Centrifugal compressor

Abstract

To suppress lowering of the operation efficiency of a centrifugal compressor without applying additional processing to a rotating shaft.SOLUTION: A first clearance 81, a second clearance 82, a third clearance 83 and a fourth clearance 84 are formed inside a second penetration hole 26. Air is gradually decompressed as it flows from the first clearance 81 toward the fourth clearance 84. Thus, the pressure of air which has flown into the second penetration hole 26 from a gap 90 between a back face 43a of a second impeller 43 and a second plate 16 is efficiently decompressed. As a result, a part of air which is decompressed by the second impeller 43 and discharged into a second discharge chamber is kept from intruding into a motor chamber via the second penetration hole 26. Since the third clearance 83 and the fourth clearance 84 can be formed inside the second penetration hole 26 only by using a shim plate 77, it is not necessary to apply additional processing to a rotating shaft 41 in order to form the third clearance 83 and the fourth clearance 84 inside the second penetration hole 26.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] For example, as disclosed in Patent Document 1, a centrifugal compressor includes a rotating 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 housing. The motor rotates the rotating shaft. The housing has an impeller chamber, a motor chamber, a partition wall, and a discharge chamber. The impeller chamber houses the impeller. The motor chamber houses the motor. The partition wall separates the impeller chamber and the motor chamber. The compressed air by the impeller is discharged into the discharge chamber. An insertion hole through which the rotating body is inserted is formed in the partition wall.

[0003] Also, the centrifugal compressor may include an annular shim plate. The shim plate is interposed, for example, between the rotating shaft and the impeller in the axial direction of the rotating shaft. By interposing the shim plate between the rotating shaft and the impeller in the axial direction of the rotating shaft, the position of the impeller in the axial direction of the rotating shaft is adjusted. Thereby, the clearance between the impeller and the housing is adjusted, so that the compression efficiency of air is improved.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In such centrifugal compressors, some of the air compressed by the impeller and discharged into the discharge chamber may flow into the gap between the back of the impeller and the partition wall. This can lead to the air that has flowed into the gap between the back of the impeller and the partition wall leaking into the motor chamber through the through-hole. As a result, the centrifugal compressor experiences increased wasted air compression, which reduces its operating efficiency. Therefore, it is desirable to suppress the decrease in the operating efficiency of the centrifugal compressor without performing any additional processing on the rotating shaft. [Means for solving the problem]

[0006] A centrifugal compressor that solves the above problems includes a rotating body including a rotating shaft and an impeller that compresses air by rotating integrally with the rotating shaft, a motor that rotates the rotating shaft, a housing having an impeller chamber for housing the impeller, a motor chamber for housing the motor, a partition wall separating the impeller chamber and the motor chamber and having an insertion hole through which the rotating body is inserted, and a discharge chamber through which the air compressed by the impeller is discharged, and the axial direction of the rotating shaft A centrifugal compressor comprising an annular shim plate interposed between a rotating shaft and an impeller, wherein the rotating shaft has a shaft portion disposed inside the insertion hole, the shaft portion having a large diameter shaft portion and a small diameter shaft portion having a smaller diameter than the large diameter shaft portion and extending from the large diameter shaft portion toward the impeller chamber, and the impeller has a boss portion protruding from the back surface of the impeller and disposed inside the insertion hole, the boss portion having a large diameter boss portion and a smaller diameter shim plate interposed between the large diameter boss portion and The shim plate has a diameter and a small diameter boss portion extending from the large diameter boss portion toward the motor chamber, and the shim plate is interposed between the end face of the small diameter shaft portion and the end face of the small diameter boss portion and protrudes radially outward from the small diameter shaft portion and the small diameter boss portion, the partition wall has an annular projection that protrudes from the inner circumferential surface of the insertion hole toward the outer circumferential surface of the small diameter boss portion, and inside the insertion hole, between the inner circumferential surface of the insertion hole and the outer circumferential surface of the large diameter boss portion A first gap, a second gap formed between the projection and the outer circumferential surface of the small-diameter boss, a third gap formed between the shim plate and the inner circumferential surface of the insertion hole, and a fourth gap formed between the inner circumferential surface of the insertion hole and the outer circumferential surface of the large-diameter shaft are provided in this order from the impeller chamber toward the motor chamber, and the first gap, the second gap, the third gap, and the fourth gap constitute a labyrinth seal that seals the space between the insertion hole and the rotating body.

[0007] According to this, the first gap, second gap, third gap, and fourth gap constitute a labyrinth seal that seals the space between 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 constricted as it passes through the first gap. The air that has passed through the first gap expands as it reaches the second gap and is constricted again as it passes through the second gap. Furthermore, the air that has passed through the second gap expands again as it reaches the third gap and is constricted again as it passes through the third gap. The air that has passed through the third gap expands again as it reaches the fourth gap and is constricted again as it passes 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 sequentially pass through sections where the air is constricted and sections where it expands, from the first gap through the second and third gaps to the fourth gap. Therefore, the pressure is successively reduced as the air flows from the first gap to the fourth gap. Therefore, the pressure of the air flowing into the through-hole from the gap between the back of the impeller and the partition wall can be efficiently reduced. As a result, leakage of some of the air compressed by the impeller and discharged into the discharge chamber into the motor chamber through the through-hole is suppressed. Consequently, in the centrifugal compressor, unnecessary compression of air is suppressed, and the decrease in the operating efficiency of the centrifugal compressor is suppressed.

[0008] For example, if a third and fourth gap were to be created inside the through-hole without using a shim plate, it would be necessary to form an annular recess on the outer surface of the shaft. Therefore, machining is required to form the recess on the outer surface of the shaft, which necessitates additional machining of the rotating shaft. To address this, the third gap was created by making the shim plate protrude radially outward from the small-diameter shaft portion and the small-diameter boss portion of the rotating shaft. This allows for the creation of a third and fourth gap inside the through-hole simply by utilizing the existing shim plate configuration. As a result, a decrease in the operating efficiency of the centrifugal compressor can be suppressed without requiring additional machining of the rotating shaft.

[0009] In the centrifugal compressor described above, the partition wall comprises a first wall structure having a first hole that partitions the impeller chamber and forms part of the insertion hole, and a second wall structure having a second hole that partitions the motor chamber and forms part of the insertion hole, the projection is a first projection that protrudes from the inner circumferential surface of the first hole toward the outer circumferential surface of the small-diameter boss, the second wall structure has an annular second projection that protrudes from the inner circumferential surface of the second hole toward the outer circumferential surface of the small-diameter shaft, a fifth gap is provided inside the insertion hole, formed between the second projection and the outer circumferential surface of the small-diameter shaft, the fifth gap is located between the third gap and the fourth gap, and the first gap, second gap, third gap, fourth gap, and fifth gap may constitute a labyrinth seal that seals the space between the insertion hole and the rotating body.

[0010] According to this, the second projection is formed on the second wall structure, which is a separate component from the first wall structure on which the first projection is formed. Therefore, when assembling the centrifugal compressor, the shim plate interposed between the end face of the small-diameter shaft and the end face of the small-diameter boss can be positioned between the first projection and the second projection in the axial direction of the rotating shaft. Furthermore, a fifth gap is provided inside the through hole. Therefore, the air is constricted as it passes through the fifth gap. Consequently, the air flowing from the first gap towards the fourth gap is further depressurized. Therefore, the pressure of the air flowing into the through hole from the gap between the back of the impeller and the partition wall can be reduced even more efficiently.

[0011] In the centrifugal compressor described above, the coefficient of thermal expansion of the shim plate is preferably smaller than the coefficient of thermal expansion of the partition wall. According to this, for example, compared to the case where the linear expansion coefficient of the shim plate is greater than or equal to that of the partition wall, even if heat is transferred from the impeller to the shim plate and the shim plate expands due to thermal stress, it becomes easier to avoid the shim plate coming into contact with the partition wall. [Effects of the Invention]

[0012] According to this invention, it is possible to suppress a decrease in the operating efficiency of a centrifugal compressor without performing any additional processing on the rotating shaft. [Brief explanation of the drawing]

[0013] [Figure 1] This is a cross-sectional view of a centrifugal compressor in an embodiment. [Figure 2] This is a cross-sectional view showing a magnified portion of a centrifugal compressor. [Figure 3] This is a cross-sectional view showing a magnified portion of a centrifugal compressor. [Modes for carrying out the invention]

[0014] Below, one embodiment of the centrifugal compressor will be described with reference to Figures 1 to 3. The centrifugal compressor in the embodiment described below is installed in a fuel cell vehicle. The centrifugal compressor compresses the air supplied to the fuel cell stack.

[0015] <Basic configuration of centrifugal compressor 10> As shown in Figure 1, the centrifugal compressor 10 includes a housing 11. The housing 11 is made of a metal material. For example, the housing 11 is made of aluminum. The housing 11 includes a motor housing 12, a first compressor housing 13, a second compressor housing 14, a first plate 15, a second plate 16, and a third plate 17.

[0016] The motor housing 12 has an end wall 12a and a peripheral wall 12b. The end wall 12a is plate-shaped. The peripheral wall 12b extends cylindrically from the outer circumference of the end wall 12a. The first plate 15 is connected to the open end of the peripheral wall 12b of the motor housing 12. The first plate 15 closes the opening of the peripheral wall 12b of the motor housing 12. The motor room 18 is partitioned by the motor housing 12 and the first plate 15. Therefore, the housing 11 has a motor room 18.

[0017] The second plate 16 is connected to the outer surface of the end wall 12a of the motor housing 12. The second plate 16 is attached to the end wall 12a of the motor housing 12 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 housing 12.

[0018] 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.

[0019] The centrifugal compressor 10 includes a first bearing holder 21. The first bearing holder 21 projects into the motor chamber 18 from the central portion of the first plate 15. Therefore, the first plate 15 has the first bearing holder 21. The first bearing holder 21 is cylindrical.

[0020] The first plate 15 has a chamber forming recess 22. The chamber forming recess 22 is formed on the end face of the first plate 15 opposite to the motor housing 12. The chamber forming recess 22 is in the shape of a circular hole. The inside of the first bearing holder 21 penetrates the first plate 15 and opens to the bottom face of the chamber forming recess 22. The axis of the chamber forming recess 22 coincides with the axis of the first bearing holder 21.

[0021] The third plate 17 is connected to the end face of the first plate 15 opposite to the motor housing 12. The third plate 17 is attached to the first plate 15 in a state where the thickness direction of the third plate 17 coincides with the thickness direction of the first plate 15. The third plate 17 has a first insertion hole 23. The first insertion hole 23 is formed 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 holder 21. And the chamber forming recess 22 and the third plate 17 define a thrust bearing housing chamber 24. The thrust bearing housing chamber 24 communicates with the inside of the first bearing holder 21. Also, the thrust bearing housing chamber 24 communicates with the first insertion hole 23.

[0022] The centrifugal compressor 10 includes a second bearing holder 25. The second bearing holder 25 protrudes into the motor chamber 18 from the central portion of the end wall 12a of the motor housing 12. Therefore, the motor housing 12 has the second bearing holder 25. The second bearing holder 25 is cylindrical.

[0023] The housing 11 has a second insertion hole 26. The second insertion hole 26 penetrates the central portion of the end wall 12a of the motor housing 12 and the central portion of the second plate 16. The second insertion hole 26 communicates with the inside of the second bearing holder 25. The axis of the second insertion hole 26 coincides with the axis of the second bearing holder 25.

[0024] The first compressor housing 13 is cylindrical and has a circular hole-shaped first suction port 27 through which air is inhaled. The first compressor housing 13 is connected to the end face on the side opposite to the first plate 15 of the third plate 17 in a state where the axis of the first suction port 27 coincides with the axis of the first insertion hole 23. The first suction port 27 opens on the end face of the first compressor housing 13 on the side opposite to the third plate 17. Cleaned air flows through the first suction port 27 by an air cleaner (not shown).

[0025] 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 partitions the first impeller chamber 28 and the motor chamber 18. The first impeller chamber 28 communicates with 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 communicates the first impeller chamber 28 and the first discharge chamber 29. The first impeller chamber 28 communicates with the first insertion hole 23.

[0026] The centrifugal compressor 10 has a first discharge passage 31. The first end of the first discharge passage 31 communicates with the first discharge chamber 29. The second end of the first discharge passage 31 opens to the outer surface of the first compressor housing 13.

[0027] The second compressor housing 14 is cylindrical and has a circular second intake port 32 into which air is drawn. The second compressor housing 14 is connected to the end face of the second plate 16 opposite to the motor housing 12, with the axis of the second intake port 32 coinciding with the axis of the second insertion hole 26. The second intake port 32 opens to the end face of the second compressor housing 14 opposite to the second plate 16.

[0028] The centrifugal compressor 10 includes a second impeller chamber 33, a second discharge chamber 34, and a second diffuser passage 35. The second impeller chamber 33, the second discharge chamber 34, and the second diffuser passage 35 are formed between the second compressor housing 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 separating the second impeller chamber 33 from the motor chamber 18. The second impeller chamber 33 communicates with the second inlet 32. The second discharge chamber 34 extends around the axis of the second inlet 32, surrounding the second impeller chamber 33. The second diffuser passage 35 communicates the second impeller chamber 33 and the second discharge chamber 34. The second impeller chamber 33 communicates with the second insertion hole 26.

[0029] The centrifugal compressor 10 has a second discharge passage 36. The first end of the second discharge passage 36 communicates with the second discharge chamber 34. The second end of the second discharge passage 36 opens to the outer 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 the fuel cell stack 38. The first end of the supply pipe 37 is connected to the second discharge passage 36. The second end of the supply pipe 37 is connected to the fuel cell stack 38. The second discharge chamber 34 is connected to the fuel cell stack 38 via the second discharge passage 36 and the supply pipe 37.

[0030] The centrifugal compressor 10 is equipped with a connecting pipe 39. The first end of the connecting pipe 39 is in communication with the first discharge passage 31. The second end of the connecting pipe 39 is in communication with the second intake port 32. Air discharged from the first discharge chamber 29 to the first discharge passage 31 flows through the connecting pipe 39. The air that has passed through the connecting pipe 39 is then drawn into the second impeller chamber 33 via the second intake port 32.

[0031] 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 44. The rotating shaft 41 is housed within the housing 11.

[0032] The rotating shaft 41 extends along the axis of the motor housing 12 and crosses the motor chamber 18. The axial direction of the rotating shaft 41 coincides with the axial direction of the motor housing 12. The first end of the rotating shaft 41 protrudes from the motor chamber 18 into the first impeller chamber 28, passing through the inside of the first bearing holder 21, the thrust bearing housing chamber 24, and the first through hole 23. Therefore, the first through 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 separates the first impeller chamber 28 and the motor chamber 18 and has the first through hole 23 through which the rotating body 40 is inserted.

[0033] The second end of the rotating shaft 41 protrudes into the second impeller chamber 33, passing from the motor chamber 18 through the inside of the second bearing holder 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 separates the second impeller chamber 33 and the motor chamber 18, and through which the second insertion hole 26 through which the rotating body 40 is inserted is formed.

[0034] The first impeller 42 is connected to the first end of the rotating shaft 41. The first impeller 42 is housed in the first impeller chamber 28. Therefore, the first impeller chamber 28 houses the first impeller 42. The first impeller 42 compresses the air drawn into the first impeller chamber 28 by rotating integrally with the rotating shaft 41. Therefore, the first impeller 42 is an impeller that compresses air. Thus, the first impeller chamber 28 is an impeller chamber that houses an impeller.

[0035] The second impeller 43 is connected to the second end of the rotating shaft 41. The second impeller 43 is housed in the second impeller chamber 33. Therefore, the second impeller chamber 33 houses the second impeller 43. The second impeller 43 compresses the air drawn into the second impeller chamber 33 by rotating integrally with the rotating shaft 41. Therefore, the second impeller 43 is an impeller that compresses air. Thus, the second impeller chamber 33 is an impeller chamber that houses the impeller. Therefore, the housing 11 has an impeller chamber that houses the impeller. The second impeller 43 compresses the air after it has been compressed by the first impeller 42.

[0036] The support portion 44 protrudes annularly from the outer circumferential surface of the rotating shaft 41. The support portion 44 is disc-shaped. The support portion 44 is fixed to the outer circumferential surface of the rotating shaft 41, protruding annularly radially outward from the outer circumferential surface of the rotating shaft 41. Therefore, the support portion 44 is separate from the rotating shaft 41. The support portion 44 is located within the thrust bearing housing chamber 24. The support portion 44 rotates integrally with the rotating shaft 41.

[0037] The centrifugal compressor 10 is equipped with 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 air leakage from the first impeller chamber 28 toward the motor chamber 18. The sealing member 45 is, for example, a sealing ring.

[0038] The motor 20 comprises 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 positioned radially inward of the stator 48. The rotor 47 rotates integrally with the rotating shaft 41. The rotor 47 has a cylindrical rotor core 49 fixed to the rotating shaft 41 and a plurality of permanent magnets (not shown) provided on the rotor core 49. The stator 48 surrounds the rotor 47. The stator 48 has 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.

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

[0040] The centrifugal compressor 10 is equipped with a first radial bearing 52. The first radial bearing 52 is cylindrical. The first radial bearing 52 is held in a first bearing holder 21. The first radial bearing 52 rotatably supports the portion of the rotating shaft 41 that is located closer to the first end of the rotating shaft 41 than the motor 20.

[0041] The centrifugal compressor 10 is equipped with a second radial bearing 53. The second radial bearing 53 is cylindrical. The second radial bearing 53 is held in a second bearing holder 25. The second radial bearing 53 rotatably supports the portion of the rotating shaft 41 that is located closer to the second end of the rotating shaft 41 than the motor 20.

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

[0043] The centrifugal compressor 10 is equipped with a thrust bearing 54. The thrust bearing 54 is housed in a thrust bearing housing chamber 24. Therefore, the thrust bearing housing chamber 24 houses the thrust bearing 54. The thrust bearing 54 supports the support portion 44 so that it can rotate in the thrust direction. Therefore, the thrust bearing 54 supports the rotating shaft 41 so that it can rotate via the support portion 44. The "thrust direction" is the direction parallel to the axial direction of the rotating shaft 41.

[0044] Air drawn into the first impeller chamber 28 via the first intake port 27 is accelerated by the rotation of the first impeller 42 and sent to the first diffuser flow path 30, where it is pressurized as it passes through the first diffuser flow path 30. The air that has passed through the first diffuser flow path 30 is then discharged into the first discharge chamber 29. The air discharged into the first discharge chamber 29 is then discharged into the first discharge passage 31. The air discharged into the first discharge passage 31 is drawn into the second impeller chamber 33 via the connecting pipe 39 and the second intake port 32. The air drawn into the second impeller chamber 33 is accelerated by the rotation of the second impeller 43 and sent to the second diffuser flow path 35, where it is pressurized as it passes through the second diffuser flow path 35. The air that has passed through the second diffuser flow path 35 is then discharged into the second discharge chamber 34. The air discharged into the second discharge chamber 34 is then discharged into the second discharge passage 36. The air discharged into the second discharge passage 36 is supplied to the fuel cell stack 38 via the supply pipe 37. Thus, 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.

[0045] The rotating body 40 includes a rotating shaft 41 and a first impeller 42 and a second impeller 43 that rotate integrally with the rotating shaft 41 to compress the air supplied to the fuel cell stack 38. Therefore, the rotating body 40 includes impellers. The second discharge passage 36 and the supply piping 37 constitute a supply passage 55 that supplies air to the fuel cell stack 38. The second discharge chamber 34 is a discharge chamber to which the air compressed by the second impeller 43 is discharged and to which the supply passage 55 is connected. Therefore, the housing 11 has a discharge chamber to which the supply passage 55 is connected.

[0046] The centrifugal compressor 10 is equipped with an introduction passage 56. The introduction passage 56 is formed in the first plate 15. The first end of the introduction passage 56 opens onto the outer circumferential surface of the first plate 15. The second end of the introduction passage 56 communicates with the thrust bearing housing chamber 24.

[0047] A branch pipe 57 is connected to the first end of the introduction passage 56. The branch pipe 57 branches off 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 through the branch pipe 57.

[0048] A portion of the air flowing through the supply pipe 37 flows into the branch pipe 57. The air flowing through the branch pipe 57 is cooled by the intercooler 58. As a result, the air that has passed through the intercooler 58 is at a lower temperature than the air discharged into the second discharge chamber 34. The air cooled by the intercooler 58 is then introduced into the motor chamber 18 by passing through the introduction passage 56, the thrust bearing housing chamber 24, and the inside of the first bearing holding section 21. Therefore, the introduction passage 56 introduces a portion 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.

[0049] The centrifugal compressor 10 is equipped with 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 communicates with the second insertion hole 26. The second end of the discharge passage 59 opens onto the outer circumferential surface of the end wall 12a of the motor housing 12. Therefore, the discharge passage 59 communicates with the outside of the housing 11. Air that flows from inside the motor chamber 18 through the inside of the second bearing holder 25 into the second insertion hole 26 is discharged to the outside of the housing 11 via the discharge passage 59.

[0050] As shown in Figure 2, the second impeller 43 is cylindrical in shape, gradually decreasing in diameter from the back surface 43a towards the tip. The back surface 43a of the second impeller 43 faces the second plate 16. Therefore, the second plate 16 has a facing surface 16a that faces 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 coincides with the rotation axis of the second impeller 43. Note that the rotation axis of the second impeller 43 is also the axis of the rotation axis 41.

[0051] <First hole 61 and second hole 64> The second plate 16 has a first hole 61 that forms part of the second insertion hole 26. The first hole 61 penetrates the central part 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 opposing surface 16a. The diameter of the first small diameter hole 63 is smaller than the diameter of the first large diameter hole 62. The first small diameter hole 63 is continuous with the end of the first large diameter hole 62 opposite to the opposing surface 16a. The second plate 16 is a first wall structure that partitions the second impeller chamber 33.

[0052] The end wall 12a of the motor housing 12 has a second hole 64 that forms 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 inside of the second bearing retaining portion 25. The diameter of the second small diameter hole 66 is smaller than the 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 opposite to the second bearing retaining portion 25. The diameter of the second small diameter hole 66 is the same as the diameter of the first small diameter hole 63. The end wall 12a of the motor housing 12 is a second wall structure that partitions the motor chamber 18. Therefore, the partition wall has a first wall structure and a second wall structure.

[0053] <Shaft portion 71> The rotating shaft 41 has a shaft portion 71. The shaft portion 71 is the part of the rotating shaft 41 that is located inside the second insertion hole 26. The shaft portion 71 has 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 to the inside of the second bearing holding portion 25, and through 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.

[0054] As shown in Figure 3, the end face 72a of the large-diameter shaft portion 72 is located inside the second small-diameter hole 66. The small-diameter shaft portion 73 has a smaller diameter than the large-diameter shaft portion 72. As shown in Figures 2 and 3, the small-diameter shaft portion 73 extends from the end face 72a of the large-diameter shaft portion 72 toward the second impeller chamber 33. The axis of the large-diameter shaft portion 72 and the axis of the small-diameter shaft portion 73 coincide. As shown in Figure 3, 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. 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 passes through the through hole 43h of the second impeller 43.

[0055] <Boss section 74> The second impeller 43 has a cylindrical boss portion 74. The boss portion 74 protrudes from the center of the back surface 43a of the second impeller 43. The inside of the boss portion 74 communicates with the through hole 43h. The rotating shaft 41 passes through the inside of the boss portion 74 and the through hole 43h. The boss portion 74 is inserted into the second through hole 26. Therefore, the boss portion 74 is located inside the second through hole 26. The boss portion 74 is the part of the rotating body 40 that is located inside the second through hole 26.

[0056] The boss portion 74 has a large-diameter boss portion 75 and a small-diameter boss portion 76. The large-diameter boss portion 75 is continuous with the back surface 43a of the second impeller 43. The outer diameter of the large-diameter boss portion 75 is the same as the outer diameter of the large-diameter shaft portion 72. The large-diameter boss portion 75 extends from the back surface 43a of the second impeller 43, passing inside the first large-diameter hole 62 of the first hole 61, to the inside of the first small-diameter hole 63 of the first hole 61. The end face 75a of the large-diameter boss portion 75 is located inside the first small-diameter hole 63.

[0057] The small-diameter boss portion 76 has a smaller diameter than the large-diameter boss portion 75. The small-diameter boss portion 76 extends from the end face 75a of the large-diameter boss portion 75 toward the motor chamber 18. The axis of the large-diameter boss portion 75 and the axis of the small-diameter boss portion 76 coincide. The end face 76a of the small-diameter boss portion 76 is located inside the first small-diameter hole 63. The outer diameter of the small-diameter boss portion 76 is the same as the outer diameter of the small-diameter shaft portion 73. The end face 76a of the small-diameter boss portion 76 faces the end face 73a of the small-diameter shaft portion 73 in the axial direction of the rotation axis 41.

[0058] <Shim Plate 77> The centrifugal compressor 10 is equipped with a shim plate 77. The shim plate 77 is annular in shape. 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 boss 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 edge of the shim plate 77 is the same as the outer diameter of the large diameter boss portion 75 and the outer diameter of the large diameter shaft portion 72. Therefore, the shim plate 77 protrudes radially outward from the rotating shaft 41 than the small diameter shaft portion 73 and the small diameter boss portion 76.

[0059] The shim plate 77 is made of a metallic material. For example, the shim plate 77 is made of stainless steel. The coefficient of thermal expansion of the shim plate 77 is smaller than that of the second plate 16. Therefore, the coefficient of thermal expansion of the shim plate 77 is smaller than that of the partition wall.

[0060] 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, thereby adjusting the axial position of the rotating shaft 41 on the second impeller 43. This adjusts the clearance between the second impeller 43 and the second compressor housing 14, thereby improving the air compression efficiency.

[0061] <First projection 78 and second projection 79> The second plate 16 has a first projection 78 as a projection. Therefore, the partition wall has a projection. The first projection 78 is annular and protrudes from the inner circumferential surface of the first small-diameter hole 63 toward the outer circumferential surface of the small-diameter boss portion 76. Therefore, the projection is the first projection 78 that protrudes from the inner circumferential surface of the first hole 61 toward the outer circumferential surface of the small-diameter boss portion 76. Thus, the first projection 78 protrudes from the inner circumferential surface of the second insertion hole 26 toward the outer circumferential surface of the small-diameter boss portion 76. The inner diameter of the first projection 78 is smaller than the outer diameter of the large-diameter boss portion 75.

[0062] The end wall 12a of the motor housing 12 has a second projection 79. Therefore, the second wall component has a second projection 79. The second projection 79 is an annular shape that protrudes from the inner circumferential surface of the second small-diameter hole 66 toward the outer circumferential surface of the small-diameter shaft portion 73. Therefore, the second projection 79 protrudes from the inner circumferential surface of the second hole 64 toward the outer circumferential surface of the small-diameter shaft portion 73. The inner diameter of the second projection 79 is smaller than the outer diameter of the large-diameter shaft portion 72. The inner diameter of the second projection 79 is the same as the inner diameter of the first projection 78.

[0063] <First gap 81, second gap 82, third gap 83, fourth gap 84, and fifth gap 85> Inside the second through hole 26, there are a first gap 81, a second gap 82, a third gap 83, a fourth gap 84, and a fifth gap 85. The first gap 81 is formed between the inner circumferential surface of the first small-diameter hole 63 and the outer circumferential surface of the large-diameter boss portion 75. Therefore, the first gap 81 is formed between the inner circumferential surface of the second through hole 26 and the outer circumferential surface of the large-diameter boss portion 75.

[0064] The second gap 82 is formed between the first projection 78 and the outer circumferential surface of the small-diameter boss portion 76. The third gap 83 is formed between the shim plate 77 and the inner circumferential surface of the first small-diameter hole 63. Therefore, the third gap 83 is formed between the shim plate 77 and the inner circumferential surface of the second insertion hole 26.

[0065] The fourth gap 84 is formed between the inner circumferential surface of the second small-diameter hole 66 and the outer circumferential surface of the large-diameter shaft portion 72. Therefore, the fourth gap 84 is formed between the inner circumferential surface of the second insertion hole 26 and the outer circumferential surface of the large-diameter shaft portion 72. The fifth gap 85 is formed between the second projection 79 and the outer circumferential surface of the small-diameter shaft portion 73. 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 are all the same.

[0066] Inside the second through hole 26, there are a first passage 86, a second passage 87, a third passage 88, and a fourth passage 89. The first passage 86 connects the first gap 81 and the second gap 82. The second passage 87 connects the second gap 82 and the third gap 83. The third passage 88 connects the third gap 83 and the fifth gap 85. The fourth passage 89 connects the fifth gap 85 and the fourth gap 84. A labyrinth seal is formed inside the second through hole 26 by the first gap 81, the first passage 86, the second gap 82, the second passage 87, the third gap 83, the third passage 88, the fifth gap 85, the fourth passage 89, and the fourth gap 84.

[0067] Therefore, inside the second through hole 26, a first gap 81, a second gap 82, a third gap 83, and a fourth gap 84 are provided in this order, from the second impeller chamber 33 toward the motor chamber 18. The first gap 81, the second gap 82, the third gap 83, and the fourth gap 84 constitute a labyrinth seal that seals the space between the second through hole 26 and the rotating body 40. In this embodiment, the fifth gap 85 is located between the third gap 83 and the fourth gap 84. 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 the space between the second through hole 26 and the rotating body 40.

[0068] [Effect of the Embodiment] Next, the operation of this embodiment will be described. The thrust bearing 54 is cooled by air introduced into the thrust bearing housing chamber 24 from the introduction passage 56. The air in the thrust bearing housing chamber 24 passes inside the first bearing holder 21. The first radial bearing 52 is cooled by the air passing inside the first bearing holder 21. The air that has passed inside the first bearing holder 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 portion of the air compressed by the second impeller 43 into the motor chamber 18 at a temperature lower than the temperature of the air discharged into the second discharge chamber 34. The air introduced into the motor chamber 18 passes inside the second bearing holder 25. The second radial bearing 53 is cooled by the air passing inside the second bearing holder 25. The air that has passed inside the second bearing retaining portion 25 is discharged to the outside of the housing 11 via the discharge passage 59.

[0069] Incidentally, some of the air compressed by the second impeller 43 and discharged into the second discharge chamber 34 may flow into the gap 90 between the back surface 43a of the second impeller 43 and the second plate 16. The air that flows into the gap 90 then flows from the gap 90 into the second insertion hole 26. In this way, for example, when air flows from the gap 90 between the back surface 43a of the second impeller 43 and the second plate 16 into the second insertion hole 26, the air is constricted as it passes through the first gap 81. The air that has passed through the first gap 81 expands as it passes through the first path 86 to the second gap 82 and is constricted again as it passes through the second gap 82. Furthermore, the air that has passed through the second gap 82 expands again as it passes through the second path 87 to the third gap 83 and is constricted again as it passes through the third gap 83. The air that has passed through the third gap 83 re-expands via the third path 88 to the fifth gap 85 and is constricted again as it passes through the fifth gap 85. Furthermore, the air that has passed through the fifth gap 85 re-expands via the fourth path 89 to the fourth gap 84 and is constricted again as it passes through the fourth gap 84. In this way, the air passes sequentially through sections where it is constricted and expanded between the first gap 81, the second gap 82, the third gap 83, and the fourth gap 84 via the fifth gap 85. Therefore, the pressure is successively reduced as the air flows from the first gap 81 to the fourth gap 84. Thus, the pressure of the air that flows from the back surface 43a of the second impeller 43 to 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, it is suppressed that a portion of the air compressed by the second impeller 43 and discharged into the second discharge chamber 34 enters the motor chamber 18 through the second insertion hole 26.

[0070] [Effects of the Embodiment] The above embodiment can be achieved to obtain the following effects. (1) Inside the second insertion hole 26, there is a first gap 81, a second gap 82, a third gap 83, and a fourth gap 84. The first gap 81, the second gap 82, the third gap 83, and the fourth gap 84 constitute a labyrinth seal that seals the space between the second insertion hole 26 and the rotating body 40. With this configuration, 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 constricted as it passes through the first gap 81. The air that has passed through the first gap 81 expands as it reaches the second gap 82 and is constricted again as it passes through the second gap 82. Furthermore, the air that has passed through the second gap 82 expands again as it reaches the third gap 83 and is constricted again as it passes through the third gap 83. The air that has passed through the third gap 83 expands again before reaching the fourth gap 84, and is then constricted again as it passes through the fourth gap 84. In this way, the air passes sequentially through constricted and expanded sections from the first gap 81 to the fourth gap 84 via the second gap 82 and the third gap 83. Therefore, the pressure is successively reduced as the air flows from the first gap 81 to the fourth gap 84. Thus, the pressure of the air that flows from the back surface 43a of the second impeller 43 to the second insertion hole 26 through the gap 90 between the back surface 43a of the second impeller 43 and the second plate 16 can be efficiently reduced. As a result, leakage of some of the air compressed by the second impeller 43 and discharged to the second discharge chamber 34 into the motor chamber 18 through the second insertion hole 26 is suppressed. Consequently, in the centrifugal compressor 10, unnecessary compression of air is suppressed, and the decrease in the operating efficiency of the centrifugal compressor 10 is suppressed.

[0071] For example, if we were to create a third gap 83 and a fourth gap 84 inside the second insertion hole 26 without using the shim plate 77, it would be necessary to form an annular recess on the outer circumferential surface of the shaft portion 71. Therefore, processing is required to form a recess on the outer circumferential surface of the shaft portion 71, which necessitates additional processing of the rotating shaft 41. To address this, the third gap 83 was formed by making the shim plate 77 protrude radially outward from the rotating shaft 41 beyond the small diameter shaft portion 73 and the small diameter boss portion 76. This allows us to create a third gap 83 and a fourth gap 84 inside the second insertion hole 26 simply by utilizing the existing shim plate 77. As a result, the decrease in the operating efficiency of the centrifugal compressor 10 can be suppressed without performing additional processing on the rotating shaft 41.

[0072] (2) The second projection 79 is formed on the end wall 12a of the motor housing 12, which is a separate component from the second plate 16 on which the first projection 78 is formed. Therefore, when assembling the centrifugal compressor 10, the shim plate 77 interposed 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 positioned between the first projection 78 and the second projection 79 in the axial direction of the rotating shaft 41. A fifth gap 85 is provided inside the second insertion hole 26. Therefore, the air is constricted as it passes through the fifth gap 85. As a result, the air flowing from the first gap 81 toward the fourth gap 84 is further reduced in pressure. Therefore, the pressure of the air flowing from the back surface 43a of the second impeller 43 to 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 reduced more efficiently.

[0073] (3) The coefficient of thermal expansion of the shim plate 77 is smaller than that of the second plate 16. For example, consider the case where the coefficient of thermal expansion of the shim plate 77 is greater than or equal to that of the second plate 16. Compared to this case, even if heat is transferred from the second impeller 43 to the shim plate 77 and the shim plate 77 expands due to thermal expansion, it becomes easier to avoid the shim plate 77 coming into contact with the second plate 16.

[0074] (4) The leakage of a portion of the air compressed by the second impeller 43 and discharged into the second discharge chamber 34 into the motor chamber 18 through the second insertion hole 26 is suppressed. Therefore, the problem of the motor 20 being heated by the air that enters the motor chamber 18 due to a portion of the air compressed by the second impeller 43 and discharged into the second discharge chamber 34 entering into the motor chamber 18 through the second insertion hole 26 is less likely to occur. Thus, by introducing a portion of the air compressed by the second impeller 43 into the motor chamber 18 at a temperature lower than the temperature of the air discharged into the second discharge chamber 34, the motor 20 can be cooled efficiently. As a result, the durability of the centrifugal compressor 10 can be improved.

[0075] [Example of changes] The above embodiment can be implemented with the following modifications. The above embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0076] ○ In this 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. The opening of the motor housing 12 is closed 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 has a configuration in which the second projection 79 is omitted. Thus, the centrifugal compressor 10 may not have the second projection 79 and may not have a fifth gap 85 inside the second insertion hole 26.

[0077] ○ In this embodiment, for example, the coefficient of thermal expansion of the shim plate 77 may be greater than or equal to the coefficient of thermal expansion of the second plate 16. ○ In this 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.

[0078] ○ In this embodiment, the shim plate 77 may be made of iron, for example. Preferably, the shim plate 77 is made of a material whose coefficient of thermal expansion is smaller than that of the second plate 16.

[0079] ○ In this embodiment, the introduction passage 56 may 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 into the second discharge chamber 34. In short, the introduction passage 56 should introduce air into the motor chamber 18 at a temperature lower than the temperature of the air discharged into the second discharge chamber 34.

[0080] ○ In this embodiment, the centrifugal compressor 10 may be configured without a second impeller 43. In this case, 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 first insertion hole 23.

[0081] ○ In this embodiment, the centrifugal compressor 10 may be configured to include a turbine wheel instead of the second impeller 43. ○ In this embodiment, the centrifugal compressor 10 does not have to be installed in the fuel cell vehicle. In short, the centrifugal compressor 10 is not limited to being installed in a vehicle.

[0082] ○ In this embodiment, the centrifugal compressor 10 is not limited to one used to compress air supplied to the fuel cell stack 38. In short, the centrifugal compressor 10 can be any compressor that compresses air. [Explanation of Symbols]

[0083] 10...Centrifugal compressor, 11...Housing, 12a...End wall (partition wall) which is the second wall component, 15...First plate (partition wall), 16...Second plate (partition wall) which is the first wall component, 17...Third plate (partition wall), 18...Motor chamber, 20...Motor, 23...First insertion hole (insertion hole), 26...Second insertion hole (insertion hole), 28...First impeller chamber (impeller chamber), 33...Second impeller chamber (impeller chamber), 34...Second discharge chamber which is the discharge chamber, 40...Rotating body, 41...Rotation shaft, 42...First impeller (impeller), 43...Second impeller (impeller), 43a...Back surface, 61...First hole, 64...Second hole, 71...Shaft section, 72...Large diameter shaft section, 73...Small diameter shaft section, 73a...End face, 74...Boss section, 75...Large diameter boss section, 76...Small diameter boss section, 76a...End face, 77...Shim plate, 78...First projection (projection), 79...Second projection, 81...First gap, 82...Second gap, 83...Third gap, 84...Fourth gap, 85...Fifth gap.

Claims

1. A rotating body including a rotating shaft and an impeller that compresses air by rotating integrally with the rotating shaft, A motor that rotates the aforementioned rotating shaft, A housing having an impeller chamber for housing the impeller, a motor chamber for housing the motor, a partition wall separating the impeller chamber and the motor chamber and having a through hole through which the rotating body is inserted, and a discharge chamber through which the air compressed by the impeller is discharged, A centrifugal compressor comprising an annular shim plate interposed between the rotating shaft and the impeller in the axial direction of the rotating shaft, The rotating shaft has a shaft portion that is positioned inside the insertion hole, The shaft portion has a large-diameter shaft portion, a small-diameter shaft portion which is smaller in diameter than the large-diameter shaft portion and extends from the large-diameter shaft portion toward the impeller chamber, and a through portion which is smaller in diameter than the small-diameter shaft portion and extends from the end face of the small-diameter shaft portion and penetrates through the through hole of the impeller. The impeller has a boss portion that protrudes from the back surface of the impeller and is positioned inside the insertion hole. The boss portion comprises a large-diameter boss portion and a small-diameter boss portion which has a smaller diameter than the large-diameter boss portion and extends from the large-diameter boss portion toward the motor chamber. The shim plate is positioned in the step formed by the small diameter shaft portion and the through portion, and is held in place between the end face of the small diameter shaft portion and the end face of the small diameter boss portion, and protrudes radially outward from the small diameter shaft portion and the small diameter boss portion. The partition wall has an annular projection that protrudes from the inner circumferential surface of the insertion hole toward the outer circumferential surface of the small-diameter boss portion. The annular projection has its tip protruding such that it is located between the large-diameter shaft portion and the small-diameter shaft portion in the radial direction of the rotation axis. Inside the aforementioned insertion hole, A first gap is formed between the inner circumferential surface of the insertion hole and the outer circumferential surface of the large-diameter boss portion, A second gap is formed between the projection and the outer circumferential surface of the small-diameter boss, A third gap formed between the shim plate and the inner circumferential surface of the insertion hole, The fourth gap formed between the inner circumferential surface of the insertion hole and the outer circumferential surface of the large-diameter shaft portion is provided in this order from the impeller chamber toward the motor chamber. A centrifugal compressor characterized in that the first gap, the second gap, the third gap, and the fourth gap constitute a labyrinth seal that seals the space between the insertion hole and the rotating body.

2. The aforementioned partition wall is, A first wall structure having a first hole that partitions the impeller chamber and forms a part of the insertion hole, It has a second wall structure having a second hole that partitions the motor chamber and forms a part of the insertion hole, The projection is a first projection that protrudes from the inner circumferential surface of the first hole toward the outer circumferential surface of the small-diameter boss portion. The second wall structure has an annular second projection that protrudes from the inner circumferential surface of the second hole toward the outer circumferential surface of the small diameter shaft portion, A fifth gap is provided inside the insertion hole, between the second projection and the outer circumferential surface of the small-diameter shaft portion. The centrifugal compressor according to claim 1, characterized in that 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 space between the insertion hole and the rotating body.

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

Images