JPH06269186A - Two degree of freedom oscillation type microactuator - Google Patents

Abstract

PURPOSE:To provide a two degree of freedom oscillation type microactuator in which a two degree of freedom oscillation system is constituted while isolating a movable part from a part to be driven by applying voltage, low voltage driving is allowed by making narrow the gap between electrodes, and a high amplitude is obtained by ensuring the movable range of the movable part. CONSTITUTION:A driving plate (electrode plate 23) subjected periodically to external force is supported by a fixed part 21 through a first elastic coupling member (torsion bar 22) and a movable plate 25 is coupled elastically with the driving plate through a second elastic coupling member (torsion bar 24). Consequently, a two degree of freedom oscillation system displaceable elastically through the elastic coupling members is configured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-degree-of-freedom vibration type microactuator using electrostatic force or electromagnetic force. More specifically, the present invention relates to a mirror drive mechanism of an optical scanner, a vibrating atmosphere sensor, and an optical shutter of a display. The present invention relates to a two-degree-of-freedom vibration type microactuator that can be effectively used for other purposes.

[0002]

2. Description of the Related Art A one-degree-of-freedom torsion oscillator having electrodes arranged in a parallel plate shape as shown in FIG. 6 has been proposed from the early stage of research on microactuators because of its simple structure (as an example). KEPetersen: "Silicon Torsi
onal Scanning Mirror ", IBM J. Res.Develop., vol.24 (19
80) See page 631). In addition, a one-degree-of-freedom electrostatic drive type oscillator using the above-mentioned torsion oscillator as a cantilever system has also been proposed (Kawamura et al .: “Study of micromechanics using Si”, Academic Conference of Precision Engineering Society Autumn Meeting, 1986). Proceedings of the Meeting, P.753).

In the one-degree-of-freedom electrostatic drive type torsion oscillator shown in FIG. 6, the movable electrode plate 3 made of a silicon single crystal plate is fixed to both ends of a glass substrate 1 with spacers 2 interposed therebetween.
a is fixed, and between the both end fixing portions 3a of the movable electrode plate 3,
A fixed electrode 4 that supports the movable electrode portion 3c via a narrow torsion bar 3b and that opposes the movable electrode portion 3c at an electrode interval is parallel to the movable electrode portion 3c on the glass substrate 1. It is arranged. Movable electrode plate 3
A power supply 5 is connected between the fixed electrode 4 and the fixed electrode 4 via a switch 6.

When a voltage is applied between the movable electrode portion 3c and the fixed electrode 4 in the torsional oscillator having the above-mentioned structure, the movable electrode portion 3 is rotated about the torsion bar 3b by electrostatic attraction.
c is the one that rotates. However, since electrostatic attraction is inversely proportional to the square of the electrode spacing, it is desirable to reduce the electrode spacing in this type of electrostatic actuator. However, in the structure with one degree of freedom described above, since the movable electrode portion 3c serves both as an electrode and a movable portion, the displacement (rotation angle) is restricted when the electrode interval is narrowed, and the electrode interval is increased in order to increase the movable range. Needs to be increased. Therefore, there is a problem that it is difficult to achieve both low voltage driving and large amplitude.

[0005]

SUMMARY OF THE INVENTION The technical problem of the present invention is to separate the drive part driven by voltage application and the movable part from each other to form a vibration system having two degrees of freedom. (EN) A two-degree-of-freedom vibration-type microactuator in which a transmission interval) is narrowed to enable low voltage driving, and at the same time, a movable range of a movable portion is secured to obtain a large amplitude.

[0006]

A two-degree-of-freedom vibration type microactuator of the present invention for solving the above-mentioned problems is provided.
The drive plate to which a periodic external force is applied is elastically supported by the fixed portion via the first elastic connecting member, and the movable plate is elastically coupled to the drive plate via the second elastic connecting member to drive the drive plate. The plate and the movable plate are formed by forming a two-degree-of-freedom vibration system that elastically displaces in each elastic connecting member.

[0007]

In the two-degree-of-freedom vibration type microactuator having the above structure, the drive plate and the movable plate respectively constitute a vibration system, and the frequency of the periodic electrostatic force or electromagnetic force applied to the drive plate from the outside is appropriately adjusted. When set, the amplitude of the drive plate can be set to almost 0 and the amplitude of the movable plate can be set to a finite value. Here, the electrostatic force or electromagnetic force that drives the drive plate is inversely proportional to the square of the distance for transmitting the drive plate. Therefore, the smaller the amplitude of the drive plate, the shorter the distance and the lower the voltage (low power) to move. It is possible to secure a movable range of the plate and obtain a large amplitude.

[0008]

1 and 2 show an example of the implementation of a microactuator according to the present invention. In the two-degree-of-freedom electrostatic drive microactuator shown in FIG. 1, a fixed electrode 18 is provided on a glass substrate 10 whose surface has been subjected to required processing by etching, and a single crystal silicon wafer is anisotropically etched into a required shape. It is configured by attaching the formed movable electrode plate 20.

The glass substrate 10 has a substantially rectangular shape, and the spacers 11 for supporting both end fixing portions 21 of the movable electrode plate 20 are formed at both ends in the longitudinal direction on the surface by the above etching. Along with the longitudinal centerline L, the blade edge 12 clearly shown in FIG.
In addition, the other portion is further thinned by excavation, and in this case, in particular, the portion 14 of the movable electrode plate 20 facing the later-described movable plate 25 is further deepened, whereby the movable electrode plate 20 is entirely formed on the glass substrate. Both end fixing portions 21 are supported on the spacer 11 in a state of being separated from the surface of 10.

On the other hand, in the movable electrode plate 20, between the fixed portions 21 provided at both ends thereof, the electrode plate 23 is provided on both sides with the narrow first torsion bar 22 along the center line L interposed therebetween.
Are continuously provided, and the inside of the electrode plate 23 is partially cut to form the second torsion bar 24 along the center line L, and the movable plate 25 is provided through the second torsion bar 24. Are installed in series. This movable electrode plate 20
The electrode plate 23 and the movable plate 25 in the above are symmetrical on both sides of the center line L.

In the movable electrode plate 20, the fixed portions 21 at both ends are adhered and supported on the spacer 11 on the glass substrate 10 by hot wax or the like, and the torsion bars 22 and 24 along the center line L thereof are supported. Edge 1 on the glass substrate
It is fixed to the glass substrate 10 by being placed in contact with the substrate 2 (FIG. 2). Further, on the glass substrate 10, on one side of the center line L, the fixed electrode 18 is arranged to face the electrode plate 23 with an electrode interval. The fixed electrode 18 can be formed by means such as vapor deposition of Ti on the glass substrate 10. Although not shown, the fixed electrode 18 and the electrode plate 23 are connected to a power source.

In the two-degree-of-freedom vibration type microactuator having the above-mentioned structure, the electrode plate 23 and the movable plate 25 respectively form a vibration system, and when a periodic voltage is applied between the fixed electrode 18 and the electrode plate 23. , The electrode plate 23 is driven by the electrostatic force and the torsion bars 22 and 24 torsionally vibrate. When the frequency of the periodic electrostatic force is appropriately set, the amplitude of the electrode plate 23 is set to almost 0 and the amplitude of the movable plate 25 is set. Can be set to a finite value. Here, the electrode plate 2
Since the electrostatic force driving 3 is inversely proportional to the square of the electrode interval, the smaller the amplitude of the driving plate, the shorter the electrode interval,
It is possible to secure a movable range of the movable plate 25 with a lower voltage and obtain a large amplitude.

FIG. 3 shows the structure of the two-degree-of-freedom vibration type microactuator by a dynamic model, and the same reference numerals are given to the portions corresponding to the above-mentioned embodiment. In this mechanical model, the electrode plate 23 is elastically supported by the first torsion bar 22 with respect to the fixed portion 21, and the movable plate 25 is elastically coupled to the electrode plate 23 by the second torsion bar 24. Therefore, the electrode plate 23 and the movable plate 25 rotate about the torsion bars 22 and 24, respectively, and form a torsional vibration system having two degrees of freedom.

In this dynamic model, I ₁ and θ ₁ are the moment of inertia and displacement of the electrode plate 23, respectively,
₂ and θ ₂ are the moment of inertia and displacement of the movable plate 25,
Further, k ₁ and k ₂ are connected to the first torsion bar 22 and the second torsion bar 22.
Assuming that the torsion spring constant of the torsion bar 24 is, the equation of motion when the periodic external force T · sinωt acts on the electrode plate 23 is given by the following equation.

[0015]

[Equation 1]

Further, the natural frequency omega ₂ of the natural frequency omega ₁ and the movable plate type electrode plate system, respectively,

[Equation 2] Given by.

Here, if θ _st is the static displacement of the electrode plate, the amplitude due to the periodic external force is given by the following equation for each of the electrode plate and the movable plate.

[Equation 3]

From the above equation, the amplitude of the electrode plate 23 due to the periodic external force becomes 0 at ω = ω ₁ . At this time, the movable plate 2
The amplitude of 5 has a finite value represented by the equation (4). The amplitude of the movable plate 25 can be set to a predetermined value by appropriately designing the electrode plate 23, the movable plate 25, and the two torsion bars.

In the trial manufacture by the present inventor, the movable electrode plate 20 has a thickness of 0.3 mm and an external dimension of about 20 mm ×
A 20 mm single crystal silicon wafer was integrally formed by anisotropic etching. In addition, the fixed electrode 18 and the electrode plate 2
The distance between the movable plate 25 and the glass substrate 10 was 38 μm.

In this trial-made two-degree-of-freedom torsional vibration type actuator, the displacement (twist angle) of the electrode plate 23 and the movable plate 25 was measured by an optical lever method. First, when a voltage of 100 V was statically applied, the electrode plate 23 and the movable plate 2 were
The displacement of 5 was in agreement, and θ _st = 0.02 °. Next, excitation was performed by applying a voltage that fluctuates periodically. Figure 4
A resonance curve of the electrode plate 23 and the movable plate 25 when a sinusoidal voltage (100 Vp-p) is applied is shown. The vertical axis represents the displacement, which is divided by the static displacement θ _st measured in advance.

From this resonance curve, the torsional vibration actuator produced as a prototype has resonance points at 241 Hz and 580 Hz, but the electrode plate 23 is located near the middle of the two resonance points.
It can be understood that the object of obtaining a large displacement of the movable plate 25 without substantially displacing the electrode plate 23 can be achieved. Therefore, by optimizing the electrode plate 23, the movable plate 25, and the torsion bars 22 and 24,
Only the displacement of the movable plate 25 can be enlarged. As a result, the displacement of the electrode plate 23 becomes small. Therefore, even if the gap between the electrode plate 23 and the fixed electrode 18 is narrowed and the power supply voltage is lower than that of the conventional one, an efficient microactuator in which the displacement of the movable plate 25 is large is provided. Obtainable.

FIG. 5 shows the structure of another embodiment of the two-degree-of-freedom vibration type microactuator by a mechanical model. In the above-mentioned embodiment, the torsional vibration of the torsion bar is utilized, whereas this mechanical model is used. In the above, the bending vibration of the elastic connecting member having substantially the same structure as the torsion bar is utilized. That is, the electrode plate 33 is elastically supported by the first elastic connecting member 32 with respect to the fixed portion 31, and the movable plate 35 is elastically connected to the electrode plate 33 by the second elastic connecting member 34. Therefore, the electrode plate 33 and the movable plate 35 are tilted by the bending of the elastic connecting members 32 and 34, respectively, to form a bending vibration system having two degrees of freedom.
The operation in this vibration system is substantially the same as that in the case of the dynamic model of FIG. 3, and therefore its explanation is omitted.

In both of the above embodiments, the case where a voltage is applied between the electrode plates 23 and 33 and the fixed electrode to apply an electrostatic force to the electrode plate has been described. However, the electrode plate side is driven by a magnetic material. A periodic external force may be applied by adopting a means such as driving a driving plate corresponding to the electrode plate by an electromagnetic force by forming the plate as a plate on the fixed electrode side on the glass substrate 10 by a coil. .

A drive plate to which a periodic external force is applied is elastically supported by a fixed portion via a first elastic connecting member, and the movable plate is elastically coupled to the drive plate via a second elastic connecting member. A two-degree-of-freedom vibration type microactuator is characterized in that the driving plate and the movable plate are formed with a two-degree-of-freedom vibration system that is elastically displaced in each elastic connecting member.

As described above in detail, according to the two-degree-of-freedom vibration type microactuator of the present invention, the two-degree-of-freedom vibration system is separated by separating the driving part and the movable part which are driven by voltage application or the like. Since it is configured, the displacement of the drive plate can be made sufficiently small to enable low voltage driving, and at the same time the displacement of the movable plate can be increased.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing an embodiment of a two-degree-of-freedom vibration type microactuator of the present invention.

FIG. 2 is a lateral cross-sectional view of a main part of the embodiment.

FIG. 3 is a perspective view showing a dynamic model of the embodiment.

FIG. 4 is a graph showing resonance curves of an electrode plate and a movable plate in the example.

FIG. 5 is a perspective view showing a dynamic model of another embodiment of the present invention.

FIG. 6 is a perspective view showing a configuration of a conventional one-degree-of-freedom torsion oscillator.

[Explanation of symbols]

 18 fixed electrode, 21,31 fixed part, 22,24 torsion bar, 23,33 electrode plate, 25,35 movable plate, 32,34 elastic connection member.

Claims (1)

[Claims] 1. A drive plate to which a periodic external force is applied is elastically supported by a fixed portion via a first elastic connecting member, and the movable plate is elastically supported by the drive plate via a second elastic connecting member. A two-degree-of-freedom vibrating microactuator, which is coupled to form a two-degree-of-freedom vibration system in which the drive plate and the movable plate are elastically displaced in respective elastic connecting members.