Centrifugal compressor

Abstract

A centrifugal compressor (10) is provided with: a nozzle (73) that generates a swirling flow of air on the upstream side, in the air flow direction, of a gap (G1) between a stator (32) and a rotor (33); and a communication passage (80) that causes the swirling flow of air generated by the nozzle (73) to flow into the gap (G1). Thus, since the swirling flow of air generated by the nozzle (73) flows into the gap (G1) between the stator (32) and the rotor (33) through the communication passage (80), the swirling flow of air flowing into the gap (G1) assists the rotation of the rotor (33). As a result, the mechanical loss, so-called "windage loss", of the rotor (33) is less likely to occur. Therefore, temperature rise due to windage loss of air flowing in the gap (G1) is suppressed.

Description

centrifugal compressor

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

[0002] A centrifugal compressor includes a rotating body including a rotating shaft and an impeller. The impeller rotates integrally with the rotating shaft to compress a fluid. The centrifugal compressor includes a motor and a housing. The motor rotates the rotating shaft. The housing has a motor chamber. The motor chamber accommodates the motor. The motor includes a cylindrical stator and a rotor. The stator is fixed to the housing. The rotor rotates integrally with the rotating shaft. The rotor is disposed inside the stator. The rotor constitutes a part of the rotating body. The rotor has a magnetic material.

[0003] In such centrifugal compressors, eddy currents are generated in the magnetic material, causing heat to be generated in the magnetic material. Therefore, cooling the magnetic material has been considered, as disclosed in, for example, Patent Document 1. The housing has an inlet passage and a discharge passage. The inlet passage introduces a portion of the fluid compressed as the impeller rotates into the motor chamber. The discharge passage discharges the fluid introduced into the motor chamber from the inlet passage and passing through the gap between the stator and rotor to the outside of the housing. The magnetic material is then cooled by the fluid passing through the gap between the stator and rotor.

[0004] Japanese Patent Application Laid-Open No. 2023-43236

[0005] In such a centrifugal compressor, when the rotor rotates at high speed, the velocity of the fluid flowing through the gap between the stator and rotor increases. This increase in fluid velocity due to the high speed rotation of the rotor is caused by increased resistance due to friction between the outer circumferential surface of the rotor and the fluid. As a result, mechanical loss of the rotor, known as "windage loss," occurs. This increases the temperature of the fluid flowing through the gap between the stator and rotor. As a result, there is a risk that the magnetic material may not be efficiently cooled by the fluid flowing through the gap between the stator and rotor.

[0006] A centrifugal compressor that solves the above problem comprises a rotating body including a rotating shaft and an impeller that rotates integrally with the rotating shaft to compress a fluid, a motor that rotates the rotating shaft, and a housing having a motor chamber that accommodates the motor, wherein the motor comprises a cylindrical stator fixed to the housing and a rotor that rotates integrally with the rotating shaft, is disposed inside the stator, and forms a part of the rotating body, the rotor having a magnetic body, and the housing has an introduction passage that introduces a part of the fluid compressed as the impeller rotates into the motor chamber, and a discharge passage that discharges the fluid that has been introduced from the introduction passage into the motor chamber and passed through a gap between the stator and the rotor to the outside of the housing, wherein the magnetic body is cooled by the fluid passing through the gap, and the centrifugal compressor further comprises: a nozzle that generates a swirling flow of the fluid upstream of the gap in the flow direction of the fluid, and a communication passage that allows the swirling flow of the fluid generated by the nozzle to flow into the gap.

[0007] According to this, the swirling flow of the fluid generated by the nozzle flows into the gap between the stator and rotor through the communication passage, and the swirling flow of the fluid that flows into the gap between the stator and rotor assists the rotation of the rotor. As a result, mechanical loss of the rotor, so-called "windage loss," is less likely to occur. Therefore, the temperature rise of the fluid flowing through the gap between the stator and rotor due to windage loss can be suppressed. The suppression of the temperature rise due to windage loss makes it possible to lower the average temperature of the fluid flowing through the gap between the stator and rotor. As a result, the magnetic body can be efficiently cooled by the fluid flowing through the gap between the stator and rotor.

[0008] In the centrifugal compressor, the stator may have a stator core and coil ends that are part of a coil wound around the stator core and protrude from an end face of the stator core, and the nozzle may be located upstream of the gap in the fluid flow direction and radially inward of the coil ends of the rotating shaft.

[0009] This allows a swirling flow of the fluid to be generated by the nozzle just before the fluid flows into the gap between the stator and the rotor. Therefore, the swirling flow of the fluid can be caused to flow into the gap between the stator and the rotor while suppressing pressure loss of the swirling flow of the fluid. As a result, it is possible to further easily suppress a temperature rise of the fluid flowing through the gap between the stator and the rotor, and therefore the magnetic body can be cooled more efficiently by the fluid flowing through the gap between the stator and the rotor.

[0010] In the centrifugal compressor, the stator may include a resin molding the stator core, the resin having an end surface covering portion that covers a portion of an end surface of the stator core that is located radially inward of the coil ends in the direction of the rotating shaft, and a plurality of nozzle vanes that protrude from the end surface covering portion and are arranged circumferentially around the axis of the rotating shaft, the nozzle vanes having a curved thin plate shape such that a downstream edge located downstream in the direction of the fluid flow is closer to the gap than an upstream edge located upstream in the direction of the fluid flow and is located ahead in the direction of rotation of the rotating shaft, and the nozzles are formed by gaps between adjacent nozzle vanes in the direction of the rotating shaft. This configuration is suitable for forming nozzles that are located upstream of the gap in the direction of the fluid flow and radially inward of the coil ends in the direction of the rotating shaft.

[0011] In the centrifugal compressor, the housing may have a facing portion that faces a portion of the end face of the stator core that is located radially inward of the coil ends in the axial direction of the rotary shaft, and may include a plurality of nozzle vanes that protrude from the facing portion and are arranged side by side in the circumferential direction around the axis of the rotary shaft, the nozzle vanes having a curved thin plate shape such that a downstream edge located downstream in the fluid flow direction is closer to the gap than an upstream edge located upstream in the fluid flow direction and is located ahead in the rotation direction of the rotary shaft, and the nozzles are formed by gaps between adjacent nozzle vanes in the circumferential direction of the rotary shaft. This configuration is suitable for forming nozzles that are located upstream of the gap in the fluid flow direction and radially inward of the coil ends of the rotary shaft.

[0012] In the centrifugal compressor, the downstream end of the introduction passage located on the motor chamber side is formed to be smaller than a flow path cross-sectional area located upstream of the downstream end in the fluid flow direction, thereby forming the nozzle, and the introduction direction of the fluid from the nozzle into the motor chamber is preferably set to be the circumferential direction of the rotating shaft.

[0013] With this, the fluid is introduced into the motor chamber from the introduction passage while a swirling flow of the fluid is generated by the nozzle, and the swirling flow of the fluid introduced into the motor chamber from the introduction passage can be made to flow into the gap between the stator and the rotor via the communication passage.

[0014] According to this invention, the magnetic body can be efficiently cooled by the fluid flowing through the gap between the stator and the rotor.

[0015] FIG. 1 is a cross-sectional view of a centrifugal compressor according to an embodiment. FIG. 2 is a cross-sectional view showing an enlarged portion of the centrifugal compressor. FIG. 3 is a cross-sectional view showing an enlarged portion of the centrifugal compressor. FIG. 4 is a perspective view for explaining a nozzle. FIG. 5 is a cross-sectional view showing an enlarged portion of a centrifugal compressor according to a modified example. FIG. 6 is a cross-sectional view showing an enlarged portion of a centrifugal compressor according to a modified example. FIG. 7 is a cross-sectional view taken along line 7-7 in FIG. 6.

[0016] A centrifugal compressor according to an embodiment of the present invention will be described below with reference to Figures 1 to 4. The centrifugal compressor according to this embodiment is mounted on a fuel cell vehicle. The centrifugal compressor compresses air as a fluid.

[0017] <Basic Configuration of Centrifugal Compressor> As shown in Fig. 1 , a centrifugal compressor 10 includes a housing 11. The housing 11 is made of a metal material. For example, the housing 11 is made of aluminum. The housing 11 is cylindrical. The housing 11 includes a motor housing 12, a first compressor housing 13, a second compressor housing 14, a first plate 15, a second plate 16, and a seal plate 17.

[0018] The motor housing 12 is cylindrical. The motor housing 12 has a plate-shaped end wall 12a and a peripheral wall 12b. The peripheral wall 12b extends cylindrically from the outer periphery of the end wall 12a. The first plate 15 is connected to the end of the peripheral wall 12b of the motor housing 12 on the opening side. The first plate 15 closes the opening of the peripheral wall 12b of the motor housing 12. The end wall 12a and the peripheral wall 12b of the motor housing 12 and the first plate 15 define a motor chamber 18. Thus, the housing 11 has the motor chamber 18.

[0019] The first plate 15 has a first recess 15a and a second recess 15b. The first recess 15a and the second recess 15b are formed on the end surface of the first plate 15 opposite the motor housing 12. The first recess 15a and the second recess 15b are circular holes. The inner diameter of the first recess 15a is larger than the inner diameter of the second recess 15b. The second recess 15b is formed on the bottom surface of the first recess 15a. The axis of the first recess 15a and the axis of the second recess 15b are aligned.

[0020] The seal plate 17 is fitted into the first recess 15a. The seal plate 17 is attached to the first plate 15, for example, by bolts (not shown). The seal plate 17 closes the opening of the second recess 15b. The seal plate 17 and the second recess 15b define a thrust bearing accommodating chamber 19. Therefore, the housing 11 has the thrust bearing accommodating chamber 19. The seal plate 17 also has a shaft insertion hole 17h. The shaft insertion hole 17h is formed in the center of the seal plate 17. The shaft insertion hole 17h opens into the thrust bearing accommodating chamber 19.

[0021] The first plate 15 has a first radial bearing retaining portion 21. The first radial bearing retaining portion 21 is cylindrical. The first radial bearing retaining portion 21 protrudes into the motor chamber 18 from the center of the end face of the first plate 15 that faces the motor housing 12. The inside of the first radial bearing retaining portion 21 communicates with the motor chamber 18. The inside of the first radial bearing retaining portion 21 penetrates the first plate 15 and opens to the bottom surface of the second recess 15b. Therefore, the inside of the first radial bearing retaining portion 21 communicates with the thrust bearing accommodating chamber 19. The axis of the first radial bearing retaining portion 21 coincides with the axis of the first recess 15a and the axis of the second recess 15b.

[0022] The first compressor housing 13 is cylindrical. The first compressor housing 13 has a first suction port 22 that is a circular hole. Therefore, the housing 11 has the first suction port 22. The first compressor housing 13 is connected to an end surface of the first plate 15 that is located opposite the motor housing 12, with the axis of the first suction port 22 coinciding with the axis of the shaft insertion hole 17h of the seal plate 17. The first suction port 22 opens to an end surface of the first compressor housing 13 that is located opposite the first plate 15. Air that has been purified by an air cleaner (not shown) flows through the first suction port 22.

[0023] The centrifugal compressor 10 includes a first impeller chamber 23, a first discharge chamber 24, and a first diffuser passage 25. The first impeller chamber 23, the first discharge chamber 24, and the first diffuser passage 25 are formed between the first compressor housing 13 and the seal plate 17. Therefore, the housing 11 has the first impeller chamber 23. The seal plate 17 separates the first impeller chamber 23 from the thrust bearing accommodating chamber 19. The first impeller chamber 23 communicates with the first suction port 22. The first impeller chamber 23 has a generally truncated conical hole shape whose diameter gradually increases with increasing distance from the first suction port 22. The first discharge chamber 24 extends around the axis of the first suction port 22 around the periphery of the first impeller chamber 23. The first diffuser passage 25 communicates the first impeller chamber 23 and the first discharge chamber 24. The first impeller chamber 23 communicates with the shaft insertion hole 17 h of the seal plate 17 .

[0024] The motor housing 12 has a second radial bearing holder 26. The second radial bearing holder 26 is cylindrical. The second radial bearing holder 26 protrudes from the center of the inner surface of the end wall 12a of the motor housing 12 into the motor chamber 18. The inside of the second radial bearing holder 26 communicates with the motor chamber 18. The inside of the second radial bearing holder 26 penetrates the end wall 12a of the motor housing 12 and opens to the outer surface of the end wall 12a. The axis of the first radial bearing holder 21 and the axis of the second radial bearing holder 26 are aligned.

[0025] The second plate 16 is connected to the outer surface of the end wall 12a of the motor housing 12. The second plate 16 has a shaft insertion hole 16h. The shaft insertion hole 16h is formed in the center of the second plate 16. The shaft insertion hole 16h communicates with the inside of the second radial bearing holder 26.

[0026] The second compressor housing 14 is cylindrical. The second compressor housing 14 has a circular hole-shaped second suction port 27. The second compressor housing 14 is connected to an end face of the second plate 16 located opposite the motor housing 12, with the axis of the second suction port 27 coinciding with the axis of the shaft insertion hole 16h of the second plate 16. The second suction port 27 opens at the end face of the second compressor housing 14 located opposite the second plate 16.

[0027] The centrifugal compressor 10 includes a second impeller chamber 28, a second discharge chamber 29, and a second diffuser passage 30. The second impeller chamber 28, the second discharge chamber 29, and the second diffuser passage 30 are formed between the second compressor housing 14 and the second plate 16. The second impeller chamber 28 is in communication with the second suction port 27. The second discharge chamber 29 extends around the axis of the second suction port 27 around the periphery of the second impeller chamber 28. The second diffuser passage 30 communicates between the second impeller chamber 28 and the second discharge chamber 29. The second impeller chamber 28 is in communication with the shaft insertion hole 16h of the second plate 16.

[0028] The centrifugal compressor 10 includes a motor 31. The motor 31 is accommodated in the motor chamber 18. Therefore, the motor chamber 18 accommodates the motor 31. The motor 31 is then accommodated in the housing 11.

[0029] The motor 31 includes a cylindrical stator 32 and a rotor 33. The stator 32 includes a cylindrical stator core 34 and coils 35. The coils 35 are wound around the stator core 34. The stator core 34 is fixed to the inner circumferential surface of the peripheral wall 12b of the motor housing 12. Therefore, the stator 32 is fixed to the housing 11. Coil ends 36, which are part of the coils 35, protrude from both end surfaces of the stator core 34. Therefore, the stator 32 has coil ends 36 that are part of the coils 35 and protrude from the end surfaces of the stator core 34. In the following description, the coil ends 36 located on the first plate 15 side of the stator core 34 will be referred to as "first coil ends 36a." Furthermore, the coil ends 36 located on the end wall 12a side of the motor housing 12 will be referred to as "second coil ends 36b."

[0030] 2, the stator 32 includes a resin 37. The resin 37 covers the stator core 34 and the coil ends 36. Thus, the resin 37 molds the stator core 34.

[0031] The resin 37 includes a first resin portion 38, a second resin portion 39, and a third resin portion 40. The first resin portion 38 is cylindrical and covers the first coil end 36a. The first resin portion 38 covers the end face of the stator core 34 that faces the first plate 15. The second resin portion 39 is cylindrical and covers the second coil end 36b. The second resin portion 39 covers the end face of the stator core 34 that faces the end wall 12a of the motor housing 12. The third resin portion 40 is cylindrical and covers the inner circumferential surface of the stator core 34. The third resin portion 40 extends inside the stator core 34 in the axial direction of the stator core 34. The third resin portion 40 connects the first resin portion 38 and the second resin portion 39.

[0032] The rotor 33 is disposed inside the stator 32. The rotor 33 has a cylindrical member 41 and a permanent magnet 42, which is a magnetic body. The cylindrical member 41 is made of, for example, a titanium alloy. The cylindrical member 41 is cylindrical with the axis of the cylindrical member 41 extending linearly. The outer diameter of the cylindrical member 41 is constant. The cylindrical member 41 passes through the inside of the third resin portion 40. The space between the outer peripheral surface of the cylindrical member 41 and the inner peripheral surface of the third resin portion 40 forms a gap G1 between the stator 32 and the rotor 33.

[0033] The permanent magnet 42 has a cylindrical shape. The permanent magnet 42 is disposed inside the cylindrical member 41. The axis of the permanent magnet 42 coincides with the axis of the cylindrical member 41. The permanent magnet 42 is press-fitted into the inner circumferential surface of the cylindrical member 41. Therefore, the permanent magnet 42 is fixed to the inside of the cylindrical member 41. The permanent magnet 42 is magnetized in the radial direction of the permanent magnet 42. Specifically, the permanent magnet 42 is magnetized in the radial direction of the permanent magnet 42, and thus has a cylindrical shape having a north pole and a south pole on both radial sides of the permanent magnet 42.

[0034] The length of the permanent magnet 42 in the axial direction is shorter than the length of the cylindrical member 41 in the axial direction. Both end faces of the permanent magnet 42 are located inside the cylindrical member 41. Therefore, both end portions located in the axial direction of the cylindrical member 41 protrude in the axial direction relative to both end faces of the permanent magnet 42. And both end portions of the cylindrical member 41 protrude in the axial direction relative to both end faces of the stator core 34.

[0035] 1, the centrifugal compressor 10 includes a rotating shaft 43. The rotating shaft 43 includes a first shaft member 44 and a second shaft member 45. The first shaft member 44 and the second shaft member 45 are provided on both sides of the permanent magnet 42 in the axial direction of the cylindrical member 41. The first shaft member 44 and the second shaft member 45 are made of, for example, iron.

[0036] A first end of the first shaft member 44 is press-fitted into the inner peripheral surface of the first end of the cylindrical member 41. Therefore, the first shaft member 44 is fixed to the cylindrical member 41. A second end of the first shaft member 44 passes from the motor chamber 18 through the inside of the first radial bearing holder 21, the thrust bearing accommodating chamber 19, and the shaft insertion hole 17h, and protrudes into the first impeller chamber 23.

[0037] A first end of the second shaft member 45 is press-fitted into the inner circumferential surface of the second end of the cylindrical member 41. Therefore, the second shaft member 45 is fixed to the cylindrical member 41. The second end of the second shaft member 45 passes from the motor chamber 18 to the inside of the second radial bearing holder 26 and through the shaft insertion hole 16h, and protrudes into the second impeller chamber 28.

[0038] The axis of the cylindrical member 41, the axis of the first shaft member 44, and the axis of the second shaft member 45 are aligned. The axial direction of each of the cylindrical member 41, the first shaft member 44, and the second shaft member 45 is the axial direction of the rotation shaft 43. The direction perpendicular to the axial direction of the rotation shaft 43 is the radial direction of the rotation shaft 43.

[0039] The centrifugal compressor 10 includes a first seal member 46. The first seal member 46 is provided between the shaft insertion hole 17h of the seal plate 17 and the first shaft member 44. The first seal member 46 suppresses air leakage from the first impeller chamber 23 toward the motor chamber 18. The centrifugal compressor 10 includes a second seal member 47. The second seal member 47 is provided between the shaft insertion hole 16h of the second plate 16 and the second shaft member 45. The second seal member 47 suppresses air leakage from the second impeller chamber 28 toward the motor chamber 18. The first seal member 46 and the second seal member 47 are, for example, seal rings.

[0040] The centrifugal compressor 10 includes a thrust collar 48. The thrust collar 48 protrudes annularly from the outer circumferential surface of the first shaft member 44. The thrust collar 48 is disk-shaped. The thrust collar 48 is fixed to the outer circumferential surface of the first shaft member 44 in a state where it protrudes annularly from the outer circumferential surface of the first shaft member 44 outward in the radial direction of the rotary shaft 43. Therefore, the thrust collar 48 is separate from the first shaft member 44. The thrust collar 48 is disposed in the thrust bearing accommodating chamber 19. The thrust collar 48 rotates integrally with the first shaft member 44.

[0041] The centrifugal compressor 10 includes a first impeller 49. The first impeller 49 is attached to the second end of the first shaft member 44. Therefore, the first impeller 49 is connected to the first shaft member 44. The first impeller 49 is disposed closer to the second end of the first shaft member 44 than the thrust collar 48 of the first shaft member 44. The first impeller 49 has a cylindrical shape whose diameter gradually decreases from the back surface toward the tip surface. The first impeller 49 is housed in the first impeller chamber 23. Therefore, the first impeller chamber 23 houses the first impeller 49. The outer edge of the first impeller 49 extends along the inner circumferential surface of the first impeller chamber 23. The first impeller 49 rotates integrally with the first shaft member 44 to compress air. Therefore, the first impeller 49 is an impeller that rotates integrally with the rotary shaft 43 to compress air.

[0042] The centrifugal compressor 10 includes a second impeller 50. The second impeller 50 is attached to a second end of the second shaft member 45. Therefore, the second impeller 50 is connected to the second shaft member 45. The second impeller 50 has a cylindrical shape whose diameter gradually decreases from the back surface to the tip surface. The second impeller 50 is housed in the second impeller chamber 28. Therefore, the second impeller chamber 28 houses the second impeller 50. The outer edge of the second impeller 50 extends along the inner circumferential surface of the second impeller chamber 28. The second impeller 50 rotates integrally with the second shaft member 45 to compress air that has been compressed as the first impeller 49 rotates. Therefore, the second impeller 50 is an impeller that rotates integrally with the rotary shaft 43 to compress air.

[0043] The rotating shaft 43, the first impeller 49, and the second impeller 50 constitute a rotating body 60. Therefore, the centrifugal compressor 10 is equipped with the rotating body 60. The rotating body 60 includes the rotating shaft 43, the first impeller 49, and the second impeller 50. The rotor 33 rotates integrally with the first shaft member 44 and the second shaft member 45. Therefore, the rotor 33 rotates integrally with the rotating shaft 43. The rotor 33 constitutes a part of the rotating body 60. The motor 31 rotates the rotating shaft 43.

[0044] The centrifugal compressor 10 includes a first radial bearing 51 and a second radial bearing 52. The first radial bearing 51 is cylindrical. The first radial bearing 51 is held by a first radial bearing holder 21. Therefore, the first radial bearing holder 21 holds the first radial bearing 51. The second radial bearing 52 is cylindrical. The second radial bearing 52 is held by a second radial bearing holder 26. Therefore, the second radial bearing holder 26 holds the second radial bearing 52.

[0045] The first radial bearing 51 supports the first shaft member 44 rotatably in the radial direction. The second radial bearing 52 supports the second shaft member 45 rotatably in the radial direction. The first radial bearing 51 and the second radial bearing 52 support the rotor 33 rotatably in the radial direction at positions on both sides of the cylindrical member 41 sandwiched in the axial direction of the cylindrical member 41. Note that the "radial direction" is a direction perpendicular to the axial direction of the cylindrical member 41.

[0046] The centrifugal compressor 10 includes a thrust bearing 53. The thrust bearing 53 is accommodated in the thrust bearing accommodation chamber 19. Therefore, the thrust bearing accommodation chamber 19 accommodates the thrust bearing 53. The thrust bearing 53 rotatably supports the thrust collar 48 in the thrust direction. Therefore, the thrust bearing 53 rotatably supports the rotating shaft 43 in the thrust direction between the first impeller 49 and the first radial bearing 51 via the thrust collar 48. Note that the "thrust direction" is a direction parallel to the axial direction of the rotating shaft 43. In this way, the rotating shaft 43 is rotatably supported by the housing 11.

[0047] The centrifugal compressor 10 includes a connecting pipe 61. A first end of the connecting pipe 61 is connected to the first discharge chamber 24. A second end of the connecting pipe 61 is connected to the second suction port 27. Air discharged to the first discharge chamber 24 flows through the connecting pipe 61. The air that has passed through the connecting pipe 61 is then drawn into the second impeller chamber 28 via the second suction port 27.

[0048] A supply pipe 62 is connected to the second discharge chamber 29. The supply pipe 62 is connected to a fuel cell stack 63. A first end of the supply pipe 62 is connected to the second discharge chamber 29. A second end of the supply pipe 62 is connected to the fuel cell stack 63.

[0049] The air drawn into the first impeller chamber 23 through the first intake port 22 is accelerated by the rotation of the first impeller 49 and sent into the first diffuser passage 25. The air is then pressurized as it passes through the first diffuser passage 25. The air that has passed through the first diffuser passage 25 is then discharged into the first discharge chamber 24. The air that has been discharged into the first discharge chamber 24 is then drawn into the second impeller chamber 28 through the connecting pipe 61 and the second intake port 27. The air drawn into the second impeller chamber 28 is accelerated by the rotation of the second impeller 50 and sent into the second diffuser passage 30. The air that has passed through the second diffuser passage 30 is then pressurized as it passes through the second diffuser passage 30. The air that has passed through the second diffuser passage 30 is then discharged into the second discharge chamber 29. The air that has been discharged into the second discharge chamber 29 is supplied to the fuel cell stack 63 through the supply pipe 62. Thus, the centrifugal compressor 10 supplies air to the fuel cell stack 63. The oxygen contained in the air supplied to the fuel cell stack 63 contributes to the power generation of the fuel cell stack 63. The air exhausted from the fuel cell stack 63 is released into the atmosphere as exhaust gas.

[0050] The motor housing 12 has an introduction passage 64. Therefore, the housing 11 has the introduction passage 64. The introduction passage 64 is formed at an end of the peripheral wall 12b of the motor housing 12 that is located on the first plate 15 side. A first end of the introduction passage 64 opens to the outer peripheral surface of the peripheral wall 12b of the motor housing 12. A second end of the introduction passage 64 opens to the inner peripheral surface of the peripheral wall 12b of the motor housing 12. The second end of the introduction passage 64 communicates with a portion of the motor chamber 18 between the resin 37 and the first plate 15.

[0051] The centrifugal compressor 10 includes a branch pipe 65. The branch pipe 65 branches off from the middle of the connection pipe 61. A first end of the branch pipe 65 is connected to the connection pipe 61. A second end of the branch pipe 65 is connected to a first end of the introduction passage 64. An intercooler 66 is provided in the middle of the branch pipe 65. The intercooler 66 cools the air flowing through the branch pipe 65.

[0052] The motor housing 12 has a discharge passage 67. Therefore, the housing 11 has a discharge passage 67. The discharge passage 67 penetrates the second radial bearing holder 26 and the end wall 12a of the motor housing 12. A first end of the discharge passage 67 communicates with the inside of the motor chamber 18. A second end of the discharge passage 67 communicates with the outside of the housing 11.

[0053] A portion of the air flowing through the connection pipe 61 flows into the branch pipe 65. The air flowing through the branch pipe 65 is cooled by the intercooler 66. The air cooled by the intercooler 66 is then introduced into the motor chamber 18 via the introduction passage 64. Therefore, the introduction passage 64 introduces a portion of the air compressed by the rotation of the first impeller 49 into the motor chamber 18.

[0054] The air introduced into the motor chamber 18 passes through the gap G1 between the stator 32 and the rotor 33. The air that has passed through the gap G1 is then discharged to the outside of the housing 11 via the discharge passage 67. Therefore, the discharge passage 67 discharges the air that has been introduced into the motor chamber 18 from the introduction passage 64 and passed through the gap G1 between the stator 32 and the rotor 33 to the outside of the housing 11. In the centrifugal compressor 10, the permanent magnets 42 are cooled by the air that passes through the gap G1.

[0055] 3 , the first resin portion 38 has an end surface covering portion 70 that covers an end surface of the stator core 34 that is located on the first plate 15 side and that is located radially inward of the rotating shaft 43 relative to the first coil end 36 a. Therefore, the resin 37 has an end surface covering portion 70 that covers a portion of the stator core 34 that is located radially inward of the rotating shaft 43 relative to the coil end 36 a. The end surface covering portion 70 faces the first radial bearing holder 21 in the axial direction of the rotating shaft 43.

[0056] <Facing portion> The tip surface of the first radial bearing retaining portion 21 is located radially inward of the rotating shaft 43 relative to the first coil end 36a. The tip surface of the first radial bearing retaining portion 21 is an end face of the stator core 34 located on the first plate 15 side, and faces a portion of the stator core 34 located radially inward of the rotating shaft 43 relative to the first coil end 36a in the axial direction of the rotating shaft 43 via an end face covering portion 70. Therefore, the tip surface of the first radial bearing retaining portion 21 is a facing portion 71 that faces a portion of the stator core 34 end face located radially inward of the rotating shaft 43 relative to the coil end 36 in the axial direction of the rotating shaft 43. Therefore, the housing 11 has the facing portion 71.

[0057] 3 and 4 , the centrifugal compressor 10 includes a plurality of nozzle vanes 72. The plurality of nozzle vanes 72 protrude from the end face covering portion 70 toward the opposing portion 71 of the first radial bearing holder 21. The plurality of nozzle vanes 72 are integrally formed with the resin 37.

[0058] 4 , the plurality of nozzle vanes 72 are arranged in a line in the circumferential direction around the axis L1 of the rotary shaft 43. The plurality of nozzle vanes 72 are arranged at equal intervals in the circumferential direction around the axis L1 of the rotary shaft 43. The nozzle vanes 72 are thin, curved plates such that a downstream edge 72a located downstream in the air flow direction is closer to the gap G1 than an upstream edge 72b located upstream in the air flow direction, and is positioned on the leading side in the rotation direction of the rotary shaft 43. Each nozzle vane 72 is formed in the resin 37 such that the downstream edge 72a of the nozzle vane 72 is positioned away from the inner circumferential surface of the third resin portion 40.

[0059] The gaps between adjacent nozzle vanes 72 in the circumferential direction of the rotary shaft 43 gradually narrow as they approach the gap G1. Therefore, the cross-sectional area of ​​the air flow path formed by the gaps between adjacent nozzle vanes 72 in the circumferential direction of the rotary shaft 43 gradually decreases as they approach the gap G1. In this manner, the nozzles 73 are formed by the gaps between adjacent nozzle vanes 72 in the circumferential direction of the rotary shaft 43. Therefore, in this embodiment, the centrifugal compressor 10 includes a plurality of nozzles 73. Each nozzle 73 is a fixed nozzle. Each nozzle 73 converts the pressure energy of the air passing through each nozzle 73 into velocity energy. Each nozzle 73 is positioned away from the inner circumferential surface of the third resin portion 40. Therefore, there is a space within the motor chamber 18 between each nozzle 73 and the gap G1.

[0060] The direction of air passing through each nozzle 73 is set to be the circumferential direction of the rotating shaft 43. Therefore, the direction of air introduced into the gap G1 from each nozzle 73 is set to be the circumferential direction of the rotating shaft 43. In this way, the nozzle 73 generates a swirling flow of air upstream of the gap G1 in the air flow direction. The nozzle 73 is located upstream of the gap G1 in the air flow direction and radially inward of the rotating shaft 43 than the coil end 36.

[0061] <Communicating Passage> The centrifugal compressor 10 includes a communicating passage 80. The communicating passage 80 allows the swirling airflow generated by the nozzles 73 to flow into the gap G1. The communicating passage 80 is a space that exists in the motor chamber 18 between each nozzle 73 and the gap G1 in the air flow direction. Therefore, the communicating passage 80 is located downstream of each nozzle 73 in the air flow direction and upstream of the gap G1 in the air flow direction. The communicating passage 80 connects each nozzle 73 and the gap G1.

[0062] [Operation of the Embodiment] Next, the operation of the embodiment will be described. The swirling airflow generated by each nozzle 73 flows into the gap G1 between the stator 32 and the rotor 33 via the communicating passage 80, and the swirling airflow that flows into the gap G1 between the stator 32 and the rotor 33 assists the rotation of the rotor 33. As a result, mechanical loss, or so-called "windage loss," of the rotor 33 is less likely to occur. This suppresses the temperature increase due to windage loss of the air flowing through the gap G1 between the stator 32 and the rotor 33. Therefore, the average temperature of the air flowing through the gap G1 between the stator 32 and the rotor 33 can be reduced by the amount of the suppression of the temperature increase due to windage loss. As a result, the permanent magnets 42 are efficiently cooled by the air flowing through the gap G1 between the stator 32 and the rotor 33.

[0063] Effects of the Embodiment The following effects can be achieved in the embodiment. (1) The centrifugal compressor 10 includes a nozzle 73 and a communication passage 80. The nozzle 73 generates a swirling flow of air upstream of the gap G1 between the stator 32 and the rotor 33 in the airflow direction. The communication passage 80 allows the swirling flow of air generated by the nozzle 73 to flow into the gap G1 between the stator 32 and the rotor 33. As a result, the swirling flow of air generated by the nozzle 73 flows into the gap G1 between the stator 32 and the rotor 33 via the communication passage 80, and the swirling flow of air that has flowed into the gap G1 between the stator 32 and the rotor 33 assists the rotation of the rotor 33. As a result, mechanical loss, or so-called "windage loss," of the rotor 33 is less likely to occur. This makes it possible to suppress a temperature rise due to windage loss of the air flowing through the gap G1 between the stator 32 and the rotor 33. Therefore, the average temperature of the air flowing through the gap G1 between the stator 32 and the rotor 33 can be lowered by the amount of the temperature rise due to windage loss being suppressed. As a result, the permanent magnets 42 can be efficiently cooled by the air flowing through the gap G1 between the stator 32 and the rotor 33.

[0064] (2) The nozzle 73 is located upstream of the gap G1 in the air flow direction and radially inward of the rotary shaft 43 relative to the coil end 36. This allows the nozzle 73 to generate a swirling flow of air just before the air flows into the gap G1 between the stator 32 and the rotor 33. This makes it possible to cause the swirling flow of air to flow into the gap G1 between the stator 32 and the rotor 33 while suppressing pressure loss of the swirling flow of air. As a result, it is possible to further easily suppress a temperature rise of the air flowing through the gap G1 between the stator 32 and the rotor 33, and therefore the permanent magnets 42 can be more efficiently cooled by the air flowing through the gap G1 between the stator 32 and the rotor 33.

[0065] (3) The centrifugal compressor 10 includes a plurality of nozzle vanes 72 that protrude from the end surface covering portion 70 and are arranged side by side in the circumferential direction around the axis L1 of the rotary shaft 43. Each nozzle vane 72 has a curved thin plate shape such that its downstream edge 72a, located downstream in the air flow direction, is closer to the gap G1 than its upstream edge 72b, located upstream in the air flow direction, and is positioned on the leading side in the rotation direction of the rotary shaft 43. A nozzle 73 is formed by a gap between adjacent nozzle vanes 72 in the circumferential direction of the rotary shaft 43. This configuration is suitable for forming a nozzle 73 that is located upstream of the gap G1 in the air flow direction and radially inward of the rotary shaft 43 relative to the coil end 36.

[0066] (4) Because the nozzle 73 is formed by a plurality of nozzle vanes 72, in order to generate a swirling flow of air, it is not necessary to set the direction of air introduced into the motor chamber 18 through the introduction passage 64 to be the circumferential direction of the rotary shaft 43. Therefore, the design of the housing 11 can be simplified, and a swirling flow of air can be generated upstream of the gap G1 in the air flow direction.

[0067] [Modifications] The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0068] As shown in FIG. 5 , the centrifugal compressor 10 may be configured to include a plurality of nozzle vanes 72 that protrude from the opposing portion 71 and are arranged side by side in the circumferential direction around the axis L1 of the rotary shaft 43. The nozzle vanes 72 are thin, curved plates whose downstream edges 72a, located downstream in the airflow direction, are closer to the gap G1 than their upstream edges 72b, located upstream in the airflow direction, and are positioned on the leading side in the rotation direction of the rotary shaft 43. The plurality of nozzle vanes 72 are integrally formed with the first plate 15. The nozzles 73 are formed by gaps between adjacent nozzle vanes 72 in the circumferential direction of the rotary shaft 43. This configuration is suitable for forming the nozzles 73 that are located upstream of the gap G1 in the airflow direction and radially inward of the coil ends 36 of the rotary shaft 43. In this case, the centrifugal compressor 10 does not need to include a plurality of nozzle vanes 72 that protrude from the end face covering portion 70 and are arranged side by side in the circumferential direction around the axis L1 of the rotary shaft 43.

[0069] 6 and 7 , the downstream end of the introduction passage 64 located on the motor chamber 18 side may constitute a nozzle 74. The nozzle 74 is formed to have a smaller flow path cross-sectional area than the flow path located upstream of the downstream end of the introduction passage 64 in the air flow direction. In this way, the downstream end of the introduction passage 64 located on the motor chamber 18 side constitutes the nozzle 74 by being smaller than the flow path cross-sectional area located upstream of the downstream end in the air flow direction. The direction in which air is introduced into the motor chamber 18 from the nozzle 74 is set to be the circumferential direction of the rotary shaft 43.

[0070] As shown in FIG. 7 , the direction in which air is introduced into the motor chamber 18 from the nozzle 74 is tangential to the inner circumferential surface of the peripheral wall 12b of the motor housing 12. The centrifugal compressor 10 has a scroll wall 75. The scroll wall 75 protrudes from an end face of the first plate 15 that faces the motor housing 12. The scroll wall 75 is integrally formed with the first plate 15. The scroll wall 75 extends around the axis L1 of the rotary shaft 43 around the first radial bearing holder 21. The inner surface of the scroll wall 75 guides the air introduced from the nozzle 74 in the circumferential direction of the rotary shaft 43 and gradually approaches the axis L1 of the rotary shaft 43. In this way, a swirling flow of air introduced into the motor chamber 18 from the introduction passage 64 is generated.

[0071] Within the motor chamber 18, the space inside the scroll wall 75, the space inside the first resin portion 38, and the space between the end surface covering portion 70 and the opposing portion 71 form a communication passage 81 that allows the swirling air flow generated by the nozzle 74 to flow into the gap G1. The communication passage 81 is a space that exists within the motor chamber 18 between the nozzle 74 and the gap G1 in the air flow direction. Therefore, the communication passage 81 is located downstream of the nozzle 74 in the air flow direction and upstream of the gap G1 in the air flow direction. The communication passage 81 connects the nozzle 74 and the gap G1.

[0072] According to this, air is introduced into the motor chamber 18 from the introduction passage 64 in a state where a swirling flow of air is generated by the nozzle 74. Then, the swirling flow of air introduced into the motor chamber 18 from the introduction passage 64 can be made to flow into the gap G1 between the stator 32 and the rotor 33 via the communication passage 81.

[0073] 6 and 7, the direction in which the nozzle 74 introduces air into the motor chamber 18 does not have to be tangential to the inner circumferential surface of the peripheral wall 12b of the motor housing 12. The key is that the direction in which the nozzle 74 introduces air into the motor chamber 18 needs to be set to be the circumferential direction of the rotary shaft 43.

[0074] In the embodiment, for example, the nozzle 73 and the gap G1 may be directly connected. In this case, the communication passage 80 corresponds to the boundary between the nozzle 73 and the gap G1. In the embodiment, the intercooler 66 does not have to be provided midway through the branch pipe 65.

[0075] In the above embodiment, the introduction passage 64 may introduce a portion of the air compressed in accordance with the rotation of the second impeller 50 into the motor chamber 18. In the above embodiment, the centrifugal compressor 10 may not include the second impeller 50.

[0076] In the embodiment, the centrifugal compressor 10 may be configured to include a turbine wheel instead of the second impeller 50. In the embodiment, the magnetic body is not limited to the permanent magnet 42, and may be, for example, a laminated core, an amorphous core, or a powder core.

[0077] In the embodiment, the cylindrical member 41 may be made of, for example, carbon fiber reinforced plastic. In other words, the material of the cylindrical member 41 is not particularly limited. In the embodiment, the rotor 33 may be configured to include, for example, a cylindrical rotor core configured by laminating multiple electromagnetic steel plates and a magnetic body embedded in the rotor core. In such a configuration, the rotating shaft 43 passes through the inside of the rotor core.

[0078] In the embodiment, the centrifugal compressor 10 does not have to be mounted on a fuel cell vehicle. In other words, the centrifugal compressor 10 is not limited to being mounted on a vehicle. In the embodiment, the centrifugal compressor 10 is not limited to being used to compress air supplied to the fuel cell stack 63. In other words, the centrifugal compressor 10 may be used in any manner as long as it compresses a fluid.

[0079] REFERENCE SIGNS LIST 10 Centrifugal compressor 11 Housing 18 Motor chamber 31 Motor 32 Stator 33 Rotor 34 Stator core 35 Coil 36 Coil end 37 Resin 42 Permanent magnet as magnetic body 43 Rotating shaft 49 First impeller as impeller 50 Second impeller as impeller 60 Rotating body 64 Inlet passage 67 Discharge passage 70 End surface covering portion 71 Opposing portion 72 Nozzle vane 72a Downstream edge 72b Upstream edge 73, 74 Nozzle 80, 81 Communication passage G1 Gap

Claims

1. A centrifugal compressor comprising: a rotating body including a rotating shaft and an impeller rotating integrally with the rotating shaft to compress a fluid; a motor for rotating the rotating shaft; and a housing having a motor chamber in which the motor is housed, wherein the motor comprises: a cylindrical stator fixed to the housing; and a rotor which rotates integrally with the rotating shaft, is disposed inside the stator, and constitutes a part of the rotating body, the rotor having a magnetic body, and the housing comprising: an introduction passage for introducing into the motor chamber a part of the fluid compressed as the impeller rotates; and a discharge passage for discharging to the outside of the housing the fluid which has been introduced from the introduction passage into the motor chamber and passed through a gap between the stator and the rotor, wherein the magnetic body is cooled by the fluid passing through the gap, the centrifugal compressor comprising: a nozzle for generating a swirling flow of the fluid upstream of the gap in the flow direction of the fluid; and a connecting passage for allowing the swirling flow of the fluid generated by the nozzle to flow into the gap.

2. A centrifugal compressor as described in claim 1, characterized in that the stator has a stator core and a coil end which is a part of a coil wound around the stator core and protrudes from an end face of the stator core, and the nozzle is located upstream of the gap in the flow direction of the fluid and radially inward of the coil end of the rotating shaft.

3. The centrifugal compressor according to claim 2, characterized in that the stator comprises a resin that molds the stator core, the resin having an end face covering portion that covers a portion of the end face of the stator core that is located radially inward of the rotating shaft relative to the coil ends, the resin having a plurality of nozzle vanes that protrude from the end face covering portion and are arranged side by side in the circumferential direction around the axis of the rotating shaft, the nozzle vanes being thin plates that are curved so that their downstream edges located downstream in the flow direction of the fluid are closer to the gap than their upstream edges located upstream in the flow direction of the fluid and are located on the leading side in the rotation direction of the rotating shaft, and the nozzles are formed by gaps between adjacent nozzle vanes in the circumferential direction of the rotating shaft.

4. The centrifugal compressor according to claim 2, characterized in that the housing has an opposing portion that faces a portion of the end face of the stator core that is located radially inward of the rotating shaft relative to the coil end in the axial direction of the rotating shaft, and is provided with a plurality of nozzle vanes that protrude from the opposing portion and are arranged side by side in the circumferential direction around the axis of the rotating shaft, the nozzle vanes are thin plates that are curved so that their downstream edges located downstream in the flow direction of the fluid are closer to the gap than their upstream edges located upstream in the flow direction of the fluid and are located on the leading side in the rotation direction of the rotating shaft, and the nozzles are formed by gaps between adjacent nozzle vanes in the circumferential direction of the rotating shaft.

5. A centrifugal compressor as described in claim 1, characterized in that the downstream end of the introduction passage located on the motor chamber side is formed to be smaller than the flow path cross-sectional area located upstream of the downstream end in the flow direction of the fluid, thereby forming the nozzle, and the introduction direction of the fluid into the motor chamber from the nozzle is set to be the circumferential direction of the rotating shaft.

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