RU2778161C1 - Method for increasing piezosensitivity of bending-type bimorphi - Google Patents

Abstract

FIELD: piezosensitivity increasing.

SUBSTANCE: invention relates to a method for increasing the piezosensitivity of a bending-type bimorph. To increase the piezosensitivity, a bending-type bimorph is used in two modes, namely: in the mode of a flexible piezoactuator and in the generator mode as a flexible piezoelectric sensor. In the piezoactuator mode, a control electromagnetic action is applied to the bimorph in order to mechanically influence the bimorph on external objects. In the piezoelectric sensor mode, the values ​​of the emerging informative electromagnetic signal of the bimorph are measured in order to measure the magnitude of the external force effect on the surface of the bimorph in a certain way.

EFFECT: increase in the piezosensitivity of the bimorph in the piezoactuator mode and an increase in the values of the emerging informative signal in the piezoelectric sensor mode for the case of a quasi-static or dynamic (cyclic) external influence are provided.

3 cl, 3 dwg, 1 tbl

Description

The invention relates to a method for increasing the sensitivity of a piezoelectric transducer (piezoelectric or magnetostrictive) of a bimorph type (bimorph), namely a bimorph piezoactuator or a bending type bimorph piezosensor and is intended for use in micromechanics, electronics, controlled optics, medicine.

Known way to increase the piezosensitivity bending type piezoelectric element [Nikiforov V.G., Klimashin V.M., Safronov A.Ya. Bimorphic piezoelectric elements: actuators and sensors // Components and technologies. - 2003. - No. 4. - S.46-48], in which bimorph piezoelements (bimorphs) of the bending type are used. The bimorph consists of two or more homogeneous piezoelectric plates of equal thickness connected to each other with the same or opposite polarization, internal and external electrodes.

The disadvantage of this method is a small increase in the piezosensitivity of the bending type bimorph due to the smallness of the absolute values of the piezoelectric or magnetostrictive piezoconstants of the material of the bimorph layers.

к электродам биморфа с целью механического воздействия биморфа на внешние объекты или осуществляют (в режиме гибкого датчика) измерение значений информативного электрического напряжения

или электрического заряда

на электродах биморфа с целью измерения величины внешнего силового воздействия.The closest method of the same purpose to the claimed invention in terms of the combination of features is a method for increasing the piezosensitivity of the bimorph as part of the structure [see. patent RU No. 2723567, publ.: 06/16/2020], in which the flexible bimorph is fixed on a flexible substrate (structural element - the skin of the airfoil of the blade), and the increase in the piezosensitivity of the bimorph is carried out by using the initial compression of the flexible substrate. The bimorph is used to operate in two modes: in the flexible piezoactuator mode and in the generator mode as a flexible piezoelectric sensor, while the initial compression of the bimorph is carried out (indirectly through compression of its substrate), and the control voltage is applied (in the piezoactuator mode)

to the bimorph electrodes in order to mechanically influence the bimorph on external objects or carry out (in the flexible sensor mode) measurement of the values of the informative electrical voltage

or electric charge

on the electrodes of the bimorph in order to measure the magnitude of the external force.

The disadvantage of the known method, taken as a prototype, is a small increase in the piezosensitivity of the bending type bimorph, due to the indirect (through the contact area of the bimorph with the substrate) action on the bimorph of the compressive load and the presence of significant bending rigidity of the substrate in relation to the bending rigidity of the bimorph.

Signs of the prototype, coinciding with the essential features of the claimed invention - use a bending type bimorph to operate in two modes: in the mode of a flexible piezoactuator and in the generator mode as a flexible piezoelectric sensor; carry out the initial compression of the bimorph; carry out in the piezoactuator mode the application of a control electromagnetic action to the bimorph in order to mechanically influence the bimorph on external objects or carry out in mode piezoelectric sensor measuring the values of the emerging informative electromagnetic signal of the bimorph in order to measure the magnitude of the external force impact on the surface of the bimorph.

The problem to be solved by the invention is to create a method for increasing the piezosensitivity of a bending-type bimorph with an increase in the range of permissible values of bending deformations (deflections) in the piezoactuator mode and with an increase in the values of the emerging informative electromagnetic signal of the bimorph in the piezosensor mode for the case of a quasi-static or dynamic (cyclic) external impact.

The problem was solved due to the fact that in the known method of increasing the piezosensitivity of a bending-type bimorph, in which a bending-type bimorph is used to operate in two modes: in the mode of a flexible piezoactuator and in the generator mode as a flexible piezoelectric sensor, the initial compression of the bimorph is carried out, carried out in the mode piezoactuator application of a control electromagnetic action to the bimorph in order to mechanically influence the bimorph on external objects

or carry out in the piezo sensor mode the measurement of the values of the emerging informative electromagnetic signal of the bimorph in order to measure the magnitude of the external force effect on the surface of the bimorph, according to the invention, the direct initial compression of the bimorph along the neutral line of the rod-type bimorph by the applied longitudinal force P at the ends of the rod or the initial compression of the bimorph in the plane of the neutral layer of a membrane-type bimorph by the applied pressure p along the outer contour of the membrane, while the value of the force P < P ₁ or the pressure p < p _{1 of} the initial compression is less than the value of the force P ₁ or the pressure p ₁ of the buckling of the bimorph, taking into account its geometric, physical and mechanical characteristics and fastening method.

к электродам биморфа с целью механического воздействия биморфа на внешние объекты или осуществляют в режиме гибкого датчика измерение значений информативного электрического напряжения

или электрического заряда

на электродах биморфа с целью измерения величины внешнего силового воздействия на поверхность биморфа.In particular, a bending-type piezoelectric bimorph is used to operate in two modes: in the flexible piezoelectric actuator mode and in the generator mode as a flexible piezoelectric sensor, while in the piezoelectric actuator mode, a control voltage is applied

to the electrodes of the bimorph in order to mechanically influence the bimorph on external objects or carry out measurement in the flexible sensor mode informative electrical voltage

or electric charge

on the electrodes of the bimorph in order to measure the magnitude of the external force on the surface of the bimorph.

In particular, a bending-type magnetostrictive bimorph is used to operate in the mode of a flexible piezoelectric actuator, while applying a control magnetic field to the bimorph.

к электродам биморфа с целью механического воздействия биморфа на внешние объекты или осуществляют в режиме гибкого датчика измерение значений информативного электрического напряжения

или электрического заряда

на электродах биморфа с целью измерения величины внешнего силового воздействия на поверхность биморфа; используют магнитострикционный биморф изгибного типа для работы в режиме гибкого пьезоэлектрического актюатора, при этом осуществляютThe features of the proposed technical solution, which are different from the prototype, use the direct initial compression of the bimorph along the neutral line of the rod-type bimorph by the applied longitudinal force P at the ends of the rod or the initial compression of the bimorph in the plane of the neutral layer of the membrane-type bimorph by the applied pressure p along the outer contour of the membrane, while the value force P < P ₁ or pressure p < p _{1 of} the initial compression is less than the value of the force P ₁ or pressure p _{1 of} the loss of stability of the bimorph, taking into account its geometric, physical and mechanical characteristics and the method of fixing; a bending-type piezoelectric bimorph is used to operate in two modes: in the flexible piezoelectric actuator mode and in the generator mode as a flexible piezoelectric sensor, while in the piezoelectric actuator mode, the control voltage is applied

to the bimorph electrodes in order to mechanically influence the bimorph on external objects or measure the values of the informative electrical voltage in the flexible sensor mode

or electric charge

on the electrodes of the bimorph in order to measure the magnitude of the external force on the surface of the bimorph; a bending-type magnetostrictive bimorph is used to operate in the mode of a flexible piezoelectric actuator, while carrying out

application of a control magnetic field to a bimorph.

Distinctive features in conjunction with the known ones make it possible to increase the piezosensitivity of a bending-type bimorph with an increase in the range of permissible values of bending deformations (deflections) in the piezoactuator mode and with an increase in the values of the emerging informative electromagnetic signal of the bimorph in the mode piezoelectric transducer for the case of quasi-static or dynamic (cyclic) external action.

In the piezoactuator mode, an increase in the piezosensitivity of a bending-type bimorph and an increase in the range of permissible values of its bending deformations (deflections) is achieved as a result of the appearance of additional deflections due to the action of an initial compressive mechanical load on a curved (due to the inverse piezoelectric effect) bimorph, i.e. the initial compressive mechanical load as an "amplifier" increases the bending deformations (deflections) of the bimorph from the action of the control electromagnetic action on the bimorph.

на электродах биморфа меняется на противоположное направление изгиба биморфа с сохранением эффекта «усиления» от действия начальной сжимающей механической нагрузки.When changing the sign of the control, in particular, electrical voltage

on the electrodes of the bimorph changes to the opposite direction of the bending of the bimorph with the preservation of the effect of "gain" from the action of the initial compressive mechanical load.

= 0 биморф не искривляется (так как сжимающая механическая нагрузка лишь сжимает, но не изгибает биморф в исходном прямолинейном состоянии) или возвращается из изогнутого в исходное прямолинейное состояние (так как величина сжимающей механической нагрузки не превышает соответствующее значение нагрузки для потери устойчивости биморфа).At

= 0 the bimorph does not bend (because the compressive mechanical load only compresses but does not bend the bimorph in the initial rectilinear state) or returns from the bent to the initial rectilinear state (since the value of the compressive mechanical load does not exceed the corresponding load value for the loss of stability of the bimorph).

и электрического заряда

на электродах биморфа достигается также в результате эффекта «усиления» - появления дополнительных прогибов, обусловленных действием начальной сжимающей механической нагрузки на искривленный (под действием диагностируемого силового воздействия) биморф в силу прямого пьезоэффекта биморфа.In the flexible sensor mode, an increase in the piezosensitivity of the bending type bimorph and an increase in the range of allowable values of the informative electrical voltage

and electric charge

on the electrodes of the bimorph is also achieved as a result of the effect of "amplification" - the appearance of additional deflections due to the action of the initial compressive mechanical load on the curved (under the action of a diagnosed force) bimorph due to the direct piezoelectric effect of the bimorph.

The applicant is not aware of the use in science and technology of the distinctive features of the claimed method of increasing the piezosensitivity of a bending type bimorph with obtaining the specified technical result.

> 0 (знак величины

определяет направление отклонения изогнутой продольной оси стержня или нейтрального слоя мембраны биморфа от начального прямолинейного вида) иллюстрируется чертежами, представленными на фиг.1-3.The proposed method for increasing the piezosensitivity of a bending-type bimorph in the mode, in particular, of a piezoelectric actuator, for example, with a positive value of the control voltage applied to the bimorph electrodes

> 0 (sign of magnitude

determines the direction of deviation of the curved longitudinal axis of the rod or the neutral layer of the bimorph membrane from the initial rectilinear view) is illustrated by the drawings shown in Fig.1-3.

на электроды биморфа, где начальное прямолинейнее расположение оси биморфа (график 1), без учета (график 2) и с учетом (график 3) действия продольной сжимающей силы P, результирующие величины компонент перемещения

,

(прогиб) по продольной

и поперечной

осям и угла поворота θ торца биморфа.Figure 1 shows the design scheme of the bending deformation cantilever fixed bimorph due to the action of the control voltage

on the bimorph electrodes, where the initial rectilinear location of the bimorph axis (graph 1), without taking into account (graph 2) and taking into account (graph 3) the action of the longitudinal compressive force P , the resulting values of the displacement components

,

(deflection) along the longitudinal

and transverse

axes and rotation angle θ of the bimorph end.

на электроды биморфа с учетом и без учета действия продольной сжимающей силы P.Figure 2 shows the design scheme of the bending deformation of the hinged bimorph due to the action of the control voltage

on the bimorph electrodes with and without taking into account the action of the longitudinal compressive force P .

на электроды биморфа с учетом и без учета действия (в плоскости мембраны) распределенной по внешнему контуру мембраны сжимающей нагрузки (давления) p, где

- результирующий прогиб в центре мембраны биморфа с учетом действия давления p.Figure 3 shows the design scheme of the bending deformation of the hinged round bimorph membrane, due to the action of the control voltage

on the electrodes of the bimorph with and without taking into account the action (in the plane of the membrane) of the compressive load (pressure) distributed over the outer contour of the membrane p , where

- the resulting deflection in the center of the bimorph membrane, taking into account the action of pressure p .

, а взаимопротивоположные направления поляризаций двух пьезоэлектрических слоев биморфа коллинеарны поперечной оси

. Для мембраны (фиг.3) нейтральный слой биморфа в исходном (первоначальном) состоянии расположен, например, в плоскости

, а взаимопротивоположные направления поляризаций двух пьезоэлектрических слоев биморфа коллинеарны поперечной оси

.We believe that in the initial (initial) state (Fig.1, 2) the neutral line (longitudinal axis) of the bimorph is located, for example, on the coordinate axis

, and mutually opposite directions of polarizations of two piezoelectric layers of the bimorph are collinear to the transverse axis

. For the membrane (figure 3) the neutral bimorph layer in the initial (initial) state is located, for example, in the plane

, and mutually opposite directions of polarizations of two piezoelectric layers of the bimorph are collinear to the transverse axis

.

The method is carried out as follows.

начально сжатого прямолинейного биморфа (фиг.1,2) инициируется действием, в частности, на электроды биморфа управляющего электрического напряжения

, при этом направление изгиба (от исходного положения) оси биморфа определяется знаком величины

. При приложении к электродам биморфа управляющего электрического напряжения

продольная ось биморфа искривляется по дуге с радиусом кривизны

, где

- пьезоэлектрический изгибающий момент вокруг оси

, известные величины:

- пьезоэлектрический коэффициент пропорциональности,

- пьезомодуль материала,

- жесткость поперечного сечения биморфа на изгиб,

- продольный модуль Юнга пьезоэлектрика вдоль оси

,

- осевой момент инерции прямоугольного поперечного сечения биморфа относительно оси

,

- ширина,

- толщина биморфа. Величину угла дуги изогнутой продольной оси биморфа

находим через угловой коэффициент пропорциональности

с учетом выражения длины биморфа

. Считаем, что величина приложенной к торцу биморфа продольной силы P < P ₁, где величина силы потери устойчивости по Эйлеру

, в частности, имеем значение μ=2 для консольного (фиг.1) и μ=1 для шарнирного (фиг.2) закрепления торцов биморфа. Поэтому, после «выключения» управляющего электрического напряжения

биморф возвращается из изогнутого в первоначальное прямолинейное состояние, а при смене знака управляющего электрического напряжения

(например, при знакопеременном электрическом напряжении

во времени

) контролируемо изменяется «направление» изгиба биморфа в плоскости

, т.е. изменяется на обратный знак величин

,

(фиг.1) и

(фиг.2, 3). Bending in plane

initially compressed rectilinear bimorph (Fig.1,2) is initiated by the action, in particular, on the electrodes of the bimorph of the control voltage

, while the direction of bending (from the initial position) of the bimorph axis is determined by the sign of the quantity

. When applied to the electrodes of the bimorph control voltage

the longitudinal axis of the bimorph is curved along an arc with a radius of curvature

, where

- piezoelectric bending moment around the axis

, known quantities:

- piezoelectric coefficient of proportionality,

- piezomodulus of the material,

- bending stiffness of the bimorph cross section,

- longitudinal Young's modulus of the piezoelectric along the axis

,

- axial moment of inertia of the rectangular cross section of the bimorph about the axis

,

- width,

- bimorph thickness. The value of the angle of the arc of the curved longitudinal axis of the bimorph

we find through the angular coefficient of proportionality

taking into account the bimorph length expression

. We consider that the value of the longitudinal force applied to the end of the bimorph is P < P ₁ , where the value of the buckling force according to Euler

, in particular, we have the value μ=2 for cantilever (figure 1) and μ=1 for hinged (figure 2) fixing the ends of the bimorph. Therefore, after "turning off" the control voltage

the bimorph returns from the bent to the original rectilinear state, and when the sign of the control voltage changes

(for example, with an alternating electrical voltage

in time

) the “direction” of the bimorph bending in the plane changes in a controlled manner

, i.e. changes to the opposite sign of quantities

,

(Fig.1) and

(figure 2, 3).

имеем результирующие значения компонентов перемещения

,

, угла поворота

торца изогнутой консоли

,

,

или в видеThus, for the case of cantilever fixing bimorph (Fig.1) when applying a control voltage

we have the resulting values of the displacement components

,

, rotation angle

curved console end

,

,

or in the form

,

,

,

,

. under the action of a longitudinal force on the end of the bimorph

.

имеем результирующее значение прогиба

в середине биморфа при наличии продольной силы P’ на торце биморфа, где начальная пьезоэлектрическая величина прогиба

с учетом

и поправка

, обусловленная действием на торец биморфа продольной силы P’ < P’ ₁. For the case of hinged bimorph (figure 2) when applying a control voltage

we have the resulting deflection value

in the middle of the bimorph in the presence of a longitudinal force P' at the end of the bimorph, where the initial piezoelectric deflection value

taking into account

and amendment

, due to the action of the longitudinal force P' <P' ₁ on the end of the bimorph.

Table

The resulting "gain factors" of the bimorph console

0 one one 0.2 1.21 1.16 0.6 1.62 1.49 0.8 1.82 1.66

,

для различных относительных значений силы

, где

,

- соответствующие значения перемещения и угла поворота торцевого сечения при P = 0, константы

,

- характеристики биморфа. Для рассматриваемого случая имеем значения констант

= 0.0154 1/Н,

= 0.0123 1/Н, значение продольной силы потери устойчивости P ₁ = 66.62 Н.The table gives the numerical values of the resulting "gain factors" of the bimorph console

,

for various relative force values

, where

,

- the corresponding values of displacement and angle of rotation of the end section at P = 0, constants

,

- bimorph characteristics. For the case under consideration, we have the values of the constants

= 0.0154 1/N,

= 0.0123 1/N, the value of the longitudinal buckling force P ₁ = 66.62 N.

= 1.21, 1,62, 1,82 результирующего «коэффициента усиления» биморфа

при относительной величине силы

= 0.2, 0.6, 0.8 соответственно, константа

= 0.00385 1/Н, значение продольной силы потери устойчивости P’ ₁ = 266.48 Н.For a hinged bimorph (figure 2) we have the values

= 1.21, 1.62, 1.82 of the resulting "gain" of the bimorph

with a relative magnitude of force

= 0.2, 0.6, 0.8 respectively, constant

= 0.00385 1/N, the value of the longitudinal buckling force P' ₁ = 266.48 N.

и электрического заряда

на электродах биморфа в режиме гибкого датчика для случая квазистатического или динамического (циклического) внешнего воздействия.Thus, the proposed technical solution makes it possible to significantly increase the piezosensitivity of a bending-type bimorph with an increase in the range of allowable values of bending deformations (deflections) in the piezoelectric actuator mode and with an increase in the informative electrical voltage

and electric charge

on the bimorph electrodes in the mode flexible sensor for the case of quasi-static or dynamic (cyclic) external influence.

Claims (3)

1. A method for increasing the piezosensitivity of a bending-type bimorph, in which a bending-type bimorph is used to operate in two modes: in the flexible piezoactuator mode and in the generator mode as a flexible piezoelectric sensor, the bimorph is initially compressed, and in the piezoactuator mode, a control electromagnetic action is applied to the bimorph in order to mechanical impact of the bimorph on external objects or, in the piezo sensor mode, measure the values of the emerging informative electromagnetic signal of the bimorph in order to measure the magnitude of the external force effect on the surface of the bimorph, characterized in that the direct initial compression of the bimorph along the neutral line of the rod-type bimorph by the applied longitudinal force P at the ends is used of the rod or the initial compression of the bimorph in the plane of the neutral layer of the membrane-type bimorph by the applied pressure p along the outer contour of the membrane, while the value of the force P < P ₁ or pressure p < p _{1 of} the initial compression less than the value of the force P ₁ or pressure p _{1 of} the loss of stability of the bimorph, taking into account its geometric, physical and mechanical characteristics and the method of fixing. 2. The method according to claim 1, characterized in that a bending-type piezoelectric bimorph is used to operate in two modes: in the flexible piezoelectric actuator mode and in the generator mode as a flexible piezoelectric sensor, while in the piezoelectric actuator mode, a control voltage is applied

to the bimorph electrodes in order to mechanically influence the bimorph on external objects or measure the values of the informative electrical voltage in the flexible sensor mode

or electric charge

on the electrodes of the bimorph in order to measure the magnitude of the external force on the surface of the bimorph. 3. The method according to claim 1, characterized in that a bending-type magnetostrictive bimorph is used to operate in the mode of a flexible piezoelectric actuator, while applying a control magnetic field to the bimorph.

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