Dynamic optical information storage or retrieval – Dynamic mechanism optical subsystem – Optical storage medium support
Reexamination Certificate
2001-12-28
2004-08-17
Davis, David (Department: 2652)
Dynamic optical information storage or retrieval
Dynamic mechanism optical subsystem
Optical storage medium support
C720S709000
Reexamination Certificate
active
06779192
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a disk clamping device, and in particular to a disk clamping device which is capable of preventing a slip of a disk when the disk rotates at a high speed by increasing frictional force acting on the disk.
2. Description of the Conventional Art
Recently, with a need of a mass storage optical disk as an information recording and reproducing medium, densification of a disk is in progress. According to it, improving a data access speed of a CD-ROM (compact disk-read only memory) or a DVD-ROM (compact video disk-read only memory), etc. of a desktop or a portable computer is on the move. For that reason, a disk clamping device rotating at high speed comes to the fore.
FIG. 1
is a perspective view illustrating a conventional disk clamping device,
FIG. 2
is a sectional view illustrating a hub of a turntable of the disk clamping device of
FIG. 1
taken along the line A—A, and
FIGS. 3A and 3B
are state diagrams illustrating states before and after mounting a disk onto the clamping device of FIG.
1
.
As depicted in
FIG. 1
, the conventional disk clamping device includes a spindle motor
10
as a rotational power source of a disk
30
, a turntable
20
installed to the spindle motor
10
and rotating, a plurality of clamping grooves
21
formed at a hub
25
centering around a rotational axis of the hub
25
of the turntable
20
at regular angles and intervals, a plurality of springs
22
and a plurality of balls
23
respectively installed inside each clamping groove
21
for clamping the disk
30
, and a circular lubber plate
24
installed at the outside of the hub
25
of the turntable
20
and contacted to the bottom surface of the disk
30
.
The operation of the conventional disk clamping device will be described as below.
As depicted in
FIG. 1
, in a disk driver structure such as a thin optical disk player, the turntable
20
rotates by a rotational operation of the spindle motor
10
.
As depicted in
FIG. 3B
, when the disk
30
is mounted onto the turntable
20
, the hub
25
of the turntable
20
is inserted into a centrical hole
32
of the disk
30
, the outer circumference
25
a
of the hub
25
is tightly contacted to the inner circumference
31
of the centrical hole
32
of the disk
30
, accordingly the disk
30
rotates together with the turntable
20
.
Herein, as depicted in
FIGS. 3A and 3B
, each ball
23
applied an elastic force of each spring
22
installed inside each of the three clamping grooves
21
formed centering around the rotational axis of the hub
25
of the turntable
20
at regular intervals projects over the outer circumference
25
a
of the hub
25
and contacts with the inner circumference
31
of the centrical hole
32
of the disk
30
in order to clamp the disk
30
.
In more detail, as depicted in
FIG. 2
, the three clamping grooves
21
are formed at the hub
25
at regular angles (about 120°) and intervals centering around the rotational axis of the hub
25
, the plurality of springs
22
respectively inserted into the three clamping grooves
21
apply pressure to the plurality of balls
23
, each ball
23
applies pressure to the inner circumference
31
of the disk centrical hole
32
, accordingly the clamping operation is performed.
In the meantime, in the above-mentioned structure, because a clamping force of the disk
30
, namely, a frictional force acting on the disk
30
is determined only by a push force of the spring
22
applied to the ball
22
, when an inertia force of the disk
30
is larger than a clamping force of the spring
22
in a high speed rotation of the disk
30
, a slip of the disk
30
occurs naturally.
In order to prevent the slip, the circular lubber plate
24
is installed onto the turntable
20
in order to increase the frictional force acting on the disk
30
.
However, because the circular lubber plate
24
is made of lubber materials, hardness and surface roughness of the circular lubber plate
24
are varied according to temperature and humidity. Accordingly, when the turntable
20
rotates and speeds up according to the rotation and speed-up of the spindle motor
10
, the disk
30
may move in a direction opposite to the rotation direction of the turntable
20
due to an inertia force.
In addition, when a spring force is increased in order to increase a clamping force, it is difficult to mount the disk
30
onto the turntable
20
, if the disk
30
is mounted by applying a pressure, the disk
30
may be deformed.
In addition, if each spring force is different, when the disk
30
is mounted and rotated, a vibration occurs due to an increase of an eccentricity of the disk
30
, accordingly it is impossible to read/write the disk
30
normally.
FIG. 4
is a graph showing a natural frequency in a stop of a disk.
As depicted in
FIG. 4
, a natural frequency of a disk is divided into a forward traveling wave mode and a backward traveling wave mode in a rotating system, namely, in a rotation of a CD-ROM drive, etc.
FIG. 5
is a graph showing a relation between rotation speed and natural frequency.
As depicted in
FIG. 5
, a critical speed is between 7000~8000 rpm in a (0, 2) mode in which a natural frequency is decreased according to an increase of a rotation speed (for example: an increase of a speed of a CD-ROM). The natural frequency is increased due to characteristics of a rotating dynamic system.
In addition, the natural frequency does not increase continually, at a very high speed a flutter occurs due to a ductility problem of a fluid (air) and a solid (disk), accordingly it is impossible to read/write a disk normally.
FIG. 6
is a graph showing a flutter phenomenon according to an increase of a rotation speed of a disk and a natural frequency.
As depicted in
FIG. 6
, it is possible to increase a speed of an optical disk player by increasing a flutter speed, it means data can be read/written faster.
Accordingly, a flutter speed can be increased by increasing a critical speed.
Therefore, in order to increase a critical speed, a clamping force of a disk has to be increased, for that a spring force is increased in the conventional disk clamping device, however it may cause a deformation of a disk by applying excessive pressure to the disk in order to mount it onto a turntable.
SUMMARY OF THE INVENTION
In order to solve above-mentioned problems, it is an object of the present invention to provide a disk clamping device which is capable of preventing a slip of a disk in a rotation at high speed by increasing a frictional force between a hub and the inner circumference of a centrical hole of the disk.
In order to achieve the above-mentioned object, the present invention provides a disk clamping device for a disk drive having a hub insertable into a centrical hole of a disk, which includes a clamping means formed at a hub of a disk and increasing a normal force acting on the inner circumference of the disk so as to increase a frictional force between the hub and an inner surface of the disk in order to prevent a slip of the disk in accordance with rotation of the disk.
Also, the present invention provides a disk clamping device for a disk drive having a hub insertable into a centrical hole of a disk, which includes a plurality of clamping grooves formed at the hub at regular angles and intervals centering around the hub in a radial direction, a plurality of springs respectively inserted into the plurality of clamping grooves, a plurality of balls respectively inserted into the plurality of clamping grooves, pushed toward the outer circumference of the hub by the plurality of springs and contacting to the disk when the hub is inserted into the centrical hole of the disk and a fluid filled inside the plurality of clamping grooves in order to increase a frictional force between the plurality of balls and the disk in accordance with a rotation of the disk and the hub.
Also, the present invention provides a disk clamping device for a disk drive having a hub insertable into a centrical hole of a disk, which includes a plurality
Kim Young Joong
Park Kwan Woo
Birch & Stewart Kolasch & Birch, LLP
Davis David
LG Electronics Inc.
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