DD288485A5 - ELECTROMECHANICAL BENDING ELEMENT - Google Patents

Abstract

The invention relates to an electromechanical bending element, which consists of at least three fins and finds z. B. Application for precision devices. According to the invention, the inner lamella made of ferroelectric material exerts a compressive stress on the external lamellae made of piezoelectric or electrostrictive material. For the embodiment of the invention variants of the polarization of the individual slats are given. Fig. 1 {bending element, electromechanical; slats; Praezisionsgeraet; Lamella, inside, ferroelectric; Lamellae, auszen, piezoelectric, electrostrictive; Compressive stress}

Description

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Field of application of the invention

The invention relates to the field of electronic components. It relates to an electromechanical bending element, which consists of at least two outer plates and at least one inner plate, between which electrodes are arranged, wherein all the plates are connected flat and congruent with each other. The bending element is used in particular for installation in precision devices.

Characteristic of the known state of the art

Electromechanical bending elements are known in various forms of construction. Thus, for example, strips of piezoelectric material, which are correspondingly provided with electrode layers, glued to each other surface. This strip composite is usually clamped on one side (DE 3240884). The individual strips are correspondingly polarized, so that when creating an electrical voltage, the desired Verbiogung is achieved.

In order to achieve high values for the bending or the setting force in a given design, materials with high piezoelectric deformation constants perpendicular to the applied field (transverse deformation) must be used. Especially the bending elements of such materials with a maximum transverse deformation, but have very low tensile strength, so that it can cause the tearing of the active ceramic blade, especially if the bending element is mechanically stressed, ie must work against an external force. This fact is contrary to the use of materials with very large Querdaformation or limited their use to small bends and small forces.

Object of the invention

The aim of the invention is to realize an electromechanical bending element, which when using a piezoelectric or elektrostriktion material with large transverse deformation ^! On operation, a wider use possible, even if large occurring tensile stresses oppose that.

Explanation of the essence of the invention The object of the invention is to provide an electromechanical bending element whose novel structure it

ensures that the object of the invention is achieved.

The electromechanical bending element consists of at least two outer plates and at least one inner plate,

between which electrodes are arranged. All slats are flat and congruent with each other.

According to the invention, the inner, made of ferroelectric material lamination exerts on the outer, of piezoelectric

or electrostrictive material lamellae from a compressive stress.

In an embodiment of the invention, the inner lamella is polarized only after production of the composite with the outer

polarized piezoelectric or electrostrictive lamellae.

A further embodiment of the invention provides that all fins are polarized only in the composite. embodiment

The invention will be explained in more detail below using an exemplary embodiment. The accompanying drawing shows the bending element according to the invention in a schematic diagram.

A bender strip with a length I = 50mm and a width b «= 5.5mm is made of two outer slats 2 with a thickness of

each 0.3 mm of a polarized (arrows 6,7) piezoelectric ceramic (eg Ba or Sr-modified PZT ceramic) with a Großslgnalquerdeformationsmodul d ₃₎ = 5 · 10 "'mm mm V ^-1 and an inner lamella. 1 from unpolarized

piezoelectric ceramic (eg PZT ceramic) with a remanent contraction when polarizing ΔΙ / Ι = 1 · 10 ^-3 , glued together. The individual fins are provided with the corresponding electrodes 3.

After the adhesive has hardened, the inner lamella ^{1 is} polarized with an electric field strength of 2 ... 3 kV · mm ^-1 Arrows 4 indicate the direction of polarization. This causes a compression (arrows 5) of the entire bender at about 20pm and

so that the pressure bias of the invention outer lamellae.

A second variant is based on the same design of the bending element, as described above, with the difference that

Also, the outer plates 2 are unpolarized before they are glued to the inner plate 1. Only then will the whole

Composite by applying the poling voltage U _B to the outer electrodes of the outer plates 2 completely polarized. Since that

piezoelectric material of the outer plate 2 has a substantially larger cross deformation modulus (d ₃₁ = 5 x 10 ~ '° m · V ^-1) and a much smaller residual contraction ΔΙ / Ι = 0.5 x 10 ~ ⁴ than the material of the inner fin 1 (d ₃ , = 3 × 10 ^-10 m -ν ', ΔΙ / Ι = 1 × 10 ^-3 ), only slight differences in the expansion of the different lamellae occur when the polarization voltage is applied. If the polarization voltage is switched off, the outer plates 2 are biased due to the much larger remanent contraction of the inner plate 1 to pressure.

The disadvantage of a lower compressive bias than in the variant described first is reduced by the fact that the Polarizing the outer fins before bonding, which involves a high risk of breakage, can be omitted.

Claims (3)

1. Electromechanical bending element consisting of at least two outer slats and at least one inner slat, between which electrodes are arranged, wherein all slats are connected flat and congruent with each other, characterized in that the inner, consisting of ferroelectric material slat (1) on the outer, consisting of piezoelectric or electrostrictive material slats (2) sine compressive stress exerts. 2. Electromechanical bending element according to claim 1, characterized in that the inner plate (1) after preparation of the composite with the outer polarized piezoelectric or electrostrictive plates (2) is polarized. 3. Electromechanical bending element according to claim 1, characterized in that all lamellae (1,2) are only polarized in the composite.