centrifugal compressor

Abstract

To provide a centrifugal compressor that can reduce a pressure loss of cooling fluid.SOLUTION: A centrifugal compressor comprises a metal housing comprising a flow passage R through which cooling water flows. The flow passage R comprises a motor cooling flow passage R2, a bearing cooling flow passage R3, a dividing flow passage R5, and a merging flow passage R6. The housing comprises a cylindrical inner housing for housing a stator, and a cylindrical outer housing for housing the inner housing. The motor cooling flow passage R2 is partitioned by an outer peripheral surface of the inner housing and an inner peripheral surface of the outer housing. The motor cooling flow passage R2 comprises a guide wall provided in at least one of the inner housing and the outer housing, and for guiding the cooling water in the motor cooling flow passage R2 so that it flows in a circumferential direction of the stator. The dividing flow passage R5 divides the cooling water into the motor cooling flow passage R2 and the bearing cooling flow passage R3. The merging flow part R6 merges the cooling water flowing through the bearing cooling flow passage R3, into the motor cooling flow passage R2.SELECTED DRAWING: Figure 7

Description

[Technical Field]

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

[0002] A centrifugal compressor includes 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 rotatably supports the rotating shaft.

[0003] The housing of the electric compressor in Patent Document 1 has a flow path through which a cooling fluid flows. The flow path includes a motor cooling flow path through which the cooling fluid flows to cool the electric motor, and a bearing cooling flow path through which the cooling fluid flows to cool the bearings. The motor cooling flow path and the bearing cooling flow path are serial flow paths connected in series. The cooling fluid flows through the motor cooling flow path and then through the bearing cooling flow path. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2018 / 139497 Summary of the Invention [Problem to be solved by the invention]

[0005] When the motor cooling channel and the bearing cooling channel are connected in series as in Patent Document 1, all of the cooling fluid introduced into the channel flows through both the motor cooling channel and the bearing cooling channel, which increases the flow rate of the cooling fluid flowing through each of the motor cooling channel and the bearing cooling channel, thereby increasing the pressure loss of the cooling fluid. [Means for solving the problem]

[0006] A centrifugal compressor for solving the above problems includes a rotating shaft, an electric motor having a cylindrical stator and rotating the rotating shaft, an impeller that rotates integrally with the rotating shaft to compress a fluid, a thrust bearing that rotatably supports the rotating shaft, and a metal housing having a flow path through which a cooling fluid flows, the flow path having a motor cooling flow path through which the cooling fluid flows to cool the electric motor and a bearing cooling flow path through which the cooling fluid flows to cool the thrust bearing, and the housing includes a cylindrical inner housing that accommodates the stator, and a cylindrical outer housing that accommodates a bearing housing, the motor cooling passage being partitioned by the outer peripheral surface of the inner housing and the inner peripheral surface of the outer housing, the passage having a branch passage that branches the cooling fluid into the motor cooling passage and the bearing cooling passage, and a merging passage that merges the cooling fluid flowing through the bearing cooling passage into the motor cooling passage, the motor cooling passage being provided in at least one of the inner housing and the outer housing and having a guide wall that guides the cooling fluid in the motor cooling passage to flow in the circumferential direction of the stator.

[0007] The cooling fluid is divided into the motor cooling channel and the bearing cooling channel by the branch channel. Therefore, the flow rate of the cooling fluid flowing through each of the motor cooling channel and the bearing cooling channel is reduced compared to when the motor cooling channel and the bearing cooling channel are connected in series. This reduces the pressure loss of the cooling fluid.

[0008] One possible method for reducing the pressure loss of the cooling fluid is to form the motor cooling channel and the bearing cooling channel as completely independent parallel channels. This also reduces the flow rate of the cooling fluid through the motor cooling channel and the bearing cooling channel, thereby reducing the pressure loss of the cooling fluid. However, because the electric motor is more likely to reach higher temperatures than the thrust bearing, a reduction in the flow rate of the cooling fluid through the motor cooling channel could result in insufficient cooling of the electric motor. In contrast, with the above configuration, the cooling fluid flowing through the bearing cooling channel merges with the motor cooling channel via the merger channel. Therefore, although the flow rate of the cooling fluid through the motor cooling channel decreases when the cooling fluid is split between the motor cooling channel and the bearing cooling channel, it returns to the flow rate before splitting when the cooling fluid merges with the motor cooling channel after flowing through the bearing cooling channel. This makes it less likely that the electric motor will be insufficiently cooled.

[0009] In the centrifugal compressor, the motor cooling passage may be a spiral passage that makes multiple revolutions around the stator, the bearing cooling passage may be a passage that surrounds the thrust bearing, and the merging passage may cause the cooling fluid flowing through the bearing cooling passage to merge with the motor cooling passage at a point where the motor cooling passage has made one revolution around the stator.

[0010] In the above configuration, the bearing cooling channel surrounds the thrust bearing. Therefore, compared to when the bearing cooling channel does not surround the thrust bearing, the thrust bearing is cooled in a more balanced manner in the circumferential direction. Furthermore, the confluence channel merges the cooling fluid flowing through the bearing cooling channel with the motor cooling channel at a point where the motor cooling channel has made one full revolution around the stator. Therefore, compared to when the cooling fluid flowing through the bearing cooling channel merges with the motor cooling channel at a point where the motor cooling channel has made two revolutions around the stator, the flow rate of the cooling fluid flowing through the motor cooling channel can be quickly restored to the flow rate before the split. This allows for better cooling of the electric motor.

[0011] In the centrifugal compressor described above, the inner housing may have an inner end wall continuous with one axial end of the inner peripheral wall of the inner housing, the outer housing may have an outer end wall continuous with one axial end of the outer peripheral wall of the outer housing, the inner end wall may be located between the stator and the outer end wall in the axial direction of the rotating shaft, the flow path may have a downstream cooling flow path that is defined by the inner end wall and the outer end wall and into which the cooling fluid that has flowed through the motor cooling flow path flows, and the stator may be located between the bearing cooling flow path and the downstream cooling flow path in the axial direction of the rotating shaft.

[0012] In the above configuration, the stator is also cooled by the cooling fluid flowing through the bearing cooling passage and the downstream cooling passage, thereby further cooling the electric motor. [Effects of the Invention]

[0013] According to the present invention, the pressure loss of the cooling fluid can be reduced. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view showing a centrifugal compressor according to an embodiment. [Figure 2] FIG. 2 is a perspective view showing an inner housing in the embodiment. [Figure 3] FIG. 2 is a perspective view showing an inner housing in the embodiment. [Figure 4] FIG. 2 is a cross-sectional view showing a housing in the embodiment. [Figure 5] FIG. 2 is a cross-sectional view showing a housing in the embodiment. [Figure 6] FIG. 1 is a partial front view showing a centrifugal compressor according to an embodiment. [Figure 7] FIG. 4 is an explanatory diagram for explaining the flow of a cooling fluid in a flow path. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, one embodiment of a centrifugal compressor will be described with reference to Figs. 1 to 7. The centrifugal compressor of this embodiment is mounted on a fuel cell vehicle. The fuel cell vehicle is equipped with a fuel cell stack that generates electricity through a chemical reaction between hydrogen and oxygen. The centrifugal compressor of this embodiment is used in a supply device that supplies air containing oxygen to the fuel cell stack.

[0016] <Configuration of centrifugal compressor> 1, a 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). The housing 11 in this embodiment is made of aluminum.

[0017] <Housing> 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.

[0018] 2 and 3, the inner housing 30 has a cylindrical inner peripheral wall 31 and an annular inner end wall 32 that is continuous with 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.

[0019] 2, the inner housing 30 has a guide wall 33 that protrudes from the outer peripheral surface of the inner peripheral wall 31. The guide wall 33 in this embodiment extends in a substantially spiral shape. The guide wall 33 of this embodiment has a first circumferential wall portion 33a, a second circumferential wall portion 33b, a third circumferential wall portion 33c, and a fourth circumferential wall portion 33d. The first to fourth circumferential wall portions 33a to 33d extend in the circumferential direction of the inner circumferential wall 31. The first to fourth circumferential wall portions 33a to 33d are arranged in this order from the end of the inner circumferential wall 31 opposite to the inner end wall 32 in the axial direction toward the end on the inner end wall 32 side. The first circumferential wall portion 33a is annular.

[0020] The guide wall 33 also 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 circumferential direction of the inner circumferential wall 31. The first to third connecting wall portions 33e to 33g are aligned in this order from the end of the inner circumferential wall 31 opposite the inner end wall 32 in the axial direction toward the end of the inner end wall 32. The first connecting wall portion 33e connects the first circumferential wall portion 33a to a first end of the second circumferential wall portion 33b. The second connecting wall portion 33f connects a second end of the second circumferential wall portion 33b opposite the first end to a first end of the third circumferential wall portion 33c. The third connecting wall portion 33g connects a second end of the third circumferential wall portion 33c opposite the first end to a first end of the fourth circumferential wall portion 33d.

[0021] The inner housing 30 of this embodiment has first fins 34 that protrude from the outer peripheral surface of the inner peripheral wall 31. The amount by which the first fins 34 protrude from the outer peripheral surface of the inner peripheral wall 31 is smaller than the amount by which the guide wall 33 protrudes from the outer peripheral surface of the inner peripheral wall 31. The first fins 34 are provided in three rows in 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 that are adjacent in the axial direction of the inner peripheral wall 31.

[0022] As shown in Fig. 3, 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 the direction opposite to the inner circumferential wall 31. The first rib 35 and the second rib 36 each extend in the radial direction of 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 a portion of the inner circumferential wall 31 in the circumferential direction where the fourth circumferential wall portion 33d is not provided. The second rib 36 is disposed at a position shifted 180 degrees from the first rib 35 in the circumferential direction of the inner end wall 32.

[0023] The inner housing 30 of this embodiment has second fins 37. The second fins 37 protrude from the inner end wall 32 in the direction opposite to the inner peripheral wall 31. The second fins 37 extend in an arc shape along the circumferential direction of the inner end wall 32. The second fins 37 are provided in two rows in the radial direction of the inner end wall 32 between the first rib 35 and the second rib 36.

[0024] As shown in FIG. 1 , the outer housing 40 is cylindrical and has a bottom, a cylindrical outer peripheral wall 41, and a disk-shaped outer end wall 42 that is continuous with one axial end of the outer peripheral wall 41. The outer end wall 42 has a shaft insertion hole 42a. The shaft insertion hole 42a penetrates the outer end wall 42 in the axial direction of the outer peripheral wall 41. The outer housing 40 has a cylindrical first bearing holder 43. The first bearing holder 43 extends from the inner surface of the outer end wall 42 in the axial direction of the outer peripheral wall 41. The axis of the first bearing holder 43 coincides with the axis of the outer peripheral wall 41. The inside of the first bearing holder 43 communicates with the shaft insertion hole 42a. The first bearing holder 43 holds a cylindrical second radial bearing 17.

[0025] As shown in FIG. 4 , the outer housing 40 has a first branch flow path forming portion 44. The first branch flow path forming portion 44 is provided at an end portion on the opening side of the outer peripheral wall 41. In this embodiment, the first branch flow path forming portion 44 is T-shaped. The first branch flow path forming portion 44 has a radial path 44a extending in the radial direction of the outer peripheral wall 41 and an axial path 44b extending in the axial direction of the outer peripheral wall 41. The radial path 44a penetrates the outer peripheral wall 41 in the radial direction. A first end of the radial path 44a communicates with the outside of the outer housing 40. A second end of the radial path 44a, which is the end opposite to the first end, opens at the inner circumferential surface of the outer peripheral wall 41. A first end of the axial path 44b is connected to the middle of the radial path 44a. A second end of the axial path 44b, which is the end opposite to the first end, opens at the tip end surface 41a of the outer peripheral wall 41.

[0026] As shown in FIG. 5 , the outer housing 40 has a first merging flow path forming portion 45. The first merging flow path forming portion 45 is provided at an end portion on the opening side of the outer circumferential wall 41. The first merging flow path forming portion 45 is provided at a position different from the first branch flow path forming portion 44 in the circumferential direction of the outer circumferential wall 41. The first merging flow path forming portion 45 in this embodiment is L-shaped. A first end of the first merging flow path forming portion 45 opens at the tip end surface 41 a of the outer circumferential wall 41. A second end of the first merging flow path forming portion 45, which is the end opposite to the first end, opens at the inner circumferential surface of the outer circumferential wall 41.

[0027] As shown in FIG. 1 , the outer housing 40 accommodates the inner housing 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 coincides 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 tip surface of the guide wall 33 abuts against the inner peripheral surface of the outer peripheral wall 41. The first bearing retaining portion 43 is inserted inside the inner end wall 32. The inner surface of the outer end wall 42 faces the inner end wall 32.

[0028] 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 each perpendicular to the thickness direction of the outer plate 21. The second surface 21b is a surface located on the opposite side of the first surface 21a in the thickness direction of the outer plate 21.

[0029] The outer plate 21 has a first recess 21c and a second recess 21d. The first recess 21c and the second recess 21d are each recessed from the first surface 21a of the outer plate 21. The first recess 21c is provided on the inner periphery of the outer plate 21. The first recess 21c is annular.

[0030] 6, the second recess 21d extends in the circumferential direction of the outer plate 21. The second recess 21d surrounds the first recess 21c. The second recess 21d has a shape that is partially discontinued in the circumferential direction of the outer plate 21, i.e., a C-shape.

[0031] As shown in Fig. 4, the outer plate 21 has a second branch flow path forming portion 27. In this embodiment, the second branch flow path forming portion 27 is L-shaped. A first end of the second branch flow path forming portion 27 opens in the first surface 21a of the outer plate 21. A second end of the second branch flow path forming portion 27, which is the end opposite to the first end, communicates with a first end of the second recess 21d in the circumferential direction of the outer plate 21.

[0032] As shown in FIG. 5 , the outer plate 21 has a second confluence flow path forming portion 28. The second confluence flow path forming portion 28 is provided at a position different from the second branch flow path forming portion 27 in the circumferential direction of the outer plate 21. The second confluence flow path forming portion 28 in this embodiment is L-shaped. A first end of the second confluence flow path forming portion 28 communicates with a second end, which is the end opposite to the first end of the second recess 21d. The second end, which is the end opposite to the first end of the second confluence flow path forming portion 28, opens in the first surface 21a of the outer plate 21.

[0033] 1, the outer plate 21 is connected to the end of the outer housing 40 on the opening side. The outer plate 21 closes the opening of the outer housing 40. A motor chamber S1 is defined by the inner surface of the outer housing 40 and the outer plate 21. The motor chamber S1 accommodates the inner housing 30, the inner plate 22, and the electric motor 12.

[0034] 4, the first surface 21a of the outer plate 21 abuts against the tip surface 41a of the outer peripheral wall 41 of the outer housing 40. A first end of the second branch flow path forming portion 27 is connected to a second end of the axial passage 44b of the first branch flow path forming portion 44. Therefore, the second branch flow path forming portion 27 is in communication with the first branch flow path forming portion 44.

[0035] 5, a second end of the second merging flow path forming portion 28 is connected to a first end of the first merging flow path forming portion 45. Therefore, the second merging flow path forming portion 28 is in communication with the first merging flow path forming portion 45.

[0036] As shown in Fig. 1, the inner plate 22 is an annular plate. The inner plate 22 is disposed between the outer plate 21 and the inner housing 30 in the axial direction of the motor housing 20. The inner plate 22 abuts against the first surface 21a of the outer plate 21. A bearing accommodating chamber S2 is defined by the inner plate 22 and the first recess 21c of the outer plate 21. The bearing accommodating chamber S2 accommodates the annular thrust bearing 18.

[0037] The inner plate 22 has a cylindrical second bearing holder 25. The second bearing holder 25 stands upright from the inner periphery of the inner plate 22 in the opposite direction to the outer plate 21. The axis of the second bearing holder 25 coincides with the axis of the first bearing holder 43. The inside of the second bearing holder 25 communicates with the inside of the outer plate 21 via the bearing accommodating chamber S2. The second bearing holder 25 holds the cylindrical first radial bearing 16.

[0038] The first compressor housing 23 is cylindrical. The first compressor housing 23 has a first scroll passage 23a. The first scroll passage 23a is spirally circumferential. The first compressor housing 23 is connected to the second surface 21b of the outer plate 21.

[0039] A first impeller chamber S3 is defined by the inner circumferential surface of the first compressor housing 23 and the outer plate 21. A first diffuser passage S4 is provided between the first compressor housing 23 and the second surface 21b of the outer plate 21. The first diffuser passage S4 connects the first impeller chamber S3 and the first scroll passage 23a.

[0040] The second compressor housing 24 is cylindrical. The second compressor housing 24 has a second scroll passage 24a. The second scroll passage 24a is spirally circumferential. The second compressor housing 24 is connected to the outer surface of the outer end wall 42 of the outer housing 40.

[0041] A 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 housing 40. A second diffuser passage S6 is provided between the second compressor housing 24 and the outer end wall 42 of the outer housing 40. The second diffuser passage S6 connects the second impeller chamber S5 and the second scroll passage 24a.

[0042] <Electric motor> As shown in FIG. 1, the electric motor 12 has a cylindrical stator 51 and a rotor 52 disposed inside the stator 51.

[0043] 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 coincides with the axis of the inner peripheral wall 31. The coil 54 is wound around the stator core 53. The inner housing 30 accommodates the stator 51. The inner end wall 32 of the inner housing 30 is located between the stator 51 and the outer end wall 42 of the outer housing 40 in the axial direction of the motor housing 20. The stator 51 is located between the inner plate 22 and the inner end wall 32 of the inner housing 30 in the axial direction of the motor housing 20. The rotor 52 has a cylindrical rotor core 55 and a permanent magnet (not shown) provided in the rotor core 55. The axis of the rotor core 55 coincides with the axis of the stator core 53.

[0044] <Rotating shaft, first impeller, second impeller> The rotating shaft 13 has a shaft main body portion 13a, a first support portion 13b, a second support portion 13c, and a third support portion 13d. The rotating shaft 13 is accommodated in the housing 11. The direction in which the shaft main 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.

[0045] Shaft main body 13a is inserted into rotor core 55 in motor chamber S1. Shaft main body 13a is fixed to rotor core 55. Shaft main body 13a is rotatable integrally with rotor 52.

[0046] A first end of shaft main body 13a protrudes from motor chamber S1 into first impeller chamber S3, passing through the inside of second bearing holder 25, bearing accommodating chamber S2, and the inside of outer plate 21. First impeller 14 is connected to the first end of shaft main body 13a. First impeller 14 is accommodated in first impeller chamber S3. First impeller 14 is rotatable integrally with shaft main body 13a.

[0047] A second end portion of shaft main body 13a, which is the end portion opposite to the first end portion, passes from motor chamber S1 through the inside of first bearing holder 43 and the inside of shaft insertion hole 42a and protrudes into second impeller chamber S5. Second impeller 15 is connected to the second end portion of shaft main body 13a. Second impeller 15 is housed in second impeller chamber S5. Second impeller 15 is rotatable integrally with shaft main body 13a.

[0048] First support portion 13b is provided on the outer peripheral surface of shaft body 13a at a location closer to the first end than the center of shaft body 13a. First support portion 13b is disposed inside second bearing holder 25. First support portion 13b is formed integrally with shaft body 13a. First support portion 13b protrudes from the outer peripheral surface of shaft body 13a.

[0049] Second support portion 13c is provided on the outer circumferential surface of shaft body 13a at a position closer to the second end than the center of shaft body 13a. Second support portion 13c is arranged inside first bearing holder 43. Second support portion 13c is fixed to the outer circumferential surface of shaft body 13a and protrudes in an annular shape from the outer circumferential surface of shaft body 13a. Second support portion 13c is rotatable integrally with shaft body 13a.

[0050] Third support portion 13d is provided on the outer circumferential surface of shaft main body 13a at a position closer to the first end than first support portion 13b. Third support portion 13d is disposed in bearing accommodating chamber S2. Third support portion 13d is fixed to the outer circumferential surface of shaft main body 13a and protrudes in an annular shape from the outer circumferential surface of shaft main body 13a. Third support portion 13d is rotatable integrally with shaft main body 13a.

[0051] <First radial bearing, second radial bearing, thrust bearing> The first radial bearing 16, the second radial bearing 17, and the thrust bearing 18 rotatably support the rotating shaft 13. The first radial bearing 16 rotatably supports the first support portion 13b of the rotating shaft 13 in the radial direction. The second radial bearing 17 rotatably supports the second support portion 13c of the rotating shaft 13 in the radial direction. The "radial direction" is a direction perpendicular to the axial direction of the rotating shaft 13. Therefore, the "radial direction" is the radial direction of the rotating shaft 13. The thrust bearings 18 are arranged on both sides of the third support portion 13d in the axial direction of the rotating shaft 13. The thrust bearings 18 rotatably support the third support portion 13d of the rotating shaft 13 in the thrust direction. The "thrust direction" is a direction parallel to the axial direction of the rotating shaft 13.

[0052] The first radial bearing 16, the second radial bearing 17, and the thrust bearing 18 are each a gas bearing. Each bearing 16, 17, and 18 supports the rotating shaft 13 while in contact with the rotating shaft 13 until the rotation speed of the rotating shaft 13 reaches a floating rotation speed at which the rotating shaft 13 is floated by each bearing 16, 17, and 18. When the rotation speed of the rotating shaft 13 reaches the floating rotation speed, the dynamic pressure of a fluid film generated between the rotating shaft 13 and each bearing 16, 17, and 18 causes the rotating shaft 13 to float relative to the bearings 16, 17, and 18. As a result, each bearing 16, 17, and 18 supports the rotating shaft 13 without contacting the rotating shaft 13.

[0053] <Flow path> The housing 11 has a flow path R through which coolant (LLC) flows as a cooling fluid. 7, 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 branch flow path R5, and a confluence flow path R6. The branch flow path R5 is a flow path for branching the cooling fluid into the motor cooling flow path R2 and the bearing cooling flow path R3. The confluence flow path R6 is a flow path for merging the cooling fluid flowing through the bearing cooling flow path R3 into the motor cooling flow path R2.

[0054] As shown in Figures 4 and 5, the motor cooling passage R2 is defined 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 passage R2 is provided around the stator 51. As described above, the 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 passage R2 has the guide wall 33. The guide wall 33 guides the coolant flowing through the motor cooling passage R2 so that it flows in the circumferential direction of the stator 51. In this embodiment, the motor cooling passage R2 is defined in a spiral shape by the guide wall 33. In other words, the motor cooling passage R2 is a spiral passage.

[0055] The motor cooling flow path R2 in this embodiment wraps around the stator 51 three times. The motor cooling flow path R2 has a first-turn flow path R21, a second-turn flow path R22, and a third-turn flow path R23. The first-turn flow path R21 is defined by the outer peripheral surface of the inner circumferential wall 31, the inner circumferential surface of the outer circumferential wall 41, the first circumferential wall portion 33a, and the second circumferential wall portion 33b. The second-turn flow path R22 is defined by the outer peripheral surface of the inner circumferential wall 31, the inner circumferential surface of the outer circumferential wall 41, the second circumferential wall portion 33b, the third circumferential wall portion 33c, the first connecting wall portion 33e, and the second connecting wall portion 33f. The third circulation 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.

[0056] The bearing cooling passage R3 is defined by the inner plate 22 and the second recess 21d of the outer plate 21. The bearing cooling passage R3 in this embodiment surrounds the bearing accommodating chamber S2, and therefore surrounds the thrust bearing 18.

[0057] The downstream cooling passage 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 passage R4 is an annular passage that extends in the circumferential direction of the stator 51. The stator 51 is located between the bearing cooling passage R3 and the downstream cooling passage R4 in the axial direction of the rotating shaft 13.

[0058] As shown in FIG. 4 , the branch flow passage R5 is formed by the first branch flow passage component 44 and the second branch flow passage component 27. The inlet of the branch flow passage R5 is the first end of the path 44a of the first branch flow passage component 44. The inlet of the branch flow passage R5 is connected to the external cooling passage R1. The branch flow passage R5 branches into a path connected to the motor cooling passage R2 and a path connected to the bearing cooling passage R3. The path connected to the motor cooling passage R2 is a portion of the path 44a located closer to the inner circumferential surface of the outer circumferential wall 41 than the shaft path 44b. The path connected to the bearing cooling passage R3 is the shaft path 44b and the second branch flow passage component 27. The outlet of the path connected to the motor cooling passage R2 is the second end of the path 44a. The outlet of the path connected to the bearing cooling passage R3 is the second end of the second branch flow passage component 27.

[0059] The second end of the path 44a of the first branch flow path forming portion 44 is located between the first circumferential wall portion 33a and the second circumferential wall portion 33b in the axial direction of the motor housing 20. Therefore, the outlet of the branch flow path R5 that connects to the motor cooling flow path R2 is connected to the first turn flow path R21 of the motor cooling flow path R2. As described above, the second end of the second branch flow path forming portion 27 is connected to the first end of the second recess 21d. Therefore, the outlet of the branch flow path R5 that connects to the bearing cooling flow path R3 is connected to the bearing cooling flow path R3. In other words, the branch flow path R5 is in communication with both the motor cooling flow path R2 and the bearing cooling flow path R3.

[0060] 5, the junction flow path R6 is constituted by a first junction flow path forming portion 45 and a second junction flow path forming portion 28. The inlet of the junction flow path R6 is a first end of the second junction flow path forming portion 28. The outlet of the junction flow path R6 is a second end of the first junction flow path forming portion 45.

[0061] As described above, the first end of the second merging passage-forming portion 28 is connected to the second end of the second recess 21d. Therefore, the inlet of the merging passage R6 is connected to the bearing-cooling passage R3. The second end of the first merging passage-forming portion 45 is located between the first circumferential wall portion 33a and the second connecting wall portion 33f in the axial direction of the motor housing 20. Therefore, the outlet of the merging passage R6 is connected to the motor-cooling passage R2. In this embodiment, the outlet of the merging passage R6 is connected to the inlet of the second-turn passage R22, i.e., at a point where the motor-cooling passage R2 has made one turn around the periphery of the stator 51. In other words, the merging passage R6 connects the bearing-cooling passage R3 and the motor-cooling passage R2.

[0062] <Operation of a centrifugal compressor> When the inverter supplies power to the coil 54, a rotating magnetic field is generated in the stator 51, causing the rotor 52 to rotate. When the rotor 52 rotates, the rotating shaft 13 rotates integrally with the rotor 52. In other words, the inverter drives the electric motor 12. The electric motor 12 rotates the rotating shaft 13.

[0063] When the rotary shaft 13 rotates, the first impeller 14 and the second impeller 15 rotate integrally with the rotary shaft 13. Then, air as a fluid is drawn into the first impeller chamber S3 from the outside. The drawn 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 rotary shaft 13. The air compressed in the first impeller chamber S3 is decelerated when passing through the first diffuser passage S4, and the velocity energy of the air is converted into pressure energy. Then, the pressurized air is discharged into the first scroll passage 23a and then exhausted to the outside of the housing 11.

[0064] In this embodiment, air discharged from the first scroll passage 23a to the outside of the housing 11 is drawn into the second impeller chamber S5 via a piping (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 rotary shaft 13. The air compressed in the second impeller chamber S5 is decelerated as it passes through the second diffuser passage S6, thereby converting the velocity energy of the air into pressure energy. In other words, the centrifugal compressor 10 of this embodiment is a two-stage compression centrifugal compressor in which air compressed by the first impeller 14 is compressed again by the second impeller 15. The pressurized air is then discharged into the second scroll passage 24a and supplied to the fuel cell stack. The oxygen contained in the air supplied to the fuel cell stack contributes to power generation in the fuel cell stack. Note that only about 20% of the air contains oxygen that contributes to power generation in the fuel cell stack. Therefore, approximately 80% of the air supplied to the fuel cell stack is discharged from the fuel cell stack as exhaust gas without contributing to power generation in the fuel cell stack.

[0065] <Cooling water flow in the flow path> As shown in Figure 7, the cooling water flows through the external cooling flow path R1. For example, heat from the inverter is dissipated into the cooling water flowing through the external cooling flow path R1. In other words, the cooling water flows through the external cooling flow path R1 to cool the inverter. After flowing through the external cooling flow path R1, the cooling water flows into the branch flow path R5.

[0066] 4, the cooling water is diverted by the diverting flow path R5 into the first loop 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 through the motor cooling flow path R2 and the flow rate of the cooling water flowing through the bearing cooling flow path R3 are each reduced from the flow rate of the cooling water flowing through the external cooling flow path R1.

[0067] 6, the cooling water diverted to the bearing cooling passage R3 flows around the thrust bearing 18. Heat from the thrust bearing 18 is dissipated to the outer plate 21 and the inner plate 22 via the atmosphere in the bearing accommodation chamber S2. The heat dissipated from the thrust bearing 18 to the outer plate 21 and the inner plate 22 is dissipated to the cooling water flowing through the bearing cooling passage R3. In other words, the bearing cooling passage R3 cools the thrust bearing 18 by the cooling water flowing therethrough.

[0068] Furthermore, heat from the electric motor 12 is dissipated to the outer plate 21 and the inner plate 22 via the atmosphere in the motor chamber S1. The heat dissipated from the electric motor 12 to the outer plate 21 and the inner plate 22 is dissipated to the cooling water flowing through the bearing cooling passage R3. In other words, the bearing cooling passage R3 also cools the electric motor 12 by the cooling water flowing therethrough.

[0069] Furthermore, the heat of the first radial bearing 16 is dissipated to the cooling water flowing through the bearing cooling passage R3 via the inner plate 22. In other words, the first radial bearing 16 is also cooled by the cooling water flowing through the bearing cooling passage R3.

[0070] The cooling water flows through the bearing cooling flow passage R3 and then flows into the merging flow passage R6. 5, the junction passage R6 causes the cooling water flowing through the bearing cooling passage R3 to merge with the motor cooling passage R2. In this embodiment, the junction passage R6 causes the cooling water flowing through the bearing cooling passage R3 to merge with the inlet of the second-circumference passage R22 of the motor cooling passage R2. In other words, the junction passage R6 causes the cooling water flowing through the bearing cooling passage R3 to merge with the motor cooling passage R2 at the point where the motor cooling passage R2 has made one revolution around the periphery of the stator 51.

[0071] As shown in FIG. 2 , the cooling water diverted to the first-turn flow path R21 of the motor cooling flow path R2 flows around the stator 51 once and then flows into the second-turn flow path R22. As a result, both the cooling water that has flowed through the first-turn flow path R21 and the cooling water that has flowed through the bearing cooling flow path R3 flow through the second-turn flow path R22. Therefore, the flow rate of the cooling water flowing through the second-turn flow path R22 returns to the flow rate before the divergence. The cooling water that has flowed through the second-turn flow path R22 flows around the stator 51 once and then flows into the third-turn flow path R23. The cooling water that has flowed into the third-turn flow path R23 flows around the stator 51 once. In this way, the cooling water in the motor cooling flow path R2 flows in the circumferential direction of the stator 51 by being guided by the guide wall 33. In this embodiment, the cooling water flows in a spiral around the stator 51.

[0072] Heat from the electric motor 12 is dissipated to the cooling water flowing through the motor cooling passage R2 via the inner peripheral wall 31 of the inner housing 30. In other words, the electric motor 12 is cooled by the cooling water flowing through the motor cooling passage R2.

[0073] As shown in FIG. 3, the cooling water flows through a third circulation flow path R23 of the motor cooling flow path R2, and then flows into the downstream cooling flow path R4. The cooling water that has flowed into the downstream cooling flow passage R4 is separated by the first rib 35 into cooling water that flows in a first direction in the circumferential direction of the stator 51 and cooling water that flows in a second direction that is 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 halfway around the circumferential direction of the stator 51. The cooling water then collides with the second rib 36. As a result, the flow direction of the cooling water changes from a direction along the circumferential direction of the stator 51 to a direction toward the radial outside of the stator 51.

[0074] 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 in 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 through the downstream cooling passage R4. In other words, the cooling water flows through the downstream cooling passage R4 to cool the electric motor 12.

[0075] Additionally, heat from the second radial bearing 17 is dissipated to the cooling water flowing through the downstream cooling passage R4 via the first bearing retaining portion 43 and the outer end wall 42 of the outer housing 40. In other words, the cooling water flowing through the downstream cooling passage R4 also cools the second radial bearing 17.

[0076] 7, the cooling water flows through the downstream cooling passage R4 and then flows into the external cooling passage R1. In other words, the cooling water returns to the external cooling passage R1. The cooling water circulates through the passage R.

[0077] [Actions and Effects of This Embodiment] The operation and effects of this embodiment will be described. (1) The cooling water flowing through the flow path R is divided into the motor cooling flow path R2 and the bearing cooling flow path R3 by the flow branching flow path R5. As a result, the flow rate of the cooling water flowing through each of the motor cooling flow path R2 and the bearing cooling flow path R3 is reduced compared to when the motor cooling flow path R2 and the bearing cooling flow path R3 are connected in series. This reduces the pressure loss of the cooling water.

[0078] One possible method for reducing the pressure loss of the coolant is to form the motor cooling channel R2 and the bearing cooling channel R3 as completely independent parallel channels. This also reduces the flow rate of the coolant flowing through the motor cooling channel R2 and the bearing cooling channel R3, thereby reducing the pressure loss of the coolant. However, because the electric motor 12 is prone to reach higher temperatures than the thrust bearing 18, a reduction in the flow rate of the coolant flowing through the motor cooling channel R2 could result in insufficient cooling of the electric motor 12. In contrast, in this embodiment, the coolant flowing through the bearing cooling channel R3 merges with the motor cooling channel R2 via the merger channel R6. Therefore, although the flow rate of the coolant flowing through the motor cooling channel R2 decreases when the coolant is diverted between the motor cooling channel R2 and the bearing cooling channel R3, it returns to the flow rate before the divergence when the coolant flows through the bearing cooling channel R3 and merges with the motor cooling channel R2. This reduces the likelihood of insufficient cooling of the electric motor 12.

[0079] (2) For example, if the motor cooling passage R2 does not have the guide wall 33, the cooling water that flows into the motor cooling passage R2 may flow in the axial direction of the stator 51. As a result, the stator 51 may have some areas that are easily cooled and some areas that are difficult to cool in the circumferential direction. Furthermore, if the motor cooling passage R2 does not have the guide wall 33, the cooling water may be more likely to be diverted into the motor cooling passage R2 than into the bearing cooling passage R3. As a result, the flow rate of the cooling water flowing through the bearing cooling passage R3 may be insufficient, which may result in insufficient cooling of the thrust bearing 18.

[0080] In contrast, in this embodiment, the motor cooling passage R2 has a guide wall 33 that guides the cooling water in the motor cooling passage R2 to flow in the circumferential direction of the stator 51. Therefore, the stator 51 can be cooled in a well-balanced manner in the circumferential direction. Furthermore, since the cooling water is less likely to flow into the motor cooling passage R2 than if the motor cooling passage R2 did not have the guide wall 33, it is also diverted to the bearing cooling passage R3. Therefore, insufficient cooling of the thrust bearing 18 due to an insufficient flow rate of the cooling water flowing through the bearing cooling passage R3 is less likely to occur.

[0081] (3) The bearing cooling channel R3 surrounds the thrust bearing 18. Therefore, compared to when the bearing cooling channel R3 does not surround the thrust bearing 18, the thrust bearing 18 is cooled in a well-balanced manner in the circumferential direction. The motor cooling channel R2 is a spiral channel that makes multiple turns around the stator 51. The confluence channel R6 causes the cooling water flowing through the bearing cooling channel R3 to merge with the motor cooling channel R2 at a point where the motor cooling channel R2 has made one turn around the stator 51. Therefore, compared to when the cooling water flowing through the bearing cooling channel R3 merges with the motor cooling channel R2 at a point where the motor cooling channel R2 has made two turns around the stator 51, for example, the flow rate of the cooling water flowing through the motor cooling channel R2 can be quickly returned to the flow rate before the split. This allows the electric motor 12 to be cooled more effectively.

[0082] (4) The inner housing 30 has an inner end wall 32 that is continuous with one axial end of the inner circumferential wall 31. The outer housing 40 has an outer end wall 42 that is continuous with one axial end of the outer circumferential wall 41. The inner end wall 32 is located between the stator 51 and the outer end wall 42 in the axial direction of the rotating shaft 13. The flow path R is defined by the inner end wall 32 and the outer end wall 42 and has a downstream cooling flow path R4 into which the cooling water that has flowed 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 rotating shaft 13. Therefore, the stator 51 is also cooled by the cooling water flowing through the bearing cooling flow path R3 and the downstream cooling flow path R4. This allows the electric motor 12 to be cooled more effectively.

[0083] (5) The bearing cooling passage R3 is defined by the inner plate 22 that holds the thrust bearing 18. Therefore, the bearing cooling passage R3 can cool not only the thrust bearing 18 but also the first radial bearing 16 by the cooling water flowing therethrough.

[0084] (6) The downstream cooling passage R4 is defined by the outer housing 40 that holds the second radial bearing 17. Therefore, the cooling water flowing through the downstream cooling passage R4 can cool not only the stator 51 but also the second radial bearing 17.

[0085] (7) For example, if the first rib 35 is not provided in the downstream cooling flow passage R4, the cooling water that flows into the downstream cooling flow passage R4 may flow in one direction in the circumferential direction of the stator 51. As a result, the stator 51 will have portions that are easily cooled and portions that are difficult to cool in the circumferential direction. In contrast, in the present embodiment, the first rib 35 separates the cooling water that flows into the downstream cooling flow passage R4 into cooling water that flows in a first direction in the circumferential direction of the stator 51 and cooling water that flows in a second direction that is opposite to the first direction. Therefore, the stator 51 can be cooled in a balanced manner in the circumferential direction.

[0086] (8) The inner peripheral wall 31 of the inner housing 30 has the first fins 34. This increases the surface area of ​​the inner peripheral wall 31, improving the heat dissipation performance of the inner peripheral wall 31. This increases the cooling effect of the electric motor 12.

[0087] (9) The inner end wall 32 of the inner housing 30 has the second fins 37. This increases the surface area of ​​the inner end wall 32, improving the heat dissipation of the inner end wall 32. This improves the cooling effect of the electric motor 12.

[0088] (10) The second impeller 15 recompresses the air 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 first impeller chamber S3 side, which has a lower temperature than the second impeller chamber S5. Therefore, the temperature rise of the thrust bearing 18 can be suppressed compared to when the thrust bearing 18 is disposed on the second impeller chamber S5 side.

[0089] (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 housing 40 that defines the second impeller chamber S5 is likely to become hot. However, in this embodiment, the heat of the outer end wall 42 is dissipated to the cooling water flowing through the downstream cooling flow passage R4. Therefore, the outer end wall 42 can be cooled.

[0090] [Example of change] The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0091] The cooling fluid flowing through the flow path R is not limited to cooling water (LLC). The external cooling channel R1 may be omitted. The number of times that the motor cooling passage R2 goes around the stator 51 may be changed as appropriate.

[0092] As long as the guide wall 33 guides the cooling fluid in the motor cooling passage R2 to flow in the circumferential direction of the stator 51, the configuration of the guide wall 33 may be changed as appropriate. For example, guide wall 33 may be a wall that divides the cooling fluid in motor cooling flow channel R2 into a fluid flowing in a first direction in the circumferential direction of stator 51 and a fluid flowing in a second direction opposite to the first direction. In this case, the cooling fluid flowing in the first direction and the cooling fluid flowing in the second direction each flow halfway around stator 51 before joining together.

[0093] The guide wall 33 may protrude from the inner circumferential surface of the outer circumferential wall 41 of the outer housing 40, instead of protruding from the outer circumferential surface of the inner circumferential wall 31 of the inner housing 30. The guide wall 33 may also protrude from both the outer circumferential surface of the inner circumferential wall 31 of the inner housing 30 and the inner circumferential surface of the outer circumferential wall 41 of the outer housing 40. In other words, the guide wall 33 may be provided on at least one of the inner housing 30 and the outer housing 40. Note 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.

[0094] The bearing cooling channel R3 does not have to surround the thrust bearing 18. As long as the thrust bearing 18 is cooled by the cooling fluid flowing through the bearing cooling channel R3, the shape of the bearing cooling channel R3 may be changed as appropriate. For example, the bearing cooling channel R3 may be a semicircular arc channel provided around half the circumference of the thrust bearing 18.

[0095] The bearing cooling channel R3 does not have to be a channel in which the cooling fluid flows in one direction in the circumferential direction of the thrust bearing 18. For example, the bearing cooling channel R3 may be an annular channel that surrounds the thrust bearing 18. The inlet and outlet of the bearing cooling channel R3 are located at positions that are offset by 180 degrees in the circumferential direction of the bearing cooling channel R3. In this case, the cooling fluid that flows into the bearing cooling channel R3 is divided into fluid that flows in a first direction in the circumferential direction of the thrust bearing 18 and fluid that flows in a second direction that is opposite to the first direction. After flowing halfway around the thrust bearing 18, the cooling fluid merges at the outlet of the bearing cooling channel R3.

[0096] The downstream cooling passage R4 may be omitted. In this case, the inner end wall 32 of the inner housing 30 is omitted. The downstream cooling passage R4 does not have to be defined by the inner end wall 32 of the inner housing 30 and the outer end wall 42 of the outer housing 40.

[0097] For example, the outer housing 40 does not have to have the outer end wall 42. In other words, the outer housing 40 may be formed only by the outer peripheral wall 41. The outer plate 21 closes one opening of the outer housing 40. The housing 11 has a closing plate that closes the other opening of the outer housing 40. The closing plate has a first bearing retaining portion that retains the second radial bearing 17. In this case, the downstream cooling flow passage R4 is defined by the inner end wall 32 of the inner housing 30 and the closing plate.

[0098] The downstream cooling channel R4 does not have to be a channel through which the cooling fluid flows in the first and second directions in the circumferential direction of the stator 51. For example, the downstream cooling channel R4 may be a channel that is partially interrupted in the circumferential direction of the stator 51, i.e., a C-shaped channel. In this case, the cooling fluid flows through the downstream cooling channel R4 in one direction in the circumferential direction of the stator 51. The configuration of the downstream cooling channel R4 may be changed as appropriate depending on the position of the outlet of the downstream cooling channel R4 that connects to the external cooling channel R1.

[0099] As long as the cooling fluid is diverted into the motor cooling channel R2 and the bearing cooling channel R3 by the diverted channel R5, the shape of the diverted channel R5 may be modified as appropriate. For example, the first diverted channel component 44 may be Y-shaped. In order to reduce the pressure loss of the cooling fluid flowing through the diverted channel R5, it is preferable that the shape of the diverted channel R5 is not complicated.

[0100] As long as the cooling fluid flowing through the bearing cooling channel R3 merges with the motor cooling channel R2 through the merge channel R6, the shape of the merge channel R6 may be modified as appropriate. In order to reduce the pressure loss of the cooling fluid flowing through the merge channel R6, it is preferable that the shape of the merge channel R6 is not complicated.

[0101] The point at which the merging passage R6 merges the cooling fluid flowing through the bearing cooling passage R3 into the motor cooling passage R2 is not limited to the point at which the motor cooling passage R2 makes one full revolution around the stator 51.

[0102] For example, the confluence passage R6 may cause the cooling fluid flowing through the bearing cooling passage R3 to merge with the second circulation passage R22 or the third circulation passage R23 of the motor cooling passage R2. For example, if the bearing cooling passage R3 is provided around half of the circumference of the thrust bearing 18, the confluence passage R6 may cause the cooling fluid flowing through the bearing cooling passage R3 to merge midway into the first-circumference passage R21 of the motor cooling passage R2.

[0103] The merging passage R6 does not have to merge the cooling fluid flowing through the bearing cooling passage R3 into the motor cooling passage R2 at one location. For example, the merging passage R6 may merge the cooling fluid flowing through the bearing cooling passage R3 into both the second-turn passage R22 and the third-turn passage R23 of the motor cooling passage R2.

[0104] The centrifugal compressor 10 may also be operated as follows. The air as a fluid drawn into the first impeller chamber S3 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 rotary shaft 13. The air compressed in the first impeller chamber S3 is decelerated as it passes through the first diffuser passage S4, and the velocity energy of the air is converted into pressure energy. The pressurized air is then discharged into the first scroll passage 23a and then supplied to the fuel cell stack.

[0105] Exhaust gas discharged from the fuel cell stack is drawn into the second scroll passage 24a. The exhaust gas drawn into the second scroll passage 24a is introduced into the second impeller chamber S5 through the second diffuser passage S6. The second impeller 15 is rotated by the kinetic energy of the exhaust gas introduced into the second impeller chamber S5. In other words, the kinetic energy of the exhaust gas is converted into rotational energy of the second impeller 15. The rotation of the second impeller 15 assists the rotation of the rotary shaft 13. Therefore, the second impeller 15 is a turbine impeller that assists the rotation of the rotary shaft 13. The exhaust gas that has passed through the second impeller chamber S5 is discharged to the outside of the housing 11.

[0106] The exhaust gas flowing through the second impeller chamber S5 contains water, so it is preferable to arrange the thrust bearing 18 on the first impeller chamber S3 side to prevent the thrust bearing 18 from rusting due to the water contained in the exhaust gas.

[0107] The centrifugal compressor 10 is not limited to being mounted on a vehicle. The housing 11 is not limited to being made of aluminum. The housing 11 may be made of other metals.

[0108] The configurations of the rotor 52 and the rotary shaft 13 of the electric motor 12 are not limited to those in the above embodiment. The centrifugal compressor 10 does not have to include the second impeller 15.

[0109] The thrust bearing 18 may rotatably support a portion of the rotary shaft 13 on the second impeller 15 side, instead of a portion of the rotary shaft 13 on the first impeller 14 side. The centrifugal compressor 10 may have a thrust bearing that rotatably supports a portion of the rotating shaft 13 on the side of the second impeller 15, in addition to the thrust bearing 18 that rotatably supports a portion of the rotating shaft 13 on the side of the first impeller 14.

[0110] The first rib 35 may be omitted. Instead of projecting from the inner end wall 32 of the inner housing 30 , the first rib 35 may project from the inner surface of the outer end wall 42 of the outer housing 40 .

[0111] The second rib 36 may be omitted. Instead of projecting from the inner end wall 32 of the inner housing 30 , the second rib 36 may project from the inner surface of the outer end wall 42 of the outer housing 40 .

[0112] The inner peripheral wall 31 of the inner housing 30 does not have to have the first fins 34 . The number and shape of the first fins 34 may be changed as appropriate.

[0113] The inner end wall 32 of the inner housing 30 does not necessarily have to have the second fins 37 . The number and shape of the second fins 37 may be changed as appropriate. [Explanation of symbols]

[0114] 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...division flow path, R6...merging flow path.

Claims

1. A rotation axis; an electric motor having a cylindrical stator and rotating the rotary shaft; an impeller that compresses a fluid by rotating integrally with the rotary shaft; a thrust bearing that rotatably supports the rotary shaft; a metal housing having a flow path through which a cooling fluid flows; Equipped with the flow path includes a motor cooling flow path through which the cooling fluid flows to cool the electric motor, and a bearing cooling flow path through which the cooling fluid flows to cool the thrust bearing, The housing includes a cylindrical inner housing that accommodates the stator, and a cylindrical outer housing that accommodates the inner housing, the motor cooling passage is defined by an outer peripheral surface of the inner housing and an inner peripheral surface of the outer housing, the flow path includes a branch flow path that branches the cooling fluid into the motor cooling flow path and the bearing cooling flow path, and a confluence flow path that merges the cooling fluid flowing through the bearing cooling flow path into the motor cooling flow path, the motor cooling passage is provided in at least one of the inner housing and the outer housing, and has a guide wall that guides the cooling fluid in the motor cooling passage so that the cooling fluid flows in a circumferential direction of the stator, the motor cooling passage is a spiral passage that makes a plurality of turns around the periphery of the stator, the bearing cooling passage is a passage surrounding the thrust bearing, the merging passage causes the cooling fluid flowing through the bearing cooling passage to merge with the motor cooling passage at a point where the motor cooling passage has made one full revolution around the stator, or midway through the motor cooling passage making one full revolution around the stator.

2. the inner housing has an inner end wall connected to one axial end of the inner peripheral wall of the inner housing, the outer housing has an outer end wall that is continuous with one axial end of the outer peripheral wall of the outer housing, the inner end wall is located between the stator and the outer end wall in the axial direction of the rotary shaft, the flow path has a downstream cooling flow path that is defined by the inner end wall and the outer end wall and into which the cooling fluid that has flowed through the motor cooling flow path flows, 2. The centrifugal compressor according to claim 1, wherein the stator is located between the bearing cooling passage and the downstream cooling passage in the axial direction of the rotating shaft.

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