JP6295045B2 - Centrifugal pump - Google Patents

Description

  The present invention relates to a centrifugal pump for transferring various liquids (delivered fluid) such as fresh water, sludge liquid, pulp liquid, slurry liquid containing fine particles, and sand, and in particular, a shaft seal provided on the back side of an expeller. The present invention relates to a structure that prevents liquid leakage from the part.

A shaft seal portion of this type of centrifugal pump is known which has a seal structure using a seal packing made of an elastomer or the like in addition to a gland packing seal or a mechanical seal. An example of a conventional seal structure of the shaft seal portion is shown in FIGS. In each figure, the upper side from the center line of the rotating shaft (drive shaft) represents the state when the pump is stopped, and the lower side represents the state during operation.
As shown in FIGS. 6 and 7, this type of centrifugal pump includes a casing 1 whose front surface is the suction side, an impeller (impeller) 2 provided in the casing 1, and a rotating shaft that rotates the impeller 2. 3 and an expeller (auxiliary impeller) 4 mounted on the rotary shaft 3 at a position on the back side (drive side) of the impeller 2. The impeller 2 has a plurality of blades 5 on its front surface and a plurality of back blades 6 on its back surface. The expeller 4 has a smooth surface on its front surface and a plurality of blades 7 on its back surface. Here, in this specification, in each of the impeller 2 and the expeller 4, the suction side of the casing 1 is also referred to as “front surface” and the drive side is also referred to as “back surface”.

  In the example shown in FIG. 6, the casing 1 is provided with a shaft seal portion 100 on the back side of the expeller 4. The shaft sealing portion 100 has a stuffing box 101 that extends in the axial direction so as to surround the rotating shaft 3 on the back side of the casing 1. In the example shown in the figure, a sleeve 110 is attached to the rotary shaft 3 at a position opposite to the shaft seal portion 100. On the inner peripheral surface of the stuffing box 101, a plurality of seal packings 102 made of an elastomer or the like are disposed apart in the axial direction. The lip portion 102 a of each seal packing 102 is in sliding contact with the outer peripheral surface of the sleeve 110. When the rotating shaft 3 rotates, the sleeve 110, the impeller 2 and the expeller 4 rotate together, and the fluid to be fed can be pressurized and transferred by the impeller 2. In addition, the casing 1, the stuffing box 101, and each seal packing 102 remain stationary.

  Here, the shaft seal portion of this type of centrifugal pump will be described with reference to FIG. 6. During the operation of the pump, the suction pressure Ps acts on the suction side of the casing 1, and the impeller 2 on the outer peripheral portion of the impeller 2. Pump pressure Pi due to rotation of the front blades 5 acts. Further, when the back blade 6 is provided on the back surface of the impeller 2, centrifugal force is applied to the surrounding liquid by the rotation of the back blade 6. Therefore, the pressure reduction Pb with respect to the pump pressure Pi occurs.

On the other hand, in the expeller 4, centrifugal force is applied to the liquid by the rotation of its blades 7 on the back surface of the expeller, and decompression Pe is generated with respect to the pressure on the front surface of the expeller. Assuming that the atmospheric pressure is Pa in the vicinity of the axis center on the back surface of the expeller, the relationship between these pressures during the pump operation is expressed by the following (Equation 1).
(Ps + Pi) − (Pb + Pe) = Pa (Equation 1)
When (Equation 1) holds, a boundary surface between the liquid and air is formed on the back surface of the expeller 4 as shown in FIG. When the suction pressure Ps, the pump pressure Pi, and the pressure reduction Pb due to the back blade 6 of the impeller 2 change due to variations in pump usage conditions and rotational speed, the boundary surface moves in the radial direction and the action of the expeller 4 The pressure reduction Pe due to fluctuates, and (Expression 1) holds in a range where the boundary surface is between the outer edge and the inner edge of the blade 7 of the expeller 4.

On the other hand, when the pump is stopped, neither the impeller 2 nor the expeller 4 rotates. Therefore, the above (Formula 1) does not hold, Pi = 0, Pb = 0, and Pe = 0, and the suction pressure Ps is uniformly applied from the suction side of the pump to the shaft seal portion.
When the water level on the suction side of the pump is lower than the pump center height, there is no liquid from the suction side to the shaft seal portion, so the suction pressure Ps = 0. On the other hand, when the water level on the suction side is higher than the pump center height, the pushing pressure Po corresponding to the water level acts uniformly from the suction side to the shaft seal portion. For this reason, in the shaft seal portion based on this principle, a shaft seal portion having a structure as shown in FIGS. 6 and 7 has been conventionally used for the purpose of preventing liquid leakage when the pump is stopped due to the pushing pressure Po. Has been.

JP 2009-115088 A

  Incidentally, in the shaft seal portion 100 shown in FIG. 6, a plurality of seal packings 102 made of elastomer or the like are used. Therefore, if the flexible lip 102a at the tip is in contact with the sleeve 110 with a necessary and sufficient tightening allowance, the liquid can be sealed regardless of whether the pump is running or stopped. However, during the pump operation, the lip portion 102a is stationary while the sleeve 110 is rotating at a high speed together with the rotary shaft 3. Therefore, there is a problem that the lip portion 102a and the sleeve 110 are worn, and eventually the sealing performance is impaired and liquid leakage occurs when the pump is stopped.

In addition, the centrifugal pump that transports slurry liquid and sand containing fine particles prevents solids in the fluid from entering the shaft seal and causing the seal member to wear early or generate heat. In order to do this, a shaft seal portion that pours water from the outside into the stuffing box internal space of the shaft seal portion is also used at all times during operation (for example, water is injected from a water injection port indicated by reference numeral 103 in the figure). .
However, there are many production lines for chemicals and the like in which water injection from the outside is not allowed to mix during pumping, and in such a case, it is not possible to adopt a specification for injecting water into the shaft seal part from the outside. In addition, at sites where continuous operation is performed, there is a problem that the amount of external water injection becomes a factor that increases the operating cost.

  On the other hand, in the shaft seal portion 200 shown in FIG. 7, an elastomeric seal member 202 having an annular plate shape is provided on the end surface on the back side of the stuffing box 201 and is opposed to the seal member 202. A cylindrical set ring 210 is provided on the rotary shaft 3. The seal member 202 is attached to the set ring 210 with a properly managed facing gap (see, for example, Patent Document 1).

  Therefore, the seal member 202 does not come into contact with the set ring 210 because the above-described pressing pressure Po does not act in a situation where the above-described formula (1) is satisfied during the pump operation (see the lower side of the figure). On the other hand, when the pushing pressure Po is applied when the pump is stopped, the seal member 202 is elastically deformed toward the back side, and thereby the seal member 202 comes into close contact with the surface facing the set ring 210 to prevent liquid leakage. (See the upper side of the figure). The seal of the shaft seal portion based on this principle is expected to have a longer life than the example of FIG. 6 because the set ring 210 and the seal member 202 are not in contact with each other during operation. Moreover, since it is non-contact during operation, it does not assume water injection and is unnecessary.

However, in the shaft seal portion 200 shown in FIG. 7, when (1) a liquid containing solid particles or a liquid that precipitates and adheres is transferred, a stuffing box from the expeller 4 to the seal member 202 while the pump is stopped. There is a problem that solids accumulate in the inner space 201 and the shape restoration of the annular plate-shaped sealing member 202 may be hindered.
(2) When the seal member 202 comes into close contact with the set ring 210 when the pump is stopped, if an air pocket is formed inside the stuffing box 201 of the shaft seal portion 200, the close contact state is uniform in the circumferential direction of the seal member 202. There is a problem that the sealing performance is not stable.

(3) When the pumping pressure Po when the pump is stopped is small, if the seal member 202 is not sufficiently elastically deformed toward the back side, a sufficient seal surface pressure cannot be ensured, resulting in a problem of liquid leakage. .
Furthermore, (4) when the indentation pressure Po is very high, or when the rotation speed of the impeller 2 or the expeller 4 is slow and sufficient pressure reducing effect cannot be obtained, the above formula (1) does not hold (that is, (the left side )> (Right side)), there is a problem that the desired sealing performance cannot be exhibited.
Therefore, the present invention has been made paying attention to such problems, and does not require external water injection, and even when the pushing pressure fluctuates, the sealing performance is made as much as possible. An object of the present invention is to provide a centrifugal pump that is stable and can secure a sufficient seal surface pressure.

  In order to solve the above problems, a centrifugal pump according to an aspect of the present invention includes a casing having a suction port on a front surface, an impeller and an expeller provided in the casing, a rotating shaft that rotates the impeller and the expeller, A centrifugal pump provided with a shaft seal provided on the back side of the expeller, wherein the shaft seal is a back side and an inner side of the expeller among wall surfaces defining a rotation area of the expeller within the casing. An annular wall surface portion that is provided as a peripheral portion and elastically deforms in the axial direction in accordance with the pressing pressure, and a shaft sealing cylinder that is mounted on the rotating shaft and is opposed to the back side of the annular wall surface portion The annular wall surface portion has an annular seal portion that seals between the back surface side and the inner peripheral side of the annular wall surface portion with an end surface facing the annular wall surface portion side of the shaft sealing cylinder. The features. In addition, if the said annular wall surface part is made from the elastomer which has flexibility, it is suitable as a raw material which elastically deforms to an axial direction according to indentation pressure.

  According to the centrifugal pump according to one aspect of the present invention, the shaft seal portion is provided on the back surface side and the inner peripheral side of the expeller among the wall surfaces defining the rotation region of the expeller in the casing, and the indentation pressure. And an annular wall portion that is elastically deformed in the axial direction according to the shaft, and a shaft sealing cylinder that is attached to the rotating shaft and is disposed opposite to the back side of the annular wall portion. Since it is configured to have an annular seal portion that seals between the back surface and the inner peripheral side between the end surface facing the annular wall surface of the shaft sealing cylinder, the shaft seal does not have a conventional stuffing box itself. Has become a department.

  Therefore, the problem itself that a solid substance accumulates in the internal space of the stuffing box or an air pocket is formed inside the stuffing box is fundamentally solved. Thereby, compared with the prior art example described with reference to FIGS. 6 and 7, the seal portion of the annular wall surface portion and the end surface of the shaft sealing cylinder can be uniformly adhered over the circumference. . Therefore, even if the indentation pressure fluctuates, the sealing performance can be stabilized as much as possible, and a sufficient sealing surface pressure can be ensured.

  Here, in the centrifugal pump according to one aspect of the present invention, the shaft sealing cylinder has an end surface facing the annular wall surface side of the shaft sealing body when the annular wall surface portion is not subjected to pressing pressure. It is preferable that the annular seal portion is not in contact with the annular seal portion, or is mounted at a predetermined facing position where the annular wall surface portion contacts the annular seal portion with a weaker surface pressure than when the pressing pressure is applied. .

With such a configuration, the sealing portion of the annular wall surface portion does not act on the end surface of the shaft sealing cylinder because the pushing pressure does not act in the situation where the above expression (1) is satisfied during the pump operation. While the non-contact or annular wall surface is in contact with a surface pressure that is weaker than when the indentation pressure is applied, the annular wall surface is elastically deformed toward the back side when the indentation pressure is applied when the pump is stopped. It is suitable for preventing liquid leakage by bringing the seal portion into close contact with the end face of the shaft sealing cylinder.
In particular, by optimizing the spring constant of the annular wall surface part and the predetermined facing position of the shaft sealing cylinder, even when the centrifugal pump is stopped, it is evenly distributed from the suction port to the shaft sealing part in the casing. The annular wall surface is elastically deformed toward the back side by the applied pressing pressure, and liquid leakage from the shaft sealing portion can be prevented by contacting the annular sealing portion and the end surface of the shaft sealing cylinder.

  Further, when the centrifugal pump is in operation, if the decompression effect by the expeller is sufficiently obtained, liquid leakage from the shaft seal portion does not occur due to the effect, and the annular wall surface portion Since the hydraulic pressure does not act, a predetermined facing gap is maintained between the annular seal portion and the shaft sealing cylinder, thereby preventing contact, and wear of the seal portion is prevented. Furthermore, even if the decompression effect by the expeller is insufficient, if a uniform fluid pressure acts on the annular wall surface, an appropriate seal surface pressure is provided between the annular seal and the shaft seal cylinder. Can be secured. Therefore, since heat generation due to early wear and sliding of the seal portion is suppressed, water injection from the outside becomes unnecessary.

Further, in the centrifugal pump according to one aspect of the present invention, the shaft sealing portion restrains movement of the annular wall surface portion to the expeller side by a predetermined distance or more, while the shaft sealing of the annular wall surface portion. It is preferable to have a wall surface position restricting portion that allows movement to the cylinder side.
The wall surface position restricting portion is provided on the annular wall surface portion at a position on the inner peripheral side thereof, and protrudes toward the back surface side, and the casing side so as to engage with the first flange portion. It is preferable to have an engaging convex portion fixed to the.
With such a configuration, even when the pump internal pressure pulsates and the annular wall surface portion is exposed to negative pressure, the position of the annular wall surface portion is regulated by the wall surface position regulating portion. Since the movement beyond the predetermined distance to the expeller side is restrained, the contact between the expeller and the annular wall surface portion can be reliably prevented.

Moreover, the centrifugal pump which concerns on 1 aspect of this invention WHEREIN: It is preferable that the said annular | circular shaped wall surface part has the 2nd collar part projected on the said expeller side in the surface which faces the inner peripheral side and the front side.
In such a configuration, the second collar portion projecting to the expeller side is provided on the inner circumferential side and the front side of the annular wall surface portion, so that when the pump is stopped, the inner circumference from the outer circumference of the expeller is stopped. Since the liquid flowing to the side hits the second collar portion from the inside, the amount of axial displacement of the annular wall surface portion can be increased. Therefore, it is possible to widen an allowable range for an appropriate value of a predetermined facing gap between the seal portion and the shaft sealing cylinder, simplify maintenance, and improve adhesion between the seal portion and the shaft sealing cylinder. For this reason, the sealing performance is further stabilized.

In addition, during pump operation, even if the decompression effect by the expeller is insufficient and the gas-liquid boundary surface is not stable, the second collar portion protruding to the expeller side functions as a labyrinth seal, The liquid can be prevented or suppressed from reaching the rotating shaft side.
Further, in the centrifugal pump according to one aspect of the present invention, the annular seal portion or the shaft sealing cylinder has a circumferential surface on a seal surface where the annular seal portion and the shaft sealing cylinder are in contact with each other. It is preferable to have an annular groove or a ridge or a recess along the direction.
With such a configuration, the seal surface pressure per unit area can be increased by reducing the contact area by the annular groove or the ridge or recess along the circumferential direction of the seal surface. In contrast, it is more suitable for securing a sufficient sealing surface pressure between the sealing portion of the annular wall surface and the end surface of the shaft sealing cylinder, and contributes to stable sealing performance.

  As described above, according to the present invention, water injection from the outside is not necessary, and even when the indentation pressure fluctuates, the sealing performance is stabilized as much as possible to ensure a sufficient sealing surface pressure. can do.

BRIEF DESCRIPTION OF THE DRAWINGS It is a longitudinal cross-sectional view along the axis explaining one Embodiment of the centrifugal pump provided with the shaft seal part which concerns on 1 aspect of this invention (In the same figure, the upper side from the centerline of a rotating shaft is a state at the time of a pump stop. The lower side represents the state during operation, and the same applies to the other figures below). It is a principal part enlarged view of FIG. It is explanatory drawing which shows the 1st modification of FIG. It is explanatory drawing which shows the 2nd modification of FIG. It is a figure explaining the modification of a wall surface position control part, The figure has shown the principal part enlarged view corresponding to FIG. It is a figure explaining an example of the shaft seal part of the conventional centrifugal pump. It is a figure explaining an example of the shaft seal part of the conventional centrifugal pump.

Hereinafter, an embodiment of a centrifugal pump including a shaft seal according to an aspect of the present invention will be described with reference to the drawings as appropriate. In addition, the same code | symbol is attached | subjected and demonstrated about the structure similar to the centrifugal pump mentioned above.
As shown in FIG. 1, the centrifugal pump includes a casing 1 having a suction port 9 on a front surface on the suction side. In the casing 1, the front and rear in the axial direction are partitioned as two rotation areas 50, 60. The impeller 2 is arranged in the large rotation area 50 on the suction side, and the small rotation area 60 on the back side of the impeller 2 is arranged. An expeller 4 is arranged. The impeller 2 and the expeller 4 are coaxially fixed to one rotating shaft (drive shaft) 3 so as to rotate integrally. The impeller 2 has a plurality of blades 5 on its front surface and a plurality of back blades 6 on its back surface. The expeller 4 has a smooth surface on its front surface and a plurality of blades 7 on its back surface.

Here, the shaft seal portion 10 is provided on the back side of the rotation region 60 of the expeller 4. In addition, the shaft sealing part 10 of this embodiment is not provided with the stuffing box extended in the axial direction as described above.
Specifically, the shaft seal portion 10 includes a flexible elastomer-made annular wall surface portion 20, a metal fixing cover 30 that is an annular plate-like member that fixes the annular wall surface portion 20, and the rotation described above. A cylindrical shaft sealing cylinder 12 is provided that is mounted on the shaft 3 and is disposed opposite to the back side of the annular wall surface portion 20. The material of the shaft sealing cylinder 12 can be a metal or a hard resin. In the present embodiment, the shaft sealing cylinder 12 is made of a fluororesin.

  As shown in an enlarged view in FIG. 2, the annular wall surface portion 20 is provided as a portion on the back side and the inner peripheral side of the expeller 4 among the wall surfaces defining the rotation region 60 of the expeller 4 in the casing 1. The inner surface 20n is provided so as to be in liquid contact with the rotation region 60. The annular wall surface portion 20 is formed with a step portion 20d on the outer peripheral portion 20g up to a middle portion in the radial direction, and the stepped portion 20d of the outer peripheral portion 20g is sandwiched between the fixed cover 30 and the back surface 1r of the casing 1. It is fixed. The elastomer material constituting the annular wall surface portion 20 has sufficient flexibility (softness) to be elastically deformed by a displacement amount that exhibits the desired performance in the axial direction in accordance with the indentation pressure. In addition, it is preferable to make the thickness of the annular wall surface portion 20 as thick as possible as long as the desired amount of elastic deformation according to the pressing pressure is secured.

  The outer periphery of the fixed cover 30 is directly fixed to the back surface 1 r of the casing 1 by a plurality of fastening screws 32. In a state where the pressing pressure is not applied, the stepped portion 20d of the annular wall surface portion 20 makes the surface 60n inside the rotation region 60 and the surface 20n inside the annular wall surface portion 20 flush with each other. Furthermore, in the state where the pressing pressure is applied, the inner surface 20n of the annular wall surface portion 20 is inclined so that the width in the axial direction of the rotation region 60 increases toward the inner diameter side due to elastic deformation. ing. The inner peripheral end surface 20p of the annular wall surface portion 20 is opposed to the outer peripheral surface 3g of the rotating shaft 3 (in this example, the outer peripheral surface of the sleeve 8) with a slight gap therebetween.

Between the annular wall surface 20 and the fixed cover 30, a gap K is provided in a region on the inner diameter side of the step 20 d of the annular wall 20. The annular wall surface 20 is exposed to the atmosphere at the surface where the gap K is provided. The gap K ensures the amount of displacement required for elastic deformation in the axial direction of the annular wall surface portion 20.
Further, the annular wall surface portion 20 has an annular seal portion 40 made of an elastomer or the like as a material. In the example of the present embodiment, the seal portion 40 is made of a soft elastomer (rubber) made of a member separate from the annular wall surface portion 20, and is bonded to a position on the back surface side and inner peripheral side of the annular wall surface portion 20. Has been. Further, the annular wall surface portion 20 is formed with a concave step portion 20u at an end portion on the back surface side and the inner peripheral side, and the seal portion 40 is fitted into the concave step portion 20u.

  Furthermore, in the example of the present embodiment, the seal portion 40 has a substantially U-shaped cross section, and an end surface 40r facing the back side of the seal portion 40 having the U-shaped cross section has the shaft sealing cylinder 12 described above. It is set as the lip seal which opposes the end surface 12m which faces the front surface. Further, in the seal portion 40, the concave surface 40d of the U-shaped cross section faces the outer peripheral surface 3g of the rotating shaft 3 (in this example, the outer peripheral surface of the sleeve 8) with a slight gap therebetween. In the present embodiment, the end surface 12m of the shaft sealing cylinder 12 is a flat surface.

  The shaft sealing cylinder 12 is fitted on the outer periphery of the sleeve 8 fitted on the rotary shaft 3, and is fixed to the sleeve 8 by a push screw 14. An annular groove is formed on the inner peripheral surface of the shaft sealing cylinder 12 at a position near the seal portion 40, and an annular O-ring 16 is mounted in the groove. The shaft sealing cylinder 12 has a front end face 12m facing the annular wall surface 20 at a predetermined facing position with a predetermined facing gap (clearance) S from the annular seal portion 40. The position in the axial direction is adjusted so as to be mounted. In this embodiment, the outer peripheral surface of the sleeve 8 is an outer peripheral surface 3g of the rotary shaft 3, but when the sleeve 8 is not used, the outer peripheral surface of the rotary shaft 3, that is, the drive shaft (shaft) itself. It can also be.

  The annular wall surface 20 has an annular first collar portion 20t that is provided at the position on the inner peripheral side thereof and that protrudes toward the back surface at the portion exposed to the atmosphere. On the other hand, the fixed cover 30 fixed to the casing 1 side has an engaging convex portion 30t formed at the inner peripheral tip portion over the entire inner periphery. The engagement convex portion 30t is provided at a position facing the first collar portion 20t from the gap K side so as to be engaged with the first collar portion 20t over the entire circumference in the axial direction. The first collar portion 20t and the engaging convex portion 30t constitute a wall surface position restricting portion. That is, the wall surface position restricting portion restrains the movement of the annular wall surface portion 20 to the expeller side by a predetermined distance or more by the first collar portion 20t and the engaging convex portion 30t engaged therewith, Movement of the annular wall portion 20 toward the shaft sealing cylinder 12 is allowed. The “predetermined distance” can be substantially zero (zero) if the first collar portion 20t and the engaging convex portion 30t are engaged from the beginning (see the lower side in FIG. 2). .

  Further, the annular wall surface 20 is provided with an annular second collar portion 20v projecting toward the expeller 4 on the inner circumferential side and the surface facing the front surface side. The protruding height (axial length) of the second collar portion 20v is set to a dimension that does not interfere with the expeller 4. The second collar portion 20v is configured to increase the amount of axial displacement of the seal portion 40 by effectively applying a pressing force to the back side to the annular wall surface portion 20. The cross-sectional shape of the second collar portion 20v is such that an inclined surface is provided on the inner peripheral end surface 20p, the proximal end side is thickened, and the thickness is gradually reduced toward the distal end side.

  Here, when the pump is stopped, as shown in the upper side of FIGS. 1 and 2, the casing 1 is filled with the liquid in the rotation regions 50 and 60 from the suction port 9 on the suction side to the shaft seal portion 10. A pressing pressure acts on the annular wall surface portion 20 toward the back side. Thereby, the annular wall surface portion 20 is elastically deformed toward the back side along the axial direction, and at the same time, the annular seal portion 40 comes into contact with the end surface 12 m of the shaft sealing cylinder 12.

  At this time, a sufficient surface pressure that does not cause liquid leakage is secured on the seal surface where the end surface 40r of the annular seal portion 40 and the end surface 12m of the shaft sealing cylinder 12 are in contact with each other. Since the shaft sealing cylinder 12 is detachably fixed to the outer peripheral surface of the sleeve 8 from the radial direction with a push screw 14, by adjusting a predetermined facing position in the axial direction, the annular sealing portion 40 and The surface pressure of the sealing surface can be easily adjusted by changing the predetermined facing gap S with the shaft sealing cylinder 12.

  As described above, in the present embodiment, the end surface 40r of the seal portion 40 of the annular wall surface portion 20 and the front-side end surface 12m of the shaft sealing tubular body 12 are in the axial direction in a state where the above-described pressing pressure is not applied. While mounted with a predetermined opposing gap S, the end surface 40r of the seal portion 40 and the front-side end surface 12m of the shaft sealing cylinder 12 are in close contact with each other when the above-described pressing pressure is applied. The annular wall surface 20 is elastically deformed toward the back side.

  That is, the shaft seal portion 10 having the above configuration optimizes the spring constant of the annular wall surface portion 20 and the predetermined facing position of the shaft seal cylinder 12 so that the centrifugal pump is stopped, The annular wall surface portion 20 is elastically deformed toward the back side by the pressing pressure uniformly applied from the suction port to the shaft seal portion 10 in the casing, and the annular seal portion 40 and the shaft sealing cylinder 12 come into contact with each other. As a result, liquid leakage from the shaft seal portion 10 is prevented.

  Further, when the centrifugal pump is in operation, if the decompression effect by the expeller 4 is sufficiently obtained, liquid leakage from the shaft seal portion 10 does not occur, and the annular wall surface portion 20 Since the hydraulic pressure does not act, a predetermined facing gap S is maintained between the annular seal portion 40 and the shaft sealing cylinder 12 so as to be non-contact, and the decompression effect by the expeller 4 is insufficient, and the annular shape When a uniform hydraulic pressure acts on the wall surface portion 20, a seal surface pressure is ensured between the annular seal portion 40 and the shaft sealing cylinder 12.

Next, operation | movement of the shaft seal part 10 of this centrifugal pump and an effect are demonstrated.
In this centrifugal pump, when the pump is operated, the rotary shaft 3 rotates, and the pumped fluid can be pressurized and transferred by the impeller 2. As the rotating shaft 3 rotates, the expeller 4 and the shaft sealing cylinder 12 also rotate. At this time, the casing 1 and the annular wall surface portion 20 remain stationary regardless of whether the pump is operating or stopped.

  The expeller 4 reduces the pressure on the back side of the impeller 2 by its rotation. In the shaft seal portion 10, the back pressure is reduced due to the rotation of the expeller 4 on the front surface side of the shaft seal portion 10, so that the fluid to be fed is prevented from leaking outside through the shaft seal portion 10. . Further, during operation of the pump, the pressure on the back surface is reduced by the action of the expeller 4, so that the seal portion 40 is restored to the original state where it is not elastically deformed to the back surface side, and the seal surface 40r is the shaft sealing cylinder. 12 is separated from the front end surface 12m of the front surface 12, so that wear of the seal portion 40 is also prevented.

  On the other hand, when the rotation of the rotating shaft 3 is stopped, the leakage preventing action due to the effect of reducing the pressure on the back side of the expeller 4 is lost, but the annular wall surface portion 20 is moved to the back side (right direction in the figure) by the above-mentioned pressing pressure. As a result, the seal portion 40 is automatically brought into close contact with the front end surface 12m of the shaft sealing cylinder 12, so that the fluid to be fed is prevented from leaking outside through the shaft seal portion 10. The At this time, since the pump is stopped, the wear of the seal portion 40 does not occur.

  Here, as described above, in the centrifugal pump that transfers the slurry liquid and sand containing fine particles as the fluid to be fed, solid matter in the fluid enters the shaft seal portion, and wears the seal packing at an early stage. Or it is necessary to prevent heat generation. For this reason, some centrifugal pumps that transfer a fluid to be transported containing fine particles constantly inject water from the outside into the shaft seal during the pump operation. However, there are many production lines for chemicals that cannot be mixed with pumping water from the outside, and the amount of external water injection is a factor that increases the operating cost at sites that operate continuously. Become. With respect to such a problem, if it is the shaft seal part 10 of the centrifugal pump of this embodiment, the water injection from the outside is unnecessary and it can be used without water injection.

That is, according to the shaft seal portion 10 of the centrifugal pump, the annular wall surface portion 20 that is elastically deformed in the axial direction in accordance with the pressing pressure, the wall surface that defines the rotation region 60 of the expeller 4 in the casing, This is because it is provided as a part on the back side and the inner peripheral side of the expeller 4 so that it is a shaft seal portion that does not have the stuffing box itself as in the prior art.
Specifically, when this embodiment (FIG. 2) is compared with the above-described prior art (FIG. 7), in the conventional example shown in FIG. 7, an elastomeric sealing member 202 having a circular plate shape is used as a stuffing box. It is disposed away from the expeller 4 by passing through 201. Therefore, in the case of the arrangement of the prior art shown in FIG. 7, air accumulation and solid matter accumulation are likely to occur inside the stuffing box 201 from the expeller 4 to the seal member 202, and it is liquid to obtain a stable sealing performance in the long term. There is a problem that there are many limited cases.

  On the other hand, in the present embodiment, as shown in FIG. 2, there is a great structural difference in that the annular wall surface portion 20 made of elastomer is disposed facing each other as a wall surface that defines the expeller 4. In other words, in the case of the present embodiment, since the annular annular wall 20 made of elastomer is directly opposite the expeller 4, even if an air pool is formed in the defined area 60 of the expeller 4, the air is lighter than the liquid. Moves to the area above the expeller. Therefore, the hydraulic pressure can be applied uniformly to the annular wall surface portion 20. Therefore, according to the shaft seal part 10 of this embodiment, the problem itself that solid matter accumulates in the internal space of the stuffing box or an air pocket is formed inside the stuffing box is solved.

Further, since the facing gap between the inner peripheral end surface 20p of the annular wall surface portion 20 (including the annular seal portion 40) and the outer peripheral surface (3g) of the sleeve 8 is narrow, even if solid matter accumulates in this space, The amount is small, and the deposit is sucked into the pump by the suction force generated by the blades 7 of the expeller 4. Therefore, according to the shaft seal portion 10 of the present embodiment, solid matter does not accumulate in the internal space of the shaft seal portion 10.
Therefore, since the possibility that the annular wall surface portion 20 is unexpectedly deformed by the accumulated solids or the like and the expected elastic deformation is hindered is extremely low, the seal portion 40 and the shaft seal for the annular wall surface portion 20 are sealed. The end surface of the cylindrical body 12 can be uniformly adhered over the circumference. Therefore, even if the indentation pressure fluctuates, the sealing performance can be stabilized as much as possible, and a sufficient sealing surface pressure can be ensured.

  Further, according to the shaft seal portion 10 of the centrifugal pump of the present embodiment, even if the decompression effect by the expeller 4 is insufficient as compared with the above-described conventional technique (FIG. 7), the annular wall surface portion 20 has one. When such a hydraulic pressure acts, there is an effect of stably ensuring a uniform sealing surface pressure between the annular seal portion 40 and the shaft sealing cylinder 12. By optimizing the predetermined facing position of the shaft sealing cylinder 12 so as to be a constant or the predetermined facing gap S, a sufficient seal surface pressure can be appropriately ensured. Further, in the case of a liquid quality that causes solidification when it comes into contact with air, it is possible to prevent sticking of the seal portion 40 by exhausting the air pool, which contributes to a longer seal life.

  Further, according to the shaft seal portion 10 of the centrifugal pump of the present embodiment, the movement of the annular wall surface portion 20 toward the expeller side is restrained, while the movement of the annular wall surface portion 20 toward the shaft seal cylinder 12 side is restricted. Since the wall surface position restricting part to be allowed (in the example of the above embodiment, the first collar part 20t and the engaging convex part 30t), the pump internal pressure pulsates and the annular wall face part 20 is exposed to a negative pressure. Even so, the position of the annular wall surface portion 20 is restricted by the wall surface position restricting portion, and the movement of the annular wall surface portion 20 toward the expeller side is restricted, so that the contact between the expeller 4 and the annular wall surface portion 20 is achieved. Can be reliably prevented.

  That is, when the pump internal pressure is pulsated due to various factors during the pump operation and the shaft seal portion 10 is instantaneously exposed to a negative pressure, the elastomeric annular wall surface portion 20 may be pulled to the expeller side and come into contact. There is. On the other hand, in this embodiment, as shown in FIG. 2, the first collar portion 20t is provided on the annular wall surface portion 20 as the wall surface position restricting portion, and the fixed cover 30 is provided with the first collar portion 20t. Since the engaging convex part 30t to be engaged is provided at a position facing the gap K side and restrains the movement beyond the predetermined distance to the expeller side, the first collar part 20t is fixed even if a negative pressure is assumed. Since it hits the engaging convex part 30t of the cover 30 and plays the role of a stopper, the annular wall surface part 20 is prevented from contacting the expeller 4.

  In the present embodiment, the “wall surface position restricting portion” is an example configured by the first collar portion 20t and the engaging convex portion 30t, but the configuration of the wall surface position restricting portion is not limited thereto. In other words, the wall surface position restricting portion restrains the movement of the annular wall surface portion 20 to the expeller side by a predetermined distance or more, and allows various movements of the annular wall surface portion 20 to the shaft sealing cylinder side. Can be adopted.

For example, FIG. 5 shows a modification of the wall surface position restricting portion.
As shown in the figure, this modification does not have the first collar portion 20t and the engagement convex portion 30t in the example of the above embodiment. Instead, in the wall surface position restricting portion of this modification, the fixed cover 30 has a plurality of through holes 30h penetrating in the axial direction at appropriate positions in the circumferential direction. On the other hand, a screw-headed pin 21 is attached to the annular wall surface 20 along the axial direction at a position facing the through hole 30h in the axial direction on the surface 20m of the portion defining the gap K. Yes. The screw-headed pin 21 is integrally formed with a base end portion embedded in the annular wall surface portion 20. The pin 21 with the screw head has a male screw at the tip, and a step portion 21d is provided at the base end of the male screw.

In the mounted state shown in the figure, the screw head pin 21 has its own shaft portion inserted into the through hole 30h, and in this state, the washer 23 is brought into contact with the step portion 21d from the back side of the fixed cover 30. The nut 22 is tightened, and the front surface of the washer 23 is opposed to the rear surface of the fixed cover 30 in the axial direction. The inner diameter of the through hole 30h of the fixed cover 30 is set to a dimension that does not hinder the movement toward the back side when the annular wall surface portion 20 is elastically deformed, and the inner peripheral surface of the through hole 30h and the pin with screw head Interference with the shaft portion 21 is prevented.
Even in such a configuration, even if a negative pressure is generated, the annular wall surface portion 20 is brought into contact with the front surface of the washer 23 and the rear surface of the fixed cover 30 at a predetermined position, so While movement beyond a predetermined distance is restrained, movement of the annular wall surface portion 20 toward the shaft sealing cylinder 12 can be allowed.

  Further, according to the shaft seal portion 10 of the centrifugal pump of the present embodiment, the second collar portion 20v that protrudes toward the expeller side is provided on the inner circumferential side of the annular wall surface portion 20 and the surface facing the front surface side. When the pump is stopped, the liquid flowing from the outer periphery to the inner periphery of the expeller 4 hits the second collar portion 20v from the inside, so that the axial displacement amount of the annular wall surface portion 20 can be increased. Therefore, the allowable range for the appropriate value of the predetermined facing gap S between the seal portion 40 and the shaft seal cylinder 12 can be widened, the maintenance can be simplified, and the seal portion 40 and the shaft seal cylinder 12 Since the adhesion of the sealant increases, the sealing performance is further stabilized.

Further, even when the decompression effect by the expeller 4 is insufficient during the pump operation and the gas-liquid boundary surface is not stable, the second collar portion 20v protruding to the expeller side functions as a labyrinth seal, Thereby, it can prevent or suppress that a liquid reaches | attains to the rotating shaft 3 side.
The shaft seal portion of the centrifugal pump according to the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

  For example, in the above-described embodiment, the seal portion 40 is provided as a separate component from the annular wall surface portion 20, and the seal portion 40 has a U-shaped cross section, and the back side of the seal portion 40 having the U-shaped cross section. Although an example in which the end surface is in contact with the end surface (plane) of the shaft sealing cylinder 12 is described, the present invention is not limited to this, and the annular wall surface portion 20 and the seal portion 40 may be integrally formed. Further, the material and form of the annular wall surface 20 and the seal portion 40 and the parts to be contacted can be variously modified. For example, various rubbers, metals, and other highly wear-resistant sliding materials can be appropriately selected as the material for the annular seal portion 40 and the shaft sealing cylinder 12.

  However, it is preferable that the annular wall surface portion 20 and the seal portion 40 have a separation structure constituted by separate parts. The advantage of the separation structure is that different materials can be selected for the annular wall surface portion 20 and the annular seal portion 40. For example, an appropriate spring constant can be set for the indentation pressure on the annular annular wall portion 20 made of elastomer, and various rubbers and metals can be used for the annular seal portion 40 in consideration of corrosion resistance and wear resistance. Since it is possible to select an optimal material, it is easy to extend the life of the sealing function. Furthermore, not only the material but also the sealing surface pressure can be further increased by devising the sealing shape such as providing an annular groove or a convex shape along the circumference on the sealing surface.

  For example, in contrast to the above embodiment, in the first modification shown in FIG. 3, the seal portion 40 of the annular wall surface portion 20 has a rectangular cross section, and the end surface 12 m of the shaft sealing cylinder 12 has a circumference. The point which has the annular groove (concave part) 12d along a direction differs. In addition, it can replace with the cyclic | annular groove | channel (concave part) 12d, and can provide the convex part along the circumferential direction of a sealing surface. Further, the number of annular grooves (concave portions) and convex portions is not limited to one, and various shapes such as a plurality of annular grooves can be selected.

  In such a configuration, since the annular groove (or ridge or recess) 12d is provided along the circumferential direction of the seal surface, the contact area of the seal surface is reduced to reduce the seal surface per unit area. The pressure can be increased. Therefore, it is more suitable and stable for securing a sufficient sealing surface pressure between the seal portion 40 of the annular wall surface portion 20 and the end surface 12m of the shaft sealing cylinder 12 even with a low indentation pressure. Contributes to sealing performance. In particular, if the protrusion is a sealing surface, the contact area can be reduced and the surface pressure per unit area can be increased. It is suitable for securing a sufficient seal surface pressure during the interval.

Moreover, in the 1st modification shown in FIG. 3, the structure of the cylinder 12 for shaft seals is also different. That is, in the above-described example, the shaft sealing cylinder 12 is fixed by the push screw 14, but in this modification, the shaft sealing cylinder 12 includes a cylinder body 12a made of a soft elastomer (rubber). The difference is that it is composed of an annular hugging member 12b that surrounds the cylinder body 12a so as to be huggable. The hugging member 12b is divided into two in the circumferential direction, and can be tightened in the circumferential direction by the upper and lower mounting screws 14, and by tightening the mounting screw 14 of the hugging member 12b from above and below, the hugging member 12b is radially The cylinder main body 12a can be fixed by being reduced in diameter. Further, the first modification is different in that the annular seal portion 40 is made of metal or hard resin (for example, fluororesin). A general hose band can also be used as the hugging member 12b.
With such a configuration, since the shaft sealing cylinder 12 is fixed by hugging, the sleeve surface is prevented from being scratched as compared with the case where the shaft sealing cylinder 12 is fixed by a push screw. Therefore, it is suitable for the case where the fixing position of the shaft sealing cylinder 12 is repeatedly adjusted over a long period of time.

  In the above embodiment (FIG. 2), as the lip seal of the annular wall surface portion 20, the annular seal portion 40 is made of soft elastomer (rubber), and the shaft sealing cylinder 12 is made of metal or hard resin (for example, The combination example made of fluororesin has been shown, but as shown in the first modification (FIG. 3), the combination opposite to that of the above embodiment (FIG. 2) (that is, the annular seal portion 40 is made of metal or It may be made of a hard resin (for example, a fluororesin), and the shaft sealing cylinder 12 may be made of a soft elastomer (rubber).

Further, the spring constant of the annular wall surface portion 20 and the predetermined facing gap (clearance) S between the annular seal portion 40 and the end surface of the shaft sealing cylinder 12 can be appropriately set as necessary. By optimizing the spring constant of the wall surface portion 20 and the predetermined facing gap S, an appropriate seal surface pressure can be secured between the annular seal portion 40 and the shaft sealing cylinder 12.
For example, in the above formula (1), when the indentation pressure Ps is relatively large with respect to the pressure reduction Pb on the back surface of the impeller 2 and the pressure reduction Pe on the back surface of the expeller 4, or the rotational speed of the impeller 2 and the expeller 4 is low, Pb and Pe Is small (that is, (Ps + Pi) − (Pb + Pe)> Pa), there is no interface between the liquid and air on the back surface of the expeller 4, and the entire rotation region 60 of the expeller 4 is filled with the liquid. .

  At this time, since the hydraulic pressure proportional to the difference between the first term and the second term on the left side in the equation (1) acts on the annular annular wall portion 20 made of elastomer, the seal surface pressure also depends on the hydraulic pressure. Increase or decrease. The seal surface pressure can also be adjusted by moving the mounting position of the shaft sealing cylinder 12 in the axial direction of the rotary shaft 3. That is, the material of the annular wall surface portion 20, the annular seal portion 40, and the shaft sealing cylinder 12 is appropriately selected according to the liquidity and operating conditions, and the end faces of the annular seal portion 40 and the shaft sealing cylinder 12 are selected. By appropriately setting a predetermined facing gap (clearance) S, it is possible to arbitrarily select the non-contact state or the contact state of the seal surface during pump operation.

  For example, FIG. 4 shows a second modification. In the modification shown in the figure, the shaft sealing cylinder 12 includes a metal cylinder main body 12a and a rubber packing 12c having an L-shaped cross section that is fitted into an annular recess in the front inner peripheral surface of the cylinder main body 12a. And an annular second seal portion 12f fitted in the L-shaped concave portion of the rubber packing 12c, and these are integrally formed by shrink fitting or the like. In the shaft sealing cylinder 12, the cylinder main body 12 a is fixed to the outer peripheral surface 3 g of the rotating shaft 3 by a push screw 14. Here, in the second modification shown in the figure, a sliding material (for example, SiC, cemented carbide) having high wear resistance is provided on the (first) seal portion 40 and the second seal portion 12f of the shaft sealing cylinder 12. Etc.). Thereby, in this 2nd modification, about the said predetermined opposing clearance (clearance) S, as shown in FIG. 4 lower side, it is not necessarily between sliding materials (that is, the annular seal part 40 and the shaft sealing cylinder 12). The second seal portions 12f need not be in contact with each other, and as shown in the upper side of FIG.

  That is, in the present invention, the predetermined facing position of the shaft sealing cylinder 12 has a predetermined facing gap (clearance) S, and the end surface 12m of the shaft sealing cylinder 12 and the annular seal portion. Not only in the case of non-contact with 40, you may mount | wear to the position which mutually contacts when the annular | circular shaped wall surface part 20 is not receiving pushing pressure. For example, the annular wall surface portion 20 can be mounted at a predetermined facing position such that the annular wall surface portion 20 is slidably contacted with a weaker surface pressure than when the indentation pressure is received.

DESCRIPTION OF SYMBOLS 1 Casing 2 Impeller 3 Rotating shaft 4 Expeller 5 Blade | wing (impeller front) blade | wing 6 (impeller's) back blade 7 (expeller's blade | wing) 8 Sleeve 10 Shaft sealing part 12 Shaft sealing cylinder 20 Toroidal wall part 30 Fixed cover 40 Seal part 50 (impeller) rotation area 60 (expeller) rotation area S Predetermined gap

Claims (5)

A centrifugal pump comprising a casing having a suction port on the front surface, an impeller and an expeller provided in the casing, a rotating shaft for rotating the impeller and the expeller, and a shaft seal provided on the back side of the expeller. ,
The shaft sealing portion is a circle that is provided as a portion on the back surface side and the inner peripheral side of the expeller among the wall surfaces that define the rotation region of the expeller in the casing, and elastically deforms in the axial direction in accordance with the pushing pressure. An annular wall surface, and a shaft sealing cylinder that is attached to the rotating shaft and is disposed opposite to the back side of the annular wall surface,
The annular wall surface portion includes an annular seal portion that seals between an end surface facing the annular wall surface portion side of the shaft sealing cylinder on the back surface side and the inner peripheral side of the annular wall surface. The surface on the inner peripheral side of the wall surface portion is flush with the surface facing the back surface of the expeller on the inner surface of the rotating region in the casing in a state where the pressing pressure is not acting, A centrifugal pump characterized in that the surface is inclined so that the width in the axial direction of the rotation region is expanded by elastic deformation in a state in which the pressing pressure is applied.   The shaft sealing cylinder has its end surface facing the annular wall surface side being in non-contact with the annular seal portion when the annular wall surface portion is not subjected to pressing pressure or the annular ring surface 2. The centrifugal pump according to claim 1, wherein the centrifugal pump is mounted at a predetermined facing position where the wall surface portion comes into contact with the annular seal portion with a weaker surface pressure than when the wall surface portion receives the pressing pressure. The shaft seal is
When the centrifugal pump is stopped, the annular wall surface portion is elastically deformed toward the back side by the pressing pressure uniformly applied from the suction port to the shaft seal portion in the casing, and the annular seal portion Liquid leakage from the shaft sealing portion is prevented by contacting the shaft sealing cylinder,
When the centrifugal pump is in operation, if the decompression effect by the expeller is sufficiently obtained, liquid leakage from the shaft seal portion does not occur, and liquid pressure is applied to the annular wall surface portion. Does not act so that a predetermined facing gap is maintained between the annular seal portion and the shaft sealing cylinder so as to be non-contact, and the decompression effect by the expeller is insufficient, so that the annular wall surface portion is not in contact with the annular wall portion. The seal surface pressure is secured between the annular seal portion and the shaft sealing cylinder when such a hydraulic pressure is applied. Centrifugal pump. The shaft seal portion is not less than a predetermined distance to the expeller side even when the annular wall surface portion located in the same plane is exposed to negative pressure due to pulsation of internal pressure during pump operation . movement is restrained, centrifugation according to any one of claims 1 to 3 transfer to the shaft sealing for tube side by the boost pressure in the pump stopped, characterized in that it comprises a wall surface position regulating section which permits pump. 5. The centrifugal pump according to claim 1, wherein the annular wall surface portion has a flange portion projecting toward the expeller side on a surface facing the inner peripheral side and the front surface side thereof.

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