JP2006211767A - Inertially driving actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a micro-actuator and a manufacturing method therefor, capable of attaining size and weight reductions and accurately driving in a two-dimensional direction. <P>SOLUTION: This inertially driving actuator (10) includes an outer frame (11), an inside inner frame (12) of the outer frame, an inside movable mass (15) of the inner frame, an outside support spring (13) for jointing the outer frame with the inner frame, an inside support spring (14) for jointing the inner frame with the movable mass, two pairs of driving electrodes (16), (17) disposed at four corners of the movable mass with a clearance from the movable mass, and a power circuit (19) which applies voltage between the driving electrodes and the movable mass. Voltage is applied between the driving electrodes and the movable mass, the movable mass is attracted to the driving electrodes by an attractive force, thus moving the whole actuator by an inertial force which is generated at the time of attracting the movable mass. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an actuator using inertia, in particular, a microactuator using an electrostatic impact mechanism and a manufacturing method thereof.

In recent years, a technique for accurately moving a minute distance with a precision positioning mechanism, a small robot, or the like is a very important technique.
Also, spacecraft actuators that operate in outer space are required to be small, high-performance, and inexpensive.

  However, it is difficult to reduce the size of the conventional actuator. In addition, it can move only in one direction and requires two actuators to drive in a two-dimensional direction. When two actuators are attached, when moving in one direction, only one actuator operates and the other actuator does not operate and becomes a load. Further, since the actuators are individually manufactured, there is a disadvantage that the cost becomes high.

  The present inventors have developed a microactuator using the electrostatic impact mechanism shown in Patent Document 1 and a processing method thereof. This microactuator generates an electrostatic attractive force between a drive electrode and a movable mass, and moves the actuator by causing the movable mass to collide with a stopper. The microactuator of Patent Document 1 moves in one direction. Also included are those in which drive electrodes are provided on the top, bottom, left and right to move the movable mass in a two-dimensional direction. The microactuator is made from a single silicon substrate using micromachine technology.

However, since this microactuator is made from a single silicon substrate, it is difficult to make it multi-layered and there are few structural degrees of freedom.
Therefore, it is desired to develop a microactuator that can move more accurately in a two-dimensional direction that is smaller and lighter. Also, a method for manufacturing such a microactuator at low cost is desired.

International publication WO 01/68512 A1

An object of the present invention is to provide a small and light actuator that can be driven in a two-dimensional direction. It is another object of the present invention to provide an actuator that has a high degree of design freedom and can be moved with high accuracy.
Another object of the present invention is to provide a method for manufacturing such an actuator using micromachining technology.

The actuator of the present invention has a two-layer structure in which a first layer is a drive structure and a second layer is a support structure using a silicon substrate on an insulator obtained by bonding two silicon substrates through a silicon oxide film. . The drive structure of the first layer has two pairs of drive electrodes, and the movable mass arranged in the center can be moved by applying a voltage between the drive electrodes and the movable mass. The first layer can be provided with a stopper for causing the movable mass to collide.
The support structure of the second layer is a double gimbal structure of an outer frame and an inner frame, the inner frame is movable in a one-dimensional direction supported by a support spring in the outer frame, and the movable mass is in the inner frame. It is supported by the support spring and can move in the other one-dimensional direction, and as a result, the movable mass can move in the two-dimensional direction.

One aspect of the present invention includes an outer frame, an inner frame inside the outer frame, a movable mass inside the inner frame,
An outer support spring that couples the outer frame and the inner frame, an inner support spring that joins the inner frame and the movable mass, and two pairs arranged in four directions of the movable mass at an interval from the movable mass Drive electrode, and a power supply circuit for applying a voltage between the drive electrode and the movable mass,
An inertial drive characterized in that a voltage is applied between the drive electrode and the movable mass, the movable mass is attracted to the drive electrode by electrostatic attraction, and the entire actuator is moved by the inertial force generated at that time. Type actuator.

The drive electrode is disposed on the first layer to drive the movable mass by electrostatic attraction,
The inner frame, the outer support spring, and the inner support spring are arranged in a second layer to support the movable mass in a movable manner,
The movable mass is preferably disposed over both the upper layer and the lower layer.
The inner frame is supported by the outer support spring so as to be movable in a one-dimensional direction relative to the outer frame, and the movable mass is movable in the other one-dimensional direction with respect to the inner frame by the inner support spring. As a result, the movable mass is preferably movable in a two-dimensional direction.
It is preferable to provide a stopper for causing the movable mass to collide. The stopper is preferably in the first layer.
It is preferable that there are four outer support springs and four inner support springs.

Since the constituent elements are created in two layers on the silicon substrate on the insulator, the degree of freedom of arrangement of the constituent elements is great, and an extremely small microactuator can be realized.
By providing an inner frame and a movable mass in the outer frame and restricting the moving direction of the movable mass and the inner frame to one direction, the actuator can move in a two-dimensional direction and move with extremely high accuracy. be able to.

According to another aspect of the present invention, there is provided a first layer including a drive structure for driving a movable mass disposed in an outer frame, and a support structure for supporting the movable mass so as to be movable in a two-dimensional direction. Comprising two layers, including a second layer,
The driving structure of the first layer has two pairs of driving electrodes arranged on four sides of the movable mass at an interval from the movable mass,
The support structure of the second layer includes an inner frame inside an outer frame, an outer support spring that couples the outer frame and the inner frame, and an inner support spring that couples the inner frame and the movable mass. And
And a power supply circuit for applying a voltage between the drive electrode and the movable mass,
An inertial drive characterized in that a voltage is applied between the drive electrode and the movable mass, the movable mass is attracted to the drive electrode by electrostatic attraction, and the entire actuator is moved by the inertial force generated at that time. Type actuator.
It is preferable to provide a stopper for causing the movable mass to collide with the first layer.

Another aspect of the present invention includes an outer frame, an inner frame, a movable mass, an outer support spring, and an inner support spring from a silicon substrate on an insulator in which two silicon substrates are bonded via a silicon oxide film. A manufacturing method for integrally forming an inertial drive type actuator comprising two pairs of drive electrodes,
(a) depositing and patterning a silicon oxide film on the back surface, depositing and patterning an aluminum layer on the silicon oxide film, depositing and patterning an aluminum layer on the surface of the silicon-on-insulator substrate,
(b) Etching a portion other than the portion masked with the aluminum layer from the back surface, forming a lower portion of the movable mass and the support spring,
(c) removing the aluminum layer on the back surface, exposing the silicon oxide film, performing etching from the back surface again, etching portions other than the portion masked with the silicon oxide film, and the movable mass and the inner frame And a structure in which the outer and inner support springs float,
(d) Etching from the surface, etching other than the portion masked by the aluminum layer, forming the drive electrode and the upper portion of the movable mass,
(e) A manufacturing method comprising a step of removing a silicon oxide film of the silicon substrate on the insulator by sacrificial layer etching, and separating the movable mass, the inner frame, and the outer and inner support springs from the outer frame. It is.

  The etching steps (b), (c), and (d) are preferably performed by deep reactive ion etching.

  According to this method, a silicon substrate on an insulator in which two silicon substrates are bonded via a silicon oxide film is used, and the components of the actuator are formed on a single substrate by using a micromachining technique. Thus, it is possible to reduce the size, and it is not necessary to assemble individually created components, and the manufacturing is simple and can be manufactured at low cost.

There are the following types of driving methods using the inertial force of the actuator of the present invention.
The movable mass is attracted to the drive electrode by electrostatic attraction, and the movable mass collides with the stopper, the kinetic energy of the movable mass is transmitted to the stopper, and the entire actuator can be moved in the moving direction of the movable mass.
Alternatively, without causing the movable mass to collide with the stopper, the movable mass is attracted to the drive electrode by electrostatic attraction, and the entire actuator is moved in the direction opposite to the moving direction of the movable mass by the reaction force of the movement of the movable mass at that time. be able to.

Slowly move the movable mass to an obliquely upper position, rapidly apply a voltage between the movable mass and the drive electrode, rapidly accelerate the movable mass obliquely downward, and the reaction causes the actuator to move obliquely upward Can be hopped.
The movable mass can collide with the stopper, and the actuator can be hopped obliquely upward.

According to the present invention, a small and light actuator that can be driven in a two-dimensional direction can be obtained. Since the actuator has a two-layer structure, the design freedom is high and a high-performance actuator can be obtained. In addition, the double gimbal structure allows more accurate movement.
Moreover, since the manufacturing method is simple, such an actuator can be manufactured at low cost.

Embodiments of the present invention will be described below.
FIG. 1 is a perspective view of an inertial drive type microactuator according to a first embodiment of the present invention, in which a part of a second layer (lower layer) is cut away and a part of the first layer (upper layer) is removed. Indicates the state. FIG. 2A is a plan view of the first layer, and FIG. 2B is a plan view of the second layer with the first layer removed. For convenience of explanation, the horizontal direction in FIG. 2 is the x direction and the vertical direction is the y direction. FIG. 3 is a cross-sectional view taken along line 3-3 in FIG. Although the first layer is described as an upper layer and the second layer is a lower layer in this embodiment mode, the first layer may be a lower layer and the second layer may be an upper layer.

  Referring to the plan view of the second layer in FIG. 2B, the inertial drive type microactuator 10 according to the embodiment of the present invention has an outer frame 11 having a substantially quadrangular outer shape, and an outer shape inside the outer frame 11. Comprises a substantially rectangular inner frame 12. Center portions 12a of two sides in the y direction of the inner frame 12 are coupled to the inside of the outer frame 11 by two outer support springs 13 parallel to the x axis, respectively, and the inner frame 12 can move in the y direction. It is like that. A movable mass 15 is provided at the center of the inner frame 12. The central portions 15a of the two sides in the x direction of the movable mass 15 are coupled to the inside of the outer frame 11 by two inner support springs 14 parallel to the y axis, respectively, so that the movable mass 15 can move in the x direction. It is like that.

Referring to the plan view of the first layer of FIG. 2A, the microactuator 10 includes a pair of drive electrodes 16 in the x direction and a pair of drive electrodes 17 in the y direction. The surfaces of the drive electrodes 16 and 17 facing the movable mass 15 are parallel to the outer side of the movable mass 15 and spaced apart from each other. A power supply circuit including a power supply and a switch is connected between the drive electrodes 16 and 17 and the movable mass 15 (not shown). By applying a voltage between the drive electrodes 16 and 17 and the movable mass 15, the movable mass 15 is attracted to the drive electrodes 16 and 17 by electrostatic force. In the present embodiment, the movable mass 15 does not collide with the drive electrodes 16 and 17, and the microactuator 10 moves by the reaction force of the movement of the movable mass 15.
A portion of the outer frame 11 where the drive electrodes 16 and 17 are not present is a ground 18. The ground 18 is electrically grounded and has the same potential as the movable mass 15.

  FIG. 4 is a plan view of the first layer of the second embodiment of the present invention, and corresponds to FIG. 2A of the first embodiment. The second embodiment is different from the first embodiment in that it is separate from the drive electrodes 16 and 17, a stopper 20 is provided in a part of the ground 18, and protrusions 15 a at four corners of the movable mass 15. Is provided. The movable mass 15 is attracted to the drive electrodes 16 and 17 by electrostatic force, the projecting portion 15a collides with the stopper 20, and the microactuator 10 moves. The movable mass 15 is not in contact with the drive electrodes 16 and 17. The other points are the same as in the first embodiment.

FIG. 5 is a plan view of the second layer of the microactuator 10 showing a structure for displacing the movable mass 15 in a two-dimensional direction. (a) shows a state where the initial movable mass 15 is not displaced. (b) shows a state in which the movable mass 15 is displaced in the x direction and the y direction (upper right direction in the figure).
Center portions 12a of two sides in the y direction of the inner frame 12 are coupled to the inner side of the outer frame 11 by two outer support springs 13 parallel to the x axis. The four outer support springs 13 restrain the inner frame 12 so that it can move only in the y direction with respect to the outer frame 11. In a state where no force is applied, the inner frame 12 is positioned at the center of the left and right outer frames 11.
Central portions 15a of two sides in the x direction of the movable mass 15 are coupled to the inner frame 12 by two inner support springs 14 parallel to the y axis. The four inner support springs 14 restrain the movable mass 15 so that it can move only in the x direction with respect to the inner frame 12. In a state where no force is applied, the movable mass 15 is located at the center of the left and right inner frames 12.

  Thus, the structure of the present invention is a double gimbal structure having two frames, the outer frame 11 and the inner frame 12. It has an outer support spring 13 parallel to the x axis and an inner support spring 14 parallel to the y axis. With this structure, the movable mass 15 can be driven separately in the x-axis direction and the y-axis direction. Therefore, the movable mass 15 can be displaced in a two-dimensional direction with respect to the outer frame 11 without rotating. Further, by making the resonance frequencies of the two axes different, interference between the two axes can be prevented.

  Next, an operation principle of driving the actuator of the present invention by inertia force will be described with reference to FIGS. FIG. 6 shows a case where a collision is used, and FIG. 7 shows a case where a collision is not used. For simplicity, FIG. 6 shows only one stopper 20 in the x direction, and FIG. 7 shows only one drive electrode 16 in the x direction. Further, only one support spring 14 in the x direction is schematically shown in the form of a spiral spring.

  FIG. 6 is a conceptual diagram illustrating the operating principle when using collision. In FIG. 6A, the switch of the power supply circuit 19 is turned on, and a voltage is applied between the movable mass 15 and the drive electrode 16. Then, the movable mass 15 is attracted in the direction of the drive electrode 16 by the electrostatic attraction generated between the movable mass 15 and the drive electrode 16, and is accelerated. At this time, the actuator 10 receives a reaction force from the floor in the direction opposite to the acceleration direction of the movable mass 15, but this reaction force is prevented from exceeding the static friction force between the actuator 10 and the floor.

As shown in (b), the movable mass 15 is accelerated and collides with the stopper 20, the kinetic energy F _imp of the movable mass 15 is transmitted to the actuator 10, and the reaction force that the actuator 10 receives from the floor is the static friction force. The actuator 10 moves beyond that. The actuator 10 moves by a distance D until the kinetic energy obtained by the collision is lost by the dynamic friction force between the actuator 10 and the floor.

Next, as shown in (c), when the switch of the power supply circuit is turned OFF and the voltage between the movable mass 15 and the drive electrode 16 is zero, the movable mass 15 is moved to the initial position by the restoring force of the support spring 14. Return. The reaction force generated at this time is prevented from exceeding the static friction force between the actuator 10 and the floor.
By repeating these cycles (a) to (c), the entire actuator 10 can move on the floor in the direction of accelerating the movable mass 15.

  FIG. 7 is a conceptual diagram illustrating the operating principle when collision is not used. In FIG. 7A, the switch of the power supply circuit is turned on, and a step-like voltage is suddenly applied between the movable mass 15 and the drive electrode 16.

  Then, as shown in (b), the movable mass 15 is rapidly accelerated in the direction of the drive electrode 16 by the electrostatic attractive force generated between the movable mass 15 and the drive electrode 16. At this time, the actuator 10 receives a reaction force from the floor in the direction opposite to the acceleration direction of the movable mass 15, and this reaction force exceeds the static friction force between the actuator 10 and the floor, and the actuator 10 is in the direction opposite to the movable mass 15. Is moved by a distance D.

Next, as shown in (c), when the switch of the power supply circuit is turned off and the voltage between the movable mass 15 and the drive electrode 16 is slowly lowered, the movable mass 15 is returned to the initial position by the restoring force of the support spring 14. Return. At this time, the movable mass 15 may be attracted to the other drive electrode 16 (not shown). The reaction force generated at this time is prevented from exceeding the static friction force between the actuator 10 and the floor.
By repeating these cycles (a) to (c), the entire actuator 10 can travel on the floor in a direction opposite to the direction in which the movable mass 15 is accelerated by the reaction force.

If the voltage application is repeatedly turned ON / OFF between the other drive electrode 16 and the movable mass 15 which are omitted in FIGS. 6 and 7, the actuator 10 can move in the opposite direction. If the voltage application is repeatedly turned on and off between the drive electrode 17 and the movable mass 15 in the y direction, the actuator 10 can advance in the y direction. It is possible to repeat ON / OFF of voltage application between the drive electrode 16 and the movable mass 15 in the x direction and between the drive electrode 17 and the movable mass 15 in the y direction and advance in an oblique direction. If the drive voltages in the x and y directions are changed, the actuator 10 can move in any direction.
Further, the movement of the actuator is restricted by the power supply line, but if the wireless power feeding is used, the restriction on the movement of the actuator becomes small.

  FIG. 8 is a conceptual diagram illustrating the principle of a hopping operation in which the actuator 10 jumps. Although FIG. 8 describes a case where the movable mass 15 does not collide with the stopper 20 (or the drive electrode 16), the hopping operation can be performed similarly when the movable mass 15 collides with the stopper 20. The movable mass 15 can move only in the horizontal direction in the figure with respect to the inner frame 12. The inner frame 12 can move only in the vertical direction in the figure with respect to the outer frame 11. In FIG. 8, the drive electrode and the stopper are not shown.

In (a), move the movable mass 15 slowly to the upper right position. That is, the movable mass 15 is moved to the right in the inner frame 12 and the inner frame 12 is moved upward in the outer frame 11. (b) A voltage is rapidly applied between the movable mass 15 and the drive electrode, and the movable mass 15 is rapidly accelerated in the lower left direction. That is, the movable mass 15 is moved to the left in the inner frame 12 and the inner frame 12 is moved downward in the outer frame 11. Then, the actuator 10 hops in the upper right direction by the reaction. After the actuator 10 is landed by the action of gravity, the movable mass 15 is returned to the initial position shown in (c). Slowly return the movable mass 15 to the position shown in the upper right (a). By repeating the cycles (a) to (c), the entire actuator 10 can move while hopping on the floor.
Under microgravity on the planet, movement by hopping is efficient.

FIG. 9 shows a method for producing the actuator 10 according to the embodiment of the present invention. FIG. 9 is a cross-sectional view taken along line 3-3 of FIGS. (a) First, a silicon on insulator (SOI (Silicon on Insulator)) substrate is prepared. This SOI substrate has a silicon layer 22 formed on the upper surface of a silicon oxide film 21 and a silicon layer 23 formed on the lower surface.
In the following description, in order to distinguish two surfaces, they are called a front surface and a back surface, but the two surfaces are interchangeable.
A silicon oxide film 24 is deposited on the back surface of the SOI substrate, and is patterned into a desired shape in order to make the movable part floating by using a photolithography technique. An aluminum layer 25 is deposited on the silicon oxide film 24, and is patterned into a desired shape in order to form a lower layer (second layer) structure of the actuator 10 by using a photolithography technique. An aluminum layer 26 is deposited on the surface of the SOI substrate, and is patterned into a desired shape in order to form a structure of the upper layer (first layer) of the actuator 10 by using a photolithography technique.

  (b) A portion other than the portion masked by the aluminum layer 25 is etched by deep reactive ion etching (RIE (RIE)) from the back surface, and the lower portion of the movable mass 15, the inner frame 12, and the outer Inner support springs 13 and 14 are formed. The inner frame 12 and the outer and inner support springs 13 and 14 constitute a support structure. At this time, since the silicon oxide film 21 becomes an etching stop layer, the silicon layer 22 thereon is not etched.

(c) The mask of the aluminum layer 25 on the back surface is removed, the silicon oxide film 24 is exposed, RIE is performed again from the back surface, and portions other than the portion masked by the silicon oxide film 24 are etched. Thus, the movable mass 15, the inner frame 12, and the movable portions of the outer and inner support springs 13 and 14 are lifted from the bottom surface.
(d) Deep RIE is performed from the surface, and portions other than the portion masked by the aluminum layer 26 are etched to form the drive electrodes 16 and 17 and the upper portion of the movable mass 15. The drive electrodes 16 and 17 constitute a drive structure. If there is a stopper 20 as in the second embodiment, it is also formed.
(e) The silicon oxide film 21 of the SOI substrate is removed by sacrificial layer etching, and the movable portion of the movable mass 15, inner frame 12, outer and inner support springs 13, 14 is separated from the support portion of the outer frame 11. Thereby, the movable part can be moved.

According to the present invention, a small and highly movable actuator can be obtained. By using this microactuator, a highly accurate positioning mechanism and a highly accurate transfer device can be realized. Moreover, this actuator can be used for a small rover.
Moreover, it can be used for the attitude | position control apparatus and position control apparatus for satellites and spacecraft.

The perspective view which notched a part of microactuator by a 1st embodiment of the present invention. (a) is a top view of the 1st layer of a microactuator, (b) is a top view of the 2nd layer in the state where the 1st layer was removed. Sectional drawing along line 3-3 in FIGS. The top view of the 1st layer of the microactuator by the 2nd Embodiment of this invention. The top view of the 2nd layer which shows the structure which displaces a movable mass to a two-dimensional direction. The conceptual diagram explaining the operation principle of the microactuator in the case of utilizing a collision. The conceptual diagram explaining the operation principle of the microactuator when not using a collision. The conceptual diagram explaining the hopping operation | movement of a microactuator. Sectional drawing which shows the production method of the microactuator by embodiment of this invention.

Explanation of symbols

10 Micro actuator
11 Outer frame
12 Inner frame
13 Outer support spring
14 Inner support spring
15 Movable mass
16 Drive electrode
17 Drive electrode
18 ground
19 Power circuit
20 Stopper
21 Silicon oxide layer
22 Silicon layer
23 Silicon layer
24 Silicon oxide film
25 Aluminum layer
26 Aluminum layer

Claims (7)

An outer frame,
An inner frame inside the outer frame;
A movable mass inside the inner frame;
An outer support spring that couples the outer frame and the inner frame;
An inner support spring that couples the inner frame and the movable mass;
Two pairs of drive electrodes disposed on four sides of the movable mass at an interval from the movable mass;
A power supply circuit for applying a voltage between the drive electrode and the movable mass;
An inertial drive characterized in that a voltage is applied between the drive electrode and the movable mass, the movable mass is attracted to the drive electrode by electrostatic attraction, and the entire actuator is moved by the inertial force generated at that time. Type actuator. The drive electrode is disposed on the first layer to drive the movable mass by electrostatic attraction,
The inner frame, the outer support spring, and the inner support spring are arranged in a second layer to support the movable mass in a movable manner,
The inertial drive actuator according to claim 1, wherein the movable mass is disposed over both the first layer and the second layer.   The inertial drive type actuator according to claim 1, further comprising a stopper for causing the movable mass to collide. Two layers of a first layer including a driving structure for driving a movable mass disposed in the outer frame and a second layer including a support structure for supporting the movable mass so as to be movable in a two-dimensional direction. With
The driving structure of the first layer has two pairs of driving electrodes arranged on four sides of the movable mass at an interval from the movable mass,
The support structure of the second layer includes an inner frame inside an outer frame, an outer support spring that couples the outer frame and the inner frame, and an inner support spring that couples the inner frame and the movable mass. And
And a power supply circuit for applying a voltage between the drive electrode and the movable mass,
An inertial drive characterized in that a voltage is applied between the drive electrode and the movable mass, the movable mass is attracted to the drive electrode by electrostatic attraction, and the entire actuator is moved by the inertial force generated at that time. Type actuator.   The inertial drive type actuator according to claim 4, further comprising a stopper for causing the movable mass to collide with the first layer. An outer frame, an inner frame, a movable mass, an outer support spring, an inner support spring, and two pairs of drive electrodes are formed from a silicon substrate on an insulator obtained by bonding two silicon substrates through a silicon oxide film. A manufacturing method for integrally forming an inertial drive type actuator comprising:
(a) depositing and patterning a silicon oxide film on the back surface, depositing and patterning an aluminum layer on the silicon oxide film, depositing and patterning an aluminum layer on the surface of the silicon-on-insulator substrate,
(b) Etching a portion other than the portion masked with the aluminum layer from the back surface, forming a lower portion of the movable mass and the support spring,
(c) removing the aluminum layer on the back surface, exposing the silicon oxide film, performing etching from the back surface again, etching portions other than the portion masked with the silicon oxide film, and the movable mass and the inner frame And a structure in which the outer and inner support springs float,
(d) Etching from the surface, etching other than the portion masked by the aluminum layer, forming the drive electrode and the upper portion of the movable mass,
(e) removing the silicon oxide film of the silicon substrate on the insulator by sacrificial layer etching, and separating the movable mass, the inner frame, and the outer and inner support springs from the outer frame;
A manufacturing method comprising steps.   The manufacturing method according to claim 6, wherein the etching steps (b), (c), and (d) are performed by deep reactive ion etching.

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