KR840001016B1 - Active suspension piezoelectric polymer transducer - Google Patents

Abstract

In a piezoelectric polymer tranducer, the PVF (vinylidene polyfluoride) film (24) is fixed at the circumference jaws (20) (23). The jaws (21) (22) are moved until they are parallel with an XX-axis and extend in a single direction against the suspension (25).

Description

Method of manufacturing active suspension electromechanical transducers

1 is a cross-sectional view of a transducer according to the invention.

2 is a cross-sectional view of another embodiment of a transducer according to the invention.

3 and 4 are perspective views of the star changer shown in cross section in FIGS. 1 and 2.

5 to 8 are explanatory views.

9 is a cross-sectional view of another embodiment of a transducer according to the present invention.

FIG. 10 is a top view of the electrodes with the converter of FIG.

11, 12 and 13 are explanatory diagrams of a converter manufacturing process according to the present invention.

14 is a cross-sectional view of a dual suspension transducer.

The present invention relates to a method for producing an electromechanical transducer comprising a polymer element in which anisotropy is present in the form of anodic directions of transient electrical discharges or polymers themselves. In particular, the present invention relates to a transducer, such as a loudspeaker, a microphone, a hydrophone, and an probe of an echograph, in which an active structure is formed by at least one polymerized membrane which forms a difficult form. Indeed, two ways of transformation arise depending on whether the thin layer structure is homogeneous or heterogeneous.

The simplest example is a single film with metal on both flat surfaces. Such a film exposed to an excited electric field is deformed in three directions, ie perpendicular to the plane and in two directions on the plane. In the case of a homogeneous structure formed from two films joined together, the induced strain is one of the entire bent. It is easy to distinguish from others.

Apart from thickness variations, other deformations are due to stretching occurring during the shaping of the membrane. When stretching occurs in one direction, the deformations increase in the stretching direction. On the other hand, when there is no height or height is uniform, the deformations are also uniform.

For transducers using a portion of the sphere as an active element, the circumferential fixation does not cause any local circumferential deformation, so the motion depends heavily on the supporting effect along the meridian. By replacing the circumferential stationary with the passive annular wave suspension, the structure becomes more free, but the oscillating piston effect still does not approach the radial motion characterized by the spherical sphere. The result is a loss of radiation and efficiency that is clearly distinguished from the effect of precise sources.

The present invention provides a method for producing an electromechanical transducer having a self-supporting radial structure comprising at least one active element formed of at least one membrane of polymeric material and having at least one edge attachment acting as a support, the radial structure being active Formed by a membrane that accurately takes the form of at least one active suspension with two edges connected by a wall, a first edge connected to this attachment, a second corner sphere of this active suspension connected to the element to close this radial structure. This closing element is characterized by the movement of the second circular edge of the active suspension exposed along the edge radius of this sphere.

Before entering the details of the invention, it is useful to remember that the electromechanical transducer is electrically excited across the front of the structure of the electrodes and emits through a radiation plane connected to a medium carrying longitudinal oscillation waves. However, these linear transducers also work in the opposite direction. The transducer effect of inducing polarized polymer films is a piezoelectric effect. In nonpolar polymer membranes, permanent overdischarge can be induced, which linearizes the attractive action of the electrical discharge and piezoelectrics the transducer. According to the construction of the polymerized structure, deformation of the active element is necessary (in the case of homogeneous structure). Accumulated bending is caused by isotropic or anisotropic surface vibrations with corresponding curvature radii or, on the other hand, transverse movements (in the case of heterogeneous structures).

Useful polymers can be polar homopolymers such as PVF ₂ (vinylidene polyfluoride) and PVF ₂ -other polar polypolymers such as PVF ₂ -PTEE. It can be used with the excess electrical discharge obtained Many organic resin nonconductors can be used, such as polyurethane (PU) and ethylenepolytrafluorine (PTFE).

In figure 1 a cross section of an electromechanical transducer according to the invention can be seen. The transducer includes an annular support 2 having a fixed polymer film 1 along with a rotation axis XX, the shape of which has a spherical protrusion at an angle of α angle to one side having a C center point on the XX axis. Between the circumference and the support, the membrane has a truncated cone shape along the peripheral radius of the spherical protrusion. The radial truncated cone of FIG. 1 forms an active suspension. For this purpose, two faces of the electrodes 3 and 4 are covered. As a non-limiting example, a thin film of vinylidene rollifluoride having a radial structure of FIG. 2 having a thickness of 25 μm can be obtained by thermoforming. The electrodes 3 and 4 are obtained by thermal expansion in a vacuum state of aluminum to a thickness of 1500 kPa. Of the film 1 which forms a spherical protrusion when the truncated cone portion extends in one direction along the radius shown by the dotted line. The part is drawn on two axes. After the electrical polarization treatment between the electrodes 3 and 4, a high density transverse electric field (1 MV / cm) is generated, activating the circumferential suspension of the central dome. By connecting the fields 3 and 4 to the alternating voltage generator 5, the active circumferential suspension acts as a piezoelectric transducer. The construction of the conical walls of the alternating elongation and active circumferential suspension is configured as shown by the double arrows 8. The result is that the passive spherical protrusion is forced along a peripheral radius causing motion parallel to the axis XX. The dashed line 6 shows the low position of the reflecting structure and the dashed line 7 shows the high position. Although this is not active, the circumferential strength can be reduced, as shown in FIG. 3, in order for the transducer action to obtain conical mechanical flexibility with maximum sensitivity of deformation along the hardness. It is obtained by the unique form which consists of the radially inclined protrusion 11 which changes to ().

Each projection 11 provides a sealing of the radial structure to neutralize the acoustic short between the radial surfaces of the vibrating piston. Then, the circumferential strength can prevent the active sector 12 from following the deformation motion of the central dome. Because the central dome can move the manual roll and cause it to bend, it can be truncated conical active suspension or other It may be formed of a material other than the wall thickness. It acts as a piezoelectric factor and can be polarized in a small radial state in proportion to the ratio of the active surface to the passive surface in consideration of the opening angle α.

In FIG. 2 a cross-sectional view of another embodiment of the radiation structure of FIG. 1 is shown. FIG. 4 is a perspective view of the present variant.

The same elements in FIGS. 1 and 3 use the same reference numerals, and the active circumferential suspension is heterogeneous. In FIG. 1, the circumference of the support 2 is pivoted around the support circumference due to the hinge action in the outer tribe. As the suspension is carried out the results are set up differently. Another difference is due to the fact that the connection between the spherical protrusion and the active truncated conical suspension does not include the 90 ° fold shown in FIG.

In order to obtain heterogeneous operation, the active suspension of FIG. 2 is provided with a truncated conical membrane 10 which is completely bonded to the truncated cone of membrane 1. The representational deformation of membrane 1 is that of membrane 10. By selecting a state other than, the alternating bending action of the heterogeneous active suspension can be observed. The alternating bending action of the active suspension along the peripheral radius can be observed along the line connected with the spherical protrusion. Along the line associated with the spherical protrusion, the tilting motion along the peripheral radius can be observed. This movement is shown by a double curved arrow 9 and if we refer to FIG. 1 we can see that it is slightly different from the motion represented by the double arrow 8. As far as is considered, the two forms of active suspension are very contrasting. The mechanical flexibility of the active suspension of FIG. 1 may indicate that the suspension of FIG. 2 is longer than that, and the edge of the spherical protrusion of FIG. The result is a precise movement along the side radius.

The structure shown in FIGS. 1 and 2 has a slightly more direct radial shape than that of the active projection which hangs directly on the retaining ring 2.

According to the invention the spinning of the precise source can be further approached by the arrangement of the active suspension and the spherical protrusions to have the same deformation along the connecting circumference.

Article 5 shows a spherical surface 13 in coordinates of axes 1, 2, 3 at point A. The axis 3 extends along a radius, the axis 1 tangential to the parallel and the axis 2 tangential to the longitude. FIG. 6 is a cross-sectional view of a spherical transducer having omnidirectional radiation by a square wave at phase center C. FIG. Polymer film 16 has e as its wall thickness and it carries metallizations 14 and 15 on its inner and outer surfaces. The hole is required to contact the metallization 15. Such transducers are very difficult to fabricate and have drawbacks that include a small amount of air, which significantly increases the strength of the radial structure.

In order to overcome this drawback, it can be envisaged to emit a wave with the phase center C of the oscillating piston formed by the spherical surface portion. Such a piston is shown in FIG. It is a spherical protrusion 13 with a radius R and a half opening angle α. It can be seen that the ideally deformed condition is an extended projection 17 of radius R + ΔR, all points going in radial displacement ΔR. FIG. 8 shows the fixation of this spherical protrusion in a strong annular support 18 which does not regenerate the simple radial displacement of FIG. 7. The center of curvature reports from C to C 'and the radius of curvature passes from R to R'. .

The present invention provides a connection by active circumferential suspension which ensures the fixation of the center C and regenerates the above conditions at the limits of the pulsating sphere from which it is extracted so as to maintain the potential of the ideal spherical protrusion.

In FIG. 9, a cross section of a radial structure with a fixed phase center is shown. It is formed by stretching the film 1 of vinylidene polyfluoride to form a protrusion with a thickness e, a radius of curvature R and a semi-opening angle α. After electrical polarization, this protrusion exhibits a piezoelectric coefficient for grinding the size of, for example, d ₃₁ = d ₃₂ = 5.10 ^-12 CN ^-1 . Forming by unidirectional stretching is applied to an active truncated conical suspension of length L semi-opening angle α and thickness e '. ₃₁ = 2.10 ^-12 CN ^-1 , d _'32 = 15 10 ^-12 CN ^-1 .

은

과 같아야만 하고 또 발전기(5)는 만약 R이 증가하면 L이 감소하는 그런 극성을 갖는 전압 V와 V′를 제공해야 한다.To achieve the intermediate connection between the spherical protrusion and the active suspension,

silver

And the generator 5 must provide voltages V and V 'with such polarity that L decreases if R increases.

ΔR (the radius of curvature radius) is measured from equation (1).

ΔR (suspension of suspension length) is measured from equation (2).

으로 가정한다면, R=50mm일때

,

8.33mm를 얻는다.For example, V = V ′ and e ′ =

Assume that R = 50mm

,

Get 8.33mm

Since the angle α remains constant, the active suspension vibrates without its own number of radiations. The radiation pattern is determined only by the pulsation projection of the central dome.

In order for the central dome to work as an active element, electrodes 18 and 19 must be provided. 10 is a top view of the metallizations 18 and 3 from which the polymerized film 1 emerges from the top surface. These metallizations 3 and 18 are each independently such that the electropolarization of the spherical protrusions and the active suspension can indicate that the application of the excitation voltage is facilitated.

After polarization, the electrodes 18 and 3 can be connected to one another if the same excitation voltage is applied to the spherical protrusion and the circumferential suspension. The electrodes 19 and 4 are the same as the electrodes 18 and 3. One of the faces of the film 1 can be completely metallized without any drawbacks. The use of active spherical protrusions in the form of FIG. 2 is also possible. However, the active suspension of FIG. 2 provides part of the total radiation.

The complex relationship of the voltages that excite the active spherical protrusion and the active circumferential suspension may not be constant.

These two components can be excited with voltages that no longer guarantee the neutrality of the above strains, respectively, connecting the extraneous lines of the negative spectrum.

In fact, at low frequencies, the piston is practically non-unidirectionally pulsating spherical.

It is possible to vary the ratio of the excitation voltage with frequency for the purpose of obtaining an optimum frequency response curve within a predetermined radiation angle.

Fabrication of a structure such as that shown in FIG. 9 can be performed by separating the spherical protrusions and the protruding conical suspensions.

Figures 11 to 13 show a fabrication method for obtaining these two active elements from a flat membrane of vinylidene polyfluoride. In the first state, the PVF ₂ membrane 24 is formed with circumferential jaws 20. And at 23.

In the second state, as shown in FIG. 12, the jaws 21 and 2 are moved parallel to the axis XX to extend unidirectionally to the suspension 25.

In the third state, the jaws 20, 21, 22 and 23 are fixed and the punch 26 forms a spherical protrusion by biaxial stretching. The state of the structure is shown in FIG.

The invention is not limited to passive or active spherical surface portions in the form of spherical protrusions.

14 shows a cross section of the transducer according to the invention in which the basic radiating element is formed by a spherical region connected to two active conical circumferential suspensions. The transducer comprises an upper support 2 on which two truncated conical suspensions are hung. The lower suspension has electrodes 27 and 28 because the upper suspension receives electrodes 29 and 30. The spherical region has electrodes 18 and 19.

All electrodes are connected to an excitation generator 5 which provides a pulsating sphere of operation. Of course, the spherical zone can be purely passive and has an upper curvature with the same curvature connected to the upper active suspension by electrodes 29 and 30. It is possible to mate with passive or active spherical protrusions.

Spherical zones can be produced by placing one tube of polymeric material in a two-part mold. A truncated conical suspension can be formed and added by other operations of stretching the polymeric tube and FIG. 14 shows the active truncated conical suspension widening out of the direction of the support or converging towards the support. This type of duality is also shown in Figs. 1 and 9. The active suspension of Fig. 14 can be replaced by the heterogeneous suspension shown in Fig. 2. These latter are involved in the forward yarn of the radial structure. It may be formed of a heterogeneous film and may be formed of a single film of another. In the case of protrusions or passive spherical zones, it may be advantageous to form spherical surface portions of a material with greater chance of occurrence than active suspensions. For example, polyurethane is used as passive element and vinylidene polyfluoride is used as active suspension element.

Although the active suspensions described were formed of polymerized membranes, the active suspensions are transmission forces. Don't forget to use the magnetic force, that the active suspension structures can reduce the spatial yog of the heterogeneous structure, while providing more bending than the length of their folding.

Polymeric spinning structures are vulnerable to the thrust on their convexities. To protect it, cushions through which sound can pass can be applied and used for the recessed names.

Finally, it should be noted that the present invention is not limited to radial planes with rotational symmetry. The active suspension is in the form of a pyramid or truncated cone with spherical surface portions and nonrotating directional connections. When the active suspension has to regenerate the motion of the pulsating sphere, it is advantageous to make the vertex of the truncated cone or pyramid equal to the center of the sphere. On the other hand, the invention is not limited to the sphere surface portion used as the piston. This also includes the deformation of pistons which are generally spherical in shape but have low amplitude variations to increase mechanical flexibility.

Claims (1)

A method of manufacturing an electromechanical transducer having at least one active element made of at least one polymer material comprising clamping the polymer membrane in different jaws and forming the clamped membrane by stretching. The membrane is clamped between the inner sets of jaws 21 and 22 to define the limits of the jaws, and of the jaws 20 and 23 to define the limits of the periphery 25 around the central region. Clamping between the outer set, and wherein the forming is obtained by extension of the zones (24) and (25).

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