JP6685043B2 - Thermoelectric hydrogen sensor - Google Patents

Description

  The present invention relates to a thermoelectric hydrogen sensor for detecting leakage of hydrogen gas in an internal combustion engine, a fuel cell or the like using hydrogen gas.

  In recent years, hydrogen gas has attracted attention as a clean and renewable energy source from the viewpoint of environmental protection problems and fossil fuel depletion problems. On the other hand, since hydrogen gas is highly explosive, establishment of technology for safe use is essential, and development of a hydrogen sensor that detects leaked hydrogen with high accuracy is desired.

  As a conventional hydrogen sensor, there is a catalytic combustion thermoelectric hydrogen sensor that detects the temperature when hydrogen is selectively burned using a platinum (Pt) catalyst.

  The combustion-type thermoelectric hydrogen sensor includes a Pt catalyst for burning hydrogen gas, a heater for heating to a temperature at which a combustion reaction occurs, and a temperature sensor for detecting a temperature rise due to combustion. As the temperature sensor, a platinum thermometer that utilizes the temperature change of the electric resistance of the Pt wire or a thermoelectric element that uses a semiconductor thin film such as SiGe is used. When the hydrogen sensor comes into contact with hydrogen gas, the Pt catalyst heated in advance by the heater causes combustion between oxygen and hydrogen gas in the atmosphere, and the temperature of the temperature sensor rises. The presence of hydrogen is detected by the temperature increase.

  This combustion-type thermoelectric hydrogen sensor has a simple principle and can be miniaturized. However, it responds only in the coexistence of oxygen, and a catalyst temperature of 100 ° C. to 200 ° C. or higher is required to realize a stable combustion reaction, which requires heating of the entire hydrogen sensor. There was a point. Further, since the presence of hydrogen is detected as the temperature rise of the sensor, there is a drawback that it is easily affected by ambient temperature changes.

JP, 2009-42047, A

  The above-mentioned combustion-type thermoelectric hydrogen sensor using the conventional Pt catalyst has a problem that it is necessary to heat the catalyst using a heater and maintain the temperature at a temperature required for combustion of hydrogen gas. Further, there is a drawback that the measured voltage value fluctuates depending on the temperature of the external environment and the hydrogen detection accuracy decreases, that is, it is easily affected by the change in the external temperature.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a thermoelectric hydrogen sensor that has a simple structure, is less affected by disturbance, and performs hydrogen detection operation efficiently and stably.

  The thermoelectric hydrogen sensor of the present invention for solving the above-mentioned problems includes one end of a first metal body made of a first metal and a second metal body made of a second metal different from the first metal. One end of the metal body is connected with the first storage body formed of a hydrogen storage material that stores hydrogen and generates heat, and the other end of the first metal body is connected to the other end of the second metal body. A thermocouple having ends connected to each other with a second storage body formed of the hydrogen storage material interposed therebetween, and hydrogen protection covering the surface of the first storage body so that the first storage body does not come into contact with hydrogen gas. A member is provided, and the thermoelectromotive force generated in the thermocouple is detected based on the temperature difference between the first occlusion body and the second occlusion body.

  A thermoelectric hydrogen sensor according to another aspect of the present invention is one end of a first metal body made of a first metal and a second metal body made of a second metal different from the first metal. Of the thermocouple in which one end of the thermocouple is connected to the other end of the first metal body and the other end of the second metal body is connected to Installed an occlusion body made of a substance, and provided either one of the occlusion bodies with a hydrogen protection member that covers the surface of the occlusion body so that it does not come into contact with hydrogen gas. A thermocouple is generated due to the temperature difference between the occlusion bodies. It is characterized by detecting the thermoelectromotive force that occurs.

  A thermoelectric hydrogen sensor according to another aspect of the present invention is one end of a first metal body made of a first metal and a second metal body made of a second metal different from the first metal. Is connected to one end of the first metal body, and the other end of the first metal body is connected to the other end of the second metal body, one of the connection portions of the thermocouple stores hydrogen to generate heat. It is characterized in that an occlusion body made of a hydrogen occlusion substance is installed, and a thermoelectromotive force generated by a thermocouple is detected by a temperature difference between the connecting portions.

  According to the thermoelectric hydrogen sensor of the present invention, it is possible to efficiently and stably perform the hydrogen detection operation with a simple configuration without being affected by disturbance.

It is a circuit block diagram of the thermoelectric hydrogen sensor 1 of this invention. It is a circuit block diagram of the thermoelectric hydrogen sensor 2 of this invention. It is a circuit block diagram of the thermoelectric hydrogen sensor 3 of this invention. It is a circuit block diagram of the thermoelectric hydrogen sensor 4 of this invention. 1 is an overall view showing a configuration of a thermoelectric hydrogen sensor 5 according to an embodiment of the present invention. 5A is a sectional view taken along line AA of FIG. 5, and FIG. 6B is a sectional view taken along line BB of FIG. 3 is a graph showing a voltage value of a thermocouple when hydrogen gas and nitrogen gas are brought into contact with a thermoelectric hydrogen sensor according to an embodiment of the present invention at predetermined time intervals. It is a whole figure which shows the structure of the thermoelectric hydrogen sensor 6 by another form. It is the whole figure which shows the constitution of the thermoelectric hydrogen sensor 7 by other form. (A) is CC sectional drawing of FIG. 9, (b) is DD sectional drawing of FIG. It is the whole figure which shows the constitution of thermoelectric hydrogen sensor 8 by other form. 11A is a sectional view taken along line EE of FIG. 11, and FIG. 11B is a sectional view taken along line FF of FIG. 11. It is the whole figure which shows the constitution of the thermoelectric hydrogen sensor 9 by other form.

  As an embodiment of the present invention, a thermoelectric type using a thermocouple configured by connecting ends of two kinds of metals (or alloys) with each other sandwiching palladium (Pd) or Pd alloy, which is a hydrogen storage material, between them. The hydrogen sensor will be described. The two types of metals (or alloys) used for the thermoelectric hydrogen sensor should have a higher sensitivity as the relative Seebeck coefficient (thermoelectromotive force of the thermocouple) having a unique value for each combination increases. You can Examples of thermocouple metal (or alloy) combinations for forming a high-sensitivity hydrogen sensor include platinum-platinum rhodium, iron-constantan, copper-constantan, chromel-constantan, and chromel-alumel. In the form, platinum (Pt) -gold (Au) having high chemical durability and temperature stability was used. In addition, as the metal body used as the thermocouple, it is possible to use a simple substance of Rh, Fe, Ni, Cu, Pb, or Pd or an alloy thereof. As the palladium (Pd) or Pd alloy, which is a hydrogen storage material, linear, rod-shaped, plate-shaped, or paste-shaped palladium (Pd) or Pd alloy can be used.

  As shown in FIG. 1, the thermoelectric hydrogen sensor 1 according to the present embodiment has one end of the first metal body 11 and one end 12-1 of the second metal body formed of a metal different from the first metal body 11, The first storage body 13-1 formed of Pd or a Pd alloy, which is a hydrogen storage material that stores hydrogen and generates heat, is connected with the contact 15-1 and the contact 15-2 with the first storage body 13-1 interposed therebetween, and The other end and the other end 12-2 of the second metal body are connected as a thermocouple by a contact 15-3 and a contact 15-4 with a second storage 13-2 made of Pd interposed therebetween. The circuit 10-1, the hydrogen protective film 20 covering the surface of the first storage 13-1 so that the hydrogen gas does not contact the first storage 13-1, and the second metal body 12-in the circuit 10-1. The lead wire 14-1 is connected to the contact point 15-5 in the first metal body 1 and the contact point 15-6 in the second metal body 12-2. Connect the pre 14-2 comprises a voltmeter 30 for measuring the voltage in the circuit 10-1.

  Since the circuit configuration only needs to be able to detect heat generation due to hydrogen storage of Pd or Pd alloy, the first storage bodies 13-1 and 13-2 are formed by forming electrical contacts with dissimilar metals as shown in FIG. Besides being installed in the circuit 10-1, the thermoelectric hydrogen sensor 2 of FIG. 2 and the thermoelectric hydrogen sensor 3 of FIG. 3 may be configured without being incorporated in the circuits 10-2 and 10-3.

  In the thermoelectric hydrogen sensor 2 of FIG. 2, one end of the first metal body 11 and one end 12-1 of the second metal body are connected by a contact point 15-7, and the other end of the first metal body 11 and the second metal body are connected. Circuit 10-2 in which the other end 12-2 of the contact is connected by a contact point 15-8, a first occlusion body 13-1 installed in the vicinity of the contact point 15-7, and a second storage object installed in the vicinity of the contact point 15-8. An occlusion body 13-2, a hydrogen protection film 20 provided on the first occlusion body 13-1, and a voltmeter 30 connected in the circuit 10-2 in the same manner as the circuit 10-1 are provided.

  Further, in the thermoelectric hydrogen sensor 3 of FIG. 3, one end of the first metal body 11 and one end 12-1 of the second metal body are connected by a contact 15-7, and the other end of the first metal body 11 and the second metal body are connected. The circuit 10-3 in which the other end 12-2 of the body is connected to the contact point 15-8, the occlusion body 13-3 installed only in the vicinity of the contact point 15-8, and the circuit 10-3 is similar to the circuit 10-1. And a voltmeter 30 connected to.

  The thermoelectric hydrogen sensor of the present invention, as shown in FIGS. 1, 2, and 3, has two kinds of metals 11, 12 (12-1, 12) opposite to the current direction so as to cancel out thermoelectromotive force. -2) is connected in series to form a thermocouple, and a storage element 13 (13) formed of Pd or a Pd alloy that occludes hydrogen to generate heat is stored. -1, 13-2, or 13-3). Since different kinds of metals are connected to the same number of contacts in the circuits 10-1, 10-2, and 10-3 in the opposite direction to the current direction, even if the temperature around the sensor fluctuates The thermoelectromotive force of will cancel each other out. Therefore, if this circuit configuration is used, the thermoelectromotive forces due to causes other than the temperature change due to hydrogen storage are canceled out, so that only the thermoelectromotive force difference due to temperature change due to hydrogen storage can be detected with high sensitivity. With a simple circuit, it is possible to detect only the temperature change due to hydrogen absorption with high sensitivity without the influence of disturbance.

  Further, the thermoelectric hydrogen sensor 4 of FIG. 4 connects one end of the first metal body 11-1 and one end 12-1 of the second metal body with a contact point 15-7 like the thermoelectric hydrogen sensor 3 of FIG. In addition, the other end of the first metal body 11-1 and one end of the second metal body 12-3 are connected by a contact point 15-8, and the other end of the second metal body 12-3 is connected to the first metal body 11-. 2 is connected with one end of the contact 15-9 and the contact 15-9 is arranged in the vicinity of the contact 15-7, and the other end of the first metal body 11-2 contacts with one end of the second metal body 12-4. The contact point 15-10 is arranged near the contact point 15-8 by connecting with the contact point 15-10, and the other end of the second metal body 12-4 is connected to one end of the first metal body 11-3 by the contact point 15-11. Then, the contact 15-11 is arranged in the vicinity of the contacts 15-7 and 15-9, and the other end of the first metal body 11-3 is connected to the second metal body 12-5. A conductor 14 which is connected to an end by a contact 15-12, is arranged in the vicinity of the contacts 15-8 and 15-10, and is connected to the other end of the second metal body 12-5 by a contact 15-6. -2 and the conducting wire 14-1 connected to the other end of the second metal body 12-1 by the contact point 15-5, the voltmeter 30 is connected, so that a plurality of thermocouples are connected in series. The circuit 10-4 and the occlusion body 13-3 installed near the contacts 15-8, 15-10, and 15-12 are provided. That is, the plurality of first metal bodies 11-1, 11-2, 11-3 and the plurality of second metal bodies 12-1, 12-3, 12-4, 12-5 are alternately connected, and A plurality of contacts 15-7, 15-9, in which the second metal body is upstream and the first metal body is downstream with respect to the current direction, by connecting the metal body of FIG. 15-11 are arranged close to each other as a first contact group 17-1, and a plurality of contacts 15-8, 15-10, and 15- in which the first metal body is upstream and the second metal body is downstream 12 are arranged close to each other as a second contact group 17-2, and an occlusion body 13-3 is installed in the vicinity of either one of the contact groups (contact group 17-2 in FIG. 4).

  With this configuration, the thermoelectromotive forces due to causes other than the temperature change due to hydrogen storage are canceled out, and the thermoelectromotive force difference due to the temperature change due to hydrogen storage is added, and the thermoelectromotive force difference is amplified, so Can be detected with sensitivity.

<Thermoelectric hydrogen sensor according to one embodiment>
As a thermoelectric hydrogen sensor according to an embodiment of the present invention, a configuration of a thermoelectric hydrogen sensor 5 which is a specific example of the thermoelectric hydrogen sensor of FIG. 1 will be described with reference to FIGS. 5 and 6. 5 is an overall view showing the configuration of the thermoelectric hydrogen sensor 5, FIG. 6 (a) is a sectional view taken along line AA of FIG. 5, and FIG. 6 (b) is a sectional view taken along line BB of FIG. It is a figure.

  In the thermoelectric hydrogen sensor 5, one end of a Pt foil 111 as a first metal body having a U-shape and a first Au foil 121-1 constituting one end of a second metal body are formed of Pd. Also, the other end of the Pt foil 111 and the second Au foil 121-2 forming the other end of the second metal body are connected with the first Pd body 13-1 as the first occlusion body sandwiched therebetween by Pd. The formed second Pd body 13-2 as the second occlusion body is sandwiched and connected. And the 1st Au foil 121-1 and the 2nd Au foil 121-2 are connected to the voltmeter 30 by the conductors 14-1 and 14-2, and the closed circuit 10-5 is comprised. In the thermoelectric hydrogen sensor 5, the platinum foil 111 having a U-shape is used as the first metal body, but one end and the other end of the first metal body are electrically connected to the second metal body. So long as it has any shape. In the thermoelectric hydrogen sensor 5, plate-shaped Pd bodies were used as the first Pd body and the second Pd body.

  The first Pd body 13-1 and the second Pd body 13-2 described above are fixedly installed on the substrate 16 in a state of being separated from each other, and the first Pd body 13-1 is arranged so that hydrogen gas does not come into contact therewith. The surface is covered with a hydrogen protection film 20. An alarm device 40 is connected to the voltmeter 30.

  The first Pd body 13-1 and the second Pd body 13-2 of the thermoelectric hydrogen sensor 1 according to the present embodiment are formed by using Pd or a Pd alloy that selectively absorbs hydrogen to generate heat. In addition, in the present embodiment, the lead wires 14-1 and 14-2 are formed of copper (Cu), but a compensating lead wire corresponding to the thermocouple used can also be used. The contact point between the conductor wire 14-1 and the first Au foil 121-1 and the contact point between the conductor wire 14-2 and the second Au foil 121-2 have the same temperature, and these contact points have two kinds of metal in the circuit. Are connected in the opposite direction to the current direction (the first Au foil 121-1 is connected to the upstream side of the conductive wire 14-1, and the second Au foil 121-2 is connected to the downstream side of the conductive wire 14-2. Therefore, the generated thermoelectromotive force is canceled out, and there is little influence on hydrogen sensing, and it can be suitably used.

  Further, in the circuit 10-5 in the thermoelectric hydrogen sensor 5 according to the present embodiment, the first Pd body 13-1 and the second Pd body 13-2 have Pt foil and Au foil at both ends thereof in the current direction. And are connected in series in a state where they are provided in the opposite direction to form a closed circuit. By forming the circuit in this manner, the contact point between the Pt foil 111 and the first Pd body 13-1, the contact point between the first Pd body 13-1 and the first Au foil 121-1 and the first Au foil 121-1. The electromotive force generated at the contact point with the conducting wire 14-1 is the contact point between the Pt foil 111 and the second Pd body 13-2 and the second Pd body 13-2 and the second Au foil 121-2 connected in reverse phase. It is offset by the electromotive force generated at the contact point and the contact point between the second Au foil 121-2 and the conducting wire 14-2. Therefore, when the hydrogen gas is not in contact, no electromotive force is generated in the circuit 10-5, and the value measured by the voltmeter 30 is 0V.

  As described above, since the electromotive forces generated at the contacts in the circuit 10-5 cancel each other out, even if the number of contacts increases even if the number of contacts increases in the circuit configuration in which the Pd body is sandwiched between the metal bodies used in the circuit 10-5. The electromotive force does not affect hydrogen sensing. Therefore, it is not necessary to be aware of the insulation state of the Pd body when constructing the circuit, and the metal material used for the circuit 10-5 can be selected by placing importance on the chemical stability rather than the magnitude of the electromotive force. .

  When hydrogen gas comes into contact with the thermoelectric hydrogen sensor 5 configured as described above, the temperature does not change because the first Pd body 13-1 covered with the hydrogen protection film 20 does not store hydrogen, and the second Pd body 13- In 2, the hydrogen gas is occluded and the temperature rises, causing a temperature difference between the first Pd body 13-1 and the second Pd body 13-2 and generating an electromotive force in the circuit 10-5. When an electromotive force is generated in the circuit 10-5, the value measured by the voltmeter 30 increases, and when it exceeds a predetermined value, alarm information for notifying that hydrogen gas has been detected is output from the alarm device 40.

  By operating in this manner, the thermoelectric hydrogen sensor 5 according to the present embodiment has a simple structure that does not require contact compensation and does not need to be aware of the insulation state of the contact, and is less affected by disturbance and efficiently. Stable and sensitive hydrogen detection operation can be performed.

  When the thermoelectric hydrogen sensor 5 was contacted with a predetermined concentration of hydrogen gas and nitrogen gas alternately at intervals of 5 minutes, the change in the voltage value of the circuit 10 was examined, and the characteristics shown in FIG. 7 were obtained. It was The vertical axis of the graph in FIG. 7 shows the elapsed time (min), and the horizontal axis shows the measured electromotive force (mV). As shown in FIG. 7, immediately after the time (t = 5, 15, 25) when the hydrogen gas was brought into contact, electromotive force was generated due to heat generation due to hydrogen absorption of the second Pd body 13-2, and the voltage was measured by the voltmeter 30. Voltage value has risen. Immediately after the time (t = 10, 20, 30) at which the nitrogen gas was brought into contact, the voltage value decreased due to the heat absorption due to the hydrogen release of the second Pd body 13-2. When hydrogen gas is contacted for the first time (t = 5), hydrogen absorbed cannot be completely released even by contact with nitrogen gas, so when hydrogen is contacted for the second time or later (t = 15, 25 It was found that hydrogen gas could be detected although the increase in the voltage value was smaller than that at the first contact.

<Thermoelectric hydrogen sensor according to another embodiment>
In addition, as another embodiment, like the thermoelectric hydrogen sensor 6 shown in FIG. 8, the Pt foil 111 and the first Au foil 121-1 provided at both ends of the first Pd body 13-1 are connected to each other. A voltmeter 31 for measuring the voltage of the closed circuit, and a voltage for measuring the voltage of the closed circuit configured by connecting the Pt foil 111 and the second Au foil 121-2 provided at both ends of the second Pd body 13-2. By further installing a total of 32 and monitoring respective measured values, it is possible to detect an error when a disconnection or the like occurs at any place in the circuit 10-6. Good.

  A thermoelectric hydrogen sensor 6, which is a specific example of the thermoelectric hydrogen sensor 2 described above, will be described with reference to FIGS. 9 and 10. 9 is an overall view showing the configuration of the thermoelectric hydrogen sensor 7, FIG. 10 (a) is a CC sectional view of FIG. 9, and FIG. 10 (b) is a DD sectional view of FIG. It is a figure. As in the thermoelectric hydrogen sensor 7 shown in FIG. 9, the second metal bodies 122-1 and 122-2 are directly connected to both ends of the first metal body 112 formed in a U-shape to form a thermocouple. The first Pd body 13-1 whose surface is covered with a hydrogen protective film and the second Pd body 13-2 whose surface is not covered with a hydrogen protective film are connected to each of the connection parts in the circuit 10-7. Good.

Further, as shown in FIG. 11, the thermoelectric hydrogen sensor 8 can be configured by deforming the shapes of the first metal body 112 and the second metal bodies 122-1 and 122-2. The thermoelectric hydrogen sensor 8 has a shape in which the first metal body 112 is not U-shaped but is closer to one side of the substrate 16, and the second metal bodies 122-1 and 122-2 are directly connected thereto. . 12 is a sectional view taken along line EE of FIG. 11, and FIG. 12B is a sectional view taken along line FF of FIG.
9 to 12 show circuits in which constantan is used as the first metal body 112 and copper (Cu) is used as the second metal bodies 122-1 and 122-2. With this configuration, the number of contacts between different metals in the circuit is reduced, the influence of electromotive force generated at each contact is reduced, and the detection accuracy of the thermoelectric hydrogen sensor as a whole is further improved.

  In addition, in the thermoelectric hydrogen sensor shown in FIGS. 9 and 11, the Pd body 13-1 whose surface is covered with the hydrogen protection film 20 is not installed, but as shown in FIG. You may make it install only the Pd body 13-3 which is not covered. With this configuration, the number of components of the thermoelectric hydrogen sensor can be further reduced, and the sensor can be downsized.

1-9 Thermoelectric hydrogen sensor 10 Circuit 11, 11-1 to 11-3 1st metal body 12-1 to 12-5 2nd metal body 13-1 1st Pd body (1st storage body)
13-2 Second Pd body (second storage body)
14-1, 14-2 Conductive wires 15-1 to 15-12 Contact point 16 Substrate 20 Hydrogen protective film 30, 31, 32 Voltmeter 40 Alarm device 111 Pt foil (first metal body)
121-1 First Au foil (second metal body)
121-2 Second Au foil (second metal body)

Claims (5)

  A hydrogen storage material in which one end of a first metal body formed of a first metal and one end of a second metal body formed of a second metal different from the first metal store hydrogen and generate heat. And the other end of the first metal body and the other end of the second metal body form a second storage body formed of the hydrogen storage material. A thermocouple that is sandwiched and connected, and a hydrogen protection member that covers the surface of the first storage body so that the first storage body does not come into contact with hydrogen gas are provided, and the first storage body and the second storage body are provided. A thermoelectric hydrogen sensor, wherein the thermoelectromotive force generated in the thermocouple is detected by the temperature difference between the two.   One end of the first metal body formed of the first metal and one end of the second metal body formed of the second metal different from the first metal are connected, and An occlusion body made of a hydrogen occlusion substance that absorbs hydrogen to generate heat is installed at each connection portion of the thermocouples to which the other end and the other end of the second metal body are connected, and either one of the occlusions is stored. A thermoelectric hydrogen sensor characterized in that a hydrogen protective member is provided on the body so as to cover the surface of the occlusion body so as not to come into contact with hydrogen gas, and the thermoelectromotive force generated in the thermocouple is detected by the temperature difference between the occlusion bodies. . In order to detect the thermoelectromotive force, a voltmeter that measures the voltage in the thermocouple is installed,
The thermoelectric hydrogen sensor according to claim 1 or 2, wherein the detection of hydrogen is detected when the measured value measured by the voltmeter exceeds a predetermined value.   The thermoelectric hydrogen sensor according to claim 1, wherein the storage body is formed of palladium or a palladium alloy.   The first metal body and the second metal body are formed of Pt, Rh, Fe, Ni, Cu, Au, Pb, or Pd alone or in an alloy. The thermoelectric hydrogen sensor according to item 1.

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