JP7739044B2 - Liquid Detection Sensor - Google Patents

Description

The present invention relates to a liquid detection sensor equipped with a metal-air battery, and in particular to a liquid detection sensor that has excellent power generation performance and excellent long-term storage properties.

Liquid detection sensors are sometimes used in buildings, underground facilities, factories, medical facilities, etc. to detect leaks and flooding. Liquid detection sensors are placed in locations where leaks and flooding must be prevented. Liquid detection sensors detect leaks by detecting electrical changes that occur when external liquid comes into contact with the battery contained within the liquid detection sensor.

One example of a liquid detection sensor is a liquid detection sensor for use in medical settings that is equipped with a water cell that generates electricity from leaked liquid (Patent Document 1). In the liquid detection sensor in Patent Document 1, the water cell is fixed to an absorbent member with adhesive fixing tape, and when liquid such as blood or intravenous fluid that has been absorbed and dispersed into the absorbent member comes into contact with the entire water cell, the water cell generates electricity and detects liquid leakage.

Another example of a liquid detection sensor is a liquid detection sensor for use in medical settings that includes a liquid leakage sensor unit made of a magnesium battery (Patent Document 2). In the liquid detection sensor of Patent Document 2, the magnesium battery is made up of a positive electrode sheet, a catalyst sheet, a sheet-like separator, and a negative electrode sheet stacked in that order, and is equipped with a transmitter that is electrically connected to the liquid leakage sensor unit and transmits a detection signal using power from the magnesium battery, a receiver that receives the detection signal transmitted from the transmitter, and a receiving terminal that has alarm means for issuing an alarm about a liquid leakage state based on the detection signal from the receiver. The liquid leakage sensor unit detects, as a liquid leakage state, a state in which the magnesium battery generates electricity using blood or injection fluid leaking from the syringe needle as the electrolyte.

Liquid detection sensors need to detect liquid leaks with high accuracy, but the liquid detection sensors in Patent Documents 1 and 2, in which the detection target, such as blood, functions as an electrolyte, are not specifically proposed for use in detecting liquids other than blood in medical settings, and are therefore not very versatile.

However, detecting liquid leaks and flooding is required not only in medical settings, but also in a wide range of other fields, such as buildings, underground facilities, factories, and flood control sites, and liquid detection sensors are often required to be versatile, capable of detecting water, oil, etc. However, as mentioned above, the liquid detection sensors in Patent Documents 1 and 2 suffer from a lack of versatility.

Furthermore, in order to make liquid detection sensors more versatile, when using liquid detection sensors to monitor for leaks in buildings, underground facilities, factories, etc., or for flooding around rivers, etc., it can be more convenient for monitors to monitor from a location away from the site of the leak or flooding. In order for the liquid detection sensor to reliably transmit an alarm to a location away from the site of the leak or flooding, it is necessary to improve the power generation performance of the battery installed in the liquid detection sensor.

When a metal-air battery is used as the power source for a liquid detection sensor, the power generation performance of the metal-air battery can be improved by using an alkali metal salt such as sodium chloride or potassium chloride as the electrolyte. For example, if an alkali metal salt is pre-impregnated into the separator placed between the positive and negative electrodes of the metal-air battery, when the separator containing the alkali metal salt comes into contact with water, the liquid to be detected, the action of the water containing the alkali metal salt improves ionic conductivity between the positive and negative electrodes, allowing the metal-air battery to demonstrate excellent power generation performance.

However, if a liquid detection sensor is left installed for a long period of time while the separator contains alkali metal salts, the alkali metal salts in the separator may absorb moisture and liquefy, causing deterioration of the metal-air battery's negative electrode. If the metal-air battery's negative electrode deteriorates while the liquid detection sensor is installed for a long period of time, it will be unable to accurately detect leaks or flooding, and the metal-air battery will not be able to demonstrate its excellent power generation performance.

International Publication No. 2012/020507 JP 2017-148332 A

In light of the above circumstances, the present invention aims to provide a versatile liquid detection sensor that can prevent deterioration of the metal-air battery that serves as its power source even after long-term installation, and that enables the metal-air battery to demonstrate excellent power generation performance.

The gist of the configuration of the present invention is as follows.
[1] A metal-air battery including a positive electrode, a negative electrode having a first portion facing the positive electrode, and an electrolyte component disposed opposite a second portion of the negative electrode different from the first portion,
The liquid detection sensor has the electrolyte constituent components sealed inside a resin bag, and the resin of the resin bag has solubility or dispersibility in the liquid to be detected.
[2] A liquid detection sensor as described in [1], wherein the second portion of the resin bag in which the electrolyte constituent components are sealed is arranged opposite to the first portion and has an area opposite to the first portion.
[3] A liquid detection sensor according to [1] or [2], further comprising a support member between the positive electrode and the first portion, which supports the positive electrode and the first portion at a predetermined distance, and the support member having an extension portion extending from the first portion to the position of the resin bag opposite the second portion in which the components of the electrolyte solution are sealed.
[4] A liquid detection sensor as described in [3], wherein an extension portion of the support member is arranged between the resin bag in which the electrolyte constituent components are sealed and the second portion.
[5] A liquid detection sensor as described in [3], wherein the resin bag containing the electrolyte constituents is disposed between the extension portion of the support member and the second portion.
[6] The liquid detection sensor according to any one of [1] to [5], wherein the resin of the resin bag is a water-soluble resin or an oil-soluble resin.
[7] The liquid detection sensor according to any one of [1] to [6], wherein the resin bag in which the electrolyte constituents are sealed is one or more.
[8] The liquid detection sensor according to any one of [1] to [7], wherein the electrolyte component includes water, an alkali metal salt, or an aqueous solution of an alkali metal salt.
[9] The liquid detection sensor according to any one of [1] to [8], wherein the active material of the negative electrode contains at least one metal selected from the group consisting of magnesium (Mg), aluminum (Al), lithium (Li), calcium (Ca), and zinc (Zn).
[10] The liquid detection sensor according to any one of [1] to [9], which has an alarm unit that receives power from the metal-air battery and notifies of liquid detection.
[11] The liquid detection sensor according to any one of [1] to [9], which has an alarm unit capable of wirelessly transmitting a detection signal from the metal-air battery to a receiver unit.
[12] The liquid detection sensor according to any one of [1] to [11], which is a water detection sensor.
[13] The liquid detection sensor according to any one of [1] to [11], which is an oil detection sensor.

In the above aspect [1], when the liquid to be detected by the liquid detection sensor comes into contact with the resin bag of the metal-air battery, the resin of the resin bag dissolves or disperses in the liquid to be detected, causing the electrolyte components sealed inside the resin bag to be released into the negative electrode of the metal-air battery and between the positive and negative electrodes. The release of the electrolyte components into the negative electrode of the metal-air battery and between the positive and negative electrodes improves the power generation or power generation performance of the metal-air battery, and the liquid detection sensor notifies the outside world that the liquid to be detected has been detected as the metal-air battery generates electricity.

According to one aspect of the liquid detection sensor of the present invention, the electrolyte components of the metal-air battery, which serves as the power source, are sealed inside a resin bag that is soluble or dispersible in the liquid to be detected. By appropriately selecting the type of resin for the resin bag, the versatility of the detection target, such as detecting water or oil, is improved. Furthermore, according to another aspect of the liquid detection sensor of the present invention, the electrolyte components of the metal-air battery are sealed inside the resin bag, preventing the metal-air battery from deteriorating due to the electrolyte components, even when the liquid detection sensor is installed for a long period of time. Furthermore, according to another aspect of the liquid detection sensor of the present invention, the electrolyte components of the metal-air battery are sealed inside the resin bag, preventing deterioration of the metal-air battery while allowing the use of electrolyte components that impart excellent power generation performance to the metal-air battery. This allows the metal-air battery to demonstrate excellent power generation performance and reliably transmit an alarm to locations far from the site of a leak or flooding. Therefore, the liquid detection sensor of the present invention can reliably transmit an alarm to locations far from the site of a leak or flooding, improving convenience and versatility.

In this aspect of the liquid detection sensor of the present invention, a resin bag containing electrolyte components is positioned opposite a second portion of the negative electrode that is different from the first portion of the negative electrode facing the positive electrode. This prevents corrosion of the components that make up the metal-air battery, such as the positive and negative electrodes, due to leakage of the electrolyte components, even if the resin bag is damaged by the effects of atmospheric humidity or moisture.

Furthermore, according to an embodiment of the liquid detection sensor of the present invention, the second portion of the negative electrode, which is arranged opposite the resin bag containing the electrolyte components, has an area facing the first portion of the negative electrode facing the positive electrode. This more reliably prevents corrosion of the components that make up the metal-air battery, such as the positive and negative electrodes, due to leakage of the electrolyte components, even if the resin bag is damaged.

In this embodiment of the liquid detection sensor of the present invention, the resin in the resin bag is a water-soluble resin, allowing it to function as a water detection sensor that can more reliably detect the target substance, water. In this embodiment, the resin in the resin bag is an oil-soluble resin, allowing it to function as an oil detection sensor that can more reliably detect the target substance, oil.

In this embodiment of the liquid detection sensor of the present invention, the electrolyte components are enclosed in multiple resin bags, which allows the electrolyte components to be smoothly supplied throughout the metal-air battery, further improving the power generation efficiency of the metal-air battery.

1 is a side view illustrating an outline of a liquid detection sensor according to a first embodiment of the present invention. 1 is a side view illustrating a state in which the liquid detection sensor according to the first embodiment of the present invention detects a liquid. FIG. FIG. 10 is a side view illustrating an outline of a liquid detection sensor according to a second embodiment of the present invention. FIG. 10 is a side view illustrating a state when a liquid is detected by a liquid detection sensor according to a second embodiment of the present invention. FIG. 10 is a side view illustrating an outline of a liquid detection sensor according to a third embodiment of the present invention. FIG. 10 is a side view illustrating a state when a liquid is detected by a liquid detection sensor according to a third embodiment of the present invention. FIG. 10 is a side view illustrating an outline of a liquid detection sensor according to a fourth embodiment of the present invention. FIG. 10 is a side view illustrating a state when a liquid is detected by a liquid detection sensor according to a fourth embodiment of the present invention. 1 is an explanatory diagram of an example of a method of using the liquid detection sensor of the present invention.

The liquid detection sensor according to an embodiment of the present invention will be described in detail with reference to the drawings. First, the liquid detection sensor according to the first embodiment of the present invention will be described. Note that FIG. 1 is a side view illustrating an overview of the liquid detection sensor according to the first embodiment of the present invention, and FIG. 2 is a side view illustrating the state of the liquid detection sensor according to the first embodiment of the present invention when detecting liquid.

As shown in FIG. 1, the liquid detection sensor 1 according to the first embodiment of the present invention includes a metal-air battery 10 and an alarm unit 100 connected to the metal-air battery 10 via an electrical wire unit 101. The alarm unit 100 has the function of notifying the detection of liquid via an alarm means when it receives power generated by the metal-air battery 10 via the electrical wire unit 101.

The metal-air battery 10 includes a positive electrode 11, a negative electrode 12 facing the positive electrode 11, and a support member 13 located between the positive electrode 11 and the negative electrode 12. In the metal-air battery 10 of the liquid detection sensor 1, the positive electrode 11, the support member 13, and the negative electrode 12 are all sheet-shaped and have a laminate structure in which the positive electrode 11, the support member 13, and the negative electrode 12 are stacked in this order. The negative electrode 12 has a first region 41 facing the positive electrode 11 and a second region 42 different from the first region 41. In the metal-air battery 10, the second region 42 is an area facing the first region 41, with the first region 41 being the surface portion of the negative electrode 12 and the second region 42 being the back surface portion of the negative electrode 12. Therefore, the second portion 42 faces the positive electrode 11 via the first portion 41, and the second portion 42 is positioned farther away from the positive electrode 11 than the first portion 41.

The support member 13 is disposed between the positive electrode 11 and the first portion 41 of the negative electrode 12, and supports the positive electrode 11 and the negative electrode 12 with a predetermined distance between the first portion 41. The peripheral edge 14 of the support member 13 extends outward beyond the positive electrode 11 and the negative electrode 12 and is exposed from the positive electrode 11 and the negative electrode 12. The support member 13 acts as a separator and supports the positive electrode 11 and the negative electrode 12 with a predetermined distance between them to prevent short circuits caused by contact between the positive electrode 11 and the negative electrode 12. The support member 13 also has an extension portion 15 that extends to cover the second portion 42 of the negative electrode 12. Therefore, the negative electrode 12 and the extension portion 15 of the support member 13 form a laminated structure on the side of the second portion 42 of the negative electrode 12.

In the metal-air battery 10 of the liquid detection sensor 1, the electrolyte constituent component 20 is disposed opposite the second portion 42 of the negative electrode 12. That is, the electrolyte constituent component 20 is disposed independently of the positive electrode 11, the negative electrode 12, and the support member 13. In the metal-air battery 10 of the liquid detection sensor 1, the extension portion 15 of the support member 13 is disposed between the electrolyte constituent component 20 and the second portion 42. The electrolyte constituent component 20 is a component that constitutes the electrolyte of the metal-air battery 10 or the electrolyte of the metal-air battery 10. The metal-air battery 10 begins self-power generation when the positive electrode 11 and the negative electrode 12 come into contact with the electrolyte.

As shown in FIG. 1, the electrolyte solution constituents 20 are sealed inside a resin bag 21. Therefore, the electrolyte solution constituents 20 are not in contact with any of the positive electrode 11, support member 13, and negative electrode 12. The resin bag 21 may be, for example, a thin film bag-shaped member, a film bag-shaped member, or a capsule-shaped member such as a microcapsule. The resin bag 21 encapsulates the electrolyte solution constituents 20 and seals and packages a certain amount of the electrolyte solution constituents 20. Therefore, the resin bag 21 functions as a shell.

As described above, the second region 42 of the negative electrode 12 faces the first region 41, and the resin bag 21 containing the electrolyte component 20 is disposed opposite the second region 42 of the negative electrode 12. The extension portion 15 of the support member 13 extends from the first region 41 to the position of the resin bag 21 containing the electrolyte component 20, which is disposed opposite the second region 42. The extension portion 15 of the support member 13 is disposed between the resin bag 21 containing the electrolyte component 20 and the second region 42. Therefore, the resin bag 21 containing the electrolyte component 20 faces the second region 42 of the negative electrode 12 via the extension portion 15 of the support member 13.

The metal-air battery 10 of the liquid detection sensor 1 includes multiple resin bags 21 containing electrolyte constituents 20. The electrolyte constituents 20 are divided into multiple portions, each containing a fixed amount, and sealed inside each of the resin bags 21. A support 22 is disposed opposite the second portion 42 of the negative electrode 12, and the multiple resin bags 21, 21, 21... containing the electrolyte constituents 20 are held by the support 22. The support 22 is a separate member from the positive electrode 11, negative electrode 12, and support member 13, and is also a separate member from the positive electrode 11, negative electrode 12, and support member 13. Examples of the support 22 include a porous member.

The resin bag 21 containing the electrolyte component 20 is held by the support 22, which faces the second portion 42 of the negative electrode 12. This allows the resin bag 21 to be positioned independently of the positive electrode 11, the negative electrode 12, and the support member 13. Furthermore, the resin bag 21 containing the electrolyte component 20 is held by the support 22, which faces the second portion 42 of the negative electrode 12. This allows the resin bag 21 containing the electrolyte component 20 to be positioned farther from the positive electrode 11 than the first portion 41 of the negative electrode 12, which faces the positive electrode 11. Therefore, the extension 15 of the support member 13 is positioned between the support 22, which holds the resin bag 21 containing the electrolyte component 20, and the second portion 42. Furthermore, the support 22 faces the second portion 42 of the negative electrode 12 via the extension 15 of the support member 13.

The support 22 is arranged so as to overlap substantially the entire negative electrode 12 in a plan view, i.e., when viewed from the stacking direction of the positive electrode 11, support member 13, and negative electrode 12. Resin bags 21 containing electrolyte solution components 20 are arranged in a dispersed state on the surface and inside of the support 22. In the liquid detection sensor 1, multiple resin bags 21, 21, 21... containing electrolyte solution components 20 are arranged throughout the support 22. The multiple resin bags 21, 21, 21... containing electrolyte solution components 20 are arranged so as to overlap substantially the entire negative electrode 12 in a plan view.

The resin bag 21 is made of a resin that is soluble or dispersible in the liquid that is the detection target of the liquid detection sensor 1. If the liquid that is the detection target of the liquid detection sensor 1 is water or a liquid that contains water, the resin bag 21 is made of, for example, a water-soluble resin. By making the resin bag 21 of a water-soluble resin, the resin bag 21 is soluble or dispersible in water, and the liquid detection sensor 1 functions as a water detection sensor.

An example of a water-soluble resin is a resin composition containing 100 parts by mass of a polyvinyl alcohol-based resin (A) containing copolymer units consisting of sulfonic acid groups or carboxyl groups, and 3 to 100 parts by mass of an addition reaction product (B) obtained by addition reaction of 1 to 4 moles of alkylene oxide with 1 mole of a trihydric to hexahydric polyhydric alcohol.

The polyvinyl alcohol resin (A) is a saponified polyvinyl ester containing copolymer units consisting of sulfonic acid groups or carboxyl groups. Examples of vinyl esters include vinyl acetate, vinyl propionate, and vinyl formate. These compounds may be used alone or in combination of two or more.

The sulfonic acid group-containing monomer is not particularly limited as long as it is copolymerizable with vinyl ester and the sulfonic acid group or its salt is present in the polyvinyl alcohol resin after saponification. Specific examples include 2-(meth)acrylamido-2-methylpropanesulfonic acid, alkali metal salts of 2-(meth)acrylamido-2-methylpropanesulfonic acid, 2-(meth)acrylamido-1-methylpropanesulfonic acid, alkali metal salts of 2-(meth)acrylamido-1-methylpropanesulfonic acid, olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid, and methallyl sulfonic acid, and metal salts of the above olefin sulfonic acids. These compounds may be used alone or in combination of two or more. In this specification, "(meth)acrylic" means "acrylic and/or methacrylic."

The carboxyl group-containing monomer is not particularly limited, as long as it is copolymerizable with vinyl ester and a carboxylic acid or its salt is present in the polyvinyl alcohol resin after saponification. Specific examples include maleic anhydride, monoalkyl maleate esters, dialkyl maleate esters, itaconic acid, itaconic acid alkyl esters, (meth)acrylic acid, allylcarboxylic acid, and (meth)acrylic acid esters derived from carboxylic acids or their salts after saponification. These compounds may be used alone or in combination of two or more.

The content of the copolymerized units in the polyvinyl alcohol-based resin (A) is not particularly limited, but may be, for example, 0.1 to 20 mol % in order to achieve a good balance between water solubility and mechanical strength. The degree of saponification of the polyvinyl alcohol-based resin (A) is, for example, 40 mol % or more and 100 mol % or less. The viscosity-average degree of polymerization of the polyvinyl alcohol-based resin (A) is, for example, 200 or more and 10,000 or less.

Examples of trihydric to hexahydric polyhydric alcohols, which are raw materials for addition reactant (B), include glycerin, trimethylolpropane, diglycerin, pentaerythritol, xylose, arabinose, ribulose, and sorbitol. Examples of alkylene oxides, which are raw materials for addition reactant (B), include ethylene oxide and propylene oxide. These compounds may be used alone or in combination of two or more.

A method for forming a film from the resin composition includes, for example, casting an aqueous solution of the resin composition. The resin bag 21 made from the resin composition dissolves quickly in water, retains its water solubility even when filled with electrolyte solution components 20 for a long period of time, and has excellent mechanical strength.

An example of a water-soluble resin is a resin composite of a polyvinyl alcohol polymer and at least one polymer selected from a polysaccharide and an acrylic resin. An example of a resin bag 21 using the above-described resin composite is a resin laminate having a first layer containing a polyvinyl alcohol polymer and a second layer containing at least one polymer selected from a polysaccharide and an acrylic resin.

Examples of polyvinyl alcohol polymers include polymers prepared by polymerizing vinyl ester monomers and saponifying the resulting polyvinyl ester polymers. Examples of vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl laurate, vinyl stearate, and vinyl benzoate. These compounds may be used alone or in combination of two or more.

The polyvinyl alcohol polymer may also be a copolymer of a vinyl ester monomer and another monomer polymerizable with the vinyl ester monomer. Examples of other monomers polymerizable with the vinyl ester monomer include olefins having 2 to 30 carbon atoms, such as ethylene, propylene, and butene; (meth)acrylic acid; (meth)acrylic acid esters, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, ethylhexyl (meth)acrylate, dodecyl (meth)acrylate, and octadecyl (meth)acrylate; (meth)acrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, diacetone (meth)acrylamide, and (meth)acrylamidopropyl diacrylate. (Meth)acrylamides such as methylamine and N-methylol (meth)acrylamide; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, dodecyl vinyl ether, and stearyl vinyl ether; vinyl cyanides such as (meth)acrylonitrile; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride, and vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride, maleic acid; maleic acid esters; itaconic acid; itaconic acid esters; vinylsilyl compounds such as vinyltrimethoxysilane; isopropenyl acetate; N-vinylformamide, N-methyl-N Examples include vinylamides such as N-vinylformamide, N-vinylacetamide, and N-methyl-N-vinylacetamide; N-vinyl-2-pyrrolidones; N-vinyl-2-caprolactam; and sulfonic acid group-containing monomers such as 2-(meth)acrylamido-2-methylpropanesulfonic acid, 2-(meth)acrylamido-1-methylpropanesulfonic acid, ethylenesulfonic acid, allylsulfonic acid, and methacrylsulfonic acid. These compounds may be used alone or in combination of two or more.

The degree of saponification of the polyvinyl alcohol polymer is, for example, 75 mol% or more and 99 mol% or less. The viscosity-average degree of polymerization of the polyvinyl alcohol polymer is, for example, 300 or more and 2500 or less. Examples of methods for preparing the first layer of the resin bag 21 include methods using a polyvinyl alcohol polymer solution in which a polyvinyl alcohol polymer is dissolved in a solvent (e.g., a casting method, a solution coating method, a wet film-forming method, a gel film-forming method, etc.).

The second layer of the resin bag 21 contains at least one resin selected from polysaccharides and (meth)acrylic resins. Examples of polysaccharides used in the second layer include starches and cellulose-based resins.

Examples of starches include naturally occurring starches such as potato starch, corn starch, wheat starch, and rice starch; starches obtained by heating and gelatinizing naturally occurring starches and drying them; and processed starches such as acetylated oxidized starch, starch sodium octenyl succinate, starch acetate, oxidized starch, hydroxypropyl starch, hydroxypropylated phosphate cross-linked starch, phosphate monoesterified phosphate cross-linked starch, phosphated starch, and starch nitrate. These compounds may be used alone or in combination of two or more. Examples of cellulose-based resins include carboxymethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, and methyl cellulose. These compounds may be used alone or in combination of two or more.

An example of a (meth)acrylic resin is poly(meth)acrylamide.

Examples of methods for preparing the second layer of the resin bag 21 include methods using a resin solution in which at least one resin selected from polysaccharides and (meth)acrylic resins is dissolved in a solvent (e.g., a casting method, a solution coating method, or a wet film-forming method).

Methods for preparing the resin bag 21, which is a resin laminate having a first layer and a second layer, include, for example, a method of preparing the first and second layers in advance and laminating them; a method of coating a prepared first layer with a coating liquid for forming a second layer containing at least one resin selected from polysaccharides and (meth)acrylic resins; a method of coating a prepared second layer with a coating liquid for forming a first layer containing a polyvinyl alcohol polymer; a method of co-extruding the first and second layers; and a method of extruding or coating the second layer onto the first layer and laminating them before the first layer is completely dried or cooled during the production of the first layer, and then drying or cooling the first and second layers simultaneously.

Other water-soluble resins include, for example, water-soluble vinyl resins such as polyvinyl alcohol, polyvinylpyrrolidone, poly(meth)acrylamide, and polyvinyl methylene ether; polyether resins such as polyethylene oxide; cellulose resins such as carboxymethyl cellulose, hydroxypropyl cellulose, and hydroxyethyl cellulose; (meth)acrylic resins such as poly(meth)acrylate; and polysaccharide polymers such as alginic acid, pullulan, and xanthan.

The method for encapsulating the electrolyte solution components 20 in the resin bag 21 is not particularly limited, and examples include a method in which the electrolyte solution components 20 are poured into the resin bag 21 through the opening of the resin bag 21 and then sealed by gluing or heat-sealing the opening of the resin bag 21; or a method using a microencapsulation method using a W/O dispersion or O/W dispersion. The method for holding multiple resin bags 21 encapsulating the electrolyte solution components 20 on the support 22 is also not particularly limited, and examples include a method in which the resin bags 21 are pressed into the voids of the support 22; a method in which the resin bags 21 are dispersed in a dispersion medium such as a solvent and then impregnated into the support 22, followed by drying and removing the dispersion medium; or a method in which the support 22 is divided into multiple pieces, the resin bags 21 are placed between the pieces, and then the support 22 is glued together.

Examples of the electrolyte constituents 20 enclosed in the resin bag 21, whose resin type is a water-soluble resin, include alkali metal salts such as salts of alkali metals and halogens, such as sodium chloride and potassium chloride, and aqueous solutions of the alkali metal salts. Other examples of the electrolyte constituents 20 include water. Even if water, alkali metal salts, or aqueous solutions of alkali metal salts are placed inside the resin bag 21, which is a water-soluble resin, salting out occurs inside the resin bag 21, so the resin bag 21 does not dissolve and functions as a shell.

In addition, a shielding material such as a coating may be applied, if necessary, to areas other than the boundary between the first portion 41 of the negative electrode 12 and the support member 13. Specifically, for example, a shielding material such as a coating may be applied to the boundary between the second portion 42 of the negative electrode 12 and the extension portion 15 of the support member 13, or the boundary between the extension portion 15 of the support member 13 and the support 22. By applying a shielding material such as a coating to these areas, corrosion of the positive electrode 11, negative electrode 12, etc. caused by the electrolyte components 20 sealed in the resin bag 21 can be prevented, even if the resin bag 21 is damaged by corrosion due to atmospheric humidity or the effects of atmospheric moisture. Among the shielding materials, it is desirable for the coating material to have insulating properties, and examples of such materials include silicone-based, fluorine-based, epoxy-based, polyvinyl chloride-based, polyethylene-based, and polyamide-based resins. Examples of shielding materials other than coatings include insulating tapes, rubber sheets, resin plates, films, and papers.

Examples of active materials for the negative electrode 12 include magnesium (Mg), magnesium alloys, aluminum (Al), aluminum alloys, lithium (Li), lithium alloys, calcium (Ca), calcium alloys, zinc (Zn), zinc alloys, etc. Of these, magnesium (Mg) and magnesium alloys are preferred in terms of power generation efficiency and availability.

The support member 13, which functions as a separator, is made of a material that is electrically insulating, ion-permeable, and liquid-permeable. Examples of materials that can be used to form the support member 13 include resins such as polyethylene, polypropylene, polyethylene terephthalate, cellulose, polyamide, and (meth)acrylic resin, as well as glass. The support member 13 is also made of a material with voids, such as nonwoven fabric, glass fiber, woven fabric with a mesh structure, and membranes with independent or interconnected pores. Examples of materials with voids that can form the support member 13 include materials with a porous structure.

The positive electrode 11 has a positive electrode current collector and a catalyst layer. The positive electrode current collector is a material that is conductive enough to transfer electrons emitted from the negative electrode 12 to the catalyst layer and breathable enough to allow oxygen to pass through. Examples of the positive electrode current collector include wire mesh and metal foam. The catalyst layer functions as the reaction section of the positive electrode 11.

Next, a power generation system for the metal-air battery 10 will be described when water, which is the detection target of the liquid detection sensor 1, comes into contact with the metal-air battery 10. For ease of explanation, the case where the negative electrode 12 is made of magnesium (Mg) will be described here. When water comes into contact with the metal-air battery 10 and permeates the entire metal-air battery 10, an oxidation reaction shown in (1) below occurs at the negative electrode 12. Furthermore, a reduction reaction shown in (2) below occurs at the positive electrode 11. From the above, the reaction shown in (3) below occurs in the metal-air battery 10 as a whole, and the metal-air battery 10 discharges, i.e., generates power by itself.
(1) 2Mg→2Mg2 ⁺ +4e ^-
(2) O ₂ +2H ₂ O+4e ^- →4OH ^-
(3) 2Mg+O ₂ +2H ₂ O→2Mg(OH) ₂

Next, we will explain the detection operation when the liquid detection sensor 1 detects water as its detection target. As shown in FIG. 2 , when water 110, the detection target of the liquid detection sensor 1, comes into contact with the support 22 of the metal-air battery 10 of the liquid detection sensor 1, it then permeates throughout the support 22. As the detection target water 110 permeates throughout the support 22, the resin bag 21, which is made of a resin that is soluble or dispersible in water 110, dissolves or disperses. In other words, the resin bag 21 is destroyed by the detection target water 110. When the resin bag 21 dissolves or disperses, the electrolyte components 20 (e.g., sodium chloride, water containing sodium chloride) sealed within the resin bag 21 are released into the water 110. Furthermore, when the detection target water 110 permeates from the support 22 into the support member 13, the water 110 acts as an electrolyte, causing the metal-air battery 10 to discharge. When the metal-air battery 10 discharges, the water 110 acting as the electrolyte contains the electrolyte constituents 20 released from the resin bag 21. The electrolyte constituents 20 act to improve ionic conductivity between the positive electrode 11 and the negative electrode 12, thereby improving the power generation performance of the metal-air battery 10.

When the metal-air battery 10 generates power, the power from the metal-air battery 10 is supplied to the alarm unit 100 through the electrical wire unit 101. When the alarm unit 100 receives the power generated by the metal-air battery 10, it notifies the detection of liquid using the alarm means provided in the alarm unit 100.

In the liquid detection sensor 1, the electrolyte constituents 20 of the metal-air battery 10, which serves as the power source, are sealed inside a resin bag 21 that is soluble or dispersible in the liquid to be detected (water 110). This allows the sensor to be used in any field where water 110 is to be detected, improving its versatility. Furthermore, in the liquid detection sensor 1, the electrolyte constituents 20 of the metal-air battery 10 are sealed inside the resin bag 21, preventing the metal-air battery 10 from deteriorating due to the electrolyte constituents 20, even when the liquid detection sensor 1 is installed for an extended period of time. Furthermore, in the liquid detection sensor 1, the electrolyte constituents 20 of the metal-air battery 10 are sealed inside the resin bag 21, preventing deterioration of the metal-air battery 10 while providing the metal-air battery 10 with excellent power generation performance. This allows the metal-air battery 10 to demonstrate excellent power generation performance and reliably transmit alarms to locations far from the site of a leak or flooding. Therefore, the liquid detection sensor 1 can reliably transmit an alarm to a location far from the site of the liquid leak or flooding, improving convenience and versatility.

Furthermore, in the liquid detection sensor 1, the resin bag 21 containing the electrolyte constituents 20 is disposed opposite the second portion 42 of the negative electrode 12, which is different from the first portion 41 of the negative electrode 12 facing the positive electrode 11. This prevents corrosion of the components constituting the metal-air battery 10, such as the positive electrode 11, negative electrode 12, and support member 13, caused by leakage of the electrolyte constituents 20, even if the resin bag 21 is damaged due to the effects of atmospheric humidity or moisture. In particular, in the liquid detection sensor 1, the second portion 42 of the negative electrode 12, which is disposed opposite the resin bag 21 containing the electrolyte constituents 20, faces the first portion 41 of the negative electrode 12 facing the positive electrode 11. This more reliably prevents corrosion of the components constituting the metal-air battery 10, such as the positive electrode 11, negative electrode 12, and support member 13, caused by leakage of the electrolyte constituents 20, even if the resin bag 21 is damaged.

In addition, the liquid detection sensor 1 has multiple resin bags 21 in which the electrolyte constituents 20 are sealed, which allows the electrolyte constituents 20 to be smoothly supplied throughout the metal-air battery 10, further improving the power generation efficiency of the metal-air battery 10.

Next, we will explain the liquid detection sensor according to the second embodiment of the present invention. The main components of the liquid detection sensor according to the second embodiment are the same as those of the liquid detection sensor according to the first embodiment, so the same components as those of the liquid detection sensor according to the first embodiment will be described using the same reference numerals. Figure 3 is a side view illustrating the outline of the liquid detection sensor according to the second embodiment of the present invention, and Figure 4 is a side view illustrating the state of the liquid detection sensor according to the second embodiment of the present invention when detecting liquid.

In the liquid detection sensor 1 according to the first embodiment, the extension 15 of the support member 13 was positioned between the support 22 holding the resin bag 21 containing the electrolyte component 20 and the second portion 42 of the negative electrode 12. Instead, as shown in FIG. 3 , in the liquid detection sensor 2 according to the second embodiment, the support 22 holding the resin bag 21 containing the electrolyte component 20 is positioned between the extension 15 of the support member 13 and the second portion 42 of the negative electrode 12. In other words, the resin bag 21 containing the electrolyte component 20 is positioned between the extension 15 of the support member 13 and the second portion 42 of the negative electrode 12. Therefore, the extension 15 of the support member 13 faces the second portion 42 of the negative electrode 12 via the resin bag 21 containing the electrolyte component 20.

In addition, in the liquid detection sensor 2, a coating may be applied, if necessary, to areas other than the boundary between the first portion 41 of the negative electrode 12 and the support member 13. Specifically, for example, a coating may be applied to the boundary between the second portion 42 of the negative electrode 12 and the support member 22, or the boundary between the extension portion 15 of the support member 13 and the support member 22. By applying a coating to these areas, corrosion of the positive electrode 11, negative electrode 12, etc. caused by the electrolyte constituents 20 sealed in the resin bag 21 can be prevented, even if the resin bag 21 is damaged by corrosion due to atmospheric humidity or the effects of atmospheric moisture.

As shown in FIG. 4 , in the liquid detection sensor 2, when the water 110 to be detected comes into contact with the support 22 of the metal-air battery 10 of the liquid detection sensor 2, it permeates throughout the support 22. As the water 110 to be detected permeates throughout the support 22, the resin bag 21, which is made of a resin that is soluble or dispersible in the water 110, dissolves or disperses. When the resin bag 21 dissolves or disperses, the electrolyte constituents 20 (e.g., sodium chloride, water containing sodium chloride) sealed in the resin bag 21 are released into the water 110. Furthermore, when the water 110 to be detected permeates from the support 22 into the support member 13, the water 110 acts as an electrolyte, causing the metal-air battery 10 to discharge. When the metal-air battery 10 discharges, the water 110 acting as the electrolyte contains the electrolyte constituents 20 released from the resin bag 21. The electrolyte constituents 20 act to improve ionic conductivity between the positive electrode 11 and the negative electrode 12, thereby improving the power generation performance of the metal-air battery 10.

In the liquid detection sensor 2, the electrolyte constituent components 20 of the metal-air battery 10 are sealed inside a resin bag 21 that is soluble or dispersible in the liquid to be detected (water 110), making it possible to use it in any field for detecting water 110, improving versatility. Furthermore, in the liquid detection sensor 2, the electrolyte constituent components 20 of the metal-air battery 10 are sealed inside a resin bag 21, making it possible to prevent the metal-air battery 10 from being deteriorated by the electrolyte constituent components 20 even if the liquid detection sensor 2 is installed for a long period of time. Furthermore, in the liquid detection sensor 2, the resin bag 21 containing the electrolyte constituents 20 is positioned opposite a second portion 42 of the negative electrode 12 that is different from the first portion 41 of the negative electrode 12 that faces the positive electrode 11. This prevents corrosion of the components that make up the metal-air battery 10, such as the positive electrode 11, negative electrode 12, and support member 13, caused by leakage of the electrolyte constituents 20, even if the resin bag 21 is damaged due to the effects of humidity or moisture in the air.

Next, we will explain the liquid detection sensor according to the third embodiment of the present invention. Note that the main parts of the liquid detection sensor according to the third embodiment are common to the liquid detection sensors according to the first and second embodiments, and therefore the same components as those of the liquid detection sensors according to the first and second embodiments will be described using the same reference numerals. Note that Figure 5 is a side view illustrating an overview of the liquid detection sensor according to the third embodiment of the present invention, and Figure 6 is a side view illustrating the state of the liquid detection sensor according to the third embodiment of the present invention when detecting liquid.

The liquid detection sensor 1 according to the first embodiment is a water detection sensor, and the resin bag 21 is formed from a resin that is soluble or dispersible in water. Instead, the liquid detection sensor 3 according to the third embodiment is an oil detection sensor, and therefore the resin bag 31 in which the electrolyte constituents 30 are sealed is formed from a resin that is soluble or dispersible in oil.

In this way, the liquid detection sensor of the present invention can appropriately change the type of liquid to be detected by appropriately changing the solubility or dispersibility of the resin that forms the resin bag. In other words, the liquid detection sensor of the present invention is highly versatile in that it can appropriately change the type of liquid to be detected.

As shown in FIG. 5 , the second region 42 of the negative electrode 12 of the liquid detection sensor 3 faces the first region 41, and a resin bag 31 containing electrolyte constituents 30 is disposed opposite the second region 42 of the negative electrode 12. The extension portion 15 of the support member 13 extends from the first region 41 to the position of the resin bag 31 containing electrolyte constituents 30, which is disposed opposite the second region 42. The extension portion 15 of the support member 13 is disposed between the resin bag 31 containing electrolyte constituents 30 and the second region 42. Therefore, the resin bag 31 containing electrolyte constituents 30 faces the second region 42 of the negative electrode 12 via the extension portion 15 of the support member 13.

The metal-air battery 10 of the liquid detection sensor 3 also has multiple resin bags 31 containing electrolyte constituents 30, each divided into a fixed amount and sealed inside each resin bag 31. A support 22 is positioned opposite the second portion 42 of the negative electrode 12, and the multiple resin bags 31, 31, 31... containing electrolyte constituents 30 are held by the support 22. The support 22 is a separate member from the positive electrode 11, negative electrode 12, and support member 13, and is also a separate member from the positive electrode 11, negative electrode 12, and support member 13.

The resin bag 31 is formed, for example, from an oil-soluble resin, which is a resin that is soluble or dispersible in oil. By forming the resin bag 31 from an oil-soluble resin, the liquid detection sensor 3 functions as an oil detection sensor.

Examples of oil-soluble resins include terpene-based resins such as candelilla resin, hydrogenated pentaerythrityl rosinate, and hydrogenated glyceryl abietate; silicone-based resins such as trimethylsiloxysilicate, polymethylsilsesquioxane, and acrylic-silicone graft copolymer; and hydrocarbon-based resins such as polyvinyl isobutyl ether and polyisobutylene. These compounds may be used alone or in combination of two or more.

The method for encapsulating the electrolyte solution components 30 in the resin bag 31 is not particularly limited, and examples include a method in which the electrolyte solution components 30 are placed in the resin bag 31 through the opening, and then the opening of the resin bag 31 is glued or heat-sealed to encapsulate the components; or a method using a microencapsulation method using a water-in-oil or oil-in-water dispersion. Furthermore, the method for supporting multiple resin bags 31 encapsulating the electrolyte solution components 30 on the support member 13 is not particularly limited, and examples include a method in which the resin bags 31 are pressed into the voids of the support member 13; a method in which the resin bags 31 are dispersed in a dispersion medium such as a solvent, and then the support member 13 is impregnated with the dispersion medium and the dispersion medium is dried and removed; or a method in which the support member 13 is divided into multiple sections, the resin bags 31 are placed between the sections, and the support member 13 is then glued together.

The oil detected by the liquid detection sensor 3 is not a component of the electrolyte solution in the metal-air battery 10. Therefore, the resin bag 31, made of an oil-soluble resin, contains an electrolyte solution as the electrolyte solution component 30. Examples of the electrolyte solution component 30 include water containing an alkali metal salt such as sodium chloride or potassium chloride (aqueous solution of an alkali metal salt), or water.

Next, we will explain the detection operation when the liquid detection sensor 3 detects oil, which is the detection target. As shown in FIG. 6 , when the oil 120, which is the detection target of the liquid detection sensor 3, comes into contact with the support 22 of the metal-air battery 10 of the liquid detection sensor 3, it then permeates throughout the support 22. As the oil 120, which is the detection target, permeates throughout the support 22, the resin bag 31, which is made of a resin that is soluble or dispersible in the oil 120, dissolves or disperses. In other words, the resin bag 31 is destroyed by the oil 120, which is the detection target. When the resin bag 31 dissolves or disperses, the electrolyte constituents 30 (e.g., an aqueous solution of an alkali metal salt) sealed in the resin bag 31 are released into the oil 120. The electrolyte constituents 30 released into the oil 120 act as an electrolyte, causing the metal-air battery 10 to discharge. When the metal-air battery 10 discharges, an aqueous solution of alkali metal salt is released from the resin bag 31 as the electrolyte, and the electrolyte constituents 30 act to improve ionic conductivity between the positive electrode 11 and the negative electrode 12, thereby improving the power generation performance of the metal-air battery 10.

The liquid detection sensor 3 can be used to detect oil because the electrolyte constituents 30 of the metal-air battery 10, which serves as the power source, are sealed inside a resin bag 31 that is soluble or dispersible in the oil 120 to be detected. Furthermore, because the electrolyte constituents 30 of the metal-air battery 10 are sealed inside the resin bag 31, the liquid detection sensor 3 can prevent the metal-air battery 10 from deteriorating due to the electrolyte constituents 30, even if the liquid detection sensor 3 is installed for an extended period of time. Furthermore, in the liquid detection sensor 3, the resin bag 31 containing the electrolyte constituents 30 is positioned opposite a second portion 42 of the negative electrode 12 that is different from the first portion 41 of the negative electrode 12 facing the positive electrode 11. Therefore, even if the resin bag 31 is damaged, corrosion of the components that make up the metal-air battery 10, such as the positive electrode 11, negative electrode 12, and support member 13, due to leakage of the electrolyte constituents 30 can be prevented.

Next, we will explain the liquid detection sensor according to the fourth embodiment of the present invention. The main components of the liquid detection sensor according to the fourth embodiment are common to the liquid detection sensors according to the first to third embodiments, so the same components as those of the liquid detection sensors according to the first to third embodiments will be described using the same reference numerals. Figure 7 is a side view illustrating the outline of the liquid detection sensor according to the fourth embodiment of the present invention, and Figure 8 is a side view illustrating the state of the liquid detection sensor according to the fourth embodiment of the present invention when detecting liquid.

In the liquid detection sensor 3 according to the third embodiment, the extension 15 of the support member 13 was positioned between the support 22 holding the resin bag 31 containing the electrolyte component 30 and the second portion 42 of the negative electrode 12. Instead, as shown in FIG. 7 , in the liquid detection sensor 4 according to the fourth embodiment, the support 22 holding the resin bag 31 containing the electrolyte component 30 is positioned between the extension 15 of the support member 13 and the second portion 42 of the negative electrode 12. In other words, the resin bag 31 containing the electrolyte component 30 is positioned between the extension 15 of the support member 13 and the second portion 42 of the negative electrode 12. Therefore, the extension 15 of the support member 13 faces the second portion 42 of the negative electrode 12 via the resin bag 31 containing the electrolyte component 30.

As shown in FIG. 8 , when the oil 120 to be detected by the liquid detection sensor 4 comes into contact with the support 22 of the metal-air battery 10 of the liquid detection sensor 4, the oil 120 subsequently permeates throughout the support 22. As the oil 120 to be detected permeates throughout the support 22, the resin bag 31, which is made of a resin that is soluble or dispersible in the oil 120, dissolves or disperses. When the resin bag 31 dissolves or disperses, the electrolyte constituents 30 (e.g., an aqueous solution of an alkali metal salt) enclosed in the resin bag 31 are released into the oil 120. The electrolyte constituents 30 released into the oil 120 act as an electrolyte, causing the metal-air battery 10 to discharge. When the metal-air battery 10 discharges, the aqueous solution of the alkali metal salt is released from the resin bag 31 as the electrolyte. The electrolyte constituents 30 act to improve ionic conductivity between the positive electrode 11 and the negative electrode 12, thereby improving the power generation performance of the metal-air battery 10.

The liquid detection sensor 4 can also be used to detect oil because the electrolyte constituents 30 of the metal-air battery 10 are sealed inside a resin bag 31 that is soluble or dispersible in the oil 120 to be detected. Furthermore, because the electrolyte constituents 30 of the metal-air battery 10 are sealed inside the resin bag 31, the liquid detection sensor 4 can prevent the metal-air battery 10 from being deteriorated by the electrolyte constituents 30, even if the liquid detection sensor 4 is installed for a long period of time. Furthermore, because the resin bag 31 containing the electrolyte constituents 30 is positioned opposite a second portion 42 of the negative electrode 12 that is different from the first portion 41 of the negative electrode 12 facing the positive electrode 11, even if the resin bag 31 is damaged, corrosion of the components that make up the metal-air battery 10, such as the positive electrode 11, negative electrode 12, and support member 13, due to leakage of the electrolyte constituents 30 can be prevented.

Next, an example of how to use the liquid detection sensor of the present invention will be described. For ease of explanation, this example will be described using the liquid detection sensor 1 according to the first embodiment of the present invention. Note that Figure 9 is an explanatory diagram of an example of how to use the liquid detection sensor of the present invention.

As shown in FIG. 9 , the alarm unit 100 connected to the metal-air battery 10 via the electric wire unit 101 is, for example, a transmitter that receives power generated from the metal-air battery 10 and activates its transmission function to the receiver unit 200. When the metal-air battery 10 detects the liquid to be detected (water 110 in FIG. 9 ) and generates power, the alarm unit 100 receives power from the metal-air battery 10, activates its transmission function, and transmits a detection signal to the receiver unit 200. Examples of transmitters include wireless transmitters and wired transmitters. In FIG. 9 , a wireless transmitter is used as the alarm unit 100, allowing the detection signal to be wirelessly transmitted from the alarm unit 100 to the receiver unit 200. Existing wireless methods such as wireless LAN, Bluetooth (registered trademark), and Wi-Fi can be used for wireless communication.

When the receiving unit 200 receives a detection signal from the alarm unit 100 of the liquid detection sensor 1, it detects that a leak or other problem has occurred in the liquid being detected (in Figure 9, this is a water leak or flooding), notifies the administrator of the occurrence of the water leak or flooding, and automatically shuts down the device, etc., if necessary.

Next, we will explain liquid detection sensors according to other embodiments of the present invention. In the liquid detection sensors according to the first to fourth embodiments described above, multiple resin bags containing electrolyte components were distributed over the entire support body, but instead, a single resin bag may be provided. In this case, the electrolyte components are sealed together in the resin bag.

In addition, while the resin bag in the liquid detection sensors according to the first and second embodiments is formed from a water-soluble resin, and the resin bag in the liquid detection sensors according to the third and fourth embodiments is formed from an oil-soluble resin, a single metal-air battery may alternatively use a combination of a resin bag made from a water-soluble resin and a resin bag made from an oil-soluble resin. By using a combination of a resin bag made from a water-soluble resin and a resin bag made from an oil-soluble resin, a single liquid detection sensor can detect both water and oil.

In addition, in the above example of how to use the liquid detection sensor, the notification unit was a transmitter with a transmission function to the receiver, but instead it may be a liquid detection display unit that receives power from the metal-air battery and notifies the administrator of liquid detection. Examples of display means for the liquid detection display unit include turning on a warning light or emitting a warning sound.

The liquid detection sensor of the present invention is versatile and can prevent deterioration of the metal-air battery that serves as its power source, even when installed over long periods of time. Furthermore, the metal-air battery that serves as its power source can exhibit excellent power generation performance, making it suitable for use in a wide range of liquid detection applications, including detecting water and rain leaks in buildings, detecting water and oil leaks in various facilities and factories, detecting flooding in roads and underground facilities, detecting dangerous water levels by detecting water levels in rivers, lakes, and other ponds, detecting blood and drug leaks in medical settings, and detecting urination in nursing care settings.

REFERENCE SIGNS LIST 1, 2, 3, 4 Liquid detection sensor 10 Metal-air battery 11 Positive electrode 12 Negative electrode 20, 30 Electrolyte constituents 21, 31 Resin bag 41 First portion 42 Second portion 100 Notification portion

Claims (11)

a metal-air battery including a positive electrode, a negative electrode having a first portion facing the positive electrode, and an electrolyte solution component disposed opposite a second portion of the negative electrode different from the first portion;
An oil detection sensor in which the electrolyte constituent components are sealed inside a resin bag, and the resin of the resin bag has solubility or dispersibility in the liquid to be detected. 2. The oil detection sensor according to claim 1, wherein the second portion of the resin bag in which the electrolyte constituents are sealed is arranged opposite to the first portion and has an area facing the first portion. 3. The oil detection sensor according to claim 1, wherein a support member is further provided between the positive electrode and the first portion to support the positive electrode and the first portion at a predetermined distance, and the support member has an extension portion extending from the first portion to the position of the resin bag body in which the electrolyte constituent components are sealed, facing the second portion. 4. The oil detection sensor according to claim 3, wherein the extending portion of the support member is disposed between the resin bag in which the electrolyte constituents are sealed and the second portion. 4. The oil detection sensor according to claim 3, wherein the resin bag containing the electrolyte constituents is disposed between the extending portion of the support member and the second portion. 6. The oil detection sensor according to claim 1, wherein the resin of the resin bag is an oil- soluble resin. 7. The oil detection sensor according to claim 1, wherein the resin bag in which the electrolyte constituents are sealed is one or more. 8. The oil detection sensor according to claim 1, wherein the electrolyte contains water and an aqueous solution of an alkali metal salt. The oil detection sensor according to any one of claims 1 to 8, wherein the active material of the negative electrode contains at least one metal selected from the group consisting of magnesium (Mg), aluminum (Al), lithium (Li), calcium (Ca) and zinc (Zn). The oil detection sensor according to any one of claims 1 to 9, further comprising an alarm unit that receives power from the metal-air battery and notifies the detection of liquid. The oil detection sensor according to claim 1 , further comprising an alarm unit capable of wirelessly transmitting a detection signal from the metal-air battery to a receiver unit.