JPH06165432A - Motor assembly - Google Patents

Abstract

PURPOSE:To provide a motor assembly where the position accuracy in rotation and the speed accuracy can be achieved at the same time. CONSTITUTION:A stator 33 and a bearing 34 are provided on a base 31. A rotary shaft 36, at the center, and a magnet, on the inside, are fixed to a rotor yoke 37. A rotary shaft 36 is born with a bearing 34, and the magnet of the rotor yoke 37 is opposed to the stator 33. A recess 32 is made covering 270 deg. at the circular section opposed to the magnet of a base 31. The base 31 is made of magnetic substance, and the magnet works strong attraction to the flat part 39 of the circular part, and works weak attraction to the recess 32. Accordingly, the rotary shaft 36 receives force to incline, and keeps the clearance to the bearing 34 always in a fixed condition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor assembly, and more particularly to a motor assembly which supports a fixed shaft through a bearing in a fixed portion.

[0002]

2. Description of the Related Art Generally, in a motor assembly, the characteristics of the bearing have a great influence on the rotation characteristics of the motor. The bearing must have a clearance for the purpose of supporting the rotating shaft. However, if this clearance is large, the tip end of the rotating shaft will shake during rotation due to nonuniformity of the magnetic circuit of the motor, etc., and the accuracy of the rotational position will deteriorate. Therefore, it is necessary to set the clearance of the bearing as small as possible in order to improve the accuracy of the rotational position.

On the other hand, if the clearance is too small, the bearing loss increases, the power consumption of the motor increases, and the bearing loss fluctuates unless the precision of the parts is increased, which adversely affects the accuracy of the rotation speed. Further, since the fluctuation of the bearing loss is also caused by the mixing of fine dust, the small clearance also has a drawback that the rotation speed easily fluctuates in this respect as well.

Therefore, it is necessary to properly determine the clearance according to the purpose.

[0005]

A spindle motor of a disk storage device is an example of use of the above-mentioned motor assembly.

Due to the increase in storage capacity of disk storage devices in recent years, the recording density has increased in both the circumferential and radial directions of the disk. Therefore, in the spindle motor of the disk storage device, it is necessary to satisfy both the accuracy of the rotational position and the accuracy of the rotational speed described above, and a bearing with sufficient accuracy must be used. However, the disk storage device tends to be downsized, and it is necessary to consider the downsizing of the device depending on the position and size of the bearing.

In view of the above situation, it is an object of the present invention to provide a motor assembly which has a simple structure and is capable of satisfying the accuracy of rotational position and the accuracy of rotational speed.

[0008]

SUMMARY OF THE INVENTION A motor assembly according to the present invention has a rotating shaft in a certain direction even during rotation.
Means for exerting a biasing force are included.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a spindle motor for rotating a magnetic disk medium of a magnetic disk device will be described with reference to the drawings.

First, the first embodiment is an example of application to a spindle motor of a hard disk device. This will be described with reference to FIGS. 1 and 2.

A stator 2 of a cylindrical spindle motor is fixed to a part of a base 1 which is a base of the apparatus. A magnetic pole portion 3 for generating lines of magnetic force is fixed to the outer peripheral surface 2b of the stator 2. The magnetic pole portion 3 acts so as to generate a magnetic force line that is changed by a drive circuit (not shown).

On the other hand, outer rings 5b and 4b of the upper and lower two ball bearings 5 and 4 are fixed to the inner peripheral surface of the stator 2. Inner rings 5a, 4a of the ball bearings 5, 4 are fixed to the rotary shaft 7. Inner ring 5 of ball bearings 5 and 4
a, 4a and outer rings 5b, 4b between the plurality of balls 5
There are c and 4c, and by the movement of these balls 5c and 4c,
The inner rings 5a and 4a rotate smoothly with respect to the outer rings 5b and 4b. A slight clearance is provided between the inner rings 5a, 4a and the balls 5c, 4c and the outer rings 5b, 4b so that the balls 5c, 4c can move smoothly.

A hub 8 is fixed to one end of the shaft 7.
The hub 8 has a bowl-like shape and supports a plurality of magnetic disk media 10 on its outer peripheral surface.
The medium 10 has a disc shape, and a ring-shaped spacer 11 is provided between the medium 10 and the medium 10 to which the medium 10 is fixed.

A magnet 12 is fixed to the inner peripheral surface 8a of the hub 8. The poles of the magnet 12 are regularly arranged and face the magnetic pole portion 3 of the stator 2 described above.

With this structure, the hub 8 is rotated by the action of the changing magnetic force lines generated from the magnetic pole portion 3, and the medium is also rotated.

A configuration provided for applying the present invention to the spindle motor of this magnetic disk device will be described. The hub 8 described above is formed of a magnetic material, and the magnet 6 is provided on a part of the base where the surface of the hub 8 that closely faces the base 1 faces. With this configuration, the hub 8 is attracted by the magnet 6, but since the magnet 6 is provided only on a part of the base, the hub 8 receives a force that tilts toward the magnet 6. In FIG. 1, the left side of the hub 8 receives a downward force. This force acts on the ball bearings 5 and 4 having the only clearance in the configuration of this spindle motor, and the clearance distribution is always kept constant. This makes it possible to construct a spindle motor which is most important in magnetic disk drive and has excellent reproducibility.

Next, a second embodiment will be described. This embodiment is applicable to a spindle motor of a floppy disk device. In this embodiment, a particularly simplified spindle motor is used.

The configuration will be described with reference to FIGS. 3 and 4. A base 35, which is the base of the device, is formed with a recess 35 for a bearing. On the side where the recess 35 is formed, a circular stator 33 is formed concentrically with the center of the recess 35 and fixed to the base 31. The stator 33 has a plurality of electromagnets (not shown) inside,
This electromagnet is driven by a drive circuit (not shown) to generate changing magnetic force lines. The electromagnets are radially arranged at equal intervals.

An oil-impregnated fuel-bonded gold bearing 34 is fixed to the inside of the stator 33. A bearing hole 34a is formed in the center of the bearing 34. The center of this hole is the recess 35
Coincide with the center of. The shaft 36 is inserted into the hole 34a. The shaft 36 has a columnar shape, and a lower end portion 36 a thereof is formed into a spherical shape and is in contact with the recess 35 of the base 31. There is a minute clearance between the outer peripheral surface of the shaft 36 and the hole 34a. The shaft 36 is rotatable while sliding on the hole 34a of the bearing 34 and the recess 35.

The shaft 36 is fixed to the center of a disk-shaped rotor yoke 37. A hub (not shown) is usually formed on the rotor yoke 37 to support and fix the mounted floppy disk medium. A magnet 38 is formed inside the rotor yoke 37 and closely faces the outer peripheral surface of the stator 33.

By driving the electromagnet inside the stator 33, changing magnetic lines of force are output from the stator 33, and the rotor yoke 37 rotates.

Next, a peculiar structure for applying the present invention to this structure will be described. The base 31 is made of a magnetic material. A portion of the base 31 that closely faces the magnet 38 of the rotor yoke 37 has an annular shape. The concave portion 32 is formed in the annular portion over an angle of 270 degrees.

In general, in this kind of spindle motor, the base 31 is a magnetic material in order to prevent the rotor yoke 37 from coming off, and the rotor yoke 37 is attracted by the action of the magnet 38 of the rotor yoke 37. However, because of the formation of the concave portion 32, the magnet 38 can be provided in a portion close to the base 31 and a portion separated from the base 31, so that the attraction force to be used can be different. That is, strong suction is carried out in a close portion, and weak suction is carried out in a distant portion. Therefore, for example, in FIG. 3, the flat portion 39 of the base 31 is close to the flat portion 39, and the concave portion 32 is far from the flat portion 39, and a counterclockwise force is used. This force acts on the clearance between the oil-impregnated fuel-bonded metal receiver 34 and the shaft 36, and keeps this clearance constant.

FIG. 5 shows the bearing 34 and the shaft 36 in this state.
It emphasizes the relationship with. Since the shaft 36 always maintains this state regardless of whether it is stationary or rotating, a spindle motor with high reproducibility can be obtained. In addition, in this embodiment, this effect is realized by an extremely simple structure in which a recess is formed on the base 31.

In this second embodiment, the recess 32 is formed into two.
Although it is formed over 70 degrees, the effect of the present invention can be obtained by providing portions having different heights (or depths) in the annular portions of the bases 31 of the magnet 38 facing each other, regardless of this configuration. That is, it can also be configured by providing a projection on a part. Further, in the case of the concave portion 32, the forming range is not limited to 270 degrees. However, a high effect can be obtained when the angle is 180 degrees or more and less than 360 degrees.

Next, a third embodiment will be described.

This embodiment is a spindle motor of a floppy disk device similar to that of the second embodiment described above, and the description of the same construction as that of the second embodiment will be omitted.

The difference is that there is no recess 32 of the second embodiment,
The point is that the magnetic body 61 is provided on the stator. Two magnetic bodies 61 are provided. As described above, the electromagnets are radially arranged in the stator.
1 is arranged between the electromagnets so as not to interfere with the generation of magnetic force lines.

In this structure, the magnet of the rotor yoke is attracted to the magnetic body 61, but its direction is a rightward force in FIG. Therefore, as shown in FIG. 5 in the second embodiment, the shaft is not subjected to a force, but is simply displaced so that the shaft is translated rightward. Even in this configuration, the clearance can be kept constant.

A method of forming such a magnetic body 61 will be described. Although it was mentioned earlier that the electromagnet is formed in the stator, in practice the stator can be formed by molding. That is, the electromagnet is wrapped with resin to form the resin into a disc shape. At this time, the magnetic body 61 can also be formed by fixing with a resin.

It is also possible to cut and raise a part of the base, and this method is advantageous in terms of manufacturing cost and the like.

[0032]

As described above, the motor assembly of the present invention is provided with means for exerting a force for urging the rotating shaft in a constant direction, so that the clearance between the rotating shaft and the bearing is always kept constant. Therefore, it is possible to perform a rotating operation, and there is an effect that an error in rotation can be eliminated.

[Brief description of drawings]

FIG. 1 is a sectional view taken along line XX in FIG. 2 of the first embodiment of the present invention.

FIG. 2 is a perspective view of a fixing portion of the first embodiment shown in FIG.

FIG. 3 is a sectional view taken along line YY in FIG. 4 of the second embodiment of the present invention.

FIG. 4 is an exploded perspective view of the second embodiment shown in FIG.

FIG. 5 is a sectional view showing the operation of the second embodiment of the present invention.

FIG. 6 is a sectional view taken along line ZZ in FIG. 7 of the third embodiment of the present invention.

FIG. 7 is an exploded perspective view of the third embodiment shown in FIG.

[Explanation of symbols]

 1 base 6 magnet

Claims (1)

[Claims] 1. A rotary shaft, a movable part provided on the rotary shaft, a fixed part provided corresponding to the movable part, and a bearing provided on the fixed part for pivotally supporting the rotary shaft. A motor assembly comprising: a motor assembly including a biasing unit that biases the rotary shaft in at least one direction other than an axial direction of the rotary shaft.