JP2020106482A - Diaphragm type gas sensor and sensor unit - Google Patents

Abstract

To provide a diaphragm type gas sensor and a sensor unit utilizing an electrochemical technique, with which it is possible to improve the long-term stability of sensitivity and reduce the variation of sensitivity in initial stages and during maintenance work.SOLUTION: A diaphragm type gas sensor 100 for detecting a detection object gas in a sample gas utilizing an electrochemical technique, comprises: a container 1; a working electrode 2; a diaphragm 5; a reinforcing member 6 for suppressing the elongation of the diaphragm 5 and arranged in adjacency to the diaphragm 5 on the side of the diaphragm 5 opposite the working electrode 2; a spacer 7 arranged in adjacency to the diaphragm 5 and the working electrode 2 on the working electrode 2 side of the diaphragm 5, which an electrolyte solution S is permeable; and a holding members 9, 10 for holding the diaphragm 5 in the container 1 while the diaphragm 5 is pressed toward the working electrode 2 via the spacer 7.SELECTED DRAWING: Figure 1

Description

The present invention relates to a diaphragm-type gas sensor using an electrochemical method for detecting a gas to be detected in a sample gas, and a sensor unit including the same.

BACKGROUND ART Conventionally, a diaphragm-type gas sensor using an electrochemical method has been widely used, for example, for measuring the concentration of a detection target gas in a sample gas such as an exhaust gas in a semiconductor manufacturing process or various industries and for detecting leaks (Patent Reference 1). As such a diaphragm type gas sensor, those based on the measurement of the electric current by an electrochemical reaction such as a constant potential electrolysis type and a galvanic cell type are widely used, and as the gas to be detected, for example, ammonia (NH ₃ ) and hydrogen cyanide ( HCN), hydrogen chloride (HCl), hydrogen fluoride (HF), arsine (AsH ₃ ), phosphine (PH ₃ ), diborane (B ₂ H ₃ ), and other toxic gases.

FIG. 6A is a schematic sectional view of an example of a conventional diaphragm type gas sensor 100. In this example, the diaphragm-type gas sensor 100 has a three-pole type, but there are also two-pole type. The diaphragm-type gas sensor 100 has a container 1 containing an electrolytic solution S, which has an opening 1a at a lower end in the figure. The diaphragm gas sensor 100 also has a working electrode 2, a counter electrode 3, and a reference electrode 4. Further, the diaphragm gas sensor 100 has a diaphragm 5 which is attached to the container 1 so as to seal the opening 1a and which is capable of blocking the permeation of the liquid and permeating the gas to be detected. The diaphragm 5 is attached to the container 1 such that the O-ring 8 is sandwiched between the diaphragm 5 and the end surface 1c of the attachment portion 1b at the lower end of the container 1 in the figure. In this example, the annular pressing member 9 on which the diaphragm 5 is placed is sandwiched between the cap nut-shaped mounting member 10 and the mounting portion 1b of the container 1, and the mounting member 10 is screwed onto the mounting portion 1b of the container 1. The diaphragm 5 is attached to the container 1 by combining. Further, although schematically shown in the figure, at this time, by bringing the diaphragm 5 into close contact with the surface of the working electrode 2, the electrolytic solution S inside the container 1 is separated between the diaphragm 5 and the surface of the working electrode 2. And penetrates into the membrane to form an electrolyte layer Sa between the diaphragm 5 and the surface of the working electrode 2. Then, at the interface between the working electrode 2 and the electrolytic solution S, which are maintained at a potential within a predetermined range with respect to the potential of the reference electrode 4, the detection target gas that has passed through the diaphragm 5 is electrolyzed, so that the working electrode 2 and the counter electrode The current generated between the sensor and the sensor 3 is measured by a measuring circuit (not shown). Thereby, the concentration measurement or detection of the gas to be detected is performed. As the diaphragm 5, a polymer film having gas permeability, a porous polymer film, or the like is used. For example, a polymer film made of fluororesin such as PTFE (polytetrafluoroethylene) or FEP (tetrafluoroethylene/hexafluoroethylene copolymer), or PTFE (polytetrafluoroethylene) or PVDF (polyvinylidene fluoride). Such as a porous polymer membrane.

FIG. 6B is a schematic cross-sectional view of a sensor unit 300 in which the conventional diaphragm type gas sensor 100 is attached to a flow cell 200. As shown in FIG. 6B, the diaphragm type gas sensor 100 is used by being attached to a flow cell 200 into which a sample gas is introduced from a measurement target environment such as an exhaust gas processing apparatus in a semiconductor manufacturing process through a pipe or the like. May be The flow cell 200 has a chamber 201 for containing the sample gas, an inlet 202 for introducing the sample gas into the chamber 201, and an outlet 203 for discharging the sample gas from the chamber 201.

In the diaphragm type gas sensor 100 having the above-described configuration, the initial performance is restored by appropriately replacing the diaphragm 5, replenishing or replacing the electrolytic solution S, and the like. Therefore, there is an advantage that the running cost can be kept relatively low.

Patent No. 5688955

However, the conventional diaphragm-type gas sensor having the above-mentioned configuration has the following problems to be improved.

In the conventional diaphragm-type gas sensor 100, the diaphragm 5 may stretch when it is used for a long period of time. Then, the diaphragm 5 may be separated from the surface of the working electrode 2 to thicken the electrolytic solution layer Sa, or conversely, the diaphragm 5 may stick to the surface of the working electrode 2 and the electrolytic solution layer Sa may be lost. When the thickness of the electrolytic solution layer Sa changes in this way, the sensitivity of the diaphragm type gas sensor 100 is lowered. This phenomenon becomes remarkable when the diaphragm gas sensor 100 is used by being attached to the flow cell 200 connected to the measurement target environment via a pipe or the like. That is, in this case, the diaphragm 5 of the diaphragm gas sensor 100 is always exposed to the pressure condition in the pipe connected to the flow cell 200. As described above, since the diaphragm 5 is a thin resin film made of, for example, PTFE, it may be deformed with time when a pressure load is applied. In particular, PTFE, which is often used as a material for the diaphragm 5, has a property of being very easily plastically deformed. For example, when the diaphragm-type gas sensor 100 is used in a state where the inside of the chamber 201 of the flow cell 200 is in a negative pressure with respect to the inside of the container 1 of the diaphragm-type gas sensor 100, the diaphragm 5 is extended and the working electrode 2 is extended. Easily deforms away from the surface. On the contrary, when the diaphragm type gas sensor 100 is used in a state where the inside of the chamber 201 of the flow cell 200 has a positive pressure with respect to the inside of the container 1 of the diaphragm type gas sensor 100, the diaphragm 5 extends and acts. It may stick to the surface of pole 2.

Further, in the conventional diaphragm type gas sensor 100, the electrolytic solution S of the electrolytic solution layer Sa is evaporated and reduced, and the thickness of the electrolytic solution layer Sa is changed, so that the sensitivity of the diaphragm type gas sensor 100 is lowered. Sometimes. This phenomenon also becomes noticeable when the diaphragm gas sensor 100 is attached to the flow cell 200 for use. That is, when the inside of the chamber 201 of the flow cell 200 has a negative pressure with respect to the inside of the container 1 of the diaphragm type gas sensor 100 and the humidity of the sample gas is low, the electrolytic solution S of the electrolytic solution layer Sa evaporates through the diaphragm 5. Then, it is easy to decrease.

Further, in the conventional diaphragm type gas sensor 100, the thickness of the electrolytic solution layer Sa is likely to change and the sensitivity of the diaphragm type gas sensor 100 is likely to change due to the difference in pressing strength of the diaphragm 5 against the working electrode 2. For example, as shown in FIG. 6A, the attachment member 10 is screwed onto the attachment portion 1b of the container 1 to bring the diaphragm 5 into close contact with the surface of the working electrode 2 and to provide a space between the diaphragm 5 and the surface of the working electrode 2. When the electrolytic solution layer Sa is formed on, the thickness of the electrolytic solution layer Sa may change depending on the tightening amount (angle) of the mounting member 10, and the sensitivity of the diaphragm gas sensor 100 may change.

As described above, in the conventional diaphragm-type gas sensor 100, factors such as the elongation of the diaphragm 5, the evaporation of the electrolytic solution S, and the difference in the pressing strength of the diaphragm 5 act independently or in combination, and the diaphragm-type gas sensor 100 is short-term. The stability of the sensitivity (such as the stability of the sensitivity immediately after the replacement of the diaphragm 5) and the long-term stability of the sensitivity (such as the stability of the sensitivity from the time when the diaphragm 5 is new to the time immediately before replacement) are easily affected.

Therefore, an object of the present invention is to improve the long-term stability of sensitivity and to reduce the variation in sensitivity during initial and maintenance work (replacement of diaphragm, replenishment or replacement of electrolyte, etc.). (EN) Provided are a diaphragm type gas sensor and a sensor unit using an electrochemical method that can be performed.

The above object is achieved by the diaphragm type gas sensor and the sensor unit according to the present invention. In summary, the present invention relates to a diaphragm gas sensor for detecting a gas to be detected in a sample gas using an electrochemical method, and a container having an opening for accommodating an electrolytic solution, and the opening. And a working electrode for detecting the gas to be detected, which is provided adjacent to the container, and a diaphragm, which is attached to the container so as to seal the opening, and is permeable to the gas to be detected. A reinforcing member disposed adjacent to the diaphragm on the side opposite to the working electrode of the diaphragm, and a reinforcing member for suppressing extension of the diaphragm, and the diaphragm and the working electrode on the working electrode side of the diaphragm. A spacer that is permeable to the electrolytic solution, and a holding member that holds the diaphragm in the container in a state in which the diaphragm is pressed toward the working electrode via the spacer. This is a diaphragm-type gas sensor.

According to another aspect of the present invention, there is provided a diaphragm gas sensor according to the present invention, and a flow cell that forms a space for accommodating a sample gas adjacent to the diaphragm of the diaphragm gas sensor, the sample gas being introduced into the space. And a flow cell having a discharge part for discharging the sample gas from the space.

According to the present invention, it is possible to improve the long-term stability of sensitivity in a diaphragm-type gas sensor and a sensor unit using an electrochemical method, and to perform initial and maintenance work (replacement of the diaphragm, replenishment of electrolyte solution, It is possible to reduce variations in sensitivity when exchanging).

It is a schematic sectional drawing of one Example of a diaphragm type gas sensor and a sensor unit (3 pole type). It is a schematic sectional drawing of one Example of a diaphragm type gas sensor and a sensor unit (two pole type). FIG. 3 is a schematic plan view and a perspective view showing a diaphragm, a reinforcing member, and a spacer in the diaphragm gas sensor of one example. It is a graph which shows the effect of an Example. It is a graph which shows the effect of an Example. It is a schematic sectional drawing of the conventional diaphragm type gas sensor and a sensor unit.

Hereinafter, the diaphragm gas sensor and the sensor unit according to the present invention will be described in more detail with reference to the drawings.

[Example 1]
1. Configuration of Diaphragm Gas Sensor FIG. 1A is a schematic cross-sectional view of the diaphragm gas sensor 100 of this embodiment. The diaphragm type gas sensor 100 of the present embodiment is of a three-pole type. In FIG. 1A, elements having the same or corresponding functions or configurations as those of the conventional diaphragm gas sensor described with reference to FIG. 6A are designated by the same reference numerals.

The diaphragm type gas sensor 100 has a container 1 for containing an electrolytic solution S. The container 1 has an opening 1a at the lower end in the figure. Further, the diaphragm gas sensor 100 includes a working electrode 2 for detecting a gas to be detected, a counter electrode 3 for passing a current between the working electrode 2, and a reference electrode 4 for controlling the potential of the working electrode 2. And. The working electrode 2 is supported by the support 11 and is disposed adjacent to the opening 1a. Further, the diaphragm gas sensor 100 has a diaphragm 5 which is attached to the container 1 so as to seal the opening 1a and which is capable of blocking the permeation of the liquid and permeating the gas to be detected. The container 1 and the diaphragm 5 form a chamber (detection tank) 1f for containing the electrolytic solution S therein.

The container 1 has a generally stepped cylindrical shape, and has a large diameter portion on the upper side in the drawing and a small diameter portion on the lower side in the drawing, and the mounting portion for the small diameter portion on the lower side in the drawing to attach the diaphragm 5. 1b, and an opening 1a having a substantially circular shape in plan view is formed at the lower end of the mounting portion 1b in the figure. The diaphragm 5 is attached to the container 1 such that the O-ring 8 as a seal member is sandwiched between the diaphragm 5 and the end surface 1c of the attachment portion 1b which is substantially circular in plan view. The seal member is not limited to the O-ring 8 and may be packing or the like. Further, the container 1 is provided with a pressure compensating port 1e which is a pressure compensating portion, and the pressure compensating port 1e is provided with a gas permeable pressure compensating film so as to maintain a liquid tight state. The pressure compensation screw 12 is screwed.

The diaphragm-type gas sensor 100 further includes a reinforcing member 6 disposed adjacent to the diaphragm 5 on the side opposite to the working electrode 2 of the diaphragm 5, and a reinforcing member 6 for suppressing the elongation of the diaphragm 5, and on the working electrode 2 side of the diaphragm 5. And a spacer 7 which is disposed adjacent to the diaphragm 5 and the working electrode 2 and through which the electrolytic solution S can penetrate. In this embodiment, the reinforcing member 6 is placed on the edge of the pressing opening 9a formed in the annular (annular in this embodiment) pressing member 9 and having a substantially circular shape in plan view, and the working electrode 2 of the reinforcing member 6 is placed. The diaphragm 5 is arranged on the side, and the spacer 7 is placed on the working electrode 2 side of the diaphragm 5. Further, the pressing member 9 on which the reinforcing member 6, the diaphragm 5 and the spacer 7 are arranged is placed on the edge of the mounting member opening 10a formed in the cap nut-shaped mounting member 10 and having a substantially circular shape in plan view. .. Then, the mounting member 10 is screwed into the mounting portion 1b of the container 1 via the screw 10b formed on the inner periphery of the mounting member 10 and the screw 1d formed on the outer periphery of the mounting portion 1b of the container 1. As a result, the diaphragm 5 and the reinforcing member 6 are attached to the container 1 in a state of being pressed toward the container 1 via the O-ring 8, and are opened by the diaphragm 5 so that the electrolytic solution S inside the container 1 does not leak. The portion 1a is sealed in a liquid tight state. Further, as a result, the diaphragm 5 is pressed toward the working electrode 2 via the spacer 7. At this time, the electrolytic solution S inside the container 1 permeates into the spacer 7 arranged so as to be sandwiched between the diaphragm 5 and the surface of the working electrode 2, so that the diaphragm 5 and the surface of the working electrode 2 are separated from each other. The electrolyte layer Sa is formed between the two. As a result, the counter electrode 3 and the reference electrode 4 are electrically connected to the working electrode 2 via the electrolytic solution S inside the container 1. In this embodiment, the pressing member 9 and the attachment member 10 function as a holding member that holds the diaphragm 5 in the container 1 in a state where the diaphragm 5 is pressed toward the working electrode 2 via the spacer 7. The reinforcing member 6 and the spacer 7 will be further described later.

The working electrode 2, the counter electrode 3, and the reference electrode 4 are drawn out of the container 1 so as to maintain a liquid-tight state, and connected to a measurement circuit (not shown) which is a potentiostat circuit via a lead wire. To be done. Then, the detection target gas that has permeated the diaphragm 5 is electrolyzed at the interface between the working electrode 2 and the electrolytic solution S while the potential of the working electrode 2 is maintained within a predetermined range with respect to the potential of the reference electrode 4. Then, a current corresponding to the concentration of the gas to be detected is generated between the working electrode 2 and the counter electrode 3. This current is measured by the measuring circuit. Thereby, the concentration measurement or detection of the gas to be detected is performed.

The diaphragm gas sensor 100 can be applied to the detection of various detection target gases by appropriately setting the materials of the working electrode 2, the counter electrode 3, and the reference electrode 4, the composition of the electrolytic solution S, the potential of the working electrode 2, and the like. it can. The diaphragm type gas sensor 100 is not limited to these, for example, chlorine (Cl ₂ ), bromine (Br ₂ ), fluorine (F ₂ ), ammonia (NH ₃ ), hydrogen chloride (HCl), hydrogen fluoride. (HF), silane (SiH ₄ ), hydrogen cyanide (HCN), arsine (AsH ₃ ), phosphine (PH ₃ ), diborane (B ₂ H ₃ ), etc. Can be applied.

For example, in the case of a hydrogen chloride gas sensor in which the gas to be detected is hydrogen chloride gas, the configuration of the diaphragm gas sensor 100 can be set as follows. As the material of the working electrode 2, gold, platinum or the like is used. Moreover, as the material of the counter electrode 3, platinum, silver, silver iodide, or the like is used. As the material of the reference electrode 4, silver/silver chloride (silver plated with silver chloride), silver/silver iodide (silver plated with silver iodide), or the like is used. Further, as the electrolytic solution S, a solution in which 20 to 80% by volume of ethylene glycol is added as a basic component of an aqueous solution of potassium iodide and potassium iodate is used. The working electrode 2 has a potential of −300 to +300 V with respect to the reference electrode 4. Note that the reference electrode 4 is omitted in the case of the two-pole sensor, while the reference electrode is provided in the case of the three-pole sensor as described above. FIG. 2A is a schematic cross-sectional view of an embodiment of the bipolar membrane gas sensor 100 to which the present invention is applied. In FIG. 2A, elements having the same or corresponding functions or configurations as those of the three-electrode type diaphragm gas sensor 100 of the present embodiment shown in FIG. 1A are designated by the same reference numerals.

The diaphragm 5 can be appropriately selected from the viewpoints that it is possible to transmit the gas to be detected and that the composition is stable in the measurement environment for a long period of time. A fluororesin, a silicone resin, a low-density polyethylene or the like can be used as a material forming the diaphragm 5. As the fluororesin, PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxy fluororesin), FEP (tetrafluoroethylene/hexafluoropropylene copolymer) and ETFE (ethylene/tetrafluoroethylene copolymer) Etc. can be used. For example, as the diaphragm 5, a PTFE porous film having a mean pore diameter of 0.1 μm to 5.0 μm and a thickness of 50 μm to 300 μm, which is a fluororesin porous film, is suitable. Can be used for. The diaphragm 5 does not have to be porous with pores provided that the gas to be detected can be sufficiently transmitted.

2. Sensor Unit FIG. 1B is a schematic cross-sectional view of a sensor unit 300 in which the diaphragm type gas sensor 100 of this embodiment is attached to a flow cell 200. In FIG. 1B, elements having the same or corresponding functions or configurations as those of the conventional sensor unit described with reference to FIG. 6B are designated by the same reference numerals.

The diaphragm-type gas sensor 100 of the present embodiment is used to detect a gas to be detected in the indoor environment in an open state as shown in FIG. 1(a), and also to a flow cell 200 as shown in FIG. 1(b). It is attached and used to detect the detection target gas in the sample gas introduced into the flow cell 200 from the measurement target environment such as an exhaust gas processing apparatus in a semiconductor manufacturing process through a pipe or the like. The sensor unit 300 has a diaphragm gas sensor 100 and a flow cell 200. The flow cell 200 includes a chamber 201 which is a space for accommodating the sample gas adjacent to the diaphragm 5 of the diaphragm gas sensor 100, an inlet 202 which is an inlet for introducing the sample gas into the chamber 201, and a sample from the chamber 201. And a discharge port 203 which is a discharge unit for discharging gas. In the present embodiment, the diaphragm-type gas sensor 100 keeps the flow cell 200 in an airtight state by fitting the attachment member 10 attached to the lower part of the container 1 in the drawing in the opening portion forming the chamber 201 of the flow cell 200. It is installed so as to maintain it.

When the diaphragm gas sensor 100 is used by being attached to the flow cell 200 as described above, the diaphragm 5 of the diaphragm gas sensor 100 is exposed to the pressure condition in the pipe connected to the flow cell 200. When the pressure of the sample gas is low or when the sample gas is pumped through the discharge port 203, the inside of the chamber 201 of the flow cell 200 has a negative pressure with respect to the inside of the container 1 of the diaphragm gas sensor 100. As described above, in this case, the diaphragm 5 is likely to be stretched and deformed away from the working electrode 2. Further, when the pressure of the sample gas is high or when the sample gas is pushed by the pump through the inlet 202, the inside of the chamber 201 of the flow cell 200 has a positive pressure with respect to the inside of the container 1 of the diaphragm gas sensor 100. .. As described above, in this case, the diaphragm 5 tends to stretch and stick to the surface of the working electrode 2.

Note that FIG. 2B is a schematic cross-sectional view of a sensor unit 300 configured by attaching the bipolar membrane gas sensor 100 shown in FIG. 2A to the flow cell 200. In FIG. 2B, elements having the same or corresponding functions or configurations as those of the sensor unit 300 shown in FIG. 1B are designated by the same reference numerals.

3. Reinforcing member and spacer By arranging the reinforcing member 6 on the outer side of the diaphragm 5, it is possible to reinforce the diaphragm 5, prevent the diaphragm 5 from being stretched, and suppress deformation of the diaphragm 5. Further, by disposing the spacer 7 having a liquid retaining function (water retaining function) inside the diaphragm 5, the distance between the diaphragm 5 and the surface of the working electrode 2 is made substantially constant regardless of the pressing strength of the diaphragm 5. It is possible to make the thickness of the electrolytic solution layer Sa substantially constant, and to prevent the diaphragm 5 from sticking to the surface of the working electrode 2. As described above, by improving the dimensional stability of the diaphragm 5 and the electrolytic solution layer Sa between the working electrode 2 and the diaphragm 5, the stability of the short-term sensitivity and the long-term sensitivity of the diaphragm gas sensor 100 are improved. The stability of can be improved. That is, it is possible to improve the long-term stability of the sensitivity of the diaphragm gas sensor 100, and also the fluctuation of the sensitivity at the time of initial and maintenance work of the diaphragm gas sensor 100 (replacement of the diaphragm, replenishment or replacement of the electrolyte, etc.) Can be reduced. The reinforcing member 6 is particularly effective in suppressing the deformation of the diaphragm 5 due to the elongation during long-term use, but suppresses the fluctuation of the thickness of the electrolyte layer Sa due to the elongation of the diaphragm 5 due to the short-term pressure fluctuation. There is also an effect. Further, the spacer 7 makes the thickness of the electrolytic solution layer Sa constant regardless of the pressing strength of the diaphragm 5 when the diaphragm 5 is attached to the container 1 (initial stage), and holds the electrolytic solution S in long-term use. It is particularly effective in maintaining the electrolyte solution layer Sa, but also has an effect of suppressing the diaphragm 5 from sticking to the working electrode 2 during long-term use.

FIG. 3A is a schematic plan view for explaining the positional relationship among the diaphragm 5, the reinforcing member 6, and the spacer 7 in this embodiment. Further, FIG. 3B is a schematic exploded perspective view of the diaphragm 5, the reinforcing member 6, and the spacer 7. In this embodiment, the diaphragm 5, the reinforcing member 6 and the spacer 7 are substantially circular in a plan view, the reinforcing member 6 has the same outer diameter as the diaphragm 5, and the spacer 7 is smaller than the diaphragm 5 and smaller than the working electrode 2. Also has a large outer diameter. In this embodiment, the reinforcing member 6 is formed integrally with the diaphragm 5, and the spacer 7 is formed separately from the diaphragm 5.

The reinforcing member 6 may be arranged along the surface of the diaphragm 5 on the side opposite to the working electrode 2 and can prevent the diaphragm 5 from being stretched and deformed. However, since it is desired that the reinforcing member 6 can be pressed against the surface of the working electrode 2 along the surface of the diaphragm 5, the material forming the reinforcing member 6 is preferably a resin having elasticity. As the reinforcing member 6, a sheet having a mesh structure or a non-woven structure made of resin fibers can be used.

Here, the net-like structure (net) may be constituted by fibers (including fiber bundles and yarns) extending in one direction and a direction intersecting with the one direction (not limited to the orthogonal direction). Good. The mesh structure is not limited to the fibers extending in two directions, and may be formed of fibers intersecting with each other in three or more directions. The network structure is typically a structure in which fibers extending in each direction are bonded by a thermal, mechanical or chemical action, but may be a woven fabric. Further, the non-woven fabric-like structure may be one that is configured without weaving fibers. The non-woven fabric structure is typically formed by intertwining fibers, but the fibers may be bonded by a thermal, mechanical, or chemical action.

As the resin forming the reinforcing member 6, polyester (PET (polyethylene terephthalate) or the like), polyimide, polycarbonate, polyvinylidene fluoride, polyethylene, polypropylene or the like can be used. It is preferable that the resin forming the reinforcing member 6 is less likely to be plastically deformed than the resin forming the diaphragm 5. The reinforcing member 6 may be formed integrally with the diaphragm 5 or may be formed separately from the diaphragm 5. If the reinforcing member 6 is integrated with the diaphragm 5, the integration may be done by thermal, mechanical or chemical action. The thickness of the reinforcing member 6 is preferably 1 μm or more and 500 μm or less. When the thickness of the reinforcing member 6 is less than 1 μm, it may be difficult to suppress the elongation of the diaphragm 5 sufficiently, and when the thickness of the reinforcing member 6 exceeds 500 μm, the reinforcing member 6 is arranged along the surface of the diaphragm 5. It can be difficult to do. The thickness of the reinforcing member 6 is more preferably 10 μm or more and 300 μm or less. For example, the diaphragm 5 and the reinforcing member 6 which is a sheet having a mesh structure made of resin fibers are integrally formed as a reinforcing film, and the diaphragm 5 made of porous PTFE and the polypropylene fiber A supported PTFE type membrane filter (manufactured by Toyo Roshi Kaisha, Ltd.) in which the reinforcing member 6 composed of a net is integrated can be preferably used. Further, a PTFE type filter (manufactured by Hangzhou Kahyaku Special Equipment Co., Ltd.) is used as a reinforced membrane in which the diaphragm 5 and the reinforcing member 6 which is a non-woven sheet made of resin fibers are integrally formed. Can be preferably used.

The spacer 7 is arranged between the diaphragm 5 and the working electrode 2 so that the distance between the diaphragm 5 and the working electrode 2 can be maintained substantially constant, and at the same time, the electrolytic solution S can penetrate and hold the electrolytic solution S. Any liquid having a liquid retaining function (water retaining function) that can be used may be used. As the spacer 7, a sheet having a mesh structure or a non-woven structure made of resin, cellulose or glass fibers can be used. As the spacer 7, a filter material (filter paper) made of resin, cellulose, or glass fiber may be used. Further, as the spacer 7, a sponge or a porous film made of resin may be used. As the resin forming the spacer 7, polyester (PET or the like), polyimide, polycarbonate, polyvinylidene fluoride, polyethylene, polypropylene or the like can be used. The spacer 7 may be formed separately from the diaphragm 5, or may be integrally formed with the diaphragm 5. If the spacer 7 is integrated with the diaphragm 5, the integration may be done by thermal, mechanical or chemical action. The thickness of the spacer 7 is preferably 1 μm or more and 100 μm or less. If the thickness of the spacer 7 is less than 1 μm, it may be difficult to sufficiently retain the electrolytic solution S. If the thickness of the spacer 7 exceeds 100 μm, the diaphragm 5 and the working electrode 2 are too far apart from each other. The response speed of the gas sensor 100 may slow down. The thickness of the spacer 7 is more preferably 1 μm or more and 60 μm or less. For example, as the spacer 7 formed separately from the diaphragm 5, a polyester non-woven fabric (manufactured by Vilene Co., Ltd.) which is a non-woven fabric composed of polyester fibers can be preferably used.

4. Experimental Example Next, the effect of the present embodiment will be further described using an experimental example.

<Experimental Example 1>
A sensor unit 300 including the diaphragm gas sensor 100 of the present embodiment (FIG. 1B) and a sensor unit 300 including the conventional diaphragm gas sensor 100 as a comparative example (FIG. 6B) are used. Then, an experiment was conducted to examine the change with time of the indicated value of the diaphragm gas sensor 100.

In the present experimental example, the atmosphere (temperature 25° C., humidity 30 to 40% RH) is continuously sucked at a suction pressure of −5 kPa by the suction means connected to the discharge port 203 of the flow cell 200, and the inside of the chamber 201 is separated by a diaphragm. A negative pressure was applied to the inside of the container 1 of the gas sensor 100. Then, at a proper timing, a detection target gas having a constant concentration was introduced into the atmosphere (sample gas) sucked into the chamber 201, and the concentration of the detection target gas was measured.

In the present experimental example, the diaphragm type gas sensor 100 was configured as a hydrogen chloride gas sensor whose detection target gas was hydrogen chloride gas and an ammonia gas sensor whose detection target gas was ammonia gas, and the same experiment was performed. When configured as a hydrogen chloride gas sensor, the working electrode 2 is gold, the counter electrode 3 is silver, the reference electrode 4 is silver, and the electrolytic solution S is potassium iodide or potassium iodate aqueous solution in any of the present examples and comparative examples. Assuming that 50% by volume of ethylene glycol was added as a basic component, the potential of the working electrode 2 was set to +200 V with respect to the reference electrode 4, and the current flowing between the working electrode 2 and the counter electrode 3 was measured to measure the hydrogen chloride gas concentration. It was converted to the indicated value (ppm). When configured as an ammonia gas sensor, the working electrode 2 is silver, the counter electrode 3 is silver, the reference electrode 4 is silver, the electrolytic solution S is silver nitrate, and the aqueous solution of acetate is 50 as a basic component in both the present example and the comparative example. Assuming that a volume% of ethylene glycol was added, the electric potential of the working electrode 2 was set to 0 V with respect to the reference electrode 4, and the current flowing between the working electrode 2 and the counter electrode 3 was measured to give an ammonia gas concentration indicating value (ppm). Converted to.

In the present embodiment, as the diaphragm 5 and the reinforcing member 6, a supported PTFE type membrane filter (manufactured by Toyo Roshi Kaisha, Ltd., product name J010A system, average pore diameter 0) is a reinforcing film in which the diaphragm 5 and the reinforcing member 6 are integrally formed. .10 μm, the thickness of the PTFE film was 30 μm, and the thickness of the net was 100 μm). In this filter, a porous PTFE membrane (diaphragm 5) and a polypropylene fiber net (reinforcing member 6) are integrated. Further, in this embodiment, this filter is a circular shape having a diameter of about 22 mm, the O-ring 8 has a diameter of about 20.3 mm, the working electrode 2 has a diameter of about 10 mm for the hydrogen chloride gas sensor and about 8 mm for the ammonia gas sensor. It was Further, in this example, as the spacer 7, a polyester non-woven fabric (manufactured by Vilene Co., Ltd.) which is a non-woven fabric composed of polyester fiber and having a thickness of 38 μm was used. In this embodiment, the spacer 7 is a circle having a diameter of about 13 mm.

In addition, in the comparative example, a porous PTFE membrane (manufactured by Sumitomo Electric Co., Ltd., product name Poreflon, pore diameter 0.10 μm, thickness 80 μm) was used as the diaphragm 5. The respective diameters of the diaphragm 5, the O-ring 8 and the working electrode 2 in the comparative example are substantially the same as those in the present embodiment.

FIG. 4A shows the result when the diaphragm type gas sensor 100 of the present example and the comparative example is configured as a hydrogen chloride gas sensor, and FIG. 4B shows the result when it is configured as an ammonia gas sensor. The results obtained by using two test sensors are shown for both the present example and the comparative example.

As can be seen from FIGS. 4A and 4B, in the comparative example, there was a large variation in the indicated value for each sensor to be tested. It is considered that this is because the thickness of the electrolytic solution layer Sa was not constant for each test sensor. In addition, in the comparative example, there was a case where the indicated value became almost zero in a short period of time. This is because the sample gas has a relatively low humidity and the inside of the chamber 201 has a negative pressure so that the electrolytic solution S in the electrolytic solution layer Sa is evaporated and reduced, and the inside of the chamber 201 has a negative pressure. It is considered that this is because the thickness of the electrolytic solution layer Sa changed due to the expansion of the diaphragm 5 and the occurrence of bending.

On the other hand, as can be seen from FIGS. 4A and 4B, in the present embodiment, the variation in the indicated value for each sensor to be tested was small. It is considered that this is because the spacer 7 was provided between the diaphragm 5 and the surface of the working electrode 2, so that the distance between the diaphragm 5 and the working electrode 2 was kept substantially constant. Further, in this example, the change in the indicated value with time was small. This is because by providing the reinforcing member 6 on the outer side of the diaphragm 5, it is possible to suppress the diaphragm 5 from being stretched and bending, and the spacer 7 holds the electrolytic solution S and the electrolytic solution of the electrolytic solution layer Sa. It is considered that the decrease in S due to evaporation was suppressed.

<Experimental example 2>
The diaphragm type gas sensor 100 of this embodiment (FIG. 1A) and the conventional diaphragm type gas sensor 100 (FIG. 6A) as a comparative example are used to separate the diaphragm 5 depending on the pressing strength of the diaphragm 5. An experiment was conducted to examine the change in the indicated value of the gas sensor 100.

In the present experimental example, as the diaphragm type gas sensor 100 of the present example and the comparative example, substantially the same hydrogen chloride gas sensors as those described in Experimental example 1 were used. Then, for each of the diaphragm-type gas sensors 100 of the present example and the comparative example, the tightening amount (angle) from the tightening starting point of the mounting member 10 is changed in the range of 0 degrees to 210 degrees so that the concentration of the gas to be detected is constant. The test sensor was arranged in the atmosphere, and the outputs of the test sensor (relative output to the output when the tightening angle was 120 to 150 degrees) were compared.

The results for the diaphragm-type gas sensor 100 of the comparative example are shown in FIG. 5A, and the results for the diaphragm-type gas sensor 100 of the present embodiment are shown in FIG. 5B. The results obtained using three test sensors are shown for both the present example and the comparative example.

As can be seen from FIG. 5A, in the comparative example, the output of the diaphragm type gas sensor 100 has a relatively large variation due to the difference in the tightening amount (angle) of the mounting member 10, that is, the pressing strength of the diaphragm 5. .. It is considered that this is because the thickness of the electrolytic solution layer Sa was different due to the difference in pressing strength of the diaphragm 5.

On the other hand, as shown in FIG. 5B, in the present embodiment, even if there is a difference in the tightening amount (angle) of the mounting member 10, that is, the pressing strength of the diaphragm 5, the diaphragm gas sensor 100 of the diaphragm type gas sensor 100. The output difference was small. Then, by setting the tightening angle to 120 degrees or more, a substantially constant output was obtained. This is because the spacer 7 is provided between the diaphragm 5 and the surface of the working electrode 2, so that the thickness of the electrolytic solution layer Sa can be kept substantially constant even if the pressing strength of the diaphragm 5 is different. This is probably because it was done. That is, in the present embodiment, it is understood that even if the pressing strength of the diaphragm 5 varies depending on the operator's individual difference, it is possible to reduce the variation in sensitivity by making the thickness of the electrolytic solution layer Sa substantially constant.

5. Effect As described above, according to the present embodiment, the dimensional stability of the diaphragm 5 and the electrolytic solution layer Sa between the working electrode 2 and the diaphragm 5 is improved, so that the diaphragm gas sensor 100 in the short-term is improved. The stability of sensitivity and the stability of long-term sensitivity can be improved. That is, according to the present embodiment, in the diaphragm type gas sensor 100 and the sensor unit 300 using the electrochemical method, the long-term stability of the sensitivity can be improved, and the initial and maintenance work of the diaphragm type gas sensor 100 can be performed. It is possible to reduce variations in sensitivity during replacement of the diaphragm, replenishment or replacement of the electrolytic solution, and the like.

1 Container 2 Working Electrode 3 Counter Electrode 4 Reference Electrode 5 Diaphragm 6 Reinforcing Member 7 Spacer 100 Diaphragm Gas Sensor 200 Flow Cell 300 Sensor Unit

Claims (8)

In the diaphragm type gas sensor for detecting the detection target gas in the sample gas using the electrochemical method,
A container having an opening for containing the electrolytic solution,
Provided in the container adjacent to the opening, a working electrode for detecting the gas to be detected,
A diaphragm that is attached to the container so as to seal the opening and is capable of transmitting a gas to be detected,
A reinforcing member arranged adjacent to the diaphragm on the side opposite to the working electrode of the diaphragm, for suppressing the elongation of the diaphragm,
A spacer, which is arranged adjacent to the diaphragm and the working electrode on the working electrode side of the diaphragm, and in which the electrolytic solution is permeable,
A holding member for holding the diaphragm in the container in a state in which the diaphragm is pressed toward the working electrode via the spacer;
A membrane-type gas sensor having: The diaphragm type gas sensor according to claim 1, wherein the reinforcing member is a sheet having a mesh structure or a non-woven structure made of resin fibers. The spacer is made of resin, a sheet having a mesh structure or a non-woven structure made of cellulose or glass fibers, a filter material made of resin, cellulose or glass fibers, or made of resin. The diaphragm type gas sensor according to claim 1 or 2, which is a sponge or a porous film. The diaphragm type gas sensor according to claim 2 or 3, wherein the resin is selected from the group including polyester, polyimide, polycarbonate, polyvinylidene fluoride, polyethylene, and polypropylene. The diaphragm-type gas sensor according to claim 1, wherein the reinforcing member has a thickness of 1 μm or more and 500 μm or less. The diaphragm-type gas sensor according to any one of claims 1 to 5, wherein the spacer has a thickness of 1 µm or more and 100 µm or less. 7. The diaphragm type gas sensor according to claim 1, wherein the diaphragm is made of a resin selected from the group including a fluororesin, a silicone resin, and a low density polyethylene. It is a flow cell which forms the space which accommodates sample gas adjacent to the diaphragm of the diaphragm type gas sensor according to any one of claims 1 to 7, and introduces sample gas into the space. And a flow cell having a discharge part for discharging the sample gas from the space.

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