JPH1061782A - Magnetic seal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic seal device of high reliability by preventing generation of turbulence in magnetic flux distribution in the magnetic seal device, in the magnetic seal device arranged with a plurality of ring-shaped magnets in a condition making the fellow N or S poles opposed so as to form a strong magnetic fluid film. SOLUTION: By a plurality of ring-shaped magnets 9a to 9b, between an inner circumferential end of each ring-shaped pole piece 8 and a rotary shaft 17, a magnetic passage is formed, along this magnetic passage, a magnetic fluid 12 is converged, a plurality of steps of magnetic fluid films are formed, and, by these magnetic fluid films, a pressure difference is held between an atmospheric region P and a vacuum region Q. A plurality of magnet pairs 9A, 9B comprising a pair of magnets opposing the fellow equal polarity surfaces are arranged in an axial direction of a motion shaft, and also mutually between these magnet pairs 9A, 9B, the fellow different polarity surfaces, that is, the N/S polarity is arranged so as to be opposed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic seal device for shielding two space regions formed around a motion axis such as a rotation axis and a linear motion axis by using a magnetic fluid.

[0002]

2. Description of the Related Art In the industry, a space in which the inside is hermetically sealed is maintained at a pressure state different from the external pressure, that is, a differential pressure state, and various processes are performed under the differential pressure state. Various devices exist. Further, in addition to the differential pressure state, various processes may be performed while the inside is kept in a dustproof state or a special gas atmosphere state. For example, in a decompression processing apparatus for semiconductor wafers, a vacuum dryer, a rotating anti-cathode type X-ray generator, and the like, a predetermined process is performed under a dustproof state in which the pressure is reduced to a vacuum. The magnetic seal device is used to shield two space regions, that is, a space region where the predetermined processing is performed and an atmospheric pressure region, from each other.

For example, taking a rotary anti-cathode X-ray generator as an example, as shown in FIG. 2, a magnetic field is generated between a vacuum-free area Q and an atmospheric pressure area P inside a casing 1. The differential pressure state and the dustproof state are maintained by the sealing device 2. In this X-ray generator, the interior of the casing 1 is evacuated to a vacuum state by an exhaust device 4 composed of a turbo-molecular pump, a rotary pump, and the like, and the cylindrical target 5 is rotated by a rotary driving device 3 such as a motor. Let it. The thermoelectrons emitted from the filament 6 by energization collide with the surface of the target 5 at high speed, and X-rays are generated from the collision portion. The generated X-rays are extracted to the outside through an X-ray extraction window 7 formed of beryllium or the like provided at a predetermined position of the casing 1. This X
The lines are used for physical analysis such as X-ray diffraction measurement.

[0004] As the magnetic sealing device 2, a conventional Japanese Patent Publication No. Sho 6
As disclosed in Japanese Patent Application Laid-Open No. 3-24196, a plurality of magnets are arranged side by side in the axial direction of a movement axis such that the same magnetic pole faces, that is, N poles or S poles are opposed to each other. There is known a magnetic sealing device in which a pressure difference applied to a magnetic fluid is reduced by exhausting a pressure side, that is, a high pressure side. According to this magnetic seal device, since the magnetic pole surfaces of adjacent magnets are the same magnetic pole surface, the magnetic lines of force between the respective magnets repel each other, and the magnetic lines of force formed between the individual magnets and the motion axis are narrowed. High density focusing. For this reason, a strong and strong magnetic fluid film can be formed in the gap between the pole piece and the movement axis, and the pressure difference between the two space regions defined by the magnetic fluid films can be reliably ensured. Can be held in
Moreover, leakage of the magnetic fluid to the low pressure side can be prevented.

[0005]

However, according to the experience of the present inventors, it has been found that with this conventional magnetic sealing device, the high-precision shaft sealing ability assumed at the beginning of design cannot be obtained as desired. , Was often seen. In addition, although the desired shaft sealing ability was obtained at the beginning of the operation, it was also found that the shaft sealing ability decreased more than expected after a relatively short period of time. The present inventors have conducted various experiments on why such a phenomenon occurs. As a result, when the magnets are arranged so that their magnetic pole faces face each other to form a high-density magnetic fluid film between the pole piece and the movement axis, a large disturbance occurs in the magnetic flux distribution of each magnet. Has been found to be a cause of the inconvenience described above.

The present invention has been made on the basis of the above-mentioned findings, and it has been made possible to secure as much as possible a technique of forming a strong magnetic fluid film by arranging adjacent magnets such that their magnetic pole faces face each other. In addition, it is an object of the present invention to provide a magnetic seal device capable of preventing a magnetic flux from being disturbed as much as possible and maintaining a stable shaft sealing ability for a long period of time.

[0007]

SUMMARY OF THE INVENTION A magnetic seal device according to the present invention includes a plurality of pole pieces arranged around a motion axis formed by a magnetic material, and a magnetic passage between each pole piece and the motion axis. And a magnetic seal device having a plurality of magnets forming a magnetic field and a magnetic fluid filled between each pole piece and a motion axis, and shielding two space regions around the motion axis with the magnetic fluid. It is. The feature of the present invention is that the plurality of magnets
A plurality of magnet pairs composed of a pair of magnets having the same pole faces are arranged in the axial direction of the movement axis, and at least one of the plurality of magnet pairs adjacent to each other is different. This means that the pole faces face each other.

As disclosed in Japanese Patent Publication No. 63-24196, an intermediate exhaust chamber may be provided in a magnetic seal device in order to reduce a pressure difference applied to a magnetic fluid. This intermediate exhaust chamber may be provided at a higher pressure side than all of the plurality of magnets, as shown in JP-B-63-24196, but separately at an intermediate position between the plurality of magnets. It may be placed. In this case, regarding the magnet where the intermediate exhaust chamber is provided, in particular,
It was found that the disturbance of the magnetic flux was large. Therefore, when the intermediate exhaust chamber is disposed at an intermediate position between the plurality of magnets, it is desirable that the different magnetic pole faces be opposed to each other with respect to the magnet pairs located on both sides of the intermediate exhaust chamber.

In general, when the vacuum chamber side is constantly evacuated, the magnetic fluid forming the partition is pulled toward the vacuum side by the pressure difference, and the force for drawing back the magnetic fluid is covered by the magnetic flux. Therefore, if the suction force on the vacuum side becomes larger than the magnetic flux force due to some inconvenience, the magnetic fluid enters the vacuum side and contaminates the vacuum chamber. Intermediate exhaust is performed to avoid this phenomenon, and the details will be described below.

The plurality of small chambers formed by the magnetic fluid film to maintain the vacuum state are all at the initial atmospheric pressure at the time of assembling, and when the vacuum is evacuated, these small chambers gradually increase the degree of vacuum. Go on. The gradual increase in the degree of vacuum in each of the small chambers in this way is nothing less than the fact that those chambers are open to the vacuum chamber, and this must be kept clean in the first place. It means that the vacuum chamber must be polluted.

In recent years, in semiconductor manufacturing processes and the like,
It has become necessary to keep the atmosphere in the room for carrying out the process very clean. When using a magnetic seal device in a semiconductor manufacturing process in such a situation, poor cleanliness in the process chamber may be pointed out during a long-time operation. Iron as a component was sometimes detected in the process chamber.

It is considered that such mixing of iron is mainly caused by the magnetic fluid scattering into the vacuum chamber as described above. Furthermore, when it is insufficient to remove the water used during the manufacturing process of the magnetic fluid from the magnetic fluid, the components mixed in the magnetic fluid may be exhausted at the time of evacuation of the process chamber or during the vacuum maintenance operation. It is thought that this may also cause the shards to scatter as a result, such as the rupture of bubbles seen during defoaming or when a soap bubble bursts.

In order to solve the above inconvenience, an exhaust mechanism is provided at an intermediate position between the vacuum chamber and the atmospheric pressure, and most of the pressure difference between the vacuum chamber and the atmospheric pressure is supplied to the exhaust mechanism. By sharing the pressure, the pressure difference between the exhaust mechanism and the vacuum chamber is reduced as much as possible, and as a result, components in the magnetic fluid near the vacuum chamber are prevented from scattering and leaching into the vacuum chamber. You do it.

In the present invention, since a plurality of magnet pairs each composed of a pair of magnets whose magnetic pole faces face each other are arranged in the axial direction of the movement axis, the magnetic flux is concentrated by the repulsion of the lines of magnetic force within one magnet pair. Is obtained, whereby a strong magnetic fluid film can be obtained. In addition, at least one magnet pair adjacent to each other among the plurality of magnet pairs is arranged so that different magnetic pole faces face each other.
At this point, no repulsion of the lines of magnetic force occurs, and the magnet pair behaves as if it were a single magnet, thereby stabilizing the magnetic flux around the plurality of magnets. Due to the stability of the magnetic flux, the shaft sealing ability of the magnetic seal device can be secured in a stable state for a long period of time. Further, since the magnetic flux is stabilized, it becomes easy to design the magnetic force characteristics of the magnetic seal device.

[0015]

FIG. 1 shows an embodiment of a magnetic seal device according to the present invention. As shown in FIG. 1A, the magnetic seal device has a cylindrical housing 10.
have. A bearing 16 is fixedly fitted inside the right side of the housing 10, and a motion axis 17 formed of a magnetic material is supported by the bearing. The movement axis 17 may be a rotation axis or a linear motion axis. The magnetic material is a material having a property of being magnetized by a magnet, and is formed of, for example, a steel material. Around the movement axis 17, there are set two space regions of an atmospheric pressure region, ie, a high pressure region P, and a vacuum region, ie, a low pressure region Q, and a pressure difference between these regions is maintained by the present magnetic seal device. In addition, the present magnetic seal device prevents dust, dust, gas, and the like in the high-pressure area P from entering the low-pressure area Q and maintains the low-pressure area Q in a clean state.

Inside the housing 10, five ring-shaped pole pieces 8 and four ring-shaped magnets 9a, 9b, 9c, 9d sandwiched between the pole pieces are housed. . As shown in FIG. 1B, the left pair of magnets 9a and 9b constitute a first magnet pair 9A, and the right pair of magnets 9c and 9d constitute a second magnet pair 9B. An intermediate exhaust chamber 20 is formed between the first magnet pair 9A and the second magnet pair 9B, and an exhaust port 21 of the intermediate exhaust chamber is formed.
Is connected to a vacuum pump or other exhaust device 22.

The pair of magnets 9a and 9b in the first magnet pair 9A have their N magnetic pole faces facing each other, that is, their magnetic pole faces face each other. The pair of magnets 9c and 9d in the second magnet pair 9B have their S magnetic pole faces facing each other, that is, their magnetic pole faces face each other. Further, the magnet pairs 9A and 9B facing each other with the intermediate exhaust chamber 20 interposed therebetween have different magnetic pole faces facing each other, that is, the N magnetic pole face and the S magnetic pole face face each other. In other words, a pair of magnets 9b and 9c adjacent to each other with the intermediate exhaust chamber 20 interposed therebetween have different magnetic pole faces facing each other, and the remaining magnets 9a and 9d are respectively opposed to the adjacent magnets 9b and 9c. The magnetic pole faces face each other.

The gap formed between the inner peripheral end of each pole piece 8 and the movement axis 17 is filled with a magnetic fluid 12, ie, filled. The magnetic fluid 12 is a fluid formed by dispersing magnetic metal fine particles in a non-magnetic fluid medium in a colloidal state, and includes, for example, hydrocarbons,
A fluid in which ferrite or other magnetic substance powder is dispersed in a fluid such as a fluorocarbon or a fatty acid can be used.
The filled magnetic fluid exits from the N pole of each magnet 9a to 9d, passes through each pole piece 8 and the movement axis 17,
A magnetic fluid film is formed concentrated on the lines of magnetic force reaching the poles.
The differential pressure state between the high-pressure region P and the low-pressure region Q and the clean atmosphere in the low-pressure region Q are maintained by the magnetic fluid films of a plurality of stages formed at appropriate positions on the inner peripheral end of each pole piece.

The cooling water passage 1 is provided inside the pole piece 8a sandwiched between the magnets 9a and 9b and inside the pole piece 8b sandwiched between the magnets 9c and 9d.
A cooling water supply device 15 is connected to these cooling water passages 13 as shown in FIG. The cooling water flowing in the cooling water passage 13 is
The magnetic fluid 12 is cooled to prevent the fluorine oil and the alkyl oil contained in the magnetic fluid 12 from evaporating.

Since the magnetic seal device according to the present embodiment is configured as described above, the magnetic fluid film 12 formed between each pole piece 8 and the movement axis 17 by the action of the magnetic force reduces the low pressure. The low pressure state and the clean state in the region Q are maintained. Also, a first magnet pair 9A made up of a pair of magnets 9a and 9b whose N poles, which are the same magnetic pole faces, face each other, and a second magnet made up of a pair of magnets 9c, 9d, whose S poles which are the same magnetic pole faces face each other. Movement axis 1 with pair 9B
7, the individual magnet pairs 9A or 9A
In each of B, magnetic flux is converged due to repulsion of magnetic lines of force, whereby a strong magnetic fluid film 12 can be obtained.

Moreover, in the relationship between the first magnet pair 9A and the second magnet pair 9B adjacent to each other, they are arranged so that different magnetic pole faces face each other, that is, the N pole and the S pole face each other. Therefore, no repulsion of the lines of magnetic force occurs at this point, and the magnet pair behaves as if it were a single magnet, so that the magnetic flux around the plurality of magnets 9a to 9d is stabilized. Due to the stability of the magnetic flux, the shaft sealing ability of the magnetic sealing device can be maintained in a stable state for a long period of time. Further, since the magnetic flux is stabilized, it becomes easy to design the magnetic force characteristics of the magnetic seal device.

As described above, the present invention has been described with reference to the preferred embodiments. However, the present invention is not limited to the embodiments, and can be variously modified within the technical scope described in the claims. For example, in the embodiment shown in FIG. 1, the case where two magnet pairs are formed by four ring-shaped magnets is shown. However, three magnet pairs are formed by six magnets, or more. More magnet pairs can be formed by more magnets. However, even in such a case, the magnetic pole faces of the pair of magnets in each magnet pair face each other, and the different magnetic pole faces of at least one pair of adjacent magnet pairs face each other.

Further, the magnetic sealing device according to the third aspect is not restricted to the above-mentioned idea of the magnet pair, but at least a pair of a plurality of magnets adjacent to each other across the intermediate exhaust chamber. The gist of the invention is that the different magnetic pole faces face each other. Therefore, considering the concept of magnet pairs, inevitably,
Although the total number of magnets is an even number, in the magnetic seal device according to the third aspect, the total number of the magnets may be even or odd. However, according to the experiment of the present inventor, it was more effective to set the number of magnets to an even number in achieving the stabilization of the magnetic flux in the magnetic seal device.

[0024]

According to the magnetic seal device of the present invention, magnets adjacent to each other among a plurality of magnets arranged along the movement axis are arranged so that their magnetic pole faces face each other. After securing the technology of forming a strong magnetic fluid film as much as possible, and further forming a magnet pair having different magnetic pole faces facing each other in at least one position in the magnet row group, Disturbance in the magnetic flux distribution was prevented as much as possible. This allows
A magnetic sealing device capable of maintaining a stable shaft sealing ability for a long period of time was obtained.

According to the magnetic seal device of the second and third aspects, the magnets located on both sides of the intermediate exhaust chamber, in which the magnetic flux is apt to be disturbed, are arranged so that different magnetic phases face each other. Thus, the state of the magnetic flux in the magnetic sealing device could be further stabilized.

[0026]

[Brief description of the drawings]

FIG. 1 is a view showing an embodiment of a magnetic seal device according to the present invention, in particular, (a) is a side sectional view of the entire magnetic seal device, and (b) is an enlarged sectional view of a main part.

FIG. 2 is a schematic cross-sectional view showing a rotating anti-cathode type X-ray generator as an example of a system using a magnetic seal device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Casing 2 Magnetic seal device 3 Rotation drive device 4 Exhaust device 5 Target 6 Filament 7 X-ray extraction window 8, 8a, 8b Pole piece 9a, 9b, 9c, 9d Magnet 9A, 9B Magnet pair 10 Housing 12 Magnetic fluid 13 Cooling Water passage 15 Cooling water supply device 16 Bearing 17 Motion axis 20 Intermediate exhaust chamber 21 Intermediate exhaust port 22 Exhaust device

Claims (3)

[Claims] A plurality of pole pieces disposed about an axis of motion formed by a magnetic material; a plurality of magnets forming a magnetic path between each pole piece and the axis of motion;
In a magnetic seal device having a magnetic fluid filled between each pole piece and a motion axis, and shielding two space regions around the motion axis with the magnetic fluid, the plurality of magnets have the same magnetic pole It is constituted by arranging a plurality of magnet pairs composed of a pair of magnets whose surfaces are opposed to each other in the axial direction of the movement axis, and at least one of the plurality of magnet pairs adjacent to each other has a different magnetic pole surface. A magnetic sealing device, which is opposed to each other. 2. The magnetic sealing device according to claim 1, wherein an intermediate exhaust chamber is provided at an intermediate position between the plurality of magnets, and magnet pairs located on both sides of the intermediate exhaust chamber are arranged such that different magnetic pole surfaces face each other. Characteristic magnetic sealing device. 3. A plurality of pole pieces disposed about an axis of motion formed by a magnetic material; a plurality of magnets forming a magnetic path between each pole piece and the axis of motion;
It has a magnetic fluid filled between each pole piece and the motion axis, and an intermediate exhaust chamber disposed at an intermediate position between the plurality of magnets, and magnetically separates two space regions around the motion axis. A magnetic seal device for shielding with a fluid, wherein a pair of magnets adjacent to each other across an intermediate exhaust chamber face different magnetic pole faces, and the remaining magnets face the same magnetic pole faces.