JP2016099139A - Ultrasonic flowmeter - Google Patents

Ultrasonic flowmeter Download PDF

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JP2016099139A
JP2016099139A JP2014233859A JP2014233859A JP2016099139A JP 2016099139 A JP2016099139 A JP 2016099139A JP 2014233859 A JP2014233859 A JP 2014233859A JP 2014233859 A JP2014233859 A JP 2014233859A JP 2016099139 A JP2016099139 A JP 2016099139A
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ultrasonic
fluid
axis
receiving
upstream
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伊藤 健太郎
Kentaro Ito
健太郎 伊藤
浩之 堀田
Hiroyuki Hotta
浩之 堀田
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愛知時計電機株式会社
Aichi Tokei Denki Co Ltd
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PROBLEM TO BE SOLVED: To provide an ultrasonic flowmeter which is hardly affected by acoustic noise.SOLUTION: An ultrasonic flowmeter 10 comprises a pair of ultrasonic elements 20, 20 which is arranged on an element facing axis L0 obliquely intersecting the axial direction of a measurement pipe 11 in which fluid passes in one direction. The propagation central axis of each ultrasonic element 20 overlaps the element facing axis L0 when the flow speed becomes the maximum value by inclining central axes L1, L1 of ultrasonic transmission/reception surfaces 22, 22 of the ultrasonic elements 20, 20 to the upstream side of the fluid with respect to the element facing axis L0.SELECTED DRAWING: Figure 1

Description

本発明は、超音波素子を利用して流体の流量を検出する超音波流量計に関する。   The present invention relates to an ultrasonic flowmeter that detects the flow rate of a fluid using an ultrasonic element.
従来、この種の超音波流量計として、計測管の軸方向に対して斜めに交差する方向に1対の超音波素子を配置して備え、一方から他方の超音波素子までの超音波の伝播時間と、他方から一方の超音波素子までの超音波の伝播時間との差分に基づいて流体の流量を検出するものが知られている(例えば、特許文献1参照)。   Conventionally, as this type of ultrasonic flowmeter, a pair of ultrasonic elements are arranged in a direction obliquely intersecting with the axial direction of the measurement tube, and the propagation of ultrasonic waves from one to the other ultrasonic element is provided. One that detects the flow rate of a fluid based on the difference between the time and the propagation time of an ultrasonic wave from the other to one ultrasonic element is known (for example, see Patent Document 1).
特開2008−111690号公報(図8,図9)JP 2008-111690A (FIGS. 8 and 9)
しかしながら、上記した従来の超音波流量計では、音響ノイズ源が近くにあると流量が大きくなるに従って計測エラーの頻度が高くなることが問題になっていた。即ち、流量が大きくなるに従って、超音波素子が受信する正規の超音波とそれ以外の音響ノイズとの比率であるS/N比が悪化するという問題があった。なお、音響ノイズとは、例えば、超音波流量計の近傍に配置されているガバナやバルブ等のノイズ源が発生するノイズのうち超音波流量計が計測で用いる超音波の周波数成分の近傍の周波数のノイズである。   However, the conventional ultrasonic flowmeter described above has a problem that the frequency of measurement errors increases as the flow rate increases when an acoustic noise source is nearby. That is, as the flow rate increases, there is a problem that the S / N ratio, which is the ratio between normal ultrasonic waves received by the ultrasonic element and other acoustic noise, deteriorates. The acoustic noise is, for example, a frequency in the vicinity of the frequency component of the ultrasonic wave used by the ultrasonic flow meter in the noise generated by a noise source such as a governor or a valve disposed in the vicinity of the ultrasonic flow meter. Noise.
本発明は、上記事情に鑑みてなされたもので、音響ノイズの影響を受け難い流量計測が可能な超音波流量計の提供を目的とする。   The present invention has been made in view of the above circumstances, and an object thereof is to provide an ultrasonic flowmeter capable of measuring a flow rate that is hardly affected by acoustic noise.
本願発明者は、流体が流れる方向に対して斜めに交差する方向に1対の超音波素子を対向配置して双方間で超音波を送受波する場合、流体の流速が0であるときには、超音波素子の超音波送受波面から送波される超音波の伝播経路のうち超音波の強度が最も大きくなる部分の中心軸(以下、これを、適宜、「伝播中心軸」という)と、超音波送受波面の中心を貫通する中心軸(以下、これを、適宜、「送波面中心軸」)とが一致するが、流体の流速が大きくなるに従って送波面中心軸に対する下流側への伝播中心軸のズレ角δが、後に詳説する下記[数3」の関係性に従って徐々に大きくなっていくことを見いだした。   The inventor of the present application transmits and receives an ultrasonic wave between a pair of ultrasonic elements in a direction obliquely intersecting with the direction in which the fluid flows, and when the flow velocity of the fluid is 0, The central axis of the ultrasonic wave propagation path transmitted from the ultrasonic wave transmitting / receiving surface of the ultrasonic wave element (hereinafter referred to as “propagation central axis” as appropriate) and the ultrasonic wave The central axis that penetrates the center of the transmission / reception surface (hereinafter referred to as “transmission surface central axis” as appropriate) coincides with the center axis of propagation downstream to the transmission surface central axis as the fluid flow velocity increases. It has been found that the deviation angle δ gradually increases according to the relationship of the following [Equation 3] described in detail later.
但し、上記式において「v」は流体の流速、「c」は、流体の平均温度でその流体を伝番する超音波の音速、「ψ」は、流体が内側を流れる計測管の軸方向に対する上流側の超音波素子の送波面中心軸の鋭角の傾斜角である。   However, in the above formula, “v” is the flow velocity of the fluid, “c” is the velocity of the ultrasonic wave transmitted through the fluid at the average temperature of the fluid, and “ψ” is the axial direction of the measuring tube through which the fluid flows. This is an acute inclination angle of the central axis of the transmission surface of the upstream ultrasonic element.
また、流体の流速が大きくなるに従って伝播していく超音波の振幅は小さくなっていく。そして、従来の超音波流量計では、1対の超音波素子の送波面中心軸同士を一致させた構造になっていたので、流速の増加に伴う超音波の振幅の減衰と、送波面中心軸に対する超音波の伝播中心軸のズレ量増加との両方が共に各超音波素子による超音波の受波強度を低下させるように作用し、その結果、流体の流速が増加すると超音波素子の受信波におけるS/N比が著しく低下していた。このことに鑑み、本願発明者は、「両前記超音波素子の送波面中心軸を、前記素子対向軸に対して流体の上流側に予め傾けておいて、超音波素子の受信波におけるS/N比の低下を抑える」という見知に至った。   Moreover, the amplitude of the ultrasonic wave propagating as the fluid flow velocity increases decreases. In the conventional ultrasonic flowmeter, the transmission surface central axes of a pair of ultrasonic elements are made to coincide with each other. Both the increase in the amount of deviation of the center axis of the ultrasonic wave propagation with respect to the wave acts to reduce the received wave intensity of the ultrasonic wave by each ultrasonic element, and as a result, when the flow velocity of the fluid increases, the received wave of the ultrasonic wave element The S / N ratio was significantly reduced. In view of this, the inventor of the present application stated that “the transmission surface central axis of both the ultrasonic elements is tilted in advance to the upstream side of the fluid with respect to the element facing axis, and the S / It came to the knowledge that "the decrease in the N ratio is suppressed."
即ち、上記目的を達成するためになされた請求項1の発明は、流体が内側を一方向に通過する計測管の軸方向に対して斜めに交差する素子対向軸上に1対の超音波素子を配置し、一方から他方の前記超音波素子までの超音波の伝播時間と、他方から一方の前記超音波素子までの超音波の伝播時間との差分に基づいて前記流体の流量を検出する超音波流量計において、両前記超音波素子の超音波送受波面の中心軸が、前記素子対向軸に対して流体の上流側に傾けられ、前記計測管の軸方向に対する素子対向軸上の鋭角側の傾斜角をθとし、超音波の音速をcとし、前記流体の流速の最大値をvとすると、上流側の前記超音波素子の前記超音波送受波面の中心軸が前記素子対向軸に対して上流側にずれるズレ角φ1と、下流側の前記超音波素子の前記超音波送受波面の中心軸が前記素子対向軸に対して上流側にずれるズレ角φ2とは、
になっている超音波流量計である。
That is, in order to achieve the above-mentioned object, the invention according to claim 1 is characterized in that a pair of ultrasonic elements on an element opposing axis that obliquely intersects with the axial direction of a measuring tube through which fluid passes in one direction. And detecting the flow rate of the fluid based on the difference between the propagation time of the ultrasonic wave from one to the other ultrasonic element and the propagation time of the ultrasonic wave from the other to the one ultrasonic element. In the sonic flow meter, the central axis of the ultrasonic wave transmitting / receiving surface of both of the ultrasonic elements is inclined to the upstream side of the fluid with respect to the element facing axis, and is on the acute angle side on the element facing axis with respect to the axial direction of the measuring tube. When the inclination angle is θ, the sound velocity of the ultrasonic wave is c, and the maximum value of the flow velocity of the fluid is v, the central axis of the ultrasonic wave transmitting / receiving surface of the ultrasonic element on the upstream side is relative to the element facing axis. Deviation angle φ1 shifted to the upstream side and in front of the ultrasonic element on the downstream side The deviation angle φ2 at which the central axis of the ultrasonic wave transmitting / receiving surface is shifted to the upstream side with respect to the element facing axis is:
This is an ultrasonic flowmeter.
本発明に構成では、流体の流速増加に伴い送波面中心軸に対する超音波の伝播中心軸のズレ量が減少していき、超音波の強度を高めるように作用するので、流体の流速増加に伴い超音波の振幅が減衰しても、従来に比べて超音波の受波強度は低下せず、S/N比が改善されて、音響ノイズの影響を受け難くい流量計測が可能になる。   In the configuration of the present invention, the amount of deviation of the ultrasonic propagation center axis with respect to the transmission surface central axis decreases as the fluid flow velocity increases, and the ultrasonic wave acts to increase the intensity of the ultrasonic wave. Even if the amplitude of the ultrasonic wave is attenuated, the received wave intensity of the ultrasonic wave is not lowered as compared with the conventional case, the S / N ratio is improved, and the flow rate measurement that is hardly affected by the acoustic noise can be performed.
請求項2の発明は、流体が内側を一方向に通過する計測管の軸方向に対して斜めに交差する素子対向軸上に1対の超音波素子を配置し、一方から他方の前記超音波素子までの超音波の伝播時間と、他方から一方の前記超音波素子までの超音波の伝播時間との差分に基づいて前記流体の流量を検出する超音波流量計において、両前記超音波素子の超音波送受波面の中心軸が、前記素子対向軸に対して流体の上流側に傾けられ、前記計測管の軸方向に対する素子対向軸上の鋭角側の傾斜角をθとし、超音波の音速をcとし、前記流体の流速の中央値をvとすると、上流側の前記超音波素子の前記超音波送受波面の中心軸が前記素子対向軸に対して上流側にずれるズレ角φ1と、下流側の前記超音波素子の前記超音波送受波面の中心軸が前記素子対向軸に対して上流側にずれるズレ角φ2とは、
になっている超音波流量計である。
In the invention of claim 2, a pair of ultrasonic elements are arranged on an element facing axis that obliquely intersects the axial direction of the measuring tube through which the fluid passes in one direction, and the ultrasonic waves from one to the other are arranged. In the ultrasonic flowmeter that detects the flow rate of the fluid based on the difference between the propagation time of the ultrasonic wave to the element and the propagation time of the ultrasonic wave from the other to the one ultrasonic element, both of the ultrasonic elements The central axis of the ultrasonic wave transmitting / receiving surface is tilted upstream of the fluid with respect to the element facing axis, and the acute angle on the element facing axis with respect to the axial direction of the measuring tube is θ, and the ultrasonic sound velocity is where c is the median value of the flow velocity of the fluid, and v is the deviation angle φ1 at which the central axis of the ultrasonic wave transmitting / receiving surface of the ultrasonic element on the upstream side is shifted upstream with respect to the element facing axis; The center axis of the ultrasonic wave transmitting / receiving surface of the ultrasonic element is opposed to the element The deviation angle φ2 that shifts upstream from the axis is
This is an ultrasonic flowmeter.
本願発明の構成によれば、流体の流速が中央値になったときに送波面中心軸に対する超音波の伝播中心軸のズレ量が0になり、流速が中央値近傍で変化する状況下で、積算流量を正確に計測することができる。   According to the configuration of the present invention, when the flow velocity of the fluid reaches the median value, the amount of deviation of the propagation center axis of the ultrasonic wave with respect to the transmission surface central axis becomes 0, and the flow velocity changes near the median value, Accumulated flow rate can be measured accurately.
請求項3の発明は、流体が内側を一方向に通過する計測管の軸方向に対して斜めに交差する素子対向軸上に1対の超音波素子を配置し、一方から他方の前記超音波素子までの超音波の伝播時間と、他方から一方の前記超音波素子までの超音波の伝播時間との差分に基づいて前記流体の流量を検出する超音波流量計において、両前記超音波素子の超音波送受波面の中心軸が、前記素子対向軸に対して流体の上流側に傾けられ、前記計測管の軸方向に対する素子対向軸上の鋭角側の傾斜角をθとし、超音波の音速をcとし、前記流体の流速の平均値をvとすると、上流側の前記超音波素子の前記超音波送受波面の中心軸が前記素子対向軸に対して上流側にずれるズレ角φ1と、下流側の前記超音波素子の前記超音波送受波面の中心軸が前記素子対向軸に対して上流側にずれるズレ角φ2とは、
になっている超音波流量計である。
According to the invention of claim 3, a pair of ultrasonic elements is arranged on an element facing axis that obliquely intersects the axial direction of the measuring tube through which the fluid passes in one direction, and the ultrasonic waves from one to the other are arranged. In the ultrasonic flowmeter that detects the flow rate of the fluid based on the difference between the propagation time of the ultrasonic wave to the element and the propagation time of the ultrasonic wave from the other to the one ultrasonic element, both of the ultrasonic elements The central axis of the ultrasonic wave transmitting / receiving surface is tilted upstream of the fluid with respect to the element facing axis, and the acute angle on the element facing axis with respect to the axial direction of the measuring tube is θ, and the ultrasonic sound velocity is where c is the average value of the flow velocity of the fluid and v is the deviation angle φ1 at which the central axis of the ultrasonic wave transmitting / receiving surface of the ultrasonic element on the upstream side is shifted upstream with respect to the element facing axis; The center axis of the ultrasonic wave transmitting / receiving surface of the ultrasonic element is opposed to the element The deviation angle φ2 that shifts upstream from the axis is
This is an ultrasonic flowmeter.
本願発明の構成によれば、流体の流速が平均値になったときに送波面中心軸に対する超音波の伝播中心軸のズレ量が0になり、流速が平均値近傍で変化する状況下で、積算流量を正確に計測することができる。   According to the configuration of the present invention, when the flow velocity of the fluid becomes an average value, the deviation amount of the ultrasonic propagation center axis with respect to the transmission surface central axis becomes 0, and the flow velocity changes in the vicinity of the average value, Accumulated flow rate can be measured accurately.
請求項4の発明は、前記超音波の音速cは、前記計測管の内側を通過し得る流体の種類及び温度の相違によって変わり得る範囲の中央値である請求項1乃至3の何れか1の請求項に記載の超音波流量計である。   According to a fourth aspect of the present invention, the ultrasonic sound velocity c is a median value in a range that can vary depending on the type of fluid that can pass through the inside of the measuring tube and the temperature. The ultrasonic flowmeter according to claim.
本願発明の構成によれば、超音波流量計が複数種類の流体に使用されても、従来より音響ノイズの影響を受け難くい流量計測が可能になる。   According to the configuration of the present invention, even when the ultrasonic flowmeter is used for a plurality of types of fluids, it is possible to measure a flow rate that is less susceptible to acoustic noise than in the past.
請求項5の発明は、前記計測管の内側面には、前記素子対向軸上に1対の素子受容凹部が設けられて、それら素子受容凹部に各前記超音波素子の全体が受容され、各前記素子受容凹部の内面のうち前記超音波送受波面より上流側部分と下流側部分との間で、前記超音波送受波面の中心軸に対する傾斜角又は直線距離を異ならせた請求項1乃至4の何れか1の請求項に記載の超音波流量計である。   According to a fifth aspect of the present invention, a pair of element receiving recesses are provided on the element facing axis on the inner surface of the measuring tube, and the entire ultrasonic element is received in the element receiving recesses, The inclination angle or linear distance with respect to the central axis of the ultrasonic wave transmitting / receiving surface is made different between an upstream portion and a downstream portion of the inner surface of the element receiving recess. The ultrasonic flowmeter according to any one of the claims.
この構成によれば、一方の超音波素子が送波した超音波が他方の超音波素子を受容した素子受容凹部の内面で反射して音響ノイズとなり、他方の超音波素子に受信され得る。しかしながら、本願発明では、各素子受容凹部の内面のうち超音波送受波面より上流側部分と下流側部分との間で超音波送受波面の中心軸に対する傾斜角又は距離を異ならせたので、それら上流側部分と下流側部分とで超音波が反射して生じる音響ノイズが超音波素子の超音波送受波面に到達する各時間が相違する。これにより、超音波の音響ノイズの強度が抑えられてS/N比が大きくなり、このことによっても、音響ノイズの影響を受け難くい流量計測が可能になる。   According to this configuration, the ultrasonic wave transmitted by one ultrasonic element is reflected by the inner surface of the element receiving recess that has received the other ultrasonic element, becomes acoustic noise, and can be received by the other ultrasonic element. However, in the present invention, since the inclination angle or distance with respect to the central axis of the ultrasonic wave transmitting / receiving surface is made different between the upstream portion and the downstream portion of the inner surface of each element receiving recess, Each time that the acoustic noise generated by the reflection of the ultrasonic waves at the side portion and the downstream portion reaches the ultrasonic wave transmitting / receiving surface of the ultrasonic element is different. As a result, the intensity of ultrasonic acoustic noise is suppressed and the S / N ratio is increased. This also makes it possible to measure a flow rate that is not easily affected by acoustic noise.
なお、上記した流体の流速の最小値及び最大値、中央値、平均値、流体の温度は、統計的又は仕様から求めればよい。   The minimum value and maximum value, median value, average value, and fluid temperature of the fluid flow velocity described above may be obtained from statistics or specifications.
本発明の一実施形態に係る超音波流量計の側断面図1 is a side sectional view of an ultrasonic flowmeter according to an embodiment of the present invention. 超音波流量計の側断面図Side view of ultrasonic flowmeter 超音波流量計の側断面図Side view of ultrasonic flowmeter
以下、本発明の一実施形態を図1〜図3に基づいて説明する。図1に示すように、本実施形態の超音波流量計10は、直線状に延びた計測管11の内側に1対の超音波素子20,20を備えている。計測管11は、例えば、ガス配管の途中に取り付けられ、内側の計測流路12を一方向(図1の左から右に向かう方向)に流体(例えば、商用ガス)が流れる。なお、本実施形態では、計測流路12の断面が例えば円形になっているが、計測流路12は、断面長方形、長円形又は楕円形であってもよい。   Hereinafter, an embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the ultrasonic flowmeter 10 of the present embodiment includes a pair of ultrasonic elements 20 and 20 inside a measurement tube 11 extending linearly. The measurement pipe 11 is attached, for example, in the middle of a gas pipe, and a fluid (for example, commercial gas) flows in one direction (a direction from the left to the right in FIG. 1) through the inner measurement flow path 12. In the present embodiment, the measurement channel 12 has a circular cross section, for example. However, the measurement channel 12 may be rectangular, oval, or elliptical in cross section.
計測管11の内面には、その計測管11の軸方向と斜めに交差する直線上に1対の素子受容凹部13,13が陥没形成され、それら素子受容凹部13,13に1対の超音波素子20,20が受容されている。超音波素子20は、偏平円柱状のベース部21の一端に、ドーム状に膨出した形状の超音波送受波面22を有し、この超音波送受波面22にて超音波を送受波する。また、両超音波素子20,20は、計測流路12側にはみ出すことなく素子受容凹部13,13に受容されて、両超音波素子20,20の超音波送受波面22,22同士が対向している。そして、公知な超音波流量計と同様に、一方の超音波素子20から他方の超音波素子20までの超音波の伝播時間と、他方の超音波素子20から一方の超音波素子20までの超音波の伝播時間との差分に基づいて計測管11を通過する流体の流速を計測し、その流速に計測管11の流体通過面積を乗じて流体の流量を検出するようになっている。   On the inner surface of the measuring tube 11, a pair of element receiving recesses 13, 13 are formed in a recess on a straight line that obliquely intersects the axial direction of the measuring tube 11, and a pair of ultrasonic waves is formed in the element receiving recesses 13, 13. Elements 20, 20 are received. The ultrasonic element 20 has an ultrasonic transmission / reception surface 22 having a dome-like shape at one end of a flat cylindrical base portion 21, and transmits and receives ultrasonic waves on the ultrasonic transmission / reception surface 22. Further, the ultrasonic elements 20 and 20 are received by the element receiving recesses 13 and 13 without protruding to the measurement flow path 12 side, and the ultrasonic wave transmitting and receiving surfaces 22 and 22 of the ultrasonic elements 20 and 20 face each other. ing. Then, similarly to a known ultrasonic flow meter, the propagation time of the ultrasonic wave from one ultrasonic element 20 to the other ultrasonic element 20 and the ultrasonic wave from the other ultrasonic element 20 to one ultrasonic element 20 are the same. The flow rate of the fluid passing through the measurement tube 11 is measured based on the difference from the propagation time of the sound wave, and the flow rate of the fluid is detected by multiplying the flow rate by the fluid passage area of the measurement tube 11.
図2に示すように、各素子受容凹部13の内面は、それぞれ受容した超音波素子20の超音波送受波面22より上流側部分13Aと下流側部分13Bとが非対称な形状になっている。具体的には、一般的な超音波流量計における素子受容凹部の内面は、超音波送受波面22と同心の円筒面になっているが、本実施形態の素子受容凹部13の内面は、超音波送受波面22より上流側部分13Aと下流側部分13Bとが超音波送受波面22の中心軸(図2のL1参照)に対する傾斜角も距離も異なっている。   As shown in FIG. 2, the inner surface of each element receiving recess 13 has an asymmetric shape between the upstream portion 13 </ b> A and the downstream portion 13 </ b> B from the ultrasonic transmission / reception surface 22 of the received ultrasonic element 20. Specifically, the inner surface of the element receiving recess in a general ultrasonic flowmeter is a cylindrical surface concentric with the ultrasonic wave transmitting / receiving surface 22, but the inner surface of the element receiving recess 13 of the present embodiment is ultrasonic. The upstream portion 13A and the downstream portion 13B from the transmission / reception surface 22 are different in inclination angle and distance from the central axis (see L1 in FIG. 2) of the ultrasonic transmission / reception surface 22.
超音波素子20は、公知な超音波流量計にも使用されている超音波素子と同様に、高い指向性を有する超音波を送波する。具体的には、流体の流速が「0」の状態では、超音波素子20の超音波送受波面22から送波される超音波の伝播経路のうち超音波の強度が最も大きくなる部分の中心軸である伝播中心軸L2は、超音波送受波面22の中心を貫通する中心軸である送波面中心軸L1と一致し、送波面中心軸L1上において超音波の強度が最も高なる。そして、送波面中心軸L1上の超音波の強度を100%とすると、送波面中心軸L1から例えば6度ずれると強度が50%に減衰し、10度ずれると10%にまで減衰するほどの指向性を有する超音波を超音波素子20は送波する。   The ultrasonic element 20 transmits an ultrasonic wave having high directivity, similarly to the ultrasonic element used in a known ultrasonic flowmeter. Specifically, in the state where the flow velocity of the fluid is “0”, the central axis of the portion of the ultrasonic wave propagation path transmitted from the ultrasonic wave transmitting / receiving surface 22 of the ultrasonic element 20 where the ultrasonic wave intensity is the highest. The transmission center axis L2 coincides with the transmission surface center axis L1 that is the center axis passing through the center of the ultrasonic transmission / reception surface 22, and the intensity of the ultrasonic wave is highest on the transmission surface center axis L1. Then, assuming that the intensity of the ultrasonic wave on the transmission surface central axis L1 is 100%, the intensity is attenuated to 50% when deviating from the transmission surface central axis L1, for example, by 6 degrees, and is attenuated to 10% when deviating 10 degrees. The ultrasonic element 20 transmits ultrasonic waves having directivity.
ところで、超音波素子20が送波する超音波の伝播中心軸L2は、伝播中心軸L2と交差する方向に流れる流体の流速によってずれる。具体的には、図3に示すように、計測管11の軸方向に対して送波面中心軸L1が傾斜角ψだけ傾いた上流側の超音波素子20から音速cで送波された超音波は、流体の流速vによって伝播方向の交差する方向に吹き流され、音速cと流速vとの合成した合成音速c1となって伝播される。そして、その合成音速c1は、以下の[数5]の式で表すことができる。   By the way, the propagation center axis L2 of the ultrasonic wave transmitted by the ultrasonic element 20 is shifted by the flow velocity of the fluid flowing in the direction intersecting the propagation center axis L2. Specifically, as shown in FIG. 3, the ultrasonic wave transmitted at the speed of sound c from the upstream ultrasonic element 20 in which the transmission surface center axis L1 is inclined by the inclination angle ψ with respect to the axial direction of the measurement tube 11. Is blown in the direction in which the propagation direction intersects with the flow velocity v of the fluid, and propagates as a synthesized sound velocity c1 obtained by synthesizing the sound velocity c and the flow velocity v. The synthesized sound velocity c1 can be expressed by the following [Equation 5].
ここで、計測管11の軸方向に対する合成音速c1の傾斜角をθとすると、以下の[数6]の式で表すことができる。   Here, when the inclination angle of the synthesized sound velocity c1 with respect to the axial direction of the measuring tube 11 is θ, it can be expressed by the following [Equation 6].
また、上記した[数5],[数6]の式からc1を消去すると、次の[数7]で示したcosψの二次方程式を得る。   Further, when c1 is eliminated from the equations [Equation 5] and [Equation 6] described above, a quadratic equation of cosψ shown by the following [Equation 7] is obtained.
さらに、この二次方程式を解いてψを求めると、次の[数8]となる。
Further, when this quadratic equation is solved to obtain ψ, the following [Equation 8] is obtained.
よって、流速vの増加に伴って送波面中心軸L1の下流側へのズレ角δは、以下の[数3]で示した関係式に従って大きくなることがわかる。   Therefore, it can be seen that as the flow velocity v increases, the deviation angle δ toward the downstream side of the transmission surface central axis L1 increases according to the relational expression shown in the following [Equation 3].
これと同様に、流体が内側を流れる計測管11の軸方向に対する下流側の超音波素子20の送波面中心軸L1の鋭角の傾斜角をψとし、流体の流速をvとし、流体の平均温度でその流体を伝番する超音波の音速をcとすると、流速vの増加に伴って送波面中心軸L1の下流側へのズレ角λは、以下の[数4]で示した関係式に従って大きくなっていく。   Similarly, the acute inclination angle of the transmission surface central axis L1 of the ultrasonic element 20 on the downstream side with respect to the axial direction of the measurement tube 11 through which the fluid flows is ψ, the flow velocity of the fluid is v, and the average temperature of the fluid When the sound velocity of the ultrasonic wave transmitted through the fluid is c, the deviation angle λ toward the downstream side of the transmission surface center axis L1 as the flow velocity v increases is in accordance with the relational expression shown in the following [Equation 4]. It gets bigger.
また、流体の流速が大きくなるに従って伝播していく超音波の振幅は小さくなっていく。これら現象に鑑み、本実施形態の超音波流量計10は、図3に示すように、上流側の超音波素子20が、超音波送受波面22の中心軸L1が素子対向軸L0に対して流体の上流側にずれ角φ1だけずれた状態に配置されると共に、下流側の超音波素子20が、超音波送受波面22の中心軸L1が素子対向軸L0に対して流体の上流側にずれ角φ2だけずれた状態に配置されている。そして、流体の流速が最大値になったときに各超音波素子20の伝播中心軸L2が、1対の超音波素子20,20における両超音波送受波面22,22の中心点P1,P1を結ぶ素子対向軸L0と重なるようになっている。   Moreover, the amplitude of the ultrasonic wave propagating as the fluid flow velocity increases decreases. In view of these phenomena, as shown in FIG. 3, the ultrasonic flowmeter 10 of the present embodiment has an upstream ultrasonic element 20 in which the central axis L1 of the ultrasonic transmission / reception surface 22 is fluid with respect to the element facing axis L0. Of the ultrasonic element 20 on the downstream side is shifted to the upstream side of the fluid with respect to the element facing axis L0. It is arranged in a state shifted by φ2. Then, when the flow velocity of the fluid reaches the maximum value, the propagation center axis L2 of each ultrasonic element 20 has the center points P1 and P1 of the ultrasonic transmission / reception surfaces 22 and 22 in the pair of ultrasonic elements 20 and 20, respectively. It overlaps with the element opposing axis L0 to be connected.
具体的には、上記[数3],[数4]の関係式に鑑み、計測管11の軸方向に対する素子対向軸L0上の鋭角側の傾斜角をθとし、超音波の音速をcとし、流体の流速の最大値をvとすると、上流側の超音波素子20の送波面中心軸L1の素子対向軸L0するズレ角φ1と下流側の超音波素子20の送波面中心軸L1の素子対向軸L0に対するズレ角φ2は、以下の[数1],[数2]で示した大きさになっている。   Specifically, in view of the relational expressions of [Equation 3] and [Equation 4], the inclination angle on the acute angle side on the element facing axis L0 with respect to the axial direction of the measuring tube 11 is θ, and the sound velocity of the ultrasonic wave is c. When the maximum value of the flow velocity of the fluid is v, the deviation angle φ1 of the element opposing axis L0 of the transmission surface central axis L1 of the upstream ultrasonic element 20 and the element of the transmission surface central axis L1 of the downstream ultrasonic element 20 The deviation angle φ2 with respect to the opposing axis L0 has the sizes indicated by the following [Equation 1] and [Equation 2].
以上の構成により本実施形態の超音波流量計10では、流体の流速増加に伴い送波面中心軸L1に対する超音波の伝播中心軸L2のズレ量が減少していき、超音波の強度を高めるように作用するので、流体の流速増加に伴い超音波の振幅が減衰しても、従来に比べて超音波の受波強度は低下せず、S/N比が改善されて、音響ノイズの影響を受け難くい流量計測が可能になる。   With the above configuration, in the ultrasonic flowmeter 10 of the present embodiment, the amount of deviation of the ultrasonic propagation center axis L2 with respect to the transmission surface central axis L1 decreases as the fluid flow velocity increases, so that the intensity of the ultrasonic wave is increased. Therefore, even if the amplitude of the ultrasonic wave attenuates as the fluid flow velocity increases, the received wave intensity of the ultrasonic wave does not decrease compared to the conventional case, the S / N ratio is improved, and the influence of acoustic noise is reduced. This makes it possible to measure flow rates that are difficult to receive.
また、本実施形態では、上記した音速cは、計測管11の内側を通過し得る流体の種類及び温度の相違によって変わり得る範囲の中央値に設定されている。具体的には、計測管11内を通過し得る流体には、A,B,Cの3種類があり、それら流体の温度がt1〜t2[℃]で変化し、その温度変化範囲においてAを伝播する音速が300〜350[m/s]で変化し、Bを伝播する音速が330〜360[m/s]で変化し、Cを伝播する音速が340〜380[m/s]で変化するとしたら、上記した[数1],[数2]の式中の音速cは、(300+380)/2=340[m/s]になる。   In the present embodiment, the above-described sound velocity c is set to a median value in a range that can change depending on the type of fluid that can pass inside the measurement tube 11 and the temperature. Specifically, there are three types of fluids A, B, and C that can pass through the measuring tube 11, and the temperature of these fluids changes from t1 to t2 [° C.], and A is changed in the temperature change range. The speed of sound that propagates changes from 300 to 350 [m / s], the speed of sound that propagates through B changes from 330 to 360 [m / s], and the speed of sound that propagates through C changes from 340 to 380 [m / s]. Then, the sound velocity c in the above equations [Expression 1] and [Expression 2] is (300 + 380) / 2 = 340 [m / s].
このように音速cを設定して上記ズレ角φ1,φ2を決定してことにより、超音波流量計10が複数種類の流体に使用されても、従来より音響ノイズの影響を受け難くい流量計測が可能になる。   By setting the speed of sound c and determining the deviation angles φ1 and φ2 in this way, even if the ultrasonic flowmeter 10 is used for a plurality of types of fluids, it is less likely to be affected by acoustic noise than in the past. Is possible.
[他の実施形態]
本発明は、前記実施形態に限定されるものではなく、例えば、以下に説明するような実施形態も本発明の技術的範囲に含まれ、さらに、下記以外にも要旨を逸脱しない範囲内で種々変更して実施することができる。
[Other Embodiments]
The present invention is not limited to the above-described embodiment. For example, the embodiments described below are also included in the technical scope of the present invention, and various other than the following can be made without departing from the scope of the invention. It can be changed and implemented.
(1)前記実施形態では、流体の流速の最大値をvとして上記[数1],[数2]の関係式が成り立つ構成になっていたが、流体の流速の平均値や中央値をvとして上記[数1],[数2]の関係式が成り立つ構成としてもよい。 (1) In the above embodiment, the maximum value of the flow velocity of the fluid is v, and the relational expressions of [Expression 1] and [Expression 2] are satisfied. As above, the relational expressions of [Expression 1] and [Expression 2] may be satisfied.
(2)前記実施形態において、素子対向軸L0に対する送波面中心軸L1の傾斜角を変更する調整部(例えば、調整螺子)を設けた構成にしてもよい。 (2) In the embodiment described above, an adjustment unit (for example, an adjustment screw) that changes the inclination angle of the transmission surface central axis L1 with respect to the element facing axis L0 may be provided.
10 超音波流量計
11 計測管
13 素子受容凹部
13A 上流側部分
13B 下流側部分
20 超音波素子
22 超音波送受波面
DESCRIPTION OF SYMBOLS 10 Ultrasonic flowmeter 11 Measuring tube 13 Element receiving recessed part 13A Upstream part 13B Downstream part 20 Ultrasonic element 22 Ultrasonic wave receiving / transmitting surface

Claims (5)

  1. 流体が内側を一方向に通過する計測管の軸方向に対して斜めに交差する素子対向軸上に1対の超音波素子を配置し、一方から他方の前記超音波素子までの超音波の伝播時間と、他方から一方の前記超音波素子までの超音波の伝播時間との差分に基づいて前記流体の流量を検出する超音波流量計において、
    両前記超音波素子の超音波送受波面の中心軸が、前記素子対向軸に対して流体の上流側に傾けられ、
    前記計測管の軸方向に対する素子対向軸上の鋭角側の傾斜角をθとし、
    超音波の音速をcとし、
    前記流体の流速の最大値をvとすると、
    上流側の前記超音波素子の前記超音波送受波面の中心軸が前記素子対向軸に対して上流側にずれるズレ角φ1と、下流側の前記超音波素子の前記超音波送受波面の中心軸が前記素子対向軸に対して上流側にずれるズレ角φ2とは、
    になっている超音波流量計。
    A pair of ultrasonic elements is arranged on an element facing axis that obliquely intersects the axial direction of the measuring tube through which the fluid passes in one direction, and propagation of ultrasonic waves from one to the other ultrasonic element In the ultrasonic flowmeter that detects the flow rate of the fluid based on the difference between the time and the propagation time of the ultrasonic wave from the other to the one ultrasonic element,
    The central axis of the ultrasonic wave transmitting / receiving surface of both the ultrasonic elements is inclined to the upstream side of the fluid with respect to the element facing axis,
    The inclination angle on the acute angle side on the element facing axis with respect to the axial direction of the measuring tube is θ,
    Let c be the velocity of ultrasonic waves,
    When the maximum value of the fluid flow velocity is v,
    A deviation angle φ1 at which the central axis of the ultrasonic wave transmitting / receiving surface of the ultrasonic element on the upstream side is shifted upstream with respect to the element facing axis, and the central axis of the ultrasonic wave transmitting / receiving surface of the ultrasonic element on the downstream side are The deviation angle φ2 shifted upstream from the element facing axis is
    Ultrasonic flow meter that is.
  2. 流体が内側を一方向に通過する計測管の軸方向に対して斜めに交差する素子対向軸上に1対の超音波素子を配置し、一方から他方の前記超音波素子までの超音波の伝播時間と、他方から一方の前記超音波素子までの超音波の伝播時間との差分に基づいて前記流体の流量を検出する超音波流量計において、
    両前記超音波素子の超音波送受波面の中心軸が、前記素子対向軸に対して流体の上流側に傾けられ、
    前記計測管の軸方向に対する素子対向軸上の鋭角側の傾斜角をθとし、
    超音波の音速をcとし、
    前記流体の流速の中央値をvとすると、
    上流側の前記超音波素子の前記超音波送受波面の中心軸が前記素子対向軸に対して上流側にずれるズレ角φ1と、下流側の前記超音波素子の前記超音波送受波面の中心軸が前記素子対向軸に対して上流側にずれるズレ角φ2とは、
    になっている超音波流量計。
    A pair of ultrasonic elements is arranged on an element facing axis that obliquely intersects the axial direction of the measuring tube through which the fluid passes in one direction, and propagation of ultrasonic waves from one to the other ultrasonic element In the ultrasonic flowmeter that detects the flow rate of the fluid based on the difference between the time and the propagation time of the ultrasonic wave from the other to the one ultrasonic element,
    The central axis of the ultrasonic wave transmitting / receiving surface of both the ultrasonic elements is inclined to the upstream side of the fluid with respect to the element facing axis,
    The inclination angle on the acute angle side on the element facing axis with respect to the axial direction of the measuring tube is θ,
    Let c be the velocity of ultrasonic waves,
    If the median of the flow velocity of the fluid is v,
    A deviation angle φ1 at which the central axis of the ultrasonic wave transmitting / receiving surface of the ultrasonic element on the upstream side is shifted upstream with respect to the element facing axis, and the central axis of the ultrasonic wave transmitting / receiving surface of the ultrasonic element on the downstream side are The deviation angle φ2 shifted upstream from the element facing axis is
    Ultrasonic flow meter that is.
  3. 流体が内側を一方向に通過する計測管の軸方向に対して斜めに交差する素子対向軸上に1対の超音波素子を配置し、一方から他方の前記超音波素子までの超音波の伝播時間と、他方から一方の前記超音波素子までの超音波の伝播時間との差分に基づいて前記流体の流量を検出する超音波流量計において、
    両前記超音波素子の超音波送受波面の中心軸が、前記素子対向軸に対して流体の上流側に傾けられ、
    前記計測管の軸方向に対する素子対向軸上の鋭角側の傾斜角をθとし、
    超音波の音速をcとし、
    前記流体の流速の平均値をvとすると、
    上流側の前記超音波素子の前記超音波送受波面の中心軸が前記素子対向軸に対して上流側にずれるズレ角φ1と、下流側の前記超音波素子の前記超音波送受波面の中心軸が前記素子対向軸に対して上流側にずれるズレ角φ2とは、
    になっている超音波流量計。
    A pair of ultrasonic elements is arranged on an element facing axis that obliquely intersects the axial direction of the measuring tube through which the fluid passes in one direction, and propagation of ultrasonic waves from one to the other ultrasonic element In the ultrasonic flowmeter that detects the flow rate of the fluid based on the difference between the time and the propagation time of the ultrasonic wave from the other to the one ultrasonic element,
    The central axis of the ultrasonic wave transmitting / receiving surface of both the ultrasonic elements is inclined to the upstream side of the fluid with respect to the element facing axis,
    The inclination angle on the acute angle side on the element facing axis with respect to the axial direction of the measuring tube is θ,
    Let c be the velocity of ultrasonic waves,
    If the average value of the flow velocity of the fluid is v,
    A deviation angle φ1 at which the central axis of the ultrasonic wave transmitting / receiving surface of the ultrasonic element on the upstream side is shifted upstream with respect to the element facing axis, and the central axis of the ultrasonic wave transmitting / receiving surface of the ultrasonic element on the downstream side are The deviation angle φ2 shifted upstream from the element facing axis is
    Ultrasonic flow meter that is.
  4. 前記超音波の音速cは、前記計測管の内側を通過し得る流体の種類及び温度の相違によって変わり得る範囲の中央値である請求項1乃至3の何れか1の請求項に記載の超音波流量計。   The ultrasonic wave according to any one of claims 1 to 3, wherein the ultrasonic sound velocity c is a median value in a range that can vary depending on a difference in the type and temperature of the fluid that can pass inside the measuring tube. Flowmeter.
  5. 前記計測管の内側面には、前記素子対向軸上に1対の素子受容凹部が設けられて、それら素子受容凹部に各前記超音波素子の全体が受容され、
    各前記素子受容凹部の内面のうち前記超音波送受波面より上流側部分と下流側部分との間で、前記超音波送受波面の中心軸に対する傾斜角又は直線距離を異ならせた請求項1乃至4の何れか1の請求項に記載の超音波流量計。
    On the inner surface of the measurement tube, a pair of element receiving recesses are provided on the element facing axis, and the entirety of each ultrasonic element is received in these element receiving recesses,
    5. An inclination angle or a linear distance with respect to a central axis of the ultrasonic wave transmitting / receiving surface is made different between an upstream portion and a downstream portion of the inner surface of each of the element receiving recesses from the ultrasonic wave transmitting / receiving surface. The ultrasonic flowmeter according to claim 1.
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Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6451868U (en) * 1987-09-26 1989-03-30
JPH05502298A (en) * 1989-12-15 1993-04-22
JPH0915011A (en) * 1995-06-27 1997-01-17 Aichi Tokei Denki Co Ltd Ultrasonic wave transmitter and receiver device
JP2007067500A (en) * 2005-08-29 2007-03-15 Matsushita Electric Ind Co Ltd Ultrasonic transceiver
JP2007322186A (en) * 2006-05-31 2007-12-13 Tokyo Keiso Co Ltd Ultrasonic flow meter
JP2009058444A (en) * 2007-08-31 2009-03-19 Institute Of National Colleges Of Technology Japan Flowmeter for artificial respirator
US20100288055A1 (en) * 2009-05-12 2010-11-18 Roland Mueller Transit time correction in a flow sensor
US20120266679A1 (en) * 2011-04-21 2012-10-25 General Electric Company Ultrasonic coupler assembly

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6451868U (en) * 1987-09-26 1989-03-30
JPH05502298A (en) * 1989-12-15 1993-04-22
JPH0915011A (en) * 1995-06-27 1997-01-17 Aichi Tokei Denki Co Ltd Ultrasonic wave transmitter and receiver device
JP2007067500A (en) * 2005-08-29 2007-03-15 Matsushita Electric Ind Co Ltd Ultrasonic transceiver
JP2007322186A (en) * 2006-05-31 2007-12-13 Tokyo Keiso Co Ltd Ultrasonic flow meter
JP2009058444A (en) * 2007-08-31 2009-03-19 Institute Of National Colleges Of Technology Japan Flowmeter for artificial respirator
US20100288055A1 (en) * 2009-05-12 2010-11-18 Roland Mueller Transit time correction in a flow sensor
US20120266679A1 (en) * 2011-04-21 2012-10-25 General Electric Company Ultrasonic coupler assembly

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