Read/write head and magnetic recording device

Details Read/write head and magnetic recording device Read/write head and magnetic recording device

2002-01-25

2004-01-06

Holder, Regina N. (Department: 2651)

Dynamic magnetic information storage or retrieval

General recording or reproducing

Thermomagnetic recording or transducers

C360S077030

Reexamination Certificate

active

06674594

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a recording/reproducing head for recording information on magnetic media and reproducing recorded information. The invention also relates to a magnetic recording apparatus using such a recording/reproducing head.
BACKGROUND ART
In a magnetic recording apparatus which records a magnetic information mark on a code track of a magnetic recording medium by scanning the medium with a recording/reproducing head, and reproduces information by detecting with this head the magnetic field leaking from the information mark, it is necessary for the head to accurately follow up the track. In order to solve this problem, a track servo method is used in general. The track servo method involves causing a recording/reproducing head to accurately follow up a code track of a magnetic recording medium on which servo burst patterns for track servo are recorded in advance. According to this method, the reproduction of the servo burst patterns with the recording/reproducing head makes it possible to detect the offset (deviation) of the head from the code track. On the basis of the detected offset, it is possible to correct the position of the recording/reproducing head. Such track servo needs an actuator for moving the recording/reproducing head to any track and causing the head to follow up the track. In general, a rotary actuator for turning a swing arm is used. A linear actuator may alternatively be used, but the rotary actuator is used more widely because it enables the configuration of the servo system to be simpler, enabling the magnetic recording apparatus to be smaller and the cost to be lower.
FIG. 6
schematically shows a magnetic recording medium
200
and a recording/reproducing head
204
for use with a rotary actuator. The recording/reproducing head
204
is mounted on a slider
110
, which is fitted to the front end of a swing arm
133
. During track servo, the swing arm
133
pivots on the axis of the rotary actuator
201
to position the recording/reproducing head
204
on any code track of the recording medium
200
.
The prevailing recording/reproducing head is a combined recording/reproducing head, which consists of a recording magnetic head
203
for recording information and a reproducing magnetic head
202
for reproducing recorded information and management information such as addresses.
FIG. 8
schematically shows a conventional combined recording/reproducing head. As shown in
FIG. 8
, the recording/reproducing head
204
is mounted on the rear of a slider
110
, which is fitted to the front end of a swing arm
133
. The movement (rotation) of a magnetic recording medium
200
in the direction indicated by an arrow shown in
FIG. 8
forces air in under the slider
110
. The air lifts the slider
110
from the recording medium
200
. In the meantime, the swing arm
133
pushes the slider
110
toward the recording medium
200
. The lifting and pushing forces counterbalance each other, causing the slider
110
and the recording/reproducing head
204
to float at a predetermined distance from the recording medium
200
.
FIG.
9
(
a
) is an enlarged section of the recording/reproducing head
204
shown in FIG.
8
. The reproducing magnetic head
202
consists basically of magnetic shields
251
and
252
and a magnetoresistive element
253
. The recording magnetic head
203
for recording information consists basically of the magnetic shield
252
, a coil
254
and an upper magnetic pole
255
. The magnetic shield
251
is formed adjacent to a substrate during the production process and referred to as a lower magnetic shield. The other magnetic shield
252
is formed over the magnetic shield
251
and referred to as an upper magnetic shield.
The lower and upper magnetic shields
251
and
252
of the reproducing magnetic head
202
function to improve spatial resolution by absorbing magnetic fields that leak from the peripheries of the shields and that are not necessary for reproduction. Some of the leaking magnetic fields may be magnetic fields (crosstalk) leaking from the information marks recorded on the code tracks adjacent to a code track from which information is being reproduced. Others of the magnetic fields leaking from the peripheries may be magnetic fields (interference between codes) leaking from the information marks preceding and succeeding a track from which information is being reproduced. For less crosstalk and/or for easier production of the recording/reproducing head
204
, it is preferable that the shields
251
and
252
be wider than the spacing of the code tracks.
The electric resistance of the magnetoresistive element
253
of the reproducing magnetic head
202
is changed by the magnetic field leaking from a record mark recorded on the magnetic recording medium
200
. By applying a suitable bias to the magnetoresistive element
253
, it is possible to detect the existence or nonexistence of a record mark as the amplitude of an electric signal. The magnetoresistive element
253
is more sensitive than the conventional inductive heads and can detect the existence or nonexistence of an information mark. Therefore, the magnetoresistive element
253
is used widely in particular to reproduce information from magnetic recording media on which information is recorded densely. However, because the magnetoresistive element
253
can generate no magnetic field for recording, the separate recording magnetic head
203
is necessary which can generate recording magnetic fields.
The recording magnetic head
203
is basically identical in structure with the conventional inductive heads and needs a lower magnetic pole for pairing with the upper magnetic pole
255
. If a lower magnetic pole were separately provided, however, the space between the recording and reproducing heads
203
and
202
would be too large. Therefore, in many common cases, the upper magnetic shield
252
of the reproducing magnetic head
202
is shared also as the lower magnetic pole of the recording magnetic head
203
. In fact, the wider the space between the heads
203
and
202
, the larger the offset between the tracks followed up by the heads
202
and
203
. The offset is caused by the yaw angle made by the use of the rotary actuator. This problem will be explained below in detail.
With reference to
FIG. 7
, the conventional track servo method during information recording and reproduction will be described with the rotary actuator shown in
FIG. 6
, the recording/reproducing head
204
shown in
FIG. 8
, and the magnetic recording medium
200
, on which servo burst patterns
220
-
223
for track servo are recorded in advance. During track servo, as shown in
FIG. 7
, the reproducing magnetic head
202
reproduces the patterns
220
and
221
, and the position of this head
202
is controlled in such a manner that the reproduced patterns
220
and
221
are equal in amplitude. Specifically, the difference between the signals representing the reproduced patterns
220
and
221
is the basis for generating a tracking error signal
226
, which represents the offset of the reproducing magnetic head
202
from a track. The position of this magnetic head
202
is controlled in such a manner that the level of the error signal
226
is 0. Hereinafter, the “0” level of the error signal
226
will be referred to as a reproducing servo target position
224
.
The recording/reproducing head
204
is fitted to the front end of the swing arm
133
, which, as shown in
FIG. 6
, pivots on the axis of the rotary actuator
201
. Consequently, the axis of the recording/reproducing head
204
inclines at an angle of &thgr; (yaw angle) with (the line direction of) the code tracks (FIG.
7
). If this head
204
is a combined recording/reproducing head as mentioned above, the yaw angle of &thgr; causes the loci described by the reproducing and recording magnetic heads
202
and
203
to differ from each other. The yaw angle is a function of the radius of the magnetic recording medium and the space of D between the heads
202
and
203
. The larger the yaw angle or t

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