Dynamic information storage or retrieval – Dynamic mechanism subsystem – Specific detail of storage medium support or motion production
Reexamination Certificate
2001-02-05
2004-03-23
Chen, Tianjie (Department: 2652)
Dynamic information storage or retrieval
Dynamic mechanism subsystem
Specific detail of storage medium support or motion production
Reexamination Certificate
active
06711117
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a disc drive apparatus in which a vibration damper is integrated. The vibration damper arrests self-vibration of a disc due to unbalance of the disc per se. The disc is a medium used in a CD-ROM drive apparatus or a CD-R drive apparatus. This vibration damper allows the disc drive apparatus to record/reproduce data in a stable manner.
BACKGROUND ART
A data transfer rate of a disc drive apparatus—recording/reproducing data—employed in a CD-ROM or CD-R drive apparatus has recently become higher and higher. This requires a disc to revolve at a higher speed.
In general, many discs have uneven thickness, which causes unbalance in mass of the disc. When such a disc is driven at a high speed, the following inconveniences are produced: Self-vibration is produced by unbalance force of the disc, and the vibration travels to overall apparatus, so that data cannot be reproduced in a stable manner, and the vibration yields noise as well as shortens the service life of the motor. When the disc drive apparatus is integrated into a computer system, the vibration may travel to other peripherals and adversely affect them.
At a higher data-transfer-rate by spinning the disc at a higher speed, i.e. revolutions per minute (rpm), the self-vibration due to disc's unbalance is desirably arrested. For that purpose, various measures have been proposed to cancel the unbalance of the disc. The Japanese Patent Application Non-Examined Publication No. H10-83622 proposes one of the measures.
A disc drive apparatus having a conventional canceling function is described hereinafter.
FIG. 5
is a perspective view of a conventional optical disc drive apparatus having a balancer to cancel the unbalance of centrifugal force at revolving the disc.
FIG. 6
is a lateral cross section of the essential part of the same apparatus.
FIG. 7
is a cross section viewed from the top illustrating the balancer.
In
FIG. 5
, on main base
8
of the optical disc drive apparatus, the following elements are arranged to function as described below:
Spindle motor
2
spins disc
1
. Photo pickup
3
reads data recorded in disc
1
or write data into disc
1
. Photo pickup driving system
5
comprises a rack and a pinion. Driving system
5
transduces rotational motion of motor
4
into linear motion of pickup
3
. Motor
4
is used for driving the photo pickup. At this time, driving system
5
moves pickup
3
in radial direction of disc
1
. Spindle motor
2
, motor
4
and driving system
5
are mounted on sub-base
6
.
Elastic isolator
7
damps vibrations and shocks coming from the outside of the apparatus and travelling to sub-base
6
. Sub-base
6
is mounted to main base
8
with isolator
7
in between. At a high rpm of disc
1
, isolator
7
is deformed, which produces a resonant frequency of sub-base
6
. The resonant frequency is set at a lower level than a rotating frequency of disc
1
driven at a high rpm, so that the vibrations or shocks from the outside is damped by isolator
7
.
In
FIG. 6
, ferromagnetic yoke
11
is fixed to turntable
9
, and turntable
9
spins unitarily with spindle motor
2
. Clamp
10
incorporates magnet
271
. Disc
1
is held by turntable
9
and clamp
10
due to magnet attraction between magnet
271
and yoke
11
, and is unitarily spun with turntable
9
.
Polarized face
28
of magnet
271
is usually polarized two polarities (N and S poles in pair), as shown in
FIG. 7
, for easy manufacturing as well as due to a simple application. On the other hand, back-yoke
15
made of ferromagnetic substance is disposed on non-polarized face
29
of magnet
271
. Back-yoke
15
shuts out leakage magnetic flux from others except polarized face
28
, so that magnetic flux travelling from face
28
to yoke
11
is efficiently secured. This strengthens attraction between magnet
271
and yoke
11
. As a result, disc
1
is held more firmly between clamp
10
and turntable
9
.
Hollow annular section
14
of clamp
10
accommodates a plurality of movable balls
13
(single ball position
131
,
132
, and onward) made of magnetic substance. Ball position
131
indicates its location at a high rpm, and centrifugal force urges ball position
131
against outer wall
20
of hollow annular section
14
. In this condition, ball
13
at position
131
revolves. Ball position
132
, on the other hand, indicates its location at a low rpm. In this case, ball
13
at position
132
is attracted to the inner wall of hollow annular section
14
, i.e. the outer wall of magnet
271
, by attraction of magnet
271
. The balancer comprises clamp
10
, balls
13
, magnet
271
and back yoke
15
. This balancer is mounted on sub-base
6
via disc
1
, turntable
9
and spindle motor
2
. Sub-base
6
is coupled to main base
8
via isolator
7
. As already discussed, high speed rotation of disc
1
deforms isolator
7
, and the resonant frequency of sub-base
6
due to the deformation of isolator
7
is set at a lower level than the rotating frequency of disc
1
revolving at a high rpm.
FIG. 7
is a cross section of clamp
10
viewed from the top.
FIG. 7
illustrates how the unbalance is cancelled at a high rpm of disc
1
by the movement of balls
13
housed in clamp
10
.
A status of balls
13
at a low rpm of unbalance disc
1
is described, and how the unbalance of disc
1
is cancelled at a high rpm is also described hereinafter.
In a CD-ROM drive apparatus, in general, the disc is spun at a higher speed (in eight times mode, max ca. 4200 rpm) in order to increase data transfer rate in the data read mode. On the other hand, the disc is spun at a standard rate (ca. 200-500 rpm) in an audio play mode. As such, a high rpm for data read and a low rpm for audio play are intermingled.
When disc
1
having unbalance is spun at a high rpm, unbalance force, namely centrifugal force, acts to gravity center
17
of disc
1
, and the act-direction revolves together with disc
1
. This unbalance force
18
deforms isolator
7
, and sub-base
6
vibrates at a rotating frequency of disc
1
. Since the resonant frequency of sub-base
6
is set at a lower level than the rotating frequency of disc
1
, the displacement direction of sub-base
6
is always reverse to the direction of unbalance force
18
. As a result, balls
13
housed movably in clamp
10
receive resultant force of centrifugal force
19
and resistant force
21
from wall
20
to which balls
13
are urged. This resultant force functions as moving force
22
. Balls
13
thus move away from vibrating center
23
and collect in the right reverse direction to unbalance force
18
. Finally, a total mass of balls
13
gathered at ball position
131
at the high rpm cancels unbalance volume of disc
1
.
In a low rpm area including a standard rate, centrifugal force
19
of balls
13
decreases, which cannot keep urging balls
13
onto wall
20
. Balls
13
then become unstable, so that various noises are generated such as rolling and sliding of balls
13
on the walls within clamp
10
, and collision between balls
13
.
In the low rpm area, if the unbalance force is negligible small and centrifugal force urges balls
13
against wall
20
, the unbalance force would increase because the centrifugal force acts to balls
13
.
For avoiding this problem, balls
13
are to be made of magnetic substance, and balls
13
are urged to outer wall
26
of magnet
271
and back yoke
15
by utilizing leakage magnetic flux
24
of magnet
271
or magnetic flux
25
travelling from polarized face
28
to back yoke
15
. As a result, balls
13
are rested at ball position
132
at a low rpm, thereby preventing the noises from being generated.
However, in the conventional structure discussed above, there may be the following problem when disc
1
suddenly changes its rotating rate from a high rpm to a low rpm.
A disc to be loaded to a CD-ROM drive apparatus includes normal data intermingled with audio data. When such a disc is played back, the normal data are read at the high rpm and then the rpm is changed to the standard one to pl
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