JP4973138B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system including a fuel cell that generates electrical energy by an electrochemical reaction between hydrogen and oxygen, and is effective when applied to a mobile generator such as a vehicle, a ship, and a portable generator. .

  The polymer electrolyte fuel cell needs to be humidified in order to maintain the conductivity of the electrolyte membrane inside the fuel cell. When the amount of moisture in the fuel cell is small and the electrolyte membrane is dry, the internal resistance increases and the output voltage of the fuel cell decreases. On the other hand, when the internal water content of the fuel cell is excessive, the electrode of the fuel cell is covered with water, so that the diffusion of oxygen and hydrogen as reactants is hindered, and the output voltage decreases.

For this reason, as a method of diagnosing the internal moisture content of the fuel cell, a method of diagnosing that flooding or dry-up has occurred when the cell voltage exceeds a threshold when the generated power or air flow rate of the fuel cell changes (Patent Document) 1) and a method of diagnosing that flooding or dry-up has occurred when there is a cell that is not within the deviation of the cell voltage (see Patent Document 2).
JP 2005-228688 A JP 2005-108673 A

  However, in the moisture diagnosis methods of Patent Documents 1 and 2, since the internal moisture state of the fuel cell is diagnosed based on the change in the cell voltage, if the internal moisture content of the fuel cell does not change significantly, it appears in the change in the cell voltage. Therefore, there is a problem that it is difficult to accurately diagnose the internal moisture state of the fuel cell.

  In view of the above points, an object of the present invention is to provide a fuel cell system that can accurately diagnose the internal moisture state of a fuel cell.

In order to achieve the above object, the present invention is characterized by a solid polymer electrolyte type fuel cell (10) that generates an electric energy by electrochemical reaction of an oxidant gas and a fuel gas, and an output of the fuel cell (10). A fuel cell system comprising current detection means (12) for detecting current and voltage detection means (13) for detecting output voltage of the fuel cell (10), wherein the output current of the fuel cell (10) Current control means for changing at a rate of change; voltage change rate measuring means for obtaining a rate of change of the output voltage with respect to a temporal change in the output current of the fuel cell (10); Capacitance of the capacitor component generated at the hydrogen electrode of the fuel cell (10) based on the difference between the reference change rate acquisition means for acquiring the change rate and the difference between the acquired reference change rate and the acquired output voltage change rate Get And an internal moisture amount diagnostic means for diagnosing the internal moisture content on the hydrogen electrode side of the fuel cell (10) based on the capacitance of the capacitor component , Using the mapped relationship between the difference between the rate of change and the rate of change of the output voltage and the capacitance of the capacitor component generated at the hydrogen electrode of the fuel cell (10), The capacitance of the capacitor component generated at the hydrogen electrode of the fuel cell (10) is acquired based on the difference from the obtained change rate of the output voltage .

  In this way, the output voltage change rate when the output current of the fuel cell (10) changes is obtained, and the change in the capacitance of the capacitor component of the hydrogen electrode is obtained, so that the internal moisture content of the fuel cell, particularly the three of the hydrogen electrode, The amount of water present at the phase interface can be accurately diagnosed. When the fuel cell (10) has a stack structure in which a plurality of cells (100) are stacked, the voltage change rate of each cell may be measured by the voltage change rate measuring means, or a plurality of cells may be integrated. You may measure a voltage change rate for every block made into a group. When measuring the voltage change rate of each cell, the moisture content of each cell can be diagnosed. When measuring the voltage change rate for each block consisting of a plurality of cells, the moisture content of each block can be diagnosed. it can.

  Further, the internal water content diagnosis means is configured to determine the internal water content of the entire fuel cell (10) based on the internal water content on the hydrogen electrode side of the fuel cell (10) and the water content gradient of the electrolyte membrane (101) of the fuel cell (10). The amount can be diagnosed.

  Further, the current control means can diagnose the internal water content at the time of load fluctuation by controlling the current change rate at the initial stage of fluctuation of the output current to a predetermined change rate at the time of load fluctuation of the fuel cell (10). . Furthermore, the current change rate at which the deviation of the voltage change rate with respect to the current change rate of the fuel cell (10) becomes large is obtained experimentally, and the current change rate is set to a predetermined current change rate, whereby the internal moisture of the fuel cell is determined. The amount can be diagnosed more accurately.

  Further, by providing temperature detecting means (44) for detecting the temperature of the fuel cell (10) and correcting means for correcting the reference change rate and the output voltage change rate based on the fuel cell temperature, the fuel cell ( Even when the temperature of 10) changes, the internal moisture content of the fuel cell can be accurately diagnosed.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

(First embodiment)
A fuel cell system according to a first embodiment of the present invention will be described. FIG. 1 is a schematic diagram showing a fuel cell system according to this embodiment, and this fuel cell system is applied to, for example, an electric vehicle.

  As shown in FIG. 1, the fuel cell system of this embodiment includes a fuel cell 10 that generates electric power by utilizing an electrochemical reaction between hydrogen and oxygen. The fuel cell 10 is configured to supply power to the power device 11 and a secondary battery (not shown). In the case of an electric vehicle, an electric motor as a vehicle driving source corresponds to the electric power device 11.

  In the present embodiment, a solid polymer electrolyte fuel cell is used as the fuel cell 10, and a plurality of cells serving as basic units are stacked and electrically connected in series. The configuration of the cell will be described later. In the fuel cell 10, the following electrochemical reaction between hydrogen and oxygen occurs to generate electric energy.

(Hydrogen electrode: anode) H ₂ → 2H ⁺ + 2e ⁻
(Air electrode: cathode) 2H ⁺ + 1 / 2O ₂ + 2e ⁻ → H ₂ O
The fuel cell system is provided with a current sensor 12 that detects an output current of the fuel cell 10 and a cell monitor 13 that detects an output voltage for each cell. The current signal detected by the current sensor 12 and the cell voltage signal detected by the cell monitor 13 are input to the control unit 50 described later.

  The fuel cell system includes an air flow path 20 for supplying air (oxygen) to the air electrode (positive electrode) side of the fuel cell 10 and hydrogen for supplying hydrogen to the hydrogen electrode (negative electrode) side of the fuel cell 10. A flow path 30 is provided. Air corresponds to the oxidant gas of the present invention, and hydrogen corresponds to the fuel gas of the present invention.

  An air supply device 21 for pumping air sucked from the atmosphere to the fuel cell 10 is provided at the most upstream portion of the air flow path 20. For example, a compressor can be used as the air supply device 21. A humidifier 22 that humidifies the air is provided between the air supply device 21 and the fuel cell 10 in the air flow path 20, and the fuel cell 10 is disposed downstream of the fuel cell 10 in the air flow path 20. An air pressure regulating valve 23 for adjusting the pressure of the supplied air is provided.

  A hydrogen supply device 31 is provided at the most upstream part of the hydrogen flow path 30. In the present embodiment, a high-pressure hydrogen tank filled with hydrogen is used as the hydrogen supply device 31. Adjustment of the hydrogen supply amount from the hydrogen supply device 31 to the fuel cell 10 is performed by the control unit 50 described later. The downstream side of the fuel cell 10 in the hydrogen channel 30 is connected to the upstream side of the fuel cell 10 so that the hydrogen channel 30 is configured in a closed loop. Thus, hydrogen is circulated in the hydrogen flow path 30 so that unused hydrogen in the fuel cell 10 is resupplied to the fuel cell 10. A hydrogen pump 32 for circulating hydrogen in the hydrogen flow path 30 is provided on the downstream side of the fuel cell 10 in the hydrogen flow path 30.

  The fuel cell 10 needs to be maintained at a constant temperature (for example, about 80 ° C.) during operation to ensure power generation efficiency. For this reason, a cooling system for cooling the fuel cell 10 is provided. The cooling system is provided with a cooling water path 40 that circulates cooling water (cooling medium) in the fuel cell 10, a water pump 41 that circulates the cooling water, and a radiator 43 that includes a fan 42. In the vicinity of the outlet side of the fuel cell 10 in the cooling water path 40, a temperature sensor 44 is provided as a temperature detecting means for detecting the temperature of the cooling water flowing out from the fuel cell 10. By detecting the cooling water temperature by the temperature sensor 44, the temperature of the fuel cell 10 can be indirectly detected.

  The control unit (ECU) 50 includes a well-known microcomputer including a CPU, a ROM, a RAM, and the like and its peripheral circuits. The controller 50 receives a current signal from the current sensor 12, a cell voltage signal from the cell monitor 13, a temperature signal from the temperature sensor 44, and the like. Further, the fuel cell control unit 50 outputs a control signal to the air supply device 21, the humidifier 22, the air pressure regulating valve 23, the hydrogen pump 32, and the like based on the calculation result.

  FIG. 2 is a schematic diagram showing the configuration of the cell 100 constituting the fuel cell 10. FIG. 3 is an enlarged schematic view of the hydrogen electrode side of the cell 100. As shown in FIG. 2, the cell 100 includes an electrolyte membrane 101, a hydrogen electrode side diffusion layer 102, an air electrode side diffusion layer 103, and a separator 104. The diffusion layers 102 and 103 constitute an electrode. Diffusion layers 102 and 103 are disposed on both sides of the electrolyte membrane 101, and a separator 104 is disposed outside each diffusion layer 102 and 103. A catalyst is provided on the boundary surface between the electrolyte membrane 101 and the diffusion layers 102 and 103.

As shown in FIG. 3, at the three-phase interface of the electrolyte membrane 101, the diffusion layer 102, and the catalyst 105, a reaction in which hydrogen molecules are separated into protons and electrons occurs. In order for this reaction to occur, water must be present at the three-phase interface. At this time, reaction resistance Ra is generated at the hydrogen electrode. Then, electrons flow to the diffusion layer 102 and protons flow to the electrolyte membrane 101. Protons that have moved to the electrolyte membrane 101 are hydrated and move as H ₃ O ⁺ to the cathode side in the electrolyte membrane 101. Thus, in order for protons to be generated at the hydrogen electrode of the cell 100 and move within the electrolyte membrane 101, it is necessary that moisture be present in the hydrogen electrode of the cell 100. For this reason, in order for the electrochemical reaction of the fuel cell 10 to occur, the moisture at the hydrogen electrode of the cell 100 plays an important role.

  4A schematically shows protons in the electrolyte membrane 101, and FIG. 4B shows proton concentration gradients in the electrolyte membrane 101. FIG. As shown in FIGS. 4A and 4B, in the electrolyte membrane 101, the proton concentration is highest near the hydrogen electrode, and the proton concentration decreases from the hydrogen electrode side toward the air electrode side. Yes. On the hydrogen electrode side of the electrolyte membrane 101, an electric double layer is generated, and a capacitor component (electric double layer capacitor) exists. The capacitance of the electric double layer capacitor varies depending on the water content of the hydrogen electrode. Hereinafter, this point will be described.

  FIG. 5 shows the relationship between the effective area Sa of the hydrogen electrode catalyst 105 and the water content of the hydrogen electrode. As shown in FIG. 5, the effective catalyst area Sa increases in proportion to the water content of the hydrogen electrode until the water content of the hydrogen electrode reaches a predetermined value, and when the water content of the hydrogen electrode exceeds the predetermined value, The effective catalyst area Sa is constant. For this reason, the water | moisture content exceeding a predetermined value does not contribute to the reaction in a hydrogen electrode.

  FIG. 6 shows an equivalent circuit of the cell 100. As shown in FIG. 6, a reaction resistance Ra and an electric double layer capacitor are present in the hydrogen electrode of the cell 100, a membrane resistance Rm is present in the electrolyte membrane 101, and (reaction resistance + diffusion resistance) Rc is present in the air electrode. Is present. The capacitance Ca of the electric double layer capacitor can be obtained by Ca = ε · Sa / d. Where ε is the dielectric constant of the electrolyte membrane 101, d is the thickness of the electric double layer, and Sa is the effective catalyst area (the area of the three-phase interface).

  Thus, the electric double layer capacitor capacitance Ca varies depending on the effective catalyst area Sa. Specifically, the larger the effective catalyst area Sa, the larger the electric double layer capacitor capacitance Ca, and the smaller the effective catalyst area Sa, the smaller the electric double layer capacitor capacitance Ca. As described above, the effective catalyst area Sa increases as the water content of the hydrogen electrode increases, and the effective catalyst area Sa decreases as the water content of the hydrogen electrode decreases. Therefore, the electric double layer capacitor capacitance Ca increases as the water content of the hydrogen electrode increases, and the electric double layer capacitor capacitance Ca decreases as the water content of the hydrogen electrode decreases.

  FIG. 7 shows the relationship between the internal moisture content of the fuel cell 10 and the electric double layer capacitor capacitance Ca and the resistors Ra, Rm, and Rc. As shown in FIG. 7, the electric double layer capacitor capacitance Ca increases in proportion to the internal moisture content of the fuel cell 10 (the moisture content present at the three-phase interface of the hydrogen electrode), and the moisture content is excessive (flooding region). ) Is a constant value. For this reason, in the region where the electric double layer capacitor capacitance Ca increases in proportion to the moisture content, the internal moisture content of the fuel cell 10 can be obtained based on the electric double layer capacitor capacitance Ca. The relationship between the electric double layer capacitor capacitance Ca and the internal moisture content of the fuel cell 10 may be experimentally obtained in advance and mapped.

  Next, the moisture amount diagnosis control of the fuel cell system of the present embodiment will be described. FIG. 8 is a flowchart showing a flow of moisture amount diagnosis control performed by the CPU of the control unit 50 in accordance with a control program stored in a ROM or the like. The moisture amount diagnosis control shown in FIG. 8 is repeatedly performed at predetermined control intervals.

  As shown in FIG. 8, first, it is determined whether or not the operation of the fuel cell system is to be terminated (S10). As a result, when it is determined that the operation of the fuel cell system is to be terminated (S10: YES), the system is stopped. On the other hand, when it is determined not to end the operation of the fuel cell system (S10: NO), the output current of the fuel cell 10 is changed at a constant rate of change (S11). In order to change the output current of the fuel cell 10 at a constant rate of change, the amount of hydrogen supplied from the hydrogen supply device 31 to the fuel cell 10 may be changed.

  Next, when the output current of the fuel cell 10 is changing, the change rate of the output voltage of each cell 100 is measured by the cell monitor 13 (S12), and the change rate of the output current of the fuel cell 10 is measured by the current sensor 12. Measure (S13). Then, the voltage change rate corresponding to the output current change rate measured in S13 is calculated as the reference voltage change rate (S14).

  Here, changes in the output voltage when the output current of the fuel cell 10 is changed will be described. FIG. 9 shows changes in the output current and output voltage of the fuel cell 10 when performing moisture amount diagnosis control. (A) shows a case where the output current is increased, and (b) shows a decrease in the output current. The case where it was made to show is shown. In both FIG. 9A and FIG. 9B, the upper part shows the change rate of the output current, and the lower part shows the change rate of the output voltage corresponding to the change rate of the output current. The broken line in FIG. 9 indicates the reference voltage change rate.

  First, as shown in FIG. 9A, when the output current is increased at a constant change rate, the reference voltage change rate decreases at a constant change rate. When the output current is increased at a constant rate of change, electric charge is stored in the electric double layer capacitor present at the hydrogen electrode of the cell 100. For this reason, when the output current is increased at a constant rate of change, the rate of change of the output voltage is shifted in a direction in which the slope becomes larger than the reference voltage rate of change. As described above, the electric double layer capacitor capacitance Ca increases as the internal water content of the fuel cell 10 increases, and decreases as the internal water content of the fuel cell 10 decreases, so that the internal water content of the fuel cell 10 is large. The change rate of the output voltage shifts in a direction in which the inclination is large, and when the amount of moisture in the fuel cell 10 is small, the change rate of the output voltage shifts in a direction in which the inclination is small.

  Next, as shown in FIG. 9B, when the output current is decreased at a constant change rate, the reference voltage change rate increases at a constant change rate. When the output current is reduced at a constant rate of change, charge is released from the electric double layer capacitor. For this reason, the change rate of the output voltage when the output current is decreased at a constant change rate also shifts in a direction in which the slope becomes larger than the reference voltage change rate. When the internal moisture amount of the fuel cell 10 is large, the change rate of the output voltage shifts in a direction in which the slope is large, and when the internal moisture amount of the fuel cell 10 is small, the change rate of the output voltage has a small slope. Deviation in direction.

  From the above, the electric double layer capacitor capacitance Ca can be obtained from the difference between the reference voltage change rate of the cell 100 with respect to the change of the output current of the fuel cell 10 and the actually measured voltage change rate of the cell 100. The relationship between the voltage change rate difference and the electric double layer capacitor capacitance Ca may be experimentally obtained in advance and mapped.

  Returning to FIG. 8, the electric double layer capacitor capacitance Ca at the hydrogen electrode of the cell 100 is obtained from the difference between the reference voltage change rate calculated in S14 and the measured voltage change rate measured in S12 (S15). Then, the internal moisture content of the fuel cell 10 is diagnosed based on the electric double layer capacitor capacity Ca (S16). The diagnosis process of S16 is performed using a map (see FIG. 7) in which the electric double layer capacitor capacity Ca and the internal moisture content of the fuel cell 10 are related. Here, the amount of water in the hydrogen electrode of the fuel cell 10 can be diagnosed. For example, when the upper limit value and the lower limit value of the electric double layer capacitor capacitance Ca corresponding to the appropriate range of the internal moisture content are set in advance, and the electric double layer capacitor capacitance Ca acquired in S15 exceeds the upper limit value. Diagnosis of excessive water content and diagnosis of water shortage can be made when it is below the lower limit.

  Next, the internal moisture content of the fuel cell 10 is controlled based on the diagnosis result of S16 (S17). Control of the internal moisture content of the fuel cell 10 can be performed, for example, by adjusting the humidification amount of air supplied to the fuel cell 10 by the humidifier 22. Furthermore, the amount of water evaporation in the fuel cell 10 is adjusted by adjusting the air supply amount to the fuel cell 10 by the air supply device 21 and adjusting the air supply pressure to the fuel cell 10 by the air pressure regulating valve 23. The internal moisture content can be controlled.

  As described above, the rate of change of the cell voltage when the output current of the fuel cell 10 is changed is obtained, and the change in the capacitance of the electric double layer capacitor of the hydrogen electrode is obtained. It is possible to accurately diagnose the amount of water present at the three-phase interface of the hydrogen electrode. Note that the current control means, reference change rate acquisition means, capacitance acquisition means, and internal moisture amount diagnosis means of the present invention are each constituted by the processing of the control unit 50, and the current control means performs the processing of S11. Correspondingly, the reference change rate acquisition means corresponds to the process of S12, the capacitance acquisition means corresponds to the process of S15, and the internal moisture amount diagnosis means corresponds to the process of S16.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. Hereinafter, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted. Only parts different from those in the first embodiment will be described.

  FIG. 10 shows the water content gradient in the electrolyte membrane 101 of the cell 100. As shown in FIG. 10, in the electrolyte membrane 101, the amount of water on the air electrode side is the largest, and the amount of water gradually decreases toward the hydrogen electrode side. The gradient of the amount of water in the electrolyte membrane 101 is determined by the diffusion coefficient of the electrolyte membrane 101 and the like, and the gradient is almost constant even when the total amount of moisture changes. The water content gradient in the electrolyte membrane 101 may be mapped in advance. For this reason, the water content of the cell 100 can be obtained, and the water content of the cell 100 can be obtained by applying the water content of the hydrogen electrode to the water content gradient shown in FIG.

(Third embodiment)
Next, a third embodiment of the present invention will be described. In the third embodiment, the water amount diagnosis control is performed when the load of the fuel cell 10 changes. Hereinafter, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted. Only parts different from those in the first embodiment will be described.

  FIG. 11 is a flowchart showing the flow of moisture amount diagnosis control according to the third embodiment. As shown in FIG. 11, after the operation end determination process S10, it is determined whether or not there has been a load fluctuation of the fuel cell 10, that is, whether or not the required power generation amount for the fuel cell 10 has changed (S20). As a result, when it is determined that there is no load fluctuation of the fuel cell 10 (S20: NO), the process returns without doing anything, and when it is determined that there is a load fluctuation of the fuel cell 10 (S20: YES). Then, the amount of hydrogen supplied to the fuel cell 10 is changed, and the output current of the fuel cell 10 is changed at a constant rate of change (S11). In the third embodiment, the output current of the fuel cell 10 is changed at a preset predetermined change rate. For example, the rate of change of the output current of the fuel cell 10 can be adjusted by flowing current from a secondary battery (not shown).

  FIG. 12 shows changes in the output current and the output voltage of the fuel cell 10 when the moisture diagnosis control of the third embodiment is performed. In the third embodiment, the current change control of S11 is performed for a certain period of time at the initial stage of the current change with respect to the load change of the fuel cell 10. In the current change control of S11, the current is changed at a predetermined current change rate regardless of the target current value set from the required power generation amount. A current change rate at which the difference between the reference voltage change rate with respect to the current change rate of the fuel cell 10 and the actual output voltage change rate is determined experimentally, and the current change rate may be set as a predetermined current change rate. .

  Returning to FIG. 11, after measuring the rate of voltage change at the time of current change (S12, S13), the output current of the fuel cell 10 is changed to the target current value (S21).

  As described above, when the load of the fuel cell 10 changes, the voltage change rate can be measured by making the current change rate constant at the beginning of the current change, and the internal moisture content of the fuel cell 10 can be diagnosed.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described. In the fourth embodiment, temperature correction is performed in the moisture amount diagnosis control. Hereinafter, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted. Only parts different from those in the first embodiment will be described.

  As the temperature of the fuel cell 10 increases, the internal resistance of the fuel cell 10 decreases. For this reason, the output voltage of the cell 100 changes as the temperature of the fuel cell 10 changes, and the voltage behavior when the output current of the fuel cell 10 is changed is affected by the temperature of the fuel cell 10. The change in the voltage change rate with respect to the fuel cell temperature may be experimentally obtained in advance and mapped.

  FIG. 13 is a flowchart showing the flow of moisture amount diagnosis control according to the fourth embodiment. As shown in FIG. 13, in the fourth embodiment, after the reference voltage change rate calculation process S14, the temperature of the fuel cell is detected using the temperature sensor 44 (S30). Then, a temperature correction process for correcting the reference voltage change rate and the measured voltage change rate based on the fuel cell temperature is performed (S31). The temperature correction process in S31 may be performed using a map in which the fuel cell temperature and the voltage change rate are associated with each other.

  As described above, by correcting the voltage change rate based on the fuel cell temperature, the internal moisture content of the fuel cell 10 can be accurately diagnosed even when the temperature of the fuel cell 10 changes. The correcting means of the present invention is constituted by the processing of the control unit 50, and the processing of S31 corresponds to the correcting means.

(Other embodiments)
In each of the above embodiments, the cell monitor 13 is configured to measure the output voltage for each individual cell 100. However, the present invention is not limited to this, and a plurality of (for example, ten) cells 100 are grouped to form a fuel cell. 10 may be divided into a plurality of blocks, and the output voltage may be measured for each block including the plurality of cells 100.

1 is a schematic diagram showing a fuel cell system according to a first embodiment. It is a schematic diagram which shows the structure of the cell which comprises a fuel cell. It is the schematic diagram which expanded the hydrogen electrode side of the cell. (A) is the figure which showed typically the proton in an electrolyte membrane, (b) is the figure which showed the proton concentration gradient in an electrolyte membrane. It is a characteristic view which shows the relationship between the effective area Sa of the catalyst of a hydrogen electrode, and the moisture content of a hydrogen electrode. It is a circuit diagram which shows the equivalent circuit of a cell. It is a characteristic view which shows the relationship between the internal moisture content of a fuel cell, the electrostatic capacitance of an electric double layer capacitor, and the resistance of a cell. It is a flowchart which shows the flow of the moisture content diagnostic control of 1st Embodiment. It is a characteristic view which shows the change of the output voltage at the time of changing the output current of a fuel cell, (a) shows the case where output current is increased, (b) shows the case where output current is decreased. Yes. It is a figure which shows the moisture content gradient of the electrolyte membrane in 2nd Embodiment. It is a flowchart which shows the flow of the moisture content diagnostic control of 3rd Embodiment. It is a characteristic view which shows the change of the output current and output voltage of a fuel cell at the time of performing the moisture diagnostic control of 3rd Embodiment. It is a flowchart which shows the flow of the moisture content diagnostic control of 4th Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Solid polymer electrolyte type fuel cell, 100 ... Cell, 101 ... Electrolyte membrane, 12 ... Current sensor, 13 ... Cell monitor, 20 ... Air path, 21 ... Air supply device, 22 ... Humidifier, 23 ... Air pressure regulating valve, DESCRIPTION OF SYMBOLS 30 ... Hydrogen path | route, 31 ... Hydrogen supply apparatus, 40 ... Cooling water path | route, 44 ... Temperature sensor, 50 ... Control part.

Claims (1)

A solid polymer electrolyte type fuel cell (10) for generating electric energy by electrochemical reaction of an oxidant gas and a fuel gas;
Current detection means (12) for detecting the output current of the fuel cell (10);
A fuel cell system comprising voltage detection means (13) for detecting an output voltage of the fuel cell (10),
Current control means for changing the output current of the fuel cell (10) at a predetermined rate of change;
A voltage change rate measuring means for obtaining a change rate of the output voltage with respect to a temporal change of the output current of the fuel cell (10);
Reference change rate acquisition means for acquiring a reference change rate of the output voltage corresponding to the change rate of the output current;
And the electrostatic capacity acquisition unit that acquires an electrostatic capacitance of the capacitor components generated in the hydrogen electrode of the fuel cell (10) based on the difference between the rate of change of the obtained output voltage and the acquired reference change rate ,
An internal water amount diagnosis means for diagnosing the internal water content on the hydrogen electrode side of the fuel cell (10) based on the capacitance of the capacitor component ;
The capacitance acquisition means is mapped between a difference between the reference change rate and the change rate of the output voltage and a capacitance of a capacitor component generated at a hydrogen electrode of the fuel cell (10). Using the relationship, the capacitance of the capacitor component generated at the hydrogen electrode of the fuel cell (10) is acquired based on the difference between the acquired reference change rate and the acquired output voltage change rate. And
The internal moisture amount diagnosis means is configured to determine the entire fuel cell (10) based on the internal moisture amount on the hydrogen electrode side of the fuel cell (10) and the moisture amount gradient of the electrolyte membrane (101) of the fuel cell (10). Diagnose the internal moisture content,
The current control means controls the current change rate at the initial stage of output current fluctuation to a predetermined change rate when the load of the fuel cell (10) fluctuates .

Images