JP4630108B2 - Galvanic cell oxygen sensor - Google Patents

Description

  A galvanic cell type comprising a positive electrode containing a metal, a negative electrode, and an electrolyte solution in contact with the positive electrode and the negative electrode, and an oxygen permeable film that does not transmit the electrolyte solution is provided on one surface of the positive electrode. The present invention relates to an oxygen sensor.

  In general, a galvanic cell type oxygen sensor measures an oxygen concentration by causing an oxidation-reduction reaction between positive and negative electrodes in the presence of oxygen. Specifically, when oxygen passes from the outside through the oxygen permeable membrane and enters the sensor, oxygen is dissolved in the electrolytic solution. The oxygen dissolved in the electrolytic solution moves onto the positive electrode and is reduced, and oxidizes the negative electrode through the electrolytic solution. Thereby, a current corresponding to the amount of oxygen flows from the positive electrode to the negative electrode, and the oxygen concentration can be determined by measuring this current as a sensor output voltage.

  In such a galvanic cell type oxygen sensor, a metal piece is used as the positive electrode, the installation interval between the positive electrode and the oxygen permeable membrane is kept constant, and an electrolyte layer having a constant thickness is provided between the positive electrode and the oxygen permeable membrane. Let it form. However, it is difficult to keep the thickness of the electrolyte layer constant due to a change in external pressure or the like, causing problems such as unstable sensor output.

  In order to solve the above problem, a structure in which a positive electrode is integrally bonded to one surface of an oxygen permeable membrane (for example, see Patent Document 1) has been studied. Specifically, a film is provided by sputtering gold on one surface of the oxygen permeable film. According to this, since the oxygen permeable membrane and the positive electrode are integrated, the sensor output does not change even when the external pressure changes.

JP-A-6-109694

  However, in a galvanic cell type oxygen sensor in which a film is formed by sputtering gold on one surface of the oxygen permeable membrane and the oxygen permeable membrane and the positive electrode are integrated, the oxygen permeable membrane is in contact with the gold while the sensor is in use. A film formed by sputtering may be peeled off. For this reason, there was a problem that the electrolyte solution entered between the oxygen permeable film and the film formed by sputtering of gold, resulting in unstable sensor output.

  Further, in the galvanic cell type oxygen sensor, oxygen that has permeated through the oxygen permeable membrane is dissolved in the electrolyte solution soaked in the pores of the membrane formed by gold sputtering and reacts in the pores of the membrane. For this reason, the area which reacts with oxygen becomes small, and there is a possibility that the speed of reducing oxygen, that is, the response speed to oxygen becomes slow.

  Furthermore, since a step of sputtering gold on the oxygen permeable membrane is required separately, there is a problem that the cost is increased.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a galvanic cell type oxygen sensor having a stable sensor output and a high response speed to oxygen.

A first characteristic configuration of a galvanic cell type oxygen sensor according to the present invention for achieving the above object includes a positive electrode including a metal, a negative electrode, and an electrolytic solution in contact with the positive electrode and the negative electrode in a container, A galvanic cell type oxygen sensor in which an oxygen permeable membrane that does not transmit the electrolyte solution is stacked on one surface of the positive electrode, wherein the positive electrode is a metal foil and has a communication hole through which the electrolyte solution can pass. However, it is provided so as to be capable of reacting with oxygen on the one surface side.

That is, according to this configuration, since the oxygen permeable film is provided so as to overlap the positive electrode of the metal foil having a communicating hole through which the electrolyte can permeate, the positive electrode and the oxygen permeable film are brought into close contact with each other. The electrolyte solution can be oozed out between the permeable membrane. The oxygen that has permeated the oxygen permeable membrane from the outside is dissolved in the electrolyte that has oozed between the positive electrode and the oxygen permeable membrane, and immediately reacts on the surface of the positive electrode that is in close contact with the oxygen permeable membrane.
Moreover, since metal foil has a micro crack and a pinhole inside, it can permeate | transmit electrolyte solution moderately.
Therefore, the electrolyte solution can be present at the interface while maintaining the state where the positive electrode and the oxygen permeable membrane are substantially in close contact with each other, and the sensor output can be stabilized. And since the reaction area with oxygen in a positive electrode becomes large, the response speed with respect to oxygen gas can be made quick.

The second characteristic configuration of the galvanic cell type oxygen sensor according to the present invention is that the oxygen permeable membrane is subjected to a hydrophilic treatment on the surface on which the positive electrode is superimposed.

  That is, according to this configuration, the wettability of the oxygen permeable membrane is improved, and the electrolytic solution that has permeated the positive electrode can be spread at the interface between the positive electrode and the oxygen permeable membrane.

According to a third characteristic configuration of the galvanic cell type oxygen sensor according to the present invention, the container includes a metal container main body and a metal lid portion insulated from the container main body, and the positive electrode is attached to the container main body. The negative electrode is connected to the lid portion.

  That is, according to this configuration, since the container body and the lid part serve as a positive electrode and a negative electrode, it is not necessary to provide lead wires connected to the positive electrode and the negative electrode from the inside of the sensor. For this reason, the structure of the sensor can be simplified.

According to a fourth characteristic configuration of the galvanic cell oxygen sensor according to the present invention, the positive electrode has a contact portion that contacts the inner surface of the container body, and a current collector provided to overlap the other surface of the positive electrode. It is in the point connected with the said container main body through.

  That is, according to this structure, a positive electrode and a container main body can be reliably connected via a collector.

The galvanic cell type oxygen sensor according to the present invention includes a positive electrode containing a metal, a negative electrode, and an electrolytic solution in contact with the positive electrode and the negative electrode in a container, and does not transmit the electrolytic solution to one surface of the positive electrode. A galvanic cell type oxygen sensor provided with an oxygen permeable membrane in an overlapping manner, wherein the positive electrode is a metal foil and has a communication hole through which the electrolyte can permeate, and reacts with oxygen on the one surface side. This is possible. As a result, the electrolyte can be present at the interface while keeping the positive electrode and the oxygen permeable membrane substantially in close contact with each other. Therefore, in the positive electrode, the gas phase (oxygen gas), liquid phase (electrolyte), solid A three-phase interface of phases (electrodes) can be easily formed, and sensor output can be stabilized. And since the reaction area with oxygen in a positive electrode becomes large, the response speed with respect to oxygen gas can be made quick.

  Hereinafter, an embodiment of a galvanic cell type oxygen sensor according to the present invention will be described with reference to the drawings. As shown in FIG. 1, the galvanic cell type oxygen sensor according to this embodiment has a so-called button-type battery-shaped container 1 having a diameter of 13 mm and a thickness of 6 mm.

  The container 1 is made of stainless steel and includes a container body 1a and a lid 1b. The container main body 1a is provided with a hole 1c having a diameter of 2 mm at the center of the bottom so that oxygen can be introduced into the container 1. In addition, a 1 mm diameter inlet 1d is provided at the center of the lid 1b so that the electrolytic solution 10 can be injected after the lid 1b is attached to the container body 1a. The material of the container main body 1a and the lid 1b is not limited to stainless steel, but other metals and resins can be applied. However, when the container main body 1a and the lid 1b are applied as electrodes as will be described later. It is preferable that it is made of metal, and if it is made of metal, evaporation of the electrolytic solution 10 inside can be prevented as compared with resin.

At the bottom of the container body 1a, a polyethylene sealing film 2 having a 2.5 mm diameter opening at the center is provided so that the opening fits the hole 1c of the container body 1a. An oxygen-permeable membrane 3 having a thickness of 25 μm, a positive electrode 4 made of a metal foil having a thickness of 1 μm, and a ring-shaped current collector 8 having a thickness of 0.05 mm are laminated in this order on 2. . Furthermore, a negative electrode 7 which is a 9 mm diameter, 0.5 mm thick lead plate having a 4 mm diameter non-woven separator 5, a pressing member 6, and a 2 mm diameter opening is sequentially laminated at the center of the upper surface of the positive electrode 4, A gasket 9 is provided on the upper surface of the current collector 8. These are configured to be pressed and attached to each other by attaching the lid 1b. The lid 1b can be attached by caulking after covering the container main body 1a. Furthermore, after caulking, for example, a UV adhesive (not shown) is provided between the container main body 1a and the lid 1b. Can be applied to increase the strength.

  Further, the inside of the container 1 is filled with the electrolytic solution 10, and the electrolytic solution 10 is always kept in contact with the positive electrode 4 and the negative electrode 7. The electrolytic solution 10 can be filled in the container 1 by injecting the electrolytic solution 10 from the inlet 1d of the lid portion 1b after the lid portion 1b is attached. In addition, a 1.1 mm diameter sealed ball 11 made of the same material as that of the lid portion 1b is press-fitted into the injection port 1d after the electrolyte solution 10 is injected, and the inside of the container 1 is sealed. Furthermore, in order to increase the sealing degree, a UV adhesive (not shown) may be applied on the encapsulating sphere 11 to cover the encapsulating sphere 11.

  With such a configuration, in particular, the oxygen permeable membrane 3 and the positive electrode 4 are brought into close contact with each other, the positive electrode 4 can be connected to the container body 1a through the current collector 8, and the negative electrode 7 can be connected to the lid portion 1b. it can. As a result, there is no need to provide lead wires that are directly connected to the positive electrode 4 and the negative electrode 7, and there is no possibility that the electrolyte solution 10 leaks from the gap between the lead wires and the container 1 or the like. And since the container main body 1a and the cover part 1b play the role of the positive electrode 4 and the negative electrode 7, for example, the galvanic cell type oxygen sensor of this embodiment is directly fitted in a known circuit such as an oximeter, etc. 1a and the cover part 1b can be applied in contact with the circuit, and the measurement apparatus can be simplified.

Since the positive electrode 4 is a metal foil , the positive electrode 4 and the oxygen permeable film 3 can be brought into close contact with each other by being provided over the oxygen permeable film 3. As the positive electrode 4, a gold foil, a platinum foil, a silver foil, a copper foil, or the like can be used. These metal foils have, for example, a plurality of communication holes such as cracks and pinholes of about 0.1 to 10 μm, such as gold foils shown in FIG. 2A and platinum foils shown in FIG. The cage electrolyte 10 can be permeated appropriately. For this reason, the electrolyte solution 10 can be oozed out between the positive electrode 4 and the oxygen permeable membrane 3 that are in close contact with each other, and oxygen that has permeated the oxygen permeable membrane 3 from the outside is removed from the surface of the positive electrode 4 on the oxygen permeable membrane 3 side. Can be reduced. That is, by providing the positive electrode 4 and the oxygen permeable film 3 in an overlapping manner, the electrolyte solution 10 can be appropriately permeated through the communication hole, so that the solid phase, the liquid phase, the gas, together with the oxygen that has permeated the oxygen permeable film 3. A three-phase interface of phases can be easily formed. For this reason, the reaction area with oxygen spreads, and the response speed of the sensor can be increased. Then, the electrolytic solution 10 can be interposed while the positive electrode 4 and the oxygen permeable membrane 3 are kept in a substantially close contact state, and the electrolytic solution 10 enters more than necessary, and the distance between the positive electrode 4 and the oxygen permeable membrane 3 is increased. The sensor output can be kept stable without greatly changing.
In addition to the metal foil, the positive electrode 4 can be applied as long as it is in the form of a film and has a communication hole through which the electrolytic solution 10 can pass and can react with oxygen on the oxygen permeable membrane 3 side. For example, it is also possible to use a film obtained by forming a thin film by sputtering a metal such as gold on the film substrate and then partially removing the film substrate.

  The oxygen permeable membrane 3 is a diaphragm that selectively permeates oxygen and separates the outside from the electrolyte solution 10 from the inside of the container 1. The material of the oxygen permeable membrane 3 is not particularly limited as long as it does not transmit the electrolytic solution 10 and has oxygen permeation performance. Are applicable. Further, the surface of the oxygen permeable membrane 3 on the positive electrode 4 side in the present embodiment is subjected to a hydrophilic treatment. As a result, the affinity with the electrolytic solution 10 that oozes out from the positive electrode 4 is improved, and the electrolytic solution 10 is likely to exist at the interface between the positive electrode 4 and the oxygen permeable membrane 3.

  In addition, the seal film 2 is not necessarily provided. However, since the seal film 2 can be brought into close contact with the container main body 1 and the oxygen permeable membrane 3, oxygen contained in the hole 10 of the container main body 1 Without being diffused between the oxygen permeable membrane 3, it can be guided to the oxygen permeable membrane 3 with the shortest distance.

  The separator 5 can hold the electrolytic solution 10 and is not necessarily provided. However, the separator 5 is disposed at a position corresponding to the hole 1c of the container body 1a of the positive electrode 4 so that the positive electrode 4 reacts with oxygen. The electrolyte solution 10 can always exist. In the present embodiment, a non-woven fabric is used, but it is sufficient that the electrolytic solution 10 can be held, and for example, a sponge-like material may be used. Moreover, the material of the separator 5 is not specifically limited, For example, conventionally well-known things, such as a fluorinated olefin by which the surface was fluorinated, can be selected arbitrarily, and a shape, a magnitude | size, etc. are not specifically limited.

  The pressing member 6 is used to press and bring the container body 1a, the seal film 2, the oxygen permeable membrane 3 and the positive electrode 4 into close contact with each other when the cover 1b is attached, and to make the negative electrode 7 and the cover 1b in close contact with each other. The shape is not particularly limited. In the present embodiment, four holes are provided in the vicinity of the central portion of the pressing member 6 so that the electrolytic solution 10 can be moved back and forth between the positive electrode 4 side and the negative electrode 7 side. What is necessary is just to comprise so that an electric current may flow between the positive electrode 4 and the negative electrode 7 so that ten ions can come and go. The material is selected according to the type of the electrolytic solution 10. For example, polycarbonate can be used in the case of an acidic aqueous solution, and polyacryl can be used in the case of a basic aqueous solution.

  The negative electrode 7 is provided with an opening so as not to obstruct the electrolyte 10 when the electrolyte 10 is injected from the inlet of the lid 1d. Further, the end of the negative electrode 7 is provided so as to be externally fitted to the pressing member 6, so that the negative electrode 7 is not displaced when the sensor is assembled and when the sensor is used. The shape of the negative electrode 7 is not particularly limited as long as the position is fixed and the negative electrode 7 can come into contact with the lid portion 1b. As the material of the negative electrode 7, a conventionally known negative electrode material can be used, and in particular, a material containing a base metal such as lead as in this embodiment can be preferably applied. Examples of the base metal include zinc, aluminum and the like in addition to lead.

  The current collector 8 is for connecting the positive electrode 4 and the container body 1a and is made of stainless steel. The current collector 8 is provided in a hollow so as not to prevent the contact between the positive electrode 4 and the electrolytic solution 10. Further, the current collector 8 is provided with an abutting portion 8a that abuts against the inner surface of the container main body 1a so that the current collector 8 can contact the container main body 1a more reliably. In addition, in this embodiment, although it was set as the structure which provides the one contact part 8a, it is not restricted to this, For example, you may provide the some contact part 8a, or the contact part 8a in a different shape, Further, the contact portion 8a is not necessarily provided. Moreover, the material of the electrical power collector 8 should just be able to electrically connect the positive electrode 4 and the container main body 1a, and not only stainless steel but another conductor can be applied. As for the shape of the current collector 8, an example in which the current collector 8 is provided in a hollow ring shape has been shown. However, the positive electrode 4 and the container are not obstructed by preventing contact between the positive electrode 4 and the electrolytic solution 10, such as providing a plurality of openings. If it can connect with the main body 1a reliably, there will be no limitation in particular.

  The gasket 9 presses the current collector 8 by attaching the lid portion 1b so that the positive electrode 4 and the current collector 8 are in close contact with each other, and electrically insulates the container body 1a and the lid portion 1b. . For this reason, the material of the gasket 9 needs to be an insulator, and for example, a resin such as polypropylene can be applied. The shape of the gasket 9 is not limited to the shape of the present embodiment as long as the current collector 8 can be pressed and the container body 1a and the lid portion 1b can be separated from each other. Can be applied.

  The electrolytic solution 10 can use either a basic aqueous solution or an acidic aqueous solution. For example, a conventional galvanic cell type oxygen sensor such as a KOH aqueous solution as a basic aqueous solution and a buffer solution of CH3COOH and CH3COOK as an acidic aqueous solution can be used. It is possible to use an electrolytic solution 10 applicable to the above.

  Other configurations and functions are the same as those of a conventionally known galvanic cell type oxygen sensor. The galvanic cell type oxygen sensor according to the present invention can be applied to an oxygen concentration meter or the like by being incorporated in a known circuit or the like.

Examples will be described below.
Example 1
In the galvanic cell type oxygen sensor according to the present embodiment, a buffer solution of 4 mol / L CH3COOH and 4 mol / L CH3COOK is used as an acidic aqueous solution for the electrolyte solution 10, and a gold foil, a silver foil, a platinum foil, When copper foil is used, a resistance of 1 kΩ is attached between the positive electrode and the negative electrode, and each atmosphere of nitrogen gas (oxygen concentration 0%), oxygen concentration 9.24% gas, and air (oxygen concentration 21%) Below, the value of the current flowing on the circuit was measured as the sensor output.
As a result, as shown in FIG. 3, it was found that the output value increased linearly with increasing oxygen concentration, and any metal foil functions as an electrode material.
Moreover, although the same measurement was performed when a 3 mol / L KOH aqueous solution was used as the basic aqueous solution for the electrolytic solution 10, the same result as that obtained when the acidic aqueous solution was used was obtained.

(Example 2)
In the galvanic cell type oxygen sensor used in Example 1, the atmosphere gas was changed from air (oxygen concentration 21%) to nitrogen gas (oxygen concentration 0%) when the positive electrode 4 was made of gold foil, silver foil, platinum foil, and copper foil. ) Was measured for the response time until it was detected that the oxygen concentration was reduced by 90%. As a result, as shown in FIG. 4, it was found that in any case, it was within 20 seconds (represented by diamonds), which is the 90% response time of the oxygen sensor defined by JIS.

(Example 3)
In the galvanic cell type oxygen sensor used in Example 1, when a gold foil was used for the positive electrode 4, the oxygen concentration was changed when the atmosphere gas was replaced with air having an oxygen concentration of 9.24% from air (oxygen concentration of 21%). The response time until 18% was detected was examined. As a result, as shown in FIG. 5, it was found that it was faster than 5 seconds (indicated by diamonds), which is the response time when the concentration of the oxygen sensor determined by JIS was reduced to 18%.

Example 4
In the galvanic cell type oxygen sensor used in Example 1, in the case where a gold foil, a silver foil, a platinum foil, and a copper foil were used for the positive electrode 4, the atmosphere gas was air (oxygen concentration 21 %) To a nitrogen gas mixed with an oxygen concentration of 3.5% and a carbon dioxide concentration of 10%, and further to air (oxygen concentration 21%), the response and recovery curves are shown. As a result, as shown in FIG. 6, it was found that even if any metal foil was used, the initial sensor output value was recovered.

(Example 5)
In the galvanic cell type oxygen sensor used in Example 1, the time-dependent change of the output value with respect to air (21% oxygen concentration) was examined in the case where a gold foil, a silver foil, a platinum foil, and a copper foil were used for the positive electrode 4, respectively. As a result, as shown in FIG. 7, it was found that a relatively stable output was maintained in each case, and more stable output was maintained particularly when a gold foil and a platinum foil were used.

[Another embodiment]
In the above embodiment, the separator 5 and the pressing member 6 are provided between the positive electrode 4 and the negative electrode 7, but as shown in FIG. 8, a water absorbing material 12 such as a sponge is used instead of the separator 5 and the pressing member 6. It is good also as providing. Moreover, in this embodiment, with the use of the water absorbing material 12, the shape of the negative electrode 7 is provided in a disc shape so as to be fixed by the lid portion 1b.
In this case, it is possible to save the trouble of injecting the electrolytic solution 10 later by arranging the electrolytic solution holding material 12 containing the electrolytic solution 10 in advance. For this reason, the injection port 1d of the lid portion 1b and the enclosing ball 11 are not required, and the configuration can be simplified. Other configurations are the same as those in the above embodiment.
Moreover, the water absorbing material 12 is not limited to a sponge, and any material having water absorbing performance can be applied, and a nonwoven fabric or the like can be applied.
In addition, in this embodiment, although the case where the water absorbing material 12 was comprised from one member was shown as an example, you may provide two or more water absorbing materials 12 in piles.

  The galvanic cell type oxygen sensor according to the present invention can be applied to conventional gas sensors, gas alarms, gas measuring devices and the like.

Schematic of galvanic cell type oxygen sensor according to this embodiment Photo showing the state of the surface of the metal foil The graph which shows the linearity of the galvanic-cell-type oxygen sensor which concerns on this embodiment Graph showing 90% response time for nitrogen gas Graph showing response time for oxygen concentration 18% Graph showing coherence to carbon dioxide gas Graph showing change with time of output value for air (21% oxygen concentration) Schematic of galvanic cell type oxygen sensor according to another embodiment

DESCRIPTION OF SYMBOLS 1 Container 3 Oxygen permeable film 4 Positive electrode 7 Negative electrode 8 Current collector 10 Electrolyte

Claims (4)

A galvanic cell type comprising a positive electrode containing a metal, a negative electrode, and an electrolyte solution in contact with the positive electrode and the negative electrode, and an oxygen permeable film that does not transmit the electrolyte solution is provided on one surface of the positive electrode. An oxygen sensor,
The galvanic cell type oxygen sensor, wherein the positive electrode is a metal foil and has a communication hole through which the electrolytic solution can pass, and is provided so as to be able to react with oxygen on the one surface side. The galvanic cell type oxygen sensor according to claim 1, wherein the oxygen permeable membrane is subjected to a hydrophilic treatment on a surface on which the positive electrode is superimposed. The container includes a metal container body and a metal lid part insulated from the container body, wherein the positive electrode is connected to the container body, and the negative electrode is connected to the lid part. 3. A galvanic cell type oxygen sensor according to 1 or 2 . The positive electrode has an inner surface abutment portion abutting of the container body, said superimposed on the other surface of the positive electrode through a current collector provided according to claim 3 which is connected to the container body Galvanic cell oxygen sensor.