JP2005322579A - Fuel cell hydrogen gas leak detector - Google Patents

Abstract

A fuel capable of accurately detecting leakage of hydrogen gas even by using a small and inexpensive hydrogen gas sensor that is easily affected by gas other than hydrogen gas, thereby suppressing an increase in size and cost of the apparatus. A hydrogen gas leakage detection device for a battery is provided.
A case housing a fuel cell, a first sensor that outputs a value (V1) indicating a hydrogen gas concentration outside the case, and a value indicating a hydrogen gas concentration inside the case (see FIG. And a second sensor 132 that outputs V2), and detects leakage of hydrogen gas based on the deviation between the outputs V1 and V2 of the sensors 130 and 132.
[Selection] Figure 1

Description

  The present invention relates to a hydrogen gas leak detection device for a fuel cell.

Conventionally, a hydrogen gas leakage detection device for a fuel cell that detects leakage of hydrogen gas supplied to the fuel cell has been proposed. For example, in the apparatus described in Patent Document 1, a sensor that detects hydrogen gas is attached to a case containing a fuel cell, and the hydrogen gas leakage is detected by measuring the hydrogen gas concentration in the case. It is configured.
JP 2001-27626 (Fig. 2 etc.)

  In order to accurately detect leakage of hydrogen gas, it is desirable to use a hydrogen gas sensor with high detection accuracy. However, a hydrogen gas sensor with high detection accuracy is generally large and expensive, and there is a problem that the apparatus is increased in size and cost. On the other hand, a relatively small and inexpensive sensor is easily affected by a gas other than hydrogen gas (the output fluctuates in response to a gas other than hydrogen gas) and is not always satisfactory in terms of detection accuracy. It was.

  Accordingly, the object of the present invention is to solve the above-described problems, and to detect leakage of hydrogen gas with high accuracy even when using a small and inexpensive hydrogen gas sensor that is easily affected by gas other than hydrogen gas. An object of the present invention is to provide a hydrogen gas leakage detection device for a fuel cell that suppresses the increase in cost and cost.

  In order to solve the above-mentioned object, in claim 1, in a hydrogen gas leakage detection device for a fuel cell that detects leakage of hydrogen gas supplied to a fuel cell, a case for housing the fuel cell, A first sensor that outputs a value indicating a hydrogen gas concentration outside the case; a second sensor that outputs a value indicating the hydrogen gas concentration inside the case; the first sensor and the second sensor; Leakage detection means for detecting leakage of the hydrogen gas based on the output deviation.

  According to a second aspect of the present invention, the first and second sensors are constituted by self-heating thermistors.

  In the hydrogen gas leakage detection device for a fuel cell according to claim 1, in the hydrogen gas leakage detection device for a fuel cell that detects leakage of hydrogen gas supplied to the fuel cell, a case for housing the fuel cell; A first sensor that outputs a value indicating the hydrogen gas concentration outside the case; a second sensor that outputs a value indicating the hydrogen gas concentration inside the case; the first sensor; and the second sensor. And a leakage detection means for detecting leakage of the hydrogen gas based on a deviation in the output of the sensor. In other words, an output caused by a gas other than hydrogen gas by obtaining a deviation in the output of each sensor. Since fluctuations are offset and only output fluctuations due to hydrogen gas leaking into the case are detected, hydrogen gas can be detected even if a small and inexpensive sensor that is easily affected by gases other than hydrogen gas is used. Motor can be detected accurately, thus size and cost of the apparatus can be suppressed.

  In the hydrogen gas leakage detection device for a fuel cell according to claim 2, the first and second sensors are made of self-heating thermistors (specifically, heat conduction type hydrogen gas sensors). Since it comprised, the enlargement and cost increase of an apparatus can be suppressed more effectively. In addition, the reliability of the apparatus can be improved by using a self-heating thermistor that has been widely used.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS The best mode of a hydrogen gas leakage detection device for a fuel cell according to the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a schematic view showing a hydrogen gas leakage detection device for a fuel cell according to a first embodiment of the present invention as part of a fuel cell unit.

  In FIG. 1, reference numeral 10 indicates a power generation unit including a hydrogen gas leakage detection device for a fuel cell according to the first embodiment. The power generation unit 10 is packaged in a portable size in which elements necessary for power generation, such as the fuel cell 12 and piping to be described later, are accommodated in a case 14.

  The fuel cell 12 (specifically, a stacked body (cell stack)) is formed by stacking a plurality of, specifically 70, single cells (cells) 16 and generates a rated output of 1.05 kW. The unit cell 16 is a known solid comprising an electrolyte membrane (solid polymer membrane), an air electrode (cathode electrode) and a fuel electrode (anode electrode) sandwiching the membrane, and a separator disposed outside them. Since it is a polymer type fuel cell, detailed description is omitted.

  An air supply system 20 that supplies cooling air and reaction air to the fuel cell 12 is connected to the fuel cell 12. The air supply system 20 includes an air blower 22 that sucks cooling air and reaction air, and a cooling air supply path 24 that connects a discharge port (not shown) of the air blower 22 to a cooling air flow path (not shown) of the fuel cell 12. And a reaction air supply path 26 that connects the discharge port of the air blower 22 to the air electrode of the fuel cell 12, and an intake pipe 28 that communicates the suction port (not shown) of the air blower 22 to the outside of the case 14. The intake pipe 28 is provided with a communication port 28 a that communicates with the inside of the case 14.

  In addition, a hydrogen gas supply system 30 that supplies hydrogen gas to the fuel cell 12 is connected to the fuel cell 12. The hydrogen gas supply system 30 includes a hydrogen gas cylinder 32 in which hydrogen is sealed at a high pressure, flow paths 34 a to 34 d that connect the hydrogen gas cylinder 32 to the fuel cell 12, and respective elements that will be described later disposed in the middle thereof.

  The hydrogen gas cylinder 32 is connected to a regulator 38 through a cylinder valve 36 that can be manually operated from the outside of the case 14, and the regulator 38 is connected to an ejector 40 through a first flow path 34a. In the middle of the first flow path 34a, a main valve 42 that can be manually operated from the outside of the case 14 is disposed, and a second flow path 34b that bypasses the main valve 42 is connected. A first electromagnetic valve 44 and a second electromagnetic valve 46 are disposed in the middle of the second flow path 34b.

  The ejector 40 is connected to each fuel electrode of the fuel cell 12 through the third flow path 34c and the fourth flow path 34d. The third flow path 34c is a supply-side flow path, and the fourth flow path 34d is a discharge-side flow path.

  Further, a nitrogen gas supply system 50 that supplies a purge gas (inert gas, for example, nitrogen gas) to the fuel cell 12 is connected downstream of the main valve 42 in the first flow path 34a. The nitrogen gas supply system 50 includes a nitrogen gas cylinder 52 filled with nitrogen at a high pressure, a fifth flow path 54 that connects the nitrogen gas cylinder 52 to the first flow path 34a, and each element that will be described later disposed in the middle of them. It consists of.

  The nitrogen gas cylinder 52 is connected to the regulator 58 via a cylinder valve 56 that can be manually operated from the outside of the case 14, and the regulator 58 is connected to the first flow path 34 a via the fifth flow path 54. . A third electromagnetic valve 60 is disposed in the middle of the fifth flow path 54.

  An air exhaust system 70 is further connected to the fuel cell 12. The air discharge system 70 includes an exhaust manifold 72 and an air discharge path 74 that connects the fuel cell 12 to the exhaust manifold 72. The air discharge path 74 is branched into a cooling air discharge path 74a and a reaction air discharge path 74b, and is connected to the cooling air flow path and the air electrode of the fuel cell 12, respectively.

  A purge gas discharge system 80 is connected to the ejector 40 described above. The purge gas discharge system 80 includes a purge gas discharge path 82 that connects the ejector 40 to the exhaust manifold 72, and a fourth electromagnetic valve 84 that is disposed in the middle of the purge gas discharge path 82.

  In FIG. 1, each flow path serving as a flow path for hydrogen gas and purge gas is indicated by a thick solid line, and each flow path serving as a flow path for air is indicated by a double line.

  Continuing the description of FIG. 1, the electrical box 100 is disposed inside the case 14. The electrical box 100 accommodates a first DC-DC converter 102, a relay 104, a second DC-DC converter 106, and an ECU (electronic control unit) 110 formed of a microcomputer.

  The output terminal of the fuel cell 12 is connected to an external device (not shown) via a first DC-DC converter 102 and a relay 104 housed in the electrical equipment box 100, and via a second DC-DC converter 106. Connected to ECU 110. The ECU 110 is connected to an operation switch 112 that can be manually turned on and off from the outside of the case 14 and the relay 104 described above.

  In addition, the electrical box 100 is provided with a ventilation port 120 that communicates the outside of the case 14 and the interior of the electrical box 100, and an exhaust port 122 that communicates the interior of the electrical box 100 and the interior of the case 14.

  A first sensor 130 is disposed in the vicinity of the ventilation opening 120 outside the case 14. Further, a second sensor 132 is disposed in the case 14 in the vicinity of the communication port 28a. The first sensor 130 and the second sensor 132 are heat-conducting hydrogen gas sensors composed of self-heating thermistors, and the same (same type) sensors are used. The first sensor 130 outputs a value (voltage) indicating the hydrogen gas concentration outside the case 14, and the output V <b> 1 is input to the ECU 110. The second sensor 132 outputs a value (voltage) indicating the hydrogen gas concentration inside the case 14, and the output V <b> 2 is input to the ECU 110.

  Next, the power generation operation of the fuel cell 12 will be described based on the above configuration.

  The high-pressure hydrogen sealed in the hydrogen gas cylinder 32 is supplied to the regulator 38 when the cylinder valve 36 is manually opened. The hydrogen gas depressurized and regulated by the regulator 38 is supplied to the ejector 40 via the first flow path 34a when the main valve 42 is manually operated (opened), and further the third flow path 34c. To the fuel electrode of the fuel cell 12. The first to fourth electromagnetic valves 44, 46, 60, 84 shown in FIG. 1 prevent the hydrogen gas or nitrogen gas from flowing out when the fuel cell 12 is not in operation. It is assumed that all valves are closed at the end of operation. In other words, each of the first to fourth electromagnetic valves 44, 46, 60, 84 is a normal / close type electromagnetic valve (an electromagnetic valve that closes when not energized and opens when energized).

  In each unit cell 16 of the fuel cell 12, the hydrogen gas supplied to the fuel electrode generates an electrochemical reaction with the reaction air (oxygen) present in the air electrode, thereby starting power generation. Of the hydrogen gas supplied to the fuel electrode, unreacted gas that has not been subjected to an electrochemical reaction with air is recirculated to the ejector 40 via the fourth channel 34d, and the third channel 34c. Then, it is supplied again to the fuel electrode.

  When the power generation of the fuel cell 12 is started, the electric power is converted into a DC voltage of an appropriate magnitude by the second DC-DC converter 106 and then supplied to the ECU 110 as an operating power source.

  The ECU 110 activated upon receiving the supply of electric power opens the first electromagnetic valve 44 and the second electromagnetic valve 46 and supplies hydrogen gas to the fuel cell 12 through the second flow path 34b.

  Further, the ECU 110 operates the air blower 22 to supply cooling air and reaction air to the fuel cell 12 and ventilates the inside of the case 14. Specifically, when the air blower 22 operates, air (cooling air and reaction air) is sucked from the outside of the case 14 through the intake pipe 28. At the same time, air is sucked from the ventilation port 120 of the electrical box. The air sucked from the ventilation port 120 cools the interior of the electrical box 100 and is discharged from the exhaust port 122. The air discharged from the exhaust port 122 passes through the inside of the case 14 and then flows into the intake pipe 28 from the communication port 28a and is supplied to the fuel cell 12 as cooling air or reaction air.

  The cooling air and the reaction air that have passed through the fuel cell 12 flow out of the fuel cell 12 through the cooling air discharge path 74a and the reaction air discharge path 74b, respectively, and then are discharged to the outside through the exhaust manifold 72. . Thereby, the inside of the case 14 is always ventilated.

  When the ECU 110 is activated and the first electromagnetic valve 44 and the second electromagnetic valve 46 are opened, there is no need to manually operate the main valve 42. For this reason, the ECU 110 appropriately notifies means (such as a voice or a display) that the ECU 110 is started after power generation of the fuel cell 12 is started, in other words, that the power supply to the external device is ready. (Not shown) to inform the operator.

  Then, when the operation switch 112 is manually operated (turned on) by an operator who knows that the power supply to the external device is ready, the ECU 110 operates the relay 104 to operate the first DC-DC converter. 102 and the external device are conducted. As a result, the electric power generated by the fuel cell 12 is converted into a direct current voltage having an appropriate magnitude by the first DC-DC converter 102 and then supplied to an external device via the relay 104.

  The ECU 110 also purges the fuel cell 12 by operating each electromagnetic valve based on the output of a voltage sensor (not shown). Specifically, when the detection value of the voltage sensor falls below a predetermined value, the first electromagnetic valve 44 and the second electromagnetic valve 46 arranged in the second flow path 34b are closed, and the fifth The third electromagnetic valve 60 disposed in the flow path 54 and the fourth electromagnetic valve 84 disposed in the purge gas discharge path 82 are opened.

  As a result, the supply of hydrogen gas is cut off, while the high-pressure nitrogen sealed in the nitrogen gas cylinder 52 is supplied to the regulator 58 through the cylinder valve 56, where it is depressurized and regulated, and then the fifth flow path 54. Then, it is supplied to the fuel electrode of the fuel cell 12 through the ejector 40 and the third flow path 34c. The cylinder valve 56 is assumed to be opened in advance by the operator when the operation of the fuel cell 12 is started.

  The nitrogen gas supplied to the fuel electrode pushes the fourth flow path 34d, the ejector 40, the purge gas discharge path 82, and the exhaust manifold 72 while pushing out the unreacted gas and generated water staying in the fuel electrode from the fuel cell 12. It is discharged to the outside.

  The ECU 110 detects the leakage of hydrogen gas based on the outputs V1 and V2 of the first sensor 130 and the second sensor 132. Specifically, the hydrogen gas is supplied from the fuel cell 12 or the hydrogen gas supply system 30. It is determined whether the hydrogen gas concentration in the case 14 has increased due to leakage.

  Hereinafter, detection of leakage of hydrogen gas will be described.

  As described above, each of the first sensor 130 and the second sensor 132 is a heat conduction type hydrogen gas sensor including a self-heating thermistor.

  Here, the first sensor 130 and the second sensor 132 will be described. The heat dissipation constant of the thermistor self-heated (specifically, supplied with a predetermined current so as to reach a predetermined temperature) depends on the thermal conductivity of the gas present around the thermistor element. That is, the output of the self-heating thermistor varies according to the thermal conductivity of the gas present around it.

  The thermal conductivity of the gas changes according to its humidity. Therefore, the self-heating thermistor is small and inexpensive, and has been widely used as an absolute humidity sensor.

  Further, the thermal conductivity of the gas varies depending on the type. Therefore, the self-heating thermistor can also be applied as a gas sensor for detecting a specific gas. The first sensor 130 and the second sensor 132 measure the concentration of hydrogen gas using such characteristics.

  However, if a gas other than the measurement target is present in the atmosphere, the heat conduction type gas sensor is affected by them and causes a measurement error. Therefore, in the hydrogen gas leakage detection device for a fuel cell according to the present invention, the hydrogen gas leakage is eliminated by eliminating the influence of gas other than hydrogen gas while using a small and inexpensive self-heating thermistor as the hydrogen gas sensor. Was detected accurately.

  As shown in FIG. 1, since the first sensor 130 is disposed in the vicinity of the ventilation opening 120 outside the case 14, its output V <b> 1 is outside the case 14 (specifically, from the outside of the case 14. This shows the hydrogen gas concentration in the air being introduced into the interior. On the other hand, since the second sensor 132 is arranged in the vicinity of the communication port 28a inside the case 14, its output V2 is inside the case 14 (specifically, from the inside of the case 14 to the outside). Indicates the hydrogen gas concentration in the air being discharged.

  As described above, since the inside of the case 14 is constantly ventilated, the gas component in the case 14 and the external gas component usually coincide with each other. That is, the outputs of the first sensor 130 and the second sensor 132 usually match. On the other hand, when hydrogen gas leaks, the hydrogen gas concentration in the case 14 increases, and the outputs of the first sensor 130 and the second sensor 132 differ.

  Therefore, in the hydrogen gas leakage detection device for a fuel cell according to the present invention, the leakage of hydrogen gas is detected based on the deviation between the output V1 of the first sensor 130 and the output V2 of the second sensor 132. did.

  FIG. 2 is a flowchart showing the operation of the hydrogen gas leakage detection device for a fuel cell according to the present invention. The illustrated program is executed by the ECU 110 at predetermined intervals (for example, every 100 msec).

  In the following, first, in S10, the output V1 of the first sensor 130 is subtracted from the output V2 of the second sensor 132 to calculate the deviation ΔV. That is, by obtaining the output deviation between the first sensor 130 and the second sensor 132, the output fluctuation caused by the gas other than the hydrogen gas is canceled out, and only the output fluctuation caused by the hydrogen gas leaked into the case 14 is obtained. Detected.

  Next, in S12, it is determined whether or not the calculated deviation ΔV exceeds a predetermined value C. When the result in S12 is negative, the program proceeds to S14, where it is determined that no leakage of hydrogen gas has occurred. On the other hand, when the result in S12 is affirmative, the program proceeds to S16, in which it is determined that hydrogen gas has leaked, and the program further proceeds to S18 to execute a danger avoidance operation. Specifically, an appropriate notification means notifies the operator that hydrogen gas is leaking, and the first and second electromagnetic valves 44 and 46 are closed to supply the hydrogen gas to the fuel cell 12. Stop supplying.

  Next, the hydrogen gas leakage detection will be described with specific numerical values.

  FIG. 3 is a characteristic diagram showing output characteristics of the first sensor 130 and the second sensor 132 with respect to various gas concentrations. The characteristics shown in the figure are obtained when a self-heating thermistor manufactured by Oizumi Manufacturing Co., Ltd. (industrial absolute humidity sensor D5AH-05B3-1240) is used as the first sensor 130 and the second sensor 132.

  The outputs V1 and V2 of the first and second sensors 130 and 132 are, if the ambient temperature is less than 30 [° C.] and the relative humidity is less than 80 [%], and the hydrogen gas concentration is 0 [%]. 0 to 4 (± 1) [mV]. In addition, the output fluctuation of 0-4 [mV] originates in temperature and relative humidity. Further, ± 1 [mV] is a tolerance due to manufacturing variation.

  On the other hand, when the hydrogen gas concentration in the case 14 increases by 0.1 [vol%], the outputs V1 and V2 of the first and second sensors 130 and 132 increase by about 1 [mV] as shown in FIG.

  By the way, the explosion limit of hydrogen gas in the air is about 4 [vol%]. Therefore, it is desirable that the leakage of hydrogen gas can be detected at a concentration sufficiently lower than 4 [vol%].

  Therefore, in this embodiment, the predetermined value C is set to 7 [mV]. Thereby, leakage can be detected before the hydrogen gas concentration in the case 14 reaches 0.7 (± 1) [vol%] which is sufficiently lower than the explosion limit.

  For example, when hydrogen gas is obtained by reforming methane gas or the like, methane gas or carbon dioxide may leak into the case 14. However, since the thermal conductivity of methane gas and carbon dioxide is smaller than that of hydrogen gas, as shown in FIG. 3, the output fluctuations of the first and second sensors 130 and 132 with respect to their concentration changes are small.

  Specifically, when the concentration of methane gas increases by 1 [vol%], the outputs V1 and V2 of the first and second sensors 130 and 132 increase by about 1.1 [mV] as shown in FIG. On the other hand, when the concentration of carbon dioxide increases by 1 [vol%], the outputs V1 and V2 of the sensors 130 and 132 decrease by about 1 [mV]. Thus, since the output fluctuations of the first and second sensors 130 and 132 with respect to changes in the concentrations of methane gas and carbon dioxide are sufficiently small (about 1/10) as compared with that of hydrogen gas, the case 14 Even if methane gas or carbon dioxide leaks inside, leakage detection of hydrogen gas can be accurately performed.

  Further, as shown in FIG. 3, the output fluctuation of the first and second sensors 130 and 132 with respect to the change in the water vapor concentration is also sufficiently smaller than that of the hydrogen gas. Even if it occurs, leakage detection of hydrogen gas can be accurately performed.

  As described above, in the hydrogen gas leakage detection device for a fuel cell according to the first embodiment of the present invention, the case 14 for housing the fuel cell 12 and the hydrogen gas supply system 30 connected thereto, A first sensor 130 that outputs a value (V1) that indicates the external hydrogen gas concentration and a second sensor 132 that outputs a value (V2) that indicates the hydrogen gas concentration inside the case 14 are provided. The leakage of hydrogen gas is detected based on the deviation ΔV of the outputs V1 and V2 of 130 and 132. In other words, the output fluctuation caused by gas other than hydrogen gas is canceled by obtaining the deviation ΔV, and the case Since only output fluctuations caused by hydrogen gas leaking into the gas 14 are detected, the accuracy of hydrogen gas leakage is good even with a small and inexpensive sensor that is easily affected by gases other than hydrogen gas. Therefore, an increase in size and cost of the apparatus can be suppressed.

  In particular, since the first and second sensors 130 and 132 are small and inexpensive self-heating thermistors (heat conduction type hydrogen gas sensors), the increase in size and cost of the apparatus can be more effectively suppressed. In addition, the reliability of the apparatus can be improved by using a self-heating thermistor that has been widely used.

  As described above, according to the first embodiment of the present invention, in the hydrogen gas leakage detection device for a fuel cell that detects leakage of hydrogen gas supplied to the fuel cell (12), the fuel cell (12) A housing case (14), a first sensor (130) that outputs a value (V1) indicating a hydrogen gas concentration outside the case (14), and a hydrogen gas concentration inside the case (14); Detection of leakage of the hydrogen gas based on a second sensor (132) that outputs a value (V2), and a deviation (ΔV) between outputs of the first sensor (130) and the second sensor (132) Leakage detection means (ECU 110, S10 to S16 in the flowchart of FIG. 2).

  The first and second sensors (130, 132) are constituted by self-heating thermistors.

  In the above description, the first sensor 130 and the second sensor 132 are heat-conducting hydrogen gas sensors including self-heating thermistors, but other types of hydrogen gas sensors may be used. Further, the attachment positions of the sensors 130 and 132 are not limited to the above. Further, the deviation ΔV is calculated by subtracting the output V1 of the first sensor 130 from the output V2 of the second sensor 132, but the ratio of V1 and V2 may be regarded as the deviation.

It is the schematic which shows the hydrogen gas leak detection apparatus of the fuel cell which concerns on 1st Example of this invention as a part of fuel cell unit. It is a flowchart which shows operation | movement of the hydrogen gas leak detection apparatus of the fuel cell which concerns on 1st Example of this invention. It is a characteristic view showing the output characteristic with respect to the density | concentration of various gas of the 1st sensor and 2nd sensor which are shown in FIG.

Explanation of symbols

12 Fuel Cell 14 Case 110 ECU (Leakage Detection Means)
130 first sensor 132 second sensor

Claims (2)

  In a hydrogen gas leakage detection device for a fuel cell that detects leakage of hydrogen gas supplied to a fuel cell, a case that houses the fuel cell, and a first sensor that outputs a value indicating a hydrogen gas concentration outside the case And a second sensor that outputs a value indicating the hydrogen gas concentration inside the case, and a leak detection that detects a leak of the hydrogen gas based on a deviation between outputs of the first sensor and the second sensor. And a hydrogen gas leakage detection device for a fuel cell. 2. The hydrogen gas leakage detection device for a fuel cell according to claim 1, wherein the first and second sensors are self-heating thermistors.

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