Temperature detection circuit and temperature detection method

Abstract

To realize a temperature detection circuit and temperature detection method that are highly sensitive and accurate, and can be supplied at low cost. [Solution] The temperature detection circuit 10CT1 according to the present invention is electrically connected to a temperature sensor having an element part 10S in which an equivalent circuit including an equivalent series resistance Rs and capacitance C is formed between a first terminal and a second terminal, and is a temperature detection circuit that outputs a detection value for detecting the ambient temperature of the temperature sensor, and is characterized by having a power supply and discharge part CTA that causes a change in the electromagnetic state in the equivalent circuit over time by charging or discharging the capacitance C through the equivalent series resistance Rs, and a detection part CTB that outputs a detection value that reflects the temperature dependence of the change in the electromagnetic state in the equivalent circuit over time due to the temperature characteristics of the equivalent series resistance Rs and capacitance C.

Description

Technical Field

[0001] The present invention relates to a temperature detection circuit and a temperature detection method.

Background Art

[0002] Conventionally, temperature sensors have been used in heating products such as electric blankets and electric ankle warmers, and a typical example of a temperature sensor is a thermistor. However, due to reasons such as its thickness, it is not suitable for being attached to and used on specific objects such as electric blankets.

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

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the above-described sheet-like temperature sensor, since a heat-sensitive sheet (resin film) made of a polymer material or the like is used, the temperature dependence of the heat-sensitive sheet itself is low, so there is a problem that the sensitivity and accuracy as a temperature sensor are poor. Also, in order to increase the temperature dependence of the heat-sensitive sheet, it is necessary to use an expensive resin film or it is difficult to reduce the manufacturing cost, so there is also a problem that it is difficult to supply at a low cost.

[0006] Therefore, the present invention solves the above problems, and its objective is to realize a temperature detection circuit and temperature detection method that have high sensitivity and accuracy and can be supplied at low cost. [Means for solving the problem]

[0007] To solve the above problems, the temperature detection circuit according to the present invention is electrically connected to a temperature sensor having an element part in which an equivalent circuit including an equivalent series resistance and capacitance is configured between a first terminal and a second terminal, and outputs a detection value for detecting the ambient temperature of the temperature sensor, characterized in that it has a power supply and discharge unit that causes a change in the electromagnetic state over time in the equivalent circuit by charging or discharging the capacitance through the equivalent series resistance, and a detection unit 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, in the temperature sensor, it is preferable that the equivalent series resistance has a negative temperature coefficient and the capacitance has a positive temperature coefficient, and that the negative temperature coefficient in the equivalent series resistance and the positive temperature coefficient in the capacitance both act in the same direction with respect to the detection value, or at least do not interfere with each other.

[0008] In the above temperature detection circuit, the power supply and elimination unit has a charging resistor connected in series with the equivalent series resistance in the charging path of the capacitance, or a discharge resistor connected in series with the equivalent series resistance in the discharge path of the capacitance, and it is preferable that the resistance value of the charging resistor or the discharge resistor is in the range of 0.1 to 10 times the resistance value of the equivalent series resistance. Here, it is desirable that this resistance value range is valid in the room temperature range, for example, in the temperature range of 5°C to 35°C. Furthermore, if the temperature detection range of the temperature sensor is defined, it is desirable that the above resistance value range is valid within that temperature detection range.

[0009] Furthermore, in the above temperature detection circuit, it is desirable that the power supply and discharge unit has a charging resistor connected in series with the equivalent series resistance in the charging path of the capacitance, or a discharge resistor connected in series with the equivalent series resistance in the discharge path of the capacitance, and has means for switching or adjusting the resistance value of the charging resistor or the discharge resistor. Here, it is desirable that the means for switching or adjusting the resistance value of the charging resistor or the discharge resistor can be switched or adjusted so that the resistance value of the charging resistor or the discharge resistor is in the range of 0.1 to 10 times the resistance value of the equivalent series resistance. For example, it is desirable that the means for switching or adjusting the resistance value of the charging resistor or the discharge resistor can be switched or adjusted so that the above range of resistance values ​​is valid in the room temperature range, for example, 5°C to 35°C. Also, if the temperature detection range of the temperature sensor is defined, it is desirable that the means for switching or adjusting the resistance value of the charging resistor or the discharge resistor can be switched or adjusted so that the above range of resistance values ​​is valid within that temperature detection range.

[0010] Furthermore, the temperature detection method according to the present invention is a temperature detection method that outputs a detected value for detecting the ambient temperature of a temperature sensor having an element portion in which an equivalent circuit including an equivalent series resistance and capacitance is configured between a first terminal and a second terminal, characterized in that a change in the electromagnetic state over time occurs in the equivalent circuit by charging or discharging the capacitance through the equivalent series resistance, and the detected value is output that reflects the temperature dependence of the change in the electromagnetic state over time in the equivalent circuit caused by 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 in the equivalent series resistance and the positive temperature coefficient in the capacitance both act in the same direction with respect to the detected value, or at least do not interfere with each other.

[0011] In the temperature detection circuit and temperature detection method according to the present invention, the element portion of the temperature sensor preferably includes a first electrode electrically connected to the first terminal, a second electrode electrically connected to the second terminal, and an electrolyte disposed between the first electrode and the second electrode. With this, by having an electrolyte disposed between the first electrode and the second electrode, and by bringing at least one electrode into contact with the electrolyte via an insulating layer, the rate of change due to temperature change in equivalent series resistance and capacitance can be increased compared to the rate of change due to temperature change in a conventional heat-sensitive sheet made of resin film, due to the influence of the insulating layer and the electrolyte. Therefore, the detection sensitivity of the temperature detected based on the change in electromagnetic characteristics due to the temperature change between the first electrode and the second electrode can be improved. In particular, since the temperature coefficient of resistivity of the electrolyte is larger than that of the polymer resin film, the detection accuracy can also be increased. Furthermore, there is the advantage that the composition of the electrolyte can be adjusted according to the detection characteristics required for the temperature sensor, and that it is easy to prepare the electrolyte in this adjusted form. In addition, since an electrolytic capacitor structure is used in which an electrolyte is interposed between electrodes, it can be manufactured at a lower cost than a thermistor using semiconductors.

[0012] In the above-described temperature sensor, it is preferable that at least one of the first electrode and the second electrode has a fine surface unevenness structure on the electrolyte-side surface. This allows for an increase in the area between the electrode and the electrolyte without increasing the area of ​​the temperature sensor, thereby increasing the capacitance of the element. This makes it possible to further improve the sensitivity and accuracy of the sensor based on the temperature coefficient of capacitance. The above-described fine surface unevenness structure can be formed by etching (removing) the surface of the electrode material or by fixing (attaching) fine powder, such as by forming a sintered body.

[0013] In the above-described temperature sensor, it is preferable that an insulating layer is formed on the surface layer on the electrolyte side of at least one of the first electrode and the second electrode. By forming an insulating layer on the surface of the electrode, the stability of capacitance can be increased, thereby reliably improving the sensitivity and accuracy of temperature detection and enabling stable detection. In this case, it is preferable that the insulating layer is formed on the surface layer having a fine surface uneven structure. This allows for an increase in capacitance, further improving the sensitivity and accuracy of temperature detection.

[0014] In the above-described temperature sensor, it is preferable that at least one of the electrodes is made of valve metal, and the insulating layer is a passivation film formed on the surface of the electrode. This allows for a thin yet dense insulating film to be formed by the composition of the valve metal as the insulating layer, thereby reducing leakage current while increasing capacitance. In this case, the valve metal is preferably aluminum, chromium, titanium, zinc, or an alloy mainly composed of these materials. The passivation film can be formed by electrochemical oxidation or sulfidation, such as an anodic oxide film or a surface treatment film formed by chemical conversion. The electrode material is not limited to the valve metal described above; corrosion-resistant metals such as gold, silver, copper, and stainless steel, or alloys mainly composed of these materials, can be suitably used. Furthermore, carbon materials such as graphite, graphene, glassy carbon, carbon nanotubes, and fullerenes, as well as conductive polymers such as polyacetylene, poly(p-phenylenevinylene), polyaniline, polythiophene, polypyrrole, and poly(3,4-dioxythiophene), can be suitably used.

[0015] In the above temperature sensor, the electrolyte contains an electrolyte and a solvent, and it is preferable that the solvent 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. If it is below this range, it will not show sufficient resistivity change, and if it is above this range, the impregnation and contact properties of the electrolyte will deteriorate. Specifically, it is preferable that the solvent mainly consists of glycerin, ethylene glycol, polyethylene glycol, or a mixture thereof. With this, since these solvents have a large resistivity change due to temperature changes in the measurement temperature range near room temperature, the detection sensitivity and accuracy can be improved mainly by the electrical properties of the electrolyte. Moreover, because the vapor pressure is low, swelling at high temperatures can be suppressed, and the lifespan of the temperature sensor 10 can be extended. If a temperature detection range is defined for the temperature sensor, it is preferable that the viscosity is within the range specified above, instead of the room temperature range.

[0016] In the above-described temperature sensor, it is preferable to further provide a housing that seals the element portion having a laminated structure of the first electrode, the second electrode, and the electrolyte, such that the first and second terminals are exposed to the outside. In this case, it is preferable that the housing is made of a sheet material having an insulating film layer and a conductive film layer or a gas-impermeable film layer laminated together. This ensures the required insulation with the insulating film layer, and provides an electrostatic shielding effect with the presence of the conductive film layer, thereby suppressing the influence of the external electric field, and prevents deterioration of the electrolyte (such as drying up) with the presence of the gas-impermeable film layer. Furthermore, as an example, it is desirable that the insulating housing has a heat-sealable weldable 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 outer 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.

[0017] In the above temperature sensor, alwaysIn a temperature range, for example, 5[°C] - 35[°C], it is desirable that the product of the equivalent series resistance Rs[Ω] and the capacitance C[μF] is 10 or more. According to this, since the product of the equivalent series resistance and the capacitance is 10 or more, the time constant of the equivalent circuit (τ = Rs·C) increases, so that the influence on the detection value due to the above temperature coefficient can be increased, and thus the sensitivity and accuracy of temperature detection can be further improved. Further, when the temperature detection range is defined in the temperature sensor, it is preferable that the above conditions are satisfied in the temperature detection range instead of the above normal temperature range.

[0018] In the above temperature sensor, it is preferable that an insulating separator capable of holding the electrolytic solution is disposed between the first electrode and the second electrode. According to this, while ensuring the insulation between the first electrode and the second electrode, the holding property of the electrolytic solution can be improved, so that the detection characteristics of the temperature sensor can be stabilized.

[0019] In the above temperature sensor, it is preferable that the first terminal is made of the same material as the main metal material of the first electrode, and the second terminal is made of the same material as the main metal material of the second electrode. According to this, it does not react with the electrolytic solution, or the reaction with the electrolytic solution is less likely to be a problem, and corrosion due to contact of different metals can also be avoided.

Effects of the Invention

[0020] According to the present invention, it is possible to realize a temperature detection circuit and a temperature detection method that are highly sensitive and accurate and can be supplied at a low cost.

Brief Description of the Drawings

[0021] [Figure 1] It is an exploded perspective view schematically showing a schematic configuration of an embodiment of a temperature sensor used in an embodiment according to the present invention. [Figure 2] It is a cross-sectional view schematically showing an example of a laminated structure before sealing of the same embodiment. [Figure 3] It is a cross-sectional view schematically showing a cross-sectional structure of the same embodiment. [Figure 4] It is a plan view of the same embodiment. [Figure 5] It is an enlarged cross-sectional view schematically showing the internal structure of the same embodiment. [Figure 6] It is a circuit diagram showing a simplified equivalent circuit of the temperature sensor of the same embodiment. [Figure 7] It is a graph showing the temperature dependence of the capacitance of the same embodiment for each frequency. [Figure 8] It is a graph showing the temperature dependence of the ESR (equivalent series resistance) of the same embodiment for each frequency. [Figure 9] It is a graph showing a comparison of the temperature dependence of the ESR (equivalent series resistance) of the same embodiment and the temperature dependence of the resistance value of the thermistor. [Figure 10] It is a circuit diagram showing a first example of a temperature detection circuit using the temperature sensor of the same embodiment. [Figure 11] It is a graph showing the time change of the voltage detection value during charging in an example of the circuit of the first example. [Figure 12] It is a graph showing the time change of the voltage detection value in another example of the circuit of the first example. [Figure 13] It is a circuit diagram showing a second example of a temperature detection circuit using the temperature sensor of the same embodiment. [Figure 14] It is a graph showing the voltage detection waveform in the circuit of the second example. [Figure 15] It is a circuit diagram showing a third example of a temperature detection circuit for measuring the equivalent series resistance. [Figure 16] They are an internal structure perspective view (a), a perspective view of the housing (b), and a perspective view of the completed body (c) showing the structure and manufacturing process of the temperature sensor of the second embodiment.

Mode for Carrying Out the Invention

[0022] Next, embodiments of the present invention will be described in detail with reference to the attached drawings. First, the overall configuration of an embodiment of a temperature sensor used in a temperature detection circuit and temperature detection method according to the present invention will be described with reference to Figures 1 to 4. Figure 1 schematically shows an exploded perspective view of the temperature sensor 10 in this embodiment. Figure 2 schematically shows the cross-sectional structure of the laminated configuration (before sealing) shown in Figure 1. The temperature sensor 10 constitutes 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 this electrolyte 12L is in contact with the anode foil 11 and the cathode foil 13.

[0023] The electrode foils (anode foil 11 and cathode foil 13) are not particularly limited as long as they are conductors, but 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 that contains 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 [weight%] or less. In addition to the above aluminum or aluminum alloy, the electrode foils (anode foil 11 and cathode foil 13) are preferably valve metals such as titanium, chromium, zinc, or alloys thereof. The surfaces of the electrode foils (anode foil 11 and cathode foil 13) that are in contact with the electrolyte 12L preferably have a fine surface uneven structure. In the illustrated example, the electrode foils are configured as etched foils that have undergone etching treatment. Examples of etching processes include electrochemical etching, such as passing an electric current through an aqueous chloride solution on the electrode sheet material. Furthermore, the electrode foils (anode foil 11 and cathode foil 13) having a fine surface uneven structure may be formed by creating a sintered body of powder made of aluminum or the above-mentioned aluminum alloy on the surface of the core material. In this case, the purity of the metal (aluminum) in the powder is preferably 99.8% by weight or higher. The average particle size of the powder is preferably 1 μm or larger. If the average particle size is smaller than 1 μm, the desired dielectric strength may not be obtained. Furthermore, the average particle size is preferably 80 μm or smaller. If the average particle size is larger than 80 μm, the desired capacitance may not be obtained. The average particle size can be calculated using the laser diffraction particle size measurement method based on ISO 13320, regardless of the shape of the filler. In any case, by providing a fine surface uneven structure, the surface area of ​​the electrode can be increased without increasing the size (area) of the temperature sensor 10, thereby increasing the capacitance C. The fine surface uneven structure preferably has a surface roughness (arithmetic mean roughness Ra) within the range of 0.1 [μm] to 1000 [μm], and more preferably within the range of 1 [μm] to 100 [μm].

[0024] The electrodes (first electrode 11 and second electrode 13) preferably have a thickness range of 150 [μm] - 15 [μm]. If the electrodes are thicker than the above thickness range, the entire temperature sensor tends to become thicker, and if they are thinner than the above thickness range, it becomes difficult to form a fine surface uneven structure, which tends to reduce capacitance and the strength required for bonding with the terminals decreases, making structural defects and performance problems more likely to occur. In this specification, the notation "A - B" (A, B are numerical values ​​or symbols) is used to indicate a range between A and B. Also, the notation "[C]" (C is a unit) is used to indicate a unit in a manner separate from the numerical value displayed before it.

[0025] It is preferable to form a chemical conversion film (oxide film) on the surface of the anode foil 11 as an insulating layer by applying a chemical conversion treatment. For example, an oxide film that is a dielectric with dielectric strength is formed by a predetermined anodic oxidation treatment. The chemical conversion voltage for the above chemical conversion treatment is usually 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 a natural film alone may also be used.

[0026] The electrode foils (anode foil 11 and cathode foil 13) are preferably within the thickness range of 15 [μm] to 150 [μm]. If they are thicker than this range, the entire temperature sensor 10 becomes too thick, and the flexibility of the temperature sensor 10 itself decreases. If the thickness is below the above range, etching to form a fine surface uneven structure becomes difficult, leading to a decrease in capacitance, a decrease in sensitivity to temperature, and a decrease in the foil strength required for bonding with terminals or for uses that utilize the flexibility of the temperature sensor 10.

[0027] The separator 12 is not particularly limited, but it can be made from cellulose material, such as Manila hemp or plant pulp, and woven fabrics, nonwoven fabrics, sheets, or films made from natural fibers produced by processes such as dust removal, washing, beating, and papermaking. Alternatively, woven fabrics, nonwoven fabrics, sheets, or films made from synthetic fibers such as rayon, nylon, polyester, polyvinyl compounds, aramid, acrylic, or polyurethane can also be used. Furthermore, blended products of natural and synthetic fibers can also be used. In the element section 10S described above, the separator 12 is not necessarily required as long as the electrolyte solution described later can be placed between the anode foil 11 and the cathode foil 13. However, the use of the separator 12 prevents contact (electrical short circuit) between the anode foil 11 and the cathode foil 13, thus enabling the stable production of a sheet-like temperature sensor 10. Furthermore, by maintaining the electrolyte in an impregnated state, a sufficient amount of electrolyte can be secured to counteract the evaporation of electrolyte over time.

[0028] The separator 12 is preferably made of a material with a thickness in the range of 10 μm to 90 μm. If the thickness exceeds this range, the thickness of the temperature sensor 10 will increase, and if it falls below this range, there is a concern that the insulating properties and the amount of electrolyte that can be held will decrease. Furthermore, it is desirable that the separator has an affinity that allows it to be impregnated with the electrolyte. For example, if the solvent of the electrolyte is a polar solvent, examples of the separator include cellulose fibers having hydroxyl groups, and if the solvent is nonpolar, examples include polypropylene.

[0029] The electrolyte solution 12L contains at least an electrolyte and a solvent. Additives, as described later, may also be added. As the solvent for dissolving the electrolyte and additives, an organic solvent can be used alone, or a water-organic solvent system, i.e., a mixture of an organic solvent and water, can be used. As described below, the electrolyte solution 12L can be used with various materials individually or in combination, which has the advantage that the composition can be adjusted according to the characteristics such as the detection temperature range and detection sensitivity required for the temperature sensor 10. Furthermore, because the electrolyte solution 12L is a liquid, it has the manufacturing advantage that it can be easily prepared by mixing, etc., to correspond to the above characteristics. In addition, for the temperature sensor 10, the fluidity of the electrolyte solution 12L makes it easier to ensure uniformity across the entire planar range, which has the advantage of increasing detection sensitivity and improving stability.

[0030] As the organic solvent, protic solvents or aprotic solvents can be used individually or in combination of two or more. If necessary, one or more protic solvents and one or more aprotic solvents may be used in any combination. Suitable protic solvents include, for example, alcohol compounds. Specific examples of alcohol compounds that can be advantageously used here are not particularly limited, but include 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; dihydric alcohols (glycols) such as 1,4-butanediol and 1,3-butanediol; trihydric alcohols such as glycerin; or derivatives thereof. Furthermore, suitable aprotic solvents are not particularly limited, but include the following: 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; their derivatives; and other intramolecular polarizing compounds.

[0031] In the electrolyte according to this embodiment, as described above, instead of using an organic solvent alone, a water-organic solvent system can also be used. By using such a water-organic solvent system, the freezing point of the solvent can be lowered. As a result, temperature measurement at low temperatures can be made possible. To explain in more detail, taking the case where ethylene glycol is used as the organic solvent as an example, this protonated organic solvent has a boiling point of +198 [°C] and a melting point of approximately -13 [°C]. The temperature range required for the temperature sensor 10 is generally often -20 [°C] to +120 [°C], so while the electrolyte using this solvent has a margin of error at high temperatures, at low temperatures, the measurement accuracy may decrease due to increased viscosity or freezing of the electrolyte.

[0032] Therefore, in this embodiment, the electrolyte uses an organic solvent with excellent temperature characteristics, either alone or in a mixture of several types. When using an organic solvent with a relatively high freezing point, water can be added to create a water-organic solvent system, thereby lowering the freezing point of the solvent and ensuring measurement functionality in the low-temperature range. Consequently, a temperature sensor 10 using such an electrolyte can naturally have good temperature characteristics in the low-temperature range, 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 [mass%] to 20 [mass%] of the total mass of the electrolyte. This allows for the realization of the above-mentioned good oxide film repair characteristics, and the water molecules are utilized to repair the oxide film on the electrode foil, resulting in relatively excellent oxide film repair characteristics. Various combinations of such solvents greatly expand the adjustment range of the temperature characteristics of the temperature sensor 10 and contribute to the design of a temperature sensor suited to various situations. However, if the amount of water added exceeds 20 [mass%], the vapor pressure of water increases, raising concerns that the temperature sensor may swell at high temperatures.

[0033] Furthermore, as electrolytes, organic acids, preferably carboxylic acids or their salts, boron complexes of dicarboxylic acids or hydroxycarboxylic acids or their salts, and inorganic acids or their salts are used. These electrolyte components may be used individually, or two or more electrolyte components may be used in any combination. When inorganic acids or their salts are used in combination with carboxylic acids or their salts, or boron complexes of dicarboxylic acids or hydroxycarboxylic acids or their salts as electrolyte components, a freezing point depression of the electrolyte can be expected, thereby contributing to further improvement of the low-temperature properties of the electrolyte.

[0034] Examples of carboxylic acids that can be used as electrolyte components are not limited to those listed below, but include monocarboxylic acids and their derivatives 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, tert-butylbenzoic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, fumaric acid, maleic acid, phthalic acid, azelaic acid, and sebaci acid. Examples of dicarboxylic acids and their derivatives include nic 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-methyl nonanandioic acid, 3-tert-butylhexandioic acid, brassic acid, octadecendioic acid, 12-vinyl-8-octadecendioic acid, and dimethyloctadecadenetetracarboxylic acid. Carboxylic acids containing hydroxyl groups, such as citric acid, can also be used.

[0035] Furthermore, the dicarboxylic acids or hydroxycarboxylic acids in boron complexes of dicarboxylic acids or hydroxycarboxylic acids that can also be used as electrolyte components are not limited to those listed below, but examples include borodi-fusic acid, borodi-malonic acid, borodi-succinic acid, borodiadipic acid, borodi-maleic acid, borodiglycolic acid, borodi-lactic acid, borodi-malic acid, borodi-tartaric acid, borodi-citric acid, borodi-salicylic acid, borodi-phthalic acid, borodi(2-hydroxy)isobutyric acid, borodi-mandelic acid, and borodi(3-hydroxy)propionic acid.

[0036] 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, alkyl phosphoric acid, phosphomolybdic acid, boric acid, and sulfamic acid. Derivatives of such inorganic acids may also be used as needed.

[0037] Furthermore, various commonly known salts can be used as the salts of the carboxylic acids or inorganic acids mentioned above. Suitable salts are not particularly limited, but may include one or more selected from sodium salts, potassium salts, ammonium salts, alkylammonium salts, and the amine salts and amidine salts listed below. As amine salts, salts of primary amines, secondary amines, and tertiary amines can be used, and examples include salts of 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 salts of 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. Other examples include tetraalkylammonium salts and imidazolium salts.

[0038] 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 the improvement of the electrolyte's low-temperature characteristics. In addition, by using such an inorganic acid or its salt as an electrolyte component in combination with the aforementioned carboxylic acid or its salt, the lifespan of the temperature sensor 10 is significantly extended compared to when the carboxylic acid or its salt is used alone. In the electrolyte according to this embodiment, the amount of electrolyte contained therein can be appropriately determined according to conditions such as the required characteristics of the electrolyte, the type of solvent used, and the type of electrolyte used. Generally speaking, for example, when using a carboxylic acid or its salt as an electrolyte, the amount is preferably around 0.5 [mass%] - 30 [mass%] of the total mass of the electrolyte. If the amount of electrolyte is less than 0.5 [mass%], the desired conductivity cannot be sufficiently secured, and if it exceeds 30 [mass%], the effect saturates and it becomes difficult to dissolve in the solvent.

[0039] Furthermore, when using inorganic acids or their salts as electrolytes, the amount should generally be around 0.1% by mass to 15% by mass of the total mass of the electrolyte. If the amount of electrolyte is less than 0.1% by mass, it becomes difficult to secure the desired conductivity sufficiently, and if it exceeds 15% by mass, the conductivity gradually saturates and the electrolyte becomes less soluble in the solvent. When using carboxylic acids or their salts in combination with inorganic acids or their salts, the amount can be used within the range of 0.1% by mass to 15% by mass of the total mass of the electrolyte. However, as mentioned above, the amount of electrolyte can be appropriately determined according to conditions such as the required characteristics of the electrolyte and the type of electrolyte used. For example, phosphorus oxyacids (phosphoric acid, phosphorous acid, hypophosphorous acid, etc.) extend the lifespan of the temperature sensor 10 by suppressing the hydration reaction of the electrode foil, and this effect is achieved if phosphorus oxyacids or their salts are contained in an amount of at least 0.01% by mass of the total mass of the electrolyte. Therefore, the desired conductivity and desired characteristics can be obtained by combining multiple electrolyte components as needed and adjusting the amount of each electrolyte component. Furthermore, it is preferable to add the following additives to the electrolyte according to this embodiment as needed: (1) chelate compounds, (2) sugars, (3) gluconic acid and / or gluconolactone, (4) nitro compounds, (5) polymer compounds, and (6) phosphate esters. These additives may be used individually or in any combination of two or more additives. Each additive will be described below.

[0040] (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), ethylenethylenetriamine-N,N,N',N'',N''-pentaacetic acid (DTPA), diaminopropanoltetraacetic acid (DPTA-OH), ethylenediaminediacetic acid (EDDA), ethylenediamine-N,N<-bis(methylenephosphonic acid) 1 / 2 hydrate (EDDPO), glycol etherdiaminetetraacetic acid (GEDTA), and hydroxyethylethylenediaminetriacetic acid (EDTA-OH). Generally, it is preferable to add the chelating compound in an amount ranging from 0.01 [mass%] to 3 [mass%] of the total mass of the electrolyte. Such chelate compounds can provide effects such as extending the lifespan of the temperature sensor 10 by suppressing the hydration reaction of the aluminum (Al) electrode foil in a low-impedance capacitor, improving the low-temperature characteristics of the temperature sensor 10, and improving corrosion resistance.

[0041] (2) Sugars Examples of sugars include monosaccharides such as glucose, fructose, xylose, galactose, ribose, mannose, arabinose, lyxose, allose, altose, growth, and idostalose, as well as their derivatives; sugar alcohols such as erythritol, xylitol, and mannitol; disaccharides such as maltose, sucrose, lactose, cellobiose, sucrose, and agarobiose, as well as their derivatives; trisaccharides such as maltotriose, as well as their derivatives; and polysaccharides such as starch, glycogen, alginic acid, agar, and mannan, as well as their derivatives. Generally, it is preferable to add sugars in an amount ranging from 0.01% by mass to 5% by mass of the total mass of the electrolyte. Such sugars can provide several benefits, including extending the lifespan of the temperature sensor 10 by protecting the electrode foil, extending the lifespan of the temperature sensor 10 in low-impedance capacitors by suppressing the hydration reaction of the aluminum (Al) electrode foil, suppressing the degradation of certain electrolyte components (for example, suppressing the decomposition and activation of carboxylic acids), and improving the low-temperature characteristics of the temperature sensor 10 (because the solvent has a composition close to that of a non-freezing state, the change in impedance between room temperature and low temperature becomes smaller). When such sugars are used together with boric acid or its derivatives, the solubility of the sugars is improved by the formation of esters. Therefore, it becomes possible to reliably add a predetermined amount of sugars and allow them to act sufficiently in the electrolyte. As a result, a stable and sufficiently long lifespan for the temperature sensor 10 can be achieved. In this case, boric acid or its derivatives may be added to the electrolyte as an electrolyte component (solute component), or they may be added solely for the purpose of reacting with sugars. On the other hand, mannitol and the like are suitably applied as sugars added together with boric acid or its derivatives. Furthermore, the preferred ratio of boric acid or its derivatives to sugars is within the range of "boric acid or its derivatives: sugars = 10:1 - 1:5". If too much sugar is added, it will become difficult to dissolve in the solvent.

[0042] (3) Gluconic acid and / or gluconolactone The electrolyte according to this embodiment may contain gluconic acid and / or gluconolactone, either alone or in combination, as needed. Generally, it is preferable to add this type of additive in an amount ranging from 0.01% by mass to 5% by mass of the total mass of the electrolyte.

[0043] (4) Nitro compounds The electrolyte according to this embodiment may, if necessary, contain 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.

[0044] In the electrolyte according to this embodiment, when the nitro compound described above is used, it has the effect of absorbing hydrogen gas generated in the electrode foil. Furthermore, a more favorable effect can be expected when two or more nitro compounds are mixed and used rather than using the nitro compound alone. In addition, it is generally preferable to add the nitro compound in an amount ranging from 0.01 [mass%] 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 cannot be obtained to any extent, and conversely, if it exceeds 5 [mass%], further improvement of the desired effect cannot be expected, and in some cases, adverse effects on other properties may occur.

[0045] To further explain the use of nitro compounds, the absorption of hydrogen gas generated during the reaction of aluminum and water tends to decrease as the water content in the solvent increases when nitro compounds are used alone. This decrease in absorption effect becomes more pronounced when the electrolyte is exposed to high temperatures. However, these problems arising from the use of nitro compounds alone can be resolved by using two or more nitro compounds in combination.

[0046] (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, silicon dioxide, etc. These may be used individually or in any combination of two or more types. The total amount of these added is preferably in the range of 0.1 [mass%] to 30 [mass%] of the total mass of the electrolyte. Such polymer compounds can provide effects depending on the action of each polymer compound, such as improving the voltage resistance characteristics of the temperature sensor 10 and extending the lifespan of the temperature sensor 10. The molecular weight of the polymer compounds can be broadly used, from relatively low molecular weight (oligomers) to high molecular weight, depending on the action of each polymer compound, its solubility and dispersibility in the solvent, or the desired effect.

[0047] (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, and triethyl phosphate ester. Similar to chelate compounds, such phosphate esters suppress the hydration reaction of the electrode foil, thereby suppressing the deterioration of the electrode foil and the generation of hydrogen gas, and thus extending the lifespan of the temperature sensor 10.

[0048] Furthermore, the electrolyte according to this embodiment may also contain, in addition to the additives described above, other additives commonly used in the field of aluminum electrolytic capacitors and other electrolytic capacitors. Suitable additives include, for example, silane coupling agents, polymer electrolytes, and colloidal silica.

[0049] As described above, the electrolyte according to this embodiment can use electrolytes and solvents consisting of various single materials or mixtures of multiple materials, and therefore has the advantage that the temperature coefficient of the electrical resistance (impedance) of the electrolyte can be adjusted according to various requirements. However, in this embodiment, the electrolyte 12L constitutes the element part 10S of the temperature sensor 10, and the characteristics of the electrolyte 12L greatly affect the equivalent series resistance (ESR) included in the equivalent circuit of the element part 10S. Therefore, from the viewpoint of improving the sensitivity and accuracy of temperature detection, it is important that the temperature coefficient of the electrolyte 12L, which is the main component of the equivalent series resistance, is large, that is, that the change in resistivity with temperature is large. For this reason, it is preferable that the solvent of the electrolyte 12L also has a large temperature coefficient. Examples of such solvents include glycerin, ethylene glycol, polyethylene glycol, or mixtures thereof. Here, the temperature coefficient of the equivalent series resistance and the resistivity of the electrolyte 12L (specifically, the temperature coefficient of viscosity for the electrolyte 12L) is negative. The electrolyte of the temperature sensor used in the present invention also includes those that have been sol-gelled by adding a polymer compound to some electrolyte. Here, using a sol- or gel-formed electrolyte has the advantage of reducing the risk of leakage.

[0050] The glycerin, ethylene glycol, polyethylene glycol, or mixtures thereof mentioned above have high viscosity in the detection temperature range (room temperature range), which is thought to result in a large absolute value of the temperature coefficient of resistivity due to the large absolute value of the negative temperature coefficient of viscosity. Here, the viscosity of the electrolyte (solvent) is preferably in the range of 10 [mPa·s] to 5000 [mPa·s] in the detection temperature range or at room temperature (e.g., 5 [°C] - 35 [°C]). If it is below 10 [mPa·s], it will not show a sufficient resistivity change rate, and if it is above 5000 [mPa·s], the impregnation and contact properties of the electrolyte when manufacturing the element part 10S will deteriorate. As mentioned above, if the viscosity is within the above range in the detection temperature range, high sensitivity and accuracy can be ensured throughout the entire detection temperature range. Furthermore, if the viscosity is within the above range at room temperature, temperature detection with practical sensitivity and accuracy becomes possible in many detection temperature ranges centered on that room temperature. The viscosity values ​​shown in this specification are measured according to the measurement method based on JIS Z 8803:2011.

[0051] As mentioned above, the effective detection temperature range can be changed by adding water to the solvent. However, if too much water is added, the absolute value of the temperature coefficient of resistivity (specifically, the temperature coefficient of viscosity) decreases. Therefore, from the perspective of improving the sensitivity and accuracy of temperature detection, when the detection range is in the room temperature range (for example, 5°C - 35°C), the amount of water added to the water-organic solvent system should preferably be in the range of 0.1% to 3% of the total mass of the electrolyte. On the other hand, in the low temperature range such as below -20°C, water shows a large change in resistivity, so it is desirable to use a solvent that contains a lot of water. In addition to the above considerations, it is preferable for the solvent to have a low vapor pressure. This is because it can suppress swelling at high temperatures and prevent solvent leakage, thereby extending the lifespan of the temperature sensor 10.

[0052] The anode foil (first electrode) 11 is electrically connected to the first terminal 14 by welding or the like. The cathode foil (second electrode) 13 is electrically 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 it is preferable that they be metals that do not react with the electrolyte. It is also desirable that they be made of the same material as the electrode foils (anode foil 11 and cathode foil 13) to avoid corrosion due to contact between dissimilar metals. The above terminals (first terminal 14, second terminal 15) may be lead-shaped terminals that are pulled out or protrude from the housing as shown in the figure, or they may be surface-mount type terminals that have a terminal surface along the surface.

[0053] The element portion 10S is sealed by covering it with outer films 16 and 17. The outer films 16 and 17 are not particularly limited as long as they constitute a housing that houses the functional structural portion of the element portion 10S, but it is preferable that the outer and inner surfaces have insulating properties. Furthermore, it is preferable that the inner surfaces of the outer films 16 and 17 do not react with the electrolyte. Furthermore, it is preferable that the inner surfaces can seal the electrolyte. In the illustrated example, both the outer and inner surfaces are made of insulating material. For example, the inner surface is made of an insulating film layer such as polypropylene that does not react with the electrolyte (has good chemical resistance). In the illustrated example, the inner surfaces are sealed by welding by heating. In this case, the outer surface is made of an insulating film layer such as nylon with a high melting point that has heat resistance to the welding treatment of the inner surface. Furthermore, electromagnetic shielding can be obtained by placing a conductive film layer such as aluminum foil between these insulating film layers. In addition, by interposing a gas-impermeable film layer such as aluminum foil, the risk of solvent loss in the electrolyte can be reduced.

[0054] As shown in Figure 2, the outer films 16 and 17 have a laminated film structure in which three layers—an insulating outer film layer, a conductive and / or gas-impermeable intermediate film layer, and an insulating inner film layer—are laminated together via an adhesive or the like. 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. As in this specific example, if the inner film layer is weldable, the element portion 10S can be sealed by the welded regions 16m and 17m, as shown in Figures 3 and 4, by overlapping the outer films 16 and 17 and performing a heat seal. Furthermore, as shown by the dashed line in Figure 4, by interposing separate weldable films (such as polypropylene) 14p and 15p between the terminals (first terminal 14, second terminal 15) and the outer films 16 and 17 (on both sides), a more reliable sealing can be ensured.

[0055] Figure 5 is a schematic diagram illustrating the cross-sectional structure of the element section 10S. Fine surface irregularities 11s and 13s are formed on the surface of the electrode foils 11 and 13 by etching, and the surface layers of these fine surface irregularities are insulating layers (oxide films) 11t and 13t, such as passivation films. The insulating layer 11t has a thickness corresponding to the conversion voltage formed by the above conversion treatment, and is formed so that the element section 10S exhibits a predetermined withstand voltage. As described above, in the case of this embodiment, the above conversion voltage is generally preferably 1[V]-6[V]. In this case, for example, the predetermined withstand voltage is ensured by setting a conversion voltage of 1[V] or more than the maximum voltage (e.g., 5[V]) applied to the element section 10S by the temperature detection circuit described later. On the other hand, the insulating layer 13t is usually composed of a naturally occurring oxide film that forms naturally on the surface of a valve metal such as aluminum. However, the insulating layer 13t may also be formed by the same conversion treatment as described above.

[0056] The element portion 10S described above only needs to be arranged such that the electrolyte 12L is in contact with a pair of film-like electrodes 11 and 13, each having an insulating layer 11t and 13t formed on at least one of their surface layers. Therefore, the laminated structure formed in the order of the first electrode 11, the electrolyte 12L, and the second electrode 13 may be repeatedly laminated. For example, a structure can be repeatedly laminated as follows: first electrode 11, electrolyte 12L, second electrode 13, electrolyte 12L, first electrode 11, electrolyte 12L, second electrode 13, ... Furthermore, the above-described laminated structure, consisting of a laminated unit of the first electrode 11, electrolyte 12L, and second electrode 13, or a plurality of such laminated units repeated, may be provided by stacking multiple such laminated structures in an electrical connection structure where they are electrically connected to each other in parallel.

[0057] Figure 6 is a simplified equivalent circuit diagram of the element section 10S of the temperature sensor 10 in this embodiment. The element section 10S has a circuit structure in which capacitance C, equivalent series resistance (ESR) Rs, and equivalent series inductance (ESL) Ls are connected in series between the first terminal 14 and the second terminal 15. In some cases, an insulation resistance Ri may be assumed to be connected in parallel with capacitance C. Capacitance C usually correlates with temperature, and specifically has a positive correlation (positive temperature coefficient) with respect to temperature. Figure 7 shows the temperature dependence of capacitance C. Here, the multiple graphs arranged vertically represent the capacitance values ​​measured at the frequencies [kHz] indicated by the indicators arranged vertically on the right. Capacitance C has a positive temperature coefficient at any frequency within the range shown. In this case, the temperature dependence of capacitance C changes as the measurement frequency increases. From a state where the temperature coefficient is large in the low temperature range (e.g., -20°C to +5°C), the region with a large temperature coefficient gradually expands to the high temperature range, and eventually the temperature coefficient becomes even larger in the high temperature range (e.g., 0°C to +60°C). In this embodiment, the temperature sensor 10 employs a structure using an insulating layer 11t and an electrolyte 12L, resulting in a characteristic of larger frequency variation compared to conventional temperature sensors using resin films or the like as temperature sensing elements. Therefore, it is desirable to perform measurements in the DC range or low frequency range, where the influence of frequency on the detected value is small, in order to improve sensitivity and accuracy. In this embodiment, as shown in Figure 7, capacitance C shows a positive temperature coefficient within the range of -20°C to +60°C. However, if a temperature detection range is defined, it is preferable that capacitance C shows a positive temperature coefficient within that temperature detection range, or it is preferable that capacitance C shows a positive temperature coefficient within the room temperature range (5°C to 35°C).

[0058] In the temperature sensor 10 of this embodiment, the equivalent series resistance Rs is mainly composed of the electrical resistance of the electrolyte 12L, which is usually correlated with temperature and specifically has a negative temperature coefficient. The temperature dependence of the equivalent series resistance Rs is shown in Figure 8. Here, the multiple graphs arranged vertically represent the resistance values ​​measured at the frequencies [kHz] indicated by the indicators arranged vertically on the right. It can be seen that all graphs have a large negative temperature coefficient. Figure 9 shows a comparison of the temperature dependence of the equivalent series resistance Rs of a conventional high-sensitivity thermistor using semiconductors and the temperature sensor 10 of this embodiment. 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 a high-sensitivity thermistor. In this embodiment, as shown in Figure 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 defined, it is preferable that the equivalent series resistance Rs exhibits a negative temperature coefficient within that 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).

[0059] The data shown in Figures 7, 8, and 9 were measured in a temperature sensor 10 that, as a specific example of this embodiment, uses aluminum etched foil with vertical and horizontal planar dimensions of 12 [mm] × 25 [mm] as the anode foil 11 and cathode foil 13, a separator 12 made of cellulose fiber with a thickness of 70 [μm], and an electrolyte solution of glycerin with 2 [mass] ammonium adipate dissolved in it.

[0060] Figure 10 shows a temperature detection circuit 10CT1 of a first embodiment using the temperature sensor 10 of this embodiment. In this temperature detection circuit, the equivalent series inductance Ls can be ignored by increasing the switching cycles of switches SW1 and SW2 and lowering the measurement frequency, so the equivalent circuit of the element section 10S is considered to be 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), the capacitance C is charged by the power supply E through the charging resistance Rc and the equivalent series resistance Rs. Conversely, during the discharge period when switch SW1 is OFF (open) and switch SW2 is ON (closed), the capacitance C is discharged through the discharge resistance Rd and the equivalent series resistance Rs. In this example of the temperature detection circuit 10CT1, during the charging period, the capacitance C is charged through the equivalent series resistance Rs while the charging current is limited by the charging resistance Rc. Furthermore, during the discharge period described above, the capacitance C is discharged through the equivalent series resistance Rs while the discharge current is limited by the discharge resistance Rd.

[0061] In this temperature detection circuit 10CT1, during both the charging period and the discharging period, a change occurs over time in the electromagnetic state of the equivalent circuit of the equivalent series resistance Rs and capacitance C. The manner 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 the equivalent series resistance Rs and capacitance C. Here, the power supply E, the switches SW1 and SW2, the part with resistors Rc and Rd, and the ground part constitute a charge supply and discharge unit CTA that charges or discharges the RC circuit (equivalent circuit) via the charging resistor Rc or the discharging resistor Rd, supplying or removing charge from the equivalent circuit. On the other hand, the detection unit CTB measures the voltage value across the element part 10S (equivalent circuit). In this case, the manner of change of voltage values, current values, or their rate of change (derivative values) during the charging period and the discharging period reflects the temperature dependence corresponding to the temperature characteristics of the equivalent series resistance Rs and capacitance C. In other words, the manner in which the electromagnetic state of an RC circuit changes over time is influenced by the temperature characteristics of the equivalent series resistance Rs and capacitance C. For example, if the charging resistance Rc and discharge resistance Rd are sufficiently larger than the equivalent series resistance Rs, the voltage change will be approximately as shown in the graph in Figure 11. In this case, if the voltage value after a certain time τ after the start of the charging period reflects the manner in which the electromagnetic state changes over time due to temperature change, the temperature corresponding to capacitance C and equivalent series resistance Rs can be determined by detecting this voltage value. Here, the certain time τ is a predetermined time shorter than the charging time or discharge time.

[0062] In the temperature detection circuit 10CT1 shown in Figure 10, the voltage ect) applied to the capacitance C of element section 10S after time t from the start of charging during the charging period is given by the following equation (1). ec(t)=E {1-exp[-t / (C(Rc+Rs))]}…(1) Furthermore, the current i(t) after time t is given by i(t) = {E / (Rc+Rs)}·exp[-t / (C(Rc+Rs))], so the voltage eRs(t) applied to the equivalent series resistance Rs of element section 10S is given by the following equation (2). eRs(t)={(E·Rs) / (Rc+Rs)}·exp[-t / (C(Rc+Rs))]…(2) Therefore, the voltage value Vd (detection voltage) applied to the element 10S is given by the following equation (3). Vd = ec(t) + eRs(t) ... (3)

[0063] From the above relationship, generally, the detected value Vd (=initial value Vds) at t=0 in equation (3) above is E·{Rs / (Rc+Rs)}. Since the equivalent series resistance Rs has a negative temperature coefficient, the initial value Vds increases as the temperature decreases and decreases as the temperature increases. Figure 12 shows the results of simulating the detected value Vd during the charging period for temperatures of 0[℃], 20[℃], 40[℃], and 60[℃], assuming that the charging resistance Rc is not significantly different from the equivalent series resistance Rs shown in Figure 7 (for example, the difference between the two resistances is about one order of magnitude) in the temperature detection circuit 10CT1, with Rc = 500[Ω], and using the equivalent series resistance Rs and capacitance C values ​​at 0.06[kHz] (60[Hz]) in Figures 7 and 8. Here, E = 5[V]. Thus, the initial value Vds changes with temperature due to the negative temperature coefficient of the equivalent series resistance Rs, and the subsequent change in the detected value Vd 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 of the charging period; 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 setting ts << charging period, the detected value Vd can be considered as the initial value Vds, so it becomes possible to determine 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.

[0064] 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 in FIGS. 7 and 8, as the temperature is higher, the equivalent series resistance Rs with a negative temperature coefficient becomes smaller, and the capacitance C with a positive temperature coefficient becomes larger. 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. Thus, 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) with respect to 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.

[0065] As shown in Figure 7, when the measurement frequency is low, or when the measurement is considered to be performed in DC as in this embodiment, the temperature dependence of capacitance C is not necessarily large, and in practice, the sensitivity of temperature detection may be substantially determined by the temperature dependence of the equivalent series resistance Rs. However, in either case, the temperature dependence of capacitance C may help the temperature detection sensitivity due to the temperature dependence of the equivalent series resistance Rs, but it will not hinder the temperature detection sensitivity due to the temperature dependence of the equivalent series resistance Rs. Furthermore, as in this embodiment, the structure having a thin insulating layer 11t formed on a fine surface uneven structure and an electrolyte 12L in contact with this insulating layer 11t allows the capacitance C to be easily set to a large value. By increasing the capacitance C, even if the positive temperature coefficient of capacitance C is small, the effect on the detection sensitivity of the actual detected values ​​Vds and Vdt can be increased. Moreover, in this temperature detection method, if the 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 or reduce sensitivity and accuracy. However, in this embodiment, since 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, thereby reducing the cost of the temperature detection circuit and improving its sensitivity and accuracy.

[0066] In the temperature detection circuit 10CT1 of this embodiment, it is preferable that the charging resistance Rc and the discharge resistance Rd each 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 compared to the equivalent series resistance Rs, the detected value Vds will be close to E, which reduces the temperature dependence of the change in the electromagnetic state over time, thus decreasing the sensitivity of temperature detection. Conversely, if the charging resistance Rc is too large compared to the equivalent series resistance Rs, the detected value Vds itself will be small, which again reduces the temperature dependence of the change in the electromagnetic state over time, thus decreasing the sensitivity of temperature detection. During discharge, the initial value (t=0) Vds of the detected value Vd is Vds = E{1-Rs / (Rd+Rs)}. At this time, if the discharge resistance Rd is too small compared to the equivalent series resistance Rs, the detected value Vds itself will be small, approaching 0, which reduces the temperature dependence of the change in the electromagnetic state over time, thus decreasing the sensitivity of temperature detection. Conversely, if the discharge resistance Rd is too large compared to the equivalent series resistance Rs, the detected value Vds will be close to E, which reduces the temperature dependence of the change in the electromagnetic state over time, thus decreasing the sensitivity of temperature detection. The above resistance range is preferably valid in the room temperature range (5°C - 35°C), or in the temperature detection range of the temperature sensor 10 if one is set.

[0067] Furthermore, simulations using equation (3) above show that during charging, the sensitivity of the temperature sensor 10 (the rate of change of the detected value Vd relative to the rate of change of Rs) is best around the temperature at which the equivalent series resistance Rs equals Rc. Similarly, during discharge, the sensitivity of the temperature sensor 10 (the rate of change of the detected value Vd relative to the rate of change of Rs) is best around the temperature at which the equivalent series resistance Rs equals Rd. Based on this, it is conceivable to install multiple charging resistors Rc and discharge 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 to be adjustable as variable resistors. It is desirable to be able to select and use multiple charging resistors Rc or discharge resistors Rd by switching depending on the installation location and application, or to be able to use them by adjusting the resistance values ​​of the charging resistors Rc or discharge resistors Rd. In this case, it is desirable that the device be configured so that the resistance values ​​of the charging resistance Rc or the discharging resistance Rd can be switched or adjusted to be within a range of 0.1 to 10 times the equivalent series resistance Rs, respectively, within the normal temperature range of 5°C to 35°C, or, if a temperature detection range is defined, within that temperature detection range.

[0068] Next, a temperature detection circuit 10CT2 of a second embodiment using the temperature sensor 10 of this embodiment will be described with reference to Figure 13. In this second embodiment, the equivalent series resistance Rs and capacitance C of the element section 10S, and a diode D1 for preventing reverse current flow are connected in parallel to a power supply Ep that outputs a clock signal of a predetermined frequency via a charging resistor R1. Furthermore, a parallel circuit section consisting of a capacitor C1 for maintaining a peak voltage Vp and a discharge resistor R2 is connected in series with the diode D1, and the voltage across this parallel circuit section is measured. In this temperature detection circuit 10CT2 as well, the capacitance C is charged and discharged through the equivalent series resistance Rs by the power supply and discharge section CTA, and the temperature can be derived by the detection section CTB which outputs a detected value that reflects the temperature dependence of the change in the electromagnetic state of the equivalent circuit over time during charging or discharging. Here, in this temperature detection circuit 10CT2, the power supply and elimination section CTA corresponds to the circuit part and ground part 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).

[0069] Figure 14 is a schematic graph showing the voltage waveform of the detected value Vd of the temperature detection circuit 10CT2 in the second embodiment. When a pulse waveform (for example, a square wave of 0[V] and 5[V]) is output from the power supply Ep, the capacitance C is charged in the element section 10S through the equivalent series resistance Rs via the charging resistor R1, corresponding to the pulse waveform. Eventually, after the pulse waveform has passed, the capacitance C is discharged in the element section 10S through the equivalent series resistance Rs, after showing a peak voltage Vp. The output waveform shown in Figure 14 repeats a cycle in which the detected value Vd increases as the capacitance C is charged, shows a peak voltage Vp, and then decreases 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 of the electromagnetic state of the equivalent circuit (equivalent direct resistance Rs and capacitance C) during the charging or discharging period. In other words, the larger 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 in Figures 7 and 8, as the temperature increases, the equivalent series resistance Rs decreases and the capacitance C increases, so the peak voltage Vp decreases from both viewpoints. For this reason, with respect to the peak voltage Vp detected in this way, both the positive temperature coefficient of capacitance C and the negative temperature coefficient of equivalent series resistance Rs act in the same direction on the detection sensitivity of the detected value Vp, or at least they do not interfere with each other. Thus, by detecting the peak voltage Vp, highly sensitive and accurate temperature detection becomes possible. In this embodiment, in order to obtain a detected value that reflects the temperature dependence of the above-mentioned change over time, the peak voltage Vp between the charging period and the discharging period is detected.

[0070] The peak voltage Vp described above is lower when the temperature is high because the equivalent series resistance Rs decreases, reducing the voltage effect on the charging current, and the capacitance C increases, suppressing the rise in charging voltage relative to the charging current. Therefore, the equivalent circuit voltage Vd does not tend to rise. On the other hand, when the temperature is low, the equivalent series resistance Rs increases, increasing the voltage effect on the charging current, and the capacitance C decreases, promoting the rise in charging voltage relative to the charging current. Therefore, the equivalent circuit voltage Vd tends to rise. For this reason, when the measured peak voltage Vp is large, the temperature is low, and when the peak voltage Vp is small, the temperature is high. Even in this case, as mentioned above, both the negative temperature coefficient of the equivalent series resistance Rs and the positive temperature coefficient of the capacitance C act in the same direction on the detected peak voltage Vp, or at least do not interfere with each other.

[0071] Figure 15 schematically shows the configuration of a temperature detection circuit 10CT3 having an automatic balancing bridge circuit used in a method for measuring the electrical resistance of a substance with a temperature coefficient. As described above, the equivalent series resistance Rs of the temperature sensor 10 in this embodiment has a large negative temperature coefficient, so it is also possible to detect the temperature by directly measuring this equivalent series resistance Rs. However, since most 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 with DC and is measured with AC. In this detection circuit, using the automatic balancing bridge method, one of the resistances Ra and Rb of the bridge circuit supplied with power Em from the AC power source is set to an electrical resistance with a known resistance value, and the other to an equivalent series resistance Rs. By changing the ratio of the dividing resistance values ​​Rac and Rbc of the variable resistor Rc, and bringing the AC detector D to a state where no current flows (equilibrium state), the equivalent series resistance Rs can be determined from the above one of the resistances Ra and Rb (the electrical resistance with a known resistance value) and the dividing resistance values ​​Rac and Rbc. Although the cost of the temperature detection circuit increases slightly with this temperature detection circuit 10CT3 and its temperature detection method, the negative temperature coefficient of the equivalent series resistance Rs is large and stable, enabling highly sensitive, accurate, and stable temperature measurement.

[0072] As described above, the temperature sensor 10 of this embodiment has an electrolyte 12L disposed between the anode foil (first electrode) 11 and the cathode foil (second electrode) 13. By bringing at least one electrode 11 into contact with the electrolyte 12L via the insulating layer 11t on its surface, the rate of change due to temperature change in the equivalent series resistance Rs and capacitance C can be increased compared to the rate of change due to temperature change in a conventional heat-sensitive sheet made of resin film, due to the influence of the insulating layer 11t and the electrolyte 12L. Therefore, the detection sensitivity of the temperature detected based on the change in electromagnetic characteristics due to the temperature change between the first electrode and the second electrode can be improved. In particular, the temperature coefficient of resistivity of the electrolyte 12L is larger than that of the polymer resin film, so the detection sensitivity can be increased. In addition, the composition of the electrolyte 12L can be easily adjusted according to the detection characteristics required for the temperature sensor, and it is also easy to prepare the electrolyte in this adjusted form. Furthermore, since an electrolytic capacitor structure is used in which the electrolyte 12L is interposed between the film electrodes 11 and 13, it can be manufactured at low cost. Furthermore, since the temperature sensor 10 is configured in a sheet shape, it can easily and uniformly absorb heat when it comes into contact with the object whose temperature is to be measured. Therefore, from the perspective of this installation method, the sensitivity and accuracy of temperature detection can be improved.

[0073] In this embodiment, it is preferable that the insulating layer 11t is formed on the surface layer having a fine surface uneven structure. This allows the surface 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. As a result, it becomes possible to further improve 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 valve metal, and the insulating layer 11t is a passivated film formed on the surface layer of the electrode 11, the insulating layer 11t is composed of a passivated film of valve metal, which allows for a thin yet dense insulating film, making it easier to increase capacitance while reducing leakage current.

[0074] 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, the equivalent circuit of the element portion 10S of the temperature sensor 10 generates a change in the electromagnetic state over time by charging or discharging the capacitance C through the equivalent series resistance Rs. By outputting detection values ​​Vds, Vdt, and Vp that reflect the temperature dependence of the change in the electromagnetic state over time in the equivalent circuit caused by the temperature characteristics of the equivalent series resistance Rs and capacitance C, it becomes possible to derive the temperature characteristics of the equivalent series resistance Rs and capacitance C of the equivalent circuit. In this case, the temperature sensor 10 has a negative temperature coefficient for the equivalent series resistance Rs and a positive temperature coefficient for the capacitance C, and the negative temperature coefficient in the equivalent series resistance Rs and the positive temperature coefficient in the capacitance C both act in the same direction on the detection sensitivity, or at least do not interfere with each other, thereby further improving the sensitivity and accuracy of the temperature sensor 10.

[0075] Figure 16 is an explanatory diagram showing the structure and manufacturing process of the temperature sensor 20 of the second embodiment. As shown in Figure 16(a), this temperature sensor 20, like the temperature sensor 10 of the first embodiment, includes an element section 20S containing an insulating layer and an electrolyte between electrodes. The element section 20S is provided with a (cylindrical) columnar first electrode 21 and a second electrode 23. The first electrode 21 has a first terminal 24 having a lead wire structure such as a CP wire electrically connected to its outer end face by welding or the like. The inner end face of the first electrode 21 has an insulating layer, and may have a fine surface uneven structure similar to that of the anode foil 11. The second electrode 23 has a second terminal 25 similar to that of the first terminal 24 electrically connected to its outer end face by welding or the like. The inner end face of the second electrode 23 may have an insulating layer, and may also have a fine surface uneven structure similar to that of the cathode foil 13. An electrolyte 22L, similar to that in the first embodiment, is placed between the inner end face of the first electrode 21 and the inner end face of the second electrode 23. Preferably, this electrolytic solution 22L is held in place by being impregnated into a separator 22, similar to that in the first embodiment. If a resin coating is applied to the outer circumferential surfaces of the first electrode 21 and the second electrode 23, adhesion can be improved by heat fusion or compression bonding between the resin coating layer and the housing 26, which will be described later.

[0076] Figure 16(b) shows the housing 26 for the temperature sensor 20. This housing 26 has a cylindrical structure (tube structure) made of metal, resin, or the like. Preferably, this housing 26 has a thickness sufficient to maintain the internal pressure rise and physical strength of the element portion 20S of the temperature sensor 20. The housing 26 may also be made of a sheet material consisting of the outer films 16 and 17 of the first embodiment. Preferably, this housing 26 is inserted so as to be positioned on the outer circumference of the element portion 20S, and the element portion 20S is sealed by methods such as drawing from the outer circumference or heat fusion with the resin coating. When metal is used for the housing 26, it is necessary to provide an insulating layer such as a resin sheet or resin coating between the first electrode 21 and the housing 26, and between the second electrode 22 and the housing 26.

[0077] It should be noted that the temperature detection circuit and temperature detection method of the present invention are not limited to the illustrated examples described above, and various modifications can be made without departing from the spirit of the present invention. For example, in the first and second embodiments of the temperature sensor used in the embodiments of the present invention, lead-shaped terminals 14, 15, 24, and 25 are led out from the sealed structure of housings 16, 17, and 26, but a surface-mount type terminal structure having a terminal surface exposed on the outer surface of the housing may also be provided. [Explanation of symbols]

[0078] 10, 20…Temperature sensor, 10S, 20S…Element section, 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…Welding film, 15…Second terminal, 16, 17…Outer film (housing), 16m, 17m…Welding area, C…Capacitance, Rs…Equivalent series resistance, 21…First electrode, 23…Second electrode, 26…Housing

Claims

1. A temperature detection circuit is electrically connected to a temperature sensor having an element section in which an equivalent circuit including equivalent series resistance and capacitance is formed between a first terminal and a second terminal, and outputs a detected value for detecting the ambient temperature of the temperature sensor, A power supply and discharge unit that causes a change in the electromagnetic state in the equivalent circuit over time by charging or discharging the capacitance through the equivalent series resistance, A detection unit that outputs a detected value that reflects the temperature dependence of the change over time of the electromagnetic state in the equivalent circuit, which is caused by the temperature characteristics of the equivalent series resistance and the capacitance, A temperature detection circuit characterized by having the following features.

2. 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 in the equivalent series resistance and the positive temperature coefficient in the capacitance both act in the same direction with respect to the detected value, or at least do not interfere with each other. The temperature detection circuit according to claim 1.

3. The power supply and elimination unit has a charging resistor connected in series with the equivalent series resistance in the charging path of the capacitance, or a discharge resistor connected in series with the equivalent series resistance in the discharge path of the capacitance. The resistance value of the charging resistance or the discharge resistance is within the range of 0.1 to 10 times the resistance value of the equivalent series resistance in the room temperature range of 5°C to 35°C, or, if a temperature detection range is defined, within that temperature detection range. The temperature detection circuit according to claim 1.

4. The power supply and elimination unit has a charging resistor connected in series with the equivalent series resistance in the charging path of the capacitance, or a discharge resistor connected in series with the equivalent series resistance in the discharge path of the capacitance. The device has means for switching or adjusting the resistance value of the charging resistor or the discharging resistor. The temperature detection circuit according to claim 1.

5. The element portion includes a first electrode electrically connected to the first terminal, a second electrode electrically connected to the second terminal, and an electrolyte solution disposed between the first electrode and the second electrode. A temperature detection circuit according to any one of claims 1 to 4.

6. The electrolyte-side surface of at least one of the first electrode and the second electrode has a fine surface uneven structure. The temperature detection circuit according to claim 5.

7. An insulating layer is formed on the electrolyte-side surface of at least one of the first electrode and the second electrode. The temperature detection circuit according to claim 5.

8. The insulating layer is formed on the surface layer having a fine surface uneven structure. The temperature detection circuit according to claim 7.

9. The at least one of the electrodes is made of valve metal, and the insulating layer is a passivation film formed on the surface of the electrode. The temperature sensor according to claim 7.

10. The electrolyte comprises an electrolyte and a solvent, the solvent having a viscosity in the range of 10 mPa·s to 5000 mPa·s within a temperature range of 5 [°C] to 35 [°C]. The temperature detection circuit according to claim 5.

11. In the room temperature range of 5°C to 35°C, or within the temperature detection range if one is defined, the product of the equivalent series resistance Rs [Ω] and the capacitance C [μF] is 10 or more. The temperature detection circuit according to claim 5.

12. A temperature detection method for outputting a detected value for detecting the ambient temperature of a temperature sensor having an element portion in which an equivalent circuit including equivalent series resistance and capacitance is formed between a first terminal and a second terminal, The charging or discharging of the capacitance through the equivalent series resistance causes a change in the electromagnetic state over time in the equivalent circuit. A temperature detection method characterized by outputting a detected value that reflects the temperature dependence of the change over time of the electromagnetic state in the equivalent circuit, which is caused by the temperature characteristics of the equivalent series resistance and the capacitance.

13. 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 in the equivalent series resistance and the positive temperature coefficient in the capacitance both act in the same direction with respect to the detected value, or at least do not interfere with each other. The temperature detection method according to claim 12.

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