JP3256449B2 - Sealing device using magnetic fluid - Google Patents

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 having a plurality of chambers for gradually eliminating a pressure difference between both sides separated by a sealing device, and to effectively reduce the pressure state of these chambers. The present invention relates to a technology capable of improving the pressure resistance characteristics and sealing performance of a magnetic fluid seal portion by using the magnetic fluid seal portion.

[0002]

2. Description of the Related Art Conventionally, particles of a magnetic substance suspended in a fluid such as a surfactant are magnetically attracted by a magnetic force of an external magnetic field such as a permanent magnet or an electromagnet, and have a characteristic capable of holding the position. There are various sealing devices using a magnetic fluid provided.

FIG. 4A is a diagram illustrating a cross-sectional configuration of a conventional sealing device 100 using such a magnetic fluid. The sealing device 100 includes a rotating shaft 1 extending between two regions of a high pressure side H ′ and a low pressure side L ′ having a pressure difference.
01 and the bearing 103 of the rotating shaft 101.

[0004] The bearing portion 103 has a cylindrical portion 103a for holding and sealing the rotary shaft 101, and an open end of the container 102 having an internal space in a vacuum state (low pressure side L ') at one end of the cylindrical portion 103a. A flange portion 103b is provided on the portion 102a with 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.
Are provided. Then, a plurality of circumferentially continuous concave grooves 107 are formed in a portion of the rotating shaft 101 facing the magnetic pole members 105 and 106.
, 107b,...
6, convex ridges 108a, 108b,...
.. are generated such that the magnetic flux concentrates in the gaps with the top surfaces of the magnetic fluids (that is, the magnetic flux density increases on the top surfaces of the ridges 108a, 108b,...)
L ′ is held to form a magnetic fluid seal portion.

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. 4B is a view for explaining the strength of the magnetic field of the portion D1 in FIG. 4 of the sealing device 100. In this figure, the distribution of the magnetic flux in the gap in the axial direction between the magnetic pole member 105 and the rotating shaft 101 is schematically shown below 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. Then a break (pressure equilibrium phenomenon) occurs,
With the break, the pressure on the low pressure side L 'is 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'.

Therefore, in this prior art, the pressure in each chamber is determined by the pressure resistance C (C ≒ (ab) m of the ridge.
(Where m is a constant representing the characteristics of the magnetic fluid), the pressure distribution is made, and assuming that the pressure on the low pressure side L ′ (expressed as an absolute value) is 0 kgf / cm ² , the chamber 1
09a, 109b,..., Respectively, C, 2C, 3
C gradually increases the pressure to isolate the low pressure side L 'and the high pressure side H'.

Here, the pressure resistance of the ridge is 0.2 kgf /
cm ² , as shown at the bottom of FIG.
... from 09a to 0.2, 0.4 ...
1.0 kgf / cm ^{2 which} is almost equal to the pressure on the high pressure side H ′.
On the high-pressure side H 'than the chamber 109e, the pressure is 1.0 kgf / cm ² in all the chambers.

Accordingly, in this state, the pressure in each chamber is increasing in order from the low pressure side L 'with a pressure difference close to the limit of the pressure resistance, and the total pressure difference held in each chamber is 1 kgf / cm ^2.
There is no pressure difference between the chambers on the high pressure side H ′ compared to the chamber (109e in FIG. 5), and the pressure resistance does not affect the actual sealing performance.

However, the members constituting the sealing device 100 include, for example, eccentricity of the shaft 101 with respect to the bearing 103,
Subtle eccentricity occurs in the magnetic fluid holding portion due to variations in dimensional accuracy during processing of the magnetic pole members 105 and 106 and problems such as the assembly accuracy of the sealing device 100. Therefore, each ridge 108a holding the magnetic fluid ML '
The gap G 'between the magnetic pole member 105 and the inner peripheral surface 105a is not constant in the circumferential direction, and the gap G' changes when the shaft 101 rotates. And the magnetic fluid M
Similarly, the strength of the field holding L 'also changes, and the holding force for holding the magnetic fluid ML' changes, so that the pressure resistance of each ridge 108a also changes.

Therefore, the pressure resistance of each of the ridges 108a... Varies depending on the operating state of the sealing device 100. Therefore, when the sealing is performed near the limit of the pressure resistance, the above-mentioned fluctuations cause the respective chambers to change. Pressure balance is lost, and a break occurs.

The pressure balance is maintained by the break, and the brake is instantaneously recovered from the break state. However, since the protrusion 108a adjacent to the low pressure side L 'is used up to the vicinity of the limit of the pressure resistance, the air that has been broken is used. Flows into the low pressure side L ′ and changes the pressure on the low pressure side L ′.

In particular, the container 102 is a vacuum chamber,
In a use situation in which the shaft 101 is not rotated during the pressure drop and the shaft is rotated after the pressure drop ends, the degree of vacuum may be deteriorated by rotating the shaft 101,
The handling of materials that need to maintain a high degree of vacuum in the vacuum chamber can have adverse effects.

The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to improve the sealing performance of a sealing device using a magnetic fluid. It is an object of the present invention to provide a sealing device using a magnetic fluid capable of suppressing the influence of a break caused by a change in the holding force of the magnetic fluid due to the eccentricity and maintaining the sealing performance.

[0022]

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, An annular first magnetic pole portion disposed on one peripheral wall side of the annular gap, and a plurality of axially aligned plural magnetic poles arranged on the other peripheral wall side of the annular gap opposed to the first magnetic pole portion. A second magnetic pole portion having an annular groove, and a ridge between the annular grooves; magnetic force generating means for forming a magnetic field passing between the first and second magnetic pole portions; A magnetic fluid comprising a magnetic fluid between the magnetic pole portion and a protruding ridge of a second magnetic pole portion facing the magnetic pole portion, the magnetic fluid being held by the magnetic field to make the plurality of annular grooves a plurality of sealed regions. The first and second magnetic pole parts are relatively movable in the axial direction, and the second magnetic pole is A plurality of annular grooves of, characterized in that it is formed by extending the area in the moving direction of the first magnetic pole portion.

According to this configuration, the first and second magnetic pole portions move relative to each other in the axial direction, so that the annular groove that has been opened before the movement and adjacent to the sealing region is newly sealed by the magnetic fluid. It is possible to use as a region, and it is possible to form a plurality of sealed regions that are sealed with substantially equal pressure according to the moving distance.

Further, the first magnetic pole portion is disposed on one of the peripheral wall surfaces so as to be movable in the axial direction, and biases the first magnetic pole portion to be at a predetermined position in the axial direction. It is also preferable that a biasing means is provided, and the first magnetic pole portion moves in the axial direction by a pressure difference generated between the inside and the outside of the housing member.

According to this, the pressure difference generated between the inside and the outside of the housing member separated by the sealing device causes
The first magnetic pole portion moves along the axial direction from the high voltage side to the low voltage side. At that time, the annular groove that was opened before moving adjacent to the sealing area can be used as a plurality of sealing areas that hold the pressure on the low pressure side, and the pressure resistance on the low pressure side of the sealing device can be used. Improve characteristics.

It is also preferable to provide a movement restricting means for restricting the movement of the first magnetic pole portion, and when a pressure difference between the inside and the outside of the housing member becomes large,
By moving the sealing device, it is possible to form a plurality of sealing regions on the moving direction side of the first magnetic pole portion that hold a pressure substantially equal to the pressure on the moving direction side of the first magnetic pole portion of the housing member. it can.

The first magnetic pole portion is disposed on one of the peripheral wall surfaces so as to be movable in the axial direction, and moving means for moving the first magnetic pole portion to a predetermined position in the axial direction. It is also preferable to provide a predetermined timing and an amount of movement by an operator or a control means, and to move the first magnetic pole portion of the housing member in the moving direction side. It is possible to change the pressure stepwise. By moving the first magnetic pole part to the high pressure side, it is possible to use the first magnetic pole part as a plurality of sealed areas for holding the pressure on the high pressure side, and to improve the pressure resistance characteristics of the sealing device on the high pressure side. Is also possible.

[0028]

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 cross-sectional configuration of a sealing device 1 using a magnetic fluid, and shows characteristic components of the present invention.

The sealing device 1 is provided as a housing member at, for example, 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. FIG. 1A shows a state from a stop of the vacuum chamber VC to a start of operation.
FIG. 1B is an enlarged view of the portion D1. FIG. 1C shows a state of the vacuum chamber VC from the start of operation to the time of operation. FIG. 1D is an enlarged view of the portion D1. FIG.

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 has a cylindrical portion 3a for holding and sealing the rotary shaft 2 and a shaft of a vacuum chamber VC for vacuuming the internal space (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 (shown in FIG. 1B) interposed in a magnetic circuit MC formed by an annular magnet 6 as a magnetic force generating means provided inside the cylindrical portion 3a of the bearing portion 3. I have.

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. The rotary shaft 2 has a plurality of circumferentially continuous concave grooves 8a, 8 at respective portions of the peripheral wall surface 2a facing the magnetic pole members 7a, 7b.
.. are formed.

In this embodiment, the magnet 6 and the magnetic pole members 7a and 7b are integrated by bonding or the like, and the cylindrical portion 3a
It is formed in such a size that it can slide and move in the axial direction (direction of arrow A1) on the inside. Annular grooves are provided on the outer peripheral surfaces of the magnetic pole members 7a and 7b, and seal rings 7c and 7d for preventing leakage of fluid are fitted.

Also, 15a and 15b are magnetic pole members 7a,
7b is a spring as urging means for urging 7b from both sides to stop at a predetermined position in the axial direction. As a specific embodiment, a bellows-like rubber bellows having a metal spring embedded therein is used. It is also possible to use.

.. Between the concave grooves 8a, 8b,.
are formed at substantially the same height as the height of a, and the concave grooves 8a, 8b.
.. function as the second magnetic pole portion 10.
(Because the magnetic pole member 7a and the magnetic pole member 7b have the same configuration on the left and right with the magnet 6 as the center, in the following description, the magnetic pole member 7a side will be described as a representative.) The second magnetic pole portion Reference numeral 10 is formed over a region longer than the axial length of the magnetic pole member 7a. That is, FIG.
As shown in (b), the magnetic pole member 7a is moved from the low pressure side L to the high pressure side H.
To provide grooves 8a to 8k and ridges 9a to 9k,
The length of the ridges 9a to 9k is longer than the axial length of the magnetic pole member 7a.

When the pressure on the low pressure side L and the high pressure side H before operation of the vacuum chamber VC are substantially equal, the position of the magnetic pole member 7a is recessed to a lower pressure side L than the magnetic pole member 7a by the springs 15a and 15b. The grooves 8a, 8b, 8c, 8d are stopped at certain positions.

The top surface of each of the ridges 9a to 9k has a magnetic fluid ML for sealing the space between the top surface of the magnetic pole member 7a and the inner peripheral wall 7b.
Are held to form a magnetic fluid seal portion (as an aggregate of the magnetic fluid ML).

The formed magnetic fluid seal portion is connected to the low pressure side L
And a plurality of chambers 11e as sealed areas between
11j (before the movement of the magnetic pole member 7a) is formed so as to exhibit a sealing property.

These chambers have an effective sealing performance even when there is a high pressure difference on both sides of the sealed area as in the vacuum chamber VC, because the pressure changes sequentially within the pressure range of each magnetic fluid seal. Can be demonstrated.

Reference numeral 16 denotes a trimmer as a movement restricting means for restricting the axial movement of the magnetic pole member 7a before and at the start of operation of the vacuum chamber VC.

Next, the operation of the sealing device 1 when operating the vacuum chamber VC will be described. In the state of FIG. 1A, the inside of the vacuum chamber VC is evacuated. At this time, since the magnetic pole member 7a is fixed by the trimmer 16, it does not move in the axial direction.

When the pressure on the low pressure side L is reduced, a pressure difference starts to be generated between the low pressure side L and the chamber 11e. When the pressure difference becomes equal to or higher than the pressure resistance of the ridge 9d, a break occurs. A pressure equalization phenomenon) occurs, and the pressure on the low pressure side L is gradually propagated to the high pressure side H chamber with a break. However, the flow of air moves from the chamber on the high pressure side H to the low pressure side L.

Here, the pressure resistance of the ridge is 0.2 kgf /
cm ² , the height rises from the chamber 11 e to 0.2, 0.4... as shown at the bottom of FIG.
In i, 1.0 kgf / cm ^{2 which} is almost equal to the pressure on the high pressure side H
On the high-pressure side H of the chamber 11i, the pressure is 1.0 kgf / cm ² in all the chambers.

Therefore, in this state, the pressure in each chamber is lower than the low pressure side L.
From the pressure difference close to the limit of pressure resistance capability in order,
There is no pressure difference between the chambers on the high pressure side H as compared with the chamber where the sum of the pressure differences held in each chamber is 1 kgf / cm ² (chamber 11i in FIG. It is not involved in the sealing performance.

When the movement of the magnetic pole member 7a is stopped by pulling the trimmer 16 from this state, the magnetic pole member 7a (actually, the magnet 6 and the magnetic pole member 7b are also brought together by the pressure difference between the low pressure side L and the high pressure side H). ) Moves to the low pressure side L (FIG. 1).
(C) FIG. 1 (d)).

The stop after the movement of the magnetic pole member 7a is stopped at a position where the biasing force of the springs 15a and 15b and the suction force due to the pressure difference between the low pressure side L and the high pressure side H are balanced. In order to prevent the spring 15a from being excessively crushed, the spring 15a may be stopped by being brought into contact with a member that determines a stop position.

After the movement of the magnetic pole member 7a, the sealed area becomes the chambers 11b to 11h as shown in FIG. 1D, and the pressure state of each chamber at this time is 0 kgf / cm from the chamber 11b to the chamber 11d.
^2, rising from chamber 11e and 0.2, 0.4., The chamber in 11h 0.8 kgf / cm ^2, and this chamber 1
The groove on the high pressure side than 1h has a sealed area opened to 1.0
kgf / cm ² .

This is because the concave grooves 8a to 8d exposed on the low pressure side L before the movement of the magnetic pole member 7a are evacuated to a vacuum state by the evacuation, and the chamber 11b is moved from the chamber 11b to the chamber 1 with the movement of the magnetic pole member 7a.
A sealed area having a pressure of 0 kgf / cm ² up to 1 d is formed.

The chambers 11i to 11k on the high pressure side H are opened to the high pressure side H with the movement of the magnetic pole member 7a.

Therefore, FIG. 1 after the movement of the magnetic pole member 7a
According to the pressure holding state of each chamber in (d), the pressures in the three-stage chambers 11b to 11d on the low pressure side L side, which is in a vacuum state, are all 0 kgf / cm ² , and there is no pressure difference. When the eccentricity or vibration is applied when is rotated, a break hardly occurs between these chambers 11b to 11d,
Further, when a break occurs in another chamber on the high pressure side H, a preliminary withstand voltage capability for stopping propagation of a break from the high pressure side H is exhibited.

With this preliminary pressure resistance, it is possible to suppress the occurrence of a phenomenon in which the air flows into the chamber 11b which is closest to the low pressure side L and breaks into the air, thereby improving the pressure resistance.
Consequently, the sealing performance of the sealing device 1 can be improved.

For simplicity of explanation, of the two magnetic pole members 7a and 7b, the left magnetic pole member 7a in the drawing is used.
It has been described that the differential pressure between the vacuum and the atmospheric pressure (1 kgf / cm ² ) has been eliminated, but 0.5 kgf / cm ^{2 is} shared by both the magnetic pole members 7 a and 7 b to eliminate the differential pressure. It can be anything.

(Embodiment 2) FIG. 2 is a view for explaining a second embodiment. The feature of this embodiment lies in a trimmer 16. FIG. 2A is an enlarged view of a portion of the trimmer 16 in FIG. The trimmer 16 is pulled upward by an operator or a control unit (not shown) at a predetermined timing after the evacuation is performed, whereby the movement restriction of the magnetic pole member 7b is released, and the trimmer 16 is moved by the pressure difference (the magnetic pole member 7b). The magnetic pole member 7a integrated with the magnetic pole member 7b also moves at the same time.)
You are allowed to.

FIG. 2 (b) shows the trimmer 17 having an R-shaped tip, which is urged by a spring 17a to be fitted to the magnetic pole member 7b, and the pressure difference between the low pressure side L and the high pressure side H. When a predetermined pressure difference occurs when the magnetic pole member 7b moves in the axial direction, the trimmer 17 is dented and the movement restriction of the magnetic pole member 7b is released.

According to this, a vacuum is drawn and the low pressure side L
When the pressure difference between the magnetic pole member 7b and the high-pressure side H reaches a predetermined value, the movement restriction of the magnetic pole member 7b is automatically released, and the magnetic pole member 7b moves to a predetermined balanced position. When the pressure difference is eliminated, the urging force of the springs 15a and 15b causes
Returning to the initial position, the trimmer 17 is fitted to the magnetic pole member 7b to restrict the movement.

Even without using the trimmers 16 and 17, the biasing force of the springs 15a and 15b and the frictional force when the magnetic pole members 7a and 7b slide inside the cylindrical portion 3a can be set to appropriate values. By setting and slowing down the moving speed due to the pressure difference generated by evacuation, it becomes possible to move the magnetic pole members 7a, 7b after the low pressure side L has become sufficiently low pressure, and to operate the sealing device 1 according to the present invention. It is possible to do.

(Embodiment 3) The first and second embodiments aim at applying the present invention to a vacuum chamber VC and maintaining the degree of vacuum inside the vacuum chamber VC. Conversely, the present invention can be applied for the purpose of maintaining the internal pressure of the pressure chamber PC whose inside is higher than the atmospheric pressure and preventing the high-pressure fluid sealed inside from flowing out.

FIG. 3 is a diagram for explaining a characteristic configuration of the third embodiment. The pressure chamber PC has a high pressure side H higher than the atmospheric pressure, and its main body structure is different from the vacuum chamber VC in that it employs an internal pressure resistant structure that does not burst due to internal pressure. The configuration of the shaft hole for taking in the rotational driving force of No. 2 inside is almost the same,
1A are denoted by the same reference numerals, and description thereof will be omitted.

The structure of the sealing device 21 of this embodiment is characterized in that a pressing screw 28 is used as a moving means in order to move the magnetic pole member 7a and the magnetic pole member 27 as the first magnetic pole portion in the axial direction. 3a. The magnetic pole member 27 is provided with a contact surface 27a with which the pressing screw 28 contacts.

Magnetic pole member 7a (the magnet 6 and the magnetic pole member 27 are also integrated, and are representative of the first magnetic pole portion)
Is biased toward the low pressure side L (the right side in FIG. 3) by the spring 15a. The axial position of the magnetic pole member 7a can be determined by the amount of protrusion of the pressing screw 28.

Next, the operation of the sealing device 21 will be described with reference to FIGS. 3 (b) and 3 (c) (each of which is an enlarged view of the portion D1 in FIG. 3 (a)). PC
, And the magnetic pole member 7a is moved by being pressed by the pressing screw 28 to the high pressure side H prior to pressing.

Then, for example, when the pressure on the high pressure side H is 2 kgf /
cm ² and the pressure on the low pressure side L is 1 kgf / cm ^2, and the chambers 11b to 11d on the high pressure side H
Pressure. When the breakdown voltage capability of each convex portions similarly as 0.2 kgf / cm ² in the first embodiment, 0.2 kgf / cm ² over a period from the chamber 11e to the chamber 11h
The pressure gradually decreases to 1.2 kgf / cm ² in the chamber 11h.

In this state, when the rotary shaft 2 is rotated, the chamber on the low pressure side L breaks due to an unstable element such as eccentricity.
It is conceivable that 1 h breaks and the sealed fluid leaks to the low pressure side L.

Therefore, as shown in FIG. 3C, when the pressure is increased to a certain level, the pressing screw 28 is turned to reduce the amount of protrusion, and the magnetic pole member 7a is moved to the low pressure side L. . Then, the chambers 11i to 11k having substantially the same pressure as the low-pressure side L are formed on the low-pressure side L, and the reduction in the pressure resistance of each chamber when the rotating shaft 2 rotates is reduced by a plurality of chambers (chambers 11i).
To 11k) to prevent leakage of the sealed fluid.

Further, depending on the nature of the sealed fluid on the high pressure side H, some leakage of the sealed fluid is permitted, but for the purpose of keeping the internal pressure of the pressure chamber PC constant, at the start of pressurization, The magnetic pole member 7a is positioned on the low pressure side L shown in FIG. 3C, and after pressing, the pressing screw 28 is turned to increase the amount of protrusion, and the magnetic pole member 7a is moved to the high pressure side H.
It is also possible to move to.

Therefore, in order to increase the pressure resistance, the pressure balance state of each chamber can be appropriately changed, and the sealing performance can be improved.

[0069]

According to the sealing device using the magnetic fluid of the present invention described in the above embodiment, it is possible to change the pressure state of a plurality of sealing regions arranged in the axial direction, and to maintain the holding force of the magnetic fluid. Can suppress the influence of a break caused by the change of the pressure, improve the pressure resistance, and maintain the sealing performance.

By moving the first magnetic pole portion in the axial direction by the pressure difference generated between the inside and the outside of the housing member, when the pressure difference occurs, the pressure state of the sealed area is automatically changed. When the pressure difference is eliminated, the biasing means returns to the original position, so that the first magnetic pole portion is automatically moved.

The movement restricting means restricts the movement of the first magnetic pole portion until a predetermined pressure difference is generated, so that the pressure states of the plurality of sealed areas on the movement direction side after the movement are reduced. The pressure is made substantially equal to the pressure, and the pressure resistance is improved to maintain the sealing performance.

By the moving means, the first magnetic pole portion can be moved with a predetermined timing and moving amount set, and the holding pressure of the plurality of sealed areas on the moving direction side of the first magnetic pole portion of the housing member is maintained. Can be changed.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a cross-sectional configuration of a sealing device to which the present invention is applied. FIG. 1 (a) shows a state before the first magnetic pole portion moves, FIG. 1 (c) shows a state after the movement, 1B and 1D are enlarged views of a portion D1 in FIGS. 1A and 1C, respectively.

FIG. 2 is an explanatory cross-sectional configuration diagram illustrating a trimmer.

FIG. 3 is a sectional configuration explanatory view of a third embodiment of the sealing device to which the present invention is applied;

FIG. 4 is a diagram illustrating a cross-sectional configuration of a conventional sealing device and a diagram illustrating the strength of a magnetic field.

FIG. 5 is an enlarged view of a portion D101 in FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sealing device 2 Rotating shaft 2a Peripheral wall surface 3 Bearing part 4 Annular clearance 5a, 5b Bearing 6 Magnet (magnetic force generation means) 7a, 7b Magnetic pole member (first magnetic pole part) 7c, 7d Seal ring 8a-8k Concave groove 9a- 9k ridge 10 second magnetic pole 11a to 11k chamber 15a, 15b spring (biasing means) 16 trimmer (movement restricting means) H high pressure side L low pressure side MC magnetic circuit ML magnetic fluid VC vacuum chamber VCa shaft hole

──────────────────────────────────────────────────の Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F16J 15/43

Claims (4)

(57) [Claims] 1. An annular first member 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 plurality of annular grooves arranged in the axial direction on the other peripheral wall surface side of the annular gap opposed to the first magnetic pole portion, and a ridge between the annular grooves. 2 magnetic pole portions; magnetic force generating means for forming a magnetic field passing between the first and second magnetic pole portions; and a ridge of the second magnetic pole portion facing the first magnetic pole portion. A magnetic fluid that is held by the magnetic field to make the plurality of annular grooves a plurality of sealed regions; and a magnetic fluid using: a magnetic fluid, wherein the first and second magnetic pole portions are arranged in an axial direction. Wherein the plurality of annular grooves of the second magnetic pole portion are formed to extend in a region in the moving direction of the first magnetic pole portion. apparatus. 2. The first magnetic pole portion is disposed on one peripheral wall side so as to be movable in the axial direction, and biases the first magnetic pole portion to be at a predetermined position in the axial direction. The sealing device according to claim 1, further comprising a biasing unit, wherein the first magnetic pole portion moves in an axial direction by a pressure difference generated between the inside and the outside of the housing member. 3. The sealing device according to claim 2, further comprising a movement restricting means for restricting the movement of the first magnetic pole portion. 4. A moving means for moving the first magnetic pole portion so as to be axially movable on one peripheral wall side and moving the first magnetic pole portion to a predetermined position in the axial direction. The sealing device according to claim 1, further comprising: