【発明の名称】流量計測装置
【特許請求の範囲】
【請求項１】流体管路に設けられ超音波信号を送受信する第１振動子及び第２振動子と、前記振動子へ周期的駆動信号を送出する送信回路と、前記両振動子間相互の超音波伝達を複数回行う繰り返し手段と、前記送信回路の駆動周期を基準として遅延時間を変更するタイマ変更手段と、前記タイマ変更手段によって前記繰り返し時に信号伝達を遅らせる遅延手段と、前記両振動子間の超音波の伝搬時間に基づいて流量を算出する流量演算手段とを備えた流量計測装置。
【請求項２】タイマ変更手段は予め設定した固定値を有し、この固定値に送信回路の駆動周期をｎ分割した時間を基準とした時間を付加して遅延時間を順次変更する請求項１記載の流量計測装置。
【請求項３】タイマ変更手段で送信回路の駆動周期をｎ分割した時間は繰り返し手段の設定している繰り返し回数の公約数になるように分割数を調節する請求項１記載の流量計測装置。
【請求項４】超音波を送受信する２つの振動子の送信機能と受信機能を切り替え設定する切り替え手段を有し、送受信する方向にかかわらず同じ遅延状態で遅延時間を調節する請求項１、２又は３記載の流量計測装置。
【請求項５】超音波を送受信する２つの振動子の送信機能と受信機能を切り替え設定する切り替え手段を有し、送受信する方向にかかわらず同じ総遅延時間になるよう遅延時間を調節する請求項１、２又は３記載の流量計測装置。
【請求項６】タイマ変更手段は超音波の伝搬時間に基づいて流量を算出する流量演算手段の出力を入力し流量に応じて前記送信回路の駆動周期をｎ分割した時間を基準として遅延時間を順次変更するタイマ変更手段と、前記タイマ変更手段によって前記繰り返し時に信号伝達を遅らせる遅延時間を調節する請求項１〜５のいずれか１項記載の流量計測装置。
【発明の詳細な説明】
【０００１】
【発明の属する技術分野】
本発明は、特に超音波によってガスなどの流体の流量を測定する装置に関するものである。
【０００２】
【従来の技術】
従来のこの種の流量計測装置は、特開昭６１−１０４２２４号公報に示すように送信指令パルスから遅延手段を介して送信回路に供給することが行われていた。遅延手段は図９に示すようにトリガ入力Ｙが入ると、増幅器と１とコンデンサ２〜４、トランジスタ５および抵抗器６〜８からなる遅延手段が作動し交流信号Ａの重畳によってモノステーブルマルチバイブレータ９の出力幅を例えば数μ〜数１００μ秒の間で不規則に変化させるものである。
【０００３】
【発明が解決しようとする課題】
しかしながら、上記従来の流量計測装置ではこの遅延時間の再現性が十分でなく、１時間に３リットル／時間のような微少な流量を計測する際に必要なナノ秒の再現性を得ることができず、流量計測の分解能を高くすることができなかった。
【０００４】
【課題を解決するための手段】
本発明は上記課題を解決するために、流体管路に設けられ超音波信号を送受信する第１振動子及び第２振動子と、前記振動子へ周期的駆動信号を送出する送信回路と、前記両振動子間相互の超音波伝達を複数回行う繰り返し手段と、前記送信回路の駆動周期を基準として遅延時間を変更するタイマ変更手段と、前記タイマ変更手段によって前記繰り返し時に信号伝達を遅らせる遅延手段と、前記両振動子間の超音波の伝搬時間に基づいて流量を算出する流量演算手段とを備え、タイマ変更手段の駆動周期を基準として遅延時間を変更し、遅延時間と送信周期とを調節することで、再現性の高い遅延時間と送信周期を得、流量計測精度を高める。
【０００５】
【発明の実施の形態】
本発明は、例えば都市ガス、プロパンガス等の燃料ガスの流量計測部に実施して極めて有用である。それは燃料ガスにおける流量計測は１時間あたり３リットルを越える流量変化を的確に把握することが、わが国においては必要とされているからである。そこで本発明は、流量の変化が極めて少ない場合から１時間あたり何万リットルという様な広範囲にわたって、流量を計測できる便利なものとしたものである。以上の趣旨に沿う正確な流量を計測する必要のある各分野において本発明は実施して有用なものである。
【０００６】
そして、当業者が本発明を実施するには各請求項に記載した構成とすることにより実現できるものであるが、本発明の内容の理解を助けて容易に実施形態を把握することができるように各請求項の作用効果を手段、構成に加えて以下に説明する。
【０００７】
すなわち、流体管路に設けられ超音波信号を送受信する第１振動子及び第２振動子と、前記振動子へ周期的駆動信号を送出する送信回路と、前記振動子間相互の超音波伝達を複数回行う繰り返し手段と、前記送信回路の駆動周期をｎ分割した時間を基準として遅延時間を順次変更するタイマ変更手段と、前記タイマ変更手段によって前記繰り返し時に信号伝達を遅らせる遅延手段と、前記振動子間の超音波の伝搬時間に基づいて流量を算出する流量演算手段とを備えることで，タイマ変更手段の駆動周期をｎ分割した時間を基準として遅延時間を順次変更し、遅延時間と送信周期とを調節することで、再現性の高い遅延時間と送信周期を得、流量計測精度を高めることができる。
【０００８】
また、タイマ変更手段は予め設定した固定値に送信回路の駆動周期をｎ分割した時間を基準とした時間を付加して遅延時間を順次変更することで送信周期をより最適化し、流量計測精度を高めることができる。
【０００９】
また、タイマ変更手段で送信回路の駆動周期をｎ分割した時間は繰り返し手段の設定している繰り返し回数の公約数になるように分割数を調節することで、順次変更していく遅延時間の変更状態が常に繰り返し回数内で一定回数で安定し、遅延時間のバラツキが測定時毎に大きくずれてしまうことが無くなり安定した計測状態を維持することが可能になる。
【００１０】
また、超音波を送受信する２つの振動子の送信機能と受信機能を切り替え設定する切り替え手段を有し、送受信する方向にかかわらず同じ遅延状態で遅延時間を調節することで流量計測精度を高めることができる。
【００１１】
また、超音波を送受信する２つの振動子の送信機能と受信機能を切り替え設定する切り替え手段を有し、送受信する方向にかかわらず同じ総遅延時間になるよう遅延時間を調節することで送信方向による流量計測の誤差を少なくすることができる。
【００１２】
また、タイマ変更手段は流量に応じて繰り返し時に信号伝達を遅らせる遅延時間を調節することで、最適な流量計測精度を維持することができる。
【００１３】
【実施例】
以下、本発明の実施例について図面を用いて説明する。
【００１４】
（実施例１）
図１は請求項１に係る実施例１に関する流量計測装置の構成ブロック図である。
【００１５】
図１において、流体管路１０の途中に超音波を発信する第１振動子１１Ａと受信する第２振動子１１Ｂが流れ方向に配置されている。１２は第１振動子１１Ａへの送信回路、１３は第２振動子１１Ｂで受信した信号の増幅回路で、この増幅された信号は基準信号と比較回路１４で比較され、基準信号以上の信号が検出されたとき設定された回数だけ繰り返し手段１５で遅延手段１６によって信号を遅延させた後超音波信号を繰り返し送信する。遅延手段１６は前記送信回路１２の駆動周期をｎ分割した時間を基準とするタイマ変更手段１７の出力で順次変更して遅延時間を設定する。
【００１６】
この遅延時間は繰り返し超音波を送信させたとき受信側の振動子からの反射と送信、または受信と第ｍ次反射波が重なって波形が乱れないように設定される。超音波の送信が設定された回数が繰り返されて終了したときの時間をタイマカウンタのような計時手段１８で求める。次に切換手段１９で第１振動子１１Ａと第２振動子１１Ｂの発信受信を切り換えて、第２振動子１１Ｂから第１振動子１１Ａすなわち下流から上流に向かって超音波信号を送信し、この送信を前述のように繰り返しその時間を計時する。そしてその時間差から管路の大きさや流れの状態を考慮して流量演算手段２０で流量値を求める。
【００１７】
タイマ変更手段１７は図２に示すように送信手段１２の周期Ｔをｎ分割する分割手段１７ａと、分割した時間成分を基準として遅延時間を組み立てる時間組み立て手段１７ｂから成る。
【００１８】
送信手段１２から振動子を駆動する高周波信号を送出するが、この高周波信号の周期Ｔを分割手段１７ａでｎ分割し、このｎ分割した時間成分を基準として時間組み立て手段１７ｂが遅延時間を組み立てる。組み立てられた遅延時間は遅延手段１６に送られる。遅延手段１６は比較手段１４で信号を受信したことを検知した後、この遅延時間だけ時間を遅らせてから送信信号を送出する送信手段に信号を伝達する。
【００１９】
ここで周期をｎ分割する分割手段１７ａは実際に周期を測定してからそれを分割する回路でも、予め周期を設定しておく送信手段１４であればｎ分割した時間をつくるＣＲタイマ回路等で実現しても良い。
【００２０】
このように遅延時間を発振周期のｎ分割した時間を単位を基準として順次変更していくことで受信側から反射してきた前回発振した信号の位相に影響される発振信号を送出することや、反対に前回発振した信号の２回反射波と今回発振した信号の合成信号が受信することが無くなり受信波形も反射波が重畳したノイズ成分が入ることが無くなる。このため信号波形がひずむことが無く受信を判断する比較回路での精度が上がり、その結果流量精度が向上する。
【００２１】
一連の流れは図３に示すタイミング図のようになる。
【００２２】
（実施例２）
図４は本発明の実施例２の流量計測装置のタイマ変更手段１７を示したもので実施例１と異なるところは、固定値設定手段１７ｃを有し、組み立て手段１７ｂは分割手段１７ａの時間成分に前記固定値設定手段１７ｃの固定時間を付加して遅延時間を組み立てるものである。
【００２３】
これにより、タイマ変更手段１７は予め設定した固定値に送信回路１４の駆動周期をｎ分割した時間を基準とした時間を付加して遅延時間を順次変更することで送信周期をより最適化し、流体管路内に反射波による残響が十分減衰してから、または送信や受信に影響の無い時間帯に送信信号を送出するため流量計測精度を高めることができる。
【００２４】
（実施例３）
図５は本発明の実施例３の流量計測装置のブロック図を示したもので実施例１と異なるところは、タイマ変更手段１７の内部で送信回路１４の駆動周期をｎ分割する際に、そのｎ分割した時間を繰り返し手段１５の設定している繰り返し回数の公約数になるように分割数を調節するものである。
【００２５】
送信手段１２から振動子を駆動する高周波信号を送出するが、この高周波信号の周期Ｔを分割手段１７ａでｎ分割し、このｎ分割した時間成分を基準として時間組み立て手段１７ｂが遅延時間を組み立てる。この時、ｎ分割する分割数は繰り返し手段１５で設定している繰り返し回数の公約数になるよう分割する。分割方法は図５のように繰り返し手段１５からの信号を基に行っても良いし予め繰り返し回数が設定されている場合はその公約数を分割手段１７ａで設定しても良い。
【００２６】
このように繰り返し回数の公約数で分割した時間を基準として遅延時間を順次変更していくことにより、順次変更していく遅延時間の変更状態が常に繰り返し回数内で一定回数で安定する。このため遅延時間のバラツキが測定時毎に大きくずれてしまうことが無くなり安定した計測状態を維持することが可能になる。その結果流量精度が安定する。
【００２７】
（実施例４）
図６は本発明の実施例４の流量計測装置のブロック図を示したもので実施例１と異なるところは、切換手段１９の切換え信号をタイマ変更手段１７が入力しているものである。
【００２８】
繰り返し手段で設定している回数だけ第１振動子１１Ａを送信側として超音波信号を繰り返し送信した後は、第２発進子１１Ｂが送信側となるよう切換手段１９を切換える。この時に切換えたことをタイマ変更手段１７にも伝達する。タイマ変更手段１７はこの切換え信号を入力すると、前回第１振動子１１Ａを送信側としていた時の順次変更していた遅延時間と同じ状態で第２振動子１１Ｂを送信側とした時も遅延時間を順次変更していく。
【００２９】
このように超音波を上流から下流に向かって発振する時と、反対に下流から上流に向かって発振する時で繰り返し時における順次変更していく遅延時間の状態を同じにすることで、送受信する方向にかかわらず同じ遅延状態で遅延時間を調節することができ繰り返し回路における誤差を無くすことができ測定も同じ状態でできることから流量計測精度を高めることができる。
【００３０】
（実施例５）
図７は本発明の実施例５の流量計測装置のブロック図を示したもので実施例４と異なるところは、タイマ変更手段１７内部で遅延時間を組み立てる組み立て手段を少なくとも２つ有し切換手段１９の切換え信号でこの組み立て手段を切り替えて使用するものである。
【００３１】
例えば第１振動子１１Ａを送信側として超音波信号を繰り返し送信している時は組み立て手段１７ｂ−１を使用し、第２発進子１１Ｂが送信側となる時は組み立て手段１７ｂ−２を使用することで遅延時間の組み立ては異なるが総遅延時間を同じとするように調節するものである。
【００３２】
このように超音波を上流から下流に向かって発振する時と、反対に下流から上流に向かって発振する時で繰り返し時における順次変更していく遅延時間の総時間を同じにすることで、送受信する方向にかかわらず総遅延時間を調節することができ繰り返し回路における誤差を無くすことができ測定もほぼ同じ状態でできることから流量計測精度を高めることができる。
【００３３】
（実施例６）
図８は本発明の実施例６の流量計測装置のブロック図を示したもので実施例１と異なるところは、流量演算手段２０の信号をタイマ変更手段１７が受け流量に応じて遅延時間を調節するものである。
【００３４】
例えば流量が多い場合と微少の場合では遅延時間による流量誤差の考え方は大きく異なる。流量が数千リットル／時間の場合と数リットル／時間では同じ遅延時間でも流量に対する誤差が大きく違ってくる。このため流量が多い場合は組み立て手段による順次変更する遅延時間は流量が少ない場合の遅延時間よりやや大き目に設定しても問題は無い。微少流量では遅延時間の差がすぐに流量誤差となってしまうため、順次変更する遅延時間の組み立て方を上下方向で極力誤差のでないようにする。
【００３５】
このように、タイマ変更手段は流量に応じて繰り返し時に信号伝達を遅らせる遅延時間を調節することで、最適な流量計測精度を維持することができる。
【００３６】
以上のように、各実施例によれば次の効果が得られる。
【００３７】
（１）タイマ変更手段の駆動周期をｎ分割した時間を基準として遅延時間を順次変更し、遅延時間と送信周期とを調節することで、再現性の高い遅延時間と送信周期を得、流量計測精度を高めることができる。
【００３８】
（２）固定値に送信回路の駆動周期をｎ分割した時間を基準とした時間を付加して遅延時間を順次変更することで送信周期をより最適化し、流体管路内に反射波による残響が十分減衰してから、または送信や受信に影響の無い時間帯に送信信号を送出するため流量計測精度を高めることができる。
【００３９】
（３）繰り返し回数の公約数で分割した時間を基準として遅延時間を順次変更していくことにより、順次変更していく遅延時間の変更状態が常に繰り返し回数内において一定回数で安定するため、遅延時間のバラツキが測定時毎に大きくずれてしまうことが無くなり安定した計測状態を維持することが可能になり、結果流量精度が安定する。
【００４０】
（４）超音波を上流から下流に向かって発振する時と、反対に下流から上流に向かって発振する時で繰り返し時における順次変更していく遅延時間の状態を同じにすることで、送受信する方向にかかわらず同じ遅延状態で遅延時間を調節することができ繰り返し回路における誤差を無くすことができ測定も同じ状態でできることから流量計測精度を高めることができる。
【００４１】
（５）超音波を上流から下流に向かって発振する時と、反対に下流から上流に向かって発振する時で繰り返し時における順次変更していく遅延時間の総時間を同じにすることで、送受信する方向にかかわらず総遅延時間を調節することがで き繰り返し回路における誤差を無くすことができ測定もほぼ同じ状態でできることから流量計測精度を高めることができる。
【００４２】
（６）タイマ変更手段は流量に応じて繰り返し時に信号伝達を遅らせる遅延時間を調節することで、最適な流量計測精度を維持することができる。
【００４３】
【発明の効果】
以上のように本発明の流量計測装置によれば、タイマ変更手段の駆動周期を基準として遅延時間を変更し、遅延時間と送信周期とを調節することで、再現性の高い遅延時間と送信周期を得、流量計測精度を高めることができるものである。
【図面の簡単な説明】
【図１】本発明の実施例１の流量計測装置を示すブロック図
【図２】同タイマ変更手段を示すブロック図
【図３】（ａ）同流量計測装置の送信波の動作を示すタイミングチャート（ｂ）同流量計測装置の受信波の動作を示すタイミングチャート（ｃ）同流量計測装置の遅延手段の動作を示すタイミングチャート
【図４】本発明の実施例２のおける流量計測装置を示すブロック図
【図５】本発明の実施例３における流量計測装置を示すブロック図
【図６】本発明の実施例４における流量計測装置を示すブロック図
【図７】本発明の実施例５における流量計測装置を示すブロック図
【図８】本発明の実施例６における流量計測装置を示すブロック図
【図９】従来の流量計測装置の遅延回路図
【符号の説明】
１０ 流体管路
１１Ａ 第１振動子
１１Ｂ 第２振動子
１２ 送信回路
１５ 繰り返し手段
１６ 遅延手段
１７ タイマ変更手段
１７ａ 分割手段
１７ｂ 組み立て手段
１７ｃ 固定値設定手段
１８ 計時手段
１９ 切換手段
２０ 流量演算手段Patent application title: Flow rate measuring device
1. A first transducer and a second transducer provided in a fluid channel for transmitting and receiving ultrasonic signals, a transmission circuit for sending a periodic drive signal to the transducer, and a mutual relationship between the two transducers and repeating means for performing a plurality of times ultrasound transmission, a timer changing means to change the delay time driving period of said transmission circuit as standards, a delay means for delaying the signal transmitted during the repetition by the timer change means, said both And a flow rate measuring device for calculating a flow rate based on a propagation time of ultrasonic waves between the transducers.
2. The timer changing means has a preset fixed value, and a delay time is sequentially changed by adding a time based on a time obtained by dividing the drive cycle of the transmission circuit by n to this fixed value. Flow rate measuring device as described.
3. A flow rate measuring apparatus as set forth in claim 1, wherein the number of divisions is adjusted so that the time obtained by dividing the drive cycle of the transmission circuit by n by the timer changing means is a common divisor of the number of repetitions set by the repeating means.
4. The apparatus according to claim 1, further comprising switching means for switching between transmission functions and reception functions of two transducers transmitting and receiving ultrasonic waves, and adjusting delay times in the same delay state regardless of transmission and reception directions. Or the flow rate measuring device according to 3.
5. The apparatus according to claim 1, further comprising switching means for switching and setting the transmission function and the reception function of the two transducers for transmitting and receiving the ultrasonic waves, and adjusting the delay time to have the same total delay time regardless of the transmitting and receiving directions. The flow rate measuring device according to 1, 2 or 3.
6. The timer changing means receives the output of the flow rate calculating means for calculating the flow rate based on the propagation time of the ultrasonic wave, and the delay time is based on the time obtained by dividing the drive cycle of the transmission circuit by n according to the flow rate. The flow rate measuring apparatus according to any one of claims 1 to 5, wherein a timer changing means for changing sequentially and a delay time for delaying signal transmission at the time of repetition are adjusted by the timer changing means.
Detailed Description of the Invention
[0001]
Field of the Invention
The present invention relates in particular to an apparatus for measuring the flow rate of a fluid such as a gas by ultrasonic waves.
[0002]
[Prior Art]
In the conventional flow rate measuring apparatus of this type, as shown in JP-A-61-104224, it has been performed to supply a transmission command pulse to a transmission circuit via a delay means. As the delaying means is shown in FIG. 9, when the trigger input Y comes in, the delaying means consisting of the amplifier, 1 and the capacitors 2 to 4, the transistor 5 and the resistors 6 to 8 is activated and the monostable multivibrator The output width of 9 is changed irregularly, for example, between several μs and several hundred μs.
[0003]
[Problems to be solved by the invention]
However, in the above-mentioned conventional flow rate measuring device, the reproducibility of this delay time is not sufficient, and it is possible to obtain the nanosecond reproducibility necessary for measuring a small flow rate such as 3 liters / hour per hour. As a result, the resolution of flow rate measurement could not be increased.
[0004]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a first vibrator and a second vibrator provided in a fluid channel and transmitting and receiving ultrasonic signals, a transmission circuit for transmitting a periodic drive signal to the vibrator, and the transmission circuit. delaying and repeating means for performing a plurality of times ultrasonic transmission cross between the two oscillators, and a timer change means to change the delay time driving period of said transmission circuit as standards, signaling during the repetition by the timer change means delay means, and a flow rate calculation means for calculating a flow rate based on the ultrasonic propagation time between the two transducers, the delay time driving period of the timer changing means as referenced to varying puff, transmits a delay time By adjusting the period, a highly reproducible delay time and transmission period can be obtained, and the flow measurement accuracy can be enhanced.
[0005]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention is very useful when applied to, for example, a flow rate measuring unit of a fuel gas such as city gas or propane gas. The reason is that it is necessary in Japan for the flow rate measurement in fuel gas to accurately grasp the change in flow rate over 3 liters per hour. Therefore, the present invention is convenient because the flow rate can be measured over a wide range such as tens of thousands of liters per hour from a very small change in flow rate. The present invention is practical and useful in each of the fields where it is necessary to measure an accurate flow rate in accordance with the above gist.
[0006]
And although the person skilled in the art can realize the present invention by the configuration described in each claim, it helps the understanding of the contents of the present invention so that the embodiment can be easily grasped. The action and effect of each claim will be described below in addition to the means and the configuration.
[0007]
That is, a first transducer and a second transducer provided in the fluid channel for transmitting and receiving ultrasonic signals, a transmission circuit for sending a periodic drive signal to the transducers, and ultrasonic wave transmission between the transducers. Repeating means performed a plurality of times, timer changing means for sequentially changing delay time based on n divided time of drive cycle of the transmission circuit, delay means for delaying signal transmission at the time of repetition by the timer changing means, and vibration By providing the flow rate calculating means for calculating the flow rate based on the propagation time of the ultrasonic wave between the daughters, the delay time is sequentially changed based on the time obtained by dividing the driving period of the timer changing means by n, delay time and transmission period By adjusting and, it is possible to obtain a highly reproducible delay time and transmission period, and to improve the flow measurement accuracy.
[0008]
In addition, the timer change means optimizes the transmission cycle by adding the time based on the time obtained by dividing the drive cycle of the transmission circuit by n to the preset fixed value, and optimizing the transmission cycle, thereby improving the flow measurement accuracy. It can be enhanced.
[0009]
Also, the delay time is sequentially changed by adjusting the number of divisions so that the time when the drive cycle of the transmission circuit is divided by n by the timer changing means becomes a common divisor of the number of repetitions set by the repeating means. The state is always stabilized at a fixed number of times within the number of repetitions, and it is possible to maintain a stable measurement state without the delay time variation being largely deviated at each measurement time.
[0010]
In addition, it has switching means for switching and setting the transmission function and reception function of two transducers that transmit and receive ultrasonic waves, and improves the flow measurement accuracy by adjusting the delay time in the same delay state regardless of the transmission and reception direction Can.
[0011]
In addition, it has switching means to switch and set the transmission function and reception function of the two transducers that transmit and receive ultrasonic waves, and adjusts the delay time to achieve the same total delay time regardless of the transmission and reception direction. Errors in flow measurement can be reduced.
[0012]
Further, the timer changing means can maintain the optimum flow rate measurement accuracy by adjusting the delay time to delay the signal transmission at the time of repetition depending on the flow rate.
[0013]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0014]
Example 1
FIG. 1 is a block diagram of a flow rate measuring apparatus according to a first embodiment of the present invention.
[0015]
In FIG. 1, a first transducer 11A for transmitting an ultrasonic wave and a second transducer 11B for receiving an ultrasonic wave are disposed in the flow direction in the middle of the fluid channel 10. Reference numeral 12 is a transmission circuit to the first vibrator 11A, and 13 is an amplifier circuit for the signal received by the second vibrator 11B. This amplified signal is compared with the reference signal by the comparison circuit 14, and the signal above the reference signal is When it is detected, the signal is delayed by the delay means 16 by the repeating means 15 by the number of times set, and then the ultrasonic signal is repeatedly transmitted. The delay means 16 sequentially changes the output of the timer changing means 17 based on the time obtained by dividing the drive cycle of the transmission circuit 12 by n to set the delay time.
[0016]
This delay time is set so that when ultrasonic waves are repeatedly transmitted, reflection and transmission from the transducer on the reception side, or reception and the m-th order reflection wave do not overlap to disturb the waveform. The time when the transmission of the ultrasonic waves is repeated for the set number of times is ended by a timer 18 such as a timer counter. Next, the transmission and reception of the first transducer 11A and the second transducer 11B are switched by the switching means 19, and an ultrasonic signal is transmitted from the second transducer 11B toward the first transducer 11A, that is, from downstream to upstream The transmission is repeated as described above and its time is timed. Then, from the time difference, the flow rate calculating means 20 determines the flow rate value in consideration of the size of the conduit and the state of the flow.
[0017]
The timer changing means 17 comprises a dividing means 17a for dividing the cycle T of the transmitting means 12 by n as shown in FIG. 2 and a time assembling means 17b for assembling a delay time based on the divided time components.
[0018]
A high frequency signal for driving the vibrator is sent from the transmission means 12. The period T of this high frequency signal is divided by n by the dividing means 17a, and the time assembling means 17b assembles the delay time on the basis of the n divided time components. The assembled delay time is sent to the delay means 16. After detecting that the signal is received by the comparison means 14, the delay means 16 delays the time by this delay time and transmits the signal to the transmission means for transmitting the transmission signal.
[0019]
The division means 17a for dividing the cycle by n here is a CR timer circuit or the like which generates n divided time if it is the transmission means 14 in which the cycle is set in advance even by a circuit which measures the cycle and then divides it. It may be realized.
[0020]
In this way, the delay time is sequentially changed based on the unit time of the oscillation cycle divided by n as a unit to send an oscillation signal affected by the phase of the previously oscillated signal reflected from the receiving side, or The composite signal of the twice-reflected wave of the signal oscillated last time and the signal oscillated this time is not received, and the reception waveform is also free from the noise component on which the reflected wave is superimposed. For this reason, the accuracy in the comparison circuit that determines reception without distortion of the signal waveform is improved, and as a result, the flow accuracy is improved.
[0021]
A series of flows are as shown in the timing chart of FIG.
[0022]
(Example 2)
FIG. 4 shows the timer changing means 17 of the flow rate measuring apparatus according to the second embodiment of the present invention, which differs from the first embodiment in having the fixed value setting means 17c and the assembling means 17b is a time component of the dividing means 17a. The delay time is assembled by adding the fixed time of the fixed value setting means 17c to the above.
[0023]
By this, the timer changing means 17 adds the time based on the time obtained by dividing the drive cycle of the transmission circuit 14 by n to the fixed value set in advance, and changes the delay time sequentially to further optimize the transmission cycle, The flow measurement accuracy can be improved because the transmission signal is sent out in a pipe line after the reverberation due to the reflected wave is sufficiently attenuated or in a time zone in which transmission or reception is not affected.
[0024]
(Example 3)
FIG. 5 is a block diagram of a flow rate measuring apparatus according to a third embodiment of the present invention, which differs from the first embodiment in that when the driving cycle of the transmission circuit 14 is divided into n within the timer changing means 17. The number of divisions is adjusted so that the time divided by n becomes a common divisor of the number of repetitions set by the repetition means 15.
[0025]
A high frequency signal for driving the vibrator is sent from the transmission means 12. The period T of this high frequency signal is divided by n by the dividing means 17a, and the time assembling means 17b assembles the delay time on the basis of the n divided time components. At this time, the number of divisions to be divided into n is divided so as to be a common divisor of the number of repetitions set by the repetition means 15. The dividing method may be performed based on the signal from the repeating unit 15 as shown in FIG. 5, or when the number of repetitions is set in advance, the common divisor may be set by the dividing unit 17a.
[0026]
As described above, by sequentially changing the delay time based on the time divided by the common divisor of the number of repetitions, the change state of the delay time to be sequentially changed is always stabilized at a fixed number of times within the number of repetitions. For this reason, the variation in delay time does not largely shift for each measurement, and a stable measurement state can be maintained. As a result, the flow accuracy is stabilized.
[0027]
(Example 4)
6 shows a block diagram of a flow rate measuring apparatus according to a fourth embodiment of the present invention, which differs from the first embodiment in that the timer changing means 17 inputs a switching signal of the switching means 19.
[0028]
After the ultrasonic signal is repeatedly transmitted with the first transducer 11A as the transmitting side the number of times set by the repeating means, the switching means 19 is switched so that the second launcher 11B becomes the transmitting side. At this time, the timer change means 17 is also notified of the switching. When the timer changing means 17 receives this switching signal, the delay time is also set when the second vibrator 11B is set as the transmission side in the same state as the delay time which was sequentially changed when the first vibrator 11A was set as the transmission side last time. Change in order.
[0029]
As described above, transmission and reception are performed by making the state of the delay time changing repeatedly at the same time the same when oscillating ultrasonic waves from upstream to downstream and vice versa. The delay time can be adjusted in the same delay state regardless of the direction, so that the error in the repetitive circuit can be eliminated and the measurement can be performed in the same state, so that the flow measurement accuracy can be enhanced.
[0030]
(Example 5)
7 shows a block diagram of a flow rate measuring apparatus according to a fifth embodiment of the present invention, which differs from the fourth embodiment in having at least two assembling means for assembling delay times in the timer changing means 17 and switching means 19 This assembly means is switched and used by the switching signal of.
[0031]
For example, when ultrasonic waves are repeatedly transmitted with the first transducer 11A as the transmission side, the assembly means 17b-1 is used, and when the second launcher 11B is the transmission side, the assembly means 17b-2 is used. In particular, the setup of the delay time is adjusted to make the total delay time the same.
[0032]
As described above, transmission and reception are performed by making the total time of the delay time which is sequentially changed the same at the same time when the ultrasonic wave oscillates from the upstream to the downstream and the oscillation from the downstream to the upstream. The total delay time can be adjusted regardless of the direction of movement, and errors in the repetitive circuit can be eliminated, and the measurement can be performed in substantially the same state, so that the flow measurement accuracy can be enhanced.
[0033]
(Example 6)
8 shows a block diagram of a flow rate measuring apparatus according to a sixth embodiment of the present invention. The difference from the first embodiment is that the timer changing means 17 receives the signal of the flow rate calculating means 20 and adjusts the delay time according to the flow rate. It is
[0034]
For example, in the case where the flow rate is high and the case where the flow rate is very small, the concept of the flow rate error due to the delay time is largely different. When the flow rate is several thousand liters per hour and several liters per hour, the error for the flow rate is greatly different even with the same delay time. For this reason, when the flow rate is high, there is no problem even if the delay time sequentially changed by the assembling means is set slightly larger than the delay time when the flow rate is low. Since the difference in delay time immediately becomes a flow rate error at a small flow rate, the method of assembling the delay time to be sequentially changed is made as close as possible to the maximum error.
[0035]
Thus, the timer changing means can maintain the optimum flow rate measurement accuracy by adjusting the delay time to delay the signal transmission at the time of repetition depending on the flow rate.
[0036]
As described above, according to each embodiment, the following effects can be obtained.
[0037]
(1) The delay time is sequentially changed based on the time obtained by dividing the drive cycle of the timer changing means by n, and the delay time and the transmission cycle are adjusted to obtain a highly reproducible delay time and transmission cycle, and the flow rate measurement Accuracy can be improved.
[0038]
(2) The transmission cycle is optimized by adding the time based on the time obtained by dividing the drive cycle of the transmission circuit by n to a fixed value and sequentially changing the delay time, and reverberation due to reflected waves in the fluid channel Since the transmission signal is sent out after sufficient attenuation or in a time zone in which transmission and reception are not affected, flow measurement accuracy can be enhanced.
[0039]
(3) By sequentially changing the delay time based on the time divided by the common divisor of the number of repetitions, the change state of the delay time to be sequentially changed is always stabilized at a fixed number of times within the number of repetitions. The variation in time does not shift greatly at each measurement, and it becomes possible to maintain a stable measurement state, and as a result, the flow accuracy is stabilized.
[0040]
(4) Transmission and reception are performed by making the state of the delay time which changes repeatedly at the same time the same when oscillating ultrasonic waves from upstream to downstream and oscillating from downstream to upstream conversely The delay time can be adjusted in the same delay state regardless of the direction, so that the error in the repetitive circuit can be eliminated and the measurement can be performed in the same state, so that the flow measurement accuracy can be enhanced.
[0041]
(5) Transmitting and receiving by making the total time of the delay time changing repeatedly at the same time the same when oscillating ultrasonic waves from upstream to downstream and oscillating from downstream to upstream conversely it is possible to increase the flow rate measurement accuracy because it can almost same state also measured it is possible to eliminate the error in the repeating circuit Ki out to adjust the total delay time regardless of the direction of.
[0042]
(6) The timer changing means can maintain the optimum flow rate measurement accuracy by adjusting the delay time to delay the signal transmission at the time of repetition depending on the flow rate.
[0043]
【Effect of the invention】
As described above, according to the flow rate measuring apparatus of the present invention, the delay time is changed with high repeatability by changing the delay time on the basis of the drive cycle of the timer changing means and adjusting the delay time and the transmission cycle. The flow rate measurement accuracy can be enhanced .
Brief Description of the Drawings
1 is a block diagram showing a flow rate measuring apparatus according to a first embodiment of the present invention. FIG. 2 is a block diagram showing the timer changing means. FIG. 3 (a) a timing chart showing the operation of the transmission wave of the flow rate measuring apparatus. (B) A timing chart showing the operation of the received wave of the flow rate measuring device (c) A timing chart showing the operation of the delay means of the flow rate measuring device [Fig. 4] A block showing the flow rate measuring device in Example 2 of the present invention 5 is a block diagram showing a flow rate measuring apparatus according to a third embodiment of the present invention. FIG. 6 is a block diagram showing a flow rate measuring apparatus according to a fourth embodiment of the present invention. FIG. 7 is a flow rate measurement according to the fifth embodiment of the present invention 8 is a block diagram showing a flow rate measuring apparatus according to a sixth embodiment of the present invention. FIG. 9 is a delay circuit diagram of a conventional flow rate measuring apparatus.
DESCRIPTION OF SYMBOLS 10 Fluid conduit 11A 1st vibrator 11B 2nd vibrator 12 Transmission circuit 15 Repeating means 16 Delaying means 17 Timer changing means 17a Division means 17b Assembling means 17c Fixed value setting means 18 Timing means 19 Switching means 20 Flow rate calculating means