JPS6240212Y2 - - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to improvements in magnetic fluid seal devices.

Conventionally, a magnetic fluid seal device used, for example, in a magnetic disk spindle has a structure shown in FIGS. 1 and 2.

That is, Fig. 1 is an example of the structure of a magnetic disk spindle, and is a cross-sectional view of the main part thereof, and Fig. 2 is an enlarged cross-section of the main part (dotted line part in Fig. 1) that uses the magnetic fluid seal device. In the figure, 1 is the axis, 2
a is a housing, and a retaining ring 6 is positioned between the shaft and the housing in the axial direction.
Two bearings 8a, 8a are provided at a predetermined distance in the axial direction and rotatably support the shaft.

A rotor 3 is fixed to one end of the shaft, a magnetic disk 4 is provided on the outer periphery of the rotor, and a pulley 5 fixed to the other end of the shaft is connected to a belt (not shown). The rotor is rotated by being driven by.

Further, the rotor and magnetic disk have a sealed structure covered with a cover 7 in order to prevent them from becoming dirty due to adhesion of dust and foreign matter, and to isolate them from the outside.

There is a labyrinth A with a narrow gap between the rotor and the housing, and a seal 9a using magnetic fluid is provided in the space between the rotor and the upper bearing adjacent to the rotor. The structure is such that the lubricant sealed in the bearing, such as grease, is completely sealed so that the mist obtained by evaporation of oil does not leak through the labyrinth to the magnetic disk side.

This means that if mist-like oil leaking from the bearing adheres to the disk, the memory function will be impaired, so it is absolutely necessary to prevent the oil from moving from the bearing to the disk side. .

In other words, the magnetic fluid seal portion is required to have perfect sealing performance.

In order to fulfill this function, the conventional seal structure consists of a pair of pole pieces 91a and a plastic magnet 92a, as shown in the enlarged view of the main part in FIG.
A seal body 9a consisting of a seal body 9a is provided adjacent to the bearing 8a with a sealing plate through a spacer 10 of a non-magnetic material, and the outer circumference of the seal body is loosely fitted into the inner circumference of the housing 2a and fixed with an adhesive or the like. The inner periphery of the seal body faces the shaft with a slight gap therebetween, and a magnetic fluid 11 is injected into the gap to form a sealed structure.

However, in this conventional example, when the rotation speed of the shaft is extremely high, exceeding 10,000 rpm, or when the distance from the rotor end face to the magnetic fluid is short and the rotor and magnetic fluid come into contact (to make the spindle smaller), ), the magnetic fluid is shaken off by centrifugal force, unable to fulfill its original purpose of blocking grease mist and dust, and the magnetic fluid itself becomes labyrinth A as shown by the dotted line La. There is a drawback that the particles pass through and scatter toward the magnetic disk side, becoming contaminants.

The present invention was devised to eliminate this drawback, and the purpose of this invention is to create a magnetic fluid seal that can prevent magnetic fluid from scattering by forming a trap in the labyrinth between the rotor and the housing. It provides equipment.

Next, embodiments of the present invention will be described with reference to the drawings. Note that for parts that are the same as the structures shown in FIGS. 1 and 2 of the conventional example, explanations will be omitted using the symbols in FIGS. 1 and 2, and structures related to different parts will be described in detail below. .

FIG. 3 shows a first embodiment of the present invention, in which a flat pole piece 91a and a cylindrical extending portion 931 in the axial direction (rotor side) protruding from the end surface 21a of the housing 2a are shown. A seal 9 consisting of a substantially L-shaped pole piece 93 and a magnet 92a held between the two pole pieces,
It is loosely fitted onto the inner circumferential surface of the housing 2a through a spacer 10 adjacent to the bearing 8a and fixed with an adhesive or the like, and is fixed to the extending portion 931 of the L-shaped pole piece and one end of the shaft 1. A trap part B with a narrow gap is formed between the flat part 31 of the rotor 3 made of magnetic material, and a magnetic circuit shown by the dotted line M is created, and the scattered magnetic material is Prevents fluid from scattering.

Next, FIG. 4 shows a second embodiment of the present invention, in which, compared to the first embodiment, the flat part 31 of the rotor 3 made of a magnetic material has a cylindrical extension part 931 of the L-shaped pole piece 93. An annular groove 32 is provided in a portion facing the
The extending portion is fitted into the annular groove so that a certain gap exists, and a magnetic circuit shown by a dotted line M is formed in the gap.

Therefore, the gap forms a curved labyrinth and effectively blocks the flying magnetic fluid.

In the above embodiment, the extension part 931 is integrated with the pole piece 93, but it may be a separate cylindrical member.

Further, FIG. 5 shows a third embodiment of the present invention, and in this figure, the rotor side end surface 21 of the housing 2a is
A is provided with an annular groove 22a, and a first annular pole piece 121, a second annular pole piece 122,
Cylindrical magnetic seal 12 consisting of an annular magnet 123
A trap part B is formed by fixing the magnetic rotor 3 to the flat part 31 of the magnetic rotor 3 fixed to one end of the shaft 1 with a small gap, and creating a magnetic circuit shown by the dotted line M. There is.

In this case, since a magnetic circuit generating means separate from the magnetic fluid magnetic circuit is provided, the lines of magnetic force can be strengthened. If the so-called magnetic lines of force for seals are made too strong, the magnetic particles in the magnetic fluid will aggregate, so there is an upper limit to the strength of the lines of magnetic force.However, if the lines of force for traps are separated, the lines of magnetic force can be set to be strong regardless of whether they are for seals. The magnetic fluid scattering prevention effect is improved. As described above in the first to third embodiments, by providing an annular magnetic trap on the flat surface of the magnetic rotor, the magnetic fluid can close the labyrinth A between the rotor and the end of the housing. Because it can prevent it from passing through and scattering,
It becomes possible to use it in a high speed range of 10,000 rpm or more, and also to create a compact design in which the magnetic fluid seal and rotor are brought close together, making it possible to achieve a level that could not be achieved with conventional technology.

In the embodiments, the entire rotor is made of magnetic material, but it is not necessarily necessary that the entire rotor be made of magnetic material, and a portion may be made of magnetic material to form a magnetic circuit.

[Brief explanation of the drawing]

Figure 1 is a sectional view of the main part of a magnetic disk spindle using a conventional magnetic fluid seal, and Figure 2 is a cross-sectional view of the main part of a magnetic disk spindle using a conventional magnetic fluid seal.
3 to 5 are enlarged views of the main parts of the figure, and FIGS. 3 to 5 are views corresponding to FIG. 2 showing the embodiment of the present invention, and FIG.
Examples, FIG. 4 shows the second embodiment, and FIG. 5 shows the third embodiment. Explanation of symbols, 1...shaft, 2a...housing,
3... Rotor, 9... Magnetic fluid seal, 931...
... Cylindrical extension part, 11... Magnetic fluid, A... Labyrinth, B... Trap part, M... Lines of magnetic force.

Claims (1)

[Claims for Utility Model Registration] (1) A rotor fixed to one end of a shaft rotatably supported by a housing, and an end face facing the rotor of one bearing installed close to the rotor. A magnetic fluid seal is provided in the space between the inner peripheral surface of the housing located on the side and the outer peripheral surface of the shaft.
Furthermore, the magnetic fluid sealing device includes a labyrinth portion between the flat surface portion of the rotor and the end portion of the housing, wherein the labyrinth portion includes an annular trap portion protruding from the housing side and facing the rotor flat surface. A magnetic fluid sealing device characterized in that a magnetic circuit is formed in the trap portion. (2) The magnetic fluid seal device according to claim 1, wherein the trap portion is formed of a cylindrical member extending from the housing side toward the rotor side. (3) The magnetic fluid sealing device according to claim 2, wherein the cylindrical member is an extension of an L-shaped pole piece toward the rotor. (4) The magnetic fluid seal device according to claim 2 or 3, wherein the cylindrical member is a separate member from the pole piece and forms part of an L-shape. (5) The magnetic fluid sealing device according to claim 2, wherein the cylindrical member is fitted into a circumferential groove provided in the flat surface of the rotor. (6) The magnetic fluid sealing device according to claim 2, wherein the cylindrical member is composed of two pole pieces and a magnet held between the two pole pieces, and is fixed to the end face of the housing. .