JP6221420B2 - Electrostatic motor - Google Patents

Description

  The present invention relates to an electrostatic motor having an electrode made of an electret material.

An electrostatic motor is known as one of electrostatic motors that do not use a magnet. Electrostatic motors have the merits of being light, thin, and simple in structure, but have not yet been put into practical use because they have a smaller output torque and require a higher voltage than electromagnetic motors using magnets. In order to increase the output torque, a semiconductor process technology is used to form a plurality of electrodes on a film, and by laminating the films on which the plurality of electrodes are formed, a method of extracting a large torque or a permanent electrification called an electret There is already known a method of reducing the driving voltage by using the prepared material as an electrode.
In Patent Document 1 (Japanese Patent Laid-Open No. 6-311763), a sacrificial layer is formed on an electrode on a stator, an electret layer and a polycrystalline silicon layer are formed on the sacrificial layer, and the sacrificial layer is removed. A configuration is disclosed in which an electret layer and a polycrystalline silicon layer are peeled off, and the peeled electret layer and polycrystalline silicon layer become a mover. In this case, since the stator and the mover are produced in pairs, the gap between the electret and the electrode facing it can be formed with high accuracy.
However, the configuration of Patent Document 1 has problems such as poor productivity and high cost. In recent years, electret materials based on fluororesins with a high surface charge density (amorphous fluororesin, trade name “Cytop” manufactured by Asahi Glass Co., Ltd.) have been developed. It is desirable to use an electret material. However, in Patent Document 1, it is expected that it is difficult to use a fluororesin electret material for process reasons.

  In Patent Document 2 (Japanese Patent Laid-Open No. 2012-257368), an electret material is formed on a metal material to a thickness of about 15 μm to form one electrode (electret electrode), and the other electrode is separated by a distance (gap) of 100 μm. A configuration of a power generation element that disposes (opposite electrode) and generates power by electrostatic induction between one electrode and the other electrode is disclosed. In the configuration of Patent Document 2, the distance (gap) is sufficiently separated from 100 μm with respect to the thickness of 15 μm of the electret material to constitute the power generating element. In this case, it is expected that the power generation efficiency is improved by narrowing the distance (gap). However, when the gap is narrowed, there is a concern about contact between one electrode and the other electrode. That is, the method of increasing the electric field strength formed between the electret material and the counter electrode by narrowing the gap distance has problems in terms of cost, productivity, and device stability.

  An object of the present invention is to improve the output torque without reducing the distance between the movable element and the stator facing each other.

In order to achieve the above object, an electrostatic motor according to the present invention has a stator having a plurality of strip-like electrodes that are insulated from each other and arranged in a predetermined direction and at a predetermined interval so as to face the stator. And a movable element having a plurality of band-shaped electrodes made of electret material, and applying a predetermined voltage to the band-shaped electrode of the stator, and a movable element by electrostatic coulomb force acting between the electrodes of the stator and the movable element It is one that moves the, by separating the distance from the substrate surface to dispose the strip-shaped electrodes made of an electret material of the movable element to the surface of the strip electrode, thereby an electric field is applied from the strip electrode to the strip electrodes of the stator In addition, the distance from the surface of the substrate on which the belt-like electrode is arranged to the surface of the belt-like electrode is d1, and the surface of the belt-like electrode of the stator located on the side facing the surface from the surface of the belt-like electrode of the mover When the distance is d in, it is characterized in that the d1> d.

According to the present invention, by increasing the distance from the substrate surface to dispose the strip-shaped electrodes made of an electret material of the movable element to the surface of the strip electrode, so that an electric field is applied from the strip electrode to the strip electrodes of the stator since the, without narrowing the distance between the stator and the mover, it is possible to form efficiently the electric field between the strip electrodes made of electret material strip electrodes and the movable element of the stator side. Thereby, even if the distance between the stator and the mover is large, the electric field strength is not weakened, and the output torque can be improved.

The perspective view which shows the main structures of 1st Embodiment of the electrostatic motor which concerns on this invention. (A) is a top view which shows the structure of the stator in 1st Embodiment, (b) is sectional drawing of (a). (A) is a top view which shows the structure of the needle | mover in 1st Embodiment, (b) is sectional drawing of (a). It is a partial expanded sectional view of a stator and a mover, (a), (d) is a figure showing a characterizing portion of the present invention provided with an insulating layer between a conductive layer and an electret electrode, (c) is a stator and The figure which shows the state which extended the distance of the needle | mover, (d) is the figure which shows the state which narrowed the distance of a stator and a needle | mover. The partial expanded sectional view which shows the structure of the needle | mover which concerns on this invention, and the relationship between a stator. The partial expanded sectional view which shows another embodiment of the needle | mover which concerns on this invention. The partial expanded sectional view which shows another embodiment of the needle | mover which concerns on this invention. The partial expanded sectional view which shows another embodiment of the needle | mover which concerns on this invention. The perspective view which shows schematic structure of 2nd Embodiment of the electrostatic motor which concerns on this invention. The perspective view which shows the main structures of 3rd Embodiment of the electrostatic motor which concerns on this invention. The drive control when the ratio of the number of electrodes of the stator and the mover is 3 to 2 is shown. (A) is a diagram schematically showing the voltage switching and the moving state of the mover, and (b) is the diagram showing the movement to the stator. The figure which shows the switching pattern of the voltage to apply. The figure which shows typically the voltage switching pattern and the movement state of a needle | mover in case the electrode number ratio of a stator and a needle | mover is 3 to 4. 1 is a schematic configuration diagram of a corona charging device used for charge injection. The figure which shows the 3-dimensional electric field simulation model used for the analysis of the relationship between the thickness of the electrode of electret material and electric field strength The figure which shows the relationship between the thickness of the electrode of electret material, and electric field strength. The figure which shows the analysis result of SU-8 construction method examination model. The electric field vector diagram which shows the electric field strength of a perpendicular direction, and the electric field strength of a horizontal direction. The figure which demonstrated that the electric field strength became large when the thickness of the electrode of the electret material of a needle | mover side was increased, with a capacitor | condenser model.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In each drawing, the same member or a member having the same function is basically denoted by the same reference numeral, and redundant description is appropriately omitted.

(First embodiment)
The configuration of the first embodiment of the electrostatic motor according to the present invention will be described with reference to FIGS. 1, 2, and 3.
The electrostatic motor according to the first embodiment is an axial gap type electrostatic motor 1. As shown in FIG. 1, an electrostatic motor 1 is a movable element in which a stator 2 (hereinafter referred to as “stator”) in which a pattern electrode 5 as a strip electrode is formed on a thin plane and a pattern electrode 6 as a strip electrode are formed. A child 3 (hereinafter referred to as “rotor”) and a drive shaft 4 are provided. The stator 2 and the rotor 3 are arranged to face each other, and a plurality of layers are laminated while maintaining a minute gap. The drive shaft 4 is made of metal, is connected only to the rotor 3, and is configured to rotate integrally when the rotor 3 rotates. As a method of providing a minute gap between the stator 2 and the rotor 3, for example, as described in JP-A-2005-278324, beads of several tens of μm are inserted between the stator 2 and the rotor 3, or JP-A-2005 This can be achieved by using a well-known technique in which a spacer is sandwiched between the side surfaces of the rotor 3 as described in JP-A-210852.

  Here, to the plurality of pattern electrodes 5 formed on the stator 2, three-phase wirings are connected to the three pattern electrodes 5 as one set. This three-phase wiring is described as U, V, and W. In the first embodiment shown in FIG. 1, three-phase wirings of U, V, and W are connected to the pattern electrode 5 of the stator 2 to configure the number of poles as three layers. Is not limited to three phases, and may be driven with two-phase wiring.

The configuration of the stator 2 will be described in more detail with reference to FIG.
As shown in FIGS. 2A and 2B, the stator 2 has a plurality of pattern electrodes 5 formed on an annular substrate 2A having a through hole 2C in the center. The substrate 2A is made of an insulator such as glass, ceramics, glass epoxy resin, or polyimide. The plurality of pattern electrodes 5 formed on the substrate 2A are formed by patterning a plurality of metal electrodes, and three-phase wiring is performed on each individual electrode. In the example of FIG. 2, only one set of wirings of U, V, and W is illustrated. In the present embodiment, the individual electrode that forms the U wiring and becomes the U electrode is denoted by reference numeral 5A, and the individual electrode that is formed by the V wiring and becomes the V electrode is denoted by reference numeral 5B, and the W wiring is formed. Thus, the individual electrodes to be the W electrodes are distinguished by being denoted by reference numeral 5C. The drive shaft 4 is inserted into the through hole 2C of the substrate 2A via an insulating member or in a non-contact state. The electrode shape of the pattern electrode 5 is formed as a radial pattern as shown in FIG. Further, the individual electrodes 5A, 5B, and 5C of the pattern electrode 5 may be subjected to a curvature process in order to prevent dielectric breakdown from the edge.
The configuration of the rotor 3 will be described in more detail with reference to FIG.
As shown in FIG. 3A, the rotor 3 has a plurality of pattern electrodes 6 formed on an annular substrate 3A having a through hole 3C at the center. The pattern electrode 6 is formed on the surface of the substrate 3A via the stacked conductive layer 3B. In the present embodiment, the surface of the substrate 3A refers to the surface 3B1 of the conductive layer 3B.

In the present embodiment, the pattern electrode 6 is formed as an electret in which charges are injected into the belt-shaped pattern film. Here, the electret refers to a material in which an electric field is applied to an insulator such as a fluororesin to cause electric polarization (a state divided into positive and negative electricity) and the state is maintained semipermanently. In the case of this embodiment, as shown in FIG. 3B, since the conductive layer 3B is formed on the glass substrate 3A, the state of electric polarization when an electric field is applied is stabilized, so that the pattern electrode 6 Can be formed in a stable state as an electret.
In Patent Document 1 described above, for the purpose of increasing torque by using repulsive force (repulsive force) in addition to electrostatic attraction, an even number of electrets are formed at equal intervals, and adjacent electrets have opposite polarities. The electrodes are a multiple of the number of each electret and are arranged at equal intervals so as to face the electret, and the two electrodes are associated with each electret to form a stator. A drive circuit that drives the mover by sequentially switching the polarities of the electrodes is disclosed. However, in order to increase the torque with this configuration, it is necessary to increase the number of poles of the electret.However, as the number of poles increases, the adjacent reverse polarity patterns become closer to each other, and the adjacent patterns (individual electrodes) are adjacent to each other. May cause discharge. In addition, it is very difficult to charge the polarity alternately.

Therefore, as in the present embodiment, the individual electrodes 6A that are electret electrodes formed on the same plane of the substrate 3A are all charged to the same pole (single pole) of either the positive pole or the negative pole. An electrode was obtained. For this reason, it can form easily on manufacture.
Thus, when the rotor 3 formed with the electret pattern electrode 6 is brought close to the pattern electrode 5 of the stator 2, an electric field is generated between the stator 2 and the rotor 3, so that no power feeding means is required for the rotor 3. The motor structure can be greatly simplified. Furthermore, by improving the surface charge density of the electret electrodes (pattern electrode 6 / individual electrode 6A) of the rotor 3, the two-phase or three-phase AC voltage applied to the stator 2 side can be reduced. For this reason, low voltage driving becomes possible, and not only the motor body but also the drive driver can be miniaturized.

The individual electrode 6A will be described in more detail.
As shown in FIGS. 4 (c) and 4 (d), when the individual electrode 6A serving as the electret electrode is formed on the substrate 3A via the conductive layer 3B, the thickness of the electret material is about 5 to 20 μm. It is common. Then, an electric field is formed between the facing surface 6A1 as the surface of the individual electrode 6A and the facing surface 5A1 serving as the surface of the individual electrode 5A on the side of the stator 2 facing the individual electrode 6A. The electric field at this time can be transmitted to the opposing individual electrode 5A as the gap distance d between the opposing surface 6A1 of the individual electrode 6A and the opposing surface 5A1 of the individual electrode 5A is shorter. Therefore, it is better to install the individual electrodes 5A with a gap distance d smaller than the gap distance d shown in FIG. 4C, as shown in FIG .
However, it is difficult to drive the electrostatic motor or the electrostatic actuator while maintaining the short gap distance d from the viewpoint of surface accuracy of the substrates 2A and 3A and variations in the thickness of the individual electrodes 5A and 6A. In order to realize this, the stator 2 and the rotor 3 (movable element) with high surface accuracy are required, and the accuracy of the processing machine is also required, which is disadvantageous in terms of cost. Therefore, in reality, as shown in FIG. 4C, the distance D between the stator 2 and the rotor 3 is set so as not to contact even if the rotor 3 (movable element) moves. In terms of cost and stability, it is preferable to configure the device by increasing the gap distance d between the electrode 5A and the facing surface 5A1.
However, if the distance D or gap distance d between the stator 2 and the rotor 3 is increased in this way, the distance d1 between the opposing surface 6A1 of the individual electrode 6A and the conductive layer 3B of the rotor 3, that is, the film of the individual electrode 6A here. The thickness d1 is shorter than the gap distance d, and an electric field is easily formed between the individual electrode 6A and the conductive layer 3B. Thus, in the configuration in which the electret individual electrodes 6A are formed on the conductive layer 3B, it is difficult to efficiently form an electric field between the individual electrodes 5A facing the individual electrodes 6A. In FIG. 4, the individual electrode 5A is representatively illustrated as the electrode on the stator 2 side, but the same phenomenon occurs between the individual electrodes 5B and 5C and the individual electrode 6A. The facing surfaces of the individual electrodes 5B and 5C are denoted as 5A1 for convenience.

In order to solve such a problem, it is desirable to increase the distance d1 between the facing surface 6A1 of the individual electrode 6A and the conductive layer 3B of the rotor 3 while ensuring a sufficient distance D between the stator 2 and the rotor 3. Therefore, in this embodiment, as shown in FIGS. 4A and 4B, an insulating layer 60 is provided between the individual electrode 6A of the electret on the rotor 3 side and the conductive layer 3B. 4 (a) and 4 (b), the gap distance d between the facing surface 6A1 of the individual electrode 6A and the facing surface 5A1 of the individual electrode 5A is the same as that in FIG. 4 (c). The difference between FIG. 4A and FIG. 4B is the difference in the thickness d2 of the insulating layer 60.
When comparing FIG. 4B and FIG. 4C, the distance d1 between the facing surface 6A1 and the conductive layer 3B is increased by the thickness d2 of the insulating layer 60. As a result, the ratio d / d1 between the gap distance d between the opposing surface 6A1 and the opposing surface 5A1 of the opposing electrode 5A and the distance d1 between the opposing surface 6A1 and the conductive layer 3B is reduced, and the electric field escaping to the conductive layer 3B is reduced. In the configuration of FIG. 4B, an electric field can be formed between the individual electrode 6A and the opposing electrode 5A more efficiently than the configuration of FIG. 4C.
Further, by making the thickness d2 of the insulating layer 60 larger than the gap distance d between the opposing surface 6A1 and the opposing surface 5A1, as shown in FIG. 4A, the opposing surface 6A1 of the individual electrode 6A and the individual electrode While maintaining the gap distance d between the opposing surface 5A1 of 5A and the distance d1 between the conductive layer 3B and the opposing surface 6A1 as compared with FIG. 4B, the distance D between the stator 2 and the rotor 3 is increased. Can expand (enlarge). For this reason, an electric field can be formed between the opposing surfaces of the individual electrode 6A and the individual electrode 5A more efficiently.

FIG. 5 is an enlarged cross-sectional view when the configuration of FIG. 4A is applied to the rotor 3 shown in FIG.
In FIG. 5, the stator 2 is disposed on the upper side and the rotor 3 is disposed on the lower side, and a distance D is formed between them so as to face each other. The rotor 3 is formed by laminating a conductive layer 3B made of metal on an insulating substrate 3A such as glass. A pattern of the insulating layer 60 is formed on the conductive layer 3B, and a pattern is formed on the pattern of the insulating layer 60 with an electret material to form the pattern electrode 6 (individual electrode 6A). In FIG. 5, an insulating substrate 3A such as glass on which the conductive layer 3B is formed is used, but a metal material may be used for the substrate 3A. The conductive layer 3B is grounded.

Here, the manufacturing method of the rotor 3 according to the present embodiment will be specifically described.
The rotor 3 serving as a mover is formed on a glass substrate 3A by a method such as vapor deposition of a metal film such as aluminum with a thickness of about 0.1 to 1 μm. A negative resist SU8 (Nippon Kayaku Co., Ltd.) made of an epoxy resin is formed on the aluminum film with a thickness of about 10 to 100 μm by spin coating or slit coater. The negative resist SU8 is exposed to a predetermined pattern and developed to form a pattern having a thickness (height) of about 10 to 100 μm and a width of about 5 to 300 μm. On this, CYTOP EGG-811 (manufactured by Asahi Glass Co., Ltd.) for electrets is formed by spin coating about 5 to 20 μm. When the thickness of the CYTOP is 10 um or more, it can be made 10 um or more by performing spin coating a plurality of times and recoating.
Furthermore, a metal film such as an aluminum film is formed on the CYTOP by vapor deposition or the like, and a photoresist TSMR-8800 (manufactured by Tokyo Ohka Kogyo Co., Ltd.) is formed on the metal film by spin coating. Then, the photoresist is exposed and developed, and the metal is etched to form a photoresist and a metal pattern. Using a photoresist and metal pattern as a mask, ash top is ashed with ozone plasma. In the ashing of ozone plasma, the photoresist and the cytotop of the pattern opening are removed. The metal remaining on the CYTOP is etched, and the thickness (height) is 5 to 20 μm on the pattern of the negative resist SU8 having a thickness (height) of about 10 to 100 μm and a width of about 50 to 300 μm. The individual electrode 6A made of Cytop is formed.
With the manufacturing method as described above, the rotor 3 (movable element) using the negative resist SU8 as the insulating layer 60 and the cytop as the individual electrode 6A serving as the electret electrode can be obtained.

As a method of charging the electret material of the rotor 3, any method can be used as long as it is a method of charging an insulator in general. For example, G. M.M. Corona discharge method, electron beam collision method, ion beam collision method, radiation contact method described in Sessler, Electrets Third Edition, pp20, Chapter 2.2 “Charging and Polarizing Methods” (Laplacian Press, 1998) The method and the liquid contact charging method can be applied. In the present invention, it is particularly preferable to use a corona discharge method or an electron beam collision method.
FIG. 13 shows a schematic diagram of a corona charger. In the corona charging device, a corona needle 72 and an electrode 73 are arranged to face each other, and a high voltage is applied between the corona needle 72 and the electrode 73 by a DC high-voltage power supply device 71 (for example, HAR-20R5; manufactured by Matsusada Precision Co., Ltd.). Can be applied. A grid 74 is disposed between the corona needle 72 and the electrode 73, and a grid voltage can be applied to the grid 74 from a grid power supply 75. In order to stabilize the charge injected into the pattern film, the hot plate 76 can heat the pattern film during the charge injection process to a glass transition temperature or higher. Reference numeral 77 is an ammeter. A substrate on which a pattern film is formed is placed on the electrode 73 of the corona device, heated by a hot plate 76, a grid voltage is applied from the grid power supply 75 to the grid 74, and a corona is applied by the DC high voltage power supply device 71. A high voltage is applied between the needle 72 and the electrode 73. As a result, the negative ions discharged from the corona needle 72 are made uniform by the grid 74 and then poured onto the pattern film on the surface of the glass substrate 61 placed on the electrode 73 to inject charges.
A high voltage of about −5 to −20 kV is applied to the corona needle 72 to charge the corona. The electret material on the mover charged by the above method maintains a permanent charge with a surface charge density of −1 to −2 mC / m 2.
Thus, by providing the insulating layer 60 between the individual electrode 6A of the pattern of the electret material and the conductive layer 3B formed on the substrate 3A via the conductive layer 3B, the opposing surface 6A1 of the individual electrode 6A is formed. The electric field can be efficiently formed between the counter electrodes 5A to 5C and the individual electrodes 6A, away from the conductive layer 3B on the rotor 3. Thereby, even if the distance D between the stator 2 and the rotor 2 is separated, the electric field strength is not weakened, and the torque of the electrostatic motor 1 can be increased.
In the present embodiment, since the conductive layer 3B is grounded, the potential of the conductive layer 3B is fixed at 0V, the potential of the individual electrode 6A does not change, and the charged state of the individual electrode 6A is stabilized. For this reason, voltage control when used as the electrostatic motor 1 can be easily performed. In addition, when the electrostatic motor is an axial gap type, the pattern electrodes 5 and 6 are formed on a flat surface, so that the production is easy. For A key tangential gap Furthermore, as a pair of stator 2 and the rotor 3, by increasing the number of these stacked, it is possible to increase the driving torque. That is, the driving torque can be easily increased by stacking a plurality of stators 2 and rotors 3 as a pair.

Next, another embodiment of the mover will be described.
In the rotor 3 shown in FIG. 5, the insulating layer 60 is interposed between the conductive layer 3 </ b> B on the substrate 3 </ b> A and the individual electrode 6 </ b> A made of the electret material, but in the embodiment shown in FIG. The individual electrode 6A is formed of an electret material so as to cover the side surfaces of the individual electrode 6A, and the individual electrode 6A and the conductive layer 3B are connected to each other.
In the embodiment shown in FIG. 6, since the conductive layer 3B of the rotor 3 is grounded, the potential of the conductive layer 3B is fixed at 0V, and the potential of the individual electrode 6A of the electret material does not vary, and the individual electrode 6A The charged state of becomes stable. For this reason, when such a rotor is applied to the electrostatic motor 1 shown in FIG. 1, voltage control can be easily performed. In the case of the configuration shown in FIG. 6, the individual electrode 6 </ b> A is formed so as to cover the side surface of the insulating layer 60 by adjusting the mask size of the photoresist when ashing the cytop with ozone plasma using the photoresist as a mask. There is also an advantage that can be easily manufactured.
In the rotor 3 shown in FIG. 6, the individual electrode 6 </ b> A and the conductive layer 3 </ b> B are made to communicate with each other so as to cover the insulating layer 60 with the individual electrode 6 </ b> A, but the rotor 3 in the embodiment shown in FIG. The individual electrode 6A was formed on the upper portion, and the conductive portion 9 for allowing the individual electrode 6A and the conductive layer 3B to communicate with each other was formed on the conductive layer 3B.
Even in this configuration, since the conductive layer 3B of the rotor 3 is grounded, the potential of the conductive layer 3B is fixed at 0V, and the potential of the individual electrode 6A of the electret material does not fluctuate. The charged state of becomes stable. For this reason, when such a rotor 3 is applied to the electrostatic motor 1 shown in FIG. 1, voltage control can be easily performed.

The production of the structure of the rotor 3 shown in FIG. 7 will be described.
After forming the pattern of the negative resist SU8 of the insulating layer 60, a metal film such as aluminum is formed to a thickness of about 0.1 to 1 μm by a method such as vapor deposition. A photoresist TSMR-8800 (manufactured by Tokyo Ohka Kogyo Co., Ltd.) is formed on the aluminum film by spin coating, and the photoresist is exposed and developed to form a photoresist pattern. Using the photoresist pattern as a mask, a predetermined portion of the aluminum film is removed with an aluminum etching solution (manufactured by Tokyo Ohka Kogyo Co., Ltd.). Further, the photoresist TSMR-8800 is removed with a solvent or the like, and the side surface of the negative resist SU8 of the insulating layer 60 is covered with the conductive layer 9. Thereafter, in the same manner as the manufacturing method described with reference to FIG. 5, formation of Cytop EGG-811 (manufactured by Asahi Glass Co., Ltd.), formation of photoresist TSMR-8800 (manufactured by Tokyo Ohka Kogyo Co., Ltd.), exposure and development are performed. The structure shown in FIG. 7 can be manufactured by ashing the cytop with ozone plasma and removing the photoresist TSMR-8800.

  In the above embodiment, in order to increase the distance d1 between the opposing surface 6A1 of the individual electrode 6A and the conductive layer 3B, the insulating layer 60 is provided between the individual electrode 6A and the conductive layer 3B, and the position of the opposing surface 6A1 is raised from the conductive layer 3B. Thus, the gap distance d between the opposing surface 5A1 and the opposing surface 6A1 of the individual electrode 5A is reduced. In order to raise the position of the facing surface 6A1 from the conductive layer 3B, it is not always necessary to provide the insulating layer 60. For example, as shown in FIG. 8, a plurality of individual electrodes 6A having a predetermined thickness are stacked to form a conductive layer. You may form so that the position of 6 A1 of opposing surfaces may be separated from 3B. That is, a plurality of individual electrodes 6A having a predetermined thickness may be stacked to increase the distance d1 between the opposing surface 6A1 and the conductive layer 3B, and the gap distance d between the opposing surface 5A1 and the opposing surface 6A1 of the individual electrode 5A may be reduced. .

  In this embodiment, the pattern electrode 6 of the axial gap type rotor 3 is an electret. However, the embodiment using the pattern electrode 6 of the electret is not limited to such a form, and other forms of static electricity are used. You may apply to an electric motor.

Next, the inventors examined the influence of the thickness of the electret electrode (individual electrode 6A) on the electric field between the individual electrode 6A and the individual electrode 5A in a three-dimensional electric field simulation using a computer. The electret electrode is simply referred to as an electret.
Two methods are conceivable for generating a strong electric field with the electret.
• Use materials with high surface charge density.
-Increase the thickness of the electret.
Realizing high surface charge density depends largely on the material, so here we consider increasing the thickness of the electret.
(Analysis conditions)
1. Electret Thickness FIG. 14 shows a three-dimensional electric field simulation model. Table 1 shows analysis setting conditions.

The total length of the model is x = 1800 μm, height y = 560 μm + electret thickness, width z = 500 μm. As the boundary conditions, the upper and lower boundaries are set to 0 V, and the left and right boundaries are set to symmetrical boundaries. The stator has a three-phase electrode disposed on a glass epoxy, and the rotor has an electret disposed on a metal. The GAP bracket between the stator and rotor is fixed to 50 μm, and the thickness of the electret is changed. The vertical electric field strength Ey acting on the air layer at that time was compared.
The analysis result is shown in FIG.
FIG. 15 shows the relationship between the thickness of the electret and the electric field strength. In FIG. 15, the vertical axis represents the vertical maximum electric field strength Ey (kV / mm), and the horizontal axis represents the electret thickness t (μm).
From this analysis result, when the thickness of the electret is increased, the electric field strength can be increased while keeping the gap between the stator and the rotor constant.

However, it is not practical to actually apply a thick CYTOP (electret material) on a metal substrate. Therefore, a method of applying a thick insulating layer of SU-8, which is an insulating material for photoresist, which can be manufactured relatively easily with a high aspect ratio, as an insulating layer, and applying CYTOP (electret material) thereon was studied. Here, it was examined in the simulation whether the electric field strength is affected by the difference between the following three methods.
(Analysis conditions)
SU-8 method study model (1). SU-8 (insulating layer) thickness 50μm + electret (CYTOP) thickness 10μm
(2). Single electret thickness 60μm (default)
(3). Electret single unit thickness 10μm (default)
Note that the simulation uses almost the same model as in FIG. In this simulation, the surface charge density of the electret was set to -0.3 mC / m ² and the voltage of the three-phase electrode was set to 150 V in consideration of the dielectric breakdown strength of air.

FIG. 16 shows the analysis result of the SU-8 method study model.
In FIG. 16, the vertical axis represents the electric field strength (kV / mm), and the horizontal axis represents the distance in the X direction (μm). In FIG. 16, the electric field strength is as follows in descending order.
Electret single unit 60 μm (2)> SU-8 50 μm + Electret 10 μm (1)> Electret 10 μm (3)
The combination of SU-8 + electret in (1) is slightly inferior to the electret single body of 60 μm in (2), and it can be said that there is no problem with the electric field strength.
In FIG. 16, the electric field strength distribution due to the difference in the rotor manufacturing process is also shown. In FIG. 16, symbol Ey indicates the electric field strength (attraction and repulsive force) in the vertical direction, and Ex indicates the electric field strength in the horizontal direction.

FIG. 17 shows electric field vector diagrams comparing the respective construction methods. In FIG. 17, the electric field strength is shown in the electric field strength display unit 200 by changing the color. The electric field strength indicates the electric field strength at which the other end 200b of the electric field strength display unit 200 is stronger than the one end 200a.
As a result, the electric field strength is larger in (1) SU-8 50 μm + electret 10 μm and (2) electret 60 μm than in (3) electret single 10 μm.
The single electret (3 μm) of (3) appears to have a repulsive force near the surface charge density of −0.3 mC / m 2 and the electrode of −150 V, but the SU-8 of (1) 50 μm + the electret of 10 μm, the electret of (2) When the single unit is 60 μm, an attractive electric field is drawn to the electret side.
Since this is an attractive electric field, care must be taken when switching. To generate a repulsive force, it is preferable to apply a voltage higher than −150 V to the electrode side in accordance with the electric field strength.

Considering the fact that the electric field strength increases as the thickness of the electret increases, the capacitor model shown in FIG. 18 was used.
As shown in FIG. 18, it is assumed that the dielectric holds the surface charge Qs and the dielectric surface potential Vs. Here, the charge Q of the capacitor can be expressed by the following formula 1 from the capacitance C and the voltage V.

  When the area Ca is constant and the capacitance Ca on the air side and the capacitance Cb on the dielectric side are defined, Equations 2 and 3 below are obtained.

  In Equation 2 and Equation 3, the dielectric constant ε0 in vacuum, the dielectric constant ε of the dielectric, the gap g, and the thickness d of the dielectric are shown.

  Next, when the dielectric surface potential Vs is defined using the surface charge Qs and Equations 2 and 3, Equation 4 is obtained.

  Thus, the electric field strength E can be defined by Equation 5 using the dielectric surface potential Vs and the gap g.

  Here, if ε = g = 1, Equation 5 is expressed as the following Equation 6.

When the thickness of the dielectric is changed using Equation 6, Equation 7 and Equation 8 are obtained.
When the dielectric thickness d = 1

  In case of dielectric thickness d = 2

Therefore, as shown in Equations 7 and 8, it can be seen that increasing the thickness of the dielectric increases the electric field strength. For this reason, when the thickness of the electret is increased, the electric field strength increases, and the construction method using SU-8 has no practical problem from the viewpoint of the electric field strength.
That is, the individual electrode 6A may be formed by laminating the individual electrode 6A on the conductive layer 3B, or the electric field strength may be reduced even if the individual electrode 6A is formed on the conductive layer 3B via the insulating layer 60. Can be suppressed.

(Second Embodiment)
Next, a second embodiment will be described with reference to FIG. The second embodiment shows a radial gap type electrostatic motor 10 as an electrostatic motor. As shown in FIG. 9, the electrostatic motor 10 includes a stator 12 serving as a cylindrical stator and a columnar rotor 13 serving as a mover disposed in the stator 12. The stator 12 and the rotor 13 are arranged so as to have a gap D in the radial direction, and are configured so that the pattern electrode 15 and the pattern electrode 16 formed as a strip electrode do not contact each other. The pattern electrode 15 extends in the line direction and is formed by patterning a plurality of metal electrodes in the circumferential direction of the inner peripheral surface 12A of the insulating stator 12, and a three-phase wiring line is formed on each individual electrode. It has been broken. In the example of FIG. 9, only one set of wiring of U, V, and W is illustrated. In the present embodiment, the individual electrode that becomes the U electrode by the U wiring is denoted by reference numeral 15A, the individual electrode that becomes the V wiring and becomes the V electrode is denoted by reference numeral 15B, and the W wiring is formed. Thus, the individual electrodes to be the W electrodes are identified by reference numeral 15C.
A pattern electrode 16 made of a plurality of electret materials is formed on the outer peripheral surface 13A of the cylindrical rotor 13 having an insulating layer. The pattern electrode 16 has a plurality of individual electrodes 16A extending in the axial direction by metal on the outer peripheral surface 13A and formed in the circumferential direction. A single-phase wiring 7 is connected to the slip ring 8 and driven to each individual electrode 16A. They are connected via a shaft 14. In this embodiment, a metal drive shaft 14 is mounted at the rotation center of the rotor 13, and the drive shaft 14 and the metal electrode 16A are in contact with each other inside the rotor.

In such a configuration, a three-phase alternating current is supplied to the individual electrodes 15A, 15B, and 15C of the stator 12, and the individual electrode 16A of the rotor 13 is set to a negative pole, and the poles of the individual electrodes 15A, 15B, and 15C are sequentially switched. Thus, static Coulomb force acts between the stator 12 and the rotor 13. This Coulomb force generates an attractive force between the individual electrode on the stator side that is a positive pole with respect to the negative pole of the individual electrode 16A of the rotor 13, and between the individual electrode on the stator side that is a negative pole. Repulsive force is generated. For this reason, the stator 13 can be moved in the switching direction of the poles of the individual electrodes 15A, 15B, and 15C, that is, the direction in which the combined magnetic field of the electric field generated in each phase changes its direction. Further, as in the present embodiment, since each individual electrode 16A of the pattern electrode 16 of the rotor 13 is a single pole, the power feeding means to the rotor 13 can be simplified, and the number of parts of the drive driver can be reduced. It becomes easy to reduce the size. Further, it is possible to obtain a larger amount of electrostatic Coulomb force between the pattern electrodes 15 and 16 than when the power is not supplied to the rotor 13 and to obtain a sufficient driving force.
In the axial gap type as in the first embodiment, when the electrode pattern 5A is formed radially, the pitch is variable because the lengths of the inner periphery and the outer periphery are different, but in the radial type as in the present embodiment, the pitch is variable. Is not variable and easy to assemble. In the case of the radial gap type, the torque can be increased by increasing the length of each electrode in the axial direction. The pole switching control for the individual electrodes 15A, 15B, and 15C will be described later.

The individual electrode 16A composed of the electret material of the rotor 13 having the above-described configuration is formed on the outer peripheral surface 13A of the rotor 13 via the conductive layer 3B, like the individual electrode 6A of the rotor 3 described above. Then, by providing the insulating layer 60 between the individual electrode 16A and the conductive layer 3B, the opposing surface of the individual electrode 16A is separated from the conductive layer 3B on the rotor 13, and between the counter electrodes 15A to 15C and the individual electrode 16A. An electric field can be efficiently formed. Thereby, even if the distance D between the stator 12 and the rotor 13 is separated, the electric field strength is not weakened, and the torque of the electrostatic motor 10 can be increased.
Further, the conductive layer 3B is grounded, and the conductive layer 3B and the individual electrode 16A are connected to each other through the conductive layer 9, so that the potential of the conductive layer 3B is fixed at 0V, and the potential of the individual electrode 16A is also set. There is no fluctuation and the charged state of the individual electrode 16A is stabilized. For this reason, voltage control when used as the electrostatic motor 10 can be easily performed.

(Third embodiment)
Next, a third embodiment will be described with reference to FIG. In the third embodiment, a linear electrostatic motor 20 is described as an electrostatic motor. The basic configuration is the same as the axial gap type and the radial gap type, and includes a stator 22 as a stator having a pattern electrode 25 as a strip electrode, and a pattern electrode 26 made of an electret material as a strip electrode. The movable element 23 is configured with a gap D therebetween.
In the stator 22, a plurality of pattern electrodes 25 extend in a direction orthogonal to the movable direction on the insulating substrate 22A, and are formed at intervals in the movable direction. The plurality of pattern electrodes 25 formed on the substrate 22A are formed by patterning a plurality of metal electrodes, and three-phase wiring is performed on each individual electrode. In this embodiment, only one set of wirings of U, V, and W is illustrated. In this embodiment, the individual electrode that becomes the U electrode by the U wiring is denoted by reference numeral 25A, the individual electrode that becomes the V wiring and becomes the V electrode is denoted by reference numeral 25B, and the W wiring is formed. Thus, the individual electrodes to be the W electrodes are identified by the reference numeral 25C.
The movable element 23 is formed by extending a plurality of individual electrodes 26 </ b> A in a direction orthogonal to the movable direction on the insulating substrate 23 </ b> A with an interval in the movable direction. In the pattern electrode 26, a plurality of individual electrodes 26A are formed of metal on a substrate 23A, and a single-phase wiring 7 is connected to each individual electrode 26A.

  In such a configuration, a three-phase alternating current is passed through the individual electrodes 25A, 25B, and 25C of the stator 22, the individual electrode 26A of the mover 23 is set as a negative pole, and the poles of the individual electrodes 25A, 25B, and 25C are sequentially set. By switching, static Coulomb force acts between the rotor 22 and the mover 23. This Coulomb force generates an attractive force between the individual electrode on the stator side that is a positive pole with respect to the negative pole of the individual electrode 26A of the mover 23, and between the individual electrode on the stator side that is a negative pole. Repulsive force is generated. For this reason, the mover 23 can be moved in the switching direction of the poles of the individual electrodes 25A, 25B, and 25C, that is, the direction in which the combined magnetic field of the electric field generated in each phase changes its direction. Moreover, since each individual electrode 26A of the pattern electrode 26 of the mover 23 is a single pole as in the present embodiment, wiring to the mover 23 can be simplified, so that the electrostatic motor 20 and the application are applied. Therefore, it is possible to reduce the size and weight of the drive driver. More electrostatic coulomb force between the pattern electrodes 25 and 26 can be obtained than when no power is supplied to the mover 23, and a sufficient driving force can be obtained.

  The linear type electrostatic motor is characterized in that the dimensional accuracy of the electrode patterns 25 and 26 can be relaxed and is relatively easy to manufacture as compared to the axial gap type and radial gap type which are rotary types. In the case of such a linear electrostatic motor 20, the power feeding means to the mover 23 can be simplified and the number of components of the drive driver can be reduced, so that it is easy to reduce the size. Moreover, it is also possible to produce the rotor 22 and the needle | mover 23 by using a polyimide film as a base material.

The individual electrode 26A composed of the electret material of the mover 23 having such a configuration is replaced with the individual electrode 26A via the conductive layer 3B on the substrate 23A of the mover 23 like the individual electrode 6A of the rotor 3 described above. By forming the insulating layer 60 between the individual electrode 26A and the conductive layer 3B, the opposing surface of the individual electrode 26A is separated from the conductive layer 3B on the mover 23, and the counter electrodes 25A to 25C and the individual electrode 26A are separated. An electric field can be efficiently formed between them. Thereby, even if the distance D between the stator 22 and the mover 23 is separated, the electric field strength is not weakened, and the torque of the linear electrostatic motor 20 can be increased.
Further, the conductive layer 3B is grounded, and the conductive layer 3B and the individual electrode 26A are connected to each other through the conductive layer 9, so that the potential of the conductive layer 3B is fixed at 0V, and the potential of the individual electrode 26A is also set. There is no fluctuation, and the charged state of the individual electrode 26A is stabilized. For this reason, voltage control when used as the linear electrostatic motor 20 can be easily performed.

Next, an embodiment of polarity switching control, which is the driving principle of the electrostatic motor described above, will be described.
(Fourth embodiment)
FIG. 11A schematically shows the individual electrodes of the stator and the mover, and the voltage application state to each individual electrode, and FIG. 11B shows the switching pattern of the voltage applied to the stator. . In this embodiment, the mover (rotor) side has one phase, and the stator side applies a three-phase AC voltage. Then, the ratio of the number of individual electrodes of the stator and the mover is made different on the stator side larger than the mover side. In the example of FIG. 11, the individual electrodes of the stator are 450 poles, and the individual electrodes of the mover are 300 poles. FIG. 11A shows a state where the rotation angle is 0 ° and the rotation angle is 0.6 °.
In this embodiment, the electret electrode of the mover is in a charged state. In the present embodiment, the electret electrode of the mover is charged to the negative pole (minus pole), but can be charged to the positive pole (plus pole).
As shown in FIG. 11 (b), the stator side supplies power to a three-phase alternating current, and at a predetermined angle (here, 0.1 °), a positive electrode with respect to the V electrode, the W electrode, and the U electrode, 0 The polarity switching control of the electrode is performed on the negative electrode. The predetermined angle is not limited to 0.1 °.

When each individual electrode is defined in this way, an attractive force is generated between the positive pole of the stator and the negative pole of the mover. At the same time, repulsive force is generated between the −pole of the stator and the −pole of the mover. An attractive force is generated between the zero of the stator and the negative pole of the mover, but is smaller than the attractive force generated between the positive pole of the stator and the negative pole of the movable element. In the example of FIG. 11A, the mover moves to the right using these attractive force and repulsive force (electrostatic Coulomb force). In this way, by switching the voltage applied to the stator electrodes to +, 0, and − for each angle so as to control the polarity switching, the mover continuously moves in the right direction. That is, in the polarity switching control shown in FIG. 11, since both repulsive force and attractive force are used as driving force, a sufficient driving force can be obtained.
By applying this polarity switching control to each of the electrostatic motors shown in the first and second embodiments, the drive shafts 4 and 14 can be continuously driven to rotate, which is shown in the third embodiment. By using it for the electrostatic motor 20, it becomes possible to continuously drive a linear electrostatic motor other than the motor.
By adopting such a driving method of the electrostatic motor, it is possible to drive even if the mover is a single phase, so that it is possible to achieve a practically sufficient driving torque and rigidity, while being small, light and thin. An electrostatic motor can be realized.

(Fifth embodiment)
Another embodiment of the polarity switching control will be described with reference to FIG.
FIG. 12 schematically shows the individual electrodes of the stator and the mover, and the voltage application state to each individual electrode. In this embodiment, the mover (rotor) side has one phase, and the stator side applies a pulse voltage. The ratio of the number of individual electrodes of the stator and the mover is made different by making the mover side larger than the stator side. In the example of FIG. 12, the individual electrode of the stator has 450 poles and the individual electrode of the mover has 600 poles. FIG. 11 shows a state where the rotation angle is 0 ° and the rotation position is 0.2 °.
In this embodiment, the electret electrode of the mover is in a charged state. In the present embodiment, the electret electrode of the mover is charged to the negative pole (minus pole), but can be charged to the positive pole (plus pole).
The stator side supplies power to the pulse voltage, and here, with respect to the V electrode, the W electrode, and the U electrode, it is initially set as a positive pole, a negative pole, and a negative pole, and after moving a first predetermined angle (0.15 °). The polarity switching control of the electrode is performed to be + pole, + pole, and −pole, and when the second predetermined angle (0.2 °) is reached, the polarity switching control of the electrode is performed to be −pole, + pole, and −pole. .

When each individual electrode is defined in this way, an attractive force is generated between the positive pole of the stator and the negative pole of the movable element, and the movable element moves to the right in the drawing using this attractive force. In this way, by switching the voltage polarity switching control to the individual electrodes of the stator, the mover continuously moves in the right direction. That is, in the polarity switching control shown in FIG. 11, only the attractive force is used as the driving force. In the case of this embodiment, the driving torque is increased by increasing the number of poles on which the positive pole of the stator and the negative pole of the mover face each other and the attractive force acts, thereby obtaining a sufficient driving force. Can do.
By applying this polarity switching control to each of the electrostatic motors shown in the first and second embodiments, the drive shafts 4 and 14 can be continuously driven to rotate, which is shown in the third embodiment. By using it for the electrostatic motor 20, it becomes possible to continuously drive the linear electrostatic motor other than the motor.

Next, the driving force of the electrostatic motor will be described.
Here, Equations 9 and 10 for obtaining the propulsive force Fxtotal and the average torque T of the electrostatic motor are described below.
ε0: dielectric constant of air G: gap between stator and mover [mm]
L: Electrode length [mm]
V: Applied voltage [V]
N: Number of electrodes (stator and mover)
t: Number of layers (stator and mover)
r: outer radius [mm]
r0: inner radius [mm]

From the above formulas 9 and 10, the following methods can be considered to increase the torque.
(1) Increase the voltage.
(2) Increase the number of electrodes and the number of stacked layers formed on the substrate of the stator or mover.
(3) Narrow the gap between the stator and mover.
(4) Increase the length of each individual electrode.
The method of increasing the voltage in (1) is the most effective way to increase the driving torque, but there are problems of dielectric breakdown and an increase in the size of the driving driver. For this reason, the applied voltage can be raised only by about 1 kV at the maximum. Further, the method (3) for narrowing the gap between the stator and the mover is difficult from the viewpoint of mechanical tolerances and blurring at the time of rotation, and even if it can be realized, the cost is greatly increased. Increasing the length of each individual electrode in (4) increases the size of the electrostatic motor.
From this point of view, the method (2) of increasing the number of individual electrodes and the number of stacked layers formed on the stator or mover substrate is preferable in order to increase the driving torque while realizing miniaturization of the electrostatic motor. In addition, as described above, by providing an insulating layer between the individual electrode and the conductive layer of the electret material pattern formed on the movable member substrate via the conductive layer, the individual electrode is placed on the rotor. The distance from the conductive layer is increased, and an electric field can be efficiently formed between the opposing electrode and the individual electrode. Thereby, even if the distance between the stator and the mover is increased, the electric field strength is not weakened, and the torque of the electrostatic motor can be increased. That is, the output torque can be improved without reducing the distance (D) between the mover and the stator (the gap distance d between the electret electrode and the counter electrode).

1,10 Electrostatic motor (electrostatic motor)
2, 12, 22 Stator (stator)
3,13 Rotor (mover)
5, 15, 25 Plural strip electrodes 6, 16, 26 Plural strip electrodes made of electret material 5A1 Opposing surface (surface of strip electrode)
6A1 Opposite surface (surface of strip electrode)
Distance d2 insulation between 20 static denden motive 23 mover 3A substrate 3B conductive layer 3B1 substrate surface 60 insulating layer d the distance d1 substrate surface and the strip electrodes surface with the surface of the strip electrode surface and the stator of the strip electrodes of the movable element Layer thickness D Distance between stator and mover

JP-A-6-311763 JP 2012-257368 A

Claims (7)

A stator having a plurality of strip-shaped electrodes that are insulated from each other, arranged in a predetermined direction and at a predetermined interval, and a movable having a plurality of strip-shaped electrodes made of electret material, arranged so as to face the stator In an electrostatic motor that applies a predetermined voltage to a child and a strip-like electrode of the stator, and moves the mover by electrostatic coulomb force acting between the electrodes of the stator and the mover,
By increasing the distance from the substrate surface to dispose the strip-shaped electrodes made of electret material of the movable element to the surface of the strip-shaped electrodes, the electric field from the strip electrodes in conjunction with the action to strip electrodes of said stator,
The distance from the surface of the substrate on which the belt-like electrode is disposed to the surface of the belt-like electrode is d1, and the distance from the surface of the belt-like electrode of the mover to the surface of the belt-like electrode of the stator located on the side facing the surface D1> d, where d is an electrostatic motor. The static distance according to claim 1, wherein the distance d1 is formed by interposing an insulating layer thicker than the belt-like electrode of the mover between the belt-like electrode of the mover and the substrate. Electric motor. The distance d1 is an electrostatic motor according to claim 1 or 2, characterized in that it is formed by laminating the strip electrodes of said movable element. The substrate has a conductive layer on its surface;
Strip electrodes of said movable element, an electrostatic motor according to claim 1 or 2, characterized in that it is formed through an insulating layer on the conductive layer. The electrostatic motor according to claim 4, wherein the conductive layer is grounded . The electrostatic motor according to claim 4 , wherein the belt-like electrode of the mover and the conductive layer are grounded. It said pair of stator and said mover, an electrostatic motor according to any one of claims 1 to 6, characterized in that it is stacked.

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