Dynamic magnetic information storage or retrieval – Record transport with head stationary during transducing – Disk record
Reexamination Certificate
1998-09-24
2001-01-30
Ometz, David L. (Department: 2754)
Dynamic magnetic information storage or retrieval
Record transport with head stationary during transducing
Disk record
Reexamination Certificate
active
06181512
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a disk drive for driving a disk-shaped recording medium, such as a floppy disk, and, more specifically, to a disk drive provided with a turntable capable of centering the central hub of a disk mounted thereon.
2. Description of the Related Art
A floppy disk has a flexible disk, i.e., a flexible magnetic recording medium, provided with a central metal hub. The metal hub is provided with a center hole and a drive hole. A disk drive for driving the disk for rotation is provided with a turntable provided with a magnet for attracting the metal hub of the disk, a center shaft projecting from the support surface of the turntable, and a drive pin supported on a plate spring or a swing arm so as to be able to project from the support surface of the turntable.
When a floppy disk is loaded into the disk drive, the center hole of the hub receives the center shaft of the disk drive, and the drive pin plunges into the drive hole immediately after the turntable has started rotation. Subsequently, a centering operation is executed to position the hub correctly on the turntable. During the centering operation, the center shaft comes into contact with the edge of the center hole from one direction and the drive pin comes into contact with the edge of the drive hole from the opposite direction as the turntable rotates, and the hub slides slightly on the support surface of the turntable.
In this centering operation, the hub comes into close contact with the support surface of the turntable upon the entrance of the drive pin into the drive hole of the hub, and is attracted by a large force by magnetic attraction. The hub must be caused to slide on the turntable against the magnetic attraction to bring the center shaft and the drive pin into contact with the edges of the center hole and the drive hole, respectively. This centering operation nips the flexible disk between magnetic heads to move the hub relative to the turntable.
If the magnetic heads are unable to exert sufficient pressure to the disk, the hub cannot be moved on the turntable and the centering operation cannot successfully be achieved. In a disk drive for driving the disk of a high-capacity floppy disk for rotation at several thousands revolutions per minutes, the moving speed of the magnetic heads relative to the disk is very high. Therefore, the magnetic heads cannot be pressed by a high pressure to the disk in view of suppressing the abrasion of the magnetic heads. In a disk drive which drives a disk for rotation at 2400 rpm, pressure exerted by the magnetic head on the disk is on the order of ten and some gram force or several gram force so that the magnetic heads will exert a very low resistance, i.e., torque, on the disk. Accordingly, this disk drive is unable to achieve a reliable centering operation for centering the hub on the turntable.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a disk drive capable of positioning the hub of a disk in a high accuracy on a turntable without increasing torque that may be exerted on the disk by magnetic heads.
According to one aspect of the present invention, a disk drive for driving a floppy disk having a disk provided with a center hub provided with a center hole and a drive hole comprises: a turntable capable of exerting magnetic attraction on the hub of the disk to attract the hub to a support surface thereof and having a center shaft projecting from the support surface thereof so as to be inserted in the center hole of the hub when the disk is placed on the support surface; and a drive pin supported so as to be projected from the support surface of the turntable and inserted in the drive hole of the hub when the disk is placed on the support surface. In this disk drive, an angular acceleration at which the hub is accelerated by the rotating turntable and the magnetic attraction are determined so that inertia couple generated by the agency of the angular acceleration of the hub rotated by the turntable and the inertial moment of a rotating body including the hub or their components exerted on the hub supported on the turntable by the center shaft and the drive pin at points of contact of the center shaft and the drive pin with the hub are greater than a frictional force acting between the support surface of the turntable and the hub magnetically attracted to the support surface, and the edge of the center hole of the hub is brought into contact with the center shaft from one direction and the edge of the drive hole of the hub is brought into contact with the drive pin from the other direction by the inertia couple or their components.
The inertia couple are exerted on the hub fitted on the center shaft and the drive pin at the points of contact between the edges of the center hole and the drive hole of the hub, and the center shaft and the drive pin by the agency of the angular acceleration of the hub immediately after the turntable has started rotating and the inertial moment of the rotating body, and the inertia couple are used for moving the hub on the turntable for centering. Since the torque need not be exerted on the disk by magnetic heads for centering, the hub can be positioned in a high accuracy on the turntable immediately after the start of rotation of the turntable even if the magnetic heads are pressed by a low pressure against the disk of a high-capacity floppy disk or even at a stage before the magnetic heads are brought into contact with the disk. For example, the following expression is satisfied.
Fg
·
μ
<
I
·
2
π
·
m
L
·
t
(
1
)
where the left side (Fg·&mgr;) expresses frictional force and the right side expresses inertia couple, Fg is attraction acting on the hub, &mgr; is the coefficient of static friction between the hub and the support surface, the right side expresses inertia couple, I is the moment of inertia of the rotating body including the hub, m is an increment of rotating speed in time t, and L is the center distance between the center shaft and the drive pin.
If the inertia couple acting on the hub exceed the frictional force, the hub can be slid for centering on the turntable without using torque which can be applied to the disk by the magnetic heads. Conditions meeting Expression (1) are effective in centering a hub as shown in FIG.
2
. In
FIG. 2
, centering forces for bringing the edges of a center hole and a drive hole formed in the hub into contact with the center shaft and the drive pin are substantially equal to inertia couple F
1
. When the inertia couple F
1
are greater than the frictional force, the hub can be slid for centering relative to the support surface of the turntable by the centering forces F
1
.
If a centering force Fc is a components of the inertia couple F
1
and is smaller than F
1
as shown in
FIG. 4A
, a reduction of the centering force by the component of the inertia couple F may be taken into consideration when determining the inertia couple F
1
and the frictional force.
Time for which the angular velocity of the hub is changed at the angular acceleration is longer than a time interval between a moment when the drive pin comes into contact with a forward part of the edge of the drive hole and a moment hen the edge of the center hole is brought into contact with the center shaft by the inertia couple.
If the drive hole has the shape of a slot extending in the direction of rotation of the hub as shown in
FIG. 3
, the start of acceleration of the hub and duration of acceleration of the hub may be determined so that the drive pin moves in the drive hole, and the centering operation is carried out after the drive pin has come into contact with the edge of the drive hole.
REFERENCES:
patent: 4825314 (1989-04-01), Maekawa et al.
patent: 5010427 (1991-04-01), Taguchi et al.
patent: 5072321 (1991-12-01), Kanai et al.
patent: 5183350 (1993-02-01), Kramer
patent: 5274519 (1993-12-01), Saito et al.
patent: 5432352 (1995-07-01), van Bavel
patent: 55
Furuki Shigeru
Masuda Atsushi
Alps Electric Co. ,Ltd.
Altman Franklin D.
Brinks Hofer Gilson & Lione
Ometz David L.
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