JP2014163671A - Gas detector - Google Patents

Abstract

An object of the present invention is to provide a gas detection device that is small and light and can be handled safely.
A gas sensor includes a solid electrolyte membrane and a first electrode and a second electrode sandwiching the solid electrolyte membrane. The gas detection device 30 includes a circuit board 32, a sensor holding member 34 for attaching the gas sensor 10 to the circuit board 32, a detection circuit mounted on the circuit board 32, and a power supply 36 for driving the detection circuit. The gas sensor 10 and the battery 36 are held on different surfaces of the circuit board 32.
[Selection] Figure 2

Description

  The present invention relates to a gas detection apparatus using a gas sensor that detects a predetermined gas in the air.

  In recent years, fuel cells have been developed as energy sources for automobiles and households. A fuel cell is a battery that generates electricity by reacting hydrogen and oxygen. Hydrogen molecules, which are energy sources for fuel cells, are stable at room temperature, but are highly reactive and easily cause chemical reactions with various substances. When hydrogen and oxygen are mixed at a volume ratio of 2: 1 and ignited, they explode vigorously. Therefore, a gas sensor for detecting hydrogen is required at a place where hydrogen is used. In order to carry a gas sensor in a place where hydrogen is used or to easily install a gas sensor in a necessary place, the gas sensor is desirably small and light, and needs to be handled safely.

  For example, in the hydrogen gas sensor disclosed in Patent Document 1 below, an electromotive force measurement is performed in which a proton conductor is sandwiched between a first electrode and a second electrode made of platinum-supporting carbon, and an electromotive force is measured between the first electrode and the second electrode. Means. When the gas to be measured comes into contact with the first electrode side, an electromotive force is generated, and the concentration of the gas can be obtained from the value of the electromotive force.

  However, it is necessary that the hydrogen partial pressure value of the gas in contact with the second electrode side is known in advance. Since such a gas is used, the configuration becomes complicated and it is difficult to reduce the size.

  Patent Document 2 discloses an oxygen concentration sensor having a button battery shape. The oxygen concentration sensor is formed into a button battery shape, an ammeter is connected to the oxygen concentration sensor, and the oxygen concentration is obtained according to the current flowing through the oxygen concentration sensor. Miniaturization is possible by making the button battery shape. In actual use, a battery is used to drive components such as a control circuit and an alarm.

  Patent Document 2 discloses the use of an air battery, but when applied to other gas sensors, it is conceivable to use a button battery for miniaturization. If the shape of the sensor is a button battery, there is a risk that the sensor and the battery will be mistaken when the battery is replaced. The circuit is broken, or a predetermined gas cannot be detected, which causes a safety problem.

JP 2003-270200 A JP-A-9-274209

  An object of the present invention is to provide a gas detection device that is small and light and can be handled safely.

  The gas detection device of the present invention includes the above gas sensor, a circuit board, a sensor holding member for attaching the gas sensor to the circuit board, and mounted on the circuit board and electrically connected to the gas sensor, and an output of the gas sensor is input thereto. A detection circuit, a power source for driving the detection circuit, and a housing for housing the circuit board, a sensor holding member, the detection circuit, and the power source. The gas sensor and the power source are held on different surfaces of the circuit board.

  The casing can be opened and closed, and when the casing is opened, the power supply side surface of the circuit board is opened. When replacing the power supply, the gas sensor cannot be seen, but only the power supply can be seen.

  The power source is a button-type or coin-type battery, and the gas sensor is a button-type or coin-type battery. The external shape of the gas sensor and the external shape of the power source are the same or similar to those of a button-type or coin-type battery, and the external shapes of the gas sensor and the power source are the same or similar.

  The gas sensor includes a solid electrolyte membrane, a first electrode and a second electrode arranged on both surfaces of the solid electrolyte membrane so as to be in contact with at least a part of the solid electrolyte membrane, and a metal that houses the solid electrolyte membrane and the electrode A cover, a conductive elastic body disposed between either the first electrode or the second electrode and the metal cover; an opening disposed between the conductive elastic body and the first electrode or the second electrode; A metal plate.

  In the gas detection device of the present invention, the gas sensor and the power source are held on different surfaces of the circuit board, so there is no possibility of mistakenly replacing the power source and the gas sensor. The gas detection device can be used safely, and gas detection can be performed reliably. The gas sensor used in the gas detection device does not need to have a known hydrogen partial pressure value, and does not have a complicated configuration, and can be reduced in size and weight.

It is a schematic diagram which shows a gas sensor, (a) shows the cross section of a gas sensor, (b) is a figure which shows a solid electrolyte membrane and an electrode. It is a figure which shows a gas detection apparatus, (a) is the figure seen from the one surface side of the circuit board, (b) is the figure seen from the other surface side of the circuit board. It is a figure which shows a detection circuit. It is a figure which shows an example of a housing | casing, (a) is a top view of a housing | casing, (b) is a front view of a housing | casing, (c) is a circuit board etc. accommodated in a housing | casing. It is a figure. It is the figure which opened one surface of the circuit board.

  The gas detection apparatus of the present invention will be described with reference to the drawings. As a gas sensor used in the gas detection device, a hydrogen gas sensor for detecting the hydrogen concentration in the air will be described below.

  A gas sensor 10 shown in FIG. 1A includes a solid electrolyte membrane 12 and a first electrode 14 and a second electrode 16 that sandwich the solid electrolyte membrane 12.

  The solid electrolyte membrane 12 is made of perfluorosulfonic acid, perfluorocarboxylic acid, or other perfluorinated polymer having high proton conductivity, or partially sulfonated styrene-olefin copolymer, such as Poly (styrene-ran-ethylen) or sulfonated. It is preferable to employ a solid polymer electrolyte membrane comprising: Specifically, Nafion (manufactured by DuPont, registered trademark: NAFION), Aciplex (manufactured by Asahi Kasei Corporation, registered trademark: ACIPLEX) and the like can be suitably used. Further, conductive particles may be dispersed in the solid electrolyte membrane 12.

  The first electrode 14 and the second electrode 16 contain a metal having a catalytic action capable of dissociating hydrogen into protons. Examples of the metal include platinum group metals such as platinum, palladium, rhodium, ruthenium, iridium, and osmium. Moreover, the 1st electrode 14 and the 2nd electrode 16 should just contain the above metals, for example, the carbon which carry | supported the said metal may be sufficient. Specifically, the first electrode 14 and the second electrode 16 can use carbon carrying a platinum group metal. Further, the first electrode 14 made of a platinum group metal can be used, and the second electrode 16 made of carbon carrying a platinum group metal can be used. Even if the amount of the metal having a catalytic action is small, the area where the second electrode 16 comes into contact with oxygen and hydrogen in the atmosphere increases, and the proton concentration in the solid electrolyte membrane 12 can be lowered.

When hydrogen gas exists in the vicinity of the gas sensor 10, hydrogen is dissociated into protons and electrons as shown in the following formula (1).
H ₂ → 2H ⁺ + 2e ⁻ (1)
Protons generated by dissociation diffuse in the first electrode 14 and the second electrode 16 and reach the solid electrolyte membrane 12. At the same time, a reaction in which protons disappear due to oxygen present in the atmosphere in the vicinity of the first electrode 14 and the second electrode 16 as shown in the following equation (2) occurs.
2H ⁺ + 1 / 2O ₂ + 2e ⁻ → H ₂ O (2)
Therefore, by electrically connecting the first electrode 14 and the second electrode 16, reactions of the above formulas (1) and (2) occur in the first electrode 14 and the second electrode 16. After the hydrogen molecules contained reach the electrode surface, the concentration of hydrogen molecules or protons decreases as they diffuse from the electrode surface to the inside. By forming such a concentration gradient, protons move. By connecting the detection circuit to the electrode, a current corresponding to the hydrogen concentration flows through the detection circuit.

  In order to efficiently generate the concentration gradient as described above, the thicknesses of the first electrode 14 and the second electrode 16 may be changed. For example, as shown in FIG. 1B, the second electrode 16 is made thicker than the first electrode 14. The difference between the thickness b of the second electrode 16 and the thickness a of the first electrode 14 is 10 to 200 nm, preferably 30 to 80 nm. If the difference between the thicknesses a and b is less than 10 nm, the difference in proton concentration is reduced, and the current corresponding to the hydrogen concentration is also reduced. When it exceeds 200 nm, the response speed is lowered, the solid electrolyte membrane 12 is curled, and the like.

  The thickness a of the first electrode 14 is 1 to 25 nm, preferably 5 to 10 nm. When the thickness a is less than 1 nm, the electrical resistance increases and it becomes difficult to extract current. If the thickness a exceeds 25 nm, the number of protons that reach the solid electrolyte membrane 12 decreases, and the current corresponding to the hydrogen concentration decreases.

  Further, the gas sensor 10 can obtain the hydrogen concentration if the first electrode 14 and the second electrode 16 are directly connected to the conducting wire of the detection circuit, but the current is taken out from a part, and the efficiency is lowered. There is a case. Therefore, the gas sensor 10 includes a metal plate 18, a gas permeable conductor 20, a second electrode 16, a solid electrolyte membrane 12, a first electrode 14, and a gas permeable conductor 22, which are stacked in order. The gas permeable conductor 22 is pressed against the metal cover 24 by pressing the metal plate 18 with the conductive elastic body 26. Examples of the conductive elastic body 26 include a coil spring and a corrugated spring made of a conductive material such as metal.

  The metal plate 18 has an opening and is made of stainless steel or the like. By having the opening, the second electrode 16 can be exposed. Further, current can be taken out from the metal plate 18 through the conductive elastic body 26 and the metal cover 24.

  The gas permeable conductors 20 and 22 are made of carbon paper or foam metal. Carbon paper is a porous body made of carbon fiber and carbon, and has gas permeability and conductivity. When the foam metal has a porosity of 90% or more, gas permeability is particularly good, and since it is a metal, conductivity is also good. When the gas permeable conductors 20 and 22 are in contact with the electrodes 16 and 14, current can be taken out from the entire surfaces of the electrodes 16 and 14 while supplying hydrogen to the electrodes 16 and 14.

  There are two metal covers 24, the conductive elastic body 26 is in contact with one metal cover 24, and the laminated gas permeable conductor 22 is pressed against the other metal cover 24. The two metal covers 24 are integrated with each other through an insulating spacer 28. Since the metal covers 24 are insulated from each other and one metal cover 24 is connected to one electrode 14 (or 16), current can be taken out.

  The metal cover 24 is made of stainless steel or the like and has a cylindrical shape. Note that the height of the cylindrical shape is not limited, and includes the case of 1 to 2 mm, etc., and the same shape as a battery having a button shape (or coin shape) size defined by the International Electrotechnical Commission (IEC). It may be. For example, the outer shape of the metal cover 24 is the same shape as the shape of the batteries LR44 and CR2016. The metal cover 24 can be easily manufactured by using the same shape as a known battery. The insulating spacer 28 is a resin such as polypropylene. An opening is provided in the metal cover 24 so that hydrogen gas enters the inside of the metal cover 24.

  Unlike the prior art, the present invention does not require that the hydrogen partial pressure value of the gas is known in advance, and the configuration is not complicated. The gas sensor 10 can be reduced in size, and can be the same shape as a coin-type or button-type battery.

  Next, a gas detection apparatus using the gas sensor 10 will be described. 2 includes a circuit board 32, a sensor holding member 34 for holding the gas sensor 10 with respect to the circuit board 32, a detection circuit mounted on the circuit board 32, and a power source for driving the detection circuit. 36.

  Examples of the circuit board 32 include a plate body obtained by impregnating a glass cloth with an epoxy resin and circuit wiring with a conductive foil. A sensor holding member 34, a detection circuit, and a power source 36 are provided on the circuit board 32.

  The sensor holding member 34 is made of metal and is attached to the circuit board 32. An electrode is provided on the circuit board 32 so as to face the sensor holding member 34. A spring portion 42 is provided on a part of the sensor holding member 34, and the gas sensor 10 is pressed against the electrode of the circuit board 32, and the gas sensor 10 is held by the circuit board 32. The sensor holding member 34 and the electrode of the circuit board 32 are connected to a detection circuit, and when a desired gas is present, a current flows through the detection circuit. The gas sensor 10 is not completely fixed to the circuit board 32, and the type of the gas sensor 10 can be changed as necessary.

  The detection circuit 50 shown in FIG. 3 is a circuit that receives the output of the gas sensor 10 and obtains the gas concentration. The detection circuit 50 receives the switch SW for switching the detection circuit 50 on and off, the amplification unit 52 connected to the gas sensor 10, the output of the amplification unit 52, the calculation unit 54 for obtaining the gas concentration, and an alarm according to the gas concentration Is provided. Note that the detection circuit 50 is omitted from the circuit board 32 of FIG.

  The switch SW is a component that selects power supply and cutoff to circuits such as the detection circuit 50 and the arithmetic unit 54. When power supply is selected (connected to the power supply 36 side), the detection circuit 50 is driven, and at the same time, the connection between the inverting input terminal of the operational amplifier OP of the gas sensor 10 and the amplifier 52 and the switch SW is disconnected, and the operational amplifier of the amplifier 52 By the operation of OP, both ends of the gas sensor 10 and the inverting input terminal and the non-inverting input terminal of the operational amplifier OP of the amplifying unit 52 are kept at the same potential. When the cutoff is selected, the power supply is cut off and the detection circuit 50 is stopped. At the same time, both ends of the gas sensor 10 and the inverting input terminal and the non-inverting input terminal of the operational amplifier OP of the amplifying unit 52 are kept in a state of no potential difference. ing. That is, regardless of the state of the switch SW, both ends of the gas sensor 10 and the inverting input terminal and the non-inverting input terminal of the operational amplifier OP of the amplifying unit 52 are kept at the same potential.

  When the switch SW is cut off, if the gas sensor 10 and the inverting input terminal of the operational amplifier OP of the amplifier 52 do not maintain the same potential, the operational amplifier of the amplifier 52 immediately after selecting the power supply with the switch SW Due to the operation of OP, a transient current may be generated to try to keep both ends of the gas sensor 10 and the inverting input terminal and the non-inverting input terminal of the operational amplifier OP of the amplifier 52 at the same potential. For this reason, the calculation unit 54 makes a mistake in output, or a waiting time from immediately after power supply to the start of gas detection is required. However, if the structure of the present detection circuit 50 is adopted, since a transient output is eliminated, the time from immediately after power supply to the start of gas detection can be shortened.

  The amplifying unit 52 includes an operational amplifier OP, a capacitor C, and a resistor R. When the gas sensor 10 reacts and a current flows as described above, the value is amplified. The output of the amplifying unit 52 is input to the arithmetic unit 54, and analog / digital conversion is performed as necessary.

  The calculation unit 54 is constituted by a microcomputer or the like, obtains a gas concentration according to the current value, and issues a signal to the output unit 56 when a certain value is exceeded. The output unit 56 is an LED 58 or a speaker 60, and emits light or emits sound when receiving a signal from the calculation unit 54. By constituting the LED 58, the speaker 60, and the like, the gas detection device 30 can be prevented from being enlarged.

  The detection circuit 50 is not limited to the above circuit as long as it can measure the current when the gas sensor 10 reacts. Further, an output terminal 62 for outputting to an external computer is connected to the arithmetic unit 54 as necessary.

  The power source 36 uses a battery having a button-type (or coin-type) size in order to make the gas detection device 30 small (thin) and light. Examples include LR44 and CR2032, which are defined by the International Electrotechnical Commission (IEC). That is, the shape of the power source 36 is the same as or similar to that of the gas sensor 10. By using the battery as the power source 36, the gas detection device 30 can be carried. Hereinafter, the power source 36 is referred to as a battery.

  As shown in FIG. 2A, the battery 36 is held on the circuit board 32 by the battery holding member 62 similar to the sensor holding member 34 used in the gas sensor 10, similarly to the gas sensor 10. The battery holding member 62 is made of metal and includes a spring portion 64. The spring portion 64 presses the battery 36 against the circuit board 32, and the battery is held. An electrode is formed on the circuit board 32, and the battery 36 is connected to the detection circuit 50 by the electrode and the battery holding member 62, and electric power is taken out.

  As shown in FIG. 4, the gas detection device 30 includes a housing 70 for housing the circuit board 32 and the like. The housing 70 can be formed of, for example, ABS resin (copolymer synthetic resin of Acrylonitrile, Butadiene, and Styrene).

  The housing 70 includes a first housing 72 and a second housing 74, and the gas sensor 10, the circuit board 32, the sensor holding member 34, the detection circuit 50, and the battery are formed in an internal space formed by the housings 72 and 74. 36 and the like are stored. A plurality of openings 76 are provided to introduce gas into the internal space. A claw portion 78 is provided at the peripheral edge of the second housing 74 so as to be fitted into a recess 80 provided on the inner surface of the first housing 72. By fitting the claw portion 78 and the recess 80, the first housing 72 and the second housing 74 are fixed to each other to form the housing 70. The first casing 72 and the second casing 74 can be separated from each other by removing the claw portion 78 from the recess 80 using the elasticity of the casing 70. Since the first casing 72 and the second casing 74 can be separated, the battery 36 can be replaced.

  The gas sensor 10, the sensor holding member 34, the detection circuit 50, and the battery 36 are attached (mounted) to the circuit board 32, and the circuit board 32 and the housing 70 are fixed by a fixing member such as a screw 82. The circuit board 32 is fixed to either the first casing 72 or the second casing 74. In this description, the circuit board 32 is fixed to the second housing 74.

  The gas sensor 10 and the battery 36 are held on different surfaces of the circuit board 32. The battery 36 is held on one surface 38 of the circuit board 32, and the gas sensor 10 is held on the other surface 40. For this purpose, the battery holding member 62 is attached to one surface 38 of the circuit board 32, and the sensor holding member 34 is attached to the other surface 40.

  When the circuit board 32 is fixed to the second casing 74, the other surface 40 of the circuit board 32 faces the second casing 74 so that the gas sensor 10 is hidden by the circuit board 32 and the second casing 74. . When the first casing 72 and the second casing 74 are fixed to each other, the one surface 38 faces the first casing 72.

  When the first housing 72 and the second housing 74 are separated for battery replacement, the one surface 38 of the circuit board 32 is opened as shown in FIG. A battery 36 is held on one surface 38 and can be replaced. The battery 36 can be visually recognized by the user, and the gas sensor 10 cannot be visually recognized. This is because the gas sensor 10 and the battery 36 have the same or similar shape. Since the holding members 34 and 62 are formed in accordance with the shapes of the gas sensor 10 and the battery 36, the holding members 34 and 62 have the same or similar shape. This is for preventing the gas sensor 10 from being mistakenly removed and the battery 36 being attached.

  As described above, the present invention is a button-type (or coin-type) gas sensor 10 that can be carried, and is small (thin) and lightweight. In addition, the gas sensor 10 and the battery 36 have the same or similar shape, but when the battery is replaced, only the battery 36 is visible, and the gas sensor 10 and the battery 36 are replaced by mistake. There is no. The gas detection device 30 can be prevented from being broken and can be used safely. Since there is no transient output of the amplifying unit 52, it is possible to shorten the time from when the detection circuit 50 is driven to when gas detection is started.

  As mentioned above, although embodiment was described about this invention, this invention is not limited to said embodiment. For example, although the gas sensor 10 that measures hydrogen gas is shown, a gas sensor that measures other gases may be used. When the shape of the gas sensor 10 and the shape of the battery 36 are the same or similar, they are held on different surfaces of the circuit board 32 as in the present application. When the casing 70 is opened for battery replacement, the battery 36 is visible, but the gas sensor 10 is not visible.

  In addition, the present invention can be carried out in a mode in which various improvements, modifications, and changes are added based on the knowledge of those skilled in the art without departing from the spirit of the present invention.

10: Gas sensor 12: Solid electrolyte membrane 14, 16: Electrode 18: Metal plate 20, 22: Gas permeable conductor 24: Metal cover 26: Conductive elastic body 28: Insulating spacer 30: Gas detector 32: Circuit board 34 : Sensor holding member 36: Power supply (battery)
50: Detection circuit 52: Amplification unit 54: Calculation unit 56: Output unit 58: LED
60: speaker 62: battery holding member 70: housing 72: first housing 74: second housing 76: opening 78: claw portion 80: recess 82: screw (fixing member)

Claims (4)

A gas sensor;
A circuit board;
A sensor holding member for holding the gas sensor with respect to the circuit board;
A detection circuit mounted on the circuit board and electrically connected to the gas sensor, to which an output of the gas sensor is input;
A power source for driving the detection circuit;
A housing for storing the circuit board, a sensor holding member, a detection circuit, and a power source;
With
A gas detection device in which the gas sensor and a power source are held on different surfaces of a circuit board. The gas detection device according to claim 1, wherein the housing is openable and closable, and the power supply side surface of the circuit board is opened when the housing is opened. 3. The gas detection device according to claim 1, wherein the power source is a button-type battery, and the outer shape of the gas sensor is a button type. The gas sensor is
A solid electrolyte membrane;
A first electrode and a second electrode disposed on both sides of the solid electrolyte membrane so as to be in contact with at least a part of the solid electrolyte membrane;
A metal cover for housing the solid electrolyte membrane, the first electrode and the second electrode;
A conductive elastic body disposed between either the first electrode or the second electrode and the metal cover;
A metal plate disposed between the conductive elastic body and the first electrode or the second electrode, and having an opening;
The gas detection device according to claim 1, further comprising:

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