Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2000-07-28
2002-09-17
Budd, Mark O. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S328000
Reexamination Certificate
active
06452309
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to a piezoelectric/electrostrictive device comprising a movable portion to be operated by a displacement of a piezoelectric/electrostrictive element, or a piezoelectric/electrostrictive device capable of detecting a displacement of a movable portion by a piezoelectric/electrostrictive element, and more particularly relates to a piezoelectric/electrostrictive device which is superior in the mechanical strength, impact resistance, and humidity resistance, and is capable of having the movable portion efficiently operated in large magnitude.
In recent years, in the fields of optics and magnetic recording, precision machining, and the like, a displacement element capable of adjusting an optical path length or position in sub-micron order has been required, and development has been progressed of a displacement element utilizing a displacement due to the inverse piezoelectric effect or the electrostrictive effect caused when a voltage is applied on a piezoelectric/electrostrictive material (for example, a ferroelectric substance, or the like). For example, as shown in
FIG. 20
, a piezoelectric actuator
21
, in which, by providing a hole
28
on a plate-like body composed of a piezoelectric/electrostrictive material, a fixing portion
25
, a movable portion
24
, and a beam
26
connecting therewith are integrally formed, and an electrode layer
22
is further provided on the beam
26
, is disclosed in JP-A-10-136665.
In the actuator
21
, when a voltage is applied across the electrode layer
22
, the beam
26
expands or contracts in a direction in which the fixing portion
25
is connected with the movable portion
24
by the inverse piezoelectric effect or the electrostrictive effect, thus enabling the movable portion
24
to displace in an arc-shaped mode or a rotational mode in-plane of the plate-like body. On the other hand, JP-A-63-64640 discloses a technique with regard to an actuator utilizing a bimorph, wherein an electrode of the bimorph is split to be provided thereon, and the actuator is driven by selecting the split electrodes to perform precise positioning at a high speed, and for example, a structure in which two bimorphs are used mutually opposing is shown in
FIG. 4
of the specification thereof.
However, with the actuator
21
, as a displacement in the expansion/contraction direction (namely, in-plane direction of the plate-like body) of the piezoelectric/electrostrictive material is transmitted per se to the movable portion, there is a problem that an operational quantity of the movable portion
24
is small.
Further, the actuator
21
, having all members thereof composed of a piezoelectric/electrostrictive material, which is fragile and relatively heavy in weight, has further problems, in addition to the mechanical strength being low, and being inferior in handling property, impact resistance, and humidity resistance, that the actuator
21
per se is heavy and is likely to be influenced by harmful vibrations (for example, residual vibrations or noise vibrations when operated at a high speed) in operation. In order to solve the above-described problems of the actuator
21
, a proposition is made that the hole
28
is filled with a filler having flexibility, however, it is apparent that the efficiency of the displacement due to the inverse piezoelectric effect or the electrostrictive effect is decreased, when the filler is used.
On the other hand, what is shown in
FIG. 4
of JP-A-63-64640 is that, in a bonding manner of a relaying member with a bimorph and a head with a bimorph, a so-called piezoelectric/electrostrictive operating portion expressing strain strides over each of the jointed portions, i.e., the bimorph strides continuously from the relaying member and the head. As a result, the displacement motion occurring from the jointed portion between the relaying member and the bimorph as a fulcrum and the displacement motion occurring from the jointed portion between the head and the bimorph as a fulcrum interfere with each other and hinder the development of the displacement when the bimorph is operated, and thus the structure is that an action for effectively displacing the head per se toward the outer space is unable to be obtained. In addition, the actuator disclosed in JP-A-63-64640 is so structured that a displacement generating member and a so-called frame member (intermediary member or the like) are separately prepared, and then adhered together to be incorporated, and consequently it is a structure where the joined state of the frame with the bimorph is likely to vary with time, and also drifting of a displacement, exfoliation, or the like is likely to be caused. Further, the structure having an adhesive intervened at the joined portion of a bimorph with an intermediary member and at the joined portion of a head with the bimorph, namely at a holding portion for a displacement member is also a structure where rigidity of the holding portion per se is low and it is difficult to obtain a higher resonant frequency which is required in high speed operation.
Although the present applicants have, of course, proposed a piezoelectric/electrostrictive device capable of solving such problems in the specification of the Japanese Patent Application No. 11-375581 and the like, development of a piezoelectric/electrostrictive device capable of obtaining still larger displacement quantity as well as capable of high speed response has been sought after as a precise positioning mechanism in the optical and magnetic recording fields.
The present invention is made in view of such current situation, and an object thereof is to provide a displacement element which is capable of increasing mechanical rigidity of joined portions of the thin plate portions with the movable portion and the thin plate portions with the fixing portion, facilitating higher resonant frequency, and further increasing displacement quantity of the movable portion, and a sensor element capable of efficiently detecting vibrations of the movable portion in higher precision.
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 by a drive of the driving portion, a fixing portion for holding the driving portion and the movable portion, the movable portion being coupled with the fixing portion via the driving portion, and a hole formed by inner walls of the driving portion, an inner wall of the movable portion, and an inner wall of the fixing portion; in which the driving portion comprises a pair of mutually opposing thin plate portions and a piezoelectric/electrostrictive element including a piezoelectric/electrostrictive operating portion comprising a pair or more of electrodes and a piezoelectric/electrostrictive layer formed at least on a part of the outer surface of at least one thin plate portion of the pair of thin plate portions, one end of the piezoelectric/electrostrictive operating portion in a direction in which the fixing portion is connected with the movable portion exists on the fixing portion or the movable portion, the other end of the piezoelectric/electrostrictive operating portion is arranged on the thin plate portion, and at least the piezoelectric/electrostrictive layer of the piezoelectric/electrostrictive element exists extended over the movable portion and the fixing portion. Here, all of the movable portion, the thin plate portions, and the fixing portion may be comprised of either ceramics or metals, and additionally respective members may be comprised of different materials of metals or ceramics to give a hybrid structure.
Further, the present invention provides a piezoelectric/electrostrictive device in which the movable portion, the thin plate portions, and the fixing portion are integrally formed by simultaneously sintering a ceramic green sheet laminate, a piezoelectric/electrostrictive dev
Kimura Koji
Komazawa Masato
Nanataki Tsutomu
Takeuchi Yukihisa
Budd Mark O.
Burr & Brown
NGK Insulators Ltd.
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