WO2017022812A1 - Constant potential electrolytic gas sensor - Google Patents
Constant potential electrolytic gas sensor Download PDFInfo
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- WO2017022812A1 WO2017022812A1 PCT/JP2016/072872 JP2016072872W WO2017022812A1 WO 2017022812 A1 WO2017022812 A1 WO 2017022812A1 JP 2016072872 W JP2016072872 W JP 2016072872W WO 2017022812 A1 WO2017022812 A1 WO 2017022812A1
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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
- G01N27/403—Cells and electrode assemblies
- G01N27/404—Cells with anode, cathode and cell electrolyte on the same side of a permeable membrane which separates them from the sample fluid, e.g. Clark-type oxygen sensors
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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
- a reaction electrode for electrochemically reacting a gas to be detected as a gas electrode for detecting gas, a counter electrode with respect to the reaction electrode, and a reference electrode for controlling the potential of the reaction electrode are brought into contact with an electrolytic solution accommodated in an electrolytic cell.
- the present invention relates to a constant potential electrolysis gas sensor.
- a conventional constant potential electrolytic gas sensor is configured such that an electrode is provided facing an electrolytic solution storage part of an electrolytic cell in which an electrolytic solution is densely stored. For example, an electrode is detected as a gas electrode that detects gas.
- an electrode is detected as a gas electrode that detects gas.
- a potentiostat circuit for setting the potential is connected.
- a gas-permeable porous PTFE film having water repellency is coated with a noble metal catalyst such as platinum, gold, palladium, etc.
- an electrolyte an acidic aqueous solution such as sulfuric acid or phosphoric acid is used. Was used.
- the constant potential electrolytic gas sensor generates a current corresponding to the change in the surrounding environment between the reaction electrode and the counter electrode by controlling the potential of the reaction electrode to be constant with respect to the change in the surrounding environment. . Then, by utilizing the fact that the potential of the reaction electrode does not change and the oxidation-reduction potential varies depending on the gas type, it becomes possible to selectively detect the gas depending on the set potential of the potentiostat circuit. Further, by changing the catalyst used for the gas electrode, it is possible to have high selectivity for the target gas.
- constant potential electrolytic gas sensor which is a conventional technique in the present invention, is a general technique, and thus does not show conventional technical documents such as patent documents.
- the air layer may expand and bubbles may enter the sensor through a through hole formed on the gas ventilation part side.
- the contact area wetting area
- the contact area wetting area
- an object of the present invention is to provide a constant potential electrolytic gas sensor that can suppress the formation of bubbles at least on the surface of the counter electrode.
- a constant potential electrolytic gas sensor controls a reaction electrode for electrochemically reacting a gas to be detected as a gas electrode for detecting gas, a counter electrode for the reaction electrode, and a potential of the reaction electrode.
- a constant potential electrolytic gas sensor provided with a reference electrode in contact with an electrolyte contained in an electrolytic cell, the first characteristic configuration of which is a bubble that suppresses the formation of bubbles at least on the surface of the counter electrode It is in the point provided with formation suppression means.
- the bubble formation suppressing means even when the temperature of the sensor changes suddenly due to the influence of the disturbance, for example, it is difficult for bubbles to be mixed from a through hole formed on the counter electrode side.
- the bubbles mixed on the surface of the counter electrode are difficult to reach. Accordingly, it is possible to suppress the formation of bubbles at least on the surface of the counter electrode, and thus it is possible to suppress a sudden change in the indicated value of the sensor.
- the second characteristic configuration of the constant potential electrolytic gas sensor according to the present invention is that the bubble formation suppressing means is a water retaining member that absorbs and holds the electrolytic solution.
- the bubble formation suppressing means is a water retaining member, it is more difficult for bubbles mixed in at least the surface of the counter electrode facing the electrolyte container to reach, and it is ensured that bubbles are formed on the surface of the counter electrode. Can be suppressed.
- a third characteristic configuration of the constant potential electrolytic gas sensor according to the present invention is that an oxygen permeable membrane that transmits oxygen is disposed in a gas ventilation portion that discharges gas formed on the counter electrode and the reference electrode. .
- the fourth characteristic configuration of the potentiostatic gas sensor according to the present invention is that the filling rate of the water retaining member is 90% or more.
- each gas electrode since the surface of each gas electrode can be reliably covered, it is difficult for the mixed bubbles to reach the surface of each gas electrode, and it is ensured that bubbles are formed on the surface of each gas electrode. Can be suppressed.
- bubbles generated due to electrode reactions or the like in each gas electrode, or air dissolved in the electrolyte solution due to a rapid temperature change, or by intrusion of air in a sudden pressurization state It can be avoided that the surface of each gas electrode is covered with air, the reaction area of each gas electrode is reduced, and the indication becomes unstable.
- a fifth characteristic configuration of the constant potential electrolytic gas sensor according to the present invention is that the water retention member has a bulk density of 0.05 to 0.30 g / cm 3 .
- the water retention member when the water retention member is disposed in the electrolyte container, the water retention member can be disposed so as to press each gas electrode to some extent, so that the contact state between the water retention member and each gas electrode is ensured. Can be secured. Thereby, at least the bubbles mixed on the surface of the counter electrode are more difficult to reach.
- the constant potential electrolytic gas sensor X controls a reaction electrode 11 that causes a gas to be detected to electrochemically react as a gas electrode 10 that detects gas, a counter electrode 12 with respect to the reaction electrode 11, and a potential of the reaction electrode 11.
- the reference electrode 13 is provided so as to be in contact with the electrolytic solution 20 accommodated in the electrolytic cell 30.
- This constant potential electrolytic gas sensor X includes a bubble formation suppressing means 50 that suppresses the formation of bubbles on at least the surface of the counter electrode 12.
- the reaction electrode 11, the counter electrode 12, and the reference electrode 13 are formed by applying and baking a paste made of a known electrode material on the surface of a porous gas permeable film 14 having water repellency.
- the gas permeable membrane 14 may be any membrane as long as it is hydrophobic and has a property of transmitting gas.
- a porous PTFE (polytetrafluoroethylene) membrane having chemical resistance may be used. it can.
- the reaction electrode 11, the counter electrode 12, and the reference electrode 13 are composed of a gas diffusion electrode including a catalyst and a hydrophobic resin (gas permeable membrane 14).
- a catalyst platinum (Pt), gold (Au), ruthenium (Ru), Ruthenium oxide (RuO2), palladium (Pd), platinum-supported carbon (Pt / C), etc. are preferably used.
- the counter electrode 12 and the reference electrode 13 of the present embodiment have a mode in which the counter electrode 12 is formed in the upper half and the reference electrode 13 is formed in the lower half in one gas permeable membrane 14, but is limited to such a mode. It is not something. Between the counter electrode 12 and the reference electrode 13, the slit 14a in which an electrode is not formed is formed.
- the reaction electrode 11 and the reference electrode 13 are arranged to face each other, and the counter electrode 12 and the reference electrode 13 are arranged on the gas ventilation part 33 side.
- a space between the reaction electrode 11, the counter electrode 12, and the reference electrode 13 serves as an electrolyte solution storage unit 31 that stores the electrolyte solution 20.
- the electrolytic solution 20 may be an acidic aqueous solution such as sulfuric acid or phosphoric acid, but is not limited thereto.
- the gas to be detected is introduced into the sensor from the gas introduction part 32 and reacts on the reaction electrode 11.
- the buffer filter 35 is a buffer film that prevents deformation of each electrode and prevents leakage of the electrolyte solution 20.
- a porous Teflon (registered trademark) film having a porosity of about 80% can be used. It is not limited to.
- Each gas electrode 10, gas permeable membrane 14, buffer filter 35, and O-ring 15a are fixed by a lid member 16 (16A, 16B) of the electrolytic cell 30.
- An internal pressure adjusting hole 17 having a small diameter of about 0.5 to 2 mm is formed at one end of the electrolytic cell 30.
- a porous sheet 18 is disposed on the internal pressure adjusting hole 17 on the side of the electrolytic solution containing portion 31.
- the electrolyte storage unit 31 has two large-diameter storage units 31b through a small-diameter channel 31a. When the flow path 31a has a small diameter of about 2 to 4 mm, the electrolytic solution 20 is unlikely to flow backward from one housing portion 31b to the other housing portion 31b due to the surface tension of the electrolytic solution 20.
- the electrolytic cell 30 and the lid member 16 constituting the housing may be made of a synthetic resin having corrosion resistance, for example, a metal such as hard vinyl chloride or nickel alloy.
- Through holes 16a and 16b are respectively formed in the lid member 16A formed on the gas introduction part 32 side and the lid member 16B formed on the gas ventilation part 33 side, and gas is introduced through the through hole 16a.
- the gas is discharged and introduced through the through hole 16b. Since the position where the through hole 16b is formed corresponds to the position of the slit 14a where no electrode is formed, gas can be discharged or introduced through the slit 14a and the through hole 16b.
- the gas layer 33 that discharges the gas formed on the side of the counter electrode 12 and the reference electrode 13 is provided with an air layer 40 and an oxygen permeable membrane 41 that transmits oxygen.
- the oxygen permeable membrane 41 is not particularly limited as long as it has oxygen permeation performance.
- FEP tetrafluoroethylene hexafluoropropylene copolymer resin
- PFA perfluoroalkyl vinyl ether copolymer
- the oxygen permeable film 41 By disposing the oxygen permeable film 41 as in this configuration, it is possible to prevent the surrounding interference gas (other than oxygen) from entering the counter electrode 12 and the reference electrode 13 from the gas ventilation portion 33.
- the constant potential electrolytic gas sensor X of the present invention includes bubble formation suppressing means 50 that suppresses the formation of bubbles on at least the surface of the counter electrode 12.
- the bubble formation suppressing means 50 may be configured to suppress the formation of bubbles on the surface of the other gas electrode 10 (reaction electrode 11 and reference electrode 13) in addition to the counter electrode 12.
- the air layer 40 may expand greatly and air bubbles may be mixed in through the through holes 16b formed on the gas ventilation part 33 side. If the mixed bubbles reach the surface of the electrode and, for example, bubbles are formed on the surface of the counter electrode 12, the contact area between the electrolytic solution 20 and the counter electrode 12 may decrease, and the indicated value of the sensor may suddenly increase. .
- the bubble formation suppressing means 50 of the present invention it is difficult for air bubbles to be mixed from the through hole 16b even when the temperature of the sensor is suddenly changed due to the influence of disturbance, and the bubble is prevented from passing through the through hole 16b.
- the bubble formation suppressing means 50 is the water retaining member 37, it is more difficult for bubbles mixed in at least the surface of the counter electrode 12 facing the electrolyte container 31 to reach, and it is ensured that bubbles are formed on the surface of the counter electrode 12. Can be suppressed.
- the water retaining member 37 may be disposed so as to suppress at least the formation of bubbles on the surface of the counter electrode 12, and preferably suppresses the formation of bubbles on the surfaces of the reaction electrode 11 and the reference electrode 13. What is necessary is just to arrange
- the water retaining member 37 can be filled in the entire surface (100%) of one accommodating portion 31b (the side where the gas electrode 10 is disposed) in the electrolyte accommodating portion 31 as in the present embodiment.
- the present invention is not limited to such an embodiment, and the water retaining member 37 is filled with, for example, 90% or more, specifically about 90 to 95% of one accommodating portion 31b (side on which the gas electrode 10 is disposed). What is necessary is just to fill so that it may become a rate.
- the surface of each gas electrode 10 can be reliably covered, so that the mixed bubbles are less likely to reach the surface of each gas electrode 10. It is possible to reliably suppress the formation of bubbles on the surface.
- the water retaining member 37 is an aspect that absorbs and holds the electrolytic solution 20, the water retaining member 37 has a space in which the electrolytic solution 20 can be retained. Therefore, even if it is a case where the water retention member 37 is filled in the whole surface of the accommodating part 31b, the contact state of each gas electrode 10 and the electrolyte solution 20 can be maintained favorable.
- the water retaining member 37 is not particularly limited as long as it is a water absorbing member capable of holding the electrolytic solution 20 such as a water retaining fiber (for example, glass fiber, ceramic fiber, etc.) or a water absorbing polymer.
- the bulk density of the water retaining member 37 is preferably 0.05 to 0.30 g / cm 3 .
- MGP manufactured by Nippon Sheet Glass Co., Ltd.
- the density is about 0.18 g / cm 3 and the space ratio is about 90%
- MC paper manufactured by Nippon Sheet Glass Co., Ltd.
- the bulk density of the water retaining member 37 is 0.08 g.
- OR-125 manufactured by Asahi Textile Industry Co., Ltd.
- the bulk density of the water retaining member 37 and the actual product are not limited to these.
- a plurality of such water retaining members 37 may be arranged in the electrolyte solution storage unit 31 in a stacked manner.
- the water retaining member 37 With the structure of the water retaining member 37 described above, the water retaining member 37 can be pushed to some extent to fill the accommodating portion 31b, and the water retaining member 37 can be disposed so as to press each gas electrode 10 to some extent. And the contact state between the gas electrodes 10 can be reliably ensured. As a result, at least air bubbles mixed on the surface of the counter electrode 12 are more difficult to reach.
- Such a constant potential electrolytic gas sensor X includes a current measuring unit capable of detecting a current based on electrons generated on the reaction electrode 11 due to a reaction of the gas to be detected, and a potential control unit capable of controlling the potential of the reaction electrode 11. It is used as a gas detection device by connecting to a gas detection circuit (not shown).
- the constant potential electrolytic gas sensor X of the present invention is used for detecting oxygen gas, hydride gas such as silane, phosphine, germane, arsine and diborane, and detecting toxic gas such as carbon monoxide and hydrogen sulfide.
- the filter means 60 for filtering the interference gas is provided on the lid member 16A on the gas introduction part 32 side.
- the filter means 60 is disposed on a frame 16c formed on the lid member 16A.
- the filter means 60 has a structure in which a plurality of filter layers 61 including activated carbon and silica gel for filtering interference gas are accommodated in a cylindrical container 60a, and both sides of the filter layers 61 are holding members such as meshes.
- the present invention is not limited to such a mode.
- cylindrical member 34 examples include ceramics such as alumina and zirconia, but are not limited thereto.
- the long dimension of the cylindrical member is 2.0 mm or more, preferably 2.0 to 6.0 mm.
- the diameter of the pinhole 34a is preferably about 0.05 mm.
- the gas ventilation part 33 side may be sealed with a sealing means 36 such as an adhesive or packing in order to ensure airtightness other than the pinhole 34a.
- the gas flow on the gas ventilation part 33 side can be limited to the pinhole 34a.
- the through hole 16b on the gas ventilation portion 33 side small and long, interference gas or the like is less likely to be mixed into the inside of the sensor (electrolyte accommodating portion 31 or the like).
- the cylindrical member 34 in which the pinhole 34a is formed can be used as the air bubble formation suppressing means 50.
- the water retaining member 37 in the above-described embodiment may be provided, or even if not provided, at least the surface of the counter electrode 12 by the cylindrical member 34. It is possible to suppress the formation of bubbles on the surface, and thus it is possible to suppress a sudden change in the indicated value of the sensor.
- the shape of the cylindrical member 34 is preferably a cylindrical shape, but is not limited to this, and may be a prismatic shape or the like.
- the pin member 34a provided in the cylindrical member 34 may be one or plural.
- the number of pinholes 34a is not particularly limited. In the present embodiment, a case where one pinhole 34a is formed in each cylindrical member 34 will be described.
- the amount of gas introduced can be adjusted by the number of pinholes 34a. Even if condensation occurs in the gas introduction part 32, if a plurality of pinholes 34a are formed, all the pinholes 34a are not easily blocked by condensation, and gas discharge or introduction due to gas reaction is hindered. Can be prevented in advance. Since the amount of gas introduced can be adjusted not only by the number of pinholes but also by the length and diameter of the pinholes, it may be set appropriately according to the interference gas to be suppressed.
- the constant potential electrolytic gas sensor X of the present example was set as the following mode. That is, in the controlled potential electrolytic gas sensor X of the embodiment of FIG. 1, the buffer filter 35 having a thickness of 1 mm is a porous Teflon (registered trademark) membrane (PTFE membrane), the water retaining member 37 is a glass fiber member, and oxygen permeation is performed.
- the membrane 41 was made of tetrafluoroethylene hexafluoropropylene copolymer resin (FEP), the filter layer 61 was made of four activated carbon layers, and the holding member 62 was made of SUS mesh. Further, the diameters of the through holes 16a and 16b were 2 mm, and the width of the slit 14a formed between the counter electrode 12 and the reference electrode 13 was 1.5 mm.
- the constant potential electrolytic gas sensor X of the present embodiment is configured such that the water retaining member 37 and the oxygen permeable membrane 41 are not used, and the cylindrical member 34 in which the pinhole 34a is formed is disposed.
- the long dimension of the said cylindrical member 34 was 3.0 mm, and the diameter of the pinhole 34a was 0.05 mm.
- the sensor which does not provide a pinhole was used as a constant potential electrolysis type gas sensor of a comparative example. That is, the diameter of the through hole 16b on the gas ventilation part 33 side in this sensor was 2.0 mm, and the long dimension was 2.0 mm.
- the controlled potential electrolytic gas sensor X of the present invention As a result, in the controlled potential electrolytic gas sensor X of the present invention (FIG. 5), the sensor indicated no significant fluctuations and was considered stable. Therefore, it was confirmed that the constant potential electrolysis gas sensor X of the present invention has the same performance as the case where the oxygen permeable membrane is used even if interference gas exists in the surroundings.
- the indicated value of the sensor fluctuated greatly, and the sensor output was considered to be unstable.
- the diameter of the through hole 16b is larger than the pinhole 34a of the constant potential electrolytic gas sensor X of the present invention. It was confirmed that gas could easily enter and the instructions were not stable.
- a reaction electrode for electrochemically reacting a gas to be detected as a gas electrode for detecting gas, a counter electrode with respect to the reaction electrode, and a reference electrode for controlling the potential of the reaction electrode are brought into contact with an electrolytic solution accommodated in an electrolytic cell. It can utilize for the constant potential electrolytic gas sensor provided.
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Abstract
A constant potential electrolytic gas sensor X comprising as gas electrodes 10 that detect gas a reaction electrode 11 that causes a gas to be detected to undergo an electrochemical reaction, a counter electrode 12 facing the reaction electrode 11, and a reference electrode 13 that controls the potential of the reaction electrode 11 in a manner making contact with an electrolyte solution 20 in an electrolytic bath 30, wherein the constant potential electrolytic gas sensor comprises an air bubble formation inhibiting means 50 that inhibits the formation of air bubbles on the surface of at least the counter electrode 12.
Description
本発明は、ガスを検知するガス電極として被検知ガスを電気化学反応させる反応極、前記反応極に対する対極および前記反応極の電位を制御する参照極を、電解槽に収容した電解液に接触するように備えた定電位電解式ガスセンサに関する。
In the present invention, a reaction electrode for electrochemically reacting a gas to be detected as a gas electrode for detecting gas, a counter electrode with respect to the reaction electrode, and a reference electrode for controlling the potential of the reaction electrode are brought into contact with an electrolytic solution accommodated in an electrolytic cell. The present invention relates to a constant potential electrolysis gas sensor.
従来の定電位電解式ガスセンサは、電極を電解液が密に収容される電解槽の電解液収容部内に臨んで設けて構成してあり、例えば電極としては、ガスを検知するガス電極として被検知ガスを電気化学反応させる反応極、当該反応極に対する対極、反応極の電位を制御する参照極の3電極を設けてあり、また、これらが接触自在な電解液を収容した電解槽と、各電極の電位を設定するポテンシオスタット回路等を接続してある。前記3電極の材料としては撥水性を有するガス透過性の多孔質PTFE膜に白金や金、パラジウム等の貴金属触媒等を塗布したものが、電解液としては、硫酸やリン酸等の酸性水溶液等が用いられていた。
A conventional constant potential electrolytic gas sensor is configured such that an electrode is provided facing an electrolytic solution storage part of an electrolytic cell in which an electrolytic solution is densely stored. For example, an electrode is detected as a gas electrode that detects gas. There are provided three electrodes: a reaction electrode for electrochemically reacting gas, a counter electrode for the reaction electrode, and a reference electrode for controlling the potential of the reaction electrode. A potentiostat circuit for setting the potential is connected. As the material of the three electrodes, a gas-permeable porous PTFE film having water repellency is coated with a noble metal catalyst such as platinum, gold, palladium, etc. As an electrolyte, an acidic aqueous solution such as sulfuric acid or phosphoric acid is used. Was used.
また、定電位電解式ガスセンサは、周囲の環境変化に対して反応極の電位を制御して一定に維持することによって、反応極と対極との間に周囲の環境変化に相当する電流を生じさせる。そして、反応極の電位が変化せず、またガス種によって酸化還元電位が異なることを利用することにより、ポテンシオスタット回路の設定電位によってはガスの選択的な検知が可能になる。また、ガス電極に用いる触媒を変えることで、目的とするガスに対して高い選択性を持たすことができる。
In addition, the constant potential electrolytic gas sensor generates a current corresponding to the change in the surrounding environment between the reaction electrode and the counter electrode by controlling the potential of the reaction electrode to be constant with respect to the change in the surrounding environment. . Then, by utilizing the fact that the potential of the reaction electrode does not change and the oxidation-reduction potential varies depending on the gas type, it becomes possible to selectively detect the gas depending on the set potential of the potentiostat circuit. Further, by changing the catalyst used for the gas electrode, it is possible to have high selectivity for the target gas.
尚、本発明における従来技術となる上述した定電位電解式ガスセンサは、一般的な技術であるため、特許文献等の従来技術文献は示さない。
Note that the above-described constant potential electrolytic gas sensor, which is a conventional technique in the present invention, is a general technique, and thus does not show conventional technical documents such as patent documents.
上述した定電位電解式ガスセンサにおいて、対極および参照極の側に形成したガス通気部には、空気層および酸素を透過する酸素透過膜を配設してあるものがあった。
In the above-described constant potential electrolytic gas sensor, there is a gas vent formed on the side of the counter electrode and the reference electrode, in which an air layer and an oxygen permeable membrane that transmits oxygen are disposed.
例えば低温から高温に急激に温度が変化した場合、空気層が膨張してガス通気部の側に形成した貫通孔を介して気泡がセンサ内部に混入する虞がある。混入した気泡が電極の表面に到達し、例えば対極の表面に気泡が形成されれば、電解液および対極の接触面積(濡れ面積)が減少してセンサの指示値が突発的に上昇する虞がある。この場合、対極の表面に形成された気泡が消失してセンサ出力が安定化するまで時間を要することとなるため、センサの運用上、不都合であった。
For example, when the temperature suddenly changes from low temperature to high temperature, the air layer may expand and bubbles may enter the sensor through a through hole formed on the gas ventilation part side. If the mixed bubbles reach the surface of the electrode, for example, bubbles are formed on the surface of the counter electrode, the contact area (wetting area) between the electrolyte and the counter electrode may decrease, and the indicated value of the sensor may suddenly increase. is there. In this case, since it takes time until the bubbles formed on the surface of the counter electrode disappear and the sensor output is stabilized, it is inconvenient in the operation of the sensor.
従って、本発明の目的は、少なくとも対極の表面に気泡が形成されるのを抑制することができる定電位電解式ガスセンサを提供することにある。
Therefore, an object of the present invention is to provide a constant potential electrolytic gas sensor that can suppress the formation of bubbles at least on the surface of the counter electrode.
上記目的を達成するための本発明に係る定電位電解式ガスセンサは、ガスを検知するガス電極として被検知ガスを電気化学反応させる反応極、前記反応極に対する対極および前記反応極の電位を制御する参照極を、電解槽に収容した電解液に接触するように備えた定電位電解式ガスセンサであって、その第一特徴構成は、少なくとも前記対極の表面に気泡が形成されるのを抑制する気泡形成抑制手段を備えた点にある。
In order to achieve the above object, a constant potential electrolytic gas sensor according to the present invention controls a reaction electrode for electrochemically reacting a gas to be detected as a gas electrode for detecting gas, a counter electrode for the reaction electrode, and a potential of the reaction electrode. A constant potential electrolytic gas sensor provided with a reference electrode in contact with an electrolyte contained in an electrolytic cell, the first characteristic configuration of which is a bubble that suppresses the formation of bubbles at least on the surface of the counter electrode It is in the point provided with formation suppression means.
本構成によれば、気泡形成抑制手段を設けることで、外乱の影響でセンサの温度が急激に変化した場合であっても、例えば対極の側に形成された貫通孔から気泡が混入し難くなり、また、当該貫通孔を介して気泡が混入した場合であっても、少なくとも対極の表面に混入した気泡が到達し難くなる。従って、少なくとも対極の表面に気泡が形成されるのを抑制することができるため、センサの指示値が急激に変化するのを抑制することができる。
According to this configuration, by providing the bubble formation suppressing means, even when the temperature of the sensor changes suddenly due to the influence of the disturbance, for example, it is difficult for bubbles to be mixed from a through hole formed on the counter electrode side. In addition, even when bubbles are mixed through the through hole, at least the bubbles mixed on the surface of the counter electrode are difficult to reach. Accordingly, it is possible to suppress the formation of bubbles at least on the surface of the counter electrode, and thus it is possible to suppress a sudden change in the indicated value of the sensor.
本発明に係る定電位電解式ガスセンサの第二特徴構成は、前記気泡形成抑制手段を、前記電解液を吸水して保持する保水部材とした点にある。
The second characteristic configuration of the constant potential electrolytic gas sensor according to the present invention is that the bubble formation suppressing means is a water retaining member that absorbs and holds the electrolytic solution.
本構成によれば、気泡形成抑制手段を保水部材とすれば、電解液収容部に臨む少なくとも対極の表面に混入した気泡がより到達し難くなり、対極の表面に気泡が形成されるのを確実に抑制することができる。
According to this configuration, if the bubble formation suppressing means is a water retaining member, it is more difficult for bubbles mixed in at least the surface of the counter electrode facing the electrolyte container to reach, and it is ensured that bubbles are formed on the surface of the counter electrode. Can be suppressed.
本発明に係る定電位電解式ガスセンサの第三特徴構成は、前記対極および前記参照極の側に形成したガスを排出するガス通気部に、酸素を透過する酸素透過膜を配設した点にある。
A third characteristic configuration of the constant potential electrolytic gas sensor according to the present invention is that an oxygen permeable membrane that transmits oxygen is disposed in a gas ventilation portion that discharges gas formed on the counter electrode and the reference electrode. .
本構成によれば、酸素透過膜を配設することで、周囲の干渉ガス(酸素以外)がガス通気部から対極および参照極に入り込むのを防ぐことができる。
According to this configuration, by arranging the oxygen permeable membrane, it is possible to prevent the surrounding interference gas (other than oxygen) from entering the counter electrode and the reference electrode from the gas vent.
本発明に係る定電位電解式ガスセンサの第四特徴構成は、前記保水部材の充填率を90%以上とした点にある。
The fourth characteristic configuration of the potentiostatic gas sensor according to the present invention is that the filling rate of the water retaining member is 90% or more.
本構成によれば、各ガス電極の表面を確実に覆うことができるため、混入した気泡が各ガス電極の表面により到達し難くなり、各ガス電極の表面に気泡が形成されるのを確実に抑制することができる。これにより、各ガス電極における電極反応等で発生した気泡や、急激な温度変化に伴い電解液中に溶解していた空気が発生した場合や、急激な加圧状態における空気の侵入により、直接、各ガス電極の表面が空気で覆われて各ガス電極の反応面積が減少し、指示が不安定になることを回避することができる。
According to this configuration, since the surface of each gas electrode can be reliably covered, it is difficult for the mixed bubbles to reach the surface of each gas electrode, and it is ensured that bubbles are formed on the surface of each gas electrode. Can be suppressed. As a result, when bubbles generated due to electrode reactions or the like in each gas electrode, or air dissolved in the electrolyte solution due to a rapid temperature change, or by intrusion of air in a sudden pressurization state, It can be avoided that the surface of each gas electrode is covered with air, the reaction area of each gas electrode is reduced, and the indication becomes unstable.
本発明に係る定電位電解式ガスセンサの第五特徴構成は、前記保水部材の嵩密度を0.05~0.30g/cm3とした点にある。
A fifth characteristic configuration of the constant potential electrolytic gas sensor according to the present invention is that the water retention member has a bulk density of 0.05 to 0.30 g / cm 3 .
本構成によれば、保水部材を電解液収容部に配設したとき、保水部材が各ガス電極をある程度押圧するように配置することができるため、保水部材と各ガス電極との接触状態を確実に確保することができる。これにより、少なくとも対極の表面に混入した気泡がより到達し難くなる。
According to this configuration, when the water retention member is disposed in the electrolyte container, the water retention member can be disposed so as to press each gas electrode to some extent, so that the contact state between the water retention member and each gas electrode is ensured. Can be secured. Thereby, at least the bubbles mixed on the surface of the counter electrode are more difficult to reach.
以下、本発明の実施形態を図面に基づいて説明する。
図1に示すように、定電位電解式ガスセンサXは、ガスを検知するガス電極10として被検知ガスを電気化学反応させる反応極11、当該反応極11に対する対極12、反応極11の電位を制御する参照極13を、電解槽30に収容した電解液20に接触するように備えている。この定電位電解式ガスセンサXは、少なくとも対極12の表面に気泡が形成されるのを抑制する気泡形成抑制手段50を備える。 Hereinafter, embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the constant potential electrolytic gas sensor X controls areaction electrode 11 that causes a gas to be detected to electrochemically react as a gas electrode 10 that detects gas, a counter electrode 12 with respect to the reaction electrode 11, and a potential of the reaction electrode 11. The reference electrode 13 is provided so as to be in contact with the electrolytic solution 20 accommodated in the electrolytic cell 30. This constant potential electrolytic gas sensor X includes a bubble formation suppressing means 50 that suppresses the formation of bubbles on at least the surface of the counter electrode 12.
図1に示すように、定電位電解式ガスセンサXは、ガスを検知するガス電極10として被検知ガスを電気化学反応させる反応極11、当該反応極11に対する対極12、反応極11の電位を制御する参照極13を、電解槽30に収容した電解液20に接触するように備えている。この定電位電解式ガスセンサXは、少なくとも対極12の表面に気泡が形成されるのを抑制する気泡形成抑制手段50を備える。 Hereinafter, embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the constant potential electrolytic gas sensor X controls a
反応極11、対極12及び参照極13は、撥水性を有する多孔質のガス透過膜14の表面に、公知の電極材料より作製したペーストを塗布・焼成して形成してある。ガス透過膜14は、例えば疎水性でガスを透過する性質を有するものであればどのような膜でもよく、例えば耐薬品性を有する多孔質PTFE(ポリテトラフルオロエチレン)膜などを使用することができる。
The reaction electrode 11, the counter electrode 12, and the reference electrode 13 are formed by applying and baking a paste made of a known electrode material on the surface of a porous gas permeable film 14 having water repellency. The gas permeable membrane 14 may be any membrane as long as it is hydrophobic and has a property of transmitting gas. For example, a porous PTFE (polytetrafluoroethylene) membrane having chemical resistance may be used. it can.
反応極11、対極12及び参照極13は、触媒および疎水性樹脂(ガス透過膜14)を含むガス拡散電極からなり、触媒としては、白金(Pt)、金(Au)、ルテニウム(Ru)、酸化ルテニウム(RuO2)、パラジウム(Pd)、白金担持カーボン(Pt/C)などが好適に用いられる。
The reaction electrode 11, the counter electrode 12, and the reference electrode 13 are composed of a gas diffusion electrode including a catalyst and a hydrophobic resin (gas permeable membrane 14). As the catalyst, platinum (Pt), gold (Au), ruthenium (Ru), Ruthenium oxide (RuO2), palladium (Pd), platinum-supported carbon (Pt / C), etc. are preferably used.
本実施形態の対極12及び参照極13は、一枚のガス透過膜14において上半分に対極12を形成し、下半分に参照極13を形成した態様としてあるが、このような態様に限定されるものではない。対極12及び参照極13の間には、電極が形成されないスリット14aが形成してある。
The counter electrode 12 and the reference electrode 13 of the present embodiment have a mode in which the counter electrode 12 is formed in the upper half and the reference electrode 13 is formed in the lower half in one gas permeable membrane 14, but is limited to such a mode. It is not something. Between the counter electrode 12 and the reference electrode 13, the slit 14a in which an electrode is not formed is formed.
反応極11と参照極13とは対向して配置してあり、また、ガス通気部33の側に対極12および参照極13を配設してある。反応極11と、対極12および参照極13との間の空間が電解液20を収容する電解液収容部31となる。電解液20は硫酸やリン酸等の酸性水溶液等を使用することができるが、これらに限定されるものではない。被検知ガスはガス導入部32よりセンサの内部に導入され、反応極11上で反応する。
The reaction electrode 11 and the reference electrode 13 are arranged to face each other, and the counter electrode 12 and the reference electrode 13 are arranged on the gas ventilation part 33 side. A space between the reaction electrode 11, the counter electrode 12, and the reference electrode 13 serves as an electrolyte solution storage unit 31 that stores the electrolyte solution 20. The electrolytic solution 20 may be an acidic aqueous solution such as sulfuric acid or phosphoric acid, but is not limited thereto. The gas to be detected is introduced into the sensor from the gas introduction part 32 and reacts on the reaction electrode 11.
反応極11におけるガス導入部32の側、および、対極12および参照極13におけるガス通気部33の側には、それぞれ2枚のバッファーフィルター35が配設してある。当該バッファーフィルター35は、各電極の変形防止や電解液20の漏洩を防止する緩衝膜であり、例えば空孔率80%程度の多孔質テフロン(登録商標)膜を使用することができるが、これに限定されるものではない。
Two buffer filters 35 are disposed on the gas introduction part 32 side of the reaction electrode 11 and on the gas ventilation part 33 side of the counter electrode 12 and the reference electrode 13, respectively. The buffer filter 35 is a buffer film that prevents deformation of each electrode and prevents leakage of the electrolyte solution 20. For example, a porous Teflon (registered trademark) film having a porosity of about 80% can be used. It is not limited to.
それぞれのガス電極10、ガス透過膜14、バッファーフィルター35、Oリング15aは電解槽30の蓋部材16(16A、16B)によって固定される。
Each gas electrode 10, gas permeable membrane 14, buffer filter 35, and O-ring 15a are fixed by a lid member 16 (16A, 16B) of the electrolytic cell 30.
電解槽30の一端には、0.5~2mm程度の小径とした内圧調整孔17が形成されている。内圧調整孔17における電解液収容部31の側には、多孔質シート18が配設してある。電解液収容部31は、小径の流路31aを介して大径の二つの収容部31bを有する態様とする。当該流路31aを2~4mm程度の小径とした場合、電解液20の表面張力で電解液20が一方の収容部31bから他方の収容部31bに逆流し難くなる。筐体を構成する電解槽30および蓋部材16は、耐食性を有する合成樹脂、例えば硬質塩化ビニル或いはニッケル合金等の金属で構成すればよい。
An internal pressure adjusting hole 17 having a small diameter of about 0.5 to 2 mm is formed at one end of the electrolytic cell 30. A porous sheet 18 is disposed on the internal pressure adjusting hole 17 on the side of the electrolytic solution containing portion 31. The electrolyte storage unit 31 has two large-diameter storage units 31b through a small-diameter channel 31a. When the flow path 31a has a small diameter of about 2 to 4 mm, the electrolytic solution 20 is unlikely to flow backward from one housing portion 31b to the other housing portion 31b due to the surface tension of the electrolytic solution 20. The electrolytic cell 30 and the lid member 16 constituting the housing may be made of a synthetic resin having corrosion resistance, for example, a metal such as hard vinyl chloride or nickel alloy.
ガス導入部32の側に形成した蓋部材16A、および、ガス通気部33の側に形成した蓋部材16Bにそれぞれ貫通孔16a,16bが形成してあり、当該貫通孔16aを介してガスの導入が行われ、貫通孔16bを介してガスの排出や導入が行われる。当該貫通孔16bが形成される位置は、電極が形成されないスリット14aの位置に対応しているため、当該スリット14aおよび貫通孔16bを介してガスの排出や導入を行うことができる。
Through holes 16a and 16b are respectively formed in the lid member 16A formed on the gas introduction part 32 side and the lid member 16B formed on the gas ventilation part 33 side, and gas is introduced through the through hole 16a. The gas is discharged and introduced through the through hole 16b. Since the position where the through hole 16b is formed corresponds to the position of the slit 14a where no electrode is formed, gas can be discharged or introduced through the slit 14a and the through hole 16b.
対極12および参照極13の側に形成したガスを排出するガス通気部33には、空気層40および酸素を透過する酸素透過膜41を配設してある。酸素透過膜41は酸素透過性能を有するものであれば、特に限定されず、例えば4フッ化エチレン6フッ化プロピレン共重合樹脂(FEP)、テトラフルオロエチレン・パーフルオロアルキルビニルエーテル共重合体(PFA)等、従来公知のものが適用可能である。
The gas layer 33 that discharges the gas formed on the side of the counter electrode 12 and the reference electrode 13 is provided with an air layer 40 and an oxygen permeable membrane 41 that transmits oxygen. The oxygen permeable membrane 41 is not particularly limited as long as it has oxygen permeation performance. For example, tetrafluoroethylene hexafluoropropylene copolymer resin (FEP), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA). A conventionally well-known thing is applicable.
本構成のように酸素透過膜41を配設することで、周囲の干渉ガス(酸素以外)がガス通気部33から対極12および参照極13に入り込むのを防ぐことができる。
By disposing the oxygen permeable film 41 as in this configuration, it is possible to prevent the surrounding interference gas (other than oxygen) from entering the counter electrode 12 and the reference electrode 13 from the gas ventilation portion 33.
本発明の定電位電解式ガスセンサXは、少なくとも対極12の表面に気泡が形成されるのを抑制する気泡形成抑制手段50を備える。当該気泡形成抑制手段50は、対極12以外に、他のガス電極10(反応極11、参照極13)の表面に気泡が形成されるのを抑制するように構成してもよい。
The constant potential electrolytic gas sensor X of the present invention includes bubble formation suppressing means 50 that suppresses the formation of bubbles on at least the surface of the counter electrode 12. The bubble formation suppressing means 50 may be configured to suppress the formation of bubbles on the surface of the other gas electrode 10 (reaction electrode 11 and reference electrode 13) in addition to the counter electrode 12.
例えば低温から高温に急激に温度が変化した場合、空気層40が大きく膨張してガス通気部33の側に形成した貫通孔16bを介して気泡が混入する虞がある。混入した気泡が電極の表面に到達し、例えば対極12の表面に気泡が形成されれば、電解液20および対極12の接触面積が減少してセンサの指示値が突発的に上昇する虞がある。本発明の気泡形成抑制手段50を設けることで、外乱の影響でセンサの温度が急激に変化した場合であっても貫通孔16bから気泡が混入し難くなり、また、貫通孔16bを介して気泡が混入した場合であっても、少なくとも対極12の表面に混入した気泡が到達し難くなる。従って、少なくとも対極12の表面に気泡が形成されるのを抑制することができるため、センサの指示値が急激に変化するのを抑制することができる。
For example, when the temperature suddenly changes from a low temperature to a high temperature, the air layer 40 may expand greatly and air bubbles may be mixed in through the through holes 16b formed on the gas ventilation part 33 side. If the mixed bubbles reach the surface of the electrode and, for example, bubbles are formed on the surface of the counter electrode 12, the contact area between the electrolytic solution 20 and the counter electrode 12 may decrease, and the indicated value of the sensor may suddenly increase. . By providing the bubble formation suppressing means 50 of the present invention, it is difficult for air bubbles to be mixed from the through hole 16b even when the temperature of the sensor is suddenly changed due to the influence of disturbance, and the bubble is prevented from passing through the through hole 16b. Even when the bubbles are mixed, at least the bubbles mixed on the surface of the counter electrode 12 are difficult to reach. Accordingly, it is possible to suppress the formation of bubbles at least on the surface of the counter electrode 12, and thus it is possible to suppress a sudden change in the indicated value of the sensor.
本実施形態では、気泡形成抑制手段50として、電解液20を吸水して保持する保水部材37を電解液収容部31に配設する場合について説明するが、これに限定されるものではない。
In the present embodiment, a case where the water retention member 37 that absorbs and holds the electrolytic solution 20 as the bubble formation suppressing unit 50 is disposed in the electrolytic solution storage unit 31 will be described, but the present invention is not limited thereto.
気泡形成抑制手段50を保水部材37とすれば、電解液収容部31に臨む少なくとも対極12の表面に混入した気泡がより到達し難くなり、対極12の表面に気泡が形成されるのを確実に抑制することができる。
If the bubble formation suppressing means 50 is the water retaining member 37, it is more difficult for bubbles mixed in at least the surface of the counter electrode 12 facing the electrolyte container 31 to reach, and it is ensured that bubbles are formed on the surface of the counter electrode 12. Can be suppressed.
保水部材37は、少なくとも対極12の表面に気泡が形成されるのを抑制できるように配設すればよく、好ましくは反応極11および参照極13の表面に気泡が形成されるのを抑制できるように配設すればよい。このとき、各ガス電極10の全面(或いは大部分)を覆うように保水部材37を配設するのがよい。
The water retaining member 37 may be disposed so as to suppress at least the formation of bubbles on the surface of the counter electrode 12, and preferably suppresses the formation of bubbles on the surfaces of the reaction electrode 11 and the reference electrode 13. What is necessary is just to arrange | position. At this time, the water retention member 37 is preferably disposed so as to cover the entire surface (or most) of each gas electrode 10.
例えば保水部材37は、本実施形態のように、電解液収容部31において一方の収容部31b(ガス電極10が配設してある側)の全面(100%)に充填することができる。しかし、このような態様に限定されず、保水部材37を、一方の収容部31b(ガス電極10が配設してある側)の例えば90%以上、具体的には90~95%程度の充填率となるように充填してあればよい。このような割合で保水部材37を充填することで、各ガス電極10の表面を確実に覆うことができるため、混入した気泡が各ガス電極10の表面により到達し難くなり、各ガス電極10の表面に気泡が形成されるのを確実に抑制することができる。これにより、各ガス電極10における電極反応等で発生した気泡や、急激な温度変化に伴い電解液中に溶解していた空気が発生した場合や、急激な加圧状態における空気の侵入により、直接、各ガス電極10の表面が空気で覆われて各ガス電極10の反応面積が減少し、指示が不安定になることを回避することができる。
For example, the water retaining member 37 can be filled in the entire surface (100%) of one accommodating portion 31b (the side where the gas electrode 10 is disposed) in the electrolyte accommodating portion 31 as in the present embodiment. However, the present invention is not limited to such an embodiment, and the water retaining member 37 is filled with, for example, 90% or more, specifically about 90 to 95% of one accommodating portion 31b (side on which the gas electrode 10 is disposed). What is necessary is just to fill so that it may become a rate. By filling the water retaining member 37 at such a ratio, the surface of each gas electrode 10 can be reliably covered, so that the mixed bubbles are less likely to reach the surface of each gas electrode 10. It is possible to reliably suppress the formation of bubbles on the surface. As a result, when bubbles generated by electrode reactions or the like in each gas electrode 10 or air dissolved in the electrolyte solution due to a rapid temperature change occurs, or when air invades rapidly in a pressurized state, It can be avoided that the surface of each gas electrode 10 is covered with air, the reaction area of each gas electrode 10 is reduced, and the indication becomes unstable.
保水部材37は電解液20を吸水して保持する態様であるため、その内部に電解液20を保持できる空間を有する。そのため、仮に保水部材37を収容部31bの全面に充填した場合であっても、各ガス電極10および電解液20の接触状態を良好に維持することができる。
Since the water retaining member 37 is an aspect that absorbs and holds the electrolytic solution 20, the water retaining member 37 has a space in which the electrolytic solution 20 can be retained. Therefore, even if it is a case where the water retention member 37 is filled in the whole surface of the accommodating part 31b, the contact state of each gas electrode 10 and the electrolyte solution 20 can be maintained favorable.
保水部材37は、例えば保水性の繊維(例えばガラス繊維、セラミックス繊維など)、吸水性の高分子等、電解液20を保持できる吸水性の部材であれば、特に限定されるものではない。保水部材37の嵩密度は0.05~0.30g/cm3とするのがよい。例えば保水部材37の嵩密度を0.22g/cm3程度、空間率を90%程度とした場合、具体的にはMGP(日本板硝子株式会社製)を使用することができ、保水部材37の嵩密度を0.18g/cm3程度、空間率を90%程度とした場合、具体的にはMCペーパー(日本板硝子株式会社製)を使用することができ、保水部材37の嵩密度を0.08g/cm3程度、空間率を90%程度とした場合、具体的にはOR-125(アサヒ繊維工業株式会社製)を使用することができる。しかし、保水部材37の嵩密度や実施品は、これらに限定されるものではない。このような保水部材37を、例えば複数枚重ねて電解液収容部31に配設してもよい。上述した保水部材37の構造により、保水部材37をある程度押し込んで収容部31bに充填することができ、保水部材37が各ガス電極10をある程度押圧するように配置することができるため、保水部材37と各ガス電極10との接触状態を確実に確保することができる。これにより、少なくとも対極12の表面に混入した気泡がより到達し難くなる。
The water retaining member 37 is not particularly limited as long as it is a water absorbing member capable of holding the electrolytic solution 20 such as a water retaining fiber (for example, glass fiber, ceramic fiber, etc.) or a water absorbing polymer. The bulk density of the water retaining member 37 is preferably 0.05 to 0.30 g / cm 3 . For example, when the bulk density of the water retaining member 37 is about 0.22 g / cm 3 and the space ratio is about 90%, specifically, MGP (manufactured by Nippon Sheet Glass Co., Ltd.) can be used. When the density is about 0.18 g / cm 3 and the space ratio is about 90%, specifically, MC paper (manufactured by Nippon Sheet Glass Co., Ltd.) can be used, and the bulk density of the water retaining member 37 is 0.08 g. In the case of about / cm 3 and a space ratio of about 90%, specifically, OR-125 (manufactured by Asahi Textile Industry Co., Ltd.) can be used. However, the bulk density of the water retaining member 37 and the actual product are not limited to these. For example, a plurality of such water retaining members 37 may be arranged in the electrolyte solution storage unit 31 in a stacked manner. With the structure of the water retaining member 37 described above, the water retaining member 37 can be pushed to some extent to fill the accommodating portion 31b, and the water retaining member 37 can be disposed so as to press each gas electrode 10 to some extent. And the contact state between the gas electrodes 10 can be reliably ensured. As a result, at least air bubbles mixed on the surface of the counter electrode 12 are more difficult to reach.
このような定電位電解式ガスセンサXは、被検知ガスの反応によって反応極11上で生じた電子に基づく電流を検知自在な電流測定部と、反応極11の電位制御自在な電位制御部とを備えたガス検知回路(図外)に接続して、ガス検知装置として用いられる。本発明の定電位電解式ガスセンサXは、例えば酸素ガスや、シラン、ホスフィン、ゲルマン、アルシン、ジボランなどの水素化物ガスの検知や、一酸化炭素、硫化水素等の毒性ガスの検知に用いられる。
Such a constant potential electrolytic gas sensor X includes a current measuring unit capable of detecting a current based on electrons generated on the reaction electrode 11 due to a reaction of the gas to be detected, and a potential control unit capable of controlling the potential of the reaction electrode 11. It is used as a gas detection device by connecting to a gas detection circuit (not shown). The constant potential electrolytic gas sensor X of the present invention is used for detecting oxygen gas, hydride gas such as silane, phosphine, germane, arsine and diborane, and detecting toxic gas such as carbon monoxide and hydrogen sulfide.
ガス導入部32の側には、蓋部材16Aに、干渉ガスをフィルタリングするフィルタ手段60を備えてある。当該フィルタ手段60は、蓋部材16Aに形成した枠体16cに配設してある。具体的にはフィルタ手段60の構造は、円筒状の容器60aに、干渉ガスをフィルタリングする活性炭やシリカゲルを備えた複数のフィルタ層61を収納し、これらフィルタ層61の両側をメッシュ等の保持部材62で挟むように配設して構成してあるが、このような態様に限定されるものではない。
The filter means 60 for filtering the interference gas is provided on the lid member 16A on the gas introduction part 32 side. The filter means 60 is disposed on a frame 16c formed on the lid member 16A. Specifically, the filter means 60 has a structure in which a plurality of filter layers 61 including activated carbon and silica gel for filtering interference gas are accommodated in a cylindrical container 60a, and both sides of the filter layers 61 are holding members such as meshes. However, the present invention is not limited to such a mode.
〔別実施の形態〕
上述した実施形態では、ガス通気部33には、空気層40および酸素を透過する酸素透過膜41を配設する態様について説明した。しかし、このような態様に限らず、空気層40および酸素透過膜41を設けず、ガス通気部33の側における貫通孔16bに、ピンホール34aを形成した筒部材34を配設するように構成してもよい(図2)。 [Another embodiment]
In the above-described embodiment, the aspect in which thegas vent 33 is provided with the air layer 40 and the oxygen permeable membrane 41 that transmits oxygen has been described. However, the present invention is not limited thereto, and the air layer 40 and the oxygen permeable membrane 41 are not provided, and the cylindrical member 34 in which the pinhole 34a is formed is disposed in the through hole 16b on the gas ventilation portion 33 side. You may do it (FIG. 2).
上述した実施形態では、ガス通気部33には、空気層40および酸素を透過する酸素透過膜41を配設する態様について説明した。しかし、このような態様に限らず、空気層40および酸素透過膜41を設けず、ガス通気部33の側における貫通孔16bに、ピンホール34aを形成した筒部材34を配設するように構成してもよい(図2)。 [Another embodiment]
In the above-described embodiment, the aspect in which the
筒部材34は、例えばアルミナ、ジルコニア等のセラミックスが挙げられるが、これらに限定されるものではない。筒部材の長寸は2.0mm以上であり、好ましくは2.0~6.0mmとするのがよい。また、ピンホール34aの直径は0.05mm程度とするのがよい。
Examples of the cylindrical member 34 include ceramics such as alumina and zirconia, but are not limited thereto. The long dimension of the cylindrical member is 2.0 mm or more, preferably 2.0 to 6.0 mm. The diameter of the pinhole 34a is preferably about 0.05 mm.
貫通孔16bに筒部材34を配設した後、ピンホール34a以外の気密性を確保するため接着剤あるいはパッキンなどの封止手段36でガス通気部33の側を封止するとよい。
After the cylindrical member 34 is disposed in the through hole 16b, the gas ventilation part 33 side may be sealed with a sealing means 36 such as an adhesive or packing in order to ensure airtightness other than the pinhole 34a.
本構成のように筒部材34を設けることにより、ガス通気部33の側におけるガスの流通をピンホール34aのみとすることができる。これにより、温度の急変時に空気層40の膨張によってセンサ内部へ気泡が浸入するのを未然に防止することができる。また、ガス通気部33の側の貫通孔16bを小径かつ長くすることでセンサの内部(電解液収容部31など)に干渉ガス等が混入し難くなる。これにより、貫通孔16bから気泡が混入しに難くなるため、ピンホール34aを形成した筒部材34を気泡形成抑制手段50とすることができる。
By providing the cylindrical member 34 as in this configuration, the gas flow on the gas ventilation part 33 side can be limited to the pinhole 34a. Thereby, it is possible to prevent bubbles from entering the inside of the sensor due to the expansion of the air layer 40 when the temperature changes suddenly. In addition, by making the through hole 16b on the gas ventilation portion 33 side small and long, interference gas or the like is less likely to be mixed into the inside of the sensor (electrolyte accommodating portion 31 or the like). Thereby, since it becomes difficult for air bubbles to be mixed from the through hole 16b, the cylindrical member 34 in which the pinhole 34a is formed can be used as the air bubble formation suppressing means 50.
そのため、ピンホール34aを形成した筒部材34を設けた場合は、上述した実施形態における保水部材37は設けてもよいし、設けない場合であっても、当該筒部材34によって少なくとも対極12の表面に気泡が形成されるのを抑制することができるため、センサの指示値が急激に変化するのを抑制することができる。
Therefore, when the cylindrical member 34 in which the pinhole 34a is formed is provided, the water retaining member 37 in the above-described embodiment may be provided, or even if not provided, at least the surface of the counter electrode 12 by the cylindrical member 34. It is possible to suppress the formation of bubbles on the surface, and thus it is possible to suppress a sudden change in the indicated value of the sensor.
筒部材34および保水部材37を両方設けた場合は、より確実に対極12の表面に気泡が形成されるのを抑制することができる。
When both the cylindrical member 34 and the water retaining member 37 are provided, it is possible to more reliably suppress the formation of bubbles on the surface of the counter electrode 12.
筒部材34の形状は円柱状とするのがよいが、これに限定されるものではなく、角柱状等の態様であってもよい。
The shape of the cylindrical member 34 is preferably a cylindrical shape, but is not limited to this, and may be a prismatic shape or the like.
筒部材34に設けるピンホール34aは、一つでもよいし、複数設けてもよい。ピンホール34aの数については、特に制限はしない。本実施形態では、それぞれの筒部材34に、一つのピンホール34aが形成してある場合について説明する。
The pin member 34a provided in the cylindrical member 34 may be one or plural. The number of pinholes 34a is not particularly limited. In the present embodiment, a case where one pinhole 34a is formed in each cylindrical member 34 will be described.
ピンホール34aを複数設けることで、導入されるガスの量をピンホール34aの数によって調節することができる。仮にガス導入部32において結露が発生した場合であっても、ピンホール34aを複数形成してあれば、全てのピンホール34aが結露によって塞がれ難くなり、ガス反応によるガス排出あるいは導入の妨げになることを未然に防止することができる。尚、ピンホールの数だけでなく、ピンホールの長さや直径によっても導入されるガスの量を調節することができるため、抑制したい干渉ガスごとに応じて適宜設定すればよい。
By providing a plurality of pinholes 34a, the amount of gas introduced can be adjusted by the number of pinholes 34a. Even if condensation occurs in the gas introduction part 32, if a plurality of pinholes 34a are formed, all the pinholes 34a are not easily blocked by condensation, and gas discharge or introduction due to gas reaction is hindered. Can be prevented in advance. Since the amount of gas introduced can be adjusted not only by the number of pinholes but also by the length and diameter of the pinholes, it may be set appropriately according to the interference gas to be suppressed.
〔実施例1〕
本発明の実施例について説明する。
本実施例の定電位電解式ガスセンサXを以下の態様とした。
即ち、図1の態様の定電位電解式ガスセンサXにおいて、厚さ1mmのバッファーフィルター35を多孔質テフロン(登録商標)膜(PTFE膜)とし、保水部材37をガラス繊維製の部材とし、酸素透過膜41を4フッ化エチレン6フッ化プロピレン共重合樹脂(FEP)とし、フィルタ層61を四層の活性炭層とし、保持部材62をSUSメッシュとした。また、貫通孔16a,16bの直径を2mmとし、対極12及び参照極13の間に形成したスリット14aの幅を1.5mmとした。 [Example 1]
Examples of the present invention will be described.
The constant potential electrolytic gas sensor X of the present example was set as the following mode.
That is, in the controlled potential electrolytic gas sensor X of the embodiment of FIG. 1, thebuffer filter 35 having a thickness of 1 mm is a porous Teflon (registered trademark) membrane (PTFE membrane), the water retaining member 37 is a glass fiber member, and oxygen permeation is performed. The membrane 41 was made of tetrafluoroethylene hexafluoropropylene copolymer resin (FEP), the filter layer 61 was made of four activated carbon layers, and the holding member 62 was made of SUS mesh. Further, the diameters of the through holes 16a and 16b were 2 mm, and the width of the slit 14a formed between the counter electrode 12 and the reference electrode 13 was 1.5 mm.
本発明の実施例について説明する。
本実施例の定電位電解式ガスセンサXを以下の態様とした。
即ち、図1の態様の定電位電解式ガスセンサXにおいて、厚さ1mmのバッファーフィルター35を多孔質テフロン(登録商標)膜(PTFE膜)とし、保水部材37をガラス繊維製の部材とし、酸素透過膜41を4フッ化エチレン6フッ化プロピレン共重合樹脂(FEP)とし、フィルタ層61を四層の活性炭層とし、保持部材62をSUSメッシュとした。また、貫通孔16a,16bの直径を2mmとし、対極12及び参照極13の間に形成したスリット14aの幅を1.5mmとした。 [Example 1]
Examples of the present invention will be described.
The constant potential electrolytic gas sensor X of the present example was set as the following mode.
That is, in the controlled potential electrolytic gas sensor X of the embodiment of FIG. 1, the
このような定電位電解式ガスセンサXを使用して、外乱の影響でセンサの温度が急激に変化(-10℃から50℃へ急変)した場合にセンサの指示値がどのように変化するか、調べた。尚、比較例の定電位電解式ガスセンサとして、気泡形成抑制手段50(保水部材37)を設けないセンサを使用した。
Using such a constant potential electrolytic gas sensor X, how the indicated value of the sensor changes when the temperature of the sensor changes suddenly (from -10 ° C to 50 ° C) due to the influence of disturbance, Examined. In addition, the sensor which does not provide the bubble formation suppression means 50 (water retention member 37) was used as the constant potential electrolytic gas sensor of the comparative example.
この結果、本発明の定電位電解式ガスセンサX(図3)では、急激な温度変化を与えても、保水部材37によって少なくとも対極12の表面に気泡が形成されるのを抑制することができるため、センサの指示値は大きな変動は認められず、安定していると考えられた。
As a result, in the constant potential electrolysis gas sensor X (FIG. 3) of the present invention, it is possible to suppress the formation of bubbles at least on the surface of the counter electrode 12 by the water retaining member 37 even when a sudden temperature change is applied. The sensor reading did not show any significant fluctuations and was considered stable.
一方、比較例の定電位電解式ガスセンサ(図4)では、急激な温度変化を与えると、保水部材37を設けないため、気泡がセンサ内部に侵入し、外乱の影響によって当該気泡が電極に触れたり離れたりするためセンサの指示値は大きく変動し、センサ出力は不安定であると考えられた。
On the other hand, in the constant potential electrolysis gas sensor (FIG. 4) of the comparative example, when a sudden temperature change is applied, the water retaining member 37 is not provided, so that bubbles enter the sensor and the bubbles touch the electrode due to the influence of disturbance. It was thought that the sensor output fluctuated greatly because of moving away and away, and the sensor output was unstable.
〔実施例2〕
上述した別実施形態の定電位電解式ガスセンサXにおいて、外乱の影響でセンサの温度が急激に変化(-10℃から50℃へ急変)した場合にセンサの指示値がどのように変化するか、調べた。 [Example 2]
In the constant potential electrolysis gas sensor X of another embodiment described above, how the indicated value of the sensor changes when the temperature of the sensor changes abruptly (from -10 ° C. to 50 ° C.) due to disturbance, Examined.
上述した別実施形態の定電位電解式ガスセンサXにおいて、外乱の影響でセンサの温度が急激に変化(-10℃から50℃へ急変)した場合にセンサの指示値がどのように変化するか、調べた。 [Example 2]
In the constant potential electrolysis gas sensor X of another embodiment described above, how the indicated value of the sensor changes when the temperature of the sensor changes abruptly (from -10 ° C. to 50 ° C.) due to disturbance, Examined.
本実施例の定電位電解式ガスセンサXは、保水部材37および酸素透過膜41を使用せず、ピンホール34aを形成した筒部材34を配設した態様とした。当該筒部材34の長寸を3.0mmとし、ピンホール34aの直径を0.05mmとした。
The constant potential electrolytic gas sensor X of the present embodiment is configured such that the water retaining member 37 and the oxygen permeable membrane 41 are not used, and the cylindrical member 34 in which the pinhole 34a is formed is disposed. The long dimension of the said cylindrical member 34 was 3.0 mm, and the diameter of the pinhole 34a was 0.05 mm.
尚、比較例の定電位電解式ガスセンサとして、ピンホールを設けないセンサを使用した。即ち、このセンサにおけるガス通気部33の側における貫通孔16bの直径は2.0mm、長寸は2.0mmであった。
In addition, the sensor which does not provide a pinhole was used as a constant potential electrolysis type gas sensor of a comparative example. That is, the diameter of the through hole 16b on the gas ventilation part 33 side in this sensor was 2.0 mm, and the long dimension was 2.0 mm.
この結果、本実施例の定電位電解式ガスセンサXおよび比較例の定電位電解式ガスセンサの何れのセンサにおいても図3と同様のデータが得られたため(データは示さない)、気泡の侵入は無く、センサの指示値は大きな変動は認められず、安定していると考えられた。
As a result, since the same data as in FIG. 3 was obtained in any of the constant potential electrolysis gas sensor X of this example and the constant potential electrolysis gas sensor of the comparative example (data not shown), there was no invasion of bubbles. The sensor reading did not show any significant fluctuations and was considered stable.
一方、外乱の影響として周囲の干渉ガスの影響があった場合にセンサの指示値がどのように変化するか、調べた。
On the other hand, it was examined how the indicated value of the sensor changes when there is an influence of the surrounding interference gas as an influence of the disturbance.
このとき、干渉ガスの影響を考慮してガス導入部32の側を塞いだ状態で、水素ガス1000ppmを拡散状態としたときの指示値の変動を調べた。結果を図5(本発明の定電位電解式ガスセンサX)および図6(比較例の定電位電解式ガスセンサ)に示した。各センサともに2検体のセンサを使用した。
At this time, in consideration of the influence of the interference gas, the change of the indicated value when the hydrogen gas of 1000 ppm was in a diffusion state in the state where the gas introduction part 32 side was closed was examined. The results are shown in FIG. 5 (constant potential electrolytic gas sensor X of the present invention) and FIG. 6 (constant potential electrolytic gas sensor of comparative example). Two sensors were used for each sensor.
この結果、本発明の定電位電解式ガスセンサX(図5)では、センサの指示値は大きな変動は認められず、安定していると考えられた。そのため、本発明の定電位電解式ガスセンサXでは、周囲に干渉ガスが存在しても酸素透過膜を用いた場合と同等の性能であることが確認できた。
As a result, in the controlled potential electrolytic gas sensor X of the present invention (FIG. 5), the sensor indicated no significant fluctuations and was considered stable. Therefore, it was confirmed that the constant potential electrolysis gas sensor X of the present invention has the same performance as the case where the oxygen permeable membrane is used even if interference gas exists in the surroundings.
一方、比較例の定電位電解式ガスセンサ(図6)では、センサの指示値は大きく変動し、センサ出力は不安定であると考えられた。そのため、比較例の定電位電解式ガスセンサでは、貫通孔16bの直径が本発明の定電位電解式ガスセンサXのピンホール34aよりも直径が大きい為、周囲に干渉ガスが存在すると、参照極に干渉ガスが侵入し易く、指示が安定しないことが確認できた。
On the other hand, in the controlled potential electrolysis gas sensor (FIG. 6) of the comparative example, the indicated value of the sensor fluctuated greatly, and the sensor output was considered to be unstable. For this reason, in the constant potential electrolytic gas sensor of the comparative example, the diameter of the through hole 16b is larger than the pinhole 34a of the constant potential electrolytic gas sensor X of the present invention. It was confirmed that gas could easily enter and the instructions were not stable.
これより、酸素透過膜41を設けない別実施形態の定電位電解式ガスセンサXにおいては、直径の小さいピンホール34aを形成した筒部材34を配設する必要があると認められた。
From this, it was recognized that in the constant potential electrolysis gas sensor X of another embodiment in which the oxygen permeable membrane 41 is not provided, it is necessary to dispose a cylindrical member 34 having a pinhole 34a having a small diameter.
本発明は、ガスを検知するガス電極として被検知ガスを電気化学反応させる反応極、前記反応極に対する対極および前記反応極の電位を制御する参照極を、電解槽に収容した電解液に接触するように備えた定電位電解式ガスセンサに利用できる。
In the present invention, a reaction electrode for electrochemically reacting a gas to be detected as a gas electrode for detecting gas, a counter electrode with respect to the reaction electrode, and a reference electrode for controlling the potential of the reaction electrode are brought into contact with an electrolytic solution accommodated in an electrolytic cell. It can utilize for the constant potential electrolytic gas sensor provided.
X 定電位電解式ガスセンサ
10 ガス電極
11 反応極
12 対極
13 参照極
20 電解液
30 電解槽
37 保水部材
41 酸素透過膜
50 気泡形成抑制手段 X Constant PotentialElectrolytic Gas Sensor 10 Gas Electrode 11 Reaction Electrode 12 Counter Electrode 13 Reference Electrode 20 Electrolytic Solution 30 Electrolytic Tank 37 Water Retaining Member 41 Oxygen Permeation Membrane 50 Bubble Formation Inhibiting Means
10 ガス電極
11 反応極
12 対極
13 参照極
20 電解液
30 電解槽
37 保水部材
41 酸素透過膜
50 気泡形成抑制手段 X Constant Potential
Claims (5)
- ガスを検知するガス電極として被検知ガスを電気化学反応させる反応極、前記反応極に対する対極および前記反応極の電位を制御する参照極を、電解槽に収容した電解液に接触するように備えた定電位電解式ガスセンサであって、
少なくとも前記対極の表面に気泡が形成されるのを抑制する気泡形成抑制手段を備えた定電位電解式ガスセンサ。 As a gas electrode for detecting gas, a reaction electrode for electrochemically reacting a gas to be detected, a counter electrode for the reaction electrode, and a reference electrode for controlling the potential of the reaction electrode were provided so as to come into contact with an electrolytic solution contained in an electrolytic cell. A constant potential electrolytic gas sensor,
A constant potential electrolytic gas sensor provided with bubble formation suppressing means for suppressing formation of bubbles on at least the surface of the counter electrode. - 前記気泡形成抑制手段が、前記電解液を吸水して保持する保水部材である請求項1に記載の定電位電解式ガスセンサ。 The constant potential electrolytic gas sensor according to claim 1, wherein the bubble formation suppressing means is a water retention member that absorbs and holds the electrolytic solution.
- 前記対極および前記参照極の側に形成したガスを通気するガス通気部に、酸素を透過する酸素透過膜を配設した請求項2に記載の定電位電解式ガスセンサ。 The constant potential electrolytic gas sensor according to claim 2, wherein an oxygen permeable film that allows oxygen to pass through is provided in a gas ventilation portion that vents a gas formed on the side of the counter electrode and the reference electrode.
- 前記保水部材の充填率を90%以上としてある請求項2または3に記載の定電位電解式ガスセンサ。 The constant potential electrolytic gas sensor according to claim 2 or 3, wherein a filling rate of the water retaining member is 90% or more.
- 前記保水部材の嵩密度を0.05~0.30g/cm3としてある請求項2~4の何れか一項に記載の定電位電解式ガスセンサ。
The constant potential electrolytic gas sensor according to any one of claims 2 to 4, wherein the water retention member has a bulk density of 0.05 to 0.30 g / cm 3 .
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GB8430803D0 (en) * | 1984-12-06 | 1985-01-16 | Bergman I | Electrochemical cell |
JP4507235B2 (en) * | 2003-10-30 | 2010-07-21 | 理研計器株式会社 | Electrochemical gas sensor |
CN101275923B (en) * | 2007-03-26 | 2013-04-10 | 华瑞科学仪器(上海)有限公司 | Gas sensor |
JP6212768B2 (en) * | 2013-03-30 | 2017-10-18 | 新コスモス電機株式会社 | Electrochemical gas sensor |
JP6315983B2 (en) * | 2013-12-26 | 2018-04-25 | 新コスモス電機株式会社 | Constant potential electrolytic gas sensor |
CN204142678U (en) * | 2014-10-24 | 2015-02-04 | 荆州市爱尔瑞科技有限公司 | A kind of three-electrode electro Chemical gas sensor |
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JPS6140557A (en) * | 1984-07-31 | 1986-02-26 | Japan Storage Battery Co Ltd | Galvanic battery type oxygen sensor |
JPH03125959A (en) * | 1989-10-11 | 1991-05-29 | New Cosmos Electric Corp | Electrolytic type gas sensor |
JPH06242059A (en) * | 1993-02-19 | 1994-09-02 | Gastec:Kk | Electrochemical gas sensor |
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JP6752558B2 (en) | 2020-09-09 |
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