Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2000-07-28
2002-05-28
Sircus, Brian (Department: 2839)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S328000
Reexamination Certificate
active
06396193
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to a piezoelectric/electrostrictive device comprising a movable portion being operated based on a displacement of a piezoelectric/electrostrictive element, or to 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 capable of having the movable portion efficiently operated in large magnitude substantially in parallel toward the direction of a specific axis.
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 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 to a piezoelectric/electrostrictive material (for example, a ferroelectric substance or the like). For example, as shown in
FIG. 27
, a piezoelectric actuator
21
is disclosed, in which, by providing a hole
28
on a board-like shaped body composed of a piezoelectric/electrostrictive material, a fixing portion
25
, movable portion
24
, and a beam
26
connecting therewith are integrally formed, and the beam
26
is further provided with an electrode layer
22
(See 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 plate
25
is connected with the movable portion
24
, by the inverse piezoelectric effect or the electrostrictive effect, thus enabling the movable portion
24
to have an arc-shaped displacement or a rotational displacement in-plane of the board-like shaped body. On the other hand, the 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, and by driving the actuator by selecting the split electrodes, precise positioning can be performed at a high speed, and, for example, a structure for using two bimorphs opposed each other is shown in the specification thereof.
However, in the above-described actuator
21
, as the displacement in an expanding or contracting direction (namely, in-plane direction of the board-like shaped body) of a 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. Moreover, the actuator
21
, having all the members thereof being composed of a piezoelectric/electrostrictive material which is fragile and comparatively heavy, has another problem that the actuator
21
per se is heavy and operationally likely to be influenced by harmful vibrations, for example, residual vibrations or noise vibrations when operated at a high speed, in addition to being low in the mechanical strength, inferior in the handling property, impact resistance, and humidity resistance.
In order to solve the above-described problems in the actuator
21
, a proposition has been made that a filler having plasticity is filled to the hole
28
, however, when the filler is used, it is apparent that the efficiency of the displacement due to the inverse piezoelectric effect or the electrostrictive effect is reduced.
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 (relaying member, or the like) are separately prepared, and then adhered to be incorporated, and consequently the structure is that the joined state of the frame with the bimorph is likely to vary with time in accordance with operation of the bimorph, and that drifting of the displacement, exfoliation, or the like is also likely to be caused. Furthermore, a structure having an adhesive agent at a joined portion of the bimorph with the relaying member and at a joined portion of the head with the bimorph, namely at a holding portion of a displacement member, is low in stiffness of the holding portion per se, thus increase in the resonant frequency which is required in high speed operation is difficult to be obtained.
Of course, the applicant of the present invention and the others have made a proposition of a piezoelectric/electrostrictive device capable of solving such problems in the specification of Japanese Patent Application No. 11-375581, or the like, however, a piezoelectric/electrostrictive device which is capable of further increasing the displacement quantity of a movable portion, and making the displacement path of the movable portion substantially parallel relative to the fixing portion, is sought after specifically as a precise positioning device in the fields of magnetic recording and optics.
The present invention is made in view of the above-described current situation, and an object thereof is to provide a displacement element which is capable of further increasing displacement quantity of the movable portion and making a displacement path of the movable portion substantially in parallel relative to the fixing portion without reducing resonance frequency, and a sensor element capable of detecting vibrations of the movable portion in high precision.
SUMMERY 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 the drive of the driving portion, and 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 being formed by inner walls of the driving portion, an inner wall of the movable portion, and an inner wall of the fixing portion, and the piezoelectric/electrostrictive device comprises the driving portion comprising 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 arranged on at least at a part of the outer surface of at least one thin plate portion out of the 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, and the other end of the piezoelectric/electrostrictive operating portion is arranged on the thin plate portion, and at least one end of the piezoelectric/electrostrictive layer of the piezoelectric/electrostrictive element exists on the fixing portion or the movable portion, and the other end thereof is arranged on the thin plate portion, and the Young's modulus Y
1
of a material composing the thin plate portions and the Young's modulus Y
2
of a material composing a material of the piezoelectric/electrostrictive layer
Kimura Koji
Komazawa Masato
Nanataki Tsutomu
Takeuchi Yukihisa
Burr & Brown
NGK Insulators Ltd.
Sircus Brian
Zarroli Michael C.
LandOfFree
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