JP3687288B2 - Sealing device using magnetic fluid - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sealing device using a magnetic fluid, and relates to a technique that makes it possible to detect the state of a sealing device and the maintenance time.
[0002]
[Prior art]
Conventionally, particles of magnetic material can be suspended in a fluid such as a surfactant, and the position of the fluid can be maintained by magnetically attracting the particles by the magnetic force of an external magnetic field such as a permanent magnet or an electromagnet. There are various sealing devices that utilize the properties of magnetic fluids.
[0003]
  Figure5(A) is a figure explaining the cross-sectional structure of the sealing device 100 as one prior art example using such a magnetic fluid,5(B)5The figure explaining the intensity | strength of the magnetic field of D101 part of (a), a figure6The figure5It is an enlarged view of D101 part of (a). Figure5And figure6The sealing device 100 will be described.
[0004]
The sealing device 100 includes a rotary shaft 101 extending between two regions of a high pressure side H ′ having a pressure difference (in this conventional example, the atmospheric side) and a low pressure side L ′ (in this conventional example, in a vacuum chamber container). It is provided between the bearing portions 103 of the rotating shaft 101.
[0005]
The bearing portion 103 includes a cylindrical portion 103a that holds and seals the rotating shaft 101, and an open end portion 102a of the container 102 that has an internal space in a vacuum state (low pressure side L ′) at one end portion of the cylindrical portion 103a. The flange part 103b attached with a volt | bolt is provided.
[0006]
The cylindrical portion 103a of the bearing portion 103 and the rotating shaft 101 are dynamically held against relative rotational motion by the bearings B1 and B2.
[0007]
The sealing performance is achieved by a magnetic fluid ML ′ interposed in a magnetic circuit MC ′ formed by an annular magnet 104 provided inside the cylindrical portion 103 a of the bearing portion 103.
[0008]
The magnet 104 has different polarities (shown as N and S) in the axial direction, and the magnetic pole members 105 and 106 that serve as the magnetic poles of the magnet 104 are provided on both sides in the axial direction. To be represented).
[0009]
A plurality of circumferentially continuous concave grooves 107 a, 107 b,... Are formed in a portion of the rotating shaft 101 facing the magnetic pole member 105, and the gap between the inner peripheral surface 105 a of the magnetic pole member 105 and each concave groove is formed. It is generated so that magnetic flux concentrates in the gap with the top surface of the ridges 108a, 108b,... (That is, the magnetic flux density is increased at the top surface of the ridges 108a, 108b,. The regions of the gap in which the magnetic fluid ML ′ is held are a plurality of stage portions.) The magnetic fluid ML ′ is held in these gaps, that is, the stage portions, so as to form a magnetic fluid seal portion.
[0010]
And the magnetic fluid seal part formed in this way forms a plurality of chambers 109a, 109b,... Between the low pressure side L ′ and the high pressure side H ′, and the pressure in each chamber is the pressure of each stage part. By changing within the pressure resistance range, even when there is a pressure difference between both sides of the sealed region, effective sealing performance can be exhibited. For example, the total sum of pressure resistance at all stages is 100 KPa (1.0 kgf / cm² If it becomes above, it can utilize as a vacuum seal.
[0011]
110a and 110b are spacer rings for determining the axial positions of the magnet 104 and the magnetic pole members 105 and 106 between the bearings B1 and B2. The fixed ring members 112 and 113 are O-rings that maintain the sealing performance between the inner peripheral surface side of the cylindrical portion 103 a and the outer peripheral surface side of the magnetic pole members 105 and 106.
[0012]
  Figure5(B) is a figure explaining the intensity | strength of the magnetic field of D101 part of the sealing device 100. FIG. This figure is a figure6The magnetic flux distribution in the axial gap G ′ between the magnetic pole member 105 and the rotating shaft 101 is schematically represented as the strength of the magnetic field.
[0013]
That is, since the magnetic flux of the magnetic circuit MC ′ formed by the magnet 104 is concentrated on the convex portion 108a (all of the plurality of convex portions correspond to each other, which is representatively described) that is a magnetic body, It is divided into a high density area and a low density area. Therefore, the magnetic field strength 120a on the top surface of the ridge 108a is stronger than the magnetic field strengths 121a and 121b in the concave grooves 107a and 107b on both sides thereof, and there is a difference Δf.
[0014]
Further, the strength of the holding force at which the magnetic fluid ML ′ is held by the ridge 108a is determined by the difference Δf in the strength of the magnetic field, and the strength of the holding force is proportional to the pressure resistance of each stage portion. Will do.
[0015]
Such a sealing device 100 is, for example, 10^-7When functioning as a vacuum seal for equipment that requires a degree of vacuum of about Pa (for example, a vacuum chamber for sputtering), the pressure on the low-pressure side L ′ and the high-pressure side H ′ is about 0 and about 1.0 kgf / cm² It becomes. In addition, as an apparatus which requires a vacuum degree, for example, 10^-1Even in a device that requires a lower degree of vacuum such as Pa, the pressure on the low pressure side L 'is about 0 kgf / cm.² It can be applied similarly.
[0016]
Therefore, in this usage pattern, the sum total of the pressure resistance capacity of the protruding strips 108a in the magnetic pole members 105 and 106 is 1.0 kgf / cm.² It is designed to be the above.
[0017]
For example, the pressure resistance of each stage part is 0.1 kgf / cm² In this case, it is necessary to have at least 10 stage units and 9 chambers that are independently divided by these stage units. In addition, when considering the safety factor, a plurality of stage units and chambers are added. It is the composition to prepare.
[0018]
And in this prior art, it is set as the structure which can demonstrate the pressure | voltage resistant capability as a vacuum seal only by the magnetic member (one of the magnetic pole members 105 or 106) of one side.
[0019]
At the start of the operation of the sealing device 100, the pressure on the low-pressure side L ′ is gradually reduced by a vacuum pump or the like. First, a pressure difference is generated between the low-pressure side L ′ and the chamber 109a. First, when the pressure difference becomes a pressure difference greater than the pressure resistance capability of the magnetic fluid ML ′ existing in the stage portion corresponding to the ridge portion 108a, a break (pressure balancing phenomenon) occurs, and the low pressure side enters the adjacent chamber 109b. The pressure of L ′ is gradually transmitted to the chamber on the high pressure side H ′.
[0020]
Therefore, in a state where the low pressure side L ′ is completely evacuated, the pressure in each chamber (109a...) Of the magnetic pole member 105 changes stepwise, and approximately 1.. 0kgf / cm² It is possible to seal the low pressure side L 'while maintaining the pressure difference.
[0021]
In addition, when the sealing performance of the magnetic pole member 105 is reduced, the high-pressure side H ′ magnetic pole member 106 directly enters the container 102 and the vacuum level on the low-pressure side L ′ decreases. Can be prevented.
[0022]
[Problems to be solved by the invention]
In such a sealing device 100, when the magnetic fluid ML ′ is consumed and deteriorated with the operation of the device, the sealing performance cannot be maintained. Replenishment and replacement (maintenance of the sealing device) are performed.
[0023]
In particular, when used to seal the inside and outside of the container 102 where the inside is in a vacuum state as described above, or when used in an environment exposed to high temperatures, the deterioration of the magnetic fluid ML ′ is promoted and the inspection time is increased. Attention is paid to the frequency and the maintenance of the sealing device is performed to ensure sufficient safety.
[0024]
  Figure7These are the figures which showed typically the state of deterioration of magnetic fluid ML 'of the sealing device 100 used for the bearing part 103 of a vacuum chamber. In the figure, each of the magnetic pole members 105 and 106 has four stage portions, and the pressure resistance of each stage portion is 0.25 kgf / cm.²However, it is merely a simple configuration for schematically explaining the state of deterioration of the magnetic fluid ML ', and does not show an actual form. The numbers in parentheses indicate the atmospheric pressure (kgf / cm²) Is displayed.
[0025]
  When the magnetic fluid ML 'is used in a low pressure environment even at the same temperature, evaporation of volatile components is promoted.7(A) → (b) → (c) → (d), the deterioration proceeds from the low pressure side L ′.
[0026]
In this case, when the magnetic fluid ML ′ existing in the stage portion on the low pressure side L ′ of the magnetic pole member 105 deteriorates, a break occurs in the stage portion and the pressure resistance disappears, the stage portion related to maintaining the degree of vacuum. Is shifted to one high-pressure side H ′, and this is repeated in sequence, and the total pressure resistance capacity of each stage portion is 1.0 kgf / cm 2.² Below that, the magnetic fluid seal breaks (burst), making it impossible to maintain the degree of vacuum.
[0027]
  That is, in the sealing device 100, even with either one of the magnetic pole members 105 or 106, about 1.0 kgf / cm inside and outside (atmosphere side) the container 102.²It is possible to maintain a pressure difference of7Until the state of (c), the degree of vacuum inside the container 102 is set to a high degree of vacuum (10^-7Pa), but when the magnetic fluid ML ′ of the magnetic pole member 106 deteriorates (see FIG.7(D) state) The degree of vacuum cannot be maintained, and the total pressure resistance of the stage is 1.0 kgf / cm.²Less than, and a burst is generated, and the degree of vacuum is reduced at once.
[0028]
  Figure8The figure7State of magnetic fluid ML '7(A), (b), (c), and (d) are shown on the horizontal axis corresponding to the operating time. ) Corresponding to a decrease in the degree of vacuum inside the container 102 (indicated by the vertical axis as the atmospheric pressure in the figure).
[0029]
Operation start T of the sealing device 100₀ From the high pressure side H ′ to the low pressure side L ′, the high vacuum degree is maintained from the high pressure side H ′ to the low pressure side L ′. The pressure on the low pressure side L ′ rises discontinuously, and the inside of the container 102 is contaminated.
[0030]
  Therefore, considering the occurrence of problems due to the consumption and deterioration of such magnetic fluid, the maintenance of the sealing device is not recommended.8The operation time is managed so as to be performed at the timing of Tm at the timing of Tm ′ at the latest.
[0031]
However, Tm and Tm ′ can be experimentally obtained when the sealing device 100 is operated under specific conditions. However, when the sealing device 100 is operated under different conditions, the container 102 When the state of Tm and Tm ′ is reached earlier than the maintenance timing set by an internal chemical reaction or the like, a burst may occur during the operation of the sealing device 100.
[0032]
In order to prevent this, it is necessary to set the safety factor to be high and perform maintenance at a high frequency, resulting in a decrease in work efficiency and an increase in maintenance cost.
[0033]
  The present invention has been made to solve the above-described problems of the prior art.A sealing device that can cause pressure changes to detect the state of wear and deterioration of the magnetic fluid in the sealing device so that maintenance can be performed at an appropriate timing and seal breakage (burst) can be prevented. Is to provide.
[0034]
[Means for Solving the Problems]
  In order to achieve the above object, in the present invention, a plurality of stages are arranged in the axial direction in the annular gap between the shaft hole provided in the sealed container and the shaft inserted through the shaft hole, and the magnetic flux An annular stage portion through which the gas passes, a magnetic fluid held by the plurality of annular stage portions, and a pressure chamber formed between the plurality of annular stage portions by the magnetic fluid and arranged in at least one stage in the axial direction And a sealing device using a magnetic fluid that seals the annular gap while eliminating the pressure difference generated between the inside and the outside of the sealed container by the pressure chamber.An annular magnetic pole member having a fitting portion that fits into either the shaft hole portion or the shaft of the annular gap, and the side facing the fitting portion as the annular stage portion; and the fitting portion Sealing means provided on the sealing side, sealing means provided on the anti-sealing side of the fitting portion, the sealing means on the anti-sealing side having a lower sealing performance than the sealing means on the sealing side, and A vent path for communicating the fitting portion and the pressure chamber between the sealing means on the sealing side and the sealing means on the anti-sealing side, and the fitting portion, and the sealing means on the anti-sealing side, The ventilation path forms a ventilation means for allowing fluid to communicate from the pressure chamber to the outside of the apparatus, and the magnetic fluid is retained when the holding of the magnetic fluid from the sealed container to the pressure chamber is lost. The part where the retention of Via the gas means, fluid communication from the sealed container to the outside of the deviceIt is characterized by that.
[0035]
  According to this configuration, when the pressure chamber on the sealed side of the pressure chamber to which the ventilation means is connected is broken, a small amount of fluid can communicate with the inside of the sealed container through the ventilation means.The As a result, a pressure change that can detect that the pressure chamber on the sealed side relative to the pressure chamber to which the venting means of the sealing device is connected is detected is generated inside the sealed container.
[0037]
According to this configuration, when the pressure chamber on the sealed side of the pressure chamber to which the ventilation means is connected is broken, a small amount of fluid can communicate with the inside of the sealed container from the anti-sealing side sealing means via the ventilation path. Change the pressure inside the sealed container. By detecting the pressure change inside the sealed container, it is possible to detect that the pressure chamber on the sealed side of the pressure chamber connected to the venting means of the sealing device is damaged. Further, in a normal state where the pressure chamber is not damaged, the sealing means on the sealing side seals the fitting portion of the annular magnetic pole member, so that the pressure of the sealed container can be maintained.
[0038]
The annular magnetic pole member divided into two in the axial direction;
A magnetic force generating means disposed between the two annular magnetic pole members and generating a magnetic flux passing through the annular stage portion;
In the venting means, it is preferable that the pressure chamber to be connected is a region between the two annular magnetic pole members, and the ventilation path is a gap between the contact surfaces of the annular magnetic pole member and the magnetic force generating means.
[0039]
With this configuration, the ventilation path can be provided with a simple configuration.
[0040]
  Further, each of the two annular magnetic pole members can hold a pressure difference between the pressure inside the sealed container that is in a vacuum state and the atmospheric pressure, and the sealing means on the anti-sealing side includes:When the holding of the magnetic fluid from the sealed container to the pressure chamber is lostIn order to reduce the degree of vacuum inside the sealed container,BigIt is also suitable for communication.
[0041]
According to this configuration, even if the pressure chamber formed by the annular magnetic pole member on the sealed side is damaged, the pressure inside the sealed container that is in a vacuum state can be maintained by the annular magnetic pole member on the anti-sealed side. And when the pressure chamber formed by the annular magnetic pole member on the sealed side breaks, a very small amount of air communicates from the sealing means on the anti-sealed side to lower the degree of vacuum inside the sealed container. By detecting the pressure change inside the sealed container, the state of the sealing device can be detected.
[0042]
It is also preferable that the anti-sealing side sealing means has gas permeability.
[0043]
In order to allow a very small amount of air to communicate, the gas permeability of the sealing means can be used, and a desired pressure change can be generated by specifying the material and shape of the sealing means.
[0046]
DETAILED DESCRIPTION OF THE INVENTION
(Embodiment 1)
Hereinafter, the present invention will be described based on the first embodiment shown in the drawings. FIG. 1 is a cross-sectional view of a principal part of a sealing device 1 using a magnetic fluid, and FIG. 2 is an enlarged view of a portion D1 in FIG.
[0047]
The sealing device 1 is provided in a rotational driving force introduction portion VC1 of a rotary shaft 2 that transmits rotational power from the outside to the inside of a vacuum chamber VC that is in a vacuum state as a sealed container.
[0048]
During operation of the vacuum chamber VC, an internal vacuum is drawn by a vacuum pump or the like, so that the internal pressure is reduced to the vacuum side L, and there is a pressure difference with the atmospheric side H which is the high pressure side outside the vacuum chamber VC. Occur.
[0049]
Therefore, the sealing device 1 of this embodiment is configured to introduce rotational power into the vacuum chamber VC by the rotary shaft 2 while maintaining the degree of vacuum on the vacuum side L while separating the two regions having the pressure difference. It is provided in an annular gap 4 between the rotary shaft 2 and the shaft hole portion 3 through which the rotary shaft 2 is inserted.
[0050]
The shaft hole portion 3 includes a cylindrical portion 3a that holds and seals the rotary shaft 2, and a flange portion 3b that is attached to the rotational driving force introduction portion VC1 of the vacuum chamber VC at one end portion of the cylindrical portion 3a. .
[0051]
In the sealing device 1, the shaft hole portion 3 and the rotary shaft 2 are dynamically held against relative rotational motion by bearings 5a and 5b. The sealing performance is achieved by a magnetic fluid ML interposed in a magnetic circuit MC formed by a magnet 6 as a magnetic force generating means provided inside the cylindrical portion 3a of the shaft hole portion 3.
[0052]
The magnet 6 is provided with different polarities in the axial direction, and annular magnetic pole members 7a and 7b that are in contact with the magnet 6 and serve as magnetic poles are provided on both sides in the axial direction.
[0053]
The rotating shaft 2 has a plurality of (in this embodiment, five) annular ridges 8a, 8b,... That are continuous in the circumferential direction from the peripheral wall surface 2a to the magnetic pole members 7a, 7b. Are projecting and the outer peripheral surfaces of the ridges 8a, 8b,... Are stage portions 9a, 9b,.
[0054]
In the stage portions 9a, 9b,..., The magnetic flux of the magnetic circuit MC is converged and the magnetic fluid ML is held. Then, a plurality of pressure chambers PDa, PDb,..., PDf, PDg,... Are formed in the axial direction (in this embodiment, four stages for each of the magnetic pole members 7a and 7b). Note that the region between the magnetic pole members 7a and 7b is also regarded as the pressure chamber PDs.
[0055]
Reference numeral 10 denotes a spacer ring that keeps the gap between the magnetic pole member 7b and the bearing 5b, and 11 denotes a stationary ring member that seals and fixes each component member provided inside the cylindrical portion 3a.
[0056]
Reference numerals 12 and 13 denote O-rings as sealing means for maintaining the sealing performance between the outer peripheral surface side as the fitting portion of the magnetic pole members 7a and 7b and the inner peripheral surface side of the cylindrical portion 3a.
[0057]
Reference numeral 14 denotes a metal seal as a sealing means for sealing the axial end surface on the vacuum side L of the magnetic pole member 7 a and the thrust surface portion 3 c of the shaft hole portion 3.
[0058]
In FIG. 2, a gap G1 is described between the cylindrical portion 3a and the outer peripheral surface side as a fitting portion of the magnetic pole members 7a and 7b, but actually there is a large gap G1 as shown in this figure. It is not a thing, but the existence of a predetermined fitting allowance (clearance fit) is schematically expressed.
[0059]
Therefore, a minute gap G1 exists as a ventilation means in the fitting portion between the inner peripheral surface side of the cylindrical portion 3a and each component member loaded in the cylindrical portion 3a, but the O-rings 12 and 13 and the metal Sealed by a seal 14.
[0060]
Further, the gap G1 and the pressure chamber PDs communicate with each other using the gaps G2 and G3 formed by fine irregularities on the contact surface between the magnet 6 and the magnetic pole members 7a and 7b as ventilation paths.
[0061]
Here, the O-rings 12 and 13 are made of fluoro rubber, and the metal seal 14 employs a copper gasket. Therefore, the sealing performance by the O-ring 12 and the metal seal 14 provided on the magnetic pole member 7a side is superior to the sealing performance by the O-ring 13 alone of the magnetic pole member 7b.
[0062]
According to the sealing device 1 having such a configuration, the magnetic fluid ML held on all the stage portions of the magnetic pole members 7a and 7b is on the side of the peripheral wall 2a during normal operation in a state where no deterioration has occurred. Is sealed with magnetic fluid ML, and the gap G1 side is sealed with O-rings 12 and 13 and a metal seal 14.
[0063]
In a state where the magnetic fluid ML is not deteriorated, the degree of vacuum of the vacuum chamber VC is increased (10^-7-10^-9(About Pa)).
[0064]
When breakage occurs due to deterioration or evaporation of the magnetic fluid ML sequentially from the stage portion 9a on the vacuum side L as the operation time of the vacuum chamber VC elapses, the pressure chamber is sequentially damaged with the pressure chambers PDa, PDb,. I will do it.
[0065]
FIG. 2 shows a state where all the pressure chambers on the magnetic pole member 7a side are damaged. Since any one of the magnetic pole members 7a and 7b can maintain the pressure difference between the vacuum side L and the atmospheric side H, the pressure chamber of the magnetic pole member 7a is damaged as shown in FIG. Even in this case, the magnetic pole member 7b can maintain the sealing on the peripheral wall surface 2a side.
[0066]
However, in a state where the pressure chamber PDs and the vacuum side L communicate with each other, the sealing means for sealing the gap G1 is only the O-ring 13, and the air that has passed through the O-ring 13 passes through the gaps G2 and G3 to the vacuum side L. And invade. Then, the degree of vacuum inside the vacuum chamber VC is set to 10 at the normal time.^-7-10^-910 when the magnetic fluid deteriorates from (Pa)^-Five-10^-6(Pa).
[0067]
Therefore, it is possible to know the deterioration state of the sealing device 1 by detecting the timing when the degree of vacuum is reduced by about 1 to 3 digits by the vacuum gauge provided in the vacuum chamber VC. At this timing, maintenance and repair are possible. -By performing the replacement, it is possible to prevent seal breakage (burst) that greatly reduces the degree of vacuum of the vacuum chamber VC.
[0068]
In addition, the fall of a vacuum degree is reliably detectable by setting so that an alarm may be set when a vacuum gauge falls 1-2 digits from the vacuum degree at the time of normal operation.
[0069]
In addition, since the degree of vacuum reduction depends on the gas permeability of the O-ring 13, it is important to appropriately select and set the material, shape, surface treatment, etc. of the O-ring, which is a preferred form. Thus, it is possible to set the degree of vacuum reduction to a desired value.
[0070]
However, if the gas permeability of the O-ring 13 is too low or not at all (the airtight performance is good), the degree of vacuum of the vacuum chamber VC cannot be reduced by about 1 to 3 digits, and suddenly the seal breaks (burst ), So be careful.
[0071]
The material of the O-rings 12 and 13 may be butyl rubber or nitrile rubber in addition to fluorine rubber, but it is necessary to consider that the heat resistance and chemical resistance are inferior to fluorine rubber.
[0072]
Further, in this embodiment, the metal seal 14 exhibits a very high airtightness by receiving a predetermined thrust load, and is excellent in availability, ease of handling, mass productivity, reliability and economy. It was adopted.
[0073]
In addition, a metal O-ring formed of oxygen-free copper wire in a ring shape by pressure welding, a metal O-ring gasket with a built-in coil spring, Helicoflex (trade name of CEFILA), and a metal ring were used. A metal hollow O-ring whose surface is coated with a metal such as silver or nickel in order to enhance the sealing performance, and a C-seal (Eagle Industry Product name) can also be adopted as appropriate.
[0074]
(Embodiment 2)
FIG. 3 is a diagram for explaining the second embodiment. In the sealing device 21 of this embodiment, instead of the metal seal 14 of the first embodiment, an O-ring made of a rubber-like elastic material that is inferior in gas permeability (highly airtight) to the O-rings 12 and 13. 14B.
[0075]
Other configurations, operations, and effects are the same as those in the first embodiment, and thus description thereof is omitted.
[0076]
(Embodiment 3)
FIG. 4 is a diagram for explaining the third embodiment. In the sealing device 31 of this embodiment, the metal seal 14 for sealing the thrust surface portion on the vacuum side L of the magnetic pole member is removed from the first embodiment.
[0077]
  In this embodiment, the O-ring 12B is, MagnetismIn order to increase the degree of vacuum when the magnetic fluid ML is not deteriorated, use a more airtight one.The
[0078]
Other configurations, operations, and effects are the same as those in the first and second embodiments, and thus description thereof is omitted.
[0087]
【The invention's effect】
According to the sealing device using the magnetic fluid of the present invention described in the above embodiment, when the pressure chamber on the sealed side of the pressure chamber to which the ventilation means is connected is damaged, a small amount of fluid is passed through the ventilation means. It becomes possible to communicate with the inside of the sealed container, and the pressure inside the sealed container is changed. By detecting the pressure change inside the sealed container, it is possible to detect that the pressure chamber on the sealed side is damaged with respect to the pressure chamber to which the venting means of the sealing device is connected, and the magnetic fluid of the sealing device is consumed. It is possible to detect the state of deterioration and deterioration, and to prevent seal breakage (burst) by performing maintenance at an appropriate timing.
[0088]
According to the ventilation means including the ventilation path and the sealing means, a small amount of fluid can communicate with the inside of the sealed container from the anti-sealing side sealing means via the ventilation path, and the pressure inside the sealed container is changed. By detecting the pressure change inside the sealed container, it is possible to detect that the pressure chamber on the sealed side of the pressure chamber connected to the venting means of the sealing device is damaged. Further, in a normal state where the pressure chamber is not damaged, the sealing means on the sealing side seals the fitting portion of the annular magnetic pole member, so that the pressure of the sealed container can be maintained.
[0089]
By setting the ventilation path as a gap between the contact surface of the annular magnetic pole member and the magnetic force generating means, it is possible to provide the ventilation path with a simple configuration.
[0090]
Each of the two annular magnetic pole members can hold a pressure difference between the pressure inside the sealed container that is in a vacuum state and the atmospheric pressure, and the sealing means on the anti-sealing side can be used when the pressure chamber on the sealing side is damaged. Even if the pressure chamber formed by the annular magnetic pole member on the sealed side is damaged by passing a small amount of air to reduce the degree of vacuum inside the sealed container, the vacuum state is established by the annular magnetic pole member on the anti-sealed side. The pressure inside the sealed container can be maintained. And when the pressure chamber formed by the annular magnetic pole member on the sealed side breaks, a very small amount of air communicates from the sealing means on the anti-sealed side to lower the degree of vacuum inside the sealed container. By detecting the pressure change inside the sealed container, the state of the sealing device can be detected.
[0091]
In order to allow a very small amount of air to communicate, the gas permeability of the sealing means can be used, and a desired pressure change can be generated by specifying the material and shape of the sealing means.
[Brief description of the drawings]
FIG. 1 is a cross-sectional configuration explanatory view of a sealing device to which the present invention is applied.
FIG. 2 is an explanatory diagram of a cross-sectional configuration in the vicinity of a stage unit according to the first embodiment.
FIG. 3 is an explanatory diagram of a cross-sectional configuration in the vicinity of a stage unit according to a second embodiment.
FIG. 4 is an explanatory diagram of a cross-sectional configuration in the vicinity of a stage unit according to a third embodiment.
[Figure 5]FIG. 5 is a cross-sectional configuration explanatory diagram of a conventional sealing device and a diagram illustrating the strength of a magnetic field.
[Fig. 6]FIG. 6 is an enlarged view of a portion D101 in FIG.
[Fig. 7]FIG. 7 is a diagram for explaining a deteriorated state of the magnetic fluid.
[Fig. 8]FIG. 8 is a diagram showing the relationship between the deterioration state of the magnetic fluid and the degree of vacuum.
[Explanation of symbols]
1 Sealing device
2 Rotating shaft
2a Surrounding wall
3 Shaft hole
3a Cylindrical part
3b Flange part
3c Thrust surface
4 annular gap
5a, 5b Bearing
6 Magnet (magnetic force generation means)
7a, 7b Magnetic pole member
8a, 8b ridges
9a, 9b Stage part
10 Spacer ring
11 Fixed ring member
12, 13 O-ring (sealing means)
14 Metal seal (sealing means)
G1 gap
G2, G3 gap (ventilation path)
H Atmosphere side
L Vacuum side
MC magnetic circuit
ML Magnetic fluid
PDa, PDb ... PDs Pressure chamber
VC vacuum chamber (sealed container)
VC1 Rotation driving force introduction part

Claims (4)

In the annular gap between the shaft hole provided in the sealed container and the shaft inserted through the shaft hole,
A plurality of stages arranged in the axial direction, an annular stage part through which magnetic flux passes,
A magnetic fluid held by the plurality of annular stage portions;
A pressure chamber formed between the plurality of annular stage portions by the magnetic fluid and disposed at least one stage in the axial direction;
In a sealing device using a magnetic fluid that seals the annular gap while eliminating the pressure difference generated between the inside and the outside of the sealed container by the pressure chamber ,
Before SL has a fitting portion fitted to one of the axial hole part or axis of the annular gap, the annular magnetic pole member to the annular stage portion side facing the unit fits Me fitting,
Sealing means on the sealing side provided on the sealing side of the fitting portion;
Sealing means provided on the anti-sealing side of the fitting portion, the sealing means on the anti-sealing side having a lower sealing performance than the sealing means on the sealing side;
A ventilation path for communicating the fitting portion and the pressure chamber between the sealing means on the sealing side and the sealing means on the anti-sealing side, and
The fitting portion, the sealing means on the anti-sealing side, and the ventilation path form a ventilation means that allows fluid to communicate from the pressure chamber to the outside of the apparatus,
When the holding of the magnetic fluid from the sealed container to the pressure chamber is lost, the fluid communicates from the sealed container to the outside of the apparatus through the portion where the holding of the magnetic fluid is lost and the ventilation means. The sealing device using the magnetic fluid characterized by this. The annular magnetic pole member divided into two in the axial direction;
A magnetic force generating means disposed between the two annular magnetic pole members and generating a magnetic flux passing through the annular stage portion;
2. The ventilation means according to claim 1, wherein the pressure chamber to be connected is a region between two annular magnetic pole members, and the ventilation path is a gap between the contact surface of the annular magnetic pole member and the magnetic force generation means. A sealing device using the magnetic fluid described . The two annular magnetic pole members can hold a pressure difference between the pressure inside the sealed container and the atmospheric pressure, each of which is in a vacuum state,
Said sealing means opposite to the sealed side, to reduce the degree of vacuum inside of the sealed container when the holding of the magnetic fluid from the sealed container until the pressure chamber is blinking, characterized thereby communicate the atmosphere Sealing device using magnetic fluid. The sealing device using a magnetic fluid according to any one of claims 1 to 3, wherein the sealing means on the anti-sealing side has gas permeability .

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