Metal working – Piezoelectric device making
Reexamination Certificate
2002-03-15
2004-01-06
Tugbang, A. Dexter (Department: 3729)
Metal working
Piezoelectric device making
C029S594000, C029S830000, C029S831000
Reexamination Certificate
active
06671939
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a piezoelectric/electrostrictive device which is provided with a movable section to be operated on the basis of a displacement action of a piezoelectric/electrostrictive element, or a piezoelectric/electrostrictive device which is capable of detecting displacement of a movable section by the aid of a piezoelectric/electrostrictive element, and a method for producing the same. In particular, the present invention relates to a piezoelectric/electrostrictive device which is excellent in strength, shock resistance, and moisture resistance and which makes it possible to efficiently operate a movable section to a great extent, and a method for producing the same.
2. Background of the Invention
Recently, a displacement element, which makes it possible to adjust the optical path length and the position in an order of submicron, is required, for example, in the fields of the optics, the magnetic recording, and the precision machining. Development is advanced for the displacement element based on the use of the displacement brought about by the inverse piezoelectric effect or the electrostrictive effect caused when a voltage is applied to a piezoelectric/electrostrictive material (for example, a ferroelectric material).
As shown in
FIG. 32
, for example, those hitherto disclosed as such a displacement element include a piezoelectric actuator comprising a fixation section
204
, a movable section
206
, and a beam section
208
for supporting them which are formed in an integrated manner with a hole
202
provided through a plate-shaped member
200
composed of a piezoelectric/electrostrictive material and with an electrode layer
210
provided on the beam section
208
(see, for example, Japanese Laid-Open Patent Publication No. 10-136665).
The piezoelectric actuator is operated such that when a voltage is applied to the electrode layer
210
, the beam section
208
makes expansion and contraction in a direction along a line obtained by connecting the fixation section
204
and the movable section
206
in accordance with the inverse piezoelectric effect or the electrostrictive effect. Therefore, the movable section
206
can perform circular arc-shaped displacement or rotational displacement in the plane of the plate-shaped member
200
.
On the other hand, Japanese Laid-Open Patent Publication No. 63-64640 discloses a technique in relation to an actuator based on the use of a bimorph. In this technique, electrodes for the bimorph are provided in a divided manner. The actuator is driven due to the selection of the divided electrodes, and thus the highly accurate positioning is performed at a high speed. This patent document discloses a structure especially in
FIG. 4
in which, for example, two bimorphs are used in an opposed manner.
However, the piezoelectric actuator described above involves such a problem that the amount of operation of the movable section is small, because the displacement in the direction of extension and contraction of the piezoelectric/electrostrictive material (i.e., in the in-plane direction of the plate-shaped member) is transmitted to the movable section as it is.
All of the parts of the piezoelectric actuator are made of the piezoelectric/electrostrictive material which is a fragile material having a relatively heavy weight. Therefore, the following problems arise. That is, the mechanical strength is low, and the piezoelectric actuator is inferior in handling performance, shock resistance, and moisture resistance. Further, the piezoelectric actuator itself is heavy, and its operation tends to be affected by harmful vibrations (for example, residual vibration and noise vibration during high speed operation).
In order to solve the problems described above, it has been suggested that the hole is filled with a filler material having flexibility. However, it is clear that the amount of displacement, which is brought about by the inverse piezoelectric effect or the electrostrictive effect, is decreased even when the filler material is merely used.
On the other hand, the following structure is disclosed in
FIG. 4
in Japanese Laid-Open Patent Publication No. 63-64640. That is, in a joined form between a mediating member and a bimorph and between a head and the bimorph, so-called piezoelectric operating sections, both of which cause the strain, extend over respective joined portions. In other words, the bimorph is formed continuously ranging from the mediating member to the head.
As a result, when the bimorph is operated, the displacement action, which is effected with the supporting point of the joined portion between the mediating member and the bimorph, mutually interferes with the displacement action which is effected with the supporting point of the joined point between the head and the bimorph. The expression of the displacement is inhibited. In this structure, it is impossible to obtain such a function that the head is greatly displaced with respect to the external space.
The conventional device of this type involves a problem that in order to displace sufficiently the movable section, a large amount of voltage must be applied.
SUMMARY OF THE INVENTION
The present invention has been made taking the foregoing problems into consideration, an object of which is to provide a piezoelectric/electrostrictive device and a method for producing the same which make it possible to obtain a displacement element that is scarcely affected by harmful vibration during operation and capable of high speed response with high mechanical strength while being excellent in handling performance, shock resistance, and moisture resistance, which is liable to cause the displacement in a specific axis direction and can increase the displacement amount of a movable section while keeping a voltage applied to a piezoelectric/electrostrictive element at a low level, as well as a sensor element that makes it possible to detect vibration of the movable section with good accuracy and high sensitivity.
According to the present invention, there is provided a piezoelectric/electrostrictive device comprising a pair of mutually opposing thin plate sections, a movable section, and a fixation section for supporting the thin plate sections and the movable section; one or more piezoelectric/electrostrictive elements arranged on at least one thin plate section of the pair of thin plate sections; and a hole formed by both inner walls of the pair of thin plate sections, an inner wall of the movable section, and an inner wall of the fixation section; wherein at least one thin plate section of the pair of thin plate sections is previously bent in a direction to make mutual approach.
According to another aspect of the present invention, there is provided a piezoelectric/electrostrictive device as described above, wherein the pair of thin plate sections are previously bent in directions to make mutual approach. In this arrangement, it is also preferable that at least one thin plate section of the pair of thin plate sections, or the pair of thin plate sections are previously bent inwardly in convex configurations.
Usually, a thin plate section is bent as a voltage is applied to a piezoelectric/electrostrictive element, whereby a movable section causes displacement. In the present invention, since the pair of thin plate sections are previously bent in directions to make mutual approach and deformed in a direction substantially the same as bending directions of the thin plate sections due to the action of the piezoelectric/electrostrictive element, the thin plate sections are bent by a relatively small force, whereby the movable section causes displacement. Namely, in the present invention, as compared with the conventional piezoelectric/electrostrictive devices, equivalent displacement (displacement in the movable section) can be obtained with a low voltage, whereby an electric power consumption of electronic instruments installed with the piezoelectric/electrostrictive device can be reduced.
Further, the structure in which
Kimura Koji
Nanataki Tsutomu
Takeuchi Yukihisa
Burr & Brown
NGK Insulators Ltd.
Nguyen Tai
Tugbang A. Dexter
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