Dynamic magnetic information storage or retrieval – Record transport with head stationary during transducing – Disk record
Reexamination Certificate
2001-10-23
2004-08-31
Klimowicz, William (Department: 2652)
Dynamic magnetic information storage or retrieval
Record transport with head stationary during transducing
Disk record
C360S099120
Reexamination Certificate
active
06785090
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to the structure of a disk clamp which rotatably and securely holds recording disks that rotate at a high speed in an disk recording apparatus. The disk clamp connects the disks to a spindle motor, which is a rotary drive.
2. Description of the Prior Art
A hard disk drive, which is an disk recording apparatus in which recording media is magnetic recording disks. The magnetic recording disks rotate at a high speed in an recording apparatus used in an information processing apparatus such as a computer. More than one magnetic recording disk (hereafter referred to as a recording disk) rotates at a high speed and writes or reads information data by means of magnetic heads individually disposed for the top and bottom faces of the recording disks.
A recording disk for a hard disk drive is rotated by a spindle motor, which is a rotary drive. A recording disk rotates at a speed as high as a few thousand revolutions per minute. Therefore, a disk clamp that secures each recording disk to the spindle shaft of the spindle motor must have a structure and strength for holding each recording disk.
A hard disk drive of 3.5-inch type, for instance, may not change its dimensions but is demanded to increase the storage capacity by several tens of percent or greater each year, and is demanded to reduce the thickness and the other outer dimensions as much as possible to keep up with the miniaturization of internal units or the like. Accordingly, disk clamp has also been desired to reduce the thickness and the other outer dimensions as much as possible. But a certain physical dimensions in the disk clamp are required to securely hold the recording disks and stand their high-speed revolutions, so that it is difficult to make the current dimensions smaller or slimmer.
On the other hand, the recording disk, like a compact disc for instance, on which recording is performed with magnetically, in that it has the disc shape and a hole at its center. And the recording disk has a large number of magnetic recording tracks which are concentrically formed on its surfaces. To satisfy the recording density which has been increasing year after year, the recording disk is required to have a highly flatness level. The surfaces of a glass substrate can be easily smoothed out. So, the glass substrate become more popular than the conventional aluminum substrate in recent years.
FIG. 10
is a cross-sectional view showing the structure of a conventional disk clamp which holds recording disks using three glass substrates. The disk clamp shown in
FIG. 10
holds three recording disks
17
(A),
17
(B), and
17
(C) together from the top and bottom. The member that holds the recording disk
17
(C) from the bottom is the stainless steel hub
23
, and the member that holds the recording disk
17
(A) from the top is the stainless steel top clamp
21
. Stainless steel is one of materials that are stable in terms of chemical properties over the whole temperature range in which the disk recording apparatus (hard disk drive) would be used. And the stainless steel has such a coefficient of elasticity that a clamping force required to clamp the recording disks
17
(A) to
17
(C) while the disk recording apparatus(describe later) is in use. The clamping force can be obtained from the tightening force to tighten the screws
22
. The hub
23
is secured to the spindle shaft
18
, which is the axis of rotation of the spindle motor
25
. The top clamp
21
is secured by tightening the screws
22
into the hub
23
. In the spaces among the three recording disks
17
(A),
17
(B), and
17
(C), the ring-shaped spacers
24
formed by a ceramic material are inserted. The thermal expansion coefficient of the spacers
24
is close to that of the glass substrate.
The radius of the cylindrical portion
23
a
of the hub
23
that goes through the center holes of the recording disks
17
(A),
17
(B), and
17
(C) is smaller than the radius of the perimetric portion
23
b
which holds the recording disk
17
(C) from the bottom. Likewise, the radius at which screwing positions
21
a
are disposed in the top clamp
21
is smaller than the radius of the perimetric portion
21
b
which holds the recording disk
17
(A) from the top.
The screwing positions
21
a
and the perimetric portion
21
b
of the top clamp
21
are integrally formed in a stainless steel member, and the thickness of the connecting portion
21
c
is L
1
. The cylindrical portion
23
a
and the perimetric portion
23
b
of the hub
23
are also integrally formed in a stainless steel member, and the thickness of the connecting portion
23
c
is L
2
.
FIG. 11
illustrates that the tightening force by the screws
22
for securing the recording disks
17
shown in
FIG. 10
is transferred through the disk clamp up to the perimetric portion
21
b
or
23
b.
The tightening force FC
1
of the screws
22
travels through the cylindrical portion
23
a
of the hub
23
and works to press the cylindrical portion
23
a
and the screwing position
21
a
in a direction to close each other, as represented by the arrows in FIG.
11
. The tightening force FC
1
also travels through the connecting portion
21
c
of the top clamp
21
up to the perimetric portion
21
b
, but the magnitude of this force varies with the distance L
3
, coefficient of elasticity (Young's modulus), and thickness L
1
. For instance, the tightening force FC
2
in the perimetric portion
21
b
grows weaker with increase in distance L
3
, with decrease in coefficient of elasticity, or with decrease in thickness L
1
. The tightening force traveling through the connecting portion
21
c
is defined as transfer force Ml. The magnitude of the transfer force M
1
of the connecting portion
21
c
is proportional to the thickness L
1
of the connecting portion
21
c
if the material has uniform properties, like stainless steel. The transfer force M
1
traveling in this way is transferred by the perimetric portion
21
b
to the clamp portion
17
a
of the recording disk
17
(A) and combined with the force transferred by the perimetric portion
23
b
of the hub
23
(described later), to form the tightening force FC
2
, which presses the clamp portion
17
a
from the top.
Likewise, the tightening force FC
1
which travels through the cylindrical portion
23
a
of the hub
23
is transferred through the connecting portion
23
c
by distance L
3
up to the perimetric portion
23
b
. The transfer force through the connecting portion
23
c
is defined as M
2
. The transfer force M
2
varies with the distance L
3
, coefficient of elasticity (Young's modulus), and thickness L
2
. And the transfer force M
2
is proportional to the thickness L
2
of the connecting portion
23
c
, for instance, if the material has uniform properties. The transfer force M
2
traveling in this way is transferred by the perimetric portion
23
b
to the clamp portion
17
c
of the recording disk
17
(C). And the transfer force M
2
is combined with the force from the perimetric portion
21
b
of the top clamp
21
, which was described earlier, to form the tightening force FC
2
. The FC
2
presses the clamp portion
17
b
from the bottom.
The tightening force FC
2
, which is the resultant of the force pressing the clamp portion
17
a
of the recording disk
17
(A) from the top and the force pressing the clamp portion
17
b
of the recording disk
17
(C) from the bottom, is transferred through the recording disks
17
(A),
17
(B), and
17
(C) and the spacers
24
among the recording disks
17
(A),
17
(B), and
17
(C) and secures the recording disks. The spacers
24
are inserted to maintain spaces between the recording disks
17
(A) and
17
(B) and between
17
(B) and
17
(C) and are made of ceramics of which thermal expansion coefficient is almost the same as that of the recording disks
17
.
The hard disk drive is generally used in an environment of room temperature (about 20 to 25 degrees Celsius), and the internal temperature rises to about 50 to 60 degrees Celsius by the heat gen
Koyanagi Ichiroh
Nakamoto Tatsuo
Takeuchi Kohichi
Hitachi Global Storage Technologies - Netherlands B.V.
Klimowicz William
Martin Robert B.
LandOfFree
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