JP2000240809A - Sealing equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide sealing equipment, using magnetic fluid capable of achieving easy pre-injection of the magnetic fluid and easily supporting the magnetic fluid in a specific position with improving its pressure tightness in a stationary state. SOLUTION: A non-magnetic inner shield 7 is inserted into a space between a nonmagnetic outer shied 5 in a media side and a nonmagnetic outer shield 6 in a bearing 2 side. An annular magnet 4 is supported by an outer tip of the inner shield 7, magnetic fluid 9 is supported between the annular magnet 4 and the outer shields 5 and 6, and the surface of the inner shied 7 except for the described space, and an adhesive part of the inner diameter is coated with oil repelling material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor for driving a magnetic recording medium in the information industry and a sealing device using a magnetic fluid applied to other fields.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 2, a sealing device of this type has a rotating shaft 23 rotatably supported on a housing 21 via a ball bearing 22 so that a ball (upper side in the drawing) and a media side are connected. An annular magnet 24 is interposed between the bearing 22 and the pole pieces 25 and 26 whose inner diameters are slightly larger than the diameter of the rotary shaft 23 on both sides thereof, and are formed between the pole pieces 25 and 26 and the rotary shaft 23. The magnetic fluid 27 is interposed in the gap, and the magnetic fluid 27 is held in the gap by the magnetic force of the annular magnet 24 so that the space on both sides is cut off and sealed.

However, in the sealing device having such a configuration, the shaft needs to be made of a magnetic material. In addition to the necessity of polishing in order to prevent bleeding of the magnetic fluid, when the relative rotation between the rotating shaft 23 and the housing 21 starts, a centrifugal force acts on the magnetic fluid 27, and when the centrifugal force exceeds an allowable range. Breakage of the seal will occur. In addition, the cover 29 is usually attached to the injected magnetic fluid so that the magnetic fluid is not touched by the hand during handling.

Therefore, as shown in FIG.
5 and 26, an inner shielding plate 28 is provided from the opposite side to bypass the gap between the housing 21 and the rotating shaft 23 in a U-shape. A device has been developed in which the magnetic fluid 27 is securely held in combination with the magnetic force lines by moving the magnetic fluid 27 to the side (Japanese Patent Publication No. 7-54153, US Pat. No. 4,200,296).
Etc.).

[0005]

However, in the above-mentioned improved prior art, it is difficult to inject the magnetic fluid into the U-shaped bypass passage, and it is quite difficult to inject the magnetic fluid after assembling it in the actual machine. This is a problem in production, for example, it is difficult to control the injection amount of the magnetic fluid after mounting on the actual machine. Therefore, a proposal for delivery with a magnetic fluid injected in advance (US Pat. No. 425,235)
3). However, such proposals have not yet been adopted in practical equipment.

According to the present invention, from such a viewpoint, it is possible to easily inject a magnetic fluid into a predetermined place before mounting the spindle motor, and to provide a sealing so that the magnetic fluid does not leak during transfer or mounting work. Provide equipment.

[0007]

The present invention comprises the following (1) and (2).

(1) A device which is provided between a media side and a bearing side and seals a part which rotates relatively coaxially, wherein a non-magnetic outer shield on the media side and a non-magnetic outer shield on the bearing side. Insert the nonmagnetic inner shield into the space between the outer shields, hold the annular magnet at the outer peripheral end of the inner shield, and hold the magnetic fluid between the annular magnet and each of the outer shields. A sealing device, wherein an oil-repellent material is coated on the surface of the inner shield body outside the space and the inner diameter bonding portion.

(2) The sealing device according to (1), wherein the inner diameter of the outer shield on the bearing side is larger than the inner diameter of the outer shield on the media side.

That is, the magnetic fluid is held in a space defined by the outer shield on the media side, the outer shield on the bearing side, and the annular magnet attached to the outer peripheral end of the inner shield. By coating the surface of the body outside the space and the surface outside the inner diameter bonding portion with an oil-repellent material such as Teflon, for example, it becomes easy to inject the magnetic material into the space, and the magnetic fluid can be used during transfer or mounting work. The surface tension at the end is increased, so that the magnetic fluid does not leak during transfer or mounting work. Further, the magnetic fluid adhered to the oil-repellent material at the time of injection of the magnetic fluid can be attracted to the inner end portion by the magnetic force.

By setting the position of the annular magnet at the tip of the inner shield from the depth of the space as in the related art, the depth of the space can be reduced by that much, and the apparatus can be downsized. .

Further, by making the inner diameter of the outer shield on the bearing side larger than the inner diameter of the outer shield on the media side, the length of the outer shield on the media side which forms the space chamber is reduced. Be longer than body. When mounted on an actual machine, the pressure on the media side is lower than the pressure on the bearing side, so the magnetic fluid tends to migrate to the media side. Therefore, if the outer shield on the media side is made longer, the length of the outer shield is longer even if the magnetic fluid slightly moves to the media side due to the pressure difference, so that the magnetic fluid is not covered by the edge of the inner shield on the media side. There is no danger of getting over the club. Conversely, increasing the inner diameter of the outer shield on the bearing side allows the magnetic fluid holding portion to approach the magnetic fluid holding portion and secure a wide inlet for the magnetic fluid, facilitating the injection of the magnetic fluid.

[0013]

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

FIG. 1 shows a basic embodiment of the present invention. This is an example in which a device having a rotating shaft 3 rotatably supported by a housing 1 via a ball bearing 2 is provided with a sealing device for maintaining the airtightness between the media side (upper side in the figure) and the bearing side. . FIG. 1 shows a rotational movement about the rotation center axis C, but the description on the left side is omitted. Reference numeral 4 denotes an annular magnet,
It is attached to the outer peripheral end. 5 is an outer shield on the media side, and 6 is an outer shield on the bearing side. These are all annular, and the inner diameter is smaller in the order of the annular magnet 4, the bearing-side outer shield 6, and the media-side outer shield 5. An annular space is formed by the outer shields 5 and 6 and the housing 1, and the media-side outer shield 5 forming the space is longer inside than the bearing-side outer shield 6. The annular magnet 4 attached to the outer peripheral portion of the inner shield 7 is inserted and fixed in such a space so as not to contact the inner peripheral surface. A coating 8 made of an oil-repellent material is provided on the surface of the inner shield 7 outside the space and the inner diameter bonded portion and on the surface outside the inner diameter bonded portion. Then, the magnetic fluid 9 is held around the annular magnet 4 at the back in the space. When injecting the magnetic fluid 9 into the space in advance,
When injected from the bearing 2 side, the opening is relatively wide, and the inside of the coating 8 made of a water-repellent material restricts the movement of the magnetic fluid 9 in that direction and smoothly moves to the space side. Becomes

[0015]

According to the present invention, the coating of the oil-repellent material on the inner shield facilitates the injection of the magnetic fluid.
It becomes easy to inject a magnetic fluid in advance into the interior of the U-shaped space formed by the outer shielding material, the inner shielding material, and the annular magnet at the outer periphery prior to shipping and mounting work, and moreover, the magnetic fluid is injected. The magnetic fluid does not easily fall off due to vibrations during transfer or mounting work. Conventionally, a magnetic fluid is injected into a predetermined portion after assembly to an actual machine, which is a rather difficult and time-consuming operation. However, according to the present invention, the assembly of the sealing device to the actual machine becomes extremely easy. .
This does not exclude the injection of the magnetic fluid after the assembly, and even in such a case, the injection is still easy. Also, the withstand voltage at rest increases.

Further, in the present invention, since the annular magnet is mounted not on the inner side of the space but on the outer peripheral portion of the inner shielding member, the size can be shortened by that amount, and the apparatus can be downsized.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of an example of a conventional sealing device.

FIG. 3 is an explanatory diagram of an improved example of a conventional sealing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Housing 2 Ball bearing 3 Rotation axis 4 Annular magnet 5 Media side outer shield 6 Bearing side outer shield 7 Inner shield 8 Coating 9 Magnetic fluid

Claims (2)

[Claims] 1. An apparatus for sealing a part which is coaxially and relatively rotatable between a media side and a bearing side, comprising a non-magnetic outer shield on the media side and a non-magnetic outer shield on the bearing side. A non-magnetic inner shield is inserted into the space between the outer shields, an annular magnet is held at the outer peripheral end of the inner shield, and a magnetic fluid is held between the annular magnet and each of the outer shields. And a surface of the inner shield outside the space and outside the inner diameter bonding portion is coated with an oil-repellent material. 2. The sealing device according to claim 1, wherein the inner diameter of the outer shield on the bearing side is larger than the inner diameter of the outer shield on the media side.