JPH0472109B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a magnetic fluid sealing device for sealing a gap between two members that are combined concentrically with each other to perform relative rotation or relative axial movement. Dust seals for computer magnetic disk drives,
The present invention relates to a magnetic fluid sealing device suitable for use in vacuum sealing of various vacuum devices.

(Prior Art) As a conventional magnetic fluid seal device, one illustrated in FIG. 5 is known.

The magnetic fluid sealing device shown in the figure includes a housing 6 concentrically combined with a shaft 1, a magnetic force source 2 made of an annular permanent magnet, and a minute gap 4 disposed on both sides of the magnetic force source 2 between the housing 6 and the shaft 1. The structure is such that the magnetic fluid 5 is held in a minute gap 4 and sealed by a magnetic circuit formed in the shaft 1 and the magnetic pole piece 3 by the magnetic force source 2.

(Problems to be Solved by the Invention) In the assembly process of the magnetic fluid seal device described above, it is difficult to inject the magnetic fluid 5 into the minute gap 4 after the shaft 1 is inserted. First, as shown by the two-dot chain line in the figure, the magnetic fluid is held in the space formed between the magnetic force source 2 and both magnetic pole pieces 3, and the shaft 1 is inserted. Accordingly, a method is used in which the magnetic fluid 5 is attracted into the minute gap 4 by a magnetic circuit formed in the magnetic pole piece 3 and the shaft 1.

In the above assembly method, the attraction of the magnetic fluid into the minute gap 4 occurs simultaneously with the insertion of the shaft 1, and the magnetic fluid 5 adheres to the circumferential surface of the shaft 1, but the magnetic fluid has extremely good wettability. Therefore, as the shaft 1 moves, a part of it flows out from the minute gap 4.
Since the magnetic fluid that flows out does not contribute to the sealing function at all, it is necessary to inject extra magnetic fluid in advance to ensure the desired sealing performance, but the amount of magnetic fluid that flows out depends on the type of magnetic fluid 5, Since it depends on various conditions such as the surface quality of the shaft 1, the distance and speed of movement, and the magnetic force, it is difficult to predict the amount of outflow, and large variations cannot be avoided.

On the other hand, the amount of magnetic fluid 5 held in the minute gap 4 has a large effect on sealing performance. That is,
If the amount of adhesion is small, the seal performance will be kept low and the seal life will be shortened, and if the amount of adhesion is too large, part of the magnetic fluid 5 will be scattered due to the centrifugal force caused by the rotation of the shaft 1 and the pressure difference on both sides in the axial direction. There is a risk of contaminating the surrounding area.

Therefore, in the magnetic fluid sealing device according to the above-mentioned conventional technology, variations in sealing performance are unavoidable, and if the spilled magnetic fluid is left unattended, it will further scatter and contaminate the surrounding area, so it must be wiped off and cleaned. However, reusing the magnetic fluid that has been wiped off is difficult due to problems with recovery methods, cleanliness, etc., and there is a problem in that the expensive magnetic fluid is wasted.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and provide a magnetic fluid sealing device that does not waste magnetic fluid and exhibits consistent and good sealing performance.

(Means for Solving the Problems) In view of the problems in the magnetic fluid seal devices according to the above-mentioned conventional technology, the present invention has been developed by molding a shape memory polymer into a substantially snake-eye shape and keeping the inner part at room temperature. The reservoir body, which has been bent and deformed by After insertion, each reservoir is heated to return to its original shape, and each reservoir is opened to attract the magnetic fluid within each reservoir into the minute gap between the respective pole piece and shaft. , constitutes a magnetic fluid seal device.

(Function) In the magnetic fluid seal device described above, the magnetic fluid seal device is formed into a substantially snake-eye shape using a shape memory polymer.
After being bent and deformed at room temperature, each storage chamber is attached to the side of each magnetic pole piece to form a storage chamber between each magnetic pole piece, and the magnetic fluid injected into the storage chamber prior to insertion of the shaft is It is held when the shaft is inserted, and returns to its original shape by heating after the shaft is inserted, opening the storage chamber and causing magnetic fluid to be attracted to the microgap side.

(Embodiment) In the embodiment shown in FIG. 1, polynorbornene, which is a shape memory polymer, is contained in the annular cavity formed by the magnetic pole piece 3 and the magnetic force source 2, which are arranged with the magnetic force source 2 in between. A reservoir body 7 is formed into an annular body having a cylindrical part and two radial parts, and each radial part is bent and deformed back to back. The magnetic fluid 5 is held within the reservoir chamber 8 .

After insertion of the shaft 1, which is indicated by a dashed double-dashed line in FIG. As shown in FIG. 2, when the reservoir body 7 is heated to a temperature of The magnetic fluid 5 held within the magnet 8 is attracted to the minute gap 4 between the shaft 1 and the magnetic pole piece 3, thereby exhibiting a sealing function.

In the embodiment shown in FIG. 3, a plurality of sets of seal units each having a reservoir 7 made of a shape memory polymer arranged in the same manner as in the embodiment shown in FIG. Spacer 9 made of
By arranging the magnetic fluid 5 on both sides, a multi-stage magnetic fluid sealing device is formed, thereby eliminating variations in the amount of magnetic fluid 5 in the minute gap 4 of each seal unit.

In the embodiment shown in FIG. 4, a reservoir 7 made of a shape memory polymer is placed outside the pole piece 3.

(Effects of the Invention) As described above, the magnetic fluid sealing device of the present invention is provided by attaching a bendingly deformed reservoir made of a shape memory polymer to the sides of each magnetic pole piece sandwiching a magnetic force source. A storage chamber is formed between the magnetic pole pieces, and the shaft is inserted with the magnetic fluid held in each storage chamber.By heating and opening the storage chamber, the magnetic fluid in the storage chamber is released between the shaft and the magnetic pole piece. By having a structure that attracts the magnetic fluid into the minute gaps between the magnetic pole pieces, the magnetic fluid does not adhere to the shaft circumferential surface and flow out when the shaft is inserted, and furthermore, the magnetic fluid is drawn into each minute gap by heating. Since the amount of attraction to the magnetic fluid is equalized, variations in sealing performance that were unavoidable in conventional magnetic fluid sealing devices are prevented.

[Brief explanation of the drawing]

1 and 2 are longitudinal cross-sectional views of one embodiment of the present invention, with FIG. 1 showing the state before the shaft is inserted, and FIG.
The figure shows the state after the shaft is inserted, and FIGS. 3 and 4 are longitudinal cross-sectional views of other embodiments of the present invention, respectively.
FIG. 5 is a longitudinal sectional view of a magnetic fluid seal device according to the prior art. 1... Axis, 2... Magnetic force source, 3... Magnetic pole piece, 4...
...Minute gap, 5...Magnetic fluid, 6...Housing, 7...Reservoir, 8...Reservoir, 9...Spacer.

Claims (1)

[Claims] 1. A shaft 1, a plurality of annular magnetic pole pieces 3 which are held in a housing 6 that is coaxially assembled with the shaft 1 and move relative to the shaft 1, and oppose the shaft 1 through a minute gap 4; A magnetic fluid sealing device comprising a magnetic force source 2 for forming a magnetic circuit between the shaft 1 and the magnetic pole piece 3, and a magnetic fluid 5 located within the micro space 4, which is made of a shape memory polymer and has a diameter. The storage body 7, whose inner part is bent and deformed, is attached to the side surface of each magnetic pole piece 3, and the magnetic pole piece 3 is
A storage chamber 8 is formed between the storage chambers 8 , and the shaft 1 is inserted with the magnetic fluid 5 held in each storage chamber 8 , and heated to open the storage body 7 .
A magnetic fluid sealing device in which a magnetic fluid 5 inside is moved into each minute space 4 inside each magnetic pole piece 3.