JP3942534B2 - Fuel gas supply control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel gas supply control device for a fuel cell that generates an electromotive force using a fuel gas and an oxidant gas.
[0002]
[Prior art]
For example, a fuel cell system is known in which fuel gas is supplied to a fuel cell and energy obtained by reacting the fuel gas with an oxidant gas is converted into electric energy.
[0003]
As a fuel cell, a solid polymer type in which an electrolyte membrane (electrolyte) / electrode structure in which an anode electrode and a cathode electrode are arranged on both sides of an electrolyte membrane made of a polymer ion exchange membrane (cation exchange membrane) is sandwiched by separators There is a fuel cell. This type of fuel cell is usually used as a fuel cell stack by laminating a predetermined number of electrolyte membrane / electrode structures and separators.
[0004]
In a fuel cell, a fuel gas supplied to an anode electrode, for example, a hydrogen-containing gas, moves to the cathode electrode side through an electrolyte membrane that is appropriately humidified and hydrogen is ionized on the electrode catalyst. The electrons generated in the meantime are taken out to an external circuit and used as direct current electric energy. Since the cathode electrode is supplied with an oxidant gas, for example, an oxygen-containing gas such as air, hydrogen ions, electrons, and oxygen gas react to generate water at the cathode electrode.
[0005]
By the way, in such a fuel cell, a part of hydrogen gas supplied to the anode electrode may be discharged without contributing to power generation, depending on the operating condition. Further, depending on the state of the electrolyte membrane, hydrogen gas may be discharged from the cathode electrode side. In this case, if the amount of hydrogen gas discharged is large, the fuel consumption rate increases, which is uneconomical.
[0006]
Therefore, for example, in the prior art disclosed in Patent Document 1, when a hydrogen gas detector is connected to the gas discharge line of the fuel cell, and the hydrogen gas detector detects the discharge of the hydrogen gas, the hydrogen-containing gas fuel cell The supply to is cut off.
[0007]
Further, in the prior art disclosed in Patent Document 2, it is stored as a history whether or not the fuel cell has been repeatedly activated and stopped in a relatively short period, and whether or not the next activation can be performed based on the history. If there is a possibility that the concentration of the discharged hydrogen gas may increase, the fuel cell is prohibited from starting.
[0008]
[Patent Document 1]
JP-A-6-223850 (abstract, FIG. 1)
[Patent Document 2]
JP 2002-198075 (abstract, FIG. 1)
[0009]
[Problems to be solved by the invention]
In this case, in the configuration of Patent Document 1, if the detection threshold of hydrogen gas is too low, the discharge detection sensitivity is improved, but the possibility of frequent interruption of the hydrogen-containing gas supplied to the fuel cell increases. There is a possibility that the battery cannot be operated efficiently.
[0010]
Further, in the configuration of Patent Document 2, since it is determined whether or not the fuel cell can be started based only on the start and stop history of the fuel cell, it is ensured against a situation where hydrogen gas is actually excessively discharged. There is a possibility that it cannot be dealt with.
[0011]
The present invention solves this type of problem, and can appropriately determine whether or not fuel gas can be supplied to the fuel cell and control the fuel cell. Also, the fuel gas consumption rate can be kept low, and the fuel cell can be made efficient. It is an object of the present invention to provide a fuel gas supply control device that can be operated in an automated manner.
[0012]
[Means for Solving the Problems]
According to the first aspect of the present invention, when the emission value of the fuel gas discharged from the fuel cell is detected by the emission value detection unit, and the first determination unit determines that the emission value is larger than the first determination value, the supply The control unit prohibits the supply of the fuel gas to the fuel cell because the discharge is abnormal. In addition, the second determination unit compares the discharge value with a second determination value that is smaller than the first determination value, determines that the discharge value is larger than the second determination value, and that there has been a discharge abnormality as a previous determination result. Even when the determination result is stored in the determination result storage unit, the supply control unit prohibits the supply of the fuel gas to the fuel cell on the assumption that the discharge is abnormal. As a result, it is possible to avoid in advance a situation in which the fuel gas is excessively discharged.
[0013]
On the other hand, when the emission value is smaller than the first determination value and the discharge abnormality is not stored in the determination result storage unit as the previous determination result, the fuel gas is allowed to be supplied and the electromotive force of the fuel cell is reduced. Enable generation. Further, since although discharge abnormality is stored in the determination result storage section as a previous determination result, the discharge value is smaller than the second determination value, which is assumed to discharge abnormality is avoided, fuel Allow supply of gas. Accordingly, the fuel gas is supplied to the fuel cell, and the electromotive force can be efficiently generated.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a fuel cell system 10 to which a fuel gas supply control device of the present invention is applied. In FIG. 1, a line indicated by a double line represents a gas flow path, and a line indicated by a single line represents an electrical signal line.
[0015]
The fuel cell system 10 includes a fuel cell stack 12 (fuel cell) and a fuel gas supply control device 14 that controls supply of fuel gas to the fuel cell stack 12.
[0016]
The fuel cell stack 12 includes a large number of cells formed by connecting an anode electrode 16 supplied with a fuel gas containing hydrogen gas and a cathode electrode 18 supplied with an oxidant gas containing oxygen gas via an electrolyte membrane 20. Are connected in series. A fuel gas supply valve 22 that controls the supply of the fuel gas is disposed on the fuel gas supply side of the anode electrode 16. A fuel gas sensor 24 (exhaust value detection unit) that detects hydrogen gas, which is a fuel gas to be discharged, is disposed on the fuel gas discharge side of the anode electrode 16.
[0017]
The fuel gas supply control device 14 includes a gas concentration calculation unit 26 that calculates the gas concentration D from the detected value (discharge value) of hydrogen gas detected by the fuel gas sensor 24, the calculated gas concentration D, and the first determination value DTH1. , A gas leakage determination unit 28 (first determination unit, second determination unit) that determines the presence or absence of gas leakage using the second determination value DTH2 (DTH1> DTH2) and the record of the gas leakage history, and a gas leakage determination unit 28 A fuel cell control unit 30 (supply control unit) that controls the fuel gas supply valve 22 based on the determination result of
[0018]
In the gas leakage determination unit 28, a determination value storage unit 32 that stores a first determination value DTH1 and a second determination value DTH2 that are set in advance, and a gas leakage determination result by the gas leakage determination unit 28 are stored as a gas leakage history. The gas leak history storage unit 34 (determination result storage unit) and a flag storage unit 36 that stores various flags in the determination process in the gas leak determination unit 28 are connected. The fuel cell control unit 30 is connected to a start switch 38 for starting the fuel cell stack 12.
[0019]
The fuel cell system 10 of the present embodiment is basically configured as described above. Next, the operation will be described with reference to the flowcharts shown in FIGS.
[0020]
When the start switch 38 of the fuel cell stack 12 is operated by the operator, the fuel cell control routine shown in FIG. 2 is started, and first, a gas leak determination process is performed (step S1). This process is executed by a gas leak determination routine shown in FIGS.
[0021]
That is, the fuel gas sensor 24 measures the discharge value of hydrogen gas, which is the fuel gas discharged from the anode electrode 16, and supplies it to the gas concentration calculation unit 26 (step S21). The gas concentration calculation unit 26 calculates the gas concentration D of hydrogen gas from the measurement signal from the fuel gas sensor 24, and supplies it to the gas leak determination unit 28 (step S22).
[0022]
The gas leak determination unit 28 checks the state of the start determination processing flag stored in the flag storage unit 36 (step S23). In this case, the start-time determination processing flag is ON when the gas leak determination unit 28 has already determined the gas leak after the start switch 38 is operated, and is OFF when the determination has not been performed yet. It shall be set.
[0023]
When the start determination flag is OFF, the gas leak determination unit 28 determines whether or not there is a gas leak history in the gas leak history storage unit 34 (see step S24, FIG. 4), and there is no gas leak history. In this case, the detected gas concentration D is compared with the first determination value DTH1 stored in the determination value storage unit 32 (step S25).
[0024]
When D ≦ DTH1, it is determined that hydrogen gas, which is a fuel gas having an allowable concentration or more, does not leak from the fuel cell stack 12 (step S26), and the gas leak flag is set to OFF (step S27). Further, since the gas leak determination is performed in step S26, the start determination processing completion flag is set to ON (step S28). The gas leak flag and the start-time determination process completion flag are stored in the flag storage unit 36.
[0025]
When D> DTH1, it is determined that fuel gas having an allowable concentration or more is leaking from the fuel cell stack 12 (step S29), and the determination result is stored in the gas leakage history storage unit 34 as an abnormal discharge (step S30). ). Next, the gas leakage present flag is set to ON (step S31), and the start-time determination process completion flag is set to ON (step S28).
[0026]
On the other hand, when the gas leak history as the discharge abnormality is already stored in the gas leak history storage unit 34 (step S24), the gas leak determination unit 28 is stored in the detected gas concentration D and the determination value storage unit 32. The second determination value DTH2 smaller than the first determination value DTH1 is compared (step S32).
[0027]
If D> DTH2, the fuel gas leak continues and the concentration of the discharged fuel gas may increase. Therefore, it is determined that there is a gas leak (step S29), and the determination result of the discharge abnormality is the gas. The data is stored in the leakage history storage unit 34 (step S30), and the gas leakage present flag and the start time determination processing flag are set to ON (steps S31 and S28).
[0028]
In the case of D ≦ DTH2, even if the gas leak history is stored, the detected gas concentration D is extremely low, so it is determined that there is no gas leak (step S33), and the gas leak flag is set to OFF. (Step S34). Further, since the gas leakage determination is performed in step S33, the start determination processing flag is set to ON (step S28).
[0029]
As described above, after the initial gas leak determination process immediately after the start switch 38 is operated, the gas leak determination unit 28 determines that the fuel cell stack 12 has not yet started (step S2). ) The gas leak presence flag stored in the flag storage unit 36 is confirmed (step S3). When the gas leakage present flag is set to ON, a prohibition command signal for prohibiting starting of the fuel cell stack 12 is output to the fuel cell control unit 30 (step S4). In this case, the fuel cell control unit 30 maintains the fuel gas supply valve 22 in a closed state. Therefore, no fuel gas is supplied to the fuel cell stack 12 and no gas leakage occurs, and no power generation by the fuel cell stack 12 is performed.
[0030]
On the other hand, when the gas leak flag checked in step S3 is OFF, it can be determined that there is no risk of gas leak, so the gas leak determination unit 28 determines whether the fuel cell stack 12 is in the fuel cell control unit 30. A permission command signal for permitting start is output. The fuel cell control unit 30 opens the fuel gas supply valve 22 based on the permission command signal and the start signal from the start switch 38 (step S5). In this case, the fuel gas is supplied to the anode electrode 16 of the fuel cell stack 12 through the fuel gas supply valve 22 to start power generation (step S6).
[0031]
Next, the gas leak determination process is executed again (step S1). In this case, in step S23 of the gas leakage processing routine shown in FIG. 3, it is confirmed that the start determination processing completion flag is set to ON. Therefore, the gas leak determination unit 28 checks the gas leak flag stored in the flag storage unit 36 (step S35). In this case, if the gas leak flag is set to ON, the gas leak determination process is terminated.
[0032]
When the gas leak flag is OFF, the gas concentration D detected in step S21 is compared with the first determination value DTH1 (step S36). When D> DTH1, it is determined that fuel gas having an allowable concentration or more is leaking from the fuel cell stack 12 (step S39), and the determination result is stored in the gas leak history storage unit 34 as an abnormal discharge (step S40). ). Next, the gas leak flag is set to ON (step S41). If D ≦ DTH1, it is determined that there is no gas leak (step S37), and the gas leak present flag is set to OFF (step S38).
[0033]
Next, when power generation of the fuel cell stack 12 is started in step S6 (step S2), the gas leakage present flag is confirmed (step S7), and when the gas leakage present flag is set to ON, the fuel cell A prohibition command signal for prohibiting power generation of the fuel cell stack 12 is output to the control unit 30. The fuel cell control unit 30 closes the fuel gas supply valve 22 based on this prohibition command signal (step S8). Accordingly, the supply of the fuel gas to the anode electrode 16 of the fuel cell stack 12 is stopped, and the power generation is stopped (step S9). If the gas leak flag is OFF (step S7), the power generation state is continued (step S10).
[0034]
As described above, in the present embodiment, by controlling the supply of hydrogen gas as the fuel gas to the fuel cell stack 12, the fuel consumption rate is suppressed to a low level without discharging excessive hydrogen gas to the outside. Power can be generated.
[0035]
【The invention's effect】
According to the present invention, the fuel gas supply value is determined according to the comparison result between the fuel gas discharge value and the first determination value. On the other hand, if the previous determination result is abnormal discharge, the first determination value is determined. By determining whether or not the fuel gas can be supplied using a smaller second determination value, whether or not the fuel gas can be supplied can be appropriately determined and controlled. Accordingly, it is possible to reduce the fuel gas emission rate and reduce the fuel consumption rate, and it is possible to efficiently operate the fuel cell and generate the electromotive force.
[Brief description of the drawings]
FIG. 1 is a configuration block diagram of a fuel cell system according to an embodiment of the present invention.
FIG. 2 is a flowchart of a fuel cell control routine in the fuel cell system shown in FIG.
3 is a flowchart of a gas leak determination routine in the fuel cell system shown in FIG.
4 is a flowchart of a gas leak determination routine in the fuel cell system shown in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Fuel cell system 12 ... Fuel cell stack 14 ... Fuel gas supply control apparatus 22 ... Fuel gas supply valve 24 ... Fuel gas sensor 26 ... Gas concentration calculation part 28 ... Gas leak determination part 30 ... Fuel cell control part 32 ... Determination value memory | storage 34: Gas leakage history storage unit 36: Flag storage unit 38: Start switch

Claims (1)

A fuel gas supply control device for a fuel cell that generates an electromotive force using a fuel gas and an oxidant gas,
An emission value detector for detecting an emission value of the fuel gas discharged from the fuel cell;
A first determination unit that compares the discharge value with a first determination value and determines a discharge abnormality when the discharge value is greater than the first determination value;
A second determination unit that compares the discharge value with a second determination value that is smaller than the first determination value, and determines that the discharge is abnormal when the discharge value is greater than the second determination value;
A determination result storage unit for storing determination results by the first determination unit and the second determination unit;
When the first determination unit determines that the discharge is abnormal, or when the second determination unit determines that the discharge is abnormal, and the determination result storage unit stores a determination result as discharge abnormality, While prohibiting the supply of the fuel gas to the fuel cell, the second determination unit does not determine that there is a discharge abnormality and the determination result storage unit stores a determination result as a discharge abnormality , or A supply control unit that allows the fuel gas to be supplied to the fuel cell when the determination unit does not determine that the discharge is abnormal and the determination result storage unit does not store the determination result as the discharge abnormality;
A fuel gas supply control device comprising:

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