Actuator

Generally speaking, the design of piezoelectric thin film actuator mainly depends on various applications, such as speed, displacement, force and power supply. The piezo film technology can provide different design schemes to achieve the above application requirements, which include:

A single or double-sided electrode pattern made for the customer.

Multilayer laminated structure or double piezoelectric film;

Fold or drum type multilayer structure;

Extrusion forming piezo tube and piezoelectric cable;

Piezo copolymers are cast on various substrates.

Moulded three-dimensional structure.

All of the above design schemes have their own advantages and disadvantages.

For example, the drum type multilayer executor can produce relatively high

The force, but at the expense of a certain amount of displacement.

Double piezoelectric film

Similar to the bimetallic sheet, two piezoelectric films with opposite polarity are stuck together to form a curved element, or a "double piezoelectric film" (Figure 29). After adding a voltage to the double piezoelectric film, one of them is lengthened, and the other is shortened, thus forming a bend. When the opposite polarity is added to the voltage, it is bent in the opposite direction. This kind of structure changes the small length change into a large end bend, but the force is small. If the thickened piezoelectric film and multilayer structure are used, the force produced by this double piezoelectric film can be increased, but a certain amount of displacement should be sacrificed.

The amount of end bending and the force produced by the press are calculated by the press.

X = 3/4d31 (1 - /t - V meters)

F = 3/2Ywd31 (t/l) V Newton

In the form:

Displacement of delta x = DC

F = force generated

D31 = the piezoelectric constant in the "1" direction

L, t, w = length, thickness and width of a piezoelectric film

V = added voltage (volt)

Young's modulus = Y piezoelectric film (2 x - 109N/m)

When the AC voltage is added, the double piezoelectric film becomes a fan like the insect's wings. Although the dual piezoelectric film does show a direct current response, the maximum end bend is obtained only at resonance, which is determined by its length and thickness.

Example four:

The 2cm consists of two mPVDF 9 cantilever piezoelectric film composed of two piezoelectric diaphragm two terminal 100V voltage, the end displacement x is equal to:

As shown above, the longer double piezoelectric films can obtain larger displacement, while the wider double diaphragm can obtain greater force. The displacement of the resonant frequency and DC is determined by the Q value representing the mechanical gain, and the typical Q value of the double piezoelectric patch is 20~25.

For example, in a long 5mm, thickness of 70 m DC voltage double piezoelectric diaphragm 120V, displacement generated by 57 M. However, the same double piezoelectric film, at the resonance frequency of 580Hz, can obtain the displacement of 1.4mm. The multi-layer structure can be considered for more powerful applications, such as cooling fans. The force generated is increased proportionately with the increase of the number of layers.

There are two basic methods for the electrical connection of a double piezoelectric diaphragm, such as figure 30

It is shown in series and parallel. In order to obtain the same displacement, in parallel

The required voltage is lower than in the series. But on the other hand, the series is required.

The current is less than the parallel. These two wiring methods are general to the actuator

The electric power is the same. However, it is clear that, for processing, string

The connection is much simpler than the parallel.