Title:

PIEZOELECTRIC/ELECTROSTRICTIVE DEVICE

Document Type and Number:

United States Patent 20070170817

Kind Code:

Abstract:

A piezoelectric/electrostrictive device has a rotor substantially in the form of a rectangular parallelepiped, and a rotary actuator for angularly displacing the rotor 12. The rotary actuator includes a stationary member, a first vibratory plate and a second vibratory plate extending in one direction from opposite sides of the stationary member, a first piezoelectric/electrostrictive element for actuating the first vibratory plate, and a second piezoelectric/electrostrictive element for actuating the second vibratory plate. The rotor includes a pair of opposite surfaces, one of the surfaces having a first end secured to an end of the first vibratory plate and a second end, which is diagonally opposite to the first end, and which is secured to an end of the second vibratory plate.

Inventors:

Ikeda, Koji (Tsu-City, JP)
Shibata, Kazuyoshi (Mizunami-City, JP)
Takahashi, Nobuo (Kasugai-City, JP)

Plaque It!

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Patent Applications No. 2006-015684 filed on Jan. 24, 2006 and No. 2006-118159 filed on Apr. 21, 2006, in the Japanese Patent Office, of which the contents are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a piezoelectric/electrostrictive device having a rotor which rotates based on displacement of a piezoelectric/electrostrictive element, or to a piezoelectric/electrostrictive device for detecting angular displacement of a rotor with a piezoelectric/electrostrictive element, for use in controlling an actuator for positional control of a hard disk drive (HDD), controlling the angle of a small reflecting mirror, controlling rotation of an antenna, controlling the θ-axis of an XY stage, and controlling rotation of a manipulator.

2. Description of the Related Art

Recently, optical, magnetic recording, and precision machining fields have been in need of displacement elements, which are capable of adjusting optical path lengths and positions within a range of submicrons. The development of displacement elements, which utilize displacement based on an inverse piezoelectric effect or an electrostrictive effect caused when a voltage is applied to a piezoelectric/electrostrictive material such as a ferroelectric substance, is under way.

Conventional piezoelectric actuators are problematic in that the movable member thereof moves a small distance because the displacement of a piezoelectric/electrostrictive material as it is expanded or contracted is directly transferred to the movable member.

There has been proposed a piezoelectric/electrostrictive device having a long service life, which can be handled better, allows a component to be mounted easily on the movable member thereof, and can be fixed securely in position. For details, reference should be made to Japanese Laid-Open Patent Publication No. 2002-26411, for example. The disclosed piezoelectric/electrostrictive device permits the movable member to be displaced a large distance under a relatively low voltage applied thereto, and allows the movable member to be displaced at a high speed, i.e., at a high resonant frequency. The disclosed piezoelectric/electrostrictive device can provide a displacement element that is not susceptible to harmful vibrations, which can respond at a high speed, has high mechanical strength, can be handled better, and is highly resistant to shocks and humidity, and further, which also can provide a sensor element capable of detecting movable member vibrations with good accuracy.

If a piezoelectric/electrostrictive device is used as a two-stage actuator for positioning a magnetic head in a HDD (Hard Disk Drive), then the moment of inertia thereof is reduced, for enabling highly accurate positioning control by alignment of the center of gravity of a slider with the rotational axis of the actuator.

Most HDDs that are in use today are of a type in which the axial direction of a head/stack assembly, which is actuatable by an actuator such as a voice coil motor or the like, is close to a direction that is tangential to the tracks. When the slider located at a distal portion of the head/stack assembly of the HDD of this type moves radially with respect to a given track, the skew angle of the axial direction of the head/stack assembly with respect to the direction tangential to the track varies, or in other words, the tangential direction and the axial direction deviate from each other.

The slider supports thereon a head element for recording and reproducing data, which is pressed against the surface of the magnetic disk under spring forces of the head/stack assembly. When the magnetic disk rotates, the slider is lifted off the magnetic disk under a lifting force generated by an air stream produced by rotation of the magnetic disk, and remains spaced a small gap from the surface of the magnetic disk due to a state of balance between the pressing force acting on the slider and the lifting force applied to the slider.

When the axial direction of the head/stack assembly deviates from the direction tangential to the tracks, since the vector of the air stream changes greatly, the lifted state of the magnetic head also changes greatly, and the gap by which the magnetic head is lifted off the magnetic disk becomes unstable. As a result, it becomes difficult to stably utilize the electromagnetic conversion capability of the magnetic disk itself.

According to one solution, it has been practiced to modify the air bearing surface configuration of the slider for stabilizing the lifted state of the magnetic head. If the slider is angularly displaceable so as to keep the skew angle small, then inasmuch as the above problems do not arise, the lifted state of the magnetic head becomes stable for high operational reliability.

Perpendicular magnetic recording, in particular, tends to suffer a side write problem, depending on the configuration of the main magnetic pole. HDDs based on the principles of perpendicular magnetic recording are subject to side write/side erase problems on the main magnetic pole of the write head, particularly if the skew angle is large.

When a surface of the main magnetic pole that is parallel to the track deviates from the direction tangential to the track upon recording of data, a magnetic flux leaving from the deviating surface of the main magnetic pole interferes with an adjacent track and writes an unwanted signal in the adjacent track, tending to weaken the magnetic field of the signal originally recorded in the adjacent track, or to weaken a signal read from the adjacent track, thereby causing a readout error.

For solving the above problems, it has been proposed to employ an inversely trapezoidal main magnetic pole having a width that is greater on its trailing end and smaller on its leading end. There has also been proposed a discrete recording medium with nonmagnetic layers disposed between tracks.

However, it is very difficult to manufacture inversely trapezoidal main magnetic poles of stable dimensions and to impart highly accurate angles to such inversely trapezoidal main magnetic poles. In addition, the discrete recording medium is highly costly to manufacture.

SUMMARY OF THE INVENTION

The present invention has been made taking the foregoing problems into consideration, it is an object of the present invention to provide a piezoelectric/electrostrictive device, which is capable of angularly displacing an object with its center of gravity moving a reduced distance, thereby reducing reactive forces generated in a region where the piezoelectric/electrostrictive device is fixed in position, so that the object can be actuated under an easy control and with an increased actuating frequency, i.e., an increased response speed.

According to a first aspect of the present invention, there is provided a piezoelectric/electrostrictive device comprising a rotor and a rotary actuator for angularly displacing the rotor, the rotary actuator having a stationary member, with a first vibratory plate and a second vibratory plate extending in one direction from opposite sides of the stationary member, and a piezoelectric/electrostrictive element mounted on at least one of the first and second vibratory plates for actuating the at least one of the first and second vibratory plates, and the rotor having a pair of opposite surfaces, one of the opposite surfaces including a first end secured to the first vibratory plate, and the other of the opposite surfaces having a second end, which is diagonally opposite to the first end, secured to the second vibratory plate.

In the first aspect of the present invention, the distance between the first end of the rotor that is secured to the first vibratory plate and a boundary region between the first vibratory plate and the stationary member is represented by L 1 , and the distance between the second end of the rotor that is secured to the second vibratory plate and a boundary region between the second vibratory plate and the stationary member is represented by L 2 , wherein the distance L 1 and the distance L 2 may satisfy the relationship L 1 =L 2 .

According to a second aspect of the present invention, there is provided a piezoelectric/electrostrictive device comprising a rotor and a rotary actuator for angularly displacing the rotor, the rotary actuator having a first stationary member and a second stationary member which are spaced from each other, a first vibratory plate extending in one direction from one side of the first stationary member, a second vibratory plate extending in one direction from one side of the second stationary member, and a piezoelectric/electrostrictive element mounted on at least one of the first and second vibratory plates for actuating the at least one of the first and second vibratory plates, and the rotor having a pair of opposite surfaces, one of the opposite surfaces including a first end secured to the first vibratory plate, and the other of the opposite surfaces having a second end, which is diagonally opposite to the first end, secured to the second vibratory plate.

In the second aspect of the present invention, the first vibratory plate may have a first protrusion mounted on a surface thereof which faces the one surface of the rotor, and the second vibratory plate may have a second protrusion mounted on a surface thereof which faces the other surface of the rotor, wherein the first protrusion and the one surface of the rotor are secured to each other, and the second protrusion and the other surface of the rotor are secured to each other.

In the second aspect of the present invention, the first stationary member may have a third protrusion mounted on a surface thereof which faces the rotor, and the second stationary member may have a fourth protrusion mounted on a surface thereof which faces the rotor, wherein the third protrusion and the rotor are secured to each other, and the fourth protrusion and the rotor are secured to each other.

According to a third aspect of the present invention, there is provided a piezoelectric/electrostrictive device comprising a rotor and a rotary actuator for angularly displacing the rotor, the rotary actuator having a central member extending in a first direction, a first arm extending from a first end of the central member in a second direction, a second arm extending from a second end of the central member in a third direction which is opposite to the second direction, a first vibratory plate extending from an end of the first arm in the first direction, a third arm extending from an end of the first vibratory plate in the third direction, a second vibratory plate extending from an end of the second arm in the first direction, a fourth arm extending from an end of the second vibratory plate in the second direction, and a piezoelectric/electrostrictive element mounted on at least one of the first and second vibratory plates for actuating the at least one of the first and second vibratory plates.

In the third aspect of the present invention, the central member may comprise a stationary member, and the rotor may have, on a principal surface thereof, a first corner secured to the third arm and a second corner, which is diagonally opposite to the first corner, secured to the fourth arm.

In the third aspect of the present invention, each of the third arm and the fourth arm may comprise a stationary member, wherein the rotor is secured to the central member.

According to a fourth aspect of the present invention, there is provided a piezoelectric/electrostrictive device comprising a rotor and a rotary actuator for angularly displacing the rotor, the rotary actuator having a first stationary member and a second stationary member which are spaced from each other, a central member disposed between the first stationary member and the second stationary member and extending in a first direction, a first vibratory plate extending from a first end of the first stationary member toward the second stationary member, a second vibratory plate extending from a second end, which is diagonally opposite to the first end, of the second stationary member toward the first stationary member, a first displacement transmitter connected between a third end, which is closer to the first stationary member, of the central member on a surface thereof which faces the first vibratory plate, and an end of the first vibratory plate, for transmitting displacement of the first vibratory plate to the central member, a second displacement transmitter connected between a fourth end, which is closer to the second stationary member, of the central member on a surface thereof which faces the second vibratory plate, and an end of the second vibratory plate, for transmitting displacement of the second vibratory plate to the central member, and a piezoelectric/electrostrictive element mounted on at least one of the first and second vibratory plates for actuating the at least one of the first and second vibratory plates, wherein the rotor is secured to the central member.

According to a fifth aspect of the present invention, there is provided a piezoelectric/electrostrictive device comprising a rotor and a rotary actuator for angularly displacing the rotor, the rotary actuator having a first stationary member and a second stationary member which are spaced from each other, a first metal vibratory plate extending from the first stationary member toward the second stationary member, a second metal vibratory plate extending from the second stationary member toward the first stationary member, and a piezoelectric/electrostrictive element mounted on at least one of the first and second vibratory plates for actuating the at least one of the first and second vibratory plates, and the rotor having a pair of opposite surfaces, one of the opposite surfaces having a first end secured to the first vibratory plate, and the other of the opposite surfaces having a second end, which is diagonally opposite to the first end, secured to the second vibratory plate.

In the fifth aspect of the present invention, the first stationary member and the second stationary member may be integrally combined with each other by a frame.

In the fifth aspect of the present invention, the first stationary member, the first vibratory plate, the second stationary member, and the second vibratory plate may be formed by punching and bending a single metal plate.

According to a sixth aspect of the present invention, there is provided a piezoelectric/electrostrictive device comprising a rotor and a rotary actuator for angularly displacing the rotor, the rotary actuator having a first stationary member and a second stationary member which are spaced from each other, a first metal vibratory plate extending from the first stationary member toward the second stationary member, a second metal vibratory plate extending from the second stationary member toward the first stationary member, a rotor mount secured to an end of the first vibratory plate and to an end of the second vibratory plate, and a piezoelectric/electrostrictive element mounted on at least one of the first and second vibratory plates for actuating the at least one of the first and second vibratory plates, wherein the rotor is mounted on the rotor mount.

In the sixth aspect of the present invention, the first stationary member and the second stationary member may be integrally combined with each other by a frame.

In the sixth aspect of the present invention, the first stationary member, the first vibratory plate, the second stationary member, the second vibratory plate, and the rotor mount may be formed by punching and bending a single metal plate.

According to a seventh aspect of the present invention, there is provided a piezoelectric/electrostrictive device comprising a rotor and a rotary actuator for angularly displacing the rotor, the rotary actuator having a stationary member, a first metal vibratory plate having an end secured to the stationary member and extending in one direction, a second metal vibratory plate having an end secured to the stationary member and extending along an extension of the first vibratory plate, a third metal vibratory plate having an end secured to the stationary member, the third vibratory plate being spaced from the first vibratory plate and extending substantially parallel thereto, a fourth metal vibratory plate having an end secured to the stationary member and extending along an extension of the third vibratory plate, and a piezoelectric/electrostrictive element mounted on at least one of the first through fourth vibratory plates for actuating the at least one of the first through fourth vibratory plates, and the rotor having a pair of opposite surfaces, one of the opposite surfaces having a first end secured to the first vibratory plate, and the other of the opposite surfaces having a second end, which is diagonally opposite to the first end, secured to the fourth vibratory plate.

In the seventh aspect of the present invention, the stationary member may comprise a frame, the first vibratory plate and the second vibratory plate may be secured to a first arm extending from one of two opposite surfaces of the frame to the other surface thereof, and the third vibratory plate and the fourth vibratory plate may be secured to a second arm extending from the other surface of the frame to the one surface thereof.

In the seventh aspect of the present invention, the stationary member may have a rectangular planar shape, the first vibratory plate and the second vibratory plate may be secured to a first arm extending upwardly from one of two opposite surfaces of the stationary member, and the third vibratory plate and the fourth vibratory plate may be secured to a second arm extending upwardly from the other of the two opposite surfaces of the stationary member.

In the seventh aspect of the present invention, the stationary member and the first through fourth vibratory plates may be formed by punching and bending a single metal plate.

In the seventh aspect of the present invention, those of the first through fourth vibratory plates which are free of the piezoelectric/electrostrictive element may comprise a spring.

According to an eighth aspect of the present invention, there is provided a piezoelectric/electrostrictive device comprising a rotor and a rotary actuator for angularly displacing the rotor, the rotary actuator having a stationary member, a first metal vibratory plate having an end secured to the stationary member and extending in one direction, a second metal vibratory plate having an end secured to the stationary member and extending along an extension of the first vibratory plate, a third metal vibratory plate having an end secured to the stationary member, the third vibratory plate being spaced from the first vibratory plate and extending substantially parallel thereto, a fourth metal vibratory plate having an end secured to the stationary member and extending along an extension of the third vibratory plate, a rotor mount secured to respective ends of the first through fourth vibratory plates, and a piezoelectric/electrostrictive element mounted on at least one of the first through fourth vibratory plates for actuating the at least one of the first through fourth vibratory plates, wherein the rotor is mounted on the rotor mount.

In the eighth aspect of the present invention, the stationary member may comprise a frame, wherein the first vibratory plate and the second vibratory plate are secured to a first arm extending from one of two opposite surfaces of the frame to the other surface thereof, and the third vibratory plate and the fourth vibratory plate are secured to a second arm extending from the other surface of the frame to the one surface thereof.

In the eighth aspect of the present invention, the stationary member may have a rectangular planar shape, wherein the first vibratory plate and the second vibratory plate are secured to a first arm extending upwardly from one of two opposite surfaces of the stationary member, and the third vibratory plate and the fourth vibratory plate are secured to a second arm extending upwardly from the other of the two opposite surfaces of the stationary member.

In the eighth aspect of the present invention, the rotor mount may comprise a plurality of feet fixed to respective ends of the first through fourth vibratory plates.

In the eighth aspect of the present invention, the stationary member, the first through fourth vibratory plates, and the rotor mount may be formed by punching and bending a single metal plate.

In the eighth aspect of the present invention, those of the first through fourth vibratory plates which are free of the piezoelectric/electrostrictive element may comprise a spring.

According to a ninth aspect of the present invention, there is provided a piezoelectric/electrostrictive device comprising a rotor and a rotary actuator for angularly displacing the rotor, the rotary actuator having a stationary member, a first vibratory plate and a second vibratory plate which have respective ends secured to the stationary member and are angularly spaced from each other by a predetermined angle, a movable member connected between the other end of the first vibratory plate and the other end of the second vibratory plate, and a piezoelectric/electrostrictive element mounted on at least one of the first and second vibratory plates for actuating the at least one of the first and second vibratory plates, wherein the rotor is secured to the movable member.

In the ninth aspect of the present invention, the predetermined angle may comprise an acute angle or an obtuse angle. Further, the predetermined angle may be 90 degrees or 180 degrees.

According to a tenth aspect of the present invention, there is provided a piezoelectric/electrostrictive device comprising a rotor and a rotary actuator for angularly displacing the rotor, the rotary actuator having a stationary member, with a first vibratory plate and a second vibratory plate extending in one direction from opposite sides of the stationary member, and a piezoelectric/electrostrictive element mounted on at least one of the first and second vibratory plates for actuating the at least one of the first and second vibratory plates, and the rotor having a first connector extending from a first portion thereof, which faces the first vibratory plate, to the first vibratory plate, the first connector interconnecting the first portion and the first vibratory plate, and a second connector extending from a second portion thereof, which faces the first vibratory plate, to the second vibratory plate, the second connector interconnecting the second portion and the second vibratory plate.

In the tenth aspect of the present invention, the rotor may have a constricted portion, wherein the first portion is positioned on the constricted portion, which faces the first vibratory plate, and the second portion is positioned on the constricted portion, which faces the second vibratory plate.

In the tenth aspect of the present invention, the first connector may be of a shape having a cross-sectional area that is substantially uniform from the constricted portion to the first vibratory plate, and the second connector may be of a shape having a cross-sectional area that is substantially uniform from the constricted portion to the second vibratory plate.

In the tenth aspect of the present invention, the first connector may be of a shape having a cross-sectional area that progressively varies from the constricted portion to the first vibratory plate, and the second connector may be of a shape having a cross-sectional area that progressively varies from the constricted portion to the second vibratory plate.

In the tenth aspect of the present invention, the first connector and the first vibratory plate may be secured to each other by an adhesive, and the second connector and the second vibratory plate may be secured to each other by an adhesive.

In the tenth aspect of the present invention, the first connector and the second connector may be formed integrally with the rotor, the first vibratory plate, and the second vibratory plate by punching and bending a metal plate.

In the tenth aspect of the present invention, a first joint position between the first connector and the first vibratory plate, and a second joint position between the second connector and the second vibratory plate, may be in a substantially confronting positional relationship.

In the tenth aspect of the present invention, a third joint position between the first portion of the rotor and the first connector, and a fourth joint position between the second portion of the rotor and the second connector, may be positionally related to each other in point symmetry with respect to a center of gravity of the rotor.

According to the first through tenth aspects of the present invention, the rotor sandwiched by the vibratory plates, or the rotor mounted on the rotor mount to which the vibratory plates are secured, or the rotor secured to the movable member to which the vibratory plates are secured, is angularly displaced when the vibratory plates are actuated by the piezoelectric/electrostrictive element. When the rotor is angularly displaced in this manner, the center of gravity of the rotor essentially is not moved.

When the rotor or an object to which the rotor is fixed is angularly displaced, because movement of the center of gravity of the rotor is small, reactive forces generated in a region at which the piezoelectric/electrostrictive device is fixed in place are small, so that the piezoelectric/electrostrictive device can actuate the object under an easy control with an increased actuating frequency and an increased response speed.

Therefore, the rotor can be controlled with high accuracy when it is angularly displaced. The piezoelectric/electrostrictive device is thus suitable for use in controlling an actuator for positional control of a hard disk drive (HDD). Additionally, the piezoelectric/electrostrictive device may be used successfully for controlling the angle of a small reflecting mirror, controlling the rotation of an antenna, controlling the θ-axis of an XY stage, or controlling the rotation of a manipulator.

Particularly, if the piezoelectric/electrostrictive device is used as an actuator for positioning the magnetic head of an HDD, then the slider can be angularly displaced with high accuracy, making it possible to eliminate or reduce the skew angle. Limitations on the configuration of the pole of the head are lessened for enabling greater freedom of design. Furthermore, inasmuch as interference with adjacent tracks is avoided, gaps, which typically have been provided in view of such interference, are unnecessary and the density of the tracks can be increased. Since the formation of side shields and inversely trapezoidal shapes is facilitated or made unnecessary, the piezoelectric/electrostrictive device for use as an actuator can be manufactured at a reduced cost.

Since the rotor can be translated at a constant skew angle, functions for performing track positioning and skew angle positioning can be realized by a single actuator. The HDD can thus be designed for higher performance and further be reduced in size.

As described above, the piezoelectric/electrostrictive device according to the present invention is capable of angularly displacing an object to which the rotor is secured. When the object is angularly displaced, any movement of the center of gravity of the rotor is small, and reactive forces generated in a region at which the piezoelectric/electrostrictive device is fixed in place are small. Thus, the piezoelectric/electrostrictive device can actuate the object under an easy control with an increased actuating frequency and an increased response speed.

The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which preferred embodiments of the present invention are shown by way of illustrative example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing a first piezoelectric/electrostrictive device according to the present invention;

FIG. 2 is a view showing a second piezoelectric/electrostrictive device according to the present invention;

FIG. 3 is a view showing a first modification of the first piezoelectric/electrostrictive device;

FIG. 4 is a view showing a third piezoelectric/electrostrictive device according to the present invention;

FIG. 5 is a view showing a manner in which the third piezoelectric/electrostrictive device operates according to a first process;

FIG. 6 is a view showing a manner in which the third piezoelectric/electrostrictive device operates according to a second process;

FIG. 7 is a view showing a fourth piezoelectric/electrostrictive device according to the present invention;

FIG. 8 is a plan view of a first ceramic substrate of the fourth piezoelectric/electrostrictive device;

FIG. 9 is a plan view of a second ceramic substrate of the fourth piezoelectric/electrostrictive device;

FIG. 10 is a plan view of a third ceramic substrate of the fourth piezoelectric/electrostrictive device;

FIG. 11 is a view showing a fifth piezoelectric/electrostrictive device according to the present invention;

FIG. 12 is a view showing a manner in which the fifth piezoelectric/electrostrictive device operates in a first mode;

FIG. 13 is a view showing a manner in which the fifth piezoelectric/electrostrictive device operates in a second mode;

FIG. 14 is a view showing a first modification of the fifth piezoelectric/electrostrictive device;

FIG. 15 is a view showing a step (punching step) for manufacturing the fifth piezoelectric/electrostrictive device;

FIG. 16 is a view showing a step (bending step) for manufacturing the fifth piezoelectric/electrostrictive device;

FIG. 17 is a view showing a sixth piezoelectric/electrostrictive device according to the present invention;

FIG. 18 is a view showing a manner in which the sixth piezoelectric/electrostrictive device operates;

FIG. 19 is a view showing a step (punching step) for manufacturing the sixth piezoelectric/electrostrictive device;

FIG. 20 is a view showing a step (bending step) for manufacturing the sixth piezoelectric/electrostrictive device;

FIG. 21 is a view showing a first modification of the sixth piezoelectric/electrostrictive device;

FIG. 22 is a view showing a second modification of the sixth piezoelectric/electrostrictive device;

FIG. 23 is a perspective view showing the sixth piezoelectric/electrostrictive device with a rotor fixed to a rotary actuator;

FIG. 24 is a view showing a step (punching step) for manufacturing the second modification of the sixth piezoelectric/electrostrictive device;

FIG. 25 is a view showing a step (bending step) for manufacturing the second modification of the sixth piezoelectric/electrostrictive device;

FIG. 26 is a perspective view of a seventh piezoelectric/electrostrictive device according to the present invention;

FIG. 27 is a plan view of a first modification of the seventh piezoelectric/electrostrictive device;

FIG. 28 is a plan view of a second modification of the seventh piezoelectric/electrostrictive device;

FIG. 29 is a plan view of a third modification of the seventh piezoelectric/electrostrictive device;

FIG. 30 is a plan view of a fourth modification of the seventh piezoelectric/electrostrictive device;

FIG. 31 is a plan view of a fifth modification of the seventh piezoelectric/electrostrictive device;

FIG. 32 is a view showing an eighth piezoelectric/electrostrictive device according to the present invention;

FIG. 33 is a view of a first modification of the eighth piezoelectric/electrostrictive device;

FIG. 34 is a view of a second modification of the eighth piezoelectric/electrostrictive device;

FIG. 35 is a view showing a ninth piezoelectric/electrostrictive device according to the present invention;

FIG. 36 is a view showing a tenth piezoelectric/electrostrictive device according to the present invention;

FIG. 37 is a view of a first modification of the tenth piezoelectric/electrostrictive device;

FIG. 38 is a view of a second modification of the tenth piezoelectric/electrostrictive device;

FIG. 39 is a view showing a step (punching step) for manufacturing the second modification of the tenth piezoelectric/electrostrictive device;

FIG. 40 is a view showing a step (rotary actuator fabricating step) for manufacturing the second modification of the tenth piezoelectric/electrostrictive device;

FIG. 41 is a view showing a step (adhesive applying step) for manufacturing the second modification of the tenth piezoelectric/electrostrictive device;

FIG. 42 is a view showing a step (assembling step) for manufacturing the second modification of the tenth piezoelectric/electrostrictive device;

FIG. 43 is a view showing a step (adhesive applying step) for manufacturing the second modification of the tenth piezoelectric/electrostrictive device;

FIG. 44 is a view showing a step (parts mounting step) for manufacturing the second modification of the tenth piezoelectric/electrostrictive device;

FIG. 45 is a view showing another step used in manufacturing the second modification of the tenth piezoelectric/electrostrictive device;

FIG. 46 is a view showing an eleventh piezoelectric/electrostrictive device according to the present invention; and

FIG. 47 is a view showing a modification of the eleventh piezoelectric/electrostrictive device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following descriptions, like or corresponding parts are denoted using like or corresponding reference characters throughout the views.

Piezoelectric/electrostrictive devices according to various embodiments of the present invention shall be described below with reference to FIGS. 1 through 47.

The concept of the piezoelectric/electrostrictive device according to the present embodiment covers devices for converting electric energy into mechanical energy and vice versa using a piezoelectric/electrostrictive element. Therefore, the piezoelectric/electrostrictive device can be used most preferably in connection with active devices, such as actuators, vibrators, etc., particularly as displacement devices utilizing displacements based on an inverse piezoelectric effect or an electrostrictive effect. The piezoelectric/electrostrictive device can also preferably be used in connection with passive devices, such as acceleration sensor devices, impact sensor devices, etc.

As shown in FIG. 1, a piezoelectric/electrostrictive device 10 A according to a first embodiment of the present invention (hereinafter referred to as a first piezoelectric/electrostrictive device 10 A) comprises a rotor 12 substantially in the form of a rectangular parallelepiped, the rotor 12 having a pair of opposite surfaces 12 a , 12 b , and a rotary actuator 14 for angularly displacing the rotor 12 . A slider, a sensor, a stage, or the like may be mounted on the rotor 12 . Alternatively, the rotor 12 itself may serve as a slider, a stage, or the like.

The rotary actuator 14 includes a stationary member 16 , a first vibratory plate 18 a and a second vibratory plate 18 b extending in one direction from opposite sides of the stationary member 16 , a first piezoelectric/electrostrictive element 20 a mounted on and extending from a side surface of the first vibratory plate 18 a to the stationary member 16 for actuating the first vibratory plate 18 a , and a second piezoelectric/electrostrictive element 20 b mounted on and extending from a side surface of the second vibratory plate 18 b to the stationary member 16 for actuating the second vibratory plate 18 b.

Of the opposite surfaces 12 a , 12 b of the rotor 12 , the surface 12 a has a first end 22 a secured to an end of the first vibratory plate 18 a by an adhesive 24 , for example. The other surface 12 b has a second end 22 b , which is diagonally opposite to the first end 22 a , secured to an end of the second vibratory plate 18 b by an adhesive 24 , for example. Therefore, the length of the second vibratory plate 18 b is smaller than the length of the first vibratory plate 18 a. The adhesive 24 may comprise an ultraviolet-curable resin, an epoxy resin, or the like.

A first plate member 26 a used for positioning is interposed between the stationary member 16 and the first vibratory plate 18 a , and a second plate member 26 b and a third plate member 26 c , also used for positioning, are interposed between the stationary member 16 and the second vibratory plate 18 b.

When the first piezoelectric/electrostrictive element 20 a actuates the first vibratory plate 18 a so as to curve outwardly, in a direction to bring the end of the first vibratory plate 18 a away from the end of the second vibratory plate 18 b , and when the second piezoelectric/electrostrictive element 20 b actuates the second vibratory plate 18 b so as to curve outwardly, in a direction to bring the end of the second vibratory plate 18 b away from the end of the first vibratory plate 18 a , the rotor 12 is displaced angularly clockwise in FIG. 1.

Conversely, when the first piezoelectric/electrostrictive element 20 a actuates the first vibratory plate 18 a so as to curve inwardly, in a direction to bring the end of the first vibratory plate 18 a toward the end of the second vibratory plate 18 b , and when the second piezoelectric/electrostrictive element 20 b actuates the second vibratory plate 18 b so as to curve inwardly, in a direction to bring the end of the second vibratory plate 18 b toward the end of the first vibratory plate 18 a , the rotor 12 is displaced angularly counterclockwise in FIG. 1.

It is assumed that the distance between the first end 22 a of the rotor 12 that is secured to the first vibratory plate 18 a and the boundary region between the first vibratory plate 18 a and the stationary member 16 is represented by L 1 , and the distance between the second end 22 b of the rotor 12 that is secured to the second vibratory plate 18 b and the boundary region between the second vibratory plate 18 b and the stationary member 16 is represented by L 2 . Angular displacement of the rotor 12 is increased if L 1 =L 2 .

When the first piezoelectric/electrostrictive element 20 a actuates the first vibratory plate 18 a so as to curve outwardly, and the second piezoelectric/electrostrictive element 20 b actuates the second vibratory plate 18 b so as to curve inwardly, the rotor 12 is translated to the right in FIG. 1. When the first piezoelectric/electrostrictive element 20 a actuates the first vibratory plate 18 a so as to curve inwardly, and the second piezoelectric/electrostrictive element 20 b actuates the second vibratory plate 18 b so as to curve outwardly, the rotor 12 is translated to the left in FIG. 1.

The stationary member 16 , the first vibratory plate 18 a , the second vibratory plate 18 b , and the first through third plate members 26 a through 26 c may comprise an integrally sintered assembly of laminated ceramic green sheets. The first piezoelectric/electrostrictive element 20 a and the second piezoelectric/electrostrictive element 20 b may be formed by screen printing, on respective side surfaces of the first vibratory plate 18 a and the second vibratory plate 18 b. The first vibratory plate 18 a and the second vibratory plate 18 b may alternatively be made of metal. If the first vibratory plate 18 a and the second vibratory plate 18 b are made of metal, then the first piezoelectric/electrostrictive element 20 a and the second piezoelectric/electrostrictive element 20 b are secured to respective side surfaces of the first vibratory plate 18 a and the second vibratory plate 18 b by an adhesive, for example.

With the first piezoelectric/electrostrictive device 10 A, therefore, the first vibratory plate 18 a and the second vibratory plate 18 b sandwich the rotor 12 therebetween, and are actuated respectively by the first piezoelectric/electrostrictive element 20 a and the second piezoelectric/electrostrictive element 20 b in order to angularly displace the rotor 21 .

In this case where the rotor 12 is sandwiched by the first vibratory plate 18 a and the second vibratory plate 18 b , since the first end 22 a of one surface 12 a of the rotor 12 is fixed to the end of the first vibratory plate 18 a , and the second end 22 b , which is diagonally opposite to the first end 22 a , of the other surface 12 b of the rotor 12 is fixed to the end of the second vibratory plate 18 b , the center of gravity of the rotor 12 essentially is not moved when the rotor 12 is angularly displaced.

When the rotor 12 , or an object to which the rotor 12 is fixed, is angularly displaced, because movement of the center of gravity of the rotor 12 is small, reactive forces generated in a region (i.e., the region of the stationary member 16 ) at which the first piezoelectric/electrostrictive device 10 A is fixed in place are small, the first piezoelectric/electrostrictive device 10 A can actuate the object under an easy control with an increased actuating frequency and an increased response speed.

Therefore, the rotor 12 can be controlled with high accuracy when it is angularly displaced. The first piezoelectric/electrostrictive device 10 A is thus suitable for use in controlling an actuator for positional control of a hard disk drive (HDD), as well as for controlling the angle of a small reflecting mirror, controlling the rotation of an antenna, controlling the θ-axis of an XY stage, or controlling the rotation of a manipulator.

A piezoelectric/electrostrictive device 10 B according to a second embodiment (hereinafter referred to as a second piezoelectric/electrostrictive device 10 B) of the present invention shall be described below with reference to FIG. 2.

As shown in FIG. 2, the second piezoelectric/electrostrictive device 10 B comprises a rotor 12 substantially in the form of a rectangular parallelepiped, the rotor 12 having a pair of opposite surfaces 12 a , 12 b , and a rotary actuator 14 for angularly displacing the rotor 12 .

The rotary actuator 14 includes a first stationary member 16 A and a second stationary member 16 B, which are spaced from each other, a first vibratory plate 18 a extending in one direction from one side of the first stationary member 16 A, a second vibratory plate 18 b extending in one direction from one side of the second stationary member 16 B, a first piezoelectric/electrostrictive element 20 a mounted on and extending from a side surface of the first vibratory plate 18 a to the first stationary member 16 A for actuating the first vibratory plate 18 a , and a second piezoelectric/electrostrictive element 20 b mounted on and extending from a side surface of the second vibratory plate 18 b to the second stationary member 16 B for actuating the second vibratory plate 18 b.

Conversely, when the first piezoelectric/electrostrictive element 20 a actuates the first vibratory plate 18 a so as to curve inwardly, and the second piezoelectric/electrostrictive element 20 b actuates the second vibratory plate 18 b so as to curve inwardly, the rotor 12 is angularly moved clockwise in FIG. 2.

In the second piezoelectric/electrostrictive device 10 B, as with the first piezoelectric/electrostrictive device 10 A, therefore, when the rotor 12 and an object to which the rotor 12 is connected are angularly displaced, any movement of the center of gravity of the rotor 12 is small. Therefore, reactive forces generated within a region (i.e., a region of the first stationary member 16 A and the second stationary member 16 B) at which the second piezoelectric/electrostrictive device 10 B is fixed in place are small, and hence the second piezoelectric/electrostrictive device 10 B can actuate the rotor 12 and the object under an easy control with an increased actuating frequency and an increased response speed.

In the second embodiment shown in FIG. 2, the rotary actuator 14 is fixed to the rotor 12 at two locations. FIG. 3 shows a modified piezoelectric/electrostrictive device 10 Ba. In FIG. 3, the first vibratory plate 18 a has a first protrusion 28 a mounted on a surface thereof which faces one surface 12 a of the rotor 12 at a longitudinally central position, and the second vibratory plate 18 b has a second protrusion 28 b mounted on a surface thereof which faces another surface 12 b of the rotor 12 at a longitudinally central position. The protrusion 28 a is bonded to the one surface 12 a of the rotor 12 by an adhesive 24 , and the protrusion 28 b is bonded to the other surface 12 b of the rotor 12 by an adhesive 24 .

The first stationary member 16 A has a third protrusion 28 c mounted on a surface thereof which faces the rotor 12 at a longitudinally central position thereof, and the second stationary member 16 B has a fourth protrusion 28 d mounted on a surface thereof which faces the rotor 12 at a longitudinally central position thereof. The third protrusion 28 c is bonded to the rotor 12 by an adhesive 24 , and the fourth protrusion 28 d also is bonded to the rotor 12 by an adhesive 24 .

The modified piezoelectric/electrostrictive device 10 Ba shown in FIG. 3 is effective to prevent the rotor 12 from being torsionally and transversely displaced, and to cause the rotor 12 to be only angularly displaced.

A piezoelectric/electrostrictive device 10 C according to a third embodiment (hereinafter referred to as a third piezoelectric/electrostrictive device 10 C) of the present invention shall be described below with reference to FIG. 4.

As shown in FIG. 4, the third piezoelectric/electrostrictive device 10 C comprises a rotor 12 (not shown in FIG. 4) substantially in the form of a rectangular parallelepiped, and a rotary actuator 14 for angularly displacing the rotor 12 .

The rotary actuator 14 includes a central member 30 extending in a first direction, a first arm 32 a extending from a first end 30 a of the central member 30 in a second direction, a second arm 32 b extending from a second end 30 b of the central member 30 in a third direction that is opposite to the second direction, a first vibratory plate 18 a extending from an end of the first arm 32 a in the first direction, a third arm 32 c extending from an end of the first vibratory plate 18 a in the third direction, a second vibratory plate 18 b extending from an end of the second arm 32 b in the first direction, a fourth arm 32 d extending from an end of the second vibratory plate 18 b in the second direction, a first piezoelectric/electrostrictive element 20 a mounted on at least one side surface of the first vibratory plate 18 a for actuating the first vibratory plate 18 a , and a second piezoelectric/electrostrictive element 20 b mounted on at least one side surface of the second vibratory plate 18 b for actuating the second vibratory plate 18 b.

The third piezoelectric/electrostrictive device 10 C can be used according to at least two processes.

According to a first process, as shown in FIG. 5, the central member 30 is used as a stationary member, wherein the rotor 12 has a first corner 12 c on its principal surface, which is secured to the third arm 32 c by an adhesive, for example. Also, the rotor 12 has a second corner 12 d on its principal surface, which is diagonally opposite to the first corner 12 c, and which is secured to the fourth arm 32 d by an adhesive, for example. The first piezoelectric/electrostrictive element 20 a is mounted on and extends from a side surface of the first vibratory plate 18 a to the first arm 32 a , and the second piezoelectric/electrostrictive element 20 b is mounted on and extends from a side surface of the second vibratory plate 18 b to the second arm 32 b.

When the first piezoelectric/electrostrictive element 20 a actuates the first vibratory plate 18 a so as to curve outwardly in a direction to bring the end of the third arm 32 c away from the central member 30 , and the second piezoelectric/electrostrictive element 20 b actuates the second vibratory plate 18 b so as to curve outwardly in a direction to bring the end of the fourth arm 32 d away from the central member 30 , the rotor 12 is angularly displaced counterclockwise in FIG. 5.

Conversely, when the first piezoelectric/electrostrictive element 20 a actuates the first vibratory plate 18 a so as to curve inwardly in a direction to bring the end of the third arm 32 c toward the central member 30 , and the second piezoelectric/electrostrictive element 20 b actuates the second vibratory plate 18 b so as to curve inwardly in a direction to bring the end of the fourth arm 32 d toward the central member 30 , the rotor 12 is angularly displaced clockwise in FIG. 5.

According to a second process, as shown in FIG. 6, the third arm 32 c and the fourth arm 32 d are used as stationary members, and the rotor 12 is secured to the central member 30 by an adhesive, for example. The first piezoelectric/electrostrictive element 20 a is mounted on and extends from a side surface of the first vibratory plate 18 a to the third arm 32 c, whereas the second piezoelectric/electrostrictive element 20 b is mounted on and extends from a side surface of the second vibratory plate 18 b to the fourth arm 32 d.

When the first piezoelectric/electrostrictive element 20 a actuates the first vibratory plate 18 a so as to curve outwardly in a direction to bring the first arm 32 a away from the fourth arm 32 d, and the second piezoelectric/electrostrictive element 20 b actuates the second vibratory plate 18 b so as to curve outwardly in a direction to bring the second arm 32 b away from the third arm 32 c, the rotor 12 is angularly displaced clockwise in FIG. 6.

Conversely, when the first piezoelectric/electrostrictive element 20 a actuates the first vibratory plate 18 a so as to curve inwardly in a direction to bring the first arm 32 a toward the fourth arm 32 d, and the second piezoelectric/electrostrictive element 20 b actuates the second vibratory plate 18 b so as to curve inwardly in a direction to bring the second arm 32 b toward the third arm 32 c, the rotor 12 is angularly displaced counterclockwise in FIG. 6.

In the third piezoelectric/electrostrictive device 10 C, as with the first piezoelectric/electrostrictive device 10 A, therefore, when the rotor 12 and an object to which the rotor 12 is connected are angularly displaced, movement of the center of gravity of the rotor 12 is small. Therefore, reactive forces generated in a region (i.e., a region of the central member 30 or the third arm 32 c and the fourth arm 32 d ) at which the third piezoelectric/electrostrictive device 10 C is fixed in place are small, and the third piezoelectric/electrostrictive device 10 C can actuate the rotor 12 and the object under an easy control with an increased actuating frequency and an increased response speed.

A piezoelectric/electrostrictive device 10 D according to a fourth embodiment (hereinafter referred to as a fourth piezoelectric/electrostrictive device 10 D) of the present invention shall be described below with reference to FIG. 7.

As shown in FIG. 7, the fourth piezoelectric/electrostrictive device 10 D comprises a rotor 12 substantially in the form of a rectangular parallelepiped, and a rotary actuator 14 for angularly displacing the rotor 12 .

The rotary actuator 14 includes a first stationary member 16 A and a second stationary member 16 B, which are spaced from each other, a central member 30 disposed between the first stationary member 16 A and the second stationary member 16 B and extending in a first direction, a first vibratory plate 18 a extending from a first end 34 a of the first stationary member 16 A toward the second stationary member 16 B, a second vibratory plate 18 b extending from a second end 34 b , which is diagonally opposite to the first end 34 a , of the second stationary member 16 B toward the first stationary member 16 A, a first piezoelectric/electrostrictive element 20 a mounted on a principal surface of the first vibratory plate 18 a for actuating the first vibratory plate 18 a , a second piezoelectric/electrostrictive element 20 b mounted on a principal surface of the second vibratory plate 18 b for actuating the second vibratory plate 18 b , a first displacement transmitter 36 a , and a second displacement transmitter 36 b. The rotor 12 is secured to the central member 30 by an adhesive, for example.

The first displacement transmitter 36 a is connected between a third end 38 a , which is closer to the first stationary member 16 A, of the central member 30 , on a surface thereof which faces the first vibratory plate 18 a , and an end of the first vibratory plate 18 a. The first displacement transmitter 36 a serves to transmit displacement of the first vibratory plate 18 a to the central member 30 .

The first displacement transmitter 36 a has an elongate rectangular wide first flat plate 40 a , and an elongate rectangular narrow second flat plate 40 b.

The first flat plate 40 a has a longer side disposed in facing relation to a side surface of the central member 30 , and is connected to the central member 30 on the third end 38 a thereof by a first hinge 42 a.

The second flat plate 40 b has a longer side thereof disposed in facing relation to a shorter side of the first flat plate 40 a , and a shorter side thereof disposed in facing relation to the side surface of the central member 30 . The second flat plate 40 b is connected to the first flat plate 40 a by a second hinge 42 b that is disposed between a portion of a longer side thereof, which is close to the central member 30 , and a portion of the shorter side of the first flat plate 40 a , which is close to the central member 30 . The second flat plate 40 b has an opposite longer side connected to the second stationary member 16 B by a third hinge 42 c.

The second displacement transmitter 36 b is connected between a fourth end 38 b , which is closer to the second stationary member 16 B, of the central member 30 , on a surface thereof which faces the second vibratory plate 18 b , and an end of the second vibratory plate 18 b. The second displacement transmitter 36 b serves to transmit displacement of the second vibratory plate 18 b to the central member 30 .

The second displacement transmitter 36 b has an elongate rectangular wide third flat plate 40 c and an elongate rectangular narrow fourth flat plate 40 d.

The third flat plate 40 c has a longer side disposed in facing relation to an opposite side surface of the central member 30 , and is connected to the central member 30 by a fourth hinge 42 d on the fourth end 38 b.

The fourth flat plate 40 d has a longer side thereof disposed in facing relation to a shorter side of the third flat plate 40 c , and a shorter side thereof disposed in facing relation to the opposite side surface of the central member 30 . The fourth flat plate 40 d is connected to the third flat plate 40 c by a fifth hinge 42 e that is disposed between a portion of a longer side thereof, which is close to the central member 30 , and a portion of the shorter side of the third flat plate 40 c , which is close to the central member 30 . The fourth flat plate 40 d has an opposite longer side connected to the first stationary member 16 A by a sixth hinge 42 f.

When the first piezoelectric/electrostrictive element 20 a actuates the first vibratory plate 18 a so as to develop a compressive strain in the first vibratory plate 18 a , and the second piezoelectric/electrostrictive element 20 b actuates the second vibratory plate 18 b so as to develop a compressive strain in the second vibratory plate 18 b , the rotor 12 is angularly displaced counterclockwise in FIG. 7.

Conversely, when the first piezoelectric/electrostrictive element 20 a actuates the first vibratory plate 18 a so as to develop a tensile strain in the first vibratory plate 18 a , and the second piezoelectric/electrostrictive element 20 b actuates the second vibratory plate 18 b so as to develop a tensile strain in the second vibratory plate 18 b , the rotor 12 is angularly displaced clockwise in FIG. 7.

In the fourth piezoelectric/electrostrictive device 10 D, as with the first piezoelectric/electrostrictive device 10 A, therefore, when the rotor 12 and an object to which the rotor 12 is connected are angularly displaced, any movement of the center of gravity of the rotor 12 is small. Therefore, reactive forces generated in a region (i.e., a region of the first stationary member 16 A and the second stationary member 16 B) at which the fourth piezoelectric/electrostrictive device 10 D is fixed in place are small, and the fourth piezoelectric/electrostrictive device 10 D can actuate the rotor 12 and the object under an easy control with an increased actuating frequency and an increased response speed.

If the rotary actuator 14 of the fourth piezoelectric/electrostrictive device 10 D is made of ceramics, then a first ceramic substrate 44 a , which serves as a base as shown in FIG. 8, a second ceramic substrate 44 b incorporating the first stationary member 16 A, the second stationary member 16 B, the central member 30 , the first displacement transmitter 36 a , and the second displacement transmitter 36 b as shown in FIG. 9, and a frame-shaped third ceramic substrate 44 c , having the first vibratory plate 18 a and the second vibratory plate 18 b as shown in FIG. 10, may be stacked together, wherein only portions of the first through third ceramic substrates 44 a through 44 c , which serve as the first stationary member 16 A and the second stationary member 16 B, are secured in place by an adhesive. The third ceramic substrate 44 c may have recesses 46 defined therein, forming the third hinge 42 c and the sixth hinge 42 f.

A piezoelectric/electrostrictive device 10 E according to a fifth embodiment (hereinafter referred to a fifth piezoelectric/electrostrictive device 10 E) of the present invention shall be described below with reference to FIG. 11.

As shown in FIG. 11, the fifth piezoelectric/electrostrictive device 10 E comprises a rotor 12 substantially in the form of a rectangular parallelepiped, the rotor 12 having a pair of opposite surfaces 12 a , 12 b , and a rotary actuator 14 for angularly displacing the rotor 12 .

The rotary actuator 14 includes a first stationary member 16 A and a second stationary member 16 B, which are made of metal and spaced from each other, a first metal vibratory plate 18 a extending from the first stationary member 16 A toward the second stationary member 16 B, a second metal vibratory plate 18 b extending from the second stationary member 16 B toward the first stationary member 16 A, a first piezoelectric/electrostrictive element 20 a mounted on a side surface of the first vibratory plate 18 a for actuating the first vibratory plate 18 a , and a second piezoelectric/electrostrictive element 20 b mounted on a side surface of the second vibratory plate 18 b for actuating the second vibratory plate 18 b.

Of the opposite surfaces 12 a , 12 b of the rotor 12 , the surface 12 a has a first end 22 a secured to the first vibratory plate 18 a by an adhesive 24 , for example, whereas the other surface 12 b has a second end 22 b , which is diagonally opposite to the first end 22 a , and which is secured to the second vibratory plate 18 b by an adhesive 24 , for example.

The fifth piezoelectric/electrostrictive device 10 E is similar to the second piezoelectric/electrostrictive device 10 B shown in FIG. 2, except that the first stationary member 16 A, the second stationary member 16 B, the first vibratory plate 18 a , and the second vibratory plate 18 b are all made of metal.

When the first piezoelectric/electrostrictive element 20 a actuates the first vibratory plate 18 a so as to curve outwardly and the second piezoelectric/electrostrictive element 20 b actuates the second vibratory plate 18 b so as to curve outwardly, the rotor 12 is angularly displaced clockwise in FIG. 12.

Conversely, when the first piezoelectric/electrostrictive element 20 a actuates the first vibratory plate 18 a so as to curve inwardly and the second piezoelectric/electrostrictive element 20 b actuates the second vibratory plate 18 b so as to curve inwardly, the rotor 12 is angularly displaced counterclockwise in FIG. 13.

With the fifth piezoelectric/electrostrictive device 10 E, as with the first piezoelectric/electrostrictive device 10 A, therefore, when the rotor 12 and an object to which the rotor 12 is connected are angularly displaced, any movement of the center of gravity of the rotor 12 is small. Therefore, reactive forces generated in a region (i.e., a region of the first stationary member 16 A and the second stationary member 16 B) at which the fifth piezoelectric/electrostrictive device 10 E is fixed in place are small, and the fifth piezoelectric/electrostrictive device 10 E can actuate the rotor 12 and the object under an easy control with an increased actuating frequency and an increased response speed.

In the above embodiment, the first stationary member 16 A and the second stationary member 16 B are separate from each other. FIG. 14 shows a modified piezoelectric/electrostrictive device 10 Ea, wherein the first stationary member 16 A and the second stationary member 16 B are integrally combined with each other by a metal frame 48 . A rotor mount 50 is joined to an end of the first vibratory plate 18 a and to an end of the second vibratory plate 18 b , wherein the rotor 12 (not shown in FIG. 14) is mounted on the rotor mount 50 .

The modified piezoelectric/electrostrictive device 10 Ea is fabricated as follows: As shown in FIG. 15, a single metal plate 52 is prepared. Then, the metal plate 52 is punched to form a first slot 54 and a second slot 56 therein, thereby shaping the first stationary member 16 A, the second stationary member 16 B, the first vibratory plate 18 a , the second vibratory plate 18 b , and the rotor mount 50 .

Thereafter, the second vibratory plate 18 b and the first vibratory plate 18 a are bent upwardly respectively about a straight portion 54 a of the first slot 54 , which extends along the second vibratory plate 18 b as a first fold line 58 a , and a straight portion 56 a of the second slot 56 , which extends along the first vibratory plate 18 a as a second fold line 58 b , as shown in FIG. 16. At this time, the metal frame 48 is formed.

Thereafter, the first piezoelectric/electrostrictive element 20 a is secured onto a side surface of the first vibratory plate 18 a by an adhesive, for example, whereas the second piezoelectric/electrostrictive element 20 b is secured onto a side surface of the second vibratory plate 18 b by an adhesive, for example.

Then, as shown in FIG. 14, the rotor 12 , not shown, is mounted on the rotor mount 50 , thereby completing the modified piezoelectric/electrostrictive device 10 Ea.

Since the piezoelectric/electrostrictive device 10 Ea can easily be produced by punching and bending a single metal plate 52 , the manufacturing process is simplified and manufacturing costs are lowered.

Inasmuch as all components of the rotary actuator 14 are made of metal, the modified piezoelectric/electrostrictive device 10 Ea offers the following additional advantages:

Since the rotary actuator 14 is made of metal, it is highly resistant to shocks. Because the rotor 12 is angularly displaced when the first vibratory plate 18 a and the second vibratory plate 18 b that face each other are bent, stresses are distributed within the rotary actuator 14 . Accordingly, the piezoelectric/electrostrictive device 10 Ea is less liable to suffer from metal fatigue, and has a longer service life and better reliability.

If the rotary actuator is made of ceramics, then stresses tend to concentrate on the hinges thereof. However, such stress concentration can be avoided if the rotary actuator is made of metal.

Since the first piezoelectric/electrostrictive element 20 a and the second piezoelectric/electrostrictive element 20 b are formed as a unimorph/bimorph structure on a metal base, they are less subject to stress concentration due to electrostrictive strains, external forces, or shocks, and further, are highly resistant to shocks and thus have a longer service life.

The rotary actuator 14 made of metal is simple in structure. Since the first vibratory plate 18 a and the second vibratory plate 18 b are surrounded by the frame 48 , the rotary actuator 14 can be designed so as to occupy a reduced volume and have a reduced weight, with greater freedom than if the rotary actuator were constructed of a laminated assembly of green sheets.

Since the first vibratory plate 18 a and the second vibratory plate 18 b extend perpendicularly from the metal plate 52 , the rotary actuator 14 is highly resistant to vertical shocks, in particular, and can produce a large angular displacement under relatively weak forces.

A piezoelectric/electrostrictive device 10 F according to a sixth embodiment (hereinafter referred to as a sixth piezoelectric/electrostrictive device 10 F) of the present invention shall be described below with reference to FIG. 17.

As shown in FIG. 17, the sixth piezoelectric/electrostrictive device 10 F comprises a rotor 12 (not shown in FIG. 17) substantially in the form of a rectangular parallelepiped, and a rotary actuator 14 for angularly displacing the rotor 12 .

The rotary actuator 14 includes a frame-shaped stationary member 16 made of metal, a first metal vibratory plate 18 a having an end secured to the stationary member 16 and extending in one direction, a second metal vibratory plate 18 b having an end secured to the stationary member 16 and extending along an extension of the first vibratory plate 18 a , a third metal vibratory plate 18 c having an end secured to the stationary member 16 , the third vibratory plate 18 c being spaced from the first vibratory plate 18 a and extending substantially parallel thereto, a fourth metal vibratory plate 18 d having an end secured to the stationary member 16 and extending along an extension of the third vibratory plate 18 c , a rotor mount 50 joined to ends of the first through fourth vibratory plates 18 a through 18 d , a first piezoelectric/electrostrictive element 20 a mounted on a side surface of the first vibratory plate 18 a for actuating the first vibratory plate 18 a , a second piezoelectric/electrostrictive element 20 b mounted on a side surface of the second vibratory plate 18 b for actuating the second vibratory plate 18 b , a third piezoelectric/electrostrictive element 20 c mounted on a side surface of the third vibratory plate 18 c for actuating the third vibratory plate 18 c , and a fourth piezoelectric/electrostrictive element 20 d mounted on a side surface of the fourth vibratory plate 18 d for actuating the fourth vibratory plate 18 d. The rotor 12 is fixedly mounted on a rotor mount 50 , although the rotor 12 has been omitted from illustration in FIG. 17.

The stationary member 16 comprises a metal frame 48 . The first vibratory plate 18 a and the second vibratory plate 18 b are secured to an eleventh arm 60 a extending from one of two opposite surfaces of the frame 48 to the other surface thereof. The third vibratory plate 1 . 8 c and the fourth vibratory plate 18 d are secured to a twelfth arm 60 b extending from the other surface of the frame 48 to the one surface thereof.

When the second piezoelectric/electrostrictive element 20 b actuates the second vibratory plate 18 b so as to develop a compressive strain in the second vibratory plate 18 b , and the third piezoelectric/electrostrictive element 20 c actuates the third vibratory plate 18 c so as to develop a compressive strain in the third vibratory plate 18 c , the rotor 12 is angularly displaced counterclockwise in FIG. 18.

Conversely, when the first piezoelectric/electrostrictive element 20 a actuates the first vibratory plate 18 a so as to develop a compressive strain in the first vibratory plate 18 a , and the fourth piezoelectric/electrostrictive element 20 d actuates the fourth vibratory plate 18 d so as to develop a compressive strain in the fourth vibratory plate 18 d , the rotor 12 is angularly displaced clockwise in FIG. 18.

In the sixth piezoelectric/electrostrictive device 10 F, as with the first piezoelectric/electrostrictive device 10 A, therefore, when the rotor 12 and an object to which the rotor 12 is connected are angularly displaced, any movement of the center of gravity of the rotor 12 is small. Therefore, reactive forces generated in a region (i.e., a region of the stationary member 16 ) at which the sixth piezoelectric/electrostrictive device 10 F is fixed in place are small, and the sixth piezoelectric/electrostrictive device 10 F can actuate the rotor 12 and the object under an easy control with an increased actuating frequency and an increased response speed. Furthermore, since the sixth piezoelectric/electrostrictive device 10 F is made of metal, as with the fifth piezoelectric/electrostrictive device 10 E, it offers advantages based on the components made of metal.

The first through fourth piezoelectric/electrostrictive elements 20 a through 20 d may be controlled so as to enable the rotor 12 to be torsionally and angularly displaced at the same time.

The sixth piezoelectric/electrostrictive device 10 F is fabricated as follows: As shown in FIG. 19, a single metal plate 52 is prepared. Then, the metal plate 52 is punched to form eleventh through fourteenth slots 62 a through 62 d therein, thereby shaping the stationary member 16 , the eleventh arm 60 a , the twelfth arm 60 b , the first through fourth vibratory plates 18 a through 18 d , and the rotor mount 50 .

Thereafter, the first through fourth vibratory plates 18 a through 18 d are bent upwardly, as shown in FIG. 20, about a straight portion, which interconnects ends of the eleventh slot 62 a and the twelfth slot 62 b , and a straight portion, which interconnects opposite ends of the eleventh slot 62 a and the twelfth slot 62 b , forming an eleventh fold line 64 a and a twelfth fold line 64 b.

Thereafter, the first through fourth piezoelectric/electrostrictive elements 20 a through 20 d are secured to respective side surfaces of the first through fourth vibratory plates 18 a through 18 d by an adhesive, for example.

Then, as shown in FIG. 17, the rotor 12 , not shown, is mounted on the rotor mount 50 , thereby completing the sixth piezoelectric/electrostrictive device 10 F.

Since the sixth piezoelectric/electrostrictive device 10 F can easily be produced by punching and bending a single metal plate 52 , the manufacturing process is simplified and manufacturing costs are lowered.

In the above embodiment, the first through fourth piezoelectric/electrostrictive elements 20 a through 20 d are secured to respective side surfaces of the first through fourth vibratory plates 18 a through 18 d by an adhesive. FIG. 21 shows a piezoelectric/electrostrictive device 10 Fa according to a first modification. In the piezoelectric/electrostrictive device 10 Fa according to the first modification, the first vibratory plate 18 a comprises a first compression spring 66 a , and the third vibratory plate 18 c comprises a second compression spring 66 b.

When the first piezoelectric/electrostrictive element 20 a actuates the first vibratory plate 18 a so as to develop a compressive strain therein, the first compression spring 66 a is extended. Therefore, the rotor 12 is angularly displaced counterclockwise in FIG. 21.

Conversely, when the fourth piezoelectric/electrostrictive element 20 d actuates the fourth vibratory plate 18 d so as to develop a compressive strain therein, the second compression spring 66 b is extended. Therefore, the rotor 12 is angularly displaced clockwise in FIG. 21.

The first compression spring 66 a and the second compression spring 66 b make it possible to greatly increase the angular displacement of the rotor 12 .

In the above embodiment, the stationary member 16 is in the form of a frame 48 . FIG. 22 shows a piezoelectric/electrostrictive device 10 Fb according to a second modification. In the modified piezoelectric/electrostrictive device 10 Fb, the stationary member 16 has a rectangular planar shape. The first vibratory plate 18 a and the second vibratory plate 18 b are secured to a twenty-first arm 68 a extending upwardly from one of two opposite surfaces of the stationary member 16 , whereas the third vibratory plate 18 c and the fourth vibratory plate 18 d are secured to a twenty-second arm 68 b extending upwardly from the other of the two opposite surfaces of the stationary member 16 . The rotor mount 50 comprises first through fourth feet 70 a through 70 d , which are fixed to respective ends of the first through fourth vibratory plates 18 a through 18 d. The rotor 12 is mounted on the first through fourth feet 70 a through 70 d , as shown in FIG. 23.

The piezoelectric/electrostrictive device 10 Fb according to the second modification is fabricated as follows: As shown in FIG. 24, a single metal plate is punched to produce a blank plate 72 made up of the stationary member 16 , the twenty-first arm 68 a , the twenty-second arm 68 b , the first through fourth vibratory plates 18 a through 18 d , and the first through fourth feet 70 a through 70 d.

Thereafter, the end of the first vibratory plate 18 a , the end of the second vibratory plate 18 b , the end of the third vibratory plate 18 c , and the end of the fourth vibratory plate 18 d are bent respectively about a twenty-first fold line 74 a near the end of the first vibratory plate 18 a , a twenty-second fold line 74 b near the end of the second vibratory plate 18 b , a twenty-third fold line 74 c near the end of the third vibratory plate 18 c , and a twenty-fourth fold line 74 d near the end of the fourth vibratory plate 18 d. Then, the end of the first vibratory plate 18 a , the end of the second vibratory plate 18 b , the end of the third vibratory plate 18 c , and the end of the fourth vibratory plate 18 d are bent respectively about a first boundary line 76 a between the first vibratory plate 18 a and the first foot 70 a , a second boundary line 76 b between the second vibratory plate 18 b and the second foot 70 b , a third boundary line 76 c between the third vibratory plate 18 c and the third foot 70 c , and a fourth boundary line 76 d between the fourth vibratory plate 18 d and the fourth foot 70 d . In addition, the twenty-first arm 68 a is bent about a twenty-fifth fold line 78 a near the stationary member 16 , and the twenty-second arm 68 b is bent about a twenty-sixth fold line 78 b near the stationary member 16 . The first through fourth vibratory plates 18 a through 18 d are thus bent upwardly, whereas the first through fourth feet 70 a through 70 d lie horizontally, as shown in FIG. 25.

The rotor 12 is then mounted on the horizontal first through fourth feet 70 a through 70 d , thereby completing the piezoelectric/electrostrictive device 10 Fb according to the second modification, as shown in FIG. 23.

Since the piezoelectric/electrostrictive device 10 Fb can easily be produced by punching and bending a single metal plate, the manufacturing process is simplified and manufacturing costs are lowered.

A piezoelectric/electrostrictive device 10 G according to a seventh embodiment (hereinafter referred to as a seventh piezoelectric/electrostrictive device 10 G) of the present invention shall be described below with reference to FIG. 26.

As shown in FIG. 26, the seventh piezoelectric/electrostrictive device 10 G comprises a rotor 12 (not shown in FIG. 26) substantially in the form of a rectangular parallelepiped, and a rotary actuator 14 for angularly displacing the rotor 12 .

The rotary actuator 14 includes a stationary member 16 made of metal, a first vibratory plate 18 a and a second vibratory plate 18 b , which have respective ends secured to the stationary member 16 , and which also are made of metal and angularly spaced from each other by a predetermined angle 0 , a metal movable member 80 connected between the other end of the first vibratory plate 18 a and the other end of the second vibratory plate 18 b , a first piezoelectric/electrostrictive element 20 a mounted on a side surface of the first vibratory plate 18 a for actuating the first vibratory plate 18 a , and a second piezoelectric/electrostrictive element 20 b mounted on a side surface of the second vibratory plate 18 b for actuating the second vibratory plate 18 b. The rotor 12 , not shown, is secured, for example, to a lower surface of the movable member 80 by an adhesive or the like.

The stationary member 16 , the first vibratory plate 18 a , the second vibratory plate 18 b , and the movable member 80 may easily be fabricated by punching and bending a single metal plate, for example.

When the first piezoelectric/electrostrictive element 20 a actuates the first vibratory plate 18 a to develop a compressive strain in the first vibratory plate 18 a , and the second piezoelectric/electrostrictive element 20 b actuates the second vibratory plate 18 b to develop a tensile strain in the second vibratory plate 18 b , the rotor 12 is angularly displaced clockwise in FIG. 26.

Conversely, when the first piezoelectric/electrostrictive element 20 a actuates the first vibratory plate 18 a to develop a tensile strain in the first vibratory plate 18 a , and the second piezoelectric/electrostrictive element 20 b actuates the second vibratory plate 18 b to develop a compressive strain in the second vibratory plate 18 b , the rotor 12 is angularly displaced counterclockwise in FIG. 26.

Since the rotary actuator 14 angularly moves about a center near the point of intersection between an extension of the first vibratory plate 18 a and an extension of the second vibratory plate 18 b , the rotor 12 should preferably be secured to the movable member 80 such that the center of gravity of the rotor 12 is in conformity with the center of angular movement.

The predetermined angle θ may be an acute angle, as indicated in the piezoelectric/electrostrictive device 10 Ga according to a first modification shown in FIG. 27, or may be an obtuse angle, as indicated in the piezoelectric/electrostrictive device 10 Gb according to a second modification shown in FIG. 28. The predetermined angle θ may be 90 degrees, or may be 180 degrees, as indicated in the piezoelectric/electrostrictive device 10 Gc according to a third modification shown in FIG. 29. In the piezoelectric/electrostrictive devices 10 Ga, 10 Gb and 10 Gc according to the first through third modifications, one side surface of the movable member 80 and an end of the first vibratory plate 18 a are integrally connected to each other by a thirty-first arm 82 a , whereas the other side surface of the movable member 80 and an end of the second vibratory plate 18 b are integrally connected to each other by a thirty-second arm 82 b.

FIG. 30 shows a piezoelectric/electrostrictive device 10 Gd according to a fourth modification. In the piezoelectric/electrostrictive device 10 Gd, the predetermined angle θ is 180 degrees. A central portion of the surface of the movable member 80 , which faces the stationary member 16 , and an end of the first vibratory plate 18 a are integrally connected to each other by an L-shaped forty-first arm 84 a. The central portion of the surface of the movable member 80 and an end of the second vibratory plate 18 b are integrally connected to each other by an L-shaped forty-second arm 84 b.

FIG. 31 shows a piezoelectric/electrostrictive device 10 Ge according to a fifth modification. In the piezoelectric/electrostrictive device 10 Ge, the predetermined angle