Magnetic disk drive unit and production method therefor

Details Magnetic disk drive unit and production method therefor Magnetic disk drive unit and production method therefor

2001-05-16

2003-05-27

Tupper, Robert S. (Department: 2652)

Dynamic magnetic information storage or retrieval

Record transport with head stationary during transducing

Disk record

C360S254700, C360S264700

Reexamination Certificate

active

06570736

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic disk drive unit and a production method therefor which is superior in shock resistance, light weight and portability.
2. Description of the Related Art
The conventional magnetic disk drive unit has a construction for enclosing a magnetic disk and a magnetic head for reading and writing information on the magnetic disk, within a metallic body generally called as a base and a cover. Such magnetic disk drive unit may have a construction as illustrated and disclosed in Japanese Unexamined Patent Publication No. Heisei 3-207076. The construction will be shown in FIG.
7
.
In
FIG. 7
, a motor
26
with a magnetic disk
24
is secured within a base
38
made of aluminum by means of screws. Then, a carriage
30
mounting a magnetic head
28
is fixed on the base
38
together with a magnetic circuit
166
by screws. In addition, a flexible circuit board
90
is fixed on the base
38
by screws. Finally, a cover
32
is fitted over and fixed by screws. The construction set forth above is a portion referred to as DE (disk enclosure). The DE is completely sealed except for ventilation aperture with a filter in order to prevent penetration of the foreign matter.
As the magnetic disk drive unit, a PCBA (circuit package)
88
is externally fitted on the DE and is connected to the flexible circuit board
90
for inputting and outputting a signal from the magnetic head.
In such magnetic disk drive unit, the base, the cover as well as the carriage and motor are required high precision and rigidity. Therefore, these components are formed of a metal, such as s aluminum, stainless or the like and are designed to provide a thickness as thick as possible.
As a result, in case of the magnetic disk drive unit employing a 3.5 inch disk, a weight becomes 500 g to 1000 g as a whole. The drive is substantially heavy to handle as precise instrument.
On the other hand, upon handling, if falling down of the magnetic disk drive unit is accidentally caused, since the magnetic disk drive unit is covered by metal, an impact is directly transmitted to the major component (carriage, motor and so forth) housed therein.
Here, reason why high precision and rigidity is required and reason why the PCBA is mounted outside of the DE will be discussed briefly.
Concerning the dimensional precision, the magnetic disk drive unit achieves high recording density by floating the magnetic head on the magnetic disk in low floating amount in order of several tens nm. In order to stably maintain low floating amount, a relative height between an arm, on which the magnetic disk is mounted, and the disk surface has to be set strictly. If significant error is caused in the relative height, the magnetic head may be tilted in floating condition, and load to bias the magnetic head toward the magnetic disk may be varied to cause difficulty in maintaining low floating amount. On the other hand, by long period use, damage, such as head crush can be caused.
Therefore, it is generally required to manage an error of relative height between the arm and the disk to be less than or equal to 30 &mgr;m to 50 &mgr;m. In order to realize such tolerance, it is not only required to increase dimensional precision of the carriage and motor but also required high precision for the base mounting the arm and disk. The base is formed of aluminum. Upon manufacturing, the base is formed by aluminum die casting. In case of casting surface of aluminum die casting, it is difficult to achieve surface precision less than or equal to 50 &mgr;m. Therefore, a surface to be a reference for mounting the carriage or motor, re-working is effected to achieve the foregoing precision.
On the other hand, in the magnetic disk drive unit nowadays, a ramp load system, in which the magnetic disk is retracted in a ramp provided outside of the magnetic disk upon stand-by state of the magnetic head, is employed. In this case, it is also required to strictly set the relative height between the ramp and the magnetic disk. The ramp is set above 100 &mgr;m to 200 &mgr;m. Upon loading the magnetic head, the magnetic head is slid on the magnetic disk, and upon unloading the magnetic head, the magnetic head is retracted to the retracted position. Therefore, if the relative height is contains an error, the magnetic head may contact on the disk surface of the magnetic disk upon loading or the magnetic head and the tip end of the ramp may contact to make it impossible to return to the retracted position.
Therefore, it is required to precisely set the height of a base surface on the base to mount the ramp by reworking.
The foregoing relative height relationship may be greater according to increase number of disks for accumulation of tolerance. Furthermore, inclination may also be accumulated to cause difficulty in management for achieving necessary precision.
In the conventional magnetic disk drive unit, the dimensional precision has to be strictly managed by reworking the metallic base.
Next, discussion will be given for demand for high rigidity in the magnetic disk drive unit.
In the recent magnetic disk drive disk unit, recording density is increasing to be higher and higher and a track pitch has reached in the extent of 1 &mgr;m. In order to realize such high recording density, development has been progressed to make fluctuation 3&sgr; in positioning precision of the magnetic head to be less than or equal to 50 nm. In such case, resonance design depending upon the base and the arm becomes important. If stiffness of these members is low, resonance can be caused in low frequency range to rise a servo band for positioning of the magnetic head to make impossible to realize high positioning precision. Therefore, by making stiffness of the arm and base as much as possible, designing has been done for shifting resonance point shifted toward higher frequency range.
Finally, reason why the PCBA is mounted outside of the DE is prevention of penetration of dust or other foreign matter within the DE. In the PCBA, a large amount of corrosive elements contained in solder or flux is present. If such element is housed within the DE, corrosion may be caused in the magnetic head and the storage medium. Therefore, a construction is taken to mount the PCBA on the back surface of the DE after completion of assembling of the DE.
As set forth above, in the conventional magnetic disk drive unit, for realizing high performance and high reliability, a construction is taken to cover the DE with a touch base cover and to arrange the PCBA outside of the DE. Therefore, the weight of the whole unit becomes heavy and impact resistance becomes low. Furthermore, electronic parts mounted on the PCBA is exposed to make handling ability of the unit low. At the present, there is not large capacity hard disk drive unit achieving removing ability and portability. In nature, the magnetic disk drive unit is adapted to be used for stationary type unit (desktop type unit), such as workstation, personal computer and the like. For such purpose, the magnetic disk drive unit of the conventional construction has been sufficient.
However, associating with digitizing of video data in nowadays, demand for storage media which can store the video data and is adapted for removable application, has being getting more and more strong. Currently, in this field, as a useful medium, removable recording medium, such as a magnetic tape, DVD and so forth are typically used. However, in case of the magnetic tape, similarly to the existing VHS video recording type magnetic tape, is far lower in versing-up performance and so forth as compared with DVD. On the other hand, DVD currently available merely achieved storage capacity in the extent of 4.7 GB which is not sufficient to record a movie of two hours in high picture quality.
Therefore, in order to solve the problem set forth above, it becomes necessary to develop a large capacity removable medium employing a magnetic disk drive unit.
A simple type removable magnetic disk drive employing a 2.5 inch size

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