JP2005249405A - Hydrogen detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrogen detector constituted so as to use a hydrogen occluding alloy, having high selectivity with respect to hydrogen to easily defect the concentration of hydrogen gas contained in gas. <P>SOLUTION: First and second detection elements 11 and 12 comprising the hydrogen occluding alloy which are mutually different in the temperature change characteristics of hydrogen occluding pressure are set so that a state change (e.g., volume expansion, generation of heat, weight increase and the like), caused at the occlusion of hydrogen or a state change (e.g., volume contraction, absorption of heat, weight lowering and the like) becomes different from each other. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a hydrogen detector that detects a hydrogen concentration in a gas.

Conventionally, for example, as a device for detecting hydrogen using a hydrogen storage alloy, the volume when hydrogen storage alloy has occluded hydrogen by attaching a hydrogen storage alloy to one surface of the substrate and attaching a strain gauge to the other surface. 2. Description of the Related Art A hydrogen detection device (see, for example, Patent Document 1) that detects strain of a substrate caused by expansion with a strain gauge and detects a hydrogen storage amount based on the detected strain magnitude is known.
Japanese Patent Laid-Open No. 10-73530

However, in the hydrogen detection device according to the above-described prior art, for example, by providing a hydrogen storage alloy (for example, a hydrogen storage alloy tank) together with a hydrogen storage alloy, a relatively high concentration hydrogen stored in the device is provided. Although suitable for detecting the amount, there is a problem that it is difficult to accurately detect the hydrogen concentration in the gas over a relatively wide concentration range.
The present invention has been made in view of the above circumstances, and a hydrogen detector capable of easily and accurately detecting the concentration of hydrogen gas contained in a gas by using a hydrogen storage alloy having high selectivity for hydrogen. The purpose is to provide.

  In order to solve the above problems and achieve the object, the hydrogen detector of the invention according to claim 1 includes a plurality of detection elements (for example, implementation elements) made of hydrogen storage alloys having different hydrogen storage pressures at the same temperature. First and second detection elements 11 and 12) in the form, detection means for detecting a change in state when each of the detection elements occludes hydrogen (for example, the crystal resonator 14 in the embodiment), Temperature detecting means (for example, the Peltier element 16 in the embodiment) for controlling all the detecting elements to substantially the same temperature, and each detecting element has a different state change (for example, when hydrogen is occluded) (for example, (Weight change in the embodiment) is generated.

According to the hydrogen detection device having the above configuration, the hydrogen storage alloy constituting the detection element suppresses hydrogen storage when the hydrogen partial pressure in the atmosphere of the hydrogen detection device is lower than a predetermined hydrogen storage pressure corresponding to the temperature. When the hydrogen partial pressure in the atmosphere reaches a predetermined hydrogen storage pressure corresponding to the temperature, hydrogen storage is started. When the hydrogen storage alloy stores hydrogen, state quantities such as volume, temperature, and weight change. Therefore, the detection element can detect that the detection element has stored hydrogen by detecting this change. When the temperature of the plurality of detection elements is controlled to be almost the same temperature by the temperature control means, the hydrogen storage alloys constituting each detection element have different temperature change characteristics of the hydrogen storage pressure. Depending on whether the element occludes hydrogen, the hydrogen concentration range of the atmosphere of the hydrogen detector can be detected easily and accurately.
In addition, since the state change that occurs when hydrogen is occluded for each detection element is set to be different from each other, for example, an abnormality such as deterioration occurs in any one of the detection elements, so that hydrogen is occluded. When it becomes difficult to detect a change in the state that does not occur in the normal state, in addition to the occurrence of an abnormal state such as deterioration, which detection element is the detection element in which the abnormality has occurred Can be detected.

  According to the hydrogen detector of the first aspect of the present invention, it is possible to easily detect whether or not an abnormal state such as deterioration of each detection element has occurred.

Hereinafter, an embodiment of the hydrogen detector of the present invention will be described with reference to the accompanying drawings.
A hydrogen detection apparatus 10 according to the present embodiment is sandwiched from both sides by a plurality (for example, two) of first and second detection elements 11 and 12 and a pair of electrodes 13a and 13b, as shown in FIG. The crystal resonator 14, the internal temperature sensor 15, the Peltier element 16, the heat transfer material 17, the water repellent filter 18, the external temperature sensor 19, and the control device 20 are configured.
And the inside of the box-shaped housing | casing 21 which has the opening part into which test object gas is introduce | transduced is formed as a gas detection chamber, and inside this housing | casing 21, each detection element 11 and 12 and a pair of electrode 13a, The quartz crystal resonator 14 provided with 13b, the internal temperature sensor 15, the Peltier element 16, the heat transfer material 17, and the water repellent filter 18 are accommodated, and the external temperature sensor 19 and the control device 20 are provided outside the housing 21. And are arranged.

The first and second detection elements 11 and 12 are made of hydrogen storage alloys having different temperature change characteristics of the hydrogen storage pressure, and the hydrogen of the first detection element 11 at a predetermined operating temperature (for example, 100 ° C.). The occlusion pressure (for example, 0.005 atm) is set to a value lower than the hydrogen occlusion pressure (for example, 0.01 atm) of the second detection element 12, and these hydrogen occlusion pressures are the hydrogen partial pressure in the atmosphere. Is set to correspond to different hydrogen concentrations. (For example, hydrogen partial pressures of 0.005 atm and 0.01 atm correspond to hydrogen concentrations of 0.5% and 1.0%, respectively.)
Furthermore, the first and second detection elements 11 and 12 change state (for example, volume expansion, heat generation, weight increase, etc.) that occurs when hydrogen is occluded, or change in state that occurs when occluded hydrogen is released (for example, For example, volume shrinkage, endotherm, weight reduction, etc.) are set to be different from each other. For example, when the first detection element 11 occludes hydrogen when the hydrogen partial pressure of the gas to be inspected is 0.005 atm or more and less than 0.01 atm, the weight increases by an increment Δm, whereas the gas to be inspected is increased. When the second detection element 12 occludes hydrogen in a state where the hydrogen partial pressure is 0.01 atm or more, the weight increases by a three-fold increment 3Δm.
The first and second detection elements 11 and 12 are bonded onto the surface of the one electrode 13a of the crystal resonator 14 by an appropriate bonding method having heat resistance such as sintering, pressure bonding, thermal spraying, and adhesion. Yes.

  The substantially plate-shaped crystal resonator 14 is sandwiched from both sides in the thickness direction by a pair of electrodes 13a and 13b for exciting the crystal resonator 14, and is bonded to the surface of one electrode 13a. A change in the resonance frequency of the crystal resonator 14 according to a change in the state of the second detection elements 11 and 12 is output as an electric signal to the control device 20 via the pair of electrodes 13a and 13b.

An internal temperature sensor 15 such as a thermistor is disposed on the surface of the other electrode 13 b of the crystal resonator 14. Further, the internal temperature sensor 15 and a heat transfer material disposed on the inner wall surface of the housing 21. 17, a Peltier element 16 is disposed as a temperature holding device for holding the detection elements 11 and 12 at substantially the same temperature.
The Peltier element 16 sets the temperature of each of the detection elements 11 and 12 to a predetermined operating temperature by absorbing or radiating heat according to energization control by the control device 20. The detected value of the internal temperature T 1 detected by the internal temperature sensor 15 is output to the control device 20.

A plurality of heat radiation fins 22,..., 22 are provided on the outer surface of the housing 21 in which the heat transfer material 17 is disposed.
In addition, the opening of the housing 21 is provided with a water repellent filter 18 that can transmit the gas to be inspected and restricts the permeation of moisture contained in the gas to be inspected.
Further, the detected value of the external temperature T2 detected by the external temperature sensor 19 outside the housing 21 is output to the control device 20.

The hydrogen detection device 10 according to the present embodiment has the above-described configuration. Next, the operation of the hydrogen detection device 10 will be described.
The hydrogen storage alloy constituting each of the detection elements 11 and 12 suppresses the storage of hydrogen when the hydrogen partial pressure of the atmosphere inside the casing 21 serving as the gas detection chamber is lower than each hydrogen storage pressure corresponding to the temperature, When the hydrogen partial pressure reaches each hydrogen storage pressure corresponding to the temperature, storage of hydrogen starts. Since the hydrogen storage alloy increases in weight when storing hydrogen, a change in the resonance frequency of the crystal resonator 14 is detected by the control device 20.
Here, if the temperature of each of the detection elements 11 and 12 is controlled to be a predetermined operating temperature, the hydrogen storage alloys constituting each of the detection elements 11 and 12 have different temperature change characteristics of the hydrogen storage pressure. Depending on which of the detection elements 11 and 12 occludes hydrogen, the change in the resonance frequency of the crystal resonator 14 to be detected differs, and based on this change in the resonance frequency, the concentration range of the hydrogen concentration in the atmosphere Can be detected.

  For example, as shown in FIG. 2, in a state where the temperature of each of the detection elements 11 and 12 is maintained at a predetermined operating temperature (for example, 100 ° C. or the like), the hydrogen partial pressure of the atmosphere is When the hydrogen storage pressure (for example, 0.005 atm, 0.01 atm) is not satisfied, each of the detection elements 11 and 12 does not store hydrogen, and the weight change of the hydrogen detection device 10 is zero, so that the crystal resonator 14 It is detected that the change in the resonance frequency is zero and the hydrogen concentration in the atmosphere is less than 0.5%.

  When the hydrogen partial pressure in the atmosphere is equal to or higher than the hydrogen storage pressure (for example, 0.005 atm) of the first detection element 11 and less than the hydrogen storage pressure (for example, 0.01 atm) of the second detection element 12, Only one detection element 11 occludes hydrogen, and the weight of the hydrogen detection device 10 increases by an increment Δm. By detecting a change in the resonance frequency of the crystal resonator 14 according to the increase in weight, it is detected that the hydrogen concentration in the atmosphere is 0.5% or more and less than 1.0%.

  Further, when the hydrogen partial pressure in the atmosphere is equal to or higher than the hydrogen occlusion pressure (for example, 0.01 atm) of the second detection element 12, the second detection element 12 occludes hydrogen in addition to the first detection element 11. As the weight of the detection device 10 further increases by an increment of 3Δm, the integrated amount of the weight change becomes an increment of 4Δm. By detecting a change in the resonance frequency of the crystal resonator 14 according to the increase in weight, it is detected that the hydrogen concentration in the atmosphere is 1.0% or more.

Here, the first and second detection elements 11 and 12 are set so that the increments of the weight increase generated when hydrogen is occluded are different from each other (that is, Δm and 3Δm). By detecting a change in the resonance frequency of the crystal resonator 14, it is possible to detect the state of each of the detection elements 11 and 12, more specifically, whether or not the first detection element 12 is normal.
For example, when an abnormality such as deterioration occurs in the first detection element 11 and it becomes difficult to occlude hydrogen, the hydrogen partial pressure of the atmosphere is equal to or higher than the hydrogen occlusion pressure of the first detection element 11 (for example, 0.005 atm). Even when the hydrogen storage pressure of the second detection element 12 is less than 0.01 atm (for example, 0.01 atm), the detection elements 11 and 12 do not store hydrogen, and the weight change of the hydrogen detection device 10 is zero. Therefore, the change in the resonance frequency of the crystal unit 14 becomes zero, and the hydrogen concentration in the atmosphere is detected to be less than 0.5%. Thereafter, the hydrogen partial pressure in the atmosphere becomes equal to or higher than the hydrogen occlusion pressure (for example, 0.01 atm) of the second detection element 12, the second detection element 12 occludes hydrogen, and the weight of the hydrogen detection device 10 increases by 3Δm. For example, as shown by a broken line in FIG. 2, the integrated amount of weight change becomes an increment 3Δm, which is a value that is impossible in the normal state of the first detection element 11. By detecting a change in the resonance frequency of the crystal resonator 14 according to the increase in weight, it is detected that an abnormality such as deterioration has occurred in the first detection element 11.

Note that the Peltier element 16 that is energized and controlled by the control device 20 sets the internal temperature T1 higher than the external temperature T2 in addition to setting the temperature of each of the detection elements 11 and 12 to a predetermined operating temperature.
For example, in step S01 shown in FIG. 3, the control device 20 determines whether or not the internal temperature T1 is higher than the external temperature T2.
If the determination result is “NO”, the process proceeds to step S02, and energization is performed so that the Peltier element 16 is in a heat generation state, or energization to the endothermic Peltier element 16 is stopped, and the internal temperature T1 To end the series of processing.
On the other hand, if this determination is “YES”, the flow proceeds to step S 03, the energized state of the Peltier element 16 is maintained, and the series of processes is terminated.
In this way, by setting the internal temperature T1 higher than the external temperature T2, it is possible to prevent moisture in the gas to be inspected flowing from the outside into the gas detection chamber inside the housing 21 from condensing in the gas detection chamber, For example, it is possible to prevent an increase in the weight of the hydrogen detector 10 due to the generation of condensed water.

  As described above, according to the hydrogen detection device 10 according to the present embodiment, in addition to being able to easily and accurately detect the hydrogen concentration range of the atmosphere of the hydrogen detection device 10, the first and second detection elements 11. , 12 are state changes that occur when hydrogen is occluded (eg, volume expansion, heat generation, weight increase, etc.) or state changes that occur when occluded hydrogen is released (eg, volume shrinkage, heat absorption, weight loss, etc.) ) Are set to be in different state changes, for example, when abnormality such as deterioration occurs in the first detection element 11 and it becomes difficult to occlude hydrogen, a state that does not occur in a normal state A change is detected, and in addition to the presence or absence of an abnormal state such as deterioration, it is possible to detect which detection element is the detection element in which the abnormality has occurred.

In the above-described embodiment, the two first and second detection elements 11 and 12 are provided. However, the present invention is not limited to this. As the number increases, the detectable density range can be set in detail.
In the above-described embodiment, the change in the weight of each of the detection elements 11 and 12 is detected by the crystal resonator 14. However, the present invention is not limited to this. For example, the change in volume may be detected by a strain gauge or the like. The temperature change may be detected by a temperature sensor.

It is a block diagram of the hydrogen detection apparatus which concerns on one Embodiment of this invention. It is a graph which shows an example of the relationship between the weight change of the hydrogen detection apparatus shown in FIG. 1, and hydrogen concentration. It is a flowchart which shows operation | movement of the hydrogen detection apparatus shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Hydrogen detection apparatus 11 1st detection element 12 2nd detection element 14 Crystal oscillator (detection means)
16 Peltier element (temperature control means)

Claims (1)

A plurality of detection elements made of hydrogen storage alloys having different hydrogen storage pressures at the same temperature;
Detection means for detecting a change in state when each of the detection elements occludes hydrogen;
Temperature control means for controlling all the detection elements to substantially the same temperature,
Each of the detection elements generates a different state change when hydrogen is occluded.

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