Centrifugal compressor

Abstract

A bearing (52) for supporting a rotating shaft (41) of this centrifugal compressor (10) is provided to an inner peripheral surface demarcating an insertion hole (H2) into which the rotating shaft (41) is inserted. An introduction passage (56) opening on the inner peripheral surface toward the rotating shaft (41) is provided to a housing (11) so that a cooling fluid for cooling the bearing (52) is introduced into the insertion hole (H2). A seal section (60) for sealing the flow of the fluid is provided to the inner peripheral surface on the side opposite the bearing (52) across the opening of the introduction passage (56). A bypass passage (61) opening on the seal section (60) toward the rotating shaft (41) is provided to the housing (11) so that leaked fluid leaking between a back surface (43a) of an impeller (43) and a partition wall (S2) as the impeller (43) rotates bypasses the bearing (52) and flows towards the exterior of the housing (11) or towards a motor chamber (18).

Description

Centrifugal compressor

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

[0002] For example, as disclosed in Patent Document 1, a centrifugal compressor includes a rotating shaft, an impeller, a motor, and a housing. The impeller compresses fluid by rotating integrally with the rotating shaft. The motor rotates the rotating shaft. The housing defines an impeller chamber and a motor chamber. The impeller chamber accommodates the impeller. The motor chamber accommodates the motor. The housing has a partition wall. The partition wall partitions the impeller chamber and the motor chamber. An insertion hole is formed in the partition wall. The rotating shaft is inserted through the partition wall. The rotating shaft is supported by a bearing provided on an inner circumferential surface that defines the insertion hole. An introduction passage opens on the inner circumferential surface that defines the insertion hole. The introduction passage opens toward the rotating shaft so that a cooling fluid for cooling the bearing is introduced into the insertion hole.

[0003] Japanese Unexamined Patent Application Publication No. 2015-155696

[0004] In such a centrifugal compressor, there is a risk that leaked fluid that has leaked between the back surface of the impeller and the partition wall as the impeller rotates flows to the bearing. When the leaked fluid flows to the bearing, the bearing is warmed by the leaked fluid.

[0005] A centrifugal compressor according to one aspect of the present disclosure includes a rotating shaft, an impeller configured to compress a fluid by rotating integrally with the rotating shaft, a motor configured to rotate the rotating shaft, and a housing that partitions an impeller chamber housing the impeller and a motor chamber housing the motor. The housing has a partition wall separating the impeller chamber and the motor chamber. A through hole is formed in the partition wall through which the rotating shaft is inserted. A bearing configured to support the rotating shaft is provided on the inner circumferential surface partitioning the through hole. The housing is provided with an introduction passage that opens toward the rotating shaft and on the inner circumferential surface so that a cooling fluid for cooling the bearing is introduced into the through hole. A sealing portion is provided on the inner circumferential surface on the side opposite to the bearing, with the opening of the introduction passage in between, which is configured to seal the flow of fluid. The housing is provided with a bypass passage that opens to the seal portion toward the rotating shaft, such that leaked fluid that leaks between the back surface of the impeller and the partition wall as the impeller rotates can bypass the bearing and flow toward the outside of the housing or toward the motor chamber.

[0006] According to this design, a bypass passage is provided in the seal. The bypass passage opens toward the rotating shaft so that leak fluid that leaks between the back of the impeller and the partition wall as the impeller rotates can bypass the bearing and flow outwards to the outside of the housing or to the motor chamber. Therefore, it is possible to prevent the leak fluid from flowing into the bearing. This prevents the bearing from being heated by the leak fluid. As a result, the durability of the centrifugal compressor can be improved.

[0007] In the centrifugal compressor described above, the sealing portion is preferably a labyrinth seal formed by at least one groove. Such a labyrinth seal formed by at least one groove is suitable as a sealing portion for sealing the flow of fluid.

[0008] In the centrifugal compressor described above, the seal portion is preferably configured such that the cooling fluid and the leak fluid flow through the bypass passage. This configuration allows the leak fluid to flow more easily through the bypass passage. As a result, the bypass passage efficiently directs the leak fluid towards the outside of the housing or the motor chamber. Therefore, it becomes easier to further suppress the flow of leak fluid into the bearings.

[0009] In the centrifugal compressor described above, the seal portion is preferably provided with a throttling mechanism configured to suppress the flow of the leaking fluid toward the bearing between the bypass passage and the bearing.

[0010] According to this design, the seal section is provided with a throttling mechanism between the bypass passage and the bearing to prevent leakage fluid from flowing toward the bearing. This allows the leakage fluid to be efficiently directed toward the outside of the housing or toward the motor chamber.

[0011] In the centrifugal compressor described above, the impeller includes a first impeller configured to rotate integrally with the rotating shaft and compress a fluid, and a second impeller configured to rotate integrally with the rotating shaft and compress the compressed fluid compressed by the first impeller, wherein the introduction passage is configured to receive a portion of the compressed fluid, the leaked fluid is fluid that has leaked between the back surface of the second impeller and the partition wall, and the bypass passage is preferably configured to allow the leaked fluid to flow out of the housing or to the motor chamber while bypassing the bearing.

[0012] The pressure of the compressed fluid compressed by the second impeller is higher than the pressure of the compressed fluid compressed by the first impeller. Therefore, the pressure of the leaked fluid between the back of the second impeller and the partition wall is higher than the pressure of the cooling fluid introduced to the bearing from the introduction passage. In this case, the bypass passage directs the leaked fluid between the back of the second impeller and the partition wall towards the outside of the housing or the motor room, bypassing the bearing. Thus, the leaked fluid, which has a higher pressure than the cooling fluid introduced to the bearing from the introduction passage, can be directed towards the outside of the housing or the motor room, bypassing the bearing, via the bypass passage. As a result, the flow of leaked fluid into the bearing can be suppressed.

[0013] This invention makes it possible to improve the durability of centrifugal compressors.

[0014] Figure 1 is a cross-sectional view of a centrifugal compressor in an embodiment. Figure 2 is a cross-sectional view showing an enlarged portion of the centrifugal compressor in Figure 1. Figure 3 is a cross-sectional view showing an enlarged portion of a centrifugal compressor in a modified example. Figure 4 is a cross-sectional view showing an enlarged portion of a centrifugal compressor in another modified example.

[0015] An embodiment of a centrifugal compressor will be described below with reference to Figures 1 and 2. The centrifugal compressor of the embodiment described below is installed in a fuel cell vehicle. The centrifugal compressor compresses air, which is the fluid supplied to the fuel cell stack.

[0016] <Basic Configuration of Centrifugal Compressor> As shown in Figure 1, the centrifugal compressor 10 is equipped with a housing 11. The housing 11 is made of a metal material. For example, the housing 11 is made of aluminum. The housing 11 has a motor housing member 12, a first compressor housing member 13, a second compressor housing member 14, a first plate 15, a second plate 16, and a third plate 17.

[0017] The motor housing member 12 has an end wall 12a and a peripheral wall 12b. The end wall 12a is plate-shaped. The peripheral wall 12b is cylindrical and extends from the outer circumference of the end wall 12a. The peripheral wall 12b has an opening on the side opposite to the end wall 12a. The first plate 15 is connected to the open end of the peripheral wall 12b. The first plate 15 closes the opening of the peripheral wall 12b. The motor chamber 18 is partitioned by the motor housing member 12 and the first plate 15. Therefore, the housing 11 partitions the motor chamber 18.

[0018] The second plate 16 is connected to the outer surface of the end wall 12a of the motor housing member 12. The second plate 16 is attached to the end wall 12a such that the thickness direction of the second plate 16 coincides with the thickness direction of the end wall 12a.

[0019] The centrifugal compressor 10 is equipped with a motor 20. The motor 20 is housed in a motor chamber 18. Therefore, the motor chamber 18 houses the motor 20. The motor housing member 12 surrounds the motor 20.

[0020] The centrifugal compressor 10 is equipped with a first radial bearing housing 21. The first radial bearing housing 21 is cylindrical. The first radial bearing housing 21 protrudes into the motor chamber 18 from the center of the first plate 15. Therefore, the first plate 15 has the first radial bearing housing 21. The inner hole of the first radial bearing housing 21 communicates with the motor chamber 18.

[0021] 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 to the motor housing member 12. The chamber-forming recess 22 has a circular inner end face and an inner circumferential surface extending from the outer circumference of the inner end face. The inner hole of the first radial bearing housing 21 penetrates the first plate 15 and opens to the inner end face of the chamber-forming recess 22. The axis of the chamber-forming recess 22 coincides with the axis of the first radial bearing housing 21.

[0022] The third plate 17 is connected to the end face of the first plate 15 opposite to the motor housing member 12. The third plate 17 is attached to the first plate 15 such that the thickness direction of the third plate 17 coincides with the thickness direction of the first plate 15.

[0023] The housing 11 has a first hole 23. The first hole 23 is formed in the third plate 17. The first hole 23 penetrates the central part of the third plate 17. The axis of the first hole 23 coincides with the axis of the chamber-forming recess 22 and the axis of the first radial bearing housing 21. The chamber-forming recess 22 and the third plate 17 form a thrust bearing housing 24. The thrust bearing housing 24 is cylindrical. The thrust bearing housing 24 communicates with the inner hole of the first radial bearing housing 21. The first hole 23 and the thrust bearing housing 24 are in communication. The first hole 23 and the inner hole of the first radial bearing housing 21 are in communication via the thrust bearing housing 24. The thrust bearing housing 24 is provided between the first hole 23 and the first radial bearing housing 21.

[0024] The centrifugal compressor 10 is equipped with a second radial bearing housing 25. The second radial bearing housing 25 is cylindrical. The second radial bearing housing 25 protrudes into the motor chamber 18 from the center of the end wall 12a of the motor housing member 12. Therefore, the housing 11 has the second radial bearing housing 25. The inner hole of the second radial bearing housing 25 communicates with the motor chamber 18.

[0025] The housing 11 has a second hole 26. The second hole 26 is formed in the second plate 16. The second hole 26 penetrates the central part of the second plate 16. The axis of the second hole 26 coincides with the axis of the second radial bearing housing 25. A communication hole 12c is formed in the end wall 12a of the motor housing member 12. The communication hole 12c is formed in the central part of the end wall 12a. The axis of the communication hole 12c coincides with the axis of the second radial bearing housing 25 and the axis of the second hole 26. The first end of the communication hole 12c communicates with the second hole 26. The second end of the communication hole 12c communicates with the inner hole of the second radial bearing housing 25. Therefore, the second hole 26 communicates with the inner hole of the second radial bearing housing 25 via the communication hole 12c.

[0026] The first compressor housing member 13 is cylindrical. The first compressor housing member 13 has a first intake port 27. The first intake port 27 is a circular hole. Air is drawn into the first intake port 27. The first compressor housing member 13 is connected to the end face of the third plate 17 opposite to the first plate 15, with the axis of the first intake port 27 coinciding with the axis of the first hole 23. The first intake port 27 opens to the end face of the first compressor housing member 13 opposite to the third plate 17. Air purified by an air cleaner (not shown) flows into the first intake port 27.

[0027] 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 member 13 and the third plate 17. Therefore, the housing 11 partitions the first impeller chamber 28. The first plate 15 and the third plate 17 separate the first impeller chamber 28 from the motor chamber 18. Therefore, the first plate 15 and the third plate 17 constitute a first partition wall S1, which is a partition wall separating the first impeller chamber 28 from the motor chamber 18. Thus, the housing 11 has a first partition wall S1. The first impeller chamber 28 communicates with the first intake port 27. The first discharge chamber 29 extends around the axis of the first intake port 27, surrounding the first impeller chamber 28. The first diffuser flow path 30 connects the first impeller chamber 28 to the first discharge chamber 29. The first impeller chamber 28 is connected to the first hole 23.

[0028] The centrifugal compressor 10 has a first discharge passage 31. The first end of the first discharge passage 31 communicates with the first discharge chamber 29. The second end of the first discharge passage 31 opens to the outer circumferential surface of the first compressor housing member 13.

[0029] The second compressor housing member 14 is cylindrical. The second compressor housing member 14 has a second intake port 32. The second intake port 32 is a circular hole. Air is drawn into the second intake port 32. The second compressor housing member 14 is connected to the end face of the second plate 16 opposite to the motor housing member 12, with the axis of the second intake port 32 coinciding with the axis of the second hole 26. The second intake port 32 opens to the end face of the second compressor housing member 14 opposite to the second plate 16.

[0030] 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 member 14 and the second plate 16. Therefore, the housing 11 partitions the second impeller chamber 33. The end wall 12a of the motor housing member 12 and the second plate 16 partition the second impeller chamber 33 and the motor chamber 18. Therefore, the end wall 12a and the second plate 16 constitute a second partition wall S2, which is a partition wall separating the second impeller chamber 33 and the motor chamber 18. Thus, the housing 11 has a second partition wall S2. The second plate 16 is a partition wall that partitions the second impeller chamber 33. The second impeller chamber 33 is in communication with the second intake port 32. The second discharge chamber 34 extends around the axis of the second intake port 32, surrounding the second impeller chamber 33. The second diffuser flow path 35 connects the second impeller chamber 33 to the second discharge chamber 34. The second impeller chamber 33 is in communication with the second hole 26.

[0031] The centrifugal compressor 10 has a second discharge passage 36. The first end of the second discharge passage 36 communicates with the second discharge chamber 34. The second end of the second discharge passage 36 opens onto the outer surface of the second compressor housing member 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. The first end of the supply pipe 37 is connected to the second discharge passage 36. The 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.

[0032] The centrifugal compressor 10 is equipped with a connecting pipe 39. The first end of the connecting pipe 39 is in communication with the first discharge passage 31. The second end of the connecting pipe 39 is in communication with the second intake port 32. Air discharged from the first discharge chamber 29 to the first discharge passage 31 flows through the connecting pipe 39. The air that has passed through the connecting pipe 39 is drawn into the second impeller chamber 33 via the second intake port 32.

[0033] The centrifugal compressor 10 comprises a rotating shaft 41, a first impeller 42, a second impeller 43, and a support portion 44. The rotating shaft 41 is housed within the housing 11. The rotating shaft 41 extends along the axis of the motor housing member 12 and crosses the motor chamber 18. The axial direction of the rotating shaft 41 coincides with the axial direction of the motor housing member 12. The first end of the rotating shaft 41 protrudes from the motor chamber 18 into the first impeller chamber 28, passing through the inner hole of the first radial bearing housing portion 21, the inner hole of the thrust bearing housing portion 24, and the first hole 23. Therefore, the inner hole of the first radial bearing housing portion 21, the inner hole of the thrust bearing housing portion 24, and the first hole 23 constitute a first through-hole H1 through which the rotating shaft 41 is inserted. In this way, the first through-hole H1 is formed in the first partition wall S1.

[0034] The second end of the rotating shaft 41 protrudes from the motor chamber 18 into the second impeller chamber 33, passing through the inner hole, communication hole 12c, and second hole 26 of the second radial bearing housing 25. Therefore, the inner hole, communication hole 12c, and second hole 26 of the second radial bearing housing 25 constitute the second insertion hole H2, which is an insertion hole through which the rotating shaft 41 is inserted. In this way, the second insertion hole H2 is formed in the second partition wall S2.

[0035] The first impeller 42 is connected to the 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 compresses the air drawn into the first impeller chamber 28 by rotating integrally with the rotating shaft 41. Therefore, the first impeller 42 is an impeller that compresses air by rotating integrally with the rotating shaft 41. Thus, the first impeller chamber 28 is an impeller chamber that houses an impeller.

[0036] 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 drawn 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 by rotating integrally with the rotating shaft 41. Thus, the second impeller chamber 33 is an impeller chamber that houses the impeller. The second impeller 43 compresses the compressed air, which is a compressed fluid compressed by the first impeller 42. Thus, the impeller includes a first impeller 42 that rotates integrally with the rotating shaft 41 and compresses air, and a second impeller 43 that rotates integrally with the rotating shaft 41 and compresses the compressed air compressed by the first impeller 42.

[0037] The support portion 44 protrudes radially outward in an annular shape from the outer circumferential surface of the rotating shaft 41. The support portion 44 is disc-shaped. The support portion 44 is fixed to the outer circumferential surface of the rotating shaft 41. Therefore, the support portion 44 is separate from the rotating shaft 41. The support portion 44 is located within the thrust bearing housing 24. The support portion 44 rotates integrally with the rotating shaft 41.

[0038] The motor 20 has a cylindrical motor rotor 47 and a cylindrical motor stator 48. The motor chamber 18 houses the motor rotor 47. The motor rotor 47 is fixed to the rotating shaft 41. The motor stator 48 is fixed to the housing 11. The motor rotor 47 is positioned radially inward of the motor stator 48. The motor rotor 47 rotates integrally with the rotating shaft 41. The motor rotor 47 has 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 motor stator 48 surrounds the motor rotor 47. The motor stator 48 has a cylindrical stator core 50 and a motor coil 51. The stator core 50 is fixed to the inner circumferential surface of the motor housing member 12. The motor coil 51 is wound around the stator core 50.

[0039] The rotating shaft 41 rotates integrally with the motor rotor 47 when current flows from a battery (not shown) to the motor coil 51. Therefore, the motor 20 rotates the rotating shaft 41. The motor 20 is driven by the power supplied to the motor coil 51. The motor 20 is positioned between the first impeller 42 and the second impeller 43 in the axial direction of the rotating shaft 41.

[0040] 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 housed in a first radial bearing housing 21. The first radial bearing 52 is held on the inner circumferential surface of the first radial bearing housing 21. Therefore, the first radial bearing 52 is a bearing provided on the inner circumferential surface that partitions the first through hole H1. The first radial bearing 52 rotatably supports the portion of the rotating shaft 41 located between the motor 20 and the first end of the rotating shaft 41. Therefore, the rotating shaft 41 is supported by the first radial bearing 52.

[0041] 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 housed in a second radial bearing housing 25. The second radial bearing 53 is held on the inner circumferential surface of the second radial bearing housing 25. Therefore, the second radial bearing 53 is a bearing provided on the inner circumferential surface that partitions the second through hole H2. The second radial bearing 53 rotatably supports the portion of the rotating shaft 41 located between the motor 20 and the second end of the rotating shaft 41. Therefore, the rotating shaft 41 is supported by the second radial bearing 53.

[0042] The first radial bearing 52 and the second radial bearing 53 support the rotating shaft 41 so that it can rotate in the radial direction, at positions on both sides of the motor 20 in the axial direction of the rotating shaft 41. The "radial direction" is the direction perpendicular to the axial direction of the rotating shaft 41.

[0043] The centrifugal compressor 10 includes a thrust bearing 54. The thrust bearing 54 is housed in a thrust bearing housing portion 24. The thrust bearing 54 rotatably supports the support portion 44 from a thrust direction. Therefore, the thrust bearing 54 rotatably supports the rotating shaft 41 via the support portion 44. The "thrust direction" is a direction parallel to the axial direction of the rotating shaft 41.

[0044] Air sucked into the first impeller chamber 28 via the first suction port 27 is accelerated by the rotation of the first impeller 42 and fed into the first diffuser flow path 30. The air fed into the first diffuser flow path 30 has its pressure increased while passing through the first diffuser flow path 30. The air that has passed through the first diffuser flow path 30 is discharged into the first discharge chamber 29. The air discharged into the first discharge chamber 29 is discharged into the first discharge passage 31. The air discharged into the first discharge passage 31 is sucked into the second impeller chamber 33 via the connection pipe 39 and the second suction port 32. The air sucked into the second impeller chamber 33 is accelerated by the rotation of the second impeller 43 and fed into the second diffuser flow path 35. The air fed into the second diffuser flow path 35 has its pressure increased while passing through the second diffuser flow path 35. The air that has passed through the second diffuser flow path 35 is 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 a fuel cell stack 38 via a supply pipe 37. Therefore, the centrifugal compressor 10 supplies air to the fuel cell stack 38. Oxygen contained in the air supplied to the fuel cell stack 38 contributes to power generation of the fuel cell stack 38.

[0045] An introduction passage 56 is open on the inner peripheral surface of the communication hole 12c. Therefore, the introduction passage 56 is open on the inner peripheral surface that defines the second insertion hole H2. As described above, the housing 11 has the introduction passage 56. The introduction passage 56 is formed in an end wall 12a of the motor housing member 12. A first end of the introduction passage 56 is open on the outer peripheral surface of the end wall 12a. A second end of the introduction passage 56 communicates with the communication hole 12c. The introduction passage 56 opens toward the rotating shaft 41.

[0046] A branch pipe 57 is connected to a first end of the introduction passage 56. The branch pipe 57 is branched from the middle of the connection pipe 39. A first end of the branch pipe 57 is connected to the connection pipe 39. A second end of the branch pipe 57 is connected to the first end of the introduction passage 56.

[0047] Part of the air flowing through the connection pipe 39 flows into the branch pipe 57. The air that has flowed into the branch pipe 57 passes through the introduction passage 56, the communication hole 12c, and the inner hole of the second radial bearing housing portion 25, and flows out into the motor chamber 18. Therefore, part of the compressed air compressed by the first impeller 42 is introduced into the introduction passage 56. The compressed air introduced into the introduction passage 56 is cooling air, which is a cooling fluid for cooling the second radial bearing 53. The introduction passage 56 opens toward the rotating shaft 41 such that the cooling air for cooling the second radial bearing 53 is introduced into the second insertion hole H2.

[0048] The centrifugal compressor 10 is provided with a discharge passage 59. The discharge passage 59 is formed at a position close to the end wall 12a on the peripheral wall 12b of the motor housing member 12. A first end of the discharge passage 59 communicates with a portion between the stator core 50 and the end wall 12a of the motor housing member 12 in the motor chamber 18. A second end of the discharge passage 59 opens to the outer peripheral surface of the peripheral wall 12b of the motor housing member 12. Therefore, the discharge passage 59 communicates with the outside of the housing 11. The air in the motor chamber 18 is discharged to the outside of the housing 11 via the discharge passage 59.

[0049] <Sealing Section> As shown in Figure 2, a sealing section 60 is provided on the inner circumferential surface of the second hole 26. The sealing section 60 is a labyrinth seal composed of a plurality of grooves G1. The sealing section 60 is composed of two grooves G1. Therefore, the sealing section 60 is a labyrinth seal formed by at least one groove G1. The two grooves G1 are formed in an annular shape on the inner circumferential surface of the second hole 26. The two grooves G1 are arranged side by side in the axial direction of the rotating shaft 41. The sealing section 60 seals the airflow on the side opposite to the second radial bearing 53, with the opening of the introduction passage 56 in between. The sealing section 60 prevents leaked air, which is leaked fluid that leaks between the back surface 43a of the second impeller 43 and the second partition wall S2 as the second impeller 43 rotates, from flowing towards the second radial bearing housing 25 through the second hole 26. Thus, the leaked air is the air that leaked between the back surface 43a of the second impeller 43 and the second partition wall S2.

[0050] <Bypass passage> A bypass passage 61 opens into the seal portion 60. The bypass passage 61 is formed in the housing 11. The bypass passage 61 has a first passage 62 and a second passage 63. The first passage 62 is formed in the second plate 16. The first passage 62 extends radially outward from the inner circumferential surface of the second hole 26 to the rotation axis 41. The first end of the first passage 62 opens into the portion between the two grooves G1 on the inner circumferential surface of the second hole 26. The first end of the first passage 62 communicates with the second hole 26. The first end of the first passage 62 forms a bypass inlet 64 of the bypass passage 61. Therefore, the bypass passage 61 has a bypass inlet 64 that opens into the second insertion hole H2. The second end of the first passage 62 is located inside the second plate 16.

[0051] The second passage 63 extends axially with respect to the rotating shaft 41 inside the end wall 12a of the second plate 16 and the motor housing member 12. The second passage 63 extends axially with respect to the rotating shaft 41 from the second end of the first passage 62 toward the motor chamber 18. The first end of the second passage 63 communicates with the second end of the first passage 62. The second end of the second passage 63 opens into the motor chamber 18. The second end of the second passage 63 forms the bypass outlet 65 of the bypass passage 61. Therefore, the bypass passage 61 has a bypass outlet 65 that opens into the motor chamber 18.

[0052] <Restriction> A restrictor 66 is provided in the seal portion 60. The restrictor 66 is made up of one of the two grooves G1, the groove G1 located between the bypass inlet 64 of the bypass passage 61 and the second radial bearing 53. The restrictor 66 is provided between the bypass inlet 64 and the introduction passage 56. The restrictor 66 prevents leak air from flowing toward the second radial bearing 53 at the position between the bypass passage 61 and the second radial bearing 53.

[0053] The pressure in the introduction passage 56 is greater than the pressure in the bypass passage 61. A portion of the cooling air that flows from the introduction passage 56 into the communication hole 12c flows toward the second hole 26. The cooling air flowing toward the second hole 26 passes through the throttle 66 and flows toward the bypass inlet 64.

[0054] [Operation of the Embodiment] Next, the operation of the embodiment will be described. Most of the cooling air that flows from the introduction passage 56 into the communication hole 12c passes through the inner hole of the second radial bearing housing 25. The second radial bearing 53 is cooled by the cooling air passing through the inner hole of the second radial bearing housing 25. The cooling air that has passed through the inner hole of the second radial bearing housing 25 flows out into the motor chamber 18 and is also discharged from inside the motor chamber 18 to the outside of the housing 11 via the discharge passage 59.

[0055] As the second impeller 43 rotates, some of the compressed air leaks between the back surface 43a of the second impeller 43 and the second plate 16. The leaked air between the back surface 43a of the second impeller 43 and the second plate 16 flows into the inside of the second hole 26.

[0056] The leak air flowing inside the second hole 26 flows towards the bypass inlet 64. At this time, a portion of the cooling air introduced from the introduction passage 56 flows towards the bypass inlet 64. In this way, the seal portion 60 is configured so that cooling air and leak air flow through the bypass passage 61. This makes it easier for leak air to flow to the bypass inlet 64.

[0057] Leaky air flowing towards the bypass inlet 64 flows through the first passage 62 and the second passage 63 via the bypass inlet 64. Leaky air flowing through the second passage 63 flows out into the motor chamber 18 from the bypass outlet 65 and is discharged from the motor chamber 18 to the outside of the housing 11 via the discharge passage 59. In this way, the bypass passage 61 opens toward the rotating shaft 41 so that leaky air that leaks between the back surface 43a of the second impeller 43 and the second plate 16 as the second impeller 43 rotates bypasses the second radial bearing 53 and flows toward the outside of the housing 11. Therefore, the bypass passage 61 directs the leaky air toward the outside of the housing 11 while bypassing the second radial bearing 53. In this way, the flow of leaky air into the second radial bearing 53 is suppressed.

[0058] [Effects of the Embodiment] The above embodiment provides the following effects: (1) A bypass passage 61 is provided in the seal portion 60. The bypass passage 61 is provided in the direction of the rotating shaft 41 so that leaked air that leaks between the back surface 43a of the second impeller 43 and the second partition wall S2 as the second impeller 43 rotates bypasses the second radial bearing 53 and flows outwards to the outside of the housing 11. Therefore, it is possible to suppress the flow of leaked air to the second radial bearing 53. Thus, it is possible to suppress the second radial bearing 53 from being heated by leaked air. As a result, the durability of the centrifugal compressor 10 can be improved.

[0059] (2) The seal portion 60 is a labyrinth seal formed by at least one groove G1. Such a labyrinth seal formed by at least one groove G1 is suitable as a seal portion for sealing airflow.

[0060] (3) The seal portion 60 is configured such that cooling air and leak air flow through the bypass passage 61. Therefore, leak air flows more easily into the bypass passage 61. As a result, the bypass passage 61 allows the leak air to flow efficiently toward the outside of the housing 11. Therefore, it is possible to further suppress the flow of leak air toward the second radial bearing 53.

[0061] (4) In the seal portion 60, a throttling 66 is provided in the portion between the bypass passage 61 and the second radial bearing 53 to suppress the flow of leaking air toward the second radial bearing 53. As a result, leaking air can be efficiently directed toward the outside of the housing 11.

[0062] (5) The pressure of the compressed air compressed by the second impeller 43 is higher than the pressure of the compressed air compressed by the first impeller 42. Therefore, the pressure of the leaked air between the back surface 43a of the second impeller 43 and the second partition wall S2 is higher than the pressure of the cooling air introduced to the second radial bearing 53 from the introduction passage 56. However, the bypass passage 61 allows the leaked air between the back surface 43a of the second impeller 43 and the second partition wall S2 to flow out of the housing 11 while bypassing the second radial bearing 53. Therefore, the leaked air, which has a higher pressure than the cooling air introduced to the second radial bearing 53 from the introduction passage 56, can be directed out of the housing 11 by the bypass passage 61 while bypassing the second radial bearing 53. As a result, it is possible to suppress the flow of leaked air into the second radial bearing 53.

[0063] (6) The bypass outlet 65 opens into the motor chamber 18. Leaked air that flows out from the bypass outlet 65 into the motor chamber 18 is discharged from the motor chamber 18 to the outside of the housing 11 via the discharge passage 59. Therefore, since it is not necessary to open the bypass outlet 65 of the bypass passage 61 to the outside of the housing 11, the opening formed on the outer surface of the housing 11 can be minimized.

[0064] (7) In this embodiment, it is possible to suppress the flow of leaking air into the second radial bearing 53. Therefore, it is not necessary to increase the flow rate of air introduced into the second radial bearing 53 from the introduction passage 56. Consequently, it is not necessary to increase the flow rate of air compressed with the rotation of the first impeller 42 in order to cool the second radial bearing 53, and therefore it is not necessary to increase the rotational speed of the rotating shaft 41. As a result, the power consumption required to drive the motor 20 can be reduced.

[0065] (8) The throttle 66 is provided between the bypass inlet 64 and the introduction passage 56. This prevents some of the air flowing through the introduction passage 56 from flowing too far towards the bypass inlet 64. As a result, some of the air compressed by the rotation of the first impeller 42 is efficiently introduced to the second radial bearing 53, while some of the air flowing through the introduction passage 56 is directed towards the bypass inlet 64. As a result, leaky air can be efficiently directed to the outside of the housing 11 while bypassing the second radial bearing housing 25, and the second radial bearing 53 can be efficiently cooled by the air introduced to the second radial bearing 53 from the introduction passage 56.

[0066] [Examples of Modifications] The above embodiment can be implemented with the following modifications. The above embodiment and the following examples of modifications can be combined with each other to the extent that they do not contradict each other technically.

[0067] ○ As shown in Figure 3, the seal portion 60 may be a labyrinth seal formed by a single groove G1. In short, the seal portion 60 only needs to be a labyrinth seal formed by at least one groove G1. The bypass inlet 64 opens, for example, to the bottom surface of the groove G1.

[0068] ○ As shown in Figure 4, the seal portion 60 does not have to be a labyrinth seal. A step 67 is formed on the inner circumferential surface of the second hole 26. The step 67 is formed on the inner circumferential surface of the second hole 26 near the communication hole 12c. The portion between the step 67 and the communication hole 12c on the inner circumferential surface of the second hole 26 is a throttling 66. The inner circumferential surface of the second hole 26, including the step 67 and the throttling 66, is a seal portion 60 that seals the airflow on the side opposite the second radial bearing 53, with the opening of the introduction passage 56 in between.

[0069] ○ In this embodiment, the seal portion 60 does not need to be configured so that both cooling air and leak air flow through the bypass passage 61. That is, the seal portion 60 only needs to be configured so that at least leak air flows through the bypass passage 61.

[0070] ○ In this embodiment, the sealing portion 60 does not necessarily have to have a throttling 66. ○ In this embodiment, an introduction passage may be opened on the inner circumferential surface that partitions the first insertion hole H1. For example, the introduction passage is formed in the first plate 15. The introduction passage opens toward the rotating shaft 41 so that cooling air for cooling the first radial bearing 52 is introduced into the first insertion hole H1. In this case, a sealing portion is provided on the inner circumferential surface that partitions the first insertion hole H1, on the side opposite to the first radial bearing 52 with the opening of the introduction passage in between, to seal the airflow. The sealing portion is, for example, a labyrinth seal formed by at least one groove. A bypass passage may be opened in the sealing portion. The bypass passage opens toward the rotating shaft 41 so that leaked air that leaks between the back surface of the first impeller 42 and the first partition wall S1 as the first impeller 42 rotates bypasses the first radial bearing 52 and flows toward the outside of the housing 11.

[0071] ○ In this embodiment, the bypass outlet 65 of the bypass passage 61 may open to the outside of the housing 11. ○ In this embodiment, the leaked air that flows out into the motor chamber 18 from the bypass outlet 65 does not need to be discharged from the motor chamber 18 to the outside of the housing 11 via the discharge passage 59. In short, the seal portion 60 only needs to have the bypass passage 61 open toward the rotating shaft 41 so that the leaked air flows toward the motor chamber 18.

[0072] ○ In this embodiment, the introduction passage 56 may introduce a portion of the compressed air compressed by the second impeller 43 to the second radial bearing 53. In this case, a portion of the compressed air compressed by the second impeller 43 is cooled by the intercooler before being introduced to the second radial bearing 53 from the introduction passage 56.

[0073] ○ In this embodiment, the centrifugal compressor 10 may not be equipped with a second impeller 43. In this case, a bypass passage is formed in the housing 11 that allows leak air between the back surface of the first impeller 42 and the first plate 15 to flow out of the housing 11 while bypassing the thrust bearing housing 24.

[0074] ○ In this embodiment, the centrifugal compressor 10 may be equipped with a turbine wheel instead of the second impeller 43. In this case, a bypass passage is formed in the housing 11 that allows leak air between the back surface of the first impeller 42 and the first plate 15 to flow out of the housing 11 while bypassing the thrust bearing housing 24.

[0075] ○ In this embodiment, the centrifugal compressor 10 does not have to be mounted on the fuel cell vehicle. In short, the centrifugal compressor 10 is not limited to one mounted on a vehicle. ○ In this embodiment, the centrifugal compressor 10 is not limited to one used to compress the air supplied to the fuel cell stack 38. In short, the centrifugal compressor 10 can be any compressor that compresses a fluid.

[0076] 10...Centrifugal compressor, 11...Housing, 18...Motor chamber, 20...Motor, 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, 52...First radial bearing (bearing), 53...Second radial bearing (bearing), 56...Inlet passage, 60...Seal section, 61...Bypass passage, 66...Restriction, G1...Groove, H1...First insertion hole (insertion hole), H2...Second insertion hole (insertion hole), S1...First partition wall (partition wall), S2...Second partition wall (second partition wall).

Claims

1. A centrifugal compressor comprising: a rotating shaft; an impeller configured to compress a fluid by rotating integrally with the rotating shaft; a motor configured to rotate the rotating shaft; and a housing that partitions an impeller chamber housing the impeller and a motor chamber housing the motor, wherein the housing has a partition wall separating the impeller chamber and the motor chamber, the partition wall has a through hole through which the rotating shaft is inserted, and a bearing configured to support the rotating shaft is provided on the inner circumferential surface partitioning the through hole, and the housing is provided with an introduction passage that opens toward the rotating shaft and the inner circumferential surface so that a cooling fluid for cooling the bearing is introduced into the through hole, wherein the inner circumferential surface is provided with a sealing portion configured to seal the flow of fluid on the side opposite to the bearing with the opening of the introduction passage in between, A centrifugal compressor, wherein the housing is provided with a bypass passage that opens to the seal portion toward the rotating shaft, such that leaked fluid that leaks between the back surface of the impeller and the partition wall as the impeller rotates can bypass the bearing and flow toward the outside of the housing or toward the motor chamber.

2. The centrifugal compressor according to claim 1, wherein the sealing portion is a labyrinth seal formed by at least one groove.

3. The centrifugal compressor according to claim 1, wherein the sealing portion is configured such that the cooling fluid and the leak fluid flow through the bypass passage.

4. The centrifugal compressor according to claim 1, wherein the seal portion is provided with a throttling mechanism configured to suppress the flow of the leaking fluid toward the bearing between the bypass passage and the bearing.

5. The centrifugal compressor according to claim 1 or 2, wherein the impeller includes a first impeller configured to rotate integrally with the rotating shaft and to compress a fluid, and a second impeller configured to rotate integrally with the rotating shaft and to compress the compressed fluid compressed by the first impeller, the introduction passage configured to receive a portion of the compressed fluid, the leak fluid being fluid that has leaked between the back surface of the second impeller and the partition wall, and the bypass passage configured to allow the leak fluid to flow out of the housing or to the motor chamber while bypassing the bearing.

Images