Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
1999-11-17
2002-01-01
Budd, Mark O. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S328000
Reexamination Certificate
active
06335586
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED STATEMENT
The present invention relates to a piezoelectric/electrostrictive device having a movable portion to be 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 can efficiently operate the movable portion in a large magnitude.
Recently, in a field of optics or magnetic recording, precision machining, or the like, a displacement element capable of adjusting an optical path length and 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 obtained 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
and a movable portion
24
and a bridge beam
26
connecting therewith 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 by the inverse piezoelectric effect or electrostrictive effect in a direction connecting the fixing portion
25
with the movable portion
24
.
On the other hand, JP-A-63-64640 discloses a technique related to an actuator using a bimorph, wherein the bimorph is provided with divided electrodes such that a divided electrode is selected to drive the actuator to perform precise alignment at a high speed. For example, the specification shows in
FIG. 4
a structure which uses two bimorphs positioned opposing to each other.
However, the actuator
21
has a problem that an operational quantity of the movable portion
24
is small, since the displacement in an expanding or contracting direction (namely, the in-plane direction of the board-like body) of a 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 parts 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 further the actuator
21
per se is heavy and is easily influenced by a harmful vibration, for example, residual vibration or vibrational noise during high speed operation.
In order to solve above-described problems of the actuator
21
, a proposition is made that a hole
28
is filled with an elastic filler. However, it is apparent that efficiency of the displacement due to the inverse piezoelectric effect or the electrostrictive effect is lowered when the filler is added.
On the other hand, what is shown in
FIG. 4
of JP-A-63-64640 is, in bonding of an intermediary member
3
and a bimorph, a bonding of a site without the divided electrodes with the intermediary member, and therefore an advantage of the divided electrodes cannot be utilized at the bonded site. In other words, merely a site of the bimorph which is not a displacement generating portion is bonded. Further, on the other hand, a bonding formed at a bonding site of a head and the bimorph is similar. As a result, a bending displacement of the bimorph is developed toward an inner space between the intermediary member and the head, and the structure is not a type where the head per se is given an operation for effective displacement toward the outside space. In addition, the actuator disclosed in JP-A-63-64640 has a structure where a displacement generating member and a so-called frame member (an intermediary member or the like) are prepared separately, and adhered mutually to unite, thus the structure is liable to change over time the bonding condition of the frame and the bimorph, and also liable to cause drifting of the displacement, exfoliation, or the like. Further, a structure with an adhesive intervened at the bonding site of the bimorph with the intermediary member and at the bonding site of the head with the bimorph, namely at a holding portion of a displacement member, is lower in stiffness at the holding portion per se, thus making it difficult to increase a resonant frequency required for high speed operation.
The present invention is made in view of such problems in the conventional art, and an object thereof is to provide a displacement element which can largely operate a movable portion, and is hardly influenced by a harmful vibration in operation, capable of a high speed response, high in mechanical strength, and superior in handling property, impact resistance, and humidity resistance, as well as a sensor element capable of detecting a vibration of the movable portion in fine precision, and methods of fabricating 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 a drive 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 plate portions facing each other, and a film-like piezoelectric/electrostrictive element including at least a pair of an electrode films and a piezoelectric/electrostrictive film formed on at least a part of the outer surface of at least one thin plate portion of the thin plate portions, 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, at least one side of a piezoelectric operating portion of the piezoelectric/electrostrictive element in a direction connecting the fixing portion with the movable portion is structured to exist on the fixing portion or the movable portion, and a ratio a/b of the thickness a of the hole and the width b of the thin plate portion is 0.5 to 20.
Further provided in the present invention are a piezoelectric/electrostrictive device characterized in that the width of the thin plate portion is the same as the width of the piezoelectric/electrostrictive element formed on the thin plate portion; a piezoelectric/electrostrictive device characterized in that a ratio e/a of the length e of the thin plate portion and the thickness a of the hole is 0.5 to 10; a piezoelectric/electrostrictive device characterized in that a ratio a/b of the thickness a of the hole and the width b of the thin plate portion is 1 to 10, and a ratio e/a of the length e of the thin plate portion and the thickness a of the hole is 0.7 to 5; and a piezoelectric/electrostrictive device wherein the movable portion and the fixing portion are a rectangular solid 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 a drive 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 plate portions facing each other and a film-like piezoele
Hirota Toshikazu
Kimura Koji
Nanataki Tsutomu
Takeuchi Yukihisa
Budd Mark O.
Burr & Brown
NGK Insulators Ltd.
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