JP3899991B2

JP3899991B2 - Flowmeter

Info

Publication number: JP3899991B2
Application number: JP2002114549A
Authority: JP
Inventors: 康裕梅景
Original assignee: Panasonic Corp; Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Corp; Panasonic Holdings Corp
Priority date: 2002-04-17
Filing date: 2002-04-17
Publication date: 2007-03-28
Anticipated expiration: 2022-04-17
Also published as: JP2003307443A

Description

【０００１】
【発明の属する技術分野】
本発明は、液体や気体の流量を計測する流量計測装置に関し、流量変動が発生した場合にも精度よく流量値を計測する手段に関するものである。
【０００２】
【従来の技術】
従来、この種の流量計は、特開平９−１５００６号公報のようなものが知られていた。以下、その構成について図５を参照しながら説明する。
【０００３】
図５に示すように、ガス流量を計測するアナログフローセンサ１から所定の第１サンプリング時間毎に計測値を読み取るサンプリングプログラム２と、所定時間におけるガス消費流量を算出するガス消費量算出プログラム３と、第１サンプリング時間に所定時間内で第２サンプリング時間毎にアナログフローセンサの計測値を読み出してその平均値を演算する平均値演算プログラム４と、フローセンサの出力から圧力変動の周期を推定する圧力変動周期推定プログラム５と、メモリーとしてのＲＡＭ６で構成されていた。ここで、７は前記各プログラムを記憶しておくメモリーのＲＯＭ、８はそのプログラムを実行するＣＰＵである。この構成により、所定計測時間がポンプの振動周期の１周期以上、またはその周期の倍数であるように計測処理するものであり、平均化することで流量に変動が発生しても計測流量が影響されにくい構成としている。
【０００４】
【発明が解決しようとする課題】
しかしながら上記従来技術では、変動周期が変化するたびに周期を推定して計測時間を変更する必要があり、変動周期が変化した場合に適応しにくいという課題と、流量変動が大きい場合は計測精度が悪くなるという課題があった。
【０００５】
【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、流路内の流量を計測する流量計測手段と、前記流路の上流に配置しモーターにより開度を調整する開度調整手段と、前記流路内の流量変動を前記流量計測手段の計測流量値から検出する流量変動検出手段と、前記流量変動検出手段が流量変動を検出したとき前記流量計測手段による流量計測を行いながら流量変動検出手段で検出する流量変動が所定変動量以内になるように前記開度調整手段の開度を制御する開度制御手段を備えた構成とした。
【０００６】
上記発明によれば、流量変動を検知したとき流路の開度を調整して流量変動を低減することができるので、変動周期が変化しても流量変動を低減することで、高い精度で流量を計測することができる。
【０００７】
【発明の実施の形態】
本発明は、流路内の流量を計測する流量計測手段と、前記流路の上流に配置した流路開度調整手段と、前記流路内の流量変動を検出する流量変動検出手段と、前記流量変動検出手段が流量変動を検出したとき、前記流路開度調整手段の開度を制御する開度制御手段を備えた。そして、流量変動を検知したとき流路の開度を調整して流量変動を低減することができるので、変動周期が変化しても流量変動を低減することで、高い精度で流量を計測することができる。
【０００８】
また、流量計測手段の計測した流量値と、流量変動検出手段が検出した流量変動値によって、流路開度調整手段の開度を制御する開度制御手段を備えた。そして、流量値によって流路開度調整手段の開度制御を行うことで、低流量の時にのみ開度を調整することができ、低流量時の流量計測の精度を向上できるとともに、大流量時の圧力損失を最小限に小さくできる。
【０００９】
また、所定流量以下で、かつ流量変動が所定流量変動以上のときは、開度を全開時に比べて所定開度以下とするように制御する開度制御手段を備えた。そして、所定開度以下に瞬時に行うことで、流量変動を大きく低減できるとともに、低流量時の流量計測の精度を素早く向上することとができる。
【００１０】
また、流路内の圧力を検出する圧力検出手段と、前記圧力検出手段の圧力値から流量変動を検出する流量変動検出手段を備えた。そして、圧力検出手段で、流量変動を検出することで、流量変動が小さいときでも流量変動を検出することができる。
【００１１】
また、流量変動検出手段で検出する流量変動が小さくなるように流路開度調整手段の開度を制御する開度制御手段を備えた。そして、流量変動が小さくなるように流路開度調整手段を調整することで、流量変動を低減でき精度の高い流量計測を実現することができる。
【００１２】
また、流量検出手段で検出される流量値がゼロのとき、流路開度調整手段を閉止状態に制御する開度制御手段を備えた。そして、流量がゼロのとき、流路開度調整手段を閉止状態にすることで、ゼロ流量時に積算流量が増加する誤動作を防止することができる。
【００１３】
また、流路開度調整手段は、モータにより開閉駆動を行うモータ式開度調整手段を備えた。そして、モータ式開度調整手段を用いることで、開度を細かく調整することができるので、流量変動が低下する開度や、１０％以下の開度調整を行い高精度の流量計測を実現することができる。
【００１４】
また、流量計測手段は、超音波式流量計測手段を備えた。そして、瞬時に流量が計測できる超音波式流量計測手段を用いることで、流量変動を検出することが容易にでき、かつ開度を調整して瞬時に流量計測することで、高精度の流量計測を実現することができる。
【００１５】
【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。
【００１６】
（実施例１）
図１は本発明の実施例１の流量計のブロック図である。図１において、１０は流路９に設けられて超音波を送受信する音波送受信手段としての第１振動子、１１は同じく音波送受信手段としての第２振動子、１２は前記第１振動子１０と前記第２振動子１１の送受信関係を交互に切り替える切換手段、１３は前記第１振動子１０または前記第２振動子１１に超音波信号を送信する送信器、１４は前記第１振動子１０または前記第２振動子１１の信号を受信する受信器、１５は前記第１振動子１０または前記第２振動子１１を送信手段にして、それぞれ前記第２振動子１１または前記第１振動子１０で受信する信号伝搬を繰返し行う繰返手段、１６は前記繰返手段により超音波の送受信を繰り返して行われる伝搬の時間を計測する計時手段、１７は前記計時手段１６の計測時間の値に基づいて流量を検出する流量検出手段であり、これらを総括して流量計測手段とする。そして、１８は前記流量検出手段の流量値によって、流量変動の大きさを検出する流量変動検出手段、１９は流路９の開度を調整する開度調整手段としての遮断弁、２０は前記流量変動検出手段の値によって前記遮断弁１９の開度を調整する開度制御手段である。ここで、２１は遮断弁１９を駆動するステッピングモータである。
【００１７】
次に動作、作用について図１と図２を用いて説明する。本発明の流量計は、超音波波流量計であり、繰返手段１５の繰返し開始信号により計測が開始され、送信信号を第１振動子１０に入力することによって、第１振動子１０が振動して超音波を放射し、第２振動子１１が受信する。そして、この音波の伝搬時間を計時手段１６が所定クロックでカウントし時間を計測するものである。このような流量計においては、流路９内の流体に変動が発生した場合、計測流量に誤差が生じることがある。この誤差を最小限に押さえる手段について次に説明する。
【００１８】
図２に示すフローチャートのように、流量検出手段１７で計測された流量値Ｑが、ゼロ流量の場合、遮断弁１９により流路９を遮断する。これによって、流路９内に流量変動や圧力変動が発生しても、超音波が伝搬する流路９の上流側で遮断することで、超音波が伝搬する流路９内には脈動が伝搬しないので誤差を計測することはないので、流量を積算する誤動作は発生しない。そして、流量計の下流側で流体が使用された場合は、超音波の伝搬流路に流体の変化が生じるので、伝搬時間から流体の動きを検知し、遮断弁１９を開弁する。このような動きによって、下流側での流体の使用に支障を生じさせることがなく、流量変動の影響を軽減することができる。
【００１９】
そして、流量検出手段１７の計測流量値Ｑが、所定流量値Ｑａより大きいときは、開度制御手段２０が、遮断弁１９の流路抵抗を低減するために開度を大きくするような動作（開度調整Ｂ）を行う。これは、流量が所定流量より大きい時、流量変動の影響が計測流量に及ぼさないためである。
【００２０】
また、流量検出手段１７の計測流量値Ｑが、所定流量値Ｑａより小さいときは、流量変動が発生しているか否かを流量変動検出手段１８で検出する。すなわち、流量変動検出手段１８は、複数回の計測流量値から変動量Ｑｍを検出し、この変動量Ｑｍが所定の設定値Ｑｂより大きいか否かを判別して流量変動があるか否かを検出する。そして、Ｑｍ＞Ｑｂの場合、流量変動があると判断し、遮断弁１９の開度を小さくする動作（開度調整Ａ）を行う。そして、再び流量計測を行い、流量変動が所定幅以内になるように、上記動作を繰り返す。このように流量変動が所定変動量Ｑｂ以内になるまで遮断弁１９の開度を小さくしていくことで、流量変動の影響を最小限にして流量計測を行うことができる。
【００２１】
また、開度の調整度合いが全開時の所定開度（例えば１０％）以下になったときは、それ以上の開度調整を行わないようにすることで、流れている流量を止めることなく、精度の高い流量計測を行うことができる。
【００２２】
なお、繰返によって１０％以下の開度になった時の動作で説明したが、１回の動作で１０％以下に開度を調整しても良い。１回で調整することで、すばやく対応することができ、精度の高い流量を行うことができる。
【００２３】
このように、流量変動を検知したとき流路９の開度を調整して流量変動を低減することができるので、変動周期が変化しても流量変動を低減することで、高い精度で流量を計測することができる。そして、流量値によって遮断弁１９（開度調整手段）の開度制御を行うことで、低流量の時にのみ開度を調整することができ、低流量時の流量計測の精度を向上できるとともに、大流量時の圧力損失を最小限に小さくできる。さらに、所定流量以下で、１０％以下の開度とすることで、脈動にすばやく対応できる。そして、流量変動が小さくなるように遮断弁１９を調整することで、流量変動をより低減でき精度の高い流量計測を実現することができるとともに、流量がゼロのとき、遮断弁１９を閉止状態にすることで、ゼロ流量時に積算流量が増加する誤動作を防止することができる。そして、ステッピングモーター式の遮断弁１９を用いることで、開度を細かく調整することができるので、流量変動が低下する開度や、１０％以下の開度調整を行い高精度の流量計測を実現することができる。そして、瞬時に流量が計測できる超音波式流量計測手段を用いることで、流量変動を検出することが容易にでき、かつ開度を調整して瞬時に流量計測することで、高精度の流量計測を実現することができる。
【００２４】
（実施例２）
実施例２について、図３と図４を用いて説明する。図３は本発明の実施例２を示すもので、実施例１と異なる点は、圧力センサー２２と圧力検出手段２３を備えた点にある。
【００２５】
そして、圧力センサー２２と圧力検出手段２３によって検出された圧力値によって、流路９内の圧力変動の有無を流量変動検出手段１８が検出するものである。
【００２６】
図４に示すフローチャートのように、検出された複数回の圧力値Ｐから圧力変動Ｐｍを検出し、所定の変動レベルＰａより大きいか否かで圧力変動すなわち流量変動の有無を判別する。圧力変動Ｐｍが大きい時は、開度制御手段２０で遮断弁１９の開度を所定開度以下（例えば１０％以下）になるように調整する。それによって、上流側から伝わってくる圧力変動を遮断弁１９で減衰させることができるので、精度の高い流量計測を行うことができる。
【００２７】
なお、ここでは、圧力センサー２２が遮断弁１９の上流側に設置されているので、遮断した後の圧力変動の変化を知ることはできないが、流量値を用いて流量変動検出手段１８が、流量変動量を検出し、所定値以下になるように実施例１のような繰返し制御を行っても良い。圧力センサー２２を用いることは、早く流量変動を検出することができる効果がある。また、圧力センサー２２を別設したが、第１振動子１０または第２振動子１１をセンサーとして使用し検出回路を装備することでも実現できる。
【００２８】
このように、圧力検出手段２３で圧力変動を検出することで、流量計測を行いながらでも検出できることや、流路９内の変動を的確に素早く捉えることができ、流量変動や圧力変動があっても、精度の高い流量計測を実現することができる効果がある。
【００２９】
【発明の効果】
以上説明したように本発明の流量計によれば、次の効果が得られる。
【００３０】
本発明は、流量変動を検知したとき流路の開度を調整して流量変動を低減することができるので、変動周期が変化しても流量変動を低減することで、高い精度で流量を計測することができる。
【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】同流量計の動作を説明するフローチャート
【図３】本発明の他の実施例を示すブロック図
【図４】同流量計の動作を説明するフローチャート
【図５】従来の流量計を示すブロック図
【符号の説明】
９流路
１７流量検出手段（流量計測手段）
１８流量変動検出手段
１９遮断弁（開度調整手段）
２０開度制御手段
２１ステッピングモーター
２２圧力センサー
２３圧力検出手段[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flow rate measuring device that measures a flow rate of a liquid or gas, and relates to a means for accurately measuring a flow rate value even when a flow rate fluctuation occurs.
[0002]
[Prior art]
Conventionally, this type of flowmeter has been known as disclosed in JP-A-9-15006. The configuration will be described below with reference to FIG.
[0003]
As shown in FIG. 5, a sampling program 2 that reads a measured value every predetermined first sampling time from an analog flow sensor 1 that measures a gas flow rate, and a gas consumption calculation program 3 that calculates a gas consumption flow rate at a predetermined time, The average value calculation program 4 for reading the measurement value of the analog flow sensor every second sampling time within the predetermined time within the first sampling time and calculating the average value, and estimating the pressure fluctuation period from the output of the flow sensor It consists of a pressure fluctuation period estimation program 5 and a RAM 6 as a memory. Here, 7 is a ROM of a memory for storing each program, and 8 is a CPU for executing the program. With this configuration, the measurement process is performed so that the predetermined measurement time is one or more times the vibration period of the pump or a multiple of that period. It is hard to be configured.
[0004]
[Problems to be solved by the invention]
However, in the above-described prior art, it is necessary to estimate the period and change the measurement time every time the fluctuation period changes, and it is difficult to adapt when the fluctuation period changes. There was a problem of getting worse.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a flow rate measuring means for measuring the flow rate in the flow path, an opening degree adjusting means that is arranged upstream of the flow path and adjusts the opening degree by a motor , A flow rate fluctuation detecting means for detecting a flow rate fluctuation from a measured flow rate value of the flow rate measuring means, and a flow rate detected by the flow rate fluctuation detecting means while performing the flow rate measurement by the flow rate measuring means when the flow rate fluctuation detecting means detects the flow rate fluctuation. variation is configured to include an opening degree control means for controlling the opening of the front KiHiraki adjusting means such that within a predetermined fluctuation amount.
[0006]
According to the above invention, when the flow rate fluctuation is detected, the flow rate fluctuation can be reduced by adjusting the opening degree of the flow path. Can be measured.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The present invention includes a flow rate measuring means for measuring a flow rate in a flow path, a flow path opening degree adjusting means arranged upstream of the flow path, a flow rate fluctuation detecting means for detecting a flow rate fluctuation in the flow path, When the flow rate fluctuation detecting means detects flow rate fluctuation, an opening degree control means for controlling the opening degree of the flow path opening degree adjusting means is provided. And when the flow rate fluctuation is detected, the flow rate fluctuation can be reduced by adjusting the opening of the flow path, so even if the fluctuation cycle changes, the flow rate fluctuation can be reduced to measure the flow rate with high accuracy. Can do.
[0008]
In addition, opening degree control means for controlling the opening degree of the channel opening degree adjusting means based on the flow rate value measured by the flow rate measuring means and the flow rate fluctuation value detected by the flow rate fluctuation detecting means is provided. Then, by controlling the opening of the flow path opening adjusting means according to the flow rate value, the opening can be adjusted only when the flow rate is low, and the accuracy of the flow measurement at the low flow rate can be improved. The pressure loss can be minimized.
[0009]
In addition, opening degree control means for controlling the opening degree to be equal to or less than the predetermined opening degree when the flow rate fluctuation is equal to or less than the predetermined flow rate fluctuation when compared to when fully opened is provided. And by performing it instantaneously below a predetermined opening degree, while being able to reduce a flow volume largely, the precision of the flow measurement at the time of a low flow volume can be improved rapidly.
[0010]
Further, a pressure detection means for detecting the pressure in the flow path and a flow rate fluctuation detection means for detecting a flow rate fluctuation from the pressure value of the pressure detection means are provided. The flow rate fluctuation can be detected even when the flow rate fluctuation is small by detecting the flow rate fluctuation with the pressure detecting means.
[0011]
In addition, an opening degree control means for controlling the opening degree of the flow path opening degree adjusting means so as to reduce the flow rate fluctuation detected by the flow rate fluctuation detecting means is provided. The flow rate variation can be reduced and the flow rate can be measured with high accuracy by adjusting the flow path opening degree adjusting means so that the flow rate variation is reduced.
[0012]
In addition, when the flow rate value detected by the flow rate detection means is zero, an opening degree control means for controlling the flow path opening degree adjustment means to be closed is provided. When the flow rate is zero, the malfunction of the integrated flow rate increase at the zero flow rate can be prevented by closing the flow passage opening degree adjusting means.
[0013]
Further, the flow path opening degree adjusting means includes motor type opening degree adjusting means for opening and closing by a motor. Since the opening degree can be finely adjusted by using the motor type opening degree adjusting means, the opening degree at which the flow rate fluctuation is reduced or the opening degree adjustment of 10% or less is performed to realize a highly accurate flow rate measurement. be able to.
[0014]
Further, the flow rate measuring means includes an ultrasonic flow rate measuring means. And by using an ultrasonic flow measuring means that can measure the flow rate instantaneously, it is easy to detect flow rate fluctuations, and by adjusting the opening and instantaneously measuring the flow rate, highly accurate flow measurement Can be realized.
[0015]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
[0016]
Example 1
FIG. 1 is a block diagram of a flow meter according to a first embodiment of the present invention. In FIG. 1, reference numeral 10 denotes a first vibrator as a sound wave transmission / reception means provided in the flow path 9 for transmitting / receiving ultrasonic waves, 11 denotes a second vibrator as a sound wave transmission / reception means, and 12 denotes the first vibrator 10. Switching means for alternately switching the transmission / reception relationship of the second transducer 11, 13 is a transmitter for transmitting an ultrasonic signal to the first transducer 10 or the second transducer 11, and 14 is the first transducer 10 or A receiver 15 for receiving the signal of the second vibrator 11, and 15 is the second vibrator 11 or the first vibrator 10, respectively, using the first vibrator 10 or the second vibrator 11 as a transmission means. Repeating means for repeatedly performing signal propagation to be received, 16 is a timing means for measuring the time of propagation performed by repeatedly transmitting and receiving ultrasonic waves by the repeating means, and 17 is based on the value of the measurement time of the timing means 16 Flow rate A flow rate detecting means for output, and the flow rate measuring means are collectively these. 18 is a flow rate fluctuation detecting means for detecting the magnitude of the flow rate fluctuation based on the flow rate value of the flow rate detecting means, 19 is a shut-off valve as an opening degree adjusting means for adjusting the opening degree of the flow path 9, and 20 is the flow rate. It is an opening degree control means for adjusting the opening degree of the shutoff valve 19 according to the value of the fluctuation detecting means. Here, 21 is a stepping motor that drives the shut-off valve 19.
[0017]
Next, operation | movement and an effect | action are demonstrated using FIG. 1 and FIG. The flow meter of the present invention is an ultrasonic wave flow meter, and measurement is started by a repetition start signal of the repeating unit 15, and the first transducer 10 vibrates by inputting a transmission signal to the first transducer 10. Then, ultrasonic waves are radiated and received by the second vibrator 11. The time measuring means 16 counts the propagation time of the sound wave with a predetermined clock and measures the time. In such a flow meter, when fluctuation occurs in the fluid in the flow path 9 , an error may occur in the measured flow rate. Next, means for minimizing this error will be described.
[0018]
As shown in the flowchart of FIG. 2, when the flow rate value Q measured by the flow rate detection means 17 is zero, the shutoff valve 19 blocks the flow path 9 . Thus, even the flow rate fluctuation and the pressure fluctuation is generated in the flow path 9, by blocking the upstream side of the flow path 9 that ultrasound propagates, pulsations in the flow path 9 that ultrasound propagates the propagation Therefore, the error is not measured, so that the malfunction of integrating the flow rate does not occur. When a fluid is used on the downstream side of the flow meter, a change in the fluid occurs in the ultrasonic propagation channel, so that the fluid movement is detected from the propagation time, and the shutoff valve 19 is opened. By such a movement, the influence of the flow rate fluctuation can be reduced without causing any trouble in the use of the fluid on the downstream side.
[0019]
When the measured flow rate value Q of the flow rate detection means 17 is larger than the predetermined flow rate value Qa, the opening degree control means 20 operates to increase the opening degree in order to reduce the flow path resistance of the shutoff valve 19 ( Opening adjustment B) is performed. This is because when the flow rate is greater than the predetermined flow rate, the influence of the flow rate fluctuation does not affect the measured flow rate.
[0020]
Further, when the measured flow rate value Q of the flow rate detection means 17 is smaller than the predetermined flow rate value Qa, the flow rate fluctuation detection means 18 detects whether or not a flow rate fluctuation has occurred. That is, the flow rate fluctuation detecting means 18 detects the fluctuation amount Qm from a plurality of measured flow rate values, determines whether or not the fluctuation amount Qm is larger than a predetermined set value Qb, and determines whether or not there is a flow rate fluctuation. To detect. When Qm> Qb, it is determined that there is a flow rate variation, and an operation (opening adjustment A) for reducing the opening of the shutoff valve 19 is performed. Then, the flow rate is measured again, and the above operation is repeated so that the flow rate fluctuation is within a predetermined range. Thus, by reducing the opening degree of the shutoff valve 19 until the flow rate fluctuation is within the predetermined fluctuation amount Qb, the flow rate measurement can be performed with the influence of the flow rate fluctuation being minimized.
[0021]
In addition, when the degree of adjustment of the opening is less than a predetermined opening (for example, 10%) at the time of full opening, by preventing the adjustment of the opening beyond that, without stopping the flowing flow rate, Accurate flow measurement can be performed.
[0022]
In addition, although it demonstrated by the operation | movement when it became an opening degree of 10% or less by repetition, you may adjust an opening degree to 10% or less by one operation | movement. By adjusting at one time, it is possible to respond quickly and perform a highly accurate flow rate.
[0023]
In this way, the flow rate fluctuation can be reduced by adjusting the opening degree of the flow path 9 when the flow rate fluctuation is detected, so even if the fluctuation period changes, the flow rate fluctuation can be reduced, so that the flow rate can be controlled with high accuracy. It can be measured. And by controlling the opening degree of the shut-off valve 19 ( opening adjusting means ) by the flow value, the opening degree can be adjusted only when the flow rate is low, and the accuracy of the flow rate measurement at the low flow rate can be improved, Pressure loss at large flow rate can be minimized. Furthermore, it can respond to a pulsation rapidly by setting it as 10% or less opening degree below a predetermined flow rate. By adjusting the shut-off valve 19 so that the flow rate fluctuation becomes small, the flow rate fluctuation can be further reduced and high-accuracy flow rate measurement can be realized, and when the flow rate is zero, the shut-off valve 19 is closed. By doing so, it is possible to prevent a malfunction in which the integrated flow rate increases at zero flow rate. Then, by using the shut-off valve 19 of the stepping motor over expression, it is possible to finely adjust the opening, the opening and the flow rate fluctuation is reduced, the precision of the flow rate measurement performed following opening adjustment 10% Can be realized. And by using an ultrasonic flow measuring means that can measure the flow rate instantaneously, it is easy to detect flow rate fluctuations, and by adjusting the opening and instantaneously measuring the flow rate, highly accurate flow measurement Can be realized.
[0024]
(Example 2)
A second embodiment will be described with reference to FIGS. 3 and 4. FIG. 3 shows a second embodiment of the present invention, which is different from the first embodiment in that a pressure sensor 22 and a pressure detection means 23 are provided.
[0025]
The flow rate fluctuation detection means 18 detects the presence or absence of pressure fluctuation in the flow path 9 based on the pressure values detected by the pressure sensor 22 and the pressure detection means 23.
[0026]
As shown in the flowchart of FIG. 4, the pressure fluctuation Pm is detected from a plurality of detected pressure values P, and the presence or absence of pressure fluctuation, that is, flow rate fluctuation is determined based on whether or not the pressure fluctuation Pm is greater than a predetermined fluctuation level Pa. When the pressure fluctuation Pm is large, the opening degree control means 20 adjusts the opening degree of the shut-off valve 19 so as to be equal to or less than a predetermined opening degree (for example, 10% or less). As a result, the pressure fluctuation transmitted from the upstream side can be attenuated by the shut-off valve 19 , so that the flow rate can be measured with high accuracy.
[0027]
Here, since the pressure sensor 22 is installed on the upstream side of the shut-off valve 19, it is impossible to know the change in pressure fluctuation after the shut-off, but the flow rate fluctuation detecting means 18 uses the flow rate value to detect the flow rate fluctuation. The variation amount may be detected and the repetitive control as in the first embodiment may be performed so as to be equal to or less than a predetermined value. The use of the pressure sensor 22 has an effect that the flow rate fluctuation can be detected quickly. Further, although the pressure sensor 22 is provided separately, it can also be realized by using the first vibrator 10 or the second vibrator 11 as a sensor and equipped with a detection circuit.
[0028]
Thus, by detecting the pressure fluctuation with the pressure detecting means 23 , it can be detected even while measuring the flow rate, and the fluctuation in the flow path 9 can be grasped accurately and quickly. In addition, there is an effect that it is possible to realize a highly accurate flow rate measurement.
[0029]
【The invention's effect】
As described above, according to the flowmeter of the present invention, the following effects can be obtained.
[0030]
The present invention is capable of adjusting the opening degree of the flow path when detecting the flow amount change to reduce the flow rate variation, even when the fluctuation period changed by reducing the flow rate variation, the flow rate with high precision It can be measured.
[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 flowchart for explaining the operation of the flow meter. FIG. 3 is a block diagram illustrating another embodiment of the present invention. Flowchart explaining operation of meter [FIG. 5] Block diagram showing conventional flow meter [Explanation of symbols]
9 Channel 17 Flow rate detection means (flow rate measurement means)
18 Flow rate fluctuation detection means 19 Shut-off valve (opening adjustment means)
20 Opening control means 21 Stepping motor 22 Pressure sensor 23 Pressure detection means

Claims

A flow rate measuring means for measuring a flow rate in the flow path, a motor type opening degree adjusting means arranged upstream of the flow path, and a flow rate fluctuation for detecting a flow rate fluctuation in the flow path from a measured flow rate value of the flow rate measuring means. detecting means and said flow rate measuring means rate variation detected by the flow rate fluctuation detection means while performing the flow rate measurement by is within a predetermined fluctuation amount as before KiHiraki adjusting means when the flow rate fluctuation detection means detects the flow rate variation The flowmeter provided with the opening degree control means which controls the opening degree.

The flow meter according to claim 1, further comprising an opening degree control means for controlling the opening degree to be not more than the predetermined opening degree when the flow rate fluctuation is not more than the predetermined flow rate and not less than the predetermined flow rate fluctuation .

A pressure detecting means for detecting the pressure in the flow path, according to claim 1 or 2 flowmeter according with a flow rate fluctuation detection means for detecting the flow rate change from the pressure value of the pressure detecting means.

When the flow rate value detected by the flow rate detecting means is zero, the flow meter of claim 1 Symbol placement with opening control means for controlling the passage opening adjustment means in the closed state.

The flowmeter according to claim 1 , wherein the flow rate measuring means is an ultrasonic flow rate measuring means .