JPS62110080A - Sealing device - Google Patents

Abstract

PURPOSE:To prevent from exerting a bad influence upon parts and members and the like of a magnetic sealing device, in which leakage magnetic flux is disliked, by providing a magnetic shielding part between a housing and magnetic sealing device. CONSTITUTION:A shielding part T1 using a permeable material such as Permalloy as a magnetic shielding part is interposed between a magnetic sealing device C and a housing H. This shielding part is cylindrically formed out of a nonmetallic material such as a resin 22 embedding a cylindrical member 21 of Permalloy in it. Such being the constitution, a magnetic circuit is formed between the magnetic sealing device C and the cylindrical member 21 of Permalloy. As a result, the influence of leakage magnetic flux of the magnetic sealing device C is hardly exerted upon the housing part H, hence it follows that shielding is substantially accomplished by this part.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a sealing device for shielding magnetic leakage from a magnetic sealing device.

[Conventional technology]

An example of a sealing device using a conventional magnetic sealing device is one used in a magnetic disk spindle, for example. This is shown in FIGS. 4 and 5, where FIG. 4 is a sectional view thereof, and FIG. 5 is an enlarged view of the main part of FIG. 4.

In the figure, H is the housing, S is the shaft, B is the bearing interposed between the housing H and the shaft S, C is the magnetic seal device, R is the rotor attached to the shirt S, and D is the outer circumference of the rotor R. A magnetic disk P is attached to a shaft S, and is driven by a drive belt (not shown). F is a dustproof case.

The bearing B has balls 3 interposed between an outer ring l and an inner ring 2,
This is a ball bearing in which a cover 4 is provided at the end of the outer ring 1 to cover an opening between the outer ring 1 and the inner ring 2, and is positioned at a predetermined interval by a retaining ring 5 attached to the housing H.

As shown in FIG. 5, the magnetic sealing device C includes a ring-shaped sealing member 8, which is bonded together with a magnet 7 sandwiched between a pair of pole pieces 6 and 6, and is attached to a bearing via a non-magnetic spacer 9. The outer circumferential surface of the seal member 8 is adhesively fixed to the inner circumferential surface of the housing H, and a small gap g is provided between the seal member 8 and the shaft S, and the magnetic fluid is inserted into this gap g. It is constructed by injecting IO.

With this configuration, pole piece 6.6
A magnetic circuit 11 is formed between the shaft s and the shaft s, and the magnetic fluid 10 injected therebetween is held with sufficient pressure resistance. As a result, the mist generated by the lubricant sealed in the bearing B, such as grease, can be completely sealed so that it does not leak toward the magnetic disk D side.

[Problem that the invention seeks to solve]

However, even if the same sealing device is used, it is more compact and the diameter of the magnetic disk D is smaller, for example, 3.
In the case of a 5'' hard disk, the magnetic disk D is located relatively close to the magnetic seal device C, so that leakage of magnetism from the sealing member 8 toward the housing H side is caused by the magnetic disk D.
There were cases in which a reading error occurred in the memory section (magnetic material, for example, γFe2O3) of the disk D.

As a countermeasure for this, it would be better to make the magnet 7 smaller so that its leakage magnetism does not reach the magnetic disk D. If this is done, the holding force of the magnetic fluid 10 will be weakened and the pressure resistance of this part will be reduced. It is not practical because the sealing function will be impaired. For example, a bearing B with a radius of 20 cm from the axis of the shirt hs and a distance lam from the side of the pole piece 6 on the rotor R side.
If you use the magnet 7 that suppresses leakage magnetism of 20auss or less on the side, there will be no disturbance to the disk D.
In this case, the magnetic force of the magnet 7 becomes too weak to effectively hold the magnetic fluid IO.

The present invention has been made in order to solve such conventional problems, and provides an electrically sealed device in which there is no fear that leakage magnetism of the magnetic sealing device will affect magnetic components, members, etc. The purpose is to

[Means for solving problems]

The sealing device according to the present invention includes a housing, a shaft attached to the housing via a bearing, and a magnetic sealing device interposed between the shaft and the housing, and the sealing device includes: between the housing and the magnetic sealing device in a sealing device comprising a round magnet, an annular pole piece fixed to both sides of the magnet, and a magnetic fluid injected into the gap between the pole piece and the shaft. A magnetic shielding section is provided on the top.

[Effect]

Since the magnetic shielding section is provided between the housing and the magnetic seal device, magnetic leakage from the magnetic sealing device toward the housing side is substantially blocked by the magnetic shielding section.

Therefore, there is no risk that the parts 1 and the like of the magnetic seal device which are averse to leakage magnetism will be affected by the leakage magnetism. For example, like the magnetic disk in the 3,5'' hard disk mentioned above.

There is no possibility that the component that absorbs magnetism will be disturbed by the leaked magnetism and that a reading error will occur in the memory section of the disk.

〔Example〕

FIG. 1 shows a first embodiment of the invention. This figure shows the parts corresponding to the magnetic seal device of FIG. 5, and the parts not shown are the same as the structure of FIG. 5.

In the figure, the same reference numerals as in FIG. 5 indicate the same or corresponding parts. T1 is a shielding part using a magnetically permeable material 1 such as permalloy as a magnetic shielding part interposed between the magnetic seal device C and the housing H. This shielding portion T1 is formed by embedding a permalloy cylindrical member 21 and molding it into a cylindrical shape from a non-metallic material, for example, resin 22, and 23 is a groove provided on the inner circumference thereof. The distance G1 between the cylindrical member 21 and the pole piece 6 is 1 larger than the gap g between the pole piece 6 and the shaft S.
．． The shielding part T1, which is preferably set to 5 times or more, is fixed to the housing H at its outer circumference, and the seal member 8 is fitted into the groove 23 on the inner circumference and is fixed integrally.

With such a configuration, a magnetic circuit is formed between the magnetic seal device C and the permalloy cylindrical member 21. As a result, leakage magnetism from the magnetic seal device C hardly reaches the housing H portion, and is substantially shielded by this portion.

FIG. 2 shows a second embodiment.

This figure shows the parts corresponding to FIG. 1, and the configuration of the other parts is the same as that of FIG. 5.

In the figure, the same reference numerals as in FIG. 5 indicate the same or corresponding parts. T2 is a shielding part using a magnetic material as a magnetic shielding part interposed between the magnetic seal device C and the housing H. This shielding part T2 is formed by embedding a cylindrical member 24 made of a magnetically permeable material and molding it into a cylindrical shape from a rubber magnet material or a plastic magnet material 25. At the time of molding, the magnet 7 portion is also integrally molded from the same material. Only the 7th part of the magnet is magnetized. The distance G2 between the cylindrical member 24 and the pole piece 6 is larger than the gap g between the pole piece and the shaft, and 1
．． It is desirable to set it to 5 times or more. Therefore, the magnet 7 is a rubber magnet or a plastic magnet. The shielding portion T2 is fixed to the housing H at its outer peripheral surface.

Also in this embodiment, a magnetic circuit is formed between the magnetic seal device C and the magnetic cylinder 24. Therefore, as in the first embodiment, leakage magnetism from the magnetic seal device C hardly reaches the housing H portion, and is substantially shielded by this portion.

FIG. 3 shows a third embodiment.

This figure also shows the parts corresponding to FIG. 1, and the structure of the other parts is the same as that of FIG. 5.

In the figure, the same reference numerals as in FIG. 5 indicate the same or corresponding parts. T3 includes a cylindrical part that is formed integrally with the outer circumference of one pole piece 6 and extends near the other pole piece 6, and has a cylindrical part between this cylindrical part and the other pole piece 6. Gap g! is a cylindrical pole piece, with the cylindrical portion serving as a magnetic shielding portion. The above-mentioned gap g1 is preferably larger than the gap g between the pole piece 6.6 and the shirt) S, and preferably g! is set to 1.5 times or more of g.

In such a configuration, since the gap g1 is opened in the axial direction of the shaft S, a leakage magnetic circuit can be formed in the gap g1 portion. Therefore, the magnetic leakage hardly reaches the direction of the housing H, and is substantially shielded by this portion.

Note that the magnets are not limited to the plastic magnets and rubber magnets explained in the embodiments, but can be appropriately selected from ferrite magnets, rare earth magnets, and the like. Further, the non-metallic material used for the shielding part is not limited to resin, and can be selected from the viewpoint of processing surface such as rubber and attachment to the housing.

〔Effect of the invention〕

As explained above, according to the present invention, since the magnetic shielding portion is provided between the housing and the magnetic seal device, leakage magnetism of the magnetic seal device has an adverse effect on parts, members, etc. that absorb magnetism. You can prevent this from happening.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of main parts showing a first embodiment of the present invention, and a second embodiment of the present invention is shown in FIG.
FIG. 3 is a cross-sectional view of a main part similarly showing the second embodiment, FIG. 3 is a cross-sectional view of a main part similarly showing a third embodiment, and FIG. 4 is a cross-sectional view of a magnetic disk spindle in which a conventional sealing device is used.
FIG. 5 is an enlarged view of the magnetic seal device in FIG. 4. In the figure, H is a housing, B is a bearing, S is a shuttle, C is a magnetic seal device, 6 is a pole piece, 7 is a magnet, 10 is a magnetic fluid, g and gl are gaps, T1 is a shielding part using permalloy, T2 is a shielding part using a magnetic material, T3 is a cylindrical pole piece, 21 is a cylinder made of permalloy, 22 is a resin,
24 is a cylindrical member made of a magnetically permeable material, and 25 is a plastic magnet material. In each figure, the same reference numerals indicate the same or corresponding parts. Figure 1 Figure 3

Claims (7)

[Claims] (1) Consisting of a housing, a shaft attached to the housing via a bearing, and a magnetic seal device interposed between the shaft and the housing, and the seal device is connected to an annular magnet and a magnetic seal device interposed between the shaft and the housing. In a sealing device comprising an annular pole piece fixed to both sides of the housing and a magnetic fluid injected into the gap between the pole piece and the shaft, a magnetic shielding portion is provided between the housing and the magnetic sealing device. Features a sealing device. (2) The sealing device according to claim 1, wherein the magnetic shielding portion is formed into a cylindrical shape by embedding a cylindrical member made of a magnetically permeable material in a non-metallic material. (3) The sealing device according to claim 2, wherein the magnetically permeable material is permalloy. (4) The sealing device according to claim 2, wherein the non-metallic material is resin. (5) The sealing device according to claim 1, wherein the magnet is a plastic magnet. (6) The magnetic shielding part is a cylindrical body made of plastic magnet material with a magnetic tube buried therein, and is not magnetized, and the magnetic shielding tube is integrally formed with the plastic magnet at the time of molding. Claim 5 is characterized in that
Sealing device as described in section. (7) The magnetic shielding part is located on the outer periphery of one pole piece.
A cylindrical part is formed integrally with this pole piece and extends near the other pole piece, and a gap is provided between the cylindrical part and the other pole piece, and the cylindrical part is used as a magnetic shielding part. A sealing device according to claim 1, characterized in that: