Centrifugal compressor

Abstract

To improve the reliability of thrust bearings. [Solution] The outer peripheral space 58 is provided with an annular constriction portion 71 that extends around the axis of the rotating shaft 41. The bearing housing chamber 24 is divided by the constriction portion 71 into an upstream space 72 located upstream of the constriction portion 71 in the direction of airflow, and a downstream space 73 located downstream of the constriction portion 71 in the direction of airflow. The pressure in the upstream space 72 is higher than the pressure in the downstream space 73. Therefore, the thrust collar 44 is pressed in a direction away from the first thrust bearing portion 54a due to the pressure difference between the upstream space 72 and the downstream space 73, making it difficult for the thrust collar 44 to move toward the first thrust bearing portion 54a. As a result, the thrust load applied to the first thrust bearing portion 54a is reduced, and the durability of the thrust bearing 54 is improved.

Description

Technical Field

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

Background Art

[0002] For example, as disclosed in Patent Document 1, a centrifugal compressor includes a rotating shaft, an impeller, a thrust bearing, a housing, and a thrust collar. The impeller rotates integrally with the rotating shaft to compress fluid. The thrust bearing supports the rotating shaft in the thrust direction. The housing partitions an impeller chamber and a bearing housing chamber. The impeller chamber houses the impeller. The bearing housing chamber houses the thrust bearing. The thrust collar is annular. The thrust collar protrudes from the outer peripheral surface of the rotating shaft into the bearing housing chamber. The housing has a partition wall that partitions the impeller chamber and the bearing housing chamber. An insertion hole is formed in the partition wall. The rotating shaft is inserted through the insertion hole. The thrust bearing has a first thrust bearing portion and a second thrust bearing portion. The first thrust bearing portion is disposed on the impeller chamber side with respect to the thrust collar. The second thrust bearing portion is disposed on the side opposite to the impeller chamber with respect to the thrust collar.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In such centrifugal compressors, some of the fluid compressed by the rotation of the impeller may flow into the gap between the back of the impeller and the partition wall. This fluid flow increases the pressure in the gap, pushing the impeller away from the partition wall. As a result, the thrust collar attempts to move towards the first thrust bearing, increasing the thrust load applied to the first thrust bearing. Depending on the pressure in the gap between the impeller and the partition wall, the thrust load applied to the first thrust bearing may become excessively large, potentially degrading the durability of the thrust bearing. Therefore, the reliability of the thrust bearing deteriorates. [Means for solving the problem]

[0005] A centrifugal compressor that solves the above problems comprises a rotating shaft, an impeller that rotates integrally with the rotating shaft to compress a fluid, a thrust bearing that supports the rotating shaft in the thrust direction, a housing that partitions an impeller chamber that houses the impeller and a bearing housing chamber that houses the thrust bearing, and an annular thrust collar that protrudes from the outer circumferential surface of the rotating shaft into the bearing housing chamber, wherein the housing has a partition wall that separates the impeller chamber and the bearing housing chamber and has a through hole through which the rotating shaft is inserted, and the thrust bearing has a first thrust bearing portion arranged on the impeller chamber side with respect to the thrust collar, and a second thrust bearing portion arranged on the opposite side of the impeller chamber with respect to the thrust collar, A portion of the fluid compressed by the rotation of the impeller flows into the bearing housing chamber through the through-hole from the gap between the back surface of the impeller and the partition wall, and flows through the bearing housing chamber in the following order: between the first thrust bearing portion and the thrust collar, in the outer peripheral space located radially outside the rotation shaft beyond the thrust bearing within the bearing housing chamber, and between the second thrust bearing portion and the thrust collar. The outer peripheral space is provided with an annular throttling portion extending around the axis of the rotation shaft, and the bearing housing chamber is divided by the throttling portion into an upstream space located upstream of the throttling portion in the direction of fluid flow and a downstream space located downstream of the throttling portion in the direction of fluid flow, with the pressure in the upstream space being higher than the pressure in the downstream space.

[0006] According to this, a portion of the fluid compressed by the rotation of the impeller flows into the bearing housing through the through-hole in the gap between the back of the impeller and the partition wall. The fluid then flows through the bearing housing in the following order: between the first thrust bearing section and the thrust collar, in the outer peripheral space located radially outside the rotation axis of the thrust bearing within the bearing housing, and between the second thrust bearing section and the thrust collar. At this time, an annular throttling section is provided in the outer peripheral space, extending around the axis of the rotation axis. As a result, the bearing housing is divided by the throttling section into an upstream space located upstream of the throttling section in the direction of fluid flow and a downstream space located downstream of the throttling section in the direction of fluid flow. The pressure in the upstream space is higher than the pressure in the downstream space. Therefore, the difference between the pressure in the upstream space and the pressure in the downstream space pushes the thrust collar away from the first thrust bearing section. As a result, even if the impeller is pushed away from the partition wall by the pressure in the gap between the back of the impeller and the partition wall, the thrust collar is less likely to move toward the first thrust bearing. Therefore, the thrust load applied to the first thrust bearing can be reduced, thereby improving the durability of the thrust bearing. In this way, the reliability of the thrust bearing can be improved.

[0007] In the centrifugal compressor described above, the throttling portion is preferably positioned so as to overlap with the thrust collar in the axial direction of the rotation axis. For example, when the rotation axis vibrates, the thrust collar moves radially along the rotation axis. At this time, the aperture is positioned so as to overlap the thrust collar with respect to the rotation axis in the axial direction. This eliminates the need to adjust the dimensions of the aperture to account for the radial movement of the thrust collar along the rotation axis due to the vibration of the rotation axis, allowing the aperture to be easily provided in the outer periphery.

[0008] In the centrifugal compressor described above, the throttling portion is preferably positioned so as to overlap with the outer edge of the thrust collar in the axial direction of the rotation axis. According to this, the thrust collar can be suitably pressed in a direction away from the first thrust bearing portion by the pressure in the upstream space, making it easier to further reduce the thrust load applied to the first thrust bearing portion.

[0009] In the centrifugal compressor described above, the throttling portion is preferably positioned so as to overlap the thrust collar on the radially outer side of the rotation axis. Thus, arranging the aperture portion in the outer peripheral space, in a position that overlaps with the thrust collar on the radial side of the rotation axis, is a suitable configuration when the aperture portion is provided in the outer peripheral space. [Effects of the Invention]

[0010] This invention makes it possible to improve the reliability of thrust bearings. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a cross-sectional view of a centrifugal compressor in an embodiment. [Figure 2] Figure 2 is a cross-sectional view showing a magnified portion of a centrifugal compressor. [Figure 3] Figure 3 is a cross-sectional view showing a magnified portion of the centrifugal compressor in the modified example. [Figure 4] Figure 4 is a cross-sectional view showing a magnified portion of the centrifugal compressor in the modified example. [Modes for carrying out the invention]

[0012] An embodiment of the centrifugal compressor will be described below with reference to Figures 1 and 2. The centrifugal compressor in the embodiment described below is installed in a fuel cell vehicle. The centrifugal compressor compresses air, which is supplied as a fluid to the fuel cell stack.

[0013] <Basic configuration of a centrifugal compressor> As shown in Figure 1, the centrifugal compressor 10 includes a housing 11. The housing 11 is made of a metal material. For example, the housing 11 is made of aluminum. The housing 11 includes a motor housing 12, a compressor housing 13, a turbine housing 14, a first plate 15, a second plate 16, and a third plate 17.

[0014] 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 circumference of the end wall 12a. The first plate 15 is connected to the opening end of the peripheral wall 12b of the motor housing 12. The first plate 15 closes the opening of the peripheral wall 12b of the motor housing 12. The motor room 18 is partitioned by the motor housing 12 and the first plate 15. Therefore, the housing 11 partitions the motor room 18.

[0015] 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 such that the thickness direction of the second plate 16 coincides with the thickness direction of the end wall 12a of the motor housing 12.

[0016] 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 12 surrounds the motor 20.

[0017] The centrifugal compressor 10 is equipped with a first bearing holder 21. The first bearing holder 21 protrudes into the motor chamber 18 from the center of the first plate 15. Therefore, the first plate 15 has the first bearing holder 21. The first bearing holder 21 is cylindrical. The inside of the first bearing holder 21 is in communication with the motor chamber 18.

[0018] 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 12. The chamber-forming recess 22 is in the shape of a circular hole. The inside of the first bearing holding portion 21 penetrates the first plate 15 and opens to the bottom surface of the chamber-forming recess 22. The axis of the chamber-forming recess 22 coincides with the axis of the first bearing holding portion 21.

[0019] The third plate 17 is connected to the end face of the first plate 15 opposite to the motor housing 12. The third plate 17 is attached to the first plate 15 in a state where the thickness direction of the third plate 17 coincides 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 at 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 holding portion 21. And the bearing housing chamber 24 is partitioned by the chamber-forming recess 22 and the third plate 17. Therefore, the housing 11 partitions the bearing housing chamber 24. The bearing housing chamber 24 communicates with the inside of the first bearing holding portion 21. Also, the bearing housing chamber 24 communicates with the first insertion hole 23. Therefore, the inside of the first bearing holding portion 21 communicates with the first insertion hole 23 through the bearing housing chamber 24.

[0020] The centrifugal compressor 10 includes a second bearing holding portion 25. The second bearing holding portion 25 protrudes into the motor chamber 18 from the center of the end wall 12a of the motor housing 12. Therefore, the motor housing 12 has the second bearing holding portion 25. The second bearing holding portion 25 is cylindrical. The inside of the second bearing holding portion 25 communicates with the inside of the motor chamber 18.

[0021] 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 axis of the second insertion hole 26 coincides with the axis of the second bearing holding portion 25. The second insertion hole 26 communicates with the inside of the second bearing holding portion 25.

[0022] The compressor housing 13 is cylindrical and has a circular intake port 27 through which air is drawn in. The compressor housing 13 is connected to the end face of the third plate 17 opposite to the first plate 15, with the axis of the intake port 27 coinciding with the axis of the first insertion hole 23. The intake port 27 opens to the end face of the compressor housing 13 opposite to the third plate 17. Air purified by an air cleaner (not shown) flows through the intake port 27.

[0023] The centrifugal compressor 10 comprises an impeller chamber 28, a discharge chamber 29, and a diffuser passage 30. The impeller chamber 28, the discharge chamber 29, and the diffuser passage 30 are formed between the compressor housing 13 and the third plate 17. Thus, the housing 11 partitions the impeller chamber 28. The first plate 15 and the third plate 17 separate the impeller chamber 28 from the motor chamber 18. The impeller chamber 28 communicates with the intake port 27. The discharge chamber 29 extends around the axis of the intake port 27, surrounding the impeller chamber 28. The diffuser passage 30 communicates the impeller chamber 28 and the discharge chamber 29. The impeller chamber 28 communicates with the first insertion hole 23.

[0024] The centrifugal compressor 10 has a discharge passage 31. The first end of the discharge passage 31 communicates with the discharge chamber 29. The second end of the discharge passage 31 opens to the outer surface of the compressor housing 13.

[0025] The turbine housing 14 is cylindrical and has a circular discharge port 32 through which air is discharged. The turbine housing 14 is connected to the end face of the second plate 16 opposite to the motor housing 12, with the axis of the discharge port 32 coinciding with the axis of the second insertion hole 26. The discharge port 32 opens to the end face of the turbine housing 14 opposite to the second plate 16.

[0026] The centrifugal compressor 10 comprises a turbine chamber 33, a turbine scroll flow path 34, and a communication passage 35. The turbine chamber 33, turbine scroll flow path 34, and communication passage 35 are formed between the turbine housing 14 and the second plate 16. The end wall 12a of the motor housing 12 and the second plate 16 separate the turbine chamber 33 from the motor chamber 18. The turbine chamber 33 communicates with the discharge port 32. The turbine scroll flow path 34 extends around the turbine chamber 33 and around the axis of the discharge port 32. The communication passage 35 connects the turbine chamber 33 and the turbine scroll flow path 34. The turbine chamber 33 communicates with the second insertion hole 26.

[0027] The centrifugal compressor 10 has an intake passage 36. The first end of the intake passage 36 opens to the outer circumferential surface of the turbine housing 14. The second end of the intake passage 36 communicates with the turbine scroll passage 34.

[0028] The centrifugal compressor 10 comprises a rotating body 40. The rotating body 40 includes a rotating shaft 41, an impeller 42, a turbine wheel 43, and a thrust collar 44. Thus, the centrifugal compressor 10 comprises a rotating shaft 41, an impeller 42, and a thrust collar 44. The rotating shaft 41 is housed within a housing 11.

[0029] The rotating shaft 41 extends along the axis of the motor housing 12 and crosses the motor chamber 18. 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 through the inside of the first bearing holder 21, the bearing housing chamber 24, and the first insertion hole 23 into the impeller chamber 28. Therefore, the first insertion hole 23 is an insertion hole through which the rotating shaft 41 is inserted. The third plate 17 is a partition wall that separates the impeller chamber 28 and the bearing housing chamber 24 and has an insertion hole through which the rotating shaft 41 is inserted. Thus, the housing 11 has a partition wall that separates the impeller chamber 28 and the bearing housing chamber 24 and has an insertion hole through which the rotating shaft 41 is inserted. The second end of the rotating shaft 41 protrudes into the turbine chamber 33, passing from the motor chamber 18 through the inside of the second bearing retaining portion 25 and the second insertion hole 26.

[0030] The impeller 42 is connected to the first end of the rotating shaft 41. The impeller 42 is housed in the impeller chamber 28. Therefore, the impeller chamber 28 houses the impeller 42. The impeller 42 rotates integrally with the rotating shaft 41 to compress the air drawn into the impeller chamber 28. The impeller 42 is cylindrical in shape, gradually decreasing in diameter from the back surface 42a toward the tip. The back surface 42a of the impeller 42 faces the third plate 17.

[0031] The impeller 42 has a cylindrical boss portion 42b. The boss portion 42b protrudes from the center of the back surface 42a of the impeller 42. The first end of the rotating shaft 41 passes inside the boss portion 42b. The boss portion 42b is inserted into the first through hole 23. Therefore, the boss portion 42b is located inside the first through hole 23. The boss portion 42b is the part of the rotating body 40 that is located inside the first through hole 23. In the impeller 42, the boss portion 42b can also be said to constitute a part of the rotating shaft 41.

[0032] The turbine wheel 43 is connected to the second end of the rotating shaft 41. The turbine wheel 43 is housed in the turbine chamber 33. The turbine wheel 43 rotates integrally with the rotating shaft 41.

[0033] The thrust collar 44 is annular in shape. The thrust collar 44 protrudes from the outer circumferential surface of the rotating shaft 41 into the bearing housing chamber 24. Therefore, the thrust collar 44 is located within the bearing housing chamber 24. The thrust collar 44 is fixed to the rotating shaft 41 in a state where it protrudes annularly radially outward from the outer circumferential surface of the rotating shaft 41. The thrust collar 44 is a separate component from the rotating shaft 41. The thrust collar 44 rotates integrally with the rotating shaft 41.

[0034] The motor 20 has a cylindrical motor rotor 47 and a cylindrical motor stator 48. 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 located 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 12. The motor coil 51 is wound around the stator core 50.

[0035] 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 positioned between the impeller 42 and the turbine wheel 43 in the axial direction of the rotating shaft 41.

[0036] 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 in a first bearing holder 21. The first radial bearing 52 rotatably supports the portion of the rotating shaft 41 that is located closer to the first end of the rotating shaft 41 than the motor 20.

[0037] 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 in a second bearing holder 25. The second radial bearing 53 rotatably supports the portion of the rotating shaft 41 that is located closer to the second end of the rotating shaft 41 than the motor 20.

[0038] The first radial bearing 52 and the second radial bearing 53 support the motor 20 so that the rotating shaft 41 can rotate radially, positioned on both sides of the rotating shaft 41 in the axial direction of the motor 20. The "radial direction" refers to the direction perpendicular to the axial direction of the rotating shaft 41.

[0039] The centrifugal compressor 10 is equipped with a thrust bearing 54. The thrust bearing 54 is housed in a bearing housing chamber 24. Therefore, the bearing housing chamber 24 houses the thrust bearing 54. The thrust bearing 54 supports a thrust collar 44 so that it can rotate in the thrust direction. Therefore, the thrust bearing 54 supports the rotating shaft 41 in the thrust direction via the thrust collar 44. Note that "thrust direction" refers to the direction parallel to the axial direction of the rotating shaft 41.

[0040] As shown in Figure 2, the thrust bearing 54 has a first thrust bearing portion 54a and a second thrust bearing portion 54b. The first thrust bearing portion 54a is positioned between the thrust collar 44 and the third plate 17 in the axial direction of the rotating shaft 41. Therefore, the first thrust bearing portion 54a is positioned on the impeller chamber 28 side relative to the thrust collar 44. The second thrust bearing portion 54b is positioned between the thrust collar 44 and the first plate 15 in the axial direction of the rotating shaft 41. Therefore, the second thrust bearing portion 54b is positioned on the opposite side of the thrust collar 44 from the impeller chamber 28. The outer peripheral edge 44e of the thrust collar 44 is located radially outward from the rotating shaft 41 than the first thrust bearing portion 54a and the second thrust bearing portion 54b. Therefore, the outer peripheral edge 44e of the thrust collar 44 is positioned in the outer peripheral space 58, which is located radially outside the rotation axis 41 compared to the thrust bearing 54 within the bearing housing chamber 24.

[0041] As shown in Figure 1, the centrifugal compressor 10 is equipped with a first seal portion 55. The first seal portion 55 is a labyrinth seal, for example, composed of a plurality of grooves formed on the inner circumferential surface that demarcates the first through hole 23 in the third plate 17. The first seal portion 55 reduces air leakage from the gap 57 between the back surface 42a of the impeller 42 and the third plate 17 to the motor chamber 18 through the first through hole 23.

[0042] The centrifugal compressor 10 is equipped with a second seal portion 56. The second seal portion 56 is a labyrinth seal, for example, composed of a plurality of grooves formed on the inner circumferential surface that partitions the second insertion hole 26 in the second plate 16. The second seal portion 56 reduces air leakage from the gap between the back surface of the turbine wheel 43 and the second plate 16 to the motor chamber 18 through the second insertion hole 26.

[0043] <Fuel cell system> The centrifugal compressor 10 with the above configuration constitutes part of the fuel cell system 60 mounted on the fuel cell vehicle. In addition to the centrifugal compressor 10, the fuel cell system 60 includes a fuel cell stack 61, a supply pipe 62, and a discharge pipe 63. The fuel cell stack 61 is composed of multiple battery cells (not shown). The supply pipe 62 connects the discharge passage 31 to the fuel cell stack 61. The discharge pipe 63 connects the fuel cell stack 61 to the intake passage 36.

[0044] As the impeller 42 rotates, air is drawn into the impeller chamber 28 from the intake port 27. The air drawn into the impeller chamber 28 is accelerated by the rotation of the impeller 42 and sent to the diffuser passage 30, where it is pressurized as it passes through the diffuser passage 30. The air that has passed through the diffuser passage 30 is then discharged into the discharge chamber 29. Therefore, compressed air is discharged into the discharge chamber 29 as the impeller 42 rotates.

[0045] The air discharged into the discharge chamber 29 is then discharged into the discharge passage 31. The air discharged into the discharge passage 31 is supplied to the fuel cell stack 61 via the supply pipe 62. The oxygen contained in the air supplied to the fuel cell stack 61 contributes to the power generation of the fuel cell stack 61. Subsequently, the air passing through the fuel cell stack 61 is discharged into the exhaust pipe 63 as exhaust from the fuel cell stack 61.

[0046] The exhaust from the fuel cell stack 61 is drawn into the turbine scroll passage 34 via the discharge pipe 63 and the intake passage 36. The exhaust from the fuel cell stack 61 drawn into the turbine scroll passage 34 is introduced into the turbine chamber 33 via the communication passage 35. The turbine wheel 43 rotates due to the exhaust from the fuel cell stack 61 introduced into the turbine chamber 33. The rotating shaft 41 rotates not only due to the drive of the motor 20, but also due to the rotation of the turbine wheel 43, which is rotated by the exhaust from the fuel cell stack 61. The rotation of the rotating shaft 41 is assisted by the rotation of the turbine wheel 43 due to the exhaust from the fuel cell stack 61. The exhaust that has passed through the turbine chamber 33 is discharged to the outside from the discharge port 32.

[0047] A portion of the air compressed by the rotation of the impeller 42 flows into the bearing housing chamber 24 through the first insertion hole 23 from the gap 57 between the back surface 42a of the impeller 42 and the third plate 17. As shown in Figure 2, the air that flows into the bearing housing chamber 24 flows through the space between the first thrust bearing portion 54a and the thrust collar 44, the outer peripheral space 58, and the space between the second thrust bearing portion 54b and the thrust collar 44.

[0048] <Aperture section> The centrifugal compressor 10 is equipped with a throttling member 70. The throttling member 70 is annular in shape. The throttling member 70 is provided on the first plate 15. The throttling member 70 is attached to the bottom surface of the chamber forming recess 22, for example, by bolts (not shown). The throttling member 70 protrudes annularly from the bottom surface of the chamber forming recess 22. The throttling member 70 extends around the axis of the rotation shaft 41. The protruding end of the throttling member 70 from the bottom surface of the chamber forming recess 22 is a tapered tip 70e.

[0049] The diaphragm member 70 is provided on the bottom surface of the chamber-forming recess 22 such that the tip 70e of the diaphragm member 70 is positioned to overlap with the outer peripheral edge 44e of the thrust collar 44 in the axial direction of the rotation shaft 41. Therefore, the diaphragm member 70 is positioned within the bearing housing chamber 24 such that the tip 70e of the diaphragm member 70 is positioned in the outer peripheral space 58. The tip 70e of the diaphragm member 70 is spaced apart from the outer peripheral edge 44e of the thrust collar 44. An annular diaphragm portion 71 is formed between the tip 70e of the diaphragm member 70 and the thrust collar 44. Thus, an annular diaphragm portion 71 extending around the axis of the rotation shaft 41 is provided in the outer peripheral space 58. The diaphragm portion 71 is positioned to overlap with the thrust collar 44 in the axial direction of the rotation shaft 41. The diaphragm portion 71 is positioned to overlap with the outer peripheral edge 44e of the thrust collar 44 in the axial direction of the rotation shaft 41. The diaphragm 71 is positioned within the outer peripheral space 58 on the opposite side of the thrust collar 44 from the third plate 17.

[0050] The bearing housing chamber 24 is divided into an upstream space 72 and a downstream space 73 by a throttling section 71. The upstream space 72 is located upstream of the throttling section 71 in the direction of airflow. The downstream space 73 is located downstream of the throttling section 71 in the direction of airflow. The pressure in the upstream space 72 is higher than the pressure in the downstream space 73.

[0051] [Effect of the Embodiment] Next, the operation of the embodiment will be described. Incidentally, in such a centrifugal compressor 10, some of the air compressed by the rotation of the impeller 42 may flow into the gap 57 between the back surface 42a of the impeller 42 and the third plate 17. When air flows into the gap 57 between the back surface 42a of the impeller 42 and the third plate 17, the pressure in the gap 57 between the back surface 42a of the impeller 42 and the third plate 17 increases, causing the impeller 42 to be pushed in a direction that moves it away from the third plate 17.

[0052] Here, some of the air compressed by the rotation of the impeller 42 flows into the bearing housing chamber 24 through the first insertion hole 23 from the gap 57 between the back surface 42a of the impeller 42 and the third plate 17. The air then flows through the bearing housing chamber 24 in the following order: between the first thrust bearing portion 54a and the thrust collar 44, through the outer peripheral space 58, and between the second thrust bearing portion 54b and the thrust collar 44.

[0053] At this time, the outer peripheral space 58 is provided with an annular throttling portion 71 that extends around the axis of the rotating shaft 41. As a result, the bearing housing chamber 24 is divided by the throttling portion 71 into an upstream space 72 located upstream of the throttling portion 71 in the direction of airflow, and a downstream space 73 located downstream of the throttling portion 71 in the direction of airflow. The pressure in the upstream space 72 is higher than the pressure in the downstream space 73. Therefore, the thrust collar 44 is pressed in a direction away from the first thrust bearing portion 54a by the difference in pressure between the upstream space 72 and the downstream space 73. As a result, even if the impeller 42 is pressed in a direction away from the third plate 17 by the pressure in the gap 57 between the back surface 42a of the impeller 42 and the third plate 17, the thrust collar 44 is less likely to move toward the first thrust bearing portion 54a. Thus, the thrust load applied to the first thrust bearing portion 54a is reduced.

[0054] [Effects of the Embodiment] The above embodiment can be achieved to obtain the following effects. (1) The outer peripheral space 58 is provided with an annular throttling portion 71 that extends around the axis of the rotating shaft 41. As a result, the bearing housing chamber 24 is divided by the throttling portion 71 into an upstream space 72 located upstream of the throttling portion 71 in the direction of airflow, and a downstream space 73 located downstream of the throttling portion 71 in the direction of airflow. The pressure in the upstream space 72 is higher than the pressure in the downstream space 73. Therefore, the thrust collar 44 is pressed in a direction away from the first thrust bearing portion 54a by the difference in pressure between the upstream space 72 and the downstream space 73. As a result, even if the impeller 42 is pressed in a direction away from the third plate 17 by the pressure in the gap 57 between the back surface 42a of the impeller 42 and the third plate 17, the thrust collar 44 is less likely to move toward the first thrust bearing portion 54a. Therefore, the thrust load applied to the first thrust bearing section 54a can be reduced, thereby improving the durability of the thrust bearing 54. As a result, the reliability of the thrust bearing 54 can be improved.

[0055] (2) For example, when the rotating shaft 41 vibrates, the thrust collar 44 moves radially to the rotating shaft 41. At this time, the aperture portion 71 is positioned so as to overlap with the thrust collar 44 in the axial direction of the rotating shaft 41. With this arrangement, there is no need to adjust the dimensions of the aperture portion 71 to account for the radial movement of the thrust collar 44 to the rotating shaft 41 due to the vibration of the rotating shaft 41, and the aperture portion 71 can be easily provided in the outer peripheral space 58.

[0056] (3) The throttling portion 71 is positioned to overlap with the outer peripheral edge 44e of the thrust collar 44 in the axial direction of the rotation shaft 41. This allows the thrust collar 44 to be suitably pressed in a direction away from the first thrust bearing portion 54a by the pressure of the upstream space 72, thereby making it easier to further reduce the thrust load applied to the first thrust bearing portion 54a.

[0057] [Example of changes] The above embodiment can be implemented with the following modifications. The above embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0058] ○ As shown in Figure 3, the centrifugal compressor 10 does not necessarily have a throttling member 70. For example, a throttling portion 71 may be provided in the outer peripheral space 58 by providing a projection 74 that protrudes in an annular shape toward the bearing housing chamber 24 from a part of the surface of the third plate 17 that partitions the bearing housing chamber 24. The projection 74 extends around the axis of the rotating shaft 41. The projection 74 protrudes from a part of the surface of the third plate 17 that partitions the bearing housing chamber 24 so as to be positioned to overlap with the outer peripheral edge 44e of the thrust collar 44 in the axial direction of the rotating shaft 41. The projection 74 is spaced apart from the outer peripheral edge 44e of the thrust collar 44. An annular throttling portion 71 is formed between the projection 74 and the thrust collar 44. In this way, the throttling portion 71 may be positioned on the third plate 17 side relative to the thrust collar 44 within the outer peripheral space 58.

[0059] ○ As shown in Figure 4, the diaphragm portion 71 may be positioned to overlap the thrust collar 44 on the radially outer side of the rotation axis 41. The diaphragm member 70 is provided on the first plate 15. The diaphragm member 70 is attached to the inner circumferential surface of the chamber-forming recess 22, for example, by bolts (not shown). The diaphragm member 70 protrudes annularly from the inner circumferential surface of the chamber-forming recess 22. The diaphragm member 70 extends around the axis of the rotation axis 41. The protruding end of the diaphragm member 70 from the inner circumferential surface of the chamber-forming recess 22 is a tapered tip 70e.

[0060] The diaphragm member 70 is provided on the inner circumferential surface of the chamber-forming recess 22 such that the tip 70e of the diaphragm member 70 is positioned to overlap with the thrust collar 44 in the radial direction of the rotation axis 41. Therefore, the diaphragm member 70 is positioned in the bearing housing chamber 24 such that the tip 70e of the diaphragm member 70 is positioned in the outer circumferential space 58. The tip 70e of the diaphragm member 70 is spaced apart from the thrust collar 44. An annular diaphragm portion 71 is formed between the tip 70e of the diaphragm member 70 and the thrust collar 44. Thus, an annular diaphragm portion 71 extending around the axis of the rotation axis 41 may be provided in the outer circumferential space 58. The configuration in which the diaphragm portion 71 is positioned to overlap with the thrust collar 44 on the outside in the radial direction of the rotation axis 41 in the outer circumferential space 58 is a preferred configuration when providing the diaphragm portion 71 in the outer circumferential space 58.

[0061] ○ In this embodiment, the diaphragm portion 71 may be positioned so as to overlap in the axial direction of the rotation axis 41 with respect to a portion of the thrust collar 44 that is located radially inward of the rotation axis 41 than the outer peripheral edge 44e of the thrust collar 44. The diaphragm member 70 is provided in the chamber-forming recess 22 such that the tip 70e of the diaphragm member 70 is positioned so as to overlap in the axial direction of the rotation axis 41 with respect to a portion of the thrust collar 44 that is located radially inward of the rotation axis 41 than the outer peripheral edge 44e of the thrust collar 44.

[0062] ○ In this embodiment, the protruding end of the diaphragm member 70 does not have to be a tapered tip 70e. In short, the diaphragm member 70 just needs to have a shape that allows it to form an annular diaphragm 71 together with the thrust collar 44.

[0063] ○ In this embodiment, for example, the outer peripheral edge 44e of the thrust collar 44 may protrude annularly toward the bottom surface of the chamber-forming recess 22. Furthermore, an annular constriction portion 71 may be formed between the outer peripheral edge 44e of the thrust collar 44 and the bottom surface of the chamber-forming recess 22.

[0064] ○ In this embodiment, for example, a portion of the outer circumferential surface of the thrust collar 44 may be a convex portion that protrudes in an annular shape toward the inner circumferential surface of the chamber-forming recess 22. Furthermore, an annular constriction portion 71 may be formed between the convex portion of the thrust collar 44 and the inner circumferential surface of the chamber-forming recess 22.

[0065] ○ In this embodiment, the boss portion 42b does not need to be inserted into the first insertion hole 23 as part of the rotating shaft 41. ○ In this embodiment, the centrifugal compressor 10 may be configured without a turbine wheel 43.

[0066] ○ In this embodiment, the centrifugal compressor 10 may be configured to have an impeller instead of a turbine wheel 43. That is, the centrifugal compressor 10 may be configured to have impellers attached to both ends of the rotating shaft 41, such that air compressed by one impeller is compressed again by the other impeller.

[0067] ○ In this embodiment, the centrifugal compressor 10 does not have to be installed in the fuel cell vehicle. In short, the centrifugal compressor 10 is not limited to being installed in a vehicle. ○ In this embodiment, the centrifugal compressor 10 is not limited to one used to compress air supplied to the fuel cell stack 61. In short, the centrifugal compressor 10 can be any compressor that compresses a fluid. [Explanation of Symbols]

[0068] 10...Centrifugal compressor, 11...Housing, 17...Third plate which is a partition wall, 23...First insertion hole which is an insertion hole, 24...Bearing housing chamber, 28...Impeller chamber, 41...Rotating shaft, 42...Impeller, 42a...Back surface, 44...Thrust collar, 44e...Outer edge, 54...Thrust bearing, 54a...First thrust bearing section, 54b...Second thrust bearing section, 57...Gap, 58...Outer space, 71...Constriction section, 72...Upstream space, 73...Downstream space.

Claims

1. The axis of rotation and An impeller that rotates integrally with the rotating shaft to compress the fluid, A thrust bearing that supports the aforementioned rotating shaft in the thrust direction, A housing that separates the impeller chamber for housing the impeller and the bearing housing chamber for housing the thrust bearing, The rotating shaft comprises an annular thrust collar that protrudes from the outer circumferential surface into the bearing housing chamber, The housing has a partition wall that separates the impeller chamber and the bearing housing chamber, and has a through hole through which the rotating shaft is inserted. The thrust bearing is, A first thrust bearing portion is positioned on the impeller chamber side relative to the thrust collar, A centrifugal compressor having a second thrust bearing portion positioned on the opposite side of the impeller chamber from the thrust collar, A portion of the fluid compressed by the rotation of the impeller flows into the bearing housing chamber through the through-hole from the gap between the back surface of the impeller and the partition wall, and flows through the bearing housing chamber in the following order: between the first thrust bearing portion and the thrust collar, in the outer peripheral space located radially outside the rotation axis of the thrust bearing within the bearing housing chamber, and between the second thrust bearing portion and the thrust collar. The outer peripheral space is provided with an annular constricted portion extending around the axis of the rotation shaft, The bearing housing chamber is divided by the throttling portion into an upstream space located upstream of the throttling portion in the direction of fluid flow, and a downstream space located downstream of the throttling portion in the direction of fluid flow. A centrifugal compressor characterized in that the pressure in the upstream space is higher than the pressure in the downstream space.

2. The centrifugal compressor according to claim 1, characterized in that the throttling portion is positioned to overlap with the thrust collar in the axial direction of the rotation axis.

3. The centrifugal compressor according to claim 2, characterized in that the throttling portion is positioned to overlap with the outer edge of the thrust collar in the axial direction of the rotation axis.

4. The centrifugal compressor according to claim 1, characterized in that the throttling portion is positioned to overlap with the thrust collar on the radially outer side of the rotation axis.

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