JPH10146014A - Spindle motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the rotor of a spindle motor from coming off and to minimize vibration in either radial or thrust direction. SOLUTION: A bracket 12, which has a rotating shaft 2 supported rotatably through a stator core 13 and a bearing 10, and a rotor part 9, fixed to the rotating shaft 2 which a rotor magnet 8 provided in a position opposing the outside circumference of the stator core 13, are provided. On the bracket 12, an attraction member 15 made of a magnetic material is provided opposite to the rotor magnet 8 and the thrust direction so that holding action by the magnetic attraction can inhibit the rotor part 9 moving in the thrust direction and consequently suppress vibration, too.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor mainly used for a disk drive source of a magnetic disk memory device in the OA field, and more particularly to a technique for applying a thrust force to a rotor.

[0002]

2. Description of the Related Art Conventionally, as this kind of spindle motor, one having a structure shown in FIG. 6 is known.

In FIG. 6, reference numeral 21 denotes a hub fixed to the rotary shaft 22 by press-fitting or the like. A plurality of magnetic recording media 23 are mounted via spacers 24, and a clamper 2 is provided.
Fixed at 5. Further, a rotor is formed by fixing a rotor magnet 27 to a frame 26 attached to the hub 21. The bearing in the radial direction of the rotary shaft 22 is a bearing 28 made of a sintered oil-impregnated bearing or the like, and the bearing in the thrust direction is made by a thrust plate 29.
A coil 31 is mounted on a bracket 30 for holding the bearing 28.
Is mounted. The rotor magnet 27 is located at a position facing the outer periphery of the stator core 32, but the magnetic center of the rotor magnet 27 is shifted upward from the magnetic center of the stator core 32. Therefore, the rotor magnet 27 is attracted by the stator core 32 in the thrust direction, and generates a thrust force.

[0004]

Recently, with the development of technology for increasing the recording density of magnetic disks, the track pitch of disks has been rapidly reduced. Accordingly, a spindle motor must be able to accurately write and read signals even at a narrow track pitch. For that purpose, it is necessary to reduce the vibration of the motor.

Under these circumstances, the use of hydrodynamic bearings for spindle motor bearings has been expanding, and as a result, radial vibrations and run-out of asynchronous components have been significantly improved.

However, in the conventional example, the respective magnetic centers of the rotor magnet 27 and the stator core 32 are shifted in order to prevent the rotor from coming off. However, the thrust force increases or decreases as the rotational position of the rotor changes. Become or change. This change in the thrust force appears as motor vibration in the thrust direction, and also causes motor noise.

To solve such a problem, Japanese Patent Laid-Open Publication No.
The technology described in Japanese Patent No. 253 is known.

In FIG. 7, the magnetic center of the stator core 32 and the magnetic center of the rotor magnet 27 are substantially at the same position in the thrust direction. Therefore, since there is no change in the thrust force due to the change in the magnetism in the thrust direction, a very low level of vibration and noise of the motor can be realized.

However, as a matter of course, since the thrust force hardly acts, when vibration or impact is applied to the motor, the rotor is disengaged or the rotor floats while the motor is rotating, so that the data on the magnetic disk can be lost. There was a possibility of causing a reading error or the like.

An object of the present invention is to provide a spindle motor capable of preventing the rotor from coming off or floating, and suppressing the vibration in both the radial and thrust directions of the motor.

[0011]

SUMMARY OF THE INVENTION To solve the above-mentioned conventional problems, the present invention provides a bracket having a stator core on which a coil is wound and a rotating shaft rotatably supported via a bearing, and an outer periphery of the stator core. A rotor magnet opposed to the position is attached to the hub via a frame, and comprises a rotor portion fixed to the rotating shaft,
The bracket has a suction member made of a magnetic material opposed to the rotor magnet in the thrust direction, and prevents the rotor portion from moving in the thrust direction by a holding action by magnetic attraction.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is directed to a bracket having a stator core on which a coil is wound and a rotating shaft rotatably supported via a bearing, and a rotor magnet provided at an outer peripheral position of the stator core via a frame. And a rotor portion fixed to the hub and fixed to the rotating shaft, and the bracket is provided with a suction member made of a magnetic material so as to face the rotor magnet in the thrust direction.

The frame has a flange bent inside, and the suction member is shaped like a ring. The inside diameter of the flange is A, the inside diameter of the suction member is B,
C is the gap between the lower surface of the flange of the frame and one surface of the rotor magnet, and D is the gap between the other surface of the rotor magnet and the suction member.
, A = B and C = D.

As the bearing, a sintered oil-impregnated bearing or a hydrodynamic bearing was used. Further, the suction member was fixed to the depression formed in the bracket.

Further, the attraction member is set in a ring shape. When the outer diameter of the frame is E and the outer diameter of the attraction member is F, the relationship of E <F is set. Are projected from the end of the frame.

According to the above embodiment, the rotor can be prevented from moving in the thrust direction by the holding action by the magnetic attraction, and the vibration in the same direction can be suppressed.

If a sintered oil-impregnated bearing is used as the bearing,
Cost reduction can be promoted, and if a hydrodynamic bearing is used, the asynchronous component that is a high-frequency vibration component during rotation of the spindle motor can be reduced.

Further, since the suction member is attached to the recess of the bracket, the height of the rotor magnet is further increased, so that a high torque motor can be realized.

When the outer diameter of the frame is E and the outer diameter of the suction member is F, the relationship of E <F is satisfied, and the other surface of the rotor magnet protrudes longer than the end of the bracket. Thus, it is possible to increase the attraction force between the rotor magnet and the attraction member.

[0020]

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

(Embodiment 1) In FIGS. 1 and 2, reference numeral 1 denotes a hub fixed to a rotating shaft 2 by press fitting or the like. A magnetic recording medium 3 is mounted on the hub 1 with a spacer 4 interposed therebetween and fixed by a clamper 5. Reference numeral 6 denotes a frame, which is integrally fixed to the lower surface of the outer peripheral portion of the hub 1 via a flange 7 formed by being bent inward, and a rotor section 9 is formed by providing a rotor magnet 8 on the inner periphery. Reference numeral 10 denotes a bearing made of a sintered oil-impregnated bearing or the like that rotatably supports the rotary shaft 2 in the radial direction. Reference numeral 11 denotes a thrust plate that supports the rotary shaft 2 in the thrust direction, which is made of a non-magnetic material such as aluminum die cast. It is fixed to the bracket 12.
A stator core 13 is attached to the bracket 12 so as to face the inner periphery of the rotor magnet 8, and a coil 14 is wound around the stator core 13. In the present embodiment, the magnetic center in the thrust direction of the rotor magnet 8 substantially coincides with the magnetic center in the thrust direction of the stator core 13.

A circular suction member 15 made of a magnetic material is attached to the bracket 12 by a method such as bonding. The suction member 15 is disposed at a position facing the lower end surface of the rotor magnet 8 while keeping a gap.

Here, the rotor magnet 8 and the frame 6
When the gap between the flanges 7 is C and the gap between the rotor magnet 8 and the attraction member 15 is D, the positioning projection 16 is provided on the hub 1 so that the relationship of C = D is established. When the inner diameter of the flange 7 of the frame 6 is A and the inner diameter of the suction member 15 is B, the relation of A = B also holds.

With this configuration, since the rotor magnet 8 is attracted to the attracting member 15, the rotor portion 9 can be prevented from coming off and floating. In addition, the rotor magnet 8 and the attraction member 1
5. Make the gap between the frame 6 and the suction member 15 equal,
Further, by making the inner diameter of the frame 6 and the inner diameter of the suction member 15 equal, the magnetic center of the rotor magnet 8 can be set at the mechanical center position. Therefore, it is possible to suppress the vibration in the thrust direction of the motor to be small by preventing the magnetic center from being out of balance.

(Embodiment 2) FIG. 3 shows a hydrodynamic bearing in which a bearing 10 'is formed with a herringbone groove in a sleeve metal made of a metal material such as brass having a good cutting ability.
Lubricating fluid is filled between the herringbone groove, the rotating shaft 2 and the sleeve metal, and between the rotating shaft 2 and the thrust plate 11, respectively.

When the rotating shaft 2 is rotated by the herringbone groove formed in the sleeve metal, a pressure is generated in the lubricating fluid to exert a hydrodynamic bearing function. With this configuration, it is possible to reduce an asynchronous component that is a high-frequency vibration component when the spindle motor rotates.

In the above description, an example has been described in which a herringbone groove is provided in a sleeve metal as a hydrodynamic bearing. However, a hydrodynamic bearing in which a herringbone groove is provided in a rotating shaft 2 is described. A similar effect can be obtained with the configuration.

The same effect can be obtained in a configuration in which a dynamic pressure is generated in the thrust direction by means such as providing a spiral groove on one of the end face of the rotating shaft facing the thrust plate 11 or the thrust plate 11.

With this configuration, the rotor 9 can be prevented from coming off, and the vibration of the motor can be suppressed small. In particular, the asynchronous component vibration, which is a high frequency vibration component in the radial direction, can be suppressed small.

(Embodiment 3) FIG. 4 shows a case in which a recess 16 is provided at a position where the lower end surface of the rotor magnet 8 of the bracket 12 faces, and a suction member 15 is attached.

According to this configuration, the height of the rotor magnet 8 can be further increased, so that a high torque motor can be realized.

(Embodiment 4) FIG. 5 shows that when the outer diameter of the frame 6 is E and the outer diameter of the suction member 15 is F, the relationship of E <F is satisfied and the lower end surface of the rotor magnet 8 is
Is a spindle motor configured to protrude longer than the lower end surface of the spindle motor.

According to this configuration, the magnetic flux flowing from the rotor magnet 8 to the attraction member 15 increases due to the absence of the frame 6 on the outer diameter of the rotor magnet 8. Further, since the outer diameter F of the attraction member 15 is set to be larger than the outer diameter E of the frame 6, the magnetic flux from the rotor magnet 8 can be sufficiently absorbed, and the attraction force of the rotor can be increased. Becomes

[0034]

As described above, according to the present invention, there are obtained advantageous effects that the rotor can be prevented from coming off and floating, and the vibration of the motor in both the radial and thrust directions can be reduced.

[Brief description of the drawings]

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

FIG. 2 is a partially enlarged view of a spindle motor according to the first embodiment of the present invention.

FIG. 3 is a sectional view of a spindle motor according to a second embodiment of the present invention.

FIG. 4 is a partially enlarged view of a spindle motor according to a third embodiment of the present invention.

FIG. 5 is a partially enlarged view of a spindle motor according to a fourth embodiment of the present invention.

FIG. 6 is a sectional view of a conventional spindle motor.

FIG. 7 is a partially enlarged view of a conventional spindle motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hub 2 Rotating shaft 6 Frame 7 Flange 8 Rotor magnet 9 Rotor part 10, 10 'Bearing 12 Bracket 13 Stator core 14 Coil 15 Suction member 16 Depression

Claims (6)

[Claims] A bracket having a rotating shaft rotatably supported via a stator core and a bearing on which a coil is wound, and a rotor magnet opposed to an outer peripheral position of the stator core are attached to a hub via a frame, A rotor portion fixed to the rotating shaft, and the bracket is provided with a suction member made of a magnetic material facing the rotor magnet in a thrust direction, and the thrust of the rotor portion is held by a magnetic suction effect. Spindle motor that prevents directional movement. 2. The frame has a flange bent inward, and the suction member is formed in a ring shape. The inside diameter of the flange is A, the inside diameter of the suction member is B, the lower surface of the frame flange and the rotor. 2. The spindle motor according to claim 1, wherein when the gap between one surface of the magnet and the gap between the other surface of the rotor magnet and the attraction member is D, A = B and C = D. 3. A sintered oil-impregnated bearing is used as the bearing.
The spindle motor as described. 4. A hydrodynamic bearing as a bearing.
The spindle motor as described. 5. The spindle motor according to claim 1, wherein the suction member is fixed to a recess formed in the bracket. 6. The suction member is formed in a ring shape.
2. The spindle motor according to claim 1, wherein when the outer diameter of the frame is E and the outer diameter of the suction member is F, a relationship of E <F is set, and the other surface of the rotor magnet projects beyond the end of the frame. .