Patent ID: 12206341

DESCRIPTION OF EMBODIMENTS

Hereinafter, the configurations, manners of operation, and effects of the multilayer electrostatic actuator according to the present embodiment will be described in detail with reference to the embodiments illustrated inFIGS.1to9. In the following description, first, the basic structure of the multilayer electrostatic actuator according to the present embodiment will be described, and next, components of the multilayer electrostatic actuator will be described in detail. Then, the manners of operation of the multilayer electrostatic actuator will be described, and further, the relationship between the generated force of the multilayer electrostatic actuator and the resultant force of the electrostatic force and the spring force will be mentioned. Next, two types of application examples of multilayer electrostatic actuators having a function of connecting electrodes of different layers will be described, and effects of the multilayer electrostatic actuators will be mentioned. Finally, other embodiments of multilayer electrostatic actuators that partially differ in configuration will be briefly described.

First Embodiment

(1-1) Basic Structure of Multilayer Electrostatic Actuator

FIG.1is a perspective view illustrating the basic structure of a multilayer electrostatic actuator according to the first embodiment, andFIG.2is an exploded perspective view illustrating a portion of the basic structure of the actuator part of the multilayer electrostatic actuator illustrated inFIG.1. As illustrated inFIG.1, the multilayer electrostatic actuator1includes a plurality of actuator parts2a,2b,2c. . . ,2n(hereinafter may be referred to as the “actuator part2”) layered and sandwiched between end members5a,5blocated on the upper and lower surfaces in the layering direction Z. Each of the actuator parts2a,2b,2chas a planar shape that is quadrangular as viewed in the layering direction Z. As illustrated inFIG.2, the actuator parts2a,2b,2crespectively include first films3a1,3b1,3c1having a plurality of first connection regions7a1,7b1,7c1formed on one surface in a predetermined pattern, and second films3a2,3b2,3c2connected to the first films3a1,3b1,3c1via the first connection regions7a1,7b1,7c1. The second films3a2,3b2,3c2respectively have a plurality of second connection regions7a2,7b2,7c2formed on the surface opposite to the first films3a1,3b1,3c1in a pattern identical to the pattern of the first connection regions7a1,7b1,7c1. Two actuator parts2a,2b;2b,2coverlapping each other are respectively connected via the second connection regions7b2;7c2, and the actuator part2ais connected to the end member5alocated on the uppermost surface in the layering direction Z via the second connection regions7a2.

Here, the first connection regions7a1are formed in linear shapes having a uniform width, and the plurality of first connection regions7a1are arranged on the first film3a1in parallel to each other at equal intervals. Similarly, the first connection regions7b1are also formed in linear shapes having a uniform width, and the plurality of first connection regions7b1are arranged on the first film3b1in parallel to each other at equal intervals. The first connection regions7c1are also formed in linear shapes having a uniform width, and the plurality of first connection regions7c1are arranged on the first film3c1in parallel to each other at equal intervals. In addition, the second connection regions7a2,7b2,7c2are formed in the linear pattern identical to the linear pattern of the first connection regions7a1,7b1,7c1, respectively, and the plurality of second connection regions7a2,7b2,7c2are arranged on the second films3a2,3b2,3c2in parallel to each other at equal intervals. The linear pattern of the plurality of first connection regions7a1and the linear pattern of the plurality of second connection regions7a1are arranged so as not to overlap each other as viewed in the layering direction Z. The connection regions7b,7eare also arranged similarly. Therefore, on both the first films3a1,3b1,3c1and the second films3a2,3b2,3c2, a non-connection region15is formed having a linear shape and a substantially fixed width at the center between connection regions adjacent to each other as viewed in the layering direction Z.

The actuator parts2a,2b,2chaving such a configuration are layered at an intersection angle θ of 90°. Consequently, in the multilayer electrostatic actuator1, as illustrated inFIG.1, the actuator part2aof the first stage is provided under the end member5aplaced on the uppermost surface in the layering direction Z, and the actuator part2bof the second stage is provided under the actuator part2awith an angle difference of 90°. Similarly, the actuator parts2cto2nof the third to n-th stages are sequentially provided with an angle difference of 90°, and the end member5bis placed on the lowermost surface in the layering direction Z, whereby the multilayer electrostatic actuator1is formed.

Here, the term “having a substantially fixed width” as used in this context in the present specification is intended to mean not only that the width of the non-connection region formed between connection regions is fixed as viewed in the layering direction Z, but also that the width can fluctuate in the range of about ±5 to 10% for manufacturing or other purposes. Although the first embodiment describes the case where the intersection angle θ is 90° as an example, the present invention is not limited thereto. For example, it is intended to include any angle other than 0° such as 60° or 72° (strictly, the acute angle portion between axes satisfies 0°<θ≤90° (including a right angle)).

(1-2) Components of Multilayer Electrostatic Actuator

<Film>

FIG.3is a cross-sectional view illustrating the layered structure of the films of the actuator part illustrated inFIG.2.FIG.3aillustrates the layered structure of the first films3a1,3b1,3c1(hereinafter referred to as the “conductive film P”) of the actuator parts2a,2b,2c, andFIG.3billustrates the layered structure of the second films3a2,3b2,3c2(hereinafter referred to as the “insulating film Q”).

The conductive film P has a three-layer film structure including a conductive layer21at the center and insulating layers23on the front and back surfaces thereof, for example. The conductive layer21can be exemplified by a metal film such as copper (Cu) or aluminum (Al), a conductive polymer, or a conductive carbon allotrope (or a conductive mixture mainly composed of carbon). The insulating layer23can be exemplified by, but is not limited to, an insulating polymer film such as polyethylene terephthalate (PET), Kapton, parylene (registered trademark), a silicon-based material, or a carbon-based material. Here, given that the thickness of the conductive layer21is t21and the thickness of the insulating layer23is t23, the thickness t of the conductive film P is t=t21+2×t23. The thickness t of the conductive film P is, for example, several micrometers. Note that the three-layer film structure of the conductive film P is merely an example. In another example, the conductive layer21may have a multilayer structure made of dissimilar conductors having a plurality of different electrical conductivities and/or Young's moduli, and the insulating layer23may have a multilayer structure made of dissimilar insulators having a plurality of different electrical resistivities and/or Young's moduli.

On the other hand, the insulating film Q does not have any conductive layer21, and consists of an insulating layer23′. The insulating layer23′ can be exemplified by, but is not limited to, an insulating polymer film such as polyethylene terephthalate (PET), Kapton, parylene (registered trademark), a silicon-based material, or a carbon-based material. In addition, the insulating layer23′ may have a single-layer structure made of a single material, or may have a multilayer structure made of dissimilar insulators having a plurality of different electrical resistivities and/or Young's moduli. Here, given that the thickness of the insulating layer23′ is t23′, the thickness t′ of the insulating film Q is t′=t23′. The thickness t′ of the insulating film Q is, for example, several micrometers.

<Connection Portion>

FIG.4is an enlarged front view illustrating a portion of the basic structure of the actuator parts2a,2b,2cillustrated inFIG.1, andFIG.5is a corresponding side view. Both drawings indicate a state in which an external force acts between the two end members5a,5b(FIG.1) to separate the end members5a,5bin the layering direction Z, and the interval between the first films3a1,3b1,3c1and the second films3a2,3b2,3c2is extended. Because the first connection regions and the second connection regions (hereinafter may be referred to as the “connection region7”) of each actuator part are separated from each other, a space11,13is formed in the non-connection region15formed between the connection regions7,7between upper and lower ones of the first films and second films layered.

More specifically, the plurality of first connection regions7a1of the actuator part2aconnect the first film3a1and the second film3a2, and the space13is formed between adjacent first connection regions7a1,7a1(FIG.4). The plurality of second connection regions7a2connect the second film3a2and the end member5aon the uppermost surface in the layering direction Z, and the space11is formed between adjacent second connection regions7a2,7a2. The first connection regions7a1are arranged so as not to overlap the second connection regions7a2as viewed in the layering direction Z. Specifically, the first connection regions7a1and the second connection regions7a2have linear shapes or band shapes extending in the depth direction Y and are arranged at equal intervals in the width direction X, and the first connection regions7a1and the second connection regions7a2are shifted by half a pitch in the width direction X so as to be positioned at the center of the space between counterpart connection regions. Similarly, the plurality of first connection regions7c1of the actuator part2cconnect the first film3c1and the second film3c2, and the space13is formed between adjacent first connection regions7c1,7c1(FIG.4). The plurality of second connection regions7c2connect the second film3c2and the first film3b1of the actuator part2bon the upper side in the layering direction Z, and the space11is formed between adjacent second connection regions7c2,7c2.

The plurality of first connection regions7b1of the actuator part2bconnect the first film3b1and the second film3b2, and the space13is formed between adjacent first connection regions7b1,7b1(FIG.5). The second connection region7b2connect the second film3b2of the actuator part2band the first film3arof the actuator part2a, and the space11is formed between adjacent second connection regions7b2,7b2. The first connection regions7b1are arranged so as not to overlap the second connection regions7b2as viewed in the layering direction Z. In addition, the first connection regions7b1and the second connection regions7b2have linear shapes or band shapes extending in the width direction X and are arranged at equal intervals in the depth direction Y, and the first connection regions7b1and the second connection regions7b2are shifted by half a pitch in the depth direction Y so as to be positioned at the center of the space between counterpart connection regions.

An example of the material for connecting the first film and the second film in the connection region7is an adhesive, which is applied with high accuracy so as to have a constant application thickness and a predetermined pattern using a method such as relief printing, offset printing, stencil printing, or inkjet printing to form an adhesive portion. Alternatively, a chemical bonding layer may be formed on the insulating layer23or23′ (FIG.3) through chemical treatment such as surface treatment. In the case of forming an adhesive portion, the two films3a1,3a2are bonded to each other via the adhesive. In the case of forming a bonding layer through chemical treatment, the two films3a1,3a2are covalently bonded to each other. Other methods such as welding the insulating layer23or23′ can be used without limitation to form the connection region as long as the above-described coupling pattern can be formed.

<Hinge Portion>

As described above with reference toFIGS.4and5, because the second film3a2is connected at its upper and lower surfaces to the first connection regions7a1and the second connection regions7a2, respectively, the portions (hereinafter referred to as the “connection surface portions81,82” (FIG.6)) of the second film3a2corresponding to the first connection regions7a1and the second connection regions7a2have higher rigidity than the portions of the second film3a2corresponding to the other regions (non-connection regions that do not contribute to connection, hereinafter referred to as the non-connection region15). Similarly, the connection surface portions81,82of the second film3b2corresponding to the first connection regions7b1and the second connection regions7b2have higher rigidity than the non-connection region15of the second film3b2.

When a tensile force (external force) in a direction in which the two end members5a,5b(FIG.1) are separated is applied in the layering direction Z, the non-connection regions15of the second film3a2of the actuator part2aand the second film3b2of the actuator part2bare elastically deformed, and the intervals3a1-3a2,3b2-3a1,3b1-3b2between the first film and the second film are widened (FIGS.4and5), resulting in the multilayer electrostatic actuator1extending in the layering direction Z (FIG.1). A portion of the second film3a2,3b2corresponding to the non-connection region15is defined as a “hinge portion15”.

When a voltage is applied between the first film3a1of the actuator part2aand the first film3b1of the actuator part2b, the interval between the first films3a1,3b1returns to the initial state (described later) due to the electrostatic attractive force caused by the applied voltage, and the interval between the first films3a1,3b1is narrowed. The gap between the other first films3b1,3c1is similarly narrowed due to the electrostatic attractive force, resulting in the multilayer electrostatic actuator1contracting in the layering direction Z.

The first film3a1of the actuator part2ais connected at its upper surface to the second film3a2in the first connection regions7a1and connected at its lower surface to the second film3b2in the second connection regions7b2. Because the first connection regions7a1extend in the depth direction Y and the second connection regions7b2extend in the width direction X, the second connection regions7b2act as ribs with respect to the deformation of the hinge portion15extending in the depth direction Y of the first film3a1of the actuator part2a. Therefore, the first film3a1of the actuator part2ahas higher rigidity than the second film3a2. Thus, when a tensile force (external force) is applied to the multilayer electrostatic actuator1in the layering direction Z, the hinge portion15of each of the second film3a2of the actuator part2aand the second film3b2of the actuator part2bis elastically deformed (bent and extended), but the elastic deformation of the first film3a1of the actuator part2ais suppressed due to the above-described structure.

In the case where the deformation of the first film3a1,3b1is suppressed and only the hinge portion15of the second film3a2,3b2is deformed, the movement in the width direction X and the depth direction Y at the boundary position O (FIG.6) between the hinge portion15and the connection surface portion81,82on the second film3a2,3b2is restrained. When the hinge portion15is deformed under such a restraint condition, the area near the boundary position O of the second film3a2,3b2is mainly shear-deformed or bending-deformed so that the hinge portion15behaves like a soft spring: however, when an external force is applied in an attempt to cause further deformation, the hinge portion15is inclined in the layering direction Z, and the hinge portion15is tensile-deformed to behave like a hard spring. For this reason, in the small deformation range in which the multilayer electrostatic actuator1starts to extend in the layering direction Z from the initial state before external force application, the hinge portion15is soft, and the gap between the first films3a1,3b1is likely to be widened in response to the external force. On the other hand, upon an additional external force applied in an attempt to cause further deformation, the hinge portion15rapidly becomes hard, which makes the gap between the first films3a1,3b1less likely to be widened rapidly.

In other words, the spring constant of the hinge portion15of each actuator part2a,2bis small in the small deformation range of the multilayer electrostatic actuator1so that the actuator part2a,2bis softly deformed, whereas an attempt to cause further deformation beyond the small deformation range results in a rapid increase in the spring constant of the second film3a2,3b2, which makes each actuator part2a,2bless likely to be deformed rapidly. That is, the multilayer electrostatic actuator1has nonlinear spring characteristics in each actuator part2a,2b, which makes it possible to suppress excessive extension of the distance between films, in particular the distance between the first films3a1,3b1, and to obtain a sufficient electrostatic attractive force.

For the above reason, when a tensile force (external force) is applied to the multilayer electrostatic actuator1in the layering direction Z, the second film3a2,3b2is elastically deformed in the actuator part2a,2b, and the multilayer electrostatic actuator1is put into the extended state. At this time, the deformation of the first film3a1is suppressed. When a voltage is applied to the multilayer electrostatic actuator1in the extended state, an electrostatic attractive force acts between the first film3a1of the actuator part2aand the first film3b1of the actuator part2b, and the interval between the first films3a1,3b1is narrowed. As a result, the multilayer electrostatic actuator1contracts in the layering direction Z. Conversely, when the voltage is turned to zero, the non-connection region15of each of the second film3a2of the actuator part2aand the second film3b2of the actuator part2bis elastically deformed due to the external force, and the intervals3a1-3a2,3b2-3a1,3b1-3b2between the first film and the second film are widened, resulting in the multilayer electrostatic actuator1extending in the layering direction Z. Thus, the multilayer electrostatic actuator1can be extended and contracted by turning on/off the applied voltage.

<Space>

When a tensile force (external force) in the layering direction Z is applied to the multilayer electrostatic actuator1and the multilayer electrostatic actuator1is put into the extended state, the second film3a2,3b2undergoes an increase in the space11with respect to the upper layer (the end member5aon the uppermost surface in the layering direction Z and the first film3a1of the actuator part2a, respectively) and an increase in the space13with respect to the lower layer (first film3a1,3b1, respectively) (FIGS.4and5). These spaces11,13are in fluid communication with outside in order to secure a sufficient amount of extension and contraction without hindering the extension and contraction operation of the multilayer electrostatic actuator1described below, and function as an insulating fluid portion through which an insulating fluid passes. In addition, the opening areas of these spaces11and13vary depending on the difference between the extension and contraction of the actuator part2a,2b. That is, when a tensile force (external force) in the layering direction Z is applied, mainly the second film is elastically deformed, and the interval between first films is separated, resulting in an increase in the opening area of the space11,13; whereas when a voltage is applied between electrode layers to cause an electrostatic attractive force, the interval between first films is narrowed, resulting in a decrease in the opening area of the space11,13.

(1-3) Manner of Operation of Multilayer Electrostatic Actuator

In the multilayer electrostatic actuator1having the above configuration, the extension/contraction state varies depending on whether a tensile force (external force) is applied in the layering direction Z and whether a voltage is applied between first films.

<Initial State (Contracted State)>

In the initial state or when a voltage is applied between first films after application of a tensile force (external force) in the layering direction Z and an electrostatic attractive force acts and balances, the hinge portion15is not deformed, and the first film3a1and the second film3a2are in a planar state. At this time, the distance u from the conductive layer21of the first film3a1to the conductive layer21of the first film3b1(FIG.3) is uinitial=2×t23+t23′(not illustrated).

<Extended State>

When a tensile force (external force) is applied to the multilayer electrostatic actuator1in the layering direction Z, the non-connection region15(hinge portion15) of the second film3a2of the actuator part2ais elastically deformed (bent and extended), and the interval between the first film3a1and the second film3a2is widened (FIG.4), resulting in the multilayer electrostatic actuator1extending in the layering direction Z (FIG.1).FIG.6is a cross-sectional view illustrating the actuator part2ain the extended state of the multilayer electrostatic actuator1. As illustrated inFIG.6, when a tensile force (external force) is applied in the layering direction Z, the interval between the first film3a1and the second film3a2is widened. Given that the spring displacement of the hinge portion15in this case is σ, the distance u from the conductive layer21of the first film3a1to the conductive layer21of the first film3b1(FIG.3) is uextension=2×t23+t23′+σ.

As described above, the second connection regions7b2of the actuator part2bact as ribs that prevent the first film3a1of the actuator part2afrom being deformed in the layering direction Z, and the deformation of the first film3a: is suppressed, so that deformation occurs in which the fixed end of the hinge portion15moves in the layering direction Z. The above discussion mainly about the actuator part2a,2bsimilarly applies to every actuator part2a,2b,2c. . . ,2n, and thus the stroke U of the multilayer electrostatic actuator1including these n actuator parts2layered is U=n×(uextension−uinitial)=n×σ.

(1-4) Relationship Between Generated Force of Actuator Part and Resultant Force of Electrostatic Force and Spring Force

FIG.7is a graph illustrating the relationship between the resultant force of the electrostatic force and the spring force of the multilayer electrostatic actuator1and the generated force F of the actuator part2. The horizontal axis represents the spring displacement σ, and the vertical axis represents the generated force F of the actuator part2. The spring force nonlinearly increases as the spring displacement σ increases, whereas the electrostatic force decreases approximately in inverse proportion to the square of σ as the spring displacement σ increases. In addition, the resultant force of the electrostatic force and the spring force draws a U-shaped curve as illustrated in the drawing. Given that the minimum value of the resultant force is Fmin, the generated force F of the actuator part2acts in the contraction direction with a magnitude of not less than Fmin.

Second Embodiment

In the multilayer electrostatic actuator1according to the first embodiment, the first film3a1,3b1constituting the actuator part2is configured by the conductive film P, and the second film3a2,3b2is configured by the insulating film Q. A multilayer electrostatic actuator101according to the second embodiment is different from the multilayer electrostatic actuator1according to the first embodiment in that both the first and second films constituting the actuator part are configured by the conductive film P.

(2-1) Basic Structure of Multilayer Electrostatic Actuator

The basic structure of the multilayer electrostatic actuator101and the basic structure of the actuator part according to the second embodiment are the same as those of the multilayer electrostatic actuator1according to the first embodiment, andFIGS.1and2are applied in their entirety. In addition, elements identical or similar to those of the multilayer electrostatic actuator1according to the first embodiment are denoted by identical or similar reference signs, and the description thereof will be omitted.

(2-2) Components of Multilayer Electrostatic Actuator

<Film>

As described above, in the multilayer electrostatic actuator101according to the second embodiment, both the first and second films3a1,3a2constituting the actuator part are configured by the conductive film P illustrated inFIG.3a.

<Connection Portion>

The connection portion of the actuator part of the multilayer electrostatic actuator101according to the second embodiment is the same as that of the multilayer electrostatic actuator1according to the first embodiment.

<Hinge Portion>

In the multilayer electrostatic actuator1according to the first embodiment, a voltage is applied between the first films3a1,3b1of the overlapping actuator parts2. The multilayer electrostatic actuator101according to the second embodiment is different from the multilayer electrostatic actuator1according to the first embodiment in that a voltage is applied between the overlapping first and second films3a1,3a2;3b2,3a1. When a voltage is applied between the first and second films3a1,3a2, the interval between the first and second films3a1,3a2returns to the initial state due to the electrostatic attractive force (described later), resulting in the multilayer electrostatic actuator101contracting in the layering direction Z. The electrostatic attractive force caused by the voltage applied between the first film3a1and the second film3a2of the actuator part2aacts to narrow the interval between the first and second films3a1,3a2. The gap between the other first and second films3b1,3b2and the gap between the first film and the second film (e.g.3b1and3a1) of different actuator parts2overlapping each other are similarly narrowed due to the electrostatic attractive force, resulting in the multilayer electrostatic actuator101contracting in the layering direction Z.

The basic structure of the actuator part of the multilayer electrostatic actuator101according to the second embodiment is the same as that of the actuator part2of the multilayer electrostatic actuator1according to the first embodiment: therefore, the second connection regions7b2of the actuator part2bact as ribs with respect to the deformation of the non-connection region15of the first film3a1of the actuator part2ain the layering direction Z. Therefore, when a tensile force (external force) is applied to the multilayer electrostatic actuator101in the layering direction Z, the non-connection region15of each of the second film3a1of the actuator part2aand the second film3b1of the actuator part2bis elastically deformed (bent and extended), but the deformation of the first film3a1of the actuator part2ais suppressed. Thus, in the multilayer electrostatic actuator101according to the second embodiment, each actuator part has nonlinear spring characteristics as in the case of the multilayer electrostatic actuator1according to the first embodiment.

<Space>

The basic structure of the actuator part of the multilayer electrostatic actuator101according to the second embodiment is the same as that of the actuator part2of the multilayer electrostatic actuator1according to the first embodiment. Therefore, when a tensile force (external force) in the layering direction Z is applied to the multilayer electrostatic actuator101, the second film3a2is elastically deformed, and the interval between the first and second films3a1,3a2is separated, resulting in an increase in the opening area of the space11,13; whereas when a voltage is applied between the first and second films3a1,3a2to cause an electrostatic attractive force, the interval between the first and second films3a1,3a2is narrowed, resulting in a decrease in the opening area of the space11,13.

(2-3) Manner of Operation of Multilayer Electrostatic Actuator

In the multilayer electrostatic actuator101having the above configuration, the extension/contraction state varies depending on whether a tensile force (external force) is applied in the layering direction Z and whether a voltage is applied between the first and second films3a1,3a2.

<Initial State (Contracted State)>

In the initial state or when a voltage is applied between the first and second films3a1,3a2after application of a tensile force (external force) in the layering direction Z and an electrostatic attractive force acts and balances, the hinge portion15is not deformed, and the first film3a1and the second film3a2are in a planar state. At this time, the distance u from the conductive layer21of the first film3a1to the conductive layer21of the second film3a2(FIG.3) is uinitial=2×t23(not illustrated).

<Extended State>

When a tensile force (external force) is applied to the multilayer electrostatic actuator101in the layering direction Z, the interval between the first film3a1and the second film3a2is widened. The distance u from the conductive layer21of the first film3a1to the conductive layer21of the second film3a2(FIG.3) is uextension=2×t23+σ. The above discussion mainly about the actuator part2a,2bsimilarly applies to every actuator part2a,2b,2c, . . . ,2n, and thus the stroke U of the multilayer electrostatic actuator101including these n actuator parts layered is U=n×(uextension−uinitial)=n×0.

(2-4) Relationship Between Generated Force of Actuator Part and Resultant Force of Electrostatic Force and Spring Force

Because the basic structure of the multilayer electrostatic actuator101according to the second embodiment is the same as that of the multilayer electrostatic actuator1according to the first embodiment, the relationship between the resultant force of the electrostatic force and the spring force of the actuator part and the generated force F of the actuator part in the multilayer electrostatic actuator101according to the second embodiment is also the same as that of the multilayer electrostatic actuator1according to the first embodiment, andFIG.7is applied in its entirety. However, in the second embodiment, the distance between the first film3a1and the second film3a2or between the second film3b2and the first film3a1is short as compared with the first embodiment in which contraction is caused by the electrostatic attractive force between the first films3a1,3b1constituting the actuator part2, and thus a large electrostatic attractive force is generated, which increases the contraction force.

(2-5) Application Examples of Multilayer Electrostatic Actuator

For the manufacture of the multilayer electrostatic actuator101according to the second embodiment, a structure with high productivity is required. The following two application examples represent an example of a structure that allows for efficient manufacture with high productivity, in which the end portion of the actuator part2in each layer includes an outer hinge portion17connected to the end portion of the actuator part2of another layer. The outer hinge portion17eliminates the need for a post-process for connecting homopolar electrodes, leading to improvement in productivity. Furthermore, because the structures of these application examples do not have an electrode connection portion having a local discharge risk, the reliability of the multilayer electrostatic actuator is improved.

<Bent Structure>

FIG.8is a perspective view illustrating Application Example 1 in which the multilayer electrostatic actuator1illustrated inFIG.1is created with a bent structure. The multilayer electrostatic actuator1A according to Application Example 1 has a paper spring structure in which two elongated ribbon-shaped electrodes37,39are bent in a zigzag shape and alternately folded. The planar portions layered facing each other serve as the actuator parts2of different layers, and the loop-shaped connection portion extending outward from each actuator part2functions as the above-described outer hinge portion17.

The multilayer electrostatic actuator part1A with such a configuration can be efficiently manufactured as described above. In a multilayer electrostatic actuator without this configuration, the actuator parts are more likely to deform at positions closer to their end portions, which can make the distance between the actuator parts uneven. In contrast, in the multilayer electrostatic actuator part1A, the outer hinge portion17functions as a semi-cylindrical structure that suppresses the deformation of the actuator part2in the plane direction: therefore, the end portion of the actuator part2has as uniform a distance as the central portion of the actuator part2between the connection surface portions8facing in the Z direction in each actuator part2, which makes the movement in the layering direction Z stable and uniform, and can improve the driving force. Furthermore, the application of voltage to each actuator part2is performed simply on the two ribbon-shaped electrodes37,39connected via the outer hinge portion17, leading to simplified wiring.

<Wound Structure>

FIG.9is a perspective view illustrating Application Example 2 in which the multilayer electrostatic actuator1illustrated inFIG.1is created with a wound structure. The multilayer electrostatic actuator1B according to Application Example 2 has a flat spiral wound structure in which the two elongated ribbon-shaped electrodes37,39are wound in one direction from the center. The planar portions layered facing each other serve as the actuator parts2of different layers, and the loop-shaped connection portion extending outward from each actuator part2functions as the above-described outer hinge portion17.

The multilayer electrostatic actuator1B with such a configuration can also be efficiently manufactured, similarly to the multilayer electrostatic actuator1A with the bent structure. In addition, the application of voltage to the actuator part2in each layer is performed simply on the two ribbon-shaped electrodes37,39connected via the outer hinge portion17, leading to simplified wiring.

(3) Other Embodiments

The above-described embodiments are the basic embodiments of the present invention. The multilayer electrostatic actuator1according to the present embodiment is not limited to the above-described embodiments, and it is possible to change or remove a partial configuration without departing from the scope of the present embodiment, or to add a technique known and commonly used by those skilled in the art. For example, the planar shape of the multilayer electrostatic actuator1is not limited to the quadrangle described in the above-described embodiments, and may be another polygon such as a triangle or a pentagon, or may be a shape having a curve such as a circle, a semicircle, an oval, or an ellipse. In addition, the intersection angle θ of the actuator part2in each layer is not limited to 90° described in the above-described embodiments, and can be set to another angle such as 60° in the case that the planar shape of the multilayer electrostatic actuator1is a triangle, or 72° in the case that the planar shape is a pentagon.

FIG.7-1is an explanatory diagram for explaining the overlapping state of two actuator parts of the multilayer electrostatic actuator according to another embodiment, where (a) is a view as viewed in the layering direction Z, and (b) is a cross-sectional view taken along VII-VII in (a). The multilayer electrostatic actuators1according to the first and second embodiments are both configured by layering the actuator parts2a,2bat the intersection angle θ of 90°, from which the multilayer electrostatic actuator according to another embodiment is different in that the actuator parts2a,2bare layered at the intersection angle θ of an acute angle different from 90°. Elements identical or similar to the elements of the embodiments described above are denoted by identical or similar reference signs, and the description thereof will be omitted. The first connection regions7a: (indicated by solid lines) and the second connection regions7b2(indicated by broken lines) of the second film3b2are arranged on the upper and lower sides of the first film3aillustrated in (a), and the second connection regions7a2(indicated by solid lines) and the first connection regions7a1(indicated by broken lines) are arranged on the upper and lower sides of the second film3a2illustrated in (b).

As viewed in the layering direction Z, as illustrated inFIG.7-1a, the axes of the pattern of the first connection regions7a1arranged on the first film3a1of the actuator part2aand the axes of the pattern of the second connection regions7b2of the second film3b2of the actuator part2bplaced under the actuator part2aintersect at the intersection angle θ of an acute angle different from 90°. Therefore, when a tensile force (external force) in the layering direction Z is applied to the multilayer electrostatic actuator, the deformation of the first film3a1is suppressed. On the other hand, as illustrated inFIG.7-1b, the axes of the pattern of the second connection regions7a2arranged on the second film3a2and the axes of the pattern of the first connection regions7a1arranged on the first film3a1are parallel to each other and do not intersect each other. Therefore, when a tensile force (external force) in the layering direction is applied to the multilayer electrostatic actuator, the second film3a2is deformed.

FIG.7-2is an explanatory diagram for explaining the condition of intersection between the first connection regions7a1and the second connection regions7b2in the multilayer electrostatic actuator illustrated inFIG.7-1. The patterns of the first connection regions7a1and the second connection regions7b, both form linear shapes having a substantially uniform width d and arranged at equal intervals. Given that the length, on the plane as viewed in the layering direction Z, of the axes of the pattern of one of the first connection regions7a1of the actuator part2aand the second connection regions7b2of the actuator part2bis L, and the width between the non-connection regions in the one connection regions as viewed in the layering direction Z is 2×l+d (seeFIG.6), the intersection angle θ [rad] of the axes of the patterns between the two connected actuator parts2a,2bas viewed in the layering direction Z satisfies

arctan⁡(2×l+dL)<❘"\[LeftBracketingBar]"θ❘"\[RightBracketingBar]"≤π2.[Formula⁢2]

In addition, the shape and arrangement (pattern) of the connection regions7is not limited to the shape and arrangement described in the above-described embodiments. It is possible to adopt various other shapes and arrangements (patterns) such as those in which the connection regions7with a circular shape or a quadrangular shape in plan view are arranged at equal intervals in the width direction X and the depth direction Y. Furthermore, in the above description, both the first connection regions and the second connection regions of the actuator part2in each layer are formed in linear shapes having a uniform width and arranged at equal intervals such that one first connection region is positioned at the center of the space between two second connection regions as viewed in the layering direction Z. However, as long as the first connection regions and the second connection regions do not overlap each other as viewed in the layering direction Z, the first connection regions and the second connection regions do not need to be linear or be arranged at equal intervals.

REFERENCE SIGNS LIST

1,101,1A,1B multilayer electrostatic actuator2,2a,2b,2cactuator part3film3a1,3b1first film3a2,3b2second film5a,5bend member7connection region7a1,7b1first connection region7a2,7b2second connection region81,82connection surface portion11space13space15non-connection region (or hinge portion)17outer hinge portion21conductive layer23insulating layer37ribbon-shaped electrode39ribbon-shaped electrodeθ intersection angleZ layering directionX width directionY depth directionX, Y planar directionU strokeu distanceσ spring displacementd width (of connection region)l length (of hinge portion)O supporting pointF generated force (of actuator part)Z layering direction