JPH05340960A - Multi-dimensional acceleration sensor - Google Patents

Abstract

PURPOSE:To obtain a highly accurate downsized multi-dimensional acceleration sensor. CONSTITUTION:Fixed electrodes 101-112 are disposed oppositely to respective faces of a regular hexahedral movable electrode 100. The fixed electrodes impart electrostatic servo power to the movable electrode 100 which is thereby levitated in the center of a space section surrounded by the fixed electrodes 101-112. When the movable electrode 100 makes a displacement in response to multi- dimensional acceleration, an electrostatic servo control system detects variation of capacitances of the movable electrode and respective fixed electrodes and provides each fixed electrode with an electrostatic servo control signal for returning the movable electrode to a reference position (i.e., the center of space section between fixed electrodes). Multi-dimensional acceleration is detected by processing the electrostatic servo signal or the signal representative of variation of capacitance between fixed electrodes or movable electrodes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor for detecting multidimensional acceleration.

[0002]

2. Description of the Related Art Regarding conventional multidimensional acceleration sensors,
Originally, a three-dimensional acceleration sensor such as the three-dimensional acceleration sensor disclosed in JP-A-63-118667 is used.
It was like individually preparing and individually mounting these on three orthogonal planes of a cube to detect a three-dimensional acceleration.

Incidentally, as a typical acceleration sensor, there is a capacitance type acceleration sensor. This is because the movable electrode that displaces in response to acceleration is elastically supported by a beam or diaphragm, and the fixed electrode is placed oppositely with this movable electrode interposed, and the displacement of the movable electrode is fixed between each fixed electrode and movable electrode. The acceleration is detected by detecting the difference in electrostatic capacitance between the electrodes, and an electrostatic servo (electrostatic force) control signal is generated to try to restrain the movable electrode at the reference position based on the change in the electrostatic capacitance difference. Acceleration is detected from the servo control signal. In addition, various types such as a strain gauge type acceleration sensor have been proposed.

[0004]

The acceleration sensor is generally required to be small and lightweight. This is because the applications for which the acceleration sensor is used are aircraft, rockets, automobiles, etc., and the requirements for the mounting area and weight of each component are becoming extremely strict. The above-mentioned prior art merely combines three one-dimensional acceleration sensors,
It was unsatisfactory in terms of downsizing.

Further, as a multidimensional acceleration sensor, a mass portion (for example, a movable electrode in the case of a capacitance type acceleration sensor) that can detect weak and low-frequency acceleration with high accuracy and responds to the acceleration in that sense is provided. High sensitivity and high orthogonality of detected acceleration in each dimension are required. However, when the original one-dimensional acceleration sensor is randomly attached to the three orthogonal surfaces of the cube as described above, the three orthogonal axes (x axis, y axis, z axis) are accurately aligned. I had a difficult problem.

The present invention has been made in view of the above points, and an object of the present invention is to reduce the size and weight of a multidimensional acceleration sensor and to realize highly accurate acceleration detection.

[0007]

In order to achieve the above object, the present invention basically proposes the following means for solving problems.

One is a capacitance type acceleration sensor in which fixed electrodes are arranged so as to face each surface of a movable electrode of a rectangular parallelepiped, and the fixed electrodes are connected to the fixed electrodes from the fixed electrodes. When an electrostatic force is applied to float in the center of the space surrounded by, and the movable electrode is displaced in response to multidimensional acceleration, the change in electrostatic capacitance of the movable electrode and each fixed electrode is detected. An electrostatic servo control signal for generating an electrostatic force for returning the movable electrode to the reference position (here, the reference position is the center of the space between the fixed electrodes) is formed, and the electrostatic servo control signal is generated. An electrostatic servo control system applied to each of the fixed electrodes is provided, and a multidimensional acceleration is detected by processing the electrostatic servo control signal or a signal indicating a change in electrostatic capacitance between each fixed electrode / movable electrode. To set That (referred to as first means for solving problems).

The other is, in an electrostatic capacitance type acceleration sensor, a movable electrode that is displaced in response to acceleration, and two fixed electrodes that are arranged in a row and a row, respectively, facing the movable electrode. It is provided (this is a second means for solving problems).

The other is an electrostatic capacitance type acceleration sensor, in which two movable electrodes which are displaced in response to acceleration,
A plurality of fixed electrodes are arranged so as to face each of these movable electrodes (this is referred to as a third problem solving means).

The other is an electrostatic capacitance type acceleration sensor, which is provided with movable electrodes which are vertically and horizontally displaced in response to acceleration, and fixed electrodes which are arranged to face the upper and lower surfaces of the movable electrodes, respectively. The left and right surfaces and the upper and lower surfaces of the movable electrode, or the left and right surfaces or the upper and lower surfaces are comb-teeth-shaped electrode surfaces, and the electrode surface of the fixed electrode facing the comb-teeth-shaped electrode surface of the movable electrode is comb-shaped. The teeth are formed so as to mesh with the comb-shaped electrodes of the movable electrode while maintaining a minute gap (this is a fourth problem solving means).

The other is provided with a rectangular parallelepiped, a flexible printed board formed by integrally molding a plurality of surfaces corresponding to the surfaces 3 to 6 of the rectangular parallelepiped, and a couple of acceleration sensors. Each surface of the flexible printed circuit board is bent and fixed to the corresponding surface of the rectangular parallelepiped, and the acceleration sensor is individually mounted on each of the two to three orthogonal surfaces of the flexible printed circuit board ( This is the fifth
To solve the problem).

[0013]

Operation of the first problem solving means: An electrostatic servo control signal (voltage) is applied to each fixed electrode surrounding the straight six sides of the movable electrode, and an electrostatic force acting on the movable electrode from each fixed electrode. The mass of the movable electrode is balanced with that of the movable electrode, and the movable electrode is kept floating in the center of the space (reference position) surrounded by the fixed electrode without a supporting member such as a beam.

When three-dimensional acceleration acts on the movable electrode in this state, the movable electrode and the electrostatic force are out of balance, and the movable electrode is displaced in response to the acceleration direction.

Then, the electrostatic servo control system detects this displacement from the change in the electrostatic capacitance between the movable electrode and each fixed electrode, and then causes each fixed electrode to return the movable electrode to the reference position by an electrostatic servo control signal. Is applied. This balances the difference between the inertial force acting on the movable electrode (force proportional to the acceleration) and the electrostatic force acting on the movable electrode from each fixed electrode, and the movable electrode is constrained to return to the reference position.

Therefore, the three-dimensional acceleration can be detected by obtaining the electrostatic servo control signal or from the signal indicating the change in electrostatic capacitance between the movable electrode and each fixed electrode.

Further, since the rectangular parallelepiped movable electrode is in a floating state without a beam, it can be rotationally displaced in response to rotational acceleration in a three-dimensional space. For such a displacement, if two fixed electrodes facing the movable electrode of the rectangular parallelepiped are arranged in parallel with each other, the rotation is caused by the change in the electrostatic capacitance of the movable electrode and each fixed electrode as described above. It can be regarded as displacement.

If an electrostatic servo control signal is generated and applied to each fixed electrode such that an electrostatic force difference that balances this rotational displacement (torsional moment) is generated between the movable electrode and each fixed electrode, the movable electrode is The three-dimensional rotational acceleration can be detected from the electrostatic servo control signal or the signal indicating the change in the electrostatic capacitance between the movable electrode and each fixed electrode, as described above, while being constrained to return to the reference position.

Operation of the second problem-solving means: In this problem-solving means, since two fixed electrodes opposed to one movable electrode are arranged in each of the vertical and horizontal rows, acceleration in at least one axial direction (one-dimensional) is obtained. Even if the movable electrodes can be detected and are displaced in response to rotational acceleration about at least one axis, each of the fixed electrodes in the rows and columns cooperates with the movable electrodes to detect the capacitance of them. Since the information on the rotational displacement of the movable electrode can be fetched from the change, the rotational acceleration can be detected by processing this information. The rotational acceleration may be detected from the change in the electrostatic servo control signal or the electrostatic capacitance, as in the first problem solving means.

Operation of the third means for solving the problems: In this means for solving the problems, by having two movable electrodes that are displaced in response to the acceleration, it is possible to detect the acceleration with respect to the acceleration in at least one axis direction. By the two movable electrodes having different displacements with respect to the rotational acceleration about the one axis,
Rotational acceleration can be detected from changes in the electrostatic capacitances of these movable electrodes and fixed electrodes. The acceleration detection in this case may also be detected from the electrostatic servo control signal or the change in the electrostatic capacitance.

Action of Fourth Problem Solving Means ... In this problem solving means, two-dimensional acceleration can be detected. In particular, since the fixed electrode and the movable electrode are opposed to each other in a comb shape, the area of the counter electrode is large. Therefore, it is possible to apply a sufficient electrostatic force for servo from the fixed electrode to the movable electrode with a small applied voltage (electrostatic servo control signal).

Action of Fifth Problem Solving Means ... The first to third problem solving means described so far are multidimensional with one sensor (including one in which linear acceleration is added to rotational acceleration).
The acceleration is detected, but in this problem solving means, a plurality (two or three) of acceleration sensors themselves are used.

These acceleration sensors are individually mounted on a predetermined surface (two to three surfaces orthogonal to each other) of a plurality of surfaces (three to six surfaces) of the flexible printed circuit board. The remaining surface of the remaining flexible printed circuit board can be used as play or wiring such as a lead wire.

The acceleration sensor mounted on a predetermined surface of the flexible printed circuit board is designed in advance so that the mounting positions of the acceleration sensor are orthogonal to each other on three axes, and all surfaces of the flexible printed circuit board are mounted. If you fold it at a right angle and align the fold line with the corner of the straight hexahedron (which is set at the acceleration detection position) and fix the flexible printed circuit board with an adhesive, etc. Highly set on top. Therefore, it is possible to solve the problem of sensor misalignment that occurs when the conventional acceleration sensor is directly and loosely attached to the rectangular parallelepiped.

Each of these acceleration sensors detects the acceleration in the axial direction at its own mounting position, thereby enabling two-dimensional or three-dimensional multi-dimensional acceleration.

[0026]

Embodiments of the present invention will be described with reference to the drawings.

First, prior to the description of the embodiment, a conventional one-dimensional PWM (pulse width modulation) electrostatic servo type electrostatic capacitance type acceleration sensor shown in FIG. The operating principle will be described.

The detection unit 200 in FIG.
And the movable electrode 201 supported by the movable electrode 201.
2 of the movable electrodes 201 in parallel with each other.
The two fixed electrodes 202 and 203 are arranged so as to be opposed to each other while keeping a minute gap on the surface.

The movable electrode 201 and the beam 204 are formed by finely processing a semiconductor such as silicon, and the fixed electrode 2
02 and 203 are made of a conductive metal material.

When a vertical acceleration is applied to the detecting section 200, the movable electrode 201 is vertically displaced according to the acceleration.

The servo control system includes a capacitance detector 205, an amplifier 206, a pulse width modulator 207, a drive gate 208,
It consists of 209.

The capacitance detector 205 detects a difference ΔC between the electrostatic capacitance between the fixed electrode 202 and the movable electrode 201 and the electrostatic capacitance between the fixed electrode 203 and the movable electrode 201. Capacitance detector 2
The output of No. 05 is amplified by the amplifier 206, and the pulse width modulator 207 outputs the duty corresponding to the output of the amplifier 206.
Generates a tee rectangular wave (electrostatic servo control signal).

This rectangular wave is inverted by the drive gate 208 and applied to the fixed electrode 203 to exert an electrostatic force between the fixed electrode 203 and the movable electrode 201, and at the same time, the drive gate 2
08 and 209, the rectangular wave of the amplifier 206 is applied to the fixed electrode 2
02 to apply an electrostatic force between the fixed electrode 202 and the movable electrode 201.

Fixed electrodes 202 and 203 are provided on the movable electrode 201.
The difference in the electrostatic force acting from is proportional to the duty of the rectangular wave. Therefore, the electrostatic servo control signal (rectangular wave and its inverted signal) is applied to the fixed electrode so that the difference ΔC in electrostatic capacitance between the movable electrode 201 and the fixed electrode 202 and between the movable electrode 201 and the fixed electrode 203 becomes zero. If applied to 202 and 203, the inertial force acting on the movable electrode 201 (force proportional to acceleration),
The electrostatic servo control is performed so that the movable electrode 201 returns to the reference position by balancing the difference in the electrostatic force acting on the movable electrode 201 from the fixed electrodes 202 and 203. Therefore, this electrostatic servo control signal (duty) is detected. By converting this duty into an analog voltage by the low pass filter 210, an output according to the acceleration can be obtained. The output characteristics at this time are

[0035]

[Equation 1]

It is represented by

Next, a multidimensional PWM electrostatic servo type acceleration sensor according to the first embodiment of the present invention will be described with reference to FIGS. 1 and 3 to 8. The acceleration sensor of this embodiment is intended to detect a three-dimensional acceleration and a three-dimensional rotational acceleration that rotates about the X axis, the Y axis, and the Z axis.

FIG. 1 is an explanatory view showing the structural principle of the detecting portion of the multidimensional acceleration sensor of the first embodiment.

Detection unit 300 of the acceleration sensor of this embodiment
Is a movable electrode 100 of a rectangular parallelepiped (here, it may be a rectangular parallelepiped), and fixed electrodes 101, 102, 103, 104, which are arranged to face each surface of the rectangular parallelepiped.
105, 106, 107, 108, 109, 110, 1
11, 112 are arranged. Here, two fixed electrodes arranged in parallel form one set (that is, fixed electrodes 101, 102, 103, 104, 105, 10).
6, 107, 108, 109, 110, 111,
112), and is arranged to face each surface of the movable electrode 100. The movable electrode 100 and the fixed electrodes 101 to 112 are
The same material as that illustrated in FIG. 2 is used.

Then, by applying an electrostatic force that balances the mass of the movable electrode 100 to the movable electrode 100 from each of the fixed electrodes 101 to 112, the movable electrode 100 is fixed.
It is arranged in a floating state without a beam at the center (reference position) of the space surrounded by ~ 112.

In this way, the movable electrode 100 and the fixed electrodes 101 to 112 face each other with a minute gap therebetween, and the cubic movable electrode 100 is moved forward, backward, upward, downward, leftward and rightward according to the three-dimensional acceleration acting on the cubic movable electrode 100. Displaced or movable electrode 100
Depending on the rotational acceleration (torsion moment) that acts on, it can be rotationally displaced forward and backward, vertically and horizontally.

FIG. 3 is a sectional view of the detector 300 shown in FIG. 1 taken along the plane S1. FIG. 4 shows a part of the signal processing circuit of the electrostatic servo control system. The operation of detecting acceleration in the X direction and detecting rotational acceleration about the Z axis using this signal processing circuit will be described.

In FIG. 4, the capacitance detection unit 401, the amplifiers 402 and 403, the pulse width amplifiers 404 and 405, and the drive gates 406, 407, 408, and 409 are accelerations that rotate in the X-axis direction and the Z-axis. Circuit of the electrostatic servo control system for the low-pass filters 410, 41
1, the adder 412, and the subtractor 413 form a circuit of a signal processing system for calculating their accelerations. An electrostatic servo control system and acceleration calculation signal processing of a Y-axis direction acceleration and a rotation acceleration that rotates about the X-axis, and a Z-axis direction acceleration and a rotation acceleration that rotates about the Y-axis shown in FIG. The circuit of the system has the same structure, but is not shown.

In FIG. 3, when acceleration is applied to the movable electrode 100 in the right direction in the X-axis direction, the movable electrode 100 moves in the same direction, and the electrostatic capacitance between the movable electrode 100 and the fixed electrode 103 and the movable electrode 100 move. The capacitance between 100 and the fixed electrode 104 increases, and the capacitance between the movable electrode 100 and the fixed electrode 109 and the capacitance between the movable electrode 100 and the fixed electrode 110 decrease.

When a clockwise rotational acceleration (torsional moment) about the Z axis acts on the movable electrode 100, the movable electrode 100 rotates clockwise, and the electrostatic capacitance between the movable electrode 100 and the fixed electrode 103 becomes The electrostatic capacitance between the movable electrode 100 and the fixed electrode 109 increases, and the electrostatic capacitance between the movable electrode 100 and the fixed electrode 104 and the movable electrode 100 and the fixed electrode 11 increase.
The capacitance between 0 decreases.

Of these, the movable electrode 100 and the fixed electrode 10
The capacitance detector 401 detects the difference between the capacitance between the four electrodes and the capacitance between the movable electrode 100 and the fixed electrode 109, and the output of the capacitance detector 401 is amplified by the amplifier 402. A rectangular wave voltage (electrostatic servo signal) having a duty proportional to the capacitance difference is formed. Based on this electrostatic servo control signal, the drive gate 4 is attached to the fixed electrode 109.
A rectangular wave voltage having a duty corresponding to the output of the amplifier 402 is applied via 07 and 409, and the inverted voltage thereof is applied to the fixed electrode 104 via the drive gate 407.

Similarly to this, the capacitance between the movable electrode 100 and the fixed electrode 103 and the movable electrode 100 and the fixed electrode 1
Capacitance detector 401 detects the capacitance between 10 and amplifier 403, pulse width modulator 404, drive gate 40.
6, 408, a rectangular wave voltage having a duty corresponding to the output of the amplifier 403 is applied to the fixed electrode 110, and the inverted voltage thereof is applied to the fixed electrode 103.

At this time, the difference between the electrostatic force acting on the movable electrode 100 from the fixed electrodes 104 and 109 and the fixed electrode 103.
And 110, the sum of the difference between the electrostatic force acting on the movable electrode 100 and the electrostatic force acting on the movable electrode 100 (the force proportional to the acceleration) or the torsional moment acting on the movable electrode 100 (proportional to the rotational angular acceleration). Force), the movable electrode is constrained to return to the position where the electrostatic capacitance difference between the movable electrode and each fixed electrode becomes zero, that is, the central space (reference position) surrounded by the fixed electrode.

The fixed electrodes 103, 104, 10
The electrostatic force acting from 9, 110 is detected from the duty (electrostatic servo control signal), this duty is converted into an analog voltage by the low-pass filters 410, 411, and the fixed electrode 103, 110 is added by the adder 412. To movable electrode 100
Of the electrostatic force (f1-f4) acting on the fixed electrode 104,
The difference in electrostatic force acting on the movable electrode 100 from 109 (f2-
f3) is added to obtain an output corresponding to the acceleration in the X-axis direction,
In addition, the subtracter 413 outputs (f1-f4) and (f2-f3).
And can be subtracted to obtain an output according to the rotational acceleration about the Z axis. (Here, f1 is the fixed electrode 103
), F2 is an electrostatic force from the fixed electrode 104, f3 is an electrostatic force from the fixed electrode 109, and f4 is an electrostatic force from the fixed electrode 110).

That is, the value calculated by the adder 412 is

[0051]

## EQU2 ## (f1-f4) + (f2-f3) = (f1 + f2)-(f3 + f4) and the value calculated by the subtractor 413 is

[0052]

## EQU00003 ## (f1-f4)-(f2-f3) = (f1 + f3)-(f2 + f4).

From the above equations, numerical values can be expressed in the equation 2 in the case of acceleration in the X direction and numerical values in the equation 3 in the case of rotational acceleration about the Z direction.

Next, referring to FIG. 5, a cross-sectional view of the S2 plane of the detection unit 300 is shown, and the detection operation of the acceleration in the Y-axis direction and the rotational acceleration about the X-axis will be described.

In FIG. 5, when acceleration is applied to the movable electrode 100 in the left direction on the Y axis, the movable electrode 100 is displaced in the same direction, and the electrostatic capacitance between the movable electrode 100 and the fixed electrode 107 and the movable electrode 100. The electrostatic capacitance between the fixed electrodes 108 increases, and the electrostatic capacitance between the movable electrode 100 and the fixed electrode 111 and between the movable electrode 100 and the fixed electrode 112 decreases.

When the rotational acceleration in the clockwise direction about the X axis acts on the movable electrode 100, the movable electrode 100 rotates clockwise, and the electrostatic capacitance between the movable electrode 100 and the fixed electrode 111 and the movable electrode 100. The electrostatic capacitance between the fixed electrodes 107 increases, and the electrostatic capacitance between the movable electrode 100 and the fixed electrode 112 and between the movable electrode 100 and the fixed electrode 108 decreases.

Therefore, by using the electrostatic servo control system and the acceleration calculation processing circuit configured as in FIG. 4, the acceleration in the Y-axis direction and the rotational acceleration about the X-axis can be detected.

Next, FIG. 6 shows a sectional view of the S3 plane of the detecting section 300, and the detecting operation of the acceleration in the Z-axis direction and the rotational acceleration about the Y-axis will be described.

As for the acceleration in the Y-axis direction and the rotational acceleration about the Y-axis, the movable electrode 10 is also used as described above.
0 is displaced according to acceleration in the Z-axis direction or rotational acceleration about the Y-axis. Therefore, by using the electrostatic servo control system and the signal processing circuit for calculating the acceleration similar to the above, the acceleration in the Z direction and the rotational angular acceleration about the Y axis can be detected.

By combining and cooperating these electrostatic servo control systems for the respective axial directions and the signal processing circuit for calculating the acceleration, the acceleration acting in the three-dimensional space can be detected, and in addition to this, the three-dimensional acceleration can be detected. The rotational acceleration of can also be detected.

Next, a concrete example of the configuration of the capacitance detector 401 used in this embodiment will be described with reference to FIG.

The capacitance detector 401 includes an operational amplifier 701.
And the capacitance 702 and the transistor 70 in the feedback section of this.
3 and a sample-hold circuit 704, 705, 706, 707, 708, 709.

The inverting input of the operational amplifier 701 is the movable electrode 1
00, and keeps the potential of the movable electrode 100 constant.

In FIG. 7, the movable electrode 100.
The electrostatic capacity between the fixed electrodes 101 is C ₁ , the movable electrode 100
The electrostatic capacitance between the fixed electrodes 102 is C ₂ , the movable electrode 100
The electrostatic capacitance between the fixed electrodes 103 is C ₃ , the movable electrode 100
The electrostatic capacitance between the fixed electrodes 104 is C ₄ , and the movable electrode 100.
The electrostatic capacitance between the fixed electrodes 105 is C ₅ , the movable electrode 100.
The capacitance between the fixed electrodes 106 is C ₆ , the movable electrode 100
The electrostatic capacitance between the fixed electrodes 107 is C ₇ , the movable electrode 100
The electrostatic capacitance between the fixed electrodes 108 is C ₈ , the movable electrode 100.
The capacitance between the fixed electrodes 109 is C ₉ , and the movable electrode 100.
The electrostatic capacitance between the fixed electrodes 110 is C ₁₀ , the movable electrode 100
The capacitance between the fixed electrodes 111 is C ₁₁ , the movable electrode 100
The capacitance between the fixed electrodes 112 is represented by C ₁₂ .

Further, the drive gates 406, 407, 40
8,409,710,711,712,713,71
4, 715, 716, and 717 are connected to the corresponding fixed electrodes.

Timing chart of this capacitance detector 401
8 is shown in FIG. 8, and the operation of the capacitance detector 401 will be described using this.

First, the signal φ _R causes the transistor 703 to
Is turned on to discharge the electrostatic capacitance 702. At the next moment, the rectangular wave applied to the fixed electrode 101 rises and the rectangular wave applied to the fixed electrode 106 falls. At this time, the electrostatic capacitance C ₁ is charged and the electrostatic capacitance C ₆ is discharged, so that an electric charge of V _P (C ₆ −C ₁ ) flows in the electrostatic capacitance C 702.

Here, V _P is the amplitude of the rectangular wave. Therefore, assuming that the capacitance of the electrostatic capacitance 702 is C _F , the operational amplifier 7
At the output of 01, the voltage V _O represented by the equation 4 is generated.

[0069]

Equation 4] _{V O = V P (C 6} -C 1) / C F Sample E the voltage by signal phi ₁ - hold circuit 704
By sampling at, the difference between the electrostatic capacitance C ₁ and the electrostatic capacitance C ₆ can be detected.

Then, at the next timing, the signal Φ _R turns on the transistor 703 again to discharge the electrostatic capacitance 702. At the next moment, the rectangular wave applied to the fixed electrode 102 rises and the rectangular wave applied to the fixed electrode 105 falls. At this time, a signal corresponding to the difference between the electrostatic capacitance C ₂ and the electrostatic capacitance C ₅ is generated at the output of the operational amplifier 701, and this is generated by the signal φ _{2 in the} sample-hold circuit 705.
By sampling at, the difference between the electrostatic capacitance C ₂ and the electrostatic capacitance C ₅ can be detected.

Therefore, by sequentially repeating this,
The difference between capacitance C ₃ and capacitance C ₁₀ , the difference between capacitance C ₄ and capacitance C ₉ , the difference between capacitance C ₇ and capacitance C ₁₂ , the capacitance C ₈ and capacitance The difference in capacitance C ₁₁ is detected.

Next, a second embodiment of the present invention will be described with reference to FIGS.
2 will be described. FIG. 9 shows the structural principle of the detecting portion of this embodiment, FIG. 10 is a sectional view in the Y-axis direction of FIG. 9, and FIG. 11 is FIG.
0 is a sectional view taken along line aa ′ of FIG. 0, and FIG. 12 is a circuit diagram of this embodiment.

In this embodiment, a multi-dimensional PWM electrostatic servo type static sensor intended to detect acceleration in the Z-axis direction, rotational acceleration about the X-axis, and rotational acceleration about the Y-axis. It is a capacitance type acceleration sensor.

The movable electrode 900 is supported by a beam 901. This beam is supported so as to be displaced in response to acceleration in the Z-axis direction, and the beam 901 is made of an elastic member and has an X-axis. When a rotational acceleration centered on the movable electrode 900 acts on the movable electrode 900, the torsional motion corresponding to the function allows the rotational displacement of the movable electrode 900 about the X axis and the rotational acceleration about the Y axis. When acting on the movable electrode 900, the movable electrode 900 is elastically deformed as shown in FIG. 9B to give a function of allowing the rotational displacement of the movable electrode 900 around the Y axis.

As shown in FIG. 9A, the movable electrode 900
Facing the upper surface of the fixed electrodes 902, 903, 904,
Two 905s are arranged side by side in the vertical and horizontal rows, facing the lower surface of the movable electrode 900, and fixed electrodes 906, 907, 9 are provided.
Similarly, the two electrodes 08 and 909 are arranged side by side in the vertical and horizontal rows, and the movable electrode 900 is at the reference position with a small gap maintained between these fixed electrodes.

Next, FIG. 12 shows the configuration and operation of the electrostatic servo control system and the signal processing circuit for calculating the acceleration in this embodiment.
Will be explained.

The electrostatic servo control system is similar to the first embodiment in that it has a capacitance detector 1200 and amplifiers 1201, 1202.
1203, 1204, pulse width modulators 1213, 121
4,1215,1216, drive gates 1205,120
6,1207,1208,1209,1210,121
1, 1212, and the signal processing circuit for calculating the acceleration includes low-pass filters 1217, 1218, 1219, 1
It comprises 220 and an arithmetic unit 1221.

As a result, when the movable electrode 900 is displaced in response to the acceleration in the Z-axis direction, the acceleration about the X-axis, and the acceleration about the Y-axis, the electrostatic capacitance between the movable electrode 900 and the fixed electrode 902. And movable electrode 900 / fixed electrode 90
9 so that the difference in capacitance between the movable electrodes 90 is zero.
The electrostatic capacitance between the movable electrode 900 and the fixed electrode 904 and the movable electrode 900 are fixed so that the difference between the electrostatic capacitance between the fixed electrode 903 and the movable electrode 900 and the fixed electrode 908 becomes zero. In order that the electrostatic capacitance difference between the electrodes 906 becomes zero, the electrostatic capacitance difference between the movable electrode 900 and the fixed electrode 905 and the electrostatic capacitance between the movable electrodes 900 and the fixed electrode 907 becomes zero, Square wave duo applied to each fixed electrode
Control the tee.

Therefore, by balancing the inertial force due to the acceleration in the Z-axis direction or the rotational moment due to the rotational acceleration around the X-axis or the Y-axis and the electrostatic force difference acting on the movable electrode 900 from each fixed electrode, It enables electrostatic servo control such that the movable electrode 900 is restricted to the reference position.

Therefore, the electrostatic force exerted on the movable electrode 900 from each fixed electrode is obtained from the duty and converted into an analog voltage by the low pass filters 1217, 1218, 1219, 1220, and this is calculated by the calculator 1221. By doing so, the acceleration in the Z-axis direction and the rotational angular acceleration about the X-axis or the Y-axis can be detected.

Here, the acceleration in the Z-axis direction is calculated by calculating the sum of the outputs of the low-pass filters 1217, 1218, 1219, 1220, so that the rotational angular acceleration about the X-axis is calculated by the low-pass filters 1217, 1218. By calculating the difference between the sum of the outputs and the sum of the outputs of the low-pass filters 1219 and 1220, the rotational angular acceleration about the Y axis is calculated as the sum of the outputs of the low-pass filters 1217 and 1219 and the low-pass filter 1218. The rotational acceleration about the Y axis can be detected by calculating the difference between the outputs of 1220.

Next, a third embodiment of the present invention will be described with reference to FIGS.

The present embodiment is a PWM electrostatic servo type capacitance type acceleration sensor intended to detect acceleration in one axis direction and rotational acceleration rotating about one axis.

FIG. 13 shows the arrangement of the electrodes of the detection unit 1300 of this embodiment, FIG. 14 is a cross section of the detection unit, and FIG. 15 is aa '.
The cross section of FIG.

The detection unit 1300 has a total of two movable electrodes, a movable electrode 1302 supported by the beam 1301 and a movable electrode 1307 supported by the beam 1305.
Fixed electrodes 1303 and 1304 facing the upper and lower surfaces of 302
The fixed electrodes 1306 and 1308 are arranged so as to face the upper and lower surfaces of the movable electrode 1307.

The movable electrodes 1302 and 1307 move in the same direction according to the acceleration in the Z-axis direction. In addition, the movable electrode 1302 is rotated according to the rotational angular acceleration about the X axis.
And the movable electrode 1307 move in opposite directions in the Z-axis direction.

Therefore, the movable electrode 1302 and the fixed electrode 13
03 capacitance and movable electrode 1302 / fixed electrode 130
4 so that the difference in capacitance between them becomes zero, and that the difference between the capacitance between movable electrode 1307 and fixed electrode 1306 and the difference between capacitance between movable electrode 1307 and fixed electrode 1308 becomes zero. , Fixed electrodes 1303, 1304, 1306
An electrostatic servo control signal (voltage) is applied to 1308 to exert an electrostatic force on the movable electrodes 1302 and 1307.

At this time, the force acting on each movable electrode by the inertial force due to the acceleration in the Z-axis direction and the rotational angular acceleration about the X-axis and the electrostatic force difference acting on each movable electrode from each fixed electrode are balanced.

Therefore, from the fixed electrode 1306 to the movable electrode 1
The difference between the electrostatic force acting on 307 and the electrostatic force acting on the movable electrode 1302 from the fixed electrode 1303, and the electrostatic force acting on the movable electrode 1307 from the fixed electrode 1308 and the electrostatic force acting on the movable electrode 1302 from the fixed electrode 1304 is obtained. Thus, the acceleration in the Z-axis direction can be obtained.

In addition, from the fixed electrode 1306 to the movable electrode 13
Electrostatic force acting on 07 and fixed electrode 1304 to movable electrode 1
The rotational angular acceleration in the X-axis direction is obtained by obtaining the sum of the electrostatic force acting on 302, the difference between the electrostatic force acting on the movable electrode 1307 from the fixed electrode 1308 and the electrostatic force acting on the movable electrode 1302 from the fixed electrode 1303. be able to.

Next, a fourth embodiment of the present invention will be described with reference to FIGS. This embodiment is a PWM electrostatic servo type electrostatic capacitance type acceleration sensor intended for two-dimensional acceleration detection.

FIG. 16 shows a cross section of the detecting section 1300 of this embodiment, and FIG. 15 shows a cross section of aa '.

In the detecting section 1600, the movable electrode 1602 is
Fixed electrodes 1605 and 160 arranged opposite to the left and right surfaces
6 and fixed electrodes 1603, 16 arranged to face the upper and lower surfaces
04 and.

The movable electrode 1602 is a fixed beam 1601.
And the left and right electrode surfaces are comb-shaped. Further, the left and right fixed electrodes 1605 and 1606 also have comb-shaped surfaces facing the movable electrodes, and the comb-shaped electrode surfaces of these fixed electrodes and the comb-shaped electrode surfaces of the movable electrodes respectively form minute gaps. It keeps and meshes.

The movable electrode 1602 moves in the vertical direction according to the vertical acceleration, and moves in the horizontal direction according to the horizontal acceleration.

Therefore, the movable electrode 1602 and the fixed electrode 16
03 capacitance and movable electrode 1602 and fixed electrode 160
4 so that the difference in electrostatic capacitance between them becomes zero, and that the difference between the electrostatic capacitance between movable electrode 1602 and fixed electrode 1605 and the electrostatic capacitance between movable electrode 1602 and fixed electrode 1606 becomes zero. Fixed electrodes 1303, 1304, 1305, 1
A voltage is applied to 306 and an electrostatic force is exerted on the movable electrode 1602. At this time, the inertial force due to the vertical and horizontal accelerations and the electrostatic force difference acting on the movable electrode 1602 from each fixed electrode are balanced. Therefore, the vertical acceleration can be obtained by obtaining the difference between the electrostatic force acting on the movable electrode 1602 from the fixed electrode 1603 and the electrostatic force acting on the movable electrode 1302 from the fixed electrode 1604. Further, the lateral acceleration can be obtained by obtaining the difference between the electrostatic force acting on the movable electrode 1602 from the fixed electrode 1605 and the electrostatic force acting on the movable electrode 1602 from the fixed electrode 1606.

According to this embodiment, the movable electrode and the fixed electrode are meshed with each other in a comb-like shape, so that the effective area of the electrode surface can be widened and the electrostatic force used for the electrostatic servo can be reduced accordingly. ..

Next, a fifth embodiment of the present invention will be described with reference to FIG.

The present embodiment is a sensor intended to detect three-dimensional acceleration.

In this embodiment, a rectangular parallelepiped (cube) 1801 set at the acceleration detection position and this cube 180 are used.
The flexible printed board 1800 is formed by integrally molding five surfaces corresponding to the five surfaces in a cross-shaped arrangement, and three acceleration sensors 1802, 1803, 1804.
The acceleration sensor used here may be of any type such as a capacitance type or a strain gauge type.

Each surface of the flexible printed board 1800 is bent to the corresponding surface of the cube 1801 and fixed by an adhesive.

Acceleration sensors 1802, 1803, 18 are provided on three orthogonal surfaces of the flexible printed circuit board 1800.
04 are individually mounted.

The flexible printed board 1800 is formed by covering the surface of a support plate such as ceramic or acrylic with FPC resin or the like, and the acceleration sensor 18 is provided on three predetermined orthogonal planes.
02, 1803, and 1804 detecting units 1802
a, 1803a, 1804a and I which is the signal processing system thereof
C circuits (devices) 1802b, 1803b, 1804
b is electrically connected by a printed wiring to be mounted, and lead wires related to signal extraction lines and power supply lines of these acceleration sensors are printed on the remaining surface.
Of these, the detection units 1802a and 180 of each acceleration sensor
3a and 1804a are designed in advance on a printed circuit board so as to be set on three orthogonal axes.

According to this embodiment, when all the surfaces of the flexible printed circuit board 1800 are bent at right angles and the bending lines are aligned with the corners of the rectangular parallelepiped 1801, the flexible printed circuit board 1800 is fixed with an adhesive or the like. Naturally, the acceleration sensors 1802, 1803
1804 is set on the three orthogonal axes with high precision.

Each of these acceleration sensors detects the acceleration in the axial direction at its own mounting position, thereby enabling accurate three-dimensional acceleration detection.

Further, since each acceleration sensor is mounted on the printed circuit board, the installation space can be rationalized and all the acceleration sensors can be housed in one package. Therefore, it is possible to package the individual acceleration sensors individually. In comparison, the device can be downsized.

In the present embodiment, the flexible substrate has five surfaces, but if it is between three surfaces and six surfaces, mounting of each acceleration sensor and accurate positioning on the rectangular parallelepiped are possible, and the acceleration Two-dimensional acceleration can be detected by using two sensors.

[0108]

As described above, according to the present invention, in the first problem solving means to the fourth problem solving means, multi-dimensional acceleration sensors are combined to realize multi-dimensional acceleration in one detection unit. Acceleration can be detected in a small size and with high accuracy, and in the fifth problem solving means, the acceleration sensor can be integrated, so that the multidimensional acceleration sensor can be downsized and improved in accuracy.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an arrangement of electrodes of a multidimensional acceleration sensor according to a first embodiment.

FIG. 2 is an explanatory diagram showing a configuration of a one-dimensional PWM electrostatic servo type acceleration sensor.

FIG. 3 is a sectional view of the S1 surface of the detection unit of the first embodiment.

FIG. 4 is a configuration diagram of a signal processing unit of the electrostatic servo control system of the first embodiment.

FIG. 5 is a sectional view of the S2 surface of the detection unit of the first embodiment.

FIG. 6 is a cross-sectional view of the S3 surface of the detection unit of the first embodiment.

FIG. 7 is a circuit configuration diagram of the electrostatic capacitance detector according to the first embodiment.

FIG. 8 is a timing chart of the capacitance detector of the first embodiment.

FIG. 9 is an explanatory diagram showing an arrangement of electrodes of a detection unit of the multidimensional acceleration sensor of the second embodiment.

FIG. 10 is an explanatory view showing a cross section of a detecting portion of the multidimensional acceleration sensor of the second embodiment.

11 is a sectional view taken along the line aa 'in FIG.

FIG. 12 is an explanatory diagram showing a configuration of a signal processing unit according to a second embodiment.

FIG. 13 is an explanatory diagram showing an arrangement of electrodes of a detection unit of the acceleration sensor of the third embodiment.

FIG. 14 is an explanatory diagram showing a cross section of a detection portion of the acceleration sensor of the third embodiment.

FIG. 15 is a cross-sectional view of the detection unit aa ′ of FIG.

FIG. 16 is a sectional view of a detecting portion of a multidimensional acceleration sensor according to a fourth embodiment.

17 is a cross-sectional view taken along the line aa 'in FIG.

FIG. 18 is an explanatory diagram of an assembled state of the multidimensional acceleration sensor of the fifth embodiment.

[Explanation of symbols]

100 ... Movable electrodes, 101, 102, 103, 104,
105, 106, 107, 108, 109, 110, 1
11, 112 ... Fixed electrode, 200 ... Detection part, 201 ... Movable electrode, 202, 203 ... Fixed electrode, 204 ... Beam,
205 ... Capacitance detector, 206 ... Amplifier, 207 ... Pulse width modulator, 208, 209 ... Drive gate, 210 ... Low-pass filter, 300 ... Detection section, 401 ... Capacitance detector, 40
2, 403 ... Amplifier, 404, 405 ... Pulse width modulator, 406, 407 ... Drive gate, 408, 409 ... Drive gate, 410, 411 ... Low-pass filter, 412 ... Adder, 413 ... Subtractor , 701 ... Operational amplifier, 702 ...
Capacitance, 703 ... Transistor, 704, 705, 7
06, 707, 708, 709 ... Sample-hold circuit, 710, 711, 712, 713, 714, 71
5, 716, 717 ... Driving gate, 900 ... Movable electrode,
901 ... beam, 902, 903, 904, 905, 9
06, 907, 908, 909 ... Fixed electrode, 1000 ...
Detection unit 1200 ... Capacitance detector 1201, 1202
1203, 1204 ... Amplifier, 1205, 1206, 1
207, 1208, 1209, 1210, 1211, 1
212 ... Drive gate, 1213, 1214, 1215
1216 ... Pulse width modulator, 1217, 1218, 12
19, 1220 ... Low-pass filter, 1221 ... Operation unit, 1
300 ... Detecting unit, 1301 ... Beam, 1302 ... Movable electrode, 1303 ... Fixed electrode, 1304 ... Fixed electrode, Beam ... 1305, 1306 ... Fixed electrode, 1307 ... Movable electrode, 1308 ... Fixed electrode, 1600 ... Detection Part, 1601
... beam, 1602 ... movable electrode, 1603, 1604,
1605, 1606 ... Fixed electrode, 1800 ... Substrate, 18
01 ... cube

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeki Tsuchiya 4026 Kuji Town, Hitachi City, Hitachi City, Ibaraki Prefecture Hitachi Research Laboratory, Hiritsu Manufacturing Co., Ltd.

Claims (6)

[Claims] 1. In a capacitance type acceleration sensor, a fixed electrode is arranged so as to face each surface of a movable electrode of a rectangular parallelepiped, and the movable electrode is surrounded by the fixed electrode from these fixed electrodes. When the movable electrode is displaced in response to a multi-dimensional acceleration, an electrostatic force is applied to float in the center of the space where the movable electrode and each fixed electrode change, and the movable electrode is moved. An electrostatic servo control signal for generating an electrostatic force for returning the electrode to the reference position (here, the reference position is the center of the space between the fixed electrodes) is formed, and the electrostatic servo control signal is generated by Equipped with an electrostatic servo control system for applying to the fixed electrode, set to detect multi-dimensional acceleration by processing this electrostatic servo control signal or a signal indicating the change in electrostatic capacitance between each fixed electrode and movable electrode To be done Multidimensional acceleration sensor, wherein 2. The fixed electrode according to claim 1, wherein two fixed electrodes are arranged so as to face each surface of the rectangular parallelepiped so that two fixed electrodes are arranged in parallel so as to detect acceleration and rotational acceleration in a three-dimensional space. A multi-dimensional acceleration sensor characterized in that 3. An electrostatic capacitance type acceleration sensor is provided with movable electrodes that are displaced in response to acceleration, and two fixed electrodes that are arranged in a row and a row so as to face the movable electrodes. A multi-dimensional acceleration sensor characterized in that 4. A capacitance type acceleration sensor is provided with two movable electrodes that are displaced in response to acceleration, and a plurality of fixed electrodes that are arranged to face these movable electrodes. A multi-dimensional acceleration sensor characterized in that 5. An electrostatic capacitance type acceleration sensor is provided with a movable electrode which is vertically and horizontally displaced in response to acceleration, and fixed electrodes which are arranged to face the upper and lower surfaces of the movable electrode, respectively. The left and right surfaces and the upper and lower surfaces of the electrodes, or the left and right surfaces or the upper and lower surfaces are comb-teeth-shaped electrode surfaces, while the electrode surface of the fixed electrode facing the comb-teeth-shaped electrode surface of the movable electrode is comb-teeth-shaped. A multidimensional acceleration sensor, characterized in that it is set so as to mesh with the comb-teeth-shaped electrode of the movable electrode while maintaining a minute gap. 6. A flexible printed board comprising a rectangular parallelepiped, a plurality of surfaces corresponding to surfaces 3 to 6 of the rectangular parallelepiped integrally molded, and a couple of acceleration sensors. Each surface of the substrate is bent and fixed to the corresponding surface of the rectangular parallelepiped, and the acceleration sensor is individually mounted on each of the two to three orthogonal surfaces of the flexible substrate. Multi-dimensional acceleration sensor.