KR20030087512A - Multi-mode vibration damper using negative capacitive shunt circuit - Google Patents

Abstract

PURPOSE: A multi-mode attenuator by using a cathode capacitor dividing circuit is provided to attenuate the vibration and/or noise at an overall frequency bandwidth with the multi-mode by using a piezoelectric material and/or a cathode capacitor dividing circuit. CONSTITUTION: A multi-mode attenuator by using a cathode capacitor dividing circuit includes a structure(1), a pair of piezoelectric materials(2,2') and a pair of dividing circuits(3,3'). The structure(1) generates a vibration and a noise by a mechanical energy such as a force, a pressure or a stress. The pair of piezoelectric materials(2,2') attached to the structure(1) generate an electrical energy by the stress due to the vibration and the noise and deforms its shape when a predetermined electrical energy is applied thereto. And, the pair of dividing circuits(3,3') induce the deformation of the pair of piezoelectric materials(2,2') by feeding back the electrical energy generated at the pair of piezoelectric materials(2,2') to the pair of piezoelectric materials(2,2').

Description

Multi-mode vibration damper using negative capacitive shunt circuit

The present invention relates to a multimode attenuator using a cathode capacitor branch circuit capable of attenuating vibration and / or noise in a multi mode using a piezoelectric material and / or a cathode capacitor branch circuit.

Meanwhile, the present invention uses a piezoelectric material that is light, easy to install, and low in manufacturing and installation cost, to attenuate noise and vibration of sports goods such as skis, tennis rackets, golf clubs, and the like in automobiles, ships, aircrafts, spacecrafts, etc. in a multi-mode. The present invention relates to a multimode attenuator using a cathode capacitor branch circuit.

On the other hand, the present invention relates to a multi-mode attenuator using a cathode capacitor branch circuit capable of controlling and attenuating the noise vibration of the system without adding an additional weight to a system requiring noise vibration attenuation in the automobile industry or the aerospace industry. will be.

As is well known, piezoelectric materials are widely used as sensors and actuators in the field of noise and vibration because of their low volume, weight and excellent effects. Piezoelectrics currently in use include PVDF (poly-vinylidene flouride), semicrystalline polymer film (PZT) and lead zirconate titanate (PZT). When is applied, the shape is deformed, and when the force or stress is applied, voltage is generated.

On the other hand, the piezoelectric as described above was also used as a study subject of the structural vibration control of multiple mode using a shunt circuit, for example, a single piezoelectric (or connected to a multi-mode shunt network). The piezoelectric element was used to develop the theory for forced control of multiple modes. Another example is the development of a filter circuit that can filter out unwanted current frequencies, which is used in branch networks that can attenuate multiple vibration modes. Another example is a plate with resonance branching (RL-resistance circuit). It was used to perform simultaneous attenuation of multiple vibration modes using multiple piezoelectrics attached to the surface of.

However, the conventional multi-mode attenuation using the piezoelectric branch circuit as described above has defects due to the limitation of vibration amplification attenuation and an increase in manufacturing and installation costs.

The present invention has been made to solve the above problems, and an object thereof is to provide a multimode attenuator using a so-called negative capacitive branch circuit. That is, an object of the present invention is to provide a multimode attenuator using a cathode capacitor branch circuit capable of attenuating vibration and / or noise in a multimode using a piezoelectric material and / or a cathode capacitor branch circuit.

Another object of the present invention is to attenuate the noise and vibration of sports goods such as skis, tennis rackets, golf clubs, etc. and automobiles, ships, aircrafts, spacecrafts, etc. by using a piezoelectric material that is light, easy to install, and low in manufacturing and installation cost. To provide a multi-mode attenuator using a cathode capacitor branch circuit that can be.

It is still another object of the present invention to provide a multi-mode attenuator using a negative electrode capacitor branch circuit capable of controlling and damping the system's noise vibration without adding additional weight to a system requiring noise vibration damping in the automotive or aerospace industry. To provide.

1 is a block diagram of a multi-mode attenuator using a negative electrode capacitor circuit according to the present invention.

2A and 2B are circuit diagrams each connecting a piezoelectric modeling circuit with a series branch circuit and a parallel branch circuit according to the present invention;

3 is a schematic diagram for explaining that the branch voltage generated in the branch impedance according to the present invention is fed back to the piezoelectric body.

4A is a circuit diagram in which an artificial cathode capacitor circuit according to the present invention is connected in series with a branch resistor;

4b is a circuit diagram in which an artificial cathode capacitor circuit according to the present invention is connected in parallel with a branch resistor;

Figure 5 is a graph of the stiffness ratio by the series and parallel resistor-cathode capacitor branch circuit according to the present invention.

Figure 6 is a graph of the loss coefficient by series and parallel resistor-cathode capacitor branch circuit according to the present invention.

7 is a graph of the frequency response function when the series branch circuit according to the present invention is operated (shunt circuit) and not (open circuit).

8 is a graph of the frequency response function when the parallel branch circuit according to the invention is activated (shunt circuit) and not (open circuit).

9 is a graph of frequency response function when the series and parallel branch circuits according to the present invention are operated simultaneously (shunt circuit) and not (open circuit).

<Description of the symbols for the main parts of the drawings>

1: Structure

2,2 ': piezoelectric

3: resistor-cathode capacitor series branch circuit

3 ': resistor-cathode capacitor branch circuit part

4,4 ': Cathode capacitor

5,5 ': Resistor

6,6 ', 7,7': electrode terminal

8: Base

12,12 ': branch impedance

18,18 ': artificial negative impedance circuit

19,19 ': operational amplifier

In order to achieve the above object, the multi-mode attenuator using a negative electrode capacitor branch circuit according to the present invention, in the multi-mode attenuator using a branch circuit consisting of a resistance element and a negative electrode capacitor element, by the mechanical energy such as force, pressure and stress A structure causing vibration and noise; A piezoelectric body attached to the structure and generating electrical energy by stress due to the vibration and noise and causing deformation of a shape when a predetermined electrical energy is applied to itself; And branch circuit means connected to the piezoelectric body to feed back electrical energy generated by the piezoelectric material to the piezoelectric body to induce deformation of the piezoelectric body.

In a preferred embodiment of the present invention, the branch circuit means includes both a circuit in which a resistance element and a cathode capacitor element are connected in series and a circuit in parallel.

In a preferred embodiment of the present invention, the cathode capacitor,

(1) interposed between an operational amplifier driven by a predetermined voltage, a capacitor interposed between a positive (+) input terminal and an output terminal of the operational amplifier, and an inverting (-) input terminal and an output terminal of the operational amplifier (1). -a) a negative impedance circuit means comprising a resistor, an inverting (-) input terminal of the operational amplifier and a resistor (a) having a common contact with the (1-a) resistor.

In a preferred embodiment of the present invention, the cathode impedance circuit means has the same capacity as the cathode capacitor, and the phase angle is made to be opposite to the cathode capacitor.

In a preferred embodiment of the present invention, the relationship between the (1-a) resistance and the (a) resistance is in inverse proportion to each other.

In a preferred embodiment of the present invention, the resistance value of the resistance (1-a) and the resistance value of the resistance (a) are adjusted so that the capacitance of the negative impedance circuit means and the capacitance of the inside of the piezoelectric body are equal.

In a preferred embodiment of the present invention, the piezoelectric body is configured to have a polarity in the thickness direction.

In a preferred embodiment of the present invention, when the electrical energy is fed back to the piezoelectric body, the piezoelectric body extends in the longitudinal direction to act on the transverse vibration mode.

Hereinafter, a preferred embodiment of a multimode attenuator using a negative electrode capacitor branch circuit according to the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, when it is determined that detailed descriptions of related well-known technologies or configurations may unnecessarily obscure the subject matter of the present invention, the detailed description will be omitted. In addition, terms to be described below are terms defined in consideration of functions in the present invention, which may vary according to the intention or custom of a user or an operator. Therefore, the definition should be made based on the contents throughout the specification.

1 is a configuration diagram of a multi-mode attenuator using a cathode capacitor branch circuit according to the present invention, and FIGS. 2A and 2B are circuit diagrams connecting a piezoelectric modeling circuit to a series branch circuit and a parallel branch circuit according to the present invention. 3 is a schematic diagram for explaining that the branch voltage generated in the branch impedance according to the present invention is fed back to the piezoelectric body, and FIG. 4A is a circuit diagram in which an artificial cathode capacitor circuit according to the present invention is connected in series with a branch resistor. 4B is a circuit diagram in which an artificial cathode capacitor circuit according to the present invention is connected in parallel with a branch resistor. 5 is a graph of the stiffness ratio by the series and parallel resistor-cathode capacitor branch circuit according to the present invention, Figure 6 is a graph of the loss coefficient by the series and parallel resistor-cathode capacitor branch circuit according to the present invention. 7 is a graph of the frequency response function when the series branch circuit according to the present invention is operated (shunt circuit) and when it is not operated (open circuit), and FIG. 8 is when the parallel branch circuit according to the present invention is operated (shunt circuit). Fig. 9 is a graph of the frequency response function when the series and parallel branch circuits according to the present invention are operated simultaneously (shunt circuit) and when not in operation (open circuit). to be.

Referring to FIG. 1, a multimode attenuator using a negative electrode capacitor branch circuit according to the present invention includes a structure (1) that generates vibration and / or noise by mechanical energy such as force, pressure, and stress, and the structure (1). A piezoelectric body (2), and a piezoelectric body (2), which are attached to and generate electrical energy (voltage, current) by stress caused by the vibration and / or noise, and cause deformation of a shape when a predetermined electrical energy is applied to itself. It is configured to include a series branch circuit portion 3 which is connected to and feeds back the electrical energy generated in the piezoelectric body 2 to the piezoelectric body 2 to induce deformation of the piezoelectric body 2. As shown in the series branch circuit section 3 of FIG. 1, the resistor 5 and the cathode capacitor 4 are configured in series, which preferably adjusts the low frequency vibration amplitude. On the other hand, the present invention is connected to the lower piezoelectric material 2 'and the lower piezoelectric material 2' attached to the lower portion of the structure 1 as shown, the resistor 5 'and the negative electrode capacitor 4' is connected in parallel A parallel branch circuit portion 3 'consisting of an integrated circuit is included, which preferably adjusts the high frequency vibration amplitude. In FIG. 1, reference numeral 8 is a support base of the structure 1, and in a preferred embodiment of the present invention, the piezoelectric element 2 is attached to the structure 1 at a distance of 0.1 cm from the support end. do. In the present invention, the branch circuit part 3 (3 ') serves as an attenuator of the structure 1, which will be described later.

As shown in FIG. 4A, the negative electrode capacitor 4 of FIG. 1 includes an operational amplifier 19 driven by a predetermined voltage, for example, a ± 15 volt power supply, and a positive input terminal of the operational amplifier 19. The capacitor 15 interposed between the output terminal and the output terminal Out, the (1-a) resistor 16 interposed between the inverting (-) input terminal and the output terminal Out of the operational amplifier 19, It can be replaced by a negative impedance circuit section 18 comprising an inverting (-) input terminal of the amplifier 19 and a resistor (17) having a common contact with the resistor (1-a). The negative impedance circuit portion 18 preferably has the same capacitance as the negative electrode capacitor 4, the phase angle is made to be opposite to the negative electrode capacitor 4, and the (1-a) resistance (16) and the (a) resistance (17) is inversely related to each other.

Similarly, the negative electrode 4 'associated with the lower piezoelectric 2' in FIG. 1 also has an operational amplifier 19 'driven by a predetermined voltage, for example, a ± 15 volt power source, as shown in FIG. Between the capacitor 15 'interposed between the positive (+) input terminal and the output terminal (Out) of the operational amplifier 19', and between the inverting (-) input terminal and the output terminal (Out) of the operational amplifier 19 '. A resistance (16 ') interposed therebetween, an inverting (-) input terminal of the operational amplifier 19', and a resistance (17) having a common contact with the resistance (1-a). Can be replaced by a cathode impedance circuit portion 18 ', wherein the cathode impedance circuit portion 18' preferably has the same capacitance as the cathode capacitor 4 ', the phase angle of which is equal to the cathode capacitor 4'. (1-a) resistor (16 ') and (a) resistor (17') are inversely related to each other.

The operation of the multimode attenuator using the negative electrode capacitor branch circuit according to the present invention configured as described above will be described below with reference to FIGS.

Referring to FIG. 1, as described above, the upper piezoelectric element 2 is attached to the structure 1, and the lower piezoelectric element 2 ′ is attached to the lower portion of the structure 1. The piezoelectric element 2 on the structure 1 is connected to the branch circuit 3 in which the resistor 5 and the negative electrode capacitor 4 are connected in series, and the piezoelectric element 2 'under the structure 1 is connected to the resistor 5'. ) And the negative electrode capacitor 4 'are connected to the branch circuit 3' connected in parallel. At this time, when the structure 1 is subjected to force or pressure, the piezoelectric body 2, 2 'attached to the structure 1 is subjected to stress, and due to the stress, the piezoelectric body 2, 2' is charged. q is accumulated and current I 14 (Fig. 3) is generated due to the movement of the stored charge. The current I 14 is input to the series branch circuit 3 and the parallel branch circuit 3 ', respectively, and the voltage V _SH 13 applied to the branch impedance Z _SH 12, 12'; Feedback is applied back to the piezoelectric elements 2 and 2 'via terminals 6 and 6'. It will be apparent to those skilled in the art that the branched impedances Z _SH 12, 12 'are impedances caused by resistors 5, 5' and cathode capacitors 4, 4 ', respectively.

When the feedback voltage V _SH 13 as described above is applied to the piezoelectric bodies 2 and 2 ', the piezoelectric bodies 2 and 2' cause deformation of the shape according to the characteristics of the piezoelectric bodies 2 and 2 'so that the structure 1 The vibration of the will be controlled. That is, when the feedback voltage V _SH 13 is applied to the piezoelectric body 2, 2 ′, the piezoelectric body 2, 2 ′ is deformed in shape so as to affect the vibration existing in the structure 1. And acts as an attenuator, resistors 5 and 5 'of branching impedances 12 and 12' and cathode capacitors 4 and 4 'for applying the feedback voltage V _SH 13 to the piezoelectric elements 2 and 2'. By adjusting the value of, it is possible to control the degree of attenuation of the attenuator. Therefore, the resistor branch circuit or the inductor resonant branch circuit attenuator, which is a conventional branch circuit attenuator, has a limitation that can control vibration only in a limited frequency range, while the attenuator according to the present invention can simultaneously attenuate the vibration modes of the entire frequency band. Can have performance. That is, the resistor-cathode capacitor series branch circuit part 3 of the present invention connected to the piezoelectric element 2 attached to the upper part of the structure 1 controls and attenuates the vibration of the low frequency band that may occur in the structure 1, 1) The resistor-cathode capacitor parallel branch circuit portion 3 'of the present invention connected to the piezoelectric element 2' attached to the lower portion controls and attenuates the vibration of the high frequency band which may occur in the structure 1. Thus, the attenuator according to the present invention can simultaneously attenuate the multiple vibration modes of the entire frequency domain occurring in the attenuation object by using a resistor-cathode capacitor branch circuit connected in series and in parallel.

Due to the electrical properties of the piezoelectric elements 2 and 2 ', the piezoelectric elements 2 and 2' of FIG. 1 are formed as shown in FIGS. 2A and 2B, and the current source sources 10 and 10 'and the piezoelectric elements 2 and 2, respectively. It is possible to model a circuit in which the capacitors 9, 9 'inside') are connected in parallel. In the modeling circuit of FIGS. 2A and 2B, the two electrode terminals 6, 7 (6 ′, 7 ′) have branch circuits 3, consisting of resistors 5, 5 ′ and cathode capacitors 4, 4 ′. 3 ') respectively. 2A and 2B, the state in which the two electrode terminals 6, 7 (6 ', 7') are not connected is called an open circuit, and it is apparent to those skilled in the art that no current flows in this state.

3 shows that the current I 14 generated in the piezoelectric body 2, 2 'by the force or vibration applied to the structure 1 again passes through the branching impedance Z _SH 12, 12'. , 2 '). As shown in Fig. 3, the branch voltage V _sub.SH applied to the branch impedance Z _SH (12, 12 ') is _obtained by the following equation.

V _sub.SH = -Z _SH × I

On the other hand, the present invention is equivalent to the capacitance of the capacitor inside the piezoelectric body (2, 2 '), and can use the artificial negative impedance circuit portion (18, 18') to generate a negative electrode capacitance of the opposite phase angle This is shown in Figures 4a and 4b.

The artificial negative impedance circuitry 18, 18 ′ shown in FIGS. 4A and 4B has capacitors 15, 15 ′ and two resistors 16, 17 (16 ′, 17 ′) and ± 15 volts as shown. It consists of operational amplifiers 19, 19 'driven by a power supply.

4A and 4B, the resistors 16, 17 (16 ', 17') and the capacitors 15, 15 'in the cathode impedance circuit portion 18, 18' to avoid instability due to the fluctuation of the circuit itself. It will be apparent to those skilled in the art that there is a need for adjustment. In FIGS. 4A and 4B, the capacitance C _sub.n and the piezoelectric _force generated in the negative impedance circuit portion 18, 18 'by adjusting the parameter a values of the two resistors 16, 17 (16', 17 ') are shown. It is possible to match the capacitance (C _sub.p ) inside (2, 2 '). In Figs. 4A and 4B, the resistors 17 and 17 'of the artificial negative impedance circuit portion 18 and 18' are connected with the branch resistors 5 and 5 'so that the series or parallel resistors as shown in Figs. Since the same circuits as the cathode capacitor branch circuit sections 3 and 3 'are configured, the branch circuit sections are connected to the output terminals 6 and 7 (6' and 7 ') of the piezoelectric bodies 2 and 2', respectively. Do.

5 and 6, the stiffness ratio and the loss coefficient of the series branch circuit section 3 and the parallel branch circuit section 3 'according to the present invention are shown for non-dimensional frequencies, respectively. The electromechanical ductility factor used in FIGS. 5 and 6 is preferably 0.33. As shown in FIG. 5, in the case of the series branch circuit unit 3, the stiffness ratio gradually increases from zero (zero) as the dimensionless frequency increases, and in the case of the parallel branch circuit unit 3 ′. As the dimensionless frequency increases, the stiffness ratio decreases, and it can be seen that it tends to approach zero (zero).

The electromechanical ductility factor k _sub.ij is generally used as a reference to measure the strength of piezoelectric materials. Such ductility modulus is defined as the ratio of stored mechanical energy to total energy, and examples are shown that show that the electro-mechanical ductility coefficient is 1 when the stiffness coefficient is zero (Lesieutre, G. and Davis, C, 1997, "Can a Coupling Coefficient of a piezoelectric Device be Higher than Those of Its Active Materials" Proc. Of SPIE, Vol. 3041 pp. 281-292). This means that when the electromechanical ductility factor is 1, energy is converted 100% between mechanical energy and electrical energy. Therefore, when the series branch circuit unit 3 is used, mechanical energy due to vibration in the low frequency band can be converted into electrical energy by the piezoelectric body 2 to 100%. When the parallel branch circuit unit 3 'is used, high frequency Since the stiffness coefficient is zero in the band, the ductility coefficient is 1, and likewise, the mechanical energy can be 100% converted into electrical energy by the piezoelectric body 2 '.

Referring to FIG. 6, the loss coefficient of the material decreases as the dimensionless frequency increases in series connection, and the loss coefficient increases as the dimensionless frequency increases in parallel connection. Therefore, according to the present invention, high energy attenuation can be obtained by consuming mechanical energy due to vibration. In other words, this particular characteristic shows that the cathode capacitor branch circuit has multiple attenuation capabilities.

A pair of piezoelectric bodies 2, 2 'is attached to the support end 8 side of the structure 1 as shown in Fig. 1, and the cathode capacitor branch circuit portions 3, 3' are used to damp vibrations. I looked at it. In the embodiment of the present invention, the piezoelectric bodies 2 and 2 'are preferably attached 0.1 cm away from the supporting end 8 of the structure 1. The piezoelectric bodies 2, 2 'are polarized in the thickness direction and extend in the longitudinal direction to act in the transverse mode.

FIG. 7 analytically illustrates the response to a piezoelectric / structure connected with series resistor-cathode capacitor branch circuit 3, showing that the high attenuation ratio at low frequencies decreases with increasing frequency. This phenomenon will be understood by considering the material loss coefficient (see Fig. 6) of the resistor-cathode capacitor series branch circuit portion as described above. In order to obtain the same result as in FIG. 7, in the preferred embodiment of the present invention, a 5 ohm resistor was used as the resistor 5, and a capacitance of 200 nF was used as the cathode capacitor 4.

FIG. 8 analytically shows the frequency response response of the piezoelectric / structure connected to the parallel resistor-cathode capacitor branch circuit portion 3 '. In the case of FIG. 8, the opposite behavior is shown in which the amplitude decreases as the frequency increases, as opposed to the case of the series branch circuit 3. This phenomenon will be understood by considering the fact that the material loss coefficient (see Fig. 6) of the resistor-cathode capacitor parallel branch circuit portion increases as the non-dimensionalized frequency increases as described above. In order to achieve the same result as in FIG. 8, in the preferred embodiment of the present invention, a resistor of 200 ohm was used as the resistor 5 'and a capacitance of 200 nF was used as the cathode capacitor 4'.

FIG. 9 analytically shows the frequency response response to the piezoelectric body / structure when the series branch circuit section 3 and the parallel branch circuit section 3 'are applied simultaneously. As a result of using the resistor-cathode capacitor branch circuit portions 3 and 3 'having the resistance value and the capacitance as described above, it was possible to reduce more than 20 dB from the peak value of the open circuit amplitude over the entire frequency band. By reducing the resistance of the branch resistor in the series branch circuit section and increasing the resistance value of the branch resistor in the parallel branch circuit section, it is possible to reduce the vibration more effectively. Will be judged by consideration. Thus, the resistor-cathode capacitor branch circuit according to the present invention can be used as a multimode vibration damper in various applications of engineering, and in some cases the branch circuit portion can be located and used inside the structure.

The multimode attenuator using the negative electrode capacitor branch circuit according to the present invention as described above can attenuate the vibration and / or noise in the multi-mode in the entire frequency band by using a piezoelectric material and / or a negative electrode capacitor branch circuit. Provide an advantage.

In addition, the multi-mode attenuator using the cathode capacitor branch circuit according to the present invention can simplify the overall configuration, and can be configured with a small volume and weight, which can attenuate noise and vibration without significantly affecting the system. To provide.

Although a preferred embodiment of the present invention has been described in detail above, those skilled in the art to which the present invention pertains may make various changes without departing from the spirit and scope of the invention as defined in the appended claims. It will be appreciated that modifications or variations may be made. Therefore, changes in the future embodiments of the present invention will not be able to escape the technology of the present invention.

Claims (8)

In the multi-mode attenuator using a branch circuit consisting of a resistor element and a cathode capacitor element, Structures that cause vibration and noise by mechanical energy such as force, pressure and stress; A piezoelectric body attached to the structure and generating electrical energy by stress due to the vibration and noise and causing deformation of a shape when a predetermined electrical energy is applied to itself; And a branch circuit means connected to the piezoelectric element and feeding back the electrical energy generated by the piezoelectric material to the piezoelectric material to induce deformation of the piezoelectric material. The multi-mode attenuator using a negative electrode capacitor branch circuit according to claim 1, wherein the branch circuit means includes both a circuit in which a resistor element and a cathode capacitor element are connected in series and a circuit connected in parallel. The negative electrode capacitor of claim 1 or 2, (1) interposed between an operational amplifier driven by a predetermined voltage, a capacitor interposed between a positive (+) input terminal and an output terminal of the operational amplifier, and an inverting (-) input terminal and an output terminal of the operational amplifier (1). -a) a negative impedance circuit means comprising a resistor, an inverting (-) input terminal of said operational amplifier and a resistor (a) having a common contact with said (1-a) resistance, characterized in that it is replaced by Multimode Attenuator Using Cathode Capacitor Branch Circuit. 4. The multi-mode attenuator using a negative electrode capacitor circuit as claimed in claim 3, wherein the negative impedance circuit means has the same capacity as the negative electrode capacitor, and the phase angle is opposite to that of the negative electrode capacitor. 4. The multi-mode attenuator using a negative electrode capacitor branch circuit as claimed in claim 3, wherein the relationship between the resistance (1-a) and the resistance (a) is in inverse proportion to each other. 4. The resistance value of the resistance (1-a) and the resistance value of the resistance (a) are adjusted so that the capacitance of the cathode impedance circuit means and the capacitance of the inside of the piezoelectric body are the same. Multimode Attenuator Using Cathode Capacitor Branch Circuit. The multimode attenuator using a cathode capacitor branch circuit according to claim 1, wherein the piezoelectric body is configured to have a polarity in the thickness direction. The multimode attenuator using a negative electrode capacitor branch circuit as claimed in claim 1, wherein when the electric energy is fed back to the piezoelectric body, the piezoelectric body extends in the longitudinal direction to act in a transverse vibration mode.