JP2006145413A - Capacitance-type proximity sensor - Google Patents

Capacitance-type proximity sensor Download PDF

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JP2006145413A
JP2006145413A JP2004337001A JP2004337001A JP2006145413A JP 2006145413 A JP2006145413 A JP 2006145413A JP 2004337001 A JP2004337001 A JP 2004337001A JP 2004337001 A JP2004337001 A JP 2004337001A JP 2006145413 A JP2006145413 A JP 2006145413A
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capacitance
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JP4319970B2 (en
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Yasushi Nakamura
靖 中村
Nobumasa Misaki
信正 見崎
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Fujikura Ltd
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Abstract

<P>PROBLEM TO BE SOLVED: To properly compensate for environmental characteristics, such as temperature characteristics and humidity characteristics. <P>SOLUTION: The capacitance-type proximity sensor comprises a detection electrode 11 placed in a detection area D; a reference electrode 21 placed outside the detection area D and formed similarly as the detection electrode 11; first detection circuits 32, 33 for outputting a first detection signal on the basis of the capacitance between the detection electrode 11 and ground; second detection circuits 36, 37 for outputting a second detection signal, on the basis of the capacitance between the reference electrode 21 and ground; and a subtraction circuit 34 for outputting a compensated detection signal, by subtracting the second detection signal from the first detection signal. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、物体の近接を静電容量の変化で検出する静電容量式近接センサに関し、特に温度、湿度等の環境特性の補正機能を有する静電容量式近接センサに関する。   The present invention relates to a capacitive proximity sensor that detects proximity of an object by a change in capacitance, and more particularly to a capacitive proximity sensor having a function of correcting environmental characteristics such as temperature and humidity.

従来より、被検出物体の近接による検知電極と接地電極との間の静電容量変化を発振回路の発振周波数の変化に変換し、この発振回路の発振周波数を測定し、直線化すると共に、比較回路で所定の閾値と比較して物体の近接の有無を判別するようにした静電容量式近接センサが知られている（特許文献１）。この静電容量式センサでは、温度変化によって発振回路の電圧フォロワ回路の利得が変化し、これによって発振回路の発振周波数が変動する。そこで、上記静電容量式センサでは、温度変化による発振周波数の変動を防止するため、発振回路を構成する分圧回路の抵抗に温度特性を有するサーミスタを使用して発振周波数の変動を打ち消すようにしている。
特開平１４−１４１７４号公報（段落００８２〜００８９，図８，図９） Conventionally, the capacitance change between the sensing electrode and the ground electrode due to the proximity of the object to be detected is converted into a change in the oscillation frequency of the oscillation circuit. The oscillation frequency of this oscillation circuit is measured, linearized, and compared. A capacitive proximity sensor is known in which a circuit is used to determine whether or not an object is approaching compared to a predetermined threshold (Patent Document 1). In this capacitance type sensor, the gain of the voltage follower circuit of the oscillation circuit changes due to a temperature change, and thereby the oscillation frequency of the oscillation circuit varies. Therefore, in the above capacitive sensor, in order to prevent fluctuations in the oscillation frequency due to temperature changes, a thermistor having temperature characteristics is used as the resistance of the voltage dividing circuit constituting the oscillation circuit to cancel the fluctuations in the oscillation frequency. ing.
Japanese Patent Laid-Open No. 14-14174 (paragraphs 0082 to 0089, FIGS. 8 and 9)

しかし、温度特性や湿度特性といった環境特性は、電極の形状、個々の電子部品によってそれぞれ異なるため、上述したサーミスタを使用した従来の静電容量式近接センサでは、パラメータの設定が難しく、温度変動を良好に打ち消すことが不可能である。   However, environmental characteristics such as temperature characteristics and humidity characteristics vary depending on the shape of the electrode and the individual electronic components. Therefore, it is difficult to set parameters in the conventional capacitive proximity sensor using the thermistor described above, and temperature fluctuations are difficult. It is impossible to negate well.

本発明は、このような点に鑑みてなされたもので、温度特性及び湿度特性などの環境特性に対して良好な補償を行うことができる静電容量式近接センサを提供することを目的とする。   The present invention has been made in view of these points, and an object of the present invention is to provide a capacitive proximity sensor that can satisfactorily compensate for environmental characteristics such as temperature characteristics and humidity characteristics. .

本発明に係る静電容量式近接センサは、検知エリア内に配置された検知電極と、前記検知エリア外に配置され前記検知電極と同様に形成された参照電極と、前記検知電極と接地との間の静電容量に基づく第１の検知信号を出力する第１の検知回路と、前記参照電極と接地との間の静電容量に基づく第２の検知信号を出力する第２の検知回路と、前記第１の検知回路の出力から前記第２の検知回路の出力を減算して補償済み検知信号を出力する減算回路とを備えたことを特徴とする。   The capacitive proximity sensor according to the present invention includes a detection electrode arranged in a detection area, a reference electrode arranged outside the detection area and formed in the same manner as the detection electrode, and the detection electrode and ground. A first detection circuit that outputs a first detection signal based on the capacitance between the second detection circuit and a second detection circuit that outputs a second detection signal based on the capacitance between the reference electrode and the ground; And a subtracting circuit for subtracting the output of the second detection circuit from the output of the first detection circuit and outputting a compensated detection signal.

本発明に係る静電容量式近接センサは、また、検知エリア内に配置された検知電極と、前記検知エリア外に配置され前記検知電極と同様に形成された参照電極と、前記検知電極と前記参照電極とに選択的に接続されるスイッチ回路と、このスイッチ回路を介して前記検知電極と前記参照電極とに選択的に接続され、前記検知電極と接続されているときには、前記検知電極と接地との間の静電容量に基づく第１の検知信号を出力し、前記参照電極と接続されているときには、前記参照電極と接地との間の静電容量に基づく第２の検知信号を出力する検知回路と、 前記第１の検知信号から前記第２の検知信号を減算して補償済み検知信号を出力する演算手段とを備えたことを特徴とする。   The capacitive proximity sensor according to the present invention also includes a detection electrode arranged in a detection area, a reference electrode arranged outside the detection area and formed in the same manner as the detection electrode, the detection electrode, A switch circuit selectively connected to a reference electrode, and the detection electrode and ground when selectively connected to the detection electrode and the reference electrode via the switch circuit and connected to the detection electrode And outputs a second detection signal based on the capacitance between the reference electrode and the ground when connected to the reference electrode. It is characterized by comprising: a detection circuit; and calculation means for subtracting the second detection signal from the first detection signal to output a compensated detection signal.

検知エリア内に配置された検知電極によって検出される第１の検知信号には、被検出物の近接による静電容量変化分に加えて、環境変動による静電容量変化分が含まれている。これに対し、検知エリア外に配置された参照電極によって検出される第２の検知信号は、環境変動による静電容量変化分のみを含む信号である。検知電極と参照電極が同様に形成され、第１及び第２の検知回路が同様の電子部品から構成されていれば、又は同一の検知回路を時分割で使用すれば、検知回路による環境変動分は、殆ど同じ値になる。   The first detection signal detected by the detection electrodes arranged in the detection area includes a capacitance change due to environmental fluctuations in addition to a capacitance change due to the proximity of the detection object. On the other hand, the second detection signal detected by the reference electrode arranged outside the detection area is a signal including only the change in capacitance due to environmental fluctuation. If the detection electrode and the reference electrode are formed in the same manner and the first and second detection circuits are composed of the same electronic components, or if the same detection circuit is used in a time-sharing manner, the environmental variation caused by the detection circuit can be reduced. Are almost the same value.

本発明によれば、検知エリア内に配置された検知電極によって検出された第１の検知信号から、検知エリア外に配置された参照電極によって検出された第２の検知信号を減算することにより、補償済み検知信号を得るようにしているので、電極及び回路構成部品に生じる環境特性による変動分を良好に補償することができ、検出感度を向上させることができる。   According to the present invention, by subtracting the second detection signal detected by the reference electrode arranged outside the detection area from the first detection signal detected by the detection electrode arranged in the detection area, Since the compensated detection signal is obtained, it is possible to satisfactorily compensate for variations due to environmental characteristics occurring in the electrodes and circuit components, and to improve detection sensitivity.

以下、添付の図面を参照して、本発明の実施の形態を説明する。   Embodiments of the present invention will be described below with reference to the accompanying drawings.

図１は、本発明の第１の実施形態に係る静電容量式近接センサの概略構成を示す図である。   FIG. 1 is a diagram showing a schematic configuration of a capacitive proximity sensor according to the first embodiment of the present invention.

この近接センサは、一対のセンサ部１０，２０と、主回路部３０とを備えて構成されている。   The proximity sensor includes a pair of sensor units 10 and 20 and a main circuit unit 30.

センサ部１０は、被検出物を検知可能な検知エリアＤ内に配置されている。このセンサ部１０は、フレキシブルプリント回路（ＦＰＣ）、リジットプリント回路（ＲＰＣ）等により構成されたもので、ポリエチレンテレフタレート（ＰＥＴ）、ポリエチレンナフタレート（ＰＥＮ）、又はエポキシ樹脂などの絶縁体からなる絶縁基板と、この絶縁基板上にパターン形成された銅、銅合金又はアルミニウムなどからなる電極、すなわち検知電極１１、ガード電極１２及び接地電極１３とにより構成されている。接地電極１３は、正方形又は長方形で、検知電極１１は、この接地電極１３の両辺及び他の一辺を取り囲むコの字形に形成されている。また、ガード電極１２は、検知電極１１と接地電極１３との間に両者に対して絶縁状態でコの字状に配置されている。   The sensor unit 10 is disposed in a detection area D that can detect an object to be detected. This sensor unit 10 is composed of a flexible printed circuit (FPC), a rigid printed circuit (RPC), etc., and is an insulating material made of an insulator such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), or epoxy resin. A substrate and electrodes made of copper, copper alloy, or aluminum patterned on the insulating substrate, that is, a detection electrode 11, a guard electrode 12, and a ground electrode 13 are formed. The ground electrode 13 is square or rectangular, and the detection electrode 11 is formed in a U shape surrounding both sides of the ground electrode 13 and the other side. Further, the guard electrode 12 is disposed in a U shape between the detection electrode 11 and the ground electrode 13 in an insulated state with respect to both.

一方、センサ部２０は、被検出物の影響を受けないように、検知エリアＤの外に配置されている。センサ部２０もセンサ部１０と同様の絶縁基板と電極とからなるが、電極は、参照電極２１，ガード電極２２及び接地電極２３からなる。参照電極２１は、検知電極１３と同じ形状及び大きさに設定され、ガード電極２２及び接地電極２３は、それぞれガード電極１２及び接地電極１３と同様の形状及び大きさに設定されている。   On the other hand, the sensor unit 20 is disposed outside the detection area D so as not to be affected by the detected object. The sensor unit 20 also includes an insulating substrate and electrodes similar to the sensor unit 10, but the electrodes include a reference electrode 21, a guard electrode 22, and a ground electrode 23. The reference electrode 21 is set to the same shape and size as the detection electrode 13, and the guard electrode 22 and the ground electrode 23 are set to the same shape and size as the guard electrode 12 and the ground electrode 13, respectively.

なお、これらセンサ部１０，２０は、例えばメンブレンスイッチの一部として構成されたり、メンブレンスイッチの一部として接触センサと併用されるものでも良い。   In addition, these sensor parts 10 and 20 may be comprised, for example as a part of membrane switch, or may be used together with a contact sensor as a part of membrane switch.

主回路部３０は、次のように構成されている。検知電極１１及びガード電極１２と接続される主回路部３０側の接続端の間に、検知電極１１側を入力、ガード電極１２側を出力とするバッファ３１が接続されている。バッファ３１は、検知電極１１及びガード電極１２と主回路部３０との間を接続するシールドケーブルにおける芯線とシールド線とを常に同電位として両者の間の充放電を防止する。検知電極１１からの信号は、検知回路３２に入力されている。検知回路３２は、検知電極１１及び接地電極１３の間の静電容量に応じたデューティーのパルス信号を出力する。このパルス信号はローパスフィルタ（ＬＰＦ）３３に入力されている。ＬＰＦ３３は、検知回路３２からのパルス信号を平滑化して第１の検知信号を出力する。   The main circuit unit 30 is configured as follows. A buffer 31 having the detection electrode 11 side as an input and the guard electrode 12 side as an output is connected between connection terminals on the main circuit unit 30 side connected to the detection electrode 11 and the guard electrode 12. The buffer 31 always keeps the core wire and the shield wire in the shielded cable connecting between the detection electrode 11 and the guard electrode 12 and the main circuit unit 30 at the same potential to prevent charging / discharging between them. A signal from the detection electrode 11 is input to the detection circuit 32. The detection circuit 32 outputs a pulse signal with a duty corresponding to the capacitance between the detection electrode 11 and the ground electrode 13. This pulse signal is input to a low-pass filter (LPF) 33. The LPF 33 smoothes the pulse signal from the detection circuit 32 and outputs a first detection signal.

一方、参照電極２１及びガード電極２２の主回路部３０側の接続端の間にもバッファ３５が接続されている。参照電極２１からの信号は、検知回路３６に入力されている。検知回路３６は、参照電極２１及び接地電極２３の間の静電容量に応じたデューティーのパルス信号を出力する。このパルス信号はＬＰＦ３７に入力されている。ＬＰＦ３７は、検知回路３６からのパルス信号を平滑化して第２の検知信号を出力する。減算回路３４は、ＬＰＦ３３からの第１の検知信号からＬＰＦ３７からの第２の検知信号を減算し、補償済み検知信号を出力する。   On the other hand, the buffer 35 is also connected between the connection ends of the reference electrode 21 and the guard electrode 22 on the main circuit portion 30 side. A signal from the reference electrode 21 is input to the detection circuit 36. The detection circuit 36 outputs a pulse signal with a duty corresponding to the capacitance between the reference electrode 21 and the ground electrode 23. This pulse signal is input to the LPF 37. The LPF 37 smoothes the pulse signal from the detection circuit 36 and outputs a second detection signal. The subtraction circuit 34 subtracts the second detection signal from the LPF 37 from the first detection signal from the LPF 33 and outputs a compensated detection signal.

ここで、検知回路３２とＬＰＦ３３は第１の検知回路を構成し、検知回路３６とＬＰＦ３７は第２の検知回路を構成する。両者の構成は、ほぼ等しいことが望ましい。検知回路３２，３６は、検知電極１１及び接地電極１３の間の静電容量並びに参照電極２１及び接地電極２３の間の静電容量に応じて周波数又はデューティー比が変化するもの等を使用することができる。   Here, the detection circuit 32 and the LPF 33 constitute a first detection circuit, and the detection circuit 36 and the LPF 37 constitute a second detection circuit. It is desirable that the configurations of both are substantially equal. As the detection circuits 32 and 36, a circuit whose frequency or duty ratio changes according to the capacitance between the detection electrode 11 and the ground electrode 13 and the capacitance between the reference electrode 21 and the ground electrode 23 is used. Can do.

図２は、静電容量Ｃに応じてデューティー比が変化する検知回路３２（３６も同様）の一例を示す回路図である。検知回路３２は、一定周期のトリガ信号ＴＧを出力するトリガ信号発生回路３２１と、入力端に接続された静電容量の大きさによってデューティー比が変化するパルス信号Ｐoを出力するタイマー回路３２２とを備えて構成されている。   FIG. 2 is a circuit diagram showing an example of the detection circuit 32 (same for 36) whose duty ratio changes according to the capacitance C. The detection circuit 32 includes a trigger signal generation circuit 321 that outputs a trigger signal TG having a fixed period, and a timer circuit 322 that outputs a pulse signal Po whose duty ratio changes depending on the capacitance connected to the input terminal. It is prepared for.

タイマー回路３２２は、例えば２つの比較器３２２１，３２２２と、これら比較器３２２１，３２２２の出力がそれぞれリセット端子Ｒ及びセット端子Ｓに入力されるＲＳフリップフロップ回路（以下、「ＲＳ−ＦＦ」と呼ぶ）３２２３と、このＲＳ−ＦＦ３２２３の出力ＤＩＳをＬＰＦ３３に出力するバッファ３２２４と、ＲＳ−ＦＦ３２２３の出力ＤＩＳでオンオフ制御されるトランジスタ３２２５とを備えて構成されている。   The timer circuit 322 includes, for example, two comparators 3221 and 3222 and an RS flip-flop circuit (hereinafter referred to as “RS-FF”) in which outputs of the comparators 3221 and 3222 are input to the reset terminal R and the set terminal S, respectively. 3223, a buffer 3224 that outputs the output DIS of the RS-FF 3223 to the LPF 33, and a transistor 3225 that is on / off controlled by the output DIS of the RS-FF 3223.

比較器３２２２は、トリガ信号発生回路３２１から出力される図３に示すようなトリガ信号ＴＧを、抵抗Ｒ１，Ｒ２，Ｒ３によって分割された所定のしきい値Ｖth2と比較して、トリガ信号ＴＧに同期したセットパルスを出力する。このセットパルスは、ＲＳ−ＦＦ３２２３のＱ出力をセットする。このＱ出力は、ディスチャージ信号ＤＩＳとしてトランジスタ３２２５をオフ状態にし、検知電極１１及び接地電極１３の間を、両電極１１，１３間の静電容量Ｃ及び入力端と電源ラインとの間に接続された抵抗Ｒ４による時定数で決まる速度で充電する。これにより、図３に示すように、入力信号Ｖinの電位が静電容量によって決まる速度で上昇する。入力信号Ｖinが、抵抗Ｒ１，Ｒ２，Ｒ３で決まるしきい値Ｖth1を超えたら、比較器３２２１の出力が反転してＲＳ−ＦＦ２１２３の出力を反転させる。この結果、トランジスタ３２２５がオン状態となって検知電極１１に蓄積された電荷がトランジスタ３２２５を介して放電される。従って、このタイマー回路３２２は、図３に示すように、検知電極１１及び接地電極１３間の静電容量に基づくデューティー比で発振するパルス信号Ｐoを出力する。ＬＰＦ３３は、この出力を平滑化することにより、図３に示すような、直流の検知信号Ｖout（第１の検知信号）を出力する。なお、図４中、実線で示す波形と点線で示す波形は、前者が後者よりも静電容量が小さいことを示しており、例えば後者が物体近接状態を示している。   The comparator 3222 compares the trigger signal TG as shown in FIG. 3 output from the trigger signal generation circuit 321 with a predetermined threshold value Vth2 divided by the resistors R1, R2, and R3, and generates a trigger signal TG. Output synchronized set pulse. This set pulse sets the Q output of RS-FF 3223. The Q output turns off the transistor 3225 as the discharge signal DIS, and is connected between the detection electrode 11 and the ground electrode 13 between the capacitance C between the electrodes 11 and 13 and the input terminal and the power supply line. The battery is charged at a speed determined by the time constant of the resistor R4. Thereby, as shown in FIG. 3, the potential of the input signal Vin increases at a speed determined by the capacitance. When the input signal Vin exceeds a threshold value Vth1 determined by the resistors R1, R2, and R3, the output of the comparator 3221 is inverted and the output of the RS-FF 2123 is inverted. As a result, the transistor 3225 is turned on, and the charge accumulated in the detection electrode 11 is discharged through the transistor 3225. Accordingly, the timer circuit 322 outputs a pulse signal Po that oscillates at a duty ratio based on the capacitance between the detection electrode 11 and the ground electrode 13 as shown in FIG. The LPF 33 smoothes this output to output a DC detection signal Vout (first detection signal) as shown in FIG. In FIG. 4, the waveform indicated by the solid line and the waveform indicated by the dotted line indicate that the former has a smaller capacitance than the latter, and for example, the latter indicates an object proximity state.

なお、検知回路３６も基本的にはこれと同様の構成とすれば良いが、トリガ信号発生回路３２１については、検知回路３２，３６で共有することも可能である。この場合、図２の点線矢印で示すように、検知回路３２から検知回路３６にトリガ信号ＴＧを供給するようにすれば良い。   The detection circuit 36 may basically have the same configuration as this, but the trigger signal generation circuit 321 can be shared by the detection circuits 32 and 36. In this case, the trigger signal TG may be supplied from the detection circuit 32 to the detection circuit 36 as indicated by a dotted arrow in FIG.

このように構成された本実施形態の静電容量式近接センサによれば、センサ部１０で被検出物の近接による変動分と温度特性、湿度特性等の環境特性に起因する変動分との加算分が検出され、センサ部２０で環境特性に起因する変動分のみが検出される。従って、ＬＰＦ３３からの第１の検知信号からＬＰＦ３７からの第２の検知信号を減算回路３４で減算することにより、環境特性分が除去された補償済み検知信号を得ることができる。   According to the capacitive proximity sensor of the present embodiment configured as described above, the sensor unit 10 adds the variation due to the proximity of the object to be detected and the variation due to environmental characteristics such as temperature characteristics and humidity characteristics. Minutes are detected, and the sensor unit 20 detects only fluctuations due to environmental characteristics. Therefore, by subtracting the second detection signal from the LPF 37 from the first detection signal from the LPF 33 by the subtraction circuit 34, it is possible to obtain a compensated detection signal from which the environmental characteristics have been removed.

図４は、本発明の第２の実施形態に係る静電容量式近接センサのブロック図である。   FIG. 4 is a block diagram of a capacitive proximity sensor according to the second embodiment of the present invention.

この実施形態では、センサ部２０が被検出物の影響を受けないようにシールドＳにより、シールドされている点が先の実施形態とは異なる。他の構成は先の実施形態と同様である。   This embodiment is different from the previous embodiment in that the sensor unit 20 is shielded by the shield S so as not to be affected by the object to be detected. Other configurations are the same as in the previous embodiment.

図５は、本発明の第３の実施形態に係る静電容量式近接センサのブロック図である。   FIG. 5 is a block diagram of a capacitive proximity sensor according to the third embodiment of the present invention.

この実施形態では、先の実施形態における２つの検知回路３２，３６及び２つのＬＰＦ３３，３７を、それぞれ共通の１つの検知回路３２及び１つのＬＰＦ３３とし、これらをセンサ部１０とセンサ部２０とで時分割で使用するように主回路部４０を構成した例である。切り換え回路４２は、外部からの制御信号に基づき、スイッチ回路４１を切り替える。スイッチ回路４１は、検知回路３２の入力が検知電極１１に接続され、バッファ３１の出力がガード電極１２に接続される第１状態と、検知回路３２の入力が参照電極２１に接続され、バッファ３１の出力がガード電極２２に接続される第２状態とを選択的に切り替える。信号保持回路４４は、第１の状態でＬＰＦ３３から出力される第１の検知信号と、第２状態でＬＰＦ３３から出力される第２の検知信号とをそれぞれ保持し、減算回路３４は、これら保持された第１及び第２の検知信号を減算処理して補償済み検知信号を出力する。   In this embodiment, the two detection circuits 32 and 36 and the two LPFs 33 and 37 in the previous embodiment are respectively used as one common detection circuit 32 and one LPF 33, and these are the sensor unit 10 and the sensor unit 20. This is an example in which the main circuit unit 40 is configured to be used in time division. The switching circuit 42 switches the switch circuit 41 based on an external control signal. The switch circuit 41 has a first state in which the input of the detection circuit 32 is connected to the detection electrode 11 and the output of the buffer 31 is connected to the guard electrode 12, and the input of the detection circuit 32 is connected to the reference electrode 21. Is selectively switched to the second state in which the output of is connected to the guard electrode 22. The signal holding circuit 44 holds the first detection signal output from the LPF 33 in the first state and the second detection signal output from the LPF 33 in the second state, and the subtraction circuit 34 holds these. The compensated detection signal is output by subtracting the first and second detection signals.

このような構成によれば、共通の検知回路３２及びＬＰＦ３３から２つの検知信号を得ることができるので、回路構成要素の相違による誤差成分が削除されて、更に精度良く環境特性分を除去することができる。   According to such a configuration, since two detection signals can be obtained from the common detection circuit 32 and the LPF 33, an error component due to a difference in circuit components is deleted, and the environmental characteristic component can be further accurately removed. Can do.

なお、上述した実施形態では、時分割で得られる２つの検知信号を、信号保持回路４４に一旦保持して減算回路３４で減算処理したが、例えば図６に示す主回路部５０のように、２つの検知信号を、直接Ａ／Ｄ変換機能を有するＣＰＵ５１に供給し、ＣＰＵ５１の内部演算処理で補償済み検知信号を得るようにしても良い。   In the above-described embodiment, the two detection signals obtained by time division are temporarily held in the signal holding circuit 44 and subtracted by the subtraction circuit 34. For example, as in the main circuit unit 50 shown in FIG. The two detection signals may be directly supplied to the CPU 51 having the A / D conversion function, and the compensated detection signal may be obtained by internal calculation processing of the CPU 51.

本発明の第１の実施形態に係る静電容量式近接センサの概略構成を示す回路図である。1 is a circuit diagram showing a schematic configuration of a capacitive proximity sensor according to a first embodiment of the present invention. 同近接センサの検知回路の一構成例を示す回路図である。It is a circuit diagram which shows one structural example of the detection circuit of the proximity sensor. 同近接センサの動作波形図である。It is an operation | movement waveform diagram of the proximity sensor. 本発明の第２の実施形態に係る静電容量式近接センサの概略構成を示す回路図である。It is a circuit diagram which shows schematic structure of the capacitive proximity sensor which concerns on the 2nd Embodiment of this invention. 本発明の第３の実施形態に係る静電容量式近接センサの概略構成を示す回路図である。It is a circuit diagram which shows schematic structure of the electrostatic capacitance type proximity sensor which concerns on the 3rd Embodiment of this invention. 本発明の第４の実施形態に係る静電容量式近接センサの概略構成を示す回路図である。It is a circuit diagram which shows schematic structure of the electrostatic capacitance type proximity sensor which concerns on the 4th Embodiment of this invention.

符号の説明Explanation of symbols

１０，２０…センサ部、１１…検知電極、１２，２２…ガード電極、１３，２３…接地電極、２１…参照電極、３０，４０，５０…主回路部、３１，３５…バッファ、３２，３６…検知回路、３３，３７…ＬＰＦ、３４…減算回路、４１…スイッチ回路、４２…切り換え回路、４４…信号保持回路、５１…ＣＰＵ。   DESCRIPTION OF SYMBOLS 10,20 ... Sensor part, 11 ... Detection electrode, 12, 22 ... Guard electrode, 13, 23 ... Ground electrode, 21 ... Reference electrode, 30, 40, 50 ... Main circuit part, 31, 35 ... Buffer, 32, 36 Detecting circuit 33, 37 LPF 34 Subtracting circuit 41 Switch circuit 42 Switching circuit 44 Signal holding circuit 51 CPU

Claims (6)

検知エリア内に配置された検知電極と、
前記検知エリア外に配置され前記検知電極と同様に形成された参照電極と、
前記検知電極と接地との間の静電容量に基づく第１の検知信号を出力する第１の検知回路と、
前記参照電極と接地との間の静電容量に基づく第２の検知信号を出力する第２の検知回路と、
前記第１の検知回路の出力から前記第２の検知回路の出力を減算して補償済み検知信号を出力する減算回路と
を備えたことを特徴とする静電容量式近接センサ。 A sensing electrode arranged in the sensing area;
A reference electrode disposed outside the detection area and formed in the same manner as the detection electrode;
A first detection circuit that outputs a first detection signal based on a capacitance between the detection electrode and ground;
A second detection circuit that outputs a second detection signal based on a capacitance between the reference electrode and ground;
A capacitance-type proximity sensor comprising: a subtraction circuit that subtracts the output of the second detection circuit from the output of the first detection circuit and outputs a compensated detection signal. 前記参照電極は、前記検知エリアからシールドされていることを特徴とする請求項１記載の静電容量式近接センサ。   The capacitive proximity sensor according to claim 1, wherein the reference electrode is shielded from the detection area. 前記第１及び第２の検知回路は、共用可能な部品を除き同様の部品にて構成されていることを特徴とする請求項１記載の静電容量式近接センサ。   2. The capacitive proximity sensor according to claim 1, wherein the first and second detection circuits are configured by similar parts except for parts that can be shared. 前記検知電極と対をなす第１の接地電極と、
前記参照電極と対をなす第２の接地電極とを更に備えたことを特徴とする請求項１記載の静電容量式近接センサ。 A first ground electrode paired with the sensing electrode;
The capacitive proximity sensor according to claim 1, further comprising a second ground electrode paired with the reference electrode. 前記検知電極と第１の接地電極との間及び前記参照電極と第２の接地電極との間にそれぞれ第１のガード電極及び第２のガード電極をそれぞれ配置してなることを特徴とする請求項４記載の静電容量式近接センサ。   The first guard electrode and the second guard electrode are respectively disposed between the detection electrode and the first ground electrode and between the reference electrode and the second ground electrode. Item 5. The capacitive proximity sensor according to item 4. 検知エリア内に配置された検知電極と、
前記検知エリア外に配置され前記検知電極と同様に形成された参照電極と、
前記検知電極と前記参照電極とに選択的に接続されるスイッチ回路と、
このスイッチ回路を介して前記検知電極と前記参照電極とに選択的に接続され、前記検知電極と接続されているときには、前記検知電極と接地との間の静電容量に基づく第１の検知信号を出力し、前記参照電極と接続されているときには、前記参照電極と接地との間の静電容量に基づく第２の検知信号を出力する検知回路と、
前記第１の検知信号から前記第２の検知信号を減算して補償済み検知信号を出力する演算手段と
を備えたことを特徴とする静電容量式近接センサ。 A sensing electrode arranged in the sensing area;
A reference electrode disposed outside the detection area and formed in the same manner as the detection electrode;
A switch circuit selectively connected to the sensing electrode and the reference electrode;
A first detection signal based on a capacitance between the detection electrode and the ground is selectively connected to the detection electrode and the reference electrode via the switch circuit and is connected to the detection electrode. And a detection circuit that outputs a second detection signal based on a capacitance between the reference electrode and ground when connected to the reference electrode;
An electrostatic capacity proximity sensor comprising: an arithmetic means for subtracting the second detection signal from the first detection signal and outputting a compensated detection signal.
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