JP2000055709A - Ultrasonic flowmeter - Google Patents
Ultrasonic flowmeterInfo
- Publication number
- JP2000055709A JP2000055709A JP10231190A JP23119098A JP2000055709A JP 2000055709 A JP2000055709 A JP 2000055709A JP 10231190 A JP10231190 A JP 10231190A JP 23119098 A JP23119098 A JP 23119098A JP 2000055709 A JP2000055709 A JP 2000055709A
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- Prior art keywords
- pulsation
- fluid
- flow rate
- ultrasonic
- flow
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、自動車の排気ガス
の流量などの計測に利用される超音波流量計に関するも
のである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic flowmeter used for measuring the flow rate of exhaust gas from an automobile.
【０００２】[0002]
【従来の技術】従来、気体や液体などの流体の流量を測
定するために、超音波流量計が広く使用されてきた。こ
の超音波流量計は、流体中に超音波を放射し、その伝播
速度の上流と下流への差や、流体内で生じた反射波の周
波数のドップラーシフト量などの受信された超音波の特
性に基づき流体の流速と流量とを測定するように構成さ
れている。2. Description of the Related Art Conventionally, ultrasonic flowmeters have been widely used to measure the flow rate of fluids such as gas and liquid. This ultrasonic flow meter emits ultrasonic waves into the fluid, and the characteristics of the received ultrasonic waves, such as the difference between the upstream and downstream of the propagation velocity and the Doppler shift amount of the frequency of the reflected wave generated in the fluid Is configured to measure the flow velocity and flow rate of the fluid based on
【０００３】近年、自動車の排気ガス中に含まれる窒素
酸化物や硫黄酸化物などの有害物質による大気汚染を防
止するために、そのような有害物質の排出量の規制の強
化が必要となってきている。このような有害物質は、排
気ガス中の含有率（排気ガスに対する重量比や体積比）
で測定されるが、個々の自動車による有害物質の排出量
は、そのような含有率と排気ガスの流量（質量あるいは
体積流量）との積で与えられる。このため、個々の自動
車を規制の対象とする場合には、有害物質の含有率と共
に排気ガスの流量を測定することが必要になる。In recent years, in order to prevent air pollution caused by harmful substances such as nitrogen oxides and sulfur oxides contained in exhaust gas from automobiles, it has become necessary to tighten regulations on the emission of such harmful substances. ing. The content of such harmful substances in exhaust gas (weight ratio or volume ratio to exhaust gas)
The emission of harmful substances by an individual vehicle is given by the product of such a content rate and the flow rate (mass or volume flow rate) of the exhaust gas. For this reason, when individual automobiles are subject to regulation, it is necessary to measure the flow rate of exhaust gas together with the content of harmful substances.
【０００４】従来、自動車の排気ガスの流量の測定方法
の典型的なものは、自動車の排気管に１対の超音波セン
サを排気ガスの流れに沿って取付け、一定の周期で、超
音波の伝播方向を上流側から下流側に、下流側から上流
側へと交番させながら、送受波を行わせることにより流
速を周期的に測定して時間平均値を算定し、この流速の
時間平均値から流量の時間平均値を算定している。Conventionally, a typical method of measuring the flow rate of the exhaust gas of an automobile is to attach a pair of ultrasonic sensors to the exhaust pipe of the automobile along the flow of the exhaust gas, and to generate ultrasonic waves at a constant cycle. While alternating the propagation direction from upstream to downstream and from downstream to upstream, transmit and receive waves are periodically measured to calculate the time average, and the time average is calculated from this time average. The time average of the flow rate is calculated.
【０００５】[0005]
【発明が解決しようとする課題】自動車の排気ガスは、
エンジンの回転に伴う周期的かつ間欠的な排気工程によ
って発生するため、その流量がある周期で脈動する。す
なわち、図５に単純化して例示するように、排気ガスの
流速Ｖ（従って流量Ｑ））が、時間軸ｔ上である周期Ｔ
で正弦波状に変動する。この脈動する排気ガスの流速Ｖ
が、ある周期τで伝播方向を交番させながら超音波の送
受波が行われる超音波流量計によって測定されることに
なる。The exhaust gas of automobiles is
Since the flow rate is generated by a periodic and intermittent exhaust process accompanying the rotation of the engine, the flow rate pulsates at a certain cycle. That is, as illustrated in a simplified manner in FIG. 5, the flow velocity V of the exhaust gas (therefore, the flow rate Q) is equal to the period T on the time axis t.
Fluctuates sinusoidally. Velocity V of this pulsating exhaust gas
Is measured by an ultrasonic flowmeter that transmits and receives ultrasonic waves while alternating the propagation direction at a certain period τ.
【０００６】排気ガスの脈動の周期Ｔは、自動車のエン
ジンの回転数などによって変動するため、超音波の送受
波の周期τとは全く無関係になる。このため、周期τで
測定される排気ガスの流速Ｖが測定のたびごとに広範囲
にわたって変動する。すなわち、図５において、○印の
時点では超音波を上流から下流側に伝播させることによ
って伝播所要時間の測定が行われ、●印は逆に、超音波
を下流側から上流側に伝播させることによって伝播所要
時間の測定が行われる。このように脈動が存在すると、
超音波の伝播方向を逆転させる間に、測定対象の流速が
変化してしまうため、正確な流速が得られなくなる。The cycle T of the pulsation of the exhaust gas varies depending on the number of revolutions of the engine of the automobile and the like, and is completely independent of the cycle τ of the transmission and reception of the ultrasonic waves. Therefore, the flow velocity V of the exhaust gas measured at the period τ fluctuates over a wide range for each measurement. That is, in FIG. 5, the time required for propagation is measured by propagating the ultrasonic wave from the upstream to the downstream side at the time of the mark, and the mark of the reverse sign indicates that the ultrasonic wave is propagated from the downstream side to the upstream side at the time of the mark. The measurement of the required propagation time is carried out. When such pulsation exists,
While reversing the propagation direction of the ultrasonic wave, the flow velocity of the measurement object changes, so that an accurate flow velocity cannot be obtained.
【０００７】上記脈動に伴う測定誤差は、測定を何回も
繰り返すことによって、平均化されて相殺される。しか
しながら、その時間平均値を算定するまでには多数個の
測定値、すなわち、多数回の測定が必要になる。この結
果、１個のデータの測定所要時間が増大し、自動車の発
進や急停止などに伴って発生する流量の急激な変動に追
随できなくなるという問題がある。従って、本発明の一
つの目的は、自動車の発進や急停止などに伴って発生す
る流量の急激な変動に追随可能な、測定所要時間が短縮
された超音波流量計を提供することにある。The measurement error due to the pulsation is averaged out by repeating the measurement many times. However, a large number of measured values, that is, a large number of measurements are required before the time average value is calculated. As a result, there is a problem in that the time required for measuring one piece of data increases, and it becomes impossible to follow a sudden change in the flow rate that occurs when the vehicle starts or stops suddenly. Accordingly, it is an object of the present invention to provide an ultrasonic flowmeter with a reduced measurement time, which can follow a rapid change in the flow rate generated when the vehicle starts or stops suddenly.
【０００８】[0008]
【課題を解決するための手段】上記従来技術の課題を解
決する本発明の第１の超音波流量計は、流量計測対象の
流体の脈動の状態を検出する脈動状態検出手段と、この
検出した脈動の状態がほぼ同一の時点においてこの流体
の流速を反復して検出する流速検出手段とを備えてい
る。A first ultrasonic flow meter according to the present invention for solving the above-mentioned problems of the prior art comprises a pulsation state detecting means for detecting a pulsation state of a fluid to be measured, and a pulsation state detecting means for detecting the pulsation state. Flow rate detecting means for repeatedly detecting the flow rate of the fluid when the pulsation state is substantially the same.
【０００９】本発明の第２の超音波流量計は、流量計測
対象の流体の脈動の周期を検出する脈動周期検出手段
と、この検出した脈動の周期と適宜な関係を有する周期
でこの流体の流速を反復して検出する流速検出手段とを
備えている。A second ultrasonic flowmeter according to the present invention comprises a pulsation cycle detecting means for detecting a pulsation cycle of a fluid to be measured, and a cycle of the fluid having a proper relationship with the detected pulsation cycle. Flow rate detecting means for repeatedly detecting the flow rate.
【００１０】本発明の第３の超音波流量計は、流量計測
対象の流体の脈動の状態を検出する脈動状態検出手段
と、この流体の流速を一定の周期で反復して検出する流
速検出手段と、この流速検出手段で検出された流速につ
いて上記脈動状態検出手段で検出された脈動の状態を考
慮しながら時間的な平均化処理を行う処理手段とを備え
ている。A third ultrasonic flowmeter according to the present invention comprises a pulsation state detecting means for detecting a pulsating state of a fluid to be measured, and a flow rate detecting means for repeatedly detecting the flow rate of the fluid at a constant cycle. And a processing means for performing a temporal averaging process on the flow velocity detected by the flow velocity detection means while taking into account the pulsation state detected by the pulsation state detection means.
【００１１】[0011]
【発明の実施の形態】上記第１の発明の好適な実施の形
態によれば、上記脈動の状態がほぼ同一の時点は、この
脈動の最大ピーク値と最小ピーク値との中間に設定さ
れ、あるいは、適宜な複数の状態について設定される。According to a preferred embodiment of the first invention, the point in time when the pulsation state is substantially the same is set at an intermediate point between the maximum peak value and the minimum peak value of the pulsation, Alternatively, it is set for a plurality of appropriate states.
【００１２】上記第２の発明の好適な実施の形態によれ
ば、上記脈動の周期は基本波について検出され、この脈
動の周期と上記流速検出周期との間の適宜な関係は整数
倍又は整数分の１倍の関係を有する。According to a preferred embodiment of the second invention, the period of the pulsation is detected for a fundamental wave, and an appropriate relationship between the period of the pulsation and the flow velocity detection period is an integer multiple or an integer. It has a one-fold relationship.
【００１３】上記第３の発明の好適な実施の形態によれ
ば、上記脈動の状態を考慮しながら行う時間的な平均化
処理は、脈動の振幅に応じて設定した係数を用いて前記
検出された流速を補正することにより行われる。According to the preferred embodiment of the third aspect of the present invention, the temporal averaging process performed in consideration of the pulsation state is performed by using the coefficient set according to the pulsation amplitude. This is performed by correcting the flow velocity.
【００１４】上記第１，第２，第３の発明に共通する好
適な実施の形態によれば、上記脈動の状態は流路内の圧
力に基づき検出され、さらに、この流体は自動車の排気
ガスから成る。According to a preferred embodiment common to the first, second, and third inventions, the pulsation state is detected based on the pressure in the flow passage, and the fluid is exhausted from an automobile exhaust gas. Consists of
【００１５】[0015]
【実施例】図１は、本発明の一実施例の超音波流量計の
概略の構成を示す機能ブロック図であり、１はＣＰＵ、
２は送信回路、３，４は送受波器（トランスジュー
サ）、５は受信回路、６は送受切替器、７は入出力イン
ターフェイス回路、８は圧力センサ、９はＡ／Ｄ変換器
である。FIG. 1 is a functional block diagram showing a schematic configuration of an ultrasonic flowmeter according to one embodiment of the present invention.
2 is a transmission circuit, 3 and 4 are transducers (transducers), 5 is a reception circuit, 6 is a transmission / reception switch, 7 is an input / output interface circuit, 8 is a pressure sensor, and 9 is an A / D converter.
【００１６】送受波器３と４とは、図示しない自動車の
排気管内を流れる排気ガスの流路に沿ってかつこの流路
を挟んで互いに対向するようにこの排気管の管軸に対し
て斜めに、その管壁に取付けられている。送信回路２で
発生されたパルス状の駆動信号が送受切替器６を経て送
受波器３と４の一方に供給され、この一方の送受波器で
発生された超音波信号が排気ガス中に送信される。排気
ガス中を伝播した超音波信号は、送受波器３と４の他方
に受信され、送受波切替器６を経て受信回路５に受信さ
れる。The transducers 3 and 4 are inclined with respect to the pipe axis of the exhaust pipe along the flow path of the exhaust gas flowing through the exhaust pipe (not shown) of the automobile so as to face each other with the flow path interposed therebetween. And is attached to the tube wall. The pulse-like drive signal generated by the transmission circuit 2 is supplied to one of the transducers 3 and 4 via the transmission / reception switch 6, and the ultrasonic signal generated by this one transducer is transmitted to the exhaust gas. Is done. The ultrasonic signal that has propagated in the exhaust gas is received by the other one of the transducers 3 and 4, and is received by the receiving circuit 5 via the transducer 6.
【００１７】上記超音波信号の送信と受信が、ＣＰＵ１
の制御のもとに動作する送受切替器６によって、送信側
と受信側の送受波器を交互に切替えながら反復して行わ
れる。ＣＰＵ１は、送信回路２に超音波信号の送信を指
令したのち、受信回路５から超音波信号を受信した旨を
通知する受信通知信号を入出力インターフェイス回路７
を介して受信し、上記超音波信号の送信から受信までの
経過時間を、流体中の超音波信号の伝播所要時間として
検出する。The transmission and reception of the ultrasonic signal are performed by the CPU 1
The transmission / reception switch 6 which operates under the above control repeatedly performs the switching while alternately switching the transmission / reception side transducers. After instructing the transmission circuit 2 to transmit an ultrasonic signal, the CPU 1 transmits a reception notification signal notifying that the ultrasonic signal has been received from the reception circuit 5 to the input / output interface circuit 7.
, And detects an elapsed time from transmission of the ultrasonic signal to reception thereof as a propagation time of the ultrasonic signal in the fluid.
【００１８】ＣＰＵ１は、超音波信号を排気ガスの流れ
の上流に向けて伝播させた場合、例えば送受波器３から
送信させ送受波器４で受信した場合の伝播所要時間と、
逆に超音波信号を下流に向けて伝播させた場合、例えば
送受波器４から送信させ送受波器３で受信した場合の伝
播所要時間とから、排気ガスの流路の横断面内の空間平
均流速を算定し、この流路断面内の空間平均流速に流路
の断面積を乗算することにより、排気ガスの体積流量を
算定する。When the ultrasonic signal is propagated toward the upstream of the flow of the exhaust gas, the CPU 1 transmits the ultrasonic signal, for example, when the ultrasonic signal is transmitted from the transmitter / receiver 3 and received by the transmitter / receiver 4,
Conversely, when the ultrasonic signal is propagated downstream, for example, from the required propagation time when transmitted from the transducer 4 and received by the transducer 3, the spatial average in the cross section of the flow path of the exhaust gas is obtained. The flow velocity is calculated, and the volume flow rate of the exhaust gas is calculated by multiplying the spatial average flow velocity in the cross section of the flow passage by the cross-sectional area of the flow passage.
【００１９】ＣＰＵ１は、図示しない密度センサを使用
して実測した排気ガスの密度や、予め設定されている排
気ガスの密度を、上述の手順に従って算出した排気ガス
の体積流量に乗算することにより、排気ガスの重量流量
を算定する。ＣＰＵ１は、図示しない適宜な成分センサ
を使用して実測した排気ガス中の着目するＮＯｘなどの
有害物質の含有率に、上記排気ガスの重量流量を乗算す
ることにより着目する有害物質の排出重量を算定する。The CPU 1 multiplies the exhaust gas density actually measured using a density sensor (not shown) or a preset exhaust gas density by the exhaust gas volume flow rate calculated according to the above-described procedure. Calculate the exhaust gas weight flow rate. The CPU 1 multiplies the content of the harmful substance such as NOx of interest in the exhaust gas actually measured using an appropriate component sensor (not shown) by the weight flow rate of the exhaust gas to calculate the weight of the harmful substance discharged from the exhaust gas. Calculate.
【００２０】上述のように、流路に斜めに設置した１対
の送受波器を使用して排気ガスの空間平均流速と体積流
量を測定したり、この体積流量から密度センサなどとの
組合せによって排気ガスの重量流量を測定したり、さら
には、成分センサとの組合せによって排気ガスに含まれ
る有害物質の排出重量を算定する技術そのものは従来か
ら知られている。本実施例の特徴は、以下で述べるよう
に、超音波の放射と受信による流速測定の時点を、検出
した圧力に基づいて制御する点にある。As described above, the spatial average flow velocity and the volume flow rate of the exhaust gas are measured by using a pair of transducers installed diagonally in the flow path, and the volume flow rate is determined by a combination with a density sensor or the like. Techniques for measuring the weight flow rate of exhaust gas or calculating the weight of exhausted harmful substances contained in exhaust gas by combination with a component sensor have been conventionally known. The feature of this embodiment is that the time point of the flow velocity measurement by the emission and reception of the ultrasonic wave is controlled based on the detected pressure, as described below.
【００２１】まず、上記排気ガスの流量の測定は、精度
を高めたり、測定対象の排気ガスが脈動状態にあること
などを考慮して繰り返して行われ、これによって得られ
た多数のサンプルについての時間的な平均値が算定され
る。本実施例によれば、ＣＰＵ１は、排気ガスの脈動の
状態を検出し、この検出した脈動の状態がほぼ同一の時
点において排気ガスの流速を反復して検出するように、
送信回路２と送受切替器６の動作を制御する。First, the measurement of the flow rate of the exhaust gas is repeatedly performed in consideration of increasing the accuracy and the fact that the exhaust gas to be measured is in a pulsating state. An average over time is calculated. According to the present embodiment, the CPU 1 detects the state of the pulsation of the exhaust gas, and repeatedly detects the flow velocity of the exhaust gas when the detected pulsation state is substantially the same.
The operation of the transmission circuit 2 and the transmission / reception switch 6 is controlled.
【００２２】すなわち、本実施例の超音波流量計では、
ダイヤフラムと電歪素子などを組み合わせた適宜な形式
の圧力センサ８が排気ガスの流路内に設置されており、
その出力がＡ／Ｄ変換器９でディジタル信号に変換さ
れ、ＣＰＵ１に供給される。この検出された排気ガスの
圧力Ｐの典型的なものは、図２に例示するように、経過
時間ｔに対して正弦波状の脈動を示す。そして、排気ガ
スの流速Ｖの規格化波形は、典型的には、上記圧力Ｐの
正弦波形とほぼ同位相になることが本発明者によって確
認されている。That is, in the ultrasonic flowmeter of the present embodiment,
An appropriate type of pressure sensor 8 combining a diaphragm and an electrostrictive element is installed in the exhaust gas flow path,
The output is converted into a digital signal by the A / D converter 9 and supplied to the CPU 1. A typical example of the detected exhaust gas pressure P exhibits a sinusoidal pulsation with respect to the elapsed time t, as illustrated in FIG. It has been confirmed by the present inventors that the normalized waveform of the flow velocity V of the exhaust gas typically has substantially the same phase as the sine waveform of the pressure P.
【００２３】この排気ガスの圧力Ｐと流速Ｖの脈動の周
期は、車種や自動車の走行状態によって変化するが、典
型的な一例は、ディーゼルエンジンの自動車では概ね30
Hzから120Hz の範囲であり、ガソリンエンジンの自動車
では概ね30Hzから200Hz の範囲である。The cycle of the pulsation of the exhaust gas pressure P and the flow velocity V varies depending on the type of the vehicle and the running state of the vehicle. A typical example is approximately 30 in a diesel engine vehicle.
The range is from Hz to 120Hz, and for gasoline-powered vehicles it is generally in the range from 30Hz to 200Hz.
【００２４】ＣＰＵ１は、圧力センサ８で検出した排気
ガスの圧力Ｐの極大値Ｐmax と極小値Ｐmin とからこれ
らの中間の値Ｐｏを検出し、圧力Ｐが上記中間値Ｐo に
ほぼ等しくなるたびに、送信回路２と送受切替器６とを
起動することにより、図中○印で示す上流側から下流側
への伝播による測定と、●印で示す下流側から上流側へ
の伝播による流速の測定を交互に行わせる。ＣＰＵ１
は、上述したように、下流側と上流側へのトーン・バー
スト信号の伝播時間の差から排気ガスの流速Ｖを算定
し、この流速Ｖから流量Ｑを算定する。The CPU 1 detects an intermediate value Po between the maximum value Pmax and the minimum value Pmin of the exhaust gas pressure P detected by the pressure sensor 8, and each time the pressure P becomes substantially equal to the intermediate value Po. By activating the transmission circuit 2 and the transmission / reception switch 6, the measurement by propagation from the upstream side to the downstream side indicated by a circle and the measurement of the flow velocity by the propagation from the downstream side to the upstream side indicated by a circle Are performed alternately. CPU1
Calculates the flow velocity V of the exhaust gas from the difference between the propagation times of the tone burst signal to the downstream side and the upstream side as described above, and calculates the flow rate Q from the flow velocity V.
【００２５】○印と●印とによって示す各測定点では、
排気ガスの脈動の状態がほぼ同一であるため、流速Ｖも
ほぼ同一であり、これらほぼ同一の流速について下流方
向と上流方向への伝播速度の差が検出される。圧力がＰ
o の時点の流速をＶo とし、送受波器３と４の間隔を
Ｌ、送受波器３と４を結ぶ直線（超音波の伝播経路）と
排気管の管軸（排気ガスの流れの方向）とがなす角度を
θ、下流方向と上流方向への伝播所要時間をそれぞれｔ
ｄ、ｔｕ、超音波の伝播速度をｃとおくと、 ｔd ＝Ｌ／（ｃ＋Ｖo cosθ） ・・・(1) ｔu ＝Ｌ／（ｃ−Ｖo cosθ） ・・・(2) At each measurement point indicated by a circle and a circle,
Since the pulsation state of the exhaust gas is substantially the same, the flow velocity V is also substantially the same, and the difference between the propagation velocity in the downstream direction and the propagation velocity in the upstream direction is detected for the substantially same flow velocity. Pressure is P
The flow velocity at time o is Vo, the distance between the transducers 3 and 4 is L, the straight line connecting the transducers 3 and 4 (the ultrasonic wave propagation path) and the pipe axis of the exhaust pipe (the direction of the exhaust gas flow). And the time required for propagation in the downstream and upstream directions is t, respectively.
Assuming that d, tu, and the propagation speed of the ultrasonic wave are c, td = L / (c + Vocosθ) (1) tu = L / (c−Vocosθ) (2)
【００２６】(1) 式と(2) 式とから、次式を得る。 Δｔo ＝ｔｕ−ｔｄ ＝２Ｖo Ｌ cosθ／（ｃ2 −Ｖｏ2 cos2θ） ・・・ (3) 通常、ｃ2 ≪Ｖｏ2 cos2θであるから、(3) 式から、 Ｖo ≒（ｃ2 ／２Ｌ cosθ）Δｔo ・・・ (4)From the equations (1) and (2), the following equation is obtained. Δto = tu−td = 2Vo L cos θ / (c 2 −Vo 2 cos 2 θ) (3) Usually, c 2 ≪Vo 2 cos 2 θ, so from equation (3), Vo ≒ (c 2 / 2L cosθ) Δto (4)
【００２７】各測定の時点の流速がほぼ一定の値Ｖｏと
なるため、(4) 式によって算定される流速は誤差が少な
く、かつ少数回の時間平均化により、高精度の計測値が
得られる。Since the flow velocity at the time of each measurement has a substantially constant value Vo, the flow velocity calculated by the equation (4) has a small error, and a highly accurate measurement value can be obtained by averaging a small number of times. .
【００２８】図３は、ＣＰＵ１による他の測定時点の設
定方法を示している。排気ガスの圧力Ｐ0 、Ｐ1 、Ｐ2
の三点について、○印と●印で示すように、伝播方向を
交番させながら測定が反復され、同一の圧力の測定点ど
うしで、伝播所要時間の差の算定とその時間的平均化が
行われる。Ｐ0 ，Ｐ1 ，Ｐ2 の三点における流速ＶをＶ
0 ，Ｖ1 ，Ｖ2 とおき、下流方向と上流方向への伝播所
要時間の差をそれぞれΔｔ0 ，Δｔ1 ，Δｔ2 とおく
と、各時点の流速は次式で与えられる。 Ｖ1 ≒（ｃ2 ／２Ｌ cosθ）Δｔ1 ・・・ (5) Ｖ0 ≒（ｃ2 ／２Ｌ cosθ）Δｔ0 ・・・ (6) Ｖ2 ≒（ｃ2 ／２Ｌ cosθ）Δｔ2 ・・・ (7)FIG. 3 shows a method of setting another measurement time by the CPU 1. Exhaust gas pressure P 0 , P 1 , P 2
The measurement is repeated for the three points as shown by the circles and circles while alternating the propagation direction, and the difference in the time required for propagation is calculated between the measurement points with the same pressure and the time is averaged. Will be The flow velocity V at three points P 0 , P 1 , and P 2 is represented by V
0 , V 1 , and V 2 , and the differences between the required propagation times in the downstream and upstream directions are Δt 0 , Δt 1 , and Δt 2 , respectively. V 1 ≒ (c 2 / 2L cos θ) Δt 1 (5) V 0 ≒ (c 2 / 2L cos θ) Δt 0 (6) V 2 ≒ (c 2 / 2L cos θ) Δt 2.・ (7)
【００２９】三点における流速Ｖ0 ，Ｖ1 ，Ｖ2 のそれ
ぞれについて、複数の測定値を検出して平均値を算定
し、各平均値について更に平均値を算定することによ
り、流速の時間平均値が算定される。このように、異な
る圧力の複数の時点について流速を検出することによ
り、脈動の周期が短くなって圧力と流速との間に位相の
ずれが生ずる場合でも、流速についての正確な平均値の
算定が可能となる。For each of the flow velocities V 0 , V 1 , and V 2 at the three points, a plurality of measured values are detected and an average value is calculated, and the average value is further calculated for each of the average values. The value is calculated. As described above, by detecting the flow velocity at a plurality of points of time at different pressures, even if the pulsation cycle is shortened and a phase shift occurs between the pressure and the flow velocity, an accurate average value of the flow velocity can be calculated. It becomes possible.
【００３０】以上、脈動の振幅の時間変化の様子を検出
し、超音波信号の送受波のタイミングを設定する方法を
説明した。しかしながら、スペクトルアナライザなどの
適宜な周波数検出回路を使用して脈動の周波数（周期）
を検出し、この脈動の周期、あるいは、この脈動の周期
の整数倍の周期で送受波を反復させる構成とすれば、脈
動の振幅の時間変化を意識することなく、脈動がほぼ同
一の状態の時点での超音波信号の送受波を反復すること
ができる。脈動の周期の整数分の１倍の周期で超音波信
号を送受波する場合も同様である。As described above, the method of detecting the temporal change of the amplitude of the pulsation and setting the transmission / reception timing of the ultrasonic signal has been described. However, the frequency (period) of the pulsation using an appropriate frequency detection circuit such as a spectrum analyzer
Is detected, and the transmission and reception are repeated at a period of this pulsation or a period of an integral multiple of the period of this pulsation. The transmission and reception of the ultrasonic signal at the time can be repeated. The same applies to the case where an ultrasonic signal is transmitted and received at a cycle that is a fraction of the cycle of the pulsation.
【００３１】図４は、図１の実施例の超音波流量計によ
る他の流量測定方法を説明するための概念図である。こ
の測定方法によれば、脈動の周期とは無関係の一定の周
期τで超音波信号の送受波が行われると共に、送受波が
行われた各時点の圧力Ｐ1 ，Ｐ2 ，Ｐ3 ，Ｐ4 ・・・が
計測される。そして、中間の値Ｐ0 を用いて、各送受波
時点の流速Ｖ1 ，Ｖ2 ，Ｖ3 ，Ｖ4 ・・・に対する補正
係数として、α1 （＝Ｐ1/Ｐ0 ) , α2(＝Ｐ2/Ｐ0)，α
3(＝Ｐ3/Ｐ0)，α4(＝Ｐ4/Ｐ0) ・・・が算定される。FIG. 4 is a conceptual diagram for explaining another flow measuring method using the ultrasonic flow meter of the embodiment of FIG. According to this measuring method, the transmission and reception of the ultrasonic signal are performed at a constant period τ independent of the period of the pulsation, and the pressures P 1 , P 2 , P 3 , and P at each time when the transmission and reception are performed. 4 ... is measured. Then, using the intermediate value P 0 , α 1 (= P 1 / P 0 ), α 2 (, as correction coefficients for the flow velocities V 1 , V 2 , V 3 , V 4 ... = P 2 / P 0 ), α
3 (= P 3 / P 0 ), α 4 (= P 4 / P 0 )...
【００３２】そして、超音波信号の各送受波時点の流速
Ｖ1 ，Ｖ2 ，Ｖ3 ，Ｖ4 ・・・は、上記各送受波時点の
補正係数を用いて、Ｖ1 ＝α1 Ｖ0 ，Ｖ2 ＝α2 Ｖ0 ，
Ｖ3＝α3 Ｖ0 ，Ｖ4 ＝α4 Ｖ0 ・・・で与えられる。
例えば、図４中の送受波の時点１と２については、(1)
式と(2) 式とから、伝播所要時間は、次式に基づいて算
定される。 ｔd 1 ＝Ｌ／（ｃ−α1 Ｖ0 cosθ） ・・・(8) ｔu 2 ＝Ｌ／（ｃ＋α2 Ｖ0 cosθ） ・・・(9) Then, the flow velocities V 1 , V 2 , V 3 , V 4 ... Of the ultrasonic signals at the time of transmission / reception are calculated by using the correction coefficients at the time of transmission / reception, V 1 = α 1 V 0. , V 2 = α 2 V 0 ,
V 3 = α 3 V 0 , V 4 = α 4 V 0 .
For example, regarding the time points 1 and 2 of the transmission and reception in FIG. 4, (1)
From equation (2) and equation (2), the required propagation time is calculated based on the following equation. td 1 = L / (c−α 1 V 0 cos θ) (8) tu 2 = L / (c + α 2 V 0 cos θ) (9)
【００３３】上述のように、超音波信号の各送受波の時
点に検出した圧力値によって流速の補正を行う方法にお
いては、超音波信号の各送受波の周期を必ずしも一定と
する必要がなく、必要であれば、この送受波のタイミン
グを不定期にすることもできる。As described above, in the method of correcting the flow velocity based on the pressure value detected at the time of each transmission and reception of the ultrasonic signal, the period of each transmission and reception of the ultrasonic signal does not necessarily have to be constant. If necessary, the timing of the transmission and reception can be irregular.
【００３４】また、上述の手法によって算定した流速を
メモリに保存しておき、この保存した過去の流速の変化
のデータを、超音波信号の送受波の時点の設定や補正係
数の算定に利用するというフィードバック系を構成する
こともできる。Further, the flow velocity calculated by the above-described method is stored in a memory, and the stored data of the change of the flow velocity in the past is used for setting the transmission / reception time of the ultrasonic signal and calculating the correction coefficient. A feedback system can also be configured.
【００３５】また、排気ガスの圧力や速度の脈動が基本
波のみから成る単純な場合を例示した。しかしながら、
一般的には、脈動は多くの高調波を含む複雑な波形とな
る場合もある。このような場合には、ハードウエアやソ
フトウエアによる濾波を行ったり、あるいは、スペクト
ラムアナライザを利用することなどによって基本波を抽
出し、この基本波に基づいて上述した処理を行えばよ
い。Further, the simple case in which the pulsation of the pressure and the speed of the exhaust gas consists of only the fundamental wave has been described. However,
In general, the pulsation may be a complex waveform including many harmonics. In such a case, filtering may be performed by hardware or software, or a fundamental wave may be extracted by using a spectrum analyzer, and the above-described processing may be performed based on the fundamental wave.
【００３６】更に、送受波器の間に超音波信号を伝播さ
せ、その伝播所要時間から流速を測定する場合を例にと
って本発明の流量計を説明した。しかしながら、流体中
に超音波信号を送出し、流体からの反射波を受信し、そ
の周波数のドップラーシフト量から流体の流速を計測す
るドップラー型の流量計に対しても本発明を適用できる
ことは明らかである。Further, the flow meter according to the present invention has been described by taking as an example a case where an ultrasonic signal is propagated between a transducer and a flow velocity is measured from the required propagation time. However, it is clear that the present invention can be applied to a Doppler type flow meter that transmits an ultrasonic signal into a fluid, receives a reflected wave from the fluid, and measures the flow velocity of the fluid from the Doppler shift amount of the frequency. It is.
【００３７】[0037]
【発明の効果】以上詳細に説明したように、本発明の超
音波流量計は、流量計測対象の流体の脈動の状態を検出
し、この検出した脈動の状態がほぼ同一の時点などにお
いてこの流体の流速を反復して検出する構成であるか
ら、測定所要時間が短縮され、自動車の発進や急停止な
どに伴って発生する流量の急激な変動に追随可能な、高
性能の超音波流量計が提供される。As described above in detail, the ultrasonic flow meter of the present invention detects the pulsation state of the fluid to be measured, and detects the pulsation state when the detected pulsation state is substantially the same. High-performance ultrasonic flow meter that can detect the flow velocity repeatedly, shortens the time required for measurement, and can follow sudden changes in the flow rate that occurs when the vehicle starts or stops suddenly. Provided.
【図１】本発明の一実施例の超音波流量計の構成を示す
機能ブロック図である。FIG. 1 is a functional block diagram showing a configuration of an ultrasonic flowmeter according to one embodiment of the present invention.
【図２】上記実施例の超音波流量計の動作の一例を説明
するための波形図である。FIG. 2 is a waveform chart for explaining an example of the operation of the ultrasonic flowmeter of the embodiment.
【図３】上記実施例の超音波流量計の動作の他の一例を
説明するための波形図である。FIG. 3 is a waveform chart for explaining another example of the operation of the ultrasonic flowmeter of the embodiment.
【図４】上記実施例の超音波流量計の動作の更に他の一
例を説明するための波形図である。FIG. 4 is a waveform chart for explaining still another example of the operation of the ultrasonic flowmeter of the embodiment.
【図５】従来の超音波流量計の動作の一例と問題点を説
明するための波形図である。FIG. 5 is a waveform chart for explaining an example of the operation of the conventional ultrasonic flowmeter and a problem.
1 ＣＰＵ 2 送信回路 3,4 送受波器 5 受信回路 6 送受切替器 8 圧力センサ 9 Ａ／Ｄ変換器 1 CPU 2 Transmitter circuit 3,4 Transducer 5 Receiver circuit 6 Transmitter / receiver switch 8 Pressure sensor 9 A / D converter
Claims (10)
この流体の流速に関する情報を含む超音波を受信してこ
の流体の流速を検出する超音波流量計において、 前記流量計測対象の流体の脈動の状態を検出する脈動状
態検出手段と、 前記検出した脈動の状態がほぼ同一の時点において前記
流体の流速を反復して検出する流速検出手段とを備えた
ことを特徴とする超音波流量計。An ultrasonic wave is radiated into a fluid to be measured for flow rate,
An ultrasonic flowmeter that receives an ultrasonic wave including information on the flow velocity of the fluid and detects the flow velocity of the fluid; a pulsation state detection unit that detects a pulsation state of the fluid whose flow rate is to be measured; and the detected pulsation. And a flow rate detecting means for repeatedly detecting the flow rate of the fluid at substantially the same point in time.
ーク値と最小ピーク値との中間に設定されることを特徴
とする超音波流量計。2. The ultrasonic flowmeter according to claim 1, wherein the time point at which the pulsation states are substantially the same is set at an intermediate point between the maximum peak value and the minimum peak value of the pulsation.
て設定されることを特徴とする超音波流量計。3. The ultrasonic flowmeter according to claim 1, wherein the times when the pulsation states are substantially the same are set for a plurality of states.
この流体の流速に関する情報を含む超音波を受信してこ
の流体の流速を検出する超音波流量計において、 前記流量計測対象の流体の脈動の周期を検出する脈動周
期検出手段と、 前記検出した脈動の周期と適宜な関係を有する周期で前
記流体の流速を反復して検出する流速検出手段とを備え
たことを特徴とする超音波流量計。4. An ultrasonic wave is emitted into a fluid to be measured for flow rate,
An ultrasonic flowmeter that receives an ultrasonic wave including information on the flow velocity of the fluid and detects the flow velocity of the fluid; a pulsation cycle detection unit that detects a pulsation cycle of the fluid to be measured for the flow rate; and the detected pulsation. And a flow rate detecting means for repeatedly detecting the flow rate of the fluid in a cycle having an appropriate relationship with the cycle of the ultrasonic flow meter.
とする超音波流量計。5. The ultrasonic flowmeter according to claim 4, wherein the cycle of the pulsation is detected for a fundamental wave.
分の１倍の関係であることを特徴とする超音波流量計。6. The ultrasonic flowmeter according to claim 4, wherein an appropriate relationship with the pulsation cycle is an integral multiple or a fraction of an integral.
この流体の流速に関する情報を含む超音波を受信してこ
の流体の流速を検出する超音波流量計において、 前記流量計測対象の流体の脈動の状態を検出する脈動状
態検出手段と、 前記流体の流速を一定又は不定の周期で反復して検出す
る流速検出手段と、 この流速検出手段で検出された流速について前記脈動状
態検出手段で検出された脈動の状態を考慮しながら時間
的な平均化処理を行う処理手段とを備えたことを特徴と
する超音波流量計。7. An ultrasonic wave is radiated into a fluid to be measured for flow rate,
An ultrasonic flowmeter that receives an ultrasonic wave including information on the flow velocity of the fluid and detects the flow velocity of the fluid; a pulsation state detection unit that detects a pulsation state of the fluid to be measured for the flow rate; Flow rate detecting means for repeatedly detecting the pulsation state detected by the pulsation state detecting means with respect to the flow rate detected by the flow rate detecting means. An ultrasonic flowmeter, comprising:
な平均化処理は、脈動の振幅に応じて設定した係数を用
いて前記検出された流速を補正することにより行われる
ことを特徴とする超音波流量計。8. The temporal averaging process performed while considering the pulsation state is performed by correcting the detected flow velocity using a coefficient set according to the pulsation amplitude. Ultrasonic flow meter.
とを特徴とする超音波流量計。9. The ultrasonic flowmeter according to claim 1, wherein the pulsation state is detected based on a pressure in a flow path.
特徴とする超音波流量計。10. The ultrasonic flowmeter according to claim 1, wherein the fluid to be measured is an exhaust gas of an automobile.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10231190A JP3121794B2 (en) | 1998-08-03 | 1998-08-03 | Ultrasonic flow meter |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10231190A JP3121794B2 (en) | 1998-08-03 | 1998-08-03 | Ultrasonic flow meter |
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| Publication Number | Publication Date |
|---|---|
| JP2000055709A true JP2000055709A (en) | 2000-02-25 |
| JP3121794B2 JP3121794B2 (en) | 2001-01-09 |
Family
ID=16919753
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|---|---|---|---|
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| Country | Link |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001241984A (en) * | 2000-03-01 | 2001-09-07 | Matsushita Electric Ind Co Ltd | Gas safety device |
-
1998
- 1998-08-03 JP JP10231190A patent/JP3121794B2/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001241984A (en) * | 2000-03-01 | 2001-09-07 | Matsushita Electric Ind Co Ltd | Gas safety device |
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| Publication number | Publication date |
|---|---|
| JP3121794B2 (en) | 2001-01-09 |
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