JPH10220595A - Sealing device using magnetic fluid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To capture gas evaporated from a magnetic fluid so as to prevent the evaporated gas from flowing into the low pressure side by providing a cooling means having a cooling face for liquefying gas to capture it, on the lower pressure side than a magnetic fluid seal part in an annular clearance. SOLUTION: A magnetic fluid seal part MS has a magnet 6 with unlike poles arranged in an axial direction, and magnetic pole members 7a, 7b serving as first magnetic pole parts brought into contact with both axial sides of the magnet 6 so as to be magnetic poles, and a space to the peripheral wall surface 2a of a rotary shaft 2 is sealed with a magnetic fluid ML interposed at a magnetic circuit MC where magnetic flux generated by the magnet 6 is formed. During operation of the sealing device 1, when a solvent of the magnetic fluid ML is evaporated as gas by heating generated in assocaition with the rotation of the rotary shaft 2 and pressure drop of each chamber and is going to flow into the lower pressure side L, this gas is liquefied at the cooling face 10b of an annular member 10 where cooling water A1 flows through and captured by the cooling face 10b so as to restrain the evaporated gas from flowing into the low pressure side L.

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 treating gas generated in a magnetic fluid sealing portion.

[0002]

2. Description of the Related Art Conventionally, particles of a magnetic substance are suspended in a fluid containing oil or a surfactant, and the particles are magnetically attracted by a magnetic flux by a magnetic force of an external magnetic field such as a permanent magnet or an electromagnet. There are various types of sealing devices that use the characteristics of magnetic fluid that can maintain the position of the fluid itself.

FIG. 5A is a view for explaining a sectional configuration of a sealing device 100 as a conventional example using such a magnetic fluid, and FIG. FIG. 6 is an enlarged view of a portion D101 in FIG. 5A. 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 is concentrated on the top surface of the magnetic fluid ML ′ (ie, the magnetic flux density is increased on the top surface of the ridges 108a, 108b,...). Is a plurality of stage portions.), And the magnetic fluid ML ′ is held in these gaps, that is, the stage portions, to form a magnetic fluid seal portion.

Then, the formed magnetic fluid seal portion is
A plurality of chambers 109a, 1 are provided between the low pressure side L 'and the high pressure side H'.
09b,... Are formed, and the pressure in each chamber is sequentially changed within the pressure-resistant range of each stage, so that effective sealing performance can be exhibited even when there is a pressure difference on both sides of the sealing area. It has become. For example, if the sum of the withstand pressures at all the stage portions becomes 100 KPa (1 kgf / cm ² ) or more, it can be used as a vacuum seal.

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. 5 (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 radial gap G ′ between the magnetic pole member 105 and the rotating shaft 101 shown in FIG. 6 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]

However, when the evacuation of the low pressure side L 'is started, the pressure of the magnetic fluid seal portion also decreases, and depending on the component of the magnetic fluid ML' used, the evaporative gas is removed. This may cause contamination of the low pressure side L ′.

The low pressure side L 'is generally used as a vacuum chamber. When the rotating shaft 101 for transmitting power to the inside of the vacuum chamber is rotated, the magnetic fluid ML' existing in each stage is also reduced. The ridge 10 of the rotating shaft 101
8a, 108b,... Flows with rotation, and generates a shear stress inside the magnetic fluid ML ′ to generate heat.

In particular, when the magnetic fluid ML 'is used at a high speed, the temperature rise due to the heat generation of the magnetic fluid ML' becomes large, and the evaporating gas is more easily generated.

By the way, as the prior art relating to the prevention of temperature rise due to heat generation of the magnetic fluid ML ', Japanese Utility Model Laid-Open No. 7-29361 (see FIG. 7) and Japanese Utility Model Laid-Open No.
No. 25369 (see FIG. 8).

In Japanese Unexamined Utility Model Publication No. 7-29361, the housing 205 is provided with a cooling passage 213 for flowing the fluid heat medium 212, and the yokes 202a, 202b...
.. Can reduce the temperature of the magnetic fluid ML ′ existing in the magnetic fluid seal portion having the multilayer structure.

In Japanese Utility Model Laid-Open No. 7-25369, an annular spacer 309 is provided between pole pieces 305 and 306 made of a magnetic material, and a plurality of magnets 3 are provided outside the annular spacer 309.
13 is provided such that a gap 307 exists.
7 is used as a cooling fluid circulation passage to circulate a fluid heat medium from the port 314 to cool the pole pieces 305 and 306. Then, the temperature of the magnetic fluid ML ′ existing in the magnetic fluid seal portion formed between the pole pieces 305 and 306 and the shaft 304 can be reduced. FIG. 8A is a cross-sectional explanatory view parallel to the axial direction of the shaft 304, and FIG. 8B is a cross-sectional view of S1 in FIG. 8A.

However, in comparison with the sealing device 100 of FIG. 5 which is not provided with a cooling means, in any of the prior arts, the temperature of the magnetic fluid ML 'is lowered to make the magnetic fluid ML' less likely to evaporate. However, the gas once evaporated flows into the low-pressure side L 'as it is or through a bearing.

When liquid nitrogen or the like having a high cooling effect due to the fluid heat medium for cooling is used, the viscosity of the magnetic fluid ML 'increases due to supercooling, so that the rotational torque of the shaft 304 increases, It is also necessary to consider the problem that the sealing performance of the magnetic fluid is reduced due to the reduction in the sealing performance.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and an object of the present invention is to capture gas evaporated from a magnetic fluid present in a magnetic fluid seal portion of a sealing device and reduce the pressure on a low pressure side. It is an object of the present invention to provide a sealing device using a magnetic fluid capable of reducing or preventing the inflow of fluid into a container.

[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, 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 flux passing between the first and second magnetic poles, and a stage of a second magnetic pole facing the first magnetic pole; In a sealing device using a magnetic fluid having a magnetic fluid seal having a magnetic fluid held by the magnetic flux, a gas is liquefied and trapped on a lower pressure side of the annular fluid gap than the magnetic fluid seal. A cooling means having a cooling surface is provided.

As a result, the gas generated in the magnetic fluid seal portion and going to move to the low pressure side is cooled and liquefied by the cooling surface of the cooling means, and is trapped on the cooling surface and stays there. Is reduced. On the other hand, the gas sealed on the low pressure side is captured by the cooling surface, and the flow into the magnetic fluid seal portion is reduced.

Further, the cooling surface of the cooling means is provided with a groove, and the liquefied gas is trapped in the groove.

Thus, the area of the cooling surface is increased by the concave groove, the cooling efficiency of the gas is improved, and the liquefied gas is prevented from flowing out from the cooling surface.

Further, a bearing is provided for supporting a shaft inserted into the shaft hole of the housing member in the annular gap, and the cooling means is arranged on a lower pressure side than the bearing.

In this configuration, the gas generated from the lubricating oil or the like provided in the bearing is also cooled and liquefied by the cooling surface of the cooling means, and is trapped and retained on the cooling surface.

[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 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 that transmits rotary power from the outside to the inside of a vacuum chamber VC that makes 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 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 seal portion MS provided inside the cylindrical portion 3a of the bearing portion 3. The magnetic fluid seal portion MS includes a magnet 6 having different poles arranged in the axial direction, and magnetic pole members 7a and 7 as first magnetic pole portions which are in contact with both sides in the axial direction of the magnet 6 to be magnetic poles.
The magnetic fluid ML interposed between the magnetic circuit MC in which the magnetic flux generated by the magnet 6 is formed between b and the peripheral wall surface 2a of the rotating shaft 2.

A magnetic pole member 7 is provided on the peripheral wall surface 2a of the rotating shaft 2.
A plurality of circumferentially continuous annular ridges 8a, 8b,... are formed at respective portions facing the a, 7b, and the outer peripheral top surfaces of the ridges 8a, 8b. , 9
b,..., and the magnetic fluid ML is
are held between the stage and the magnetic pole member by the magnetic flux passing through b,.

Numeral 10 denotes an annular member as a cooling means, and a low pressure side L which is a lower pressure side than the magnetic fluid seal portion MS.
It is attached so as to fit into the cylindrical portion 3a of the bearing 3 on the side. The annular member 10 has a groove 10a on the outer peripheral side that forms an annular flow path with the inner peripheral surface of the cylindrical portion 3a. The fluid heat medium such as cooling water flows through the communication passage 3c passing through the cylindrical portion 3a and connecting to the groove 10a.
And the annular member 10 is cooled. Therefore, the inner peripheral surface of the annular member 10 functions as the cooling surface 10b. It is also possible to provide a discharge path (not shown) at a position in the circumferential direction different from the communication path 3c of the groove 10a in order to cause the fluid heat medium flowing into the groove 10a to flow out.

Reference numeral 11 denotes a magnetic pole member 7b and a bearing 5b.
Spacer rings for determining the gap between
Is an O-ring for maintaining the sealing between the inner peripheral surface of the cylindrical portion 3a and the outer peripheral surfaces of the magnetic pole members 7a and 7b. Further, the O-ring for maintaining such sealing performance is provided with the groove 10 of the annular member 10.
a, it is possible to appropriately improve the sealing performance between the outer peripheral surface of the annular member 10 and the inner peripheral surface of the cylindrical portion 3a.

In the sealing device 1, a plurality of chambers R1, R2,... Are formed between the low pressure side L and the high pressure side H by the magnetic fluid ML held on each stage. When the vacuum chamber VC is evacuated, the pressure in the chambers R1, R2,... Decreases stepwise from the high-pressure side H to the low-pressure side L within the withstand pressure limit of each stage, and two areas having a pressure difference (The inside of the vacuum chamber VC and the high-pressure side H, which is an atmosphere side area).

The power can be transmitted to the inside of the vacuum chamber VC by rotating the rotary shaft 2 in a state where the pressure balance in each chamber is stable.

During the operation of the sealing device 1, the magnetic fluid ML is generated by the pressure drop in each chamber and the heat generated by the rotation of the rotating shaft 2.
When the solvent (for example, a fluid containing oil or a surfactant) evaporates as a gas and tries to flow into the low-pressure side L,
The generated gas is the cooling surface 10b of the annular member 10 having a low temperature.
As a result, the liquid is liquefied, and is trapped and retained on the cooling surface 10b, so that inflow into the low-pressure side L, that is, into the vacuum chamber VC is suppressed.

In the vacuum chamber VC, various kinds of gases are often used for chemical treatment. The cooling surface 10b of the annular member 10 conveys the active gas used at that time to the magnetic fluid seal portion MS. Also, the magnetic fluid ML is prevented from deteriorating, and the performance of the sealing device 1 can be maintained and the life can be extended.

(Embodiment 2) FIG. 2 is a view for explaining a second embodiment of the present invention. In the figure, the same components as those in the first embodiment of FIG. 1 are denoted by the same reference numerals. The feature of the sealing device 21 of the second embodiment resides in an annular member 22 as a cooling means.

In FIG. 2, the annular member 22 is provided with a plurality of annular grooves 22b which are circumferentially continuous with the cooling surface 22a, with the inner surface being a cooling surface 22a. Therefore,
As the area of the cooling surface 22a increases, the cooling efficiency for liquefying the gas generated in the magnetic fluid seal portion MS improves, and the trapped liquid flows along the annular groove 22b, so that it flows to the bearing 5a side. Is prevented.

The liquid that liquefies on the cooling surface 22a and flows downward in the annular groove 22b stays at the lowest position of the annular member 22.
Is formed, and a communication hole 23 communicating from the concave portion 22c to the outer periphery is formed to allow the liquid to flow into this portion, so that the liquid does not overflow from the cooling surface 22a.

Further, the liquid existing in the recess 22c and the communication hole 23 can be drained to the outside by opening the drain plug 25 closing the drain port 24 when the vacuum chamber VC is stopped. .

(Embodiment 3) FIG. 3 is a sectional view for explaining a third embodiment of the present invention. In FIG.
The same reference numerals are given to the same components as in the first embodiment. The sealing device 31 according to the third embodiment is characterized in that the annular member 32 is cooled by a method of cooling the annular member 32.
Is provided with a plurality of Peltier elements 32a on the outer periphery of the Peltier device.

The configuration other than the cooling by the Peltier element 32a is the same as that of the first and second embodiments, and has the same operation and effect, but as in the first and second embodiments. The annular member is provided with an annular groove, and a complicated structure of flowing a fluid heat medium such as cooling water into the annular member is not required, so that maintenance and operability can be improved.

(Embodiment 4) FIG. 4 is a view for explaining a fourth embodiment of the present invention. In the figure, the same components as those in the first embodiment of FIG. 1 are denoted by the same reference numerals. In the fourth embodiment, the annular member 42 as a cooling means is provided on the low pressure side L which is a lower pressure side than the magnetic fluid seal portion MS and the bearing 5a.

In this manner, the gas generated from the lubricating oil or the like provided in the bearing 5a is also cooled and liquefied by the cooling surface 42a of the annular member 42, and is captured and retained by the cooling surface 42a.

[0049]

According to the sealing device using the magnetic fluid of the present invention described in the above embodiment, the gas generated in the magnetic fluid sealing portion and going to the low pressure side is cooled by the cooling surface of the cooling means. The liquid is cooled and liquefied, and is trapped and retained on the cooling surface, so that the inflow to the low pressure side is reduced. Therefore, the low pressure side is not contaminated by gas generated from the magnetic fluid seal portion.

Further, the gas flowing from the low-pressure side into the magnetic fluid seal portion is also trapped and retained on the cooling surface, thereby preventing the deterioration of the magnetic fluid due to the low-pressure gas.

By providing a concave groove on the cooling surface of the cooling means,
The area of the cooling surface is increased, the cooling efficiency of the gas is improved, and the liquefied gas is prevented from flowing out from the cooling surface.

Further, the gas generated from the lubricating oil and the like provided in the bearing by the cooling means disposed on the low pressure side of the bearing is also trapped and retained on the cooling surface.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view of a sealing device according to a first embodiment of the present invention;

FIG. 2 is an explanatory sectional view of a sealing device according to a second embodiment of the present invention;

FIG. 3 is an explanatory sectional view of a sealing device according to a third embodiment of the present invention;

FIG. 4 is an explanatory sectional view of a sealing device according to a fourth embodiment of the present invention;

FIG. 5 is a diagram illustrating a cross-sectional configuration of a conventional sealing device and a diagram illustrating the strength of a magnetic field.

FIG. 6 is an enlarged view of a portion D101 in FIG. 5;

FIG. 7 is an explanatory view of a cross-sectional configuration of a conventional sealing device.

FIG. 8 is an explanatory sectional view of a conventional sealing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sealing device 2 Rotating shaft 2a Peripheral wall surface 3 Bearing part 3a Cylindrical part 3b Flange part 3c Communication path 4 Annular clearance 5a, 5b Bearing 6 Magnet (magnetic force generating means) 7a, 7b Magnetic pole member 8a, 8b Protrusion 9a, 9b Stage Part 10 Annular member (cooling means) 10a Groove 10b Cooling surface 11 Spacer ring 12, 13 O-ring 22c Concave part 24 Drain port 25 Drain plug 32a Peltier element H High pressure side L Low pressure side MC Magnetic circuit ML Magnetic fluid MS Magnetic fluid seal part R1 , R2 room VC vacuum chamber

Claims (3)

[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 fluid generating unit that forms a magnetic flux, and a magnetic fluid held by the magnetic flux between the first magnetic pole unit and the stage of the second magnetic pole unit facing the first magnetic pole unit. In a sealing device using a magnetic fluid, a lower pressure side of the annular gap than the magnetic fluid seal portion,
A sealing device using a magnetic fluid, comprising cooling means having a cooling surface for liquefying and capturing gas. 2. The sealing device using a magnetic fluid according to claim 1, wherein the cooling surface of the cooling means has a groove, and the liquefied gas is trapped in the groove. 3. A bearing for supporting a shaft inserted into a shaft hole of a housing member in the annular gap, wherein the cooling means is arranged on a lower pressure side than the bearing. Or a sealing device using the magnetic fluid according to 2.