JP2024093313A - Centrifugal Compressor - Google Patents

Abstract

The present invention aims to improve the durability of a centrifugal compressor.
[Solution] An end wall 12a of a motor housing 12 is formed with a plurality of communication holes 68 that communicate between a fluid passage 75 and a motor chamber 18 and are provided radially outward of a rotating shaft 41 than a second hole 62. Air leaking to a back surface 43a of a second impeller 43 flows into the fluid passage 75 through a first hole 61, and flows into the motor chamber 18 through the communication holes 68 and the second hole 62. The end wall 12a of the motor housing 12 is provided with a plurality of cooling fins 70 that are provided in the fluid passage 75 and that extend radially relative to the rotation axis of the rotating shaft 41 and are arranged around the rotating shaft 41. The plurality of cooling fins 70 are arranged between the plurality of communication holes 68 that are adjacent to each other in the circumferential direction of the rotating shaft 41.
[Selected figure] Figure 2

Description

The present invention relates to a centrifugal compressor.

For example, as disclosed in Patent Document 1, a centrifugal compressor includes a rotating shaft and an impeller. The impeller rotates integrally with the rotating shaft to compress the fluid. The centrifugal compressor includes a motor and a housing. The motor rotates the rotating shaft. The housing has an impeller chamber, a motor chamber, and a partition wall. The impeller chamber houses the impeller. The motor chamber houses the motor. The partition wall separates the impeller chamber from the motor chamber. The partition wall has an insertion hole through which the rotating shaft is inserted.

In such centrifugal compressors, it is desirable to cool the motor in order to improve the durability of the centrifugal compressor. Therefore, it has been considered to introduce a part of the fluid compressed by the impeller into the motor chamber at a temperature lower than the temperature of the fluid after it has been compressed by the impeller. In this way, the motor is cooled by the fluid by introducing a part of the fluid compressed by the impeller into the motor chamber at a temperature lower than the temperature of the fluid after it has been compressed by the impeller.

JP 2015-187444 A

In such centrifugal compressors, there is a risk that fluid leaking behind the impeller may enter the motor chamber through the insertion hole. If the fluid leaking behind the impeller enters the motor chamber through the insertion hole, the motor will be warmed by the fluid that has entered the motor chamber. As a result, it may become difficult to cool the motor. This will reduce the durability of the centrifugal compressor.

A centrifugal compressor that solves the above problem is a centrifugal compressor that includes a rotating shaft, an impeller that rotates integrally with the rotating shaft to compress a fluid, a motor that rotates the rotating shaft, and a housing having an impeller chamber that houses the impeller, a motor chamber that houses the motor, and a partition wall that separates the impeller chamber from the motor chamber and has an insertion hole through which the rotating shaft is inserted, the partition wall including a first wall component that defines the impeller chamber and has a first hole that forms a part of the insertion hole, a second wall component that defines the motor chamber and has a second hole through which a bearing is disposed between the rotating shaft and the first wall component, and a second wall component that defines the motor chamber and forms a part of the insertion hole and has a second hole through which a bearing is disposed between the rotating shaft and the first wall component. The impeller has a fluid passage surrounded by the first wall constituent and the second wall constituent, and the second wall constituent has a plurality of communication holes that communicate the fluid passage with the motor chamber and are provided radially outward of the rotating shaft from the second hole, and the fluid leaking to the back surface of the impeller flows through the first hole into the fluid passage, and flows through the communication holes and the second hole into the motor chamber, and the partition wall has a plurality of cooling fins that are provided in the fluid passage and extend radially relative to the rotation axis of the rotating shaft, and are arranged around the rotating shaft, and the plurality of cooling fins are arranged between the plurality of communication holes that are adjacent to each other in the circumferential direction of the rotating shaft.

With this, when the fluid leaked to the rear surface of the impeller flows through the fluid passage through the first hole, heat is dissipated to the housing via the multiple cooling fins. Therefore, the fluid leaked to the rear surface of the impeller can be cooled. The cooled air then flows from the fluid passage through the communication hole and the second hole to the motor chamber. Therefore, the motor can be cooled using the fluid leaked to the rear surface of the impeller. As a result, the durability of the centrifugal compressor can be improved.

In the centrifugal compressor, the fluid passage may be provided with a guide wall that guides the fluid that flows into the fluid passage through the first hole toward the plurality of cooling fins.
According to this, the guide wall guides the fluid flowing into the fluid passage through the first hole toward the cooling fins, so that the heat of the fluid is easily dissipated to the housing via the cooling fins. Therefore, the fluid leaking to the rear surface of the impeller can be efficiently cooled. As a result, the motor can be efficiently cooled by using the fluid leaking to the rear surface of the impeller.

In the centrifugal compressor, the guide wall may be provided on the rotating shaft and may protrude in an annular shape from an outer circumferential surface of the rotating shaft.
According to this, since the guide wall is provided on the rotating shaft, the guide wall rotates integrally with the rotating shaft. And since the guide wall protrudes in an annular shape from the outer circumferential surface of the rotating shaft, the fluid guided by the guide wall is likely to spread radially outward of the rotating shaft due to centrifugal force accompanying the rotation of the rotating shaft. Therefore, the guide wall makes it easier for the fluid flowing into the fluid passage through the first hole to be guided toward the multiple cooling fins, so that the fluid is likely to dissipate heat to the housing via the multiple cooling fins. Therefore, the fluid leaking to the back surface of the impeller can be efficiently cooled. As a result, the motor can be efficiently cooled by utilizing the fluid leaking to the back surface of the impeller.

In the centrifugal compressor, the guide wall may have a cylindrical fixing portion fixed to an end edge of the plurality of cooling fins on the side of the rotary shaft.
According to this, the guide wall is thermally coupled to the plurality of cooling fins via the fixed portion. Therefore, the air flowing into the fluid passage through the first hole is guided by the guide wall toward the plurality of cooling fins, and at the same time, heat is dissipated to the housing via the fixed portion and each cooling fin. Therefore, the fluid leaking to the rear surface of the impeller can be efficiently cooled. As a result, the motor can be efficiently cooled by utilizing the fluid leaking to the rear surface of the impeller.

In the centrifugal compressor, the guide wall may be provided around the first hole in the first wall structure and guide the air that has passed through the first hole toward the cooling fins.

With this, the guide wall is provided around the first hole in the first wall component. Therefore, the guide wall can be provided integrally with the housing. This simplifies the configuration of the centrifugal compressor.

In the centrifugal compressor, the guide wall may be formed on an outer circumferential surface of the rotating shaft.
According to this, since the outer circumferential surface of the rotating shaft functions as a guide wall that guides the fluid flowing into the fluid passage through the first hole toward the cooling fins, there is no need to dispose a member separate from the rotating shaft as a guide wall in the fluid passage, and therefore the configuration of the centrifugal compressor can be simplified.

This invention makes it possible to improve the durability of the centrifugal compressor.

1 is a cross-sectional view of a centrifugal compressor according to a first embodiment. FIG. FIG. 2 is an enlarged cross-sectional view of a portion of the centrifugal compressor. This is a cross-sectional view taken along line 3-3 in FIG. FIG. 6 is an enlarged cross-sectional view showing a part of a centrifugal compressor according to a second embodiment. This is a cross-sectional view taken along line 5-5 in FIG. FIG. 11 is an enlarged cross-sectional view showing a part of a centrifugal compressor according to a third embodiment. FIG. 10 is an enlarged cross-sectional view showing a part of a centrifugal compressor according to a fourth embodiment.

[First embodiment]
A centrifugal compressor according to a first embodiment will be described below with reference to Figures 1 to 3. The centrifugal compressor according to the embodiment described below is mounted on a fuel cell vehicle. The centrifugal compressor compresses air as a fluid to be supplied to a fuel cell stack.

<Basic configuration of centrifugal compressor 10>
As shown in Fig. 1, the centrifugal compressor 10 includes a housing 11. The housing 11 is made of a metal material, for example, aluminum. 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 third plate 17.

The motor housing 12 has an end wall 12a and a peripheral wall 12b. The end wall 12a is plate-shaped. The peripheral wall 12b extends cylindrically from the outer periphery of the end wall 12a. A cooling water passage 12c is formed in the peripheral wall 12b. Cooling water flows through the cooling water passage 12c. The motor housing 12 is cooled by the cooling water flowing through the cooling water passage 12c.

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 motor housing 12 and the first plate 15 define a motor chamber 18. Therefore, the housing 11 has a motor chamber 18.

The second plate 16 is connected to the outer surface of the end wall 12a of the motor housing 12. The second plate 16 is attached to the end wall 12a of the motor housing 12 with the thickness direction of the second plate 16 coinciding with the thickness direction of the end wall 12a of the motor housing 12.

The centrifugal compressor 10 is equipped with a motor 20. The motor 20 is housed in the motor chamber 18. Thus, the motor chamber 18 houses the motor 20. The motor housing 12 surrounds the motor 20.

The centrifugal compressor 10 is equipped with a first bearing retaining portion 21. The first bearing retaining portion 21 protrudes from the center of the first plate 15 into the motor chamber 18. Therefore, the first plate 15 has the first bearing retaining portion 21. The first bearing retaining portion 21 is cylindrical. The inside of the first bearing retaining portion 21 is connected to the motor chamber 18.

The first plate 15 has a chamber-forming recess 22. The chamber-forming recess 22 is formed on the end face of the first plate 15 opposite the motor housing 12. The chamber-forming recess 22 is a circular hole. The inside of the first bearing holder 21 penetrates the first plate 15 and opens to the bottom face of the chamber-forming recess 22. The axis of the chamber-forming recess 22 and the axis of the first bearing holder 21 are aligned.

The third plate 17 is connected to the end face of the first plate 15 on the side opposite to the motor housing 12. The third plate 17 is attached to the first plate 15 with the thickness direction of the third plate 17 coinciding with the thickness direction of the first plate 15. The third plate 17 has a first insertion hole 23. The first insertion hole 23 is formed in the center of the third plate 17. The axis of the first insertion hole 23 coincides with the axis of the chamber forming recess 22 and the axis of the first bearing holder 21. The chamber forming recess 22 and the third plate 17 define a thrust bearing accommodating chamber 24. The thrust bearing accommodating chamber 24 communicates with the inside of the first bearing holder 21. The thrust bearing accommodating chamber 24 also communicates with the first insertion hole 23. Therefore, the first bearing holder 21 communicates with the first insertion hole 23 via the thrust bearing accommodating chamber 24.

The centrifugal compressor 10 is provided with a second bearing retaining portion 25. The second bearing retaining portion 25 protrudes from the center of the end wall 12a of the motor housing 12 into the motor chamber 18. Thus, the motor housing 12 has the second bearing retaining portion 25. The second bearing retaining portion 25 is cylindrical. The inside of the second bearing retaining portion 25 is connected to the motor chamber 18.

The housing 11 has a second insertion hole 26. The second insertion hole 26 penetrates the center of the end wall 12a of the motor housing 12 and the center of the second plate 16. The inside of the second bearing holder 25 is part of the second insertion hole 26.

The first compressor housing 13 is cylindrical and has a first suction port 27, which is a circular hole through which air is drawn. The first compressor housing 13 is connected to the end face of the third plate 17 opposite the first plate 15, with the axis of the first suction port 27 coinciding with the axis of the first insertion hole 23. The first suction port 27 opens to the end face of the first compressor housing 13 opposite the third plate 17. Air that has been purified by an air cleaner (not shown) flows through the first suction port 27.

The centrifugal compressor 10 includes a first impeller chamber 28, a first discharge chamber 29, and a first diffuser passage 30. The first impeller chamber 28, the first discharge chamber 29, and the first diffuser passage 30 are formed between the first compressor housing 13 and the third plate 17. Therefore, the housing 11 has the first impeller chamber 28. The first plate 15 and the third plate 17 form a partition wall that separates the first impeller chamber 28 and the motor chamber 18. The first impeller chamber 28 is connected to the first suction port 27. The first discharge chamber 29 extends around the axis of the first suction port 27 around the first impeller chamber 28. The first diffuser passage 30 connects the first impeller chamber 28 and the first discharge chamber 29. The first impeller chamber 28 is connected to the first insertion hole 23.

The centrifugal compressor 10 has a first discharge passage 31. A first end of the first discharge passage 31 is connected to the first discharge chamber 29. A second end of the first discharge passage 31 opens to the outer peripheral surface of the first compressor housing 13.

The second compressor housing 14 is cylindrical and has a circular second intake port 32 through which air is drawn. The second compressor housing 14 is connected to the end face of the second plate 16 opposite the motor housing 12 with the axis of the second intake port 32 coinciding with the axis of the second insertion hole 26. The second intake port 32 opens to the end face of the second compressor housing 14 opposite the second plate 16.

The centrifugal compressor 10 includes a second impeller chamber 33, a second discharge chamber 34, and a second diffuser passage 35. The second impeller chamber 33, the second discharge chamber 34, and the second diffuser passage 35 are formed between the second compressor housing 14 and the second plate 16. Thus, the housing 11 has the second impeller chamber 33. The end wall 12a of the motor housing 12 and the second plate 16 form a partition wall that separates the second impeller chamber 33 and the motor chamber 18. The second impeller chamber 33 is connected to the second intake port 32. The second discharge chamber 34 extends around the axis of the second intake port 32 around the second impeller chamber 33. The second diffuser passage 35 connects the second impeller chamber 33 and the second discharge chamber 34. The second impeller chamber 33 is connected to the second insertion hole 26.

The centrifugal compressor 10 has a second discharge passage 36. A first end of the second discharge passage 36 is connected to the second discharge chamber 34. A second end of the second discharge passage 36 opens to the outer peripheral surface of the second compressor housing 14. A supply pipe 37 is connected to the second discharge passage 36. The supply pipe 37 is connected to the fuel cell stack 38. A first end of the supply pipe 37 is connected to the second discharge passage 36. A second end of the supply pipe 37 is connected to the fuel cell stack 38. The second discharge chamber 34 is connected to the fuel cell stack 38 via the second discharge passage 36 and the supply pipe 37.

The centrifugal compressor 10 is equipped with a connection pipe 39. A first end of the connection pipe 39 is connected to the first discharge passage 31. A second end of the connection pipe 39 is connected to the second suction port 32. Air discharged from the first discharge chamber 29 to the first discharge passage 31 flows through the connection pipe 39. The air that passes through the connection pipe 39 is then sucked into the second impeller chamber 33 via the second suction port 32.

The centrifugal compressor 10 includes a rotor 40. The rotor 40 includes a rotor shaft 41, a first impeller 42, a second impeller 43, and a support portion 44. The rotor shaft 41 is housed in the housing 11.

The rotating shaft 41 crosses the motor chamber 18 while extending along the axis of the motor housing 12. The axial direction of the rotating shaft 41 coincides with the axial direction of the motor housing 12. The first end of the rotating shaft 41 protrudes from the motor chamber 18 into the first impeller chamber 28, passing through the inside of the first bearing holder 21, the thrust bearing accommodating chamber 24, and the first insertion hole 23. Therefore, the first insertion hole 23 is a hole through which the rotating shaft 41 is inserted. In this way, the housing 11 has a partition wall that separates the first impeller chamber 28 and the motor chamber 18 and in which the first insertion hole 23 through which the rotating shaft 41 is inserted is formed.

The second end of the rotating shaft 41 passes through the second insertion hole 26 from the motor chamber 18 and protrudes into the second impeller chamber 33. Therefore, the second insertion hole 26 is a hole through which the rotating shaft 41 is inserted. In this way, the housing 11 has a partition wall that separates the second impeller chamber 33 and the motor chamber 18 and in which the second insertion hole 26 through which the rotating shaft 41 is inserted is formed.

The first impeller 42 is connected to a first end of the rotating shaft 41. The first impeller 42 is housed in the first impeller chamber 28. Therefore, the first impeller chamber 28 houses the first impeller 42. The first impeller 42 rotates integrally with the rotating shaft 41 to compress the air drawn into the first impeller chamber 28. Therefore, the first impeller 42 is an impeller that compresses air. Therefore, the first impeller chamber 28 is an impeller chamber that houses an impeller.

The second impeller 43 is connected to the second end of the rotating shaft 41. The second impeller 43 is housed in the second impeller chamber 33. Therefore, the second impeller chamber 33 houses the second impeller 43. The second impeller 43 compresses the air sucked into the second impeller chamber 33 by rotating integrally with the rotating shaft 41. Therefore, the second impeller 43 is an impeller that compresses air. Therefore, the second impeller chamber 33 is an impeller chamber that houses an impeller. Therefore, the housing 11 has an impeller chamber that houses an impeller. The second impeller 43 compresses the air after it has been compressed by the first impeller 42.

The support portion 44 protrudes in an annular shape from the outer peripheral surface of the rotating shaft 41. The support portion 44 is disk-shaped. The support portion 44 is fixed to the outer peripheral surface of the rotating shaft 41 in a state where it protrudes in an annular shape radially outward from the outer peripheral surface of the rotating shaft 41. Therefore, the support portion 44 is separate from the rotating shaft 41. The support portion 44 is disposed in the thrust bearing housing chamber 24. The support portion 44 rotates integrally with the rotating shaft 41.

The centrifugal compressor 10 is provided with a seal member 45. The seal member 45 is provided between the first insertion hole 23 and the rotating shaft 41. The seal member 45 suppresses air leakage from the first impeller chamber 28 toward the motor chamber 18. The seal member 45 is, for example, a seal ring.

The motor 20 includes a cylindrical rotor 47 and a cylindrical stator 48. The rotor 47 is fixed to the rotating shaft 41. The stator 48 is fixed to the housing 11. The rotor 47 is disposed radially inside the stator 48. The rotor 47 rotates integrally with the rotating shaft 41. The rotor 47 includes a cylindrical rotor core 49 fixed to the rotating shaft 41 and a plurality of permanent magnets (not shown) provided on the rotor core 49. The stator 48 surrounds the rotor 47. The stator 48 includes a cylindrical stator core 50 and a coil 51. The stator core 50 is fixed to the inner peripheral surface of the motor housing 12. The coil 51 is wound around the stator core 50.

The rotating shaft 41 rotates integrally with the rotor 47 when a current flows through the coil 51 from a battery (not shown). Therefore, the motor 20 rotates the rotating shaft 41. The motor 20 is disposed between the first impeller 42 and the second impeller 43 in the axial direction of the rotating shaft 41.

The centrifugal compressor 10 is equipped with a first radial bearing 52. The first radial bearing 52 is cylindrical. The first radial bearing 52 is held by the first bearing holder 21. The first radial bearing 52 rotatably supports a portion of the rotating shaft 41 that is located closer to the first end of the rotating shaft 41 than the motor 20. Therefore, the first radial bearing 52 is a bearing that rotatably supports the rotating shaft 41. And the first bearing holder 21 is a bearing holder that holds the bearing.

The centrifugal compressor 10 is equipped with a second radial bearing 53. The second radial bearing 53 is cylindrical. The second radial bearing 53 is held by the second bearing holder 25. The second radial bearing 53 rotatably supports a portion of the rotating shaft 41 that is located closer to the second end of the rotating shaft 41 than the motor 20. Therefore, the second radial bearing 53 is a bearing that rotatably supports the rotating shaft 41. And the second bearing holder 25 is a bearing holder that holds the bearing.

The first radial bearing 52 and the second radial bearing 53 support the rotating shaft 41 so that the rotating shaft 41 can rotate in the radial direction at positions on both sides of the motor 20 sandwiched in the axial direction of the rotating shaft 41. Note that the "radial direction" is a direction perpendicular to the axial direction of the rotating shaft 41.

The centrifugal compressor 10 is equipped with a thrust bearing 54. The thrust bearing 54 is accommodated in the thrust bearing accommodation chamber 24. Therefore, the thrust bearing accommodation chamber 24 accommodates the thrust bearing 54. The thrust bearing 54 rotatably supports the support portion 44 in the thrust direction. Therefore, the thrust bearing 54 rotatably supports the rotating shaft 41 via the support portion 44. Note that the "thrust direction" is a direction parallel to the rotational axis direction of the rotating shaft 41.

The air drawn into the first impeller chamber 28 through the first intake port 27 is accelerated by the rotation of the first impeller 42 and sent into the first diffuser passage 30, where it is pressurized by passing through the first diffuser passage 30. The air that has passed through the first diffuser passage 30 is then discharged into the first discharge chamber 29. The air discharged into the first discharge chamber 29 is then discharged into the first discharge passage 31. The air discharged into the first discharge passage 31 is then drawn into the second impeller chamber 33 through the connecting pipe 39 and the second intake port 32. The air drawn into the second impeller chamber 33 is accelerated by the rotation of the second impeller 43 and sent into the second diffuser passage 35, where it is pressurized by passing through the second diffuser passage 35. The air that has passed through the second diffuser passage 35 is then discharged into the second discharge chamber 34. The air discharged into the second discharge chamber 34 is discharged into the second discharge passage 36. The air discharged into the second discharge passage 36 is supplied to the fuel cell stack 38 via the supply pipe 37. Thus, the centrifugal compressor 10 supplies air to the fuel cell stack 38. The oxygen contained in the air supplied to the fuel cell stack 38 contributes to the power generation of the fuel cell stack 38.

The rotating body 40 includes a rotating shaft 41, and a first impeller 42 and a second impeller 43 that rotate integrally with the rotating shaft 41 to compress air. Thus, the rotating body 40 includes impellers. The first discharge chamber 29 is a discharge chamber from which air compressed by the first impeller 42 is discharged. The second discharge chamber 34 is a discharge chamber from which air compressed by the second impeller 43 is discharged. Thus, the housing 11 has a discharge chamber.

The centrifugal compressor 10 is provided with an introduction passage 56. The introduction passage 56 is formed in the first plate 15. A first end of the introduction passage 56 opens to the outer peripheral surface of the first plate 15. A second end of the introduction passage 56 communicates with the thrust bearing housing chamber 24.

A branch pipe 57 is connected to a first end of the introduction passage 56. The branch pipe 57 branches off from the middle of the supply pipe 37. A first end of the branch pipe 57 is connected to the supply pipe 37. A second end of the branch pipe 57 is connected to the first end of the introduction passage 56. An intercooler 58 is provided in the middle of the branch pipe 57. The intercooler 58 cools the air flowing through the branch pipe 57.

A portion of the air flowing through the supply pipe 37 flows into the branch pipe 57. The air flowing through the branch pipe 57 is cooled by the intercooler 58. As a result, the air passing through the intercooler 58 has a lower temperature than the air discharged into the second discharge chamber 34. The air cooled by the intercooler 58 then passes through the introduction passage 56, the thrust bearing housing chamber 24, and the inside of the first bearing holder 21 and is introduced into the motor chamber 18. Therefore, the introduction passage 56 introduces a portion of the air compressed by the second impeller 43 into the motor chamber 18 at a lower temperature than the air discharged into the second discharge chamber 34.

The centrifugal compressor 10 is provided with a discharge passage 59. The discharge passage 59 is formed in the peripheral wall 12b of the motor housing 12. A first end of the discharge passage 59 is connected to the inside of the motor chamber 18. A second end of the discharge passage 59 is open to the outer circumferential surface of the peripheral wall 12b of the motor housing 12. Therefore, the discharge passage 59 is connected to the outside of the housing 11. And, the air in the motor chamber 18 is discharged to the outside of the housing 11 via the discharge passage 59.

As shown in FIG. 2, the second impeller 43 is cylindrical and gradually narrows in diameter from the back surface 43a to the tip. The back surface 43a of the second impeller 43 faces the second plate 16. Therefore, the second plate 16 has an opposing surface 16a that faces the back surface 43a of the second impeller 43. The second impeller 43 has a through hole 43h. The axis of the through hole 43h coincides with the rotation axis of the second impeller 43. The rotation axis of the second impeller 43 is also the rotation axis of the rotating shaft 41. The rotation axis of the rotating shaft 41 is the rotation axis L1 of the rotating body 40.

The second impeller 43 has a cylindrical boss portion 43b. The boss portion 43b protrudes from the center of the back surface 43a of the second impeller 43. The inside of the boss portion 43b communicates with the through hole 43h. The rotating shaft 41 passes through the inside of the boss portion 43b and the through hole 43h. The boss portion 43b enters the second insertion hole 26. Therefore, the boss portion 43b is disposed inside the second insertion hole 26. The boss portion 43b is the portion of the rotating body 40 that is located inside the second insertion hole 26.

In the second impeller 43, the boss portion 43b and the portion of the second impeller 43 that overlaps with the boss portion 43b in the axial direction of the rotating shaft 41 can be said to constitute part of the rotating shaft 41. In addition, in the second impeller 43, the portions other than the boss portion 43b and the portion of the second impeller 43 that overlaps with the boss portion 43b in the axial direction of the rotating shaft 41 can be said to function as an impeller that compresses air by rotating integrally with the rotating shaft 41.

<First hole 61 and second hole 62>
The second plate 16 has a first hole 61 which forms a part of the second insertion hole 26. The first hole 61 penetrates a center part of the second plate 16. The first hole 61 is continuous with the opposing surface 16a. The second plate 16 is a first wall constituent element which defines the second impeller chamber 33.

The end wall 12a of the motor housing 12 has a second hole 62 that forms part of the second through hole 26. The second hole 62 is inside the second bearing holder 25. A second radial bearing 53 is arranged in the second hole 62 between the rotating shaft 41 and the end wall 12a of the motor housing 12. The end wall 12a of the motor housing 12 is a second wall component that defines the motor chamber 18, forms part of the second through hole 26, and has the second hole 62 between the rotating shaft 41 and the end wall 12a. Therefore, the partition wall has a first wall component and a second wall component.

<Fluid passage 75>
A passage forming recess 12d is formed on the outer surface of the end wall 12a of the motor housing 12. The passage forming recess has a large diameter hole 62a and a small diameter hole 62b. The diameter of the small diameter hole 62b is smaller than the diameter of the large diameter hole 62a. The small diameter hole 62b communicates with the second hole 62. The inner peripheral surface of the second hole 62 and the inner peripheral surface of the small diameter hole 62b are connected by an annular first step surface 62d. The end of the small diameter hole 62b opposite to the second hole 62 communicates with the large diameter hole 62a. The inner peripheral surface of the small diameter hole 62b and the inner peripheral surface of the large diameter hole 62a are connected by an annular second step surface 62e. The end of the large diameter hole 62a opposite to the small diameter hole 62b opens on the outer surface of the end wall 12a of the motor housing 12. The second plate 16 closes the opening of the large diameter hole 62a. The end of the large diameter hole 62a opposite to the small diameter hole 62b communicates with the first hole 61. Therefore, the space inside the passage forming recess 12d communicates with the first hole 61 and the second hole 62. The rotating shaft 41 passes through the space inside the passage forming recess 12d.

The space inside the passage forming recess 12d is a fluid passage 75. The fluid passage 75 is the outer peripheral region of the rotating shaft 41 and is surrounded by the second plate 16 and the end wall 12a of the motor housing 12. Therefore, the partition wall has a fluid passage 75 that is the outer peripheral region of the rotating shaft 41 and is surrounded by the second plate 16 and the end wall 12a of the motor housing 12.

<Shaft portion 63>
The rotating shaft 41 has a shaft portion 63. The shaft portion 63 has a first shaft portion 64, a second shaft portion 65, a third shaft portion 66, and a fourth shaft portion 67. The outer diameter of the first shaft portion 64 is larger than the outer diameters of the second shaft portion 65, the third shaft portion 66, and the fourth shaft portion 67. The outer diameter of the second shaft portion 65 is larger than the outer diameters of the third shaft portion 66 and the fourth shaft portion 67. The outer diameter of the third shaft portion 66 is larger than the outer diameter of the fourth shaft portion 67.

The second shaft portion 65 protrudes from the end face of the first shaft portion 64. The third shaft portion 66 protrudes from the end face of the second shaft portion 65. The fourth shaft portion 67 protrudes from the end face of the third shaft portion 66. The axis of the first shaft portion 64, the axis of the second shaft portion 65, the axis of the third shaft portion 66, and the axis of the fourth shaft portion 67 are all coincident. Therefore, the axis of the first shaft portion 64, the axis of the second shaft portion 65, the axis of the third shaft portion 66, and the axis of the fourth shaft portion 67 extend in the same straight line.

The first shaft portion 64 extends from inside the motor chamber 18 through the second hole 62 and into the small diameter hole 62b. The second shaft portion 65 extends from the small diameter hole 62b into the large diameter hole 62a. The third shaft portion 66 is disposed in the large diameter hole 62a. The fourth shaft portion 67 is inserted into the first hole 61 and passes through the inside of the boss portion 43b and the through hole 43h.

<Communication hole 68>
As shown in Figs. 2 and 3, a plurality of communication holes 68 are formed in the end wall 12a of the motor housing 12. Each communication hole 68 penetrates the end wall 12a of the motor housing 12. A first end of each communication hole 68 opens to the first step surface 62d. A second end of each communication hole 68 opens to the surface of the end wall 12a of the motor housing 12 on the motor chamber 18 side. Each communication hole 68 communicates between the fluid passage 75 and the motor chamber 18. Therefore, the plurality of communication holes 68 communicate between the fluid passage 75 and the motor chamber 18 and are provided radially outward of the rotating shaft 41 than the second hole 62. The communication holes 68 communicate between the inside of the second insertion hole 26 and the motor chamber 18. The plurality of communication holes 68 are arranged at predetermined intervals in the circumferential direction of the rotating shaft 41.

<Cooling fin 70>
The end wall 12a of the motor housing 12 is provided with a plurality of cooling fins 70. The plurality of cooling fins 70 are provided in a fluid passage 75. Each cooling fin 70 is a flat thin plate. Each cooling fin 70 protrudes from the inner peripheral surface of the small diameter hole 62b toward the rotation axis of the rotating shaft 41. The plurality of cooling fins 70 extend radially with respect to the rotation axis of the rotating shaft 41. The plurality of cooling fins 70 are arranged around the rotating shaft 41. The lengths of each cooling fin 70 from the inner peripheral surface of the small diameter hole 62b are the same. The end edges of each cooling fin 70 on the rotating shaft 41 side are located on the same circle centered on the rotation axis of the rotating shaft 41.

As shown in FIG. 3, each cooling fin 70 is disposed between a plurality of communication holes 68 adjacent to each other in the circumferential direction of the rotating shaft 41. Therefore, each cooling fin 70 is disposed at a position that does not block each communication hole 68. As shown in FIG. 2, each cooling fin 70 is continuous with the first step surface 62d. Each cooling fin 70 is integrally formed with the end wall 12a of the motor housing 12. Each cooling fin 70 is thermally coupled to the end wall 12a of the motor housing 12. Each cooling fin 70 guides the air flowing into the fluid passage 75 through the first hole 61 toward the outer periphery with respect to the rotation axis of the rotating shaft 41. Each cooling fin 70 exchanges heat with the air flowing into the fluid passage 75 through the first hole 61.

<Guide wall 71>
As shown in FIG. 2 and FIG. 3, the fluid passage 75 is provided with a guide wall 71. The guide wall 71 is annular. The guide wall 71 is provided on the rotating shaft 41. The guide wall 71 protrudes in an annular shape from the outer circumferential surface of the third shaft portion 66 of the rotating shaft 41. Therefore, the guide wall 71 is provided on the rotating shaft 41 and protrudes in an annular shape from the outer circumferential surface of the rotating shaft 41. The guide wall 71 is fixed by being pressed into the outer circumferential surface of the third shaft portion 66. The guide wall 71 is disposed in the large diameter hole 62a. The guide wall 71 rotates integrally with the rotating shaft 41. The guide wall 71 is disposed closer to the first hole 61 than the multiple cooling fins 70. The outer circumferential portion of the guide wall 71 overlaps with the multiple cooling fins 70 in the axial direction of the rotating shaft 41. The guide wall 71 guides the air flowing into the fluid passage 75 through the first hole 61 toward the multiple cooling fins 70.

[Operation of the First Embodiment]
Next, the operation of the first embodiment will be described.
The thrust bearing 54 is cooled by air introduced into the thrust bearing accommodating chamber 24 from the introduction passage 56. The air in the thrust bearing accommodating chamber 24 passes through the inside of the first bearing retaining portion 21. The first radial bearing 52 is cooled by air passing through the inside of the first bearing retaining portion 21. The air passing through the inside of the first bearing retaining portion 21 is introduced into the motor chamber 18. The motor 20 is cooled by the air introduced into the motor chamber 18. In the centrifugal compressor 10, a part of the air compressed by the second impeller 43 is introduced into the motor chamber 18 at a temperature lower than the temperature of the air discharged into the second discharge chamber 34, thereby cooling the thrust bearing 54, the first radial bearing 52, and the motor 20. The air introduced into the motor chamber 18 is discharged to the outside of the housing 11 through the discharge passage 59.

Some of the air compressed by the second impeller 43 and discharged into the second discharge chamber 34 leaks to the back surface 43a of the second impeller 43. Specifically, some of the air compressed by the second impeller 43 and discharged into the second discharge chamber 34 flows into the gap 72 between the back surface 43a of the second impeller 43 and the second plate 16. The air that leaks to the back surface 43a of the second impeller 43 flows into the first hole 61.

The air that passes through the first hole 61 flows into the fluid passage 75. The air that flows into the fluid passage 75 then collides with the guide wall 71. The air that collides with the guide wall 71 spreads radially outward from the rotating shaft 41 due to the centrifugal force that accompanies the rotation of the rotating shaft 41, and is guided toward the multiple cooling fins 70.

The air guided by the guide wall 71 toward the multiple cooling fins 70 exchanges heat with the multiple cooling fins 70, and dissipates heat to the motor housing 12 via the multiple cooling fins 70. In this way, the multiple cooling fins 70 exchange heat with the air that has leaked onto the back surface 43a of the second impeller 43. This cools the air that has leaked onto the back surface 43a of the second impeller 43.

After heat exchange with the cooling fins 70, the air flows through the communication holes 68 and the second hole 62 into the motor chamber 18. Therefore, the air leaking to the back surface 43a of the second impeller 43 flows through the first hole 61 into the fluid passage 75, and then flows through the communication hole 68 and the second hole 62 into the motor chamber 18. The second radial bearing 53 is cooled by the air passing through the second hole 62.

[Effects of the First Embodiment]
The first embodiment can provide the following effects.
(1-1) In the end wall 12a of the motor housing 12, a plurality of communication holes 68 are formed which communicate the fluid passage 75 and the motor chamber 18 and are provided radially outward of the rotary shaft 41 relative to the second hole 62. Air leaking to the back surface 43a of the second impeller 43 flows into the fluid passage 75 through the first hole 61, and flows into the motor chamber 18 through the communication hole 68 and the second hole 62. The end wall 12a of the motor housing 12 is provided with a plurality of cooling fins 70 which are provided in the fluid passage 75 and extend radially with respect to the rotation axis of the rotary shaft 41 to be arranged around the rotary shaft 41. The plurality of cooling fins 70 are arranged between the plurality of communication holes 68 adjacent to each other in the circumferential direction of the rotary shaft 41. According to this, when the fluid leaking to the back surface 43a of the second impeller 43 flows through the fluid passage 75 through the first hole 61, heat is dissipated to the motor housing 12 via the plurality of cooling fins 70. Therefore, it is possible to cool the air leaking to the rear surface 43a of the second impeller 43. Then, the cooled air flows from the fluid passage 75 through the communication hole 68 and the second hole 62 to the motor chamber 18. Therefore, it is possible to cool the motor 20 by utilizing the air leaking to the rear surface 43a of the second impeller 43. As a result, it is possible to improve the durability of the centrifugal compressor 10.

(1-2) The fluid passage 75 is provided with a guide wall 71 that guides the air that flows into the fluid passage 75 through the first hole 61 toward the multiple cooling fins 70. As a result, the guide wall 71 guides the air that flows into the fluid passage 75 through the first hole 61 toward the multiple cooling fins 70, making it easier for the air to dissipate heat to the motor housing 12 via the multiple cooling fins 70. Therefore, the air that leaks onto the back surface 43a of the second impeller 43 can be efficiently cooled. As a result, the motor 20 can be efficiently cooled by utilizing the air that leaks onto the back surface 43a of the second impeller 43.

(1-3) Since the guide wall 71 is provided on the rotating shaft 41, the guide wall 71 rotates integrally with the rotating shaft 41. Since the guide wall 71 protrudes in an annular shape from the outer circumferential surface of the rotating shaft 41, the air guided by the guide wall 71 tends to spread radially outward from the rotating shaft 41 due to the centrifugal force accompanying the rotation of the rotating shaft 41. Therefore, the guide wall 71 makes it easier for the air flowing into the fluid passage 75 through the first hole 61 to be guided toward the multiple cooling fins 70, so that the air is more likely to dissipate heat to the motor housing 12 via the multiple cooling fins 70. Therefore, the air leaking to the back surface 43a of the second impeller 43 can be efficiently cooled. As a result, the motor 20 can be efficiently cooled by utilizing the air leaking to the back surface 43a of the second impeller 43.

(1-4) The second radial bearing 53 can be cooled by the air passing through the second hole 62. On the other hand, the temperature of the air that has cooled the second radial bearing 53 has increased compared to the temperature before cooling the second radial bearing 53. At this time, the temperature of the air flowing from the fluid passage 75 into the motor chamber 18 through each communication hole 68 is lower than the temperature of the air flowing through the second hole 62 into the motor chamber 18. Therefore, the motor 20 can be efficiently cooled by the air that does not pass through the second hole 62 but flows into the motor chamber 18 through each communication hole 68.

(1-5) The air compressed by the second impeller 43 is a recompression of the air compressed by the first impeller 42, and therefore has a higher temperature than the air compressed by the first impeller 42. In addition, the air compressed by the second impeller 43 has a higher pressure than the air compressed by the first impeller 42, and therefore the air is likely to leak into the motor chamber 18 through the second insertion hole 26. Therefore, if the air leaking to the back surface 43a of the second impeller 43 enters the motor chamber 18 without being cooled, it will warm up the motor 20. However, in this embodiment, the air leaking to the back surface 43a of the second impeller 43 can be cooled, and therefore the motor 20 can be prevented from being heated.

[Second embodiment]
A second embodiment of a centrifugal compressor will be described below with reference to Fig. 4 and Fig. 5. In the embodiment described below, the same components as those in the first embodiment will be denoted by the same reference numerals, and the description thereof will be omitted or simplified. The second embodiment differs from the first embodiment in that the guide wall is fixed to a plurality of cooling fins, rather than being provided on the rotating shaft.

As shown in Figures 4 and 5, the guide wall 81 has a fixed portion 82 and a guide portion 83. The fixed portion 82 is cylindrical. The guide portion 83 is annular. The guide portion 83 protrudes radially outward from the outer circumferential surface of the axial end of the fixed portion 82.

The fixing portion 82 is inserted inward from the end edge of the cooling fins 70 on the rotating shaft 41 side. The fixing portion 82 is fitted into the end edge of the cooling fins 70 on the rotating shaft 41 side. The fixing portion 82 is fixed to the end edge of the cooling fins 70 on the rotating shaft 41 side. Therefore, the guide wall 81 is thermally coupled to the cooling fins 70 via the fixing portion 82.

The guide portion 83 is positioned closer to the first hole 61 than the cooling fins 70. The guide portion 83 is positioned inside the large diameter hole 62a. The guide portion 83 overlaps with the cooling fins 70 in the axial direction of the rotating shaft 41.

[Operation of the second embodiment]
Next, the operation of the second embodiment will be described.
The air that has passed through the first hole 61 flows into the fluid passage 75. Then, the air that has flowed into the fluid passage 75 collides with the guide portion 83 of the guide wall 81. The air that has collided with the guide portion 83 is guided toward the multiple cooling fins 70. Therefore, the guide wall 81 guides the air that flows into the fluid passage 75 through the first hole 61 toward the multiple cooling fins 70.

The air guided by the guide portion 83 toward the cooling fins 70 exchanges heat with the cooling fins 70, and dissipates heat to the motor housing 12 via the cooling fins 70. The air that flows into the fluid passage 75 through the first hole 61 is guided by the guide wall 81 toward the cooling fins 70, and at the same time dissipates heat to the motor housing 12 via the fixed portion 82 and each cooling fin 70. This cools the air that leaks onto the back surface 43a of the second impeller 43.

[Effects of the second embodiment]
In the second embodiment, in addition to all the effects of the first embodiment except for the effects (1-3), the following effects can be obtained.

(2-1) The guide wall 81 has a cylindrical fixing portion 82 that is fixed to the end edge of the cooling fins 70 on the rotating shaft 41 side. This allows the guide wall 81 to be thermally coupled to the cooling fins 70 via the fixing portion 82. Therefore, the air that flows into the fluid passage 75 through the first hole 61 is guided by the guide wall 81 toward the cooling fins 70, and at the same time, heat is dissipated to the motor housing 12 via the fixing portion 82 and each cooling fin 70. Therefore, the air that leaks to the back surface 43a of the second impeller 43 can be efficiently cooled. As a result, the motor 20 can be efficiently cooled by utilizing the air that leaks to the back surface 43a of the second impeller 43.

[Third embodiment]
A centrifugal compressor according to a third embodiment will be described below with reference to Fig. 6. The third embodiment is different from the first and second embodiments in that the guide wall is provided on the second plate, not on the rotating shaft or the cooling fins.

As shown in FIG. 6, the guide wall 91 has a fixed portion 92 and a guide portion 93. The fixed portion 92 is cylindrical. The guide portion 93 is annular. The guide portion 93 protrudes radially inward from the inner circumferential surface of the axial end of the fixed portion 92.

The fixing portion 92 is provided around the first hole 61 in the second plate 16. Therefore, the guide wall 91 is provided around the first hole 61 in the second plate 16. The fixing portion 92 is provided around the first hole 61 in the second plate 16 with the axial direction of the fixing portion 92 coinciding with the thickness direction of the second plate 16. The guide wall 91 is integrally formed with the second plate 16. A plurality of slits 94 are formed in the fixing portion 92. Each slit 94 connects the space inside the fixing portion 92 to the space outside the fixing portion 92.

The guide portion 93 extends from the fixed portion 92 toward the outer peripheral surface of the third shaft portion 66. The inner peripheral surface of the guide portion 93 extends along the outer peripheral surface of the third shaft portion 66. The inner peripheral surface of the guide portion 93 is spaced apart from the outer peripheral surface of the third shaft portion 66. The end of the guide portion 93 opposite the fixed portion 92 faces the first hole 61 in the axial direction of the rotation shaft 41.

[Operation of the Third Embodiment]
Next, the operation of the third embodiment will be described.
The air that has passed through the first hole 61 flows into the fluid passage 75. In detail, the air that has passed through the first hole 61 flows into the space inside the fixed part 92. The air that has flowed into the space inside the fixed part 92 collides with the guide part 93. The air that has collided with the guide part 93 spreads outward in the radial direction of the rotating shaft 41 and flows into the space outside the fixed part 92 through the multiple slits 94. Then, the air that has flowed into the space outside the fixed part 92 flows toward the multiple cooling fins 70. Therefore, the guide wall 91 guides the air that has passed through the first hole 61 toward the multiple cooling fins 70. Therefore, the guide wall 91 guides the air that flows into the fluid passage 75 through the first hole 61 toward the multiple cooling fins 70.

The air guided by the guide wall 91 toward the multiple cooling fins 70 exchanges heat with the multiple cooling fins 70, and the heat is dissipated to the motor housing 12 via the multiple cooling fins 70. This cools the air that leaks onto the back surface 43a of the second impeller 43.

[Effects of the third embodiment]
In the third embodiment, in addition to all the effects of the first embodiment except for the effects (1-3), the following effects can be obtained.

(3-1) The guide wall 91 is provided around the first hole 61 in the second plate 16 and guides the air that has passed through the first hole 61 toward the multiple cooling fins 70. This allows the guide wall 91 to be provided integrally with the second plate 16. This simplifies the configuration of the centrifugal compressor 10.

[Fourth embodiment]
A centrifugal compressor according to a fourth embodiment will be described below with reference to Fig. 7. The fourth embodiment is different from the first, second and third embodiments in that a guide wall is formed on the outer circumferential surface of a rotating shaft.

As shown in FIG. 7, the rotating shaft 41 has a shaft portion 95. The shaft portion 95 has a first shaft portion 95a and a second shaft portion 95b. The outer diameter of the first shaft portion 95a is larger than the outer diameter of the second shaft portion 95b. The second shaft portion 95b protrudes from the end face of the first shaft portion 95a. The axis of the first shaft portion 95a and the axis of the second shaft portion 95b are aligned.

The first shaft portion 95a extends from the motor chamber 18 through the second hole 62 and the small diameter hole 62b to the large diameter hole 62a. The second shaft portion 95b is inserted into the first hole 61 and passes through the inside of the boss portion 43b and the through hole 43h.

The portion of the outer circumferential surface of the first shaft portion 95a located within the large diameter hole 62a is an inclined surface 96. The inclined surface 96 is continuous with the end face of the first shaft portion 95a. The inclined surface 96 gradually expands in diameter as it moves away from the end face of the first shaft portion 95a. The inclined surface 96 is a curved surface that curves in an arc in a direction away from the axis of the first shaft portion 95a as it moves away from the end face of the first shaft portion 95a. The inclined surface 96 guides the air that flows into the fluid passage 75 through the first hole 61 toward the multiple cooling fins 70. Therefore, the portion of the first shaft portion 95a having the inclined surface 96 is a guide wall 97 that guides the air that flows into the fluid passage 75 through the first hole 61 toward the multiple cooling fins 70. The guide wall 97 is formed on the outer circumferential surface of the rotating shaft 41.

[Operation of the Fourth Embodiment]
Next, the operation of the fourth embodiment will be described.
The air that has passed through the first hole 61 flows into the fluid passage 75. The air that has flowed into the fluid passage 75 is guided by the inclined surface 96 of the guide wall 97 and flows toward the multiple cooling fins 70. Thus, the guide wall 97 guides the air that has flowed into the fluid passage 75 through the first hole 61 toward the multiple cooling fins 70.

The air guided by the guide wall 97 toward the multiple cooling fins 70 exchanges heat with the multiple cooling fins 70, and the heat is dissipated to the motor housing 12 via the multiple cooling fins 70. This cools the air that leaks onto the back surface 43a of the second impeller 43.

[Effects of the Fourth Embodiment]
In the fourth embodiment, in addition to all the effects of the first embodiment except for the effects (1-3), the following effects can be obtained.

(4-1) The guide wall 97 is formed on the outer peripheral surface of the rotating shaft 41. As a result, the outer peripheral surface of the rotating shaft 41 functions as a guide wall 97 that guides the air that flows into the fluid passage 75 through the first hole 61 toward the multiple cooling fins 70. For this reason, there is no need to place a member separate from the rotating shaft 41 as a guide wall in the fluid passage 75. This makes it possible to simplify the configuration of the centrifugal compressor.

[Example of change]
The above-described embodiments may be modified as follows: The above-described embodiments and the following modifications may be combined with each other to the extent that no technical contradiction occurs.

In each of the above-described embodiments, the fluid passage 75 does not necessarily have to have the guide walls 71 , 81 , 91 , 97 .
In each of the above-described embodiments, the number of communication holes 68 is not particularly limited.

In each of the above-described embodiments, the number of cooling fins 70 is not limited to a specific number.
In each of the above-described embodiments, the cooling water passage 12c does not necessarily have to be formed in the peripheral wall 12b of the motor housing 12.

In the first embodiment, for example, the boss portion 43b may extend through the first hole 61 to the fluid passage 75, and a guide wall 71 may be provided on the outer peripheral surface of the boss portion 43b. In this case, the guide wall 71 protrudes in an annular shape from the outer peripheral surface of the boss portion 43b.

In the second embodiment, the fixing portion 82 may be fixed to the end edge of the cooling fins 70 on the side of the rotating shaft 41, for example, by welding or the like. In short, as long as the fixing portion 82 is fixed to the end edge of the cooling fins 70 on the side of the rotating shaft 41, the fixing method is not particularly limited.

In the third embodiment, the guide wall 91 is integrally formed with the second plate 16, but this is not limited thereto, and the guide wall 91 may be a separate part from the second plate 16. In this case, the guide wall 91 may be fixed to the second plate 16 by, for example, welding or the like, or may be fixed by a fastener such as a bolt.

In each of the above embodiments, the introduction passage 56 may introduce a portion of the air compressed by the first impeller 42 into the motor chamber 18. The temperature of the air compressed by the first impeller 42 is lower than the temperature of the air compressed by the second impeller 43 and discharged into the second discharge chamber 34. In short, the introduction passage 56 may introduce air into the motor chamber 18 at a temperature lower than the temperature of the air discharged into the second discharge chamber 34.

○ In each of the above embodiments, the centrifugal compressor 10 may be configured without the second impeller 43. In this case, the partition wall separating the first impeller chamber 28 and the motor chamber 18 may have a first wall component, a second wall component, and a fluid passage. A plurality of communication holes are formed in the second wall component. Air leaking to the back surface of the first impeller 42 flows through the first hole into the fluid flow path, and flows through the communication hole and the second hole into the motor chamber 18. A plurality of cooling fins are provided in the fluid passage. The plurality of cooling fins are arranged between the plurality of communication holes adjacent to each other in the circumferential direction of the rotating shaft 41.

In each of the above-described embodiments, the centrifugal compressor 10 may be configured to include a turbine wheel instead of the second impeller 43 .
In each of the above-described embodiments, 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 each of the above embodiments, the centrifugal compressor 10 is not limited to being used to compress the air supplied to the fuel cell stack 38. In short, the centrifugal compressor 10 may be used to compress a fluid.

10... centrifugal compressor, 11... housing, 12a... end wall (partition wall) which is the second wall component, 15... first plate (partition wall), 16... second plate (partition wall) which is the first wall component, 17... third plate (partition wall), 18... motor chamber, 20... motor, 23... first insertion hole (insertion hole), 26... second insertion hole (insertion hole), 28... first impeller chamber (impeller chamber), 33... second impeller chamber (impeller chamber), 41... rotating shaft, 42... first impeller (impeller), 43... second impeller (impeller), 43a... back surface, 61... first hole, 62... second hole, 68... communication hole, 70... cooling fin, 71, 81, 91, 97... guide wall, 75... fluid passage, 82, 92... fixed part.

Claims (6)

A rotation axis;
an impeller that rotates integrally with the rotary shaft to compress a fluid;
A motor that rotates the rotary shaft;
a housing having an impeller chamber that houses the impeller, a motor chamber that houses the motor, and a partition wall that separates the impeller chamber and the motor chamber and has an insertion hole through which the rotating shaft is inserted,
The partition wall is
a first wall constituent body defining the impeller chamber and having a first hole forming a part of the insertion hole;
a second wall constituent that defines the motor chamber and forms a part of the insertion hole, and has a second hole in which a bearing is disposed between the second wall constituent and the rotating shaft;
a fluid passage in an outer circumferential region of the rotating shaft and surrounded by the first wall structure and the second wall structure;
The second wall constituent has a plurality of communication holes that communicate the fluid passage and the motor chamber and are provided radially outward of the rotary shaft with respect to the second hole,
The fluid leaking to the rear surface of the impeller flows through the first hole into the fluid passage, and flows through the communication hole and the second hole into the motor chamber,
the partition wall includes a plurality of cooling fins provided in the fluid passage and extending radially with respect to a rotation axis of the rotation shaft to be arranged around the rotation shaft,
The centrifugal compressor, characterized in that the plurality of cooling fins are arranged between the plurality of communication holes adjacent to each other in the circumferential direction of the rotating shaft. The centrifugal compressor according to claim 1, characterized in that the fluid passage is provided with a guide wall that guides the fluid that flows into the fluid passage through the first hole toward the multiple cooling fins. The centrifugal compressor according to claim 2, characterized in that the guide wall is provided on the rotating shaft and protrudes annularly from the outer circumferential surface of the rotating shaft. The centrifugal compressor according to claim 2, characterized in that the guide wall has a cylindrical fixing portion that is fixed to the end edge of the cooling fins on the rotating shaft side. The centrifugal compressor according to claim 2, characterized in that the guide wall is provided around the first hole in the first wall structure and guides the air that has passed through the first hole toward the multiple cooling fins. The centrifugal compressor according to claim 2, characterized in that the guide wall is formed on the outer circumferential surface of the rotating shaft.