JPH0854068A - Magnetic fluid seal - Google Patents

Abstract

(57) [Abstract] [Purpose] To satisfactorily cool a magnetic fluid without hindering the passage of a magnetic flux toward the magnetic fluid. [Structure] A rotating shaft 1 supported by a bearing 2, a cylindrical housing 3 provided outside the bearing 2 so as to surround the rotating shaft 1, and an appropriate space in the housing in the axial direction. A pair of pole pieces 41a, 41b that are provided and are attached to the inner surface of the housing and that form an annular cooling channel between the inner surface of the housing and the pair of pole pieces 41a and 41b are held between the opposing surfaces of the pole pieces so as to be concentric with the rotation axis. A plurality of permanent magnets 6 provided, a plurality of annular minute protrusions 11 provided on the outer peripheral surface of the rotating shaft corresponding to the inner peripheral surface of the pole piece, and a gap between the annular minute protrusions and the rotating shaft. Magnetic fluid that seals the gap by the action of the magnetic flux from the permanent magnet 12
And the pair of pole pieces gradually increase in radial dimension axially away from the permanent magnet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic fluid seal as a magnetic fluid for sealing a gap between a rotating body and a stationary body.

[0002]

2. Description of the Related Art As a magnetic fluid seal for sealing a gap between a rotating body and a stationary body, there is one having a structure shown in FIG. In FIG. 3, 1 is a rotating shaft made of a magnetic material, 2
Is a pair of bearings for rotatably supporting the rotating shaft 1 with an appropriate interval, and 3 is a housing made of a non-magnetic material provided so as to cover between the pair of bearings 2.

In a space between the pair of bearings 2, a pair of pole pieces 4 made of a magnetic material having a substantially U-shaped cross section are symmetrically arranged at a predetermined interval in the axial direction. One end of 4 is attached to the inner surface of the housing 3 via an O-ring 5.

A permanent magnet 6 is sandwiched between the opposing surfaces of the pole piece 4 on the other end side, and a non-magnetic material is connected via an O-ring 7 between the other ends of the pole piece 4 on the outer circumference side. The member 8 is attached, and the cooling passage 9 is provided between the housing 3 and the back side of the pole piece 4 and the connecting member 8.
Are formed.

On the other hand, a plurality of annular minute projections 11 are provided on the peripheral surface corresponding to the inner peripheral surface 10 of the pole piece 4 of the rotary shaft 1, and these annular minute projections 11 and the inner peripheral surface 10 of the pole piece 4 are provided. The magnetic fluid 12 is present between them.

Next, the operation of the magnetic fluid seal having such a structure will be described. The magnetic flux from the N pole of the permanent magnet 6 is
After passing through the pole piece 4, the annular minute projections 11 of the rotating shaft 1 are concentrated from the inner peripheral surface 10 of the pole piece 4, and pass through the rotating shaft 1 from the plurality of annular minute projections 11 on the S pole side.
It returns to the south pole of the permanent magnet 6 through the pole piece 4 on the pole side.

By following such a magnetic flux path, a plurality of annular minute projections 11 and the inner peripheral surface 10 of the pole piece 4 are formed.
The magnetic fluid 12 existing between and is trapped in the gap between the rotating surface of the rotating shaft 1 and the inner peripheral surface 10 of the pole piece 4 by the concentrated magnetic flux, and as a result, the high pressure side and the low pressure side of the rotating shaft 1 are Both ends having a pressure difference are blocked so that gas does not leak, and rotation of the rotary shaft 1 is allowed.

The heat generation of the magnetic fluid 11 caused by agitation loss during rotation is cooled by flowing a cooling medium through a cooling passage 9 formed on the back side of the pole piece 4 and the permanent magnet 6.

[0009]

In the magnetic fluid seal described above, when the rotary shaft 1 is rotated at a high speed,
The magnetic fluid 12 near the rotating surface rotates at a speed substantially equal to the peripheral speed of rotation, and the magnetic fluid 12 in contact with the stationary inner peripheral surface of the pole piece 4 is stationary, so that the rotating shaft 1 rotates. Shearing stress is generated in the magnetic fluid 12 during the operation.

However, since the magnetic fluid 12 has a large viscosity coefficient, the rotary stirring loss is relatively large. Therefore, when the rotating shaft 1 is rotated at a high speed due to the loss of rotational stirring, the temperature of the magnetic fluid 12 rises.

This temperature rise is cooled by flowing a coolant through the back surface of the permanent magnet 6 and the cooling passage 9 provided in the pole piece 4, but the cooling is performed so as not to prevent the passage of the magnetic flux in the pole piece 4. Since it is necessary to provide the flow passage 9, it is desirable to increase the cross-sectional area of the cooling flow passage 9, but the magnetic flux density and the flow passage cross-sectional area are in a trade-off relationship.

When the temperature of the magnetic fluid 12 rises,
The surfactant for dispersing iron oxide or the like in a colloidal state is destroyed, or the base liquid such as water, oil, ester or hydrocarbon in the magnetic fluid 12 is evaporated and disappears, and only fine particles such as iron oxide or the like remain. However, the hermeticity is impaired and the sealing function of the magnetic fluid seal is lost.

It is an object of the present invention to provide a magnetic fluid seal capable of ensuring a cooling flow path capable of favorably cooling the magnetic fluid without obstructing passage of magnetic flux toward the magnetic fluid. .

[0014]

In order to achieve the above object, the present invention provides a bearing for supporting a rotary shaft, and a cylindrical housing provided outside the bearing so as to surround the rotary shaft. A pair of pole pieces that are provided in the housing at appropriate intervals in the axial direction and are supported by the housing, and that have cooling channels formed on the back surface side,
A plurality of permanent magnets which are held between the facing surfaces of the pole pieces and are provided concentrically with the rotating shaft; and the inner peripheral surface of the pole piece or the outer peripheral surface of the rotating shaft corresponding to the inner peripheral surface. A plurality of annular micro-projections provided on one side or the other, and a magnetic flux passing through a magnetic circuit formed between the rotary shaft and the pole piece by the permanent magnet enclosed in the gap between the annular micro-projections and the rotary shaft. A magnetic fluid that seals the gap by an action, and the cooling channel is enlarged stepwise or continuously in the radial direction as the pair of pole pieces is separated from the permanent magnet on the support portion and the axial rear surface side. It is configured by a magnet gripping portion having a plurality of steps or inclined surfaces.

[0015]

[Function] In the magnetic fluid seal having such a structure,
The radial dimension of the cooling channel increases as it moves away from the permanent magnet so that it does not hinder the passage of the magnetic flux toward the magnetic fluid. , The flow rate increases with the same head, and the cooling effect improves due to the expanded heat transfer surface. Further, since the cooling flow passage does not prevent the passage of the magnetic flux toward the magnetic fluid, the magnetic force acting on the magnetic fluid does not decrease.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view showing a structural example of a magnetic fluid seal according to the present invention, and the same parts as those in FIG. 3 are designated by the same reference numerals. In FIG. 1, 1 is a rotary shaft made of a magnetic material, 2 is a pair of bearings that rotatably support the rotary shaft 1 with an appropriate interval, and 3 is provided so as to cover between the pair of bearings 2. It is a housing made of non-magnetic material.

In the space between the pair of bearings 2, a pair of pole pieces 41 made of a magnetic material having a support portion 41a and a magnet gripping portion 41b having a plurality of stepped back surfaces in the axial direction are formed in the axial direction. Symmetrically arranged with an interval of
The support portions 41a of the pole pieces 41 are attached to the inner surface of the housing 3 via the O-rings 5, respectively.

Further, the magnet gripping portion 41 of the pole piece 41
The permanent magnet 6 is sandwiched between the facing surfaces of b, and the connecting member 8 made of a non-magnetic material is attached via the O-ring 7 between the outer peripheral end surfaces of the magnet gripping portion 41b on the outer peripheral side thereof. A cooling channel 9 is formed between the back side of the connecting member 8 and the housing 3.

In this case, the cooling passage 9 is provided on the axial rear surface side of the magnet gripping portion 41b of the pole piece 41.
It is formed in a step shape that gradually increases in size in the radial direction with increasing distance from.

On the other hand, a plurality of annular minute projections 11 are provided on the peripheral surface corresponding to the inner peripheral surface 10 of the magnet gripping portion 41b of the pole piece 41 of the rotary shaft 1, and these annular minute projections 11 and the pole piece 41 are provided. The magnetic fluid 12 is allowed to exist between the inner surface 10 of the magnet grip portion 41b.

In the magnetic fluid seal having such a structure, the magnet gripping portion 41b is formed between the housing 3 and the pole piece 41 and the permanent magnet 6 on the rear side in the axial direction to form a plurality of steps. Since the cooling flow passage 9 is made to gradually increase in size in the radial direction as the cooling flow passage 9 moves away from the permanent magnet 6, the cross-sectional area of the cooling flow passage becomes larger and the water flow resistance of the refrigerant decreases as compared with the conventional configuration. With the same head, the flow rate increases and the cooling effect is further improved by the expanded heat transfer surface.

Further, even if the cooling flow path is enlarged, the passage of the magnetic flux from the permanent spherical magnet 6 toward the magnetic fluid 12 is not hindered.
The magnetic force acting on the magnetic fluid does not decrease. In the above embodiment, the case where the annular minute projection 11 is provided on the rotary shaft 1 side has been described, but the magnet gripping portion 41 of the pole piece 41 is described.
You may make it provide an annular microprojection on the inner peripheral surface side of b.

The rotating shaft 1 may be formed by fitting a magnetic cylinder into the outer circumference of a non-magnetic rotating shaft, or may be any of a solid shaft and a hollow shaft. 2 is a vertical cross-sectional view showing another embodiment of the magnetic fluid seal according to the present invention. The same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. Only different points will be described here.

In the present embodiment, as shown in FIG. 2, a pair of magnetic members having a support portion 42a and a magnet gripping portion 42b having an inclined rear surface in the axial direction in a space portion existing between the pair of bearings 2. The pole pieces 42 are symmetrically arranged at a predetermined interval in the axial direction, and are configured in the same manner as in the above embodiment.

In this case, an inclined surface is formed on the axial rear surface side of the magnet gripping portion 42b so that the cooling flow path 9 continuously increases in the radial direction as the cooling flow path 9 moves away from the permanent magnet 6.

Even in the magnetic fluid seal having such a structure, the magnetic flux density passing between the inner peripheral surface 10 of the magnet gripping portion 42b of the pole piece 42 and the annular minute projection 11 is secured as in the above-described embodiment. The pressure resistance is not deteriorated, and the seal cooling can be efficiently performed even if the rotating shaft 1 rotates at a high speed and the magnetic fluid 12 has a rotational stirring loss.

[0027]

As described above, according to the present invention, it is possible to secure a cooling flow path capable of favorably cooling the magnetic fluid without obstructing the passage of the magnetic flux toward the magnetic fluid. A fluid seal can be provided.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of a magnetic fluid seal according to the present invention.

FIG. 2 is a vertical sectional view showing another embodiment of the present invention.

FIG. 3 is a vertical sectional view showing a conventional magnetic fluid seal.

[Explanation of symbols] 1 ... Rotary shaft, 2 ... Bearing, 3 ... Housing, 41,
42 ... Pole piece, 41a, 42a ... Supporting part, 4
1b, 42b ... Magnet grip portion, 5, 7 ... O-ring, 6
...... Permanent magnet, 8 ...... Coupling member, 9 ...... Cooling channel, 1
0 ... Inner peripheral surface of magnet gripping part, 11 ... Annular minute projection, 1
2 ... Magnetic fluid.

Claims (2)

[Claims] 1. A bearing for supporting a rotating shaft, a cylindrical housing provided outside the bearing so as to surround the rotating shaft, and provided in the housing with an appropriate interval in the axial direction. A pair of pole pieces supported by the housing and having a cooling passage formed on the back side thereof, and a plurality of permanent pieces provided concentrically with the rotating shaft by being held between the facing surfaces of the pole pieces. A magnet, a plurality of annular micro-protrusions provided on one of the inner peripheral surface of the pole piece or the outer peripheral surface of the rotating shaft corresponding to the inner peripheral surface, and the annular micro-protrusion and the rotating shaft. A magnetic fluid that is sealed in the gap by the action of a magnetic flux passing through a magnetic circuit formed between the rotating shaft and the pole piece by the permanent magnet and that seals the pair of pole pieces with a support portion and an axial direction. A magnetic fluid seal characterized in that it is constituted by a magnet gripping portion in which a plurality of stepped portions are formed such that the cooling flow passage gradually increases in size in the radial direction on the back side facing away from the permanent magnet. 2. The magnetic fluid seal according to claim 1, wherein the cooling passages are continuously provided in the radial direction as the support portion for supporting the pair of pole pieces on the housing and the permanent magnet on the axial rear surface side are separated from each other. A magnetic fluid seal characterized in that it is constituted by a magnet gripping portion having an inclined surface that becomes large.