Method of centering a disk of hard disk drive

A method of centering a disk of a hard disk drive includes arranging a disk on an upper end portion of a hub on which a plurality of disks are rotatably assembled, and assembling the disk on the hub by vibrating the hub. Accordingly, the disks and/or spacers may be easily assembled on the hub, a time of centering may be relatively much reduced, and a superior centering quality may be obtained.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119(a) from Korean Patent Application No. 10-2010-0006760, filed on Jan. 26, 2010, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.

BACKGROUND

1. Field of the Invention

The present general inventive concept relates to a method of centering a disk of a hard disk drive (HDD), and more particularly, to a method of centering a disk of an HDD by which a disk or a spacer may be easily assembled on a hub, a time of centering may be relatively much reduced, and a superior centering quality may be obtained.

2. Description of the Related Art

Hard disk drives (HDDs) are memory devices formed of electronic apparatuses and mechanical apparatuses for recording and reproducing data by converting a digital electronic pulse into a permanent magnetic field. The HDD is widely used as an auxiliary memory device for a computer system because it can access a large amount of data at high speed.

The HDD may include a disk stack assembly having a disk for recording and storing data, a head stack assembly (HSA) for reading out data from the disk by pivoting across the disk around a predetermined pivot shaft, a printed circuit board assembly (PCBA) for controlling the above constituent elements by mounting most circuit parts on a printed circuit board (PCB), a base on which the above constituent elements are assembled, and a cover for covering the base.

Imbalance in a rotating system such as a head stack assembly or a disk stack assembly is an amount of imbalance generated by eccentrically distributed mass of a rotary body with respect to each rotation center. The imbalance generates vibrations and noise during rotation. Especially, in a disk stack assembly, the eccentricity of a disk damages a ball bearing or a fluid bearing of a spindle motor so that reliability of an HDD may be deteriorated. Also, the imbalance has an ill effect on a servo track write (STW) process in a manufacturing process of an HDD.

Although there are various reasons for generation of imbalance in the disk stack assembly, due to tolerance of constituent elements such as a spindle motor, a disk, or a spacer constituting the disk stack assembly, the rotation center of each of the constituent elements does not match a weight center to the rotation center of assembled constituent elements in the assembly of the constituent elements so that imbalance may be generated due to the eccentricity.

Many studies on technologies to improve the imbalance of a disk stack assembly have been performed and some of the technologies are introduced herein.

First, a spacer or a disk is pushed to one side and a displacement is measured. Then, the spacer or disk is pushed in the opposite direction by half of the measured displacement so that alignment may be achieved.

Second, when disks are assembled on a hub, the amount of imbalance between the disks and the hub is measured. By giving an impact to one side of a disk, a state in which the amount of balance is the minimum is obtained. This is referred to as a dynamic imbalance method.

Third, when a plurality of disks are assembled, one disk is pushed to one side whereas another one is pushed to the opposite side. Thus, the disks are assembled in a zigzag or biased form so that the amount of imbalance is reduced in terms of probability.

Fourth, the amount of imbalance is measured during assembly of a disk, and mass balance is added to a side having a relatively less.

The above methods are used because making tolerance between the hub and the spacer tight in order to continuously stack a plurality of disks is difficult. In detail, when the tolerance is made too tight, the centering process may not be needed by greatly reducing the amount of imbalance.

However, when the tolerance of the hub, the disk, and the spacer is made tight, it is difficult to push the spacer and the disk down to the lower portion of the hub, that is, the bottom side, to sequentially stack the spacer and the disk. If the spacer and the disk are forcibly pushed down, scratches or cuts may be highly likely to be generated on the hub.

The scratches and cuts may generate particles and then the particles may scratch the disk so that the quality of an HDD may be badly affected. Also, when the spacer and the disk are forcibly pushed down as described above, a degree of flatness of a surface of the spacer during stacking the spacer and the disks is affected so that the quality of STW, that is, repeatable run out (RRO) or non-repeatable run out (NRRO), may be badly affected.

In the above-described conventional method for centering a disk of an HDD, imbalance is reduced not by accurately performing the centering of a disk by allowing the hub, the disk, and the spacer to have tight tolerance, but by using a method of reducing the amount of imbalance by an additional process of measuring the amount of imbalance after assembly or by allowing imbalance that an HDD basically keeps, to a degree. As a result, the quality characteristic of each of the HDDs varies due to an assembly state and thus there is a certain limit in productivity and improvement of a recording characteristic. Until now, the limit has been overlooked due to the problem in the assembly of a disk as described above.

SUMMARY

The present general inventive concept provides a method of centering a disk of a hard disk drive (HDD) by which a disk and/or a spacer may be easily assembled on a hub, a time of centering may be relatively much reduced, and a superior centering quality may be obtained.

According to a feature of the present general inventive concept, a method of centering a disk of a hard disk drive includes arranging a disk on an upper end portion of a hub on which a plurality of disks are rotatably assembled, and assembling the disk on the hub by vibrating the hub.

The method may further include arranging a spacer on the upper end portion of the hub, and assembling the spacer on the hub by vibrating the hub.

The operations of the arranging of a spacer, the assembling of the spacer, the arranging of a disk, and the assembling of the disk may be sequentially repeated a plurality of times to sequentially stack the plurality of disks along the hub such that each of the disk contact an upper surface of each of a plurality of spacers.

A gap between an outer circumferential surface of the hub and an inner diameter of the disk may have a width ranging from about 1 μm to about 10 μm.

The hub may be a hub of a spindle motor of the hard disk drive. During assembling one or more disks on the hub, the hub may be vibrated as a vibration generation unit coupled to a base of the hard disk drive vibrates the base.

The hub may be a hub of an offline servo track writer of an offline servo track write (OLSTW) process, and the offline servo track writer may further include a flange portion provided in a lower end of the hub and supporting a spacer disposed at the lowermost side, and a mounting portion provided by extending toward the opposite side to the hub with respect to the flange portion.

The offline servo track writer may further include a hub housing to support the mounting portion and, in the assembling of the disk on the hub, the hub is vibrated as a vibration generation unit coupled to the hub housing vibrates the hub housing.

In the assembling of the disk on the hub, the hub may be vibrated as a vibration generation unit coupled to the mounting portion vibrates the mounting portion.

The vibration generation unit may generate a high frequency displacement in the hub.

The vibration generation unit may generate a high frequency displacement in an upward direction in the hub by a voltage that is externally applied and, in the assembling of the disk on the hub, the hub may be vibrated by applying a high frequency displacement in an upward direction to the hub by increasing a voltage to a preset voltage during a preset first time so that the disk is relatively lowered with respect to the hub, and by applying a high frequency displacement in a downward direction by decreasing a voltage to a preset voltage during a second time that is longer than the preset first time so that the disk is relatively lowered downwardly with the hub.

The vibration generation unit may include a piezoelectric device.

The vibration may be generated in a vertical direction or a horizontal direction.

In another feature, a disk holder to hold a plurality of disks comprises a flange portion including a first surface to support a flat portion of a disk and including a second surface, a hub extending from the first surface of the flange to engage a through-hole of the disks to center the disks with respect to the flange portion, and a mounting portion extending from the second surface of the flange portion and in the opposite direction from the hub to be coupled to a disk rotation driving unit that rotates the disk holder.

In yet another feature, a servo track writer comprises a disk rotation driving unit to generate a rotation about an axis, and a disk holder to hold a plurality of disks. The disk holder comprises a flange portion including a first surface to support a flat portion of a disk and including a second surface, a hub extending from the first surface of the flange to engage a through-hole of the disks to center the disks with respect to the flange portion, and a mounting portion extending from the second surface of the flange portion and in the opposite direction from the hub and being coupled to the disk rotation driving unit. The servo track writer further includes a vibration generation unit coupled to the mounting portion of the disk holder to vibrate the hub in at least one of a vertical direction and a horizontal direction.

In still another feature of the general inventive concept, a hard disk drive comprises a base, a disk holder including a flange portion disposed against the base, a hub extending from the flange to engage at least one of a spacer and a disk, and a vibration generation unit coupled to the base that vibrates the base in at least one of a vertical and a horizontal direction to induce a vibration of the hub.

DETAILED DESCRIPTION OF THE EMBODIMENTS

A method of centering a disk of a hard disk drive (HDD) according to an exemplary embodiment of the present general inventive concept is used to center a disk and a spacer with respect to a hub71in a drive assembly process or a servo track write (STW) process. According to an exemplary method, a conventional gap D between a hub and a disk/spacer may be reduced to a level of several micrometers so that, when the disk/spacer is stacked on the hub, they may be centered by themselves and no additional centering process is needed. The gap D may have a width ranging, for example, from about 1 μm to about 10 μm. The gap D denotes an interval between an inner circumferential surface of a disk through-hole11ato stack the disk/spacer, and an outer circumferential surface of the hub71. In an exemplary embodiment, the gap D may be disposed between an outer circumferential surface of the hub71and an inner diameter of the disk11.

As illustrated in the drawings, exemplary methods of centering a disk of an HDD according the present general inventive concept may perform centering by inserting a plurality of disks11and spacers77around a hub71of an offline servo track writer60in order to write servo information to the disks11of an offline servo track write (OLSTW) process.

Thus, an offline servo track writer employing the methods of centering a disk of an HDD according to an exemplary embodiment and another exemplary of the present general inventive concept will be described with reference toFIGS. 2-4.

The offline servo track writer60according to an exemplary embodiment includes a bed61, a disk holder70provided above the bed61where disks11to record servo track information are stacked, a disk rotation driving unit62coupled to the disk holder70to rotate the disks11, a head unit80having a plurality of servo track write heads81to write servo track information to recording surfaces of the disks11, and a head unit driving unit63coupled to the head unit80to drive the head unit80. The a head unit driving unit63drives the head unit80to a predetermined work position such that the servo track write heads81may be positioned in a spacing between adjacent disks11. Accordingly, the write head81may write the servo track information to a corresponding disk.

The bed61may support the offline servo track writer60. More specifically, the disk holder70to stack the above-described disks11, the disk rotation driving unit62, the head unit80, and the head unit driving unit63are supported on the bed61. Although the offline servo track writer60includes an exemplary shape illustrated inFIG. 2, the shape of the servo track writer60is not limited thereto.

The servo track writer60may further include a disk holder housing90. The disk holder housing90includes a cover91and a plurality of ribs92defining slots93which may receive a corresponding disk11. Accordingly, the disks11may be protected by the surrounding ribs92. The cover91may be coupled to an end of the disk holder housing90adjacent to an end disk11. The cover91may further include an opening to receive a spacer77, a clamp74and a clamp coupling screw75, which are described in greater detail below.

The disk rotation driving unit62rotates the disk holder70, thereby rotating the disks11stacked on the disk holder70. A typical rotary motor may be used as the disk rotation driving unit62. For example, although not illustrated, the disk rotation driving unit62may include a rotary chuck that is rotationally coupled to the disk holder70to rotate the disk rotation driving unit62.

As illustrated, for example, inFIG. 4, the disk holder70includes a hub71on which the disks11to record servo track information are stacked. The disk holder70further includes a flange portion72provided at a lower end of the hub71to support the lowermost spacer77. A mounting portion73is provided at the side facing the hub71with respect to the flange portion72. The mounting portion73may be coupled to a rotary chuck of the disk rotation driving unit62, as mentioned above. More specifically, a clamp74having a clamp through-hole74amay be arranged above the uppermost spacer77. A clamp coupling screw75may be disposed through the clamp through-hole74asuch that the clamp74and clamp coupling screw75are coupled to the hub71. Accordingly, the disks11and the spacers77may be positioned between the flange portion72and the clamp74and supported against the hub.

As discussed above, the hub71may support the disks11such that the disks11are substantially stacked one next to the other. The hub71may have, for example, a column shape having a certain length. A disk through-hole11a is formed in each of the disks11so that the disks11may be stacked next to each other, while being supported on the hub71.

The flange portion72supports the lowermost spacer77. The flange portion72may be formed, for example, in a shape of a circular plate having a certain diameter. The flange portion72may further include a protruding disk portion72athat protrudes upwardly from a central area of the flange portion72to support the lowermost spacer77. Alternatively, the protruding disk portion72amay not be formed such that the protruding disk portion72amay be regarded as a portion of the flange portion72.

As mentioned above, the mounting portion73may be coupled to the disk rotation driving unit62ofFIG. 2. As the mounting portion73is coupled to the disk rotation driving unit62, when the disk rotation driving unit62is rotated, the disk holder70rotates accordingly so that the disks11stacked on the disk holder70may be rotated.

The clamp74may be arranged at the top of the uppermost spacer77. Accordingly, the disks11and the spacers77may be prevented from escaping between the flange portion72and the clamp74. In an exemplary embodiment, the clamp74may be manufactured to have a diameter larger than that of the spacers77.

The clamp coupling screw75is coupled to a screw-hole71aof the hub71via a through-hole74aof the clamp74, thereby supporting the disks11and the spacers77between the flange portion72and the clamp74.

The methods of centering a disk of an HDD according to the exemplary embodiments of the present general inventive concept may be applied when the disks11and the spacers77are stacked, or assembled, on the hub71before the mounting portion73is coupled to disk rotation driving unit62.

Thus, the offline servo track writer60according to an exemplary embodiment may further include a hub housing50and a vibration generation unit10, which will be discussed in greater detail below. The hub housing50may receive the mounting portion73inserted therein to support and facilitate stacking of the disks11, as illustrated inFIGS. 5-9. Additionally, the hub housing50may be removed after the centering of a disk of an HDD is complete.

The methods of centering a disk of an HDD according to exemplary embodiments of the present general inventive concept will be described in detail with reference toFIGS. 1,5-9, and10-15.

Referring toFIG. 1, an exemplary method of centering a disk of an HDD is illustrated. The method includes arranging the spacers77on an upper end portion of the hub71of the offline servo track writer60to write servo information to the disks11(S100), assembling the spacer77on the hub71by vibrating the hub71(S200), arranging the disks11on the upper end portion of the hub71(S300), and assembling the disk77on the hub71by vibrating the hub71(S400).

More specifically, the spacers77are arranged on the upper end portion of the hub71of the offline servo track writer60to write servo information to the disks11(S100). That is, the spacer77is arranged such that the through-hole11aformed in the each of the disks11is partially inserted around the hub71.

The vibration generation unit10may be coupled to the bottom surface of the hub housing50, as illustrated, for example, inFIGS. 5-9. Alternatively, the vibration generation unit10may be coupled directly to the mounting portion73, as illustrated, for example, inFIGS. 10-14. A voltage may be applied to the vibration generation unit10to generate a high frequency displacement in a vertical and/or horizontal direction in the hub71. The vibration generation unit10may include, but is not limited to, a piezoelectric device and a voice coil motor. For example,FIGS. 5,6,10and11illustrate a vibration generation unit10generating a high frequency displacement of the hub71in a vertical direction. While the voltage is applied to the vibration generation unit10, the hub71vibrates in the vertical direction so that the spacer77is assembled on the hub71(S200).

Referring now to an exemplary process of assembling the disks11to the hub71, the vibration generation unit10may apply a high frequency or ultrasonic displacement in the hub71to allow the hub71to vibrate in a vertical and/or horizontal direction according to the displacement of the disks11, similar to the process of assembling the spacers described in detail above. As a result, the vibration of the hub71couples the spacers77to the disks11, which are inserted around and stacked on the hub71, as illustrated, for example, inFIGS. 7,8,12and13. As mentioned above, the vibration generation unit10may include, but is not limited to, a piezoelectric device and a voice coil motor.

In exemplary embodiments, while the amount of displacement varies according to the amount of a voltage that is externally applied, the vibration generation unit10may be configured to generate vibration in a vertical direction by generating a displacement in the vertical direction, vibration in a horizontal direction by generating a displacement in the horizontal direction, or vibrations both in the vertical and horizontal directions by generating displacements in the vertical and horizontal directions.

Unlike conventional technology, since the vibration generation unit10vibrates the hub71, and thus the spacers77and the disks11assembled on the hub71, as described above, even when a gap D between the hub71, and the spacers77and the disks11, is managed to be less than several micrometers, the spacers77and the disks11may be easily assembled on the hub71. Additionally, a time of centering may be substantially reduced. Furthermore, a superior centering quality is achieved since the amount of imbalance is reduced, as compared to the conventional technology.

According to exemplary embodiments, a voltage waveform having a saw-toothed shape may be output to the vibration generation unit over a continuous period of time. Accordingly, the vibration generation unit10induces a vibration of the hub71. When vibration in the vertical direction is to be generated, not by equalizing, but by differentiating a time to increase a voltage and a time to decrease a voltage, the spacers77and the disks11may be easily assembled on the hub71.

According to the voltage waveform of a saw-toothed shape, in which there is a difference between the time to increase a voltage and the time to decrease a voltage, as illustrated inFIG. 15, a high frequency displacement may be applied to the hub71in an upward direction by increasing a voltage relatively rapidly to a preset voltage during a first time T1so that the spacers77and the disks11may relatively descend with respect to the hub71due to the upward high frequency displacement of the hub71. Also, to descend the spacers77and the disks11with the hub71, a voltage may be relatively gradually decreased to a preset voltage during a second time T2that is longer than the first time T1so that a downward displacement is applied to the hub71, thereby vibrating the hub71.

More specifically, in an initial stage in which the spacers77and the disks11are partially inserted around the upper end portion of the hub71, when a rapid voltage waveform is applied to the vibration generation unit10during the first time T1, a rapid displacement in the upward direction is generated in the hub71. At this moment, since the spacers77and the disks11relatively has a characteristic to remain at the initially inserted position due to inertia, a relative displacement is generated between the hub71and the spacers77or the disks11, so that the spacers77or the disks11may be further inserted around the hub71compared to the initial stage.

Alternatively, when a relatively gradual voltage waveform, as compared to that of the first time T1, is applied to the vibration generation unit10during the second time T2, no relative displacement is generated between the hub71and the spacers77or the disks11so that the hub71and the spacers77or the disks11may be moved downward.

In the centering method, after one of the spacers77is inserted, one of the disks11may be arranged at the upper end portion of the hub71(S300). For example, the disk11is arranged such that the through-hole11aformed at the central portion of the disk11may be partially inserted around the hub71.

As in operation S200, a voltage is applied to the vibration generation unit10to generate a displacement in the vertical direction in the hub71. The voltage waveform applied to the vibration generation unit10may be the same as that in the operation S200. Consequently, the disks11are assembled on the hub71in a way similar to the above-described assembly process of the spacers77(S400).

In operation S500, it may be determined whether the required number of the disks11are all assembled on the hub71. If not, the operations from S100through S400are sequentially repeated a plurality of times. After the above process, as illustrated inFIGS. 9 and 14, the spacers77and the disks11are inserted around and stacked on the hub71.

As described above, in the exemplary embodiments of the present general inventive concept, since the spacers77and the disks11are assembled on the hub71by vibrating the hub71using the vibration generation unit10, compared to the conventional technology, the gap D having a width being less than several micrometers between the hub71, and the spacers77and the disks11, may be obtained. For example, the gap D may have a width ranging from about 1 μm to about 10 μm. Thus, centering is performed spontaneously at the same time when assembly is performed so that a separate centering process may not be needed. Since the quality of centering is determined by each part compared to the conventional separate centering method, superior and uniform centering quality may be achieved. Also, the ultrasonic vibration may remove dust from the hub71before stacking the spacers77and the disks11. In addition, in a state where the spacers77and the disks11are already stacked, dust adhering to a surface of the hub71may be removed due to the ultrasonic vibration.

FIG. 16is a flowchart illustrating an exemplary method of centering a disk of an HDD according to a third exemplary embodiment of the present general inventive concept.FIGS. 17-21illustrate a process of inserting the disk and the spacer around the hub by the method of centering a disk of an HDD according to the third exemplary embodiment of the present general inventive concept.

Referring toFIGS. 16-21, according to the method of centering a disk of an HDD according to an exemplary embodiment of the present general inventive concept, unlike the above-described exemplary embodiments, vibration is applied to a base2of an HDD1in an assembly process of the HDD1to vibrate a spindle hub94of a spindle motor (not shown) so that the spacers77and the disks11may be sequentially inserted around and stacked on the hub94of the spindle motor.

More specifically, the present general inventive concept provides easy insertion of the disks11around the hub94such that the disks11may be stacked in a state where the gap D between the hub94of the spindle motor, and the spacers77and the disks11, is reduced compared to a convention technology. According to another exemplary embodiment of the present general inventive concept, although it is the same as the above-described exemplary embodiments to reduce the gap D between the hub94of the spindle motor, and the spacers77and the disks11, to be less than several micrometers unlike the conventional technology, the vibration generation unit10may alternatively vibrate the base2of the HDD1. Accordingly, the spacers77and the disks11may be inserted around the hub94as they move downward along the hub94of the spindle motor.

The alternative exemplary method of centering a disk of an HDD mentioned above may include arranging one of the spacers77on the upper end portion of the hub94of the spindle motor assembled on the base2of the HDD1(S600), applying vibration to the base2to vibrate the hub94of the spindle motor, thereby assembling the spacer77on the hub94(S700), arranging one of the disks11on the upper end portion of the hub94of the spindle motor (S800), and applying vibration to the base2to vibrate the hub94of the spindle motor, thereby assembling the disk11on the hub94(S900).

More specifically, one of the spacers77is arranged on the upper end portion of the hub94of the spindle motor that is assembled on the base2of the HDD1(S600). That is, the spacer77is arranged such that the through-hole11aformed at the central portion of the spacer77may be partially inserted around the hub94.

Next, a voltage is applied to the vibration generation unit10that is coupled to the base2so that an upward high frequency displacement may be generated in the hub94of the spindle motor. When the voltage is applied to the vibration generation unit10, the hub94is vibrated and thus the spacer77is assembled on the hub94(S700). The vibration generation unit10may be installed to simultaneously generate displacements in the vertical and horizontal directions of the hub94.

As in the above-described exemplary embodiments, a voltage is applied to the vibration generation unit10based on the voltage waveform of a saw-toothed shape having a difference in the time to increase a voltage and the time to decrease a voltage, and thus, vibration is induced in the hub94by the vibration generation unit10.

Accordingly, one of the disk11is arranged on the upper end portion of the hub94of the spindle motor (S800). That is, the disk11is arranged such that the through-hole11aformed at the central portion of the disk11may be partially inserted.

Then, as in the operation S700, a voltage is applied to the vibration generation unit10to vibrate the hub94of the spindle motor. That is, a voltage is applied to the vibration generation unit10based on the voltage waveform of a saw-toothed shape having a difference in the time to increase a voltage and the time to decrease a voltage, and thus, vibration is induced in the hub94by the vibration generation unit10. As a result, the disk11is inserted around the hub94in a way similar to the insertion process of the spacer77(S900).

Then, it is determined whether the required number of the disks11are all assembled on the hub94(S1000). If not, the operations from S600through S900are sequentially repeated a plurality of times. After the above process, as illustrated inFIG. 94, the spacers77and the disks11are inserted around and stacked on the hub71.

As described above, according to exemplary methods of centering a disk of an HDD according to the present general inventive concept, disks and/or spacers may be easily assembled on a hub, a time of centering may be substantially reduced, and a superior centering quality may be obtained.