JP5081852B2 - Capacitive sensor and angular velocity sensor - Google Patents

Capacitive sensor and angular velocity sensor Download PDF

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JP5081852B2
JP5081852B2 JP2009045025A JP2009045025A JP5081852B2 JP 5081852 B2 JP5081852 B2 JP 5081852B2 JP 2009045025 A JP2009045025 A JP 2009045025A JP 2009045025 A JP2009045025 A JP 2009045025A JP 5081852 B2 JP5081852 B2 JP 5081852B2
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capacitive sensor
capacitance
capacitance detector
signal
modulator
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JP2010197317A (en
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昌大 松本
敏明 中村
寛 岩澤
哲 浅野
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Hitachi Astemo Ltd
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Hitachi Automotive Systems Ltd
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本発明は容量式センサ及び角速度センサに係り、特に微小な容量変化をデジタル値に変換して検出する容量式センサ及び角速度センサに関する。   The present invention relates to a capacitive sensor and an angular velocity sensor, and more particularly to a capacitive sensor and an angular velocity sensor that detect a minute capacitance change by converting it into a digital value.

微小な容量変化を検出する容量式センサで容量変化をデジタル値に変換して検出する従来例には特表2001−519534号公報に記載された静電帰還モータを備えた可動プレート型加速度計などがある。   A conventional example of detecting a capacitance change by converting it into a digital value with a capacitance type sensor that detects a minute capacitance change is a movable plate type accelerometer provided with an electrostatic feedback motor described in JP-A-2001-519534. There is.

特表2001−519534号公報JP-T-2001-519534

マイクロマシニングを利用した容量式センサは加速度センサや角速度センサと言った力学センサへ利用されている。このため、容量式センサの小型化への要求が強く、これに伴い検出素子の小型化が進み検出素子自身の容量変化が小さくなっている。このことにより、容量式センサの容量検出器には高感度,高精度化が要求されている。また、加速度センサや角速度センサの様な力学センサはマイコンに接続される用途が多くデシタル出力が要求されている。   Capacitive sensors using micromachining are used for dynamic sensors such as acceleration sensors and angular velocity sensors. For this reason, there is a strong demand for downsizing of the capacitive sensor, and along with this, the downsizing of the detection element advances and the capacitance change of the detection element itself becomes small. As a result, the capacitance detector of the capacitive sensor is required to have high sensitivity and high accuracy. In addition, a dynamic sensor such as an acceleration sensor or an angular velocity sensor has many uses connected to a microcomputer and requires a digital output.

特表2001−519534号公報に記載の静電帰還モータを備えた可動プレート型加速度計では容量式センサの検出素子自身をΔΣ変調器の一部として使用して、容量式センサの静電容量値に応じた値をΔΣ変調器の出力として得ることで回路の小型化とデジタル出力化を実現した。また、ΔΣ変調器を採用することでSN比の向上を図っていた。しかし、上記従来技術では容量式センサの小型化の進行による感度低下に対する配慮が欠けていた。   In the movable plate type accelerometer provided with the electrostatic feedback motor described in JP-A-2001-515534, the capacitance sensor detection element itself is used as a part of the ΔΣ modulator, and the capacitance value of the capacitance sensor is detected. By obtaining a value according to the output of the ΔΣ modulator, the circuit was downsized and digital output was realized. In addition, the S / N ratio is improved by employing a ΔΣ modulator. However, the above prior art lacks consideration for sensitivity reduction due to the progress of miniaturization of the capacitive sensor.

また、最近の容量式センサ、特に角速度センサにおいては感度の更なる低下、静電気力による共振周波数の調整機能の追加,加振回路からの影響低減など容量検出器に要求される機能が増加し上記従来例では限界があった。   In addition, in recent capacitive sensors, especially angular velocity sensors, the functions required for capacitive detectors such as further reduction of sensitivity, addition of resonance frequency adjustment function due to electrostatic force, and reduction of influence from vibration circuit have increased. The conventional example has a limit.

本発明は上記事情に鑑みてなされたものであり、その目的は微小な静電容量の変化を検出可能で、静電気力による共振周波数の調整機能を追加可能で、加振回路からの影響を低減できる高感度且つSN比の高い容量式センサを提供することにある。   The present invention has been made in view of the above circumstances, and its purpose is to detect minute changes in capacitance, and to add a function for adjusting a resonance frequency by electrostatic force, thereby reducing the influence from an excitation circuit. An object of the present invention is to provide a capacitive sensor with high sensitivity and high S / N ratio.

上記課題を解決するためには所定の物理量の変化に応じて静電容量が変化する物理量検出素子と、前記物理量検出素子に交流信号を印加する交流信号発生手段と、前記物理量検出素子に前記交流信号発生手段により充放電される電荷に応じた交流電圧を発生させる容量検出器と、前記容量検出器の発生させる交流電圧の振幅に応じたΔΣ変調信号列を発生させるΔΣ変調器とを構成することで達成される。   In order to solve the above problems, a physical quantity detection element whose capacitance changes in accordance with a change in a predetermined physical quantity, an AC signal generating means for applying an AC signal to the physical quantity detection element, and the alternating current to the physical quantity detection element A capacitance detector that generates an AC voltage corresponding to the charge charged / discharged by the signal generator and a ΔΣ modulator that generates a ΔΣ modulation signal sequence corresponding to the amplitude of the AC voltage generated by the capacitance detector are configured. Is achieved.

本発明によれば、微小な静電容量の変化を高精度に検出可能で、静電気力により共振周波数の調整機能を追加可能で、加振回路からの影響を低減できる高感度且つSN比の高い容量式センサを提供することができる。   According to the present invention, a minute change in electrostatic capacitance can be detected with high accuracy, a resonance frequency adjustment function can be added by electrostatic force, and the sensitivity from the excitation circuit can be reduced, and the SN ratio is high. A capacitive sensor can be provided.

第1の実施例の容量式センサの構成。The structure of the capacitive sensor of the first embodiment. 第1の実施例の容量式センサの信号処理回路のタイミングチャート。The timing chart of the signal processing circuit of the capacity type sensor of the 1st example. 第2の実施例の容量式センサの構成。The structure of the capacitive sensor of the second embodiment. 第3の実施例の容量式センサの構成。The structure of the capacitive sensor of a 3rd Example. 第4の実施例の容量式センサの構成。The structure of the capacitive sensor of the fourth embodiment. 第4の実施例の容量式センサの信号処理回路のタイミングチャート。The timing chart of the signal processing circuit of the capacity type sensor of the 4th example. 第4の実施例の容量式センサのΔΣ変調器51の構成。Configuration of ΔΣ modulator 51 of the capacitive sensor of the fourth embodiment. 第5の実施例の容量式角速度センサの構成。The structure of the capacity | capacitance type angular velocity sensor of a 5th Example. 第6の実施例の容量式加速度センサの構成。The structure of the capacitive acceleration sensor of the sixth embodiment.

以下、本発明の実施の形態について、図面を参照して説明する。   Embodiments of the present invention will be described below with reference to the drawings.

まず、本発明の第1の実施例である容量式センサを図1,図2により説明する。なお、図1は第1の実施例の容量式センサの構成、図2は第1の実施例の容量式センサの信号処理回路のタイミングチャートである。   First, a capacitive sensor according to a first embodiment of the present invention will be described with reference to FIGS. 1 is a configuration of the capacitive sensor of the first embodiment, and FIG. 2 is a timing chart of the signal processing circuit of the capacitive sensor of the first embodiment.

本実施例の容量式センサの検出素子2は所定の物理量の変化に応じて静電容量の変化する素子で電気回路的には可変コンデンサとして表される。信号処理回路は検出素子2に交流信号を印加する交流信号発生器1と、検出素子2の静電容量に応じた信号を出力する容量検出器3と、容量検出器3の出力の振幅に応じたΔΣ変調信号を出力するΔΣ変調器8より構成される。容量検出器3は演算増幅器6の帰還部にコンデンサ5とスイッチ4を配置した構成で、図2に示す様に検出素子2の静電容量値に応じた振幅を持つ矩形波を出力する。また、可変電源7により検出素子2の両端電圧を任意に変更できるようにしている。ΔΣ変調器8は容量検出器3の発生させる検出素子2の静電容量に応じた振幅を持つ矩形波で充放電される検出コンデンサ9と、検出コンデンサ9を充放電させるスイッチ10,11と、演算増幅器13とコンデンサ12より構成され、検出コンデンサ9の充電あるいは放電電荷と基準コンデンサ17の充放電電荷を積分する積分器と、演算増幅器13の出力を比較する比較器14と、比較器14の出力値に応じて離散的な電圧を発生する局部DA変換器20と、局部DA変換器20の出力電圧に応じて充放電する基準コンデンサ17と、基準コンデンサ17を充放電させるスイッチ15,16,18,19により構成される。   The detection element 2 of the capacitive sensor of the present embodiment is an element whose capacitance changes in accordance with a change in a predetermined physical quantity, and is expressed as a variable capacitor in terms of an electric circuit. The signal processing circuit includes an AC signal generator 1 that applies an AC signal to the detection element 2, a capacitance detector 3 that outputs a signal corresponding to the capacitance of the detection element 2, and the amplitude of the output of the capacitance detector 3. The ΔΣ modulator 8 outputs a ΔΣ modulation signal. The capacitance detector 3 has a configuration in which a capacitor 5 and a switch 4 are arranged in the feedback section of the operational amplifier 6 and outputs a rectangular wave having an amplitude corresponding to the capacitance value of the detection element 2 as shown in FIG. The variable power source 7 can arbitrarily change the voltage across the detection element 2. The ΔΣ modulator 8 includes a detection capacitor 9 charged and discharged with a rectangular wave having an amplitude corresponding to the capacitance of the detection element 2 generated by the capacitance detector 3, and switches 10 and 11 for charging and discharging the detection capacitor 9. An operational amplifier 13 and a capacitor 12, an integrator that integrates the charge or discharge charge of the detection capacitor 9 and the charge / discharge charge of the reference capacitor 17, a comparator 14 that compares the output of the operational amplifier 13, and a comparator 14 A local DA converter 20 that generates a discrete voltage according to the output value, a reference capacitor 17 that charges and discharges according to the output voltage of the local DA converter 20, and switches 15 and 16 that charge and discharge the reference capacitor 17. 18 and 19.

次に本実施例の動作を図2により説明する。期間Iにおいて交流信号発生器1の出力はローレベルで、スイッチ4はクロック信号P1によって動作するのでオン状態にある。このため、コンデンサ5及び検出素子2は放電され、演算増幅器6の出力は可変電源7の出力電圧と演算増幅器6のオフセット電圧の和の電圧VHになる。期間IIでは交流信号発生器1の出力はハイレベルで、スイッチ4はクロック信号P1によって動作するのでオフ状態になる。このため、検出素子2及びコンデンサ5は充電され、演算増幅器6の出力は検出素子2の静電容量に応じた電圧だけ変化してVLになる。つまり、容量検出器3の出力には図2に示す波形が現れ、期間Iで出力される電圧VHと期間IIで出力される電圧VLの差電圧、即ち振幅が検出素子2の静電容量の値に応じて変化する。   Next, the operation of this embodiment will be described with reference to FIG. In the period I, the output of the AC signal generator 1 is at a low level, and the switch 4 operates in accordance with the clock signal P1, so that it is in the ON state. Therefore, the capacitor 5 and the detection element 2 are discharged, and the output of the operational amplifier 6 becomes a voltage VH that is the sum of the output voltage of the variable power source 7 and the offset voltage of the operational amplifier 6. In the period II, the output of the AC signal generator 1 is at a high level, and the switch 4 is operated by the clock signal P1 and thus is turned off. Therefore, the detection element 2 and the capacitor 5 are charged, and the output of the operational amplifier 6 changes by a voltage corresponding to the capacitance of the detection element 2 and becomes VL. That is, the waveform shown in FIG. 2 appears at the output of the capacitance detector 3, and the difference voltage between the voltage VH output in the period I and the voltage VL output in the period II, that is, the amplitude is the capacitance of the detection element 2. It changes according to the value.

次に、ΔΣ変調器8の動作について説明する。期間Iにおいてはクロック信号P1がハイレベルなので、スイッチ11,16,19がオン状態にある。検出コンデンサ9には容量検出器3の出力電圧VHが充電され、基準コンデンサ17は放電される。期間IIにおいてはクロック信号P2がハイレベルになるので、スイッチ10,15,18がオン状態になり、検出コンデンサ9には容量検出器3の出力電圧VLが充電されることで、演算増幅器13とコンデンサ12で構成される積分器には、容量検出器3の出力電圧VHとVLの差電圧、即ち振幅と検出コンデンサ9の静電容量の積の電荷が充電される。また、基準コンデンサ17は局部DA変換器20の出力電圧に充電される。このことにより、演算増幅器13とコンデンサ12で構成される積分器には、容量検出器3の出力の振幅と検出コンデンサ9の静電容量の積の電荷と局部DA変換器20の出力電圧と基準コンデンサ17の静電容量の積の電荷の和が充電され、演算増幅器13の出力が変化する。演算増幅器13の出力は比較器14で比較され、この比較器14の出力に応じて局部DA変換器20の出力を変化させることで、比較器14の出力に容量検出器3の出力の振幅に応じたΔΣ変調信号を生成する。   Next, the operation of the ΔΣ modulator 8 will be described. In the period I, since the clock signal P1 is at a high level, the switches 11, 16, and 19 are in the on state. The detection capacitor 9 is charged with the output voltage VH of the capacitance detector 3, and the reference capacitor 17 is discharged. In the period II, since the clock signal P2 becomes high level, the switches 10, 15 and 18 are turned on, and the output voltage VL of the capacitance detector 3 is charged in the detection capacitor 9, whereby the operational amplifier 13 and The integrator constituted by the capacitor 12 is charged with the difference voltage between the output voltages VH and VL of the capacitance detector 3, that is, the product of the amplitude and the capacitance of the detection capacitor 9. The reference capacitor 17 is charged to the output voltage of the local DA converter 20. As a result, the integrator composed of the operational amplifier 13 and the capacitor 12 has a product of the amplitude of the output of the capacitance detector 3 and the capacitance of the detection capacitor 9, the output voltage of the local DA converter 20, and the reference. The sum of the charges of the capacitance product of the capacitor 17 is charged, and the output of the operational amplifier 13 changes. The output of the operational amplifier 13 is compared by the comparator 14, and the output of the local DA converter 20 is changed in accordance with the output of the comparator 14, thereby changing the output of the comparator 14 to the amplitude of the output of the capacitance detector 3. A corresponding ΔΣ modulation signal is generated.

次に本実施例の容量式センサの特徴について説明する。本実施例の容量式センサでは容量検出器3の出力電圧の振幅のみを検出するので可変電源7の出力電圧の影響を受けないので検出素子2の両端電圧を可変電源7によって任意に変更できる。容量式角速度センサでは検出素子2を構成する静電容量の両端に電圧を印加することで静電気力を発生させて共振周波数の調整や振動漏れの調整などに利用される。つまり、本実施例の容量式センサは検出素子2の両端電圧を可変電源7によって任意に変更できるので、角速度センサに利用して検出素子2を構成する静電容量の両端に電圧を印加して静電気力を発生させて共振周波数の調整や振動漏れの調整などに利用できる。   Next, the features of the capacitive sensor of this embodiment will be described. In the capacitive sensor of this embodiment, only the amplitude of the output voltage of the capacitance detector 3 is detected, so that it is not affected by the output voltage of the variable power source 7, so that the voltage across the detection element 2 can be arbitrarily changed by the variable power source 7. In the capacitive angular velocity sensor, an electrostatic force is generated by applying a voltage to both ends of the capacitance constituting the detection element 2 to be used for adjustment of resonance frequency, adjustment of vibration leakage, and the like. That is, in the capacitive sensor of this embodiment, the voltage at both ends of the detection element 2 can be arbitrarily changed by the variable power source 7, so that a voltage is applied to both ends of the capacitance constituting the detection element 2 using an angular velocity sensor. It can be used to adjust resonance frequency and vibration leakage by generating electrostatic force.

また、容量式加速度センサでは検出素子2を構成する静電容量の両端に電圧を印加することで静電気力を発生させて診断に利用したり静電バネ効果を利用して感度の調整や周波数特性の調整などに利用したりする。つまり、本実施例の容量式センサは検出素子2の両端電圧を可変電源7によって任意に変更できるので、加速度センサに利用して検出素子2を構成する静電容量の両端に電圧を印加して静電気力を発生させて診断に利用でき、静電バネ効果を利用して感度の調整や周波数特性の調整などに利用できる。   Further, in the capacitive acceleration sensor, an electrostatic force is generated by applying a voltage to both ends of the capacitance constituting the detection element 2 and used for diagnosis, or sensitivity adjustment and frequency characteristics using the electrostatic spring effect. It can be used to adjust That is, in the capacitive sensor of this embodiment, the voltage at both ends of the detection element 2 can be arbitrarily changed by the variable power source 7, so that a voltage is applied to both ends of the capacitance constituting the detection element 2 using an acceleration sensor. Electrostatic force can be generated and used for diagnosis, and electrostatic spring effect can be used for sensitivity adjustment and frequency characteristic adjustment.

また、本実施例の容量式センサでは容量検出器3の出力電圧の振幅のみを検出するので演算増幅器6のオフセット電圧やf分の1ノイズの影響を受けないので高精度に検出素子2の静電容量を検出することができる。また、検出素子2とΔΣ変調器8の間に容量検出器3を挿入することで検出素子2の両端電位を低インピーダンスに保つことができ外来ノイズの影響を低減すると共に容量検出器3によって検出信号を増幅することで高感度化を図れ、また、検出素子2の対地間の寄生容量の影響を受けないので静電容量の検出信号である交流信号発生器1の周波数の高周波化を図れるので容量検出の高精度,高感度化を実現できる。   In addition, since the capacitance type sensor of this embodiment detects only the amplitude of the output voltage of the capacitance detector 3, it is not affected by the offset voltage of the operational amplifier 6 or 1 / f noise, so that the detection element 2 can be statically accurately detected. Capacitance can be detected. Further, by inserting the capacitance detector 3 between the detection element 2 and the ΔΣ modulator 8, the potential at both ends of the detection element 2 can be kept at a low impedance, thereby reducing the influence of external noise and detecting by the capacitance detector 3. By amplifying the signal, high sensitivity can be achieved, and since it is not affected by the parasitic capacitance between the detection element 2 and the ground, the frequency of the AC signal generator 1 that is a detection signal of the capacitance can be increased. Capacitance detection with high accuracy and high sensitivity can be realized.

また、容量検出器3とΔΣ変調器8の動作クロックを同一にすることで、容量検出器3の出力を直流化してからAD変換する必要が無いので回路の簡素化が図れると共に容量検出器3の動作クロックとΔΣ変調器8の動作クロックが干渉してノイズを発生することも無い。また、スイッチ4によってコンデンサ5をリセットすることで、容量検出器3は低周波を除去し、動作クロックの周波数成分のみを抽出する効果がある。   Further, by making the operation clocks of the capacitance detector 3 and the ΔΣ modulator 8 the same, it is not necessary to convert the output of the capacitance detector 3 into a direct current and then to perform AD conversion, so that the circuit can be simplified and the capacitance detector 3. The operation clock of the ΔΣ modulator 8 and the operation clock of the ΔΣ modulator 8 do not interfere with each other to generate noise. Further, by resetting the capacitor 5 with the switch 4, the capacitance detector 3 has an effect of removing the low frequency and extracting only the frequency component of the operation clock.

次に、本発明の第2の実施例である容量式センサを図3により説明する。なお、図3は第2の実施例の容量式センサの構成である。なお、第2の実施例の容量式センサは第1の実施例の容量式センサのスイッチ4を抵抗21に変更したものである。   Next, a capacitive sensor according to a second embodiment of the present invention will be described with reference to FIG. FIG. 3 shows the configuration of the capacitive sensor of the second embodiment. The capacitive sensor of the second embodiment is obtained by changing the switch 4 of the capacitive sensor of the first embodiment to a resistor 21.

本実施例の容量式センサではスイッチ4を抵抗21に変更することでスイッチ4のオンオフ動作で生じるスイッチングノイズの低減を図ると共に容量検出器3で低周波を除去し、動作クロックの周波数成分のみを抽出する様にした。   In the capacitive sensor of this embodiment, the switch 4 is changed to the resistor 21 to reduce the switching noise generated by the on / off operation of the switch 4 and the low frequency is removed by the capacitance detector 3 so that only the frequency component of the operation clock is obtained. I tried to extract.

次に、本発明の第3の実施例である容量式センサを図4により説明する。なお、図4は第3の実施例の容量式センサの構成である。なお、第3の実施例の容量式センサは第1の実施例の容量式センサに増幅回路22,27を付加したものである。   Next, a capacitive sensor according to a third embodiment of the present invention will be described with reference to FIG. FIG. 4 shows the configuration of the capacitive sensor of the third embodiment. The capacitive sensor of the third embodiment is obtained by adding amplifier circuits 22 and 27 to the capacitive sensor of the first embodiment.

本実施例の容量式センサの増幅回路22は入力コンデンサ25,帰還コンデンサ24,クロック信号P2で動作するスイッチ23,演算増幅器26から構成され、容量検出器3の出力を増幅する。また、増幅回路27は入力コンデンサ30,帰還コンデンサ29,クロック信号P1で動作するスイッチ28,演算増幅器31から構成され、増幅回路22の出力を増幅する。   The amplifying circuit 22 of the capacitive sensor according to the present embodiment is composed of an input capacitor 25, a feedback capacitor 24, a switch 23 operated by a clock signal P2, and an operational amplifier 26, and amplifies the output of the capacitance detector 3. The amplifier circuit 27 includes an input capacitor 30, a feedback capacitor 29, a switch 28 that operates with the clock signal P 1, and an operational amplifier 31, and amplifies the output of the amplifier circuit 22.

本実施例の容量式センサでは増幅回路22,27を設けることで、容量検出器3の出力である矩形波をより大きく増幅することで高感度化を実現した。また、増幅回路22,27は交流成分のみ増幅するように演算増幅器26,31の負帰還回路に入力コンデンサ25,30と帰還コンデンサ24,29を用いた。また、スイッチ23,28を設けて低周波成分を除去した。また、スイッチ23,28の動作周波数を容量検出器3及びΔΣ変調器8と同一周波数にすることで、容量検出器3の出力を交流信号のまま増幅すると共にΔΣ変調器8との接続を容易にし、且つ、演算増幅器26,31のオフセット電圧の影響を除去した。   In the capacitive sensor of the present embodiment, by providing the amplification circuits 22 and 27, the rectangular wave that is the output of the capacitance detector 3 is further amplified to achieve high sensitivity. The amplifier circuits 22 and 27 use input capacitors 25 and 30 and feedback capacitors 24 and 29 in the negative feedback circuit of the operational amplifiers 26 and 31 so that only the AC component is amplified. Further, switches 23 and 28 are provided to remove low frequency components. Further, by setting the operating frequency of the switches 23 and 28 to the same frequency as that of the capacitance detector 3 and the ΔΣ modulator 8, the output of the capacitance detector 3 is amplified as an AC signal and is easily connected to the ΔΣ modulator 8. In addition, the influence of the offset voltage of the operational amplifiers 26 and 31 is eliminated.

次に、本発明の第4の実施例である容量式センサを図5〜図7により説明する。なお、図5は第4の実施例の容量式センサの構成、図6は第4の実施例の容量式センサの信号処理回路のタイミングチャート、図7は第4の実施例の容量式センサのΔΣ変調器51の構成である。   Next, a capacitive sensor according to a fourth embodiment of the present invention will be described with reference to FIGS. 5 shows the configuration of the capacitive sensor according to the fourth embodiment, FIG. 6 shows a timing chart of the signal processing circuit of the capacitive sensor according to the fourth embodiment, and FIG. 7 shows the capacitive sensor according to the fourth embodiment. This is a configuration of the ΔΣ modulator 51.

本実施例の容量式センサの検出素子35は所定の質量を持ち所定の振動周波数fdで振動する振動子38と、振動子38に対向して配置され振動子38を加振する駆動電極36,39と、振動子38の変位に応じて静電容量の変化する検出電極37,40により構成される。また、信号処理部は振動子38を静電気力で加振するために駆動電極36,39に電圧を印加する駆動信号発生器33,42と、駆動信号発生器33,42の高周波成分を除去するLPF(ローパスフィルタ)34,41と、振動子38と検出電極37の間の静電容量と振動子38と検出電極40の間の静電容量の差分を検出して振動子38の変位を検出する容量検出器43と、容量検出器43の出力をΔΣ変調するΔΣ変調回路51により構成される。容量検出器43は演算増幅器46,48と、帰還コンデンサ45,49と、図2で示したクロック信号P1で動作するスイッチ44,50と、基準電圧発生器47とにより構成される。ΔΣ変調器51は、容量検出器43の出力に応じて充放電するコンデンサ52,76,81,105と、図2で示したクロック信号P1で動作しコンデンサ52,76,81,105を放電させるスイッチ54,75,83,104と、図2で示したクロック信号P2で動作しコンデンサ52,76,81,105を充電させるスイッチ53,77,82,106と、ΔΣ変調器を構成するスイッチドキャパシタ回路を構成するコンデンサ56,61,68,73,76,85,90,97,102、図2で示したクロック信号P1で動作するスイッチ58,59,63,64,65,66,70,71,87,88,92,93,94,95,99,100、図2で示したクロック信号P2で動作するスイッチ55,57,60,62,67,69,72,74,84,86,89,91,96,98,101,103と、積分器を構成する差動増幅器79,108、コンデンサ78,80,107,109と、比較器110とDフリップフロップ112と、局部DA変換器111,113により構成される。   The detection element 35 of the capacitive sensor of the present embodiment has a predetermined mass and a vibrator 38 that vibrates at a predetermined vibration frequency fd, and a drive electrode 36 that is disposed facing the vibrator 38 and vibrates the vibrator 38. 39, and detection electrodes 37 and 40 whose capacitance changes according to the displacement of the vibrator 38. Further, the signal processing unit removes the high frequency components of the drive signal generators 33 and 42 for applying a voltage to the drive electrodes 36 and 39 and the drive signal generators 33 and 42 for exciting the vibrator 38 with electrostatic force. The displacement of the transducer 38 is detected by detecting the difference between the capacitance between the LPF (low-pass filter) 34, 41, the transducer 38 and the detection electrode 37, and the capacitance between the transducer 38 and the detection electrode 40. And a ΔΣ modulation circuit 51 that ΔΣ modulates the output of the capacitance detector 43. The capacitance detector 43 includes operational amplifiers 46 and 48, feedback capacitors 45 and 49, switches 44 and 50 that operate with the clock signal P <b> 1 shown in FIG. 2, and a reference voltage generator 47. The ΔΣ modulator 51 operates with the capacitors 52, 76, 81, 105 that charge and discharge according to the output of the capacitance detector 43 and the clock signal P 1 shown in FIG. 2, and discharges the capacitors 52, 76, 81, 105. Switches 54, 75, 83, and 104, switches 53, 77, 82, and 106 that operate with the clock signal P2 shown in FIG. 2 to charge the capacitors 52, 76, 81, and 105, and a switch that constitutes the ΔΣ modulator. Capacitors 56, 61, 68, 73, 76, 85, 90, 97, 102 constituting a capacitor circuit, switches 58, 59, 63, 64, 65, 66, 70 operating with the clock signal P1 shown in FIG. 71, 87, 88, 92, 93, 94, 95, 99, 100, switches 55, 57, 60, 62, 67 operated by the clock signal P2 shown in FIG. 69, 72, 74, 84, 86, 89, 91, 96, 98, 101, 103, differential amplifiers 79, 108 constituting capacitors, capacitors 78, 80, 107, 109, comparators 110 and D A flip-flop 112 and local DA converters 111 and 113 are included.

次に、本実施例の容量式センサの動作を図6により説明する。本容量式センサでは駆動信号発生器33,42により振動子38を振動子38の共振周波数で駆動して振動子38を振動させる。また、振動子38の変位検出は振動子38に交流信号発生器32の出力信号を印加して、振動子38から検出電極37を介して容量検出器43へ移動する電荷と振動子38から検出電極40を介して容量検出器43へ移動する電荷との差分を検出することで図6に示す出力信号を得る。ここで、容量検出器43の出力に重畳される駆動信号の漏れ込みを低減するためにLPF34,41を設けて駆動信号発生器33,42の出力信号から高周波を除去して、容量検出の精度を向上させた。また、容量検出のための信号である交流信号発生器32の周波数を駆動信号発生器33,42の周波数の整数倍にすることで回路を簡素化すると共に漏れ込み量が一定になるようにして、後処理で除去可能にした。更には、容量検出のための信号である交流信号発生器32の周波数を駆動信号発生器33,42の周波数の奇数倍にして、ΔΣ変調器51の出力を駆動信号発生器33,42の周波数で同期検波することで振動子38の変位を精度良く検出すると共に、漏れ込み信号を同期検波で除去することも可能である。また、ΔΣ変調器51は容量検出器43の振幅のみを検出するようにコンデンサ52,76,81,105は図2で示した期間Iで容量検出器53の出力を充電し、図2で示した期間IIでは容量検出器53の出力を充電すると共にスイッチ53,77,82,106をオン状態にすることで容量検出器53の出力の振幅のみ検出するようにした。また、ΔΣ変調器51の差動増幅器108の出力をコンデンサ56,スイッチ55,57,58,59で構成されるスイッチドキャパシタ回路とコンデンサ73,スイッチ70,71,72で構成されるスイッチドキャパシタ回路で差動増幅器78で構成される積分器にフィードバックさせることで、ΔΣ変調器51の周波数特性に振動子38の共振周波数でSN比が向上するようにバンドパス特性を持たせた。このことにより振動子38の変位信号を高SN比で検出できるようにした。   Next, the operation of the capacitive sensor of this embodiment will be described with reference to FIG. In this capacitive sensor, the vibrator 38 is vibrated by driving the vibrator 38 at the resonance frequency of the vibrator 38 by the drive signal generators 33 and 42. The displacement of the vibrator 38 is detected by applying the output signal of the AC signal generator 32 to the vibrator 38 and detecting from the vibrator 38 the charge moving from the vibrator 38 to the capacitance detector 43 via the detection electrode 37. The output signal shown in FIG. 6 is obtained by detecting the difference from the charge moving to the capacitance detector 43 via the electrode 40. Here, in order to reduce the leakage of the drive signal superimposed on the output of the capacitance detector 43, LPFs 34 and 41 are provided to remove high frequencies from the output signals of the drive signal generators 33 and 42, and the accuracy of capacitance detection. Improved. Further, by making the frequency of the AC signal generator 32, which is a signal for detecting the capacitance, an integer multiple of the frequency of the drive signal generators 33 and 42, the circuit is simplified and the leakage amount is made constant. It can be removed by post-processing. Further, the frequency of the AC signal generator 32, which is a signal for detecting the capacitance, is set to an odd multiple of the frequency of the drive signal generators 33 and 42, and the output of the ΔΣ modulator 51 is set to the frequency of the drive signal generators 33 and 42. Thus, it is possible to detect the displacement of the vibrator 38 with high accuracy and to remove the leakage signal by synchronous detection. Further, the capacitors 52, 76, 81, and 105 charge the output of the capacitance detector 53 in the period I shown in FIG. 2 so that the ΔΣ modulator 51 detects only the amplitude of the capacitance detector 43, and it is shown in FIG. During period II, the output of the capacitance detector 53 is charged and the switches 53, 77, 82, and 106 are turned on to detect only the amplitude of the output of the capacitance detector 53. Further, the output of the differential amplifier 108 of the ΔΣ modulator 51 is a switched capacitor circuit composed of a capacitor 56 and switches 55, 57, 58 and 59, and a switched capacitor composed of a capacitor 73 and switches 70, 71 and 72. The circuit is fed back to an integrator composed of a differential amplifier 78 so that the frequency characteristic of the ΔΣ modulator 51 has a bandpass characteristic so that the SN ratio is improved at the resonance frequency of the vibrator 38. As a result, the displacement signal of the vibrator 38 can be detected with a high S / N ratio.

次に、本発明の第5の実施例である容量式角速度センサを図8により説明する。なお、図8は第5の実施例の容量式角速度センサの構成である。   Next, a capacitive angular velocity sensor according to a fifth embodiment of the present invention will be described with reference to FIG. FIG. 8 shows the configuration of the capacitive angular velocity sensor of the fifth embodiment.

本実施例の容量式角速度センサの検出素子114は所定の質量を持ち所定の振動周波数fdで振動する振動子117と、振動子117に対向して配置され振動子117に働くコリオリ力による変位を検出する固定電極116,119と、振動子117に働くコリオリ力を打ち消す様に振動子117に静電気力を働かせる固定電極115,118により構成される。また、信号処理部は振動子117と固定電極116の間の静電容量と振動子117と固定電極119の間の静電容量の差分を検出して振動子117に働くコリオリ力による変位を検出する容量検出器120と、容量検出器120の出力をΔΣ変調するΔΣ変調器121と、ΔΣ変調器121の出力を振動子117の変位信号と同位相の信号で乗算する乗算器122と、ΔΣ変調器121の出力を振動子117の変位信号と90度位相遅れの信号で乗算する乗算器125と、乗算器122の出力を積分する積分器123と、乗算器125の出力を積分する積分器126と、積分器123の出力を振動子117の変位信号と90度位相遅れの信号で乗算する乗算器124と、積分器126の出力を振動子117の変位信号と同位相の信号で乗算する乗算器127と、乗算器124と乗算器127の出力を加算する加算器128と、加算器128の信号に−1を乗算する乗算器129と、加算器128の出力にバイアス電圧Vbを加算する加算器130と、乗算器129の出力にバイアス電圧Vbを加算する加算器131とにより構成される。   The detection element 114 of the capacitive angular velocity sensor of the present embodiment has a predetermined mass and a vibrator 117 that vibrates at a predetermined vibration frequency fd, and a displacement caused by a Coriolis force that is disposed opposite to the vibrator 117 and acts on the vibrator 117. Fixed electrodes 116 and 119 to be detected, and fixed electrodes 115 and 118 for applying an electrostatic force to the vibrator 117 so as to cancel the Coriolis force acting on the vibrator 117. In addition, the signal processing unit detects the displacement due to the Coriolis force acting on the vibrator 117 by detecting the difference between the electrostatic capacity between the vibrator 117 and the fixed electrode 116 and the electrostatic capacity between the vibrator 117 and the fixed electrode 119. Capacitance detector 120, ΔΣ modulator 121 that ΔΣ modulates the output of capacitance detector 120, multiplier 122 that multiplies the output of ΔΣ modulator 121 by a signal having the same phase as the displacement signal of vibrator 117, and ΔΣ Multiplier 125 that multiplies the output of modulator 121 by the displacement signal of vibrator 117 and a signal that is delayed by 90 degrees, integrator 123 that integrates the output of multiplier 122, and integrator that integrates the output of multiplier 125. 126, the multiplier 124 that multiplies the output of the integrator 123 by the displacement signal of the vibrator 117 and the signal that is 90 degrees phase lag, and the output of the integrator 126 is multiplied by a signal that has the same phase as the displacement signal of the vibrator 117. Multiplication A multiplier 127, an adder 128 for adding the outputs of the multiplier 124 and the multiplier 127, a multiplier 129 for multiplying the signal of the adder 128 by -1, and an addition for adding the bias voltage Vb to the output of the adder 128. And an adder 131 for adding the bias voltage Vb to the output of the multiplier 129.

本実施例の容量式角速度センサにおいては容量検出器120とΔΣ変調器121に第4の実施例で示した容量検出器とΔΣ変調器を使用した。第4の実施例で示した容量検出器を使用することで次の利点がある。まず、固定電極116,119の電圧を任意に変更できるので振動子117の共振周波数を変更できる。また、振動子117の微小変位を高精度に検出できる。また、ΔΣ変調器121に振動子117の振動周波数のSN比が良くなる様にバンドパス特性を持たすことができるので、高精度に振動子117の振動周波数の変位を高SN比で検出することができる。   In the capacitance type angular velocity sensor of this embodiment, the capacitance detector and the ΔΣ modulator shown in the fourth embodiment are used for the capacitance detector 120 and the ΔΣ modulator 121. Use of the capacitance detector shown in the fourth embodiment has the following advantages. First, since the voltages of the fixed electrodes 116 and 119 can be arbitrarily changed, the resonance frequency of the vibrator 117 can be changed. Further, a minute displacement of the vibrator 117 can be detected with high accuracy. Further, since the ΔΣ modulator 121 can have a band pass characteristic so that the SN ratio of the vibration frequency of the vibrator 117 is improved, the displacement of the vibration frequency of the vibrator 117 can be detected with a high SN ratio with high accuracy. Can do.

次に、本発明の第6の実施例である容量式加速度センサを図9により説明する。なお、図9は第6の実施例の容量式加速度センサの構成である。   Next, a capacitive acceleration sensor according to a sixth embodiment of the present invention will be described with reference to FIG. FIG. 9 shows the configuration of the capacitive acceleration sensor of the sixth embodiment.

本実施例の容量式加速度センサの検出素子132は所定の質量を持ち外部から働く加速度で変位する可動電極134と、可動電極134に対向して配置され可動電極134に働く加速度による変位を検出する固定電極133とにより構成される。また、信号処理部は第1の実施例で示した容量検出器3とΔΣ変調器8を使用した。第1の実施例で示した容量検出器を使用することで次の利点がある。まず、固定電極133の電圧を任意に変更できるので固定電極133と可動電極134の間に静電気力を発生させて可動電極134を強制的に変位させて可動電極134の固着を診断することができる。   The detection element 132 of the capacitive acceleration sensor of this embodiment has a predetermined mass and a movable electrode 134 that is displaced by an externally acting acceleration, and a displacement due to the acceleration acting on the movable electrode 134 that is disposed opposite to the movable electrode 134. And a fixed electrode 133. The signal processing unit uses the capacitance detector 3 and the ΔΣ modulator 8 shown in the first embodiment. Use of the capacitance detector shown in the first embodiment has the following advantages. First, since the voltage of the fixed electrode 133 can be arbitrarily changed, an electrostatic force is generated between the fixed electrode 133 and the movable electrode 134 to forcibly displace the movable electrode 134 to diagnose the fixation of the movable electrode 134. .

1 交流信号発生器
2 検出素子
3 容量検出器
4,10,11,15,16,18,19,23 スイッチ
5,12 コンデンサ
6,13 演算増幅器
7 可変電源
8 ΔΣ変調器
9 検出コンデンサ
14 比較器
17 基準コンデンサ
20 局部DA変換器
21 抵抗
22 増幅回路
24 帰還コンデンサ
DESCRIPTION OF SYMBOLS 1 AC signal generator 2 Detection element 3 Capacitance detectors 4, 10, 11, 15, 16, 18, 19, 23 Switch 5, 12 Capacitor 6, 13 Operational amplifier 7 Variable power supply 8 ΔΣ modulator 9 Detection capacitor 14 Comparator 17 Reference Capacitor 20 Local DA Converter 21 Resistor 22 Amplifier 24 Feedback Capacitor

Claims (13)

物理量の変化に応じて静電容量が変化する物理量検出素子と、
前記物理量検出素子に交流信号を印加する交流信号発生手段と、
前記交流信号発生手段により前記物理量検出素子の静電容量を充放電することで生じる充放電電荷に応じた交流電圧を発生させる容量検出器と、
前記容量検出器の発生させる交流電圧をΔΣ変調するΔΣ変調器とを有する容量式センサにおいて、
前記ΔΣ変調器が前記容量検出器の発生させる交流電圧の振幅に応じたΔΣ変調信号列を発生させることを特徴とする容量式センサ。
A physical quantity detecting element whose capacitance changes in accordance with a change in physical quantity;
AC signal generating means for applying an AC signal to the physical quantity detection element;
A capacitance detector for generating an AC voltage corresponding to charge / discharge charges generated by charging / discharging the capacitance of the physical quantity detection element by the AC signal generating means;
In a capacitive sensor having a ΔΣ modulator that ΔΣ modulates the AC voltage generated by the capacitance detector,
The capacitive sensor characterized in that the ΔΣ modulator generates a ΔΣ modulation signal sequence corresponding to the amplitude of the AC voltage generated by the capacitance detector.
物理量の変化に応じて静電容量が変化する物理量検出素子と、
前記物理量検出素子に交流信号を印加する交流信号発生手段と、
前記交流信号発生手段により前記物理量検出素子の静電容量を充放電することで生じる充放電電荷に応じた交流電圧を発生させる容量検出器と、
前記容量検出器の発生させる交流電圧をΔΣ変調するΔΣ変調器とを有する容量式センサにおいて、
前記ΔΣ変調器が前記容量検出器の発生させる交流電圧で充放電される検出コンデンサと、前記検出コンデンサの充電あるいは放電電荷を積分する積分器と、前記積分器の出力電圧を比較する比較器と、前記比較器の値に応じて離散的な電圧を発生する局部DA変換器と、前記局部DA変換器の出力電圧に応じて充放電する基準コンデンサと、前記基準コンデンサの充電あるいは放電電荷を前記積分器に印加する手段とを有することを特徴とする容量式センサ。
A physical quantity detecting element whose capacitance changes in accordance with a change in physical quantity;
AC signal generating means for applying an AC signal to the physical quantity detection element;
A capacitance detector for generating an AC voltage corresponding to charge / discharge charges generated by charging / discharging the capacitance of the physical quantity detection element by the AC signal generating means;
In a capacitive sensor having a ΔΣ modulator that ΔΣ modulates the AC voltage generated by the capacitance detector,
A detection capacitor that is charged and discharged by the AC voltage generated by the capacitance detector by the ΔΣ modulator, an integrator that integrates the charge or discharge charge of the detection capacitor, and a comparator that compares the output voltage of the integrator; A local DA converter that generates a discrete voltage according to the value of the comparator, a reference capacitor that charges and discharges according to an output voltage of the local DA converter, and a charge or discharge charge of the reference capacitor And a means for applying to the integrator.
請求項1または2のいずれかにおいて、
前記ΔΣ変調器の動作周波数と前記交流信号発生手段の発生する交流信号の周波数が等しいことを特徴とする容量式センサ。
In either claim 1 or 2,
The capacitive sensor characterized in that the operating frequency of the ΔΣ modulator is equal to the frequency of the AC signal generated by the AC signal generating means.
請求項3に記載の容量式センサにおいて、
前記容量検出器が低周波を遮断することを特徴とする容量式センサ。
The capacitive sensor according to claim 3,
A capacitive sensor, wherein the capacitive detector blocks low frequencies.
請求項4に記載の容量式センサにおいて、
前記容量検出器が前記物理量検出素子に印加する直流電圧を変化させる手段を有することを特徴とする容量式センサ。
The capacitive sensor according to claim 4,
A capacitive sensor, characterized in that the capacitance detector has means for changing a DC voltage applied to the physical quantity detection element.
請求項5に記載の容量式センサにおいて、
前記容量検出器の帰還回路にコンデンサを有する増幅器で構成されることを特徴とする容量式センサ。
The capacitive sensor according to claim 5, wherein
A capacitive sensor comprising an amplifier having a capacitor in a feedback circuit of the capacitance detector.
請求項6に記載の容量式センサにおいて、
前記容量検出器の帰還回路に前記コンデンサを放電するスイッチを有することを特徴とする容量式センサ。
The capacitive sensor according to claim 6,
A capacitive sensor comprising a switch for discharging the capacitor in a feedback circuit of the capacitance detector.
請求項7に記載の容量式センサにおいて、
前記容量検出器の出力を増幅する増幅手段を有し、前記増幅手段の帰還回路にコンデンサと前記コンデンサを放電するスイッチを有することを特徴とする容量式センサ。
The capacitive sensor according to claim 7,
A capacitive sensor comprising amplification means for amplifying the output of the capacitance detector, and having a capacitor and a switch for discharging the capacitor in a feedback circuit of the amplification means.
請求項8において、
前記容量式センサが振動子を有し、
前記ΔΣ変調器が前記振動子の振動周波数に対してバンドパス特性を有することを特徴とする容量式センサ。
In claim 8,
The capacitive sensor has a vibrator;
The capacitive sensor, wherein the ΔΣ modulator has a bandpass characteristic with respect to a vibration frequency of the vibrator.
請求項9に記載の容量式センサにおいて、
前記容量検出器の発生させる交流電圧の周波数が前記振動子の振動周波数の整数倍であることを特徴とする容量式センサ。
The capacitive sensor according to claim 9,
The capacitive sensor, wherein the frequency of the alternating voltage generated by the capacitance detector is an integral multiple of the vibration frequency of the vibrator.
請求項10に記載の容量式センサにおいて、
前記容量検出器の発生させる交流電圧の周波数が前記振動子の振動周波数の奇数倍であることを特徴とする容量式センサ。
The capacitive sensor according to claim 10,
A capacitive sensor, wherein the frequency of the alternating voltage generated by the capacitance detector is an odd multiple of the vibration frequency of the vibrator.
請求項11に記載の容量式センサにおいて、
前記振動子を加振する加振信号を発生させる加振信号発生手段と、前記加振信号の高周波成分を除去する手段とを有することを特徴とする容量式センサ。
The capacitive sensor according to claim 11, wherein
A capacitive sensor comprising: an excitation signal generating means for generating an excitation signal for exciting the vibrator; and means for removing a high-frequency component of the excitation signal.
振動子と、
角速度による前記振動子の変位を静電容量として検出する角速度検出素子と、
前記物理量検出素子に交流信号を印加する交流信号発生手段と、
前記交流信号発生手段により前記物理量検出素子の静電容量を充放電することで生じる充放電電荷に応じた交流電圧を発生させる容量検出器と、
前記容量検出器の発生させる交流電圧をΔΣ変調するΔΣ変調器とを有する角速度センサにおいて、
前記ΔΣ変調器が前記容量検出器の発生させる交流電圧の振幅に応じたΔΣ変調信号列を発生させることを特徴とする角速度センサ。
A vibrator,
An angular velocity detecting element for detecting displacement of the vibrator due to the angular velocity as a capacitance;
AC signal generating means for applying an AC signal to the physical quantity detection element;
A capacitance detector for generating an AC voltage corresponding to charge / discharge charges generated by charging / discharging the capacitance of the physical quantity detection element by the AC signal generating means;
In the angular velocity sensor having a ΔΣ modulator that ΔΣ modulates the AC voltage generated by the capacitance detector,
The angular velocity sensor, wherein the ΔΣ modulator generates a ΔΣ modulation signal sequence corresponding to the amplitude of the AC voltage generated by the capacitance detector.
JP2009045025A 2009-02-27 2009-02-27 Capacitive sensor and angular velocity sensor Expired - Fee Related JP5081852B2 (en)

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