JPH0819271A - Moving element for electrostatic actuator and driving method thereof - Google Patents

Abstract

(57) [Summary] [Object] To provide a moving element for an electrostatic actuator that can be efficiently driven and a driving method thereof. [Structure] Electrodes are embedded in a stator 10 at a predetermined pitch, and three-phase drive signals φ1 to φ3 are supplied. Mover 2
0 is on the support insulator layer 21 made of PET film,
The charge holding medium layer 23 is formed. In the charge retentive medium layer 23, at a cycle three times the electrode pitch in the stator 10,
Positive charge is stored. When a fluoropolymer having a cyclic structure having a volume resistivity of 10 ¹⁸ Ω · cm or more is used as the material of the charge retaining medium layer 23, it is possible to perform a charge image forming process using air discharge. The electric charge accumulated by is retained for a long period of time. The mover 20 on the stator 10 can be driven in the left and right directions by three-phase drive signals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moving element for an electrostatic actuator, and more particularly to a moving element for an electrostatic actuator using a charge holding medium having a function of holding charges for a long time.

[0002]

2. Description of the Related Art An actuator which has been mainly used in the field of mechanical engineering so far uses an electromagnetic force, but in recent years, an electrostatic actuator using an electrostatic force has been actively researched. . An actuator using electromagnetic force needs to generate a strong magnetic field, as represented by a motor, and an iron core and a coil having a certain size are indispensable elements. Therefore, it is inevitable that the entire actuator has a certain weight, and it is difficult to reduce the size and weight. On the other hand, the electrostatic actuator has a merit that it does not require an iron core or a coil because it is a mechanism that generates a driving force by using an electrostatic force, and that it is easy to reduce its size and weight.

The history of the principle of such an electrostatic actuator has a long history, and there is a record that research has already been done since the 18th century, but recently, due to the progress of material technology,
Very small and efficient electrostatic actuators are being put to practical use. For example, Japanese Unexamined Patent Publication No. 2-285978 discloses an electrostatic actuator using a polymer film such as polyethylene terephthalate.

The basic principle of the electrostatic actuator is that a movable element having a dielectric is placed on a stator having a large number of electrodes arranged at a predetermined pitch, and multi-phase drive signals are applied to the electrodes on the stator side. As a result, the mover is moved on the stator. When a voltage having a predetermined polarity is applied to each electrode on the stator side, electric charges having opposite polarities are induced in the dielectric material on the mover side. Next, when the polarity phase of each electrode on the stator side is switched to the next phase, each charge induced on the mover side starts to generate an attractive force with the adjacent electrode on the stator side, and the mover The whole will move by one pitch of the electrodes. In this way, the mover moves on the stator at a predetermined speed according to the cycle of the drive signal given to each electrode on the stator side.

[0005]

As described above, in the conventional electrostatic actuator, the dielectric is used for the moving element, and the electric charge having the opposite polarity to the electric charge given to the electrode on the stator side is induced on the dielectric side. I am driving. Therefore, at the time of initial driving, a predetermined charging time τ is required until electric charges are induced on the dielectric side. This charging time τ is a time constant determined by the product of the electrostatic capacity between the stator and the mover and the resistivity. Therefore, the longer the charging time τ, the longer the initial drive takes. In addition, since the electric charge of the moving element changes a little during the driving due to discharge or the like, it is necessary to perform the driving while recharging so that the moving element can maintain a predetermined electric charge. This recharge takes a shorter time than the charge at the time of initial drive, but if the time required for recharge becomes long, the mover cannot be moved at a high speed. If the dielectric used as the mover has a low dielectric constant, sufficient charging cannot be performed, so that sufficient driving force cannot be obtained.

As described above, since the conventional electrostatic actuator moving element operates by inducing a predetermined electric charge based on the electric charge given to the electrode on the stator side, it cannot be efficiently driven. There was a problem.

Therefore, an object of the present invention is to provide a moving element for an electrostatic actuator which can be efficiently driven and a driving method thereof.

[0008]

[Means for Solving the Problems]

(1) A first aspect of the present invention is a moving body for an electrostatic actuator, which constitutes an electrostatic actuator by being used with a stator having a plurality of electrodes arranged at a predetermined pitch, and has a volume resistivity of 10 ¹⁸ Ω. A state in which a charge holding medium layer made of a resin of cm or more is used, and a plurality of unit regions are defined in the charge holding medium body layer at the same pitch as the stator electrodes, and each unit region holds a positive charge, A state in which a negative charge is held, a state in which no charge is held, and one state selected from the three state groups are taken, and the state distribution of the unit region is a periodic distribution. It was done like this.

(2) A second aspect of the present invention is the above-mentioned first aspect.
In the electrostatic actuator moving element according to the above aspect, a fluoropolymer having a cyclic structure having a volume resistivity of 10 ¹⁸ Ω · cm or more is used as the charge retention medium layer.

(3) A third aspect of the present invention is the above-mentioned first aspect.
Alternatively, in the electrostatic actuator moving element according to the second aspect, the state distribution in three adjacent unit regions is set to 1
As a cycle, the state distribution of the unit area is periodic.

(4) A fourth aspect of the present invention relates to the above-mentioned first aspect.
Alternatively, in the electrostatic actuator moving element according to the second aspect, the polarity of the electric charge to be retained is set to only one of positive and negative polarities, and the first unit area is selected from the n unit areas adjacent to each other. Holds the electric charge of one polarity and does not hold the electric charges in the second unit area to the nth unit area, and the state distribution of the unit areas is periodic with n unit areas as one cycle. It was made to become.

(5) A fifth aspect of the present invention is based on the above-mentioned fourth aspect.
In the mover for the electrostatic actuator according to the aspect,
= 3 is set.

(6) A sixth aspect of the present invention is the above-mentioned fifth aspect.
In the method of driving the mover for an electrostatic actuator according to the above aspect, the first drive signal is applied to the (i + 1) th electrode (where i is 0, 1, 2, ...) Arranged on the stator. The second drive signal is applied to the (i + 2) th electrode, the third drive signal is applied to the (i + 3) th electrode, and either the positive polarity or the negative polarity is applied to the first
And the other is defined as the second polarity, and any of the three drive signals has three states per unit time, which are the first polarity state, the second polarity state, and the second polarity state. The signals are periodically taken in order, and the signals have different phases.

(7) A seventh aspect of the present invention is the above-mentioned fifth aspect.
In the method of driving the mover for an electrostatic actuator according to the above aspect, the first drive signal is applied to the (i + 1) th electrode (where i is 0, 1, 2, ...) Arranged on the stator. The second drive signal is applied to the (i + 2) th electrode, the third drive signal is applied to the (i + 3) th electrode, and either the positive polarity or the negative polarity is applied to the first
And the other is defined as the second polarity, and all of the three drive signals are cyclically defined in the order of three unit times, that is, the first polarity state, the second polarity state, and the ground state. In this case, the signals have different phases, and the signals have different phases.

[0015]

[Operation] In a general dielectric used in a conventional electrostatic actuator moving element, an electric charge having an opposite polarity is induced by the action of an electric charge given to an electrode on the stator side. However, this induced charge is temporary and disappears after a few seconds unless recharged. On the other hand, it has recently been confirmed that there is a charge holding medium having a function of holding the electric charge for a long time once the process of accumulating the electric charge is performed. The inventor of the present application has found that, among such charge retention media, the volume resistivity is 10 in particular.
It has been found that a charge retention medium made of a resin of ¹⁸ Ω · cm or more has properties suitable for use as a moving element of an electrostatic actuator. The inventor of the present application has confirmed that there are some fluoropolymers having a cyclic structure as resins satisfying such conditions. When charges are accumulated in these charge holding media by a charge image forming method using air discharge, the charges are held for about one week.

The present invention utilizes the charge holding medium having such properties as a moving element for an electrostatic actuator. That is, if a layer made of this charge holding medium is provided on the mover side and a predetermined charge is periodically held on this charge holding medium layer at the same pitch as the electrode pitch on the stator side, the conventional It is possible to operate on the same principle as the electrostatic actuator. Moreover, since the charge on the mover side is originally held, there is no need to wait for the charging time τ at the time of initial drive, and there is no need to recharge during drive, enabling extremely efficient drive. Become.

The moving element according to the present invention can be driven by using three-phase driving signals as in the conventional electrostatic actuator. Moreover, the inventor of the present application has discovered that even if the polarity of the electric charge held on the mover side is only positive or negative, it can be sufficiently driven as an electrostatic actuator. . If the charges held on the mover side can be made unipolar in this way, the separation discharge process for accumulating the charges will be simplified, and mutual annihilation caused by arranging charges of opposite polarities adjacent to each other. Does not occur, it becomes possible to retain charges for a longer time.

[0018]

The present invention will be described below based on illustrated embodiments.

§1. Basic Principle of Electrostatic Actuator First, the basic principle of a general electrostatic actuator will be described. FIG. 1 is a perspective view showing a conventional general electrostatic actuator. As shown in the figure, band-shaped electrodes 11 to 18 are arranged on the stator 10 at a predetermined pitch, and the mover 20 is mounted on the stator 10. The mover 20 is made of a dielectric material such as a plastic film. Three-phase drive signals φ1 to φ3 are supplied to the electrodes 11 to 18 on the side of the stator 10 in a cycle of three lines, respectively. Here, the drive signals φ1 to φ3 are periodic signals that are out of phase with each other.

Next, the principle of operation of this electrostatic actuator will be described with reference to the sectional views of FIGS. Now
As shown in FIG. 2, electrodes 11 to 18 are embedded in the stator 10, and each electrode has a drive signal φ as shown in the drawing.
1 to φ3 is supplied. On the other hand, mover 2
0 has a two-layer structure of a supporting insulator layer 21 and a charge dielectric layer 22. The support insulator layer 21 is made of an insulating material having a certain degree of rigidity, and the charge dielectric layer 22
Consists of a high resistance material suitable for charge induction. actually,
The mover 20 is placed on the stator 10, but here, for convenience of illustration, a certain amount of space is provided between the two.

Now, as shown in FIG. 3, when a positive voltage is applied as the driving signal φ1, a negative voltage is applied as φ2, and a ground voltage is applied as φ3, respectively, each electrode in the stator 10 is shown in the drawing. Such a charge is supplied (the circled "+" sign indicates the presence of a positive charge, the circled "-" sign indicates the presence of a negative charge, and the "0" sign indicates the absence of a charge. Respectively). When such a charge distribution is generated on the side of the stator 10, charges of opposite polarities are induced in the charge derivative layer 22 of the mover 20. FIG. 3 shows the state at this time. However, it takes a predetermined charging time τ until the charges are induced on the charge derivative layer 22 side.
is necessary. Note that, in reality, the charges generated on the charge derivative layer 22 side are concentrated near the upper surface of the charge derivative layer 22 in the drawing, but in the present specification, for convenience of description, the central portion of the charge derivative layer 22 is described. The symbol indicating the generated charge is described in.

Now, when the charge distribution τ elapses and a charge distribution as shown in FIG. 3 is obtained in the charge derivative layer 22, the voltages of the drive signals φ1 to φ3 are switched. That is, as shown in FIG. 4, as the drive signal φ1, a negative voltage,
When a positive voltage is applied as φ2 and a negative voltage is applied as φ3, electric charges as shown are supplied to each electrode in the stator 10. At this time, the charges on the side of the mover 20 are still in the previous state (FIG. 3). Therefore, the negative charge on the side of the mover 20 repels the negative charge on the side of the stator 10, and the positive charge on the side of the mover 20 repels the positive charge on the side of the stator 10 to move. The child 20 is slightly raised above the stator 10. Moreover, the negative charge on the side of the mover 20 is attracted to the positive charge on the right side by one pitch on the side of the stator 10, and the positive charge on the side of the mover 20 is adjacent to the right by one pitch on the side of the stator 10. As a result, the mover 20 moves to the right on the stator 10 by one pitch, as shown in FIG.

Similarly, by appropriately switching the voltages of the drive signals φ1 to φ3, the mover 20 can be moved to the right in the figure at a predetermined speed (speed corresponding to the switching cycle of the drive signals). it can. By changing the waveforms of the drive signals φ1 to φ3, the drive signals can be moved to the left in the figure.

However, in such a conventional electrostatic actuator moving element, it is necessary to induce a predetermined charge to the moving element 20 side at the time of initial movement, and it is necessary to wait for the charging time τ. In addition, the amount of electric charge in the moving element 20 is gradually lost during driving, so it is necessary to recharge during driving (for example, if the state shown in FIG. 5 is maintained for a while, recharging is performed. Will be). As described above, the conventional electrostatic actuator moving element has a problem that it cannot be efficiently driven.

§2. Charge image formation method using air discharge
Accumulation of Charge in Charge Retaining Medium Due to the function of the mover 20 according to the present invention, once the process of accumulating the charge is performed, the charge is retained for a long time instead of the conventional general charge derivative layer 22. A layer composed of a charge-retaining medium having a layer is used. The material preferable as the charge holding medium will be described in detail later, but the present inventor has found that a resin having a ring structure having a volume resistivity of 10 ¹⁸ Ω · cm or more, particularly a fluoropolymer, is used for the electrostatic actuator. I think it is the best to use as a child. In such a charge retention medium, once the charge is accumulated, the charge is retained for a long period of one week or more.

A charge image forming method using air discharge is suitable for accumulating charges in the charge holding medium used as a moving element. The basic technique of this method is described in, for example, the Electrophotographic Society of Japan, Vol. 17, No. 3, (1979), pp. 36 to 51, but here, it is suitable for use as a moving element for an electrostatic actuator. The method used is described below.

First, as shown in FIG. 6, the supporting insulator layer 2
1 and a carrier 2 having a laminated structure of a charge retentive medium layer 23.
Prepare 0. In this example, a 25 μm thick PET (polyethylene terephthalate) or polyimide film was used as the support insulator layer 21, and a 2 μm thick fluororesin layer was used as the charge retention medium layer 23.

On the other hand, an electrode substrate 30, a frame 40, and a counter electrode 50 are prepared as a device for accumulating charges in the mover 20. The electrode substrate 30 includes a conductive material (for example, chromium,
Pattern electrode 3 made of metal such as aluminum or copper)
2 is formed. The pattern electrode 32 has a pattern corresponding to the distribution pattern of the charges to be accumulated in the charge holding medium layer 23, and in this example, the band-shaped pattern electrodes 32 arranged at a predetermined pitch are formed. Here, the arrangement pitch of the pattern electrodes 32 is set to be equal to the electrode pitch of the stator 10 used with the mover 20. In this embodiment, the pattern electrodes 32 having a width of 160 μm, a thickness of 0.2 μm and a length of 5 cm are used, and the arrangement pitch is set to 320 μm. The frame body 40 is for ensuring a predetermined discharge distance between the pattern electrode 32 and the charge retention medium layer 23. In this embodiment, an opening window is formed at the center of a polyimide film having a thickness of about 5 to 10 μm. The one that is formed is used. Counter electrode 5
0 is used as an electrode facing the pattern electrode 32 in discharging, and is formed of an aluminum layer in this embodiment.

Now, as shown in FIG. 6, the electrode substrate 30,
The frame 40, the mover 20, and the counter electrode 50 are stacked in this order to form a structure as shown in FIG. The mover 20 is placed with the charge holding medium layer 23 side down, and the counter electrode 50 is placed thereon. In addition, each pattern electrode 32 formed on the substrate 31 is opposed to the charge retentive medium layer 23 with a predetermined discharge space formed by the frame 40 interposed therebetween.

It is assumed that a predetermined discharge voltage is applied between each pattern electrode 32 and the counter electrode 50 in such a state. FIG. 8 is a sectional view showing such a state. FIG.
As shown in the left half of FIG. 1, when a discharge voltage (about 1000 V in this embodiment) is applied with a polarity such that the pattern electrode 32 side is negative and the counter electrode 50 side is positive, the pattern electrode 32 is caused by air discharge. From which electrons are emitted, and the electrons reach the charge retention medium layer 23. At this time,
It is known that negative charges are accumulated on the surface of the charge retaining medium layer 23 (the lower surface of the charge retaining medium layer 23 in FIG. 8). It is considered that this is because the supporting insulator layer 21 and the charge retention medium layer 23 function as a dielectric and a polarization action occurs. On the contrary, as shown in the right half of FIG. 8, when a discharge voltage is applied with a polarity such that the pattern electrode 32 side is positive and the counter electrode 50 side is negative, the lower surface of the charge retentive medium layer 23 is caused by air discharge. Electrons are emitted from the side, and the electrons reach the pattern electrode 32. At this time, positive charges are accumulated on the surface of the charge holding medium layer 23 (the lower surface of the charge holding medium layer 23 in FIG. 8) due to the emission of electrons. Note that, in practice, as described above, the surface of the charge retentive medium layer 23 (the charge retentive medium layer 2 in FIG.
Each charge is generated on the lower surface of No. 3), but here, for convenience of description, a symbol indicating the generated charge is shown in the central portion of the charge holding medium layer 23.

As described above, by causing a discharge current to flow between the lower surface of the charge retention medium layer 23 and the pattern electrode 32,
The phenomenon in which charges of a predetermined polarity appear on the surface of the charge retentive medium layer 23 by polarization is generally known as a charge image forming method using air discharge, but the theoretical analysis of this phenomenon is as follows. However, it is being discussed at academic societies. The important point here is to use a pattern electrode 32 having a unique shape and arrangement as shown in FIG.
By applying a discharge voltage having a predetermined polarity to perform an air discharge, a desired unit region in the charge retentive medium layer 23,
The point is that charges having a desired polarity can be accumulated.

Here, for example, wiring as shown in FIG. 9 (top view) is performed on the pattern electrode 32 formed on the substrate 31, and + V or −V is applied to the counter electrode 50.
Consider a case in which the following voltage is applied to perform air discharge (actually, + V application discharge and -V application discharge are performed separately). In this case, each pattern electrode 32
Since electric charges as shown in the sectional view of FIG. 10 are given to the charge holding medium layer 23, electric charges as shown in the sectional view of FIG. 10 are also accumulated. That is,
"+", "-", "0", "+", "-", "0", ...
A periodic charge pattern that repeats every three unit regions is obtained. When the charge pattern is accumulated in this way, only the mover 20 can be taken out and used as a mover for the electrostatic actuator.

§3. Electrostatic actuator according to the present invention
Driving Method for Mobile Movable Device Next, a driving method for the electrostatic actuator using the moving device 20 in which electric charges are accumulated by the charge image forming method using the air discharge described in the above-mentioned §2 will be described. First, FIG.
As shown in the sectional view of FIG. 1, the mover 20 is placed on the stator 10. In the separation discharge described in §2, the mover 20 is set with the charge holding medium layer 23 side facing downward, but when used as an electrostatic actuator, conversely, the charge holding medium layer 23 side is facing upward. Will be set. In addition,
The charges are accumulated on the surface of the charge retaining medium layer 23 (the upper surface in FIG. 11), but here, for convenience of description, a symbol indicating the accumulated charge is described in the central portion of the charge retaining medium layer 23. The charges thus accumulated are retained as they are for one week or more.

In this state, as shown in FIG. 12, a positive voltage is applied as the drive signal φ1, a ground voltage is applied as φ2, and a negative voltage is applied as φ3. Then, in the unit region where the positive charge “+” on the side of the mover 20 is accumulated, a repulsive action is generated with the positive charge “+” given to the electrode on the side of the stator 10, and the mover 20 moves to the stator 10 It will be slightly raised from above. In this state, each drive signal φ1-
Switch the voltage of φ3. That is, as shown in FIG. 13, when a ground voltage is applied as the drive signal φ1, a negative voltage is applied as φ2, and a positive voltage is applied as φ3, the respective electrodes in the stator 10 are charged as shown in the figure. Is supplied. Of course, the charges on the side of the mover 20 remain unchanged. The polarity pattern appearing on the stator 10 side shown in FIG. 13 is obtained by shifting the polarity pattern on the stator 10 side shown in FIG. 12 to the left by one unit area. Then, as indicated by an arrow in FIG. 14, the unit area in which the positive charge “+” on the side of the mover 20 is accumulated is the stator 10
Side one unit area, an attractive force is generated between the negative charge “−” given to the electrode at the position on the right side, and similarly, the unit area where the negative charge “−” on the mover 20 side is accumulated. Is the stator 10
An attractive force is generated between the positive charge "+" applied to the electrode on the right side of one unit area on the side, and the entire mover 20 moves one unit area to the right in the figure. . Figure 15 shows
This shows a state in which such movement has been completed.

Considering the state shown in FIG. 15 in which the polarity pattern appearing on the side of the stator 10 is further shifted to the left by one unit area, the stator 10 at this time is considered.
It can be seen that the relative positional relationship between the moving element 20 and the mover 20 is exactly the same as in FIG. 12 before the movement.
After all, if the moving process for one unit area described above is repeatedly executed, the mover 20 sequentially moves to the right in the figure. In other words, in order to move the mover 20 to the right in the figure, each drive signal φ1 to φ is changed so that the polarity pattern on the side of the stator 10 in FIG. 12 is shifted to the left in the figure.
3 should be supplied. FIG. 16 is a waveform diagram of such a drive signal. If the mover 20 is to be moved to the left in the figure, the polarity pattern on the side of the stator 10 may be reversed left and right from the above example, and this may be shifted to the right in the figure.

As described above, the mover 20 according to the present invention is
Similar to the conventional mover 20, if three-phase drive signals are prepared on the side of the stator 10, it is possible to freely drive right and left. Moreover, since a predetermined electric charge is originally accumulated on the side of the moving element 20, it is not necessary to wait for the charging time τ at the time of initial movement unlike the case of using the conventional moving element 20. Further, since it can be considered that the charge amount in the mover 20 is kept substantially constant during driving, recharging during driving is not necessary. As described above, by using the electrostatic actuator moving element according to the present invention, efficient driving can be performed.

§4. Transfer for unipolar electrostatic actuator
Mover described in Doko above §3 20 is a charge image forming method using the air discharge, positive "bipolar both charges and negative charges are in a state of being held in place For the electrostatic actuator ”. Here, the "moving element for a unipolar electrostatic actuator" in which only one of positive charge and negative charge is held will be described.

For example, in the moving element 20 shown in FIG.
The first unit region is in a state where positive charges “+” are held (“+”), and the second and third unit regions are in a state where neither charges are held (“0”). "), And this polarity pattern is repeated after the fourth unit area. Such a “moving element for unipolar electrostatic actuator” has the following advantages over the “moving element for bipolar electrostatic actuator” described above.

The first advantage is that the charge image forming process using air discharge for accumulating charges is simplified. In the principle diagram of FIG. 8, a figure is shown in which two kinds of air discharges with opposite polarities of the charges to be accumulated are simultaneously performed. However, due to reasons such as circuit insulation, each polarity is actually different. It is preferable to perform the air discharge. Therefore, in FIG. 9, the first operation is performed by applying the voltage + V.
It is necessary to separately perform the air discharge for the second time and the air discharge for the second time by applying the voltage -V. However, the electric charge accumulation process in the "moving element for unipolar electrostatic actuator" requires only one air discharge. For example, in the case of the mover 20 shown in FIG. 17, only the air discharge to which the voltage + V is applied in FIG. 9 may be performed.

The second advantage is that the mutual annihilation of charges caused by arranging charges of opposite polarities adjacent to each other does not occur, so that the charges can be held for a longer time. FIG.
In the mover 20 shown in FIG. 1, the positive charges and the negative charges are adjacently accumulated, and therefore, the smaller the pitch of the unit regions, the easier the two charges are to disappear due to bonding. On the other hand, in the mover 20 shown in FIG. 17, since only positive charges are accumulated, such a phenomenon does not occur.

[0041]§5. Transfer for unipolar electrostatic actuator
How to drive the pendulum  Then, such a "transfer for a monopolar electrostatic actuator is performed.
Even with a "mover", it can be driven on the stator without problems.
Let's show that Now, as shown in FIG. 17, positive charge
Place the mover 20 with only accumulated on the stator 10.
Think about the case. In this state, as shown in FIG.
A positive voltage as the motion signal φ1, a negative voltage as φ2, and φ3
As a negative voltage, respectively. Do
And the unit area in which the positive charge “+” on the side of the mover 20 is accumulated.
Region, the positive charge applied to the electrode on the side of the stator 10
A repulsive action is generated with "+", and the mover 20 is on the stator 10.
It will be slightly raised. Moreover, the arrow in the figure
As marked, the positive charge “+” on the side of the mover 20 is accumulated.
The stacked unit area is on the right side of one unit area on the side of the stator 10.
Attraction between the negative charge "-" given to the electrode at the position
A force is generated, and the entire mover 20 moves to the right in the figure by one unit area.
It will only move. Figure 19 shows the completion of such a move.
It shows the state of being done.

In the state shown in FIG. 19, the voltages of the drive signals φ1 to φ3 are switched. That is, as shown in FIG. 20, when a negative voltage is applied as the drive signal φ1, a positive voltage is applied as φ2, and a negative voltage is applied as φ3, the electrodes in the stator 10 are provided with the voltages as shown in the figure. Electric charge is supplied. Of course, the charges on the side of the mover 20 remain unchanged. The polarity pattern appearing on the side of the stator 10 shown in FIG. 20 is obtained by shifting the polarity pattern on the side of the stator 10 shown in FIG. 19 to the right by one unit area. Then, as indicated by the arrow in FIG. 20, the unit region on the side of the mover 20 where the positive charge “+” is accumulated is given to the electrode at the position on the right side by one unit region on the side of the stator 10. An attractive force is generated between the electric charge “−” and the electric charge “−”, and the entire mover 20 moves one unit area further to the right in the figure.

After all, "+,-,-, +,-,-, +,
−, −, ...
The unipolar mover 20 can be moved to the right by shifting to the right by one unit area on the 0 side. That is, it can be seen that, like a bipolar mover, it can be driven by three-phase drive signals.

However, the operation during the initial movement may be briefly mentioned. In the above description, it was described that the moving element 20 moves to the right because the suction force is generated in the portion indicated by the arrow in FIG. 20, but this is not always correct at the time of initial movement. Considering the force acting on the position a in FIG. 20, the repulsive force from the electrode (“+”) immediately below,
The attraction force is exerted from the lower right electrode (“−”), and the attraction force is exerted from the lower left electrode (“−”). Therefore, the position a is sucked to the right side of the drawing and also to the left side of the drawing. Nevertheless, in FIG. 20, the mover 20 has moved to the right because the mover 20 has an inertial force to the right in the figure due to the movement from the previous stage shown in FIG. . That is, when FIG.
It is not decided which side will move to the left or right, but once it starts moving, it will always continue to move in the direction of inertial force. This is the same as the operating principle of a two-pole motor or the like.

Therefore, let us consider the phenomenon that occurs during the initial movement. Here, for convenience of explanation, as shown in FIG. 21, it is assumed that there is only one point a having a positive charge on the mover side. In this state, when a drive signal having a polarity pattern as shown in the figure is applied to the stator 10 side, the attraction force acts on the point a from both left and right sides as described above. If the point a is in a stationary state, whether the point a actually moves to the left or right is determined based on the fact that the position of the point a deviates to the left or right from the equilibrium state shown in the figure. In other words, if the point a is within the range of section X in the figure, it moves to the left, and if it lies within the range of section Y in the figure, it moves to the right. Therefore, even if a drive signal having a polarity pattern as shown in FIG. 21 is given with the intention of moving the mover 20 to the right,
If the point a happens to be within the range of the section X in the figure, the point a moves to the left, which is the opposite direction to the intended direction. FIG. 22 shows the state when the point a moves to the left in this way. However, the mover 20
If you intend to move the arrow to the right,
Since a cyclic polarity pattern "-,-, +,-,-, +,-,-, ..." is shifted rightward by one unit area on the stator 10 side, the next step is performed. Then, the polarity pattern on the side of the stator 10 is as shown in FIG. In this state, only the suction force from the right acts on the point a, and it always moves to the right.

As described above, when a unipolar moving element is used, at the initial movement, it may move up to 1 pitch in the opposite direction to the intended direction, but the moving direction is immediately changed to the intended direction. Since it reverses to, there is no big problem. Particularly, in a practical electrostatic actuator, since one pitch is on the order of several hundreds of μm, even if such an initial movement in the opposite direction occurs, no problem occurs.

Although the method of driving the unipolar mover holding only the positive charges has been described above, conversely, for the unipolar mover holding only the negative charges, "+,-, -, +,
It is possible to move to the right by shifting the periodic polarity pattern "-,-, +,-,-, ..." By one unit area on the stator 10 side to the right.
For example, as shown in FIG. 24, consider a case where a moving element 20 in which only negative charges are accumulated is placed on the stator 10. In this state, as shown in FIG. 25, a positive voltage is applied as the drive signal φ1, a negative voltage is applied as φ2, and a negative voltage is applied as φ3. This polarity pattern is the same as the pattern shown in FIG. 18 when the mover holding the positive charge is initially moved. In this state, the unit area in which the negative charge “−” on the side of the mover 20 is accumulated generates a positive charge “+” given to the electrode on the side of the stator 10 directly below the unit area and attracts the unit area to the left and right. Does not happen. However, when the periodic polarity pattern on the stator 10 side is shifted to the right, the state shown in FIG. 26 is obtained. In this state, a repulsive action occurs between the unit area where the negative charge “−” on the side of the mover 20 is accumulated and the negative charge “−” given to the electrode on the side of the stator 10 directly below the unit area. The mover 20 is slightly raised above the stator 10. Moreover,
As indicated by the arrow in the figure, the unit area in which the negative charge “−” on the side of the mover 20 is accumulated is the positive charge “” given to the electrode on the right side of one unit area on the side of the stator 10. ＋ ”
A suction force is generated between the and, and the entire mover 20 moves to the right in the figure by one unit area. FIG. 27 shows a state in which such movement is completed (at the time of initial movement, it may move to the left in the opposite direction, but it is immediately reversed in the correct movement direction).

By the above explanation, "+,-,
-, +,-,-, +,-,-, ... "Periodic polarity pattern (hereinafter, referred to as" (+,-,-) pattern "by using only the portion of the periodic repeating unit. Do)
Is shifted to the right on the side of the stator 10, both the mover 20 holding only positive charges and the mover 20 holding only negative charges can be driven to the right. I understood. Conversely, this polarity pattern
It will be easily understood that these movers 20 can be driven to the left by shifting to the left on the side of the stator 10. FIG. 28 is a diagram showing the concept of this driving operation. FIG. 28 (a) shows that on the stator side (moving element having a polarity pattern of “+, 0, 0, +, 0, 0, ...)” that accumulates only positive charges, +,-,
−) A pattern is given and the pattern is shifted to the right to drive the mover to the right. In short, the mover moves to the right in a state where the charge “+” on the mover side always follows the charge “−” on the stator side. FIG. 28 (b) shows that the moving element storing only negative charges (moving element having a polar pattern of “−, 0, 0, −, 0, 0, ...)” is the same on the stator side. A (+,-,-) pattern is given, and the pattern is shifted to the right to drive the mover to the right. In this case, the mover moves to the right in a state where the charge “−” on the mover side always follows the charge “+” on the stator side.

However, the electrode patterns of the three-phase drive signals capable of driving the unipolar mover are not limited to the (+,-,-) patterns described above. In addition to the above, the inventor of the present application has (−, +, +) patterns, (+,
It was confirmed that the −, 0) pattern and the (−, +, 0) pattern existed. 29, 30, and 31 are conceptual diagrams of the driving operation by these three types of driving patterns. In each case, Fig. (A) shows the case where it is applied to the mover that accumulates only positive charges, and Fig. (B) shows the case where it is applied to the mover that accumulates only negative charges.

In the above example, the unipolar polarity pattern to be accumulated on the side of the mover 20 is "+, 0, 0,
+, 0,0, ... "or"-, 0,0,-, 0,0,
The pattern is repeated for each of the three unit areas "...," but "+, 0, 0, 0, +, 0, 0, 0, ..." or "-, 0, 0, 0,-, 0, 0 , 0, ... ”4
The pattern can be driven as an electrostatic actuator by using a pattern repeated for each unit area (in this case, the drive signal given to the stator 10 side also needs to be a signal corresponding to this). In general, of the n unit areas adjacent to each other, the first unit area is made to hold the charge of either polarity, and the second to nth unit areas are not made to hold the charge, and If the state distribution of the unit areas is set periodically with n unit areas of 1 as one cycle, a unipolar mover that functions as an electrostatic actuator can be realized. However, in terms of driving efficiency, the above-described embodiment in which n = 3 is most preferable.

The polarity pattern given as the drive signal can be given as a rectangular wave pattern as shown in FIG. 16, for example, but it can also be given as a sinusoidal pattern.

§6. Form the counter electrode on the mover side
The moving element 20 described so far has the supporting insulator layer 21.
The charge retaining medium layer 23 and the charge retaining medium layer 23 are laminated to each other, but a conductive layer may be further added thereto to form a three layer structure. Such a conductive layer can be used as a substitute for the counter electrode 50 used in the charge storage device. Hereinafter, such a usage mode will be described.

When the mover according to the present invention is used as an electrostatic actuator, it is necessary to form a predetermined electrostatic pattern on the charge holding medium layer 23 by using a charge storage device as shown in FIG. Is as described above. In this device, the mover 20 is connected to the electrode substrate 30 and the counter electrode 50.
A separate discharge is performed so as to be sandwiched between and. Here, considering the function of the counter electrode 50 placed on the mover 20, it functions as the counter electrode of the pattern electrode 32 in performing the separate discharge, and does not require a particular thickness. Any layer may be used as long as it is a conductive layer that functions as an electrode. Therefore, this counter electrode 5
It is also possible to form a conductive layer instead of 0 on the side of the mover 20. That is, in FIG. 6, the mover 20 is composed of a three-layer structure including a charge holding medium layer 23, a supporting insulator layer 21, and a conductive layer (in place of the counter electrode 50). Even the mover 20 having such a three-layer structure has no problem in using it as an electrostatic actuator.

Specifically, as the mover 20 having such a three-layer structure, a metal such as aluminum is vapor-deposited on one surface of a PET (polyethylene terephthalate) or polyimide film, and the other surface will be described later. It is possible to use the one in which a layer of a fluororesin having a function as a charge holding medium is formed. A PET or polyimide film functions as the supporting insulator layer 21, a fluororesin layer functions as the charge retention medium layer 23, and a metal vapor deposition layer such as aluminum is formed on the side of the moving element 20 as a conductive layer (instead of the counter electrode 50). ). This conductive layer only needs to be able to function as a counter electrode at the time of separation discharge, and therefore, a thickness of several hundreds nm is sufficient.

If an electrostatic pattern is formed on the mover 20 having such a three-layer structure, it is not necessary to prepare the counter electrode 50 on the charge storage device side, and the structure is simplified. However, even when the mover 20 having a three-layer structure is used, the counter electrode 50 may be prepared on the charge storage device side as shown in FIG. In this case, the counter electrode 5 is formed on the conductive layer on the mover 20 side.
0 is put on and it makes electrical contact. Also,
It is also possible to configure the moving element 20 side with more layers.

§7. Materials Preferred as Charge Retaining Medium Finally, materials preferred as a charge retaining medium for use in the moving element for electrostatic actuator according to the present invention will be mentioned. According to the inventor's recognition, the volume resistivity is 10
A resin having a resistance of ¹⁸ Ω · cm or more is considered to be usable as the charge retention medium in the present invention, and it is particularly preferable to use a fluoropolymer having a cyclic structure having a volume resistivity of 10 ¹⁸ Ω · cm or more. Since these polymers solidify when heated and dried at about 180 ° C., they can be applied to the support film by a method such as a spin coating method or a bar coating method, and then dried by heating. Can be formed.

More specific material names will be listed below. (1) Polytetrafluoroethylene (PTFE) The chemical formula is shown below.

[0058]

Embedded image (2) Tetrafluoroethylene-hexafluoropropylene copolymer (FEP) The chemical formula is shown below.

[0059]

Embedded image (3) Tetrafluoroethylene-perfluoro (alkyl vinyl ether) copolymer (PFA) The chemical formula is shown below.

[0060]

Embedded image (4) Tetrafluoroethylene-hexafluoropropylene-perfluoro (propyl vinyl ether) terpolymer (EPE) The chemical formula is shown below.

[0061]

[Chemical 4] (5) General formula

[0062]

Embedded image And / or

[0063]

[Chemical 6] A fluorine-containing thermoplastic resin-like polymer having a molecular weight such that it essentially consists of a repeating unit group (a) represented by the formula (a) and has an intrinsic viscosity of at least 0.1 (6). In the polymer shown in, the group (a) of repeating units is derived from perfluoroallyl vinyl ether and / or perfluorobutenyl vinyl ether. (7) General formula

[0064]

[Chemical 7] And / or

[0065]

Embedded image A group (a) of repeating units having a ring structure represented by

[0066]

[Chemical 9] Essentially consists of the group (b) of repeating units represented by
Fluorine-containing thermoplastic resin-like polymer containing at least 80% by weight of group (a) of repeating units and having a molecular weight such that the intrinsic viscosity is at least 0.1 (8) The polymer described in (7) above. In which the group (a) of repeating units is derived from perfluoroallyl vinyl ether and / or perfluorobutenyl vinyl ether (9) In the polymer shown in (7) or (8) above, the group of repeating units (B) is a general formula

[0067]

[Chemical 10] Polymer derived from comonomer represented by

[0068]

As described above, according to the present invention, since the charge holding medium is used as the moving element for the electrostatic actuator, the electric charge can be held on the moving element side, and the charge holding medium can be held at the time of initial driving. The charging time τ and recharging during driving are unnecessary, and very efficient driving becomes possible.

[Brief description of drawings]

FIG. 1 is a perspective view showing a conventional general electrostatic actuator.

FIG. 2 is a cross-sectional view for explaining a driving operation of the electrostatic actuator shown in FIG.

FIG. 3 is a cross-sectional view illustrating a state at an initial stage when driving the electrostatic actuator shown in FIG.

FIG. 4 is a cross-sectional view illustrating a state in which a drive signal is advanced to the next stage from the state shown in FIG.

FIG. 5 is a cross-sectional view illustrating a state in which the mover has moved by one step in the state shown in FIG.

FIG. 6 is an exploded perspective view showing the configuration of a charge storage device for storing charges in the mover 20 according to the present invention.

7 is a perspective view showing a state in which the charge storage device shown in FIG. 6 is operated.

8 is a cross-sectional view showing an operating state of the charge storage device shown in FIG.

9 is a top view of a substrate 31 of the charge storage device shown in FIG.

10 is a cross-sectional view showing a state where desired charge storage in the charge storage medium layer 23 is completed by the charge storage device shown in FIG.

FIG. 11 is a cross-sectional view for explaining the driving operation of the electrostatic actuator using the bipolar mover according to the present invention.

FIG. 12 is a cross-sectional view illustrating a state at an initial stage when driving the electrostatic actuator illustrated in FIG.

FIG. 13 is a cross-sectional view illustrating a state in which the drive signal is advanced to the next stage from the state shown in FIG.

FIG. 14 is a cross-sectional view illustrating a state in which the mover has started to move rightward from the state shown in FIG.

FIG. 15 is a cross-sectional view illustrating a state in which the mover has moved by one step in the state shown in FIG.

FIG. 16 is a waveform diagram of three-phase drive signals necessary for driving operation of the electrostatic actuator using the bipolar mover according to the present invention.

FIG. 17 is a cross-sectional view for explaining a driving operation of an electrostatic actuator using a unipolar moving element that holds only positive charges according to the present invention.

FIG. 18 is a cross-sectional view illustrating a state at an initial stage when driving the electrostatic actuator illustrated in FIG. 17.

FIG. 19 is a cross-sectional view illustrating a state in which the mover has moved by one step from the state shown in FIG.

20 is a cross-sectional view illustrating a state in which the drive signal is advanced to the next stage from the state shown in FIG.

FIG. 21 is a cross-sectional view illustrating a factor that determines the moving direction of an electrostatic actuator using a unipolar moving element at the time of initial movement.

FIG. 22 is a cross-sectional view illustrating a state in which the moving element moves in a direction opposite to the intended direction when the electrostatic actuator using the unipolar moving element initially moves.

FIG. 23 is a cross-sectional view illustrating that, when an electrostatic actuator using a unipolar moving element is initially moved, a moving element that has moved in a direction opposite to an intended direction moves in a reversed and correct moving direction.

FIG. 24 is a cross-sectional view for explaining a driving operation of an electrostatic actuator using a unipolar moving element that holds only negative charges according to the present invention.

25 is a cross-sectional view illustrating a state at an initial stage when driving the electrostatic actuator illustrated in FIG.

FIG. 26 is a cross-sectional view illustrating a state where the drive signal is advanced to the next stage from the state shown in FIG. 25.

27 is a cross-sectional view illustrating a state in which the mover has moved by one step from the state shown in FIG.

FIG. 28 is a diagram showing a stator according to the present invention, which is provided with a polarity pattern of (+, −, −) on the stator side and is shifted to the right to drive the slider to the right. It is a conceptual diagram which shows a drive operation.

FIG. 29 is a schematic diagram showing that a polarity pattern of (−, +, +) is given to the stator side of the mover according to the present invention, and this pattern is shifted rightward to drive the mover rightward. It is a conceptual diagram which shows a drive operation.

FIG. 30: For the mover according to the present invention, a polarity pattern of (+, −, 0) is applied to the stator side, and this pattern is shifted to the right to drive the mover to the right. It is a conceptual diagram which shows a drive operation.

FIG. 31 is a diagram showing a stator according to the present invention in which a polarity pattern of (-, +, 0) is applied to the stator side, and the pattern is shifted to the right to drive the mover to the right. It is a conceptual diagram which shows a drive operation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Stator 11-18 ... Electrode 20 ... Mover 21 ... Support insulator layer 22 ... Charge induction layer 23 ... Charge holding medium layer 30 ... Electrode substrate 31 ... Substrate 32 ... Pattern electrode 40 ... Frame body 50 ... Counter electrode

Claims (7)

[Claims] 1. A moving body for an electrostatic actuator, which constitutes an electrostatic actuator when used together with a stator having a plurality of electrodes arranged at a predetermined pitch, the resin having a volume resistivity of 10 ¹⁸ Ω · cm or more. And a plurality of unit areas are defined at the same pitch as the pitch, and each unit area holds a positive charge and holds a negative charge. Is a selected state, a state in which none of the charges is held, a state selected from three state groups, and a state distribution of the unit region is a periodic distribution. Mover for electrostatic actuator. 2. The electrostatic actuator moving element according to claim 1, wherein the charge holding medium layer has a volume resistivity of 10 ¹⁸ Ω · cm.
A mover for an electrostatic actuator, which is characterized by using the above-mentioned fluoropolymer having a cyclic structure. 3. The electrostatic actuator moving element according to claim 1, wherein the state distribution in three adjacent unit areas is set as one cycle, and the state distributions of the unit areas are cyclic. A mover for an electrostatic actuator characterized by: 4. The electrostatic actuator moving element according to claim 1, wherein the polarity of the electric charge to be retained is set to only one of positive and negative polarities, and among the n unit regions adjacent to each other, The first unit region is made to hold the charge of the one polarity, the second unit region to the nth unit region are not made to hold the charge, and the n unit regions are set as one cycle. A moving element for an electrostatic actuator, characterized in that the state distribution of is taken to be periodic. 5. The mover for an electrostatic actuator according to claim 4, wherein n = 3 is set. 6. The method for driving a slider for an electrostatic actuator according to claim 5, wherein the (i + 1) th (where i is 0, 1, 2, ...) Electrodes arranged on the stator. A first drive signal, a (i + 2) th electrode is supplied with a second drive signal, and a (i + 3) th electrode is supplied with a third drive signal. One of the polarities is the first polarity,
The other is defined as the second polarity, and each of the three drive signals is cycled in this order in three unit time states: a first polarity state, a second polarity state, a second polarity state. So that it becomes a signal that
A method for driving a moving element for an electrostatic actuator, which is characterized in that signals having different phases are provided. 7. The method for driving a slider for an electrostatic actuator according to claim 5, wherein the (i + 1) th (where i is 0, 1, 2, ...) Electrodes arranged on the stator. A first drive signal, a (i + 2) th electrode is supplied with a second drive signal, and a (i + 3) th electrode is supplied with a third drive signal. One of the polarities is the first polarity,
The other is defined as the second polarity, and all of the three drive signals periodically take three unit time states, that is, the first polarity state, the second polarity state, and the ground state. Be a signal, and
A method of driving a moving element for an electrostatic actuator, characterized in that signals having different phases are provided.