JP2001346367A - Spindle motor for driving recording medium and method of fabricating the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spindle motor for driving a recording medium which can adjust rotation balance with good accuracy without deteriorating reduction in thickness and size and a method of fabricating the same spindle motor. SOLUTION: A symmetrically rotating annular cutaway portion 36 which is opened to the lower side and internal side in the diameter direction is provided at the lower end portion of internal circumference of the part except for a collar portion 20a at a hub 20. At the annular cutaway portion 36, the hub 20 is held with a chuck for the cutting process of the hub 20. Within the annular cutaway portion 36, a weight 38 for correcting rotation balance which can be obtained by solidifying a liquid adhesive is fixed. The annular cutaway portion 36 is located at the external side in the diameter direction in the lower part of a lower ball bearing 28 provided adjacent to an armature to fix the weight 38 to this location.

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 recording medium, the rotational balance of which is adjusted by a weight, and a method of manufacturing the spindle motor.

[0002]

2. Description of the Related Art In order to adjust the rotational balance of a spindle motor, a member (such as a spindle motor disclosed in Japanese Patent Application Laid-Open No. 7-85580) holding a bearing and a magnetic fluid seal is used. A configuration is known in which a screw hole is provided on the outer surface of the bush, and a weight is screwed into the screw hole.

[0003] However, recently, the spindle motor has been increasingly miniaturized, and it has become difficult to find a member capable of forming a structure for correcting the rotational balance.

[0004] Even in such a situation, as the speed of the spindle motor increases, vibration, noise, whirling, and the like due to imbalance in the rotational balance have become more prominent problems. There is a need for highly accurate rotation balance adjustment.

The present invention has been made in view of the above-mentioned problems in the prior art, and has as its object to improve the rotational balance thereof without impairing the reduction in thickness and size. An object of the present invention is to provide a spindle motor for driving a recording medium that can be adjusted with high accuracy, and a method of manufacturing a spindle motor for driving a recording medium that can efficiently manufacture the spindle motor.

[0006]

(1) A spindle motor for driving a recording medium according to the present invention comprises: a rotating section having a hub for rotating around a fixed rotation axis while supporting a recording medium; A spindle motor having a bearing portion rotatably supporting a rotating portion, wherein the inner peripheral portion of the hub is located between both ends of the rotating portion in the rotating axis direction, It has an annular groove or an annular notch that opens in one or both radially inward, and a weight body for correcting rotational balance is fixed in the annular groove or the annular notch.

The annular groove or annular notch to which the weight body for correcting the rotational balance is fixed is located between both ends of the rotating part in the direction of the rotational axis of the inner peripheral side portion of the hub, and is located in the direction of the rotational axis. And one or both radially inward. Even if this annular groove or annular notch is provided, it hardly affects the other internal structure or outer shape of the spindle motor. Therefore, the rotation balance of the spindle motor can be adjusted by fixing the weight for correcting the rotation balance in the annular groove or the annular cutout without impairing the thinning and miniaturization of the spindle motor. In addition, since the weight body for rotation balance correction is fixed to the annular groove or the annular notch, it can be fixed at any position in the circumferential direction.

A weight body for correcting the rotation balance fixed to the annular groove or the annular notch is located between both ends of the rotating portion in the rotation axis direction on the inner peripheral side portion of the hub. Since it is closer to the position of the center of gravity of the rotating part in the direction of the rotation axis than when providing weights at both ends of
The rotation balance of the spindle motor can be adjusted more accurately.

The hub for rotating around a fixed rotation axis while supporting the recording medium is, for example, a hub capable of supporting a hard disk or the like as a recording medium in a state where the hard disk or the like is fitted to the outer peripheral portion, and has a cylindrical or bowl shape. It can have a shape or the like.

[0010] The rotating portion may be composed of, for example, one or both of a rotor frame and a hub, a rotor magnet, and a rotor yoke which is a yoke of the rotor magnet.

As the bearing portion, for example, a ball bearing (one or two or more ball bearings which are arranged apart from or close to each other in the rotation axis direction), a dynamic pressure sliding bearing and the like can be mentioned.

The inner peripheral side portion of the hub may be, for example, an inner peripheral surface portion of the cylindrical portion of the hub, or a rotational axis between the inner diameter portions when the inner diameter of the cylindrical portion of the hub is a plurality of steps.
An annular plane portion or a curved surface portion forming an angle of 90 to 90 degrees can be used.

Both the annular groove and the annular notch may be rotationally symmetric with respect to the rotation axis.
In addition, it is efficient and preferable that the annular groove or the annular notch should be used to hold the hub (by a chuck such as a lathe) at the time of processing the hub such as cutting of the hub.

The annular groove or the annular notch is, for example, an annular groove that opens in one direction of the rotation axis, or an annular notch that opens in one direction of the rotation axis and radially inward, or opens radially inward. It can be an annular groove or the like. Further, an annular groove or an annular cutout that is open at least in the direction of the rotation axis is preferable because the operation of fixing the weight for correcting rotational balance can be performed from the direction of the rotation axis.

As a weight body for correcting the rotational balance,
For example, a liquid material that can be solidified by being fixed to an annular groove or an annular notch (for example, an adhesive having little or substantially no volatile components such as an adhesive synthetic resin, an adhesive, and an ultraviolet-curable adhesive); A metal C-ring or the like can be used.

When the above-mentioned liquid material is used as a weight for correcting the rotational balance, it is preferable to use a liquid having a relatively high viscosity and specific gravity. When the above-mentioned liquid material is used as a weight for correcting the rotational balance, it is possible to accurately position the liquid at the balance correction position by inclining the hub at the time of solidification.

(2) The spindle motor for driving a recording medium according to the above (1), wherein at least one of the armature and the field portion and the bearing portion are adjacent to each other in the rotation axis direction, and the armature or the field The rotational axis position of the bearing part adjacent to the magnetic part,
Alternatively, at least a part of the hub is located at a position in the rotation axis direction between the bearing portion and the armature or the field portion adjacent to the bearing portion, and the hub has the annular groove or the annular cutout at that position. Is preferred.

At least the hub is located at the position in the rotation axis direction of the bearing portion adjacent to the armature or the field portion in the direction of the rotation axis, or at the position in the rotation axis direction between the bearing portion and the armature or the field portion adjacent thereto. A portion is located and has an annular groove or notch at that position in the hub where a weight for correcting rotational balance is fixed. Even if this annular groove or annular notch is provided, it hardly affects the other internal structure or outer shape of the spindle motor. Therefore, the annular groove or annular notch can be provided without impairing the thinning and miniaturization of the spindle motor. A rotational balance correcting weight is fixed in the section, and the rotational balance of the spindle motor can be adjusted.

The weight for rotating balance correction fixed to the annular groove or annular notch is provided at the position in the rotation axis direction of the armature or the bearing adjacent to the field portion, or the bearing and the armature adjacent thereto. Since it is located at the position in the rotation axis direction between the field portions, it is closer to the position of the center of gravity of the rotation unit in the direction of the rotation axis, and the rotation balance of the spindle motor can be adjusted with higher accuracy. In the case where a yoke is provided in the field portion, an annular groove or an annular cutout portion to which a weight body for correcting the rotational balance is fixed is provided in the vicinity of the yoke, which generally has a large effect on the rotational balance. It is suitable for adjustment.

Examples of the field portion include a field magnet and a yoke. In addition, at least one of the bearing portions means at least one of the plurality of bearing portions when there are a plurality of bearing portions.

The position in the rotation axis direction of the bearing portion adjacent to the armature or the field portion means the position in the rotation axis direction occupied by the bearing portion. The preferred position of the annular groove or annular notch is a position in the direction of the rotation axis near the armature or the field portion adjacent thereto.

The annular groove or annular notch may be open to the armature or field portion side in the rotation axis direction but not to the opposite side. For example, in the case of an annular groove, it can be opened to the armature or the field portion side in the rotation axis direction, and in the case of the annular notch portion, the armature or the field side in the rotation axis direction and in the radial direction. It can be open to the side. In this case, it is possible to prevent the dust and the like from being scattered to the outside when the dust or the like is generated from the weight body for correcting the rotational balance or the annular groove or the annular notch.

(3) The method of manufacturing a recording medium driving spindle motor according to the present invention comprises: a rotating unit having a hub for rotating about a fixed rotation axis while supporting the recording medium;
A method of manufacturing a spindle motor having a bearing portion that rotatably supports the rotating portion, wherein the hub is located between inner ends of the rotating portion in the direction of a rotation axis on an inner peripheral side portion of the hub. Providing an annular groove or an annular notch that opens at least in the direction of the rotation axis, processing the hub while holding the hub in the annular groove or the annular notch, and then rotating the annular groove or the annular notch. It is characterized in that the balance for correcting the balance is fixed and the rotational balance is adjusted.

According to this manufacturing method, the annular groove or the annular notch provided for holding the hub in the processing of the hub,
Since it is used for fixing the weight body for correcting the rotational balance, the manufacturing efficiency is good. Even if this annular groove or annular notch is provided, it hardly affects the other internal structure or outer shape of the spindle motor. Therefore, the annular groove can be formed without impairing the thinning and miniaturization of the spindle motor. Alternatively, a weight for correcting the rotational balance can be fixed in the annular notch, and the rotational balance of the spindle motor can be adjusted. Further, since the position of the weight body is closer to the position of the center of gravity of the rotating part in the direction of the rotation axis as compared with the case where weight bodies are provided at both ends of the rotating part, the rotation balance of the spindle motor can be adjusted more accurately. .

The processing of the hub can be performed by, for example, cutting. The holding of the hub in the annular groove or the annular notch may be, for example, holding by a chuck of a lathe.

The method of manufacturing the above-described spindle motor for driving a recording medium is such that the spindle motor has an armature or a field part and at least one of the bearings is adjacent to each other in the rotation axis direction. At least a part of the hub is located at a position in the rotation axis direction of the bearing portion adjacent to the portion, or at a position in the rotation axis direction between the bearing portion and the armature or the field portion adjacent thereto. The annular groove or the annular notch may be provided at the position in the rotation axis direction in.

[0027]

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

FIG. 1 is a sectional view of a spindle motor for driving a hard disk as an example of an embodiment of the present invention. However, the spindle motor of the present invention can also be used for driving a recording medium other than a hard disk.

The recess 1 at the upper opening of the bracket 10
The lower portion of the fixed shaft 12 is fixedly fitted inside the cylindrical portion 10b formed upward at the center of the fixed shaft 12a, and the fixed shaft 12 is erected. A stator 14 (armature) formed by winding 14b is externally fixed.

The rotating portion 16 has a substantially cylindrical hub 20 having a flange 20a provided on the outer periphery of the lower end thereof fixedly coaxially to a substantially cylindrical bearing holder 18, and the rotation of the flange 20a. An upper portion of a cylindrical rotor yoke 24, in which a cylindrical rotor magnet 22 is coaxially fitted and fixed, is internally fitted and fixed to the inner peripheral portion. Above the flange portion 20a of the outer peripheral portion of the hub 20, a plurality of hard disks (not shown) are externally fitted and supported with a spacer or the like interposed therebetween.

The rotating portion 16 is rotatably supported by the bearing holder 18 supported on the fixed shaft 12 above the stator 14 via upper and lower ball bearings 26 and 28. Thereby, the rotor magnet 22
Are opposed to the radial direction of the stator 14, and the hub 20 is driven to rotate about a fixed rotation axis in a state where the flange 20 a is opposed to the upper outer peripheral portion of the recess 10 a in the bracket 10.

The upper and lower ball bearings 26 and 28 are
The lower ball bearing 28 is adjacent to the upper side of the stator 14 with the annular inward projection 18a at the center in the direction of the rotation axis at the center. The lower surface of the lower ball bearing 28 is covered by an annular bearing cap 30 whose outer peripheral portion is fixed to the bearing holder 18. The upper portion of the upper ball bearing 26 is sealed between the bearing holder 18 and the fixed shaft 12 by a magnetic fluid seal 32 in which a pole piece and an annular permanent magnet body are fixed to the bearing holder 18. An annular seal cap 34 is disposed on the upper side.

A rotationally symmetric annular notch 36 which opens downward and radially inward is provided at the lower end of the inner periphery of the hub 20 except for the flange 20a. , Is closed by the outer peripheral surface of the lower end portion of the bearing holder 18.

In the annular notch 36, the hub 20 is held by a chuck such as a lathe to perform cutting of the hub 20, and a weight body 38 for correcting rotational balance is fixed in the annular notch 36. I have.

The weight body 38 is made of a liquid adhesive having a relatively high viscosity and specific gravity fixed in the annular cutout portion 36 and solidified. By tilting the hub 20 during the solidification, the weight body 38 is moved to the balance correction position. Accurately positioned.

The annular notch 36 is located radially outward of the lower portion of the lower ball bearing 28 adjacent to the armature, and has a weight body 38 at that position. Even if the annular notch 36 is provided, it hardly affects the internal structure or the outer shape of the hub 20 and the spindle motor. Therefore, the annular notch 36 can be formed without impairing the thickness and size of the spindle motor.
The rotation balance of the spindle motor can be adjusted by fixing the weight body 38 therein.

Weight body 38 fixed to annular notch 36
Is located radially outward of the lower portion of the lower ball bearing 28 adjacent to the armature, that is, in the vicinity of the rotor yoke 24, which has a large effect on rotational balance, and close to the position of the center of gravity of the rotating portion 16 in the rotational axis direction. The rotation balance of the spindle motor can be well adjusted.

FIG. 2 is a cross-sectional view of a rotating unit 16 of a spindle motor for driving a hard disk as another example of the embodiment of the present invention.

The same reference numerals in FIG. 2 as those in FIG. 1 indicate the same parts as in FIG. A detailed description of them will be omitted.

The hub 42 of the rotating section 40 is similar to that of FIG.
Corresponds to the one in which the hub 20 and the bearing holder 18 are integrally formed.

A rotationally symmetric annular groove 44 which opens downward is provided at the lower end on the inner peripheral side of the hub 42 except for the flange 42a.

In the annular groove 44, the hub 42 is held by a chuck such as a lathe and the hub 42 is cut, and a metal C-ring is provided in the annular groove 44 as a weight body 46 for correcting rotational balance. Fixed.

It should be noted that the vertical positional relationship in the description of the above embodiment is merely for convenience of explanation based on the drawings, and does not limit the actual use state and the like.

[0044]

According to the spindle motor for driving a recording medium of the present invention, a weight for correcting the rotational balance is fixed in an annular groove or an annular notch provided without impairing the thinning and miniaturization, and the spindle motor is rotated with high accuracy. The balance can be adjusted.

According to the second aspect of the present invention, the position of the rotational balance correcting weight fixed to the annular groove or the annular notch is closer to the position of the center of gravity of the rotating part in the direction of the rotational axis. Therefore, the rotation balance of the spindle motor can be adjusted with higher accuracy.

According to the manufacturing method of the spindle motor for driving the recording medium of the present invention, the annular groove or the annular notch provided for holding the hub in the processing of the hub is used for fixing the weight body for correcting the rotational balance. Therefore, the recording medium driving spindle motor of the present invention can be manufactured with good manufacturing efficiency.

[Brief description of the drawings]

FIG. 1 is a sectional view of a spindle motor for driving a hard disk.

FIG. 2 is a cross-sectional view of a rotating unit in a spindle motor for driving a hard disk.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Bracket 10a Recess 10b Tubular part 12 Fixed shaft 14 Stator 14a Stator core 14b Stator coil 16 Rotating part 18 Bearing holder 18a Inward projection 20 Hub 20a Flange part 22 Rotor magnet 24 Rotor yoke 26 Upper ball bearing 28 Lower ball bearing 30 Bearing Cap 32 Magnetic fluid seal 34 Seal cap 36 Annular notch 38 Weight body 40 Rotating part 42 Hub 42a Flange part 44 Annular groove part 46 Weight body

Claims (3)

[Claims] 1. A spindle motor comprising: a rotating portion provided with a hub for rotating about a fixed rotation axis while supporting a recording medium; and a bearing portion rotatably supporting the rotating portion. In the inner peripheral side portion of the hub, an annular groove or an annular notch, which is located between both ends of the rotating portion in the rotation axis direction and opens in one or both of the rotation axis direction and the radially inward direction, A spindle motor for driving a recording medium, wherein a weight body for correcting rotational balance is fixed in the annular groove or the annular notch. 2. An armature or a field portion and at least one of the bearing portions are adjacent to each other in the rotation axis direction, and a position of the bearing portion adjacent to the armature or the field portion in the rotation axis direction or the bearing. The hub according to claim 1, wherein at least a part of the hub is located at a position in the rotation axis direction between the armature and the armature or the field part adjacent thereto, and the hub has the annular groove or the annular notch at the position. Spindle motor for driving recording media. 3. A spindle motor comprising: a rotating portion provided with a hub for rotating about a fixed rotation axis while supporting a recording medium; and a bearing portion rotatably supporting the rotating portion. In the inner peripheral portion of the hub, an annular groove or an annular notch, which is located between both ends of the rotating portion in the rotational axis direction and opens at least in the rotational axis direction, is provided. Processing the hub while holding the hub in the groove or annular notch,
A method for manufacturing a spindle motor for driving a recording medium, characterized in that a rotational balance correcting weight is fixed to the annular groove or annular notch to adjust the rotational balance.