JPH10196799A - Sealing device using magnetic fluid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the movement of scattered magnetic fluids so as to prevent a reduction in magnetic fluids in a stage part by providing an annular projecting part in a first magnetic pole part, the annular projecting part being positioned adjacently to the stage part of a second magnetic pole part for suppressing the movement of magnetic fluids in a width direction, in a sealing device using the magnetic fluids. SOLUTION: A sealing device 1 provided in a rotary shaft 2 for transmitting rotational power obtains its sealing capability by a magnetic fluid ML provided in a magnetic circuit MC composed of a magnet 6 provided inside the cylindrical part 3a of a bearing part 3. This magnet 6 has, in both sides of an axial direction, magnetic pole members 7a and 7b as first magnetic pole parts to be contacted with the magnet 6 and become magnetic poles, and in the rotary shaft 2, the outer peripheral surfaces of annular projecting parts 8a, 8b,..., projectingly formed in positions from its peripheral wall surface 2a and facing the magnetic pole members 7a and 7b are made stage parts 9a and 9b. Thus, by preventing the movement of magnetic fluids scattered between the magnetic pole parts opposite the stage parts 9a and 9b and a reduction in the magnetic fluid, reductions in sealing performance and life are suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealing device using a magnetic fluid, and more particularly to a technique for preventing a magnetic fluid from moving in a magnetic fluid sealing portion.

[0002]

2. Description of the Related Art Conventionally, particles of a magnetic substance are suspended in a fluid such as a surfactant, and the particles are magnetically attracted by a magnetic force of an external magnetic field such as a permanent magnet or an electromagnet, thereby causing the fluid to be absorbed. There are various types of sealing devices that make use of the properties of a magnetic fluid that can maintain position.

FIG. 7A is a diagram illustrating a cross-sectional configuration of a conventional sealing device 100 using such a magnetic fluid, and FIG. 7B is a diagram illustrating the strength of the magnetic field of a D101 portion. FIG. 8 is an enlarged view of a portion D101 in FIG. 7A. The sealing device 100 will be described with reference to FIGS.

[0004] The sealing device 100 includes a rotating shaft 10 extending between two regions of a high pressure side H 'and a low pressure side L' having a pressure difference.
1 and the bearing portion 103 of the rotating shaft 101. The bearing portion 103 includes a cylindrical portion 103a that holds and seals the rotary shaft 101, and one end of the cylindrical portion 103a.
The container 102 is provided with a flange portion 103b which is attached to the opening end portion 102a of the container 102 which is in a vacuum state (low pressure side L ') by a bolt.

The cylindrical portion 103a of the bearing portion 103 and the rotating shaft 101 are dynamically held against relative rotational motion by bearings B1 and B2.

[0006] With respect to the sealing performance, the magnetic fluid M interposed in a magnetic circuit MC 'formed by an annular magnet 104 provided inside the cylindrical portion 103a of the bearing portion 103.
L '.

The magnet 104 is provided with different poles (shown as N and S) in the axial direction, and the magnets 104 are provided on both sides in the axial direction.
(In the following description, the magnetic pole member 105 is used as a representative). A plurality of circumferentially continuous concave grooves 107a, 1 are formed in a portion of the rotating shaft 101 facing the magnetic pole member 105.
, And the inner peripheral surface 10 of the magnetic pole member 105 is formed.
Projecting portions 108a, 108b,...
Are generated in such a manner that the magnetic flux concentrates in the gap with the top surface of the magnetic fluid ML ′ (that is, the magnetic flux density is increased at the top surface of the ridges 108a, 108b,...). The magnetic fluid ML ′ is held in these gaps to form a magnetic fluid seal.

The formed magnetic fluid seal portion has a plurality of chambers 109a, 109 between the low pressure side L 'and the high pressure side H'.
By forming b,... and sequentially changing the pressure of each chamber within the pressure resistance range of the magnetic fluid seal portion, effective sealing performance can be exhibited even when there is a pressure difference on both sides of the sealed area. It has become.

Note that 110a and 110b are bearings B
1 and B2 between the magnet 104 and the magnetic pole members 105 and 10
6, a spacer ring 111 for determining the axial position; 111, a fixed ring member for sealing and fixing each component provided inside the cylindrical portion 103a; 112, 113, an inner peripheral surface of the cylindrical portion 103a and the magnetic pole member 105; An O-ring for maintaining the sealing property with respect to the outer peripheral surface side of 106.

FIG. 7 (b) shows the D101 of the sealing device 100.
FIG. 4 is a diagram illustrating the strength of a magnetic field of a part. This diagram schematically shows the distribution of the magnetic flux in the axial gap G ′ between the magnetic pole member 105 and the rotating shaft 101 shown in FIG. 8 as the strength of the magnetic field.

That is, the magnetic flux of the magnetic circuit MC 'formed by the magnet 104 is generated by the magnetic ridges 108a.
(All of the multiple ridges are applicable, but are listed as representatives.)
Since the magnetic flux is concentrated in the region, the magnetic flux is divided into a region having a large magnetic flux density and a region having a small magnetic flux density. Accordingly, the magnetic field strength 120a on the top surface of the ridge 108a is reduced by the concave grooves 107a on both sides thereof.
There is a difference Δf from the magnetic field strengths 121a and 121b at 107b.

The strength of the holding force for holding the magnetic fluid ML 'on the ridge 108a is the difference Δf of the strength of the magnetic field.
And the strength of the holding force is proportional to the pressure resistance capability of each magnetic fluid seal portion.

[0013]

By the way, when the sealing device 100 functions as a vacuum seal,
When the pressures on the low pressure side L ′ and the high pressure side H ′ are about 0 and about 1.0 kgf / cm ² , respectively,
08a... Are designed to be 1.0 kgf / cm ² or more. Then, in an actual use state, a pressure difference between the low pressure side L 'and the high pressure side H' is generated by gradually lowering the pressure on the low pressure side L 'with a vacuum pump or the like. When the pressure on the low-pressure side L ′ is reduced by a vacuum pump or the like, a pressure difference starts to be generated between the low-pressure side L ′ and the chamber 109a, and the pressure difference is reduced by the magnetic fluid ML ′ existing in the ridge 108a. When the pressure difference exceeds the pressure resistance, a break (pressure equilibrium phenomenon) occurs, and the break causes the pressure on the low pressure side L 'to be gradually propagated to the chamber on the high pressure side H'. However, the air flow moves from the high pressure side H 'chamber to the low pressure side L'.

When the chamber 109a adjacent to the low-pressure side L 'breaks as shown in FIG. 8, the magnetic fluid ML' held by the magnetic force on the stage between the ridge 108a and the inner peripheral surface 105a is removed. Although it is a small amount, it scatters and the inner peripheral surface 1
The magnetic fluid ML'1 adheres to the low-pressure side L 'of the magnetic fluid ML'05 on the low-pressure side L' of the concave groove 107a.
It adheres as 2.

Since this break occurs continuously until the pressure difference between the low-pressure side L 'and the high-pressure side H' is balanced, it frequently occurs on the low-pressure side L ', and every time a vacuum is generated in the vessel 102. Even if the amount of magnetic fluid ML 'scattered by one break is extremely small, the magnetic fluid ML' is gradually reduced by operating the apparatus many times, and it is sealed. This leads to reduced performance and shorter life.

This is because the magnetic fluid ML 'once moved from the stage does not keep its existing position due to the magnetic force, does not return to the original stage, and gradually starts to move to the high pressure side H'.
This is because the magnetic fluid ML ′ moves from to the low pressure side L ′.

A break may occur when vibration is applied, for example, when the rotating shaft 101 is rotating at a high speed, and the movement of the magnetic fluid ML 'is also caused by such a break. I do.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art. It is an object of the present invention to prevent the magnetic fluid scattered by a break from moving, and to use the moved magnetic fluid for the original stage. Another object of the present invention is to provide a sealing device using a magnetic fluid that can prevent a decrease in the magnetic fluid in the stage by returning the magnetic fluid to the stage.

[0019]

In order to achieve the above object, according to the present invention, there is provided an annular gap between a shaft hole of a housing member and a shaft inserted into the shaft hole, A second magnetic pole portion having a first magnetic pole portion disposed on one peripheral wall surface side of the annular gap and a stage portion on the other peripheral wall surface side of the annular gap opposed to the first magnetic pole portion on which magnetic flux is concentrated; A magnetic pole generating means for forming a magnetic field passing between the first and second magnetic poles, and a stage of the second magnetic pole facing the first magnetic pole; And a magnetic fluid held by the magnetic field, wherein the first magnetic pole portion is positioned adjacent to the stage portion of the second magnetic pole portion in the axial direction of the magnetic fluid. It is characterized by having an annular convex portion for suppressing movement.

Accordingly, even when the magnetic fluid scatters from between the magnetic pole portions opposing the stage at the start of generation of a differential pressure on both sides of the sealed area, the movement of the magnetic fluid is prevented by the annular convex portion.

Further, the first magnetic pole portion has a peripheral wall surface parallel to the axial direction facing the stage portion of the second magnetic pole portion, and the annular convex portion is provided to protrude from the peripheral wall surface. Are also suitable.

According to this, the magnetic fluid which has moved to the annular convex portion by the break moves back to the position opposite to the original stage portion by the magnetic force on the peripheral wall parallel to the axial direction.

Also, it is preferable that the annular convex portion of the first magnetic pole portion is located on a lower pressure side than the stage portion of the second magnetic pole portion.

As a result, the scattering of the magnetic fluid due to the break occurs mainly on the low pressure side, but the movement of the magnetic fluid to the low pressure side is prevented.

The annular projection of the first magnetic pole portion is
It is also preferable that the magnetic pole part is provided for each of the plurality of stage parts.

According to this, the magnetic fluid present in each stage is prevented from moving to another stage due to a break, and the amount of the magnetic fluid in each stage is less likely to be non-uniform.

It is also preferable that the annular projection of the first magnetic pole is made of a non-magnetic material.

Since it is a non-magnetic material, the magnetic fluid that has moved is not magnetically attracted to the annular projection, and does not prevent the magnetic fluid from returning to the original stage.

Further, the annular convex portion may have an inclined side end surface.

According to this, when the side end surface is inclined toward the high pressure side, the magnetic fluid located on the inclined surface of the annular convex portion rotates and flows together with the magnetic fluid rotating and flowing on the stage surface. Thus, when the inclined surface moves toward the high pressure side due to centrifugal force, and when the side end surface moves toward the low pressure side, the trapped area of the scattered magnetic fluid can be increased.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) The present invention will be described below based on a first embodiment shown in the drawings. FIG. 1 is an explanatory view of a sectional configuration of a sealing device 1 using a magnetic fluid.

The sealing device 1 is provided as a housing member, for example, at a rotary motion introducing portion of a rotary shaft 2 for transmitting rotary power from the outside to the inside of a vacuum chamber VC for making the inside a vacuum state.

During the operation of the vacuum chamber VC, the inside thereof is evacuated by a vacuum pump or the like, so that the inside becomes the low pressure side L, and a pressure difference is generated between the inside and the high pressure side H which is the atmospheric pressure side.

Therefore, in this embodiment, the sealing device 1 introduces rotational power into the vacuum chamber VC by the rotating shaft 2 while maintaining the degree of vacuum on the low pressure side L, between the two regions having the pressure difference. In addition, an annular gap 4 is provided between the rotating shaft 2 and the bearing 3 through which the rotating shaft 2 is inserted.

The bearing portion 3 includes a cylindrical portion 3a for holding and sealing the rotary shaft 2 and a shaft of a vacuum chamber VC having an internal space in a vacuum state (low pressure side L) at one end of the cylindrical portion 3a. It has a flange 3b attached to the hole VCa.

In the sealing device 1, the bearing 3 and the rotating shaft 2
With the bearings 5a and 5b, dynamic holding against relative rotational movement is performed. And regarding the sealing,
This is performed by a magnetic fluid ML interposed in a magnetic circuit MC formed by magnets 6 as magnetic force generating means provided inside the cylindrical portion 3a of the bearing portion 3.

The magnet 6 is provided with different poles in the axial direction. Magnetic pole members 7a and 7b are provided on both sides in the axial direction as first magnetic pole portions which contact the magnet 6 and become magnetic poles. A plurality of circumferentially extending annular ridges 8a, 8b,... Protruding from the peripheral wall surface 2a at respective portions facing the magnetic pole members 7a, 7b are formed on the rotation shaft 2. , 8
are set as stage portions 9a, 9b,...

The bearings 10a and 10b are bearings 5a and 5b.
b, a spacer ring for determining the axial positions of the magnet 6 and the magnetic pole members 7a, 7b between the fixed ring member 11 and a fixed ring member 11 for sealing and fixing each constituent member provided inside the cylindrical portion 3a;
Reference numerals 2 and 13 denote inner peripheral surfaces of the cylindrical portion 3a and magnetic pole members 7a and 7b.
O-ring that maintains the sealing performance with the outer peripheral surface side of the O-ring.

FIG. 2 is an enlarged view of a portion D1 in FIG. 1 for explaining a characteristic configuration of the present embodiment. In the sealing device 1 as well, at the start of use of the vacuum chamber VC, a pressure difference is generated between the low-pressure side L and the high-pressure side H, and each stage 9a, 9b,. Until the pressure balance becomes stable, or in a state where the evacuation of the vacuum chamber VC is completed and the rotating shaft is driven at a high speed, etc., the magnetic fluid ML by the break
Scattering occurs.

The scattering of the magnetic fluid ML can be prevented by providing the annular convex portion 15 at the inner peripheral end of the low pressure side L of the magnetic pole member 7a. Without moving to L, as shown in FIG. 2, the magnetic fluid ML1 stays between the annular convex portion 15 and the stage portion 9a.

Also, since the inner peripheral wall surface 7c of the magnetic pole member 7a is parallel to the axial direction so as to face the respective stage portions 9a, 9b,... In parallel, the magnetic fluid ML1 is held by the stage portion 9a. It is integrated with the magnetic fluid ML, and gradually moves to the stage 9a side where the magnetic flux density is large. In this case, by setting the gap interval G1 of the stage portion 9a smaller than the gap interval G2 between the inner peripheral end portion 15b of the annular convex portion 15 and the outer peripheral surface of the rotary shaft 2, the magnetic flux density is G1 portion> G2 portion. Therefore, the effect of moving to the stage 9a side can be expected.

(Embodiment 2) FIG. 3 is a diagram for explaining a second embodiment. In this embodiment, the annular projection 15 of the first embodiment is replaced with a non-magnetic annular member 2.
1. In other configurations, the same components as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

As the material of the annular member, a non-magnetic metal or resin material can be used, and the joining with the inner peripheral surface of the magnetic pole member 7a is not limited. Method), bonding, screw fastening, and the like.

In this embodiment, since the annular member 21 is a non-magnetic material, the magnetic flux density does not increase in the vicinity of the annular member 21 and the magnetic fluid ML1 whose axial movement is suppressed by the annular member 21 is suppressed. Move more smoothly to the stage 9a side where the magnetic flux density is large.

(Embodiment 3) In the third embodiment,
As shown in FIG. 4, each stage 9a, 9b,.
Are preferably provided with annular members 22a, 22b,. When positioning the annular members, a spacer is provided between the annular members, or a shallow groove is formed in the inner peripheral surface of the magnetic pole member 7a, and each annular member is fitted into this groove. Is also good.

At the start of use of the vacuum chamber VC,
Until the pressure balance stabilizes, the magnetic fluid scattered by the break generated at each stage is trapped and moved to the original stage at each stage, so that the magnetic fluid retained at the stage is The amount is not likely to be uneven.

(Embodiment 4) In the fourth embodiment,
As shown in FIG. 5, each of the annular members 31, 32a,.
The side end surface of the high pressure side H is inclined (the inclined surface 3 of the annular member 31).
As shown in 1a, it is inclined in the high-pressure side H direction toward the radial direction. ).

With the rotation of the rotating shaft 2, each stage 9
Using the fact that the magnetic fluid ML held at a, 9b,... rotates and flows little by little, the magnetic fluid ML1 attached to the inclined surface is held by the magnetic fluid ML held at the stage.
The centrifugal force (arrow A1) generated by this rotational flow assists in moving the magnetic fluid ML1 to the high pressure side H (arrow A2).

(Embodiment 5) In the fifth embodiment,
As shown in FIG. 6, each of the annular members 41, 42a, 42b
The high-pressure side H has an inclined surface facing the low-pressure side L (inclined in the high-pressure side H direction toward the axis), contrary to the fourth embodiment.

With this inclined surface, the trapping area of the magnetic fluid ML scattered on the low pressure side L is increased with respect to the burst generated when the pressure on the low pressure side L is evacuated to generate a pressure difference with the high pressure side H. be able to. After the burst, the magnetic fluid captured on the inclined surfaces of the annular members is magnetically attracted to the strong local stage and pulled back.

[0051]

According to the sealing device using the magnetic fluid of the present invention described in the above embodiment, even if the magnetic fluid scatters from between the magnetic pole portions facing the stage portion, the magnetic fluid is formed by the annular convex portion. Of the first magnetic pole portion to move to the original position, thereby preventing a decrease in the magnetic fluid, thereby suppressing a decrease in sealing performance and life.

Since the annular convex portion of the first magnetic pole portion is located on a lower pressure side than the stage portion of the second magnetic pole portion, the movement of the magnetic fluid to the lower pressure side is prevented.

Since the annular projection is provided for each of the plurality of stages, the amount of the magnetic fluid in each stage is less likely to be non-uniform.

Since the annular convex portion is a non-magnetic material, the magnetic fluid that has moved is not magnetically attracted to the annular convex portion, and the magnetic fluid easily returns to the original stage.

In the case where the side end surface of the annular convex portion has an inclined surface, when the side end surface is inclined toward the high pressure side,
The magnetic fluid located on the inclined surface of the annular convex portion rotates and flows together with the magnetic fluid rotating and flowing on the stage portion, so that the inclined surface moves to the high pressure side due to centrifugal force. In contrast, when the side end face is directed to the low pressure side, the trapped area of the scattered magnetic fluid can be enlarged, and the decrease of the magnetic fluid can be prevented.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a sectional configuration of a sealing device to which the present invention is applied.

FIG. 2 is an explanatory cross-sectional configuration diagram of the vicinity of a stage according to the first embodiment;

FIG. 3 is an explanatory cross-sectional configuration diagram near a stage unit according to a second embodiment;

FIG. 4 is a cross-sectional configuration explanatory view near a stage unit according to a third embodiment.

FIG. 5 is an explanatory view of a cross-sectional configuration near a stage section according to a fourth embodiment.

FIG. 6 is a cross-sectional configuration explanatory view near a stage section according to a fifth embodiment.

FIG. 7 is a diagram illustrating a cross-sectional configuration of a conventional sealing device and a diagram illustrating the strength of a magnetic field.

FIG. 8 is an enlarged view of a portion D101 in FIG. 7;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sealing device 2 Rotation shaft 2a Peripheral wall surface 3 Bearing part 5a, 5b Bearing 6 Magnet (magnetic force generation means) 7a, 7b Magnetic pole member 8a, 8b Protrusion 9a, 9b Stage part 10a, 10b Spacer ring 11 Fixed ring member 12, 13 O-ring 15,21,22a, 31,32a Annular convex part 15a Wall surface G1, G2 Gap interval H High pressure side L Low pressure side MC Magnetic circuit ML, ML1 Magnetic fluid VC Vacuum chamber

Claims (6)

[Claims] 1. A first magnetic pole portion disposed in an annular gap between a shaft hole of a housing member and a shaft inserted into the shaft hole, and disposed on one peripheral wall surface side of the annular gap. A second magnetic pole portion having a stage on which the magnetic flux concentrates on the other peripheral wall surface side of the annular gap opposed to the first magnetic pole portion, and passing between the first and second magnetic pole portions A magnetic force generated by a magnetic fluid generated between the first magnetic pole portion and a stage portion of a second magnetic pole portion facing the first magnetic pole portion. In the apparatus, the first magnetic pole portion includes a ring-shaped convex portion at a position adjacent to the stage portion of the second magnetic pole portion to suppress the axial movement of the magnetic fluid. Sealing device. 2. The first magnetic pole part includes a peripheral wall parallel to an axial direction facing a stage part of the second magnetic pole part,
The sealing device according to claim 1, wherein the annular protrusion is provided to protrude from the peripheral wall surface. 3. The magnetic fluid according to claim 1, wherein the annular convex portion of the first magnetic pole portion is located on a lower pressure side than the stage portion of the second magnetic pole portion. Sealing device. 4. The magnetic fluid according to claim 3, wherein the annular convex portion of the first magnetic pole portion is provided for each of a plurality of stage portions provided on the second magnetic pole portion. Sealing device using. 5. The sealing device according to claim 1, wherein the annular projection of the first magnetic pole portion is a non-magnetic material. 6. The sealing device using a magnetic fluid according to claim 1, wherein the annular convex portion has an inclined side end surface.