JPH064140Y2 - Magnetic fluid sealing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a magnetic fluid sealing device.

[Conventional technology]

As a conventional sealing device of this type, there is one used in a magnetic disk device as shown in FIGS. This is disclosed by the applicant in Japanese Utility Model Laid-Open No. 58-191423.

In the figure, 1 is a cylindrical housing and 2 is a housing 1.
The shaft is attached to the shaft via bearings 3, and C is an annular seal member formed by an annular magnet 6 and annular pole pieces 4 and 5 coaxially fixed to both end surfaces thereof. A seal gap g is provided between the inner ring 3 and the inner ring 3a of the bearing 3, and is fixed to the inner peripheral surface of the outer ring 3b of the bearing 3 with an adhesive. The inner ring 3a is fixed to the shaft 2 and the outer ring 3b is fixed to the housing 1. The inner ring 3a and the pole pieces 4 and 5 are made of a magnetic material. Reference numeral 7a denotes a magnetic fluid retained by the magnetic force in the seal gap g, that is, a magnetic fluid retained by the magnetic field formed between the inner ring 3a and the seal member C by the magnet 6. Reference numeral 8 is a disk fitted on the shaft 2, 9 is a magnetic head, 10 is a ball, 1 is a ball holder, and 12 is a seal plate.

With such a configuration, the space between the seal member C and the inner ring 3a is sealed by the magnetic fluid 7 held between the seal members C and 3a, and is directed to a clean zone such as dust (grease dust) generated from the bearing. Are prevented from entering.

[Problems to be solved by the device]

By the way, in the conventional sealing device, as shown in FIG. 11, two seals are formed on the peripheral portion of the seal member C facing the inner ring 3a.
An annular groove m formed by the inner side surfaces 4a and 5a of the pole pieces 4 and 5 and the outer peripheral surface 6a of the magnet 6 is formed.

The magnetic fluid 7b trapped by the leakage magnetic flux passing through the groove m when the magnetic fluid 7a is injected into the seal gap g is retained in the groove m as shown in FIG.

The magnetic fluid 7b staying in the groove m has a seal gap g
If the magnetic fluid 7a is moved so as to be replenished as the magnetic fluid 7a decreases, the retained magnetic fluid 7b effectively acts to prolong the life of the seal. In order to facilitate the movement of the magnetic fluid, it is necessary to inject a sufficiently large amount of the magnetic fluid, but in this case, the magnetic fluid 7a in the gap g protrudes from the gap g, which is the centrifugal force of rotation. Will scatter and pollute the surroundings. From the viewpoint of preventing scattering, the amount of the magnetic fluid to be injected is smaller, but in this case, the magnetic fluid 7b is strongly restrained by the above-mentioned leakage magnetic flux and remains at its position, and does not easily move to the seal gap g. Therefore, the bent magnetic fluid 7b does not contribute to the extension of the seal life.

Therefore, even when the injection amount of the magnetic fluid is small, facilitating the movement of the magnetic fluid so that the magnetic fluid 7a in the gap g is replenished from the retained magnetic fluid 7b can prolong the seal life. Has been a challenge to achieve.

The present invention has been made in order to solve such a conventional problem, and makes it possible to replenish the magnetic fluid staying in the annular groove to the seal gap. An object of the present invention is to provide a magnetic fluid seal device that can be realized.

[Means for Solving the Problems]

In the magnetic fluid sealing device according to the present invention, a seal gap is formed between a seal member formed by coaxially fixing two annular pole pieces on both end surfaces of an annular magnet, and the two annular pole pieces. In the peripheral portion of the seal member, which is composed of a magnetic member that rotates relative to the seal member coaxially and a magnetic fluid held by the magnetic force of a magnet in the seal gap, and that faces the magnetic member via the magnetic fluid. ,
In a sealing device having an annular groove formed by two annular pole pieces and an annular magnet, the magnet-side surfaces of the two pole pieces are uneven.

[Action]

Since the surface of the pole piece on the magnet side is uneven, the surface tension is effectively increased in the concave portion having a small radius of curvature, and the magnetic fluid is easily introduced into this portion. Has good wettability.

For this reason, the magnetic fluid staying in the annular groove is likely to spread and expand in a film shape as the surface tension of the pole piece increases.

Further, when the surface of the pole piece is made uneven, the magnetic fluid easily stays on the surface due to the increase of the surface tension and the surface area, and the pole piece has a function of accumulating the magnetic fluid.

Therefore, when the magnetic fluid in the seal gap is reduced, the magnetic fluid in the groove easily moves to the seal gap so as to compensate for this.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

Each of the embodiments is an example in which the present invention is applied to the magnetic disk device shown in FIGS.

(Embodiment 1) FIG. 1 shows a first embodiment of the present invention and corresponds to FIG. In the figure, the same parts as those in FIGS. 9 to 11 are designated by the same reference numerals.

C ₁ is a seal member formed by coaxially fixing two ring-shaped pole pieces 14 and 15 to both end faces of a ring-shaped magnet 16, and is fixed to the inner peripheral surface of the outer ring 3b. Pole piece 1
As shown in FIG. 2, the surfaces of the magnets 4 and 15 on the side of the magnet 16 are made to have an uneven surface K ₁ by forming a large number of minute depressions in the entire surface. Reference numeral 3a denotes an inner ring fixed to the shaft 2 with a seal gap g provided between the inner peripheral surfaces of the pole pieces 14 and 15 and rotating coaxially with the seal member C ₁ .

The inner ring 3a is a member made of a magnetic material, which is the magnetic member referred to in the present invention. 7a is a magnet 1 in the seal gap g
The magnetic fluid held by the magnetic force of 6, m is the two pole pieces 14, on the peripheral edge of the seal member C ₁ facing the inner ring 3a.
It is an annular groove formed by the surface of the magnet 16 on the magnet 16 side and the inner peripheral surface of the magnet 16. Therefore, the uneven surface K ₁ of the pole pieces 14 and 15 is exposed on the inner side surface of the groove m.
Reference numeral 7b is a magnetic fluid that is trapped by the leakage magnetic flux passing through the annular groove m when the magnetic fluid 7a is injected into the seal gap g.

Next, the operation will be described.

The surface tension of the uneven surface K ₁ of the pole pieces 14 and 15 exposed in the annular groove m is considerably larger than that of the conventional pole pieces 4 and 5 shown in FIG. 11 and has good wettability.

Therefore, the magnetic fluid 7b staying in the annular groove m is
As the surface tension of the pole pieces 14 and 15 increases, the pole pieces 14 spread out in a film shape and can be easily expanded. Further, the pole piece can store the magnetic fluid on the surface having the irregularities.

Therefore, when the magnetic fluid 7a in the seal gap g is reduced, first, the magnetic fluid accumulated in the uneven portion on the surface of the pole piece moves toward the seal gap g,
Further, as a result of this, the magnetic fluid staying in the groove m is attracted by the surface tension increased by the unevenness and moves on the uneven surface so as to compensate for the reduced magnetic fluid of the unevenness of the surface.

Therefore, the magnetic fluid staying in the groove m is effectively replenished in the seal gap g, which contributes to extending the life of the seal.

Although the uneven surface K ₁ of the pole pieces 14 and 15 is formed by a minute recessed hole, like the uneven surface K ₂ of the pole pieces 14 and 15 of FIG. 3, it has a concentric circular groove or a spiral groove. Such a groove may be formed along the circumferential direction. Further, the uneven surfaces K ₁ and K ₂ are an example in the case of being formed on the entire surfaces of the pole pieces 14 and 15, but as shown in FIG. 4, for example, the uneven surface K ₃ is formed only in the portion exposed in the annular groove m. May be formed.
In either case, the effects are the same.

(Embodiment 2) The second embodiment is not shown, but instead of the pole pieces 14 and 15 of the first embodiment, the pole piece 2 of FIG.
It is an example using 4,25.

The uneven surface K ₄ of the pole pieces 24, 25 is formed by providing a large number of narrow grooves K ₁ having a U-shaped cross section and provided at substantially equal intervals in the radial direction, as shown in FIG.

Also in the case of this embodiment, the magnetic fluid 7b easily expands along the groove K ₁ , so that the magnetic fluid 7a having the seal gap g is expanded.
When it decreases, it moves to make up for it and contributes to prolonging the life of the seal.

The same action and effect can be obtained by using, instead of the pole pieces 24, 25, a groove K ₂ having a V-shaped cross section provided in the radial direction as shown in FIG. 6 to form an uneven surface K ₅ . Also,
As shown in FIGS. 7 and 8, the pole pieces 24 and 25 having the concave and convex surfaces K ₆ and K ₇ are provided by providing the grooves K ₃ and K ₄ only in the portions exposed in the annular groove m. Even if the same effect is obtained.

In each of the above embodiments, the case where the shaft 2 (inner ring 3a) rotates has been described.
The same can be said for the case where b) rotates. Further, in each of the embodiments, the case where the present invention is applied to the magnetic disk device has been described, but the same description can be applied to the case where the present invention is applied to a laser beam printer, a bar code reader, a semiconductor device and the like.

[Effect of device]

As described above, according to the present invention, since the inner surface of the pole piece exposed in the annular groove of the seal member is the uneven surface, the magnetic fluid staying in the annular groove easily expands,
When the magnetic fluid in the seal gap decreases, it moves to the gap so as to make up for it. Therefore, according to this invention, the life of the seal can be kept long.

[Brief description of drawings]

FIG. 1 is a sectional view of a first embodiment of the present invention, and FIG.
Fig. 3 is a perspective view of the pole piece in the drawings, Fig. 3 and Fig. 4 are perspective views showing other aspects of the pole piece of Fig. 2, and Fig. 5
FIG. 8 to FIG. 8 are perspective views of the non-magnetic member in the second embodiment.
9 is a sectional view of a magnetic disk device using a conventional magnetic fluid seal device, FIG. 10 is an enlarged sectional view of an essential part of FIG. 9, and FIG. 11 is an enlarged view of an essential part of FIG. C ₁ ...... Seal member 3a ...... Inner ring (magnetic member) 3b ...... Outer ring 7a ...... Magnetic fluid with seal gap g 7b ...... Magnetic fluid staying in annular groove m 14, 15 ...... Annular pole piece 16 ... ... annular magnet m ...... annular groove K ₁ ~K ₇ ...... uneven surface K ₁ groove of ...... U-shaped section K ₂ ...... V-shaped cross section of the grooves K _{3, K 4} ...... groove g ...... sealing gap In each drawing, the same reference numerals indicate the same or corresponding parts.

Claims (3)

[Scope of utility model registration request] 1. A seal member formed by coaxially fixing two annular pole pieces to both end faces of an annular magnet, and a seal gap is provided between the two annular pole pieces. And a magnetic member held in the seal gap by the magnetic force of a magnet, and two annular members are provided at the peripheral edge of the seal member facing the magnetic member through the magnetic fluid. In a sealing device having an annular groove formed by a pole piece and an annular magnet, a magnet-side surface of the two pole pieces is an uneven surface. 2. The magnetic fluid seal device according to claim 1, wherein the concavo-convex surface is formed by concentric circular or spiral grooves in the circumferential direction. 3. The magnetic fluid seal device according to claim 1, wherein the uneven surface is formed by providing grooves in the radial direction.