Rotating machinery

Abstract

To efficiently restrain a leakage flow during rotation.SOLUTION: A rotary machine according to an embodiment of the disclosure includes a shaft, an impeller which is attached to the shaft, a housing which stores the shaft and the impeller, a flow passage which is formed between an inner wall surface of the housing and an outer peripheral surface of the shaft and extends along the shaft on a back surface side of the impeller, and a labyrinth seal which is formed in the flow passage. The labyrinth seal has a first protrusion and a second protrusion protruding from the outer peripheral surface or the inner wall surface, and the second protrusion is arranged in a position farther from the impeller than the first protrusion in an axial direction of the shaft. The shaft has a gap formed in a radial inner side with respect to the second protrusion.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to a rotating machine.

Background Art

[0002] Conventionally, in a rotating machine, in order to suppress the leakage flow of fluid from the gap between the shaft and the housing, a non-contact labyrinth seal portion (see, for example, Patent Documents 1 to 4) may be used. Generally, the labyrinth seal portion has a plurality of fins. The plurality of fins complicate the flow path of the fluid in the gap between the shaft and the housing, causing energy loss of the fluid. Thereby, suppression of the leakage flow of the fluid from the gap between the shaft and the housing is achieved.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the labyrinth seal portion as described above, in order to suppress the leakage flow of the fluid, it may be considered to design the gap between the tips of the plurality of fins and the inner wall surface of the housing facing the tips to be sufficiently small. However, considering the influence of tolerances during processing, there is a limit to processing the above gap to be small. Therefore, there is a limit to suppressing the leakage flow of the fluid by such a method.

[0005] This disclosure describes a rotating machine that can effectively suppress leakage flow during rotation. [Means for solving the problem]

[0006] A rotating machine according to one embodiment of the present disclosure comprises a shaft rotatable about a rotation axis, an impeller attached to the shaft, a housing housing the shaft and the impeller, a flow path formed between the inner wall surface of the housing and the outer circumferential surface of the shaft and extending along the shaft on the rear side of the impeller, and a labyrinth seal portion formed in the flow path, wherein the labyrinth seal portion has a first projection and a second projection protruding from the outer circumferential surface or the inner wall surface, the second projection being positioned further from the impeller than the first projection in the axial direction of the shaft, and the shaft having a gap formed radially inward with respect to the second projection.

[0007] In this rotating machine, when the shaft rotates, the area near the impeller, which rotates with the shaft, becomes high pressure, and the pressure decreases as you move away from the impeller. Therefore, the fluid flowing through the passage between the outer surface of the shaft and the inner wall surface of the housing flows in the direction from the first projection on the high-pressure side to the second projection on the low-pressure side. The inventors have diligently studied the relationship between the gap between these projections and the inner wall surface or outer surface and the amount of fluid leakage through that gap, and have found that reducing the gap between the second projection on the low-pressure side and the inner wall surface or outer surface is effective in suppressing fluid leakage. Therefore, in the above rotating machine, in order to reduce the gap between the second projection and the inner wall surface or outer surface, the shaft has a void formed radially inward relative to the second projection. When such a void exists in the shaft, the centrifugal force generated when the shaft rotates makes the part of the shaft outside the void more likely to be displaced radially outward. As a result, the gap between the second projection on the low-pressure side and the inner wall or outer surface can be reduced when the shaft rotates, effectively suppressing fluid leakage in the labyrinth seal. Furthermore, by utilizing the centrifugal force during shaft rotation in this way, advanced assembly techniques to reduce the gap during assembly become unnecessary, and a configuration that reduces the gap between the second projection and the inner wall or outer surface during rotation can be easily realized.

[0008] In some embodiments, the shaft has a first region including a first internal region located radially inward with respect to the first projection, and a second region including a second internal region located radially inward with respect to the second projection and located on the opposite side of the impeller from the first region, wherein the gap is formed only in the second region of the two regions, and may be formed in at least the second internal region within the second region. In this case, the gap between the second projection on the low-pressure side and the inner wall surface or outer surface can be reduced, while the gap between the first projection on the high-pressure side and the inner wall surface or outer surface can be maintained.

[0009] In some embodiments, the second region has an opening that opens axially on the opposite side from the first region, and the void may be formed continuously from the opening to a position that reaches at least the second internal region in the axial direction. In this case, the void can be easily formed by a simple operation of cutting away the second region from the opening.

[0010] In some embodiments, when the shaft is stationary, the radial gap between the first projection and the inner wall surface or outer surface may be the same as the radial gap between the second projection and the inner wall surface or outer surface. In this case, a configuration that reduces the gap between the second projection and the inner wall surface or outer surface when the shaft rotates can be suitably realized.

[0011] In some embodiments, the void may be continuously formed radially between the second projection and the axis of rotation, extending over the entire circumference in the circumferential direction around the axis of rotation. In this case, the centrifugal force during shaft rotation can be used to uniformly reduce the gap between the second projection and the inner wall surface or outer surface at each position along the circumferential direction. As a result, fluid leakage in the labyrinth seal can be suppressed more effectively.

[0012] In some embodiments, the gap may be located radially between the second projection and the axis of rotation, closer to the second projection than to the axis of rotation. In this case, the centrifugal force during shaft rotation can be used to further reduce the gap between the second projection and the inner wall surface or outer surface. As a result, fluid leakage in the labyrinth seal can be more effectively suppressed.

[0013] In some embodiments, the shaft may have a cylindrical portion centered on the axis of rotation and a cylindrical portion centered on the axis of rotation and housing the cylindrical portion, and the gap may be formed by the radial gap between the cylindrical portion and the cylindrical portion. In this case, the centrifugal force during the rotation of the shaft can be used to evenly reduce the gap between the second projection and the inner wall surface or outer surface at each position along the circumferential direction in accordance with the radial outward deformation of the cylindrical portion. As a result, fluid leakage flow in the labyrinth seal can be suppressed more effectively.

[0014] In some embodiments, the shaft may have a cylindrical portion centered on the axis of rotation, and the void may be composed of the entire internal space of the cylindrical portion. In this case, compared to the case where the void is cylindrical, the gap between the second projection and the inner wall surface or outer surface can be made smaller by utilizing the centrifugal force during the rotation of the shaft. As a result, fluid leakage flow in the labyrinth seal can be suppressed more effectively.

[0015] In some embodiments, the rotating machine further comprises a third projection that is further from the impeller in the axial direction than the second projection, and the shaft has a first region including a first internal region located radially inward with respect to the first projection, a second internal region located radially inward with respect to the second projection, and a third internal region located radially inward with respect to the third projection, and a second region located opposite the impeller with respect to the first region, and the gap is formed only in the second of the two regions, and may be formed in at least the second internal region and the third internal region within the second region. In this case, the centrifugal force during rotation of the shaft can be used to reduce the gap between the second projection on the low-pressure side and the inner wall surface or outer surface, and the gap between the third projection and the inner wall surface or outer surface. As a result, fluid leakage flow in the labyrinth seal can be effectively suppressed.

[0016] In some embodiments, the void may be formed only in a portion of the axial direction of the second internal region, or it may be formed throughout the entire axial direction of the third internal region. In this case, the centrifugal force during shaft rotation can be used to make the gap between the third projection, located on the lower pressure side, and the inner wall or outer surface even smaller than the gap between the second projection and the inner wall or outer surface. In other words, the further the projection is located on the lower pressure side, the smaller the gap between the projection and the inner wall or outer surface can be made in stages. As a result, fluid leakage flow in the labyrinth seal can be suppressed more effectively.

[0017] A rotating machine according to another embodiment of the present disclosure comprises a shaft rotatable about a rotation axis, an impeller attached to the shaft, a housing housing the shaft and the impeller, a flow path formed between the inner wall surface of the housing and the outer circumferential surface of the shaft and extending along the shaft on the rear side of the impeller, and a labyrinth seal portion formed in the flow path, the labyrinth seal portion having a cylindrical member arranged to surround the outer circumferential surface of the shaft, and a first projection and a second projection protruding from the outer or inner wall surface of the cylindrical member, wherein the second projection is positioned further from the impeller than the first projection in the axial direction of the shaft, and the cylindrical member has a thin-walled portion that is thinner than the rest of the member at a position facing radially inward from the second projection.

[0018] In this rotating machine, when the shaft rotates, the vicinity of the impeller that rotates with the shaft becomes high pressure, and the pressure becomes lower as the distance from the impeller increases. Therefore, the fluid flowing through the flow path between the outer peripheral surface of the shaft and the inner wall surface of the housing flows in the direction from the first protrusion on the high-pressure side toward the second protrusion on the low-pressure side. Here, as a result of intensive studies on the relationship between the gap between these protrusions and the inner wall surface or the outer peripheral surface and the leakage amount of the fluid flowing through the gap, the inventors have found that reducing the gap between the second protrusion on the low-pressure side and the inner wall surface is effective in suppressing the leakage amount of the fluid. Therefore, in the above rotating machine, in order to reduce the gap between the second protrusion and the inner wall surface or the outer peripheral surface, the cylindrical member has a thin portion on the inner side in the radial direction with respect to the second protrusion. When such a thin portion exists in the cylindrical member, the portion of the cylindrical member outside the thin portion is likely to be displaced outward in the radial direction due to the centrifugal force generated when the shaft rotates. As a result, the gap between the second protrusion on the low-pressure side and the inner wall surface or the outer peripheral surface can be reduced when the shaft rotates, and the leakage amount of the fluid in the labyrinth seal portion can be effectively suppressed. Furthermore, by utilizing the centrifugal force during rotation of the shaft in this way, advanced assembly techniques and the like for reducing the gap during assembly are not required, and a configuration for reducing the gap between the second protrusion and the inner wall surface or the outer peripheral surface during rotation can be easily realized.

Effects of the Invention

[0019] According to some aspects of the present disclosure, a rotating machine capable of effectively suppressing the leakage flow during rotation is provided.

Brief Description of the Drawings

[0020] [Figure 1] FIG. 1 is a cross-sectional view showing a rotating machine according to the first embodiment. [Figure 2] FIG. 2 is a side view showing an enlarged peripheral structure of a labyrinth seal portion included in the rotating machine of FIG. 1. [Figure 3] FIG. 3 is a front view showing a large-diameter portion of a shaft where the labyrinth seal portion of FIG. 2 is provided. [Figure 4]FIG. 4 is a cross-sectional view showing the peripheral structure of the labyrinth seal portion in FIG. 2. [Figure 5] FIG. 5 is an enlarged cross-sectional view showing the peripheral structure of the labyrinth seal portion in FIG. 4. [Figure 6] FIG. 6 is a diagram showing a simulation result indicating the flow of fluid around a conventional labyrinth seal portion during rotation of the shaft. [Figure 7] FIG. 7 is a diagram showing a simulation result indicating the state of deformation of the labyrinth seal portion in FIG. 2 during rotation of the shaft. [Figure 8] FIG. 8 is a cross-sectional view showing a deformation example of the gap formed in the shaft. [Figure 9] FIG. 9 is a cross-sectional view showing another deformation example of the gap formed in the shaft. [Figure 10] FIG. 10 is a cross-sectional view showing a deformation example of the labyrinth seal portion. [Figure 11] FIG. 11 is a cross-sectional view showing a rotating machine according to the second embodiment. [Figure 12] FIG. 12 is a cross-sectional view showing the peripheral structure of the labyrinth seal portion included in the rotating machine of FIG. 11. [Figure 13] FIG. 13 is an enlarged cross-sectional view showing the peripheral structure of the labyrinth seal portion of FIG. 11. <​​​​​​​​​​​Referring to Figure 1, a rotating machine 1 according to the first embodiment will be described. The rotating machine 1 is, for example, an electric supercharger. The rotating machine 1 is applied to, for example, an internal combustion engine in a vehicle or a ship. As shown in Figure 1, the rotating machine 1 comprises a compressor impeller 3 (hereinafter simply referred to as "impeller 3") that rotates around a rotation axis L, a motor 5 which is the power source for the rotation of the impeller 3, and a housing 7 that houses the impeller 3 and the motor 5. The housing 7 has an impeller housing 11 that houses the impeller 3 and a motor housing 13 that houses the motor 5. The impeller housing 11 and the motor housing 13 may each be composed of multiple parts, and the parts that make up each housing and how they are combined can be freely designed.

[0023] The rotating machine 1 further comprises a shaft 12 rotatably arranged around a rotation axis L within the housing 7. The shaft 12 is a cylindrical member extending in the axial direction D1 along which the rotation axis L extends. The shaft 12 is made of a metallic material such as chromium-molybdenum steel (SCM). The outer circumferential surface 12a of the shaft 12 is a circular surface centered on the rotation axis L. The impeller housing 11 and the motor housing 13 are connected to each other in the axial direction D1 along which the rotation axis L extends, and the shaft 12 is provided extending from the inside of the impeller housing 11 to the inside of the motor housing 13. An impeller 3 is attached to one end 12b of the shaft 12 in the axial direction D1. The impeller 3 is fixed to the one end 12b of the shaft 12 by, for example, bolt fastening. Therefore, the impeller 3 rotates together with the shaft 12 around the rotation axis L.

[0024] The motor 5 includes a stator 5a provided in the motor housing 13 and a rotor 5b provided on the shaft 12. The impeller housing 11 includes an intake port 11a, a scroll section 11b, and a discharge port 11c. When an alternating current is passed through the stator 5a, the interaction between the rotor 5b and the stator 5a causes the impeller 3 and the shaft 12 to rotate together around the axis of rotation L. As the impeller 3 rotates, it draws in outside air through the intake port 11a, compresses the intake air through the scroll section 11b, and discharges the compressed air from the discharge port 11c. The compressed air discharged from the discharge port 11c is supplied to the internal combustion engine mentioned above. The type of motor 5 is not limited to the example shown in Figure 1 and can be changed as appropriate according to the required specifications.

[0025] The shaft 12, located within the housing 7, is rotatably supported around the axis of rotation L by, for example, two bearings 20a and 20b. Each of the bearings 20a and 20b is, for example, a grease-lubricated radial ball bearing. Each of the bearings 20a and 20b may be a deep groove ball bearing or an angular contact ball bearing. Bearing 20a is located at one end 12b of the shaft 12, and bearing 20b is located at the other end 12c on the opposite side of the shaft 12. Bearing 20a is located on the rear side of the impeller 3 at one end 12b of the shaft 12.

[0026] The motor housing 13 includes a wall portion 13a that surrounds the bearing 20a on the rear side of the impeller 3. The bearing 20a is fitted inside the wall portion 13a. The fitting relationship between the bearing 20a and the wall portion 13a may be a clearance fit, a partial fit, or a tight fit, and is arbitrary. The wall portion 13a includes an annular projection 13b that protrudes axially D1 toward the impeller 3 from the bearing 20a. The projection 13b surrounds a large-diameter portion 12d provided at one end 12b of the shaft 12. The large-diameter portion 12d is a portion that has a larger outer diameter than the other parts of the shaft 12 and is located between the impeller 3 and the bearing 20a. Here, "other parts" may refer to the parts located before and after the large-diameter portion 12d in the axial direction D1, that is, the parts located on both sides of the large-diameter portion 12d in the axial direction D1.

[0027] The large-diameter portion 12d includes an end face S1 facing the bearing 20a in the axial direction D1, and an end face S2 facing the back surface of the impeller 3 in the axial direction D1. The protruding portion 13b includes an inner circumferential surface 13c (inner wall surface) that faces the outer circumferential surface 12a of the large-diameter portion 12d with a gap in the radial direction D2 of the rotation axis L. The inner circumferential surface 13c is, for example, a circular surface centered on the rotation axis L. The distance between the inner circumferential surface 13c and the outer circumferential surface 12a in the radial direction D2 is constant at each position along the circumferential direction D3 (see Figure 3) centered on the rotation axis L. The outer circumferential surface 12a and the inner circumferential surface 13c are, for example, cylindrical surfaces (side surfaces of a cylinder) centered on the rotation axis L. In this embodiment, the outer circumferential surface 12a and the inner circumferential surface 13c are cylindrical surfaces, but are not necessarily limited to that. For example, in the cross-section shown in Figure 4, which will be described later, the outer circumferential surface 12a and the inner circumferential surface 13c may be represented by straight lines or curved lines that are inclined with respect to the axial direction D1.

[0028] The rotating machine 1 further includes a labyrinth seal portion 30 that seals the flow path G (see Figure 2) between the inner circumferential surface 13c of the wall portion 13a and the outer circumferential surface 12a of the shaft 12. The labyrinth seal portion 30 is positioned on the outer circumferential surface 12a of the shaft 12, facing the back surface of the impeller 3 in the axial direction D1. The back surface of the impeller is the outer surface of the impeller 3 that faces away from the intake port 11a in the axial direction D1. The position facing the back surface of the impeller 3 in the axial direction D1 is a position at one end 12b of the shaft 12 that faces the back surface of the impeller 3 in the axial direction D1, for example, a position between the back surface of the impeller 3 and the bearing 20a in the axial direction D1. In this embodiment, the labyrinth seal portion 30 is provided on the outer circumferential surface 12a of the large diameter portion 12d between the back surface of the impeller 3 and the bearing 20a. The flow path G is a flow path that forms the gap between the inner circumferential surface 13c of the wall portion 13a and the outer circumferential surface 12a of the shaft 12. The flow path G extends along the axial direction D1 in which the shaft 12 extends on the back side of the impeller 3.

[0029] When the shaft 12 rotates, the impeller 3, which rotates with the shaft 12, generates compressed air. As a result, the space near the back of the impeller 3 becomes more pressure than atmospheric pressure, and the pressure decreases as you move away from the back of the impeller 3. Therefore, when the shaft 12 rotates, fluid flows in the direction from the impeller 3 toward the motor 5 (i.e., from left to right in Figure 1). Consequently, leakage flow can occur where the fluid inside the impeller housing 11 passes through the flow path G between the inner circumferential surface 13c and the outer circumferential surface 12a and flows into the motor housing 13. To suppress such leakage flow, a labyrinth seal portion 30 is provided to seal the flow path G between the inner circumferential surface 13c and the outer circumferential surface 12a.

[0030] The labyrinth seal portion 30 and its surrounding structure will be described in detail below. As shown in Figure 2, the labyrinth seal portion 30 has a plurality of fins 31 (a plurality of protrusions). Each fin 31 is integrally formed with the shaft 12. That is, each fin 31 is formed by a part of the shaft 12. Each fin 31 protrudes in an annular shape outward in the radial direction D2 from the outer circumferential surface 12a of the large diameter portion 12d toward the inner circumferential surface 13c, and is arranged at intervals along the axial direction D1. The fact that the plurality of fins 31 protrude in an annular shape outward in the radial direction D2 means that the shape of each fin 31, when viewed from the axial direction D1, is an annular shape that is centered on the axis of rotation L and extends outward in the radial direction D2. Each fin 31 has, for example, the same dimensions and shape as the others. Therefore, the height in the radial direction D2 of each fin 31 (i.e., the distance in the radial direction D2 from the outer circumferential surface 12a to the tip of each fin 31 in the radial direction D2) is the same as the others.

[0031] The multiple fins 31 include, for example, a first fin 31A (first projection), a second fin 31B (second projection), and a third fin 31C (third projection), arranged in order from the impeller 3 (see Figure 1) side in the axial direction D1. The first fin 31A is positioned closest to the impeller 3 among the multiple fins 31. The second fin 31B is positioned further from the impeller 3 than the first fin 31A in the axial direction D1. The third fin 31C is positioned even further from the impeller 3 than the second fin 31B in the axial direction D1. Therefore, the third fin 31C is positioned furthest from the impeller 3 among the multiple fins 31. The first fin 31A, the second fin 31B, and the third fin 31C are, for example, arranged at equal intervals along the axial direction D1. Therefore, the axial distance D1 between the first fin 31A and the second fin 31B is the same as the axial distance D1 between the second fin 31B and the third fin 31C.

[0032] The first fin 31A, the second fin 31B, and the third fin 31C are close to the inner circumferential surface 13c with a gap between them in the radial direction D2. In the stationary state of the shaft 12 (i.e., non-rotating state), the radial gap GA between the first fin 31A and the inner circumferential surface 13c, the radial gap GB between the second fin 31B and the inner circumferential surface 13c, and the radial gap GC between the third fin 31C and the inner circumferential surface 13c are set to be the same, for example, when stationary. Setting the gaps GA, GB, and GC to be the same means that the respective design values ​​of the gaps GA, GB, and GC, taking manufacturing tolerances into account, are the same. Therefore, even if the gaps GA, GB, and GC are slightly different from each other due to manufacturing errors, etc., if the amount of the difference is within the manufacturing tolerance, the gaps GA, GB, and GC can be considered to be set to be the same. Each of the gaps GA, GB, and GC is set to, for example, 100 μm or more. The gaps GA, GB, and GC are all constant at each position along the circumferential direction D3 (see Figure 3).

[0033] As shown in Figure 4, the shaft 12 has a first region R1 where the first fin 31A is located, and a second region R2 where the second fin 31B and the third fin 31C are located. The first region R1 may be, for example, the region from the base end of the first fin 31A (specifically, the end end of the first fin 31A facing the second fin 31B) to the end face S2 in the axial direction D1. The second region R2 is the region located in the axial direction D1 on the opposite side of the impeller 3 from the first region R1. The second region R2 may be, for example, the region from the base end of the first fin 31A to the end face S1 in the axial direction D1.

[0034] A void 40 is formed in the second region R2. On the other hand, no void 40 is formed in the first region R1. In other words, the void 40 is formed only in the second region R2 of the two regions R2. The void 40 is, for example, a hollowed-out portion of the second region R2. The void 40 is, for example, cylindrical with respect to the axis of rotation L and extends in the axial direction D1 in the second region R2. As shown in Figure 3, an opening Sa into which the void 40 opens is formed on the end face S1 of the second region R2. The void 40 is annular when viewed from the axial direction D1 with respect to the axis of rotation L and is formed continuously over the entire circumference in the circumferential direction D3.

[0035] Therefore, the gap 40 is located in the radial direction D2 between the axis of rotation L and the second fin 31B, and also between the axis of rotation L and the third fin 31C. That is, the gap 40 is located inward in the radial direction D2 relative to the second fin 31B and the third fin 31C, and outward in the radial direction D2 relative to the axis of rotation L. The gap 40 is located closer to the second fin 31B and the third fin 31C than to the axis of rotation L in the radial direction D2. In other words, the distance between the gap 40 and the second fin 31B in the radial direction D2 (or the distance between the gap 40 and the third fin 31C in the radial direction D2) is shorter than the distance between the gap 40 and the axis of rotation L in the radial direction D2. Therefore, the thickness of the wall portion of the cylindrical portion 52, which will be described later, in the radial direction D2 is thinner than the width of the cylindrical portion 51 in the radial direction D2. The width of the void 40 in the radial direction D2 is constant at each position along the circumferential direction D3, for example.

[0036] The void 40 is formed continuously along the axial direction D1 from the opening Sa to a position that does not reach the first region R1 in the axial direction D1. The void 40 is formed, for example, by cutting a second region R2 from the opening Sa in the axial direction D1 using an end mill. The second region R2 has a cylindrical portion 51 located inside the void 40 in the radial direction D2 and a cylindrical portion 52 located outside the void 40 in the radial direction D2. The cylindrical portion 51 is cylindrical with respect to the axis of rotation L and is surrounded by the void 40. The cylindrical portion 52 is cylindrical with respect to the axis of rotation L and surrounds the void 40. Therefore, the cylindrical portion 51 is housed in the cylindrical portion 52 and is positioned inside the cylindrical portion 52 in the radial direction D2 via the void 40. In the radial direction D2, the thickness of the wall portion of the cylindrical portion 52 is thinner than the thickness of the cylindrical portion 51 (i.e., the diameter of the cylindrical portion 51). The gap 40 can also be described as being formed by the gap between the cylindrical portion 51 and the cylindrical portion 52 in the radial direction D2. The gap 40 can be defined as the gap region (space region) enclosed by the outer circumferential surface of the cylindrical portion 51 and the inner circumferential surface of the cylindrical portion 52.

[0037] Referring further to Figure 5, the surrounding structure of the void 40 will be described in more detail. As shown in Figure 5, the first region R1 includes at least the first internal region R11. The first internal region R11 is the internal region of the large-diameter portion 12d surrounded by the first fin 31A (i.e., located radially inward D2 relative to the first fin 31A). The first internal region R11 can also be described as the internal region that overlaps with the first fin 31A in the radial direction D2.

[0038] The second region R2 includes at least the second internal region R21 and the third internal region R31. The second internal region R21 is the internal region of the large-diameter portion 12d surrounded by the second fin 31B (i.e., located radially inward D2 relative to the second fin 31B). The second internal region R21 can also be described as the internal region that overlaps with the second fin 31B in the radial direction D2. The third internal region R31 is the internal region of the large-diameter portion 12d surrounded by the third fin 31C (i.e., located radially inward D2 relative to the third fin 31C). The third internal region R31 can also be described as the internal region that overlaps with the third fin 31C in the radial direction D2.

[0039] The second region R2 further includes internal regions R22, R32, and R33. Internal region R22 is located between the first internal region R11 and the second internal region R21 in an axial direction D1. Internal region R22 is surrounded by the outer circumferential surface 12a between the first fin 31A and the second fin 31B, and is located radially inward of the outer circumferential surface 12a in a direction D2. Internal region R32 is located between the second internal region R21 and the third internal region R31 in an axial direction D1. Internal region R32 is surrounded by the outer circumferential surface 12a between the second fin 31B and the third fin 31C, and is located radially inward of the outer circumferential surface 12a in a direction D2. Internal region R33 is located between the third internal region R31 and the end face S1 (see Figure 1). The internal region R33 is surrounded by the outer peripheral surface 12a on the opposite side of the second fin 31B from the third fin 31C, and is located radially inward in the direction D2 with respect to the outer peripheral surface 12a.

[0040] As shown in Figure 5, the void 40 is formed continuously in the axial direction D1 in the second region R2, from the opening Sa (see Figure 3) through the internal region R33, the third internal region R31, and the internal region R32 to the position where it reaches the second internal region R21. Therefore, the void 40 faces the second fin 31B and the third fin 31C in the radial direction D2. The bottom 40a of the void 40 does not reach the internal region R22 of the first internal region R11, but is located in the second internal region R21. The bottom 40a is located in a position that overlaps with the second fin 31B in the radial direction D2. Note that the bottom 40a refers to the end of the void 40 opposite the opening Sa in the axial direction D1. On the other hand, the void 40 is not formed in the first internal region R11 and does not face the first fin 31A in the radial direction D2. In this way, because the gap 40 is formed only at positions facing the second fin 31B and the third fin 31C in the radial direction D2, the portion of the cylindrical part 52 where the second fin 31B and the third fin 31C are located deforms radially outward in D2 more than the portion of the cylindrical part 52 where the first fin 31A is located when subjected to centrifugal force during the rotation of the shaft 12. In other words, the second fin 31B and the third fin 31C are displaced radially outward in D2 more than the first fin 31A when the shaft 12 rotates.

[0041] In the second internal region R21, the tip of the gap 40 is located on the side opposite the opening Sa. Therefore, the tip of the gap 40 is positioned opposite the second fin 31B in the radial direction D2. In the second internal region R21, the gap 40 is not formed over the entire axial direction D1, but only in a part of the axial direction D1. For example, the gap 40 is formed only in the part between the center of the second internal region R21 and the boundary between the second internal region R21 and the internal region R32 in the axial direction D1. In this way, the gap 40 is positioned radially D2 opposite a part of the axial direction D1 of the second fin 31B. Note that in the second region R2, the gap 40 may be formed in a region closer to the internal region R32 than the center of the second internal region R21, or in a region closer to the internal region R22 than the center of the second internal region R21.

[0042] On the other hand, in internal region R32, third internal region R31, and internal region R33, a gap 40 is formed over the entire axial direction D1. Therefore, the gap 40 is opposite to the entire axial direction D1 of the third fin 31C in the radial direction D2. The bottom 40a of the gap 40 is in the same position as the second fin 31B in the axial direction D1, but is spaced apart from the third fin 31C. Therefore, the third fin 31C is further from the bottom 40a of the gap 40 in the axial direction D1 than the second fin 31B. When the cylindrical portion 52 is subjected to centrifugal force during the rotation of the shaft 12, it deforms starting from the bottom 40a of the gap 40. Therefore, the portion of the cylindrical portion 52 where the third fin 31C, which is far from the bottom 40a, is located, deforms more outward in the radial direction D2 than the second fin 31B, which is closer to the bottom 40a, when subjected to centrifugal force during the rotation of the shaft 12. In other words, the third fin 31C is displaced more radially outward in D2 than the second fin 31B when the shaft 12 rotates. As a result, when the shaft 12 rotates, the gap GB between the second fin 31B and the inner surface 13c becomes smaller than the gap GA between the first fin 31A and the inner surface 13c, and the gap GC between the third fin 31C and the inner surface 13c becomes even smaller than the gap GB.

[0043] Thus, by forming a gap 40 in the second internal region R21 and the third internal region R31, it becomes possible to displace the second fin 31B and the third fin 31C outward in the radial direction D2 by utilizing the centrifugal force when the shaft 12 rotates. The amount of displacement of the second fin 31B and the third fin 31C outward in the radial direction D2 when subjected to the centrifugal force when the shaft 12 rotates can be adjusted by the position of the bottom 40a (starting point) of the gap 40 and the thickness of the shaft 12 outside the gap 40 in the radial direction D2 (i.e., the thickness of the wall of the cylindrical portion 52). As described above, when the cylindrical portion 52 is subjected to the centrifugal force when the shaft 12 rotates, it deforms starting from the bottom 40a of the gap 40. Therefore, the further the third fin 31C is from the bottom 40a of the gap 40 in the axial direction D1, the greater the amount of deformation of the third fin 31C outward in the radial direction D2. Furthermore, this deformation amount can also be adjusted by the thickness of the wall portion constituting the cylindrical portion 52. The thicker the wall portion of the cylindrical portion 52, the easier the cylindrical portion 52 is to deform. Therefore, by increasing the thickness of the portion of the cylindrical portion 52 where the third fin 31C is located, the amount of outward displacement of the third fin 31C in the radial direction D2 becomes larger. The displacement amounts of the second fin 35B and the third fin 35C are adjusted to a range in which the second fin 31B and the third fin 31C do not reach the inner circumferential surface 13c. For example, if the design value of the gap GB,GC is set to 100 μm, these displacement amounts are set within a range greater than 0 and less than 100 μm.

[0044] <Effects and Effects> The effects and benefits of the rotating machine 1 described above will now be explained along with the conventional challenges. Conventionally, rotating machines equipped with a labyrinth seal to suppress fluid leakage from the gap between the shaft and the housing have been known. In such rotating machines, in order to improve the sealing performance of the labyrinth seal, it is conceivable to make the design value of the gap between the multiple fins of the labyrinth seal and the inner surface of the housing sufficiently small. However, if this gap is set to a small design value such as less than 100 μm, advanced assembly techniques are required during the assembly of the rotating machine to achieve this gap, so there are limits to how small this gap can be made. Even if the gap between the multiple fins and the inner surface of the housing is adjusted to a design value of less than 100 μm, such adjustment is a minute difference that falls within the range of manufacturing tolerances during assembly, so considering manufacturing tolerances, it is extremely difficult to assemble the machine to achieve such a small gap.

[0045] Furthermore, considering the fluid flow field of the fluid flowing through the labyrinth seal, it is not necessarily effective to sufficiently reduce the gap between the fins and the inner circumferential surface of the housing in order to suppress fluid leakage. The reason for this will be explained with reference to the simulation results shown in Figure 6. The simulation results shown in Figure 6 show the fluid streamlines flowing around the labyrinth seal 130 when the shaft 112 rotates. In Figure 6, the multiple fins 131A, 131B, and 131C of the labyrinth seal 130 are arranged at equal intervals on the outer circumferential surface 112a of the shaft 112. The dimensions and shape of each fin 131A, 131B, and 131C are identical, and the gap between each fin 131A, 131B, and 131C and the inner circumferential surface 113c is identical.

[0046] A compressor impeller is located on the left side of Figure 6. Therefore, when the shaft 112 rotates, the space on the left side of Figure 6 becomes high pressure, and the space on the right side of Figure 6 becomes low pressure. Consequently, the fluid flowing through the labyrinth seal section 130 passes through fins 131A, 131B, and 131C in order. Fluid with high energy flows into fin 131A on the high-pressure side. This fluid diffuses through the gap between fin 131A and the inner circumferential surface 113c into the space between fin 131A and fin 131B, resulting in fluid energy loss. Subsequently, the fluid with reduced energy diffuses through the gap between fin 131B and the inner circumferential surface 113c into the space between fin 131B and fin 131C, resulting in fluid energy loss. Finally, the fluid with further reduced energy diffuses downstream through the gap between fin 131C and the inner circumferential surface 113c.

[0047] Here, the inventors have diligently investigated the relationship between the gap between each fin 131A, 131B, 131C and the inner circumferential surface 113c, and the amount of fluid leakage from the gap. As a result, they have found that reducing the gap between the low-pressure fins 131B, 131C and the inner circumferential surface 113c is effective in suppressing fluid leakage. Since a fluid with high energy flows into the high-pressure fin 131A, if the gap between the fin 131A and the inner circumferential surface 113c is reduced, the expansion angle θ of the fluid that passes through the gap becomes smaller, and the energy loss of the fluid after passing through the gap becomes insufficient. Therefore, even if the gap between the high-pressure fin 131A and the inner circumferential surface 113c is reduced, the amount of fluid leakage cannot be effectively suppressed. On the other hand, since a fluid with reduced energy flows through the low-pressure fins 131B and 131C, reducing the gap between the fins 131B and 131C and the inner circumferential surface 113c is more effective in suppressing the amount of fluid leakage through the gap than in ensuring a fluid expansion angle. However, as mentioned above, there are limits to how much the gap between the fins 131B and 131C and the inner circumferential surface 113c can be reduced.

[0048] Therefore, the inventors conceived of reducing the gap between the second fin 31B and the third fin 31C on the low-pressure side and the inner circumferential surface 13c by displacing the second fin 31B and the third fin 31C outward in the radial direction D2 due to the centrifugal force when the shaft 12 rotates. The inventors then came up with the idea of ​​forming a gap 40 inside the second fin 31B and the third fin 31C in the radial direction D2 in order to displace the second fin 31B and the third fin 31C outward in the radial direction D2 using centrifugal force.

[0049] The simulation results shown in Figure 7 illustrate the deformation of the surrounding structure of the labyrinth seal portion 30 during rotation of the shaft 12 (large diameter portion 12d). In Figure 7, the deformation of the surrounding structure of the labyrinth seal portion 30 is represented by the density of the dots, with denser dots indicating greater deformation. As shown in Figure 7, when the shaft 12 rotates, the cylindrical portion 52 on the outside of the gap 40 deforms due to centrifugal force, expanding outward in the radial direction D2. In response to this deformation, the second fin 31B and the third fin 31C on the outside of the cylindrical portion 52 are displaced outward in the radial direction D2. At this time, as described above, the portion of the cylindrical portion 52 where the third fin 31C, which is farther from the bottom 40a of the gap 40, is located deforms more significantly outward in the radial direction D2. Therefore, the third fin 31C is displaced more far outward in the radial direction D2 than the second fin 31B. As a result, the gap GB between the second fin 31B and the inner surface 13c becomes smaller than the gap GA between the first fin 31A and the inner surface 13c, and the gap GC between the third fin 31C and the inner surface 13c becomes even smaller than the gap GB between the second fin 31B and the inner surface 13c. In the example shown in Figure 7, the gap GB is about 5 μm smaller than the gap GA, and the gap GC is about 7 μm smaller than the gap GB.

[0050] Thus, according to this embodiment, by forming a gap 40 in the second region R2, the gap GB between the second fin 31B on the low-pressure side and the inner circumferential surface 13c, and the gap GC between the third fin 31C on the even lower-pressure side and the inner circumferential surface 13c can be reduced by utilizing the centrifugal force when the shaft 12 rotates. This effectively suppresses fluid leakage flow in the labyrinth seal portion 30. Furthermore, by utilizing the centrifugal force when the shaft 12 rotates, advanced assembly techniques to reduce the gaps GB and GC during assembly are no longer required, and the gaps GB and GC can be easily reduced during rotation. Therefore, according to this embodiment, it is possible to effectively suppress leakage flow during rotation.

[0051] In this embodiment, when the shaft 12 is stationary, the gap GA between the first fin 31A and the inner circumferential surface 13c is the same as the gap GB between the second fin 31B and the inner circumferential surface 13c. In this case, a configuration that reduces the gap GB between the second fin 31B and the inner circumferential surface 13c when the shaft 12 rotates can be suitably realized.

[0052] In this embodiment, the void 40 is formed continuously in the axial direction D1 from the opening Sa to a position that reaches at least the second internal region R21. In this case, the void 40 can be easily formed by a simple operation of cutting away the second region R2 from the opening Sa.

[0053] In this embodiment, the gap is continuously formed over the entire circumference in the circumferential direction D3 between the second fin 31B and the rotation axis L in the radial direction D2. In this case, the centrifugal force during the rotation of the shaft 12 can be used to displace the second fin 31B evenly outward in the radial direction D2, thereby uniformly reducing the gap GB between the second fin 31B and the inner circumferential surface 13c. As a result, fluid leakage flow in the labyrinth seal portion 30 can be suppressed more effectively.

[0054] In this embodiment, the gap 40 is located between the second fin 31B and the rotation axis L in the radial direction D2, and is closer to the second fin 31B than to the rotation axis L. In this case, when the shaft 12 rotates, the second fin 31B can be displaced more significantly outward in the radial direction D2, and the gap GB between the second fin 31B and the inner circumferential surface 13c can be made smaller. As a result, fluid leakage flow in the labyrinth seal portion 30 can be suppressed more effectively.

[0055] In this embodiment, the second region R2 has a cylindrical portion 51 centered on the axis of rotation L and a cylindrical portion 52 centered on the axis of rotation L and housing the cylindrical portion 51, and the gap 40 is formed by the radial gap D2 between the cylindrical portion 51 and the cylindrical portion 52. In this case, the centrifugal force when the shaft 12 rotates can be used to displace the second fin 31B evenly outward in the radial direction D2, and the gap GB between the second fin 31B and the inner circumferential surface 13c can be evenly reduced. As a result, fluid leakage flow in the labyrinth seal portion 30 can be suppressed more effectively.

[0056] In this embodiment, the gap 40 is formed in the second region R2, at least in the second internal region R21 and the third internal region R31. In this case, the centrifugal force during the rotation of the shaft 12 can be used to reduce the gap GB between the second fin 31B, which is farther from the impeller 3 (i.e., located on the low-pressure side), and its inner surface 13c, and the gap GC between the third fin 31C and its inner surface 13c. As a result, fluid leakage flow in the labyrinth seal portion 30 can be suppressed more effectively.

[0057] In this embodiment, the gap 40 is formed only in a portion of the axial direction D1 of the second internal region R21, and is formed throughout the entire axial direction D1 of the third internal region R31. In this case, by utilizing the centrifugal force when the shaft 12 rotates, the gap GC between the third fin 31C, which is located on the lower pressure side, and its inner surface 13c can be made even smaller than the gap GB between the second fin 31B and its inner surface 13c. In other words, the gap between the fin 31 and its inner surface 13c can be reduced in stages, with the fin 31 being located on the lower pressure side. As a result, fluid leakage flow in the labyrinth seal portion 30 can be suppressed more effectively.

[0058] Although a first embodiment of the present disclosure has been described above, the present disclosure is not limited to the first embodiment. As shown in Figure 8, a cylindrical void 40A centered on the axis of rotation L may be formed in the second region R2. In this case, the second region R2 does not have the cylindrical portion 51 of the first embodiment, but only has the cylindrical portion 52, and the entire internal space of the cylindrical portion 52 is configured as the void 40A. In other words, in the example shown in Figure 8, the portion of the second region R2 in which the void 40A is formed is hollow. In the second region R2, the void 40A is formed continuously in the axial direction D1 from the opening Sa (see Figure 3) to the second internal region R21 (see Figure 5) facing the second fin 31B, similar to the first embodiment.

[0059] In the example shown in Figure 8, similar to the first embodiment described above, a gap 40A exists radially D2 inward relative to the second fin 31B and third fin 31C on the low-pressure side. Therefore, by utilizing the centrifugal force during the rotation of the shaft 12, the gap GB between the second fin 31B and the inner circumferential surface 13c, and the gap GC between the third fin 31C and the inner circumferential surface 13c can be reduced. Furthermore, since the third fin 31C is further from the bottom 40a (starting point) of the gap 40A than the second fin 31B in the axial direction D1, when subjected to centrifugal force, the third fin 31C is displaced more radially D2 outward than the second fin 31B. As a result, when the shaft 12 rotates, the gap GC becomes smaller than the gap GB. Therefore, in the example shown in Figure 8, it is possible to reduce the gaps GB and GC when the shaft 12 rotates. As a result, fluid leakage flow in the labyrinth seal portion 30 can be effectively suppressed.

[0060] As shown in Figure 9, a thickened portion 52b may be formed on the wall portion 52a of the cylindrical portion 52A. The cylindrical portion 52A has a configuration in which a thickened portion 52b is formed on the cylindrical portion 52 shown in Figure 8. In the example shown in Figure 9, the void 40B that constitutes the entire internal space of the cylindrical portion 52A extends in the axial direction D1 to a position that extends beyond the second internal region R21 to the internal region R22. That is, the bottom portion 40a of the void 40B is located in the internal region R22 of the second region R2. Therefore, the void 40B is opposite in the radial direction D2 to the entire axial direction D1 of the second fin 31B and the entire axial direction D1 of the third fin 31C.

[0061] The thickened portion 52b is formed continuously, for example, in the axial direction D1 from the bottom portion 40a to a position where it reaches the internal region R32. The thickened portion 52b is the thicker part of the wall portion 52a of the cylindrical portion 52A. The thickened portion 52b protrudes radially inward in D2 more than the other parts of the wall portion 52a excluding the thickened portion 52b, and has a thicker wall than those other parts. As a result, the inner surface S52b of the thickened portion 52b is positioned to protrude radially inward in D2 more than the inner surface S52a of those other parts. The thickened portion 52b is formed at a position facing the second fin 31B in the radial direction D2. On the other hand, the thickened portion 52b is not formed at a position facing the third fin 31C in the radial direction D2. The thickness of the thickened portion 52b may be constant at each position along the axial direction D1, for example.

[0062] In the example shown in Figure 9, the third fin 31C is further from the bottom 40a (starting point) of the gap 40B than the second fin 31B in the axial direction D1. Therefore, when subjected to centrifugal force, the third fin 31C is displaced more significantly outward in the radial direction D2 than the second fin 31B. As a result, the gap GB between the second fin 31B and the inner surface 13c becomes smaller than the gap GA between the first fin 31A and the inner surface 13c, and the gap GC between the third fin 31C and the inner surface 13c becomes even smaller than the gap GB between the second fin 31B and the inner surface 13c.

[0063] In the example shown in Figure 9, a thickened portion 52b is formed at a position opposite to the second fin 31B in the radial direction D2. Therefore, the thickness of the cylindrical portion 52A below the second fin 31C is greater than the thickness of the cylindrical portion 52A below the third fin 31C. The gap between the fin and the inner circumferential surface 13c narrows as it moves away from the bottom 40a in the axial direction D1. However, in this embodiment, the gap between the fin and the inner circumferential surface 13c does not narrow uniformly as it moves away from the bottom 40a in the axial direction D1. Compared to the case where the thickness of the cylindrical portion 52A is constant, when the thickness of the cylindrical portion 52A changes, the amount of deformation of the third fin 31C changes due to the centrifugal force and rigidity of the third fin 31C, with the bottom 40a as the fulcrum. Thus, in the example shown in Figure 9, by forming a portion with a changing thickness (thickened portion 52b) in the cylindrical portion 52A, the amount of change in the gap at the axial position D1 of the fin (i.e., the gap between the fin and the inner circumferential surface 13c) can be adjusted. This makes it possible to more effectively suppress fluid leakage flow in the labyrinth seal portion 30.

[0064] As shown in Figure 10, the labyrinth seal portion 30A may be provided on the inner circumferential surface 13c of the motor housing 13 instead of the outer circumferential surface 12a of the shaft 12 in the flow path G. In this case, each fin 31 of the labyrinth seal portion 30A protrudes radially inward by D2 from the inner circumferential surface 13c toward the outer circumferential surface 12a, and is close to the outer circumferential surface 12a with a gap in the radial direction D2. In the stationary state of the shaft 12 (i.e., non-rotating state), the radial gap GA between the first fin 31A and the inner circumferential surface 13c, the radial gap GB between the second fin 31B and the inner circumferential surface 13c, and the radial gap GC between the third fin 31C and the inner circumferential surface 13c are set to be the same, for example, in the stationary state.

[0065] In the example shown in Figure 10, the third fin 31C is further from the bottom 40a (starting point) of the gap 40 than the second fin 31B. Therefore, when subjected to centrifugal force, the portion of the outer circumferential surface 12a facing the third fin 31C deforms more outward in the radial direction D2 than the portion of the outer circumferential surface 12a facing the second fin 31B. As a result, during rotation, the gap GC between the third fin 31C and the outer circumferential surface 12a becomes smaller than the gap GB between the second fin 31B and the outer circumferential surface 12a. Thus, even in the example shown in Figure 10, similar to the embodiment described above, the gaps GB and GC can be reduced during rotation, making it possible to effectively suppress fluid leakage in the labyrinth seal portion 30A.

[0066] [Second Embodiment] Next, the rotating machine 1A according to the second embodiment will be described with reference to Figures 11 to 13. In describing the second embodiment, the differences from the first embodiment will be the main focus, and explanations that overlap with the first embodiment will be omitted as appropriate.

[0067] The rotating machine 1A according to the second embodiment differs from the rotating machine 1 according to the first embodiment in that it is equipped with a labyrinth seal portion 30B instead of the labyrinth seal portion 30. In the first embodiment, the labyrinth seal portion 30 was integrally formed with the shaft 12, but in the second embodiment, the labyrinth seal portion 30B is formed separately from the shaft 12. As shown in Figure 12, the labyrinth seal portion 30B has a cylindrical member 33 through which the shaft 12 is inserted, and a plurality of fins 35 (a plurality of protrusions) formed on the outer circumferential surface 33a of the cylindrical member 33. The cylindrical member 33 is a cylindrical member centered on the axis of rotation L. As shown in Figure 11, the cylindrical member 33 is attached to the shaft 12 between the impeller 3 and the bearing 20a in the axial direction D1 (see Figure 11). The cylindrical member 33 includes an end face S11 facing the bearing 20a in the axial direction D1, and an end face S12 facing the back surface of the impeller 3 in the axial direction D1.

[0068] As shown in Figure 12, the cylindrical member 33 surrounds the shaft 12, and the inner circumferential surface 33b of the cylindrical member 33 faces the outer circumferential surface 12a of the shaft 12 in the radial direction D2. The cylindrical member 33 rotates together with the shaft 12 around the axis of rotation L. The outer circumferential surface 33a of the cylindrical member 33 faces the inner circumferential surface 13c with a gap between them. The plurality of fins 35 have the same configuration as the plurality of fins 31, except that they are formed on the outer circumferential surface 33a of the cylindrical member 33. The plurality of fins 35 have a first fin 35A (first projection), a second fin 35B (second projection), and a third fin 35C (third projection), corresponding to the first fin 31A, the second fin 31B, and the third fin 31C, respectively. The outer circumferential surface 33a and the inner circumferential surface 13c are, for example, cylindrical surfaces (side surfaces of a cylinder) centered on the axis of rotation L. In this embodiment, the outer circumferential surface 33a and the inner circumferential surface 13c are cylindrical surfaces, but are not necessarily limited to this. For example, in the cross-section shown in Figure 12, which will be described later, the outer circumferential surface 33a and the inner circumferential surface 13c may be represented by straight lines or curved lines inclined with respect to the axial direction D1.

[0069] As shown in Figure 12, the cylindrical member 33 has a first region R1A where the first fin 35A is located, and a second region R2A where the second fin 35B and the third fin 35C are located. The first region R1A may be the region from the base end of the first fin 35A (specifically, the side of the first fin 35A facing the second fin 35B) to the end face S12 (see Figure 11) in the axial direction D1. The second region R2A may be the region from the base end of the first fin 35A to the end face S11 (see Figure 11) in the axial direction D1.

[0070] In this embodiment, a thin-walled portion 33c is formed in the second region R2A. On the other hand, a thin-walled portion 33c is not formed in the first region R1A. In other words, the thin-walled portion 33c is formed only in the second region R2A of the two regions R2A. The thin-walled portion 33c is composed of a part of the cylindrical member 33 and has a thinner wall thickness (i.e., a thickness in the radial direction D2) than the other part 33d of the cylindrical member 33. Therefore, the thickness Tc of the thin-walled portion 33c is thinner than the thickness Td of the other part 33d (see Figure 13). As a result, a gap 41 is formed between the inner circumferential surface 33b of the thin-walled portion 33c and the outer circumferential surface 12a of the shaft 12. The thicknesses Tc and Td may be constant at each position along the axial direction D1, for example.

[0071] As shown in Figure 13, the first region R1A includes at least the first portion R11A of the cylindrical member 33. The first portion R11A is the portion of the cylindrical member 33 surrounded by the first fin 35A, that is, the portion located radially inward D2 relative to the first fin 35A. The first portion R11A can also be described as the portion that overlaps with the first fin 35A when viewed from the radial direction D2. The second region R2A includes at least the second portion R21A and the third portion R31A of the cylindrical member 33. The second portion R21A is the portion of the cylindrical member 33 surrounded by the second fin 35B, that is, the portion located radially inward D2 relative to the second fin 35B. The second portion R21A can also be described as the portion that overlaps with the second fin 35B when viewed from the radial direction D2. The third portion R31A is the portion of the cylindrical member 33 surrounded by the third fin 35C, that is, the portion located radially inward D2 relative to the third fin 35C. The third section R31A can be described as the part that overlaps with the third fin 35C when viewed from the radial direction D2.

[0072] The second region R2A further includes portions R22A, R32A, and R33A. Portion R22A is located between the first portion R11A and the second portion R21A in an axial direction D1. Portion R32A is located between the second portion R21A and the third portion R31A in an axial direction D1. Portion R33A is located between the third portion R31A and the end face S11 (see Figure 11). As shown in Figure 13, the thin-walled portion 33c is formed continuously in the second region R2A across portions R33A, the third portion R31A, portion R32A, and the second portion R21A. Thus, the thin-walled portion 33c faces the second fin 35B and the third fin 35C in the radial direction D2. The bottom 41a of the gap 41 does not reach portion R22A of the first portion R11A, but is located in the second internal region R21. The bottom 41a is located in a position that overlaps with the second fin 35B in the radial direction D2. Note that the bottom 41a refers to the end of the gap 41 opposite to the opening Sa in the axial direction D1. On the other hand, the thin-walled portion 33c is not formed in the first portion R11A and does not face the first fin 35A in the radial direction D2. In this way, by forming the thin-walled portion 33c only in a position that faces the second fin 35B and the third fin 35C in the radial direction D2, the portion of the cylindrical member 33 where the second fin 35B and the third fin 35C are located deforms radially outward in the radial direction D2 more than the portion of the cylindrical member 33 where the first fin 35A is located when subjected to centrifugal force during the rotation of the shaft 12. In other words, the second fin 35B and the third fin 35C are displaced radially outward in D2 compared to the first fin 35A when the shaft 12 rotates.

[0073] In the second portion R21A, the thin-walled portion 33c is not formed over the entire axial direction D1, but only in a portion of the axial direction D1. For example, in the axial direction D1, the thin-walled portion 33c is formed only in the portion between the center of the second portion R21A and the boundary between the second portion R21A and portion R32A. In addition, the thin-walled portion 33c may be formed in the second region R2A in a region closer to portion R32A than the center of the second portion R21A, or in a region closer to portion R22A than the center of the second portion R21A. In this way, the thin-walled portion 33c faces the radial direction D2 with respect to a portion of the axial direction D1 of the second fin 35B.

[0074] On the other hand, in sections R32A, the third section R31A, and R33A, a thin-walled portion 33c is formed over the entire axial direction D1. Therefore, the thin-walled portion 33c faces the radial direction D2 with respect to the entire axial direction D1 of the third fin 35C. The bottom 41a of the gap 41 is in the same position as the second fin 35B in the axial direction D1, while being spaced apart from the third fin 35C. Therefore, the third fin 35C is further from the bottom 41a of the gap 41 in the axial direction D1 than the second fin 35B. When the cylindrical member 33 is subjected to centrifugal force during the rotation of the shaft 12, it deforms starting from the bottom 41a of the gap 41. Therefore, the portion of the cylindrical member 33 where the third fin 35C, which is farther from the starting point (bottom 41a), is located, deforms more outward in the radial direction D2 than the second fin 35B, which is closer to the bottom 41a, when subjected to the centrifugal force during the rotation of the shaft 12. In other words, the third fin 35C is displaced more outward in the radial direction D2 than the second fin 35B when the shaft 12 rotates. As a result, when the shaft 12 rotates, the gap GB between the second fin 35B and the inner circumferential surface 13c becomes smaller than the gap GA between the first fin 35A and the inner circumferential surface 13c, and the gap GC between the third fin 35C and the inner circumferential surface 13c becomes even smaller than the gap GB.

[0075] The amount of displacement of the second fin 35B and the third fin 35C outward in the radial direction D2 when subjected to centrifugal force during the rotation of the shaft 12 can be adjusted by the position of the bottom 41a of the gap 41 and the thickness Tc of the wall portion of the cylindrical member 33 outside the gap 41 in the radial direction D2. As described above, when the cylindrical member 33 is subjected to centrifugal force during the rotation of the shaft 12, it deforms starting from the bottom 41a of the gap 41. Therefore, the further the third fin 35C is from the bottom 41a of the gap 41 in the axial direction D1, the greater the amount of outward deformation of the third fin 35C in the radial direction D2. Furthermore, this amount of deformation can also be adjusted by the thickness Tc of the wall portion constituting the cylindrical member 33. The thicker the wall portion Tc of the cylindrical member 33, the easier the cylindrical member 33 is to deform. A thin-walled portion 33c is formed in the cylindrical member 33 where the third fin 35C is located. By reducing the thickness Tc of the wall portion, it is also possible to further reduce the amount of outward displacement of the third fin 35C in the radial direction D2. The position of the bottom 41a of the gap 41 can be adjusted by the range in which the thin-walled portion 33c is formed in the axial direction D1. The amount of displacement of the second fin 35B and the third fin 35C is adjusted so that the second fin 35B and the third fin 35C do not reach the inner circumferential surface 13c. For example, if the design value of the gap GB,GC is set to 100 μm, these displacement amounts are set within a range greater than 0 and less than 100 μm.

[0076] <Effects and Effects> The rotating machine 1A according to the second embodiment described above can obtain the same effects as the rotating machine 1 according to the first embodiment. Specifically, by forming a thin-walled portion 33c in the second region R2A of the cylindrical member 33, the gap GB between the second fin 35B on the low-pressure side and the inner circumferential surface 13c, and the gap GC between the third fin 35C on the even lower-pressure side and the inner circumferential surface 13c can be reduced by utilizing the centrifugal force when the shaft 12 rotates. As a result, for the same reasons as described above, the effect of suppressing fluid leakage flow in the labyrinth seal portion 30B can be effectively obtained. Furthermore, by utilizing the centrifugal force when the shaft 12 rotates, advanced assembly techniques to reduce the gaps GB and GC during assembly are no longer required, and the gaps GB and GC can be easily reduced during rotation. Therefore, according to this embodiment, it is possible to effectively suppress leakage flow during rotation.

[0077] The rotating machinery described herein is not limited to the embodiments and modifications described above, and various other modifications are possible. For example, the embodiments and modifications described above may be combined with each other to the extent that they do not contradict each other, depending on the required purpose and effect. For example, the rotating machinery 1A shown in Figure 11 may be fitted with the thickened section 52b shown in Figure 9, or the labyrinth seal section 30A shown in Figure 10. In the embodiments described above, a configuration in which a compressor impeller is attached to the end of the shaft has been described, but a configuration in which a compressor impeller and a turbine impeller are attached to both ends of the shaft, respectively, is also possible. In this case, the "impeller" in this disclosure may be either a compressor impeller or a turbine impeller. When the shaft rotates, the pressure is high near the rotating compressor impeller and turbine impeller, and decreases as you move away from the compressor impeller and turbine impeller (i.e., as you approach the central part of the shaft).

[0078] If the “impeller” in this disclosure is considered as a compressor impeller attached to one end of a shaft, then the fin on the high-pressure side closer to the compressor impeller at that end can be considered the “first projection,” and the fin on the low-pressure side further from the compressor impeller (i.e., closer to the center of the shaft) can be considered the “second projection.” If the “impeller” in this disclosure is considered as a turbine impeller attached to the other end of a shaft, then the fin on the high-pressure side closer to the turbine impeller at that other end can be considered the “first projection,” and the fin on the low-pressure side further from the turbine impeller (i.e., closer to the center of the shaft) can be considered the “second projection.” Therefore, regardless of whether the “impeller” in this disclosure is considered as a compressor impeller or a turbine impeller, the “second projection” is located on the low-pressure side than the “first projection.” By displacing the “second projection” on the low-pressure side radially outward through the formation of a gap or thin-walled section, it becomes possible to effectively suppress fluid leakage flow in the labyrinth seal section.

[0079] In the embodiments described above, the first fin on the high-pressure side is considered the "first projection" of this disclosure, and the second fin on the low-pressure side adjacent to the first fin is considered the "second projection" of this disclosure. However, the "first projection" and the "second projection" do not necessarily have to be adjacent, and another projection may be positioned between the "first projection" and the "second projection". For example, the first fin may be considered the "first projection," and the third fin on the low-pressure side, which is aligned with the first fin via the second fin, may be considered the "second projection." Furthermore, in the embodiments described above, the cases in which the "first projection," "second projection," and "third projection" are fins have been explained, but these projections do not have to be fin-shaped and may have other shapes. For example, these projections may be rectangular convex portions that protrude radially outward.

[0080] [Note] A rotating machine according to one embodiment of the present disclosure is described in the following [1] to

[11] , and these have been described in detail based on the embodiments and modifications described above. [1] A shaft that can rotate around the axis of rotation, An impeller attached to the aforementioned shaft, A housing that accommodates the shaft and the impeller, A flow path is formed between the inner wall surface of the housing and the outer circumferential surface of the shaft, and extends along the shaft on the rear side of the impeller, The flow path comprises a labyrinth seal portion formed therein, The labyrinth seal portion has a first projection and a second projection that protrude from the outer circumferential surface or the inner wall surface, The second projection is positioned further from the impeller than the first projection in the axial direction of the shaft. The shaft has a gap formed radially inward relative to the second projection, and is a rotating machine. [2] The shaft is A first region including a first internal region located radially inward with respect to the first projection, It includes a second internal region located radially inward from the second projection and a second region located on the opposite side from the impeller relative to the first region, The rotating machine according to [1], wherein the void is formed only in the second region of the first and second regions, and is formed in at least the second internal region within the second region. [3] The second region has an opening that opens in the axial direction opposite to the first region, The rotating machine according to [2], wherein the gap is formed continuously in the axial direction from the opening to a position that reaches at least the second internal region. [4] The rotating machine according to [1] or [2], wherein, in the stationary state of the shaft, the radial gap between the first projection and the inner wall surface or the outer circumferential surface is the same as the radial gap between the second projection and the inner wall surface or the outer circumferential surface. [5] The gap is formed continuously over the entire circumference in the circumferential direction with respect to the rotation axis, between the second projection and the rotation axis in the radial direction, according to any one of [1] to [4]. [6] The rotating machine according to [5], wherein the gap is located between the second projection and the axis of rotation in the radial direction, and is closer to the second projection than to the axis of rotation. [7] The shaft has a cylindrical portion centered on the axis of rotation and a cylindrical portion centered on the axis of rotation and housing the cylindrical portion, The rotating machine according to [5] or [6], wherein the gap is formed by the radial gap between the cylindrical portion and the cylindrical portion. [8] The shaft has a cylindrical portion centered on the axis of rotation, The aforementioned void is comprised of the entire internal space of the cylindrical portion, as described in any one of [1] to [4]. [9] Further comprising a third projection that is further further from the impeller than the second projection in the axial direction, The aforementioned shaft is A first region including a first internal region located radially inward with respect to the first projection, The second region includes a second internal region located radially inward with respect to the second projection, and a third internal region located radially inward with respect to the third projection, and is located on the opposite side of the impeller from the first region, The rotating machine according to any one of [1] to [8], wherein the void is formed only in the second region of the first and second regions, and is formed in at least the second internal region and the third internal region within the second region.

[10] The rotating machine according to [9], wherein the gap is formed only in a portion of the axial direction of the second internal region and extends throughout the entire axial direction of the third internal region.

[11] A shaft that can rotate around the axis of rotation, An impeller attached to the aforementioned shaft, A housing that accommodates the shaft and the impeller, A flow path is formed between the inner wall surface of the housing and the outer circumferential surface of the shaft, and extends along the shaft on the rear side of the impeller, The flow path comprises a labyrinth seal portion formed therein, The labyrinth seal portion comprises a cylindrical member arranged to surround the outer circumferential surface of the shaft, and a first projection and a second projection protruding from the outer circumferential surface or the inner wall surface of the cylindrical member. The second projection is positioned further from the impeller than the first projection in the axial direction of the shaft. The cylindrical member has a thin-walled portion that is thinner than the rest of the cylindrical member, located radially inward from the second projection. [Explanation of symbols]

[0081] 1.1A Rotating Machinery 3. Compressor impeller 7 Housing 12 shafts 12a Outer surface 12b One end 13c Inner peripheral surface (inner wall surface) 30, 30A, 30B Labyrinth seal section 31,35 Fins (protrusions) 31A, 35A First fin (first projection) 31B, 35B Second fin (second protrusion) 31C, 35C Third fin (third protrusion) 33 Cylindrical member 33c Thin wall part 40,40A,40B void 51 Cylindrical section 52 Cylindrical section D1 Axial direction D2 radial direction D3 Circumferential direction G channel GA, GB, GC gap L Rotation axis R1,R1A 1st area R2,R2A 2nd area R11 1st internal area R11A 1st part R21 2nd internal area R21A 2nd part R31 3rd internal area Sa opening

Claims

1. A shaft that can rotate around the axis of rotation, An impeller attached to the aforementioned shaft, A housing that accommodates the shaft and the impeller, A flow path is formed between the inner wall surface of the housing and the outer circumferential surface of the shaft, and extends along the shaft on the rear side of the impeller, The flow path comprises a labyrinth seal portion formed therein, The labyrinth seal portion has a first projection and a second projection that protrude from the outer circumferential surface or the inner wall surface, The second projection is positioned further from the impeller than the first projection in the axial direction of the shaft. The shaft has a gap formed radially inward with respect to the second projection. The aforementioned shaft is A first region including a first internal region located radially inward from the first projection, It includes a second internal region located radially inward from the second projection and a second region located on the opposite side from the impeller relative to the first region, The gap is formed only in the second region of the first and second regions, and is formed in at least the second internal region within the second region, in a rotating machine.

2. The second region has an opening that opens in the axial direction opposite to the first region, The rotating machine according to claim 1, wherein the gap is formed continuously in the axial direction from the opening to a position that reaches at least the second internal region.

3. The rotating machine according to claim 1, wherein, in the stationary state of the shaft, the radial gap between the first projection and the inner wall surface or the outer circumferential surface is the same as the radial gap between the second projection and the inner wall surface or the outer circumferential surface.

4. The rotating machine according to claim 1 or 2, wherein the gap is formed continuously over the entire circumference in the circumferential direction centered on the rotation axis, between the second projection and the rotation axis in the radial direction.

5. The rotating machine according to claim 4, wherein the gap is located closer to the second projection than to the rotation axis in the radial direction between the second projection and the rotation axis.

6. The shaft has a cylindrical portion centered on the axis of rotation and a cylindrical portion centered on the axis of rotation and housing the cylindrical portion. The rotating machine according to claim 4, wherein the gap is formed by the radial gap between the cylindrical portion and the cylindrical portion.

7. The shaft has a cylindrical portion centered on the axis of rotation, The rotating machine according to claim 1 or 2, wherein the gap is formed by the entire internal space of the cylindrical portion.

8. The system further comprises a third projection that is further located further from the impeller than the second projection in the axial direction, The second region further includes a third internal region located radially inward with respect to the third projection, The rotating machine according to claim 1 or 2, wherein the gap is formed in at least the second internal region and the third internal region in the second region.

9. The rotating machine according to claim 8, wherein the gap is formed only in a portion of the axial direction of the second internal region and is formed over the entire axial direction of the third internal region.

10. A shaft that can rotate around the axis of rotation, An impeller attached to the aforementioned shaft, A housing that accommodates the shaft and the impeller, A flow path is formed between the inner wall surface of the housing and the outer circumferential surface of the shaft, and extends along the shaft on the rear side of the impeller, The flow path comprises a labyrinth seal portion formed therein, The labyrinth seal portion comprises a cylindrical member arranged to surround the outer circumferential surface of the shaft, and a first projection and a second projection protruding from the outer circumferential surface or the inner wall surface of the cylindrical member. The second projection is positioned further from the impeller than the first projection in the axial direction of the shaft. The cylindrical member has a thin-walled portion that is thinner than the other portion, radially inward from the second projection. The cylindrical member is A first region located radially inward with respect to the first projection, It has a second region located radially inward from the second projection and on the opposite side of the impeller from the first region, The thin-walled portion is formed only in the second region of the first region and the second region. A rotating machine in which a gap is formed between the inner surface of the thin-walled portion and the outer surface of the shaft.

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