JPH0510451A - Magnetic fluid shaft sealing device - Google Patents

Abstract

PURPOSE:To provide a magnetic fluid shaft sealing device formed in such a way as to prevent a magnetic fluid from being splashed into a vacuum chamber. CONSTITUTION:Around a rotary shaft 2 disposed between a vacuum chamber V and atmospheric air A, plural yokes 4 are disposed at spaces apart along the axial direction of the rotary shaft 2. A magnetic fluid film 5 is formed between each yoke 4 and the rotary shaft 2 by magnetic force, and the rotary shaft 2 is sealed in the state of partial pressure chambers 6 being formed between the respectively adjacent fluid films 5. In this case, a communicating passage 7 for allowing the flow of air but impeding the flow of a magnetic fluid is provided between the vacuum chamber 6 and the partial pressure chamber 6a closest to the vacuum chamber V.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shaft sealing device for sealing a motion shaft, such as a rotary shaft or a linear motion shaft, arranged between a low pressure region and a high pressure region. In particular, it relates to a magnetic fluid shaft sealing device that seals a motion shaft using a magnetic fluid.

[0002]

2. Description of the Related Art A magnetic fluid shaft sealing device is provided on the axis of a motion shaft arranged in a space or liquid having a pressure difference, and moves the motion shaft while maintaining the pressure difference, that is, in a sealed state. It is a mechanical element for making.

In the above magnetic fluid shaft sealing device, a magnet, a yoke and a magnetic fluid are arranged around a motion axis, and a magnetic path is formed between the yoke and the motion axis. It is already known that a magnetic fluid film is formed so as to extend between motion axes, and the motion axis is sealed by this magnetic fluid film to maintain a pressure difference around the motion axis. Usually, the magnetic fluid film is provided at a plurality of locations along the axial direction of the movement axis. One magnetic fluid film is about 0.2
Since it can withstand a differential pressure of up to 0.5 Kg / cm ² , it can withstand a large pressure difference by being provided at multiple locations, that is, by being provided on the axis of the motion shaft in multiple stages. Is possible.

[0004]

A pressure dividing chamber, which is a space, is formed between the magnetic fluid films provided in multiple stages on the axis of motion. When the magnetic fluid shaft sealing device is assembled on the movement shaft, air is sealed inside these pressure dividing chambers. In this state, if one region with the magnetic fluid shaft sealing device as a boundary is made to have a low pressure by vacuuming, the air trapped in each pressure dividing chamber may break through the magnetic fluid film and fall to the low pressure side. The phenomenon of blowing out to occurs. in this case,
When air blows out from the pressure dividing chamber closest to the low pressure region to the low pressure side, that is, the low pressure region, the magnetic fluid itself forming the pressure dividing chamber scatters inside the low pressure region and contaminates the region.

Generally, in the low pressure region, various precision processings required to be performed in a clean environment space are performed. The conventional magnetic fluid shaft sealing device has a problem that the magnetic fluid is scattered in the low-pressure region as described above, so that there is a large possibility that the precision processing thereof may be hindered.

The present invention has been made in view of the above problems in the conventional magnetic fluid shaft sealing device, and provides a magnetic fluid shaft sealing device in which the magnetic fluid does not scatter into the low pressure region. With the goal.

[0007]

In order to achieve the above-mentioned object, a magnetic fluid shaft sealing device according to the present invention includes a magnetic fluid shaft sealing device around a movement shaft disposed between a low pressure region and a high pressure region. A state in which a plurality of yokes are arranged at intervals along the axial direction, a magnetic fluid film is formed by magnetic force between each yoke and the movement axis, and a pressure dividing chamber is formed between each magnetic fluid film. In a magnetic fluid shaft sealing device that seals a motion shaft with a low pressure region and a pressure dividing chamber by allowing air flow between the pressure dividing chamber closest to the low pressure region of the pressure dividing chamber and the low pressure region. It is characterized in that a communication passage for equalizing the pressures of and is provided.

[0008]

By providing the communication passage, the air enclosed in the pressure-dividing chamber closest to the low-pressure region flows into the low-pressure region through the communication hole, so that the pressure-dividing chamber and the low-pressure region become equal in pressure to each other. Become. Therefore, the pressure difference between the partial pressure chamber and the low pressure region is
It is always kept below the pressure resistance of the magnetic fluid film. This allows
It is possible to reliably avoid the phenomenon that the magnetic fluid film facing the low pressure region is ruptured and the inside of the low pressure region is contaminated by the magnetic fluid particles.

[0009]

FIG. 1 shows an embodiment of a magnetic fluid shaft sealing device according to the present invention. The magnetic fluid shaft sealing device 1 includes a motion shaft provided between a vacuum chamber V serving as a low pressure region and an atmosphere A serving as a high pressure region, and a rotary shaft 2 rotating in a direction of an arrow B in the embodiment. Used to make a seal. That is, the magnetic fluid shaft sealing device 1 is
Air is prevented from leaking from the atmosphere A to the vacuum chamber V to maintain the pressure difference.

The magnetic fluid shaft sealing device 1 includes a plurality of magnetic fluid shaft sealing devices 1 arranged around the rotary shaft 2 in the axial direction of the rotary shaft 2.
In the embodiment, it has five annular magnets 3, a plurality of yokes 4 surrounding each magnet 3, six yokes 4 in the embodiment, and a magnetic fluid 5 filled between each yoke 4 and the rotary shaft 2. ing. The magnetic fluid 5 is a colloidal solution prepared by dispersing magnetic fine metal particles in a base solution.

The magnetic field lines emitted from the N pole of each magnet 3 reach the S pole of each magnet 3 through the yoke 4, the rotary shaft 5, and the yoke 4 to form a magnetic path. The magnetic fluid 5 is laid in a film shape between the tip of the yoke 4 and the rotating shaft 2 along each magnetic path thus formed. In the case of the embodiment, eleven magnetic fluid films 5 are formed along the axial direction of the rotary shaft 2. An annular partial pressure chamber 6 which is a space sealed by the magnetic fluid films 5 is formed between the magnetic fluid films 5. In the embodiment, ten pressure dividing chambers are formed.

One magnetic fluid film 5 is approximately 0.2 to 0.5.
It has the ability to maintain a differential pressure of Kg / cm ² . Therefore, the pressure in each of the pressure dividing chambers 6 is gradually divided from the atmospheric pressure A toward the vacuum V and decreases.

A small-diameter communication passage 7 is provided between the vacuum chamber V and the pressure-dividing chamber closest to the vacuum chamber V in each of the pressure-dividing chambers 6, that is, the pressure-dividing chamber 6a located at the left end of the drawing. Has been. This communication passage 7 is finished in a shape that bends at approximately 90 degrees.

Since the magnetic fluid shaft sealing device according to this embodiment is constructed as described above, the pressure difference is maintained by the magnetic fluid films 5 while the rotary shaft 2 rotates, and the vacuum chamber V is evacuated. Held in. In the vacuum chamber V held in vacuum, various operations such as vacuum discharge from filaments and vacuum thin film forming processing are performed. In this magnetic fluid shaft sealing device 1, since the sealing process is performed via the magnetic fluid 5, the rotating shaft 2 and the yoke 4 are hardly worn, and a long life is guaranteed.

By the way, the magnetic fluid shaft sealing device 1 is attached to the rotary shaft 2.
At the time of assembling to, the air is enclosed in each pressure dividing chamber 6. The enclosed air usually stays in each of the partial pressure chambers 6 as it is, or gradually escapes to the low pressure side through the magnetic fluid film 5. However, if the amount of trapped air is too large or if a large vibration is applied, the trapped air may break through the magnetic fluid film 5 and blow out toward the low pressure side. In particular, when the air in the partial pressure chamber 6a closest to the vacuum chamber V blows out toward the low pressure side, the magnetic fluid film 6a facing the vacuum chamber V scatters into the vacuum chamber V and the inside of the vacuum chamber 6 becomes magnetic. May be contaminated with flying particles of fluid. In this case, it is conceivable that an abnormality will occur in various processes performed in the vacuum chamber V.

In order to solve the above problems, in this embodiment, the communication passage 7 is provided between the vacuum chamber V and the partial pressure chamber 6a closest to the vacuum chamber V. By providing this communication passage 7, the air in the lowermost partial pressure chamber 6a flows out into the vacuum chamber V through the communication passage 7. Therefore, the pressure in the partial pressure chamber 6a does not become abnormally high, and the magnetic fluid film 5a does not burst. In this way, the inside of the vacuum chamber V is always maintained in a clean state.

The magnetic fluid is a highly viscous oil-and-fat base solution mixed with metallic magnetic powder, and when it bursts, it does not become a fine magnetic powder alone, but becomes a viscous mass and scatters. To do. If the magnetic fluid film 5 on the right side, which forms the pressure dividing chamber 6a, is ruptured, the above-mentioned viscous mass is scattered in the pressure dividing chamber 6a. The scattered mass is
It is guided to the communication passage 7 and adheres to the wall of the communication passage due to viscosity, or adheres to the bottommost magnetic fluid film 5a.
In this way, the bottommost magnetic fluid film 5a facing the vacuum chamber V will not be ruptured in a chain, and the vacuum chamber V will not be contaminated by the scattered particles.

FIG. 2 shows a modified embodiment relating to a communication passage for communicating the lowermost partial pressure chamber 6a (FIG. 1) and the vacuum chamber V (FIG. 1). The communication passage 17 shown here has a shape that extends annularly around the rotation shaft 2. In the illustrated embodiment, the annular communication passage has a double-wound shape, but it may have a single or triple or more shape. The reference numerals 17a and 17b denote communication passages 17
It is an opening at both ends.

In the embodiment shown in FIG. 1, since the path length of the communication passage 7 is short, the magnetic fluid particles existing in the lowermost pressure dividing chamber 6a are adhered to the path wall and flow out into the vacuum chamber V. It is also possible that the function of blocking is not sufficient. On the other hand, if the annular communication passage 17 is used as in the embodiment of FIG. 2, the length of the passage becomes long, and since it is not a mere linear communication passage, it is bent, so that the inside of the lowermost partial pressure chamber 6a is formed. The residual air flows out into the vacuum chamber V through the communication passage 17, but the magnetic fluid particles are surely adhered to the road wall of the communication passage 17 and their progress is surely blocked and discharged into the vacuum chamber V. There is no.

FIG. 3 shows the essential parts of another embodiment of the magnetic fluid shaft sealing device according to the present invention. In this embodiment, the communication passage 7 in the embodiment shown in FIG. 1 is improved. The parts not shown in FIG. 3 have exactly the same configuration as the embodiment of FIG.

In FIG. 3, the communication passage 7 facing the vacuum chamber V is shown.
A filter 8 is attached to the opening. This filter 8
Is formed of a member having air permeability and preventing passage of particulate matter such as magnetic fluid particles, for example, a cotton-like member, a sponge, a foam material, or the like. The provision of the filter 8 can reliably prevent the magnetic fluid particles from flowing out to the vacuum chamber V even in the communication path 7 having a short path length.

FIG. 4 shows the essential parts of another embodiment. This embodiment is also the same as the embodiment shown in FIG. 1 in the part not shown. In this embodiment, the inside of the communication passage 7 is filled with a filter 18. The filter 18 may be made of the same material as that of the filter 8 in FIG. 3, or other permeable filler such as activated carbon. Also in this embodiment, the filter 18 can surely prevent the magnetic fluid particles from flowing out to the vacuum chamber V.

Although the present invention has been described with reference to some preferred embodiments, the present invention is not limited to these embodiments. For example, the shapes of the magnet 3 and the yoke 4 are not limited to those shown in FIG. Moreover, the number of them is not limited to a specific number.

[0024]

According to the present invention, the residual air in the lowermost partial pressure chamber is sent into the low pressure region through the communication passage without containing the magnetic fluid particles, so that the residual air faces the low pressure region. It did not break through the magnetic particle film and blow out to the low pressure region, and as a result, there was no scattering of the magnetic fluid into the low pressure region.

[Brief description of drawings]

FIG. 1 is a side sectional view showing an embodiment of a magnetic fluid shaft sealing device according to the present invention.

FIG. 2 is a partially cutaway front view showing a modified example of the communication passage.

FIG. 3 is a sectional view showing a main part of another embodiment of the magnetic fluid shaft sealing device according to the present invention.

FIG. 4 is a cross-sectional view showing the main parts of still another embodiment of the magnetic fluid shaft sealing device according to the present invention.

[Explanation of symbols]

2 rotating shaft 3 magnet 4 yoke 5 magnetic fluid film 6 partial pressure chamber 7 continuous passage 8 filters 18 filters V vacuum chamber A atmosphere

Claims (3)

[Claims] 1. A plurality of yokes are arranged at intervals around an axis of motion disposed between a low pressure region and a high pressure region along the axial direction of the axis of motion, and each yoke and the axis of motion are arranged. In the magnetic fluid shaft sealing device that forms a magnetic fluid film by a magnetic force between the magnetic fluid films and seals the motion shaft in the state where the pressure dividing chamber is formed between each magnetic fluid film, in the low pressure region of the pressure dividing chamber, A magnetic fluid shaft sealing device, characterized in that a communication passage is provided between a pressure-dividing chamber and a low-pressure region that are close to each other, and allows passage of air to equalize the pressure in the low-pressure region and the pressure-dividing chamber. 2. The magnetic fluid shaft sealing device according to claim 1, wherein the communication passage extends annularly around the movement axis. 3. The magnetic fluid shaft sealing device according to claim 1, wherein a filter having air permeability but blocking passage of particulate matter is provided inside or at the end of the communication passage. .