JPH1089490A - Sealing device utilized with magnetic fluid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve sealing performance by performing the stable holding of a magnetic fluid in the tip end of a magnetic pole, and enhancing a pressure tightness characteristic in a sealing part of this magnetic fluid. SOLUTION: This sealing device 1 is constituted so as to utilize a magnetic fluid to be set up in an annular clearance 4 lying between a bearing part 3 (housing member) and a turning shaft 2. In this case, a position of a tip end 7b of a pole member 7 (first pole part) is set to the position being opposed to the other side peripheral wall surface 2a adjacent to a ring groove 8a formed in a second pole part 10, while a magnetic fluid ML is provided in space between an inner circumferetial wall surface 7a in and around the tip end 7b of this pole member 7 and the peripheral wall surface 2a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealing device using a magnetic fluid, and more particularly to a technique capable of stably holding a magnetic fluid, improving the pressure resistance of a magnetic fluid sealing portion, and improving sealing performance.

[0002]

2. Description of the Related Art Conventionally, a magnetic fluid having a characteristic of being able to maintain its position by magnetically attracting magnetic particles suspended in a fluid such as a surface active agent by a magnetic force of an external magnetic field is used. Various sealing devices are available.

FIG. 2 shows a sealing device 10 using a magnetic fluid.
0 is a cross-sectional configuration explanatory view, and the sealing device 100 is provided on a rotating shaft 101 and a bearing portion 103 of the rotating shaft 101 spanning two regions of a high pressure side H ′ and a low pressure side L ′ having a pressure difference. .

[0004] The bearing portion 103 has a cylindrical portion 103a for holding and sealing the rotary shaft 101, and an open end of the container 102 having an internal space in a vacuum state (low pressure side L ') at one end of the cylindrical portion 103a. A flange portion 103b is provided on the portion 102a with a bolt.

The bearing 103 and the rotating shaft 101 are dynamically held by a bearing B1, B2 with respect to a relative rotational movement.

[0006] With respect to the sealing performance, the magnetic fluid M interposed in a magnetic circuit MC 'formed by an annular magnet 104 provided inside the cylindrical portion 103a of the bearing portion 103.
L '.

The magnet 104 is provided with different poles (shown as N and S) in the axial direction, and the magnets 104 are provided on both sides in the axial direction.
Are provided. Then, a plurality of circumferentially continuous concave grooves 107 are formed in a portion of the rotating shaft 101 facing the magnetic pole members 105 and 106.
, 107b,...
6, convex ridges 108a, 108b,...
.. are generated such that the magnetic flux concentrates in the gaps with the top surfaces of the magnetic fluids (that is, the magnetic flux density increases on the top surfaces of the ridges 108a, 108b,...)
L ′ is held to form a magnetic fluid seal portion.

The formed magnetic fluid seal portion has a plurality of chambers 109a, 109 between the low pressure side L 'and the high pressure side H'.
By forming b,... and sequentially changing the pressure of each chamber within the pressure resistance range of the magnetic fluid seal portion, effective sealing performance can be exhibited even when there is a pressure difference on both sides of the sealed area. It has become.

Note that 110a and 110b are bearings B
1 and B2 between the magnet 104 and the magnetic pole members 105 and 10
6, a spacer ring 111 for determining the axial position; 111, a fixed ring member for sealing and fixing each component provided inside the cylindrical portion 103a; 112, 113, an inner peripheral surface of the cylindrical portion 103a and the magnetic pole member 105; An O-ring for maintaining the sealing property with respect to the outer peripheral surface side of 106.

[0010]

FIG. 3 shows a sealing device 10.
FIG. 3 is a diagram illustrating the strength of a magnetic field of 0, and an enlarged view of a portion D1 in FIG.
The distribution of the magnetic flux in the gap (the position shown by the line S1-S1) between them is schematically shown on the lower side as the strength of the magnetic field.

That is, the magnetic flux of the magnetic circuit MC 'formed by the magnet 104 is generated by the magnetic ridges 108a.
(All of the multiple ridges are applicable, but are listed as representatives.)
Since the magnetic flux is concentrated in the region, the magnetic flux is divided into a region having a large magnetic flux density and a region having a small magnetic flux density. Accordingly, the magnetic field strength 120a on the top surface of the ridge 108a is reduced by the concave grooves 107a on both sides thereof.
An extremely large difference Δf exists between the magnetic field strengths 121a and 121b at 107b.

The strength of the holding force for holding the magnetic fluid ML 'on the ridge 108a is the difference Δf of the strength of the magnetic field.
And the strength of the holding force is proportional to the pressure resistance performance of each magnetic fluid seal portion.

However, in the prior art, the axial positional relationship between the concave groove provided on the rotating shaft 101 and the ridge portion with respect to the magnetic pole member 105 is determined by the end portion 104 of the magnetic pole member 105.
a is inside the groove 107a at the end (the convex ridge 1).
08a side). Therefore, a small peak 122 was generated at a position facing the end 104a as the strength of the magnetic field.

In general, in order to stably hold the magnetic fluid, it is preferable to hold the magnetic fluid with as large a holding force as possible.
It is not used for holding L ′, and causes a loss of magnetic force, causing a decrease in the holding force of the magnetic fluid ML ′ at the protruding ridge 108 a at the end. The withstand voltage characteristics are reduced.

The peak 112 may exhibit an unintended behavior due to a small magnetic fluid holding force, in addition to the loss of magnetic force at the protruding ridge 108a at the end. This has been a cause of deterioration in characteristics and pressure fluctuation.

FIG. 4 illustrates this phenomenon. FIG. 4A shows a state in which no pressure difference is generated between the low-pressure side L 'and the high-pressure side H'. ',
The chambers 109a, 109b,..., High-pressure side H ′ are in the same atmospheric pressure state.

Next, for example, when the pressure on the low pressure side L 'is reduced by a vacuum pump or the like, the pressure on the high pressure side H' is constant at atmospheric pressure, but the pressure on the low pressure side L 'starts to decrease gradually. (State of FIG. 4B).

When the pressure difference between the pressure on the low pressure side L 'and the pressure in the chamber 109a exceeds the pressure resistance of the magnetic fluid ML' held in the gap between the ridge 108a and the magnetic pole member 105, a pressure balance called a burst occurs. And the low pressure side L '
And the chamber 109a are conducted, and the pressure difference is eliminated (the state of FIG. 4C). At this time, since the end portion 104a has a small magnetic fluid holding force, the magnetic fluid ML 'is moved to the low pressure side L'.
And the pressure resistance becomes smaller than other parts, or a part of the flowed magnetic fluid ML ′ stays at the end 104a, and the amount of the magnetic fluid ML ′ tends to decrease ( FIG. 4D).

This pressure equalization phenomenon occurs intermittently as the pressure on the low pressure side L 'decreases, and is gradually propagated to the chamber on the high pressure side H'. Therefore, the frequency of occurrence on the low-pressure side L 'is the highest, and pressure fluctuations and disturbances on the low-pressure side L' tend to occur frequently.

In Japanese Unexamined Patent Publication No. 1-220777, as a countermeasure against this problem, as shown in FIG.
Although the width of the concave groove 107a 'on the low-pressure side L' is widened for the purpose of reducing the magnitude of the magnetic field formed in 4a, even in this configuration, the small magnetic field peaks at the end 104a. 130 appear, and this small peak 13
The problem with 0 was still present, albeit to a lesser extent.

In order to reduce the small peak 130 of the magnetic field at the end 104a, as shown in FIG. 5B, even when chamfering 104b is performed, 131,
132, a small peak was generated, and the above problem was not solved.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art. It is an object of the present invention to increase the magnitude of a magnetic field in a portion for holding a magnetic fluid and to increase Is to prevent an unnecessary magnetic field from being formed in the vicinity of the magnetic fluid, stably hold the magnetic fluid, improve the pressure resistance of the magnetic fluid seal portion, and improve the sealing performance.

[0023]

In order to achieve the above object, according to the present invention, there is provided an annular gap between a housing member and a shaft inserted through the housing member and performing relative rotational movement. A magnetic force generating means for forming a magnetic field passing through the annular gap, an annular first magnetic pole portion protruding from one of the inner or outer peripheral wall surfaces of the annular gap, and the other peripheral wall surface of the annular gap, A second magnetic pole portion having a plurality of annular grooves provided to face the first magnetic pole portion, and a ridge having substantially the same height as the peripheral wall surface between the annular grooves; Between the first magnetic pole portion and the ridge of the second magnetic pole portion,
A magnetic fluid that is held by a magnetic field and seals the annular gap. In a sealing device using a magnetic fluid, the position of at least one end of the first magnetic pole portion is set to the second fluid.
At the position opposite to the other peripheral wall surface adjacent to the groove at the end of the annular groove formed at the magnetic pole portion, and the magnetic fluid is provided between the end portion of the first magnetic pole portion and the other peripheral wall surface. It is characterized by having.

According to the sealing device using the magnetic fluid, the magnetic fluid held by the magnetic field between the ridges of the first magnetic pole and the second magnetic pole forms the annular gap between the housing and the shaft. Since it is divided into a plurality of regions and sealed, the end of the first magnetic pole portion faces the other peripheral wall surface adjacent to the groove at the end of the annular groove formed in the second magnetic pole portion. 1
At the end of the magnetic pole portion, a magnetic field having the same strength as the magnetic field formed between the other first magnetic pole portion and the ridge portion of the second magnetic pole portion is formed, and the magnetic fluid is stably held. Is performed.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the illustrated embodiment. FIG. 1A is an explanatory diagram of a cross-sectional configuration of a sealing device 1 using a magnetic fluid, and shows characteristic components of the present invention.

This sealing device 1 is provided, for example, in a rotary motion introducing portion of a rotary shaft 2 for transmitting rotary power from the outside to the inside of a vacuum chamber for making the inside a vacuum.
The rotary shaft 2 extending between two regions of the low-pressure side L and the high-pressure side H having a pressure difference is provided in an annular gap 4 between the bearing portions 3 as a housing member through which the rotary shaft 2 is inserted.

The bearing portion 3 includes a cylindrical portion 3a for holding and sealing the rotating shaft 2 and a container (not shown) provided at one end of the cylindrical portion 3a with an internal space in a vacuum state (low pressure side L). It has a flange 3b attached to the opening end.

In the sealing device 1, the bearing 3 and the rotating shaft 2
The dynamic holding of the relative rotational movement is performed by the bearing 5 (only one side is shown). The sealing is performed by a magnetic fluid ML interposed in a magnetic circuit MC formed by an annular magnet 6 as a magnetic force generating means provided inside the cylindrical portion 3a of the bearing portion 3.

The magnet 6 is provided with different poles (shown as N and S) in the axial direction, and a magnetic pole member 7 as a first magnetic pole portion which contacts the magnet 6 and becomes a magnetic pole on both sides in the axial direction. (Only one side is shown). On the rotating shaft 2,
A plurality of circumferentially continuous concave grooves 8a to 8d are formed in a portion of the peripheral wall surface 2a facing the magnetic pole member 7.

The protruding ridges 9a to 9d having substantially the same height as the height of the peripheral wall surface 2a are formed between the concave grooves, and the concave grooves 8a to 8d and the protruding ridges 9a to 9d are formed in the second Function as the magnetic pole portion 10.

The end 7b of the magnetic pole member 7 on the low pressure side L in the axial direction is connected to the end 2c of the peripheral wall surface 2a of the rotary shaft 2 adjacent to the concave groove 8a located at the end in the low pressure side L direction. They are located to overlap. The end 2c also functions as a part of the second magnetic pole 10.

Accordingly, between the top surfaces of the ridges 9a to 9d and the inner peripheral wall surface 7a of the first magnetic pole member 7, and the inner periphery near the end 2c and the end 7b of the first magnetic pole member 7. The magnetic fluid ML is held between the magnetic fluid ML and the wall surface 7a, and forms a magnetic fluid seal portion (as an aggregate of the magnetic fluid ML).

The formed magnetic fluid seal portion is connected to the low pressure side L
And a plurality of chambers 11a to 11d are formed between
By sequentially changing the pressure of each chamber within the pressure-resistant range of the magnetic fluid seal portion, effective sealing can be exhibited even when there is a pressure difference on both sides of the sealed area.

Reference numeral 12 denotes a spacer ring that determines the axial position of the magnet 6 and the magnetic pole member 7, and 13 denotes an O-ring that maintains the sealing between the inner peripheral surface of the cylindrical portion 3a and the outer peripheral surface of the magnetic pole member 7. is there.

FIG. 1B is a diagram for explaining the strength of the magnetic field in the magnetic fluid seal portion of the sealing device 1, and shows the gap (S 2 -S 2) between the magnetic pole member 7 and the second magnetic pole portion 10 of the rotating shaft 2. The distribution of the magnetic flux at the position indicated by the line) is schematically represented as the strength of the magnetic field.

That is, the magnetic flux of the magnetic circuit MC formed by the magnet 6 concentrates on the ridges 9a to 9d and the end 2c. It is divided into low density areas.

The strength of the magnetic field at the end 2c is represented by a peak 21, and the strength of the magnetic field at the ridges 9a to 9d is 2
In addition to showing the same strength as 2a to 22d, the small peak of the unnecessary magnetic field at the end of the magnetic pole member generated in the prior art is not generated in the rising portion 21a of the peak 21.

Accordingly, the strength of the magnetic field at the end portion 7b is not reduced, and the magnetic fluid ML is stably held in this region. As a result, the pressure resistance of the magnetic fluid seal portion is increased, and the sealing performance is improved. I do.

In order to confirm the effect of the present invention, an effect confirmation test was conducted in the following specific examples. As a test object,
The arrangement of the magnetic pole members is as shown in FIG. 1, the diameter of the magnetic pole portion of the shaft is 15 mm, and the number of the ridges is 20. A withstand voltage characteristic of a conventional sample having the arrangement shown in FIG. 2 was tested.

As a result of the test, the sample according to the prior art exhibited a withstand voltage of 2.7 kgf / cm ² , while the sample to which the present invention was applied exhibited a withstand voltage of 3.0 kgf / cm ² , The effect was confirmed.

[0041]

According to the sealing device using the magnetic fluid of the present invention described in the above embodiment, even at the end of the magnetic pole holding the magnetic fluid, the magnetic field is equal to the magnetic field formed at other than the end. A strong magnetic field is formed, and an unnecessary magnetic field is prevented from being formed near the portion where the magnetic fluid is held.

Accordingly, the magnetic fluid is stably held, the pressure resistance is improved, and the sealing performance is improved.

[Brief description of the drawings]

FIG. 1A is a cross-sectional configuration diagram of a sealing device to which the present invention is applied, and FIG. 1B is a diagram illustrating the strength of a magnetic field in a magnetic fluid seal portion.

FIG. 2 is an explanatory view of a cross-sectional configuration of a conventional sealing device.

FIG. 3 is a diagram illustrating a cross-sectional configuration of a conventional sealing device and a diagram illustrating the strength of a magnetic field.

FIG. 4 is a diagram illustrating a pressure balancing phenomenon when a pressure exceeding the pressure resistance characteristic is applied.

FIG. 5 is an explanatory view of a sectional configuration of a sealing device according to another conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sealing device 2 Rotating shaft 2a Peripheral wall surface 2c End part 3 Bearing part (housing member) 4 Annular clearance 5 Bearing 6 Magnet (magnetic force generating means) 7 Magnetic pole member (first magnetic pole part) 7a Inner peripheral wall surface 7b End part 8a, 8b, 8c, 8d Grooves 9a, 9b, 9c, 9d Convex ridges 10 Second magnetic poles 11a, 11b, 11c, 11d Chamber 12 Spacer ring 13 O-ring 21 Mountain (magnetic field strength) 21a Rising portion 22a 22b, 22c, 22d Magnetic field strength

Claims (1)

[Claims] 1. A magnetic force generating means disposed in an annular gap between a housing member and a shaft inserted through the housing member and performing relative rotational movement, the magnetic force generating means forming a magnetic field passing through the annular gap; An annular first magnetic pole portion protruding from one peripheral wall surface inside or outside the gap; and a plurality of annular grooves provided on the other peripheral wall surface of the annular gap so as to face the first magnetic pole portion And a second magnetic pole portion having between the annular grooves a convex ridge having substantially the same height as the other peripheral wall surface; and between the first magnetic pole portion and the convex ridge portion of the second magnetic pole portion. A magnetic fluid that is held by a magnetic field and seals the annular gap. A sealing device using a magnetic fluid, comprising: forming a position of at least one end of the first magnetic pole portion on the second magnetic pole portion. Facing the other peripheral wall surface adjacent to the groove at the end of the formed annular groove. A sealing device using a magnetic fluid, wherein the magnetic fluid is provided between an end of the first magnetic pole portion and the other peripheral wall surface.