JPH07305778A - Magnetic fluid seal device - Google Patents

Abstract

PURPOSE:To prevent outflow and flying of magnetic fluid to the outer peripheral side owing to rotation of a rotary shaft and to reduce the occurrence of a problem on contamination of surroundings. CONSTITUTION:A barrier 10 protruded further outward from the outer surface of a pole piece is formed on a pole piece 1 and a magnetic fluid holding surface 12 is formed in a portion extending from the tip surface 4 of the pole piece 1 through the outer surface to the barrier 10. Magnetic fluid 7 is held between the tip surface 4 of the pole piece 1 and a magnetic body 6. The barrier 10 is formed of a material with which the contact angle of the magnetic fluid 7 is higher than that of the magnetic fluid with the pole pieces 1 and 2, and this constitution prevents outflow and flying of the magnetic fluid 7 to surroundings. Further, a prevention effect is ensured by forming a stepped part 13 at the vicinity of the barrier 10.

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 used in a hard disk drive or the like.

[0002]

2. Description of the Related Art Conventionally, a magnetic fluid sealing device has been constructed as shown in FIG. That is, as shown in FIG. 9, a donut-shaped disc magnet 22 having an inner diameter larger than that of the pair of pole pieces 21, 21 formed of a magnetic material having a donut-shaped disc shape is provided between the inner side faces. After sandwiching,
The periphery of these is fixed to the housing 25, the rotary shaft 24 made of a magnetic material is inserted into the central hole, and the rotary shaft 2
The magnetic fluid 26 is held by the magnetic circuit formed by the magnet 22 in the gap between the pole piece 4 and the tip surfaces 23, 23 of the pole pieces 21, 21 facing each other.

[0003]

However, in the above magnetic fluid sealing device, the magnetic fluid 26 is scattered outward by the relative rotation of the rotary shaft 24 at a high speed, and the magnetic fluid 26 is dispersed.
And the magnetic fluid 26 flows out onto the outer surfaces of the pole pieces 21 and contaminates the surroundings.

The present invention has been made to solve the above-mentioned conventional drawbacks, and an object thereof is to prevent the magnetic fluid from scattering to the surroundings, thereby preventing contamination of the surroundings and improving the life. Another object is to provide a magnetic fluid seal device capable of

[0005]

Therefore, in the magnetic fluid sealing device according to the first aspect, the magnet 3 is sandwiched between the inner side surfaces of the pair of plate-shaped pole pieces 1 and 2, and the tip end surface 4 of the pole piece 1 is fixed. In a magnetic fluid sealing device in which a magnetic fluid 7 is held between the pole piece 1 and the magnetic body 6 by a magnetic circuit formed by the magnet 3 so as to face the magnetic body 6, the pole piece 1 has It is characterized in that the barrier 10 is formed so as to project further outward from the outer side surface.

The magnetic fluid sealing device according to a second aspect is characterized in that the barrier 10 is made of a material having a larger contact angle with the magnetic fluid 7 than that of the pole piece 1.

Further, the magnetic fluid sealing device according to claim 3 is
A bent portion is formed in the pole piece 1 in the vicinity of the barrier 10, and at this bent portion, the tip surface 4 side of the pole piece 1 is bent inward. .

The magnetic fluid sealing device according to a fourth aspect of the invention is characterized in that the bent portion is formed as a step portion 13, and the barrier 10 is formed in the vicinity of the step portion 13.

According to another aspect of the magnetic fluid sealing device of the present invention, a step portion 13 is formed on the pole piece 1, and the tip surface 4 side of the pole piece 1 of the step portion 13 is closer to the base end surface side of the pole piece 1. It is characterized in that it is inward and the surface of the stepped portion 13 facing the magnetic body 6 is the barrier 10.

The magnetic fluid sealing device according to claim 6 is characterized in that the angle formed by the barrier 10 and the outer surface of the pole piece 1 is an acute angle.

The magnetic fluid sealing device according to claim 7 is characterized in that the pole piece 1 is provided with a cover 14 for covering the magnetic fluid 7 held therein.

[0012]

In the magnetic fluid sealing device according to the first aspect, the barrier 10 can prevent the magnetic fluid 7 from flowing out and scattering.

Further, in the magnetic fluid sealing device of claim 2,
Since the barrier 10 is made of a material having a large oil repellency with respect to the magnetic fluid 7, a reliable outflow prevention effect can be obtained.

Furthermore, in the magnetic fluid sealing device of the third and fourth aspects, since the pole piece 1 is provided with the bent portion and the stepped portion 13, the outflow preventing effect can be further enhanced.

In the magnetic fluid sealing device of the fifth aspect, since the pole piece 1 is provided with the stepped portion 13 and the stepped portion 13 is used as a barrier, the magnetic fluid 7 is prevented from flowing out, but the structure thereof is changed. It can be simplified.

In the magnetic fluid seal device according to the sixth aspect, the magnetic fluid 7 is less likely to protrude outward from the barrier 10 and the outflow diffusion can be prevented.

In the magnetic fluid sealing device of the seventh aspect, even if the magnetic fluid 7 tries to scatter to the outside of the pole piece 1,
The cover 12 can prevent scattering.

[0018]

EXAMPLES Specific examples of the magnetic fluid seal device of the present invention will now be described in detail with reference to the drawings. The following examples show preferred structures for application to a hard disk drive device. ing.

In the first embodiment of FIG. 1, a donut-shaped disc having a larger inner diameter than the inner surface of a pair of pole pieces 1 and 2 formed of a magnetic material having a donut-shaped disc shape. The magnet 3 is sandwiched so that the centers of these holes overlap with each other, and the periphery thereof is fixed to the housing 8. And the rotating shaft 6 made of a magnetic material in the central hole
And insert the tip of the pole pieces 1, 2
To face the rotating shaft 6.

In the above description, a protrusion 9 having a semicircular cross section is formed in a ring shape on the outer surface of one pole piece 1 at a position facing the inner end of the magnet 3. Here, the protrusion 9 is the magnetic fluid 7
The contact angle is larger than that of the pole piece 1. Examples of the forming material thereof include an ultraviolet curing (deformable acrylate) adhesive, an adhesive such as an epoxy adhesive, a thermoplastic resin such as nylon, and a metal. Further, as a method of forming the protrusions 9, in the case of the above-mentioned adhesive, application by screen printing, and in the case of a thermoplastic resin, adhesion by ultrasonic fusion or the like is used.

In the above structure, the surface of the projection 9 facing the rotating shaft 6 serves as a barrier 10 for the magnetic fluid 7.
The tip surface 4 of the pole piece 1, the outer surface 11 of the pole piece 1 from the outer end of the tip surface 4 to the projection 9, and the barrier 10 form a magnetic fluid holding surface 12. Magnetic fluids 7, 7 are filled between the tip surfaces 4, 5 of the pole pieces 1, 2 and the rotary shaft 6. Here, the magnet 3 is magnetized in the axial direction like N and S shown in FIG. 1, and the magnet 3 and both pole pieces 1 and 2,
A magnetic circuit is formed with the rotating shaft 6, and the filled magnetic fluid 7 is held.

Since the protrusion 9 is made of a material having a larger contact angle with the magnetic fluid 7 than the pole piece 1, the oil repellency with respect to the magnetic fluid 7 is large on the surface of the barrier 10. Therefore, even if the magnetic fluid 7 gets over the barrier 10 and tries to flow out and diffuse on the outer surface of the pole piece 1 toward the base end side, it is difficult to get over the barrier 10 and the outflow and diffusion hardly occur, so that the surrounding pollution is prevented. At the same time, it is possible to prevent a decrease in life due to a decrease in the amount of the magnetic fluid 7 retained.

Next, other embodiments will be described below. The basic structure of these is the same as that of the first embodiment, and the barrier forming material and method are also the same. Therefore, in the drawings used for these explanations, the same components as those in the first embodiment are designated by the same reference numerals and the description thereof is omitted.

In the second embodiment shown in FIG. 2, in the pole piece 1, a bent portion is formed by bending a portion of the pole piece 1 closer to the rotary shaft 6 inwardly. In this embodiment, similarly to the above, the magnetic fluid holding surface 12 is formed by the tip surface 4, the outer surface 11 and the barrier 10 of the pole piece 1. According to this embodiment, the magnetic fluid 7 can be surely prevented from flowing out and scattering due to the bent portion.

In the third embodiment shown in FIG. 3, a projection 9 having a rectangular cross section is formed on the outer surface of the pole piece 1, and the surface of the projection 9 facing the rotating shaft 6 is the barrier 10. Then, the portion of the pole piece 1 closer to the rotary shaft 6 than the projection 9 is first bent inward at a right angle along the end surface of the magnet 3, and then the end surface 4 side thereof is parallel to the other pole piece 2. Bend at a right angle to form the stepped portion 13. Here, the step portion 13 is formed so that the surface of the step portion 13 facing the rotating shaft 6 is continuous with the barrier 10. In this structure, the basic structure is the same as that of the second embodiment, and the only difference is that the bent portion is formed as the step portion 13. Also in this embodiment, the magnetic fluid holding surface 12 is formed by the tip surface 4, the outer surface 11 and the barrier 10 of the pole piece 1.
Is formed. Further, in this embodiment, the outflow / scattering prevention effect in the second embodiment can be made more reliable.

In the fourth embodiment of FIG. 4, instead of the projection 9 on the pole piece 1 having the step portion 13 of FIG. 3, the projection 9 of FIG. 3 is formed on the surface of the step portion 13 facing the rotary shaft 6. The barrier 10 is made of the same material as the above. In this embodiment, the tip surface 4 and the tip outer surface 11 of the pole piece 1 are used.
And the barrier 10 form the magnetic fluid holding surface 12.
In this embodiment, similarly to the above, surrounding contamination due to the outflow diffusion of the magnetic fluid 7 can be reliably prevented. Further, by preventing the outflow and diffusion, it is possible to prevent the holding amount of the magnetic fluid 7 from decreasing.

The fifth embodiment of FIG. 5 is the same as the third embodiment except that the protrusion 9 is not formed in FIG. In this case, the surface of the step portion 13 facing the rotating shaft 6 serves as the barrier 10. In this embodiment, the magnetic fluid holding surface 12 is formed by the tip surface 4, the outer surface 11 and the barrier 10 of the pole piece 1. In this case as well, by having the step portion 13, the outflow and scattering of the magnetic fluid 7 can be prevented, and the structure thereof can be simplified as described above.

In the sixth embodiment of FIG. 6, the barrier 10,
That is, the angle formed by the surface of the step portion 13 facing the rotating shaft 6 and the outer surface of the pole piece 1 having the step portion 13 closer to the base end than the step portion 13 is an acute angle. Other than this, it is the same as the fifth embodiment, and the tip surface 4 of the pole piece 1 is
The outer surface 11 and the barrier 10 form a magnetic fluid holding surface 12. In this case, the barrier 10 is arranged so as to cover the magnetic fluid 7 held on the tip surface 4 of the pole piece 1 obliquely from the inside to the outside, so that the magnetic fluid 7 flows out and diffuses. Can be reliably prevented.

In the seventh embodiment shown in FIG. 7, a cover 14 is attached to the outside of the projection 9, and the magnetic fluid 7 held between the tip surface 4 of the pole piece 1 and the rotary shaft 6 is attached by the cover 14. It is covered, and in this case also pole piece 1
The front end surface 4, the outer end surface 11 and the barrier 10 form a magnetic fluid holding surface 12. In this structure, even if the magnetic fluid 7 held is scattered outside the pole piece 1, the magnetic fluid 7 is blocked by the cover 14, and the scattering can be reliably prevented.

In the eighth embodiment of FIG. 8, a cover 14 similar to that of FIG. 7 is attached to the outside of the pole piece 1 having the step portion 13 of FIG. The other points are the same as those in the fifth embodiment. In this case as well, like the seventh embodiment, it is possible to reliably prevent the magnetic fluid 7 from scattering.

Although not shown, as yet another embodiment of the present invention, the pole piece is formed with a bent portion in which the front end surface side is bent inward without forming a barrier, and this bent portion is formed. It is also possible to mount a cover similar to that shown in FIG. 8 on the outside of the pole piece having the curved portion. In this case, the tip surface of the pole piece and the outer surface of the bent portion covered with the cover function as a barrier and a magnetic fluid holding surface.

In the above embodiment, the barrier and the bent portion are formed only on one pole piece.
The present invention is not limited to this, and it is also possible to perform both pole pieces. Further, the shape of the bent portion of the pole piece, the shape of the barrier and the cover, the forming position, and the positional relationship between them are not limited to those in the above embodiment. Further, in the above embodiment, the pole piece is fixed to the housing, and the rotating shaft facing the pole piece rotates, but the shaft facing the pole piece is replaced with the rotating shaft as a fixed shaft, and the pole piece is attached. It is also possible to adopt a system in which the housing that is rotating rotates. Further, in the above embodiment, the tip end surface of the pole piece faces the rotating shaft, but the present invention is not limited to this, and the housing is made of a magnetic material, and the outer tip end surface of the pole piece is formed of this housing. It is also possible to face the inner peripheral surface.

[0033]

As described above, in the magnetic fluid sealing device of the first aspect, the barrier can prevent the magnetic fluid from flowing out and scattering.

Further, in the magnetic fluid sealing device of claim 2,
Since the barrier is made of a material having a large oil repellency to the magnetic fluid, a reliable outflow prevention effect can be obtained.

Further, in the magnetic fluid sealing device according to the third and fourth aspects, since the pole piece is provided with the bent portion and the stepped portion, the outflow preventing effect can be further enhanced.

In the magnetic fluid seal device of the fifth aspect, since the pole piece is provided with the stepped portion and the stepped portion is used as the barrier, the structure can be simplified.

In the magnetic fluid sealing device according to the sixth aspect, the outward protrusion of the magnetic fluid from the barrier is less likely to occur.
This outflow diffusion can be prevented.

According to the magnetic fluid sealing device of the seventh aspect, even if the magnetic fluid tries to scatter to the outside of the pole piece, the scatter can be prevented by the cover.

[Brief description of drawings]

FIG. 1 is a one-sided sectional view of a first embodiment of a magnetic fluid sealing device of the present invention.

FIG. 2 is a one-sided sectional view of a second embodiment of the magnetic fluid seal device of the present invention.

FIG. 3 is a one-sided sectional view of a third embodiment of the magnetic fluid seal device of the present invention.

FIG. 4 is a one-sided sectional view of a magnetic fluid seal device according to a fourth embodiment of the present invention.

FIG. 5 is a half sectional view of a fifth embodiment of the magnetic fluid seal device of the present invention.

FIG. 6 is a half sectional view of a sixth embodiment of the magnetic fluid seal device of the present invention.

FIG. 7 is a half sectional view of a seventh embodiment of the magnetic fluid seal device of the present invention.

FIG. 8 is a one-sided sectional view of an eighth embodiment of the magnetic fluid seal device of the present invention.

FIG. 9 is a one-sided cross-sectional view of a conventional magnetic fluid seal device.

[Explanation of symbols]

 1 pole piece 2 pole piece 3 magnet 4 tip surface 5 tip surface 6 rotating shaft (magnetic material) 7 magnetic fluid 10 barrier 11 outer surface 12 magnetic fluid holding surface 13 stepped portion 14 cover

Claims (7)

[Claims] 1. A pair of plate-shaped pole pieces (1) (2)
The magnet (3) is sandwiched by the inner surface of the pole piece (1), the tip end surface (4) of the pole piece (1) faces the magnetic body (6), and the pole piece is formed by a magnetic circuit formed by the magnet (3). In a magnetic fluid seal device in which a magnetic fluid (7) is held between (1) and the magnetic body (6), the pole piece (1) has a barrier ( 10) The magnetic fluid sealing device characterized by being formed. 2. The magnetic fluid seal according to claim 1, wherein the barrier (10) is made of a material having a larger contact angle of the magnetic fluid (7) than that of the pole piece (1). apparatus. 3. A bent portion is formed in the pole piece (1) in the vicinity of the barrier (10), and in this bent portion, the tip surface (4) side of the pole piece (1) is located. The magnetic fluid seal device according to claim 2, wherein the magnetic fluid seal device is bent inward. 4. The magnetic fluid seal according to claim 3, wherein the bent portion is formed as a step portion (13), and the barrier (10) is formed in the vicinity of the step portion (13). apparatus. 5. The step (1) is provided on the pole piece (1).
3) is formed, and the step portion (13) has the pole piece (1) on the side of the tip surface (4) of the pole piece (1).
2. The magnetic fluid sealing device according to claim 1, wherein the barrier (10) is located on the inner side from the base end face side of the above, and the surface of the stepped portion (13) facing the magnetic body (6) is the barrier (10). 6. The magnetic fluid seal device according to claim 5, wherein an angle formed by the barrier (10) and an outer surface of the pole piece (1) is an acute angle. 7. The pole piece (1) is provided with a cover (14) for covering the magnetic fluid (7) held therein, according to any one of claims 1 to 6. Magnetic fluid sealing device.