Dynamic magnetic information storage or retrieval – Head mounting – For adjusting head position
Reexamination Certificate
2003-05-08
2004-04-13
Tupper, Robert S. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head mounting
For adjusting head position
C310S311000
Reexamination Certificate
active
06721136
ABSTRACT:
BACKGROUND OF THE INVENTION
i) Field of the Invention
The present invention relates to a piezoelectric actuator, and an information storage apparatus in which the piezoelectric actuator is used.
ii) Description of Related Art
As an information storage apparatus built in or connected to electronic apparatuses such as a personal computer and a word processor, a hard disk drive has been heretofore known. The hard disk drive is generally provided with a disk as an information storage medium, and a head for reading/writing a recording bit with respect to the disk, and is also provided with an arm for holding the head in the vicinity of the disk, and an electromagnetic actuator for driving the arm to move the head along the disk.
A recording density of the hard disk drive has increased with development of the personal computer or the like, and particularly in recent years, has rapidly increased with an increasing demand for handling of image or music with the personal computer or the like. Moreover, with enhancement of the recording density of the hard disk drive, recording bit on the disk has been finely divided, disk rotation speed has increased, and high precision and high rate in positioning the head have been requested. Furthermore, miniaturization, lightening and power saving of the hard disk drive have also been promoted.
Therefore, in order to position the head at high precision and high rate, a hard disk drive has been proposed in which a piezoelectric actuator independent of the conventional electromagnetic actuator is disposed midway on the arm.
However, the heretofore proposed piezoelectric actuator and hard disk drive have problems that sufficient displacement cannot be obtained, drive voltage is high, dimension and weight are large, inertia moment during head driving is large, and manufacture cost is high.
These problems are not generated only in the hard disk drive, and are generally generated with respect to the information storage apparatus in which the head is held and moved by the arm.
SUMMARY OF THE INVENTION
The present invention has been developed in consideration of the aforementioned situations, and an object thereof is to provide a piezoelectric actuator in which large displacement is obtained at low voltage, which is small-sized and lightweight, and whose manufacture cost is low, and an information storage apparatus in which the piezoelectric actuator is incorporated, whose inertia moment during head driving is small, and which is high in recording density, small-sized and lightweight.
In order to achieve the aforementioned object, according to the present invention, there is provided a first piezoelectric actuator comprising:
a piezoelectric layer which is formed of a piezoelectric material of a two-dimensional shape provided with a central portion, and a group of arm portions extended to the outside from the central portion in rotation symmetry and nonlinear symmetry, and which is compressed/extended in an in-layer direction; and
a plurality of electrode layers for holding the piezoelectric layer.
Here, the piezoelectric layer may be a flat layer having the two-dimensional shape, or a layer curved in the two-dimensional shape.
When a voltage is applied to the piezoelectric layer, the piezoelectric layer is contracted in the in-layer direction. In this case, if tip ends of respective arm portions constituting the arm portion group are fixed to a common rigid body, because of the two-dimensional shape, the central portion largely rotates at a low voltage. Moreover, since the structure of the first piezoelectric actuator of the present invention is easily manufactured, the first piezoelectric actuator can inexpensively be manufactured as a small-sized lightweight actuator.
In the first piezoelectric actuator of the present invention, the arm portion constituting the arm portion group is preferably turned to a backside via the central portion with respect to a root by which the arm portion is connected to the central portion.
Moreover, the first piezoelectric actuator of the present invention is preferably provided with a plurality of the piezoelectric layers.
For the piezoelectric actuator including the arm portion turned to the backside of the central portion, rotation amount of the central portion is large for contraction amount of the arm portion. For the piezoelectric actuator provided with a plurality of piezoelectric layers, the contraction amount of the piezoelectric layer is large for the voltage applied between the electrode layers. Therefore, by these piezoelectric actuators, larger displacement can be obtained at a lower voltage.
When the first piezoelectric actuator of the present invention is provided with a plurality of piezoelectric layers, the plurality of the electrode layers of the same potential are preferably connected to one another by a via hole.
The piezoelectric actuator employing the via hole as means for connecting the electrode layers to one another is easy in manufacture and low in manufacture cost.
Moreover, in the first piezoelectric actuator of the present invention, the piezoelectric layer is formed preferably of lead zirconate titanate (PZT) based piezoelectric ceramic, more preferably of PNN-PT-PZ based piezoelectric ceramic.
As the piezoelectric material for forming the piezoelectric layer, PZT, PT, barium titanate, layered perovskite and other piezoelectric materials can be utilized, but PZT based piezoelectric ceramic is inexpensive, large in piezoelectric constant, and suitable as the piezoelectric material for forming the piezoelectric layer. Particularly, a PNN-PT-PZ based piezoelectric material indicates a particularly high piezoelectric constant among the PZT based piezoelectric materials, is superior in sinterability and is therefore particularly preferable as the piezoelectric material to form the piezoelectric layer.
To achieve the aforementioned object, according to the present invention, there is provided a second piezoelectric actuator comprising:
a driving portion provided with a lamination structure including at least one piezoelectric layer of a piezoelectric material and a plurality of electrode layers for holding the piezoelectric layer, and compressed/extended in a lamination direction of the lamination structure; and
a holding portion for holding a plurality of the driving portions in an arrangement of rotation symmetry and nonlinear symmetry including the lamination direction in a predetermined common plane.
For the second piezoelectric actuator of the present invention, when the plurality of driving portions held by the holding portion are all compressed/extended, the aforementioned arrangement causes large rotation displacement at a low voltage. Moreover, since the structure of the second piezoelectric actuator of the present invention is easily manufactured, the second piezoelectric actuator can inexpensively be manufactured as the small-sized lightweight actuator.
The second piezoelectric actuator of the present invention is typically provided with two driving portions, and the typical second piezoelectric actuator is provided with an immobile portion adjacent to the driving portion in a direction intersecting the direction in which the driving portion is compressed/extended,
Wherein the holding portion holds two pairs of the driving portion and the immobile portion opposite to each other in such a manner that the driving portion of one pair turns the compressed/extended direction of the driving portion to the immobile portion of the other pair.
Moreover, for the typical second piezoelectric actuator of the present invention, the holding portion preferably holds two pairs of the driving portion and the immobile portion in such a manner that the driving portion is disposed opposite to the immobile portion via a slit.
According to the piezoelectric actuator in which the driving portion is disposed opposite to the immobile portion via the slit in this manner, the driving portion is easily compressed/extended, and larger displacement can be obtained at a lower voltage.
To achieve the aforementioned obj
Kurihara Kazuaki
Kutami Michinori
LandOfFree
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