Centrifugal compressor

Abstract

The invention relates to a centrifugal compressor. The connection path is configured from a first impeller housing, a motor housing, and a second impeller housing. Thus, a gap is not formed between the housing and a pipe in the centrifugal compressor, such as a configuration in which the first discharge port and the second suction port are connected by attaching the pipe, which is a member separate from the housing, to the housing. A connection path is formed only by sequentially overlapping and assembling the first impeller housing, the motor housing, and the second impeller housing in the axial direction of the rotating shaft. As a result, there is no need to provide a structure for absorbing dimensional tolerances generated between the housing and the pipe when the pipe is attached to the housing, for example, to the pipe.

Description

Technical Field

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

[0002] A centrifugal compressor includes a rotating shaft, a motor, and a housing. The motor rotates the rotating shaft. In addition, the centrifugal compressor sometimes includes a first impeller and a second impeller. The first impeller rotates integrally with the rotating shaft to compress fluid. The second impeller is sometimes provided on the side opposite to the first impeller with the motor interposed therebetween with respect to the rotating shaft.

[0003] The housing has a first impeller chamber, a second impeller chamber, a first suction port, a first discharge port, a second suction port, and a second discharge port. The first impeller chamber houses the first impeller. The second impeller chamber houses the second impeller. The first suction port sucks fluid into the first impeller chamber. The first discharge port discharges the fluid compressed by the rotation of the first impeller. The second suction port sucks fluid into the second impeller chamber. The centrifugal compressor includes a connection path. The second discharge port discharges the fluid compressed by the rotation of the second impeller. The connection path connects the first discharge port and the second suction port so that the fluid flows from the first discharge port toward the second suction port. The connection path is formed by a pipe as a member separate from the housing, for example, as disclosed in Japanese Unexamined Patent Application Publication No. 2015-209845. And by installing the pipe on the housing, the first discharge port and the second suction port are connected by the connection path. Summary of the Invention

[0004] Problems to be Solved by the Invention

[0005] In a configuration in which the first discharge port and the second suction port are connected by a connection path by installing a pipe, which is a member separate from the housing, on the housing as disclosed in Japanese Unexamined Patent Application Publication No. 2015-209845, a gap is formed between the housing and the pipe in the centrifugal compressor. The gap formed between the housing and the pipe becomes an ineffective space in the centrifugal compressor. Therefore, the centrifugal compressor is uselessly enlarged corresponding to the gap formed between the housing and the pipe.

[0006] In addition, dimensional tolerances are generated between the housing and the pipe. Therefore, measures such as providing a structure that can absorb the dimensional tolerances generated between the housing and the pipe when the pipe is installed on the housing in the pipe are required, which is a factor that reduces the productivity of the centrifugal compressor. Therefore, it is desired to suppress the enlargement of the centrifugal compressor and improve the productivity.

[0007] Means for Solving the Problems

[0008] In one aspect of the present disclosure, a centrifugal compressor is provided. The centrifugal compressor includes: a rotating shaft; a motor that rotates the rotating shaft; a first impeller that rotates integrally with the rotating shaft to compress a fluid; a second impeller that is disposed on the side opposite to the first impeller with respect to the rotating shaft, and the motor is disposed between the first impeller and the second impeller, and the second impeller rotates integrally with the rotating shaft; a housing having a first impeller housing, a motor housing, and a second impeller housing, the first impeller housing defining a first impeller chamber that houses the first impeller, having a first suction port that sucks the fluid into the first impeller chamber and a first discharge port that discharges the fluid compressed by the rotation of the first impeller, the motor housing defining a motor chamber that houses the motor, the second impeller housing defining a second impeller chamber that houses the second impeller, having a second suction port that sucks the fluid into the second impeller chamber and a second discharge port that discharges the fluid compressed by the rotation of the second impeller; and a connection path that connects the first discharge port and the second suction port so that the fluid flows from the first discharge port toward the second suction port. The connection path includes: a first impeller housing connection path that is provided on the first impeller housing and is connected to the first discharge port; a second impeller housing connection path that is provided on the second impeller housing and is connected to the second suction port; and a motor housing connection path that is formed through the motor housing and connects the first impeller housing connection path and the second impeller housing connection path. The connection path is formed by sequentially overlapping the first impeller housing, the motor housing, and the second impeller housing in the axial direction of the rotating shaft. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a cross-sectional view of the centrifugal compressor.

[0010] Figure 2 is a cross-sectional view of the first impeller housing.

[0011] Figure 3 is a cross-sectional view of the second impeller housing.

[0012] Figure 4 is a rear view showing the base of the second impeller housing.

[0013] Figure 5 is a rear view showing the base and the cover of the second impeller housing. DETAILED DESCRIPTION

[0014] Hereinafter, Figures 1 to 5 an embodiment for embodying the centrifugal compressor will be described. The centrifugal compressor of this embodiment is mounted on a fuel cell vehicle. The centrifugal compressor compresses air as the fluid.

[0015] <Basic Structure of the Centrifugal Compressor>

[0016] As Figure 1 shown, the centrifugal compressor 100 includes a housing 10. The housing 10 is made of a metal material. The housing 10 is, for example, made of aluminum. The housing 10 has a motor housing 10a, a first impeller housing 10b, and a second impeller housing 10c. The motor housing 10a has a first motor housing 14 and a connection path forming housing 13. The first impeller housing 10b has a first compressor housing 11 and a second plate 17. The second impeller housing 10c has a second compressor housing 12 and a third plate 18. The second compressor housing 12 is composed of a second impeller housing base portion 12a and a second impeller housing cover portion 19. That is, the second impeller housing 10c has the second impeller housing base portion 12a and the second impeller housing cover portion 19.

[0017] The first motor housing 14 has an end wall 14a and a peripheral wall 14b. The first motor housing 14 is cylindrical. The end wall 14a is plate-shaped. The peripheral wall 14b extends in a cylindrical shape from the outer peripheral portion of the end wall 14a. The first motor housing 14 is manufactured by die casting.

[0018] The connection path forming housing 13 is formed by a second motor housing 15 and a first plate 16. That is, the motor housing 10a has the first motor housing 14 and the second motor housing 15. The second motor housing 15 and the first plate 16 are manufactured by die casting.

[0019] The second motor housing 15 is cylindrical. The second motor housing 15 has a motor housing receiving hole 15c. The second motor housing 15 has a receiving hole defining surface 15a. The receiving hole defining surface 15a defines the motor housing receiving hole 15c. The motor housing receiving hole 15c extends in the axial direction of the second motor housing 15 and opens at both end faces in the axial direction of the second motor housing 15. The motor housing receiving hole 15c receives the first motor housing 14 such that the outer peripheral surface of the peripheral wall 14b of the first motor housing 14 faces the receiving hole defining surface 15a in the radial direction of the second motor housing 15. The axis of the second motor housing 15 coincides with the axis of the peripheral wall 14b of the first motor housing 14.

[0020] The centrifugal compressor 100 is provided with a cooling medium passage 13a. The cooling medium passage 13a is defined by the outer peripheral surface of the peripheral wall 14b of the first motor housing 14 and the defining surface 15a of the receiving hole. The cooling medium passage 13a is defined in such a way that cooling water flows between the first motor housing 14 and the second motor housing 15. That is to say, the cooling medium passage 13a is defined by the first motor housing 14 and the second motor housing 15. The cooling medium passage 13a is annular and extends along the peripheral wall 14b of the first motor housing 14 and surrounds the peripheral wall 14b. The second motor housing 15 has a supply port 13e and a discharge port 13f. The supply port 13e supplies cooling water to the cooling medium passage 13a. The discharge port 13f discharges the cooling water that has flowed through the cooling medium passage 13a to the outside of the housing 10. The cooling water flowing in the cooling medium passage 13a cools the first motor housing 14 and the second motor housing 15.

[0021] A plurality of fins 14d are provided on the outer peripheral surface of the peripheral wall 14b of the first motor housing 14. The plurality of fins 14d project from the outer peripheral surface of the peripheral wall 14b of the first motor housing 14 into the cooling medium passage 13a. Each fin 14d is an annular thin plate extending along the outer peripheral surface of the peripheral wall 14b. The plurality of fins 14d are arranged at intervals in the axial direction of the first motor housing 14 on the outer peripheral surface of the peripheral wall 14b of the first motor housing 14. The plurality of fins 14d are integrally formed on the first motor housing 14. The cooling water flows along each fin 14d in the circumferential direction of the first motor housing 14 and the second motor housing 15 inside the cooling medium passage 13a.

[0022] The first plate 16 is connected to the end of the peripheral wall 14b of the first motor housing 14 on the side opposite to the end wall 14a and the first end of the second motor housing 15. The first plate 16 is connected to the peripheral wall 14b of the first motor housing 14 and the second motor housing 15 in a state where the thickness direction of the first plate 16 is aligned with the axial direction of the peripheral wall 14b of the first motor housing 14 and the axial direction of the second motor housing 15. The first plate 16 closes the opening of the peripheral wall 14b of the first motor housing 14. Thus, a motor chamber 14c is defined by the first motor housing 14 and the first plate 16. Therefore, the motor housing 10a defines the motor chamber 14c.

[0023] The first plate 16 has a first bearing holding portion 21. The first bearing holding portion 21 is cylindrical. The first bearing holding portion 21 projects into the motor chamber 14c. The axis of the first bearing holding portion 21 is aligned with the axis of the peripheral wall 14b of the first motor housing 14.

[0024] The end wall 14a of the first motor housing 14 has a second bearing holding portion 25. The second bearing holding portion 25 is cylindrical. The second bearing holding portion 25 projects into the motor chamber 14c. The axis of the second bearing holding portion 25 is aligned with the axis of the first bearing holding portion 21.

[0025] The second plate 17 is manufactured by die casting. The second plate 17 is connected to the end face of the first plate 16 on the side opposite to the first motor housing 14 and the second motor housing 15. The second plate 17 is connected to the first plate 16 in a state where the thickness direction of the second plate 17 coincides with the thickness direction of the first plate 16. The second plate 17 has a first insertion hole 23. The axis of the first insertion hole 23 coincides with the axis of the first bearing holding portion 21. The first insertion hole 23 communicates with the inside of the first bearing holding portion 21.

[0026] The third plate 18 is manufactured by die casting. The third plate 18 is connected to the outer surface of the end wall 14a of the first motor housing 14 and the second end of the second motor housing 15. The third plate 18 is connected to the end wall 14a of the first motor housing 14 and the second motor housing 15 in a state where the thickness direction of the third plate 18 coincides with the thickness direction of the end wall 14a of the first motor housing 14.

[0027] A second insertion hole 26 is formed in the third plate 18. The second insertion hole 26 penetrates the third plate 18 in the thickness direction of the third plate 18. The second insertion hole 26 communicates with the inside of the second bearing holding portion 25. The axis of the second insertion hole 26 coincides with the axis of the second bearing holding portion 25.

[0028] The centrifugal compressor 100 includes a motor 20. The motor 20 is housed in the motor chamber 14c. Therefore, the motor chamber 14c houses the motor 20. The first motor housing 14 surrounds the motor 20. In addition, the heat generated from the motor 20 is dissipated to the first motor housing 14. Since the first motor housing 14 is cooled by the cooling water flowing in the cooling medium path 13a, the heat generated from the motor 20 is efficiently dissipated to the first motor housing 14. Thereby, the motor 20 is cooled. That is, the motor housing 10a has a cooling medium path 13a through which the cooling water as the cooling medium for cooling the motor 20 flows.

[0029] The first compressor housing 11 is manufactured by die casting. The first compressor housing 11 has a circular hole-shaped first suction port 35 for sucking air. Therefore, the first impeller housing 10b has the first suction port 35. The first compressor housing 11 is connected to the end face of the second plate 17 on the side opposite to the first plate 16 in a state where the axis of the first suction port 35 coincides with the axis of the first insertion hole 23. The first suction port 35 opens at the end face of the first compressor housing 11 on the side opposite to the second plate 17. The air purified by an air cleaner (not shown) flows to the first suction port 35.

[0030] The centrifugal compressor 100 includes a first impeller chamber 36, a first discharge chamber 37, and a first diffuser flow path 38. The first impeller chamber 36, the first discharge chamber 37, and the first diffuser flow path 38 are formed between the first compressor housing 11 and the second plate 17. Accordingly, the first impeller housing 10b defines the first impeller chamber 36. The first impeller chamber 36 communicates with the first suction port 35. The first suction port 35 sucks air into the first impeller chamber 36. The first discharge chamber 37 extends around the axis of the first suction port 35 around the first impeller chamber 36. The first diffuser flow path 38 connects the first impeller chamber 36 and the first discharge chamber 37. The first impeller chamber 36 communicates with the first insertion hole 23.

[0031] As Figure 2 shown, a first discharge port 39 is formed in the first compressor housing 11. Accordingly, the first impeller housing 10b has the first discharge port 39. The first end of the first discharge port 39 communicates with the first discharge chamber 37.

[0032] As Figure 1 shown, the second impeller housing base 12a is manufactured by die casting. The second impeller housing base 12a has a circular hole-shaped second suction port 40. The second suction port 40 opens in the second impeller housing base 12a. Thus, the second impeller housing 10c has the second suction port 40. The second impeller housing base 12a is connected to the end face of the third plate 18 on the side opposite to the first motor housing 14 and the second motor housing 15 in a state where the axis of the second suction port 40 coincides with the axis of the second insertion hole 26.

[0033] The centrifugal compressor 100 includes a second impeller chamber 41, a second discharge chamber 42, and a second diffuser flow path 43. The second impeller chamber 41, the second discharge chamber 42, and the second diffuser flow path 43 are formed between the second impeller housing base 12a and the third plate 18. Accordingly, the second impeller housing 10c defines the second impeller chamber 41. The second impeller chamber 41 communicates with the second suction port 40. The second suction port 40 sucks air into the second impeller chamber 41. The second discharge chamber 42 extends around the axis of the second suction port 40 around the second impeller chamber 41. The second diffuser flow path 43 connects the second impeller chamber 41 and the second discharge chamber 42. The second impeller chamber 41 communicates with the second insertion hole 26.

[0034] A second discharge port 44 is formed in the second impeller housing base 12a. The second discharge port 44 opens in the second impeller housing base 12a. In other words, the second impeller housing 10c has the second discharge port 44. The first end of the second discharge port 44 communicates with the second discharge chamber 42. The second end of the second discharge port 44 opens on the outer peripheral surface of the second impeller housing base 12a.

[0035] A supply pipe 45 is connected to the second row outlet 44. The supply pipe 45 is connected to the fuel cell stack 46. The first end of the supply pipe 45 is connected to the second row outlet 44. The second end of the supply pipe 45 is connected to the fuel cell stack 46.

[0036] The centrifugal compressor 100 includes a rotating shaft 50. The rotating shaft 50 passes through the inside of the motor chamber 14c in a state where the axis of the rotating shaft 50 coincides with the axis of the peripheral wall 14b of the first motor housing 14. The first end, which is one axial end of the rotating shaft 50, protrudes into the first impeller chamber 36 from inside the motor chamber 14c through the inside of the first bearing holding portion 21 and the first insertion hole 23. The second end, which is the other axial end of the rotating shaft 50, protrudes into the second impeller chamber 41 from inside the motor chamber 14c through the inside of the second bearing holding portion 25 and the second insertion hole 26.

[0037] The motor 20 includes a cylindrical stator 52 and a rotor 51. The rotor 51 is fixed to the rotating shaft 50. The rotor 51 has a cylindrical rotor core 53 fixed to the rotating shaft 50 and a plurality of permanent magnets (not shown) provided on the rotor core 53. The rotor 51 is provided on the rotating shaft 50 and rotates integrally with the rotating shaft 50.

[0038] The stator 52 is fixed to the first motor housing 14. The stator 52 is disposed outside the rotor 51. The stator 52 has a cylindrical stator core 54 and a coil 55. The stator core 54 is fixed to the inner peripheral surface of the peripheral wall 14b of the first motor housing 14. That is, the motor housing 10a has the first motor housing 14 with the stator 52 fixed to its inner peripheral surface. The coil 55 is wound around the stator core 54. And, by current flowing from a battery (not shown) to the coil 55, the rotating shaft 50 rotates integrally with the rotor 51. Therefore, the motor 20 rotates the rotating shaft 50.

[0039] The centrifugal compressor 100 includes a first hydrodynamic journal bearing 56 and a second hydrodynamic journal bearing 57. The first hydrodynamic journal bearing 56 is cylindrical. The first hydrodynamic journal bearing 56 is held by the first bearing holding portion 21. The first hydrodynamic journal bearing 56 rotatably supports the rotating shaft 50 relative to the first plate 16.

[0040] The second hydrodynamic journal bearing 57 is cylindrical. The second hydrodynamic journal bearing 57 is held by the second bearing holding portion 25. The second hydrodynamic journal bearing 57 rotatably supports the rotating shaft 50 relative to the end wall 14a of the first motor housing 14. Therefore, the first hydrodynamic journal bearing 56 and the second hydrodynamic journal bearing 57 are bearings that rotatably support the rotating shaft 50 relative to the housing 10. The first hydrodynamic journal bearing 56 and the second hydrodynamic journal bearing 57 rotatably support the rotating shaft 50 relative to the housing 10 in the radial direction.

[0041] In addition, the centrifugal compressor 100 may also be provided with a known thrust bearing that rotatably supports the rotating shaft 50 relative to the housing 10 in the thrust direction.

[0042] The centrifugal compressor 100 includes a first impeller 61 and a second impeller 62. The first impeller 61 is connected to the first end of the rotating shaft 50. The first impeller 61 is housed in the first impeller chamber 36. Therefore, the first impeller chamber 36 houses the first impeller 61. The first impeller 61 rotates integrally with the rotating shaft 50 to compress air.

[0043] The second impeller 62 is connected to the second end of the rotating shaft 50. In other words, the second impeller 62 is disposed on the side opposite to the first impeller 61 with the motor 20 interposed therebetween with respect to the rotating shaft 50. The second impeller 62 is housed in the second impeller chamber 41. Therefore, the second impeller chamber 41 houses the second impeller 62. The second impeller 62 rotates integrally with the rotating shaft 50 to compress the air that has been compressed by the rotation of the first impeller 61. The first impeller 61 and the second impeller 62 rotate to compress the air supplied to the fuel cell stack 46.

[0044] The first impeller 61 and the second impeller 62 rotate integrally with the rotating shaft 50 by the drive of the motor 20. Therefore, the motor 20 causes the first impeller 61 and the second impeller 62 to rotate.

[0045] <Converter (inverter)>

[0046] The centrifugal compressor 100 includes a converter 65. The converter 65 is electrically connected to the motor 20. The converter 65 controls the drive of the motor 20 by controlling the power supplied to the coil 55.

[0047] The centrifugal compressor 100 includes a converter housing 66. The converter housing 66 houses the converter 65. The converter housing 66 is provided on the outer surface of the second motor housing 15. In other words, the converter 65 is provided on the outer surface of the housing 10, i.e., the housing outer surface 10e. The heat generated from the converter 65 is dissipated to the second motor housing 15 via the converter housing 66. Since the second motor housing 15 is cooled by the cooling water flowing in the cooling medium passage 13a, the heat generated from the converter 65 is efficiently dissipated to the second motor housing 15. Thus, the converter 65 is cooled.

[0048] The centrifugal compressor 100 includes a sealing member 63. The sealing member 63 is provided between the first insertion hole 23 and the rotating shaft 50. The sealing member 63 suppresses the leakage of air from the first impeller chamber 36 through the first insertion hole 23 and the inside of the first bearing holding portion 21 into the motor chamber 14c. The sealing member 63 is, for example, an O-ring.

[0049] The centrifugal compressor 100 includes a sealing member 64. The sealing member 64 is disposed between the second insertion through-hole 26 and the rotating shaft 50. The sealing member 64 suppresses the leakage of air from the second impeller chamber 41 through the inside of the second insertion through-hole 26 and the second bearing holding portion 25 into the motor chamber 14c. The sealing member 64 is, for example, an O-ring.

[0050] <Connection path>

[0051] As Figure 1 and Figure 2 As shown, the centrifugal compressor 100 includes a connection path 70. The connection path 70 connects the first discharge port 39 and the second suction port 40 such that air flows from the first discharge port 39 toward the second suction port 40. The connection path 70 has a first impeller housing connection path 101, a second impeller housing connection path 102, and a motor housing connection path 13b. Thus, in the present embodiment, the connection path 70 is formed by the first impeller housing connection path 101, the second impeller housing connection path 102, and the motor housing connection path 13b.

[0052] The first compressor housing 11 has a first passage 11a. The first compressor housing 11 has a first passage defining surface 11b. The first passage defining surface 11b defines the first passage 11a. The first end of the first passage 11a is connected to the first discharge port 39. The second end of the first passage 11a opens at a portion of the end surface on the second plate 17 side of the first compressor housing 11 that is located radially outside the first discharge chamber 37 with respect to the rotating shaft 50. The first passage defining surface 11b is a curved surface extending from the opening edge of the second end of the first passage 11a.

[0053] The second plate 17 has a second plate hole 17a. The second plate 17 has a second plate hole defining surface 17b. The second plate hole defining surface 17b defines the second plate hole 17a. The second plate hole defining surface 17b is continuous with the first passage defining surface 11b. That is, the second plate hole 17a communicates with the first passage 11a. The second plate hole 17a opens at both end surfaces in the thickness direction of the second plate 17. The second plate hole 17a is connected to the second end of the first passage 11a.

[0054] The first impeller housing connection path 101 is formed by the first path 11a and the second plate hole 17a. That is to say, the first impeller housing connection path 101 is formed in the first impeller housing 10b. Therefore, the first impeller housing connection path 101 is formed inside the housing 10. The first end of the first impeller housing connection path 101 is connected to the first discharge port 39. And air flows from the first discharge port 39 into the first impeller housing connection path 101. Therefore, the first impeller housing connection path 101 is provided in the first impeller housing 10b and connected to the first discharge port 39. The second end of the first impeller housing connection path 101 opens at a portion of the end face of the first plate 16 side of the second plate 17 that is located radially outside the first discharge chamber 37 with respect to the rotation axis 50.

[0055] Here, the boundary L1 between the first end of the first impeller housing connection path 101 and the first discharge port 39 is shown by a double-dashed line in Figure 2 The portion of the first impeller housing 10b corresponding to the boundary L1 between the first end of the first impeller housing connection path 101 and the first discharge port 39 corresponds to the portion connected to the first end of the pipe conventionally used to connect the first discharge port 39 and the second suction port 40. The first impeller housing connection path 101 of the present embodiment extends from the portion corresponding to the portion connected to the first end of the conventional pipe.

[0056] The second compressor housing 12 has a second path 12b. As Figure 1 , Figure 3 and Figure 4 shown, the second path 12b has a first axial path (axial path) 401, a second axial path 402, and a radial path (radial path) 403. The first axial path 401 is formed in the second impeller housing base 12a. That is to say, an axial path, namely the first axial path 401, which forms a part of the second path 12b, is formed in the second impeller housing base 12a. The second impeller housing base 12a has a first axial path defining surface 401a that defines the first axial path 401. The first axial path 401 is located radially outside the second suction port 40 with respect to the rotation axis 50 and extends in the axial direction of the rotation axis 50. The first axial path 401 penetrates the second impeller housing base 12a in the axial direction of the rotation axis 50. The first end of the first axial path 401 opens at the end face of the second impeller housing base 12a on the side of the third plate 18. The second end of the first axial path 401 opens at the end face of the second impeller housing base 12a on the side opposite to the third plate 18. The end face of the second impeller housing base 12a on the side opposite to the third plate 18 is the axial end face 12d of the second impeller housing base 12a that is located in the axial direction of the rotation axis 50. Therefore, the first axial path 401 opens at the axial end face 12d.

[0057] The first flow path 401 has an opening at the first end, namely the third suction port 401b, and an opening at the second end, namely the third discharge port 401c. That is to say, the second impeller housing 10c has the third suction port 401b and the third discharge port 401c. The third suction port 401b and the third discharge port 401c open at the base 12a of the second impeller housing.

[0058] The second flow path 402 is formed in the base 12a of the second impeller housing. The first end of the second flow path 402 is connected to the second suction port 40. That is to say, the second passage 12b is provided in the second compressor housing 12 and is connected to the second suction port 40. The second end of the second flow path 402 opens at the axial end face 12d. Therefore, the second suction port 40 extends along the axial direction of the rotating shaft 50 from the second impeller chamber 41 and opens at the axial end face 12d via the second flow path 402. The axis of the second suction port 40 and the axis of the second flow path 402 coincide. The base 12a of the second impeller housing has a second flow path defining surface 402a that defines the second flow path 402.

[0059] As Figure 1 and Figure 5 shown, the second impeller housing cover 19 is manufactured by die casting. The second impeller housing cover 19 is connected to the axial end face 12d of the base 12a of the second impeller housing. The second impeller housing cover 19 closes the opening on the axial end face 12d side of the second suction port 40 and the opening on the axial end face 12d side of the first flow path 401.

[0060] As Figure 1 shown, the second impeller housing cover 19 has an opposing surface 19b that opposes the axial end face 12d of the base 12a of the second impeller housing. That is to say, the second impeller housing cover 19 has an opposing surface 19b that opposes the base 12a of the second impeller housing in the axial direction of the rotating shaft 50. The opposing surface 19b is a flat surface.

[0061] A guiding portion 19d is formed on the opposing surface 19b of the second impeller housing cover portion 19. The guiding portion 19d is in the shape of a groove. In this way, the second impeller housing 10c has the second impeller housing cover portion 19 on which the groove-shaped guiding portion 19d is formed. In a state where the second impeller housing cover portion 19 is connected to the axial end surface 12d of the second impeller housing base portion 12a, the inside of the guiding portion 19d connects the second end of the first shaft path 401 and the second end of the second shaft path 402. In other words, the guiding portion 19d is connected to the first shaft path 401 via the third discharge port 401c. A path 403 is formed between the inner surface 19c of the guiding portion 19d and the axial end surface 12d of the second impeller housing base portion 12a. Therefore, a path 403 that forms a part of the second impeller housing connection path 102 and extends in the radial direction of the rotating shaft 50 to direct the air from the first shaft path 401 toward the second suction port 40 is formed between the second impeller housing cover portion 19 and the second impeller housing base portion 12a. In this way, the guiding portion 19d delimits the path 403.

[0062] The inner surface 19c of the guiding portion 19d has a first cover connection surface 191, a second cover connection surface 192, and a bottom surface 193. The bottom surface 193 is in the shape of a flat surface extending in the radial direction of the rotating shaft 50. The first cover connection surface 191 extends from the opening edge 19e of the guiding portion 19d and is connected to the bottom surface 193. The first cover connection surface 191 extends from the portion of the opening edge 19e of the guiding portion 19d located on the side of the first shaft path 401. The first cover connection surface 191 is bent in such a way that the direction of extension from the opening edge 19e of the guiding portion 19d toward the bottom surface 193 goes from the axial direction of the first shaft path 401 to a direction orthogonal to the axial direction of the first shaft path 401. The first cover connection surface 191 is bent in such a way that the direction of air flow passing through the first shaft path 401 becomes the direction in which the path 403 extends. The first cover connection surface 191 smoothly connects the first shaft path delimiting surface 401a and the bottom surface 193.

[0063] The second cover connection surface 192 extends from the opening edge 19e of the guiding portion 19d and is connected to the bottom surface 193. The second cover connection surface 192 extends from the portion of the opening edge 19e of the guiding portion 19d located on the side of the second suction port 40. The second cover connection surface 192 is bent in such a way that the direction of extension from the opening edge 19e of the guiding portion 19d toward the bottom surface 193 goes from the axial direction of the second shaft path 402 to a direction orthogonal to the axial direction of the second shaft path 402. The second cover connection surface 192 is bent in such a way that the direction of air flow passing through the path 403 becomes the direction of inflow into the second suction port 40. The second cover connection surface 192 smoothly connects the second shaft path delimiting surface 402a and the bottom surface 193.

[0064] The third plate hole 18a is formed in the third plate 18. The third plate 18 has a third plate hole defining surface 18b. The third plate hole defining surface 18b defines the third plate hole 18a. The diameter of the third plate hole 18a is the same as the diameter of the first axial path 401. The axis of the third plate hole 18a coincides with the axis of the first axial path 401. The third plate hole defining surface 18b is continuous with the first axial path defining surface 401a. The third plate hole 18a opens at both end faces in the thickness direction of the third plate 18. The third plate hole 18a is connected to the first end of the first axial path 401 and communicates with the third suction port 401b.

[0065] The second impeller housing connection path 102 is formed by the second passage 12b and the third plate hole 18a. That is, the second impeller housing 10c defines the second impeller housing connection path 102 through which air flows toward the second suction port 40.

[0066] Here, the boundary L2 between the second impeller housing connection path 102 and the second suction port 40 is shown by a double-dashed line in Figure 1 ... The portion of the second impeller housing 10c corresponding to the boundary L2 between the second impeller housing connection path 102 and the first suction port 35 corresponds to the portion connected to the second end of the pipe conventionally used for connecting the first discharge port 39 and the second suction port 40. The second impeller housing connection path 102 of the present embodiment extends from the portion corresponding to the portion connected to the second end of the conventional pipe.

[0067] The second motor housing 15 has a connection hole 15d. The second motor housing 15 has a connection hole defining surface 15b. The connection hole defining surface 15b defines the connection hole 15d. The connection hole 15d extends in the axial direction of the second motor housing 15 and opens at both end faces in the axial direction of the second motor housing 15. The connection hole 15d is located radially outside the motor housing receiving hole 15c with respect to the rotation axis 50. The direction in which the connection hole 15d extends coincides with the axial direction of the rotation axis 50. The axis of the connection hole 15d coincides with the axis of the third plate hole 18a. The diameter of the connection hole 15d is the same as the diameter of the third plate hole 18a. The connection hole defining surface 15b is continuous with the third plate hole defining surface 18b. The connection hole 15d is connected to the third plate hole 18a.

[0068] The first plate 16 has a first plate hole 16a. The first plate 16 has a first plate hole defining surface 16b. The first plate hole defining surface 16b defines the first plate hole 16a. The diameter of the first plate hole 16a is the same as the diameters of the connection hole 15d and the second plate hole 17a. The axis of the first plate hole 16a is aligned with the axes of the connection hole 15d and the second plate hole 17a. The first plate hole defining surface 16b is continuous with the connection hole defining surface 15b and the second plate hole defining surface 17b. The first plate hole 16a opens at both end faces in the thickness direction of the first plate 16. The first end of the first plate hole 16a is connected to the end of the second plate hole 17a in the axial direction that is not connected to the first passage 11a. The second end of the first plate hole 16a is connected to the first end of the connection hole 15d.

[0069] The connection hole 15d and the first plate hole 16a form a motor housing connection path 13b. The connection hole defining surface 15b and the first plate hole defining surface 16b form a third passage defining surface 13c that defines the motor housing connection path 13b. In this way, the connection path forming housing 13 defines the motor housing connection path 13b. The motor housing connection path 13b penetrates through the motor housing 10a and connects the first impeller housing connection path 101 and the second impeller housing connection path 102. The motor housing connection path 13b penetrates through the second motor housing 15. The first end of the third plate hole 18a is connected to the motor housing connection path 13b. The third suction port 401b faces the motor housing connection path 13b and sucks air in the axial direction of the rotating shaft 50. The cooling medium path 13a is provided between the motor 20 and the motor housing connection path 13b in the radial direction of the rotating shaft 50.

[0070] In this way, the connection path 70 is formed by the first impeller housing connection path 101, the second impeller housing connection path 102, and the motor housing connection path 13b. The connection path 70 is formed by the first impeller housing 10b, the second impeller housing 10c, and the connection path forming housing 13. That is to say, the connection path 70 is constituted by the first impeller housing 10b, the motor housing 10a, and the second impeller housing 10c overlapping in the axial direction of the rotating shaft 50 in sequence.

[0071] The centrifugal compressor 100 includes a third sealing member 83. The third sealing member 83 is located between the second plate 17 and the first plate 16. The third sealing member 83 is, for example, an O-ring. The third sealing member 83 seals between the second plate 17 and the first plate 16. In the centrifugal compressor 100, the first impeller housing 10b and the motor housing 10a are connected in a state where the third sealing member 83 is located therebetween. As a result, the first impeller housing connection path 101 and the motor housing connection path 13b communicate.

[0072] The centrifugal compressor 100 has a fifth sealing member 85 and an eighth sealing member 88. The fifth sealing member 85 and the eighth sealing member 88 are located between the motor housing 10a and the third plate 18. The fifth sealing member 85 is located between the second motor housing 15 and the third plate 18. The eighth sealing member 88 is located between the first motor housing 14 and the third plate 18. The fifth sealing member 85 and the eighth sealing member 88 are, for example, O-rings. The fifth sealing member 85 seals between the second motor housing 15 and the third plate 18. The eighth sealing member 88 seals between the first motor housing 14 and the third plate 18. That is to say, the fifth sealing member 85 and the eighth sealing member 88 seal between the motor housing 10a and the third plate 18. In the centrifugal compressor 100, the motor housing 10a and the second impeller housing 10c are connected in a state where the fifth sealing member 85 and the eighth sealing member 88 are therebetween. Thereby, the second impeller housing connection path 102 and the motor housing connection path 13b communicate with each other.

[0073] In addition, the centrifugal compressor 100 includes a first sealing member 81, a second sealing member 82, a fourth sealing member 84, a sixth sealing member 86, and a seventh sealing member 87. The first sealing member 81 seals between the first compressor housing 11 and the second plate 17. The second sealing member 82 seals between the third plate 18 and the second compressor housing 12. The fourth sealing member 84 seals between the second motor housing 15 and the first plate 16. The sixth sealing member 86 seals between the second impeller housing base portion 12a and the second impeller housing cover portion 19. The seventh sealing member 87 seals between the first plate 16 and the first motor housing 14. The first sealing member 81, the second sealing member 82, the fourth sealing member 84, the sixth sealing member 86, and the seventh sealing member 87 are, for example, O-rings.

[0074] [Function of the present embodiment]

[0075] The air sucked into the first impeller chamber 36 via the first suction port 35 is accelerated while passing through the rotation of the first impeller 61 and is sent to the first diffuser flow path 38, and is pressurized by passing through the first diffuser flow path 38. And, the air that has passed through the first diffuser flow path 38 is discharged to the first discharge chamber 37. The air discharged to the first discharge chamber 37 is discharged from the first discharge port 39. Therefore, the first discharge port 39 discharges the air compressed by the rotation of the first impeller 61.

[0076] The air discharged to the first row outlet 39 flows from the first row outlet 39 to the first impeller housing connection path 101. The air that has flowed through the first impeller housing connection path 101 is introduced into the motor housing connection path 13b. When the air introduced into the motor housing connection path 13b passes through the connection hole 15d in the motor housing connection path 13b, it is cooled by the cooling water flowing in the cooling medium path 13a. That is, the motor 20 is cooled by the cooling water flowing in the cooling medium path 13a, and the air flowing in the connection path 70 is also cooled.

[0077] The air that has passed through the motor housing connection path 13b is introduced into the first shaft path 401 via the third suction port 401b. In other words, the third suction port 401b faces the motor housing connection path 13b and sucks air in the axial direction of the rotating shaft 50. The air that has passed through the first shaft path 401 is introduced into the radial path 403 via the third discharge port 401c. In other words, the third discharge port 401c is opened in such a way as to discharge the air sucked from the third suction port 401b toward the guide portion 19d.

[0078] The air introduced into the radial path 403 flows smoothly along the first cover connection surface 191. In other words, the guide portion 19d guides the air sucked in the axial direction of the rotating shaft 50 from the third suction port 401b in the radial direction of the rotating shaft 50 so as to approach the second suction port 40. Specifically, when the air flows from the first shaft path 401 into the radial path 403, the air flows along the first cover connection surface 191. As a result, the flow direction of the air changes from the axial direction of the first shaft path 401 to the direction in which the radial path 403 extends. Therefore, the first cover connection surface 191 changes the flow direction of the air from the direction along the first shaft path defining surface 401a to the direction along the bottom surface 193. The second impeller housing cover portion 19 suppresses a sharp change in the flow direction in the air flow by guiding the air flowing from the first shaft path 401 into the radial path 403 using the first cover connection surface 191. Thereby, the second impeller housing cover portion 19 suppresses the generation of vortices when the air changes its flow direction from the axial direction of the first shaft path 401 to the direction in which the radial path 403 extends. In this way, the generation of vortices in the air flowing from the first shaft path 401 into the radial path 403 is suppressed.

[0079] The air introduced into the path 403 flows through the path 403 and then is introduced into the second axial path 402. The air flowing in the path 403 flows smoothly along the second cover connection surface 192. In other words, the guiding portion 19d guides the air flowing in the radial direction of the rotating shaft 50 further in the axial direction of the rotating shaft 50 toward the second suction port 40. Specifically, when the air flows from the path 403 into the second axial path 402, the air flows along the second cover connection surface 192. As a result, the flow direction of the air changes from the direction extending from the path 403 to the axial direction of the second axial path 402. Therefore, the second cover connection surface 192 changes the flow direction of the air from the direction along the bottom surface 193 to the direction along the second axial path 402. The second impeller housing cover portion 19 suppresses a sharp change in the flow direction in the air flow by guiding the air flowing from the path 403 into the second axial path 402 using the second cover connection surface 192. Thereby, the second impeller housing cover portion 19 suppresses the generation of vortices when the flow direction of the air changes from the direction extending from the path 403 to the axial direction of the second axial path 402. In this way, the generation of vortices in the air flowing from the path 403 toward the second suction port 40 is suppressed.

[0080] As described above, the third discharge port 401c and the second suction port 40 are connected by the guiding portion 19d. In other words, a groove-shaped guiding portion 19d is formed in the second impeller housing cover portion 19 so that air flows from the third discharge port 401c toward the second suction port 40.

[0081] The air that has passed through the second axial path 402 is inhaled into the second impeller chamber 41 via the second suction port 40. The air inhaled into the second impeller chamber 41 is accelerated while passing through the rotation of the second impeller 62 and is then sent to the second diffuser flow path 43, and is pressurized by passing through the second diffuser flow path 43. And the air that has passed through the second diffuser flow path 43 is discharged to the second discharge chamber 42. The air discharged to the second discharge chamber 42 is discharged from the second discharge port 44. Therefore, the second discharge port 44 discharges the air compressed by the rotation of the second impeller 62. The air discharged from the second discharge port 44 is supplied to the fuel cell stack 46 via the supply pipe 45. The oxygen contained in the air supplied to the fuel cell stack 46 participates in the power generation of the fuel cell stack 46.

[0082] [Effects of the present embodiment]

[0083] Explain the effects of the present embodiment.

[0084] (1) The connecting path 70 is composed of the first impeller housing 10b, the motor housing 10a, and the second impeller housing 10c of the housing 10. That is to say, the connecting path 70 is formed inside the housing 10. Therefore, there will be no gap formed between the housing 10 and the piping as in the configuration where, for example, a piping which is a member separate from the housing 10 is installed on the housing 10 to connect the first discharge port 39 and the second suction port 40. Thus, the centrifugal compressor 100 will not be uselessly enlarged corresponding to the gap formed between the housing 10 and the piping. In addition, the connecting path 70 can be constituted only by overlapping and assembling the first impeller housing 10b, the motor housing 10a, and the second impeller housing 10c in the axial direction of the rotating shaft 50 in sequence. Thereby, there is no need to adopt measures such as providing a structure capable of absorbing dimensional tolerances generated between the housing 10 and the piping when the piping is installed on the housing 10, for example, on the piping. Therefore, the productivity of the centrifugal compressor 100 can be improved. To sum up, it is possible to improve the productivity while suppressing the enlargement of the centrifugal compressor 100.

[0085] (2) The cooling medium path 13a is provided between the motor 20 and the motor housing connecting path 13b in the radial direction of the rotating shaft 50. Thereby, the cooling water flowing in the cooling medium path 13a can be used to cool not only the motor 20 but also the air flowing in the motor housing connecting path 13b. Therefore, the air cooled by the cooling water can be sucked into the second impeller chamber 41 via the motor housing connecting path 13b, the second impeller housing connecting path 102, and the second suction port 40. The air cooled by the cooling water has a smaller density than the uncooled air. That is to say, if the air is cooled before being sucked into the second impeller chamber 41, the mass of the air sucked into the second impeller chamber 41 increases. Therefore, compared with the case of compressing uncooled air, the second impeller 62 can compress a larger mass of air. As a result, the compression efficiency of the air accompanying the rotation of the second impeller 62 can be improved.

[0086] (3) For example, when using one housing member to constitute the cooling medium path 13a, in order to manufacture such a housing member, it is necessary to manufacture it by a casting method using a core. The manufacturing method using a core has a higher manufacturing cost than the manufacturing method without using a core. Therefore, the cooling medium path 13a is defined in such a way that the cooling water flows between the first motor housing 14 and the second motor housing 15. The first motor housing 14 and the second motor housing 15 that define the cooling medium path 13a do not need to be manufactured by a casting method using a core respectively. That is to say, in the motor housing 10a having the first motor housing 14 and the second motor housing 15, the cooling medium path 13a can be formed by using a manufacturing method without using a core. As a result, the above configuration can both suppress the manufacturing cost and form the cooling medium path 13a in the motor housing 10a.

[0087] (4) The third suction port 401b sucks in the air that has flowed through the motor housing connection path 13b in the axial direction of the rotating shaft 50. The guiding portion 19d guides the air sucked in from the third suction port 401b in the axial direction of the rotating shaft 50 in the radial direction of the rotating shaft 50 so as to approach the second suction port 40. Moreover, the guiding portion 19d further guides the air flowing in the radial direction of the rotating shaft 50 toward the second suction port 40 in the axial direction of the rotating shaft 50. As a result, the guiding of the air by the guiding portion 19d can suppress the generation of vortices when the flow direction of the air changes. Therefore, by the second impeller housing 10c having the guiding portion 19d, the pressure loss of the air flowing from the third suction port 401b toward the second suction port 40 can be reduced, and thus the compression efficiency of the air accompanying the rotation of the second impeller 62 can be improved.

[0088] (5) For example, consider the case of forming a flow path for air to flow from the third suction port 401b to the second suction port 40 using a single housing member. Here, the second suction port 40 extends in the axial direction of the rotating shaft 50 from the second impeller chamber 41. The flow path from the third suction port 401b to the third discharge port 401c extends in the axial direction of the rotating shaft 50 along the motor housing connection path 13b on the outer side in the radial direction of the rotating shaft 50 with respect to the second suction port 40. That is, the flow path for air to flow from the third discharge port 401c to the second suction port 40 extends in the radial direction of the rotating shaft 50. In order to manufacture a housing member having such a flow path from the third suction port 401b to the third discharge port 401c and a flow path from the third discharge port 401c to the second suction port 40, it may be necessary to manufacture it by a casting method using a core, and thus the manufacturing cost may increase.

[0089] Therefore, the second impeller housing 10c has a second impeller housing base portion 12a and a second impeller housing cover portion 19. The second suction port 40 and a flow path connecting the third suction port 401b and the third discharge port 401c are formed in the second impeller housing base portion 12a. The second impeller housing cover portion 19 is connected to the surface of the second impeller housing base portion 12a in which the third discharge port 401c opens. Thereby, the second impeller housing cover portion 19 closes the opening on one end side of the second suction port 40 and the opening formed by the third discharge port 401c. And, a flow path connecting the third discharge port 401c and the second suction port 40, which is defined by the guiding portion 19d and the second impeller housing base portion 12a, is formed between the second impeller housing cover portion 19 and the second impeller housing base portion 12a. Thereby, it is not necessary to manufacture it by a casting method using a core as in the case of forming a flow path for air to flow from the third suction port 401b to the second suction port 40 using a single housing member. Thus, an increase in the manufacturing cost can be avoided.

[0090] (6) The converter 65 is disposed on the outer surface 10e of the housing. That is, the cooling water flowing in the cooling medium path 13a can cool the motor 20, the air flowing in the connection path 70, and the converter 65. That is, forming the connection path 70 inside the housing 10 and disposing the converter 65 on the outer surface of the housing 10 can achieve miniaturization of the centrifugal compressor 100. In addition, the motor 20, the air flowing in the connection path 70, and the converter 65 can be cooled simultaneously by a single cooling medium path 13a. As a result, in addition to being able to suppress the enlargement of the centrifugal compressor 100 and improve the compression efficiency of the second impeller 62, the heat generated during the operation of the centrifugal compressor 100 can be efficiently dissipated.

[0091] (7) A plurality of annular fins 14d extending along the outer peripheral surface of the peripheral wall 14b are formed on the outer peripheral surface of the first motor housing 14. Thus, the cooling water flowing in the cooling medium path 13a flows in the circumferential direction of the first motor housing 14 and the second motor housing 15 along each fin 14d. Thus, efficient heat exchange can be performed with the first motor housing 14, the second motor housing 15, and the converter housing 66. That is, the cooling water can efficiently cool the motor 20, the air flowing in the cooling medium path 13a, and the converter 65 by flowing along each fin 14d. Here, for example, consider a configuration in which a single housing member forms an annular fin 14d extending along the outer peripheral surface of the peripheral wall 14b of the first motor housing 14 and projects into the cooling medium path 13a and a connection path 70 is formed inside the housing 10. To manufacture such a housing member, it is necessary to manufacture it by a casting method using a core, so the manufacturing cost increases. Therefore, in the present embodiment, the first motor housing 14 is formed as a member separate from the second motor housing 15. Thus, it is not necessary to manufacture the first motor housing 14 and the second motor housing 15 respectively by a casting method using a core. Therefore, both the manufacturing cost can be suppressed and the annular fin 14d extending along the outer peripheral surface of the peripheral wall 14b of the first motor housing 14 can project into the cooling medium path 13a and a connection path 70 can be formed inside the housing 10.

[0092] [Modification example]

[0093] In addition, the above-described embodiment can be modified and implemented as follows. The above-described embodiment and the following modification examples can be implemented in combination with each other within a technically non-contradictory range.

[0094] The guiding portion 19d may not be formed on the opposing surface 19b of the second impeller housing cover portion 19. In this case, for example, a recess extending in the radial direction of the rotary shaft 50 may be formed on the axial end surface 12d of the second impeller housing base portion 12a, and this recess functions as the guiding portion 19d. That is to say, the second impeller housing base portion 12a may have the guiding portion 19d.

[0095] The second impeller housing 10c may not include the second impeller housing cover portion 19. In this case, the second impeller housing 10c is formed by the second impeller housing base portion 12a and the third plate 18. Additionally, in this case, the first passage 401 and the second suction port 40 do not open at the axial end surface 12d and are connected through the interior of the second impeller housing base portion 12a. That is to say, in this case, the second impeller housing 10c may not include the third discharge port 401c.

[0096] The second passage 402 may not be formed in the second impeller housing base portion 12a. In this case, the second suction port 40 is directly connected to the passage 403.

[0097] The motor housing 10a may not include the first motor housing 14 and the second motor housing 15. That is to say, the motor housing 10a may be constituted by a single housing member. In this case, the cooling medium passage 13a is formed inside the housing 10.

[0098] The cooling medium passage 13a may not be provided between the motor 20 and the motor housing connection passage 13b in the radial direction of the rotary shaft 50.

[0099] The centrifugal compressor 100 may not include the cooling medium passage 13a.

[0100] The centrifugal compressor 100 may also be configured such that one thin plate fin extending in a spiral shape is provided on the outer peripheral surface of the peripheral wall 14b of the first motor housing 14.

[0101] Fins may not be provided on the outer peripheral surface of the peripheral wall 14b of the first motor housing 14. In this case, the cooling water flowing in the cooling medium passage 13a may flow axially along the outer peripheral surface of the peripheral wall 14b of the first motor housing 14.

[0102] The cooling medium flowing in the cooling medium passage 13a may be other than cooling water. For example, it may be a refrigerant or may also be air.

[0103] The converter 65 may not be provided on the outer surface 10e of the housing.

[0104] The fluid compressed by the centrifugal compressor 100 is not limited to air. Therefore, the application object of the centrifugal compressor 100 and the fluid to be compressed are arbitrary. For example, the centrifugal compressor 100 can also be used in an air conditioning device, and the fluid to be compressed can also be a refrigerant. In addition, the mounting object of the centrifugal compressor 100 is not limited to vehicles and is arbitrary.

Claims

1. A centrifugal compressor comprising: Axis of rotation; a motor to rotate the rotating shaft; a first impeller that rotates integrally with the rotating shaft to compress the fluid; a second impeller disposed on the opposite side of the first impeller with respect to the rotating shaft, the motor being disposed between the first impeller and the second impeller, and the second impeller rotating integrally with the rotating shaft; a casing having a first impeller casing, a motor casing, and a second impeller casing, the first impeller casing defining a first impeller chamber for accommodating the first impeller, having a first suction port for sucking fluid into the first impeller chamber, and a first discharge port for discharging fluid compressed by the rotation of the first impeller, the motor casing defining a motor chamber for accommodating the motor, the second impeller casing defining a second impeller chamber for accommodating the second impeller, having a second suction port for sucking fluid into the second impeller chamber, and a second discharge port for discharging fluid compressed by the rotation of the second impeller; and a connecting passage connecting the first discharge port and the second suction port in such a manner that the fluid flows from the first discharge port toward the second suction port, The connecting path has: a first impeller casing connecting passage, provided in the first impeller casing and connected to the first discharge port; a second impeller casing connecting passage, provided in the second impeller casing and connected to the second suction port; and a motor casing connection passage, formed through the motor casing and connecting the first impeller casing connection passage and the second impeller casing connection passage, The connection passage is formed by sequentially stacking the first impeller casing, the motor casing, and the second impeller casing in the axial direction of the rotating shaft.

2. The centrifugal compressor according to claim 1, The motor housing includes a cooling medium passage through which a cooling medium for cooling the motor flows. The cooling medium passage is provided between the motor and the motor case connection passage in the radial direction of the rotating shaft.

3. The centrifugal compressor according to claim 2, The motor includes a cylindrical stator and a rotor provided on the rotating shaft and rotating integrally with the rotating shaft. The motor housing has: a first motor housing having the stator fixed on the inner circumference thereof; and The second motor housing has the motor housing connection passage formed therethrough. The cooling medium path is defined so that a cooling medium flows between the first motor case and the second motor case.

4. The centrifugal compressor according to claim 1, The second impeller housing has a third suction port and a guide portion. The third suction port is opposite to the motor housing connection path and sucks fluid in the axial direction. The guide portion guides the fluid sucked in the axial direction from the third suction port in a radial direction of the rotating shaft in a manner close to the second suction port, and further guides the fluid flowing in the radial direction toward the second suction port in the axial direction.

5. The centrifugal compressor according to claim 4, The second impeller housing has: a second impeller casing base, the third suction port, the second suction port, and the second discharge port opening at the second impeller casing base, and the third discharge port opening in a manner to discharge the fluid sucked from the third suction port toward the guide portion opening at the second impeller casing base; and The second impeller casing cover has the groove-shaped guide portion that connects the third discharge port and the second suction port and opens so that the fluid flows from the third discharge port toward the second suction port.

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