JP4157342B2 - Safety device in fluid supply path - Google Patents

Description

【００１０】
表１に示すテーブルを用いて遮断弁２を遮断するか否かを判断する手順は図７のようになる。図７に示す手順はサブルーチン化されており、メインルーチンから３０秒ごとに呼び出される。すなわち、図７に示すサブルーチンでは、メインルーチンから３０秒間の平均流量Ｑａｖｅ（ｉ）を取得した後（Ｓ１）、流量の有無と流量の変化の有無を判定する。流量の有無は、平均流量Ｑａｖｅ（ｉ）が５０Ｌ／ｈ以上であるか否かにより判定し（Ｓ２）、平均流量Ｑａｖｅ（ｉ）が５０Ｌ／ｈ未満であれば許容連続使用時間の計時動作を解除し（Ｓ３）、メインルーチンに戻る（Ｓ４）。つまり、ステップＳ３では許容連続使用時間を時限するタイマ部をリセットして許容連続使用時間の時限を中止する。つまり、許容連続使用時間の設定値を「制限なし」にする。
【００１１】
一方、ステップＳ２において流量があると判断されると、流量の変化の有無が判定される（Ｓ５）。流量の変化の有無を判定するにあたっては、３０秒毎に求められる平均流量の時系列における現在値Ｑａｖｅ（ｉ）と１期間前の値Ｑａｖｅ（ｉ−１）との差分（＝｜Ｑａｖｅ（ｉ）−Ｑａｖｅ（ｉ−１）｜）が求められる。この差分が基準値よりも大きいときには平均流量に変化が生じたと判断する。平均流量の変化の有無を判断する基準値は２種類の値で与えられ、両値のうちの大きいほうを用いる。基準値としては、たとえば平均流量の現在値Ｑａｖｅ（ｉ）に対する３％の値と５０Ｌ／ｈとのうち大きいほうを採用する。ステップＳ５において流量の変化があると判断されると許容連続使用時間を時限するタイマ部をリセットし（Ｓ６）、変化後の平均流量（つまり、現在値Ｑａｖｅ（ｉ））が属する流量区分に対応する許容連続使用時間を求めた後（Ｓ７）、メインルーチンに戻る（Ｓ４）。一方、ステップＳ５において流量の変化がないと判断されると、計時中の時間と許容連続使用時間とを比較し（Ｓ８）、計時中の時間が許容連続使用時間に達しているときには遮断弁２を遮断した後に（Ｓ９）、メインルーチンに戻る（Ｓ４）。また、ステップＳ８において、計時中の時間が許容連続使用時間に達していないと判断したときには、何も行わずにメインルーチンに戻る（Ｓ４）。
【００１２】
ところで、超音波流量計を用いて瞬時流量を計測したときに瞬時流量が図８に示すように推移したとする。図示例では瞬時流量が正弦波状に変化しており、瞬時流量は１分程度の周期でかつ約２００Ｌ／ｈの振幅で変化している。図から明らかなように、この状態では瞬時流量は一定値を中心として変動しているように見え、ＧＨＰやガスエンジンによる圧力脈動のみが生じていると考えられるにもかかわらず、３０秒間ごとの区間で区切ると、最大で８０Ｌ／ｈ程度の変動を生じており、図７に示した手順で処理を行うとすれば、ステップＳ５において流量に変化があると判定されることになる。つまり、許容連続使用時間の計時が中止されて新たな許容連続使用時間が設定される可能性がある。なお、図８において、実線は３０秒の期間内で得られる瞬時流量の１５個の値の平均値、一点鎖線は３０秒の期間内で得られる瞬時流量の１５個の値のうちの最大値、二点鎖線は３０秒の期間内で得られる瞬時流量の１５個の値のうちの最小値を意味する。
【００１３】
要するに、超音波流量計を用いて上記公報に記載された技術をそのまま適用すると、供給路内において流量に変化が生じていないにもかかわらず、圧力変動による瞬時流量の変動を実際の流量の変化と誤認して許容連続使用時間の計時を中止してしまうおそれがある。その結果、ガス漏れやガス使用機器の消し忘れを検出できない場合が生じるという問題を有している。
【００１４】
本発明は上記事由に鑑みて為されたものであり、その目的は、超音波流量計のような瞬時流量を計測する流量計を採用しながらも流体の使用状態の異常を確実に検出できるようにした流体供給路における安全装置を提供することにある。
【００１５】
【課題を解決するための手段】
請求項１の発明は、流体の供給路を通過する流体の瞬時流量を間欠的に計測する流量計測部と、一定個数の瞬時流量が得られる検出期間毎に平均値と最大値と最小値とを求める演算部と、複数段階の流量区分を規定するとともに各流量区分ごとに許容連続使用時間を対応付けたテーブルと、現在の検出期間における最小値から所定期間前の検出期間における最大値を減算した差値および前記所定期間前の検出期間における最小値から現在の検出期間における最大値を減算した差値を求め両差値をそれぞれ規定の基準値と比較する比較部と、前記検出期間毎の前記平均値が属する流量区分に対応して前記テーブルから求めた許容連続使用時間を時限するタイマ部と、前記タイマ部による時限終了までに前記比較部において前記両差値のいずれかに前記基準値以上の変化が検出されると前記タイマ部をリセットし、変化後の前記平均値が属する流量区分に対応して前記テーブルから求めた許容連続使用時間を前記タイマ部に時限させ、前記タイマ部による時限終了をもって異常と判定する判定部とを備えることを特徴とする。
【００１６】
請求項２の発明は、請求項１の発明において、前記供給路に挿入された遮断弁を備え、前記判定部は、異常と判定したときに前記遮断弁の遮断を指示することを特徴とする。
【００１８】
請求項３の発明は、請求項１または請求項２の発明において、前記判定部が、前記平均値が所定値以下であると前記タイマ部をリセットして動作を停止させることを特徴とする。
【００１９】
請求項４の発明は、請求項１ないし請求項３の発明において、前記検出期間が３０秒であることを特徴とする。
【００２０】
請求項５の発明は、請求項４の発明において、前記所定期間が３期間であることを特徴とする。
【００２１】
【発明の実施の形態】
本実施形態では流体供給路における安全装置をガスメータに適用した例を示し、図１に示すように、都市ガスのような燃料ガスを供給する供給路１に遮断弁２と流量計測部３とを設けている。図示例では遮断弁２の下流側に流量計測部３を設けているが、遮断弁の２の上流側に流量計測部３を設けることも可能である。また、流量計測部３には従来構成として図６に示した超音波流量計を採用している。
【００２２】
流量計測部３は比較的短い時間（２〜３秒）ごとに瞬時流量を間欠的に出力するように構成され、流量計測部３から間欠的に出力される瞬時流量はマイクロコンピュータ（以下、「マイコン」と略称する）を用いて構成された制御回路部４に入力される。ここに、流量計測部３も同じマイコンを用いて制御される。つまり、図示する流量計測部３は、超音波の送受波の制御を行うとともに送受波の結果から瞬時流量を求める演算を行うためにマイコンの一部を含んでいる。ただし、本発明では超音波の送受波の制御については要旨ではないからとくに説明しない。また、ガスメータとして燃料ガスの使用量を表示する機能や供給路１内の圧力を検出する圧力センサなども要旨ではないから省略している。
【００２３】
制御回路部４は、流量計測部３から間欠的に出力される瞬時流量を３０秒毎の検出期間ごとに収集しており、各３０秒の検出期間で得られる１５個ずつの瞬時流量に基づいて供給路１における流量の有無および流量の変化の有無を判定する機能を有し、さらにガス漏れないしガス使用機器の消し忘れがあると判断したときには遮断弁２を遮断する機能を有している。すなわち、流量計測部３で得られた瞬時流量は演算部１１に入力され、演算部１１では１５個ずつの瞬時流量が得られる３０秒の検出期間毎に瞬時流量の平均値と最大値と最小値とを求める。演算部１１は瞬時流量について１５個のデータを格納することができ、格納したデータの平均値と最大値と最小値とを検出期間の終了時に求めてレジスタ１２に引き渡し、レジスタ１２への値の引き渡し後にはすべてのデータを消去して、次のデータから１５個分を格納するという動作を繰り返すように構成されている。
【００２４】
レジスタ１２は、平均値と最大値と最小値とをそれぞれ４個ずつ格納するシフトレジスタを備える。いま、流量の平均値、最大値、最小値の現在値をそれぞれＱａｖｅ（ｉ）、Ｑｍａｘ（ｉ）、Ｑｍｉｎ（ｉ）と表し、１期間前の平均値、最大値、最小値をそれぞれＱａｖｅ（ｉ−１）、Ｑｍａｘ（ｉ−１）、Ｑｍｉｎ（ｉ−１）、２期間前の平均値、最大値、最小値をそれぞれＱａｖｅ（ｉ−２）、Ｑｍａｘ（ｉ−２）、Ｑｍｉｎ（ｉ−２）、３期間前の平均値、最大値、最小値をそれぞれＱａｖｅ（ｉ−３）、Ｑｍａｘ（ｉ−３）、Ｑｍｉｎ（ｉ−３）と表すことにする。この場合、レジスタ１２には、Ｑａｖｅ（ｉ）、Ｑｍａｘ（ｉ）、Ｑｍｉｎ（ｉ）、Ｑａｖｅ（ｉ−１）、Ｑｍａｘ（ｉ−１）、Ｑｍｉｎ（ｉ−１）、Ｑａｖｅ（ｉ−２）、Ｑｍａｘ（ｉ−２）、Ｑｍｉｎ（ｉ−２）、Ｑａｖｅ（ｉ−３）、Ｑｍａｘ（ｉ−３）、Ｑｍｉｎ（ｉ−３）の１２個の値が格納されることになる。なお、レジスタ１２には、最大値および最小値については現在値を含めて３期間前まで（最新の検出期間を含めて４期間分）の４個の値がそれぞれ格納することが必要であるが、平均値については現在値（最新の検出期間の平均値）のみを格納するようにしてもよい。以下では、検出期間における瞬時流量の平均値を平均流量と呼ぶ。
【００２５】
従来構成では、流量の変化の有無の判定に際して一定期間における平均流量を用い、現在の平均流量Ｑａｖｅ（ｉ）と１期間前の平均流量Ｑａｖｅ（ｉ−１）との差分について基準値との大小比較を行うことにより流量の変化の有無を判定していたのに対して、本実施形態では、流量の変化の有無の判定に際して３０秒の検出期間における流量の最大値と最小値とを用いる。具体的には、現在（最新）の検出期間における最小値Ｑｍｉｎ（ｉ）から３期間前の検出期間における最大値Ｑｍａｘ（ｉ−３）を減算した差値と、３期間前の検出期間における最小値Ｑｍｉｎ（ｉ−３）から現在（最新）の検出期間における最大値Ｑｍａｘ（ｉ）を減算した差値とについて基準値との大小比較を行うことにより流量の変化の有無を判定する。Ｑｍｉｎ（ｉ）−Ｑｍａｘ（ｉ−３），Ｑｍｉｎ（ｉ−３）−Ｑｍａｘ（ｉ）の演算および基準値との比較は、レジスタ１２の後段に設けた比較部１３で行う。また、基準値には従来構成と同様に、現在の平均流量Ｑａｖｅ（ｉ）の３％と５０Ｌ／ｈとの大きいほうを用いることとする。この値は、圧力脈動が生じていない場合を考慮して従来構成と同じ値に設定してある。Ｑｍｉｎ（ｉ）−Ｑｍａｘ（ｉ−３）は３０秒毎の検出期間における平均流量が増加した場合に正値となって基準値よりも大きくなる可能性が高く、逆にＱｍｉｎ（ｉ−３）−Ｑｍａｘ（ｉ）は３０秒毎の検出期間における平均流量が減少した場合に正値となって基準値よりも大きくなる可能性が高い。したがって、両条件のうちのいずれかが成立すれば、流量が増加側または減少側に変化したと判断することができる。
【００２６】
レジスタ１２の後段には比較部１３とは別にテーブル１５および流量検出部１７も設けられている。テーブル１５は流量を複数段階に区分した流量区分と遮断弁２を遮断するまでの許容連続使用時間とを対応付けたものであって、一例としては表１のように設定される。テーブル１５にはレジスタ１３に格納された現在の平均流量Ｑａｖｅ（ｉ）が照合され、平均流量Ｑａｖｅ（ｉ）の属する流量区分に対応する許容連続使用時間が求められる。求められた許容連続使用時間は、比較部１３の後段に判定部１６を介して設けたタイマ部１４における時限時間としてセットされる。
【００２７】
また、流量検出部１７では現在の平均流量Ｑａｖｅ（ｉ）を用いて燃料ガスが供給路１を通過しているか否かを判断する。すなわち、流量検出部１７では、現在の平均流量Ｑａｖｅ（ｉ）がガス使用機器においてパイロットバーナを点火している程度の５０Ｌ／ｈ以上であるときには流量があると判断して比較部１３における上述した処理を行わせる。また、流量が検出されない（平均流量Ｑａｖｅ（ｉ）が５０Ｌ／ｈに満たない）ときは、判定部１６を介してタイマ部１４をリセットする。
【００２８】
タイマ部１４は、流量検出部１７において流量が検出された状態では、テーブル１５により設定された許容連続使用時間を時限時間として時限動作を行う。時限動作の開始時点は、平均流量Ｑａｖｅ（ｉ）がいずれかの流量区分に達した時点またはテーブル１５で求めた許容連続使用時間が時限時間としてセットされた状態でタイマ部１４がリセットされた時点になる。タイマ部１４の時限が終了した場合には、タイマ部１４は弁駆動部１８を通して遮断弁２を遮断させる。一方、時限中において比較部１３で流量の変化が検出されたときには、判定部１６を介してタイマ部１４がリセットされ、その時点での平均流量Ｑａｖｅ（ｉ）に対応する許容連続使用時間を時限時間として時限動作が再開されることになる。要するに流量が変化すれば、平均流量Ｑａｖｅ（ｉ）に応じた時限時間であらためて時限動作を行うのである。言い換えると、判定部１６は、タイマ部１４による時限終了までに比較部１３において両差値のいずれかに基準値以上の変化が検出されるとタイマ部１４をリセットして変化後の平均値の流量区分に対応する時限時間をタイマ部１４に時限させ、タイマ部１４による時限終了まで両差値のいずれにも基準値以上の変化が検出されなければ前記タイマ部１４により遮断弁２の遮断を指示させる。
【００２９】
上述した制御回路部４における主要部の動作を図２に示す。図２に示す手順は基本的には図７に示した動作と同様であってサブルーチン化されており、メインルーチンから３０秒ごとに呼び出される。すなわち、図２に示すサブルーチンでは、メインルーチンから３０秒間の検出期間毎に演算部１１で求めた平均流量Ｑａｖｅ（ｉ）と最大値Ｑｍａｘ（ｉ）と最小値Ｑｍｉｎ（ｉ）とを取得して（Ｓ１）レジスタ１２に格納し（Ｓ２）、最新の平均流量Ｑａｖｅ（ｉ）に基づいて流量の有無を判定する（Ｓ３）。その後、レジスタ１２に格納されている瞬時流量の最新の検出期間における平均流量Ｑａｖｅ（ｉ）、最大値Ｑｍａｘ（ｉ）、最小値Ｑｍｉｎ（ｉ）と、３期間前の検出期間における最大値Ｑｍａｘ（ｉ−３）、最小値Ｑｍｉｎ（ｉ−３）とを用いて流量の変化の有無を判定する（Ｓ６）。流量の有無は、平均流量Ｑａｖｅ（ｉ）が５０Ｌ／ｈ以上であるか否かにより判定し（Ｓ３）、平均流量Ｑａｖｅ（ｉ）が５０Ｌ／ｈ未満であれば許容連続使用時間の計時動作を解除し（Ｓ４）、メインルーチンに戻る（Ｓ５）。つまり、ステップＳ４では許容連続使用時間の計時を中止するとともに、許容連続使用時間の設定値を「制限なし」にする。
【００３０】
一方、ステップＳ３において流量があると判断されると、流量の変化の有無が判定される（Ｓ６）。流量の変化の有無を判定するにあたっては、比較部１３においてＱｍｉｎ（ｉ）−Ｑｍａｘ（ｉ−３），Ｑｍｉｎ（ｉ−３）−Ｑｍａｘ（ｉ）を基準値と比較する。基準値は従来と同様に、平均流量の現在値Ｑａｖｅ（ｉ）に対する３％の値と５０Ｌ／ｈとのうち大きいほうを用いる。ステップＳ６において流量の変化があると判断されると判定部１６を介してタイマ部１４をリセットし（Ｓ７）、変化後の平均流量（つまり、現在値Ｑａｖｅ（ｉ））が属する流量区分に対応する許容連続使用時間を求めた後（Ｓ８）、メインルーチンに戻る（Ｓ５）。一方、ステップＳ６において流量の変化がないと判断されると、計時中の時間と許容連続使用時間とを比較し（Ｓ９）、計時中の時間が許容連続使用時間に達しているときには遮断弁２を遮断した後に（Ｓ１０）、メインルーチンに戻る（Ｓ５）。また、ステップＳ９において、計時中の時間が許容連続使用時間に達していないと判断したときには、何も行わずにメインルーチンに戻る（Ｓ５）。
【００３１】
上述のように３０秒毎の各検出期間の最大値と最小値との差値を用いて流量の増加あるいは減少を判定する際に、現在の値と３期間前の値とを用いるのは１期間前の値あるいは２期間前の値を用いると以下の問題が生じるからである。まず、現在の値と１期間前の値とを用いる場合について考察する。この場合、Ｑｍｉｎ（ｉ）−Ｑｍａｘ（ｉ−１）あるいはＱｍｉｎ（ｉ−１）−Ｑｍａｘ（ｉ）について基準値との大小を比較することになる。図４のように圧力脈動が生じていない場合を考え、１期間前において流量に変化が生じたとすると、Ｑｍｉｎ（ｉ）＝Ｑｍａｘ（ｉ−１）になるから、Ｑｍｉｎ（ｉ）−Ｑｍａｘ（ｉ−１）＝０になり、流量の変化の程度にかかわらず流量の変化を検出することができない。つまり、現在の値と１期間前の値とを用いても流量の変化の有無を検出することができない。
【００３２】
次に、現在の値と２期間前の値とを用いる場合について考察する。この場合には、Ｑｍｉｎ（ｉ）−Ｑｍａｘ（ｉ−２）あるいはＱｍｉｎ（ｉ−２）−Ｑｍａｘ（ｉ）について基準値との大小を比較することになる。一般に、流量の変化は瞬時に生じるのではなく数秒〜３０秒程度の時間幅を有している。したがって、流量が変化するタイミングによっては図５のように３０秒毎の２つの期間に跨って流量が変化することがある。図５においては圧力脈動が生じていない場合を示しており、流量の変化幅は８０Ｌ／ｈ程度であって流量に５０Ｌ／ｈを越える変化があるものの、Ｑｍｉｎ（ｉ）−Ｑｍａｘ（ｉ−２）は３０Ｌ／ｈ程度であって流量に変化があることを検出することができない。つまり、現在の値と２期間前の値との比較によっても流量の変化を検出することができない場合がある。
【００３３】
以上の考察から現在の値と３期間以上前の値との差を用いるのが望ましい。また、４期間以上前の値を用いると流量の変化の判定に要する時間が長くなるから、流量の変化を検出可能であってかつ判定に要する時間が最小になるように本実施形態では３期間前の値を用いている。
【００３４】
ここで、従来構成と比較するために流量計測部３で検出した瞬時流量が図８のように変化する場合を例として動作を考える。すなわち、供給路１において圧力脈動のみが生じており、流量は実質的に変化していない状態について考える。この場合、瞬時流量の最大値と最小値とは時間の経過にかかわりなく略一定になるから、Ｑｍｉｎ（ｉ）−Ｑｍａｘ（ｉ−３）とＱｍｉｎ（ｉ−３）−Ｑｍａｘ（ｉ）とはともに負値になる。つまり、従来構成のように３０秒毎の平均流量を比較した場合には許容連続使用時間の計時が中止する可能性があったのに対して、瞬時流量が図８のように変化する場合に対して、本実施形態の条件では許容連続使用時間の計時が中止されることがなくなり、結果的に、ガス漏れが生じている場合あるいはガス使用機器を消し忘れている場合には許容連続使用時間の経過時点で遮断弁２を閉じることが可能になる。
【００３５】
一方、図３のように平均流量が増加した場合には（図３において、実線は３０秒の期間内で得られる瞬時流量の１５個の値の平均値、一点鎖線は３０秒の期間内で得られる瞬時流量の１５個の値のうちの最大値、二点鎖線は３０秒の期間内で得られる瞬時流量の１５個の値のうちの最小値を意味し、後述する図４、図５も同様である）、通常はＱｍｉｎ（ｉ）−Ｑｍａｘ（ｉ−３）は正値になり、Ｑｍｉｎ（ｉ−３）−Ｑｍａｘ（ｉ）は負値になる。ただし、Ｑｍｉｎ（ｉ）−Ｑｍａｘ（ｉ−３）は、必ずしも平均流量Ｑａｖｅ（ｉ）の３％と５０Ｌ／ｈとのうちの大きいほうよりも大きな値になるとは限らない。つまり、流量が変化したとしても許容連続使用時間の計時が継続される可能性が高くなり、遮断弁２を遮断する確率が高くなる。つまり、圧力脈動が生じているときに流量に変化が生じても検出できない場合があるものの、ガス漏れが生じている場合やガス使用機器を消し忘れていることは確実に検出することになるから、結果的にガス漏れや過熱が生じている可能性のあるときには、確実に遮断弁２を閉じて安全を確保することができる。
【００３６】
なお、本実施形態では、流量計測部３として超音波流量計を用いる例を示したが、瞬時流量を検出することができるものであれば、フルイディック流量計、フローセンサによる流量計（熱線式流量計）などの他の流量計を用いることが可能である。また、燃料ガスの流量を計測する例を示したが、本発明の技術思想は他の流体についても適用可能である。さらに、上述した各種数値は一例であって、流量計測部３の構成、流体の種類、供給路１に許容された最大流量などに応じて適宜に変更可能である。さらに、異常時に遮断弁２を遮断するのではなく異常の報知のみ行う構成としてもよい。
【００３７】
【発明の効果】
請求項１の発明は、瞬時流量について一定の検出期間ごとに平均値と最大値と最小値とを求め、現在の検出期間における最小値から所定期間前の検出期間における最大値を減算した差値および前記所定期間前の検出期間における最小値から現在の検出期間における最大値を減算した差値を求めるとともに両差値を規定の基準値と比較し、瞬時流量の平均値が属する流量区分に対応付けて規定した許容連続使用時間をタイマ部により時限し、タイマ部による許容連続使用時間の時限終了までに両差値のいずれかが基準値以上になるとタイマ部をリセットし、変化後の前記平均値が属する流量区分に対応して前記テーブルから求めた許容連続使用時間を前記タイマ部に時限させ、前記タイマ部による時限終了をもって異常と判定するので、流体の供給路内で圧力に変動が生じる場合に、流量には実質的に変化が生じていないにもかかわらず流量に変化が生じたと誤検出することがなく、しかも圧力の変動幅が比較的小さければ流量の変化を検出することによってタイマ部をリセットするから必要以上に異常と判定されることがない上に、異常を失敗なく確実に検出することができる。加えて、流量区分ごとにタイマ部の時限時間を変化させることによって、たとえば単位時間当たりの流体の流出量が多い場合ほど短時間で異常を報知するというような動作が可能になる。
【００３８】
請求項２の発明は、請求項１の発明において、前記供給路に挿入された遮断弁を備え、判定部は、異常と判定したときに遮断弁の遮断を指示するものであり、必要以上に異常と判定されることがないから、遮断弁が必要以上に遮断されることがなく、その一方、遮断弁の遮断が必要な状況では遮断弁を失敗なく確実に遮断することができる。
【００４０】
請求項３の発明は、請求項１または請求項２の発明において、判定部が、前記平均値が所定値以下であるとタイマ部をリセットして動作を停止させるので、流量が実質的に生じていないときにはタイマ部による時限動作を停止し、流量が実質的に生じていないにもかかわらずタイマ部が不必要に動作するのを防止することができる。
【００４１】
請求項４の発明は、請求項１ないし請求項３の発明において、前記検出期間を３０秒としたので、流体の使用量が変化したときにほとんどの場合において検出期間の２期間内には流量変化が終了することになり、前記所定期間を３期間以上とすれば圧力に変動が生じていないときに流量の変化を失敗なく検出することができる。
【００４２】
請求項５の発明は、請求項４の発明において、前記所定期間を３期間としたので、圧力に変動が生じていないときに流量の変化を失敗なく検出することができ、しかも流量の変化の有無を失敗なく検出することができる時間としては最小時間になる。
【図面の簡単な説明】
【図１】本発明の実施形態を示すブロック図である。
【図２】同上の動作説明図である。
【図３】同上の動作説明図である。
【図４】比較例を示す動作説明図である。
【図５】比較例を示す動作説明図である。
【図６】要部の概略構成図である。
【図７】従来例の動作説明図である。
【図８】従来例の動作説明図である。
【符号の説明】
１ 供給路
２ 遮断弁
３ 流量計測部
４ 制御回路部
１１ 演算部
１２ レジスタ
１３ 比較部
１４ タイマ部
１５ テーブル
１６ 判定部
１７ 流量検出部
１８ 弁駆動部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a safety device in a fluid supply path that monitors the use state of a fluid based on the instantaneous flow rate of a fluid such as fuel gas that passes through the supply path and detects an abnormality in the use state of the fluid.
[0002]
[Prior art]
In general, fuel gas such as city gas and propane gas has a large amount of unburned raw gas because the gas hose that supplies the fuel gas is disconnected from the gas using equipment or the flame disappears in the gas using equipment that burns the gas. It is dangerous to leak out. In addition, there is a possibility that the gas using device is overheated by forgetting to turn off the gas using device. Therefore, by monitoring the flow rate change in the fuel gas supply path, it is judged whether there is any outflow of raw gas or whether the gas using equipment has been forgotten to be turned off. There has been proposed a safety device that shuts off a shutoff valve arranged on the supply path when it is determined that there is a possibility of forgetting to turn off the gas (for example, Japanese Patent Publication No. 62-30350).
[0003]
The above publication shows a gas meter configured to generate a pulse signal every time a certain volume of fuel gas passes through a supply path, and obtains an average flow rate per minute by counting pulse signals and changes the average flow rate. A technology that shuts off the shut-off valve inserted in the supply channel when it reaches the specified time limit (continuous use safety time) without deciding that the raw gas has flowed out or forgotten to turn off the gas-using equipment. Proposed. That is, the continuous use safety time is determined according to which flow rate class the average flow rate of fuel gas per minute belongs to, and the state where the average flow rate of fuel gas per minute does not change has reached the continuous use safety time Sometimes, the shutoff valve is shut off by judging that raw gas is flowing out or that the gas using equipment is being used continuously. However, when the average flow rate changes before reaching the continuous use safety time, the continuous use safety time measurement is canceled, and the continuous use safety time is newly measured in the flow rate category to which the average flow after the change belongs. ing. Here, the continuous use safety time is set for each flow rate section in which the average flow rate per minute is divided into a plurality of stages, and is defined so as to be shorter as the average flow rate is larger.
[0004]
[Problems to be solved by the invention]
By the way, in the technique described in the above publication, by fixing a disk to a rotating shaft that rotates with the passage of fuel gas, attaching a permanent magnet to the periphery of the disk, and detecting the position of the permanent magnet with a Hall IC, A flow rate measuring apparatus configured to output one pulse signal from the Hall element each time the disk rotates once is adopted.
[0005]
On the other hand, recently, the use of an ultrasonic flowmeter has been studied to measure the amount of fuel gas used. In the ultrasonic flowmeter, as shown in FIG. 6, ultrasonic sensors 3a and 3b for transmitting and receiving ultrasonic waves are arranged on the upstream side and the downstream side of the supply path 1, respectively, and the ultrasonic sensors 3a and 3b are arranged. The flow rate of the fuel gas is obtained by transmitting and receiving ultrasonic waves between the two. The two ultrasonic sensors 3a and 3b face each other, and the traveling direction of the ultrasonic waves transmitted and received between the ultrasonic sensors 3a and 3b and the direction in which the fluid passes through the supply path 1 form an angle θ. Arranged to intersect.
[0006]
In order to measure the flow rate using the ultrasonic flowmeter having the illustrated configuration, the ultrasonic wave propagation time t1 when the ultrasonic wave is transmitted from the upstream ultrasonic sensor 3a toward the downstream ultrasonic sensor 3b. And the ultrasonic wave propagation time t2 when the ultrasonic wave is transmitted from the downstream ultrasonic sensor 3b toward the upstream ultrasonic sensor 3a. When the distance between the ultrasonic sensors 3a and 3b is d, the fluid flow velocity is v, and the sound velocity is c, the following relationship is obtained.
(C + v · cos θ) t1 = d
(Cv−cos θ) t2 = d
Therefore, the flow velocity v can be expressed as follows:
v = (d / 2 cos θ) {(1 / t1) − (1 / t2)}
A value obtained by multiplying the flow velocity v thus obtained by the cross-sectional area S of the supply passage 1 is the instantaneous flow rate q. That is, the instantaneous flow rate q is expressed by the following equation.
q = v · S
In the ultrasonic flowmeter, each ultrasonic sensor 3a, 3b is used as a transmission side to transmit and receive an ultrasonic wave once to form a set of operations. If at least one set of operations is performed, an instantaneous flow rate q is obtained. Can do. The instantaneous flow rate q is measured intermittently (for example, every 2 to 3 seconds), and the supply flow path 1 is measured within the time for measuring the instantaneous flow rate q by multiplying the instantaneous flow rate q by the time interval obtained for the instantaneous flow rate q. Obtain the total amount of fuel gas that has passed.
[0007]
By the way, when a gas heat pump (GHP) or a gas engine is used in a fuel gas consumer or in the vicinity of the consumer, the pressure in the supply path varies. The flow rate measuring device described in the above publication is a configuration adopted in a so-called membrane meter, and since the membrane meter is a volume meter, the pressure fluctuation of a relatively short cycle caused by the above-mentioned causes is detected. There is little need to consider the impact. That is, there is little possibility that the average flow rate will change due to pressure fluctuation, and the continuous use safety time can be accurately measured.
[0008]
However, since the ultrasonic flowmeter obtains the instantaneous flow rate based on the flow velocity, the instantaneous flow rate may fluctuate due to pressure fluctuation. Now, an average flow rate for 30 seconds is obtained using an ultrasonic flowmeter, and it is determined whether to shut off the shut-off valve 2 based on the average flow rate, judging whether a gas leak or forgetting to turn off the gas-using device. . Here, it is assumed that the correspondence relationship between the flow rate classification with respect to the average flow rate for 30 seconds and the continuous use safety time (hereinafter referred to as “allowable continuous use time”) is set as a table shown in Table 1. However, L represents a liter.
[0009]
[Table 1]

[0010]
The procedure for determining whether or not to shut off the shutoff valve 2 using the table shown in Table 1 is as shown in FIG. The procedure shown in FIG. 7 is made into a subroutine and is called from the main routine every 30 seconds. That is, in the subroutine shown in FIG. 7, after obtaining the average flow rate Qave (i) for 30 seconds from the main routine (S1), it is determined whether or not there is a flow rate and whether there is a change in the flow rate. The presence or absence of the flow rate is determined by whether or not the average flow rate Qave (i) is 50 L / h or more (S2). If the average flow rate Qave (i) is less than 50 L / h, the operation for measuring the allowable continuous use time is performed. Cancel (S3) and return to the main routine (S4). That is, in step S3, the timer unit that limits the allowable continuous use time is reset and the time limit of the allowable continuous use time is stopped. That is, the set value of the allowable continuous use time is set to “no limit”.
[0011]
On the other hand, if it is determined in step S2 that there is a flow rate, it is determined whether there is a change in the flow rate (S5). In determining whether or not there is a change in flow rate, the difference (= | Qave (i) between the current value Qave (i) and the value Qave (i−1) one period before in the time series of the average flow rate obtained every 30 seconds. ) -Qave (i-1) |) is obtained. When this difference is larger than the reference value, it is determined that the average flow rate has changed. The reference value for judging whether or not there is a change in the average flow rate is given as two types of values, and the larger of the two values is used. As the reference value, for example, the larger one of 3% of the current average flow rate Qave (i) and 50 L / h is adopted. If it is determined in step S5 that the flow rate has changed, the timer unit that limits the allowable continuous use time is reset (S6), and the flow rate classification to which the changed average flow rate (that is, the current value Qave (i)) belongs is assigned. After obtaining the allowable continuous use time (S7), the process returns to the main routine (S4). On the other hand, if it is determined in step S5 that there is no change in flow rate, the time being measured is compared with the allowable continuous use time (S8), and when the time being measured has reached the allowable continuous use time, the shutoff valve 2 (S9), the process returns to the main routine (S4). If it is determined in step S8 that the time being measured has not reached the allowable continuous use time, the process returns to the main routine without performing anything (S4).
[0012]
By the way, it is assumed that the instantaneous flow rate changes as shown in FIG. 8 when the instantaneous flow rate is measured using an ultrasonic flowmeter. In the illustrated example, the instantaneous flow rate changes in a sine wave shape, and the instantaneous flow rate changes with a period of about 1 minute and an amplitude of about 200 L / h. As is apparent from the figure, in this state, the instantaneous flow rate appears to fluctuate around a constant value, and it is considered that only pressure pulsation due to GHP or a gas engine is generated, but every 30 seconds. When divided into sections, a fluctuation of about 80 L / h occurs at the maximum, and if processing is performed according to the procedure shown in FIG. 7, it is determined in step S5 that there is a change in the flow rate. That is, there is a possibility that the measurement of the allowable continuous use time is stopped and a new allowable continuous use time is set. In FIG. 8, the solid line represents the average value of 15 instantaneous flow rates obtained within a 30-second period, and the alternate long and short dash line represents the maximum value of 15 instantaneous flow rates obtained within a 30-second period. The two-dot chain line means the minimum value among the 15 values of the instantaneous flow rate obtained within a period of 30 seconds.
[0013]
In short, if the technique described in the above publication is applied as it is using an ultrasonic flowmeter, the change in the instantaneous flow rate due to the pressure fluctuation is changed even though there is no change in the flow rate in the supply path. There is a risk of mistaking it to stop measuring the allowable continuous use time. As a result, there is a problem in that it may not be possible to detect a gas leak or forgetting to turn off the gas using device.
[0014]
The present invention has been made in view of the above reasons, and its purpose is to be able to reliably detect abnormalities in the use state of a fluid while adopting a flow meter that measures an instantaneous flow rate such as an ultrasonic flow meter. Another object of the present invention is to provide a safety device in the fluid supply path.
[0015]
[Means for Solving the Problems]
  The invention of claim 1 includes a flow rate measurement unit that intermittently measures an instantaneous flow rate of a fluid passing through a fluid supply path, and an average value, a maximum value, and a minimum value for each detection period in which a fixed number of instantaneous flow rates are obtained. Subtracting the maximum value in the detection period before the predetermined period from the minimum value in the current detection period The difference value obtained by subtracting the maximum value in the current detection period from the difference value and the minimum value in the detection period before the predetermined period, and comparing both difference values with a prescribed reference value, and for each detection period A timer unit that limits the allowable continuous use time obtained from the table corresponding to the flow rate category to which the average value belongs, and either of the difference values in the comparison unit until the time limit is ended by the timer unit. Resetting the timer and the change over the reference value is detectedThen, the timer unit is allowed to time the allowable continuous use time obtained from the table corresponding to the flow rate category to which the average value after the change belongs,And a determination unit that determines that the timer unit is abnormal upon completion of the time limit.
[0016]
The invention of claim 2 is the invention of claim 1, further comprising a shutoff valve inserted into the supply path, wherein the determination unit instructs the shutoff of the shutoff valve when determined to be abnormal. .
[0018]
  Claim 3The invention of claim 1Or claim 2In the invention, the determination unit resets the timer unit to stop the operation when the average value is a predetermined value or less.
[0019]
  Claim 4The invention of claim 1 to claim 1Claim 3In the invention, the detection period is 30 seconds.
[0020]
  Claim 5The invention ofClaim 4In the invention, the predetermined period is three periods.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
In this embodiment, an example in which a safety device in a fluid supply path is applied to a gas meter is shown. As shown in FIG. 1, a shutoff valve 2 and a flow rate measuring unit 3 are provided in a supply path 1 for supplying a fuel gas such as city gas. Provided. In the illustrated example, the flow rate measuring unit 3 is provided on the downstream side of the cutoff valve 2, but the flow rate measuring unit 3 may be provided on the upstream side of the cutoff valve 2. Moreover, the ultrasonic flowmeter shown in FIG. 6 is employ | adopted for the flow volume measurement part 3 as a conventional structure.
[0022]
The flow rate measuring unit 3 is configured to intermittently output an instantaneous flow rate every relatively short time (2 to 3 seconds), and the instantaneous flow rate intermittently output from the flow rate measuring unit 3 is a microcomputer (hereinafter, “ And is input to the control circuit unit 4 configured using a microcomputer. Here, the flow rate measuring unit 3 is also controlled using the same microcomputer. That is, the flow rate measuring unit 3 shown in the figure includes a part of a microcomputer in order to control the transmission / reception of ultrasonic waves and to calculate the instantaneous flow rate from the result of transmission / reception. However, in the present invention, control of transmission / reception of ultrasonic waves is not a gist and will not be described in particular. Further, a function for displaying the amount of fuel gas used as a gas meter and a pressure sensor for detecting the pressure in the supply channel 1 are omitted because they are not the gist.
[0023]
The control circuit unit 4 collects the instantaneous flow rate intermittently output from the flow rate measurement unit 3 for every detection period of 30 seconds, and based on 15 instantaneous flow rates obtained in each detection period of 30 seconds. And has a function of judging whether or not there is a flow rate in the supply path 1 and whether or not there is a change in the flow rate, and further has a function of shutting off the shut-off valve 2 when it is judged that there is a gas leak or forgetting to turn off the gas using device. . That is, the instantaneous flow rate obtained by the flow rate measurement unit 3 is input to the calculation unit 11, and the average value, maximum value, and minimum value of the instantaneous flow rate are obtained every 30 seconds in which the calculation unit 11 obtains 15 instantaneous flow rates. Find the value. The calculation unit 11 can store 15 pieces of data regarding the instantaneous flow rate. The average value, the maximum value, and the minimum value of the stored data are obtained at the end of the detection period and transferred to the register 12, and the value of the value to the register 12 is stored. After delivery, all data is erased, and the operation of storing 15 data from the next data is repeated.
[0024]
The register 12 includes a shift register that stores four average values, four maximum values, and one minimum value. Now, the average value, the maximum value, and the minimum value of the flow rate are expressed as Qave (i), Qmax (i), and Qmin (i), respectively, and the average value, the maximum value, and the minimum value of one period before are respectively expressed as Qave ( i-1), Qmax (i-1), Qmin (i-1), the average value, the maximum value, and the minimum value before two periods are respectively represented by Qave (i-2), Qmax (i-2), Qmin (i -2) The average value, the maximum value, and the minimum value before three periods are expressed as Qave (i-3), Qmax (i-3), and Qmin (i-3), respectively. In this case, the register 12 has Qave (i), Qmax (i), Qmin (i), Qave (i-1), Qmax (i-1), Qmin (i-1), and Qave (i-2). , Qmax (i−2), Qmin (i−2), Qave (i−3), Qmax (i−3), and Qmin (i−3) are stored. It should be noted that the register 12 needs to store four values of the maximum value and the minimum value up to three periods before the current value (four periods including the latest detection period). For the average value, only the current value (the average value of the latest detection period) may be stored. Hereinafter, the average value of the instantaneous flow rates in the detection period is referred to as the average flow rate.
[0025]
In the conventional configuration, when determining whether or not there is a change in the flow rate, the average flow rate during a certain period is used, and the difference between the current average flow rate Qave (i) and the average flow rate Qave (i−1) one period before is larger or smaller than the reference value. Whereas the presence or absence of a change in the flow rate is determined by comparison, in the present embodiment, the maximum value and the minimum value of the flow rate in the detection period of 30 seconds are used when determining the presence or absence of the change in the flow rate. Specifically, the difference value obtained by subtracting the maximum value Qmax (i−3) in the detection period three periods before from the minimum value Qmin (i) in the current (latest) detection period and the minimum value in the detection period three periods before. By comparing the difference value obtained by subtracting the maximum value Qmax (i) in the current (latest) detection period from the value Qmin (i-3) with the reference value, it is determined whether there is a change in the flow rate. The calculation of Qmin (i) −Qmax (i−3), Qmin (i−3) −Qmax (i) and the comparison with the reference value are performed by the comparison unit 13 provided at the subsequent stage of the register 12. Further, as in the conventional configuration, the larger one of 3% of the current average flow rate Qave (i) and 50 L / h is used as the reference value. This value is set to the same value as the conventional configuration in consideration of the case where no pressure pulsation occurs. Qmin (i) -Qmax (i-3) is likely to be a positive value and larger than the reference value when the average flow rate in the detection period of every 30 seconds increases, and conversely, Qmin (i-3) -Qmax (i) is likely to be a positive value and larger than the reference value when the average flow rate in the detection period every 30 seconds decreases. Therefore, if either of the two conditions is satisfied, it can be determined that the flow rate has changed to the increase side or the decrease side.
[0026]
In addition to the comparison unit 13, a table 15 and a flow rate detection unit 17 are also provided at the subsequent stage of the register 12. The table 15 correlates the flow rate division into which the flow rate is divided into a plurality of stages and the allowable continuous use time until the shutoff valve 2 is shut off, and is set as shown in Table 1 as an example. The table 15 is compared with the current average flow rate Qave (i) stored in the register 13, and the allowable continuous use time corresponding to the flow rate classification to which the average flow rate Qave (i) belongs is obtained. The obtained allowable continuous use time is set as a time limit in the timer unit 14 provided in the subsequent stage of the comparison unit 13 via the determination unit 16.
[0027]
Further, the flow rate detector 17 determines whether or not the fuel gas passes through the supply path 1 using the current average flow rate Qave (i). In other words, the flow rate detection unit 17 determines that there is a flow rate when the current average flow rate Qave (i) is 50 L / h or more that ignites the pilot burner in the gas using device, and the comparison unit 13 described above. Let the process do. When the flow rate is not detected (average flow rate Qave (i) is less than 50 L / h), the timer unit 14 is reset via the determination unit 16.
[0028]
In a state where the flow rate is detected by the flow rate detection unit 17, the timer unit 14 performs a timed operation with the allowable continuous use time set by the table 15 as a time limit. The start time of the timed operation is the time when the average flow rate Qave (i) reaches one of the flow rate categories or the time when the timer unit 14 is reset in the state where the allowable continuous use time obtained in the table 15 is set as the timed time. become. When the time limit of the timer unit 14 ends, the timer unit 14 blocks the shutoff valve 2 through the valve drive unit 18. On the other hand, when a change in the flow rate is detected by the comparison unit 13 during the time limit, the timer unit 14 is reset via the determination unit 16, and the allowable continuous use time corresponding to the average flow rate Qave (i) at that time is set to the time limit. The timed operation is resumed as time. In short, if the flow rate changes, the timed operation is performed again for the timed time corresponding to the average flow rate Qave (i). In other words, the determination unit 16 resets the timer unit 14 and detects the average value after the change when the comparison unit 13 detects a change greater than the reference value in either of the difference values before the timer unit 14 ends the time limit. The timer unit 14 sets a time limit corresponding to the flow rate classification, and the timer unit 14 shuts off the shut-off valve 2 if no change beyond the reference value is detected in any of the difference values until the timer unit 14 ends the time limit. Let me tell you.
[0029]
  The operation of the main part of the control circuit unit 4 described above is shown in FIG. The procedure shown in FIG. 2 is basically the same as the operation shown in FIG. 7, is a subroutine, and is called from the main routine every 30 seconds. That is, in the subroutine shown in FIG. 2, the average flow rate Qave (i), the maximum value Qmax (i), and the minimum value Qmin (i) obtained by the calculation unit 11 are obtained every detection period of 30 seconds from the main routine. (S1) The data is stored in the register 12 (S2), and the presence / absence of a flow rate is determined based on the latest average flow rate Qave (i) (S3). Thereafter, the average flow rate Qave (i), the maximum value Qmax (i) in the latest detection period of the instantaneous flow rate stored in the register 12,Minimum value Qmin (i)And the maximum value Qmax (i-3) in the detection period three periods before,Minimum value Qmin (i-3)Is used to determine whether there is a change in flow rate (S6). The presence or absence of the flow rate is determined by whether or not the average flow rate Qave (i) is 50 L / h or more (S3). If the average flow rate Qave (i) is less than 50 L / h, the operation for measuring the allowable continuous use time is performed. Cancel (S4) and return to the main routine (S5). That is, in step S4, the measurement of the allowable continuous use time is stopped and the set value of the allowable continuous use time is set to “no limit”.
[0030]
On the other hand, if it is determined in step S3 that there is a flow rate, it is determined whether there is a change in the flow rate (S6). In determining whether there is a change in the flow rate, the comparison unit 13 compares Qmin (i) −Qmax (i−3) and Qmin (i−3) −Qmax (i) with a reference value. As in the prior art, the larger one of 3% of the average flow rate value Qave (i) and 50 L / h is used as the reference value. If it is determined in step S6 that there is a change in the flow rate, the timer unit 14 is reset via the determination unit 16 (S7), and corresponds to the flow rate category to which the average flow rate after change (that is, the current value Qave (i)) belongs. After obtaining the allowable continuous use time (S8), the process returns to the main routine (S5). On the other hand, if it is determined in step S6 that there is no change in the flow rate, the time being measured is compared with the allowable continuous use time (S9), and when the time being measured has reached the allowable continuous use time, the shutoff valve 2 Is shut off (S10), the process returns to the main routine (S5). If it is determined in step S9 that the time being measured has not reached the allowable continuous use time, the process returns to the main routine without performing anything (S5).
[0031]
As described above, when the increase or decrease in the flow rate is determined using the difference between the maximum value and the minimum value of each detection period every 30 seconds, the current value and the value before three periods are used. This is because if the value before the period or the value before two periods is used, the following problems occur. First, consider the case where the current value and the value one period before are used. In this case, Qmin (i) −Qmax (i−1) or Qmin (i−1) −Qmax (i) is compared with the reference value. Considering the case where pressure pulsation does not occur as shown in FIG. 4 and assuming that a change occurs in the flow rate one period ago, Qmin (i) = Qmax (i−1), so that Qmin (i) −Qmax (i -1) = 0, and a change in flow rate cannot be detected regardless of the degree of change in flow rate. That is, it is not possible to detect whether or not the flow rate has changed even if the current value and the value one period before are used.
[0032]
Next, consider the case of using the current value and the value two periods ago. In this case, Qmin (i) −Qmax (i−2) or Qmin (i−2) −Qmax (i) is compared with the reference value. In general, the change in flow rate does not occur instantaneously but has a time width of about several seconds to 30 seconds. Therefore, depending on the timing at which the flow rate changes, the flow rate may change over two periods every 30 seconds as shown in FIG. FIG. 5 shows a case where no pressure pulsation occurs, and the change width of the flow rate is about 80 L / h, and there is a change exceeding 50 L / h in the flow rate, but Qmin (i) −Qmax (i−2). ) Is about 30 L / h, and it cannot be detected that there is a change in the flow rate. That is, there is a case where the change in the flow rate cannot be detected by comparing the current value with the value two periods before.
[0033]
From the above considerations, it is desirable to use the difference between the current value and the value three or more periods ago. In addition, if a value before four periods is used, the time required for determining the change in the flow rate becomes long. Therefore, in this embodiment, three periods are used so that the change in the flow rate can be detected and the time required for the determination is minimized. The previous value is used.
[0034]
Here, in order to compare with the conventional configuration, the operation will be considered by taking as an example the case where the instantaneous flow rate detected by the flow rate measuring unit 3 changes as shown in FIG. That is, a state where only pressure pulsation occurs in the supply path 1 and the flow rate does not substantially change will be considered. In this case, since the maximum value and the minimum value of the instantaneous flow rate are substantially constant regardless of the passage of time, Qmin (i) -Qmax (i-3) and Qmin (i-3) -Qmax (i) Both are negative. In other words, when the average flow rate is compared every 30 seconds as in the conventional configuration, the measurement of the allowable continuous use time may stop, whereas the instantaneous flow rate changes as shown in FIG. On the other hand, under the conditions of this embodiment, the allowable continuous use time is not stopped, and as a result, the allowable continuous use time when gas leakage occurs or when the gas use device is forgotten to be turned off. It becomes possible to close the shut-off valve 2 at the time point elapses.
[0035]
On the other hand, when the average flow rate is increased as shown in FIG. 3 (in FIG. 3, the solid line is an average value of 15 instantaneous flow rates obtained within a period of 30 seconds, and the alternate long and short dash line is within a period of 30 seconds. The maximum value among the 15 values of the instantaneous flow rate obtained, and the two-dot chain line means the minimum value among the 15 values of the instantaneous flow rate obtained within a period of 30 seconds, and will be described later with reference to FIGS. In general, Qmin (i) −Qmax (i−3) is a positive value and Qmin (i−3) −Qmax (i) is a negative value. However, Qmin (i) −Qmax (i−3) is not necessarily a larger value than the larger one of 3% of the average flow rate Qave (i) and 50 L / h. In other words, even if the flow rate changes, there is a higher possibility that the allowable continuous use time will continue to be measured, and the probability of shutting off the shutoff valve 2 is increased. In other words, even if there is a change in the flow rate when pressure pulsation occurs, it may not be detected, but it will reliably detect when a gas leak has occurred or forgetting to turn off the gas-using equipment. As a result, when there is a possibility of gas leakage or overheating, the shutoff valve 2 can be reliably closed to ensure safety.
[0036]
In the present embodiment, an example in which an ultrasonic flowmeter is used as the flow rate measuring unit 3 has been described. However, a fluidic flow meter or a flow sensor using a flow sensor (hot wire type) can be used as long as an instantaneous flow rate can be detected. It is possible to use other flow meters, such as a flow meter). Moreover, although the example which measures the flow volume of fuel gas was shown, the technical thought of this invention is applicable also to another fluid. Furthermore, the various numerical values described above are examples, and can be appropriately changed according to the configuration of the flow rate measuring unit 3, the type of fluid, the maximum flow rate allowed in the supply path 1, and the like. Furthermore, it is good also as a structure which does not interrupt | block the cutoff valve 2 at the time of abnormality, but only alert | reports abnormality.
[0037]
【The invention's effect】
  According to the first aspect of the present invention, an average value, a maximum value, and a minimum value are obtained for a certain detection period with respect to the instantaneous flow rate, and a difference value obtained by subtracting the maximum value in a detection period before a predetermined period from the minimum value in the current detection period. The difference value obtained by subtracting the maximum value in the current detection period from the minimum value in the detection period before the predetermined period is obtained, and both difference values are compared with a prescribed reference value to correspond to the flow rate classification to which the average value of the instantaneous flow rate belongs. The allowable continuous use time specified by the timer is timed by the timer part, and the timer part is reset if either of the difference values exceeds the reference value by the end of the time limit of the allowable continuous use time by the timer part.Then, the timer unit is allowed to time the allowable continuous use time obtained from the table corresponding to the flow rate category to which the average value after the change belongs,Since it is determined that there is an abnormality at the end of the time limit by the timer unit, when there is a change in pressure in the fluid supply path, it is erroneously detected that the flow rate has changed even though the flow rate has not changed substantially. If the pressure fluctuation range is relatively small, the timer unit is reset by detecting the change in the flow rate, so it is not judged as abnormal more than necessary, and the abnormality is reliably detected without failure. can do.In addition, by changing the time limit of the timer unit for each flow rate segment, for example, an operation can be performed in which an abnormality is notified in a shorter time as the amount of fluid flowing out per unit time increases.
[0038]
The invention of claim 2 comprises the shut-off valve inserted into the supply passage in the invention of claim 1, and the determination unit instructs the shut-off of the shut-off valve when judged to be abnormal, and more than necessary. Since it is not determined to be abnormal, the shut-off valve is not shut off more than necessary. On the other hand, in a situation where the shut-off valve needs to be shut off, the shut-off valve can be reliably shut off without failure.
[0040]
  Claim 3The invention of claim 1Or claim 2In the invention, the determination unit resets the timer unit and stops the operation when the average value is equal to or less than the predetermined value. Therefore, when the flow rate is not substantially generated, the time limit operation by the timer unit is stopped and the flow rate is reduced. It is possible to prevent the timer section from operating unnecessarily even though it does not substantially occur.
[0041]
  Claim 4The invention of claim 1 to claim 1Claim 3In the present invention, since the detection period is 30 seconds, in most cases, when the amount of fluid used changes, the flow rate change ends within two detection periods, and the predetermined period is three periods. By doing so, it is possible to detect a change in flow rate without failure when there is no fluctuation in pressure.
[0042]
  Claim 5The invention ofClaim 4In the present invention, since the predetermined period is set to 3 periods, it is possible to detect a change in the flow rate without failure when there is no fluctuation in pressure, and to detect whether there is a change in the flow rate without failure. As a minimum time.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of the present invention.
FIG. 2 is an operation explanatory view of the above.
FIG. 3 is an operation explanatory diagram of the above.
FIG. 4 is an operation explanatory diagram illustrating a comparative example.
FIG. 5 is an operation explanatory diagram illustrating a comparative example.
FIG. 6 is a schematic configuration diagram of a main part.
FIG. 7 is an operation explanatory diagram of a conventional example.
FIG. 8 is an operation explanatory diagram of a conventional example.
[Explanation of symbols]
1 Supply path
2 Shut-off valve
3 Flow measurement unit
4 Control circuit
11 Calculation unit
12 registers
13 Comparison part
14 Timer section
15 tables
16 Judgment part
17 Flow rate detector
18 Valve drive

Claims (5)

A flow rate measurement unit that intermittently measures the instantaneous flow rate of the fluid passing through the fluid supply path, a calculation unit that calculates an average value, a maximum value, and a minimum value for each detection period in which a fixed number of instantaneous flow rates are obtained; A table in which the flow rate divisions of the stages are defined and the allowable continuous use time is associated with each flow rate division, the difference value obtained by subtracting the maximum value in the detection period before the predetermined period from the minimum value in the current detection period, and the predetermined period A comparison unit that obtains a difference value obtained by subtracting the maximum value in the current detection period from the minimum value in the previous detection period and compares both difference values with a specified reference value, and a flow rate classification to which the average value for each detection period belongs Corresponding to the timer unit that limits the allowable continuous use time obtained from the table, and before the time limit is expired by the timer unit, either of the difference values is equal to or greater than the reference value in the comparison unit. Reduction resets the timer to be detected, in response to the flow rate classification to the average value after the change belongs is timed to permit continuous use time obtained from the table to the timer unit, timed terminated by the timer section A safety device in the fluid supply path, comprising: a determination unit that determines that the fluid is abnormal.   The safety device in the fluid supply path according to claim 1, further comprising: a shutoff valve inserted into the supply path, wherein the determination unit instructs the shutoff of the shutoff valve when it is determined to be abnormal. 3. The safety device in the fluid supply path according to claim 1, wherein the determination unit resets the timer unit to stop the operation when the average value is equal to or less than a predetermined value . The safety device for a fluid supply path according to any one of claims 1 to 3, wherein the detection period is 30 seconds . Safety equipment in the fluid supply passage according to claim 4, wherein the predetermined period is 3 periods.

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