JPH04340371A - Electrostatic actuator - Google Patents

Abstract

PURPOSE:To make it possible to drive smoothly by providing holes or a pattern with projected and recessed portions satisfying particular mathematical equations on the surface at the side of contacting with a moving member of a stator and/or on the surface at the side of contacting with a stator of a moving member. CONSTITUTION:A pattern with recessed and projected portions satisfying 0.01<h/t and 10(mum)<t or holes satisfying 20<D are provided at a rate of 0.1 hole/cm<2> on the surface of the side contacting with a moving member 6 of a stator 3 and/or on the surface of the side contacting with a stator of a moving member 6. [In each equation described above, h means the height (RMAX, mum) of the projected portion of the pattern with recessed and projected portions, t means the thickness (mum) of stator or an insulating thin leaf body of the moving member, and D means the diameter of hole (mum).] By having roughened surface, sufficient air can enter between the surfaces, by which the contact area between the stator 3 and the moving member 6 can be reduced thereby reducing friction and improving the sliding ability of the moving member 6.

Description

Description: TECHNICAL FIELD The present invention relates to an electrostatic actuator, and more particularly, to an electrostatic actuator that has been improved so that it can be driven smoothly. [0002] An electrostatic actuator consists of a stator in which band-shaped electrodes are arranged at predetermined intervals on an insulating support, and a mover in which a resistor layer is provided on an insulating thin body such as an insulating film. The stator and the movable element are arranged so as to be in contact with each other. Then, due to the action of static electricity, the mover is momentarily levitated and moved while preventing friction (Proceedings of the National Conference of the Institute of Electrical Engineers of Japan, 1989, 6-1).
91, Nikkei Mechanical 1989.5.29, 112-1
13 pages, etc.) [0003] Electrostatic actuators are characterized in that force density can be increased by reducing the dimensions of electrodes and gaps, and that they can be easily miniaturized. Therefore, electrostatic actuators are expected to be applied as small drive devices such as paper transport mechanisms in word processors, facsimile machines, etc., and drive devices for other micromechanical systems. FIGS. 2(a) to 2(d) are explanatory diagrams of the driving principle of an electrostatic actuator (electrostatic film actuator) whose mover is made of an insulating film.
1) is an insulating support, (2) is a strip electrode, (3) is a stator, (4) is an insulating film, (5) is a resistor layer, (6)
) indicates a mover, and (7) to (9) indicate electric wires. First, as shown in FIG. 2(a), an electric wire (7
) and apply a negative voltage to the wire (8). As a result, the electric charge ■ existing in the electrode connected to the electric wire (7) and the electric wire (8
) A current flows through the resistor layer (5) due to the potential difference in the charge ■ existing in the electrode connected to the electrode, and a charge is induced at the boundary between the insulating film (4) of the mover (6) and the resistor layer (5). and reaches an equilibrium state. For convenience of explanation, this charge is shown in Figure 2(b).
can be replaced by the mirror image charge shown by the dotted line. Since the polarities of these charges ■ and ■ are different from the polarities of charges ■ and ■, respectively, in the state of FIG. 2(b), the mover (6)
is attracted to the stator (3). Next, as shown in FIG. 2(c), the electric wire (7
), a positive voltage is applied to the electric wire (8), and a negative voltage is applied to the electric wire (9). As a result, the charges in the electrodes can be moved instantaneously, but the induced charges in the mover (6) cannot be moved immediately because the resistance value of the resistor layer (5) is high. As a result, a repulsive force is generated between the mover (6) and the stator (3). Due to the generation of repulsive force, the stator (3) and the mover (6)
) is reduced, and a driving force in the right direction is generated by the negative charge (■) and positive induced charge (■ in terms of mirror image charge) generated as a result of applying voltage to the electric wire (9). FIG. 2(d) shows the result of the mover (6) being moved rightward by one electrode pitch due to the above driving force. When moving the mover (6) to the left,
A positive voltage may be applied to the electric wire (9). The applied voltage pattern (the pattern shown in FIG. 2(c)) in the above-described movement operation for each pitch of the electrodes is such that a voltage of the opposite sign to that shown in FIG. 2(a) is applied to the electric wires (7) and (8). Therefore, the induced charges (in terms of mirror image charges, ■ and ■) in FIG. 2(c) are attenuated. [0008] Therefore, in order to continuously move the mover (6) in the right direction every electrode pitch, it is necessary to repeatedly apply a voltage in the following pattern, which repeats the charge charging operation and the moving operation. . In addition, the voltage pattern illustrated in [Table 1] below is a voltage pattern of one cycle,
(G) shows the state where no voltage is applied, (C) and (
A) shows a charge charging operation and a moving operation, respectively, the first (C) is the state shown in FIG. 2(a), and the first (A) is the state shown in FIG. 2(c). [0009] [Table 1] [0010] In order to move the electrostatic actuator stably and continuously for each electrode pitch, the surface specific resistivity of the mover (6) (resistance layer (5)) must be 1012 ~1015
It is said that it must be in the range of Ω/□. The reason is as follows. That is, when the surface resistivity of the mover (6) is large, it takes a relatively long time to charge the charge, and when it is small, the induced charge attenuates instantly. However, in the case of the electrostatic actuator shown in Figure 2, the resistance value of the insulating film constituting the mover is too large, so a resistor layer as described above is provided on the insulating film to reduce the slight electrical conductivity. It is necessary to give gender. Note that, of course, in the known electrostatic actuator shown in FIG. 2, other insulating thin film having a similar resistance value may be used instead of the insulating film (4). . [0011] However, electrostatic actuators are still in the research stage, and in order to put them into practical use, it is necessary to study the details of each element. In particular, if the thin insulating body of the mover is smooth, air will not be able to enter between the stator and the mover sufficiently, increasing the friction between the two and preventing the mover from moving smoothly. There's a problem. In particular, in the charge charging operation described above, since the movable element is attracted to the stator in close contact with the stator, the friction between the two is large. [Means for Solving the Problems] In view of the above-mentioned circumstances, the inventors of the present invention have made various studies and found that if the contact surfaces of the stator and mover film are brought into a specific state, there will be no difference between the two. It has been found that sufficient air can be allowed to enter and the above problems can be effectively solved. The present invention was completed based on the above findings, and an object of the present invention is to provide an improved electrostatic actuator that can be driven smoothly. The above-mentioned object of the present invention is, according to the present invention, to be a static stator comprising a stator in which band-shaped electrodes are arranged at predetermined intervals on an insulating support and a mover in which an insulating thin film body is provided with positive and negative charges, which are arranged so as to be in contact with each other. In the electric actuator, the formulas [Math.
A concavo-convex pattern that satisfies the equation [Equation 2] is provided, or a hole that satisfies the equation [Equation 3] described in the claims is provided.
The present invention resides in an electrostatic actuator characterized in that the number of actuators is 1/cm2 or more. The present invention will be explained in detail below. The basic configuration of the electrostatic actuator of the present invention is that in FIG. 2, the constituent material of the mover (6) is not limited to an insulating film,
Further, the structure of the moving element is the same as that of the known electrostatic actuator shown in the figure, except that the structure of the moving element is not limited to that provided with a resistor layer. Therefore, in the following explanation,
For convenience, FIG. 2 will be referred to with reference to (4) in FIG. 2 as an insulating thin film body. The electrostatic actuator of the present invention has an insulating support (
Stator (3) with strip electrodes (2) arranged at predetermined intervals on 1)
and a mover (
6). First, the stator (3) will be explained. The insulating support (1) constituting the stator (3) is composed of a film, sheet, or the like made of an insulating material. The insulating material is not particularly limited, and various synthetic resins, ceramics, glass, etc. with good insulating properties can be used. Specifically, a material is selected that is suitable for the form of a concavo-convex pattern, etc., which will be described later. Specific examples of the insulating resin include epoxy resin, polyimide resin, polyester resin, polypropylene resin, polyvinylidene chloride resin, polystyrene resin, polyamide resin, polyvinyl chloride resin, polyethylene resin, polyvinyl alcohol resin, and the like. Preferred insulating resins are epoxy resins and polyester resins. The strip electrodes (2) provided on the insulating support (1) may be arranged side by side on the surface of the insulating support (1) or embedded within the insulating support (1). It may be provided. In addition, the interval between the strip electrodes (2) is not particularly limited, but is usually 0.1 to 2 mm. Finer spacing is desirable. Next, the mover (6) will be explained. The insulating thin film body (4) constituting the mover (6) is preferably made of the same synthetic resin as the above-mentioned insulating resin constituting the stator (3). It can also be made of glass or ceramics having similar resistance values. In this case as well, a material suitable for the form of the uneven pattern, etc., which will be described later, is selected. When the insulating thin body (4) is composed of an insulating film, a particularly preferable film is a polyethylene terephthalate film from the viewpoint of density, flexural modulus, wrinkle resistance, and the like. The method for applying positive and negative charges to the insulating thin film body (4) is to apply a resistor layer (5) to the insulating thin film body (4) in the same way as the known electrostatic film actuator shown in FIG. An example of this method is to provide one. Specifically, for example, a method may be used in which an antistatic agent having a weak antistatic effect is applied to the surface of the insulating thin film (4). In this case, the resistor layer (5
) should be in the range of 1012 to 1015 Ω/□, preferably around 1014 Ω/□. The direction in which the resistor layer (5) is provided is determined by the direction in which the resistor layer (5) is provided.
) may be either the surface in contact with the stator (3) or the other surface, but the latter surface is preferred. Furthermore, the method of imparting positive and negative charges to the insulating thin film body (4) is not limited to the above method, and various other methods obvious to those skilled in the art may be employed. For example, when the insulating thin film (4) is composed of an insulating film, a conductive substance such as carbon black is kneaded into the insulating thin film (4) itself to form a resistor having the same resistivity as above. A method of providing a strip-shaped electrode on an insulating thin film (4),
Examples include a method using an ion generator and a method using an electret material for the insulating thin film (4). Although the method of providing the strip electrodes on the insulating thin film body (4) is not particularly illustrated, in FIG. This is a method in which positive and negative voltages are always applied to these electric wires, and the positive and negative charges existing in each strip electrode are used in place of the mirror image charges (1) and (2). In addition, a method using an ion generator is to place an insulating thin film (4) in contact with the stator (3), and
), after applying positive and negative voltages to the electric wire (8) to induce charges, an ion generator known as a static eliminator (positive and negative ions generated by applying alternating current voltage to the needle electrode to cause corona discharge) A method of applying ionized wind from a blower to the surface of an insulating thin material (4) from a device configured to apply air to a charged object, the ionization being formed on the surface of the insulating thin material (4). This is a method that uses an air layer in place of the mirror image charges (1) and (2). And as an ion generator,
Various static eliminators described in "Static Electricity Handbook" (published by the Society of Electrostatics, Ohmsha Publishing, 1st edition, pages 819 onwards) can be used. The thickness of the insulating thin film (4) cannot be determined unconditionally because the force generated by the electrostatic actuator varies depending on the method of applying electric charge to the insulating thin film, but it is usually 10 μm or more. Ru. When a method of providing a resistor layer (5) on an insulating thin film (4) is adopted as a method of imparting electric charge, the thickness is preferably in the range of 10 to 200 μm. In addition, no matter which method is used to impart charges, the thickness of the insulating thin film body (4) is determined by the distance between the band-shaped electrodes (2) arranged on the insulating support (1) being P, and the thickness of the insulating thin film body (4) The surface of the electrode (2), the insulating thin film (4), and the resistor layer (5) (if a strip electrode is provided on the insulating thin film (4), the strip electrode; if an ionized air layer is formed, it is itself) and the boundary surface is 0.15
It is preferable that the range satisfies the relationship <G/P<0.4. The most important feature of the present invention is that the surface of the stator (3) on the side that comes into contact with the mover (6) and/or the mover (
6), apply the following formula [
Either provide an uneven pattern that satisfies Equation 4] (same as Equation 1) and Equation 5 (same as Equation 2), or use the following equation [Equation 6] (same as Equation 3). The hole that satisfies 0.1
The point is that the number of particles/cm2 or more is provided. Such surface roughening can reduce the contact area between the stator (3) and the mover (6), thereby reducing friction and improving the sliding properties of the mover (6). The above roughening is applied to the stator (
3) and the movable element (6), it is preferable that one surface is made flat and only the other surface is roughened. [Formula 4] 0.01<h/t [Formula 5] 10 (μm)<t [Formula 6] 20<D [0023] In each of the above formulas, h is the height of the convex part of the concavo-convex pattern (Rmax., μm), t represents the thickness (μm) of the insulating thin film body (4) of the mover or the stator (3), and D represents the hole diameter (μm). Then, the insulating thin film body (4
) The thickness of the insulating thin film material (4
) itself as a resistor, it means the thickness of the mover (6) itself, and when the insulating thin film (4) is provided with a resistance layer (5), the thickness of the resistor layer Even if it is negligibly thin, it means the thickness of the mover (6) itself. In each of the above formulas, the preferable value of Equation [4] is 0.05, the preferable value of Equation [5] for stator (3) is 50, and the preferable value of Equation [Math 5] for mover (6) is A preferable value of the formula is 25, and a preferable value of the formula [Equation 6] is 50. [0024] The method for forming the above-mentioned uneven pattern is not particularly limited, and may vary depending on the type of material of the surface on which the uneven pattern is applied.
The methods exemplified below may be employed as appropriate. (a) Method of coating a smooth surface with a coating liquid containing inorganic particles, etc. (b) Method of crystallization promotion treatment and addition of a crystallization promoter, etc. (c) Method of coating inorganic particles such as silicon dioxide, titanium dioxide, calcium carbonate, etc. (d) Method of adding incompatible polymers, etc. (d) Method of mechanical embossing, sandblasting (e) Method of surface treatment such as solvent treatment, corona discharge, plasma discharge, electron beam irradiation, X-ray irradiation, etc. (f) Method of transferring independent cells or grooves by gravure coating The above methods (b) and (c) are mainly applied when synthetic resin is used. Among the above-mentioned methods, in particular, spherical particles (e.g. glass heath) with a substantially uniform particle size (in the range of 5 to 20 μm) were used as the inorganic particles (
Method a) is preferred. [0025] Further, the holes can be easily formed by, for example, a mechanical punching method or other suitable methods. [0026] Then, the above uneven pattern is formed on the stator (3).
), it is preferable that the height (Rmax.) of the convex portion of the concavo-convex pattern is 5 μm or more. Moreover, it is preferable that the above-mentioned hole is provided in the mover. The electrostatic actuator of the present invention consists of a stator and a mover constructed as described above, and is driven according to the same driving principle as known electrostatic actuators. [Examples] The present invention will be explained in more detail with reference to examples below, but the present invention is not limited to the following examples unless the gist of the invention is exceeded. Example 1 Polyethylene terephthalate film with a thickness of 50 μm (
A polyurethane resin coating solution (solvent: tetradrofuran, solid content concentration: 15% by weight, glass Bead concentration: approximately 1% by weight) was applied using a bar coater and dried. The thickness of the coating film after drying was 1 to 2 μm. Surface roughness Rmax of the above roughened film
．． was measured, and the height (hμm) of the convex portion was calculated to calculate h/t. As a result, Rmax. =8μm, h/t
=0.16. 100m of the above roughened film
Cut the insulating film of the mover into m x 100mm pieces (4)
Then, an antistatic agent with a weak antistatic effect is spray applied to the smooth surface side to form a resistor layer (5), and the mover (
6) was prepared (the surface resistivity of the resistor layer was 1×101
4Ω/□). Electrode width is 0.4mm, electrode pitch is 1.2
A stator (3) equipped with a 7mm three-phase structure strip electrode (2).
) (insulating support: epoxy resin sheet) and the above-mentioned mover (6) were arranged so as to be in contact with each other, and an electrostatic actuator of the present invention shown in the conceptual diagram of FIG. 1 was produced. When the above electrostatic actuator was driven according to the procedure shown in Figs. 2(a) to 2(d) and under the driving conditions shown in [Table 2] below, the mover (6) moved continuously and smoothly. did. [Table 2] <Driving conditions> Initial charging time: 10s Charging time: 450ms Travel time: 50ms Driving frequency: 2Hz Driving voltage: ±800v Example 2 Polyethylene terephthalate film with a thickness of 100 μm (Diafoil Co., Ltd.) A concavo-convex pattern was formed on one surface of the fabric (S-100) by an embossing roll. The conditions for forming the uneven pattern are as shown in the following [Table 3]. [Table 3] Embossing roll
#800 Emboss roll temperature
170℃ Backup roll linear pressure
100kg/cm film winding speed
2m/min 0
[033] Surface roughness Rmax. of the above-mentioned roughened film. was measured, and the height (hμm) of the convex portion was calculated to calculate h/t. As a result, Rmax. =5μm, h/t=0
．． It was 05. The electrostatic actuator shown in FIG. 1 was manufactured in the same manner as in Example 1 except that the above roughened film was used as the insulating film (4) of the mover.
When driven under the same conditions, the mover (6) moved continuously and smoothly. Example 3 Polyethylene terephthalate film with a thickness of 25 μm (
A concavo-convex pattern was transferred onto one surface of a sheet (manufactured by Diafoil Co., Ltd., S-100) using a gravure roll. The transfer processing conditions for the uneven pattern are as shown in the following [Table 4]. [Table 4] Gravure roll
13.3 lines/cm coating liquid

Cell size 150μm Nitrocellulose (
Cellnova BTH1/2) 100 parts by weight Aerosil Silica R972
2 parts by weight methyl ethyl ketone

150 parts by weight toluene

40 parts by weight Surface roughness Rmax. of the above-mentioned roughened film. was measured, and the height (hμm) of the convex portion was calculated to calculate h/t. As a result, Rmax. =5μ
m, h/t=0.2. The electrostatic actuator shown in FIG. 1 was produced in the same manner as in Example 1, except that the above-mentioned roughened film was used as the insulating film (4) of the mover, and it was driven under the same conditions as in Example 1. , mover (
6) moved continuously and smoothly. Example 4 Four holes/cm2 each having a diameter of 0.2 mm were formed in a polyethylene terephthalate film (S-100, manufactured by Diafoil Co., Ltd.) having a thickness of 100 μm by a mechanical punching method. The electrostatic actuator shown in FIG. 1 was produced in the same manner as in Example 1, except that the above-mentioned roughened film was used as the insulating film (4) of the mover, and it was driven under the same conditions as in Example 1. , the mover (6) moved continuously and smoothly. Example 5 A band-shaped electrode having a two-phase structure with an electrode width of 0.2 mm and an electrode pitch of 0.4 mm was formed on the flat surface side of the roughened film used in Example 1, and a slider ( 6) was produced. A stator (3) provided with a strip electrode (2) having a three-phase structure with an electrode width of 0.2 mm and an electrode pitch of 0.4 mm (insulating support:
An electrostatic actuator of the present invention as shown in the conceptual diagram of FIG. 1 was produced by arranging a polyethylene terephthalate film (polyethylene terephthalate film) and the above-mentioned mover (6) so as to be in contact with each other. Next, when a voltage of ±600 V was applied to the two-phase strip-shaped electrode and the movable element (6) was driven under the driving conditions shown in Table 5 below, the mover (6) moved continuously and smoothly. [Table 5] <Driving conditions> Charging time: 450ms Moving time: 50ms Driving frequency: 2Hz Driving voltage: ±600v [0039] Example 6 In Example 1, antistatic agent was spray applied to the roughened film. The roughened film and the stator (3) were placed in contact with each other in the same manner as in Example 1 except that . Then, ion wind was applied to the surface of the roughened film while applying positive and negative voltages to the strip electrodes (7) and (8) of the stator (3). As the ionization device, a static eliminator model SH-2 manufactured by Nippon Statec was used. Next, when driven under the same conditions as in Example 1, the mover (6) moved continuously and smoothly. In addition, in the continuous drive test, it was confirmed that the surface of the roughened film was driven more smoothly when ion wind was continuously applied to the surface. Comparative Example 1 Surface roughness Rmax of 100 μm thick polyethylene terephthalate film (manufactured by Diafoil Co., Ltd., S-100)
．． were measured, and the height (hμm) of the convex portion was calculated to calculate h/t. As a result, Rmax. =0.2μm, h
/t=0.002. Example 1 except that the above flat film was used as the insulating film (4) of the mover.
The electrostatic actuator shown in FIG. 1 was produced in the same manner as
When driven under the same conditions as Example 1, the mover (6)
did not move at all. Then, increase the driving voltage by ±100
Even if the force density is increased to 0V, the mover (6)
Didn't move. [0041] According to the present invention as described above, an electrostatic actuator that is improved so that it can be driven smoothly is provided. Therefore, the present invention greatly contributes to the practical application of electrostatic actuators.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram showing an example of an electrostatic actuator of the present invention.

FIG. 2 is an explanatory diagram of the driving principle of an electrostatic actuator.

[Explanation of symbols]

(1): Insulating support (2): Strip electrode (3): Stator (4): Insulating film or thin film (5): Resistor (6): Mover (7) to (9) ):Electrical wire

Claims (1)

[Claims] 1. An electrostatic actuator comprising a stator in which band-shaped electrodes are arranged at predetermined intervals on an insulating support and a mover in which a positive and negative charge is applied to an insulating thin film body are arranged so as to be in contact with each other, the stator The surface of the side that comes into contact with the mover and/or
Alternatively, the surface of the mover that contacts the stator is provided with an uneven pattern that satisfies the following formulas [Math. 1] and [Math. 2], or holes that satisfy the following formula [Math. 3] are provided. An electrostatic actuator characterized in that .1 piece/cm2 or more is provided. [Formula 1] 0.01<h/t [Formula 2] 10 (μm)<t [Formula 3] 20<D (In each of the above formulas, h is the height of the convex part of the concave-convex pattern (R
max. , μm), t is the thickness of the insulating thin film of the mover or the stator (μm), D is the hole diameter (μm))