JP7429628B2 - mechanical seal - Google Patents

Description

The present invention relates to mechanical seals.

A mechanical seal 100 shown in FIG. 4 is known for sealing a slurry fluid containing a large amount of solid particles such as iron chips, sand, and stones inside a rotating device. The mechanical seal 100 includes a rotary seal ring 102 that is rotatably provided on the rotating shaft 101 side, a stationary seal ring 104 that is provided on the casing 103 side on which the rotary seal ring 102 slides, and a stationary seal ring 104 that is rotatably provided on the rotating shaft 101 side. A bellows 105 that presses against the rotary sealing ring 102 side is provided (see Patent Document 1).

Such a mechanical seal 100 has an introduction path 107 for constantly introducing flushing fluid (external flushing), which is a clean fluid different from the slurry fluid, into the internal region 106 where the slurry fluid is sealed. It is formed. The flushing fluid introduced into the in-machine area 106 from the introduction path 107 passes through an annular gap 109 between the annular neck bush 108 provided in the casing 103 and the rotation shaft 101 to the axially deep side of the in-machine area 106. It is discharged. At this time, the flow velocity of the flushing fluid in the annular gap 109 increases, so that the slurry fluid located on the back side of the neck bush 108 in the axial direction passes through the annular gap 109 and connects the rotating seal ring 102 and the stationary seal ring 104. This prevents it from flowing into the vicinity of sliding parts. Thereby, the vicinity of the sliding portion between the rotating seal ring 102 and the stationary seal ring 104 in the in-machine region 106 is made into an atmosphere of flushing fluid.

Japanese Patent Application Publication No. 2018-146079

In the mechanical seal 100 described above, when the flow velocity of the flushing fluid in the annular gap 109 between the neck bushing 108 and the rotating shaft 101 becomes low, as shown in FIG. It passes through the gap 109 and easily flows into the vicinity of the sliding portion between the rotating seal ring 102 and the stationary seal ring 104. In this case, solid particles in the slurry fluid are likely to get caught in the sliding portion, and there is a risk that the slurry fluid may leak. Further, solid particles in the slurry fluid tend to accumulate on the bellows 105, so that the pressing force of the bellows 105 may be insufficient and the stationary sealing ring 104 may fail to follow.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a mechanical seal that can suppress slurry fluid from flowing into the vicinity of the sliding portion between the rotating seal ring and the stationary seal ring. shall be.

(1) The present invention is provided with a rotating side unit that is provided to be integrally rotatable with a rotating shaft and has a rotating sealing ring, and a casing that surrounds the rotating shaft, so that the rotating sealing ring slides. a stationary side unit having a stationary seal ring for sealing the slurry fluid in the interior area, the stationary side unit having an introduction path for introducing flushing fluid into the interior area, and the stationary side unit having a stationary sealing ring for sealing the slurry fluid in the interior area; A mechanical seal that creates an atmosphere of the flushing fluid near the sliding part between the ring and the stationary sealing ring, the mechanical seal being provided on the casing side in the in-machine area, and having a first gap, which is a labyrinth gap, between the rotary shaft and the rotary shaft. a first cylindrical portion formed between the first cylindrical portion and a second cylindrical portion provided on the casing side so as to be continuously disposed on the back side in the axial direction of the in-machine area of the first cylindrical portion and larger than the first gap; A gap is provided on the casing side such that the second cylindrical part formed between the second cylindrical part and the second cylindrical part is continuous with the rear side in the axial direction of the second cylindrical part, and the second cylindrical part is formed between the second cylindrical part and the rotating shaft. A third cylindrical portion is formed between the rotary shaft and the third gap that generates a flow that sends the flushing fluid from the second gap to the back side of the in-machine area in the axial direction. .

According to the present invention, the flushing fluid introduced into the in-machine area from the introduction path of the stationary side unit is transferred from the vicinity of the sliding portion between the rotating seal ring and the stationary seal ring to the back side in the axial direction by the first gap (labyrinth gap). becomes difficult to flow to. Thereby, the vicinity of the sliding portion can be maintained in an atmosphere of flushing fluid. Furthermore, the flushing fluid that has flowed into the first gap from near the sliding portion flows into the second gap, which is larger than the first gap, thereby generating turbulent flow of the flushing fluid within the second gap. Further, within the third gap, a flow is generated that sends the flushing fluid from the second gap toward the back side in the axial direction due to the rotation of the rotating shaft. Therefore, the slurry fluid on the back side of the third gap in the axial direction is caused by the flow that sends the flushing fluid to the back side in the axial direction in the third gap, the turbulent flow of the flushing fluid in the second gap, and the turbulent flow of the flushing fluid in the first gap. The labyrinth gaps can prevent fluid from flowing into the vicinity of the sliding portion through these gaps.

(2) In order to form the third gap, the third cylindrical portion has a female thread formed on its inner periphery such that the rotation direction of the rotation shaft is the tightening direction when the rotation shaft is viewed from the front side in the axial direction. It is preferable that the
In this case, as the rotating shaft rotates, the flushing fluid is sent out to the back side in the axial direction between the third cylindrical portion and the rotating shaft along the groove of the female thread. Thereby, it is possible to easily form the third gap S3 that generates a flow that sends the flushing fluid to the back side in the axial direction.

(3) It is preferable that the first cylindrical part, the second cylindrical part, and the third cylindrical part are constituted by a single member.
In this case, the configuration of the mechanical seal can be simplified.

(4) Preferably, the single member is configured as a part of the stationary unit.
In this case, the first to third gaps can be formed by providing the stationary side unit in the casing, so that the mechanical seal can be easily assembled.

(5) The stationary side unit includes an axially expandable bellows that presses the stationary sealing ring toward the rotating sealing ring, and is provided on the casing side on the radially outer side of the rotating shaft to prevent the expansion and contraction of the bellows. Preferably, the device further includes a guide member for guiding, and the guide member is the single member.
In this case, since the guide member that guides the expansion and contraction of the bellows also serves as a single member that forms the first to third gaps, the structure of the mechanical seal can be further simplified.

According to the present invention, it is possible to suppress slurry fluid from flowing into the vicinity of the sliding portion between the rotating seal ring and the stationary seal ring.

FIG. 1 is a sectional view showing a mechanical seal according to an embodiment of the present invention. FIG. 3 is a cross-sectional view showing a state in which slurry fluid on the axially rear side of the neck bushing in the mechanical seal passes through the annular gap and flows into the axially front side of the in-machine area. FIG. 3 is an enlarged cross-sectional view showing the first guide member. FIG. 2 is a sectional view showing a conventional mechanical seal. FIG. 3 is a cross-sectional view showing a conventional mechanical seal in which slurry fluid on the axially rear side of the neck bush passes through an annular gap and flows into the axially front side of the in-machine area.

Next, preferred embodiments of the present invention will be described with reference to the accompanying drawings.
[overall structure]
FIG. 1 is a sectional view of a mechanical seal according to an embodiment of the present invention. In FIG. 1, a mechanical seal 1 is used in a rotating device such as a pump that handles a slurry fluid (sealed fluid) containing a large amount of solid particles such as iron chips, sand, and stones. The mechanical seal 1 is arranged along the axial direction of the rotating shaft 71 (hereinafter simply referred to as the "axial direction") between a rotating shaft 71 of a rotating device and a casing 72 surrounding the rotating shaft 71. There is.

The mechanical seal 1 of this embodiment is a double mechanical seal, and includes a rotating unit 2 that is rotatably provided on a rotating shaft 71 and a stationary unit 3 that is provided on a casing 72. In this specification, the left side of FIG. 1 is referred to as the axial front side, and the right side of FIG. 1 is referred to as the axial back side (the same applies to FIGS. 2 and 3).

[Rotating side unit]
The rotating unit 2 includes a sleeve 11, a first drive ring 12, a first rotary seal ring (rotary seal ring) 13, a second drive ring 14, and a second rotary seal ring 15 as main components. . The sleeve 11 includes a cylindrical sleeve body 11a that is fitted and fixed to the outer periphery of the axially front end of the rotating shaft 71, and an annular flange portion that extends radially outward from an axially intermediate portion of the sleeve body 11a. 11b. A seal (secondary seal) is provided between the inner circumferential surface of the sleeve body 11a and the outer circumferential surface 71a of the rotating shaft 71 by an O-ring 16.

The first drive ring 12 is fitted onto the outer periphery of the sleeve body 11a adjacent to the axially inner side of the flange portion 11b. The first drive ring 12 is fixed to the flange portion 11b with bolts 17. The first rotary sealing ring 13 is fitted and fixed to the inner circumference of the first drive ring 12 on the axially rear side. A sealing surface 13a is formed on the end surface of the first rotary sealing ring 13 on the back side in the axial direction.

A plurality of pin grooves 13b (only one pin groove 13b is shown in FIG. 1) are formed at predetermined intervals in the circumferential direction on the axially front side of the first rotary sealing ring 13. A pin 18 protruding from the first drive ring 12 is inserted into each pin groove 13b. Thereby, relative rotation of the first rotary sealing ring 13 with respect to the first drive ring 12 is restricted. A seal (secondary seal) is provided between the outer circumferential surface of the sleeve body 11a on the axially rear side and the inner circumferential surface of the first rotary sealing ring 13 by an O-ring 19.

The second drive ring 14 is fitted onto the outer periphery of the sleeve main body 11a at a position before the flange portion 11b in the axial direction. A plurality of set screws 20 (only one set screw is shown in FIG. 1) are screwed into the second drive ring 14 at predetermined intervals in the circumferential direction on the back side in the axial direction. By tightening these set screws 20, the second drive ring 14 is fixed to the sleeve body 11a. A seal (secondary seal) is provided between the outer peripheral surface of the sleeve body 11a on the axially front side and the inner peripheral surface of the second drive ring 14 by an O-ring 21.

The second rotary sealing ring 15 is fitted and fixed to the inner periphery of the second drive ring 14 on the front side in the axial direction. A sealing surface 15a is formed on the front end surface of the second rotary sealing ring 15 in the axial direction. A plurality of pin grooves 15b (only one pin groove 15b is shown in FIG. 1) are formed at predetermined intervals in the circumferential direction on the axially rear side of the second rotary sealing ring 15. A pin 22 protruding from the second drive ring 14 is inserted into each pin groove 15b. As a result, the second rotary sealing ring 15 is restricted from rotating relative to the second drive ring 14.

[Stationary unit]
The stationary unit 3 includes, as main components, a first seal case 30, a first bellows 31, a first stationary seal ring (stationary seal ring) 32, a first guide member (guide member) 33, and a second It includes a seal case 34, a second bellows 35, a second stationary seal ring 36, and a second guide member 37. The first seal case 30 and the second seal case 34 are each formed in a cylindrical shape, and are arranged in a partition area that partitions an outside area A and an inside area B.

Specifically, the first seal case 30 is arranged at the front end of the casing 72 in the axial direction. The second seal case 34 is arranged on the front side of the first seal case 30 in the axial direction. The first seal case 30 and the second seal case 34 are fixed to the casing 72 by bolts (not shown). A seal (secondary seal) is provided between the first seal case 30 and the second seal case 34 by an O-ring 38.

The first seal case 30 includes an outer case portion 30a disposed on the front side surface of the casing 72 in the axial direction, an inner case portion 30b fitted to the inner circumferential surface of the casing 72 on the near side in the axial direction, and an inner case portion 30a. It has an annular protrusion 30c that protrudes radially inward from the axially inner end of the portion 30b. A seal (secondary seal) is provided between the inner case portion 30b and the casing 72 by an O-ring 39.

The first bellows 31 is a cylindrical member made of metal such as Inconel or stainless steel. The first bellows 31 has a fixed part 31a, an extendable part 31b, and a connecting part 31c. The fixing part 31a is adjacent to the protruding part 30c on the axial front side and is fitted and fixed to the inner periphery of the inner case part 30b. The extensible portion 31b is formed in a bellows shape and is freely extensible and retractable in the axial direction. An end portion of the extensible portion 31b on the back side in the axial direction is connected to the fixed portion 31a. The front end of the extensible portion 31b in the axial direction is connected to the connecting portion 31c. The connecting portion 31c is configured to move in the axial direction with respect to the fixed portion 31a as the extensible portion 31b expands and contracts.

The first stationary sealing ring 32 is fitted into and fixed to the inner periphery of the connecting portion 31c of the first bellows 31 on the axially front side. The first stationary sealing ring 32 is urged toward the front side in the axial direction by the urging force of the first bellows 31. A sealing surface 32a is formed on the front end surface of the first stationary sealing ring 32 in the axial direction. The sealing surface 32a of the first stationary sealing ring 32 is pressed against the sealing surface 13a of the first rotating sealing ring 13 by the urging force of the first bellows 31. As a result, the sealing surface 13a of the first rotary sealing ring 13 slides while being pressed by the sealing surface 32a of the first stationary sealing ring 32.

The first guide member 33 guides the expansion and contraction of the first bellows 31 and is disposed between the first bellows 31 and the rotating shaft 71. The first guide member 33 has an annular flange portion 33a fixed to the protruding portion 30c of the first seal case 30, and a cylindrical portion 33b extending in the axial direction at the inner peripheral end of the flange portion 33a. The cylindrical portion 33b is formed to extend from the radially inner side of the axially inner end of the inner case portion 30b to the radially inner side of the first stationary sealing ring 32.

A guided portion 31d formed to protrude toward the inner peripheral side of the connecting portion 31c of the first bellows 31 is in contact with the outer circumferential surface 33b1 of the cylindrical portion 33b so as to be slidable in the axial direction. A plurality of guided parts 31d (only one guided part is shown in FIG. 1) are formed at intervals in the circumferential direction of the connecting part 31c. Thereby, the first guide member 33 guides the expansion and contraction of the first bellows 31 by sliding while the guided portion 31d is in contact with the outer peripheral surface 33b1 of the cylindrical portion 33b.

The second bellows 35, like the first bellows 31, is a cylindrical member made of metal such as Inconel or stainless steel. The second bellows 35 includes a fixed part 35a, an extendable part 35b, and a connecting part 35c. The fixing portion 35a is fixed to the inner periphery of the second seal case 34 on the near side in the axial direction. The extensible portion 35b is formed in a bellows shape and is freely extensible and retractable in the axial direction. The axially front end of the expandable portion 35b is connected to the fixed portion 35a. The axially rear end of the extendable portion 35b is connected to the connecting portion 35c. The connecting portion 35c is configured to move in the axial direction with respect to the fixed portion 35a as the extensible portion 35b expands and contracts.

The second stationary sealing ring 36 is fitted into and fixed to the inner periphery of the connecting portion 35c of the second bellows 35 on the back side in the axial direction. The second stationary sealing ring 36 is urged toward the back side in the axial direction by the urging force of the second bellows 35. A sealing surface 36a is formed on the end surface of the second stationary sealing ring 36 on the axially rear side. The sealing surface 36a of the second stationary sealing ring 36 is pressed against the sealing surface 15a of the second rotating sealing ring 15 by the urging force of the second bellows 35. As a result, the sealing surface 15a of the second rotary sealing ring 15 slides while being pressed by the sealing surface 36a of the second stationary sealing ring 36.

The second guide member 37 guides the expansion and contraction of the second bellows 35, and is disposed between the second bellows 35 and the sleeve main body 11a. The second guide member 37 is fixed to the second seal case 34 (not shown). The second guide member 37 has a cylindrical portion 37b extending in the axial direction. The cylindrical portion 37b is formed to extend from the radially inner side of the axially front end of the second seal case 34 to the radially inner side of the second stationary seal ring 36.

A guided portion 35d formed to protrude toward the inner peripheral side of the connecting portion 35c of the second bellows 35 is in contact with the outer peripheral surface 37b1 of the cylindrical portion 37b so as to be slidable in the axial direction. Thereby, the second guide member 37 guides the expansion and contraction of the second bellows 35 by sliding while the guided portion 35d is in contact with the outer peripheral surface 37b1 of the cylindrical portion 37b.

[Sealing liquid]
An annular sealing liquid area C is formed between the outside area A and the inside area B, into which a sealing liquid (water, oil, etc.) for sealing and cooling is introduced. The sealing liquid region C is formed from the radially outer side of the first bellows 31 to the radially outer side of the second bellows 35. The first rotating sealing ring 13 and the first stationary sealing ring 32 seal between the in-machine area B and the liquid sealing area C by sliding their sealing surfaces 13a and 32a. Thereby, the slurry fluid is sealed in the interior area B. The second rotating seal ring 15 and the second stationary seal ring 36 seal between the external region A and the liquid sealing region C by sliding their seal surfaces 15a and 36a.

A supply path 34a for supplying sealing liquid to the sealing liquid area C is formed in the second seal case 34. The first seal case 30 is formed with a discharge path 30d for discharging the sealing liquid in the sealing liquid region C to the outside. The sealing liquid supplied from the supply path 34a to the sealing liquid region C during operation of the rotating equipment cools both sealing surfaces 15a and 36a, which are the sliding parts of the second rotating sealing ring 15 and the second stationary sealing ring 36. do. Further, the sealing liquid supplied to the sealing liquid region C cools both sealing surfaces 13a and 32a, which are the sliding parts of the first rotating sealing ring 13 and the first stationary sealing ring 32. The sealing liquid that has cooled each sliding portion is discharged to the outside from the discharge path 30d. Hereinafter, the sliding portions between the first rotary sealing ring 13 and the first stationary sealing ring 32 are also referred to as sliding portions 13a and 32a.

[Flushing fluid]
The first seal case 30 is formed with an introduction path 40 that constantly introduces flushing fluid into the interior area B of the machine. As the flushing fluid, a clean fluid (water, oil, etc.) is used, which is a different type of fluid from the sealing fluid and which does not cause problems even if mixed with the slurry fluid in the interior area B. The introduction path 40 includes a first path portion 40a extending radially on the axially inner side of the sealing liquid discharge path 30d, and a second path portion 40a extending radially toward the axially inner side from the radially inner end of the first path portion 40a. 40b, and a third road portion 40c extending radially inward from the axially rear end of the second road portion 40b.

The first passage portion 40a is formed in the outer case portion 30a. The second passage portion 40b is formed to extend from the radially inner side of the outer case portion 30a toward the axially inner side along the inner circumferential surface of the casing 72 on the outer circumferential side of the inner case portion 30b. The third passage portion 40c is formed so as to penetrate through the inside of the protruding portion 30c from the axially rear end of the inner case portion 30b.

Thereby, the flushing fluid passes through the first passage section 40a, the second passage section 40b, and the third passage section 40c in this order. The flushing fluid that has passed through the third passage portion 40c passes between the first bellows 31 and the cylindrical portion 33b of the first guide member 33, and is introduced into the interior region B near the sliding portions 13a and 32a. The flushing fluid introduced near the sliding parts 13a and 32a passes between the cylindrical part 33b of the first guide member 33 and the rotating shaft 71, and then between the neck bushing 73 and the rotating shaft 71. , is discharged to the back side of the interior area B in the axial direction.

The neck bush 73 is an annular member attached to the inner peripheral surface of the casing 72. An annular gap 74 is formed between the neck bush 73 and the rotation shaft 71, which is narrower than between the casing 72 and the rotation shaft 71 on both sides of the neck bush 73 in the axial direction. By increasing the flow rate of the flushing fluid passing through this annular gap 74, slurry fluid located further back in the axial direction than the neck bushing 73 is prevented from passing through the annular gap 74 and flowing into the vicinity of the sliding parts 13a and 32a. It's suppressed. Thereby, the vicinity of the sliding parts 13a and 32a in the interior area B can be made into an atmosphere of flushing fluid.

In the in-machine region B, the pressure of the slurry fluid is set higher than the pressure of the flushing fluid. This suppresses the slurry fluid located on the back side of the interior area B in the axial direction from flowing into the front side of the interior area B in the axial direction. Further, the pressure of the sealing liquid in the sealing liquid region C is set higher than the pressure of the slurry fluid in the in-machine region B. This suppresses the slurry fluid and flushing fluid in the in-machine area B from leaking into the sealing liquid area C.

By the way, when the flow velocity of the flushing fluid in the annular gap 74 between the neck bush 73 and the rotating shaft 71 becomes low, as shown in FIG. It may pass through and flow into the axial direction of the in-machine area B. In this case, solid particles in the slurry fluid are likely to get caught in the sliding portions 13a, 32a, and there is a possibility that the slurry fluid may leak. In addition, solid particles in the slurry fluid tend to accumulate on the expandable portion 31b of the first bellows 31, so there is a risk that the pressing force of the first bellows 31 will be insufficient and the first stationary sealing ring 32 will not follow properly.

In the mechanical seal 1 of the present embodiment, the flow velocity of the flushing fluid in the annular gap 74 is low, and even if the slurry fluid on the axially inner side of the neck bush 73 passes through the annular gap 74, the slurry fluid flows into the sliding portion 13a. , 32a. Specifically, slurry fluid is applied to the inner peripheral side of the first guide member 33 disposed between the annular gap 74 and the sliding parts 13a and 32a in the in-machine region B from the axially rear side to the axially front side. Measures have been taken to prevent it from flowing into the area. The details will be explained below.

[First guide member]
FIG. 3 is an enlarged sectional view showing the first guide member 33. As shown in FIG. 2 and 3, the cylindrical portion 33b of the first guide member 33 includes a first cylindrical portion 331, a second cylindrical portion 332, and a third cylindrical portion in order from the axial front side to the axial back side. 333.

On the inner periphery of the first cylindrical portion 331, a plurality of annular recesses 331a and annular protrusions 331b are formed alternately over the entire axial direction. The inner diameter of the annular convex portion 331b is slightly larger than the outer diameter of the rotating shaft 71. As a result, a first gap S1, which is a labyrinth gap, is formed in an annular shape on the inner circumference of the first cylindrical portion 331 and between it and the outer circumferential surface 71a of the rotating shaft 71.

The first gap S1 can prevent the flushing fluid introduced from the introduction path 40 into the in-machine region B from flowing toward the back side in the axial direction from the vicinity of the sliding portions 13a and 32a. As a result, the vicinity of the sliding parts 13a and 32a can be maintained in an atmosphere of flushing fluid. Furthermore, the first gap S1 can also suppress the slurry fluid from flowing from the axially rear side to the axially front side of the first gap S1.

The second cylindrical portion 332 is disposed continuously on the back side of the first cylindrical portion 331 in the axial direction. The second cylindrical portion 332 has an inner circumferential surface 332a that is flat in cross-sectional view. The diameter D2 of the inner peripheral surface 332a is larger than the diameter D1 of the annular recess 331a of the first cylindrical portion 331. As a result, a second gap S2, which is larger than the first gap S1, is formed in an annular shape between the inner circumferential surface 332a of the second cylindrical portion 332 and the outer circumferential surface 71a of the rotating shaft 71. As a result, the flushing fluid that has flowed into the first gap S1 from around the sliding parts 13a and 32a flows into the second gap S2, which is larger than the first gap S1, and a turbulent flow of the flushing fluid occurs within the second gap S2. do. By generating such a turbulent flow, it is possible to suppress the slurry fluid that has flowed into the second gap S2 from the back side in the axial direction from flowing into the first gap S1.

The third cylindrical portion 333 is disposed continuously on the back side of the second cylindrical portion 332 in the axial direction. A third gap S3 is formed in an annular shape on the inner circumference of the third cylindrical portion 333 and between the third cylindrical portion 333 and the outer circumferential surface 71a of the rotating shaft 71. The third gap S3 is formed so that the rotation of the rotating shaft 71 generates a flow that sends the flushing fluid from the second gap S2 to the back side of the interior area B in the axial direction.

In this embodiment, a female thread 333a is formed on the inner periphery of the third cylindrical portion 333 in order to form such a third gap S3. The tightening direction of the female thread 333a is the rotation direction of the rotating shaft 71 when the rotating shaft 71 is viewed from the front side in the axial direction. A diameter D3 of the female thread 333a is smaller than a diameter D2 of the inner peripheral surface 332a of the second cylindrical portion 332. Thereby, a third gap S3 smaller than the second gap S2 is formed in an annular shape between the female thread 333a of the third cylindrical portion 333 and the outer peripheral surface 71a of the rotating shaft 71.

Due to the third gap S3, as the rotating shaft 71 rotates, a flow is generated that sends the flushing fluid from the second gap S2 to the back side in the axial direction along the groove of the female thread 333a. By generating such a flow of the flushing fluid, it is possible to suppress the slurry fluid located further back in the axial direction than the third gap S3 from flowing into the third gap S3.

In this embodiment, the length of the second gap S2 in the axial direction is longer than the length of the first gap S1 in the axial direction. Further, the length of the third gap S3 in the axial direction is longer than the length of the second gap S2 in the axial direction.

As described above, the first cylindrical part 331, the second cylindrical part 332, and the third cylindrical part 333, which respectively form the first to third gaps S1 to S3 with the rotating shaft 71, are made of a single member. 1 guide member 33. Thereby, the first cylindrical part 331, the second cylindrical part 332, and the third cylindrical part 333 are configured as a part of the stationary unit 3.

[Actions and effects of this embodiment]
According to the mechanical seal 1 of the present embodiment, the flushing fluid introduced from the introduction path 40 of the first seal case 30 into the in-machine area B is transferred between the first rotary seal ring 13 and the first rotary seal ring 13 through the first gap S1 (labyrinth gap). 1. It becomes difficult for the liquid to flow from the vicinity of the sliding parts 13a and 32a with the stationary sealing ring 32 toward the back side in the axial direction. Thereby, the vicinity of the sliding parts 13a and 32a can be maintained in an atmosphere of flushing fluid. Furthermore, the slurry fluid on the back side in the axial direction from the third gap S3 is a flow that sends out the flushing fluid in the third gap S3 to the back side in the axial direction, a turbulent flow of the flushing fluid in the second gap S2, and a flow of the flushing fluid in the third gap S3. The labyrinth gap of one gap S1 can suppress flowing into the vicinity of the sliding parts 13a and 32a through these gaps S3, S2, and S1.

Further, by forming a female thread 333a on the inner circumference of the third cylindrical portion 333, the rotation direction of the rotation shaft 71 when the rotation shaft 71 is viewed from the front side in the axial direction is the tightening direction. Between the third cylindrical portion 333 and the rotating shaft 71, flushing fluid is sent out to the back side in the axial direction along the groove of the female thread 333a. Thereby, it is possible to easily form the third gap S3 that generates a flow that sends the flushing fluid to the back side in the axial direction.

Further, since the first to third cylindrical portions 331 to 333 are made of a single member, the structure of the mechanical seal 1 can be simplified.
Furthermore, since the first to third cylindrical parts 331 to 333 are configured as a part of the stationary side unit 3, by providing the stationary side unit 3 in the casing 72, the first to third gaps S1 to S3 are respectively can be formed. Thereby, the mechanical seal 1 can be easily assembled.

Furthermore, since the first guide member 33 that guides the expansion and contraction of the first bellows 31 also serves as the first to third cylindrical parts 331 to 333 that form the first to third gaps S1 to S3, the structure of the mechanical seal 1 can be changed. It can be further simplified.

[others]
In this embodiment, one first cylindrical part 331 and one second cylindrical part 332 are provided on the front side of the third cylindrical part 333 in the axial direction. A plurality of them may be provided alternately. Moreover, if a third gap S3 that generates a flow that sends the flushing fluid to the back side in the axial direction from the second gap S2 can be formed on the inner circumference of the third cylindrical part 333, in addition to the female thread 333a, a spiral groove or the like can be formed. Other shapes may also be formed.

Although the first to third cylindrical portions 333 in the above embodiment are composed of a single member (first guide member 33), they may be composed of separate members. Further, the first to third cylindrical portions 333 in the above embodiment are provided on the first guide member 33 of the stationary side unit 3, but are provided on other members of the stationary side unit 3, the casing 72, or the neck bush 73. may be provided. Further, the mechanical seal of the present invention is not limited to a double mechanical seal, but can also be applied to a single mechanical seal.

The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is indicated by the claims rather than the above-mentioned meaning, and is intended to include meanings equivalent to the claims and all changes within the scope.

1 Mechanical seal 2 Rotating side unit 3 Stationary side unit 13 First rotating seal ring (rotating seal ring)
13a, 32a Sliding part 31 First bellows (bellows)
32 First stationary sealing ring (static sealing ring)
33 First guide member (guide member)
40 Introduction path 71 Rotating shaft 72 Casing 331 First cylindrical part 332 Second cylindrical part 333 Third cylindrical part 333a Female thread B In-machine area S1 First gap S2 Second gap S3 Third gap

Claims (5)

a rotating side unit that is rotatably provided on the rotating shaft and has a rotating sealing ring;
a stationary side unit having a stationary sealing ring provided in a casing surrounding the rotating shaft and sealing the slurry fluid in the interior of the machine when the rotating sealing ring slides;
The stationary side unit is formed with an introduction passage for introducing flushing fluid into the interior area of the machine, and a mechanical mechanism that creates an atmosphere of the flushing fluid near the sliding part of the rotary seal ring and the stationary seal ring in the interior area of the machine. It is a sticker,
a first cylindrical portion provided on the casing side in the in-machine region, and in which a first gap, which is a labyrinth gap, is formed between the first gap and the rotating shaft;
a second cylinder provided on the casing side so as to be continuously disposed on the back side in the axial direction of the first cylindrical part, and having a second gap larger than the first gap formed between the second cylinder and the rotating shaft; Department and
The flushing fluid is provided on the casing side so as to be disposed continuously on the axially inner side of the second cylindrical part, and the flushing fluid is directed from the second gap to the axially inner side of the in-machine area by rotation of the rotating shaft. A mechanical seal comprising: a third cylindrical portion in which a third gap for generating a flow to be sent out is formed between the rotating shaft and the rotating shaft. In order to form the third gap, the third cylindrical portion has a female thread formed on its inner periphery such that the rotational direction of the rotational shaft is the tightening direction when the rotational shaft is viewed from the front side in the axial direction. , The mechanical seal according to claim 1. The mechanical seal according to claim 1 or 2, wherein the first cylindrical part, the second cylindrical part, and the third cylindrical part are composed of a single member. 4. A mechanical seal according to claim 3, wherein the single member is configured as part of the stationary unit. The stationary side unit is
an axially expandable bellows that presses the stationary sealing ring toward the rotating sealing ring;
further comprising a guide member provided on the casing side on the radially outer side of the rotating shaft and guiding expansion and contraction of the bellows;
The mechanical seal according to claim 4, wherein the guide member is the single member.

Images