Metal working – Piezoelectric device making
Reexamination Certificate
2001-10-03
2004-04-06
Vo, Peter (Department: 3729)
Metal working
Piezoelectric device making
C029S594000, C029S833000, C029S835000, C029S851000, C310S321000, C310S328000, C310S330000, C310S331000, C310S332000
Reexamination Certificate
active
06715192
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to a piezoelectric/electrostrictive device having a movable portion being operated based on a displacement of a piezoelectric/electrostrictive element, or a piezoelectric/electrostrictive device capable of detecting a displacement of the movable portion by the piezoelectric/electrostrictive element, and more particularly relates to a piezoelectric/electrostrictive device which is superior in mechanical strength, impact resistance, and humidity resistance and in which the movable portion can be efficiently operated in a large magnitude.
In recent years, in the fields of optics, magnetic recording, precision machining, and the like, a displacement element capable of adjusting an optical path length or a position in sub-micron order has been required, and development has progressed of a displacement element utilizing a displacement due to the inverse piezoelectric effect or electrostrictive effect caused when a voltage is applied to a piezoelectric/electrostrictive material, for example, a ferroelectric substance or the like.
For example, as shown in
FIG. 2
, a piezoelectric actuator
21
in which a fixing portion
25
, a movable portion
24
and a bridge beam
26
connecting the two, are integrally formed by providing a hole
28
on a board-like body composed of a piezoelectric/electrostrictive material, and an electrode layer
22
is further provided on the bridge beam
26
, is disclosed in JP-A-10-136665.
In the actuator
21
, when a voltage is applied to an electrode layer
22
, the movable portion
24
can have an arc-shaped displacement or a rotational displacement in the plane of the board-like body, since the bridge beam
26
expands or contracts in a direction connecting the fixing portion
25
with the movable portion
24
by the inverse piezoelectric effect and the electrostrictive effect.
However, in the actuator
21
, there is a problem that an operational quantity of the movable portion
24
is small, since the displacement in the expanding or contracting direction, namely, the in-plane direction of the board-like body of the piezoelectric/electrostrictive material, is transmitted per se to the movable portion.
Further, the actuator
21
has another problem that the actuator
21
, having all the members thereof constituted with a piezoelectric/electrostrictive material which is fragile and comparatively heavy, is low in mechanical strength, and inferior in handling property, impact resistance and humidity resistance, and in addition the actuator
21
per se is heavy and is easily subjected to an effect of harmful vibrations, for example, residual vibrations or vibrational noises under high speed operation.
In order to solve above-described problems of the actuator
21
, a proposition is made that the hole
28
is filled with an elastic filler; it is apparent, however, that efficiency of the displacement due to the inverse piezoelectric effect or the electrostrictive effect is lowered when the filler is added.
The present invention is made in view of such problems of the conventional art, and an object of the present invention is to provide: a displacement element in which a movable portion can be operated in a large magnitude, and which is hardly subject to an effect of harmful vibrations in operation, and is superior in mechanical strength, handling property, impact resistance, and humidity resistance; a sensor element capable of detecting vibrations of the movable portion in fine accuracy; and a fabricating method for the elements.
SUMMARY OF THE INVENTION
According to the present invention, firstly provided is a piezoelectric/electrostrictive device comprising a driving portion to be driven by a displacement of a piezoelectric/electrostrictive element, a movable portion to be operated based on driving of the driving portion, and a fixing portion for holding the driving portion and the movable portion, said piezoelectric/electrostrictive device being characterized in that the driving portion is formed of a pair of thin plates facing each other and a film-like piezoelectric/electrostrictive element formed on an outer surface of at least one thin plate of the thin plates, the fixing portion is coupled with the movable portion via the driving portion, a hole is defined by an inner wall of the driving portion, an inner wall of the movable portion, and an inner wall of the fixing portion, and a ratio a/b of the thickness a of the piezoelectric/electrostrictive device and the width b of the piezoelectric/electrostrictive device is 0.5 to 20.
Further, in the present invention provided is a piezoelectric/electrostrictive device characterized in that a ratio e/a of the maximum length e of a length of a hole in parallel with the longitudinal direction of the piezoelectric/electrostrictive device and the thickness a of the piezoelectric/electrostrictive device is 0.5 to 10, more preferably a ratio a/b of the thickness a of the piezoelectric/electrostrictive device and the width b of the piezoelectric/electrostrictive device is 1 to 10, and a ratio e/a of the maximum length e of the length of the hole in parallel with the longitudinal direction of the piezoelectric/elec-trostrictive device and the thickness a of the piezoelectric/electrostrictive device is 0.7 to 5.
Although a shape of the movable portion or the fixing portion changes depending on the mode of application as an element, normally, it is preferable to be in rectangular solid form. Further, one having at least two driving portions is preferable, since function as a plurality of elements can be effectively performed. A piezoelectric/electrostrictive element to be mounted on the driving portion is preferably a laminated-type piezoelectric/electrostrictive element laminated by a lower electrode, a piezoelectric/electrostrictive film, and an upper electrode. Further, more preferable is a piezoelectric/electrostrictive element in which the piezoelectric/electrostrictive element comprises a piezoelectric/electrostrictive film, and a first electrode and a second electrode each of a comb-type structure, and the first electrode and the second electrode are structured to alternatively bite with a gap of a predetermined width between each tooth of respective combs. A piezoelectric/electrostrictive device constituted of ceramics with a movable portion, thin plates, and a fixing portion integrally formed is preferable from the standpoint of fabricating cost. Further, it is preferable that the piezoelectric/electrostrictive device be made of a laminated body.
According to the present invention, secondly provided is a piezoelectric/electrostrictive device comprising a driving portion to be driven by a displacement of a piezoelectric/electrostrictive element, a movable portion to be operated based on driving of the driving portion, and a fixing portion for holding the driving portion and the movable portion, wherein the piezoelectric/electrostrictive device is characterized in that the driving portion is formed of a pair of thin plates facing each other and a film-like piezoelectric/electrostrictive element formed on an outer surface of at least one thin plate of the thin plates, the fixing portion is coupled with the movable portion via the driving portion, a hole is defined by an inner wall of the driving portion, an inner wall of the movable portion, and an inner wall of the fixing portion, and the thickness a of the piezoelectric/electrostrictive device is 100 &mgr;m to 2000 &mgr;m, and the width b of the piezoelectric/electrostrictive device is 100 &mgr;m to 2000 &mgr;m.
Further, provided are a piezoelectric/electrostrictive device characterized in that the thickness a of the piezoelectric/electrostrictive device is 200 &mgr;m to 1000 &mgr;m and the width b of the piezoelectric/electrostrictive device is 100 &mgr;m to 500 &mgr;m, and a piezoelectric/electrostrictive device characterized in that the thickness d of the thin plate of the piezoelectric/electrostrictive device is 2 &mgr;m to 100 &mgr;m, and further a piezoelectric/electrostrict
Hirota Toshikazu
Kimura Koji
Nanataki Tsutomu
Takeuchi Yukihisa
Burr and Brown
Kim Paul D
NGK Insulators Ltd.
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