JP2009021328A - Electrostrictive element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostrictive element which is small, the displacement of which is large, and which can output large force. <P>SOLUTION: An electrostrictive element 1 is constituted of an electrostrictive layer 2 composed of a dielectric film 20 and a plurality of electrodes arranged via the dielectric film 20, an insulating layer 30 which is laminated on the electrostrictive layer 2, which is composed of an insulating material selected from resin and elastomer, and which plays a role in maintaining the shape of the element, and output members 50 and 51 which are arranged on at least one end in the direction of the lamination of the electrostrictive layer 2 and the insulating layer 30, which have higher rigidity than that of the dielectric film 20, and which aligns the displacement direction of the electrostrictive layer 2. The electrostrictive element 1 outputs force in the lamination direction by changing the film thickness of the dielectric film 20 by changing an application voltage to a portion between the plurality of electrodes. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrostrictive element that outputs a force in the film thickness direction of a dielectric film by changing an applied voltage.

In the fields of industrial and nursing robots, medical equipment, micromachines, etc., the need for highly flexible, small and lightweight actuators is increasing. As this type of actuator material, polymer materials such as conductive polymers and dielectric elastomers are known. For example, Patent Documents 1 and 2 introduce an electrostrictive actuator in which a dielectric film made of a dielectric elastomer is held between a pair of electrodes.
Special table 2003-506858 Special table 2003-505865 gazette

  As shown in Patent Documents 1 and 2 above, in the conventional electrostrictive actuator, the dielectric film is installed in a stretched state (prestrained state), and the expansion and contraction in the surface direction of the dielectric film is utilized. Driving force is output. That is, when the applied voltage between the electrodes is increased, the dielectric film is compressed by the electrostatic attractive force between the electrodes, and the dielectric film expands in the surface direction (direction parallel to the electrode surface). On the other hand, when the applied voltage between the electrodes is reduced, the dielectric film is restored to its original shape and thus contracts in the surface direction. Here, when the applied voltage between the electrodes is increased in a state where the expansion in the surface direction of the dielectric film is restricted, the dielectric film is bent by an amount that cannot be expanded. In a conventional electrostrictive actuator, the driving force is output using this amount of bending.

  However, according to the conventional electrostrictive actuator, since the expansion and contraction in the surface direction of the dielectric film is used, the amount of displacement is small and it is difficult to extract a large force. Further, when it is desired to increase the amount of displacement, it is necessary to apply a high voltage, and durability such as dielectric breakdown of the dielectric film becomes a problem.

  The present invention has been completed in view of such circumstances, and an object thereof is to provide an electrostrictive element that is small in size, has a large amount of displacement, and can output a large force.

  (1) In order to solve the above-described problem, a first electrostrictive element of the present invention includes an electrostrictive layer including a dielectric film, and a plurality of electrodes arranged via the dielectric film, and the electrostrictive element. An insulating layer made of an insulating material selected from an elastomer and a resin and serving to maintain the element shape, and disposed at least at one end in the stacking direction of the electrostrictive layer and the insulating layer, An output member that is more rigid than a dielectric film and that orients the direction of displacement of the electrostrictive layer, and changes the film thickness of the dielectric film by changing the voltage applied between the electrodes, A force in the stacking direction is output (corresponding to claim 1).

  For example, when the applied voltage between the electrodes of the electrostrictive layer is increased, the electrostatic attractive force between the electrodes is increased. For this reason, the dielectric film interposed between the electrodes is compressed from the film thickness direction, and the film thickness is reduced. According to the first electrostrictive element of the present invention, the output member is disposed at at least one end in the stacking direction of the electrostrictive layer and the insulating layer (the film thickness direction of the dielectric film). The output member is more rigid than the dielectric film, and plays a role of aligning the displacement direction of the dielectric film in the film thickness direction. Therefore, the change in the thickness of the dielectric film due to compression from the electrode can be taken out as a driving force as it is. Thus, according to the first electrostrictive element of the present invention, since the displacement in the film thickness direction of the dielectric film is used, the displacement amount is large even when the voltage is low, and a large force can be output. Further, unlike a conventional electrostrictive actuator that utilizes expansion and contraction in the surface direction, preliminary stretching of the dielectric film is not necessary. In addition, the electrostrictive layer and the insulating layer to be laminated can be reduced in size by reducing the thickness. Further, the amount of displacement and the magnitude of force can be easily adjusted by the number of laminated dielectric films. For example, a larger displacement amount and force can be output by increasing the number of stacked dielectric films.

  In the first electrostrictive element of the present invention, the insulating layer is laminated with the electrostrictive layer. The insulating layer is made of an insulating material and serves to maintain the element shape. As a result, the element shape can be maintained even when an electrostrictive layer is formed by laminating a large number of dielectric films or when a large number of electrostrictive layers are laminated. Increasing the number of dielectric films stacked increases the amount of displacement and force. However, since heat generated during driving is concentrated accordingly, dielectric breakdown is likely to occur, and durability may be reduced. In this respect, by arranging the insulating layers in layers and transferring heat generated during driving to the insulating layers, concentration of heat can be suppressed and durability can be improved.

  (2) Preferably, in the configuration of (1) above, a flexible adhesive layer that is further laminated with the electrostrictive layer, adheres adjacent layers, and has a Young's modulus equal to or lower than the Young's modulus of the dielectric film It is good to set it as the structure provided with (corresponding to claim 2).

  The flexible adhesive layer serves to bond adjacent layers together. Here, the “adjacent layer” means an electrostrictive layer and an insulating layer, an electrostrictive layer and an output member, an electrostrictive layer and an electrostrictive layer, an insulating layer and an output member, and adjacent layers ( Member). Further, the Young's modulus of the flexible adhesive layer is less than or equal to the Young's modulus of the dielectric film. As described above, since the flexible adhesive is soft, for example, when it is disposed between the electrostrictive layer and a layer adjacent thereto, the two can be bonded without hindering expansion and contraction in the surface direction of the dielectric film. Thereby, the displacement of the dielectric film in the film thickness direction becomes smooth, and a larger displacement amount and force can be output.

  (3) Preferably, in the configuration of (1) or (2), the insulating layer may be disposed on both sides of the electrostrictive layer in the stacking direction (corresponding to claim 3). As described in (1) above, increasing the number of dielectric films or the number of electrostrictive layers increases the amount of displacement and force, but may reduce durability due to heat generated during driving. . According to this configuration, since the insulating layers are disposed on both sides of the electrostrictive layer in the stacking direction, heat generated during driving is easily transferred to the insulating layer. For this reason, durability improves more.

  (4) Preferably, in the configuration of (2) above, the flexible adhesive layer may be arranged on both sides of the electrostrictive layer in the stacking direction (corresponding to claim 4). According to this configuration, the flexible adhesive layer is disposed between the electrostrictive layer and the adjacent layer. For this reason, expansion and contraction in the surface direction of the dielectric film is not easily prevented. Thereby, since the displacement of the dielectric film in the film thickness direction becomes smooth, a larger displacement and force can be output.

  (5) Preferably, in any one of the configurations (2) to (4), a plurality of the electrostrictive layers are stacked via at least one of the insulating layer and the flexible adhesive layer. (Corresponding to claim 5).

  For example, when the number of dielectric films stacked in the electrostrictive layer is simply increased, the dielectric films are continuously stacked. In this case, durability becomes a problem due to heat generation during driving. On the other hand, according to this configuration, a plurality of electrostrictive layers are laminated via at least one of an insulating layer and a flexible adhesive layer. That is, a predetermined number of dielectric films are arranged in the stacking direction via at least one of the insulating layer and the flexible adhesive layer. Thereby, the concentration of heat generated during driving can be suppressed, and durability is improved. Also, by laminating a plurality of electrostrictive layers, the number of dielectric films can be increased as a whole, so that the amount of displacement and force can be increased.

  (6) Moreover, the 2nd electrostrictive element of this invention is laminated | stacked with the electrostrictive layer which consists of a dielectric film and the some electrode arrange | positioned through this dielectric film, and this electrostrictive layer. Disposed adjacent to each other, and disposed at at least one end in the stacking direction of the flexible adhesive layer having a Young's modulus equal to or lower than the Young's modulus of the dielectric film, and the electrostrictive layer and the flexible adhesive layer, An output member that is more rigid than the film and that orients the direction of displacement of the electrostrictive layer, and changes the film thickness of the dielectric film by changing the applied voltage between the electrodes. A directional force is output (corresponding to claim 6).

  Similar to the first electrostrictive element of the present invention of (1) above, according to the second electrostrictive element of the present invention, the displacement amount in the film thickness direction of the dielectric film is used. Is large and can output a large force. Further, unlike a conventional electrostrictive actuator that utilizes expansion and contraction in the surface direction, preliminary stretching of the dielectric film is not necessary. In addition, the electrostrictive layer and the insulating layer to be laminated can be reduced in size by reducing the thickness. Further, the amount of displacement and the magnitude of force can be easily adjusted by the number of laminated dielectric films. For example, a larger displacement amount and force can be output by increasing the number of laminated dielectric films.

  In the second electrostrictive element of the present invention, the flexible adhesive layer is disposed so as to be laminated with the electrostrictive layer. As described in (2) above, the flexible adhesive layer plays a role of adhering adjacent layers. Further, the Young's modulus of the flexible adhesive layer is lower than the Young's modulus of the dielectric film, and is soft. For this reason, if it arrange | positions between an electrostrictive layer and the layer adjacent to it, for example, both can be adhere | attached, without preventing the expansion-contraction to the surface direction of a dielectric film. Thereby, the displacement of the dielectric film in the film thickness direction becomes smooth, and a larger displacement amount and force can be output.

  The second electrostrictive element of the present invention further includes an insulating layer that is laminated with the electrostrictive layer and is made of an insulating material selected from an elastomer and a resin and serves to maintain the element shape. Good. Incidentally, this configuration is the same as the configuration of (2) above.

  (7) Preferably, in any one of the constitutions (1) to (5), the insulating material is ethylene-propylene-diene terpolymer (EPDM), acrylic rubber, silicone rubber, polyethylene terephthalate (PET). It is good to set it as the structure which consists of 1 or more types chosen from these (corresponding to claim 7). Since these are easy to transfer heat, they are effective in suppressing dielectric breakdown and improving durability. In addition, since it is more rigid than the dielectric film, it is excellent in element shape maintainability.

  (8) Preferably, in any one of the constitutions (2) to (6), the flexible adhesive layer may be composed of one or more selected from acrylic rubber, natural rubber, silicone rubber, and urethane rubber ( (Corresponding to claim 8). Since these have a small Young's modulus and are flexible, even if they are arranged between an electrostrictive layer and a layer adjacent thereto, it is difficult to prevent expansion and contraction of the dielectric film in the plane direction.

  (9) Preferably, in any one of the constitutions (1) to (8), the dielectric film is composed of one or more selected from acrylic rubber, silicone rubber, fluororubber, and urethane rubber. Corresponds to item 9).

  The type of the dielectric film is not particularly limited as long as it is deformable according to the electrostatic attractive force between the electrodes. Acrylic rubber, silicone rubber, fluororubber, and urethane rubber in this configuration are all suitable because of their high relative dielectric constant and dielectric breakdown.

  (10) Preferably, in any one of the configurations (1) to (9), the plurality of electrodes may be configured to expand and contract according to deformation of the dielectric film (corresponding to claim 9). .

  If the electrode is difficult to expand and contract together with the dielectric film, the electrode prevents the dielectric film from being deformed, making it difficult to obtain a desired amount of displacement. In this regard, according to the present configuration, the electrode can be expanded and contracted according to the expansion and contraction of the dielectric film. That is, the electrode can be deformed integrally with the dielectric film. For this reason, it becomes easier to obtain a desired amount of displacement.

  Hereinafter, embodiments of the electrostrictive element of the present invention will be described.

<First embodiment>
First, the configuration of the electrostrictive element of this embodiment will be described. FIG. 1 shows a cross-sectional view of the electrostrictive element of this embodiment. FIG. 1 shows the electrostrictive element in an off state, that is, a state in which no voltage is applied between the electrodes. As shown in FIG. 1, the electrostrictive element 1 of this embodiment includes an electrostrictive layer 2, an insulating layer 30, a flexible adhesive layer 40, and iron plates 50 and 51.

  The iron plates 50 and 51 have a rectangular plate shape, and are disposed at upper and lower ends in the stacking direction of the electrostrictive layer 2, the insulating layer 30, and the flexible adhesive layer 40. The iron plate 51 is fixed to the surface of the base material 9. The iron plates 50 and 51 are included in the output member in the present invention.

  The electrostrictive layer 2 includes a single dielectric film 20 and a pair of electrodes (not shown). The dielectric film 20 is made of acrylic rubber and has a rectangular thin film shape. The pair of electrodes are disposed on both upper and lower surfaces of the dielectric film 20 and each has a rectangular thin film shape slightly smaller than the dielectric film 20. The electrode is made of a conductive thin film. The electrode can be expanded and contracted according to the expansion and contraction of the dielectric film 20. In addition, a terminal (not shown) protruding outward is disposed at one end of each electrode. The terminals have a strip shape, and are each connected to a power source via a conducting wire.

  The insulating layer 30 is made of EPDM and has a rectangular thin plate shape. One insulating layer 30 is disposed above and below the electrostrictive layer 2.

  The flexible adhesive layer 40 is made of acrylic rubber and has a rectangular thin plate shape. The flexible adhesive layer 40 is arranged in a total of four layers between the electrostrictive layer 2 and the pair of insulating layers 30 (two places) and between the pair of insulating layers 30 and the iron plates 50 and 51 (two places). Yes. That is, the flexible adhesive layer 40 bonds the electrostrictive layer 2 and the pair of insulating layers 30, and the pair of insulating layers 30 and the iron plates 50 and 51, respectively. As described above, the electrostrictive element 1 includes the flexible adhesive layer 40, the insulating layer 30, the flexible adhesive layer 40, the electrostrictive layer 2, the flexible adhesive layer 40, the insulating layer 30, and the flexible between the iron plates 50 and 51 in order from the top. The adhesive layer 40 is laminated.

  Next, the movement of the electrostrictive element of this embodiment will be described. When a voltage is applied between the pair of electrodes of the electrostrictive layer 2, the state is switched from the off state to the on state. When a voltage is applied, the dielectric film 20 is compressed by electrostatic attraction generated between the pair of electrodes. At this time, since the displacement direction of the dielectric film 20 is oriented downward by the iron plates 50 and 51, the film thickness of the dielectric film 20 is reduced, and the dielectric film 20 extends in the surface direction. At the same time, the iron plate 50, the insulating layer 30, and the flexible adhesive layer 40 are integrated and displaced in the direction in which the film thickness of the dielectric film 20 decreases (downward). Thus, the electrostrictive element 1 can be driven downward by switching from the off state to the on state.

  When switching from the on state to the off state, application of voltage between the pair of electrodes is stopped. When the voltage application is stopped, the dielectric film 20 contracts due to its own restoring force. For this reason, the film thickness of the dielectric film 20 is restored. At the same time, the iron plate 50, the insulating layer 30, and the flexible adhesive layer 40 are integrated and displaced in the direction in which the film thickness of the dielectric film 20 increases (upward). Thus, the electrostrictive element 1 can be driven upward by switching from the on state to the off state.

  Next, the effect of the electrostrictive element of this embodiment is demonstrated. According to the electrostrictive element 1 of the present embodiment, the change in the film thickness of the dielectric film 20 can be taken out as a driving force as it is. For this reason, even if it is a low voltage, a displacement amount is large and a big force can be output. Further, since the expansion and contraction in the surface direction of the dielectric film 20 is not used, it is not necessary to stretch the dielectric film 20 in advance. Further, by reducing the thickness of the laminated electrostrictive layer 2, insulating layer 30, and flexible adhesive layer 40, the size can be easily reduced.

  In addition, since the insulating layer 30 is disposed one layer above and below the electrostrictive layer 2, the element shape can be easily maintained even during driving. In addition, since heat generated during driving is also transmitted to the insulating layer 30, dielectric breakdown of the dielectric film 20 is suppressed, and the electrostrictive element 1 has high durability. A flexible adhesive layer 40 is disposed between the electrostrictive layer 2 and the insulating layer 30. For this reason, even if the electrostrictive layer 2 and the insulating layer 30 are bonded, it is difficult to prevent expansion and contraction of the dielectric film 20 in the surface direction. Furthermore, the electrodes disposed on the upper and lower surfaces of the dielectric film 20 can also be deformed integrally with the dielectric film 20. Therefore, the dielectric film 20 can be smoothly displaced in the film thickness direction, and a large displacement amount and force can be output.

<Second embodiment>
The difference between the electrostrictive element of the present embodiment and the electrostrictive element of the first embodiment is that the electrostrictive layer is composed of five dielectric films. Therefore, only the differences will be described here.

  FIG. 2 is an exploded perspective view of the electrostrictive layer in the electrostrictive element of the present embodiment. As shown in FIG. 2, the electrostrictive layer 2 includes five dielectric films 20a, 20b, 20c, 20d, and 20e, and six electrodes 21a, 21b, 21c, 21d, 21e, and 21f. . The dielectric films 20a to 20e are interposed one by one between the electrodes 21a to 21f. That is, the dielectric films 20a to 20e and the electrodes 21a to 21f are alternately stacked in the vertical direction. Specifically, from top to bottom, electrode 21a → dielectric film 20a → electrode 21b → dielectric film 20b → electrode 21c → dielectric film 20c → electrode 21d → dielectric film 20d → electrode 21e → dielectric film 20e → electrode 21f. They are stacked in order.

  Terminals 22a to 22f protruding outward are disposed at one ends of the electrodes 21a to 21f. The terminals 22a to 22f are alternately arranged at positions facing each other by 180 °. The terminal is made of acrylic rubber and has a strip shape. Each of the terminals 22a to 22f is connected to a power source via a conducting wire.

  The electrostrictive element 1 of the present embodiment has the same function and effect as those of the electrostrictive element of the first embodiment with respect to the parts having the same configuration. Moreover, according to the electrostrictive element 1 of this embodiment, since the electrostrictive layer 2 consists of the five dielectric films 20a-20e, a larger displacement amount and force can be output. In addition, since the insulating layer 30 is disposed one layer above and below the electrostrictive layer 2, even when the five dielectric films 20a to 20e are stacked, concentration of heat during driving is suppressed. For this reason, the fall of the durability by a dielectric breakdown is suppressed. Further, the self-supporting property of the electrostrictive element 1 can be maintained by the insulating layer 30 even when the five dielectric films 20 a to 20 e are stacked.

<Third embodiment>
The difference between the electrostrictive element of the present embodiment and the electrostrictive element of the first embodiment is that the insulating layer is disposed directly on both sides of the electrostrictive layer, and the iron plate is disposed only at the upper end in the stacking direction. Is a point. Therefore, only the differences will be described here.

  FIG. 3 shows a cross-sectional view of the electrostrictive element of this embodiment. In addition, about the site | part corresponding to FIG. 1, it shows with the same code | symbol. As shown in FIG. 3, the insulating layers 30 are arranged one layer on each side of the electrostrictive layer 2 in the vertical direction. The flexible adhesive layer 40 is not interposed between the electrostrictive layer 2 and the insulating layer 30. The flexible adhesive layer 40 is disposed between the insulating layer 30 and the iron plate 50 and between the insulating layer 30 and the base material 9. That is, the electrostrictive element 1 is formed by laminating the iron plate 50, the flexible adhesive layer 40, the insulating layer 30, the electrostrictive layer 2, the insulating layer 30, and the flexible adhesive layer 40 in order from the top.

  The electrostrictive element 1 of the present embodiment has the same function and effect as those of the electrostrictive element of the first embodiment with respect to the parts having the same configuration. Further, according to the electrostrictive element 1 of the present embodiment, since the insulating layer 30 is directly disposed on both sides of the electrostrictive layer 2, heat generated during driving is easily transferred to the insulating layer 30. For this reason, durability improves more. Moreover, in this embodiment, only the iron plate 50 is arrange | positioned as an output member. For this reason, the number of parts is small.

<Fourth embodiment>
The difference between the electrostrictive element of this embodiment and the electrostrictive element of the first embodiment is that three electrostrictive layers are laminated. Therefore, only the differences will be described here.

  FIG. 4 shows a cross-sectional view of the electrostrictive element of this embodiment. In addition, about the site | part corresponding to FIG. 1, it shows with the same code | symbol. As shown in FIG. 4, in the electrostrictive element 1 of the present embodiment, three layers of electrostrictive layers 2 are laminated via an insulating layer 30 and a flexible adhesive layer 40. That is, one insulating layer 30 is disposed above and below each electrostrictive layer 2 via the flexible adhesive layer 40. Each of the electrostrictive layers 2 includes a single dielectric film 20 and a pair of electrodes (not shown).

  The electrostrictive element 1 of the present embodiment has the same function and effect as those of the electrostrictive element of the first embodiment with respect to the parts having the same configuration. In addition, since the electrostrictive element 1 of the present embodiment includes three electrostrictive layers 2, in other words, three dielectric films 20, a larger displacement amount and force can be output. Here, the electrostrictive layer 2 is laminated via the insulating layer 30 and the flexible adhesive layer 40. That is, the dielectric film 20 is divided into three parts in the stacking direction via the insulating layer 30 and the flexible adhesive layer 40. For this reason, concentration of heat generated during driving can be suppressed, and durability is improved.

  The insulating layer 30 is disposed so as to sandwich each electrostrictive layer 2. For this reason, it is easy to maintain the element shape even during driving. In addition, since the heat generated during driving is also transmitted to the insulating layer 30, the electrostrictive element 1 has high durability. A flexible adhesive layer 40 is disposed between the electrostrictive layer 2 and the insulating layer 30. Therefore, the electrostrictive layer 2 and the insulating layer 30 can be bonded without hindering expansion and contraction of the dielectric film 20 in the surface direction.

<Fifth embodiment>
The difference between the electrostrictive element of the present embodiment and the electrostrictive element of the fourth embodiment is that the electrostrictive layers are each composed of five dielectric films. Therefore, only the differences will be described here.

  As shown in FIG. 2, each of the three electrostrictive layers 2 includes five dielectric films 20a, 20b, 20c, 20d, and 20e and six electrodes 21a, 21b, 21c, 21d, and 21e. , 21f. The dielectric films 20a to 20e are interposed one by one between the electrodes 21a to 21f. That is, the dielectric films 20a to 20e and the electrodes 21a to 21f are alternately stacked in the vertical direction.

  Terminals 22a to 22f protruding outward are disposed at one ends of the electrodes 21a to 21f. The terminals 22a to 22f are alternately arranged at positions facing each other by 180 °. The terminal is made of acrylic rubber and has a strip shape. Each of the terminals 22a to 22f is connected to a power source via a conducting wire.

  The electrostrictive element 1 of the present embodiment has the same function and effect as those of the electrostrictive element of the fourth embodiment with respect to the parts having the same configuration. Further, since each electrostrictive layer 2 is composed of five dielectric films 20a to 20e, the electrostrictive element 1 of this embodiment includes a total of fifteen dielectric films 20. For this reason, a larger displacement amount and force can be output. Since the insulating layer 30 is disposed so as to sandwich the electrostrictive layer 2, even when five dielectric films 20a to 20e are stacked on each electrostrictive layer 2, concentration of heat during driving is suppressed. Is done. For this reason, the fall of the durability by a dielectric breakdown is suppressed. Further, the self-standing property of the electrostrictive element 1 can be maintained by the insulating layer 30.

<Sixth embodiment>
The difference between the electrostrictive element of this embodiment and the electrostrictive element of the fourth embodiment is that an insulating layer is directly disposed on both sides of the electrostrictive layer. Therefore, only the differences will be described here.

  FIG. 5 shows a cross-sectional view of the electrostrictive element of the present embodiment. In addition, about the site | part corresponding to FIG. 4, it shows with the same code | symbol. As shown in FIG. 5, the insulating layers 30 are arranged one layer on each side of each electrostrictive layer 2 in the vertical direction. The flexible adhesive layer 40 is not interposed between the electrostrictive layer 2 and the insulating layer 30. The flexible adhesive layer 40 is disposed between the insulating layer 30 and the insulating layer 30 disposed between the adjacent electrostrictive layers 2 and between the iron plates 50 and 51 and the insulating layer 30.

  The electrostrictive element 1 of the present embodiment has the same function and effect as those of the electrostrictive element of the fourth embodiment with respect to the parts having the same configuration. Further, according to the electrostrictive element 1 of the present embodiment, since the insulating layer 30 is directly disposed on both sides of the electrostrictive layer 2, heat generated during driving is easily transferred to the insulating layer 30. For this reason, durability improves more.

<Others>
The embodiment of the electrostrictive element of the present invention has been described above. However, the embodiment is not particularly limited to the above embodiment. Various modifications and improvements that can be made by those skilled in the art are also possible.

  For example, in the above embodiment, an electrostrictive element is configured by laminating an electrostrictive layer, an insulating layer, and a flexible adhesive layer. However, an embodiment in which only one of the insulating layer and the flexible adhesive layer is used, that is, an embodiment in which the electrostrictive layer and one of the insulating layer and the flexible adhesive layer are laminated may be employed. Further, the configuration of the electrostrictive element, that is, the number of layers stacked, the arrangement method, and the like are not limited to the above embodiment.

  For example, the number of electrostrictive layers stacked and the number of dielectric films in the electrostrictive layer are not limited. As the number of electrostrictive layers stacked and the number of dielectric films per electrostrictive layer increase, a larger displacement and force can be output. In this case, it is only necessary to increase the number of dielectric films per electrostrictive layer. However, it is desirable that the electrostrictive layers including a predetermined number of dielectric films are laminated via an insulating layer or the like. By so doing, heat generated during driving is dispersed, and the number of dielectric films can be increased as a whole of the electrostrictive element without lowering durability.

  Further, the dielectric film is not necessarily continuous in the plane direction of the electrostrictive layer. That is, a plurality of dielectric films may be arranged in the plane direction. When the area of the surface of the dielectric film is large, the friction with respect to the adjacent layers and the dielectric film is increased, so that it is difficult to expand and contract in the surface direction. Therefore, the displacement in the film thickness direction becomes small. In this regard, if a plurality of dielectric films are arranged in the plane direction, the area in contact with the adjacent layer or dielectric film can be reduced, and friction can be reduced. As a result, it becomes easy to expand and contract in the surface direction, and displacement in the film thickness direction increases.

  In the above embodiment, the dielectric film made of acrylic rubber is used, but the material of the dielectric film is not particularly limited. For example, what is necessary is just to select suitably from rubber | gum and a thermoplastic elastomer. Of these, silicone rubber, fluorine rubber, urethane rubber and the like are preferably used in addition to the acrylic rubber from the viewpoint of high relative dielectric constant and dielectric breakdown. Further, the shape and thickness of the dielectric film are not particularly limited, and may be appropriately determined according to the use of the electrostrictive element. For example, it is desirable that the thickness of the dielectric film is small from the viewpoint of miniaturization of the electrostrictive element, low potential drive, and increase in the amount of displacement. In this case, the thickness of the dielectric film is preferably set to 1 μm or more and 500 μm or less in consideration of dielectric breakdown properties and the like. It is more preferable that the thickness is 10 μm or more and 200 μm or less.

  Moreover, the material of the electrode is not particularly limited. Since it is desirable that the electrode can be expanded and contracted according to the expansion and contraction of the dielectric film, for example, when the electrode is formed from a paste or paint obtained by mixing oil or elastomer as a binder with conductive carbon such as carbon black or carbon nanotube. Good. Examples of the elastomer used as the binder include flexible rubbers such as silicone rubber, acrylic rubber, EPDM, natural rubber, butyl rubber, isoprene rubber, acrylonitrile-butadiene copolymer rubber, hydrogenated nitrile rubber, hydrin rubber, chloroprene rubber, and urethane rubber. Those are preferred. Alternatively, an electrode may be formed by directly attaching a conductive fine powder such as carbon black or carbon nanotube to the surface of the dielectric film.

  In the above embodiment, an insulating layer made of EPDM is disposed. However, the material of the insulating layer is not particularly limited as long as it is an insulating material selected from an elastomer and a resin and serves to maintain the element shape. For example, a flexible material is desirable to obtain a large displacement. As the flexible material, acrylic rubber, silicone rubber, and the like are suitable in addition to the above EPDM. Further, although it is poor in flexibility, a resin such as polyethylene terephthalate (PET) may be used.

  In the above embodiment, a flexible adhesive layer made of acrylic rubber is disposed. However, the material of the flexible adhesive layer is not particularly limited as long as adjacent layers can be bonded to each other and the Young's modulus is equal to or lower than the Young's modulus of the dielectric film. In addition to the acrylic rubber, natural rubber, silicone rubber, urethane rubber and the like are suitable.

  Moreover, in the said embodiment, it is not necessary to consider so much the expansion-contraction to a surface direction about an iron plate and an insulating layer. Therefore, you may arrange | position the contact bonding layer different from a flexible contact bonding layer between an iron plate and an insulating layer.

  In the said embodiment, the iron plate was used as an output member. However, the material of the output member is not particularly limited as long as it has higher rigidity than the dielectric film and can orient the displacement direction of the electrostrictive layer. For example, what is necessary is just to select suitably from a metal, resin, etc. Moreover, it is good also considering a part of other party member as an output member.

  In the above embodiment, the electrostrictive element is operated by switching from the off state (0 V) to the on state. However, the voltage value before operation is not necessarily 0V. For example, the applied voltage may be increased from a predetermined voltage value.

  Next, the present invention will be described more specifically with reference to examples.

(1) Measurement of Displacement Amount and Frequency Characteristic With respect to the electrostrictive element of the embodiment, the displacement amount and the frequency characteristic with respect to the applied voltage were measured. For the measurement, the electrostrictive element of the first embodiment (one dielectric film; see FIG. 1; hereinafter referred to as “electrostrictive element of Example 1”), the electrostrictive element of the second embodiment (five dielectric films) The electrostrictive elements in which the number of dielectric films of the electrostrictive layer is changed to 3, 8, and 11 are used in the electrostrictive elements of the second embodiment. The electrostrictive elements of the second embodiment are the electrostrictive elements of Example 2, Example 3, Example 4, and Example 5 in order from the smallest number of dielectric films. Here, in the electrostrictive elements of Examples 1 to 5, the size of the iron plate is 10 mm long × 50 mm wide, the size of the dielectric film is 18 mm long × 76 mm wide, the thickness is about 0.1 mm, and the size of the insulating layer is vertical. The size of the flexible adhesive layer is 10 mm long × 66 mm wide and about 0.5 mm thick.

  A laser displacement meter was installed so that the laser was irradiated near the center of the upper surface of the electrostrictive elements of Examples 1 to 5, and the amount of displacement in the film thickness direction of each electrostrictive element with respect to the applied voltage was measured. The measurement result of the displacement amount is shown in FIG. 6, and the measurement result of the frequency characteristic is shown in FIG. In FIG. 6, the “displacement rate (%)” on the vertical axis is the ratio of the displacement amount to the state where no voltage is applied (initial state) (hereinafter the same in FIGS. 8, 9 and 11). In FIG. 7, the “decrease rate (%)” on the vertical axis is the ratio of each displacement when the displacement at the frequency of 2 Hz is 100%.

  As shown in FIG. 6, in any of the electrostrictive elements of Examples 1 to 5, the applied voltage increased and the displacement rate increased. For the electrostrictive element of Example 5, the displacement rate was smaller than the electrostrictive elements of Examples 3 and 4 when the applied voltage was small. As a whole, the displacement rate increased as the number of dielectric films increased. Became bigger. Thus, it was confirmed that the amount of displacement can be increased by increasing the number of dielectric films. Further, as shown in FIG. 7, the displacement amount (decrease rate) decreased as the frequency increased. Thereby, it can be said that the electrostrictive elements of Examples 1 to 5 are suitable for use in a low frequency region. For example, application to a vibration isolator is suitable.

  Next, with respect to the electrostrictive element of the fourth embodiment (three electrostrictive layers and three dielectric films in total; see FIG. 4, hereinafter referred to as “electrostrictive element of Example 6”), similarly to the above, applied voltage The amount of displacement was measured. The measurement result of the displacement is shown in FIG. 8 together with the result of the electrostrictive element (three dielectric films) of Example 2 having the same number of dielectric films as a whole. As shown in FIG. 8, the electrostrictive element of Example 2 in which the dielectric films are collectively stacked in one place is more than the electrostrictive element in Example 6 in which the electrostrictive element is divided into three pieces and arranged one by one. The displacement rate was slightly larger.

  Next, the electrostrictive element of the fifth embodiment (3 electrostrictive layers, 15 dielectric films in total; see FIGS. 4 and 2; hereinafter referred to as “electrostrictive element of Example 7”) is the same as described above. The displacement with respect to the applied voltage was measured. The measurement results of the displacement amount are shown in FIG. 9 together with the results of the electrostrictive elements of Examples 1 to 5 described above. As shown in FIG. 9, the electrostrictive element of Example 7 having the largest number of dielectric films as a whole had the largest displacement rate. As shown in FIG. 8, if the number is the same as a whole, the displacement rate is larger when the dielectric films are arranged in one place. However, if they are put together in one place, there is a risk of dielectric breakdown due to heat when the number of dielectric films is increased. On the other hand, when a plurality of electrostrictive layers are arranged as in the electrostrictive element of Example 7, the dielectric film can be dispersed and arranged at a plurality of locations. Thereby, the concentration of heat is alleviated and the number of dielectric films as a whole can be increased. As a result, the amount of displacement can be increased.

(2) Measurement of force The force generated with respect to the applied voltage was measured for various electrostrictive elements in which the sizes of the electrostrictive elements of Examples 1 to 4 were changed. The electrostrictive elements in which the sizes of the first to fourth examples are changed to the electrostrictive elements of the eighth to eleventh examples, respectively, and the number of dielectric films of the electrostrictive layer is 15 with the same configuration. Was added to obtain an electrostrictive element of Example 12. In the electrostrictive elements of Examples 8 to 12, the size of the iron plate is 10 mm long × 10 mm wide, the size of the dielectric film is 18 mm long × 30 mm wide, the thickness is about 0.1 mm, and the size of the insulating layer is 10 mm long × horizontal. The size of the flexible adhesive layer is 10 mm long × 20 mm wide and about 0.5 mm thick. The force with which the electrostrictive element pushes back upward was measured when a voltage was applied with a load of 1 N applied from above the electrostrictive element. The force measurement results are shown in FIG.

  As shown in FIG. 10, the force generated increases as the number of dielectric films increases. As a result, it was confirmed that if the number of dielectric films was increased, a large force could be output.

(3) Effect of electrostrictive element size on displacement amount and generated force The electrostrictive element of Example 2 and the electrostrictive element of Example 9 are compared (both have three dielectric films). The influence of the size of the electrostrictive element on the generated force was investigated. The electrostrictive element of Example 9 is smaller than the electrostrictive element of Example 2. FIG. 11 shows a measurement result of the displacement amount of both, and FIG.

  As shown in FIGS. 11 and 12, the small electrostrictive element of Example 9 was larger than the electrostrictive element of Example 2 which was larger than that of the displacement rate and the generated force. The reason is considered as follows. That is, when the electrostrictive element is small, the surface area of the dielectric film is small compared to the large one. For this reason, the friction with respect to an adjacent flexible contact bonding layer or a dielectric film becomes small, and the expansion-contraction to a surface direction becomes smooth by that much. Therefore, it is considered that the displacement in the film thickness direction is increased and the generated force is also increased.

  The electrostrictive element of the present invention is useful for, for example, artificial muscles for industrial, medical, and welfare robots, small pumps for cooling electronic components and medical devices, medical instruments, and the like. It can be used as an alternative to a piezoelectric element actuator or the like.

It is sectional drawing of the electrostrictive element of 1st embodiment of this invention. It is a disassembled perspective view of the electrostrictive layer in the electrostrictive element of 2nd embodiment of this invention. It is sectional drawing of the electrostrictive element of 3rd embodiment of this invention. It is sectional drawing of the electrostrictive element of 4th embodiment of this invention. It is sectional drawing of the electrostrictive element of 6th embodiment of this invention. It is a graph which shows the displacement amount with respect to an applied voltage about the electrostrictive element of the Example from which the number of dielectric films differs. It is a graph which shows a frequency characteristic about the electrostrictive element of the Example from which the number of dielectric films differs. It is a graph which shows the displacement amount with respect to the applied voltage about the electrostrictive element of the Example from which arrangement | positioning of a dielectric film differs. It is a graph which shows the displacement amount with respect to an applied voltage about the electrostrictive element of the Example from which the number of sheets of dielectric films and arrangement differ. It is a graph which shows the force with respect to an applied voltage about the electrostrictive element of the small Example from which the number of dielectric films differs. It is a graph which shows the displacement amount with respect to an applied voltage about the electrostrictive element of the Example from which magnitude | size differs. It is a graph which shows the force with respect to the applied voltage about the electrostrictive element of the Example from which magnitude | size differs.

Explanation of symbols

1: Electrostrictive element 2: Electrostrictive layer 20: Dielectric films 20a to 20e: Dielectric films 21a to 21f: Electrodes 22a to 22f: Terminals 30: Insulating layer 40: Flexible adhesive layer 50, 51: Iron plate (output member) 9: Base material

Claims (10)

An electrostrictive layer comprising a dielectric film and a plurality of electrodes disposed via the dielectric film;
An insulating layer that is laminated with the electrostrictive layer and is made of an insulating material selected from an elastomer and a resin and serves to maintain the element shape;
An output member that is disposed at at least one end in the stacking direction of the electrostrictive layer and the insulating layer, and is more rigid than the dielectric film and orients the displacement direction of the electrostrictive layer,
An electrostrictive element that outputs a force in a stacking direction by changing a thickness of the dielectric film by changing a voltage applied between the plurality of electrodes.   2. The electrostrictive element according to claim 1, further comprising a flexible adhesive layer that is disposed to be laminated with the electrostrictive layer, adheres adjacent layers, and has a Young's modulus equal to or lower than the Young's modulus of the dielectric film.   The electrostrictive element according to claim 1, wherein the insulating layer is disposed on both sides of the electrostrictive layer in the stacking direction.   The electrostrictive element according to claim 2, wherein the flexible adhesive layer is disposed on both sides of the electrostrictive layer in the stacking direction.   The electrostrictive element according to any one of claims 2 to 4, wherein a plurality of the electrostrictive layers are laminated via at least one of the insulating layer and the flexible adhesive layer. An electrostrictive layer comprising a dielectric film and a plurality of electrodes disposed via the dielectric film;
A flexible adhesive layer that is laminated with the electrostrictive layer, adheres adjacent layers, and has a Young's modulus equal to or lower than the Young's modulus of the dielectric film;
An output member that is disposed at least at one end in the stacking direction of the electrostrictive layer and the flexible adhesive layer, and is more rigid than the dielectric film and orients the displacement direction of the electrostrictive layer,
An electrostrictive element that outputs a force in a stacking direction by changing a thickness of the dielectric film by changing a voltage applied between the plurality of electrodes.   The said insulating material consists of 1 or more types chosen from an ethylene-propylene-diene terpolymer (EPDM), an acrylic rubber, a silicone rubber, and a polyethylene terephthalate (PET). Electrostrictive element.   The electrostrictive element according to claim 2, wherein the flexible adhesive layer is made of at least one selected from acrylic rubber, natural rubber, silicone rubber, and urethane rubber.   The electrostrictive element according to any one of claims 1 to 8, wherein the dielectric film is made of one or more selected from acrylic rubber, silicone rubber, fluorine rubber, and urethane rubber.   The electrostrictive element according to claim 1, wherein the plurality of electrodes can be expanded and contracted according to deformation of the dielectric film.

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