Hard disk drive having a disk fluttering reducing unit that uses an air damping effect to reduce the fluttering of a rotation disk

A hard disk drive having a disk fluttering reducing unit includes a lower air damper forming member provided on an upper surface of a base plate to face a bottom surface of an outer circumferential side of the disk, and an upper air damper forming member provided on a bottom surface of a cover plate to face an upper surface of an outer circumferential side of the disk. At least one air compression surface is inclined in a circumferential direction of the disk so that a gap formed between the disk and the corresponding air damper forming members decreases along a rotational direction of the disk and is formed at each of surfaces of the air damper forming members facing the disk. The air compression surface is inclined in a radial direction of the disk so that the gap decreases from an inner circumferential side of the disk to an outer circumferential side of the disk. When at least two disks are provided, a middle air damper forming member disposed between the two disks is provided. Thus, disk fluttering is reduced by an air damping operation of the disk fluttering reducing unit so that a reliability of data recording and reproducing is improved.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Patent Application No. 2002-16085, filed Mar. 25, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a hard disk drive, and more particularly, to hard disk drive having a disk fluttering reducing unit which reduces fluttering of a rotating disk.

2. Description of the Related Art

A hard disk drive (HDD) is one of auxiliary memory devices of a computer, which reads out data stored in a magnetic disk or records data on the magnetic disk by using a magnetic head. Recently, a variety of research and development efforts are being performed to realize the hard disk drive having a high speed, a high capacity, low fluttering, and a low noise.

FIG. 1is a plan view showing a conventional hard disk drive, andFIG. 2is an enlarged perspective view of a portion of the hard disk drive ofFIG. 1.

Referring toFIGS. 1 and 2, the hard disk drive includes a magnetic disk (a hard disk)20which is a recording medium storing of data, a spindle motor30installed on a base10to rotate the disk20, and an actuator40having a magnetic head41to reproduce the data recorded in the disk20.

As the disk20, a single disk or a plurality of disks are installed to be rotated by the spindle motor30and separated by a predetermined distance from each other. A parking zone21where a slider42is located when power of the hard disk drive is off is provided at an inner circumferential side of the disk20, and a data zone22where a magnetic signal is recorded is provided outside the parking zone21. A servo signal indicating a position of information to be recorded is recorded on several tens of thousands of tracks formed along a circumference of the disk20.

The actuator40is installed to be capable of pivoting by a voice coil motor48around a pivot shaft47installed on the base10. The actuator40includes an arm46coupled to the pivot shaft47to be capable of pivoting, and a suspension44which supports a slider42installed at the arm46to be elastically biased toward a surface of the disk20. The magnetic head41is mounted on the slider42.

When the power of the hard disk drive is off, the slider42is disposed in the parking zone21of the disk20by an elastic force of the suspension44. When the power is turned on, and the disk20starts to rotate, a lift force is generated by air pressure, and accordingly the slider42is lifted. The slider42being lifted is moved to the data zone22of the disk20as the actuator40pivots. The slider42moved to the data zone22of the disk20maintains a lifted state at a height where the lift force by a rotation of the disk20and the elastic force by the suspension44are balanced, as shown inFIG. 3. Thus, the magnetic head41mounted on the slider42records and reproduces data on and from the disk20as it maintains a predetermined distance from the disk20that is rotating.

However, in the conventional hard disk drive having the above structure, fluttering of the disk20is caused by defective parts of the spindle motor30, eccentricity in an assembly of the disk20, or an irregular air flow occurring during the rotation of the disk20in the hard disk drive. As the fluttering, there is RRO (repeatable runout) that is a component repeated at each of rotations and NRRO (non-repeatable runout) that is a component which is not repeated. The RRO which regularly repeats can be compensated by a servo control system to a certain degree whereas the NRRO is difficult to be anticipated and compensated. The disk fluttering reduces a data recording and reproduction capability of the magnetic head41and finally exerts a bad influence on a performance of the hard disk drive.

Conventionally, when the disk fluttering is generated at the disk20, an interval between the slider42and the disk20can be maintained to a certain degree by a damping effect by air existing therebetween. However, as a rotation speed of the disk20increases, and a thickness of the disk20decreases, the disk fluttering is amplified so that accurate recording or reproduction of data is made difficult by only a servo control system and an air damping effect between the slider42and the disk20. Further, as TPI (track per inch) increases recently, the disk fluttering makes an accurate control of a position of the magnetic head41difficult.

In light of the above, it is necessary to reduce the disk fluttering occurring during an operation to secure reliability in the performance of the hard disk drive. Furthermore, as the hard disk drive recently exhibits a high speed, a high capacity, and a low noise, it is important to reduce disk fluttering.

SUMMARY OF THE INVENTION

To solve the above-described problems, it is an aspect of the present invention to provide a hard disk drive having a disk fluttering reducing unit so that fluttering of a rotating disk is reduced by using an air damping effect.

To achieve the above and/or other aspects, a hard disk drive includes a housing having a base plate and a cover plate, a spindle motor installed on the base plate, a disk installed at the spindle motor to store data, an actuator installed on the base plate to be capable of pivoting and having a magnetic head to record and reproduce data on and from the disk, and a disk fluttering reducing unit forming an air damper above a surface of the disk to reduce fluttering of the disk, wherein the disk fluttering reducing unit comprises a lower air damper forming member provided on an upper surface of the base plate to face a bottom surface of an outer circumferential side of the disk, and an upper air damper forming member provided on a bottom surface of the cover plate to face an upper surface of an outer circumferential side of the disk, and at least one air compression surface formed on the lower and/or upper air damper forming members and inclined with respect to a circumferential direction of the disk so that a gap formed between the air compression surface and the disk decreases along a rotational direction of the disk.

It is possible that the lower air damper forming member is integrally formed with the base plate, and the upper air damper forming member is integrally formed with the cover plate.

It is possible that the air compression surface is inclined in a radial direction of the disk so that a gap with the disk decreases from an inner circumferential of the disk side to an outer circumferential side of the disk.

It is possible that the disk fluttering reducing unit is provided close to and in front of the actuator.

It is possible that disk fluttering reducing units are provided at corresponding ones of two positions opposite to each other with respect to the spindle motor.

It is possible that each of the air damper forming members of the disk fluttering reducing unit has a C shape in which a portion is open not to interfere with the actuator, to face an overall surface at an outer circumferential side of the disk except for a range of an operation of the actuator.

It is possible that a plurality of air compression surfaces are sequentially formed from one end portion of each of the air damper forming members to the other end portion thereof along the circumferential direction of the disk.

In a hard disk drive in which at least two disks are provided according to another aspect of the present invention, a disk fluttering reducing unit includes a middle air damper forming member disposed between the disks in addition to a lower air damper forming member and an upper air damper forming member which are disposed to face corresponding ones of the disks, respectively.

It is possible that the lower and upper air damper forming members are integrally formed with the base plate and the cover plate, respectively, and the middle air damper forming member is installed on the base plate to be capable of pivoting with respect to the base plate.

Thus, fluttering of the disk is reduced by an air damping operation of the disk fluttering reducing unit so that reliability of data recording and/or reproducing on/from the disk is improved.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, hard disk drives having a disk fluttering reducing unit according to embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Referring toFIGS. 4 and 5, a hard disk drive according to an embodiment of the present invention includes a housing110having a predetermined inner space. A spindle motor130, magnetic disks120aand120b, an actuator140, and a disk fluttering reduction unit150are installed in the housing110.

The housing110is formed with a base plate111supporting the spindle motor130and the actuator140and a cover plate112coupled to the base plate111and enclosing and protecting the disks120aand120b, and is installed inside a main body of a computer. The housing110is typically formed of a stainless or aluminum material.

A single or a plurality of the disks120aand120bare installed in the housing110. Conventionally, four or more disks are installed in the hard disk drive to increase a data storing capacity. Recently, as a recording density of a disk surface increases, only one or two disks can store a sufficient amount of data. Thus, the hard disk drive having one or two disks is a main stream in recent days. Accordingly, the hard disk drive having the two disks120aand120bwill be used in a description of the present invention as an example. However, the present invention is not limited to the hard disk drive having two disks. Accordingly, the present invention can be applied to a hard disk drive having a single disk or two or more disks.

The spindle motor130is fixedly installed on the base plate111to rotate the disks120aand120b. When the two disks120aand120bare installed at the spindle motor130, a ring type spacer132maintains an interval between the two disks120aand120band is inserted therebetween. A clamp134preventing an escape of the disks120aand120bfrom a shaft of the spindle motor130is coupled to an upper end portion of the spindle motor130.

The actuator140is installed on the base plate111to be capable of pivoting to record or produce data on or from the disks120aand120b. The actuator140includes an arm146coupled to a pivot shaft147to be capable of pivoting and a suspension144installed at the arm146to support a slider142where a magnetic head is mounted to be elastically biased toward a surface of the disks120aand120b.

The disk fluttering reducing unit150reducing disk fluttering when the disks120aand120brotate, is provided in the hard disk drive. The disk fluttering reducing unit150includes a lower air damper forming member151disposed under the first disk120aand an upper air damper forming member152disposed above the second disk120b. When the two disks120aand120bare installed, as shown inFIG. 4, the disk fluttering reducing unit150may further include a middle air damper forming member153disposed between the two disks120aand120b.

The air damper forming members151,152, and153are installed close to and in front of the actuator140. Since the slider142installed at an end portion of the actuator140and having the magnetic head mounted thereon, and the air damper forming members151,152, and153are disposed closer to each other, a disk fluttering reduction effect by the slider142and the air damper forming members151,152and153is improved during a rotation of the magnetic head more definitely.

The air damper forming members151,152, and153are installed to face corresponding outer circumferential surfaces of the disks120aand120b. Also, the air damper forming members151,152, and153are installed at corresponding positions with the disks120aand120b. In detail, the lower air damper forming member151is installed on an upper surface of the base plate111to face a bottom surface of the first disk120a. The upper air damper forming member152is installed on a bottom surface of the cover plate112to face an upper surface of the second disk120b. Preferably, the lower air damper forming member151and the upper air damper forming member152are integrally formed with the base plate111and the cover plate112, respectively. Since the lower air damper forming member151and the upper air damper forming member152can be simultaneously formed when the base plate111and the cover plate152are manufactured, a manufacturing process can be simplified and a manufacturing cost can be lowered. Alternatively, it is possible to fixedly install the lower air damper forming member151and the upper air damper forming member152at the base plate111and the cover plate112, respectively, after the lower air damper forming member151and the upper air damper forming member152are manufactured as separate members.

The middle air damper forming member153is installed such that one end portion thereof is coupled to a pivot pin113installed to protrude at a corner of the base plate111to be capable of pivoting and the other end portion thereof is installed to be interposed between the two disks120aand120b. The middle air damper forming member153is installed to be capable of pivoting to avoid an interference with the disks120aand120band the middle air damper forming member153when the disks120aand120bare coupled to the spindle motor130since the middle air damper forming member153is disposed between the two disks120aand120bunlike the lower and upper air damper forming members151and152.

FIG. 6is a view explaining an operation of the middle air damper forming member shown inFIG. 4. Referring toFIG. 6, before the first disk120ais assembled to the spindle motor130, the middle air damper forming member153pivots around the pivot pin113so that the other end portion thereof is located outside the base plate111or the first disk120a, as indicated by a dot-dash line inFIG. 6. Next, after the first disk120ais assembled to the spindle motor130, the middle air damper forming member153is rotated in a direction indicated by an arrow so that the other end portion thereof is located above the first disk120a. Next, the second disk120bis assembled to the spindle motor130. Accordingly, the two disks120aand120bcan be assembled to the spindle motor130without the interference with the middle air damper forming member153. In the meantime, the middle air damper forming member153can be rotated in the direction indicated by the arrow so that the other end portion thereof can be inserted between the two disks120aand120bafter the two disks120aand120bare assembled to the spindle motor130.

Referring back toFIGS. 4 and 5, at least one air compression surface151a,152a, or153ais formed on each of surfaces of the air damper forming members151,152, and153facing the corresponding disks120aand120b. The air compression surfaces151a,152a, and153aare inclined along a rotational direction of the disks120aand120bsuch that a gap formed between the air compression surface151a,152a, and153aand the disks120aand120bdecreases. That is, since the air compression surface151a,152a, and153aare inclined with respect to a circumferential direction of the disks120aand120b, a gap varies between the air compression surface151a,152a, and153aand the corresponding disks120aand120b. A first gap G1of an air inlet end151bwhere air is input, is greater than a second gap G2of an air outlet end151cwhere air is exhausted. For example, the first gap G1at the air inlet end151bis about 1–1.5 mm while the second gap G2at the air outlet end151cis about 0.1–0.6 mm.

The air damper forming members151,152, and153having the air compression surfaces151a,152a, and153agenerate air dampers between the disks120aand120bto reduce disk fluttering. That is, the air taken into the air inlet end151bby the rotation of the disks120aand120bis compressed while it flows along the inclined air compression surfaces151a,152a, and153a. Accordingly, pressure by the compressed air is applied to both surfaces of each of the disks120aand120b, and the pressure by the compressed air applied to both surfaces of each of the disks120aand120breduces the disk fluttering. In other words, the compressed air between the disks120aand120band the corresponding air compression surfaces151a,152a, and153aproduces an air damping effect to reduce the disk fluttering. Thus, a stable rotation of the disks120aand120bis possible so that the data recording/reproducing capability and reliability of the magnetic head are improved.

As shown inFIG. 5, the air compression surface151a,151b,151c, of each of the air damper forming members151,152,153, comprise a first inclined surface and may further comprise a second and a third inclined surface. That is, the first inclined surface forms a first inclined surface angle151xwith the major surface of the disk, a second inclined surface forms a second inclined surface angle151zwith the major surface of the disk, and a middle inclined surface forms a third inclined surface angle151y, which is greater than the first or second inclined surface angle, with the major surface of the disk.

The air compression surfaces151a,152a, and153amay be formed on each one of the air damper forming members151,152, and153. However, it is possible to form a plurality of the air compression surfaces in series because the air damper can be formed in a larger area of the disks120aand120b. The sizes of the gaps G1and G2can be set appropriately by considering the rotation speed of the disks120aand120band a distance between the two disks120aand120bso that a sufficient air damping effect can be obtained. Also, sizes of the gaps G1and G2can be set out of the above ranges. In particular, the gap G2at the air outlet end151cis an important factor in the air damping effect. When the gap G2is too wide, a sufficient air damping effect cannot be obtained. In contrast, when the gap G2is too narrow, the disks120aand120bmay contact the air damper forming members151,152, and153by fluttering of the disks120aand120bso that the surfaces of the disks120aand120bcan be damaged.

FIG. 7is a cross-sectional view showing the air damper forming members in a radial direction of the hard disk drive shown inFIG. 4.

Referring toFIG. 7, each of the air damper forming members151,152, and153is inclined such that the gap between the disks120aand120band the air damper forming members151,152, and153decreases in a direction from an inner circumferential side to an outer circumferential side. That is, the air damper forming members151,152, and153are inclined in the radial direction of the disks120aand120bso that a fourth gap G4at an edge portion of the disks120aand120bis narrower than a third gap G3at an inner portion of the disks120aand120b. Thus, even when fluttering is generated during the rotation of the disks120aand120b, the edge portion or the disks120aand120bwhere no data is recorded, contacts the corresponding air compression surfaces151a,152a, and153a, so that the data recording surfaces of the disks120aand120bare prevented from contacting the air compression surfaces151a,152a, and153a.

FIGS. 8 and 9show hard disk drives having disk fluttering reducing units according to an embodiment of the present invention. Here, the same reference numerals used in describing the embodiment shown inFIG. 4indicate the same elements.

Referring toFIG. 8, first, in the hard disk drive, a set of air damper forming members251,252, and253of a disk fluttering reducing unit250is provided at two positions corresponding to each other with respect to the spindle motor130. That is, the air damper forming members251,252, and253are provided not only in front of the actuator140, but also at a position separated by 180° therefrom in a circumferential direction of the disks120aand120b. A structure, an installation method, and an operation of each of the air damper forming members251,252, and253are the same as those of the above-described embodiment shown inFIGS. 4 through 7. When respective pair of air damper forming members251,252, and253of the disk fluttering reducing unit250are provided at corresponding ones of two positions opposite to each other with respect to the spindle motor130, since the forces applied by the air damper forming members251,252, and253to the disks120aand120bare balanced, the disks120aand120bcan rotate stably.

Next, referring toFIG. 9, in the hard disk drive according to this embodiment of the present invention, the air damper forming members351,352, and353of a disk fluttering reducing unit350are installed to face an overall surface at the outer circumference of the disks120aand120bexcept for a range of an operation of the actuator140. That is, each of the air damper forming members351,352, and353has a “C” shape in which a portion is open not to interfere with the arm146. A structure, an installation method, and an operation of each of the air damper forming members351,352, and353are the same as those of the above-described embodiment shown inFIGS. 4 through 8. In detail, a plurality of air compression surfaces351a,352a, and353aare sequentially formed at the surfaces of the air damper forming members351,352, and353facing the corresponding disks120aand120balong the circumferential direction of the disks120aand120b. Also, the middle air damper forming member353is divided into at least two parts, and each of the parts is coupled to the pivot pin113protruding from the base plate111to be capable of pivoting. According to the air damper forming members351,352, and353having the C shape with an open part, since a uniform force is substantially applied to the overall outer circumference of the disks120aand120b, not only fluttering of the disks120aand120bis further reduced, but also the disks120aand120bcan rotate stably.

The disk fluttering effect in the hard disk drive having the above disk fluttering reducing unit is described below in comparison with the conventional hard disk drive.

FIGS. 10A through 10Care graphs showing a displacement of fluttering, and a velocity and an acceleration of the displacement in the hard disk drive shown inFIG. 8in comparison with a conventional hard disk drive. Here, the graphs show test results under conditions that air damper forming members having one air compression surface, a 15 mm width in a radial direction of a disk, and a 30 mm length in a circumferential direction of the disk are installed to have the maximum gap (G1ofFIG. 5) of 1.2 mm and the minimum gap (G2ofFIG. 5) of 0.1 mm from the disk.

First,FIG. 10Ashows a maximum displacement of disk fluttering according to frequencies. Here, it can be seen that the maximum displacement of the disk fluttering in the hard disk drive having the air damper forming members according to the present invention is reduced by about 50% compared to that of the conventional hard disk drive which does not have the air damper forming members.

FIG. 10Bshows the velocity of the displacement of the disk fluttering according to frequencies.FIG. 10Cshows the acceleration of the displacement of the disk fluttering according to frequencies. Referring toFIGS. 10B and 10C, it can be seen that the velocity and the acceleration of the displacement in the hard disk drive having the air damper forming members according to the present invention are lower by about 50% than those of the conventional hard disk drive.

In light of the above, it can be seen that, in a hard disk drive having a disk fluttering reducing unit according to the present invention, disk fluttering is considerably reduced compared to a conventional technology. In particular, a disk fluttering reducing effect is noticeable in a relatively low frequency area (600–750 Hz) and a relatively high frequency area (950 Hz or more). Accordingly, although in the conventional hard disk drive, a deviation of values of the displacement, the velocity, and the acceleration of the disk fluttering according to frequencies are relatively great, the deviation of the values according to frequencies is remarkably reduced in the present invention.

As described above, according to the hard disk drive having the disk fluttering reducing unit according to the present invention, since the disk fluttering is reduced by the air damping operation of the disk fluttering reducing unit, the reliability in data recording/reproducing is improved. Also, a noise caused by the disk fluttering is reduced as the disk fluttering is reduced.