Read/write head including displacement generating means that...

Details Read/write head including displacement generating means that... Read/write head including displacement generating means that...

1998-09-24

2001-06-12

Davis, David (Department: 2652)

Dynamic magnetic information storage or retrieval

Head mounting

For adjusting head position

Reexamination Certificate

active

06246552

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a read/write head, a read/write head positioning mechanism, and a read/write system such as a magnetic or optical disk drive.
DISCUSSION OF THE BACKGROUND
FIG. 32
is a plan schematic illustrative of a flying type magnetic head and a positioning mechanism therefor used in a conventional magnetic or hard disk drive (HDD).
As shown in
FIG. 32
, the magnetic head is built up of a slider
2
having an electromagnetic transducer element
1
, and a suspension
3
for supporting the slider
2
. For the purpose of simplification, interconnecting lines to make electric connections between the electromagnetic transducer element
1
and a signal processing circuit in the hard disk drive for the transmission of read/write signals are not illustrated.
A VCM (voice coil motor)
5
is used in an actuator for magnetic head positioning. The VCM
5
is built up of a coil
51
, a permanent magnet
52
, a bearing
53
and an arm
54
. The arm
54
is provided with the coil
51
at one end and with the suspension
3
of the magnetic head at the other end. It is noted that, although not illustrated, another permanent magnet is provided on the coil
51
.
The electromagnetic transducer element
1
comprises a magnetic pole and coil for converting electric signals to magnetic signals, and vice versa, and a magnetoresistance effect element for transforming magnetic signals into a voltage change, etc., each being fabricated by thin film techniques, assembly techniques, etc. The slider
2
is formed of non-magnetic ceramics such as Al
2
O
3
—TiC or CaTiO
3
or a magnetic material such as ferrite, and has a generally cuboidal shape. The surface (air bearing surface) of the slider
2
opposite to a disk medium
6
is processed into a shape suitable for generating pressure to fly the slider
2
on the disk medium
6
at a small spacing. The suspension
3
is formed by bending, punching or otherwise processing a resilient stainless sheet.
Then, an account is given of the recording, and reproducing operations of the magnetic head. The disk medium
6
rotates at high speed, e.g., several thousand rpm, and so an amount of air enters between the disk medium
6
and the slider
2
to apply flying force on the slider
2
. On the other hand, the slider
2
is pressed by the suspension
3
toward the disk medium
6
under a given load, so that the slider
2
is filed on the disk medium
6
at a small spacing on the basis of a flying force vs. pressure relation.
The magnetic head is connected to the VCM
5
, and so is movable in the radial direction of the disk medium
6
by its swing motion around the bearing
53
, allowing positioning control of the electromagnetic transducer element
1
, i.e., seek control for moving the element
1
onto any read/write track, and read/write track-following control.
For positioning control of the electromagnetic transducer element
1
, the electromagnetic transducer element
1
first detects a track position signal recorded in the disk medium
6
. Then, the signal is operated in a head positioning control circuit
7
so that a given current is passed through the coil
51
in the VCM
5
via an amplifier
8
to control force generated between the coil
51
and the permanent magnet
52
. Upon positioned on the target track, the electromagnetic transducer element
1
writes and reads magnetic signals in and from the disk medium
6
.
As mentioned above, it has so far been general to use a voice coil motor as magnetic head positioning means.
A problem with a magnetic disk drive is a track misregistration that is an offset between the magnetic head and the recording tracks caused by vibrations of the disk medium surface in synchronism or a synchronism with the rotation of the disk medium, eccentricity of the disk medium, thermal expansion and extraneous vibrations of the magnetic disk drive including the magnetic head and disk medium, etc. This track misregistration leads to problem, for instance, erasion upon recording of signal information stored in adjacent tracks due to overwriting, a drop upon reproduction of the level of signals outputted from the track concerned, and a quality drop of output signals due to the entrance of signals from adjacent tracks in the form of crosstalk noises.
For read/write purposes, it is thus required to allow the position of the electromagnetic transducer element in the magnetic head to follow a given recording track on the disk medium precisely and rapidly.
A grave problem attendant to the conventional magnetic disk drive is, however, that there is a limit in positioning precision, especially recording track-following precision due to the swing motion of the whole of a massive structure comprising the magnetic head, arm and coil, the movement of the slider via the resilient suspension, and the fact that the bearing providing the center of the swing motion has in itself friction resistance, eccentricity, and so on.
On the other hand, a magnetic disk drive is increasingly required to have ever-higher recording density, and so have ever-higher track density and ever-narrower track width and, with this, it is required to make magnetic head positioning precision ever-higher. So far, a positioning control bandwidth is up to about 500 Hz and positioning precision is about 0.3 &mgr;m. As the recording track width becomes as narrow as about 1 &mgr;m, however, it is required that the control bandwidth be extended to a few kHz and the positioning precision be on the order of about 0.1 &mgr;m or less. For these reasons, the problems associated with a conventional magnetic head positioning mechanism become even more troublesome.
The flying height of the magnetic head is generally within the range of about 50 nm to about 100 nm. As the read/write track pitch becomes as narrow as about 1 &mgr;m while such a flying height is maintained, however, several problems arise, for instance, erasion upon recording of signal information stored in adjacent tracks due to a recording magnetic field leakage, and an S/N degradation upon reproduction due to a drop of signal level absolute output. To maintain stable read/write characteristics, it is therefore required to reduce the flying height of the magnetic head with respect to the disk medium to 50 nm or lower. As the flying height decreases, however, it is required to more severely control the flying characteristics (fluctuations in the flying height) of the magnetic head upon seek control or read/write track-following control, and the smoothness of the disk medium.
In recent years a magnetic head called a pseudo-contact type magnetic head having a very small flying height or a contact type head that is always in contact with a disk medium, too, is under development. For these magnetic heads taking aim at achieving much higher recording densities, it is very difficult to conduct seek control or read/write track-following control.
For one approach to improving magnetic head positioning precision, it has been proposed to provide a magnetic head mounting arm or supporting spring (suspension) with a micro-displacement actuator such as a piezoelectric element (see JP-A's 5-28670 and 5-47216). With this approach some improvement may be introduced in the magnetic head positioning precision. However, this approach, too, is unavoidably affected by vibrations of the suspension because the slider is driven via the suspension having resiliency as in the case of the aforesaid VCM positioning mechanism. Thus there is a limit in positioning precision improvements.
For slider displacement, it has also been put forward to use an electrostatic force microactuator (“Magnetic Recording Head Positioning at Very High Track Densities Using a Microactuator-Based, Two-Stage Servo System”, IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, Vol. 42, No. 3, pp. 222-233, June 1995) or an electromagnetic force microactuator (“Silicon Microstructures and Microactuators for Compact Computer Disk Drives”, IEEE CONTROL SYSTEMS, pp. 52-57, December 1994). However, it is found that with the electrostatic forc

Affiliated with

Also associated with

Rating

Read/write head including displacement generating means that... does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Read/write head including displacement generating means that..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Read/write head including displacement generating means that... will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2503654