JP2004294254A - Capacitive load sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a capacitance type load sensor capable of raising load sensitivity to an offset capacity and operating speedily. <P>SOLUTION: On both ends of a balance stage 10 supported by a fulcrum P of a balance structure, a first object 11 and a second object 12 to be objects of load measurement are put and a coil spring 13 is attached to the left end below the balance stage 10. To the left end below the balance stage 10, a displacement transmission rod 14 for transmitting the displacement of the coil spring 13 is attached and inserted in a capacitive displacement sensor 30. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００４１】
この式をＶａについて解くと、
【００４２】
【数２】

【００４３】
次に、第２のチャージアンプ７３の伝達関数をラプラス演算子ｓを用いて求める。第２のセンサ９２の容量Ｃｄ１，Ｃｄ２の和をＣｄとすると、Ｃｄは次式で表される。
【００４４】
【数３】

【００４５】
第２のチャージアンプ７３の出力信号をＶｂとすると、次式が成り立つ。
【００４６】
【数４】

【００４７】
これをＶｂについて解くと、
【００４８】
【数５】

【００４９】
この式にＣｄを代入すると、
【００５０】
【数６】

【００５１】
ここで、Ｖｏｕｔ＝Ｖａ×Ｖｂなので、数２，数５の式を掛け合わせると、
【００５２】
【数７】

【００５３】
が得られる。
【００５４】
このように、このセンサ信号処理回路によれば、容量の和と差の成分を並列処理により高速に抽出することができる。従って、上述の静電容量型変位センサ３０と、このセンサ信号処理回路を組み合わせることで、高速な荷重変化を高感度で検出することができるものである。
【００５５】
【発明の効果】
本発明の静電容量型荷重センサにより得られる、主な効果をまとめれば以下の通りである。
（１）Ｈ型構造等による可動電極板を平行に変位させるセンサ構造は、オフセット容量（＝荷重が印加されていない状態のセンサの静電容量）に対する荷重感度の割合を大きくできる。
（２）Ｈ型構造等による可動電極板を平行に変位させるセンサ構造は、板バネやコイルバネの小さな変位、即ち各部に生じた小さな歪みにおいても大きな荷重感度が得られる。
（３）Ｈ型構造等による可動電極板を平行に変位させるセンサ構造は、板バネやコイルバネの小さな変位、即ち各部に生じた小さな歪みにおいても大きな圧力感度が得られ、これはコイルバネの荷重と変位の関係における線形性を高める効果がある。
（４）Ｈ型構造等による可動電極板を平行に変位させるセンサ構造は、ダイアフラム等の板バネやコイルバネに生じさせる歪みを小さくでき、コイルバネには極めて小さな永久歪み、即ち極めて小さな塑性変形を生じるのみとなり、コイルバネに理想弾性材料を用いることなしに、再現性の高い（＝ヒステリシスの小さい）計測器を作ることができる。
（５）センサの温度特性（＝距離・面積成分変動）、湿度特性（＝ε成分変動）、雰囲気ガス成分の変化（＝ε成分変動）、センサキャパシタとなる平行平板コンデンサの電極板の位置ズレ（＝面積成分変動）等の影響を排除するためのレシオメトリック信号処理を行うため、同一平板上に平行平板コンデンサを２個配置し、さらに相補動作、即ち差（差圧力、差荷重）の計測のために、これを対称構造とする。これにより合計４つのキャパシタを持つこととなる。
（６）中央電極（＝可動電極）を仮想接地させる信号処理回路を用いると、測定誤差となる寄生容量の影響を小さくできる。
（７）電極材料に導電性接着剤を用いることで、簡単な印刷を用いて電極パターンが作成できる。用いる導電性接着剤には室温硬化型のものも多く存在し、Ｍｏ−Ｍｎ法、ガラスペースト法、メッキ法等で必要な焼成等の熱処理を必要としない。従って工程を簡素化でき、センサに熱応力も与えない利点がある。
【図面の簡単な説明】
【図１】本発明の第１の実施形態に係る静電容量型荷重センサの基本構造を示す図である。
【図２】図１の静電容量型変位センサ３０の構造を示す断面図である。
【図３】本発明の第２の実施形態に係る静電容量型荷重センサの基本構造を示す図である。
【図４】図３の静電容量型変位センサ５０の構造を示す断面図である。
【図５】センサ信号処理回路を示す回路図である。
【図６】センサ信号処理回路のブロック線図である。
【図７】従来の静電容量型圧力センサ１００の断面図である。
【符号の説明】
１０ 天秤台 １１ 第１の被測定物 １２ 第２の被測定物
１３ コイルバネ １４ 変位伝達棒 ３０ 静電容量型変位センサ
３１ 筐体 ３２ 第１のダイアフラム
３３ 第２のダイアフラム ３４ 第３のダイアフラム
３９〜４６ 電極パターン ４７ 貫通孔
５０ 静電容量型変位センサ ５１ 筐体 ５２ 貫通孔
５３ 可動板 ５４〜５７ 電極パターン
６１ 第１のコンデンサ ６２ 第２のコンデンサ
６３ 第３のコンデンサ ６４ 第４のコンデンサ
６５〜６８ 電極パターン ７０ 交流入力信号
７１ 反転増幅器 ７２ 第１のチャージアンプ
７３ 第２のチャージアンプ ７４ 乗算器
８１ 第１のコンデンサ ８２ 第２のコンデンサ
８３ 第３のコンデンサ ８４ 第４のコンデンサ
９１ 第１のセンサ ９２ 第２のセンサ
１００ 静電容量型圧力センサ １０１ 第１の固定電極板
１０２ 第２の固定電極板 １０３ ダイアフラム
１０４ 絶縁板 １０５ 空洞部
１０６ 第１の貫通孔 １０７ 空洞部 １０８ 第２の貫通孔[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a capacitive load sensor for detecting a load difference.
[0002]
[Prior art]
The load sensor detects the load of the object, but since the load can be converted into a hydraulic pressure, a capacitance type pressure sensor will be described below as a conventional example.
[0003]
FIG. 7 is a cross-sectional view of a conventional capacitance type pressure sensor 100. In the figure, a diaphragm 103 as a movable electrode plate is disposed between a first fixed electrode plate 101 and a second fixed electrode plate 102. Both ends of the diaphragm 103 are embedded and fixed in an insulating plate 104, and the insulating plate 104 electrically insulates the first fixed electrode plate 101 and the second fixed electrode plate 102 from the diaphragm 103. .
[0004]
Further, a first through hole 106 for introducing the hydraulic pressure P1 is provided in a hollow portion 105 between the first fixed electrode plate 101 and the diaphragm 103, and the second fixed electrode plate 102 and the diaphragm 103 are similarly provided. A second through hole 108 for introducing the hydraulic pressure P2 is provided in the hollow portion 107 between the two.
[0005]
Here, the capacitance C1 between the first fixed electrode plate 101 and the diaphragm 103 is represented by C1 = ε (S / d). ε is the dielectric constant of the oil, S is the electrode area, and d is the gap width between the electrodes. The capacitance C2 between the second fixed electrode plate 102 and the diaphragm 103 is represented by C2 = ε (S / d).
[0006]
Accordingly, the capacitances C1 and C2 change in inverse proportion to the electrode gap width d. On the other hand, since there is a certain relationship between the pressure difference between the oil pressures P1 and P2 and the electrode gap width d, the pressure can be known by detecting the capacitances C1 and C2. In addition, since the load can be known from the relationship between the pressure and the load, a load sensor can be configured using the capacitance type pressure sensor 100.
[0007]
Further, basically, by calculating the ratio (C1 / C2) of the capacitances C1 and C2, the capacitances C1 and C2 due to changes in the dielectric constant ε of the oil and the electrode area S due to temperature / humidity changes and aging changes. Can be eliminated.
[0008]
A pressure sensor using a parallel plate type capacitor as described above is described in Patent Document 1.
[0009]
[Patent Document 1]
JP-A-11-295175
[Problems to be solved by the invention]
However, it has been difficult for the conventional capacitance type pressure sensor 100 to increase the pressure sensitivity. This problem will be described with reference to FIG. Now, it is assumed that the hydraulic pressure P2 is higher than the hydraulic pressure P1 (P2> P1). Then, as shown by the broken lines in the figure, since both ends of the diaphragm 103 are fixed, a large displacement Δd1 is generated at the center portion Q of the diaphragm 103, but the diaphragm 103 moves from the center portion of the diaphragm 103 toward both ends. The displacement of 103 becomes smaller (Δd1> Δd2).
[0011]
That is, when the capacitance C1 is subdivided into a number of capacitances Ci (C1 = ΣCi) along the diaphragm 103, the capacitance Ci (Q) at the central portion Q of the diaphragm 103 has a pressure difference (P2 −P1), a large capacitance change occurs due to the displacement Δd1, but only a small capacitance change occurs at the capacitance Ci (R) at a location R distant from the central portion Q because the displacement Δd2 of the diaphragm 103 is small. . The capacitance C1 has a high pressure sensitivity even in the central portion Q, but has a low pressure sensitivity in a location R remote from the central portion Q.
[0012]
Therefore, in the conventional capacitance type pressure sensor 100, the pressure sensitivity to the offset capacitance (capacitance without a pressure difference) cannot be increased. There is also a problem that the linearity in the relationship between the pressure difference (P2-P1 and the displacement of the diaphragm is low).
[0013]
[Means for Solving the Problems]
Therefore, a first characteristic configuration of the present invention is that a displacement transmission rod that transmits an applied load, first and second fixed electrodes, and a first transmission electrode and a second fixed electrode are disposed between the first and second fixed electrodes. A capacitive load sensor comprising a movable electrode, wherein the displacement transmission rod presses the movable electrode.
A movable electrode is formed by a first movable plate having both ends fixed, and second and third movable plates symmetrically branched with respect to the first movable electrode to form an H-shaped structure. Between the fixed electrode and the second movable plate, two parallel plate capacitors are formed. Further, between the second fixed electrode and the third movable plate, another two parallel plate capacitors are formed. It is what constituted.
[0014]
A second characteristic configuration of the present invention includes a spring that generates a displacement according to a difference in applied load, a displacement transmission rod that transmits a displacement of the spring, first and second fixed electrodes, A capacitive electrode comprising a movable electrode disposed between the first and second fixed electrodes,
The movable electrode has a movable plate connected to the displacement transmission rod and extending in a direction crossing a longitudinal direction thereof, and is adjacent to each other between the first fixed electrode and a surface of the movable plate. And third and fourth capacitors adjacent to each other between the second fixed electrode and the back surface of the movable plate. .
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a basic structure of the capacitance type load sensor. In the figure, a first object to be measured 11 and a second object to be measured 12 to be subjected to load measurement are mounted on both ends of a balance platform 10 supported by a fulcrum P of the balance structure. A load transmission rod 13 is attached below the left end of the balance platform 10 and is inserted into an electrostatic capacitance type displacement sensor 30 described later to press the diaphragm.
[0016]
The operation of the capacitance type load sensor will be described. The load on the first DUT 11 is W1, the load on the second DUT 12 is W2, and the distance between the first DUT 11 placed on the left end of the balance 10 and the fulcrum P is L1. Assuming that the distance between the second measured object 12 placed on the right end of the balance platform 10 and the fulcrum P is L2, a torque T of (W1 × L1−W2 × L2) is generated around the fulcrum P. I do. When L1 = L2 = L, T = (W1-W2) L.
[0017]
If the torque T> 0 now, the left end of the balance platform 10 moves downward. The load transmission rod 13 has one end fixed to the balance platform 10 and the other end connected to a diaphragm that functions as a spring, so that the load transmission rod 13 transmits a displacement Δx according to a load difference. Therefore, if the displacement Δx is detected by the capacitance type displacement sensor 30, the load difference (W1−W2) can be known from the relationship between the displacement Δx and the torque T.
[0018]
Next, the structure of the capacitance type displacement sensor 30 will be described with reference to FIG. This capacitance type displacement sensor 30 includes four parallel plate type capacitors that operate complementarily.
[0019]
A movable electrode plate having an H-shaped structure is housed in a cylindrical housing 31, and a first diaphragm 32, both ends of which are embedded and fixed in a wall of the housing 31, and a first diaphragm 32 of the first diaphragm 32. A second diaphragm 33 branched from the central portion Q so as to approach and oppose the wall of the housing 31, and opposes from the central portion Q of the first diaphragm 32 to an opposing wall of the housing 31 on the opposite side. And a third diaphragm 34 that branches off. Then, the second diaphragm 33 and the third diaphragm 34 are connected symmetrically with respect to the first diaphragm 32 to form an H-shaped structure.
[0020]
Electrode patterns 39 and 40 are formed on the surface of the second diaphragm 33, and electrode patterns 41 and 42 are formed on the inner wall surface of the housing 31 so as to face these electrode patterns 39 and 40, respectively. I have. Accordingly, the first capacitor 61 is constituted by the pair of electrode patterns 39 and 41, and the second capacitor 62 is constituted by the pair of electrode patterns 40 and 42 adjacent thereto.
[0021]
Similarly, electrode patterns 43 and 44 are formed on the surface of the third diaphragm 34, and electrode patterns 45 and 46 are formed on the inner wall surface of the housing 31 so as to face the electrode patterns 43 and 44, respectively. Have been. Accordingly, the third capacitor 63 is constituted by the pair of electrode patterns 43 and 45, and the fourth capacitor 64 is constituted by the pair of electrode patterns 44 and 46 adjacent thereto. Each of these four capacitors is a parallel plate type. The electrode pattern can be formed by simple printing by using a conductive adhesive as an electrode material. Further, it is assumed that wiring is connected to each electrode pattern and is taken out to the outside.
[0022]
The distal end of the load transmission rod 13 is in contact with or connected to the central portion R of the second diaphragm 33 through a through hole 47 provided in the housing 31. Then, when the load transmission rod 13 moves down by the displacement Δx based on the load difference, the load transmission rod 13 presses the central portion of the second diaphragm 33, and this displacement Δx is reduced by the second diaphragm 33 and the third diaphragm 33. It is transmitted to the diaphragm 34. As a result, both the second diaphragm 33 and the third diaphragm 34 move downward in parallel by the displacement Δx, and the capacitance values of the four capacitors change.
[0023]
Here, assuming that the capacity of the first capacitor 61 is Cs1, the capacity of the second capacitor 62 is Cd1, the capacity of the third capacitor 63 is Cs2, and the capacity of the fourth capacitor 64 is Cd2. Is represented by
[0024]
Cs1 = εS / (d0−Δx)
Cd1 = εS / (d0−Δx)
Cs2 = εS / (d0 + Δx)
Cd2 = εS / (d0 + Δx)
Here, d0 is the electrode gap width when there is no pressure difference (P1 = P2), and ε is the dielectric constant of air between the electrode gaps. S is the electrode area, and the four capacitors have the same electrode area. Therefore, the first capacitor 61 and the third capacitor 63 operate complementarily, and the second capacitor 62 and the fourth capacitor 64 operate complementarily.
[0025]
Therefore, the following equation is obtained by performing signal processing of (Cs1−Cs2) / (Cd1 + Cd2).
(Cs1−Cs2) / (Cd1 + Cd2) = Δx / d0
Therefore, the load difference (W1-W2) can be known from the relationship between Δx and the load difference. In addition, by this signal processing, it is possible to remove the influence of fluctuations due to changes in the dielectric constant ε of the air and the electrode area S due to changes in temperature and humidity and changes over time. Further, since the capacitance type displacement sensor 30 uses four capacitors, (Cs1−Cs2) and (Cd1 + Cd2) can be subjected to parallel signal processing as described later, so that High-speed sensing can be performed as compared with a sensor that requires signal processing.
[0026]
A second embodiment of the present invention will be described in detail with reference to the drawings. FIG. 3 is a diagram showing a basic structure of the capacitive load sensor. This capacitance type load sensor is obtained by replacing the capacitance type displacement sensor 30 of the first embodiment with another type of capacitance type displacement sensor 50. The capacitance type displacement sensor 50 will be described in detail with reference to FIG.
[0027]
In the capacitance type displacement sensor 30 of the first embodiment, the diaphragm is deformed by pressing the H-shaped diaphragm with the load transmission rod 13. A movable electrode plate is vertically movably connected to a displacement transmission rod 14 attached below the left end of the base 10. A coil spring 15 for converting a load difference into a displacement is attached between the left end of the balance platform 10 and the capacitance type displacement sensor 50. The coil spring 15 may be a leaf spring.
[0028]
The movable electrode plate is housed in a cylindrical housing 51, is connected to the displacement transmitting rod 14 passed through a through hole 52 provided in the housing 51, and extends in a direction intersecting the longitudinal direction. Movable plate 53. Further, electrode patterns 54 and 55 are formed on the surface of the movable plate 53, and electrode patterns 56 and 57 are formed on the inner wall surface of the housing 51 so as to face these electrode patterns 54 and 55, respectively. Accordingly, the first capacitor 81 is constituted by the pair of electrode patterns 54 and 56, and the second capacitor 82 is constituted by the pair of electrode patterns 55 and 57 adjacent thereto.
[0029]
Similarly, electrode patterns 65 and 66 are formed adjacent to the back surface of the movable plate 53, and electrode patterns 67 and 68 are formed on the inner wall surface of the housing 51 so as to face the electrode patterns 65 and 66, respectively. Is formed. Accordingly, the third capacitor 83 is constituted by the pair of electrode patterns 65 and 67, and the fourth capacitor 84 is constituted by the pair of electrode patterns 66 and 68 adjacent thereto. Each of these four capacitors is a parallel plate type. The electrode pattern can be formed by simple printing by using a conductive adhesive as an electrode material. Further, it is assumed that wiring is connected to each electrode pattern and is taken out to the outside.
[0030]
Here, assuming that the capacity of the first capacitor 81 is Cs1, the capacity of the second capacitor 82 is Cd1, the capacity of the third capacitor 83 is Cs2, and the capacity of the fourth capacitor 84 is Cd2. It is expressed by the following equation as in the embodiment.
[0031]
Cs1 = εS / (d0−Δx)
Cd1 = εS / (d0−Δx)
Cs2 = εS / (d0 + Δx)
Cd2 = εS / (d0 + Δx)
Therefore, by performing the signal processing of Cs1−Cs2) / (Cd1 + Cd2), the load difference (W1−W2) can be known from the relationship between Δx and the load difference.
[0032]
Next, a sensor signal processing circuit of the above-described capacitance type displacement sensor 30 will be described. Note that the same circuit can be used for the capacitance type displacement sensor 50 of the second embodiment.
[0033]
FIG. 5 is a circuit diagram showing the sensor signal processing circuit. FIG. 6 is a block diagram of the sensor signal processing circuit.
[0034]
In FIG. 5, an AC signal source 70 generates an AC input signal Vin. 71 is an inverting amplifier composed of an operational amplifier A1 and two fixed resistors R; 91 is a first sensor composed of the first and third capacitors 61 and 63; 72 is a capacitor Ca; A first charge amplifier composed of an operational amplifier A2, a second sensor 92 composed of the second and fourth capacitors 62 and 64, and a condenser 73, a capacitor Cb, a second sensor 92, and an operational amplifier A3. This is a second charge amplifier composed of 74 is a multiplier.
[0035]
More specifically, in the first charge amplifier 72, the non-inverting input terminal (+) of the operational amplifier A2 is grounded, and the inverting input terminal (-) is connected to the electrodes of the first and third capacitors 61 and 63 ( The electrode patterns on the movable electrode plate side are connected, and these are virtually grounded. In the second charge amplifier 73, the non-inverting input terminal (+) of the operational amplifier A3 is grounded, and the inverting input terminal (-) is connected to the electrodes (movable electrodes) of the second and fourth capacitors 62 and 64. The electrode patterns on the plate side are connected, and these are virtually grounded.
[0036]
The output signals of the first charge amplifier 72 and the second charge amplifier 73 are multiplied by a multiplier 74, and as a result, an output signal Vout is obtained.
[0037]
As described above, the first sensor 91 operates complementarily so that when the capacitance Cs1 of one capacitor, for example, the first capacitor 61 increases, the capacitance Cs2 of the third capacitor 63 decreases.
[0038]
Therefore, a transfer function of the sensor signal processing circuit is obtained. First, the block before being input to the multiplier 74 can be considered by being divided into a portion formed by the inverting amplifier 71 and the first charge amplifier 72 and a portion formed by the second charge-up 73. These two components perform arithmetic processing in parallel.
[0039]
If the transfer functions of the respective parts are obtained and then multiplied, the entire transfer function can be obtained. First, a transfer function of a portion constituted by the inverting amplifier 71 and the first charge amplifier 72 is obtained by using the Laplace operator s. Assuming that the output signal of the first charge amplifier 72 is Va, the following equation holds.
[0040]
(Equation 1)

[0041]
Solving this equation for Va gives
[0042]
(Equation 2)

[0043]
Next, the transfer function of the second charge amplifier 73 is determined using the Laplace operator s. Assuming that the sum of the capacitances Cd1 and Cd2 of the second sensor 92 is Cd, Cd is represented by the following equation.
[0044]
[Equation 3]

[0045]
Assuming that the output signal of the second charge amplifier 73 is Vb, the following equation holds.
[0046]
(Equation 4)

[0047]
Solving this for Vb gives
[0048]
(Equation 5)

[0049]
Substituting Cd into this equation gives
[0050]
(Equation 6)

[0051]
Here, since Vout = Va × Vb, multiplying the expressions of Expressions 2 and 5 gives
[0052]
(Equation 7)

[0053]
Is obtained.
[0054]
Thus, according to this sensor signal processing circuit, the sum and difference components of the capacitance can be extracted at high speed by parallel processing. Therefore, by combining the above-mentioned capacitance type displacement sensor 30 and this sensor signal processing circuit, a high-speed load change can be detected with high sensitivity.
[0055]
【The invention's effect】
The main effects obtained by the capacitance type load sensor of the present invention are summarized as follows.
(1) A sensor structure that displaces the movable electrode plate in parallel with an H-shaped structure or the like can increase the ratio of the load sensitivity to the offset capacitance (= the capacitance of the sensor in a state where no load is applied).
(2) The sensor structure for displacing the movable electrode plate in parallel with an H-shaped structure or the like can provide a large load sensitivity even with a small displacement of a leaf spring or a coil spring, that is, a small strain generated in each part.
(3) The sensor structure that displaces the movable electrode plate in parallel by an H-shaped structure or the like can provide a large pressure sensitivity even with a small displacement of a leaf spring or a coil spring, that is, a small strain generated in each part. This has the effect of increasing linearity in the relationship of displacement.
(4) The sensor structure for displacing the movable electrode plate in parallel with an H-shaped structure or the like can reduce the distortion generated in a leaf spring such as a diaphragm or a coil spring, and causes a very small permanent distortion, that is, a very small plastic deformation in the coil spring. Thus, a measuring instrument with high reproducibility (= small hysteresis) can be produced without using an ideal elastic material for the coil spring.
(5) Temperature characteristics of the sensor (= distance / area component fluctuation), humidity characteristics (= ε component fluctuation), change of atmospheric gas component (= ε component fluctuation), misalignment of the electrode plate of the parallel plate capacitor serving as the sensor capacitor In order to perform ratiometric signal processing to eliminate the effects of (= area component fluctuation), two parallel plate capacitors are placed on the same plate, and the complementary operation, that is, the difference (differential pressure, differential load) is measured. For this reason, this is made a symmetric structure. This results in having a total of four capacitors.
(6) The use of a signal processing circuit for virtually grounding the center electrode (= movable electrode) can reduce the influence of the parasitic capacitance that causes a measurement error.
(7) By using a conductive adhesive as the electrode material, an electrode pattern can be created using simple printing. There are many conductive adhesives that can be cured at room temperature, and do not require heat treatment such as firing required for the Mo-Mn method, the glass paste method, the plating method, and the like. Therefore, there is an advantage that the process can be simplified and no thermal stress is applied to the sensor.
[Brief description of the drawings]
FIG. 1 is a diagram showing a basic structure of a capacitive load sensor according to a first embodiment of the present invention.
FIG. 2 is a sectional view showing a structure of the capacitance type displacement sensor 30 of FIG.
FIG. 3 is a diagram showing a basic structure of a capacitive load sensor according to a second embodiment of the present invention.
FIG. 4 is a sectional view showing the structure of the capacitance type displacement sensor 50 of FIG.
FIG. 5 is a circuit diagram showing a sensor signal processing circuit.
FIG. 6 is a block diagram of a sensor signal processing circuit.
FIG. 7 is a sectional view of a conventional capacitance type pressure sensor 100.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Balance base 11 1st measured object 12 2nd measured object 13 Coil spring 14 Displacement transmission rod 30 Capacitive displacement sensor 31 Housing 32 1st diaphragm 33 2nd diaphragm 34 3rd diaphragm 39- 46 Electrode pattern 47 Through hole 50 Capacitive displacement sensor 51 Housing 52 Through hole 53 Movable plate 54 to 57 Electrode pattern 61 First capacitor 62 Second capacitor 63 Third capacitor 64 Fourth capacitor 65 to 68 Electrode pattern 70 AC input signal 71 Inverting amplifier 72 First charge amplifier 73 Second charge amplifier 74 Multiplier 81 First capacitor 82 Second capacitor 83 Third capacitor 84 Fourth capacitor 91 First sensor 92 Second sensor 100 Capacitive pressure sensor 101 First fixed electrode plate 1 2 the second fixed electrode plate 103 diaphragm 104 insulating plate 105 cavity 106 first through-hole 107 cavity 108 the second through hole

Claims (5)

A load transmitting body for transmitting an applied load; first and second fixed electrodes; and a movable electrode disposed between the first and second fixed electrodes. A capacitance-type load sensor configured to press a movable electrode,
The movable electrode includes a first movable plate having both ends fixed,
A second movable plate branched from a central portion of the first movable plate so as to face the first fixed electrode;
A third movable plate symmetrically branched from the second movable plate so as to face the second fixed electrode from a central portion of the first movable plate;
First and second capacitors adjacent to each other are formed between the first fixed electrode and the second movable plate, and mutually connected between the second fixed electrode and the third movable plate. An electrostatic capacitance type load sensor, wherein adjacent third and fourth capacitors are formed. The second and third movable plates are made of an insulator, the electrode patterns for the first and second capacitors are provided on the second movable plate, and the third and third movable plates are provided on the third movable plate. The capacitance type load sensor according to claim 1, further comprising an electrode pattern for a fourth capacitor. A spring that generates a displacement in accordance with the applied load difference, a displacement transmission rod that transmits the displacement of the spring, first and second fixed electrodes, and a first and a second fixed electrode between the first and the second fixed electrodes. A capacitive load sensor comprising a movable electrode disposed thereon,
The movable electrode has a movable plate connected to the displacement transmission rod and extending in a direction intersecting with a longitudinal direction of the displacement transmission rod, between the first fixed electrode and a surface of the movable plate. And first and second capacitors adjacent to each other are configured, and third and fourth capacitors adjacent to each other are configured between the second fixed electrode and the back surface of the movable plate. Capacitive load sensor. The second and third movable plates are made of an insulator, the first and second capacitor electrode patterns are provided on the surface of the movable plate, and the third and fourth capacitors are provided on the movable back surface. 5. An electrostatic capacitance type load sensor according to claim 4, wherein an electrode pattern is provided. The capacitance type load sensor according to claim 2, wherein the electrode pattern is formed of a conductive adhesive.

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