Metal working – Piezoelectric device making
Reexamination Certificate
2002-10-25
2004-11-16
Tugbang, A. Dexter (Department: 3729)
Metal working
Piezoelectric device making
C029S594000, C029S896220, C029S412000, C029S417000, C029S830000, C029S831000
Reexamination Certificate
active
06817072
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 optics, magnetic recording, and 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. 53
, for example, those hitherto disclosed as such a displacement element include a piezoelectric actuator comprising a fixation section
404
, a movable section
406
, and a beam section
408
for supporting them which are formed in an integrated manner with a hole
402
provided through a plate-shaped member
400
composed of a piezoelectric/electrostrictive material and with an electrode layer
410
provided on the beam section
408
(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
410
, the beam section
408
makes expansion and contraction in a direction along a line obtained by connecting the fixation section
404
and the movable section
406
in accordance with the inverse piezoelectric effect or the electrostrictive effect. Therefore, the movable section
406
can perform circular arc-shaped displacement or rotational displacement in the plane of the plate-shaped member
400
.
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 in accordance with the selection of the divided electrodes, and thus the highly accurate positioning is performed at a high speed. This document (especially in
FIG. 4
) discloses a structure 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
406
is small, because the displacement in the direction of expansion and contraction of the piezoelectric/electrostrictive material (i.e., in the in-plane direction of the plate-shaped member
400
) is transmitted to the movable section
406
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
402
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.
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 and capable of high speed response with high mechanical strength while being excellent in handling performance, shock resistance, and moisture resistance, making it possible to realize a long service life of a device, and improve the handling performance of the device and the attachment performance for parts to be attached to the movable section or the fixation performance of the device, so that the movable section may be greatly displaced at a relatively low voltage, and it is possible to achieve a high speed of the displacement action of the device, especially of the movable section (realization of a high resonance frequency), as well as a sensor element which makes it possible to accurately detect vibration of the movable section.
According to the present invention, there is provided a piezoelectric/electrostrictive device comprising a pair of mutually opposing thin plate sections made of metal and a fixation section secured to the thin plate sections by the aid of an adhesive; a movable section provided at forward end portions of the pair of thin plate sections; and one or more piezoelectric/electrostrictive elements arranged on at least one thin plate section of the pair of thin plate sections; wherein any one of the movable section and the fixation section has mutually opposing end surfaces; and a distance between the end surfaces is not less than a length of the movable section.
The device is excellent in strength and toughness, and the device is capable of responding to any quick displacement action, because the thin plate section is made of metal. That is, according to the present invention, it is possible to sufficiently respond to any variation of the environment of the use and any severe state of the use. The device is excellent in shock resistance. It is possible to realize a long service life of the piezoelectric/electrostrictive device, and it is possible to improve the handling performance of the piezoelectric/electrostrictive device. Further, the thin plate section can be greatly displaced at a relatively low voltage, and it is possible to achieve the realization of a high speed of the displacement action of the thin plate section (realize a high resonance frequency), because the thin plate section has high rigidity, and the actuator film has a thick film thickness and high rigidity.
It is also preferable that the piezoelectric/electro-strictive element has a film-shaped configuration, and it is secured to the thin plate section by the aid of an adhesive. It is also preferable that the piezoelectric/electrostrictive element is constructed to have a piezoelectric/electrostrictive layer and a pair of electrodes formed on the piezoelectric/electrostrictive layer. In this arrangement, the vibration, which is caused by the piezoelectric/electrostrictive element, can be efficiently transmitted via the thin plate section to the movable section or the fixation section. It is possible to improve the response performance.
Especially, it is preferable that the piezoelectric/electrostrictive element is constructed in a stacked form comprising a plurality of units each including the piezoelectric/electrostrictive layer and the pair of electrodes. When the arrangement as described above is adopted, the following feature is achieved. That is, the generated force of the piezoelectric/electrostrictive element is increased, and thus it is possible to obtain large displacement. Further, it is possible to obtain a high resonance frequency owing to the increase in rigidity of the device itself, making it easy to achieve the high speed of the displacement action.
Those usable for the adhesive include or
Namerikawa Masahiko
Shibata Kazuyoshi
Takeuchi Yukihisa
Burr & Brown
NGK Insulators Ltd.
Nguyen Tai
Tugbang A. Dexter
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