JP2003243254A - Variable capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make variation of an electrostatic capacitance of a variable capacitor sufficiently larger and, at the same time, to simplify a control circuit which controls the electrostatic capacitance. <P>SOLUTION: On a substrate 1, a square shallow step 3 is provided and a square deep step 5 is provided at a position which is lower than that of the part 3 by one level. In addition, a mobile electrode 2 is constituted as a cantilever by fixing an electrode pad 2A of the electrode 2 on the fixed end side to a surface 1A of the substrate 1. On the substrate 1, a driving electrode 4 which is extended to the groove bottom 2A of the shallow step 3 from the surface 1A of the substrate 1 is fixed. In addition, a detecting electrode 6 which is extended to a groove bottom 5A of the deep step 5 from the surface 1A of the substrate 1 is also fixed. Thus, an interval W1 between the mobile electrode 2 and the detecting electrode 6 is made wider than that W2 between the mobile electrode 2 and the driving electrode 4. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable capacitor suitable for use in, for example, changing capacitance.

[0002]

2. Description of the Related Art Generally, a variable capacitance capacitor includes a substrate, a movable electrode whose fixed end is provided on the substrate and whose free end is displaced in a direction perpendicular to the substrate, and the substrate at a position facing the movable electrode. A drive electrode provided on the substrate to displace the free end side of the movable electrode in the vertical direction, and a free electrode side of the movable electrode provided on the substrate located closer to the free end side of the movable electrode than the drive electrode. It is composed of a detection electrode whose electrostatic capacitance changes according to the inter-electrode spacing.

By applying a voltage to the drive electrode, the variable capacitance capacitor generates an electrostatic attractive force between the drive electrode and the movable electrode, thereby vertically moving the movable electrode toward the drive electrode. In this configuration, the electrostatic capacitance generated between the movable electrodes and the detection electrodes is changed in accordance with the electrode spacing between the movable electrodes and the detection electrodes at this time.

In another conventional technique, both ends of the lengthwise intermediate portion of a rectangular movable electrode are supported by a torsion spring on the substrate, and the torsion spring is sandwiched between the two substrates. There is a configuration in which the drive electrodes are provided in parallel and one detection electrode facing the movable electrode is provided (for example, Japanese Patent Laid-Open No. 9-153436).

In this prior art, a voltage is selectively applied to the two drive electrodes to swing the movable electrode with a torsion spring as a fulcrum, whereby the movable electrode and the detection electrode are separated. The space between these electrodes is changed by widening or narrowing the space.
In this case, the torsion spring can sufficiently increase the amount of displacement of the movable electrode in the vertical direction, and the capacitance of the detection electrode can be increased.

[0006]

By the way, in the above-mentioned prior art, the free end side of the movable electrode placed parallel to the substrate is vertically displaced by the drive electrode so as to approach the detection electrode. . In this case, for example, if it is attempted to reduce the electrode interval to about ⅔ of the initial state, the movable electrode is easily attracted to the drive electrode by electrostatic attraction, and therefore, simply displacing the movable electrode with respect to the substrate causes
There is a problem that the capacitance cannot be changed sufficiently.

In the variable capacitor disclosed in the above-mentioned Japanese Patent Laid-Open No. 9-153436, the movable electrode is provided with a torsion spring by selectively applying a voltage to the two drive electrodes provided on the substrate. Swing as a fulcrum,
The electrostatic capacitance of the detection electrode is changed by widening or narrowing the gap between the movable electrode and the detection electrode.

However, in the case of swinging the movable electrode as described above, it is necessary to apply different voltages to the two drive electrodes, which causes a problem that the control circuit for controlling the electrostatic capacitance becomes complicated.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to make it possible to change the capacitance sufficiently large and to simplify the control circuit for controlling the capacitance. It is to provide a variable capacitor that can be used.

[0010]

In order to solve the above-mentioned problems, a variable capacitor according to the present invention comprises a substrate,
A movable electrode whose fixed end side is provided on the substrate and whose free end side is displaced in the vertical direction with respect to the substrate, and a free end side of the movable electrode which is provided on the substrate at a position facing the movable electrode and which is displaced vertically A detection electrode whose capacitance changes according to the electrode distance between the drive electrode and the free end side of the movable electrode, which is located closer to the free end side of the movable electrode than the drive electrode. It consists of and.

The feature of the configuration adopted by the invention of claim 1 is that at least one of the substrate and the movable electrode has an electrode interval between the movable electrode and the detection electrode.
It is configured to be formed to be larger than the electrode interval between the movable electrode and the drive electrode.

With this configuration, in the initial state of the capacitor, the electrode gap between the movable electrode and the detection electrode can be formed larger than the electrode gap between the movable electrode and the drive electrode, and the capacitor can be moved by the drive electrode. When displacing the electrodes, the electrode spacing between the movable electrode and the detection electrode can be changed in a range larger than these electrode spacings. Therefore, the amount of change in the electrostatic capacitance between the movable electrode and the detection electrode can be set to be larger than that in the case where the drive electrode and the detection electrode are on the same plane.

According to a second aspect of the present invention, a step portion is provided in a portion of the substrate facing the movable electrode, the drive electrode is disposed on the front surface side of the substrate, and the detection electrode is on the step portion side. It is configured to be installed in. With this configuration, the electrode gap between the detection electrode and the movable electrode and the electrode gap between the drive electrode and the movable electrode can be set larger by the step portion.

According to the invention of claim 3, the substrate is provided with a shallow step portion and a deep step portion, a drive electrode is provided in the shallow step portion, and a detection electrode is provided in the deep step portion. With this configuration, the electrode spacing between the detection electrode and the movable electrode provided in the deep step portion is made larger than the electrode spacing between the drive electrode and the movable electrode provided in the shallow step portion. be able to.

Further, in the invention of claim 4, the step portion is constituted by a bent portion which is provided on the free end side of the movable electrode and is bent in a direction away from the substrate as compared with a portion facing the drive electrode. With this configuration, the electrode gap between the movable electrode and the detection electrode can be set larger than the electrode gap between the movable electrode and the drive electrode by the bent portion.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION A variable capacitor according to an embodiment of the present invention will be described in detail below with reference to the accompanying drawings of FIGS. Here, FIGS. 1 to 4 show a first embodiment of the present invention.

Reference numeral 1 is a substrate according to the present embodiment.
Is formed as a quadrangular insulating substrate using a semiconductor material such as a silicon material or an insulating material such as a glass material, and the surface 1A thereof has a shallow step portion 3 and a deep step portion 5 which will be described later.
Are respectively recessed.

Reference numeral 2 denotes a movable electrode composed of a cantilever whose base end side is fixed to the substrate 1. The movable electrode 2 is an elongated flat plate made of a conductive metal material such as aluminum or gold. It is formed and has a length of about several hundred μm. Further, the movable electrode 2 is not limited to a single metal, but may be a metal thin film grown by using a semiconductor material such as silicon or an insulating material such as a glass material as a base so as to face the drive electrode 4 and the detection electrode 6.

The fixed end side (base end side) of the movable electrode 2 serves as an electrode pad 2A connected to, for example, ground, and the electrode pad 2A is fixed to the surface 1A of the substrate 1. Further, the tip end side of the movable electrode 2 becomes a free end 2B facing the shallow step portion 3, and the substrate 1 is formed by the drive electrode 4 described later.
It is displaced in the vertical direction with respect to.

Reference numeral 3 denotes a shallow stepped portion provided on the surface 1A of the substrate 1. The shallow stepped portion 3 is, as shown in FIG. 1 and FIG. And has a groove bottom 3A.

Reference numeral 4 denotes a drive electrode fixedly provided on the substrate 1 at a position facing the movable electrode 2. The drive electrode 4 is formed in an elongated rectangular shape using a conductive metal material such as aluminum. There is. The tip end side of the drive electrode 4 is located on the shallow step portion 3 side and is arranged orthogonal to the movable electrode 2. Therefore, the drive electrode 4 has a base end on the surface 1 of the substrate 1.
It becomes the electrode pad 4A provided on A, and the tip side 4B is L
It is bent in a letter shape and extends to the groove bottom 3A of the shallow step portion 3.

A drive signal from the outside is input to the electrode pad 4A of the drive electrode 4, and the free end 2 of the movable electrode 2 is
An electrostatic attractive force is generated between the B side and the free end 2B side to be vertically displaced.

Reference numeral 5 is a free end 2B of the movable electrode 2 of the substrate 1.
The deep step portion 5 is formed as a quadrangular concave recess having a deeper depth than the shallow step portion 3, and is arranged continuously with the shallow step portion 3. ing. Further, the deep step portion 5 has a groove bottom 5A.

Reference numeral 6 denotes a detection electrode which is located closer to the free end 2B of the movable electrode 2 than the drive electrode 4 and is fixedly provided on the substrate 1. The detection electrode 6 is made of a conductive metal material such as aluminum. It has a long and narrow rectangular shape. The tip end side of the detection electrode 6 is arranged orthogonal to the movable electrode 2. Therefore, the detection electrode 6 has an electrode pad 6A provided on the front surface 1A of the substrate 1 on the base end side, and has a tip end side 6B bent in an L shape to extend to the groove bottom 5A of the deep step portion 5.

Therefore, the electrode spacing W1 between the movable electrode 2 and the detection electrode 6 is set to be larger than the electrode spacing W2 between the movable electrode 2 and the drive electrode 4, as shown in FIG. The capacitance between the detection electrode 6 and the movable electrode 2 changes according to the electrode spacing W1, and this capacitance is output to the outside from the electrode pad 6A as a detection signal.

The variable capacitor according to the present embodiment has the above-mentioned structure, and its operation will be described below.

First, when a drive signal is externally input to the electrode pad 4A of the drive electrode 4, the movable electrode 2 and the drive electrode 4 are
An electrostatic attractive force acts between and, and the free end 2B side of the movable electrode 2 attracted by this electrostatic attractive force is elastically deformed downward as shown in FIG. As a result, the electrode distance W1 between the movable electrode 2 and the detection electrode 6 is reduced, the electrostatic capacitance between them is increased, and the change amount of this electrostatic capacitance is output to the outside from the electrode pad 6A as a detection signal. To do.

Here, in the present embodiment, the deep step portion 5 provided with the detection electrode 6 is formed deeper than the shallow step portion 3 provided with the drive electrode 4, so that as shown in FIG. In addition, the electrode distance W1 between the movable electrode 2 and the detection electrode 6 is made larger than the electrode distance W2 between the movable electrode 2 and the drive electrode 4.

Therefore, in the initial state in which no voltage is applied to the driving electrode 4, when the movable electrode 2 is displaced by the driving electrode 4, the movable electrode 2 and the detection electrode 6 are separated from each other within a range larger than the electrode interval W2. Since the electrode interval W1 between them can be changed, for example, the drive electrode 4 and the detection electrode 6
The change amount (change range) of the capacitance can be set to be larger than that of and on the same plane.

Further, when displacing the movable electrode 2, it suffices to apply a voltage to one drive electrode 4, and it is necessary to apply a different voltage to each of the two drive electrodes as described in the prior art. Is eliminated, and the control circuit for controlling the capacitance can be simplified.

Next, FIGS. 5 and 6 show a second embodiment of the present invention. The feature of the present embodiment is that the free electrode side of the movable electrode is a portion of the movable electrode facing the drive electrode. In addition, a bent portion that is bent in a direction away from the substrate is provided. In addition, in the present embodiment, the same components as those in the first embodiment described above are designated by the same reference numerals, and the description thereof will be omitted.

Reference numeral 11 is a substrate according to this embodiment, and a step portion 12 having a horizontal groove bottom 12A is provided on the surface 11A of the substrate 11.

Reference numeral 13 denotes a movable electrode used in this embodiment,
The movable electrode 13 is also a cantilever which is fixed to the surface 11A of the substrate 11 by forming the electrode pad 13A on the base end side (fixed end) in substantially the same manner as the movable electrode 2 described in the first embodiment. It is configured. Further, the tip side of the movable electrode 13 is a free end 13B.

However, a bent portion 13C is provided on the free end 13B side of the movable electrode 13. For this reason, the movable electrode 13 is located closer to the detection electrode 1 than the portion facing the drive electrode 14.
The side of the free end 13B facing 5 is arranged in a direction away from the substrate 11.

Reference numeral 14 is a drive electrode fixed to the substrate 11,
The tip side 14A of the drive electrode 14 is provided on the groove bottom 12
It is located on A. Reference numeral 15 is a detection electrode fixed to the substrate 11 together with the drive electrode 14, and the tip side 15A of the detection electrode 15 is arranged on the groove bottom 12A of the step portion 12 on the same plane as the tip side 14A of the drive electrode 14. ing.

Thus, in the present embodiment configured as described above, the bent portion 13 is provided on the free end 13B side of the movable electrode 13.
Since C is formed, the electrode distance W3 between the movable electrode 13 and the detection electrode 15 can be made larger than the electrode distance W4 between the movable electrode 13 and the drive electrode 14 as shown in FIG.

As a result, in the initial state where no voltage is applied to the drive electrode 14, the drive electrode 14 causes the movable electrode 13 to move.
When displacing, the electrode spacing W3 between the movable electrode 13 and the detection electrode 15 can be changed within a range larger than the electrode spacing W4. Therefore, for example, the drive electrode 14 and the detection electrode 15 are on the same plane. Compared with the one described in (1), the amount of change in the electrostatic capacitance between the drive electrode 14 and the detection electrode 15 can be set to be large, and the same operational effect as that of the first embodiment can be obtained.

Next, FIGS. 7 and 8 show a third embodiment of the present invention. The feature of this embodiment is that both ends of the intermediate portion in the length direction of the movable electrode having a rectangular shape are formed on the substrate. On the other hand, a torsion spring is used for supporting, and two drive electrodes are provided in parallel on the substrate with the torsion spring interposed therebetween.
One of the movable electrodes is arranged in parallel with one of the movable electrodes, and one detection electrode is provided, and the detection electrode is arranged at a position one step lower than the movable electrode.

Reference numeral 21 is a substrate according to the present embodiment. The substrate 21 has a thick portion 21A on which a drive electrode 24 described later is provided.
And a thin portion 21B provided with the detection electrode 25. The thin portion 21B is provided with the thick portion 2 through the step portion 21C.
It is located one step lower than 1A.

Reference numeral 22 denotes a movable electrode which is swingably provided on the thick portion 21A of the substrate 21. The movable electrode 22 is a substantially rectangular flat plate portion 22A and the flat electrode portion 22A is bent in a crank shape. It is composed of a pair of torsion springs 22B, 22B integrally formed on both sides of the intermediate portion in the length direction.

The movable electrode 22 is provided with a torsion spring 22B on the fixed end side through the electrode pad 23 and the substrate 21.
Of the flat plate portion 22A, which is fixed to the thick portion 21A of the flat plate portion 22A by an electrostatic attractive force generated between the thick electrode portion 21A and the drive electrode 24 described later.
A1 swings in the direction of the arrow shown in FIG.

Reference numerals 24 and 24 are located on both sides of the movable electrode 22 with the torsion spring 22B interposed therebetween, and the thick portion 21 of the substrate 21 is provided.
With a pair of drive electrodes provided on A, a drive signal is selectively input to the drive electrode 24 from the outside, whereby the movable electrode 22 is supported by the torsion spring 22B as a fulcrum.
It is made to oscillate like the one-dot chain line and two-dot chain line shown inside.

Reference numeral 25 denotes a detection electrode provided on the thin portion 21B of the substrate 21, and the detection electrode 25 is arranged at a position one step lower than the driving electrode 24 via the step portion 21C of the substrate 21. The electrode distance W5 between the movable electrode 22 and the detection electrode 25 is set larger than the electrode distance W6 between the movable electrode 22 and the drive electrode 24 as shown in FIG. The capacitance of the detection electrode 25 changes according to the electrode distance W5 between the detection electrode 25 and the movable electrode 22, and the capacitance is output to the outside as a detection signal.

Thus, also in the present embodiment having such a configuration, in the initial state where no voltage is applied to the drive electrode 24, when the movable electrode 22 is displaced by the drive electrode 24, a range larger than the electrode interval W6 is provided. Since the electrode distance W5 between the movable electrode 22 and the detection electrode 25 can be changed by, the amount of change in electrostatic capacitance can be compared with that in which the drive electrode 24 and the detection electrode 25 are on the same plane. Can be set to a large value, and substantially the same operational effect as that of the first embodiment can be obtained.

[0045]

As described in detail above, according to the invention of claim 1, at least one of the substrate and the movable electrode is provided with an electrode interval between the movable electrode and the detection electrode. Since it is configured to be larger than the electrode interval between the drive electrode, in the initial state of the capacitor,
For example, the amount of change in the electrostatic capacitance between the movable electrode and the detection electrode can be set to be larger than that when the drive electrode and the detection electrode are on the same plane.

According to a second aspect of the present invention, a step portion is provided in a portion of the substrate facing the movable electrode, the drive electrode is arranged on the front surface side of the substrate, and the detection electrode is arranged on the step portion side. Because of the configuration, the stepped portion can set the electrode interval between the detection electrode and the movable electrode larger than the electrode interval between the drive electrode and the movable electrode, and the detection electrode when the voltage is applied to the drive electrode The amount of change in the capacitance of can be set large.

Further, according to the third aspect of the invention, since the drive electrode is provided in the shallow step portion and the detection electrode is provided in the deep step portion, the detection electrode and the movable electrode provided in the deep step portion are It is possible to surely set the inter-electrode spacing larger than the inter-electrode spacing between the drive electrode and the movable electrode provided in the shallow step portion.

Further, according to the invention of claim 4, the bent portion provided on the movable electrode is arranged so that the portion of the movable electrode facing the detection electrode is located farther from the substrate than the portion facing the drive electrode. The electrode gap between the movable electrode and the detection electrode can be set larger than the electrode gap between the movable electrode and the drive electrode by the bent portion, and the amount of change in the capacitance of the detection electrode when a voltage is applied to the drive electrode. Can be set large.

[Brief description of drawings]

FIG. 1 is a perspective view showing a variable capacitor according to a first embodiment of the present invention.

FIG. 2 is a plan view showing a variable capacitance capacitor according to the first embodiment.

FIG. 3 is a cross-sectional view of the variable capacitor seen from the direction of arrows III-III in FIG.

FIG. 4 is a sectional view similar to FIG. 3, showing a state in which the free end side of the movable electrode is displaced to the detection electrode side.

FIG. 5 is a sectional view similar to FIG. 3, showing a variable capacitor according to a second embodiment of the present invention.

6 is a sectional view similar to FIG. 5, showing a state in which the free end side of the movable electrode is displaced to the detection electrode side.

FIG. 7 is a perspective view showing a variable capacitance capacitor according to a third embodiment of the present invention.

8 is a sectional view of a variable capacitance capacitor according to a third embodiment of the present invention as viewed in the direction of arrows VIII-VIII in FIG. 7.

[Explanation of symbols]

1,11,21 substrate 2,13,22 movable electrode 2B, 13B Free end 3 shallow steps 4,14,24 Drive electrodes 5 Deep step 6,15,25 detection electrode 12,21C step W1, W2, W3, W4, W5, W6 Electrode spacing

Claims (4)

[Claims] 1. A substrate, a movable electrode whose fixed end is provided on the substrate and whose free end is displaced in a direction perpendicular to the substrate, and a movable electrode which is provided on the substrate at a position facing the movable electrode. Depending on the electrode spacing between the drive electrode that displaces the free end side in the vertical direction and the free electrode side of the movable electrode that is located on the free end side of the movable electrode with respect to the drive electrode. In a variable capacitance capacitor including a detection electrode whose capacitance changes, at least one member of the substrate and the movable electrode is
A variable capacitance capacitor characterized in that an electrode interval between the movable electrode and the detection electrode is formed larger than an electrode interval between the movable electrode and the drive electrode. 2. A step portion is provided in a portion of the substrate facing the movable electrode, the drive electrode is arranged on the front surface side of the substrate, and the detection electrode is arranged on the step portion side. The variable capacitor according to Item 1. 3. The variable capacitor according to claim 1, wherein the substrate is provided with a shallow step portion and a deep step portion, a drive electrode is provided in the shallow step portion, and a detection electrode is provided in the deep step portion. Capacitors. 4. The free end side of the movable electrode is provided with a bent portion bent in a direction away from the substrate rather than a portion facing the drive electrode, and the detection electrode is arranged at the position of the bent portion. The variable capacitor according to claim 1, 2, or 3.