Disk rotating device

Details Disk rotating device Disk rotating device

1999-02-09

2002-03-05

Miller, Brian E. (Department: 2652)

Dynamic information storage or retrieval

Dynamic mechanism subsystem

Specific detail of storage medium support or motion production

C369S282000

Reexamination Certificate

active

06353591

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a disk rotating device in a disk drive on which a disk such as a CD (compact disk) or DVD (digital versatile disk) is mounted, and particularly to a disk rotating device that secures a disk, whereby a disk drive using this disk rotating device can be made thinner.
2. Description of the Related Art
Conventional disk rotating devices include the so-called movable type disk rotating device in which a hub (centering member) inserted through the center hole of a disk can move up and down, and the so-called fixed type disk rotating device in which the hub does not move.
FIG. 4
is a sectional view illustrating the structure and principle of a conventional movable type disk rotating device, and
FIG. 5
is a sectional view illustrating the structure and principle of a conventional fixed type disk rotating device.
In the movable type disk rotating device T
1
shown in
FIG. 4
, a rotating plate
1
whose circumference is made into a disc-like shape is fastened to a rotating shaft M
1
of a spindle motor M. The rotating plate
1
has a recess
1
a formed in its center. Inside of the recess
1
a
is a movable hub (centering member)
2
A energized by a coil spring S, which is mounted movably in the vertical (Z) direction. The movable hub
2
A has a cylindrical slide part
2
a
formed on its inner fringe part, and extends in the vertical (Z) direction. The slide part
2
a
slides and is guided on the circumference of the rotating shaft M
1
, so that the movable hub
2
A is verticallymoveable. The rotating shaft M
1
is provided with a stopper
3
on the end (Z
1
side) thereof, which prevents the movable hub
2
A from falling off in the Z
1
direction. The rotating plate
1
has a support plane
1
c
formed around the entire circumference thereof, which is formed slightly higher than the remaining portion of the rotating plate
1
. A disk D is mounted on the support plane
1
c.
On the other hand, in a fixed type disk rotating device T
2
shown in
FIG. 5
, a substantially disc-formed rotating plate
4
is fastened to a rotating shaft M
2
of a spindle motor M. The rotating plate
4
has a fixed hub (centering member)
2
B projecting from the center thereof. And, in the same manner as the foregoing movable type disk rotating device T
1
, the rotating plate
4
has a support plane
4
c
formed around the entire circumference thereof, on which the disk D is mounted. The foregoing fixed hub
2
B and the rotating plate
4
are formed into one body by machining or injection molding so as not to be separated from each other.
In either of the foregoing disk rotating devices, the outer circumferential planes
2
b
of the hubs (movable hub
2
A and fixed hub
2
B) are tapered. The outer circumference of the hub is inserted through the center hole D
0
of the disk D, and thereby the disk D is guided to be centered by the tapered outer circumferential plane
2
b.
Here, the inside diameter of the disk D, for example a CD (compact disk), loaded on the foregoing disk rotating device, namely the diameter of the center hole D
0
, is 15.0 mm on the specification. The diameter has the allowance on the specification which is from 0.0 through +0.1 mm. Consequently, the inside diameter is specified within the range from 15.0 mm through 15.1 mm. The foregoing specification is the ‘IEC (International Electrotechnical Communication) 908 Standard’.
The maximum outer diameter &phgr;E of the movable hub
2
A shown in
FIG. 4
is set larger than the maximum inside diameter (15.1 mm) on the specification of the normal CD. Here, the maximum outer diameter &phgr;E of the movable hub
2
A is the diameter of the movable hub
2
A on a virtual plane that includes the support plane
1
c
in the state in which the movable hub
2
A is maximally moved in the Z
1
direction (the lowering of the hub is 0).
Also, the outer diameter of the head of the movable hub
2
A is set smaller than the minimum inside diameter (15.0 mm) on the specification of the CD. Therefore, in the movable type disk rotating device T
1
, the peripheral edge of the center hole D
0
of the disk D necessarily comes into contact with the tapered outer circumferential plane
2
b
of the movable hub
2
A on some position on the outer circumferential plane
2
b.
Accordingly, the center of the center hole D
0
of the disk D coincides with the axis of the rotating shaft M
1
. In addition, a damper (not illustrated) is lowered to press the disk D in the Z
2
direction, whereby the movable hub
2
A is lowered in the Z
2
direction, and the disk D is held in a space between the damper and the support plane
1
c.
In
FIG. 4
, the lowering of the movable hub
2
A is illustrated by the symbol h.
On the other hand, in case of the fixed type disk rotating device T
2
, the maximum outer diameter &phgr;F of the fixed hub
2
B is set slightly smaller than the minimum inside diameter (15.0 mm) on the specification of the center hole D
0
of the disk D, which is about 14.98 mm, for example. Accordingly, all the disks D of which diameters of the center holes D
0
are within the foregoing specification can be mounted on the rotating plate
4
, with the fixed hub
2
B completely inserted through the center holes D
0
of the disks D.
Here, the maximum outer diameter &phgr;F of the fixed hub
2
B is the diameter of the outer circumferential plane
2
b
of the fixed hub
2
B, which is on a virtual plane that includes the support plane
4
c.
However, both the foregoing rotating disk devices are intended for CDs. Accordingly, when they are used in a disk drive that can both record and reproduce data to and from disks in which data are recorded with high density, such as a DVD (digital versatile disk), they have the following problems.
FIG. 6
illustrates a distribution chart of inside diameter errors of DVDs, in which the horizontal axis indicates the diameter &phgr;D of the center hole of a DVD and the vertical axis indicates the distribution frequency. A DVD is made of two sheets of laminated discs. From the specification (DVD format), the inside diameter of an individual disc before lamination is 15.00 mm to 15.15 mm, and the inside diameter of a disk after lamination is defined as 15.00 at minimum. That is, the minimum value Dmin of the inside diameter &phgr;D on the DVD specification is 15.00 mm, and the maximum value Dmax is 15.15 mm.
In the conventional movable disk rotating device T
1
, the peripheral edges of the center holes D
0
of all the disks D are made to come into contact with the outer circumferential plane
2
b
of the movable hub
2
A. Therefore, the maximum outer diameter &phgr;E of the movable hub
2
A is needed to be set more than the maximum value Dmax of the diameters &phgr;D of the center holes D
0
of all the disks D as shown in FIG.
6
.
Assuming that the inside diameter of the disk D actually loaded as shown in
FIG. 4
is &phgr;D
1
, the difference of the inside diameter between the maximum outer diameter &phgr;E and the inside diameter of the disk D actually loaded is &phgr;E−&phgr;D
1
, which is a value indicated by the symbol &dgr;
1
in FIG.
6
. Further, the maximum difference of the inside diameter &dgr; 1max is given when the inside diameter &phgr;D
1
of the disk D is Dmin (&phgr;D
1
=&phgr;Dmin), and it is expressed by &dgr; 1max=(&phgr;E−&phgr;Dmin). And, the minimum difference of the inside diameter &dgr; 1min is given when &phgr;D
1
is equal to Dmax, which is expressed by &dgr; 1min=(&phgr;E−&phgr;Dmax). And, as the inside diameter &phgr;D
1
becomes smaller, namely, as the difference of the inside diameter &dgr; 1 (=&phgr;E−&phgr;D
1
) becomes larger, the center hole D
0
of the disk D comes in contact with the outer circumferential plane
2
b
at a position closer to the head of the movable hub
2
A. That is, the lowering h of the disk D to the support plane
1
c
of the rotating plate
1
becomes larger. Accordingly, the lowering h is determined by the difference of the inside diameter &dgr;

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