WO2016067975A1 - Gas sensor - Google Patents

Gas sensor Download PDF

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Publication number
WO2016067975A1
WO2016067975A1 PCT/JP2015/079585 JP2015079585W WO2016067975A1 WO 2016067975 A1 WO2016067975 A1 WO 2016067975A1 JP 2015079585 W JP2015079585 W JP 2015079585W WO 2016067975 A1 WO2016067975 A1 WO 2016067975A1
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Prior art keywords
gas
sensor
electrode
measured
housing
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PCT/JP2015/079585
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French (fr)
Japanese (ja)
Inventor
祐輔 河本
祐介 藤堂
貴司 荒木
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株式会社デンソー
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Priority claimed from JP2015184367A external-priority patent/JP6561719B2/en
Application filed by 株式会社デンソー filed Critical 株式会社デンソー
Priority to DE112015004954.1T priority Critical patent/DE112015004954T5/en
Priority to US15/521,967 priority patent/US11933757B2/en
Publication of WO2016067975A1 publication Critical patent/WO2016067975A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/416—Systems

Definitions

  • the present invention relates to a gas sensor that detects a predetermined gas component concentration in a gas to be measured.
  • a general gas sensor that detects the concentration of a predetermined gas component such as NOx in a measured gas such as exhaust gas from an internal combustion engine adjusts the oxygen concentration in the measured gas by a pump cell, and the oxygen concentration is adjusted by the sensor cell.
  • the predetermined gas component concentration in the measured gas is detected.
  • the electrode constituting the pump cell and the electrode constituting the sensor cell need to be operated within an appropriate temperature range. Specifically, the electrode constituting the pump cell is operated in a temperature range that does not decompose the predetermined gas component while decomposing oxygen, and the electrode constituting the sensor cell does not decompose water while decomposing the predetermined gas component. Operating in range.
  • Japanese Patent Application Laid-Open No. 2008-28183 discloses a gas sensor having a sensor element that measures a predetermined gas component in a gas to be measured, and an inner protective cover and an outer protective cover that cover the tip of the sensor element.
  • This gas sensor is configured such that the total opening area A1 of the inner gas introduction holes of the inner protective cover and the total opening area A2 of the outer gas introduction holes of the outer protective cover have a relationship of A1 / A2 ⁇ 1.
  • the flow rate at which the gas to be measured introduced from the outer gas introduction hole into the outer protective cover passes through the inner gas introduction hole is reduced.
  • the ratio of the total opening area of all the gas introduction holes temperature fluctuations of the sensor element due to the gas to be measured entering the protective cover are suppressed.
  • the entire gas detection part provided with the pump electrode, the sensor electrode, and the like in the sensor element protrudes from the front end surface of the housing toward the front end of the gas sensor.
  • a state in which the gas to be measured easily collides is formed around the portion of the sensor element where the pump electrode and the sensor electrode are provided.
  • the gas sensor controls the temperature of the sensor element by utilizing the fact that the impedance of the pump cell changes with temperature.
  • the temperature of the sensor cell is indirectly controlled by controlling the temperature of the pump electrode according to the impedance of the pump cell. For this reason, if the gas to be measured is likely to collide with the periphery of the portion of the sensor element provided with the sensor electrode, the temperature of the sensor electrode is likely to fluctuate.
  • the present invention has been made in view of such a background, and provides a gas sensor capable of suppressing the temperature fluctuation of a sensor electrode and increasing the detection accuracy of a predetermined gas component concentration.
  • One embodiment of the present invention includes a housing; An insulator held on the inner periphery of the housing; A sensor element inserted through the insulator, having a solid electrolyte body having oxygen ion conductivity, and having a distal end portion in the longitudinal direction of the gas sensor protruding from the distal end surface of the insulator;
  • a gas sensor comprising: a protective cover that is attached to the distal end portion of the housing so as to cover the distal end portion of the sensor element, and in which a cover introduction hole for guiding a gas to be measured to the distal end portion of the sensor element is formed.
  • the front end portion of the solid electrolyte body in the longitudinal direction is exposed to the gas to be measured to adjust the oxygen concentration in the gas to be measured, and the oxygen concentration is exposed to the gas to be measured and is pumped by the pump electrode.
  • a sensor electrode for detecting a predetermined gas component concentration in the gas to be measured after the gas is adjusted is characterized in that the base end in the longitudinal direction of the sensor electrode is located closer to the base end side of the gas sensor than the front end surface of the housing.
  • the positional relationship between the front end surface of the housing and the sensor electrode in the sensor element is devised. Specifically, the base end in the longitudinal direction of the sensor electrode in the sensor element is positioned closer to the base end side than the front end surface of the housing. And at least a part of the part where the sensor electrode is provided in the sensor element is in the housing.
  • the gas to be measured When detecting a predetermined gas component concentration in the gas to be measured by the gas sensor, the gas to be measured is introduced into the protective cover from the introduction hole of the protective cover, and is applied to the front end of the sensor element (solid electrolyte body) in the longitudinal direction. Contact.
  • the gas to be measured since the base end in the longitudinal direction of the sensor electrode is located on the base end side with respect to the front end surface of the housing, the gas to be measured does not easily collide with the periphery of the sensor element where the sensor electrode is provided.
  • the flow velocity of the gas to be measured that collides with the periphery of the portion where the sensor electrode is provided in the sensor element becomes slow. Thereby, the temperature of the sensor electrode can be made less likely to fluctuate due to the temperature change of the gas to be measured.
  • the detection accuracy of the predetermined gas component concentration can be improved by suppressing the temperature fluctuation of the sensor electrode.
  • FIG. 3 is a diagram illustrating the sensor element according to the embodiment, and is a cross-sectional explanatory view taken along line III-III in FIG. 2. Plane explanatory drawing which shows the formation state of the pump electrode and sensor electrode in a sensor element concerning embodiment. Cross-sectional explanatory drawing which shows the front end side part of the other gas sensor concerning embodiment. Cross-sectional explanatory drawing which shows the front end side part of the other gas sensor concerning embodiment. Cross-sectional explanatory drawing which shows the front end side part of the other gas sensor concerning embodiment. Cross-sectional explanatory drawing which shows the front end side part of the other gas sensor concerning embodiment.
  • the graph which shows the relationship between the position of the longitudinal direction of a sensor electrode concerning a confirmation test, and the flow velocity of the to-be-measured gas which contacts the front-end
  • the graph which shows the relationship between the position of the longitudinal direction of a sensor electrode concerning a confirmation test, and the fluctuation
  • the gas sensor 1 includes housings 11A and 11B, an insulator 12, a sensor element 10, and protective covers 13A and 13B.
  • the housings 11A and 11B are made of metal.
  • the insulator 12 is made of insulating ceramics and is held on the inner peripheral side of the housing 11A.
  • the sensor element 10 is inserted through an insulator 12 and has a solid electrolyte body 2 having oxygen ion conductivity.
  • the sensor element 10 has a predetermined length and has a tip portion 100. The distal end portion 100 protrudes from the distal end surface 121 of the insulator 12 along the longitudinal direction L of the sensor element 10.
  • the protective covers 13A and 13B are made of metal, and are attached to the distal end (lower part of the figure) of the housing 11A so as to cover the distal end portion 100 of the sensor element 10.
  • cover introduction holes 131 and 132 for guiding the gas G to be measured to the tip portion 100 of the sensor element 10 are formed.
  • the solid electrolyte body 2 has a tip portion 200.
  • the tip portion 200 is exposed to the gas G to be measured to adjust the oxygen concentration in the gas G to be measured, and the oxygen concentration is adjusted by the pump electrode 21 that is exposed to the gas G to be measured.
  • a sensor electrode 23 for detecting a predetermined gas component concentration in the gas G to be measured.
  • the base end edge 231 of the sensor electrode 23 is closer to the base end side of the gas sensor 1 (that is, the sensor element 10) than the front end surface 111 of the housing 11 ⁇ / b> A in the longitudinal direction L of the sensor element 10. positioned.
  • a portion where the sensor element 10 protrudes from the insulator 12 is referred to as a tip side.
  • the lower side is the distal end side
  • the upper side is the proximal end side. 2 to 4
  • the sensor element 10 is schematically shown, and the pump electrode 21, the sensor electrode 23, and the like are shown shorter than actual ones.
  • the gas sensor 1 uses an exhaust gas passing through an exhaust pipe of an internal combustion engine as a measurement gas G, and is used to detect the concentration of NOx as a predetermined gas component in the measurement gas G.
  • the sensor element 10 includes an insulator 31 for forming the measurement gas space 101 and a heater 5 for heating the solid electrolyte body 2, which are stacked between the sensor element 10 and the solid electrolyte body 2. Is formed.
  • the solid electrolyte body 2 has opposite surfaces 201 and 202 in the thickness direction.
  • the insulator 31 is laminated on the surface 201 with the spacer 33 interposed therebetween.
  • a measurement gas space 101 into which the measurement gas G is introduced is formed by being surrounded by one surface 201 of the solid electrolyte body 2, the insulator 31 and the spacer 33.
  • an inlet 331 for introducing the measurement gas G into the measurement gas space 101 via the diffusion resistor 32 is formed at the tip 103 of the sensor element 10.
  • the introduction port 331 is formed at the tip portion of the spacer 33.
  • the diffusion resistor 32 is composed of a porous body that allows the gas G to be measured to pass under a predetermined diffusion resistance, and is embedded in the inlet 331.
  • the pump electrode 21 and the sensor electrode 23 are provided on the surface 201 of the solid electrolyte body 2 and are exposed to the measurement gas G introduced into the measurement gas space 101.
  • the monitor electrode 22 is provided adjacent to the sensor electrode 23 on the surface 201 of the solid electrolyte body 2.
  • the monitor electrode 22 detects the oxygen concentration in the measurement gas G after being exposed to the measurement gas G and the oxygen concentration being adjusted by the pump electrode 21.
  • the pump electrode 21 is provided at the tip of the solid electrolyte body 2 of the sensor element 10, which is close to the introduction port 331.
  • the sensor electrode 23 and the monitor electrode 22 are adjacent to the proximal end side of the pump electrode 21 and are provided at positions spaced apart from each other by an equal distance from the pump electrode 21. That is, the sensor electrode 23 and the monitor electrode 22 are located at an equal distance from the base edge of the pump electrode 21 along the longitudinal direction L.
  • the heater 5 is laminated on the surface 202 of the solid electrolyte body 2 via the spacers 34.
  • the heater 5 includes a pair of ceramic substrates 51 and a heat generation layer 52 sandwiched between the ceramic substrates 51.
  • a reference gas space 102 into which a reference gas (atmospheric gas) A is introduced is formed by being surrounded by the surface 202 of the solid electrolyte body 2, the heater 5 and the spacer 34.
  • a region on the surface 202 where the pump electrode 21, the monitor electrode 22 and the sensor electrode 23 are projected in the thickness direction of the solid electrolyte body 2 (the solid electrolyte body 2 is sandwiched between the pump electrode 21, the monitor electrode 22 and the sensor electrode 23.
  • a reference electrode 25 is provided so as to be exposed to the reference gas A introduced into the reference gas space 102.
  • the reference electrode 25 is provided over the entire area of the surface 202 onto which the three electrodes, the pump electrode 21, the monitor electrode 22, and the sensor electrode 23 are projected.
  • the reference electrode 25 can be provided separately for the pump electrode 21, the monitor electrode 22, and the sensor electrode 23.
  • a voltage is applied between the pump electrode 21 and the reference electrode 25 via the solid electrolyte body 2, so that the measurement gas G in the measurement gas space 101 is in the measurement gas G.
  • a pump cell 41 is formed for adjusting the oxygen concentration to a predetermined concentration or less. Further, in the sensor element 10, the oxygen ion current flowing between the monitor electrode 22 and the reference electrode 25 is detected via the solid electrolyte body 2, and the oxygen concentration is adjusted by the pump cell 41 in the measured gas space 101. After that, a monitor cell 42 for detecting the oxygen concentration in the measured gas G is formed.
  • an oxygen ion current flowing between the sensor electrode 23 and the reference electrode 25 is detected via the solid electrolyte body 2, and the oxygen concentration is adjusted by the pump cell 41 in the measured gas space 101.
  • the oxygen ion current value in the monitor cell 42 is subtracted from the oxygen ion current value in the sensor cell 43 to detect the NOx concentration in the measurement gas G.
  • the housings 11A and 11B are a first housing 11A located on the outer periphery of the insulator 12 and a second housing 11B located on the outer periphery of the first housing 11A.
  • the front end portion of the first housing 11A protrudes toward the front end side of the gas sensor 1 from the front end of the second housing 11B.
  • the assembly of the protective covers 13A and 13B has a double wall structure.
  • the protective covers 13A and 13B are a first protective cover 13A attached to the outer periphery of the front end portion of the first housing 11A and a second protective cover 13B attached to the outer periphery of the first protective cover 13A.
  • the cover introduction holes 131 and 132 for guiding the gas G to be measured to the distal end portion 100 of the sensor element 10 include the cover introduction holes 131 formed in the outer peripheral portion and the distal end portion of the first protective cover 13A, and the second protective cover.
  • 13B is a cover introduction hole 132 formed at the outer periphery and the tip of 13B.
  • the gas G to be measured passes through the outer peripheral portion of the first protective cover 13A and the outer peripheral portion of the second protective cover 13B, flows into the second protective cover 13B, contacts the distal end portion 100 of the sensor element 10, and then It flows out of the protective covers 13A and 13B through the front end of the first protective cover 13A and the front end of the second protective cover 13B.
  • the tip of the first protective cover 13A is disposed in a cover introduction hole 132 formed in the tip of the second protective cover 13B.
  • the measured gas G flowing to the base end side through the cover introduction hole 131 in the outer peripheral portion of the first protective cover 13A comes into contact with the distal end portion 100 of the sensor element 10 arranged in the first protective cover 13A. .
  • the distal end portion of the first protective cover 13A is separated from the distal end portion of the second protective cover 13B toward the proximal end side of the gas sensor 1, and the distal end portion of the first protective cover 13A and the second protective cover are separated.
  • a space can also be formed between the tip of 13B.
  • the gas G to be measured flows through the space between the tip of the first protective cover 13A and the tip of the second protective cover 13B from the cover introduction hole 132 in the outer periphery of the second protective cover 13B. Then, it flows through the cover introduction hole 131 in the outer peripheral portion of the first protective cover 13A.
  • the assembly including the protective covers 13A and 13B may have a single wall structure.
  • the gas sensor 1 is configured to control the temperature of the sensor element 10. Specifically, the gas sensor 1 measures the impedance between the pump electrode 21 and the reference electrode 25 through the solid electrolyte body 2 in the pump cell 41, and heats the heater 5 so that this impedance becomes a predetermined value. It is configured to control the amount.
  • the pump electrode 21 is heated to a temperature in the range of 830 to 920 ° C. in order to decompose oxygen but not NOx.
  • the sensor electrode 23 is heated to a temperature in the range of 650 to 740 ° C. in order to decompose NOx but not water.
  • the insulator 12 secures insulation with the sensor element 10 and fixes the sensor element 10 to the first housing 11A.
  • the distal end surface 121 of the insulator 12 is located closer to the proximal end side of the gas sensor 1 than the distal end surface 111 of the first housing 11A.
  • the base end edge 231 in the longitudinal direction L of the sensor electrode 23 and the base end edge 221 in the longitudinal direction L of the monitor electrode 22 are on the base end side of the gas sensor 1 with respect to the front end surface 111 of the first housing 11A. It is located in the recessed part 14 formed by the front end surface 121 of the insulator 12 and the inner peripheral surface 112 of the first housing 11A.
  • the sensor electrode 23 and the monitor electrode 22 have their centers 232 and 222 in the longitudinal direction L positioned on the proximal end side of the gas sensor 1 with respect to the distal end surface 111 of the first housing 11A.
  • the distal end portion 100 in the longitudinal direction L of the sensor element 10 provided with the pump electrode 21, the sensor electrode 23, the monitor electrode 22, and the reference electrode 25 is as close to the first housing 11A as possible. It is located on the end side.
  • the gas sensor 1 detects the NOx concentration in the gas G to be measured
  • the gas G to be measured is introduced into the protective covers 13A and 13B from the cover introduction holes 131 and 132, and comes into contact with the tip 100 of the sensor element 10. To do.
  • the measurement gas G is introduced into the measurement gas space 101 from the introduction port 331 formed at the tip 103 of the sensor element 10.
  • the flow of the gas G to be measured introduced into the protective covers 13A and 13B is gentle in the recess 14 formed by the tip surface 121 of the insulator 12 and the inner peripheral surface 112 of the first housing 11A. Further, the centers 232 and 222 of the sensor electrode 23 and the monitor electrode 22 in the longitudinal direction L are located on the proximal end side of the gas sensor 1 with respect to the distal end surface 111 of the first housing 11A, and at least a part of them is in the recess 14. Is arranged.
  • the gas G to be measured does not easily collide with the periphery of the portion of the sensor element 10 where the sensor electrode 23 and the monitor electrode 22 are provided, or the sensor electrode 23 and the monitor electrode 22 of the sensor element 10 are provided.
  • the flow velocity of the gas G to be measured that collides with the periphery of the region becomes slower. Therefore, the temperature of the sensor electrode 23 and the monitor electrode 22 can be made less likely to fluctuate due to the temperature change of the measurement gas G.
  • the gas sensor 1 suppresses the temperature fluctuation of the sensor electrode 23 and increases the detection accuracy of the NOx concentration.
  • the entire sensor electrode 23 may be located closer to the base end side of the gas sensor 1 than the front end surface 111 of the first housing 11 ⁇ / b> A. In this case, the temperature change of the sensor electrode 23 and the monitor electrode 22 can be further suppressed. Further, in the gas sensor 1, as shown in FIG. 6, the tip (tip position) 103 of the sensor element 10 may be located closer to the base end side of the gas sensor 1 than the tip surface 111 of the first housing 11A. In this case, the entire sensor element 10 is disposed in the recess 14 formed by the distal end surface 121 of the insulator 12 and the inner peripheral surface 112 of the first housing 11A. In this case, the temperature of the sensor electrode 23 and the monitor electrode 22 can be made even more difficult to change.
  • the flow rate of the measurement gas G contacting the tip portion 100 of the sensor element 10 and the temperature fluctuation generated in the sensor electrode 23 when the measurement gas G flows into the protective covers 13A and 13B were obtained.
  • the fluctuations in the flow velocity and temperature were obtained by appropriately changing the position of the sensor electrode 23 in the longitudinal direction L.
  • FIG. 8 shows the relationship between the position in the longitudinal direction L of the sensor electrode 23 and the flow velocity of the gas G to be measured contacting the tip portion 100 of the sensor element 10.
  • the position of the sensor electrode 23 in the longitudinal direction L is 0 mm when the base end edge 231 of the sensor electrode 23 in the longitudinal direction L is at the same position as the distal end surface 111 of the housing 11A. Further, the position in the longitudinal direction L of the sensor electrode 23 indicates a negative value when the proximal end edge 231 in the longitudinal direction L of the sensor electrode 23 is located on the proximal end side of the gas sensor 1 with respect to the distal end surface 111 of the housing 11A. .
  • the position of the sensor electrode 23 in the longitudinal direction L indicates a positive value when the base end edge 231 of the sensor electrode 23 in the longitudinal direction L is located on the distal end side of the gas sensor 1 with respect to the distal end surface 111 of the housing 11A.
  • FIG. 9 shows the relationship between the position of the sensor electrode 23 in the longitudinal direction L of the gas sensor 1 and the temperature variation that occurs in the sensor electrode 23.
  • This variation in temperature is caused when the sensor electrode 23 is at a predetermined temperature, the flow rate of the gas G to be measured is 0 mm / s as a reference state, and the flow rate of the gas G to be measured is 20 mm / s. It shows how much the temperature of 23 has changed compared to the reference state where the flow rate is 0 mm / s.
  • the value indicated by the position in the longitudinal direction L of the sensor electrode 23 is the same as in the case of FIG. As shown in FIG.

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Abstract

　The gas sensor according to the present invention is provided with: a housing; an insulator retained on the internal periphery of the housing; a sensor element, the distal-end part of which protrudes from the distal-end face of the insulator; and a protective cover for covering the distal-end part of the sensor element. In the present invention, a pump electrode for adjusting the oxygen concentration in a gas to be measured, the pump electrode being exposed to the gas to be measured, and a sensor electrode for detecting the concentration of a predetermined gas component in the gas to be measured after the oxygen concentration thereof is adjusted by the pump electrode, the sensor electrode being exposed to the gas to be measured, are provided to the distal-end part of a solid electrolyte. The proximal-end part of the sensor electrode in the longitudinal direction thereof is positioned closer to the proximal end of the gas sensor than to the distal-end face of the housing. Temperature variation in the sensor electrode is thereby suppressed, and the concentration of the predetermined gas component is detected with higher precision.

Description

ガスセンサGas sensor
本発明は、被測定ガス中の所定ガス成分濃度を検出するガスセンサに関する。
背景技術 The present invention relates to a gas sensor that detects a predetermined gas component concentration in a gas to be measured.
Background art
　内燃機関からの排気ガス等の被測定ガス中のＮＯｘ等の所定ガス成分の濃度を検出する一般的なガスセンサは、ポンプセルによって被測定ガス中の酸素濃度を調整し、センサセルによって、酸素濃度が調整された被測定ガス中の所定ガス成分濃度を検出している。
　ポンプセルを構成する電極及びセンサセルを構成する電極は、適切な温度範囲内で動作させる必要がある。具体的には、ポンプセルを構成する電極は、酸素を分解する一方、所定ガス成分を分解しない温度範囲で動作させ、センサセルを構成する電極は、所定ガス成分を分解する一方、水を分解しない温度範囲で動作させている。 A general gas sensor that detects the concentration of a predetermined gas component such as NOx in a measured gas such as exhaust gas from an internal combustion engine adjusts the oxygen concentration in the measured gas by a pump cell, and the oxygen concentration is adjusted by the sensor cell. The predetermined gas component concentration in the measured gas is detected.
The electrode constituting the pump cell and the electrode constituting the sensor cell need to be operated within an appropriate temperature range. Specifically, the electrode constituting the pump cell is operated in a temperature range that does not decompose the predetermined gas component while decomposing oxygen, and the electrode constituting the sensor cell does not decompose water while decomposing the predetermined gas component. Operating in range.
　例えば、特開２００８－２８１５８３号公報は、被測定ガス中の所定ガス成分を測定するセンサ素子と、センサ素子の先端部を覆う内側保護カバー及び外側保護カバーとを有するガスセンサを開示している。このガスセンサは、内側保護カバーの内側ガス導入孔の合計開口面積Ａ１と外側保護カバーの外側ガス導入孔の合計開口面積Ａ２とが、Ａ１／Ａ２≧１の関係を有するように構成されており、外側ガス導入孔から外側保護カバー内に導入された被測定ガスが内側ガス導入孔を通過する流速が低減される。このように、全ガス導入孔の合計開口面積の比を規定することにより、保護カバー内への被測定ガスの進入によるセンサ素子の温度変動を抑えている。 For example, Japanese Patent Application Laid-Open No. 2008-28183 discloses a gas sensor having a sensor element that measures a predetermined gas component in a gas to be measured, and an inner protective cover and an outer protective cover that cover the tip of the sensor element. This gas sensor is configured such that the total opening area A1 of the inner gas introduction holes of the inner protective cover and the total opening area A2 of the outer gas introduction holes of the outer protective cover have a relationship of A1 / A2 ≧ 1. The flow rate at which the gas to be measured introduced from the outer gas introduction hole into the outer protective cover passes through the inner gas introduction hole is reduced. Thus, by regulating the ratio of the total opening area of all the gas introduction holes, temperature fluctuations of the sensor element due to the gas to be measured entering the protective cover are suppressed.
　ところで、上記タイプの従来のガスセンサは、センサ素子における、ポンプ電極、センサ電極等が設けられたガス検知部の全体が、ハウジングの先端面よりもガスセンサの先端の方に突出している。そして、センサ素子における、ポンプ電極及びセンサ電極が設けられた部位の周辺には、被測定ガスが衝突しやすい状態が形成されている。
　また、ガスセンサは、ポンプセルのインピーダンスが温度によって変化することを利用して、センサ素子の温度の制御を行っている。具体的には、ポンプセルのインピーダンスに応じてポンプ電極の温度を制御することによって、センサセルの温度も間接的に制御している。そのため、被測定ガスが、センサ電極が設けられたセンサ素子の部位の周辺に衝突しやすいようになっていると、センサ電極の温度に変動が生じやすくなる。 By the way, in the conventional gas sensor of the above-described type, the entire gas detection part provided with the pump electrode, the sensor electrode, and the like in the sensor element protrudes from the front end surface of the housing toward the front end of the gas sensor. A state in which the gas to be measured easily collides is formed around the portion of the sensor element where the pump electrode and the sensor electrode are provided.
In addition, the gas sensor controls the temperature of the sensor element by utilizing the fact that the impedance of the pump cell changes with temperature. Specifically, the temperature of the sensor cell is indirectly controlled by controlling the temperature of the pump electrode according to the impedance of the pump cell. For this reason, if the gas to be measured is likely to collide with the periphery of the portion of the sensor element provided with the sensor electrode, the temperature of the sensor electrode is likely to fluctuate.
　本発明は、かかる背景に鑑みてなされたもので、センサ電極の温度変動を抑えて、所定ガス成分濃度の検出精度を高めることができるガスセンサを提供する。 The present invention has been made in view of such a background, and provides a gas sensor capable of suppressing the temperature fluctuation of a sensor electrode and increasing the detection accuracy of a predetermined gas component concentration.
本発明の一態様は、ハウジングと、
　該ハウジングの内周に保持された碍子と、
　該碍子に挿通された、酸素イオン伝導性を有する固体電解質体を有し、ガスセンサの長手方向における先端部が上記碍子の先端面から突出するセンサ素子と、
　該センサ素子の上記先端部を覆うよう上記ハウジングの先端部に取り付けられ、被測定ガスを上記センサ素子の上記先端部に導くためのカバー導入孔が形成された保護カバーと、を備えるガスセンサにおいて、
　上記固体電解質体の上記長手方向の先端部には、被測定ガスに晒されて被測定ガス中の酸素濃度を調整するためのポンプ電極と、被測定ガスに晒されて上記ポンプ電極によって酸素濃度が調整された後の被測定ガス中の所定ガス成分濃度を検出するためのセンサ電極とが設けられており、
　該センサ電極の上記長手方向の基端は、上記ハウジングの先端面よりもガスセンサの基端側に位置していることを特徴とするガスセンサである。 One embodiment of the present invention includes a housing;
An insulator held on the inner periphery of the housing;
A sensor element inserted through the insulator, having a solid electrolyte body having oxygen ion conductivity, and having a distal end portion in the longitudinal direction of the gas sensor protruding from the distal end surface of the insulator;
In a gas sensor comprising: a protective cover that is attached to the distal end portion of the housing so as to cover the distal end portion of the sensor element, and in which a cover introduction hole for guiding a gas to be measured to the distal end portion of the sensor element is formed.
The front end portion of the solid electrolyte body in the longitudinal direction is exposed to the gas to be measured to adjust the oxygen concentration in the gas to be measured, and the oxygen concentration is exposed to the gas to be measured and is pumped by the pump electrode. And a sensor electrode for detecting a predetermined gas component concentration in the gas to be measured after the gas is adjusted,
The gas sensor is characterized in that the base end in the longitudinal direction of the sensor electrode is located closer to the base end side of the gas sensor than the front end surface of the housing.
　上記ガスセンサにおいては、ハウジングの先端面と、センサ素子におけるセンサ電極との位置関係に工夫をしている。
　具体的には、センサ素子におけるセンサ電極の長手方向の基端を、ハウジングの先端面よりも基端側に位置させている。そして、センサ素子にセンサ電極が設けられた部位の少なくとも一部は、ハウジング内に入っている。 In the gas sensor, the positional relationship between the front end surface of the housing and the sensor electrode in the sensor element is devised.
Specifically, the base end in the longitudinal direction of the sensor electrode in the sensor element is positioned closer to the base end side than the front end surface of the housing. And at least a part of the part where the sensor electrode is provided in the sensor element is in the housing.
　ガスセンサによって被測定ガス中の所定ガス成分濃度を検出する際には、被測定ガスは、保護カバーの導入孔から保護カバー内に導入され、センサ素子（固体電解質体）の長手方向の先端部に接触する。このとき、センサ電極の長手方向の基端がハウジングの先端面よりも基端側に位置していることにより、センサ素子における、センサ電極が設けられた部位の周辺に被測定ガスが衝突しにくくなる、あるいは、センサ素子における、センサ電極が設けられた部位の周辺に衝突する被測定ガスの流速が遅くなる。これにより、被測定ガスの温度変化によって、センサ電極の温度が変動しにくくすることができる。 When detecting a predetermined gas component concentration in the gas to be measured by the gas sensor, the gas to be measured is introduced into the protective cover from the introduction hole of the protective cover, and is applied to the front end of the sensor element (solid electrolyte body) in the longitudinal direction. Contact. At this time, since the base end in the longitudinal direction of the sensor electrode is located on the base end side with respect to the front end surface of the housing, the gas to be measured does not easily collide with the periphery of the sensor element where the sensor electrode is provided. Alternatively, the flow velocity of the gas to be measured that collides with the periphery of the portion where the sensor electrode is provided in the sensor element becomes slow. Thereby, the temperature of the sensor electrode can be made less likely to fluctuate due to the temperature change of the gas to be measured.
　それ故、上記ガスセンサによれば、センサ電極の温度変動を抑えることにより、所定ガス成分濃度の検出精度が高められる。 Therefore, according to the gas sensor, the detection accuracy of the predetermined gas component concentration can be improved by suppressing the temperature fluctuation of the sensor electrode.
実施形態にかかる、ガスセンサの先端側部分を示す断面説明図。Cross-sectional explanatory drawing which shows the front end side part of the gas sensor concerning embodiment. 実施形態にかかる、センサ素子を示す断面説明図。Cross-sectional explanatory drawing which shows the sensor element concerning embodiment. 実施形態にかかる、センサ素子を示す図で、図２のＩＩＩ－ＩＩＩ線断面説明図。FIG. 3 is a diagram illustrating the sensor element according to the embodiment, and is a cross-sectional explanatory view taken along line III-III in FIG. 2. 実施形態にかかる、センサ素子におけるポンプ電極及びセンサ電極の形成状態を示す平面説明図。Plane explanatory drawing which shows the formation state of the pump electrode and sensor electrode in a sensor element concerning embodiment. 実施形態にかかる、他のガスセンサの先端側部分を示す断面説明図。Cross-sectional explanatory drawing which shows the front end side part of the other gas sensor concerning embodiment. 実施形態にかかる、他のガスセンサの先端側部分を示す断面説明図。Cross-sectional explanatory drawing which shows the front end side part of the other gas sensor concerning embodiment. 実施形態にかかる、他のガスセンサの先端側部分を示す断面説明図。Cross-sectional explanatory drawing which shows the front end side part of the other gas sensor concerning embodiment. 確認試験にかかる、センサ電極の長手方向の位置と、センサ素子の先端部に接触する被測定ガスの流速との関係を示すグラフ。The graph which shows the relationship between the position of the longitudinal direction of a sensor electrode concerning a confirmation test, and the flow velocity of the to-be-measured gas which contacts the front-end | tip part of a sensor element. 確認試験にかかる、センサ電極の長手方向の位置と、センサ電極に生じる温度の変動との関係を示すグラフ。The graph which shows the relationship between the position of the longitudinal direction of a sensor electrode concerning a confirmation test, and the fluctuation | variation of the temperature which arises in a sensor electrode.
　以下、本実施例にかかるガスセンサ１を図面を参照して説明する。
　ガスセンサ１は、図１に示すように、ハウジング１１Ａ，１１Ｂ、碍子１２、センサ素子１０及び保護カバー１３Ａ，１３Ｂを備えている。ハウジング１１Ａ，１１Ｂは、金属から構成されている。碍子１２は、絶縁性のセラミックスによって構成されており、ハウジング１１Ａの内周側に保持されている。センサ素子１０は、碍子１２に挿通されており、酸素イオン伝導性を有する固体電解質体２を有している。センサ素子１０は所定の長さを有しており、先端部１００を有している。先端部１００は、センサ素子１０の長手方向Ｌにそって、碍子１２の先端面１２１から突出している。保護カバー１３Ａ，１３Ｂは、金属から構成されており、センサ素子１０の先端部１００を覆うようハウジング１１Ａの先端(図の下部)に取り付けられている。保護カバー１３Ａ，１３Ｂには、被測定ガスＧをセンサ素子１０の先端部１００に導くためのカバー導入孔１３１，１３２が形成されている。 Hereinafter, the gas sensor 1 according to the present embodiment will be described with reference to the drawings.
As shown in FIG. 1, the gas sensor 1 includes housings 11A and 11B, an insulator 12, a sensor element 10, and protective covers 13A and 13B. The housings 11A and 11B are made of metal. The insulator 12 is made of insulating ceramics and is held on the inner peripheral side of the housing 11A. The sensor element 10 is inserted through an insulator 12 and has a solid electrolyte body 2 having oxygen ion conductivity. The sensor element 10 has a predetermined length and has a tip portion 100. The distal end portion 100 protrudes from the distal end surface 121 of the insulator 12 along the longitudinal direction L of the sensor element 10. The protective covers 13A and 13B are made of metal, and are attached to the distal end (lower part of the figure) of the housing 11A so as to cover the distal end portion 100 of the sensor element 10. In the protective covers 13A and 13B, cover introduction holes 131 and 132 for guiding the gas G to be measured to the tip portion 100 of the sensor element 10 are formed.
　固体電解質体２は先端部２００を有している。この先端部２００には、被測定ガスＧに晒されて被測定ガスＧ中の酸素濃度を調整するためのポンプ電極２１と、被測定ガスＧに晒されてポンプ電極２１によって酸素濃度が調整された後の被測定ガスＧ中の所定ガス成分濃度を検出するためのセンサ電極２３とが設けられている。図１、図４に示すように、センサ電極２３基端縁２３１は、センサ素子１０の長手方向Lにおいて、ハウジング１１Ａの先端面１１１よりもガスセンサ１（すなわち、センサ素子１０）の基端側に位置している。なお、本実施例において、碍子１２からセンサ素子１０が突出する部分を先端側という。図１においては、下側が先端側になり、上側が基端側になる。なお、図２～図４においては、センサ素子１０を模式的に示しており、ポンプ電極２１、センサ電極２３等は実際よりも短く示されている。 The solid electrolyte body 2 has a tip portion 200. The tip portion 200 is exposed to the gas G to be measured to adjust the oxygen concentration in the gas G to be measured, and the oxygen concentration is adjusted by the pump electrode 21 that is exposed to the gas G to be measured. And a sensor electrode 23 for detecting a predetermined gas component concentration in the gas G to be measured. As shown in FIGS. 1 and 4, the base end edge 231 of the sensor electrode 23 is closer to the base end side of the gas sensor 1 (that is, the sensor element 10) than the front end surface 111 of the housing 11 </ b> A in the longitudinal direction L of the sensor element 10. positioned. In the present embodiment, a portion where the sensor element 10 protrudes from the insulator 12 is referred to as a tip side. In FIG. 1, the lower side is the distal end side, and the upper side is the proximal end side. 2 to 4, the sensor element 10 is schematically shown, and the pump electrode 21, the sensor electrode 23, and the like are shown shorter than actual ones.
　以下、ガスセンサ１を、図１～図７を参照して詳説する。
　ガスセンサ１は、内燃機関の排気管を通過する排気ガスを被測定ガスＧとして、この被測定ガスＧ中の所定ガス成分としてのＮＯｘの濃度を検出するために用いる。
　図２に示すように、センサ素子１０は、固体電解質体２との間に、被測定ガス空間１０１を形成するための絶縁体３１、及び固体電解質体２を加熱するためのヒータ５を積層して形成されている。固体電解質体２はその厚み方向において対向する表面２０１と２０２を有する。表面２０１には、スペーサ３３を介して絶縁体３１が積層されている。センサ素子１０においては、固体電解質体２の一方の表面２０１、絶縁体３１及びスペーサ３３によって囲まれて、被測定ガスＧが導入される被測定ガス空間１０１が形成されている。 Hereinafter, the gas sensor 1 will be described in detail with reference to FIGS.
The gas sensor 1 uses an exhaust gas passing through an exhaust pipe of an internal combustion engine as a measurement gas G, and is used to detect the concentration of NOx as a predetermined gas component in the measurement gas G.
As shown in FIG. 2, the sensor element 10 includes an insulator 31 for forming the measurement gas space 101 and a heater 5 for heating the solid electrolyte body 2, which are stacked between the sensor element 10 and the solid electrolyte body 2. Is formed. The solid electrolyte body 2 has opposite surfaces 201 and 202 in the thickness direction. The insulator 31 is laminated on the surface 201 with the spacer 33 interposed therebetween. In the sensor element 10, a measurement gas space 101 into which the measurement gas G is introduced is formed by being surrounded by one surface 201 of the solid electrolyte body 2, the insulator 31 and the spacer 33.
　図２に示すように、センサ素子１０の先端１０３には、拡散抵抗体３２を介して被測定ガス空間１０１に被測定ガスＧを導入するための導入口３３１が形成されている。導入口３３１は、スペーサ３３の先端部分に形成されている。拡散抵抗体３２は、被測定ガスＧを所定の拡散抵抗下で通過させる多孔質体から構成されているとともに、導入口３３１内に埋設されている。ポンプ電極２１及びセンサ電極２３は、固体電解質体２の表面２０１に設けられているとともに、被測定ガス空間１０１に導入される被測定ガスＧに晒されている。 As shown in FIG. 2, an inlet 331 for introducing the measurement gas G into the measurement gas space 101 via the diffusion resistor 32 is formed at the tip 103 of the sensor element 10. The introduction port 331 is formed at the tip portion of the spacer 33. The diffusion resistor 32 is composed of a porous body that allows the gas G to be measured to pass under a predetermined diffusion resistance, and is embedded in the inlet 331. The pump electrode 21 and the sensor electrode 23 are provided on the surface 201 of the solid electrolyte body 2 and are exposed to the measurement gas G introduced into the measurement gas space 101.
　図３、図４に示すように、固体電解質体２の表面２０１において、センサ電極２３に隣接して、モニタ電極２２が設けられている。モニタ電極２２は、被測定ガスＧに晒されてポンプ電極２１によって酸素濃度が調整された後の被測定ガスＧ中の酸素濃度を検出する。
　ポンプ電極２１は、導入口３３１に近い、センサ素子１０の固体電解質体２の先端に設けられている。センサ電極２３及びモニタ電極２２は、ポンプ電極２１の基端側に隣接して、ポンプ電極２１から互いに等しい距離だけ離間した位置に設けられている。すなわち、センサ電極２３及びモニタ電極２２は、長手方向Lにそって、ポンプ電極２１の基端縁から等距離に位置している。 As shown in FIGS. 3 and 4, the monitor electrode 22 is provided adjacent to the sensor electrode 23 on the surface 201 of the solid electrolyte body 2. The monitor electrode 22 detects the oxygen concentration in the measurement gas G after being exposed to the measurement gas G and the oxygen concentration being adjusted by the pump electrode 21.
The pump electrode 21 is provided at the tip of the solid electrolyte body 2 of the sensor element 10, which is close to the introduction port 331. The sensor electrode 23 and the monitor electrode 22 are adjacent to the proximal end side of the pump electrode 21 and are provided at positions spaced apart from each other by an equal distance from the pump electrode 21. That is, the sensor electrode 23 and the monitor electrode 22 are located at an equal distance from the base edge of the pump electrode 21 along the longitudinal direction L.
　図２、図３に示すように、固体電解質体２の表面２０２には、スペーサ３４を介してヒータ５が積層されている。ヒータ５は、一対のセラミックス基板５１と、セラミックス基板５１の間に挟まれた発熱層５２とによって構成されている。センサ素子１０においては、固体電解質体２の表面２０２、ヒータ５及びスペーサ３４によって囲まれて、基準ガス（大気ガス）Ａが導入される基準ガス空間１０２が形成されている。ポンプ電極２１、モニタ電極２２及びセンサ電極２３を、固体電解質体２の厚み方向において投影する表面２０２上の領域（ポンプ電極２１、モニタ電極２２及びセンサ電極２３に対して固体電解質体２を挟んで対向するように）に、基準ガス空間１０２に導入される基準ガスＡに晒される基準電極２５が設けられている。
　基準電極２５は、ポンプ電極２１、モニタ電極２２及びセンサ電極２３の３つの電極を投影する表面２０２の領域全体に設けられている。基準電極２５は、ポンプ電極２１、モニタ電極２２及びセンサ電極２３に対して別々に設けることもできる。 As shown in FIGS. 2 and 3, the heater 5 is laminated on the surface 202 of the solid electrolyte body 2 via the spacers 34. The heater 5 includes a pair of ceramic substrates 51 and a heat generation layer 52 sandwiched between the ceramic substrates 51. In the sensor element 10, a reference gas space 102 into which a reference gas (atmospheric gas) A is introduced is formed by being surrounded by the surface 202 of the solid electrolyte body 2, the heater 5 and the spacer 34. A region on the surface 202 where the pump electrode 21, the monitor electrode 22 and the sensor electrode 23 are projected in the thickness direction of the solid electrolyte body 2 (the solid electrolyte body 2 is sandwiched between the pump electrode 21, the monitor electrode 22 and the sensor electrode 23. A reference electrode 25 is provided so as to be exposed to the reference gas A introduced into the reference gas space 102.
The reference electrode 25 is provided over the entire area of the surface 202 onto which the three electrodes, the pump electrode 21, the monitor electrode 22, and the sensor electrode 23 are projected. The reference electrode 25 can be provided separately for the pump electrode 21, the monitor electrode 22, and the sensor electrode 23.
　図２，３に示すように、センサ素子１０においては、固体電解質体２を介してポンプ電極２１と基準電極２５との間に電圧を印加して、被測定ガス空間１０１における被測定ガスＧ中の酸素濃度を所定の濃度以下に調整するポンプセル４１が形成されている。また、センサ素子１０においては、固体電解質体２を介してモニタ電極２２と基準電極２５との間に流れる酸素イオン電流を検出して、被測定ガス空間１０１における、ポンプセル４１によって酸素濃度が調整された後の被測定ガスＧ中の酸素濃度を検出するモニタセル４２が形成されている。また、センサ素子１０においては、固体電解質体２を介してセンサ電極２３と基準電極２５との間に流れる酸素イオン電流を検出して、被測定ガス空間１０１における、ポンプセル４１によって酸素濃度が調整された後の被測定ガスＧ中のＮＯｘ濃度及び酸素濃度を検出するセンサセル４３が形成されている。
　ガスセンサ１においては、センサセル４３における酸素イオン電流値からモニタセル４２における酸素イオン電流値が差し引かれて、被測定ガスＧ中のＮＯｘ濃度が検出される。 As shown in FIGS. 2 and 3, in the sensor element 10, a voltage is applied between the pump electrode 21 and the reference electrode 25 via the solid electrolyte body 2, so that the measurement gas G in the measurement gas space 101 is in the measurement gas G. A pump cell 41 is formed for adjusting the oxygen concentration to a predetermined concentration or less. Further, in the sensor element 10, the oxygen ion current flowing between the monitor electrode 22 and the reference electrode 25 is detected via the solid electrolyte body 2, and the oxygen concentration is adjusted by the pump cell 41 in the measured gas space 101. After that, a monitor cell 42 for detecting the oxygen concentration in the measured gas G is formed. Further, in the sensor element 10, an oxygen ion current flowing between the sensor electrode 23 and the reference electrode 25 is detected via the solid electrolyte body 2, and the oxygen concentration is adjusted by the pump cell 41 in the measured gas space 101. A sensor cell 43 for detecting the NOx concentration and the oxygen concentration in the measured gas G after that is formed.
In the gas sensor 1, the oxygen ion current value in the monitor cell 42 is subtracted from the oxygen ion current value in the sensor cell 43 to detect the NOx concentration in the measurement gas G.
　図１に示すように、ハウジング１１Ａ，１１Ｂは、碍子１２の外周に位置する第１ハウジング１１Ａと、第１ハウジング１１Ａの外周に位置する第２ハウジング１１Ｂである。第１ハウジング１１Ａの先端部分は、第２ハウジング１１Ｂの先端よりもガスセンサ１の先端側に突出している。 As shown in FIG. 1, the housings 11A and 11B are a first housing 11A located on the outer periphery of the insulator 12 and a second housing 11B located on the outer periphery of the first housing 11A. The front end portion of the first housing 11A protrudes toward the front end side of the gas sensor 1 from the front end of the second housing 11B.
　保護カバー１３Ａ，１３Ｂのアッセンブリは、二重壁構造を有するものである。保護カバー１３Ａ，１３Ｂは、第１ハウジング１１Ａの先端部の外周に取り付けられた第１保護カバー１３Ａと、第１保護カバー１３Ａの外周に取り付けられた第２保護カバー１３Ｂである。被測定ガスＧをセンサ素子１０の先端部１００に導くためのカバー導入孔１３１，１３２には、第１保護カバー１３Ａの外周部及び先端部に形成されたカバー導入孔１３１と、第２保護カバー１３Ｂの外周部及び先端部に形成されたカバー導入孔１３２である。被測定ガスＧは、第１保護カバー１３Ａの外周部及び第２保護カバー１３Ｂの外周部を通って、第２保護カバー１３Ｂ内に流入し、センサ素子１０の先端部１００に接触した後、第１保護カバー１３Ａの先端部及び第２保護カバー１３Ｂの先端部を通って、各保護カバー１３Ａ，１３Ｂの外部へ流出する。 The assembly of the protective covers 13A and 13B has a double wall structure. The protective covers 13A and 13B are a first protective cover 13A attached to the outer periphery of the front end portion of the first housing 11A and a second protective cover 13B attached to the outer periphery of the first protective cover 13A. The cover introduction holes 131 and 132 for guiding the gas G to be measured to the distal end portion 100 of the sensor element 10 include the cover introduction holes 131 formed in the outer peripheral portion and the distal end portion of the first protective cover 13A, and the second protective cover. 13B is a cover introduction hole 132 formed at the outer periphery and the tip of 13B. The gas G to be measured passes through the outer peripheral portion of the first protective cover 13A and the outer peripheral portion of the second protective cover 13B, flows into the second protective cover 13B, contacts the distal end portion 100 of the sensor element 10, and then It flows out of the protective covers 13A and 13B through the front end of the first protective cover 13A and the front end of the second protective cover 13B.
　図１に示すように、第１保護カバー１３Ａの先端部は、第２保護カバー１３Ｂの先端部に形成されたカバー導入孔１３２内に配置されている。そして、第１保護カバー１３Ａ内に配置されたセンサ素子１０の先端部１００には、第１保護カバー１３Ａの外周部におけるカバー導入孔１３１を通って基端側へ流れる被測定ガスＧが接触する。 As shown in FIG. 1, the tip of the first protective cover 13A is disposed in a cover introduction hole 132 formed in the tip of the second protective cover 13B. The measured gas G flowing to the base end side through the cover introduction hole 131 in the outer peripheral portion of the first protective cover 13A comes into contact with the distal end portion 100 of the sensor element 10 arranged in the first protective cover 13A. .
　また、図７に示すように、第１保護カバー１３Ａの先端部を、第２保護カバー１３Ｂの先端部からガスセンサ１の基端側に離し、第１保護カバー１３Ａの先端部と第２保護カバー１３Ｂの先端部との間に空間を形成することもできる。この場合には、被測定ガスＧは、第２保護カバー１３Ｂの外周部におけるカバー導入孔１３２から第１保護カバー１３Ａの先端部と第２保護カバー１３Ｂの先端部との間の空間を流れた後、第１保護カバー１３Ａの外周部におけるカバー導入孔１３１を流れる。そして、センサ素子１０の先端部１００には、第１保護カバー１３Ａの外周部におけるカバー導入孔１３１を通って内周側へ流れる被測定ガスＧが接触する。
　なお、保護カバー１３Ａ，１３Ｂからなるアッセンブリは、一重壁構造を有するものとすることもできる。 Further, as shown in FIG. 7, the distal end portion of the first protective cover 13A is separated from the distal end portion of the second protective cover 13B toward the proximal end side of the gas sensor 1, and the distal end portion of the first protective cover 13A and the second protective cover are separated. A space can also be formed between the tip of 13B. In this case, the gas G to be measured flows through the space between the tip of the first protective cover 13A and the tip of the second protective cover 13B from the cover introduction hole 132 in the outer periphery of the second protective cover 13B. Then, it flows through the cover introduction hole 131 in the outer peripheral portion of the first protective cover 13A. And the to-be-measured gas G which flows to the inner peripheral side through the cover introduction hole 131 in the outer peripheral part of the 1st protective cover 13A contacts the front-end | tip part 100 of the sensor element 10. FIG.
Note that the assembly including the protective covers 13A and 13B may have a single wall structure.
　ガスセンサ１は、センサ素子１０の温度を制御するよう構成されている。具体的には、ガスセンサ１は、ポンプセル４１における、固体電解質体２を介するポンプ電極２１と基準電極２５との間のインピーダンスを測定し、このインピーダンスが所定の値になるように、ヒータ５の加熱量を制御するよう構成されている。
　ポンプ電極２１は、酸素を分解する一方、ＮＯｘを分解しないために、８３０～９２０℃の範囲内の温度に加熱される。また、センサ電極２３は、ＮＯｘを分解する一方、水を分解しないために、６５０～７４０℃の範囲内の温度に加熱される。 The gas sensor 1 is configured to control the temperature of the sensor element 10. Specifically, the gas sensor 1 measures the impedance between the pump electrode 21 and the reference electrode 25 through the solid electrolyte body 2 in the pump cell 41, and heats the heater 5 so that this impedance becomes a predetermined value. It is configured to control the amount.
The pump electrode 21 is heated to a temperature in the range of 830 to 920 ° C. in order to decompose oxygen but not NOx. The sensor electrode 23 is heated to a temperature in the range of 650 to 740 ° C. in order to decompose NOx but not water.
　図１に示すように、碍子１２は、センサ素子１０との絶縁性を確保して、センサ素子１０を第１ハウジング１１Ａに固定している。碍子１２の先端面１２１は、第１ハウジング１１Ａの先端面１１１よりもガスセンサ１の基端側に位置している。図４に示すように、センサ電極２３の長手方向Ｌの基端縁２３１及びモニタ電極２２の長手方向Ｌの基端縁２２１は、第１ハウジング１１Ａの先端面１１１よりもガスセンサ１の基端側に位置して、碍子１２の先端面１２１と第１ハウジング１１Ａの内周面１１２とによって形成される凹部１４内に配置されている。センサ電極２３及びモニタ電極２２は、それらの長手方向Ｌの中心２３２，２２２が、第１ハウジング１１Ａの先端面１１１よりもガスセンサ１の基端側に位置している。 As shown in FIG. 1, the insulator 12 secures insulation with the sensor element 10 and fixes the sensor element 10 to the first housing 11A. The distal end surface 121 of the insulator 12 is located closer to the proximal end side of the gas sensor 1 than the distal end surface 111 of the first housing 11A. As shown in FIG. 4, the base end edge 231 in the longitudinal direction L of the sensor electrode 23 and the base end edge 221 in the longitudinal direction L of the monitor electrode 22 are on the base end side of the gas sensor 1 with respect to the front end surface 111 of the first housing 11A. It is located in the recessed part 14 formed by the front end surface 121 of the insulator 12 and the inner peripheral surface 112 of the first housing 11A. The sensor electrode 23 and the monitor electrode 22 have their centers 232 and 222 in the longitudinal direction L positioned on the proximal end side of the gas sensor 1 with respect to the distal end surface 111 of the first housing 11A.
　ガスセンサ１においては、ポンプ電極２１、センサ電極２３、モニタ電極２２及び基準電極２５が設けられた、センサ素子１０の長手方向Ｌの先端部１００が、第１ハウジング１１Ａに対してできるだけガスセンサ１の基端側に位置するようにしている。
　ガスセンサ１によって被測定ガスＧ中のＮＯｘ濃度を検出する際には、被測定ガスＧは、カバー導入孔１３１，１３２から保護カバー１３Ａ，１３Ｂ内に導入され、センサ素子１０の先端部１００に接触する。そして、被測定ガスＧは、センサ素子１０の先端１０３に形成された導入口３３１から被測定ガス空間１０１内に導入される。 In the gas sensor 1, the distal end portion 100 in the longitudinal direction L of the sensor element 10 provided with the pump electrode 21, the sensor electrode 23, the monitor electrode 22, and the reference electrode 25 is as close to the first housing 11A as possible. It is located on the end side.
When the gas sensor 1 detects the NOx concentration in the gas G to be measured, the gas G to be measured is introduced into the protective covers 13A and 13B from the cover introduction holes 131 and 132, and comes into contact with the tip 100 of the sensor element 10. To do. Then, the measurement gas G is introduced into the measurement gas space 101 from the introduction port 331 formed at the tip 103 of the sensor element 10.
　保護カバー１３Ａ，１３Ｂ内に導入された被測定ガスＧの流れは、碍子１２の先端面１２１と第１ハウジング１１Ａの内周面１１２とによって形成される凹部１４においては緩やかになる。また、センサ電極２３及びモニタ電極２２の長手方向Ｌの中心２３２，２２２が第１ハウジング１１Ａの先端面１１１よりもガスセンサ１の基端側に位置しており、これらの少なくとも一部が凹部１４内に配置されている。これにより、センサ素子１０における、センサ電極２３及びモニタ電極２２が設けられた部位の周辺に被測定ガスＧが衝突しにくくなる、あるいは、センサ素子１０における、センサ電極２３及びモニタ電極２２が設けられた部位の周辺に衝突する被測定ガスＧの流速が遅くなる。そのため、被測定ガスＧの温度変化によって、センサ電極２３及びモニタ電極２２の温度が変動しにくくすることができる。 The flow of the gas G to be measured introduced into the protective covers 13A and 13B is gentle in the recess 14 formed by the tip surface 121 of the insulator 12 and the inner peripheral surface 112 of the first housing 11A. Further, the centers 232 and 222 of the sensor electrode 23 and the monitor electrode 22 in the longitudinal direction L are located on the proximal end side of the gas sensor 1 with respect to the distal end surface 111 of the first housing 11A, and at least a part of them is in the recess 14. Is arranged. As a result, the gas G to be measured does not easily collide with the periphery of the portion of the sensor element 10 where the sensor electrode 23 and the monitor electrode 22 are provided, or the sensor electrode 23 and the monitor electrode 22 of the sensor element 10 are provided. The flow velocity of the gas G to be measured that collides with the periphery of the region becomes slower. Therefore, the temperature of the sensor electrode 23 and the monitor electrode 22 can be made less likely to fluctuate due to the temperature change of the measurement gas G.
　それ故、ガスセンサ１は、センサ電極２３の温度変動を抑え、ＮＯｘ濃度の検出精度を高める。 Therefore, the gas sensor 1 suppresses the temperature fluctuation of the sensor electrode 23 and increases the detection accuracy of the NOx concentration.
　また、ガスセンサ１においては、図５に示すように、センサ電極２３の全体が、第１ハウジング１１Ａの先端面１１１よりもガスセンサ１の基端側に位置していてもよい。この場合には、センサ電極２３及びモニタ電極２２の温度変化をさらに抑えることができる。
　また、ガスセンサ１においては、図６に示すように、センサ素子１０の先端（先端位置）１０３が、第１ハウジング１１Ａの先端面１１１よりもガスセンサ１の基端側に位置していてもよい。この場合には、センサ素子１０の全体が碍子１２の先端面１２１と第１ハウジング１１Ａの内周面１１２とによる凹部１４内に配置される。この場合には、センサ電極２３及びモニタ電極２２の温度がさらに一層変動しにくくすることができる。 In the gas sensor 1, as shown in FIG. 5, the entire sensor electrode 23 may be located closer to the base end side of the gas sensor 1 than the front end surface 111 of the first housing 11 </ b> A. In this case, the temperature change of the sensor electrode 23 and the monitor electrode 22 can be further suppressed.
Further, in the gas sensor 1, as shown in FIG. 6, the tip (tip position) 103 of the sensor element 10 may be located closer to the base end side of the gas sensor 1 than the tip surface 111 of the first housing 11A. In this case, the entire sensor element 10 is disposed in the recess 14 formed by the distal end surface 121 of the insulator 12 and the inner peripheral surface 112 of the first housing 11A. In this case, the temperature of the sensor electrode 23 and the monitor electrode 22 can be made even more difficult to change.
　確認試験
　センサ電極２３の長手方向Ｌの位置と、センサ電極２３に生じる温度の変動との関係を調べるテストを行った。この温度の変動は、図１に示した保護カバー１３Ａ、１３Ｂを用いる場合（試験品１）と、図７に示した保護カバー１３Ａ，１３Ｂを用いる場合（試験品２）とについて、シミュレーションを行って求めた。　このシミュレーションは、ガスセンサ１が配置された排気管における被測定ガスＧの流れ方向、すなわちガスセンサ１に対してセンサ素子１０の長手方向Ｌに直交する方向から被測定ガスＧが２０ｍ／ｓの流速で流れる場合を想定した。そして、被測定ガスＧが保護カバー１３Ａ，１３Ｂ内に流れるときに、センサ素子１０の先端部１００に接触する被測定ガスＧの流速と、センサ電極２３に生じる温度の変動とを求めた。また、流速及び温度の変動は、センサ電極２３の長手方向Ｌの位置を適宜変更して求めた。 Confirmation Test A test was conducted to examine the relationship between the position in the longitudinal direction L of the sensor electrode 23 and the variation in temperature generated in the sensor electrode 23. This temperature fluctuation is simulated when the protective covers 13A and 13B shown in FIG. 1 are used (test product 1) and when the protective covers 13A and 13B shown in FIG. 7 are used (test product 2). Asked. In this simulation, the measurement gas G flows at a flow rate of 20 m / s from the flow direction of the measurement gas G in the exhaust pipe in which the gas sensor 1 is arranged, that is, from the direction perpendicular to the longitudinal direction L of the sensor element 10 with respect to the gas sensor 1. The case of flowing was assumed. Then, the flow rate of the measurement gas G contacting the tip portion 100 of the sensor element 10 and the temperature fluctuation generated in the sensor electrode 23 when the measurement gas G flows into the protective covers 13A and 13B were obtained. The fluctuations in the flow velocity and temperature were obtained by appropriately changing the position of the sensor electrode 23 in the longitudinal direction L.
　図８は、センサ電極２３の長手方向Ｌの位置と、センサ素子１０の先端部１００に接触する被測定ガスＧの流速との関係を示す。センサ電極２３の長手方向Ｌの位置は、センサ電極２３の長手方向Ｌの基端縁２３１がハウジング１１Ａの先端面１１１と同じ位置にある場合を０ｍｍとする。また、センサ電極２３の長手方向Ｌの位置は、センサ電極２３の長手方向Ｌの基端縁２３１がハウジング１１Ａの先端面１１１よりもガスセンサ１の基端側に位置する場合を負の値で示す。また、センサ電極２３の長手方向Ｌの位置は、センサ電極２３の長手方向Ｌの基端縁２３１がハウジング１１Ａの先端面１１１よりもガスセンサ１の先端側に位置する場合を正の値で示す。 FIG. 8 shows the relationship between the position in the longitudinal direction L of the sensor electrode 23 and the flow velocity of the gas G to be measured contacting the tip portion 100 of the sensor element 10. The position of the sensor electrode 23 in the longitudinal direction L is 0 mm when the base end edge 231 of the sensor electrode 23 in the longitudinal direction L is at the same position as the distal end surface 111 of the housing 11A. Further, the position in the longitudinal direction L of the sensor electrode 23 indicates a negative value when the proximal end edge 231 in the longitudinal direction L of the sensor electrode 23 is located on the proximal end side of the gas sensor 1 with respect to the distal end surface 111 of the housing 11A. . Further, the position of the sensor electrode 23 in the longitudinal direction L indicates a positive value when the base end edge 231 of the sensor electrode 23 in the longitudinal direction L is located on the distal end side of the gas sensor 1 with respect to the distal end surface 111 of the housing 11A.
　図８に示すように、試験品１，２のいずれにおいても、センサ電極２３の基端縁２３１がハウジング１１Ａの先端面１１１よりもガスセンサ１の基端側に位置する場合（負の値の場合）には、被測定ガスＧの流速が小さく抑えられることが分かる。また、センサ電極２３の長手方向Ｌの基端縁２３１がハウジング１１Ａの先端面１１１よりもガスセンサ１の基端側へ離れるほど、被測定ガスＧの流速は小さくなる。 As shown in FIG. 8, in any of the test products 1 and 2, when the base end edge 231 of the sensor electrode 23 is located closer to the base end side of the gas sensor 1 than the front end surface 111 of the housing 11A (in the case of a negative value) ) Shows that the flow rate of the gas G to be measured can be kept small. Further, as the base end edge 231 in the longitudinal direction L of the sensor electrode 23 is further away from the front end surface 111 of the housing 11A toward the base end side of the gas sensor 1, the flow rate of the gas G to be measured decreases.
　図９は、センサ電極２３のガスセンサ１の長手方向Ｌにおける位置と、センサ電極２３に生じる温度の変動との関係を示す。この温度の変動は、センサ電極２３が所定の温度にあり、被測定ガスＧの流速が０ｍｍ／ｓの場合を基準状態とし、被測定ガスＧの流速を２０ｍｍ／ｓとした場合に、センサ電極２３の温度が、流速が０ｍｍ／ｓの基準状態と比べてどれだけ変動したかを示す。
　センサ電極２３の長手方向Ｌの位置が示す値は図８の場合と同様である。図９に示すように、試験品１，２のいずれにおいても、センサ電極２３の長手方向Ｌの基端縁２３１がハウジング１１Ａの先端面１１１よりもガスセンサ１の基端側に位置する場合（負の値の場合）には、センサ電極２３に生じる温度の変動が小さく抑えられることが分かる。また、センサ電極２３の長手方向Ｌの基端縁２３１がハウジング１１Ａの先端面１１１よりもガスセンサ１の基端側へ離れるほど、センサ電極２３に生じる温度の変動は小さくなる。 FIG. 9 shows the relationship between the position of the sensor electrode 23 in the longitudinal direction L of the gas sensor 1 and the temperature variation that occurs in the sensor electrode 23. This variation in temperature is caused when the sensor electrode 23 is at a predetermined temperature, the flow rate of the gas G to be measured is 0 mm / s as a reference state, and the flow rate of the gas G to be measured is 20 mm / s. It shows how much the temperature of 23 has changed compared to the reference state where the flow rate is 0 mm / s.
The value indicated by the position in the longitudinal direction L of the sensor electrode 23 is the same as in the case of FIG. As shown in FIG. 9, in any of the test products 1 and 2, when the base end edge 231 in the longitudinal direction L of the sensor electrode 23 is located closer to the base end side of the gas sensor 1 than the front end surface 111 of the housing 11A (negative In the case of the value of (5), it can be seen that temperature fluctuations occurring in the sensor electrode 23 can be suppressed to a small level. Further, as the proximal end edge 231 in the longitudinal direction L of the sensor electrode 23 is further away from the distal end surface 111 of the housing 11A toward the proximal end side of the gas sensor 1, the temperature fluctuation generated in the sensor electrode 23 becomes smaller.
　また、図９においては、センサ電極２３の中心２３２が、ハウジング１１Ａの先端面１１１と長手方向Lにおいて、同じ位置にある場合（本確認試験においては、センサ電極２３の長手方向Ｌの位置が－０．８ｍｍの場合）を破線で示す。また、センサ電極２３の長手方向Ｌの先端が、ハウジング１１Ａの先端面１１１と同じ位置にある場合（本確認試験においては、センサ電極２３の長手方向Ｌの位置が－１．６ｍｍの場合）も破線で示す。
　本確認試験の結果より、センサ電極２３の長手方向Ｌの位置は、ハウジング１１Ａの先端面１１１よりも基端側に位置するほど、センサ電極２３に生じる温度の変動が小さくなることが分かった。 Further, in FIG. 9, when the center 232 of the sensor electrode 23 is at the same position in the longitudinal direction L as the front end surface 111 of the housing 11A (in this confirmation test, the position of the sensor electrode 23 in the longitudinal direction L is − (In the case of 0.8 mm) is indicated by a broken line. Further, when the front end in the longitudinal direction L of the sensor electrode 23 is at the same position as the front end surface 111 of the housing 11A (in this confirmation test, the position in the longitudinal direction L of the sensor electrode 23 is −1.6 mm). Shown in broken lines.
From the result of this confirmation test, it has been found that the temperature variation generated in the sensor electrode 23 becomes smaller as the position in the longitudinal direction L of the sensor electrode 23 is located closer to the base end side than the distal end surface 111 of the housing 11A.
　１　ガスセンサ
　１０　センサ素子
　１１Ａ，１１Ｂ　ハウジング
　１２　碍子
　１３Ａ，１３Ｂ　保護カバー
　１３１，１３２　カバー導入孔
　２　固体電解質体
　２１　ポンプ電極
　２２　モニタ電極
　２３　センサ電極
　２３１　基端縁 DESCRIPTION OF SYMBOLS 1 Gas sensor 10 Sensor element 11A, 11B Housing 12 insulator 13A, 13B Protective cover 131,132 Cover introduction hole 2 Solid electrolyte body 21 Pump electrode 22 Monitor electrode 23 Sensor electrode 231 Base edge

Claims (5)

  1. 　ハウジング（１１Ａ，１１Ｂ）と、
    　該ハウジング（１１Ａ，１１Ｂ）の内周に保持された碍子（１２）と、
    　該碍子（１２）に挿通された、酸素イオン伝導性を有する固体電解質体（２）を有し、ガスセンサの長手方向（Ｌ）における先端部（１００）が上記碍子（１２）の先端面（１２１）から突出するセンサ素子（１０）と、
    　該センサ素子（１０）の上記先端部（１００）を覆うよう上記ハウジング（１１Ａ，１１Ｂ）の先端部に取り付けられ、被測定ガス（Ｇ）を上記センサ素子（１０）の上記先端部（１００）に導くためのカバー導入孔（１３１）が形成された保護カバー（１３Ａ，１３Ｂ）と、を備えるガスセンサ（１）において、
    　上記固体電解質体（２）の上記長手方向（Ｌ）の先端部（２００）には、被測定ガス（Ｇ）に晒されて被測定ガス（Ｇ）中の酸素濃度を調整するためのポンプ電極（２１）と、被測定ガス（Ｇ）に晒されて上記ポンプ電極（２１）によって酸素濃度が調整された後の被測定ガス（Ｇ）中の所定ガス成分濃度を検出するためのセンサ電極（２３）とが設けられており、
    　該センサ電極（２３）の上記長手方向（Ｌ）の基端（２３１）は、上記ハウジング（１１Ａ，１１Ｂ）の先端面（１１１）よりもガスセンサ（１）の基端側に位置していることを特徴とするガスセンサ（１）。     A housing (11A, 11B);
    An insulator (12) held on the inner periphery of the housing (11A, 11B);
    It has a solid electrolyte body (2) having oxygen ion conductivity inserted through the insulator (12), and the distal end portion (100) in the longitudinal direction (L) of the gas sensor is the distal end surface (121) of the insulator (12). ) Protruding from the sensor element (10);
    It is attached to the tip of the housing (11A, 11B) so as to cover the tip (100) of the sensor element (10), and the gas to be measured (G) is sent to the tip (100) of the sensor element (10). In the gas sensor (1), comprising a protective cover (13A, 13B) formed with a cover introduction hole (131) for guiding to
    A pump electrode for adjusting the oxygen concentration in the gas to be measured (G) at the tip (200) in the longitudinal direction (L) of the solid electrolyte body (2) is exposed to the gas to be measured (G). (21) and a sensor electrode for detecting a predetermined gas component concentration in the gas to be measured (G) after being exposed to the gas to be measured (G) and adjusting the oxygen concentration by the pump electrode (21) ( 23) and
    The base end (231) of the sensor electrode (23) in the longitudinal direction (L) is located closer to the base end of the gas sensor (1) than the front end surface (111) of the housing (11A, 11B). A gas sensor (1).
  2. 　上記センサ電極（２３）の上記長手方向（Ｌ）の中心（２３２）が、上記ハウジング（１１Ａ，１１Ｂ）の先端面（１１１）よりもガスセンサ（１）の基端側に位置していることを特徴とする請求項１に記載のガスセンサ（１）。 The center (232) in the longitudinal direction (L) of the sensor electrode (23) is located on the proximal end side of the gas sensor (1) with respect to the distal end surface (111) of the housing (11A, 11B). Gas sensor (1) according to claim 1, characterized in that it is characterized in that
  3. 　上記センサ電極（２３）の全体が、上記ハウジング（１１Ａ，１１Ｂ）の先端面（１１１）よりもガスセンサ（１）の基端側に位置していることを特徴とする請求項１に記載のガスセンサ（１）。 2. The gas sensor according to claim 1, wherein the entire sensor electrode (23) is located closer to the base end side of the gas sensor (1) than the distal end surface (111) of the housing (11 </ b> A, 11 </ b> B). (1).
  4. 　上記センサ素子（１０）の上記長手方向（Ｌ）の先端（１０３）が、上記ハウジング（１１Ａ，１１Ｂ）の先端面（１１１）よりもガスセンサ（１）の基端側に位置していることを特徴とする請求項１に記載のガスセンサ（１）。 The front end (103) of the sensor element (10) in the longitudinal direction (L) is positioned closer to the base end side of the gas sensor (1) than the front end surface (111) of the housing (11A, 11B). Gas sensor (1) according to claim 1, characterized in that it is characterized in that
  5. 　上記センサ素子（１０）は、上記固体電解質体（２）の表面に被測定ガス（Ｇ）を導入する被測定ガス空間（１０１）を有しており、
    　上記ポンプ電極（２１）及び上記センサ電極（２３）は、上記被測定ガス空間（１０１）に導入される被測定ガス（Ｇ）に晒されており、
    　上記センサ素子（１０）の先端（１０３）には、拡散抵抗体（３２）を介して上記被測定ガス空間（１０１）に被測定ガス（Ｇ）を導入するための導入口（３３１）が形成されていることを特徴とする請求項１～４のいずれか一項に記載のガスセンサ（１）。     The sensor element (10) has a measured gas space (101) for introducing the measured gas (G) to the surface of the solid electrolyte body (2).
    The pump electrode (21) and the sensor electrode (23) are exposed to a measured gas (G) introduced into the measured gas space (101),
    An inlet (331) for introducing the measurement gas (G) into the measurement gas space (101) via the diffusion resistor (32) is formed at the tip (103) of the sensor element (10). The gas sensor (1) according to any one of claims 1 to 4, wherein the gas sensor (1) is provided.
PCT/JP2015/079585 2014-10-30 2015-10-20 Gas sensor WO2016067975A1 (en)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH09507916A (en) * 1994-11-08 1997-08-12 ローベルト ボツシユ ゲゼルシヤフト ミツト ベシユレンクテル ハフツング Electrochemical sensor for measuring nitrogen oxides in air-fuel mixtures
JP2009150719A (en) * 2007-12-19 2009-07-09 Toyota Motor Corp Nox sensor
JP2009175135A (en) * 2007-12-27 2009-08-06 Yamaha Motor Co Ltd Gas sensor, and air-fuel ratio control system and transportation apparatus equipped with the same
JP2009265085A (en) * 2008-04-02 2009-11-12 Ngk Spark Plug Co Ltd Gas sensor
JP2012002805A (en) * 2010-05-18 2012-01-05 Ngk Insulators Ltd Gas concentration detection sensor

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH09507916A (en) * 1994-11-08 1997-08-12 ローベルト ボツシユ ゲゼルシヤフト ミツト ベシユレンクテル ハフツング Electrochemical sensor for measuring nitrogen oxides in air-fuel mixtures
JP2009150719A (en) * 2007-12-19 2009-07-09 Toyota Motor Corp Nox sensor
JP2009175135A (en) * 2007-12-27 2009-08-06 Yamaha Motor Co Ltd Gas sensor, and air-fuel ratio control system and transportation apparatus equipped with the same
JP2009265085A (en) * 2008-04-02 2009-11-12 Ngk Spark Plug Co Ltd Gas sensor
JP2012002805A (en) * 2010-05-18 2012-01-05 Ngk Insulators Ltd Gas concentration detection sensor

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