Electrochemical oxygen sensor

Abstract

To provide an electrochemical oxygen sensor which can maintain an excellent resistance to vibrations for a long period of time.SOLUTION: The electrochemical oxygen sensor is formed by storing an electric solution including a positive electrode, a negative electrode, and an electrolyte, in an exterior body. The electrochemical oxygen sensor has a separator between the positive electrode and the negative electrode. The separator has a hole which penetrates one surface from another surface and has an opening diameter of at least 0.5 mm. The separator does not have a hole of which opening diameter is larger than 7 mm.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electrochemical oxygen sensor capable of maintaining good vibration resistance for a long period of time. [Background technology]

[0002] Electrochemical oxygen sensors (hereafter referred to as oxygen sensors) have the advantages of being inexpensive, easy to use, and capable of operating at room temperature, and therefore are used in a wide range of applications, such as checking for oxygen deficiencies inside ship holds and manholes, and detecting oxygen concentrations in medical equipment such as anesthesia machines and artificial ventilators.

[0003] In such electrochemical oxygen sensors, the internal pressure of the sensor may fluctuate due to the moisture in the electrolyte evaporating and dissipating outside the cell, or moisture in the air being absorbed into the electrolyte, which may cause problems. In Patent Document 1, a space is provided in the container constituting the galvanic cell oxygen sensor to solve the problem of the internal pressure fluctuation. Patent Document 1 points out that providing a space in the container causes air to be present near the positive electrode, which may result in an extreme drop in output due to the electrolyte not being supplied to the positive electrode. In the technology described in Patent Document 1, a porous or cotton-like body made of cellulose, synthetic polymer fiber, or glass fiber is placed in the space, and the electrolyte can be supplied to the positive electrode by the capillary phenomenon of the porous or cotton-like body, and the porous or cotton-like body can suppress the air bubbles from reaching the positive electrode, thereby solving the above problem.

[0004] Furthermore, Patent Document 2 describes that the decrease in output stability caused by air bubbles generated when an electrochemical oxygen sensor is subjected to an impact or the like can be suppressed by capturing the air bubbles in a porous body provided in the side region of the negative electrode. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 61-40557 [Patent Document 2] JP 2017-187279 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the inventors' investigations have revealed that in an electrochemical oxygen sensor, when a partition such as a separator having a small pore size between the positive and negative electrodes is provided, the ion conductivity of the partition decreases, the output voltage decreases, and the life of the sensor is shortened, for reasons that are unclear, when the sensor is used or stored for a long period of time, as shown in Patent Documents 1 and 2. On the other hand, it has been revealed that when the partition is not provided, air bubbles are formed in the sensor container after a long period of time has passed since manufacture, and when mechanical vibration or impact is applied to the sensor from the outside, the output voltage fluctuates significantly.

[0007] Therefore, it is necessary for electrochemical oxygen sensors to have characteristics that ensure that a certain level of output voltage can be obtained even long after a period of time has passed since manufacture, and that stable measurement results can be obtained even when mechanical vibrations or shocks are applied from the outside.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electrochemical oxygen sensor capable of maintaining good vibration resistance for a long period of time. [Means for solving the problem]

[0009] The electrochemical oxygen sensor of the present invention (hereinafter sometimes simply referred to as "oxygen sensor") comprises a positive electrode, a negative electrode, and an electrolyte solution composed of an aqueous solution containing an electrolyte, housed within an exterior body, and has a separator between the positive electrode and the negative electrode, the separator having at least one hole penetrating from one side to the other with an opening diameter of 0.5 mm or more, and having no holes with an opening diameter larger than 7 mm. Effect of the Invention

[0010] According to the present invention, it is possible to provide an electrochemical oxygen sensor capable of maintaining good vibration resistance for a long period of time. [Brief description of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view showing a schematic diagram of an example of an electrochemical oxygen sensor according to the present invention. [Diagram 2] 1 is a diagram illustrating a state of a conventional electrochemical oxygen sensor after a long period of time has passed since its manufacture. [Diagram 3] FIG. 2 is a cross-sectional view showing a schematic diagram of another example of an electrochemical oxygen sensor according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] A cross-sectional view showing a schematic example of an electrochemical oxygen sensor of the present invention is shown in Fig. 1. The electrochemical oxygen sensor 1a shown in Fig. 1 is an example of a galvanic cell type oxygen sensor, which is one embodiment of the electrochemical oxygen sensor of the present invention.

[0013] 1 has a positive electrode 50, a negative electrode 80, and an electrolyte 90 in a bottomed cylindrical container 20. The container 20 is composed of a container body 21 that holds the electrolyte 90 therein, and a sealing lid 10 for fixing a protective film 40, a diaphragm 60, and the positive electrode 50 to the opening of the container body 21. The sealing lid 10 is composed of a first sealing lid (inner lid) 11 and a second sealing lid (outer lid) 12 for fixing the first sealing lid 11, and has an air vent 120 for taking in oxygen into the oxygen sensor 1, and is attached to the container body 21 via an O-ring 30.

[0014] Inside the container body 21 that contains the electrolyte 90, the negative electrode 80 is disposed in a state of being immersed in the electrolyte 90, and the negative electrode 80 is formed with a lead portion 81. The positive electrode 50 is configured by laminating a catalyst layer (catalytic electrode) 51 and a positive electrode current collector 52, and a lead wire 53 is attached to the positive electrode current collector 52. A perforation 70 is provided in the lower portion of the container body 21 that holds the electrolyte 90 in the container 20, for passing the lead wire 53 attached to the positive electrode current collector 52. Although not shown in FIG. 1, a perforation for supplying the electrolyte to the positive electrode 50 is also provided in the lower portion of the container body 21 in addition to the perforation 70.

[0015] A compensation resistor 100 and a temperature compensation thermistor 110 are connected in series between the lead portion 81 of the negative electrode 80 and the lead wire 53 attached to the positive electrode current collector 52, and are housed inside the container body 21. A negative electrode terminal 82 is connected to the lead portion 81 of the negative electrode 80, and a positive electrode terminal 54 is connected to the lead wire 53 attached to the positive electrode current collector 52, and each is led out to the outside of the container body 21.

[0016] A diaphragm 60 that selectively allows oxygen to pass through and limits the amount of oxygen passing therethrough to match the battery reaction is disposed on the outer surface side of the positive electrode 50, and oxygen from a vent hole 120 provided in the sealing lid 10 is introduced into the positive electrode 50 through the diaphragm 60. In addition, a protective film 40 that prevents dirt, dust, water, and the like from adhering to the diaphragm 60 is disposed on the outer surface side of the diaphragm 60 and is fixed by a first sealing lid 11.

[0017] That is, the first sealing lid 11 functions as a pressing end plate for the protective film 40, the diaphragm 60, and the positive electrode 50. In the oxygen sensor 1a shown in Fig. 1, a threaded portion is formed on the inner periphery of the second sealing lid 12 so as to screw into a threaded portion formed on the outer periphery of the opening of the container body 21. Then, by screwing the sealing lid 10, the first sealing lid 11 is pressed against the container body 21 via the O-ring 30, so that the protective film 40, the diaphragm 60, and the positive electrode 50 can be fixed to the container body 21 while maintaining airtightness and liquid tightness.

[0018] In addition, a separator 130 is disposed between the positive electrode 50 and the negative electrode 60. The separator 130 has one hole (hereinafter referred to as a "through hole") 131 penetrating from one surface (e.g., the upper surface in the figure) to the other surface (e.g., the lower surface in the figure). Note that in FIG. 1, since a cross section of the oxygen sensor 1a is shown, the separator 130 is depicted as being divided into two with the through hole 131 in between, but in reality, the separator 130 has one through hole 131 in one sheet.

[0019] As mentioned above, when an oxygen sensor is used for a long time after manufacture, if the sensor is subjected to external mechanical vibrations or shocks, the output voltage will fluctuate significantly. The reasons for this are presumed to be as follows.

[0020] Fig. 2 is a diagram illustrating the state of a conventional electrochemical oxygen sensor after a long period of time has passed since its manufacture. The oxygen sensor 2 is shown upside down compared to the oxygen sensor 1a shown in Fig. 1, assuming that it will be used under conditions of large vibration.

[0021] In the oxygen sensor 2, the diaphragm 60 for introducing oxygen into the positive electrode 50 is permeable to gases such as water vapor and air, so that the water, which is the solvent of the electrolyte 90, gradually evaporates and dissipates to the outside of the oxygen sensor 2 through the ventilation hole 120, and accordingly, air enters the inside of the container body 21 of the oxygen sensor 2, which contains the electrolyte 90. The air that enters the inside of the container body 21 initially forms small bubbles in the electrolyte 90, but as the amount of air that has entered increases, the small bubbles gather together when the oxygen sensor 2 vibrates, forming large bubbles 200 as shown by the dotted line in the figure. When the oxygen sensor 2 is placed under a condition in which the positive electrode 50 is located at the top, the bubbles 200 are located at the top of the electrolyte 90 as shown in FIG. 2. When the oxygen sensor 2 vibrates in this state, some of the bubbles 200 come into contact with the positive electrode 50, generating a voltage different from the output voltage corresponding to the original oxygen concentration, and the output voltage of the oxygen sensor 2 fluctuates greatly.

[0022] When not much time has passed since the manufacture of the oxygen sensor 2, the amount of air that has entered the container body is small and large bubbles are not formed, so even if the oxygen sensor is placed in the state shown in Fig. 2 and vibration is applied, the air bubbles generated inside the container body 21 will not come into contact with the positive electrode and cause fluctuations in the output voltage. Therefore, even if an oxygen sensor has a stable output voltage even when subjected to vibration or impact when it is manufactured not long ago, it is thought that when it is manufactured a long time ago, the output voltage may fluctuate greatly when subjected to vibration or impact.

[0023] Therefore, in the electrochemical oxygen sensor of the present invention, as shown in Fig. 1, a separator having at least one hole with an opening diameter of 0.5 mm or more and no holes with an opening diameter larger than 7 mm is disposed between the positive electrode and the negative electrode. According to the present invention, the action of the holes with an opening diameter of 0.5 mm or more formed in the separator does not hinder the flow of the electrolyte even after a long time has passed since manufacture, and it is possible to prevent a decrease in output voltage due to the placement of the separator. On the other hand, since the opening diameter of the holes formed in the separator is limited to 7 mm or less, even if bubbles are generated inside the container body, they are difficult to pass through the holes, and it is possible to suppress the bubbles from moving and gathering near the positive electrode, so that it is possible to prevent fluctuations in output voltage due to contact between the positive electrode and large bubbles, and therefore the excellent vibration resistance of the electrochemical oxygen sensor can be maintained for a long period of time.

[0024] 1 and 3, the lead wire 53 may be inserted into the separator 130 and passed through the separator 130, or a hole for the lead wire 53 may be provided in the separator 130 and the lead wire 53 may be passed through the hole. When a hole for the lead wire 53 is provided in the separator 130, the opening diameter may be 0.5 mm or more, or may be less than 0.5 mm, but is 7 mm or less.

[0025] For the separator of the oxygen sensor, the above-mentioned through holes may be formed in a porous film that is usually used in primary or secondary batteries. For the porous film, polyvinyl alcohol nonwoven fabric, nonwoven fabric mainly made of vinylon and rayon, vinylon-rayon nonwoven fabric (vinylon-rayon mixed paper), polyamide nonwoven fabric, polyolefin-rayon nonwoven fabric, vinylon paper, vinylon-linter pulp paper, vinylon-mercerized pulp paper, etc. may be used. In addition, a hydrophilically treated microporous polyolefin film (microporous polyethylene film, microporous polypropylene film, etc.) may be used. For the separator, a film made of the same material as the above-mentioned nonwoven fabric, paper, or microporous film (a film having no microscopic holes other than the through holes described later), a resin plate, glass, ceramics, metal, etc. may also be used.

[0026] The separator has at least one through hole, which may be formed perpendicular to the surface of the separator (the upper and lower surfaces in the figure) as shown in FIG. 1, or may be formed diagonally in the cross section as shown in FIG. 1, or may be bent inside the separator.

[0027] From the viewpoint of effectively preventing air bubbles from migrating and gathering near the positive electrode, the through-holes in the separator have an opening diameter of 7 mm or less, and preferably 4 mm or less. Also, from the viewpoint of effectively allowing the electrolyte to flow from one side of the separator to the other side through the through-holes and maintaining favorable output characteristics of the oxygen sensor, the opening diameter of the through-holes is 0.5 mm or more, and preferably 1 mm or more.

[0028] Since various shapes are possible for the through hole, in the present invention, the opening diameter is defined as the diameter of the largest sphere among the spheres that can pass through the hole.

[0029] The separator may have one through hole, but may have multiple (2, 3, 4, etc.) through holes from the viewpoint of improving the fluidity of the electrolyte. However, if the number of through holes is too large, the strength of the separator may be reduced, and the effect of the separator in maintaining the vibration resistance of the oxygen sensor for a long period of time may be reduced. Therefore, in a separator having multiple through holes, the number of through holes may be adjusted so that the total opening area of ​​the multiple through holes is 50% or less of the area of ​​the separator in a plan view.

[0030] The thickness of the separator is not particularly limited, but is preferably, for example, 0.1 mm or more.

[0031] The shape of the separator is not particularly limited. Fig. 3 shows a cross-sectional view that typically illustrates another example of the electrochemical oxygen sensor of the present invention. As in the oxygen sensor 1b of Fig. 3, by disposing the through-hole 131 on the negative electrode 80 side, compared to the flat separator of the oxygen sensor 1a shown in Fig. 1, when the oxygen sensor 1b is disposed so that the positive electrode 50 is located at the bottom, air bubbles tend to move from the positive electrode 50 side to the negative electrode 80 side. However, when the oxygen sensor 1b is disposed so that the positive electrode 50 is located at the top, the movement of air bubbles from the negative electrode 80 side to the positive electrode 50 side is prevented, which is preferable.

[0032] The electrolyte used in the oxygen sensor is an aqueous solution containing an electrolyte, but the electrolyte to be contained is not particularly limited, and various acids (organic acids and inorganic acids), alkalis, and their salts can be used.Specific examples of the electrolyte include acidic aqueous solutions containing carboxylic acids or their salts, such as an aqueous solution containing acetic acid, potassium acetate, and lead acetate, and an aqueous solution containing citric acid and citrates (such as alkali metal salts); alkaline aqueous solutions such as an aqueous solution of sodium hydroxide and an aqueous solution of potassium hydroxide; and weakly alkaline aqueous solutions containing cesium carbonate and cesium hydrogen carbonate.

[0033] Furthermore, the aqueous solution constituting the electrolytic solution may contain various organic acids, inorganic acids, or alkalis as necessary for the purpose of adjusting the pH.

[0034] From the viewpoint of extending the life of the oxygen sensor, it is preferable to use an aqueous solution containing a chelating agent as the electrolyte, and the electrolyte may be the chelating agent. It is presumed that the chelating agent has an effect of chelating the constituent metals of the negative electrode and dissolving them in the electrolyte (hereinafter referred to as "chelating effect"), which is believed to contribute to extending the life of the oxygen sensor.

[0035] The term "chelating agent" as used herein refers to a molecule (including ions) having multiple coordination sites (coordinating atoms) that form coordinate bonds with metal ions, and stabilizes the metal ions by forming a complex (complexation) with the metal ions, and can be contained in the electrolyte in the form of an acid or its salt that generates the molecule in the solvent that constitutes the electrolyte. Therefore, those with a single coordination site (coordinating atom), such as phosphoric acid, acetic acid, carbonic acid, and their salts, which have weak complexing power, are not included in the "chelating agent" as used herein.

[0036] Chelating agents generally have a chelating effect as well as a pH buffering ability (the ability to maintain the pH of a solution approximately constant even when a small amount of acid or base is added). Specific examples include succinic acid, fumaric acid, maleic acid, citric acid, tartaric acid, glutaric acid, adipic acid, malic acid, malonic acid, aspartic acid, glutamic acid, and salts thereof, and one or more of these may be used.

[0037] It is more preferable to use a chelating agent that has high solubility in water from the viewpoint of enhancing the chelating action, specifically, citric acid, tartaric acid, glutamic acid and its salts. Among these, citric acid and its salts have high solubility in water [citric acid: 73 g / 100 ml (25° C.), trisodium citrate: 71 g / 100 ml (25° C.), tripotassium citrate: 167 g / 100 ml (25° C.)], and since citric acid has a large number of dissociable hydrogen atoms and has multiple pH values ​​at which it exerts its pH buffering ability (pKa1=3.13, pKa2=4.75, pKa3=6.40), it is more preferable to use citric acid. Therefore, when citric acid is used as a chelating agent, it has high solubility in water and high pH buffering ability, which further improves the life of the oxygen sensor.

[0038] In order to prevent corrosion of the negative electrode material, the pH of the electrolyte is preferably 3 or more, and more preferably 4 or more. On the other hand, in order to prevent carbon dioxide from dissolving in the electrolyte and causing a deterioration in the characteristics, the pH of the electrolyte is preferably 9 or less, and more preferably 8 or less.

[0039] The concentration of the chelating agent in the electrolyte is, for example, preferably 2.3 mol / L or more, more preferably 2.5 mol / L or more, and particularly preferably 2.7 mol / L or more.

[0040] In addition, when the metal from the negative electrode dissolved in the electrolyte reaches a saturation concentration, an oxide of the metal is generated, which may cause the negative electrode to become inactive, thereby impairing the life of the oxygen sensor, and even if a chelating agent is added to the electrolyte, the effect of extending the life of the oxygen sensor may be limited. In this case, it is preferable to further add ammonia to the electrolyte to increase the molar concentration of the chelating agent in the electrolyte, which delays the metal from the negative electrode dissolved in the electrolyte from reaching saturation, thereby making it possible to further extend the life of the oxygen sensor.

[0041] The concentration of ammonia in the electrolyte is set to 0.01 mol / L or more in order to facilitate the above-mentioned action of ammonia, and is preferably set to 0.1 mol / L or more in order to further enhance the above-mentioned action, and more preferably set to 1 mol / L or more. Although there is no particular upper limit for the concentration of ammonia in the electrolyte, since ammonia is a compound specified in Appendix 2 of the Poisonous and Deleterious Substances Control Law of Japan, from the viewpoint of safety, the concentration of ammonia in the electrolyte is preferably less than 10 mass%.

[0042] The positive electrode of the oxygen sensor is, for example, one that is made up of a catalytic electrode and a positive electrode current collector, as shown in Fig. 1. The material of the catalytic electrode is not particularly limited as long as it can generate a current by electrochemically reducing oxygen on the positive electrode, but metal elements such as gold (Au), silver (Ag), platinum (Pt), titanium (Ti), and alloys thereof are preferably used. The catalytic electrode may be made up of a single material, or may be a laminate of different materials or a functionally gradient material whose composition changes in the thickness direction.

[0043] The negative electrode of the oxygen sensor is not particularly limited, but can be formed of, for example, lead (Pb), zinc (Zn), antimony (Sb), tin (Sn), or an alloy of these.

[0044] Examples of Sn alloys include Sn-Ag alloys, Sn-Cu alloys, Sn-Ag-Cu alloys, and Sn-Sb alloys from the viewpoint of corrosion resistance, but they may also be alloys containing metal elements such as Al, Bi, Fe, Mg, Na, Zn, Ca, Ge, In, Ni, and Co.

[0045] As shown in Figs. 1 and 3, it is preferable to dispose a diaphragm on the outer surface of the positive electrode of the oxygen sensor to control the intrusion of oxygen so that too much oxygen does not reach the catalytic electrode. The diaphragm is preferably one that selectively allows oxygen to pass through and can limit the amount of oxygen gas that passes through. There are no particular restrictions on the material or thickness of the diaphragm, but typically, fluororesins such as polytetrafluoroethylene and tetrafluoroethylene-hexafluoropropylene copolymers; polyolefins such as polyethylene; and the like are used. As the diaphragm, a porous membrane, a non-porous membrane, or even a membrane having holes in which capillaries are formed, called a capillary type, can be used.

[0046] Furthermore, in order to protect the diaphragm, it is preferable to place a protective film made of a porous resin film on the diaphragm as shown in Figures 1 and 3. There are no particular limitations on the material or thickness of the protective film as long as it can prevent the adhesion of dirt, dust, water, etc. to the diaphragm and has the function of allowing air (including oxygen) to pass through, but typically a fluororesin such as polytetrafluoroethylene is used.

[0047] The container body 21 of the oxygen sensors 1a and 1b can be made of, for example, acrylonitrile-butadiene-styrene (ABS) resin. The sealing lid 10 (first sealing lid 11 and second sealing lid 12) placed at the opening of the container body 21 can be made of, for example, ABS resin, polypropylene, polycarbonate, fluororesin, or the like.

[0048] Furthermore, the O-ring 30 interposed between the container body 21 of the container 20 and the sealing lid 10 (first sealing lid 11) is pressed and deformed by screwing the container body 21 and the second sealing lid 12 together, thereby maintaining the airtightness and liquid-tightness of the oxygen sensors 1a, 1b. There are no particular restrictions on the material of the O-ring, but typically nitrile rubber, silicone rubber, ethylene propylene rubber, fluororesin, etc. are used.

[0049] So far, the present invention has been described using a galvanic cell type oxygen sensor as an example of one embodiment of the electrochemical oxygen sensor of the present invention, but the electrochemical oxygen sensor of the present invention is not limited to the above embodiment and can be modified in various ways within the scope of the technical concept. Also, the oxygen sensor shown in Figure 1 can be modified in various ways as long as it has the function of an oxygen sensor and the above-mentioned oxygen supply path.

[0050] The electrochemical oxygen sensor of the present invention can also be in the form of a constant-potential oxygen sensor. A constant-potential oxygen sensor is a sensor in which a constant voltage is applied between the positive and negative electrodes, and the applied voltage is set according to the electrochemical characteristics of each electrode and the type of gas to be detected. In a constant-potential oxygen sensor, when an appropriate constant voltage is applied between the positive and negative electrodes, the current flowing between them and the oxygen gas concentration are proportional to each other. Therefore, if the current is converted into a voltage, the oxygen gas concentration of an unknown gas can be detected by measuring the voltage, just like a galvanic cell oxygen sensor.

[0051] The electrochemical oxygen sensor of the present invention can be used for the same applications as conventionally known electrochemical oxygen sensors, but because it has good vibration resistance, it is particularly useful for applications in which measurements are made under vibrating conditions. EXAMPLES

[0052] The present invention will be described in detail below with reference to examples, although the present invention is not limited to the following examples.

[0053] Example 1 <Preparation of electrolyte> An electrolyte solution was prepared by dissolving citric acid, tripotassium citrate, and ammonia in water. The molar concentrations in the aqueous solution were citric acid: 2.5 mol / L, tripotassium citrate: 0.5 mol / L, and ammonia: 3.0 mol / L. The pH of this aqueous solution was 4.30 at 25°C.

[0054] <Assembling the oxygen sensor> 5.4 g of the electrolyte was poured into the inside of the container body 21 made of ABS resin, and a galvanic cell type oxygen sensor having the configuration shown in Fig. 1 was assembled. The sealing lid 10 (first sealing lid 11 and second sealing lid 12) was also made of ABS resin, like the container body 21. In addition, a porous polytetrafluoroethylene sheet was used for the protective film 40, and a tetrafluoroethylene-hexafluoropropylene copolymer film was used for the diaphragm 60.

[0055] The catalyst layer (catalytic electrode) 51 of the positive electrode 50 was made of gold, and the positive electrode current collector 52 and the lead wire 53 were made of titanium, and the positive electrode current collector 52 and the lead wire 53 were integrated by welding. The negative electrode 80 was made of a Sn-Sb alloy (Sb content: 5% by mass).

[0056] The separator is 1 mm thick and has a planar area of ​​255 mm 2 The polyvinyl alcohol nonwoven fabric was used, which had one through-hole with an opening diameter of 3 mm (the opening shape was a circle with a diameter of 3 mm). As shown in FIG. 1, the positive electrode lead wire 53 was inserted through a part of the separator 130, and the separator 130 was placed between the positive electrode 50 and the negative electrode 80.

[0057] In addition, a compensation resistor 100 and a temperature compensation thermistor 110 are connected in series between the positive electrode lead wire 53 and the negative electrode lead portion 81, and further, a positive electrode terminal 54 and a negative electrode terminal 82 are led out from the positive electrode lead wire 53 and the negative electrode lead portion 81, respectively, to the outside of the container body 21, thereby making it possible to detect the oxygen concentration from the output voltage.

[0058] Example 2 A galvanic cell type oxygen sensor was produced in the same manner as in Example 1, except that the opening diameter of the through-hole formed in the separator was changed to 5 mm (the shape of the opening was a circle with a diameter of 5 mm).

[0059] Comparative Example 1 A galvanic cell type oxygen sensor was produced in the same manner as in Example 1, except that no separator was used.

[0060] Comparative Example 2 A galvanic cell type oxygen sensor was produced in the same manner as in Example 1, except that the opening diameter of the through-hole formed in the separator was changed to 8 mm (the shape of the opening was a circle with a diameter of 8 mm).

[0061] Comparative Example 3 A galvanic cell type oxygen sensor was produced in the same manner as in Example 1, except that the polyvinyl alcohol nonwoven fabric was not formed with through holes and was used as it is as a separator.

[0062] For each of the oxygen sensors of Examples 1 and 2 and Comparative Examples 1 to 3, an accelerated test was conducted in which 100% oxygen gas was passed through an atmosphere at a temperature of 40° C. to accelerate the electrochemical reaction. At 40° C., the electrochemical reaction proceeds at about twice the speed at room temperature. Furthermore, when 100% oxygen gas is passed through, the electrochemical reaction proceeds at about five times the speed in the atmosphere. Therefore, when 100% oxygen gas is passed through at a temperature of 40° C., the oxygen sensor can undergo aging at a speed about ten times faster than when the sensor is left in the atmosphere at room temperature.

[0063] In this test, the oxygen sensors were evaluated as follows at each of the elapsed times (converted value) at room temperature, calculated by multiplying the retention time of each oxygen sensor at 40°C by 10, from 0 years (at the start of the test) to 7 years.

[0064] [Vibration resistance evaluation] A vibration test was conducted in which the oxygen sensor was rotated 270 degrees vertically per second in the air at room temperature, and this was repeated 10 times. The change in output voltage during this time was measured, and vibration resistance was evaluated from the difference between the maximum and minimum voltage values ​​(fluctuation in output voltage). Those whose difference was within ±0.5 mV were deemed to have good vibration resistance. The results are shown in Table 1. In Table 1, cases in which vibration resistance was evaluated as good are indicated with "◯", and cases in which it was not evaluated as good are indicated with "X". Furthermore, for the oxygen sensor of Comparative Example 3, the output voltage had dropped so much after three years that it could no longer be measured, and so it was marked with "-".

[0065] [Table 1]

[0066] As shown in Table 1, the oxygen sensors of Examples 1 and 2, which used separators with appropriate opening areas, were able to suppress fluctuations in output voltage during the vibration test for a long period of time. In contrast, the oxygen sensor of Comparative Example 1, which did not use a separator, and the oxygen sensor of Comparative Example 2, which used a separator with too large an opening area, showed large fluctuations in output voltage during the vibration test relatively early on as the accelerated test progressed. [Explanation of symbols]

[0067] 1a, 1b, 2 Electrochemical oxygen sensor 10 Sealing lid 11 First sealing lid (inner lid) 12 Second sealing lid (outer lid) 20 containers 21 Container body 30 O-ring 40 Protective film 50 positive electrode 51 Positive electrode body (catalytic electrode) 52 Positive electrode current collector 53 Positive lead wire 54 Positive terminal 60 Diaphragm 70 Drilling holes for lead wires 80 negative electrode 81 Negative electrode lead 82 Negative terminal 90 Electrolyte 100 Compensation Resistor 110 Temperature compensation thermistor 120 Vent 130 Separator 131 Through hole

Claims

[Claim 1] An electrochemical oxygen sensor having a positive electrode, a negative electrode, and an electrolyte solution formed of an aqueous solution containing an electrolyte housed in an exterior body, A separator is provided between the positive electrode and the negative electrode, 13. An electrochemical oxygen sensor comprising: said separator having at least one hole penetrating from one surface to the other surface, the hole having an opening diameter of 0.5 mm or more, and no hole having an opening diameter of more than 7 mm.

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