WO2019150850A1 - Transducer and power-generating system using same - Google Patents

Abstract

This transducer (10) comprises: a piezoelectric element (20) having a piezoelectric layer (21) containing an elastomer and piezoelectric particles, electrode layers (22a, 22b) disposed so as to sandwich the piezoelectric layer (21), and elastic body layers (23a, 23b) disposed at least in the outermost layer; and an exterior material (30) accommodating the piezoelectric element (20). A buffer part (31) is demarcated between the piezoelectric element (20) and the exterior material (30) in the direction in which the piezoelectric element (20) extends under pressure, the buffer part accommodating at least one among a gas, a non-volatile liquid, and a solid that has a smaller elasticity than the elastic body layers (23a, 23b).

Description

Transducer and power generation system using the same

The present invention relates to a transducer including a flexible piezoelectric element and a power generation system using the transducer as a power generation device.

Piezoelectric material generates electric charge when strain is generated by applying pressure. A power generation system for generating electric power by converting vibration energy such as environmental vibration into electric energy by utilizing the characteristics of the piezoelectric material has been developed. For example, Patent Document 1 describes a power generation system in which a piezoelectric element is installed on a road surface of a road and a person or a vehicle passes over the piezoelectric element to generate power. In this type of power generation system, it is necessary to install piezoelectric elements over a wide range and a large amount of power generation is required. In addition, in the piezoelectric element, durability against repeated deformation is required, and influence from the environment such as moisture and dust must be eliminated as much as possible.

Known piezoelectric materials include ceramics such as lead zirconate titanate (PZT), polymers such as polyvinylidene fluoride (PVDF) and polylactic acid, and composites in which polymer particles are filled in a polymer matrix. . Among these, when ceramics are used, it is not easy to increase the area. When a polymer is used, it is easy to increase the area, but there is a problem that the amount of power generation is small. In particular, in the case of resin, since it is poor in flexibility, it is difficult to install on a curved surface or the like, and there is a problem in durability.

As a technique for increasing the amount of power generation in a piezoelectric element using a polymer material, for example, Patent Document 2 uses a power generation body in which an electret dielectric and an electrode are partially joined to form a gap therebetween. In addition, a laminated power generator is described in which a plurality of the power generators are stacked and a support member is interposed between the power generators. In the laminated power generator described in Patent Document 2, the power is generated by electrostatic induction according to the change in the distance between the gap formed between the electret dielectric and the electrode, and external force is easily transmitted by the support member. Thus, the distance change of the gap is increased.

Patent Document 3 describes a power generation device including a resin film having a plurality of pores, a power generation element having a pair of electrodes disposed on both sides thereof, and an elastic body laminated on the power generation element. . In the power generation device described in Patent Document 3, by providing a plurality of pores in a resin film and pressing the resin film with an elastic body having irregularities, the deformation amount of the pores is increased and the piezoelectricity is improved. Yes.

In Patent Document 4, a piezoelectric film and an elastically deformable flat plate-like base material are alternately used as components of a power generator for a mobile body that generates power based on the relative flow of an external fluid when the mobile body moves. The power generation units stacked on each other are described. In the power generation unit described in Patent Document 4, the piezoelectric film is deformed by deformation of the base material. FIG. 7 of Patent Document 4 describes a form in which the surface of the power generation unit is covered with a resin coating material.

JP 2006-197704 A Japanese Patent Application Laid-Open No. 2014-121201 JP 2014-207391 A International Publication No. 2015/068427

As described above, in addition to a large amount of power generation, the piezoelectric element also needs durability. As a method for imparting durability to the piezoelectric element and eliminating the influence from the environment, a method of covering the piezoelectric element with a covering material as described in FIG. However, when the covering material is made of resin, the flexibility is poor, and thus the deformation of the piezoelectric element is hindered. For this reason, even if it is possible to increase the amount of power generation by making the piezoelectric element easy to deform, the effect is diminished by the presence of the covering material, and the effect of increasing the amount of power generation cannot be exhibited. Thus, in the piezoelectric element, it has been difficult to achieve both an increase in power generation and an improvement in durability.

The present invention has been made in view of such circumstances, and an object thereof is to provide a transducer having a large amount of generated charges and excellent durability using a flexible piezoelectric element. It is another object of the present invention to provide a power generation system having a large power generation amount and excellent durability using the transducer.

(1) In order to solve the above problems, a transducer according to the present invention includes a piezoelectric layer including an elastomer and piezoelectric particles, an electrode layer disposed with the piezoelectric layer interposed therebetween, and an elastic layer disposed at least on the outermost layer. A piezoelectric element having a piezoelectric element, and an exterior material that houses the piezoelectric element, and between the exterior material and the piezoelectric element in a direction in which the piezoelectric element expands due to pressing, a gas, a non-volatile liquid, And a buffer portion in which at least one solid having a smaller elastic modulus than that of the elastic body layer is accommodated.

(2) In order to solve the above-described problem, a power generation system of the present invention is characterized by including the transducer of the present invention and an electric circuit for extracting electric energy from the transducer.

(1) According to the transducer of the present invention, the matrix (base material) of the piezoelectric layer constituting the piezoelectric element is an elastomer, and the elastic layer is disposed on the outermost layer of the piezoelectric element. Since the piezoelectric element is flexible and can be manufactured by an extrusion method or a coating method, the area can be easily increased. Further, if a relatively flexible material is used for the exterior material, it can be placed in a place having a complicated shape such as a curved surface. An elastic layer is disposed on at least the outermost layer of the piezoelectric element. That is, the elastic body layer is disposed on the outer side in the stacking direction of the piezoelectric layer and the electrode layer. When a force is applied to the piezoelectric element in the stacking direction (thickness direction) of the piezoelectric layer and the electrode layer (when the piezoelectric element is compressed), the elastic layer expands in the plane direction, so that shear force is applied to the piezoelectric layer. Works. Thereby, in addition to the pressing force in the thickness direction, a tensile force in the surface direction is applied to the piezoelectric layer, and the distortion of the piezoelectric layer increases. As a result, the amount of charge generated in the piezoelectric layer increases, and the sensitivity (S / N ratio (Signal-Noise Ratio)) and power generation amount in the piezoelectric element are improved.

In the transducer of the present invention, a buffer portion is defined between the exterior material and the piezoelectric element. The buffer unit accommodates at least one of a gas, a non-volatile liquid, and a solid having a smaller elastic modulus than the elastic layer. The buffer portion is arranged in a direction that expands when the piezoelectric element is pressed in the thickness direction. FIG. 1 shows a schematic cross-sectional view of an example of the transducer of the present invention. FIG. 1A shows a state before compression, and FIG. 1B shows a state after compression.

As shown in FIG. 1A, the transducer 10 includes a piezoelectric element 20 and an exterior material 30. The exterior material 30 is made of an elastomer and has a bag shape. The piezoelectric element 20 is accommodated in the exterior material 30. A buffer portion 31 is disposed between the piezoelectric element 20 and the exterior material 30. The buffer portion 3 is disposed so as to surround the side surface of the piezoelectric element 20, in other words, the outer periphery. The buffer 31 contains air. The piezoelectric element 20 includes a piezoelectric layer 21, a pair of electrode layers 22a and 22b, and a pair of elastic layers 23a and 23b. The piezoelectric layer 21 contains an elastomer and piezoelectric particles. The pair of electrode layers 22a and 22b is disposed on each of both surfaces in the thickness direction with the piezoelectric layer 21 interposed therebetween. The elastic body layer 23a is disposed on the upper surface (outside) of the electrode layer 22a. The elastic body layer 23b is disposed on the lower surface (outside) of the electrode layer 22b.

1B, when a load is applied from above the transducer 10, the exterior material 30 is deformed so as to be recessed downward, and the elastic body layer 23a of the piezoelectric element 20 is also pressed. Stretch in the direction. Along with this, the piezoelectric layer 21 and the electrode layers 22a and 22b also expand in the surface direction. Since there is a buffer portion 31 in which air is accommodated in the direction in which the piezoelectric element 20 extends, that is, on the outer peripheral side, even if the piezoelectric element 20 bulges in the outer peripheral direction, the deformation is not easily restricted by the exterior material 30.

As described above, since the buffer portion exists between the exterior material and the piezoelectric element, even when the exterior material has poor flexibility, the expansion deformation of the piezoelectric element is not easily inhibited by the exterior material. Therefore, according to the transducer of the present invention, it is possible to realize both the effect of increasing the amount of generated charges by the elastic layer and the effect of improving the durability by the exterior material.

The transducer of the present invention is suitable as a power generation device because the amount of power generated by the piezoelectric element is large. Moreover, since the sensitivity of the piezoelectric element is high, it is easy to detect a small load. For this reason, the transducer of the present invention is used not only as a power generator, but also as a biological information sensor for measuring a pulse rate or a respiratory rate by being directly disposed on the human skin or indirectly through clothes. Can do.

(2) The power generation system of the present invention includes the above-described transducer of the present invention. For this reason, the power generation amount is large and the durability is excellent. In addition, the transducer can be installed in a wide area with a large area. Therefore, the power generation system of the present invention is suitable for a system that generates power by being embedded in roads, bridges, railroad rails, and the like and pressed by a moving body passing therethrough.

It is a cross-sectional schematic diagram of an example of the transducer of this invention, Comprising: Fig.1 (a) shows the state before compression, FIG.1 (b) shows the state after compression. It is the schematic of the electric power generation system of 1st embodiment. It is thickness direction sectional drawing of the transducer which comprises the power generation system. It is a circuit diagram of the power generation system. It is a permeation | transmission top view of the transducer of 2nd embodiment. It is a permeation | transmission top view of the transducer of 3rd embodiment. It is a permeation | transmission top view of the transducer of 4th embodiment. It is radial direction sectional drawing of the transducer of 5th embodiment.

Hereinafter, embodiments of the transducer and the power generation system of the present invention will be described.

(1) 1st embodiment First, the structure of the transducer and power generation system of 1st embodiment is demonstrated. In FIG. 2, the schematic of the electric power generation system of 1st embodiment is shown. FIG. 3 is a sectional view in the thickness direction of the transducer constituting the power generation system. FIG. 4 shows a circuit diagram of the power generation system. In FIG. 2, the transducer is shown in a top view and is shown through the exterior material for convenience of explanation.

<Power generation system>
As shown in FIG. 2, the power generation system 1 includes a transducer 10 and an electric circuit 40. The transducer 10 is electrically connected to the electric circuit 40 via the wiring 41. In FIG. 4, the electric circuit 40 includes a rectifier circuit 42, a capacitor 43, a switch 44, and a load 45, as indicated by being surrounded by a one-dot chain line. The rectifier circuit 42 converts the AC voltage output from the transducer 10 into a DC voltage. The capacitor 43 stores the rectified power. The electric power stored in the capacitor 43 is supplied to the load 45 via the switch 44. Thus, electrical energy is extracted from the transducer 10 by the electrical circuit 40.

<Transducer>
As illustrated in FIG. 2 and a cross-sectional view in the thickness direction, the transducer 10 includes a piezoelectric element 20 and an exterior material 30. The piezoelectric element 20 has a rectangular sheet shape (indicated by solid line hatching in FIG. 2), and includes five units 24 and six elastic layers 230. The units 24 and the elastic body layers 230 are alternately arranged in the thickness direction (vertical direction).

Each of the five units 24 has a piezoelectric layer and a pair of electrode layers arranged therebetween (electrode layer / piezoelectric layer / electrode layer, not shown). The piezoelectric layer includes an elastomer and piezoelectric particles. The pair of electrode layers includes an elastomer and a conductive material. One pair of electrode layers is disposed on each of both surfaces in the thickness direction (vertical direction) of the piezoelectric layer. That is, the piezoelectric element 20 has five piezoelectric layers, and the piezoelectric layers are stacked via the electrode layers. A wiring 41 is connected to each electrode layer. The electrode layer and the electric circuit 40 are electrically connected by wiring 41.

The six elastic layers 230 are all made of a thermoplastic elastomer and have an elastic modulus of 19 MPa. The six elastic layers 230 are arranged between the upper surface of the uppermost unit 24 and the lower surface of the lowermost unit 24 (that is, the outermost layer of the piezoelectric element 20) and between the adjacent units 24.

The exterior material 30 is composed of an upper sheet and a lower sheet, and has a bag shape by the peripheral edges of both sheets being bonded together (indicated by dotted hatching in FIG. 2). Both the upper sheet and the lower sheet are made of an elastomer having excellent durability and moisture resistance. The piezoelectric element 20 is accommodated in the exterior material 30. An insertion hole for taking out the wiring 41 connected to the transducer 10 is formed in a part of the peripheral portion of the exterior member 30.

A buffer portion 31 is disposed between the piezoelectric element 20 and the exterior material 30. The buffer portion 31 is arranged so as to surround the side surface in the thickness direction of the piezoelectric element 20, in other words, the outer periphery of the piezoelectric element 20. The buffer 31 contains air. That is, there is a gap between the outer periphery of the piezoelectric element 20 and the exterior material 30. The upper and lower surfaces of the piezoelectric element 20 are in contact with the exterior member 30 but are not bonded.

<Effect>
Next, the effect of the transducer and power generation system of the first embodiment will be described. When a load is applied from above the transducer 10, the elastic body layer 230 of the piezoelectric element 20 is pressed and expanded in the surface direction. Then, the unit 24 is also stretched in the surface direction so as to be pulled by the elastic layer 230. At this time, since a tensile force in the surface direction is applied to the piezoelectric layer constituting the unit 24 in addition to the pressing force, the distortion of the piezoelectric layer is increased. Here, on the outer peripheral side of the elastic layer 230 and the unit 24 (piezoelectric element 20), there is a buffer part 31 (gap) in which air is accommodated. Further, the upper and lower surfaces of the piezoelectric element 20 are not bonded to the exterior material 30. Therefore, even if the piezoelectric element 20 bulges in the outer circumferential direction, the deformation is not easily restricted by the exterior material 30. Therefore, a large amount of charge can be generated by the piezoelectric element 20. The piezoelectric element 20 has five units 24. For this reason, compared with the case where the unit 24 is used alone (see FIG. 1 above), the amount of generated charge is larger. Further, the exterior material 30 is made of an elastomer having excellent durability and moisture resistance. Therefore, in the transducer 10, both the effect of increasing the generated charge amount by the elastic layer 230 and the effect of improving the durability by the exterior material 30 are compatible. Further, since the transducer 10 is mainly composed of an elastomer material, the transducer 10 is likely to have a large area and can be easily disposed in a place having a complicated shape such as a curved surface.

(2) Second Embodiment The transducer and power generation system of the present embodiment are different from those of the first embodiment only in the shape and arrangement of the piezoelectric elements constituting the transducer. Therefore, the difference will be mainly described here. FIG. 5 shows a transparent top view of the transducer of this embodiment. FIG. 5 corresponds to the transducer shown in FIG. In FIG. 5, members corresponding to those in FIG.

As shown in FIG. 5, the transducer 10 includes five piezoelectric elements 20 and an exterior material 30. Each of the five piezoelectric elements 20 has a strip shape (indicated by solid line hatching in FIG. 5). The five piezoelectric elements 20 are arranged in parallel with each other at a predetermined interval in the short direction. The outer periphery of each piezoelectric element 20 is surrounded by an exterior material 30 with a buffer portion 31 therebetween. That is, the exterior material 30 is stuck not only at the peripheral portion but also between the adjacent piezoelectric elements 20 (indicated by dotted hatching in FIG. 5). The buffer portion 31 is disposed between the piezoelectric element 20 and the exterior material 30, that is, so as to surround the outer periphery of the piezoelectric element 20. The buffer 31 contains air. The configuration of each piezoelectric element 20 is the same as the configuration of the piezoelectric element 20 of the first embodiment (see FIG. 3 above).

In the present embodiment, a plurality of piezoelectric elements 20 are arranged in the exterior material 30. Thereby, the freedom degree of a shape improves, for example, it is possible to generate electricity only at a place where it is desired to generate electricity, or to thin out a piezoelectric element according to the application, thereby improving flexibility. Further, when the transducer 10 of the present embodiment is used as a sensor, it becomes easy to specify the place where the load is applied.

(3) Third Embodiment The transducer and power generation system of the present embodiment are different from those of the second embodiment only in the length of a part of the piezoelectric elements constituting the transducer. Therefore, the difference will be mainly described here. FIG. 6 is a transparent top view of the transducer of this embodiment. FIG. 6 corresponds to FIG. In FIG. 6, members corresponding to those in FIG.

As shown in FIG. 6, the transducer 10 includes five piezoelectric elements 20 and an exterior material 30. Each of the five piezoelectric elements 20 has a band shape and is different only in length (indicated by solid hatching in FIG. 5). That is, the three left piezoelectric elements 20 as viewed from above are shorter than the two right piezoelectric elements 20. The five piezoelectric elements 20 are arranged in parallel with each other at a predetermined interval in the short direction. The outer periphery of each piezoelectric element 20 is surrounded by an exterior material 30 with a buffer portion 31 therebetween.

(4) Fourth Embodiment The transducer and power generation system of the present embodiment are different from those of the second embodiment only in the number and arrangement of piezoelectric elements constituting the transducer. Therefore, the difference will be mainly described here. FIG. 7 shows a transparent top view of the transducer of this embodiment. FIG. 7 corresponds to FIG. In FIG. 7, members corresponding to those in FIG.

As shown in FIG. 7, the transducer 10 includes ten piezoelectric elements 200 to 209 and an exterior material 30. Each of the ten piezoelectric elements 200 to 209 has a strip shape (indicated by solid line hatching in FIG. 7). The ten piezoelectric elements 200 to 209 are arranged in two upper and lower two layers. The upper five piezoelectric elements 200 to 204 extend in the front-rear direction, and are arranged in parallel to each other at a predetermined interval in the left-right direction. The lower five piezoelectric elements 205 to 209 extend in the left-right direction, and are arranged in parallel to each other at a predetermined interval in the front-rear direction. When viewed from above, the upper five piezoelectric elements 200 to 204 and the lower five piezoelectric elements 205 to 209 are arranged in a lattice pattern. The electrode layers in the piezoelectric elements 200 to 209 and the electric circuit 40 are electrically connected by wirings 410 and 411.

The exterior material 30 is partially attached not only to the peripheral portion but also to a section where the piezoelectric elements 200 to 209 are not arranged (indicated by dotted line hatching in FIG. 7). The buffer portion 31 is disposed between the piezoelectric elements 200 to 209 and the exterior material 30. The buffer 31 contains air. The configuration of each of the piezoelectric elements 200 to 209 is the same as the configuration of the piezoelectric element 20 of the first embodiment (see FIG. 3 above).

In the present embodiment, a plurality of piezoelectric elements 20 are arranged in two stages in the exterior material 30. Thereby, power generation amount becomes larger. In addition, it is possible to improve the flexibility by generating power only at a place where power generation is desired or by thinning out the piezoelectric element according to the application. In addition, when the transducer 10 of the present embodiment is used as a sensor, it is possible to increase the detection area in addition to facilitating identification of a place where a load is applied.

(5) Fifth Embodiment The transducer and power generation system of this embodiment are different from those of the first embodiment only in the usage pattern of the transducer. Therefore, the difference will be mainly described here. FIG. 8 shows a radial cross-sectional view of the transducer of this embodiment. In FIG. 8, members corresponding to those in FIG.

As shown in FIG. 8, the transducer 10 is obtained by winding the sheet-like transducer 10 of the first embodiment toward one end of the sheet-like transducer 10 toward the other end. When the radial cross section of the transducer 10 is viewed, the piezoelectric element 20 has a spiral shape in which six layers are stacked in the radial direction. According to the present embodiment, it is possible to realize a form in which a large number of piezoelectric elements 20 are stacked by simply manufacturing the transducer 10 in a sheet shape as in the first embodiment and winding it. Therefore, when a load is applied from the radial direction of the transducer 10, a larger amount of power generation can be obtained. Further, according to the present embodiment, the present invention can be applied to a place where it is difficult to arrange a sheet-like transducer.

(6) Other Embodiments The transducer and the power generation system of the present invention are not limited to the above-described embodiments, and various modifications and improvements that can be made by those skilled in the art without departing from the gist of the present invention. It can be implemented in the form.

For example, in the above-described embodiment, the power generation system is configured from one transducer and an electric circuit, but a power generation system may be configured by connecting a plurality of stacked transducers to the electric circuit. In the above embodiment, the transducer is used as a power generation device, but the transducer of the present invention may be used as a sensor. When used as a sensor, a small load is easy to detect because the S / N ratio is high. The components of the transducer of the present invention will be described in detail below.

<Piezoelectric element>
The piezoelectric element includes a piezoelectric layer including an elastomer and piezoelectric particles, an electrode layer disposed with the piezoelectric layer interposed therebetween, and an elastic layer disposed at least on the outermost layer. The number of piezoelectric layers may be one layer or two or more layers. From the viewpoint of increasing the amount of power generation, it is desirable that a plurality of, for example, several tens to several hundreds of piezoelectric layers are laminated via the electrode layers. The elastic body layer may be disposed at least in the outermost layer. However, as shown in the above embodiment, when a plurality of piezoelectric layers are stacked via electrode layers, they may be disposed between adjacent electrode layers in the middle of the stacked body. That is, an elastic body layer may be disposed between units including a piezoelectric layer and an electrode layer sandwiching the piezoelectric layer. In this case, the power generation amount can be further increased. In the fifth embodiment, an embodiment is shown in which one piezoelectric element is wound and used together with an exterior material. However, only a piezoelectric element may be wound and accommodated in a tubular exterior material.

[Piezoelectric layer]
As the elastomer constituting the piezoelectric layer, one or more selected from crosslinked rubber and thermoplastic elastomer may be used. Relatively small and flexible elastomers such as urethane rubber, silicone rubber, nitrile rubber (NBR), hydrogenated nitrile rubber (H-NBR), acrylic rubber, natural rubber, isoprene rubber, ethylene-propylene-diene rubber (EPDM) Ethylene-vinyl acetate copolymer, ethylene-vinyl acetate-acrylic ester copolymer, butyl rubber, styrene-butadiene rubber, fluororubber, epichlorohydrin rubber, chloroprene rubber, chlorinated polyethylene, chlorosulfonated polyethylene, and the like. Further, an elastomer modified by introducing a functional group or the like may be used. Examples of the modified elastomer include carboxyl group-modified nitrile rubber (X-NBR), carboxyl group-modified hydrogenated nitrile rubber (XH-NBR), and the like.

The generated charge amount (C) generated when a load is applied to the piezoelectric layer is expressed by the following equation (a) by the piezoelectric strain constant (C / N) of the piezoelectric layer and the applied load (N).
Generated charge amount = piezoelectric strain constant × load (a)
Piezoelectric particles are particles of a compound having piezoelectricity. Ferroelectric materials having a perovskite crystal structure are known as piezoelectric compounds, for example, barium titanate, strontium titanate, potassium niobate, sodium niobate, lithium niobate, potassium sodium niobate , Potassium sodium niobate, lead zirconate titanate (PZT), barium strontium titanate (BST), bismuth lanthanum titanate (BLT), bismuth strontium tantalate (SBT), and the like. As the piezoelectric particles, one or more of these may be used.

The particle size of the piezoelectric particles is not particularly limited. For example, when a plurality of types of piezoelectric particle powders having different average particle sizes are used, a large particle size piezoelectric particle and a small particle size piezoelectric particle can be mixed in the elastomer. In this case, piezoelectric particles having a small particle diameter enter between piezoelectric particles having a large particle diameter, and pressure is easily transmitted to the piezoelectric particles. As a result, the piezoelectric strain constant of the piezoelectric layer is increased, and the amount of generated charges can be increased.

The blending amount of the piezoelectric particles may be determined by taking into account the flexibility of the piezoelectric layer, and thus the piezoelectric element, and the piezoelectric performance of the piezoelectric layer. When the amount of the piezoelectric particles is increased, the piezoelectric performance of the piezoelectric layer is improved, but the flexibility is lowered. Therefore, it is desirable to adjust the blending amount of the piezoelectric particles so that desired flexibility can be realized in the combination of the elastomer and the piezoelectric particles to be used.

The piezoelectric layer may contain reinforcing particles having a relative dielectric constant smaller than that of the piezoelectric particles, in addition to the elastomer and the piezoelectric particles. The relative permittivity of the reinforcing particles is preferably 100 or less, and more preferably 30 or less, on condition that the relative permittivity of the reinforcement particles is smaller than that of the piezoelectric particles.

Since the structure in which piezoelectric particles having a large relative dielectric constant are connected is easy to transmit external force to the piezoelectric particles, an improvement in the piezoelectric strain constant of the formula (a) described above can be expected. However, when the piezoelectric particles having a large relative dielectric constant are connected, the dielectric constant of the entire piezoelectric layer is increased. On the other hand, when both the piezoelectric particles and the reinforcing particles are included in the piezoelectric layer, the connection between the piezoelectric particles having a large relative dielectric constant is divided by the intervening reinforcing particles having a smaller relative dielectric constant. Thereby, the raise of the dielectric constant as the whole piezoelectric layer can be suppressed. On the other hand, since the connection structure of the particles is maintained by the reinforcing particles and the piezoelectric particles, the piezoelectric strain constant can be maintained. That is, when the reinforcing particles are included in the piezoelectric layer, the dielectric constant of the entire piezoelectric layer can be made smaller than when only the piezoelectric particles are included while maintaining the piezoelectric strain constant. Therefore, a large amount of generated charge can be obtained by the above-described formula (a).

As the reinforcing particles, particles having a large electric resistance are desirable. When the electrical resistance of the reinforcing particles is large, the dielectric breakdown strength of the piezoelectric layer is increased. Thereby, in the polarization process of the piezoelectric layer which will be described later, the processing time can be shortened by applying a high electric field. In addition, since the number of piezoelectric elements that are destroyed during the polarization process can be reduced, productivity is improved.

Also, it is desirable that the reinforcing particles are chemically bonded to the elastomer. In this case, since a network of reinforcing particles is formed in the elastomer, impurity ions obtained by ionizing a crosslinking agent, an additive, moisture in the air, and the like are difficult to move, and the electric resistance of the piezoelectric layer is increased. The chemical bond between the reinforcing particles and the elastomer can be realized, for example, by surface-treating the reinforcing particles. As a surface treatment method, a surface treatment agent having a functional group capable of reacting with an elastomer polymer is reacted with the reinforcing particles in advance, and the reinforcing particles are mixed with the elastomer polymer. Or the method of mixing with the elastomer polymer which has a functional group which can react with a hydroxyl group after melt | dissolving with subcritical water and producing | generating a hydroxyl group etc. is mentioned. When the reinforcing particles are chemically bonded to the elastomer, the reinforcing particles are unlikely to be displaced even if the expansion and contraction are repeated. Further, since the reinforcing particles are difficult to peel off from the elastomer, fluctuations from the initial values of physical properties and output are reduced. Therefore, the output is stabilized and the sag resistance of the piezoelectric layer is improved. In addition, since the elongation at break of the piezoelectric layer is increased, it is possible to suppress a decrease in piezoelectric performance due to local fracture during expansion. As a result, high piezoelectric performance can be maintained even in an extended state.

The type of reinforcing particles is not particularly limited. For example, particles such as oxides such as titanium dioxide, silica, and barium titanate, rubber, and resin can be used. However, when relatively soft particles such as rubber particles are included, the applied load may be attenuated by the resin particles and may not be transmitted to the piezoelectric particles. From the viewpoint of facilitating the transmission of force to the piezoelectric particles, increasing the piezoelectric strain constant of the piezoelectric layer in the above-described formula (a), and increasing the amount of generated charges, the reinforcing particles are more elastic than the matrix elastomer. It is better to use large particles. For example, metal oxide particles such as titanium dioxide are preferable because they have a small relative dielectric constant and a large effect of improving dielectric breakdown resistance. As a method for producing metal oxide particles, a sol-gel method is preferable because particles having low crystallinity and a low relative dielectric constant can be obtained.

The piezoelectric layer is manufactured by curing a composition obtained by adding a powder of a piezoelectric particle or a crosslinking agent to an elastomer polymer under predetermined conditions. Thereafter, the piezoelectric layer is subjected to polarization treatment. That is, a voltage is applied to the piezoelectric layer to align the polarization direction of the piezoelectric particles in a predetermined direction.

[Electrode layer]
What is necessary is just to arrange | position an electrode layer so as to oppose the polarization direction of a piezoelectric particle. The electrode layer may be formed on the entire surface of the piezoelectric layer, or may be formed on only a part. The electrode layer is desirably deformable following the piezoelectric layer. The flexible electrode layer can be formed from, for example, a conductive material in which a conductive material is blended with a binder, conductive fibers, or the like. As the binder, it is desirable to use at least one selected from elastomers, that is, crosslinked rubber and thermoplastic elastomer. Examples of the elastomer having a relatively small elastic modulus and good adhesion to the piezoelectric layer include acrylic rubber, silicone rubber, urethane rubber, urea rubber, fluorine rubber, and H-NBR. Moreover, you may use the elastomer modified | denatured by introduce | transducing a functional group like an epoxy group modified acrylic rubber, a carboxyl group modified hydrogenated nitrile rubber, etc.

The type of conductive material is not particularly limited. For example, metal particles made of silver, gold, copper, nickel, rhodium, palladium, chromium, titanium, platinum, iron, and alloys thereof, metal oxide particles made of zinc oxide, titanium oxide, etc., titanium carbonate, etc. What is necessary is just to select suitably from electroconductive carbon materials, such as metal nanowire which consists of metal carbide particles, silver, gold | metal | money, copper, platinum, nickel, etc., carbon black, a carbon nanotube, graphite, thin-layer graphite, and graphene. Alternatively, particles coated with a metal such as silver-coated copper particles may be used. As the conductive material, one of these can be used alone, or two or more can be mixed and used.

The blending amount of the conductive material may be appropriately determined so that the electrode layer can achieve a desired volume resistivity. When the amount of the conductive material is increased, the volume resistivity of the electrode layer can be reduced, but the flexibility is lowered. The electrode layer may contain a crosslinking agent, a crosslinking accelerator, a dispersant, a reinforcing material, a plasticizer, an antiaging agent, a coloring agent, and the like as other components.

For example, when an elastomer is used as a binder, a conductive paint is prepared by adding a conductive material and, if necessary, an additive to a polymer solution obtained by dissolving the polymer for the elastomer in a solvent, and stirring and mixing. Can do. The electrode layer may be formed by directly applying the prepared conductive paint to one surface of the piezoelectric layer. Alternatively, an electrode layer may be formed by applying a conductive paint to the releasable film, and the formed electrode layer may be transferred to one surface of the piezoelectric layer.

The volume resistivity of the electrode layer is desirably 100 Ω · cm or less both in the natural state and in the stretched state from the stretched state to 10% in the uniaxial direction. More preferably, it is 10 Ω · cm or less. This is because when the electrical resistance of the electrode layer is large or the electrical resistance is increased due to stretching, the electromotive voltage generated in the piezoelectric layer drops at the electrode layer, and the output voltage becomes small. The natural state means a state in which a load is not applied and is not deformed (no load state). The state of 10% extension in the uniaxial direction means a state in which the length in the uniaxial direction is 1.1 times the natural state. In the present invention, the volume resistivity of the electrode is measured in both a natural state and a state in which the electrode is stretched by 10% in the uniaxial direction. If any volume resistivity is 100 Ω · cm or less, the “natural state and then the uniaxial direction” It is determined that the condition that the volume resistivity of the stretched state until reaching the stretched state by 10% is 100 Ω · cm or less ”is satisfied. In addition, it cannot be overemphasized that the piezoelectric element in this invention can expand | extend not only to a uniaxial direction but to a biaxial direction, a diameter expansion direction.

From the viewpoint of making the piezoelectric element flexible, the breaking elongation of a unit (electrode layer / piezoelectric layer / electrode layer) composed of a piezoelectric layer and a pair of electrode layers disposed therebetween is 10% or more. It is desirable. More preferably, it is 30% or more. In this specification, elongation at break is a value of elongation at break measured by a tensile test specified in JIS K6251: 2010 regardless of the form of a single layer, a unit, or the like. The tensile test is performed using a dumbbell-shaped No. 5 test piece and a tensile speed of 100 mm / min.

[Elastic layer]
The elastic layer may be arranged so as to cover the outermost electrode layer, for example. When the elastic body layer is disposed, the elastic body layer expands in the surface direction, whereby a shearing force can be applied to the piezoelectric layer. Thereby, in addition to the pressing force in the stacking direction, a tensile force in the surface direction is applied to the piezoelectric layer, and the distortion in the surface direction of the piezoelectric layer increases. As the strain in the surface direction of the piezoelectric layer increases, the amount of generated charge increases. As a result, the sensitivity of the piezoelectric element is improved and the amount of power generation is increased.

The effect of increasing the generated charge amount by the elastic layer is more remarkable as the elastic modulus in the stretching direction of the elastic layer is smaller. For example, the elastic modulus of the elastic body layer is desirably 50 MPa or less. Further, in order to prevent the elastic layer from breaking and the piezoelectric element from being broken when stretched, it is desirable that the breaking elongation of the elastic layer is larger than the breaking elongation of the piezoelectric layer. In this specification, the elastic modulus is a value calculated from a stress-elongation curve obtained by a tensile test specified in JIS K7127: 1999. The tensile test is performed using a test piece type 2 test piece and a tensile speed of 100 mm / min.

Desirably, the elastic layer is made of an elastomer. In other words, the elastic layer may be one or more selected from a crosslinked rubber and a thermoplastic elastomer. Elastomers with relatively low elastic modulus and good adhesion to the electrode layer include natural rubber, isoprene rubber, butyl rubber, acrylic rubber, silicone rubber, urethane rubber, urea rubber, fluoro rubber, NBR, thermoplastic polyurethane, heat Examples thereof include plastic polyester. In particular, thermoplastic polyurethane can be firmly bonded to the electrode layer and the piezoelectric layer by being heated and temporarily melted. By firmly adhering the elastic body layer, a decrease in sensitivity can be reduced when the elastic layer is stretched by repeated strain.

The Poisson's ratio of the elastomer is about 0.5. For this reason, in the elastic body layer made of elastomer, the force applied in the thickness direction acts as the force in the surface direction as it is. For this reason, the greater the thickness of the elastic layer, the greater the effect of increasing the distortion of the piezoelectric layer and the greater the effect of increasing the amount of generated charge. On the other hand, when the thickness of the elastic layer is increased, the piezoelectric element is increased, and thus the power generation amount per unit volume may be decreased. For this reason, the thickness per elastic layer is preferably 5 μm or more and 1000 μm or less, for example.

<Exterior material>
The characteristics required of the exterior material that accommodates the piezoelectric element include durability against repeated loads, water resistance, moisture resistance, flame resistance, and the like, and varies depending on the application of the transducer. Therefore, the material of the exterior material may be appropriately determined according to the use of the transducer.

For example, in the form of being embedded in a road or used on a road, in addition to durability, water resistance, moisture resistance, ozone resistance and the like are required. In this case, butyl rubber, silicone rubber, NBR, H-NBR, acrylic rubber, natural rubber, isoprene rubber, EPDM and the like are suitable as the material for the exterior material. Examples of butyl rubber include regular butyl rubber, chlorinated butyl rubber, and brominated butyl rubber. One kind of these may be used alone, or two or more kinds may be mixed and used. Moreover, in order to suppress the permeation | transmission of a water | moisture content, you may mix | blend low moisture-permeable materials, such as a talc, clay, a montmorillonite, and a synthetic smectite. What is necessary is just to adjust suitably addition of fillers, such as a low moisture-permeable material, according to the place which arrange | positions a transducer. For example, when embedded in a road, the water resistance, moisture resistance, and ozone resistance do not have to be so high as compared with the case of being placed on the road. On the other hand, if it is placed under a hard object such as concrete, it is difficult to apply force to the piezoelectric element, so it is necessary to increase sensitivity. In this case, it is necessary to take measures such as increasing the flexibility by reducing the amount of filler for improving durability. When placed on the road, conditions such as water and ozone become stricter rather than giving priority to sensitivity because it is close to the load source.

Depending on the material of the exterior material, part or all of the surface of the piezoelectric element (the surface extending in the extension direction) may be bonded to the exterior material. However, in order to prevent deformation of the piezoelectric element as much as possible, it is desirable that the surface of the piezoelectric element and the exterior material are not bonded. The exterior material may be one that seals the inside, or may have a communication hole through which the contents of the buffer portion can move between the inside and the outside. Moreover, you may provide the bag part which can accommodate the accommodation of a buffer part temporarily in the exterior of an exterior material.

<Buffer part>
Between the exterior material and the piezoelectric element in the direction in which the piezoelectric element expands due to the pressing, a buffer portion that stores at least one of gas, a non-volatile liquid, and a solid having a smaller elastic modulus than the elastic layer is defined. The Examples of the gas include air and inert gases such as nitrogen and argon. Examples of the non-volatile liquid include process oil and ionic liquid. Examples of the solid include elastomers and foams having a smaller elastic modulus than the elastic layer.

Next, the present invention will be described more specifically with reference to examples. A piezoelectric layer, an electrode layer, an elastic body layer, and an exterior material were manufactured, and these were appropriately combined to manufacture a transducer, and its sensitivity, generated charge amount, and durability were evaluated.

<Manufacture of piezoelectric layer>
[Piezoelectric layer 1]
First, 100 parts by mass of a carboxyl group-modified hydrogenated nitrile rubber polymer (“Terban (registered trademark) XT8889” manufactured by LANXESS) as an elastomer was dissolved in acetylacetone to prepare a polymer solution. Next, a powder of potassium sodium niobate ((K _0.5 Na _0.5 Nb _1.0 ) O ₃ ) as piezoelectric particles (d50% particle diameter (median diameter): 3 μm) 385 is added to the prepared polymer solution. A part by mass was added and kneaded. Subsequently, the kneaded material was repeatedly passed through three rolls five times to obtain a slurry. Then, 5 parts by mass of tetrakis (2-ethylhexyloxy) titanium as a cross-linking agent was added to the obtained slurry and kneaded with an air stirrer, and then the slurry was applied onto a substrate by a bar coating method. This was heated at 150 ° C. for 1 hour to produce a piezoelectric layer 1 having a thickness of 0.06 mm (60 μm). The content of the piezoelectric particles in the piezoelectric layer 1 is 42% by volume when the elastomer is 100% by volume. The breaking elongation of the piezoelectric layer 1 was 320%.

The used potassium sodium niobate powder was produced by the following steps.
(1) First mixing step K ₂ CO ₃ , Na ₂ CO ₃ , and Nb ₂ O ₅ powder were used as raw materials. These powders were weighed based on the composition of the desired sintered body (K _0.5 Na _0.5 Nb _1.0 ) O ₃ and then wet mixed in anhydrous acetone for 16 hours. The obtained mixed powder was evaporated and further dried in an oven to volatilize acetone.
(2) Pre-baking process The mixed powder after volatilizing acetone was put in the alumina crucible, and the crucible was put in a large crucible once. The inner crucible was placed face down so as to cover the mixed powder. This double crucible was put in an electric furnace and pre-baked at 910 ° C. for 10 hours.
(3) Second mixing step After the obtained calcined product was pulverized into a powder in a mortar, this powder was wet mixed in anhydrous acetone for 16 hours. The obtained mixed powder was evaporated and further dried in an oven to volatilize acetone.
(4) Main firing step The mixed powder after volatilizing acetone is put into a double crucible in the same manner as in (2), followed by firing at 150 ° C for 1 hour, 550 ° C for 3 hours, and 1098 ° C for 2 hours. went.
(5) Pulverization process The obtained fired product was pulverized into single particles by a ball mill.
(6) Classification process The obtained powder is mixed with methyl ethyl ketone, classified with a centrifuge ("CR22G" manufactured by Hitachi Koki Co., Ltd.), separated by decantation, dried, and niobic acid. Sodium potassium single particle powder was obtained.

[Piezoelectric layer 2]
A piezoelectric layer 2 was produced in the same manner as the piezoelectric layer 1 except that the blending amount of the piezoelectric particles with respect to the elastomer was changed to 840 parts by mass. The piezoelectric particle content in the piezoelectric layer 2 is 67.7% by volume when the elastomer is 100% by volume. The elongation at break of the piezoelectric layer 2 was 5%.

<Manufacture of electrode layer>
[Electrode layer 1]
First, three monomers of ethyl acrylate (EA), acrylonitrile (AN), and allyl glycidyl ether (AGE) were subjected to suspension polymerization to produce a glycidyl ether group-modified acrylic rubber polymer as an elastomer. The blending ratio of the monomers was 96 mass% EA, 2 mass% AN, and 2 mass% AGE. Next, 68 parts by mass of a glycidyl ether group-modified acrylic rubber polymer is dissolved in butyl cellosolve acetate. In this polymer solution, 35 parts by mass of a conductive material, 25 parts by mass of a dispersant, 6 parts by mass of a crosslinking agent, and crosslinking acceleration are added. A liquid composition was prepared by adding 1 part by mass of an agent (details of raw materials such as a conductive material will be described later). Subsequently, the liquid composition was pulverized by a wet jet mill (“Nanovaita (registered trademark)” manufactured by Yoshida Kikai Kogyo Co., Ltd.). The pulverization process was performed a total of 6 times by the pass operation (6-pass process). The first pass was performed with a straight nozzle (nozzle diameter 170 μm) and a processing pressure of 90 MPa, and the second and subsequent passes were performed with a cross-type nozzle (nozzle diameter 170 μm) and a processing pressure of 130 MPa. The liquid composition after the pulverization treatment was applied to a release-treated polyethylene terephthalate (PET) film by a bar coating method. This was heated at 150 ° C. for 2 hours to produce an electrode layer 1 having a thickness of 0.015 mm (15 μm). The breaking elongation of the electrode layer 1 was 320%, the volume resistivity in the natural state was 0.05 Ω · cm, and the volume resistivity in the 10% stretched state was 0.1 Ω · cm. The volume resistivity of the electrode layer 1 in the natural state and 10% stretched state was measured with a resistivity meter (“Loresta (registered trademark) GP” manufactured by Mitsubishi Chemical Analytech Co., Ltd.) (hereinafter, the same applies to the electrode layer 2). ).

The details of the raw materials used for preparing the liquid composition are as follows.
Conductive material: Thin-layer graphite, “iGurafen-α” manufactured by ITEC.
Dispersant: High molecular weight polyester acid amidoamine salt, Enomoto Kasei Co., Ltd. “Disparon (registered trademark) DA7301”.
Cross-linking agent: amino-terminated butadiene-acrylonitrile copolymer, CVC Thermoset Specialties Ltd. “ATBN1300 × 16”.
Cross-linking accelerator: zinc complex, KING INDUSTRIES, INC “XK-614”.

[Electrode layer 2]
A conductive silver paste (“DW250-H-5” manufactured by Toyobo Co., Ltd.) was applied to the release-treated PET film by a bar coating method. This was heated at 150 ° C. for 1 hour to produce an electrode layer 2 having a thickness of 0.015 mm (15 μm). The elongation at break of the electrode layer 2 was 4%, the volume resistivity in the natural state was 0.0002 Ω · cm, and the volume resistivity in the 10% stretched state could not be measured due to the break.

<Elastic body layer>
[Elastic body layer 1]
A thermoplastic polyether-based polyurethane sheet (“Esmer (registered trademark) URS” manufactured by Nippon Matai Co., Ltd., thickness 0.25 mm) was used as the elastic layer 1. The elastic body layer 1 had an elongation at break of 600% and an elastic modulus of 23 MPa.

[Elastic body layer 2]
A thermoplastic polyester elastomer (“Hytrel (registered trademark) 3046” manufactured by Toray DuPont Co., Ltd.) was molded into a sheet shape having a thickness of 0.18 mm (180 μm) to obtain an elastic body layer 2. The elastic body layer 2 had an elongation at break of 550% and an elastic modulus of 19 MPa.

[Elastic body layer 3]
A thermoplastic polyester elastomer (“Hytrel 4047” manufactured by Toray DuPont Co., Ltd.) was molded into a sheet shape having a thickness of 0.18 mm (180 μm) to obtain an elastic body layer 3. The elastic body layer 3 had an elongation at break of 500% and an elastic modulus of 46 MPa.

[Elastic body layer 4]
A polyester film (“Diafoil (registered trademark)” manufactured by Mitsubishi Chemical Corporation, thickness 0.1 mm (100 μm)) was used as the elastic body layer 4. The elastic body layer 4 had an elongation at break of 90% and an elastic modulus of 1500 MPa.

<Exterior material>
First, 90 parts by mass of chlorinated butyl rubber (“HT1066” manufactured by JSR Corp.), 10 parts by mass of regular butyl rubber (“JSR butyl 365” manufactured by JSR Corp.), and polyacrylate powder (( 150 parts by mass “Aquaric (registered trademark) CS-S6” manufactured by Nippon Shokubai Co., Ltd., an average particle size of 15 μm), 5 parts by mass of zinc oxide as a crosslinking assistant, and “Tacchiroll” manufactured by Taoka Chemical Industry Co., Ltd. (Registered trademark) 201 ") 10 parts by mass and 200 parts by mass of talc (" Microace (registered trademark) K-1 "manufactured by Nippon Talc Co., Ltd.) were kneaded with a roll to prepare a masterbatch. Next, the masterbatch was dissolved in toluene to prepare a paint. And after applying the prepared coating material to a base material and drying a coating film, it heated at 150 degreeC for 20 minute (s), and was hardened. The obtained sheet was used as an exterior material. The obtained sheet had an elastic modulus of 60 MPa and an elongation at break of 60%.

<Manufacture of transducer>
A laminated body was manufactured by appropriately combining the manufactured piezoelectric layer, electrode layer, and elastic body layer, and was housed in an exterior material to manufacture a transducer. The laminate was manufactured as follows. First, electrode layers were respectively arranged on two surfaces (upper surface and lower surface) in the thickness direction of the piezoelectric layer, and the piezoelectric layer and the electrode layer were pressure-bonded using a laminator (“LPD3223” manufactured by Fuji Pla Co., Ltd.). Next, the elastic layer is laminated on the upper electrode layer, or both upper and lower electrode layers, and the elastic layer is softened by applying an iron to the surface of the elastic layer to soften the elastic layer. I let you. In the former case, the structure of the laminated body is “elastic layer / unit (electrode layer / piezoelectric layer / electrode layer)” (hereinafter referred to as “first laminated body”), and in the latter case, the structure of the laminated body. Becomes “elastic layer / unit (electrode layer / piezoelectric layer / electrode layer) / elastic layer” (hereinafter referred to as “second laminate”). All the laminates have a square thin plate shape with a length of 30 mm and a width of 30 mm. A direct current power source was connected to the electrode layer of the laminate, and an electric field of 20 V / μm was applied to the piezoelectric layer for 5 minutes to perform polarization treatment. Then, the aging process was performed by holding at 120 ° C. for 30 minutes.

[Example 1]
A transducer was manufactured by combining the first laminated body using the piezoelectric layer 1, the electrode layer 1, and the elastic body layer 1 with the second laminated body. First, four first laminates were stacked, and one second stack was further stacked to manufacture a piezoelectric element composed of a total of five laminates. The structure of the manufactured piezoelectric element (laminated structure of each layer) is the same as that of the transducer of the first embodiment (see FIG. 3 above).

A square-shaped exterior material sheet having a length of 40 mm and a width of 40 mm was placed on two surfaces (upper surface and lower surface) of the piezoelectric element in the thickness direction so that the centers of the surfaces coincided. And the peripheral part from 1 mm to 2 mm from the outer periphery of an exterior material sheet | seat was welded with the techno impulse clip sealer Z1. In this manner, a frame-shaped buffer portion having a width of 4 mm was defined between the piezoelectric element and the exterior material sheet in the diameter expansion direction of the piezoelectric element. Air is accommodated in the buffer portion. The manufactured transducer is referred to as the transducer of Example 1.

[Example 2]
A piezoelectric element is composed only of the second laminated body (elastic body layer 1 / electrode layer 1 / piezoelectric layer 1 / electrode layer 1 / elastic body layer 1) using the piezoelectric layer 1, the electrode layer 1, and the elastic body layer 1. Except for this point, a transducer was manufactured in the same manner as in Example 1. The manufactured transducer is referred to as the transducer of Example 1.

[Example 3]
A transducer was manufactured in the same manner as in Example 1 except that an elastic body was accommodated in the buffer portion instead of air. A silicone rubber sheet (“KE1950-10” manufactured by Shin-Etsu Chemical Co., Ltd., elastic modulus 0.4 MPa) was used as the elastic body. The method of accommodating the elastic body in the buffer portion is as follows. First, a square silicone rubber sheet having a length of 35 mm and a width of 35 mm was prepared, and a central portion thereof was cut into a square shape having a length of 30 mm and a width of 30 mm. Next, a piezoelectric element was disposed in the cut-out portion of the silicone rubber sheet, and the outer periphery of the piezoelectric element was surrounded by silicone rubber. In this state, square-shaped exterior material sheets each having a length of 40 mm and a width of 40 mm were arranged on two surfaces in the thickness direction of the piezoelectric element so that the centers of the surfaces coincided with each other. And the peripheral part from 4 mm to 5 mm from the outer periphery of an exterior material sheet | seat was welded with the techno impulse clip sealer Z1. In this manner, a frame-shaped buffer portion having a width of 5 mm in which silicone rubber was accommodated was defined between the piezoelectric element and the exterior material sheet in the diameter expansion direction of the piezoelectric element. The manufactured transducer is referred to as the transducer of Example 3.

[Example 4]
A transducer was manufactured in the same manner as in Example 1 except that the elastic layer of the piezoelectric element was changed to the elastic layer 2. The manufactured transducer is referred to as the transducer of Example 4.

[Example 5]
A transducer was manufactured in the same manner as in Example 1 except that the elastic layer of the piezoelectric element was changed to the elastic layer 3. The manufactured transducer is referred to as the transducer of Example 5.

[Example 6]
A transducer was manufactured in the same manner as in Example 1 except that the entire two surfaces (upper surface and lower surface) in the thickness direction of the piezoelectric element were bonded to the exterior material. First, a square-shaped exterior material sheet having a length of 40 mm and a width of 40 mm is attached to a square-shaped adhesive sheet having a length of 30 mm and a width of 30 mm (“Elfan (registered trademark) UH370” manufactured by Nippon Matai Co., Ltd.) on each surface. They were pasted so that the centers coincided. Next, the laminated sheets were arranged one by one on two surfaces in the thickness direction of the piezoelectric element so that the centers of the surfaces coincided with each other. And the piezoelectric element and the exterior material were adhere | attached through the adhesive sheet by heating the surface of the lamination sheet corresponding to the part of an adhesive sheet with an iron. Then, the peripheral part from 1 mm to 2 mm from the outer periphery of the exterior material sheet was welded with a techno impulse clip sealer Z1. In this manner, a frame-shaped buffer portion having a width of 4 mm was defined between the piezoelectric element and the exterior material sheet in the diameter expansion direction of the piezoelectric element. Air is accommodated in the buffer portion. The manufactured transducer is referred to as the transducer of Example 6.

[Example 7]
A transducer was manufactured in the same manner as in Example 6 except that the size of the adhesive sheet was changed to 5 mm in length and 5 mm in width. The manufactured transducer is referred to as the transducer of Example 7. In the transducer of Example 7, a part (5 mm square) of two surfaces (upper surface and lower surface) in the thickness direction of the piezoelectric element is bonded to the exterior material.

[Comparative Example 1]
A transducer was manufactured in the same manner as in Example 6 except that the size of the adhesive sheet was changed to 40 mm in length and 40 mm in width as the size of the exterior material. The manufactured transducer is referred to as the transducer of Comparative Example 1. In the transducer of Comparative Example 1, the entire two surfaces (upper surface and lower surface) in the thickness direction of the piezoelectric element are bonded to the exterior material. Further, since the peripheral portion of the exterior material that is not laminated with the piezoelectric element is also bonded via the adhesive sheet, the buffer portion is partitioned between the piezoelectric element and the exterior material sheet in the diameter expansion direction of the piezoelectric element. Not.

[Comparative Example 2]
A transducer was manufactured in the same manner as in Example 3 except that the type of the elastic body was changed to a polyester film ("Diafoil (registered trademark)" manufactured by Mitsubishi Chemical Corporation, elastic modulus 1500 MPa). The manufactured transducer is referred to as the transducer of Comparative Example 2.

[Comparative Example 3]
A transducer was manufactured in the same manner as in Example 1 except that no exterior material was used. The manufactured transducer is referred to as the transducer of Comparative Example 3. The transducer of Comparative Example 3 is composed of only piezoelectric elements composed of a total of five laminated bodies.

[Reference Example 1]
A transducer was manufactured in the same manner as in Example 1 except that the piezoelectric layer and the electrode layer of the piezoelectric element were changed to the piezoelectric layer 2 and the electrode layer 2. The manufactured transducer is referred to as the transducer of Reference Example 1.

[Reference Example 2]
A transducer was manufactured in the same manner as in Example 1 except that the elastic layer of the piezoelectric element was changed to the elastic layer 4. The manufactured transducer is referred to as the transducer of Reference Example 2.

<Evaluation of transducer>
Table 1 shows the configuration and evaluation results of the manufactured transducer. In Table 1, evaluation methods of unit elongation at break, volume resistivity of the electrode layer, amount of generated charges, sensitivity, and durability are as follows.

[Unit elongation at break]
The elongation at break of the unit composed of the piezoelectric layer and a pair of electrode layers arranged between them is measured by the method described above. If the elongation at break is 10% or more, good (indicated by a circle in Table 1), 10% If it was less than that, it was evaluated as defective (indicated by x in Table 1).

[Volume resistivity of electrode layer]
Good when both the volume resistivity in the natural state of the electrode layer and the volume resistivity in the 10% stretched state are 100 Ω · cm or less (indicated by ○ in Table 1), either one is 100 Ω · cm The case where the value exceeds or was not measurable was evaluated as defective (indicated by x in Table 1).

[Amount of generated charge]
The transducer was installed in a fatigue endurance tester (“MMT-101N” manufactured by Shimadzu Corporation), and a sine wave (frequency 1 Hz) with a compression load of 6 N was applied with a cylindrical jig having a diameter of 10 mm. The amount of charge generated at that time was measured using a charge amplifier (“NEXUS Charge Amplifier type 2692” manufactured by Brüel & Kjær) and an oscilloscope (Yokogawa Electric Corporation “DLM2022”).

[sensitivity]
The transducer was installed in a fatigue endurance tester (same as above), and sine waves (frequency 1 Hz) having a compression load of 2N, 4N, and 6N were sequentially applied with a cylindrical jig having a diameter of 10 mm. The amount of charge generated at that time was measured using a charge amplifier (same as above) and an oscilloscope (same as above). Then, the generated charge amount measured for each compressive load was divided by the added stress, and the average value was calculated to obtain the sensitivity of the transducer.

[durability]
The transducer was allowed to stand for 3000 hours in an environment of a temperature of 60 ° C. and a humidity of 90%. Then, the transducer was installed in a fatigue endurance tester (same as above), and a sine wave (frequency 10 Hz) with a compression load of 10 N was applied 100,000 times with a cylindrical jig having a diameter of 10 mm, and then a constant displacement vibration 5 in the tensile direction. % Sin wave (frequency 10 Hz) was applied 10,000 times. Thereafter, the sensitivity and the generated charge amount were measured by the method described above. Durability is good when both sensitivity and generated charge are 80% or more of the value before the fatigue endurance test (indicated by a circle in Table 1), and durability is less than 80%. It was evaluated as defective (indicated by x in Table 1).

As shown in Table 1, according to the transducers of Examples 1 to 7 having the buffer portion, the generated charge amount was as large as 10 ⁻⁹ C order, and the sensitivity was good. Since the generated charge amount is large, it can be seen that the power generation amount is large. Further, the durability after repeated displacement was at a satisfactory level. On the other hand, according to the transducer of Comparative Example 1 having no buffer portion, the amount of generated charges was as small as 10 ⁻¹⁰ C order, and the sensitivity was greatly reduced. Further, in the transducer of Comparative Example 2 in which a solid (polyester film) having a larger elastic modulus than the elastic layer is disposed in the buffer portion, the generated charge amount is small and the sensitivity is low. Further, according to the transducer of Comparative Example 3 having no exterior material, the generated charge amount was large and the sensitivity was good, but the durability was deteriorated. In the transducer of Reference Example 1, since the piezoelectric layer and the electrode layer were poor in flexibility, the volume resistivity of the electrode layer and the breaking elongation of the unit were both poor. For this reason, although the amount of generated charges was large and the sensitivity was satisfactory, the durability deteriorated. In addition, since the transducer of Reference Example 2 uses a polyester film having a very large elastic modulus for the elastic layer, the effect of increasing the distortion of the piezoelectric layer by the elastic layer is not exhibited, and a desired generated charge amount and sensitivity can be obtained. There wasn't.

Since the transducer of the present invention has a large amount of power generation and excellent durability, it is useful for a power generation device that is embedded in a road and generates power by vibration from a person or a car. Moreover, since the transducer of the present invention is highly sensitive and can detect a small load, it is suitable as a biological information sensor for measuring a respiratory state and a heart rate. In addition, it is suitable as a pressure sensor for robots (including industrial use and communication use), medical use, nursing care, health use, sports equipment, and automobiles.

1: power generation system, 10: transducer, 20, 200 to 209: piezoelectric element, 21: piezoelectric layer, 22a, 22b: electrode layer, 23a, 23b, 230: elastic layer, 24: unit (electrode layer / piezoelectric layer / Electrode layer), 30: exterior material, 31: buffer, 40: electric circuit, 41, 410, 411: wiring, 42: rectifier circuit, 43: capacitor, 44: switch, 45: load.

Claims (11)

A piezoelectric element having a piezoelectric layer including an elastomer and piezoelectric particles, an electrode layer disposed with the piezoelectric layer interposed therebetween, and an elastic body layer disposed at least on the outermost layer;
An exterior material that houses the piezoelectric element,
A buffer that accommodates at least one of gas, a non-volatile liquid, and a solid having a smaller elastic modulus than the elastic layer between the exterior material and the piezoelectric element in a direction in which the piezoelectric element expands due to pressing. A transducer characterized in that the section is partitioned. The transducer according to claim 1, wherein gas is accommodated in the buffer section. The transducer according to claim 1 or 2, wherein the piezoelectric element has a plurality of the piezoelectric layers, and the piezoelectric layers are stacked via the electrode layers. 4. The transducer according to claim 3, wherein the elastic layer is interposed between adjacent electrode layers. The transducer according to any one of claims 1 to 4, wherein the elastic layer has an elastic modulus of 50 MPa or less. The transducer according to any one of claims 1 to 5, wherein a breaking elongation of a unit including the piezoelectric layer and a pair of the electrode layers disposed between the piezoelectric layers is 10% or more. The transducer according to any one of claims 1 to 6, wherein a volume resistivity of the electrode layer in a natural state and a stretched state from that state to a stretched state in a uniaxial direction is 10 Ω · cm or less. In the piezoelectric element, when the surface extending in the extension direction is the surface,
The transducer according to claim 1, wherein a surface of the piezoelectric element is not bonded to the exterior material. The transducer according to any one of claims 1 to 8, which is used as a power generator. A transducer according to claim 9;
An electrical circuit for extracting electrical energy from the transducer;
A power generation system comprising: The power generation system according to claim 10, comprising a plurality of the transducers.

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