JP4082246B2

JP4082246B2 - Flowmeter

Info

Publication number: JP4082246B2
Application number: JP2003066452A
Authority: JP
Inventors: 康裕梅景; 行夫長岡; 紀夫新村
Original assignee: Panasonic Corp; Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Corp; Panasonic Holdings Corp
Priority date: 2003-03-12
Filing date: 2003-03-12
Publication date: 2008-04-30
Anticipated expiration: 2023-03-12
Also published as: JP2004271490A

Description

【０００１】
【発明の属する技術分野】
本発明は、超音波を利用して空気、ガス、水などの流体の流量を計測する超音波式の流量計に関するものである。
【０００２】
【従来の技術】
従来この種の超音波式流量計は、図９に示すように流路内１に備えた一対の音響トランスジューサ２、３を設けて実現する超音波式流速測定手段４と、前記超音波式流速測定手段４の測定間隔を変更する測定間隔変更手段５と、流路内の圧力を検知する圧力検知手段６と、圧力判定手段７と、判定値調整手段８と、脈波検出手段９とで構成される。
【０００３】
ここで、１０はランダム時間発生手段、１１は流量計測手段、１２は流量積算手段、１３は表示手段、１４は遮断弁手段、１５は弁制御手段である（例えば、特許文献１参照）。
【０００４】
上記構成において、流路中の流体の脈波を監視し、予め定めた判定値より大きい脈波を検出した時、測定間隔を短くするようにして計測精度をあげて流速を測定するようにしたものである。
【０００５】
また、図１０に示すように、計測流量部１６と、流量値積算部１７と、第１のバッファ１８と、第２のバッファ１９と、流量積算値記憶部２０とから構成されているものも知られている（例えば、特許文献２参照）。
【０００６】
上記構成において、流体中の脈動の発生に起因して発生する流量計測誤差を、第１バッファ１８と第２バッファ１９を用いて解消するものである。
【０００７】
すなわち、第１バッファ１８では、流量計測部１６から送られてくる流量値を積算してカウンタ値をインクリメントしていき、その積算値が所定の積算桁上げしきい値以上に達すると、流量積算値を１単位量ずつカウントアップすると共に、そのとき積算桁上げしきい値を超えた剰余の値を切り捨ててカウンタ値をゼロリセットする。
【０００８】
そしてその切り捨てられた剰余の値は第２のバッファ１９が積算可能に保持しておき、所定のタイミングで流量積算値のカウントアップに反映させ加算することとしていたものである。
【０００９】
よって、脈動による流量値が発生しても、第１バッファが吸収し、すぐに１単位量のカウントアップには至らないので、脈動時の流量計測誤差を吸収できる。
【００１０】
【特許文献１】
特開平１１−２５８０１８号公報
【００１１】
【特許文献２】
特開２００１−３４９７５２号公報
【００１２】
【発明が解決しようとする課題】
しかしながら前記従来の構成では、計測間隔を短くして計測すると計測に使用する消費電力が多くなり、電池で使用する場合には長時間の使用に耐えられないという課題があった。
【００１３】
また、バッファの方法では、積算流量のカウントアップが遅れるという課題と、剰余の値だけが残っていく第２バッファの値を最終的には加算しているので、脈動による誤差を加算していくことになり、累積誤差は解消できなく精度も悪くなるという課題があった。
【００１４】
本発明はこのような従来の課題を解決するもので、計測精度の向上と省電力化を高めた流量計を提供することを目的とするものである。
【００１５】
【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、流路の上流側から下流側へ超音波の送受信を繰返し行った時の第１伝搬時間計測と流路の下流側から上流側へ超音波の送受信を繰返し行った時の第２伝搬時間計測とを１つの計測単位とする送受信繰返手段と、前記送受信繰返手段の計測を複数回繰り返す計測繰返手段と、前記送受信繰返手段と前記計測繰返手段とで繰り返された時の総第１伝搬時間および総第２伝搬時間から流量を検出する流量検出手段と、所定時間内の前記流量検出手段による検出流量値から流量変動を検出する変動検出手段と、前記変動検出手段が流量変動を検出した場合には高精度流量計測手段に、それ以外の場合には低消費電力流量計測手段に切り替える計測切替手段とを具備し、前記高精度流量計測手段および低消費電力流量計測手段は、前記送受信繰返手段による送受信繰返し回数と計測繰返手段の計測回数とが以下（１）、（２）のように設定されていることを特徴とするものである。
【００１６】
（１）高精度流量計測手段：送受信繰返手段による送受信繰返し回数を少なくし、計測繰返手段による計測回数を多くする。
【００１７】
（２）低消費電力流量計測手段：送受信繰返手段による送受信繰返し回数を多くし、計測繰返手段による計測回数を少なくする。
【００１８】
上記発明によれば、精度の高い流量計測と、低消費電力の流量計測を両立して実現することができる。
【００１９】
【発明の実施の形態】
本発明の実施の形態は、流路の上流側から下流側へ超音波の送受信を繰返し行った時の第１伝搬時間計測と流路の下流側から上流側へ超音波の送受信を繰返し行った時の第２伝搬時間計測とを１つの計測単位とする送受信繰返手段と、前記送受信繰返手段の計測を複数回繰り返す計測繰返手段と、前記送受信繰返手段と前記計測繰返手段とで繰り返された時の総第１伝搬時間および総第２伝搬時間から流量を検出する流量検出手段と、所定時間内の前記流量検出手段による検出流量値から流量変動を検出する変動検出手段と、前記変動検出手段が流量変動を検出した場合には高精度流量計測手段に、それ以外の場合には低消費電力流量計測手段に切り替える計測切替手段とを具備し、前記高精度流量計測手段および低消費電力流量計測手段は、前記送受信繰返手段による送受信繰返し回数と計測繰返手段の計測回数とが以下（１）、（２）のように設定されていることを特徴とするものである。
【００２０】
（１）高精度流量計測手段：送受信繰返手段による送受信繰返し回数を少なくし、計測繰返手段による計測回数を多くする。
【００２１】
（２）低消費電力流量計測手段：送受信繰返手段による送受信繰返し回数を多くし、計測繰返手段による計測回数を少なくする。
【００２２】
したがって、精度の高い流量計測と、低消費電力の流量計測を両立して実現することができる。
【００２３】
また、高精度流量計測手段の計測値から流量範囲を判別する流量判別手段を具備し、前記流量判別手段が小流量と判別したときは高精度流量計測手段による流量計測を継続し、前記流量判別手段が大流量と判別したときは低消費電力流量計測手段に切り替えるようにした。
【００２４】
その結果、流量値に適した精度と消費電力で計測することができ、より一層、無駄な消費電力を抑えることができる。
【００２５】
【実施例】
以下、本発明の実施例について図面を参照して説明する。
【００２６】
（実施例１）
図１において、２１は流体を流す流路、２２は超音波を送受信するために流路の上流側に設置された音波送受信手段、２３は超音波を送受信するために流路の下流側に設置された音波送受信手段、２４は音波の送受信を繰り返して行う繰返手段、２５は前記繰返手段２４で繰返し行われる音波の伝搬時間を計測する計時手段、２６は前記計時手段２５で計測された時間情報を基に流量を検出する流量検出手段である。
【００２７】
また、２７は音波の送受信の繰返し回数を変更する繰返し回数変更手段、２８は所定条件によって繰返し回数を都度変更する超音波式流量計測手段である。
【００２８】
そして、超音波式流量計測手段２８は、繰返し回数変更手段２７によって繰返し回数を増加して高精度流量計測手段を実現し、逆に繰返し回数を減少して低消費電力流量計測手段を実現するものであり、この計測手段の計測切替えを行う手段が計測切替手段２９である。
【００２９】
ここで、３０は変動検出手段、３１は流量判別手段、３２は流量積算手段、３３は流量異常判定手段、３４は警告表示手段、３５は電池、３６は流量記憶手段、３７は流量表示手段、３８は計測異常判別手段である。
【００３０】
以上のような構成の流量計の計測原理について説明する。
【００３１】
図１に示す流路の上流側の音波送受信手段２２から下流側の音波送受信手段２３に向かって音波が伝搬する伝搬時間Ｔ１を計測すると、伝搬時間Ｔ１は、式（１）のようになる。
【００３２】
Ｔ１＝Ｌ／（Ｃ＋Ｖｃｏｓθ）（１）
また、下流側の音波送受信手段２３から上流側の音波送受信手段２２に向かって伝搬する伝搬時間Ｔ２を計測すると、伝搬時間Ｔ２は、式（２）のようになる。
【００３３】
Ｔ２＝Ｌ／（Ｃ−Ｖｃｏｓθ）（２）
ここで、Ｖは流路内の流速、Ｌは音波送受信手段間の距離、θは流路に対する音波送受信手段の対向する角度、Ｃは音速である。
【００３４】
そして、Ｔ１とＴ２の逆数の差をとり、式を変形するとＴ１、Ｔ２から流速Ｖは、式（３）のように求めることができる。
【００３５】
Ｖ＝（Ｌ／２ｃｏｓθ）・（１／Ｔ１−１／Ｔ２）（３）
そして、この流速Ｖに流路の断面積などを考慮して流量Ｑを算出することができるのである。以上は、１回の送受信の計測で説明しているが、繰返手段２４で伝搬時間を繰り返して計測する方法で積算伝搬時間を求めることによって、より精度よく流速Ｖを求めることができることは明白であろう。
【００３６】
しかしながら、この計測は上流側からの送信時の流速Ｖ１と、下流側からの送信時流速Ｖ２が同じであることが条件である。実際には脈動のように流量変動を発生している場合がある。もし、図２のように流速に変動があった場合、計測している時間が短いと、上流側からの伝搬時間を測定している時の平均流速Ｖ１は、下流側からの伝搬時間を測定しているときの平均流速Ｖ２とは同じにはならず、計測誤差を生じることになる。
【００３７】
そのため図３のように、繰り返し回数を多くして変動の１周期以上を計測範囲とすることによって、流速を平均化して伝播時間を計測することで、流速Ｖ１とＶ２が同じような状態になり、精度を向上、維持することができる。この原理を利用した方法が繰返し回数を増加して実現する高精度流量計測手段である。
【００３８】
また、繰返し回数が少ないと動作時間が短いので処理に使用される消費電力が少なくなるのは明白である。このように繰返し回数を少なくして消費電力を低減する計測方法が低消費電力流量計測手段である。
【００３９】
次に、図４と図５に示すフローチャートを用いて動作の流れを説明する。図４に示すように流量計測は、通常、低消費電力流量計測手段による低消費電力モードで計測が行われる（ＳＴＥＰ１０）。
【００４０】
そして、計測された瞬時流量値から変動検出手段３０により流量変動が判定される（ＳＴＥＰ１１）。流量変動がない場合は、流量積算処理（ＳＴＥＰ１２）を経て低消費電力モード（ＳＴＥＰ１０）で継続して流量計測が行われる。
【００４１】
ここで、変動検出手段３０（ＳＴＥＰ１１）について説明する。例えば、変動検出手段３０は、流量検出手段２６により検出された瞬時流量値から、所定時間内の最大流量値Ｑｍａｘと、所定時間内の最小流量値Ｑｍｉｎの差（Ｑｍａｘ−Ｑｍｉｎ）を求めて流量変動を検出する。
【００４２】
そして、その流量変動（Ｑｍａｘ−Ｑｍｉｎ）が、所定流量としての１０リッター／時間以上の時は、変動があると検出し、１０リッター／時間未満の時は、変動がないと変動検出手段３０が検出するのである。
【００４３】
次に、このような変動検出手段３０により変動が検出された場合、流量判別手段３１により流量判別が行われる（ＳＴＥＰ１３）。
【００４４】
流量判別手段３１は、流量範囲を大流量範囲（例えば、３０００リッター／時間以上）と判別すると、繰返し回数を最適な最小回数（例えば８回から１２８回、最適は６４回）に減少して低消費電力モードで計測する。
【００４５】
また、流量判別手段３１が流量範囲を小流量範囲（例えば、３０００リッター／未満）と判別すると、繰返し回数を最適な回数（例えば６４から５１２回、最適は２５２回）に増加して高精度流量計測手段として高精度計測モードで継続して計測を行うことができる（ＳＴＥＰ１４）。
【００４６】
この高精度計測モード時においても、変動検出（ＳＴＥＰ１１）が繰返し行われ、変動がなくなったときは、流量積算処理（ＳＴＥＰ１２）を経て低消費電力計測モード（ＳＴＥＰ１０）に戻ることにしている。
【００４７】
また、大流量範囲と判別した場合において、最初から低消費電力モードで計測している場合は、繰返し回数は変更しない。
【００４８】
そして、それぞれの計測モードにおいて計測した流量値は、流量積算手段３２によって積算処理が行われる。
【００４９】
図５にその積算処理のフローチャートを示す。積算処理は、所定時間内の流量増加が所定時間内（例えば、所定時間１２分内）で所定流量値以上（例えば、所定流量１リッター以上）になったか否かを判別して（ＳＴＥＰ２０）、高精度計測モードで計測を行う（ＳＴＥＰ２１）ものである。
【００５０】
所定流量値未満の場合は、その所定時間内の積算値をクリア（ＳＴＥＰ２２）して、計測に異常かないか否かを判断して（ＳＴＥＰ２３）計測モードに戻る（ＳＴＥＰ２４）。
【００５１】
これにより、脈動のような流量変動時の計測誤差値や計測分解能以下の微小流量値の積算誤差による積算流量値のカウントアップを防止することができるのである。
【００５２】
また、蓄積してきた積算値と、新たに高精度計測モードで計測した瞬時流量値とを、同じ所定時間当たりに換算して比較し、その積算値が正しいか否かを流量異常判定手段３３が判定する（ＳＴＥＰ２５）。
【００５３】
異常なしと判定された時、積算値は加算され（ＳＴＥＰ２６）、計測モードへ戻る（ＳＴＥＰ２４）。
【００５４】
しかし、異常があると判定されたときは、現在の流量値は記憶手段に記憶され（ＳＴＥＰ２７）、その流量値と積算値はクリアされる（ＳＴＥＰ２８）。
【００５５】
流量計の警告表示手段３４には異常の警告表示が行われ（ＳＴＥＰ２９）、高精度計測モードへ戻る（ＳＴＥＰ３０）。
【００５６】
すなわち、クリアする前の所定時間当たりの積算値を流量記憶手段３６に記憶しておくことによって、異常が判定されるごとにその記憶手段に流量値を加算しつつ記憶していくことができ、異常時の積算流量を知ることができる。
【００５７】
例えば、この記憶手段の積算値がゼロに収束していくようであれば、異常の現象はランダムに発生していると考えられ、処理上短時間で判定している故の誤差と考えられるので、将来的な問題は少ないと学習することができる。
【００５８】
また、例えば２秒に１回の測定であれば、１回の計測で１リッターを超える流量は１８００リッター／時間になる。
【００５９】
通常、こんなに大流量が一度に流れることはないので、１リッターの積算流量を超えるまでに、２回、３回の計測を繰り返すことになる。脈動流のようにランダムな流れの場合は、おおよそプラス側、マイナス側の流量が繰り返されることになり、平均するとゼロに収束することになる。
【００６０】
また、計測タイミングも２秒に１回ではあるが、僅かにタイミングをランダム化して計測しているので、おおよそプラス側、マイナス側の流量が繰り返されることになる。よって、積算を続けていけば、通常はゼロに収束していくはずである。
【００６１】
しかし、この流量記憶手段３６の積算値がゼロに収束しない場合、何らかの改善が必要であることがわかり、記憶手段に積算される積算値から学習していくこと（ＳＴＥＰ３１）で、流量計の設置された環境に対処することができる。
【００６２】
例えば、記憶手段の積算値がゼロに収束していくような時期であれば、所定時間の１２分を長くすることでカウントアップは防止できるし、ゼロに収束しない時期であれば、１リッターの量を増やして短時間でカウントアップしないように修正することでカウントアップは防止できる。このように学習しながら所定時間や所定流量を修正することで、誤計測を防止することができる。
【００６３】
そして、変動なしの時の異常か、変動ありの時の異常かまで表示することによって、流路の異常状態をつかむことができ、異常が確認された後、早期に対応をとり異常を改善することが可能である。
【００６４】
異常が確認されると、さらに精度よく計測するために高精度計測モードへ戻るので、消費電力が多くなり電池３５の寿命を短くすることがあるので、警告表示により早期に流路の改善が必要であることを促すわけである。
【００６５】
さらに、計測異常判別手段３８の計測異常判別処理（ＳＴＥＰ２３）は、流量のカウントアップを判別する所定時間（例えば、１２分）とその所定時間内の積算流量値（例えば、１リッター）と計測手法の変更回数から異常を判別する。
【００６６】
例えば、所定時間になる前に頻繁に所定積算流量の１リッターを超える場合や、計測手法が低消費電力モードと高精度計測モードの計測手法変更が頻繁（例えば、１日に１００回以上）に行われる場合、明らかに正常ではないので、計測異常判別手段３８が異常と判定して、警告表示手段３４に異常警告を表示する。
【００６７】
これによって、早期に計測モードの切替異常を検出でき、安定した流量計測を実現して計測精度を向上することができる。
【００６８】
なお、計測処理を整理すると図６に示すような階層構造に示すこともできる。また、超音波式流量計測手段で説明したが、フローセンサやフルイディク流量計、または膜式メータのような機械式流量計などの流量計を用いて複数の流量計測手法を用いた場合も、機械式流量計を低消費電力流量計測手段とし、フローセンサを高精度流量計測手段として、低消費電力化と高精度化の両立を実現できることは容易に類推できる。
【００６９】
以上は大流量と小流量の２分類で説明したが、大流量、中流量、小流量の３分類以上に細かく分けて行えば、より一層精度を向上できる。さらに、積算流量が所定流量以上として説明したが、所定流量になる前に検出することでも同様である。そして、変動として説明したが、ガス配管に発生する脈動流の計測に対して効果があることは明白である。
【００７０】
また、ガス流を計測するガスメーターの場合、ガス漏洩やガス器具の使用状態を把握して安全管理する保安機能が付加されているが、それらの保安機能からの要求により高精度流量計測手段が処理される場合もあり得る。
【００７１】
異常を判別した場合は、警告表示のみならずガス遮断を行うようにガス遮断手段を装備しておくことも容易である。
【００７２】
さらに、電池を駆動電源としているため、電池の消耗状況に応じて低消費電力流量計測手段に切り替えることによって、長寿命化を実現することも十分考えられ、電池交換までの間は保安機能優先で安全メーターとして利用できる。
【００７３】
（実施例２）
実施例２について、図７を用いて説明する。実施例１と異なる点は、超音波の送受信を繰返し行う送受信繰返手段３９と、前記送受信繰返手段３９の計測をさらに繰返し行う計測繰返手段４０を備えたことにある。
【００７４】
すなわち、流路２１の上流側から下流側への送受信を繰返し行った時の第１伝搬時間計測Ｔ１と、下流側から上流側への送受信を繰返し行った時の第２伝搬時間計測Ｔ２を１つの計測単位とする送受信繰返手段３９と、前記送受信繰返手段３９の計測を少なくとも１回以上繰り返す計測繰返手段４０と、前記送受信繰返手段３９と前記計測繰返手段４０で繰り返された時の総第１伝搬時間ΣＴ１と総第２伝搬時間ΣＴ２から流量を検出する流量検出手段４１と、繰返し回数変更手段２７によって前記送受信繰返手段３９の送受信繰返し回数Ｎと前記計測繰返手段４０の計測繰返し回数Ｍとを変更して高精度流量計測手段と低消費電力流量計測手段を実現する超音波式流量計測手段４２を備えたしたものである。
【００７５】
具体的には、高精度流量計測手段は、繰返し回数変更手段２７によって送受信繰返し回数Ｎは少なく（例えば、１回から１６回で、最適には２回）し、逆に計測繰返し回数Ｍを多く（例えば、１６回から１０２４回で、最適には１２６回）してトータルの積Ｎ＊Ｍが多くなるように設定する。
【００７６】
このような設定とすることで、時間変化の激しい脈動流速の変化を細かく計測し、かつ長時間計測することで高精度化を実現するものである。
【００７７】
また、低消費電力流量計測手段は、繰返し回数変更手段２７によって送受信繰返し回数Ｎを多く（例えば、８回から５１２回、最適には６４回）して、計測繰返し回数Ｍを少なく（例えば、１回から８回、最適には１回）して短時間で計測が完了するようにして実現するものである。この計測手段の計測切替えを行う手段が計測切替手段２９である。
【００７８】
本実施例の構成によれば、図８に示すように、送受信繰返し回数を少なくして計測することで、上流からの伝搬時間と下流からの伝搬時間を計測するタイミングが近接でき、時間変化が激しく起こる脈動においても、計測精度を上げることができる。
【００７９】
そして、送受信の計測単位を計測繰返手段４０によって繰返し行うことできるとともに、長時間の計測が行えるので、変動する伝搬時間を平均化することができ、さらに精度を向上することができる。
【００８０】
なお、計測単位の繰返しは待ち時間を介して連続的に行うものであるが、この待ち時間を調整して総計測時間を調整することで計測精度を向上することもできる。
【００８１】
待ち時間を短くすることで計測がより精密になり高精度計測が行えることは明白である。そして、送受信繰返し回数Ｎと計測繰返し回数Ｍを組み合わせることによって、低消費電力モードと高精度計測モードの中間計測モードを作り出すこともできる。
【００８２】
例えば、脈動が大きく、流量範囲が小流量の範囲の場合、少し精度の高い計測でかつ消費電力も抑えた計測モードとして中間計測モードをいくつも実現することができる。
【００８３】
さらに、繰返し回数を変えて脈動の周期に合わせることで、脈動の影響を極力低減することができ、流量計測精度を向上することも可能である。
【００８４】
【発明の効果】
以上の説明から明らかなように本発明の流量計によれば、精度の高い流量計測と、低消費電力の流量計測を両立して実現す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の流量計のブロック図
【図２】同流量計の原理説明図
【図３】同流量計の原理説明図
【図４】同流量計のフローチャート
【図５】同流量計のフローチャート
【図６】同流量計のフローチャート
【図７】本発明の実施例２を示すブロック図
【図８】同流量計の原理説明図
【図９】従来の流量計のブロック図
【図１０】従来の他の流量計のブロック図
【符号の説明】
２１流路
２２、２３音波送受信手段
２４繰返手段
２５計時手段
２６流量検出手段
２７回数変更手段
２８超音波式流量計測手段
２９計測切替手段
３０変動検出手段
３１流量判別手段
３２流量積算手段
３３流量異常判定手段
３４警告表示手段
３５電池
３６流量記憶手段
３７流量表示手段
３８計測異常判別手段[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultrasonic flowmeter that measures the flow rate of a fluid such as air, gas, or water using ultrasonic waves.
[0002]
[Prior art]
Conventionally, this type of ultrasonic flowmeter includes an ultrasonic flow velocity measuring means 4 realized by providing a pair of acoustic transducers 2 and 3 provided in the flow path 1 as shown in FIG. The measurement interval changing means 5 for changing the measurement interval of the measuring means 4, the pressure detecting means 6 for detecting the pressure in the flow path, the pressure determining means 7, the determination value adjusting means 8, and the pulse wave detecting means 9 Composed.
[0003]
Here, 10 is a random time generating means, 11 is a flow rate measuring means, 12 is a flow rate integrating means, 13 is a display means, 14 is a shut-off valve means, and 15 is a valve control means (see, for example, Patent Document 1).
[0004]
In the above configuration, the pulse wave of the fluid in the flow path is monitored, and when a pulse wave larger than a predetermined determination value is detected, the measurement interval is shortened to increase the measurement accuracy and measure the flow velocity. Is.
[0005]
In addition, as shown in FIG. 10, there are also those constituted of a measurement flow rate unit 16, a flow rate value integration unit 17, a first buffer 18, a second buffer 19, and a flow rate integration value storage unit 20. It is known (see, for example, Patent Document 2).
[0006]
In the above configuration, the flow rate measurement error caused by the occurrence of pulsation in the fluid is eliminated by using the first buffer 18 and the second buffer 19 .
[0007]
That is, in the first buffer 18 , the flow rate value sent from the flow rate measurement unit 16 is integrated and the counter value is incremented. When the integrated value reaches a predetermined integration carry threshold or more, the flow integration is performed. The value is counted up by one unit amount, and at that time, the remainder value exceeding the accumulated carry threshold is rounded down to reset the counter value to zero.
[0008]
The rounded-off remainder value is held in the second buffer 19 so as to be accumulative, and is reflected and added to the count-up of the flow rate integrated value at a predetermined timing.
[0009]
Therefore, even if a flow rate value due to pulsation occurs, the first buffer absorbs and does not immediately count up one unit amount, so that it is possible to absorb a flow measurement error during pulsation.
[0010]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-258018
[Patent Document 2]
Japanese Patent Laid-Open No. 2001-349752
[Problems to be solved by the invention]
However, in the conventional configuration, if the measurement interval is shortened, the power consumption used for measurement increases, and there is a problem that the battery cannot be used for a long time when used with a battery.
[0013]
In addition, in the buffer method, the problem that the count-up of the integrated flow rate is delayed and the value of the second buffer in which only the surplus value remains are finally added, so an error due to pulsation is added. As a result, there is a problem that the accumulated error cannot be eliminated and the accuracy is deteriorated.
[0014]
The present invention solves such a conventional problem, and an object of the present invention is to provide a flow meter with improved measurement accuracy and power saving.
[0015]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention performs first propagation time measurement when ultrasonic transmission / reception is repeatedly performed from the upstream side to the downstream side of the flow path and transmission / reception of ultrasonic waves from the downstream side to the upstream side of the flow path. Transmission / reception repeating means having the second propagation time measurement when repeated as one measurement unit, measurement repeating means for repeating the measurement of the transmission / reception repeating means a plurality of times, the transmission / reception repeating means, and the measurement repetition A flow rate detecting means for detecting a flow rate from the total first propagation time and the total second propagation time when repeated by the return means, and a fluctuation detection for detecting a flow rate fluctuation from a flow rate value detected by the flow rate detecting means within a predetermined time. And a high-precision flow rate measurement means when the fluctuation detection means detects flow rate fluctuations, and a measurement switching means for switching to low power consumption flow rate measurement means in other cases. Means and low power consumption Measuring means, a transmission and reception number of repetitions by the transceiver repeating unit and the number of times of measuring the measuring repetition means the following (1), is characterized in that it is set as (2).
[0016]
(1) High-accuracy flow rate measurement means: The number of transmission / reception repetitions by the transmission / reception repetition means is reduced, and the number of measurement times by the measurement repetition means is increased.
[0017]
(2) Low power consumption flow rate measuring means: increasing the number of repetitions of transmission / reception by the transmission / reception repetition means and decreasing the number of times of measurement by the measurement repetition means.
[0018]
According to the above invention, it is possible to achieve both high-accuracy flow rate measurement and low-power consumption flow rate measurement.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
In the embodiment of the present invention, the first propagation time measurement when ultrasonic transmission / reception is repeatedly performed from the upstream side to the downstream side of the flow path and the ultrasonic wave transmission / reception are repeatedly performed from the downstream side to the upstream side of the flow path. Transmission / reception repeating means having the second propagation time measurement of time as one measurement unit, measurement repeating means for repeating the measurement of the transmission / reception repeating means a plurality of times, the transmission / reception repeating means, and the measurement repeating means, A flow rate detecting means for detecting a flow rate from the total first propagation time and the total second propagation time when it is repeated in the step, a fluctuation detecting means for detecting a flow rate fluctuation from a flow rate value detected by the flow rate detecting means within a predetermined time, A high-accuracy flow measurement means when the fluctuation detection means detects a flow fluctuation, and a measurement switching means for switching to a low power consumption flow measurement means in the other cases. Power consumption flow measurement means A reception number of repetitions by the transceiver repeating unit and the number of times of measuring the measuring repetition means the following (1), is characterized in that it is set as (2).
[0020]
(1) High-accuracy flow rate measurement means: The number of transmission / reception repetitions by the transmission / reception repetition means is reduced, and the number of measurement times by the measurement repetition means is increased.
[0021]
(2) Low power consumption flow rate measuring means: increasing the number of repetitions of transmission / reception by the transmission / reception repetition means and decreasing the number of times of measurement by the measurement repetition means.
[0022]
Therefore, it is possible to achieve both high-accuracy flow rate measurement and low-power consumption flow rate measurement.
[0023]
In addition, a flow rate discriminating unit for discriminating a flow range from a measurement value of the high-accuracy flow rate measuring unit is provided, and when the flow rate discriminating unit discriminates a small flow rate, the flow measurement by the high-accuracy flow rate measuring unit is continued, When the means is determined to be a large flow rate, it is switched to a low power consumption flow rate measuring means.
[0024]
As a result, measurement can be performed with accuracy and power consumption suitable for the flow rate value, and wasteful power consumption can be further suppressed.
[0025]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
[0026]
Example 1
In FIG. 1, 21 is a flow path for flowing a fluid, 22 is a sound wave transmitting / receiving means installed on the upstream side of the flow path for transmitting and receiving ultrasonic waves, and 23 is installed on the downstream side of the flow path for transmitting and receiving ultrasonic waves. The sound wave transmitting / receiving means, 24 is a repeating means for repeatedly transmitting and receiving sound waves, 25 is a time measuring means for measuring the propagation time of sound waves repeatedly performed by the repeating means 24, and 26 is measured by the time measuring means 25. It is a flow rate detection means for detecting a flow rate based on time information.
[0027]
Reference numeral 27 denotes a repetition number changing means for changing the number of repetitions of sound wave transmission / reception, and 28 denotes an ultrasonic flow rate measuring means for changing the number of repetitions according to a predetermined condition.
[0028]
The ultrasonic flow rate measuring means 28 realizes a high precision flow rate measuring means by increasing the number of repetitions by the repetition number changing means 27, and conversely reduces the number of repetitions to realize a low power consumption flow rate measuring means. The means for switching the measurement of the measurement means is the measurement switching means 29.
[0029]
Here, 30 is a fluctuation detecting means, 31 is a flow rate determining means, 32 is a flow rate integrating means, 33 is a flow rate abnormality determining means, 34 is a warning display means, 35 is a battery, 36 is a flow rate storage means, 37 is a flow rate display means, Reference numeral 38 denotes measurement abnormality determination means.
[0030]
The measurement principle of the flow meter having the above configuration will be described.
[0031]
When the propagation time T1 in which the sound wave propagates from the sound wave transmitting / receiving unit 22 on the upstream side of the flow path shown in FIG. 1 toward the sound wave transmitting / receiving unit 23 on the downstream side is measured, the propagation time T1 is expressed by the equation (1).
[0032]
T1 = L / (C + V cos θ) (1)
Further, when the propagation time T2 propagating from the downstream acoustic wave transmission / reception means 23 toward the upstream acoustic wave transmission / reception means 22 is measured, the propagation time T2 is expressed by Expression (2).
[0033]
T2 = L / (C−Vcos θ) (2)
Here, V is the flow velocity in the flow path, L is the distance between the sound wave transmitting / receiving means, θ is the angle of the sound wave transmitting / receiving means facing the flow path, and C is the speed of sound.
[0034]
Then, taking the difference between the reciprocals of T1 and T2 and modifying the equation, the flow velocity V can be obtained from T1 and T2 as in equation (3).
[0035]
V = (L / 2 cos θ) · (1 / T1-1 / T2) (3)
Then, the flow rate Q can be calculated in consideration of the flow velocity V and the cross-sectional area of the flow path. Although the above has been described with a single transmission / reception measurement, it is obvious that the flow velocity V can be obtained more accurately by obtaining the accumulated propagation time by a method of repeatedly measuring the propagation time by the repeating means 24. Will.
[0036]
However, this measurement is based on the condition that the flow velocity V1 at the time of transmission from the upstream side and the flow velocity V2 at the time of transmission from the downstream side are the same. Actually, there may be a flow rate fluctuation such as pulsation. If the flow rate fluctuates as shown in FIG. 2 and the measurement time is short, the average flow velocity V1 when the propagation time from the upstream side is measured is the propagation time from the downstream side. This is not the same as the average flow velocity V2 during the measurement, and a measurement error occurs.
[0037]
Therefore, as shown in FIG. 3, by increasing the number of repetitions and setting one or more cycles of fluctuation as the measurement range, the flow velocity is averaged and the propagation time is measured, so that the flow velocity V1 and V2 are in the same state. , Improve and maintain accuracy. A method using this principle is a high-precision flow rate measuring means realized by increasing the number of repetitions.
[0038]
In addition, if the number of repetitions is small, the operation time is short, so it is clear that the power consumption used for processing is small. A measurement method for reducing power consumption by reducing the number of repetitions in this way is a low power consumption flow rate measuring means.
[0039]
Next, the flow of operation will be described using the flowcharts shown in FIGS. As shown in FIG. 4, the flow rate measurement is usually performed in a low power consumption mode by a low power consumption flow rate measuring means (STEP 10).
[0040]
Then, the flow rate variation is determined by the variation detecting means 30 from the measured instantaneous flow rate value (STEP 11). When there is no flow rate fluctuation, the flow rate measurement is continuously performed in the low power consumption mode (STEP 10) through the flow rate integration process (STEP 12).
[0041]
Here, the fluctuation detecting means 30 (STEP 11) will be described. For example, the fluctuation detection unit 30 obtains a difference between the maximum flow rate value Qmax within a predetermined time and the minimum flow rate value Qmin within a predetermined time (Qmax−Qmin) from the instantaneous flow rate value detected by the flow rate detection unit 26. Detect fluctuations.
[0042]
When the flow rate fluctuation (Qmax−Qmin) is 10 liters / hour or more as the predetermined flow rate, it is detected that there is a fluctuation, and when it is less than 10 liters / hour, the fluctuation detection means 30 indicates that there is no fluctuation. It detects.
[0043]
Next, when a variation is detected by such a variation detection means 30, the flow rate discrimination means 31 performs flow rate discrimination (STEP 13).
[0044]
When the flow rate discriminating means 31 discriminates the flow rate range as a large flow rate range (for example, 3000 liters / hour or more), the number of repetitions is reduced to an optimal minimum number (for example, 8 to 128 times, optimally 64 times) and reduced. Measure in power consumption mode.
[0045]
Further, when the flow rate discriminating means 31 discriminates the flow rate range as a small flow rate range (for example, less than 3000 liters), the number of repetitions is increased to an optimal number (for example, 64 to 512 times, optimally 252 times), and a high-precision flow rate Measurement can be continuously performed in the high-accuracy measurement mode as a measurement means (STEP 14).
[0046]
Even in the high-accuracy measurement mode, the fluctuation detection (STEP 11) is repeatedly performed. When the fluctuation disappears, the flow returns to the low power consumption measurement mode (STEP 10) through the flow rate integration process (STEP 12).
[0047]
Further, when it is determined that the flow rate is within the large flow range, the number of repetitions is not changed when measurement is performed in the low power consumption mode from the beginning.
[0048]
Then, the flow rate values measured in the respective measurement modes are subjected to integration processing by the flow rate integration means 32.
[0049]
FIG. 5 shows a flowchart of the integration process. In the integration process, it is determined whether or not the increase in the flow rate within a predetermined time is equal to or greater than a predetermined flow rate value (for example, a predetermined flow rate of 1 liter or more) within a predetermined time (for example, within a predetermined time of 12 minutes) (STEP 20). Measurement is performed in the high-accuracy measurement mode (STEP 21).
[0050]
If it is less than the predetermined flow rate value, the integrated value within the predetermined time is cleared (STEP 22), it is determined whether or not the measurement is abnormal (STEP 23), and the measurement mode is returned (STEP 24).
[0051]
As a result, it is possible to prevent the accumulated flow value from being counted up due to the measurement error value at the time of flow rate fluctuation such as pulsation or the accumulated error of the minute flow rate value below the measurement resolution.
[0052]
Further, the accumulated flow value and the instantaneous flow rate value newly measured in the high-accuracy measurement mode are converted at the same predetermined time and compared, and the flow rate abnormality determining means 33 determines whether or not the accumulated value is correct. Determine (STEP 25).
[0053]
When it is determined that there is no abnormality, the integrated value is added (STEP 26), and the process returns to the measurement mode (STEP 24).
[0054]
However, when it is determined that there is an abnormality, the current flow rate value is stored in the storage means (STEP 27), and the flow rate value and the integrated value are cleared (STEP 28).
[0055]
An abnormality warning is displayed on the warning display 34 of the flow meter (STEP 29), and the flow returns to the high-accuracy measurement mode (STEP 30).
[0056]
That is, by storing the integrated value per predetermined time before clearing in the flow rate storage means 36, every time an abnormality is determined, it can be stored while adding the flow rate value to the storage means, You can know the integrated flow rate at the time of abnormality.
[0057]
For example, if the integrated value of this storage means seems to converge to zero, the abnormal phenomenon is considered to have occurred at random, and it can be considered as an error due to determination in a short time in processing. Can learn with few future problems.
[0058]
For example, if the measurement is performed once every 2 seconds, the flow rate exceeding 1 liter in one measurement is 1800 liters / hour.
[0059]
Normally, such a large flow rate does not flow at a time, so the measurement is repeated twice or three times until the integrated flow rate of 1 liter is exceeded. In the case of a random flow such as a pulsating flow, the flow rate on the positive side and the negative side is repeated repeatedly, and on average, it converges to zero.
[0060]
Further, although the measurement timing is once every 2 seconds, the measurement is performed by slightly randomizing the timing, so that approximately positive and negative flow rates are repeated. Therefore, if the integration is continued, it should normally converge to zero.
[0061]
However, if the integrated value of the flow rate storage means 36 does not converge to zero, it can be seen that some improvement is necessary, and learning from the integrated value integrated in the storage means (STEP 31) allows the flow meter to be installed. Can cope with the environment.
[0062]
For example, if the accumulated value of the storage means converges to zero, the count-up can be prevented by increasing the predetermined time of 12 minutes, and if it does not converge to zero, it is 1 liter. Counting up can be prevented by increasing the amount so that it does not count up in a short time. By correcting the predetermined time and the predetermined flow rate while learning in this way, erroneous measurement can be prevented.
[0063]
By displaying whether there is an abnormality when there is no fluctuation or whether there is an abnormality when there is a fluctuation, you can grasp the abnormal state of the flow path, and after the abnormality is confirmed, take action early to improve the abnormality It is possible.
[0064]
If an abnormality is confirmed, it returns to the high-accuracy measurement mode in order to measure more accurately, so the power consumption increases and the life of the battery 35 may be shortened. It encourages to be.
[0065]
Further, the measurement abnormality determination process (STEP 23) of the measurement abnormality determination means 38 includes a predetermined time (for example, 12 minutes) for determining the flow rate count-up, an integrated flow rate value (for example, 1 liter) within the predetermined time, and a measurement method. Abnormality is determined from the number of changes.
[0066]
For example, when the predetermined integrated flow rate frequently exceeds 1 liter before the predetermined time, or the measurement method is frequently changed between the low power consumption mode and the high accuracy measurement mode (for example, 100 times or more per day) If it is carried out, it is clearly not normal, so the measurement abnormality determination means 38 determines that there is an abnormality and displays an abnormality warning on the warning display means 34.
[0067]
Thereby, measurement mode switching abnormality can be detected at an early stage, stable flow rate measurement can be realized, and measurement accuracy can be improved.
[0068]
If the measurement process is organized, it can be shown in a hierarchical structure as shown in FIG. In addition, as described in the ultrasonic flow measurement means, a plurality of flow measurement methods using a flow meter such as a flow sensor, a fluidic flow meter, or a mechanical flow meter such as a membrane meter may be used. It can be easily analogized that both the low power consumption and the high accuracy can be realized by using the flow meter as the low power consumption flow measuring means and the flow sensor as the high precision flow measuring means.
[0069]
Although the above has been described with respect to the two categories of large flow rate and small flow rate, the accuracy can be further improved if it is divided into three or more categories of large flow rate, medium flow rate, and small flow rate. Furthermore, although it has been described that the integrated flow rate is equal to or higher than the predetermined flow rate, the same applies to detection before the predetermined flow rate is reached. And although demonstrated as a fluctuation | variation, it is clear that there exists an effect with respect to the measurement of the pulsation flow which generate | occur | produces in gas piping.
[0070]
In addition, in the case of a gas meter that measures gas flow, a safety function is added to ensure safety management by grasping gas leakage and the usage state of gas appliances. It can be done.
[0071]
When an abnormality is determined, it is easy to provide a gas shut-off means so as to shut off the gas as well as a warning.
[0072]
Furthermore, since the battery is used as the driving power source, switching to low-power consumption flow rate measurement means according to the battery consumption status can be considered to achieve a long service life. Can be used as a safety meter.
[0073]
(Example 2)
Example 2 will be described with reference to FIG. The difference from the first embodiment is that a transmission / reception repeating unit 39 that repeatedly transmits and receives ultrasonic waves and a measurement repeating unit 40 that further repeats the measurement of the transmission / reception repeating unit 39 are provided.
[0074]
That is, the first propagation time measurement T1 when the transmission / reception from the upstream side to the downstream side of the flow path 21 is repeated and the second propagation time measurement T2 when the transmission / reception from the downstream side to the upstream side is repeated are 1 The transmission / reception repeating means 39 as one measurement unit, the measurement repeating means 40 for repeating the measurement of the transmission / reception repeating means 39 at least once, the transmission / reception repeating means 39 and the measurement repeating means 40 are repeated. The flow rate detecting means 41 for detecting the flow rate from the total first propagation time ΣT1 and the total second propagation time ΣT2, and the repeat count changing means 27 by the repeat count changing means 27 and the repeat count number N of the send / receive repeat means 39 and the measurement repeat means 40 Is provided with an ultrasonic flow rate measuring means 42 that realizes a high-precision flow rate measuring means and a low power consumption flow rate measuring means by changing the number of measurement repetitions M.
[0075]
Specifically, the high-precision flow rate measuring means reduces the number of transmission / reception repetitions N by the repetition number changing means 27 (for example, 1 to 16 times, optimally 2 times), and conversely increases the number of measurement repetitions M. (For example, 16 times to 1024 times, and optimally 126 times), and the total product N * M is set to be large.
[0076]
By adopting such a setting, it is possible to achieve high accuracy by finely measuring changes in the pulsating flow velocity that undergo rapid changes in time and measuring them for a long time.
[0077]
Further, the low power consumption flow rate measuring means increases the transmission / reception repetition count N by the repetition count changing means 27 (for example, 8 to 512, optimally 64) and decreases the measurement repetition count M (for example, 1). This is realized by completing the measurement in a short period of time from 8 times to 8 times, optimally once). A means for performing measurement switching of the measurement means is a measurement switching means 29.
[0078]
According to the configuration of the present embodiment, as shown in FIG. 8, by measuring with a small number of transmission / reception repetitions, the timing for measuring the propagation time from the upstream and the timing for measuring the propagation time from the downstream can be close, and the time change Measurement accuracy can be improved even in the case of intense pulsations.
[0079]
The transmission / reception measurement unit can be repeatedly performed by the measurement repeating means 40, and since the measurement can be performed for a long time, the fluctuation propagation time can be averaged, and the accuracy can be further improved.
[0080]
In addition, although the measurement unit is repeated continuously through a waiting time, the measurement accuracy can be improved by adjusting the waiting time to adjust the total measurement time.
[0081]
Obviously, shortening the waiting time makes the measurement more precise and enables high-precision measurement. Then, by combining the transmission / reception repetition count N and the measurement repetition count M, an intermediate measurement mode between the low power consumption mode and the high accuracy measurement mode can be created.
[0082]
For example, when the pulsation is large and the flow rate range is a small flow rate range, a number of intermediate measurement modes can be realized as a measurement mode with slightly high accuracy and low power consumption.
[0083]
Furthermore, by changing the number of repetitions to match the pulsation cycle, the influence of the pulsation can be reduced as much as possible, and the flow rate measurement accuracy can be improved.
[0084]
【The invention's effect】
As is apparent from the above description , according to the flowmeter of the present invention, it is possible to achieve both high-accuracy flow measurement and low power consumption flow measurement.
[Brief description of the drawings]
FIG. 1 is a block diagram of a flow meter according to a first embodiment of the present invention. FIG. 2 is a diagram for explaining the principle of the flow meter. FIG. 3 is a diagram for explaining the principle of the flow meter. Flowchart of the same flow meter [FIG. 6] Flow chart of the same flow meter [FIG. 7] Block diagram showing a second embodiment of the present invention [FIG. 8] Explanatory diagram of the flow meter [FIG. 9] Conventional flow meter block Fig. 10 Block diagram of another conventional flow meter [Explanation of symbols]
DESCRIPTION OF SYMBOLS 21 Flow path 22, 23 Sound wave transmission / reception means 24 Repeating means 25 Time measuring means 26 Flow rate detection means 27 Frequency change means 28 Ultrasonic flow measurement means 29 Measurement switching means 30 Fluctuation detection means 31 Flow rate determination means 32 Flow rate accumulation means 33 Flow rate abnormality means 33 Determination means 34 Warning display means 35 Battery 36 Flow rate storage means 37 Flow rate display means 38 Measurement abnormality determination means

Claims

First propagation time measurement when ultrasonic transmission / reception is repeatedly performed from the upstream side to the downstream side of the flow path, and second propagation time measurement when ultrasonic transmission / reception is repeatedly performed from the downstream side to the upstream side of the flow path, Transmission / reception repeating means with one measurement unit, measurement repeating means for repeating the measurement of the transmission / reception repeating means a plurality of times, and the total number of times when the transmission / reception repeating means and the measurement repeating means are repeated. A flow rate detecting means for detecting a flow rate from one propagation time and a total second propagation time, a fluctuation detecting means for detecting a flow fluctuation from a flow rate value detected by the flow rate detecting means within a predetermined time, and the fluctuation detecting means A high-accuracy flow rate measurement means when detected, and a measurement switching means for switching to a low-power consumption flow rate measurement means in other cases, the high-precision flow rate measurement means and the low-power consumption flow rate measurement means, For transmission and reception repeating means That receive the number of repetitions and the number of times of measuring the measuring repetition means the following (1), flowmeter, characterized in that it is set as (2).
(1) High-accuracy flow rate measurement means: The number of transmission / reception repetitions by the transmission / reception repetition means is reduced, and the number of measurement times by the measurement repetition means is increased.
(2) Low power consumption flow rate measuring means: increasing the number of repetitions of transmission / reception by the transmission / reception repetition means and decreasing the number of times of measurement by the measurement repetition means.

A second propagation time measurement when performed repeatedly transceiver to the upstream side of the ultrasonic waves from the downstream side of the first propagation time measurement and the flow path when was repeated transmission and reception of ultrasonic waves from the upstream side to the downstream side of the flow path Transmission / reception repeating means with one measurement unit, measurement repeating means for repeating the measurement of the transmission / reception repeating means a plurality of times, and the total number of times when the transmission / reception repeating means and the measurement repeating means are repeated. A flow rate detecting means for detecting a flow rate from one propagation time and a total second propagation time, a fluctuation detecting means for detecting a flow fluctuation from a flow rate value detected by the flow rate detecting means within a predetermined time, and the fluctuation detecting means A measurement switching unit that switches to a high-accuracy flow rate measurement unit when detected, and a flow rate determination unit that discriminates a flow range from the measurement value of the high-accuracy flow measurement unit in other cases. With high precision In the quantity measuring means and the low power consumption flow measuring means, the transmission / reception repetition count by the transmission / reception repetition means and the measurement repetition count by the measurement repetition means are set as follows (1), (2), When the flow rate discriminating means discriminates a small flow rate, the flow measurement by the high-accuracy flow rate measuring unit is continued, and when the flow rate discriminating means discriminates the large flow rate, the flow rate is switched to the low power consumption flow rate measuring unit flowmeter for.
(1) High-accuracy flow rate measurement means: The number of transmission / reception repetitions by the transmission / reception repetition means is reduced, and the number of measurement times by the measurement repetition means is increased.
(2) Low power consumption flow rate measuring means: increasing the number of repetitions of transmission / reception by the transmission / reception repetition means and decreasing the number of times of measurement by the measurement repetition means.