JP2008209363A - Liquid leakage sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid leakage sensor capable of detecting leakage by separating oil from moisture in leaked liquid. <P>SOLUTION: This liquid leakage sensor is equipped with an optical liquid leakage sensor part comprising a light emitter, a prism and a light receiver, for detecting leakage liquid by a light receiving amount by the light receiver; and a conductive liquid leakage sensor part for oscillating by using a pair of electrodes as oscillation elements, and detecting the leakage liquid by a variation of an oscillation frequency. The sensor is characterized by detecting liquid leakage of two kinds of liquids. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a leak sensor, and more particularly to a leak sensor that can detect oil and water separately.

  In facilities such as conventional factories, liquids are supplied by piping, or liquids are stored in tanks. However, pipes are provided with connecting joints at many locations, and the tank is provided with a liquid inlet / outlet, so that the liquid often leaks from the joint or the inlet / outlet. In addition, rainwater or the like may flow from the outside, and the occurrence of water leakage is fatal in semiconductor manufacturing lines and food processing lines. Therefore, it is necessary to constantly monitor liquid leakage, and optical and conductive methods are known as conventional leakage monitoring means.

  Japanese Patent No. 3220440 (Patent Document 1) detects leakage of electrically conductive liquids such as water, acidic solutions and alkaline solutions, and organic and insulating liquids such as alcohol, thinner and benzine. An optical leak sensor is disclosed. FIGS. 1A and 1B show a principle configuration diagram of an optical liquid leakage sensor 100. Light 102 is emitted from a light emitter 101, and the light 102 is reflected by a prism 104 and incident on a light receiver 105. FIG. . In the case of FIG. 1A where there is no leakage, the light 102A from the prism 104 is input to the light receiver 105 along the correct optical axis. However, as shown in FIG. 1B, when there is a liquid leak 110, the light reflection angle (refractive angle) or transmitted light amount (transmittance) of the prism 104 changes due to the liquid leak 110, and the incident light quantity to the light receiver 105 is changed. Changes. As described above, the optical liquid leakage sensor 100 detects the presence or absence of the liquid leakage 110 by making the light emission amount of the light emitter 101 constant and detecting the incident light amount of the light receiver 105.

Japanese Patent Laying-Open No. 2005-156541 (Patent Document 2) includes at least one leak detection unit that can come into contact with a leak via a gas layer or a leak penetration layer through which the leak can permeate. The liquid detector includes an optical leak detector including at least one optical reflective interface, and a conductive leak detector including an electrode pair whose impedance between electrodes changes due to the presence of the conductive / insulating liquid. A liquid sensor is disclosed. 2 (A) and 2 (B) show the detection principle of the conductive leakage sensor disclosed in Patent Document 2, and electrodes 210A and 211A are connected in series via a resistor 202 to a battery 201 as a DC power source. ... and electrodes 210B, 211B, ... are connected to face each other. Then, the current flowing through the resistor 202 is measured by the voltmeter 203. In the state of FIG. 2A, no current flows, but when there is a liquid leakage 220 as shown in FIG. 2B, the current flows because the electrodes 211A and 211B are electrically connected, and a voltmeter In step 203, the voltage V corresponding to the current is measured to detect the liquid leakage 220.
Japanese Patent No. 3220440 JP 2005-156541 A

  However, the liquid leakage sensor 100 disclosed in Patent Document 1 is a detection based on the difference in refractive index between the resin of the housing and the liquid or air of interest, so that only water or oil can be detected. In a liquid with water mixed in, the oil component is lighter in specific gravity than water, so the oil will reach the upper layer of the water and light will be transmitted, thus accurately separating the water leak from the oil leak. Cannot be detected. If the leak sensor is reversed, the water will theoretically come to the lower layer and the oil will come to the upper layer, so detection in a mixed state of oil and water is possible. Have difficulty.

  Moreover, since the leak sensor 200 disclosed in Patent Document 2 depends on the conductivity of an object, it reacts with conductive water, but reacts with oil closer to an insulator than water. It is difficult to conduct the current and the oil leakage cannot be detected. In addition, it is thought that detection is possible by measuring the continuity and capacitance with AC input power, but the difference between air and oil is minute, and complicated and expensive measurement circuits are required. is there.

  In recent years, in addition to gasoline leaks at gasoline stations, it has been strongly desired that water leaks be detected so that water does not enter gasoline tanks. It becomes a fatal wound and the need to detect water and oil separately is increasing. Nevertheless, conventional leak sensors could not detect water and oil separately.

  The present invention has been made under the circumstances as described above, and the object of the present invention is to pay attention to the fact that the characteristics of oil and water are different. The advantages of the optical leak sensor and the conductive leak sensor are as follows. It is an object of the present invention to provide a liquid leakage sensor that can easily distinguish and detect water leakage and oil leakage without increasing the cost.

  The present invention relates to a liquid leakage sensor, and the above object of the present invention includes a light emitter, a prism, and a light receiver. An optical liquid leakage sensor unit that detects a liquid leakage with the amount of light received by the light receiver and a pair of electrodes. A conductive leakage sensor unit that oscillates as an oscillating element and detects the leakage according to the amount of change in the oscillation frequency is provided to separate and detect leakage of two types of liquid.

  A detection circuit for processing the signal output from the optical leakage sensor unit as a liquid presence / absence signal and the signal output from the conductive leakage sensor unit as a discrimination signal for distinguishing between water and oil; This is achieved by notifying with such as.

  According to the liquid leakage sensor of the present invention, the features of the optical liquid leakage sensor and the continuity (conductive) liquid leakage sensor are combined. Separate detection is possible. Therefore, it is particularly useful for detecting leaks at a gas station, a semiconductor manufacturing line, a food processing line, or the like.

Further, according to the liquid leakage sensor of the present invention, an electrically conductive liquid such as water, an acidic solution or an alkaline solution, or an insulating liquid such as an organic solution such as ultrapure water, alcohol, thinner or benzine. Liquid with a low surface tension of 6 × 10 ⁻² N / m or less at 20 ° C., particularly 3 × 10 ⁻² N / Even a leakage of a thin layered liquid having a low surface tension of m or less can be detected at high speed. Gasoline, kerosene, machine oil, silicone oil, edible oil, etc. can also be detected.

  The present invention detects the presence or absence of liquid leakage with an optical liquid leakage sensor unit, and a conductive liquid leakage sensor unit (for example, water) and non-electrically conductive oil or organic solution Are detected and distinguished. Moreover, it is structurally simple and does not increase costs.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 3A shows a configuration example of the liquid leakage sensor 10 of the present invention. The liquid leakage sensor 10 is installed on the floor 1 for detecting liquid leakage and constitutes an optical liquid leakage sensor unit. A light emitter 11, a prism 12 and a light receiver 13 are provided, and the bottom surface of the prism 12 is installed on the floor 1. The light emitter 11 and the light receiver 13 are connected to a detection circuit 20, and a pair of electrode plates 14 and 15 constituting a conductive leak sensor unit are provided at the bottom of the casing of the leak sensor 10. In addition, the electrode plates 14 and 15 are connected to the detection circuit 20, and the lower portions of the electrode plates 14 and 15 protrude from the housing.

The configuration of the detection circuit 20 is as shown in FIG. 4, and the detection signal DT from the light receiver 13 is amplified by the amplifier 21 and input to the comparator 22. The comparator 22 compares the detection signal DTa from the amplifier 21 with the reference value V _r2 and outputs a binary liquid presence / absence signal LS according to the magnitude of the reference value V _r2 . Further, in the present invention, the pair of electrode plates 14 and 15 act as a capacitance and are used as one element from the oscillator 23. An output (frequency signal) F of the oscillator 23 is input to the F-V converter 24, converted to a voltage V corresponding to the frequency f, and the voltage V is input to the comparator 25. The comparator 25 compares the voltage V with the reference value V _r1 and outputs a binary oil / water discrimination signal DS according to the magnitude of the reference value V _r1 . The characteristic of the FV converter 24 is that the voltage V increases as the frequency f increases as shown in FIG. 5, for example.

  The discrimination signal DS output from the comparator 25 is input to the AND circuit 26A, is input to the AND circuit 26C via the NOT circuit 26B, and the liquid presence / absence signal LS output from the comparator 22 is input to the AND circuit 26A. , And input to the NOT circuit 26B. When the output of the AND circuit 26A becomes “H”, the lamp 20A is turned on. When the output of the NOT circuit 26B becomes “H”, the lamp 20B is turned on, and the output of the AND circuit 26C becomes “H”. The lamp 20C is turned on.

  In such a configuration, when there is no water or oil leakage on the floor 1 as shown in FIG. 3A, the comparator 22 outputs a liquid presence / absence signal LS indicating “no liquid”. Therefore, regardless of the discrimination signal DS from the comparator 25, the output of the NOT circuit 26B becomes “H” and the lamp 20B is lit. Thereby, it can be known that there is no liquid at present, that is, there is no leakage.

Next, when the liquid 2 leaks onto the floor 1 as shown in FIG. 3B, the liquid presence / absence signal LS, which is the output of the comparator 22, is changed by changing the refractive index or transmittance of the prism 12 as described above. Changes from "L" to "H", the output of the NOT circuit 26B becomes "L", the lamp 20B is turned off, and it can be known that there is a liquid leak. And the electrostatic capacitance comprised by the electrode plates 14 and 15 changes by the presence of the liquid leak 2, and the oscillation frequency f of the oscillator 23 changes, and this is converted into the voltage V by the FV converter 24. Since the dielectric constant is different between water and oil, the capacitance is also different. As a result, the oscillation frequency of the oscillator 23 is also different, and the voltage V is different between water and oil. Therefore, for the reference value V _r1 , the discrimination signal DS from the comparator 25 can be “L” for water and “H” for oil and air. When the discrimination signal DS is “H”, that is, oil and air, the output of the AND circuit 26A becomes “H” and the lamp 20A is turned on. Thereby, it turns out that it is an oil leak. When the discrimination signal DS is “L”, that is, water, the output of the AND circuit 26C becomes “H” and the lamp 20C is lit. Thereby, it turns out that it is a water leak.

  In the above description, the detection circuit 20 is provided in the leak sensor 10. However, the detection circuit 20 may be provided outside by wiring or wirelessly. Moreover, it is also possible to notify by sound or the like instead of the lamps 20A to 20C or in addition to the lamp.

  Further, by using a microcomputer with an A / D converter (or electronic processing means such as a CPU), the comparator 22, the FV converter 24, and the comparator 25 can be dispensed with. Further, if a microcomputer is used, it is possible to perform a logical operation without providing the AND circuits 26A and 26C and the NOT circuit 26B, which is simple.

  FIG. 6 shows an example of an oscillation circuit applicable to the present invention. A capacitor C is formed by the electrode plates 14 and 15, an amplifier 231 is connected to the electrode plate 15, and a band-pass filter (phase adjustment) 233 and an amplifier are provided. 234 is connected, and the output Fa of the amplifier 234 is connected to the electrode plate 14 (as feedback). The amplifier 231 is provided with a gain adjustment unit 232, and the gain adjustment unit 232 varies the gain of the amplifier 231.

  In such a configuration, when a liquid (water, oil, etc.) contacts the electrode plates 14 and 15, the capacitance C between the electrode plates 14 and 15 changes. Therefore, it is possible to detect the presence or absence of the liquid by not oscillating when the capacity C is small and oscillating when the capacity C reaches an appropriate value (at the time of leakage).

  FIG. 7 shows an example of the structure of the liquid leakage sensor 30 of the present invention. A substrate 32 is disposed in a disk-shaped housing 31, and a light emitter 33 and a light receiver 34 are provided on the substrate 32. . A prism 35 is provided below the light emitter 33 and the light receiver 34 so as to face the light emitter 33 and the light receiver 34, and a pair of electrodes 36A and 36B are further provided. A detection circuit may be attached on the substrate 32, and the casing 31 may be formed of a synthetic resin member formed so as to be detachable in a vertical direction. As the synthetic resin member having such a structure, polyethylene terephthalate, amorphous polyethylene terephthalate, polyethylene, polystyrene, polypropylene or the like can be used, and a polybutadiene resin can be used as the thermoplastic elastomer for integral molding.

  Furthermore, FIG. 8 shows and explains the liquid leakage sensor 40 of another embodiment. The disc-shaped main body is formed so as to be split between the housing main body 41 and the cap portion 42, and a prism 43 is disposed at the center of the bottom of the housing main body 41. In this example, four pairs of electrodes 44a, 44b to 47a, 47b are provided. Provided at the bottom of the housing body 41. In addition, a wiring tube 48 for connecting a power source, a signal line, and the like is connected to the casing. The electrodes 44a, 44b to 47a, 47b may be connected in series or in parallel.

  By providing a plurality of pairs of electrodes 44a, 44b to 47a, 47b as described above, it is possible to detect liquid leakage in a wide range. In this example, four pairs of electrodes are provided, but the number of pairs of electrodes is arbitrary.

According to the liquid leakage sensor of the present invention, leakage of an electrically conductive liquid such as water, an acidic solution or an alkaline solution, or an insulating liquid such as an organic solution such as ultrapure water, alcohol, thinner or benzine. The liquid can be reliably detected even with a small amount of liquid leakage, and has a low surface tension of 6 × 10 ⁻² N / m or less at 20 ° C., particularly 3 × 10 ⁻² N / m or less. Even a leakage of a thin layered liquid having a low surface tension can be detected at high speed. It is optimal for detecting gasoline, kerosene, machine oil, silicone oil, edible oil, etc.

It is a figure which shows the detection principle of the conventional optical leak sensor. It is a figure which shows the detection principle of the conventional electroconductive (conduction) type | formula leak sensor. It is a block diagram which shows the structural example of the leak sensor of this invention. It is a block diagram which shows an example of the detection circuit of the leak sensor of this invention. It is a figure which shows the example of a characteristic of a FV converter. It is a circuit diagram which shows the other example of an oscillation circuit. It is a block diagram which shows the other structural example of the leak sensor of this invention. It is the bottom view and side view showing other examples of composition of the leak sensor of the present invention.

Explanation of symbols

1 Floor 10, 30, 40 Leak sensor 11, 33, 101 Light emitter 12, 35, 43, 104 Prism 13, 34, 105 Light receiver 14, 15 Electrode plate 20 Detection circuit 20A-20C Lamp 21, 231, 234 Amplifier 22, 25 Comparator 23 Oscillator 24 FV converter 26A, 26C AND circuit 26B NOT circuit 31 Housing 32 Substrate 41 Housing body 42 Cap section 48 Wiring tube 100 Optical leak sensor 102 Light 103 Detector bottom surface 110, 220 Leakage 200 Conductive leak sensor 201 Battery 202 Resistance 203 Voltmeter 232 Gain adjusting unit 233 Band pass filter

Claims (8)

An optical leak sensor unit that includes a light emitter, a prism, and a light receiver and detects a liquid leak with the amount of light received by the light receiver, and oscillates with a pair of electrodes as an oscillation element, A liquid leakage sensor comprising: a conductive liquid leakage sensor unit for detecting liquid leakage, and detecting leakage of two types of liquids. 2. The liquid leakage according to claim 1, further comprising a detection circuit that determines and outputs the presence / absence of liquid leakage and the type of liquid leakage based on outputs of the optical liquid leakage sensor unit and the conductive liquid leakage sensor unit. Sensor. The liquid leakage sensor according to claim 2, wherein the detection circuit outputs a liquid presence / absence signal by processing the detection signal output from the optical liquid leakage sensor unit with an amplifier and a comparator. The detection circuit is connected to an electrode plate of the conductive leakage sensor unit, and the electrode plate acts as a capacitance, is used as one element of an oscillator, and is processed by an FV converter and a comparator. The liquid leakage sensor according to claim 2, which outputs a discrimination signal for discriminating between water and oil. A first amplifier having a gain adjustment unit connected to the pair of electrodes; a band-pass filter connected to an output of the first amplifier; and an output of the band-pass filter connected to the input; The liquid leakage sensor according to claim 2, further comprising a second amplifier that feeds back to one of the electrodes to form an oscillation circuit. The liquid leakage sensor according to any one of claims 2 to 5, wherein the detection circuit comprises a lamp for notifying the output when the liquid presence / absence signal or the discrimination signal is output. The detection circuit is connected to an electrode plate of the conductive leak sensor unit, causes the electrode plate to act as a capacitance, is used as one element of an oscillator, and directly measures and processes the oscillation frequency of the oscillator The liquid leakage sensor according to claim 2, further comprising a microcomputer or electronic processing means. 8. The liquid leakage sensor according to claim 7, further comprising display means for displaying a processing result of the microcomputer or electronic processing means.

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