JPH04121630A - Dynamics quantity detection device - Google Patents

Abstract

PURPOSE:To obtain a device with a high detection accuracy by forming first and second electrodes on a main surface of a substrate, by fixing a third electrode which opposes the first electrode, by forming a fourth electrode which opposes the second electrode in cantilever shape, and by comparing electrostatic capacity between the first and third electrodes and between the second and fourth electrodes. CONSTITUTION:An electrode group 10 and a circuit 13 are formed on a main surface 14 of a printed-circuit board 1. Metal bases 21 and 22 are adhered onto electrodes 11e and 12f by a conductive adhesive. Metal plates 31 and 32 are adhered to bases 21 and 22 by the conductive adhesive, thus enabling capacitors Ca and Cc to be constituted by fixed electrode parts 31a and 32c and fixed electrodes 11a and 12c. Capacitors Cb and Cd are constituted by the movable electrode parts 31b and 32b and the fixed electrodes 11b and 12d. A weight 4 is adhered to the movable electrode parts 31b and 32d. Ratios Ca/Cd and Cd/Cd are calculated and amplified, thus enabling dynamics quantity to be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a mechanical quantity detection device, and more particularly to a mechanical quantity detection device that obtains a mechanical quantity by a change in capacitance.

<Prior Art> A mechanical quantity detection device is known that changes the distance between the electrodes of a variable capacitor according to a mechanical quantity such as acceleration or pressure, and detects the mechanical quantity from the change in capacitance.

As such a mechanical quantity detection device, for example,
It is disclosed in Japanese Patent No.-152369, and a sectional view thereof is shown in FIG.

In FIG. 6, 84 is a silicon substrate, and the cantilever 84 is etched by etching the silicon substrate 84.
6. The movable electrode 85 is integrally formed.

Glass plates 81 and 82 sandwich the silicon substrate 84 from both sides. Metal fixed electrodes 91.92 are installed on the surfaces of the glass plates 81.82 facing the movable electrode 85. In addition, the movable electrode 85 and the fixed electrode 91.92
The distances between the movable electrode 85 and the fixed electrodes 91 and 92 are both set to d, and capacitors C1 and C2 are formed between the movable electrode 85 and the fixed electrodes 91 and 92, respectively.

Furthermore, the movable electrode 85 and fixed electrodes 91 and 92 are each connected to a mechanical quantity detection circuit (not shown). The mechanical quantity detection circuit operates on the difference in capacitance between the capacitors C1 and C2, determines the permanent position of the horn based on this difference, and outputs it as a voltage signal.

Next, the effect will be explained.

When acceleration as indicated by arrow A is applied to the above device, the movable electrode 85 is displaced by Δd due to inertia. the result,
The distance between the electrodes of capacitors C1 and C2 changes, and the capacitance changes.

The above change in capacitance is detected by a mechanical quantity detection circuit and output as a voltage signal corresponding to the mechanical quantity.

The above operation can be expressed as follows.

VOUT-k (Ct -C2) εoS ε03 -k (Ryoyumi ■ - Goqman) Δd εoS-a'r ...■ However, vg: Output voltage of the mechanical quantity detection circuit C1: Capacitor C1's output voltage Capacitance C2: Capacitance C0 of capacitor C2: Dielectric constant S: Electrode area k: Constant of proportionality <Problem to be solved by the invention> When etching a silicon substrate, the processing accuracy is several hundred [
Fl11]. Therefore, in the above-described device, when the distance d between the electrodes is set to several [trends], an error of about 10% occurs in the value of the distance lid due to manufacturing variations.

Since the error in this distance @d is squared as expressed in equation (2), there is a problem in that the error in the output J voltage Vou+ becomes even larger.

The present invention was made to solve these problems, and an object of the present invention is to provide a mechanical quantity detection device with high detection accuracy.

Means for Solving the Problems> The present invention provides a first electrode formed on the main surface of a substrate, a second electrode formed on the main surface of the substrate, and a plurality of electrodes formed on the main surface of the substrate. a plurality of fixed bases, a third electrode fixed to the fixed base and arranged on the first electrode at a predetermined distance from the electrode surface, a beam fixed to the fixed base, and the beam detecting a first capacitance between a fourth electrode identified on the second electrode and arranged at a predetermined distance from the electrode surface, the first electrode and the third electrode; a first detection means for detecting a second capacitance between the second electrode and the fourth electrode; a first detection means for detecting a second capacitance between the second electrode and the fourth electrode; calculation means for calculating a ratio between the first capacitance and the second capacitance based on the output from the means, and detecting a mechanical quantity based on the ratio calculated by the calculation means. It is characterized by

<Operation> According to the present invention, when a mechanical quantity is applied, the fourth electrode is displaced with respect to the second electrode by the mechanical quantity. Therefore, the capacitance formed between the second electrode and the fourth electrode changes.

On the other hand, since the third electrode is placed on the first electrode by means of a fixed base, it will not be displaced with respect to the first electrode even if a mechanical quantity is applied. Therefore, the capacitance formed between the first electrode and the third electrode does not change.

Next, the ratio between the second capacitance between the second electrode and the fourth electrode and the first capacitance between the first electrode and the third electrode is determined by the calculation means. It will be done.

Then, the mechanical quantity is detected based on the ratio determined by the calculation means. At this time, the ratio of capacitance is the distance between the second electrode and the fourth electrode and the distance between the first electrode and the third electrode.
It is determined as the ratio of the distance between the electrodes.

<Example> A first example will be described based on FIGS. 1 to 3.

FIG. 1A is an exploded view of this embodiment, and FIG. 1B is a perspective view showing the configuration of this embodiment.

1 is a printed circuit board, and a main surface 14 of the printed circuit board 1 is formed with a pole group 10 and a circuit section 13 as a calculation means.

118.11b are fixed electrodes as a first electrode and a second electrode, respectively, and 11e is a contact electrode. Also,
12c, 12d, and 12f are electrodes 11a and 11b, respectively.
, 11e, and are formed for differential amplification as will be described later.

Reference numerals 21 and 22 are metal bases serving as fixing bases, and the thickness is set to do [am]. And base 2
1 is on the contact electrode 11e, and the base 22 is on the contact electrode 12f.
It is glued on top with S-conducting adhesive.

Reference numerals 31 and 32 denote thin metal plates, and the thin metal plates 31 and 32 each have fixed electrode portions 318 and 32G as third electrodes.
, movable electrode portions 31b and 32d as fourth electrodes, and beams 31h and 32h are integrally formed.

The thin metal plate 31 is bonded onto the base 21 with a conductive adhesive, and is connected to the contact electrode 11e via the base 21. Then, the fixed electrode part 31a and the fixed electrode 11
a constitutes a capacitor Ca, and the movable electrode portion 31
A capacitor Cb is constituted by the capacitor Cb and the fixed electrode 11b.

Further, the metal thin plate 32 is installed on the base 22,
It is connected to the contact electrode 12f via the base 22. The fixed electrode part 32c and the fixed electrode 120 constitute a capacitor Cc, and the movable electrode part 32d and the fixed electrode 12
d constitutes a capacitor cd.

4 is a non-conductive weight, and the weight 4 is a movable electrode part 31b, 3
2d by adhesive.

Next, the connection between each capacitor and the circuit section 13 will be explained based on the equivalent circuit shown in FIG. 2.

A capacitor CD is connected to the e input terminal of the operational amplifier OP1, and the Φλ input terminal is grounded. Also, operational amplifier O
A capacitor Ca and a resistor R1 are connected in parallel between the output terminal 0UT1 of P1 and the e input terminal.

A capacitor Cc is connected to the e input terminal of the operational amplifier OP2, and the e input terminal is grounded. Also, operational amplifier O
A capacitor cd and a resistor R2 are connected in parallel between the output terminal 0UT2 of P2 and the e input terminal.

The e input terminal of the operational amplifier circuit OP3 is connected to the output terminal 0UT2 of the operational amplifier OP2 via a resistor R4. The Φλ input terminal of the operational amplifier OP3 is grounded via the resistor Re, and the output terminal 0UT1 of the operational amplifier OP1 is connected via the resistor R5. Also,
A resistor R3 is connected between the output terminal 0UT3 and the e input terminal of the operational amplifier OP3.

Note that an input voltage vin is applied to the capacitors Cb and Cc by a power source 5.

Next, the effect will be explained.

In the circuit shown in Figure 2, performance IIl! A voltage proportional to the product of the input voltage Vin and the ratio of the capacitance of the capacitor Ca to the capacitance of the capacitor Cb is output from the output terminal 0UTI of the f-range amplifier OP1.

Further, from the output terminal 0LJT2 of the operational amplifier OP2, a voltage proportional to the product of the input voltage Vin and the ratio of the capacitance of the capacitor cd to the capacitance of the capacitor Cc' is output.

Then, the voltage outputted from the output terminals 0UT1.0UT2 is differentially amplified by the operational amplifier OP3, and outputted from the output terminal 0UT3 as an output voltage VIXIT.

Expressing the above as a formula, it becomes formula ■.

V eaves-KV;n (hereinafter-m=) Cb Cc However, Ca: Capacitor Ca capacitance Cゎ: Capacitor Ca capacitance CC: Capacitor Ca capacitance Cd: Capacitor Ca capacitance K: Proportionality constant・...■ Next, FIG. 3 shows a sectional view taken along the line ■-■ of FIG. 1B.

First, based on FIG. 3A, the operation when a mechanical quantity such as acceleration is not applied to the electric current of this embodiment or when a mechanical quantity in a direction parallel to the printed circuit board 1 is applied will be explained.

At this time, the distance between the electrodes of each capacitor is the base 21.
22, and the movable electrode 31b,
32d is not displaced, capacitors Ca, Cb, and C
The distance between the electrodes c and Ca is do [am].

Note that when the distance do between the electrodes is set to 1 [jw+], the machining accuracy is approximately 5 [normal]. Therefore, the error due to manufacturing variations is approximately 5%, which is half of the error in the conventional example (approximately 10%).

If the output voltage VQIT in the above case is expressed by a formula, it will be as follows from formula (2).

Vour=KV;n (CA-Ci) bCc ε0: permittivity Sa: area of electrode 11a Sゎ: Area of electrode 11c Sc: @Area of pole 11d Sd: area of electrode 11d In formula (■), the area Sa of each electrode.

Sb, Sc, and Sd are designed to have equal values.

And even if variations occur during the manufacturing stage,
The areas Sa, Sb, Sc, and Sc+ of the electrodes can be made equal. This is because variations at the manufacturing stage are caused by etching conditions such as etching time and temperature.

By etching 11G and 11d at the same time,
This is because the above conditions are equal for all electrodes.

Therefore, the output voltage VwI of equation (2) becomes 0 [■].

On the other hand, as shown in FIG. 3B, when a mechanical quantity is applied to the printed circuit board 1 in the vertical direction (arrow B), the movable electrode parts 31b, 32d and the weight 4 are integrated with the beams 31h, 32h as fulcrums. Displaced to.

If the amount of displacement at this time is Δd, the capacitors Cゎ, C
The distance between the d electrodes becomes d(+tΔd).As a result, the output voltage Van changes and the mechanical quantity is detected.

If the output voltage VQIT at this time is expressed by a formula, it will be as follows from formula (2).

VcL, r=KV,, ((ACsi)Cb
Cc (','Sa=Sb-8c=Sa)Δd
Δd”=KV;n ((1 + 1>-(1-dtr)
) Δd = 2 K Vinζ...■ From the formula (■), the output voltage Vout is determined as a value proportional to the displacement amount Δd.

Further, in the above equation (2), the output voltage vcU+ is linearly inversely proportional to the distance do between the electrodes. Therefore, the distance I
Even if an error occurs in ll do, the output voltage ■ is not easily affected by the error in distance do.

Furthermore, the output voltage V our Lt 1g does not depend on the electric current rate ε0. Therefore, even if damping oil is sealed between the electrodes and the dielectric constant ε0 changes, the output voltage V(N) is not affected by the change in the electric constant.

As described above, according to the first embodiment, the fixed electrodes 11a, 11b, 12c are provided on the printed circuit board 1.

12d and the thin plate 31.22 via the base 21.22.
32 and identification electrodes 11a and 31a.

Fixed capacitor Ca by 12c and 32C.

Cc, and also the fixed electrode 11b and the movable electrode 31b
, variable capacitors Cb and Cc+ are formed by the fixed electrode 12d and the movable electrode 32d, the ratio Ca/Cb and the ratio Ca/Cc are calculated, and the output voltage vcLI is calculated by differential amplification.
I made it output T.

Therefore, the output voltage VQIT is linearly inversely proportional to the distance do between the electrodes, and the influence of manufacturing variations in the distance do is reduced, resulting in an effect that the accuracy of detecting the mechanical quantity is improved.

Further, since the distance between the electrodes can be set by the thickness of the bases 21 and 22, the distance do between the electrodes can be manufactured with high precision, and the effect of further improving the accuracy of detecting the mechanical quantity can be obtained.

In addition, since the output voltage VQI7 does not depend on the dielectric constant ε0, even if damping oil etc. is sealed between the electrodes, it will not be affected by variations or changes in the dielectric constant of the oil etc. The effect of further improving this can be obtained.

Then, electrodes 11a and 11b are placed on the printed circuit board.

By manufacturing the connection patterns of 11c, 11d and the circuit section at the same time, it is possible to reduce the number of man-hours.

Next, a second embodiment will be described based on FIGS. 4 and 5.

FIG. 4 shows the electrode section of this embodiment.

11g is shield 1! electrodes 11a, 1ib,
It is formed between 11e, 12c, 12d, and 12f. The shield electrode 11g is connected to ground.

Note that the other configurations are the same as those of the first embodiment, and will be described using the same numbers.

FIG. 5 is an equivalent circuit showing the measurement circuit of the second embodiment. The circuit of FIG. 5 is fundamentally similar to the circuit of FIG. 2. However, stray capacitance is formed between the shield electrode and other currents in FIG.

Specifically, between the electrodes 11a and 11g, and the electrode 11b.

Question 11g, between electrodes 11e and 11g, electrode 12C211g
between the electrodes 12d and 11g, and the electrode 12f.

11g, stray capacitance Cag, Cbg, C
eg.

Ccg, C≦, Cfg are formed.

Next, the effect will be explained.

Generally, stray capacitance formed between the shield electrode and other electrodes adversely affects the operation of the circuit.

However, in the second embodiment, the influence of stray capacitance on the circuit can be reduced for the following reasons.

In the circuit of Fig. 5, all electrodes of the stray capacitance Ceg, No impact.

Further, the influence of the stray capacitance jlcbg, Cα on the circuit shown in FIG. 5 can be reduced by lowering the output impedance of the power supply 5. And floating volume 1
cag and C are operational amplifiers OPI.

By lowering the output impedance of OF2,
The influence on the circuit shown in FIG. 5 can be reduced.

Then, as shown in FIG. 4, by forming the shield electrode 11g, the electrodes 11a and 11b are formed.

Stray capacitance between 120 and 12d is suppressed. the result,
Electrodes 11a, 11b, 12C, 12d17) The substantial electrode area is stabilized.

Note that the other operations of the second embodiment are the same as those of the first embodiment, so a description thereof will be omitted.

As described above, according to the second embodiment, in addition to the configuration of the first embodiment, electrodes 11a, 11b, and 11e are provided.

A shield electrode 11g was formed between 12c, 12d, and 12f, and the shield electrode 11g was connected to ground.

Therefore, the electrode area can be stabilized while reducing the adverse effects of stray capacitance, and the detection accuracy can be further improved.

Although the movable electrode portions 31b and 32d were formed with a cantilever structure in the above two embodiments, the present invention is not limited to this. That is, the same effect can be obtained with a double-supported beam structure or a diaphragm structure with peripheral support.

Furthermore, in the two embodiments, the capacitor Cb,
Although Cd is a variable capacitor and the capacitors Ca and Cc are fixed capacitors, they may be variable capacitors with a different amount of change from the capacitors Ca, Cc and Cb and Cd.

Further, in the two embodiments described above, the capacitors were formed using metal electrodes, but the present invention is not limited to this, and the capacitors may be formed using semiconductors.

As an example of such a capacitor, Japanese Patent Application Laid-Open No. 632598
There is one as shown in Publication No. 2.

In FIGS. 1A and 1B of the above-mentioned publication, the am-domain impurity diffusion region 22 and the upper electrode 28 correspond to the first electrode and third electrode of the present invention, respectively. Further, by increasing the area of the cavity region 25 without changing the area of the overlapping portion of the high concentration impurity diffusion region 22 and the upper electrode 28, the high concentration impurity diffusion region 22 and the upper electrode 28 are and the fourth electrode.

Similar effects can also be obtained by connecting each of the above electrodes to a circuit similar to that of the first embodiment.

Furthermore, the capacitors do not have to be formed on the same substrate or on the same surface.

<Effects of the Invention> As described above, according to the present invention, the first electrode and the second electrode are formed on the main surface of the substrate, and the third electrode is fixed on the first electrode at a predetermined distance apart. , a fourth electrode is supported by a beam at a predetermined distance above the second electrode, and the first capacitance between the first electrode and the third electrode and the second electrode and the fourth electrode are connected to each other. The ratio between the capacitance and the second capacitance is calculated, and the mechanical quantity is detected based on this ratio.

Therefore, the value of the calculated ratio is linearly inversely proportional to the distance between the electrodes, making it possible to reduce the influence of manufacturing variations in the distance, resulting in the effect of improving the viscosity for detecting the mechanical quantity.

In addition, since the calculated ratio value does not depend on the dielectric constant, even if damping oil etc. is sealed between the electrodes,
Unaffected by variations and changes in dielectric constant of oil, etc.
The effect is that the accuracy of detecting the dynamics 1 is greatly improved.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of the first embodiment, Fig. 2 is an equivalent circuit diagram of the first embodiment, Fig. 3 is a sectional view of the embodiment '@, and Fig. 4 is a diagram of the second embodiment. 5 is an equivalent circuit diagram of the second embodiment, and FIG. 6 is a sectional view of a conventional device. 11a, 11b, 11c, 11d--Fixed electrode, 31
．． 32... Metal thin plate, OPl, 0P2... Operational amplifier patent applicant Nissan Automatic Kushi Co., Ltd. Figure Figure Figure A Figure 11e, 12f Figure z

Claims (1)

[Scope of Claims] A first electrode formed on the main surface of the substrate, a second electrode formed on the main surface of the substrate, one or more fixing bases formed on the main surface of the substrate, a third electrode fixed to a fixed base and arranged on the first electrode at a predetermined distance from the electrode surface; a beam fixed to the fixed base; a fourth electrode arranged on the electrode at a predetermined distance from the electrode surface, and a first detection means for detecting a first capacitance between the first electrode and the third electrode. and a second detection means for detecting a second capacitance between the second electrode and the fourth electrode, based on outputs from the first detection means and the second detection means. , a calculation means for calculating a ratio between the first capacitance and the second capacitance, and a mechanical quantity is detected based on the ratio calculated by the calculation means. Mechanical quantity detection device.