Method of producing a piezoelectric/electrostrictive device

A piezoelectric/electrostrictive device includes a base having a pair of right and left movable parts and a fixing part disposed at one end thereof, and piezoelectric/electrostrictive elements disposed on the sides of the movable parts of the base. Accordingly, the piezoelectric/electrostrictive device is fabricated to have a construction with fewer components. The piezoelectric/electrostrictive device having a construction with fewer components is provided by adopting a base having an integral structure formed by bending an original plate stamped into a shape that delineates a plane development of the base.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a piezoelectric/electrostrictive device and a method of producing the same.

2. Description of the Background Art

As one form of piezoelectric/electrostrictive device, there is known a piezoelectric/electrostrictive device that includes a base having a pair of right and left movable parts and a fixing part that connects the movable parts with each other at one end thereof and a piezoelectric/electrostrictive element is disposed on at least one side of the movable parts of the base. There is also known a piezoelectric/electrostrictive device that includes a base having a pair of right and left movable parts, a fixing part that connects the movable parts with each other at one end thereof, and a mounting part that connects the movable parts with each other at the other end thereof and a piezoelectric/electrostrictive element disposed on at least one side of the movable parts of the base. The above-mentioned piezoelectric/electrostrictive devices are disclosed in the specification of European Patent EP1017116A2.

The piezoelectric/electrostrictive device of such a form has a function of operating the movable parts caused by the displacement operation of the piezoelectric/electrostrictive element or a sensing function of sensing the displacement of the movable parts input from the side that is sensed, with the use of the piezoelectric/electrostrictive element. By effectively using these functions, the piezoelectric/electrostrictive device is used in a wide range of fields, such as those described below.

Piezoelectric/electrostrictive devices of such a form are used as active elements such as various transducers, various actuators, frequency region functional components (filters), transformers, vibrators and resonators for communication or mechanical power, oscillators, and discriminators, various sensor elements such as supersonic wave sensors, acceleration sensors, angular velocity sensors, impact sensors, and mass sensors, and various actuators that are put to use for displacement, positioning adjustment, and angle adjustment mechanism for various precision components of optical instruments and precision apparatuses.

Piezoelectric/electrostrictive devices are formed typically by cutting a device master into a suitable size, and the device master is constructed by bonding a piezoelectric/electrostrictive element onto both of the front and rear surfaces of a base master via an adhesive, or is constructed by integrally forming these. Here, the base master is constructed by laminating and baking plural sheets.

Thus, the piezoelectric/electrostrictive device having such a form has a large number of construction components, so that the device is produced at a high cost and through a cumbersome assembling work. Moreover, since the construction components are bonded via an adhesive, there arises a variation of adhesion between the construction components, giving rise to a fear that the device characteristics may be adversely affected.

Further, the piezoelectric/electrostrictive device having such a form is produced by adopting means to cut a device master suitably into a large number of devices. Therefore, the piezoelectric/electrostrictive devices formed by cutting are contaminated with dusts generated at the time of cutting, cutting liquid, and organic components such as an adhesive or wax used for holding the device master at the time of cutting, so that it is not easy to clean the piezoelectric/electrostrictive device.

Also, in the case where the base is constructed with ceramics, one must adopt a hard ceramic material such as zirconia, since the ceramics are liable to be split. Even if a hard ceramic material is adopted, one must choose a suitable cutting condition to prevent a loss of material through nicks or cracks. Further, since the base is made of a hard ceramic material, the machining process is difficult to be designed and, in order to increase the number of machining products, one must give a careful consideration such as use of a large number of machining apparatuses having different functions.

The base can be constructed with a metal material. The use of a metal material, however, gives rise to an oxidized end surface caused by friction heat during the cutting process and burrs remain on the processed end surface. Consequently, another processing step must be added to remove the burrs. Further, the piezoelectric/electrostrictive element can be tested only after the device master is cut.

Meanwhile, the device cut out from the device master is preferably cleaned by adopting ultrasonic cleaning that can easily remove the contamination. However, if a strong ultrasonic wave is used to obtain a high cleaning effect in ultrasonic cleaning, the device may be damaged, and the piezoelectric/electrostrictive element may be broken or peeled off from the base. For this reason, if the ultrasonic cleaning is adopted, one must select a weak ultrasonic wave that does not give damages to the device. However, if such a cleaning condition is adopted, a long period of time is needed in removing the contamination that has adhered at the time of cutting.

Dust generation from the piezoelectric/electrostrictive device may cause the following problems. For example, in the case where the piezoelectric/electrostrictive device is used in an actuator of a magnetic head in a hard disk drive, if dust is generated in the drive, the dust may cause crash of the floating slider onto the medium, thereby raising a fear of data destruction. Also, for the piezoelectric/electrostrictive device itself, the dust may adhere to the electrode of the piezoelectric/electrostrictive element, thereby giving rise to a fear of short circuit. For this reason, a high level of cleaning is required not only in the hard disk drive but also in the device itself.

Therefore, an object of the present invention is to solve the aforementioned problems of the prior art by allowing the base constituting the piezoelectric/electrostrictive device of that form to have an integral structure using one sheet of flat plate as an original plate.

SUMMARY OF THE INVENTION

The present invention relates to a piezoelectric/electrostrictive device and a method of producing the piezoelectric/electrostrictive device. The piezoelectric/electrostrictive devices according to the present invention are piezoelectric/electrostrictive devices provided in the following three forms.

A piezoelectric/electrostrictive device of the first form according to the present invention is a piezoelectric/electrostrictive device that includes a base having a pair of right and left movable parts and a fixing part that connects the movable parts with each other at one end thereof. A piezoelectric/electrostrictive element is disposed on at least one side of the movable parts of the base.

A piezoelectric/electrostrictive device of the second form according to the present invention is a piezoelectric/electrostrictive device that includes a base having a pair of right and left movable parts, a fixing part that connects the movable parts with each other at one end thereof, and a mounting part that is separate from the fixing part and connects the movable parts with each other at the other end thereof. A piezoelectric/electrostrictive element is disposed on at least one side of the movable parts of the base.

A piezoelectric/electrostrictive device of the third form according to the present invention is a piezoelectric/electrostrictive device that includes a base having a pair of right and left movable parts, a fixing part that connects the movable parts with each other at one end thereof, a mounting part that is separate from the fixing part and connects the movable parts with each other at the other end thereof, and a connecting part that is integral with the mounting part and surrounds the mounting part, the movable parts, and the fixing part. A piezoelectric/electrostrictive element is disposed on at least one side of the movable parts of the base.

In the piezoelectric/electrostrictive device of the first form according to the present invention, the base is constructed with one sheet of flat plate; the fixing part has a flat plate shape; and the movable parts are erect by a predetermined height from side peripheries of the fixing part to face each other and extend beyond the other end of the fixing part along the side peripheries of the fixing part.

The piezoelectric/electrostrictive device can be constructed in such a manner that a slit-shaped groove extending from the other end of the fixing part intervenes between a base part of the movable parts constituting the base and the side peripheries of the fixing part. Further, the piezoelectric/electrostrictive device can be constructed in such a manner that a connecting portion between a base part of the movable parts and the side peripheries of the fixing part constituting the base has a circular arc shape.

In the piezoelectric/electrostrictive device of the second form according to the present invention, the base is constructed with one sheet of flat plate; the fixing part and the mounting part have a flat plate shape; and the movable parts are erect by a predetermined height from side peripheries of the fixing part and the mounting part to face each other and extend along the side peripheries of the fixing part and the mounting part.

The piezoelectric/electrostrictive device can be constructed in such a manner that a laterally extending slit-shaped groove intervenes between the other end of the fixing part and the one end of the mounting part constituting the base, and a longitudinally extending slit-shaped groove intervenes between a base part of the movable parts and the side peripheries of the fixing part and the mounting part. Alternatively, the piezoelectric/electrostrictive device can be constructed in such a manner that a laterally and longitudinally extending rectangular opening intervenes between the other end of the fixing part and the one end of the mounting part constituting the base. Further, the piezoelectric/electrostrictive device can be constructed in such a manner that a connecting portion between a base part of the movable parts and the side peripheries of the fixing part constituting the base has a circular arc shape.

In the piezoelectric/electrostrictive device of the third form according to the present invention, the base is constructed with one sheet of flat plate; the fixing part and the mounting part have a flat plate shape; the movable parts are erect by a predetermined height from side peripheries of the fixing part and the mounting part to face each other and extend along the side peripheries of the fixing part and the mounting part; and the movable parts, the fixing part, and the mounting part are positioned within a central space of the connecting part.

The piezoelectric/electrostrictive device can be constructed in such a manner that the central space of the connecting part on a side of the one end of the fixing part is either closed or open. Further, the piezoelectric/electrostrictive device can be constructed in such a manner that a connecting portion between a base part of the movable parts and the side peripheries of the fixing part constituting the base has a circular arc shape. Still further, the piezoelectric/electrostrictive device can be constructed in such a manner that a connecting portion between a base part of the movable parts and the side peripheries of the fixing part and the mounting part constituting the base has a circular arc shape.

The piezoelectric/electrostrictive devices of these forms according to the present invention can employ the following constructions, namely, a construction such that the base is constructed with a flat plate made of metal; a construction such that a central portion, as viewed in a length direction, of the movable parts constituting the base is formed to have a smaller thickness than other portions of the movable parts; a construction such that the movable parts constituting the base has a reinforcing part located at an end thereof on the fixing part side and bent from an upper edge of the end to extend towards and abut against a surface of the fixing part; a construction such that the movable parts constituting the base has a reinforcing part located at an end thereof on the fixing part side and bent from a front edge of the end to extend towards an inner side and abut against a surface of the fixing part; and a construction such that a reinforcing member intervenes between the movable parts on the fixing part constituting the base. Furthermore, the piezoelectric/electrostrictive devices can employ a construction such that the fixing part constituting the base extends from the one end side of the movable parts and is enlarged as compared with a case of being located within the movable parts, and a construction such that the mounting part constituting the base extends from the other end side of the movable parts and is enlarged as compared with a case of being located within the movable parts.

The methods of producing a piezoelectric/electrostrictive device according to the present invention are directed to methods of respectively producing piezoelectric/electrostrictive devices of the above-described three forms, and the methods of producing the piezoelectric/electrostrictive devices of these various forms are as follows.

The first production method according to the present invention is a method of producing a piezoelectric/electrostrictive device of the first form according to the present invention, wherein the method includes the steps of preparing a flexible and bendable flat plate as a material for forming the base, stamping the flat plate into a shape that delineates a plane development of the base to form a stamped structure, and bending the stamped structure at a predetermined site to form the base having the movable parts and the fixing part.

The production method can be carried out in such a manner that the stamped structure has a gate-shaped opening composed of a pair of straight side grooves located at right and left sides of a rectangular flat plate and extending along side peripheries and an opening formed by cutting and removing a portion between the two grooves, and the side peripheries of the flat plate are bent along the side grooves to form the side peripheries into the movable parts and to form a portion between the side grooves into the fixing part.

The second production method according to the present invention is a method of producing a piezoelectric/electrostrictive device of the second form according to the present invention, wherein the method includes the steps of preparing a flexible and bendable flat plate as a material for forming the base, stamping the flat plate into a shape that delineates a plane development of the base to form a stamped structure, and bending the stamped structure at a predetermined site to form the base having the movable parts, the fixing part, and the mounting part.

The production method can be carried out in such a manner that the stamped structure has an H-shaped opening composed of a pair of straight side grooves located at right and left sides of a rectangular flat plate and extending along side peripheries and a straight central groove that connects the two side grooves with each other at a middle part, and the side peripheries of the flat plate are bent along the side grooves to form the side peripheries into the movable parts and to form a portion between the side grooves into the fixing part and the mounting part. Further, the production method can be carried out in such a manner that the stamped structure has a rectangular opening at a central part of a rectangular flat plate, and side peripheries of the flat plate are bent along side peripheries of the opening to form the side peripheries into the movable parts and to form a portion between the side peripheries into the fixing part and the mounting part.

The third production method according to the present invention is a method of producing a piezoelectric/electrostrictive device of the third form according to the present invention, wherein the method includes the steps of preparing a flexible and bendable flat plate as a material for forming the base, stamping the flat plate into a shape that delineates a plane development of the base to form a stamped structure, and bending the stamped structure at a predetermined site to form the base having the movable parts, the fixing part, the mounting part, and the connecting part.

The production method can be carried out in such a manner that the stamped structure has a rectangular flat plate part located inside a central opening of a rectangular flat plate and has an H-shaped opening composed of a pair of straight side grooves located at right and left sides of the flat plate part and extending along side peripheries and a straight central groove that connects the two side grooves with each other at a middle part, and the side peripheries of the flat plate part are bent along the side grooves to form the side peripheries into the movable parts, to form a portion between the side grooves into the fixing part and the mounting part, and to form a portion around the central opening into the connecting part.

The production methods according to the present invention can be carried out in such a manner that a flat plate made of metal is adopted as a material for forming the base, and an opening of the stamped structure is formed by stamping simultaneously with stamping the flat plate or formed by a hole-forming process after stamping the flat plate.

It is essential in the principle of operation that the fixing part or the fixing part and the mounting part are closely connected to the two flexible side peripheries. Since these are integrally formed in the piezoelectric/electrostrictive devices according to the present invention, the most preferable modes are embodied in view of the principle of operation.

For example, in the case where the aforesaid two or three essential parts are made of metal and welded with each other, one must take into consideration the problems in the heat treatment step, such as distortion by heat of welding, deterioration of material quality, and annealing. In contrast, in the case where the base is integrally formed as in the piezoelectric/electrostrictive devices according to the present invention, these fears are absent even if the base is made of metal, and also an improvement in the strength of the connecting part by process hardening at the time of integral forming can be expected.

If the piezoelectric/electrostrictive device according to the present invention is combined with a component (for example, a magnetic head of a hard disk drive), the height after assemblage will not be equal to the sum of the height of the component and the height of the device but will be smaller than the sum, thereby producing an advantage that the device can have a compact construction. Regarding the height of the device, the thickness of the plate of the movable parts and the thickness of the adhesive are added to the height of the component; however, as compared with the known devices described at the beginning, the height after assemblage can be reduced, thereby providing an effect of space reduction. Further, the assemblage can be carried out with ease simply by bonding the component onto the fixing part, and the bonding area can be enlarged, thereby advantageously increasing the bonding strength and providing a structure that will not be easily dropped off by impact.

In the first and second piezoelectric/electrostrictive devices among the piezoelectric/electrostrictive devices according to the present invention, it is easy in view of their structure to form, by pressing, a recess to accommodate an adhesive at the bonding site of the mounting part and the fixing part to the component to be controlled. This can increase the bonding strength and can restrain the squeeze-out of the adhesive. Also, it is easy to form a standard position (hole or the like) for positioning that is used in assembling the component. For this reason, the assembling precision in assembling the component onto the mounting part on the device and in mounting the fixing part onto the gimbal of the suspension in later steps can be increased to further improve the yield of the products. By testing the piezoelectric/electrostrictive element in advance before assembling the device, the deterioration of device characteristics after assembling the device can be greatly reduced.

The piezoelectric/electrostrictive device of the third form according to the present invention can produce the functions and effects that are produced by the first and second piezoelectric/electrostrictive devices. In particular, since the third piezoelectric/electrostrictive device has a connecting part that is integral with the mounting part, the device provides a great advantage that the connecting part can be allowed to function as a gimbal for supporting the magnetic head (slider) of the hard disk drive.

The piezoelectric/electrostrictive devices according to the present invention are based on the piezoelectric/electrostrictive devices of the above-described three forms. In these piezoelectric/electrostrictive devices having a basic structure, the base of each device has an integral structure formed from an original plate made of a flat plate, so that the base is in principle constructed with only one construction component. Therefore, the construction components of each device are two kinds, namely, the base and the piezoelectric/electrostrictive elements, so that the number of construction components of the piezoelectric/electrostrictive device can be greatly reduced, and the number of steps for assembling the construction components can be greatly reduced, thereby leading to large reduction of costs.

Further, in each piezoelectric/electrostrictive device according to the present invention, since the number of construction components is extremely small and the number of bonding sites between the construction components is extremely small, there is little or no variation in the adhesion between the construction components, whereby the piezoelectric/electrostrictive device has device characteristics in which the set precision is high.

Further, in forming each piezoelectric/electrostrictive device according to the present invention, there is no need to adopt means for cutting a device master at numerous sites, so that there is no contamination caused by dusts and other contaminants generated at the time of cutting the device master. For this reason, if the base and the piezoelectric/electrostrictive elements are cleaned in advance in assembling the piezoelectric/electrostrictive device, the assembled piezoelectric/electrostrictive device has little or no contamination, thereby providing a great advantage that the step of cleaning the piezoelectric/electrostrictive device can be omitted or carried out in a simple manner.

Regarding the piezoelectric/electrostrictive devices according to the present invention, the piezoelectric/electrostrictive device of the first form, the piezoelectric/electrostrictive device of the second form, and the piezoelectric/electrostrictive device of the third form can be produced with ease and at a low cost respectively by the first method according to the present invention, the second method according to the present invention, and the third method according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The piezoelectric/electrostrictive devices according to the present invention will now be described. A piezoelectric/electrostrictive device of the first form includes a base having a pair of right and left movable parts and a fixing part that connects the movable parts with each other at one end thereof, and a piezoelectric/electrostrictive element is disposed on at least one side of the movable parts of the base. A piezoelectric/electrostrictive device of the second form includes a base having a pair of right and left movable parts, a fixing part that connects the movable parts with each other at one end thereof, and a mounting part that is separate from the fixing part and connects the movable parts with each other at the other end thereof, and a piezoelectric/electrostrictive element is disposed on at least one side of the movable parts of the base. A piezoelectric/electrostrictive device of the third form includes a base having a pair of right and left movable parts, a fixing part that connects the movable parts with each other at one end thereof, a mounting part that is separate from the fixing part and connects the movable parts with each other at the other end thereof, and a connecting part that is integral with the mounting part and surrounds the mounting part, the movable parts, and the fixing part, and a piezoelectric/electrostrictive element is disposed on at least one side of the movable parts of the base.FIGS. 1A to 1Killustrate numerous embodiments (first embodiment to eleventh embodiment) of the piezoelectric/electrostrictive devices of various forms.

The first piezoelectric/electrostrictive device10ashown inFIG. 1Abelongs to the category of the piezoelectric/electrostrictive device of the second form according to the present invention and is used in a state shown inFIG. 2. The first piezoelectric/electrostrictive device10ais formed by the method shown inFIGS. 3 and 4. The first piezoelectric/electrostrictive device10ais made of a base11and a pair of piezoelectric/electrostrictive elements12a,12b. Base11is constructed with a pair of right and left long and narrow plate-shaped movable parts11a,11b, a flat plate-shaped fixing part11c that connects the movable parts11a,11bwith each other at one end thereof, and a flat plate-shaped mounting part11dthat connects the movable parts11a,11bwith each other at the other end thereof.

An H-shaped opening11esections base11into movable parts11a,11b, fixing part11c, and mounting part11d. Opening lie is made of a pair of right and left side grooves11e1,11e2and a central groove11e3that connects the two side grooves11e1,11e2with each other at the central part thereof as viewed in the longitudinal direction. Movable part11aon the left side is bent at side groove11e1along groove11e1and is erect perpendicularly to fixing part11cand mounting part11d. Similarly, movable part11bon the right side is bent at side groove11e2along groove11e2and is erect perpendicularly to fixing part11cand mounting part11d.

In base11having such a construction, piezoelectric/electrostrictive elements12a,12bare bonded respectively onto outer sides of the movable parts11a,11bvia an adhesive made of epoxy resin or the like. Piezoelectric/electrostrictive elements12a,12bare each a multi-layer body made of piezoelectric/electrostrictive layers and electrode films. Piezoelectric/electrostrictive elements12a,12bare formed to have the same shape as movable parts11a,11band are shorter than movable parts11a,11bby a predetermined length. Piezoelectric/electrostrictive elements12a,12bare respectively bonded in alignment to the end of movable parts11a,11bon the fixing part11cside, and extend to a site that leaves a predetermined length from the end of movable parts11a,11bon the mounting part11dside.

In the base11, a magnetic head H (slider) for a hard disk, which is a component to be controlled, for example, is bonded and fixed onto the upper side of mounting part11d, and the lower side is bonded and fixed onto a gimbal of the suspension. Here, in this case, the positions of mounting the magnetic head H and the suspension can be changed to fixing part11c, contrary to the above. This does not change the device functions at all. Also, the positions of mounting the magnetic head H and the suspension with respect to fixing part11cand mounting part11dcan be changed to a configuration in which the roles of the front and rear surfaces are reversed. This does not change the device functions at all, either. However, the wirings of external electrodes that are brought into contact with the terminals of piezoelectric/electrostrictive elements12a,12bmust be wired in a reversed manner on the suspension.

Now, base11constituting the piezoelectric/electrostrictive device10ais formed by using an original plate11A shown inFIG. 3Aas a material for molding and by bending original plate11A as shown inFIG. 3B. Original plate11A is a stamped structure that is stamped out from a flexible and bendable flat plate and is formed in a shape that delineates a plane development of base11. The flat plate constituting the original plate11A is preferably made of metal in view of strength.

The flat plate is preferably made of a metal having a Young's modulus of at least 100 GPa and, as a ferrous metals material, one can mention austenite-series stainless steels such as SUS301, SUS304, AISI653, and SUH660, ferrite-series stainless steels such as SUS430 and SUS434, martensite-series stainless steels such as SUS410 and SUS630, semiaustenite-series stainless steels such as SUS6312 and AISI632, maraging stainless steel, various spring steel materials, and others. As a nonferrous metals material, one can mention superelastic titanium alloys such as a titanium-nickel alloy, brass, cupro-nickel, aluminum, tungsten, molybdenum, beryllium copper, phosphorus bronze, nickel, a nickel iron alloy, titanium, and others.

Original plate11A is formed by subjecting a flat plate to a stamping process, and is provided with an H-shaped opening11e. Opening11eis formed simultaneously at the time of stamping the flat plate, and is made of a pair of straight side grooves11e1,11e2located at right and left sides of original plate11A and extending to the front and rear ends and a straight central groove11e3that connects the two side grooves11e1,11e2with each other at the central parts thereof. Base11is formed by perpendicularly bending the right and left side peripheries of original plate11A at the side grooves11e1,11e2along central lines L1, L2that extend at the center of the width of the grooves11e1,11e2in the longitudinal direction thereof. By bending the right and left sides of original plate11A in such a manner, the sites located outside the side grooves11e1,11e2are formed into movable parts11a,11b, and the sites on the front end side and on the rear end side of the central groove11e3are formed into fixing part11cand mounting part11d, respectively.

In base11thus integrally constructed from original plate11A, piezoelectric/electrostrictive elements12a,12bare bonded via an adhesive onto the outer sides of movable parts11a,11bas shown inFIG. 4Ato form piezoelectric/electrostrictive device10ashown inFIG. 4B. Piezoelectric/electrostrictive device10athus formed functions in the same manner as the conventional piezoelectric/electrostrictive devices of this form and, since base11is integrally constructed from original plate11A, piezoelectric/electrostrictive device10aproduces the following functions and effects.

Namely, in the first piezoelectric/electrostrictive device10a, base11has an integral structure made of one sheet of original plate11A alone and is constructed with one construction component. Therefore, the construction components of the device10aare two kinds, i.e. base11and piezoelectric/electrostrictive elements12a,12b, so that the number of construction components of piezoelectric/electrostrictive device10acan be greatly reduced, and the number of steps for assembling the construction components can be greatly reduced, thereby leading to large reduction of costs.

Further, in the first piezoelectric/electrostrictive device10a, since the number of construction components is extremely small and the number of bonding sites between the construction components is extremely small, there is little or no variation in the adhesion between the construction components, whereby the first piezoelectric/electrostrictive device10ahas device characteristics in which the set precision is high.

Further, in forming the first piezoelectric/electrostrictive device10a, there is no need to adopt means for cutting a device master at numerous sites as in the prior art, so that there is no contamination caused by adhesion of dusts and other contaminants generated at the time of cutting the device master. For this reason, if base11and piezoelectric/electrostrictive elements12a,12bare cleaned in advance in assembling the first piezoelectric/electrostrictive device10a, the assembled piezoelectric/electrostrictive device10ahas little or no contamination, thereby providing a great advantage that the step of cleaning the piezoelectric/electrostrictive device10acan be omitted or carried out in a simple manner.

The second piezoelectric/electrostrictive device10bshown inFIG. 1Bbelongs to the category of the piezoelectric/electrostrictive device of the second form according to the present invention. The second piezoelectric/electrostrictive device10bhas a base constructed in a slightly different manner from that of the first piezoelectric/electrostrictive device10a. Referring toFIG. 6B, the second piezoelectric/electrostrictive device10bis made of a base13and a pair of piezoelectric/electrostrictive elements12a,12b. Base13is constructed with a pair of right and left long and narrow plate-shaped movable parts13a,13b, a flat plate-shaped fixing part13cthat connects the movable parts13a,13bwith each other at one end thereof, and a flat plate-shaped mounting part13dthat connects the movable parts13a,13bwith each other at the other end thereof.

An H-shaped opening13esections base13into movable parts13a,13b, fixing part13c, and mounting part13d. As far as such a construction is concerned, the base13of the second piezoelectric/electrostrictive device10bhas the same construction as the base11of the first piezoelectric/electrostrictive device10a.

However, in base13, the bent parts13a1,13b1, which are the sites for connecting movable parts13a,13bto fixing part13cand mounting part13d, have a circular arc shape in which the bent parts13a1,13b1are recessed from the surface of fixing part13cand mounting part13d. Referring toFIG. 5A, the original plate13A constituting the base13is the same as the original plate11A of base11, and has a different bent shape in bending the original plate to form movable parts13a,13b. Namely, in the bending process, circular arc-shaped bent parts13a1,13b1are formed at the base part of movable parts13a,13b. Referring toFIG. 6A, piezoelectric/electrostrictive elements12a,12bare bonded onto the outer sides of movable parts13a,13bof the base13to form the second piezoelectric/electrostrictive device10b.

The second piezoelectric/electrostrictive device10bhas the same functions as the first piezoelectric/electrostrictive device10aand produces approximately similar actions and effects as the first piezoelectric/electrostrictive device10a. In particular, since movable parts13a,13bare connected to fixing part13cand mounting part13dvia circular arc-shaped bent parts13a1,13b1, the movability of movable parts13c,13dis improved to produce high device functions.

Further, the second piezoelectric/electrostrictive device10bfacilitates making a highly precise degree of orthogonality of movable parts13a,13bto fixing part13cand mounting part13d, thereby restraining displacements in the flapping direction. Moreover, since the position of movable parts13a,13bin the Y-axis direction with respect to fixing part13cand mounting part13dcan be set by changing the degree of bending the circular arc-shaped bent parts, the device designing can have a larger width.

The third piezoelectric/electrostrictive device10cshown inFIG. 1Cbelongs to the category of the piezoelectric/electrostrictive device of the second form according to the present invention. The third piezoelectric/electrostrictive device10chas a base constructed to have slightly different parts from those of the second piezoelectric/electrostrictive device10b, but the other parts are the same.

Referring toFIG. 8B, the third piezoelectric/electrostrictive device10cis made of a base14and a pair of piezoelectric/electrostrictive elements12a,12b. Base14is constructed with a pair of right and left long and narrow plate-shaped movable parts14a,14b, a flat plate-shaped fixing part14cthat connects the movable parts14a,14bwith each other at one end thereof, and a flat plate-shaped mounting part14dthat connects the movable parts14a,14bwith each other at the other end thereof.

In base14, the middle portion of movable parts14a,14bin the longitudinal is formed into thin parts14a1,14b1for a predetermined length; however, except this point, base14is constructed in the same manner as base13. Further, referring toFIG. 7A, the original plate14A of base14has thin parts14a1,14b1on the right and left sides of an H-shaped opening14ewhich are to be formed into movable parts14a,14blater. Base14is subjected to a bending process along the two-dot chain lines L1, L2shown inFIG. 7Bin the same manner as base13. Referring toFIG. 8A, piezoelectric/electrostrictive elements12a,12bare bonded onto outer sides of movable parts14a,14bto form the third piezoelectric/electrostrictive device10c.

The third piezoelectric/electrostrictive device10chas the same functions as the second piezoelectric/electrostrictive device10band produces approximately similar actions and effects as the second piezoelectric/electrostrictive device10b. In particular, since movable parts14a,14bare provided with thin parts14a1,14b1that are located in the middle thereof and extending in the longitudinal direction, the movability of movable parts14a,14bis more enhanced to produce further high device functions.

As means for forming thin parts14a1,14b1of original plate14A, one can adopt a method of reducing the thickness by partially removing the material using chemical etching, microblasting, ion-milling, or the like, or a method of reducing the thickness by cutting through grinding, or the like method. Further, as a special means, one can adopt a plate formed by superposing and bonding one plate that has been drilled to have a hole of a predetermined length onto the other plate without a hole to substitute the site corresponding to the hole for the thin parts, as an original plate.

The fourth piezoelectric/electrostrictive device10dshown inFIG. 1Dbelongs to the category of the piezoelectric/electrostrictive device of the second form according to the present invention. The fourth piezoelectric/electrostrictive device10dhas a base constructed to have slightly different parts from those of the first piezoelectric/electrostrictive device10a, but the other parts are the same.

Referring toFIG. 10B, the fourth piezoelectric/electrostrictive device10dis made of a base15and a pair of piezoelectric/electrostrictive elements12a,12b. Base15is constructed with a pair of right and left long and narrow plate-shaped movable parts15a,15b, a flat plate-shaped fixing part15cthat connects the movable parts15a,15bwith each other at one end thereof, a flat plate-shaped mounting part15dthat connects the movable parts15a,15bwith each other at the other end thereof, and a pair of right and left reinforcing parts15f,15gthat extend from an upper fringe on ends of movable parts15a,15band abut against the surface of fixing part15c.

Base15is constructed in the same manner as base11except that base15is provided with reinforcing parts15f,15g. Further, referring toFIG. 9A, the original plate15A of base15is provided with portions to become reinforcing parts15f,15gthat are extending outward from ends of the right and left sides of an H-shaped opening15ewhich are to be formed into movable parts15a,15blater. Base15is subjected to a bending process along two-dot chain lines L1, L2and others as shown inFIG. 9B. Referring toFIG. 10A, piezoelectric/electrostrictive elements12a,12bare bonded onto outer sides of movable parts15a,15bto form the fourth piezoelectric/electrostrictive device10d.

The fourth piezoelectric/electrostrictive device10dhas the same functions as the first piezoelectric/electrostrictive device10aand produces approximately similar actions and effects as the first piezoelectric/electrostrictive device10a. In particular, fixing part15cis reinforced by reinforcing parts15f,15g. Reinforcing parts15f,15gare bonded onto fixing part15c. As the bonding means therefor, one can adopt a bonding means such as spot welding, press-bonding, caulking, soldering, brazing, or using an adhesive such as epoxy resin or UV-curing type resin or the like. Among these bonding means, spot welding is especially preferable.

The fifth piezoelectric/electrostrictive device10eshown inFIG. 1Ebelongs to the category of the piezoelectric/electrostrictive device of the second form according to the present invention. The fifth piezoelectric/electrostrictive device10ehas a base constructed to have slightly different parts from those of the fourth piezoelectric/electrostrictive device10d, but the other parts are the same.

Now, referring toFIG. 12B, the fifth piezoelectric/electrostrictive device10eis made of a base16and a pair of piezoelectric/electrostrictive elements12a,12b. Base16is constructed with a pair of right and left long and narrow plate-shaped movable parts16a,16b, a flat plate-shaped fixing part16cthat connects the movable parts16a,16bwith each other at one end thereof, a flat plate-shaped mounting part16dthat connects the movable parts16a,16bwith each other at the other end thereof, and reinforcing parts16f,16gthat bend inwardly from the end of movable parts16a,16bin a manner like a flange.

Base16is constructed in the same manner as base15except that the shape of reinforcing parts16f,16gis different from the shape of reinforcing parts15f,15g. Further, referring toFIG. 11A, the original plate16A of base16is constructed in such a manner that the right and left sides of an H-shaped opening16e, which are to be formed into movable parts16a,16blater, protrude both forwardly and rearwardly for a predetermined length. Referring toFIG. 11B, base16is subjected to a bending process along two-dot chain lines L1, L2and others shown inFIG. 11A. Referring toFIG. 12A, piezoelectric/electrostrictive elements12a,12bare bonded onto outer sides of movable parts16a,16bto form the fifth piezoelectric/electrostrictive device10e.

In the fifth piezoelectric/electrostrictive device10e, reinforcing parts16f,16gare bonded to neither fixing part16cnor mounting part16d; however, reinforcing parts16f,16gare more preferably bonded to fixing part16cand mounting part16d. As the bonding means therefor, one can adopt a bonding means such as spot welding, press-bonding, caulking, soldering, brazing, or using an adhesive such as epoxy resin or UV-curing type resin or the like. Among these bonding means, spot welding is especially preferable.

The fifth piezoelectric/electrostrictive device10ehas the same functions as the first piezoelectric/electrostrictive device10aand produces approximately similar actions and effects as the first piezoelectric/electrostrictive device10a. In particular, fixing part16cand mounting part16dare reinforced by reinforcing parts16f,16g.

The sixth piezoelectric/electrostrictive device10fshown inFIG. 1Fbelongs to the category of the piezoelectric/electrostrictive device of the second form according to the present invention. The sixth piezoelectric/electrostrictive device10fis different from the first piezoelectric/electrostrictive device10ain that a reinforcing member is added to the base, but the other parts are the same.

Now, referring toFIG. 14B, the sixth piezoelectric/electrostrictive device10fis made of a base17and a pair of piezoelectric/electrostrictive elements12a,12b. Base17is constructed with a pair of right and left long and narrow plate-shaped movable parts17a,17b, a flat plate-shaped fixing part17cthat connects the movable parts17a,17bwith each other at one end thereof, a flat plate-shaped mounting part17dthat connects the movable parts17a,17bwith each other at the other end thereof, and a plate-shaped reinforcing member17finserted between the sides at ends of movable parts17a,17band bonded to the surface of fixing part17c.

Referring toFIG. 13A, the original plate17A of base17has the same shape as the original plate11A of base11. Referring toFIG. 13B, base17is subjected to a bending process along two-dot chain lines L1, L2. Referring toFIG. 14A, reinforcing member17fis bonded onto the surface of fixing part17cbetween the sides at one end of movable parts17a,17b, and piezoelectric/electrostrictive elements12a,12bare bonded onto outer sides of movable parts17a,17bto form the sixth piezoelectric/electrostrictive device10f. The sixth piezoelectric/electrostrictive device10fhas the same functions as the fourth piezoelectric/electrostrictive device10dand produces approximately similar actions and effects as the fourth piezoelectric/electrostrictive device10d.

The seventh piezoelectric/electrostrictive device10gshown inFIG. 1Gbelongs to the category of the piezoelectric/electrostrictive device of the second form according to the present invention. The seventh piezoelectric/electrostrictive device10gis different from the first piezoelectric/electrostrictive device10ain that the fixing part and the mounting part of the base are differently shaped, but the other parts are the same.

Referring toFIG. 16Bthe seventh piezoelectric/electrostrictive device10gis made of a base18and a pair of piezoelectric/electrostrictive elements12a,12b. Base18is constructed with. a pair of right and left long and narrow plate-shaped movable parts18a,18b, a flat plate-shaped fixing part18cthat connects the movable parts18a,18bwith each other at one end thereof, and a flat plate-shaped mounting part18dthat connects the movable parts18a,18bwith each other at the other end thereof. Fixing part18cprotrudes for a predetermined length from ends of movable parts18a,18b, and mounting part18dprotrudes for a predetermined length from the ends of movable parts18a,18b. Therefore, fixing part18cand mounting part18dare an enlargement of fixing part11cand mounting part11din base11of the first piezoelectric/electrostrictive device10a, thereby ensuring a larger area.

Base18is constructed in the same manner as base11except that the areas of fixing part18cand mounting part18dare enlarged. Further, referring toFIG. 15A, the original plate18A of base18is constructed in such a manner that the front and rear sides of an H-shaped opening18e, which are to be formed into fixing part18cand mounting part18dlater, protrude forwardly and rearwardly for a predetermined length. Referring toFIG. 15B, base18is subjected to a bending process along two-dot chain lines L1, L2. Referring toFIG. 16A, piezoelectric/electrostrictive elements12a,12bare bonded onto outer sides of movable parts18a,18bto form the seventh piezoelectric/electrostrictive device10g.

The seventh piezoelectric/electrostrictive device10ghas the same functions as the first piezoelectric/electrostrictive device10aand produces approximately similar actions and effects as the first piezoelectric/electrostrictive device10a. In particular, since fixing part18cand mounting part18deach have a larger area, the bonding area to the gimbal of the suspension can be enlarged, and the bonding area to the component to be controlled, such as the magnetic head of the hard disk drive, can be enlarged.

The eighth piezoelectric/electrostrictive device20ashown inFIG. 1Hbelongs to the category of the piezoelectric/electrostrictive device of the first form according to the present invention. The eighth piezoelectric/electrostrictive device20ahas a base constructed in a greatly different manner from that of the first piezoelectric/electrostrictive device10a.

Referring toFIG. 18B, the eighth piezoelectric/electrostrictive device20ais made of a base21and a pair of piezoelectric/electrostrictive elements22a,22b. Base21is constructed with a pair of right and left long and narrow plate-shaped movable parts21a,21band a flat plate-shaped fixing part21cthat connects the movable parts21a,21bwith each other at one end thereof. However, a mounting part is not provided on the other ends of movable parts21a,21b.

Referring toFIG. 17A, the original plate21A of base21is formed by subjecting a flat plate to a stamping process, and is provided with a gate-shaped opening21d. Opening21dhas a shape provided with a pair of straight side grooves21d1,21d2located at right and left sides of the flat plate and extending to the front and rear ends, and an open site21d3obtained by cutting and removing the other end located between these two grooves21d1,21d2. Base21is formed by perpendicularly bending the right and left sides of original plate21A at the side grooves21d1,21d2along central lines L1, L2that extend at the center of the width of the grooves21d1,21d2in the longitudinal direction thereof, as shown inFIG. 17B. By bending the right and left sides of original plate21A in such a manner, the sites located outside the side grooves21d1,21d2are formed into movable parts21a,21b, and the site between the side grooves21d1,21d2is formed into fixing part21c.

In base21thus integrally constructed from original plate21A, piezoelectric/electrostrictive elements22a,22bare bonded via an adhesive onto the outer sides of movable parts21a,21bas shown inFIG. 18Ato form piezoelectric/electrostrictive device20ashown inFIG. 18B. Piezoelectric/electrostrictive device20athus formed functions in the same manner as the conventional piezoelectric/electrostrictive devices of this form by being used in a state in which a component to be controlled, such as a magnetic head, is bonded between the other ends of movable parts21a,21b. However, since base21is integrally constructed from one sheet of original plate21A, piezoelectric/electrostrictive device20aproduces the following functions and effects.

Namely, in the eighth piezoelectric/electrostrictive device20a, base21has an integral structure made of original plate21A and is constructed with one construction component. Therefore, the construction components are two kinds, i.e. base21and piezoelectric/electrostrictive elements22a,22b, so that the number of construction components of piezoelectric/electrostrictive device20acan be greatly reduced, and the number of steps for assembling the construction components can be reduced, thereby leading to large reduction of costs.

Further, in the eighth piezoelectric/electrostrictive device20a, since the number of construction components is extremely small and the number of bonding sites between the construction components is extremely small, there is little or no variation in the adhesion between the construction components, whereby the eighth piezoelectric/electrostrictive device20ahas device characteristics in which the set precision is high.

Further, in forming the eighth piezoelectric/electrostrictive device20a, there is no need to adopt means for cutting a device master at numerous sites as in the prior art, so that there is no contamination caused by adhesion of dusts and other contaminants generated at the time of cutting the device master. For this reason, if base21and piezoelectric/electrostrictive elements22a,22bare cleaned in advance in assembling the eighth piezoelectric/electrostrictive device20a, the assembled piezoelectric/electrostrictive device20ahas little or no contamination, thereby providing a great advantage that the step of cleaning the piezoelectric/electrostrictive device20acan be omitted or carried out in a simple manner.

The mounting of the component to be controlled and others onto the eighth piezoelectric/electrostrictive device20ais carried out by fixing them onto the inner surfaces21a1,21b1on the tip end side of movable parts21a,21bvia an adhesive. In this case, as will be clear if reference is made toFIG. 19illustrating a later-mentioned piezoelectric/electrostrictive device20cwhich is a modification of the piezoelectric/electrostrictive device20a, if the height Hi of device20ais smaller than the height H2of the component to be controlled, the height H3in the state in which device20aand the component to be controlled are assembled will be equal to the height H2of the component to be controlled (H3=H2), whereby the height H1of device20acan be ignored. This provides an advantage that a further reduction of space can be achieved as compared with the piezoelectric/electrostrictive devices according to other embodiments of the present invention.

In the assembled structure, since the component to be controlled is sandwiched between the two movable parts21a,21b, the interval between the inner surfaces21a1,21b1on the tip end side of movable parts21a,21bmust be set substantially equal to the width dimension including the width of the component to be controlled and the thickness of the intervening adhesive layer. If this is neglected, when the interval between the inner surfaces21a,21b1on the tip end side of movable parts21a,21bis too narrow, the component cannot be placed between the inner surfaces21a1,21b1on the tip end side of movable parts21a,21b, thereby making the assemblage impossible, whereas if the interval between the inner surfaces21a1,21b1on the tip end side of movable parts21a,21bis too wide, the component to be controlled cannot be bonded to both of the inner surfaces21a1,21b1on the tip end side of movable parts21a,21b, thereby making the assemblage impossible.

Further, if this assembled structure is adopted, even if the interval between the inner surfaces21a1,21b1on the tip end side of movable parts21a,21bis set to be at a width dimension such that the component can be placed and bonded to both of the inner surfaces21a1,21b1on the tip end side of movable parts21a,21b, if the thickness of the adhesive layer for bonding the component to be controlled onto the inner surfaces21a1,21b1on the tip end side of movable parts21a,21bvaries, the displacement and the resonance frequency of the two movable parts21a,21bis changed, thereby causing variation in the device characteristics. For this reason, in a bending process for forming base21, a press-molding means of high precision is adopted to enable mass production of bases21bent in a highly precise manner. This will reduce the variation in the thickness of the adhesive layer for bonding the component onto the inner surfaces21a1,21b1on the tip end side of movable parts21a,21bas much as possible, whereby the device will have a quality with extremely reduced variation of device characteristics.

FIG. 19illustrates a piezoelectric/electrostrictive device20cwhich is a first modification of the eighth piezoelectric/electrostrictive device20a. The piezoelectric/electrostrictive device20chas the same basic construction as the piezoelectric/electrostrictive device20a, and is different in construction from the piezoelectric/electrostrictive device20aonly in that the tip ends of movable parts21a,21bare inwardly bent. Namely, movable parts21a,21bhave bent portions21a2,21b2at the tip ends thereof. The bent portions21a2,21b2are formed by bending the tip ends of movable parts21a,21binwardly by about 180°, and the inside surfaces of the bent portions21a2,21b2face each other to provide mounting sites for mounting the component H to be controlled. The component H to be controlled is mounted by being bonded to the inside surfaces of bent portions21a2,21b2via a suitable adhesive.

Here, since the other parts of piezoelectric/electrostrictive device20care the same as those of piezoelectric/electrostrictive device20a, like constituent members and like constituent sites are denoted with like reference numerals, and their detailed description will be omitted.

Thus, in the piezoelectric/electrostrictive device20c, the bonding length and the bonding area to the component H to be controlled can be defined by the two bent portions21a2,21b2, thereby effectively eliminating the variation of the bonding length and the bonding area to the component H to be controlled among individual devices. This can eliminate the variation in the value of displacement and the resonance frequency among individual devices caused by the variation in the bonding length and the bonding area to the component H to be controlled.

Here, in the piezoelectric/electrostrictive device20c, as described in the function and effects of the eighth piezoelectric/electrostrictive device20a, since the height H1of device20cis smaller than the height H2of the component to be controlled, the height H3in the state in which the component H to be controlled is mounted on device20cis equal to the height H2of the component H to be controlled (H3=H2), so that the height H1of device20ccan be ignored, thereby providing an advantage of further reduction in the space as compared with the piezoelectric/electrostrictive devices according to other embodiments of the present invention.

FIG. 20illustrates a piezoelectric/electrostrictive device20dwhich is a second modification of the eighth piezoelectric/electrostrictive device20a. The piezoelectric/electrostrictive device20dhas the same basic construction as the piezoelectric/electrostrictive device20a, and is different in construction from the piezoelectric/electrostrictive device20aonly in that the movable parts21a,21bare formed to be narrow band-shaped plates with steps, and the tip ends of movable parts21a,21bconstitute crooked portions21a3,21b3that are slightly biased inwardly from the principal part. The crooked portions21a3,21b3of movable parts21a,21bare positioned to face each other, and the inside surfaces of these crooked portions21a3,21b3constitute mounting sites for mounting the component H to be controlled, in the same manner as the bent portions21a2,21b2in piezoelectric/electrostrictive device20c. The component H to be controlled is bonded onto the inside surfaces of crooked portions21a3,21b3via a suitable adhesive. Therefore, the piezoelectric/electrostrictive device20dfunctions in the same manner as the piezoelectric/electrostrictive device20c, and produces the same actions and effects as the piezoelectric/electrostrictive device20c.

Here, since the other parts of piezoelectric/electrostrictive device20dare the same as those of piezoelectric/electrostrictive device20c, the same constituent members and the same constituent sites as in piezoelectric/electrostrictive device20care denoted with the same reference numerals as in piezoelectric/electrostrictive device20c, and their detailed description will be omitted.

The ninth piezoelectric/electrostrictive device20bshown inFIG. 1Ibelongs to the category of the piezoelectric/electrostrictive device of the second form according to the present invention. The ninth piezoelectric/electrostrictive device20bhas a base constructed in a greatly different manner from that of the first piezoelectric/electrostrictive device10a.

Referring toFIG. 22B, the ninth piezoelectric/electrostrictive device20bis made of a base23and a pair of piezoelectric/electrostrictive elements22a,22b. Base23is constructed with a pair of right and left long and narrow plate-shaped movable parts23a,23b, a flat and narrow plate-shaped fixing part23cthat connects the movable parts23a,23bwith each other at one end thereof, and a flat and narrow plate-shaped mounting part23dthat connects the movable parts23a,23bwith each other at the other end thereof.

Referring toFIG. 21A, the original plate23A of base23is formed by subjecting a flat plate to a stamping process, and is provided with a generally square-shaped opening23e. Base23is formed by perpendicularly bending the right and left sides of original plate23A at the opening peripheries of opening23ealong central lines L1, L2that extend along the opening peripheries in the longitudinal direction, as shown inFIG. 21B. By bending the right and left sides of original plate23A in such a manner, the sides of the opening peripheries are formed into movable parts23a,23b, and the sites between the sides of the opening peripheries are formed into fixing part23cand mounting part23d.

In base23thus integrally constructed from original plate23A, piezoelectric/electrostrictive elements22a,22bare bonded via an adhesive onto the outer sides of movable parts23a,23bas shown inFIG. 22Ato form piezoelectric/electrostrictive device20bshown inFIG. 22B. The assembled piezoelectric/electrostrictive device20bfunctions in the same manner as the conventional piezoelectric/electrostrictive devices of this form. However, since base23is integrally constructed from one sheet of original plate23A, piezoelectric/electrostrictive device20bproduces approximately the same functions and effects as the first piezoelectric/electrostrictive device10aand the eighth piezoelectric/electrostrictive device20a.

In the ninth piezoelectric/electrostrictive device20b, fixing part23cand mounting part23dare small, and the bonding area to the actuator or the component to be controlled is small. However, if one can adopt means for firmly joining the component with a small bonding area, such as spot welding, the ninth piezoelectric/electrostrictive device20bhas no disadvantage. A large fixing part or mounting part acts as a superfluous weight (mass). In this respect, the ninth piezoelectric/electrostrictive device20bis different from the other piezoelectric/electrostrictive devices10ato10g. Since a superfluous mass is absent, the resonance frequency can be set to be high, thereby providing an advantage that the actuator can be operated at a higher speed.

Regarding the piezoelectric/electrostrictive devices10ato10g,20ato20daccording to the above-described embodiments, in the stamped structure adopted as an original plate for forming the bases11to18,21, and23, the openings11eto18e,21d, and23eare formed by stamping simultaneously at the time of the stamping process. However, these openings11eto18e,21d, and23eof the original plate can be formed by machining the original plate stamped out into a predetermined shape, using means other than the stamping means, for example, a hole-forming machining means such as laser machining, electric discharge machining, drill machining, ultrasonic machining, or etching. Regarding the hole-forming machining means, if means other than etching is used, burrs may be generated at the edge of the machined hole; however, the burrs can be easily removed by an etching process or a blasting process.

Further, the movable parts11a,11b. . . constituting the bases11,13to18,21,23of the piezoelectric/electrostrictive devices10ato10g,20ato20dare preferably bent at an angle of about 90° to the fixing parts11c. . . and the mounting parts11d. . . , and the intersecting angle is within the range of 90°±10°, preferably 90°±5°, more preferably 90°±1°. If the angle of bending the movable parts11a,11b. . . is deviated from 90°, the displacement in the flapping direction will be large. Here, the above notation . . . is used to mean that the reference numerals of the other corresponding sites are omitted, and is used to abbreviate the description.

The bases11to18,21,23formed by bending are preferably subjected to a ultrasonic cleaning process using a detergent, an organic solvent, or the like. With the use of ultrasonic cleaning, the bases are not destroyed even if the power is increased, so that ultrasonic cleaning with a large power can remove the contamination easily.

Further, the piezoelectric/electrostrictive devices10ato10g,20ato20dare constructed in such a manner that the base and the piezoelectric/electrostrictive elements are formed as separate bodies, and the piezoelectric/electrostrictive elements are bonded to the movable parts of the base. However, in the piezoelectric/electrostrictive devices according to the present invention, a piezoelectric/electrostrictive layer and electrodes can be formed as films by means of sputtering, CVD, MBE, or the like or formed as films by the sol-gel method onto the portions to become the movable parts in the original plate before being formed into the base, or onto the movable parts of the base, thereby to form the piezoelectric/electrostrictive elements directly on the base.

The piezoelectric/electrostrictive elements12a,12b,22a,22bconstituting the piezoelectric/electrostrictive devices10ato10g,20ato20daccording to the above-described embodiments are each provided with a piezoelectric/electrostrictive layer and a pair of electrodes for applying an electric field thereto, and are piezoelectric/electrostrictive elements of unimorph type, bimorph type, or the like. Among these, piezoelectric/electrostrictive elements of unimorph type are excellent in the stability of the generating displacement, and are also advantageous for weight reduction, so that they are suitable as a construction component of piezoelectric/electrostrictive devices.

FIGS. 23 and 24illustrate several examples of piezoelectric/electrostrictive elements31to34that are suitably adopted as the piezoelectric/electrostrictive elements12a,12b,22a,22bconstituting the piezoelectric/electrostrictive devices10ato10g,20ato20d.

Piezoelectric/electrostrictive element31shown inFIG. 23Ahas a one-layer structure in which the piezoelectric/electrostrictive layer consists of one layer, and is constructed with a piezoelectric/electrostrictive layer31a, a pair of lower first and upper second electrodes31b,31c, and a pair of terminals31d,31e. Piezoelectric/electrostrictive element32shown inFIG. 23Bhas a two-layer structure in which the piezoelectric/electrostrictive layer consists of two layers, and is constructed with piezoelectric/electrostrictive layers32a,32b, a first electrode32cthat intervenes between the two piezoelectric/electrostrictive layers32a,32b, a second electrode32dthat surrounds the outer sides of the two piezoelectric/electrostrictive layers32a,32b, and a pair of terminals32e,32f.

Piezoelectric/electrostrictive elements33,34shown inFIG. 24each have a four-layer structure in which the piezoelectric/electrostrictive layer consists of four layers. Piezoelectric/electrostrictive element33shown inFIG. 24Ais constructed with piezoelectric/electrostrictive layers33a,33b,33c,33d, first and second electrodes33e,33fthat intervene between and surround the four piezoelectric/electrostrictive layers33a,33b,33c,33d, and a pair of terminals33g,33h. The piezoelectric/electrostrictive element34shown inFIG. 24Bis different from the piezoelectric/electrostrictive element33in that the terminals are placed at different sites. Piezoelectric/electrostrictive element34is constructed with piezoelectric/electrostrictive layers34a,34b,34c,34d, first and second electrodes34e,34fthat intervene between and surround the four piezoelectric/electrostrictive layers34a,34b,34c,34d, and a pair of terminals34g,34h.

These piezoelectric/electrostrictive elements31to34are suitably adopted as the piezoelectric/electrostrictive elements12a,12b,22a,22bof the piezoelectric/electrostrictive devices10ato10g,20ato20din accordance with the usage of the piezoelectric/electrostrictive devices.

In addition to piezoelectric ceramic, one can use electrostrictive ceramic, ferroelectric ceramic, antiferroelectric ceramic, or the like as well in the piezoelectric/electrostrictive layers constituting the piezoelectric/electrostrictive elements31to34. However, if the piezoelectric/electrostrictive device is used for positioning the magnetic head of a hard disk drive or the like purpose, it is preferable to use a material whose striction (distortion) hysteresis is small because the linearity between the displacement amount of the mounting part and the driving voltage or the output voltage is essential. It is preferable to use a material having a coercive electric field of at most 10 kV/mm.

As a material for forming the piezoelectric/electrostrictive layers, one can specifically mention lead zirconate, lead titanate, magnesium lead niobate, zinc lead niobate, manganese lead niobate, antimony lead stannate, manganese lead tungstate, cobalt lead niobate, barium titanate, bismuth sodium titanate, potassium sodium niobate, strontium bismuth tantalate, and others, which are used either alone or as a suitable mixture thereof. Particularly, a material containing lead zirconate, lead titanate, or magnesium lead niobate as a major component, or a material containing bismuth sodium titanate as a major component is suitable.

The characteristics of the piezoelectric/electrostrictive layers can be adjusted by adding a suitable material to the materials for forming the piezoelectric/electrostrictive layers. As a material to be added, one can mention oxides of lanthanum, calcium, strontium, molybdenum, tungsten, barium, niobium, zinc, nickel, manganese, cesium, cadmium, chromium, cobalt, antimony, iron, yttrium, tantalum, lithium, bismuth, tin, and others, or materials that eventually become oxides, which are used either alone or as a suitable mixture thereof.

For example, by allowing lanthanum or strontium to be contained in lead zirconate, lead titanate, magnesium lead niobate, or the like constituting the major component, there will be provided an advantage that the coercive electric field or the piezoelectric property can be adjusted. Here, it is preferable to avoid addition of a material that easily undergoes vitrification, such as silica. This is because a material such as silica that easily undergoes vitrification is liable to react with the piezoelectric/electrostrictive layers at the time of thermal treatment of the piezoelectric/electrostrictive layers, and changes their composition to deteriorate the piezoelectric properties.

The electrodes constituting the piezoelectric/electrostrictive elements31to34are preferably made of a metal material that is solid at room temperature and excellent in electrical conductivity. As a metal material, one can mention metals such as aluminum, titanium, chromium, iron, cobalt, nickel, copper, zinc, niobium, molybdenum, ruthenium, palladium, rhodium, silver, tin, tantalum, tungsten, iridium, platinum, gold, or lead, which are used as a single metal or an alloy of these metals. Further, one can use a thermet material obtained by dispersing ceramics made of the same materials as or made of different materials from the piezoelectric/electrostrictive layers into these metal materials.

Piezoelectric/electrostrictive elements31to34are preferably formed by integrally baking the piezoelectric/electrostrictive layers and the electrodes in a mutually laminated state. In this case, as the electrodes, it is preferable to adopt those made of a high-melting-point metal material such as platinum, palladium, or an alloy of these, or an electrode made of a thermet material which is a mixture of a high-melting-point metal material and the materials for forming the piezoelectric/electrostrictive layers or other ceramic materials. The thickness of the electrodes preferably has a film shape as thin as possible because the thickness becomes a factor that affects the displacement of the piezoelectric/electrostrictive elements. For this reason, in order that the electrodes formed by being integrally baked with the piezoelectric/electrostrictive layers have a film shape as thin as possible, it is preferable to use the material for forming the electrodes in a form of a metal paste, for example, a gold resinate paste, platinum resinate paste, silver resinate paste, or the like.

The thickness of each of the piezoelectric/electrostrictive elements31to34is preferably within a range from 40 μm to 180 μm if piezoelectric/electrostrictive elements31to34are to be used as the piezoelectric/electrostrictive elements12a,12b,22a,22bof the piezoelectric/electrostrictive device according to each embodiment. If the thickness is below 40 μm, piezoelectric/electrostrictive elements31to34are liable to be broken during the handling, whereas if the thickness exceeds 180 μm, the scale reduction of the device will be difficult. Further, by allowing the piezoelectric/electrostrictive elements to have a multi-layer structure such as in the piezoelectric/electrostrictive elements33,34, one can increase the output of the piezoelectric/electrostrictive elements to enlarge the displacement of the device. Furthermore, by allowing the piezoelectric/electrostrictive elements to have a multi-layer structure, the rigidity of the device will be improved, thereby advantageously raising the resonance frequency of the device to increase the speed of the displacement operation of the device.

Piezoelectric/electrostrictive elements31to34are prepared using means for cutting an original plate of a large area, which is formed by laminating and baking the piezoelectric/electrostrictive layers and the electrodes by printing or tape molding, out into a predetermined dimension in a large number with the use of a dicing machine, a slicer, a wire-saw, or the like. Piezoelectric/electrostrictive elements31to34are thinner and have a lower hardness than known ceramic bases, so that the speed of cutting the original plate can be set to be high, whereby the original plates can be processed in a large mass and at a high speed.

Piezoelectric/electrostrictive elements31to34have a simple plate-shaped structure and can be easily handled with. Also, since the surface area is small, the amount of adhering dust is small, and the dust can be easily removed. However, since the piezoelectric/electrostrictive elements are mainly made of a ceramic material, a suitable cleaning condition must be set in ultrasonic cleaning. In a piezoelectric/electrostrictive element cut out from the original plate, it is preferable to perform a precision cleaning treatment by US cleaning and then perform a heat treatment at 100° C. to 1000° C. in atmospheric air so as to completely remove the moisture and organic substances that have penetrated into fine pores of the ceramic material.

If the piezoelectric/electrostrictive elements31to34are to be adopted as the piezoelectric/electrostrictive elements12a,12b,22a,22bconstituting the piezoelectric/electrostrictive devices10ato10g,20ato20daccording to each embodiment, it is preferable to use a resin-series adhesive such as epoxy resin, UV resin, or hot-melt adhesive, or an inorganic adhesive such as glass, cement, solder, or brazing material as a bonding means to the base of each of the piezoelectric/electrostrictive elements31to34. Also, a mixture of resin-series adhesive with metal powder or ceramic powder can be used as well. The hardness of the adhesive is preferably not less than 80 in terms of Shore D hardness.

Here, it is preferable to perform a surface roughening treatment such as blasting, etching, or plating on the surface site of the base where the piezoelectric/electrostrictive element is to be bonded. By allowing the surface roughness of the bonding site to be Ra=about 0.1 μm to 5 μm, the bonding area can be enlarged to improve the adhesive strength. In this case, the surface of the bonding site on the piezoelectric/electrostrictive element side is preferably rough as well. If one wishes that the electrodes are not electrically conducted to the base, the electrodes are not disposed on the surface of the piezoelectric/electrostrictive layer constituting the lowermost layer.

If solder or brazing material is to be used as the adhesive, it is preferable to dispose an electrode layer made of a metal material on the surface of the piezoelectric/electrostrictive element in order to improve the wettability. The thickness of the adhesive is preferably within the range from 1 μm to 50 μm. The thickness of the adhesive is preferably small in view of reducing variations in the displacement and in the resonance characteristics of the device and in view of saving space; however, in order to ensure the characteristics such as the bonding strength, displacement, and resonance frequency, the optimal thickness is set for each adhesive to be adopted.

In bonding the piezoelectric/electrostrictive element to the base, the piezoelectric/electrostrictive element is bonded to the base so that the piezoelectric/electrostrictive element completely overlaps the bending position of the fixing part while allowing the electrodes of the piezoelectric/electrostrictive element to be on the side of the fixing part of the base. The piezoelectric/electrostrictive element is preferably bonded so as to align with the end of the base on the fixing part side; however, in order to facilitate the connection between the terminals of the piezoelectric/electrostrictive element and the external terminals, one may bond the piezoelectric/electrostrictive element to protrude outward from the end of the base. However, since the piezoelectric/electrostrictive element is liable to be broken as compared with the base which is made of metal, one must take care in handling the piezoelectric/electrostrictive element.

FIG. 25illustrates an example in which the piezoelectric/electrostrictive element34is adopted as the piezoelectric/electrostrictive elements12a,12bin the first piezoelectric/electrostrictive device10athat belongs to the category of the piezoelectric/electrostrictive device of the second form according to the present invention. Hereafter, the first piezoelectric/electrostrictive device10aof this embodiment will be used as a representative example having a basic construction of the piezoelectric/electrostrictive device according to the present invention. The construction and operation as well as functions and effects of the piezoelectric/electrostrictive device according to the present invention will be described in detail with reference to the first piezoelectric/electrostrictive device10a.

If a part of piezoelectric/electrostrictive element34is positioned at the fixing part11cof the base11in the piezoelectric/electrostrictive device10a, (1−Lb/La) is preferably at least 0.4, more preferably from 0.5 to 0.8, where La is the shortest distance between the boundary to the mounting part11dand the boundary to the fixing part11cin the pair of movable parts11a,11b, and Lb is the shorter one of the distances from the boundary part between the mounting part11dand the movable parts11a,11bto either end of the electrodes34e,34fof the piezoelectric/electrostrictive element34, as illustrated inFIG. 26. If this value is less than 0.4, one cannot obtain a large displacement of the device. If this value is within a range from 0.5 to 0.8, compatibility between the displacement and the resonance frequency of the device can be more easily achieved. In this case, one can adopt a construction in which the piezoelectric/electrostrictive element34is bonded to only one of the movable parts11a,11b, thereby providing a more preferable embodiment. Here, the same applies to the case in which a part of the piezoelectric/electrostrictive element34is positioned at a part of the mounting part11d.

In the piezoelectric/electrostrictive device10a, application of voltage to the electrodes34e,34fof the two piezoelectric/electrostrictive elements34is carried out through terminals34g,34h. The terminals34g,34hare positioned in such a manner that the terminal34gto one electrode34eis formed toward the rear of fixing part11c, and the terminal34hto the other electrode34fis formed toward the front direction of fixing part11c. Either one of the terminals34g,34hcan be omitted by being electrically conducted to base11to be grounded commonly with base11. The width of the piezoelectric/electrostrictive element34to be bonded need not be the same as the width of the bonding site of base11(bonding site of movable parts11a,11b), and the difference in width does not raise any problem in the functions of the device.

Piezoelectric/electrostrictive device10ais formed, for example, to have a total length of 1.9 mm and a total width of 1.5 mm by forming base11with SUS3O4 having a plate thickness of 40 μm. Piezoelectric/electrostrictive element34adopted as piezoelectric/electrostrictive elements12a,12bis a four-layer structure in which PZT is used. The thickness of one layer of the piezoelectric/electrostrictive layers34ato34dis 15 μm. The electrodes34e,34fare made of platinum of 3 μm, and terminals34g,34hare thin films made of gold paste. The piezoelectric/electrostrictive elements34are bonded onto outer sides of movable parts11a,11bvia a one-liquid thermosetting epoxy resin adhesive.

In the piezoelectric/electrostrictive device10athus constructed to have such a size, the displacement of mounting part11dwas measured when the piezoelectric/electrostrictive element34was driven by a sinusoidal wave of 1 kHz with a driving voltage of 20±20 V. The displacement was found to be ±1.5 μm. Further, the resonance frequency showing the maximum value of the displacement was measured by sweeping the frequency at sinusoidal wave voltage ±0.5 V, and was found out to be 45 kHz.

Next, the operation of the piezoelectric/electrostrictive device according to the present invention will be described with reference to the above-described first piezoelectric/electrostrictive device10a.

The piezoelectric/electrostrictive device10ais in a state shown inFIG. 26at the time of non-operation when a voltage is not applied to piezoelectric/electrostrictive elements12a,12b. In this state, the longitudinal axis m (longitudinal axis of fixing part11c) of piezoelectric/electrostrictive device10ais almost coincident with the central axis n of mounting part11d. In this state, a sinusoidal wave Wb having a predetermined bias voltage Vb is applied to the pair of electrodes34e,34fin one piezoelectric/electrostrictive element12b, for example, as shown in the waveform diagram ofFIG. 27A, and a sinusoidal wave Wa having a phase different by approximately 180° from that of the aforesaid sinusoidal wave Wb is applied to the pair of electrodes34e,34fin the other piezoelectric/electrostrictive element12a, for example, as shown inFIG. 27B.

Now, at the stage when for example the maximum voltage is applied to the pair of electrodes34e,34fin the one piezoelectric/electrostrictive element12b, the piezoelectric/electrostrictive layers34ato34din the one piezoelectric/electrostrictive element12bundergo shrinking displacement in the principal surface direction thereof.

This generates a stress that warps one movable part11bin the illustrated right direction (direction shown by arrow A) in piezoelectric/electrostrictive device10a, for example, as shown inFIG. 28. By this stress, movable part11bis warped in that direction. In this case, the pair of electrodes34e,34fin the other piezoelectric/electrostrictive element12aare in a state in which a voltage is not applied. Therefore, the other movable part11afollows the warp of the one movable part11bso as to warp in the same direction as that of movable part11b. As a result of this, movable parts11a,11bboth displace in the illustrated right direction with respect to the longitudinal axis m of piezoelectric/electrostrictive device10a. The displacement amount of this displacement changes in accordance with the maximum value of the voltage applied to each of the piezoelectric/electrostrictive elements12a,12b. The larger the maximum value of the voltage is, the larger the displacement amount will be.

In particular, if a piezoelectric/electrostrictive material having a high coercive electric field is adopted as a material for constructing the piezoelectric/electrostrictive layers34ato34dconstituting the piezoelectric/electrostrictive element34, the aforesaid bias voltage may be adjusted so that the minimum level will be at a slightly negative level, as illustrated by waveforms drawn in two-dot chain lines inFIGS. 27A and 27B. In this case, by driving the piezoelectric/electrostrictive element to which the bias voltage of negative level is applied, for example, by driving the other piezoelectric/electrostrictive element12a, for example, a stress is generated in the other movable part11ain the same direction as the warping direction of the one movable part11b, thereby providing a larger displacement amount of mounting part11d. In other words, by using the waveforms shown in two-dot chain lines inFIGS. 27A and 27B, the piezoelectric/electrostrictive elements12a,12bto which the bias voltage of negative level is applied can have a function of supporting the piezoelectric/electrostrictive element12b,12aacting as a main agent of displacement operation.

Thus, in piezoelectric/electrostrictive device10a, a minute displacement of piezoelectric/electrostrictive elements12a,12bis amplified to become a large displacement operation by utilizing the warp of movable parts11a,11b, and is transmitted to movable parts11a,11b. This makes it possible to displace the mounting part11dto a large extent with respect to the longitudinal axis m of piezoelectric/electrostrictive device10a.

In the piezoelectric/electrostrictive device10a, it is preferable to give the following consideration so as to allow the functions thereof to be exhibited with more certainty. Namely, in order to ensure the displacement operation of mounting part11d, the distance Ld by which the substantial driving part Lc of piezoelectric/electrostrictive elements12a,12boverlaps the fixing part11c or mounting part11dis preferably not less than a half of the thickness b of movable parts11a,11b. Further, the device is constructed in such a manner that the ratio c/d of the distance c between the inner walls of movable parts11a,11b(distance in the X-axis direction) to the width d of movable parts11a,11b(distance in the Y-axis direction) is from 0.5 to 20. The ratio c/d is preferably from 1 to 15, more preferably from 1 to 10. The defined values of the ratio c/d are based on the knowledge that the displacement amount of mounting part11dcan be increased and the displacement in the X-axis-Z-axis plane can be dominantly obtained.

The ratio e/c of the substantial movable length e in movable parts11a,11bhaving a total length of e0 to the distance c between the inner walls of movable parts11a,11bis preferably from 0.5 to 10, more preferably from 0.5 to 5. The length f1of the connecting part between the mounting part11dand the movable parts11a,11b(distance in the Z-axis direction) and the length f2of the connecting part between the fixing part11cand the movable parts11a,11b(distance in the Z-axis direction) are preferably short. By providing a short mounting part11d, the device can have a reduced weight, and the resonance frequency can be increased. However, in order to ensure the rigidity of mounting part11din the X-axis direction to make a firm displacement, the ratios f1/b and f2/b to the thickness b of movable parts11a,11bis preferably at least 2, more preferably at least 5. Further, the distance e1x from the bending position L1of base11to fixing part11cor mounting part11dand the distance e1y from L1to movable part11apreferably satisfy (e1x/b)>1 and (e1y/b)>1, more preferably (e1x/b)≧2 and (e1y/b)≧2.

It is essential to set the real dimension of the parts of the piezoelectric/electrostrictive device10ain consideration of the bonding area of mounting part11dfor mounting the component, the bonding area for mounting the fixing part11cto another member, the bonding area for mounting the terminals for the electrodes and others, the strength of the whole device, the durability, the necessary displacement amount and resonance property, the driving voltage, and others.

Specifically, for example, the distance c between the inner walls of movable parts11a,11bis preferably from 100 μm to 2000 μm, more preferably from 200 μm to 1600 μm. The width d of movable parts11a,11bis preferably from 50 μm to 2000 μm, more preferably from 100 μm to 500 μm. In order that the flapping displacement, which is a displacement component in the Y-axis direction, may be effectively restrained, the thickness b of movable parts11a,11band the width d of movable parts11a,11bsatisfy d>b, and the thickness b is preferably from 2 μm to 300 μm, more preferably from 10 μm to 80 μm.

The substantial movable length e in movable parts11a,11bis preferably from 200 μm to 3000 μm, more preferably from 300 μm to 2000 μm. The connecting length f1 between mounting part11dand movable parts11a,11band the connecting length f2 between fixing part11cand movable parts11a,11bare preferably from 50 μm to 2000 μm, more preferably from 100 μm to 1000 μm.

The distance e1x from the bending position L1of base11to fixing part11cor mounting part11dis preferably from 1 μm to 300 μm, more preferably from 5 μm to 80 μm. Further, the distance e1y from the bending position L1of base11to movable part11ais preferably from 1 μm to 1000 μm, more preferably from 5 μm to 500 μm. Here, the distance from the bending position L2 of base11to fixing part11cor mounting part11d(distance corresponding to distance e1x) and the distance from the bending position L2of base11to movable part11a(distance corresponding to distance e1y) are similar to distance e1x and distance e1y.

By constructing the piezoelectric/electrostrictive device10ain such a manner, the displacement in the Y-axis direction can be prevented from exceeding 10% of the displacement in the X-axis direction. However, by suitably setting the dimension ratios and the real dimensions within the aforesaid ranges, the device can be driven at a low voltage, and it produces an excellent effect that the displacement in the Y-axis direction can be restrained to be not more than 5% of the displacement in the X-axis direction. In other words, mounting part11ddisplaces substantially in one axial direction, i.e. the X-axis direction, thereby providing an excellent property that the high-speed response is excellent and a large displacement is obtained at a low voltage.

Further, in the piezoelectric/electrostrictive device10a, base11constituting the principal construction component has a specific shape, and the movable parts11a,11bare approximately perpendicular to fixing part11cand mounting part11dto function as ribs, so that the rigidity of the device in the Y-axis direction can be set high. For this reason, in the piezoelectric/electrostrictive device10a, the operation of mounting part11dcan be selectively generated in a plane (in X-axis-Z-axis plane) alone, and the operation of mounting part11din the Y-axis-Z-axis plane, i.e. operation in the so-called flapping direction, can be restrained.

Here, in the device according to the present invention, by devising the shapes of the fixing part and the mounting part of the base, the gimbal of the suspension of the hard disk drive can be integrated with the base of the device.

Here,FIGS. 29 and 30illustrate two modifications of the first piezoelectric/electrostrictive device10a. The piezoelectric/electrostrictive devices10a1,10a1according to these modifications have basically the same construction as the first piezoelectric/electrostrictive device10a. However, in the piezoelectric/electrostrictive device10a1, circular recesses11c1,11d1are formed by press-molding generally at the central parts of fixing part11c and mounting part11dof base11. In the piezoelectric/electrostrictive device10a1, circular through-holes11c2,11d2are formed by stamping generally at the central parts of fixing part11c and mounting part11dof base11.

In piezoelectric/electrostrictive device10a1, circular recesses11c1,11d1disposed in the fixing part11c and mounting part11dof base11serve to accommodate an adhesive for bonding the component to be mounted to fixing part11cand mounting part11d, whereby the adhesive accommodated in the recesses11c1,11d1increases the bonding strength to the component and the squeeze-out of the adhesive from the bonding site can be prevented.

Further, in piezoelectric/electrostrictive device10a1, circular through-holes11c2,11d2disposed in the fixing part11cand mounting part11dof base11act as a standard for positioning in assembling (bonding) the component onto fixing part11cand mounting part11d, whereby the precision of assembling in later steps can be improved, and the yield of the products can be improved.

The base24constituting the tenth piezoelectric/electrostrictive device20eshown inFIG. 31includes a pair of right and left movable parts24a,24b, a fixing part24cthat connects the two movable parts24a,24bwith each other at one end thereof, a mounting part24dthat connects the two movable parts24a,24bwith each other at the other end thereof, and a connecting part24ethat is integral with the mounting part24d.

The base24has such a configuration that a connecting part is added to the base18constituting the seventh piezoelectric/electrostrictive device10g. The connecting part24eof base24has a flat plate shape having a square-shaped opening24f1at the central part thereof, where movable parts24a,24b, fixing part24c, and mounting part24dare placed in an integral state in the opening24f1. The connecting part24esurrounds the principal construction parts of base24, and the two side peripheries24e1,24e2of connecting part24ehave a spring function.

Referring toFIG. 32A, the original plate24A of base24has a rectangular opening24f1that will constitute the connecting part24eand a gate-shaped opening24f2that will integrally constitute the movable parts24a,24b, fixing part24c, and mounting part24d. Base24shown inFIG. 32Bis formed by bending the original plate24A along two-dot chain lines L1, L2shown inFIG. 32A. In the base24thus formed, piezoelectric/electrostrictive elements22a,22bare bonded onto the outer sides of movable parts24a,24bto form the tenth piezoelectric/electrostrictive device20eshown inFIG. 31.

The tenth piezoelectric/electrostrictive device20ehas the same function as the seventh piezoelectric/electrostrictive device10gand produces approximately the same actions and effects as the seventh piezoelectric/electrostrictive device10g. However, since the tenth piezoelectric/electrostrictive device20ein particular integrally includes the connecting part24ehaving a spring function, the connecting part24ecan be allowed to function as a gimbal of the suspension constituting the hard disk drive. In other words, the base24has a function of a gimbal as well.

The base25constituting the eleventh piezoelectric/electrostrictive device20fshown inFIG. 33includes a pair of right and left movable parts25a,25b, a fixing part25cthat connects the two movable parts25a,25bwith each other at one end thereof, a mounting part25dthat connects the two movable parts25a,25bwith each other at the other end thereof, and a connecting part25ethat is integral with the mounting part25d.

The base25has such a configuration that a connecting part is added to the base18constituting the seventh piezoelectric/electrostrictive device10g. The connecting part25eof base25has a flat plate shape having a gate-shaped opening25f1at the central part thereof and having a rectangular opening25f2, whose one end is open, on the tip end side thereof, where movable parts25a,25b, fixing part25c, and mounting part25dare placed in an integral state in the opening25f2. The connecting part25esurrounds the principal construction parts of base25, and the two side peripheries25e1,25e2outside the connecting part25eas well as the two side peripheries25e3,25e4inside the connecting part25ehave a spring function.

Referring toFIG. 34A, the original plate25A of base25has a gate-shaped opening25f1and a rectangular opening25f2that will constitute the connecting part25eand a gate-shaped opening25f3that will integrally constitute the movable parts25a,25b, fixing part25c, and mounting part25d. Base25shown inFIG. 34Bis formed by bending the original plate25A along two-dot chain lines L1, L2shown inFIG. 34A. In the base25thus formed, piezoelectric/electrostrictive elements22a,22bare bonded onto the outer sides of movable parts25a,25bto form the eleventh piezoelectric/electrostrictive device20fshown inFIG. 33.

The eleventh piezoelectric/electrostrictive device20fhas the same function as the seventh piezoelectric/electrostrictive device10gand produces approximately the same actions and effects as the seventh piezoelectric/electrostrictive device10g. However, since the eleventh piezoelectric/electrostrictive device20fin particular integrally includes the connecting part25ehaving a spring function, the connecting part25ecan be allowed to function as a gimbal of the suspension constituting the hard disk drive. In other words, the base25has a function of a gimbal as well. Furthermore, since the eleventh piezoelectric/electrostrictive device20fhas a higher spring function than the tenth piezoelectric/electrostrictive device20e, the function of a gimbal can be exhibited with more certainty.

FIG. 35illustrates a hard disk drive40having the eleventh piezoelectric/electrostrictive device20f, which is a piezoelectric/electrostrictive device of the third form according to the present invention, mounted thereon. The hard disk drive40is a known one provided with a suspension. Base41has a voice coil43and a magnet42mounted thereon, and the suspension45having the eleventh piezoelectric/electrostrictive device20fmounted thereon is attached to an arm44disposed on the base41. Here, the reference numeral46denotes a magnetic disk.

Referring toFIGS. 36A and 36B, the eleventh piezoelectric/electrostrictive device20fhas a magnetic head47(slider) fixed onto the mounting part25dof the base25via an adhesive, and is fixed by means of spot welding or the like to the rear side of the suspension45on the rear side of the connecting part25eof the base25. In such a mounting structure of the eleventh piezoelectric/electrostrictive device20f, the connecting part25eof the base25has a function of a conventional gimbal, thereby providing an advantage that the use of a conventional gimbal can be omitted in mounting the eleventh piezoelectric/electrostrictive device20fonto the suspension45.

While the invention has been shown and described in detail, the foregoing description is in all aspects illustrative and not restrictive. It is therefore understood that numerous other modifications and variations can be devised without departing from the scope of the invention.