Electrostatic actuator
The electrostatic actuator design with overlapping bag portions and electrodes enhances displacement and simplifies manufacturing by reducing electrode count and friction, addressing the limitations of existing actuators.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- NIDEC CORP(JP)
- Filing Date
- 2025-11-25
- Publication Date
- 2026-06-04
Smart Images
Figure JP2025040904_04062026_PF_FP_ABST
Abstract
Description
Electrostatic actuator
[0001] The present disclosure relates to an electrostatic actuator. This application claims priority based on Japanese Patent Application No. 2024-208300 filed in Japan on November 29, 2024, and incorporates its content herein by reference.
[0002] An electrostatic actuator that utilizes the electrostatic attraction generated between two electrodes as a driving force is known.
[0003] In recent years, as such an electrostatic actuator, the HASEL (Hydraulically Amplified Self-healing Electrostatic) actuator has attracted attention. The HASEL actuator has a structure in which a pair of electrodes are provided at both ends of a shell filled with a dielectric liquid. When a voltage is applied to the pair of electrodes, the dielectric liquid inside the shell is polarized and an electrostatic attraction is generated between the electrodes. As a result, the pair of electrodes are attracted, causing the dielectric liquid inside the shell to move and the shell to deform. By utilizing this deformation of the shell, the HASEL actuator can, for example, push or pull an object. The HASEL actuator is a type of artificial muscle and is expected to be utilized in soft robots.
[0004] Patent Document 1 discloses a HASEL actuator in which a plurality of shells are connected in a row. The HASEL actuator in which a plurality of shells are connected in a row can increase the tensile force of the artificial muscle when bundled together.
[0005] U.S. Patent Application Publication No. 2023 / 0091400
[0006] However, there is room for improvement in an electrostatic actuator in which a plurality of HASEL actuators in which a plurality of shells are connected in a row are bundled together, from the perspective of increasing the displacement amount.
[0007] The present disclosure has been made in view of the above, and an object thereof is to provide an electrostatic actuator capable of increasing the displacement amount.
[0008] An electrostatic actuator according to one aspect of the present disclosure comprises a first electrode, a plurality of first bag portions, a plurality of second bag portions, a second electrode, and a third electrode. The first electrode is strip-shaped. The plurality of first bag portions are located on a first surface of the first electrode. The plurality of first electrodes are arranged along the longitudinal direction of the first electrode. The plurality of first electrodes are sealed with a dielectric liquid. The plurality of second bag portions are located on a second surface of the first electrode opposite to the first surface. The plurality of second bag portions are arranged along the longitudinal direction of the first electrode. The plurality of second bag portions are sealed with a dielectric liquid. The second electrode is located on the opposite side of the first electrode, across the first bag portions. The third electrode is located on the opposite side of the first electrode, across the second bag portions. The first electrode, the second electrode, and the third electrode are flexible. The first bag portions are located in a position that overlaps with the boundary between adjacent second bag portions in a planar transparent view. The second pouch portion is located in a position that overlaps with the boundary between adjacent first pouch portions in a planar transparent view.
[0009] An electrostatic actuator according to one aspect of this disclosure can increase the amount of displacement.
[0010] Figure 1 is an explanatory diagram showing a side cross-section of a proportional electrostatic actuator. Figure 2 is an explanatory diagram showing a side cross-section of a proportional electrostatic actuator. Figure 3 is an explanatory diagram showing a side cross-section of an electrostatic actuator according to an embodiment. Figure 4 is an explanatory diagram showing a side cross-section of an electrostatic actuator according to an embodiment. Figure 5 is an explanatory diagram showing a side cross-section of an electrostatic actuator according to a first modified example of the embodiment. Figure 6 is an explanatory diagram of a plan view of an electrostatic actuator according to a second modified example of the embodiment. Figure 7 is an explanatory diagram of a plan view of an electrostatic actuator according to a second modified example of the embodiment. Figure 8 is an explanatory diagram of a plan view of an electrostatic actuator according to a second modified example of the embodiment.
[0011] Hereinafter, embodiments of the electrostatic actuator structure will be described in detail with reference to the attached drawings. However, this invention is not limited to the embodiments described below. In the following description, components that perform the same function are denoted by the same reference numerals, and redundant descriptions are omitted.
[0012] Furthermore, the configuration and operation of the proportional electrostatic actuator 100 will be described below with reference to Figures 1 and 2, followed by a description of the configuration and operation of the electrostatic actuator 2 according to the embodiment.
[0013] Figures 1 and 2 are explanatory diagrams showing side cross-sections of the proportional electrostatic actuator 100. Figure 1 shows the proportional electrostatic actuator 100 in a non-operating state (extended state). Figure 2 shows the proportional electrostatic actuator 100 in an operating state (contracted state).
[0014] As shown in Figure 1, the electrostatic actuator 100 is composed of two HASEL (Hydraulically Amplified Self-healing Electrostatic) actuators bundled together. Each HASEL actuator has a plurality of bag portions 101 connected in a row. Each bag portion 101 is filled with a dielectric liquid (hereinafter referred to as "dielectric liquid 102").
[0015] Furthermore, a first electrode 103 is provided on the first surface of each bag portion 101. Each first electrode 103 extends from one end in the longitudinal direction where the bag portions 101 are connected to the middle of each bag portion 101. In addition, a second electrode 104 is provided on the second surface of each bag portion 101, opposite to the first surface, with the dielectric liquid 102 in between. Each second electrode 104 extends from one end in the longitudinal direction where the bag portions 101 are connected to the middle of each bag portion 101.
[0016] In one example, each first electrode 103 is connected to a power supply that can switch between starting and stopping the application of voltage. In one example, each second electrode 104 is connected to ground. When in the non-operating state shown in Figure 1, the application of voltage to the first electrode 103 is stopped.
[0017] At this time, there is no potential difference between the opposing first electrode 103 and the second electrode 104, and no electrostatic attraction is generated, so the dielectric liquid 102 is located in the space within the bag portion 101 sandwiched between the opposing first electrode 103 and the second electrode 104.
[0018] When a voltage is applied to the first electrode 103 from this state, a potential difference is generated between the opposing first electrode 103 and the second electrode 104, and an electrostatic attraction is generated, causing the opposing first electrode 103 and the second electrode 104 to come into contact, as shown in Figure 2.
[0019] As a result, the electrostatic actuator 100 moves into the space within the bag portion 101 where the dielectric liquid 102 is not sandwiched between the opposing first electrode 103 and second electrode 104, deforming the bag portion 101 and entering the operating state.
[0020] In the operating state, the electrostatic actuator 100 has a shorter longitudinal length in which the bag portions 101 are connected, compared to the non-operating state, due to the deformation of each bag portion 101. The difference between the length of the electrostatic actuator 100 in the non-operating state and the length of the electrostatic actuator 100 in the operating state is the displacement of the electrostatic actuator 100.
[0021] In such an electrostatic actuator 100, the first electrode 103 and the second electrode 104, which are V-shaped in cross-sectional view when not in operation, come into contact when in operation, so the longitudinal length to which the bag portion 101 is connected increases slightly. For this reason, there is room for improvement in the electrostatic actuator 100 in terms of increasing the amount of displacement.
[0022] Therefore, the electrostatic actuator according to the embodiment is configured such that when it moves from a non-operating state to an operating state, each electrode is displaced in a shape that reduces the longitudinal length of the electrostatic actuator.
[0023] Figures 2 and 3 are explanatory diagrams showing side cross-sections of the electrostatic actuator 2 according to the embodiment. Figure 3 shows the electrostatic actuator 2 in a non-operating state (extended state). Figure 4 shows the electrostatic actuator 2 in an operating state (contracted state) relative to the operating state.
[0024] As shown in Figure 3, the electrostatic actuator 2 includes a strip-shaped first electrode 3. The electrostatic actuator 2 also includes a plurality of first bag portions 4 and a plurality of second bag portions 5. The plurality of first bag portions 4 are located on the first surface of the first electrode 3 and, in one example, are arranged along the longitudinal direction of the first electrode 3. The plurality of second bag portions 5 are located on the second surface of the first electrode 3, opposite to the first surface, and, in one example, are arranged along the longitudinal direction of the first electrode 3.
[0025] Hereinafter, the longitudinal direction of the first electrode 3, where the first bag portion 4 and the second bag portion 5 are aligned, will be referred to as the longitudinal direction. Depending on the configuration of the electrostatic actuator 2, the multiple first bag portions 4 and second bag portions 5 may be aligned in a direction different from the longitudinal direction of the first electrode 3. Dielectric liquid 6 is sealed inside each of the multiple first bag portions 4 and second bag portions 5.
[0026] Furthermore, the electrostatic actuator 2 comprises a plurality of second electrodes 7 and a plurality of third electrodes 8. The second electrodes 7 are arranged in a plurality along the longitudinal direction. The third electrodes 8 are also arranged in a plurality along the longitudinal direction. In a planar transmission view, the second electrodes 7 and the third electrodes 8 partially overlap so as to cover the portion beyond the midpoint of each other, and in a side cross-sectional view, they are arranged alternately (in a zigzag pattern).
[0027] Multiple second electrodes 7 are located on the opposite side of the first bag portion 4 from the first electrode 3. Multiple third electrodes 8 are located on the opposite side of the second bag portion 5 from the first electrode 3. The first electrode 3, the multiple second electrodes 7, and the multiple third electrodes 8 are flexible. As materials for the flexible second electrodes 7 and third electrodes 8, for example, metal foils such as aluminum foil and gold foil, metal vapor deposition, conductive resin film, conductive paint containing conductive substances such as metal powder and carbon powder, liquid metal, carbon grease, conductive liquids such as water, or cloth impregnated with these can be used.
[0028] Furthermore, each first bag portion 4 is positioned so as to overlap with the boundary between adjacent second bag portions 5 in a planar transparent view. Also, each second bag portion 5 is positioned so as to overlap with the boundary between adjacent first bag portions 4 in a planar transparent view.
[0029] Furthermore, the second electrode 7 extends from one end in the longitudinal direction of each first bag portion 4 (the left end in Figure 4) to the middle of the longitudinal direction of each first bag portion 4. The third electrode 8 extends from one end in the longitudinal direction of each second bag portion 5 (the left end in Figure 4) to the middle of the longitudinal direction of each second bag portion 5.
[0030] In one example, the first electrode 3 is connected to ground. In one example, each second electrode 7 and each third electrode 8 is connected to a power supply that can switch the application of voltage on and off. When in the non-operating state shown in Figure 3, the application of voltage to the second electrode 7 and the third electrode 8 is stopped.
[0031] At this time, there is no potential difference between the opposing first electrode 3 and the second electrode 7, and no electrostatic attraction is generated, so the dielectric liquid 6 is located in the space within the first bag portion 4 sandwiched between the opposing first electrode 3 and the second electrode 7.
[0032] Furthermore, since there is no potential difference between the opposing first electrode 3 and the third electrode 8, and no electrostatic attraction is generated, the dielectric liquid 6 is located in the space within the second bag portion 5 sandwiched between the opposing first electrode 3 and the third electrode 8.
[0033] When a voltage is applied to the second electrode 7 from this state, a potential difference is created between the opposing first electrode 3 and the second electrode 7, generating an electrostatic attraction. As a result, the dielectric liquid 6 that was located between the opposing first electrode 3 and the second electrode 7 moves to the side of the first bag portion 4 that is not covered by the second electrode 7 (the right side in Figure 4), causing the side of the first bag portion 4 that is not covered by the second electrode 7 to expand. This reduces the length of the first bag portion 4 in the longitudinal direction.
[0034] Furthermore, when voltage is applied to the third electrode 8, a potential difference is generated between the opposing first electrode 3 and the third electrode 8, creating an electrostatic attraction. As a result, the dielectric liquid 6 that was located between the opposing first electrode 3 and the third electrode 8 moves to the side of the second bag portion 5 that is not covered by the third electrode 8 (the right side in Figure 4), causing the side of the second bag portion 5 that is not covered by the third electrode 8 to expand. This reduces the longitudinal length of the second bag portion 5.
[0035] Thus, in the electrostatic actuator 2, the second electrode 7 extends to the middle of one end (the left end in Figure 4) in the longitudinal direction of each first bag portion 4, and the third electrode 8 extends from one end (the left end in Figure 4) in the longitudinal direction of each second bag portion 5 to the middle. As a result, the electrostatic actuator 2 can efficiently inflate the portion of the first bag portion 4 and the second bag portion 5 that is not in the middle (the right end in Figure 4) when in operation, thereby reaching the operating state.
[0036] In this configuration, the first electrode 3, the multiple second electrodes 7, and the multiple third electrodes 8 are flexible. Each first bag portion 4 is positioned to overlap with the boundary between adjacent second bag portions 5 in a planar transmitted view. Each second bag portion 5 is positioned to overlap with the boundary between adjacent first bag portions 4 in a planar transmitted view.
[0037] Therefore, in a planar transmission view, the first electrode 3 and the third electrode 8 in the portion that overlaps with the expanded portion of the first bag portion 4 are displaced to conform to the shape of the expanded first bag portion 4. Similarly, in a planar transmission view, the first electrode 3 and the second electrode 7 in the portion that overlaps with the expanded portion of the second bag portion 5 are displaced to conform to the shape of the expanded second bag portion 5. In other words, when the electrostatic actuator 2 moves from a non-operating state to an operating state, the first electrode 3, the second electrode 7, and the third electrode 8 are displaced to conform to the shape of the expanded second bag portion 5.
[0038] Thus, when the electrostatic actuator 2 transitions from a non-operating state to an operating state, not only are the first bag portion 4 and the second bag portion 5 displaced in a shape that reduces their longitudinal length, but the first electrode 3, the second electrode 7, and the third electrode 8 are also displaced in a shape that reduces their longitudinal length. As a result, the electrostatic actuator 2 can increase the amount of displacement compared to the electrostatic actuator 100, which operates on a proportional basis.
[0039] Furthermore, the electrostatic actuator 2 includes a single strip-shaped first electrode 3 that is shared by multiple second electrodes 7 and third electrodes 8. As a result, the electrostatic actuator 2 can reduce the number of electrodes required compared to the proportional electrostatic actuator 100, thus simplifying the manufacturing process and reducing manufacturing costs.
[0040] Further, the first electrode 3 is covered with an insulating film 10 that forms the first bag portion 4 and an insulating film 11 that forms the second bag portion 5. Thereby, when a voltage is applied to the second electrode 7 and the third electrode 8, the electrostatic actuator 2 can prevent a short circuit between the first electrode 3 and the second electrode 7 and a short circuit between the first electrode 3 and the third electrode 8.
[0041] Further, as shown in FIG. 3, in the non-operating state where there is no potential difference between the first electrode 3 and the second electrode 7, the electrostatic actuator 2 has a distance between the first electrode 3 and the second electrode 7 that increases from one end portion (left end portion) in each first bag portion 4 toward the middle portion in each first bag portion 4. Also, the electrostatic actuator 2 has a distance between the first electrode 3 and the third electrode 8 that increases from one end portion (left end portion) in each second bag portion 5 toward the middle portion in each second bag portion 5.
[0042] In this case, when a voltage is applied to the second electrode 7, the first electrode 3 and the second electrode 7 sequentially come into contact with each other from the portion with a narrow distance toward the portion with a wide distance. Also, when a voltage is applied to the third electrode 8, the first electrode 3 and the third electrode 8 sequentially come into contact with each other from the portion with a narrow distance toward the portion with a wide distance. Thereby, when the electrostatic actuator 2 changes from the non-operating state to the operating state, the first bag portion 4 and the second bag portion 5 can be efficiently expanded by the zipper effect.
[0043] Also, in the electrostatic actuator 100 according to the comparative example, when changing from the non-operating state to the operating state, the bag portion 101 of one HASEL actuator and the bag portion 101 of the other HASEL actuator may contact each other, and the bag portion 101 may be damaged by friction.
[0044] In contrast, in the electrostatic actuator 2, since the first electrode 3 is interposed between the first bag portion 4 and the second bag portion 5, the first bag portion 4 and the second bag portion 5 do not contact each other, and the occurrence of damage due to friction can be suppressed.
[0045] Next, referring to FIG. 5, the electrostatic actuator 20 according to the first modification of the embodiment will be described. FIG. 5 is an explanatory diagram showing a side cross-section of the electrostatic actuator 20 according to the first modification of the embodiment.
[0046] As shown in FIG. 5, in the electrostatic actuator 20 according to the first modification, the shapes of the second electrode 70 and the third electrode 80 are different from those of the electrostatic actuator 2 shown in FIG. 3. Other configurations of the electrostatic actuator 20 are the same as those of the electrostatic actuator 2 shown in FIG. 3. Note that the first bag portion 4 and the second bag portion 5 are deformed according to the shapes of the second electrode 70 and the third electrode 80, so their shapes are different between FIG. 2 and FIG. 5.
[0047] The second electrode 70 is a single electrode that covers the surfaces of the plurality of first bag portions 4 on the side opposite to the surfaces facing the first electrode 3. The third electrode 80 is a single electrode that covers the surfaces of the plurality of second bag portions 5 on the side opposite to the surfaces facing the first electrode 3.
[0048] As described above, in the electrostatic actuator 20, one second electrode 70 is provided for the plurality of first bag portions 4, and one third electrode 80 is provided for the plurality of second bag portions 5. Therefore, the number of required electrodes can be reduced, and the manufacturing process can be simplified and the manufacturing cost can be reduced.
[0049] In a state where there is no potential difference between the first electrode 3 and the second electrode 70, the rate of increase in the distance between the first electrode 3 and the second electrode 70, which increases from one end portion in the longitudinal direction of each first bag portion 4 toward the other end portion in the longitudinal direction of each first bag portion 4, is smaller than the rate of increase from the other end portion of each first bag portion 4 toward one end portion of each first bag portion 4.
[0050] Also, in a state where there is no potential difference between the first electrode 3 and the third electrode 80, the rate of increase in the distance between the first electrode 3 and the third electrode 80, which increases from one end portion in the longitudinal direction of each second bag portion 5 toward the other end portion in the longitudinal direction of each second bag portion 5, is smaller than the rate of increase from the other end portion of each second bag portion 5 toward one end portion of each second bag portion 5.
[0051] In this case, when a voltage is applied to the second electrode 70, the first electrode 3 and the second electrode 70 sequentially come into contact from the portion with a narrow interval toward the portion with a wide interval. When a voltage is applied to the third electrode 80, the first electrode 3 and the third electrode 80 sequentially come into contact from the portion with a narrow interval toward the portion with a wide interval.
[0052] As a result, the electrostatic actuator 20 can efficiently inflate the first bag portion 4 and the second bag portion 5 by the zipper effect when transitioning from a non-operating state to an operating state, even without the provision of multiple second electrodes 7 and multiple third electrodes 8.
[0053] Furthermore, the second electrode 70 has folds 71 extending in a direction that crosses the longitudinal direction of the second electrode 70 in each region that covers each first bag portion 4. Similarly, the third electrode 80 has folds 81 extending in a direction that crosses the longitudinal direction of the third electrode 80 in each region that covers each second bag portion 5.
[0054] As a result, the second electrode 70 is less likely to deform in the direction of approaching the first electrode 3 and more likely to deform in the direction of moving away from the first electrode 3 at the location of the fold 71 than at the location without the fold 71. Similarly, the third electrode 80 is less likely to deform in the direction of approaching the first electrode 3 and more likely to deform in the direction of moving away from the first electrode 3 at the location of the fold 81 than at the location without the fold 81. In other words, the locations with folds 71 and 81 are more easily deformed in response to the expansion of the first bag portion 4 and the second bag portion 5. As a result, when the electrostatic actuator 20 moves from a non-operating state to an operating state, the locations with folds 71 and 81 are less likely to approach the first electrode 3, making it easier to transport the dielectric liquid 6 from the locations without folds 71 and 81 to the locations with folds 71 and 81. In addition, the locations with folds 71 and 81 are more easily deformed in response to the expansion of the first bag portion 4 and the second bag portion 5, making it easier to efficiently expand the first bag portion 4 and the second bag portion 5.
[0055] In this way, by providing the second electrode 70 and the third electrode 80 with locations that are difficult to deform in the direction approaching the first electrode 3 and easy to deform in the direction away from the first electrode 3, the electrostatic actuator 20 can efficiently inflate the first bag portion 4 and the second bag portion 5 by the zipper effect.
[0056] Next, with reference to Figures 6 and 7, a second modified example of the embodiment, an electrostatic actuator 21, will be described. Figures 6 and 7 are explanatory plan views of the electrostatic actuator 21 according to the second modified example of the embodiment.
[0057] The electrostatic actuator 21 in the second modified example is similar to the first modified example in that one second electrode is provided for each of the multiple first bag portions 4, and one third electrode is provided for each of the multiple second bag portions 5. However, the shape of the second and third electrodes in the second modified example differs from that of the first modified example in plan view.
[0058] The shapes of the second and third electrodes in plan view are the same in the second modified example. Therefore, the shape of the second electrode 72 in plan view in the second modified example will be described here with reference to Figures 6 and 7, and the shape of the third electrode in plan view in the second modified example will not be shown.
[0059] As shown in Figure 6, the second electrode 72 according to the second modification has a first region 73 and a second region 75 in which a plurality of slits 74 are provided. Similarly, the third electrode according to the second modification has a first region 73 and a second region 75 in which a plurality of slits 74 are provided, just like the second electrode 72.
[0060] The second electrode 72 is provided such that the first region 73 is located on one end of the first bag portion 4 in the longitudinal direction, and the second region 75 is located on the other end of the first bag portion 4 in the longitudinal direction. The third electrode according to the second modification is provided similarly to the second electrode 72, such that the first region 73 is located on one end of the second bag portion 5 in the longitudinal direction, and the second region 75 is located on the other end of the second bag portion 5 in the longitudinal direction.
[0061] The second region 75 is more easily deformable than the first region 73 because it is provided with multiple slits 74. In other words, the second region 75 is more easily deformed than the first region 73 in response to the expansion of the first bag portion 4 and the second bag portion 5. Furthermore, because the second region 75 is provided with multiple slits 74, the area facing the first electrode 3 is smaller than that of the first region 73, so the amount of charge stored when current is supplied to the electrostatic actuator 21 is reduced.
[0062] In other words, in the second region 75, the pressure generated in the dielectric liquid 6 located between the first electrode 3 and the dielectric liquid decreases. As a result, the dielectric liquid 6 moves from one end of the first bag portion 4 and the second bag portion 5 in the longitudinal direction where the first region 73 is located to the other end of the first bag portion 4 and the second bag portion 5 in the longitudinal direction where the second region 75 is located, causing the first bag portion 4 and the second bag portion 5 to expand.
[0063] Thus, the electrostatic actuator 21 according to the second modified example can efficiently inflate the first bag portion 4 and the second bag portion 5 when transitioning from a non-operating state to an operating state, even without providing a plurality of second electrodes 7 and a plurality of third electrodes 8. In other words, the electrostatic actuator 21 according to the second modified example, like the electrostatic actuator 20, can reduce the number of electrodes required, enabling simplification of the manufacturing process and reduction of manufacturing costs.
[0064] Furthermore, in the second modified electrostatic actuator 21, instead of the slit 74 shown in Figure 6, a plurality of through holes 76 penetrating the front and back surfaces of the second electrode 72 and the third electrode may be provided in the second region 75, as shown in Figure 7.
[0065] Even with this configuration, the second electrode 72 and the third electrode in the second modified example are similar to the second electrode 72 shown in Figure 6, with the second region 75 being more easily deformed than the first region 73. As a result, the electrostatic actuator 21 can efficiently inflate the first bag portion 4 and the second bag portion 5, and, similar to the electrostatic actuator 20, the number of electrodes required can be reduced, simplifying the manufacturing process and reducing manufacturing costs.
[0066] Next, with reference to Figure 8, a third modified example of the embodiment, specifically the electrostatic actuator 22, will be described. Figure 8 is a plan view explanatory diagram of the electrostatic actuator 22 according to the third modified example of the embodiment.
[0067] As shown in Figure 8, the electrostatic actuator 22 has its peripheral edges welded in a plan view of each first bag portion 4. Note that the peripheral edges of the first bag portion 4 are not limited to welding; for example, they may be bonded using a photocurable resin. In each first bag portion 4, the welding width from the peripheral edge to the outer end of the electrostatic actuator 22 decreases as you move from one end in the longitudinal direction (upper end in Figure 8) to the other end (lower end in Figure 8). In other words, in each first bag portion 4, the area of the welded portion 41 at the peripheral edge in a plan view decreases as you move from one end in the longitudinal direction (upper end in Figure 8) to the other end (lower end in Figure 8).
[0068] Although the second bag portion 5 is not shown in Figure 8, the peripheral edge of the second bag portion 5 is also welded in a plan view, and the area of the welded portion 41 at the peripheral edge in a plan view decreases from one end (the upper end in Figure 8) to the other end (the lower end in Figure 8) in the longitudinal direction.
[0069] The first bag portion 4 and the second bag portion 5 are less prone to deformation the larger the area of the welded portion 41 at the periphery, and more prone to deformation the smaller the area of the welded portion 41 at the periphery. For this reason, the electrostatic actuator 22 is more prone to deformation in the portion of the first bag portion 4 that is not covered by the second electrode 7 than in the portion that is covered by the second electrode 7.
[0070] Similarly, with respect to the second bag portion 5, the portion not covered by the third electrode 8 is more easily deformed than the portion covered by the third electrode 8. As a result, the electrostatic actuator 22 can efficiently expand the first bag portion 4 and the second bag portion 5 when transitioning from a non-operating state to an operating state.
[0071] Furthermore, this technology can take the following configurations: (1) An electrostatic actuator comprising: a strip-shaped first electrode; a plurality of first bag portions located on the first surface of the first electrode and sealed with dielectric liquid arranged along the longitudinal direction of the first electrode; a plurality of second bag portions located on the second surface of the first electrode opposite to the first surface and sealed with dielectric liquid arranged along the longitudinal direction of the first electrode; a second electrode located on the opposite side of the first bag portion from the first electrode; and a third electrode located on the opposite side of the second bag portion from the first electrode, wherein the first electrode, the second electrode, and the third electrode are flexible; the first bag portion is located at a position that overlaps with the boundary between adjacent second bag portions in a planar transparent view; and the second bag portion is located at a position that overlaps with the boundary between adjacent first bag portions in a planar transparent view. (2) The electrostatic actuator according to (1), wherein the first electrode is covered with an insulating film. (3) The electrostatic actuator according to (1) or (2), wherein the second electrode extends from one end in the longitudinal direction of each first bag portion to the middle of the longitudinal direction of each first bag portion, and the third electrode extends from one end in the longitudinal direction of each second bag portion to the middle of the longitudinal direction of each second bag portion. (4) The electrostatic actuator according to (3), wherein, in a state where there is no potential difference between the first electrode and the second electrode, the distance between the first electrode and the second electrode increases from one end in each first bag portion towards the middle of each first bag portion, and the distance between the first electrode and the third electrode increases from one end in each second bag portion towards the middle of each second bag portion. (5) The electrostatic actuator according to (1) or (2), wherein the second electrode covers the surface of the plurality of first bag portions opposite to the surface facing the first electrode, and the third electrode covers the surface of the plurality of second bag portions opposite to the surface facing the first electrode.(6) In a state where there is no potential difference between the first electrode and the second electrode, the rate of increase in the distance between the first electrode and the second electrode increasing from one end in the longitudinal direction of each first bag portion toward the other end in the longitudinal direction of each first bag portion is smaller than the rate of increase from the other end in each first bag portion toward the first end in each first bag portion, and the rate of increase in the distance between the first electrode and the third electrode increasing from one end in the longitudinal direction of each second bag portion toward the other end in the longitudinal direction of each second bag portion is smaller than the rate of increase from the other end in each second bag portion toward the first end in each second bag portion, as described in (5). (7) The electrostatic actuator according to (5) or (6), wherein the second electrode has folds extending in a direction transverse to the longitudinal direction of the second electrode in each region covering each of the first bag portions, and the third electrode has folds extending in a direction transverse to the longitudinal direction of the third electrode in each region covering each of the second bag portions. (8) The electrostatic actuator according to any one of (5) to (7), wherein the second electrode has a first region and a second region having a plurality of slits, the third electrode has a first region and a second region having a plurality of slits, the first region of the second electrode is located on one end side in the longitudinal direction of the first bag portion, the second region of the second electrode is located on the other end side in the longitudinal direction of the first bag portion, the first region of the third electrode is located on one end side in the longitudinal direction of the second bag portion, and the second region of the third electrode is located on the other end side in the longitudinal direction of the second bag portion. (9) The electrostatic actuator according to any one of (3) to (8) above, wherein each of the first bag portion and each of the second bag portion has its peripheral edge welded in a plan view, and the welded area of the peripheral edge in a plan view decreases from one end to the other in the longitudinal direction.
[0072] Further effects and modifications can be readily derived by those skilled in the art. Therefore, broader aspects of the present invention are not limited to the specific details and representative embodiments expressed and described above. Accordingly, various modifications are possible without departing from the spirit or scope of the overall concept of the invention as defined by the appended claims and their equivalents.
[0073] 2, 20, 21, 22 Electrostatic actuator 3 First electrode 4 First bag section 5 Second bag section 6 Dielectric liquid 7, 70 Second electrode 8, 80 Third electrode 10, 11 Insulating film 41 Welded section
Claims
1. An electrostatic actuator comprising: a strip-shaped first electrode; a plurality of first bag portions located on the first surface of the first electrode and sealed with dielectric liquid arranged along the longitudinal direction of the first electrode; a plurality of second bag portions located on the second surface of the first electrode opposite to the first surface and sealed with dielectric liquid arranged along the longitudinal direction of the first electrode; a second electrode located on the opposite side of the first bag portion from the first electrode; and a third electrode located on the opposite side of the second bag portion from the first electrode, wherein the first electrode, the second electrode, and the third electrode are flexible; the first bag portions are located in a position that overlaps with the boundary between adjacent second bag portions in a planar transparent view; and the second bag portions are located in a position that overlaps with the boundary between adjacent first bag portions in a planar transparent view.
2. The electrostatic actuator according to claim 1, wherein the first electrode is covered with an insulating film.
3. The electrostatic actuator according to claim 1, wherein the second electrode extends from one end in the longitudinal direction of each first bag portion to the middle of the longitudinal direction of each first bag portion, and the third electrode extends from one end in the longitudinal direction of each second bag portion to the middle of the longitudinal direction of each second bag portion.
4. In a state where there is no potential difference between the first electrode and the second electrode, the distance between the first electrode and the second electrode increases from one end of each first bag portion toward the middle portion of each first bag portion, and the distance between the first electrode and the third electrode increases from one end of each second bag portion toward the middle portion of each second bag portion, according to claim 3.
5. The electrostatic actuator according to claim 1, wherein the second electrode covers the surface of the plurality of first bag portions opposite to the surface facing the first electrode, and the third electrode covers the surface of the plurality of second bag portions opposite to the surface facing the first electrode.
6. The electrostatic actuator according to claim 5, wherein, in a state where there is no potential difference between the first electrode and the second electrode, the rate of increase in the distance between the first electrode and the second electrode increasing from one end in the longitudinal direction of each first bag portion toward the other end in the longitudinal direction of each first bag portion is smaller than the rate of increase from the other end in each first bag portion toward the first end in each first bag portion, and the rate of increase in the distance between the first electrode and the third electrode increasing from one end in the longitudinal direction of each second bag portion toward the other end in the longitudinal direction of each second bag portion is smaller than the rate of increase from the other end in each second bag portion toward the first end in each second bag portion.
7. The electrostatic actuator according to claim 5, wherein the second electrode has folds extending in a direction transverse to the longitudinal direction of the second electrode in each region covering each of the first bag portions, and the third electrode has folds extending in a direction transverse to the longitudinal direction of the third electrode in each region covering each of the second bag portions.
8. The electrostatic actuator according to claim 5, wherein the second electrode has a first region and a second region provided with a plurality of slits, the third electrode has a first region and a second region provided with a plurality of slits, the first region of the second electrode is located on one end side in the longitudinal direction of the first bag portion, the second region of the second electrode is located on the other end side in the longitudinal direction of the first bag portion, the first region of the third electrode is located on one end side in the longitudinal direction of the second bag portion, and the second region of the third electrode is located on the other end side in the longitudinal direction of the second bag portion.
9. The electrostatic actuator according to any one of claims 3 to 8, wherein each of the first bag portion and each of the second bag portion has its peripheral edge welded in a plan view, and the welded area of the peripheral edge in a plan view decreases from one end to the other in the longitudinal direction.