Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2000-09-29
2003-12-02
Dougherty, Thomas M. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S324000, C310S323010, C310S323170, C310S368000, C310S330000
Reexamination Certificate
active
06657364
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.
2. Description of the Related Art
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; 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. 12
, 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 highly accurate positioning is performed at a high speed. This patent 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
206
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
200
) is transmitted to the movable section
206
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
202
is filled with a filler material having flexibility. However, in this case, it is clear that the amount of displacement, which is brought about by the inverse piezoelectric effect or the electrostrictive effect, is decreased.
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 which makes it possible to realize a long service life of the device and miniaturize the device and which 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.
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 for supporting the thin plate sections; an object attached to 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 an areal size of a surface of the object opposed to the thin plate section is larger than an areal size of an object attachment surface of the thin plate section.
Accordingly, it is possible to displace the pair of thin plate sections to a great extent, and it is possible to realize a high speed of the device, especially of the pair of thin plate sections (realize a high resonance frequency). Further, it is possible to obtain a displacement element which is scarcely affected by any harmful vibration, which is capable of high speed response, which has a high mechanical strength, and which is excellent in handling performance, shock resistance, and humidity resistance. Furthermore, it is possible to obtain a sensor element which makes it possible to accurately detect the vibration of the movable section.
Especially, in the present invention, 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. Therefore, according to the present invention, it is possible to sufficiently respond to any variation of the environment of use and any severe state of use. It is possible to realize a long service life of die piezoelectric/electrostrictive device, and it is possible to contemplate 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).
In the device constructed as described above, it is also preferable that a first adhesive is allowed to intervene between the piezoelectric/electrostrictive element and the thin plate section. It is also preferable that the object is secured to the object attachment surface of the thin plate section by the aid of a second adhesive.
In the arrangements as described above, the first adhesive and/or the second adhesive may be composed of organic resin, or the first adhesive and/or the second adhesive may be composed of glass, brazing material, or solder.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.
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Shibata Kazuyoshi
Takeuchi Yukihisa
Burr & Brown
Dougherty Thomas M.
NGK Insulators Ltd.
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