JP2024039921A - centrifugal compressor - Google Patents

Abstract

[Problem] To provide a centrifugal compressor capable of suppressing a local increase in stress generated in the impeller due to the rotation of the impeller while reducing the flow of fluid between the back surface of the impeller and a partition wall. [Solution] A back surface S2 of a hub 411 of the centrifugal compressor is provided with a plurality of protrusions 80 that protrude toward the plate of the housing. The blades 412 of the impeller 41 and the protrusions 80 are arranged to be offset from each other in the circumferential direction C so as not to overlap in the axial direction of the rotating shaft. [Selected Figure] Figure 4

Description

The present invention relates to a centrifugal compressor.

A centrifugal compressor includes a rotating shaft, a drive section, an impeller, and a housing. The drive unit rotates the rotating shaft. The impeller rotates integrally with the rotating shaft. The impeller has a hub and multiple blades. The hub has an outer peripheral surface and a back surface. The outer circumferential surface has a shape that gradually increases in diameter from one side of the rotating shaft to the other side. The back surface is formed on the other side of the rotating shaft. The housing accommodates the rotating shaft, the impeller, and the drive section. The housing has a partition wall facing the back surface of the impeller.

Patent Document 1 discloses a centrifugal compressor in which an impeller rotates integrally with the rotating shaft when the rotating shaft is rotated by a motor unit serving as a driving unit. The housing included in the centrifugal compressor described in Patent Document 1 includes a compressor chamber that accommodates an impeller and a motor chamber that accommodates a motor section. A bearing that supports the rotating shaft is provided on the partition wall of the housing. A plurality of cylindrical protrusions extending toward the partition wall are provided on the back surface of the impeller. Each protrusion is provided concentrically around the rotation axis. In the centrifugal compressor described in Patent Document 1, even if gas attempts to flow between the back surface of the impeller and the partition wall due to the rotation of the impeller, the plurality of protrusions prevent the gas from flowing between the back surface of the impeller and the partition wall. Gas flow is reduced. As a result, it takes time for the pressure between the back surface of the impeller and the partition wall to rise, so that it becomes difficult for the through airflow from the compressor chamber toward the motor chamber to pass through the bearing immediately after the pressure in the compressor chamber increases. Therefore, the grease from the bearing is prevented from flowing out due to the through-air flow.

JP2022-67667A

However, since the cylindrical protrusion in Patent Document 1 is concentric with the rotation axis, the blade and the cylindrical protrusion overlap in the axial direction. Therefore, as the impeller rotates, centrifugal force acts on the blades and cylindrical protrusion of the impeller, resulting in stress generated in the impeller due to the centrifugal force acting on the blades and centrifugal force acting on the protrusion. The stress generated in the impeller due to this acts on the same location of the impeller. In other words, as the impeller rotates, the stress generated in the impeller may locally increase.

A centrifugal compressor that solves the above problems includes a rotating shaft, a driving section that rotates the rotating shaft, an impeller that rotates integrally with the rotating shaft, and housing the rotating shaft, the driving section, and the impeller. , a housing having a partition wall that supports the rotating shaft and partitions the drive unit and the impeller, and the impeller has a shape whose diameter gradually increases from one side of the rotating shaft to the other side. A centrifugal compressor comprising: a hub having an outer circumferential surface; and a back surface on the back side of the outer circumferential surface in the axial direction of the rotating shaft; and a plurality of blades provided on the outer circumferential surface of the hub, the centrifugal compressor comprising: is provided with a plurality of protrusions that protrude toward the partition wall, the plurality of wings have a first predetermined interval in the circumferential direction of the hub, and the plurality of protrusions have a second predetermined interval in the circumferential direction of the hub, and the plurality of blades and the plurality of protrusions are staggered from each other in the circumferential direction of the hub so that they do not overlap in the axial direction of the rotating shaft.

According to the above configuration, even if fluid attempts to flow between the back surface of the impeller and the partition wall due to rotation of the impeller, at least the protrusion interferes with the flow of the fluid. Therefore, the flow of fluid between the back surface of the impeller and the partition wall can be reduced.

Further, the plurality of wings have a first predetermined interval in the circumferential direction of the hub, the plurality of protrusions have a second predetermined interval in the circumferential direction of the hub, and the plurality of wings and the plurality of protrusions rotate. They are arranged offset from each other in the circumferential direction of the hub so as not to overlap in the axial direction of the shaft. Therefore, when the impeller rotates, the stress generated in the impeller due to the centrifugal force acting on the blades of the impeller and the stress generated in the impeller due to the centrifugal force acting on the protrusion do not act on the same location of the impeller. Therefore, it is possible to suppress stress generated in the impeller from increasing locally due to rotation of the impeller. As described above, while reducing the flow of fluid between the back surface of the impeller and the partition wall, it is possible to suppress the stress generated in the impeller from increasing locally due to rotation of the impeller.

In the above centrifugal compressor, the back surface includes a first back surface that is closer to the outer diameter side of the impeller than all of the protrusions, and a second back surface that is closer to the inner diameter side of the impeller than all of the protrusions; and the plurality of protrusions have the second predetermined interval, so that a space between the protrusions adjacent to each other in the circumferential direction of the hub is formed from the first back surface to the second predetermined interval by the rotation of the impeller. 2. A gap is formed in which fluid flows toward the rear surface, and an end surface of the protruding portion leading in the rotational direction of the impeller extends radially outward of the hub in the rotational direction of the impeller. good.

According to the above configuration, the end surface of the protruding portion leading in the rotational direction of the impeller can create a flow that draws the fluid back from the outer diameter side of the impeller toward the inner diameter side. Therefore, even if fluid tries to flow toward the impeller from between the partition wall and the rotating shaft due to differential pressure, for example, it becomes difficult to pass between the back surface of the impeller and the partition wall.

In the centrifugal compressor described above, the plurality of protrusions are formed around the hub in a plurality of circumferences in the radial direction of the hub at third predetermined intervals, and the protrusions are arranged around the plurality of protrusions that are adjacent to each other in the radial direction of the hub. The end face of the protruding part located on the radially outer side of the hub precedes the end face of the protruding part located on the radially inner side of the hub in the rotational direction of the impeller. Good.

According to the above configuration, in the protrusions adjacent in the radial direction of the hub, the fluid pulled back from the outer diameter side of the impeller toward the inner diameter side by the end face of the protrusion part located on the radially outer side of the hub is It is pulled back toward the inner diameter side of the impeller by the end face of the protrusion located on the radially inner side, or passes between adjacent protrusions in the radial direction of the hub. Therefore, while the end face of the protrusion located on the radially inner side of the hub makes it easier to pull the fluid back from the outer diameter side of the impeller toward the inner diameter side, the fluid passes between adjacent protrusions in the radial direction of the hub. By doing so, it is possible to release a portion of the load when fluid collides with protrusions adjacent in the radial direction of the hub. Therefore, while making it easier to pull the fluid back from the outer diameter side of the impeller toward the inner diameter side, it is possible to reduce the stress generated in both protrusions when the fluid collides with the end surfaces of the protrusions adjacent in the radial direction of the hub.

In the above centrifugal compressor, it is preferable that the partition wall is provided with an annular groove into which the protrusion enters and forms a labyrinth in a radial direction of the hub.
According to the above configuration, even if fluid tries to flow between the back surface of the impeller and the partition wall, the labyrinth formed by the protrusion and the groove further reduces the flow of fluid between the back surface of the impeller and the partition wall. can.

According to this invention, while reducing the flow of fluid between the back surface of the impeller and the partition wall, it is possible to suppress the stress generated in the impeller from increasing locally due to rotation of the impeller.

It is a sectional view of the centrifugal compressor in an embodiment. FIG. 2 is an enlarged cross-sectional view of a portion of the centrifugal compressor. It is a perspective view showing the back side of an impeller. It is a front view of the back of an impeller.

An embodiment of a centrifugal compressor will be described below with reference to FIGS. 1 to 4. The centrifugal compressor of this embodiment is mounted on a fuel cell vehicle that runs using a fuel cell as a power source, and supplies air to the fuel cell.

<Housing>
As shown in FIG. 1, the centrifugal compressor 10 includes a cylindrical housing 11. The housing 11 includes a motor housing 12, a speed increaser housing 13, a plate 14, and a compressor housing 15. The motor housing 12, the speed increaser housing 13, the plate 14, and the compressor housing 15 are made of metal, for example, aluminum.

The motor housing 12 has a plate-shaped end wall 12a and a cylindrical peripheral wall 12b. The peripheral wall 12b extends from the outer periphery of the end wall 12a. The speed increaser housing 13 has a plate-shaped end wall 13a and a cylindrical peripheral wall 13b. The peripheral wall 13b extends from the outer periphery of the end wall 13a.

An end of the peripheral wall 12b of the motor housing 12 located on the opposite side of the end wall 12a is connected to an end wall 13a of the speed increaser housing 13. The opening of the peripheral wall 12b of the motor housing 12 is closed by the end wall 13a of the speed increaser housing 13. A through hole 13h is formed in the center of the end wall 13a of the speed increaser housing 13.

The plate 14 is arranged at the end of the peripheral wall 13b of the speed increaser housing 13 on the opposite side to the end wall 13a. An insertion hole 14h is formed in the center of the plate 14. The plate 14 has a first surface 141a and a second surface 141b. The first surface 141a is in contact with the end of the peripheral wall 13b of the speed increaser housing 13 on the opposite side to the end wall 13a. The opening of the peripheral wall 13b of the speed increaser housing 13 is closed by the first surface 141a of the plate 14. The second surface 141b is a surface located on the opposite side of the first surface 141a in the thickness direction of the plate 14.

Compressor housing 15 is connected to second surface 141b of plate 14. The motor housing 12, the speed increaser housing 13, the plate 14, and the compressor housing 15 are arranged in this order in the axial direction of the housing 11.

The compressor housing 15 is defined with a suction passage 15a through which air is sucked. The suction passage 15a opens at the center of the end surface of the compressor housing 15 opposite to the plate 14. The suction passage 15a extends in the axial direction of the housing 11 from the center of the end surface of the compressor housing 15 opposite to the plate 14.

<Low speed shaft and electric motor>
The centrifugal compressor 10 includes a low-speed shaft 16 and an electric motor 17. Electric motor 17 rotates low speed shaft 16 . Therefore, the low speed shaft 16 is rotated by the electric motor 17.

A motor chamber 25 that accommodates the electric motor 17 is defined inside the housing 11 . The motor chamber 25 is defined by the inner surface of the end wall 12a of the motor housing 12, the inner peripheral surface of the peripheral wall 12b, and the outer surface of the end wall 13a of the speed increaser housing 13. The low-speed shaft 16 is housed in the motor housing 12 with the axial direction of the low-speed shaft 16 aligned with the axial direction of the motor housing 12. The low-speed shaft 16 is made of metal, such as iron or an alloy.

A cylindrical boss portion 12f protrudes from the inner surface of the end wall 12a of the motor housing 12. One end portion of the low-speed shaft 16 is inserted into the boss portion 12f. A first bearing 18 is provided between one end of the low-speed shaft 16 and the boss portion 12f. One end of the low-speed shaft 16 is rotatably supported by the end wall 12a of the motor housing 12 via a first bearing 18.

The other end of the low-speed shaft 16 is inserted into the through hole 13h. A second bearing 19 is provided between the other end of the low-speed shaft 16 and the through hole 13h. The other end of the low-speed shaft 16 is rotatably supported by the end wall 13a of the speed increaser housing 13 via a second bearing 19. Therefore, the low-speed shaft 16 is rotatably supported by the housing 11. The other end of the low-speed shaft 16 passes through the through hole 13h from the motor chamber 25 and projects into the speed increaser housing 13.

A seal member 20 is provided between the other end of the low-speed shaft 16 and the through hole 13h. The seal member 20 seals between the outer peripheral surface of the low-speed shaft 16 and the inner peripheral surface of the through hole 13h.

<Speed up gear, high speed shaft, and speed up gear room>
The centrifugal compressor 10 includes a speed increaser 30 and a high-speed shaft 31 as a rotating shaft. The high-speed shaft 31 is made of metal, such as iron or an alloy. The high-speed shaft 31 is housed in the speed increaser housing 13 with the axial direction of the high-speed shaft 31 aligned with the axial direction of the speed increaser housing 13 . The end of the high-speed shaft 31 on the side opposite to the motor housing 12 passes through the insertion hole 14h of the plate 14 and projects into the compressor housing 15. The end of the high-speed shaft 31 opposite to the motor housing 12 is one end of the high-speed shaft 31 . The high-speed shaft 31 is inserted through the insertion hole 14h. The axis of the high-speed shaft 31 coincides with the axis of the low-speed shaft 16. The high-speed shaft 31 has an annular flange portion 31a disposed within the insertion hole 14h. The flange portion 31a has a shaft end surface 31b located in the axial direction of the high-speed shaft 31. The shaft end surface 31b of the flange portion 31a extends in the radial direction of the high-speed shaft 31.

The speed increaser 30 is, for example, a traction drive type (friction roller type). The speed increaser 30 is connected to the other end of the low speed shaft 16. When the electric motor 17 is driven and the low-speed shaft 16 rotates, the speed increaser 30 causes the high-speed shaft 31 to rotate at a higher speed than the low-speed shaft 16 . Therefore, the speed increaser 30 transmits the power of the low speed shaft 16 to the high speed shaft 31. The speed increaser 30 is a drive unit that rotates the high-speed shaft 31.

A speed increaser chamber 40 that accommodates the speed increaser 30 is partitioned inside the housing 11 . The speed increaser chamber 40 is defined by the inner surface of the end wall 13a of the speed increaser housing 13, the inner peripheral surface of the peripheral wall 13b, and the first surface 141a of the first plate 141. The speed increaser chamber 40 accommodates oil together with the speed increaser 30. The sealing member 20 suppresses oil stored in the speed increaser chamber 40 from leaking into the motor chamber 25 through the space between the outer circumferential surface of the low-speed shaft 16 and the inner circumferential surface of the through hole 13h. There is.

<Impeller and impeller chamber>
2, the centrifugal compressor 10 includes an impeller 41. The impeller 41 has a generally truncated conical cylindrical shape.

One end of the high-speed shaft 31 is inserted into the impeller 41 . The impeller 41 has a hub 411 and a plurality of blades 412. Hereinafter, the axial direction of the hub 411 will be simply referred to as "axial direction A." The axial direction A coincides with the axial direction of the high-speed shaft 31. The radial direction of the hub 411 is simply referred to as "radial direction B." The radial direction B coincides with the radial direction of the high-speed shaft 31. The circumferential direction of the hub 411 is simply referred to as "circumferential direction C." The circumferential direction C coincides with the circumferential direction of the high-speed shaft 31.

The hub 411 has an outer peripheral surface S1, a back surface S2, and an insertion hole 41d. The outer circumferential surface S1 has a shape whose diameter gradually increases from one side of the high-speed shaft 31 to the other side. All the blades 412 have a first predetermined interval in the circumferential direction C. All the blades 412 are provided on the outer circumferential surface S1 of the hub 411 at first predetermined intervals in the circumferential direction C. Each blade 412 extends from the innermost side in the radial direction B on the outer circumferential surface S1 to the outermost side in the radial direction B on the outer circumferential surface S1.

The insertion hole 41d penetrates the impeller 41 in the axial direction A. The insertion hole 41d opens at the center of the back surface S2. The high-speed shaft 31 is inserted through the insertion hole 41d. A portion of one end of the high-speed shaft 31 passes through the impeller 41. A male thread 31d is formed in a portion of the high-speed shaft 31 that passes through the impeller 41. A nut 95 is screwed onto the male screw 31d. By screwing the nut 95 onto the external thread 31d of the high-speed shaft 31, the impeller 41 is sandwiched between the nut 95 and the flange portion 31a in the axial direction A. Thereby, the impeller 41 is fixed to the high speed shaft 31. Therefore, the impeller 41 rotates integrally with the high-speed shaft 31.

The back surface S2 is a surface formed on the other side of the high-speed shaft 31 in the impeller 41. The back surface S2 is located on the back side of the high-speed shaft 31 in the axial direction of the outer circumferential surface S1. A portion of the back surface S2 faces the second surface 141b of the plate 14. Among the second surfaces 141b of the plate 14, the surface facing the back surface S2 is referred to as an opposing surface 141c. The space formed between the back surface S2 and the opposing surface 141c is defined as a first space G1.

An impeller chamber 42 that accommodates an impeller 41 is defined inside the housing 11 . The impeller chamber 42 communicates with the suction passage 15a. The impeller chamber 42 has a substantially truncated conical hole shape whose diameter gradually increases as it moves away from the suction passage 15a. The impeller chamber 42 is partitioned by the compressor housing 15 and the plate 14. The centrifugal compressor 10 includes a seal member 48. The seal member 48 is provided between the outer peripheral surface of the high-speed shaft 31 and the inner peripheral surface of the insertion hole 14h of the plate 14. The seal member 48 is, for example, a mechanical seal. The seal member 48 suppresses oil stored in the speed increaser chamber 40 from leaking into the impeller chamber 42 through the insertion hole 14h. The high-speed shaft 31 is rotatably supported by the plate 14 via a seal member 48 . Thus, the housing 11 supports the high speed shaft 31.

As shown in FIG. 1, the plate 14 is a partition wall that partitions the impeller 41 and the speed increaser 30. The housing 11 accommodates a high-speed shaft 31, a speed increaser 30, and an impeller 41. The plate 14 faces the back surface S2.

<Diffuser channel, discharge chamber, and discharge port>
The centrifugal compressor 10 includes a diffuser flow path 43, a discharge chamber 44, and a discharge port 45. The diffuser flow path 43 is defined by the plate 14 and a surface of the compressor housing 15 that faces the plate 14 . The diffuser flow path 43 is located outside the impeller chamber 42 in the radial direction of the high-speed shaft 31 . Diffuser flow path 43 communicates with impeller chamber 42 . The diffuser flow path 43 is formed in an annular shape surrounding the impeller 41 and the impeller chamber 42 .

The discharge chamber 44 is located on the radially outer side of the high-speed shaft 31 than the diffuser flow path 43 is. The discharge chamber 44 communicates with the diffuser flow path 43. The discharge chamber 44 is annular. The impeller chamber 42 and the discharge chamber 44 communicate with each other via a diffuser flow path 43. The discharge port 45 communicates with the discharge chamber 44 . The discharge port 45 communicates with the outside of the compressor housing 15.

As the impeller 41 rotates, air sucked from the suction passage 15a is sucked into the impeller chamber 42. The air sucked into the impeller chamber 42 is compressed by the impeller 41. Air compressed by the impeller 41 is discharged into the diffuser flow path 43. The air discharged into the diffuser flow path 43 is further compressed by passing through the diffuser flow path 43 and is discharged into the discharge chamber 44 . The air discharged into the discharge chamber 44 is supplied from the discharge port 45 to the fuel cell provided outside the housing 11.

<Configuration of the back side of the impeller>
As shown in FIG. 2, the back surface S2 of the impeller 41 has a base end surface 41a, a tapered surface 41b, and an annular flat surface 41c. The base end surface 41a faces the flange portion 31a of the high-speed shaft 31. The base end surface 41a is in contact with the shaft end surface 31b of the flange portion 31a. An insertion hole 41d is opened in the base end surface 41a. The base end surface 41a extends in the radial direction B.

The tapered surface 41b is a surface whose diameter gradually increases from the outer peripheral edge of the base end surface 41a toward the outer peripheral surface S1 side in the axial direction A as it goes outward in the radial direction B. The flat surface 41c extends in the radial direction B from the outer peripheral edge of the tapered surface 41b. The tapered surface 41b and the flat surface 41c are separated from the plate 14 when the impeller 41 is fixed to the high-speed shaft 31.

The flat surface 41c is annular. A plurality of protrusions 80 that protrude toward the plate 14 are provided on the back surface S2. The protrusion 80 is provided on the flat surface 41c.
As shown in FIG. 3, all the protrusions 80 have a second predetermined interval in the circumferential direction C. All the protrusions 80 are provided on the flat surface 41c at second predetermined intervals in the circumferential direction C. Since all the protrusions 80 have the second predetermined interval, a gap Vs is formed between adjacent protrusions 80 in the circumferential direction C.

As shown in FIG. 4, a region obtained by projecting the bottom portion 412a of each blade 412 onto the flat surface 41c of the impeller 41 is defined as a first region 91. The bottom portion 412a is a portion of the blade 412 that connects to the outer circumferential surface S1 of the hub 411. The bottom portion 412a is a portion of the blade 412 on the outer peripheral surface S1 side of the hub 411, and is a portion on which stress is applied when the impeller 41 rotates. The first region 91 is indicated by diagonal lines in FIG. The first regions 91 are provided at predetermined intervals in the circumferential direction C. That is, all the blades 412 have the first predetermined interval in the circumferential direction C. The area between the first areas 91 adjacent to each other in the circumferential direction C on the flat surface 41c is defined as a second area 92. The second region 92 is a region of the flat surface 41c on which the bottom portion 412a of each wing 412 is not projected. The first region 91 and the second region 92 are arranged alternately in the circumferential direction C.

Each protrusion 80 is provided in the second region 92 . A bottom portion 80b of each protrusion 80 is provided in the second region 92. The bottom portion 80b is a connection portion of the protrusion 80 with the second region 92. The bottom portion 80b is a portion of the protrusion 80 on the second region 92 side, and is a portion on which stress is applied when the impeller 41 rotates. The second regions 92 are provided at predetermined intervals in the circumferential direction C. That is, all the protrusions 80 have the second predetermined interval in the circumferential direction C. Therefore, the bottom portions 412a of the blades 412 and the bottom portions 80b of the protruding portions 80 are arranged alternately in the circumferential direction C. The projection plane of the bottom 412a of the blade 412 in the axial direction A and the projection plane of the bottom 80b of the protrusion 80 are arranged alternately in the circumferential direction C. Each protrusion 80 is provided on the back surface S2 so as not to overlap the bottom 412a of each wing 412 in the axial direction A. In other words, all the blades 412 have a first predetermined interval in the circumferential direction C, and all the protrusions 80 have a second predetermined interval in the circumferential direction C. Therefore, all the blades 412 and all the protrusions The portions 80 are arranged offset from each other in the circumferential direction C so as not to overlap in the axial direction of the high-speed shaft 31.

The back surface S2 has a first back surface 411c and a second back surface 412c. The first back surface 411c is a surface located closer to the outer diameter side of the impeller 41 than all the protrusions 80 are. The outer diameter side of the impeller 41 with respect to all the protrusions 80 has the same meaning as the outer peripheral edge side of the flat surface 41c with respect to all the protrusions 80. The first back surface 411c is a part of the flat surface 41c. The second back surface 412c is a surface that is closer to the inner diameter side of the impeller 41 than all the protrusions 80 are. The inner diameter side of the impeller 41 relative to all the protrusions 80 has the same meaning as the side closer to the insertion hole 41d of the impeller 41 than all the protrusions 80. The second back surface 412c includes a portion of the flat surface 41c that is closer to the inner diameter of the impeller 41 than all the protrusions 80, a tapered surface 41b, and a base end surface 41a.

All the protrusions 80 are composed of a plurality of first protrusions 81 and a plurality of second protrusions 82. All the first protrusions 81 are provided on the same virtual circle extending in the circumferential direction C. All the first protrusions 81 are arranged intermittently so as to go around once in the circumferential direction C. A row formed by intermittently arranging all the first protrusions 81 so as to go around once in the circumferential direction C is referred to as a first row L1.

All the second protrusions 82 are located on the outer side in the radial direction B than all the first protrusions 81. All the second protrusions 82 are arranged intermittently so as to go around once in the circumferential direction C. A row formed by intermittently arranging all the second protrusions 82 so as to go around once in the circumferential direction C is referred to as a second row L2.

Each second protrusion 82 faces each first protrusion 81 in the radial direction B. Each of the second protrusions 82 faces each of the first protrusions 81 at a third predetermined interval in the radial direction B. The first row L1 and the second row L2 are arranged at a third predetermined interval in the radial direction B. That is, the plurality of protrusions 80 are formed around a plurality of circumferences in the radial direction B at third predetermined intervals in the radial direction B. Among the protrusions 80 adjacent in the radial direction B, the second protrusion 82 is the protrusion 80 located on the outside in the radial direction B, and the first protrusion 81 is the protrusion 80 located on the inside in the radial direction B. be.

A bottom portion 80b of the protrusion 80 is formed by the connection portion of the first protrusion 81 with the second region 92. Further, a bottom portion 80b of the protrusion 80 is formed by a connecting portion of the second protrusion 82 with the second region 92.

The first protrusion 81 extends in the circumferential direction C in an arc shape. All the first protrusions 81 have a first inner surface 81a, a first outer surface 81b, a first tip surface 81c, and a first rear end surface 81d. The first inner surface 81a and the first outer surface 81b are arcuate surfaces located in the radial direction B of the first protrusion 81. The first inner surface 81a faces toward the inner diameter side of the impeller 41. The first outer surface 81b faces toward the outer diameter side of the impeller 41.

The first tip surface 81c and the first rear end surface 81d are end surfaces located at both ends of the first protrusion 81 in the circumferential direction C. The first tip surface 81c is an end surface of the first protrusion 81 that precedes the impeller 41 in the rotation direction D. The first tip surface 81c is an end surface of the protrusion 80 that precedes the rotation direction D of the impeller 41. The first tip surface 81c is continuous with the first inner surface 81a and the first outer surface 81b. The width from the first inner surface 81a to the first outer surface 81b of the first tip surface 81c is sufficiently smaller than the width in the circumferential direction C of each of the first inner surface 81a and the first outer surface 81b.

The first tip surface 81c is an inclined surface extending in the rotation direction D from the first inner surface 81a toward the first outer surface 81b. The first tip surface 81c extends outward in the radial direction B as it goes in the rotation direction D. The first rear end surface 81d is continuous with the first inner surface 81a and the first outer surface 81b. The width from the first inner surface 81a to the first outer surface 81b of the first rear end surface 81d is sufficiently smaller than the width in the circumferential direction C of each of the first inner surface 81a and the first outer surface 81b. The width from the first inner surface 81a to the first outer surface 81b of the first rear end surface 81d is smaller than the width from the first inner surface 81a to the first outer surface 81b of the first tip surface 81c. The first rear end surface 81d extends in the radial direction B.

In the first protruding portions 81 adjacent in the circumferential direction C, the circumferential direction between the edge that is furthest in the rotational direction D among the first tip surfaces 81c and the first rear end surface 81d that opposes the first tip surface 81c. Let the interval at C be interval W1.

The second protrusion 82 extends in the circumferential direction C in an arc shape. All the second protrusions 82 have a second inner surface 82a, a second outer surface 82b, a second tip surface 82c, and a second rear end surface 82d. The second inner surface 82a and the second outer surface 82b are arcuate surfaces located in the radial direction B of the second protrusion 82. The second inner surface 82a faces toward the inner diameter side of the impeller 41. A portion of the second inner surface 82a faces a portion of the first outer surface 81b of the first protrusion 81 in the radial direction B.

The second front end surface 82c and the second rear end surface 82d are end surfaces located at both ends of the second protrusion 82 in the circumferential direction C. The second tip surface 82c is an end surface of the second protrusion 82 that precedes the impeller 41 in the rotation direction D. The second tip surface 82c is an end surface of the protrusion 80 that precedes the impeller 41 in the rotation direction D. The second tip surface 82c is continuous with the second inner surface 82a and the second outer surface 82b. The width from the second inner surface 82a to the second outer surface 82b of the second tip surface 82c is sufficiently smaller than the width in the circumferential direction C of each of the second inner surface 82a and the second outer surface 82b. The width from the second inner surface 82a to the second outer surface 82b of the second tip surface 82c is the same as the width from the first inner surface 81a to the first outer surface 81b of the first tip surface 81c.

The second tip surface 82c is an inclined surface extending in the rotation direction D from the second inner surface 82a toward the second outer surface 82b. The second tip surface 82c extends outward in the radial direction B as it goes in the rotation direction D. The second tip surface 82c precedes the first tip surface 81c in the rotation direction D.

The second rear end surface 82d is continuous with the second inner surface 82a and the second outer surface 82b. The width from the second inner surface 82a to the second outer surface 82b of the second rear end surface 82d is sufficiently smaller than the width in the circumferential direction C of each of the second inner surface 82a and the second outer surface 82b. The width from the second inner surface 82a to the second outer surface 82b of the second rear end surface 82d is smaller than the width from the second inner surface 82a to the second outer surface 82b of the second tip surface 82c. The second rear end surface 82d extends in the radial direction B. The second rear end surface 82d is provided at the same position as the first outer surface 81b of the first protrusion 81 in the circumferential direction C.

In the second protruding portions 82 adjacent in the circumferential direction C, the circumferential direction between the edge of the second tip surface 82c that is furthest in the rotational direction D and the second rear end surface 82d opposing the second tip surface 82c. Let the interval at C be interval W2. The interval W2 is larger than the interval W1. Note that the second predetermined interval is the interval in the circumferential direction C between the protrusions 80 in each of the first row L1 and the second row L2. Therefore, the second predetermined interval in the first row L1 is the interval between the first protrusions 81 adjacent in the circumferential direction C, and the second predetermined interval in the second row L2 is the interval between the first protrusions 81 in the circumferential direction C. This is the distance between adjacent second protrusions 82. The gap Vs is such that the space between the first protrusions 81 adjacent in the circumferential direction C in the first row L1 and the space between the second protrusions 82 adjacent in the circumferential direction C in the second row L2 are radially It is formed by arranging B.

<Labyrinth seal part>
As shown in FIG. 2, the opposing surface 141c of the plate 14 is provided with two annular grooves 141d. The width of each groove 141d in the radial direction B is larger than the thickness of each protrusion 80 in the radial direction B. The depth of each groove 141d from the opposing surface 141c is greater than the protrusion length of each protrusion 80 from the flat surface 41c. The first row L1 fits into one groove 141d, and the second row L2 fits into the remaining groove 141d. The protrusion 80 does not contact the inner surface of the groove 141d. The space formed between the protrusion 80 and the inner surface of the groove 141d is referred to as a second space G2. The second space G2 is continuous with the first space G1.

The second space G2 includes at least a space extending in the axial direction A. That is, the second space G2 includes at least a space extending in a direction intersecting the radial direction B. The second space G2 has a meandering direction in which it extends from the first back surface 411c toward the second back surface 412c or from the second back surface 412c toward the first back surface 411c. Therefore, each groove 141d forms a labyrinth in the radial direction B into which the protrusion 80 enters. Therefore, even if fluid tries to flow through the first space G1, the labyrinth-shaped second space G2 makes it difficult for the fluid to flow in the radial direction B. Therefore, each groove 141d and the protruding portion 80 form a labyrinth seal portion 100 having a function of reducing the flow of fluid flowing into the first space G1. The centrifugal compressor 10 includes a labyrinth seal section 100.

[Operation of this embodiment]
The operation of this embodiment will be explained.
For example, if the pressure in the impeller chamber 42 becomes lower than the pressure in the speed increaser chamber 40, oil in the speed increaser chamber 40 may leak into the first space G1 through the insertion hole 14h. be. In some cases, oil flows from the inner diameter side of the impeller 41 toward the outer diameter side.

In this embodiment, even if oil attempts to flow between the back surface S2 of the impeller 41 and the facing surface 141c of the plate 14 due to the rotation of the impeller 41, at least the protrusion 80 interferes with the flow of oil. Furthermore, the second space G2 of the labyrinth seal portion 100 obstructs the flow of oil. Therefore, the flow of oil between the back surface S2 of the impeller 41 and the plate 14 is reduced. Further, as shown by arrow E in FIG. 4, as the impeller 41 rotates, the first tip surface 81c and the second tip surface 82c form a flow that draws air back from the first back surface 411c toward the second back surface 412c. do. Therefore, air flows through the gap Vs from the first back surface 411c toward the second back surface 412c as the impeller 41 rotates. Therefore, even if oil tries to flow between the back surface S2 of the impeller 41 and the plate 14, the flow of oil from the inner diameter side to the outer diameter side of the impeller 41 is further reduced.

Further, since all the blades 412 have a first predetermined interval in the circumferential direction of the hub 411 and all protrusions 80 have a second predetermined interval in the circumferential direction of the hub 411, all the blades 412 The bottom portion 412a of the protruding portion 80 and the bottom portions 80b of all the protruding portions 80 are arranged to be shifted in the circumferential direction C so that they do not overlap in the axial direction of the high-speed shaft 31. Therefore, when the impeller 41 rotates, the stress generated in the impeller 41 due to the centrifugal force acting on the blades 412 of the impeller 41 and the stress generated in the impeller 41 due to the centrifugal force acting on the protrusion 80 are It does not act on the same location.

[Effects of this embodiment]
The effects of this embodiment will be explained.
(1) Even if oil attempts to flow between the back surface S2 of the impeller 41 and the plate 14 as the impeller 41 rotates, at least the protrusion 80 interferes with the oil flow. Therefore, the flow of oil between the back surface S2 of the impeller 41 and the plate 14 can be reduced.

Further, since all the blades 412 have a first predetermined interval in the circumferential direction of the hub 411 and all protrusions 80 have a second predetermined interval in the circumferential direction of the hub 411, all the blades 412 and all the protrusions 80 are arranged to be shifted in the circumferential direction C so that they do not overlap in the axial direction of the high-speed shaft 31. Therefore, when the impeller 41 rotates, the stress generated in the impeller 41 due to the centrifugal force acting on the blades 412 of the impeller 41 and the stress generated in the impeller 41 due to the centrifugal force acting on the protrusion 80 are It does not act on the same location. Therefore, it is possible to suppress the stress generated in the impeller 41 from increasing locally due to the rotation of the impeller 41. As described above, while reducing the flow of oil between the back surface S2 of the impeller 41 and the plate 14, it is possible to suppress the stress generated in the impeller 41 from increasing locally due to the rotation of the impeller 41.

(2) The first tip surface 81c and the second tip surface 82c can create a flow that draws the fluid back from the outer diameter side of the impeller 41 toward the inner diameter side. Therefore, for example, even if oil as a fluid tries to flow toward the impeller 41 from between the plate 14 and the high-speed shaft 31 due to the differential pressure between the impeller chamber 42 and the speed increaser chamber 40, the back surface S2 of the impeller 41 It becomes difficult to pass between the plate 14 and the plate 14.

(3) In the protrusions 80 adjacent in the radial direction B, the oil as a fluid pulled back from the outer diameter side of the impeller 41 toward the inner diameter side by the second tip surface 82c of the second protrusion part 82 is transferred to the first protrusion 80. It is pulled back toward the inner diameter side of the impeller 41 by the first tip surface 81c of the portion 81, or passes between adjacent protrusions 80 in the radial direction B. Therefore, the oil passes between adjacent protrusions 80 in the radial direction B while the first tip surface 81c of the first protrusion 81 facilitates pulling the oil back from the outer diameter side to the inner diameter side of the impeller 41. As a result, part of the load when oil collides with adjacent protrusions 80 in the radial direction B can be released. Therefore, while making it easier to pull the oil back from the outer diameter side to the inner diameter side of the impeller 41, when the oil collides with the first tip surface 81c and the second tip surface 82c of the protruding portion 80 adjacent in the radial direction B, Stress generated in both protrusions 80 can be reduced.

(4) Even if oil tries to flow between the back surface S2 of the impeller 41 and the plate 14, the labyrinth seal portion 100 can further reduce the flow of oil between the back surface S2 of the impeller 41 and the plate 14.

(5) The first protrusion 81 and the second protrusion 82 have an arc shape extending in the circumferential direction C. As described above, the oil passing between the adjacent protrusions 80 in the radial direction B flows along the first outer surface 81b of the first protrusion 81 and the second inner surface 82a of the second protrusion 82. Therefore, the oil flowing between the first protruding part 81 and the second protruding part 82 stays between the first protruding part 81 and the second protruding part 82, so that the first protruding part 81 and the second protruding part 82 Generation of stress in the portion 82 can be suppressed. In other words, stress generated in adjacent protrusions 80 in the radial direction B can be further reduced.

[Example of change]
Note that the above embodiment can be modified and implemented as follows. The above embodiment and the following modification examples can be implemented in combination with each other within a technically consistent range.

In the embodiment, in addition to the first row L1 and the second row L2, a third row formed by arranging a plurality of protrusions 80 intermittently so as to go around once in the circumferential direction C is provided on the back surface S2. Good too. The end surfaces of all the protrusions 80 forming the third row that precede the rotational direction D are preferably formed like the first tip surface 81c and the second tip surface 82c. Further, it is preferable that the end faces of all the protrusions 80 that are located earlier in the rotational direction D are located on the outer side of the radial direction B. Note that the number of rows formed by the plurality of protrusions 80 may be changed as appropriate. The number of grooves 141d may be changed depending on the number of rows.

In the embodiment, the two grooves 141d formed on the opposing surface 141c may be omitted. In this case, one annular groove into which all the protrusions 80 adjacent in the radial direction B fit may be newly added. Note that it is not necessary to add one annular groove into which all the protrusions 80 adjacent in the radial direction B fit.

○ In the embodiment, the interval W1 and the interval W2 may be the same size. Alternatively, the interval W1 may be larger than the interval W2.
In the embodiment, the first row L1 may be omitted and only the second row L2 may be formed on the back surface S2. Alternatively, the second row L2 may be omitted and only the first row L1 may be formed on the back surface S2.

○ The first tip surface 81c and the second tip surface 82c may be arcuate surfaces. The first tip surface 81c and the second tip surface 82c only need to extend outward in the radial direction B as they go in the rotation direction D.

The first tip surface 81c and the second tip surface 82c may extend in the radial direction B. That is, the first tip surface 81c and the second tip surface 82c do not need to extend outward in the radial direction B as they go in the rotation direction D. Note that the shapes of the first tip surface 81c and the second tip surface 82c are not particularly limited, and may be changed as appropriate.

Although the centrifugal compressor 10 rotates the impeller 41 by rotating the high-speed shaft 31 using the speed increaser 30, the invention is not limited thereto. The centrifugal compressor 10 may be one in which the speed increaser 30 and the speed increaser chamber 40 are omitted. For example, in the centrifugal compressor 10, the impeller 41 may rotate integrally with a rotating shaft rotated by the electric motor 17. In this modification, the electric motor 17 is a drive unit that rotates a rotating shaft. In this case, the impeller chamber 42 and the motor chamber 25 are changed to be adjacent to each other in the axial direction of the rotating shaft.

In this modification, preferably, the first tip surface 81c and the second tip surface 82c extend outward in the radial direction B in a direction opposite to the rotation direction D. The second tip end surface 82c may be arranged in a direction opposite to the rotational direction D than the first tip end surface 81c.

With this change, when the impeller 41 rotates, the first tip surface 81c and the second tip surface 82c form a flow that pushes air from the second back surface 412c toward the first back surface 411c. Even if the liquid tries to flow between the back surface S2 of the impeller 41 and the plate 14 from the outer diameter side to the inner diameter side of the impeller 41 due to the rotation of the impeller 41, each protrusion 80 at least interferes with the flow of the liquid. At the same time, the liquid is dammed up by the flow that pushes out the air. Therefore, the fluid flowing between the back surface S2 of the impeller 41 and the plate 14 can be reduced. As a result, it becomes difficult for liquid to reach the motor chamber 25 from the impeller chamber 42, so that a short circuit in the electric motor 17 can be prevented.

In the embodiment, the back surface S2 may be a flat surface.
In the embodiment, all the blades 412 and all the protrusions 80 are arranged offset in the circumferential direction C so as not to overlap in the axial direction of the high-speed shaft 31, but the present invention is not limited to this. For example, some of all the protrusions 80 and the blades 412 disposed at positions sandwiching each of the plurality of protrusions 80 in the circumferential direction C may be arranged so that they do not overlap in the axial direction of the high-speed shaft 31. may be arranged offset from each other. Further, one protrusion 80 and the blades 412 disposed at positions sandwiching the one protrusion 80 in the circumferential direction C are arranged so as to be shifted from each other in the circumferential direction C so that they do not overlap in the axial direction of the high-speed shaft 31. You can leave it there. That is, at least one of all the protrusions 80 and the blades 412 disposed at positions sandwiching the at least one protrusion 80 in the circumferential direction C are mutually arranged in the circumferential direction C so that they do not overlap in the axial direction of the high-speed shaft 31. It is sufficient if they are staggered. In other words, at least one of all the protrusions 80 overlaps in the axial direction of the high-speed shaft 31 with a portion between the blades 412 adjacent in the circumferential direction C on the outer circumferential surface S1, and is located between the adjacent blades 412 and the high-speed shaft. It is sufficient if they are arranged so as not to overlap in the axial direction of 31.

In the embodiment, for example, the centrifugal compressor 10 may be mounted on a vehicle that uses an engine as a driving source. Further, for example, the centrifugal compressor 10 may omit the electric motor 17. In this case, the low-speed shaft 16 may be rotated by, for example, an engine mounted on the vehicle.

In the embodiment, the centrifugal compressor 10 is not limited to one installed in a fuel cell vehicle and used for supplying air to a fuel cell, but for example, the centrifugal compressor 10 is used in a vehicle air conditioner to supply refrigerant as a fluid. It may also be compressed. Furthermore, the centrifugal compressor 10 is not limited to one that is mounted on a vehicle.

DESCRIPTION OF SYMBOLS 10... Centrifugal compressor, 11... Housing, 14... Plate as a partition wall, 30... Speed increaser as a drive part, 31... High speed shaft as a rotating shaft, 41... Impeller, 80... Projection part, 81... Projection part 81c...an end face of the first protrusion that precedes the rotational direction of the impeller; 82...a second protrusion as a protrusion; 82c...an end face of the second protrusion that precedes the rotational direction of the impeller; 141d...groove, 411...hub, 411c...first back surface, 412c...second back surface, 412...blade, B...radial direction of hub, C...circumferential direction of hub, D...rotational direction of impeller, S1...outer periphery of hub Surface, S2...Back side of hub, Vs...Void.

Claims (4)

a rotating shaft;
a drive unit that rotates the rotating shaft;
an impeller that rotates integrally with the rotating shaft;
a housing that accommodates the rotation shaft, the drive unit, and the impeller, supports the rotation shaft, and has a partition wall that partitions the drive unit and the impeller;
The impeller includes a hub having an outer circumferential surface having a shape whose diameter gradually increases from one side of the rotating shaft to the other side, and a back surface of the outer circumferential surface on the back side in the axial direction of the rotating shaft, and the hub. A centrifugal compressor having a plurality of blades provided on the outer peripheral surface of the centrifugal compressor,
The back surface is provided with a plurality of protrusions that protrude toward the partition wall,
The plurality of blades have a first predetermined interval in a circumferential direction of the hub,
The plurality of protrusions have a second predetermined interval in the circumferential direction of the hub,
A centrifugal compressor, wherein the plurality of blades and the plurality of protrusions are arranged so as to be offset from each other in the circumferential direction of the hub so that they do not overlap in the axial direction of the rotating shaft. The back surface is
a first back surface located closer to the outer diameter side of the impeller than all of the protrusions;
a second back surface located closer to the inner diameter side of the impeller than all of the protrusions;
Since the plurality of protrusions have the second predetermined spacing, there is a space between the protrusions adjacent in the circumferential direction of the hub from the first back surface to the second back surface as the impeller rotates. A gap is formed through which fluid flows,
The centrifugal compressor according to claim 1, wherein an end surface of the protrusion that precedes the rotation direction of the impeller extends radially outward of the hub in the rotation direction of the impeller. The plurality of protrusions are formed around a plurality of circumferences in the radial direction of the hub at third predetermined intervals in the radial direction of the hub,
Among the protrusions adjacent in the radial direction of the hub, the end face of the protrusion located on the radially outer side of the hub is larger than the end face of the protrusion located on the radially inner side of the hub. The centrifugal compressor according to claim 2, which precedes the impeller in the rotational direction. The centrifugal compression according to any one of claims 1 to 3, wherein the partition wall is provided with an annular groove into which the protrusion enters and forms a labyrinth in the radial direction of the hub. Machine.

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