JP2003302365A - Hydrogen-detecting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve reliability to the detection result of a hydrogen-detecting apparatus 1. <P>SOLUTION: The hydrogen-detecting apparatus 1 comprises a hydrogen sensor 25 that is installed at an air discharge path 22 for circulating an air exhausted gas being discharged from the cathode of a fuel cell 2 for detecting hydrogen in the air exhausted gas, and a controller 30 for correcting the detection value of the hydrogen sensor 25 according to the flow rate of the air exhausted gas flowing through the air discharge path 22. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrogen detector for detecting hydrogen in a gas to be inspected on a flow path of the gas to be inspected.

[0002]

2. Description of the Related Art For example, a solid polymer membrane fuel cell is provided with a stack composed of a plurality of cells formed by sandwiching a solid polymer electrolyte membrane between an anode and a cathode from both sides. Hydrogen is supplied as the fuel, air is supplied as the oxidant to the cathode, and hydrogen ions generated by the catalytic reaction at the anode move to the cathode through the solid polymer electrolyte membrane, and oxygen and electrochemical at the cathode. It reacts to generate electricity.

In such a fuel cell as a solid polymer membrane fuel cell, an oxygen detector and an oxygen detector are provided in the exhaust system on the cathode side of the fuel cell as disclosed in, for example, Japanese Patent Publication No. 6-52662. 2. Description of the Related Art A protective device that includes a hydrogen detector and that stops the operation of a fuel cell when the value detected by each detector exceeds a predetermined threshold value is known. Further, as disclosed in JP-A-6-223850, a hydrogen detector is provided in the exhaust system on the cathode side of the fuel cell, and when the hydrogen is detected by the hydrogen detector, the fuel cell is operated. Protective devices that stop are known.

[0004]

By the way, since the hydrogen detector detects hydrogen in the flowing gas, as shown in FIG. 3, even when the hydrogen concentration in the gas to be inspected is constant, the gas flow rate is reduced. It has an output characteristic that the detection output (hydrogen concentration) is different depending on, and it was found that the gas flow rate affects the detection accuracy of the hydrogen detector.

However, in the fuel cell, since the flow rate of air supplied to the cathode is controlled according to the operating state of the fuel cell, the flow rate of reacted air (hereinafter referred to as air off gas) discharged from the cathode is also changed. There is a problem that the detection accuracy of the hydrogen detector may have a detection error due to the change depending on the operating state of the fuel cell. Therefore, the present invention provides a hydrogen detection device capable of improving the reliability of the detection result.

[0006]

In order to solve the above-mentioned problems, the present invention provides a gas flow path (for example, an embodiment described later) through which a gas to be inspected (for example, an air off gas in an embodiment described later) flows. In accordance with the flow rate of the gas to be inspected flowing through the gas passage, and a hydrogen detecting means (for example, a hydrogen sensor 25 in an embodiment described later) installed in the air exhaust passage 22) to detect hydrogen in the gas to be inspected. Correction means for correcting the detection value of the hydrogen detection means (for example, the control device 3 in the embodiment described later).
0) and are included. With this configuration, the detection error caused by the gas flow rate can be eliminated, and as a result, the reliability of the detection result of the hydrogen detection device can be improved.

Further, in the present invention, the gas to be inspected is a cathode off gas discharged from a cathode of a fuel cell (for example, a fuel cell 2 in an embodiment described later) (eg, an air off gas in an embodiment described later). May be With this structure, the reliability of hydrogen concentration control in the cathode offgas is improved.

Further, in the present invention, the correction means may correct the detection value of the hydrogen detection means in accordance with a physical quantity related to the flow rate of the cathode off gas. With this configuration, the detection value of the hydrogen detection means can be corrected without detecting the actual flow rate of the cathode off gas, and the device configuration can be simplified. Further, in the present invention, the hydrogen detecting means may be a catalytic combustion type hydrogen sensor. Here, the catalytic combustion type hydrogen sensor is a sensor that detects the hydrogen concentration from the difference in electric resistance between the detection element and the temperature compensation element by using the heat of combustion when hydrogen contacts the catalyst. With this configuration, hydrogen in the inspection target gas can be detected with high accuracy.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a hydrogen detector according to the present invention will be described below with reference to the drawings of FIGS. 1 and 2. FIG. 1 is a configuration diagram of a fuel cell system including a hydrogen detection device 1 according to the present invention. In this embodiment, a fuel cell system including the hydrogen detection device 1 is mounted on a vehicle such as an electric vehicle.

The fuel cell 2 is composed of a stack formed by stacking a plurality of cells formed by sandwiching a solid polymer electrolyte membrane made of, for example, a solid polymer ion exchange membrane from both sides with an anode and a cathode. In the fuel cell 2, hydrogen as a fuel is supplied to the anode from a hydrogen supply device (not shown) through the hydrogen supply passage 11, and air as an oxidant is supplied to the cathode through the air supply passage 21 by the compressor 23. The hydrogen ions generated by the catalytic reaction at the anode move through the solid polymer electrolyte membrane to the cathode, and cause an electrochemical reaction with oxygen at the cathode to generate electricity.
Then, unreacted hydrogen, that is, hydrogen off gas, is discharged from the hydrogen discharge passage 12, and reacted air, that is, air off gas (cathode off gas) is discharged from the air discharge passage (gas passage) 22. The compressor 23 is
The control device 30 controls to supply the fuel cell 2 with air at a flow rate according to the output current of the fuel cell 2.

In the middle of the air discharge path 22, the air discharge path 2
Flow sensor 2 for detecting the flow rate of air off-gas flowing through 2
4 and a hydrogen sensor (hydrogen detecting means) 25 for detecting the hydrogen concentration in the air off gas. Hydrogen sensor 2
5 is fixed on the outer peripheral surface of the air discharge path 22, and is installed so that the detection unit 25a for detecting hydrogen projects into the air discharge path 22. The hydrogen sensor 25 is used in the detection unit 2
It is also possible to install so that 5a is substantially flush with the inner surface of the air discharge passage 22. The hydrogen sensor 25 is a so-called gas contact combustion type hydrogen sensor, and detects the hydrogen concentration from the difference in electric resistance between the detection element and the temperature compensation element by using the heat of combustion when hydrogen contacts the catalyst. It has become. The output signal of the flow rate sensor 24 and the output signal of the hydrogen sensor 25 are input to the control device 30.

In this fuel cell system, as described above, the flow rate of the air supplied to the fuel cell 2 is controlled by controlling the operation of the compressor 23 according to the output current of the fuel cell 2, so that the fuel cell 2 As the output increases, the flow rate of the air off gas discharged from the fuel cell 2 and flowing to the air discharge passage 22 also increases. Further, as described above, since the hydrogen sensor 25 has the characteristic that the detection accuracy varies depending on the flow rate of the gas to be inspected, the hydrogen concentration in the air off-gas detected by the hydrogen sensor 25 is equal to the true hydrogen concentration. May have different values.

Therefore, the hydrogen detection device 1 of this embodiment
Then, the relationship between the flow rate of the gas to be inspected and the detection accuracy of the hydrogen sensor 25 is experimentally obtained in advance, and based on the experimental result,
From the detected concentration (detection value) A detected by the hydrogen sensor 25 and the flow rate Q of the gas to be inspected, the true hydrogen concentration (corrected concentration) B
Then, a function B = f (A, Q) is calculated, and based on this, a three-dimensional concentration correction map composed of the detected concentration A, the gas flow rate Q to be inspected, and the corrected concentration B is created. The correction map to the control device 30
I decided to store it in the ROM. FIG. 2 shows an example of the density correction map.

In the hydrogen detector 1, the controller 30 corrects the concentration based on the hydrogen concentration in the air off gas detected by the hydrogen sensor 25 and the flow rate of the air off gas detected by the flow sensor 24. The corrected concentration was obtained by referring to the map, and the corrected concentration was managed as the actual hydrogen concentration in the air off gas. This allows
The detection error caused by the air off-gas flow rate is eliminated, and the reliability of hydrogen concentration management in the air off-gas discharged from the fuel cell 2 is improved. The corrected density can be calculated from the function B = f (A, Q) without using the density correction map. In this embodiment, the control device 30 realizes a correction unit that corrects the detection value of the hydrogen detection unit in accordance with the flow rate of the gas to be inspected flowing through the gas passage, and the hydrogen detection device 1 includes the hydrogen sensor 25 and the flow rate. It is composed of a sensor 24 and a control device 30.

In the above-described embodiment, the actual flow rate of the air off-gas is detected by the flow rate sensor 24 and the detection value of the hydrogen sensor 25 is corrected according to the actual flow rate. It is also possible to carry out without detecting the flow rate. In that case, the detection value of the hydrogen sensor 25 is corrected according to the physical quantity related to the flow rate of the air off gas. Here, the physical quantity relating to the flow rate of the air off-gas is a physical quantity that increases or decreases in a predetermined relationship with the flow rate of the air off-gas, and includes the output current of the fuel cell 2, the target current value of the fuel cell 2, and the compressor 23. The number of revolutions, the target power generation amount of the fuel cell 2, and the like can be exemplified. The reason will be described below.

Since the flow rate of the air off-gas can be estimated from the output current of the fuel cell 2, the detection value of the hydrogen sensor 25 can be corrected by using the output current of the fuel cell 2 instead of the actual flow rate of the air off-gas. it can. The flow rate of the air off gas discharged from the fuel cell 2 is determined according to the flow rate of the air supplied to the fuel cell 2, and the current target value of the fuel cell 2 is determined according to the target power generation amount of the fuel cell 2. Is
The air flow rate to be supplied to the cathode of the fuel cell 2 is determined according to the current target value, and the rotation speed of the compressor 23 is controlled according to the determined air flow rate. The flow rate of the air off gas can be estimated from the rotation speed of the compressor 23 or the target power generation amount. Therefore, the detected value of the hydrogen sensor 25 can be corrected using the current target value of the fuel cell 2, the rotation speed of the compressor 23, or the target power generation amount instead of the actual flow rate of the air off gas. As described above, when the physical quantity relating to the flow rate of the air off gas is used instead of the flow rate of the air off gas, the flow rate sensor 24 becomes unnecessary, and the configuration of the hydrogen detection device 1 can be simplified.

[Other Embodiments] The present invention is not limited to the above-described embodiments. For example, the hydrogen detection means is not limited to the catalytic combustion type hydrogen sensor,
The form is not limited as long as hydrogen can be detected in the gas flow. The gas to be inspected is
The gas is not limited to the cathode off gas discharged from the cathode of the fuel cell, and other gas may be used.

[0018]

As described above, according to the present invention, there is provided hydrogen detection means for detecting hydrogen in the gas to be inspected, which is installed in the gas passage through which the gas to be inspected flows; By including a correction unit that corrects the detection value of the hydrogen detection unit according to the flow rate of the gas to be inspected, it is possible to eliminate the detection error due to the gas flow rate, as a result, to the detection result of the hydrogen detection device. The excellent effect of improving reliability is exhibited.

Further, in the present invention, when the gas to be inspected is the cathode off gas discharged from the cathode of the fuel cell, there is an effect that the reliability of hydrogen concentration control in the cathode off gas is improved. Further, in the present invention, when the correction means corrects the detection value of the hydrogen detection means according to the physical quantity related to the flow rate of the cathode off gas, the actual flow rate of the cathode off gas is not detected. Since the detection value of the hydrogen detecting means can be corrected, there is an effect that the device configuration can be simplified. Further, in the present invention, when the hydrogen detecting means is a catalytic combustion type hydrogen sensor, there is an effect that hydrogen in the gas to be inspected can be detected with high accuracy.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of a hydrogen detection device according to the present invention.

FIG. 2 is a concentration correction map for correcting the detection value of the hydrogen sensor according to the gas flow rate.

FIG. 3 is an output characteristic diagram of a hydrogen sensor when a gas to be inspected having the same hydrogen concentration is detected.

[Explanation of symbols]

1 Hydrogen detector 2 Fuel cell 22 Air exhaust path (gas flow path) 25 Hydrogen sensor (hydrogen detection means) 30 Control device (correction means)

Continued front page    (72) Inventor Hiroshi Machida             1-4-1 Chuo Stock Market, Wako City, Saitama Prefecture             Inside Honda Research Laboratory F-term (reference) 2G060 AA01 AB03 AE19 AF07 BA03                       BB08 BB18 BC02 BD02 HC02                       HC08 HC13 HC18 HD03                 5H026 AA02 AA06 HH05                 5H027 AA02 AA06 BC11 KK26 KK31

Claims (4)

[Claims] 1. A hydrogen detecting unit installed in a gas flow path through which a gas to be inspected flows, for detecting hydrogen in the gas to be inspected, and the hydrogen detecting unit according to a flow rate of the gas to be inspected flowing through the gas passage. A hydrogen detection device comprising: a correction unit that corrects the detection value of. 2. The hydrogen detection device according to claim 1, wherein the gas to be inspected is cathode off gas discharged from the cathode of the fuel cell. 3. The hydrogen detection device according to claim 2, wherein the correction unit corrects the detection value of the hydrogen detection unit according to a physical quantity related to the flow rate of the cathode offgas. 4. The hydrogen detection device according to claim 1, wherein the hydrogen detection means is a catalytic combustion type hydrogen sensor.