JPH10275410A - Spindle motor and magnetic disk device equipped with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress backlash of a bearing and also to make the spindle motor and the magnetic disk device equipped this motor thinner in structure. SOLUTION: An axis 20 of a hub 12 functioning as a rotor is coaxially arranged in a supporting sleeve 14 of a base part 10, and is borne by a ball bearing 24 to be freely rotatable in the supporting sleeve. The base part is fitted with a receiving plate 30 opposite to the extended end of the axis. A dynamic pressure fluid bearing 34 for impressing a preload in the thrust direction upon the ball bearing via the axis is provided between the extended end of the axis and the receiving plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a spindle motor, and more particularly to a spindle motor used for supporting and driving a magnetic disk in a magnetic disk device, and a magnetic disk device provided with the same.

[0002]

2. Description of the Related Art In general, a spindle motor used in a magnetic disk drive includes a cylindrical hub that functions as a rotor, and a bracket having a cylindrical support sleeve. , Inserted into the support sleeve. The hub is rotatably supported by two ball bearings fitted between the pivot and the inner surface of the support sleeve. Also, the magnetic disk
It is attached to the outer periphery of the hub and is driven to rotate integrally with the hub.

[0003] Generally, in a ball bearing, there is play along the axial direction between an inner ring and an outer ring. Such play of the bearings is an obstacle in performing the recording and reproduction of information on the magnetic disk with high accuracy. Therefore, in this type of spindle motor, two ball bearings are arranged side by side in the axial direction of the pivot of the hub, and preload along the axial direction is applied to each other by these ball bearings, so that each ball bearing has a play. Has been reduced.

[0004]

In recent years, along with the miniaturization of electronic equipment, there has been a demand for a reduction in the size of a magnetic disk drive, particularly a reduction in the size in the thickness direction. However, in the spindle motor described above, since two ball bearings are used side by side along the pivot, there is a limit in reducing the dimension in the thickness direction, that is, the dimension along the axis of the pivot, It is difficult to face downsizing of the magnetic disk drive.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to provide a spindle motor capable of suppressing rattling of a bearing and further reducing the thickness thereof, and a magnetic disk device having the same. It is in.

[0006]

In order to achieve the above object, according to the spindle motor of the present invention, only one ball bearing is provided, and a preload in the axial direction is applied to the ball bearing. The preload applying means for suppressing the backlash is separately provided.

That is, a spindle motor according to a first aspect of the present invention has a cylindrical main body having one end closed by an end wall, and is provided coaxially with the main body inside the main body, extending from the end wall. A hub having a supporting shaft, a base having a supporting sleeve disposed between the inner peripheral surface of the main body and the supporting shaft, and a base fitted between the supporting shaft and the supporting sleeve. A ball bearing rotatably supporting the hub with respect to a sleeve, and a ball bearing provided opposite to the extended end of the pivot to apply a preload along the axial direction to the pivot to play the ball bearing. And a hydrodynamic bearing for suppressing the pressure.

According to the spindle motor having the above configuration, the pivot of the hub is rotatably supported by a single ball bearing against the support sleeve of the base portion and against a radial load. In addition, the hydrodynamic bearing generates dynamic pressure in accordance with the rotation of the hub, supports a load in the thrust direction of the pivot, and applies a preload to the ball bearing via the pivot to suppress rattling of the ball bearing. Since the hydrodynamic bearing can be formed thinner than a ball bearing, the overall spindle motor can be made thinner.

According to a third aspect of the present invention, there is provided a spindle motor having a cylindrical main body having one end closed by an end wall, and extending coaxially with the main body inside the main body, extending from the end wall. A base having a support sleeve disposed between the inner peripheral surface of the main body and the pivot; a support sleeve fitted between the pivot and the support sleeve; A ball bearing rotatably supporting the hub, and a contact portion fixed to the base portion so as to face the extended end of the pivot, and having a point contact with the extended end of the pivot. And a receiving plate for applying a preload along the axial direction to the pivot to suppress backlash of the ball bearing.

According to the spindle motor having the above configuration, the pivot of the hub is rotatably supported by a single ball bearing against the support sleeve of the base portion and against a radial load. In the receiving plate, the load in the thrust direction of the pivot is supported by the receiving plate, and a preload is applied to the ball bearing via the pivot to suppress rattling of the ball bearing. By using the receiving plate instead of the ball bearing, the entire spindle motor can be reduced in thickness. Further, since the receiving plate and the pivot are in point contact with each other, friction and wear therebetween can be reduced.

According to a seventh aspect of the present invention, there is provided a magnetic disk drive comprising: a spindle motor for supporting and rotating a magnetic disk; a magnetic head for recording and reproducing information on and from the magnetic disk; A carriage assembly movably supported by the carriage assembly.

The spindle motor includes a hub having a cylindrical main body having one end closed by an end wall, and a pivot extending from the end wall and provided coaxially with the main body inside the main body. A base having a support sleeve disposed between the inner peripheral surface of the main body and the pivot; and a base fitted between the pivot and the support sleeve, rotating the hub relative to the support sleeve. A ball bearing freely supported, and a hydrodynamic fluid bearing provided opposite to the extended end of the pivot to apply a preload along the axial direction to the pivot to suppress backlash of the ball bearing. , Is provided.

According to another aspect of the present invention, there is provided a magnetic disk drive comprising: a spindle motor for supporting and rotating a magnetic disk; a magnetic head for recording and reproducing information on and from the magnetic disk; A carriage assembly movably supported with respect to the disk.

The spindle motor includes a hub having a cylindrical main body one end of which is closed by an end wall, and a pivot extending from the end wall and provided coaxially with the main body inside the main body. A base having a support sleeve disposed between the inner peripheral surface of the main body and the pivot; and a base fitted between the pivot and the support sleeve, the hub being rotatable relative to the support sleeve. One supported ball bearing and a contact portion fixed to the base portion so as to face the extended end of the pivot, and having a point contacting the extended end of the pivot at a point in the axial direction of the pivot. And a receiving plate for applying a preload along the axis to suppress backlash of the ball bearing.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which a magnetic disk drive according to an embodiment of the present invention is applied to a hard disk drive (hereinafter referred to as an HDD) will be described in detail with reference to the drawings.

As shown in FIG. 1, the HDD has a rectangular box-shaped case 50 having an open upper surface, and a top cover (not shown) which is screwed to the case with a plurality of screws to close an upper end opening of the case. doing.

A case 50 includes a magnetic disk 52 as a magnetic recording medium, a spindle motor 53 for supporting and rotating the magnetic disk, and a plurality of magnetic heads for recording and reproducing information on and from the magnetic disk. , A voice coil motor (hereinafter referred to as VCM) 56 for rotating and positioning the carriage assembly, and a substrate unit 57 having a preamplifier and the like. I have.

A printed circuit board (not shown) for controlling the operations of the spindle motor 53, the VCM 56, and the magnetic head is screwed to the outer surface of the case 50 via a board unit 57, and faces the bottom wall of the case. positioned.

The carriage assembly 54 includes a case 5
A magnetic head assembly 68 including a magnetic head is fixed to the end of each arm, comprising a bearing assembly 58 fixed on the bottom wall of the O. 0 and two arms extending from the bearing assembly. . The VCM 56 includes a pair of yokes 70 fixed on the bottom wall of the case 50, and a boil coil (not shown) supported by the bearing assembly 58 and arranged between the pair of yokes.

As shown in FIG. 2A, the spindle motor 53 includes a bracket 10 functioning as a base,
A hub 12 rotatably supported by the bracket and functioning as a rotor is provided. A cylindrical support sleeve 14 is integrally formed at the center of the bracket 10.

The hub 12 comprises a cylindrical body 16, an end wall 18 closing the upper end of the body, and a pivot 20 projecting from the center of the end wall and extending simultaneously inside the body.
It is formed integrally. The extended end surface of the pivot 20, that is, the lower end surface 20a is formed flat. An annular flange 22 is formed on the outer periphery of the lower end of the main body 16.

The hub 12 includes a main body 16 and a support sleeve 14.
And the pivot 20 is disposed coaxially inserted into the support sleeve 14,
A ball bearing 24 is fitted between the support sleeve 14 and the support sleeve 14. The ball bearing 24 has an outer ring 24 a fitted on the inner peripheral surface of the support sleeve 14 and an inner ring 24 b fitted on the outer peripheral surface of the pivot 20.
It is rotatably supported with respect to.

An annular permanent magnet 26 is coaxially fixed on the inner peripheral surface of the hub body 16, and a stator 28 having a core and a coil is disposed on the outer periphery of the support sleeve 14.
Is attached and is adjacently opposed to the permanent magnet 26. Then, by energizing the coils of the stator 28, a driving torque is generated and the hub 12 is rotationally driven.

A flat receiving plate 30 is fixed to the base portion 10, closes the lower end opening of the support sleeve 14, and faces the lower end surface 20 a of the pivot 20 in parallel. As shown in FIG. 2B, the inner surface of the receiving plate 30
A large number of dynamic pressure generating grooves 32 extending substantially radially are formed in a region facing the lower end surface of the pivot 20. These dynamic pressure generating grooves 32 are formed side by side in the annular region 31 coaxial with the pivot. In the space surrounded by the pivot 20, the support sleeve 14, the ball bearing 24, and the receiving plate 30,
As the working fluid, for example, silicone oil is sealed.
The dynamic pressure generating groove 32 provided in the receiving plate 30 is shown in FIG.
As shown in FIG.

The lower end surfaces 20 of these pivots 20
a, a bearing plate 30 having a dynamic pressure generating groove 32 and a working fluid constitute a dynamic pressure fluid bearing 34. Hub 12
Is driven to rotate, the hydrodynamic bearing 34 generates a dynamic pressure along the axial direction of the pivot 20 by the action of the working fluid and the dynamic pressure generating groove 32, and the dynamic pressure
And a preload along the axial direction of the pivot is applied to the ball bearing 24 via the pivot 20. Thereby, the ball bearing 24 rotatably supports the pivot while the backlash along the axial direction of the pivot 20 is suppressed.

For example, when the backlash in the thrust direction of the ball bearing 24 is several tens μm, the pivot 20 is provided with a hydrodynamic bearing 34.
Floating in the thrust direction by a few μm by the dynamic pressure generated by the above, and a preload is applied to the ball bearing 24.

When the spindle motor 53 described above is incorporated in a magnetic disk drive, the magnetic disk 52
The flange 2 is fitted with the outer peripheral surface of the hub body 16.
2 and clamped between the flange by a clamp screwed to the end wall 18. By operating the spindle motor 53, the magnetic disk 52
Is driven to rotate integrally with the hub 12.

According to the spindle motor configured as described above, the pivot 20 of the hub 12 is rotatably supported on the support sleeve 14 of the base 10 by a single ball bearing 24. As a preload applying means for applying a preload to the ball bearing 24 and suppressing rattling of the ball bearing, a hydrodynamic fluid bearing 34 provided opposite to the extended end of the pivot is used. Since the hydrodynamic bearing 34 can be formed to be thinner than a ball bearing, the thickness H of the motor can be significantly reduced and the thickness can be reduced compared with a conventional spindle motor having two ball bearings arranged side by side. Can be achieved. At the same time, rattling of the ball bearings 34 is reduced, and stable rotation of the hub 12 can be performed. Furthermore, the hydrodynamic bearing 3
By the dynamic pressure generated by 4, a preload can be applied to the ball bearing 24 in a state where the ball bearing 24 is not in contact with the pivot 20, and the friction in the spindle motor can be reduced.

FIG. 3 shows a spindle motor according to another embodiment of the present invention. According to this spindle motor, the preload applying means is constituted by bringing the receiving plate 30 into direct contact with the lower end surface 20a of the pivot 20, instead of the above-described hydrodynamic bearing.

That is, the receiving plate 30 has a contact portion 30 a in contact with the lower end surface 20 a of the pivot 20, and applies a preload in the thrust direction to the ball bearing 24 via the pivot 20. Here, in order to reduce friction and wear between the lower end surface 20a of the pivot 20 and the contact portion 30a, the lower end surface of the pivot is formed in a spherical shape that is convex toward the receiving plate 30 side.
Point contact with

The other structure is the same as that of the above-described embodiment, and the same parts are denoted by the same reference numerals and detailed description thereof will be omitted. According to the other embodiment configured as described above, by configuring the preload applying means using the flat receiving plate 30, it is possible to reduce the number of ball bearings conventionally provided in a row to two. The spindle motor thickness H
Can be greatly reduced, and the thickness can be reduced. at the same time,
The rattling of the ball bearings 34 can be reduced, and stable rotation of the hub 12 can be performed.

In the other embodiments described above,
The lower end surface 20a of the pivot 20 has a spherical shape and is in point contact with the contact portion 30a of the receiving plate 30. However, the present invention is not limited to this, and the lower end surface 20a of the pivot 20 is flattened as shown in FIG. The contact part 30a of the pivot 30 may be formed into a spherical shape that is convex toward the pivot, or, as shown in FIG.
0a may be spherical.

[0033]

As described in detail above, according to the present invention, by using a hydrodynamic bearing or a flat receiving plate as the preload applying means, one ball bearing conventionally used side by side is used. Thus, it is possible to provide a spindle motor capable of suppressing the backlash of the bearing and further reducing the thickness, and a magnetic disk device including the same.

[Brief description of the drawings]

FIG. 1 is a perspective view of a magnetic disk drive according to an embodiment of the present invention.

FIG. 2 is a sectional view of a spindle motor of the magnetic disk device, and a plan view of a receiving plate on which a dynamic pressure generating groove is formed.

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

FIG. 4 is a sectional view showing a modification of the spindle motor shown in FIG. 3;

FIG. 5 is a sectional view showing another modification of the spindle motor shown in FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Bracket 12 ... Hub 14 ... Support sleeve 16 ... Main body 18 ... End wall 20 ... Axis 20 ... Lower end surface 24 ... Ball bearing 26 ... Permanent magnet 28 ... Stator 30 ... Receiving plate 30a ... Contact part 32 ... Dynamic pressure generating groove 34 ... hydrodynamic bearing 50 ... case 52 ... magnetic disk 53 ... spindle motor 54 ... carriage assembly 56 ... VCM

Claims (8)

[Claims] A hub having a cylindrical main body one end of which is closed by an end wall, a pivot extending from the end wall and provided coaxially with the main body inside the main body; A base portion having a support sleeve disposed between an inner peripheral surface and the pivot; fitted between the pivot and the support sleeve to rotatably support the hub with respect to the support sleeve; A ball bearing, and a hydrodynamic fluid bearing provided opposite to the extended end of the pivot to apply a preload along the axial direction to the pivot to suppress backlash of the ball bearing. A spindle motor. 2. A dynamic pressure fluid bearing comprising: a receiving plate fixed to the base portion and facing an extended end of the pivot; and a working fluid sealed between the extended end of the pivot and the receiving plate. A dynamic pressure generating groove formed on the receiving plate so as to face the extended end of the pivot, and for generating a dynamic pressure along the axial direction of the pivot according to the rotation of the pivot. The spindle motor according to claim 1, wherein: 3. A hub having a cylindrical main body one end of which is closed by an end wall, a pivot extending from the end wall and provided inside the main body and coaxial with the main body; A base portion having a support sleeve disposed between an inner peripheral surface and the pivot; fitted between the pivot and the support sleeve to rotatably support the hub with respect to the support sleeve; Two ball bearings, and a contact portion that is fixed to the base portion so as to face the extended end of the pivot, and has a contact portion that is in point contact with the extended end of the pivot. A bearing plate for applying a preload to suppress backlash of the ball bearing. 4. The spindle motor according to claim 3, wherein at least one of the extended end of the pivot and the contact portion of the receiving plate is formed in a spherical shape and is in point contact with each other. 5. The extension according to claim 3, wherein the extension end of the pivot is formed in a spherical shape convex toward the receiving plate and is in contact with a contact portion of the receiving plate. Spindle motor. 6. A contact portion of the receiving plate, wherein the contact portion is formed in a spherical shape protruding toward the extended end of the pivot and is in contact with the extended end of the pivot. The spindle motor according to any one of the above. 7. A spindle motor for supporting and rotating a magnetic disk, a magnetic head for recording and reproducing information on and from the magnetic disk, and a carriage assembly for supporting the magnetic head movably with respect to the magnetic disk. A hub having a cylindrical body whose one end is closed by an end wall, and a pivot extending from the end wall and provided coaxially with the main body inside the main body. A base portion having a support sleeve disposed between the inner peripheral surface of the main body and the pivot; and a base fitted between the pivot and the support sleeve, the hub being rotatable relative to the support sleeve. One supported ball bearing, and a hydrodynamic fluid provided opposite to the extended end of the pivot to apply a preload along the axial direction to the pivot to suppress backlash of the ball bearing. And a bearing. 8. A spindle motor for supporting and rotating a magnetic disk, a magnetic head for recording and reproducing information on and from the magnetic disk, and a carriage assembly for supporting the magnetic head movably with respect to the magnetic disk. A hub having a cylindrical body whose one end is closed by an end wall, and a pivot extending from the end wall and provided coaxially with the main body inside the main body. A base portion having a support sleeve disposed between the inner peripheral surface of the main body and the pivot; and a base fitted between the pivot and the support sleeve, the hub being rotatable relative to the support sleeve. A supporting ball bearing, a contact portion fixed to the base portion so as to face the extended end of the pivot, and having a point of contact with the extended end of the pivot; A magnetic disk drive, comprising: a receiving plate for applying a preload to the shaft along the axial direction thereof to suppress backlash of the ball bearing.