Dynamic magnetic information storage or retrieval – Record transport with head stationary during transducing – Disk record
Reexamination Certificate
1995-01-31
2001-04-03
Davis, David (Department: 2652)
Dynamic magnetic information storage or retrieval
Record transport with head stationary during transducing
Disk record
Reexamination Certificate
active
06212030
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic disk drive, and particularly to a magnetic disk drive having means for reducing disk deformation.
A flying head with a small air gap between the head and a disk are used in a magnetic disk drive. A high density recording requires an accurate positioning of the flying head. The position of the flying head can be divided into vertical and lateral components. The vertical position is the flying height or the air gap of the head. The lateral position is the position along the radius of the disk.
Preferably, the air gap is decreased because the decreased air gap enhances the electromagnetic transducing characteristic and allows the storage capacity to be increased. Products with an air gap of less than 0.1 &mgr;m have recently been marketed.
However, the decreased air gap increases the probability of a head crash in which a head crashes against a disk and destroys information stored in the disk. A factor causing a head crash is disk deformation such as warpage and “wave” (e.g., buckling or waviness) illustrated in FIG.
1
.
Referring to
FIG. 1
, warpage and wave are deformation radially and concentrically of the disk, respectively. More specifically, warpage of a disk is the difference in height between an innermost point A and an outermost point B on a radius. The disk deformation causes variation of the air gap. The variation of the air gap produces data read/write errors and may ultimately result in a head crash.
The extent of the disk deformation depends on a clamping mechanism that fixes the disks to a spindle hub. Referring to
FIG. 2
, a structure of a conventional magnetic disk is illustrated having four disks
100
, and a spindle assembly
10
which comprises a spindle shaft
1
and a spindle hub
2
. The spindle hub
2
is supported rotatably by the spindle shaft
1
via bearings
3
A and
3
B.
The spindle hub
2
has a cylindrical shape and has a flange
2
A at its bottom end. The magnetic disks
100
and spacer rings
4
are alternately stacked on the flange
2
A of the spindle hub
2
while the spindle hub
2
is fittedly inserted in the openings of the disks and spacer rings. A disk-like clamp ring
5
is placed on the top disk
100
and is attached to the top of the spindle hub
2
with screws (unreferenced). The disks
100
and spacer rings
4
are clamped between the clamp ring
5
and the flange
2
A of the spindle hub
2
. The disks
100
are affixed to the spindle hub
2
by pressure exerted by the screws.
The bottom surface of the clamp ring
5
and the top surface of the flange
2
A of the spindle hub
2
that contact the disks
100
are flat so as to keep the disks
100
flat and parallel to one another.
However, this conventional clamping structure cannot reduce warpage of the disks
100
to less than 20 &mgr;m because of an unavoidable irregular distribution of the clamping pressure.
Furthermore, in magnetic disk devices, the lateral positioning of the head must be precise to follow data tracks because track width has been generally decreased to increase track density. Lateral positioning accuracy is deteriorated by deformation of holder arms holding the heads. Arm deformation becomes critical when the track widths are decreased to less than 10 &mgr;m. To complicate problems, the arms are becoming thinner so as to downsize the disk drive. This makes the holder arms prone to deformation.
Moreover, the deformation of the holder arms during manufacturing is unavoidable as stated below.
Specifically, the holder arms are formed by die-casting. However, since the arms are relatively thin, molten metal does not flow smoothly especially at the end portion of the die mold. This results in deformation of the arms and in blow holes being formed in the arms. Vibrations and loads during the processing also cause arm deformation.
SUMMARY OF THE INVENTION
In view of the foregoing problems of the conventional system, one object of the present invention is to enhance the positioning accuracy of a head.
Another object of the present invention is to enhance the accuracy of a vertical head position or an air-gap.
Another object of the present invention is to enhance the accuracy of a lateral head position.
Another object of the present invention is to reduce disk deformation.
Another object of the present invention is to reduce deformation of holder arms.
According to the present invention, a clamping structure for clamping a plurality of disks includes a spindle hub for receiving the disks, a first spacer, and a clamp ring. The spindle hub has a flange at a first end thereof. The flange has a first protruding portion. The disks are stacked on the first protruding portion. The first spacer is interposed between adjacent ones of the disks.
The clamp ring is fixed to a second end of the spindle hub. The clamp ring has a second protruding portion for biasing the magnetic disks toward the flange of the spindle hub.
Among the aforementioned structure, the first and second protruding portions are one feature of the present invention and are for reducing the deformation of the disks.
Other spacers can be added to the aforementioned structure for reducing the waviness as well as the warpage of the discs.
In a first embodiment, a second spacer is interposed between the second protruding portion of the clamp ring and an uppermost one of the disks.
In a second embodiment, a third spacer is interposed between the first protruding portion of the spindle hub and a lowermost one of the disks.
The first and second protruding portions preferably have an annular shape. They can have various cross-section such as rectangular, trapezoidal, triangular, and elliptical cross-sections.
The deformation of the disks can be minimized when the diameters of the first and second protruding portions are substantially identical.
A groove may be provided in an outer circumference of the first spacer for further reducing the disk deformation when the second and third spacers cannot be provided. The groove should be provided in the uppermost and lowermost ones of the first spacers.
The fourth embodiment of the present invention is a process for reducing deformation of holder arms. The holder arm is used in a disk drive for holding a head. The fourth embodiment reduces the deformation occurring during a contouring of a tip of the holder arm.
In step (a) of the process, a metal body is cut and the holder arm is formed. In step (b), the tip of the holder arm is contoured by a wire cutting method.
The wire cutting method generally comprises the following steps. In step (b-1), a voltage is placed between the metal body and a wire. In step (b-2), the wire is moved. In step (b-3), the wire is brought into contact with the metal body. The metal body is preferably produced by extruding metal through a die to form the metal body.
The wire cutting method can contour the tip of the holder arm with less deformation than that of the conventional method such as die casting.
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Itoh Kenji
Iwamoto Misa
Koriyama Hiroshi
Suzuki Takahiro
Tagawa Norio
Davis David
McGuireWoods LLP
NEC Corporation
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