JP2602065Y2 - Magnetic fluid sealing device - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic fluid sealing device for sealing various fluids (mainly gases) using a magnetic fluid, and more particularly to a magnetic fluid for sealing a fluid having a relatively high pressure such as a vacuum or gas. The present invention relates to a sealing device.

[0002]

2. Description of the Related Art Conventionally, as this type of magnetic fluid sealing device, for example, there is one as shown in FIG.

This magnetic fluid sealing device is a multi-stage magnetic fluid sealing device for sealing a fluid having a relatively high pressure such as vacuum gas or the like, and has an annular permanent magnet as an annular magnetic force source magnetized in the axial direction. 104 and a pair of annular magnetic pole pieces 10 provided in contact with both end faces of the annular permanent magnet 104.
2, a cylindrical housing 107 in which an annular permanent magnet 104 and a pair of annular magnetic pole pieces 102, 120 are fixed to the inner peripheral surface; and a pair of the annular magnetic pole pieces 102, 12
Shaft 101 that penetrates through the inner peripheral surface of the cylinder 0 through the minute gap 103
And a plurality (four in FIG. 9) of annular projections 106, 160 provided on the outer peripheral surface of the shaft 101 facing the inner peripheral surfaces of the pair of annular magnetic pole pieces 102, 120.
A, 160B, 160C, 160D and the annular projection 10
6,160 (A to D) and a magnetic fluid 105 interposed in the minute gap 103 between opposing surfaces of the pair of annular magnetic pole pieces 102 and 120 and inner peripheral surfaces thereof. .

[0004]

However, the conventional magnetic fluid sealing device described above has the following problems. That is, the annular projection 16 facing the inner peripheral surface of the annular magnetic pole piece 120 located on the low pressure side L (the right side in FIG. 9).
At 0 (A to D), as the annular projection 160A is closer to the annular permanent magnet 104, the distance of the line of magnetic force passing through the annular magnetic pole piece 120 becomes shorter, and the magnetic resistance in the annular magnetic pole piece 120 becomes smaller. As a result, the magnetic field in the minute gap 103 becomes large, and as a result, as shown by a black circle and a dotted line in FIG.
There is a problem in that the magnetic field in the minute gap 103 in the annular projection 160D adjacent to the low pressure side L is reduced, and the seal withstand pressure in this portion is reduced.

Therefore, when the partial pressure balance of the annular projections 106 and 160 (A to D) and the portion sealed by the magnetic fluid 105 is lost due to a change in pressure difference between the high pressure side H and the low pressure side L, the low pressure side Since the seal withstand pressure at the annular projection 160D adjacent to L is small, the seal breaks or leaks, and gas is released from the seal internal space to the low pressure side L and the magnetic fluid 105 scatters to the low pressure side L. There was a problem.

The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a magnetic fluid sealing device capable of preventing gas discharge to a low pressure side and scattering of a magnetic fluid. It is in.

[0007]

To achieve the above object SUMMARY OF THE INVENTION, in the present invention, between two members disposed can concentrically relative rotation to each other, the seal portion by the magnetic fluid in the axial direction 3 FOB provided, in the magnetic fluid seal device for sealing the second space with a pressure difference of the respective sealing portions
Other sealing portion of the magnetic resistance of at least one seal portion
Characterized in that the magnetic resistance is independently changed.

An annular magnetic source capable of being magnetized in the axial direction and a pair of annular magnetic pole pieces engaged with both end surfaces of the annular magnetic force source are provided on the inner peripheral side of the cylindrical housing. At least one of the outer peripheral surface of the shaft facing the inner peripheral surface of the pair of annular magnetic pole pieces or the inner peripheral surface side of the annular magnetic pole piece.
Three or more annular projections are provided, a magnetic fluid is interposed in a minute gap between the annular projections and the opposing surface to form a seal portion, and at least the magnetic portion of the seal portion facing the low pressure side of the seal portion Preferably, the resistance is smaller than the magnetic resistance of the other seals.

Further, an annular magnetic source capable of being magnetized in the axial direction and a pair of annular magnetic pole pieces engaged with both end surfaces of the annular magnetic force source are provided on the outer peripheral side of the shaft. Three or more annular projections are provided on at least one of the outer peripheral surface of the annular magnetic pole piece or the inner peripheral surface side of the cylindrical housing opposed to the outer peripheral surfaces of the pair of annular magnetic pole pieces, and the annular projection is opposed to the annular projection. A magnetic fluid may be interposed in the minute gap between the seals to form a seal part, and the magnetic resistance of the seal part facing at least the low pressure side of the seal part may be smaller than the magnetic resistance of the other seal parts. it can.

The magnetic resistance of the seal portion may be the magnetic resistance of the annular projection.

The magnetic resistance of the seal portion may be the magnetic resistance of the minute gap.

[0012]

In the magnetic fluid sealing device configured as described above, the magnetic resistance of each seal is changed so that the magnetic resistance of the seal facing the low pressure side can be made smaller than the magnetic resistance of the other seals.

By doing so, the magnetic flux flowing through the seal facing the low pressure side becomes larger than the magnetic flux flowing through the other seals.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiment.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention. This magnetic fluid sealing device is a multi-stage magnetic fluid sealing device for sealing a fluid having a relatively high pressure such as a vacuum or gas, and has an annular permanent magnet 4 as an axially magnetized annular magnetic force source. And a pair of annular magnetic pole pieces 2 and 20 provided in contact with both end surfaces of the annular permanent magnet 4, and a cylinder in which the annular permanent magnet 4 and the pair of annular magnetic pole pieces 2 and 20 are fixed to the inner peripheral surface. Housing 7 and the pair of annular magnetic pole pieces 2, 20
A shaft 1 penetrating through an inner peripheral surface of the pair of annular magnetic pole pieces 2 and 20 through a minute gap 3 and the shaft 1 facing an inner peripheral surface of the pair of annular magnetic pole pieces 2 and 20;
Annular projections 6, 60A, 60B, which are a plurality of (four in this embodiment, four on each side) seal portions provided on the outer peripheral surface side of
A magnetic fluid 5 interposed in the minute gap 3 between the outer peripheral surfaces of the annular projections 60 and 60 (A to D) and the inner peripheral surfaces of the pair of annular magnetic pole pieces 2 and 20; And annular projections 60 (A to D) facing the inner peripheral surface of the annular magnetic pole piece 20 located on the low pressure side L (the right side in this embodiment).
In the above, the width of the annular projections 60 (A to D) in the axial direction is set such that the distance from the annular permanent magnet 4 is short (for example, the annular projections 6).
0A).

In the magnetic fluid sealing device of this embodiment having the above-described configuration, the width of the annular projection 60A, which is shorter with respect to the annular permanent magnet 4, becomes narrower, so that the magnetic flux density inside the projection becomes supersaturated. The magnetic resistance becomes large, and the magnetic flux becomes difficult to flow.

Therefore, the amount of magnetic flux flowing through the annular projection 60D increases as the distance from the annular permanent magnet 4 increases, and the magnetic field in the minute gap 3 at that portion increases. As shown by a white circle and a solid line in FIG. As the distance from the annular permanent magnet 4 to the annular projection 60D increases, the seal withstand pressure increases.

Therefore, even if the partial pressure balance of the portions sealed by the annular projections 6, 60 (A to D) and the magnetic fluid 5 is lost due to a pressure change between the high pressure side H and the low pressure side L, the annular permanent Since the annular projection 60D furthest from the magnet 4 and adjacent to the low-pressure side L has a high sealing pressure, the annular projection 60 (A to C) having a lower sealing pressure inside (closer to the annular permanent magnet 4) than the annular projection 60D. ) Causes temporary seal breakage and leakage for partial pressure equilibrium, and the annular projection 60D adjacent to the low pressure side L
Does not cause seal breakage or leakage.

With such a configuration, it is possible to prevent the release of gas to the low pressure side L and the scattering of the magnetic fluid 5.

(Second Embodiment) Next, FIG. 2 shows a second embodiment of the present invention. This magnetic fluid sealing device chamfers both edge portions of the annular projections 61 (A to D) at the annular projections 61 (A to D) facing the inner peripheral surface of the annular magnetic pole piece 20 located on the low pressure side L. The amount of chamfer is increased as the distance from the ring-shaped permanent magnet 4 is reduced, so that the magnetic resistance is increased. Also, the annular projection 6 'facing the inner peripheral surface of the annular magnetic pole piece 2 located on the high voltage side H is chamfered to the same extent as the annular projection 61D adjacent to the low voltage side L.

As described above, when the edge portions at both ends of the annular projections 61 (A to D) are chamfered, each of the annular projections 6 ′, 61 (A
To D), the total seal pressure, which is the sum of the seal pressures, increases.

Other configurations and operations are the same as those of the first embodiment, and therefore, the same components will be denoted by the same reference numerals and description thereof will be omitted.

(Third Embodiment) Next, a third embodiment of the present invention is shown in FIG. In this magnetic fluid sealing device, in the annular projections 62 (A to D) opposed to the inner peripheral surface of the annular magnetic pole piece 20 located on the low pressure side L, the annular projection 62A with a shorter distance from the annular permanent magnet 4 The magnetic resistance is increased by increasing the height of the projection in the radial direction.

Since other constructions and operations are the same as those of the first and second embodiments, the same components are denoted by the same reference numerals and description thereof is omitted.

(Fourth Embodiment) Next, a fourth embodiment of the present invention is shown in FIG. This magnetic fluid sealing device is a combination of the above-described first to third embodiments, and has a circular projection 63 (A to D) facing the inner peripheral surface of the annular magnetic pole piece 20 located on the low pressure side L. The smaller the distance between the annular projection 63A and the annular permanent magnet 4, the narrower the width of the projection, the larger the amount of chamfering of both end edges, and the higher the height of the projection, thereby increasing the magnetic resistance. .

As described above, when several means for adjusting the magnetic resistance of the annular projections 63 (A to D) are combined, the magnetic resistance of the annular projection 63 A closest to the annular permanent magnet 4 and the most The difference between the magnetic resistance of the annular projection 63D and the magnetic resistance of the annular projection 63D is further increased, and the effect is further enhanced.

As means for increasing the magnetic resistance of the annular projection, there are various methods other than the above-mentioned means, such as a method of changing the material (magnetic characteristics) of the annular projection for each projection, and these are limited to these. However, various combinations thereof can be selected.

Further, in addition to changing the magnetic resistance of the annular projection, as shown in FIG. 5, the size of the minute gap 3 'is changed for each annular projection 63', that is, the distance from the annular permanent magnet 4 is changed. The smaller the annular projection 63'A, the smaller the gap 3 '.
It is even more effective to increase the magnetic resistance of the minute gap 3 'by increasing the size of the small gap 3'.

(Fifth Embodiment) Next, FIG. 6 shows a fifth embodiment of the present invention. In this magnetic fluid sealing device, the annular projections 64 (A to D) facing the inner peripheral surface of the annular magnetic pole piece 20 located on the low pressure side L are larger than the annular projection 64 D farthest from the annular permanent magnet 4. An annular projection 64 on the inner side (closer to the annular permanent magnet 4)
The widths of the projections (A to C) are reduced to have the same dimensions.

In the above-described first to fourth embodiments, the example has been described in which the magnetic resistance of the annular projection gradually increases as the distance from the annular permanent magnet 4 decreases.
At least the magnetic resistance at the annular projection position A closest to the annular permanent magnet 4 should be greater than the magnetic resistance at the annular projection position D farthest from the annular permanent magnet 4. The magnetic resistance of (A to C) may be the same value larger than the magnetic resistance of the annular projection 64D, and conversely, the magnetic resistance of the annular projections 64B and 64C may be the same value smaller than the magnetic resistance of the annular projection 64A. good.

Further, the present invention can be implemented in various modes without departing from the spirit of the present invention.

(Sixth Embodiment) Next, FIG. 7 shows a sixth embodiment of the present invention. This magnetic fluid sealing device is a magnetic fluid sealing device that can be used even when the high-pressure side H and the low-pressure side L are switched according to use conditions, and faces the inner peripheral surface of the annular magnetic pole piece 20 located on the low-pressure side L. An annular projection 6 "opposed to the annular projection 60 (A to D) and the inner peripheral surface of the annular magnetic pole piece 2 located on the high voltage side H.
In both (A 'to D'), the magnetic resistance is increased by reducing the width of the annular projections 6 "A 'and 60A as the distance to the annular permanent magnet 4 is short. As described above, when the high pressure side H and the low pressure side L are formed in a symmetrical structure, the high pressure side H and the low pressure side L are switched depending on the use conditions, and even when the pressure difference is reversed, the gas discharge to the low pressure side L and It is possible to prevent the magnetic fluid 5 from scattering.

While the embodiments of the present invention have been described based on the illustrated embodiments, the present invention is not limited to these embodiments.

For example, the number of annular projections provided on each side is four, but it is sufficient if there are at least two annular projections facing the inner peripheral surface of the annular magnetic pole piece 20 located at least on the low pressure side L. The number of annular projections facing the inner peripheral surface of the annular magnetic pole piece 2 located on the high voltage side H may be one.

Although the example in which the annular projection is provided on the outer peripheral surface side of the shaft 1 has been described, the annular projection may be provided on the inner peripheral surface side of the annular magnetic pole pieces 2 and 20, or may be provided on both. .

In the above embodiment, the annular magnetic pole pieces 2 and 20 are fixed to the inner peripheral surface of the housing 7 so as to form a small gap 3 between the inner peripheral surface of the annular magnetic pole pieces 2 and 20 and the outer peripheral surface of the shaft 1. Magnetic fluid 5
The annular magnetic pole pieces 2 and 20 are fixed to the outer peripheral surface of the shaft 1 as shown in FIG. An annular projection 60 ′ is formed on at least one of the inner peripheral surface sides of the housing 7 so as to interpose the opposed surface and the minute gap 3, and a magnetic fluid sealing device in which the magnetic fluid 5 is interposed in the minute gap 3 may be used. .

Furthermore, the holding force of the magnetic fluid 5 can be increased by shortening the distance from the annular permanent magnet 4 by using only one annular projection of the annular magnetic pole piece 20 on the low pressure side.

On the other hand, although an example is shown in which a permanent magnet is used as the annular magnetic force source, an electromagnet may be used, or a combination of both a permanent magnet and an electromagnet may be used.

[0039]

The present invention has the above-described structure and operation, and can change the magnetic resistance of each seal portion so that the magnetic resistance of the seal portion facing the low pressure side can be made smaller than the magnetic resistance of the other seal portions.

By doing so, the magnetic flux flowing through the seal portion facing the low pressure side becomes larger than the magnetic flux flowing through the other seal portions, and the magnetic fluid holding force is increased.

Accordingly, since the seal withstand pressure of the seal portion is increased, even if the partial pressure balance is lost, no breakage or leakage of the seal occurs at this portion, and gas discharge to the low pressure side and scattering of the magnetic fluid are prevented. can do.

[Brief description of the drawings]

FIG. 1 is a first embodiment of a magnetic fluid sealing device according to the present invention.
It is a longitudinal section showing an example.

FIG. 2 is a second embodiment of the magnetic fluid sealing device according to the present invention;
It is a longitudinal section showing an example.

FIG. 3 is a third embodiment of the magnetic fluid sealing device according to the present invention;
It is a longitudinal section showing an example.

FIG. 4 is a fourth embodiment of the magnetic fluid sealing device according to the present invention;
It is a longitudinal section showing an example.

FIG. 5 is a longitudinal sectional view showing another embodiment of the magnetic fluid sealing device according to the present invention.

FIG. 6 is a fifth embodiment of the magnetic fluid sealing device according to the present invention.
It is a longitudinal section showing an example.

FIG. 7 is a sixth embodiment of the magnetic fluid sealing device according to the present invention;
It is a longitudinal section showing an example.

FIG. 8 is a longitudinal sectional view showing another embodiment of the magnetic fluid sealing device according to the present invention.

FIG. 9 is a longitudinal sectional view showing a conventional magnetic fluid sealing device.

FIG. 10 is a graph showing seal pressure resistance characteristics of respective seal portions corresponding to a low-pressure side annular magnetic pole piece in a conventional magnetic fluid sealing device.

[Explanation of symbols]

L Low pressure side H High pressure side 1 axis 2,20 annular magnetic pole piece 3,3 'minute gap 4 annular permanent magnet (annular magnetic force source) 5 magnetic fluid 6,6', 6 ", 60,60 ', 61, 62, 63, 6
3 ', 64 Annular protrusion (seal part) 7 Cylindrical housing

Claims (5)

(57) [Scope of request for utility model registration] 1. Three axially sealed portions made of magnetic fluid are provided between two members provided concentrically and rotatably relative to each other.
The magnetic fluid sealing device provided above and sealing two spaces having a pressure difference, wherein a magnetic resistance of at least one of the seal portions is independent of a magnetic resistance of another seal portion. magnetic fluid seal device is characterized in that varied. 2. An annular magnetic source capable of being magnetized in the axial direction and a pair of annular magnetic pole pieces engaged with both end surfaces of the annular magnetic force source are provided on an inner peripheral side of the cylindrical housing. Three pieces are provided on at least one of the outer peripheral surface of the shaft facing the inner peripheral surface of the pair of annular magnetic pole pieces or the inner peripheral surface side of the annular magnetic pole piece.
The above annular projection is provided, a magnetic fluid is interposed in a minute gap between the annular projection and the opposing surface to form a seal portion, and at least the magnetic resistance of the seal portion facing the low pressure side of the seal portion is reduced. 2. The magnetic fluid sealing device according to claim 1, wherein the magnetic resistance is smaller than the magnetic resistance of the other seal portions. 3. An annular magnetic force source capable of being magnetized in the axial direction and a pair of annular magnetic pole pieces engaged with both end surfaces of the annular magnetic force source are provided on the outer peripheral side of the shaft, and the pair of circular magnetic force sources are provided. Three or more annular projections are provided on at least one of the outer peripheral surface of the annular magnetic pole piece or the inner peripheral surface side of the cylindrical housing opposed to the outer peripheral surfaces of the pair of annular magnetic pole pieces, and the annular projection is opposed to the annular projection. A magnetic fluid is interposed in the minute gap between the seal portions to form a seal portion, and at least the magnetic resistance of the seal portion facing the low pressure side of the seal portion is made smaller than the magnetic resistance of the other seal portions. The magnetic fluid sealing device according to claim 1, wherein: 4. The magnetic resistance of the seal portion is the magnetic resistance of the annular projection.
3. The magnetic fluid sealing device according to claim 1. 5. The magnetic fluid sealing device according to claim 2, wherein the magnetic resistance of the seal portion is a magnetic resistance of the minute gap.