JP3262358B2 - Electrostatic actuator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic actuator.

[0002]

2. Description of the Related Art A conventional actuator mainly uses an electromagnetic force, and must be provided with an electromagnetic coil, a permanent magnet, and the like due to its characteristics, and has a complicated structure and very large power consumption. Was. Therefore, the amount of heat generated by the actuator was also large.

[0003] For this reason, electrostatic motors and electrostatic actuators have attracted attention because of their low power consumption, high efficiency, and miniaturization as compared with electromagnetic types.

[0004] As the electrostatic motor, there are an induction motor using a dielectric and a motor using a resistor instead of the dielectric. An induction motor using a dielectric focuses on the polarization of a dielectric placed in an electric field, and utilizes a time delay of the polarization. Further, the motor using the resistor utilizes the fact that the electric charge induced in the resistor within the rotating electric field is delayed with respect to the direction of the electric field.

[0005] However, the conventional electrostatic motor includes a stator and a rotor, and requires a rotating mechanism having a certain gap. Therefore, it is necessary to use a mechanism such as a bearing to maintain the gap, and to increase the rigidity of the stator and the rotor to maintain a more uniform gap. Therefore, it is difficult to make the above device compact, and its power density is low.

In view of the above situation, an electrostatic force is generated between solid surfaces by utilizing a time delay of polarization of a dielectric substance placed in an electric field, and the electrostatic force obtains a driving force as an actuator. The electric actuator is disclosed in
5978.

This electrostatic actuator has a stator 1 and a moving element 10 as shown in FIGS.

The stator 1 has a plurality of strip electrodes 4 arranged at a constant pitch in a film-shaped insulator 2.
The mover 10 is composed of an insulator layer 11 and a high resistance layer 12 and is mounted on the stator 1. Then, the electrostatic actuator generates an electrostatic force between the stator 1 and the movable element 10 by switching the applied voltage to the strip-shaped electrode 4 by a drive control circuit (not shown). It is designed to float and move from the stator 1.

Next, the operation of the electrostatic actuator will be described with reference to FIG.

[0010] First, as shown in FIG.
Of the first electrode group (I
Positive voltage + V to the electrodes 4a1, 4a2, 4a3
A negative voltage -V is applied to the electrodes 4b1, 4b2, 4b3 of the electrode group (phase II), and the electrodes 4c1, 4c of the third electrode group (phase III).
0V is applied to each of 2, 4c3. Then, a current flows in the high-resistance layer 12 in which no charge was initially present, and a charge is induced at the boundary between the high-resistance layer 12 and the insulator layer 11 to be in an equilibrium state.

This charge can be replaced by a mirror image charge (charge of opposite polarity) at the position shown by the dotted line in FIG. In this state, the moving element 10 is sucked by the stator 1. This stage is called a charging step.

Next, as shown in FIG. 5C, the voltage applied to each electrode is switched. That is, the first electrode group (I phase)
The negative voltage −V is applied to the electrodes 4a1, 4a2, 4a3, and the positive voltage + V is applied to the electrodes 4b1, 4b2, 4b3, which are the second electrode group (II phase).
To the electrodes 4c1, 4c2, 4c, which are the third electrode group (phase III).
A negative voltage -V is applied to c3. Then, the charges in each electrode move instantaneously, but the mirror image charges induced in the high-resistance layer 12 do not move immediately due to the high resistance of the same layer material. Therefore, the electrodes 4a1, 4b1, 4a2, 4
When the charge on b2 and the mirror image charge on the mover 10 immediately above it have the same polarity (the same sign), a repulsive force is generated,
The moving element 10 floats from the surface of the stator 1.

The negative charge on the electrode 4c1 and the mirror image positive charge immediately above the adjacent electrode 4b1 have different polarities (signs), and are attracted to each other.
Since the mirror image negative charge immediately above the electrode 4a2 has the same polarity (the same sign) and repels each other, the mover 10 receives a driving force in the right direction and moves to the right. This stage is called a driving step.

When the moving element 10 moves one pitch to the right, as shown in FIG. 5D, the electrodes 4b1, 4c1, 4b2,
Since the electric charge of 4c2 and the mirror image electric charge on them have different polarities, an attractive force acts, and the moving element 10 is positioned at that position and stopped.

While the image charge is diffused while the moving element 10 moves, 0 V is applied to the electrodes 4a1, 4a2, 4a3, which are the first electrode group (I phase), as shown in FIG. 5 (e). The positive voltage + V is applied to the electrodes 4b1, 4b2, 4b3 of the second electrode group (phase II), and the electrodes 4c1, 4c of the third electrode group (phase III).
By applying a negative voltage -V to c2 and 4c3, respectively, a mirror image charge is induced (charged) on the movable element 10 again.
This stage is also called a charging step.

In the same manner, the movable element 10 is moved by one pitch by sequentially switching the voltage applied to each electrode group.

FIG. 6 shows a time change of the voltage applied to each phase in this example. The drive control circuit controls charging and driving by alternately executing the charging step and the driving step.

In this electrostatic actuator, since the movable member 10 has no electrode and the pattern of the band-shaped electrode 4 on the stator 1 side is transferred to the movable member 10 by a charging operation, the movable member 10 moves with the stator 1. This is advantageous in that the positioning of the child 10 is unnecessary, and the strip electrode 4 does not need to be processed with high accuracy.

Since the distance (gap) between the stator 1 and the movable element 10 is maintained by bringing the stator 1 and the movable element 10 into contact with each other, the distance can be extremely reduced. This is advantageous in that a thin and compact structure can be obtained, and a large force density (force generated per unit) can be obtained.

[0020]

However, according to the paper entitled "Characteristics of No. 912 Electrostatic Film Actuator (Sataru Karakawa, Toshiro Higuchi)" at the 1990 Robotics and Mechatronics Conference of the Japan Society of Mechanical Engineers, It is shown that an optimum value exists for the distance (gap) d between the child 1 and the moving element 10.

That is, according to the above-mentioned paper, "the driving force (the force density per unit area) at the time of driving is such that as the gap d becomes smaller, the driving force in the lateral direction (moving direction) increases, but the driving force in the vertical direction increases. The repulsive force becomes the maximum value at about 1/4 of the electrode pitch, decreases when the gap d is less than that, and becomes a suction force. , The net driving force taken out to the outside decreases. "Has been confirmed experimentally.

In other words, in the conventional electrostatic actuator, even if the gap is made small in order to increase the driving force, if the gap d is too small, the suction force acts on the contrary, so that the friction is increased. Leads to an increase in power,
Therefore, there was a problem that the result was a negative effect.

The present invention has been made in view of such a conventional problem, and rationally solves the above-mentioned inconsistency with respect to the size of the gap d, and increases the driving force with a simple structure. An object of the present invention is to provide an electrostatic actuator that can be increased and to solve the above-mentioned problem.

[0024]

According to the present invention, there is provided a film-shaped stator having a plurality of band-shaped electrodes arranged in an insulator, a film-shaped movable member mounted on the stator, and the band-shaped moving member. A drive circuit that generates an electrostatic force between the stator and the movable member by switching the voltage applied to the electrodes, thereby causing the movable member to float from the stator and move along the arrangement direction of the strip electrodes, A plurality of small-diameter through holes are formed in the stator in a direction perpendicular to the moving direction of the mover, and the mover is moved from one surface of the stator through the through holes. This problem has been solved by providing a blower that sends air toward the mounting surface.

[0025]

According to the present invention, a number of small-diameter through holes are formed in the stator in a direction perpendicular to the moving direction of the moving element, and then the moving element is moved from one surface of the stator through the through holes. The air was sent to the surface on which was placed.

As a result, the driving force in the horizontal direction (moving direction of the moving element) is ensured by making the gap d as small as possible, and the increase in the suction force in the vertical direction is offset by the air pressure for lifting the moving element. To be able to
Almost 100% of the driving force in the lateral direction can be effectively taken out as the driving force of the moving element.

The air sent through the through-hole may be air appropriately processed in consideration of the purpose of the electrostatic actuator. For example, 199
Papers of the Fall Meeting of Precision Engineering 2009 (Toshiro Higuchi, Satoshi Karakawa,
According to Toshiki Niino), this type of electrostatic actuator is
It is shown that paper can be directly conveyed under certain "specific conditions".

According to the same paper, paper feeding by this type of electrostatic actuator has the following features.

The paper feed mechanism is composed of only electrodes and a drive circuit, and has no mechanically movable parts such as rollers.
The structure is simple, there are few failures, and it is suitable for miniaturization.

Since a force is directly applied to the entire surface of the driven material, even extremely thin paper can be transported without wrinkling.

Although the repulsive force and the suction force act alternately between the main body and the object, as shown in FIG. 6, the time ratio is longer in the suction force. Therefore, a force for holding the object to be conveyed to the main body acts as a whole, and the apparatus can be conveyed in any direction without dropping the object to be conveyed.

However, according to the same paper, as the “specific condition”, the surface resistance of the conveyed paper is 10%.
¹³ (Ω / □) or more is required, and data confirming this both theoretically and experimentally are shown.

For this reason, the conventional electrostatic actuator has a problem in that high-quality paper such as PPC paper cannot be transported in a normal environment (normal temperature and normal humidity).

However, according to the present invention, the paper can be dried by sending dry air heated to a predetermined temperature using the through-holes, and a surface resistance value that meets the paper transport conditions can be provided. Will be able to

As a result, it is possible to obtain an electrostatic actuator capable of transporting high-quality paper which could not be transported under normal temperature and normal humidity.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a perspective view showing an embodiment of an electrostatic actuator 20 according to the present invention, and FIG. 2 is a sectional view taken along the line II-II.

The stator 21 comprises a base layer 23 made of a film-like insulator, a strip electrode 24 arranged on the base layer 23, and a film-like dielectric layer 25 formed thereon. .

The stator 21 is provided with the band-shaped electrode 2.
A small-diameter through hole 31 is formed at a position that does not interfere with the hole 4. The through-hole 31 is formed in a direction Y perpendicular to the moving direction X of the moving element 30, and a surface 21 </ b> B on which the moving element is mounted from one surface 21 </ b> A of the stator 21 by the blower 33. The air can be sent to.

The blower 33 is capable of adjusting the amount of air to be blown in. In this embodiment, the blower is designed so that the suction force in the vertical direction due to the electrostatic force and the floating force due to the air pressure are substantially balanced. It has been set.

The moving element 30 is placed on the stator 21 in a state of being in contact therewith. This movable element 30 can be driven by this electrostatic actuator as long as it has appropriate physical property values, and there is no particular limitation on the material and the like.

However, in the case where high quality paper such as PPC paper is used as the movable element 30, since the movable element 30 does not have a surface resistance value that can be transported as it is, the air sent from the through hole 31 is heated by a heating device (not shown). It is preferable to perform a drying process. This makes it possible to carry high-quality paper that could not be carried under normal temperature and normal humidity.

Gap between stator 21 and movable element 30 (more specifically, gap between strip electrode 24 and movable element 30)
d is set to a smaller value than before. Thereby, the driving force in the lateral direction is increased.

On the other hand, when the gap d is reduced as described above, the suction force in the vertical direction Y increases, and this suction force conventionally increases the friction, which adversely affects the performance at the time of conveyance. In the embodiment, since the levitation force (due to the blowing air pressure) that substantially balances the vertical suction force due to the electrostatic force acts on the moving element 30 through the through hole 31, the driving force in the increased movement direction X is substantially reduced. It works 100% effectively and can dramatically improve the transport performance.

The levitation force that can be generated by the air pressure varies depending on parameters such as the diameter of the through-holes 31, the number of through-holes formed per unit area, and the flow rate of air to be blown. Therefore, these parameters may be determined by comprehensively considering the vertical suction force due to the electrostatic force, the hardness of the moving element 30, its own weight, the suction force to be finally left, and the like.

The smaller the suction force to be finally left, the more effectively the driving force in the moving direction X can be utilized. However, if the remaining suction force is moderately remaining, it is positively used as a kind of braking function. Can be used,
For example, when positioning accuracy is required,
It is good to determine the above parameters so that some suction force remains. In addition, even when the moving element 30 is made of paper, it may be easier to control the transport if a slight suction force remains.

[0047]

As described above, according to the present invention, a force acting as a transport resistance, such as the weight of the moving element or the electrostatic attraction force in the vertical direction, can be favorably canceled. Therefore, the electrostatic driving force in the moving direction can be effectively utilized, and as a result, an electrostatic actuator having excellent transport performance can be obtained.

Further, by applying a heating / drying process to the air to be blown, it is possible to obtain an effect that high-quality paper such as PPC paper, which is difficult to be conveyed under normal temperature and normal humidity, can be conveyed. become.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of an embodiment of an electrostatic actuator according to the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a perspective view showing a configuration of a conventional electrostatic actuator.

FIG. 4 is a sectional view taken along the line IV-IV in FIG. 3;

FIG. 5 is a diagram sequentially showing the operation of this type of electrostatic actuator.

FIG. 6 is a diagram showing a voltage pattern applied to the electrostatic actuator.

[Explanation of symbols]

4 ... electrodes, 4a1, 4a2, 4a3, 4b1, 4b2, 4b3, 4c1, 4c2, 4
c3: electrode, 10: mover, 20: electrostatic actuator, 21: stator, 23: base layer, 24: dielectric layer, 25: strip electrode, 26: heating wire, 28: power supply, 29: current control unit Reference numeral 30: mover (for example, PPC high-quality paper), 31: through hole, 33: blower, X: moving direction, Y: direction perpendicular to the moving direction.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-285978 (JP, A) JP-A-3-169277 (JP, A) JP-A-4-133907 (JP, A) JP-A-5-205 91761 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02N 1/00 B65H 5/00

Claims (2)

(57) [Claims] 1. A film-shaped stator having a plurality of band-shaped electrodes arranged in an insulator, a film-shaped movable member mounted on the stator, and switching of a voltage applied to the band-shaped electrodes. A driving circuit that generates an electrostatic force between the stator and the movable element, thereby causing the movable element to float from the stator and move along the arrangement direction of the band-shaped electrodes, On the stator, a large number of small-diameter through holes are formed in a direction perpendicular to the moving direction of the mover, and air is supplied from one surface of the stator toward the mounting surface of the mover through the through holes. An electrostatic actuator comprising a blower for sending air. 2. The electrostatic actuator according to claim 1, wherein said air is dry air heated to a predetermined temperature.