JPH05274780A - Spindle motor for magnetic disk device - Google Patents

Abstract

PURPOSE:To increase storage capacity without increasing the thickness of a magnetic disk device in the spindle motor of the magnetic disk device having the spindle motor where a magnetic fluid seal is arranged on the outside of a bearing and lubricant, etc., from the bearing is prevented from scattering to the outside. CONSTITUTION:This motor is constituted so that the magnetic fluid seal 18 is placed on the outside of the related bearing 19 and arranged between a member 12 arranged forming a gap between with the bearing and a spindle 10, and a distance between the bearings is enlarged by a length related to the thickness of the magnetic fluid and a motor coil 13 with a large thickness is allowed to be mounted in the spindle. Thus, since the torque of the motor is increased without increasing the height of the spindle motor the thin magnetic disk device with large storage capacity is obtained and the extremely thin and compact magnetic disk device is obtained when the increase of the storage capacity is neglected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor of a magnetic disk device, and more particularly to improvement of a spindle motor for rotating a disk.

[0002]

2. Description of the Related Art In a magnetic disk device having a high recording density and a large capacity, a spindle motor for rotating a disk has a magnetic fluid seal incorporated therein as described in, for example, Japanese Unexamined Patent Publication No. 1-105381. ..
In other words, this type of motor has a spindle of, for example, three.
Since it rotates at a high speed of 600 rpm or more, dust is generated due to scattering of lubricating oil such as grease enclosed in the motor, especially grease enclosed in the bearing, and this dust flows into the space where the disk and head are installed, When the head adheres to the surface of a disk or the like, the adhered dust is caught in a minute gap between the disk and the head, destroys the magnetic recording film formed on the surface of the disk, or causes magnetic recording. It prevents the strength from decreasing,
It is essential for reliability in a large-capacity magnetic disk drive with a small head flying height, high recording density.

FIG. 3 shows an example of such a spindle motor. The spindle A is composed of two members, and is held by a shaft B penetrating these members with bearings D and E interposed. The bearing D is held by one member forming the spind, and the bearing E is held by the other member forming the spindle. The motor coil F and the magnet G are arranged inside a sealed space H formed inside the spindle, and are attached to the shaft and the spindle, respectively. The magnetic fluid seal J is arranged in tandem on the outside of the bearing D, and the magnetic fluid seal K is arranged in tandem on the outside of the bearing E. The magnetic fluid seal K is held by each of the members constituting the spindle. Prevents grease from splashing outside the motor.

Incorporation into a magnetic disk device is as follows.
This is done by fixing the shaft B to the base of the magnetic disk drive, incorporating a hub and clamp outside the spindle A, fitting the disk to the spindle, and fixing the disk to the spindle with these hubs and clamps.

[0005]

In such a spindle motor, when the number of disks is increased to form a magnetic disk device having a large storage capacity, the height becomes large and the thickness of the magnetic disk device also becomes large. .. That is, when the number of disks is increased, a larger motor torque is required, but in the conventional spindle motor, the magnetic fluid seals J and K are arranged in tandem outside the bearings D and E, and the magnetic fluid seals are built in. Since the distance between the bearing D and the bearing E cannot be made larger than that of a spindle motor which is not equipped, the distance between the bearings must be increased in order to install a coil having a large thickness. Becomes larger, and the thickness of the magnetic disk device also increases accordingly.

It is an object of the present invention to provide an improved spindle motor for a magnetic disk device which can increase the storage capacity without increasing the thickness of the magnetic disk device.

[0007]

In order to achieve the above object, the present invention provides a hollow spindle for holding a disk, a shaft penetrating the spindle, and a spindle and a shaft located outside the inner space of the spindle. Between the bearing and the magnet, the coil and the magnet, which are located in the inner space of the spindle and are incorporated in the spindle and the shaft to form the magnetic circuit of the motor, and which are located coaxially with the bearing. It is characterized by comprising a member arranged to form a space therebetween and a magnetic fluid seal arranged between the spindle.

[0008]

[Function] The magnetic fluid seal is arranged coaxially with the bearing, and the distance between the bearing and the bearing is increased by a length related to the thickness of the magnetic fluid seal. It can be incorporated so that an increase in motor torque can be achieved without increasing the height of the motor. Further, since the magnetic fluid seal is arranged between the member and the spindle that form a space between the bearing and the spindle, the lubricating oil from the bearing is trapped in this space and scattered outside the motor. do not do.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a spindle motor of a magnetic disk device according to the present invention will be described below with reference to FIGS.

This spindle motor includes a spindle 10 for supporting a disk, a shaft 11 for rotatably holding the spindle, a substrate 12 for supporting the shaft, a motor coil 13 and a magnet 14 attached to each of the shaft and the spindle, and a magnetic fluid seal. 21, 22
It is equipped with.

The spindle 10 has two members 15, 16
It consists of The member 15 has an overall shape of a hollow cylinder whose one end is open, and a protrusion is integrally formed at a portion forming the open end. Also, the member 16
Has an overall shape of a ring having a thin thickness having two parts having different diameters, and a part having a small diameter is located outside the member 16 and a part having a large diameter is engaged with the open end of the member 15. It is also fixed and forms a closed space 17 with the member 15.

The shaft 11 penetrates the spindle 12. Bearings 18, 19 are arranged between the shaft 11 and each of the two members 15, 16 forming the spindle. The bearing 18 is arranged between the end wall of the member 15 and the shaft 11, the inner ring is fixed to the shaft 11 and the outer ring is fixed to the member 15, and the end face of the bearing 19 is flush with the large diameter portion of the member 16. Thus, the inner ring is fixed to the shaft 11 and the outer ring is fixed to the member 16, so that the spindle 10 can rotate on the shaft 11. .. Also, the shaft 11
The lower end of is engaged with and fixed to the substrate 12. This substrate, which has a substantially disc shape, is located outside the bearing 19 or outside the member 16 forming the spindle and is arranged close to them.

The coil 13 and the magnet 14 form a magnetic circuit of a motor for rotating the spindle 10. The coil 13 is arranged inside the closed space 17 of the spindle 12 and is fixed to the shaft 11. The magnet 14 is arranged inside the closed space 17 of the spindle 12 corresponding to the coil 13, and is fixed to a member 15 forming the spindle.

Among the magnetic fluid seals, the magnetic fluid seal 21 arranged at the upper portion is installed between the shaft 15 and the member 15 which is located outside the bearing 18 and forms the spindle. However, the magnetic fluid seal 22 is located coaxially with the bearing 19 and in the same plane as the bearing 19, and is arranged between the small diameter portion of the member 15 forming the spindle and the substrate 12, and the magnetic fluid seal 22 is provided.
Although it is arranged outside the spindle 10, the diameter of the motor is prevented from increasing.
The substrate 12 has a bearing 19 and a magnetic fluid seal 22.
There is a closed space or passage 24 connecting the two. The magnetic fluid seal itself consists of a magnet and a magnetic fluid. The magnet in the magnetic fluid seal 21 is a member 23 fixed to the member 15 forming the spindle.
The magnetic fluid is held in the space between the yoke extending from the magnet and the shaft 11.
The magnet of the magnetic fluid seal 22 is held by the substrate 12, and the magnetic fluid is injected into the space between the yoke extending from the magnet and the small diameter portion of the member 16 forming the spindle. The magnetic fluid is injected into the magnetic fluid seal 22 by, for example, injecting the magnetic fluid from a hole provided in the substrate 12 corresponding to the above-mentioned void, injecting it, and then closing this hole with a plug. ..

For example, as shown in FIG. 2, this spindle motor is incorporated in a container constituted by a cover 33 and a base 34 together with a disk 31, a head 32 and a head positioning mechanism to form one magnetic disk device. To be made.

In this magnetic disk device, the head 3
2 are arranged on both sides of each disk 31. The head positioning mechanism is, for example, of a so-called swing arm type in which the head 32 makes an arc motion on the disk around a single point. In the figure, among these, only the coil 37, the magnet 38, and the member 39 that supports the magnet in the actuator that rotates the swing arm are shown. The coil 37 is fixed to the swing arm, and the magnet is fixed to the substrate 34 by the member 39.

The spindle motor according to the present invention is arranged in the internal space of the container consisting of the cover 33 and the base 34, and the surface of the substrate 12 facing the member 16 forming the spindle is the same surface as the surface of the base 34. Is fitted and fixed to the base 34. A hub 35 and a chuck 36 for supporting the disk 32 are incorporated in the spindle 10, the disk 31 is fitted to the spindle 10 so as to be located between these hubs, and the chuck 36 prevents the disk 31 from coming off. A wire or cable 40 connecting the coil 13 and the control device is pulled out of the container from the lower end of the spindle 10 through a hole in the shaft 11.

In the magnetic disk device incorporating the spindle motor according to the present invention, even if a large number of disks 31 are incorporated in the spindle 15, the magnetic fluid seal 22 is provided in the bearing 1.
9, the distance between the bearing 19 and the bearing 18 is related to the thickness of the magnetic fluid seal 22 as compared to the conventional spindle motor in which the magnetic fluid seal is arranged in tandem outside the bearing. In addition to increasing the size, the magnetic fluid seal 19 is arranged in the same plane as the bearing 19 so that the magnetic fluid seal 19 does not get inside the spindle 15 and the distance between the bearing 19 and the bearing 18 is increased. Since it is maximized, a coil 13 having a larger thickness can be incorporated, so that the required motor torque can be obtained and the spindle 10
Does not reduce the rigidity of. In addition, the spindle motor
In addition to the fact that the height of the motor does not increase in this manner, the magnetic fluid seal 19 is located in the smallest diameter portion of the spindle 10 and the diameter of the motor does not change, so that the recording capacity is large but the size is small. A magnetic disk device can be obtained. In this spindle motor, if it is not necessary to increase the motor torque,
Since the distance between the bearing 18 and the bearing 19 can be made smaller, the height of the motor becomes lower and a thinner magnetic disk device can be obtained.

Also, in this magnetic disk device, an electric current is applied to the coil 13, the spindle 10 is rotated together with the disk 31, the head 32 is levitated, and the actuator moves the head 32 to an arbitrary position on the disk. Then, writing to or reading from the disc 31 is performed. However, at this time, the bearing 1
Even if the grease lubricating 8 is scattered from this bearing,
The magnetic fluid seal 21 prevents the scattered grease from entering the container constituted by the cover 33 and the base 34. Then, the grease from the bearing 19 passes through the passage 24.
Is attached to the magnetic fluid seal 22 only through the passage 24, the cover 33 and the base 3
The disk 3 does not enter the container constituted by 4
No accidents due to surfaces such as 4 will occur.

In the embodiment described above, since the thickness of the magnetic fluid seal 18 is smaller than the thickness of the disc clamp 36, only the magnetic fluid seal 22 is arranged coaxially with the bearing 19, and the magnetic fluid seal 18 is placed outside the bearing 18. However, the magnetic fluid seal 18 may be arranged coaxially with the bearing in the same manner as the magnetic fluid seal 19 depending on the configuration of the magnetic disk device. By doing so, a larger recording capacity can be obtained. Alternatively, a thin magnetic disk device can be obtained. At this time, the length and shape of the passage 24 connecting the bearings 18 and 19 and the magnetic fluid seals 21 and 22 are selected so that a part of the grease is accumulated in the lowermost region of the passage 24. Since the amount of grease toward each related magnetic fluid seal is small, the lubricating oil affects the magnetic fluid of the magnetic fluid seal, but it is possible to use one having good lubricating performance. Further, the substrate 12 may be configured by a base 34 that forms a container in the magnetic disk device, if necessary, to configure a thinner magnetic disk device.

[0021]

As described above, the spindle motor for a magnetic disk device according to the present invention can increase the motor torque without increasing the height of the spindle motor, so that it has a large storage capacity. Regardless, a magnetic disk device having a thin thickness can be obtained, and the height of the spindle motor can be reduced unless an increase in storage capacity is required, so that a magnetic disk device having an extremely thin thickness can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a spindle motor for a magnetic disk device of the present invention.

2 is a cross-sectional view showing an example of a magnetic disk device incorporating the spindle motor shown in FIG.

FIG. 3 is a cross-sectional view of a spindle motor in a conventional disk device for a magnetic disk device.

[Explanation of symbols]

10 ... Spindle, 11 ... Shaft, 12 ... Member, 13
... coil, 14 ... magnet, 17 ... internal space of spindle, 18, 19 ... bearing, 21, 22 ... magnetic fluid seal, 24 ... space between bearing and member.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Sayao Hatori 7 Mitsudoshiro-cho, Kanda, Chiyoda-ku, Tokyo Japan Servo Co., Ltd.

Claims (3)

[Claims] 1. A hollow spindle that holds a disk, a shaft that penetrates the spindle, a bearing that is located outside the internal space of the spindle and that is located between the spindle and the shaft, and a magnetic circuit of the motor. Between the magnet and the coil, which are located in the inner space of the spindle and are incorporated in the spindle and the shaft, and the member which is located coaxially with the bearing and forms a space between the bearing and the spindle. A spindle motor for a magnetic disk drive, comprising: 2. The spindle motor according to claim 1, wherein the magnetic fluid seal is arranged in the same plane as the bearing. 3. The spindle motor according to claim 2, wherein the spindle has a small diameter portion outside the internal space therein, and the magnetic fluid seal is located in the small diameter portion and arranged.