DuraAct貼片換能器技術

制造

DuraAct貼片換能器的有源層構成一塊壓電闆。這些壓電闆根據一種已獲專利的方法被嵌入纖維增強塑料(GRP)中,然後被粘合起來形成一個複合體。層壓過程通過注入法在真空中的壓熱器中完成,從而形成完全無泡的高質量層合闆。

由于材料具有不同的熱膨脹系數,因此選用壓熱器的固化溫度曲線來得出壓電陶瓷闆的規定内在預載。GRP聚合物塗層還可用作電氣絕緣和機械預載。這項專利技術能實現堅固耐用又可彎曲的換能器元件的大批量生産。

Design & Production

The active layer in DuraAct patch transducers consists of one or more piezoceramic plates with metallized surfaces for electrical contacting. These plates typically measure between 200 and 500 μm in thickness. They are embedded in fiber-reinforced plastic (GRP) using a patented process and bonded to form a composite. The bonding process is carried out in an autoclave in a vacuum by means of an injection process to produce completely bubble-free laminates of the highest quality.

The curing temperature profile of the autoclave is selected so that a defined mechanical preload of the piezoceramic plates will result due to the different thermal expansion coefficients of the materials involved. The polymer coating of the GRP also serves as electrical insulation. Robust, bendable transducer elements that can be manufactured in large batches are the result of this patented technology.

DuraAct patch transducers are solid body actuators without moving parts. This means that wear and failure proneness are minimal. The electrical connection is made via two contact points to which wires can be soldered, glued or clamped, depending on the application.

How Do DuraAct Patch Transducers Work?

The piezoceramic plates that are used in all-ceramic DuraAct patch transducers are structurally similar to a capacitor. The ceramic serves as a dielectric between the metallic surfaces of the ceramic, which form the electrodes. When an electric voltage is applied, an electric field is created with lines running through the ceramic perpendicular to the plates. This causes a staggered contraction of the ceramic at 90° to the field lines so that the actuator constricts evenly along the plane. This behavior is called the transverse piezoelectric (d31) effect.

In the DuraAct Power patch transducer the multi-layer piezo element draws on the longitudinal or d33 effect. The displacement occurs parallel to the electric field E and the polarization direction P of the piezo actuator. The piezoelectric charge coefficients d33 for the longitudinal displacement are considerably higher than for the transversal displacement, meaning that the possible displacements are greater than for all-ceramic transducers.

The occurrence of acoustic surface waves can be converted using DuraAct Shear patch transducers. The shearing motion of the patch transducer is produced by the orthogonal application of an electric field E to the direction of the polarization P. The shear deformation coefficients d15 are generally the largest of the piezoelectric coefficients. When controlled with nominal voltages, the piezo ceramics achieve d15 (GS) values of up to 2000 pm/V. The permissible control field strength is limited in order to prevent a reversal of the vertically oriented polarization.

The electric field strength of the DuraAct patch transducers determines the displacement of the ceramic, therefore, allowing the simple control of the modules. This deformation is transmitted effectively to the structural elements via an uncomplicated bonding. The force is transmitted across the entire surface of the actuator by thrust and not at discrete points as is the case with conventional actuators. Massive force transfer points are therefore unnecessary. Conversely, structural deformations are converted to an electrical charge by the transducer, making it possible to use the element as a sensor or power generator. Division of the sensor and actuator functionality is achieved using an isolated contacting of several layers.

The reaction to a change in the electrical field or a deformation is extremely fast. This allows oscillations to be generated into the kilohertz range or also measured. Depending on the active piezo element used and its dimensions, different actuators produce different values with respect to control voltage and contraction. The relationship between deformation and control voltage is not linear.

DuraAct Patch Transducer Performance Graph

The actuator characteristics of piezoceramic transducers are primarily described by means of two parameters: the blocking force FB and the free displacement S0. If the unimpeded (free) actuator is controlled with a voltage U, it reaches its maximum displacement S0. The force required to push the maximally displaced actuator back to its original length is called the blocking force FBI.

If both parameters are plotted on a graph and connected with a line, the result is the performance graph of the actuator. The connecting line is called the load line. The ratio of external force to displacement can be read from the graph. In most applications, the actuator works against an elastic structure such as when deforming a spring or bending a plate. If the actuator deforms a spring, for example, the characteristic curve of the spring is plotted on the performance graph with the stiffness cF. The intersection point of the load lines and the characteristic curve denotes the operating point. The actuator works most effectively when the operating point is in the middle of the load lines.

DuraAct促動器通常被粘合在襯底上,其在整個表面上傳遞收縮,而非幾個連接點。在這種配置中,該DuraAct/襯底組合充當一個彎曲元促動器。彎曲元促動器可實現快速、高精度和可重複的變形,被廣泛用于打印機、閥和紡織工業等多種應用。

DuraAct貼片換能器基于橫向壓電效應,施加電場時将産生收縮。彎曲元折曲并施加一個正交力,如圖所示。

自由、未閉鎖彎曲元的自由變形為W0。将變形減小至0所需的力稱為彎曲元閉鎖力FBW,其明顯小于促動器閉鎖力。穿過這兩點的曲線為襯底厚度和彈性的彎曲元特性曲線 

這些曲線反映實際的變形和力,通過由不同材料制成的50毫米襯底樣本和P-876.A15 DuraAct貼片換能器測量。

除了DuraAct的特性曲線,彎曲元特性是特定應用中對促動器性能進行有效估算的基礎,因此PI在所有數據表中都加入了這些曲線。

彎曲元促動器的參數

DuraAct Patch Transducer Power Requirements

To estimate the electrical requirements necessary for the operation of an actuator, the capacitance of the transducer plays an important role. The capacitance values of DuraAct patch transducers are typically in the nanofarad range and in each case are provided on the datasheets.

Here, the capacitance C is dependent on the type, thickness and area of the piezo ceramic used. To estimate the average electrical output Pm, the control frequency as well as the capacitance of the transducer and the voltage swing are required.
 

Pm = C · f · Uh2

f: frequency, Uh: voltage swing
 

The maximum power requirement Pmax can be calculated by multiplying the average electrical output by pi (π):
 

Pmax = Pm ・ π

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DuraAct壓電貼片換能器

靈活、高效、耐用
版本/日期
BRO07E R1 2019-06
版本/日期
BRO07D R1 2019-06
文件語言
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