JPS6162672A - Sealing device using magnetic fluid - Google Patents

Abstract

PURPOSE:To provide a low-priced sealing device by assembling a pair of permanent magnets magnetized in the axial direction of the periphery to be adhered to each other, which is forced into a hollow cylinder in such a manner that the inner peripheral side has the central portion hollowed out like a groove, with both end portions left. CONSTITUTION:The first permanent magnet 8a and the second permanent magnet 8b are assembled in such a manner as to join S-pole and N-pole, and formed into a hollow cylinder in such a manner that the inner peripheral side has the central portion hollowed out like a groove, with both ends thereof left. As magnetic flux from N-pole passes through a flange portion at the end portion, magnetized magnetic fluid, a shaft, a magnetic fluid and the other end portion, and returns to S-pole to generate a closed-loop, a magnetic fluid 7 is retained between a shaft 3 and a rotary shaft sealing device formed by the first permanent magnet 8a and the second permanent magnet 8b to fulfill a sealing function as a dust seal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a sealing device using a magnetic fluid used in a rotating part of a device such as a fixed magnetic disk device, in particular where dust contamination is a problem.

[Prior art] A conventional sealing device of this type will be explained with reference to the drawings.

FIG. 1 is a sectional view of a magnetic disk drive motor schematically showing a rotary shaft sealing device included in a disk drive motor used in a fixed disk device.

In the figure, (1) is a rotor equipped with a permanent magnet, (2)
) is a stator installed inside the rotor, which consists of a core and a coil wound around it. (3) is a magnetic shaft that is a rotating body integrated with rotor (1), (4) is a ball bearing in which the shaft is inserted on the outer circumferential side of shaft (3), and (5) holds a disk. The spindle hub is press-fitted into the shaft (3) at all ends. (6) is a rotating shaft sealing device that functions as a dust seal to the disk surface.

FIG. 2 is an enlarged view of the main parts without showing the rotating shaft density 11 device of FIG. 1. Here, (6a) is a hollow cylindrical permanent magnet, (
6b) is a magnetic pole piece glued to both sides of permanent magnet 6a), and 7) is a magnetic fluid.

The operation of a magnetic disk drive using the fixed disk drive motor shown in FIG. 1 will be explained, mainly focusing on the function of this rotary shaft sealing device. In FIG. 1, the rotor (1) is provided outside the spacer (2), and is an outer rotor type motor in which the rotor (1), shaft (3), and spindle hub (5) rotate together.

A magnetic disk device using this disk drive motor employs a floating head system in which the head floats due to the airflow generated by the rotation of the magnetic disk. There, the fixed disk installed on the spindle hub (5) rotates while the head is kept floating about 0.3 μm above the disk surface. Therefore, if particles with a diameter of 0.3 μm or more, such as mist or dust from the lubricating oil of the ball bearing (4), are scattered while the disk is rotating, it may cause a head crash and cause a failure of the magnetic disk drive. be. Therefore, the magnetic disk drive motor is provided with a rotating shaft sealing device (6) for dust sealing. As shown in Fig. 2, in this rotary shaft sealing device (6), magnetic flux passes from the N pole of a permanent magnet (6a) through a pole piece (6b), and from a magnetized magnetic fluid (7) to a magnetic shaft (3). ), passes through the magnetic fluid (7), the pole piece (6b), and returns to the S pole of the permanent magnet (6a) to form a closed loop.
7) is held between the shaft (3) and the pole piece (6b), and functions as a sealing device for the shaft (3), which is the rotating shaft.

As mentioned above, the conventional rotary shaft sealing device has a configuration in which magnetic pole pieces are attached to both ends of a hollow permanent magnet, so there are only three components, which is expensive and requires assembly. There was also a problem in that it was difficult to maintain dimensional accuracy during the bonding work.

[Summary of the Invention] This invention was made to solve the above-mentioned problems, and in a rotating shaft sealing device using magnetic fluid,
The purpose is to reduce the number of component parts and provide a sealing device using magnetic fluid that is easy to manufacture and assemble by using a permanent magnet instead of pole pieces that sandwich the permanent magnet. It is.

The object of the present invention is to provide a first permanent magnet having a hollow cylindrical shape and having a flange at the inner circumferential end and magnetized in the axial direction of the cylinder, and a first permanent magnet having the same shape as the first permanent magnet. The magnet is combined with a second permanent magnet magnetized in the direction of the cylinder axis opposite to the magnet, and is made into a hollow cylindrical shape with the inner circumference leaving both ends and the central part hollowed out in the shape of a groove. Achieved by configuring a sealing device such that a sealing shaft is passed through a cylindrical hollow part and a magnetic fluid is held between the flanges at the ends of the first permanent magnet and the second permanent magnet and the shaft. be done.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a sectional view showing a sealing device using magnetic fluid, which is an embodiment of the present invention. In the figure, (3) is the shaft,
(7) is a magnetic fluid; (8a) and (8b) are respectively the first permanent magnets which are the main components of the sealing device of the present invention;
The second permanent magnet (9) is an adhesive surface that joins the first permanent magnet and the second permanent magnet. First permanent magnet (8
The cylinder a) has a hollow cylindrical shape with a flange at the inner circumferential end, and the magnetization direction is configured to be an N pole and an S pole in the axial direction of the cylinder as shown in the figure. Second permanent magnet (
8b) has a hollow cylindrical shape and is on the inner circumferential side. It has a shape with a flange at the end, and its shape is the same as the first permanent magnet, but its magnetization direction is opposite to that of the first permanent magnet, and it is oriented in the axial direction of the cylinder as shown in the figure. It is configured to have a south pole and a north pole. The S and N poles of the first permanent magnet and the second permanent magnet are combined so as to be joined to form a hollow cylindrical shape with both ends left on the inner circumferential side and a groove-shaped central part hollowed out. . A sealed shaft of a magnetic material is passed through the cylindrical hollow part of the combination of the first permanent magnet and the second permanent magnet, and a magnetic fluid is passed between the flanges at the ends of the first permanent magnet and the second permanent magnet and the shaft. hold.

In the rotating shaft sealing device of the present invention in which a first permanent magnet and a second permanent magnet are combined and bonded together, the magnetic flux emitted from the N pole is transferred to the flange portion at the end, the magnetized magnetic fluid , the shaft, the magnetic fluid, and the other end to draw a closed loop returning to the south pole, so the magnetic fluid (a)
) and is held between a first permanent magnet (8a) and a second permanent magnet (8b) constituting a rotating IItlI sealing device,
Performs a sealing function as a dust seal.

In addition, although the above-mentioned embodiment shows the case where the rotary shaft sealing device is in one stage, if a plurality of rotary shaft sealing devices are installed and used in multiple stages, the sealing effect will be doubled.

Further, in the above-described embodiment, the case of a rotary shaft sealing device for a fixed disk drive motor was described, but the present invention can be applied to any device that requires a dust seal, regardless of whether the rotary shaft is a rotary shaft or not.

[Effects of the Invention] As explained above, the sealing device using magnetic fluid of the present invention has a pair of permanent magnets magnetized in the axial direction of the hollow cylinder and having a flange at the inner peripheral end. Two magnets are assembled and glued together to form a hollow cylindrical shape with both ends left on the inner periphery and a groove hollowed out in the center, making the sealing device inexpensive and highly accurate in assembly. You can get something.

In addition, if the permanent magnet is integrated, it is difficult to cut out the groove shape at the center of the inner circumference of the hollow cylinder, but in the present invention, two permanent magnets are combined, so processing is easy. It is.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a magnetic disk drive motor using a rotating shaft sealing device, Fig. 2 is a sectional view of a rotating shaft sealing device schematically showing a conventional rotating shaft sealing device using a magnetic fluid, and Fig. 3 is a sectional view of a rotating shaft sealing device using a conventional magnetic fluid.
The figure is a sectional view of a rotating shaft sealing device that is an embodiment of the present invention. In the figure, (1) is the rotor, (2) is the stator, (3
) is the shaft, (4) is the ball bearing, (5) is the spindle hub, (6a) is the permanent magnet, (6b) is the pole piece, (7) is the magnetic fluid, (8a) is the first permanent magnet, ( 8b) is a second permanent magnet. In the figure, the same reference numerals and the same symbols indicate the same or corresponding parts.

Claims (1)

[Claims] (1) A first permanent magnet having a hollow cylindrical shape and having a flange at the inner peripheral end and magnetized in the axial direction of the cylinder, and a first permanent magnet having the same shape as the first permanent magnet. In combination with a second permanent magnet magnetized in the direction of the cylinder axis opposite to the magnetization direction, the magnetic material is made into a hollow cylinder with the inner circumference leaving both ends and the central part hollowed out in the shape of a groove. A magnetic fluid utilization method characterized in that a sealed shaft of the first permanent magnet is passed through a cylindrical hollow part, and a magnetic fluid is held between the flanges at the ends of the first permanent magnet and the second permanent magnet and the shaft. Sealing device.