JP2949316B2 - Spindle motor - Google Patents

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 drive.

[0002]

2. Description of the Related Art Conventionally, as this kind of spindle motor, there is one shown in FIG. 2 (Japanese Utility Model Laid-Open No. 63-21456). This spindle motor has a flange 43 and a cylindrical part 4.
4 and a fixed sleeve 42
The rotary shaft 40 inserted in the cylindrical portion 44 of the rotary shaft 40 and rotatably supported by two ball bearings 45 and 46 spaced apart in the axial direction.
A hub 41 integrated with one end 40a of the rotating shaft 40 and covering the cylindrical portion 44 of the fixed sleeve 42;
1 and a rotary drive part 47 of a rotary shaft 40 composed of a permanent magnet 49 and a stator 48 provided between the cylindrical part 44 of the fixed sleeve 42 and a spherical part 50 provided as a thrust bearing part provided at a tip 40 b of the rotary shaft 40. It has.

[0003]

However, in the above-mentioned conventional spindle motor, the rotating shaft 40 is mounted on the ball bearings 45 and 4.
6, the friction torque loss during rotation of the rotary shaft 40 is inevitably increased. Furthermore, ball bearings 45,
Since the preload to the pressure 46 is necessary, the preload adjustment is troublesome, and the rotation accuracy may be unstable due to the variation of the preload. SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned technical problems and to provide a spindle motor capable of obtaining low friction torque and stable rotation accuracy.

[0004]

In order to achieve the above object, the present invention provides a fixed sleeve having a flange portion and a cylindrical portion, a rotatable bearing inserted into the cylindrical portion of the fixed sleeve and having a spherical tip. A rotating shaft that is a part, a hub that is integrated with the rotating shaft and covers the cylindrical portion of the fixed sleeve,
A spindle motor having a rotating shaft drive unit provided between the hub and the cylindrical portion of the fixed sleeve, wherein first and second permanent magnets attached to both ends of the rotating shaft;
Third and fourth permanent magnets attached to the cylindrical portion of the fixed sleeve so as to face the first and second permanent magnets at a radial distance from each other, and the rotating shaft of the fixed sleeve is The first and third permanent magnets and the second and fourth permanent magnets are rotatably supported in a non-contact manner on the cylindrical portion so as to oppose each other with the same polarity.
Are fixed to the spherical portion side of the rotating shaft by a predetermined distance from the opposing third and fourth permanent magnets, and a step is formed at the end of the flange portion of the fixed sleeve. In addition, the dynamic pressure bearing is configured such that the end portion of the hub faces the step portion, and a dynamic pressure groove is formed in at least one of the step side surface of the flange portion and the end side surface of the hub. It is characterized by.

[0005]

According to the above construction, the rotating shaft is supported radially in a non-contact state when the rotating shaft is stopped and during rotation by utilizing the repulsive force of the magnetic force of the permanent magnet on the cylindrical portion of the fixed sleeve.
Since friction occurs only at the spherical portion at the tip of the rotating shaft, that is, only at the thrust bearing, a low friction torque can be obtained. In addition, the permanent magnets are arranged at both ends of the rotating shaft, and the rotating shaft is supported by the dynamic pressure bearing while the rotating shaft is rotating. Therefore, the rotating shaft is stabilized and the rotation accuracy is stabilized.

Further, since the dynamic pressure grooves are formed in the annular sleeve, the overall structure becomes compact. Furthermore, when the dynamic pressure bearing is formed between the step end face of the flange and the end face of the hub, the bearing is formed at a position radially away from the permanent magnet section, so that the rotation is more stable.

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of a spindle motor according to the present invention. In this embodiment, a fixed sleeve 3 having a flange portion 4 and a cylindrical portion 5, a rotary shaft 1 rotatably inserted into the cylindrical portion 5 of the fixed sleeve 3, and one end 1a of the rotary shaft 1 are integrally formed. And a hub 2 that covers the cylindrical portion 5 of the fixed sleeve 3. After the hub 2 is formed separately, it may be integrated with the rotating shaft 1 by means such as press fitting.

The rotary shaft 1 is provided with a through hole 17 in the axial direction, and the ball 6 is fixed to the tip 1b so that a part thereof projects in the axial direction from the end surface of the rotary shaft. The tip 1b is a spherical portion. The ball 6 comes into point contact with the bed 7 to form a thrust bearing 15. Instead of fixing the ball 6 to the rotating shaft 1, the tip of the rotating shaft 1 may be directly formed into a spherical surface. The bed 7 is bolted 16 to the flange 4 of the fixed sleeve 3.

An annular first permanent magnet 11 and an annular second permanent magnet 12 are fitted and fixed to both ends of the outer peripheral surface of the rotary shaft 1 at an axial interval. Furthermore,
On the inner peripheral surface of the cylindrical portion 5 of the fixed sleeve 3, an annular third ring is provided at an axial interval so as to face the first and second permanent magnets 11 and 12 at a radial interval. The permanent magnet 13 and the annular fourth permanent magnet 14 are fitted and fixed. The axial length of the opposing first permanent magnet 11 and third permanent magnet 13 and the axial length of the opposing second permanent magnet 12 and fourth permanent magnet 14 are substantially the same. ing. Further, the first permanent magnet 11 and the third permanent magnet 13 facing each other and the second permanent magnet 11
The fourth permanent magnet 12 and the fourth permanent magnet 14 are arranged so as to oppose each other with the same polarity and repel magnetic force. Due to the repulsive force of the magnetic force, the rotating shaft 1 is rotatably supported on the cylindrical portion 5 of the fixed sleeve 3 in a radially non-contact manner. In addition, in order to increase the contact stability in the thrust bearing 15, the ball 6 of the first permanent magnet 11 is closer to the ball 6 than the opposing ball 6 of the third permanent magnet 13 is. Side by a predetermined distance h. Similarly, the anti-ball 6 of the second permanent magnet 12
The side end surface 12a is also shifted by a predetermined distance h from the opposite end surface 14a of the fourth permanent magnet 14 opposite the ball 6. As a result, the repulsive force of the magnet acts more on the ball 6 side, and the rotating shaft 1 is pressed more strongly on the ball 6 side. The distance to be shifted may be shifted by the same distance as described above, or may be changed as necessary. In short, the first and second permanent magnets 11 and 12 are respectively moved to the third and fourth permanent magnets. Ball 6 than permanent magnets 13 and 14
It is only necessary to place it on the side. Further, in the embodiment of FIG. 1, each of the permanent magnets 11, 12, 13, and 14 is used. However, the present invention is not limited to this. As shown in FIG. 3, which is another embodiment described later. May be used as a pair, and any combination of them may be used.

A drive unit 8 for rotating the rotary shaft 1 is arranged between the cylindrical portion 5 of the fixed sleeve 3 and the hub 2. The driving unit 8 is provided with the cylindrical portion 5 of the fixed sleeve 3.
And a permanent magnet 10 attached to the hub 2.

A recessed step 4a is provided at an end of the flange portion 4 of the fixed sleeve 3, and a flange 2a extending outward in the axial direction is provided at an end of the hub 2, and an axial outer surface 2b of the flange 2a is provided. The side surface 2b of the flange 2a faces the inside of the concave step portion 4a so as to face the side surface 4b inside the concave step portion 4a at a distance.
A dynamic pressure bearing 30 is formed between the flange 2 a and the recessed step 4 a of the flange 4. In this embodiment, the permanent magnets 11, 1
2, 13, 14 are set as a pair. The end of the hub 2 and the end of the flange 4 have the above-described configuration. However, the present invention is not limited to this.
A step may be formed at the end of the hub 2 so that the side of the end of the hub 2 faces the side of the step. Further, the dynamic pressure groove 30 may be formed on the side surface 4b of the concave step portion 4a, and may be formed on both the side surface 2b of the flange 2a and the side surface 4b of the concave step portion 4a as necessary.

According to the embodiment shown in FIG. 1, since the dynamic pressure bearing portion is arranged at a distance from the non-contact support portion made of a permanent magnet in the axial direction, the rotation of the rotary shaft 1 is further stabilized.

[0014]

As is apparent from the above description, the spindle motor according to the present invention has a fixed sleeve having a flange portion and a cylindrical portion, and is rotatably supported by being inserted into the cylindrical portion of the fixed sleeve and having a spherical end at the tip. A rotating shaft, a hub integrated with the rotating shaft and covering the cylindrical portion of the fixed sleeve, and a rotary shaft driving portion provided between the hub and the cylindrical portion of the fixed sleeve. First and second permanent magnets attached to both ends of the rotating shaft, and attached to the cylindrical portion of the fixed sleeve so as to face the first and second permanent magnets at a radial distance from each other. The rotation shaft is rotatably supported by the third and fourth permanent magnets in a non-contact manner with the cylindrical portion of the fixed sleeve, and the first and third permanent magnets and the second and fourth permanent magnets are supported. Permanent magnets with the same polarity And the first and second permanent magnets are displaced toward the spherical portion of the rotating shaft by a predetermined distance from the opposing third and fourth permanent magnets. Forming a step at the end of the portion, facing the end of the hub to the step, and forming a dynamic pressure groove on at least one of the step side surface of the flange portion and the end side surface of the hub. , The rotation of the rotating shaft is more stabilized, and the rotation accuracy is improved. In addition, it is not necessary to adjust the preload as in a conventional ball bearing.

[Brief description of the drawings]

FIG. 1 is a sectional view of a spindle motor according to an embodiment of the present invention.

FIG. 2 is a sectional view of a conventional spindle motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rotation shaft 2 Hub 2a Flange 2b Axial outer surface of flange 2a 3 Fixed sleeve 4 Flange part of fixed sleeve 4a Concave step 11 First permanent magnet 12 Second permanent magnet 13 Third permanent magnet 14 Fourth Permanent magnet 30 Dynamic pressure groove

──────────────────────────────────────────────────続 き Continuation of the front page (56) References Japanese Utility Model 63-142422 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F16C 32/00-32/06 F16C 17 / 02

Claims (1)

(57) [Claims] 1. A fixed sleeve having a flange portion and a tubular portion, a rotating shaft inserted into the tubular portion of the fixed sleeve and rotatably supported and having a spherical end portion, and integrated with the rotating shaft. In a spindle motor having a hub that covers the cylindrical portion of the fixed sleeve, and a rotary shaft driving unit provided between the hub and the cylindrical portion of the fixed sleeve, first and second motors mounted on both ends of the rotary shaft. And the third and fourth permanent magnets mounted on the cylindrical portion of the fixed sleeve so as to face the first and second permanent magnets at intervals in the radial direction, respectively. The shaft is rotatably supported on the cylindrical portion of the fixed sleeve in a non-contact manner.
And the third and fourth permanent magnets, and the second and fourth permanent magnets are respectively opposed to each other with the same polarity, and the first and second permanent magnets are respectively opposed to the third and fourth permanent magnets opposed to each other. The fixed shaft is attached by being shifted to the spherical portion side of the rotating shaft by a predetermined distance, a step is formed at an end of a flange portion of the fixed sleeve, and an end of the hub is made to face the step portion, and the flange portion is formed. A hydrodynamic bearing formed by forming a hydrodynamic groove in at least one of the step side surface and the end side surface of the hub.