Dynamic magnetic information storage or retrieval – Head mounting – For adjusting head position
Reexamination Certificate
2001-01-19
2003-02-04
Korzuch, William (Department: 2653)
Dynamic magnetic information storage or retrieval
Head mounting
For adjusting head position
Reexamination Certificate
active
06515835
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a piezoelectric actuator for precisely positioning an object, to a piezoelectric actuator for precisely positioning a thin-film magnetic head element used in a magnetic hard disk drive (HDD) and to a head gimbal assembly (HGA) with the precise positioning actuator.
DESCRIPTION OF THE RELATED ART
In the magnetic HDD, thin-film magnetic head elements for writing magnetic information into and/or reading magnetic information from magnetic disks are in general formed on magnetic head sliders flying in operation above the rotating magnetic disks. The sliders are supported by suspensions of the HGAs at their top end sections.
Recently, recording and reproducing density along the radial direction or track width direction in the magnetic disk (track density) rapidly increase to satisfy the requirement for ever increasing data storage capacities and densities in today's HDDs.
For advancing the track density, the position control of the magnetic head element with respect to the track in the magnetic disk by only a voice coil motor (VCM) has never presented enough accuracy. In order to solve this problem, another actuator is additionally mounted at a position nearer to the magnetic head slider than the VCM so as to perform fine precise positioning that cannot be realized by the VCK only. These techniques for realizing precise positioning of the magnetic head are described in for example U.S. Pat. No. 5,745,319 and Japanese unexamined patent publication No. 08180623A.
A typical structure of a conventional piezoelectric precise positioning actuator as the another actuator is shown in FIG.
1
. This actuator called as a bimorph piezoelectric actuator has a metal plate or common electrode
12
sandwiched and adhered between two piezoelectric blocks
10
and
11
, and drive electrodes
13
and
14
adhered to outer surfaces of the piezoelectric blocks
10
and
11
, respectively. When electrical fields directed to opposite directions with each other are produced in the piezoelectric blocks
10
and
11
by respectively applying voltages with opposite phases between the drive electrode
13
and the common electrode
12
and between the drive electrode
14
and the Common electrode
12
, these blocks
10
and
11
will expand and contract, respectively, causing the actuator to bend in a direction perpendicular to the electrodes.
However, this bimorph piezoelectric actuator can be formed only in a simply shaped single layer structure as shown in FIG.
1
. Namely, it is very difficult to realize a piggyback bimorph multi-layered actuator with a shape of a tuning fork due to its complicated shape, weak mechanical strength depending upon the stacked direction and complicated layout of external electrodes.
Japanese examined patent publication No. 10225146A discloses a unimorph piezoelectric actuator with piezoelectric ceramics layers stacked on a non-piezoelectric bottom ad. The thicknesses of the respective stacked piezoelectric ceramics layers are gradually thinned in order outward from the bottom layer, the piezoelectric constants d
u
of the respective stacked ceramics are gradually increased in order outward from the bottom layer, or the voltages applied to the respective stacked ceramics layers are gradually increased in order outward from the bottom layer so that the stacked ceramics layers bend toward the stacked direction.
However, since this bimorph piezoelectric actuator has to a stack piezoelectric ceramics layers with gradually differed thicknesses, gradually differ ed piezoelectric constants d
u
or gradually differed applied voltages, not only the structure increases in complexity but also the manufacturing process becomes very complicated.
The assignee of the instant application has already proposed a piggyback unimorph actuator shown in FIG.
2
. This piggyback actuator has two fixing parts
20
and
21
at its end sections and two rod shaped beam parts
22
and
23
arranged in parallel for coupling these fixing parts
20
and
21
. An air gap
24
is formed between these beam parts
22
and
23
. The fixing parts
20
and
21
have a larger width than that of the beam parts
22
and
23
so that sufficient fixing force can be ensured. Thus, the actuator is formed ion a tuning fork shape. The actuator has a stacked structure fabricated by alternately stacking one piezoelectric layer with a common electrode formed thereon and another piezoelectric layer with a drive electrode formed thereon. By applying voltages with the reversed phase across the drive electrode and the common electrode of the beam part
22
and across the drive electrode and the common electrode of the beam part
23
, these beam parts will expand and contract, respectively, causing the actuator to bend in a plane of the electrodes.
However, since the air gap
24
between the beam parts
22
and
23
in this piggyback unimorph actuator shown in
FIG. 2
is very narrow as about 50 &mgr;m for example, it is necessary to use an expensive microfabrication process such as a powder-beam etching process which utilizes very fine grains for fabricating the actuator causing the manufacturing cost to greatly increase. Also, since there is a limit in fabrication of the narrower air gap, a larger bending amount or a larger stroke of displacement of the actuator cannot be expected. In addition, such air gap will remarkably reduce the shock resistance of the actuator itself.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an actuator for precisely positioning an object, an actuator for precisely positioning a thin-film magnetic head element and a HGA with the precise positioning actuator, whereby simple structure and easy manufacture of the actuator can be expected.
Another object of the present invention is to provide an actuator for precisely positioning an object, an actuator for precisely positioning a thin-film magnetic head element and a HGA with the precise positioning actuator, whereby high shock resistance of the actuator can be expected.
Further object of the present invention is to provide an actuator for precisely positioning an object, an actuator for precisely positioning a thin-film magnetic head element and a HGA with the precise positioning actuator, whereby stroke of displacement can be easily controlled and large stroke of displacement can be expected.
According to the present invention, an actuator for precisely positioning an object to be positioned is provided. This actuator is fixed between the object and a support member and has a displacement generation part. The displacement part includes a solid piezoelectric material member, a common electrode formed on one surface of the piezoelectric material member to cover substantially whole of the one surface, and first and second electrodes formed on the other surface opposite to the one surface, of the piezoelectric material member to superimpose to the common electrode. The first and second electrodes have side edges facing with each other via a uniform width space, respectively.
Also, according to the present invention, an actuator for precisely positioning at least one thin-film magnetic head element to be positioned is provided. This actuator is fixed between a magnetic head slider with the at least one thin-film magnetic head element and a support member and has a displacement generation part. The displacement part includes a solid piezoelectric material member, a common electrode formed on one surface of the piezoelectric material member to cover substantially whole of the one surface, and first and second electrodes formed on the other surface opposite to the one surface, of the piezoelectric material member to superimpose to the common electrode. The first and second electrodes have side edges facing with each other via a uniform width space, respectively.
Furthermore, the present invention provides a HGA including a magnetic head slider with at least one thin-film magnetic head element, an actuator fixed to the magnetic head slider for performing precise
Ezaki Joichiro
Honda Takashi
Blouin Mark
Burns Doane Swecker & Mathis L.L.P.
Korzuch William
TDK Corporation
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