Dynamic information storage or retrieval – Dynamic mechanism subsystem – Specified detail of transducer assembly support structure
Reexamination Certificate
1994-03-23
2002-06-04
Letscher, George J. (Department: 2652)
Dynamic information storage or retrieval
Dynamic mechanism subsystem
Specified detail of transducer assembly support structure
Reexamination Certificate
active
06400674
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical disk drive provided with an optical pickup for recording information on and reproducing information recorded on an optical recording medium, such as an optical disk or a magnetooptical disk, and, more particularly, to an improved spindle motor holding structure for holding a spindle motor for driving an optical recording medium for rotation on the chassis of an optical disk drive.
2. Description of the Related Art
FIGS. 4
to
6
illustrate an optical disk drive disclosed in Japanese Patent Laid-open (Kokai) No. 4-229480 provided with an improved spindle motor holding structure. In this known optical disk drive, a disk cartridge
2
containing an optical recording disk
1
, such as an optical disk or a magnetooptical disk, is placed in a horizontal position on four positioning pins
4
so that the optical recording disk
1
is attracted magnetically in a horizontal position to a disk table
7
which is driven for rotation by the spindle
6
of a spindle motor
5
held on a main chassis
3
. The optical recording disk
1
is located close to the objective lens
10
of an optical pickup
9
which is shifted by a voice coil motor
8
.
While the disk table
7
is rotated together with the optical recording disk
1
by the spindle motor
5
, the objective lens
10
of the optical pickup
9
is moved along a reference scanning line P
1
crossing the center axis of the spindle
6
and the center axis of the objective lens
10
by the voice coil motor
8
to record information on the optical recording disk
1
or to reproduce recorded information from the optical recording disk
1
.
A cartridge holder, not shown, for holding the disk cartridge
2
in a horizontal position therein, and a main slider, not shown, for vertically translating the cartridge holder are mounted on the main chassis
3
.
As shown in
FIG. 4
, a loading motor
11
and a loading mechanism
12
that converts the rotative driving force of the loading motor
11
into linear driving force to drive the main slider for linear movement are mounted on the main chassis
3
. As shown in
FIGS. 4 and 5
, the loading motor
11
drives the loading mechanism
12
to place the disk cartridge
2
automatically on the positioning pins
4
.
The main chassis
3
is provided with a large opening
14
and a substantially rectangular frame
15
fastened to the main chassis
3
with a plurality of screws
16
screwed in the main chassis
3
from under the main chassis
3
. The spindle motor
5
and the voice coil motor
8
are fastened to the lower surface of the frame
15
with screws.
As shown in
FIGS. 5 and 6
, the spindle
6
of the spindle motor
5
is held in a vertical position for rotation at the center of the disk-shaped stator yoke
51
so as to project from the upper surface of the stator yoke. A cylindrical disk table
7
is integrally provided with a cylindrical rotor yoke
52
and mounted on the spindle
6
by press fit or the like. A chucking magnet
53
is fixedly mounted on the spindle
6
within the disk table
7
.
The stator yoke
51
is integrally provided with a substantially semicircular mounting flange
54
provided with three through holes
56
a
,
56
b
and
56
c
at its middle and opposite ends, respectively, and has a substantially semicircular unflanged part
55
.
As shown in
FIG. 5
, the upper part of the spindle motor
5
is inserted in one end of the frame
15
with the unflanged part
55
provided with the mounting flange part
54
facing the optical pickup
9
and three screws
17
a
,
17
b
and
17
c
are screwed respectively through the three through holes
56
a
,
56
b
and
56
c
in the frame
15
to fasten the mounting flange
54
to the lower surface of the frame
15
.
As shown in
FIG. 4 and 5
, the optical pickup
9
has a two-axis device
92
mounted on a carriage
91
and the objective lens
10
is mounted on top of the two-axis device
92
. Four guide rollers
94
supported on the four corners of the carriage
91
roll along a pair of horizontal, parallel guide shafts
93
a
and
93
b
so that the carriage
91
is able to move horizontally in the directions of a and b. An optical unit
95
which emits a light beam, such as a laser beam, toward the objective lens
10
and receives a light beam is disposed on one side of the optical pick up
9
farther from the spindle motor
5
.
As shown in
FIGS. 4 and 5
, the voice coil motor
8
comprises a pair of yokes
81
a
and
81
b
parallel to the pair of guide shafts
93
a
and
93
b
, magnets
82
a
and
82
b
, and coils
83
a
and
83
b
fixedly mounted respectively on the opposite ends of the carriage
91
.
The pair of guide shafts
93
a
and
93
b
and the yokes
81
a
and
81
b
are inserted in the frame
15
from under the same and fastened to the lower surface of the frame
15
with a pair of screws
18
a
and
18
b
and a pair of screws
19
a
and
19
b
. The optical unit
95
is fastened to the lower surface of the main chassis
3
and the frame
15
with a plurality of screws
20
.
A light beam emitted by the optical unit
95
toward the objective lens
10
of the optical pickup
9
is directed by the objective lens
10
so as to fall perpendicularly on the lower surface of the optical recording disk
1
, while the pair of coils
83
a
and
83
b
of the voice coil motor
8
are energized to move the carriage
91
in the direction of the arrow a or b along the pair of guide shafts
93
a
and
93
b
by the electromagnetic action of a magnetic circuit formed by the pair of coils
83
a
and
83
b
, the yokes
81
a
and
81
b
, and the magnets
82
a
and
82
b
. The light beam projected through the objective lens
10
scans the optical recording disk
1
along the reference scanning line P
1
to record information on or to reproduce recorded information from the optical recording disk
1
.
The two-axis device
92
of the optical pickup
9
moves the objective lens
10
to adjust the position of the light beam projected through the objective lens
10
for focusing and tracking.
The unflanged part
55
of the spindle motor
5
is essential to enable the carriage
91
to approach the center of the optical recording disk
1
closely in the direction of the arrow a so that the light beam projected through the objective lens
10
is able to scan the tracks near the inner circumference of the optical recording disk
1
.
Since the mounting flange
54
is formed in a substantially semicircular shape to form the unflanged part
55
, the mounting flange
54
is fastened to the frame
15
with the three screws
17
a
,
17
b
and
17
c
. Consequently, as shown in
FIG. 6
, the spindle motor
5
is liable to vibrate about a Y-axis perpendicular to a vertical Z-axis parallel to the center axis of the spindle
6
in the directions of the arrows c and d in a vertical plane including the vertical Z-axis and a horizontal X-axis, which is a center axis P
2
of vibration of the spindle motor
5
included in a horizontal plane including the Y-axis.
The vibration of the axis of the spindle motor
5
in the directions of the arrows c and d is magnified at the periphery of the optical recording disk
1
magnetically attracted to the disk table
7
.
In this known optical disk drive, the spindle motor
5
is disposed with its center axis P
2
of vibration aligned with the reference scanning line P
1
so that the unflanged part
55
of the spindle motor
5
is bisected by the reference scanning line P
1
.
The screw
17
a
fastening the middle part of the mounting flange
54
to the frame
15
is on the center axis P
2
of vibration, and the screws
17
b
and
17
c
are positioned on the Y-axis dislocated from an axis parallel to the Y-axis and crossing the center axis of the spindle
6
of the spindle motor
5
toward the optical pickup
9
by a greatest possible distance L to stabilize the spindle motor
5
on the frame
15
.
However, this known optical disk drive has the following problems.
FIGS. 7A and 7B
are analytic resonance diagrams produced through the computer ana
Bell Boyd & Lloyd LLC
Letscher George J.
Sony Corporation
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