Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2002-08-30
2004-04-20
Mullins, Burton S. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
Reexamination Certificate
active
06724127
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a device using a piezoelectric/electrostrictive film, particularly to the structure of a piezoelectric/electrostrictive device for improving the operational characteristic of an element for converting electrical energy into mechanical energy such as mechanical displacement, mechanical force, or vibration and etc., and vice versa. Specifically, the present invention relates to a piezoelectric/electrostrictive device to be applied to transducers, various actuators, frequency-region functional components (filters), transformers, vibrators and resonators for communication and motive power, oscillators, discriminators, and various sensors including ultrasonic sensors, acceleration sensors, angular velocity sensors, impact sensors, and mass sensors, and moreover unimorph- and bimorph-type elements used for servo shift elements described in “From Foundation Up To Application of Piezoelectric/Electrostrictive Actuator” written by Kenji Uchino {edited by Japan Industrial Technical Center and published by MORIKITA SHUPPAN (transliterated)}, and to be preferably adopted to various actuators used for mechanisms for shift and positioning adjustment and angle adjustment of various precision components and etc. of optical equipment, precision equipment, etc.
BACKGROUND ART
Recently, a shift control element for adjusting an optical-path length or position on the sub-micron order has been requested in the optical and magnetic recording fields, as well as the precision-machining field. To respond to this request, piezoelectric/electrostrictive actuators have been developed, which are elements using a displacement based on the reverse or converse piezoelectric effect or electrostrictive effect caused by applying an electric field to a piezoelectric/electrostrictive material such as a ferroelectric.
In the field of magnetic recording on a hard disc drive, storage capacity has been remarkably increased in recent years. This is because an attempt has been made to use a recording medium more efficiently by increasing the number of recording tracks to increase the recording density. Recording methods have also improved.
This attempt has been mainly made so far in the area of the voice coil motor. Moreover, as a new technical art, an electrostatic-type microactuator micromachined in Si or Ni and used as the tracking system of a magnetic head for a hard-disk drive has been attempted, as described on pp. 1081-1084 in the preliminary manuscript collection of “1997 International Conference on solid-state Sensors and Actuators” of “TRANSDUCER'97”.
Moreover, Japanese Patent Application Laid-Open No. 10-136665 discloses a piezoelectric actuator as shown in
FIG. 24
in which a fixed portion
103
, a movable portion
104
, and at least one beam portion
102
for connecting the portions
103
and
104
to each other are integrally formed by forming at least one hole on a flat body made of a piezoelectric/electrostrictive material, and a strain generation portion is constituted by forming an electrode layer
105
on at least a part of at least one beam portion
102
so that an expansion or a contraction motion occurs in the direction connecting the fixed portion
103
with the movable portion
104
, and a displacement mode of the movable portion
104
to the fixed portion
103
generated due to the expansion or contraction motion of the strain generation portion is an arc-shaped or rotational mode in the plane of the flat body.
However, in the case of the conventional art for positioning a recording head mainly using a voice coil motor, it is difficult to accurately position a recording head so as to accurately trace tracks when the number of tracks increases in order to correspond to a further increase in capacity.
The above-described technical art using an electrostatic-type microactuator obtains a displacement by applying a voltage between a plurality of flat electrodes formed through micromachining. However, it is difficult to increase a resonance frequency because of the structure. Consequently, the technical art includes such problems that vibrations are not easily attenuated when a high-speed operation is performed. Moreover, there is a feature that the technical art is displacement-theoretically inferior in the linearity of the voltage-displacement characteristic. Therefore, there are many problems to be solved from the viewpoint of accurate alignment. Furthermore, the process of micromachining itself has a problem from the viewpoint of the manufacturing cost.
Furthermore, in the case of a piezoelectric actuator disclosed in Japanese Patent Application Laid-Open No. 10-136665, the piezoelectric-operation portion has a monomorph structure. Therefore, the main-strain axis of a piezoelectric material becomes coaxial or parallel with the main-shift axis of the piezoelectric-operation portion. Thus, there are problems that the piezoelectric-operation portion itself generates only a small shift and the movable portion also shows a small displacement. Moreover, the piezoelectric actuator itself is heavy and subject to harmful vibrations for operation such as residual vibrations and vibrational noises under a high-speed operation as described in Japanese Patent Application Laid-Open No. 10-136665 and therefore, it is necessary to suppress harmful vibrations by injecting a filler into a hole. However, the use of such a filler may adversely influence displacement of the movable portion. Moreover, because it is unavoidable to constitute a piezoelectric actuator with a piezoelectric/electrostrictive material inferior in mechanical strength, there is a problem that the actuator is subject to material strength-imposed restrictions on shape and purpose.
SUMMARY OF THE INVENTION
The present invention is made to solve the problems of the above piezoelectric/electrostrictive device. According to the present invention, the following first to sixth piezoelectric/electrostrictive devices capable of accurately performing in-plane movements and operations at a high speed are provided.
That is, a piezoelectric/electrostrictive device in which a piezoelectric element is formed on at least a portion of at least one plane of a diaphragm whose one side is joined to a substrate and at least one side of one thin-walled fixing plate is joined to one side of the diaphragm so that the plane of the fixing plate and the plane of the diaphragm are perpendicularly intersected with each other, is provided as the first piezoelectric/electrostrictive device.
It is preferable that the first piezoelectric/electrostrictive device operates in accordance with at least either of a &thgr;-mode displacement in which a fixing plate is displaced like a pendulum in the direction vertical to a side of the fixing plate and vertical to the vertical axis about the vertical axis vertically passing through the center of a fixed plane by using the joining face between the fixing plate and a diaphragm as the fixed plane and a &phgr;-mode displacement in which a swing in the direction vertical to a side of the fixing plate and vertical to the vertical axis is displaced like a pendulum while being followed by a swing in the direction parallel with a side of the fixing plate, that is, the first piezoelectric/electrostrictive device drives the fixing plate by a piezoelectric element or detects the displacement amount of the fixing plate.
Moreover, a piezoelectric/electrostrictive device in which a fixing plate and a connection plate are joined with each other at their sides, and a diaphragm in which piezoelectric elements are arranged on at least a portion of at least one plane is joined to the connection plate at their sides in the direction perpendicular to the joining direction between the fixing plate and the connection plate, and at least parts of sides of the connection plate and the diaphragm are joined to a substrate, is provided as the second piezoelectric/electrostrictive device.
In this case, a part of a side of the connection plate to be joined to the substrate represents a side opposite t
Kimura Koji
Ohnishi Takao
Takeuchi Yukihisa
Addison Karen Beth
Burr & Brown
Mullins Burton S.
NGK Insulators Ltd.
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