R1.

[0089] like Figure 6 As shown, the cooling water diverted to the bearing cooling flow path R3 flows around the thrust bearing 18. Heat from the thrust bearing 18 is dissipated to the outer plate 21 and inner plate 22 via the atmosphere within the bearing housing S2. The heat dissipated from the thrust bearing 18 to the outer plate 21 and inner plate 22 is dissipated to the cooling water flowing in the bearing cooling flow path R3. In other words, the bearing cooling flow path R3 cools the thrust bearing 18 by the flow of cooling water.

[0090] Additionally, the heat from the electric motor 12 is dissipated to the outer plate 21 and inner plate 22 via the atmosphere within the motor chamber S1. The heat dissipated from the electric motor 12 to the outer plate 21 and inner plate 22 is also dissipated to the cooling water flowing in the bearing cooling path R3. That is, the bearing cooling path R3, through the flow of cooling water, also cools the electric motor 12.

[0091] Furthermore, the heat from the first radial bearing 16 is dissipated via the inner plate 22 to the cooling water flowing in the bearing cooling flow path R3. That is, the bearing cooling flow path R3 also cools the first radial bearing 16 through the flow of cooling water.

[0092] After flowing through the bearing cooling flow path R3, the cooling water flows into the confluence flow path R6.

[0093] like Figure 5 As shown, the merging flow path R6 merges the cooling water flowing in the bearing cooling flow path R3 into the motor cooling flow path R2. In this embodiment, the merging flow path R6 merges the cooling water flowing in the bearing cooling flow path R3 into the inlet of the second peripheral flow path R22 of the motor cooling flow path R2. That is, the merging flow path R6 merges the cooling water flowing in the bearing cooling flow path R3 into the motor cooling flow path R2 at a point around the stator 51 of the motor cooling flow path R2.

[0094] like Figure 2 As shown, the cooling water diverted to the first peripheral flow path R21 of the motor cooling flow path R2 flows into the second peripheral flow path R22 after circling the stator 51 once. Thus, the cooling water flowing through the first peripheral flow path R21 and the bearing cooling flow path R3 both flow through the second peripheral flow path R22. Therefore, the flow rate of the cooling water flowing through the second peripheral flow path R22 returns to the flow rate before diversion. The cooling water flowing into the second peripheral flow path R22 flows into the third peripheral flow path R23 after circling the stator 51 once. The cooling water flowing into the third peripheral flow path R23 circulates around the stator 51 once. In this way, the cooling water in the motor cooling flow path R2 is guided by the guide wall 33, thereby flowing circumferentially around the stator 51. In this embodiment, the cooling water flows in a spiral pattern around the stator 51.

[0095] The heat from the electric motor 12 is dissipated through the inner peripheral wall 31 of the inner housing 30 to the cooling water flowing in the motor cooling flow path R2. That is, the electric motor 12 is cooled by the flow of cooling water in the motor cooling flow path R2.

[0096] like Figure 3 As shown, after the cooling water flows through the third circulation path R23 of the motor cooling flow path R2, it flows into the downstream cooling flow path R4.

[0097] The cooling water flowing into the downstream cooling flow path R4 is divided by the first rib 35 into cooling water flowing in a first direction circumferentially toward the stator 51 and cooling water flowing in a second direction opposite to the first direction. The cooling water flowing in the first direction and the cooling water flowing in the second direction each flow approximately half a circumference of the stator 51. Then, the cooling water collides with the second rib 36. As a result, the direction of the cooling water flow changes from the direction along the circumference of the stator 51 to the direction radially outward toward the stator 51.

[0098] The heat from the electric motor 12 is dissipated to the inner end wall 32 of the inner housing 30 via the inner peripheral wall 31 of the inner housing 30 and the atmosphere within the motor chamber S1. The heat dissipated from the electric motor 12 to the inner end wall 32 is dissipated to the cooling water flowing in the downstream cooling flow path R4. That is, the downstream cooling flow path R4 cools the electric motor 12 by the flow of cooling water.

[0099] Additionally, the heat from the second radial bearing 17 is dissipated through the first bearing retaining portion 43 of the housing 40 and the outer end wall 42 to the cooling water flowing in the downstream cooling flow path R4. That is, the downstream cooling flow path R4 also cools the second radial bearing 17 through the flow of cooling water.

[0100] like Figure 7 As shown, after flowing through the downstream cooling flow path R4, the cooling water flows into the external cooling flow path R1. That is, the cooling water flows back to the external cooling flow path R1. The cooling water circulates in flow path R.

[0101] [The function and effects of this implementation method]

[0102] The function and effects of this implementation method are explained.

[0103] (1) The cooling water flowing in flow path R is diverted by flow path R5 to motor cooling flow path R2 and bearing cooling flow path R3. Therefore, compared to the case where the motor cooling flow path R2 and bearing cooling flow path R3 are connected in series, the flow rate of cooling water flowing in motor cooling flow path R2 and bearing cooling flow path R3 is reduced. Therefore, the pressure loss of cooling water can be reduced.

[0104] It should be noted that, as a method to reduce the pressure loss of cooling water, one could consider, for example, making the motor cooling flow path R2 and the bearing cooling flow path R3 completely independent parallel flow paths. In this case, the flow rates of cooling water flowing separately in the motor cooling flow path R2 and the bearing cooling flow path R3 are also reduced, thus reducing the pressure loss of cooling water. However, the electric motor 12 is more prone to high temperatures than the thrust bearing 18, so when the flow rate of cooling water flowing in the motor cooling flow path R2 is reduced, insufficient cooling of the electric motor 12 may occur. In contrast, in this embodiment, the cooling water flowing in the bearing cooling flow path R3 merges with the motor cooling flow path R2 through the merging flow path R6. Therefore, although the flow rate of cooling water flowing in the motor cooling flow path R2 decreases when the cooling water is split into the motor cooling flow path R2 and the bearing cooling flow path R3, it recovers to the flow rate before the split when the cooling water flowing in the bearing cooling flow path R3 merges back into the motor cooling flow path R2. Therefore, insufficient cooling of the electric motor 12 is less likely to occur.

[0105] (2) For example, if the motor cooling flow path R2 does not have a guide wall 33, the cooling water flowing into the motor cooling flow path R2 may sometimes flow axially along the stator 51. This results in parts of the stator 51 that are easily cooled and parts that are difficult to cool being created in the circumferential direction. Furthermore, if the motor cooling flow path R2 does not have a guide wall 33, the cooling water may sometimes be diverted to the motor cooling flow path R2 more easily than the bearing cooling flow path R3. This may result in insufficient flow of cooling water in the bearing cooling flow path R3, potentially leading to insufficient cooling of the thrust bearing 18.

[0106] In contrast, in this embodiment, the motor cooling flow path R2 has a guide wall 33 that guides the cooling water within the motor cooling flow path R2 to flow circumferentially along the stator 51. Therefore, the stator 51 can be cooled evenly and well in the circumferential direction. Furthermore, compared to the case where the motor cooling flow path R2 does not have a guide wall 33, cooling water is less likely to flow into the motor cooling flow path R2 and is therefore diverted to the bearing cooling flow path R3. Therefore, insufficient cooling of the thrust bearing 18 caused by insufficient flow of cooling water in the bearing cooling flow path R3 is less likely to occur.

[0107] (3) The bearing cooling flow path R3 surrounds the thrust bearing 18. Therefore, compared to the case where the bearing cooling flow path R3 does not surround the thrust bearing 18, the thrust bearing 18 is cooled well and evenly in the circumferential direction. Furthermore, the motor cooling flow path R2 is a spiral flow path that surrounds the stator 51 multiple times. The merging flow path R6 merges the cooling water flowing in the bearing cooling flow path R3 into the motor cooling flow path R2 at a point where the motor cooling flow path R2 surrounds the stator 51 once. Therefore, for example, compared to the case where the cooling water flowing in the bearing cooling flow path R3 merges into the motor cooling flow path R2 at a point where the motor cooling flow path R2 surrounds the stator 51 twice, the flow rate of the cooling water flowing in the motor cooling flow path R2 can return to the pre-diversion flow rate earlier. Therefore, the electric motor 12 can be cooled more effectively.

[0108] (4) The inner housing 30 has an inner end wall 32 connected to one end of the inner peripheral wall 31 in the axial direction. The outer housing 40 has an outer end wall 42 connected to one end of the outer peripheral wall 41 in the axial direction. The inner end wall 32 is located between the stator 51 and the outer end wall 42 in the axial direction of the rotation shaft 13. The flow path R has a downstream cooling flow path R4 divided by the inner end wall 32 and the outer end wall 42 and into which cooling water flowing through the motor cooling flow path R2 flows. The stator 51 is located between the bearing cooling flow path R3 and the downstream cooling flow path R4 in the axial direction of the rotation shaft 13. Therefore, the stator 51 is also cooled by the flow of cooling water in the bearing cooling flow path R3 and the downstream cooling flow path R4. Thus, the electric motor 12 can be cooled more effectively.

[0109] (5) The bearing cooling flow path R3 is divided by the inner plate 22 that holds the thrust bearing 18. Therefore, the bearing cooling flow path R3 is filled with cooling water, which can cool not only the thrust bearing 18, but also the first radial bearing 16.

[0110] (6) The downstream cooling flow path R4 is divided by the outer housing 40 that holds the second radial bearing 17. Therefore, the downstream cooling flow path R4, through which cooling water flows, can cool not only the stator 51, but also the second radial bearing 17.

[0111] (7) For example, if the first rib 35 is not provided in the downstream cooling flow path R4, the cooling water flowing into the downstream cooling flow path R4 may sometimes flow in a direction that is circumferentially opposite to that of the stator 51. Thus, in the stator 51, there are parts that are easily cooled and parts that are difficult to cool in the circumferential direction. In contrast, in this embodiment, the cooling water flowing into the downstream cooling flow path R4 is divided by the first rib 35 into cooling water flowing in a first direction in the circumferential direction of the stator 51 and cooling water flowing in a second direction opposite to the first direction. Therefore, the stator 51 can be cooled in a balanced and good manner in the circumferential direction.

[0112] (8) The inner peripheral wall 31 of the inner housing 30 has a first fin 34. As a result, the surface area of ​​the inner peripheral wall 31 is increased, and thus the heat dissipation of the inner peripheral wall 31 is improved. Therefore, the cooling effect of the electric motor 12 is increased.

[0113] (9) The inner end wall 32 of the inner housing 30 has a second fin 37. As a result, the surface area of ​​the inner end wall 32 is increased, and thus the heat dissipation of the inner end wall 32 is improved. Therefore, the cooling effect of the electric motor 12 is improved.

[0114] (10) The second impeller 15 further compresses the air that has been compressed by the first impeller 14. Therefore, the temperature of the air drawn into the second impeller chamber S5 is higher than the temperature of the air drawn into the first impeller chamber S3. In this embodiment, the thrust bearing 18 is disposed on the side of the first impeller chamber S3, where the temperature is lower than that of the second impeller chamber S5. Therefore, compared to the case where the thrust bearing 18 is disposed on the side of the second impeller chamber S5, the temperature rise of the thrust bearing 18 can be suppressed.

[0115] (11) As described above, the temperature of the air drawn into the second impeller chamber S5 is higher than the temperature of the air drawn into the first impeller chamber S3. Therefore, the outer end wall 42 of the outer casing 40 dividing the second impeller chamber S5 is prone to become hot, but in this embodiment, the heat of the outer end wall 42 is dissipated to the cooling water flowing in the downstream cooling flow path R4. Thus, the outer end wall 42 can be cooled.

[0116] [Example of Change]

[0117] It should be noted that the above embodiments can be modified as follows. The above embodiments and the following modifications can be combined with each other within the scope of technical inconsistency.

[0118] ○ The cooling fluid flowing in flow path R is not limited to cooling water (LLC).

[0119] ○ The external cooling flow path R1 can also be omitted.

[0120] The number of turns of the motor cooling flow path R2 around the stator 51 can also be changed appropriately.

[0121] ○As long as the cooling fluid in the motor cooling flow path R2 is guided by the guide wall 33 to flow in the circumferential direction along the stator 51, the structure of the guide wall 33 can also be appropriately modified.

[0122] For example, the guide wall 33 could also be a wall that divides the cooling fluid in the motor cooling flow path R2 into a first direction flowing toward the stator 51 in the circumferential direction and a second direction flowing toward the opposite direction. In this case, the cooling fluid flowing toward the first direction and the cooling fluid flowing toward the second direction each flow around the stator 51 for half a circumference before merging.

[0123] The guide wall 33 may protrude from the outer peripheral surface of the inner peripheral wall 31 of the inner housing 30, and from the inner peripheral surface of the outer peripheral wall 41 of the outer housing 40. Alternatively, the guide wall 33 may protrude from both the outer peripheral surface of the inner peripheral wall 31 of the inner housing 30 and the inner peripheral surface of the outer peripheral wall 41 of the outer housing 40. That is, the guide wall 33 may be provided on at least one of the inner housing 30 and the outer housing 40. It should be noted that "at least one of the inner housing 30 and the outer housing 40" means only the inner housing 30, only the outer housing 40, or both the inner housing 30 and the outer housing 40.

[0124] ○ The bearing cooling flow path R3 may not surround the thrust bearing 18. As long as the thrust bearing 18 is cooled by the flow of cooling fluid in the bearing cooling flow path R3, the shape of the bearing cooling flow path R3 can be appropriately modified. For example, the bearing cooling flow path R3 may also be a semi-circular arc-shaped flow path provided around half of the periphery of the thrust bearing 18.

[0125] The bearing cooling flow path R3 may not be a flow path that directs cooling fluid toward one direction of the thrust bearing 18 in the circumferential direction. For example, the bearing cooling flow path R3 may be an annular flow path surrounding the thrust bearing 18. The inlet and outlet of the bearing cooling flow path R3 are positioned 180 degrees offset in the circumferential direction of the bearing cooling flow path R3. In this case, the cooling fluid flowing into the bearing cooling flow path R3 is divided into fluid flowing toward the first direction of the thrust bearing 18 in the circumferential direction and fluid flowing toward the second direction, which is opposite to the first direction. Furthermore, the cooling fluid flows around the thrust bearing 18 for half a circumference and then merges at the outlet of the bearing cooling flow path R3.

[0126] The downstream cooling flow path R4 can also be omitted. In this case, the inner end wall 32 of the inner housing 30 is omitted.

[0127] ○The downstream cooling flow path R4 may not be divided by the inner end wall 32 of the inner shell 30 and the outer end wall 42 of the outer shell 40.

[0128] For example, the outer casing 40 may not have an outer end wall 42. That is, the outer casing 40 may consist only of an outer peripheral wall 41. The outer plate 21 closes one opening of the outer casing 40. The housing 11 has a blocking plate that closes the other opening of the outer casing 40. The blocking plate has a first bearing retaining portion 43 that holds the second radial bearing 17. In this case, the downstream cooling flow path R4 is divided by the inner end wall 32 of the inner housing 30 and the blocking plate.

[0129] The downstream cooling flow path R4 may not necessarily be a flow path that allows cooling fluid to flow in the first and second directions circumferentially toward the stator 51. For example, the downstream cooling flow path R4 may also be a C-shaped flow path with a partial interruption in the circumferential direction of the stator 51. In this case, the cooling fluid flows in the downstream cooling flow path R4 in one direction circumferentially toward the stator 51. The structure of the downstream cooling flow path R4 may also be appropriately modified depending on the location of the outlet of the downstream cooling flow path R4 connected to the external cooling flow path R1.

[0130] ○As long as the cooling fluid is split into motor cooling flow path R2 and bearing cooling flow path R3 by the split flow path R5, the shape of the split flow path R5 can be appropriately modified. For example, the first split flow path component 44 can also be Y-shaped. In order to reduce the pressure loss of the cooling fluid flowing in the split flow path R5, the shape of the split flow path R5 is preferably a simple shape.

[0131] ○ As long as the cooling fluid flowing in the bearing cooling flow path R3 merges with the motor cooling flow path R2 through the confluence flow path R6, the shape of the confluence flow path R6 can be appropriately modified. In order to reduce the pressure loss of the cooling fluid flowing in the confluence flow path R6, the shape of the confluence flow path R6 is preferably a simple shape.

[0132] The location where the cooling fluid flowing in the bearing cooling flow path R3 merges with the motor cooling flow path R2 is not limited to the location around the stator 51 in the motor cooling flow path R2.

[0133] For example, the merging flow path R6 can also cause the cooling fluid flowing in the bearing cooling flow path R3 to merge into the middle of the second flow path R22 and the third flow path R23 of the motor cooling flow path R2.

[0134] For example, if the bearing cooling flow path R3 is located in the half-circumference around the thrust bearing 18, the merging flow path R6 can also cause the cooling fluid flowing in the bearing cooling flow path R3 to merge into the middle of the first circumference flow path R21 of the motor cooling flow path R2.

[0135] The point where the cooling fluid flowing in the bearing cooling flow path R3 merges with the motor cooling flow path R2 in the confluence path R6 may not be a single location. For example, the confluence path R6 may also be where the cooling fluid flowing in the bearing cooling flow path R3 merges with the second peripheral flow path R22 and the third peripheral flow path R23 of the motor cooling flow path R2, respectively.

[0136] The centrifugal compressor 10 can also operate as follows.

[0137] Air, which is drawn into the first impeller chamber S3 as fluid, is compressed by the first impeller 14. Therefore, the first impeller 14 is a compressor impeller that compresses the fluid by rotating integrally with the rotating shaft 13. The air compressed in the first impeller chamber S3 is slowed down as it passes through the first diffuser flow path S4, thereby converting the air's velocity energy into pressure energy. The high-pressure air is then discharged into the first vortex flow path 23a and supplied to the fuel cell stack.

[0138] Exhaust gas discharged from the fuel cell stack is drawn into the second vortex flow path 24a. The exhaust gas drawn into the second vortex flow path 24a is then introduced into the second impeller chamber S5 through the second diffuser flow path S6. Furthermore, the second impeller 15 rotates under the influence of the kinetic energy of the exhaust gas introduced into the second impeller chamber S5. That is, the kinetic energy of the exhaust gas is converted into the rotational energy of the second impeller 15. The rotation of the second impeller 15 assists the rotation of the rotating shaft 13. Therefore, the second impeller 15 is a turbine impeller that assists the rotation of the rotating shaft 13. Finally, the exhaust gas passing through the second impeller chamber S5 is discharged to the outside of the casing 11.

[0139] It should be noted that the exhaust gas flowing in the second impeller chamber S5 contains water. Therefore, the thrust bearing 18 is preferably disposed on the side of the first impeller chamber S3 to prevent the thrust bearing 18 from rusting due to the water contained in the exhaust gas.

[0140] ○ The centrifugal compressor 10 is not limited to being installed in a vehicle.

[0141] The housing 11 is not limited to aluminum. The housing 11 can also be made of other metals.

[0142] The structure of the rotor 52 and the rotating shaft 13 of the electric motor 12 is not limited to the structure described in the above embodiment.

[0143] ○ The centrifugal compressor 10 may also be without the second impeller 15.

[0144] ○ The thrust bearing 18 can also replace the part on the first impeller 14 side of the rotating shaft 13 to support the part on the second impeller 15 side of the rotating shaft 13 so that it can rotate.

[0145] The centrifugal compressor 10 may also have a thrust bearing supporting the portion on the side of the first impeller 14 in the rotating shaft 13 as a rotatable thrust bearing 18, and also have a portion on the side of the second impeller 15 in the rotating shaft 13 as a rotatable thrust bearing.

[0146] ○The first rib, number 35, can also be omitted.

[0147] The first rib 35 can also protrude from the inner end wall 32 of the inner shell 30 instead of from the inner surface of the outer end wall 42 of the outer shell 40.

[0148] ○The second rib, number 36, can also be omitted.

[0149] The second rib 36 can also protrude from the inner end wall 32 of the inner shell 30 instead of from the inner surface of the outer end wall 42 of the outer shell 40.

[0150] ○The inner peripheral wall 31 of the inner shell 30 may also not have the first fin 34.

[0151] The number and shape of the first fin 34 can also be changed appropriately.

[0152] ○The inner end wall 32 of the inner shell 30 may also not have the second fin 37.

[0153] The number and shape of the second fin 37 can also be changed appropriately.

Claims

1. A centrifugal compressor, comprising: Rotation axis; An electric motor having a cylindrical stator that rotates the rotating shaft; An impeller that compresses fluid by rotating integrally with the rotating shaft; A thrust bearing supports the rotating shaft to enable rotation; and The metal casing has flow paths for the cooling fluid. The flow path includes a motor cooling flow path for cooling the electric motor through the flow of the cooling fluid, and a bearing cooling flow path for cooling the thrust bearing through the flow of the cooling fluid. The centrifugal compressor is characterized in that, The housing has a cylindrical inner housing that houses the stator and a cylindrical outer housing that houses the inner housing. The motor cooling airflow route is divided by the outer peripheral surface of the inner housing and the inner peripheral surface of the outer housing. The flow path has a splitting flow path that separates the cooling fluid into the motor cooling flow path and the bearing cooling flow path, and a merging flow path that merges the cooling fluid flowing in the bearing cooling flow path into the motor cooling flow path. The motor cooling flow path has a guide wall disposed on at least one of the inner housing and the outer housing, and guides the cooling fluid within the motor cooling flow path to flow circumferentially along the stator. The motor cooling flow path is a spiral flow path that surrounds the stator multiple times. The bearing cooling flow path is a flow path that surrounds the thrust bearing. The merging flow path is located at a point around the stator in the motor cooling flow path or midway around the stator in the motor cooling flow path, causing the cooling fluid flowing in the bearing cooling flow path to merge into the motor cooling flow path.

2. The centrifugal compressor according to claim 1, wherein, The inner housing has an inner end wall that is axially connected to one end of the inner peripheral wall of the inner housing. The outer casing has an outer end wall that is axially connected to one end of the outer peripheral wall of the outer casing. The inner end wall is located axially between the stator and the outer end wall of the rotating shaft. The flow path has a downstream cooling flow path that is divided by the inner end wall and the outer end wall and allows the cooling fluid flowing through the motor cooling flow path to flow in. The stator is located axially on the rotating shaft between the bearing cooling path and the downstream cooling path.

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