KR20010108276A - Packaged strain actuator - Google Patents

Abstract

The modular actuator assembly preferably comprises one or more plates or elements of an electrically active material attached to a sheet formed with electrodes by a structural polymer to form a card. The card is sealed and constitutes a practical device, such as a wing, rocker, stirrer, lever, propeller or sonicator, which is in direct contact with the solid or fluid content, or is bonded by a solid adhesive to solid work. Face-to-face mechanical connections can be made with water, devices, substrate machines or samples. Structural polymers provide bending stiffness that prevents thin plates from deforming up to their breakpoint and mechanical stiffness that allows shear forces to effectively connect from the plate to the workpiece. In other embodiments, the card may include active circuit elements for switching, powering, or signal processing and / or passive circuit elements for filtering, matching, or damping signals, such that no or little connection to the outside of the circuit is required. Not required. The actuator assembly is provided to provide a variety of actuators with uniform mechanical operating characteristics that induce negligible mass loads on the workpiece. The card itself may be arranged as an independent mechanical actuator rather than a strain transfer operation in which the induced strain changes the position of the card. Various arrangements of pinned or cantilevered cards can act as propellers, bends, or other dynamic actuators, and structures such as power corrugations can be formed directly by one or more suitably patterned cards.

Description

Packaged Strain Actuators {PACKAGED STRAIN ACTUATOR}

The present invention is a continuation of US patent application Ser. No. 08 / 188,145, filed Jan. 27, 1994, part of US patent application Ser. No. 08 / 943,645, filed Oct. 3, 1997, US patent application Ser. No. 09 / 261,475 Part of the issue is pending application.

Smart materials, such as piezoelectric, electrically distorted or magnetically distorted materials, are also used for high band width tasks such as driving or damping structural or acoustic noise, and also for precision. It can also be used for application of the arrangement. Such applications often require that the smart material be attached to the structure under control. However, general purpose actuators of such materials are generally not available. And a person who wishes to carry out such a control task will typically fix a smart material material in its original state, possibly with no electrode formed, along with any necessary electrodes, adhesives, and insulating structures on or incorporating it into the item of interest. The process must be carried out.

For such applications, connecting and attaching such materials is such that the mechanical and electrical connection to the smart material is robust and in such a way as to create strain in the smart member, displace the system or force the system; It is necessary to connect such strain, motion or force to the object to be controlled. Often, smart materials are required to be used in unfavorable environments that greatly increase their mechanical or electrical breakage.

By way of example, one such application, which is an application of vibration suppression and operation to a structure, requires attaching a piezoelectric element (or multiple elements) to the structure. These devices are then operated so that the electrical energy applied to the device by the piezoelectric effect is converted into mechanical energy distributed throughout the device. By selectively changing strain or creating mechanical impacts in the piezoelectric material, specific shape control of the underlying structure can be achieved. Rapid actuation can be used to suppress natural vibrations or to apply controlled vibrations or displacements. Examples of this application of piezoelectric elements and other intelligent materials have become increasingly common in recent years.

In typical vibration suppression and actuation applications, the piezoelectric elements are bonded to the structure in a complex series of steps. First, the surface of the structure is machined to create one or more channels to maintain the electrical leads needed to connect to the piezoelectric elements. Alternatively, instead of the machining of the channels, two different epoxies may be used to make both mechanical and electrical contact. In this alternative approach, conductive epoxy is gradually sprayed, i.e., locally applied to form conductors, and structural epoxy is applied to the rest of the structure to bond the piezoelectric element to the structure. Then everything is covered with a protective coating.

This assembly process is labor intensive and often involves a lot of rework due to problems with working with epoxy. Mechanical uniformity between different piezoelectric elements is difficult to obtain due to the variability of the process, especially with regard to the alignment and adhesion of the piezoelectric elements. Electrical and mechanical connections made in this way are often unreliable. It is common for the conductive epoxy to flow in undesired ways, causing a short across the ends of the piezoelectric element. Moreover, piezoelectric elements are very brittle and, if not supported, can break during bonding or handling.

Another drawback of the conventional manufacturing process is that if the piezoelectric element adheres to the structure and then breakage occurs, the function of the portion of the piezoelectric element that is not in contact with the conductor may be rendered ineffective. As a result, the complete operation of the device is impaired. Shielding can be a problem because in general, as well as other circuit components, people must be shielded from the electrodes of such a device through which high voltage can pass.

One attempt to incorporate piezoelectric materials such as thin piezoelectric plates, cylinders, or stacks of disks or rings into controllable structures has been described in US Pat. No. 4,849,668 to Javier de Luis and Edward F. Crawley. This technique involves precisely hand-assemblying various devices into the integrated structure, in which piezoelectric ceramic elements are included and insulated within the structure of the plywood composite, which serves as a strong support. Such support reduces the problem of electrode cracking and is implemented in such a way as to be calculated to optimize structural strength with mechanical operating efficiency, at least as described in the patent. Moreover, in the case of cylinders or laminated rings, the natural internal passages in the form of piezoelectric elements deviating from these shelf shapes simplify wiring installation to some extent that would otherwise be difficult. Nevertheless, the design is not simple, and the manufacturing is time consuming and also remains exposed to numerous failure modes during assembly and operation.

In the field of dynamic testing, a variety of actuators are needed to shake or perturb the structure so that its response can be measured or controlled. However, here, the accepted methodology for the rocking test apparatus includes the use of an electro-mechanical motor to cause linear disturbances. In order to separate the motor from the desired signal, the motor is generally applied through a stinger design. Such external motors still have the drawback that they often encounter dynamic coupling when using the motor to excite the structure. Moreover, in this type of actuator, inertia is added to the structure resulting in unwanted dynamic states. When the exciter is not an integral part of the structure, the structure can be grounded. These factors can greatly complicate the modeling or mathematical analysis of the state of interest as well as the operation of the device. The use of piezoelectric actuators can overcome many of these drawbacks, but, as mentioned above, introduces its own problems of complex configuration, variations in operating characteristics and durability. Similar problems arise when piezoelectric or electrically distorted devices are used for sensing.

Thus, although the device has a high band width actuation capability and can be easily installed, the device may be subjected to controlled or actuated structures such that it is mechanically and electrically robust and does not significantly change the mechanical properties of the structure as a whole. It is preferred that the improvement be made in such a way that it is bonded. It is also desirable to achieve high strain transfer from the piezoelectric element to the structure of interest.

The present invention relates to actuator elements that can be used for active vibration reduction, structural control, dynamic testing, precise placement, motion control, shaking, churning, and passive or active damping. More specifically, the present invention relates to a packaged actuator assembly, the actuator assembly being electronically controllable and also actively damping the mechanical state of the device to which it is attached or operating the structure. It can be applied to suppress or vibrate, or can be used independently. As described in the following sections below, the assembly may be attached or attached to a structure or system, whereby the assembly is incorporated with a system that is actuated, controlled or damped.

1A is a system diagram of a typical prior art actuator.

1B and 1C are corresponding views of two systems according to the present invention.

2A and 2B are a plan view and a cross-sectional view, respectively, of a basic actuator or sensor card in accordance with the present invention, and FIG. 2C shows an actuator or sensor card with circuit elements.

3 shows another card.

4A and 4B are cross-sectional views of the card of FIG. 3.

5 and 5A are detailed views of the layer structure of the card of FIG.

6 shows an actuator package comb-like electrode operating in a plane.

FIG. 7 illustrates a torsional actuator package using the card of FIG. 6.

8A and 8B respectively show actuators mounted as surface mount actuators on a surface or rod.

9 shows actuators mounted as mechanical elements.

10A, 10B and 10C are schematic diagrams of a line interdigitally electroded electro-active device.

FIG. 11A shows a line alternating electrode electrically active device with a common bus located on a piezoelectric element, and FIG. 11B shows a line alternating electrode with a common bus positioned over a piezoelectric element. An electrostatically active device is shown.

FIG. 12 illustrates an angleless line alternate electrode type electrically active device with multiple piezoelectric elements.

FIG. 13 illustrates an angled line alternate electrode type electrically active device with multiple piezoelectric elements.

FIG. 14A shows a state in which an angled line-positioned electrode-electrically active device is bonded to a beam structure, and FIG. 14B shows an angled line-positioned electrode-type electrically active device in a tube or bar structure. The bonded state is shown.

FIG. 15A shows electric field lines for piezoelectric devices with piezoceramic plates with solid electrodes on both surfaces of the plate, and FIG. 15B shows electric field lines of one embodiment of a piezoelectric device with alternating electrodes. Illustrated.

16 shows an S-type device with electrically active quadrants.

17 shows the relative displacement of the S-type device.

The actuator assembly according to the invention comprises at least one piezoelectric element, such as a piezoelectric or electrically distorted plate or shell, a housing constituting a protective body around the element, and mounted in the housing and connected to the strain element. Electrical contacts, which together constitute a flexible card. At least one side of the assembly includes a thin sheet attached to the main face of the strain element, and by bonding the outside of the sheet to the object, a tight, shear-free bond is obtained between the strain element and the object in the housing.

In a preferred embodiment, the strain element is a piezoelectric ceramic plate, which is very thin and preferably between slightly below 1/8 mm and a few mm thick, and also having one or both of the length and width values described above. It has a relatively large surface area that is tens to hundreds of times larger than the thickness value. Metallized films make electrode contacts, while adhesives and insulating materials seal the device like a seal against layer peeling, cracking and environmental exposure. The adhesive used may be an epoxy such as a B- or C-stage epoxy, or a thermoplastic or any other material useful for bonding together piezoelectric ceramic plates, metallized films and insulating materials. The particular adhesive used will depend upon the intended application of the intended device. In a preferred embodiment, both the metallized film and the insulating material are installed in a flexible circuit of rigid polymer material, thereby providing a robust mechanical and electrical coupling to the wrapped devices. Alternatively, the metallized film may be disposed directly on the piezoelectric ceramic plate and the insulating material may have electrical contacts.

As shown, the example below describes a configuration using a rectangular PZT plate having a thickness of 1/4 mm and having a length and width of 1 to 3 cm, respectively, so that each element has a width. It has an active strain generating surface that is 1 to 10 cm 2. PZT plates are mounted on or between rigid and strong polymer sheets, for example 0.5 mils (1 mil is 0.001 inch), 1 mil or 2 mils of polyamide, the polymer being on one or both sides thereof. The copper is coated and also has a suitable conductive electrode pattern formed in the copper layer to contact the PZT plate. Various spacers surround the plate and the entire structure is glued together into a waterproof, insulated, closed package with the structural polymer, the package having a thickness approximately equal to the plate thickness, for example 0.30 to 0.50 mm. When so closed, the package can be bent, stretched and bent, and can withstand sharp impacts without damaging the embedded brittle PZT element. In addition, because the conductor pattern is firmly attached to the polyimide sheet, even if the crack of the PZT element does not disconnect the electrode or hinder operation over the entire area of the element, otherwise its performance is severely Will be damaged.

Thin packages form a complete modular unit in the form of a small "card" with all the electrodes. The package can then be conveniently attached by adhering one side to the structure, resulting in connecting the strain between the wrapped strain element and the structure. This can be done, for example, by simply attaching the package with an adhesive, which results in a thin and high shear strength while combining with the PZT plate while adding minimal mass to the system as a whole. The plate may be an actuator that connects energy into the attached structure, or may be a sensor responsive to strain connected from the attached structure.

In another embodiment, specific electrode patterns are selectively formed on the sheet to polarize the PZT plate to either side in-plane or across the surface, and multiple layers of PZT elements may be arranged or stacked in a single card. Resulting in bending or shearing and even special twisting operations.

According to another feature of the invention, circuit elements are formed in or with a modular package to filter, short, or process a signal generated by a PZT element, or to sense a mechanical environment, or It even performs local switching or power amplification to drive the operating elements. The actuator package may, together with a preformed PZT element such as a semi-cylinder, constitute a modular surface-mounting shell suitable for attachment around a pipe, rod or shaft.

These and other preferred features of the present invention will be understood from the detailed description of the illustrated embodiments.

1A is a schematic diagram of a process and overall arrangement of a surface mount piezoelectric actuator assembly 10 of the prior art. Structural or mechanical elements, plates, airfoils or other interoperable sheets, or devices, or portions thereof, may be used in the structure 20, in which the sheet 12 of smart material is conductive and Bonded by any combination of structural polymers 14, 16. Insulators 18, which may be composed in whole or in part of structural polymers 16, wrap around and protect the smart material, while conductive wires or surface electrodes are formed or attached by conductive polymers. The external control system 30 can supply drive signals along lines 32a and 32b facing the smart material, and can also receive measurement signals from surface mount instruments such as strain gauges 35, From such a signal a proper drive signal is derived. Various forms of control are possible. For example, strain gauges may be arranged to sense excitation of inherent resonances, and control system 30 may simply operate the PZT element in response to the sensor output to reinforce the structure, thereby resonating the resonances. The frequency can be shifted. Alternatively, the vibration sensed by the sensor can be fed back as a processed phase delay drive signal to eliminate the developing dynamics, or the actuator can be driven for motion control. In a better understood mechanical system, the control device may be able to recognize empirical conditions, i.e., aerodynamic conditions or situations, and to obtain the gain of the drive signal for each actuator 12 to achieve a desired change. It can be programmed to select a special control law that specifies the phase.

In all such applications, the main task is to attach an uncovered PZT plate to its control circuitry and the workpiece. In addition, if many of the assembly processes fail, or if quantitative control is desired, the device is assembled to establish a control parameter for a useful mode of operation suitable for the specific thickness and mechanical stiffness achieved in the manufacturing process. Afterwards, extensive modeling of the device may be required.

1B illustrates an actuator in accordance with one embodiment of the present invention. As shown, the modular pack or card 40 is simply attached to the structure 20 with a rapid solidification adhesive, such as a five-minute epoxy 13, or otherwise shaped. Is attached at a point or line. Thus, sensing and control actions benefit from actuator structures that are more easily installable and uniformly modeled. In particular, the modular pack 40 has the form of a card which is a rigid but bendable plate, which card is preferably one or more electrical connectors in the form of a pad (not shown) located at the card rim. These pads can be plugged into multiple pin sockets so that the card is connected to the simplified control system 50. As described in more detail with respect to FIG. 2C below, the modular package 40 may also incorporate flat or low-profile circuit elements, which may be weighted or shunted. signal processing elements such as shunting resistors, impedance matchers, filters and signal conditioning preamplifiers, and operating under switching transistors and direct digital control. Other devices may be included, and as a result, the only external electrical connectors needed are such as microprocessors or logic controllers and power supplies.

In another embodiment, which is particularly applicable to certain low power control situations, the modular package 60 shown in FIG. 1C is a microcomputer for operating an on-board driver and classifier. It can contain a processor chip or a programmable logic array and can also contain its own power source, such as a battery or a cell, thus achieving a complete set of sense and control operations without any external circuitry. .

The present invention relates in particular to piezoelectric polymers and also to materials such as hard but brittle sintered metal zirconate, niobate crystal or piezoelectric ceramic materials. The invention also relates to an electrostrictive material. As used in the claims below, piezoelectric and electrically distorted devices in which the material of the device has electromechanical properties are both referred to as electrically active devices.

High stiffness is essential for the effective transfer of strain across the surface of the device toward an external structure or workpiece, typically made of a metal or rigid structural polymer, so in terms of actuators the present invention provides a flexible polymeric piezoelectric material. Does not target Although the terms "rigid" and "ductile" are relative, the strength applied to the actuator in this specification is a metal having a Young's modulus of approximately 0.1 × 10 ⁶ or greater, preferably 0.2 × 10 ⁶ or greater, It is the stiffness of cured epoxy, high-tech composites, or other rigid materials. When constructing a sensor instead of an actuator, the invention also targets the use of low rigid piezoelectric materials, such as polyvinylidene difluoride (PVDF) films, and the substitution of low curing temperature adhesion or adhesion materials. . However, the attempt of the main construction is made of the above-described first kind of piezoelectric material, which will now be described.

In general, the present invention encompasses novel types of actuators and methods of making such actuators, where an "actuator" is a complete, mechanically useful device that, when driven, connects force or motion or the like to an object or structure. It is understood to mean. In a broad sense, the manufacture of actuators involves the packaging of raw, electrically active devices to make them mechanically useful. By way of example, a raw electrically active piezoelectric material or "element" includes a bulk material with mechanical elements such as levers, as well as basic shapes such as sheets, rings, washers, cylinders and plates. Is commonly used in the form of a variety of semi-treated bulk materials, including raw piezoelectric materials in more complex or complex forms, such as hybrid forms or stacks. These materials or raw devices may or may not be metal coated on one or more surfaces to act as electrical connectors. As will be discussed below, piezoelectric materials will be discussed by way of example, and all these types of raw materials will be referred to as "devices", "materials" or "electrically active devices." As noted above, the present invention also includes structures or devices that are manufactured in this manner and that act as transducers to sense strain, vibration, position or other physical characteristics, rather than actuate, In the following application cases, the term "actuator" may include a sense transducer.

Embodiments of the present invention are directed to thin sheets of discs, rings, plates and cylinders or shells having a thickness of several millimeters or less and, for example, having a thickness of 1/5 to 1/4 millimeters. These rigidly electrically driven materials are employed. Advantageously, this thin dimension allows for a high electric field strength over a distance comparable to the plate thickness dimension at a relatively low potential difference, resulting in a drive of 10 to 50 volts or less. A full scale piezoelectric action can be obtained with voltage. Moreover, such thin dimensions make it possible to attach an element to a target without significantly changing the structural or physical reaction characteristics of the target. However, in the prior art, such thin elements are brittle and can also break due to irregular stress when handling, assembling or curing. Even when impacted by a few centimeters, the piezoelectric ceramic plate can break, allowing only extremely small bending deflections before breakage.

According to the present invention, an electrically driven thin device is surrounded by rigid insulator layers, at least one of which has a patterned conductor on one of its surfaces and which is thicker than the device itself. It is a thin tough film. Since the package is assembled from piezoelectric elements, insulating layers and various spacers or structural fill materials, the electrodes, piezoelectric elements and surrounding films or layers are all together, substantially no thicker than the raw actuating elements. Construct a sealed card. As will be discussed below, when the elements are placed in several layers, the package thickness is not noticeably larger than the sum of the thicknesses of the stacked actuation elements.

2A shows a basic embodiment 100 of the present invention. The thin film 110 of a highly insulating material, such as polyimide, is metallized at least on one side, typically copper coated, and consists of a rectangle of the same or slightly larger width than the finished actuator package. Suitable materials that can be used to fabricate multilayer circuit boards are provided as Flex-I-Mid 3000 adhesive circuit materials by Rogers Corporation of Chandlre, Arizona, Chandler, Arizona, which is a rolled copper foil. It consists of a polyimide formed on). The range of sizes is commercially available as 18 to 70 micrometer thick metal foil integrally coated with a 13 to 50 micrometer thick polyimide film. Other thicknesses can also be produced. In such commercial materials, the foil and polymer film are attached directly without adhesive, so that the metal layer can be patterned by conventional masking and etching, and the multiple pattern layers weaken the assembly or separate the layers. It can be assembled into a multilayer substrate in the manner described in more detail below without residual adhesive causing delamination. Rolled copper foils provide high in-plane tensile strength, while polyimide films exhibit a strong, hard and flawless electrical insulation barrier.

In the configuration described below, the film not only constitutes the insulator on the electrode, but also constitutes the outer surface of the device. Therefore, it is required to have high dielectric strength, high shear strength, waterproofness, and the ability to adhere to other surfaces. High thermal resistance is necessary in view of the thermal curing used in the preferred manufacturing process, and also for certain application environments. In general, polyamides / imides have been found to be useful, but other materials, such as polyesters or thermoplastics with similar properties, may also be used.

In the configuration of the present invention, the foil layer is formed by conventional masking and etching techniques (e.g., photoresist masking and patterning followed by ferric chloride) in order to form an electrode in contact with the surface of the piezoelectric plate element. Etching] to form a pattern. Alternatively, softer and thinner conductive layers can be used. For example, a thin conductive layer can be printed on the piezoelectric element or directly on the polymer film using silver conductive ink. In FIG. 2A, the electrode 111 extends over one or more sub-regions inside the rectangle to reach reinforced pads or lands 111a and 111b extending from the rim of the device. The electrodes are arranged in a pattern in contact with the piezoelectric element along a widely rotating path across the entire length and width of the piezoelectric element, so that the element remains connected even if a slight crack or local breakdown occurs in the electrode or piezoelectric element. Guaranteed. The frame members 120 are positioned around the periphery of the sheet 110, and at least one piezoelectric plate element 112 is positioned in the central region and is contacted by the electrode 111. The frame members serve to constrain the rim so that the thin sheets do not extend to the rim, and also as thickness spacers for the hot-press assembly action described below, and are inserted during the initial stage of assembling the laminated package. It serves as a position marker for positioning the piezoelectric plate.

FIG. 2A includes an additional translucent top layer 116 (FIG. 2B) that extends beyond the plate 112 in practice and closes the assembly with the spacer 120 and the sheet 110 to secure the device together. Since the layer structure of the apparatus is not shown, it is somewhat schematic. A similar layer 114 with an appropriate cut that allows the electrode 111 to contact the device is located below the piezoelectric device. The layers 114 and 116 are preferably made of a curable epoxy sheet material, which has a curing thickness equal to the thickness of the metal electrode layer, and also adhesives for bonding together the materials in contact with it on their respective sides. Acts as a layer. The epoxy, when cured, constitutes the structural body of the device to stiffen the assembly, extending over a substantial portion of the piezoelectric element surface to strengthen the device and prolong its life by preventing crack growth. Moreover, the epoxy from this layer is substantially finely thin but very discontinuous, covering the electrodes with a film of about 0.0025 millimeters thick to firmly adhere the electrodes to the piezoelectric plate, but to the electrodes and piezoelectric over a substantially distributed contact area. There are a sufficient number of voids and pinholes so that direct electrical contact between the devices still occurs.

FIG. 2B is a cross-sectional view of the embodiment of FIG. 2A, although not shown in scale. By approximate ratio, holding the piezoelectric plate 112 to 0.2 to 0.25 millimeters thick, the insulating film 110 is very thin, only 1/10 to 1/5 of the plate thickness, and the conductive copper electrode layer 111 is typically It can have a thickness of 10 to 50 microns, which is not a strict limit, but is useful in electrical and convenient manufacturing but not thick enough to impair strain transfer efficiency or cause layer delamination problems. The electrode thickness range is shown. Since the structural epoxy 114 fills the space between the electrodes 111 in each layer and has approximately the same thickness as those electrodes, the entire assembly constitutes a solid block. The spacer 120 is composed of a relatively compressible material with a low modulus of elasticity, such as a relatively non-crosslinked polymer, and when used with pressure cured epoxy as described below, preferably a stack of elements or piezoelectric ceramic Having a thickness approximately equal to the plate, the spacers constitute an edge that constrains other components between the top and bottom layers of the film 110.

Preferred manufacturing methods include applying pressure to the entire package as layer 116 cures. As described below with reference to FIGS. 3 to 5, the spacers serve to align any circuit elements with the piezoelectric ceramic plate, and are also slightly compressed during assembly in the curing step and leave no stress or abnormality during curing. It constitutes a frame that can be deformed to seal the rim. Compression eliminates voids and provides a dense, crack-free solid medium, while the heat of cure results in a high degree of crosslinking, resulting in high strength and stiffness.

The assembly process for the embodiment of Figures 2A and 2B is as follows. One or more copper clad polyimide films having a total thickness of approximately 0.025 to 0.050 millimeters each are cut to a size slightly larger than the final actuator package dimensions. The copper side of the film is masked and patterned to form an electrode of the desired shape in contact with the piezoelectric element, together with the conductive lead and any desired land or access terminal. Although a tuning fork electrode pattern with three lines positioned to contact both sides and the center of one side of the piezoelectric element is shown, in other embodiments an H-type or comb-type may be used. As is familiar with circuit board or semiconductor processing techniques, pattern formation is accomplished by masking, etching, and then cleaning. Masking is accomplished by photoresist pattern formation, screening, tape masking, or other suitable process. Each piece of polyimide film on which these electrodes are formed, like the conventional printed circuit board, positions the circuit element or actuator sheet and will be referred to hereinafter simply as a "flex circuit". However, the method and apparatus of the present invention also contemplate the use of piezoelectric elements, insulators and electrical contacts with electrodes formed, rather than "flexible circuits".

Next, the uncured sheet epoxy material, which is slightly thicker or equal in thickness to the electrode foil layer, is cut off, optionally with through holes matching the electrode pattern to improve electrical contact when assembled. This epoxy material is disposed on each flexible circuit, so that it is attached to the flexible circuit to form a flat layer between or around the electrodeled portions. The backing is then removed from the epoxy layer attached to the flexible circuit, and the pre-cut spacers 120 are placed in place at the edges and corners of the flexible circuit. The spacers outline the frame extending beyond the plane of the electrodes and also form one or more recesses in which the piezoelectric elements are fitted in the next assembly step. Then, the piezoelectric element or elements are disposed in the recess formed by the spacer, and the second electrode film having its own planar / adhesive layer 114 forms an electrode contact with the top of the piezoelectric element. Is placed on. If the device is to have several layers of piezoelectric elements, as in the case of certain bending actuator configurations, these assembly steps are repeated for each additional electrode film and piezoelectric plate, in this case both on the top and the bottom of the intermediate sheet. It should be noted that when constructing the intermediate electrode layer in contact with the actuator element, polyimide films coated on both sides and patterned may be used.

Once all the elements are in place, the patterned flexible circuit, the piezoelectric sheet, and the entire sandwich assembly of spacer and curable patterned epoxy layer are placed in a press between the heated platens, It is cured at elevated temperatures and pressures to strengthen the assembly with a hard, crack-free actuator card. In an exemplary embodiment, a 30 minute curing cycle is used at 350 ° F. and 50-100 psi pressure. Epoxy selects those having a curing temperature below the depoling temperature of the piezoelectric element but capable of achieving high stiffness.

Since the configuration represents a simple actuator card with a single piezoelectric plate sandwiched between two electrode films, the plate effectively transfers the shear strain through the thin film to the surface of the actuator card. When the shear modulus is divided by the layer thickness square and referred to as gamma (Γ), the measurement of the transfer efficiency is determined by modulus of the epoxy 114, the rolled foil electrode 111, and the polyimide film 110. Depends on). In an exemplary embodiment where the epoxy and copper electrode layers are 1.4 mils (1 mil is 0.001 inch) thick and the epoxy has a modulus of 0.5 × 10 ⁶ , a gamma of approximately 9 × 10 ¹⁰ pounds / inch ⁴ is achieved. Using thinner epoxy layers and films equipped with 0.8 mil foils, substantially higher Γ is achieved. In general, the gamma of the electrode / epoxy layer is greater than 5 × 10 ¹⁰ pounds / inch ⁴ , whereas that of the film is greater than 2 × 10 ¹⁰ pounds / inch ⁴ .

When using PZT actuator plates with a thickness of 10 mils, a card with three flexible circuit electrode film layers (the middle one is double-coated to contact both plates) and two PZT plates stacked on each other will 28 mil, which is only 40% larger than the thickness of the plate. In terms of mass load, the weight of the actuator element represents 90% of the total weight of this assembly. In general, the plates comprise 50% to 70% of the package thickness, and in other configurations make up 70% to 90% of the mass. Thus, the actuator itself allows for near-theoretical performance modeling. This configuration provides a high degree of versatility to implement stacking or arrangement of single sheets as well as a bender (as just described).

Another useful performance indicator of actuators constructed in accordance with the present invention is the high ratio of actuator strain (ε) to free piezoelectric element strain (Λ), which is approximately 0.8 for the two layer embodiments described herein, and generally greater than 0.5. Big. Similarly, the ratio of the package to the free element curvature K is approximately 0.85 to 0.90 in the case of the above-described configuration and is generally larger than 0.7.

Thus, in general, a package associated with constructing a piezoelectric element implanted in a flexible circuit damages its weight and electromechanical operating properties by far less than 50% and as little as 10%, while in other important respects its Significantly improves strength and mechanical operating range. For example, adding a sheet package structure to the base element appears to reduce the obtainable K, but in practical use, the fusible card configuration results in a piezoelectric bending machine configuration in which a much larger overall deflection is achieved. This is because large plate structures can be manufactured and high bending repeated operation without crack breakage or other forms of mechanical failure. Various configurations that result in such improved physical properties will be described by various figures.

Firstly, the structure of the electrically active device planted between the flexible circuits not only provides a low mass integrated mechanical structure with predictable response characteristics, but also makes it possible to integrate the circuit elements onto or into the actuator card. . FIG. 2C is a plan view of one device 70 of this type, where regions 71 and 73 each contain a wide electrically active sheet, while central region 72 is battery 75, flat power amplification. Or a circuit or power device comprising an amplifier set 77, a microprocessor 79 and a plurality of strain gauges 78. Other circuit elements 82a and 82b may be located elsewhere around the rim along the path of the circuit conductor 81. As in other embodiments, the spacers 120 define the placement and seal the rim of the device, while the electrodes 111 connect the electrically active elements to embedded processing or control circuitry. When the device is operated as a sensor or a class resistor to implement passive damping control, the circuit elements 82a and 82b may include weighted resistors. Alternatively, these circuit elements may be filter elements, amplification elements, impedance matching elements or storage elements such as capacitors, amplifiers or the like. In any case, these elements are placed away from the electrically active plate 84. The components collectively detect strain and implement various types of operation in response to the detected state, or perform other sensing or control tasks.

Turning now to the features of the actuator of the present invention, FIG. 3 is a plan view of an actuator package 200 having a size of about 1.25 × 9.00 × 0.030 inch and assembled with two layers of piezoelectric plates of four plates each. The rectangular polyimide sheet 210 having end tabs 210a is a grid of H-shaped thin copper lines connected to each other and to a single runner 211a connected to the tab ( A lattice shaped electrode 211 is maintained, thus providing a low impedance connection directly to each of the four rectangular regions holding the piezoelectric plate.

The spacer elements of the H-shaped 220a, 220b or L-shaped 220c distinguish the corners and outline the rectangular space for the placement of the piezoelectric plate 216. In this embodiment, a number of gaps 230 to be described in detail below are visible between adjacent H- or L-shaped spacers. As will be evident from the description below, the use of such small discrete spacer elements (I-type, T-type or O-type spacers may be useful) is preferred, because it distinguishes the assembly position and the receiving recess for the piezoelectric element. This is because it can be easily placed on the sticky adhesive epoxy layer 114 during assembly to form the portion. However, the spacer structure is not limited to such a set of discontinuous elements, but is formed of a single perforated sheet or molded frame to provide a recess for maintaining the operation of all or one or more of the placement / sealing edges or circuit components. Or a pair of frame fragments.

FIG. 5 is a plan view of each of three sheet, electrode and piezoelectric plate layers, and FIG. 5A shows a general layer arrangement of film, conductor and spacer / piezoelectric layers. As shown, the spacer 220 and the piezoelectric plate 216 constitute a single layer between each pair of electrode layers.

4A and 4B (not shown according to ratio) show the layer structure of the assembly actuator along the vertical section at the positions indicated by “A” and “B” in FIG. 3. As shown more clearly in FIG. 4A, the pattern adhesive layer 214 of the epoxy sheet is in the same plane as each electrode layer 211 and fills the space between the electrodes, while the spacer 220c is piezoelectric. It is in the same plane as the plate 216 and has a thickness substantially equal to or slightly thicker than the plate. Illustratively, the piezoelectric plate 216 is a commercially available PZT-5A ceramic plate with a thickness of 5 to 20 mils and has a continuous conductive layer 216a covering each side to contact the electrode 211. Spacer 220 is composed of a somewhat compressible plastic having a softening temperature of about 250 ° C. This allows a significant degree of conformability at the curing temperature, allowing the spacer material to fill a few voids 214a (FIG. 4A) during the assembly process. As shown in FIG. 4B, the gap 230 between the spacers (when provided) results in an opening 214b that drains excess epoxy from the curable adhesive layer 214 and also during the curing process. Filled with. As shown in the figure, a certain amount of epoxy also flows into the piece of film 215 between the electrode 211 and the piezoelectric plate 216. Because of the large and continuous size of the electrode 211, this small epoxy leak does not damage the electrical contact with the piezoelectric element, and the additional structural connection it provides helps prevent the electrode layer from peeling off.

With the electrode arrangement shown, each vertically stacked piezoelectric plate pair can be operated in opposition to each other to induce bending, or a larger number of individual electrodes can be operated so that different pairs of plates can be operated in different ways. It will be appreciated that it may be provided. In general, even as described above, even more complex systems involving many individual elements operating in different ways, where the sensing, control and power or damping elements are all mounted on the same card, are subject of the invention. In this respect, such availability also provides great flexibility in adapting the card to practical work. As a rule, the card has flexible flexibility comparable to the flexibility of a 30 mil thick epoxy strip, so it can be bent, knocked, or vibrated without damage. In the region of the center line CL (FIG. 3) in which the piezoelectric element is wrapped, it can be bent or bent sharply so as to coincide with the attachment surface or the corner. The elements may be polarized to vary the area of the plane or cross section, such that the actuator performs one of the control actions described above, or of a particular waveform or type, such as bending, shear or compression waves. It can be attached to transfer strain to adjacent surfaces in a manner effective to apply acoustic energy to adjacent surfaces.

6 illustrates another actuator embodiment 300. In this embodiment, as schematically shown, the epoxy adhesive layer, film and spacer elements are not shown, only the electrodes and piezoelectric sheets are shown to represent the actuation mechanism. The first set of electrodes 340 and the second set of electrodes 342 are both installed on the same layer, each of which has a comb shape in which two combs are alternately arranged, so that the electrically operated region is comb of one comb portion. Is set between and adjacent combs of other combs. As shown in FIGS. 11A and 11B, line electrode 408 (ie, a comb-shaped “comb”) is connected to common bus 402. The bus 402 may be located on or away from the piezoelectric ceramic surface 404 (FIG. 11A). 12 shows an embodiment 400 of the present invention with the bus 402 positioned away from the piezoelectric ceramic surface 404. Alternatively, the bus can be located on the opposite side of the polymer film of the flexible circuit. The line electrode makes an electrical connection with the bus through the polymer film. For example, the polymer film may have a properly positioned plate through hole or may be simply clipped to obtain electrical contact. For example, as shown in FIGS. 11A, 11B and 12, the intermeshing “comb” shape of the electrodes is referred to herein as an alternating electrode (IDE). In FIG. 6, parallel pairs of comb portions 340a and 342a are provided on the other side of the piezoelectric sheet, with comb electrodes 340 connected to comb portions 340a and comb electrodes 342 connected to comb portions 342a. As a result, an electric field having an equipotential line "e" extending through the piezoelectric sheet and an in-plane potential gradient between each pair of comb teeth from different comb-shaped portions is set. In the illustrated embodiment, the piezoelectric ceramic plate is not metallized, so direct electrical contact is made between each comb and the plate. These plates are initially in-plane polarized by applying high pressure across the comb to create an electric field strength of 12,000 volts per inch or more directed along the in-plane direction. As a result, the piezoelectric structure is oriented so that an in-plane (shear) action is then exhibited when a potential difference is subsequently applied across the two comb electrodes. Thus, direct contact of alternating electrodes provides the piezoelectric element with an electric field generally parallel to the direction of operation.

10A, 10B and 10C show various shaped embodiments of the present invention. 10A shows an IDE pattern that includes a line electrode 408 and a common bus 402, printed directly. 10B shows a line electrode 408 printed on the PZT element 404 and a common bus printed on both top and bottom films 412 and 414. 10C shows an IDE pattern that includes a common bus 402 and a line electrode 408 on both top and bottom films 412 and 414.

In addition to shearing operation, directional actuation and damping can be achieved using the method and apparatus of the present invention. For example, as shown in FIG. 7, two such actuators 300 may be crossed to provide a torsional action. Alternatively, as shown in FIGS. 13, 14A and 14B, an angled IDE patterned actuator 406 may be positioned on the structure along the structure's main strain axis to couple shear torsional energy. Since the same effect can be achieved by adhering a piezoelectric device having an angleless IDE pattern on the structure, it is effective that the IDE pattern has an angle with the main strain axis of the piezoelectric element. That is, the device is bonded at an angle.

In discussing this embodiment, the direct transfer of strain energy through any electrode / polyimide layer to any adjacent structure is recognized as a distinct and novel advantage. Such actions may be useful for various or operational tasks, such as airfoil shape control operations and noise or vibration cancellation or control. 8A and 8B show typical installations of flat and semi-cylindrical embodiments (FIG. 8B) of actuators applied to flat or slightly curved surfaces and shafts, respectively.

However, while the electromechanical materials of these actuators are actuated by strain energy conversion, the application of the present invention extends beyond strain coupling through the actuator surface, and the action, torque applied by the actuator. Or many special mechanical configurations in which force is used as a whole. In each of these embodiments, the basic strip-type or shell-type sealing actuator is employed as a rigid, resilient mechanical element that is printed or connected at one or more points along its length. As shown in FIG. 9, when electrically actuated, the strip then functions like a lever, flap, leaf spring, stack or bellow, moving by itself or with other elements. In the figures of FIGS. 9 (a) to 9 (q), elements A, A ', A' 'and the like are strip or seat actuators as shown in the figures, whereas small triangles are for example connection points or anchors to structures. Indicating a fixed or pinned position corresponding to the mounted mounting point. The arrows indicate the direction of motion or actuation or the point of contact for such actuation, while L indicates the lever attached to the actuator and S indicates the stack element or actuator.

The shapes of Figures 9 (a) through 9 (c), such as stacks, bends, or pinned bends, can replace many conventional actuators. For example, the cantilevered beam may have a stylus that provides a highly controlled single-axis displacement that constitutes a very linear and large displacement position mechanism of the pen plotter. Particularly interesting mechanical and operating characteristics are envisaged from the multi-element shapes (Fig. 9 (d), etc.) which vaporize a mechanically robust actuator with sheet size. Thus, as shown in Figures 9 (d) and (e), the pin-pin corrugated box shape is a precise one-axis Z extended by a simple face-contact motion for applications such as camera focusing. May be useful for moving position setting; Or it may be useful to implement a peristalsis-type pump using a movement that supports the entire face against flow. As described in connection with FIG. 3, the flexible circuit is very compliant so that a hinged or folded rim can be implemented by simply folding along the same position as the centerline of FIG. 3, thus closing the corrugation. The box assembly can be made from a small number of large multi-element actuator units. The flexible circuit configuration allows strips or checkerboards of actuator elements to unfold with corrugation lines between each adjacent pair of elements, and the corrugation lines can be contoured [e.g., waffles during the curing step. It can be engraved in thin contours using a waffle-iron press platen. With such a configuration, a seamless seam or other folded actuator can be made from a single flexible circuit assembly as a whole.

16 shows an embodiment of an S-type device having four piezoelectric regions 430, 432, 434 and 436. In this embodiment, the device has a generally sigmoidal shape. In the embodiment shown in FIG. 16, the device has two parts with curvatures in opposite directions. For example, one portion of the device displays curvatures 430 and 432 that are positive relative to the reference, while a second portion of the device represents bends 434 and 436 that are negative relative to the reference. ) Can be displayed. Although two parts of an S-type device may be substantially equal in length, size and degree of curvature, useful devices may include those having two or more different parts that are not equal in length, size and / or degree of curvature. have. As shown in FIG. 17, in an S-shaped device, one end of the device 452 is disposed at a slight distance 454 relative to the second end 450 of the device. This type of arrangement can be achieved by driving piezoelectric elements in regions 432 and 434 in one direction with respect to a polar electric field (negative or positive) and by driving piezoelectric elements in regions 430 and 436 in opposite directions with respect to a polar electric field. Is achieved. The arrangement of the polarity direction and the electric field direction is allowed when the arrangement results in a generally S-shaped shape. Referring to FIG. 16, the electric field may be driven from the outer electrodes of the upper limits 430 and 434 to the outer electrodes of the upper limits 432 and 436 without contact with the center. Alternatively, the electric field can be driven from each upper limit outer electrode to each upper limit inner electrode while allowing independent access to each piezoelectric element. The latter configuration allows the device to be S-type or traditional bimorph depending on the driving conditions. Embodiments of the invention are not only devices in which regions of individual piezoelectric elements or individually polarized devices are in electrical contact with individual electrodes, but also devices in which two or more regions are in electrical contact with electrodes in electrical communication with each other. Also includes.

Although FIG. 16 illustrates a Bimorph S-type device, the S-type device may be unimorph, bimorph, or multimorph in design. Regions 430, 432, 434, and 436 may represent individual piezoelectric elements, or individually polarized electric fields of piezoelectric elements, or a combination of individual piezoelectric elements and individually polarized electric fields of piezoelectric elements. For example, in an embodiment of the Unimorph device, the regions 430 and 434 may be two separate piezoelectric elements that are driven such that one has a positive curvature while the other has a negative curvature. And regions 432 and 436 may also be inactive. Inactive areas include metals such as brass or stainless steel, plastics, polyimides, polyesters, some other polymers, wood, or composites such as fiberglass, graphite or GRFP. Alternatively, the non-active area may be provided with parts of a larger system, ie through physical bonding or other bonding. For example, the non-active area may be used to move or locate a suspension structure (suspension head of a panel or beam of a panel used for acoustically emitting metal, or a disc drive suspension). Useful when required to minimize rotation of the head.

In another embodiment, the S-type device may have two piezoelectric elements. Each piezoelectric element may have two electrode regions polarized in opposite directions and driven with an electric field in the same direction relative to the thickness of the element. Alternatively, the electrode region may have two electrode regions polarized in the same direction and driven with an electric field opposite to the thickness of the device.

Embodiments of the present invention include not only packaged S-type devices, but also S-type actuators that are not packaged as a card.

The actuators of the present invention can be used to perform simple mechanical operations such as bending, twisting or shaking applied to theatrical face masks or parts of the doll, and are excellent for medium displacement operation tasks of this type of small loads. It will have operating characteristics and various mounting possibilities.

In general, a task that can be implemented with small or medium displacement air actuators can be accomplished using the flexible circuit actuator card of the present invention as a discrete mechanical element, and where the task relates to structures such as seats, flaps or walls. In other words, the flexible circuit itself may constitute a structural component. Thus, the present invention is suitable for functions such as self-moving rotary vanes, corrugated boxes or walls of pumps, mirrors and the like. In addition, as discussed above, tasks relating to surface coupling of small displacement acoustics or supersonic band frequencies can be easily implemented with low mass, highly coupled flexible circuit actuators.

As mentioned above, the piezoelectric element need not be a rigid ceramic element, and if a flexible circuit is used only as a sensor, then either a ceramic element or a soft material such as PVDF can be employed. In the case of polymers, thinner and more flexible low temperature adhesives are used for device bonding, rather than a hard curable epoxy adhesive layer.

One embodiment of the present invention is illustrated below.

Yes

Devices with fine line alternating electrodes (IDE) function using the principle of surface acoustic wave (SAW) propagation through solids, and are sometimes referred to as alternating transducers (IDTs). Many of the IDTs currently in use operate using low electric fields, high frequency propagation waves instead of high electric fields, low frequency waves. The latter condition is necessary for operational and damping applications. By the principle behind the IDE, it is more suitable for in-plane operation or damping instead of the more commonly used d ₃₁ characteristic (i.e., when charge is collected on the same surface as before but force is applied at right angles to the polar axis). Efficient d ₃₃ characteristics (i.e., forces are in three directions along the polar axis and applied on the same plane where charges collect) allow the device to use. This is achieved by arranging the electrodes such that the polarity and excitation field mainly exits parallel to the working plane. FIG. 15A shows electric field lines 422 of the d ₃₁ device 424 having a solid electrode 420 positioned on the top and bottom surfaces of the piezoelectric ceramic plate 404; FIG. 15B shows electric field lines 422 of d ₃₃ IDE device 426 with interconnect line electrode 408. The electromechanical properties in the d ₃₃ direction are generally greater than twice that in the d ₃₁ direction.

Line IDE devices are successful for certain low field applications. However, when large electric fields are applied during polarization or excitation, internal cracks or electrical shorts sometimes appear. These failures are due to internal stresses caused by non-uniform electric fields in the material near the ends of the electrode. It is also evident that the electrode lines connecting the alternating lines on the surface of the piezoelectric ceramic create additional stress concentrations. Line IDE patterns have been used in the construction of piezoelectric fiber composite devices where stress concentration does not occur.

Alternating electrode monolithic thin plate piezoelectric devices have been developed using the methods described herein (hereafter referred to alone as the "IDE device"). The result is compared with a piezoelectric device (hereinafter “solid electrode device”) using a d ₃₁ piezoelectric ceramic plate having solid electrodes on both surfaces of the plate. Experimental results of resonance measurements and electrical and mechanical energy calculations were used to quantify and compare the electromechanical coupling coefficients and damping capabilities of these devices.

Both solid electrodes and IDE devices were fabricated using PZT-5A type materials measuring 46.05 mm x 20.65 mm x 0.254 mm. Although the ratio of the piezoelectric ceramic thickness to the size of the electrode of the IDE device is important, the determination of the optimal value depends on the specific requirements of the application, including displacement, generated strain, force and available drive voltage. An exemplary design is selected among the IDE devices consisting of 0.38 mm lines on a 1.52 mm pitch. Piezoelectric ceramic materials and electrodes were packaged in a protective polyimide skin with pre-attached electrical wires.

1. Vibration Damper Experiment

Damping experiments were constructed using the IDE and solid electrode devices bonded to an aluminum beam. The beam was 229.0 mm x 31.8 mm x 2.3 mm in size with an unclamped length of 133.0 mm. The device was glued to one surface of an aluminum beam 6.35 mm from the clamp edge. Damping was calculated from the drop in tip displacement using the logarithmic decrement method. Damping measurements were taken for the following shapes: uncoated beam, beam with RC shunt IDE and solid electrode device, and beam with un-shunted IDE and solid electrode device. A second method of measuring the damping of the system was used to confirm the logarithmic attenuation results. In this method, a swept sinusoidal excitation was applied to the beam using an electromechanical vibration table attached to the beam through a load cell and measured from the applied load to the tip displacement. Damping was calculated from the function.

Because of the difficulties associated with consistently exciting the beam in the first resonant mode, very large scatter in the percentage of critical damping measured corresponding to the beam as a function of the average strain on the surface of the device bonded to the aluminum beam. ) Was observed. The shunt IDE device has been shown to provide more than twice the damping achieved by the shunt solid electrode device when compared to either non-shunt device attached to the beam.

2. Generation strain and counting experiment

Free-strains generated by the IDE and solid electrode devices were measured with strain gauges bonded to both surfaces of the device. In addition to high strain, piezoelectric ceramic devices have the ability to generate very high forces because of their inherently high material modulus. Coefficient measurements are very difficult, especially under high field excitation. Low field measurements are useful as a general indication of coefficients, although care should be taken when applying these measurements to predict AC performance of high electric fields. Device coefficients can be determined by measuring strain under known mechanical stresses. In this method, a stress-strain curve is generated to quantify the coefficient as a function of the applied electric field.

In this experiment, known mechanical stresses are applied by bonding an aluminum sheet to both sides of the device. Because of the symmetry of the device, the in-plane stress is uniform throughout the thickness of the device except around the rim. Given the measured strain and modulus (68.8 GPa) of aluminum, the stress in the aluminum can be determined from Hook's law. Neglecting the presence of a thin and low modulus adhesive layer, the product of the stress and thickness of the piezoelectric ceramic layer is the same or opposite to the same product in the aluminum layer. Strain measurements taken from the surface of aluminum can be used to determine the stresses in the device. By making these measurements on aluminum sheets of different thicknesses, it is possible to calculate device coefficients under different electric fields and mechanical strain levels.

The free strain of the device was measured at room temperature by averaging the signals from the strain gauges applied to both surfaces of the device. The applied drive signal was a 1 Hz sine wave; Maximum voltages were +/- 600 volts (1200 V _pp ) for IDE devices and +/- 100 volts (200 V _pp ) for solid electrode devices. The applied electric field was calculated based on the 0.254 mm spacing between the electrode faces for the solid electrode device and the 1.524 mm spacing between the electrode lines for the IDE device. Because the electric field in the IDE device is uneven, the value calculated in this way should be considered an average or nominal value. The strain output of the IDE device is approximately 70% higher than that of the solid electrode device for comparable field strength.

For comparison purposes, Table 1 shows the measured low field piezoelectric strain constants (d ₃₁ and d ₃₃ ) for unpackaged PZT 5A materials, as well as the high field (8 kV / cm) for IDE and solid electrode devices. Represents the strain constant. The piezoelectric constant values are practically nonlinear as a function of the electric field and depend heavily on the shape of the excitation signal (waveform, drive frequency, DC offset, etc.), while the comparison is still useful. The high field d ₃₁ constant for the solid electrode device actuator was higher than the low field constant for the unpackaged material. The strain constant of the IDE device actuator was approximately 10% lower than the d ₃₃ constant of the unpackaged material. This is due to the fact that the electric field in the IDE device is not exactly equivalent to that in the d ₃₃ device.

Comparison of Piezoelectric Strain Constants (d ₃₁ and d ₃₃ ) d ₃₁ d ₃₃ Low field of PZT @ unpackaged 180 pm / V Low field of PZT @ unpackaged 350 pm / V Solid Electrode Device @ 8kV / cm 191 pm / V IDE device @ 8kV / cm 318 pm / V

Constrained strain and modulus of elasticity were measured using 0.0375 mm, 0.0750 mm, and 0.1250 mm thick aluminum layers bonded to both sides of the unpacked piezoelectric ceramic plate, as well as to solid electrodes and IDE devices. The data points representing the stress versus the calculated stress of the unpackaged piezoelectric ceramic plate for the varying thickness of the aluminum confinement layer are obtained at four different field levels (2 kV / cm, 4 kV / cm, 6 kV / cm, And 8 kV / cm). The modulus of elasticity was obtained from the slope of the line connecting the data points obtained at the specific electric field level. Similar measurements were made for IDE and solid electrode devices.

3. Electromechanical Coupling Factor

Electromechanical coupling coefficients are useful for quantifying the performance of piezoelectric devices. It is a non-dimensional parameter that is calculated from the electrical and mechanical energy of the system. It can be seen from the equation below.

Here, the mechanical energy output of the device is denoted by W _M , and the electrical energy input to the system is denoted by W _E. Alternatively, it can be calculated from the following equation.

Where f _a and f _r are the antiresonance and resonant frequencies measured by the impedance analyzer. However, Equation 2 is strictly accurate only if the samples are rod-shaped (length / width) and satisfy the condition of ² > 10. If this condition is not met, the results can only be used to compare similar types of devices.

Table 2 contains the calculated values of the electromechanical coupling coefficients determined using both methods described above. Based on the evaluation based on Equation 1, at an applied electric field of 8 kV / cm, a coupling coefficient of 0.71 for the IDE device and 0.32 for a solid electrode device are calculated. The impedance measured using the HP Impedance Analyzer is displayed and used to determine the resonance and anti-resonant frequencies used in Equation 2. The value of (length / width) for the device is approximately 5; Since it is not greater than 10, the value obtained from equation 2 should only be used for comparison purposes. Evaluation based on Equation 2 indicates that the coupling coefficient of the IDE device is approximately 65% higher than that of the solid electrode device.

Solid electrode device IDE device Energy way 4 kV / cm 0.29 0.65 8 kV / cm 0.32 0.71 Resonance method Low electric field 0.29 0.49

Thus, in summary, the electromechanical coupling coefficients calculated using two different methods show that 0.45 to 0.71 values are achieved for IDE devices compared to 0.29 to 0.35 values for d ₃₁ devices. By the way, the results are provided to compare the performance and operation of the damping device ₃₁ d and the performance of the IDE devices. The resistor shunt IDE damper device has improved the factor in two improvements of additional damping over the conventional PZT dampers. Moreover, it has been shown that the high field generation strain of IDE actuators is about 70% greater than that produced by the d ₃₁ actuators.

The foregoing description of the manufacturing method and the illustrated embodiments is described to show the scope of construction to which the present invention is applied. The invention provides for easy breakage, general usability of circuit structures and strain actuators, strain activation assemblies and sensors, other variations in physical structure, and practical applications of the modular flexible circuit actuators and sensors of the present invention. It will be apparent to those skilled in the art that overcoming numerous deficiencies in the art, and such variations are deemed to be within the scope of the invention for which patent rights are required, as set forth in the claims appended hereto.

The present invention relates to a packaged actuator assembly, the actuator assembly being electronically controllable and also actively damping the mechanical state of the device to which it is attached, actuating the structure or suppressing vibration. May be applied to the system, or may be used independently.

Claims (33)

Electrically active elements, A conductor comprising a pair of alternating electrodes, Insulators and Including electrical contacts, Wherein said electrically active element, conductor and insulator are bonded together such that in-plane strain in said electrically active material is shear coupled between said electrically active element and insulator. The device of claim 1, wherein the electrically active device has a first surface and a second surface, and the alternating electrode comprises a first pair of alternating electrodes in direct electrical contact with the first surface of the electrically active device. And a second pair of alternating electrodes in direct electrical contact with the second surface of the electrically active element, wherein the second pair of alternating electrodes are arranged through the equipotential lines extending through the electrically active element. An actuator device, connected to the first pair of alternating electrodes. The actuator device of claim 1, wherein each pair of alternating electrodes comprises a plurality of line electrodes and a common bus disposed away from the electrically active element. The actuator device of claim 1 comprising a silver conductive ink of each pair of alternating electrodes. The actuator device of claim 1 wherein the electrically active element is not metallized. The actuator device of claim 1, wherein the electrically active element, conductor, and insulator are bonded together with a bonding agent selected from the group consisting of B-stage epoxy, C-stage epoxy, and thermoplastics. The actuator device of claim 1, wherein each pair of alternating electrodes comprises a bus in common with a plurality of inclined electrodes. The insulator of claim 1, wherein the insulator has a first surface joined to the electrically active element and the conductor and a second surface, wherein each pair of alternating electrodes comprises a plurality of line electrodes and a second surface of the insulator. Actuator device comprising a common bus located. Electrically active elements, A flexible circuit comprising an insulator and a pair of alternating electrodes, And the electrically active element is bonded to the flexible circuit such that in-plane strain in the electrically active element is shear coupled between the electrically active element and the flexible circuit. At least one electrically active element, At least one flexible circuit comprising an insulator and at least a first pair of alternating electrodes, Each of the electrically active elements has a first surface bonded to one of the at least one flexible circuit such that one of the first pair of alternating electrodes is in direct electrical contact with the at least one electrically active element, The in-plane strain of the at least one electrically active element is shear coupled between the at least one electrically active element and the at least one flexible circuit. The actuator device of claim 10, wherein one of the at least one flexible circuit comprises a first pair and a second pair of alternating electrodes disposed on opposite surfaces of the insulator. As a method of damping vibration of an object, (a) when the actuator device according to claim 1 is shear coupled to the object and an electrical signal is applied to the alternating electrode, the actuator in-plane strain of the electrically active element mechanically acts on the object through the insulator Joining the device, (b) applying an electrical signal to the alternating electrode Method comprising a. Actuator device, At least a first electrically active element and a second electrically active element; At least a first conductor and a second conductor, The first conductor is in direct electrical contact with the first electrically active element, the second conductor is in direct electrical contact with the second electrically active element, And the first and second electrically active elements and conductors are arranged such that, when the first and second electrically active elements are operated, the device forms an overall S-shape. The device of claim 13, further comprising at least one third conductor, wherein the first electrically active element comprises at least a first region and a second region, wherein the first conductor is a first region of the first electrically active element. In direct electrical contact with the third conductor and in direct electrical contact with the second region of the first electrically active element. 14. The actuator device of claim 13, further comprising a non-active element. 15. The actuator device of claim 14 wherein at least two of the three conductors are in electrical communication with each other. 15. The actuator device of claim 14, wherein the non-active element is a component of a disk drive. The method of claim 13, wherein at least one of the electrically active devices is driven in a positive orientation with respect to its polarized region, and at least one of the electrically active devices is driven in a negative orientation with respect to its polarized region. Actuator device. 15. The actuator device of claim 13, wherein the device further comprises a layer surrounding the electrically active element and the conductor, wherein the actuator device forms a card. The actuator device of claim 13, wherein the at least first conductor and the second conductor are in direct electrical contact with the at least first and second electrically active elements at a plurality of points. The actuator device of claim 13, wherein the actuator device is shear coupled to an object. The actuator device of claim 13, wherein the actuator device is configured as a stack, flexure, shell, plate, or bend. 15. The device of claim 13, further comprising an insulator, wherein the first and second electrically active elements and insulators have an in-plane strain in the first and second electrically active elements between the first and second electrically active elements and insulator. Actuator device, characterized in that bonded together to shear bond. 24. The actuator device of claim 23, further comprising at least a third conductor, wherein the third conductor is in direct electrical contact with the first or second conductor. At least one electrically active device having at least a first region and a second region. At least first and second conductors, And the first conductor is in direct electrical contact with the first region of the first electrically active element, and the second conductor is in direct electrical contact with the second region of the electrically active element. 27. The actuator device of claim 25, wherein the first and second regions of the electrically active element are polarized in opposite directions. 26. The actuator device of claim 25, wherein the first and second regions of the electrically active element are polarized in the same direction. 26. The actuator device of claim 25, wherein the actuator device is shear coupled to the object. 26. The actuator device of claim 25, wherein the actuator device is configured as a stack, flexure, shell, plate, or bend. 27. The actuator device of claim 25, further comprising an insulator, wherein the electrically active element and insulator are bonded together such that in-plane strain in the electrically active element is shear coupled between the electrically active element and the insulator. 31. The actuator device of claim 30, further comprising at least one third conductor, wherein the third conductor is in direct electrical contact with the first or second conductor. As a method of damping vibration of an object, (a) an actuator device according to claim 13, wherein an in-plane strain of the at least first and second electrically active elements mechanically acts on the object when an electrical signal is applied to at least one of the first and second conductors. Bonding the actuator device to an object; (b) applying an electrical signal to one of the conductors Method comprising a. As a method of forming an actuator device, (a) preparing a flexible circuit comprising an insulator and at least first and second conductors, (b) in-plane strain of the electrically active element is shear coupled between the electrically active element and the flexible circuit, and the electrically active element is directly bonded to the at least first and second conductors. Bonding to the circuit Method comprising a.