JP2024000122A - Rotary machine - Google Patents

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 This disclosure relates to rotating machines.

Conventionally, in rotating machines, non-contact labyrinth seals (see, for example, Patent Documents 1 to 4) are sometimes used to suppress fluid leakage from a gap between a shaft and a housing. Generally, a labyrinth seal has a plurality of fins. The plurality of fins complicates the fluid flow path in the gap between the shaft and the housing, causing energy loss of the fluid. Thereby, leakage of fluid from the gap between the shaft and the housing can be suppressed.

Japanese Patent Application Publication No. 2002-357103 Japanese Patent Application Publication No. 2018-021574 Japanese Patent Application Publication No. 11-343996 Utility Model Publication No. 3-118362

In the labyrinth seal portion as described above, in order to suppress fluid leakage, it is conceivable to design the gaps between the tips of the plurality of fins and the inner wall surface of the housing facing the tips to be sufficiently small. However, when considering the influence of tolerances during processing, there is a limit to processing the above-mentioned gap to make it smaller. Therefore, there is a limit to the ability to suppress fluid leakage by such a method.

The present disclosure describes a rotating machine that can effectively suppress leakage flow during rotation.

A rotating machine according to an embodiment of the present disclosure includes a shaft rotatable around a rotation axis, an impeller attached to the shaft, a housing that accommodates the shaft and the impeller, and an inner wall surface of the housing and an outer peripheral surface of the shaft. The labyrinth seal includes a first projection protruding from the outer circumferential surface or the inner wall surface, and a labyrinth seal portion formed in the flow path. The shaft has a second protrusion, the second protrusion is located farther from the impeller than the first protrusion in the axial direction of the shaft, and the shaft has a gap formed radially inward with respect to the second protrusion. .

In this rotating machine, when the shaft rotates, the pressure is high near the impeller that rotates with the shaft, and the pressure becomes low 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 a 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 circumferential surface and the amount of fluid leaking through the gap, the inventors found that the second protrusion on the low pressure side and the inner It has been found that reducing the gap between the wall surface or the outer peripheral surface is effective in suppressing the amount of fluid leakage. Therefore, in the above rotary machine, the shaft has a gap formed radially inside the second protrusion in order to reduce the gap between the second protrusion and the inner wall surface or the outer circumferential surface. When such a gap exists in the shaft, centrifugal force generated when the shaft rotates tends to displace the portion of the shaft outside the gap radially outward. As a result, the gap between the second protrusion on the low pressure side and the inner wall surface or outer circumferential surface can be reduced during rotation of the shaft, and the amount of fluid leaking from the labyrinth seal portion can be effectively suppressed. Furthermore, by utilizing the centrifugal force when the shaft rotates in this way, there is no need for advanced assembly techniques to reduce the gap during assembly, and the second protrusion and the inner wall surface or outer circumferential surface do not connect with each other during rotation. A configuration that reduces the gap can be easily realized.

In some aspects, the shaft includes a first region including a first interior region located radially inwardly with respect to the first projection and a second interior region located radially inwardly with respect to the second projection. and a second region located on the opposite side of the impeller with respect to the first region, the gap is formed only in the second region of the first region and the second region, and the gap is formed only in the second region of the first region and the second region. It may be formed in at least the second internal region of the two regions. In this case, it is possible to reduce the gap between the second protrusion on the low pressure side and the inner wall surface or outer circumferential surface, while maintaining the gap between the first protrusion on the high pressure side and the inner wall surface or outer circumferential surface.

In some embodiments, the second region has an opening that opens on the opposite side of the first region in the axial direction, and the void is continuous in the axial direction from the opening to at least the second interior region. may be formed. In this case, the gap can be easily formed by a simple operation of cutting the second region from the opening.

In some embodiments, when the shaft is at rest, the radial gap between the first protrusion and the inner wall surface or the outer circumferential surface may be the same as the radial gap between the second protrusion and the inner wall surface or the outer circumferential surface. good. In this case, it is possible to suitably realize a configuration in which the gap between the second protrusion and the inner wall surface or the outer circumferential surface is reduced when the shaft rotates.

In some embodiments, the gap may be continuously formed between the second protrusion and the rotation axis in the radial direction over the entire circumference in the circumferential direction centering on the rotation axis. In this case, the gap between the second protrusion and the inner wall surface or outer circumferential surface can be uniformly reduced at each position along the circumferential direction by using the centrifugal force generated when the shaft rotates. As a result, fluid leakage in the labyrinth seal can be more effectively suppressed.

In some embodiments, the gap may be located closer to the second protrusion than the rotation axis between the second protrusion and the rotation axis in the radial direction. In this case, the gap between the second protrusion and the inner wall surface or outer circumferential surface can be further reduced by utilizing the centrifugal force generated when the shaft rotates. As a result, fluid leakage in the labyrinth seal can be more effectively suppressed.

In some embodiments, 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, and the gap is formed in a radial direction between the cylindrical portion and the cylindrical portion. It may be constituted by a gap between. In this case, the gap between the second protrusion and the inner wall surface or outer circumferential surface is equalized at each position along the circumferential direction according to the deformation of the cylindrical portion radially outward by using the centrifugal force generated when the shaft rotates. It can be made smaller. As a result, fluid leakage in the labyrinth seal can be more effectively suppressed.

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

In some aspects, the rotary machine further comprises a third protrusion axially further from the impeller than the second protrusion, and the shaft includes a first interior region located radially inward with respect to the first protrusion. a first region, a second internal region located radially inward with respect to the second protrusion, and a third internal region located radially inward with respect to the third protrusion; a second region located on the opposite side of the impeller, the gap is formed only in the second region of the first region and the second region, and in the second region, at least the second internal region and It may be formed in the third internal region. In this case, the gap between the second protrusion on the low pressure side and the inner wall surface or outer circumferential surface and the gap between the third protrusion and the inner wall surface or outer circumferential surface can be reduced by using the centrifugal force generated when the shaft rotates. As a result, fluid leakage in the labyrinth seal portion can be effectively suppressed.

In some embodiments, the void may be formed only in a portion of the second internal region in the axial direction, and may be formed throughout the entire third internal region in the axial direction. In this case, by utilizing the centrifugal force generated when the shaft rotates, the gap between the third protrusion located on the lower pressure side and the inner wall surface or outer circumferential surface is further increased than the gap between the second protrusion and the inner wall surface or outer circumferential surface. Can be made smaller. In other words, the closer the protrusion is located to the low pressure side, the smaller the gap between the protrusion and the inner wall surface or the outer peripheral surface can be made in stages. As a result, fluid leakage in the labyrinth seal can be more effectively suppressed.

A rotating machine according to another embodiment of the present disclosure includes a shaft rotatable around a rotation axis, an impeller attached to the shaft, a housing that accommodates the shaft and the impeller, and an inner wall surface of the housing and an outer peripheral surface of the shaft. A flow path is formed between the impeller and extends along the shaft on the back side of the impeller, and a labyrinth seal portion is formed in the flow path, and the labyrinth seal portion is a cylinder arranged to surround the outer peripheral surface of the shaft a member, and a first protrusion and a second protrusion protruding from the outer peripheral surface or inner wall surface of the cylindrical member, the second protrusion being disposed at a position farther from the impeller than the first protrusion in the axial direction of the shaft, and the cylindrical member has a thin portion that is thinner than other portions at a position radially inwardly facing the second protrusion.

In this rotating machine, when the shaft rotates, the pressure is high near the impeller that rotates with the shaft, and the pressure becomes low 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 a 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 circumferential surface and the amount of fluid leaking through the gap, the inventors found that the second protrusion on the low pressure side and the inner It has been found that reducing the gap with the wall surface is effective in suppressing the amount of fluid leakage. Therefore, in the above-mentioned rotating machine, the cylindrical member has a thin portion on the radially inner side of the second protrusion in order to reduce the gap between the second protrusion and the inner wall surface or the outer circumferential surface. When such a thin wall portion exists in the cylindrical member, a portion of the cylindrical member outside the thin wall portion is likely to be displaced radially outward due to 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 outer circumferential surface can be reduced during rotation of the shaft, and the amount of fluid leaking from the labyrinth seal portion can be effectively suppressed. Furthermore, by utilizing the centrifugal force when the shaft rotates in this way, there is no need for advanced assembly techniques to reduce the gap during assembly, and the second protrusion and the inner wall surface or outer circumferential surface do not connect with each other during rotation. A configuration that reduces the gap can be easily realized.

According to some aspects of the present disclosure, a rotating machine that can effectively suppress leakage flow during rotation is provided.

FIG. 1 is a sectional view showing a rotating machine according to a first embodiment. FIG. 2 is an enlarged side view showing a peripheral structure of a labyrinth seal portion included in the rotating machine of FIG. 1. FIG. FIG. 3 is a front view showing a large diameter portion of the shaft where the labyrinth seal portion of FIG. 2 is provided. FIG. 4 is a sectional view showing the peripheral structure of the labyrinth seal portion of FIG. 2. FIG. FIG. 5 is an enlarged cross-sectional view showing the peripheral structure of the labyrinth seal portion of FIG. 4. FIG. FIG. 6 is a diagram showing simulation results showing the flow of fluid around a conventional labyrinth seal portion when the shaft rotates. FIG. 7 is a diagram showing simulation results showing how the labyrinth seal portion of FIG. 2 deforms when the shaft rotates. FIG. 8 is a cross-sectional view showing a modification of the gap formed in the shaft. FIG. 9 is a sectional view showing another modification of the gap formed in the shaft. FIG. 10 is a sectional view showing a modification of the labyrinth seal portion. FIG. 11 is a sectional view showing a rotating machine according to the second embodiment. FIG. 12 is a cross-sectional view showing the peripheral structure of the labyrinth seal portion included in the rotating machine of FIG. 11. FIG. 13 is an enlarged cross-sectional view showing the peripheral structure of the labyrinth seal portion of FIG. 11.

Embodiments of the present disclosure will be described below with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description will be omitted.

[First embodiment]
With reference to FIG. 1, a rotating machine 1 according to a 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 of a vehicle or a ship. As shown in FIG. 1, the rotating machine 1 includes a compressor impeller 3 (hereinafter simply referred to as "impeller 3") that rotates around a rotation axis L, a motor 5 that is a power source for rotation of the impeller 3, A housing 7 that accommodates an impeller 3 and a motor 5 is provided. The housing 7 includes an impeller housing 11 that accommodates the impeller 3 and a motor housing 13 that accommodates the motor 5. The impeller housing 11 and the motor housing 13 may each be composed of a plurality of parts, and the parts constituting each housing and the way they are combined can be freely designed.

The rotating machine 1 further includes a shaft 12 rotatably arranged around the rotation axis L inside the housing 7 . The shaft 12 is a cylindrical member extending in the axial direction D1 in which the rotation axis L extends. The shaft 12 is made of a metal material such as chromium molybdenum steel (SCM). The outer circumferential surface 12a of the shaft 12 is a circumferential 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 in which the rotational axis L extends, and the shaft 12 is provided from the inside of the impeller housing 11 to the inside of the motor housing 13. The impeller 3 is attached to one end 12b of the shaft 12 in the axial direction D1. The impeller 3 is fixed to one end 12b of the shaft 12 by, for example, bolting. Therefore, the impeller 3 rotates around the rotation axis L integrally with the shaft 12.

Motor 5 includes a stator 5a provided on motor housing 13 and a rotor 5b provided on shaft 12. Impeller housing 11 includes an intake port 11a, a scroll portion 11b, and a discharge port 11c. When an alternating current is applied to the stator 5a, the impeller 3 and the shaft 12 rotate together around the rotation axis L due to the interaction between the rotor 5b and the stator 5a. When the impeller 3 rotates, the impeller 3 sucks in external air through the suction port 11a, compresses the suction air through the scroll portion 11b, and discharges compressed air from the discharge port 11c. Compressed air discharged from the discharge port 11c is supplied to the aforementioned internal combustion engine. The type of motor 5 is not limited to the example shown in FIG. 1, and can be changed as appropriate according to required specifications.

The shaft 12 provided in the housing 7 is rotatably supported around the rotation axis 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, 20b may be a deep groove ball bearing or an angular contact ball bearing. The bearing 20a is provided at one end 12b of the shaft 12, and the bearing 20b is provided at the other end 12c on the opposite side of the shaft 12. The bearing 20a is provided on the back side of the impeller 3 at one end 12b of the shaft 12.

The motor housing 13 includes a wall portion 13a surrounding the bearing 20a on the back 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, an intermediate fit, or a tight fit, and may be arbitrary. The wall portion 13a includes an annular protrusion 13b that protrudes in the axial direction D1 toward the impeller 3 than the bearing 20a. The protruding portion 13b surrounds a large diameter portion 12d provided at one end portion 12b of the shaft 12. The large diameter portion 12d is a portion having a larger outer diameter than other portions of the shaft 12, and is located between the impeller 3 and the bearing 20a. The "other parts" here may refer to parts located before and after the large diameter part 12d in the axial direction D1, that is, parts located on both sides of the large diameter part 12d in the axial direction D1.

The large diameter portion 12d includes an end surface S1 facing the bearing 20a in the axial direction D1, and an end surface 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 circumferential 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 FIG. 3) centered on the rotation axis L. The outer circumferential surface 12a and the inner circumferential surface 13c are, for example, cylindrical surfaces centered on the rotation axis L (side surfaces of the cylinder). In addition, although the outer peripheral surface 12a and the inner peripheral surface 13c of this embodiment are cylindrical surfaces, they are not necessarily limited thereto. For example, in the cross section shown in FIG. 4, which will be described later, the outer circumferential surface 12a and the inner circumferential surface 13c may be represented by a straight line inclined with respect to the axial direction D1 or a line including a curve.

The rotating machine 1 further includes a labyrinth seal portion 30 that seals the flow path G (see FIG. 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 disposed on the outer circumferential surface 12a of the shaft 12 at a position 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 facing away from the suction port 11a in the axial direction D1. The position facing the back surface of the impeller 3 in the axial direction D1 refers to the position facing the back surface of the impeller 3 in the axial direction D1 at one end 12b of the shaft 12, for example, the position facing the back surface of the impeller 3 and the bearing 20a in the axial direction D1. A good position is between. In this embodiment, the labyrinth seal portion 30 is provided on the outer peripheral 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 constitutes a gap between the inner peripheral surface 13c of the wall portion 13a and the outer peripheral 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.

When the shaft 12 rotates, the impeller 3 rotating together with the shaft 12 generates compressed air, so the pressure in the space near the back of the impeller 3 is higher than atmospheric pressure, and the pressure becomes lower as the distance from the back of the impeller 3 increases. Therefore, when the shaft 12 rotates, fluid flows in a direction from the impeller 3 toward the motor 5 (that is, in a direction from left to right in FIG. 1). As a result, a leakage flow may occur in which the fluid inside the impeller housing 11 flows into the motor housing 13 through the flow path G between the inner circumferential surface 13c and the outer circumferential surface 12a. In order 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.

The labyrinth seal portion 30 and its surrounding structure will be described in detail below. As shown in FIG. 2, the labyrinth seal portion 30 has a plurality of fins 31 (a plurality of protrusions). Each fin 31 is constructed integrally with the shaft 12. That is, each fin 31 is constituted by a part of the shaft 12. Each fin 31 protrudes outward in the radial direction D2 in an annular shape from the outer circumferential surface 12a of the large diameter portion 12d toward the inner circumferential surface 13c, and is lined up at intervals along the axial direction D1. The plurality of fins 31 projecting outward in the radial direction D2 in an annular shape means that the shape of each fin 31 when viewed from the axial direction D1 is a circle centered on the rotation axis L and extending outward in the radial direction D2. It means to be circular. For example, each fin 31 has the same size and shape. Therefore, the height of each fin 31 in the radial direction D2 (that is, the distance in the radial direction D2 from the outer peripheral surface 12a to the tip of each fin 31 in the radial direction D2) is the same.

For example, the plurality of fins 31 include, in order from the impeller 3 (see FIG. 1) side in the axial direction D1, a first fin 31A (first protrusion), a second fin 31B (second protrusion), and a third fin 31C ( 3rd protrusion). The first fin 31A is located closest to the impeller 3 among the plurality of fins 31. The second fin 31B is located farther from the impeller 3 than the first fin 31A in the axial direction D1. The third fin 31C is located further away from the impeller 3 than the second fin 31B in the axial direction D1. Therefore, the third fin 31C is disposed farthest from the impeller 3 among the plurality of fins 31. The first fin 31A, the second fin 31B, and the third fin 31C are arranged at equal intervals along the axial direction D1, for example. Therefore, the distance between the first fin 31A and the second fin 31B in the axial direction D1 is the same as the distance between the second fin 31B and the third fin 31C in the axial direction D1.

The first fin 31A, the second fin 31B, and the third fin 31C are close to the inner circumferential surface 13c with a gap in the radial direction D2. When the shaft 12 is in a stationary state (that is, a non-rotating state), a gap GA in the radial direction D2 between the first fin 31A and the inner circumferential surface 13c, a gap GB in the radial direction D2 between the second fin 31B and the inner circumferential surface 13c, and For example, the gap GC in the radial direction D2 between the third fin 31C and the inner peripheral surface 13c is set to be the same when the fin is at rest. Setting the gaps GA, GB, and GC to be the same means that the design values of the gaps GA, GB, and GC are the same in consideration of manufacturing tolerances. Therefore, even if the gaps GA, GB, and GC slightly deviate from each other due to manufacturing errors, as long as the amount of deviation is within the manufacturing tolerance, it is assumed that the gaps GA, GB, and GC are set to be the same. It's okay. Each of the gaps GA, GB, and GC is set to, for example, 100 μm or more. Each of the gaps GA, GB, and GC is constant at each position along the circumferential direction D3 (see FIG. 3).

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

A void 40 is formed in the second region R2. On the other hand, no void 40 is formed in the first region R1. That is, the void 40 is formed only in the second region R2 of the first region R1 and the second region R2. The void 40 is, for example, a hollowed out portion in which a portion of the second region R2 is hollowed out. The void 40 has, for example, a cylindrical shape centered on the rotation axis L, and extends in the axial direction D1 in the second region R2. As shown in FIG. 3, an opening Sa through which the void 40 opens is formed in the end surface S1 of the second region R2. The gap 40 has an annular shape centered on the rotation axis L when viewed from the axial direction D1, and is continuously formed over the entire circumference in the circumferential direction D3.

Therefore, the gap 40 is located between the rotation axis L and the second fin 31B, and also between the rotation axis L and the third fin 31C in the radial direction D2. That is, the void 40 is located at a position spaced inward in the radial direction D2 with respect to the second fin 31B and the third fin 31C, and is located in a position spaced apart outward in the radial direction D2 with respect to the rotation axis L. The void 40 is located closer to the second fin 31B and the third fin 31C than the rotation axis L in the radial direction D2. In other words, the distance between the air gap 40 and the second fin 31B in the radial direction D2 (or the distance between the air gap 40 and the third fin 31C in the radial direction D2) is greater than the distance between the air gap 40 and the rotation axis L in the radial direction D2. It's also short. 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 gap 40 in the radial direction D2 is, for example, constant at each position along the circumferential direction D3.

The void 40 is continuously formed along the axial direction D1 from the opening Sa to a position that does not reach the first region R1. The void 40 is formed, for example, by cutting the second region R2 from the opening Sa in the axial direction D1 using an end mill. The second region R2 includes a cylindrical portion 51 located inside the gap 40 in the radial direction D2, and a cylindrical portion 52 located outside the gap 40 in the radial direction D2. The cylindrical portion 51 has a cylindrical shape centered on the rotation axis L, and is surrounded by the void 40. The cylindrical portion 52 has a cylindrical shape centered on the rotation axis L, and surrounds the gap 40. Therefore, the cylindrical portion 51 is accommodated in the cylindrical portion 52 and is disposed inside the cylindrical portion 52 with the gap 40 interposed therebetween in the radial direction D2. In the radial direction D2, the thickness of the wall of the cylindrical portion 52 is thinner than the thickness of the cylindrical portion 51 (that is, the diameter of the cylindrical portion 51). It can also be said that the void 40 is formed by a gap between the cylindrical portion 51 and the cylindrical portion 52 in the radial direction D2. The void 40 can be defined as a gap region (space region) surrounded by the outer circumferential surface of the cylindrical portion 51 and the inner circumferential surface of the cylindrical portion 52 .

With further reference to FIG. 5, the structure surrounding the void 40 will be described in more detail. As shown in FIG. 5, the first region R1 includes at least the first inner region R11. The first internal region R11 is an internal region of the large diameter portion 12d surrounded by the first fins 31A (that is, located inside the first fins 31A in the radial direction D2). The first internal region R11 can also be said to be an internal region that overlaps the first fin 31A in the radial direction D2.

The second region R2 includes at least a second internal region R21 and a third internal region R31. The second internal region R21 is an internal region of the large diameter portion 12d surrounded by the second fins 31B (that is, located inside the second fins 31B in the radial direction D2). The second internal region R21 can also be said to be an internal region that overlaps the second fin 31B in the radial direction D2. The third internal region R31 is an internal region of the large diameter portion 12d surrounded by the third fins 31C (that is, located inside the third fins 31C in the radial direction D2). The third internal region R31 can also be said to be an internal region that overlaps the third fin 31C in the radial direction D2.

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

As shown in FIG. 5, in the second region R2, the void 40 passes from the opening Sa (see FIG. 3) through the inner region R33, the third inner region R31, and the inner region R32 to the second inner region R21. It is continuously formed in the axial direction D1 up to the position where it reaches . 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 inner region R22 of the first inner region R11, but is located in the second inner region R21. The bottom portion 40a is located at a position overlapping the second fin 31B in the radial direction D2. Note that the bottom portion 40a means the end of the gap 40 on the opposite side to 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, by forming the void 40 only in the position facing the second fin 31B and the third fin 31C in the radial direction D2, the portion of the cylindrical portion 52 where the second fin 31B and the third fin 31C are located is When receiving centrifugal force during rotation of the shaft 12, the first fin 31A deforms outward in the radial direction D2 from the portion of the cylindrical portion 52 where the first fin 31A is located. In other words, the second fin 31B and the third fin 31C are displaced further outward in the radial direction D2 than the first fin 31A when the shaft 12 rotates.

In the second internal region R21, the tip of the void 40 on the opposite side to the opening Sa is located. Therefore, the tip of the gap 40 is located at a position facing the second fin 31B in the radial direction D2. In the second internal region R21, the void 40 is not formed throughout the axial direction D1, but is formed only in a part of the axial direction D1. For example, the void 40 is formed only in the portion 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 void 40 faces a portion of the second fin 31B in the axial direction D1 in the radial direction D2. In the second region R2, the void 40 may be formed in a region closer to the inner region R32 than the center of the second inner region R21, or in a region closer to the inner region R22 than the center of the second inner region R21. may be formed.

On the other hand, in the internal region R32, the third internal region R31, and the internal region R33, a void 40 is formed throughout the axial direction D1. Therefore, the void 40 faces the entire third fin 31C in the axial direction D1 in the radial direction D2. The bottom 40a of the gap 40 is located at 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 farther from the bottom 40a of the gap 40 in the axial direction D1 than the second fin 31B. When the cylindrical portion 52 receives centrifugal force during rotation of the shaft 12, it deforms starting from the bottom 40a of the gap 40. Therefore, when receiving the centrifugal force during rotation of the shaft 12, the portion of the cylindrical portion 52 where the third fin 31C that is far from the bottom 40a, which is the starting point, is located is more radial than the second fin 31B that is closer to the bottom 40a. It is greatly deformed to the outside of D2. That is, the third fin 31C is displaced more outwardly in the radial direction 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 circumferential surface 13c becomes smaller than the gap GA between the first fin 31A and the inner circumferential surface 13c, and the gap between the third fin 31C and the inner circumferential surface The gap GC with respect to 13c is even smaller than the gap GB.

In this way, by forming the void 40 in the second internal region R21 and the third internal region R31, the second fin 31B and the third fin 31C are moved in the radial direction D2 by using the centrifugal force when the shaft 12 rotates. It becomes possible to displace it to the outside of. The amount of displacement of the second fin 31B and the third fin 31C outward in the radial direction D2 when subjected to centrifugal force during rotation of the shaft 12 is determined by the position of the bottom 40a (starting point) of the gap 40 and the distance from the gap 40. Adjustment is possible by adjusting the thickness of the outer shaft 12 in the radial direction D2 (that is, the thickness of the wall of the cylindrical portion 52). As described above, when the cylindrical portion 52 receives centrifugal force during rotation of the shaft 12, the cylindrical portion 52 deforms starting from the bottom 40a of the gap 40. Therefore, the farther the third fin 31C is from the bottom 40a of the gap 40 in the axial direction D1, the greater the amount of outward deformation of the third fin 31C in the radial direction D2. Further, the amount of deformation can also be adjusted by adjusting the thickness of the wall portion constituting the cylindrical portion 52. The thicker the wall of the cylindrical portion 52, the more easily the cylindrical portion 52 deforms. 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 amount of the second fin 35B and the third fin 35C is adjusted within a range in which the second fin 31B and the third fin 31C do not reach the inner circumferential surface 13c. For example, when the design values of the gaps GB and GC are set to 100 μm, these displacement amounts are set within a range greater than 0 and smaller than 100 μm.

<Effect>
The effects achieved by the rotating machine 1 described above will be explained together with the conventional problems. 2. Description of the Related Art Conventionally, rotating machines have been known that include a labyrinth seal portion for suppressing fluid leakage from a gap between a shaft and a housing. In such a rotating machine, in order to improve the sealing performance of the labyrinth seal, it is conceivable to sufficiently reduce the design value of the gap between the plurality of fins included in the labyrinth seal and the inner peripheral surface of the housing. However, if this gap is set to a small design value, such as less than 100 μm, advanced assembly technology is required to realize the gap when assembling the rotating machine, so there is a limit to how small the gap can be made. be. Even if the gap between the multiple fins and the inner circumferential surface of the housing is adjusted to a design value of less than 100 μm, such adjustment is a minute difference that is included in the range of manufacturing tolerances during assembly, so manufacturing tolerances must be taken into consideration. Therefore, it is extremely difficult to assemble the parts to create such a small gap as described above.

Furthermore, considering the flow field of fluid flowing through the labyrinth seal, making the gap between the fin and the inner circumferential surface of the housing sufficiently small is not necessarily effective in suppressing fluid leakage. is not limited. The reason for this will be explained with reference to the simulation results shown in FIG. The simulation results shown in FIG. 6 show streamlines of fluid flowing around the labyrinth seal portion 130 when the shaft 112 rotates. In FIG. 6, a plurality of fins 131A, 131B, and 131C included in the labyrinth seal portion 130 are arranged at equal intervals on the outer peripheral surface 112a of the shaft 112. The dimensions and shapes of the fins 131A, 131B, 131C are the same, and the gaps between the fins 131A, 131B, 131C and the inner peripheral surface 113c are the same.

A compressor impeller is arranged on the left side of FIG. Therefore, when the shaft 112 rotates, the space on the left side of FIG. 6 becomes high pressure, and the space on the right side of FIG. 6 becomes low pressure. Therefore, the fluid flowing through the labyrinth seal portion 130 passes through the fins 131A, 131B, and 131C in this order. A fluid with high energy flows into the fins 131A on the high pressure side. This fluid passes through the gap between the fins 131A and the inner circumferential surface 113c and is diffused into the space between the fins 131A and 131B, causing fluid energy loss. Thereafter, the fluid whose energy has decreased is diffused into the space between the fins 131B and the fins 131C through the gap between the fins 131B and the inner circumferential surface 113c, causing energy loss of the fluid. Thereafter, the fluid whose energy has further decreased is diffused to the downstream side through the gap between the fins 131C and the inner circumferential surface 113c.

Here, as a result of intensive studies on the relationship between the gap between each fin 131A, 131B, 131C and the inner circumferential surface 113c and the amount of fluid leaking from the gap, the inventors found that the fin 131B on the low pressure side , 131C and the inner circumferential surface 113c is effective in suppressing the amount of fluid leakage. Since fluid with high energy flows into the fins 131A on the high pressure side, if the gap between the fins 131A and the inner circumferential surface 113c is made small, the spreading angle θ of the fluid that has passed through the gap will become small. The energy loss of the fluid after passing through the gap is insufficient. Therefore, even if the gap between the high-pressure side fin 131A and the inner circumferential surface 113c is reduced, the amount of fluid leakage cannot be effectively suppressed. On the other hand, since fluid with reduced energy flows through the fins 131B, 131C on the low pressure side, it is better to reduce the gap between the fins 131B, 131C and the inner peripheral surface 113c than to ensure the spread angle of the fluid. This is effective for suppressing the amount of leakage of flowing fluid. However, as described above, there is a limit to reducing the gap between the fins 131B, 131C and the inner peripheral surface 113c.

Therefore, the present inventors created a gap between the second fin 31B and the third fin 31C on the low pressure side and the inner circumferential surface 13c so that the second fin 31B moves outward in the radial direction D2 due to centrifugal force when the shaft 12 rotates. The idea was to reduce the size by displacing the third fin 31C. In order to displace the second fin 31B and the third fin 31C outward in the radial direction D2 using centrifugal force, the present inventors have developed We came up with the idea of forming a void 40 inside the.

The simulation results shown in FIG. 7 show the amount of deformation of the surrounding structure of the labyrinth seal portion 30 when the shaft 12 (large diameter portion 12d) rotates. In FIG. 7, the amount of deformation of the peripheral structure of the labyrinth seal portion 30 is represented by the density of the dots, and the larger the amount of deformation, the denser the dots are represented. As shown in FIG. 7, when the shaft 12 rotates, the cylindrical portion 52 outside the gap 40 deforms to expand outward in the radial direction D2 due to centrifugal force. According to this deformation, the second fin 31B and 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 located far from the bottom 40a of the gap 40 is deformed more outwardly in the radial direction D2. Therefore, the third fin 31C is displaced more outwardly in the radial direction D2 than the second fin 31B. As a result, the gap GB between the second fin 31B and the inner circumferential surface 13c becomes smaller than the gap GA between the first fin 31A and the inner circumferential surface 13c, and the gap GC between the third fin 31C and the inner circumferential surface 13c becomes smaller. , is even smaller than the gap GB between the second fin 31B and the inner peripheral surface 13c. In the example shown in FIG. 7, the gap GB is smaller than the gap GA by about 5 μm, and the gap GC is further smaller than the gap GB by about 7 μm.

As described above, according to the present embodiment, by forming the void 40 in the second region R2, the centrifugal force generated when the shaft 12 rotates is used to connect the second fin 31B on the low pressure side and the inner peripheral surface 13c. The gap GB between the third fin 31C on the low pressure side and the inner circumferential surface 13c can be made smaller. Thereby, the effect of suppressing fluid leakage in the labyrinth seal portion 30 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 are not required during assembly, and the gaps GB and GC can be easily reduced during rotation. becomes possible. Therefore, according to this embodiment, it is possible to effectively suppress leakage flow during rotation.

In this embodiment, when the shaft 12 is at rest, 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 in which the gap GB between the second fin 31B and the inner circumferential surface 13c is reduced when the shaft 12 rotates can be suitably realized.

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

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 second fin 31B can be evenly displaced outward in the radial direction D2 by using the centrifugal force generated when the shaft 12 rotates, and the gap GB between the second fin 31B and the inner circumferential surface 13c can be evenly spaced. It can be made smaller. As a result, fluid leakage in the labyrinth seal portion 30 can be more effectively suppressed.

In this embodiment, the gap 40 is located closer to the second fin 31B than the rotation axis L between the second fin 31B and the rotation axis L in the radial direction D2. In this case, when the shaft 12 rotates, the second fin 31B can be displaced more 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 in the labyrinth seal portion 30 can be more effectively suppressed.

In this embodiment, the second region R2 has a cylindrical portion 51 centered on the rotation axis L, and a cylindrical portion 52 centered on the rotation axis L and housing the cylindrical portion 51, and the gap 40 is It is constituted by a gap between the portion 51 and the cylindrical portion 52 in the radial direction D2. In this case, the second fin 31B can be evenly displaced outward in the radial direction D2 by using the centrifugal force generated when the shaft 12 rotates, and the gap GB between the second fin 31B and the inner circumferential surface 13c can be evenly spaced. It can be made smaller. As a result, fluid leakage in the labyrinth seal portion 30 can be more effectively suppressed.

In this embodiment, the void 40 is formed in at least the second inner region R21 and the third inner region R31 in the second region R2. In this case, the centrifugal force generated when the shaft 12 rotates is used to create a gap GB between the second fin 31B far from the impeller 3 (that is, located on the low pressure side) and the inner peripheral surface 13c, and a gap GB between the third fin 31C and the inner peripheral surface. The gap GC with the surface 13c can be made smaller. As a result, fluid leakage in the labyrinth seal portion 30 can be more effectively suppressed.

In this embodiment, the void 40 is formed only in a part of the second internal region R21 in the axial direction D1, and is formed over the entire third internal region R31 in the axial direction D1. In this case, by utilizing centrifugal force during rotation of the shaft 12, the gap GC between the third fin 31C located on the lower pressure side and the inner circumferential surface 13c is reduced to the gap GB between the second fin 31B and the inner circumferential surface 13c. It can be made even smaller. In other words, the closer the fin 31 is located to the low pressure side, the smaller the gap between the fin 31 and the inner circumferential surface 13c can be made in stages. As a result, fluid leakage in the labyrinth seal portion 30 can be more effectively suppressed.

Although the first embodiment of the present disclosure has been described above, the present disclosure is not limited to the first embodiment. As shown in FIG. 8, a cylindrical gap 40A centered on the rotation axis L may be formed in the second region R2. In this case, the second region R2 does not have the cylindrical portion 51 according to the first embodiment, but only the cylindrical portion 52, and the entire internal space of the cylindrical portion 52 is configured as the void 40A. ing. That is, in the example shown in FIG. 8, the portion where the void 40A is formed in the second region R2 is hollow. In the second region R2, the void 40A extends axially from the opening Sa (see FIG. 3) to the second internal region R21 (see FIG. 5) facing the second fin 31B, as in the first embodiment. It is formed continuously in the direction D1.

In the example shown in FIG. 8, as in the first embodiment, a gap 40A exists inside the second fin 31B and third fin 31C on the low pressure side in the radial direction D2. Using centrifugal force, 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. Since the third fin 31C is further away from the bottom 40a (starting point) of the gap 40A than the second fin 31B in the axial direction D1, when receiving centrifugal force, the third fin 31C It is largely displaced outward in the radial direction D2. As a result, when the shaft 12 rotates, the gap GC becomes smaller than the gap GB. Therefore, in the example shown in FIG. 8, it is possible to reduce the gaps GB and GC when the shaft 12 rotates. As a result, fluid leakage in the labyrinth seal portion 30 can be effectively suppressed.

As shown in FIG. 9, a thick wall 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 thick portion 52b is formed in the cylindrical portion 52 shown in FIG. In the example shown in FIG. 9, the void 40B that constitutes the entire internal space of the cylindrical portion 52A extends in the axial direction D1 to a position beyond the second internal region R21 to reach the internal region R22. That is, the bottom 40a of the void 40B is located in the inner region R22 of the second region R2. Therefore, the gap 40B faces the entire second fin 31B in the axial direction D1 and the entire third fin 31C in the axial direction D1 in the radial direction D2.

The thick portion 52b is, for example, continuously formed in the axial direction D1 from the bottom portion 40a to a position reaching the internal region R32. The thick portion 52b is a thick portion of the wall portion 52a of the cylindrical portion 52A. The thick portion 52b protrudes more inward in the radial direction D2 than other portions of the wall portion 52a other than the thick portion 52b, and has a thicker wall thickness than the other portions. As a result, the inner surface S52b of the thick portion 52b is located at a position that projects further inward in the radial direction D2 than the inner surface S52a of the other portion. The thick portion 52b is formed at a position facing the second fin 31B in the radial direction D2. On the other hand, the thick portion 52b is not formed at a position facing the third fin 31C in the radial direction D2. Note that the thickness of the thick portion 52b may be constant at each position along the axial direction D1, for example.

Also in the example shown in FIG. 9, the third fin 31C is further away from the bottom 40a (starting point) of the gap 40B than the second fin 31B in the axial direction D1. Therefore, when the third fin 31C receives centrifugal force, the third fin 31C is displaced more outwardly in the radial direction D2 than the second fin 31B. As a result, the gap GB between the second fin 31B and the inner circumferential surface 13c becomes smaller than the gap GA between the first fin 31A and the inner circumferential surface 13c, and the gap GC between the third fin 31C and the inner circumferential surface 13c becomes smaller. , is even smaller than the gap GB between the second fin 31B and the inner peripheral surface 13c.

Here, in the example shown in FIG. 9, since the thick portion 52b is formed at a position facing the second fin 31B in the radial direction D2, the portion of the cylindrical portion 52A below the third fin 31C is The thickness of the portion of the cylindrical portion 52A below the second fin 31B is thicker than that of the second fin 31B. The gap between the fins and the inner peripheral surface 13c becomes narrower as the distance from the bottom portion 40a in the axial direction D1 increases. However, in this embodiment, the gap between the fin and the inner peripheral surface 13c does not uniformly narrow as the distance from the bottom portion 40a in the axial direction D1 increases. 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 by the centrifugal force and rigidity of the third fin 31C with the bottom portion 40a as the fulcrum. do. In this way, in the example shown in FIG. 9, the cylindrical portion 52A has a portion where the thickness changes (the thick portion 52b), so that the gap at the position in the axial direction D1 of the fin (i.e., the gap between the fin and the inner periphery) is formed in the cylindrical portion 52A. The amount of change in the gap with respect to the surface 13c can be adjusted. Thereby, the leakage flow of fluid in the labyrinth seal portion 30 can be suppressed more effectively.

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

Also in the example shown in FIG. 10, the third fin 31C is farther away from the bottom 40a (starting point) of the gap 40 than the second fin 31B, so when it receives centrifugal force, it faces the third fin 31C. The portion of the outer circumferential surface 12a 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. Therefore, even in the example shown in FIG. 10, the gaps GB and GC can be made small during rotation, as in the embodiment described above, so that leakage and flow of fluid in the labyrinth seal portion 30A can be effectively suppressed. becomes possible.

[Second embodiment]
Next, a rotating machine 1A according to a second embodiment will be described with reference to FIGS. 11 to 13. In the description of the second embodiment, differences from the first embodiment will be mainly described, and descriptions that overlap with the first embodiment will be omitted as appropriate.

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

As shown in FIG. 12, the cylindrical member 33 surrounds the shaft 12, and the inner peripheral surface 33b of the cylindrical member 33 faces the outer peripheral surface 12a of the shaft 12 in the radial direction D2. The cylindrical member 33 rotates around the rotation axis L together with the shaft 12. The outer peripheral surface 33a of the cylindrical member 33 faces the inner peripheral surface 13c with a gap therebetween. The plurality of fins 35 have the same configuration as the plurality of fins 31 except that they are formed on the outer peripheral surface 33a of the cylindrical member 33. The plurality of fins 35 include a first fin 35A (first protrusion), a second fin 35B (second protrusion), and a third fin 35C, which correspond to the first fin 31A, second fin 31B, and third fin 31C, respectively. (third protrusion). Note that the outer circumferential surface 33a and the inner circumferential surface 13c are, for example, cylindrical surfaces (side surfaces of the cylinder) centered on the rotation axis L. In addition, although the outer peripheral surface 33a and the inner peripheral surface 13c of this embodiment are cylindrical surfaces, they are not necessarily limited thereto. For example, in a cross section shown in FIG. 12, which will be described later, the outer circumferential surface 33a and the inner circumferential surface 13c may be represented by a straight line inclined with respect to the axial direction D1 or a line including a curve.

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

In this embodiment, a thin portion 33c is formed in the second region R2A. On the other hand, the thin portion 33c is not formed in the first region R1A. That is, the thin portion 33c is formed only in the second region R2A of the first region R1A and the second region R2A. The thin portion 33c is formed by a part of the cylindrical member 33, and has a thinner wall thickness (that is, the thickness in the radial direction D2) than the other portion 33d of the cylindrical member 33. Therefore, the thickness Tc of the thin portion 33c is thinner than the thickness Td of the other portion 33d (see FIG. 13). As a result, a gap 41 is formed between the inner circumferential surface 33b of the thin wall portion 33c and the outer circumferential surface 12a of the shaft 12. For example, the thicknesses Tc and Td may be constant at each position along the axial direction D1.

As shown in FIG. 13, the first region R1A includes at least the first portion R11A of the cylindrical member 33. The first portion R11A is a portion of the cylindrical member 33 surrounded by the first fins 35A, that is, a portion located inside the first fins 35A in the radial direction D2. The first portion R11A can also be said to be a portion that overlaps 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 a portion of the cylindrical member 33 surrounded by the second fins 35B, that is, a portion located inside the second fins 35B in the radial direction D2. The second portion R21A can also be said to be a portion that overlaps the second fin 35B when viewed from the radial direction D2. The third portion R31A is a portion of the cylindrical member 33 surrounded by the third fins 35C, that is, a portion located inside the third fins 35C in the radial direction D2. The third portion R31A can also be said to be a portion that overlaps the third fin 35C when viewed from the radial direction D2.

The second region R2A further includes a portion R22A, a portion R32A, and a portion R33A. The portion R22A is located between the first portion R11A and the second portion R21A in the axial direction D1. The portion R32A is a portion located between the second portion R21A and the third portion R31A in the axial direction D1. Portion R33A is a portion located between third portion R31A and end surface S11 (see FIG. 11). As shown in FIG. 13, the thin portion 33c is continuously formed in the second region R2A over a portion R33A, a third portion R31A, a portion R32A, and a second portion R21A. Therefore, the thin portion 33c faces the second fin 35B and the third fin 35C in the radial direction D2. The bottom portion 41a of the void 41 does not reach the portion R22A of the first portion R11A, but is located in the second internal region R21. The bottom portion 41a is located at a position overlapping the second fin 35B in the radial direction D2. Note that the bottom portion 41a means the end of the gap 41 on the opposite side to the opening Sa in the axial direction D1. On the other hand, the thin 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 wall portion 33c only at the position facing 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 When subjected to centrifugal force during rotation of the shaft 12, the first fin 35A deforms outward in the radial direction D2 from the portion of the cylindrical member 33 where the first fin 35A is located. That is, the second fin 35B and the third fin 35C are displaced further outward in the radial direction D2 than the first fin 35A when the shaft 12 rotates.

In the second portion R21A, the thin portion 33c is not formed over the entire axial direction D1, but is formed only in a part of the axial direction D1. For example, the thin portion 33c is formed only in a portion between the center of the second portion R21A and the boundary between the second portion R21A and the portion R32A in the axial direction D1. In the second region R2A, the thin portion 33c may be formed in a region closer to the portion R32A than the center of the second portion R21A, or in a region closer to the portion R22A than the center of the second portion R21A. It's okay. In this way, the thin portion 33c faces a portion of the second fin 35B in the axial direction D1 in the radial direction D2.

On the other hand, in the portion R32A, the third portion R31A, and the portion R33A, a thin portion 33c is formed over the entire axial direction D1. Therefore, the thin portion 33c faces the entire third fin 35C in the axial direction D1 in the radial direction D2. The bottom portion 41a of the gap 41 is located at the same position as the second fin 35B in the axial direction D1, but is spaced apart from the third fin 35C. Therefore, the third fin 35C is farther from the bottom 41a of the gap 41 in the axial direction D1 than the second fin 35B. When the cylindrical member 33 receives centrifugal force during rotation of the shaft 12, it deforms starting from the bottom 41a of the gap 41. Therefore, when receiving centrifugal force during rotation of the shaft 12, the portion of the cylindrical member 33 where the third fin 35C that is far from the bottom 41a, which is the starting point, is located is more radially It is greatly deformed to the outside of D2. That is, the third fin 35C is displaced more outwardly 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 between the third fin 35C and the inner circumferential surface The gap GC with respect to 13c is even smaller than the gap GB.

The amount of displacement of the second fins 35B and the third fins 35C outward in the radial direction D2 when subjected to centrifugal force during rotation of the shaft 12 is determined by the position of the bottom 41a of the gap 41 and the distance from the gap 41 in the radial direction D2. The thickness can be adjusted by adjusting the thickness Tc of the wall of the outer cylindrical member 33. As described above, when the cylindrical member 33 receives centrifugal force during rotation of the shaft 12, it deforms starting from the bottom 41a of the gap 41. Therefore, the farther 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. Further, this amount of deformation can also be adjusted by adjusting the thickness Tc of the wall portion constituting the cylindrical member 33. The thicker the thickness Tc of the wall portion of the cylindrical member 33, the more easily the cylindrical member 33 deforms. A thin wall portion 33c is formed in the portion of the cylindrical member 33 where the third fin 35C is located, and by reducing the thickness Tc of the wall portion, the amount of outward displacement of the third fin 35C in the radial direction D2 is further reduced. It is also possible to make it smaller. Note that the position of the bottom portion 41a of the gap 41 can be adjusted depending on the range in which the thin 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 within a range where the second fin 35B and the third fin 35C do not reach the inner circumferential surface 13c. For example, when the design values of the gaps GB and GC are set to 100 μm, these displacement amounts are set within a range greater than 0 and smaller than 100 μm.

<Effect>
According to the rotating machine 1A according to the second embodiment described above, the same effects as the rotating machine 1 according to the first embodiment can be obtained. That is, by forming the thin wall 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 is reduced by utilizing centrifugal force when the shaft 12 rotates. Furthermore, the gap GC between the third fin 35C on the low pressure side and the inner circumferential surface 13c can be made smaller. As a result, for the same reason as described above, it is possible to effectively suppress the leakage flow of fluid in the labyrinth seal portion 30B. Furthermore, by utilizing the centrifugal force when the shaft 12 rotates, advanced assembly techniques to reduce the gaps GB and GC are not required during assembly, and the gaps GB and GC can be easily reduced during rotation. becomes possible. Therefore, according to this embodiment, it is possible to effectively suppress leakage flow during rotation.

The rotating machine according to the present disclosure 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 there is no contradiction, depending on the desired purpose and effect. For example, the thick portion 52b shown in FIG. 9 or the labyrinth seal portion 30A shown in FIG. 10 may be applied to the rotating machine 1A shown in FIG. 11. In each of the embodiments described above, a configuration in which the compressor impeller is attached to the end of the shaft has been described, but a configuration in which the compressor impeller and the turbine impeller are respectively attached to both ends of the shaft may be used. In this case, the "impeller" of the present 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 the pressure becomes low as it moves away from the compressor impeller and turbine impeller (that is, as it approaches the center of the shaft).

When the "impeller" of the present disclosure is regarded as a compressor impeller attached to one end of a shaft, the fin on the high pressure side near the compressor impeller at the one end is the "first protrusion", and the fin on the low pressure side far from the compressor impeller (In other words, the fin near the center of the shaft) may be regarded as a "second protrusion." When the "impeller" of the present disclosure is regarded as a turbine impeller attached to the other end of the shaft, the fin on the high pressure side near the turbine impeller at the other end is referred to as the "first protrusion", and the fin far from the turbine impeller is referred to as the "first projection". The fin on the low-pressure side (that is, near the center of the shaft) may be considered a "second protrusion." Therefore, even if the "impeller" of the present disclosure is considered to be either a compressor impeller or a turbine impeller, since the "second protrusion" is located on the lower pressure side than the "first protrusion", the formation of a void or a thin wall part causes the "impeller" to be on the low pressure side. By displacing the "second protrusion" outward in the radial direction, it becomes possible to effectively suppress the leakage flow of fluid in the labyrinth seal portion.

In each of the embodiments described above, the first fin on the high pressure side is considered as the "first protrusion" of the present disclosure, and the second fin on the low pressure side adjacent to the first fin is considered as the "second protrusion" of the present disclosure. However, the "first protrusion" and the "second protrusion" do not necessarily have to be adjacent to each other, and another protrusion may be arranged between the "first protrusion" and the "second protrusion". For example, the first fin may be regarded as a "first protrusion", and the third fin on the low pressure side that is arranged with respect to the first fin via the second fin may be regarded as a "second protrusion". Further, in each of the embodiments described above, a case has been described in which the "first protrusion", "second protrusion", and "third protrusion" are fins, but these protrusions do not need to be fin-shaped. Other shapes are also possible. For example, these protrusions may be rectangular protrusions that protrude outward in the radial direction.

[Additional notes]
A rotating machine according to an embodiment of the present disclosure is as described in [1] to [11] below, and these have been explained in detail based on the above-mentioned embodiments and modifications.
[1] A shaft rotatable around a rotational axis,
an impeller attached to the shaft;
a housing that accommodates the shaft and the impeller;
a flow path formed between an inner wall surface of the housing and an outer peripheral surface of the shaft and extending along the shaft on the back side of the impeller;
a labyrinth seal formed in the flow path,
The labyrinth seal portion has a first protrusion and a second protrusion that protrude from the outer peripheral surface or the inner wall surface,
The second protrusion is located farther from the impeller than the first protrusion in the axial direction of the shaft,
The shaft has a gap formed radially inside the second protrusion.
[2] The shaft is
a first region including a first internal region located inside the first protrusion in the radial direction;
a second internal region located on the inner side of the second protrusion in the radial direction, and a second region located on the opposite side of the impeller with respect to the first region;
[1], wherein the void is formed only in the second region of the first region and the second region, and is formed in at least the second internal region in the second region. rotating machine.
[3] The second region has an opening opening on a side opposite to the first region in the axial direction,
The rotating machine according to [2], wherein the gap is continuously formed in the axial direction from the opening to at least a position reaching the second internal region.
[4] When the shaft is at rest, the radial gap between the first protrusion and the inner wall surface or the outer circumferential surface is equal to the radial gap between the second protrusion and the inner wall surface or the outer circumferential surface. The rotating machine according to [1] or [2], which is the same as .
[5] The gap is continuously formed between the second projection and the rotation axis in the radial direction over the entire circumference in the circumferential direction centering on the rotation axis, [1] to [ 4]. The rotating machine according to any one of [4].
[6] The rotating machine according to [5], wherein the gap is located closer to the second protrusion than the rotation axis between the second protrusion and the rotation axis in the radial direction.
[7] The shaft has a cylindrical part centered on the rotational axis, and a cylindrical part centered on the rotational axis and housing the cylindrical part,
The rotating machine according to [5] or [6], wherein the gap is formed by a gap in the radial direction between the columnar part and the cylindrical part.
[8] The shaft has a cylindrical portion centered on the rotation axis,
The rotating machine according to any one of [1] to [4], wherein the void is formed by the entire internal space of the cylindrical portion.
[9] Further comprising a third protrusion further from the impeller than the second protrusion in the axial direction,
The shaft is
a first region including a first internal region located inside the first protrusion in the radial direction;
a second internal region located inside the second projection in the radial direction; and a third internal region located inside the third projection in the radial direction relative to the first region; a second region located on the opposite side of the impeller;
The void is formed only in the second region of the first region and the second region, and is formed in at least the second internal region and the third internal region in the second region, The rotating machine according to any one of [1] to [8].
[10] The rotating machine according to [9], wherein the gap is formed only in a part of the second internal region in the axial direction and is formed throughout the third internal region in the axial direction.
[11] A shaft rotatable around a rotational axis,
an impeller attached to the shaft;
a housing that accommodates the shaft and the impeller;
a flow path formed between an inner wall surface of the housing and an outer peripheral surface of the shaft and extending along the shaft on the back side of the impeller;
A labyrinth seal portion formed in the flow path,
The labyrinth seal portion includes a cylindrical member disposed to surround the outer circumferential surface of the shaft, and a first protrusion and a second protrusion protruding from the outer circumferential surface or the inner wall surface of the cylindrical member,
the second protrusion is located farther from the impeller than the first protrusion in the axial direction of the shaft;
The cylindrical member is a rotary machine, wherein the cylindrical member has a thin part that is thinner than other parts on the inside in the radial direction with respect to the second protrusion.

1,1A Rotating machine 3 Compressor impeller (impeller)
7 Housing 12 Shaft 12a Outer peripheral surface 12b One end 13c Inner peripheral surface (inner wall surface)
30, 30A, 30B Labyrinth seal portion 31, 35 Fin (protrusion)
31A, 35A First fin (first protrusion)
31B, 35B Second fin (second protrusion)
31C, 35C 3rd fin (3rd protrusion)
33 Cylindrical member 33c Thin wall portions 40, 40A, 40B Gap 51 Cylindrical portion 52 Cylindrical portion D1 Axial direction D2 Radial direction D3 Circumferential direction G Flow paths GA, GB, GC Gap L Rotation axis R1, R1A First region R2, R2A Second Region R11 First internal region R11A First portion R21 Second internal region R21A Second portion R31 Third internal region Sa Opening

Claims (11)

a shaft rotatable about a rotational axis;
an impeller attached to the shaft;
a housing that accommodates the shaft and the impeller;
a flow path formed between an inner wall surface of the housing and an outer peripheral surface of the shaft and extending along the shaft on the back side of the impeller;
a labyrinth seal formed in the flow path,
The labyrinth seal portion has a first protrusion and a second protrusion that protrude from the outer peripheral surface or the inner wall surface,
The second protrusion is located farther from the impeller than the first protrusion in the axial direction of the shaft,
The shaft has a gap formed radially inside the second protrusion. The shaft is
a first region including a first internal region located inside the first protrusion in the radial direction;
a second internal region located on the inner side of the second protrusion in the radial direction, and a second region located on the opposite side of the impeller with respect to the first region;
The void according to claim 1, wherein the void is formed only in the second region of the first region and the second region, and is formed in at least the second internal region in the second region. rotating machine. The second region has an opening opening on a side opposite to the first region in the axial direction,
The rotating machine according to claim 2, wherein the gap is continuously formed in the axial direction from the opening to at least a position reaching the second internal region. When the shaft is at rest, the radial gap between the first protrusion and the inner wall surface or the outer circumferential surface is the same as the radial gap between the second protrusion and the inner wall surface or the outer circumferential surface. A rotating machine according to claim 1 or 2. Any one of claims 1 to 3, wherein the gap is continuously formed between the second protrusion and the rotation axis in the radial direction over the entire circumference in the circumferential direction centered on the rotation axis. The rotating machine described in paragraph 1. The rotating machine according to claim 5, wherein the gap is located closer to the second protrusion than the rotation axis between the second protrusion and the rotation axis in the radial direction. The shaft has a cylindrical part centered on the rotational axis, and a cylindrical part centered on the rotational axis and housing the cylindrical part,
The rotating machine according to claim 5, wherein the gap is constituted by a gap in the radial direction between the columnar part and the cylindrical part. The shaft has a cylindrical portion centered on the rotation axis,
The rotating machine according to any one of claims 1 to 3, wherein the void is constituted by the entire internal space of the cylindrical portion. further comprising a third protrusion farther from the impeller than the second protrusion in the axial direction,
The shaft is
a first region including a first internal region located inside the first protrusion in the radial direction;
a second internal region located inside the second projection in the radial direction; and a third internal region located inside the third projection in the radial direction relative to the first region; a second region located on the opposite side of the impeller;
The void is formed only in the second region of the first region and the second region, and is formed in at least the second internal region and the third internal region in the second region, The rotating machine according to any one of claims 1 to 3. The rotating machine according to claim 9, wherein the gap is formed only in a part of the second internal region in the axial direction, and is formed throughout the third internal region in the axial direction. a shaft rotatable about a rotational axis;
an impeller attached to the shaft;
a housing that accommodates the shaft and the impeller;
a flow path formed between an inner wall surface of the housing and an outer peripheral surface of the shaft and extending along the shaft on the back side of the impeller;
A labyrinth seal portion formed in the flow path,
The labyrinth seal portion includes a cylindrical member disposed to surround the outer circumferential surface of the shaft, and a first protrusion and a second protrusion protruding from the outer circumferential surface or the inner wall surface of the cylindrical member,
the second protrusion is located farther from the impeller than the first protrusion in the axial direction of the shaft;
The cylindrical member is a rotary machine, wherein the cylindrical member has a thin part that is thinner than other parts on the inside in the radial direction with respect to the second protrusion.

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