JP2009103605A

JP2009103605A - Circuit and method for measuring gas concentration

Info

Publication number: JP2009103605A
Application number: JP2007276318A
Authority: JP
Inventors: Hiroteru Kato; 博照加藤; Hiromi Ishihara; 裕己石原
Original assignee: Yazaki Corp
Current assignee: Yazaki Corp
Priority date: 2007-10-24
Filing date: 2007-10-24
Publication date: 2009-05-14

Abstract

<P>PROBLEM TO BE SOLVED: To measure a wide range of concentration by a gas sensor. <P>SOLUTION: A circuit 10 for measuring gas concentration measures the concentration of a flammable gas by a bridge circuit 20 for low concentration, formed of: a gas concentration detecting element 40 reactive with the flammable gas; and a temperature compensation element 50 unreactive with the flammable gas the resistance value of which varies in response to the concentration of the flammable gas. When the concentration of the flammable gas exceeds a threshold value of a previously determined switching concentration, the gas concentration detecting element 40 and a referential resistor 25 are switched by a switching unit 26, and the concentration of the flammable gas is measured by configuring a bridge circuit 23 of the temperature compensation element 50 and the referential resistor 25. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

本発明は、可燃性ガスの濃度測定に用いられるガス濃度測定回路体及びガス濃度測定回路体で用いられる濃度測定方法に関する。 The present invention relates to a gas concentration measurement circuit body used for measuring the concentration of a combustible gas and a concentration measurement method used in the gas concentration measurement circuit body.

可燃性ガスの濃度測定においては、低濃度から高濃度までの広範囲にわたる濃度への対応が要請されている。その一方で、濃度測定に一般的に用いられる接触燃焼式ガスセンサにおいては、高精度の測定が可能であるものの、測定時に触媒によって測定対象ガスを燃焼（即ち、反応）させるので、測定対象ガスへの引火を避けるために、爆発下限界より低い濃度である低濃度領域での測定しかできず、また、熱伝導式ガスセンサにおいては、測定時に測定対象ガスが燃焼しないので広範囲の濃度測定が可能であるものの、分解能が低いために低濃度領域では十分な精度の測定ができず、これらの理由により、単一のガスセンサを備える回路体（即ち、ガスセンサユニット）では広範囲の濃度測定ができなかった。そして、この要請に対応するべく、ガスセンサユニットに低濃度領域用の接触燃焼式ガスセンサ、及び、高濃度領域用の熱伝導式ガスセンサを実装することで広範囲の濃度測定に対応した燃焼性ガス検知器が特許文献１において提案されている。
特開２００５−２０７８７９ In measuring the concentration of combustible gas, it is required to deal with a wide range of concentrations from low to high. On the other hand, the catalytic combustion type gas sensor generally used for concentration measurement can measure with high accuracy, but the measurement target gas is burned (that is, reacted) by the catalyst at the time of measurement. In order to avoid ignition, only measurements in the low concentration range, which is lower than the lower limit of explosion, can be performed, and in the heat conduction type gas sensor, the measurement target gas does not burn at the time of measurement, so a wide range of concentration measurement is possible. However, since the resolution is low, it is not possible to measure with sufficient accuracy in the low concentration region, and for these reasons, the circuit body (that is, the gas sensor unit) including a single gas sensor cannot measure concentration over a wide range. In order to meet this demand, a combustible gas detector capable of measuring a wide range of concentrations by mounting a catalytic combustion gas sensor for a low concentration region and a heat conduction gas sensor for a high concentration region in the gas sensor unit. Is proposed in Patent Document 1.
JP 2005-207879

しかしながら、特許文献１の燃焼性ガス検知器では、広範囲の濃度測定が可能であるものの、２つの異なるガスセンサを実装することから、部品数の増加による回路規模の増大及びコストの上昇という問題があった。 However, although the combustible gas detector of Patent Document 1 can measure a wide range of concentrations, since two different gas sensors are mounted, there is a problem that the circuit scale increases and the cost increases due to an increase in the number of components. It was.

したがって、本発明の目的は、複数のセンサを実装することなく、１つのガスセンサによって広範囲の濃度測定に対応可能なガス濃度測定回路体及びこのガス濃度測定回路体で用いられるガス濃度測定方法を提供することにある。 Therefore, an object of the present invention is to provide a gas concentration measuring circuit body that can handle a wide range of concentration measurements by one gas sensor without mounting a plurality of sensors, and a gas concentration measuring method used in the gas concentration measuring circuit body. There is to do.

上記課題を解決するためになされた請求項１に記載の発明は、可燃性ガスとの反応性があるガス濃度検知素子、及び、前記可燃性ガスとの反応性がない温度補償素子、を備え、前記ガス濃度検知素子と前記温度補償素子とを含むブリッジ回路の中間点電位差に基づいて前記可燃性ガスの濃度を測定するためのガス濃度測定回路体において、前記ガス濃度検知素子と切り替えることにより前記温度補償素子とともに高濃度用ブリッジ回路を形成するように配設された、前記可燃性ガスの濃度に応じて抵抗値が変化しない参照抵抗器と、前記ブリッジ回路の前記中間点電位差に基づいて測定した前記可燃性ガスの濃度が予め定められた切替濃度しきい値を超えたときに、前記温度補償素子と前記参照抵抗器とによって前記高濃度用ブリッジ回路を形成するように、前記ガス濃度検知素子を前記参照抵抗器に切り替えるための切替手段と、を有し、前記切替手段によって前記ガス濃度検知素子を前記参照抵抗器に切り替えたときに、前記高濃度用ブリッジ回路の中間点電位差に基づいて前記切替濃度しきい値を超える前記可燃性ガスの濃度測定が可能なように、前記温度補償素子が前記可燃性ガスの濃度に応じてその抵抗値を変化させる特性を有することを特徴とするガス濃度測定回路体である。 The invention according to claim 1, which has been made in order to solve the above problems, includes a gas concentration detection element that is reactive with a combustible gas, and a temperature compensation element that is not reactive with the combustible gas. In the gas concentration measurement circuit body for measuring the concentration of the combustible gas based on the midpoint potential difference of the bridge circuit including the gas concentration detection element and the temperature compensation element, by switching to the gas concentration detection element Based on the reference resistor disposed so as to form a high-concentration bridge circuit together with the temperature compensation element, the resistance value of which does not change according to the concentration of the combustible gas, and the intermediate point potential difference of the bridge circuit When the measured concentration of the combustible gas exceeds a predetermined switching concentration threshold value, the high-concentration bridge circuit is connected by the temperature compensation element and the reference resistor. Switching means for switching the gas concentration detection element to the reference resistor so that the high concentration when the gas concentration detection element is switched to the reference resistor by the switching means. The temperature compensation element changes its resistance value in accordance with the concentration of the combustible gas so that the concentration of the combustible gas exceeding the switching concentration threshold can be measured based on the potential difference of the intermediate point of the bridge circuit It is a gas concentration measuring circuit body characterized by having

請求項２に記載された発明は、請求項１に記載された発明において、前記切替手段が、前記高濃度ブリッジ回路によって測定された前記可燃性ガスの濃度が前記切替濃度しきい値以下になったときに、前記ガス濃度検知素子と前記温度補償素子とを含む前記ブリッジ回路を形成するように、前記参照抵抗器を前記ガス濃度検知素子に切り替えるための手段であることを特徴とするものである。 The invention described in claim 2 is the invention described in claim 1, wherein the switching means is configured such that the concentration of the combustible gas measured by the high concentration bridge circuit is equal to or less than the switching concentration threshold value. The reference resistor is a means for switching to the gas concentration detecting element so as to form the bridge circuit including the gas concentration detecting element and the temperature compensating element. is there.

請求項３に記載された発明は、可燃性ガスとの反応性があるガス濃度検知素子、及び、前記可燃性ガスとの反応性がなく且つ前記可燃性ガスの濃度に応じて抵抗値が変化する温度補償素子、を備え、前記ガス濃度検知素子と前記温度補償素子とを含むブリッジ回路の中間点電位差に基づいて前記可燃性ガスの濃度測定を行い、そして、前記ガス濃度検知素子と切り替えることにより前記温度補償素子とともに高濃度用ブリッジ回路を形成するように配設され且つ前記可燃性ガスの濃度に応じて抵抗値が変化しない参照抵抗器を、さらに備えたガス濃度測定回路体において用いられるガス濃度測定方法であって、前記ブリッジ回路の前記中間点電位差に基づいて前記可燃性ガスの濃度を測定する第１工程と、前記第１工程で測定した前記可燃性ガスの濃度が予め定められた切替濃度しきい値を超えたときに、前記温度補償素子と前記参照抵抗器とを含む前記高濃度用ブリッジ回路を形成するように、前記ガス濃度検知素子を前記参照抵抗器に切り替える第２工程と、前記高濃度用ブリッジ回路の中間点電位差に基づいて、前記切替濃度しきい値を超える前記可燃性ガスの濃度を測定する第３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。 The invention described in claim 3 is a gas concentration detecting element that is reactive with a combustible gas, and has no reactivity with the combustible gas, and the resistance value changes according to the concentration of the combustible gas. A temperature compensation element for measuring the concentration of the combustible gas based on a midpoint potential difference of a bridge circuit including the gas concentration detection element and the temperature compensation element, and switching to the gas concentration detection element. Is used in a gas concentration measurement circuit body further provided with a reference resistor which is arranged so as to form a high-concentration bridge circuit together with the temperature compensation element and whose resistance value does not change according to the concentration of the combustible gas. A gas concentration measurement method comprising: a first step of measuring a concentration of the combustible gas based on the intermediate point potential difference of the bridge circuit; and the combustibility measured in the first step. When the concentration of gas exceeds a predetermined switching concentration threshold value, the gas concentration detecting element is arranged to form the high concentration bridge circuit including the temperature compensating element and the reference resistor. A second step of switching to a reference resistor, and a third step of measuring a concentration of the combustible gas exceeding the switching concentration threshold based on a midpoint potential difference of the high concentration bridge circuit. This is a characteristic gas concentration measurement method.

請求項１に記載された発明によれば、可燃性ガスの濃度が予め定められた切替濃度しきい値を超えたときに、可燃性ガスとの反応性がない温度補償素子と参照抵抗器とを含む高濃度用ブリッジ回路によって可燃性ガスの濃度測定を行うことから、例えば、切替濃度しきい値を可燃性ガスの爆発下限界より小さく設定することで、可燃性ガスの濃度がその爆発下限界濃度以上の範囲にあるときでも、可燃性ガスを爆発させることなくその濃度測定を行うことができる。そのため、複数のセンサを実装することなく、１組のガスセンサによって、広範囲の濃度測定を行うことができ、部品数の増加による回路規模の増大及びコストの上昇を回避することができる。 According to the invention described in claim 1, when the concentration of the combustible gas exceeds a predetermined switching concentration threshold value, the temperature compensation element and the reference resistor that are not reactive with the combustible gas, Because the concentration of flammable gas is measured by a high concentration bridge circuit containing, for example, by setting the switching concentration threshold value to be lower than the lower limit of flammable gas explosion, Even when the concentration is within the limit concentration range, the concentration measurement can be performed without causing the flammable gas to explode. Therefore, it is possible to measure a wide range of concentrations with one set of gas sensors without mounting a plurality of sensors, and to avoid an increase in circuit scale and cost due to an increase in the number of components.

請求項２に記載された発明によれば、請求項１に記載された発明の効果に加えて、可燃性ガスの濃度が予め定められた切替濃度しきい値以下になったときに、ガス濃度検知素子と温度補償素子とを含むブリッジ回路によって可燃性ガスの濃度測定を行うことから、例えば、可燃性ガスの濃度が切替濃度しきい値を超えたあと、該切替濃度しきい値以下に戻ったときに、再度、ガス濃度検知素子による可燃性ガスの濃度測定を行うことができるため、ガス濃度検知素子及び温度補償素子それぞれに適した濃度範囲の測定を行うことができる。 According to the invention described in claim 2, in addition to the effect of the invention described in claim 1, when the concentration of the combustible gas becomes equal to or lower than a predetermined switching concentration threshold, the gas concentration Since the concentration of the combustible gas is measured by the bridge circuit including the detection element and the temperature compensation element, for example, after the combustible gas concentration exceeds the switching concentration threshold, it returns to the switching concentration threshold or less. Since the concentration measurement of the combustible gas can be performed again by the gas concentration detection element, the concentration range suitable for each of the gas concentration detection element and the temperature compensation element can be measured.

請求項３に記載された発明によれば、ブリッジ回路の中間点電圧に基づいて測定した可燃性ガスの濃度が切替濃度しきい値を超えたときに、温度補償素子と参照抵抗器とを含む高濃度用ブリッジ回路を形成し、可燃性ガスとの反応性がない温度補償素子及び参照抵抗器からなる高濃度用ブリッジ回路によって可燃性ガスの濃度測定を行うことから、例えば、切替濃度しきい値を可燃性ガスの爆発下限界より小さく設定することで、可燃性ガスの濃度がその爆発下限界濃度以上の範囲にあるときでも、可燃性ガスを爆発させることなくその濃度測定を行うことができる。そのため、複数のセンサを実装することなく、１組のガスセンサによって、広範囲の濃度測定を行うことができる。 According to the invention described in claim 3, when the concentration of the combustible gas measured based on the midpoint voltage of the bridge circuit exceeds the switching concentration threshold, the temperature compensation element and the reference resistor are included. Since the concentration circuit of the combustible gas is measured by the high concentration bridge circuit including the temperature compensation element and the reference resistor which is not reactive with the combustible gas and forms the high concentration bridge circuit, for example, the switching concentration threshold is set. By setting the value smaller than the lower limit of flammable gas explosion, even when the concentration of flammable gas is in the range of the lower limit of flammable gas concentration, the concentration can be measured without detonating the flammable gas. it can. Therefore, a wide range of concentration measurements can be performed by a set of gas sensors without mounting a plurality of sensors.

以下、本発明に係るガス濃度測定回路体を備えた水素ガス用ガス漏れ警報器の一実施形態について、図１〜図５の図面を参照して以下に説明する。 Hereinafter, an embodiment of a gas leak alarm for hydrogen gas equipped with a gas concentration measuring circuit according to the present invention will be described with reference to the drawings of FIGS.

水素ガス用ガス漏れ警報器（以下、警報器）１は、水素ガス（請求項の可燃性ガスに相当）の濃度を測定してそれを表示し、また、水素濃度が予め定められた警報濃度を超えたときに利用者に対して警報を行う装置であり、図１に示すように、ガスセンサユニット１０と、制御装置６０と、を備えている。 A gas leak alarm device for hydrogen gas (hereinafter referred to as an alarm device) 1 measures the concentration of hydrogen gas (corresponding to the combustible gas in the claims) and displays it, and an alarm concentration with a predetermined hydrogen concentration. Is a device that issues a warning to the user when the value exceeds, and includes a gas sensor unit 10 and a control device 60 as shown in FIG.

ガスセンサユニット１０は、請求項のガス濃度測定回路体に相当し、固定抵抗器２１、固定抵抗器２２、参照抵抗器２５と、切替スイッチ２６と、センサ部３０と、が実装された数ｃｍ角程度の既存の小形プリント基板である。なお、ガスセンサユニット１０は、本発明に係る回路が実現できるものであれば、プリント基板以外のものを用いてもよく、そのサイズも任意である。 The gas sensor unit 10 corresponds to the gas concentration measurement circuit body of the claims, and is a several cm square in which the fixed resistor 21, the fixed resistor 22, the reference resistor 25, the changeover switch 26, and the sensor unit 30 are mounted. It is an existing small-sized printed circuit board. In addition, as long as the circuit which concerns on this invention is realizable, things other than a printed circuit board may be used for the gas sensor unit 10, and the size is also arbitrary.

また、ガスセンサユニット１０は、切替スイッチ２６によって互いに切替可能な低濃度用ブリッジ回路２０及び高濃度用ブリッジ回路２３を備えている。 Further, the gas sensor unit 10 includes a low concentration bridge circuit 20 and a high concentration bridge circuit 23 that can be switched to each other by the changeover switch 26.

低濃度用ブリッジ回路２０は、請求項のブリッジ回路に相当し、固定抵抗器２１、２２、と、センサ部３０が備えるガス濃度検知素子４０及び温度補償素子５０と、によって構成された、既知のホイートストンブリッジ回路である。 The low-concentration bridge circuit 20 corresponds to the bridge circuit of the claims, and is configured by fixed resistors 21 and 22, and a gas concentration detection element 40 and a temperature compensation element 50 provided in the sensor unit 30. Wheatstone bridge circuit.

高濃度用ブリッジ回路２３は、固定抵抗器２１、２２と、センサ部３０が備える温度補償素子５０と、参照抵抗器２５と、によって構成された、既知のホイートストンブリッジ回路である。つまり、低濃度用ブリッジ回路２０と高濃度用ブリッジ回路２３とでは、ガス濃度検知素子４０及び参照抵抗器２５以外の部品を共用しており、切替スイッチ２６によってガス濃度検知素子４０と参照抵抗器２５とを切り替えることにより、低濃度用ブリッジ回路２０と高濃度用ブリッジ回路２３とを切り替えている。 The high-concentration bridge circuit 23 is a known Wheatstone bridge circuit configured by fixed resistors 21 and 22, a temperature compensation element 50 provided in the sensor unit 30, and a reference resistor 25. That is, the low concentration bridge circuit 20 and the high concentration bridge circuit 23 share components other than the gas concentration detection element 40 and the reference resistor 25, and the gas concentration detection element 40 and the reference resistor are switched by the changeover switch 26. 25, the low concentration bridge circuit 20 and the high concentration bridge circuit 23 are switched.

固定抵抗器２１及び固定抵抗器２２は、例えば、既存の表面実装タイプの小形固定抵抗器が用いられ、また、本実施形態において、固定抵抗器２１及び固定抵抗器２２には、抵抗値が同値のものが用いられている。なお、固定抵抗器２１及び固定抵抗器２２の少なくとも一方を可変抵抗器とし、若しくは、固定抵抗器２１及び固定抵抗器２２の少なくとも一方に直列に可変抵抗器を接続し、その抵抗値を変化させて、各ブリッジ回路のゼロ点調整に用いてもよく、また、表面実装タイプ以外の抵抗器を用いてもよい。 As the fixed resistor 21 and the fixed resistor 22, for example, an existing surface mount type small fixed resistor is used, and in this embodiment, the fixed resistor 21 and the fixed resistor 22 have the same resistance value. Is used. Note that at least one of the fixed resistor 21 and the fixed resistor 22 is a variable resistor, or at least one of the fixed resistor 21 and the fixed resistor 22 is connected in series, and the resistance value is changed. Thus, it may be used for the zero point adjustment of each bridge circuit, or a resistor other than the surface mount type may be used.

センサ部３０は、例えば、ＭＥＭＳ（ＭｉｃｒｏＥｌｅｃｔｒｏＭｅｃｈａｎｉｃａｌＳｙｓｔｅｍ (微小電子機械システム)）技術を用いて、超小型に形成された１辺数ｍｍの接触燃焼式ガスセンサであり、水素と反応して生じる燃焼熱に応じてその濃度を測定するためのガス濃度検知素子４０と、ガス濃度検知素子４０の温度補償を行うための温度補償素子５０と、を有している。 The sensor unit 30 is, for example, a contact combustion type gas sensor having a side of several millimeters and formed by using a micro electro mechanical system (MEMS) technology, and is generated by reacting with hydrogen. A gas concentration detecting element 40 for measuring the concentration in response to heat and a temperature compensating element 50 for performing temperature compensation of the gas concentration detecting element 40 are provided.

また、センサ部３０は、図２に示すように、所定の結晶方位を有するシリコン単結晶からなり且つ異方性エッチングにより形成された凹部３１ａ、３１ｂを有するシリコン基板３１と、シリコン基板３１の上面部に順次積層して形成された二酸化シリコン層３２、窒化シリコン層３３、酸化ハフニウム層３４と、で構成され、そして、ガス濃度検知素子４０と温度補償素子５０とが、熱容量を小さくして感度を向上させるために設けられた凹部３１ａ、３１ｂの上部に位置する二酸化シリコン層３２、窒化シリコン層３３、酸化ハフニウム層３４とからなる薄膜状のダイヤフラム３５ａ、３５ｂの上面部に配設されている。 Further, as shown in FIG. 2, the sensor unit 30 includes a silicon substrate 31 having recesses 31 a and 31 b made of silicon single crystal having a predetermined crystal orientation and formed by anisotropic etching, and an upper surface of the silicon substrate 31. The silicon dioxide layer 32, the silicon nitride layer 33, and the hafnium oxide layer 34, which are sequentially stacked on each other, are configured, and the gas concentration detecting element 40 and the temperature compensating element 50 have a reduced heat capacity and sensitivity. Are disposed on the upper surface of thin film diaphragms 35a and 35b comprising a silicon dioxide layer 32, a silicon nitride layer 33, and a hafnium oxide layer 34 positioned above the recesses 31a and 31b. .

ガス濃度検知素子４０は、水素ガス中に置かれ、通電により発熱することで自身が備える触媒が水素と反応し、その反応熱に応じて抵抗値が変化する接触燃焼式センサ素子であり、図２に示すように、検知ヒータ部４１と、触媒焼結体４２と、からなる。 The gas concentration detection element 40 is a contact combustion type sensor element that is placed in hydrogen gas and generates heat when energized so that the catalyst provided therein reacts with hydrogen and the resistance value changes according to the reaction heat. As shown in FIG. 2, the detection heater unit 41 and the catalyst sintered body 42 are included.

検知ヒータ部４１は、スパッタリングによって酸化ハフニウム層３４の上面部に形成された白金層を、フォトリソグラフ及びエッチングにより型抜きして形成された抵抗体であり、つづら折れ状に形成された測温部４１ａ、及び、検知ヒータ部４１を低濃度用ブリッジ回路２０に接続するための端子４１ｂ、４１ｃとからなる。そして、通電されることにより発熱してその周囲を覆う触媒焼結体４２を加熱するものであり、また、熱により自らの抵抗値が変化する性質を有している。なお、本実施形態では、検知ヒータ部４１の材料として白金を用いているが、これに限定するものではなく、例えば、タングステンなどの、抵抗温度係数が大きく、高温まで安定な金属又は化合物であればどのようなものを用いても良い。 The detection heater unit 41 is a resistor formed by punching a platinum layer formed on the upper surface portion of the hafnium oxide layer 34 by sputtering by photolithography and etching, and is a temperature measuring unit formed in a zigzag shape. 41 a and terminals 41 b and 41 c for connecting the detection heater unit 41 to the low concentration bridge circuit 20. The catalyst sintered body 42 that generates heat when energized and covers the periphery thereof is heated, and has a property that its own resistance value changes due to heat. In this embodiment, platinum is used as the material of the detection heater unit 41. However, the present invention is not limited to this. For example, a metal or a compound having a large resistance temperature coefficient and stable to a high temperature, such as tungsten. Any type may be used.

触媒焼結体４２は、パラジウム合金からなる触媒を担持したアルミナ粉体のペーストを、測温部４１ａに覆い被せるように半球状に配設したのち、７００℃程度の熱で焼成して形成したものであり、検知ヒータ部４１によって加熱され、水素と接触することによって、接触した水素を燃焼（即ち、反応）させるものである。そして、この燃焼による熱によって、検知ヒータ部４１の抵抗値が、可燃性ガスの濃度に応じて変化する。 The catalyst sintered body 42 is formed by placing a paste of alumina powder carrying a catalyst made of a palladium alloy in a hemispherical shape so as to cover the temperature measuring portion 41a, and then firing it with heat of about 700 ° C. It is heated by the detection heater unit 41 and brought into contact with hydrogen, whereby the contacted hydrogen is combusted (that is, reacted). And the resistance value of the detection heater part 41 changes with the heat | fever by this combustion according to the density | concentration of combustible gas.

温度補償素子５０は、ガス濃度検知素子４０と同様に水素ガス中に置かれて通電されることで、ガス濃度検知素子４０の温度補償を行うための素子であり、つまり、ガス濃度検知素子４０の有する触媒による燃焼熱に応じた抵抗値の変化分のみ取り出すために用いられる。温度補償素子５０は、図２に示すように、補償ヒータ部５１と、焼結体５２と、からなる。 The temperature compensation element 50 is an element for performing temperature compensation of the gas concentration detection element 40 by being placed in hydrogen gas and energized in the same manner as the gas concentration detection element 40, that is, the gas concentration detection element 40. Is used to extract only the change in resistance value corresponding to the combustion heat generated by the catalyst of the catalyst. As shown in FIG. 2, the temperature compensation element 50 includes a compensation heater portion 51 and a sintered body 52.

補償ヒータ部５１は、検知ヒータ部４１と同一の構成になるように形成されており、スパッタリングによって酸化ハフニウム層３４の上面部に形成された白金層を、フォトリソグラフ及びエッチングにより型抜きして形成された抵抗体であり、つづら折れ状に形成された測温部５１ａ、及び、補償ヒータ部５１を低濃度用ブリッジ回路２０（又は、高濃度用ブリッジ回路２３）に接続するための端子５１ｂ、５１ｃとからなる。そして、通電されることにより発熱してその周囲を覆う焼結体５２を加熱するものであり、また、熱により自らの抵抗値が変化する性質を有している。 The compensation heater unit 51 is formed to have the same configuration as the detection heater unit 41, and is formed by die-cutting a platinum layer formed on the upper surface portion of the hafnium oxide layer 34 by sputtering by photolithography and etching. A temperature measuring unit 51a that is formed in a folded shape, and a terminal 51b for connecting the compensation heater unit 51 to the low concentration bridge circuit 20 (or the high concentration bridge circuit 23), 51c. And when it supplies with electricity, it heats and heats the sintered compact 52 which covers the circumference | surroundings, and it has the property that own resistance value changes with heat.

焼結体５２は、アルミナ粉体のペーストを、測温部５１ａに覆い被せるように半球状に配設したのち、７００℃程度の熱で焼成して形成したものであり、補償ヒータ部５１によって加熱されるものである。そして、焼結体５２においては、触媒を有しないため、触媒反応による水素の燃焼が生じない。 The sintered body 52 is formed by placing a paste of alumina powder in a hemispherical shape so as to cover the temperature measuring unit 51 a and then firing it with heat of about 700 ° C. It is to be heated. And since the sintered compact 52 does not have a catalyst, the combustion of hydrogen by a catalytic reaction does not arise.

なお、温度補償素子５０は、温度補償の精度を高めるため、焼結体５２が水素と反応する触媒を有していないこと以外はガス濃度検知素子４０と材料及び形状が同一にされている。つまり、水素（ガス濃度検知素子４０の触媒に反応するガス）が含まれない雰囲気中で、ガス濃度検知素子４０と温度補償素子５０とに同様に電圧を印加したとき、それぞれの触媒焼結体４２及び焼結体５２の表面温度が同一になる。また、温度補償素子５０は、水素濃度に応じて発熱が奪われることによりその抵抗値が変化する特性を有する、熱伝導式センサ素子としても動作する。また、本実施形態では、触媒焼結体４２及び焼結体５２を半球状としているが、この形状に限定するものではなく、例えば、立方体や平板形状など、触媒焼結体４２と焼結体５２とが同じ形で、且つ、測温部４１ａ、５１ａ上に配置されているものであれば、それら形状は任意である。 The temperature compensation element 50 has the same material and shape as the gas concentration detection element 40 except that the sintered body 52 does not have a catalyst that reacts with hydrogen in order to increase the accuracy of temperature compensation. That is, when a voltage is similarly applied to the gas concentration detection element 40 and the temperature compensation element 50 in an atmosphere that does not contain hydrogen (a gas that reacts with the catalyst of the gas concentration detection element 40), the respective sintered catalyst bodies 42 and the sintered body 52 have the same surface temperature. Further, the temperature compensation element 50 also operates as a heat conduction sensor element having a characteristic that its resistance value changes due to deprivation of heat according to the hydrogen concentration. In the present embodiment, the catalyst sintered body 42 and the sintered body 52 are hemispherical. However, the present invention is not limited to this shape. For example, the catalyst sintered body 42 and the sintered body such as a cube or a flat plate shape may be used. If 52 is the same shape and it is arrange | positioned on the temperature measuring parts 41a and 51a, those shapes are arbitrary.

参照抵抗器２５は、例えば、固定抵抗器２１、２２と同様の既存の表面実装タイプの固定抵抗器が用いられており、切替スイッチ２６によってガス濃度検知素子４０と切り替えられることにより高濃度用ブリッジ回路２３を構成するものである。また、参照抵抗器２５は、水素と反応せず、温度によって抵抗値が変化しないので、ガス濃度検知素子４０及び温度補償素子５０とともに水素ガス中に置かれても、水素ガスに引火することなく、濃度測定に悪影響を与える特性の変化もない。 As the reference resistor 25, for example, an existing surface mount type fixed resistor similar to the fixed resistors 21 and 22 is used, and the reference resistor 25 is switched to the gas concentration detecting element 40 by the changeover switch 26, thereby being a high concentration bridge. The circuit 23 is configured. Further, since the reference resistor 25 does not react with hydrogen and does not change its resistance value depending on the temperature, even if it is placed in hydrogen gas together with the gas concentration detecting element 40 and the temperature compensating element 50, it does not ignite the hydrogen gas. Also, there is no change in properties that adversely affects concentration measurement.

切替スイッチ２６は、請求項の切替手段に相当し、制御装置６０からの切替要求信号Ｓに応じて、ガス濃度検知素子４０と参照抵抗器２５とを切り替えるものであり、端子ａ−ｂ間を接続したときはガス濃度検知素子４０と温度補償素子５０による低濃度用ブリッジ回路２０を構成し、端子ａ−ｃ間を接続したときは温度補償素子５０と参照抵抗器２５とによる高濃度用ブリッジ回路２３を構成する、既存の単極双投型アナログスイッチである。 The change-over switch 26 corresponds to the change-over means in the claims, and switches the gas concentration detection element 40 and the reference resistor 25 in accordance with the change request signal S from the control device 60, and connects between the terminals a and b. When connected, the low concentration bridge circuit 20 is constituted by the gas concentration detection element 40 and the temperature compensation element 50, and when connected between the terminals ac, the high concentration bridge is formed by the temperature compensation element 50 and the reference resistor 25. This is an existing single-pole double-throw analog switch constituting the circuit 23.

低濃度用ブリッジ回路２０は、ガス濃度検知素子４０と固定抵抗器２１とが、端子ａ−ｂ間を接続した切替スイッチ２６を介して直列に接続され、これらに対して並列になるように、温度補償素子５０と固定抵抗器２２とが直列に接続され、そして、固定抵抗器２１と固定抵抗器２２との接続部Ｐ１が電圧印加部６８に接続され、ガス濃度検知素子４０と温度補償素子５０との接続部Ｐ２が接地電位ＧＮＤに接続されて構成されている。そして、低濃度用ブリッジ回路２０は、接触燃焼式の濃度測定回路として動作し、切替スイッチ２６と固定抵抗器２１との接続部Ｐ３、及び、温度補償素子５０と固定抵抗器２２との接続部Ｐ４、との電位差（即ち、中間点電位差）Ｖｄを、水素ガスの濃度に応じて出力する。 In the low concentration bridge circuit 20, the gas concentration detection element 40 and the fixed resistor 21 are connected in series via a changeover switch 26 connecting the terminals a and b, and are parallel to these. The temperature compensation element 50 and the fixed resistor 22 are connected in series, and the connection portion P1 between the fixed resistor 21 and the fixed resistor 22 is connected to the voltage application unit 68, and the gas concentration detection element 40 and the temperature compensation element are connected. 50 is connected to the ground potential GND. The low concentration bridge circuit 20 operates as a contact combustion type concentration measurement circuit, and includes a connection portion P3 between the changeover switch 26 and the fixed resistor 21, and a connection portion between the temperature compensation element 50 and the fixed resistor 22. A potential difference (that is, an intermediate point potential difference) Vd from P4 is output according to the concentration of hydrogen gas.

高濃度用ブリッジ回路２３は、参照抵抗器２５と固定抵抗器２１とが、端子ａ−ｃ間を接続した切替スイッチ２６を介して直列に接続され、これらに対して並列になるように、温度補償素子５０と固定抵抗器２２とが直列に接続され、そして、固定抵抗器２１と固定抵抗器２２との接続部Ｐ１が電圧印加部６８に接続され、参照抵抗器２５と温度補償素子５０との接続部Ｐ２が接地電位ＧＮＤに接続されて構成されている。そして、高濃度用ブリッジ回路２３は、熱伝導式の濃度測定回路として動作し、切替スイッチ２６と固定抵抗器２１との接続部Ｐ３、及び、温度補償素子５０と固定抵抗器２２との接続部Ｐ４、との電位差（即ち、中間点電位差）Ｖｄを、水素ガスの濃度に応じて出力する。 In the high-concentration bridge circuit 23, the reference resistor 25 and the fixed resistor 21 are connected in series via a changeover switch 26 that connects between the terminals ac, and the temperature is adjusted so as to be parallel to these. The compensation element 50 and the fixed resistor 22 are connected in series, and the connection portion P1 between the fixed resistor 21 and the fixed resistor 22 is connected to the voltage application unit 68, and the reference resistor 25, the temperature compensation element 50, The connection portion P2 is connected to the ground potential GND. The high-concentration bridge circuit 23 operates as a heat conduction type concentration measurement circuit, and includes a connection portion P3 between the changeover switch 26 and the fixed resistor 21, and a connection portion between the temperature compensation element 50 and the fixed resistor 22. A potential difference (that is, an intermediate point potential difference) Vd from P4 is output according to the concentration of hydrogen gas.

制御装置６０は、マイクロコンピュータ（ＭＰＵ）６１と、表示部６６と、警報部６７と、電圧印加部６８と、を備えている。 The control device 60 includes a microcomputer (MPU) 61, a display unit 66, an alarm unit 67, and a voltage application unit 68.

ＭＰＵ６１は、周知のように、予め定められたプログラムに従って各種の処理や制御などを行う中央演算処理装置（ＣＰＵ）６２と、ＣＰＵ６２のためのプログラム及び制御データ等を格納した読み出し専用のメモリであるＲＯＭ６３と、各種のデータを格納するとともにＣＰＵ６２の処理作業に必要なエリアを有する読み出し書き込み自在のメモリであるＲＡＭ６４と、低濃度用ブリッジ回路２０及び高濃度用ブリッジ回路２３の中間点電位差Ｖｄを計測するために接続部Ｐ３及び接続部Ｐ４の電圧が入力されるＡ／Ｄ変換器並びに切替スイッチ２６及び電圧印加部６８の制御信号を送出する出力ポート等を備えるＩ／Ｏ部（図示なし）と、からなる。また、ＲＯＭ６３には、制御データとして、切替スイッチ２６を切り替える条件である切替濃度しきい値、濃度異常を警報する異常濃度しきい値、及び、中間点電位差Ｖｄから水素濃度を求めるための濃度変換テーブル等が格納される。また、ＭＰＵ６１は、Ｉ／Ｏ部に接続された表示部６６、警報部６７、及び、電圧印加部６８、との間で制御信号等の入出力を行う。 As is well known, the MPU 61 is a central processing unit (CPU) 62 that performs various processes and controls in accordance with a predetermined program, and a read-only memory that stores programs, control data, and the like for the CPU 62. Measures the midpoint potential difference Vd between the ROM 63, the RAM 64, which stores various data, and has an area necessary for the processing operation of the CPU 62, and the low concentration bridge circuit 20 and the high concentration bridge circuit 23. And an I / O converter (not shown) including an A / D converter to which the voltages of the connection part P3 and the connection part P4 are input, an output port for sending control signals of the changeover switch 26 and the voltage application part 68, and the like. It consists of. Further, the ROM 63 stores, as control data, a switching concentration threshold that is a condition for switching the changeover switch 26, an abnormal concentration threshold that warns of concentration abnormality, and a concentration conversion for obtaining a hydrogen concentration from the intermediate point potential difference Vd. Stores tables and the like. The MPU 61 inputs and outputs control signals and the like with the display unit 66, the alarm unit 67, and the voltage application unit 68 connected to the I / O unit.

そして、制御装置６０のＣＰＵ６２は、ＲＯＭ６３に格納されたプログラムに基づいて、低濃度用ブリッジ回路２０及び高濃度用ブリッジ回路２３の中間点電位差Ｖｄからガス濃度を求める濃度測定手段、濃度測定手段が測定した濃度とＲＯＭ６３に格納された切替濃度しきい値とを比較判定する濃度判定手段、及び、濃度判定手段の判定に基づいて切替スイッチ２６を切り替えるスイッチ切替手段、として動作するものである。 Then, the CPU 62 of the control device 60 has concentration measuring means and concentration measuring means for obtaining a gas concentration from the midpoint potential difference Vd between the low concentration bridge circuit 20 and the high concentration bridge circuit 23 based on a program stored in the ROM 63. It operates as a density determination means for comparing the measured density with the switching density threshold value stored in the ROM 63, and a switch switching means for switching the changeover switch 26 based on the determination of the density determination means.

表示部６６は、利用者に対して濃度情報を表示するための部位であり、例えば、英数字表示を行うための既存のキャラクタ表示ＬＣＤ等が用いられ、ＭＰＵ６１のＩ／Ｏ部に接続されることにより、ＣＰＵ６２から送出されるガス濃度を示す信号に応じて、利用者がガス濃度を視認できるように、ガス濃度を数値表示するものである。 The display unit 66 is a part for displaying density information to the user. For example, an existing character display LCD or the like for displaying alphanumeric characters is used and connected to the I / O unit of the MPU 61. Thus, the gas concentration is numerically displayed so that the user can visually recognize the gas concentration according to the signal indicating the gas concentration sent from the CPU 62.

警報部６７は、利用者に対して危険を警報するための部位であり、例えば、既存の圧電ブザー等が用いられ、ＭＰＵ６１のＩ／Ｏ部に接続されることにより、ＣＰＵ６２から送出される危険濃度に達したことを示す信号に応じて、利用者に対して、水素濃度が危険濃度に達したことを警報する警報音を鳴動するものである。なお、警報部６７として、警報音を鳴動するブザー等以外にも、例えば、警報メッセージが格納された音声ＩＣ及び該警報メッセージを出力するスピーカ等で構成された、音声により危険濃度を通知する音声警報ユニット等を用いてもよい。 The alarm unit 67 is a part for alarming the danger to the user. For example, an existing piezoelectric buzzer or the like is used and connected to the I / O unit of the MPU 61, so that the danger sent from the CPU 62 In response to a signal indicating that the concentration has been reached, an alarm sound is issued to warn the user that the hydrogen concentration has reached a dangerous concentration. In addition to the buzzer that sounds an alarm sound, the alarm unit 67 includes, for example, an audio IC that stores an alarm message, a speaker that outputs the alarm message, and the like that notifies the dangerous concentration by audio. An alarm unit or the like may be used.

電圧印加部６８は、低濃度用ブリッジ回路２０及び高濃度用ブリッジ回路２３に対して、濃度測定に適切な電圧を印加するための部位であり、例えば、制御装置６０の動作電源とは異なる直流電源、及び、該直流電源を低濃度用ブリッジ回路２０及び高濃度用ブリッジ回路２３に接続又は切断するためのパワーＭＯＳＦＥＴ等で構成されている。また、電圧印加部６８は、ＭＰＵ６１から送出される制御信号に基づいて、低濃度用ブリッジ回路２０に対して、ガス濃度検知素子４０及び温度補償素子５０を約４００℃に加熱する直流電圧を印加し、高濃度用ブリッジ回路２３に対しても、上記と同様に、温度補償素子を約４００℃に加熱する直流電圧を印加する。なお、適切な濃度測定が可能であれば、各ブリッジ回路に印加する電圧は、例えば、パルス電圧等の直流電圧以外であってもよく、また、電圧値およびその出力間隔（パルス電圧等のとき）等は、ガス濃度検知素子４０及び温度補償素子５０の駆動温度が、対象ガスが燃焼する温度以上になるものであればよい。 The voltage application unit 68 is a part for applying a voltage suitable for concentration measurement to the low concentration bridge circuit 20 and the high concentration bridge circuit 23, and is, for example, a direct current different from the operation power supply of the control device 60. The power source is composed of a power MOSFET for connecting or disconnecting the DC power source to the low concentration bridge circuit 20 and the high concentration bridge circuit 23. The voltage application unit 68 applies a DC voltage that heats the gas concentration detection element 40 and the temperature compensation element 50 to about 400 ° C. to the low concentration bridge circuit 20 based on a control signal sent from the MPU 61. The DC voltage for heating the temperature compensation element to about 400 ° C. is also applied to the high concentration bridge circuit 23 as described above. If an appropriate concentration measurement is possible, the voltage applied to each bridge circuit may be other than a DC voltage such as a pulse voltage, for example, and the voltage value and its output interval (when a pulse voltage or the like is used). And the like, as long as the driving temperatures of the gas concentration detecting element 40 and the temperature compensating element 50 are equal to or higher than the temperature at which the target gas burns.

次に、上述した制御装置６０のＣＰＵ６２が実行する本発明に係る接続切替処理の一例を、図４に示すフローチャートを参照して説明する。 Next, an example of the connection switching process according to the present invention executed by the CPU 62 of the control device 60 described above will be described with reference to the flowchart shown in FIG.

警報器１の電源が投入されると、所定の初期化処理が実行され、その初期化処理の一つとして、濃度不明の状態でのガス濃度検知素子４０の使用による水素ガスの引火を回避するため、水素と反応しない高濃度用ブリッジ回路２３を構成するように、切替スイッチ２６に対して切替要求信号Ｓを送出する処理が行われる。また、水素濃度が、事前に切替濃度しきい値以下であることが判明しているときは、低濃度用ブリッジ回路２０を構成するように、切替スイッチ２６に対して切替要求信号Ｓを送出してもよい。そして、初期化処理完了後にステップＳ１１０に進む。 When the power of the alarm device 1 is turned on, a predetermined initialization process is executed, and as one of the initialization processes, the ignition of hydrogen gas due to the use of the gas concentration detection element 40 in the state of unknown concentration is avoided. Therefore, a process of sending the switching request signal S to the changeover switch 26 is performed so as to constitute the high concentration bridge circuit 23 that does not react with hydrogen. When the hydrogen concentration is known in advance to be equal to or lower than the switching concentration threshold value, a switching request signal S is sent to the changeover switch 26 so as to constitute the low concentration bridge circuit 20. May be. Then, after the initialization process is completed, the process proceeds to step S110.

ステップＳ１１０では、Ａ／Ｄ変換器によって数値情報に変換された接続部Ｐ３及び接続部Ｐ４の電圧から、それら電圧の差分である中間点電位差Ｖｄを求め、中間点電位差Ｖｄをインデックスとして、ＲＯＭ６３に格納されている濃度変換テーブルから濃度情報を取得する。そして、ステップＳ１２０に進む。 In step S110, the intermediate point potential difference Vd, which is the difference between these voltages, is obtained from the voltages of the connection part P3 and the connection part P4 converted into numerical information by the A / D converter, and the intermediate point potential difference Vd is used as an index in the ROM 63. Density information is acquired from the stored density conversion table. Then, the process proceeds to step S120.

ステップＳ１２０では、ステップＳ１１０で取得した濃度情報と、ＲＯＭ６３に格納されている切替濃度しきい値とを比較し、濃度情報が切替濃度しきい値を超えている場合はステップＳ１３０に進み（Ｓ１２０でＹ）、濃度情報が切替濃度しきい値以下である場合はステップＳ１５０に進む（Ｓ１２０でＮ）。 In step S120, the density information acquired in step S110 is compared with the switching density threshold stored in the ROM 63. If the density information exceeds the switching density threshold, the process proceeds to step S130 (in S120). Y) If the density information is less than or equal to the switching density threshold value, the process proceeds to step S150 (N in S120).

ステップＳ１３０では、高濃度用ブリッジ回路２３で濃度測定を行っているか否かを判定する。ステップＳ１２０において、濃度しきい値を超えていることが判定されているので、以降の濃度測定を高濃度用ブリッジ回路２３で行うため、現在の構成が高濃度用ブリッジ回路２３でなければ、高濃度用ブリッジ回路２３を構成するように切替スイッチ２６を切り替えるためのステップＳ１４０に進み、（Ｓ１３０でＮ）、現在の構成が高濃度用ブリッジ回路２３であれば、その構成を維持して、再度、濃度測定を行うために、ステップＳ１１０に進む（Ｓ１３０でＹ）。 In step S130, it is determined whether or not the concentration measurement is performed by the high concentration bridge circuit 23. Since it is determined in step S120 that the concentration threshold value has been exceeded, the subsequent concentration measurement is performed by the high concentration bridge circuit 23. The process proceeds to step S140 for switching the changeover switch 26 so as to constitute the concentration bridge circuit 23 (N in S130). If the current configuration is the high concentration bridge circuit 23, the configuration is maintained, and again. In order to perform density measurement, the process proceeds to step S110 (Y in S130).

ステップＳ１４０では、切替スイッチ２６に対して、参照抵抗器２５と温度補償素子５０とによる高濃度用ブリッジ回路２３を構成するように切替要求信号Ｓを送出する。そして、高濃度用ブリッジ回路２３によって熱伝導式の濃度測定を行うため、ステップＳ１１０に進む。 In step S140, a change request signal S is sent to the changeover switch 26 so as to constitute a high concentration bridge circuit 23 composed of the reference resistor 25 and the temperature compensation element 50. Then, in order to perform the thermal conductivity type concentration measurement by the high concentration bridge circuit 23, the process proceeds to step S110.

ステップＳ１５０では、低濃度用ブリッジ回路２０で濃度測定を行っているか否かを判定する。ステップＳ１２０において、濃度しきい値以下であることが判定されているので、以降の濃度測定を低濃度用ブリッジ回路２０で行うため、現在の構成が低濃度用ブリッジ回路２０でなければ、低濃度用ブリッジ回路２０を構成するように切替スイッチ２６を切り替えるためのステップＳ１６０に進み（Ｓ１５０でＮ）、現在の構成が低濃度用ブリッジ回路２０であれば、その構成を維持して、再度、濃度測定を行うために、ステップＳ１１０に進む（Ｓ１５０でＹ）。 In step S150, it is determined whether or not the concentration measurement is performed by the low concentration bridge circuit 20. In step S120, since it is determined that the density is equal to or lower than the density threshold value, the subsequent density measurement is performed by the low density bridge circuit 20. Therefore, if the current configuration is not the low density bridge circuit 20, the low density The process proceeds to step S160 for switching the changeover switch 26 so as to configure the bridge circuit 20 (N in S150). If the current configuration is the low-concentration bridge circuit 20, the configuration is maintained and the concentration is increased again. In order to perform the measurement, the process proceeds to step S110 (Y in S150).

ステップＳ１６０では、切替スイッチ２６に対して、ガス濃度検知素子４０と温度補償素子５０とによる低濃度用ブリッジ回路２０を構成するように切替要求信号Ｓを送出する。そして、低濃度用ブリッジ回路２０による接触燃焼式の濃度測定を行うため、ステップＳ１１０に進む。 In step S160, a change request signal S is sent to the changeover switch 26 so as to constitute the low concentration bridge circuit 20 including the gas concentration detecting element 40 and the temperature compensating element 50. Then, in order to perform contact combustion type concentration measurement by the low concentration bridge circuit 20, the process proceeds to step S110.

なお、上述したステップＳ１１０が、請求項の第１工程及び第３工程に相当し、ステップＳ１２０、Ｓ１４０が、請求項の第２工程に相当する。 In addition, step S110 mentioned above is corresponded to the 1st process of a claim, and a 3rd process, and step S120, S140 is equivalent to the 2nd process of a claim.

次に、上述した警報器１における、本発明に係る接続切替処理（動作）の一例を、低濃度用ブリッジ回路２０及び高濃度用ブリッジ回路２３の中間点電位差Ｖｄの変化を模式的に示した図５を参照して説明する。 Next, an example of connection switching processing (operation) according to the present invention in the alarm device 1 described above is schematically shown the change in the midpoint potential difference Vd between the low concentration bridge circuit 20 and the high concentration bridge circuit 23. This will be described with reference to FIG.

警報器１においては、水素の爆発下限界濃度４％（容量％、以下同じ）に対して、警報濃度しきい値１．０％、切替濃度しきい値２．０％に設定されており、水素濃度が２．０％のときに、低濃度用ブリッジ回路２０の中間点電位差Ｖｄ及び高濃度用ブリッジ回路２３の中間点電位差Ｖｄが共に２．０Ｖになるように調整されている。また、この時点においては、切替スイッチ２６の端子ａ−ｂ間を接続して低濃度用ブリッジ回路２０を構成している。 In the alarm 1, the alarm concentration threshold is set to 1.0% and the switching concentration threshold is set to 2.0% with respect to the lower explosion limit concentration of 4% (volume%, hereinafter the same). When the hydrogen concentration is 2.0%, the midpoint potential difference Vd of the low concentration bridge circuit 20 and the midpoint potential difference Vd of the high concentration bridge circuit 23 are both adjusted to 2.0V. At this time, the low-concentration bridge circuit 20 is configured by connecting the terminals a and b of the changeover switch 26.

続いて、低濃度用ブリッジ回路２０の中間点電位差Ｖｄが０．５Ｖになったとき、濃度変換テーブルから取得した濃度情報により、水素濃度が０．５％であることを認識し、切替スイッチ２６を切り替えることなく端子ａ−ｂ間接続を維持して、引き続き、ガス濃度検知素子４０と温度補償素子５０とを備える低濃度用ブリッジ回路２０によって水素濃度を測定する。このときの濃度測定は、接触燃焼式により行われる。 Subsequently, when the midpoint potential difference Vd of the low concentration bridge circuit 20 becomes 0.5 V, it is recognized from the concentration information acquired from the concentration conversion table that the hydrogen concentration is 0.5%, and the changeover switch 26 is operated. The connection between the terminals a and b is maintained without switching, and the hydrogen concentration is continuously measured by the low concentration bridge circuit 20 including the gas concentration detecting element 40 and the temperature compensating element 50. The concentration measurement at this time is performed by a catalytic combustion method.

続いて、低濃度用ブリッジ回路２０の中間点電位差Ｖｄが１．０Ｖを超えたとき、濃度変換テーブルから取得した濃度情報により、水素濃度が１．０％を超えて上昇したことを認識し、警報部６７により警報を鳴動させて、警報濃度しきい値を超える危険な濃度を検出したことを利用者に警報する。このとき、切替スイッチ２６を切り替えることなく端子ａ−ｂ間接続を維持して、引き続き、低濃度用ブリッジ回路２０によって水素濃度を測定する。 Subsequently, when the midpoint potential difference Vd of the low concentration bridge circuit 20 exceeds 1.0 V, the concentration information acquired from the concentration conversion table recognizes that the hydrogen concentration has exceeded 1.0%, An alarm is sounded by the alarm unit 67 to alert the user that a dangerous concentration exceeding the alarm concentration threshold has been detected. At this time, the connection between the terminals a and b is maintained without switching the changeover switch 26, and the hydrogen concentration is continuously measured by the low concentration bridge circuit 20.

続いて、低濃度用ブリッジ回路２０の中間点電位差Ｖｄが２．０Ｖを超えたとき、濃度変換テーブルから取得した濃度情報により、水素濃度が２．０％を超えて上昇したこと、即ち、切替濃度しきい値を超えたことを認識し、切替スイッチ２６を端子ａ−ｃ間接続に切り替えて高濃度用ブリッジ回路２３を構成し、参照抵抗器２５と温度補償素子５０とを備える高濃度用ブリッジ回路２３によって水素濃度を測定する。このときの濃度測定は、熱伝導式により行われる。また、切替スイッチ２６の切り替えにより、中間点電位差Ｖｄは２．０Ｖ以下に下がる。 Subsequently, when the midpoint potential difference Vd of the low concentration bridge circuit 20 exceeds 2.0 V, the concentration information acquired from the concentration conversion table indicates that the hydrogen concentration has increased by more than 2.0%, ie, switching. Recognizing that the concentration threshold value has been exceeded, the changeover switch 26 is switched to the connection between the terminals a and c to form the high concentration bridge circuit 23, and the reference resistor 25 and the temperature compensation element 50 are provided. The hydrogen concentration is measured by the bridge circuit 23. The concentration measurement at this time is performed by a heat conduction method. Further, by switching the changeover switch 26, the intermediate point potential difference Vd is lowered to 2.0V or less.

続いて、高濃度用ブリッジ回路２３よる濃度測定において、その中間点電位差Ｖｄが２．０Ｖを超えたとき、水素濃度が２．０％より低下したこと、即ち、切替濃度しきい値以下に低下したことを認識し、切替スイッチ２６を端子ａ−ｂ間接続に切り替えて低濃度用ブリッジ回路２０を構成して、再度、低濃度用ブリッジ回路２０によって水素濃度を測定する。 Subsequently, in the concentration measurement by the high concentration bridge circuit 23, when the midpoint potential difference Vd exceeds 2.0 V, the hydrogen concentration has decreased below 2.0%, that is, the switching concentration threshold value has fallen below. The low-concentration bridge circuit 20 is configured by switching the changeover switch 26 to the connection between the terminals a and b, and the hydrogen concentration is measured again by the low-concentration bridge circuit 20.

なお、上述の動作例においては、低濃度用ブリッジ回路２０から高濃度用ブリッジ回路２３に切り替える中間点電位差Ｖｄの値、及び、高濃度用ブリッジ回路２３から低濃度用ブリッジ回路２０に切り替える中間点電位差Ｖｄの値、をそれぞれ同じ２．０Ｖとしたが、これに限らず、切り替えのための中間点電位差Ｖｄの値を、それぞれのブリッジ回路で異なる値としてもよい。 In the above-described operation example, the value of the intermediate point potential difference Vd that switches from the low concentration bridge circuit 20 to the high concentration bridge circuit 23 and the intermediate point that switches from the high concentration bridge circuit 23 to the low concentration bridge circuit 20. Although the value of the potential difference Vd is set to the same value of 2.0 V, the present invention is not limited to this, and the value of the midpoint potential difference Vd for switching may be set to a different value in each bridge circuit.

以上より、本実施形態によれば、警報器１がガスセンサユニット１０を有するので、水素ガスの濃度が、その爆発下限界以下に設定された切替濃度しきい値を超えたときに、水素との反応性がない温度補償素子５０と参照抵抗器２５とで形成された高濃度用ブリッジ回路２３によって水素ガスの濃度測定を行うことから、水素ガスの濃度がその爆発下限界を超える濃度領域にあるときでも、水素ガスを爆発させることなくその濃度測定を行うことができる。そのため、低濃度領域及び高濃度領域に対応した複数のセンサを実装することなく、ガス濃度検知素子と温度補償素子を備えた１つの接触燃焼式ガスセンサによって、広範囲の濃度測定を行うことができ、部品数の増加による回路規模の増大及びコストの上昇を回避することができる。 As described above, according to the present embodiment, since the alarm device 1 has the gas sensor unit 10, when the hydrogen gas concentration exceeds the switching concentration threshold set below the lower explosion limit, Since the hydrogen gas concentration is measured by the high-concentration bridge circuit 23 formed by the non-reactive temperature compensating element 50 and the reference resistor 25, the hydrogen gas concentration is in a concentration region exceeding the lower explosion limit. Even at times, the concentration of hydrogen gas can be measured without detonating. Therefore, without mounting a plurality of sensors corresponding to the low concentration region and the high concentration region, it is possible to perform a wide range of concentration measurement with one contact combustion type gas sensor including a gas concentration detection element and a temperature compensation element, An increase in circuit scale and cost due to an increase in the number of components can be avoided.

また、水素ガスの濃度が切替濃度しきい値以下になったときに、ガス濃度検知素子４０と温度補償素子５０とにより低濃度用ブリッジ回路２０を形成して、ガス濃度検知素子４０によって水素ガスの濃度測定を行うことから、水素ガスの濃度が切替濃度しきい値を超えたあとに、切替濃度しきい値以下に戻ったときに、再度、ガス濃度検知素子４０による水素ガスの濃度測定を行うことができるため、ガス濃度検知素子４０及び温度補償素子５０それぞれに適した濃度範囲の測定を行うことができ、低濃度においては接触燃焼式により高精度の測定が可能となり、高濃度においては水素ガスを爆発させることなく広範囲の測定が可能となる。 Further, when the concentration of the hydrogen gas becomes equal to or lower than the switching concentration threshold value, the low concentration bridge circuit 20 is formed by the gas concentration detecting element 40 and the temperature compensating element 50, and the hydrogen gas is detected by the gas concentration detecting element 40. Therefore, when the hydrogen gas concentration exceeds the switching concentration threshold value and then returns to the switching concentration threshold value or less, the hydrogen concentration measurement by the gas concentration detecting element 40 is performed again. Therefore, the concentration range suitable for each of the gas concentration detection element 40 and the temperature compensation element 50 can be measured. At low concentrations, high-accuracy measurement is possible by the contact combustion method, and at high concentrations, A wide range of measurements is possible without detonating hydrogen gas.

なお、本実施形態において、センサ部３０は、低濃度用ブリッジ回路２０及び高濃度用ブリッジ回路２３とともに、プリント基板であるガスセンサユニット１０に実装されているが、これに限らず、例えば、センサ部３０のみを小形基板等に実装してガスセンサユニット１０と分離し、センサ部３０とガスセンサユニット１０との間をリード線で接続する構成としてもよい。このようにすることで、ガスセンサユニット１０の構成及び形状の自由度をより高めることができる。また、このようにすることで、参照抵抗器２５が、水素ガスや一酸化炭素ガスなどの測定対象の可燃性ガスに触れることがなく配置できるため、参照抵抗器２５における可燃性ガスとの反応性、及び、温度変化に伴う抵抗値変化を考慮しなくてもよい。 In the present embodiment, the sensor unit 30 is mounted on the gas sensor unit 10 that is a printed circuit board together with the low concentration bridge circuit 20 and the high concentration bridge circuit 23. Only 30 may be mounted on a small substrate or the like and separated from the gas sensor unit 10, and the sensor unit 30 and the gas sensor unit 10 may be connected by a lead wire. By doing in this way, the freedom degree of composition and shape of gas sensor unit 10 can be raised more. In addition, by doing so, the reference resistor 25 can be disposed without touching the combustible gas to be measured such as hydrogen gas or carbon monoxide gas, so that the reference resistor 25 reacts with the combustible gas. Therefore, it is not necessary to consider the change in resistance and the resistance value accompanying the change in temperature.

また、本実施形態においては、センサ部３０として、ＭＥＭＳ技術を用いて超小型に形成された１辺数ｍｍのセンサチップを用いたが、これに限らず、らせん状に巻かれたコイル部を有する２本の白金抵抗体と、前記コイル部に配設された楕円球形状の触媒焼結体及び焼結体と、で構成された接触燃焼式センサ等を用いてもよい。 In the present embodiment, a sensor chip with a side of several millimeters formed using the MEMS technology is used as the sensor unit 30. However, the sensor unit is not limited to this, and a coil unit wound in a spiral shape is used. You may use the contact combustion type sensor etc. which were comprised by the two platinum resistors which have and the elliptical spherical shaped catalyst sintered body and sintered body which were arrange | positioned at the said coil part.

また、本実施形態においては、ガス濃度検知素子として接触燃焼式センサ素子を用いていたが、これに限定するものではなく、例えば、半導体式センサ素子やサーミスタ式センサ素子など、測定対象の可燃性ガスに反応（即ち、引火するおそれがある）するセンサ素子を用いており、且つ、測定対象ガスに反応せず且つ測定対象ガスの濃度に応じて抵抗値が変化する温度補償素子とともにブリッジ回路を形成して濃度測定するものであれば、どのようなものにも適用が可能である。 In the present embodiment, the contact combustion type sensor element is used as the gas concentration detection element. However, the present invention is not limited to this. For example, the combustibility of the measurement target such as a semiconductor type sensor element or a thermistor type sensor element is used. A bridge circuit is used together with a temperature compensating element that uses a sensor element that reacts to gas (that may ignite) and that does not react with the measurement target gas and whose resistance value changes according to the concentration of the measurement target gas. Any device can be applied as long as it is formed and the concentration is measured.

また、本実施形態においては、水素ガスの濃度を測定して警報する水素ガス用ガス漏れ警報器への適用に関するものであったが、これに限定するものではなく、例えば、一酸化炭素ガス、メタンガス、又は、プロパンガス等の可燃性ガスの濃度測定に用いられる測定機器等に適用することも可能である。このとき、切替濃度しきい値は各ガスの爆発下限界、例えば、一酸化炭素ガス１２．５％、メタンガス５．０％、プロパンガス２．２％、より小さく設定する。 Further, in the present embodiment, it was related to application to a hydrogen gas gas leak alarm device that measures and alarms the concentration of hydrogen gas, but is not limited thereto, for example, carbon monoxide gas, The present invention can also be applied to a measuring instrument used for measuring the concentration of flammable gas such as methane gas or propane gas. At this time, the switching concentration threshold is set smaller than the lower explosion limit of each gas, for example, carbon monoxide gas 12.5%, methane gas 5.0%, propane gas 2.2%.

次に、本発明者は、本発明に係るガスセンサユニット１０を用いて、接触燃焼式による水素ガスの濃度測定試験、及び、ヘリウムガスの濃度変化に伴う温度補償素子５０の抵抗値変動試験を行った。 Next, using the gas sensor unit 10 according to the present invention, the present inventor performs a contact gas combustion type hydrogen gas concentration measurement test and a resistance value fluctuation test of the temperature compensation element 50 accompanying the change in helium gas concentration. It was.

（実施例１）
接触燃焼式による水素ガスの濃度測定は、図１に示す警報器１と同等の構成の測定装置を用いて行い、切替スイッチ２６において端子ａ−ｂ間を接続して、ガス濃度検知素子４０と温度補償素子５０による低濃度用ブリッジ回路２０を構成し、センサ部３０が水素ガスに接触するように測定装置を水素ガス雰囲気中に配置し、水素ガスの濃度を０％〜４％まで上昇させて、各濃度における、中間点電位差Ｖｄを測定した。その結果を図６に示す。 (Example 1)
The concentration measurement of hydrogen gas by the contact combustion type is performed using a measuring device having a configuration equivalent to that of the alarm device 1 shown in FIG. The low-concentration bridge circuit 20 is constituted by the temperature compensation element 50, and the measuring device is arranged in the hydrogen gas atmosphere so that the sensor unit 30 is in contact with the hydrogen gas, and the hydrogen gas concentration is increased to 0% to 4% Thus, the midpoint potential difference Vd at each concentration was measured. The result is shown in FIG.

図６によれば、水素ガスの濃度に比例して、中間点電位差Ｖｄが上昇していることがわかる。このことから、本発明に係るガスセンサユニット１０を用いて、接触燃焼式による水素ガスの濃度測定が可能なことが判った。 As can be seen from FIG. 6, the midpoint potential difference Vd increases in proportion to the concentration of hydrogen gas. From this, it was found that the concentration of hydrogen gas can be measured by catalytic combustion using the gas sensor unit 10 according to the present invention.

（実施例２）
ヘリウムガスの濃度変化に伴う温度補償素子５０の抵抗値変動試験は、上記実施例１と同様に、図１に示す警報器１と同等の構成の測定装置を用いて行い、切替スイッチ２６において端子ａ−ｃ間を接続して、参照抵抗器２５と温度補償素子５０による高濃度用ブリッジ回路２３を構成し、温度補償素子５０がヘリウムガスに接触するように測定装置をヘリウムガス雰囲気中に配置し、ヘリウムガスの濃度を０％〜１００％まで上昇させて測定した中間点電位差Ｖｄから、各濃度における温度補償素子５０の抵抗値を算出した。その結果を図７に示す。 (Example 2)
The resistance value fluctuation test of the temperature compensation element 50 accompanying the change in the helium gas concentration is performed using a measuring device having the same configuration as the alarm device 1 shown in FIG. The high-concentration bridge circuit 23 is configured by connecting the ac and the reference resistor 25 and the temperature compensation element 50, and the measuring device is disposed in the helium gas atmosphere so that the temperature compensation element 50 contacts the helium gas. The resistance value of the temperature compensation element 50 at each concentration was calculated from the midpoint potential difference Vd measured by increasing the helium gas concentration from 0% to 100%. The result is shown in FIG.

図７によれば、ヘリウムガスの濃度に比例して、温度補償素子５０の抵抗値が下降していることが判る、つまり、温度補償素子５０は、ヘリウムガス濃度に応じて抵抗値が変化する熱伝導式センサとして動作することを示しており、本発明に係るガスセンサユニット１０を用いて、温度補償素子５０による熱伝導式の濃度測定が可能なことを示している。そして、本試験では、安全のためヘリウムガスを用いていたが、水素ガスにおいても、同様に熱伝導式センサとして動作することが判る。 According to FIG. 7, it can be seen that the resistance value of the temperature compensation element 50 decreases in proportion to the concentration of helium gas. That is, the resistance value of the temperature compensation element 50 changes according to the helium gas concentration. It shows that it operates as a heat conduction type sensor, and shows that it is possible to measure the heat conduction type concentration by the temperature compensation element 50 using the gas sensor unit 10 according to the present invention. In this test, helium gas was used for safety, but it can be seen that hydrogen gas also operates as a heat conduction sensor.

上記実施例より、ガスセンサユニット１０において、接触燃焼式による濃度測定、及び、熱伝導式による濃度測定が可能であることが示され、即ち、ガスセンサユニット１０を接触燃焼式及び熱伝導式のセンサユニットとして用いることで、低濃度から高濃度までの広範囲の濃度測定が可能であることが判った。 From the above embodiment, it is shown that the gas sensor unit 10 can perform concentration measurement by contact combustion type and concentration measurement by heat conduction type, that is, the gas sensor unit 10 is a sensor unit of contact combustion type and heat conduction type. As a result, it was found that concentration measurement in a wide range from low concentration to high concentration is possible.

なお、上述した各実施形態は本発明の代表的な形態を示したに過ぎず、本発明は、実施形態に限定されるものではない。即ち、本発明の骨子を逸脱しない範囲で種々変形して実施することができる。 The above-described embodiments are merely representative examples of the present invention, and the present invention is not limited to the embodiments. That is, various modifications can be made without departing from the scope of the present invention.

本発明の一実施形態の水素ガス用ガス漏れ警報器の構成図である。It is a block diagram of the gas leak alarm device for hydrogen gas of one Embodiment of this invention. 図１に示すセンサ部の上面図である。It is a top view of the sensor part shown in FIG. 図２のＡ−Ａ’線に沿う断面図である。FIG. 3 is a cross-sectional view taken along line A-A ′ of FIG. 2. 図１中の制御装置のＣＰＵが実行する本発明に係る処理の一例を示すフローチャートである。It is a flowchart which shows an example of the process which concerns on this invention which CPU of the control apparatus in FIG. 1 performs. 図１に示す水素ガス用ガス漏れ警報器における、水素濃度に対する中間点電位差の変化を模式的に示した図である。It is the figure which showed typically the change of the midpoint potential difference with respect to hydrogen concentration in the gas leak alarm for hydrogen gas shown in FIG. 図１に示す低濃度用ブリッジ回路おける、水素濃度に対する中間点電位差の変化を示したグラフである。FIG. 2 is a graph showing changes in the midpoint potential difference with respect to hydrogen concentration in the low concentration bridge circuit shown in FIG. 1. FIG. 図１に示す温度補償素子における、ヘリウム濃度に対する温度補償素子抵抗値の変化を示したグラフである。2 is a graph showing changes in resistance value of the temperature compensation element with respect to the helium concentration in the temperature compensation element shown in FIG. 1.

Explanation of symbols

１水素ガス用ガス漏れ警報器
１０ガスセンサユニット（ガス濃度測定回路体）
２０低濃度用ブリッジ回路（ブリッジ回路）
２３高濃度用ブリッジ回路
２５参照抵抗器
２６切替スイッチ（切替手段）
３０センサ部
４０ガス濃度検知素子
５０温度補償素子
６０制御装置 1 Gas leak alarm for hydrogen gas 10 Gas sensor unit (gas concentration measuring circuit)
20 Bridge circuit for low concentration (bridge circuit)
23 Bridge circuit for high concentration 25 Reference resistor 26 Changeover switch (switching means)
DESCRIPTION OF SYMBOLS 30 Sensor part 40 Gas concentration detection element 50 Temperature compensation element 60 Control apparatus

Claims

An intermediate of a bridge circuit including a gas concentration detecting element reactive with a combustible gas and a temperature compensating element not reactive with the combustible gas, and including the gas concentration detecting element and the temperature compensating element In the gas concentration measurement circuit body for measuring the concentration of the combustible gas based on the point potential difference,
A reference resistor which is arranged so as to form a high-concentration bridge circuit together with the temperature compensation element by switching to the gas concentration detection element, and whose resistance value does not change according to the concentration of the combustible gas;
When the concentration of the combustible gas measured based on the intermediate point potential difference of the bridge circuit exceeds a predetermined switching concentration threshold, the temperature compensation element and the reference resistor are used for the high concentration. Switching means for switching the gas concentration sensing element to the reference resistor so as to form a bridge circuit,
When the gas concentration detecting element is switched to the reference resistor by the switching means, the concentration of the combustible gas exceeding the switching concentration threshold can be measured based on the midpoint potential difference of the high concentration bridge circuit. Thus, the temperature compensation element has a characteristic of changing its resistance value according to the concentration of the combustible gas.

The bridge circuit including the gas concentration detection element and the temperature compensation element when the switching means has a concentration of the combustible gas measured by the high concentration bridge circuit equal to or lower than the switching concentration threshold value. The gas concentration measurement circuit body according to claim 1, wherein the reference resistor is means for switching the reference resistor to the gas concentration detection element so as to form a gas concentration.

A gas concentration detecting element that is reactive with a combustible gas, and a temperature compensating element that is not reactive with the combustible gas and has a resistance value that varies depending on the concentration of the combustible gas, A concentration measurement of the combustible gas is performed based on an intermediate point potential difference of a bridge circuit including a concentration detection element and the temperature compensation element, and a high concentration bridge is formed together with the temperature compensation element by switching to the gas concentration detection element. A gas concentration measurement method used in a gas concentration measurement circuit body, further comprising a reference resistor arranged to form a circuit and having a resistance value that does not change according to the concentration of the combustible gas,
A first step of measuring a concentration of the combustible gas based on the midpoint potential difference of the bridge circuit;
The high concentration bridge circuit including the temperature compensation element and the reference resistor is formed when the concentration of the combustible gas measured in the first step exceeds a predetermined switching concentration threshold value. A second step of switching the gas concentration sensing element to the reference resistor,
A third step of measuring a concentration of the combustible gas exceeding the switching concentration threshold based on a midpoint potential difference of the high concentration bridge circuit;
A gas concentration measuring method comprising: