Centrifugal compressor

Abstract

A first gap (81), a second gap (82), a third gap (83), and a fourth gap (84) are provided inside the second insertion hole (26). The pressure of the air is continuously reduced as the air flows from the first gap (81) to the fourth gap (84). As a result, the pressure of air flowing into the second insertion hole (26) from the gap (90) between the back surface (43a) of the second impeller (43) and the second plate (16) is efficiently reduced. As a result, a portion of the air compressed by the second impeller (43) and discharged into the second discharge chamber is prevented from entering the motor chamber through the second insertion hole (26). Since the third gap (83) and the fourth gap (84) can be provided inside the second insertion hole (26) only by using the gap filling plate (77), there is no need to perform additional processing on the rotating shaft (41) in order to provide the third gap (83) and the fourth gap (84) inside the second insertion hole (26).

Description

Technical Field

[0001] The present invention relates to centrifugal compressors. Background Art

[0002] For example, as disclosed in Patent Document 1, a centrifugal compressor includes a rotating body including a rotating shaft and an impeller. The impeller rotates integrally with the rotating shaft. The impeller compresses air. The centrifugal compressor includes a motor and a casing. The motor rotates the rotating shaft. The casing includes an impeller chamber, a motor chamber, a partition wall, and a discharge chamber. The impeller chamber accommodates the impeller. The motor chamber accommodates the motor. The partition wall separates the impeller chamber and the motor chamber. The air compressed by the impeller is discharged into the discharge chamber. An insertion hole for the rotating body to be inserted is formed in the partition wall.

[0003] In addition, a centrifugal compressor is sometimes provided with an annular shim plate. The shim plate is, for example, interposed between the rotating shaft and the impeller in the axial direction of the rotating shaft. The shim plate adjusts the position of the impeller in the axial direction of the rotating shaft by interposing between the rotating shaft and the impeller in the axial direction of the rotating shaft. As a result, the interval between the impeller and the casing is adjusted, thereby improving the compression efficiency of the air.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2015-155696 Summary of the invention

[0007] Problems to be solved by the invention

[0008] In such a centrifugal compressor, a part of the air compressed by the impeller and discharged to the discharge chamber sometimes flows into the gap between the back side of the impeller and the partition wall. As a result, the air flowing into the gap between the back side of the impeller and the partition wall may leak into the motor chamber through the insertion hole. As a result, in the centrifugal compressor, the useless compression of air increases, which becomes the main reason for the decrease in operating efficiency. Therefore, it is desired to suppress the decrease in the operating efficiency of the centrifugal compressor in a manner that does not perform additional processing on the rotating shaft.

[0009] Means for solving problems

[0010] A centrifugal compressor for solving the above-mentioned problems comprises: a rotating body including a rotating shaft and an impeller which compresses air by rotating integrally with the rotating shaft; a motor which rotates the rotating shaft; a casing having an impeller chamber for accommodating the impeller, a motor chamber for accommodating the motor, a partition wall which separates the impeller chamber from the motor chamber and is formed with an insertion hole for the rotating body to pass through, and a discharge chamber for discharging air compressed by the impeller; and an annular shim plate which is disposed between the rotating body and the impeller chamber in the axial direction of the rotating shaft. The rotating shaft has a shaft portion disposed inside the insertion hole between the rotating shaft and the impeller, the shaft portion having a large diameter shaft portion and a small diameter shaft portion, the diameter of the small diameter shaft portion is smaller than the diameter of the large diameter shaft portion and the small diameter shaft portion extends from the large diameter shaft portion toward the impeller chamber, the impeller has a protrusion portion protruding from the back side of the impeller and disposed inside the insertion hole, the protrusion portion having a large diameter protrusion portion and a small diameter protrusion portion, the diameter of the small diameter protrusion portion is smaller than the diameter of the large diameter protrusion portion and the The small-diameter protrusion extends from the large-diameter protrusion toward the motor chamber, the shim plate is interposed between the end surface of the small-diameter shaft portion and the end surface of the small-diameter protrusion and protrudes radially outward from the small-diameter shaft portion and the small-diameter protrusion, the partition wall has an annular protrusion protruding from the inner circumferential surface of the insertion hole toward the outer circumferential surface of the small-diameter protrusion, and a first gap, a second gap, a third gap, and a fourth gap are sequentially provided on the inner side of the insertion hole from the impeller chamber toward the motor chamber, The first gap is formed between the inner circumferential surface of the insertion hole and the outer circumferential surface of the large-diameter protrusion, the second gap is formed between the protrusion and the outer circumferential surface of the small-diameter protrusion, the third gap is formed between the filling plate and the inner circumferential surface of the insertion hole, and the fourth gap is formed between the inner circumferential surface of the insertion hole and the outer circumferential surface of the large-diameter shaft portion. The first gap, the second gap, the third gap and the fourth gap constitute a labyrinth seal that seals the insertion hole and the rotating body.

[0011] Thus, the first gap, the second gap, the third gap and the fourth gap constitute a labyrinth seal that seals the insertion hole and the rotating body. Specifically, for example, when air flows into the insertion hole from the gap between the back of the impeller and the partition wall, the air is throttled by passing through the first gap. Moreover, the air that has passed through the first gap expands before reaching the second gap and is throttled again by passing through the second gap. Moreover, the air that has passed through the second gap expands again before reaching the third gap and is throttled again by passing through the third gap. Moreover, the air that has passed through the third gap expands again before reaching the fourth gap and is throttled again by passing through the fourth gap. In this way, even if air flows into the insertion hole from the gap between the back of the impeller and the partition wall, the air will pass through the throttled part and the expanded part of the air in sequence from the first gap through the second gap and the third gap to the fourth gap. Therefore, the air is successively decompressed as it flows from the first gap toward the fourth gap. Thus, the pressure of the air flowing into the insertion hole from the gap between the back of the impeller and the partition wall can be efficiently reduced. As a result, a part of the air compressed by the impeller and discharged into the discharge chamber is prevented from leaking into the motor chamber through the insertion hole. As a result, in the centrifugal compressor, useless compression of air is suppressed, and thus a decrease in the operating efficiency of the centrifugal compressor is suppressed.

[0012] For example, if the third gap and the fourth gap are to be provided on the inner side of the insertion hole without using a shim plate, an annular recess needs to be formed on the outer peripheral surface of the shaft portion. Therefore, processing is required to form the recess on the outer peripheral surface of the shaft portion, and therefore, additional processing needs to be performed on the rotating shaft. Therefore, the third gap is formed by making the shim plate protrude radially outward of the rotating shaft more than the small-diameter shaft portion and the small-diameter protrusion. Thus, the third gap and the fourth gap can be provided on the inner side of the insertion hole only by using the shim plate as an existing structure. Through the above content, the decrease in the operating efficiency of the centrifugal compressor can be suppressed without performing additional processing on the rotating shaft.

[0013] In the above-mentioned centrifugal compressor, it may be that the partition wall has: a first wall constituting body, which divides the impeller chamber and has a first hole that forms a part of the insertion hole; and a second wall constituting body, which divides the motor chamber and has a second hole that forms a part of the insertion hole, the protrusion is a first protrusion that protrudes from the inner peripheral surface of the first hole toward the outer peripheral surface of the small-diameter protrusion, the second wall constituting body has an annular second protrusion that protrudes from the inner peripheral surface of the second hole toward the outer peripheral surface of the small-diameter shaft portion, a fifth gap is provided on the inner side of the insertion hole, the fifth gap is formed between the second protrusion and the outer peripheral surface of the small-diameter shaft portion, the fifth gap is located between the third gap and the fourth gap, and the first gap, the second gap, the third gap, the fourth gap and the fifth gap constitute a labyrinth seal that seals the insertion hole and the rotating body.

[0014] Thus, the second protrusion is formed on the second wall constituting body which is a member of the first wall constituting body on which the first protrusion is formed. Therefore, when assembling the centrifugal compressor, the gap filling plate between the end face of the small-diameter shaft portion and the end face of the small-diameter protrusion can be arranged between the first protrusion and the second protrusion in the axial direction of the rotating shaft. In addition, the fifth gap is provided on the inner side of the insertion hole. Therefore, the air is throttled by passing through the fifth gap. Thus, the air flowing from the first gap toward the fourth gap can be further decompressed easily. Therefore, the pressure of the air flowing into the insertion hole from the gap between the back side of the impeller and the partition wall can be further efficiently decompressed.

[0015] In the centrifugal compressor, the shim plate may have a linear expansion coefficient smaller than a linear expansion coefficient of the partition wall.

[0016] Thus, for example, compared with a case where the linear expansion coefficient of the shim plate is equal to or greater than that of the partition wall, even if the shim plate is thermally expanded due to heat transfer from the impeller to the shim plate, contact between the shim plate and the partition wall can be easily avoided.

[0017] Effects of the Invention

[0018] According to the present invention, it is possible to suppress a decrease in the operating efficiency of the centrifugal compressor without performing additional processing on the rotating shaft. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a cross-sectional view of a centrifugal compressor in the embodiment.

[0020] Figure 2 This is a cross-sectional view showing a part of the centrifugal compressor in an enlarged manner.

[0021] Figure 3 This is a cross-sectional view showing a part of the centrifugal compressor in an enlarged manner. DETAILED DESCRIPTION

[0022] Below, according to Figure 1 to Figure 3 An embodiment in which a centrifugal compressor is embodied will be described. In addition, the centrifugal compressor of the embodiment described below is mounted on a fuel cell vehicle. The centrifugal compressor compresses air supplied to a fuel cell stack.

[0023] <Basic Structure of Centrifugal Compressor 10>

[0024] like Figure 1 As shown, the centrifugal compressor 10 includes a housing 11 . The housing 11 is made of a metal material. The housing 11 is made of, for example, aluminum. The housing 11 includes a motor housing 12 , a first compressor housing 13 , a second compressor housing 14 , a first plate 15 , a second plate 16 , and a third plate 17 .

[0025] 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 in a cylindrical shape from the outer peripheral portion of the end wall 12a. The first plate 15 is connected to the end of the opening side of the peripheral wall 12b of the motor housing 12. The first plate 15 blocks the opening of the peripheral wall 12b of the motor housing 12. In addition, the motor housing 12 and the first plate 15 define a motor chamber 18. Therefore, the housing 11 has a motor chamber 18.

[0026] The second plate 16 is connected to the outer surface of the end wall 12a of the motor case 12. The second plate 16 is attached to the end wall 12a of the motor case 12 in a state where the thickness direction of the second plate 16 coincides with the thickness direction of the end wall 12a of the motor case 12.

[0027] The centrifugal compressor 10 includes a motor 20 . The motor 20 is housed in the motor chamber 18 . Therefore, the motor chamber 18 houses the motor 20 . The motor housing 12 surrounds the motor 20 .

[0028] The centrifugal compressor 10 includes a first bearing holding portion 21. The first bearing holding portion 21 protrudes from the center portion of the first plate 15 into the motor chamber 18. Therefore, the first plate 15 includes the first bearing holding portion 21. The first bearing holding portion 21 is cylindrical.

[0029] The first plate 15 has a chamber forming recess 22. The chamber forming recess 22 is formed on the end surface of the first plate 15 on the side opposite to the motor housing 12. The chamber forming recess 22 is in the shape of a circular hole. The inner side of the first bearing holding portion 21 passes through the first plate 15 and opens at the bottom surface of the chamber forming recess 22. The axis of the chamber forming recess 22 coincides with the axis of the first bearing holding portion 21.

[0030] The third plate 17 is connected to the end surface of the first plate 15 on the side opposite to the motor housing 12. The third plate 17 is mounted on the first plate 15 in a state where the thickness direction of the third plate 17 coincides with the thickness direction of the first plate 15. The third plate 17 has a first insertion hole 23. The first insertion hole 23 is formed in the central portion 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 retaining portion 21. In addition, a thrust bearing accommodating chamber 24 is defined by the chamber forming recess 22 and the third plate 17. The thrust bearing accommodating chamber 24 is connected to the inner side of the first bearing retaining portion 21. In addition, the thrust bearing accommodating chamber 24 is connected to the first insertion hole 23.

[0031] The centrifugal compressor 10 includes a second bearing holding portion 25. The second bearing holding portion 25 protrudes from the center of the end wall 12a of the motor housing 12 into the motor chamber 18. Therefore, the motor housing 12 includes the second bearing holding portion 25. The second bearing holding portion 25 is cylindrical.

[0032] The housing 11 has a second insertion hole 26. The second insertion hole 26 passes through the center of the end wall 12a of the motor housing 12 and the center of the second plate 16. The second insertion hole 26 communicates with the inner side 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.

[0033] The first compressor housing 13 is cylindrical and has a first inlet 27 in the shape of a circular hole for sucking air. The first compressor housing 13 is connected to the end surface of the third plate 17 on the side opposite to the first plate 15 in a state where the axis of the first inlet 27 coincides with the axis of the first insertion hole 23. The first inlet 27 opens at the end surface of the first compressor housing 13 on the side opposite to the third plate 17. Air purified by an air cleaner (not shown) flows into the first inlet 27.

[0034] The centrifugal compressor 10 includes a first impeller chamber 28, a first discharge chamber 29, and a first diffuser flow path 30. The first impeller chamber 28, the first discharge chamber 29, and the first diffuser flow path 30 are formed between the first compressor housing 13 and the third plate 17. Therefore, the housing 11 has the first impeller chamber 28. The first plate 15 and the third plate 17 constitute a partition wall that separates the first impeller chamber 28 from the motor chamber 18. The first impeller chamber 28 is connected to the first suction port 27. The first discharge chamber 29 extends around the first impeller chamber 28 around the axis of the first suction port 27. The first diffuser flow path 30 connects the first impeller chamber 28 and the first discharge chamber 29. The first impeller chamber 28 is connected to the first insertion hole 23.

[0035] The centrifugal compressor 10 includes a first discharge passage 31 . A first end of the first discharge passage 31 communicates with the first discharge chamber 29 . A second end of the first discharge passage 31 opens at the outer peripheral surface of the first compressor housing 13 .

[0036] The second compressor housing 14 is cylindrical and has a second inlet port 32 in the form of a circular hole for sucking air. The second compressor housing 14 is connected to the end surface of the second plate 16 on the side opposite to the motor housing 12 in a state where the axis of the second inlet port 32 coincides with the axis of the second insertion hole 26. The second inlet port 32 opens at the end surface of the second compressor housing 14 on the side opposite to the second plate 16.

[0037] The centrifugal compressor 10 includes a second impeller chamber 33, a second discharge chamber 34, and a second diffuser flow path 35. The second impeller chamber 33, the second discharge chamber 34, and the second diffuser flow path 35 are formed between the second compressor housing 14 and the second plate 16. Therefore, the housing 11 has the second impeller chamber 33. The end wall 12a of the motor housing 12 and the second plate 16 constitute a partition wall that separates the second impeller chamber 33 from the motor chamber 18. The second impeller chamber 33 is connected to the second suction port 32. The second discharge chamber 34 extends around the second impeller chamber 33 around the axis of the second suction port 32. The second diffuser flow path 35 connects the second impeller chamber 33 and the second discharge chamber 34. The second impeller chamber 33 is connected to the second insertion hole 26.

[0038] The centrifugal compressor 10 has a second discharge passage 36. The first end of the second discharge passage 36 is connected to the second discharge chamber 34. The second end of the second discharge passage 36 opens at the outer peripheral surface of the second compressor housing 14. A supply pipe 37 is connected to the second discharge passage 36. The supply pipe 37 is connected to a fuel cell stack 38. The first end of the supply pipe 37 is connected to the second discharge passage 36. The second end of the supply pipe 37 is connected to the fuel cell stack 38. The second discharge chamber 34 is connected to the fuel cell stack 38 via the second discharge passage 36 and the supply pipe 37.

[0039] The centrifugal compressor 10 includes a connecting pipe 39. A first end of the connecting pipe 39 is connected to the first discharge passage 31. A second end of the connecting pipe 39 is connected to the second suction port 32. Air discharged from the first discharge chamber 29 to the first discharge passage 31 flows in the connecting pipe 39. The air passing through the connecting pipe 39 is sucked into the second impeller chamber 33 via the second suction port 32.

[0040] The centrifugal compressor 10 includes a rotating body 40. The rotating body 40 includes a rotating shaft 41, a first impeller 42, a second impeller 43, and a support portion 44. The rotating shaft 41 is accommodated in the casing 11.

[0041] The rotating shaft 41 crosses the motor chamber 18 in a state extending along the axis of the motor housing 12. The axial direction of the rotating shaft 41 coincides with the axial direction of the motor housing 12. The first end of the rotating shaft 41 protrudes from the motor chamber 18 into the first impeller chamber 28 through the inner side of the first bearing holding portion 21, the thrust bearing accommodation chamber 24, and the first insertion hole 23. Therefore, the first insertion hole 23 is an insertion hole through which the rotating body 40 is inserted. In this way, the housing 11 has a partition wall that partitions the first impeller chamber 28 and the motor chamber 18 and forms the first insertion hole 23 through which the rotating body 40 is inserted.

[0042] The second end of the rotating shaft 41 protrudes from the motor chamber 18 into the second impeller chamber 33 through the inner side of the second bearing holding portion 25 and the second insertion hole 26. Therefore, the second insertion hole 26 is an insertion hole through which the rotating body 40 is inserted. In this way, the housing 11 has a partition wall that partitions the second impeller chamber 33 and the motor chamber 18 and has the second insertion hole 26 through which the rotating body 40 is inserted.

[0043] The first impeller 42 is connected to the first end of the rotating shaft 41. The first impeller 42 is accommodated in the first impeller chamber 28. Therefore, the first impeller chamber 28 accommodates the first impeller 42. The first impeller 42 compresses the air sucked into the first impeller chamber 28 by rotating integrally with the rotating shaft 41. Therefore, the first impeller 42 is an impeller that compresses air. Therefore, the first impeller chamber 28 is an impeller chamber that accommodates an impeller.

[0044] The second impeller 43 is connected to the second end of the rotating shaft 41. The second impeller 43 is accommodated in the second impeller chamber 33. Therefore, the second impeller chamber 33 accommodates the second impeller 43. The second impeller 43 compresses the air sucked into the second impeller chamber 33 by rotating integrally with the rotating shaft 41. Therefore, the second impeller 43 is an impeller that compresses air. Therefore, the second impeller chamber 33 is an impeller chamber that accommodates an impeller. Therefore, the housing 11 has an impeller chamber that accommodates an impeller. The second impeller 43 compresses the air compressed by the first impeller 42.

[0045] The support portion 44 protrudes in an annular shape from the outer peripheral surface of the rotating shaft 41. The support portion 44 is in the shape of a disk. The support portion 44 is fixed to the outer peripheral surface of the rotating shaft 41 in a state of protruding in an annular shape from the outer peripheral surface of the rotating shaft 41 toward the radial outer side. Therefore, the support portion 44 is separate from the rotating shaft 41. The support portion 44 is arranged in the thrust bearing accommodation chamber 24. The support portion 44 rotates integrally with the rotating shaft 41.

[0046] The centrifugal compressor 10 includes a sealing member 45. The sealing member 45 is provided between the first insertion hole 23 and the rotating shaft 41. The sealing member 45 suppresses leakage of air from the first impeller chamber 28 toward the motor chamber 18. The sealing member 45 is, for example, a seal ring.

[0047] The motor 20 includes a cylindrical rotor 47 and a cylindrical stator 48. The rotor 47 is fixed to the rotating shaft 41. The stator 48 is fixed to the housing 11. The rotor 47 is arranged radially inward of the stator 48. The rotor 47 rotates integrally with the rotating shaft 41. The rotor 47 includes a cylindrical rotor core 49 fixed to the rotating shaft 41 and a plurality of permanent magnets (not shown) provided on the rotor core 49. The stator 48 surrounds the rotor 47. The stator 48 includes a cylindrical stator core 50 and a coil 51. The stator core 50 is fixed to the inner circumferential surface of the motor housing 12. The coil 51 is wound around the stator core 50.

[0048] When a current flows from a battery (not shown) to the coil 51, the rotating shaft 41 rotates integrally with the rotor 47. Thus, the motor 20 rotates the rotating shaft 41. The motor 20 is disposed between the first impeller 42 and the second impeller 43 in the axial direction of the rotating shaft 41.

[0049] 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 the first bearing holding portion 21. The first radial bearing 52 rotatably supports a portion of the rotating shaft 41 that is located closer to the first end of the rotating shaft 41 than the motor 20.

[0050] 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 holding portion 25. The second radial bearing 53 rotatably supports a portion of the rotating shaft 41 located closer to the second end of the rotating shaft 41 than the motor 20.

[0051] The first radial bearing 52 and the second radial bearing 53 rotatably support the rotating shaft 41 in the radial direction at positions sandwiching the motor 20 in the axial direction of the rotating shaft 41. The "radial direction" refers to a direction orthogonal to the axial direction of the rotating shaft 41.

[0052] The centrifugal compressor 10 includes a thrust bearing 54. The thrust bearing 54 is accommodated in the thrust bearing accommodation chamber 24. Therefore, the thrust bearing accommodation chamber 24 accommodates the thrust bearing 54. The thrust bearing 54 supports the support portion 44 in a thrust direction so that it can rotate. Therefore, the thrust bearing 54 supports the rotating shaft 41 in a rotatable manner via the support portion 44. In addition, the "thrust direction" is a direction parallel to the axial direction of the rotating shaft 41.

[0053] The air sucked into the first impeller chamber 28 through the first suction port 27 is accelerated by the rotation of the first impeller 42, and is sent to the first diffusion channel 30, and is pressurized by passing through the first diffusion channel 30. Then, the air passing through the first diffusion channel 30 is discharged to the first discharge chamber 29. The air discharged to the first discharge chamber 29 is discharged to the first discharge passage 31. The air discharged to the first discharge passage 31 is sucked into the second impeller chamber 33 through the connecting pipe 39 and the second suction port 32. The air sucked into the second impeller chamber 33 is accelerated by the rotation of the second impeller 43, and is sent to the second diffusion channel 35, and is pressurized by passing through the second diffusion channel 35. Then, the air passing through the second diffusion channel 35 is discharged to the second discharge chamber 34. The air discharged to the second discharge chamber 34 is discharged to the second discharge passage 36. The air discharged to the second discharge passage 36 is supplied to the fuel cell stack 38 via the supply pipe 37. Therefore, the centrifugal compressor 10 supplies air to the fuel cell stack 38. The oxygen contained in the air supplied to the fuel cell stack 38 contributes to the power generation of the fuel cell stack 38.

[0054] The rotating body 40 includes a rotating shaft 41 and a first impeller 42 and a second impeller 43 that compress the air supplied to the fuel cell stack 38 by rotating integrally with the rotating shaft 41. Therefore, the rotating body 40 includes an impeller. The second discharge passage 36 and the supply pipe 37 constitute a supply flow path 55 that supplies air to the fuel cell stack 38. In addition, the second discharge chamber 34 is a discharge chamber for discharging the air compressed by the second impeller 43 and connected to the supply flow path 55. Therefore, the housing 11 has a discharge chamber connected to the supply flow path 55.

[0055] The centrifugal compressor 10 includes an introduction passage 56. The introduction passage 56 is formed in the first plate 15. A first end of the introduction passage 56 opens at the outer peripheral surface of the first plate 15. A second end of the introduction passage 56 communicates with the thrust bearing accommodation chamber 24.

[0056] A branch pipe 57 is connected to the first end of the introduction passage 56. The branch pipe 57 branches from the middle of the supply pipe 37. The first end of the branch pipe 57 is connected to the supply pipe 37. The second end of the branch pipe 57 is connected to the first end of the introduction passage 56. An intercooler 58 is provided in the middle of the branch pipe 57. The intercooler 58 cools the air flowing in the branch pipe 57.

[0057] A part of the air flowing in the supply pipe 37 flows into the branch pipe 57. The air flowing in the branch pipe 57 is cooled by the intercooler 58. Thus, the air passing through the intercooler 58 has a lower temperature than the air discharged to the second discharge chamber 34. Then, the air cooled by the intercooler 58 is introduced into the motor chamber 18 through the introduction passage 56, the thrust bearing accommodation chamber 24, and the inner side of the first bearing holding portion 21. Therefore, the introduction passage 56 introduces a part of the air compressed by the second impeller 43 into the motor chamber 18 at a lower temperature than the air discharged to the second discharge chamber 34.

[0058] 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. The first end of the discharge passage 59 is connected to the second insertion hole 26. The second end of the discharge passage 59 is opened at the outer peripheral surface of the end wall 12a of the motor housing 12. Therefore, the discharge passage 59 is connected to the outside of the housing 11. And the air that flows into the second insertion hole 26 from the motor chamber 18 through the inner side of the second bearing holding portion 25 is discharged to the outside of the housing 11 through the discharge passage 59.

[0059] like Figure 2 As shown in the figure, the second impeller 43 is a cylindrical shape that gradually decreases in diameter from the back surface 43a to the top. The back surface 43a of the second impeller 43 is opposite to the second plate 16. Therefore, the second plate 16 has an opposing surface 16a that is opposite to the back surface 43a of the second impeller 43. The second impeller 43 has a through hole 43h. The axis of the through hole 43h is consistent with the rotation axis of the second impeller 43. In addition, the rotation axis of the second impeller 43 is also the axis of the rotating shaft 41.

[0060] <First Hole 61 and Second Hole 64>

[0061] The second plate 16 has a first hole 61 forming a part of the second insertion hole 26. The first hole 61 penetrates the central portion of the second plate 16. The first hole 61 has a first large diameter hole 62 and a first small diameter hole 63. The first large diameter hole 62 is continuous with the facing surface 16a. Regarding the first small diameter hole 63, the hole diameter of the first small diameter hole 63 is smaller than the hole diameter of the first large diameter hole 62. The first small diameter hole 63 is continuous with the end portion of the first large diameter hole 62 on the side opposite to the facing surface 16a. The second plate 16 is a first wall constituent body that partitions the second impeller chamber 33.

[0062] The end wall 12a of the motor housing 12 has a second hole 64 that forms a part of the second insertion hole 26. The second hole 64 penetrates the central part of the end wall 12a of the motor housing 12. The second hole 64 has a second large diameter hole 65 and a second small diameter hole 66. The second large diameter hole 65 is continuous with the inner side of the second bearing holding portion 25. Regarding the second small diameter hole 66, the hole diameter of the second small diameter hole 66 is smaller than the hole diameter of the second large diameter hole 65. The second small diameter hole 66 is continuous with the end of the second large diameter hole 65 on the side opposite to the second bearing holding portion 25. The hole diameter of the second small diameter hole 66 is the same as the hole diameter of the first small diameter hole 63. The end wall 12a of the motor housing 12 is a second wall component that partitions the motor chamber 18. Therefore, the partition wall has a first wall component and a second wall component.

[0063] <Shaft 71>

[0064] The rotating shaft 41 includes a shaft portion 71. The shaft portion 71 is a portion of the rotating shaft 41 that is disposed inside the second insertion hole 26. The shaft portion 71 includes a large-diameter shaft portion 72 and a small-diameter shaft portion 73. The large-diameter shaft portion 72 extends from the motor chamber 18 through the inside of the second bearing holding portion 25 and the second large-diameter hole 65 of the second hole 64 to the inside of the second small-diameter hole 66 of the second hole 64.

[0065] like Figure 3 As shown, the end face 72a of the large diameter shaft portion 72 is located inside the second small diameter hole 66. The diameter of the small diameter shaft portion 73 is smaller than the diameter of the large diameter shaft portion 72. Figure 2 and Figure 3 As shown in FIG. 1 , the small diameter shaft portion 73 extends from the end surface 72a of the large diameter shaft portion 72 toward the second impeller chamber 33. The axis of the large diameter shaft portion 72 coincides with the axis of the small diameter shaft portion 73. Figure 3 As shown in the figure, the small diameter shaft portion 73 extends from the end face 72a of the large diameter shaft portion 72 through the second small diameter hole 66 of the second hole 64 to the inside of the first small diameter hole 63 of the first hole 61. The end face 73a of the small diameter shaft portion 73 is located inside the first small diameter hole 63 of the first hole 61. In addition, the rotating shaft 41 has a through portion 41e. The through portion 41e extends from the end face 73a of the small diameter shaft portion 73 and penetrates the through hole 43h of the second impeller 43.

[0066] <Protrusion 74>

[0067] The second impeller 43 has a cylindrical boss 74. The boss 74 protrudes from the center of the back surface 43a of the second impeller 43. The inner side of the boss 74 is connected to the through hole 43h. The rotating shaft 41 passes through the inner side of the boss 74 and the through hole 43h. The boss 74 enters the second insertion hole 26. Therefore, the boss 74 is arranged inside the second insertion hole 26. The boss 74 is a portion of the rotating body 40 located inside the second insertion hole 26.

[0068] The protrusion 74 includes a large diameter protrusion 75 and a small diameter protrusion 76. The large diameter protrusion 75 is continuous with the back surface 43a of the second impeller 43. The outer diameter of the large diameter protrusion 75 is the same as the outer diameter of the large diameter shaft portion 72. The large diameter protrusion 75 extends from the back surface 43a of the second impeller 43 through the inner side of the first large diameter hole 62 of the first hole 61 to the inner side of the first small diameter hole 63 of the first hole 61. The end face 75a of the large diameter protrusion 75 is located inside the first small diameter hole 63.

[0069] The diameter of the small-diameter protrusion 76 is smaller than the diameter of the large-diameter protrusion 75. The small-diameter protrusion 76 extends from the end face 75a of the large-diameter protrusion 75 toward the motor chamber 18. The axis of the large-diameter protrusion 75 coincides with the axis of the small-diameter protrusion 76. The end face 76a of the small-diameter protrusion 76 is located inside the first small-diameter hole 63. The outer diameter of the small-diameter protrusion 76 is the same as the outer diameter of the small-diameter shaft portion 73. The end face 76a of the small-diameter protrusion 76 and the end face 73a of the small-diameter shaft portion 73 face each other in the axial direction of the rotating shaft 41.

[0070] <Filling plate 77>

[0071] The centrifugal compressor 10 is provided with a shim plate 77. The shim plate 77 is annular. The shim plate 77 is interposed between the end face 73a of the small diameter shaft portion 73 and the end face 76a of the small diameter protrusion portion 76. Therefore, the shim plate 77 is interposed between the rotating shaft 41 and the second impeller 43 in the axial direction of the rotating shaft 41. The distance from the axis of the rotating shaft 41 to the outer peripheral edge of the shim plate 77 is the same as the outer diameter of the large diameter protrusion portion 75 and the outer diameter of the large diameter shaft portion 72. Therefore, the shim plate 77 protrudes radially outward of the rotating shaft 41 more than the small diameter shaft portion 73 and the small diameter protrusion portion 76.

[0072] The shim plate 77 is made of a metal material. The shim plate 77 is made of, for example, stainless steel. The linear expansion coefficient of the shim plate 77 is smaller than the linear expansion coefficient of the second plate 16. Therefore, the linear expansion coefficient of the shim plate 77 is smaller than the linear expansion coefficient of the partition wall.

[0073] The shim plate 77 adjusts the position of the second impeller 43 in the axial direction of the rotating shaft 41 by being interposed between the rotating shaft 41 and the second impeller 43 in the axial direction of the rotating shaft 41. Thus, the interval between the second impeller 43 and the second compressor housing 14 is adjusted, thereby improving the air compression efficiency.

[0074] <First Protrusion 78 and Second Protrusion 79>

[0075] The second plate 16 has a first protrusion 78 as a protrusion. Therefore, the partition wall has a protrusion. The first protrusion 78 is annular and protrudes from the inner circumference of the first small-diameter hole 63 toward the outer circumference of the small-diameter protrusion 76. Therefore, the protrusion is the first protrusion 78 that protrudes from the inner circumference of the first hole 61 toward the outer circumference of the small-diameter protrusion 76. Thus, the first protrusion 78 protrudes from the inner circumference of the second insertion hole 26 toward the outer circumference of the small-diameter protrusion 76. The inner diameter of the first protrusion 78 is smaller than the outer diameter of the large-diameter protrusion 75.

[0076] The end wall 12a of the motor housing 12 has a second protrusion 79. Therefore, the second wall structure has the second protrusion 79. The second protrusion 79 is annular and protrudes from the inner circumference of the second small-diameter hole 66 toward the outer circumference of the small-diameter shaft portion 73. Therefore, the second protrusion 79 protrudes from the inner circumference of the second hole 64 toward the outer circumference of the small-diameter shaft portion 73. The inner diameter of the second protrusion 79 is smaller than the outer diameter of the large-diameter shaft portion 72. The inner diameter of the second protrusion 79 is the same as the inner diameter of the first protrusion 78.

[0077] <First Gap 81, Second Gap 82, Third Gap 83, Fourth Gap 84, and Fifth Gap 85>

[0078] A first gap 81, a second gap 82, a third gap 83, a fourth gap 84, and a fifth gap 85 are provided inside the second insertion hole 26. The first gap 81 is formed between the inner peripheral surface of the first small diameter hole 63 and the outer peripheral surface of the large diameter protrusion 75. Therefore, the first gap 81 is formed between the inner peripheral surface of the second insertion hole 26 and the outer peripheral surface of the large diameter protrusion 75.

[0079] The second gap 82 is formed between the first protrusion 78 and the outer peripheral surface of the small-diameter boss 76. The third gap 83 is formed between the caulking plate 77 and the inner peripheral surface of the first small-diameter hole 63. Therefore, the third gap 83 is formed between the caulking plate 77 and the inner peripheral surface of the second insertion hole 26.

[0080] The fourth gap 84 is formed between the inner peripheral surface of the second small diameter hole 66 and the outer peripheral surface of the large diameter shaft portion 72. Therefore, the fourth gap 84 is formed between the inner peripheral surface of the second insertion hole 26 and the outer peripheral surface of the large diameter shaft portion 72. The fifth gap 85 is formed between the second protrusion 79 and the outer peripheral surface of the small diameter shaft portion 73. The first gap 81, the second gap 82, the third gap 83, the fourth gap 84 and the fifth gap 85 have the same flow path cross-sectional area.

[0081] A first path 86, a second path 87, a third path 88, and a fourth path 89 are provided inside the second insertion hole 26. The first path 86 connects the first gap 81 and the second gap 82. The second path 87 connects the second gap 82 and the third gap 83. The third path 88 connects the third gap 83 and the fifth gap 85. The fourth path 89 connects the fifth gap 85 and the fourth gap 84. In addition, inside the second insertion hole 26, a labyrinth seal is formed by the first gap 81, the first path 86, the second gap 82, the second path 87, the third gap 83, the third path 88, the fifth gap 85, the fourth path 89, and the fourth gap 84.

[0082] Therefore, inside the second insertion hole 26, a first gap 81, a second gap 82, a third gap 83, and a fourth gap 84 are sequentially provided from the second impeller chamber 33 toward the motor chamber 18. Furthermore, the first gap 81, the second gap 82, the third gap 83, and the fourth gap 84 constitute a labyrinth seal that seals between the second insertion hole 26 and the rotating body 40. In the present embodiment, the fifth gap 85 is located between the third gap 83 and the fourth gap 84. Furthermore, the first gap 81, the second gap 82, the third gap 83, the fourth gap 84, and the fifth gap 85 constitute a labyrinth seal that seals between the second insertion hole 26 and the rotating body 40.

[0083] [Effects of implementation methods]

[0084] Next, the operation of this embodiment will be described.

[0085] The thrust bearing 54 is cooled by the air introduced from the introduction passage 56 into the thrust bearing accommodation chamber 24. The air in the thrust bearing accommodation chamber 24 passes through the inner side of the first bearing holding portion 21. The first radial bearing 52 is cooled by the air passing through the inner side of the first bearing holding portion 21. The air passing through the inner side of the first bearing holding portion 21 is introduced into the motor chamber 18. The motor 20 is cooled by the air introduced into the motor chamber 18. Therefore, in the centrifugal compressor 10, the motor 20 is cooled by introducing a part of the air compressed by the second impeller 43 into the motor chamber 18 at a lower temperature than the air discharged into the second discharge chamber 34. The air introduced into the motor chamber 18 passes through the inner side of the second bearing holding portion 25. The second radial bearing 53 is cooled by the air passing through the inner side of the second bearing holding portion 25. The air passing through the inner side of the second bearing holding portion 25 is discharged to the outside of the housing 11 via the discharge passage 59.

[0086] A part of the air compressed by the second impeller 43 and discharged to the second discharge chamber 34 sometimes flows into the gap 90 between the back surface 43a of the second impeller 43 and the second plate 16. And the air flowing into the gap 90 flows into the second insertion hole 26 from the gap 90. In the case where the air flows into the second insertion hole 26 from the gap 90 between the back surface 43a of the second impeller 43 and the second plate 16, for example, the air is throttled by passing through the first gap 81. And the air passing through the first gap 81 expands before reaching the second gap 82 via the first path 86 and is throttled again by passing through the second gap 82. And the air passing through the second gap 82 expands again before reaching the third gap 83 via the second path 87 and is throttled again by passing through the third gap 83. Furthermore, the air passing through the third gap 83 expands again before reaching the fifth gap 85 via the third path 88 and is throttled again by passing through the fifth gap 85. Furthermore, the air passing through the fifth gap 85 expands again before reaching the fourth gap 84 via the fourth path 89 and is throttled again by passing through the fourth gap 84. In this way, the air passes through the throttled portion and the expanded portion in sequence from the first gap 81 to the fourth gap 84 via the second gap 82, the third gap 83 and the fifth gap 85. Therefore, the air is successively decompressed as it flows from the first gap 81 toward the fourth gap 84. As a result, the pressure of the air flowing into the second insertion hole 26 from the gap 90 between the back surface 43a of the second impeller 43 and the second plate 16 is efficiently decompressed. As a result, it is suppressed that a part of the air compressed by the second impeller 43 and discharged to the second discharge chamber 34 enters the motor chamber 18 via the second insertion hole 26.

[0087] [Effects of Embodiment]

[0088] In the above-described embodiment, the following effects can be obtained.

[0089] (1) The first gap 81, the second gap 82, the third gap 83, and the fourth gap 84 are provided inside the second insertion hole 26. The first gap 81, the second gap 82, the third gap 83, and the fourth gap 84 constitute a labyrinth seal that seals the second insertion hole 26 and the rotating body 40. Thus, for example, when air flows into the second insertion hole 26 from the gap 90 between the back surface 43a of the second impeller 43 and the second plate 16, the air is throttled by passing through the first gap 81. Furthermore, the air that has passed through the first gap 81 expands before reaching the second gap 82 and is throttled again by passing through the second gap 82. Furthermore, the air that has passed through the second gap 82 expands again before reaching the third gap 83 and is throttled again by passing through the third gap 83. Furthermore, the air that has passed through the third gap 83 expands again before reaching the fourth gap 84 and is throttled again by passing through the fourth gap 84. In this way, the air passes through the throttled portion and the expanded portion of the air in sequence from the first gap 81 through the second gap 82 and the third gap 83 to the fourth gap 84. Therefore, the air is successively decompressed as it flows from the first gap 81 toward the fourth gap 84. Thus, the pressure of the air flowing into the second insertion hole 26 from the gap 90 between the back surface 43a of the second impeller 43 and the second plate 16 can be efficiently decompressed. As a result, a part of the air compressed by the second impeller 43 and discharged to the second discharge chamber 34 is suppressed from leaking into the motor chamber 18 through the second insertion hole 26. As a result, in the centrifugal compressor 10, useless compression of air is suppressed, and thus a decrease in the operating efficiency of the centrifugal compressor 10 is suppressed.

[0090] For example, if the third gap 83 and the fourth gap 84 are to be provided inside the second insertion hole 26 without using the shim plate 77, it is necessary to form an annular recess on the outer peripheral surface of the shaft portion 71. Therefore, processing for forming the recess on the outer peripheral surface of the shaft portion 71 is required, and thus additional processing is required on the rotating shaft 41. Therefore, the third gap 83 is formed by making the shim plate 77 protrude radially outward of the rotating shaft 41 more than the small-diameter shaft portion 73 and the small-diameter protrusion 76. Thus, the third gap 83 and the fourth gap 84 can be provided inside the second insertion hole 26 only by using the shim plate 77 as an existing structure. Through the above, the reduction in the operating efficiency of the centrifugal compressor 10 can be suppressed without additional processing on the rotating shaft 41.

[0091] (2) The second protrusion 79 is formed on the end wall 12a of the motor housing 12 which is a member of the second plate 16 on which the first protrusion 78 is formed. Therefore, when the centrifugal compressor 10 is assembled, the gap filler plate 77 between the end face 73a of the small-diameter shaft portion 73 and the end face 76a of the small-diameter boss portion 76 can be arranged between the first protrusion 78 and the second protrusion 79 in the axial direction of the rotating shaft 41. In addition, the fifth gap 85 is provided inside the second insertion hole 26. Therefore, the air is throttled by passing through the fifth gap 85. As a result, the air flowing from the first gap 81 toward the fourth gap 84 is further easily decompressed. Therefore, the pressure of the air flowing into the second insertion hole 26 from the gap 90 between the back surface 43a of the second impeller 43 and the second plate 16 can be further efficiently decompressed.

[0092] (3) The linear expansion coefficient of the shim plate 77 is smaller than the linear expansion coefficient of the second plate 16. For example, consider a case where the linear expansion coefficient of the shim plate 77 is greater than or equal to the linear expansion coefficient of the second plate 16. Compared with this case, even if heat is transferred from the second impeller 43 to the shim plate 77 and the shim plate 77 undergoes thermal expansion, it is easier to avoid contact between the shim plate 77 and the second plate 16.

[0093] (4) It is suppressed that a part of the air compressed by the second impeller 43 and discharged to the second discharge chamber 34 leaks into the motor chamber 18 through the second insertion hole 26. Therefore, it is difficult to cause a problem that a part of the air compressed by the second impeller 43 and discharged to the second discharge chamber 34 enters the motor chamber 18 through the second insertion hole 26, so that the motor 20 is heated by the air entering the motor chamber 18. Thus, by introducing a part of the air compressed by the second impeller 43 into the motor chamber 18 in a state of lower temperature than the temperature of the air discharged to the second discharge chamber 34, the motor 20 can be efficiently cooled. As a result, the durability of the centrifugal compressor 10 can be improved.

[0094] [Example of Change]

[0095] In addition, the above-mentioned embodiment can be implemented by modification as follows. The above-mentioned embodiment and the following modification examples can be implemented by combining with each other within the range that there is no technical contradiction.

[0096] ○ In the embodiment, the partition wall separating the second impeller chamber 33 and the motor chamber 18 may be composed of, for example, only the second plate 16. In this case, the motor housing 12 is, for example, cylindrical. And, the opening of the motor housing 12 is blocked by the second plate 16. In this way, when the partition wall separating the second impeller chamber 33 and the motor chamber 18 is composed of only the second plate 16, the centrifugal compressor 10 becomes a structure in which the second protrusion 79 is deleted. In this way, the centrifugal compressor 10 may also be a structure without the second protrusion 79 and without providing the fifth gap 85 on the inner side of the second insertion hole 26.

[0097] In the embodiment, for example, the linear expansion coefficient of the filling plate 77 may be equal to or greater than the linear expansion coefficient of the second plate 16 .

[0098] In the embodiment, the flow path cross-sectional areas of the first gap 81 , the second gap 82 , the third gap 83 , the fourth gap 84 , and the fifth gap 85 may be different from each other.

[0099] In the embodiment, the shim plate 77 may be made of iron, for example. The shim plate 77 is preferably made of a material whose linear expansion coefficient is smaller than that of the second plate 16 .

[0100] In the embodiment, the introduction passage 56 may also introduce a portion of the air compressed by the first impeller 42 into the motor chamber 18. The temperature of the air compressed by the first impeller 42 is lower than the temperature of the air compressed by the second impeller 43 and discharged to the second discharge chamber 34. In short, the introduction passage 56 only needs to introduce the air into the motor chamber 18 in a state where the temperature is lower than the temperature of the air discharged to the second discharge chamber 34.

[0101] In the embodiment, the centrifugal compressor 10 may be configured without the second impeller 43 . In this case, the first gap 81 , the second gap 82 , the third gap 83 , the fourth gap 84 , and the fifth gap 85 are provided inside the first insertion hole 23 .

[0102] In the embodiment, the centrifugal compressor 10 may be configured to include a turbine instead of the second impeller 43 .

[0103] In the embodiment, the centrifugal compressor 10 may not be mounted on the fuel cell vehicle. In short, the centrifugal compressor 10 is not limited to being mounted on a vehicle.

[0104] In the embodiment, the centrifugal compressor 10 is not limited to being used for compressing air supplied to the fuel cell stack 38. In short, the centrifugal compressor 10 only needs to compress air.

[0105] Description of Reference Numerals

[0106] 10 Centrifugal compressor

[0107] 11 Shell

[0108] 12a: End wall (partition wall) of the second wall structure

[0109] 15 1st plate (partition wall)

[0110] 16: Second plate (partition wall) as first wall component

[0111] 17 The third plate (partition wall)

[0112] 18 Motor room

[0113] 20 motors

[0114] 23 1st insertion hole (insertion hole)

[0115] 26 2nd insertion hole (insertion hole)

[0116] 281st impeller chamber (impeller chamber)

[0117] 33 2nd impeller chamber (impeller chamber)

[0118] 34 Second discharge chamber as discharge chamber

[0119] 40 Rotating body

[0120] 41 Rotation axis

[0121] 421st impeller (impeller)

[0122] 43 2nd impeller (impeller)

[0123] 43a Back

[0124] 61 Hole 1

[0125] 64 Hole 2

[0126] 71 shaft

[0127] 72 Large diameter shaft

[0128] 73 Small diameter shaft

[0129] 73a end face

[0130] 74 raised part

[0131] 75 large diameter boss

[0132] 76 small diameter raised part

[0133] 76a end face

[0134] 77 Filler Plate

[0135] 78 first protrusion (protrusion)

[0136] 79 Second protrusion

[0137] 81 1st gap

[0138] 82 2nd Gap

[0139] 83 3rd Gap

[0140] 84 4th Gap

[0141] 85 5th Gap

Claims

1. A centrifugal compressor comprising: A rotating body including a rotating shaft and an impeller that compresses air by rotating integrally with the rotating shaft; a motor to rotate the rotating shaft; a casing having an impeller chamber for accommodating the impeller, a motor chamber for accommodating the motor, a partition wall that separates the impeller chamber from the motor chamber and is formed with an insertion hole for the rotating body to pass through, and a discharge chamber for discharging air compressed by the impeller; and an annular shim plate is interposed between the rotating shaft and the impeller in the axial direction of the rotating shaft, The centrifugal compressor is characterized in that The rotating shaft has a shaft portion arranged inside the insertion hole, The shaft portion includes a large diameter shaft portion and a small diameter shaft portion, the diameter of the small diameter shaft portion is smaller than the diameter of the large diameter shaft portion and the small diameter shaft portion extends from the large diameter shaft portion toward the impeller chamber, The impeller has a protrusion protruding from the back side of the impeller and arranged inside the insertion hole. The protrusion has a large-diameter protrusion and a small-diameter protrusion, the diameter of the small-diameter protrusion is smaller than the diameter of the large-diameter protrusion and the small-diameter protrusion extends from the large-diameter protrusion toward the motor chamber. The shim plate is interposed between the end surface of the small-diameter shaft portion and the end surface of the small-diameter protrusion portion and protrudes radially outward from the small-diameter shaft portion and the small-diameter protrusion portion. The partition wall has an annular protrusion protruding from the inner peripheral surface of the insertion hole toward the outer peripheral surface of the small-diameter protrusion. A first gap, a second gap, a third gap, and a fourth gap are provided in order from the impeller chamber toward the motor chamber inside the insertion hole. The first gap is formed between the inner peripheral surface of the insertion hole and the outer peripheral surface of the large-diameter protrusion. The second gap is formed between the protrusion and the outer peripheral surface of the small-diameter protrusion. The third gap is formed between the caulking plate and the inner peripheral surface of the insertion hole. The fourth gap is formed between the inner peripheral surface of the insertion hole and the outer peripheral surface of the large-diameter shaft portion. The first gap, the second gap, the third gap, and the fourth gap constitute a labyrinth seal that seals between the insertion hole and the rotating body.

2. The centrifugal compressor according to claim 1, characterized in that: The partition wall has: a first wall structure that partitions the impeller chamber and has a first hole that forms a part of the insertion hole; and a second wall structure that partitions the motor chamber and has a second hole that forms a part of the insertion hole; The protrusion is a first protrusion that protrudes from the inner peripheral surface of the first hole toward the outer peripheral surface of the small-diameter protrusion. The second wall structure has an annular second protrusion that protrudes from the inner peripheral surface of the second hole toward the outer peripheral surface of the small-diameter shaft portion. A fifth gap is provided inside the insertion hole, and the fifth gap is formed between the second protrusion and the outer peripheral surface of the small-diameter shaft portion. The fifth gap is located between the third gap and the fourth gap, and the first gap, the second gap, the third gap, the fourth gap, and the fifth gap constitute a labyrinth seal that seals between the insertion hole and the rotating body.

3. The centrifugal compressor according to claim 1 or 2, characterized in that: The linear expansion coefficient of the filling plate is smaller than the linear expansion coefficient of the partition wall.

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