Mechanical seal

Abstract

To eliminate such a defect that a conventional mechanical seal for a shaft sealing device has a great sliding resistance when a rotary ring and a fixed ring contact each other.SOLUTION: The mechanical seal is provided in the shaft sealing device for sealing a casing through which a rotary shaft rotatably penetrates. The mechanical seal includes a flange-like rotary ring fixed to the outer peripheral face of the rotary shaft, a cylindrical fixed ring provided in the casing in opposition to the rotary ring movably in the axial direction of the rotary shaft, pressing means for pressing the fixed ring against the rotary ring, and seal liquid filling means for filling seal liquid between the end face of the rotary ring and the opposed end face of the fixed ring to form a seal part. The end face of the rotary ring and the end face of the fixed ring are shaped so that a contact area at the time the end face of the rotary ring and the end face of the fixed ring contact each other is smaller than an opposed area where the end face of the rotary ring and the end face of the fixed ring are opposed to each other to form the seal part.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention particularly relates to a mechanical seal provided in a shaft seal device for sealing a casing through which a rotating shaft penetrates.

Background Art

[0002] For example, in a disperser, pump, crusher, stirrer, etc. having a rotating shaft that processes a slurry containing solids, etc., a mechanical seal may be used in a shaft seal device that seals a shaft hole of a casing (housing) of the disperser, etc. through which the rotating shaft penetrates rotatably.

[0003] The mechanical seal includes a rotating ring fixed to the rotating shaft, a fixed ring on the casing side pressed against the rotating ring, and a seal injection means for injecting a seal liquid between the rotating ring and the fixed ring. The seal portion (sliding portion) formed by the end faces of the rotating ring and the fixed ring that face and slide against each other through the seal liquid prevents foreign matter from entering the casing.

[0004] And, for example, in a disperser that processes a slurry, etc., as a shaft seal device for a rotating shaft provided in a casing, a pair of the mechanical seals are arranged separately in the axial direction of the rotating shaft, and a seal liquid is injected between the pair of mechanical seals to lubricate and cool the seal portion (sliding portion) between the rotating ring and the fixed ring, and a double mechanical seal is often adopted.

[0005] FIG. 3 and FIG. 4 show a shaft seal device 1 having the conventional double mechanical seal. The shaft seal device 1 includes a cylindrical shaft seal body 5 having a hole 4 through which a rotating shaft 3 penetrates rotatably and is fixed through a shaft hole 2a of a casing 2 such as a classifier, and a pair of mechanical seals 6 and 7 provided separately in the axial direction of the rotating shaft 3 with the casing 2 interposed therebetween, and a seal injection means 8 for injecting a seal liquid between the pair of mechanical seals 6 and 7.

[0006] The mechanical seal 6, positioned inside the casing 2, comprises, for example, as shown in Figure 4, a flange-shaped rotating ring 9 fixed to the outer circumferential surface of a sleeve 3a provided on the outer circumferential surface of the rotating shaft 3 inside the casing 2; an annular groove 10 formed on one end face 5a inside the casing of the cylindrical shaft seal body 5; a cylindrical fixing ring 11 inserted into the groove 10 and provided to be movable in the axial direction of the rotating shaft, having an annular end face 11a capable of pressing against the other end face 9a of the rotating ring 9; and a pressing means 12 such as a spring that presses the fixing ring 11 toward the rotating ring 9.

[0007] Furthermore, the other end face 9a of the rotating ring 9 and the annular end face 11a of the stationary ring 11, which slides opposite to the other end face 9a, are each formed by flat surfaces perpendicular to the axial direction of the rotation axis 3. The opposing area between the other end face 9a of the rotating ring 9 and the one end face 11a of the stationary ring 11, which constitutes the seal portion, is designed to be of a desired size in order to prevent foreign matter such as solids from entering the seal portion.

[0008] Furthermore, the mechanical seal 7, which is positioned on the outside of the casing 2, is similar to the mechanical seal 6 in that it consists of a flange-shaped rotating ring 13 fixed to the outer surface of a sleeve 3a provided on the outer surface of the rotating shaft 3 on the outside of the casing 2, an annular groove 14 formed on the other end face 5b of the cylindrical shaft seal body 5 on the outside of the casing, a cylindrical fixing ring 15 inserted into the groove 14 and provided to be movable in the axial direction of the rotating shaft 3, having an annular other end face 15a capable of pressing against one end face 13a of the rotating ring 13, and a pressing means (not shown) such as a spring that presses the fixing ring 15 toward the rotating ring 13.

[0009] Furthermore, one end face 13a of the rotating ring 13 and the other annular end face 15a of the stationary ring 15, which slides opposite to and against the one end face 13a, are each formed by flat surfaces perpendicular to the axial direction of the rotation axis, similar to the other end face 9a of the rotating ring 9 and the one end face 11a of the stationary ring 11. In addition, the opposing area between the one end face 13a of the rotating ring 13 and the other end face 15a of the stationary ring 15, which constitute the seal portion, is designed to be of a desired size in order to prevent foreign matter such as solids from entering the seal portion.

[0010] Furthermore, the sealing fluid injection means 8, as shown in Figure 3, for example, consists of a sealing fluid inlet 16 and a sealing fluid outlet 17 communicating with the grooves 10 and 14, a sealing fluid storage tank 18, and a pump 19.

[0011] Then, the sealing fluid in the tank 18 is supplied to the sealing fluid inlet 16 by the pump 19 so that the pressure inside the shaft seal device 1 is higher than the pressure inside the casing. The sealing fluid is injected through the grooves 10 and 14 into the seal between the rotating rings 9 and 13 and the stationary rings 11 and 15, providing lubrication and cooling to the seal. The remaining sealing fluid is returned to the tank 18 from the sealing fluid outlet 17, and the sealing fluid in the tank 18 is circulated within the shaft seal device.

[0012] Note that 20 and 21 indicate leak prevention measures such as O-rings.

[0013] As shown in Figure 5, in the conventional shaft sealing device 1, one end of the cylindrical fixed ring 11 is formed into a trapezoidal cylindrical tapered portion that widens in the outer direction, and the fixed ring 11 is formed from a main body portion 11b and a tapered portion 11c, and one end face 11a of the tapered portion 11c that slides opposite to the other end face 9a of the rotating ring 9 is formed to have a larger diameter than the diameter of the main body portion 11b of the fixed ring 11, so that the pulling force of the fixed ring 11 is greater than the pressing force of the fixed ring 11 against the rotating ring 9 by the sealing fluid inside the shaft sealing device 1, and the sealing fluid is allowed to flow to the inside of the casing through the seal portion between the rotating ring 9 and the fixed ring 11, thereby providing a stable sealing effect.

[0014] Examples of the aforementioned mechanical seals include those shown in Patent Document 1 (Figures 1 to 6). [Prior art documents] [Patent Documents]

[0015] [Patent Document 1] Japanese Patent Publication No. 2010-164118 [Overview of the Initiative] [Problems that the invention aims to solve]

[0016] However, in the conventional mechanical seal, the sealing portion is lubricated and cooled by a sealing fluid, but in particular, the rotating ring and the stationary ring may come into contact during startup. Because the contact area between the rotating ring and the stationary ring is large, the sliding resistance increases, requiring excessive torque during startup.

[0017] Therefore, this affected the selection of the motor that rotates the rotating shaft and also caused problems such as initial startup failures.

[0018] This invention aims to eliminate the above-mentioned drawbacks. [Means for solving the problem]

[0019] To achieve the above object, the mechanical seal of the present invention comprises a mechanical seal provided in a shaft sealing device for sealing a casing through which a rotating shaft rotates freely. The mechanical seal includes a flange-shaped rotating ring fixed to the outer peripheral surface of the rotating shaft, a cylindrical fixed ring provided in the casing, facing the rotating ring and movable axially of the rotating shaft, pressing means for pressing the fixed ring against the rotating ring, and seal liquid injection means for injecting seal liquid between the facing end surfaces of the rotating ring and the fixed ring, which constitute a seal portion. The shapes of the end surfaces of the rotating ring and the fixed ring are formed such that the contact area when the end surfaces of the rotating ring and the fixed ring are brought into contact with each other is smaller than the opposing area of the end surfaces of the rotating ring and the fixed ring that constitute the seal portion. The annular end surface of the fixed ring facing the end surface of the rotating ring that constitutes the seal portion is formed of a surface inclined from the outer periphery toward the inner periphery with respect to the end surface of the opposing rotating ring. The end face of the fixing ring is formed such that the radial line of the end face is straight, and the inclination angle of the end face of the fixing ring is formed within the range of 0.5 degrees to 5 degrees. It is characterized by the above.

[0021] Further, the end surface of the rotating ring is constituted by a flat surface orthogonal to the axial direction of the rotating shaft, and the annular end surface of the fixed ring facing the end surface of the rotating ring is formed of a surface inclined in a direction away from the rotating ring from the outer periphery toward the inner periphery.

[0023] Further, a recess is formed in at least one of the end surfaces of the rotating ring and the end surface of the fixed ring.

[0024] Further, the end surface of the rotating ring and the end surface of the fixed ring facing the end surface of the rotating ring are each formed of a flat surface orthogonal to the axial direction of the rotating shaft, and a recess is formed in the end surface of the fixed ring.

[0025] Further, the recess is a plurality of grooves or a plurality of depressions.

Effects of the Invention

[0026] According to the present invention, the opposing area where the end face of the rotating ring and the end face of the stationary ring, which constitute the sealing portion, face each other is the same size as in the prior art. Therefore, the stability of the seal can be ensured. Even when the rotating ring and the stationary ring come into contact with each other, the contact area is small. For example, the sliding resistance during startup can be reduced.

Brief Description of the Drawings

[0027] [Figure 1] It is a longitudinal side view for explaining the mechanical seal of the present invention. [Figure 2] It is a longitudinal side view for explaining another embodiment of the mechanical seal of the present invention. [Figure 3] It is a longitudinal side view of a shaft seal device having a conventional mechanical seal. [Figure 4] It is a longitudinal side view of a main part of a shaft seal device having a conventional mechanical seal. [Figure 5] It is a longitudinal side view of a main part of another embodiment of a shaft seal device having a conventional mechanical seal.

Modes for Carrying Out the Invention

[0028] Examples of modes for carrying out the present invention are shown below.

[0029] Note that the same reference numerals are given to the same parts as in the background art, and the description thereof is omitted.

Examples

[0030] Example 1 of the present invention will be described with reference to FIG. 1.

[0031] In the present invention, in the conventional shaft seal device 1, for example, as shown in FIG. 1, instead of forming the annular one end face 11a of the stationary ring 11 that faces and slides against the rotating ring 9 of the mechanical seal 6 into a flat surface perpendicular to the axial direction of the rotating shaft, it is formed into a funnel-shaped surface that is inclined in a direction away from the rotating ring 9 from the outer periphery toward the inner periphery and recessed toward the center.

[0032] Furthermore, the annular end face 11a is formed such that, for example, the radial line of the end face 11a is inclined in a straight line. The range of the inclination angle θ varies depending on the type of device, but if there is almost no inclination, the entire surface of the sliding part will come into contact at startup, resulting in little effect. On the other hand, if the inclination is too great, the inner ends of the sealing parts of the rotating ring and the stationary ring will be too far apart, making it difficult to maintain the stability of the seal, such as preventing solid matter from entering. Therefore, it is preferable that the inclination angle is formed in the range of, for example, 0.5 degrees to 5 degrees.

[0033] According to the present invention, even if the stationary ring and the rotating ring come into contact during startup, the contact area is limited to the outer ends of the sealing portions of the rotating ring and the stationary ring. As the contact area is small, sliding resistance is reduced, eliminating the need for excessive torque during startup.

[0034] Furthermore, since the same area as in the conventional design can be secured for the opposing surfaces of the end face of the rotating ring and the end face of the stationary ring that constitute the sealing portion, the stability of the seal can be maintained.

[0035] Furthermore, the inclination of the one end face 11a does not have to be formed in a straight radial line; for example, it may be curved or stepped.

[0036] Furthermore, the one end face 11a may be inclined in a direction that approaches the rotating ring as it moves from the outer circumference towards the inner circumference.

[0037] Alternatively, one end face 11a of the fixed ring 11 may be a surface perpendicular to the axial direction of the rotation axis 3, and the other end face 9a of the rotating ring 9 may be inclined.

[0038] That is, one end face 11a of the fixed ring 11 may be formed to be inclined by a desired amount relative to the other end face 9a of the rotating ring 9, from the outer circumference towards the inner circumference.

[0039] The above description pertains to mechanical seal 6, but the same applies to mechanical seal 7. [Examples]

[0040] In a second embodiment of the present invention, as shown in Figure 2, for example, one or more recesses 22 are formed on the entire circumferential surface of one end face 11a of the conventional fixing ring 11.

[0041] The recess 22 may be, for example, a groove or a depression.

[0042] The size, depth (height), shape, quantity, and range of the recess 22 are freely formed within a range that can maintain the stability of the seal, such as preventing solid matter from entering the seal portion.

[0043] In the second embodiment of the present invention, even if the stationary ring and the rotating ring come into contact during startup, the recessed portion does not come into contact, resulting in a small contact area. This reduces sliding resistance, making it possible to avoid the need for excessive torque during startup.

[0044] Alternatively, a recess may be formed on the end face of the rotating ring 9 instead of the end face of the fixed ring 11.

[0045] Alternatively, recesses may be formed on both the end faces of the fixed ring 11 and the rotating ring 9.

[0046] Furthermore, the recess 22 may be formed not only on the entire circumferential surface of the end face, but also in a portion of it.

[0047] The above description pertains to mechanical seal 6, but the same applies to mechanical seal 7. [Explanation of Symbols]

[0048] 1 Shaft sealing device 2 Casing 2a shaft hole 3 rotation axes 3a Sleeve 4 holes 5. Shaft seal body 5a One end face 5b Other end surface 6 Mechanical seals 7 Mechanical seal 8. Sealing fluid injection means 9 Rotating Rings 9a Other end surface 10 grooves 11 Fixed ring 11a One end face 11b Main body 11c tapered section 12 Pressing means 13 Rotating Rings 13a One end face 14 grooves 15 Fixed ring 15a Other end surface 16. Sealing fluid inlet 17. Sealing fluid outlet 18. Sealing fluid storage tank 19 pumps 20 Leak prevention measures 21 Leak prevention measures 22 recess

Claims

1. It consists of a mechanical seal provided in a shaft sealing device for sealing a casing through which a rotating shaft rotatably passes. The mechanical seal comprises a flange-shaped rotating ring fixed to the outer circumferential surface of the rotating shaft, A cylindrical fixed ring is provided in the casing, facing the rotating ring, and is movable in the axial direction of the rotating shaft, The aforementioned fixed ring is pressed against the aforementioned rotating ring by a pressing means, The sealing portion is formed between the end faces of the rotating ring and the stationary ring, which are opposite to each other, and includes a sealing fluid injection means for injecting sealing fluid into this space. The area of ​​the sealing portion where the end face of the rotating ring and the end face of the stationary ring face each other is greater than the area of ​​the opposing surfaces of the sealing portion. The shapes of the end faces of the rotating ring and the stationary ring are formed such that the contact area when the end face of the rotating ring and the end face of the stationary ring are in contact is reduced. The annular end face of the stationary ring, which is opposite to the end face of the rotating ring constituting the sealing portion, is formed from a surface that is inclined from the outer circumference toward the inner circumference with respect to the opposing end face of the rotating ring. A mechanical seal characterized in that the end face of the fixed ring is formed such that the radial line of the end face is straight, and the inclination angle of the end face of the fixed ring is formed within the range of 0.5 degrees to 5 degrees.

2. The end face of the rotating ring is formed by a flat surface perpendicular to the axial direction of the rotation axis, The mechanical seal according to claim 1, characterized in that the annular end face of the stationary ring, which is opposite to the end face of the rotating ring, is formed from a surface that is inclined in a direction away from the rotating ring from the outer circumference toward the inner circumference.

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