Wet sensor and wet evaluation device

Abstract

To provide a wet sensor that is able to detect even slight wet that may occur on the insulator.SOLUTION: The invention is a wet sensor (S) having a pair of electrodes (e1, e2) disposed apart from each other on a surface of an insulator (P). In the electrodes, only end faces (a1, a2) facing each other on the surface of the insulator are respectively exposed. A distance (L) between the end faces is, for example, 1 to 18 mm. The electrodes are, for example, in the form of a foil or thin plate with an end-face height of 0.01 to 1 mm. The electrode is made of, for example, gold or platinum. The insulator is made of, for example, a resin, and a typical example thereof is a coating film. The presence or absence of wet can be determined by applying an alternating current to the wet sensor of the present invention to obtain a characteristic value and comparing the characteristic value with a threshold value. Deterioration or the like of the insulator may be evaluated based on the cumulative value of the times during which wetting has occurred.SELECTED DRAWING: Figure 1A

Description

Technical Field

[0001] The present invention relates to a sensor capable of detecting the wetting of an insulator and the like.

Background Art

[0002] Moisture adhering to the surface of a substance in an atmospheric environment can have various effects on the substance. For this reason, various wetting sensors for detecting moisture have been proposed and are used in various fields.

[0003] Typical wetting sensors include a galvanic current type sensor (ACM: Atmospheric Corrosion Monitor), a resistive sensor, a capacitive sensor, a dielectric sensor, and the like. Further, Patent Document 1 below describes an electric conduction type leaf wetting sensor for a plant body.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] All conventional wetting sensors have only been capable of detecting the adhesion of water droplets due to rain, dew, or the like. That is, with conventional sensors, it has not been possible to detect slight moisture (such as a thin water film) that does not reach such water droplets, and such detection has not even been assumed.

[0006] The present invention has been made in view of such circumstances, and an object thereof is to provide a sensor and the like that can detect slight wetting that does not reach water droplets.

Means for Solving the Problems

[0007] As a result of the intensive research by the present inventor, it has been found that wetting can occur on the surface of a substance even in a dry state (non-wetting environment) without rainwater, dew, etc., and a new sensor that can detect even such slight wetting has been conceived and realized. By developing this result, the present invention described below has been completed.

[0008] 《Wetting Sensor》 (1) The present invention is a wetting sensor having a pair of electrodes disposed apart on the surface of an insulator, wherein only the end faces facing each other on the surface are exposed, and the distance between the end faces is 1 to 18 mm.

[0009] (2) According to the wetting sensor of the present invention (also simply referred to as "sensor"), even slight wetting that can occur on the surface of the insulator can be detected. Thereby, for example, it becomes possible to precisely evaluate the influence of moisture on the insulator.

[0010] Note that an insulator exposed to the outside world can be wetted by rainfall, snowfall, dew condensation, etc., and can also have wetting on its surface even in a dry environment that is not such a wetting environment. For example, when an attachment (dirt, salt, etc.) adheres to the surface of the insulator, wetting can occur on the surface of the insulator even in a dry environment due to its water absorption, deliquescence, etc. Note that such a wetting form is not limited to a thin planar shape (thin film shape), and may also be a thin linear shape (linear shape), etc.

[0011] 《Wetting Evaluation Device》 The present invention can also be understood as a wetting evaluation device. The wetting evaluation device may include, for example, the above-described wetting sensor and specific means for applying an alternating current to the wetting sensor to obtain characteristic values. By comparing the characteristic values with a threshold value, the presence or absence of wetting can also be determined (determination means). Further, the time of wetting (wetting time) may be measured and the cumulative value thereof may be obtained (measurement means). Furthermore, based on the cumulative value of the wetting time, the degree of deterioration (alteration) of the insulator, etc. may be evaluated (evaluation means).

[0012] 《Others》 (1) As used in this specification, "~ means" can be read as "~ step (process)". By doing so, the components (means) of an "object (device)" become the components (steps / processes) of a "method", and it becomes possible to understand an invention of an object as an invention of a method.

[0013] (2) Unless otherwise specified, "x to y" as used in this specification includes the lower limit value x and the upper limit value y. By using any numerical value included in various numerical values or numerical ranges described in this specification as a new lower limit value or upper limit value, a range such as "a to b" can be newly established.

Brief Description of the Drawings

[0014]

Fig. 1A

Fig. 1B

Fig. 2A

Fig. 2B

Modes for Carrying Out the Invention

[0015] One or more components arbitrarily selected from this specification can be added to the components of the present invention described above. The content described in this specification can be appropriately applied not only to "objects" but also to "methods". Whether any embodiment is the best depends on the object, required performance, etc.

[0016] 《Insulator》 The insulator on which the electrodes are disposed is an object of evaluation of wetting. That is, the insulator can have its properties, quality, etc. changed (deteriorated, altered, corroded, etc.) depending on the presence or absence and amount of wetting. The insulator is not limited by its material, degree of insulation, form (shape, size), manufacturing method, etc.

[0017] The insulator is made of, for example, a thermoplastic resin, a thermosetting resin, rubber (including elastomers), etc. The insulator may be in any form such as a film, a layer, or a bulk. A typical example of the insulator is a coating film or a skin film adhered to other members. The film-like or layer-like insulator may be a single layer or a multi-layer.

[0018] Examples of other members combined with the insulator include metal substrates such as iron substrates, aluminum substrates, titanium substrates, or magnesium substrates (such as melted materials and sintered materials), inorganic substrates (such as ceramic materials), and organic substrates (such as resin materials and papers). The insulator combined with other members may be an insert molded body, a composite member composed of a matrix and a filler, etc.

[0019] 《Electrode》 The electrode can be disposed (such as adhered) on the surface of the insulator, and any electrode can be used as long as it can appropriately perform AC measurement. Its material is preferably made of, for example, noble metals (Pt, Au, Ag), stainless steel, Ti substrates, or highly corrosion-resistant (insoluble, hardly soluble) conductive materials such as nictide conductive materials (Ti3P, FeTiP, XTiP (X: metal element), etc.). Representative electrode materials are gold and platinum. In addition, each pair of electrodes disposed opposite to each other is preferably made of the same material.

[0020] The electrode is preferably in a form that can stably detect slight wetness that can occur even in a dry environment. For example, the electrode is preferably in the form of a foil or a thin plate. Its thickness (end face height) is, for example, 0.01 - 1 mm, 0.03 - 0.5 mm, or 0.07 - 0.25 mm.

[0021] On the surface of the disposed insulator, only the end faces (side faces in the thickness direction) facing each other are exposed for the electrode. The distance between the end faces (electrode distance) is, for example, 1 - 18 mm, 3 - 16 mm, or 5 - 10 mm. If the distance is too small, the influence of dirt (adhesions, precipitates, etc.) adhered to the insulator surface on the AC characteristic values becomes large. If the distance is too large, the output between the electrodes becomes unstable, and it becomes difficult to detect slight wetness occurring on the insulator surface.

[0022] The electrode may be such that other parts (other surfaces) except the end faces facing each other on the insulator surface are shielded from the outside. For example, it may be covered with other parts using an insulating tape, paste, adhesive, holder, etc. In addition, the lower surface (back surface, adhering surface) side of the electrode in contact with the insulator surface may be further insulated and coated.

[0023] 《Characteristic Values》 As characteristic values used for wetting evaluation, there are sensor outputs obtained when applying alternating current and analysis values thereof. For example, impedance (Z = R + jX, R: resistance, X: reactance), admittance (Y = 1 / Z = G + jB, G: conductance, B: susceptance), their real parts (R, G), imaginary parts (X, B), imaginary part / angular frequency (X / ω, B / ω), and analysis values (such as capacitance C) obtained from them.

[0024] Incidentally, between a pair of electrodes arranged apart, it can often be shown by an equivalent circuit in which a resistor (r) and a capacitor (C) are connected in parallel (see Fig. 1B). Therefore, capacitive reactance (Xc), capacitive susceptance (Bc = 1 / Xc), or capacitance C (1 / ωXc, Bc / ω, ω: angular frequency) obtained from them may be used as characteristic values or index values for calculating characteristic values.

[0025] Note that the characteristic value may be, in addition to the index value based on a specific frequency (single frequency), an analysis value or a tendency value (frequency characteristic / spectrum) obtained from the index value based on a specific frequency band (plural frequencies).

[0026] 《Wetting Evaluation Device (System)》 The wetting evaluation device includes at least measurement means for measuring the output in addition to the wetting sensor.

[0027] The sensor output when applying alternating current is measured using, for example, an impedance analyzer, an LCR meter, etc. The frequency (f = ω / 2π) of the alternating current is, for example, 0.01 to 100 Hz, 0.1 to 10 Hz.

[0028] The wetness evaluation device may include a determination means for comparing a characteristic value with a threshold value to determine the presence or absence and state of wetness, a measurement means for obtaining the time when wetness occurs (wet time) or the cumulative value obtained by summing up the wet times, an evaluation means for evaluating the state (deterioration, alteration, etc.) of the insulator based on the cumulative value of the wet time, and the like. Any of these means may be configured by a computer that captures the output and data obtained from a sensor or a measuring device, or its execution program.

[0029] Note that the cumulative value of the wet time may include the wet time caused by precipitation, dew condensation, etc. The evaluation of the wet state is utilized, for example, in the maintenance (repair, replacement, etc.) of the insulator.

[0030] 《Applications》 As an example of the object to which the sensor of the present invention is provided, there is a painted vehicle body (metal body). By using the sensor and evaluation device of the present invention, in a repair factory or an automobile dealer where the vehicle is stored, etc., for the actual vehicle in use, it is possible to precisely evaluate the degree of deterioration, remaining life, necessity of repair and parts replacement, etc. of the paint and the body at any time, timely or periodically. Such circumstances are not limited to vehicles, but are the same for painted buildings, bridges, infrastructure pipes, etc.

Examples

[0031] A plurality of wetness sensors with different electrode distances were fabricated. The wetness sensor disposed on the painted surface was exposed to an environment simulating the outside world, and an alternating current was applied to the wetness sensor to measure the characteristic value. Based on such a specific example, the present invention will be described in more detail.

[0032] As shown in Fig. 1A, a wetness sensor S (simply referred to as "sensor S") was disposed on a coating film P (insulator) formed on a steel plate, and an alternating current was applied to the sensor S.

[0033] The coating film P is composed of a single layer of epoxy resin (film thickness 15 μm).

[0034] The sensor S is composed of electrodes e1 and e2 (collectively referred to as "electrode e") that are spaced apart on the surface (coated surface) of the coating film P, an adhesive tape h (fixture) that fixes each electrode e in close contact with the coated surface, and a wiring w (lead wire) that connects each electrode e to the measuring device M.

[0035] The electrode e is made of a thin plate strip-shaped gold (Au) with a thickness of 0.1 mm × width of 2 mm × length of 10 - 20 mm. The interval L (end face interval / electrode distance) between the end face a1 (0.1 mm × 2 mm) of electrode e1 and the end face a2 (0.1 mm × 2 mm) of electrode e2 was variously changed. Note that the end faces a1 and a2 are collectively simply referred to as "end face a".

[0036] Insulating polyester was used for the adhesive tape h. Except for the end face a and the back surface (the close contact surface with the coating film P) of the electrode e, the entire electrode e was covered with the adhesive tape h. That is, only the end face a (height 0.1 mm) was exposed.

[0037] The wiring w was connected to the measuring device M (electrochemical analyzer (LCR meter): ModuLab manufactured by Solartron Analytical). An alternating current of a predetermined frequency was input to the sensor S by the measuring device M, and the output obtained from the sensor S was measured.

[0038] For reference, an equivalent circuit diagram of such a measurement system is shown in FIG. 1B. The sensor S composed of the spaced electrodes e can be regarded as a circuit in which a resistor R and a capacitance C are connected in parallel.

[0039] 《Measurement》 (1) Without dirt (when clean) The measurement system (coating film P and sensor S) in a clean state without dirt or the like was placed in a thermo-hygrostat to set a predetermined temperature and humidity, and the output (admittance Y = G + jB) at that time was measured. The interval L between the electrodes e of the sensor S was set to 2 mm, 5 mm, 10 mm, or 20 mm. The temperature was set to 50°C or 80°C, and the relative humidity (RH) was set to 25% or 95%.

[0040] Conductance (G 25 ) when RH: 25% and conductance (G 95) difference (ΔG = G 95 - G 25 : characteristic value) was shown in Fig. 2A for each temperature. Similarly, the difference in capacitance (B 25 / ω) at RH: 25% and capacitance (B 95 / ω) at RH: 95% (ΔB = B 95 / ω - B 25 / ω: characteristic value) was also shown in Fig. 2A for each temperature.

[0041] Here, each capacitance (C = B / ω) was obtained as follows. An alternating current of different frequencies (f i ) was passed through the sensor S. For each frequency, the measured susceptance (B i ) was divided by the angular frequency (ω i = 2πf i ) to obtain an index value (C i = B i / ω i ). The characteristic value (C: the true number of the logarithm) was derived from the logarithmic mean value of these index values by calculation as shown in the following formula (specific means). logC = (ΣlogC i ) / N (i = 1, 2, 3 ··· N)

[0042] In this example, the logarithmic mean value was obtained for 10 points (N = 10) extracted at equal intervals from the logarithmically represented AC frequency range (f = 10 -2 ~ 10 0 Hz).

[0043] (2) With dirt A drop of sodium chloride aqueous solution (concentration 1 mol / L) was dropped onto the surface of the sensor S (between the electrode end faces) with a dropper. The sensor S was left in the air for 2 - 3 days to dry. A small amount of white substance (salt) was observed near the surface of the sensor S (between the end faces).

[0044] Using such a sensor S, the above-mentioned measurement and analysis (specification) were performed again. The results are summarized in Fig. 2B.

[0045] 《Evaluation》 (1) As can be seen from FIG. 2A, when the surface of the sensor S was clean, regardless of temperature and humidity, there was almost no sensor output (i.e., it was nearly in an insulating state), and the characteristic values (G, B / ω) were also substantially zero. In such a case, it can be determined that the coating film P was substantially not wet.

[0046] (2) On the other hand, as can be seen from FIG. 2B, when dirt (NaCl) adhered to the surface of the sensor S, corresponding sensor outputs and characteristic values (G, B / ω) were obtained. However, when the end face interval (L) increased, the output decreased significantly. Therefore, it was found that in order to obtain a stable output (characteristic value), it was necessary to keep the end face interval of the electrodes within a predetermined range.

[0047] Incidentally, the reason why sensor outputs were obtained even in a dry environment was considered to be that due to the deliquescence of NaCl adhering to the surface of the coating film P, an electrolyte (see m in FIG. 1A) was formed between the electrodes (end faces) (i.e., wetting occurred). The output or characteristic value became significantly larger in the high temperature range (around 80°C / 65 - 100°C), but was also at a level that could be sufficiently detected in the low temperature range (around 50°C / 20 - 65°C).

[0048] Incidentally, even when dirt (NaCl) adhered to the surface of the sensor S, the conductance (G 25 ) and capacitance (B 25 / ω) at RH: 25% were almost zero, the same as when the surface of the sensor S was clean. Therefore, by simply comparing these characteristic values with a predetermined threshold value (for example, 3 pS or 4 pS, 3 pF or 4 pF), it was possible to determine the presence or absence of wetting occurring on the surface of the insulator in a dry environment (RH: 50 - 100%, 75 - 99%).

[0049] Note that it is natural that sufficiently large sensor S outputs and characteristic values are obtained in a wet environment (for example, in a state where an aqueous solution is dropped).

[0050] From the above, it was confirmed that by using the wetting sensor of the present invention, it was possible to detect substantial wetting that could occur in a non-wet external environment (in the atmosphere where the insulator is exposed).

Explanation of Reference Numerals

[0051] S wet sensor P insulator e1, e2 electrodes a1, a2 end faces L distance between end faces (electrode distance) m electrolyte (wetness)

Claims

1. A wetness sensor having a pair of electrodes disposed apart on the surface of an insulator, only the end faces facing each other on the surface are exposed for the electrodes, and the distance between the end faces is 1 to 18 mm.

2. The wetness sensor according to claim 1, wherein the electrodes are in the form of a foil or a thin plate with the height of the end faces being 0.01 to 1 mm.

3. The wetness sensor according to claim 1, wherein the electrodes are made of gold or platinum.

4. The wetness sensor according to claim 1, wherein the insulator is made of resin.

5. The wetness sensor according to claim 4, wherein the resin is a coating film.

6. A wetness evaluation device comprising the wetness sensor according to any one of claims 1 to 5, and specific means for applying an alternating current to the wetness sensor to obtain characteristic values.

7. The characteristic values according to claim 6 are obtained from any of impedance, the real part (conductance) and / or the imaginary part (susceptance) of admittance, and an index value (B / ω) obtained by dividing susceptance (B) by angular frequency (ω).

8. The characteristic values according to claim 7 are a plurality of index values with different angular frequencies or values derived by calculating the plurality of index values within a predetermined angular frequency range.

9. The angular frequency according to claim 7 is selected from (0.01 to 100)×2π (rad / sec).

10. Further, the wetness evaluation device according to claim 6, wherein the characteristic values are compared with a threshold value to determine wetness or measure the wetting time.

11. The wetness evaluation device according to claim 10, which evaluates the deterioration of the insulator based on the cumulative value of the wetting time.

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