JP2011188720A - Driving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driving device capable of achieving self-holding of the shape of a polymer actuator. <P>SOLUTION: The driving device has the polymer actuator 5 expanded and contracted by charging and discharging, a driving section 10 which supplies electric charges to the polymer actuator 5, a switch section 20 which changes the connection of the polymer actuator 5, a voltage decrease detection section 30 which gives a switching instruction to the switch section 20, and a capacitive portion 40 which is connected to the polymer actuator 5 by switching of the switch section 20. The polymer actuator 5 is composed of a dielectric polymer actuator, which includes a displacement layer 501 made of a dielectric elastomer, and a pair of electrode layers sandwiching the displacement layer 501. Moreover, the voltage decrease detection section 30, when detecting that a voltage of an external power supply 150 is a voltage equal to or lower than a predetermined value, gives the switching instruction to the switch section 20, such that the polymer actuator 5 and the capacitive portion 40 are connected. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a drive device, and more particularly, to a drive device including a polymer actuator.

  Conventionally, actuators of electrostatic attraction type, piezoelectric type, ultrasonic type, shape memory alloy type, etc. have been proposed as displacement elements for generating minute displacements.

In particular, since the piezoelectric type has a large generated force per volume, it can generate a practical driving force even when it is small, and is used for an actuator of a small imaging device. The mainstream of current piezoelectric actuators is an inorganic actuator whose main material is PZT (Pb (Zr, Ti) O ₃ ).

  However, since PZT has a very small amount of displacement, it is not suitable for applications that require a large amount of displacement or a large speed. Moreover, since PZT contains lead, there is a concern that its use will be limited in the future.

  Furthermore, the inorganic actuator has a firing temperature of about 1000 ° C., and there is a problem in, for example, the hybrid property with a circuit when converted to MEMS (Micro Electro Mechanical Systems). In addition, the lack of a simple manufacturing method is one factor that hinders MEMS, miniaturization, and integration. In addition, other inorganic actuators also have problems such as limited operating environment, insufficient response, complicated structure, lack of flexibility, etc. Limited.

  In view of these problems, polymer actuators using light and flexible organic materials have been studied. In general, an organic material has a low Young's modulus (soft), so that the displacement force is small as compared with an inorganic material, but the displacement amount is large. In addition, a wet process such as an inkjet method or a printing method can be used for manufacturing, so that a large area can be manufactured at low cost. Furthermore, a flexible substrate can be supported. Taking advantage of these characteristics, the polymer actuator is expected to be applied to small motors, micropumps, medical equipment, robot drive sources, and the like.

  Examples of such polymer actuators include ion conductive polymer actuators, conductive polymer actuators, and dielectric polymer actuators. Among them, a configuration in which a flexible polymer is sandwiched between electrodes as a dielectric. This type of dielectric polymer actuator is attracting attention because it can obtain a larger displacement and operating speed.

  As an example of the polymer actuator described above, an actuator including a dielectric elastomer layer between electrodes is disclosed in Patent Document 1, for example.

JP 2009-124875 A

  However, when the drive device is configured using the polymer actuator (dielectric polymer actuator) as described above, for example, if the external power supply that supplies power is cut, the displacement state of the polymer actuator changes. There is an inconvenience. That is, the conventional driving device using the polymer actuator has a problem that it is difficult to realize self-holding of the shape of the polymer actuator.

  The present invention has been made to solve the above-described problems, and one object of the present invention is to provide a driving device capable of realizing self-holding of the shape of the polymer actuator. is there.

  In order to achieve the above object, a drive device according to one aspect of the present invention switches a connection between a polymer actuator that expands and contracts by charging and discharging, a drive unit that charges a polymer actuator, and a polymer actuator. A switch unit; an instruction unit for issuing a switching command to the switch unit; and a capacitor unit including a capacitive component connected to the polymer actuator by switching the switch unit.

  In the driving device according to this aspect, as described above, the capacitor is connected to the polymer actuator, and by switching the switch unit, the connection of the polymer actuator is switched from the drive unit to the capacitor unit. The capacity change of the actuator can be suppressed. Thereby, since leakage current can be reduced (acceleration of increase in leakage current) can be suppressed, decrease in charge accumulated in the polymer actuator can be suppressed. As a result, a change in the shape of the polymer actuator can be suppressed. Therefore, for example, even when the external power supply is disconnected, the state of the polymer actuator before the external power supply is disconnected can be maintained.

  In the driving device according to the above aspect, preferably, the indication unit includes a voltage detection unit that detects a voltage of the external power supply, and when the voltage of the external power supply is detected to be a voltage equal to or lower than a predetermined value, the polymer A switching command is issued to the switch unit so that the actuator and the capacitor unit are connected. If comprised in this way, the change of the shape of a polymer actuator can be suppressed easily.

  In the driving device according to the above aspect, the polymer actuator may include a displacement layer made of a dielectric elastomer and a pair of electrode layers sandwiching the displacement layer.

  In the drive device according to the above aspect, the capacity of the capacity portion is preferably 1/10 or more and 10/10 or less with respect to the largest capacity of the polymer actuator.

  As described above, according to the present invention, it is possible to easily obtain a drive device capable of realizing self-holding of the shape of the polymer actuator.

It is a schematic diagram which shows schematic structure of the polymer actuator by 1st Embodiment of this invention. It is a schematic diagram which shows the aspect at the time of charge of the polymer actuator by 1st Embodiment of this invention. It is a schematic diagram which shows the aspect at the time of discharge of the polymer actuator by 1st Embodiment of this invention. It is a block diagram showing a schematic structure of a drive device by a 1st embodiment of the present invention. It is a block diagram which shows schematic structure of the voltage drop detection part of the drive device by 1st Embodiment of this invention. It is a figure for demonstrating operation | movement of the voltage drop detection part by 1st Embodiment. It is the graph which showed the relationship between the leak time in the drive device by 1st Embodiment of this invention, and the thickness of a displacement layer. 3 is a graph showing a relationship between leakage time and capacitance in the driving apparatus according to the first embodiment of the present invention. 4 is a graph showing a relationship between a leakage time and a holding voltage in the driving apparatus according to the first embodiment of the present invention. 4 is a graph showing a relationship between a leakage time and a leakage current in the driving apparatus according to the first embodiment of the present invention. It is a block diagram which shows schematic structure of the drive device by 2nd Embodiment of this invention. It is the graph which showed the relationship between the leak time and the thickness of a displacement layer in the drive device by 2nd Embodiment of this invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments embodying the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic diagram showing a schematic configuration of a polymer actuator according to a first embodiment of the present invention. FIG. 2 is a schematic view showing an aspect during charging of the polymer actuator according to the first embodiment of the present invention. FIG. 3 is a schematic view showing an aspect during discharge of the polymer actuator according to the first embodiment of the present invention. First, with reference to FIGS. 1-3, the structure of the polymer actuator 5 by the 1st Embodiment of this invention and the aspect of the drive deformation | transformation are demonstrated.

  As shown in FIG. 1, the polymer actuator 5 according to the first embodiment includes a displacement layer 501 (polymer dielectric) having a flexible rubber-like polymer (dielectric elastomer, dielectric polymer) as a dielectric, and a displacement layer 501. The first electrode film (electrode layer) 502 formed on one surface and the second electrode film (electrode layer) 503 formed on the other surface of the displacement layer 501 are laminated. It consists of a dielectric polymer actuator.

  As shown in FIG. 2, when the voltage is applied between the first electrode film 502 and the second electrode film 503 from the power source 7, the polymer actuator 5 having the above configuration is charged ( Arrow P1). Then, an electrostatic attractive force acts between the electrodes by the electric field generated by the applied voltage, and the first electrode film 502 and the second electrode film 503 are attracted. Thereby, the displacement layer 501 which is an elastic body contracts in a direction perpendicular to the layer surface and expands in a phase opposite to the direction along the layer surface. That is, the displacement layer 501 is compressed and deformed so that the area increases.

  Next, as shown in FIG. 3, for example, when a capacitor 8 is connected between the first electrode film 502 and the second electrode film 503, the charge charged in the displacement layer 501 is discharged (arrow P2). As a result, the film expands in a direction perpendicular to the layer surface and contracts in an opposite phase in the direction along the layer surface.

  Thus, the polymer actuator 5 expands and contracts in the direction perpendicular to the layer surface and the direction along the layer surface by being charged and discharged.

  Since the thickness (distance between electrodes) d (see FIG. 1) of the displacement layer 501 of the polymer actuator 5 changes with charge / discharge, as will be described later, as the displacement layer 501 is displaced, the polymer actuator The capacity of 5 also changes.

  FIG. 4 is a block diagram showing a schematic configuration of the driving apparatus according to the first embodiment of the present invention. FIG. 5 is a block diagram showing a schematic configuration of the voltage drop detection unit of the driving apparatus according to the first embodiment of the present invention. FIG. 6 is a diagram for explaining the operation of the voltage drop detection unit according to the first embodiment. Next, with reference to FIGS. 4-6, the drive device by 1st Embodiment of this invention is demonstrated.

  As shown in FIG. 4, the drive device according to the first embodiment includes the polymer actuator 5 and a control unit 100 that controls the drive of the polymer actuator 5.

  The control unit 100 detects a voltage drop of the drive unit 10 that charges the polymer actuator 5, the switch unit 20 that switches the connection of the polymer actuator 5, and the external power supply 150, and instructs the switch unit 20 to switch The voltage drop detecting unit 30 for generating the voltage and the capacitor unit 40 are included. The voltage drop detection unit 30 is an example of the “instruction unit” and the “voltage detection unit” in the present invention.

  The drive unit 10 includes a booster circuit 11 and a voltage application adjustment unit 12. The booster circuit 11 has a function of boosting the voltage from the external power supply 150, and outputs the boosted voltage to the voltage application adjustment unit 12. The voltage application adjustment unit 12 applies the voltage boosted by the booster circuit 11 to the polymer actuator 5. Moreover, the voltage application adjustment part 12 adjusts an applied voltage according to the state to deform | transform. The output side of the voltage application adjusting unit 12 is connected to the switch unit 20.

  The switch unit 20 has a function of switching the input impedance unit of the circuit connected to the polymer actuator 5 to two or more types. In the first embodiment, the switch unit 20 is configured to be able to switch the connection of the polymer actuator 5 between the drive unit 10 and the capacitor unit 40. Specifically, the switch unit 20 includes terminals 21 and 22, the output side of the voltage application adjusting unit 12 is connected to the terminal 21, and the capacitor unit 40 is connected to the terminal 22. ing. When the switch unit 20 is switched to the terminal 21, the polymer actuator 5 and the drive unit 10 are connected, and when the switch unit 20 is switched to the terminal 22, the polymer actuator 5 and the capacitor unit 40 are connected. . When the polymer actuator 5 is driven, the polymer actuator 5 is connected to the drive unit 10.

  As shown in FIG. 5, the voltage drop detection unit 30 includes a capacitor C that charges the energy of the external power source 150, and a comparator unit 31 that compares a predetermined voltage applied to the input terminal 31a with the voltage of the capacitor C. It consists of The output side of the voltage drop detection unit 30 (the output terminal 31b of the comparator unit 31) is connected to the switch unit 20.

  The voltage drop detection unit 30 is configured to issue a switching command to the switch unit 20 (see FIG. 4) when the voltage of the capacitor C becomes equal to or lower than a predetermined voltage. Specifically, as shown in FIG. 6, the capacitor C of the voltage drop detection unit 30 is maintained at a constant voltage by the power from the external power supply 150 (see FIGS. 4 and 5). When 150 is disconnected (point T1), the voltage of the capacitor C starts to decrease. Then, a switching command is issued to the switch unit 20 at a timing (point T2) when the voltage of the capacitor C becomes equal to or lower than a predetermined voltage.

  4 is composed of a capacitor (for example, an electrolytic capacitor), and is connected to the polymer actuator 5 by switching the switch unit 20. In a state where the capacitor 40 and the polymer actuator 5 are connected, the capacitor 40 and the polymer actuator 5 are connected in parallel in an equivalent circuit. Moreover, it is preferable to use a capacitor having a capacitance of 1/10 or more and 10/10 or less of the capacitance when the capacitance of the polymer actuator 5 is maximized.

  FIGS. 7 to 10 are diagrams showing thickness change, capacity change, voltage change, and current change with respect to the leak time of the drive device (polymer actuator) according to the first embodiment of the present invention, respectively. Next, drive control of the polymer actuator 5 using the drive device according to the first embodiment of the present invention will be described with reference to FIGS. 7 to 10, the case where the polymer actuator 5 is connected to the capacitor 40 is indicated by a broken line, and the case where the polymer actuator 5 is connected to the drive unit 10 is indicated by a solid line. .

  As shown in FIG. 4, when the polymer actuator 5 is driven, the switch unit 20 is connected to the drive unit 10 (terminal 21). A voltage drop of the power supply 150 is detected, and a switching command is issued from the voltage drop detection unit 30 to the switch unit 20. When a switching command is issued to the switch unit 20, the switch unit 20 is switched and the polymer actuator 5 is connected to the capacitor unit 40.

  Here, unlike the first embodiment, consider a case where the polymer actuator 5 and the drive unit 10 are always connected. In this case, when the external power supply 150 is disconnected, a leakage current flows and the charge of the polymer actuator 5 decreases.

The leakage current is a current that flows through the circuit connected to the polymer actuator 5 and the polymer actuator 5 itself, and is expressed by the following equation (1).
I = V / R (1)
However, I is a leakage current, V is a holding voltage of the polymer actuator 5, and R is (resistance connected to the polymer actuator 5 + resistance of the polymer actuator 5 itself).

On the other hand, the electrostatic capacity (Cp) of the polymer actuator 5 is expressed by the following equation (2).
Cp = ε × ε ₀ × S / d (2)
Where ε is the dielectric constant of vacuum, ε ₀ is the relative dielectric constant, S is the electrode area, and d is the thickness of the displacement layer 501 (see FIG. 1).

  The electrostatic capacity (Cp) of the polymer actuator 5 varies depending on the thickness (d) of the displacement layer 501 as shown in the equation (2). For this reason, when the charge of the polymer actuator 5 decreases due to the leakage current, the thickness (d) increases as shown by the solid line in FIG. 7, and the capacitance (Cp) increases as shown by the solid line in FIG. Get smaller.

The holding voltage (V) of the polymer actuator 5 is expressed by the following equation (3).
V = Q / Cp (3)
Where Q is the charge of the polymer actuator 5 and Cp is the capacitance of the polymer actuator 5.

  When the charge (Q) decreases due to the leakage current, the electrostatic capacity (Cp) also decreases. Therefore, the apparent holding voltage (V) apparent from the polymer actuator 5 does not change so much from the equation (3). The high state is maintained as indicated by the solid line 9. Therefore, as shown by the equation (1) and the solid line in FIG. 10, the increase in leakage current (I) is accelerated (a large amount of leakage current (I) flows).

  Then, the increase in the leakage current (I) is accelerated (a large amount of leakage current (I) flows), whereby the charge of the polymer actuator 5 is further reduced, and the thickness (d) of the displacement layer 501 further varies ( growing). Thereby, when the polymer actuator 5 is connected to the drive unit 10, it becomes difficult to realize self-holding of the shape for a long time in the polymer actuator 5.

  In contrast, in the first embodiment, as described above, when the voltage drop of the external power source 150 is detected by the voltage drop detection unit 30, the switch unit 20 is switched, and the polymer actuator 5 is connected to the capacitor unit 40. Connected.

  When the polymer actuator 5 and the capacitor part 40 are connected, the electrostatic capacity (Cp) of the formula (2) is a sum of the capacity of the polymer actuator 5 and the capacity of the capacitor part 40. FIG. As indicated by the broken line, the change in the capacity of the polymer actuator 5 is reduced. For this reason, although the charge (Q) of the polymer actuator 5 decreases as the leakage current increases, the change in the capacitance (Cp) is reduced. The voltage (V) decreases (see FIG. 9).

  Further, when the holding voltage (V) of the polymer actuator 5 decreases, the leakage current I also decreases from the equation (1). As a result, as shown by the broken line in FIG. 10, it is possible to suppress the increase in the leakage current from being accelerated.

  Then, by suppressing the acceleration of the increase in leakage current, the decrease in charge in the polymer actuator 5 is suppressed, so that the variation (change) in the thickness (d) of the displacement layer 501 is as shown by the broken line in FIG. It is suppressed.

  As described above, the drive device according to the first embodiment includes the capacitor unit 40 connected to the polymer actuator 5, and the connection of the polymer actuator 5 is switched from the drive unit 10 to the capacitor unit 40 by switching the switch unit 20. As a result, the capacity change of the polymer actuator 5 can be suppressed. For this reason, since it is possible to suppress an increase in the leakage current, it is possible to suppress a decrease in the charge accumulated in the polymer actuator 5 and maintain a state in which the charge is accumulated. Thereby, since the change of the thickness (d) of the displacement layer 501 can be suppressed, even when the external power source 150 is disconnected, the shape change of the polymer actuator 5 (the thickness change of the displacement layer 501) is suppressed, The state of the polymer actuator 5 before the external power supply is cut off can be maintained. Therefore, by configuring as described above, long-time self-holding in the polymer actuator 5 can be realized.

  Further, it is effective if the capacitance of the capacitor 40 is configured to be 1/10 or more and 10/10 or less with respect to the capacitance when the capacitance of the polymer actuator 5 is maximized. Furthermore, self-holding of the shape for a long time in the polymer actuator 5 can be realized.

  By realizing self-holding of the shape of the polymer actuator 5 for a long time, when the polymer actuator 5 is used for, for example, a small motor, a micropump, a medical device, a driving source for a robot, an external power source It is possible to prevent the polymer actuator 5 from being unexpectedly displaced by cutting 150 or the like.

(Second Embodiment)
FIG. 11 is a block diagram showing a schematic configuration of the driving apparatus according to the second embodiment of the present invention. Next, a driving device according to a second embodiment of the present invention will be described with reference to FIG. In FIG. 11, corresponding components are denoted by the same reference numerals, and redundant description is omitted.

  As shown in FIG. 11, the drive device according to the second embodiment further includes a terminal 23 for connecting the polymer actuator 5 to a floating state in the switch unit 20 in the configuration of the first embodiment.

  In the second embodiment, a controller unit 50 is further connected to the voltage drop detection unit 30. When the voltage drop detection unit 30 detects a voltage drop of the external power supply 150 and issues a switching command to the switch unit 20, the controller unit 50 includes either the capacitance unit 40 (terminal 22) or the floating (terminal 23). To switch to.

  FIG. 12 is a diagram showing a change in thickness with respect to a leak time of the driving device (polymer actuator) according to the second embodiment of the present invention. Next, with reference to FIG. 1, FIG. 7, FIG. 11, and FIG. 12, the drive control of the polymer actuator using the drive device according to the second embodiment of the present invention will be described. In FIG. 12, the case where the polymer actuator 5 is connected in a floating state is indicated by a broken line, and the case where the polymer actuator 5 is connected to the drive unit 10 is indicated by a solid line. Further, since the case where the polymer actuator 5 is connected to the capacitor unit 40 is the same as that in the first embodiment, the case where the polymer actuator 5 is connected in a floating state will be described in the second embodiment. To do.

  As shown in FIG. 11, when the polymer actuator 5 is connected to the floating state (terminal 23), generation of a leak current flowing in a circuit connected to the polymer actuator 5 is suppressed. For this reason, as shown in FIG. 12, immediately after the switch part 20 is switched, the thickness (d) of the displacement layer 501 (see FIG. 1) hardly changes. On the other hand, since the electric charge of the polymer actuator 5 decreases due to the leak current flowing through the polymer actuator 5 itself, the increase in the leak current is accelerated with the passage of time.

  Here, when the polymer actuator 5 is connected to the capacitor 40 (see FIG. 11), as shown in FIG. 7, as the charge is charged from the polymer actuator 5 to the capacitor 40, the switch Immediately after the switching of the portion 20, the thickness (d) of the displacement layer 501 increases. Thereafter, the change in the thickness (d) is suppressed for a long time.

  On the other hand, when the polymer actuator 5 is connected to the floating state (terminal 23), as shown in FIG. 12, it is connected to the capacitor 40 within a certain time (t) immediately after the switching of the switch unit 20. The increase (change) in the thickness (d) of the displacement layer 501 is suppressed as compared with the case where the displacement is performed. For this reason, if the self-holding shape has a relatively short period of time, a higher self-holding effect is obtained by connecting to the floating state (terminal 23) as compared to the case of connecting to the capacitor 40 (terminal 22). be able to. That is, the shape change of the polymer actuator 5 (the change in the thickness of the displacement layer 501) can be more effectively suppressed for a relatively short time.

  Therefore, by configuring the capacitor 40 (terminal 22) and the floating state (terminal 23) to be switchable, the capacitor 40 and the floating can be used properly according to the application. For example, when it is desired to suppress the shape change of the polymer actuator 5 over a long period of time, it may be connected to the capacitor 40 and the time for suppressing the shape change may be short, but when it is desired to suppress the shape change more accurately. It can be used properly such as connecting to the floating state (terminal 23).

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and further includes all modifications within the meaning and scope equivalent to the scope of claims for patent.

5 Polymer actuator 501 Displacement layer (dielectric elastomer, polymer dielectric)
502 1st electrode film (electrode layer)
503 Second electrode film (electrode layer)
DESCRIPTION OF SYMBOLS 10 Drive part 11 Booster circuit 12 Voltage application adjustment part 20 Switch part 21, 22, 23 Terminal 30 Voltage drop detection part (indication part, voltage detection part)
31 Comparator section 31a Input terminal 31b Output terminal 40 Capacitance section 50 Controller section 100 Control section 150 External power supply

Claims (4)

A polymer actuator that expands and contracts by charging and discharging; and
A drive unit that charges the polymer actuator;
A switch unit for switching the connection of the polymer actuator;
An instruction unit for issuing a switching command to the switch unit;
A drive unit comprising: a capacitor unit including a capacitor component connected to the polymer actuator by switching of the switch unit.   The instructing unit includes a voltage detecting unit that detects a voltage of an external power source. When the voltage of the external power source is detected to be a voltage equal to or lower than a predetermined value, the polymer actuator and the capacitor unit are connected. The driving device according to claim 1, wherein a switching command is issued to the switch unit. The polymer actuator is
A displacement layer made of a dielectric elastomer;
The drive device according to claim 1, further comprising a pair of electrode layers sandwiching the displacement layer.   4. The driving device according to claim 1, wherein a capacity of the capacity unit is 1/10 or more and 10/10 or less with respect to a maximum capacity of the polymer actuator. 5. .

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