JPS6216352B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a magnetic fluid seal that seals between a fixed shaft and a rotating body of a device having a rotating body that rotates around a fixed shaft.

Prior Art and Problems Conventionally, as shown in FIG. 1, this type of magnetic fluid seal has a fixed shaft 2 fixed to a housing 1, a permanent magnet 3 having a substantially cylindrical shape such as a complete cylinder or a polygon, and a permanent magnet 3 having a substantially cylindrical shape such as a complete cylinder or a polygon. The magnet 3 is clamped from both sides, and annular yokes (hereinafter abbreviated as yokes) 4a and 4b having an outer diameter larger than the outer diameter of the permanent magnet 3 are attached. Make it airtight with adhesive or an O-ring, and attach the yoke 4.
A rotating body 5 made of ferromagnetic material such as steel is inserted while maintaining a small gap between the outer circumferences of magnets a and 4b, and the permanent magnet 3→
Yoke 4a → rotating body 5 → yoke 4b → permanent magnet 3
By forming a magnetic circuit as shown in the figure and holding the magnetic fluids 6a and 6b filled in the minute gaps between the rotating body 5 and the yokes 4a and 4b, the rotating body 5 and the yokes 4a and 4b are It is designed to completely seal the gap between the two.

Since magnetic fluid is a colloidal solution in which magnetic powder is suspended in a solvent, the solvent evaporates and the sealing performance deteriorates after long-term use. Therefore, an impregnated material 7 impregnated with magnetic fluid and serving as a replenishing magnetic fluid holding member is disposed in the space formed between the outer periphery of the permanent magnet 3 and the side surfaces of the yokes 4a and 4b to provide a self-replenishing type. As the impregnating material 7, porous sintered metal, porous polymer material, felt, etc. are used.
Porous sintered metal is difficult to cut, and when assembled, it must be fixed to the yokes 4a and 4b by adhesive, resulting in poor workability and assembly.Furthermore, the bonded parts may peel off due to vibrations caused by rotation. It was hot. In addition, porous polymer materials have poor dimensional accuracy;
Moreover, when used for a long period of time, it has the disadvantage that there is a risk that it will swell and come into contact with the rotating body. Felt also had drawbacks such as poor dimensional accuracy and the fact that its fibers would separate and scatter into the surrounding area, causing contamination.
On the other hand, instead of a self-replenishing type using such an impregnating material, there is also a type that replenishes magnetic fluid from the outside, but this has drawbacks such as a complicated structure, high manufacturing costs, and the need for periodic maintenance. It was hot.

Purpose of the Invention The present invention has been made to improve the above-mentioned drawbacks.The purpose of the present invention is to make it possible to easily assemble a magnetic fluid holding member for replenishment, and to prevent material change and deterioration over a long period of time. The purpose is to prevent this from occurring. Examples will be described in detail below.

Embodiment of the Invention FIG. 2 is a perspective sectional view showing essential parts of an embodiment of the invention, in which 11 is a fixed shaft, 12 is a cylindrical magnet member, and 13a and 13b are in close contact with both sides of the magnet member 12. The magnet member 12 and the yokes 13a and 13b are fixed to the fixed shaft 11 through a back plate 14 or directly in a sealed state. Similarly to the one shown in FIG. 1, a rotating body made of a ferromagnetic material is inserted through the outer periphery of the yokes 13a and 13b through a minute gap, and this minute gap is filled with a magnetic fluid. 15 are yokes 13a, 13 on both sides
A ring-shaped elastic body as a replenishing magnetic fluid member installed in a space formed between b and the outer periphery of the magnet member 12, and is a band-shaped elastic body made of plastic (e.g., nylon) or metal (e.g., phosphor bronze, stainless steel). An elastic member such as the above is formed into a ring shape whose diameter is smaller than the outer diameter of the magnet member 12, and then attached. By stretching this annular elastic body 15, it can be easily incorporated into the outer periphery of the magnet member 12, and since the diameter of the ring is formed smaller than the outer diameter of the magnet member, it can be contracted even in the assembled state. The force acts to press the outer circumferential wall of the magnet member 12 and firmly fix it in a position along the outer circumferential wall.

The magnetic fluid covers the outer periphery of the magnet member 12 and the yoke 13.
When the space formed between the sides of the magnet members 12a and 13b is filled, the magnetic fluid flows between the outer periphery of the magnet member 12 and the annular elastic body 15 and each layer 15' of the annular elastic body 15 due to its surface tension. 15'', 15 and stays there. 16 is the annular elastic body 15
A large number of through holes 16 are provided, and since the magnetic fluid remains in these small holes 16, the amount of magnetic fluid that can be held increases. However, if the required amount of magnetic fluid can be obtained without providing the small holes 16,
The annular elastic body may be a smooth plate, and the number of layers may be appropriately selected. In order to wind the annular elastic body 15 in multiple layers, several annular elastic bodies may be laminated concentrically as shown in FIG. It may be laminated.

Although FIG. 2 shows an example in which a large number of small holes are provided on the annular elastic body 15 in order to increase the amount of magnetic fluid that can be held, these small holes are arranged as shown in FIG. It may be provided with a recessed hole 17, or may be provided with a through hole 18 as shown in FIG. Furthermore, as shown in FIG. 7, the annular elastic body 15 has grooves 19 arranged in the axial direction, as shown in FIG. As shown in the figure, a ring-shaped elastic body with a large number of small protrusions 21 is arranged, or as shown in Fig. 10, a ring-shaped elastic body 1
5 may be formed into a wave shape. Although several examples have been shown above, the shape of the unevenness for increasing the amount of magnetic fluid retained is not limited to the above examples.

The overall length and width of the ring-shaped elastic body formed from the band-shaped member shown in the above example can be easily and accurately processed by press working or etching, and its uneven shape can also be easily formed by the same means.

FIG. 11 is a perspective sectional view showing the main parts of another embodiment of the present invention, and 22 is a yoke 13a on both sides, 1
3b and the outer periphery of the magnet member 12, the annular elastic member is a linear elastic member made of plastic, metal, etc. whose diameter is smaller than the outer diameter of the magnet member 12. It was formed into a ring shape and then attached. Incidentally, the same reference numerals as in the other figures in FIG. 2 represent the same parts.

The annular elastic body 22 can be attached in substantially the same manner as the embodiment shown in FIG. 2, and is similarly fixed along the outer circumferential wall of the magnet member 12. When the magnetic fluid is filled in the space formed between the outer periphery of the magnet member 12 and the side surfaces of the yokes 13a and 13b, the magnetic fluid is caused to flow between the outer periphery of the magnet member 12 and the annular elastic body 22 due to its surface tension. It seeps into the space formed between the annular elastic bodies and the space formed between the annular elastic bodies, and stays there. Increasing the number of turns of the annular elastic body increases the amount of magnetic fluid that can be held. The number of turns may be appropriately selected depending on the required amount of retention. To wrap a ring-shaped elastic body in multiple layers, several ring-shaped elastic bodies may be laminated concentrically.
Alternatively, one wire rod may be laminated in a spiral manner.

Note that when the magnetic fluid held in the gap between the rotating body and the yokes 13a and 13b evaporates into the outside air,
The leakage magnetic flux in the gap increases, and the replenishment magnetic fluid held by the annular elastic body is drawn into the gap by the force of the magnetic lines of force, so that the magnetic fluid in the seal part evaporates. It can maintain perfect sealing performance for a long time.

Effects of the Invention As explained above, in the present invention, the replenishing magnetic fluid holding member is constituted by a ring-shaped elastic body formed using a band-shaped or linear elastic member.
The dimensional accuracy of the annular elastic body can be easily increased, and the annular elastic body can be extremely easily attached by simply extending the annular elastic body after assembling the magnet member and the yoke, so it is excellent in mass productivity. Furthermore, since it is firmly fixed to the outer circumferential wall of the magnet member by the spring force of the annular elastic body itself in the direction of contraction, it will not be deformed due to external disturbances. Therefore, there is an advantage that a highly accurate magnetic fluid seal can be manufactured easily.

[Brief explanation of the drawing]

Fig. 1 is a perspective sectional view of a conventional example, Fig. 2 is a perspective sectional view of an embodiment of the present invention, Figs. 3 and 4 are perspective views showing different ways of winding the annular elastic body, and Fig. 5. 10 are perspective views showing different shapes of annular elastic bodies, and FIG. 11 is a perspective sectional view of another embodiment of the present invention. 1 is a housing, 2 and 11 are fixed shafts, 3 is a permanent magnet, 4a, 4b, 13a, 13b are yokes, 5
is a rotating body, 6a and 6b are magnetic fluids, 7 is an impregnated material,
12 is a magnet member, 14 is a back plate, 15,
22 is an annular elastic body, 16 to 18 are holes, 19, 20
is a groove, and 21 is a protrusion.

Claims (1)

[Claims] 1. Annular yokes are disposed facing each other in contact with both ends of a magnet member fixed to the fixed shaft, and an inner wall is formed into a cylindrical shape with a minute gap interposed between the outer periphery of the annular yoke and the oppositely disposed annular yokes. A rotating body is disposed, the minute gap is sealed with a magnetic fluid, a replenishment magnetic fluid holding member is disposed in the space formed between the magnet member and the annular yoke, and the replenishment magnetic fluid is In the magnetic fluid seal configured such that the magnetic fluid held by the holding member is supplied to the minute gap, the replenishing magnetic fluid holding member includes a ring-shaped elastic member whose diameter is smaller than the outer diameter of the magnet member. A magnetic fluid seal characterized in that it is configured to be elastically deformed along the outer circumferential wall of a magnet member and fixed to the outer circumferential wall of the magnet member by the restoring force of the elastic member against the elastic deformation. 2. The magnetic fluid seal according to claim 1, wherein the elastic member is a linear member. 3. The magnetic fluid seal according to claim 1, wherein the elastic member is a band-shaped member. 4. The magnetic fluid seal according to claim 1, wherein the elastic member is a band-shaped member having an uneven surface.