JPH06311701A - Spindle motor - Google Patents

Abstract

PURPOSE:To obtain spindle motor of low friction torque and stable rotation accuracy by fixing permanent magnets, homopolar and opposed to the corresponding permanent magnets fixed in parallel with dynamic bearings, to the internal surface of a hub cylinder. CONSTITUTION:A fixed shaft 1 comprises an upper small diameter portion 1a and lower large diameter portion 1b. A bottomed cylindrical hub 2 made of a cylindrical portion 2a and bottom 2b, is supported with the bottom 2b contacting a spherical portion 5 so that it can rotate freely. The cylindrical portion 2a of the hub 2 is fitted from outside to the fixed shaft 1. Also, ring- shaped No.1 and No.2 permanent magnets 10, 11 are fixed to under a ring- shaped bush 6 and over a ring-shaped bush 7 on the fixed shaft 1, respectively. No.3 and No. 4 ring-shaped permanent magnets 12 and 13 are fixed to the cylindrical portion 2a on the hub in such a way that, they are opposed to the permanent magnets 10 and 11, respectively. Thus, the hub cylindrical portion is supported, without contacting at both ends respectively, with two pairs of permanent magnets and dynamic bearings, contacting a thrust bearing only. The friction torque thus reduced and the dynamically supported hub enhance the rotation accuracy of the spindle motor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor used in, for example, a magnetic disk device.

[0002]

2. Description of the Related Art Conventionally, a spindle motor of this type is shown in FIG. 3 (Japanese Utility Model Laid-Open No. 63-21456). This spindle motor has a flange portion 43 and a cylinder portion 4
4 and a fixed sleeve 42
Shaft 40 inserted into the cylindrical portion 44 of the shaft and rotatably supported by two ball bearings 45 and 46 provided at intervals in the axial direction.
A hub 41 which is integrated with one end 40a of the rotary shaft 40 and covers the cylindrical portion 44 of the fixed sleeve 42;
1 and the cylindrical portion 44 of the fixed sleeve 42, the rotary drive portion 47 of the rotary shaft 40 including the permanent magnet 49 and the stator 48, and the spherical portion 50 provided at the tip 40b of the rotary shaft 40 and serving as the thrust bearing portion. Is equipped with.

[0003]

However, in the above-mentioned conventional spindle motor, the rotary shaft 40 is mounted on the ball bearings 45, 4.
Since it is supported by No. 6, friction torque loss at the time of rotation of the rotating shaft 40 is inevitably large. Furthermore, ball bearings 45,
Since the preload to 46 is required, adjustment of the preload is troublesome, and instability may remain in the rotational accuracy due to variations in the preload. SUMMARY OF THE INVENTION An object of the present invention is to solve the above technical problems and to provide a spindle motor with low friction torque and stable rotation accuracy.

[0004]

In order to achieve the above object, the present invention has a fixed shaft having a spherical end at its tip, a cylindrical part fitted on the fixed shaft, and a bottom rotatably supported on the spherical part. A bottomed tubular hub, and a hub rotation drive section between the fixed shaft and the tubular section of the hub, and the fixed shaft and the tubular section of the hub at the upper and lower ends of the fixed axis. A dynamic pressure bearing, respectively, between the upper and lower ends of the fixed shaft, the permanent magnets are fixed in axially parallel state with the dynamic pressure bearings, respectively,
Permanent magnets facing the respective permanent magnets with the same pole are fixed to the inner surface of the cylindrical portion of the hub. Further, the dynamic pressure bearing may be formed between the fixed shaft and an annular bush fixed to the inner surface of the cylindrical portion of the hub.

[0005]

According to the above construction, the hub is supported in the radial direction in a non-contact manner during the rotation by the repulsive force of the dynamic pressure bearings and the permanent magnets at the upper and lower positions of the fixed shaft, so that the rotation of the hub is stable and the rotation accuracy is high. Is improved. Also, since friction is generated only in the thrust bearing of the ball portion at the tip of the fixed shaft, low friction torque can be obtained.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, one embodiment of the present invention shown in FIG. 1 will be described in detail. A fixed shaft 1 has a small-diameter shaft portion 1a at the upper portion and a large-diameter shaft portion 1b at the lower portion. The large diameter shaft portion 1b of the fixed shaft 1 is fixed to a bed (not shown). The tip of the small-diameter shaft portion 1a of the fixed shaft 1 is formed into a spherical surface portion 5.
In the spherical portion 5, in the embodiment, the fixed shaft 1 has a cylindrical shape, and the ball 5 is provided on the inner surface 3 of the cylindrical portion, and a part of the ball 5 has the small diameter shaft portion 1.
It is constructed by fixing it by welding 14 or press fitting so as to project from the end face a. The small-diameter shaft portion 1
The tip of a may be directly formed into a spherical shape.

Reference numeral 2 denotes a bottomed tubular hub comprising a tubular portion 2a and a bottom portion 2b which is integrated with the tubular portion 2a by welding or the like. The tubular portion 2a is fitted onto the fixed shaft 1 and is attached to the spherical portion 5. The bottom portion 2b abuts and is rotatably supported. Thus, the thrust bearing 4 is formed between the spherical portion 5 of the fixed shaft 1 and the bottom portion 2b of the hub 2. The tubular portion 2a is configured by, for example, two parts including a large-diameter portion 2c and a small-diameter portion 2d, which are integrally formed with a bolt or the like not shown.

Dynamic pressure grooves 8 and 9 are formed in the upper end of the small-diameter shaft portion 1a and the lower end of the large-diameter shaft portion 1b of the fixed shaft 1 with a predetermined axial width. Annular bushes 6 and 7 that are close to and opposed to the dynamic pressure grooves 8 and 9 are fixed to the inner surface of the cylindrical portion 2 a of the hub 2. As a result, dynamic pressure bearings 17 and 18 are formed between the dynamic pressure grooves 8 and 9 and the annular bushes 6 and 7, respectively. If necessary, the annular bush 6 may be omitted and the dynamic pressure bearing 17 may be configured between the inner surface of the tubular portion 2a of the hub 2 and the fixed shaft 1.

Although the dynamic pressure grooves 8 and 9 are, for example, a single row of herringbone type grooves as shown in FIG. 2, the dynamic pressure grooves 8 and 9 are not limited to the herringbone type, and any groove can be used as long as dynamic pressure is generated. The dynamic pressure grooves 8 and 9 may be formed on the annular bushes 6 and 7 side, or may be formed on both sides of the fixed shaft 1 and the annular bushes 6 and 7 that face each other.

Further, annular first and second permanent magnets 10 and 11 are fixed to the fixed shaft 1 located below the annular bush 6 and above the annular bush 7, respectively. The third and fourth annular permanent magnets 12 and 13 are arranged so as to face the second permanent magnets 10 and 11 and the cylindrical portion 2 a of the hub 2.
Fixed to. Thereby, the first and third permanent magnets 10 and 12 and the second and fourth permanent magnets 11 and 13 that form a pair are formed.
Are axially in parallel with the dynamic pressure bearings 17 and 18, respectively. The first permanent magnet 10 and the third permanent magnet 12 facing each other, and the second permanent magnet 11 and the fourth permanent magnet facing each other,
The same pole opposes the permanent magnet 13 of FIG.
The permanent magnets 10, 12 and 11, 13 may be located on the upper side of the annular bush 6 and the lower side of the annular bush 7 if necessary, but the configuration of the embodiment of FIG. The long span between the bearings 17 and 18 is advantageous in terms of stability during rotation of the hub 1. Further, each of the permanent magnets 10, 11, 12, 13 may be a single annular permanent magnet or a plurality of them may be arranged side by side. Also, hub 2
The third and fourth permanent magnets 12 and 13 on the side are displaced from the first and second permanent magnets 10 and 11 on the fixed shaft 1 side by a predetermined distance h to the side opposite to the bottom 2b of the hub 2. ,
As a result, the hub 2 is moved to the side opposite to the bottom portion 2b by the repulsive force of the magnet, and the pressing force of the bottom portion 2b of the hub 2 against the spherical portion 5 is increased, so that the stability of the hub 2 during rotation is increased.

Further, a permanent magnet 15 is fixed to the inner surface of the central portion of the cylindrical portion 2a of the hub 2, a stator 16 is fixed to the fixed shaft 1 so as to face the permanent magnet 15, and the permanent magnet 15 is fixed.
The stator 16 and the stator 16 constitute a rotary drive unit 19 for rotating the hub 2. Reference numeral 20 is a lead wire that is inserted into the fixed shaft 1 and is connected to the stator 16.

[0012]

As described in detail above, the spindle motor of the present invention repels each other at both ends of the fixed shaft.
A pair of permanent magnets and a dynamic pressure bearing support the hub cylinder in a non-contact manner, and only the thrust bearing formed at the tip of the fixed shaft makes contact, so low friction torque is possible and the dynamic pressure bearing dynamics during rotation. Since the hub bearing is added by the pressure action, the rotation of the hub is more stable, the rotation accuracy is improved, and the preload adjustment unlike the conventional ball bearing is unnecessary.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention.

FIG. 2 is a partially developed view of the dynamic pressure groove forming portion of FIG.

FIG. 3 is a sectional view of a conventional spindle motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixed shaft 2 Hub 2a Cylinder part 2b Bottom part 5 Ball 6,7 Annular bush 8,9 Dynamic pressure groove 10,11 One opposing permanent magnet 12,13 The other opposing permanent magnet 17,18 Dynamic bearing

Claims (2)

[Claims] 1. A fixed shaft having a spherical end portion, a cylindrical hub having a cylindrical portion externally fitted to the fixed shaft and a bottom portion rotatably supported by the spherical portion, and the fixed shaft. And a hub rotation drive section between the hub and the tubular portion of the hub, and dynamic bearings are formed between the fixed shaft and the tubular portion of the hub at the upper and lower ends of the fixed shaft, respectively. The permanent magnets are fixed to the upper and lower ends in axially parallel condition with the respective dynamic pressure bearings, and the permanent magnets facing the respective permanent magnets with the same pole are fixed to the inner surface of the cylindrical portion of the hub. Characteristic spindle motor. 2. The spindle motor according to claim 1, wherein
A spindle motor, wherein the dynamic pressure bearing is formed between the fixed shaft and an annular bush fixed to the inner surface of the cylindrical portion of the hub.