JPH0242280A - Magnetic fluid seal device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a magnetic fluid seal device.

(Prior Art) FIG. 3 shows a conventional magnetic fluid sealing device. This is disclosed in Japanese Utility Model Application Publication No. 54-140163.

As shown in the figure, this sealing device consists of a rotating shaft 1, a rotating ring 2 concentrically surrounding the rotating shaft 1, a ring-shaped magnet 3 attached to the inner peripheral surface of the rotating ring 2, and a ring-shaped magnet 3 attached to the inner peripheral surface of the rotating shaft 1 and the magnet 3. It is composed of a magnetic fluid 4 interposed in the gap between the two.

Although not shown, there is also a configuration in which the magnet 3 is attached to the outer peripheral surface of the rotating shaft 1 and the magnetic fluid 4 is interposed in the gap between the magnet 3 and the rotating ring 2.

[Problem to be solved by the invention]

However, in the conventional sealing device, the magnetic force of the magnet 3 (
Since the structure is such that the magnetic fluid 4 is held only by a bundle (bundle), it is difficult to obtain sufficient sealing performance.

In particular, during relative rotation between the rotating shaft 1 and the rotating ring 2, the magnetic fluid 4 may be scattered due to centrifugal force, making it impossible to obtain sufficient sealing performance.

The present invention was made to solve these conventional problems, and an object of the present invention is to provide a magnetic fluid sealing device that has sufficient sealing performance and is inexpensive.

[Means to solve the problem]

The magnetic fluid seal device provided by the present invention includes a metal member, a plastic magnet member that faces the metal member and rotates relative to the metal member, and a magnetic fluid held in a gap between the plastic magnet member and the metal member. The plastic magnet member is provided with a dynamic pressure generating groove integrally molded at the time of molding the magnet member on the surface facing the metal member.

The synthetic resin used for the above plastic magnet member is as follows:
Polyamide resin, fluororesin, polyether sulfine resin. Polyphenylene sulfide resin etc. can be used.

The magnetic powder mixed with the resin can be barium ferrite powder, strontium ferrite powder, or rare earth magnetic powder.

When used as a seal, the stronger the magnetization is, the better, so the mixing ratio for ferrite is about 70 to 95 wt%, just like normal plastic magnets.

It is preferable to use a cylindrical plastic magnet member molded by the method for molding a fluid bearing sleeve previously filed by the present applicant (Japanese Patent Application No. 156244/1982).

When using this method, first, a mold having a structure in which a core bin having a spiral dynamic pressure generating groove is inserted into the central axis of a cylindrical cavity with a length half of a predetermined length is used. After injection molding the molten resin mixed with powder, the core bin is rotated and extracted to create a sleeve with spiral grooves for generating dynamic pressure on the inner surface.

Next, a large number of these sleeve members are inserted into an arbor having a diameter slightly larger than the desired inner diameter, and heated.
The inner surface of the sleeve member is shrunk or deformed to a specified size. Thereafter, the sleeves with opposite groove twisting directions are assembled as a pair.

In this way, it is possible to obtain a plastic magnet member having a herringbone-shaped dynamic pressure generating groove on the inner surface and having extremely good dimensions and bulk. After that, it is magnetized in the axial direction.

The herringbone-shaped groove may be formed symmetrically about the joining line of the pair of joined sleeves, or may be formed asymmetrically. The twist angle of the herringbone groove with respect to the axis can also be arbitrarily selected.

[Effect]

According to this invention, when the metal member and the plastic magnet member rotate relative to each other, high dynamic pressure is generated in the magnetic fluid by the dynamic pressure generation groove provided in the magnet member. Therefore, when the two members rotate relative to each other, the magnetic fluid is strongly held by the high dynamic pressure and the magnetic force (flux) of the magnetic member, resulting in a strong sealing force.

Further, since the dynamic pressure generating groove is integrally molded when the plastic magnet member is molded, by increasing the precision of the mold, it is possible to manufacture high-precision plastic magnet members at low cost and in large quantities.

(Example) Hereinafter, an example of the present invention will be described based on the drawings. In each figure, the same or equivalent parts are indicated by the same reference numerals.

This embodiment shows a magnetic fluid sealing device for a rotating shaft.

In the figure, 1 is a rotating shaft, and 2 is a housing. 0 A rotating shaft 1 is attached to a housing 2 via a bearing 3. 4 is an annular plastic magnet attached to the seat 5 of the housing 2. This magnet 4 is a combination of a pair of annular plastic magnets 4a and 4b, each of which has a herringbone groove 6 for generating dynamic pressure on the opposing surface of the rotating shaft 1. While making the gap C between rotation @I a little larger,
The herringbone groove 6 is formed deep to suppress torque loss and heat generation of the rotating shaft 1 due to resistance of the magnetic fluid 7 injected 17.

In the sealing device configured as described above, during rotation of the rotating shaft 1,
Since a high dynamic pressure is generated in the magnetic fluid 7, this dynamic pressure and the magnetic force (flux) of the magnet 4.

Sufficient sealing performance against internal pressure or external pressure of rotating equipment can be obtained. In particular, this sealing device is suitable for sealing gases and liquids, and exhibits significantly superior sealing performance compared to conventional magnetic fluid sealing devices.

Moreover, since the rotating shaft 1 and the plastic magnet 4 do not come into direct contact with each other, the life is long even in continuous operation for a long rotation time.

In addition, since the herringbone groove 6 for generating dynamic pressure is integrally molded when the plastic magnet 4 members are molded, by increasing the precision of the mold, the plastic magnet 4 members with high precision can be produced in large quantities at low cost. It can be made to.

FIG. 2 shows a second embodiment. The kone is a combination of a non-magnetic plastic dynamic pressure bearing and a hydrodynamic magnetic fluid seal.

In the figure, 8 was filed earlier by the 5th applicant (Japanese Patent Application No. 5
No. 6-156244) This is a split type hydrodynamic bearing sleeve, which is a non-magnetic plastic molded product, and has a herringbone groove 6 for generating dynamic pressure on the inner surface.

9.10 is a spiral groove 9a for generating dynamic pressure.

It is an annular plastic magnet having a diameter 10a on its inner surface, and is integrally assembled to sandwich the bearing sleeve 8.

During rotation, the rotating shaft 1 is aligned and supported by the dynamic pressure of the magnetic fluid 11 generated in the gap C between the sleeve 8 and the rotating shaft 10. The magnetic fluid 12 in the gap C2 between the plastic magnets 9 and 10 and the rotating shaft 1 is
It is held in the same gap c2 by the magnetic force of the plastic magnets 9 and 10, and also by the dynamic pressure generated by the rotation of the rotating shaft 1. As a result, the sealing force by the magnetic fluid 12 becomes stronger.

When the rotating shaft 1 stops, the rotating shaft 1 is seated and supported on the inner surface of the bearing sleeve 8, which has a smaller diameter than the plastic magnets 9 and 10, so that the rotating shaft 1 does not come into direct contact with the plastic magnets 9 and 10. There isn't. Therefore, the life of the seal is longer than that of FIG. 1, regardless of the frequency of startup and shutdown.

Further, as in the first embodiment, highly accurate plastic magnets 9 and 10 can be produced at low cost and in large quantities.

[Effects of the Invention] As explained above, in this invention, the groove for generating dynamic pressure is provided in the plastic magnet member for sealing, so when the metal member and the plastic magnet member rotate relative to each other, the gap between the two members is filled. The injected magnetic fluid is strongly held by the magnetic force (flux) of the plastic magnet member and the dynamic pressure generated by the dynamic pressure generating groove, and there is no risk of it scattering as in the conventional case. Further, since the dynamic pressure generating groove is molded at the same time as the plastic magnet member is molded, by increasing the precision of the mold, it is possible to manufacture high-precision plastic magnet members at low cost and in large quantities.

Therefore, according to the present invention, it is possible to obtain a magnetic fluid sealing device that has sufficient sealing performance and is inexpensive.

[Brief explanation of the drawing]

1 and 2 show a first embodiment and a second embodiment of the present invention.
FIG. 3 is a cross-sectional view of a conventional magnetic fluid seal device. 1... Rotating shaft 2... Housing 4.9.10... Annular plastic magnet 6.
...Herringbone groove 7.12 ...Magnetic fluid

Claims (1)

[Claims] The plastic magnet member is composed of one metal member, a plastic magnet member that faces the metal member and rotates relative to the metal member, and a magnetic fluid held in a gap between the plastic magnet member and the metal member, and the plastic magnet member 1. A magnetic fluid sealing device characterized by having a dynamic pressure generating groove integrally molded during molding of the magnetic member on the side facing the metal member.