JPH05248547A - Manufacture of seal ring for magnetic fluid seal device - Google Patents

Abstract

PURPOSE:To improve the bond strength of a permanent magnet and a pole piece and prevent the deformation of the pole piece. CONSTITUTION:The surface of a permanent magnet 7 is covered with an intermediate layer of elastic material and a surface layer of phenoxy resin. With this permanent magnet 7 clamped with a pair of pole pieces 8 and 9, each of members 7, 8 and 9 is heated and pressure fixed by means of dies 12 and 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The method for manufacturing a seal ring for a magnetic fluid seal device according to the present invention is, for example, a magnetic fluid seal for maintaining airtightness in a portion where a drive shaft for a hard disk incorporated in a computer or the like penetrates a wall surface of a casing. It is used when manufacturing the seal ring that constitutes the device.

[0002]

2. Description of the Related Art In a hard disk incorporated in a computer or the like, a disk, which is a magnetic storage element provided in a casing, is rotationally driven by a motor provided outside the casing, but the hard disk itself is extremely disliked by dirt and the like. Therefore, it is necessary to provide a sealing device for preventing dust from passing through a portion where the drive shaft of the motor penetrates the wall surface of the casing.

For this reason, a magnetic fluid sealing device as shown in FIGS. 1 and 2 has been conventionally used. Of these, reference numeral 1 in FIG. 1 denotes a housing made of a non-magnetic material such as aluminum or synthetic resin, which is fixed to, for example, the wall surface of the casing. Reference numeral 2 is a shaft made of a magnetic material such as iron, and a seal ring 3 is installed in a cylindrical space 6 between the inner peripheral surface 4 of the housing 1 and the outer peripheral surface 5 of the shaft 2. ..

The seal ring 3 is a pair of pole pieces 8 formed by magnetically forming a ring-shaped permanent magnet 7 which is magnetized in the axial direction (vertical direction in FIG. 1). 9
It is configured by sandwiching it in a sandwich. Then, the magnetic fluid 10 is placed in the gaps 11 and 11 between the inner peripheral edges of the pole pieces 8 and 9 and the outer peripheral surface 5 of the shaft 2.
It is held by the magnetic force of the permanent magnet 7.

The permanent magnet 7 and a pair of pole pieces 8;
The outer diameter with respect to 9 is made slightly smaller than the inner diameter of the housing 1, and the seal ring 3 constituted by the respective members 7, 8, 9 and 10 is fitted into the inner peripheral surface 4 of the housing 1 and further bonded. As a result, the seal ring 3 is fixed to the inside of the housing 1, and the sealability between the outer peripheral edge of the seal ring 3 and the inner peripheral surface 4 of the housing 1 is maintained.

Since the magnetic fluid sealing device is constructed as described above, regardless of the rotation of the shaft 2 inside the housing 1,
The magnetic fluid 10 held between the outer peripheral surface 5 of the shaft 2 and the inner peripheral edges of the pole pieces 8 and 9 maintains the sealing property between the inner peripheral surface 4 of the housing 1 and the outer peripheral surface 5 of the shaft 2. Is planned.

In the case of a structure in which the shaft 2 is fixed and the housing 1 rotates, as shown in FIG.
Is fixed to the outer peripheral surface 5 of the shaft 2 made of a non-magnetic material, and the magnetic fluid 1
0 may be held between the outer peripheral edges of the pair of pole pieces 8 and 9 and the inner peripheral surface 4 of the magnetic material housing 1. Further, the pole pieces 8 and 9 are not necessarily provided on both sides of the permanent magnet 7, and when the magnetic circuit is formed by, for example, a rolling bearing existing near the magnetic fluid seal device, the pole pieces 8 and 9 are not provided. A pole piece may be provided on only one side.

By the way, in the case of constructing the magnetic fluid sealing device configured and functioning as described above, the ring-shaped permanent magnet 7 is used.
The pole pieces 8 and 9 must be adhered to both sides (or one side) of the above so that the members 7, 8 and 9 are concentric with each other to form the seal ring 3 so that the seal ring 3 can be handled integrally. ..

As a technique for this purpose, the present inventor has previously made an invention relating to a method for manufacturing a seal ring for a magnetic fluid seal device, which is disclosed in Japanese Patent Laid-Open No. 2-46374.
In this conventionally known method for manufacturing a seal ring for a magnetic fluid seal device, the surface of a permanent magnet is coated with a resin such as phenoxy resin to form a surface layer, and then, as shown in FIG.
The permanent magnet 7 covered with the surface layer and the pole pieces 8 and 9 are coaxially overlapped. Next, as shown in FIG. 4, the permanent magnet 7 and the pole pieces 8 and 9 which are superposed on each other are heated to a temperature equal to or higher than the melting point of the resin while being pressed by the dies 12 and 13, and thus the permanent magnet is heated. 7 and the pole pieces 8 and 9 are bonded.

[0010]

However, in the conventional method for manufacturing the seal ring for the magnetic fluid seal device as described above, depending on the material of each component 7, 8, 9 of the seal ring 3, May cause problems such as those described in.

As a first problem, as a permanent magnet 7, a so-called nylon magnet in which magnetic powder is dispersed in a nylon resin is used, and a problem occurs when a phenoxy resin is used as an adhesive resin. Conceivable.

That is, since the phenoxy resin and the nylon resin are not compatible with each other and it is difficult to obtain sufficient adhesive strength, the seal ring 3 having sufficient strength due to insufficient adhesive strength at the interface between the phenoxy resin and the permanent magnet 7. Hard to get.

Next, as a second problem, since the phenoxy resin has high rigidity, due to the difference in the thermal expansion amount between the permanent magnet 7 and the pole pieces 8 and 9 adhered by the phenoxy resin, It is possible that the pole pieces 8 and 9 are deformed.

That is, when the permanent magnet 7 whose surface is covered with a phenoxy resin is sandwiched between a pair of pole pieces 8 and 9 and the members 7, 8 and 9 are bonded by being heated while pressing each other, The members 7, 8 and 9 are adhered in a thermally expanded state.
After that, when the respective members 7, 8 and 9 are adhered with the phenoxy resin and contracted due to the temperature decrease, the pole pieces 8 and 9 warp due to the difference in the contraction amount (like bimetal). There is a risk that

If a synthetic rubber type resin is used as the resin for coating the surface of the permanent magnet 7, the above-mentioned inconvenience will be eliminated, but the synthetic rubber type resin will not be affected by a specific solvent even after heat bonding. Since it elutes and reduces the adhesive strength, it is unavoidable that the application is limited, and it is impossible to reduce the cost of the magnetic fluid sealing device by making a general-purpose seal ring.

The method of manufacturing the seal ring for the magnetic fluid seal device of the present invention has been conceived in view of the above circumstances.

[0017]

A method of manufacturing a seal ring for a magnetic fluid seal device according to the present invention comprises a first step of forming an intermediate layer by coating the surface of a ring-shaped permanent magnet with an elastic material, and the above-mentioned elasticity. The second step of forming a surface layer by coating the surface of the material with a phenoxy resin and the pole piece formed in a ring shape by a permanent magnet and a magnetic material, which are covered with the intermediate layer and the surface layer, are coaxial. And the third step,
By pressing the permanent magnet and the pole piece that are superposed on each other while heating them to a temperature equal to or higher than the melting point of the elastic material and the phenoxy resin, a fourth step of bonding the permanent magnet and the pole piece together ..

The elastic material is preferably a synthetic rubber type coating agent having an elongation of 150 to 500%.

[0019]

With the magnetic fluid seal device having the seal ring manufactured by the manufacturing method of the present invention, which is constructed as described above, the relative rotation between the housing and the shaft is made possible, and The action of closing the gap between the shaft and the outer peripheral surface is similar to that of the conventionally known magnetic fluid sealing device.

However, in the case of the seal ring manufactured by the manufacturing method of the present invention, since the intermediate layer made of the elastic material is provided between the surface layer made of phenoxy resin and the permanent magnet, the permanent magnet and the pole piece are provided. Adhesive strength with is sufficiently high.

That is, the adhesive strength between the permanent magnet and the intermediate layer is
It is sufficient regardless of the material of the permanent magnet (even if the permanent magnet is a nylon magnet). Further, the adhesive strength between the intermediate layer and the surface layer and the adhesive strength between the surface layer and the pole piece are also sufficient, and as a result, the permanent magnet and the pole piece are sufficiently firmly bonded and fixed.

Further, since an intermediate layer made of an elastic material exists between the permanent magnet and the pole piece, even when the permanent magnet and the pole piece bonded to each other have a different thermal expansion amount. The force in the shearing direction generated based on this difference is absorbed by the intermediate layer, and the pole piece does not warp.

Further, since the intermediate layer made of an elastic material such as a coating agent of synthetic rubber is covered with the surface layer made of phenoxy resin, it does not come into contact with the gas or liquid existing outside,
The adhesive strength between the permanent magnet and the pole piece does not decrease even when used in the presence of solvent vapor or the like.

[0024]

EXAMPLES Next, experiments conducted to confirm the effects of the present invention will be described.

First, a chloroprene rubber-based coating agent was applied to a ring-shaped nylon magnet to prepare a permanent magnet covered with a coating agent which is an elastic material.

The above chloroprene rubber coating agent is active at about 100 ° C. and has an elongation of 20.
It reaches about 0%. The coating operation is carried out by immersing the nylon magnet in a solution in which the coating agent is dissolved in a solvent of 15% by weight, that is, by so-called soaking, to form a coating film having a thickness of about 10 μm on the surface of the nylon magnet. , As an intermediate layer. Then, the nylon magnet, after applying a chloroprene rubber-based coating agent,
The intermediate layer was completely dried by leaving it to stand for 20 minutes.

Then, after it is confirmed that the intermediate layer is completely dried, a phenoxy resin is overlaid on the surface of the intermediate layer to form a surface layer, and the surface is formed by the intermediate layer and the surface layer. A permanent magnet covered with was obtained. As the phenoxy resin, one that melts at about 120 ° C. was used. Applying this phenoxy resin to a solvent
The nylon magnet coated with the above intermediate layer was dipped in a solution dissolved by weight%, that is, so-called soaking to form a coating film having a thickness of about 10 μm, which was used as a surface layer.

Next, as shown in FIGS. 3 to 4, nylon magnets whose surfaces are covered with an intermediate layer and a surface layer are sandwiched between two annular pole pieces in a sandwich shape and coaxially overlapped. Then, the nylon magnet and the pole piece were thermocompression-bonded to each other by heating them to 150 ° C. while pressing them with a die from above and below to form a seal ring.

The seal ring obtained as a result is one in which the entire surface of the nylon magnet, which is a permanent magnet, is covered with the intermediate layer and the surface layer, and the pole piece and the magnet are not easily separated from each other. It could be put to practical use.

The seal ring obtained by the above-mentioned manufacturing method is the manufacturing method described in the above-mentioned publication in both the adhesive strength test of the bonding surface between the permanent magnet and the pole piece and the solvent resistance test. The pole piece was not deformed, which was superior to the conventional product obtained by the above method and was observed when the resin present on the adhesive surface was only phenoxy resin.

The chloroprene rubber-based coating agent and the phenoxy resin need to function as an adhesive, but the chloroprene rubber-based coating agent forming the intermediate layer forms a surface layer at about 80 ° C to 130 ° C. A phenoxy resin that is active or melts at about 120 ° C. to 200 ° C. can be preferably used because it does not deform the nylon magnet during bonding by heating.

As the solvent, hydrocarbon solvents can be preferably used. Among them, for example, cyclohexanone,
Cyclohexane, xylene, toluene, hexane, acetone, ethyl acetate, methyl ethyl ketone, methyl isobutyl ketone and the like can be particularly preferably used.

In this case, the mixing ratio of the chloroprene rubber-based coating agent and the phenoxy resin to the solvent is preferably about 5 to 20% by weight in order to secure the adhesive force between the pole piece and the permanent magnet. The thickness of the coating film forming the intermediate layer and the surface layer is preferably 5 to 30 μm.

If the mixing ratio of the chloroprene rubber-based coating agent is too small, the adhesive strength will be insufficient. On the contrary, if the mixing ratio is too large, the adhesive strength will not be improved any more.
It costs too much. Also, if the coating film is too thin, the adhesive strength will also be weak, and if it is too thick, dust on the edges of the coating film will contaminate the clean space in which the hard disk, etc. are provided. ..

As the coating agent constituting the intermediate layer, in addition to the above-mentioned chloroprene rubber-based coating agent, modified butyl-based synthetic rubber which activates at 100 ° C. to 160 ° C., and nitrile rubber-based coating agent 100 to 160 It is possible to use those which activate at 0 ° C., those which melt at 80 to 130 ° C. of a polyethylene type, and those which activate at 80 to 130 ° C. of a polyamide type.

Although all of these coating agents are liquids, hydrocarbon solvents are preferable as the solvent, and they are also dissolved in a mixing ratio of about 5 to 20% by weight to prepare a solution for dripping. The present inventor conducted a similar test using these coating agents, but it was confirmed that the same effect as when the chloroprene rubber-based coating agent was used was obtained.

[0037]

The method for manufacturing a seal ring for a magnetic fluid seal device according to the present invention is constructed and operates as described above, so that a magnetic fluid seal device having excellent durability and reliability can be provided at a low cost.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first example of a basic structure of a conventional magnetic fluid seal device.

FIG. 2 is a sectional view showing a second example of the same.

FIG. 3 is a perspective view showing an intermediate step of a conventional manufacturing method.

FIG. 4 is a perspective view showing a process following FIG.

[Explanation of sign]

 1 Housing 2 Shaft 3 Seal Ring 4 Inner Surface 5 Outer Surface 6 Space 7 Permanent Magnet 8 Pole Piece 9 Pole Piece 10 Magnetic Fluid 11 Gap 12 Die 13 Dice

Claims (1)

[Claims] 1. A first step of coating the surface of a ring-shaped permanent magnet with an elastic material to form an intermediate layer, and a second step of coating the surface of the elastic material with a phenoxy resin to form a surface layer. , A third step of coaxially superimposing a permanent magnet whose surface is covered with the intermediate layer and the surface layer and a pole piece formed in a ring shape by a magnetic material, and a permanent magnet and a pole piece superposed on each other. By heating to a temperature above the melting point of the elastic material and the phenoxy resin while applying pressure,
A method of manufacturing a seal ring for a magnetic fluid seal device, comprising the fourth step of bonding a permanent magnet and a pole piece together.