Temperature sensor, temperature detection circuit, and temperature detection method

Abstract

To provide a temperature sensor with high sensitivity and accuracy capable of being supplied at a low cost, a temperature detection circuit, and a temperature detection method.SOLUTION: A disclosed temperature sensor 10 includes: a first electrode 11; a second electrode 13; an electrolyte 12 L placed between the first electrode and the second electrode; a first terminal 14 conductively connected to the first electrode; a second terminal 15 conductively connected to the second electrode; and a pair of housing bodies 16,17 that seal an element part 10S that has a laminated structure of the first electrode, the second electrode, and the electrolyte in a mode that the first terminal and the second terminal are exposed to the outside.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a temperature sensor, a temperature detection circuit, and a temperature detection method. [Background technology]

[0002] Temperature sensors have been used in heating products such as electric blankets and electric heaters for a long time, and a typical example of such a temperature sensor is thermistor. However, due to their thickness, they are not suitable for use by attaching them to specific objects such as electric blankets.

[0003] On the other hand, a thin sheet-like temperature sensor is known in which a heat-sensitive sheet made of a polymeric heat-sensitive resistor is sandwiched between electrode sheets (see Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Specification of Japanese Utility Model Application Laid-Open No. 50-35273 [Patent Document 2] Specification of Japanese Utility Model Application Laid-Open No. 59-93090 [Patent Document 3] Special Publication No. 8-007102 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the above-mentioned sheet-type temperature sensors use a heat-sensitive sheet (resin film) made of polymeric materials, which has low temperature dependency, resulting in poor sensitivity and accuracy as a temperature sensor. Furthermore, in order to increase the temperature dependency of the heat-sensitive sheet, it is necessary to use an expensive resin film, and it is difficult to reduce manufacturing costs, making it difficult to supply them at low cost.

[0006] SUMMARY OF THE INVENTION The present invention is intended to solve the above problems, and an object of the present invention is to provide a temperature sensor, a temperature detection circuit, and a temperature detection method that are highly sensitive and accurate and can be supplied at low cost. [Means for solving the problem]

[0007] In order to solve the above problem, the temperature sensor of the present invention is characterized by comprising a first electrode, a second electrode, an electrolyte disposed between the first electrode and the second electrode, a first terminal conductively connected to the first electrode, a second terminal conductively connected to the second electrode, and a housing that seals an element portion having a layered structure of the first electrode, the second electrode, and the electrolyte in a manner that exposes the first terminal and the second terminal to the outside.

[0008] According to the present invention, by providing an electrolyte solution between a first electrode and a second electrode and contacting at least one of the electrodes with the electrolyte solution via an insulating layer, the temperature-induced change rates of equivalent series resistance and capacitance can be increased by the effects of the insulating layer and the electrolyte solution compared to the temperature-induced change rates of conventional thermal sheets made of resin films. This improves the sensitivity of temperature detection based on changes in electromagnetic properties caused by temperature changes between the first and second electrodes. In particular, the temperature coefficient of resistivity of the electrolyte solution is greater than that of polymer resin films, thereby improving detection accuracy. Another advantage is that the composition of the electrolyte solution can be adjusted to meet the detection characteristics required of the temperature sensor, and the electrolyte solution can be easily prepared in this adjusted form. Furthermore, because an electrolytic capacitor structure is used, in which an electrolyte solution is interposed between the electrodes, it can be manufactured more inexpensively than a thermistor using a semiconductor.

[0009] In the present invention, it is preferable that at least one of the first electrode and the second electrode has a finely textured surface structure on the surface facing the electrolyte. This allows the opposing area between the electrode and the electrolyte to be increased without increasing the area of ​​the temperature sensor, thereby increasing the capacitance of the element portion. This makes it possible to further improve the sensitivity and accuracy of the sensor based on the temperature coefficient of capacitance. The above-mentioned finely textured surface structure can be formed by etching (removing) the surface of the electrode material or by adhering (attaching) fine powder, such as by forming a sintered body.

[0010] In the present invention, an insulating layer is preferably formed on the surface layer of at least one of the first electrode and the second electrode on the electrolyte side. By forming an insulating layer on the surface of the electrode, the stability of the capacitance can be improved, thereby reliably improving the sensitivity and accuracy of temperature detection and enabling stable detection. In this case, it is desirable that the insulating layer be formed on the surface layer having a fine surface unevenness structure. This increases the capacitance, further improving the sensitivity and accuracy of temperature detection.

[0011] In the present invention, it is preferable that at least one of the electrodes is made of a valve metal, and the insulating layer is a passive film formed on the surface of the electrode. By using a passive film of a valve metal as the insulating layer, a thin yet dense insulating film can be formed, which facilitates reducing leakage current and increasing capacitance. In this case, the valve metal is preferably aluminum, chromium, titanium, zinc, or an alloy mainly composed of these. Examples of passive films include those formed by electrochemical oxidation or sulfurization, such as an anodic oxide film or a surface treatment film formed by chemical conversion treatment. The material of the electrode is not limited to the valve metals mentioned above, but corrosion-resistant metals such as gold, silver, copper, and stainless steel, or alloys mainly composed of these metals, can also be used. In addition, carbon materials such as graphite, graphene, glassy carbon, carbon nanotubes, and fullerene, and conductive polymers such as polyacetylene, polyparaphenylene vinylene, polyaniline, polythiophene, polypyrrole, and poly(3,4-dioxythiophene) can be suitably used.

[0012] In the present invention, the electrolyte solution contains an electrolyte and a solvent, and the solvent preferably has a viscosity within the range of 10 mPa·s to 5000 mPa·s in the room temperature range of 5°C to 35°C. Below this range, the solvent does not exhibit sufficient resistivity change, while above this range, the impregnation and contact of the electrolyte solution deteriorate. Specifically, the solvent preferably contains glycerin, ethylene glycol, polyethylene glycol, or a mixture thereof as its main component. These solvents exhibit large changes in resistivity with temperature change in the measurement temperature range near room temperature, allowing for improved detection sensitivity and accuracy primarily through the electrical properties of the electrolyte. Furthermore, their low vapor pressure reduces swelling at high temperatures, thereby extending the life of the temperature sensor 10. If a temperature detection range is specified for the temperature sensor, it is preferable for the viscosity to be within this range within the temperature detection range, instead of the room temperature range.

[0013] In the present invention, the container is preferably made of a sheet material in which an insulating film layer and a conductive film layer or a gas-impermeable film layer are laminated. This ensures the required insulation due to the insulating film layer, and the presence of the conductive film layer provides electrostatic shielding, thereby suppressing the influence of an external electric field. Furthermore, the presence of the gas-impermeable film layer prevents deterioration of the electrolyte (e.g., drying up). Furthermore, as an example, the insulating container preferably has a heat-sealable welding film layer such as PP (polypropylene) formed on the inner surface of the conductive film layer or gas-impermeable film layer, such as aluminum foil, and an exterior film layer with a high melting point and high strength, such as nylon, on the outer surface of the conductive film layer or gas-impermeable film layer.

[0014] In the present invention, the equivalent circuit of the element unit preferably includes an equivalent series resistance and a capacitance, the equivalent series resistance having a negative temperature coefficient and the capacitance having a positive temperature coefficient. With this, for a detected value that reflects the temperature dependency of the change in the electromagnetic state over time due to charging or discharging the capacitance via the equivalent series resistance, the negative temperature coefficient of the equivalent series resistance and the positive temperature coefficient of the capacitance both act in the same direction on the detected value, or at least do not interfere with each other, thereby improving the sensitivity and accuracy of the temperature sensor. Here, in the normal temperature range, for example, 5°C to 35°C, the product of the equivalent series resistance Rs [Ω] and the capacitance C [μF] is preferably 10 or greater. With this, the product of the equivalent series resistance and capacitance being 10 or greater increases the time constant (τ = Rs·C) of the equivalent circuit, thereby increasing the effect of the temperature coefficient on the detected value, thereby further improving the sensitivity and accuracy of temperature detection. Furthermore, if a temperature detection range is defined for the temperature sensor, it is preferable that the above condition be met within that temperature detection range instead of the normal temperature range.

[0015] In the present invention, it is preferable that an insulating separator capable of retaining the electrolyte is disposed between the first electrode and the second electrode, thereby improving the retention of the electrolyte while ensuring insulation between the first electrode and the second electrode, thereby stabilizing the detection characteristics of the temperature sensor.

[0016] In the present invention, it is preferable that the first terminal and the second electrode are made of the same main metal material, and the second terminal and the second electrode are made of the same main metal material, so that they do not react with the electrolyte or the reaction with the electrolyte is unlikely to be a problem, and corrosion due to contact between dissimilar metals can be avoided.

[0017] A temperature detection circuit according to the present invention is conductively connected to a temperature sensor having an element part that forms an equivalent circuit including an equivalent series resistance and a capacitance between first and second terminals, and outputs a detection value for detecting an ambient temperature of the temperature sensor, the temperature detection circuit comprising: a current supply / neutralization part that causes a change in an electromagnetic state over time in the equivalent circuit by charging or discharging the capacitance through the equivalent series resistance; and a detection part that outputs a detection value that reflects the temperature dependence of the change in the electromagnetic state over time in the equivalent circuit due to the temperature characteristics of the equivalent series resistance and the capacitance. Here, it is preferable that in the temperature sensor, the equivalent series resistance has a negative temperature coefficient and the capacitance has a positive temperature coefficient, and that the negative temperature coefficient of the equivalent series resistance and the positive temperature coefficient of the capacitance both affect the detection value in the same direction or at least do not interfere with each other.

[0018] In the temperature detection circuit, the charge supply / neutralization unit preferably includes a charging resistor connected in series with the equivalent series resistance in the charging path of the capacitance, or a discharging resistor connected in series with the equivalent series resistance in the discharging path of the capacitance, and the resistance value of the charging resistor or the discharging resistor is preferably in the range of 0.1 to 10 times the resistance value of the equivalent series resistance. Here, the resistance value range is preferably valid within a room temperature range, for example, a temperature range of 5°C to 35°C. Furthermore, if a temperature detection range of the temperature sensor is specified, the resistance value range is preferably valid within the temperature detection range.

[0019] Furthermore, in the temperature detection circuit, the power supply / neutralization unit preferably includes a charging resistor connected in series with the equivalent series resistance in the charging path of the capacitance, or a discharging resistor connected in series with the equivalent series resistance in the discharging path of the capacitance, and a means for switching or adjusting the resistance value of the charging resistor or the discharging resistor. The means for switching or adjusting the resistance value of the charging resistor or the discharging resistor preferably switches or adjusts the resistance value of the charging resistor or the discharging resistor so that the resistance value is within a range of 0.1 to 10 times the resistance value of the equivalent series resistance. For example, the means for switching or adjusting the resistance value of the charging resistor or the discharging resistor preferably switches or adjusts the resistance value so that the resistance value range is maintained within a room temperature range, for example, a temperature range of 5°C to 35°C. Furthermore, if a temperature detection range of a temperature sensor is defined, the means for switching or adjusting the resistance value of the charging resistor or the discharging resistor preferably switches or adjusts the resistance value so that the resistance range is maintained within the temperature detection range.

[0020] A temperature detection method according to the present invention is a temperature detection method for detecting an ambient temperature of a temperature sensor having an element part in which an equivalent circuit including an equivalent series resistance and a capacitance is formed between a first terminal and a second terminal, the method comprising: charging or discharging the capacitance through the equivalent series resistance to cause a change in an electromagnetic state over time in the equivalent circuit; and outputting the detection value reflecting the temperature dependence of the change in the electromagnetic state over time in the equivalent circuit due to the temperature characteristics of the equivalent series resistance and the capacitance. Here, it is preferable that in the temperature sensor, the equivalent series resistance has a negative temperature coefficient and the capacitance has a positive temperature coefficient, and that the negative temperature coefficient of the equivalent series resistance and the positive temperature coefficient of the capacitance both affect the detection value in the same direction or at least do not interfere with each other. [Effects of the Invention]

[0021] According to the present invention, it is possible to realize a temperature sensor, a temperature detection circuit, and a temperature detection method that are highly sensitive and accurate and can be supplied at low cost. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is an exploded perspective view schematically illustrating a general configuration of an embodiment of a temperature sensor according to the present invention. [Figure 2] FIG. 2 is a cross-sectional view schematically illustrating an example of a laminated structure before sealing in the embodiment. [Figure 3] FIG. 2 is a cross-sectional view schematically showing the cross-sectional structure of the embodiment. [Figure 4] FIG. [Figure 5] FIG. 2 is an enlarged cross-sectional view schematically illustrating an internal structure of the embodiment. [Figure 6] FIG. 2 is a circuit diagram showing a simplified equivalent circuit of the temperature sensor of the embodiment. [Figure 7] 10 is a graph showing the temperature dependency of capacitance for each frequency in the embodiment. [Figure 8]10 is a graph showing the temperature dependency of ESR (equivalent series resistance) for each frequency in the embodiment. [Figure 9] 10 is a graph showing a comparison between the temperature dependency of ESR (equivalent series resistance) and the temperature dependency of the resistance value of the thermistor in the same embodiment. [Figure 10] 2 is a circuit diagram showing a first example of a temperature detection circuit using the temperature sensor of the embodiment. FIG. [Figure 11] 4 is a graph showing the change over time in a voltage detection value during charging in an example of the circuit of the first embodiment. [Figure 12] 10 is a graph showing the change over time in the voltage detection value in another example of the circuit of the first embodiment. [Figure 13] FIG. 4 is a circuit diagram showing a second example of a temperature detection circuit using the temperature sensor of the embodiment. [Figure 14] 10 is a graph showing a voltage detection waveform in the circuit of the second embodiment. [Figure 15] FIG. 10 is a circuit diagram showing a third embodiment of a temperature detection circuit for measuring equivalent series resistance. [Figure 16] 10A is a perspective view of the internal structure, FIG. 10B is a perspective view of the housing, and FIG. 10C is a perspective view of the completed product, showing the structure and manufacturing process of the temperature sensor of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0023] Next, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. First, the overall configuration of an embodiment of a temperature sensor according to the present invention will be described with reference to FIGS. 1 to 4. FIG. 1 is a schematic exploded perspective view of a temperature sensor 10 according to this embodiment. FIG. 2 is a schematic cross-sectional view of the laminated structure (before sealing) shown in FIG. 1. The temperature sensor 10 includes an element section 10S formed by laminating a flexible film-like anode foil 11 (corresponding to the first electrode), a flexible film-like separator 12, and a flexible film-like cathode foil 13 (corresponding to the second electrode). The flexible film-like separator 12 is impregnated with an electrolyte 12L, and the electrolyte 12L is in contact with the anode foil 11 and the cathode foil 13.

[0024] The electrode foils (anode foil 11 and cathode foil 13) are not particularly limited as long as they are conductive. In the illustrated example, they are made of aluminum or an aluminum alloy. In the case of an aluminum alloy, it is preferable to use an aluminum alloy containing one or more elements, such as silicon (Si), iron (Fe), copper (Cu), manganese (Mn), magnesium (Mg), chromium (Cr), zinc (Zn), titanium (Ti), vanadium (V), gallium (Ga), nickel (Ni), boron (B), and zirconium (Zr), in a total amount of 1 [wt %] or less. In addition to aluminum or an aluminum alloy, the electrode foils (anode foil 11 and cathode foil 13) are preferably made of a valve metal such as titanium, chromium, zinc, or an alloy thereof. The surfaces of the electrode foils (anode foil 11 and cathode foil 13) that come into contact with the electrolyte 12L preferably have a finely textured surface. In the illustrated example, the electrode foils are etched foils. Examples of this etching treatment include electrochemical etching, such as passing a current through an electrode sheet material in a chloride aqueous solution. Furthermore, the electrode foil (anode foil 11 and cathode foil 13) having a finely textured surface may be a sintered body of a powder of a metal, such as aluminum or an aluminum alloy, formed on the surface of a core material. In this case, the purity of the metal (aluminum) in the powder is preferably 99.8% by weight or higher. Furthermore, the average particle diameter of the powder is preferably 1 μm or greater. If the average particle diameter is less than 1 μm, the desired withstand voltage may not be achieved. Furthermore, the average particle diameter is preferably 80 μm or less. If the average particle diameter is greater than 80 μm, the desired capacitance may not be achieved. The average particle diameter can be measured using a laser diffraction particle size measurement method based on ISO 13320, regardless of the shape of the filler. In any case, by providing a fine uneven surface structure, it is possible to increase the surface area of ​​the electrode without increasing the size (area) of the temperature sensor 10, thereby increasing the capacitance C. Note that the fine uneven surface structure preferably has a surface roughness (arithmetic mean roughness Ra) in the range of 0.1 μm to 1000 μm, and more preferably in the range of 1 μm to 100 μm.

[0025] The electrodes (first electrode 11 and second electrode 13) preferably have a thickness in the range of 150 μm to 15 μm. If the electrodes are thicker than this range, the entire temperature sensor is likely to become thick. If the electrodes are thinner than this range, it becomes difficult to form a fine surface unevenness structure, which tends to reduce the capacitance and the strength required for joining with the terminals, making structural defects and performance problems more likely to occur. In this specification, the notation "A - B" (A and B are numbers or symbols) is used to indicate a range between A and B. The notation "[C]" (C is a unit) is used to indicate a unit separately from the number preceding it.

[0026] It is preferable to form a chemical conversion film (oxide film) on the surface of the anode foil 11 as the insulating layer by performing a chemical conversion treatment. For example, a dielectric oxide film with voltage resistance is formed by a predetermined anodizing treatment. The chemical conversion voltage for the chemical conversion treatment is preferably set within the range of 1 V to 6 V. A chemical conversion film (oxide film) may also be formed on the cathode foil 13, but only a natural film may be used.

[0027] The electrode foils (anode foil 11 and cathode foil 13) preferably have a thickness within the range of 15 μm to 150 μm. If the thickness is greater than this range, the temperature sensor 10 as a whole becomes too thick, and the flexibility of the temperature sensor 10 itself decreases. If the thickness is less than this range, the etching process for forming the fine surface unevenness becomes difficult, resulting in a decrease in capacitance, a decrease in temperature sensitivity, and a decrease in the foil strength required for joining to the terminals or for use in a manner that takes advantage of the flexibility of the temperature sensor 10.

[0028] The separator 12 is not particularly limited, and may be a woven fabric, nonwoven fabric, sheet, film, or the like made from natural fibers, such as cellulose materials, such as Manila hemp or plant pulp, which are processed through processes such as dust removal, washing, beating, and papermaking. Woven fabric, nonwoven fabric, sheet, film, or the like made from synthetic fibers, such as rayon, nylon, polyester, polyvinyl compound, aramid, acrylic, and polyurethane, may also be used. Blends and mixed spinning products of natural and synthetic fibers may also be used. The element unit 10S does not necessarily require the separator 12 as long as the structure allows for the placement of an electrolyte solution (described later) between the anode foil 11 and the cathode foil 13. However, the separator 12 is used, and the separator 12 prevents contact (electrical short circuit) between the anode foil 11 and the cathode foil 13, allowing for stable production of the sheet-shaped temperature sensor 10. Furthermore, by maintaining the electrolyte in an impregnated state, a sufficient amount of electrolyte can be secured to counter the evaporation of the electrolyte over time.

[0029] The separator 12 preferably has a thickness within the range of 10 μm to 90 μm. If the thickness exceeds this range, the temperature sensor 10 will become too thick, while if the thickness is below this range, there is a risk of a decrease in insulation properties and a decrease in the amount of electrolyte retained. Furthermore, the separator preferably has an affinity that allows it to be impregnated with the electrolyte. For example, examples of the separator include cellulose fibers with hydroxyl groups if the electrolyte solvent is a polar solvent, and polypropylene if the electrolyte solvent is a non-polar solvent.

[0030] The electrolyte solution 12L contains at least an electrolyte and a solvent. The additives described below may be added to the electrolyte solution 12L. The solvent for dissolving the electrolyte and additives may be an organic solvent alone, or a water-organic solvent, i.e., a mixture of an organic solvent and water. As described below, the electrolyte solution 12L can be made of various materials, either alone or in combination. This offers the advantage that the composition can be tailored to the characteristics required for the temperature sensor 10, such as the temperature range and sensitivity required. Furthermore, the liquid nature of the electrolyte solution 12L offers the manufacturing advantage of being easily prepared by blending or other methods to meet the above-mentioned requirements. The fluidity of the electrolyte solution 12L also facilitates uniformity across the entire planar area, thereby enhancing the detection sensitivity and stability of the temperature sensor 10.

[0031] As the organic solvent, protic solvents or aprotic solvents can be used alone or in combination of two or more. If necessary, one or more protic solvents and one or more aprotic solvents can be used in any combination. Suitable protic solvents include, for example, alcohol compounds. Specific examples of alcohol compounds that can be advantageously used include, but are not limited to, monohydric alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, and butyl alcohol; dihydric alcohols (glycols) such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, 1,4-butanediol, and 1,3-butanediol; trihydric alcohols such as glycerin; and derivatives thereof. Suitable aprotic solvents include, but are not limited to, lactone compounds such as arbutyrolactone, arvalerolactone, and S-valerolactone, sulfolane, methylsulfolane, dimethylsulfolane, propylene carbonate, ethylene carbonate, isobutylene carbonate, methylpyrrolidone, imidazolidinone, pyrrolidine, pyrrolidinone, methylpyrrolidinone, tetrahydrofuran, acetonitrile, N-methylformamide, N,N-dimethylformamide, nitrobenzene, derivatives thereof, and other intramolecularly polarizable compounds, as listed below.

[0032] In the electrolyte according to this embodiment, instead of using an organic solvent alone as described above, a water-organic solvent can also be used. By using such a water-organic solvent, the freezing point of the solvent can be lowered. As a result, temperature measurement at low temperatures is also possible. To explain this in more detail, take the case where ethylene glycol is used as the organic solvent as an example. This protic organic solvent has a boiling point of +198°C and a melting point of approximately −13°C. Since the temperature range required for the temperature sensor 10 is generally −20°C to +120°C, an electrolyte using this solvent has sufficient performance at high temperatures, but at low temperatures, the measurement accuracy may be reduced due to increased viscosity and freezing of the electrolyte.

[0033] Therefore, the electrolyte according to this embodiment uses an organic solvent with excellent temperature characteristics, either alone or in combination with multiple types. When using an organic solvent with a relatively high freezing point, adding water to create a water-organic solvent system lowers the freezing point of the solvent, ensuring measurement functionality at low temperatures. Therefore, a temperature sensor 10 using such an electrolyte naturally exhibits excellent temperature characteristics at low temperatures, reflecting the characteristics of the electrolyte. The amount of water added to the water-organic solvent system is preferably in the range of 0.1% by mass to 20% by mass of the total mass of the electrolyte. This not only achieves the excellent oxide film repair characteristics described above, but also allows water molecules to be utilized to repair the oxide film on the electrode foil, demonstrating relatively excellent oxide film repair characteristics. Such various solvent combinations significantly expand the adjustable range of the temperature characteristics of the temperature sensor 10, contributing to the design of temperature sensors suited to various situations. However, adding more than 20% by mass of water increases the vapor pressure of water, which raises the risk of the temperature sensor swelling at high temperatures.

[0034] The electrolyte used is an organic acid, preferably a carboxylic acid or its salt, a boron complex of a dicarboxylic acid or a hydroxycarboxylic acid or its salt, and an inorganic acid or its salt. These electrolyte components may be used alone, or two or more electrolyte components may be used in any combination. The use of an inorganic acid or its salt in combination with a carboxylic acid or its salt, a boron complex of a dicarboxylic acid or a hydroxycarboxylic acid or its salt as the electrolyte component is expected to lower the freezing point of the electrolyte, thereby contributing to further improvement of the low-temperature properties of the electrolyte.

[0035] Examples of carboxylic acids that can be used as electrolyte components include, but are not limited to, monocarboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, p-nitrobenzoic acid, salicylic acid, benzoic acid, methylbenzoic acid, ethylbenzoic acid, isobutylbenzoic acid, sec-butylbenzoic acid, and tert-butylbenzoic acid, as well as derivatives thereof, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, fumaric acid, maleic acid, phthalic acid, azelaic acid, and sebacic acid. Examples of suitable dicarboxylic acids include dicarboxylic acids and derivatives thereof, such as carboxylic acid, caprylic acid, 1,6-decanedicarboxylic acid, 5,6-decanedicarboxylic acid, methyl adipic acid, ethyl adipic acid, isobutyl adipic acid, sec-butyl adipic acid, tert-butyl adipic acid, 2-methylnonanedioic acid, 3-tert-butylhexanedioic acid, brassylic acid, octadecenedioic acid, 12-vinyl-8-octadecenedioic acid, and dimethyloctadecadienetetracarboxylic acid. Carboxylic acids containing hydroxyl groups, such as citric acid, can also be used.

[0036] Furthermore, the dicarboxylic acid or hydroxycarboxylic acid in the boron complex of a dicarboxylic acid or hydroxycarboxylic acid that can also be used as an electrolyte component is not limited to those listed below, but examples include borodicarboxylic acid, borodimalonic acid, borodisuccinic acid, borodiadipic acid, borodimaleic acid, borodiglycolic acid, borodilactic acid, borodimalic acid, boroditartaric acid, borodicitric acid, borodisalicylic acid, borodiphthalic acid, borodi(2-hydroxy)isobutyric acid, borodimandelic acid, and borodi(3-hydroxy)propionic acid.

[0037] Furthermore, examples of inorganic acids that can also be used as electrolyte components include, but are not limited to, phosphoric acid, phosphorous acid, phosphonic acid, hypophosphorous acid, phosphinic acid, alkylphosphoric acid, phosphomolybdic acid, boric acid, sulfamic acid, etc. Furthermore, derivatives of such inorganic acids may also be used if necessary.

[0038] Furthermore, various commonly known salts can be used as the salts of the above-mentioned carboxylic acids or inorganic acids. Examples of suitable salts include, but are not limited to, sodium salts, potassium salts, ammonium salts, alkylammonium salts, and one or more selected from the following amine salts and amidine salts. Examples of amine salts that can be used include salts of primary amines, secondary amines, and tertiary amines, such as methylamine, ethylamine, dimethylamine, diethylamine, trimethylamine, triethylamine, ethyldimethylamine, diethylmethylamine, methanolamine, ethanolamine, dimethanolamine, diethanolamine, trimethanolamine, triethanolamine, pyrrolidine, piperidine, piperazine, morpholine, methylmorpholine, ethylmorpholine, oxazolidine, thiomorpholine, thiazolidinemorpholine, methylmorpholine, ethylmorpholine, oxazolidine, thiomorpholine, and thiazolidine. Examples of amidine salts include 1,3-dimethylimidazolinium, 1,3-diethylimidazolinium, 1,2,3-trimethylimidazolinium, 1,2,3,4-tetramethylimidazolinium, 1,3-dimethyl-2-ethylimidazolinium, 1,2-dimethyl-3-ethylimidazolinium, 1,2-dimethyl-3-ethylimidazolinium, 1,2,3-triethylimidazolinium, and 1,2,3,4-tetraethylimidazolinium. Further examples include tetraalkylammonium salts and imidazolium salts.

[0039] Furthermore, using an inorganic acid or its salt as an electrolyte component can be expected to lower the freezing point of the electrolyte, contributing to improved low-temperature characteristics of the electrolyte. Furthermore, combining an electrolyte component such as an inorganic acid or its salt with an electrolyte component such as a carboxylic acid or its salt significantly extends the life of the temperature sensor 10 compared to using a carboxylic acid or its salt alone. The amount of electrolyte contained in the electrolyte according to this embodiment can be appropriately determined depending on the required properties of the electrolyte, the type of solvent used, the type of electrolyte used, and other conditions. Generally, when using a carboxylic acid or its salt as the electrolyte, the amount should be approximately 0.5% by mass to 30% by mass of the total mass of the electrolyte. If the amount of such electrolyte is less than 0.5% by mass, the desired conductivity cannot be sufficiently achieved, while if the amount exceeds 30% by mass, the effect saturates and the electrolyte becomes less soluble in the solvent.

[0040] Generally, when an inorganic acid or its salt is used as the electrolyte, its amount should be approximately 0.1% to 15% by mass of the total mass of the electrolyte. If the amount of the electrolyte is less than 0.1% by mass, it becomes difficult to achieve the desired conductivity. If the amount exceeds 15% by mass, the conductivity gradually saturates and the electrolyte becomes less soluble in the solvent. Even when a carboxylic acid or its salt and an inorganic acid or its salt are used in combination, they can be used within a range of approximately 0.1% to 15% by mass of the total mass of the electrolyte. However, as mentioned above, the amount of electrolyte can be determined appropriately depending on the characteristics required of the electrolyte, the type of electrolyte used, and other conditions. For example, phosphorus oxyacids (phosphoric acid, phosphorous acid, hypophosphorous acid, etc.) inhibit the hydration reaction of the electrode foil, thereby extending the life of the temperature sensor 10. This effect is achieved when the phosphorus oxyacid or its salt is present in an amount of at least 0.01% by mass of the total mass of the electrolyte. Therefore, the desired conductivity and characteristics can be achieved by combining multiple electrolyte components as needed and adjusting the amount of each electrolyte component. Furthermore, additives such as (1) chelate compounds, (2) sugars, (3) gluconic acid and / or gluconolactone, (4) nitro compounds, (5) polymer compounds, and (6) phosphate esters are preferably added to the electrolyte solution according to this embodiment as needed. These additives may be used alone or in any combination of two or more. Each additive will be described below.

[0041] (1) Chelate compounds Examples of chelating compounds that can be used include ethylenediaminetetraacetic acid (EDTA), trans-1,2-diaminocyclohexane-N,N,N',N',N'-tetraacetic acid monohydrate (CyDTA), dihydroxyethylglycine (DHEG), ethylenediaminetetrakis(methylenephosphonic acid) (EDTPO), diethylenetriamine-N,N,N',N'',N''-pentaacetic acid (DTPA), diaminopropanoltetraacetic acid (DPTA-OH), ethylenediaminediacetic acid (EDDA), ethylenediamine-N,N<-bis(methylenephosphonic acid) hemihydrate (EDDPO), glycol ether diaminetetraacetic acid (GEDTA), and hydroxyethylethylenediaminetriacetic acid (EDTA-OH). The chelating compound is generally added in an amount ranging from 0.01 to 3% by mass of the total mass of the electrolyte. In low impedance capacitors, such chelate compounds can have effects such as extending the life of the temperature sensor 10 by suppressing the hydration reaction of the aluminum (Al) electrode foil, improving the low-temperature characteristics of the temperature sensor 10, and improving corrosion resistance.

[0042] (2) Sugars Examples of sugars include monosaccharides such as glucose, fructose, xylose, galactose, ribose, mannose, arabinose, lyxose, allose, altose, gulose, and isostearyl alcohols, such as erythritol, xylitol, and mannitol; disaccharides such as maltose, sucrose, lactose, cellobiose, sucrose, and agarobiose; trisaccharides such as maltotriose; and polysaccharides such as starch, glycogen, alginic acid, agar, and mannan. Sugars are generally added in a range of 0.01% to 5% by mass of the total mass of the electrolyte. Such sugars can extend the life of the temperature sensor 10 by protecting the electrode foil, inhibit the hydration reaction of aluminum (Al) electrode foil in low-impedance capacitors, and thereby extend the life of the temperature sensor 10. They can also inhibit the degradation of certain electrolyte components (e.g., inhibit the decomposition and activation of carboxylic acids), and improve the low-temperature characteristics of the temperature sensor 10 (the solvent has a composition similar to that of an antifreeze solution, thereby reducing the change in impedance between room temperature and low temperature). When such sugars are used together with boric acid or its derivatives, they form esters, which improve the solubility of the sugars. This allows for the addition of a predetermined amount of sugars and allows them to fully function in the electrolyte. As a result, the temperature sensor 10 can be stabilized and have a sufficiently long life. In this case, boric acid or its derivatives can be added to the electrolyte as an electrolyte component (solute component), or they can be added solely for the purpose of reacting with the sugars. Mannitol, for example, is a suitable sugar to be added together with boric acid or its derivatives. The ratio of boric acid or its derivatives to sugars is preferably in the range of 10:1 to 1:5. If too much sugar is added, it becomes difficult to dissolve it in the solvent.

[0043] (3) gluconic acid and / or gluconolactone The electrolyte solution according to this embodiment may contain gluconic acid and / or gluconolactone, either singly or in combination, as needed. The amount of such additives is generally preferably within the range of 0.01% by mass to 5% by mass of the total mass of the electrolyte solution.

[0044] (4) Nitro compounds The electrolyte solution according to this embodiment may contain, as needed, at least one nitro compound selected from nitrobenzene, nitrophenol (e.g., p-nitrophenol), nitrobenzoic acid (e.g., p-nitrobenzoic acid, dinitrobenzoic acid), nitroacetophenone (e.g., p-nitroacetophenone), nitroanisole, nitrobenzyl alcohol, nitroxylene, and other aromatic nitro compounds.

[0045] In the electrolyte according to this embodiment, when a nitro compound such as the one described above is used, it is effective in absorbing hydrogen gas generated in the electrode foil. Furthermore, a more favorable effect can be expected by using a mixture of two or more nitro compounds rather than using a single nitro compound. Furthermore, the nitro compound is typically added in an amount ranging from 0.01 to 5 mass% of the total mass of the electrolyte. If the amount of nitro compound added is less than 0.01 mass%, the desired effect is hardly obtained. Conversely, if the amount exceeds 5 mass%, further improvement in the desired effect cannot be expected, and in some cases, adverse effects on other properties may occur.

[0046] Regarding the use of nitro compounds, the absorption of hydrogen gas generated during the reaction of aluminum with water tends to decrease as the water content in the solvent increases. This tendency for the absorption effect to decrease becomes more pronounced when the electrolyte is placed in a high-temperature environment. However, the problems caused by the use of a nitro compound alone can be solved by combining two or more nitro compounds.

[0047] (5) Polymer compounds Examples of polymer compounds that can be used include water-soluble silicones, polyacrylic acid and its derivatives, polymethacrylic acid and its derivatives, polyacrylamide and its derivatives, polyglutamic acid and its derivatives, polyglycerin and its derivatives, polyethylene glycol and its derivatives, polypropylene glycol and its derivatives, polyvinyl alcohol and its derivatives, polyoxyethylene glycol and its derivatives, polyoxyalkylene compounds, polysiloxanes, and silicon dioxide. These compounds may be used alone or in any combination of two or more. The total amount of these compounds added is preferably in the range of 0.1% by mass to 30% by mass of the total mass of the electrolyte solution. Such polymer compounds can provide effects according to the function of each polymer compound, such as improving the voltage resistance characteristics of the temperature sensor 10 and extending its lifespan. The molecular weight of the polymer compound can range from relatively low molecular weight (oligomers) to high molecular weights, depending on the function of each polymer compound, its solubility and dispersibility in solvents, and the desired effect.

[0048] (6) Phosphate ester Examples of phosphate esters that can be used include methyl phosphate ester, ethyl phosphate ester, dimethyl phosphate ester, diethyl phosphate ester, trimethyl phosphate ester, triethyl phosphate ester, etc. Similar to chelate compounds, these phosphate esters suppress the hydration reaction of the electrode foil, thereby suppressing deterioration of the electrode foil and suppressing hydrogen gas generation, thereby extending the life of the temperature sensor 10.

[0049] Furthermore, the electrolytic solution according to the present embodiment may further contain additives commonly used in the field of aluminum electrolytic capacitors and other electrolytic capacitors, in addition to the additives described above. Suitable additives include, for example, silane coupling agents, polymer electrolytes, and colloidal silica.

[0050] As described above, the electrolyte solution according to this embodiment can use electrolytes and solvents composed of various single materials or mixtures of multiple materials. This has the advantage that the temperature coefficient of the electrolyte solution's electrical resistance (impedance) can be adjusted to meet various requirements. However, in this embodiment, the electrolyte solution 12L that constitutes the element unit 10S of the temperature sensor 10 is the electrolyte solution 12L. The characteristics of the electrolyte solution 12L have a significant impact on the equivalent series resistance (ESR) included in the equivalent circuit of the element unit 10S. Therefore, from the perspective of improving the sensitivity and accuracy of temperature detection, it is important that the temperature coefficient of the electrolyte solution 12L, which is the main component of the equivalent series resistance, is large, i.e., that the specific resistance changes significantly with temperature. To achieve this, it is preferable that the solvent for the electrolyte solution 12L also has a large temperature coefficient. Examples of such solvents include glycerin, ethylene glycol, polyethylene glycol, or a mixture of these. Here, the temperature coefficients of the equivalent series resistance and the specific resistance of the electrolyte solution 12L (specifically, the temperature coefficient of viscosity for the electrolyte solution 12L) are negative. The electrolyte solution according to this embodiment also includes a sol or gel formed by adding a polymer compound to any electrolyte solution. Here, by using a sol or gel electrolyte, there is an advantage in that the risk of leakage can be reduced.

[0051] The aforementioned glycerin, ethylene glycol, polyethylene glycol, or mixtures thereof have high viscosities in the detection temperature range (room temperature range), which is thought to increase the absolute value of the negative temperature coefficient of viscosity and therefore the absolute value of the temperature coefficient of resistivity. Here, the viscosity of the electrolyte (solvent) is preferably within the range of 10 mPa·s to 5000 mPa·s in the detection temperature range or at room temperature (e.g., 5°C to 35°C). A viscosity below 10 mPa·s will not provide a sufficient rate of change in resistivity, while a viscosity above 5000 mPa·s will deteriorate the impregnation and contact of the electrolyte during the manufacturing of the element unit 10S. As mentioned above, a viscosity within the above range in the detection temperature range ensures high sensitivity and accuracy throughout the entire detection temperature range. Furthermore, a viscosity within the above range at room temperature enables temperature detection with practical sensitivity and accuracy across a wide range of detection temperatures, centered around room temperature. The viscosity values ​​indicated in this specification are measured by a measurement method based on JIS Z 8803:2011.

[0052] As mentioned above, adding water to the solvent can change the effective detection temperature range. However, adding too much water reduces the absolute value of the temperature coefficient of resistivity (specifically, the temperature coefficient of viscosity). Therefore, from the perspective of improving the sensitivity and accuracy of temperature detection, when the detection range is room temperature (e.g., 5°C to 35°C), the amount of water added to the water-organic solvent is preferably in the range of 0.1% by mass to 3% by mass of the total mass of the electrolyte. On the other hand, at low temperatures, such as -20°C or below, water exhibits a large change in resistivity, so it is desirable to use a solvent with a high water content. In addition to the above considerations, a solvent with a low vapor pressure is preferable. This is because it can suppress swelling at high temperatures and prevent solvent leakage, thereby extending the life of the temperature sensor 10.

[0053] The anode foil (first electrode) 11 is conductively connected to the first terminal 14 by welding or the like. The cathode foil (second electrode) 13 is conductively connected to the second terminal 15 by welding or the like. The terminals (first terminal 14, second terminal 15) are not particularly limited as long as they are made of a conductive material, but are preferably made of a metal that does not react with the electrolyte. Furthermore, to avoid corrosion due to contact between dissimilar metals, it is desirable that they are made of the same material as the electrode foils (anode foil 11 and cathode foil 13). The terminals (first terminal 14, second terminal 15) may be lead-type terminals that are drawn out or protrude from the housing as shown in the figure, or may be surface-mounted terminals with terminal surfaces along the surface.

[0054] The element unit 10S is sealed (hermetically sealed) while covered with exterior films 16 and 17. The exterior films 16 and 17 are not particularly limited as long as they constitute a housing that houses the functional structural components of the element unit 10S. However, it is preferable that the exterior and interior surfaces are insulating. Furthermore, it is preferable that the interior surfaces of the exterior films 16 and 17 are non-reactive with the electrolyte solution. Furthermore, it is preferable that the interior surfaces are capable of sealing the electrolyte solution. In the illustrated example, both the exterior and interior surfaces are made of insulating materials. For example, the interior surfaces are made of an insulating film layer, such as polypropylene, that is non-reactive with the electrolyte solution (has good chemical resistance). In the illustrated example, the interior surfaces are sealed together by heat welding. In this case, the exterior surfaces are made of an insulating film layer, such as nylon, that has a high melting point and is heat resistant to the welding process of the interior surfaces. Furthermore, electromagnetic shielding properties can be achieved by placing a conductive film layer, such as aluminum foil, between these insulating film layers. Furthermore, the risk of solvent loss in the electrolyte solution can be reduced by interposing a gas-impermeable film layer, such as aluminum foil.

[0055] As shown in FIG. 2, the exterior films 16 and 17 have a laminated film structure in which three layers are laminated together using an adhesive or the like: an insulating outer film layer, a conductive and / or gas-impermeable intermediate film layer, and an insulating inner film layer. Specifically, the outer film layer is made of nylon, the intermediate film layer is made of aluminum or an aluminum alloy, and the inner film layer is made of polypropylene. If the inner film layer is weldable, as in this example, the exterior films 16 and 17 can be overlapped and heat-sealed to seal the element section 10S with welded regions 16m and 17m, as shown in FIGS. 3 and 4. Furthermore, as shown by the dashed-dotted lines in FIG. 4, by interposing separate welded films (such as polypropylene) 14p and 15p between the terminals (first terminal 14 and second terminal 15) and the exterior films 16 and 17 (on both sides), a more reliable seal can be achieved.

[0056] FIG. 5 is an explanatory diagram schematically illustrating the cross-sectional structure of the element unit 10S. Fine surface irregularities 11s, 13s are formed on the surfaces of the electrode foils 11, 13 by etching, and the surface layers of these fine surface irregularities form insulating layers (oxide films) 11t, 13t, such as passive films. The insulating layers 11t have a thickness corresponding to the chemical conversion voltage formed by the chemical conversion treatment, and are formed so that the element unit 10S can withstand a predetermined voltage. As described above, in this embodiment, the chemical conversion voltage is generally preferably 1 V to 6 V. In this case, the predetermined withstand voltage is ensured by setting the chemical conversion voltage to a value equal to or greater than the maximum voltage (e.g., 5 V) applied to the element unit 10S by a temperature detection circuit (described later). On the other hand, the insulating layer 13t is typically composed of a natural oxide film that naturally forms on the surface of a valve metal such as aluminum. However, the insulating layer 13t may also be formed by the same chemical conversion treatment described above.

[0057] The element unit 10S described above may be arranged such that the electrolyte solution 12L is in contact with a pair of film-like electrodes 11 and 13, each having an insulating layer 11t, 13t formed on at least one of the surface layers. Therefore, a laminate structure formed in this order of the first electrode 11, the electrolyte solution 12L, and the second electrode 13 may be repeatedly laminated. For example, a structure may be exemplified in which the first electrode 11, the electrolyte solution 12L, the second electrode 13, the electrolyte solution 12L, the first electrode 11, the electrolyte solution 12L, the second electrode 13, and so on are repeatedly laminated. Furthermore, a plurality of the above-described laminate structures, each consisting of a laminate unit consisting of the first electrode 11, the electrolyte solution 12L, and the second electrode 13, or each consisting of a plurality of repeated laminate units, may be laminated in parallel with each other in an electrically connected structure.

[0058] FIG. 6 is a simplified equivalent circuit diagram of the element unit 10S of the temperature sensor 10 of this embodiment. The element unit 10S has a circuit structure in which a capacitance C, an equivalent series resistance (ESR) Rs, and an equivalent series inductance (ESL) Ls are connected in series between the first terminal 14 and the second terminal 15. Note that an insulation resistance Ri may be assumed to be connected in parallel with the capacitance C. The capacitance C typically correlates with temperature, specifically, has a positive correlation with temperature (positive temperature coefficient). FIG. 7 shows the temperature dependence of the capacitance C. Here, multiple vertically arranged graphs represent capacitance values ​​measured at frequencies [kHz] indicated by indicators arranged vertically on the right. The capacitance C has a positive temperature coefficient at any frequency within the illustrated range. As the measurement frequency increases, the temperature dependence of capacitance C gradually expands from a state in which it has a large temperature coefficient in the low temperature range (e.g., −20°C to +5°C) to a region with a large temperature coefficient in the high temperature range, eventually resulting in a larger temperature coefficient in the high temperature range (e.g., 0°C to +60°C). The temperature sensor 10 of this embodiment, employing a structure including an insulating layer 11t and an electrolyte 12L, exhibits a larger frequency change characteristic than the conventional temperature sensor using a resin film or the like as a temperature sensor. Therefore, in order to improve sensitivity and accuracy, it is desirable to perform measurements in the DC or low-frequency range, where the effect of frequency on the detected value is minimal. In this embodiment, as shown in FIG. 7, capacitance C exhibits a positive temperature coefficient in the range of −20°C to +60°C. However, if a temperature detection range is specified, capacitance C preferably exhibits a positive temperature coefficient within the temperature detection range, or preferably exhibits a positive temperature coefficient within the room temperature range (5°C to 35°C).

[0059] In the temperature sensor 10 of this embodiment, the equivalent series resistance Rs is primarily composed of the electrical resistance of the electrolyte 12L, which typically correlates with temperature and, more specifically, has a negative temperature coefficient. The temperature dependence of the equivalent series resistance Rs is shown in Figure 8. The vertically arranged graphs represent resistance values ​​measured at frequencies [kHz] indicated by the indicators arranged vertically on the right. Each graph demonstrates a large negative temperature coefficient. Figure 9 compares the temperature dependence of the equivalent series resistance Rs of the temperature sensor 10 of this embodiment with that of a conventional high-sensitivity thermistor using a semiconductor. As can be seen from Figure 9, the temperature dependence of the equivalent series resistance Rs of the temperature sensor 10 of this embodiment is greater than that of the high-sensitivity thermistor. In this embodiment, as shown in FIG. 8, the equivalent series resistance Rs exhibits a negative temperature coefficient within the range of −20°C to +60°C. However, if a temperature detection range is set, it is preferable that the equivalent series resistance Rs exhibits a negative temperature coefficient within the temperature detection range, or that the equivalent series resistance Rs exhibits a negative temperature coefficient within the normal temperature range (5°C to 35°C).

[0060] The data shown in FIGS. 7, 8, and 9 were measured using a temperature sensor 10 as a specific example of this embodiment, in which etched aluminum foils having length and width planar dimensions of 12 mm × 25 mm were used as the anode foil 11 and the cathode foil 13, a separator 12 made of cellulose fiber and having a thickness of 70 μm, and an electrolyte solution in which 2 mass % of ammonium adipate was dissolved in glycerin.

[0061] FIG. 10 shows a temperature detection circuit 10CT1 of a first example using the temperature sensor 10 of this embodiment. In this temperature detection circuit, the equivalent series inductance Ls can be ignored by increasing the opening and closing cycles of switches SW1 and SW2 and lowering the measurement frequency. Therefore, the equivalent circuit of the element unit 10S is regarded as an RC circuit with equivalent series resistance Rs and capacitance C. In this temperature detection circuit 10CT1, during the charging period when switch SW1 is ON (closed) and switch SW2 is OFF (open), capacitance C is charged by power source E through charging resistance Rc and equivalent series resistance Rs. In contrast, during the discharging period when switch SW1 is OFF (open) and switch SW2 is ON (closed), capacitance C is discharged through discharge resistance Rd and equivalent series resistance Rs. In this example of the temperature detection circuit 10CT1, during the charging period, capacitance C is charged through equivalent series resistance Rs, with the charging current limited by charging resistance Rc. During the discharge period, the capacitance C is discharged through the equivalent series resistance Rs with the discharge current limited by the discharge resistor Rd.

[0062] In this temperature detection circuit 10CT1, the electromagnetic state of the equivalent circuit (equivalent series resistance Rs and capacitance C) changes over time during both the charging and discharging periods. The nature of this change over time is determined by the circuit constants Rs, Rc, Rd, and C. The temperature dependence of this change over time is determined by the temperature dependence of equivalent series resistance Rs and capacitance C. Here, the power supply E, switches SW1 and SW2, the part containing resistors Rc and Rd, and the ground part constitute a charge supply / neutralization unit CTA that charges or discharges the RC circuit (equivalent circuit) via charging resistor Rc or discharging resistor Rd, supplying or removing charge to the equivalent circuit. Meanwhile, the detection unit CTB measures the voltage across both ends of the element unit 10S (equivalent circuit). In this case, the manner of change in the voltage and current values, or their rate of change (differential values), during the charging and discharging periods reflects the temperature dependence of the equivalent series resistance Rs and capacitance C, which are dependent on the temperature characteristics. That is, the temperature characteristics of the equivalent series resistance Rs and capacitance C affect the manner in which the electromagnetic state of an RC circuit changes over time. For example, if the charge resistance Rc and discharge resistance Rd are sufficiently larger than the equivalent series resistance Rs, the voltage change will be similar to that shown in the graph in Figure 11. In this case, if the voltage value after a certain time τ from the start of the charging period reflects the manner in which the electromagnetic state changes over time due to temperature changes, then the temperature corresponding to the capacitance C and equivalent series resistance Rs can be determined by detecting that voltage value. Here, the certain time τ is a predetermined time that is shorter than the charge time or discharge time.

[0063] The voltage e applied to the capacitance C of the element unit 10S after the time t from the start of charging in the charging period in the temperature detection circuit 10CT1 of FIG. ? (t) is expressed as the following equation (1). e ? (t)=E {1-exp[-t / (C(Rc+Rs))]}…(1) In addition, the current i(t) after time t is i(t)={E / (Rc+Rs)}·exp[-t / (C(Rc+Rs))], so the voltage e applied to the equivalent series resistance Rs of the element part 10S is RS (t) is expressed as the following equation (2). e Rs(t)={(E·Rs) / (Rc+Rs)}·exp[-t / (C(Rc+Rs))]…(2) Therefore, the voltage value Vd (detection voltage) applied to the element portion 10S is given by the following equation (3). Vd=e C (t)+e Rs (t)…(3)

[0064] Based on the above relationship, the detected value Vd (= initial value Vds) at t = 0 in equation (3) is generally E·{Rs / (Rc+Rs)}. Since the equivalent series resistance Rs has a negative temperature coefficient, the lower the temperature, the larger the initial value Vds, and the higher the temperature, the smaller the initial value Vds. Figure 12 shows the results of a simulation of the detected value Vd during the charging period for the temperature detection circuit 10CT1, assuming that the charging resistance Rc is not significantly different from the equivalent series resistance Rs shown in Figure 7 (e.g., the difference between the two resistances is approximately one digit). The simulation assumes Rc = 500 Ω, and the equivalent series resistance Rs and capacitance C values ​​at 0.06 kHz (60 Hz) shown in Figures 7 and 8 are used for temperatures of 0°C, 20°C, 40°C, and 60°C. Here, E = 5 V. In this way, the initial value Vds changes with temperature due to the negative temperature coefficient of the equivalent series resistance Rs, and the manner in which the detected value Vd subsequently changes over time is such that the detected value Vd is obtained at a detection time ts earlier than the end of the charging period (preferably a time closer to the time t=0 of the initial value Vds than the end time; in the illustrated example, for example, ts=10 μs), and the temperature corresponding to the equivalent series resistance Rs and capacitance C at that time can be derived from the detected value Vd. In particular, by making ts<< the charging period, the detected value Vd can be considered to be the initial value Vds, making it possible to find the value of the equivalent series resistance Rs from the detected value Vd and derive the temperature from this value of the equivalent series resistance Rs.

[0065] Here, according to the above equations (1)-(3), as the equivalent series resistance Rs increases, the voltage value Vd at a certain time t in the initial stage (t < C(Rc + Rs)) (for example, the detection time point ts) increases. As the capacitance C increases, the voltage value Vd at a certain initial time t (for example, the detection time point ts) decreases. Therefore, considering the characteristics of FIGS. 7 and 8, as the temperature increases, the equivalent series resistance Rs with a negative temperature coefficient decreases, and the capacitance C with a positive temperature coefficient increases. So, from any perspective, the detection value Vdt, which is the voltage value detected at the detection time point ts earlier than the end point of the charging period, decreases. The detection value Vdt reflects the temporal change pattern of the electromagnetic state of the equivalent circuit and is determined by the temperature coefficients of the equivalent series resistance Rs and the capacitance C. Therefore, it becomes possible to derive the temperature from the detection value Vdt. At this time, for the detection value Vdt that reflects the temperature dependence of the temporal change of the electromagnetic state, both the positive temperature coefficient of the capacitance C and the negative temperature coefficient of the equivalent series resistance Rs act in the same direction (that is, both in the direction of increasing the detection value or both in the direction of decreasing the detection value) on the temperature detection sensitivity (detection value Vdt) of the detection value Vd, or at least do not interfere with each other (that is, when one acts in either the direction of increasing or decreasing the detection value, the other does not interfere with its action). Therefore, high-sensitivity and high-precision temperature detection become possible. Note that the above explanation was about the temporal change pattern of the electromagnetic state during the charging period, but the same applies to the temporal change pattern of the electromagnetic state during the discharging period. No matter which detection value reflecting the temporal change pattern of the electromagnetic state is output, it is similarly possible to detect the temperature, and their effects are also common. This point is the same for the following Second Embodiment.

[0066] As shown in FIG. 7, when the measurement frequency is low or when measurement is considered to be DC, as in this embodiment, the temperature dependence of capacitance C is not necessarily large. Therefore, the temperature dependence of equivalent series resistance Rs may actually determine the temperature detection sensitivity. However, in either case, the temperature dependence of capacitance C may enhance the temperature detection sensitivity due to the temperature dependence of equivalent series resistance Rs, but it does not interfere with the temperature detection sensitivity due to the temperature dependence of equivalent series resistance Rs. Furthermore, as in this embodiment, the structure including the thin insulating layer 11t formed on the fine surface unevenness structure and the electrolyte 12L in contact with this insulating layer 11t allows for a large capacitance C. Therefore, by increasing capacitance C, the effect on the detection sensitivity of the actual detected values ​​Vds and Vdt can be enhanced even if the positive temperature coefficient of capacitance C is small. Furthermore, with this temperature detection method, if capacitance C is small, the voltage value correlated with temperature can only be measured at a very early timing, which may increase the cost of the detection circuit and reduce sensitivity and accuracy. However, in this embodiment, since the capacitance C can be easily manufactured to be large, the temperature can be derived even if the detection time ts is set to a relatively late timing, which reduces the cost of the temperature detection circuit and improves its sensitivity and accuracy.

[0067] In the temperature detection circuit 10CT1 of this embodiment, the charging resistance Rc and the discharging resistance Rd each preferably have resistance values ​​in the range of 0.1 to 10 times the equivalent series resistance Rs. During charging, if the charging resistance Rc is too small relative to the equivalent series resistance Rs, the detected value Vds will be close to E, reducing the temperature dependence of the change in the electromagnetic state over time and thereby reducing the temperature detection sensitivity. Conversely, if the charging resistance Rc is too large relative to the equivalent series resistance Rs, the detected value Vds itself will be small, reducing the temperature dependence of the change in the electromagnetic state over time and thereby reducing the temperature detection sensitivity. During discharging, the initial value (t=0) of the detected value Vds is Vds = E{1-Rs / (Rd+Rs)}. If the discharging resistance Rd is too small relative to the equivalent series resistance Rs, the detected value Vds itself will be close to 0 and thus reducing the temperature dependence of the change in the electromagnetic state over time and thereby reducing the temperature detection sensitivity. Conversely, if the discharge resistance Rd is too large relative to the equivalent series resistance Rs, the detected value Vds will be close to E, which will reduce the temperature dependency of the change in the electromagnetic state over time and reduce the temperature detection sensitivity. The above resistance range is preferably established in the room temperature range (5°C - 35°C) or, if a temperature detection range for the temperature sensor 10 is set, within that temperature detection range.

[0068] Furthermore, simulations using equation (3) above show that during charging, the temperature sensor 10 has the best sensitivity (the rate of change in the detected value Vd relative to the rate of change in Rs) near the temperature where the equivalent series resistance Rs becomes equal to Rc. Similarly, during discharging, the temperature sensor 10 has the best sensitivity (the rate of change in the detected value Vd relative to the rate of change in Rs) near the temperature where the equivalent series resistance Rs becomes equal to Rd. Based on this, it is conceivable to provide multiple charging resistors Rc and discharging resistors Rd with different resistance values ​​in the temperature detection circuit 10CT1 so that they can be switched between each other, or to configure them as adjustable variable resistors. It is desirable to be able to select and use multiple charging resistors Rc or discharging resistors Rd by switching them depending on the installation location and application, or to be able to adjust the resistance values ​​of the charging resistors Rc and discharging resistors Rd. In this case, it is desirable to configure the device so that the resistance value of the charging resistor Rc or the discharging resistor Rd can be switched or adjusted so that it is within the range of 0.1 to 10 times the equivalent series resistance Rs within the normal temperature range of 5°C to 35°C, or within the temperature detection range if a temperature detection range is specified.

[0069] Next, a second embodiment of a temperature detection circuit 10CT2 using the temperature sensor 10 of this embodiment will be described with reference to FIG. 13. In this second embodiment, a power supply Ep, which outputs a clock signal of a predetermined frequency, is connected in parallel to the element unit 10S via a charging resistor R1. A parallel circuit consisting of an equivalent series resistance Rs, a capacitance C, and a diode D1 for preventing backflow of current is connected in series with the diode D1. A capacitor C1 for maintaining a peak voltage Vp and a discharge resistor R2 are connected in series with the diode D1, and the voltage across the parallel circuit is measured. In this temperature detection circuit 10CT2, the charging / discharging unit CTA charges and discharges the capacitance C through the equivalent series resistance Rs. The temperature can be calculated using the detection unit CTB, which outputs a detection value that reflects the temperature dependency of the change in the electromagnetic state of the equivalent circuit over time during charging or discharging. Here, the power supply / neutralization section CTA in this temperature detection circuit 10CT2 corresponds to the circuit parts and ground parts related to the power supply Ep, charging resistor R1, diode D1, capacitor C1, and discharge resistor R2, and the detection section CTB corresponds to the voltage detection part (voltmeter).

[0070] FIG. 14 is a graph showing a voltage waveform of the detection value Vd of the temperature detection circuit 10CT2 of the second embodiment. When a pulse waveform (e.g., a rectangular wave of 0 V and 5 V) is output from the power supply Ep, the capacitance C is charged through the equivalent series resistance Rs in the element unit 10S via the charging resistor R1 in response to the pulse waveform. When the pulse waveform passes, a peak voltage Vp is reached, and then the capacitance C is discharged through the equivalent series resistance Rs in the element unit 10S. The output waveform shown in FIG. 14 repeats a cycle in which the detection value Vd rises as the capacitance C is charged, reaches the peak voltage Vp, and then falls as the capacitance C is discharged. The period of the output waveform corresponds to the period of the pulse waveform of the power supply Ep. The peak voltage Vp of this output waveform is determined by the temperature dependence of the change over time in the electromagnetic state of the equivalent circuit (equivalent series resistance Rs and capacitance C) during the charging or discharging period. That is, the greater the equivalent series resistance Rs, the greater the peak voltage Vp, and the smaller the capacitance C, the greater the peak voltage Vp. Therefore, considering the characteristics shown in Figures 7 and 8, the higher the temperature, the lower the equivalent series resistance Rs and the higher the capacitance C, resulting in a decrease in peak voltage Vp from both perspectives. Therefore, for the peak voltage Vp detected in this manner, the positive temperature coefficient of capacitance C and the negative temperature coefficient of equivalent series resistance Rs both affect the detection sensitivity of the detected value Vp in the same direction, or at least do not interfere with each other. Therefore, detecting the peak voltage Vp enables highly sensitive and accurate temperature detection. In this embodiment, the peak voltage Vp between the charging period and the discharging period is detected to obtain a detection value that reflects the temperature dependency of the change over time.

[0071] At high temperatures, the peak voltage Vp is less likely to increase due to a decrease in the equivalent series resistance Rs, which reduces the voltage effect on the charging current. Furthermore, the capacitance C increases, suppressing the increase in charging voltage relative to the charging current. This results in a lower equivalent circuit voltage Vd. In contrast, at low temperatures, the equivalent series resistance Rs increases, which increases the voltage effect on the charging current. Furthermore, the capacitance C decreases, facilitating the increase in charging voltage relative to the charging current. This results in a higher equivalent circuit voltage Vd. Therefore, when the measured peak voltage Vp is high, the temperature is low, and when the peak voltage Vp is low, the temperature is high. Even in this case, as mentioned above, the negative temperature coefficient of the equivalent series resistance Rs and the positive temperature coefficient of the capacitance C both act in the same direction on the detected peak voltage Vp, or at least do not interfere with each other.

[0072] FIG. 15 shows a schematic diagram of a temperature detection circuit 10CT3 having an automatic balancing bridge circuit used in a method for measuring the electrical resistance of a material with a temperature coefficient. Because the equivalent series resistance Rs of the temperature sensor 10 of this embodiment has a large negative temperature coefficient, as described above, it is possible to detect temperature by directly measuring this equivalent series resistance Rs. However, because the majority of the equivalent series resistance Rs of the temperature sensor 10 is the resistance of the electrolyte 12L, the electrical resistance of the liquid cannot be determined using DC but must be measured using AC. This detection circuit uses the automatic balancing bridge method, in which one of the resistances Ra and Rb in the bridge circuit supplied with power Em from an AC power source is an electrical resistance with a known resistance, and the other is an equivalent series resistance Rs. By changing the ratio of the divided resistances Rac and Rbc of the variable resistor Rc to achieve a state where no current flows through the AC detector D (a balanced state), the equivalent series resistance Rs can be determined from one of the resistances Ra and Rb (an electrical resistance with a known resistance) and the divided resistances Rac and Rbc. According to this temperature detection circuit 10CT3 and its temperature detection method, although the cost of the temperature detection circuit increases slightly, the negative temperature coefficient of the equivalent series resistance Rs is large and stable, so that temperature measurement can be performed with high sensitivity, high accuracy, and stability.

[0073] As described above, the temperature sensor 10 of this embodiment includes an electrolyte solution 12L disposed between the anode foil (first electrode) 11 and the cathode foil (second electrode) 13. By contacting at least one of the electrodes 11 with the electrolyte solution 12L via the insulating layer 11t on its surface, the temperature-dependent change rates of the equivalent series resistance Rs and capacitance C can be increased by the effects of the insulating layer 11t and the electrolyte solution 12L compared to the temperature-dependent change rates of a conventional thermosensitive sheet made of a resin film. This improves the temperature detection sensitivity based on changes in electromagnetic properties caused by temperature changes between the first and second electrodes. In particular, the temperature coefficient of resistivity of the electrolyte solution 12L is greater than that of a polymer resin film, thereby improving detection sensitivity. Another advantage is that the composition of the electrolyte solution 12L can be easily adjusted to meet the detection characteristics required of the temperature sensor, and the electrolyte solution can be easily prepared in this adjusted form. Furthermore, the electrolytic capacitor structure in which the electrolyte solution 12L is interposed between the film-like electrodes 11 and 13 allows for inexpensive manufacturing. Furthermore, because the temperature sensor 10 is constructed in a sheet shape, it can easily and uniformly receive heat when it comes into contact with the object to be measured, and therefore, even from the perspective of this installation mode, it is possible to improve the sensitivity and accuracy of temperature detection.

[0074] In this embodiment, the insulating layer 11t is preferably formed on the surface portion having a fine surface unevenness structure. This allows the opposing area between the electrode and the electrolyte to be increased without increasing the area of ​​the temperature sensor, thereby increasing the capacitance of the element portion. This further improves the sensitivity and accuracy of the sensor due to the temperature coefficient of capacitance. Furthermore, since at least one of the electrodes 11, 13 is made of a valve metal and the insulating layer 11t is a passive film formed on the surface portion of the electrode 11, the insulating layer 11t being a passive film of a valve metal can be a thin yet dense insulating film, which facilitates increasing the capacitance while reducing leakage current.

[0075] According to the temperature detection circuits 10CT1 and 10CT2 of this embodiment, or the temperature detection method realized by these temperature detection circuits 10CT1 and 10CT2, a change in the electromagnetic state over time occurs in the equivalent circuit of the element unit 10S of the temperature sensor 10 by charging or discharging the capacitance C through the equivalent series resistance Rs, and the temperature characteristics of the equivalent circuit's equivalent series resistance Rs and capacitance C can be derived by outputting detected values ​​Vds, Vdt, and Vp that reflect the temperature dependence of the change in the electromagnetic state over time in the equivalent circuit due to the temperature characteristics of the equivalent series resistance Rs and capacitance C. In this case, in the temperature sensor 10, the equivalent series resistance Rs has a negative temperature coefficient and the capacitance C has a positive temperature coefficient, and the negative temperature coefficient of the equivalent series resistance Rs and the positive temperature coefficient of the capacitance C both affect the detection sensitivity in the same direction or at least do not interfere with each other, thereby further improving the sensitivity and accuracy of the temperature sensor 10.

[0076] FIG. 16 is an explanatory diagram showing the structure and manufacturing process of a temperature sensor 20 of the second embodiment. As shown in FIG. 16(a), this temperature sensor 20, like the temperature sensor 10 of the first embodiment, includes an element unit 20S containing an insulating layer and an electrolyte between electrodes. The element unit 20S is provided with a (cylindrical) columnar first electrode 21 and a second electrode 23. A first terminal 24 having a lead wire structure such as a CP wire is conductively connected to the outer end surface of the first electrode 21 by welding or the like. An insulating layer is formed on the inner end surface of the first electrode 21, and a fine surface unevenness structure similar to that of the anode foil 11 may be formed. Furthermore, a second terminal 25 similar to the first terminal 24 is conductively connected to the outer end surface of the second electrode 23 by welding or the like. The inner end surface of the second electrode 23 may include an insulating layer, and may also be formed with a fine surface unevenness structure similar to that of the cathode foil 13. An electrolyte solution 22L, similar to that in the first embodiment, is disposed between the inner end surface of the first electrode 21 and the inner end surface of the second electrode 23. This electrolyte solution 22L is preferably held by being impregnated into a separator 22, similar to that in the first embodiment. When a resin coating is applied to the outer peripheral surfaces of the first electrode 21 and the second electrode 23, the adhesion can be improved by heat fusion or pressure bonding between the resin coating layer and the housing 26, which will be described later.

[0077] FIG. 16(b) shows the housing 26 of the temperature sensor 20. This housing 26 has a cylindrical (tube) structure made of metal, resin, or the like. The housing 26 preferably has a thickness sufficient to withstand the internal pressure increase and maintain the physical strength of the element unit 20S of the temperature sensor 20. The housing 26 may be made of a sheet material such as the exterior films 16 and 17 of the first embodiment. The housing 26 is preferably inserted so as to be positioned on the outer periphery of the element unit 20S, and the element unit 20S is preferably sealed by a method such as drawing from the outer periphery or heat sealing with the resin coating. When a metal is used for the housing 26, an insulating layer such as a resin sheet or resin coating must be provided between the first electrode 21 and the housing 26 and between the second electrode 22 and the housing 26.

[0078] It should be noted that the method and apparatus of the present invention are not limited to the above-described illustrated examples, and various modifications can be made without departing from the spirit of the present invention. For example, in the first and second embodiments, the lead-like terminals 14, 15, 24, and 25 are led out from the sealing structure of the housings 16, 17, and 26, but they may be provided with a surface-mounted terminal structure having a terminal surface exposed on the outer surface of the housing. [Explanation of symbols]

[0079] 10, 20...Temperature sensor, 10S, 20S...Element portion, 10CT1, 10CT2, 10CT3...Temperature detection circuit, 11...Anode foil (first electrode), 12, 22...Separator, 12L, 22L...Electrolyte, 13...Cathode foil (second electrode), 14...First terminal, 14p, 15p...Fusing film, 15...Second terminal, 16, 17...Outer film (housing body), 16m, 17m...Fusing area, C...Capacitance, Rs...Equivalent series resistance, 21...First electrode, 23...Second electrode, 26...Housing body

Claims

1. A temperature sensor comprising: a first electrode, a second electrode, an electrolyte disposed between the first electrode and the second electrode, a first terminal conductively connected to the first electrode, a second terminal conductively connected to the second electrode, and a housing that seals an element portion having a layered structure of the first electrode, the second electrode, and the electrolyte in a manner that exposes the first terminal and the second terminal to the outside.

2. a surface of at least one of the first electrode and the second electrode facing the electrolyte solution having a finely textured surface structure; The temperature sensor of claim 1 .

3. an insulating layer is formed on a surface layer portion of at least one of the first electrode and the second electrode on the electrolyte solution side; The temperature sensor of claim 1 .

4. the insulating layer is formed on the surface layer portion having a fine surface unevenness structure; The temperature sensor according to claim 3 .

5. At least one of the electrodes is made of a valve metal, and the insulating layer is a passive film formed on a surface layer of the electrode.

5. The temperature sensor according to claim 3 or 4.

6. The electrolytic solution contains an electrolyte and a solvent, and the solvent has a viscosity in the range of 10 [mPa s] to 5000 [mPa s] within a temperature range of 5 [°C] to 35 [°C]. A temperature sensor according to any one of claims 1 to 4.

7. The container is made of a sheet material in which an insulating film layer and a conductive film layer or a gas-impermeable film layer are laminated. A temperature sensor according to any one of claims 1 to 4.

8. the equivalent circuit of the element unit includes an equivalent series resistance and a capacitance, the equivalent series resistance having a negative temperature coefficient, and the capacitance having a positive temperature coefficient; A temperature sensor according to any one of claims 1 to 4.

9. In the normal temperature range of 5°C to 35°C, or in a specified temperature detection range, the product of the equivalent series resistance Rs [Ω] and the capacitance C [μF] is 10 or more. The temperature sensor according to claim 8.

10. A temperature detection circuit is conductively connected to a temperature sensor having an element part that forms an equivalent circuit including an equivalent series resistance and an electrostatic capacitance between a first terminal and a second terminal, and outputs a detection value for detecting an environmental temperature of the temperature sensor, a charge supply / neutralization unit that causes a change in an electromagnetic state over time in the equivalent circuit by charging or discharging the capacitance through the equivalent series resistance; a detection unit that outputs a detection value that reflects the temperature dependency of the change over time in the electromagnetic state in the equivalent circuit caused by the temperature characteristics of the equivalent series resistance and the electrostatic capacitance; A temperature detection circuit comprising:

11. In the temperature sensor, the equivalent series resistance has a negative temperature coefficient and the capacitance has a positive temperature coefficient; The negative temperature coefficient of the equivalent series resistance and the positive temperature coefficient of the capacitance act in the same direction on the detection value, or at least do not interfere with each other. The temperature detection circuit according to claim 10.

12. the charge supply / neutralization unit has a charging resistor connected in series to the equivalent series resistance in a charging path of the capacitance or a discharging resistor connected in series to the equivalent series resistance in a discharging path of the capacitance, The resistance value of the charging resistor or the discharging resistor is in the range of 0.1 to 10 times the resistance value of the equivalent series resistance in the normal temperature range of 5°C to 35°C, or in the temperature detection range if a temperature detection range is defined. The temperature detection circuit according to claim 10.

13. the charge supply / neutralization unit has a charging resistor connected in series to the equivalent series resistance in a charging path of the capacitance or a discharging resistor connected in series to the equivalent series resistance in a discharging path of the capacitance, A means for switching or adjusting the resistance value of the charging resistor or the discharging resistor is provided. The temperature detection circuit according to claim 10.

14. A temperature detection method for detecting an ambient temperature of a temperature sensor, the temperature sensor having an element part in which an equivalent circuit including an equivalent series resistance and a capacitance is formed between a first terminal and a second terminal, the temperature detection method comprising: causing a change in electromagnetic state over time in the equivalent circuit by charging or discharging the capacitance through the equivalent series resistance; A temperature detection method, characterized in that the detection value is output which reflects the temperature dependency of the change over time in the electromagnetic state in the equivalent circuit caused by the temperature characteristics of the equivalent series resistance and the electrostatic capacitance.

15. In the temperature sensor, the equivalent series resistance has a negative temperature coefficient and the capacitance has a positive temperature coefficient; The negative temperature coefficient of the equivalent series resistance and the positive temperature coefficient of the capacitance act in the same direction on the detection value, or at least do not interfere with each other. The temperature detection method according to claim 14.

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