JP3671264B2 - Obstacle detection device - Google Patents

Description

式（１）の左辺は実数で振幅条件となり、右辺は虚数で周波数条件となる。
【００３５】
ｒd ・ｇm ・Ｚ1 ・Ｚ3 ＋Ｚ1 ・Ｚ3 ＋Ｚ1 ・Ｚ2 ≦０ ・・・・ （２）
Ｚ1 ＋Ｚ2 ＋Ｚ3 ＝０ ・・・・・ （３）
ここで、式（２）は振幅に関係し、式（３）は周波数の変化に対応する条件となる。式（２），（３）から周波数が変化すると振幅が変化することがわかる。一般に、インピーダンスＺ1 ，Ｚ3 を誘導性、インピーダンスＺ2 を容量性とする場合をハートレー型、その逆のインピーダンスＺ1 ，Ｚ3 を容量性、インピーダンスＺ2 を誘導性とするインピーダンスの組合わせをコルピッツ型と呼ばれている。
【００３６】
なお、本発明を実施する場合には、ハートレー型、コルピッツ型の何れであっても用いることができるが、ここではハートレー型の場合で説明を進めることとする。
【００３７】
また、図１（ｂ）のトランジスタＴＲを使用した発振回路についても、実質的動作は同一であるのでその説明を省略する。
【００３８】
図２は本発明の第一実施形態の障害物検出装置を説明するためのハートレー型発振回路の基本的原理説明図である。図３は図２のインピーダンスＺ3 の等価回路図であり、図４は図３の周波数とリアクタンスとの関係を示す特性図である。
【００３９】
図２において、抵抗ＲG はＦＥＴのゲートＧの直流バイアスのための抵抗で、抵抗Ｒs はＦＥＴのソースＳの直流バイアスのための抵抗で、コンデンサＣs ，コンデンサＣc はバイパス用のコンデンサである。故に、発振条件を決める要素はインピーダンスＺ1 ，Ｚ2 ，Ｚ3 となる。本実施の形態では、インピーダンスＺ2 が容量性、即ち、コンデンサＣdgで、インピーダンスＺ3 をクリスタル振動子等からなる誘導性とした。インピーダンスＺ1 を誘導性及び容量性のインダクタンスＬ及びコンデンサＣからなる共振回路で形成した。
【００４０】
インピーダンスＺ3 は、図３の等価回路に示すように、抵抗Ｒ3 及びコンデンサＣ3 及びリアクタンスＬ3 からなる直列回路と、その回路に並列接続されてコンデンサＣ0 で表される。この抵抗Ｒ3 及びコンデンサＣ3 及びリアクタンスＬ3 からなる直列回路の共振周波数ｆ3sは、
ｆ3s＝１／２π√（Ｌ3 ・Ｃ3 ）
となり、また、並列回路の共振周波数ｆ3pは、
ｆ3s＝１／２π√｛（Ｌ3 ・Ｃ3 ・Ｃ0 ）／（Ｃ3 ＋Ｃ0 ）｝
となる。即ち、図４の実線に示すように共振周波数ｆ3sと共振周波数ｆ3pの間で誘導性となる。
【００４１】
そこで、図５の破線で示されるインピーダンスＺ1 のリアクタンスを誘導性とすれば、周波数ｆ3s乃至周波数ｆ3pの間で発振することがわかる。即ち、インピーダンスＺ1 の共振周波数ｆ1 ＝１／２π√（Ｌ・Ｃ）をｆ1 ＞ｆ3p、ｆ1 ＞ｆ3sと調整すれば発振することになる。
【００４２】
一般に、電気的機械振動子のＱファクタは非常に大きく、共振周波数ｆ3p≒ｆ3sであり、この発振周波数ｆ3 とすれば、発振回路の発振周波数ｆ1 はｆ1 ＞ｆ3 であれば、式（３）を満足し、式（２）を満たす任意の周波数差Δｆ＝ｆ1 −ｆ3 の範囲で、発振周波数ｆ3 で発振する。即ち、発振周波数を固定すれば、発振レベルの変化を検出することができる。しかし、式（２）を満たす周波数差Δｆは、所定の周波数範囲を持つため、発振レベルは一定値とならない。
【００４３】
そこで、共振回路を構成するインピーダンスＺ1 の共振周波数ｆ1 を周波数条件の式（３）を満たす範囲、即ち、ｆ1 ＞ｆ3 で変化させ、発振レベルＶ0 を常に一定になるようにして、発振レベルの変化を検出し、それを脱したとき、障害物Ｇの検出とするものである。
【００４４】
図５は本発明の第一実施形態の障害物検出装置の全体回路図である。
【００４５】
図５において、ＦＥＴのドレインＤとゲートＧ間に接続されたインピーダンスＺ2 はコンデンサＣz2と、ＦＥＴのソースＳとゲートＧ間に接続された水晶振動子ＸTAL からなるインピーダンスＺ3 と、前記インピーダンスＺ2 及びインピーダンスＺ3 の両端子間、即ち、ＦＥＴのドレインＤとソースＳ間に接続されたインピーダンスＺ1 によって発振条件を定めている。これら、ＦＥＴとインピーダンスＺ1 、インピーダンスＺ2 、インピーダンスＺ3 によって発振回路を構成している。基本的回路構成は、図２に示す回路と共通しているのでその説明を省略する。
【００４６】
また、カップリングコンデンサＣ10を介してＦＥＴのドレインＤ側に接続された検波回路１は、ダイオードＤ11及びダイオードＤ12及び抵抗Ｒ11、コンデンサＣ11からなり、抵抗Ｒ11に印加された電圧がダイオードＤ12を介してコンデンサＣ11に充電される。この回路によって、発振レベルは検波回路１で直流電圧Ｖ0 に変換され、判定回路２と発振制御回路３に伝送される。
【００４７】
判定回路２は、一方に、定電圧電源Ｖccから供給した電圧を直列接続された抵抗Ｒ21及び抵抗Ｒ22に印加し、分圧した所定の閾値電圧ＶT1を入力し、他方に検波回路１で得られた直流電圧Ｖ0 を入力し、両者を比較回路ＣＯＭＰで比較している。閾値電圧ＶT1よりも検波回路１で得られた直流電圧Ｖ0 が大きいとき、比較回路ＣＯＭＰの出力は“Ｌ”となり、閾値電圧ＶT1よりも直流電圧Ｖ0 が小さいとき、比較回路ＣＯＭＰの出力は“Ｈ”となる。なお、通常状態の閾値電圧ＶT1は直流電圧Ｖ0 よりも小さく、比較回路ＣＯＭＰの出力は“Ｌ”となっている。
【００４８】
また、発振制御回路３では、定電圧電源Ｖccから供給した電圧を直列接続された抵抗Ｒ31及び抵抗Ｒ32に印加し、分圧した所定の閾値電圧Ｖ1 を入力し、他方に検波回路１で得られた直流電圧Ｖ0 を入力抵抗Ｒ30を介して入力し、その出力Ｖ2 として、Ｖ2 ＝Ｖ1 −Ｖ0 がオペアンプＯＰの出力として得られ、それが出力抵抗Ｒ33及びＲ35を介して可変容量ダイオードＶＤに印加される。オペアンプＯＰの出力の抵抗Ｒ33と抵抗Ｒ35の接続点には、抵抗Ｒ34とコンデンサＣ31の並列回路によって定電圧電源Ｖccに接続され、また、ダイオードＤ31がアースとの間に接続されており、オペアンプＯＰの出力が負にならないようにし、かつ、その変化速度を高くしている。閾値電圧Ｖ1 に設定されたオペアンプＯＰにより、検波回路１で得られた直流電圧Ｖ0 が閾値電圧Ｖ1 と等しくなるよう、制御電圧Ｖ2 が作られる。制御電圧Ｖ2 は、インピーダンスＺ1 に接続された可変容量ダイオードＶＤに加えられ、インピーダンスＺ1 の共振周波数ｆ1 を、Ｖ2 ＝Ｖ0 の一定値となるよう制御される。
【００４９】
インピーダンスＺ1 は、インダクタンスＬ及びキャパシタンスＣからなる共振回路となっており、このインダクタンスＬとしては１：ｎの巻線比の相互インダクタンスで構成されている。インダクタンスＬの巻線比１側はコンデンサＣが接続されている。インダクタンスＬの巻線比ｎ側はコンデンサＣz1及び可変容量ダイオードＶＤの直列回路が接続されている。また、インダクタンスＬの巻線比ｎ側とコンデンサＣz1との接続点には、板材または線材からなるセンサＳが配設されている。
【００５０】
次に、この実施形態の障害物検出装置の動作を説明する。
【００５１】
まず、人、建造物、金属等の障害物Ｇに近付くと、その周囲の媒介定数が変化し、アンテナとして機能するセンサＳの入力インピーダンスが変化し、それが容量の変化となってインピーダンスＺ1 に加えられ、発振回路の共振周波数ｆが変化し、検波回路１で得られた直流電圧Ｖ0 も低下し、障害物Ｇを検出し続ける。ここで発振制御回路３は直流電圧Ｖ0 と所定の閾値電圧Ｖ1 と比較し、本来の検波回路１で得られた直流電圧Ｖ0 にするために、オペアンプＯＰの出力Ｖ2 を変化させ、その出力Ｖ2 の変化は可変容量ダイオードＶＤに加えられ、インピーダンスＺ1 の共振周波数ｆを、一定値となるよう制御される。このように、所定の閾値電圧Ｖ1 の変化を環境の変化のみに応答させ、その発振回路の発振周波数ｆを一定とすることにより、発振レベルも一定となる。これにより、センサＳの容量が経時変化等の障害物Ｇに寄与しない変化を、自動的に補正することができる。また、センサＳの大きさに起因する初期容量は、並列共振回路への結合量を可変することで任意に設定できる。
【００５２】
また、センサＳと障害物Ｇが接近した位置に停止しているとき、検波回路１で得られた直流電圧Ｖ0 が低下し、障害物Ｇを検出し続ける。しかし、検波回路１で得られた直流電圧Ｖ0 の低下は環境の変化と同様の現象となる。このため、検波回路１で得られた直流電圧Ｖ0 を所定の閾値電圧Ｖ1 と等しくするようにオペアンプＯＰの出力Ｖ2 を変化させる。これによって、検波回路１で得られた直流電圧Ｖ0 は徐々に所定の閾値電圧Ｖ1 に等しくなるので障害物Ｇが無いものとみなされる。結果、障害物Ｇに接近した位置に停止したとき、時間の経過とともに障害物Ｇを検出しなくなり、その状態が環境の状態として初期状態となる。
【００５３】
一方、障害物Ｇに所定以上に近づくと、アンテナとして機能しているセンサＳのインピーダンスが変化し、その結果、それが容量の変化となってインピーダンスＺ1 に加えられ、発振回路の共振周波数ｆが変化し、周波数条件式（３）が満たされなくなり、発振が停止する。これにより、検波回路１で得られた直流電圧Ｖ0 も低下し、比較回路ＣＯＭＰの閾値電圧ＶT1よりも直流電圧Ｖ0 が小さくなり、比較回路ＣＯＭＰの出力は“Ｈ”となり、障害物Ｇに所定以上接近していることが検出される。
【００５４】
また、センサＳの入力インピーダンスが変化し、その変化がインピーダンスＺ1 に加えられ、発振回路の共振周波数ｆが変化するよりも速く、障害物Ｇに急激に接近したとき、検波回路１で得られた直流電圧Ｖ0 が低下し、比較回路ＣＯＭＰの閾値電圧ＶT1よりも直流電圧Ｖ0 が小さくなり、比較回路ＣＯＭＰの出力は“Ｈ”となり、障害物Ｇの検出状態となる。
【００５５】
この実施の形態では、障害物Ｇに接近した位置に停止したとき、時間の経過とともに障害物Ｇを検出しなくなり、その状態が環境の状態と判定するものであるが、障害物Ｇの検出を記憶しておくこともできる。
【００５６】
図６は本発明の第二実施形態の障害物検出装置の全体回路図である。
【００５７】
なお、図中、第一実施形態と同一符号及び記号は第一実施形態の構成部分と同一または相当する構成部分を示すものであるから、ここでは重複する説明を省略する。
【００５８】
図６において、インピーダンスＺ1 は、インダクタンスＬ及びキャパシタンスＣからなる共振回路となっており、このインダクタンスＬとしては１個のコイルを１：ｎの巻線比の個所で端子を出し、インダクタンスＬz10 及びインダクタンスＬz11 からなる単巻コイルで構成されている。インダクタンスＬから引出した端子には、コンデンサＣz1及び可変容量ダイオードＶＤの直列回路が接続されている。また、インダクタンスＬの端子とコンデンサＣz1との接続点には、板材または線材からなるセンサＳが配設されており、また、コンデンサＣz1と可変容量ダイオードＶＤの接続点には、発振制御回路３のオペアンプＯＰの出力Ｖ2 が入力されている。
【００５９】
なお、この回路の動作は、基本的に第一実施形態の動作と同一であるから、その説明を省略する。
【００６０】
図７は本発明の第三実施形態の障害物検出装置の全体回路図である。
【００６１】
なお、図中、上記実施形態と同一符号及び記号は上記実施形態の構成部分と同一または相当する構成部分を示すものであるから、ここでは重複する説明を省略する。
【００６２】
図７において、判定回路２は、一方に、所定の閾値電圧ＶT1を入力し、他方に検波回路１で得られた直流電圧Ｖ0 を入力し、両者を比較回路ＣＯＭＰで比較し、閾値電圧ＶT1よりも検波回路１で得られた直流電圧Ｖ0 が大きいとき、比較回路ＣＯＭＰの出力は“Ｌ”となり、閾値電圧ＶT1よりも直流電圧Ｖ0 が小さいとき、比較回路ＣＯＭＰの出力は“Ｈ”となる。なお、通常状態の閾値電圧ＶT1は直流電圧Ｖ0 よりも小さく、比較回路ＣＯＭＰの出力は“Ｌ”となっている。
【００６３】
また、ｎビットアップ／ダウンカウンタ１０は、比較回路ＣＯＭＰの出力は“Ｌ”でプリセットされている。クロック入力はカウンタ制御ロジック１３のクロックスタート・ストップで開閉されるＡＮＤゲートを介して入力され、発振回路の出力を図示しない波形成形回路を介したものを使用している。また、ｎビットアップ／ダウンカウンタ１０はカウンタ制御回路１３から加算または減算指令となるカウンタ制御信号及びｎビットアップ／ダウンカウンタ１０を動作状態とするイネーブル信号を入力している。なお、ＡＮＤゲートのクロック信号入力は、本実施の形態では自己の発振回路の信号を使用しているが、本発明を実施する場合には、他のクロック発生器からクロック信号を入力してもよい。
【００６４】
Ｄ／Ａ変換回路１１は、ｎビットアップ／ダウンカウンタ１０のカウンタ出力を受けてアナログ出力Ｖ01を出力している。
【００６５】
また、出力制御回路１２は、検波回路１で得られた直流電圧Ｖ0 とＤ／Ａ変換回路１１からのアナログ出力Ｖ01を受けて、出力差Ｖ0 −Ｖ01を補償するもので、抵抗Ｒ35を介して可変容量ダイオードＶＤに加えられ、インピーダンスＺ1 の共振周波数ｆを、一定値となるよう制御される。
【００６６】
一方、検波回路１で得られた直流電圧Ｖ0 とＤ／Ａ変換回路１１からのアナログ出力Ｖ01は、カウンタ制御回路１３に入力されており、出力差Ｖ0 −Ｖ01の極性によってｎビットアップ／ダウンカウンタ１０のカウンタ出力の増減を決定し、出力差Ｖ0 −Ｖ01の大きさが所定の範囲以上になったとき、ｎビットアップ／ダウンカウンタ１０を動作状態とするイネーブル信号を出力し、かつ、ＡＮＤゲートを開き、インピーダンスＺ1 ，Ｚ2 ，Ｚ3 で構成される発振回路から図示しない波形成形回路を介してｎビットアップ／ダウンカウンタ１０のクロック信号としている。
【００６７】
ここで、ｎビットアップ／ダウンカウンタ１０、Ｄ／Ａ変換回路１１、出力制御回路１２、カウンタ制御回路１３は、発振制御回路３０を構成する。
【００６８】
次に、この実施形態の障害物検出装置の動作を説明する。
【００６９】
まず、人、建造物、金属等の障害物Ｇに近付き、徐々に環境条件が変化すると、センサＳの入力インピーダンスが変化し、それが容量の変化となってインピーダンスＺ1 に加えられ、発振回路の共振周波数ｆが変化し、検波回路１で得られた直流電圧Ｖ0 が低下し、障害物Ｇを検出する。ここで出力制御回路１２は直流電圧Ｖ0 とＤ／Ａ変換回路１１からの所定の閾値電圧Ｖ01と比較し、本来の検波回路１で得られた直流電圧Ｖ0 にするために、出力制御回路１２の出力Ｖ2 を変化させ、その出力Ｖ2 の変化は可変容量ダイオードＶＤに加えられ、インピーダンスＺ1 の共振周波数ｆを、一定値となるよう制御される。当然、発振周波数ｆが一定であり、発振レベルも一定となる。センサＳと障害物Ｇが所定の接近した位置に停止しても、検波回路１で得られた直流電圧Ｖ0 が低下し、障害物Ｇを検出し、それを環境の変化として補正された状態を維持する。これにより、センサＳの容量が経時変化等の障害物Ｇに寄与しない変化を、自動的に補正することができる。また、センサＳの大きさに起因する初期容量は、並列共振回路への結合量を可変することで任意に設定できる。
【００７０】
しかし、障害物Ｇに所定以上に近づくと、センサＳの入力インピーダンスが変化し、その結果、容量の変化となってインピーダンスＺ1 に加えられ、発振回路の共振周波数ｆが変化し、周波数条件が満たされなくなり、発振が停止したり発振レベルが急激に低下する。これにより、検波回路１で得られた直流電圧Ｖ0 も低下し、判定回路２を構成する比較回路ＣＯＭＰの閾値電圧ＶT1よりも直流電圧Ｖ0 が小さくなり、比較回路ＣＯＭＰの出力は“Ｈ”となり、障害物Ｇの検出状態となる。
【００７１】
同時に、ｎビットアップ／ダウンカウンタ１０をプリセットし、検波回路１で得られた直流電圧Ｖ0 とＤ／Ａ変換回路１１からのアナログ出力Ｖ01は、カウンタ制御回路１３に入力され、出力差Ｖ0 −Ｖ01の極性によってｎビットアップ／ダウンカウンタ１０のカウンタ出力の増減を決定し、出力差Ｖ0 −Ｖ01の絶対値の大きさが所定の範囲以上のとき、ｎビットアップ／ダウンカウンタ１０を動作状態とするイネーブル信号を出力し、かつ、ＡＮＤゲートを開き、インピーダンスＺ1 ，Ｚ2 ，Ｚ3 で構成される発振回路から図示しない波形成形回路を介してｎビットアップ／ダウンカウンタ１０のクロック信号としている。出力差Ｖ0 −Ｖ01によってｎビットアップ／ダウンカウンタ１０が計数を行い、ｎビットアップ／ダウンカウンタ１０の計数値はＤ／Ａ変換回路１１によってアナログ値に変換され、出力差Ｖ0 −Ｖ01が所定の値以下になるまでｎビットアップ／ダウンカウンタ１０が計数を行い、そのｎビットアップ／ダウンカウンタ１０の計数値はＤ／Ａ変換回路１１によってアナログ値に変換され、所定の出力差Ｖ0 −Ｖ01、例えば、Ｖ0 −Ｖ01が略零になったとき、ｎビットアップ／ダウンカウンタ１０による制御を停止する。
【００７２】
この状態で、例えば、Ｖ0 ＞Ｖ01になったとき、発振回路は発振周波数ｆで再度発振を継続し、この間にｎビットアップ／ダウンカウンタ１０はプリセットされｎビットアップ／ダウンカウンタ１０は初期値に戻る。
【００７３】
しかし、この状態で、例えば、Ｖ0 ＞Ｖ01にならないとき、発振回路は発振周波数ｆで発振できなくなり、ｎビットアップ／ダウンカウンタ１０は停止状態となり、センサＳと障害物Ｇが接近した検出状態を維持する。即ち、センサＳと障害物Ｇが接近した障害物検出状態が維持される。
【００７４】
この実施の形態では、ｎビットアップ／ダウンカウンタ１０を用いて、Ｄ／Ａ変換回路１１からのアナログ出力Ｖ01の精度を高くしている。しかし、本発明を実施する場合には、最小カウンタ値に設定することもできる。しかし、このときには、回路的に簡単化することもできる。
【００７５】
図８は本発明の第四実施形態の障害物検出装置の全体回路図である。
【００７６】
なお、図中、上記実施形態と同一符号及び記号は上記実施形態の構成部分と同一または相当する構成部分を示すものであるから、ここでは重複する説明を省略する。
【００７７】
図８において、判定回路２は、一方に、所定の閾値電圧ＶT1を入力し、他方に検波回路１で得られた直流電圧Ｖ0 を入力し、両者を比較回路ＣＯＭＰで比較し、閾値電圧ＶT1よりも検波回路１で得られた直流電圧Ｖ0 が大きいとき、比較回路ＣＯＭＰの出力は“Ｌ”となり、閾値電圧ＶT1よりも直流電圧Ｖ0 が小さいとき、比較回路ＣＯＭＰの出力は“Ｈ”となる。なお、通常状態の閾値電圧ＶT1は直流電圧Ｖ0 よりも小さく、比較回路ＣＯＭＰの出力は“Ｌ”となっている。
【００７８】
また、ラッチ回路２０は、比較回路ＣＯＭＰの出力は“Ｌ”でリセットされている。ラッチ回路２０は、そのセットまたはリセットによって選択回路２１の切替を行う。ラッチ回路２０のセット信号は、一方に、所定の閾値電圧ＶT2を入力し、他方に検波回路１で得られた直流電圧Ｖ0 を入力し、両者を比較回路ＣＯＭＰ２で比較し、閾値電圧ＶT2よりも検波回路１で得られた直流電圧Ｖ0 が小さいとき、比較回路ＣＯＭＰ２の出力は“Ｌ”でセット信号となり、閾値電圧ＶT2よりも直流電圧Ｖ0 が大きいとき、比較回路ＣＯＭＰ２の出力は“Ｈ”となる。なお、通常状態の閾値電圧ＶT2は直流電圧Ｖ0 よりも大きく、比較回路ＣＯＭＰの出力は“Ｌ”となっている。ここで、検波回路１で得られた直流電圧Ｖ0 と閾値電圧ＶT1、閾値電圧ＶT2との関係は、Ｖ0 ＞ＶT1＞ＶT2である。
【００７９】
選択回路２１は、ラッチ回路２０がリセット状態のとき、その出力を出力Ｖ02とし、ラッチ回路２０がセット状態のとき、その出力を出力Ｖ03として、出力制御回路２２の入力としている。ここで、検波回路１で得られた直流電圧Ｖ0 と閾値電圧ＶT1、閾値電圧ＶT2との関係及び選択回路２１の出力の関係は、Ｖ02＞ＶT1＞Ｖ03＞ＶT2である。
【００８０】
また、出力制御回路２２は、検波回路１で得られた直流電圧Ｖ0 と選択回路２１の出力Ｖ02または出力Ｖ03を受けて、出力差Ｖ0 −Ｖ02または出力差Ｖ0 −Ｖ03を補償するもので、それが抵抗Ｒ35を介して可変容量ダイオードＶＤに加えられ、インピーダンスＺ1 の共振周波数ｆを、一定値となるよう制御される。
【００８１】
障害物Ｇがないとき、或いはその影響が少ないとき、ラッチ回路２０がリセット状態で、出力制御回路２２の入力は選択回路２１の出力は出力Ｖ02で、検波回路１で得られた直流電圧Ｖ0 との関係は、検波回路１で得られた直流電圧Ｖ0 と閾値電圧ＶT1、閾値電圧ＶT2との関係及び選択回路２１の出力の関係は、Ｖ0 ≒Ｖ02＞ＶT1＞Ｖ03＞ＶT2である。
【００８２】
まず、人、建造物、金属等の障害物Ｇに近付き、徐々に環境条件が変化すると、センサＳの入力インピーダンスが変化し、それが容量の変化となってインピーダンスＺ1 に加えられ、発振回路の共振周波数ｆが変化し、検波回路１で得られた直流電圧Ｖ0 が低下し、障害物Ｇを検出する。ここで出力制御回路２２は直流電圧Ｖ0 と選択回路２１からの所定の閾値電圧Ｖ02と比較し、本来の検波回路１で得られた直流電圧Ｖ0 にするために、出力制御回路２２の出力Ｖ2 を変化させ、その出力Ｖ2 の変化は可変容量ダイオードＶＤに加えられ、インピーダンスＺ1 の共振周波数ｆを、一定値となるよう制御される。このように、発振周波数ｆが一定であり、発振レベルも一定となる。センサＳと障害物Ｇが所定の接近した位置に停止しても、検波回路１で得られた直流電圧Ｖ0 が低下し、障害物Ｇを検出し、それを環境の変化として補正された状態を維持する。これにより、センサＳの容量が経時変化等の障害物Ｇに寄与しない変化を、自動的に補正することができる。また、センサＳの大きさに起因する初期容量は、並列共振回路への結合量を可変することで任意に設定できる。
【００８３】
しかし、障害物Ｇに所定以上に近づくと、センサＳの入力インピーダンスが変化し、その結果、容量の変化となってインピーダンスＺ1 に加えられ、発振回路の共振周波数ｆが変化し、周波数条件が満たされなくなり、発振が停止したり発振レベルが急激に低下する。これにより、検波回路１で得られた直流電圧Ｖ0 も低下し、判定回路２を構成する比較回路ＣＯＭＰの閾値電圧ＶT1よりも直流電圧Ｖ0 が小さくなり、比較回路ＣＯＭＰの出力は“Ｈ”となり、障害物Ｇの検出状態となる。
【００８４】
更に、発振レベルが低下し、直流電圧Ｖ0 が比較回路ＣＯＭＰ２の閾値電圧ＶＴ2 よりも小さくなると、比較回路ＣＯＭＰ２の出力が“Ｌ”となり、ラッチ回路２０はセットされ、その出力によって選択回路２１からの出力は出力Ｖ03に切替えられ、検波回路１で得られた直流電圧Ｖ0 と選択回路２１からの出力Ｖ03は、出力制御回路２２に入力されており、出力差Ｖ0 −Ｖ03のによって出力Ｖ2 を得て、その出力Ｖ2 の変化は可変容量ダイオードＶＤに加えられ、インピーダンスＺ1 の共振周波数ｆを、一定値となるよう制御される。所定の出力差Ｖ0 −Ｖ03、例えば、Ｖ0 −Ｖ03が略零になったとき、発振回路は発振周波数ｆで再度発振を継続し、センサＳと障害物Ｇが接近した検出状態を維持する。即ち、センサＳと障害物Ｇが接近した障害物検出状態が維持される。しかし、この状態で、例えば、直流電圧Ｖ0 が比較回路ＣＯＭＰの閾値電圧ＶT1よりも大きくなると、ラッチ回路２０はリセットされ初期値に戻る。
【００８５】
しかし、この状態で、例えば、Ｖ0 −Ｖ01が略零にならないとき、発振回路は発振周波数ｆで発振できなくなり、ラッチ回路２０はリセット状態を維持し、センサＳと障害物Ｇが接近した検出状態を維持する。即ち、センサＳと障害物Ｇが接近した障害物検出状態が維持される。
【００８６】
このように、本実施の形態における障害物検出装置は、障害物Ｇに接近すると発振回路のアンテナとしてのセンサＳの周囲の媒介定数が変化し、センサＳの入力インピーダンスの変化によって共振周波数を変化させるインピーダンスＺ1 と他の２個のインピーダンスＺ2 ，Ｚ3 と共に形成する発振回路と、前記発振回路からの発振レベルの低下を判定回路２で検出して、発振制御回路３で前記発振レベルの低下に対応して前記発振回路を形成するインピーダンスを変化させ、前記発振回路３の発振周波数を所定の周波数領域内とし、所定の発振レベルが維持できるか否かで障害物Ｇの検出を行うものであり、これを請求項に対応する実施の形態とすることができる。
【００８７】
したがって、アンテナとして機能するセンサＳの入力インピーダンスは、自由空間と異なる媒質が接近すると変化し、この入力インピーダンスの変化を、発振周波数を補償できるコンデンサＣz1と可変容量ダイオードＶＤからなる共振回路に加え、発振レベルの変化のみで障害物Ｇが検出できるものであるから、電圧レベルの単位時間当たりの変化量の大きさを判定し、障害物Ｇを検出することができる。或いは電圧レベルの所定量の低下を判定し、障害物Ｇを検出することができる。本発明者等の実験によれば、アンテナとして機能するセンサＳのインピーダンスの変化で検出するものであるから、４０ｃｍ前後の障害物Ｇの検出距離が維持でき、簡単な回路でそれが実現できる。そして、センサＳの容量が経時変化等障害物の寄与でない場合の変化を、自動的に補正することができる。センサＳの大きさに起因する初期の容量は、並列共振回路への結合量を可変することで任意に設定できる。
【００８８】
また、この実施の形態においては、直列接続されたインピーダンスＺ2 及びインピーダンスＺ3 と、前記インピーダンスＺ2 及びインピーダンスＺ3 の両端子に接続されたインピーダンスＺ1 によって発振条件を定め、同じ極性とするインピーダンスＺ1 及びインピーダンスＺ3 の共振回路を有する発振回路と、前記共振回路のインピーダンスＺ3 は、共振周波数をｆ3 、回路のＱファクタをＱ3 とし、また、インピーダンスＺ1 は、共振周波数をｆ1 、回路のＱファクタをＱ1 とするとき、ｆ1 ＞ｆ3 で、かつ、Ｑ3 ＞Ｑ1 となるように、インピーダンスＺ3 は電気的機械振動子とし、インピーダンスＺ1 はコイルとコンデンサで形成し、前記発振回路の発振周波数を所定の周波数領域内とし、所定の発振レベルが維持できるか否かで障害物Ｇの検出を行うものであり、これを請求項に対応する実施の形態とすることができる。
【００８９】
即ち、共振回路のインピーダンスＺ3 を共振周波数をｆ3 、回路のＱファクタをＱ3 とし、インピーダンスＺ1 を共振周波数をｆ1 、回路のＱファクタをＱ1 としたとき、ｆ1 ＞ｆ3 とすることにより、周波数の調整領域の幅を持たせ、その調整範囲を広くし、かつ、Ｑ3 ＞Ｑ1 とすることにより、周波数ｆ1 を変更してもＱ1 の変化を少なくする。当然、周波数ｆ1 を変更してもＱ1 の変化を少なくする回路のＱファクタとしてはＱ3 ＞＞Ｑ1 が好適である。
【００９０】
したがって、アンテナとして機能するセンサの入力インピーダンスは、自由空間と異なる媒質が接近すると変化し、この入力インピーダンスの変化を、発振周波数を補償できる共振回路に加え、発振レベルの変化のみで障害物Ｇが検出できるから、電圧レベルの単位時間当たりの変化量の大きさを判定し、障害物Ｇを検出することができる。故に、アンテナとして機能するセンサＳのインピーダンスの変化で検出するものであるから、４０ｃｍ前後の障害物Ｇの検出距離が維持でき、簡単な回路でそれが実現できる。そして、センサＳの容量が経時変化等障害物の寄与でない場合の変化を、自動的に補正することができる。センサＳの大きさに起因する初期の容量は、並列共振回路への結合量を可変することで任意に設定できる。
【００９１】
そして、この実施の形態においては、前記発振回路の発振レベルが一定となるようインピーダンスＺ3 の共振周波数ｆ3 と、インピーダンスＺ1 の共振周波数ｆ1 との共振周波数の差を制御するものであり、これを請求項に対応する実施の形態とすることができ、発振回路の発振周波数の制御及びそれによる発振レベルが既知となり、発振回路の発振制御が容易になる。
【００９２】
更に、この実施の形態においては、発振回路のインピーダンスＺ1 に、センサＳと障害物Ｇで形成されるコイルＬとコンデンサＣのインピーダンスに加え、発振周波数を変化させることなく、発振レベルの変化に変換するものであるから、発振回路の周波数特性に左右されることなく、発振レベルの変化速度及び変化量の大きさによって障害物Ｇの検出ができる。
【００９３】
更にまた、この実施の形態においては、インピーダンスＺ1 に加える静電容量の変化は、並列共振回路のコイルに結合されている可変容量ダイオードＶＤによって行うものであるから、前記並列共振回路の相互インダクダンスとして設定でき回路設計の自由度が高くなる。
【００９４】
ところで、この実施の形態においては、インピーダンスＺ1 のコイルＬに可変容量ダイオードＶＤを並列接続し、機械的変位を使用することなく静電容量の変化を得ているが、本発明を実施する場合には、発振制御回路３の出力を可変コンデンサの可変出力、または、可変リアクタンスの可変出力とすることができる。
【００９５】
また、この実施の形態においては、障害物Ｇの接近に伴うこの入力インピーダンスの変化を、発振周波数を一定として発振レベルの変化として検出するとき、センサの入力インピーダンスの変化を図６では共振回路コイルの２次側に加えたが、図７のように中間タップに加えても同様に使用できる。
【００９６】
【発明の効果】
以上説明したように、請求項１の障害物検出装置は、障害物に接近すると、その入力インピーダンスが変化するセンサの入力インピーダンスの変化によって共振周波数を変化させるインピーダンスと他の２個のインピーダンスと共に形成する発振回路と、前記発振回路からの発振レベルの低下を検出して、発振制御回路で前記発振レベルの低下に対応して前記発振回路を形成するインピーダンスを変化させ、前記発振回路の発振周波数を所定の周波数領域内とし、所定の発振レベルが維持できるか否かで障害物の検出を行うものである。
【００９７】
したがって、アンテナとして機能するセンサの入力インピーダンスは、自由空間と異なる媒質が接近すると変化し、この入力インピーダンスの変化を、発振周波数を補償できる共振回路に加え、発振レベルの変化のみで障害物が検出できるものであるから、電圧レベルの単位時間当たりの変化量の大きさを判定し、障害物を検出することができる。故に、４０ｃｍ前後の障害物の検出距離が維持でき、簡単な回路で実現できる。
【００９８】
請求項２の障害物検出装置は、直列接続されたインピーダンスＺ2 及びインピーダンスＺ3 と、前記インピーダンスＺ2 及びインピーダンスＺ3 の両端子に接続されたインピーダンスＺ1 によって発振条件を定め、同じ極性とするインピーダンスＺ1 及びインピーダンスＺ3 の共振回路を有する発振回路を具備し、前記インピーダンスＺ3 を、共振周波数をｆ3 、回路のＱファクタをＱ3 とし、また、前記インピーダンスＺ1 を、共振周波数をｆ1 、回路のＱファクタをＱ1 とするとき、ｆ1 ＞ｆ3 で、かつ、Ｑ3 ＞Ｑ1 となるように、インピーダンスＺ3 は電気的機械振動子とし、インピーダンスＺ1 はコイルとコンデンサで形成し、前記発振回路の発振周波数を所定の周波数領域内とし、所定の発振レベルが維持できるか否かで障害物の検出を行うものである。
【００９９】
したがって、アンテナとして機能するセンサの入力インピーダンスは、自由空間と異なる媒質が接近すると変化し、この入力インピーダンスの変化を、発振周波数を補償できる共振回路に加え、発振レベルの変化のみで障害物が検出できるから、電圧レベルの単位時間当たりの変化量の大きさを判定し、障害物を検出することができる。故に、４０ｃｍ前後の障害物の検出距離が維持でき、簡単な回路で実現できる。
【０１００】
請求項３の障害物検出装置は、前記発振回路はその発振レベルが一定となるようインピーダンスＺ1 の誘導性と容量性の並列回路の各共振周波数の差を制御するものであるから、請求項２の効果に加えて、発振回路の発振周波数の制御及びそれによる発振レベルが既知となり、制御が容易になる。
【０１０１】
請求項４の障害物検出装置は、前記発振回路のインピーダンスＺ1 に、センサと障害物で形成される静電容量を加え、発振周波数を変化させることなく、発振レベルの変化に変換するものであるから、請求項２の効果に加えて、発振回路の周波数特性に左右されることなく、障害物検出ができる。
【０１０２】
請求項５の障害物検出装置は、前記インピーダンスＺ1 に加える静電容量の変化は、並列共振回路のコイルに結合されているものであるから、請求項２の効果に加えて、前記並列共振回路の相互インダクダンスとして設定でき回路設計の自由度が高くなる。
【０１０３】
請求項６の障害物検出装置は、前記センサと前記障害物とが所定以上接近したとき、前記障害物の検出状態を保持するものであるから、請求項１の効果に加えて、障害物検出装置の動作が確認でき、それ以上に接近させるような無理な移動には応答しなくなる。
【０１０４】
請求項７の障害物検出装置は、前記センサと前記障害物とが所定以上接近したとき、前記発振回路の発振を停止させ障害物の検出状態を保持するものであるから、請求項２乃至請求項５の何れか１つに記載の効果に加えて、障害物検出装置の動作が確認でき、それ以上に接近させるような無理な移動には応答しなくなり、かつ、その検出によって発振が停止し、無用な電力消費がなくなる。
【図面の簡単な説明】
【図１】 図１は本発明の第一実施形態の障害物検出装置を説明するための公知の発振回路の基本的原理説明図である。
【図２】 図２は本発明の第一実施形態の障害物検出装置を説明するためのハートレー型発振回路の基本的原理説明図である。
【図３】 図３は図２のインピーダンスＺ3 の等価回路図である。
【図４】 図４は図３の周波数とリアクタンスとの関係を示す特性図である。
【図５】 図５は本発明の第一実施形態の障害物検出装置の全体回路図である。
【図６】 図６は本発明の第二実施形態の障害物検出装置の全体回路図である。
【図７】 図７は本発明の第三実施形態の障害物検出装置の全体回路図である。
【図８】 図８は本発明の第四実施形態の障害物検出装置の全体回路図である。
【図９】 図９は第１の従来例の自動車の障害物検出装置の原理図である。
【図１０】 図１０は第２の従来例の自動車の障害物検出装置の原理図である。
【図１１】 図１１は第３の従来例の自動車の障害物検出装置の原理図である。
【符号の説明】
ＦＥＴ 電界効果型トランジスタ
Ｚ1 インピーダンス
Ｚ2 インピーダンス
Ｚ3 インピーダンス
ＣＯＭＰ 比較回路
ＣＯＭＰ２ 比較回路
ＯＰ オペアンプ
ＶＤ 可変容量ダイオード
Ｌ インダクタンス
Ｃ コンデンサ
１ 検波回路
２ 判定回路
３，３０ 発振制御回路[0001]
[Technical field to which the invention belongs]
The present invention relates to an obstacle detection apparatus for automobiles, and more particularly to an obstacle detection apparatus for detecting obstacles that obstruct the movement of automobiles such as people, objects, buildings, and metals using an antenna. It is.
[0002]
[Prior art]
Examples of conventional techniques for detecting obstacles in automobiles include techniques disclosed in Japanese Patent Application Laid-Open No. 58-115384, Japanese Patent Application Laid-Open No. 60-111983, Japanese Patent Application Laid-Open No. 3-233390, and US Pat. No. 3,698,814. be able to.
[0003]
All of the conventional techniques of this type relate to an obstacle detection device for automobiles, and the detection principle is summarized in FIGS.
[0004]
FIG. 9 is a diagram showing the principle of an obstacle detection device for automobiles disclosed in Japanese Patent Application Laid-Open No. 60-111983. FIG. 10 is a diagram showing the principle of an obstacle detection device for automobiles disclosed in Japanese Patent Application Laid-Open No. 59-115384. FIG. 11 is a diagram showing the principle of an obstacle detection device for automobiles disclosed in Japanese Patent Laid-Open No. 3-233390.
[0005]
In FIG. 9, the output of the oscillation circuit OSC is connected to a series circuit composed of a resistor R1 and a capacitor C1, and when the electrode plate A having the area So is used as a sensor, the electrode plate is determined by the presence or absence of the obstacle G and the distance Dw. An electrostatic capacitance (capacitor) C1 which is a stray capacitance between A and the obstacle G is formed. The capacitance C1 becomes the capacitor C1 constituting the above-described series circuit. The terminal voltage of the capacitor C1 changes due to the capacitance change of the capacitor C1, and the obstacle G is detected by this voltage change. Here, when stray capacitance or its capacitance is meant, it is described as capacitance, and when it has a constant meaning as a circuit element, it is described as a capacitor, but basically both have the same meaning.
[0006]
If the capacitance C1 generally formed is an area where the obstacle G approximates the electrode plate A of the sensor, the capacitance C1 is expressed by εo · εr · S / Dw. Where εo is the dielectric constant in vacuum and εr is the relative dielectric constant of the medium.
[0007]
However, the relative dielectric constant εr of the medium changes due to environmental conditions such as the weather, and the terminal voltage level of the capacitor C1 varies.
[0008]
Therefore, in the technique shown in FIG. 10, a series resistance consisting of a capacitance C2 and a resistance R2 that change under the same conditions is prepared for changes in the capacitance C1 due to environmental conditions. If the relative dielectric constant εr of the medium changes, the terminal voltage of the capacitor C2 also changes. Therefore, the output of the oscillation circuit OSC is connected to a bridge composed of a series circuit consisting of a resistor R1 and a capacitor C1, and a series circuit consisting of a resistor R2 and a capacitor C2 with air or the like interposed between electrodes as environmental conditions. Obstacles are detected by the potential difference.
[0009]
The technique shown in FIG. 11 is an example of performing another obstacle detection.
[0010]
In FIG. 11, an oscillation circuit OSC is configured with a plurality of capacitors C2, C3, C4 and a capacitance C1 determined by environmental conditions. Then, the oscillation frequency of the oscillation circuit OSC is frequency-voltage converted by the F / V conversion circuit F, and when the obstacle G approaches, the oscillation condition of the oscillation circuit OSC changes, and as a result, the oscillation frequency changes. This change is detected and the presence or absence of the obstacle G is detected.
[0011]
Further, the former detects the obstacle by determining the magnitude of the change amount, and if the automobile is left with the distance Dw being sufficiently small, the distance Dw is constant when the automobile is moved again, so that the capacitor C1 The obstacle G cannot be detected. Therefore, the voltage level immediately after the automobile is left is stored, and the magnitude of the change amount is determined from the level.
[0012]
[Problems to be solved by the invention]
9 and 10, when the distance Dw is "0", the capacitor C1 is infinite, the terminal voltage of the capacitor C1 is very small (infinitely small), and the obstacle G is present on the electrode plate A. In a close state, the terminal voltage will detect a very small level change.
[0013]
In order to detect such a minute level change, it is generally necessary to use an amplifier having a predetermined degree of amplification. However, when the distance Dw between the sensor electrode plate A and the obstacle G is infinite, the capacitor C1 becomes infinitely small, the terminal voltage of the capacitor C1 becomes very large, and the output of the amplifier is saturated. It is necessary to set a different value for the degree according to the value of the distance Dw. That is, a variable amplifier is required.
[0014]
Further, in the vehicle obstacle detection apparatus shown in FIG. 9 to FIG. 11, since the distance Dw is targeted for a close distance, in general, the detection is performed at a minute level, and signal processing at a minute level is performed. It is necessary to remove noise, and the number of parts of the circuit is inevitably increased.
[0015]
For example, in the conventional technique described above, the distance Dw cannot be set to 40 cm or more. In addition, the initial capacitance due to the size of the sensor increases the amount of coupling to the parallel resonant circuit, thereby reducing its detection accuracy, that is, reducing the resolution.
[0016]
On the other hand, in the technology of US Pat. No. 3,688,814, a loop antenna made of metal as a sensor is connected to the other end of a coil whose one end is grounded. On the other hand, a metal foil is installed at the upper end of the window frame that is controlled to move up and down by the motor, and the capacitance formed between the metal foil and the loop antenna is detected. . This type of technology cannot detect this capacitance unless it is in close proximity or contact. This is because the formed capacitance has a very small equivalent area compared to the electrode area for attachment. In addition, it is impossible to distinguish between environmental changes (temperature, humidity, etc.) and obstacle approach.
[0017]
In general, the oscillation condition of the oscillation circuit OSC needs to satisfy both the condition related to amplitude and the condition related to frequency. However, when the obstacle G approaches the electrode plate A, the frequency changes and the amplitude also changes. Further, when the two conditions cannot be satisfied, the oscillation is stopped.
[0018]
In particular, the technique of FIG. 11 uses an F / V conversion circuit F that changes a change in frequency to a voltage level. Generally, the F / V conversion circuit F corresponds to a change in frequency when the amplitude is constant. Although voltage output is obtained, if the amplitude and frequency change simultaneously, even if the distance Dw to the obstacle G is constant, the level of the obtained signal after F / V conversion is accompanied by fractionation. Judgment that considers uncertainty is required. Furthermore, it is necessary to remove frequency and amplitude changes due to the influence of environmental conditions such as temperature and humidity, and the influence of ambient conditions, that is, to eliminate the fractation caused by these influences from the voltage output after F / V conversion. It becomes. This type of response is possible with the current technology, but considering the mass productivity and cost, the value of the product will be poor if fields such as measuring instruments are excluded. Further, since the detection of the obstacle G immediately after the power is turned on is performed after the zero point correction, a delay time is involved.
[0019]
In this way, the value of the capacitance (capacitor C1) formed by the electrodes constituting the sensor and the obstacle and its change are generally very small, resulting in a detection distance on the order of several centimeters. If this capacitance is used as part of the oscillation constant of the oscillation circuit OSC, the oscillation frequency and amplitude both vary as the obstacle approaches, and the determination becomes complicated.
[0020]
Therefore, an object of the present invention is to provide an obstacle detection device that can detect an obstacle at a distance of about 40 cm and can realize it with a simple circuit.
[0021]
[Means for Solving the Problems]
The obstacle detection device according to claim 1 is formed together with a sensor whose input impedance changes when approaching an obstacle, an impedance which changes a resonance frequency by changing the input impedance of the sensor, and other two impedances. An oscillation circuit and a decrease in an oscillation level from the oscillation circuit are detected, an impedance forming the oscillation circuit is changed in response to the decrease in the oscillation level, and an oscillation frequency of the oscillation circuit is set within a predetermined frequency range. And an oscillation control circuit.
[0022]
The obstacle detection device according to claim 2 is configured such that an oscillation condition is determined by impedance Z2 and impedance Z3 connected in series and impedance Z1 connected to both terminals of the impedance Z2 and impedance Z3, and has the same polarity. In an obstacle detection apparatus having an oscillation circuit having a resonance circuit of impedance Z3, the impedance Z3 of the resonance circuit has a resonance frequency f3 and a Q factor of the circuit Q3, and the impedance Z1 of the resonance circuit is When the resonance frequency is f1 and the Q factor of the circuit is Q1, the impedance Z3 is an electromechanical vibrator and the impedance Z1 is formed by a coil and a capacitor so that f1> f3 and Q3> Q1. Is.
[0023]
The obstacle detection apparatus according to claim 3 controls the difference between the resonance frequency f3 of the impedance Z3 and the resonance frequency f1 of the impedance Z1 so that the oscillation level of the oscillation circuit is constant.
[0024]
According to a fourth aspect of the present invention, there is provided an obstacle detection device for adding an impedance of a capacitor formed by a sensor and an obstacle to the impedance Z1 of the oscillation circuit and converting it into a change in oscillation level without changing the oscillation frequency. is there.
[0025]
In the obstacle detection device according to the fifth aspect, the change in capacitance applied to the impedance Z1 is performed by a variable capacitance diode coupled to a coil of a parallel resonance circuit.
[0026]
The obstacle detection device according to a sixth aspect of the invention holds the detection state of the obstacle when the sensor and the obstacle are closer than a predetermined distance.
[0027]
According to a seventh aspect of the present invention, the obstacle detection device stops the oscillation of the oscillation circuit and holds the obstacle detection state when the sensor and the obstacle are approached by a predetermined distance or more.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
[0029]
FIG. 1 is a diagram illustrating the basic principle of a known oscillation circuit for explaining an obstacle detection device according to a first embodiment of the present invention. FIG. 1 (a) is an oscillation circuit diagram using an FET, and FIG. An oscillation circuit diagram using a transistor, (c) is an equivalent circuit diagram.
[0030]
Here, the principle will be described with the circuit using the FET shown in FIG. 4A, but the basic operation is the same for the transistor.
[0031]
The oscillation circuit shown in FIG. 1A includes an impedance Z2 connected between a drain D and a gate G of a field effect transistor (hereinafter simply referred to as “FET”), and a connection between a source S and a gate G of the FET. Oscillation conditions are determined by the impedance Z3 and the impedance Z1 connected between the terminals of the impedance Z2 and impedance Z3, that is, between the drain D and source S of the FET.
[0032]
As shown in FIG. 1C, this equivalent circuit can be expressed as an equivalent circuit using a mutual conductance gm and a drain resistance rd as a combination of the amplifier circuit A and the feedback circuit F. In order to clarify the principle, the grounded source type is used, the gate resistance RG is assumed to be sufficiently large and omitted from the equivalent circuit, and the impedances Z1, Z2, and Z3 are pure imaginary numbers.
[0033]
The oscillation condition at this time is obtained as follows.
[0034]

The left side of equation (1) is a real number and an amplitude condition, and the right side is an imaginary number and a frequency condition.
[0035]
rd · gm · Z1 · Z3 + Z1 · Z3 + Z1 · Z2 ≤ 0 (2)
Z1 + Z2 + Z3 = 0 (3)
Here, Expression (2) relates to amplitude, and Expression (3) is a condition corresponding to a change in frequency. It can be seen from equations (2) and (3) that the amplitude changes as the frequency changes. In general, impedance Z1 and Z3 are inductive, impedance Z2 is capacitive and Hartley type, and the opposite impedance Z1 and Z3 is capacitive and impedance Z2 is inductive is called Colpitts type. ing.
[0036]
When implementing the present invention, either the Hartley type or the Colpitts type can be used, but here, the explanation will be made in the case of the Hartley type.
[0037]
Further, the oscillation circuit using the transistor TR in FIG. 1B is also substantially the same in operation, and the description thereof is omitted.
[0038]
FIG. 2 is a diagram illustrating the basic principle of a Hartley oscillation circuit for explaining the obstacle detection device according to the first embodiment of the present invention. FIG. 3 is an equivalent circuit diagram of the impedance Z3 in FIG. 2, and FIG. 4 is a characteristic diagram showing the relationship between the frequency and reactance in FIG.
[0039]
In FIG. 2, a resistor RG is a resistor for DC bias of the gate G of the FET, a resistor Rs is a resistor for DC bias of the source S of the FET, and capacitors Cs and Cc are capacitors for bypassing. Therefore, the factors that determine the oscillation conditions are impedances Z1, Z2, and Z3. In this embodiment, the impedance Z2 is capacitive, that is, the capacitor Cdg, and the impedance Z3 is inductive consisting of a crystal resonator or the like. The impedance Z1 is formed by a resonance circuit composed of an inductive and capacitive inductance L and a capacitor C.
[0040]
As shown in the equivalent circuit of FIG. 3, the impedance Z3 is represented by a series circuit composed of a resistor R3, a capacitor C3 and a reactance L3, and a capacitor C0 connected in parallel to the circuit. The resonance frequency f3s of the series circuit composed of the resistor R3, the capacitor C3 and the reactance L3 is
f3s = 1 / 2π√ (L3 · C3)
The resonance frequency f3p of the parallel circuit is
f3s = 1 / 2π√ {(L3 · C3 · C0) / (C3 + C0)}
It becomes. That is, as shown by the solid line in FIG. 4, the inductivity is between the resonance frequency f3s and the resonance frequency f3p.
[0041]
Thus, it can be seen that if the reactance of the impedance Z1 indicated by the broken line in FIG. 5 is inductive, oscillation occurs between the frequency f3s and the frequency f3p. That is, if the resonance frequency f1 = 1 / 2π√ (L · C) of the impedance Z1 is adjusted to f1> f3p and f1> f3s, oscillation will occur.
[0042]
In general, the Q factor of an electromechanical vibrator is very large, and the resonance frequency f3p≈f3s. If this oscillation frequency f3, the oscillation frequency f1 of the oscillation circuit is f1> f3, the equation (3) is obtained. Satisfies and oscillates at the oscillation frequency f3 in the range of an arbitrary frequency difference Δf = f1−f3 satisfying the expression (2). That is, if the oscillation frequency is fixed, a change in the oscillation level can be detected. However, since the frequency difference Δf satisfying Expression (2) has a predetermined frequency range, the oscillation level does not become a constant value.
[0043]
Therefore, the resonance frequency f1 of the impedance Z1 constituting the resonance circuit is changed within a range satisfying the expression (3) of the frequency condition, that is, f1> f3, and the oscillation level V0 is always kept constant to change the oscillation level. Is detected and the obstacle G is detected when it is removed.
[0044]
FIG. 5 is an overall circuit diagram of the obstacle detection apparatus according to the first embodiment of the present invention.
[0045]
In FIG. 5, an impedance Z2 connected between the drain D and the gate G of the FET is a capacitor Cz2, an impedance Z3 consisting of a crystal resonator XTAL connected between the source S and the gate G of the FET, the impedance Z2 and the impedance. The oscillation condition is determined by the impedance Z1 connected between both terminals of Z3, that is, between the drain D and source S of the FET. These FET, impedance Z1, impedance Z2 and impedance Z3 constitute an oscillation circuit. The basic circuit configuration is the same as that of the circuit shown in FIG.
[0046]
The detection circuit 1 connected to the drain D side of the FET via the coupling capacitor C10 includes a diode D11, a diode D12, a resistor R11, and a capacitor C11. The voltage applied to the resistor R11 is passed through the diode D12. The capacitor C11 is charged. By this circuit, the oscillation level is converted into a DC voltage V 0 by the detection circuit 1 and transmitted to the determination circuit 2 and the oscillation control circuit 3.
[0047]
The determination circuit 2 applies a voltage supplied from the constant voltage power source Vcc to one of the resistors R21 and R22 connected in series and inputs a predetermined divided threshold voltage VT1, and the other is obtained by the detection circuit 1 to the other. The DC voltage V0 is input, and both are compared by the comparison circuit COMP. When the DC voltage V0 obtained by the detection circuit 1 is larger than the threshold voltage VT1, the output of the comparison circuit COMP is "L". When the DC voltage V0 is smaller than the threshold voltage VT1, the output of the comparison circuit COMP is "H". " The threshold voltage VT1 in the normal state is smaller than the DC voltage V0, and the output of the comparison circuit COMP is “L”.
[0048]
In the oscillation control circuit 3, the voltage supplied from the constant voltage power source Vcc is applied to the resistors R31 and R32 connected in series, and a predetermined divided threshold voltage V1 is input. The input DC voltage V0 is input through the input resistor R30, and as the output V2, V2 = V1 -V0 is obtained as the output of the operational amplifier OP, which is applied to the variable capacitance diode VD through the output resistors R33 and R35. The The connection point between the resistors R33 and R35 at the output of the operational amplifier OP is connected to the constant voltage power source Vcc by a parallel circuit of the resistor R34 and the capacitor C31, and the diode D31 is connected between the ground and the operational amplifier OP. The output of is not negative, and the rate of change is increased. The control voltage V2 is generated by the operational amplifier OP set to the threshold voltage V1 so that the DC voltage V0 obtained by the detection circuit 1 becomes equal to the threshold voltage V1. The control voltage V2 is applied to the variable capacitance diode VD connected to the impedance Z1, and the resonance frequency f1 of the impedance Z1 is controlled to be a constant value of V2 = V0.
[0049]
The impedance Z1 is a resonance circuit composed of an inductance L and a capacitance C. The inductance L is constituted by a mutual inductance having a winding ratio of 1: n. A capacitor C is connected to the winding ratio 1 side of the inductance L. A series circuit of a capacitor Cz1 and a variable capacitance diode VD is connected to the winding ratio n side of the inductance L. A sensor S made of a plate material or a wire material is disposed at a connection point between the winding ratio n side of the inductance L and the capacitor Cz1.
[0050]
Next, the operation of the obstacle detection device of this embodiment will be described.
[0051]
First, when approaching an obstacle G such as a person, a building, or a metal, the median constant around it changes, the input impedance of the sensor S functioning as an antenna changes, and this changes the capacitance, resulting in an impedance Z1. In addition, the resonance frequency f of the oscillation circuit changes, the DC voltage V0 obtained by the detection circuit 1 also decreases, and the obstacle G is continuously detected. Here, the oscillation control circuit 3 compares the DC voltage V0 with a predetermined threshold voltage V1, and changes the output V2 of the operational amplifier OP in order to obtain the DC voltage V0 obtained by the original detection circuit 1, and the output V2 The change is applied to the variable capacitance diode VD, and the resonance frequency f of the impedance Z1 is controlled to be a constant value. In this way, by causing the change in the predetermined threshold voltage V1 to respond only to the change in the environment and making the oscillation frequency f of the oscillation circuit constant, the oscillation level becomes constant. Thereby, the change in which the capacitance of the sensor S does not contribute to the obstacle G such as a change with time can be automatically corrected. Further, the initial capacitance resulting from the size of the sensor S can be arbitrarily set by varying the amount of coupling to the parallel resonant circuit.
[0052]
Further, when the sensor S and the obstacle G are stopped at a close position, the DC voltage V0 obtained by the detection circuit 1 decreases and the obstacle G is continuously detected. However, the decrease in the DC voltage V0 obtained by the detection circuit 1 is the same phenomenon as the environmental change. Therefore, the output V2 of the operational amplifier OP is changed so that the DC voltage V0 obtained by the detection circuit 1 is equal to the predetermined threshold voltage V1. As a result, the DC voltage V0 obtained by the detection circuit 1 gradually becomes equal to the predetermined threshold voltage V1, so that it is regarded that there is no obstacle G. As a result, when the vehicle stops at a position close to the obstacle G, the obstacle G is not detected as time passes, and the state becomes an initial state as an environmental state.
[0053]
On the other hand, when the obstacle G approaches a predetermined value or more, the impedance of the sensor S functioning as an antenna changes, and as a result, it changes in capacitance and is added to the impedance Z1, and the resonance frequency f of the oscillation circuit is changed. The frequency condition formula (3) is not satisfied and oscillation stops. As a result, the DC voltage V0 obtained by the detection circuit 1 also decreases, the DC voltage V0 becomes smaller than the threshold voltage VT1 of the comparison circuit COMP, the output of the comparison circuit COMP becomes “H”, and the obstacle G is more than a predetermined value. An approach is detected.
[0054]
Further, when the input impedance of the sensor S changes, the change is added to the impedance Z1, and the resonance frequency f of the oscillation circuit fluctuates faster than when it approaches the obstacle G, the detection circuit 1 obtained. The DC voltage V0 decreases, the DC voltage V0 becomes smaller than the threshold voltage VT1 of the comparison circuit COMP, the output of the comparison circuit COMP becomes "H", and the obstacle G is detected.
[0055]
In this embodiment, when the vehicle stops at a position close to the obstacle G, the obstacle G is not detected as time passes, and the state is determined as an environmental state. You can also remember it.
[0056]
FIG. 6 is an overall circuit diagram of the obstacle detection apparatus according to the second embodiment of the present invention.
[0057]
In the figure, the same reference numerals and symbols as those in the first embodiment denote the same or corresponding components as those in the first embodiment, and therefore, duplicate description is omitted here.
[0058]
In FIG. 6, the impedance Z1 is a resonance circuit composed of an inductance L and a capacitance C. As the inductance L, one coil is connected to a terminal at a winding ratio of 1: n, and the inductance Lz10 and the inductance L It is composed of a single-winding coil made of Lz11. A terminal extracted from the inductance L is connected to a series circuit of a capacitor Cz1 and a variable capacitance diode VD. A sensor S made of a plate or wire is disposed at the connection point between the terminal of the inductance L and the capacitor Cz1, and the connection point of the oscillation control circuit 3 is connected to the connection point between the capacitor Cz1 and the variable capacitance diode VD. The output V2 of the operational amplifier OP is input.
[0059]
Since the operation of this circuit is basically the same as that of the first embodiment, the description thereof is omitted.
[0060]
FIG. 7 is an overall circuit diagram of the obstacle detection apparatus according to the third embodiment of the present invention.
[0061]
In the drawings, the same reference numerals and symbols as those in the above embodiment indicate the same or corresponding components as those in the above embodiment, and therefore, duplicate description is omitted here.
[0062]
In FIG. 7, a determination circuit 2 receives a predetermined threshold voltage VT1 on one side and a DC voltage V0 obtained by the detection circuit 1 on the other side, and compares them with a comparison circuit COMP. When the DC voltage V0 obtained by the detection circuit 1 is large, the output of the comparison circuit COMP is "L", and when the DC voltage V0 is smaller than the threshold voltage VT1, the output of the comparison circuit COMP is "H". The threshold voltage VT1 in the normal state is smaller than the DC voltage V0, and the output of the comparison circuit COMP is “L”.
[0063]
In the n-bit up / down counter 10, the output of the comparison circuit COMP is preset to “L”. The clock input is input via an AND gate that is opened and closed by the clock start / stop of the counter control logic 13, and the output of the oscillation circuit is used via a waveform shaping circuit (not shown). The n-bit up / down counter 10 receives from the counter control circuit 13 a counter control signal serving as an addition or subtraction command and an enable signal for operating the n-bit up / down counter 10. In this embodiment, the clock signal input of the AND gate uses the signal of its own oscillation circuit. However, when the present invention is implemented, the clock signal may be input from another clock generator. Good.
[0064]
The D / A conversion circuit 11 receives the counter output of the n-bit up / down counter 10 and outputs an analog output V01.
[0065]
The output control circuit 12 receives the DC voltage V0 obtained by the detection circuit 1 and the analog output V01 from the D / A conversion circuit 11, and compensates for the output difference V0-V01. In addition to the variable capacitance diode VD, the resonance frequency f of the impedance Z1 is controlled to be a constant value.
[0066]
On the other hand, the DC voltage V0 obtained by the detection circuit 1 and the analog output V01 from the D / A conversion circuit 11 are input to the counter control circuit 13, and an n-bit up / down counter is obtained depending on the polarity of the output difference V0-V01. 10 determines whether the counter output increases or decreases, outputs an enable signal for operating the n-bit up / down counter 10 when the magnitude of the output difference V0-V01 exceeds a predetermined range, and AND gate Is used as a clock signal for the n-bit up / down counter 10 from an oscillation circuit composed of impedances Z1, Z2, and Z3 through a waveform shaping circuit (not shown).
[0067]
Here, the n-bit up / down counter 10, the D / A conversion circuit 11, the output control circuit 12, and the counter control circuit 13 constitute an oscillation control circuit 30.
[0068]
Next, the operation of the obstacle detection device of this embodiment will be described.
[0069]
First, when approaching an obstacle G, such as a person, a building, or a metal, and the environmental conditions gradually change, the input impedance of the sensor S changes, which is changed in capacitance and added to the impedance Z1, and the oscillation circuit The resonance frequency f changes, the DC voltage V0 obtained by the detection circuit 1 decreases, and the obstacle G is detected. Here, the output control circuit 12 compares the DC voltage V0 with the predetermined threshold voltage V01 from the D / A conversion circuit 11, and in order to obtain the DC voltage V0 obtained by the original detection circuit 1, the output control circuit 12 The output V2 is changed, and the change of the output V2 is applied to the variable capacitance diode VD, and the resonance frequency f of the impedance Z1 is controlled to be a constant value. Naturally, the oscillation frequency f is constant and the oscillation level is also constant. Even if the sensor S and the obstacle G are stopped at a predetermined close position, the DC voltage V0 obtained by the detection circuit 1 is lowered, the obstacle G is detected, and the state corrected as an environmental change is detected. maintain. Thereby, the change in which the capacitance of the sensor S does not contribute to the obstacle G such as a change with time can be automatically corrected. Further, the initial capacitance resulting from the size of the sensor S can be arbitrarily set by varying the amount of coupling to the parallel resonant circuit.
[0070]
However, when the obstacle G approaches a predetermined value or more, the input impedance of the sensor S changes, and as a result, the capacitance is changed and added to the impedance Z1, the resonance frequency f of the oscillation circuit changes, and the frequency condition is satisfied. The oscillation stops and the oscillation level drops rapidly. As a result, the DC voltage V0 obtained by the detection circuit 1 also decreases, the DC voltage V0 becomes smaller than the threshold voltage VT1 of the comparison circuit COMP constituting the determination circuit 2, and the output of the comparison circuit COMP becomes “H”. The obstacle G is detected.
[0071]
At the same time, the n-bit up / down counter 10 is preset, the DC voltage V0 obtained by the detection circuit 1 and the analog output V01 from the D / A conversion circuit 11 are input to the counter control circuit 13, and the output difference V0 -V01 The increase / decrease of the counter output of the n-bit up / down counter 10 is determined by the polarity of the n-bit up / down counter 10, and when the magnitude of the absolute value of the output difference V0-V01 is equal to or greater than a predetermined range, the n-bit up / down counter 10 is put into an operating state. The enable signal is output, the AND gate is opened, and the clock signal of the n-bit up / down counter 10 is generated from an oscillation circuit composed of impedances Z1, Z2, and Z3 through a waveform shaping circuit (not shown). The n-bit up / down counter 10 counts based on the output difference V0-V01, the count value of the n-bit up / down counter 10 is converted into an analog value by the D / A conversion circuit 11, and the output difference V0-V01 is a predetermined value. The n-bit up / down counter 10 counts up to a value below the value, and the count value of the n-bit up / down counter 10 is converted into an analog value by the D / A conversion circuit 11, and a predetermined output difference V0-V01, For example, when V0-V01 becomes substantially zero, the control by the n-bit up / down counter 10 is stopped.
[0072]
In this state, for example, when V0> V01, the oscillation circuit continues to oscillate again at the oscillation frequency f, during which the n-bit up / down counter 10 is preset and the n-bit up / down counter 10 is set to the initial value. Return.
[0073]
However, in this state, for example, when V0> V01 is not satisfied, the oscillation circuit cannot oscillate at the oscillation frequency f, the n-bit up / down counter 10 is stopped, and a detection state in which the sensor S and the obstacle G approach each other is detected. maintain. That is, the obstacle detection state in which the sensor S and the obstacle G are close to each other is maintained.
[0074]
In this embodiment, the n-bit up / down counter 10 is used to increase the accuracy of the analog output V01 from the D / A conversion circuit 11. However, when the present invention is implemented, it can be set to the minimum counter value. However, in this case, the circuit can be simplified.
[0075]
FIG. 8 is an overall circuit diagram of the obstacle detection apparatus according to the fourth embodiment of the present invention.
[0076]
In the drawings, the same reference numerals and symbols as those in the above embodiment indicate the same or corresponding components as those in the above embodiment, and therefore, duplicate description is omitted here.
[0077]
In FIG. 8, a determination circuit 2 receives a predetermined threshold voltage VT1 on one side and a DC voltage V0 obtained by the detection circuit 1 on the other side, and compares them with a comparison circuit COMP. From the threshold voltage VT1 When the DC voltage V0 obtained by the detection circuit 1 is large, the output of the comparison circuit COMP is "L", and when the DC voltage V0 is smaller than the threshold voltage VT1, the output of the comparison circuit COMP is "H". The threshold voltage VT1 in the normal state is smaller than the DC voltage V0, and the output of the comparison circuit COMP is “L”.
[0078]
The latch circuit 20 is reset by the output of the comparison circuit COMP being “L”. The latch circuit 20 switches the selection circuit 21 by the set or reset. The set signal of the latch circuit 20 is inputted with a predetermined threshold voltage VT2 on one side and the DC voltage V0 obtained by the detection circuit 1 on the other side, compared with the comparator circuit COMP2, and compared with the threshold voltage VT2. When the DC voltage V0 obtained by the detection circuit 1 is small, the output of the comparison circuit COMP2 is "L" and becomes a set signal. When the DC voltage V0 is larger than the threshold voltage VT2, the output of the comparison circuit COMP2 is "H". Become. The threshold voltage VT2 in the normal state is larger than the DC voltage V0, and the output of the comparison circuit COMP is “L”. Here, the relationship between the DC voltage V0 obtained by the detection circuit 1, the threshold voltage VT1, and the threshold voltage VT2 is V0>VT1> VT2.
[0079]
When the latch circuit 20 is in the reset state, the selection circuit 21 uses the output as the output V02, and when the latch circuit 20 is in the set state, the output serves as the output V03 as an input to the output control circuit 22. Here, the relationship between the DC voltage V0 obtained by the detection circuit 1, the threshold voltage VT1, the threshold voltage VT2, and the relationship between the outputs of the selection circuit 21 is V02>VT1>V03> VT2.
[0080]
The output control circuit 22 receives the DC voltage V0 obtained by the detection circuit 1 and the output V02 or the output V03 of the selection circuit 21, and compensates for the output difference V0 -V02 or the output difference V0 -V03. Is added to the variable capacitance diode VD via the resistor R35, and the resonance frequency f of the impedance Z1 is controlled to be a constant value.
[0081]
When there is no obstacle G or when the influence is small, the latch circuit 20 is in the reset state, the input of the output control circuit 22 is the output V02 of the selection circuit 21, and the DC voltage V0 obtained by the detection circuit 1 is The relationship between the DC voltage V0 obtained by the detection circuit 1, the threshold voltage VT1, the threshold voltage VT2, and the relationship between the outputs of the selection circuit 21 is V0≈V02>VT1>V03> VT2.
[0082]
First, when approaching an obstacle G, such as a person, a building, or a metal, and the environmental conditions gradually change, the input impedance of the sensor S changes, which is changed in capacitance and added to the impedance Z1, and the oscillation circuit The resonance frequency f changes, the DC voltage V0 obtained by the detection circuit 1 decreases, and the obstacle G is detected. Here, the output control circuit 22 compares the DC voltage V0 with the predetermined threshold voltage V02 from the selection circuit 21, and sets the output V2 of the output control circuit 22 to obtain the DC voltage V0 obtained by the original detection circuit 1. The change in the output V2 is applied to the variable capacitance diode VD, and the resonance frequency f of the impedance Z1 is controlled to be a constant value. Thus, the oscillation frequency f is constant and the oscillation level is also constant. Even if the sensor S and the obstacle G are stopped at a predetermined close position, the DC voltage V0 obtained by the detection circuit 1 is lowered, the obstacle G is detected, and the state corrected as an environmental change is detected. maintain. Thereby, the change in which the capacitance of the sensor S does not contribute to the obstacle G such as a change with time can be automatically corrected. Further, the initial capacitance resulting from the size of the sensor S can be arbitrarily set by varying the amount of coupling to the parallel resonant circuit.
[0083]
However, when the obstacle G approaches a predetermined value or more, the input impedance of the sensor S changes, and as a result, the capacitance is changed and added to the impedance Z1, the resonance frequency f of the oscillation circuit changes, and the frequency condition is satisfied. The oscillation stops and the oscillation level drops rapidly. As a result, the DC voltage V0 obtained by the detection circuit 1 also decreases, the DC voltage V0 becomes smaller than the threshold voltage VT1 of the comparison circuit COMP constituting the determination circuit 2, and the output of the comparison circuit COMP becomes “H”. The obstacle G is detected.
[0084]
Further, when the oscillation level is lowered and the DC voltage V0 becomes smaller than the threshold voltage VT2 of the comparison circuit COMP2, the output of the comparison circuit COMP2 becomes "L", the latch circuit 20 is set, and the output from the selection circuit 21 is set by the output. The output is switched to the output V03, and the DC voltage V0 obtained by the detection circuit 1 and the output V03 from the selection circuit 21 are input to the output control circuit 22, and the output V2 is obtained by the output difference V0-V03. The change in the output V2 is applied to the variable capacitance diode VD, and the resonance frequency f of the impedance Z1 is controlled to be a constant value. When a predetermined output difference V0-V03, for example, V0-V03 becomes substantially zero, the oscillation circuit continues to oscillate again at the oscillation frequency f, and maintains a detection state in which the sensor S and the obstacle G are close to each other. That is, the obstacle detection state in which the sensor S and the obstacle G are close to each other is maintained. However, in this state, for example, when the DC voltage V0 becomes larger than the threshold voltage VT1 of the comparison circuit COMP, the latch circuit 20 is reset and returns to the initial value.
[0085]
However, in this state, for example, when V0-V01 does not become substantially zero, the oscillation circuit cannot oscillate at the oscillation frequency f, the latch circuit 20 maintains the reset state, and the detection state in which the sensor S and the obstacle G approach each other. To maintain. That is, the obstacle detection state in which the sensor S and the obstacle G are close to each other is maintained.
[0086]
As described above, in the obstacle detection device according to the present embodiment, when the obstacle G approaches the obstacle G, the median constant around the sensor S as the antenna of the oscillation circuit changes, and the resonance frequency changes due to the change in the input impedance of the sensor S. The oscillation circuit formed together with the impedance Z1 to be generated and the other two impedances Z2 and Z3, and a decrease in the oscillation level from the oscillation circuit is detected by the determination circuit 2, and the oscillation control circuit 3 responds to the decrease in the oscillation level. Then, the impedance forming the oscillation circuit is changed, the oscillation frequency of the oscillation circuit 3 is set within a predetermined frequency region, and the obstacle G is detected based on whether or not the predetermined oscillation level can be maintained. This can be the embodiment corresponding to the claims.
[0087]
Accordingly, the input impedance of the sensor S functioning as an antenna changes when a medium different from the free space approaches, and this change in input impedance is added to the resonance circuit composed of the capacitor Cz1 and variable capacitance diode VD capable of compensating the oscillation frequency, Since the obstacle G can be detected only by the change of the oscillation level, the magnitude of the change amount of the voltage level per unit time can be determined and the obstacle G can be detected. Or the fall of the predetermined amount of a voltage level can be determined and the obstruction G can be detected. According to the experiments by the present inventors, since the detection is performed by the change in impedance of the sensor S functioning as an antenna, the detection distance of the obstacle G around 40 cm can be maintained, and this can be realized with a simple circuit. Then, a change in the case where the capacity of the sensor S is not a contribution of an obstacle such as a change over time can be automatically corrected. The initial capacity resulting from the size of the sensor S can be arbitrarily set by varying the amount of coupling to the parallel resonant circuit.
[0088]
In this embodiment, the oscillation conditions are determined by the impedance Z2 and impedance Z3 connected in series and the impedance Z1 connected to both terminals of the impedance Z2 and impedance Z3, and the impedance Z1 and impedance Z3 have the same polarity. When the resonance frequency f3 and the circuit Q factor are Q3, and the impedance Z1 is the resonance frequency f1 and the circuit Q factor Q1. , F1> f3 and Q3> Q1, the impedance Z3 is an electromechanical vibrator, the impedance Z1 is formed of a coil and a capacitor, and the oscillation frequency of the oscillation circuit is within a predetermined frequency range. The obstacle G is detected based on whether or not the predetermined oscillation level can be maintained. A Umono may be the embodiment corresponding to this claim.
[0089]
In other words, when the impedance Z3 of the resonant circuit is the resonant frequency f3, the Q factor of the circuit is Q3, the impedance Z1 is the resonant frequency f1, and the Q factor of the circuit is Q1, the frequency is adjusted by setting f1> f3. By giving the width of the region, widening the adjustment range, and satisfying Q3> Q1, the change in Q1 is reduced even if the frequency f1 is changed. Naturally, Q3 >> Q1 is suitable as the Q factor of the circuit that reduces the change of Q1 even if the frequency f1 is changed.
[0090]
Therefore, the input impedance of the sensor that functions as an antenna changes when a medium different from the free space approaches, and this change in input impedance is added to the resonance circuit that can compensate for the oscillation frequency, and the obstacle G is changed only by the change in the oscillation level. Since it can be detected, the magnitude of the change amount of the voltage level per unit time can be determined, and the obstacle G can be detected. Therefore, since the detection is performed by the change in impedance of the sensor S functioning as an antenna, the detection distance of the obstacle G around 40 cm can be maintained, and this can be realized with a simple circuit. Then, a change in the case where the capacity of the sensor S is not a contribution of an obstacle such as a change over time can be automatically corrected. The initial capacity resulting from the size of the sensor S can be arbitrarily set by varying the amount of coupling to the parallel resonant circuit.
[0091]
In this embodiment, the difference in resonance frequency between the resonance frequency f3 of the impedance Z3 and the resonance frequency f1 of the impedance Z1 is controlled so that the oscillation level of the oscillation circuit is constant. In this embodiment, the oscillation frequency of the oscillation circuit can be controlled and the oscillation level thereby can be known, and the oscillation control of the oscillation circuit can be facilitated.
[0092]
Further, in this embodiment, the impedance Z1 of the oscillation circuit is converted into a change in the oscillation level without changing the oscillation frequency in addition to the impedance of the coil L and the capacitor C formed by the sensor S and the obstacle G. Therefore, the obstacle G can be detected by the change speed of the oscillation level and the magnitude of the change without depending on the frequency characteristics of the oscillation circuit.
[0093]
Furthermore, in this embodiment, since the change in the capacitance applied to the impedance Z1 is performed by the variable capacitance diode VD coupled to the coil of the parallel resonance circuit, the mutual inductance of the parallel resonance circuit is changed. The degree of freedom in circuit design is increased.
[0094]
By the way, in this embodiment, the variable capacitance diode VD is connected in parallel to the coil L having the impedance Z1, and the change in capacitance is obtained without using mechanical displacement. The output of the oscillation control circuit 3 can be a variable output of a variable capacitor or a variable output of a variable reactance.
[0095]
Further, in this embodiment, when the change in the input impedance accompanying the approach of the obstacle G is detected as a change in the oscillation level with the oscillation frequency being constant, the change in the input impedance of the sensor is shown in FIG. However, it can be used in the same manner even if it is added to the intermediate tap as shown in FIG.
[0096]
【The invention's effect】
As described above, the obstacle detection device according to claim 1 is formed together with the impedance that changes the resonance frequency by the change of the input impedance of the sensor that changes its input impedance when approaching the obstacle and the other two impedances. An oscillation circuit that detects a decrease in the oscillation level from the oscillation circuit, and an oscillation control circuit changes an impedance that forms the oscillation circuit in response to the decrease in the oscillation level, and sets an oscillation frequency of the oscillation circuit. An obstacle is detected depending on whether or not a predetermined oscillation level can be maintained within a predetermined frequency range.
[0097]
Therefore, the input impedance of the sensor functioning as an antenna changes when a medium different from the free space approaches, and this change in input impedance is added to the resonance circuit that can compensate for the oscillation frequency, and obstacles are detected only by the change in the oscillation level. Since it is possible, the magnitude of the change amount of the voltage level per unit time can be determined to detect the obstacle. Therefore, the obstacle detection distance of about 40 cm can be maintained, which can be realized with a simple circuit.
[0098]
The obstacle detection device according to claim 2 determines an oscillation condition by impedance Z2 and impedance Z3 connected in series and impedance Z1 connected to both terminals of the impedance Z2 and impedance Z3, and impedance Z1 and impedance having the same polarity. An oscillation circuit having a resonance circuit of Z3, wherein the impedance Z3 is a resonance frequency f3, a circuit Q factor is Q3, the impedance Z1 is a resonance frequency f1, and a circuit Q factor is Q1. Then, so that f1> f3 and Q3> Q1, the impedance Z3 is an electromechanical oscillator, the impedance Z1 is formed by a coil and a capacitor, and the oscillation frequency of the oscillation circuit is within a predetermined frequency range. Detect obstacles based on whether or not the predetermined oscillation level can be maintained It is.
[0099]
Therefore, the input impedance of the sensor functioning as an antenna changes when a medium different from the free space approaches, and this change in input impedance is added to the resonance circuit that can compensate for the oscillation frequency, and obstacles are detected only by the change in the oscillation level. Therefore, it is possible to detect the obstacle by determining the magnitude of the change amount of the voltage level per unit time. Therefore, the obstacle detection distance of about 40 cm can be maintained, which can be realized with a simple circuit.
[0100]
The obstacle detection device according to claim 3 controls the difference between the resonance frequencies of the inductive impedance Z1 and the capacitive parallel circuit so that the oscillation level of the oscillation circuit is constant. In addition to the above effect, the control of the oscillation frequency of the oscillation circuit and the oscillation level thereby become known, and the control becomes easy.
[0101]
The obstacle detection device according to claim 4 converts the impedance Z1 of the oscillation circuit into a change in oscillation level without changing the oscillation frequency by adding a capacitance formed by a sensor and an obstacle. Therefore, in addition to the effect of the second aspect, the obstacle can be detected without being influenced by the frequency characteristic of the oscillation circuit.
[0102]
In the obstacle detection device according to claim 5, since the change in capacitance applied to the impedance Z1 is coupled to the coil of the parallel resonance circuit, in addition to the effect of claim 2, the parallel resonance circuit The degree of freedom in circuit design is high.
[0103]
The obstacle detection device according to the sixth aspect maintains the detection state of the obstacle when the sensor and the obstacle approach each other more than a predetermined distance. The operation of the device can be confirmed, and it will not respond to an unreasonable movement that brings it closer.
[0104]
The obstacle detection device according to a seventh aspect stops the oscillation of the oscillation circuit and maintains an obstacle detection state when the sensor and the obstacle approach each other more than a predetermined distance. In addition to the effect described in any one of items 5, the operation of the obstacle detection device can be confirmed, and it does not respond to an unreasonable movement that approaches the obstacle detection device, and the oscillation stops by the detection. Eliminate unnecessary power consumption.
[Brief description of the drawings]
FIG. 1 is a basic principle explanatory diagram of a known oscillation circuit for explaining an obstacle detection apparatus according to a first embodiment of the present invention.
FIG. 2 is a basic principle explanatory diagram of a Hartley oscillation circuit for explaining the obstacle detection device of the first embodiment of the present invention.
FIG. 3 is an equivalent circuit diagram of the impedance Z3 in FIG.
FIG. 4 is a characteristic diagram showing a relationship between the frequency and reactance in FIG. 3;
FIG. 5 is an overall circuit diagram of the obstacle detection apparatus according to the first embodiment of the present invention.
FIG. 6 is an overall circuit diagram of an obstacle detection apparatus according to a second embodiment of the present invention.
FIG. 7 is an overall circuit diagram of an obstacle detection apparatus according to a third embodiment of the present invention.
FIG. 8 is an overall circuit diagram of an obstacle detection apparatus according to a fourth embodiment of the present invention.
FIG. 9 is a diagram illustrating the principle of an obstacle detection device for an automobile according to a first conventional example.
FIG. 10 is a diagram illustrating the principle of an obstacle detection device for a vehicle according to a second conventional example.
FIG. 11 is a diagram illustrating the principle of a third conventional example of an obstacle detection device for an automobile.
[Explanation of symbols]
FET Field Effect Transistor
Z1 impedance
Z2 impedance
Z3 impedance
COMP comparison circuit
COMP2 comparison circuit
OP operational amplifier
VD variable capacitance diode
L Inductance
C capacitor
1 Detection circuit
2 Judgment circuit
3,30 Oscillation control circuit

Claims (7)

A sensor whose input impedance changes when approaching an obstacle,
An oscillation circuit formed together with an impedance for changing a resonance frequency according to a change in an input impedance of the sensor and two other impedances;
Oscillation control that detects a decrease in the oscillation level from the oscillation circuit, changes the impedance that forms the oscillation circuit in response to the decrease in the oscillation level, and sets the oscillation frequency of the oscillation circuit within a predetermined frequency range An obstacle detection device comprising a circuit. An oscillation circuit having a resonance circuit of impedance Z1 and impedance Z3 having the same polarity, wherein the oscillation conditions are determined by impedance Z2 and impedance Z3 connected in series and impedance Z1 connected to both terminals of the impedance Z2 and impedance Z3. In the obstacle detection device to
The impedance Z3 of the resonance circuit has a resonance frequency f3 and the Q factor of the circuit Q3, and the impedance Z1 of the resonance circuit has a resonance frequency f1 and the circuit Q factor Q1 when f1> An obstacle detection device characterized in that the impedance Z3 is an electromechanical vibrator and the impedance Z1 is formed of a coil and a capacitor so that f3 and Q3> Q1. 3. The obstacle detection apparatus according to claim 2, wherein the difference between the resonance frequency f3 of the impedance Z3 and the resonance frequency f1 of the impedance Z1 is controlled so that the oscillation level of the oscillation circuit is constant. 3. The obstacle according to claim 2, wherein an impedance of a capacitor formed by a sensor and an obstacle is added to the impedance Z1 of the oscillation circuit to convert the oscillation frequency into a change in oscillation level without changing the oscillation frequency. Detection device. 3. The obstacle detection apparatus according to claim 2, wherein the change in capacitance applied to the impedance Z1 is performed by a variable capacitance diode coupled to a coil of a parallel resonance circuit. The obstacle detection device according to claim 1, wherein the obstacle detection state is maintained when the sensor and the obstacle are approached by a predetermined distance or more. The oscillation state of the oscillation circuit is stopped and the detection state of the obstacle is held when the sensor and the obstacle approach each other by a predetermined amount or more. Obstacle detection device.

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