Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Reexamination Certificate
1998-12-10
2001-10-23
Sniezek, Andrew L. (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
C360S078040, C360S078110
Reexamination Certificate
active
06307702
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method of writing tracks on a magnetic disc with signals for positioning a magnetic writing/reading head, which is included in a magnetic disc drive unit, and a device for executing said method.
These days, recording density of magnetic discs have been higher and higher, so the servo tracks must be correctly written thereon. The servo tracks are usually written in manufacturing factories, so time of writing the servo tracks must be shorter so as to improve manufacturing efficiency.
Usually, a plurality of the magnetic discs are accommodated in the magnetic disc drive unit and they are coaxially fixed to a spindle. In each magnetic disc, a plurality of servo tracks are coaxially written like concentric circles, and the signals for positioning the magnetic head are written on the servo tracks. In a factory, the magnetic disc drive unit is assembled and the servo tracks are written on the magnetic discs, by a device for writing the servo tracks, before the magnetic discs are tightly accommodated in the magnetic disc drive unit.
A basic structure of the magnetic disc drive unit will be explained with reference to FIG.
13
.
The magnetic disc drive unit
50
comprises: the magnetic discs
52
, which are rotated; the magnetic heads
54
for writing data on and reading data from the magnetic discs
52
; and an inner actuator
56
, which moves the magnetic heads
54
in substantially radial direction of the magnetic discs
52
.
Next, a conventional device
58
for writing the servo track on the magnetic discs
52
of the magnetic disc drive unit
50
will be explained.
An external actuator
60
is provided outside of the magnetic disc drive unit
50
. The external actuator
60
is capable of moving along a moving track of the inner actuator
56
.
The external actuator
60
includes a displacement sensor
62
, which is capable of detecting amount X
1
of displacement between the external actuator
60
and the inner actuator
56
. To detect the amount X
1
of the displacement without touching, an optical reflector
64
, e.g., a cylindrical mirror, for example, is attached to the inner actuator
56
; the displacement sensor
62
is an optical sensor, which is capable of emitting light to the optical reflector
64
and receiving the reflected light therefrom, so that it detects the amount of displacement between the optical reflector
64
and the displacement sensor
62
.
With this structure, the displacement sensor
62
is capable of detecting the amount of displacement between the optical reflector
64
and the displacement sensor
62
, and the detected amount of the displacement is the amount X
1
of the displacement between the external actuator
60
and the inner actuator
56
.
The device further has: a position sensor
66
detecting a present position Y of the external actuator
60
; a destination setting section setting a travel destination Y
0
, at which the inner actuator
56
is located when the magnetic heads
54
are located at object positions; and a first control section
70
moving the external actuator
60
to the travel destination Y
0
by checking deviation X
3
between the present position Y of the external actuator
60
, which is detected by the position sensor
66
, and the travel destination Y
0
, and controlling the movement of the external actuator
60
to maintain the deviation X
3
within a predetermined range A. A non-touch type optical sensor, for example, is employed as the position sensor
66
as well as the displacement sensor
62
, and the position sensor
66
comprises: an optical reflector
66
b
attached to the external actuator
60
; and an optical sensing member
66
a
capable of emitting light to the optical reflector
66
b
and receiving the reflected light therefrom to measure distance to the optical reflector
66
b
as amount of moving the external actuator
60
, e.g., rotational angle.
In the conventional device, voice coil motors are employed in the inner actuator
56
and the external actuator
60
as one example. Actuator arms
56
a
and
60
a
are respectively provided to the actuators
56
and
60
to move the magnetic heads
54
and the displacement sensor
62
in substantially radial direction of the magnetic discs
52
, and the arms
56
a
and
60
a
are capable of rotating about a common axis L. With this structure, the external actuator
60
is capable of moving along a moving track (an arc-shaped track) of the inner actuator
56
. The reflector
64
and the displacement sensor
62
are respectively attached to the actuator arms
56
a
and
60
a
with the same distance from the axis L, so the reflector
64
and the displacement sensor
62
are capable of moving on the same circular track around the axis L. The voice coil motor
60
b
is provided in the external actuator
60
to rotate the actuator arm
60
a.
A second control section
72
controls the inner actuator
56
to make the amount X
1
of displacement equal to a predetermined value B. Concretely, a predetermined range (an allowable error range) &lgr; is previously set, and the second control section judges the amount of the displacement is equal to the predetermined value B if &lgr;≧|X
1
−B|. On the other hand, the second control section judges the amount X
1
of the displacement is not equal to the predetermined value B if &lgr;<|X
1
−B|. In the case of &lgr;=0, the second control section
72
controls the inner actuator
56
to follow the movement of the external actuator
60
so as to satisfy the formula &lgr;≧|X
1
−B|. The predetermined value B is inputted to the second control section
72
by a setting section
74
.
In the conventional device, the first and the second control sections
70
and
72
include: a first adjusting unit
76
and a second adjusting unit
78
, each of which outputs signals corresponding to difference between two inputted signals; and a first amplifier
80
and a second amplifier
82
, which amplify the output signals of the adjusting units
76
and
78
and which output first signals and second signals for driving the inner actuator
56
and the external actuator
60
.
With above described structure, the first control section
70
moves the external actuator
60
to and positions the same at the travel destination Y
0
by inputting the travel destination Y
0
in the destination setting section
68
of the servo track writing device
58
.
Then the inner actuator
56
is controlled to follow the external actuator
60
and positioned at the travel destination Y
0
.
The action will be described in detail with reference to FIG.
14
. The travel destination Y
0
is inputted (Step
100
); the position sensor
66
always detects the present position Y of the external actuator
60
(Step
102
); the deviation X
3
between the travel destination Y
0
and the present position Y, i.e., X
3
=Y
0
−Y, is detected; and the absolute value of the deviation X
3
is checked to determine if it is in the predetermined range A or not (Step
104
).
If the absolute value of the deviation X
3
is not in the standard range A, the external actuator
60
is moved toward the travel destination Y
0
(Step
102
), and the step flow returns to Step
102
. By repeating Steps
102
-
106
, the absolute value of the deviation X
3
(=|Y
0
−Y|) is gradually reduced. When the value is in the standard range A, the external actuator
60
is judged to reach the travel destination Y
0
, and the step flow returns to Step
102
without moving the external actuator
60
.
The action will be explained in detail with reference to FIG.
15
. The displacement sensor
62
inputs the amount X
1
of the displacement between the inner actuator
56
and the external actuator
60
, i.e., the displacement between the displacement sensor
62
and the optical reflector
64
(Step
200
). Then the amount X
1
of the displacement is compared with the predetermined value B to judge if the deviation |X
1
−B| is withi
Fukushi Masanori
Nagai Tetsuya
Fujitsu Limited
Greer, Burns & Crain,Ltd.
Sniezek Andrew L.
Wong K.
LandOfFree
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