JP5483620B2 - Actuator - Google Patents

Description

  The present invention relates to an actuator that operates by electrostatic force using micromachine technology.

  In recent years, various forms of micromachines have been developed as a result of advances in micromachine technology using LSI manufacturing technology. For example, there is a fine actuator that converts electric power into mechanical motion by driving a movable electrode with an electrostatic force generated by a fixed electrode (see Non-Patent Documents 1 to 4). For example, there is a mirror element that drives a fine mirror using such an actuator. An optical switch can be realized by using this mirror element.

  As shown in FIG. 4, this actuator includes a so-called comb-like fixed electrode portion 401 and a movable electrode portion 402. This actuator draws the movable electrode portion 402 toward the fixed electrode portion 401 by electrostatic attraction. At this time, as shown in FIG. 5, the movable electrode 521 moves so as to enter between the two fixed electrodes 511 and 512.

W. Piyawattanametha et al., "Surface- and Bulk- Micromachined Two-Dimensional Scanner Driven by Angular Vertical Comb Actuators", Journal of Microelectromechanical Systems, vol.14, no.6, pp.1329-1338, 2005. D. Hah et al., "Low-Voltage, Large-Scan Angle MEMS Analog Micromirror Arrays With Hidden Vertical Comb-Drive Actuators", Journal of Microelectromechanical Systems, vol.13, no.2, pp.279-289, 2004. J. Tsai et al., "Two-axis MEMS scanners with radial vertical combdrive actuators.design, theoretical analysis, and fabrication", J. Opt. A: Pure Appl. Opt., Vol.10, 044006, 2008. Ming C. Wu, "Micromachining for Optical and Optoelectronic Systems", Proceedings of the IEEE, vol.85, no.11, pp.1833-1856, 1997.

  However, the above-described actuator has a problem that the movable range of the movable electrode cannot be increased so much. First, the thickness of the movable electrode 521 is preferably thinner in order to avoid a decrease in the resonance frequency. However, since the actuator described above stops at a position where the capacitance between the electrodes is maximized, in the actuator described above, the movable range of the movable electrode 521 in the direction of the fixed electrodes 511 and 512 is the upper end of the movable electrode 521. Is the maximum movable range up to the point where the upper end coincides with the upper ends of the fixed electrodes 511 and 512. For this reason, the movable distance of the movable electrode 521 depends on the length (thickness) of the section of the movable electrode 521 in the movable direction. When the thickness of the movable electrode 521 is thin, the movable range of the movable electrode 521 becomes narrow.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to increase the movable range of the movable electrode without increasing the thickness of the movable electrode.

  The actuator according to the present invention is arranged between four or more fixed electrodes spaced apart on a substrate and adjacent fixed electrodes, and at least one end of each of the fixed electrodes supported by a spring portion. At least a movable electrode provided with a plurality of comb-teeth portions that can be displaced in the normal direction of the substrate and has a width that does not contact an adjacent fixed electrode. The movable electrode is displaced by an electrostatic attractive force generated by applying a voltage to the fixed electrode.

  As described above, according to the present invention, it is possible to obtain an excellent effect that the movable range of the movable electrode can be increased without increasing the thickness of the movable electrode.

FIG. 1 is a configuration diagram showing a configuration of an actuator according to an embodiment of the present invention. FIG. 2 is a configuration diagram showing another configuration of the actuator according to the embodiment of the present invention. FIG. 3 is a characteristic diagram showing the relationship between applied voltage and displacement with respect to the operation of the actuator according to the embodiment of the present invention. FIG. 4 is a perspective view showing a configuration of a comb-shaped actuator. FIG. 5 is an explanatory diagram for explaining the operation of the actuator.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a configuration of an actuator according to an embodiment of the present invention.

  The actuator is disposed between a fixed electrode portion 102 composed of four or more fixed electrodes spaced apart from each other on the substrate 101 and the adjacent fixed electrodes, and enters between the adjacent fixed electrodes. The movable electrode 103 includes at least a plurality of comb-tooth portions 131 that are displaceable in the normal line direction 101 and have a width that does not contact an adjacent fixed electrode. In the present embodiment, the fixed electrode portion 102 is composed of six fixed electrodes 121 to 123. In addition, the fixed electrodes 121 to 123 are formed lower toward the center of the array. In the present embodiment, the fixed electrode 122 is formed lower than the fixed electrode 121, and the fixed electrode 123 is formed lower than the fixed electrode 122.

  By doing in this way, in the initial state where the electrostatic force does not work, the comb tooth portion 131 between the fixed electrode 121 and the fixed electrode 122 is closest to the fixed electrode 121, and when the electrostatic force is applied, The electrostatic attractive force acts strongly and the movable electrode 103 is displaced toward the substrate 101. Here, when the comb tooth portion 131 is displaced to the upper end portion of the fixed electrode 121, the pulling force on the comb tooth portion 131 between the fixed electrode 121 and the fixed electrode 122 becomes weak.

  However, since the fixed electrode 122 and the fixed electrode 123 are formed lower than the fixed electrode 121, the pulling-down force on the comb tooth portion 131 between the fixed electrode 122 and the fixed electrode 123 is still in a strong state. For this reason, the movable electrode 103 is further displaced toward the substrate 101. Next, when the comb tooth portion 131 is displaced to the upper end portion of the fixed electrode 122, the pulling-down force on the comb tooth portion 131 between the fixed electrode 122 and the fixed electrode 123 becomes weak.

  However, since the fixed electrode 123 is formed lower than the fixed electrode 122, the pulling-down force with respect to the comb-tooth portion 131 between the two fixed electrodes 123 is still in a strong state. For this reason, the movable electrode 103 is further displaced toward the substrate 101. As a result, the movable electrode 103 can be displaced until the comb tooth 131 between the two fixed electrodes 123 overlaps the upper end of the fixed electrode 123.

  As described above, according to the present embodiment, the movable electrode 103 can be displaced closer to the substrate 301, and the movable range of the movable electrode 103 can be increased. Further, according to the present embodiment, the movable range can be increased without increasing the length (thickness) of the movable electrode 103 (comb portion 131) in the normal direction of the substrate 101. In the example described above, the fixed electrode is formed so as to be lower toward the center of the array. However, the same function can be obtained regardless of the array of fixed electrodes having different heights.

  In addition, as shown in FIG. 2, the fixed electrode unit 202 may be configured from eight fixed electrodes 221 to 224. The fixed electrode 222 is formed lower than the fixed electrode 221, the fixed electrode 223 is formed lower than the fixed electrode 222, and the fixed electrode 224 is formed lower than the fixed electrode 223. Here, the interval g between each fixed electrode and the comb tooth portion 231 is 8 μm, the height of the fixed electrode 221 is 30 μm, the height of the fixed electrode 222 is 24 μm, the height of the fixed electrode 223 is 18 μm, and the height of the fixed electrode 224 is high. The thickness is set to 12 μm. Further, the thickness t of the comb tooth portion 231 of the movable electrode 203 is set to 8 μm. A beam portion (not shown) connected to the movable electrode 203 composed of the comb-tooth portion 231 has a width of 20 μm, a length of 1200 μm, and a thickness of about 8 μm.

  When a voltage is applied between the fixed electrode portion 202 and the movable electrode 203 of the actuator having the above-described configuration, the movable electrode 203 is displaced as shown by a white triangle in FIG. 3, and a displacement of about 24 μm at the maximum is obtained. On the other hand, in the configuration in which the heights of the fixed electrodes described above are all uniformly formed to 30 μm, as shown by the white circles in FIG. 3, when the displacement reaches about 8 μm, no further displacement occurs. It is limited by the thickness of the movable electrode 203. As is clear from these facts, the movable electrode can be displaced more greatly by forming the plurality of fixed electrodes so as to have different heights toward the center of the array.

  The present invention is not limited to the embodiment described above, and many modifications and combinations can be implemented by those having ordinary knowledge in the art within the technical idea of the present invention. It is obvious. For example, in the above-described embodiment, in the configuration including four or more fixed electrodes and the movable electrode provided with the comb-tooth portion, the case where the fixed electrode is formed lower toward the center of the array has been described as an example. However, it is not limited to this. The plurality of fixed electrodes may be formed at different heights.

  In the above description, the movable electrode has a plate-like cantilever structure. However, the present invention is not limited to this, and the movable electrode is displaceable with at least one end supported by a spring portion. That's fine. The spring portion may be formed of a deformable elastic member, and may have any shape. For example, it is good also as a structure which connects a movable electrode and a support structure by the connection part (spring part) which consists of an elastic member separate from a movable electrode.

  DESCRIPTION OF SYMBOLS 101 ... Board | substrate, 102 ... Fixed electrode part, 103 ... Movable electrode, 121,122,123 ... Fixed electrode, 131 ... Comb tooth part.

Claims (1)

Four or more fixed electrodes spaced apart on the substrate;
Arranged between the adjacent fixed electrodes, at least one end of which is supported by a spring portion, enters between the adjacent fixed electrodes and is displaceable in the normal direction of the substrate and contacts the adjacent fixed electrodes And at least a movable electrode having a plurality of comb teeth portions having a width in a range not to be
The fixed electrodes are formed at different heights, respectively.
The movable electrode is displaced by electrostatic attraction generated by applying a voltage to the fixed electrode.

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