Dynamic magnetic information storage or retrieval – Head mounting – For adjusting head position
Reexamination Certificate
1999-06-04
2002-07-23
Klimowicz, William (Department: 2652)
Dynamic magnetic information storage or retrieval
Head mounting
For adjusting head position
C310S309000
Reexamination Certificate
active
06424504
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a microactuator, a magnetic head device, and a magnetic recording apparatus, and more particularly, to the structure of a microactuator that is incorporated in a magnetic head device and that is suitable for use in finely adjusting the position of a magnetic head when the magnetic head is precisely positioned over a track on a magnetic recording medium.
2. Description of the Related Art
A typical magnetic recording apparatus includes a magnetic recording medium having a data recording surface, such as a magnetic disk, and comprises a magnetic head for writing on and reading information from the magnetic recording medium, a head support section for supporting the magnetic head, including a slider, a gimbal, and the like, a head driving section, such as a voice coil motor, for driving the support section to position the magnetic head with respect to a predetermined track on the magnetic recording medium, and the like. Even when the voice coil motor operation is very precise, however, the positioning of the magnetic head only by the voice coil motor limits positional accuracy, especially for finer track widths. Accordingly, a method has been proposed in which the head position is finely adjusted by using a precise actuator after coarse adjustment by a voice coil motor.
FIGS. 25 and 26
show an example of a conventional high-precision actuator that is capable of micromovement. An actuator
101
shown in
FIGS. 25 and 26
uses electrostatic attractive force as the driving force, and is generically referred to as an “electrostatic actuator”. In the electrostatic actuator
101
, two substrates, a first substrate
102
and a second substrate
103
, are spaced opposed to each other so as to allow relative motion. A first comb-like electrode
104
having a plurality of parallel teeth
104
a
is formed on a surface
102
a
of the first substrate
102
facing the second substrate
103
, and a second electrode
105
having a plurality of parallel teeth
105
a
, which are placed between the adjoining teeth
104
a
of the first electrode
104
, is formed on a surface
103
a
of the second substrate
103
facing the first substrate
102
.
In the electrostatic actuator
101
having the above-described configuration, when voltage is applied between the first electrode
104
and the second electrode
105
, electrostatic attractive force is generated therebetween, and causes the first substrate
102
and the second substrate
103
to move relative to each other so that the first electrode
104
and the second electrode
105
approach in a direction such that the degree of engagement increases between the first electrode teeth
104
a
and the second electrode teeth
105
a
. After that, when the voltage is cut off, since the electrostatic attractive force disappears, the first substrate
102
and the second substrate
103
move relative to each other so that the first electrode
104
and the second electrode
105
separate in the direction opposite from that at the time of voltage application, that is, in a direction such that the degree of engagement decreases between the first electrode teeth
104
a
and the second electrode teeth
105
a.
As described above, the electrostatic actuator is driven by electrostatic attractive force generated between two substrates. A detailed description will be now given of the electrostatic attractive force between the substrates. It is believed that a force F
1
acts to increase the area of the opposing portions of the faces of the first electrode and the second electrode in parallel to the direction of relative motion between the substrates when voltage is applied, and that a force F
2
acts so that approaching and separating faces of the first electrode and the second electrode attract each other when voltage is applied. An electrostatic attractive force F serving as the driving force is the resultant of F
1
and F
2
. The forces F
1
and F
2
are given by the following expressions, respectively:
F
1
=(&egr;
0
·V
2
·t)/g
1
(1)
F
2
=(&egr;
0
·V
2
·S)/g
2
2
(2)
where &egr;
0
is the dielectric constant of a vacuum, g
1
is the distance between the faces of the electrodes in parallel with the direction of relative motion between the substrates, t is the electrode thickness, S is the area of the approaching and separating faces of the electrodes, and g
2
is the distance between the approaching and separating face of the electrodes.
In a case in which the first electrode and the second electrode are placed somewhat apart from each other, F
1
is generally dominant because F
2
significantly decreases.
When it is assumed that the driving force F is equal to F, the dielectric constant &egr;
0
of a vacuum and the electrode thickness t are constant, and the distance g
1
between the faces of the electrodes parallel to the direction of relative motion between the substrates remains constant even when the electrodes move relative to each other. Therefore, the driving force F varies only according to the voltage V between the electrodes. For example, when this electrostatic actuator is adopted in a magnetic head device to finely adjust the head position, the substrate moving distance is controlled by controlling the driving force through the adjustment of the voltage between the electrodes. Therefore, it is necessary to previously take into consideration the relationship between the voltage and the driving force and the relationship between the driving force and the moving distance in individual actuators. Furthermore, there is a need for a system for controlling the substrate moving distance, including a voltage adjustment mechanism, which is relatively complicated. In particular, a conventional device requires a complicated moving distance control system in order to achieve stepwise micromovement, and there has been a demand for an electrostatic actuator that can simplify such a control system.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above problems, and it is accordingly an object of the present invention to provide an electrostatic microactuator that can simplify a system for controlling the moving distance, compared with the conventional microactuator, and a magnetic head device and a magnetic recording apparatus using the microactuator.
In order to achieve the above object, according to an aspect of the present invention, there is provided a microactuator wherein opposing substrates are spaced so as to move relative to each other, and a plurality of actuators for providing different distances of relative motion between the substrates are arranged between the substrates at predetermined intervals in the direction of relative motion between the substrates.
Although microactuators having a plurality of actuators to produce a strong driving force have been known hitherto, the actuators provide the same relative moving distance, and a complicated system is needed to control the relative moving distance. In contrast, since a plurality of actuators, which provide different relative moving distances are arranged between the opposing substrates in the microactuator of the present invention, only the actuator that provides a required relative moving distance can be operated, which makes it possible to change the relative moving distance of the substrates in a stepwise manner without using any complicated control system.
In a specific structure in which a plurality of actuators are provided to provide different relative moving distances, each of the actuators comprises a first comb-like electrode formed on the opposing face of the first substrate, and having a plurality of parallel teeth aligned at the leading ends thereof; and a second electrode formed on the opposing face of the second substrate, and having a plurality of parallel teeth aligned at the leading ends thereof so as to be placed between the adjoining teeth of the first electrode and to extend outside the leading ends of the teeth of the first electrode in
Abe Munemitsu
Esashi Masayoshi
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Klimowicz William
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