JP7646989B2 - Actuator - Google Patents

Description

The present invention relates to an actuator in which a dielectric sheet expands in the planar direction when a voltage is applied to the dielectric sheet via electrodes arranged on both sides of the dielectric sheet.

As an actuator of this type, the applicant has disclosed a dielectric actuator in the following Patent Document 1. This dielectric actuator is configured with a PVC gel sheet as a dielectric sheet and flexible electrodes provided on both sides of the PVC gel sheet, and expands in the planar direction when a voltage is supplied to the PVC gel sheet via the electrodes, and returns to its initial state when the voltage supply is stopped. In other words, this dielectric actuator is configured to perform expansion and contraction operations in the planar direction in response to the supply and stop of voltage. Furthermore, in this dielectric actuator, the ratio (expansion rate) of the difference in the area of the electrodes before and after the application of voltage to the area of the electrodes in a state where no voltage is applied is large compared to a dielectric actuator using a dielectric elastomer instead of a PVC gel sheet, and it is possible to obtain an expansion rate of 12% when an applied voltage is 3000V.

JP 2017-108601 A

However, the above-mentioned dielectric actuator has the following problems to be solved. Specifically, although the above-mentioned dielectric actuator using the PVC gel sheet can achieve a larger expansion rate than the dielectric actuator using a dielectric elastomer, a voltage of 3000 V must be applied to achieve a 12% expansion rate. On the other hand, this type of dielectric actuator is expected to be applied to devices worn by people, taking advantage of its flexibility. In order to realize application to such devices, it is necessary to reduce the voltage and generate a large expansion rate. However, the above-mentioned dielectric actuator requires the application of a high voltage of 3000 V, and the expansion rate is also insufficient at 12%, so there is a demand for a lower voltage and an increased expansion rate.

The present invention was made in consideration of these problems, and its main objective is to provide an actuator that can achieve low voltage and increased stretch ratio.

In order to achieve the above object, the actuator described in claim 1 comprises a dielectric sheet formed into a sheet-like shape from gel-like polyvinyl chloride, and flexible sheet-like electrodes arranged on both sides of the dielectric sheet, and when a voltage is supplied to the dielectric sheet via each of the electrodes, the dielectric sheet expands in a planar direction, and is characterized in that a plurality of restricting members are arranged in parallel at intervals along a cross direction intersecting the one direction on the at least one surface, the restricting members being formed in a linear or band-like shape from a material having low flexibility and being arranged between the at least one surface of the dielectric sheet and the electrode so as to extend in a certain direction on the at least one surface, and restricting the expansion of the dielectric sheet in the one direction.

According to the actuator of the present invention, by arranging multiple restricting members extending in one direction on the dielectric sheet in parallel along a cross direction that crosses the one direction, it is possible to restrict the expansion and contraction of the dielectric sheet in one direction, thereby sufficiently increasing the expansion and contraction rate of the dielectric sheet in the cross direction. Therefore, compared to conventional actuators, this actuator can ensure a sufficient expansion and contraction rate even when the voltage is low, and as a result, it is possible to achieve a lower voltage and an increased expansion and contraction rate.

In addition, with this actuator, by applying pre-strain in one direction to the dielectric sheet, the expansion and contraction of the dielectric sheet in one direction can be more reliably regulated, and the expansion rate of the dielectric sheet in the cross direction can be further increased, resulting in further reduction in voltage and further increase in the expansion rate.

In addition, with this actuator, multiple restricting members are arranged side by side on both sides of the dielectric sheet, so that the expansion and contraction of the dielectric sheet in one direction can be more reliably restricted, and the expansion rate of the dielectric sheet in the cross direction can be further increased, resulting in a further reduction in voltage and a further increase in the expansion rate.

In addition, with this actuator, the restricting member is made of paper, which allows the restricting member to be made lightweight and has sufficient flexibility, making it possible to reduce the weight of the actuator.

In addition, with this actuator, the electrodes are formed from a conductive oil compound, and can be formed by applying the conductive oil compound to the surface of the dielectric sheet, simplifying the manufacturing process of the actuator compared to a configuration in which the electrodes are fabricated in advance in a separate process.

In addition, with this actuator, the electrodes are formed from a mixture of gelled polyvinyl chloride and powdered carbon, so prefabricated electrodes can be arranged on each surface of the dielectric sheet, shortening the manufacturing time of the actuator compared to a configuration in which electrodes are formed by applying an electrode material to the surface of the dielectric sheet.

FIG. FIG. 2 is a diagram showing the configuration of an actuator 10. 5 is a flow chart of a PVC solution preparation process 50. 1 is a flow chart of an actuator assembly process 60. 1A to 1C are first explanatory diagrams illustrating a manufacturing method of the actuator 10. 11 is a second explanatory diagram illustrating the manufacturing method of the actuator 10. FIG. 11 is a third explanatory diagram illustrating the manufacturing method of the actuator 10. FIG. FIG. 4 is a fourth explanatory diagram illustrating the manufacturing method of the actuator 10. 13 is a fifth explanatory diagram illustrating the manufacturing method of the actuator 10. FIG. FIG. 6 is a sixth explanatory diagram illustrating the manufacturing method of the actuator 10. FIG. 11 is a characteristic diagram showing the results of a characteristic test.

The following describes an embodiment of an actuator according to the present invention with reference to the attached drawings.

First, the configuration of the actuator 10 shown in Fig. 1 will be described. The actuator 10 is an example of an actuator according to the present invention, and as shown in Figs. 1 and 2, it is formed in a band shape (rectangle) as a whole, and includes a PVC gel sheet 21, a pair of sheet-shaped electrodes 22 arranged on both sides of the PVC gel sheet 21, and a plurality of restricting members 23 formed in a band shape (an example of a line or band shape) and arranged on both sides (an example of at least one side) of the PVC gel sheet 21.

The PVC gel sheet 21 is an example of a dielectric sheet in the present invention, and is composed of polyvinyl chloride (PVC) and a plasticizer, has dielectric properties, and is in a gel state at room temperature. This PVC gel sheet 21 has the property of deforming when a voltage is applied. In addition, the PVC gel sheet 21 is formed into a rectangular (strip-shaped) sheet, as shown in Figures 1 and 2.

As shown in Figures 1 and 2, the electrode 22 is formed in a rectangular (strip-shaped) sheet shape, and is conductive and flexible. In this embodiment, the electrode 22 is formed by applying a conductive oil compound made of silicone oil mixed with carbon to both sides of the PVC gel sheet 21.

The regulating member 23 is formed of a material that is difficult to bend. In this embodiment, the regulating member 23 is formed of paper. As shown in Figs. 1 and 2, the regulating member 23 is formed in a band shape (an example of a line or band shape) and extends in the width direction (an example of one direction) of the PVC gel sheet 21 on both sides of the PVC gel sheet 21, and multiple regulating members 23 are arranged in parallel along the length direction of the PVC gel sheet 21 (an example of a cross direction that crosses (orthogonal in this example) the one direction).

In this actuator 10, when a voltage is supplied to the PVC gel sheet 21 through each electrode 22, the PVC gel sheet 21 deforms so as to expand in the surface direction, and when the supply of voltage to the PVC gel sheet 21 is stopped, the PVC gel sheet 21 contracts in the surface direction accompanied by the force caused by the restoration (release of deformation) of the PVC gel sheet 21, and it is possible to output the force generated by the deformation of the PVC gel sheet 21 as a driving force. In addition, in this actuator 10, since a plurality of restricting members 23 having a low flexibility are arranged to extend in the width direction of the PVC gel sheet 21, the expansion and contraction in the width direction of the PVC gel sheet 21 is restricted. Therefore, in this actuator 10, the expansion and contraction amount of the entire PVC gel sheet 21 is concentrated in the length direction by the amount that the expansion and contraction in the width direction of the PVC gel sheet 21 is restricted, and as a result, the PVC gel sheet 21 expands and contracts greatly in the length direction compared to a configuration in which the restricting members 23 are not provided.

Next, we will explain the manufacturing method of the actuator 10.

First, the method of preparing the PVC solution that is the material of the PVC gel sheet 21 will be described with reference to the flowchart of the PVC solution preparation process 50 shown in FIG. 3. In this PVC solution preparation process 50, first, a solvent (tetrahydrofuran as an example) is measured and poured into a stirring vessel (step 51). It is preferable to use a solvent in the range of 600 to 1000 parts by weight per 100 parts by weight of polyvinyl chloride, and in this embodiment, 800 parts by weight of the solvent is used per 100 parts by weight of polyvinyl chloride.

Next, polyvinyl chloride is weighed and added to the stirring vessel containing the solvent while stirring (step 52). In this embodiment, 100 parts by weight of polyvinyl chloride is weighed and added to 800 parts by weight of the solvent.

Next, with the polyvinyl chloride and the solvent in a fully mixed (dissolved) state, the plasticizer is weighed out and added to the stirring vessel containing the polyvinyl chloride and the solvent while stirring (step 53). In this case, various plasticizers can be used, but in this embodiment, dibutyl adipate (DBA) is used. It is preferable to use a plasticizer in the range of 100 to 500 parts by weight per 100 parts by weight of polyvinyl chloride, and in this embodiment, 400 parts by weight of the plasticizer is used per 100 parts by weight of polyvinyl chloride. Next, the stirring vessel containing the polyvinyl chloride, the solvent, and the plasticizer (a mixture of these) is set in a degassing device and a degassing process is performed (step 54). This completes the preparation of the PVC solution.

Next, the method of assembling the actuator 10 will be described with reference to the flow chart of the actuator assembly process 60 shown in FIG. 4. In this actuator assembly process 60, first, as shown in FIG. 5, a PVC solution 200 is applied onto a glass plate and a thin film of the PVC solution 200 is formed on the glass plate using a film forming machine (applicator), and then the PVC solution 200 is stored in an incubator and dried at 20°C for 5 days. As a result, a PVC gel sheet 21 is formed on the glass plate 100 (step 61).

Next, as shown in Fig. 6, the PVC gel sheet 21 on the glass plate is cut out into a predetermined shape (for example, a rectangle with a width of 20 mm and a length of 50 mm) using a cutter (step 62). Next, as shown in Fig. 7, the cut PVC gel sheet 21 is placed on the glass plate, and the PVC gel sheet 21 is then pulled in the width direction (left and right direction in the figure) to impart prestrain in the width direction (step 63). In this embodiment, a prestrain of 150% (30 mm in this example) is imparted to the width before pulling (20 mm in this example) (i.e., pulled until the width becomes 50 mm).

Next, the regulating members 23 are attached (step 64). Specifically, as shown in FIG. 8, a plurality of regulating members 23 are arranged at equal intervals in the length direction (vertical direction in the figure) so as to extend in the width direction of one side of the PVC gel sheet 21. In this case, as an example, a 70 μm thick woodfree paper cut into a strip shape with a width of 2 mm and a length of 50 mm is used as the regulating member 23. Then, both ends of the regulating member 23 and the width direction edge of the PVC gel sheet 21 are fixed with adhesive tape 300. Next, the PVC gel sheet 21 is turned over, and a plurality of regulating members 23 are arranged on the other side of the PVC gel sheet 21 in the above-mentioned procedure and fixed with adhesive tape 300. Next, as shown in FIG. 9, the PVC gel sheet 21 to which the regulating members 23 are attached is cut into a predetermined shape (for example, a rectangle with a width of 25 mm and a length of 40 mm) (step 65).

Next, the electrodes 22 are formed (step 66). Specifically, as shown in FIG. 10, a conductive oil compound is applied to cover one side of the PVC gel sheet 21 and the regulating member 23, and the conductive oil compound is left to stand until the fluidity of the conductive oil compound decreases. As a result, the electrode 22 is formed on one side. Next, the PVC gel sheet 21 and the regulating member 23 with the electrode 22 formed on one side are inverted, and a conductive oil compound is applied to cover the other side, and the conductive oil compound is left to stand until the fluidity of the conductive oil compound decreases. As a result, the electrode 22 is formed on the other side. Next, a lead wire (not shown) is connected to each electrode 22 (step 67). With the above, the actuator assembly process 60 is completed, and the actuator 10 is completed.

Next, we will explain the results of characteristic tests on the actuator of the present invention.

In the characteristic tests, the actuator 10 manufactured by the above-mentioned manufacturing method was designated as Example 1. The actuator 10 manufactured in the above-mentioned actuator assembly process 60 with a pre-strain of 70% was designated as Example 2. The actuator 10 without the restricting member 23 and without pre-strain was designated as Comparative Example 1.

In addition, in this characteristic test, the expansion rate in the length direction of the PVC gel sheet 21 when a voltage was supplied to the PVC gel sheet 21 via each electrode 22 of each actuator 10 in Examples 1 and 2 and Comparative Example 1 was measured while changing the voltage value. In this case, the length of the PVC gel sheet 21 in the initial state where no voltage was supplied was defined as L0, and the length of the PVC gel sheet 21 when a voltage was supplied was defined as L1, and the value (%) represented by (L1-L0)/L0 was defined as the expansion rate. Furthermore, L0 and L1 in Examples 1 and 2 were defined as the lengths of only the portions where the restricting members 23 were not arranged (portions that contribute to expansion and contraction).

The results of the characteristic test are shown in Figure 11. It is clear from this figure that the actuator 10 of Example 1, in which a paper restricting member 23 is provided and a prestrain of 150%, and the actuator 10 of Example 2, in which a paper restricting member 23 is provided and a prestrain of 70%, have a sufficiently large expansion/contraction ratio at the same voltage value compared to the actuator 10 of Comparative Example 1, in which the restricting member 23 is not provided and no prestrain is applied. In other words, it is clear that by providing a restricting member 23 and applying a prestrain, it is possible to achieve a sufficiently low voltage and a sufficiently large expansion/contraction ratio.

As an additional characteristic test, an actuator 10 with no pre-strain by disposing a paper restricting member 23 was used as Example 3, and an actuator 10 with a 70% pre-strain by disposing a restricting member 23 made of resin fiber with a diameter of 70 μm was used as Example 4. The longitudinal expansion rate of the PVC gel sheet 21 in each actuator 10 was measured while changing the voltage value (not shown). The actuators 10 of Examples 3 and 4 had a sufficiently large expansion rate at the same voltage value compared to the actuator 10 of Comparative Example 1, but had a smaller expansion rate at the same voltage value compared to the actuators 10 of Examples 1 and 2.

In this way, with this actuator 10, by arranging multiple restricting members 23 extending in the width direction of the PVC gel sheet 21 in parallel along the length direction, the expansion and contraction of the PVC gel sheet 21 in the width direction can be restricted, and the expansion and contraction rate of the PVC gel sheet 21 in the length direction can be sufficiently increased. Therefore, with this actuator 10, a sufficient expansion and contraction rate can be ensured even when the voltage is low compared to conventional actuators, and as a result, a lower voltage and an increased expansion and contraction rate can be achieved.

In addition, with this actuator 10, by applying pre-strain to the PVC gel sheet 21, the expansion and contraction in the width direction of the PVC gel sheet 21 can be more reliably regulated, and the expansion rate in the length direction of the PVC gel sheet 21 can be further increased, resulting in further reduction in voltage and further increase in the expansion rate.

In addition, with this actuator 10, multiple regulating members are arranged side by side on both sides of the PVC gel sheet 21, so that the expansion and contraction in the width direction of the PVC gel sheet 21 can be more reliably regulated, and the expansion rate in the length direction of the PVC gel sheet 21 can be further increased, resulting in further reduction in voltage and further increase in the expansion rate.

In addition, with this actuator 10, the restricting member 23 is made of paper, so that the restricting member can be made lightweight and has sufficient flexibility, thereby realizing a reduction in the weight of the actuator 10.

In addition, with this actuator 10, the electrodes 22 are formed from a conductive oil compound, and can be formed by applying the conductive oil compound to the surface of the PVC gel sheet 21. This simplifies the manufacturing process of the actuator 10 compared to a configuration in which the electrodes 22 are produced in a separate process and disposed on both sides of the PVC gel sheet 21.

The actuator 10 described above is an example of an actuator according to the present invention, and an appropriately modified configuration can be adopted. For example, in the actuator 10 described above, the restricting member 23 is disposed on both sides of the PVC gel sheet 21, but a configuration in which the restricting member 23 is disposed on only one side of the PVC gel sheet 21 can also be adopted. In addition, the actuator 10 described above is configured with only one PVC gel sheet 21, but a configuration in which the actuator includes multiple PVC gel sheets 21 and electrodes 22 disposed on both sides of each PVC gel sheet 21 and the restricting member 23 is disposed on at least one side of one or more PVC gel sheets 21 can also be adopted.

In addition, while the above-mentioned actuator 10 employs electrodes 22 formed from a conductive oil compound, it is also possible to employ electrodes 22 formed in a sheet shape from a mixture of gelled polyvinyl chloride and powdered carbon. With this configuration, prefabricated electrodes 22 can be disposed on each surface of the PVC gel sheet 21, so that the manufacturing time of the actuator 10 can be shortened compared to a configuration in which electrodes 22 are formed by applying an electrode material to the surface of the PVC gel sheet 21.

In addition, in the configuration of the actuator 10 described above, the PVC gel sheet 21 and the electrodes 22 that constitute the actuator 10 are each formed in a rectangular shape, but a configuration in which the PVC gel sheet 21 and the electrodes 22 are formed in other shapes in a plan view (for example, a circle, an ellipse, or a polygon other than a rectangle) can also be adopted.

In addition, in the actuator 10 described above, the width direction is defined as one direction, and the length direction perpendicular to the width direction is defined as the cross direction when the regulating member 23 is positioned, but the one direction and the cross direction can be defined arbitrarily. For example, a direction inclined at an arbitrary angle (e.g., 30°) to the width direction can be defined as one direction, and a direction inclined at an arbitrary angle (e.g., 45°) to the one direction can be defined as the cross direction.

REFERENCE SIGNS LIST 10 Actuator 21 PVC gel sheet 22 Electrode 23 Regulating member

Claims (1)

An actuator comprising a dielectric sheet formed in a sheet shape from gelled polyvinyl chloride, and flexible sheet-like electrodes disposed on both sides of the dielectric sheet, the dielectric sheet expanding in a planar direction when a voltage is supplied to the dielectric sheet via the electrodes,
An actuator comprising a plurality of restricting members formed in a linear or band-like shape from a material having low flexibility, arranged between at least one of the surfaces of the dielectric sheet and the electrode so as to extend in a certain direction on the at least one surface of the dielectric sheet, and restricting the extension of the dielectric sheet in the certain direction, the restricting members being arranged in parallel at intervals along a cross direction that crosses the one direction on the at least one surface.

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