Mechanical seal

Abstract

To provide a mechanical seal capable of reducing the running cost while suppressing deterioration of followability of a rotary seal ring to a stationary seal ring.SOLUTION: A mechanical seal 10 includes a stationary seal ring 22 provided on a casing 72 side, an annular retainer 24 movable in an axial direction with respect to a rotating shaft 71, a rotary seal ring 23 retained in one side in the axial direction of the retainer 24 and sliding on the stationary seal ring 22, an annular seal member 40 fixed to the rotating shaft 71 side and having a seal lip 42 in contact with the rotary seal ring 23, and a bellows 26 provided on the rotating shaft 71 side in the other side in the axial direction of the retainer 24 so as to restrain leakage of a sealed fluid in a device inside region C from the other side in the axial direction of the retainer 24 to the outside of the device and pressurizing the rotary seal ring 23 to the stationary seal ring 22 through the retainer 24.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a mechanical seal. [Background technology]

[0002] A mechanical seal device 100 shown in Fig. 3 is known as a device for sealing a slurry fluid containing a large amount of solid particles such as sand, stones, and metal chips inside a rotating device. The mechanical seal device 100 includes a pair of mechanical seals 103 and 104 arranged between a casing 101 and a rotating shaft 102 of the rotating device (see Patent Document 1).

[0003] An annular liquid sealing region 105, into which sealing liquid for sealing and cooling is introduced, is formed between a pair of mechanical seals 103, 104 inside the casing 101. The mechanical seal 103 on the outside seals between the liquid sealing region 105 and an outside region 106, and the mechanical seal 104 on the inside seals between the liquid sealing region 105 and an inside region 107. The pressure of the liquid sealing region 105 is set higher than the pressure of the slurry fluid in the inside region 107, preventing the slurry fluid in the inside region 107 from leaking into the liquid sealing region 105.

[0004] The mechanical seal 104 on the inside of the machine has a stationary seal ring 113 attached to the casing 101 and a rotary seal ring 114 attached to the rotary shaft 102 so as to be rotatable integrally with the rotary seal ring 114. The rotary seal ring 114 is fixed to a retainer 115. The rotary seal ring 114 and the retainer 115 are pressed toward the stationary seal ring 113 by a spring 116. This allows the rotary seal ring 114 to slide while being pressed by the stationary seal ring 113.

[0005] A rubber O-ring 117 is provided on the inner periphery of the retainer 115 to form a seal (secondary seal) between the retainer 115 and the outer periphery of the rotating shaft 102. The O-ring 117 moves axially relative to the rotating shaft 102 together with the retainer 115. The O-ring 117 prevents the slurry fluid in the in-machine region 107 from passing through the gap between the retainer 115 and the rotating shaft 102 and leaking into the liquid-sealing region 105.

[0006] In this mechanical seal device 100, an inlet passage 120 is formed in the casing 101 for constantly introducing an injection fluid, which is a clean fluid separate from the slurry fluid, near the mechanical seal 104 in the inboard region 107 where the slurry fluid is sealed. The injection fluid introduced into the inboard region 107 from the inlet passage 120 enters the gap between the O-ring 117 and the rotating shaft 102, thereby preventing solid particles of the slurry fluid from accumulating in the gap. This prevents the O-ring 117 from hindering axial movement due to solid particles accumulating in the gap. As a result, a decrease in the tracking ability of the rotary seal ring 114 relative to the stationary seal ring 113 is prevented, thereby preventing leakage of the slurry fluid. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-146079 Summary of the Invention [Problem to be solved by the invention]

[0008] The mechanical seal device 100 has a problem in that the running cost is high because the injection fluid must be constantly introduced into the interior area 107 while the rotating equipment is in operation.

[0009] The present invention has been made in view of the above circumstances, and has an object to provide a mechanical seal that can reduce running costs while suppressing a decrease in the ability of the rotating seal ring to follow the stationary seal ring. [Means for solving the problem]

[0010] (1) The present invention is a mechanical seal that includes: a stationary seal ring provided on a casing that surrounds a rotating shaft and having a seal surface; an annular retainer that is axially movable relative to the rotating shaft; and a rotary seal ring that is held on one axial side of the retainer and has a seal surface that slides on the seal surface of the stationary seal ring, and that seals a sealed fluid in an inboard area that is formed radially inward of both the seal surfaces of the stationary seal ring and the rotary seal ring, the mechanical seal including: an annular seal member that is fixed to the rotating shaft and has a seal lip that contacts the rotary seal ring; and a bellows that is provided on the rotating shaft on the other axial side of the retainer to prevent the sealed fluid in the inboard area from leaking from the other axial side of the retainer to the outside of the aircraft, and that presses the rotary seal ring toward the stationary seal ring via the retainer.

[0011] According to the present invention, on one axial side of the retainer, the seal lip of the seal member fixed to the rotating shaft contacts the rotary seal ring, thereby preventing the sealed fluid in the in-machine area from entering the inner periphery of the retainer. On the other axial side of the retainer, the bellows prevents the sealed fluid from leaking out of the machine, eliminating the need for an O-ring on the inner periphery of the retainer as in the past. Furthermore, a wider gap is formed between the bellows and the rotating shaft on the other axial side of the retainer than between a conventional O-ring and the rotating shaft. Therefore, even if the sealed fluid passes through the inner periphery of the seal member and the retainer and enters the gap, the time until solid particles contained in the sealed fluid accumulate in the gap and inhibit the axial movement of the bellows can be extended compared to the case of a conventional O-ring. As a result, the tracking ability of the rotary seal ring relative to the stationary seal ring is prevented from decreasing. Furthermore, since an O-ring is not required on the inner periphery of the retainer as described above, there is no need to introduce injection fluid into the in-machine area as in the past. This reduces running costs.

[0012] (2) It is preferable that the bearing further comprises an annular bushing provided on the inner periphery of the retainer and protruding radially inward beyond the retainer, the bushing being made of a low-friction material. In this case, when the retainer moves in the axial direction, the inner peripheral surface of the bushing made of a low-friction material slides against the rotating shaft, allowing the retainer to move smoothly in the axial direction, thereby further preventing a decrease in the ability of the rotating seal ring to follow the stationary seal ring.

[0013] (3) It is preferable that the rotary seal ring is tapered toward its sealing surface. In this case, the tapered leading end face of the rotary seal ring becomes the seal surface, so the area of the seal surface of the rotary seal ring can be made smaller than when the rotary seal ring is not tapered. This increases the surface pressure between the seal surfaces of the rotary seal ring and the stationary seal ring, thereby improving sealing performance.

[0014] (4) It is preferable that the rotary seal ring has a tapered surface whose diameter decreases from the radially inner end of the seal surface toward the inner circumferential surface, and the seal lip of the seal member contacts the tapered surface. In this case, the seal lip contacts the tapered surface of the rotary seal ring, allowing the retainer to move more smoothly in the axial direction compared to when the seal lip contacts the inner peripheral surface of the rotary seal ring, thereby further preventing a decrease in the ability of the rotary seal ring to follow the stationary seal ring.

[0015] (5) The sealing member is preferably a V-ring. In this case, a commercially available V-ring can be used as the sealing member, which further reduces costs. [Effects of the Invention]

[0016] According to the present invention, it is possible to reduce running costs while suppressing a decrease in the ability of the rotary seal ring to follow the stationary seal ring. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a cross-sectional view of a double mechanical seal device equipped with a mechanical seal according to an embodiment of the present invention. [Figure 2] FIG. 4 is an enlarged cross-sectional view showing a second mechanical seal. [Figure 3] FIG. 1 is a cross-sectional view showing a conventional mechanical seal device. DETAILED DESCRIPTION OF THE INVENTION

[0018] Next, preferred embodiments of the present invention will be described with reference to the accompanying drawings. [Double mechanical seal device] Fig. 1 is a cross-sectional view of a double mechanical seal device equipped with a mechanical seal according to an embodiment of the present invention. In Fig. 1, the double mechanical seal device 1 is used in rotating equipment such as a pump that handles a slurry fluid (sealed fluid) containing a large amount of solid particles such as sand, stones, and metal chips. The double mechanical seal device 1 is disposed along the axial direction of the rotating shaft 71 (hereinafter simply referred to as the "axial direction") between the rotating equipment's rotating shaft 71 side and the casing 72 side that surrounds the rotating shaft 71. For convenience, in this specification, the right side of Fig. 1 will be referred to as one axial side, and the left side of Fig. 1 will be referred to as the other axial side (the same applies to Fig. 2).

[0019] The double mechanical seal device 1 comprises a sleeve 2 fixed to the outer periphery of a rotating shaft 71, a seal case 3 attached to a casing 72 radially outside the sleeve 2, a first mechanical seal 10 arranged on the other axial side between the sleeve 2 and the seal case 3, and a second mechanical seal 20 arranged on one axial side between the sleeve 2 and the seal case 3.

[0020] The seal case 3 is disposed in a partition area separating the external area A and the internal area C, and is fixed to the side of the casing 72 with bolts 4. An annular sealing liquid area B is formed between the first mechanical seal 10 and the second mechanical seal 20, into which a sealing liquid for sealing and cooling is introduced. The first mechanical seal 10 provides a seal between the external area A and the sealing liquid area B. The second mechanical seal 20 provides a seal between the sealing liquid area B and the internal area C.

[0021] The seal case 3 is formed with a supply path 3a that supplies sealing liquid to the liquid sealing region B and a discharge path 3b that discharges the sealing liquid in the liquid sealing region B to the outside. The sealing liquid supplied from the supply path 3a to the liquid sealing region B while the rotating equipment is in operation cools the first and second mechanical seals 10, 20. After cooling the first and second mechanical seals 10, 20, the sealing liquid is discharged to the outside through the discharge path 3b. The pressure of the sealing liquid in the liquid sealing region B is set higher than the pressure of the slurry fluid in the in-machine region C. This prevents the slurry fluid in the in-machine region C from leaking into the liquid sealing region B.

[0022] [First mechanical seal] The first mechanical seal 10 includes a stationary seal ring 11, a rotary seal ring 12, a retainer 13, and a spring 14. A seal surface 11a is formed on one axial side of the stationary seal ring 11. The stationary seal ring 11 is fixed to the other axial end of the inner circumferential surface of the seal case 3. An O-ring 15 provides a seal (secondary seal) between the outer circumferential surface of the stationary seal ring 11 and the inner circumferential surface of the seal case 3.

[0023] The rotary seal ring 12 is disposed adjacent to one axial side of the stationary seal ring 11. A seal surface 12a that slides against the seal surface 11a of the stationary seal ring 11 is formed on the other axial side of the rotary seal ring 12. An O-ring 16 provides a seal (secondary seal) between the inner circumferential surface of the rotary seal ring 12 and the outer circumferential surface of the sleeve 2. The rotary seal ring 12 is held relative to a retainer 13 so as to be movable in the axial direction.

[0024] The retainer 13 is formed in an annular shape and is disposed on one axial side of the rotary seal ring 12. The retainer 13 is fixed to the outer peripheral surface of the sleeve 2 by a set screw 17. A plurality of springs 14 (only one is shown in FIG. 1 ) are provided between the retainer 13 and the rotary seal ring 12 and spaced apart in the circumferential direction. The springs 14 press the rotary seal ring 12 toward the other axial side (toward the stationary seal ring 11) with their biasing force.

[0025] [Second mechanical seal] <Overall structure> The second mechanical seal 20 includes a first retainer 21, a stationary seal ring 22, a rotary seal ring 23, a second retainer (retainer) 24, a third retainer 25, and a bellows 26. The first retainer 21 is fitted and fixed to the inner peripheral surface of the casing 72. An O-ring 27 and an O-ring 28 seal (secondary seal) between the outer peripheral surface of the first retainer 21 and the inner peripheral surface of the casing 72.

[0026] Fig. 2 is an enlarged cross-sectional view showing the second mechanical seal 20. In Fig. 2, the first retainer 21 is formed in an annular shape. The outer peripheral surface of the stationary seal ring 22 is fixed to the other axial side of the first retainer 21 by shrink fitting. A seal surface 22a is formed on the end face on the other axial side of the stationary seal ring 22 over the entire radial direction.

[0027] The rotary seal ring 23 is made of, for example, silicon carbide (SiC), which has excellent wear resistance and sealing performance. The rotary seal ring 23 is disposed adjacent to the other axial side of the stationary seal ring 22. A seal surface 23a that slides against the seal surface 22a of the stationary seal ring 22 is formed on one axial side of the rotary seal ring 23. An in-machine region C is formed radially inward of both the seal surfaces 22a, 23a of the stationary seal ring 22 and the rotary seal ring 23. As a result, the second mechanical seal 20 seals the sealed fluid in the in-machine region C.

[0028] One axial end of the rotary seal ring 23 is tapered toward the seal surface 23a. Specifically, the rotary seal ring 23 has a first tapered surface 23b formed radially inward from the seal surface 23a and a second tapered surface 23c formed radially outward from the seal surface 23a. The second tapered surface 23c is formed so that its diameter increases from the radial outer end of the seal surface 23a toward the outer circumferential surface of the rotary seal ring 23.

[0029] The first tapered surface 23b is formed so that its diameter decreases from the radially inner end of the seal surface 23a toward the inner circumferential surface of the rotary seal ring 23. The radially inner portion of the first tapered surface 23b protrudes radially inward beyond the inner circumferential surface of the stationary seal ring 22. The area of the seal surface 23a of the rotary seal ring 23 is smaller than the area of the seal surface 22a of the stationary seal ring 22.

[0030] The rotary seal ring 23 is held on one axial side of the second retainer 24. The second retainer 24 is made of, for example, metal and is formed in an annular shape. The second retainer 24 has an annular portion 24a and a cylindrical portion 24b extending from the outer periphery of the annular portion 24a to one axial side. The rotary seal ring 23 is fixed to the inner periphery of the cylindrical portion 24b by shrink fitting.

[0031] The third retainer 25 is disposed adjacent to one axial side of the retainer 13 of the first mechanical seal 10. The third retainer 25 is made of, for example, metal and is formed in an annular shape. The third retainer 25 is fixed to the outer peripheral surface of the sleeve 2 by a set screw 29. An O-ring 30 provides a seal (secondary seal) between the inner peripheral surface of the third retainer 25 and the outer peripheral surface of the sleeve 2.

[0032] <Bellows> The bellows 26 is provided on the other axial side of the second retainer 24, closer to the rotary shaft 71. In this embodiment, the bellows 26 is disposed between the second retainer 24 and the third retainer 25. An annular gap S is formed between the bellows 26 and the sleeve 2. A liquid-sealing region B is formed on the radially outer side of the bellows 26. The bellows 26 is a cylindrical member made of a metal such as a nickel alloy or stainless steel. The bellows 26 has a fixed ring portion 26a, an expandable / contractible cylindrical portion 26b, and a movable ring portion 26c.

[0033] The fixed ring portion 26a is fixed to one axial end portion of the third retainer 25 by welding. As a result, the other axial end portion of the bellows 26 is fixed to the sleeve 2 on the rotating shaft 71 side. The other axial end portion of the telescopic tubular portion 26b is integrally connected to one axial end portion of the fixed ring portion 26a. The telescopic tubular portion 26b is formed in a bellows shape.

[0034] One axial end of the telescopic cylindrical portion 26b is integrally connected to the other axial end of the movable ring portion 26c. The movable ring portion 26c is fixed by welding to the other axial end of the annular portion 24a of the second retainer 24. As a result, the other axial end of the bellows 26 is connected to the other axial side of the second retainer 24. The telescopic cylindrical portion 26b extends and contracts relative to the fixed ring portion 26a, allowing the movable ring portion 26c to move axially together with the rotary seal ring 23.

[0035] Both axial ends of the bellows 26 (the fixed ring portion 26a and the movable ring portion 26c) are connected to the second retainer 24 and the third retainer 25, respectively, with the telescopic cylindrical portion 26b in a state where it is contracted more than in its free state. Therefore, the bellows 26 has the function of pressing the rotary seal ring 23 toward the stationary seal ring 22 via the second retainer 24.

[0036] As described above, both axial ends of the bellows 26 are fixed to the second retainer 24 and the third retainer 25 by welding, respectively, so the bellows 26 also has the function of sealing (secondary sealing) between the liquid-sealing region B and the in-machine region C. Therefore, even if the slurry fluid in the in-machine region C passes through the inner periphery of the second retainer 24 and enters the gap S, the bellows 26 can prevent leakage into the liquid-sealing region B (outside the machine).

[0037] <Sealing material> The second mechanical seal 20 further includes an annular seal member 40 provided on the sleeve 2. The seal member 40 in this embodiment is, for example, a commercially available rubber V-ring. The seal member 40 has a seal body 41 and a seal lip 42. The seal body 41 is formed, for example, with a trapezoidal cross section. The inner circumferential surface of the seal body 41 is fitted into and fixed in an annular recess 2a formed on the outer periphery of the sleeve 2, radially inward of the stationary seal ring 22.

[0038] The seal lip 42 is formed around the entire circumference on one axial side of the seal body 41. In this embodiment, the seal lip 42 extends from the radially inner end of the end face on one axial side of the seal body 41 toward one axial side and radially outward. This allows the seal lip 42 to elastically deform in the axial direction relative to the seal body 41.

[0039] The tip end (outer peripheral end) of the seal lip 42 contacts the first tapered surface 23b of the rotary seal ring 23. As a result, the seal lip 42 prevents the slurry fluid in the in-machine area C from entering the gap between the rotary seal ring 23 and the sleeve 2, and the gap between the annular portion 24a of the second retainer 24 and the sleeve 2. Furthermore, even if the rotary seal ring 23 moves axially together with the second retainer 24, the seal lip 42 elastically deforms in the axial direction, so that the tip end of the seal lip 42 can maintain contact with the first tapered surface 23b.

[0040] <Bush> The second mechanical seal 20 further includes an annular bushing 45 provided on the inner periphery of the second retainer 24. In this embodiment, an annular groove 24c that opens radially inward is formed on the inner periphery of the annular portion 24a of the second retainer 24, and a pair of bushings 45 that are stacked in the axial direction are fitted into and fixed to this annular groove 24c. The inner circumferential end of the bushing 45 protrudes radially inward beyond the inner circumferential surface of the annular portion 24a.

[0041] The bushing 45 is made of a low-friction material such as polytetrafluoroethylene (PTFE). The inner peripheral surface of the bushing 45 is disposed with a small gap between it and the outer peripheral surface of the sleeve 2, so that the bushing 45 slides against the outer peripheral surface of the sleeve 2 when the second retainer 24 moves in the axial direction. Furthermore, because the inner peripheral surface of the bushing 45 is disposed with a small gap between it and the outer peripheral surface of the sleeve 2, axial runout of one axial end (movable ring portion 26c) of the bellows 26 can also be suppressed.

[0042] [Effects of this embodiment] According to the second mechanical seal 20 of this embodiment, on one axial side of the second retainer 24, the seal lip 42 of the seal member 40 fixed to the sleeve 2 is brought into contact with the rotary seal ring 23, thereby preventing the slurry fluid in the in-machine region C from entering the inner periphery of the second retainer 24. On the other axial side of the second retainer 24, the bellows 26 prevents the slurry fluid from leaking into the liquid-sealing region B, eliminating the need to provide an O-ring on the inner periphery of the second retainer 24 as in the past. Furthermore, a gap S is formed between the bellows 26 and the sleeve 2 on the other axial side of the second retainer 24 that is wider than a gap between an O-ring and the rotating shaft in a conventional arrangement.

[0043] Therefore, even if the slurry fluid passes through the inner periphery of the seal member 40 and the second retainer 24 and enters the gap S, the time until solid particles contained in the slurry fluid accumulate in the gap S and hinder the axial movement of the bellows 26 can be made longer than in the case of a conventional O-ring. As a result, a decrease in the followability of the rotary seal ring 23 relative to the stationary seal ring 22 can be suppressed, and leakage of the slurry fluid from between the seal surfaces 22a, 23a of the stationary seal ring 22 and the rotary seal ring 23 can be suppressed. Furthermore, because there is no need to provide an O-ring on the inner periphery of the second retainer 24 as described above, there is also no need to introduce injection fluid into the in-machine area C as in the conventional case. This reduces running costs.

[0044] When the second retainer 24 moves in the axial direction, the inner peripheral surface of the bushing 45 made of a low-friction material slides against the outer peripheral surface of the sleeve 2, allowing the second retainer 24 to move smoothly in the axial direction. This further prevents a decrease in the ability of the rotary seal ring 23 to follow the stationary seal ring 22.

[0045] The rotary seal ring 23 is tapered toward its seal surface 23a, so the area of the seal surface 23a can be made smaller than if the rotary seal ring 23 were not tapered. This increases the surface pressure between the seal surfaces 22a, 23a of the stationary seal ring 22 and the rotary seal ring 23, improving sealing performance.

[0046] The seal lip 42 of the seal member 40 contacts the first tapered surface 23b between the seal surface 23a and the inner circumferential surface of the rotary seal ring 23, and therefore the second retainer 24 can move more smoothly in the axial direction compared to when the seal lip 42 contacts the inner circumferential surface of the rotary seal ring 23. This further prevents a decrease in the ability of the rotary seal ring 23 to follow the stationary seal ring 22.

[0047] Since a commercially available V-ring is used as the seal member 40, costs can be further reduced.

[0048] [others] Although the seal member 40 in the above embodiment is in contact with the first tapered surface 23b of the rotary seal ring 23, it may also be in contact with the inner peripheral surface of the rotary seal ring 23. Also, without forming the first tapered surface 23b on the rotary seal ring 23, the seal surface 23a may be extended radially inward beyond the stationary seal ring 22, and the seal member 40 may be in contact with this extended portion.

[0049] The seal member 40 may be configured as something other than a V-ring as long as it has the seal lip 42. The number and material of the bushings 45 are not limited to this embodiment. The mechanical seal of the present invention is not limited to a double mechanical seal device, and can also be applied to a single mechanical seal.

[0050] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above meaning, and is intended to include any modifications within the scope of the claims and meaning equivalent to the claims. [Explanation of symbols]

[0051] 20 Second mechanical seal (mechanical seal) 22 Stationary sealing ring 22a sealing surface 23 Rotating seal ring 23a sealing surface 23b First tapered surface (tapered surface) 24 Second retainer (retainer) 26 Bellows 40 sealing material 42 Seal lip 45 Bush 71 Rotation axis 72 Casing C. Cabin area

Claims

1. a stationary seal ring provided on a casing surrounding the rotary shaft and having a seal surface; an annular retainer that is axially movable relative to the rotation shaft; a rotary seal ring that is held on one axial side of the retainer and has a seal surface that slides on the seal surface of the stationary seal ring, A mechanical seal that seals a sealed fluid in an in-machine region formed radially inward of both seal surfaces of the stationary seal ring and the rotary seal ring, a seal body having an inner peripheral surface fixed to the rotary shaft side on one axial side of the retainer, and an annular seal member having a seal lip formed on the seal body and in contact with the rotary seal ring; a bellows provided on the other axial side of the retainer toward the rotary shaft so as to suppress leakage of the sealed fluid in the inboard area from the other axial side of the retainer to the outside of the aircraft, and pressing the rotary seal ring toward the stationary seal ring via the retainer.

2. The retainer further includes an annular bushing that is provided on an inner periphery of the retainer and protrudes radially inward from the retainer, The mechanical seal of claim 1 , wherein the bushing is made of a low friction material.

3. 3. The mechanical seal according to claim 1, wherein the rotary seal ring is tapered toward its seal surface.

4. The rotary seal ring has a tapered surface whose diameter decreases from the radially inner end of the seal surface toward the inner circumferential surface, The mechanical seal according to claim 3 , wherein the seal lip of the seal member is in contact with the tapered surface.

5. The mechanical seal according to claim 1 , wherein the seal member is a V-ring.

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