Centrifugal compressor

Abstract

To suppress a reduction in the operation efficiency of a centrifugal compressor.SOLUTION: A second recessed part 72 is formed to insert a protruded part 71 from the second recessed part 72 through a first recessed part 70 in a first direction with the rotation of a rotary shaft 41. On this account, if a labyrinth seal has the protruded part 71 to be revolved in the first recessed part 70, on an outer peripheral face 42c of a boss part 42b, the boss part 42b can be inserted through a first insertion hole 23. Then, the protruded part 71 is revolved in the first recessed part 70. Thereby, the labyrinth seal is formed by the protruded part 71 and the first recessed part 70, and so the leakage of air leaking from a back face 42a of an impeller 42 via the first insertion hole 23 into a motor chamber is easily suppressed.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[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 a 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 houses the impeller. The motor chamber houses the motor. The housing has a partition wall that separates the impeller chamber and the motor chamber. The partition wall has an insertion hole formed therein. The rotating shaft is inserted into the insertion hole. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-155696 A Summary of the Invention [Problem to be solved by the invention]

[0004] In such a centrifugal compressor, a part of the fluid compressed by the rotation of the impeller may flow into the gap between the back surface of the impeller and the partition wall. If the fluid flows into the gap between the back surface of the impeller and the partition wall, the fluid may leak from the gap through the insertion hole into the motor chamber. As a result, the centrifugal compressor increases unnecessary compression of the fluid, which causes a decrease in operating efficiency.

[0005] In view of this, a centrifugal compressor has been conventionally known in which a labyrinth seal is provided between the rotating shaft and the insertion hole to seal the leakage fluid leaking from the back surface of the impeller. However, in order to insert the rotating shaft into the insertion hole, it is necessary to secure a certain amount of clearance between the rotating shaft and the insertion hole. The more clearance is secured between the rotating shaft and the insertion hole, the more likely it is that the leakage fluid leaking from the back surface of the impeller will leak into the motor chamber through the insertion hole. [Means for solving the problem]

[0006] A centrifugal compressor that solves the above problem 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 that defines an impeller chamber that houses the impeller and a motor chamber that houses the motor, the housing having a partition wall that separates the impeller chamber from the motor chamber and that has an insertion hole through which the rotating shaft is inserted, and a labyrinth seal that seals leakage fluid leaking from a back surface of the impeller is configured between the rotating shaft and the insertion hole, the labyrinth seal is configured to seal leakage fluid leaking from a back surface of the impeller by sealing an inner circumferential surface of the insertion hole and a circumferential surface of the rotating shaft. The rotating shaft has a convex portion provided on one side of an outer peripheral surface and protruding toward the other side, a first recess portion provided on the inner peripheral surface of the insertion hole and the other side of the outer peripheral surface of the rotating shaft and recessed in an annular shape, and a second recess portion connected to the first recess in the axial direction of the rotating shaft, wherein the convex portion extends in a first direction that intersects at an acute angle with a direction perpendicular to the axial direction in a plan view of the rotating shaft, and wherein, when viewed in the axial direction of the rotating shaft, the length of the convex portion in the circumferential direction of the rotating shaft is greater than that of the second recess portion, and the second recess portion is formed so that the convex portion can be inserted from the second recess portion into the first recess portion in the first direction by rotation of the rotating shaft, and the convex portion is rotated within the first recess portion.

[0007] According to this, the second recess is formed so that the convex portion can be inserted from the second recess to the first recess in the first direction by the rotation of the rotating shaft. Therefore, even if the labyrinth seal has a convex portion that runs in the first recess on one of the inner peripheral surface of the insertion hole and the outer peripheral surface of the rotating shaft, the rotating shaft can be inserted into the insertion hole. The convex portion runs in the first recess. According to this, since the convex portion and the first recess form a labyrinth seal, it is possible to easily prevent leakage fluid leaking from the back surface of the impeller from leaking into the motor chamber through the insertion hole. As a result, unnecessary compression of the fluid is suppressed in the centrifugal compressor, and therefore a decrease in the operating efficiency of the centrifugal compressor can be suppressed.

[0008] In the centrifugal compressor, the first recess and the second recess may be formed on the inner circumferential surface of the insertion hole, the convex portion may be formed on the outer circumferential surface of the rotating shaft, and the second recess may open to an end face of the partition wall located on the impeller chamber side.

[0009] According to this, when the leakage fluid leaking from the back surface of the impeller flows into the insertion hole, a part of the leakage fluid flows into the second recess. Then, the leakage fluid flowing into the second recess collides with the inner surface of the second recess, causing separation of the flow of the leakage fluid, resulting in a pressure loss of the leakage fluid. This makes it possible to reduce the flow rate of the leakage fluid flowing from the back surface of the impeller into the insertion hole. Therefore, it is possible to further easily prevent the leakage fluid leaking from the back surface of the impeller from leaking into the motor chamber via the insertion hole.

[0010] In the centrifugal compressor, the convex portion may extend toward an end face of the partition wall that is located on the impeller chamber side in the plan view. According to this, the leaking fluid leaking from the back surface of the impeller flows into the first recess through the second recess, causing the leaking fluid to collide with the convex portion. At this time, the convex portion extends toward the end face of the partition wall located on the impeller chamber side in a plan view. According to this, the leaking fluid that flows from the second recess into the first recess and collides with the convex portion flows along the convex portion. Therefore, a fluid flow is generated in which the leaking fluid that flows into the first recess through the second recess is returned by the convex portion toward the second recess. As a result, it is possible to further easily prevent the leaking fluid leaking from the back surface of the impeller from leaking into the motor chamber through the insertion hole.

[0011] In the centrifugal compressor, side surfaces positioned on both sides in a circumferential direction of the rotating shaft and defining the second recess may be inclined in the first direction. According to this, when the rotating shaft is inserted into the insertion hole, the convex portion easily passes through the second concave portion, which makes it easier to insert the rotating shaft into the insertion hole, thereby improving the ease of assembly.

[0012] In the centrifugal compressor, the convex portion may extend over the entire circumferential circumference of the rotating shaft when viewed in the axial direction. This makes it easier to prevent leakage fluid leaking from the back surface of the impeller from leaking into the motor chamber through the insertion hole, for example, compared to a case where the convex portion does not extend around the entire circumferential direction of the rotating shaft when viewed in the axial direction of the rotating shaft.

[0013] In the above-mentioned centrifugal compressor, it is preferable that the convex portions are provided in plurality on one of the inner circumferential surface of the insertion hole and the outer circumferential surface of the rotating shaft, and each of the convex portions extends around the entire circumferential direction of the rotating shaft as viewed in the axial direction by overlapping ends of the convex portions adjacent to each other in the axial direction, and the second recesses are provided in plurality on the other of the inner circumferential surface of the insertion hole and the outer circumferential surface of the rotating shaft, and each of the second recesses is formed so that each of the convex portions can be inserted from each of the second recesses into the first recess in the first direction by rotation of the rotating shaft.

[0014] According to this, each second recess is formed so that each protrusion can be inserted from each second recess into the first recess in the first direction by rotation of the rotating shaft, and therefore, for example, as compared with a case in which one protrusion extending around the entire circumferential direction of the rotating shaft is inserted into the second recess, it is possible to improve the ease of assembly. Effect of the Invention

[0015] According to the present invention, it is possible to suppress a decrease in the operating efficiency of the centrifugal compressor. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a cross-sectional view of a centrifugal compressor according to an embodiment. [Diagram 2] FIG. 2 is an enlarged cross-sectional view of a portion of the centrifugal compressor. [Diagram 3] FIG. 3 is a cross-sectional view taken along line 3-3 in FIG. [Figure 4] FIG. 4 is a side view of the impeller for explaining the protrusions. [Diagram 5] FIG. 5 is a front view of the impeller for explaining the protrusions. [Figure 6] FIG. 6 is a perspective view illustrating a schematic relationship between the convex portion, the first concave portion, and the second concave portion. [Figure 7] FIG. 7 is a cross-sectional view of a centrifugal compressor in a modified example. [Figure 8] FIG. 8 is a front view of the impeller for explaining the protrusions in the modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, a centrifugal compressor according to one embodiment will be described with reference to Fig. 1 to Fig. 6. 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.

[0018] <Basic configuration of a centrifugal compressor> As shown in Fig. 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.

[0019] 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. The first plate 15 is connected to an 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. Thus, the housing 11 defines the motor chamber 18.

[0020] 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.

[0021] The centrifugal compressor 10 includes a motor 20. The motor 20 is accommodated in the motor chamber 18. Thus, the motor chamber 18 accommodates the motor 20. The motor housing 12 surrounds the motor 20.

[0022] The centrifugal compressor 10 includes 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 communicates with the inside of the motor chamber 18.

[0023] 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 in the shape of a circular hole. The inside of the first bearing retaining portion 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 retaining portion 21 coincide with each other.

[0024] The third plate 17 is connected to the end face of the first plate 15 on the opposite side to the motor housing 12. The third plate 17 is attached to the first plate 15 in a state in which 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 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 an accommodation chamber 24. The accommodation chamber 24 communicates with the inside of the first bearing holder 21. The accommodation chamber 24 also communicates with the first insertion hole 23. Therefore, the inside of the first bearing holder 21 communicates with the first insertion hole 23 via the accommodation chamber 24.

[0025] The centrifugal compressor 10 includes 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 communicates with the inside of the motor chamber 18.

[0026] The housing 11 has a second insertion hole 26. The second insertion hole 26 penetrates a central portion of the end wall 12a of the motor housing 12 and a central portion of the second plate 16. The axis of the second insertion hole 26 coincides with the axis of the second bearing holder 25. The second insertion hole 26 communicates with the inside of the second bearing holder 25.

[0027] The compressor housing 13 is cylindrical and has a circular suction port 27 through which air is drawn. The compressor housing 13 is connected to an end face of the third plate 17 opposite to the first plate 15 with the axis of the suction port 27 coinciding with the axis of the first insertion hole 23. The suction port 27 opens at the end face of the compressor housing 13 opposite to the third plate 17. Air cleaned by an air cleaner (not shown) flows through the suction port 27.

[0028] The centrifugal compressor 10 includes 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. Therefore, the housing 11 defines 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 suction port 27. The discharge chamber 29 extends around the axis of the suction port 27 around the impeller chamber 28. The diffuser passage 30 communicates between the impeller chamber 28 and the discharge chamber 29. The impeller chamber 28 communicates with the first insertion hole 23.

[0029] The centrifugal compressor 10 has a discharge passage 31. A first end of the discharge passage 31 communicates with the discharge chamber 29. A second end of the discharge passage 31 opens to the outer circumferential surface of the compressor housing 13.

[0030] 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 into the end face of the turbine housing 14 opposite to the second plate 16.

[0031] The centrifugal compressor 10 includes a turbine chamber 33, a turbine scroll passage 34, and a communication passage 35. The turbine chamber 33, the turbine scroll passage 34, and the 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 passage 34 extends around the axis of the discharge port 32 around the turbine chamber 33. The communication passage 35 communicates the turbine chamber 33 and the turbine scroll passage 34. The turbine chamber 33 communicates with the second insertion hole 26.

[0032] The centrifugal compressor 10 has a suction passage 36. A first end of the suction passage 36 opens to the outer circumferential surface of the turbine housing 14. A second end of the suction passage 36 communicates with the turbine scroll passage 34.

[0033] The centrifugal compressor 10 includes 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 includes the rotating shaft 41 and the impeller 42. The rotating shaft 41 is accommodated in the housing 11.

[0034] 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 impeller chamber 28 through the inside of the first bearing holder 21, the accommodation chamber 24, and the first insertion hole 23. 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 motor chamber 18 and has an insertion hole through which the rotating shaft 41 is inserted. In this way, the housing 11 has a partition wall that separates the impeller chamber 28 and the motor chamber 18 and has an insertion hole through which the rotating shaft 41 is inserted. A second end of the rotating shaft 41 passes from the motor chamber 18 to the inside of the second bearing holder 25 and through the second insertion hole 26 , and protrudes into the turbine chamber 33 .

[0035] The impeller 42 is coupled to a first end of the rotary shaft 41. The impeller 42 is housed in the impeller chamber 28. Thus, the impeller chamber 28 houses the impeller 42. The impeller 42 rotates integrally with the rotary shaft 41 to compress the air drawn into the impeller chamber 28.

[0036] As shown in FIG. 2, the impeller 42 is cylindrical and gradually reduces in diameter from the back surface 42a toward the tip. The impeller 42 has a hub 421 that gradually reduces in diameter toward the tip, and a plurality of blades 422 provided on the outer surface of the hub 421. The back surface 42a of the impeller 42 is the back surface of the hub 421. The back surface 42a of the impeller 42 faces the third plate 17. Therefore, the third plate 17 has an opposing surface 17e that faces the back surface 42a of the impeller 42. The opposing surface 17e is an end surface of the third plate 17 that is located on the impeller chamber 28 side. The rotation axis of the impeller 42 is also the axis L1 of the rotating shaft 41. The axis L1 of the rotating shaft 41 is the rotation axis of the rotor 40.

[0037] The inner circumferential portion of the back surface 42a of the impeller 42 extends while curving in a direction away from the tip of the impeller 42 as it approaches the rotation axis of the impeller 42. The inner circumferential portion of the opposing surface 17e of the third plate 17 also extends while curving along the back surface 42a of the impeller 42.

[0038] 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. A first end of the rotating shaft 41 passes through the inside of the boss portion 42b. The boss portion 42b enters the first insertion hole 23. Therefore, the boss portion 42b is disposed inside the first insertion hole 23. The boss portion 42b is a portion of the rotating body 40 that is located inside the first insertion hole 23. In the impeller 42, the boss portion 42b can be said to constitute a part of the rotating shaft 41.

[0039] The opposing surface 17e of the third plate 17 is an end surface of the third plate 17 located on the side where the boss portion 42b is inserted into the first insertion hole 23. The end surface 42e of the boss portion 42b located on the opposite side to the back surface 42a of the impeller 42 is an end surface of the boss portion 42b located on the side where the boss portion 42b is inserted into the first insertion hole 23.

[0040] 1, the turbine wheel 43 is coupled to a second end of the rotary shaft 41. The turbine wheel 43 is housed in the turbine chamber 33. The turbine wheel 43 rotates integrally with the rotary shaft 41.

[0041] The thrust collar 44 has an annular shape. The thrust collar 44 protrudes from the outer circumferential surface of the rotating shaft 41 into the accommodating chamber 24. Therefore, the thrust collar 44 is disposed within the accommodating chamber 24. The thrust collar 44 is fixed to the rotating shaft 41 in a state in which it protrudes radially outward from the outer circumferential surface of the rotating shaft 41 in an annular shape. The thrust collar 44 is a separate body from the rotating shaft 41. The thrust collar 44 rotates integrally with the rotating shaft 41.

[0042] 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 disposed radially inside 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.

[0043] The rotating shaft 41 rotates integrally with the motor rotor 47 when a 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 disposed between the impeller 42 and the turbine wheel 43 in the axial direction of the rotating shaft 41.

[0044] The centrifugal compressor 10 includes a first radial bearing 52. The first radial bearing 52 is cylindrical. The first radial bearing 52 is held by a first bearing holder 21. The first radial bearing 52 rotatably supports a portion of the rotating shaft 41 that is located closer to a first end of the rotating shaft 41 than the motor 20 is.

[0045] The centrifugal compressor 10 includes 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 is.

[0046] The first radial bearing 52 and the second radial bearing 53 support the rotating shaft 41 rotatably in the radial direction at 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.

[0047] The centrifugal compressor 10 includes a thrust bearing 54. The thrust bearing 54 is accommodated in the accommodation chamber 24. Thus, the accommodation chamber 24 accommodates the thrust bearing 54. The thrust bearing 54 supports the thrust collar 44 so as to be rotatable in the thrust direction. Thus, the thrust bearing 54 supports the rotating shaft 41 in the thrust direction via the thrust collar 44. The "thrust direction" is a direction parallel to the direction in which the axis L1 of the rotating shaft 41 extends.

[0048] The centrifugal compressor 10 includes a seal portion 56. The seal portion 56 is, for example, a labyrinth seal constituted by a plurality of grooves formed on an inner circumferential surface that defines the second insertion hole 26 in the second plate 16. The seal portion 56 reduces air leakage from the gap between the back surface of the turbine wheel 43 and the second plate 16 through the second insertion hole 26 into the motor chamber 18.

[0049] The centrifugal compressor 10 includes an introduction passage 58. The introduction passage 58 is formed in the first plate 15. A first end of the introduction passage 58 opens to the outer circumferential surface of the first plate 15. A second end of the introduction passage 58 communicates with the accommodation chamber 24.

[0050] The centrifugal compressor 10 includes a discharge passage 59. The discharge passage 59 is formed in the end wall 12a of the motor housing 12. A first end of the discharge passage 59 communicates with a portion of the second insertion hole 26 closer to the second bearing holder 25 than the seal portion 56. A second end of the discharge passage 59 opens to the outer circumferential surface of the end wall 12a of the motor housing 12. Therefore, the discharge passage 59 communicates with the outside of the housing 11.

[0051] <Fuel cell system> The centrifugal compressor 10 configured as described above constitutes a part of a fuel cell system 60 mounted on a 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, a discharge pipe 63, a branch pipe 64, and an intercooler 65. The fuel cell stack 61 is composed of a plurality of battery cells (not shown). The supply pipe 62 connects the discharge passage 31 and the fuel cell stack 61. The discharge pipe 63 connects the fuel cell stack 61 and the suction passage 36.

[0052] The branch pipe 64 branches off from the middle of the supply pipe 62. A first end of the branch pipe 64 is connected to the supply pipe 62. A second end of the branch pipe 64 is connected to the first end of the introduction passage 58. The intercooler 65 is provided in the middle of the branch pipe 64. The intercooler 65 cools the air flowing through the branch pipe 64.

[0053] When the impeller 42 rotates, air is drawn into the impeller chamber 28 from the suction port 27. The air drawn into the impeller chamber 28 is accelerated by the rotation of the impeller 42 and sent into 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, air compressed by the rotation of the impeller 42 is discharged into the discharge chamber 29.

[0054] The air discharged into the discharge chamber 29 is discharged into a discharge passage 31. The air discharged into the discharge passage 31 is supplied to a fuel cell stack 61 via a supply pipe 62. The oxygen contained in the air supplied to the fuel cell stack 61 contributes to power generation in the fuel cell stack 61. The air passing through the fuel cell stack 61 is then discharged to an exhaust pipe 63 as exhaust air from the fuel cell stack 61.

[0055] The exhaust gas from the fuel cell stack 61 is drawn into the turbine scroll passage 34 via the exhaust pipe 63 and the suction passage 36. The exhaust gas from the fuel cell stack 61 drawn into the turbine scroll passage 34 is introduced into the turbine chamber 33 through the communication passage 35. The turbine wheel 43 is rotated by the exhaust gas from the fuel cell stack 61 introduced into the turbine chamber 33. The rotating shaft 41 is rotated not only by the drive of the motor 20 but also by the rotation of the turbine wheel 43 which is rotated by the exhaust gas from the fuel cell stack 61. The rotation of the rotating shaft 41 is assisted by the rotation of the turbine wheel 43 by the exhaust gas from the fuel cell stack 61. The exhaust gas that has passed through the turbine chamber 33 is discharged to the outside from the discharge port 32.

[0056] Also, a part of the air flowing through the supply pipe 62 flows into the branch pipe 64. The air flowing through the branch pipe 64 is cooled by the intercooler 65. As a result, the air passing through the intercooler 65 has a lower temperature than the air discharged into the discharge chamber 29. Then, the air cooled by the intercooler 65 passes through the introduction passage 58, the accommodation chamber 24, and the inside of the first bearing holder 21 and is introduced into the motor chamber 18. Therefore, the introduction passage 58 introduces a part of the air compressed by the impeller 42 into the motor chamber 18 at a lower temperature than the air discharged into the discharge chamber 29. Then, the air in the motor chamber 18 is discharged to the outside of the housing 11 through the inside of the second bearing holder 25, the second insertion hole 26, and the discharge passage 59.

[0057] <Labyrinth seal> 2, the third plate 17 has an inner circumferential surface 17a that defines the first insertion hole 23. The inner diameter of the inner circumferential surface 17a is constant. The boss portion 42b has an outer circumferential surface 42c that faces the inner circumferential surface 17a in the radial direction of the rotating shaft 41. The outer diameter of the outer circumferential surface 42c is constant.

[0058] The centrifugal compressor 10 includes a recess 69. The recess 69 is recessed in an annular shape in the radial direction of the rotating shaft 41 in the first insertion hole 23. The recess 69 includes a first recess 70. The first recess 70 is formed in the inner circumferential surface 17a. In the present embodiment, one first recess 70 is formed in the inner circumferential surface 17a. The first recess 70 is annular and extends in the circumferential direction of the rotating shaft 41. The first recess 70 is provided in the inner circumferential surface 17a of the first insertion hole 23.

[0059] The centrifugal compressor 10 includes a protruding portion 71. The protruding portion 71 protrudes from the boss portion 42b in the radial direction of the rotating shaft 41. The protruding portion 71 is formed on the outer peripheral surface 42c. In this embodiment, one protruding portion 71 is formed on the outer peripheral surface 42c. The protruding portion 71 is provided on the outer peripheral surface 42c of the boss portion 42b. The outer peripheral surface of the protruding portion 71 extends in the axial direction of the rotating shaft 41. The outer diameter of the protruding portion 71 is larger than the inner diameter of the inner peripheral surface 17a. The boss portion 42b is inserted into the first insertion hole 23 so that the protruding portion 71 is rotated within the first recess 70.

[0060] As shown in Figs. 2 and 3, the recess 69 includes a second recess 72. The second recess 72 is formed in the third plate 17. Therefore, the second recess 72 is formed in the third plate 17 in which the first recess 70 is formed. The second recess 72 is formed in the inner circumferential surface 17a. The second recess 72 is provided in the inner circumferential surface 17a of the first insertion hole 23. Therefore, the recess 69 is formed in the inner circumferential surface 17a of the third plate 17 that defines the first insertion hole 23.

[0061] One second recess 72 is formed in the inner peripheral surface 17a. The second recess 72 extends from the first recess 70 toward the opposing surface 17e in the axial direction of the rotary shaft 41. Therefore, the second recess 72 extends in the axial direction of the rotary shaft 41. The first recess 70 passes through the second recess 72 and opens to the opposing surface 17e. Therefore, the second recess 72 is connected to the first recess 70 in the axial direction of the rotary shaft 41. The second recess 72 opens to the opposing surface 17e, which is an end surface of the third plate 17 located on the impeller chamber 28 side. The second recess 72 does not open to an end surface of the third plate 17 on the first plate 15 side. In this way, the third plate 17 in which the first recess 70 is formed has a second recess 72 that communicates with the first recess 70 and opens to the opposing surface 17e, which is an end surface located on the side where the boss portion 42b is inserted into the first insertion hole 23.

[0062] 3, the bottom surface of the second recess 72 extends along the bottom surface of the first recess 70. Therefore, the depth of the second recess 72 with respect to the inner circumferential surface 17a is the same as the depth of the first recess 70 with respect to the inner circumferential surface 17a.

[0063] 4 and 5, the protrusion 71 extends in the circumferential direction of the rotating shaft 41 with a first end 71a and a second end 71b being misaligned in the axial direction of the rotating shaft 41. The protrusion 71 is plate-shaped. The thickness of the protrusion 71 is constant.

[0064] As shown in Figures 3 and 4, in a planar view of the rotating shaft 41, the convex portion 71 extends in a first direction A1 that intersects at an acute angle with a direction perpendicular to the axial direction of the rotating shaft 41, and in a planar view of the rotating shaft 41, its length in the circumferential direction of the rotating shaft 41 is greater than that of the second recessed portion 72.

[0065] 5, when viewed in the axial direction of the rotating shaft 41, the first end 71a and the second end 71b of the protruding portion 71 overlap in the axial direction of the rotating shaft 41. Thus, when viewed in the axial direction of the rotating shaft 41, the protruding portion 71 extends around the entire circumferential direction of the rotating shaft 41.

[0066] As shown in FIG. 2, when the boss portion 42b is inserted into the first insertion hole 23, the protrusion 71 passes through the second recess 72 while rotating around the axis L1 of the rotating shaft 41 and is disposed in the first recess 70. Therefore, the protrusion 71 can be inserted into the second recess 72 while rotating around the axis L1 of the rotating shaft 41 relative to the second recess 72. The protrusion 71 protrudes into the first recess 70. The protrusion 71 is rotated in the first recess 70 when the rotating shaft 41 rotates. Therefore, the second recess 72 is formed so that the protrusion 71 can be inserted from the second recess 72 into the first recess 70 in the first direction A1 by the rotation of the rotating shaft 41.

[0067] The convex portion 71 and the concave portion 69 form a labyrinth seal. In this way, a labyrinth seal that seals the leaking air, which is a leaking fluid leaking from the back surface 42a of the impeller 42, is formed between the boss portion 42b and the first insertion hole 23. Therefore, the labyrinth seal has the convex portion 71 and the concave portion 69. The "leaking air" is air that flows from the gap 73 between the back surface 42a of the impeller 42 and the opposing surface 17e of the third plate 17 toward the first insertion hole 23. Air that flows from the gap 73 into the first recess 70 through the second recess 72 collides with the convex portion 71. The labyrinth seal reduces the leakage of air from the gap 73 between the back surface 42a of the impeller 42 and the opposing surface 17e of the third plate 17 to the motor chamber 18 through the first insertion hole 23.

[0068] Fig. 6 shows a schematic relationship between the protrusion 71, the first recess 70, and the second recess 72. In Fig. 6, the axial direction of the rotating shaft 41 is indicated by an arrow X1. As shown in Fig. 6, the protrusion 71 extends while approaching the opposing surface 17e, which is the end surface of the third plate 17 located on the impeller chamber 28 side, as it moves from the leading side to the trailing side in the rotation direction R1 of the rotating shaft 41. In a plan view of the rotating shaft 41, the protrusion 71 extends toward the opposing surface 17e, which is the end surface of the third plate 17 located on the impeller chamber 28 side.

[0069] Here, in FIG. 6, the state in which the convex portion 71 passes through the second recess 72 while rotating around the axis L1 of the rotating shaft 41 relative to the second recess 72 is shown by imaginary lines. The side surfaces 72a located on both sides in the circumferential direction of the rotating shaft 41 in the second recess 72 are inclined along the convex portion 71 when the convex portion 71 passes through the second recess 72 while rotating around the axis L1 of the rotating shaft 41 relative to the second recess 72. The side surfaces 72a located on both sides in the circumferential direction of the rotating shaft 41 that define the second recess 72 are inclined in the first direction A1. The side surfaces 72a extend parallel to each other. When the convex portion 71 passes through the second recess 72, the boss portion 42b is inserted into the first insertion hole 23 while rotating the boss portion 42b around the axis L1 of the rotating shaft 41 with the first end 71a of the convex portion 71 aligned with the second recess 72. As a result, the protrusion 71 passes through the second recess 72 while rotating about the axis L1 of the rotation shaft 41 relative to the second recess 72.

[0070] [Operation of the embodiment] Next, the operation of the embodiment will be described. The thrust bearing 54 is cooled by air introduced into the accommodation chamber 24 from the introduction passage 58. The air in the accommodation chamber 24 passes inside the first bearing retaining portion 21. The first radial bearing 52 is cooled by air passing inside the first bearing retaining portion 21. The air that has passed inside the first bearing retaining portion 21 is introduced into the motor chamber 18. The motor 20 is cooled by air introduced into the motor chamber 18. The air introduced into the motor chamber 18 passes inside the second bearing retaining portion 25. The second radial bearing 53 is cooled by air passing inside the second bearing retaining portion 25. The air that has passed inside the second bearing retaining portion 25 is discharged to the outside of the housing 11 via the second insertion hole 26 and the discharge passage 59.

[0071] Incidentally, in the centrifugal compressor 10, a part of the air compressed by the rotation of the impeller 42 may flow as leakage air into the gap 73 between the back surface 42a of the impeller 42 and the opposing surface 17e of the third plate 17. The leakage air leaking from the back surface 42a of the impeller 42 flows into the first insertion hole 23.

[0072] The protrusion 71 revolves within the first recess 70 when the rotating shaft 41 rotates. As a result, a labyrinth seal is formed by the protrusion 71 and the first recess 70. This makes it easier to prevent air leaking from the back surface 42a of the impeller 42 from leaking into the motor chamber 18 through the first insertion hole 23.

[0073] Furthermore, when the leakage air leaking from the back surface 42a of the impeller 42 flows into the first insertion hole 23, a part of the leakage air flows into the second recess 72. The leakage air flowing into the second recess 72 collides with the inner surface of the second recess 72, causing separation of the flow of the leakage air, resulting in a pressure loss of the leakage air. This reduces the flow rate of the leakage air flowing from the back surface 42a of the impeller 42 into the first insertion hole 23.

[0074] As shown in FIG. 6, the leaking air leaking from the back surface 42a of the impeller 42 flows into the first recess 70 through the second recess 72, and the leaking air collides with the protrusion 71. At this time, the protrusion 71 extends toward the opposing surface 17e of the third plate 17 in a plan view. In detail, the protrusion 71 extends while approaching the opposing surface 17e of the third plate 17 as it moves from the leading side toward the trailing side in the rotation direction R1 of the rotating shaft 41. Therefore, the leaking air that flows from the second recess 72 into the first recess 70 and collides with the protrusion 71 flows along the protrusion 71 from the leading side toward the trailing side in the rotation direction R1 of the rotating shaft 41. For this reason, an air flow is generated in which the leaking air that flows into the first recess 70 through the second recess 72 is returned toward the second recess 72 by the protrusion 71. As a result, the air leaking from the rear surface 42a of the impeller 42 is more easily prevented from leaking into the motor chamber 18 via the first insertion hole 23.

[0075] [Effects of the embodiment] The above embodiment can provide the following effects. (1) The second recess 72 is formed so that the convex portion 71 can be inserted from the second recess 72 to the first recess 70 in the first direction A1 by the rotation of the rotating shaft 41. Therefore, even if the labyrinth seal has the convex portion 71 on the outer circumferential surface 42c of the boss portion 42b that is rotated in the first recess 70, the boss portion 42b can be inserted into the first insertion hole 23. The convex portion 71 is rotated in the first recess 70. According to this, since the convex portion 71 and the first recess 70 form a labyrinth seal, it is possible to easily suppress the leakage air leaking from the back surface 42a of the impeller 42 from leaking into the motor chamber 18 through the first insertion hole 23. As a result, in the centrifugal compressor 10, unnecessary compression of the air is suppressed, and therefore the decrease in the operating efficiency of the centrifugal compressor 10 can be suppressed.

[0076] (2) The second recess 72 opens to the opposing surface 17e, which is the end surface of the third plate 17 located on the impeller chamber 28 side. With this, when the leaking air leaking from the back surface 42a of the impeller 42 flows into the first insertion hole 23, a part of the leaking air flows into the second recess 72. Then, the leaking air flowing into the second recess 72 collides with the inner surface of the second recess 72, causing separation of the flow of the leaking air, resulting in a pressure loss of the leaking air. This makes it possible to reduce the flow rate of the leaking air flowing from the back surface 42a of the impeller 42 into the first insertion hole 23. Therefore, it is possible to further easily prevent the leaking air leaking from the back surface 42a of the impeller 42 from leaking into the motor chamber 18 through the first insertion hole 23.

[0077] (3) The leaking air leaking from the rear surface 42a of the impeller 42 flows into the first recess 70 through the second recess 72, and the leaking air collides with the protrusion 71. At this time, the protrusion 71 extends toward the opposing surface 17e, which is the end surface of the third plate 17 located on the impeller chamber 28 side, in a plan view. According to this, the leaking air that flows from the second recess 72 into the first recess 70 and collides with the protrusion 71 flows along the protrusion 71. Therefore, an air flow is generated in which the leaking air that flows into the first recess 70 through the second recess 72 is returned toward the second recess 72 by the protrusion 71. As a result, it is possible to further easily prevent the leaking air leaking from the rear surface 42a of the impeller 42 from leaking into the motor chamber 18 through the first insertion hole 23.

[0078] (4) The side surfaces 72a located on both circumferential sides of the rotating shaft 41 that define the second recess 72 are inclined in the first direction A1. This makes it easier for the convex portions 71 to pass through the second recesses 72 when the boss portions 42b are inserted into the first insertion holes 23. This makes it easier for the boss portions 42b to be inserted into the first insertion holes 23, thereby improving ease of assembly.

[0079] (5) The protrusion 71 extends around the entire circumferential direction of the rotating shaft 41 when viewed in the axial direction of the rotating shaft 41. This makes it easier to prevent air leaking from the back surface 42a of the impeller 42 from leaking into the motor chamber 18 through the first insertion hole 23, compared to a case in which the protrusion 71 does not extend around the entire circumferential direction of the rotating shaft 41 when viewed in the axial direction of the rotating shaft 41.

[0080] [Example of change] The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

[0081] As shown in Figs. 7 and 8, a plurality of protrusions 82 may be provided on the outer peripheral surface 42c of the boss portion 42b. In the embodiment shown in Figs. 7 and 8, three protrusions 82 are provided on the outer peripheral surface 42c of the boss portion 42b. Each protrusion 82 extends in the circumferential direction of the rotating shaft 41 with the first end 82a and the second end 82b being shifted in the axial direction of the rotating shaft 41. The lengths of each protrusion 82 in the circumferential direction of the rotating shaft 41 are the same. When viewed in the axial direction of the rotating shaft 41, each protrusion 82 extends over the entire circumferential direction of the rotating shaft 41 by overlapping ends of the protrusions 82 adjacent to each other in the axial direction of the rotating shaft 41. One first end 82a of each protrusion 82 and the other second end 82b of the protrusions 82 adjacent to each other in the circumferential direction of the rotating shaft 41 overlap in the axial direction of the rotating shaft 41.

[0082] A plurality of second recesses 72 are provided on the inner circumferential surface 17a. Three second recesses 72 are provided on the inner circumferential surface 17a. The three second recesses 72 are disposed at equal intervals in the circumferential direction of the rotation shaft 41 with respect to the inner circumferential surface 17a.

[0083] Each second recess 72 is formed so that each protrusion 82 can be inserted from each second recess 72 to the first recess 70 in the first direction A1 by the rotation of the rotating shaft 41. When each protrusion 82 is passed through each second recess 72, the boss portion 42b is inserted into the first insertion hole 23 while rotating the boss portion 42b around the axis L1 of the rotating shaft 41 with the first end 82a of each protrusion 82 aligned with the second recess 72. Each protrusion 82 protrudes into the first recess 70. Then, each protrusion 82 is rotated within the first recess 70 when the rotating shaft 41 rotates.

[0084] This improves assembly ease, for example, compared to a case in which, when viewed in the axial direction of the rotating shaft 41, a single convex portion 71 extending around the entire circumferential direction of the rotating shaft 41 is inserted into the second concave portion 72.

[0085] In the embodiment, the first recess 70 may be provided on the outer peripheral surface 42c of the boss portion 42b, and the protrusion 71 may be provided on the inner peripheral surface 17a. In this case, the boss portion 42b on which the first recess 70 is formed has a second recess 72. The second recess 72 opens to an end surface 42e of the boss portion 42b located on the side where the boss portion 42b is inserted into the first insertion hole 23. In short, the labyrinth seal may have a configuration including a protrusion 71 provided on one of the inner peripheral surface 17a of the first insertion hole 23 and the outer peripheral surface of the rotating shaft 41 and protruding toward the other, a first recess 70 provided on the other of the inner peripheral surface 17a of the first insertion hole 23 and the outer peripheral surface of the rotating shaft 41 and recessed in an annular shape, and a second recess 72 connected to the first recess 70 in the axial direction of the rotating shaft 41.

[0086] 7 and 8, the first recess 70 may be formed on the outer peripheral surface 42c of the boss portion 42b, and multiple protrusions 82 may be formed on the inner peripheral surface 17a. In this case, the boss portion 42b in which the first recess 70 is formed has a second recess 72 formed therein. The second recess 72 opens into the end surface 42e of the boss portion 42b located on the side where the boss portion 42b is inserted into the first insertion hole 23. In short, the labyrinth seal may have a configuration in which multiple protrusions 82 are provided on one of the inner peripheral surface 17a of the first insertion hole 23 and the outer peripheral surface of the rotating shaft 41.

[0087] In the embodiment, two first recesses 70 may be formed on the inner circumferential surface 17a. The two first recesses 70 are arranged side by side in the axial direction of the rotation shaft 41. The two first recesses 70 need only extend in the first direction A1 so that the protrusion 71 is wrapped around the two first recesses 70. In short, the number of first recesses 70 is not particularly limited.

[0088] In the embodiment, the protrusion 71 may extend, for example, from the leading side to the trailing side in the rotational direction R1 of the rotating shaft 41, while being spaced apart from the opposing surface 17e, which is an end surface of the third plate 17 that is located on the impeller chamber 28 side. Even in this case, it is preferable that the side surfaces 72a located on both circumferential sides of the rotating shaft 41 that define the second recess 72 are inclined in the first direction A1.

[0089] In the above embodiment, the side surfaces 72 a that define the second recess 72 and are located on both sides in the circumferential direction of the rotating shaft 41 may extend in the axial direction of the rotating shaft 41 , for example. In the above embodiment, the protrusion 71 does not have to extend around the entire circumference of the rotating shaft 41 when viewed in the axial direction of the rotating shaft 41 .

[0090] In the embodiment, the number of first recesses 70 formed on the inner circumferential surface 17a is not particularly limited. Therefore, the number of protrusions 71 formed on the outer circumferential surface 42c of the boss portion 42b may be changed as appropriate depending on the number of first recesses 70.

[0091] In the above embodiment, the depth of the second recess 72 with respect to the inner circumferential surface 17a may be greater than the depth of the first recess 70 with respect to the inner circumferential surface 17a. In the embodiment, the depth of the second recess 72 with respect to the inner circumferential surface 17a may be shallower than the depth of the first recess 70 with respect to the inner circumferential surface 17a. In this case, the depth of the second recess 72 with respect to the inner circumferential surface 17a needs to be set to a depth that allows the protrusion 71 to pass through the second recess 72 when the boss portion 42b is inserted into the first insertion hole 23.

[0092] In the above embodiment, the boss portion 42 b does not have to be inserted into the first insertion hole 23 as a part of the rotation shaft 41 . In the above-mentioned embodiment, the centrifugal compressor 10 does not necessarily have to include the turbine wheel 43.

[0093] In the embodiment, the centrifugal compressor 10 may be configured to include an impeller instead of the turbine wheel 43. That is, the centrifugal compressor 10 may be configured such that an impeller is attached to each end of the rotating shaft 41, and air compressed by one impeller is compressed again by the other impeller.

[0094] In the above-mentioned embodiment, the centrifugal compressor 10 does not have to be mounted on a fuel cell vehicle. In other words, the centrifugal compressor 10 is not limited to being mounted on a vehicle. In the above-mentioned embodiment, the centrifugal compressor 10 is not limited to be used for compressing the air supplied to the fuel cell stack 61. In short, the centrifugal compressor 10 may be used for compressing a fluid.

[0095] [Note] The technical ideas that can be understood from the above-described embodiment and modified examples will be described below. <Appendix 1> 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 defining an impeller chamber that accommodates the impeller and a motor chamber that accommodates the motor, the housing has a partition wall that separates the impeller chamber and the motor chamber and has an insertion hole through which the rotating shaft is inserted, A centrifugal compressor, comprising: a labyrinth seal between the rotating shaft and the insertion hole for sealing against leakage fluid leaking from a back surface of the impeller; The labyrinth seal comprises: a protrusion provided on one of an inner circumferential surface of the insertion hole and an outer circumferential surface of the rotating shaft and protruding toward the other; a first recess provided on the other of the inner circumferential surface of the insertion hole and the outer circumferential surface of the rotating shaft, the first recess being recessed in an annular shape, and a second recess connected to the first recess in the axial direction of the rotating shaft, the protruding portion extends in a first direction intersecting at an acute angle with a direction perpendicular to the axial direction in a plan view of the rotating shaft, and has a length in a circumferential direction of the rotating shaft greater than that of the second recessed portion in an axial view of the rotating shaft; the second recess is formed so that the protrusion can be inserted from the second recess to the first recess in the first direction by rotation of the rotation shaft, The centrifugal compressor, wherein the convex portion is rotated within the first concave portion.

[0096] <Appendix 2> The first recess and the second recess are formed on the inner circumferential surface of the insertion hole, The protrusion is formed on the outer circumferential surface of the rotating shaft, The centrifugal compressor according to <Appendix 1>, wherein the second recess is open to an end surface of the partition wall that is located on the impeller chamber side.

[0097] <Appendix 3> The centrifugal compressor according to <Appendix 2>, wherein the convex portion extends toward an end face of the partition wall that is located on the impeller chamber side in the plan view.

[0098] <Appendix 4> The centrifugal compressor according to any one of <Appendix 1> to <Appendix 3>, characterized in that side surfaces located on both circumferential sides of the rotating shaft that define the second recess are inclined in the first direction.

[0099] <Appendix 5> The centrifugal compressor according to any one of <Appendix 1> to <Appendix 4>, wherein the convex portion extends over the entire circumferential circumference of the rotating shaft when viewed in the axial direction.

[0100] <Appendix 6> the protrusion is provided on one of an inner circumferential surface of the insertion hole and an outer circumferential surface of the rotation shaft, When viewed in the axial direction, each of the protruding portions extends around the entire circumferential direction of the rotating shaft by overlapping ends of the protruding portions adjacent to each other in the axial direction, The second recess is provided in a plurality of portions on the other of the inner circumferential surface of the insertion hole and the outer circumferential surface of the rotation shaft, The centrifugal compressor according to any one of <Appendix 1> to <Appendix 5>, wherein each of the second recesses is formed so that each of the protrusions can be inserted from each of the second recesses into each of the first recesses in the first direction by rotation of the rotating shaft. [Explanation of symbols]

[0101] 10...centrifugal compressor, 11...housing, 17...third plate which is a partition wall, 17a...inner surface, 18...motor chamber, 20...motor, 23...first insertion hole which is an insertion hole, 28...impeller chamber, 41...rotating shaft, 42...impeller, 42a...rear surface, 42c...outer surface, 70...first recess, 71, 82...convex portion, 72...second recess, 72a...side surface.

Claims

1. 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 defining an impeller chamber that accommodates the impeller and a motor chamber that accommodates the motor, the housing has a partition wall that separates the impeller chamber and the motor chamber and has an insertion hole through which the rotating shaft is inserted, A centrifugal compressor, comprising: a labyrinth seal between the rotating shaft and the insertion hole for sealing against leakage fluid leaking from a back surface of the impeller; The labyrinth seal comprises: a protrusion provided on one of an inner circumferential surface of the insertion hole and an outer circumferential surface of the rotating shaft and protruding toward the other; a first recess provided on the other of the inner circumferential surface of the insertion hole and the outer circumferential surface of the rotating shaft, the first recess being recessed in an annular shape, and a second recess connected to the first recess in an axial direction of the rotating shaft, the protruding portion extends in a first direction intersecting at an acute angle with a direction perpendicular to the axial direction in a plan view of the rotating shaft, and has a length in a circumferential direction of the rotating shaft greater than that of the second recessed portion in an axial view of the rotating shaft; the second recess is formed so that the protrusion can be inserted from the second recess to the first recess in the first direction by rotation of the rotation shaft, The centrifugal compressor according to claim 1, wherein the protrusion is disposed within the first recess.

2. The first recess and the second recess are formed on the inner circumferential surface of the insertion hole, The protrusion is formed on the outer circumferential surface of the rotating shaft, The centrifugal compressor according to claim 1 , wherein the second recess is open to an end surface of the partition wall that is located on the impeller chamber side.

3. The centrifugal compressor according to claim 2 , wherein the protrusion extends toward an end surface of the partition wall that is located on the impeller chamber side in the plan view.

4. The centrifugal compressor according to any one of claims 1 to 3, characterized in that side surfaces located on both sides in a circumferential direction of the rotating shaft that define the second recess are inclined toward the first direction.

5. The centrifugal compressor according to claim 1 , wherein the protrusion extends over an entire circumferential circumference of the rotating shaft when viewed in the axial direction.

6. the protrusion is provided on one of an inner circumferential surface of the insertion hole and an outer circumferential surface of the rotation shaft, When viewed in the axial direction, each of the protruding portions extends around the entire circumferential direction of the rotating shaft by overlapping ends of the protruding portions adjacent to each other in the axial direction, The second recess is provided in a plurality of portions on the other of the inner circumferential surface of the insertion hole and the outer circumferential surface of the rotation shaft, 2. The centrifugal compressor according to claim 1, wherein each of the second recesses is formed so that each of the protrusions can be inserted from each of the second recesses into each of the first recesses in the first direction by rotation of the rotating shaft.

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