JPS648228B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a magnetic fluid seal that is composed of a magnetic fluid, a magnet, and a magnetic circuit, and obtains a seal by attaching a magnetic fluid to a magnetic pole part that forms the magnetic circuit. be.

Structure of conventional example and its problems Regarding the conventional magnetic fluid seal, Figures 1 and 2 show the conventional magnetic fluid seal.
This will be explained using figures. FIG. 1 shows a schematic diagram of the magnetic fluid shaft seal, showing the state when the shaft is rotating, and FIG. 2 shows the state when the shaft is stationary. In Figures 1 and 2, 1 is a magnetic fluid, 2 and 3 are thick cylindrical pole blocks made of magnetic material, and 4 is arranged on the circumference between two pole blocks 2 and 3. 5 is the fixed part,
6 is a shaft; 7 is a protrusion 7a fixed to the shaft 6;
7b, the shaft cover is made of a magnetic material.

The operation of the conventional magnetic fluid shaft seal configured as described above will be described below.

The pole blocks 2, 3, the shaft cover 7, and the magnet 4 form a magnetic circuit as shown by arrow A, spanning the shaft 6 side and the fixed part 5 side, as shown in FIG. Projections 7a, 7 provided on the shaft cover 7
In part b, the magnetic field is large. For this reason,
When magnetic fluid is injected into the gap between the inner walls of the pole blocks 2 and 3 and the shaft cover 7, the gaps between the tips of the projections 7a and 7b and the inner walls of the pole blocks 2 and 3 are filled in a ring shape and sealed. A closed magnetic circuit is formed.

However, in the above configuration, since the magnetic field gradient near the protrusions 7a and 7b is very high,
The colloidal particles in the magnetic fluid 1 attached to the projections 7a, 7b are subjected to a very large magnetic force, and as shown in FIG. Accumulation 1a (hatched area)
happens. Due to this effect, a phenomenon occurs in which the maximum seal pressure increases as time passes after the magnetic fluid 1 is injected into the seal part, and when an attempt is made to rotate the stationary shaft 6, it becomes a very large load. A drawback has arisen in that the starting torque increases. When the shaft 6 is rotated, the magnetic fluid 1 is stirred by the rotation, so that the dense part of the colloid particles disappears as shown in FIG. 1, and the seal pressure is restored to a constant state.

OBJECT OF THE INVENTION The present invention solves the above-mentioned conventional drawbacks.
An object of the present invention is to provide a magnetic fluid seal that can maintain a substantially constant seal pressure at all times.

Structure of the Invention The present invention comprises a cylindrical magnet with magnetic poles arranged in the axial direction, and a cylindrical magnet made of a magnetic material with the magnet sandwiched between them.
a magnetic body that forms a magnetic circuit by arranging ring-shaped protrusions facing each other and spaced apart from each other on the cylindrical inner circumferential surface of the pole piece, and the protrusion of the magnetic pole piece and the polar body. between a roughly cylindrical elastic member provided on at least one side of the magnetic pole and elastically displaceable in the radial direction, and a ring-shaped protrusion provided on one side of the magnetic pole;
In addition, it has a magnetic fluid provided between an elastic member provided on the side of the ring-shaped protrusion and the magnetic pole piece, and the elastic member is connected to the direction of the magnetic pole piece and the protrusion of the colloidal particles of the magnetic fluid generated by the magnetic force of the magnetic circuit. This is a magnetic fluid seal that displaces the elastic member in the radial direction by the accumulated force of the magnetic fluid, and maintains a substantially constant seal pressure at all times.

DESCRIPTION OF EMBODIMENTS FIG. 3 shows a block diagram of a magnetic fluid seal in an embodiment of the present invention, showing the state when the shaft is rotating. FIG. 4 shows the state in which the shaft is stationary in FIG. 3. Components that are the same as those in FIGS. 1 and 2 will be explained using the same numbers. In Figures 3 and 4, 1 is a magnetic fluid, 2 and 3 are thick cylindrical pole blocks made of magnetic material, and 4 is arranged on the circumference between two pole blocks 2 and 3. 5 is a fixed part, 6 is a shaft, 7 is a shaft cover made of a magnetic material fixed to the shaft 6, and has a ring-shaped protrusion 7a at a position facing and spaced apart from the magnetic pole parts of the pole blocks 2 and 3. , 7b are provided. 8 and 9 are ring-shaped elastic members provided between the pole blocks 2, 3 and the protrusions 7a, 7b, and between the protrusion 7a and the elastic member 8, and between the protrusion 7b and the elastic member 9, magnetic fluid is 1 is retained and sealed.

The operation of the magnetic fluid seal of this embodiment constructed as described above will be described below. By providing the pole blocks 2, 3 and the shaft cover 7, a magnetic circuit as shown by arrow A is formed spanning the shaft 6 side and the fixed part 5 side as shown in FIG. Since the magnetic field is large at the protrusions 7a and 7b of the shaft cover 7, when an elastic member is injected into the gap between the shaft cover 7 and the elastic members 8 and 9, the tips of the protrusions 7a and 7b and the elastic members 8 and 9 are The gap with the inner surface of magnet 9 is filled in a ring shape and sealed, forming a nearly closed magnetic circuit with magnet 4. Notation part 7a,
Since the magnetic field gradient near 7b is very high, the colloidal particles in the magnetic fluid 1 attached to the protrusions 7a and 7b are subjected to a very large magnetic force, and the magnetic field at the tips of the protrusions 7a and 7b is Colloidal particles tend to accumulate at the highest point. However, when the shaft 6 is rotating, as shown in FIG. 3, the magnetic fluid 1 is stirred by the rotation of the shaft 6, so no accumulation of colloid particles occurs, and a constant sealing pressure is maintained. Also, when the shaft 6 is stationary, the fourth
As shown in the figure, an accumulation of colloidal particles 1a (retarded portion) occurs, and the colloidal particles move in the direction of the magnetic flux, that is, on the cylindrical inner circumferential surface of the magnetic pole pieces 2 and 3 and on the protrusions 7a and 7b.
An accumulation force acts in the direction of . The elastic members 8 and 9 are deformed in a direction approaching the cylindrical inner circumferential surfaces of the magnetic pole pieces 2 and 3 by the gathering force of the colloid particles acting in the direction of the cylindrical inner circumferential surfaces of the magnetic pole pieces 2 and 3. Therefore, the gaps between the protrusions 7a, 7b and the elastic members 8, 9 widen, so that the magnetic pole pieces 2,
The cross-sectional area of the collection 1a of colloidal particles in the radial direction of No. 3, that is, in the direction orthogonal to the direction of magnetic flux, becomes smaller. Therefore, the increase in the holding force due to the accumulated colloidal particles of the magnetic fluid held between the protrusions 7a, 7b and the elastic members 8, 9 is reduced.
There is almost no increase in the sealing pressure, and the sealing pressure can be maintained at a substantially constant state.

In addition, although the elastic members 8 and 9 are provided between the pole blocks 2 and 3 and the projections 7a and 7b in FIGS. 3 and 4, the elastic members 8 and 9 are elastically pressed. A similar effect can be obtained by providing . Further, the elastic members 8 and 9 may be provided on the shaft cover 7 side, which is a magnetic material, or may be provided on both sides.

Effects of the Invention As described above, according to the present invention, when a magnetic circuit is formed and colloidal particles are accumulated in the magnetic fluid due to magnetic force in sealing using a magnetic fluid, the colloidal particles can be collected with a simple configuration. By widening the gap in the seal part with the accumulated force,
A nearly constant seal pressure can be maintained at all times.

[Brief explanation of drawings]

1 and 2 are cross-sectional front views of a magnetic fluid shaft seal showing an example of a conventional magnetic fluid seal, and FIGS. 3 and 4 are cross-sectional front views of a magnetic fluid seal according to an embodiment of the present invention. be. 1... Magnetic fluid, 1a... Accumulated colloid particles, 2, 3... Pole block, 4... Magnet,
5... Fixed part, 6... Shaft, 7... Shaft cover, 7
a, 7b... protrusion, 8, 9... elastic member.

Claims (1)

[Claims] 1. A cylindrical magnet with magnetic poles arranged in the axial direction; two cylindrical magnetic pole pieces sandwiching the magnet; A magnetic body is provided with a ring-shaped protrusion to form a magnetic circuit, and an elastic member having a roughly cylindrical shape and capable of being elastically displaced in the radial direction is provided on at least one side of the magnetic pole piece and the protrusion of the magnetic body. a magnetic fluid provided between the elastic member provided on one side of the magnetic pole and the ring-shaped protrusion, and between the elastic member provided on the ring-shaped protrusion side and the magnetic pole piece; the elastic member is caused by an accumulation force of colloidal particles in the magnetic fluid toward the magnetic pole piece and the protrusion, which is generated by the magnetic force of the magnetic circuit;
A magnetic fluid seal that displaces the elastic member in the radial direction and maintains a substantially constant seal pressure at all times.