Servo information writing method and storage device

Dynamic magnetic information storage or retrieval – Monitoring or testing the progress of recording

Reexamination Certificate

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Details

C360S053000, C360S075000, C360S051000, C360S077080, C360S078140

Reexamination Certificate

active

06522488

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a servo information writing method and a storage device for recording servo information including phase servo patterns discretely in a track direction of respective data surfaces of plural media and reproducing the servo information by means of heads provided with write heads and read heads integrally, and particularly relates to a servo information writing method and a storage device which do not require correction of position signals at the time of switching the heads even if read heads displace physically.
BACKGROUND ART
Conventionally, in a magnetic disk apparatus manufacturing process, at the stage that a disk enclosure is assembled and manufactured, servo patterns are written onto data surfaces of media by a servo track writer (STW), namely, servo patterns are servo-written. In the servo write using the servo track writer, heads are moved and located in objective cylinder positions successively by a laser locating apparatus or the like from an outer side towards an inner side. Write heads of the respective heads provided correspondingly to the data surfaces in the cylinder positions are switched successively so that the servo patterns are written onto the same cylinder positions of the respective data surfaces. For this reason, the positions of the servo patterns written onto the respective data surfaces are determined by positions of the write heads of the respective heads.
In order to cope with recent large capacity and high recording density, as a recording/reproduction head to be used in a magnetic disk apparatus, a combined head, in which a write head using an inductive head and a read head using, for example, an MR head are integrated, is used. Since the write head and the read head are different from each other physically, their relative positions disperse.
FIG. 1A
shows an arrangement of a write head and a read head in a downward No.
1
head
200
which is arranged on a front data surface of a medium.
FIG. 1B
shows an arrangement of a write head and a read head in an upward No.
2
head
202
which is arranged on a rear surface of the same medium. In the No.
1
head
200
, a track center
216
of the read head
208
displaces from a track center
212
of the write head
204
towards an inner side by +D
1
. On the contrary, in the No.
2
head
202
, a track center
218
of the read head
210
displaces from a track center
214
of the write head
206
towards an outer side by −D
2
. Since the No.
1
head
200
faces downward and the No.
2
head
202
face upward, their displacement directions are opposite to each other.
FIGS. 2A and 2B
show displacement of the track centers in the case where servo patterns are recorded onto the same cylinder and read therefrom by the heads
200
and
202
shown in
FIGS. 1A and 1B
. At first, in the No.
1
head
200
in
FIG. 2A
, a phase is displaced to both sides of the track center
212
by the write head
204
and servo patterns A and
2
B of a write track width are recorded alternatively. Similarly, in the No.
2
head
202
in
FIG. 2B
, a phase is displaced to both sides of the track center
214
by the write head
206
and servo patterns A and B of a write track width are recorded alternatively. The servo patterns A and B are read by the read heads
208
and
210
having amounts −D
1
and +D
2
of displacement from the track centers
212
and
214
, and track centers which satisfy the following relationship:
(pattern A read signal)=(pattern B read signal)
are obtained. In this case, the write head
204
has a track center
220
and the write head
206
has a track center
222
, and the track centers of the respective write heads are different from each other due to the respective read heads.
Further, such heads are mounted to rotary actuators, and an offset amount is different in respective cylinder positions.
FIG. 3
shows an example of the No.
1
head
200
. In the case where the head
200
is located on a medium surface
228
by a rotary actuator
226
having a rotational center
224
, an offset is zero in a center position where a yaw angle &thgr; is zero, but the offset is large according to yaw angles &thgr;
1
and &thgr;
2
on innermost and outermost positions. The directions of the offset are opposite to each other in the outer and inner sides. For this reason, in the case where the heads are located in positions where read signals of the servo patterns A and B are equal to each other by the read heads
208
and
210
at the time of data writing as shown in
FIGS. 2A and 2B
, a condition that the read signals of the servo patterns A and B are equal to each other fails every time when the head is switched in the same cylinder position. As a result, the head should be relocated at every time of switching.
In one method to eliminate the relocating due to switching of the heads, a displacement amount of the write head and the read head in each head is previously measured, displaced position signals are offset so as to be correct position signals. For example since an offset of the No.
1
head is D
1
, the offset D
1
is added to the position signal of the track center
220
where the read signals of the servo patterns A and B are equal to each other so that the correct position signal of the track center
212
can be obtained.
Due to such offset correction of the position signal, although a value of the position signals on the track center changes every time when the heads are switched, the heads do not move physically. However, in this case, displacement amounts of the write heads and the read heads in each head and each cylinder position are stored in a memory of the magnetic disk apparatus, and the displacement amounts should be read out from the memory in each head and each cylinder and the position signals should be corrected. For this reason, in the case, for example, where a number of heads is four and each data surface has 2000 cylinders, it is necessary to store 8000 displacement amounts onto the memory, and a memory capacity of the apparatus becomes larger.
In addition, in another solving method, the servo patterns A and B are displaced to the center position of the read heads so as to be written at the time of servo write using the servo track writer (STW), and the track centers read by the read head coincide with each other in each head. For example, in the No.
1
head
200
shown in
FIG. 2A
, the write head
204
is offset to the inner side by the shift amount D
1
of the read head
208
, and the servo patterns A and B are written. Moreover, in the No.
2
head
202
shown in
FIG. 2B
, the write head
206
is offset to the outer side by the shift amount D
2
of the read head
210
, and the servo patterns A and B are written. However, in this method, the offset operation of the head is required every time when the servo patterns of each head are written, thereby requiring long time for the servo writing operation. As a result, there arises a problem that the producing efficiency is deteriorated.
DISCLOSURE OF THE INVENTION
The present invention provides a servo information writing method and a storage device which uses phase servo patterns as position information of servo information, and does not require an offset operation at the time of writing corrected servo patterns of position signals at the time of switching heads even if physical displacement occurs on respective read heads.
The present invention provides a servo information writing method of writing servo information including phase servo patterns discretely in a track direction onto data surfaces of plural media in a magnetic disk apparatus in which heads integrally having write heads and read heads are arranged correspondingly to the data surfaces of the plural media.
(Phase Servo Writing which Eliminates Displacement of Read Head)
A servo information writing method is characterized by including:
the measuring step of measuring displacement amounts D of the read heads with respect to the write heads in each head and each cylinder position on the media s

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