JPH0128369Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) This invention is a shaft seal for a vertical or horizontal hydraulic machine in which a rotating body such as an impeller is attached to a drive shaft rotatably supported in a casing. Regarding the device, the hydraulic machine can be widely applied to pumps, water turbines, and others.

(Prior Art) Gland packings and mechanical seals are often used in conventional shaft sealing devices for hydraulic machines.
FIG. 3 shows an example in which a mechanical seal is used as a shaft sealing device for a vertical pump. Here, a mechanical seal 6 is used to prevent a large amount of liquid pumped from leaking into the atmosphere from the gap between the main shaft 3 and the discharge elbow 2, or to prevent air from entering the pump. There is. In the figure, 1 is a pumping pipe, 4
is an impeller, and 5 is a strainer.

FIG. 4 shows a detailed view of the shaft sealing device 6 shown in FIG. 3 above. In the figure, reference numeral 11 denotes a fixed ring, which is airtightly fixed to the shaft sealing case 6 via an O-ring 12. 13
is a rotating ring which is sealed on the rotating shaft 3 side by an O-ring 14 and rotated together with the shaft, and which is pressed toward the fixed ring 11 by a spring 16 from a spring holder 15 attached to the shaft 3. There is.
Reference numeral 17 denotes a sliding surface machined to be flat perpendicular to the shaft 3. Fresh water is supplied to the sliding surface 17 from a fresh water supply hole 18, and a water sealing action and a cooling action are performed. Both at rest and during operation, the inside and outside of the pump chamber are sealed by the sliding surface 17 pressed by the sling 16.

On the other hand, sealing devices using magnetic fluid have already been considered. FIG. 5 shows an example in which the magnetic fluid seal is used in a shaft sealing device for a vertical pump. In the diagram, 3
21 is a pump main shaft, 21 is a pump casing, 22 is a seal reservoir, 23 is a bearing metal, 24 is a yoke support part, 25a, 25b are yokes made of magnetic material, 26 is a permanent magnet, 27 is a holding plate, 28a ，
28b is a magnetic fluid, 29 is a shaft sleeve made of magnetic material, 31 is a pump chamber, and 32 is a sealing liquid.

In the magnetic fluid seal described above, a magnetic circuit is formed between the permanent magnet 26, both yokes 25a and 25b made of magnetic material, and the shaft sleeve 29. In particular, the opposing gap between the two yokes 25a and 25b and the sleeve 29 is Since the magnetic flux density is higher than that at other locations, the magnetic fluid is held in the gaps like 28a and 28b, thereby blocking and sealing the inside and outside of the casing 21.

(Problems to be solved by the invention) In the conventional shaft seal device described above, for example, as in the shaft seal of a vertical pump, positive pressure and negative pressure are alternately applied depending on the operating conditions. However, in shaft sealing devices using mechanical seals or gland packings, if the shaft seal becomes negative pressure,
It is essential to inject a clean liquid as a sealing liquid. However, depending on the location where the pump is installed, it may be impossible to obtain clean sealing fluid from outside the pump, or there is an increasing demand for eliminating the need for clean sealing fluid from the standpoint of resource conservation.
In order to meet these demands, the use of the above-mentioned magnetic fluid seal is being considered, but when the shaft seal becomes positive pressure and the magnetic fluid comes into contact with the liquid pumped, stirred, degraded,
There was a problem in that the sealing function was lost and a large amount of pumped liquid leaked outside.

The present invention solves the problems with conventional shaft seal devices as described above, and is capable of sealing the shaft under conditions where positive pressure and negative pressure are alternately repeated depending on the operating conditions, and also provides a clean seal. The purpose of this invention is to provide a shaft sealing device that does not require liquid.

(Means for Solving the Problems) In order to solve the above-mentioned problems of the prior art, the present invention provides a shaft seal device installed in the casing penetrating portion of the drive shaft using a flat contact sealing mechanism such as a mechanical seal. and a magnetic fluid seal are combined to form a magnetic fluid seal at the planar contact portion.In implementation, a permanent magnet and a magnetic fluid seal are attached to the fixed side member of the sealing mechanism by planar contact. It is desirable to provide a ferrofluid seal member that includes a ferrofluid supply hole.

(Function) The present invention is configured as described above, so that
When there is positive pressure in the working chamber and thus in the shaft sealing part, the rotating part of the sealing mechanism based on planar contact that rotates with the shaft while facing the fixed side member (fixed ring, etc.) fixed to the outer case and sealing the shaft side. The side member (rotary ring, etc.) is pushed up by the pressure balance and comes into close contact with the stationary side member, and exerts a sealing effect similar to that of a mechanical seal on the sliding surfaces of both members. At this time, since the sliding surface is sealed, the magnetic fluid does not advance into the sliding surface.

On the other hand, when the pressure inside the working chamber is negative, the rotating member rotating together with the shaft is pushed down by the pressure balance, creating a gap between the sliding surface with the stationary member. As a result, air initially enters the working chamber, but by appropriately restricting the gap between the sliding surfaces and setting it to the optimum value for the magnetic fluid seal, air enters the working chamber, but by appropriately restricting the gap between the sliding surfaces and setting it to the optimum value for the magnetic fluid seal, air can enter the chamber where the pressure is higher than that of the sliding surface. The magnetic fluid enters the sliding surface or planar contact and automatically creates a magnetic fluid seal, preventing air from entering the working chamber. At this time, by forming a magnetic circuit that spans both members so that the magnetic flux density at the sliding part is larger than other parts, the magnetic fluid concentrates on the sliding part and seals the magnetic fluid. becomes good.

(Example) Next, embodiments of the present invention will be described with reference to the drawings.

Fig. 1 is a sectional view of a main part of an embodiment in which a shaft sealing device according to the present invention is attached to the shaft sealing part of a vertical pump, showing the state under positive pressure, and Fig. 2 similarly showing the state under negative pressure. It shows. In the figure, a shaft sealing case 40 is attached to the discharge elbow 2, which is a part of the casing through which the pump main shaft 3 passes, and a fixed ring 41 made of a magnetic material is attached to an O-ring 42 inside the shaft sealing case 40. It is fixed airtight through the. Below the fixed ring 41 is a rotating ring 4 made of magnetic material.
3 is fitted so that it can rotate with the shaft and slide in the axial direction by sealing the rotating shaft side with an O-ring 44. The amount of clearance is determined by the holder 4 fixed on the shaft side.
It is regulated by a rotation stop pin 47 on 6.

On the other hand, a permanent magnet 48 is attached inside the fixed ring 41 so as to form a magnetic circuit passing through the sliding surface 45 through the protrusion 49, and a magnetic fluid is supplied to the sliding surface 45. A passage 49 is bored in such a manner that the passage 49 communicates with a built-in container 52 containing a magnetic fluid 51.

Next, to explain the operation, when the shaft seal part is under positive pressure, as shown in FIG. It comes into close contact with the sliding surface 45 of the ring 41. At this time, since the pumped liquid 53 covers the sliding surface portion, a water sealing effect is performed, and a sealing effect similar to that of a mechanical seal is exhibited.

On the other hand, when the shaft seal part is under negative pressure, as shown in FIG. 2, the rotating ring 43 is pushed down by the pressure balance, and a gap is created between the sliding surface 45 and the fixed ring 41.
Therefore, air initially flows into the pump chamber.
The clearance is set to an optimum value for the magnetic fluid seal by means of a detent pin 47. Sliding part 45
Since the pressure becomes low due to the pressure inside the container 52, the magnetic fluid 51 is supplied to the sliding part 45, and a magnetic fluid seal is automatically formed, making it possible to prevent air from entering the pump chamber. In this embodiment, the magnetic circuit includes the permanent magnet 48 inserted into the fixed ring 41, the protrusion 49 of the fixed ring 41, and the rotating ring 43.
Since the magnetic flux density of the sliding part 45 is larger than that of other parts, the magnetic fluid 51 flows into the sliding part 4.
5 to form a magnetic fluid seal.

According to this embodiment, when the shaft seal is under positive pressure,
Like a mechanical seal, it seals by plane contact and acts as a magnetic fluid seal when there is negative pressure, so there is no need to inject clean liquid from the outside whether the shaft seal is under positive pressure or negative pressure. It is possible to seal reliably.

In addition, in the above-mentioned embodiment, a structure in which the shaft sealing device of the present invention was installed in the penetration part between the discharge elbow of a vertical pump and the main shaft of the pump was explained, but this is only an example, and the shaft sealing device of the present invention can be widely used as a shaft sealing device for a penetrating portion between a rotating shaft and a casing of a hydraulic machine in which internal pressure alternately changes between positive pressure and negative pressure during operation. Furthermore, it goes without saying that the position of the permanent magnets, the formation of the magnetic circuit, etc. can be changed as appropriate.

(Effects of the invention) As explained above, according to the invention, a plane contact seal mechanism such as a mechanical seal and a magnetic fluid seal are combined, and when the shaft seal part is under positive pressure, the plane contact seal seals. Since it is now possible to automatically switch to a magnetic fluid seal when there is negative pressure, it is no longer necessary to inject water from the outside into the shaft seal of hydraulic machinery where positive pressure and negative pressure are alternately repeated. This has the effect of ensuring reliable sealing.

[Brief explanation of the drawing]

1 and 2 are sectional views of main parts of a shaft sealing device showing an embodiment of the present invention in different operating states, FIG. 3 is a side sectional view of a conventional vertical pump, and FIGS. 4 and 5
The figures are side sectional views of a conventional mechanical seal and a magnetic fluid seal, respectively. 2...Discharge elbow, 3...Pump main shaft, 41...
... Fixed ring, 43 ... Rotating ring, 45 ... Sliding surface,
47... Detent pin, 48... Permanent magnet, 51
...Magnetic fluid.

Claims (1)

[Scope of Claim for Utility Model Registration] 1. In a hydraulic machine in which a rotating body such as an impeller is attached to a drive shaft rotatably supported within a casing, a shaft seal device provided in the casing penetration part of the drive shaft is a mechanical seal. A sealing mechanism based on planar contact such as this and a magnetic fluid seal are combined to form a magnetic fluid seal at the planar contact part, and the shaft seal part can be used even under operating conditions where positive and negative pressures are repeated. A shaft sealing device characterized by being able to securely seal without injecting water into the shaft sealing part from the outside. 2. The shaft sealing device according to claim 1, wherein the fixed side member of the planar contact sealing mechanism is provided with a magnetic fluid sealing member including a permanent magnet and a magnetic fluid supply hole. 3. The shaft sealing device according to claim 1, wherein the rotating member of the planar contact sealing mechanism is configured to be displaced in the axial direction depending on the pressure balance within the casing chamber.