JP4904238B2 - Gas sensor and gas detection device - Google Patents

Gas sensor and gas detection device Download PDF

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JP4904238B2
JP4904238B2 JP2007263120A JP2007263120A JP4904238B2 JP 4904238 B2 JP4904238 B2 JP 4904238B2 JP 2007263120 A JP2007263120 A JP 2007263120A JP 2007263120 A JP2007263120 A JP 2007263120A JP 4904238 B2 JP4904238 B2 JP 4904238B2
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革宇 盧
隆之 鈴木
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Yazaki Corp
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本発明は、ガスセンサ及びガス検出装置に係り、特に、固体電解質を用いて検出対象ガスの濃度を検出するガスセンサ及びガス検出装置に関するものである。   The present invention relates to a gas sensor and a gas detection device, and more particularly to a gas sensor and a gas detection device that detect a concentration of a detection target gas using a solid electrolyte.

近年、特定のガスのみに感度を有する、いわゆるガス選択性の高いガスセンサが、固体電解質を用いた電気化学センサとして活発に提案されている。特に、車の排気ガス中の特定ガス、例えばＨＣ（炭化水素ガス）、ＣＯ、ＮＯｘなどを他ガスの存在に影響されずに測定することが大きく望まれている。このような特定ガスを測定できるガスセンサとして、図８に示す混成電位式ガスセンサが提案されている（例えば特許文献１）。   In recent years, so-called high gas selectivity gas sensors having sensitivity only to specific gases have been actively proposed as electrochemical sensors using solid electrolytes. In particular, it is highly desired to measure a specific gas, such as HC (hydrocarbon gas), CO, NOx, etc. in the exhaust gas of a vehicle without being affected by the presence of other gases. As a gas sensor capable of measuring such a specific gas, a mixed potential gas sensor shown in FIG. 8 has been proposed (for example, Patent Document 1).

同図に示すように、従来のガスセンサ１００は、一対のセラミック基板１０１Ａ、１０１Ｂと、一対のセラミック基板１０１Ａ、１０１Ｂの間に挟まれた固定電解質としての安定化ジルコニア基板１０２と、安定化ジルコニア基板１０２及び一対のセラミック基板１０１Ａ、１０１Ｂ間にスペースを作るためのセラミックスペーサ１０３Ａ、１０３Ｂと、を有している。   As shown in the figure, a conventional gas sensor 100 includes a pair of ceramic substrates 101A and 101B, a stabilized zirconia substrate 102 as a fixed electrolyte sandwiched between the pair of ceramic substrates 101A and 101B, and a stabilized zirconia substrate. 102 and ceramic spacers 103A and 103B for creating a space between the pair of ceramic substrates 101A and 101B.

また、ガスセンサ１００は、検知極１０４と、対極１０５と、参照極１０６と、ヒータ素子１０７と、を有している。検知極１０４は、安定化ジルコニア基板１０２の上面に設けられている。安定化ジルコニア基板１０２とセラミック基板１０１Ａとの間のスペース内には検出対象ガスが導入され、検知極１０４は検出対象ガスに曝される。検知極１０４は、検出対象ガス及びＯ2（酸素）に活性な電極であり、例えば検出対象ガスの還元反応及びＯ2-の酸化反応が同時に生じている。 Further, the gas sensor 100 includes a detection electrode 104, a counter electrode 105, a reference electrode 106, and a heater element 107. The detection electrode 104 is provided on the upper surface of the stabilized zirconia substrate 102. A detection target gas is introduced into the space between the stabilized zirconia substrate 102 and the ceramic substrate 101A, and the detection electrode 104 is exposed to the detection target gas. The detection electrode 104 is an electrode that is active for the detection target gas and O 2 (oxygen). For example, the reduction reaction of the detection target gas and the oxidation reaction of O 2− occur simultaneously.

対極１０５は、安定化ジルコニア基板１０２の下面に設けられている。安定化ジルコニア基板１０２とセラミック基板１０１Ｂとの間のセラミックスペーサ１０３Ｂは、上記対極１０５と参照極１０６との間に設けられている。そして、セラミックスペーサ１０３Ｂよりも対極１０５側のスペースには大気が導入され、対極１０５は大気に曝される。対極１０５は、検出対象ガスに不活性でありＯ2に活性な電極であり、Ｏ2の還元反応が生じている。この検知極１０４−対極１０５間に生じる電位差は検出対象ガス濃度に応じた値となる。よって、電圧計２００によって検知極１０４−対極１０５間に生じる電位差を測定することにより、検出対象ガスの濃度を求めることができる。 The counter electrode 105 is provided on the lower surface of the stabilized zirconia substrate 102. A ceramic spacer 103 </ b> B between the stabilized zirconia substrate 102 and the ceramic substrate 101 </ b> B is provided between the counter electrode 105 and the reference electrode 106. The atmosphere is introduced into the space on the counter electrode 105 side of the ceramic spacer 103B, and the counter electrode 105 is exposed to the atmosphere. Counter 105 is an active electrode and O 2 is inert to the target gas, the reduction reaction of O 2 is generated. The potential difference generated between the detection electrode 104 and the counter electrode 105 is a value corresponding to the concentration of the detection target gas. Therefore, by measuring the potential difference generated between the detection electrode 104 and the counter electrode 105 by the voltmeter 200, the concentration of the detection target gas can be obtained.

参照極１０６は、安定化ジルコニア基板１０２の下面に設けられている。セラミックスペーサ１０３Ｂよりも参照極１０６側のスペースには検出対象ガスが導入され、参照極１０６は検出対象ガスに曝される。上記参照極１０６と検知極１０４との間にバイアス電源Ｖ１によりバイアス電圧をかけると検知極１０４においての検出対象ガスの化学反応が促進され、ガスの選択性をより高めることができる。   The reference electrode 106 is provided on the lower surface of the stabilized zirconia substrate 102. The detection target gas is introduced into the space closer to the reference electrode 106 than the ceramic spacer 103B, and the reference electrode 106 is exposed to the detection target gas. When a bias voltage is applied between the reference electrode 106 and the detection electrode 104 by the bias power source V1, the chemical reaction of the detection target gas at the detection electrode 104 is promoted, and the gas selectivity can be further increased.

また、ヒータ素子１０７は、セラミック基板１０１Ｂ内に内蔵されている。ヒータ素子１０７は、ヒータ電源Ｖ２により電圧が印加されると発熱して、安定化ジルコニア基板１０２などを加熱して化学反応を促進する。   The heater element 107 is built in the ceramic substrate 101B. The heater element 107 generates heat when a voltage is applied from the heater power source V2, and heats the stabilized zirconia substrate 102 and the like to promote a chemical reaction.

しかしながら、図８に示すような従来のガスセンサ１００では、ヒータ素子１０７と検知極１０４とが分離しているので消費電力が大きく、また、製造プロセスが複雑で歩留まりが良くないという欠点があった。また、バイアス用のバイアス電源Ｖ１とは別にヒータ用のヒータ電源Ｖ２が必要となり、部品点数が増えてコスト的に問題があった。   However, the conventional gas sensor 100 as shown in FIG. 8 has the disadvantages that the heater element 107 and the detection electrode 104 are separated, so that the power consumption is large, the manufacturing process is complicated, and the yield is not good. In addition to the bias bias power source V1, a heater power source V2 for the heater is required, which increases the number of parts and causes a problem in cost.

また、図９に示すように安定化ジルコニア基板１０２の上面に検知極１０４と対極１０５とを設け、下面にヒータ素子１０７を設けることにより消費電力の低減を図ると共に製造プロセスを簡単にするガスセンサが提案されている（例えば特許文献２）。しかしながら、この図９に示すガスセンサ１００も、バイアスをかける場合にはバイアス用のバイアス電源Ｖ１とヒータ用のヒータ電源Ｖ２とが別々に必要であり、部品点数が増えてコスト的に問題があった。
特開２００１−９９８１０号公報 特開２００３−１６６９７２号公報 Further, as shown in FIG. 9, a gas sensor that reduces power consumption and simplifies the manufacturing process by providing a detection electrode 104 and a counter electrode 105 on the upper surface of the stabilized zirconia substrate 102 and providing a heater element 107 on the lower surface. It has been proposed (for example, Patent Document 2). However, the gas sensor 100 shown in FIG. 9 also requires a bias power source V1 for bias and a heater power source V2 for heaters separately when applying a bias, which increases the number of parts and causes a problem in cost. .
JP 2001-99810 A JP 2003-166972 A

そこで、本発明は、上記のような問題点に着目し、簡単な構成でバイアス用の電源とヒータ用の電源とを兼用することができ、部品点数を削減してコストダウンを図ったガスセンサ及びガス検出装置を提供することを課題とする。   Therefore, the present invention pays attention to the above-mentioned problems, and can be used as both a bias power source and a heater power source with a simple configuration, and the gas sensor and the cost can be reduced by reducing the number of parts. It is an object to provide a gas detection device.

上記課題を解決するためになされた請求項１記載の発明は、酸素イオン導電性を有する固体電解質と、前記固体電解質上に形成された検出対象ガス及び酸素に活性な検知極と、前記固体電解質上に形成された前記検出対象ガスに不活性であり前記酸素に活性な対極と、前記固体電解質上に形成された前記検知極との間にバイアス電圧を印加して前記検知極での前記検出対象ガスの反応を促進するための参照極と、前記固体電解質、前記検知極、前記対極及び前記参照極を加熱するヒータ素子と、が設けられたガスセンサにおいて、前記検知極及び前記参照極の両電極が、前記固体電解質の同一面上に設けられ、前記ヒータ素子が、前記検知極及び前記参照極の設けられた前記同一面と対向する対向面上に設けられ、前記固体電解質の前記ヒータ素子及び前記検知極に挟まれた部分に前記同一面から前記対向面に貫通するように第１スルーホールが、設けられ、前記固体電解質の前記ヒータ素子及び前記参照極に挟まれた部分に前記同一面から前記対向面に貫通するように第２スルーホールが、設けられ、前記ヒータ素子及び前記検知極を電気的に接続する第１接続部が、前記第１スルーホール内に挿入されるように設けられ、そして、前記ヒータ素子及び前記参照極を電気的に接続する第２接続部が、前記第２スルーホール内に挿入されるように設けられていることを特徴とするガスセンサに存する。   The invention according to claim 1, which has been made to solve the above problems, includes a solid electrolyte having oxygen ion conductivity, a detection target gas formed on the solid electrolyte and a detection electrode active with respect to oxygen, and the solid electrolyte. The detection at the detection electrode is performed by applying a bias voltage between the counter electrode which is inactive to the detection target gas formed above and active against the oxygen and the detection electrode formed on the solid electrolyte. In a gas sensor provided with a reference electrode for promoting a reaction of a target gas and a heater element for heating the solid electrolyte, the detection electrode, the counter electrode, and the reference electrode, both the detection electrode and the reference electrode An electrode is provided on the same surface of the solid electrolyte, and the heater element is provided on a surface facing the same surface on which the detection electrode and the reference electrode are provided, and the heat of the solid electrolyte is provided. A first through hole is provided in a portion sandwiched between the element and the detection electrode so as to penetrate from the same surface to the opposing surface, and the portion sandwiched between the heater element and the reference electrode of the solid electrolyte is provided with the first through hole. A second through hole is provided so as to penetrate from the same surface to the opposing surface, and a first connection portion that electrically connects the heater element and the detection electrode is inserted into the first through hole. And a second connection portion that electrically connects the heater element and the reference electrode is provided so as to be inserted into the second through hole.

請求項２記載の発明は、前記対極が、前記同一面上に設けられたことを特徴とする請求項１に記載のガスセンサに存する。   The invention according to claim 2 resides in the gas sensor according to claim 1, wherein the counter electrode is provided on the same surface.

請求項３記載の発明は、請求項１又は２に記載のガスセンサと、前記ヒータ素子の両端及び前記検知極−前記対極間に電圧を印加する電源と、前記検知極と前記対極との間の電位差に基づいて前記検出対象ガスの濃度を検出する濃度検出手段と、を備えたことを特徴とするガス検出装置に存する。   According to a third aspect of the present invention, there is provided the gas sensor according to the first or second aspect, a power source that applies a voltage between both ends of the heater element and between the detection electrode and the counter electrode, and between the detection electrode and the counter electrode. A gas detection apparatus comprising: concentration detection means for detecting the concentration of the detection target gas based on a potential difference.

以上説明したように請求項１及び３記載の発明によれば、第１接続部がヒータ素子及び検知極を接続し、第２接続部がヒータ素子及び参照極を接続するので、バイアス用の電源とヒータ用の電源とを兼用することができる。また、第１接続部を第１スルーホール内に設け、第２接続部を第２スルーホール内に設けることにより、構成が簡単となる。これにより、簡単な構成でバイアス用の電源とヒータ用の電源とを兼用することができ、部品点数を削減してコストダウンを図ることができる。   As described above, according to the first and third aspects of the invention, the first connection portion connects the heater element and the detection electrode, and the second connection portion connects the heater element and the reference electrode. And a power source for the heater can be used together. In addition, the configuration is simplified by providing the first connection portion in the first through hole and the second connection portion in the second through hole. As a result, the bias power source and the heater power source can be used together with a simple configuration, and the number of parts can be reduced to reduce the cost.

請求項２記載の発明によれば、対極が同一面上に設けられているので、ヒータ素子により対極も検知極及び参照極と同様に加熱され、検出精度向上を図ることができる。   According to the second aspect of the present invention, since the counter electrode is provided on the same surface, the counter electrode is heated by the heater element in the same manner as the detection electrode and the reference electrode, and the detection accuracy can be improved.

以下、本発明の一実施の形態を図１〜図３に基づいて説明する。なお、本実施形態においては、例えば車の排ガス中のＮＯ2（二酸化窒素）濃度を検出する例について説明する。同図に示すように、ガス検出装置１は、ガスセンサ２と、電源３と、電圧計４と、マイクロコンピュータ５（以下、μＣＯＭ５）と、を備えている。上記ガスセンサ２は、固体電解質２１と、検知極２２と、対極２３と、参照極２４と、ヒータ素子２５と、を備えている。固体電解質２１は、Ｏ2-（酸素イオン）導電性を有する例えば安定化ジルコニアやランタンガレート(ＬａＧａＯ3)から構成されていて、平板状に形成されている。 Hereinafter, an embodiment of the present invention will be described with reference to FIGS. In the present embodiment, an example in which the NO 2 (nitrogen dioxide) concentration in the exhaust gas of a car is detected will be described. As shown in the figure, the gas detection device 1 includes a gas sensor 2, a power source 3, a voltmeter 4, and a microcomputer 5 (hereinafter, μCOM 5). The gas sensor 2 includes a solid electrolyte 21, a detection electrode 22, a counter electrode 23, a reference electrode 24, and a heater element 25. The solid electrolyte 21 is made of, for example, stabilized zirconia or lanthanum gallate (LaGaO 3 ) having O 2− (oxygen ion) conductivity, and is formed in a flat plate shape.

検知極２２は、固体電解質２１の上面に設けられる。検知極２２は、図１に示すように上面側から見て略長方形状に設けられている。検知極２２は、Ｐｔ（プラチナ）、Ｐｄ（パラジウム）、Ａｕ（金）、Ｒｈ（ロジウム）、Ｒｕ（ルテニウム）及びこれらの合金などの貴金属や金属酸化物、金属酸化物と貴金属との複合物などから構成されている。   The detection electrode 22 is provided on the upper surface of the solid electrolyte 21. As shown in FIG. 1, the detection electrode 22 is provided in a substantially rectangular shape when viewed from the upper surface side. The detection electrode 22 is composed of noble metals such as Pt (platinum), Pd (palladium), Au (gold), Rh (rhodium), Ru (ruthenium), and alloys thereof, and a composite of the metal oxide and the noble metal. Etc.

この検知極２２上にはＮＯ2と活性になるような触媒が設けられていて、検知極２２はＮＯ2及びＯ2の両者に活性となる。即ち、図４に示すように、上記検知極２２、固体電解質２１及び排ガス相の界面である三相界面Ｘにおいては、式（１）に示す排ガス中のＮＯ2の還元反応、及び、式（２）に示す排ガス中のＯ2-の酸化反応、が同時に生じる。
ＮＯ2＋２ｅ-→ＮＯ＋Ｏ2- …（１）
Ｏ2-→１／２Ｏ2＋２ｅ- …（２） On the detection electrode 22, a catalyst that is active with NO 2 is provided, and the detection electrode 22 is active with both NO 2 and O 2 . That is, as shown in FIG. 4, at the three-phase interface X that is an interface of the detection electrode 22, the solid electrolyte 21, and the exhaust gas phase, the reduction reaction of NO 2 in the exhaust gas shown in the equation (1) and the equation ( The oxidation reaction of O 2− in the exhaust gas shown in 2) occurs simultaneously.
NO 2 + 2e − → NO + O 2− (1)
O 2− → 1 / 2O 2 + 2e − (2)

そして、検知極２２は、式（１）に示すＮＯ2の還元反応及び式（２）のＯ2-の酸化反応の反応速度が同じになる混成電位となり、排ガス中のＮＯ2濃度及びＯ2濃度に応じた電位となる。 The detection electrode 22 has a mixed potential at which the reaction rates of the NO 2 reduction reaction represented by the formula (1) and the O 2 -oxidation reaction represented by the formula (2) are the same, and the NO 2 concentration and the O 2 in the exhaust gas. The potential depends on the concentration.

対極２３は、固体電解質２１の上面に設けられる。即ち、検知極２２及び対極２３の両電極が、固体電解質２１の上面（同一面）に設けられる。また、対極２３は、図１に示すように上側から見て略正方形状に設けられている。対極２３は、検知極２２と同様に、Ｐｔ、Ｐｄ、Ａｕ、Ｒｈ、Ｒｕ及びこれらの合金などの貴金属や金属酸化物、金属酸化物と貴金属との複合物などから構成されている。   The counter electrode 23 is provided on the upper surface of the solid electrolyte 21. That is, both the detection electrode 22 and the counter electrode 23 are provided on the upper surface (same surface) of the solid electrolyte 21. Further, the counter electrode 23 is provided in a substantially square shape as viewed from above as shown in FIG. Like the detection electrode 22, the counter electrode 23 is composed of a noble metal such as Pt, Pd, Au, Rh, Ru, and alloys thereof, a metal oxide, a composite of a metal oxide and a noble metal, or the like.

この対極２３上にはＮＯ2と活性になるような触媒は設けられていない。よって、対極２３は、ＮＯ2に不活性となりＯ2に活性となる電極となる。即ち、上記対極２３、固体電解質２１及び排ガス相の界面である三相界面Ｘにおいては、式（２）とは逆反応である式（３）に示す排ガス中のＯ2の還元反応が生じる。
１／２Ｏ2＋２ｅ-→Ｏ2- …（３） On the counter electrode 23, no catalyst that is active with NO 2 is provided. Therefore, the counter electrode 23 becomes an electrode inactive to NO 2 and active to O 2 . That is, at the three-phase interface X, which is an interface between the counter electrode 23, the solid electrolyte 21, and the exhaust gas phase, a reduction reaction of O 2 in the exhaust gas shown in Formula (3), which is a reverse reaction to Formula (2), occurs.
1 / 2O 2 + 2e − → O 2− (3)

そして、対極２３は、式（３）に示すＯ2の還元反応による平衡電位となり、排ガス中のＯ2濃度に応じた電位となる。この検知極２２及び対極２３間に生じる電位差は、ＮＯ2濃度に応じた値となる。 The counter electrode 23 has an equilibrium potential due to the O 2 reduction reaction shown in the formula (3), and has a potential corresponding to the O 2 concentration in the exhaust gas. The potential difference generated between the detection electrode 22 and the counter electrode 23 has a value corresponding to the NO 2 concentration.

参照極２４は、固体電解質２１の上面に設けられる。即ち、検知極２２、対極２３及び参照極２４の３つの電極が、固体電解質２１の上面（同一面）に設けられる。また、参照極２４は、図１に示すように上側から見て略正方形状に設けられている。参照極２４は、検知極２２及び対極２３と同様に、Ｐｔ、Ｐｄ、Ａｕ、Ｒｈ、Ｒｕ及びこれらの合金などの貴金属や金属酸化物、金属酸化物と貴金属との複合物などから構成されている。   The reference electrode 24 is provided on the upper surface of the solid electrolyte 21. That is, the three electrodes of the detection electrode 22, the counter electrode 23, and the reference electrode 24 are provided on the upper surface (same surface) of the solid electrolyte 21. Further, the reference electrode 24 is provided in a substantially square shape when viewed from above as shown in FIG. Similar to the detection electrode 22 and the counter electrode 23, the reference electrode 24 is composed of a noble metal such as Pt, Pd, Au, Rh, Ru, and alloys thereof, a metal oxide, a composite of a metal oxide and a noble metal, or the like. Yes.

参照極２４は、検知極２２との間にバイアス電圧を印加するための電極である。検知極２２側が負となり、参照極２４側が正となるようなバイアス電圧を印加すると、固体電解質２１中のＯ2-が参照極２４側に引き寄せられて検知極２２でのＮＯ2の還元反応を促進する。図６は、ＮＯ2濃度１０００ｐｐｍのときの検知極２２−対極２３間の電位差と、検知極２２−参照極２４間に印加するバイアス電圧と、の関係を示すグラフである。同図に示すように、バイアス電圧が高いほど、ＮＯ2の感度が向上し、ガス選択性を高めることができる。 The reference electrode 24 is an electrode for applying a bias voltage to the detection electrode 22. When a bias voltage is applied so that the detection electrode 22 side becomes negative and the reference electrode 24 side becomes positive, O 2− in the solid electrolyte 21 is attracted to the reference electrode 24 side, and NO 2 reduction reaction at the detection electrode 22 occurs. Facilitate. FIG. 6 is a graph showing the relationship between the potential difference between the detection electrode 22 and the counter electrode 23 and the bias voltage applied between the detection electrode 22 and the reference electrode 24 when the NO 2 concentration is 1000 ppm. As shown in the figure, the higher the bias voltage, the higher the sensitivity of NO 2 and the higher the gas selectivity.

ヒータ素子２５は、固体電解質２１の下面に設けられている。即ち、ヒータ素子２５は、検知極２２、対極２３及び参照極２４が設けられた上面（同一面）と対向する下面（対向面）に設けられる。ヒータ素子２５は、図３に示すように、固体電解質２１の下面全体に下側から見て蛇腹状に設けられていて、これにより固体電解質２１、検知極２２、対極２３及び参照極２４を均一に加熱する。   The heater element 25 is provided on the lower surface of the solid electrolyte 21. That is, the heater element 25 is provided on the lower surface (opposing surface) opposite to the upper surface (same surface) on which the detection electrode 22, the counter electrode 23, and the reference electrode 24 are provided. As shown in FIG. 3, the heater element 25 is provided in an accordion shape when viewed from below on the entire lower surface of the solid electrolyte 21, whereby the solid electrolyte 21, the detection electrode 22, the counter electrode 23, and the reference electrode 24 are made uniform. Heat to.

また、電源３は、ヒータ素子２５の両端に電気的に接続されている。これにより、ヒータ素子２５は、電源３からの電源電圧が印加されて発熱する。電圧計４は、上述した検知極２２と対極２３との間に生じるＮＯ2濃度に応じた電位差を検出して、μＣＯＭ５に対して出力する。μＣＯＭ５は、濃度検出手段として働き、電圧計４が検出した電位差からＮＯ2濃度を検出する。 The power source 3 is electrically connected to both ends of the heater element 25. Thus, the heater element 25 generates heat when the power supply voltage from the power supply 3 is applied. The voltmeter 4 detects a potential difference corresponding to the NO 2 concentration generated between the detection electrode 22 and the counter electrode 23 described above, and outputs it to the μCOM 5. The μCOM 5 functions as a concentration detection unit and detects the NO 2 concentration from the potential difference detected by the voltmeter 4.

また、ガスセンサ２には、図２及び図３に示すように、第１スルーホール２６、第２スルーホール２７、第１接続部２８及び第２接続部２９が設けられている。図２に示すように、第１スルーホール２６は、固体電解質２１の上面から下面に貫通するように設けられている。第１スルーホール２６は、固体電解質２１のヒータ素子２５及び検知極２２に挟まれた部分に設けられている。第２スルーホール２７は、固体電解質２１の上面から下面に貫通するように設けられている。第２スルーホール２７は、固体電解質２１のヒータ素子２５及び参照極２４に挟まれた部分に設けられている。   Further, as shown in FIGS. 2 and 3, the gas sensor 2 is provided with a first through hole 26, a second through hole 27, a first connection portion 28, and a second connection portion 29. As shown in FIG. 2, the first through hole 26 is provided so as to penetrate from the upper surface to the lower surface of the solid electrolyte 21. The first through hole 26 is provided in a portion sandwiched between the heater element 25 and the detection electrode 22 of the solid electrolyte 21. The second through hole 27 is provided so as to penetrate from the upper surface to the lower surface of the solid electrolyte 21. The second through hole 27 is provided in a portion sandwiched between the heater element 25 and the reference electrode 24 of the solid electrolyte 21.

第１接続部２８は、例えばＰｔなどの導電部材から構成され、第１スルーホール２６内に挿入されて、ヒータ素子２５及び検知極２２を電気的に接続する。第２接続部２９は、例えばＰｔなどの導電部材から構成され、第２スルーホール２７内に挿入されてヒータ素子２５及び参照極２４を電気的に接続する。これにより、図５に示すように、検知極２２は、第１接続部２８、ヒータ素子２５の一部を介して電源３の負側に接続される。また、参照極２４は、第２接続部２９、ヒータ素子２５の一部を介して電源３の正側に接続される。そして、電源３によって検知極２２が負、参照極２４が正となるようなバイアス電圧が検知極２２−参照極２４間に印加される。   The first connection portion 28 is made of a conductive member such as Pt, and is inserted into the first through hole 26 to electrically connect the heater element 25 and the detection electrode 22. The second connection portion 29 is made of a conductive member such as Pt, for example, and is inserted into the second through hole 27 to electrically connect the heater element 25 and the reference electrode 24. Thereby, as shown in FIG. 5, the detection electrode 22 is connected to the negative side of the power source 3 through the first connection portion 28 and a part of the heater element 25. The reference electrode 24 is connected to the positive side of the power supply 3 through the second connection portion 29 and a part of the heater element 25. The power supply 3 applies a bias voltage between the detection electrode 22 and the reference electrode 24 so that the detection electrode 22 is negative and the reference electrode 24 is positive.

次に、上述した構成のガス検出装置１の動作について説明する。まず、μＣＯＭ５は、電源３に直列接続された図示しないスイッチをオンすると、ヒータ素子２５の両端に電源３の電源電圧を印加される。同時に、ヒータ素子２５、第１接続部２８及び第２接続部２９を介して、検知極２２−参照極２４間に電源３からのバイアス電圧が印加される。そして、検知極２２においては式（１）及び（２）に示す化学反応が生じ、対極２３においては式（３）に示す化学反応が生じ、これにより、検知極２２−対極２３間にＮＯ2濃度に応じた電位差が生じる。μＣＯＭ５が電圧計４により検出された検知極２２−対極２３間の電位差に基づいてＮＯ2濃度を検出する。 Next, the operation of the gas detection device 1 having the above-described configuration will be described. First, when the μCOM 5 turns on a switch (not shown) connected in series to the power supply 3, the power supply voltage of the power supply 3 is applied to both ends of the heater element 25. At the same time, a bias voltage from the power source 3 is applied between the detection electrode 22 and the reference electrode 24 through the heater element 25, the first connection unit 28, and the second connection unit 29. Then, the chemical reaction shown in the formulas (1) and (2) occurs in the detection electrode 22, and the chemical reaction shown in the formula (3) occurs in the counter electrode 23, whereby NO 2 is detected between the detection electrode 22 and the counter electrode 23. A potential difference according to the concentration occurs. The μCOM 5 detects the NO 2 concentration based on the potential difference between the detection electrode 22 and the counter electrode 23 detected by the voltmeter 4.

上述したガス検出装置１によれば、第１接続部２８がヒータ素子２５及び検知極２２を接続し、第２接続部２９がヒータ素子２５及び参照極２４を接続するので、バイアス用の電源３とヒータ用の電源３とを兼用することができる。また、第１接続部２８を第１スルーホール２６内に挿入するように設け、第２接続部２９を第２スルーホール２７内に挿入するように設けることにより、構成が簡単となる。これにより、簡単な構成でバイアス用の電源３とヒータ用の電源３とを兼用することができ、部品点数を削減してコストダウンを図ることができる。   According to the gas detection device 1 described above, the first connection portion 28 connects the heater element 25 and the detection electrode 22, and the second connection portion 29 connects the heater element 25 and the reference electrode 24. And the power source 3 for the heater can be used together. Further, by providing the first connecting portion 28 so as to be inserted into the first through hole 26 and providing the second connecting portion 29 so as to be inserted into the second through hole 27, the configuration is simplified. As a result, the bias power source 3 and the heater power source 3 can be used in a simple configuration, and the number of parts can be reduced to reduce the cost.

また、上述したガス検出装置１によれば、対極２３が検知極２２及び参照極２４が設けられている固体電解質２１の上面に設けられているので、ヒータ素子２５により対極２３も検知極２２及び参照極２４と同様に加熱され、検出精度向上を図ることができる。   Further, according to the gas detection device 1 described above, since the counter electrode 23 is provided on the upper surface of the solid electrolyte 21 on which the detection electrode 22 and the reference electrode 24 are provided, the counter electrode 23 is also detected by the heater element 25. Heating is performed in the same manner as the reference electrode 24, and detection accuracy can be improved.

なお、上述した実施形態では、検知極２２が負となり参照極２４が正となるようなバイアス電圧を印加してＮＯ2濃度を検出していたが、本発明はこれに限ったものではない。例えば、検知極２２上にＮＯ（一酸化窒素）との反応が促進する触媒を設けると共に検知極２２が正となり参照極２４が負となるようなバイアス電圧を印加すればＮＯ濃度を検出することができる。 In the above-described embodiment, the NO 2 concentration is detected by applying a bias voltage that makes the detection electrode 22 negative and the reference electrode 24 positive. However, the present invention is not limited to this. For example, a NO concentration can be detected by providing a catalyst that promotes reaction with NO (nitrogen monoxide) on the detection electrode 22 and applying a bias voltage that makes the detection electrode 22 positive and the reference electrode 24 negative. Can do.

上述したようにバイアス電圧を印加すれば、図７に示すように、検知極２２、固体電界室２１及び排ガス相の界面である三相界面Ｘにおいては、式（４）に示す排ガス中のＮＯの酸化反応、及び、式（５）に示す排ガス中のＯ2の還元反応が、同時に生じる。
ＮＯ＋Ｏ2-→ＮＯ2＋２ｅ- …（４）
１／２Ｏ2＋２ｅ-→Ｏ2- …（５） When the bias voltage is applied as described above, as shown in FIG. 7, at the three-phase interface X, which is the interface between the detection electrode 22, the solid electric field chamber 21, and the exhaust gas phase, NO in the exhaust gas shown in the equation (4) And the reduction reaction of O 2 in the exhaust gas shown in Formula (5) occur simultaneously.
NO + O 2− → NO 2 + 2e − (4)
1 / 2O 2 + 2e − → O 2− (5)

そして、検知極２２は、式（４）に示すＮＯの酸化反応及び式（５）に示すＯ2の還元反応の反応速度が同じになる混成電位となり、排ガス中のＮＯ濃度及びＯ2濃度に応じた電位となる。 The detection electrode 22 has a mixed potential at which the reaction rates of the NO oxidation reaction represented by the equation (4) and the O 2 reduction reaction represented by the equation (5) are the same, and the NO concentration and the O 2 concentration in the exhaust gas are reduced. The corresponding potential is obtained.

一方、対極２３、固体電解質２１及び排ガス相の界面である三相界面においては、式（５）とは逆反応である式（６）に示す排ガス中のＯ2-の酸化反応が生じる。
Ｏ2-→１／２Ｏ2＋２ｅ- …（６） On the other hand, at the three-phase interface, which is the interface of the counter electrode 23, the solid electrolyte 21, and the exhaust gas phase, an oxidation reaction of O 2− in the exhaust gas shown in Formula (6), which is a reverse reaction to Formula (5), occurs.
O 2− → 1 / 2O 2 + 2e − (6)

そして、対極２３は、式（６）に示すＯ2-の還元反応による平衡電位となり、排ガス中のＯ2濃度に応じた電位となる。この検知極２２及び対極２３間に生じる電位差は、ＮＯ濃度に応じた値となる。このようにガスセンサ２に、検知極２２側が正となり、参照極２４側が負となるようなバイアス電圧を印加すると、固体電解質２１中のＯ2-が検知極２２側に引き寄せられて検知極２２でのＮＯの反応を促進する。このため、ＮＯの感度が向上し、ガス選択性を高めることができる。 The counter electrode 23 has an equilibrium potential due to the O 2− reduction reaction shown in the equation (6), and has a potential corresponding to the O 2 concentration in the exhaust gas. The potential difference generated between the detection electrode 22 and the counter electrode 23 has a value corresponding to the NO concentration. Thus, when a bias voltage is applied to the gas sensor 2 such that the detection electrode 22 side becomes positive and the reference electrode 24 side becomes negative, O 2− in the solid electrolyte 21 is attracted to the detection electrode 22 side and is detected by the detection electrode 22. Promotes the reaction of NO. For this reason, the sensitivity of NO improves and gas selectivity can be improved.

また、上述した実施形態では、ＮＯ2とＮＯの何れかの濃度を検出するガスセンサ２について説明したが、本発明はこれに限ったものではない。例えば、μＣＯＭ５の制御によりスイッチのオンオフによって電源３の向きを変えることができるように構成しておけば、ＮＯ2及びＮＯの両検出対象ガスの濃度を検出することもできる。 In the above-described embodiment, the gas sensor 2 that detects the concentration of either NO 2 or NO has been described, but the present invention is not limited to this. For example, if the configuration is such that the direction of the power source 3 can be changed by turning on and off the switch under the control of μCOM 5, the concentrations of both NO 2 and NO detection target gases can be detected.

また、上述した実施形態では、検出対象ガスとしてＮＯ2及びＮＯについて説明していたが、本発明はこれに限ったものではない。検出対象ガスとしては、例えばＨ2（水素）であっても良いし、ＨＣ（炭化水素）であってもよい。この場合、検知極２２においては、Ｈ2、ＨＣの酸化反応及びＯ2の還元反応が生じ、対極２３においてはＯ2-の酸化反応が生じる。 Further, in the embodiment described above, but describes NO 2 and NO as a detection target gas, the present invention is not limited thereto. The detection target gas may be, for example, H 2 (hydrogen) or HC (hydrocarbon). In this case, an oxidation reaction of H 2 and HC and a reduction reaction of O 2 occur at the detection electrode 22, and an oxidation reaction of O 2− occurs at the counter electrode 23.

また、上述した実施形態によれば、対極２３を固体電解質２１の上面に設けていたが、本発明はこれに限ったものではない。本発明は、検知極２２及び参照極２４が同一面に設けられていればよく、対極２３については別の場所に設けてもよい。   Further, according to the above-described embodiment, the counter electrode 23 is provided on the upper surface of the solid electrolyte 21, but the present invention is not limited to this. In the present invention, the detection electrode 22 and the reference electrode 24 may be provided on the same surface, and the counter electrode 23 may be provided at a different location.

また、前述した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。   Further, the above-described embodiments are merely representative forms 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.

図１は本発明のガス検出装置の一実施形態を示す図である。FIG. 1 is a diagram showing an embodiment of a gas detection device of the present invention. 図２は図１に示すガスセンサのＩ−Ｉ線断面図である。2 is a cross-sectional view taken along line II of the gas sensor shown in FIG. 図３は図１に示すガスセンサの分解斜視図である。FIG. 3 is an exploded perspective view of the gas sensor shown in FIG. 図１に示す検知極でのＮＯ2の反応を説明するための図である。It is a diagram for explaining the reaction of NO 2 in the sensing electrode shown in FIG. 図１に示すガスセンサの電気接続について説明するための図である。It is a figure for demonstrating the electrical connection of the gas sensor shown in FIG. ＮＯ2濃度１０００ｐｐｍのときの検知極−対極間の電位差と、検知極−参照極間に印加するバイアス電圧と、の関係を示すグラフである。And the potential difference between the counter electrode, sensing electrode - - sensing electrode when the NO 2 concentration 1000ppm and bias voltage applied between the reference electrode is a graph showing the relationship between. 図１に示す検知極でのＮＯの反応を説明するための図である。It is a figure for demonstrating reaction of NO in the detection pole shown in FIG. 従来のガスセンサの一例を示す図である。It is a figure which shows an example of the conventional gas sensor. 従来のガスセンサの一例を示す図である。It is a figure which shows an example of the conventional gas sensor.

符号の説明Explanation of symbols

１ ガス検出装置
２ ガスセンサ
３ 電源
５ μＣＯＭ（濃度検出手段）
２１ 固体電解質
２２ 検知極
２３ 対極
２４ 参照極
２５ ヒータ素子
２６ 第１スルーホール
２７ 第２スルーホール
２８ 第１接続部
２９ 第２接続部 1 Gas detection device 2 Gas sensor 3 Power supply 5 μCOM (concentration detection means)
DESCRIPTION OF SYMBOLS 21 Solid electrolyte 22 Detection electrode 23 Counter electrode 24 Reference electrode 25 Heater element 26 1st through-hole 27 2nd through-hole 28 1st connection part 29 2nd connection part

Claims (3)

酸素イオン導電性を有する固体電解質と、前記固体電解質上に形成された検出対象ガス及び酸素に活性な検知極と、前記固体電解質上に形成された前記検出対象ガスに不活性であり前記酸素に活性な対極と、前記固体電解質上に形成された前記検知極との間にバイアス電圧を印加して前記検知極での前記検出対象ガスの反応を促進するための参照極と、前記固体電解質、前記検知極、前記対極及び前記参照極を加熱するヒータ素子と、が設けられたガスセンサにおいて、
前記検知極及び前記参照極の両電極が、前記固体電解質の同一面上に設けられ、
前記ヒータ素子が、前記検知極及び前記参照極の設けられた前記同一面と対向する対向面上に設けられ、
前記固体電解質の前記ヒータ素子及び前記検知極に挟まれた部分に前記同一面から前記対向面に貫通するように第１スルーホールが、設けられ、
前記固体電解質の前記ヒータ素子及び前記参照極に挟まれた部分に前記同一面から前記対向面に貫通するように第２スルーホールが、設けられ、
前記ヒータ素子及び前記検知極を電気的に接続する第１接続部が、前記第１スルーホール内に挿入されるように設けられ、そして、
前記ヒータ素子及び前記参照極を電気的に接続する第２接続部が、前記第２スルーホール内に挿入されるように設けられていることを特徴とするガスセンサ。 A solid electrolyte having oxygen ion conductivity; a detection target gas formed on the solid electrolyte; a detection electrode active on oxygen; and an inert gas to the detection target gas formed on the solid electrolyte. A reference electrode for promoting a reaction of the detection target gas at the detection electrode by applying a bias voltage between an active counter electrode and the detection electrode formed on the solid electrolyte, the solid electrolyte, In a gas sensor provided with a heater element that heats the detection electrode, the counter electrode, and the reference electrode,
Both the detection electrode and the reference electrode are provided on the same surface of the solid electrolyte,
The heater element is provided on a facing surface facing the same surface on which the detection electrode and the reference electrode are provided;
A first through hole is provided in a portion sandwiched between the heater element and the detection electrode of the solid electrolyte so as to penetrate from the same surface to the opposing surface,
A second through hole is provided in a portion sandwiched between the heater element and the reference electrode of the solid electrolyte so as to penetrate from the same surface to the opposing surface,
A first connecting portion for electrically connecting the heater element and the detection electrode is provided to be inserted into the first through hole; and
A gas sensor, wherein a second connection portion for electrically connecting the heater element and the reference electrode is provided so as to be inserted into the second through hole. 前記対極が、前記同一面上に設けられたことを特徴とする請求項１に記載のガスセンサ。   The gas sensor according to claim 1, wherein the counter electrode is provided on the same surface. 請求項１又は２に記載のガスセンサと、
前記ヒータ素子の両端及び前記検知極−前記対極間に電圧を印加する電源と、
前記検知極と前記対極との間の電位差に基づいて前記検出対象ガスの濃度を検出する濃度検出手段と、を備えたことを特徴とするガス検出装置。 A gas sensor according to claim 1 or 2,
A power source for applying a voltage between both ends of the heater element and the detection electrode-the counter electrode;
A gas detection apparatus comprising: a concentration detection unit configured to detect a concentration of the detection target gas based on a potential difference between the detection electrode and the counter electrode.
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