JP2520743B2 - Magnetic fluid seal device - Google Patents

Description

The present invention relates to a magnetic fluid seal device.

[Problems to be Solved by Conventional Techniques and Inventions]

Conventionally, in the fixed shaft type spindle motor as illustrated in FIG. 4, the magnetic fluid sealing device S has a problem that the magnetic fluid a is scattered by the centrifugal force acting on the magnetic fluid a. That is, on the side of the rotor b that rotates as indicated by the arrow M,
The flat ring magnet c and the outer peripheral edges of the pole pieces e, e are fixed and rotated integrally, and the magnetic fluid a is injected into a minute gap between the outer peripheral surface of the fixed shaft f and the inner peripheral edge of the pole piece e. I was holding it.

Therefore, as shown in FIG. 5, the centrifugal force Fi of the portion where the magnetic fluid a contacts the fixed shaft f (here, the peripheral velocity is zero) is zero, while the inner peripheral edge of the pole piece e is zero. A large centrifugal force Fo acts on the part in contact with. Since the pole piece e rotates at a high speed, a portion of the magnetic fluid a which is in contact with the pole piece e near the outer periphery also rotates at a high speed, and a large centrifugal force is generated.
Fo acts. This centrifugal force Fo becomes larger than the magnetic force restraining force (surface tension and attracting force) of the magnetic fluid, and the magnetic fluid a propagates along the surface g of the pole piece e and scatters in the outer diameter direction.

[Means for solving the problem]

In order to solve the above problems, the present invention provides a magnetic fluid seal device interposed between a rotary cylinder and a fixed shaft; a magnetic fluid seal device interposed between the rotary cylinder and a fixed shaft. A cylindrical portion that surrounds the outer peripheral surface of the rotating shaft with a gap, an attaching portion that is fixed to the rotating cylindrical body, and a connecting portion that connects the cylindrical portion and the attaching portion, A rotation receiving member made of a magnetic material, which has an annular recess opening outward in the axial direction from the cylindrical portion, the mounting portion, and the connecting portion; and a retainer that is loosely fitted into the annular recess of the rotation receiving member. A cylindrical portion, a mounting portion that is directly or indirectly fixed to a part of the fixed shaft, and a flat plate that connects the mounting portion and the holding tubular portion and forms the outer opening of the holding tubular portion into a lid-like shape. A seal body holding member having an annular connecting portion; a magnet and a pole piece, and an inner peripheral end of the holding cylinder portion The outer peripheral edge of the pole piece is held by the inner peripheral edge of the pole piece and the inner peripheral edge of the pole piece faces the outer peripheral surface of the cylindrical portion with a minute gap. A magnetic fluid seal body interposed therebetween; magnetism retained in a minute gap formed between the inner peripheral edge of the pole piece of the magnetic fluid seal body and the outer peripheral surface of the cylindrical portion of the rotation receiving member. And a fluid.

[Action]

The magnetic fluid is held in an annular shape between the outer peripheral surface of the cylindrical portion of the magnetic material rotation receiving member and the inner peripheral edge of the stationary magnetic fluid seal body, and the annular magnetic fluid has an inner peripheral edge. Rotates with the cylindrical portion, but the outer peripheral edge of the seal body has a stationary or low-speed rotational movement. That is, a large centrifugal force acts on the magnetic fluid on the outer peripheral surface side of the cylindrical portion of the rotation receiving member, and conversely, only zero or a slight centrifugal force acts on the magnetic fluid on the pole piece side, and the magnetic fluid is restrained. The force (surface tension and suction force) is superior to the centrifugal force on the pole piece side and is always held in the original position-the minute gap portion.

Even if the holding state of the magnetic fluid is released and the magnetic fluid is scattered inward in the axial direction, the magnetic fluid is received by the connecting portion or mounting portion of the rotation receiving member, and conversely, the magnetic fluid is moved in the axial direction. Even if it scatters to the outside, it is received by the connecting part or the holding cylinder of the seal body holding member and does not scatter to the outside of the motor.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

FIG. 1 shows a fixed shaft type spindle motor using the magnetic fluid sealing device 1, 1 according to the present invention. In this motor, a stator 3 is fixed to a fixed shaft 2 and a pair of bearings 4 and 4 are used. A hub 5 is rotatably attached to the fixed shaft 2. Reference numeral 6 denotes a bracket which is fixed to another member (not shown).

The hub 5 has a yoke 7 on the inner peripheral side, and a rotor magnet 8 is fixed to the inner peripheral surface of the yoke 7 at an axial position corresponding to the stator 3.

In this way, a pair of magnetic fluid seal devices 1, 1 are interposed between the rotating cylindrical body 9 including the hub 5 and the yoke 7 and the fixed shaft 2 in FIG.

FIG. 2 is an enlarged view of a main part of the magnetic fluid seal device 1 on the left side of FIG. In FIG. 2 and FIG. 1, 10 is a magnetic fluid seal main body composed of a flat plate annular magnet 11 and flat plate annular pole pieces 12, 12 sandwiching the flat plate magnet 11 from both sides.

Reference numeral 13 denotes a rotation receiving member made of a magnetic material.
Has a cylindrical portion 14 that surrounds the outer peripheral surface of the fixed shaft 2 with a gap, and is a cylindrical mounting portion 15 that is fitted and fixed to one end inner peripheral surface of the yoke 7 of the rotating cylindrical body 9. , And a flat plate annular connecting portion that connects the cylindrical portion 14 and the mounting portion 15
With 16. That is, the receiving member 13 has a horizontal cross section.
It is a U-shape that forms an annular recess 17 that opens to the outside of the motor.

Reference numeral 18 denotes a seal body holding member, which has a holding cylinder portion 19 facing the outer peripheral surface of the cylindrical portion 14 with a predetermined interval slightly larger than the width dimension of the seal body 10, and this holding cylinder portion.
The outer peripheral edge of the seal body 10 is fitted and held on the inner peripheral surface of 19. That is, the fixed shaft 2, the cylindrical portion 14, the seal body 10, the holding tubular portion 19, the mounting portion 15, and the yoke 7 are arranged concentrically. Further, 20 is a cylindrical mounting portion that is directly fixed to one end of the fixed shaft 2 in an externally fitted shape, and 21 is a flat plate annular connecting portion that connects the mounting portion 20 and the holding tubular portion 19, In the illustrated example, the seal body holding member 18 includes a holding tube portion 19, a connecting portion 21, and a mounting portion 20, and has a Z-shaped cross section.

Then, as is apparent from FIG. 2, a suitable number of injection holes 22 (for example, three at substantially equal intervals in the circumferential direction) are formed in the connecting portion 21, and a plastic such as polyester is formed. A blind lid 23 made of metal is attached so as to close the injection hole 22.

26,26 are the pole pieces 12,12 of the stationary seal body 10.
The magnetic fluid is retained in a minute gap portion 25 formed between the inner peripheral edge portion 24 and the outer peripheral surface of the rotating cylindrical portion 14. Since the cylindrical portion 14 is made of a magnetic material, the magnetic fluids 26, 26 are securely held as shown in FIG.

As is clear from comparing FIG. 2 with FIG. 4 of the prior art, in the present invention, the seal body 10 is mounted on the fixed side, and the inner peripheral edge of the magnetic fluid 26 comes into contact with the rotating member (cylindrical portion 14). However, it has a completely opposite correspondence relationship with the conventional fixed shaft type spindle motor.

As a result, as shown in FIG. 3, the magnetic fluid 26 has a large centrifugal force Fi on its inner peripheral edge, but the centrifugal force Fo on the outer peripheral edge that contacts the stationary pole pieces 12, 12 is zero or extremely high. small. The binding force (surface tension and adsorption force) of the magnetic fluid 26 is a centrifugal force on the outer peripheral edge side of the magnetic fluid 26.
Since it is sufficiently larger than Fo, the magnetic fluid 26 does not propagate on the surface of the pole piece 12 and does not scatter in the outer diameter direction.

In FIG. 2, the injection hole 22 is a hole for inserting the injection tool from here (before attaching the blind lid 23) to inject the magnetic fluid 26 into the minute gap portion 25. Yes, the blind lid 23 is attached after the injection work.

Further, in the structure of FIG. 2, if the magnetic fluid 26 on the inner side tries to scatter, it will adhere to the corner 27 between the connecting portion 16 and the mounting portion 15, and will fly to the outside of the motor. There are difficult advantages. In particular, it is also desirable to form the groove 28 in the corner 27 as shown in the figure. Further, if the magnetic fluid 26 on the outer side tries to scatter, it adheres to the corner 29 between the mounting portion 19 and the connecting portion 21 and does not scatter to the outside of the motor.

In addition, in FIG. 1, a seal cap 30 made of aluminum or the like is fixed to the open end of the hub 5 by press fitting or the like in order to further prevent the scattering.

Next, the magnetic fluid seal device 1 on the right side of FIG. 1 also has the same configuration (as described in FIG. 2), but the seal body holding member 18 may be fixed to the bracket 6. Is shown. Further, the receiving member 13 is attached via a bearing spacer 31.

The present invention is not limited to the embodiment shown in the drawings, the design can be freely changed, and the spindle motor can be applied to various shapes as long as the shaft is of a fixed type and various uses. Also, as the seal body 10, a pole piece
It may also be preferable to have one 12 pieces, or it is free to inject and hold the magnetic fluid 26 in only one of the two pole pieces 12, 12.

〔The invention's effect〕

Since the present invention is configured as described above, it has the following effects.

In the magnetic fluid 26, a large centrifugal force Fi acts on the side of the rotation receiving member 13 that contacts the cylindrical portion 14 (hereinafter referred to as the rotation side), and a part of this fluid flows radially outward. On the other hand, in the magnetic fluid 26, the side in contact with the seal body 10 attached to the fixed shaft 2 (hereinafter, the stationary side) is
Since the magnetic fluid 26 is stationary, the centrifugal force Fo does not substantially act (if it acts, it is very small), and does not flow like the above (rotation side).

In the magnetic fluid 26 in the above-described state, the binding force (surface tension and magnetic attraction force) of the magnetic fluid 26 is the centrifugal force Fo on the stationary side.
Large enough to be securely held and pole pieces
It does not flow along the surface of 12 and scattering is prevented. Therefore, it is possible to prevent contamination of the disk chamber in the disk motor or the like.

Even if the magnetic fluid 26 scatters from the minute gap portion 25, scattering to the outside of the motor is prevented as follows.
That is, on the inner side of the seal body 10 in the axial direction, the scattered magnetic fluid 26 is received in the accommodation space defined by the rotation receiving member 13, the seal body holding portion 18, and the seal body 10. On the other hand, on the axially outer side of the seal body 10, the scattered magnetic fluid is received in the accommodation space defined by the holding cylinder portion 19 of the seal body holding portion 18, the connecting portion 21, and the seal body 10.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing an embodiment of the present invention, FIG. 2 is an enlarged view of an essential part of FIG. 1, and FIG. Fourth
FIG. 5 is a sectional view of a main part of a conventional example, and FIG. 2 ... Fixed shaft, 9 ... Rotating cylinder, 10 ... Seal body,
11 ... Magnet, 12 ... Pole piece, 13 ... Receiving member, 14 ... Cylindrical part, 15 ... Mounting part, 16 ... Coupling part, 18 ...
… Seal body holding member, 19 …… Holding cylinder part, 20 …… Mounting part, 24 …… Inner peripheral edge part, 25 …… Small gap, 26 …… Magnetic fluid, Fo, Fi …… Centrifugal force.

Claims (1)

(57) [Claims] 1. A magnetic fluid seal device interposed between a rotating cylinder body 9 and a fixed shaft 2, wherein a cylindrical portion 14 surrounds the outer peripheral surface of the fixed shaft 2 with a gap, and the rotating cylinder. A mounting portion 15 fixed to the body 9 and a connecting portion 16 connecting the cylindrical portion 14 and the mounting portion 15 are provided. The cylindrical portion 14, the mounting portion 15 and the connecting portion 16 are axially outward from the connecting portion 16. Rotation receiving member 13 made of magnetic material having an annular recess 17 opening to
A holding cylinder portion 19 that is loosely fitted into the annular recess 17 of the rotation receiving member 13, an attachment portion 20 that is directly or indirectly fixed to a portion of the fixed shaft 2, and the attachment portion 20. A seal body holding member 18 having a flat plate annular connecting portion 21 that connects the holding tubular portion 19 with the holding tubular portion 19 and forms an outer opening of the holding tubular portion 19 into a lid shape, and includes a magnet 11 and a pole piece 12. Also, the outer peripheral edge is held by the inner peripheral edge of the holding tubular portion 19, the inner peripheral edge 24 of the pole piece 12 is a minute gap portion on the outer peripheral surface of the cylindrical portion 14 of the rotation receiving member 13. The magnetic fluid seal main body 10 facing each other with 25 and interposed between the connecting portion 16 of the rotation receiving member 13 and the connecting portion 21 of the seal main body holding member 18, and the pole piece 12 of the magnetic fluid seal main body 10. Inner peripheral edge
A magnetic fluid sealing device comprising: a magnetic fluid 26 held in a minute gap portion 25 formed between the rotation receiving member 13 and the outer peripheral surface of the cylindrical portion 14 of the rotation receiving member 13.