CENTRIFUGAL COMPRESSOR

Abstract

A centrifugal compressor includes a motor cooling passage through which cooling fluid for cooling an electric motor flows, an air passage through which cooling air for cooling a first air bearing and a second air bearing is supplied to each of the first air bearing and the second air bearing, and a heat exchanger cooling the cooling air. The motor cooling passage includes a plurality of cooling axial passages having a first cooling axial passage through which the cooling fluid is supplied to the heat exchanger and a second cooling axial passage through which the cooling fluid is discharged from the heat exchanger. The heat exchanger has a first port communicating with the first cooling axial passage, a second port communicating with the second cooling axial passage, and a third port communicating with an air axial passage extending in an axial direction of a rotary shaft.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2021-170950 filed on Oct. 19, 2021, the entire disclosure of which is incorporated herein by reference.

BACKGROUND ART

The present disclosure relates to a centrifugal compressor. A centrifugal compressor includes a rotary shaft, an electric motor, a compressor impeller, and a housing. The electric motor drives the rotary shaft. The compressor impeller is rotated together with the rotary shaft to compress fluid. The housing has a motor chamber that accommodates the electric motor. The centrifugal compressor includes a first air bearing and a second air bearing. The first air bearing and the second air bearing are arranged in the motor chamber. The first air bearing and the second air bearing are disposed on opposite sides of the electric motor in an axial direction of the rotary shaft to rotatably support the rotary shaft. The housing has a circumferential wall that surrounds the electric motor, a first end wall that closes one of opposite openings formed on the circumferential wall, and a second end wall that closes the other of the opposite openings formed on the circumferential wall. The circumferential wall, the first end wall, and the second end wall define the motor chamber. The first end wall holds the first air bearing, and the second end wall holds the second air bearing, for example.

The centrifugal compressor may include a motor cooling passage through which cooling fluid for cooling the electric motor flows, as disclosed in Korean Patent Application Publication No. 10-2017-0088588. The motor cooling passage has a plurality of cooling axial passages extending in the axial direction of the rotary shaft and spaced from each other along a circumferential direction of the circumferential wall. In the motor cooling passage formed in the housing, the cooling axial passages adjacent to each other along the circumferential direction of the circumferential wall are connected. As a result, the motor cooling passage efficiently extends along the circumferential direction of the circumferential wall. Therefore, the electric motor surrounded by the circumferential wall is efficiently cooled by the cooling fluid flowing through the motor cooling passage.

In the centrifugal compressor, heat is easily generated in each of the first air bearing and the second air bearing due to high-speed rotation of the rotary shaft. For example, International Publication No. 2019/087869 discloses a centrifugal compressor including an air passage through which cooling air for cooling the first air bearing and the second air bearing is supplied to each of the first air bearing and the second air bearing. This kind of centrifugal compressor includes a heat exchanger configured to cool the cooling air by heat exchange between the cooling air and the cooling fluid. The cooling air cooled in the heat exchanger is supplied to each of the first air bearing and the second air bearing through the air passage, so that the first air bearing and the second air bearing are efficiently cooled.

The air passage is required to have a structure in which the cooling air efficiently flows toward a part of the first end wall holding the first air bearing and a part of the second end wall holding the second air bearing. Thus, the air passage needs to extend toward each of the first end wall and the second end wall in the housing.

In the motor cooling passage formed in the housing, the cooling axial passages adjacent to each other along the circumferential direction of the circumferential wall may be connected, as disclosed in Korean Patent Application Publication No. 10-2017-0088588. In this case, the air passage needs to be formed in the housing so as to extend toward each of the first end wall and the second end wall while avoiding the air passage from interfering with the motor cooling passage. Thus, the air passage needs to extend toward each of the first end wall and the second end wall while bypassing the motor cooling passage, which may result in an increase in size of the centrifugal compressor.

SUMMARY

In accordance with an aspect of the present disclosure, there is provided a centrifugal compressor including: a rotary shaft; an electric motor that drives the rotary shaft; a compressor impeller that is rotated together with the rotary shaft to compress fluid; a housing including a motor chamber that accommodates the electric motor; a first air bearing and a second air bearing disposed on opposite sides of the electric motor in an axial direction of the rotary shaft to rotatably support the rotary shaft; a motor cooling passage through which cooling fluid for cooling the electric motor flows; an air passage through which cooling air for cooling the first air bearing and the second air bearing is supplied to each of the first air bearing and the second air bearing; and a heat exchanger configured to cool the cooling air by heat exchange between the cooling air and the cooling fluid. The housing has a circumferential wall that surrounds the electric motor and has openings on opposite ends, a first end wall that closes one of the openings of the circumferential wall and holds the first air bearing, and a second end wall that closes the other of the openings of the circumferential wall and holds the second air bearing. The motor chamber is defined by the circumferential wall, the first end wall, and the second end wall. The motor cooling passage includes a plurality of cooling axial passages extending in the axial direction of the rotary shaft and spaced from each other along a circumferential direction of the circumferential wall. The cooling axial passages adjacent to each other along circumferential direction of the circumferential wall are connected in the motor cooling passage formed in the housing. The plurality of cooling axial passages includes a first cooling axial passage through which the cooling fluid is supplied to the heat exchanger and a second cooling axial passage through which the cooling fluid is discharged from the heat exchanger. The air passage is formed between the first cooling axial passage and the second cooling axial passage in the housing. The air passage has an air axial passage extending in the axial direction of the rotary shaft toward each of the first end wall and the second end wall, and an air radial passage that communicates with the air axial passage and through which the cooling air is supplied to the first air bearing and the second air bearing. The heat exchanger has a first port communicating with the first cooling axial passage, a second port communicating with the second cooling axial passage, and a third port communicating with the air axial passage. The heat exchanger is attached to the housing such that the first port, the second port, and the third port overlap the first cooling axial passage, the second cooling axial passage, and the air axial passage, respectively, on an outer side of the housing in a radial direction of the rotary shaft.

Other aspects and advantages of the disclosure will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure, together with objects and advantages thereof, may best be understood by reference to the following description of the embodiments together with the accompanying drawings in which:

FIG. 1 is a cross-sectional view for explaining a centrifugal compressor according to an embodiment;

FIG. 2 is an exploded perspective view schematically illustrating a relationship between a motor housing, a heat exchanger, and a second radiator;

FIG. 3 is a schematic view illustrating a motor cooling passage and an air passage being modeled;

FIG. 4 is a front view of the heat exchanger;

FIG. 5 is a cross-sectional view for explaining a centrifugal compressor according to another embodiment; and

FIG. 6 is a front view of a heat exchanger according to another embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following will describe an embodiment of a centrifugal compressor with reference to FIGS. 1 to 4. The centrifugal compressor of the present embodiment is mounted on a fuel cell vehicle.

Overall Configuration of Centrifugal Compressor 10

As illustrated in FIG. 1, a centrifugal compressor 10 includes a housing 11. The housing 11 is made of a metallic material, such as aluminum. The housing 11 has a motor housing 12, a compressor housing 13, a turbine housing 14, a first plate 15, a second plate 16, and a third plate 17.

The motor housing 12 has a tubular shape. The motor housing 12 has openings on opposite ends thereof. The first plate 15 is connected to one end of the motor housing 12 and closes one of the openings of the motor housing 12. The second plate 16 is connected to the other end of the motor housing 12 and closes the other of the openings of the motor housing 12.

The motor housing 12, the first plate 15, and the second plate 16 define a motor chamber 51. The motor chamber 51 accommodates an electric motor 18. Thus, the housing 11 has the motor chamber 51. The motor housing 12 serves as a circumferential wall surrounding the electric motor 18. The first plate 15 serves as a first end wall that closes the one of the openings of the motor housing 12. The second plate 16 serves as a second end wall that closes the other of the openings of the motor housing 12.

The first plate 15 has a first bearing holding portion 20. The first bearing holding portion 20 projects from a central portion of the first plate 15 toward the electric motor 18. The first bearing holding portion 20 has a cylindrical shape.

The first plate 15 has a chamber forming recess 15a on an end surface of the first plate 15 that is opposite from the motor housing 12. The chamber forming recess 15a has a circular hole shape. An inner space of the first bearing holding portion 20 extends through the first plate 15 and is opened at a bottom surface of the chamber forming recess 15a. The chamber forming recess 15a is formed coaxially with the first bearing holding portion 20.

The second plate 16 has a second bearing holding portion 22. The second bearing holding portion 22 projects from a central portion of the second plate 16 toward the electric motor 18. The second bearing holding portion 22 has a cylindrical shape.

The second plate 16 has a shaft insertion hole 16a at the central portion of the second plate 16. The shaft insertion hole 16a communicates with an inner space of the second bearing holding portion 22. The shaft insertion hole 16a is formed coaxially with the second bearing holding portion 22.

The third plate 17 is connected to an end surface of the first plate 15 that is opposite from the motor housing 12. The third plate 17 has a shaft insertion hole 17a at a central portion of the third plate 17. The shaft insertion hole 17a communicates with an inside of the chamber forming recess 15a. The shaft insertion hole 17a is formed coaxially with the chamber forming recess 15a and the first bearing holding portion 20. The third plate 17 and the chamber forming recess 15a of the first plate 15 define a thrust bearing accommodating chamber S2. The thrust bearing accommodating chamber S2 communicates with the inner space of the first bearing holding portion 20. The thrust bearing accommodating chamber S2 communicates with the shaft insertion hole 17a.

The compressor housing 13 has a tubular shape, and has an inlet 13a having a circular hole shape from which air is drawn into the compressor housing 13. The compressor housing 13 is connected to an end surface 17b of the third plate 17 that is opposite from the first plate 15 in a state in which the inlet 13a is formed coaxially with the shaft insertion hole 17a of the third plate 17 and the first bearing holding portion 20. The inlet 13a is opened at an end surface of the compressor housing 13 that is opposite from the third plate 17.

A first impeller chamber 13b, a discharge chamber 13c, and a first diffuser passage 13d are formed between the compressor housing 13 and the end surface 17b of the third plate 17. The first impeller chamber 13b communicates with the inlet 13a. The discharge chamber 13c extends about the axis of the inlet 13a around the first impeller chamber 13b. The first impeller chamber 13b communicates with the discharge chamber 13c through the first diffuser passage 13d. The first impeller chamber 13b communicates with the shaft insertion hole 17a of the third plate 17. The compressor housing 13 has a discharge passage 13e that communicates with the discharge chamber 13c.

The turbine housing 14 has a tubular shape, and has an outlet 14a having a circular hole shape from which air is discharged from the turbine housing 14. The turbine housing 14 is connected to an end surface 16b of the second plate 16 that is opposite from the motor housing 12 in a state in which the outlet 14a is formed coaxially with the shaft insertion hole 16a of the second plate 16 and the second bearing holding portion 22. The outlet 14a is opened at an end surface of the turbine housing 14 that is opposite from the second plate 16.

A second impeller chamber 14b, a suction chamber 14c, and a second diffuser passage 14d are formed between the turbine housing 14 and the end surface 16b of the second plate 16. The second impeller chamber 14b communicates with the outlet 14a. The suction chamber 14c extends about the axis of the outlet 14a around the second impeller chamber 14b. The second impeller chamber 14b communicates with the suction chamber 14c through the second diffuser passage 14d. The second impeller chamber 14b communicates with the shaft insertion hole 16a.

Configuration of Rotary Shaft 24

The centrifugal compressor 10 includes a rotary shaft 24. The housing 11 accommodates the rotary shaft 24. The rotary shaft 24 has a shaft main body 24a, a first supporting portion 24b, a second supporting portion 24c, and a third supporting portion 24d.

The shaft main body 24a has a first end projecting into the first impeller chamber 13b through the motor chamber 51, the inside of the first bearing holding portion 20, the thrust bearing accommodating chamber S2, and the shaft insertion hole 17a. The shaft main body 24a has a second end projecting into the second impeller chamber 14b through the motor chamber 51, the inside of the second bearing holding portion 22, and the shaft insertion hole 16a. That is, the shaft main body 24a extends through the motor chamber 51 along the axis of the motor housing 12. Therefore, an axial direction of the rotary shaft 24 coincides with an axial direction of the motor housing 12.

The first supporting portion 24b is disposed on a part of an outer peripheral surface of the shaft main body 24a, closer to the first end than a central portion of the shaft main body 24a is. The first supporting portion 24b is disposed inside the first bearing holding portion 20. The first supporting portion 24b is integrally formed with the shaft main body 24a. The first supporting portion 24b projects from the outer peripheral surface of the shaft main body 24a.

The second supporting portion 24c is disposed on a part of the outer peripheral surface of the shaft main body 24a, closer to the second end than the central portion of the shaft main body 24a is. The second supporting portion 24c is disposed inside the second bearing holding portion 22. The second supporting portion 24c is fixed to the outer peripheral surface of the shaft main body 24a while annularly projecting from the outer peripheral surface of the shaft main body 24a. The second supporting portion 24c is rotatable together with the shaft main body 24a.

The third supporting portion 24d is disposed on a part of the outer peripheral surface of the shaft main body 24a, closer to the first end than the first supporting portion 24b is. The third supporting portion 24d is disposed inside the thrust bearing accommodating chamber S2. The third supporting portion 24d is fixed to the outer peripheral surface of the shaft main body 24a while annularly projecting from the outer peripheral surface of the shaft main body 24a. The third supporting portion 24d is rotatable together with the shaft main body 24a.

A first sealing member 27 is disposed between the shaft insertion hole 17a of the third plate 17 and the rotary shaft 24. The first sealing member 27 prevents leakage of the air flowing from the first impeller chamber 13b toward the motor chamber S1. A second sealing member 28 is disposed between the shaft insertion hole 16a of the second plate 16 and the rotary shaft 24. The second sealing member 28 prevents leakage of the air flowing from the second impeller chamber 14b toward the motor chamber S1. Each of the first sealing member 27 and the second sealing member 28 is a seal ring, for example.

Compressor Impeller 25

The centrifugal compressor 10 includes a compressor impeller 25. The compressor impeller 25 is connected to the first end of the shaft main body 24a. The compressor impeller 25 is disposed at a part of the shaft main body 24a, closer to the first end of the shaft main body 24a than the third supporting portion 24d is. The compressor impeller 25 is accommodated in the first impeller chamber 13b. The compressor impeller 25 is rotatable together with the shaft main body 24a. Therefore, the compressor impeller 25 is rotated together with the rotary shaft 24.

Turbine Wheel 26

The centrifugal compressor 10 includes a turbine wheel 26. The turbine wheel 26 is connected to the second end of the shaft main body 24a. The turbine wheel 26 is disposed at a part of the shaft main body 24a, closer to the second end of the shaft main body 24a than the second supporting portion 24c is. The turbine wheel 26 is accommodated in the second impeller chamber 14b. The turbine wheel 26 is rotatable together with the shaft main body 24a. Therefore, the turbine wheel 26 is rotated together with the rotary shaft 24.

Configuration of Electric Motor 18

The electric motor 18 includes a rotor 31 and a stator 32 each having a tubular shape. The rotor 31 is fixed to the shaft main body 24a. The stator 32 is fixed to an inner peripheral surface of the motor housing 12. The rotor 31 is disposed inside the stator 32 along a radial direction thereof. The rotor 31 is rotated together with the shaft main body 24a. The rotor 31 has a cylindrical rotor core 31a fixed to the shaft main body 24a and a plurality of permanent magnets (not illustrated) disposed in the rotor core 31a.

The stator 32 surrounds the rotor 31. The stator 32 includes a stator core 33 and a coil 34. The stator core 33 has a cylindrical shape and is fixed to the inner peripheral surface of the motor housing 12. The coil 34 is wound around the stator core 33. When an electric current from a battery (not illustrated) flows through the coil 34, the rotary shaft 24 is rotated together with the rotor 31. Thus, the electric motor 18 drives the rotary shaft 24. That is, the electric motor 18 is a driving power source for rotating the rotary shaft 24. The electric motor 18 is disposed between the compressor impeller 25 and the turbine wheel 26 in the axial direction of the rotary shaft 24.

First Air Bearing 21 and Second Air Bearing 23

The centrifugal compressor 10 includes a first air bearing 21 and a second air bearing 23. The first air bearing 21 has a cylindrical shape. The first air bearing 21 is held by the first bearing holding portion 20. Therefore, the first plate 15 holds the first air bearing 21. The first air bearing 21 is positioned closer to the first end of the shaft main body 24a than the electric motor 18 is. The first air bearing 21 supports the first supporting portion 24b.

The first air bearing 21 supports the rotary shaft 24 while being in contact with the first supporting portion 24b until a rotational speed of the rotary shaft 24 reaches a levitation rotational speed at which the rotary shaft 24 is levitated by the first air bearing 21. When the rotational speed of the rotary shaft 24 reaches the levitation rotational speed, the first supporting portion 24b is levitated to the first air bearing 21 due to dynamic pressure of a pneumatic layer generated between the first supporting portion 24b and the first air bearing 21. Accordingly, the first air bearing 21 supports the rotary shaft 24 without being in contact with the first supporting portion 24b.

The second air bearing 23 has a cylindrical shape. The second air bearing 23 is held by the second bearing holding portion 22. Thus, the second plate 16 holds the second air bearing 23. The second air bearing 23 is positioned closer to the second end of the shaft main body 24a than the electric motor 18 is. The second air bearing 23 supports the second supporting portion 24c.

The second air bearing 23 supports the rotary shaft 24 while being in contact with the second supporting portion 24c until the rotational speed of the rotary shaft 24 reaches a levitation rotational speed at which the rotary shaft 24 is levitated by the second air bearing 23. When the rotational speed of the rotary shaft 24 reaches the levitation rotational speed, the second supporting portion 24c is levitated to the second air bearing 23 due to dynamic pressure of a pneumatic layer generated between the second supporting portion 24c and the second air bearing 23. Accordingly, the second air bearing 23 supports the rotary shaft 24 without being in contact with the second supporting portion 24c. Therefore, the first air beating 21 and the second air bearing 23 are disposed on opposite sides of the electric motor 18 in the axial direction of the rotary shaft 24 to rotatably support the rotary shaft 24.

Thrust Bearing 29

The thrust bearing 29 rotatably supports the rotary shaft 24 in a thrust direction. The “thrust direction” corresponds to the axial direction of the rotary shaft 24. The thrust bearing 29 is disposed in the thrust bearing accommodating chamber S2. The thrust bearing 29 is an air bearing.

The thrust bearing 29 supports the rotary shaft 24 while being in contact with the third supporting portion 24d until the rotational speed of the rotary shaft 24 reaches a levitation rotational speed at which the rotary shaft 24 is levitated by the thrust bearing 29. When the rotational speed of the rotary shaft 24 reaches the levitation rotational speed, the third supporting portion 24d is levitated to the thrust beating 29 due to dynamic pressure of a pneumatic layer generated between the third supporting portion 24d and the thrust bearing 29. Accordingly, the thrust bearing 29 supports the rotary shaft 24 without being in contact with the third supporting portion 24d. Thus, the thrust bearing 29 rotatably supports the rotary shaft 24 in the thrust direction. The thrust bearing 29 receives differential pressure between the compressor impeller 25 and the turbine wheel 26.

Fuel Cell System 40

The centrifugal compressor 10 with the aforementioned configuration forms a part of a fuel cell system 40 that is mounted to the fuel cell vehicle. The fuel cell system 40 includes a fuel cell stack 41, a supply passage 42, and a discharge passage 43, in addition to the centrifugal compressor 10. The fuel cell stack 41 includes a plurality of fuel cells. The plurality of fuel cells is not illustrated for convenience of description. The fuel cell stack 41 is connected to the discharge passage 13e through the supply passage 42. The fuel cell stack 41 is connected to the suction chamber 14c through the discharge passage 43.

When the rotary shaft 24 is rotated together with the rotor 31, the compressor impeller 25 and the turbine wheel 26 are rotated together with the rotary shaft 24. Then, air drawn from the inlet 13a is compressed by the compressor impeller 25 in the first impeller chamber 13b. Therefore, the compressor impeller 25 is rotated together with the rotary shaft 24 to compress the air.

The air compressed in the first impeller chamber 13b passes through the first diffuser passage 13d and is discharged from the discharge chamber 13c. The air discharged from the discharge chamber 13c is discharged to the supply passage 42 through the discharge passage 13e. The air discharged to the supply passage 42 is supplied to the fuel cell stack 41 through the supply passage 42. Thus, the centrifugal compressor 10 supplies the air to the fuel cell stack 41. Oxygen contained in the air supplied to the fuel cell stack 41 is useful for power generation of the fuel cell stack 41.

Here, the air supplied to the fuel cell stack 41 contains merely about 20% of the oxygen being useful for the power generation of the fuel cell stack 41. Therefore, about 80% of the air supplied to the fuel cell stack 41 is discharged as a discharge gas from the fuel cell stack 41 to the discharge passage 43 without being used for the power generation of the fuel cell stack 41. The discharge gas discharged to the discharge passage 43 is drawn into the suction chamber 14c through the discharge passage 43. The discharge gas drawn into the suction chamber 14c is introduced into the second impeller chamber 14b through the second diffuser passage 14d. Then, kinetic energy of the discharge gas introduced into the second impeller chamber 14b is used to rotate the turbine wheel 26. As a result, the kinetic energy of the discharge gas is converted to rotational energy of the turbine wheel 26. The rotational energy generated in the turbine wheel 26 assists rotation of the rotary shaft 24. The discharge gas having passed through the second impeller chamber 14b is discharged from the outlet 14a to the outside.

Coolant Circuit 45

The fuel cell system 40 includes a coolant circuit 45. The coolant circuit 45 has a pump 46, a first radiator 47, and a second radiator 48. Coolant (LLC: Long Life Coolant) circulates in the coolant circuit 45. The pump 46 pumps the coolant flowing in the coolant circuit 45. The coolant circulating in the coolant circuit 45 is cooled by heat exchange between the coolant inside the coolant circuit 45 and air outside the coolant circuit 45 via the first radiator 47, when passing through the first radiator 47.

As illustrated in FIG. 2, the motor housing 12 has an attaching surface 121 to which the second radiator 48 is attached. FIG. 2 schematically illustrates the motor housing 12. The attaching surface 121 has a flat surface shape. The second radiator 48 has one surface serving as an attachment surface 481 to be attached to the attaching surface 121 of the motor housing 12. The attachment surface 481 of the second radiator 48 has a supply port 48a and a discharge port 48b.

Motor Cooling Passage 50, Air Passage 60, and Heat Exchanger 70

As illustrated in FIG. 1, the centrifugal compressor 10 includes a motor cooling passage 50, an air passage 60, and a heat exchanger 70. Coolant serving as cooling fluid for cooling the electric motor 18 flows through the motor cooling passage 50. Cooling air for cooling the first air bearing 21 and the second air bearing 23 is supplied to each of the first air bearing 21 and the second air bearing 23 through the air passage 60. The heat exchanger 70 is attached to the housing 11 in order to cool the cooling air.

Configuration of Motor Cooling Passage 50

As illustrated in FIGS. 2 and 3, the motor cooling passage 50 includes a plurality of cooling axial passages 51 extending in the axial direction of the rotary shaft 24 inside the motor housing 12 and spaced from each other along a circumferential direction of the motor housing 12. FIG. 3 illustrates the motor cooling passage 50 being modeled. In the motor cooling passage 50 formed in the housing 11, the cooling axial passages 51 adjacent to each other along the circumferential direction of the motor housing 12 are connected.

Specifically, a recess 151 is formed on an end surface of the first plate 15 close to the motor housing 12, as illustrated in FIG. 1. A recess 161 is formed on an end surface of the second plate 16 close to the motor housing 12. As illustrated in FIG. 3, the cooling axial passages 51 adjacent to each other along the circumferential direction of the motor housing 12 are connected one another via the recess 151 of the first plate 15 and the recess 161 of the second plate 16.

The plurality of cooling axial passages 51 includes a first cooling axial passage 52 through which the coolant is supplied to the heat exchanger 70 and a second cooling axial passage 53 through which the coolant is discharged from the heat exchanger 70. The plurality of cooling axial passages 51 includes a third cooling axial passage 54 through which the coolant is supplied to the second radiator 48 and a fourth cooling axial passage 55 through which the coolant is discharged from the second radiator 48. The third cooling axial passage 54 and the fourth cooling axial passage 55 are arranged adjacent to each other along the circumferential direction of the motor housing 12.

The motor cooling passage 50 includes a first connecting passage 56 and a second connecting passage 57. The first connecting passage 56 and the second connecting passage 57 are formed in the motor housing 12. One end of the first connecting passage 56 communicates with the third cooling axial passage 54. The other end of the first connecting passage 56 is opened at the attaching surface 121 of the motor housing 12. Then, the other end of the first connecting passage 56 communicates with the supply port 48a of the second radiator 48.

One end of the second connecting passage 57 communicates with the fourth cooling axial passage 55. The other end of the second connecting passage 57 is opened at the attaching surface 121 of the motor housing 12. Then, the other end of the second connecting passage 57 communicates with the discharge port 48b of the second radiator 48.

The motor cooling passage 50 includes a cooling fluid supply passage 58 and a cooling fluid discharge passage 59. The cooling fluid supply passage 58 communicates with the second cooling axial passage 53. The coolant is supplied to the second cooling axial passage 53 through the cooling fluid supply passage 58. The cooling fluid discharge passage 59 communicates with the first cooling axial passage 52. The coolant is discharged from the first cooling axial passage 52 into the cooling fluid discharge passage 59.

Configuration of Air Passage 60

The air passage 60 includes an air axial passage 61. FIG. 3 illustrates the air passage 60 being modeled. The air axial passage 61 is formed in the motor housing 12. The air axial passage 61 is positioned between the first cooling axial passage 52 and the second cooling axial passage 53 along the circumferential direction of the motor housing 12, and extends in the axial direction of the rotary shaft 24 toward each of the first plate 15 and the second plate 16.

The air passage 60 includes an air supply passage 62. The air supply passage 62 communicates with the air axial passage 61. Specifically, the air supply passage 62 communicates with a part of the air axial passage 61 that is closer to the second plate 16 than a central portion of the air axial passage 61 in the axial direction thereof is. The cooling air is supplied to the air axial passage 61 through the air supply passage 62.

As illustrated in FIG. 1, the air passage 60 includes a first air radial passage 63 and a second air radial passage 64 serving as an air radial passage that communicates with the air axial passage 61. The cooling air is supplied to the first air bearing 21 through the first air radial passage 63. The cooling air is supplied to the second air bearing 23 through the second air radial passage 64. The first air radial passage 63 is connected to one end of the air axial passage 61. The first air radial passage 63 extends in a radial direction of the rotary shaft 24 inside the first plate 15. The first air radial passage 63 communicates with the thrust bearing accommodating chamber S2. The cooling air is supplied to the thrust bearing accommodating chamber S2 through the first air radial passage 63.

The second air radial passage 64 is connected to the other end of the air axial passage 61. The second air radial passage 64 extends in the radial direction of the rotary shaft 24 inside the second plate 16. The second air radial passage 64 communicates with the shaft insertion hole 16a. The cooling air is supplied to the shaft insertion hole 16a through the second air radial passage 64.

Air Discharge Passage 65

The centrifugal compressor 10 includes an air discharge passage 65. One end of the air discharge passage 65 communicates with the motor chamber S1. The other end of the air discharge passage 65 communicates with the outlet 14a of the turbine housing 14. The air discharge passage 65 extends inside the second plate 16 and inside the turbine housing 14. The cooling air in the motor chamber S1 is discharged from the outlet 14a through the air discharge passage 65.

Attaching Surface 80

As illustrated in FIG. 2, the motor housing 12 has an attaching surface 80 to which the heat exchanger 70 is attached, on a part of the outer peripheral surface of the motor housing 12. The attaching surface 80 is a flat surface. The attaching surface 80 has an opening at which one end of the cooling fluid supply passage 58 opposite to the other end thereof in communication with the second cooling axial passage 53 is opened. The attaching surface 80 has an opening at which one end of the cooling fluid discharge passage 59 opposite to the other end thereof in communication with the first cooling axial passage 52 is opened. The attaching surface 80 has an opening at which one end of the air supply passage 62 opposite to the other end thereof in communication with the air axial passage 61 is opened. Thus, the cooling fluid supply passage 58, the cooling fluid discharge passage 59, and the air supply passage 62 are opened at the attaching surface 80. The attaching surface 80 overlaps each of the first cooling axial passage 52, the second cooling axial passage 53, and the air axial passage 61 on an outer side of the motor housing 12 in the radial direction of the rotary shaft 24.

Configuration of Heat Exchanger 70

The heat exchanger 70 has a flat square box shape. The heat exchanger 70 is attached to the attaching surface 80 of the motor housing 12 using a bolt (not illustrated), for example. The heat exchanger 70 cools the cooling air by heat exchange between the cooling air and the coolant having passed through the motor cooling passage 50. The heat exchanger 70 has an attachment surface 70a to be attached to the attaching surface 80 of the motor housing 12.

As illustrated in FIG. 4, a first port 71, a second port 72, and a third port 73 are opened at the attachment surface 70a. The first port 71 communicates with the cooling fluid discharge passage 59. Thus, the first port 71 communicates with the first cooling axial passage 52 through the cooling fluid discharge passage 59. The second port 72 communicates with the cooling fluid supply passage 58. Thus, the second port 72 communicates with the second cooling axial passage 53 through the cooling fluid supply passage 58. The third port 73 communicates with the air supply passage 62. Thus, the third port 73 communicates with the air axial passage 61 through the air supply passage 62. The heat exchanger 70 has a fourth port 74 that is opened on an end surface of the heat exchanger 70 opposite to the attachment surface 70a. As illustrated in FIG. 2, a joint 75 is coupled to the fourth port 74. The joint 75 is a pipe bent into L-shape, for example.

Branch Pipe 90

As illustrated in FIG. 1, the centrifugal compressor 10 includes a branch pipe 90. One end of the branch pipe 90 branches from a part of the discharge passage 13e and extends outward from the compressor housing 13. The other end of the branch pipe 90 opposite to the discharge passage 13e is connected to the joint 75. The one end of the branch pipe 90 communicates with the discharge passage 13e. The other end of the branch pipe 90 communicates with the fourth port 74 of the heat exchanger 70 through the joint 75. A part of air passing through the discharge passage 13e flows into the heat exchanger 70 through the branch pipe 90, the joint 75, and the fourth port 74. Therefore, the cooling air passing through the heat exchanger 70 is a part of the air compressed by the compressor impeller 25.

Operations

Next, the following will explain operations of the centrifugal compressor according to the present embodiment.

The coolant passes through the inside of the heat exchanger 70 and is discharged from the heat exchanger 70 into the cooling fluid supply passage 58 through the first port 71. Then, the coolant passes through the cooling fluid supply passage 58 and is discharged into the second cooling axial passage 53.

The coolant flows from the second cooling axial passage 53 to the third cooling axial passage 54 in the motor cooling passage 50. After that, the coolant having reached the third cooling axial passage 54 is supplied to the second radiator 48 through the first connecting passage 56 and the supply port 48a of the second radiator 48. The coolant supplied to the second radiator 48 is cooled in the second radiator 48 by heat exchange between the coolant in the second radiator 48 and the coolant circulating in the coolant circuit 45.

The coolant cooled in the second radiator 48 is discharged from the second radiator 48 to the second connecting passage 57 through the discharge port 48b. The coolant discharged to the second connecting passage 57 passes through the second connecting passage 57 and is discharged to the fourth cooling axial passage 55 in the motor cooling passage 50. The coolant flows from the fourth cooling axial passage 55 toward the first cooling axial passage 52 in the motor cooling passage 50. Then, the coolant having reached the first cooling axial passage 52 is supplied to the heat exchanger 70 through the cooling fluid discharge passage 59 and the second port 72. The coolant flows through the motor cooling passage 50 as described above, so that the electric motor 18 surrounded by the motor housing 12 is cooled by the coolant flowing through the motor cooling passage 50.

A part of the air passing through the discharge passage 13e flows into the heat exchanger 70 through the branch pipe 90, the joint 75, and the fourth port 74 and serves as the cooling air for cooling the first air bearing 21 and the second air bearing 23. The cooling air passing through the heat exchanger 70 is cooled by heat exchange between the cooling air and the coolant passing through the heat exchanger 70. Then, the cooling air having passed through the heat exchanger 70 flows into the air supply passage 62 through the third port 73. The cooling air having flowed into the air supply passage 62 flows toward both the first plate 15 and the second plate 16 through the air axial passage 61. The cooling air flowing toward the first plate 15 through the air axial passage 61 corresponds to a first cooling air, and the cooling air flowing toward the second plate 16 through the air axial passage 61 corresponds to a second cooling air.

The first cooling air flowing toward the first plate 15 through the air axial passage 61 flows into the first air radial passage 63. The first cooling air flowing through the first air radial passage 63 is supplied into the thrust bearing accommodating chamber S2. The first cooling air supplied into the thrust bearing accommodating chamber S2 cools the thrust bearing 29. Then, the first cooling air having cooled the thrust bearing 29 flows into the first bearing holding portion 20 and is supplied to the first air bearing 21 to cool the first air beating 21. The first cooling air having cooled the first air bearing 21 flows toward the air discharge passage 65 while cooling the electric motor 18 in the motor chamber S1.

On the other hand, the second cooling air flowing toward the second plate 16 through the air axial passage 61 flows toward the second air radial passage 64. The second cooling air flowing through the second air radial passage 64 is supplied into the shaft insertion hole 16a. The second cooling air supplied into the shaft insertion hole 16a flows into the second bearing holding portion 22 and is supplied to the second air bearing 23 to cool the second air bearing 23. The second cooling air having cooled the second air bearing 23 flows toward the air discharge passage 65 in the motor chamber S1. The second cooling air in the electric motor 18 passes through the air discharge passage 65 and is discharged from the outlet 14a to the outside. As described above, the thrust bearing 29, the first air bearing 21, and the second air bearing 23 are cooled by the first cooling air and the second cooling air, respectively.

Effects

The aforementioned embodiment provides following advantageous effects.

(1) The air axial passage 61 of the air passage 60 is positioned between the first cooling axial passage 52 and the second cooling axial passage 53 and extends in the axial direction of the rotary shaft 24 toward each of the first plate 15 and the second plate 16. As a result, the air passage 60 need not extend toward each of the first plate 15 and the second plate 16 while bypassing the motor cooling passage 50, which downsizes the centrifugal compressor 10. Then, the first cooling air and the second cooling air having flowed through the air axial passage 61 are supplied to the first air bearing 21 and the second air bearing 23 through the first air radial passage 63 and the second air radial passage 64, respectively, so that the first air bearing 21 and the second air bearing 23 are efficiently cooled by the first cooling air and the second cooling air. The heat exchanger 70 is attached to the motor housing 12 such that the first port 71, the second port 72, and the third port 73 overlap the first cooling axial passage 52, the second cooling axial passage 53, and the air axial passage 61, respectively, on an outer side of the motor housing 12 in the radial direction of the rotary shaft 24. The aforementioned configuration downsizes the centrifugal compressor 10.

(2) The cooling fluid supply passage 58, the cooling fluid discharge passage 59, and the air supply passage 62 are opened at the attaching surface 80 of the motor housing 12. The first port 71 communicating with the cooling fluid discharge passage 59, the second port 72 communicating with the cooling fluid supply passage 58, and the third port 73 communicating with the air supply passage 62 are opened at the attachment surface 70a of the heat exchanger 70. Accordingly, the length of each of the cooling fluid supply passage 58, the cooling fluid discharge passage 59, and the air supply passage 62 is shortened as much as possible. As a result, the aforementioned configuration further downsizes the centrifugal compressor 10.

(3) The cooling air passing through the heat exchanger 70 is a part of the air compressed by the compressor impeller 25. Accordingly, a part of the air compressed by the compressor impeller 25 is used as the first cooling air and the second cooling air for cooling the first air bearing 21 and the second air bearing 23, respectively. Thus, air that differs from the air compressed by the compressor impeller 25 need not be supplied to each of the first air bearing 21 and the second air bearing 23 through the air passage 60 while serving as the first cooling air and the second cooling air for cooling the first air bearing 21 and the second air bearing 23, respectively. As a result, a configuration in which the first air bearing 21 and the second air bearing 23 are cooled can be simplified.

Modifications

The aforementioned embodiment may be modified as follows. The embodiment may be combined with the following modifications within technically consistent range.

As illustrated in FIG. 5, the housing 11 may have an air branch passage 91 through which a part of the air compressed by the compressor impeller 25 flows. The air branch passage 91 is opened at the attaching surface 80. As illustrated in FIG. 6, the attachment surface 70a of the heat exchanger 70 has a fourth port 92 that communicates with the air branch passage 91. The air flowing through the air branch passage 91 passes through the inside of the heat exchanger 70 via the fourth port 92 while serving as cooling air for cooling the first air bearing 21 and the second air bearing 23. Therefore, the cooling air passing through the heat exchanger 70 is a part of the air corresponding to fluid compressed by the compressor impeller 25.

Accordingly, a part of the air compressed by the compressor impeller 25 is used as the cooling air for cooling the first air bearing 21 and the second air bearing 23. Thus, air that differs from the air compressed by the compressor impeller 25 need not be supplied to each of the first air bearing 21 and the second air bearing 23 through the air passage 60 while serving as the cooling air for cooling the first air bearing 21 and the second air bearing 23. As a result, a configuration in which the first air bearing 21 and the second air bearing 23 are cooled can be simplified. The housing 11 has the air branch passage 91 that is opened at the attaching surface 80 and through which a part of the air compressed by the compressor impeller 25 flows. The attachment surface 70a has the opening corresponding to the fourth port 92 that communicates with the air branch passage 91. The aforementioned configuration shortens the length of the air branch passage 91 as much as possible and further downsizes the centrifugal compressor 10.

In the aforementioned embodiment, air that differs from the air compressed by the compressor impeller 25 may be supplied to each of the first air bearing 21 and the second air beating 23 through the air passage 60 while serving as the cooling air for cooling the first air bearing 21 and the second air bearing 23.

In the aforementioned embodiment, a shape of the heat exchanger 70 is not limited to the flat square box shape.

In the aforementioned embodiment, the supply port 48a and the discharge port 48b need not be formed on the attachment surface 481 of the second radiator 48, but may be formed on a surface other than the attachment surface 481 of the second radiator 48. That is, the supply port 48a and the discharge port 48b may be formed in the second radiator 48 at any opening positions as long as the first connecting passage 56 communicates with the supply port 48a and the second connecting passage 57 communicates with the discharge port 48b.

In the aforementioned embodiment, the cooling axial passages 51 and the air axial passage 61 need not be completely parallel to the axial direction of the rotary shaft 24, and may bend or extend diagonally in the axial direction of the rotary shaft 24 within a predetermined tolerance.

In the aforementioned embodiment, the first air radial passage 63 and the second air radial passage 64 need not be completely parallel to the radial direction of the rotary shaft 24, and may bend or extend diagonally in the radial direction of the rotary shaft 24 within a predetermined tolerance.

In the aforementioned embodiment, the centrifugal compressor 10 is mounted to a fuel cell vehicle and is used for supplying air to the fuel cell stack 41, but the centrifugal compressor 10 may be used for a vehicle air conditioner and may be configured to compress refrigerant as fluid, for example. The centrifugal compressor 10 may be mounted to anything other than the vehicle.

Claims

1. A centrifugal compressor comprising:

a rotary shaft;

an electric motor that drives the rotary shaft;

a compressor impeller that is rotated together with the rotary shaft to compress fluid;

a housing including a motor chamber that accommodates the electric motor;

a first air bearing and a second air bearing disposed on opposite sides of the electric motor in an axial direction of the rotary shaft to rotatably support the rotary shaft;

a motor cooling passage through which cooling fluid for cooling the electric motor flows;

an air passage through which cooling air for cooling the first air bearing and the second air bearing is supplied to each of the first air bearing and the second air bearing; and

a heat exchanger configured to cool the cooling air by heat exchange between the cooling air and the cooling fluid,

the housing having a circumferential wall that surrounds the electric motor and has openings on opposite ends, a first end wall that closes one of the openings of the circumferential wall and holds the first air bearing, and a second end wall that closes the other of the openings of the circumferential wall and holds the second air bearing,

the motor chamber being defined by the circumferential wall, the first end wall, and the second end wall,

the motor cooling passage including a plurality of cooling axial passages extending in the axial direction of the rotary shaft and spaced from each other along a circumferential direction of the circumferential wall,

the cooling axial passages adjacent to each other along the circumferential direction of the circumferential wall being connected, in the motor cooling passage formed in the housing, wherein

the plurality of cooling axial passages includes a first cooling axial passage through which the cooling fluid is supplied to the heat exchanger and a second cooling axial passage through which the cooling fluid is discharged from the heat exchanger,

the air passage has an air axial passage being positioned between the first cooling axial passage and the second cooling axial passage in the housing and extending in the axial direction of the rotary shaft toward each of the first end wall and the second end wall, and an air radial passage that communicates with the air axial passage and through which the cooling air is supplied to the first air bearing and the second air bearing,

the heat exchanger has a first port communicating with the first cooling axial passage, a second port communicating with the second cooling axial passage, and a third port communicating with the air axial passage, and

the heat exchanger is attached to the housing such that the first port, the second port, and the third port overlap the first cooling axial passage, the second cooling axial passage, and the air axial passage, respectively, on an outer side of the housing in a radial direction of the rotary shaft.

2. The centrifugal compressor according to claim 1, wherein

the motor cooling passage includes: a cooling fluid discharge passage to which the cooling fluid is discharged from the first cooling axial passage; and a cooling fluid supply passage through which the cooling fluid is supplied to the second cooling axial passage,

the air passage includes an air supply passage through which the cooling air is supplied to the air axial passage,

a part of an outer peripheral surface of the circumferential wall is an attaching surface to which the heat exchanger is attached,

the cooling fluid supply passage, the cooling fluid discharge passage, and the air supply passage are opened at the attaching surface,

the heat exchanger has an attachment surface to be attached to the attaching surface of the housing, and

the first port communicating with the cooling fluid discharge passage, the second port communicating with the cooling fluid supply passage, and the third port communicating with the air supply passage are opened at the attachment surface of the heat exchanger.

3. The centrifugal compressor according to claim 2, wherein

the cooling air passing through the heat exchanger corresponds to a part of air compressed by the compressor impeller,

the housing has an air branch passage that is opened at the attaching surface of the housing and through which a part of the air compressed by the compressor impeller flows, and

a fourth port is further opened at the attachment surface of the heat exchanger and communicates with the air branch passage.