JP6351060B2 - Gas concentration measuring method and apparatus - Google Patents
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- 238000000034 method Methods 0.000 title claims description 19
- 239000007789 gas Substances 0.000 claims description 148
- 238000005259 measurement Methods 0.000 claims description 67
- 239000001257 hydrogen Substances 0.000 claims description 44
- 229910052739 hydrogen Inorganic materials 0.000 claims description 44
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 38
- 238000009529 body temperature measurement Methods 0.000 claims description 25
- 230000005540 biological transmission Effects 0.000 claims description 19
- 150000002431 hydrogen Chemical class 0.000 claims description 8
- 239000002184 metal Substances 0.000 claims description 8
- 229910052751 metal Inorganic materials 0.000 claims description 8
- 238000000691 measurement method Methods 0.000 claims description 6
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- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 1
- OTMSDBZUPAUEDD-UHFFFAOYSA-N Ethane Chemical compound CC OTMSDBZUPAUEDD-UHFFFAOYSA-N 0.000 description 1
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 1
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- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
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- 238000012805 post-processing Methods 0.000 description 1
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- Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
Description
本発明は、超音波を利用したガス濃度の測定技術に関する。詳細には、超音波のガス中の伝播時間を測定し、該ガス中の超音波の音速を検出すると同時に、環境の温度による音速の補正を行うことによって、当該ガスの濃度を特定する技術に関する。 The present invention relates to a gas concentration measurement technique using ultrasonic waves. Specifically, the present invention relates to a technique for measuring the propagation time of ultrasonic waves in a gas, detecting the speed of ultrasonic waves in the gas, and at the same time correcting the speed of sound according to the temperature of the environment to identify the concentration of the gas. .
近年、クリーンエネルギーとして水素利用社会の普及が言われ始め、自動車や家庭用燃料電池などの研究開発や実用化に伴い、水素利用関連技術の実用化研究開発が進められている。水素は、空気中に於いて4%強以上の濃度で爆発することが知られている。水素利用社会を実現するためには水素センサーが不可欠であり、各種水素センサーが研究され、実用化されてきつつある。 In recent years, the popularization of hydrogen-utilizing society as clean energy has begun to be said, and along with research and development and commercialization of automobiles and household fuel cells, practical research and development of hydrogen-related technologies has been promoted. Hydrogen is known to explode in air at concentrations of over 4%. Hydrogen sensors are indispensable for realizing a hydrogen-using society, and various hydrogen sensors are being researched and put into practical use.
従来の水素センサーは、半導体式、接触燃焼式など各種の検出方法が取られているが、応答時間が遅く、また、水素の検出が吸着による場合が多く、検出後の水素除去に時間がかかるなどの欠点があり、瞬時の水素検出には限界があった。 Conventional hydrogen sensors employ various detection methods such as semiconductor and catalytic combustion methods, but response time is slow, and hydrogen detection is often due to adsorption, and it takes time to remove hydrogen after detection. However, there was a limit to instantaneous hydrogen detection.
これらの改良技術として、超音波を利用した水素測定技術が、特許文献2、非特許文献1、2に開示されている。 As these improved techniques, a hydrogen measurement technique using ultrasonic waves is disclosed in Patent Document 2 and Non-Patent Documents 1 and 2.
この技術は、音波が気体の種類によって、さらには気体の濃度によって伝搬速度が変化することを利用したもので、超音波を所定の距離間に発信させ、該超音波の発信から受信するまでの時間を測定し、音速を演算することで、超音波が伝播した雰囲気の気体の種類及びその濃度を測定するようにしたものである。 This technology uses the fact that the propagation speed of sound waves changes depending on the type of gas and also the concentration of gas, and transmits ultrasonic waves within a predetermined distance until the ultrasonic waves are transmitted and received. By measuring the time and calculating the speed of sound, the type and concentration of the gas in the atmosphere through which the ultrasonic wave has propagated are measured.
ただ、気体の音速は、温度に非常に敏感であり、気体の温度を瞬時に把握し、その温度による気体の音速を補正しないことには正確な気体の音速を測定できず、ひいては気体の種類ならびに気体の濃度を正確に測定できない状況となっていた。
特に、瞬時に環境温度を測定し、その測定した環境温度を利用した超音波の音速を補正することで、精度のよい気体の種類、ならびに気体の濃度を測定する技術を安価に、かつ簡素に実現することが必要であった。
However, the speed of sound of gas is very sensitive to temperature, and if the gas temperature is grasped instantaneously and the sound speed of the gas due to that temperature is not corrected, the sound speed of the gas cannot be measured accurately. In addition, the gas concentration cannot be measured accurately.
In particular, by measuring the ambient temperature instantaneously and correcting the sound velocity of the ultrasonic wave using the measured ambient temperature, the technology for measuring the precise gas type and gas concentration is inexpensive and simple. It was necessary to realize.
本発明は、従来技術で記載した問題点に鑑み、超音波を利用して瞬時に環境温度を測定し、その測定した環境温度を利用した超音波の音速を補正することで、精度のよい気体の
種類、ならびに気体の濃度を測定する技術を安価に、かつ簡素に実現することを課題とする。
In view of the problems described in the prior art, the present invention measures the environmental temperature instantaneously using ultrasonic waves, and corrects the sound velocity of the ultrasonic waves using the measured environmental temperature, thereby providing a highly accurate gas. It is an object to realize a technique for measuring the kind of gas and the concentration of gas at low cost and simply.
本発明の第1の発明は、超音波によって測定環境のガス濃度並びに温度の測定を行なうガス濃度測定方法であって、測定環境において発信させた超音波の、あらかじめ定められた第一の距離に対する伝播時間を測定することによって前記ガス濃度を特定するガス濃度測定工程と、測定環境において発信させた超音波の、温度測定用金属棒中におけるあらかじめ定められた第二の距離に対する伝播時間を測定することによって前記温度を特定する温度測定工程と、を有することを特徴とするガス濃度測定方法である。
A first invention of the present invention is a gas concentration measurement method for measuring the gas concentration and temperature of a measurement environment by using ultrasonic waves, and the ultrasonic wave transmitted in the measurement environment with respect to a predetermined first distance. A gas concentration measurement step for specifying the gas concentration by measuring a propagation time, and a propagation time for a predetermined second distance in the metal rod for temperature measurement of the ultrasonic wave transmitted in the measurement environment is measured. And a temperature measuring step for specifying the temperature.
本発明の第2の発明は、第1の発明に付加して、前記ガスが水素であり、前記ガス濃度の特定は、測定した伝播時間とあらかじめ定められた水素濃度に対する伝播時間との比較によって特定するガス濃度測定方法である。 According to a second aspect of the present invention, in addition to the first aspect, the gas is hydrogen, and the gas concentration is specified by comparing the measured propagation time with a propagation time for a predetermined hydrogen concentration. This is a gas concentration measurement method to be specified.
本発明の第3の発明は、第1乃至第2の発明に付加して、前記ガス濃度測定のための超音波と、温度測定のための超音波は、発信時に同期を取る/あるいは同一の超音波発信装置であるガス濃度測定方法である。 According to a third aspect of the present invention, in addition to the first and second aspects, the ultrasonic waves for gas concentration measurement and the ultrasonic waves for temperature measurement are synchronized at the time of transmission or / and the same. It is a gas concentration measuring method which is an ultrasonic transmitter.
本発明の第4の発明は、超音波によって測定環境のガス濃度並びに温度の測定を行なうガス濃度測定装置であって、測定環境において発信させた超音波の、あらかじめ定められた第一の距離に対する伝播時間を測定することによって前記ガス濃度を特定するガス濃度測定手段と、測定環境において発信させた超音波の、温度測定用金属棒中におけるあらかじめ定められた第二の距離に対する伝播時間を測定することによって前記温度を特定する温度測定手段と、を有することを特徴とするガス濃度測定装置である。 According to a fourth aspect of the present invention, there is provided a gas concentration measuring apparatus for measuring a gas concentration and a temperature of a measurement environment by using an ultrasonic wave, wherein the ultrasonic wave transmitted in the measurement environment is measured with respect to a predetermined first distance. The gas concentration measuring means for determining the gas concentration by measuring the propagation time, and the propagation time of the ultrasonic wave transmitted in the measurement environment with respect to a predetermined second distance in the metal rod for temperature measurement are measured. And a temperature measuring means for specifying the temperature.
本発明の第5の発明は、第4の発明に付加して、前記ガスが水素であり、前記ガス濃度の特定は、測定した伝播時間とあらかじめ定められた水素濃度に対する伝播時間との比較によって特定するガス濃度測定装置である。 According to a fifth aspect of the present invention, in addition to the fourth aspect, the gas is hydrogen, and the gas concentration is specified by comparing the measured propagation time with a propagation time for a predetermined hydrogen concentration. This is a gas concentration measuring device to be specified.
本発明の第6の発明は、第4乃至5の発明に付加して、前記ガス濃度測定のための超音波と、温度測定のための超音波は、発信時に同期を取る/あるいは同一の超音波発信装置であるガス濃度測定装置である。 According to a sixth aspect of the present invention, in addition to the fourth to fifth aspects of the present invention, the ultrasonic waves for gas concentration measurement and the ultrasonic waves for temperature measurement are synchronized at the time of transmission or / and the same ultrasonic wave. It is a gas concentration measuring device which is a sound wave transmitting device.
本発明によれば、超音波による第1の所定距離の伝播時間を測定することで、瞬時に、気体の種類および濃度を特定することができる。 According to the present invention, it is possible to instantaneously identify the type and concentration of gas by measuring the propagation time of the first predetermined distance by ultrasonic waves.
また、超音波による第2の所定距離の伝播時間を測定することで、瞬時に、測定環境いわゆる気体の温度を瞬時に測定することができる。 Also, by measuring the propagation time of the second predetermined distance by the ultrasonic wave, the measurement environment, that is, the temperature of the gas can be instantaneously measured.
また、超音波による第1、第2の所定距離の伝播時間の測定であるため、熱源を利用せずに測定ができるため、測定器具を防爆型等にすることが不要であり安価な装置を実現できる。 In addition, since the propagation times of the first and second predetermined distances are measured by ultrasonic waves, the measurement can be performed without using a heat source. Therefore, it is not necessary to use an explosion-proof measuring instrument as an inexpensive device. realizable.
また、ガス濃度測定のための超音波と、温度測定のための超音波が、発信時に同期を取る/あるいは同一の超音波発信装置を使用することで、気体の濃度測定と気体の温度測定を瞬時に実現でき、かつ、タイムラグなく測定することができるため気体濃度測定の精度向上を図ることができる。 In addition, the ultrasonic waves for gas concentration measurement and the ultrasonic waves for temperature measurement are synchronized at the time of transmission / or by using the same ultrasonic transmission device, gas concentration measurement and gas temperature measurement can be performed. Since it can be realized instantaneously and can be measured without a time lag, the accuracy of gas concentration measurement can be improved.
また、超音波によるガス濃度測定と温度測定であるため、測定後のガス除去等の後処理が不要でそのまま繰り返し利用できるため、連続的なモニタリング等に適した測定方法、測定装置である。 In addition, since it is a gas concentration measurement and temperature measurement using ultrasonic waves, post-processing such as gas removal after measurement is unnecessary, and it can be used repeatedly as it is.
また、超音波伝播時間の測定用の第1の距離、第2の距離が非常に小さな値で実用できることによって、測定雰囲気における測定子を小型にすることができ、狭隘部等における測定においても利用することが可能である。 In addition, since the first distance and the second distance for measuring the ultrasonic propagation time can be used with very small values, the probe in the measurement atmosphere can be reduced in size, and can also be used for measurements in narrow spaces. Is possible.
さらに、本発明の実施例では水素を基に説明したが、温度と濃度を同時に測定できることから、伝搬速度が類似したガスについての測定にも利用することができる。 Furthermore, although the embodiment of the present invention has been described based on hydrogen, since the temperature and the concentration can be measured at the same time, it can also be used for measurement of gases having similar propagation velocities.
本発明は、測定環境において発信させた超音波の、あらかじめ定められた第一の距離に対する伝播時間を測定することによって前記ガス濃度を特定するガス濃度測定手段と、測定環境において発信させた超音波の、あらかじめ定められた第二の距離に対する伝播時間を測定することによって前記温度を特定する温度測定手段とによって測定環境のガス濃度を測定するガス濃度測定方法ならびにガス濃度測定装置である。 The present invention relates to a gas concentration measuring means for specifying the gas concentration by measuring a propagation time of an ultrasonic wave transmitted in a measurement environment with respect to a predetermined first distance, and an ultrasonic wave transmitted in the measurement environment. A gas concentration measuring method and a gas concentration measuring apparatus for measuring a gas concentration in a measurement environment by means of a temperature measuring means for specifying the temperature by measuring a propagation time with respect to a predetermined second distance.
測定対象のガスは、水素成分を含むガスであればいずれでもよいが、水素単独あるいは水素単独の分子成分が混在したガスであることが好ましい。
ただ、測定対象環境における測定ガスを限定する、すなわち、測定対象となるガスの濃度測定に障害となるガスの存在を制限することにより、ヘリウムを始め、その他のガス濃度の測定にも利用することができる。
The gas to be measured may be any gas as long as it contains a hydrogen component, but is preferably a gas containing hydrogen alone or a molecular component of hydrogen alone.
However, by limiting the measurement gas in the measurement target environment, that is, limiting the presence of gas that hinders the measurement of the concentration of the measurement target gas, it can also be used for the measurement of other gas concentrations, including helium. Can do.
ガス濃度測定手段は、特定ガス中における測定した超音波の伝播時間と、特定ガスに対して予め定められたガス濃度中の超音波の伝播時間との比較によって特定ガスの濃度を決定する。具体例を後述の実施例で説明する。 The gas concentration measuring means determines the concentration of the specific gas by comparing the measured propagation time of the ultrasonic wave in the specific gas with the propagation time of the ultrasonic wave in the gas concentration predetermined for the specific gas. Specific examples will be described in the examples described later.
温度測定手段は、特定ガス中における測定した超音波の伝播時間を、ガス濃度測定用の超音波あるいは該超音波と同期して発信させる他の超音波によって環境温度の測定を行い、その環境温度の測定結果を基に、特定ガス中における測定した伝播時間の温度補正を行う。この技術は、本発明者等がすでに出願済の2013−244628号の技術を利用する。 The temperature measuring means measures the environmental temperature using ultrasonic waves for measuring the gas concentration in the specific gas or other ultrasonic waves that are transmitted in synchronization with the ultrasonic waves. Based on the measurement result, temperature correction of the measured propagation time in the specific gas is performed. This technique uses the technique of 2013-244628 already filed by the present inventors.
図1に、本発明のガス濃度測定装置の装置概要を示す。
なお、以降の説明において、ガス濃度測定装置を測定装置、制御プログラム/記憶装置を制御PRGと略して説明する。
FIG. 1 shows an outline of a gas concentration measuring apparatus according to the present invention.
In the following description, the gas concentration measuring device is abbreviated as a measuring device, and the control program / storage device is abbreviated as a control PRG.
測定装置1は、大きく、ガス濃度および温度の測定に係る制御全般をつかさどる制御装置2と、測定環境への超音波の発信、受信を行う超音波センサ3とで構成する。 The measuring apparatus 1 is largely composed of a control apparatus 2 that controls all of the control related to measurement of gas concentration and temperature, and an ultrasonic sensor 3 that transmits and receives ultrasonic waves to and from the measurement environment.
制御装置2は、測定装置1内に接続された各機器の制御と、制御PRG2eの情報を基に超音波発信制御手段2e1、超音波受信制御手段2e2、ガス温度解析手段2e3、ガス濃度解析手段2e4の各手段を起動・制御する制御部2a、超音波の発信、受信等に関して超音波センサ3との信号の仲介・制御を行うI/Oポート2b、I/Oポート2bからの情報に基づき超音波センサ3への超音波信号を送信する送信回路2c、および超音波センサ3からの超音波信号を受信する受信回路2dで構成する。制御部2aには、制御部の操作用の入力部2f、表示部2gが接続され、測定者による制御部2aへの指示と、制御部2a内の測定結果などの確認を行う表示部2gが接続されている。 The control device 2 controls each device connected in the measuring device 1 and based on the information of the control PRG 2e, the ultrasonic transmission control means 2e1, the ultrasonic reception control means 2e2, the gas temperature analysis means 2e3, the gas concentration analysis means. Based on information from the control unit 2a that activates and controls each means of 2e4, the I / O port 2b that mediates and controls signals with the ultrasonic sensor 3 regarding transmission and reception of ultrasonic waves, and the information from the I / O port 2b The transmitting circuit 2 c transmits an ultrasonic signal to the ultrasonic sensor 3 and the receiving circuit 2 d receives an ultrasonic signal from the ultrasonic sensor 3. An input unit 2f for operation of the control unit and a display unit 2g are connected to the control unit 2a, and a display unit 2g for confirming an instruction to the control unit 2a by a measurer and a measurement result in the control unit 2a is provided. It is connected.
制御PRG2eは、超音波発信制御手段2e1、超音波受信制御手段2e2、ガス温度解析手段2e3、ガス濃度解析手段2e4のような制御プログラムを内蔵する。なお、超音波発信制御手段2e1、超音波受信制御手段2e2、ガス濃度解析手段2e4については、特許文献1、2、非特許文献1、2を始め、一般的に公開されている技術であり、それらの技術を適宜利用するものであるため、本発明では詳述しない。 The control PRG 2e incorporates control programs such as ultrasonic transmission control means 2e1, ultrasonic reception control means 2e2, gas temperature analysis means 2e3, and gas concentration analysis means 2e4. Note that the ultrasonic transmission control means 2e1, the ultrasonic reception control means 2e2, and the gas concentration analysis means 2e4 are commonly disclosed techniques including Patent Documents 1 and 2, Non-Patent Documents 1 and 2, Since these techniques are used as appropriate, they are not described in detail in the present invention.
超音波センサ3は、測定環境のガス中への超音波の送信と、測定環境から反射する超音波の受信を行う。 The ultrasonic sensor 3 transmits ultrasonic waves into the gas in the measurement environment and receives ultrasonic waves reflected from the measurement environment.
この超音波センサ3は、ガス濃度測定用超音波振動子5とガスの温度測定用超音波振動子4とで構成する。 The ultrasonic sensor 3 includes a gas concentration measuring ultrasonic transducer 5 and a gas temperature measuring ultrasonic transducer 4.
一般に、超音波の反射、透過については、図2で表される挙動を示すことが知られている。超音波の媒体物質同士の境界では、音響インピーダンスが比較的類似している場合には、超音波の透過率が高い数値を得ることができるが、音響インピーダンスの大きい物質から音響インピーダンスの小さい物質へ超音波を伝播させる場合、いわゆる固体から気体へ超音波を伝播させる場合には、透過率は数%止まりとなり、測定に利用することが困難になる。ちなみに、鉄棒から空気への超音波の透過率は数%未満となり、実施的に超音波は伝搬されないこととなる。従って、超音波振動子と気体の間に音響インピーダンスの小さい媒質を介して、効率よく気体に超音波を伝播させる工夫を行い、気体を超音波振動させるようにすることが必要不可欠である。 In general, it is known that the reflection and transmission of ultrasonic waves behave as shown in FIG. When the acoustic impedance is relatively similar at the boundary between the ultrasonic medium materials, a numerical value with a high ultrasonic transmittance can be obtained, but from a material with a high acoustic impedance to a material with a low acoustic impedance. When transmitting ultrasonic waves, when transmitting ultrasonic waves from a so-called solid to a gas, the transmittance is only a few percent, making it difficult to use for measurement. Incidentally, the transmittance of the ultrasonic wave from the iron bar to the air is less than several percent, and the ultrasonic wave is not practically propagated. Therefore, it is indispensable to devise a method for efficiently transmitting ultrasonic waves to the gas via a medium having a low acoustic impedance between the ultrasonic transducer and the gas so that the gas is ultrasonically vibrated.
このことから、温度測定については、気体に比して温度に対する影響の少ない固体を利用した温度の測定方法として、本発明者等が開発した2013−244628号の技術を使用することとし、温度測定超音波振動子4とした。 Therefore, for temperature measurement, the technique of 2013-244628 developed by the present inventors is used as a temperature measurement method using a solid that has less influence on temperature than gas, and temperature measurement is performed. An ultrasonic transducer 4 was obtained.
また、ガス濃度測定のための発信用超音波振動子5、反対側に受信用超音波振動子5cを配置し、超音波振動子と気体の間に音響インピーダンスの小さい媒質を介して、効率よく気体に超音波を伝播させる工夫を行い、気体を超音波振動させることとした。
ただ、この受信用超音波振動子5cの代替として超音波反射用部材5dを配置して発信された超音波を反射させ、反射した超音波を発信用超音波振動子5で受信する形態とすることもできる。この場合、反射用部材5dは、超音波を反射する平滑面を持つ固体であればよいが、ステンレス等の金属であることが好ましい。
Further, the transmitting ultrasonic transducer 5 for gas concentration measurement and the receiving ultrasonic transducer 5c are arranged on the opposite side, and a medium with low acoustic impedance is efficiently interposed between the ultrasonic transducer and the gas. The idea of propagating ultrasonic waves to the gas was made, and the gas was ultrasonically vibrated.
However, as an alternative to the receiving ultrasonic transducer 5c, an ultrasonic reflecting member 5d is arranged to reflect the transmitted ultrasonic wave, and the reflected ultrasonic wave is received by the transmitting ultrasonic transducer 5. You can also In this case, the reflecting member 5d may be a solid having a smooth surface that reflects ultrasonic waves, but is preferably a metal such as stainless steel.
温度測定超音波振動子4から温度測定用金属棒4bを伝播する超音波を4aとし、ガス濃度測定用超音波振動子5からガス中を伝播する超音波を、一方向直進波を5a、超音波反射用部材5dによって反射する超音波を5bとして図示した。超音波反射用部材5dは、前記一方向直進波5aを受信する場合には、ガス濃度測定用超音波振動子5と同一の超音波振動子を5cとして使用する。 The ultrasonic wave propagating from the temperature measuring ultrasonic transducer 4 to the temperature measuring metal rod 4b is 4a, the ultrasonic wave propagating in the gas from the gas concentration measuring ultrasonic transducer 5 is converted to a unidirectional straight wave 5a, An ultrasonic wave reflected by the sound wave reflecting member 5d is shown as 5b. When receiving the unidirectionally traveling wave 5a, the ultrasonic reflecting member 5d uses the same ultrasonic transducer as the gas concentration measuring ultrasonic transducer 5 as 5c.
ここで、温度測定超音波振動子4、ガス濃度測定用超音波振動子5、ガス濃度測定用超音波振動子5cについて説明する。
超音波振動子は小型であることが望ましいが、超音波の距離による減衰、周波数に対する振動子の厚さと減衰等の要因が大きく係ってくる。
Here, the temperature measurement ultrasonic transducer 4, the gas concentration measurement ultrasonic transducer 5, and the gas concentration measurement ultrasonic transducer 5c will be described.
Although it is desirable that the ultrasonic transducer be small, factors such as attenuation due to the distance of the ultrasonic wave and the thickness and attenuation of the transducer with respect to the frequency are greatly involved.
超音波信号の距離による減衰について実験の結果を図3に示す。 FIG. 3 shows the result of the experiment on attenuation due to the distance of the ultrasonic signal.
図3は、伝搬距離(超音波振動子間の距離)に対する信号の減衰を表す試験データである。超音波信号は伝搬距離0.05mの単位でプロットしている。
この実験結果から、周波数が高くなると、減衰は大きくなるということが分かる。
FIG. 3 shows test data representing signal attenuation with respect to propagation distance (distance between ultrasonic transducers). The ultrasonic signal is plotted in units of a propagation distance of 0.05 m.
From this experimental result, it can be seen that the attenuation increases as the frequency increases.
なお、実線は、プロットしたデータを以下の近似式(1)で信号の大きさを表したものである。
S=S(0.05)exp(−αL) (1)
ここで、S(0.05):伝搬距離0.05mでの信号の大きさ(当初の超音波信号の強度を1として表している)、α:減衰率、L:伝搬距離である。
The solid line represents the magnitude of the signal by plotting the following approximate expression (1).
S = S (0.05) exp (−αL) (1)
Here, S (0.05): the magnitude of the signal at a propagation distance of 0.05 m (the intensity of the initial ultrasonic signal is expressed as 1), α: attenuation factor, and L: propagation distance.
超音波の周波数に対する振動子の厚さと減衰について実験の結果を図4に示す。
図4は、超音波の周波数を決める振動子の厚さと、前術の減衰率とをまとめた図である。実線で示す振動子の厚さは、振動子の周波数定数N(振動子の厚さと共振周波数の積で、試験で使用した1−3コンポジット振動子の場合、約1.34×106[mm・Hz])よ
り、以下の関係式(2)で求めた。
y=N/f (2)
ここで、yは超音波振動子の厚さ(mm)、Nは超音波振動子の周波数定数、fは発信周波数(Hz)である。
図4中の破線は、前述の減衰率曲線を近似式で挿入したものである。
この関係から、用途に応じて、超音波振動子の大きさや周波数を選定することが可能である。
FIG. 4 shows the results of an experiment regarding the thickness and attenuation of the vibrator with respect to the ultrasonic frequency.
FIG. 4 is a diagram summarizing the thickness of the transducer that determines the frequency of the ultrasound and the attenuation rate of the previous operation. The thickness of the vibrator indicated by the solid line is the frequency constant N of the vibrator (the product of the vibrator thickness and the resonance frequency. In the case of the 1-3 composite vibrator used in the test, about 1.34 × 10 6 [mm・ Hz]), the following relational expression (2) was obtained.
y = N / f (2)
Here, y is the thickness (mm) of the ultrasonic transducer, N is the frequency constant of the ultrasonic transducer, and f is the transmission frequency (Hz).
The broken line in FIG. 4 is obtained by inserting the above-described attenuation rate curve by an approximate expression.
From this relationship, it is possible to select the size and frequency of the ultrasonic transducer according to the application.
これより、一般的に言われている通り、発信周波数が低いほど、振動子の厚さは厚くなり、また、振動子の径は、厚さの3倍以上とするのが一般的といえる。
その場合、発信周波数200kHzでは、超音波振動子径は約20mm(6.7×3)、800kHzでは約5mm(1.7×3)となり、周波数が低いほど超音波振動子は大きくなる。
Thus, as is generally said, the lower the transmission frequency, the thicker the vibrator, and the diameter of the vibrator is generally at least three times the thickness.
In that case, the ultrasonic transducer diameter is about 20 mm (6.7 × 3) at a transmission frequency of 200 kHz, and about 5 mm (1.7 × 3) at 800 kHz, and the ultrasonic transducer becomes larger as the frequency is lower.
例えば、広い空間のガス濃度を測定する場合、超音波動子は大きくなるが、減衰率の低い低周波数の超音波振動子が有効である。
また、空間の制約により、大きい超音波振動子が使用できない場合は、伝搬距離が長い条件には適しないが、高周波数の超音波振動子を使用して超音波振動子の大きさを小さくすることが有効となる。
For example, when measuring a gas concentration in a wide space, a low-frequency ultrasonic transducer with a low attenuation factor is effective, although the ultrasonic moving element becomes large.
Also, if a large ultrasonic transducer cannot be used due to space constraints, it is not suitable for long propagation distance conditions, but the size of the ultrasonic transducer is reduced using a high-frequency ultrasonic transducer. Is effective.
つぎに、超音波センサ3の本発明の代表的な例として、図5を基に説明する。 Next, a typical example of the ultrasonic sensor 3 according to the present invention will be described with reference to FIG.
図5a)は、ガス濃度測定用ならびに温度測定用の超音波振動子を一体型の4、5で構成し、4の部分で発信した超音波4aを温度測定用金属棒4bに伝播させ、この反射波4aを4の部分で受信する。5の部分で発信した超音波5aをガス中を伝播させ、反対側の超音波振動子5cで受信する。 FIG. 5a) shows an ultrasonic transducer for gas concentration measurement and temperature measurement composed of an integrated type 4, 5, and the ultrasonic wave 4a transmitted from the portion 4 is propagated to the temperature measuring metal rod 4b. The reflected wave 4a is received by the portion 4. The ultrasonic wave 5a transmitted in the portion 5 is propagated in the gas and received by the ultrasonic transducer 5c on the opposite side.
図5b)は、図5a)で示した構成を、ガス濃度測定用超音波振動子5と温度測定用超音波振動子4を発信制御等の同期をとることによって各々独立して配置する構成を示したものである。 FIG. 5B) shows a configuration in which the gas concentration measurement ultrasonic transducer 5 and the temperature measurement ultrasonic transducer 4 are arranged independently by synchronizing the transmission control or the like with the configuration shown in FIG. 5A). It is shown.
図5c)は、ガス濃度測定用超音波振動子5と温度測定用超音波振動子4を発信制御等の同期をとることによって各々独立して配置し、ガス濃度測定用超音波振動子5から発信した超音波5bを、反対側に設置した超音波反射用部材5dによって反射させ、ガス濃度測定用超音波振動子5で受信する構成である。 In FIG. 5c), the ultrasonic transducer 5 for measuring gas concentration and the ultrasonic transducer 4 for measuring temperature are arranged independently by synchronizing the transmission control and the like, and the ultrasonic transducer 5 for measuring gas concentration is used. The transmitted ultrasonic wave 5b is reflected by an ultrasonic wave reflecting member 5d installed on the opposite side, and is received by the ultrasonic transducer 5 for gas concentration measurement.
この構成は、測定ガスに流れがあった場合に、特に有効な方法となる。超音波の伝搬速度に測定ガスの流れが影響した場合に、超音波の「往」の伝搬速度(伝播時間)と「復」の超音波の伝搬速度(伝播時間)との差を相殺することができるため、超音波の往復の合計時間tLとすることによって、ガスの流れの影響を除去することができる。 This configuration is a particularly effective method when there is a flow in the measurement gas. When the measurement gas flow affects the ultrasonic propagation velocity, cancel the difference between the ultrasonic “forward” propagation velocity (propagation time) and the “reverse” ultrasonic propagation velocity (propagation time). Therefore, the influence of the gas flow can be eliminated by setting the total time t L of the ultrasonic reciprocation.
ここで、超音波信号の関係を模式的に図5d)示す。Lは第一の所定距離(図5c)の場合は、2Lが第一の所定距離)であり、2lは第2の所定距離を表わす。
また、第一の所定距離Lを伝播する時間tL、第二の所定距離2lを伝播する時間tlである。この図で、(I)は発信超音波のパルス信号であり、(II)は温度測定用の超音波
の受信パルス信号、(III)はガス濃度測定用の超音波の受信パルス信号を表わす。
[実施例]
Here, the relationship between the ultrasonic signals is schematically shown in FIG. In the case of the first predetermined distance (FIG. 5c), L is the first predetermined distance, and 2l represents the second predetermined distance.
Further, time t L to propagate a first predetermined distance L, and the time t l to propagate a second predetermined distance 2l. In this figure, (I) is a pulse signal of an outgoing ultrasonic wave, (II) is an ultrasonic reception pulse signal for temperature measurement, and (III) is an ultrasonic reception pulse signal for gas concentration measurement.
[Example]
本発明の実施例1として、図5b)のガス濃度測定用超音波振動子5、反対側の超音波振動子5c、その間の超音波5aを使用して、図6a)、b)の装置の配置とし、実際の水素濃度と超音波による測定水素濃度の検証を行った。 As Example 1 of the present invention, using the ultrasonic transducer 5 for gas concentration measurement in FIG. 5b), the ultrasonic transducer 5c on the opposite side, and the ultrasonic wave 5a therebetween, the apparatus of FIGS. 6a) and b) is used. The actual hydrogen concentration and the measured hydrogen concentration by ultrasonic waves were verified.
ここで、図6a)は、図6b)のガス濃度測定用超音波振動子5、反対側のガス濃度測定用超音波振動子5cを配置した実験装置の図である。温度測定用超音波振動子4は、図6a)には図示していないが本実施例では熱電対による温度測定で代用した。
ガス濃度測定用超音波振動子5は、約200kHz、印加電圧約100V(パルス)、L=50mmで構成し、測定温度は約20℃とし、測定環境のガスは、窒素ガスと水素ガスの混合ガスとした。
検証結果を図7に示す。
Here, FIG. 6a) is a diagram of an experimental apparatus in which the gas concentration measuring ultrasonic transducer 5 of FIG. 6b) and the gas concentration measuring ultrasonic transducer 5c on the opposite side are arranged. Although the ultrasonic transducer 4 for temperature measurement is not shown in FIG. 6 a), temperature measurement using a thermocouple is used in this embodiment.
The ultrasonic transducer 5 for gas concentration measurement is constituted by about 200 kHz, applied voltage about 100 V (pulse), L = 50 mm, the measurement temperature is about 20 ° C., and the measurement environment gas is a mixture of nitrogen gas and hydrogen gas. Gas was used.
The verification result is shown in FIG.
この結果から、雰囲気の水素濃度と超音波で測定した水素濃度とは高度の相関を得ることができ、良好な精度で水素濃度を測定することが可能との確証を得た。 From this result, it was confirmed that the hydrogen concentration in the atmosphere and the hydrogen concentration measured by ultrasonic waves can be highly correlated, and the hydrogen concentration can be measured with good accuracy.
本発明の実施例2として、実施例1と同一条件で、環境温度を変化させた時の超音波の音速と検出水素濃度について検証を行った。検証結果を図8に示す。
図8a)から、水素濃度毎に、例えば、水素濃度1%、2%、3%毎に、環境温度と超音波の音速とは非常に相関があり、かつ、水素濃度が高くなれば、超音波の音速も高くなることが確認できた。
このことから、環境温度と超音波の音速とから、精度よく水素濃度を計測できることが実証できた。
さらに、図8b)は、図8a)の部分を拡大したものであるが、環境温度と超音波の音速との交点から測定水素濃度を演算する様子を示したものである。
As Example 2 of the present invention, the sound velocity of ultrasonic waves and the detected hydrogen concentration when the environmental temperature was changed under the same conditions as in Example 1 were verified. The verification result is shown in FIG.
From FIG. 8a), for each hydrogen concentration, for example, every 1%, 2%, 3% of hydrogen concentration, the environmental temperature and the sound velocity of the ultrasonic wave are very correlated, and if the hydrogen concentration increases, It was confirmed that the sound velocity of sound waves also increased.
From this, it was proved that the hydrogen concentration can be accurately measured from the environmental temperature and the sound velocity of the ultrasonic waves.
Further, FIG. 8b) is an enlarged view of the part of FIG. 8a), and shows a state in which the measured hydrogen concentration is calculated from the intersection of the environmental temperature and the ultrasonic sound velocity.
環境温度が106℃、超音波の音速が402m/sとしたときのグラフの交点は、水素濃度2%と水素濃度3%との間にあり、交点をOとし、Oを通る水素濃度2%と水素濃度3%の近似線に垂線を引き、交わる点をX、Yとする。O点とX点、Y点までの距離をa、bとすると、O点の水素濃度は2%+a/(a+b)%で表すことができる。本例では1%刻みの近似線で表しているが、1%→0.1%刻みのように細かな近似線を予め作成することによって、さらに精度のよい水素濃度の測定が可能となる。 When the ambient temperature is 106 ° C. and the ultrasonic sound velocity is 402 m / s, the intersection of the graph is between the hydrogen concentration 2% and the hydrogen concentration 3%. The intersection is O, and the hydrogen concentration through O is 2%. A perpendicular line is drawn to an approximate line with a hydrogen concentration of 3%, and the intersecting points are defined as X and Y. When the distance from the point O to the points X and Y is a and b, the hydrogen concentration at the point O can be expressed as 2% + a / (a + b)%. In this example, it is represented by an approximate line in increments of 1%, but it is possible to measure the hydrogen concentration with higher accuracy by creating in advance a fine approximate line in increments of 1% → 0.1%.
この実施例2の処理内容をプログラム化して、システムに組み込んだものがガス濃度解析手段2e4である。 The gas concentration analysis means 2e4 is a program that incorporates the processing contents of the second embodiment and is incorporated in the system.
つぎに、その他のガスの濃度測定について説明する。 Next, concentration measurement of other gases will be described.
表1は、その他のガスの音速と温度に対する音速の変化率を表わしたものであるが、本実施例で説明した水素ガスが音速も早く、かつ音速の変化率も大きく、超音波によるガス濃度測定に適したガスといえる。 Table 1 shows the rate of change of sound speed with respect to the speed of sound and temperature of other gases. The hydrogen gas described in this example has a high sound speed and a large rate of change of sound speed. It can be said that the gas is suitable for measurement.
ただ、その他のガスについても、測定環境に併存するガスを制御する、いわゆる測定対象ガス以外のガスを排除する等を行うことによって、特定のガスに対する本発明によるガス濃度測定方法を利用することが可能である。例えば、エチレンの濃度測定を行いたい時には、類似の音速を持つエタン、メタノール等のガスが混合しないような環境とする等の配慮を行う。 However, for other gases, the gas concentration measurement method according to the present invention for a specific gas can be used by controlling the gas coexisting in the measurement environment, by excluding gases other than the so-called measurement target gas, etc. Is possible. For example, when it is desired to measure the ethylene concentration, consideration should be given to an environment in which gases such as ethane and methanol having similar sound speeds are not mixed.
以上説明した超音波によるガス濃度測定方法ならびにその装置によって、小型で、安価な、かつ、高精度で迅速なガス濃度測定が実現できる。
さらに、ガス濃度測定ならびにガス温度測定のいずれもが、超音波の音速の変化を検出して測定するものであるため、迅速な解析結果を得ることができるとともに、コンパクト化を容易化することができるため、例えば自動車や家庭用燃料電池への利用が容易にできる。さらに、これらの自動車や家庭用燃料電池には、制御装置としてPC、マイコン等の組み込みが通常であるため、PC、マイコン等に本発明の制御装置2の機能を組み込むことが容易に実現できる。
By the ultrasonic gas concentration measuring method and apparatus described above, it is possible to realize gas concentration measurement that is small, inexpensive, highly accurate, and rapid.
Furthermore, since both the gas concentration measurement and the gas temperature measurement are performed by detecting a change in the sound velocity of the ultrasonic wave, it is possible to obtain a quick analysis result and facilitate the compactization. Therefore, for example, it can be easily used for automobiles and household fuel cells. Furthermore, since these automobiles and household fuel cells usually incorporate a PC, a microcomputer or the like as a control device, it is easy to incorporate the function of the control device 2 of the present invention into the PC, the microcomputer or the like.
1…ガス濃度測定装置(測定装置)
2…制御装置
2a…制御部
2b…I/Oポート
2c…送信回路
2d…受信回路
2e…制御PRG(制御プログラム/記憶装置)
2f…入力部
2g…表示部
3…超音波センサ
4…温度測定用超音波振動子
4a…温度測定用反射波
4b…温度測定用金属棒
5…ガス濃度測定用超音波振動子
5a…一方向直進波
5b…ガス濃度測定用反射波
5c…ガス濃度測定用超音波振動子
5d…超音波反射用部材
L…第一の所定距離
l、lm…第二の所定距離
1 ... Gas concentration measuring device (measuring device)
2 ... Control device 2a ... Control unit 2b ... I / O port 2c ... Transmission circuit 2d ... Reception circuit 2e ... Control PRG (control program / storage device)
2f ... Input unit 2g ... Display unit 3 ... Ultrasonic sensor 4 ... Temperature measurement ultrasonic transducer 4a ... Temperature measurement reflected wave 4b ... Temperature measurement metal rod 5 ... Gas concentration measurement ultrasonic transducer 5a ... One direction Straight wave 5b ... Gas concentration measurement reflected wave 5c ... Gas concentration measurement ultrasonic transducer 5d ... Ultrasonic reflection member L ... First predetermined distance l, lm ... Second predetermined distance
Claims (6)
測定環境において発信させた超音波の、あらかじめ定められた第一の距離に対する伝播時間を測定することによって前記ガス濃度を特定するガス濃度測定工程と、
測定環境において発信させた超音波の、温度測定用金属棒中におけるあらかじめ定められた第二の距離に対する伝播時間を測定することによって前記温度を特定する温度測定工程と、
を有することを特徴とするガス濃度測定方法。 A gas concentration measurement method for measuring the gas concentration and temperature of a measurement environment by ultrasonic waves,
A gas concentration measurement step for determining the gas concentration by measuring a propagation time of a ultrasonic wave transmitted in a measurement environment with respect to a predetermined first distance;
A temperature measurement step of specifying the temperature by measuring a propagation time of a ultrasonic wave transmitted in a measurement environment with respect to a predetermined second distance in a metal rod for temperature measurement;
A gas concentration measuring method comprising:
ことを特徴とする請求項1に記載のガス濃度測定方法。 The gas is hydrogen, and the gas concentration is identified by comparing the measured propagation time with a propagation time for a predetermined hydrogen concentration,
The gas concentration measuring method according to claim 1.
測定環境において発信させた超音波の、あらかじめ定められた第一の距離に対する伝播時間を測定することによって前記ガス濃度を特定するガス濃度測定手段と、
測定環境において発信させた超音波の、温度測定用金属棒中におけるあらかじめ定められた第二の距離に対する伝播時間を測定することによって前記温度を特定する温度測定手段と、
を有することを特徴とするガス濃度測定装置。 A gas concentration measuring device that measures the gas concentration and temperature of a measurement environment by ultrasonic waves,
A gas concentration measuring means for determining the gas concentration by measuring a propagation time of a ultrasonic wave transmitted in a measurement environment with respect to a predetermined first distance;
Temperature measuring means for specifying the temperature by measuring the propagation time of the ultrasonic wave transmitted in the measurement environment to a predetermined second distance in the metal rod for temperature measurement;
A gas concentration measuring device comprising:
ことを特徴とする請求項4に記載のガス濃度測定装置。 The gas is hydrogen, and the gas concentration is identified by comparing the measured propagation time with a propagation time for a predetermined hydrogen concentration,
The gas concentration measuring apparatus according to claim 4.
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