JPH05130764A - Spindle motor - Google Patents

Abstract

PURPOSE:To provide a spindle motor where the thickness can be decreased, supporting that the distance between bearings is fixed, and where the distance between the bearings can be elongated and which cars enlarge the torque, supposing that the thickness is fixed. CONSTITUTION:This motor comprises a rotor magnet 3, a hub 5, where this rotor magnet can be mounted and also media can be mounted, a coil, a stator base 6, where this coil can be mounted, and ball bearings 1 and 2, which support the hub rotatably with respect to this data base, and this is provided with a salient shaft 6a which supports the inner ring of the ball bearing to the stator base.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor for driving a medium of a disk drive device such as a hard disk drive.

[0002]

2. Description of the Related Art FIG. 4 is a sectional view of a conventional spindle motor.
Shown in. In FIG. 4, the conventional spindle motor includes a rotor, a stator, and ball bearings 51 and 52 that rotatably support the rotor with respect to the stator. The rotor includes a cylindrical rotor magnet 53, a cylindrical back yoke 54 forming a magnetic circuit on the outer periphery of the rotor magnet 53, the rotor magnet 53 mounted via the back yoke 54, and a hard disk or the like. It consists of a hub 55 to which a medium is attached.
The hub 55 includes a cup-shaped portion to which the rotor magnet 53 is attached via the back yoke 54, a cylindrical portion to which the outer rings of the ball bearings 51 and 52 are attached to the inner periphery thereof, and the cylindrical portion and the cup-shaped portion. And a flat plate portion having a convex portion to which the medium is attached.

The stator is fixed to the stator base 56, an iron core 57 around which a coil is wound, and a shaft fixed to the center of the stator base 56 by press fitting (or bonding or the like). It consists of 58 and. This axis 58
The inner rings of the ball bearings 51 and 52 are fixed to the. Reference numeral 59 is a bearing cover. The inner ring of the ball bearings 51 and 52 is fixed to the shaft 58, and the ball bearing 5
The outer rings of 1 and 52 are attached to the hub 55 and
The bearing support system of the spindle motor in which the media is attached to the convex part of this and the media rotates is called the shaft fixing system. On the other hand, a hub is fixed to a shaft, an inner ring of a ball bearing is attached to the shaft, an outer ring of the ball bearing is attached to a stator base, and a bearing support system in which the shaft rotates together with the hub is called a shaft rotation system.
In the shaft rotation method, the hub has a thickness in the axial direction of the shaft press-fitting portion where the hub is press-fitted into the shaft, and only the shaft press-fitting portion of this hub has the ball bearing inside. As a result, the media rotates outside the ball bearing, causing whirling. Compared to the shaft rotation method, the shaft rotation method has a characteristic that the rotating medium comes in the same plane as the ball bearing 51, so that whirling of the medium due to the rotation of the medium is suppressed.

The spindle motor of the shaft fixing type having such characteristics has a large thickness in the portion of the stator base 56 into which the shaft 58 is press-fitted in order to increase the rigidity of the shaft 58 and to obtain the vertical accuracy of the shaft 58. There is a need to. If the rigidity of the shaft 58 is low,
The resonance frequency of the shaft 58 decreases, which causes uneven rotation. axis
If the vertical accuracy of 58 is not good, it will cause surface runout of the media.
Therefore, it is necessary to increase the thickness of the press-fitted portion of the shaft 58 of the stator base 56. If the press-fitted portion of the shaft 58 of the stator base 56 is made thicker, the thickness of the spindle motor in the axial direction becomes
Since the thickness of the press-fitted portion of the shaft 58 of the stator base 56 and the distance between the ball bearings 51 and 52 are determined, there is a drawback that the distance between the ball bearings 51 and 52 becomes narrower if the motor thickness is kept constant. If the distance between the bearings 51 and 52 is constant, there is a drawback that it is difficult to make the motor thinner due to the thickness of the press-fitted portion of the shaft 58 of the stator base 56.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned conventional drawbacks, and can reduce the thickness of the stator base corresponding to the conventional shaft press-fitting portion. If the distance between the bearings is constant, the thickness of the motor can be reduced. If the thickness of the motor is constant, the distance between the bearings can be increased, and the iron core of the motor and the torque generating element of the motor, that is, An object of the present invention is to provide a spindle motor which can increase the torque by increasing the thickness of the magnet and the coil.

[0006]

A spindle motor according to the present invention includes a rotor magnet, a hub to which the rotor magnet is attached, a hub to which a medium is attached, a coil, a stator base to which the coil is attached, and a stator base. On the other hand, a bearing that rotatably supports the hub is provided, and a protrusion shaft that supports an inner circumference of the bearing is provided on the stator base.

And, a hollow cylindrical shaft is fixed to the projection shaft,
The hollow cylindrical shaft supports the inner circumference of the bearing. Also, the stator base is constituted by a base of a disk drive device, and a projection shaft for supporting the inner circumference of the bearing is provided on the base. Further, the stator base is constituted by a base of a disk drive device, a projection shaft is provided on the base, a hollow cylindrical shaft is fixed to the projection shaft, and the inner circumference of the bearing is supported by the hollow cylindrical shaft. And

[0008]

[Operation] Providing a protrusion shaft at the center of the stator base,
By fixing the hollow cylindrical shaft to the projecting shaft and supporting the inner circumference of the bearing on the projecting shaft and on the hollow cylindrical shaft, it corresponds to the conventional shaft press-fitting portion of the stator base. The thickness can be reduced. Moreover, at that time, the rigidity of the shaft is not lowered, that is, the shaft resonance frequency is not lowered, and the vertical accuracy of the shaft is not lowered.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a spindle motor of a fixed shaft type in which whirling of media is suppressed. Specific embodiments to which the present invention is applied will be described below with reference to FIGS. A sectional view of the first embodiment is shown in FIG. 1, a sectional view of the second embodiment is shown in FIG. 2, and a sectional view of the third embodiment is shown in FIG.

As shown in FIG. 1, a spindle motor according to a first embodiment of the present invention comprises a rotor, a stator, and ball bearings 1 and 2 which rotatably support the stator and the rotor. This motor is a circumferential air gap motor in which the rotor rotates in opposition to the outer circumference of the stator.

The rotor is a cylindrical rotor magnet 3
And a cylindrical back yoke 4 that constitutes the magnetic circuit on the outer circumference of the rotor magnet 3, and the rotor magnet 3 is attached via the back yoke 4.
A hub 5 to which a medium such as a hard disk is attached. The hub 5 has a cup-shaped portion to which the rotor magnet 3 is attached via the back yoke 4, a cylindrical portion to which the outer rings of the ball bearings 1 and 2 are attached to the inner periphery thereof, and the cylindrical portion and the cup-shaped portion. And a flat plate portion having a convex portion to which the medium is attached.

The stator comprises a stator base 6, an iron core 7 mounted on the stator base 6 and around which a coil is wound, and a ring member 8 for mounting the iron core 7 on the stator base 6.

The feature of the present invention resides in the stator base 6. The stator base 6 is made of a thin plate such as an iron plate and an aluminum plate by pressing, but is not limited thereto. It may be made by forging or machining. The projection shaft 6a for supporting the inner rings of the ball bearings 1 and 2 is provided on the stator base 6 by drawing if it is press working. 9 is a bearing cover.

As described above, by providing the protrusion shaft 6a for supporting the inner rings of the ball bearings 1 and 2 on the stator base 6 as described above, the rigidity of the shaft is not lowered, that is, the reduction of the shaft resonance frequency is prevented, so that the rotation unevenness is prevented. In addition to improving the vertical accuracy of the shaft and thus reducing the surface runout of the media, the thickness of the stator base 6 corresponding to the conventional shaft fixing portion can be reduced, so that the distance between the ball bearings 1 and 2 is reduced. If it is constant, the thickness of the motor can be reduced. If the thickness of the motor is constant, the ball bearings 1, 2
It is possible to provide a spindle motor in which the distance between the two can be increased, the iron core of the motor can be thickened, and the torque can be increased.

FIG. 2 shows a second embodiment of the present invention, which is different from FIG. 1 in that the projection shaft 6a of the stator base 6 has a hollow cylindrical shaft.
10 is fixed, and the inner ring of the ball bearings 1 and 2 is supported by the hollow cylindrical shaft 10. Protrusion shaft 6a
In the case of drawing, the advantage that the depth can be made shallower
Since the ball bearings 1 and 2 are assembled to 10 and the main assembly can be assembled only by inserting the pre-assembled ball bearing into the protrusion shaft 6a at the time of main assembly, there is an advantage that the assembly is easy.

The spindle motor described with reference to FIGS. 1 and 2 relates to a motor in which the air gaps between the rotor and the stator oppose each other in the circumferential direction, but the structure of the present invention can also be applied to a motor having an air gap in the axial direction. .. FIG. 3 is a third embodiment of the spindle motor according to the present invention, which is an example of an axial gap type motor. Although there is a difference between the cylindrical shape and the disk shape, the first and second
The same parts as those in the embodiment are designated by the same reference numerals.

In FIG. 3, the rotor is a disk-shaped rotor magnet 3, a disk-shaped back yoke 4 that constitutes a magnetic circuit on the back surface of the rotor magnet 3, and the rotor magnet 3 includes the back yoke 4. And a hub 5 to which a medium such as a hard disk is attached. The hub 5 is mounted with the rotor magnet 3 via the back yoke 4, and a flat plate portion having a convex portion for mounting a medium on the opposite side thereof is opposed to the rotor magnet 3 and rotates together with the hub 5. The rotor magnet 3 and the disk-shaped rotor yoke 12 are arranged so as to sandwich the coil 11 on the stator side. The hub 5 further includes a hollow cylindrical portion that connects the rotary yoke attachment portion and the flat plate portion by an outer peripheral portion thereof, and has an outer peripheral portion of the ball bearings 1 and 2 attached to an inner peripheral portion thereof.

The rotor magnet 3 attached to the back yoke 3 and the disk-shaped rotor yoke 12 are arranged so as to sandwich the stator side coil 11. That is, this motor is a so-called coreless brushless motor in which the rotor includes the back yoke 4 and the rotor yoke 12, and the stator does not include the yoke.

The stator comprises a stator base 6 and the coil 11 mounted on the stator base 6, and the coil 11 does not have a yoke made of iron.

The feature of the present invention resides in the stator base 6 as in the first and second embodiments. A projection shaft that supports the inner rings of the ball bearings 1 and 2 on the stator base 6.
If 6a is pressed, it is provided by drawing. 9 is a bearing cover.

As described above, by providing the protruding shaft 6a for supporting the inner rings of the ball bearings 1 and 2 on the stator base 6, the rigidity of the shaft is not lowered, that is, the lowering of the shaft resonance frequency is prevented, so that the rotation unevenness is prevented. In addition to improving the vertical accuracy of the shaft and thus reducing the surface runout of the media, the thickness of the stator base 6 corresponding to the conventional shaft fixing portion can be reduced, so that the distance between the ball bearings 1 and 2 is reduced. If it is constant, the thickness of the motor can be reduced. If the thickness of the motor is constant, the ball bearings 1, 2
It is possible to provide a spindle motor capable of increasing the torque interval and increasing the thickness of the torque generating element of the motor, that is, the thickness of the magnet and the coil, and increasing the torque.

Although the stator base 6 has been described as one component of the motor as the first to third embodiments, the base of the disk drive device of the main body such as a hard disk drive is used to form a part of the base. The projection shaft 6a for mounting the ball bearings 1 and 2 is fixed, or the hollow cylindrical shaft 10 is fixed to the projection shaft 6a, and the projection shaft 6a is fixed to the projection shaft 6a.
To the hollow cylindrical shaft 10 with ball bearings 1, 2
By supporting the inner ring of the disk drive device, the number of parts of the disk drive device can be reduced.

The ball bearing has been described above as an example of the bearing, but the bearing is not limited to the ball bearing. The projection shaft 6a of the stator base 6 is provided on the inner circumference of a bearing such as a sliding bearing such as an oil-impregnated alloy bearing or a dynamic pressure bearing, and the same configuration can be applied when the shaft is fixed.

[0024]

As is apparent from the above description, in the present invention, the protrusion shaft is provided at the center of the stator base.
By fixing the hollow cylindrical shaft to the projecting shaft and supporting the inner circumference of the bearing on the projecting shaft and on the hollow cylindrical shaft, the rigidity of the shaft is not lowered, that is, the shaft resonance. It prevents the frequency from decreasing and thus reduces the rotation unevenness, improves the vertical accuracy of the shaft, reduces the surface runout of the media, and can reduce the thickness equivalent to the conventional shaft fixing part of the stator base. If the distance between the bearings is constant, the thickness of the motor can be reduced. If the thickness of the motor is constant, the distance between the bearings can be increased, and the iron core of the motor and the torque generating element of the motor, that is, You can increase the thickness of the magnet and the thickness of the coil,
It is possible to provide a spindle motor that can increase torque.

[Brief description of drawings]

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

FIG. 2 is a sectional view of a second embodiment of the spindle motor according to the present invention.

FIG. 3 is a sectional view of a third embodiment of the spindle motor of the present invention.

FIG. 4 is a sectional view of a conventional spindle motor.

[Explanation of symbols]

 1, 2 Ball bearing 3 Rotor magnet 4 Back yoke 5 Hub 6 Stator base 6a Projection shaft 7 Iron core 8 Ring member 9 Bearing cover 10 Hollow cylindrical shaft 11 Coil 12 Rotor yoke

Claims (4)

[Claims] 1. A rotor magnet, a hub to which the rotor magnet is attached, a medium is attached, a coil, a stator base to which the coil is attached, and the hub is rotatably supported with respect to the stator base. A spindle motor comprising a bearing and a protrusion shaft for supporting an inner circumference of the bearing provided on the stator base. 2. A spindle motor, wherein a hollow cylindrical shaft is fixed to the protruding shaft according to claim 1, and an inner circumference of the bearing is supported by the hollow cylindrical shaft. 3. A spindle motor, wherein the stator base according to claim 1 is constituted by a base of a disk drive device, and a projection shaft for supporting an inner circumference of the bearing is provided on the base. 4. A spindle motor, wherein a hollow cylinder shaft is fixed to the protrusion shaft according to claim 3, and the inner circumference of the bearing is supported by the hollow cylinder shaft.