JP2004301865A - Actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact actuator in which a large torsion (deflection angle) is efficiently given to a movable plate. <P>SOLUTION: There is provided an actuator which is furnished with a supporting body which extends from the movable plate substantially in parallel to a torsion bar, a movable comb-teeth shaped structural body which extends from the supporting body in the direction substantially orthogonal to the supporting body, and a fixed comb-shaped body which is arranged at a position at which the fixed comb-shaped body is engaged with the movable comb-teeth shaped structural body with a gap when the movable plate is displaced. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a small actuator in which a movable plate swings.
[0002]
[Prior art]
The actuator in which the movable plate swings is used, for example, for a purpose of deflecting a laser beam. There is a galvano mirror as a scanning mirror for deflecting and scanning laser light. The driving principle of the galvanomirror is that when a current flows through a movable coil disposed in a magnetic field, an electromagnetic force is generated in relation to the current and the magnetic flux, and a torque proportional to the current is generated. The moving coil rotates to the angle where the torque and spring force are balanced, and the pointer is swung through the moving coil to detect the presence or absence and magnitude of the current, using the principle of a galvanometer. In place of the pointer, a reflecting mirror is provided on a rotating shaft.
[0003]
However, a galvanomirror requires a mechanically wound drive coil and a large yoke for generating a magnetic field, and there is a limit to reducing the size of these mechanical elements mainly due to output torque. At the same time, the size of the entire device for deflecting light has been increased due to the space for assembling the components.
[0004]
As a small optical deflector, there is an optical deflector manufactured by using a micromachining technology in which a micromachine is integrally formed on a semiconductor substrate by applying a semiconductor manufacturing technology. For example, K. E. FIG. Non-Patent Document 1 proposes a torsion scanning mirror formed of silicon by Petersen et al. In this optical deflector, as shown in FIG. 13, a mechanically movable part 3 is composed of a mirror 3a as an optical deflector and a beam 3b supporting the mirror 3a, and is provided between the mirror 3a and the fixed electrode 2 formed on the substrate. The beam is given a torsional moment by an electrostatic attraction generated by applying a drive voltage to the beam, and the beam is twisted and rotated, thereby changing the deflection angle of the mirror 3a. The maximum deflection angle of the mirror unit is uniquely determined by the gap t0 between the mirror unit and the substrate. In an optical deflector, the larger the deflection angle is, the better, and it is necessary to make the air gap large. If the air gap is increased, the distance between the fixed electrode and the mirror is increased, and the driving voltage is significantly increased. Conversely, in order to achieve a low voltage, it is necessary to shorten the air gap and to suppress the deflection angle. Therefore, the reduction of the drive voltage and the increase of the deflection angle are contradictory issues.
[0005]
As another small optical deflector, R.S. S. Mueller et al. Non-Patent Document 2 has been published. FIG. 14 is a perspective view showing an optical deflector of the literature. FIG. 15 is a top view of the optical deflector of the literature. This optical deflector generates an electrostatic force acting between a comb-shaped movable electrode provided on a torsion bar and a comb-shaped fixed electrode arranged so as to mesh with the movable electrode at a position where the height is changed. There is a feature in using and driving. One capacitor is composed of a comb-shaped movable electrode made of a conductor and a fixed electrode arranged with a slight gap. When a voltage is applied between the movable electrode and the fixed electrode, an electrostatic force is generated, so that the movable electrode is attracted to the fixed electrode, and the torsion bar is twisted. The mirror connected to the torsion bar causes a rotational motion about the torsion bar as a rotation axis. Even if the rotation angle of the mirror is increased, it is not necessary to change the arrangement of the comb-shaped movable electrode and the comb-shaped fixed electrode.
[0006]
To be more specific, the optical deflector of the literature includes a mirror 804 that reflects light and can be angularly displaced, a torsion bar 801 that supports the mirror 804 from both sides, and a comb-shaped movable electrode 802 that extends from the torsion bar 801. Are integrally formed. The torsion bar 801 is fixed to a support substrate (not shown). The comb-shaped fixed electrode 803 is arranged so as to mesh with the comb-shaped movable electrode 802 at a position where the height is changed. The support substrate (not shown) is a silicon substrate, and the mirror 804, the torsion bar 801 and the comb-shaped movable electrode 802 are formed by removing the silicon substrate. The comb-shaped fixed electrode 803 is formed by removing another silicon substrate.
[0007]
[Non-patent document 1]
IBM J.M. RES. DEVELOP. , VOL. 24, NO5, 9, 1980. P631-637
[Non-patent document 2]
A FLAT HIGH-FREQUENCY SCANNING MICRMIRROR'2000 Solid-State Sensor and Actuator Workshop, pp6-9
[0008]
[Problems to be solved by the invention]
However, when the displacement angle of the torsion angle θ1 is given to the mirror of the above-mentioned small optical deflector, the two torsion bars are fixed on one side to the support substrate, respectively, and the torsion angle θ of the comb-shaped movable electrode is The maximum torsion angle is at θ1 and decreases as the position approaches the fixed portion of the torsion bar. For this reason, the amount of intermeshing area between the comb-shaped movable electrode and the comb-shaped fixed electrode near the fixed end of the torsion bar changes only slightly. That is, since the movable electrode near the fixed end does not efficiently contribute to the torque, the driving voltage is increased.
[0009]
[Means for Solving the Problems]
The present invention has been made in view of the above problems. The object of the present invention is
An object of the present invention is to provide a small actuator that efficiently generates a large torsion angle (deflection angle) on a movable plate. Such a small actuator is advantageous in providing an optical deflector and an optical device using the optical deflector.
[0010]
Therefore, the present invention
A movable plate,
At least one torsion bar for pivotally supporting the movable plate with respect to a support substrate;
A support extending from the movable plate substantially parallel to the torsion bar,
A movable comb-shaped structure extending from the support in a direction substantially orthogonal to the support,
And a fixed comb-shaped structure disposed at a position where the movable comb-shaped structure is engaged with the movable comb-shaped structure when the movable plate is displaced.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention
(1)
A movable plate,
At least one torsion bar for pivotally supporting the movable plate with respect to a support substrate;
A support extending from the movable plate substantially parallel to the torsion bar,
A movable comb-shaped structure extending from the support in a direction substantially orthogonal to the support,
A fixed comb-shaped structure disposed at a position where the movable comb-shaped structure is engaged with the movable comb-shaped structure when the movable plate is displaced.
[0012]
Also (2)
The actuator according to (1), wherein the fixed comb-shaped structure is disposed on at least one of the front side and the back side of the movable plate.
[0013]
Also (3)
The actuator according to any one of (1) and (2), wherein the movable comb-shaped structure and the fixed comb-shaped structure are made of single crystal silicon.
[0014]
Also (4)
The movable comb-shaped structure and the fixed comb-shaped structure are soft magnetic materials, and a conductor is wound around a part of the fixed comb-shaped structure. (1) or (2) The actuator according to any one of the above is also preferable.
[0015]
Also (5)
An optical deflector of the actuator according to any one of (1) to (4), wherein a reflecting mirror is provided on a surface of the movable plate is also preferable.
[0016]
Also (6)
An optical device using the optical deflector described in (5) is also preferable.
[0017]
The details and operation will be described below with a typical example. FIG. 1 is a perspective view showing the configuration of an embodiment of the actuator of the present invention. FIG. 2 is a top view showing the configuration of an embodiment of the actuator of the present invention. FIG. 3 is a diagram illustrating a method for driving an actuator according to the present invention. In this embodiment, the torsion bar 101 is positioned so as to be linear with respect to the movable plate 102 and to support the center of gravity of the movable plate on both sides. The torsion bar 101 is fixed to a support substrate (not shown) at a fixed end 105. The number of the torsion bars 101 may be one. A support 103 extends substantially parallel to the torsion burn bar 101 from the movable plate 102. A movable comb-shaped structure 104 extends from the support 103 in a direction substantially orthogonal to the support 103. The support 103 and the movable comb-shaped structure 104 may be formed at symmetrical positions with a torsion bar therebetween. The torsion bar 101, the movable plate 102, the support 103, and the movable comb-shaped structure 104 may be integrally formed by removing the support substrate. As the support substrate, for example, a single crystal silicon substrate can be used. The fixed comb-shaped structure 106 is arranged at a position where the movable comb-shaped structure 104 is engaged when the movable comb-shaped structure 104 is inclined. The fixed comb-shaped structure 106 can be formed by, for example, removing a single crystal silicon substrate. There is no electrical connection between the movable comb-shaped structure 104 and the fixed comb-shaped structure 106.
[0018]
In the actuator having this configuration, when the plus side is connected to the integrally formed torsion bar, the movable plate, the support, and the movable comb-shaped structure, and the minus side is connected to the fixed comb-shaped structure, a potential difference is applied to the actuator. The movable comb-like structure is attracted to the fixed comb-like structure by the attractive force. As a result, a torsional moment is generated in the torsion bar, and the movable plate generates a displacement angle with respect to the support substrate from state 1 to state 2 as shown in FIG. The broken line in FIG. 3 represents the outer shape of the movable plate. The gap between the fixed comb-shaped structure and the movable comb-shaped structure is small, and the comb teeth are arranged so as to engage with each other when angularly displaced. Even when angular displacement occurs, it does not interfere with (i.e., collide with) the fixed comb-shaped structure. Further, the movable comb-shaped structure is provided on a support extending from the movable plate, and the displacement angle of the movable plate and the displacement angle of the movable comb-shaped structure are substantially the same, and the per unit displacement angle The amount of change in the overlapping area between the movable comb-shaped structure and the fixed comb-shaped structure is larger by the plurality of movable comb-shaped structures since there are a plurality of movable comb-shaped structures. As a result, the amount of change in the capacitance C formed by the movable comb-shaped structure and the fixed comb-shaped structure per displacement angle increases, and a large displacement angle can be generated at a low voltage. Also, since a large large yoke or the like is not required, the size is small.
[0019]
The movable comb-shaped structure 104 and the fixed comb-shaped structure may be soft magnetic materials. For example, the coercive force of Fe-Ni (permalloy), Fe-Si, Co-Fe-B or the like is low. A soft magnetic material having small residual magnetization and large saturation magnetization can be used. Also in this case, there is no electrical connection between the movable comb-shaped structure 104 and the fixed comb-shaped structure 106. A conductor covered with insulation may be wound around the fixed comb-shaped structure 106.
[0020]
When a current flows through the conductor of the actuator having this configuration, the movable comb-shaped structure 104 is attracted to the fixed comb-shaped structure. The gap between the fixed comb-shaped structure and the movable comb-shaped structure is small, and the comb teeth are arranged so as to engage with each other when angularly displaced. Even when angular displacement occurs, it does not interfere with the fixed comb-shaped structure. Further, the movable comb-shaped structure is provided on the support extending from the movable plate, and the displacement angle of the movable plate and the displacement angle of the movable comb-shaped structure are substantially the same, so that the torque can be efficiently reduced. As a result, a large displacement angle can be obtained without requiring a large current. This results in an actuator with low power consumption. Also, since a large large yoke or the like is not required, the size is small.
[0021]
(Example)
Hereinafter, the present invention will be described in more detail with reference to Examples.
[0022]
(First embodiment)
In this embodiment, the actuator shown in FIGS. 4 to 6 was designed and manufactured. FIG. 4 is a perspective view showing the configuration of the actuator according to the present embodiment of the present invention. FIG. 5 is a diagram illustrating the driving method according to the present embodiment. The broken line in FIG. 5 indicates the outer shape of the movable plate. FIG. 6 is a diagram showing a drive voltage waveform and a response waveform of a displacement angle. A single-crystal silicon substrate having a thickness of 150 μm is used as a support substrate, and the single-crystal silicon substrate is vertically etched using an ICP-RIE apparatus, so that a torsion bar 201, a movable plate 202, a support 203, and a movable comb-tooth structure are formed. The body 204 was integrally formed. The torsion bar 201 is fixed at a fixed end 205 to a single crystal silicon substrate (not shown). Further, another single-crystal silicon substrate is removed to form a first fixed comb-shaped structure 206 and a second fixed comb-shaped structure 207, which are located above and below the movable comb-shaped structure. And the comb teeth were arranged so as to be engaged with each other. Thus, even when the movable plate and the movable comb-shaped structure are angularly displaced, they do not interfere with the fixed comb-shaped structures arranged vertically.
[0023]
A positive bias voltage is applied to the first fixed comb-shaped structure 206 disposed below the movable comb-shaped structure, and a negative bias voltage is applied to the second fixed comb-shaped structure 207 disposed above. In addition, when a driving voltage of a sawtooth wave as shown in FIG. 6, for example, is applied to the movable comb-shaped structure 204, the movable comb-shaped structure 204 becomes first and second fixed comb-shaped structures 206 and 207. , And the response waveform of the displacement angle also becomes a sawtooth wave similar to the applied voltage waveform (the states 1 to 3 in FIG. 6 match the states 1 to 3 in FIG. 5). Thereby, the movable plate swings around the torsion bar as a rotation axis.
[0024]
The actuator of this embodiment is small because it does not require a large and large yoke. Further, the gap between the fixed comb-shaped structure and the movable comb-shaped structure is small, and the comb teeth are arranged so as to mesh with each other when angularly displaced. Even when the body is angularly displaced, it does not interfere with the fixed comb-like structure. Further, the movable comb-shaped structure is provided on a support extending from the movable plate, and the displacement angle of the movable plate and the displacement angle of the movable comb-shaped structure are substantially the same, and the per unit displacement angle The amount of change in the overlapping area between the movable comb-shaped structure and the fixed comb-shaped structure is large. As a result, the amount of change in the capacitance C formed by the movable comb-shaped structure and the fixed comb-shaped structure per displacement angle is increased, and a large displacement angle can be generated at a low voltage. In addition, by arranging the fixed comb-shaped structures vertically, it is possible to increase the displacement angle as compared with the case where only one of them is arranged. In addition, the response to the drive waveform is high, and the response waveform of the displacement angle can be a triangular wave.
[0025]
(Second embodiment)
In this embodiment, the actuator shown in FIGS. 7 to 9 was designed and manufactured. FIG. 7 is a perspective view showing the configuration of the actuator of the present embodiment in the present invention. FIG. 8 is a top view showing the configuration of this embodiment of the present invention. FIG. 9 is a diagram illustrating the driving method according to the present embodiment. As shown in FIG. 8, the support portion 302 and the movable comb-shaped structure 303 of the first embodiment are arranged at positions symmetrical to the torsion bar 301, and the manufacturing method is the same as that of the first embodiment. . In addition, the fixed comb-shaped structure 304 was arranged at a total of four places (however, only two places are shown) above and below the movable comb-shaped structure.
[0026]
In a state where no potential difference is applied between the fixed comb-shaped structure 304 and the movable comb-shaped structure 303, the movable plate 305 does not generate a displacement angle as in state 1 in FIG. When a positive voltage is applied to the structure 304 and a negative voltage is applied to the movable comb-shaped structure 303, the structure is attracted to the upper and lower fixed comb-shaped structures 303 by electrostatic attraction, and changes from state 1 to state 2 I do. Thereby, the movable plate 305 generates a displacement angle with the torsion bar 301 as a rotation axis. The broken line in FIG. 9 shows the outer shape of the movable plate.
[0027]
The actuator of this embodiment is small because it does not require a large and large yoke. Further, the gap between the fixed comb-shaped structure and the movable comb-shaped structure is small, and the comb teeth are arranged so as to mesh with each other when angularly displaced. Even when the body is angularly displaced, it does not interfere with the fixed comb-like structure. Further, the movable comb-shaped structure is provided on a support extending from the movable plate, and the displacement angle of the movable plate and the displacement angle of the movable comb-shaped structure are substantially the same, and the per unit displacement angle The amount of change in the overlapping area between the movable comb-shaped structure and the fixed comb-shaped structure is large. As a result, the amount of change in the capacitance C formed by the movable comb-shaped structure and the fixed comb-shaped structure per displacement angle is increased, and a large displacement angle can be generated at a low voltage. In addition, by arranging the fixed comb-shaped structures vertically, it is possible to increase the displacement angle as compared with the case where only one of them is arranged.
[0028]
(Third embodiment)
In this embodiment, an optical deflector using the actuator shown in the first or second embodiment will be described. FIG. 10 is a perspective view of the optical deflector of the present embodiment. A reflecting mirror was formed on one surface of the movable plate of the actuator of the first embodiment or the second embodiment.
[0029]
The optical deflector of this embodiment is small because it does not require a large and large yoke. Further, the gap between the fixed comb-shaped structure and the movable comb-shaped structure is small, and the comb teeth are arranged so as to mesh with each other when angularly displaced. Even when the body is angularly displaced, it does not interfere with the fixed comb-like structure. Further, the movable comb-shaped structure is provided on a support extending from the movable plate, and the displacement angle of the movable plate and the displacement angle of the movable comb-shaped structure are substantially the same, and the per unit displacement angle The amount of change in the overlapping area between the movable comb-shaped structure and the fixed comb-shaped structure is large. As a result, the amount of change in the capacitance C formed by the movable comb-shaped structure and the fixed comb-shaped structure per displacement angle increases, and an optical deflector capable of generating a large displacement angle at a low voltage. Was produced.
[0030]
(Fourth embodiment)
In this embodiment, an optical device using the optical deflector shown in the third embodiment will be described. FIG. 11 is a diagram showing, as an example, the case of an image display device as an optical device. In FIG. 11, reference numeral 501 denotes an optical deflector group 501 in which two optical deflectors of FIG. 10 are arranged so that their deflection directions are orthogonal to each other. In this case, an optical scanner device for raster-scanning incident light in horizontal and vertical directions Used as Reference numeral 502 denotes a laser light source. Reference numeral 503 denotes a lens or a lens group, 504 denotes a writing lens or a lens group, and 505 denotes a projection surface. The laser light incident from the laser light source 502 undergoes predetermined intensity modulation related to the timing of optical scanning, and is scanned two-dimensionally by the optical deflector group 501. The scanned laser beam forms an image on the projection surface 505 by the writing lens 504.
[0031]
As a result, an optical scanner device featuring a large scanning angle and low power consumption can be realized.
[0032]
(Fifth embodiment)
FIG. 12 is a diagram showing an example in which the optical deflector of the present invention is used in an image forming apparatus. In FIG. 12, reference numeral 601 denotes the optical deflector shown in FIG. 10, which is used as an optical scanner for scanning incident light one-dimensionally. 602 is a laser light source. Reference numeral 603 denotes a lens or a lens group, 604 denotes a writing lens or a lens group, and 605 denotes a photoconductor. The laser light emitted from the laser light source undergoes predetermined intensity modulation related to the timing of optical scanning, and is scanned one-dimensionally by the optical deflector 601. The scanned laser beam forms an image on the photoconductor 605 by the writing lens 604. The photoconductor 605 is uniformly charged by a charger (not shown). By scanning the light on the photoconductor 605, an electrostatic latent image is formed. It is formed. Next, a toner image is formed on the image portion of the electrostatic latent image by a developing device (not shown), and the toner image is transferred and fixed to, for example, a paper (not shown) to form a visible image on the paper.
[0033]
As a result, an image forming apparatus characterized by a large scanning angle and low power consumption can be realized.
[0034]
【The invention's effect】
The actuator of the present invention is small because it does not require a large and large yoke. Further, the gap between the fixed comb-shaped structure and the movable comb-shaped structure is small, and when the angular displacement is performed, the comb teeth are arranged so as to engage with each other, so that the movable plate and the movable comb-shaped structure are angularly displaced. In this case, there is no interference with the fixed comb-shaped structure. Further, the movable comb-shaped structure is provided on a support extending from the movable plate, and the displacement angle of the movable plate and the displacement angle of the movable comb-shaped structure are substantially the same, and the per unit displacement angle The amount of change in the overlapping area between the movable comb-shaped structure and the fixed comb-shaped structure is large. Thus, low voltage driving is possible when considering electrostatic driving, and low power consumption is possible when considering electromagnetic driving.
[Brief description of the drawings]
FIG. 1 is a perspective view showing one embodiment of an actuator of the present invention.
FIG. 2 is a top view showing an embodiment of the actuator of the present invention.
FIG. 3 is a diagram illustrating a driving method of an embodiment of the actuator of the present invention.
FIG. 4 is a perspective view of a first embodiment of the actuator of the present invention.
FIG. 5 is a top view of the first embodiment of the actuator of the present invention.
FIG. 6 is a diagram illustrating a driving method of the first embodiment of the actuator according to the present invention.
FIG. 7 is a perspective view of a second embodiment of the optical deflector of the present invention.
FIG. 8 is a top view of a second embodiment of the optical deflector of the present invention.
FIG. 9 is a diagram illustrating a driving method of a second embodiment of the optical deflector according to the present invention.
FIG. 10 is a perspective view showing an optical deflector using the actuator of the present invention.
FIG. 11 is a diagram in which the optical deflector of the present invention is used for an optical device.
FIG. 12 is a diagram in which the optical deflector of the present invention is used in an image forming apparatus.
FIG. 13 is a diagram showing a conventional example.
FIG. 14 is a diagram showing another conventional example.
FIG. 15 is a diagram showing another conventional example.
[Explanation of symbols]
101 torsion bar 102 movable plate 103 support 104 movable comb structure 105 fixed end 106 fixed comb structure 201 torsion bar 202 movable plate 203 support 204 movable comb structure 205 fixed end 206 first fixed Comb-shaped structure 207 Second fixed comb-shaped structure 301 Torsion bar 302 Support 303 Movable comb-shaped structure 304 Fixed comb-shaped structure 305 Movable plate 401 Reflecting mirror 501 Optical deflector 502 Laser beam 503 Lens 504 Writing lens group 505 Projection surface 601 Optical deflector 602 Laser 603 Lens group 604 Writing lens group 605 Photoconductor 3 Mechanical movable unit 3a Mirror 3b Beam 2 Fixed electrode 801 Torsion bar 802 Comb-shaped movable electrode 803 Comb-shaped fixed Electrode 804 mirror

Claims (1)

A movable plate,
At least one torsion bar for pivotally supporting the movable plate with respect to a supporting substrate;
A support extending substantially parallel to the torsion bar from the movable plate,
A movable comb-shaped structure extending from the support in a direction substantially orthogonal to the support,
An actuator comprising: a fixed comb-shaped structure disposed at a position where the movable comb-shaped structure is engaged with the movable comb-shaped structure when the movable plate is displaced.

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