JPH01234663A - Magnetic fluid seal - Google Patents

Abstract

PURPOSE:To make it possible to apply a magnetic fluid seal to various kinds of nonmagnetic objects by arranging magnets in a nonmagnetic housing with their surfaces having the same polarity facing together, and by charging magnetic fluid in gaps inside and outside the magnets. CONSTITUTION:A nonmagnetic columnar shaft 7 to be sealed is fitted in annular magnets 3A, 3B which are disposed having a small space therebetween in a nonmagnetic housing 9 with their surfaces having the same polarity facing together, and magnetic fluid 5 is charged in gaps between the housing 9, the annular magnets 3A, 3B and the shaft 7 to be sealed. With this arrangement, a strong magnetic field is generated around the magnets 3A, 3B, and the magnetic fluid 5 is held by this magnetic field, thereby it is possible to apply this magnetic fluid seal to various kinds of nonmagnetic objects such as telecommunication cables, pipes and the like which cannot be applied with conventional magnetic fluid seals.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic fluid seal, and particularly to a magnetic fluid seal suitable for sealing a member made of a non-magnetic material.

(Prior technology) Magnetic fluid seals are sealed by contact between a liquid (magnetic fluid) and a solid surface (surface to be sealed), so even if there are minute irregularities on the surface to be sealed, there will be no damage to the surface to be sealed. It has the characteristic that it does not leak even if it is covered with dust etc. For this reason, it can be used as a dustproof seal for magnetic disk drives that require seal integrity, or as a vacuum seal for integrated circuit manufacturing equipment.
Often used these days.

FIG. 17 is a sectional view showing the basic structure of a conventional magnetic fluid seal used in these devices. An annular magnet 3 magnetized in the axial direction and a pole piece 4 coupled to the magnet 3 are installed between the rotating shaft 1 and the housing 2,
A magnetic fluid 5 is filled in the gap between the rotating shaft 1 and the pole piece 4. 6 is a gasket that seals between the housing and the pole piece. This magnetic fluid seal uses magnetic Hamura for the rotating shaft 1 and pole piece 4, uses a non-magnetic material for the housing, and configures a magnetic circuit as shown by the broken line in FIG. A strong magnetic field is generated in the gap.

A magnetic fluid is made by dispersing a large amount of magnetic particles such as magnetite in mineral oil or synthetic oil, and behaves as a ferromagnetic liquid. Therefore, the magnetic fluid is attracted and held in the gap between the rotating shaft 1 and the pole piece 4, where the magnetic field strength is large, and the gap is sealed. If this magnetic fluid seal is optimally designed, it can withstand a seal pressure of up to 200 gf/cm2 (
(hereinafter simply referred to as breakdown voltage).

However, when a non-magnetic material is used for the rotating shaft, the magnetic field strength in the gap between the pole piece 4 and the rotating shaft 1 becomes smaller.
The withstand voltage drops significantly and it cannot be put to practical use.

FIG. 18 is a sectional view showing the basic structure of a magnetic fluid seal conventionally proposed for application in this case. As shown in the figure, the tip of the pole piece 8 is bent and brought close to each other to increase the magnetic field strength in the gap between the rotating shaft 7 made of a non-magnetic material and the pole piece 8. However, even with this structure, the withstand voltage is still low and it has not been put to practical use.

(Invention or problem to be solved) As explained above, conventional non-RT cards such as plus decks
, i +1: There is no practical magnetic fluid seal that can be applied to a rotating shaft composed of Hamura. On the other hand, if this becomes possible, it would be extremely useful as it would be widely applicable to sealing fields where rubber backings, adhesive sealants, etc. have traditionally been used.

An object of the present invention is to provide a magnetic fluid seal that can be applied to a sealed member using a non-magnetic material and has a high withstand pressure.

[Means to solve the problem]

In order to achieve this purpose, the magnetic fluid seal of the present invention has a cylindrical shaft to be sealed made of a non-magnetic material and a magnetic pole surface of the same polarity facing each other, and a magnetic fluid seal is placed around the shaft to be sealed at a small distance. A plurality of arranged annular magnets and a cylindrical housing made of a non-magnetic material and containing the plurality of annular magnets are arranged concentrically, and the gap between the inner surface of the annular magnet and the shaft to be sealed and the outer surface of the annular magnet are arranged concentrically. The gap between the magnetic fluid and the housing is filled with magnetic fluid.

Furthermore, the magnetic fluid seal of the present invention has magnetic pole surfaces of the same polarity facing each other in a cylindrical housing made of a non-magnetic material,
A plurality of disc-shaped magnets arranged at a minute distance are arranged concentrically, and a gap between the outer surface of the disc-shaped magnets and the housing is filled with magnetic fluid. .

[For production]

The magnetic fluid seal of the present invention is produced by arranging a plurality of annular magnets or disk-shaped magnets magnetized in the thickness direction with the same magnetic pole faces facing each other and at a very small distance. Alternatively, a strong magnetic field is generated on the outer peripheral surface of a disc-shaped magnet, and the magnetic fluid is held in this magnetic field to form a seal.

Furthermore, in the present invention, both the gap between the inner surface of the magnet and the shaft to be sealed and the gap between the outer surface of the magnet and the shaft to be sealed are sealed using magnetic fluid, and the pole piece guides the magnetic flux of the permanent magnet to the shaft to be sealed. is not used.

With this configuration of the present invention, it can be applied to a wide range of objects using non-magnetic materials that could not be applied conventionally, such as communication cables and pipes using Plus Deck. In addition, plus deck molded products can be used for the sealed shaft and housing.
In addition, since there is no need for additional metal pole pieces constituting the magnetic circuit, it is inexpensive and lightweight. moreover,
Even if an annular magnet with a small cross section is used, a high seal pressure equivalent to a conventional magnetic fluid seal can be obtained. Furthermore, fluid on/off valves and fluid injection/closing valves using magnetic fluid seals are also available.
It is possible to easily configure a plug for blocking the outlet.

[Example] The magnetic fluid seal of the present invention described below can of course be applied as a seal for a rotating shaft, but it can also be widely applied as a static or quasi-static seal. Therefore, hereinafter, it will be referred to as a "sealed shaft" instead of a "rotating shaft."

First, the basic structure of the magnetic fluid seal of the present invention will be explained using the drawings. FIG. 1 is a cross-sectional view of the magnetic fluid seal of the present invention. 7 is a sealed shaft made of non-magnetic material;
38 and 3B are annular magnets (an example is shown in which the N poles are opposed), and the magnetic pole surfaces of the same polarity are set to face each other.

9 is a housing made of non-magnetic material, 9a and 9b are protrusions provided on the inner surface of the housing, and are pressed from both sides so that they do not separate from each other due to the repulsive force of the annular magnets 38 and 3B, which are generated because the same magnetic pole faces are facing each other. It is something. In the figure, gh is the gap between the housing and the annular magnet, g8 is the gap between the shaft to be sealed and the annular magnet, go is the gap between the annular magnets, and h is the height of the annular magnet.

In the magnetic fluid seal of the present invention, the annular magnet is suspended between the housing and the shaft to be sealed due to magnetic force without being structurally supported, and the gap between the inner and outer peripheries of the annular magnet is becomes uniform over time.

However, the above assumes that the shaft to be sealed and the housing are arranged concentrically, and if there is a possibility that an eccentric load will be applied to the housing or the shaft to be sealed, the gap between the inner and outer circumferential surfaces of the annular magnet must be The size becomes uneven and the withstand pressure decreases. Therefore, in such a case, it is desirable to install a spacer in the gap between the inner and outer peripheral surfaces of the annular magnet to make the gap constant. In this case, a non-magnetic material that does not affect the magnetic field distribution of the annular magnet is used for the spacer.

Next, the results of measuring the pressure resistance of the magnetic fluid seal of the present invention will be explained.

The test model of the ferrofluid seal is not shown as it is substantially the same as in FIG. The specifications of the sealed shaft, annular magnet, housing, and magnetic fluid used in the test model were
Shown in the table.

With magnetic fluid seals, the gas pressure at which leakage occurs when the gas pressure is increased is different from the gas pressure at which boiling stops when the gas pressure is decreased, and the latter is considerably smaller. Here, the gas pressure at which gas leakage or stoppage can be easily tested was defined as the withstand pressure.

Figure 2 shows the measurement system, where 10 is the test model and 11 is the test model.
is a container filled with water 12. The compressed gas supplied from 13 to the nitrogen gas phone is reduced in pressure by a pressure reducing valve 14,
It passes through valve 15 and is supplied to test model 10 . 16
1 is a gas pressure measuring device, and 17 is a pipe.

First, the valve 15 is opened and the pressure reducing valve 14 is operated to increase the gas pressure until the generation of bubbles (hereinafter referred to as gas leakage) is observed from the magnetic fluid seal portion of the test model. If a gas leak is detected, the valve 15 is closed to cut off the gas supply. After this, if left unattended, gas leakage will continue and the gas pressure will drop, but after a while the gas leakage will stop.
Gas pressure becomes constant. The gas pressure at this time was read and defined as the withstand pressure.

The withstand voltage was measured by changing the distance V4g between the annular magnets.

The test results are shown in Table 2. When the gm is 0.15 mm, the withstand pressure is about 110 gf/cm', and 0.5 m
It was 210 gf/cm2 at m. Therefore, in order to obtain high pressure resistance in the crotch of the magnetic fluid seal of the present invention,
Is it necessary to set g m appropriately?

On the other hand, the pressure resistance of the conventional magnetic fluid seal using 6R material for the shaft to be sealed is approximately 200 gf/cm2.
It can be seen that the magnetic fluid seal of the present invention has almost the same pressure resistance as this, and has a pressure resistance sufficient for practical use.

Note that the gap between the shaft to be sealed and the annular magnet in this test model (
The gap between the inner circumference of the annular magnet) gs and the gap between the annular 6n stone and the housing (gap between the outer circumference of the annular magnet) g++ are 0.15 mm and 0.2511, respectively, as shown in Table 2.
m, and the gap of conventional ferrofluidic seals (typically 0.1
(mm or less) larger. Therefore, in actual design, this gap can be made even smaller, in which case the withstand voltage will further increase.

Table 1 Specifications of the test model Table 2 Test results In the test model described above, the withstand voltage when using only one annular magnet was measured to be 20 gf/cm2 or less. This value is 1/10 of the test model in which two annular magnets are arranged. From this, it can be seen that by adopting the configuration of the present invention in which a plurality of annular magnets are used and arranged with the same polarity faces facing each other, the withstand voltage can be dramatically increased.

In this test, a rare earth iron-based ring magnet with a large maximum energy product was used to obtain a high withstand voltage.

However, this magnet is prone to rust, and if it is to be used for a long time, it is necessary to apply anti-corrosion treatment to the surface. In this case, if a rare earth cobalt-based magnet is used, a magnetic fluid seal with excellent water resistance and no rusting problem can be constructed, although the maximum energy product is slightly small.

Next, a method for designing the magnetic fluid seal of the present invention will be explained.

The pressure resistance of a magnetic fluid seal tends to be proportional to the magnetic field strength of the gap filled with the magnetic fluid and the saturation magnetization of the magnetic fluid itself, and inversely proportional to the size of the gap. Among these, the saturation magnetization of the magnetic fluid is determined by the magnetic fluid used, and the size of the gap is determined by the structural film 5]. However, the magnetic field strength in the gap is difficult to measure because the gap is small, so there has been no obvious difference in the past.

Therefore, magnetic field analysis in the magnet array of the magnetic fluid seal of the present invention was performed using the finite element method.

On the other hand, analysis of a state in which the gap is filled with magnetic fluid is difficult because the position of the magnetic fluid moves due to the magnetic field. Therefore, here, the case where no magnetic fluid was filled was conducted. Although quantitative values regarding pressure resistance cannot be directly derived from this calculation result, qualitative guidelines regarding the design of magnetic fluid seals can be obtained.

The calculation model is the same as the test model described above. Figures 3 and 4 are the calculation results, showing the magnetic field strength distribution (contour lines of the absolute value of magnetic flux strength, numerical units are Elstera 1~) and magnetic flux distribution in the area indicated by the chain line in Figure 1, respectively. . However, the shaft to be sealed and the housing are not shown.

From FIG. 3, it can be seen that the maximum point of the magnetic field strength on the outer periphery of the annular magnet is located at the corner (indicated by A in the figure) of the opposing sides of the magnet. Regarding the inner periphery, it is also located at the corner (indicated by B in the figure) of the opposing side surfaces of the magnet. Therefore, it can be seen that the pressure resistance of the magnetic fluid seal of the present invention depends on the magnetic field strength in the A and B regions. On the other hand, when comparing the magnetic field strengths of regions A and B, region B is considerably smaller, and when the gap between the outside and inside of the annular magnet is the same, the withstand voltage inside the annular magnet is lower. Therefore, in the structural design of the magnetic fluid seal of the present invention, it is desirable to make the gap on the inside of the annular magnet as small as possible than on the outside to compensate for the drop in withstand pressure and to make the withstand pressures on the inner and outer circumferences of the annular magnet the same.

On the other hand, the magnetic field strength in space is proportional to the magnetic flux density.

Therefore, next we will focus on magnetic flux distribution. From the magnetic flux distribution diagram in Figure 4, you can see how the magnetic flux goes from the north pole to the south pole.If we pay attention to the magnetic flux in areas A and B, which determine the withstand voltage, the magnetic flux in areas A and B is due to the narrow magnetic pole surface. The magnetic flux from the central part of the magnetic pole face (indicated by hatching C in Figure 4) cancels out the magnetic flux from the opposing annular magnet. mutual respect, area A,
It can be seen that it does not contribute much to the magnetic flux density of B.

Therefore, it can be concluded that in the magnetic fluid seal of the present invention, even if the height of the cross section of the annular magnet (indicated by h in FIGS. 3 and 5) is increased more than necessary, the increase in withstand pressure is small.

FIG. 5 is a sectional view of an annular magnet that is effective for use when the inner diameter of the housing is larger than the diameter of the shaft to be sealed. 3G and 3D are annular magnets with a small cross-sectional height h, and are filled with a non-magnetic material 18 such as plastic and integrated. - The commercialized magnets 3C and 3D are equivalent to the annular magnets 3A and 3B in FIG. Two or more sets of these magnets are arranged with the same polarity facing each other. Permanent magnet materials are generally expensive, but by using an annular magnet with this structure, the cost of magnet materials can be reduced, and the repulsion between the annular magnets during assembly is also reduced. Even if a wooden-structured annular magnet is used, the drop in pressure resistance is small. The heights of the annular magnets 3C and 3D may be different.

The magnetic fluid seal shown in FIG. 1 uses single annular magnets arranged side by side. For this reason, when a high withstand voltage is required, it is necessary to arrange a large number of annular magnets against the repulsive force of the magnets, which is troublesome. Figure 6 shows, in order to improve this point,
An annular magnet 3 is made of a non-magnetic material 18 such as a thermosetting resin.
A and 3B were bonded together in advance and made into a stock. This facilitates attachment of the annular magnet.

FIG. 7 is a sectional view of an annular magnet which is advantageous when the inner diameter of the housing is larger than the diameter of the shaft to be sealed. Large-diameter annular magnets 3G, 3E and small-diameter annular magnets 3D, 3F are arranged in the axial direction, and the gaps between the annular magnets are filled with non-magnetic material 18 to form a stock. The annular magnets 3J3D, 3E, and 3F are fixed by 18a and 18b.

In FIG. 8, in order to fix the annular magnets, protrusions 3cJe and 3g are provided on the inner surfaces of the annular magnets 3C, 3E and 3G with large diameters, and protrusions 3cJe and 3g are provided on the inner surfaces of annular magnets 3D and 3G with small diameters, respectively, in order to fix the annular magnets.
Similarly, protrusions 3d and 3f are provided on the outer surfaces of F and old 1, respectively.
and 3h. Each magnet is firmly fixed by each protrusion when the gap is filled with non-magnetic material 18.

Although the magnetic fluid seal of the present invention described above can be widely applied, typical examples will be described below.

Figure 9 is a sectional view, including a partially broken part, of a communication cable connection closure using an embodiment of the magnetic fluid seal of the present invention. FIG. 1O is a sectional view taken along line 8-A' in FIG. 9. In these figures, 19 is a communication cable, the jacket of which is usually made of plastic material. 20 is a core wire connection part of a communication cable, 21 is a plastic connection case divided into upper and lower halves, 21a is a flange of the connection case, and 21b is a gasket 2 for sealing the flange surface.
The groove 21c is a hole through which the connection case fastening screw 23 is passed.

In this way, in this embodiment, the gap between the cable jacket and the connection case is sealed using a magnetic fluid seal. In conventional closures, this gap is often filled with an adhesive sealant for sealing. However, if the surface of the cable or the connection case becomes dirty with hand oil, the adhesive strength of the adhesive interface between the cable jacket and the sealant, or the adhesive interface between the connection case and the sealant, may decrease, making it difficult to assemble the closure. required careful attention.

On the other hand, when using a magnetic fluid seal, a good seal can be ensured regardless of dirt on the cable surface or inside of the connection case, or minute irregularities on these surfaces, so special care is not required during assembly. There are advantages to not doing so. Therefore, the magnetic fluid seal of the present invention is ideal for communication cable connection closures that must be assembled at sites where a clean work environment is not expected, such as inside manpoles or on utility poles, and that also require high reliability. It is.

The assembly of the closure of the present invention will be briefly explained.

First, on the cable 19, ring III: 1 stone 38, 313
Connect the core wires 20 through the . Next, the magnetic fluid 5 is applied to the inner and outer surfaces of each of the annular magnets 3A and 3B, and the magnets are attached to the end face of the connection case 21. Next, the connection case 21
The gasket 22 is attached to the flange portion of the flange, and the screws are tightened to complete the closure assembly.

The process of attaching magnetic fluid to an annular magnet is not well known, but when the magnetic fluid is dropped onto the inner and outer circumferential surfaces of the annular magnet, the magnetic fluid is attracted by the strong magnetic fields on the inner and outer circumferential surfaces of the annular magnet. , goes around the inner and outer surfaces of the annular magnet and is evenly attached to the entire circumference of the annular magnet. Therefore, the work is extremely easy.

Example 2 FIG. 11 shows a pipe connection using the magnetic fluid seal of the present invention. 24 is a tube made of non-magnetic material such as plastic, 25 is a housing made of plastic, stainless steel or other non-magnetic material, and 26 is a hole having a hole through which the tube 24 passes. Ring magnet 3A.

3B is fixed by the housing 25 and screws 26. A magnetic fluid 5 is provided in the gap between the tube 24 and the annular magnets 3A, 311 and the gap between the housing 25 and the annular magnets 3A, 3[1].
is filled and tube 24 is sealed. This embodiment is effective for sealing a tube constituting a fluid flow path or a tube whose interior is kept in a vacuum state, such as on the vacuum side.

Embodiment 3 FIG. 12 is a cross-sectional view of a fluid valve using a magnetic fluid seal according to the present invention. In the same figure, 27 is a housing made of non-magnetic material such as plastic, 27a,
27a' is a connection port. Reference numeral 28 designates an arcuate spring (hereinafter referred to as a retaining ring) for fixing the annular magnet, and is fitted into a groove 2'7b on the inner surface of the housing 27. 29
is a movable shaft made of non-magnetic material such as Plus Deck, 29
a is a knob, and 30 is a lid. Each ring magnet 3A,
3B and two sets of magnetic fluid seals 3J including magnetic fluid 5
and 3K seal the shaft 5 and the housing 27, and in the state shown by the solid line, the fluid path from the connection port 27a to 27a' is blocked. When the movable shaft 2g is pulled up, it becomes the state shown by the broken line, and the fluid flows through the annular magnets 38 and 3Ll on the seal 3.
It flows through the central hole. However, the seal 3J is 1lI
Since the 129 is sealed, no fluid can escape from the lid 30.

The valve of the present invention has the advantage that since only the frictional force of the movable shaft 29 acts, it can be opened and closed with a small driving force, and the valve can be easily constructed without boiling in the flow direction when shutting off and without leaking to the outside. . This feature is the same for the valves of the following embodiments.

Embodiment 4 FIG. 13 is a cross-sectional view of a fluid valve using a magnetic fluid seal according to the present invention. In this embodiment, the annular magnets 3A, 3
A seal 3L containing B is fixed to a groove 31a provided in the movable shaft 31 using a retaining ring 32, and is movable together with the movable shaft 31. At the position indicated by the solid line with the movable axis lowered, the connection port 37
The fluid path from a to 37a' is blocked. When the movable shaft 31 is pulled up, the annular magnet 3A and
The seal 3L including 3B moves above the connection port 27a,
? It becomes a state of communication.

Embodiment 5 FIG. 14 is a sectional view of an embodiment in which the magnetic fluid seal of the present invention is applied to a plug used at a fluid inlet or outlet in a fluid container or piping.

In the figure, 33 is a housing made of non-magnetic metal or plastic deck, and 34 is a lid. Ring magnet 3A,
3B is fixed to a groove 311b provided in ITq 1134a on the back surface of the lid 34 using a retaining ring 32).

It is possible to seal between the magnetic fluid 5, the housing 33, the annular magnets 3A and 38, and the shaft 34a and the annular magnets 3A and 3B, thereby preventing the fluid from flowing out of the housing or the outside air from flowing into the housing.

Embodiment 6 FIG. 15 is a sectional view of an embodiment in which the magnetic fluid seal of the present invention is applied to a plug used for a fluid inlet or outlet. In the figure, numeral 35 is a housing made of non-magnetic metal or plastic, and numerals 36 and 36B are disc-shaped magnets, which are magnetized in the qlll1) direction and are arranged with the same magnetic pole faces facing each other. 37 is a lid.

The plug on the tree layer side uses a disc-shaped magnet, so
This eliminates the need for hole sealing when using an annular magnet, and has the advantage of simplifying the structure of the lid.

Furthermore, according to magnetic field analysis using the finite element method, the magnetic field strength distribution on the outer circumferential surface of the disc-shaped magnet is similar to that when using an annular magnet, and it is possible to obtain a high withstand voltage similarly to when using an annular magnet. I can do it.

Married Woman II〇 FIG. 16 is a sectional view of a closure plug using a magnetic fluid seal constructed by adhering a disc-shaped magnet 36A to the back surface of a lid 38. 39 is an adhesive layer. Compared to the plug of Example 6, which required insertion of two disc-shaped magnets, three disc-shaped magnets were inserted.
Assembly is easy because only one 6B is needed to be inserted.

In the above description of the present invention, an example in which two annular magnets or two disc-shaped magnets are arranged has been mainly described. However, the number of annular or disk-shaped magnets to be arranged can be determined according to the required pressure resistance of the magnetic fluid seal, and the number of arranged magnets can be set to 2.
It is not limited to individuals.

The sealing of the present invention is performed by a magnetic fluid held in a gap between magnets arranged with magnetic pole faces of the same polarity facing each other. However, when the number of arranged magnets is increased, the applied pressure decreases. The pressure is divided, and the pressure in each gap becomes smaller. Therefore, the breakdown voltage is proportional to the number of arrays. In addition,
As a result of magnetic field analysis of a structure in which three annular magnets are arranged, the magnetic field strength in the gap is almost the same as in the case where two annular magnets are arranged, and although it decreases slightly, it is negligible. Therefore, even if the number of arrays is increased, the withstand pressure of each gap does not decrease.

(Effects of the Invention) As explained above, the magnetic fluid seal of the present invention includes a sealed shaft made of a non-magnetic material, an annular or disc-shaped magnet arranged with magnetic pole surfaces of the same polarity facing each other, and a non-magnetic material It consists of a housing using magnetic fluid, and the gap between the inside and outside of the magnet is sealed with magnetic fluid. Therefore, there are the following advantages.

(a) It can be applied to a wide range of objects using non-magnetic materials that could not previously be applied, such as communication cables and pipes made of plastic.

(b) Plastic molded products can be used for the shaft to be sealed and the housing, and a metal pole piece for configuring the magnetic circuit is not required, so it is inexpensive and lightweight.

(C) Even if an annular magnet with a small cross section is applied, a high seal pressure equivalent to a conventional magnetic fluid seal can be obtained.

(d) Fluid on/off valves and fluid injection/outlet plugs using magnetic fluid seals can be easily configured.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing the basic structure of the magnetic fluid seal of the present invention, Fig. 2 is a system diagram of the pressure-resistant measurement system, Fig. 3 is a magnetic field strength distribution diagram, Fig. 4 is a magnetic flux distribution diagram, and Fig. 5 is a sectional view of an annular magnet used when the distance between the diameter of the shaft to be sealed and the inner diameter of the housing is large; FIGS. 6, 7, and 8 are sectional views of integrally constructed annular magnets, respectively; 9 is a cross-sectional view of a communication cable connection closure using the magnetic fluid seal of the present invention, FIG. 10 is a cross-sectional view taken along line A-A' in FIG. 9, and FIG.
12 and 13 are sectional views of valves using the magnetic fluid seal of the present invention, respectively. Fig. 16 is a cross-sectional view of a plug using the magnetic fluid seal of the present invention, Fig. 17 is a cross-sectional view of a conventional magnetic fluid seal, and Fig. 18 is a cross-sectional view of a rotating shaft using a non-magnetic material. 1 is a cross-sectional view of a conventional magnetic fluid seal. l... Rotating shaft, 2... Housing, 3A, 3B... Annular magnet, 4... Pole piece, 5... Magnetic fluid, 6... Gasket, 7... Non-magnetic material The shaft to be sealed (rotating shaft) used, 8... Pole piece, 9... Housing, 10... Test model, 11... Container, 12... Water, 13... Gas cylinder, 14... ...Pressure reducing valve, 15...Valve, 16...Gas pressure measuring device, 17...Piping, 18...Non-magnetic material, 19...Direct cable, 20...Core connection Part, 21... Gluing case, 22... Gasket, 23... Eagle, 24... Pipe made of non-magnetic material, 25... Housing, 26... Screw, 27...・Housing, 28... Retaining ring, 29... Movable shaft, 30... Lid, 31... Movable shaft, 32... Retaining ring, 33... Housing, 34... Lid, 35 ...housing, 368, 3611...disk-shaped magnet, 37...lid, 38...lid, 39...adhesive. Patent applicant Nippon Telegraph and Telephone Corporation

Claims (1)

[Claims] 1) A cylindrical shaft to be sealed made of a non-magnetic material, and a plurality of annular magnets arranged around the shaft to be sealed at a slight distance with magnetic pole faces of the same polarity facing each other. , a cylindrical housing made of a non-magnetic material and housing the plurality of annular magnets is arranged concentrically, and a gap between the inner surface of the annular magnet and the sealed shaft, and a gap between the outer surface of the annular magnet and the housing. A magnetic fluid seal characterized in that a magnetic fluid is filled in a gap between the two. 2) A plurality of disc-shaped magnets are arranged concentrically in a cylindrical housing made of a non-magnetic material, with magnetic pole faces of the same polarity facing each other and arranged at a very small distance. A magnetic fluid seal characterized in that a gap between an outer surface of a magnet and the housing is filled with magnetic fluid.