sealing device

Abstract

The present invention provides a sealing device that can prevent sealing gas from entering the sealed fluid space. [Solution] A sealing device 1 having an internal mechanical seal 10 that separates a sealed fluid space S1 and a seal gas space S3, and an external sealing means 30 that separates the seal gas space S3 and an external space S2 located outside the machine, wherein the sealed fluid F is a liquid or a fluid containing a liquid, the pressure P1 of the seal gas G is set lower than the pressure P2 of the sealed fluid F, the pressure of the external space S2 is set lower than the pressure P2 of the seal gas G, and a seal gas space side dynamic pressure groove 16 that communicates with the seal gas space S3 side is provided on the sliding surface 12 of the internal stationary sealing ring 11 of the internal mechanical seal 10.

Description

Technical Field

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[0001] The present invention relates to a sealing device applied to a rotating device for sealing a rotating shaft.

Background Art

[0002] Conventionally, as a sealing device for sealing the rotating shaft of a rotating device, a plurality of seals are arranged in the axial direction, and a sealing gas having a pressure higher than that of the sealed fluid is interposed in the space formed between these seals, so that the space inside the machine where the sealed fluid is accommodated and the space outside the machine are isolated, and leakage of the sealed fluid to the space outside the machine is strictly regulated.

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[0006] This invention was made in view of these problems, and aims to provide a sealing device that can prevent sealing gas from entering the sealed fluid space. [Means for solving the problem]

[0007] To solve the above problems, the sealing device of the present invention is A sealing device comprising an internal stationary sealing ring fixed to the housing side and positioned between a housing and a rotating shaft that rotates relative to the housing, and an internal rotating sealing ring fixed to the rotating shaft side, wherein the internal stationary sealing ring and the internal rotating sealing ring slide against each other by relative rotation to partition a sealed fluid space and a seal gas space, and an external sealing means partitioning the seal gas space and an external space located outside the machine beyond the seal gas space, The sealed fluid is a liquid or a fluid containing a liquid. The pressure of the sealing gas is set lower than the pressure of the fluid being sealed. The pressure in the external space of the machine is set lower than the pressure of the sealing gas. At least one of the sliding surfaces of the internal rotating sealing ring and the internal stationary sealing ring of the internal mechanical seal is provided with a seal gas space side dynamic pressure groove that communicates with the seal gas space side. This prevents the seal gas from entering the sealed fluid space. In addition, it prevents the sealed fluid from leaking into the seal gas space between the sliding surfaces.

[0008] The dynamic pressure groove on the seal gas space side may be an inclined groove that slopes downstream in the relative rotational direction from the seal gas space side toward the sealed fluid space side. According to this, the dynamic pressure groove on the seal gas space side can be simply constructed, while the suction capacity of the seal gas can be easily adjusted.

[0009] A fluid retention groove may be provided on the sliding surface of at least one of the internal rotating sealing ring and the internal stationary sealing ring, on the side of the sealed fluid space that is closer to the sealed fluid space than the dynamic pressure groove on the sealing gas space side. According to this method, friction can be reduced by using the fluid to be sealed, held in the fluid retention groove, to lubricate the sliding surfaces. Furthermore, even if the pressure of the sealing gas temporarily exceeds the pressure of the fluid to be sealed, the boundary between the fluid to be sealed and the sealing gas can be maintained between the sliding surfaces.

[0010] The fluid retention groove may also be a fluid-sealed space side dynamic pressure groove that communicates with the fluid-sealed space side. According to this method, by separating the sliding surfaces using dynamic pressure, a liquid film is reliably formed between the sliding surfaces, thereby further reducing friction.

[0011] The external sealing means may be an external mechanical seal comprising an external rotating sealing ring fixed to the rotating shaft side and rotating together with the rotating shaft, and an external stationary sealing ring positioned opposite the external rotating sealing ring and fixed to the housing side. According to this, the amount of seal gas leaking into the space outside the machine can be suppressed and the pressure of the seal gas can be stabilized.

[0012] A dynamic pressure generating mechanism may be provided on the sealing gas space side of at least one of the sliding surfaces of the external rotating sealing ring and the external stationary sealing ring of the external mechanical seal. According to this method, friction can be reduced by separating the sliding surfaces using dynamic pressure and lubricating them with a sealing gas.

[0013] A labyrinth seal consisting of irregularities between the rotating shaft side and the housing side is provided on the side of the external mechanical seal to be sealed, on the side of the fluid space to be sealed, A drain discharge port that can communicate with the outside of the machine may be provided on the side of the sealed fluid space beyond the labyrinth seal. According to this, even if the sealed fluid mixes into the seal gas, the labyrinth seal can prevent the sealed fluid from entering the outside mechanical seal, and the drain port can discharge the mixed sealed fluid to the outside.

Brief Description of the Drawings

[0014] [Figure 1] It is a longitudinal sectional view showing the sealing device of Example 1 according to the present invention. [Figure 2] It is a view of the sliding surface of the stationary seal ring constituting the inside mechanical seal in Example 1 as seen from the axial direction. [Figure 3] It is a view of the sliding surface of the rotating seal ring constituting the outside mechanical seal in Example 1 as seen from the axial direction. [Figure 4] It is a sectional view showing the sealing device of Example 2 according to the present invention. [Figure 5] It is a sectional view showing the sealing device of Example 3 according to the present invention.

Mode for Carrying Out the Invention

[0015] A mode for carrying out the sealing device according to the present invention will be described below based on examples.

Examples

[0016] The sealing device according to Example 1 will be described with reference to FIGS. 1 to 3. In this example, the sealed fluid F exists in the internal space S1 as the sealed fluid space in the rotating device in which the rotating shaft 2 is sealed by the sealing device, the atmosphere A exists in the external space S2 as the outside space, and the seal gas G exists in the seal gas space S3 between the internal space S1 and the external space S2. Further, in this example, the sealed fluid F is a liquid or a fluid containing a liquid (for example, a mist-like fluid). Also, for convenience of explanation, dots are attached to the grooves formed on the sliding surface in the drawings.

[0017] As shown in FIG. 1, the sealing device 1 includes a mechanical seal 10 as an in-cabin mechanical seal disposed on the in-cabin space S1 side, and a mechanical seal 30 as an out-cabin mechanical seal which is an out-cabin sealing means disposed on the out-cabin space S2 side. A seal gas space S3 is formed between the mechanical seals 10 and 30, into which a seal gas G is supplied.

[0018] In this embodiment, the seal gas G is supplied from a seal gas supply port 50 provided in the housing 5 into the seal gas space S3. Specifically, the seal gas G is supplied from the seal gas supply port 50 located on the outer diameter side of the mechanical seal 30 and fills the entire seal gas space S3. Further, the housing 5 is provided with a drain discharge port 51 that can communicate with the outside on the in-cabin space S1 side of the labyrinth seal 60. The drain discharge port 51 is normally closed, but by opening the drain discharge port 51, the sealed fluid F mixed in the seal gas space S3 can be discharged to the outside together with the seal gas G.

[0019] The labyrinth seal 60 is fitted into the inner circumferential surface of the housing 5 at a position on the side of the external space S2 that is closer to the drain discharge port 51, and forms a seal structure between it and the outer circumferential surface of the flange portion 4a of the outer diameter sleeve 4, which will be described later. Specifically, the seal structure is formed by irregularities consisting of a constriction formed between a plurality of protrusions projecting inward from the inner circumferential surface of the labyrinth seal 60 and the outer circumferential surface of the flange portion 4a of the outer diameter sleeve 4, and recesses formed between adjacent protrusions. A secondary seal, an O-ring 55, is sandwiched radially between the outer circumferential surface of the labyrinth seal 60 and the inner circumferential surface of the housing 5. Alternatively, the labyrinth seal 60 may form a seal structure between itself and the inner circumferential surface of the housing 5 by irregularities provided on its outer circumferential surface. In this case, the O-ring will be sandwiched radially between the inner circumferential surface of the labyrinth seal 60 and the outer circumferential surface of the flange portion 4a of the outer diameter sleeve 4. Furthermore, protrusions may protrude from both the inner circumferential surface of the labyrinth seal 60 and the outer circumferential surface of the flange portion 4a of the outer diameter sleeve 4. In this case, the protrusions protruding from the inner circumferential surface of the labyrinth seal 60 and the protrusions protruding from the outer circumferential surface of the flange portion 4a of the outer diameter sleeve 4 may be arranged to face each other in the radial direction, or they may be arranged to be staggered.

[0020] The sealing gas G is an inert gas that can be mixed with the sealed fluid F in the internal space S1 without causing problems, and can also be leaked into the external space S2 without causing problems. For example, the sealing gas G is nitrogen gas.

[0021] Furthermore, the pressure P2 of the seal gas G in the seal gas space S3 is set to be lower than the pressure P1 of the sealed fluid F in the internal space S1, and higher than the pressure of the atmosphere A in the external space S2 (P1 > P2 > atmospheric pressure).

[0022] As shown in Figure 1, the mechanical seal 30 separates the external space S2 and the seal gas space S3, and is an inside-type mechanical seal that seals the seal gas G that would otherwise leak from the seal gas space S3 on the outer diameter side toward the external space S2 on the inner diameter side.

[0023] The mechanical seal 30 of this embodiment mainly consists of a stationary sealing ring 31 as an external stationary sealing ring and a rotating sealing ring 41 as an external rotating sealing ring that rotates together with the rotating shaft 2. In this embodiment, the sliding surface 32 of the stationary sealing ring 31 is a flat surface, and as shown in Figure 3, the sliding surface 42 of the rotating sealing ring 41 is provided with a dynamic pressure generating texture 43 as a dynamic pressure generating mechanism on the outer diameter side, i.e., on the sealing gas space S3 side. The dynamic pressure generating texture 43 is not limited to Rayleigh steps, but may also be spiral grooves, herringbone shapes, etc., as appropriate. Furthermore, the dynamic pressure generating texture 43 is not limited to being provided on the sliding surface 42 of the rotating sealing ring 41; the dynamic pressure generating texture 43 may be provided on the sliding surface 32 of the stationary sealing ring 31, and the sliding surface 42 of the rotating sealing ring 41 may be a flat surface.

[0024] Furthermore, the sliding surface 32 of the stationary sealing ring 31 has a larger sliding surface area in the radial direction compared to the sliding surface 12 of the stationary sealing ring 11 which constitutes the mechanical seal 10 described later. This ensures that the mechanical seal 30 can reliably seal the seal gas G that would otherwise leak from the seal gas space S3 towards the outside space S2.

[0025] The stationary sealing ring 31 has a projection 31b that protrudes outward from approximately the axial center of the outer circumferential surface of the base portion 31a. As the rotating shaft 2 moves in the axial direction, the projection 31b of the stationary sealing ring 31 comes into contact with the restricting piece 53a of the stopper 53, which is attached to the inner circumferential surface of the housing 5 at the position of the seal gas supply port 50, thereby restricting the movement of the stationary sealing ring 31 toward the rotating sealing ring 41.

[0026] A first recess 31c is formed on the inner circumferential surface of the base portion 31a, which is recessed on the outer diameter side and open on the back surface 31d side and the inner diameter side.

[0027] A second recess 31e is formed on the back surface 31d of the base portion 31a, which is recessed on the sliding surface 32 side and open on the inner diameter side and back side.

[0028] Furthermore, the stationary sealing ring 31 is biased toward the rotating sealing ring 41 by an elastic member 34 via a retainer 33. An O-ring 35, which is a secondary seal, is held in the inner diameter portion of the retainer 33. The O-ring 35 abuts against the second recess 31e of the stationary sealing ring 31 from the axial direction and also abuts against the guide portion 52 of the housing 5, which will be described later, from the radial direction.

[0029] A recess 33a is formed on the outer circumferential surface of the retainer 33, which is recessed on the inner diameter side and open on the outer diameter side, facing the stationary sealing ring 31. The back surface 31d of the stationary sealing ring 31 abuts against the recess 33a from the axial direction, and the retainer 33 and the stationary sealing ring 31 are engaged. In other words, the retainer 33 and the stationary sealing ring 31 are arranged with a portion of their surfaces overlapping in the radial direction.

[0030] Furthermore, a guide portion 52 is formed in the inner diameter portion of the housing 5 on the side of the external space S2, extending toward the seal gas space S3 and positioned along the first recess 31c of the stationary sealing ring 31. The guide portion 52 slides against the first recess 31c of the stationary sealing ring 31 and the O-ring 35 held by the retainer 33, thereby guiding the movement of the stationary sealing ring 31 and the retainer 33.

[0031] The rotating sealing ring 41 is held in place by being fitted into a recess 4b formed in the flange portion 4a of the outer diameter sleeve 4, which is further fitted onto the inner diameter sleeve 3, which is fitted onto the rotating shaft 2. An O-ring 37, which serves as a secondary seal, is sandwiched axially between the recess 4b of the outer diameter sleeve 4 and the rotating sealing ring 41. In addition, an O-ring 36, which serves as a secondary seal, is sandwiched radially between the outer circumferential surface of the inner diameter sleeve 3 and the inner circumferential surface of the outer diameter sleeve 4.

[0032] Furthermore, the rotating sealing ring 41 is prevented from coming out in the axial direction by being held between the end of the stopper 6, which has an L-shaped cross-section and is fitted onto the end of the inner diameter sleeve 3 on the side of the external space S2, and the recess 4b of the outer diameter sleeve 4.

[0033] As shown in Figure 1, the mechanical seal 10 separates the internal space S1 and the seal gas space S3, and is an inside-type mechanical seal that seals the fluid to be sealed F that would otherwise leak from the internal space S1 on the outer diameter side toward the seal gas space S3 on the inner diameter side.

[0034] The mechanical seal 10 of this embodiment mainly consists of a stationary sealing ring 11 as an internal stationary sealing ring and a rotating sealing ring 21 as an internal rotating sealing ring that rotates together with the rotating shaft 2.

[0035] The stationary sealing ring 11 has a projection 11b that extends from the base 11a toward the rotating sealing ring 21. A sliding surface 12 is formed on the end face of the projection 11b.

[0036] Furthermore, the sliding surface 12 of the stationary sealing ring 11 has a smaller sliding portion, i.e., a smaller sliding area, with respect to the rotating sealing ring 21, compared to the sliding surface 32 of the stationary sealing ring 31 that constitutes the mechanical seal 30 described above.

[0037] As the rotating shaft 2 moves in the axial direction, the stationary sealing ring 11's movement toward the rotating sealing ring 21 is restricted when the outer diameter portion of its base 11a comes into contact with the restricting piece 54a of the stopper 54 attached to the inner circumferential surface of the housing 5.

[0038] A protrusion 11e is formed on the back surface 11d of the base portion 11a, projecting axially toward the seal gas space S3.

[0039] Furthermore, the stationary sealing ring 11 is biased toward the rotating sealing ring 21 by the elastic member 7 via the retainer 18. A secondary seal, the O-ring 39, is held on the stationary sealing ring 11 side of the retainer 18, and the O-ring 39 abuts against the convex portion 11e of the stationary sealing ring 11 from the axial direction.

[0040] The end face of the retainer 18 on the side of the stationary sealing ring 11 has a recess 18a formed therein that is recessed in the axial direction toward the seal gas space S3, and is open in the axial direction toward the inner diameter side, and engages with the convex portion 11e of the stationary sealing ring 11 from the outer diameter side.

[0041] Furthermore, a guide portion 18b is formed on the inner diameter of the retainer 18, extending axially toward the seal gas space S3 and positioned along the protrusion 57 of the housing 5. The guide portion 18b guides the movement of the retainer 18 by sliding in contact with an O-ring 56 that is radially sandwiched between the guide portion 18b and the inner circumferential surface of the protrusion 57 of the housing 5.

[0042] The rotating sealing ring 21 is held in place by being fitted into a recess 3b formed in the flange portion 3a of the inner diameter sleeve 3, which is fitted onto the rotating shaft 2. An O-ring 38, which serves as a secondary seal, is sandwiched axially between the recess 3b of the inner diameter sleeve 3 and the rotating sealing ring 21.

[0043] Furthermore, the rotating sealing ring 21 is held between the end of the outer diameter sleeve 4, which is fitted onto the inner diameter sleeve 3, and the recess 3b of the inner diameter sleeve 3, thereby preventing it from coming out in the axial direction.

[0044] As shown in Figure 2, the rotating sealing ring 21 slides relative to the stationary sealing ring 11 in a counterclockwise direction, as indicated by the solid arrows.

[0045] The sliding surface 12 of the stationary sealing ring 11 is provided with a fluid retention groove, a fluid-sealed fluid space-side dynamic pressure groove 15, which consists of a plurality of deep grooves 13 (four in this embodiment) on the outer diameter side, i.e., on the machine internal space S1 side, and Rayleigh steps 14 extending circumferentially from the deep grooves 13. In addition, the sliding surface 12 of the stationary sealing ring 11 is provided with a plurality of inclined grooves 16 (16 in this embodiment) on the inner diameter side, i.e., on the seal gas space S3 side, which serve as seal gas space-side dynamic pressure grooves.

[0046] Furthermore, the portions of the sliding surface 12 other than the deep groove 13, Rayleigh step 14, and inclined groove 16 form lands 17 that are flat surfaces arranged on the same plane. The flat surfaces of the lands 17 function as sliding surfaces that substantially slide against the sliding surface 22 of the rotating sealing ring 21. The sliding surface 22 of the rotating sealing ring 21 is a flat surface, and this flat surface does not have any recesses such as grooves. In addition, the fluid space-side dynamic pressure groove 15 and inclined groove 16 are not limited to being provided on the sliding surface 12 of the stationary sealing ring 11, but the fluid space-side dynamic pressure groove 15 and inclined groove 16 may be provided on the sliding surface 22 of the rotating sealing ring 21, and the sliding surface 12 of the stationary sealing ring 11 may be a flat surface.

[0047] The deep groove 13 communicates with the internal space S1 of the machine and extends inward from the outer edge of the sliding surface 12.

[0048] The Rayleigh step 14 extends concentrically with the sliding surface 12 in the downstream direction of relative rotation, i.e., counterclockwise, from the inner diameter end of the deep groove 13. The Rayleigh step 14 is shallower than the deep groove 13 and has a constant depth in the circumferential direction.

[0049] The inclined groove 16 communicates with the seal gas space S3 and extends from the inner edge of the sliding surface 12 toward the outer diameter. More specifically, the inclined groove 16 extends in an arc shape, inclined with a component in the downstream direction of relative rotation, i.e., counterclockwise, from the inner diameter side, i.e., the seal gas space S3 side, toward the outer diameter side, i.e., the machine interior space S1 side. In other words, the inclined groove 16 is a spiral groove.

[0050] The inclined groove 16 is formed to a constant depth in the circumferential direction. The depth of this inclined groove 16 is shallower than the depth of the deep groove 13. The inclined groove 16 only needs to have the function of guiding the sealing gas G to the outer diameter side and generating positive pressure at the closed end 16A, and is not limited to extending in an arc shape while inclined downstream in the relative rotational direction from the inner diameter side to the outer diameter side, but may also extend in a straight line.

[0051] Next, the operation of the stationary sealing ring 11 and the rotating sealing ring 21 during relative rotation will be described.

[0052] First, when the rotating sealing ring 21 is stopped and not rotating, the fluid to be sealed F flows into the deep groove 13 and Rayleigh step 14 provided on the machine interior space S1 side. Also, the sealing gas G flows into the inclined groove 16 provided on the sealing gas space S3 side.

[0053] Furthermore, since the stationary sealing ring 11 is biased toward the rotating sealing ring 21 by the elastic member 7 (see Figure 1), the sliding surfaces 12 and 22 are in contact with each other, and the amount of sealed fluid F between the sliding surfaces 12 and 22 that leaks into the sealing gas space S3 is almost zero.

[0054] During low-speed rotation when the rotating sealing ring 21 begins to rotate relative to the stationary sealing ring 11, the sealed fluid F, mainly the surface layer of the sealed fluid F, moves in the direction of rotation of the rotating sealing ring 21 due to shear with the sliding surface 22.

[0055] According to this, the sealed fluid F in the cabin space S1 is drawn into the Rayleigh step 14 through the deep groove 13.

[0056] Furthermore, the sealed fluid F within the Rayleigh step 14 moves toward the closed end 14A of the Rayleigh step 14. The sealed fluid F that has moved toward the closed end 14A of the Rayleigh step 14 flows out between the sliding surfaces 12 and 22 from the closed end 14A and its vicinity.

[0057] Furthermore, the pressure of the sealed fluid F within the Rayleigh step 14 is increased at and near the closed end 14A. In other words, positive pressure is generated at and near the closed end 14A of the Rayleigh step 14.

[0058] The positive pressure generated at and near the closed end 14A of the Rayleigh step 14 causes a slight separation between the sliding surfaces 12 and 22, allowing the fluid to be sealed F to flow from the internal space S1 to the sliding surfaces 12 and 22, and the sealing gas G to flow from the sealing gas space S3 to the sliding surfaces 12 and 22.

[0059] Meanwhile, the sealing gas G within the inclined groove 16 moves toward the closed end 16A of the inclined groove 16. The sealing gas G between the sliding surfaces 12 and 22 is drawn into the inclined groove 16 from around the open end 16B of the inclined groove 16.

[0060] The seal gas G that has moved toward the closed end 16A of the inclined groove 16 flows out between the sliding surfaces 12 and 22 from the closed end 16A and its vicinity.

[0061] Furthermore, when the relative rotation speed between the rotating sealing ring 21 and the stationary sealing ring 11 is low, the sealing gas G does not become sufficiently dense within the inclined groove 16, and high positive pressure is not generated, so there is almost no force acting to separate the sliding surfaces 12 and 22.

[0062] The seal gas G that flows out from the closed end 16A of the inclined groove 16 and its vicinity between the sliding surfaces 12 and 22 is guided to move toward the outer diameter side, but is pushed back toward the inner diameter side by the pressure P1 of the high-pressure fluid F that flows from the machine interior space S1 between the sliding surfaces 12 and 22.

[0063] Furthermore, as the relative rotational speed of the rotating sealing ring 21 increases, a large amount of sealing gas G moves toward the closed end 16A of the inclined groove 16, increasing the pressure at and near the closed end 16A of the inclined groove 16. In other words, positive pressure is generated at and near the closed end 16A of the inclined groove 16.

[0064] At this time, the positive pressure generated at the closed end 16A of the inclined groove 16 and its vicinity becomes greater than the positive pressure generated at the closed end 14A of the Rayleigh step 14 and its vicinity, causing the sliding surfaces 12 and 22 to separate further compared to when the relative rotation speed is low.

[0065] In this embodiment, the mechanical seal 10 is provided with a Rayleigh step 14 and an inclined groove 16 such that, during high-speed rotation, the pressure P1 of the high-pressure fluid F to be sealed flowing from the internal space S1 between the sliding surfaces 12 and 22 is balanced with the positive pressure generated at the closed end 14A of the Rayleigh step 14 and its vicinity, and the positive pressure generated at the closed end 16A of the inclined groove 16 and its vicinity.

[0066] Specifically, during normal operation of the rotating device (P1 > P2) where the pressure P2 of the sealing gas G in the seal gas space S3 is set lower than the pressure P1 of the sealed fluid F in the internal space S1, if the differential pressure P1 - P2 between the pressure P1 of the sealed fluid F and the pressure P2 of the sealing gas G is in the range of 0 < P1 - P2 < 500 kPa, a boundary between the liquid film of the sealed fluid F and the sealing gas G is maintained between the sliding surfaces 12 and 22.

[0067] Also, a liquid film formed by the sealed fluid F is formed on the outer diameter side between the sliding surfaces 12 and 22. Since the viscosity of the liquid film is higher than that of the sealing gas G, it is difficult for the sealing gas G between the sliding surfaces 12 and 22 to enter the internal space S1. Thus, it becomes easier to maintain the boundary between the liquid film of the sealed fluid F and the sealing gas G.

[0068] As described above, even when the pressure P2 of the sealing gas G is set lower than the pressure P1 of the sealed fluid F, the sealing device 1 is provided with a plurality of inclined grooves 16 as dynamic pressure grooves on the sealing gas space side on the sliding surface 12 of the stationary seal ring 11 that constitutes the mechanical seal 10 partitioning the internal space S1 and the sealing gas space S3. This can prevent the sealing gas G from mixing into the internal space S1 and can also prevent the sealed fluid F from leaking into the sealing gas space S3 between the sliding surfaces 12 and 22.

[0069] In addition, on the sliding surface 12 of the stationary seal ring 11, a dynamic pressure groove 15 on the sealed fluid space side as a liquid retaining groove is provided on the internal space S1 side. The liquid film of the sealed fluid F held in the deep groove 13 and the Rayleigh step 14 that constitute the dynamic pressure groove 15 on the sealed fluid space side can lubricate the sliding surfaces 12 and 22 with liquid, thus reducing friction. Furthermore, the dynamic pressure generated in the dynamic pressure groove 15 on the sealed fluid space side can separate the sliding surfaces 12 and 22 from each other, and a liquid film can be reliably formed between the sliding surfaces 12 and 22, further reducing friction.

[0070] In addition, in the conventional sealing device, since the pressure P2 of the sealing gas G is set to be higher than the pressure P1 of the fluid F to be sealed (P1 < P2), when the pressure temporarily reverses even in an unstable operating condition such as startup and shutdown, there is a risk that the sealing ring will be damaged immediately. In contrast, in the sealing device 1 of the present embodiment, even if the pressure P2 of the sealing gas G temporarily reverses to a state higher than the pressure P1 of the fluid F to be sealed (P1 < P2), the boundary between the liquid film of the fluid F to be sealed and the sealing gas G can be maintained between the sliding surfaces 12 and 22. Specifically, even during abnormal operation of the rotating device (P1 < P2), if the differential pressure P1 - P2 between the pressure P1 of the fluid F to be sealed and the pressure P2 of the sealing gas G is in the range of -500 kPa < P1 - P2 < 0, the boundary between the liquid film of the fluid F to be sealed and the sealing gas G is maintained between the sliding surfaces 12 and 22. Therefore, it is possible to prevent the sealing gas G from mixing into the internal space S1 and prevent the fluid F to be sealed from leaking into the sealing gas space S3 between the sliding surfaces 12 and 22.

[0071] In addition, since the dynamic pressure groove on the sealing gas space side is constituted by a plurality of inclined grooves 16, the dynamic pressure groove on the sealing gas space side can be simply configured. Further, since a positive pressure can be generated at the closed end portion 16A in the inclined groove 16, the fluid F to be sealed at a pressure higher than that of the sealing gas G can be effectively pushed back to the outer diameter side.

[0072] In addition, by changing the number, width, length, depth, etc. of the inclined grooves 16, it is easy to adjust the suction ability of the sealing gas G by the suction mechanism.

[0073] Furthermore, the seal gas space S3 and the external space S2 are mainly composed of a stationary sealing ring 31 and a rotating sealing ring 41 that rotates with the rotating shaft 2. As shown in Figure 3, a mechanical seal 30 is provided with a dynamic pressure generating texture 43 on the sealing gas space S3 side of the sliding surface 42 of the rotating sealing ring 41, which acts as a dynamic pressure generating mechanism. This suppresses the amount of seal gas G, which is at a higher pressure than the atmosphere A, leaking into the external space S2, and stabilizes the pressure P2 of the seal gas G in the seal gas space S3. In addition, the mechanical seal 30 reduces friction by separating the sliding surfaces 32, 42 with the dynamic pressure generated by the dynamic pressure generating texture 43 and by gaseous lubrication of the sliding surfaces 32, 42 with the seal gas G. Note that the mechanical seal 30 may also be a contact-type mechanical seal without a texture on the sliding surface.

[0074] Furthermore, the sealing device 1 is provided with a labyrinth seal 60 on the machine interior space S1 side of the mechanical seal 30, and a drain discharge port 51 is provided on the machine interior space S1 side of the labyrinth seal 60. As a result, even if the sealed fluid F, which has evaporated due to the heat generated between the sliding surfaces 12 and 22 of the mechanical seal 10, mixes with the seal gas G, the labyrinth seal 60 can prevent the sealed fluid F from entering the mechanical seal 30. Moreover, by opening the drain discharge port 51, the sealed fluid F mixed with the seal gas G can be easily discharged to the outside. Therefore, a rotating device that uses a mechanical seal 30 to contain a liquid or a fluid containing a liquid in the machine interior space S1 can be made into a simple configuration.

[0075] Still, in the sealing device 1 of the present embodiment, the mechanical seal 10 is described such that when the rotating device is operating normally (P1 > P2), a boundary between the liquid film of the fluid F to be sealed and the seal gas G is maintained between the sliding surfaces 12 and 22 if the differential pressure P1 - P2 is in the range of 0 < P1 - P2 < 500 kPa, and when the rotating device is operating abnormally (P1 < P2), the differential pressure P1 - P2 is in the range of -500 kPa < P1 - P2 < 0. Needless to say, the allowable range of the differential pressure P1 - P2 varies depending on the texture configuration of the sliding surface, the operating conditions of the rotating device, the conditions of the fluid F to be sealed and the seal gas G, etc.

Embodiment

[0076] Next, the sealing device according to Embodiment 2 will be described with reference to FIG. 4. Note that descriptions of configurations that are the same as those in Embodiment 1 will be omitted.

[0077] As shown in FIG. 4, the sealing device 101 of the present Embodiment 2 includes a mechanical seal 110 as an in-machine mechanical seal disposed on the in-machine space S1 side, and a mechanical seal 30 disposed on the out-of-machine space S2 side, and a seal gas space S3 for supplying the seal gas G is formed between the mechanical seals 110 and 30.

[0078] As shown in FIG. 4, in the sealing device 101 of the present Embodiment 2, the inner diameter side sleeve and the outer diameter side sleeve are axially divided into a first inner diameter side sleeve 103 and a first outer diameter side sleeve 104 attached to the out-of-machine space S2 side, and a second inner diameter side sleeve 106 and a second outer diameter side sleeve 107 attached to the in-machine space S1 side. Note that since the mechanical seal 30 attached to the first inner diameter side sleeve 103 and the first outer diameter side sleeve 104 has the same configuration as that in Embodiment 1, a detailed description thereof will be omitted. Also, since the seal structure formed by the labyrinth seal 60 and the first outer diameter side sleeve 104 has the same configuration as that in Embodiment 1, a detailed description thereof will be omitted.

[0079] The mechanical seal 110 differs from Embodiment 1 in that it separates the internal space S1 and the seal gas space S3, and is an outside-type mechanical seal that seals the fluid to be sealed F that would otherwise leak from the internal space S1 on the inner diameter side toward the seal gas space S3 on the outer diameter side.

[0080] The mechanical seal 110 in this embodiment mainly consists of a stationary sealing ring 111 and a rotating sealing ring 21 that rotates together with the rotating shaft 2. For the sake of explanation, the illustration is omitted, but since the mechanical seal 110 is of the outside type, the sliding surface 112 of the stationary sealing ring 111 is provided with a fluid retention groove on the inner diameter side, i.e., the internal space S1 side, which is the fluid space to be sealed side, and a seal gas space side dynamic pressure groove on the outer diameter side, i.e., the seal gas space S3 side. In other words, compared to Embodiment 1, the arrangement of the fluid space to be sealed side dynamic pressure groove and the seal gas space side dynamic pressure groove formed on the sliding surface 112 of the stationary sealing ring 111 is reversed on the inside and outside.

[0081] The stationary sealing ring 111 has a projection 111b that protrudes from the base 111a toward the rotating sealing ring 21. A sliding surface 112 is formed on the end face of the projection 111b.

[0082] As the rotating shaft 2 moves in the axial direction, the stationary sealing ring 111's movement toward the rotating sealing ring 21 is restricted when the outer diameter portion of its base 111a comes into contact with the restricting piece 54a of the stopper 54 attached to the inner circumferential surface of the housing 5.

[0083] A protrusion 111e is formed on the back surface 111d of the base portion 111a, projecting axially toward the aircraft interior space S1.

[0084] Furthermore, the stationary sealing ring 111 is biased toward the rotating sealing ring 21 by the elastic member 7 via the retainer 18. A secondary seal, the O-ring 39, is held on the stationary sealing ring 111 side of the retainer 18, and the O-ring 39 abuts against the convex portion 111e of the stationary sealing ring 111 from the axial direction.

[0085] The end face of the retainer 18 on the side of the stationary sealing ring 111 has a recess 18a formed therein that is recessed in the axial direction toward the machine interior space S1, is on the inner diameter side and open in the axial direction, and engages with the convex portion 111e of the stationary sealing ring 111 from the outer diameter side.

[0086] Furthermore, a guide portion 18b is formed on the inner diameter of the retainer 18, extending axially toward the internal space S1 and positioned along the protrusion 157 of the housing 5. The guide portion 18b guides the movement of the retainer 18 by sliding in contact with an O-ring 56 that is radially sandwiched between the inner circumferential surface of the protrusion 157 of the housing 5 and the guide portion 18b.

[0087] The rotating sealing ring 21 is held in place by being fitted into a recess 106b formed in the flange portion 106a of the second inner diameter sleeve 106, which is fitted onto the rotating shaft 2. An O-ring 38, which serves as a secondary seal, is sandwiched axially between the recess 106b of the second inner diameter sleeve 106 and the rotating sealing ring 21. In addition, an O-ring 136, which serves as a secondary seal, is sandwiched radially between the outer circumferential surface of the second inner diameter sleeve 106 and the inner circumferential surface of the second outer diameter sleeve 107.

[0088] Furthermore, the rotating sealing ring 21 is prevented from coming out in the axial direction by being held between the end of the second outer diameter sleeve 107, which is fitted onto the second inner diameter sleeve 106, and the recess 106b of the second inner diameter sleeve 106.

[0089] In this embodiment, a flange portion 105 extending inward is formed on the inner circumferential surface of the housing 5 at a position between the mechanical seal 110 and the labyrinth seal 60. The formation of the flange portion 105 gives the seal gas space S3 a folded structure. [Examples]

[0090] Next, the sealing device according to Example 3 will be described with reference to Figure 5. Note that the description of components that are identical to those in Example 1 and therefore redundant will be omitted.

[0091] As shown in Figure 5, the sealing device 201 of this embodiment 3 comprises a mechanical seal 10 located on the internal space S1 side and a mechanical seal 230 located on the external space S2 side, which is an external sealing means, and a sealing gas space S3 is formed between the mechanical seals 10 and 230, to which sealing gas G is supplied.

[0092] As shown in Figure 5, in the sealing device 201 of this embodiment 3, a stepped portion 203c is formed on the outer circumferential surface of the inner diameter sleeve 203, and the outer diameter sleeve is axially divided into two parts: a first outer diameter sleeve 204 attached to the seal gas space S3 side and a second outer diameter sleeve 205 attached to the external space S2 side. Note that the mechanical seal 10 has the same configuration as in embodiment 1, so a detailed explanation is omitted.

[0093] The mechanical seal 230 is an outside-type mechanical seal that separates the external space S2 and the seal gas space S3, sealing the seal gas G that would otherwise leak from the seal gas space S3 on the inner diameter side toward the external space S2 on the outer diameter side, and differs from Embodiment 1 in that the uneven shape constituting the labyrinth seal 260 is integrally formed on the inner circumferential surface of the housing 5.

[0094] The mechanical seal 230 in this embodiment mainly consists of a stationary sealing ring 31 and a rotating sealing ring 241 that rotates together with the rotating shaft 2. For the sake of explanation, the illustration is omitted, but since the mechanical seal 230 is an outside type, a dynamic pressure generating texture is provided on the inner diameter side, i.e., on the sealing gas space S3 side, of the sliding surface 242 of the rotating sealing ring 241. In other words, compared to Embodiment 1, the arrangement of the dynamic pressure generating texture formed on the sliding surface 242 of the rotating sealing ring 241 is reversed, with the inner and outer sides swapped.

[0095] The stationary sealing ring 31 has a protrusion 31b that projects outward from approximately the axial center of the outer peripheral surface of the base portion 31a. As the rotating shaft 2 moves in the axial direction, the movement of the stationary sealing ring 31 toward the rotating sealing ring 241 is restricted when the protrusion 31b comes into contact with the restricting piece 253a of the stopper 253 attached to the inner peripheral surface of the housing 5.

[0096] A first recess 31c is formed on the inner circumferential surface of the base portion 31a, which is recessed on the outer diameter side and open on the back surface 31d side and the inner diameter side.

[0097] A second recess 31e is formed on the back surface 31d of the base portion 31a, which is recessed on the sliding surface 32 side and open on the inner diameter side and back side.

[0098] Furthermore, the stationary sealing ring 31 is biased toward the rotating sealing ring 241 by an elastic member 34 via a retainer 33. An O-ring 35, which is a secondary seal, is held in the inner diameter portion of the retainer 33. The O-ring 35 abuts the second recess 31e of the stationary sealing ring 31 from the axial direction and abuts the guide portion 52 of the housing 5 from the radial direction. The guide portion 52 guides the movement of the stationary sealing ring 31 and the retainer 33 by sliding contact between the first recess 31c of the stationary sealing ring 31 and the O-ring 35 held in the retainer 33.

[0099] The outer circumferential surface of the retainer 33 has a recess 33a that is recessed on the inner diameter side and open on the outer diameter side, with the back surface 31d of the stationary sealing ring 31 in axial contact with the recess 33a. In other words, the retainer 33 and the stationary sealing ring 31 are arranged with a portion of their surfaces overlapping in the radial direction.

[0100] The rotating sealing ring 241 is held in place by being fitted into a recess 205b formed in the flange portion 205a of the second outer diameter sleeve 205, which is further fitted onto the inner diameter sleeve 203 that is fitted onto the rotating shaft 2. An O-ring 37, which serves as a secondary seal, is sandwiched axially between the recess 205b of the second outer diameter sleeve 205 and the rotating sealing ring 241. In addition, an O-ring 236, which serves as a secondary seal, is sandwiched radially between the outer circumferential surface of the inner diameter sleeve 203 and the inner circumferential surface of the second outer diameter sleeve 205.

[0101] Furthermore, the rotating sealing ring 241 is prevented from coming out in the axial direction by being held between the end of the first outer diameter sleeve 204, which is attached to the seal gas space S3 side, and the recess 205b of the second outer diameter sleeve 205.

[0102] The first outer diameter sleeve 204 is in axial contact with the stepped portion 203c of the inner diameter sleeve 203, and an O-ring 36, which serves as a secondary seal, is sandwiched radially between the outer circumferential surface of the inner diameter sleeve 203 and the inner circumferential surface of the first outer diameter sleeve 204.

[0103] Furthermore, a flange portion 204a extending outward is formed on the outer circumferential surface of the first outer diameter sleeve 204, corresponding to the formation position of the labyrinth seal 260 on the inner circumferential surface of the housing 5. The formation of the flange portion 204a results in an L-shaped structure for the seal gas spaces S3 formed on the left and right sides of the labyrinth seal 260.

[0104] Although embodiments of the present invention have been described above with reference to the drawings, the specific configurations are not limited to these embodiments, and any changes or additions that do not depart from the spirit of the present invention are also included.

[0105] For example, the sealing device may include an outside-type mechanical seal 110 (see Figure 4) located on the internal space S1 side of Embodiment 2, and an outside-type mechanical seal 230 (see Figure 5) located on the external space S2 side.

[0106] Furthermore, although the sealing device in Examples 1 to 3 was described as having two mechanical seals arranged in the axial direction, it is not limited to this, and three or more mechanical seals may be arranged in the axial direction.

[0107] Furthermore, if a dynamic pressure groove on the sealing gas space side is provided on the sealing gas space S3 side of the sliding surface of the stationary sealing ring that constitutes the internal mechanical seal located on the internal space S1 side, a dynamic pressure groove on the sealed fluid space side, which is a fluid retention groove, does not need to be provided on the internal space S1 side.

[0108] Furthermore, the dynamic pressure groove on the seal gas space side is not limited to an inclined groove; it may be made of other textures as long as it causes the seal gas G to be drawn in.

[0109] Furthermore, the fluid retention groove may not generate dynamic pressure.

[0110] Furthermore, in the above embodiments 1 to 3, the internal mechanical seal arranged on the machine interior space S1 side was described as having a sealing gas space side dynamic pressure groove and a sealed fluid space side dynamic pressure groove, which is a fluid retention groove, on the sliding surface of the stationary sealing ring. However, it is not limited to this, and the sealing gas space side dynamic pressure groove and the sealed fluid space side dynamic pressure groove, which is a fluid retention groove, may be provided on the sliding surface of the rotating sealing ring, or on both the sliding surfaces of the stationary sealing ring and the rotating sealing ring.

[0111] While stationary and rotating sealing rings are typically formed from SiC (hard material) or a combination of SiC (hard material) and carbon (soft material), the sliding material is not limited to this; any sliding material used for mechanical seals is applicable. SiC can be sintered using boron, aluminum, or carbon as sintering aids, or from materials consisting of two or more phases with different components and compositions, such as SiC with dispersed graphite particles, reaction-sintered SiC made of SiC and Si, SiC-TiC, or SiC-TiN. Carbon can be a mixture of carbonaceous and graphite, as well as resin-molded carbon and sintered carbon. In addition to the sliding materials mentioned above, metal materials, resin materials, surface modification materials (coating materials), and composite materials are also applicable.

[0112] Furthermore, if the sealing device is sealed at least on the aircraft interior side S1 by an internal mechanical seal, the external space S2 side does not need to be sealed by an external mechanical seal, and may be sealed by other external sealing means such as a labyrinth seal.

[0113] Furthermore, in the above embodiments 1 to 3, the sealing device was described as having labyrinth seals 60 and 260 provided on the internal space S1 side of the external mechanical seal. However, it is not limited to this, and for example, if an external mechanical seal is not used on the external space S2 side, the labyrinth seals 60 and 260 do not need to be provided.

[0114] Furthermore, the fluid in the external space S2 is not limited to the atmosphere A, but may be a gas, a liquid, or a mixture of gas and liquid (mist-like fluid). [Explanation of Symbols]

[0115] 1,101,201 Sealing device 2 rotation axes 5 Housing 7 Elastic members 10. Mechanical seal (internal mechanical seal) 11. Static sealing ring (internal static sealing ring) 12 Sliding surface 13 deep groove 14. Rayleigh Step 15 Sealed fluid space side dynamic pressure groove (liquid retention groove) 16. Inclined groove (dynamic pressure groove on the side of the sealing gas space) 17 Land 21. Rotating sealing ring (rotating sealing ring inside the machine) 22 Sliding surface 30 Mechanical seal (external sealing means, external mechanical seal) 31. Stationary sealing ring (stationary sealing ring on the outside of the machine) 32 Sliding surface 41. Rotating sealing ring (rotating sealing ring on the outside of the machine) 42 Sliding surface 43. Texture for generating dynamic pressure (dynamic pressure generation mechanism) 50 Seal gas supply ports 51 Drain discharge port 60 Labyrinth Seals 110 Mechanical seal (internal mechanical seal) 230 Mechanical seal (external sealing means, external mechanical seal) A atmosphere F Sealed fluid G Seal Gas S1 In-cabin space (sealed fluid space) S2 External space (space outside the aircraft) S3 Seal gas space

Claims

[Claim 1] A sealing device comprising an internal stationary sealing ring fixed to the housing side and positioned between a housing and a rotating shaft that rotates relative to the housing, and an internal rotating sealing ring fixed to the rotating shaft side, wherein the internal stationary sealing ring and the internal rotating sealing ring slide against each other by relative rotation to partition a sealed fluid space and a seal gas space, and an external sealing means partitioning the seal gas space and an external space located outside the machine beyond the seal gas space, The sealed fluid is a liquid or a fluid containing a liquid. The pressure of the sealing gas is set lower than the pressure of the fluid being sealed. The pressure in the external space of the machine is set lower than the pressure of the sealing gas. A sealing device in which a seal gas space side dynamic pressure groove communicating with the seal gas space side is provided on at least one sliding surface of the internal rotating sealing ring and the internal stationary sealing ring of the internal mechanical seal.

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