JP3829682B2 - Fuel cell system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement in a fuel cell system.
[0002]
[Prior art]
Conventionally, in a fuel cell system provided with a fuel cell stack, for example, there is a technique described in Japanese Patent Publication No. 8-27389 in order to improve the startability of the system. This is because an exhaust gas introduction path is provided along the water piping system, and when the fuel cell system is started, the exhaust gas generated by the combustion of methanol in the heater of the reformer is used. Is heated and thawed to improve the startability of the fuel cell system.
[0003]
[Problems to be solved by the invention]
However, this conventional technique has a problem in that it cannot detect water clogging due to freezing of the gas flow path of the fuel cell or the gas diffusion layer at the time of startup. Therefore, if the fuel cell is started when water is clogged, there is a problem that the startability of the fuel cell is remarkably lowered and the fuel consumption of the fuel gas is lowered.
[0004]
Accordingly, an object of the present invention is to provide a fuel cell system that detects the resonance frequency of a fuel cell and determines the water clogging of the fuel cell stack from a comparison between the detected resonance frequency and a reference value.
[0005]
According to a first aspect of the present invention, there is provided a fuel cell system including a fuel cell stack and a control device that controls an operating state of the fuel cell stack, wherein the control device detects a resonance frequency of the fuel cell stack and the resonant frequency of the resulting non fuel cell stack at the time of load operation is set as a reference value, the resonant frequency and the detected compared with the reference value, to determine the water clogging in the fuel cell stack.
[0006]
The second invention is the first invention, the control apparatus, the detected resonance frequency of water clogging in the fuel cell stack is determined to have occurred when not within range of the reference value.
[0009]
In the first and second aspects of the invention, the resonance frequency of the fuel cell stack is detected, the detected resonance frequency is compared with a reference value, and when the detected resonance frequency is not within the range of the reference value, Therefore, it is possible to easily detect water clogging in the fuel cell stack.
In addition, by setting the resonance frequency of the fuel cell stack during load operation without generating water clogging as a reference value, the fuel cell stack water clogging is not limited to when starting the fuel cell system, but also during the operation of the desired fuel cell stack. Can be judged.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a fuel cell system to which the present invention is applied will be described with reference to the accompanying drawings.
[0013]
Referring to FIG. 1, the fuel cell system includes a reformer 4 that generates a hydrogen-rich reformed gas based on vaporized fuel and water, and carbon monoxide (hereinafter referred to as CO) in the reformed gas. .) Is reduced to a predetermined concentration or less, a fuel cell stack that generates power based on the reformed gas supplied from the CO remover 5 and the air supplied from the compressor 7 (hereinafter referred to as a fuel cell). 2, the combustor 1 that combusts the exhaust hydrogen and exhaust air discharged from the fuel cell 2, and the fuel and water supplied from the tank are vaporized using the heat of the combustion gas from the combustor 1. An evaporator 3 for supplying vaporized fuel and steam to the reformer 4 is provided. The combustion gas which vaporizes fuel and water is discharged from the evaporator 3 to the outside.
[0014]
The fuel cell system of this embodiment further includes a cylinder 10 that is a hydrogen storage device that supplies hydrogen necessary for power generation of the fuel cell 2. The hydrogen supplied from the cylinder 10 is a sufficiently high concentration hydrogen that can be used for power generation of the fuel cell 2, in other words, the carbon monoxide in the hydrogen is controlled to a low concentration.
[0015]
The hydrogen storage device is not limited to the cylinder 10, and a hydrogen storage device including a hydrogen storage alloy or the like may be used.
[0016]
Between the cylinder 10 and the fuel cell 2, a pressure regulating valve 11 that regulates the hydrogen from the cylinder 10 and a switching valve 15 that controls the supply of hydrogen from the cylinder 10 are provided. Further, the cylinder 10 is provided with an on-off valve 12 that opens when hydrogen is replenished from the outside (not shown). A switching valve 16 for controlling the supply of the reformed gas to the fuel cell 2 is provided between the CO removing device 5 and the fuel cell 2.
[0017]
FIG. 2 is a diagram showing a configuration for detecting water clogging in the fuel cell 2 of the present invention. The fuel cell 2 of the present invention is formed in a stack structure in which a single cell comprising a solid polymer electrolyte membrane, an anode as a fuel electrode, a cathode as an oxidant electrode, and a catalyst is constructed on a stack. A control device 17 that controls the operation of the fuel cell 2 is connected to the fuel cell 2, and the control device 17 detects a resonance frequency and a frequency characteristic of at least one single cell constituting the fuel cell 2. 18, a storage device 19 that stores a signal of a reference resonance frequency and a frequency characteristic, and a comparator 20 that compares the detected resonance frequency with the reference resonance frequency. Furthermore, the detector 18 controls the vibration means 21 that resonates at least one single cell of the fuel cell 2 based on the signal.
[0018]
Next, the operation will be described.
[0019]
The present invention focuses on the fact that the resonance frequency of the fuel cell 2 or a single cell constituting the fuel cell 2 changes when water clogs occur in a gas flow path (not shown) in the fuel cell 2 or in the gas diffusion layer, The water clogging in the gas flow path and the gas diffusion layer is detected by comparison with the resonance frequency at the normal time.
[0020]
FIG. 3 shows an example of frequency characteristics, and FIG. 4 shows a flow chart for explaining the control contents executed by the control device 17 corresponding to claims 1 and 2.
[0021]
According to FIG. 4, for example, the excitation means 21 vibrates the anode of, for example, one single cell of the fuel cell 2 by vibration, sound wave or the like according to the instruction signal of the detector 18, and the resonance frequency f at that time is detected by the detector 18. Will detect. The detection signal is sent to the comparator 20, and a (f ₀ b ranging from f ₀ a in FIG. 3) and the detected resonance frequency f is compared resonant frequency range stored in advance in the storage unit 19. This resonance frequency range is a frequency range stored in advance in the storage device 19 set from the water, that is, the level that can be allowed with reference to the normal resonance frequency f ₀ as indicated by f ₀ a to f ₀ b in FIG. . This resonance frequency range may be set and stored for each operating load of the fuel cell 2, for example.
[0022]
The comparator 20 compares and determines whether the detected resonance frequency f is within the resonance frequency range, and water clogging occurs in the gas flow path and gas diffusion layer of the fuel cell 2 when the resonance frequency f is not within the resonance frequency range. Judge that you are doing.
[0023]
FIG. 5 is a flowchart for explaining the control contents of the second embodiment. The configuration is the same as in the first embodiment. This embodiment corresponds to claim 3, and after determining water clogging in the same manner as in the first embodiment, when it is determined that water clogging is selected, water, that is, an operation mode is selected. The water or operation mode is an operation mode in which the control device 17 controls the fuel cell 2 so as to eliminate water clogging by controlling the flow rate of the fuel gas and oxidant gas supplied to the fuel cell 2. For example, when water in the gas flow path is frozen and water clogging occurs when the fuel cell 2 is started, the supply of the fuel gas is stopped, and the temperature of the fuel cell 2 is gradually increased according to a predetermined sequence. , The ice in the gas flow path is thawed, and after the fuel cell 2 is in a state where normal power generation can be performed, the fuel gas can be supplied. Therefore, it is possible to improve the startability at the start of the fuel cell system, optimize the fuel gas supply, improve the fuel consumption of the fuel gas, and improve the efficiency of the fuel cell system.
[0024]
The third embodiment shown in FIG. 6 is provided with a display 22 for displaying the operating state of the fuel cell 2 in addition to the configuration of the first embodiment shown in FIG. The state of water clogging 2 is displayed on the display 22. By installing the indicator 22, it is possible to easily grasp the water, that is, the situation of the fuel cell 2. Further, a resonance frequency range (f ₀ a to f ₀ b) in which slight water clogging is determined is used as a reference for determining water clogging, and when the detected resonance frequency f falls within this frequency range, display is performed. A warning instruction may be issued to the driver or the like using the device 22.
[0025]
FIG. 7 shows a configuration diagram of the fourth embodiment, and FIG. 8 is a flowchart for explaining the control contents executed by the control device 17 in the fourth embodiment. In this embodiment, a signal for resonating the fuel cell 2 is output from the storage device 19 and a signal having a resonance frequency f from the fuel cell 2 is input.
[0026]
This configuration corresponds to claim 4, and the fuel cell 2 is added by an instruction signal from the storage device 19 when the fuel cell 2 is not clogged with water and generating a predetermined power generation output. The resonance frequency f is detected by shaking and stored in the memory 19 as the reference resonance frequency f ₀ . At this time, the instruction signal from the storage device 19 may be the same signal as the instruction signal from the detector 18.
[0027]
At the time of determination of water, the resonance frequency f at the time of determination is compared with the resonance frequency range (f ₀ a to f ₀ b) set based on the reference resonance frequency f ₀ stored after the fuel cell 2 is operated. Make a decision. In this case, the resonance frequency f in a stable operation state where the fuel cell 2 does not actually cause water clogging can be set as the reference resonance frequency f ₀ , and water clogging of the fuel cell 2 can be determined with higher accuracy.
[0028]
In the present embodiment, the resonance frequency at the time of a predetermined power generation output is used as a reference. However, the present invention is not limited to this. For example, the resonance frequency after a predetermined time has elapsed after startup or when the fuel cell 2 is at a predetermined temperature. The resonance frequency may be used as a reference.
[0029]
The present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea of the present invention.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a fuel cell system using a fuel cell of the present invention.
FIG. 2 is a configuration diagram of the fuel cell.
FIG. 3 is also an example of frequency characteristics.
FIG. 4 is a flowchart for explaining the control contents.
FIG. 5 is a flowchart for explaining control contents executed in the second embodiment of the present invention;
FIG. 6 is a configuration diagram of a fuel cell as a third embodiment of the present invention.
FIG. 7 is a configuration diagram of a fuel cell as a fourth embodiment of the present invention.
FIG. 8 is a flowchart for explaining the control contents executed in the fourth embodiment.
[Explanation of symbols]
2 Fuel cell 17 Control device 18 Detector 19 Storage device 20 Comparator 21 Excitation means

Claims (2)

In a fuel cell system comprising a fuel cell stack and a control device for controlling the operating state of the fuel cell stack,
The control device detects a resonance frequency of the fuel cell stack,
Set the resonance frequency of the fuel cell stack during load operation without water clogging as a reference value,
The resonance frequency the detected compared with the reference value,
A fuel cell system for determining water clogging in the fuel cell stack. Wherein the control device, a fuel cell system according to claim 1, characterized in that it is determined that the detected resonance frequency of water clogging in the fuel cell stack when not within range of the reference value has occurred .

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