JP3804281B2

JP3804281B2 - Ultrasonic sensor device

Info

Publication number: JP3804281B2
Application number: JP21128198A
Authority: JP
Inventors: 真武宇野; 俊昌高木; 悟朗小田
Original assignee: Matsushita Electric Works Ltd
Current assignee: Panasonic Electric Works Co Ltd
Priority date: 1998-07-27
Filing date: 1998-07-27
Publication date: 2006-08-02
Anticipated expiration: 2018-07-27
Also published as: JP2000046945A

Description

【０００１】
【発明の属する技術分野】
本発明は超音波パルス波を送波するとともに障害物からの反射波を受波して障害物の有無を検出する超音波センサ装置に関する。
【０００２】
【従来の技術】
図６は従来の超音波センサ装置を示すブロック図である。図７は従来の超音波センサ装置の動作を説明するタイミングチャートであり、図７（ａ）は送波信号、図７（ｂ）は受波信号、図７（ｃ）は検波信号、図７（ｄ）は検知ゲート信号、図７（ｅ）は検波信号と検知ゲート信号との論理積信号、図７（ｆ）は時間軸である。図８は超音波センサ装置の検知エリアを示す説明図である。
【０００３】
従来の超音波センサ装置１は、図６に示すように、基準信号発生回路２と、発振回路３と、送受波器４と、検知回路５と、信号処理部６と、表示部７とを備える。基準信号発生回路２は、パルス状の超音波の送波間隔を設定するための基準信号を発生する。発振回路３は、前記基準信号に基づいた送波間隔で所定周波数の電気振動を間欠的に発生する。送受波器４は、発振回路３の出力を超音波に変換して空中へ送波するとともに、障害物Ａからの反射波を受波する。検知回路５は、送受波器４の出力から障害物Ａからの反射波による信号成分を取り出し、障害物Ａの反射波が予め設定された所定時間範囲Ｔ_c内で、且つ予め設定された閾値レベルＴ_h0より大きいか否か検出する。信号処理部６は、検知回路５の出力から検知エリア内に障害物Ａが存在するか否かを判断する。表示部７は、信号処理部６が検知エリア内に障害物Ａが存在すると判断したときにその旨の表示を行う。
【０００４】
検知回路５は受波回路５ａと検知ゲート回路５ｂとゲート制御回路５ｃとを備える。受波回路５ａは、送受波器４の出力する受波信号が閾値レベルＴ_h0より大きい場合にのみHighになる検波信号を出力する。検知ゲート回路５ｂは、受波回路５ａの出力する検波信号のうち、所定時間範囲Ｔ_c内の検波信号のみを通過させる。ゲート制御回路５ｃは、基準信号発生回路２の出力に基づいて、検知ゲート回路５ｂを開放する時間範囲Ｔ_cを制御する。
【０００５】
上述のような従来の超音波センサ装置１にあっては、発振回路３は図７（ａ）に示すようにバースト信号を時刻ｔ₀から時刻ｔ₁まで送受波器４へ入力する。すると、送受波器４の超音波振動子は時刻ｔ₀から振動を開始するものの、図７（ｂ）に示すように、時刻ｔ₁が過ぎてからも送受波器４の超音波振動子の残響振動が残り、送受波器４の受波信号Ｗ_sが閾値レベルＴ_h0を下回るには時間がかかり、受波回路５ａは図７（ｃ）に示すような検波信号Ｋ_sを出力する。そのため、検知ゲート回路５ｂは、図７（ｄ）に示すように、前記残響振動による受波信号Ｗ_sが閾値レベルＴ_h0を下回って以降の、時刻ｔ₂にしか検知ゲートを開くことができない。
【０００６】
いま、超音波センサ装置１の送受波器４と障害物Ａとの距離をＬ、音速をＣとした場合、送波した超音波は障害物Ａに反射して２Ｌ／Ｃ秒後に反射波として返ってきて、図７（ｂ）に示す受波信号Ｗ_aとして送受波器４に受波される。そして、この障害物Ａからの反射波の受波信号Ｗ_aは、受波回路５ａから図７（ｃ）に示すように検波信号Ｋ_aとして出力され、この検波信号Ｋ_aが図７（ｄ）に示すように検知ゲート回路５ｂの開いている時刻ｔ₂から時刻ｔ₃までの間にあれば、検知ゲート回路５ｂは、図７（ｅ）に示すように、受波回路５ａの検波信号と検知ゲート回路５ｂの検知ゲート信号との論理積信号Ｐ_aを、信号処理部６へ出力する。そして、信号処理部６は障害物Ａを検出した旨の表示信号を表示部７へ出力し、表示部７はその旨を表示する。
【０００７】
【発明が解決しようとする課題】
しかしながら、送受波器４と障害物Ａとの距離Ｌが短くなればなるほど、障害物Ａからの反射波の受波信号Ｗ_aと残響振動による受波信号Ｗ_sとが近接してくる。しかし、検知ゲートは、残響振動による受波信号Ｗ_sのために、時刻ｔ₂より後にしか開くことができないため、送受波器４と障害物Ａとの距離ＬがＣ・（ｔ₂−ｔ₀）／２よりも近いところは、図８に示すように死角Ｄになってしまい、検知エリアＢは制限され、現在のところ約２０ｃｍ以下に接近する障害物Ａは検出できないという問題点があった。
【０００８】
本発明は上記の問題点を解決するためになされたもので、その目的とするところは、近距離の障害物であっても検出できる近距離障害物検出能力を向上せしめた、優れる超音波センサ装置を提供することにある。
【０００９】
【課題を解決するための手段】
本発明は上記の問題点を解決するため、請求項１記載の発明にあっては、超音波パルス波を間欠的に空間へ送波して障害物からの反射波を受波する送受波器と、該送受波器から送波された超音波パルス波の障害物からの反射波を受波するのみの受波器と、必要な反射波のみを取り出す検知ゲート回路とを備え、前記送受波器から送波された超音波パルス波の反射波の時間遅れに基づいて障害物の有無を検出するようにした超音波センサ装置であって、障害物の存在を検出する送受波器側の閾値レベルを、障害物の存在を検出する受波器側の閾値レベルよりも低く設定した検知回路を設け、検知ゲート回路は、送受波器側の検波信号を取り出す送受波器側検知ゲート回路と、受波器側の検波信号を取り出す受波器側検知ゲート回路とを有し、送受波器側検知ゲート回路は、送波信号の残響振動による受波信号が、送受波器側の閾値レベル以下になった場合に検知ゲートを開放し、受波器側検知ゲート回路は、送受波器の送波信号による回り込み信号が、受波器側の閾値レベル以下になった場合に検知ゲートを開放することを特徴とする。
【００１０】
請求項２記載の発明にあっては、前記検知ゲート回路は前記送受波器の検知ゲートと前記受波器の検知ゲートとで重ならないように設定されており、前記送受波器の検知ゲートで取り出される検波信号と前記受波器の検知ゲートで取り出される検波信号とを識別処理する信号処理部を設けたことを特徴とする。
【００１１】
【発明の実施の形態】
以下、本発明に係る超音波センサ装置の一実施の形態を図１〜図４に基づいて詳細に説明する。図１は超音波センサ装置を示すブロック図である。図２は超音波センサ装置の障害物が比較的遠方にある場合の動作を説明するタイミングチャートであり、図２（ａ）は送波信号、図２（ｂ）は送受波器の受波信号、図２（ｃ）は送受波器の受波信号の検波信号、図２（ｄ）は送受波器側の検知ゲート信号、図２（ｅ）は送受波器の受波信号の検波信号と送受波器側の検知ゲート信号との論理積信号、図２（ｆ）は受波器の受波信号、図２（ｇ）は受波器の受波信号の検波信号、図２（ｈ）は受波器側の検知ゲート信号、図２（ｉ）は受波器の受波信号の検波信号と受波器側の検知ゲート信号との論理積信号、図２（ｊ）は時間軸である。図３は超音波センサ装置の障害物が近距離にある場合の動作を説明するタイミングチャートであり、図３（ａ）は送波信号、図３（ｂ）は送受波器の受波信号、図３（ｃ）は送受波器の受波信号の検波信号、図３（ｄ）は送受波器側の検知ゲート信号、図３（ｅ）は送受波器の受波信号の検波信号と送受波器側の検知ゲート信号との論理積信号、図３（ｆ）は受波器の受波信号、図３（ｇ）は受波器の受波信号の検波信号、図３（ｈ）は受波器側の検知ゲート信号、図３（ｉ）は受波器の受波信号の検波信号と受波器側の検知ゲート信号との論理積信号、図３（ｊ）は時間軸である。図４は超音波センサ装置の検知エリアを示す説明図、図５は超音波センサ装置の受波器側の閾値レベルを高くした場合の検知エリアを示す説明図である。なお、図１に示す超音波センサ装置にあっては、従来の技術で図６を用いて説明した超音波センサ装置と同等な個所には、同じ符号を付してある。
【００１２】
この超音波センサ装置１は、図１に示すように、基準信号発生回路２と、発振回路３と、送受波器４と、受波器４１と、検知回路５と、信号処理部６と、表示部７とを備える。基準信号発生回路２は、パルス状の超音波の送波間隔を設定するための基準信号を発生する。発振回路３は、前記基準信号に基づいた送波間隔で所定周波数の電気振動を間欠的に発生する。送受波器４は、発振回路３の出力を超音波に変換して空中へ送波するとともに、障害物Ａからの反射波を受波する。受波器４１は、受波専用のもので、送受波器４と並べて配設されて、障害物Ａからの反射波を受波する。
【００１３】
検知回路５は、受波回路５ａ，５１ａと、検知ゲート回路５ｂ，５１ｂと、ゲート制御回路５ｃとを備える。受波回路５ａは、送受波器４の出力する受波信号が閾値レベルＴ_h0より大きい場合にのみHighになる検波信号を出力する。受波回路５１ａは、受波器４１の出力する受波信号が閾値レベルＴ_h1より大きい場合にのみHighになる検波信号を出力する。なお、閾値レベルＴ_h0，Ｔ_h1の関係は、Ｔ_h1＞Ｔ_h0とされている。
【００１４】
検知ゲート回路５ｂは、受波回路５ａの出力する検波信号のうち、送受波器側の検知ゲートに相当する所定時間範囲Ｔ_c内の、検波信号のみを通過させる。検知ゲート回路５１ｂは、受波回路５１ａの出力する検波信号のうち、受波器側の検知ゲートに相当する所定時間範囲Ｔ_b内の、検波信号のみを通過させる。ゲート制御回路５ｃは、基準信号発生回路２の出力に基づいて、検知ゲート回路５ｂを開放する時間範囲Ｔ_cと検知ゲート回路５１ｂを開放する時間範囲Ｔ_bとを制御する。
【００１５】
上述のような従来の超音波センサ装置にあっては、発振回路３は図２（ａ）に示すようにバースト信号を時刻ｔ₀から時刻ｔ₁まで送受波器４へ入力する。すると、送受波器４の超音波振動子は時刻ｔ₀から振動を開始するものの、図２（ｂ）に示すように、時刻ｔ₁が過ぎてからも送受波器４の超音波振動子の残響振動が残り、送受波器４の受波信号Ｗ_sが閾値レベルＴ_h0を下回るには時間がかかり、受波回路５ａは図２（ｃ）に示すような検波信号Ｋ_sを出力する。そのため、検知ゲート回路５ｂは、図２（ｄ）に示すように、前記残響振動による受波信号Ｗ_sが閾値レベルＴ_h0を下回って以降の、時刻ｔ₃にしか検知ゲートを開くことができない。
【００１６】
また、受波器４１にあっては、近接して並べて配設されている送受波器４の影響を受けて、送受波器４の送波する超音波の中の回り込み成分を図２（ｆ）に示すように受波信号Ｗ_dとして受波し、この受波器４１の受波した受波信号Ｗ_dは、受波回路５１ａから図２（ｇ）に示すように検波信号Ｋ_dとして出力される。そのため、検知ゲート回路５１ｂは、図２（ｈ）に示すように、前記受波信号Ｗ_dが閾値レベルＴ_h1を下回って以降の、時刻ｔ₂にしか検知ゲートを開くことができない。
【００１７】
しかしながら、受波器４１の受波する受波信号Ｗ_dは、送受波器４の送波する超音波の中の回り込み成分であり、受波レベルはそれほど強くなく残響振動も殆ど生じないので、仮に閾値レベルＴ_h1＝Ｔ_h0であったとしても、送受波器４の残響振動による受波信号Ｗ_sが閾値レベルＴ_h0を下回るよりも速やかに閾値レベルＴ_h1を下回ることができる。従って、障害物Ａからの反射波を受波することをもって近距離に位置する障害物Ａを検出することに対しては、送受波器４よりも受波器４１の方が適しているということができる。
【００１８】
しかも、障害物Ａからの反射波の音圧レベルは、障害物Ａが近距離にあればあるほど強くなることから、閾値レベルＴ_h1を高めることによって感度を鈍らせても障害物Ａの反射波の検出は充分可能であって、閾値レベルＴ_h0，Ｔ_h1の関係をＴ_h1＞Ｔ_h0とすることによって、検知ゲート回路５１ｂの検知ゲートを開く時刻ｔ₂を早めることが可能で、更に近距離の障害物Ａを検出可能にできる。
【００１９】
なお、この超音波センサ装置１のゲート制御回路５ｃは、基準信号発生回路２の出力に基づいて、時刻ｔ₂から時刻ｔ₃までのＴ_b期間のみ検知ゲート回路５１ｂの検知ゲートを開放するとともに、時刻ｔ₃から時刻ｔ₄までのＴ_c期間のみ検知ゲート回路５ｂの検知ゲートを開放するようにされている。このときの超音波センサ装置１の検知エリアＢは図４に示すようになり、死角Ｄの領域が狭まり検知エリアＢ₂だけ広がるのであり、検知エリアＢ₁を送受波器４と受波回路５ａと検知ゲート回路５ｂとが受け持ち、検知エリアＢ₂を受波器４１と受波回路５１ａと検知ゲート回路５１ｂとが受け持つことになる。
【００２０】
いま、超音波センサ装置の送受波器４と障害物Ａとの距離をＬ、音速をＣとした場合、送波した超音波は障害物Ａに反射して２Ｌ／Ｃ秒後に反射波として返ってきて、距離Ｌが比較的遠方であるとすると、図２（ｂ）に示すように送受波器４に受波信号Ｗ_aとして受波されるとともに、図２（ｆ）に示すように受波器４１にも受波信号Ｗ_aとして受波される。
【００２１】
そして、送受波器４に受波された障害物Ａからの反射波の受波信号Ｗ_aは、受波回路５ａから図２（ｃ）に示すように検波信号Ｋ_aとして出力され、この検波信号Ｋ_aが図２（ｄ）に示すように検知ゲート回路５ｂの開いている時刻ｔ₃から時刻ｔ₄までの間にあるので、検知ゲート回路５ｂは、図２（ｅ）に示すように、受波回路５ａの検波信号と検知ゲート回路５ｂの検知ゲート信号との論理積信号Ｐ_aを、信号処理部６へ出力できる。
【００２２】
一方、受波器４１に受波された障害物Ａからの反射波の受波信号Ｗ_aは、受波回路５１ａから図２（ｇ）に示すように検波信号Ｋ_aとして出力されるものの、この検波信号Ｋ_aが図２（ｈ）に示すように検知ゲート回路５１ｂの開いている時刻ｔ₂から時刻ｔ₃までの間にないので、検知ゲート回路５１ｂは、図２（ｉ）に示すように、受波回路５１ａの検波信号と検知ゲート回路５１ｂの検知ゲート信号との論理積信号を、信号処理部６へ出力できない。
【００２３】
そして、信号処理部６は、検知ゲート回路５１ｂからではなく検知ゲート回路５ｂから、障害物Ａを検出した旨の論理積信号Ｐ_aを受けたことに基づいて、表示信号を表示部７へ出力し、表示部７は遠方側の検知エリアＢ₁に障害物Ａのある旨を表示できる。
【００２４】
また、超音波センサ装置の送受波器４と障害物Ａとの距離をＬ、音速をＣとした場合、送波した超音波は障害物Ａに反射して２Ｌ／Ｃ秒後に反射波として返ってきて、距離Ｌが近距離であるとすると、図３（ｂ）に示すように送受波器４に受波信号Ｗ_saとして受波されるとともに、図３（ｇ）に示すように受波器４１に受波信号Ｗ_aとして受波される。
【００２５】
そして、送受波器４に受波された障害物Ａからの反射波の受波信号Ｗ_saは、受波回路５ａから図３（ｃ）に示すように検波信号Ｋ_saとして出力されるものの、この検波信号Ｋ_saは図３（ｄ）に示すように検知ゲート回路５ｂの開いている時刻ｔ₃から時刻ｔ₄までの間にない。従って、検知ゲート回路５ｂは、図３（ｅ）に示すように、受波回路５ａの検波信号と検知ゲート回路５ｂの検知ゲート信号との論理積信号を、信号処理部６へ出力できない。
【００２６】
一方、受波器４１に受波された障害物Ａからの反射波の受波信号Ｗ_aは、受波回路５１ａから図３（ｇ）に示すように検波信号Ｋ_aとして出力されるものの、この検波信号Ｋ_aが図３（ｈ）に示すように検知ゲート回路５１ｂの開いている時刻ｔ₂から時刻ｔ₃までの間にある。従って、検知ゲート回路５１ｂは、図３（ｉ）に示すように、受波回路５１ａの検波信号と検知ゲート回路５１ｂの検知ゲート信号との論理積信号Ｐ_aを、信号処理部６へ出力できる。
【００２７】
そして、信号処理部６は、検知ゲート回路５ｂからではなく検知ゲート回路５１ｂから、障害物Ａを検出した旨の論理積信号Ｐ_aを受けたことに基づいて、表示信号を表示部７へ出力し、表示部７は近傍側の検知エリアＢ₂に障害物Ａのある旨を表示できる。
【００２８】
上述のような超音波センサ装置１にあっては、従来のものは２０ｃｍ以内が死角Ｄになり障害物Ａの識別が充分でなかったのが、死角Ｄが７〜１０ｃｍに改善された。
【００２９】
なお、上述の実施の形態にあっては、閾値レベルＴ_h0，Ｔ_h1の関係をＴ_h1＞Ｔ_h0とすることによって、検知ゲート回路５１ｂの検知ゲートを開く時刻ｔ₂を早めて近距離の障害物Ａの識別を可能にしているが、受波回路５１ａの内蔵する増幅器（図示せず）の増幅率を、受波回路５ａの内蔵する増幅器（図示せず）の増幅率より低くして、閾値レベルＴ_h0，Ｔ_h1の関係はＴ_h1＝Ｔ_h0にしても原理上同じことになり、同様の作用効果を得ることが可能である。
【００３０】
つまり、閾値レベルＴ_h0，Ｔ_h1を高めることと、受波回路５ａ，５１ａの内蔵する増幅器の増幅率を低めることとは同義であり、感度を鈍らせることであり、本発明は、受波回路５１ａの経路の感度を、受波回路５ａの経路の感度よりも鈍らせることをも含むものである。
【００３１】
また、上述のような超音波センサ装置１にあっては、閾値レベルＴ_h0，Ｔ_h1を異ならしめたり、受波回路５ａ，５１ａの内蔵する増幅器の増幅率を異ならしめたりすることによって、図５に示すように近距離の検知エリアＢ₂のみを小さくするというような検知エリア制御を行なうことも可能である。
【００３２】
【発明の効果】
請求項１記載の発明によれば、超音波センサ装置の送受波器の送波時の残響振動の影響を受けることがなくなり、且つ、従来の遠距離の検知性能を損なうことなく、障害物の近距離識別能力の向上した、優れる超音波センサ装置を提供できるという効果を奏する。
【００３３】
請求項２記載の発明によれば、請求項１記載の発明の効果に加えて更に、障害物の存在が検知エリアの中の遠方領域に位置するかそれとも近距離領域に位置するかを識別できて使い勝手の良い、優れる超音波センサ装置を提供できるという効果を奏する。
【図面の簡単な説明】
【図１】本発明に係る一実施の形態の超音波センサ装置を示すブロック図である。
【図２】上記超音波センサ装置の障害物が比較的遠方にある場合の動作を説明するタイミングチャートである。
【図３】上記超音波センサ装置の障害物が近距離にある場合の動作を説明するタイミングチャートである。
【図４】上記超音波センサ装置の検知エリアを示す説明図である。
【図５】上記超音波センサ装置の受波器側の閾値レベルを高くした場合の検知エリアを示す説明図である。
【図６】従来の超音波センサ装置を示すブロック図である。
【図７】上記超音波センサ装置の動作を説明するタイミングチャートである。
【図８】上記超音波センサ装置の検知エリアを示す説明図である。
【符号の説明】
１超音波センサ装置
４送受波器
４１受波器
５検知回路
５ａ検知ゲート回路
５１ａ検知ゲート回路
Ａ障害物
Ｔ_b 受波器側の検知ゲート
Ｔ_c 送受波器側の検知ゲート
Ｔ_h0 送受波器側の閾値レベル
Ｔ_h1 受波器側の閾値レベル[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultrasonic sensor device that transmits an ultrasonic pulse wave and receives a reflected wave from an obstacle to detect the presence or absence of the obstacle.
[0002]
[Prior art]
FIG. 6 is a block diagram showing a conventional ultrasonic sensor device. FIG. 7 is a timing chart for explaining the operation of the conventional ultrasonic sensor device. FIG. 7A is a transmitted signal, FIG. 7B is a received signal, FIG. 7C is a detected signal, and FIG. (D) is a detection gate signal, FIG. 7 (e) is a logical product signal of the detection signal and the detection gate signal, and FIG. 7 (f) is a time axis. FIG. 8 is an explanatory diagram showing a detection area of the ultrasonic sensor device.
[0003]
As shown in FIG. 6, the conventional ultrasonic sensor device 1 includes a reference signal generation circuit 2, an oscillation circuit 3, a transducer 4, a detection circuit 5, a signal processing unit 6, and a display unit 7. Prepare. The reference signal generation circuit 2 generates a reference signal for setting a transmission interval of pulsed ultrasonic waves. The oscillation circuit 3 intermittently generates electrical vibration of a predetermined frequency at a transmission interval based on the reference signal. The transmitter / receiver 4 converts the output of the oscillation circuit 3 into an ultrasonic wave and transmits it to the air, and receives a reflected wave from the obstacle A. The detection circuit 5 extracts a signal component due to the reflected wave from the obstacle A from the output of the transducer 4, and the reflected wave of the obstacle A is within a predetermined time range T _c set in advance and has a preset threshold value. It is detected whether it is greater than level T _h0 . The signal processing unit 6 determines from the output of the detection circuit 5 whether or not the obstacle A exists in the detection area. When the signal processing unit 6 determines that the obstacle A exists in the detection area, the display unit 7 displays that effect.
[0004]
The detection circuit 5 includes a wave receiving circuit 5a, a detection gate circuit 5b, and a gate control circuit 5c. The wave receiving circuit 5a outputs a detection signal that becomes High only when the wave receiving signal output from the wave transmitter / receiver 4 is larger than the threshold level _Th0 . The detection gate circuit 5b passes only the detection signal within the predetermined time range _Tc among the detection signals output from the reception circuit 5a. The gate control circuit 5c controls the time range _Tc for opening the detection gate circuit 5b based on the output of the reference signal generation circuit 2.
[0005]
In the conventional ultrasonic sensor device 1 as described above, the oscillation circuit 3 inputs a burst signal to the transducer 4 from time t ₀ to time t ₁ as shown in FIG. Then, although the ultrasonic transducer of the transducer 4 starts oscillating from the time t ₀ , as shown in FIG. 7 (b), the ultrasonic transducer of the transducer 4 is oscillated even after the time t ₁ has passed. Reverberation remains and it takes time for the received signal W _s of the transmitter / receiver 4 to fall below the threshold level T _h0 , and the receiving circuit 5a outputs a detection signal K _s as shown in FIG. Therefore, the detection gate circuit 5b, as shown in FIG. 7 (d), received signal W _s by the reverberation oscillations after below the threshold level T _h0, can only be opened detection gate at time t ₂ .
[0006]
If the distance between the transducer 4 of the ultrasonic sensor device 1 and the obstacle A is L and the speed of sound is C, the transmitted ultrasonic wave is reflected by the obstacle A and reflected as a reflected wave after 2 L / C seconds. and returned, it is reception in transducer 4 as a received signal W _a shown in FIG. 7 (b). The received signal W _a of the reflected wave from the obstacle A is output from the reception circuit 5a as detection signal K _a as shown in FIG. 7 (c), the detection signal K _a Figure 7 (d if the result is between) from the time t ₂ that is open detection gate circuit 5b as shown until time t _3, the detection gate circuit 5b, as shown in FIG. 7 (e), the detection signal of the wave receiving circuit 5a the logical product signal P _a of the detection gate signal to the detection gate circuit 5b, and outputs to the signal processing unit 6. Then, the signal processing unit 6 outputs a display signal indicating that the obstacle A has been detected to the display unit 7, and the display unit 7 displays that fact.
[0007]
[Problems to be solved by the invention]
However, the shorter the distance L between the transmitter / receiver 4 and the obstacle A, the closer the received signal W _a of the reflected wave from the obstacle A and the received signal W _s due to the reverberation vibration are. However, since the detection gate can be opened only after time t ₂ due to the received signal W _s due to reverberation vibration, the distance L between the transducer 4 and the obstacle A is C · (t ₂ −t ₀ ) / 2 is a blind spot D as shown in FIG. 8, the detection area B is limited, and there is a problem that the obstacle A that approaches 20 cm or less cannot be detected at present. It was.
[0008]
The present invention has been made in order to solve the above-described problems, and an object of the present invention is to provide an excellent ultrasonic sensor with improved short-distance obstacle detection capability capable of detecting even a short-distance obstacle. To provide an apparatus.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention provides a transmitter / receiver for intermittently transmitting an ultrasonic pulse wave to a space and receiving a reflected wave from an obstacle. A receiver that only receives a reflected wave from an obstacle of an ultrasonic pulse wave transmitted from the transmitter and receiver, and a detection gate circuit that extracts only the necessary reflected wave, An ultrasonic sensor device that detects the presence or absence of an obstacle based on the time delay of the reflected wave of the ultrasonic pulse wave transmitted from the detector, and a threshold on the transmitter / receiver side that detects the presence of the obstacle level, providing a detection circuit with low rather set than the threshold level of the receivers side for detecting the presence of an obstacle, detection gate circuit includes a transducer-side detection gate circuit for taking out a detection signal of the transducer side A detector-side detection gate circuit for extracting a detector-side detection signal, The detector-side detection gate circuit opens the detection gate when the received signal due to the reverberation vibration of the transmitted signal falls below the threshold level on the transmitter-receiver side, and the receiver-side detection gate circuit The detection gate is opened when the sneak signal due to the transmitter signal of the detector becomes equal to or lower than the threshold level on the receiver side .
[0010]
In the invention according to claim 2, the detection gate circuit is set so as not to overlap the detection gate of the transducer and the detection gate of the receiver, and the detection gate of the transducer A signal processing unit is provided for discriminating between the detection signal extracted and the detection signal extracted by the detection gate of the receiver.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of an ultrasonic sensor device according to the present invention will be described in detail with reference to FIGS. FIG. 1 is a block diagram showing an ultrasonic sensor device. FIG. 2 is a timing chart for explaining the operation of the ultrasonic sensor device when the obstacle is relatively far away. FIG. 2 (a) is a transmitted signal, and FIG. 2 (b) is a received signal of a transducer. 2 (c) is a detection signal of the reception signal of the transmitter / receiver, FIG. 2 (d) is a detection gate signal on the transmitter / receiver side, and FIG. 2 (e) is a detection signal of the reception signal of the transmitter / receiver. The AND signal with the detection gate signal on the transmitter / receiver side, FIG. 2 (f) is the received signal of the receiver, FIG. 2 (g) is the detected signal of the received signal of the receiver, FIG. 2 (h) Is a detection gate signal on the receiver side, FIG. 2 (i) is a logical product signal of the detection signal of the reception signal of the receiver and the detection gate signal on the receiver side, and FIG. 2 (j) is a time axis. is there. FIG. 3 is a timing chart for explaining the operation when the obstacle of the ultrasonic sensor device is at a short distance, FIG. 3 (a) is a transmitted signal, FIG. 3 (b) is a received signal of a transducer, 3 (c) is a detection signal of the reception signal of the transducer, FIG. 3 (d) is a detection gate signal on the transducer side, and FIG. 3 (e) is a detection signal and transmission / reception of the reception signal of the transducer. FIG. 3 (f) shows the received signal of the receiver, FIG. 3 (g) shows the detected signal of the received signal of the receiver, and FIG. The detection gate signal on the receiver side, FIG. 3 (i) is the logical product signal of the detection signal of the reception signal of the receiver and the detection gate signal on the receiver side, and FIG. 3 (j) is the time axis. . FIG. 4 is an explanatory diagram showing the detection area of the ultrasonic sensor device, and FIG. 5 is an explanatory diagram showing the detection area when the threshold level on the receiver side of the ultrasonic sensor device is increased. In the ultrasonic sensor device shown in FIG. 1, the same reference numerals are given to the same portions as those of the ultrasonic sensor device described with reference to FIG. 6 in the prior art.
[0012]
As shown in FIG. 1, the ultrasonic sensor device 1 includes a reference signal generation circuit 2, an oscillation circuit 3, a transducer 4, a receiver 41, a detection circuit 5, a signal processing unit 6, And a display unit 7. The reference signal generation circuit 2 generates a reference signal for setting a transmission interval of pulsed ultrasonic waves. The oscillation circuit 3 intermittently generates electrical vibration of a predetermined frequency at a transmission interval based on the reference signal. The transmitter / receiver 4 converts the output of the oscillation circuit 3 into an ultrasonic wave and transmits it to the air, and receives a reflected wave from the obstacle A. The wave receiver 41 is dedicated for wave reception, and is arranged side by side with the wave transmitter / receiver 4 to receive the reflected wave from the obstacle A.
[0013]
The detection circuit 5 includes reception circuits 5a and 51a, detection gate circuits 5b and 51b, and a gate control circuit 5c. The wave receiving circuit 5a outputs a detection signal that becomes High only when the wave receiving signal output from the wave transmitter / receiver 4 is larger than the threshold level _Th0 . The reception circuit 51a outputs a detection signal that becomes High only when the reception signal output from the receiver 41 is greater than the threshold level _Th1 . The relationship between the threshold levels T _h0 and T _h1 is T _h1 > T _h0 .
[0014]
The detection gate circuit 5b passes only the detection signal within the predetermined time range _Tc corresponding to the detection gate on the transmitter / receiver side among the detection signals output from the reception circuit 5a. Detection gate circuit 51b, among the detection signals output from the reception circuit 51a, the predetermined time range T _b corresponding to the wave receiver side of the detection gate passes only the detection signal. Gate control circuit 5c, based on the output of the reference signal generating circuit 2, controls the time range T _b to open the time range T _c and the detection gate circuit 51b for opening the detection gate circuit 5b.
[0015]
In the conventional ultrasonic sensor device as described above, the oscillation circuit 3 inputs a burst signal to the transducer 4 from time t ₀ to time t ₁ as shown in FIG. Then, although the ultrasonic transducer of the transducer 4 starts to oscillate from the time t ₀ , as shown in FIG. 2 (b), the ultrasonic transducer of the transducer 4 will continue even after the time t ₁ has passed. Reverberation remains, and it takes time for the received signal W _s of the transmitter / receiver 4 to fall below the threshold level T _h0 , and the receiving circuit 5a outputs a detection signal K _s as shown in FIG. Therefore, the detection gate circuit 5b, as shown in FIG. 2 (d), received signal W _s by the reverberation oscillations after below the threshold level T _h0, can only be opened detection gate at a time t ₃ .
[0016]
In the receiver 41, the wraparound component in the ultrasonic wave transmitted by the transmitter / receiver 4 under the influence of the transmitter / receiver 4 arranged in close proximity is shown in FIG. and received wave as the received signal W _d as shown in), received signal W _d obtained by reception of the receivers 41, as detection signal K _d from the reception circuit 51a, as shown in FIG. 2 (g) Is output. Therefore, the detection gate circuit 51b, as shown in FIG. 2 (h), the received signal W _d is later falls below the threshold level T _h1, only be able to open the detection gate at time t _2.
[0017]
However, the received signal W _d received by the receiver 41 is a sneak component in the ultrasonic wave transmitted by the transmitter / receiver 4, and the received level is not so strong and reverberation vibration hardly occurs. Even if the threshold level T _h1 = T _h0 , the received signal W _s due to the reverberation vibration of the transmitter / receiver 4 can fall below the threshold level _{Th 1} more quickly than the threshold level _{Th 0} . Therefore, the receiver 41 is more suitable than the transmitter / receiver 4 for detecting the obstacle A located at a short distance by receiving the reflected wave from the obstacle A. Can do.
[0018]
Moreover, since the sound pressure level of the reflected wave from the obstacle A becomes stronger as the obstacle A is at a shorter distance, the reflection of the obstacle A is reflected even if the sensitivity is lowered by increasing the threshold level _Th1. Wave detection is sufficiently possible, and by setting the relationship between the threshold levels T _h0 and T _h1 to T _h1 > T _h0 , the time t ₂ when the detection gate of the detection gate circuit 51b is opened can be advanced. It is possible to detect the obstacle A at a short distance.
[0019]
The gate control circuit 5c of the ultrasonic sensor apparatus 1 based on the output of the reference signal generating circuit 2, with only opens the detection gate of the detection gate circuit 51b T _b period from time t ₂ to time t ₃ only T _c period from time t ₃ to time t ₄ is adapted to open the detection gate of the detection gate circuit 5b. The detection area B of the ultrasonic sensor device 1 at this time is as shown in FIG. 4, and the blind spot D area narrows and widens only by the detection area B ₂ , and the detection area B ₁ is transmitted through the transducer 4 and the reception circuit 5 a. and a sensing gate circuit 5b is responsible, so that the detection area B ₂ and wave receiver 41 and the reception circuit 51a and the detection gate circuit 51b takes charge.
[0020]
If the distance between the transducer 4 of the ultrasonic sensor device and the obstacle A is L and the sound velocity is C, the transmitted ultrasonic wave is reflected by the obstacle A and returns as a reflected wave after 2 L / C seconds. Assuming that the distance L is relatively far, the transmitter / receiver 4 receives the received signal as _a received signal Wa as shown in FIG. 2 (b) and receives it as shown in FIG. 2 (f). The wave 41 is also received as _a received signal Wa.
[0021]
Then, the received wave signal W _a of the reflected wave from the obstacle A received by the transmitter / receiver 4 is output from the wave receiving circuit 5a as _a detection signal Ka as shown in FIG. since the signal K _a is in the period from time t ₃ when open the detection gate circuit 5b as shown in FIG. 2 (d) until the time t _4, the detection gate circuit 5b, as shown in FIG. 2 (e) , a logical product signal P _a of the detection gate signal of the detection signal and the detection gate circuit 5b of the reception circuit 5a, can be output to the signal processing unit 6.
[0022]
On the other hand, received signal W _a of the reflected wave from the reception obstacle A to the wave receiver 41, although is output as the detection signal K _a as shown from the reception circuit 51a in FIG. 2 (g), this detection signal K _a is not in the period from time t ₂ that is open detection gate circuit 51b as shown in FIG. 2 (h) to time t _3, the detection gate circuit 51b is shown in FIG. 2 (i) Thus, the logical product signal of the detection signal of the reception circuit 51a and the detection gate signal of the detection gate circuit 51b cannot be output to the signal processing unit 6.
[0023]
Then, the signal processing unit 6 outputs _a display signal to the display unit 7 based on receiving the logical product signal Pa indicating that the obstacle A is detected from the detection gate circuit 5b instead of the detection gate circuit 51b. and, the display unit 7 may display the fact that a detection area B ₁ of the distal of the obstacle a.
[0024]
When the distance between the transducer 4 of the ultrasonic sensor device and the obstacle A is L and the sound velocity is C, the transmitted ultrasonic wave is reflected by the obstacle A and returns as a reflected wave after 2 L / C seconds. Assuming that the distance L is a short distance, the transmitter / receiver 4 receives the received signal W _sa as a received signal W _sa as shown in FIG. 3 (b) and receives the received wave as shown in FIG. 3 (g). The receiver 41 receives the received signal as _a received signal Wa.
[0025]
Then, the received wave signal W _sa of the reflected wave from the obstacle A received by the transmitter / receiver 4 is output from the wave receiving circuit 5a as the detection signal K _sa as shown in FIG. the detection signal K _sa is not during the period from the time t ₃ when open the detection gate circuit 5b as shown in FIG. 3 (d) until time t _4. Therefore, the detection gate circuit 5b cannot output a logical product signal of the detection signal of the reception circuit 5a and the detection gate signal of the detection gate circuit 5b to the signal processing unit 6, as shown in FIG.
[0026]
On the other hand, received signal W _a of the reflected wave from the reception obstacle A to the wave receiver 41, although is output as the detection signal K _a as shown from the reception circuit 51a in FIG. 3 (g), the detection signal K _a is in the period from time t ₂ that is open detection gate circuit 51b as shown in FIG. 3 (h) to time t _3. Therefore, the detection gate circuit 51b, as shown in FIG. 3 (i), the logical product signal P _a of the detection gate signal of the detection signal and the detection gate circuit 51b of the reception circuit 51a, can be output to the signal processing section 6 .
[0027]
Then, the signal processing unit 6 outputs _a display signal to the display unit 7 based on receiving the logical product signal Pa indicating that the obstacle A is detected from the detection gate circuit 51b instead of the detection gate circuit 5b. The display unit 7 can display that there is an obstacle A in the detection area B ₂ on the vicinity side.
[0028]
In the ultrasonic sensor device 1 as described above, the blind spot D was improved within 7 to 10 cm, although the conventional one had a blind spot D within 20 cm and the obstacle A was not sufficiently identified.
[0029]
In the above-described embodiment, the relationship between the threshold levels T _h0 and T _h1 is set to T _h1 > T _h0 , so that the time t ₂ when the detection gate of the detection gate circuit 51 b is opened is shortened. Although the obstacle A can be identified, the amplification factor of the amplifier (not shown) built in the receiving circuit 51a is made lower than the amplification factor of the amplifier (not shown) built in the receiving circuit 5a. The relationship between the threshold levels T _h0 and T _h1 is the same in principle even if T _h1 = T _h0 , and the same effect can be obtained.
[0030]
That is, increasing the threshold levels T _h0 and T _h1 is synonymous with lowering the amplification factor of the amplifiers included in the receiving circuits 5a and 51a, and is reducing the sensitivity. This includes making the sensitivity of the path of the circuit 51a less than the sensitivity of the path of the receiving circuit 5a.
[0031]
In the ultrasonic sensor device 1 as described above, the threshold levels T _h0 and _Th ₁ are made different, or the amplification factors of the amplifiers built in the receiving circuits 5a and 51a are made different. As shown in FIG. 5, it is also possible to perform detection area control in which only the short-range detection area B ₂ is reduced.
[0032]
【The invention's effect】
According to the first aspect of the present invention, there is no influence of reverberation vibration at the time of transmission of the transmitter / receiver of the ultrasonic sensor device, and the obstacle is detected without impairing the conventional long-range detection performance. There is an effect that it is possible to provide an excellent ultrasonic sensor device with improved short-range discrimination capability.
[0033]
According to the invention described in claim 2, in addition to the effect of the invention described in claim 1, it is further possible to identify whether the obstacle is located in a far area or a short distance area in the detection area. It is advantageous in that an excellent ultrasonic sensor device that is easy to use can be provided.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an ultrasonic sensor device according to an embodiment of the present invention.
FIG. 2 is a timing chart for explaining the operation when the obstacle of the ultrasonic sensor device is relatively far away.
FIG. 3 is a timing chart for explaining the operation of the ultrasonic sensor device when an obstacle is at a short distance.
FIG. 4 is an explanatory diagram showing a detection area of the ultrasonic sensor device.
FIG. 5 is an explanatory diagram showing a detection area when the threshold level on the receiver side of the ultrasonic sensor device is increased.
FIG. 6 is a block diagram showing a conventional ultrasonic sensor device.
FIG. 7 is a timing chart for explaining the operation of the ultrasonic sensor device.
FIG. 8 is an explanatory diagram showing a detection area of the ultrasonic sensor device.
[Explanation of symbols]
1 ultrasonic sensor device 4 transducer 41 receivers 5 detection circuit 5a detects the gate circuit 51a detects the gate circuit A obstacle T _b receivers side of the detection gate T _c transducer side of the detection gate T _h0 transducer Side threshold level _Th1 receiver side threshold level

Claims

A transmitter / receiver that intermittently transmits an ultrasonic pulse wave to space and receives a reflected wave from an obstacle, and a reflected wave from the obstacle of the ultrasonic pulse wave transmitted from the transmitter / receiver. A receiver that only receives a wave and a detection gate circuit that extracts only the necessary reflected wave, and whether or not there is an obstacle based on the time delay of the reflected wave of the ultrasonic pulse wave transmitted from the transmitter / receiver an ultrasonic sensor apparatus that detects a threshold level of the transducer side to detect the presence of obstacles, and low rather set than the threshold level of the reception-side to detect the presence of the obstacle Provide a detection circuit ,
The detection gate circuit includes a transmitter / receiver side detection gate circuit that extracts a detection signal on the transmitter / receiver side, and a receiver side detection gate circuit that extracts a detection signal on the receiver side,
The transmitter / receiver side detection gate circuit opens the detection gate when the received signal due to the reverberation vibration of the transmitted signal falls below the threshold level on the transmitter / receiver side,
The ultrasonic sensor, wherein the receiver-side detection gate circuit opens the detection gate when a sneak signal generated by the transmission signal of the transmitter / receiver becomes equal to or lower than a threshold level on the receiver side. apparatus.

The detection gate circuit is set so as not to overlap the detection gate of the transducer and the detection gate of the receiver, and the detection signal taken out by the detection gate of the transducer and the detection of the receiver 2. The ultrasonic sensor device according to claim 1, further comprising a signal processing unit that performs identification processing on the detection signal extracted by the gate.