JP2896123B2 - Electrostatic microactuator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic microactuator in which the movement of a moving element is remarkably stabilized by sealing a highly viscous fluid between the moving element and a fixed electrode.

[0002]

2. Description of the Related Art There has been almost no development of electronic and electrical equipment which applies static electricity as a driving force. The most important reason is that the energy density is smaller in order than in electronic and electrical equipment that applies electromagnetism.

[0003] In recent years, it has been found that the problem can be compensated for by making the device itself micro-sized, and the use of static electricity as a drive source for a micro-actuator has been studied recently. However, according to the Arnshaw's theorem that a system using static electricity always has motion instability, some means for obtaining stability in the system is required.

[0004] Therefore, a clutch acting in a direction perpendicular to the moving direction of the moving element in the electrostatic microactuator.
Conventionally, various methods have been proposed for stabilizing the system against the Ron force.

[0005] For example, there is a method of providing a mechanical bearing, but this becomes less feasible and less reliable as the size of the system becomes smaller. In addition, there is a method using magnetic levitation, but this method does not become a predominantly strong magnetic force in a micro region. In this respect, in the method using the Meissner effect by the superconducting substance, the Meissner effect itself is essentially a powerful force in the micro region, but the cost increases due to the preparation of liquid helium, liquid nitrogen or the like. There is also a method of utilizing ultrasonic levitation, but since the wavelength is several mm, there is a problem that the micro size of the system is limited.

[0006]

According to the present invention, a high-viscosity fluid having a high dielectric constant is sealed between a moving element and a fixed electrode, and the moving element is formed into a fluid-stable shape.
An object of the present invention is to provide an electrostatic microactuator which can maintain a stable movement of a moving element even at a low speed of 10 mm / sec or less and can be applied to artificial muscles.

For this reason, in the electrostatic microactuator of the present invention, basically, a high-viscosity fluid is sealed between the movable element and the fixed electrode, and the movable element is formed into a fluid-stable shape, whereby the movable element is formed. When configured to maintain stable movement even at low speeds, multiple movers arranged in the enclosed high-viscosity fluid are arranged in parallel with the required gap so that the directions of movement are opposite to each other Each end of these movers in the same direction is separately supported by supports on both sides, respectively.
The two supports are connected by a spring part, and
It is obtained by configuration so that to expand and contract the support via.

[0008]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. In the electrostatic microactuator according to the present invention, a high-viscosity fluid having a high dielectric constant is sealed between the moving element and the fixed electrode, and the moving element is formed into a fluid-stable shape to move the moving element. The feature is that the stable state of the moving element can be maintained even if the moving velocity of the moving element is not high.

For example, a head of a hard disk drive or the like achieves a relatively stable state by floating the head by increasing the rotation speed of the disk even in a low-viscosity gas. According to the present invention, the same stability as that of the head of a hard disk drive is obtained for the motion stability of a moving element in an electrostatic microactuator by maintaining the Reynolds number of the system in a stable range. It is.

As a practical example, the speed of the moving element is 1 to 10 m.
m / sec, kinematic viscosity of high viscosity fluid is 10-3 m2 / sec
In the case of (1), if the gap is on the order of 100 μm or less, the Reynolds number in the system becomes sufficiently smaller than the critical Reynolds number (〜1000), so that the gap becomes sufficiently laminar and the motion stability of the moving element can be expected. There was found.

FIG. 1 shows an electrostatic microactuator according to the present invention.
FIG. 2 is a diagram for explaining the concept of a heater, in which a fixed body 7 includes a plurality of fixed electrodes 1 and an electrically insulating layer 2, and each fixed electrode 1 is fixedly arranged on one surface of the electrically insulating layer 2. The two fixed bodies 7 are arranged in parallel at a required interval so that the fixed electrodes 1 face each other, and the moving element 6 is arranged between the fixed electrodes 1 arranged facing each other. Mover 6
Is configured to have a plurality of moving element electrodes 4 embedded in the electrically insulating layer 3. An insulating high-viscosity fluid 5 made of silicon-based oil, fluorine-based oil, or the like is sealed in the gap between the opposed fixed electrodes 1 where the movers 6 are arranged.

The moving element 6 can be expected to have a dynamic pressure floating effect by being formed in a step shape or a taper shape so as to have a positive pressure distribution in the gap between the fixed electrode 1 and the moving element 6. The pressure generated in the gap between the fixed electrode 1 and the moving element 6 is
Is a plate-like step shape, as shown in FIG. 2. In the two-dimensional model, a triangular area indicated by oblique lines is a pressure distribution 8 and is a total pressure applied to one surface of the moving element 6.
This total pressure is a function of the gap size, and the system retains the property that the smaller the gap, the greater the total pressure.

[0013] This qualitative phenomenon is understood that when the moving element 6 approaches one of the upper and lower fixed electrodes 1, a force is exerted to push the moving element 6 back to the equilibrium position, which is useful for stabilizing the system. It is. However, the restoring force depends on the electrode 4 of the moving element 6.
It is a requirement that it be greater than the Coulomb force generated between the electrode and the fixed electrode 1. However, this restoring force, which is the sum of the damping force and the dynamic pressure levitation force, increases dramatically as the gap size decreases qualitatively. On the other hand, the order becomes larger. Thus, in the case of microsystems, this requirement is almost always met automatically.

FIG. 3 shows a phase play intended to prove a qualitative phenomenon of the movement of the moving element 6 by stability theory.
FIG. As the analysis conditions in this figure, the size of the moving element 6 is 30 mm × 40 mm, and the average gap size is 7 mm.
0 μm, the viscosity of the fluid 5 is 0.8 Pas, and
The speed of the moving element 6 was 1 mm / sec. The horizontal axis P in FIG. 3 represents the dimensionless position of the moving element 6, the vertical axis V represents the dimensionless velocity of the moving element 6, and the broken line S at the center represents the equilibrium position of the moving element 6. .

According to this figure, there is shown a qualitative state in which the moving element 6 has a velocity in the + Y direction when it moves in the -Y direction, and has a velocity in the -Y direction when the moving element 6 moves in the + Y direction. Accordingly, since the moving element 6 during the movement is always located at the equilibrium position, the movement of the moving element 6 is stabilized.

FIG. 4 shows an external view of an example of the movable element 6. In this example, the movable element 6 is formed in a plate-like step shape so as to move in the rightward moving direction 9. If so, a tapered shape or a corrugated shape can be applied. Further, the shape can be formed symmetrically so that the moving direction is not specified unlike the reciprocating motion.

FIG. 5 is a conceptual model when the present invention is applied to artificial muscle. In this model, a large number of movers 6 as subsystems are arranged in parallel so as to be opposite to each other, and the movers 6 in the same direction contact the left and right supports 11, respectively. And a macro system which is increased by the number of subsystems connected with the generated force. The high viscosity fluid 5 is enclosed between these components.

According to the electrostatic microactuator, the muscular structure is in a muscular expansion state during its operation, and its energy is restored to the spring component 10. Then, when the operation is stopped, the energy restored to the spring component 10 is released, and each movable element 6 is returned to the initial state.
Returns to the muscle contraction state.

During this repeatable operation, the moving elements 6 try to maintain their respective positions due to the repulsive acting force due to their step shapes. As a result, it is possible to avoid unstable movement caused by the mover 6 being attracted by the Coulomb force.

[0020]

The electrostatic microactuator of the present invention
Does not require complicated electrical control of the movement of the mover or any additional equipment such as mechanical bearings, and can stabilize the movement of the mover reliably by using a highly viscous fluid like a fluid bearing. , Making it easier for the electrostatic microactuator to function as an integrated subsystem.

Therefore, by combining such electrostatic microactuators in series and in parallel, they can be applied to medical equipment, cameras, artificial muscles and the like.

Also, the electrostatic microactuator of the present invention
According to the table, external control for stabilizing the moving element is not required, and an open control can be realized.
Since it is possible to be independent as a subsystem and it is easy to make the subsystem micro-sized, it is possible to reliably achieve the stability of the movement of the moving element by this micro-sized.

[Brief description of the drawings]

FIG. 1 is a conceptual explanatory view of an electrostatic microactuator according to the present invention.

FIG. 2 is a pressure distribution diagram in a two-dimensional model of the present invention.

FIG. 3 is a phase plane diagram showing a qualitative phenomenon of the movement of the moving element.

FIG. 4 is an external view of an example of a moving element.

FIG. 5 is a conceptual model when the present invention is applied to artificial muscle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixed electrode 2 Electrical insulating layer 3 Electrical insulating layer 4 Moving element electrode 5 High viscous fluid 6 Moving element 7 Fixed body 10 Spring parts 11 Support

Claims (1)

(57) [Claims] 1. A plurality of moving elements arranged in a sealed high-viscosity fluid are arranged in parallel with a required gap so that the moving directions are opposite to each other. one end is supported to each other on both sides of the support, respectively, comprise between the two support to couple a spring component, wherein
The support is configured to expand and contract through a mover.
The micro electromechanical actuator, characterized in that formed was.