JPH10132572A - Electrostatic drive type angular velocity sensor - Google Patents

Abstract

(57) [Summary] [Problem] To shorten design time and improve sensitivity. An electrode substrate includes first to fourth electrodes.
-4 are formed around the z-axis in order at approximately 90 ° intervals in opposition to the rectangular-shaped thin portion 3c. The first and third electrodes are used as drive electrodes, and a voltage that changes differentially with respect to the diaphragm 3 is applied to the diaphragm 3 so that both the drive vibration and the output vibration (detection vibration) of the mass unit 4 are pendulum. Vibration. The input angular velocity ω in the z-axis direction is detected by detecting the capacitance that changes differentially with the diaphragm 3 using the second and fourth electrodes as detection electrodes. In the example of FIG. 1, the y-axis and the x-axis are the drive shaft and the output shaft, respectively, and the first and third (second and fourth) electrodes are ± 45 around the positive and negative directions of the y (x) axis. In the range of °, y
It is formed symmetrically with respect to the (x) axis. Further, the outer shape of each electrode is an isosceles triangle in the example of FIG.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic drive type angular velocity sensor, and more particularly to two vibrations having a rotational angular velocity of a mass section in a drive axis direction and an output axis direction, that is, resonance of drive vibration and output vibration (detection vibration). The present invention relates to a sensor having a frequency as close as possible and having high detection sensitivity and a sensor capable of shortening a design time.

[0002]

2. Description of the Related Art A conventional angular velocity sensor of this type will be described with reference to FIGS. The angular velocity sensor has a diaphragm 3
And a mass portion 4 elastically supported on the bottom surface side thereof, and an electrode substrate 6 disposed opposite to the diaphragm 3 with a gap 5 therebetween. Conventional angular velocity sensors are shown in FIG.
-of rectangular coordinates composed of y and z axes (the vertical axis is the z axis)
It is configured to detect a rotational angular velocity ω having the x axis as an input axis.

A diaphragm 3 is formed on a bottom surface of a semiconductor wafer made of silicon or the like arranged in parallel with an xy plane by a rectangular groove 3 having a side parallel to the x-axis or the y-axis by etching.
a is formed. As a result, a square central portion 3b surrounded by the square groove 3a, a square thin portion 3c corresponding to the bottom surface of the square groove, and a frame 3d outside the square groove are formed on the diaphragm 3. .

The mass portion 4 is a rectangular parallelepiped such as Pyrex glass in this example, and is fixed to the bottom surface of the central portion 3b. A base frame 7 made of Pyrex glass or the like is provided on the bottom surface of the frame 3d.
Is fixed, and the mass part 4 is arranged via the gap with the inner peripheral surface of the base frame 7. The height of the base frame 7 is slightly larger than the height of the mass section 4, and when the base frame 7 is placed on the base 8, a gap 9 is formed between the base 8 and the mass section 4.

[0005] The electrode substrate 6 has substantially the same outer shape as the diaphragm 3, and a concave portion 6 a having a depth equal to the gap 5 except for the peripheral portion is formed on the bottom surface of an insulating substrate such as Pyrex glass. A square Z electrode 6b is formed on the inner surface of the electrode substrate 6 so as to face the central portion 3b, and trapezoidal X1 electrodes 6c and X2 are provided near the Z electrode 6b in the positive and negative directions of the x-axis, respectively. The electrode 6d is formed by sputtering of gold on chromium or the like. The bottom surface of the peripheral portion 6 g of the electrode substrate 6 is fixed on the frame 3 d of the diaphragm 3.

For fixing the diaphragm 3 to the electrode substrate 6, the mass part 4, and the base frame 7, a method such as adhesion or anodic bonding is used. By applying an AC voltage having an angular frequency ωdrv between the Z electrode 6 b and the diaphragm 3,
To the mass part 4 in the z-axis direction with an angular frequency ω
A translational vibration is performed at drv. In this case, the z axis is the drive axis,
The electrode 6b is called a drive electrode. At this time, when an angular velocity of ω = dθ / dt (θ is a rotation angle, t is time) is input in the direction of the input axis (corresponding to the −x axis), −y is given to the mass unit 4.
A Coriolis force is generated in the axial direction, and the mass unit 4 adds a pendulum vibration (angular velocity ωout) in the −y-axis direction to the translational vibration in the z-axis (drive shaft) direction.

The combined vibration of the translational vibration in the z-axis direction and the pendulum vibration in the -y-axis direction makes the X1 electrodes 6c and X
The capacitances CX1 and CX2 between the two electrodes 6d and the diaphragm 3 change differentially with each other as shown in FIG.
That is, CX1 and CX2 are represented by CX1 = C01 + C1 × Fa (ωdrv · t + φ1) + C1 ′ × Fbωdrv · t, CX2 = C02−C2 × Fa (ωdrv · t + φ2) + C2 ′ × Fbωdrv · t (1) Fa and Fb are time functions (for example, sine functions) of the changing portions of CX1 and CX2, and C1, C2 and C1 'and C2' are the amplitudes of the fluctuations. φ1 and φ2 are phase angles, which are determined by the direction of the input angular velocity. C0
1 and C02 are known values of CX1 and CX2 when there is no translational vibration or input angular velocity in the multiaxial directions. The second term of the equation (1) is a change in capacity caused by the coriolio, and the third term is a change in capacity due to translational vibration in multiple axes.

C1, C2∝ω = dθ / dt (magnitude of input angular velocity) (2) Therefore, the input angular velocity can be detected by detecting a change in CX1 and CX2. The -y axis where the Coriolis force is generated is an output axis or a detection axis,
Each electrode of 1 and X2 is called a detection electrode.

[0009]

In order to improve the sensitivity of the electrostatic drive type angular velocity sensor, translational vibration in the direction of the drive shaft (z axis), that is, the resonance frequency of the drive vibration and the output shaft (-
Pendulum vibration in the y-axis) direction, that is, output vibration (detection vibration)
Must be as close as possible. For this reason, conventionally, assuming the external dimensions and thickness of the square-shaped thin portion 3c of the diaphragm 3 and the shape of the mass portion 4, the resonance frequency of the vibration in the drive shaft direction and the output shaft direction is determined by FEM (finite element analysis; fine element element method
d), that is, CAE (computer aided)
It is obtained by vibration analysis using a workstation for engineering, correcting the assumed shapes of the diaphragm and the mass part based on the result, and repeating the analysis again. 4 was designed. For this reason, considerable design time was required.

Nevertheless, it has been difficult to set the resonance frequencies of the driving vibration and the output vibration to values close to each other as desired for improving the sensitivity. The present invention aims to solve these problems.

[0011]

[Means for Solving the Problems]

(1) An electrostatic drive type angular velocity sensor to which the present invention is directed has a diaphragm, a mass part elastically supported on the bottom side of the diaphragm, and an electrode substrate opposed to the diaphragm via a gap. . In the diaphragm, a rectangular groove having a side parallel to the x-axis or the y-axis is formed on the bottom surface of a semiconductor wafer arranged in parallel with the xy plane of (x, y, z) rectangular coordinates with the z-axis as a center, It has a central portion surrounded by the square groove, a square thin portion corresponding to the bottom surface of the square groove, and a frame portion outside the square groove. The mass part is fixed to the bottom surface of the central part.

The electrode substrate has a drive electrode and a detection electrode (output electrode) formed on the inner surface of the insulating substrate. By applying an AC voltage between the drive electrode and the diaphragm, the mass part is vibrated by electrostatic force, and the input angular velocity is detected by detecting the capacitance between the detection electrode and the diaphragm. In the invention of the first aspect, in particular, the electrode substrate is formed such that the first to fourth electrodes having the same outer shape face the rectangular thin portion at intervals of approximately 90 ° around the z-axis. The first and third electrodes facing each other are used as drive electrodes, and voltages that change differentially with each other are applied to the diaphragm, so that both drive vibration and output vibration (detection vibration) of the mass unit are pendulum. Vibration. Then, the input angular velocity in the z-axis direction is detected by detecting the capacitance that changes differentially between the diaphragm and the second and fourth electrodes as the detection electrodes.

(2) In the invention of claim 2, in the above (1), the y-axis and the x-axis are a drive shaft and an output shaft, respectively. The first and third electrodes are respectively formed symmetrically with respect to the y-axis within a range of ± 45 ° about the positive and negative directions of the y-axis, and the second and fourth electrodes are respectively formed with the positive x-axis. And symmetrically with respect to the x-axis in a range of ± 45 ° about the negative direction.

(3) In the invention of claim 3, in the above (2), the shape of the first and third electrodes is an isosceles triangle having a vertex angle on the z-axis side and a base parallel to the x-axis. The shape of the second and fourth electrodes is an isosceles triangle having an apex angle on the z-axis side and a base parallel to the y-axis. (4) In the invention of claim 4, in the above (1), the β-axis and the α-axis obtained by rotating the y-axis and the x-axis by 45 ° are the drive shaft and the output shaft, respectively. The first and third electrodes are respectively ± 45 ° around the positive and negative directions of the β axis.
Are formed symmetrically with respect to the β axis, and the second and fourth
The electrodes are centered around the positive and negative directions of the α axis, respectively.
It is formed symmetrically with respect to the α axis in the range of 45 °.

(5) In the fifth aspect of the present invention, in (4), the first and third electrodes have a square shape formed in the first and third quadrants of the xy coordinate, respectively, and And the shape of the fourth electrode is a square formed in the fourth and second quadrants of the xy coordinates, respectively.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. 1 and 2, the same reference numerals are given to portions corresponding to FIG. 3, and redundant description will be omitted. According to the present invention, the first to fourth electrodes having the same outer shape are provided on the electrode substrate 6.
Electrodes 6-1 to 6-4 are formed around the z-axis in order at approximately 90 ° intervals so as to face the rectangular thin portion 3c. Using the first electrode 6-1 and the third electrode 6-3 opposed to each other as drive electrodes, applying alternating voltages (for example, sinusoidal voltages) that change differentially with the diaphragm 3. As a result, the drive vibration and output vibration (detection vibration) of the mass unit 4
Are both pendulum vibrations. By using the second electrode 6-2 and the fourth electrode 6-4 facing each other as detection electrodes and detecting the capacitance that changes differentially with the diaphragm 3, the input angular velocity in the z-axis direction can be reduced. Detect (claim 1).

In the example of FIG. 1, the y-axis and the x-axis are the drive shaft and the output shaft, respectively. The first electrode 6-1 and the third electrode 6-3 are formed symmetrically with respect to the y-axis within a range of ± 45 ° around the positive and negative directions of the y-axis, respectively. On the other hand, the second electrode 6-2 and the fourth electrode 6-4 are formed symmetrically with respect to the x-axis within a range of 45 ° around the positive and negative directions of the x-axis, respectively. .

Further, in the example of FIG. 1, the shape of the first electrode 6-1 and the third electrode 6-3 is an isosceles triangle having an apex angle on the z-axis side and a base parallel to the x-axis. , While the second electrode 6
-2 and the shape of the fourth electrode 6-4 are isosceles triangles having an apex angle on the z-axis side and a base parallel to the y-axis (claim 3). An AC voltage having an angular frequency ωdrv that changes differentially is applied between the first electrode 6-1 and the third electrode 6-3 and the diaphragm 3, respectively. As a result, a differential electrostatic force acts between the first electrode 6-1 and the diaphragm 3 and between the third electrode 6-3 and the diaphragm 3, and the mass part 4 causes the angular velocity ωdrv in the y-axis (drive axis) direction. The pendulum vibrates with. At this time, the angular velocity ω =
When an angular velocity of dθ / dt is input, a Coriolis force is generated in the x-axis (output axis) direction, and a pendulum vibration having an angular velocity ωout in the x-axis direction appears.

At this time, the second electrode 6-2 and the diaphragm 3
Between the fourth electrode 6-4 and the diaphragm 3
A1 and CA2 are represented by CA1 = C01 + C1 × Fb (Ωb · t + φ1), CA2 = C02−C2 × Fb (Ωb · t + φ2) (3) Fb is a time function (for example, a sine function) of a change portion of CA1 and CA2, Ωb is an angular frequency, C1,
C2 is the amplitude of the variation. φ1 and φ2 are phase angles, which are determined by the direction of the input angular velocity. C01, C0
2 is the value of CA1 and CA2 when there is no input angular velocity, and is known. Since the amplitudes C1 and C2 are proportional to the magnitude of the input angular velocity ω = dθ / dt as in the equation (2), CA1 and C2
By detecting the change in A2, the input angular velocity can be detected.

According to the present invention, the output of the mass unit 4 when the drive vibration (ωdrv) in the drive axis (y-axis) direction and the input angular velocity ω = dθ / dt in the z-axis (input axis) direction are applied to the mass unit 4. Output vibration in the axis (x-axis) direction (ωout)
Are both pendulum vibrations, and these two pendulum vibrations are mutually symmetric in the xy plane. From this, the resonance frequency of the pendulum vibration in the directions of the drive shaft (y-axis) and the output shaft (x-axis) can be set to a desired close value (for example, a difference of about 10 Hz), and the design of a highly sensitive sensor can be easily performed. I can do it.

In order for the two pendulum vibrations to be symmetrical, the drive electrode 6-6 with respect to the drive axis (y-axis) is required.
It is necessary that the arrangement and shape of 1, 6-3 and the arrangement and shape of output electrodes (detection electrodes) 6-2, 6-4 with reference to the output axis (x-axis) are exactly the same. FIG. 2 shows the β-axis and α-axis obtained by rotating the y-axis (drive axis) and x-axis (output axis) clockwise by 45 °, respectively, as the drive axis and output axis, and the first to fourth electrodes 6-6. The position of 1-6-4 is also 45 °
This is the case where the shape is changed from a triangle to a rectangle while rotating, and the driving electrodes 6-1 and 6-3 and the output electrodes 6-1 and 2-2 are used.
The arrangement and the shape of the drive shaft or output shaft of 6-4 are the same. Also in this case, the driving vibration and the output vibration are pendulum vibrations symmetrical to each other in the αβ plane.

The first electrode 6-1 and the third electrode 6-3 are formed symmetrically with respect to the β axis in a range of ± 45 ° around the positive and negative directions of the β axis. The second electrode 6
-2 and the fourth electrode 6-4 are formed symmetrically with respect to the α-axis within a range of ± 45 ° around the positive and negative directions of the α-axis (claim 4). Further, in the example of FIG. 2, the shapes of the first electrode 6-1 and the third electrode 6-3 correspond to the first
And a square formed in the third quadrant, respectively,
The shape of the electrode 6-2 and the fourth electrode 6-4 is a square formed in the fourth and second quadrants of the xy coordinate, respectively (claim 5). In the case of FIG. 2, characteristics similar to those of FIG. 1 are obtained.

[0023]

According to the present invention, the driving vibration and the output vibration are pendulum vibrations that are symmetrical to each other, so that the resonance frequencies of the two vibrations can be set to desired close values. Can be designed in a short time without repeating cut and try as in the related art.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, wherein A is a plan view, and B is
2 is a sectional view taken along line aa ′ of FIG.

FIG. 2 is a view showing another embodiment of the present invention, wherein A is a plan view, and B is a sectional view taken along the line aa ′ of A.

FIG. 3 is a diagram showing a conventional angular velocity sensor, where A is a plan view,
B is a sectional view taken along line aa ′ of A.

FIG. 4 is a plan view of the diaphragm 3 of FIG. 3;

5 is a waveform diagram of capacitances CX1 and CX2 between the X1 and X2 electrodes and the diaphragm in FIG.

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[Procedure amendment]

[Submission date] November 6, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction contents]

The combined vibration of the translational vibration in the z-axis direction and the pendulum vibration in the -y-axis direction makes the X1 electrodes 6c and X
The capacitances CX1 and CX2 between the two electrodes 6d and the diaphragm 3 change differentially with each other as shown in FIG.
That is, CX1 and CX2 are represented by CX1 = C01 + C1 × Fa (ωdrv · t + φ1) + C1 ′ × Fbωdrv · t, CX2 = C02−C2 × Fa (ωdrv · t + φ2) + C2 ′ × Fbωdrv · t (1) Fa and Fb are time functions (for example, sine functions) of the changing portions of CX1 and CX2, and C1, C2 and C1 'and C2' are the amplitudes of the fluctuations. φ1 and φ2 are phase angles, which are determined by the direction of the input angular velocity. C0
1 and C02 are known values of CX1 and CX2 when there is no translational vibration or input angular velocity in the z-axis direction. The second term in equation (1) is the capacitance change caused by the coriolio, and the third term is z
This is the change in capacity due to axial translational vibration.

Claims (5)

[Claims] 1. A diaphragm comprising: a diaphragm; a mass portion elastically supported on the bottom side of the diaphragm; and an electrode substrate opposed to the diaphragm via a gap, wherein the diaphragm comprises (x, y, z A) a rectangular groove having sides parallel to the x-axis or the y-axis is formed around the z-axis on the bottom surface of the semiconductor wafer arranged parallel to the xy plane of the rectangular coordinates, and the center surrounded by the rectangular groove; Part, a bottom part of the square groove corresponding to the bottom of the square groove, and a frame part outside the square groove, the mass part is fixed to the bottom of the central part, the electrode substrate is insulated A drive electrode and a detection electrode (output electrode) are respectively formed on the inner surface of the conductive substrate, and by applying an AC voltage between the drive electrode and the diaphragm, the mass section is vibrated by electrostatic force, and the detection is performed. Electrodes and the diaphragm In the electrostatic drive type angular velocity sensor configured to detect an input angular velocity by detecting a capacitance between the first to fourth electrodes having the same outer shape around the z-axis, The first and third electrodes are formed so as to be opposed to the square-shaped thin portion at approximately 90 ° intervals in order, and the opposed first and third electrodes are used as the drive electrodes.
By applying voltages that change each other differentially between the diaphragm and the diaphragm, both the drive vibration and the output vibration (detection vibration) of the mass unit are set to pendulum vibration, and the opposing second and fourth vibrations are applied. An electrode as the detection electrode,
An electrostatic drive type angular velocity sensor, wherein an input angular velocity in the z-axis direction is detected by detecting a capacitance that changes differentially with the diaphragm. 2. The device according to claim 1, wherein the y-axis and the x-axis are a drive shaft and an output shaft, respectively, and the first and third electrodes are ± 45 ° around the positive and negative directions of the y-axis, respectively. And the second and fourth electrodes are formed symmetrically with respect to the x-axis within a range of ± 45 ° around the positive and negative directions of the x-axis, respectively. An electrostatically driven angular velocity sensor characterized in that: 3. The second and third electrodes according to claim 2, wherein the shapes of the first and third electrodes are isosceles triangles having a vertex angle on the z-axis side and a base parallel to the x-axis. The shape of the four electrodes has an apex angle on the z-axis side,
An electrostatically driven angular velocity sensor, which is an isosceles triangle having a base parallel to the y-axis. 4. The apparatus according to claim 1, wherein the β-axis and the α-axis obtained by rotating the y-axis and the x-axis by 45 ° are a drive shaft and an output shaft, respectively, and the first and third electrodes are Are formed symmetrically with respect to the β-axis within a range of ± 45 ° around the positive and negative directions of the axis, and the second and fourth electrodes are respectively formed around the positive and negative directions of the α-axis ± An electrostatically driven angular velocity sensor characterized by being formed symmetrically with respect to the α axis in a range of 45 °. 5. The shape of the first and third electrodes according to claim 4, wherein the shapes of the first and third electrodes are squares formed in first and third quadrants of xy coordinates, respectively. , And xy coordinates formed in the fourth and second quadrants, respectively.