JP5243818B2 - Actuator - Google Patents

Description

  The present invention relates to an actuator that outputs a driving force by expansion and contraction of a dielectric film according to an applied voltage.

For example, as an electrostrictive actuator using a dielectric elastomer, a roll-type actuator is introduced in [FIG. 2L], [FIG. 2M], [FIG. 4C], and [FIG. 4D] of Patent Document 1. That is, the actuator described in Patent Document 1 includes a dielectric element having a dielectric film made of a dielectric elastomer and an electrode, and is wrapped around the outer periphery of a compressed spring member. When a voltage is applied to the electrodes of the dielectric element, the film thickness of the dielectric film decreases due to electrostatic attraction between the electrodes, and the dielectric film expands. Thereby, the restraining force with respect to the spring member becomes small, and the spring member, that is, the actuator extends in the axial direction.
JP 2005-522162 A

  In the case of the roll-type actuator described in Patent Document 1, the dielectric element is mounted in an extended state on the outer periphery of the spring member. That is, the dielectric element is pressed against the spring member. For example, when the voltage applied between the electrodes is increased, the dielectric element expands while being in sliding contact with the spring member. Thereby, the restraining force with respect to a spring member becomes small. Therefore, the spring member extends while being in sliding contact with the dielectric element by the stored urging force. Here, the frictional force between the dielectric element and the spring member is large. Thereby, the movement of a dielectric element and a spring member is prevented. As a result, the amount of displacement in the axial direction of the actuator is reduced.

  This invention is completed in view of such a situation, and makes it a subject to reduce the frictional force between the spring member and the adjacent member at the time of expansion-contraction, and to provide an actuator with a big displacement amount.

  (1) In order to solve the above problems, an actuator of the present invention includes a cylindrical spring member that can be expanded and contracted in the axial direction, a dielectric film made of a dielectric elastomer, and a dielectric film that is disposed radially outside the spring member. A cylindrical dielectric element having a plurality of electrodes arranged through a film, the dielectric film expanding and contracting according to a change in applied voltage between the electrodes, the spring member, and a diameter of the spring member And a low friction layer interposed between adjacent members adjacent to each other in a direction and capable of reducing a frictional force between the spring member and the adjacent member during expansion and contraction. The spring member is contracted in the axial direction in a state where the force is accumulated, and when switching from the low voltage state to a high voltage state in which the applied voltage is higher than the low voltage state, the spring member responds to an increase in the applied voltage. As the dielectric element expands, the axial direction follows the biasing force of the spring member. Characterized by extending (corresponding to claim 1).

  According to the actuator of the present invention, the low friction layer is disposed between the spring member and the adjacent member radially adjacent to the spring member. The frictional force between the spring member and the adjacent member at the time of expansion / contraction is reduced by interposing the low friction layer between the spring member sliding at the time of expansion / contraction and the adjacent member. For example, when the dielectric element is arranged so as to be adjacent to the spring member in the radial direction, the frictional force between the spring member and the dielectric element is reduced. Further, when the dielectric element is disposed around the spring member via another member radially adjacent to the spring member, the dielectric element is pressed against the spring member side by the dielectric element. The frictional force between the spring member and the spring member is reduced. As described above, since the frictional force between the spring member and the adjacent member is reduced, the movement of the dielectric element and the spring member is not easily inhibited. For this reason, the displacement amount of the actuator of the present invention is large.

  (2) Preferably, in the configuration of (1), the adjacent member is the dielectric element, and the low friction layer is a resin film formed on an inner peripheral surface of the dielectric element. (Corresponding to claim 2).

  In this configuration, the dielectric element is adjacent to the spring member in the radial direction. That is, the dielectric element is directly wrapped around the spring member. By forming a resin film on the inner peripheral surface of the dielectric element, the friction coefficient of the inner peripheral surface of the dielectric element is reduced. Thereby, the frictional force between the spring member and the dielectric element can be reduced easily and at a relatively low cost without performing any special treatment on the spring member. Also, the friction coefficient can be easily adjusted depending on the type of resin.

  (3) Preferably, in the configuration of (1) or (2), the dielectric element includes a first dielectric film, a first electrode, a second dielectric film, and a second electrode. The laminated stretchable films laminated in this order are preferably wound around the spring member in a spiral shape so that the first dielectric film is the innermost layer. Correspondence).

  According to this configuration, the actuator of the present invention can be easily manufactured by winding the laminated stretchable film in a spiral shape. Further, it is easy to stack the dielectric films. By laminating a large number of dielectric films, a larger driving force can be output. Further, by adjusting the number of turns of the laminated stretchable film, a desired driving force and displacement can be easily obtained. According to this configuration, the electrodes and the dielectric films can be easily laminated alternately by simply winding the laminated stretchable film. Thereby, each laminated dielectric film can be efficiently expanded and contracted. The first dielectric film is wound so as to be the innermost layer. For this reason, for example, a low friction layer can be easily formed on the inner peripheral surface of the dielectric element by forming a resin film on the surface of the first dielectric film.

  (4) Preferably, in the configuration according to any one of (1) to (3), a fluid chamber that is disposed radially inside the dielectric element and sucks and discharges fluid, and is disposed at one axial end of the fluid chamber. A suction port for sucking the fluid into the fluid chamber, and a discharge port disposed at the other axial end of the fluid chamber for discharging the fluid from the fluid chamber, and changing an applied voltage between the electrodes. In this case, it is preferable that the dielectric element is expanded and contracted to change the volume of the fluid chamber to suck and discharge the fluid (corresponding to claim 4).

  This configuration uses the actuator of the present invention as a pump for sucking and discharging fluids such as gas and liquid. According to this configuration, the volume of the fluid chamber changes due to expansion and contraction of the dielectric element. As described above, the frictional force between the spring member and the adjacent member is reduced by the low friction layer. Therefore, the movement of the dielectric element and the spring member is not easily inhibited. Therefore, according to this configuration, it is possible to configure a pump having a large volume change amount of the fluid chamber, in other words, a fluid having a large flow rate per unit time.

  (5) Preferably, in the configuration of (4), the fluid is a liquid having conductivity, and at least a part of the fluid chamber is partitioned by an insulating film for suppressing conduction of the fluid. It is better to have a configuration (corresponding to claim 5).

  In the case where the fluid is a liquid having conductivity, the fluid may be conducted when a voltage is applied between the electrodes. In this regard, according to this configuration, at least a part of the fluid chamber is partitioned by the insulating film. For this reason, it can suppress that a fluid conduct | electrically_connects.

  (6) Preferably, in the configuration of (4) or (5), the suction side cap member having the suction port, the discharge side cap member having the discharge port, the suction side cap member, and the discharge A cylindrical tube member that is interposed between the side cap member and that partitions at least a part of the fluid chamber and is elastically deformable. Both ends in the axial direction of the dielectric element and the spring member The tube member is expanded and contracted by changing the voltage applied between the electrodes and expanding and contracting the dielectric element, and the volume of the fluid chamber is increased. It is better to have a configuration to change (corresponding to claim 6).

  According to this configuration, the actuator of the present invention can be easily implemented as a pump that sucks and discharges fluid. Further, both axial ends of the dielectric element and the spring member are fixed to the suction side cap member and the discharge side cap member, respectively. For this reason, when the dielectric element contracts, a compressive force is applied to both axial ends of the spring member from the suction side cap member and the discharge side cap member, so that the spring member can be easily contracted.

  Hereinafter, embodiments of the actuator of the present invention will be described. In the following embodiment, the actuator of the present invention is embodied as a pump.

<First embodiment>
[Configuration of actuator]
First, the configuration of the actuator of this embodiment will be described. FIG. 1 shows a perspective view of the actuator of this embodiment. FIG. 2 shows a perspective exploded view of the actuator. FIG. 3 shows a cross-sectional view in the III-III direction of FIG. FIG. 4A shows a cross-sectional view in the IV-IV direction of FIG. FIG. 4B shows an axial sectional view of the actuator in the extended state. 1 to 3 and FIG. 4A show a low voltage state of the actuator. On the other hand, FIG. 4B shows a high voltage state of the actuator. Moreover, in FIG. 2, a fastening ring member is abbreviate | omitted and shown.

  As shown in FIGS. 1 to 4, the actuator 1 of this embodiment includes a dielectric element 2, a coil spring 3, a resin coating 4, a suction side cap member 5, a discharge side cap member 6, and a tube member 7. And a pair of fastening ring members 80, 81. The coil spring 3 is included in the spring member of the present invention.

  As shown in FIG. 4, the actuator 1 is interposed between the check valves 90 and 91. The check valves 90 and 91 can be opened only in a direction in which fluid flows from the left side to the right side. That is, the left side is upstream and the right side is downstream.

  The suction side cap member 5 is made of acrylic resin and has a cylindrical shape extending in the left-right direction. That is, the suction side cap member 5 is provided with a communication hole penetrating in the left-right direction. The suction side cap member 5 includes a partition wall portion 50, a joint portion 51, and a spring holding portion 52.

  The partition wall portion 50 is disposed substantially at the center in the axial direction of the suction side cap member 5. The partition wall portion 50 has a flange shape that spreads radially outward. A ring holding groove 500 is provided around the outer peripheral edge of the partition wall 50.

  The joint portion 51 is disposed on the left side of the partition wall portion 50. The joint part 51 has a short-axis cylindrical shape. An upstream check valve 90 is connected to the joint portion 51 via a tube (not shown). A suction port 510 is disposed at the left end of the joint portion 51.

  The spring holding part 52 is disposed on the right side of the partition wall part 50. The spring holding part 52 has a short-axis cylindrical shape. The outer peripheral surface of the spring holding portion 52 is provided with an uneven shape.

  The discharge-side cap member 6 is made of acrylic resin and has a cylindrical shape extending in the left-right direction. That is, the discharge-side cap member 6 is provided with a communication hole penetrating in the left-right direction. The discharge-side cap member 6 is opposed to the suction-side cap member 5 in the left-right direction at a predetermined interval. The discharge side cap member 6 includes a partition wall portion 60, a joint portion 61, and a spring holding portion 62.

  The partition wall 60 is disposed at the approximate center in the axial direction of the discharge side cap member 6. The partition wall portion 60 has a flange shape spreading outward in the radial direction. A ring holding groove 600 is provided around the outer peripheral edge of the partition wall 60.

  The joint portion 61 is disposed on the right side of the partition wall portion 60. The joint part 61 has a short-axis cylindrical shape. A downstream check valve 91 is connected to the joint portion 61 via a tube (not shown). A discharge port 610 is disposed at the right end of the joint portion 61.

  The spring holding part 62 is disposed on the left side of the partition wall part 60. The spring holding part 62 has a short-axis cylindrical shape. The outer peripheral surface of the spring holding part 62 has an uneven shape. The spring holding portion 62 of the discharge side cap member 6 is spaced apart from the spring holding portion 52 of the suction side cap member 5 by a predetermined distance and faces the left and right direction.

  The tube member 7 is made of acrylic rubber and has a cylindrical shape extending in the left-right direction. The tube member 7 also serves as the insulating film of the present invention. The tube member 7 is interposed between the suction side cap member 5 and the discharge side cap member 6. A spring holding portion 52 of the suction side cap member 5 is inserted into the left end opening of the tube member 7. Similarly, the spring holding portion 62 of the discharge side cap member 6 is inserted into the right end opening of the tube member 7. The communication hole of the suction side cap member 5, the internal space of the tube member 7, and the communication hole of the discharge side cap member 6 are connected in the left-right direction in this order. A fluid chamber R that is long in the left-right direction is formed by the communication hole of the suction-side cap member 5, the internal space of the tube member 7, and the communication hole of the discharge-side cap member 6.

  The coil spring 3 is made of steel and has a cylindrical shape extending in the left-right direction. The coil spring 3 is interposed between the suction side cap member 5 and the discharge side cap member 6. The coil spring 3 is disposed on the radially outer side of the tube member 7. The left end of the coil spring 3 is externally fitted to the spring holding portion 52 of the suction side cap member 5 from the radially outer side of the left end of the tube member 7. As described above, the outer peripheral surface of the spring holding portion 52 has an uneven shape. When the pitch of the coil spring 3 is hooked on the uneven shape, the tube member 7 and the left end of the coil spring 3 are prevented from falling off from the spring holding portion 52. Similarly, the right end of the coil spring 3 is externally fitted to the spring holding portion 62 of the discharge side cap member 6 from the radially outer side of the right end of the tube member 7. As described above, the outer peripheral surface of the spring holding portion 62 has an uneven shape. When the pitch of the coil spring 3 is hooked on the uneven shape, the right end of the tube member 7 and the coil spring 3 is prevented from falling off from the spring holding portion 62.

  The dielectric element 2 has a cylindrical shape extending in the left-right direction. The dielectric element 2 is interposed between the suction side cap member 5 and the discharge side cap member 6. The dielectric element 2 is disposed outside the coil spring 3 in the radial direction. The dielectric element 2 is an adjacent member of the coil spring 3. The left end opening of the dielectric element 2 is closed by the partition wall portion 50 of the suction side cap member 5. The fastening ring member 80 is externally fitted into the ring holding groove 500 from the outside in the radial direction in which the left end of the dielectric element 2 covers the outer peripheral edge of the partition wall 50. That is, the left end of the dielectric element 2 and the suction side cap member 5 are connected by the fastening ring member 80. Similarly, the right end opening of the dielectric element 2 is closed by the partition wall portion 60 of the discharge side cap member 6. The fastening ring member 81 is externally fitted into the ring holding groove 600 from the outside in the radial direction in which the right end of the dielectric element 2 covers the outer peripheral edge of the partition wall 60. That is, the right end of the dielectric element 2 and the discharge side cap member 6 are connected by the fastening ring member 81.

[Configuration of dielectric element and resin coating]
Next, the configuration of the dielectric element 2 and the resin coating 4 will be described. As shown in FIG. 3 with emphasis on the thickness, the dielectric element 2 includes a strip-shaped laminated stretchable film 2 a having a three-layer structure, the outer peripheral edge of the partition wall portion 50 of the suction side cap member 5 and the partition wall of the discharge side cap member 6. It is formed by being wound around the outer peripheral edge of the portion 60. The laminated structure of the laminated stretchable film 2a is formed by laminating the first dielectric film 20, the first electrode 21, the second dielectric film 22, and the second electrode 23 in this order. Has been. The dielectric films 20 and 22 are made of acrylic rubber. The electrodes 21 and 23 are both formed by applying a paste in which carbon black and a binder elastomer are mixed. The first dielectric film 20 constitutes the innermost layer, and the second electrode 23 constitutes the outermost layer. The dielectric element 2 has a cylindrical shape in which the multilayer stretchable film 2a is wound three times.

  The resin film 4 is formed of a paint in which a powder of polytetrafluoroethylene (PTFE) is dispersed in a binder. The resin coating 4 is formed on the inner peripheral surface of the innermost layer of the laminated stretchable film 2 a, that is, the inner peripheral surface of the dielectric element 2. For this reason, the resin coating 4 is interposed between the inner peripheral surface of the dielectric element 2 and the outer peripheral surface of the coil spring 3.

[Actuator assembly method]
Next, a method for assembling the actuator 1 of this embodiment will be described. First, the suction side cap member 5 and the discharge side cap member 6 are produced. Next, between the suction side cap member 5 and the discharge side cap member 6, the tube member 7, the coil spring 3, and the dielectric element 2 coated with the resin coating 4 on the inner peripheral surface are arranged from the radially inner side. They are installed in this order toward the outside. At this time, the coil spring 3 is disposed in a compressed state in the axial direction (left-right direction) with respect to the natural state. The extension of the coil spring 3 is regulated by the dielectric element 2. For this reason, the coil spring 3 stores an urging force that extends in the left-right direction. Thus, the actuator 1 of this embodiment is assembled. The assembled actuator 1 is interposed between the check valves 90 and 91.

[Actuator movement]
Next, the movement of the actuator 1 of this embodiment will be described. The actuator 1 of this embodiment changes the volume of the fluid chamber R in the left-right direction by repeatedly switching between the low voltage state and the high voltage state, and pumps the fluid from the left side to the right side.

  In the low voltage state, no voltage is applied between the electrodes 21 and 23. For this reason, electrostatic attraction is not generated between the electrodes 21 and 23. The coil spring 3 stores an urging force that extends in the left-right direction.

  When the low voltage state is switched to the high voltage state, a predetermined voltage is applied between the electrodes 21 and 23. For this reason, an electrostatic attractive force is generated between the electrodes 21 and 23. When an electrostatic attractive force is generated between the electrodes 21 and 23, the dielectric films 20 and 22 interposed between the electrodes 21 and 23 are compressed from the film thickness direction and expanded in the film development direction. That is, the dielectric films 20 and 22, that is, the dielectric element 2 are loosened. For this reason, the restriction | limiting with respect to the coil spring 3 is cancelled | released. Therefore, as shown in FIG. 4B, the coil spring 3 extends in the left-right direction until the slack of the dielectric element 2 is eliminated by the urging force accumulated by itself. Moreover, the tube member 7 also extends in the left-right direction by the biasing force. For this reason, the volume of the fluid chamber R partitioned inside the tube member 7 is increased by ΔV with respect to the low voltage state (see FIG. 4A). When the volume of the fluid chamber R increases by ΔV, the fluid tends to flow into the fluid chamber R by that amount. For this reason, the check valve 90 on the left side (upstream side) is opened. Accordingly, the fluid flows into the fluid chamber R from the upstream side through the suction port 510. The downstream check valve 91 prohibits the movement of fluid from the right side (downstream side) to the left side. For this reason, the check valve 91 on the downstream side remains closed.

  When the high voltage state is switched again to the low voltage state, the applied voltage between the electrodes 21 and 23 is released. For this reason, the electrostatic attractive force between the electrodes 21 and 23 is lost. When the electrostatic attractive force between the electrodes 21 and 23 disappears, the dielectric films 20 and 22 contract from the film deployment direction due to their own elastic restoring force. For this reason, the dielectric element 2 contracts from the left-right direction while resisting the biasing force of the coil spring 3. In addition, the tube member 7 also contracts from the left-right direction. Therefore, the volume of the fluid chamber R partitioned inside the tube member 7 is reduced by ΔV with respect to the high voltage state (see FIG. 4B). When the volume of the fluid chamber R decreases by ΔV, the fluid tends to flow out of the fluid chamber R by that amount. For this reason, the check valve 91 on the right side (downstream side) is opened. Therefore, the fluid is sent out from the fluid chamber R to the downstream side via the discharge port 610. The upstream check valve 90 prohibits the movement of fluid from the right side (downstream side) to the left side. Therefore, the upstream check valve 90 remains closed.

  As described above, by alternately repeating the low voltage state and the high voltage state, the actuator 1 of this embodiment changes the volume of the fluid chamber R in the left-right direction, and pumps the fluid from the left side to the right side. Yes.

[Function and effect]
Next, the effect of the actuator of this embodiment is demonstrated. In the actuator 1, the dielectric element 2 is adjacent to the coil spring 3 in the radial direction. A resin film 4 (low friction layer) is formed on the inner peripheral surface of the dielectric element 2. That is, a low friction layer is disposed between the coil spring 3 and the dielectric element 2. Thereby, the frictional force between the coil spring 3 and the dielectric element 2 is reduced. Therefore, the movement of the dielectric element 2 and the coil spring 3 is not easily disturbed, and the displacement amount of the actuator 1 is large. That is, since the volume change amount of the fluid chamber R is large, a pump with a large discharge amount can be configured.

  The dielectric element 2 is formed by winding a laminated stretchable film 2a. Therefore, the electrodes 21 and 23 and the dielectric films 20 and 22 can be easily stacked alternately. Thereby, expansion / contraction of the laminated dielectric films 20 and 22 can be efficiently performed. Further, by adjusting the number of turns of the laminated stretchable film 2a, a desired driving force and displacement can be obtained. For example, a larger driving force can be output by stacking more dielectric films.

  A part of the fluid chamber R is partitioned by the tube member 7. The tube member 7 is made of an insulating film made of acrylic rubber. Therefore, even if the fluid is a liquid having conductivity such as water, conduction can be suppressed.

  Further, both axial ends of the dielectric element 2 and the coil spring 3 are fixed to the suction side cap member 5 and the discharge side cap member 6, respectively. For this reason, when the dielectric element 2 contracts, a compressive force is applied to both ends in the axial direction of the coil spring 3 from the suction side cap member 5 and the discharge side cap member 6, and the coil spring 3 is easily contracted.

<Second embodiment>
The difference between the actuator of this embodiment and the actuator of the first embodiment is that a coil spring is accommodated inside the tube member. Therefore, only the differences will be described here.

  FIG. 5 shows a radial sectional view of the actuator of the present embodiment. In addition, about the site | part corresponding to FIG. 3, it shows with the same code | symbol. As shown in FIG. 5, the actuator 1 of this embodiment includes a spring holding portion 52, a coil spring 3, a low friction layer 40, a tube member 7, and a dielectric element 2 from the radially inner side to the outer side. That is, the spring holding portion 52, the coil spring 3, and the low friction layer 40 are disposed inside the tube member 7. For this reason, the spring holding part 52, the coil spring 3, and the low friction layer 40 are immersed in the fluid. The low friction layer 40 is a resin film formed from a paint in which PTFE powder is dispersed in a binder. The low friction layer 40 is formed on the inner peripheral surface of the tube member 7. The coil spring 3 and the tube member 7 are isolated by the low friction layer 40. The tube member 7 is an adjacent member of the coil spring 3.

  The actuator 1 of the present embodiment has the same function and effect as those of the actuator 1 of the first embodiment with respect to the parts having the same configuration. Further, according to the actuator 1 of the present embodiment, the low friction layer 40 is interposed between the coil spring 3 and the tube member 7. For this reason, the frictional force between the coil spring 3 and the tube member 7 is reduced. Moreover, when the coil spring 3 expands and contracts, it can suppress that the coil spring 3 and the tube member 7 interfere.

<Third embodiment>
The difference between the actuator of this embodiment and the actuator of the first embodiment is that the wire of the coil spring is covered with a low friction layer. Therefore, only the differences will be described here.

  FIG. 6 shows a radial cross-sectional view of the wire rod of the coil spring of the actuator of this embodiment. In addition, about the site | part corresponding to FIG. 2, it shows with the same code | symbol. As shown in FIG. 6, the surface of the wire rod 30 forming the coil spring 3 is covered with a low friction layer 41 made of a DLC (diamond-like carbon) film.

  The actuator 1 of the present embodiment has the same function and effect as those of the actuator 1 of the first embodiment with respect to the parts having the same configuration. Further, according to the actuator 1 of the present embodiment, the low friction layer 41 is arranged on the wire 30 itself of the coil spring 3. For this reason, as shown in FIG. 3, not only between the outer peripheral surface of the coil spring 3 and the inner peripheral surface of the dielectric element 2 but also between the inner peripheral surface of the coil spring 3 and the outer peripheral surface of the tube member 7. Also, the low friction layer 41 can be interposed. For this reason, when the coil spring 3 expands and contracts, the coil spring 3, the dielectric element 2, and the tube member 7 can be prevented from interfering with each other.

<Others>
The embodiment of the actuator 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, the low friction layer may be interposed between a spring member and an adjacent member that is radially adjacent to the spring member. Here, the adjacent member includes, in addition to the dielectric element, an insulating film or the like for suppressing conduction of a fluid flowing inside the dielectric element in the radial direction. Therefore, a low friction layer may be formed on the outer peripheral surface of the spring member or the inner peripheral surface of the adjacent member. Alternatively, another member may be disposed between the spring member and the adjacent member to form a low friction layer.

  In the first embodiment, as the low friction layer, a resin film is formed by applying a paint containing PTFE powder to the inner peripheral surface of the dielectric element. Here, the material and forming method of the resin coating are not particularly limited. For example, a resin film can be formed by adhering powders such as PTFE-containing fluororesin, silicone resin, urethane resin, or applying paste, paint, or the like containing these resin components. Moreover, a low friction layer is not limited to the said resin film, A various aspect is employable. For example, a coating containing a solid lubricant such as molybdenum disulfide, graphite, or boron nitride may be formed on a predetermined surface of a spring member or an adjacent member. Further, as in the third embodiment, an amorphous hard carbon film called a DLC film may be formed. Further, grease or oil may be applied. Further, a predetermined surface may be chemically treated. In addition, a film having a small surface friction coefficient and stretchability may be interposed between the spring member and the adjacent member.

  In the above embodiment, the dielectric element is configured by winding the laminated stretchable film in which two dielectric films are laminated in a spiral shape around the spring member three times. However, the configuration of the dielectric element is not limited to this. For example, a stretchable film with an insulating film having a dielectric film interposed between a pair of electrodes and an insulating film that is disposed on one surface of the electrode and suppresses conduction between electrodes adjacent in the radial direction is formed by a spring. It may be wound around the member. In addition, dielectric films and electrodes may be alternately stacked concentrically around the spring member. In any case, the number of turns of the laminated stretchable film or the stretchable film with an insulating film and the number of laminated dielectric films are not limited.

  In the above embodiment, the laminated stretchable film is wound with the first dielectric film inside. In this case, the outermost layer of the dielectric element becomes an electrode. Therefore, you may arrange | position the insulating cover which has a stretching property on the surface of outermost layer as needed. If it carries out like this, safety and design nature will improve. Alternatively, the first dielectric film may be wound outside. In this case, the outermost layer of the dielectric element is a dielectric film. Therefore, an electrode may be further arranged on the surface of the outermost layer. In this case, the outermost dielectric film can be expanded and contracted, so that a larger driving force can be obtained.

  In the above embodiment, the fluid chamber is defined by the tube member (insulating film) made of acrylic rubber. In the case of sucking and discharging a liquid having conductivity, it is desirable that the material of the tube member that partitions the fluid chamber is one that can be elastically deformed while suppressing conduction between the fluid and the electrode. In addition to the above acrylic rubber, for example, silicone rubber, ethylene-propylene-diene terpolymer (EPDM), natural rubber (NR), butyl rubber (IIR), isoprene rubber (IR), acrylonitrile-butadiene copolymer rubber (NBR) ), Hydrogenated acrylonitrile-butadiene copolymer rubber (H-NBR), hydrin rubber, chloroprene rubber (CR), fluorine rubber, urethane rubber and the like are suitable.

  In the above embodiment, a coil spring is used as the spring member. From the viewpoint of reducing the frictional force between the spring member and the adjacent member, the contact area between the coil spring and the adjacent member is desirably as small as possible. For example, a coil spring having a thin wire diameter and a wide pitch is suitable. Further, the type of the spring member is not particularly limited as long as it is a cylindrical member that can accumulate an urging force in the axial direction. For example, a bellows spring may be used.

  In the above embodiment, a dielectric film made of acrylic rubber is used. However, the material of the dielectric film is not particularly limited as long as it is deformable according to the electrostatic attractive force between the pair of front and back electrodes. For example, as dielectric elastomers having high dielectric strength and high dielectric breakdown strength, in addition to the above acrylic rubber, silicone rubber, ethylene-propylene-diene terpolymer (EPDM), ethylene-propylene rubber, natural rubber (NR), butyl rubber (IIR), isoprene rubber (IR), acrylonitrile-butadiene copolymer rubber (NBR), hydrogenated acrylonitrile-butadiene copolymer rubber (H-NBR), hydrin rubber, chloroprene rubber (CR), fluorine rubber, urethane Rubber etc. are mentioned. Further, the thickness of the dielectric film is not particularly limited, and may be appropriately determined according to the use of the actuator. For example, it is desirable that the thickness of the dielectric film is small from the viewpoints of downsizing the actuator, driving at a low potential, and increasing the amount of displacement. In this case, the dielectric film thickness is preferably 1 μm or more and 1000 μm (1 mm) or less in consideration of dielectric breakdown strength and the like. It is more preferable that the thickness be 5 μm or more and 200 μm or less.

  The material of the electrode is not limited to the above embodiment, but it is desirable that the electrode can be expanded and contracted according to the expansion and contraction of the dielectric film. When the electrode expands and contracts together with the dielectric film, the deformation of the dielectric film is not easily disturbed by the electrode, and a desired displacement amount can be obtained more easily. For example, an electrode may be formed by applying a paste or paint in which oil or elastomer is mixed as a binder to a conductive material made of a carbon material or a metal material such as carbon black or carbon nanotube. Examples of the elastomer used as the binder include silicone rubber, acrylic rubber, ethylene-propylene-diene terpolymer (EPDM), natural rubber (NR), butyl rubber (IIR), isoprene rubber (IR), and acrylonitrile-butadiene copolymer. Flexible materials such as polymer rubber (NBR), hydrogenated acrylonitrile-butadiene copolymer rubber (H-NBR), hydrin rubber, chloroprene rubber (CR), fluorine rubber, and urethane rubber are suitable. In order to further improve the stretchability of the dielectric film, conductive electrodes such as carbon black and carbon nanotubes may be directly attached to the surface of the dielectric film to form the electrode.

  In the above embodiment, the actuator 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. As the fluid, various liquids such as water, oil, fuel, and coolant can be used. Moreover, you may use gas.

  In order to evaluate the actuator of the present invention, the displacement amount with respect to the applied voltage was measured for the actuator of the second embodiment (hereinafter referred to as “actuator of example”). For comparison, an actuator similar to the actuator of the embodiment (hereinafter referred to as “actuator of comparative example”) is manufactured except that a low friction layer (resin coating) is not interposed between the coil spring and the tube member. did. Similarly, the displacement amount with respect to the applied voltage was measured for the actuator of the comparative example.

  FIG. 7 shows the relationship between the applied voltage and the amount of displacement in each actuator of the example and the comparative example. In any actuator, the length extended in the axial direction was defined as the displacement. In addition, the vertical axis | shaft of FIG. 7 has shown the displacement amount with the multiple of the reference value a. As shown in the graph of FIG. 7, the displacement amount of the actuator of the example having the low friction layer was larger than that of the actuator of the comparative example having no low friction layer. Thus, it was confirmed that the actuator of the present invention has a large amount of displacement because the frictional force between the spring member and the adjacent member is reduced by the low friction layer.

  The actuator of the present invention is useful, for example, for power assist suits, artificial muscles for industrial, medical, and welfare robots, small pumps for electronic component cooling and medical use, medical instruments, and the like. It can be used as an alternative to all actuators such as actuators and piezoelectric element actuators.

It is a perspective view of the actuator of a first embodiment of the present invention. It is a perspective exploded view of the actuator. It is the III-III direction sectional drawing of FIG. (A) is the IV-IV direction sectional drawing of FIG. (B) is an axial sectional view of the actuator in the extended state. It is radial direction sectional drawing of the actuator of 2nd embodiment of this invention. It is radial direction sectional drawing of the wire of the coil spring of the actuator of 3rd embodiment of this invention. It is a graph which shows the relationship between the applied voltage and displacement amount in each actuator of an Example and a comparative example.

Explanation of symbols

1: Actuator 2: Dielectric element 2a: Multilayer stretchable film 20: First dielectric film 21: First electrode 22: Second dielectric film 23: Second electrode 3: Coil spring (spring member) 30: Wire rod 4 : Resin coating 40: low friction layer 41: low friction layer 5: suction side cap member 50: partition wall portion 500: ring holding groove 51: joint portion 510: suction port 52: holding portion 6: discharge side cap member 60: partition wall portion 600: Ring holding groove 61: Joint portion 610: Discharge port 62: Holding portion 7: Tube member 80, 81: Fastening ring member 90, 91: Check valve R: Fluid chamber

Claims (6)

A cylindrical spring member that can extend and contract in the axial direction;
A dielectric elastomer-made dielectric film and a plurality of electrodes arranged via the dielectric film are arranged on the outer side in the radial direction of the spring member, and the dielectric is changed according to a change in applied voltage between the electrodes. A cylindrical dielectric element whose film expands and contracts;
A low friction layer interposed between the spring member and an adjacent member radially adjacent to the spring member and capable of reducing a frictional force between the spring member and the adjacent member during expansion and contraction; With
One of the adjacent members is the dielectric element, and the low friction layer is a resin film formed on the inner peripheral surface of the dielectric element,
The spring member is a coil spring, and the surface of the coil spring wire is covered with the low friction layer,
In the low voltage state, the spring member is contracted in the axial direction with the biasing force accumulated.
When switching from the low voltage state to a high voltage state in which the applied voltage is higher than the low voltage state, the dielectric element expands in response to an increase in the applied voltage, so that the axial direction according to the biasing force of the spring member An actuator characterized by extending into The dielectric element includes a laminated stretch film in which the first dielectric film, the first electrode, the second dielectric film, and the second electrode are laminated in this order, and the first dielectric film has The actuator according to claim 1 , wherein the actuator is wound around the spring member so as to be an innermost layer. Furthermore, a fluid chamber arranged inside the dielectric element in the radial direction for sucking and discharging fluid, an inlet port arranged at one axial end of the fluid chamber for sucking the fluid into the fluid chamber, an axial direction of the fluid chamber, etc. And a discharge port that discharges the fluid from the fluid chamber, and changes the volume of the fluid chamber by expanding and contracting the dielectric element by changing a voltage applied between the electrodes. The actuator according to claim 1, wherein the fluid is sucked and discharged. The fluid is a liquid having conductivity,
The actuator according to claim 3 , wherein at least a part of the fluid chamber is partitioned by an insulating film for suppressing conduction of the fluid. And a suction side cap member having the suction port; a discharge side cap member having the discharge port; and at least a part of the fluid chamber interposed between the suction side cap member and the discharge side cap member. A tubular tube member that is partitioned and elastically deformable, and
Both ends of the dielectric element and the spring member in the axial direction are fixed to the suction side cap member and the discharge side cap member, respectively.
5. The actuator according to claim 3 , wherein the tube member is expanded and contracted by changing a voltage applied between the electrodes to expand and contract the dielectric element to change the volume of the fluid chamber. The actuator according to claim 5, wherein the tube member is the other of the adjacent members.

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