JPH07143764A - Electrostatic actuator and its driving method - Google Patents

Abstract

PURPOSE:To obtain high output by providing a radial bearing, having the rotary side and the fixed side which come into contact with each other and connected electrically during stoppage whereas separated from each other during rotation, with a charging electrode forming a capacitor between the rotor electrode and the stator electrode at the shaft end part of rotor. CONSTITUTION:When positive and negative voltages are applied to a stator electrode 7 and a charging electrode 6, respectively, from a power supply section through lead wires 12, 13 while being controlled by a control circuit 11 under stationary state, the electrode of a rotor 2 is charged negatively whereas the stator electrode 7 is charged positively because an aerodynamic radial bearing 4 and the charging electrode 6 are conducting through contact. When the application of charging voltage is interrupted and a three-phase driving voltage is applied to the stator electrode 7, the rotor 2 is rotated. When the rotational speed is increased, noncontact supporting of the rotor 2 is realized by means of the aerodynamic radial bearing 4 and a thrust bearing 5 and the rotation is sustained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic actuator used in micromachines and the like and a driving method thereof.

[0002]

2. Description of the Related Art A conventional electrostatic actuator has a structure in which electrodes are arranged at a constant interval on an inner peripheral portion of a stator, and rotor electrodes are arranged at a predetermined interval with respect to the stator electrode, for example, pitch 3/4. There is. Since this electrostatic actuator needs to generate an electric field between the rotor and the stator, a voltage is constantly applied to the rotor electrode, and in this state, a driving voltage is sequentially applied to the rotor electrode to drive the rotor. Was there. As a method of constantly applying a voltage to the rotor electrode, a method of connecting a conductive wire directly to obtain conduction, a method of slidingly contacting the electrode, a method of ensuring conduction with a sliding bearing, etc. have been taken (for example, Japanese Patent Laid-Open Publication No. Sho. 63-95858, JP-A-4-96669).

[0003]

However, in the conventional method of attaching the direct conductive wire, the conductive wires interfere with each other, so that the rotation speed is limited and the output torque is lowered. Not only does the structure become complicated, but wear and friction increase due to contact, which reduces output torque and causes damage. In addition, in the method of ensuring continuity in the bearing part, non-contact bearings such as air bearings and magnetic bearings to reduce frictional resistance, and bearings made of non-conductive solid lubricant when used in special environments such as vacuum There was a problem that it could not be used. Furthermore, the output torque is 2 of the drive voltage.
Since it is proportional to the power, the voltage must be increased to obtain a relatively large force. Therefore, there is a problem that the controller and the power supply device cannot be downsized and cannot be used as an actuator of a micromachine. Therefore, an object of the present invention is to provide a small-sized electrostatic actuator which is free from interference by a conductive wire, can use a non-contact bearing, and can obtain a high output with a small driving voltage.

[0004]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a cylindrical rotor having a plurality of convex rotor electrodes arranged at a constant pitch, and a predetermined rotor electrode pitch. In an electrostatic actuator including a cylindrical stator in which a plurality of stator electrodes having the above relationship are arranged, a bearing that supports the rotor, and a power supply unit that is connected to the rotor electrode and the stator electrode by conductors respectively, When the charging electrode that forms a capacitor between the rotor electrode and the stator electrode is stopped at the main body or the shaft end, the rotating side and the fixed side are in contact with each other when they are stopped, and they are electrically conducting. The radial bearing is insulated from the above. In order to drive this electrostatic actuator, a voltage is applied between the charging electrode and the stator electrode to form a capacitor between them, and then a driving voltage is applied to the stator electrode to drive it. In addition,
It is more effective if the voltage for charging the capacitor of the charging electrode is higher than the drive voltage of the stator.

[0005]

Since the charging electrode is provided by the above means,
When a voltage is applied between the charging electrode and the stator electrode, a capacitor is formed between the rotor electrode and the stator electrode, and the convex portion of the rotor electrode has a high charge density. When a positive voltage is applied to the stator electrode in this state, excess charge in the rotor is attracted to the stator electrode and concentrates on the protrusions of the rotor electrode, attracting force between the stator electrode and the rotor electrode, and causing the rotor to rotate. receive. The electrode for applying the voltage is the R phase,
The rotor rotates by sequentially switching between the S phase and the T phase. Since the rotor is separated from the conductive wire in this way, it does not interfere with each other and rotates smoothly, and there is no loss of thrust.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. First Embodiment FIG. 1 is a side sectional view of an electrostatic actuator showing a first embodiment of the present invention, and FIG. 2 is a sectional view taken along the line AA ′ in FIG. In the drawing, 1 is a cylindrical stator, 2 is a rotor, 3 is a rotary shaft provided integrally with the rotor 2, 4 is a radial bearing using dynamic pressure air that supports the rotary shaft 3, and 5 is axial support. A thrust bearing using dynamic air, 6 is a charging electrode, 7 is a stator electrode of the stator 1, 8 is an insulator that insulates the stator electrodes from each other, 10 is a power supply unit, and 11 is a control circuit including a switching circuit. Reference numeral 12 is a conductor wire that connects the stator electrode 7 and the power supply unit 10. In the stator 1, stator electrodes 7 are arranged inside a cylindrical casing made of an insulating material at a constant pitch in the circumferential direction with an insulator 8 interposed therebetween. The rotor 2 is made of a light metal such as aluminum, and a plurality of rotor electrodes 21 having a single-phase convex shape are arranged on the surface of the rotor 2, which is integrated with the rotating shaft. The surface of the rotor electrode 21 is covered with an insulating film (not shown) to prevent short circuit and dielectric breakdown due to contact with the stator electrode. The charging electrode 6 is provided on the outer peripheral portion of the radial bearing 4, and is connected to the power supply unit 10 by a conductor 13 (G ₁ ). Next, the operation will be described with reference to FIG. 3 which is a schematic diagram showing the connection wiring for voltage application and charge distribution, and FIG. 4 which is a pattern diagram of the applied voltage. First, the charging state in which the stator 1 and the rotor 2 are charged is shown in the "charging" portion of FIG. 3 (a) and FIG. When the actuator is stationary, the control circuit 11 controls the power supply unit 10 to connect the conductor 1
A positive voltage is applied to the stator electrode 7 via 2 and a negative voltage is applied to the charging electrode 6 via the lead wire 13 (G ₁ ). The radial bearing 4 and the charging electrode 6 are electrically connected by contact. Therefore, the rotor electrode 21 is charged with a negative (−) electric charge, and the stator electrode 7 is charged with a positive (+) electric charge. Next, the state of driving the rotor after charging is shown in FIG. 3 (b) and the portion of "driving the rotor" in FIG. The voltage application to the stator electrode 7 and the charging electrode 6 is stopped, and the driving voltage is applied to the stator electrode 7. As a result, the electric charges on the surface of the rotor electrode 21 are concentrated on the electric field between the rotor electrode 21 and the stator electrode 7, and an electrostatic force is generated. Drive voltage is square wave, 1
The R, S, and T phases that are different in phase by 20 degrees are slightly overlapped so that a voltage is always applied to some electrode. By using this voltage pattern, the rotor 2 can be continuously rotated. When the rotation speed of the rotor 2 increases, the rotor 2 is supported in a non-contact manner by the radial bearing 4 and the thrust bearing 5 using dynamic pressure air. Although the rotor 2 is insulated from the surroundings, the rotor 2
The rotational force is continuously applied by the (-) charge trapped inside. By supporting the rotor in a non-contact manner as described above, the conductor wire is not directly connected, so that friction loss can be eliminated and an efficient actuator can be obtained. Further, by increasing the capacitance of the charging electrode, the voltage applied during driving can be suppressed to a low level without reducing the output. In this embodiment, light metal is used as the material of the rotor 2, but synthetic resin may be used instead of the metal, and the entire surface of the rotor body and the rotary shaft may be covered with a metal film. In this case, since the weight can be reduced, the driving force can be further improved. Second Embodiment FIG. 5 is a side sectional view of an electrostatic actuator showing a second embodiment of the present invention, and FIG. 6 is a pattern diagram of its applied voltage.
In addition to the charging electrode 6 of the first embodiment, the thrust bearing 5 is used to form the auxiliary capacitor electrode 91 for forming the auxiliary capacitor 9. The charging electrode 6 is connected to apply a negative voltage (G ₁ ) and the auxiliary capacitor electrode 91 is applied to apply a positive voltage (G ₂ ). First, the thrust bearing 5 is operated to bring the rotating side and the fixed side into non-contact with each other. Thereafter, the voltage for charging is supplied from the power supply unit 10 to the stator electrode 7 and the auxiliary capacitor electrode 91 by the control circuit 11.
To the charging electrode 6 and a negative voltage to the charging electrode 6. Then, capacitors are formed both between the stator electrode 7 and the rotor electrode 21 and between the fixed side 51 and the rotating side 52 of the thrust bearing 5. That is, (+) charges are excited on the fixed side 51 of the stator electrode 7 and the thrust bearing 5, and (−) charges are excited on the rotating side 52 of the rotor electrode 21 and the thrust bearing 5. This (−) charge is accumulated on the rotor electrode 21. In this state, the rotor 2 can be continuously rotated by sequentially applying a voltage to the three-phase stator electrode 7 as in the first embodiment. During rotation, the rotor 2 is supported by the radial bearing 4 in a non-contact manner. Third Embodiment FIG. 7 is a side sectional view of an electrostatic actuator showing a third embodiment of the present invention. This is one in which the auxiliary capacitor of the second embodiment is formed on the end surface of the rotor 2 and the bearing holding portion 11 of the stator 1. A donut disk-shaped auxiliary capacitor electrode 9 is formed on the inner surface of the bearing holding portion 11 and is connected to the power supply portion 10 so as to apply a positive voltage (G ₂ ). The operation is similar to that of the second embodiment. In addition,
Although the radial gap electrostatic actuator is described in the present embodiment, the present invention can be effectively applied to a wobble type or axial gap type electrostatic actuator. Further, although the air dynamic pressure bearing was used as the non-contact bearing, other dynamic pressure fluid bearings, static pressure bearings, magnetic bearings, and other bearings can be used. Not limited to Further, by making the two power sources for charging and driving separate, it is possible to reduce the size and power consumption of the driving controller and the power source.

[0007]

As described above, according to the present invention, a capacitor is formed between the rotor and the stator before driving, and the conductor is disconnected during driving, or the rotor is rotated by using a non-contact bearing. As a result, the interference of the lead wires and the frictional resistance of the bearing are eliminated, and there is an effect that a compact and high-power electrostatic actuator can be obtained.

[Brief description of drawings]

FIG. 1 is a side sectional view of an electrostatic actuator showing a first embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along the line A-A ′ in FIG.

FIG. 3 is a schematic view showing the operating principle of the present invention.

FIG. 4 is a drive pattern diagram of the first embodiment of the present invention.

FIG. 5 is a side sectional view of an electrostatic actuator showing a second embodiment of the present invention.

FIG. 6 is a drive pattern diagram of a second embodiment of the present invention.

FIG. 7 is a side sectional view of an electrostatic actuator showing a third embodiment of the present invention.

[Explanation of symbols]

 1: Stator 11: Bearing holding part 2: Rotor 21: Rotor electrode 3: Rotating shaft 4: Radial bearing 5: Thrust bearing 51: Fixed side 52: Rotating side 6: Charging electrode 7: Stator electrode 8: Insulator 9: Auxiliary capacitor 91: Auxiliary capacitor electrode 10: Power supply unit 11: Control circuit 12, 13: Conductor

Claims (7)

[Claims] 1. A cylindrical rotor having a plurality of convex rotor electrodes arranged at a constant pitch, and a plurality of stator electrodes having a predetermined relationship with the rotor electrode pitch. An electrostatic actuator comprising a cylindrical stator, a bearing for supporting the rotor, and a power source section connected to the rotor electrode and the stator electrode by conductors respectively, wherein the rotor body is attached to the rotor body or the shaft end portion. An electrostatic actuator comprising a charging electrode for forming a capacitor between an electrode and the stator electrode. 2. The electrostatic bearing according to claim 1, wherein the charging electrode is provided on a radial bearing whose rotating side and fixed side are in contact with each other when the rotor is stopped and which are not in contact with each other when rotating the rotor. Actuator. 3. The electrostatic actuator according to claim 1, wherein an auxiliary capacitor is provided at the shaft end of the rotor in addition to the capacitor. 4. The electrostatic actuator according to claim 3, wherein the auxiliary capacitor is provided in a non-contact thrust bearing. 5. The electrostatic actuator according to claim 3, wherein the capacity of the auxiliary capacitor is larger than the capacity of the capacitor between the rotor electrode and the stator electrode. 6. A cylindrical rotor having a plurality of convex rotor electrodes arranged at a constant pitch, and a plurality of stator electrodes having a predetermined relation to the electrode pitch of the rotor. An electrostatic capacitor that is composed of a cylindrical stator, a bearing that supports the rotor, and a power supply unit that is connected to the rotor electrode and the stator electrode by conductors, and that is driven by sequentially switching the voltage applied to the stator electrode. In the driving method of the actuator, a charging electrode for forming a capacitor between the rotor electrode and the stator is provided on a main body portion or a shaft end portion of the rotor, and a charging electrode between the rotor and the stator electrode is provided. A voltage is applied between the electrodes to form a capacitor therebetween, and then a driving voltage is applied to the stator electrode. How to drive Eta. 7. The method of driving an electrostatic actuator according to claim 6, wherein the charging voltage for charging the capacitor of the charging electrode is set higher than the driving voltage of the stator.