JP2017073376A - Fuel battery system and method for enhancement in fuel battery system performance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the performance of a fuel battery single cell reliably by an activation process.SOLUTION: A fuel battery system comprises: a processing part which executes an activation process for lowering a cathode potential of a fuel battery single cell to an ultimate potential over a duration temporarily at a process frequency; a cation impurity amount estimation part which estimates an amount of cation impurities included in an electrolyte membrane of the fuel battery single cell; and a processing degree-deciding part. The processing degree-deciding part decides the condition of the activation process so as to raise the degree of the activation process by any one or a combination of at least two of the following means, when the amount of cation impurities is large: making the ultimate potential lower than that when the cation impurity amount is small; making the duration longer; and increasing the process frequency. The processing part executes the activation process with a degree decided by the processing degree-deciding part.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fuel cell system and a method for improving the performance of the fuel cell system.

  An activation process is performed to improve the performance of the electrode catalyst in the single fuel cell by temporarily reducing the cathode potential in at least one single fuel cell of the fuel cell system to the ultimate potential over a continuous period of time. A fuel cell system configured as described above is known (see, for example, Patent Document 1).

  In the electrode catalyst of the cathode electrode of a single fuel cell, an oxide film is formed on the surface by use, and the performance of the electrode catalyst may be lowered. The above activation treatment reduces the electrode catalyst by temporarily lowering the cathode potential in the fuel cell single cell, thereby removing the oxide film covering the electrode catalyst and reducing the performance of the electrode catalyst. Thus, the performance of the single fuel cell can be improved.

Special table 2003-536232 gazette

  The inventors of the present invention have examined the above activation treatment, and it may be that the performance of the fuel cell single cell may not be sufficiently improved even if the activation treatment is performed on the single fuel cell at a predetermined cathode potential. There was found. If the activation process is performed on the single cell of the fuel cell at a cathode potential lower than the predetermined cathode potential, that is, by increasing the degree of the activation process, the performance of the electrocatalyst is improved regardless of the state of the single cell of the fuel cell. It can be improved. However, if the activation treatment is performed with the degree of the activation treatment being increased, the activation treatment becomes excessive, the dissolution of the metal in the electrode catalyst is promoted, and the durability of the electrode catalyst may deteriorate. There is a demand for a technique that can carry out the activation process to an appropriate degree and can reliably improve the performance of the single fuel cell.

  According to one aspect of the present invention, when the fuel cell system is idling, the cathode potential of at least one fuel cell single cell of the fuel cell system is temporarily processed with a processing frequency over a continuous time period. A processing unit configured to execute an activation process for lowering to an ultimate potential, and a cationic impurity amount estimation unit configured to estimate the amount of cationic impurities contained in the electrolyte membrane of the fuel cell single cell When the amount of the cation impurity is large, the activation treatment condition is set lower than the time when the amount of the cation impurity is low, the duration is increased, and the treatment is performed. The degree of the activation process is determined to be high by combining any one of the increasing frequencies or at least two of them. A processing order determining unit has, wherein the processing unit executes the activation process with a degree determined by the processing order determining unit, the fuel cell system is provided.

  According to another aspect of the present invention, when the fuel cell system is idling, the cathode potential of at least one fuel cell single cell of the fuel cell system is temporarily processed with a processing frequency over a duration of time. A processing unit configured to execute an activation process for lowering to an ultimate potential, and when the fuel cell system is operated with a base output current and a base output voltage, the output current of the fuel cell single cell is Increase from the base output current to a predetermined increase current in a stepwise manner and hold it for an increase time, measure the output voltage of the fuel cell single cell at the increase time, and step the output current until the increase current When the output voltage decreases in a stepped manner from the base output voltage to the minimum voltage, The output voltage after a predetermined set time shorter than the increase time after the output current is increased to the increase current when the output current increases toward a steady voltage lower than the output voltage. As the difference in the minimum voltage with respect to the base voltage increases, the difference in the minimum voltage with respect to the base output voltage increases, or until the output voltage reaches the steady voltage after the output current is increased to the increased current. As the time required for the activation process becomes longer, the condition for the activation process is any one of or lowering the final potential, increasing the duration, and increasing the process frequency. A processing level determination unit that determines to increase the level of the activation processing by combining at least two, and the processing unit includes: Executing the activation process with a degree determined by the processing order determining unit, the fuel cell system is provided.

  According to still another aspect of the present invention, when the fuel cell system is idling, the cathode potential of at least one single fuel cell of the fuel cell system is temporarily processed with a processing frequency over a continuous time. A processing unit configured to execute an activation process for lowering to an ultimate potential, and an output at a predetermined output voltage after holding the output voltage of the fuel cell single cell at a predetermined voltage value for a predetermined time Obtaining an output voltage at a current and / or a predetermined output current, and when the value of the output current at the predetermined output voltage and / or the value of the output voltage at the predetermined output current are relatively small, Compared to a relatively large condition, the activation process conditions are such that the ultimate potential is lowered, the duration is increased, and the process frequency is increased. A processing degree determining unit that determines to increase the degree of the activation processing by combining at least two of them or the two of them, and the processing unit includes the processing degree determining unit A fuel cell system is provided that performs the activation process to a degree determined by

  The activation process can be performed to an appropriate degree, and the performance of the fuel cell single cell can be reliably improved.

It is a block diagram of a fuel cell system. It is a fragmentary sectional view of a fuel cell single cell. It is a graph which shows the relationship between the output current and output voltage of a fuel cell single cell which does not contain a cation impurity. It is a graph which shows the relationship between the output current and output voltage of a fuel cell single cell containing a cation impurity. It is a graph which shows the relationship between the output current density in the predetermined output voltage of the fuel cell single cell which does not contain a cation impurity, and a pre-holding voltage. It is a graph which shows the relationship between the output current density in the predetermined output voltage of a fuel cell single cell containing a little cationic impurities, and a pre-holding voltage. It is a graph which shows the relationship between the output current density in the predetermined output voltage of the fuel cell single cell containing many cationic impurities, and a pre-holding voltage. It is a figure explaining the reason of the phenomenon of FIGS. It is a graph which shows an example of the relationship between the membrane resistance of an electrolyte membrane, and the amount of cationic impurities. It is a graph for determining the grade of an activation process. It is a figure explaining the performance improvement method of a fuel cell single cell. It is a figure explaining the method to estimate the amount of cationic impurities. It is a figure explaining the method to estimate the amount of cationic impurities. It is a figure explaining the method to estimate the amount of cationic impurities. It is a graph which shows an example of the relationship between the amount of voltage drops, and the amount of cationic impurities. It is a graph which shows an example of the relationship between the amount of minimum value fall, and the amount of cationic impurities. It is a graph which shows an example of the relationship between required time and the amount of cationic impurities. It is a flowchart which shows the routine of the performance improvement control of a fuel cell system. It is a flowchart which shows the routine of the cation impurity amount estimation control of a fuel cell system. It is a flowchart which shows the activation process determination control routine of a fuel cell system. It is a flowchart which shows the activation process control routine of a fuel cell system. It is a figure explaining the method to estimate the amount of cationic impurities of another Example. It is a table which shows the relationship between an output electric current and the amount of cationic impurities. It is a figure explaining the method to estimate the amount of cationic impurities of another Example. It is a table which shows the relationship between an output voltage and the amount of cationic impurities. It is a table which shows the relationship between output voltage and output current, and the amount of cationic impurities. It is a table which shows the relationship between operation time and the amount of cationic impurities. It is a block diagram of the fuel cell system of another Example.

  Referring to FIG. 1, the fuel cell system A includes a fuel cell stack 10. The fuel cell stack 10 includes a stacked body including a plurality of single fuel cell cells 2 stacked in the stacking direction. Each fuel cell single cell 2 of the laminate includes a membrane electrode gas diffusion layer assembly 20 and separators (not shown) arranged on both sides of the membrane electrode gas diffusion layer assembly 20. The membrane electrode gas diffusion layer assembly 20 includes an electrolyte membrane and an anode electrode and a cathode electrode provided on both sides of the electrolyte membrane.

  The anode electrode of the fuel cell single cell 2 is connected to the cathode electrode of another fuel cell single cell 2 adjacent to one end side, and the cathode electrode is connected to the anode electrode of another fuel cell single cell 2 adjacent to the other end side via a separator. Are electrically connected. The anode electrode of the fuel cell single cell 2 on one end side of the laminate and the cathode electrode of the fuel cell single cell 2 on the other end side constitute an electrode of the fuel cell stack 10. The electrode of the fuel cell stack 10 is electrically connected to the inverter 12 via the DC / DC converter 11, and the inverter 12 is electrically connected to the motor generator 13. Further, the fuel cell system A includes a capacitor 14, and this capacitor 14 is electrically connected to the above-described inverter 12 via a DC / DC converter 15. The DC / DC converter 11 controls the magnitude of the output current / output voltage output from the fuel cell stack 10 and converts the magnitude of the output current / output voltage to be supplied to the inverter 12. is there. The inverter 12 is for converting a direct current from the DC / DC converter 11 or the battery 14 into an alternating current. The DC / DC converter 15 is for reducing the voltage from the fuel cell stack 10 or the motor generator 13 to the battery 14 or increasing the voltage from the battery 14 to the motor generator 13. In the fuel cell system A shown in FIG. 1, the battery 14 is composed of a battery.

  Further, in the fuel cell single cell 2, a fuel gas flow passage for supplying hydrogen gas as fuel gas to the anode electrode, and an oxidant gas flow passage for supplying air as oxidant gas to the cathode electrode And a cooling water flow passage for supplying cooling water to the single fuel cell 2 are formed. The fuel gas flow paths of the plurality of fuel cell single cells 2 are connected in parallel, the oxidant gas flow paths of the plurality of fuel cell single cells 2 are connected in parallel, and the cooling water flow paths of the plurality of fuel cell single cells 2 Are connected in parallel, the fuel cell stack 10 is formed with a fuel gas passage 30, an oxidant gas passage 40, and a cooling water passage 50, respectively. The fuel gas passage 30, the oxidant gas passage 40, and the cooling water passage 50 each include a fuel gas manifold, an oxidant gas manifold, and a cooling water manifold.

  A fuel gas supply pipe 31 is connected to the inlet of the fuel gas passage 30, and the fuel gas supply pipe 31 is connected to a fuel gas source 32. In the embodiment shown in FIG. 1, the fuel gas source 32 is formed from a hydrogen tank. In the fuel gas supply pipe 31, in order from the upstream side, the shutoff valve 33, the regulator 34 for adjusting the pressure of the fuel gas in the fuel gas supply pipe 31, and the fuel gas from the fuel gas source 32 are supplied to the fuel cell stack 10. A fuel gas injector 35 for supply is arranged. On the other hand, an anode off gas pipe 36 is connected to the outlet of the fuel gas passage 30. When the shutoff valve 33 is opened and the fuel gas injector 35 is opened, the fuel gas in the fuel gas source 32 is supplied into the fuel gas passage 30 in the fuel cell stack 10 via the fuel gas supply pipe 31. The At this time, the gas flowing out from the fuel gas passage 30, that is, the anode off gas flows into the anode off gas pipe 36. A gas-liquid separator 37 that gas-liquid separates the anode off-gas and a discharge control valve 38 that controls the discharge of the liquid accumulated in the gas-liquid separator 37 are disposed in the anode off-gas pipe 36 in order from the upstream side. An inlet of a fuel gas circulation pipe 81 is communicated with an upper portion of the gas-liquid separator 37, and an outlet of the fuel gas circulation pipe 81 is communicated with a location upstream of the fuel gas injector 35 in the fuel gas supply pipe 31. In the fuel gas circulation pipe 81, a fuel gas circulation pump 39 for pressure-feeding the gas in the gas-liquid separator 37, that is, the gas-liquid separated anode off-gas is disposed. When the fuel gas circulation pump 39 is driven, the anode off gas accumulated in the gas-liquid separator 37 is circulated to the fuel gas supply pipe 31. In another embodiment not shown, the gas-liquid separator 37 in the anode off-gas pipe 36 is omitted.

  An oxidant gas supply pipe 41 is connected to the inlet of the oxidant gas passage 40, and the oxidant gas supply pipe 41 is connected to an oxidant gas source 42. In the embodiment shown in FIG. 1, the oxidant gas source 42 is formed from the atmosphere. In the oxidant gas supply pipe 41, in order from the upstream side, a gas cleaner 43, an air supply unit or turbo compressor 44 for pumping the oxidant gas, and an oxidant gas sent from the turbo compressor 44 to the fuel cell stack 10 are cooled. And an intercooler 45 is arranged. On the other hand, a cathode off-gas pipe 46 is connected to the outlet of the oxidant gas passage 40. A cathode offgas control valve 47 for controlling the amount of cathode offgas flowing in the cathode offgas pipe 46 or the pressure in the oxidant gas passage 40 of the fuel cell stack 10 is disposed in the cathode offgas pipe 46. Further, the inlet of the oxidant gas bypass pipe 49 is connected to the oxidant gas supply pipe 41 downstream of the intercooler 45, and the outlet of the oxidant gas bypass pipe 49 is connected to the cathode offgas pipe 46 downstream of the cathode offgas control valve 47. . An oxidant gas bypass control valve 48 is disposed in the oxidant gas bypass pipe 49. The oxidant gas bypass control valve 48 bypasses the fuel cell stack 10 and controls the flow rate of air flowing from the oxidant gas supply pipe 41 to the cathode offgas pipe 46. In the fuel cell system A shown in FIG. 1, the oxidant gas bypass control valve 48 is formed of a three-way valve. The turbo compressor 44 is driven, and the oxidant gas bypass control valve 48 is connected to the upstream oxidant gas supply pipe 41U upstream of the oxidant gas bypass control valve 48 in the oxidant gas supply pipe 41. When the downstream oxidant gas supply pipe 41 </ b> D downstream of the oxidant gas bypass control valve 48 in 41 is communicated, the oxidant gas is supplied into the oxidant gas passage 40 in the fuel cell stack 10. At this time, the gas flowing out from the oxidant gas passage 40, that is, the cathode off gas flows into the cathode off gas pipe 46. Further, when the oxidant gas bypass control valve 48 communicates the oxidant gas bypass pipe 49 with the upstream side oxidant gas supply pipe 41U, a part or all of the air discharged from the turbo compressor 44 passes through the oxidant gas bypass pipe 49. To the cathode off-gas pipe 46. In the embodiment shown in FIG. 1, the turbo compressor 44 is constituted by a centrifugal or axial flow type turbo compressor. A centrifugal turbo compressor is preferably used in terms of downsizing and the like.

  A diluter 80 is provided in the cathode offgas pipe 46 downstream of the outlet of the oxidant gas bypass pipe 49. The diluter 80 is connected to the outlet of the anode off gas pipe 36. In the diluter 80, the hydrogen gas contained in the anode off gas is diluted with the cathode off gas so that the concentration of hydrogen gas in the gas discharged from the diluter 80 to the atmosphere is below an allowable value. Note that the cathode off-gas flowing into the diluter 80 includes the oxidant gas from the oxidant gas bypass pipe 49.

  One end of the cooling water supply pipe 51 is connected to the inlet of the cooling water passage 50, and the other end of the cooling water supply pipe 51 is connected to the outlet of the cooling water passage 50. A cooling water pump 52 that pumps cooling water and a radiator 53 are disposed in the cooling water supply pipe 51. The cooling water supply pipe 51 upstream of the radiator 53 and the cooling water supply pipe 51 downstream of the radiator 53 and between the radiator 53 and the cooling water pump 52 are connected to each other by a radiator bypass pipe 54. Further, a radiator bypass control valve 55 that controls the amount of cooling water flowing in the radiator bypass pipe 54 is provided. In the fuel cell system A shown in FIG. 1, the radiator bypass control valve 55 is formed of a three-way valve and is disposed at the inlet of the radiator bypass pipe 54. When the cooling water pump 52 is driven, the cooling water discharged from the cooling water pump 52 flows into the cooling water passage 50 in the fuel cell stack 10 through the cooling water supply pipe 51, and then passes through the cooling water passage 50. Then, it flows into the cooling water supply pipe 51 and returns to the cooling water pump 52 via the radiator 53 or the radiator bypass pipe 54.

  The electronic control unit 60 is composed of a digital computer and includes a ROM (Read Only Memory) 62, a RAM (Random Access Memory) 63, a CPU (Microprocessor) 64, an input port 65, and an output port 66 connected to each other by a bidirectional bus 61. It comprises. An output signal of an output sensor 16 that measures an output current and an output voltage of the fuel cell stack 10, an output signal of an output sensor 17 that measures an output current and an output voltage of each of the plurality of fuel cell single cells 2 in the stack, The output signal of the temperature sensor 18 that measures the temperature of the stack 10, the output signal of the range sensor 19 that detects the range of the transmission of the vehicle, and the output signal of the pressure sensor (not shown) in the fuel cell system A and the like correspond. Is input to the input port 65 via the AD converter 67 at predetermined time intervals (example: 0.1 ms). An output signal from each sensor or the like input to the input port 65 is stored as data in the RAM 63 and is stored as an operation history. On the other hand, the output port 66 is connected to the shut-off valve 33, the regulator 34, the fuel gas injector 35, the discharge control valve 38, the fuel gas circulation pump 39, the turbo compressor 44, the cathode offgas control valve 47, the oxidant gas via the corresponding drive circuit 68. The bypass control valve 48, the coolant pump 52, and the radiator bypass control valve 55 are electrically connected.

By the way, when the fuel cell stack 10 is to generate power, the shutoff valve 33 and the fuel gas injector 35 are opened, and the fuel gas is supplied to the fuel cell stack 10. Further, the turbo compressor 44 is driven, and the oxidant gas is supplied to the fuel cell stack 10. As a result, an electrochemical reaction (H ₂ → 2H ⁺ + 2e ⁻ , (1/2) O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O) occurs in the single fuel cell, and electric energy is generated. The generated electrical energy is sent to the motor generator 13. As a result, the motor generator 13 is operated as an electric motor for driving the vehicle, and the electric vehicle is driven. On the other hand, for example, when the vehicle is braked, the motor generator 13 operates as a regenerative device, and the electrical energy regenerated at this time is stored in the capacitor 14.

  As shown in FIG. 2, in the fuel cell single cell 2, the anode 5a formed on one side of the electrolyte membrane 5e of the membrane electrode gas diffusion layer assembly 20 includes an anode electrode catalyst layer 5as and an anode gas diffusion layer 5ad. The cathode 5c formed on the other side of the electrolyte membrane 5e includes a cathode electrode catalyst layer 5cs and a cathode gas diffusion layer 5cd. An anode separator 3a is disposed on the anode electrode 5a side of the membrane electrode gas diffusion layer assembly 20, and a cathode separator 3c is disposed on the cathode electrode 5c side.

  Examples of the material of the electrolyte membrane 5e, that is, the electrolyte material include a fluorine-based cation exchange resin having cation conductivity such as perfluorosulfonic acid, and specifically, Nafion (registered trademark) is exemplified. . Examples of the electrode catalyst material of the anode electrode catalyst layer 5as and the cathode electrode catalyst layer 5cs include catalyst-supported carbon supporting platinum or a platinum alloy. In another embodiment not shown, an electrolyte material similar to the electrolyte membrane 5e, for example, an ionomer formed of a fluorine-based cation exchange resin is added to the catalyst-supporting carbon. As materials for the anode gas diffusion layer 5ad and the cathode gas diffusion layer 5cd, conductive porous materials, for example, carbon porous materials such as carbon paper, carbon cloth, glassy carbon, metals such as metal mesh and foam metal A porous body is mentioned. Examples of the material of the anode separator 3a and the cathode separator 3c include metals such as stainless steel and Ti.

  In the fuel cell system A shown in FIG. 1, when power generation is to be performed, a target current value of the fuel cell stack 10 is obtained in accordance with, for example, the load of the motor generator 13 expressed by the amount of depression of the accelerator pedal and the charged amount of the battery 14. It is done. Next, the fuel gas flow rate and the oxygen gas flow rate necessary for setting the output current value of the fuel cell stack 10 to the target current value, that is, the target fuel gas flow rate and the target oxygen gas flow rate are obtained, and the target based on the target oxygen gas flow rate is obtained. An oxidant gas flow rate is required. Next, the regulator 34 and the fuel gas injector 35 are controlled so that the fuel gas flow rate sent to the fuel cell stack 10 becomes the target fuel gas flow rate, and the oxidant gas flow rate sent to the fuel cell stack 10 becomes the target oxidant gas flow rate. Thus, the turbo compressor 44 and the cathode offgas control valve 47 are controlled.

  By the way, in the fuel cell system A, an oxide film is formed on the electrode catalyst (eg, platinum or platinum alloy) of the cathode electrode catalyst layer 5cs of the fuel cell single cell 2 in the fuel cell stack 10 during the operation of the fuel cell system A. As a result, the performance of the electrode catalyst may be reduced, and the performance of the single fuel cell 2 may be reduced. In order to cope with this, in the fuel cell system A, during the operation of the fuel cell system A, the air on the cathode electrode 5c side is throttled, and an activation process for temporarily lowering the cathode potential of the fuel cell single cell 2 is performed. The performance of the electrode catalyst is improved. However, even if the activation process is performed, the cause may not be known, but the performance of the single fuel cell may not be sufficiently improved. Therefore, in order to elucidate the cause when the performance of the fuel cell single cell 2 is not sufficiently improved by the activation treatment, the inventor of the present invention has as its cause the amount of metal cation (cation) impurities in the electrolyte membrane 5e. Focused on.

Here, the cation enters the fuel cell unit cell 2 of the fuel cell stack 10 by being accompanied by the air supplied to the fuel cell stack 10 during the operation of the fuel cell system A. It is. As this cation, Ca, Na, etc. contained in a snow melting agent, Fe, Mo, Cr, Al, etc. contained in the components of the fuel cell system A can be considered. Since the cation exchange membrane exemplified by Nafion (registered trademark) is used as the electrolyte membrane 5e of the fuel cell single cell 2, when the cation enters the fuel cell single cell 2, the inside of the cation exchange membrane Enters the membrane and stays in the membrane as it is, replacing the sulfonic acid group in the membrane. Therefore, when the amount of cations in the membrane increases, the sulfonic acid groups involved in H ⁺ ion conduction decrease in the cation exchange membrane, making it difficult for H ⁺ ions to move, that is, proton conductivity decreases. Battery performance will deteriorate. Therefore, when the amount of the cation impurity is large, the effect of the activation treatment may be hidden in the deterioration of the battery performance due to the cation impurity, and may not lead to the improvement of the performance of the single fuel cell 2.

  As a result of examining the relationship between the amount of cationic impurities in the electrolyte membrane 5e and the activation treatment, the inventors of the present invention have found the following facts. That is, when the activation treatment is performed, when the amount of cationic impurities is small, the degree of improvement in the performance of the fuel cell single cell 2 is almost the same regardless of whether the degree of activation treatment is low or high. When the number of activation processes is low, the degree of performance improvement of the single fuel cell 2 is small, and when the degree of activation processing is high, the degree of performance improvement of the single fuel cell 2 is large. That is, the degree of performance improvement of the fuel cell single cell 2 by the activation treatment depends on the amount of the cation impurity, and the performance of the fuel cell single cell 2 is improved despite the activation treatment. The reason for not being sufficient is that the degree of the activation treatment is low despite the large amount of cationic impurities in the electrolyte membrane 5e, that is, the activation treatment in consideration of the amount of cationic impurities is not performed. Therefore, in order to reliably improve the performance of the fuel cell single cell 2 by the activation process, it is necessary to change the degree of the activation process according to the amount of cationic impurities. Hereinafter, the fuel cell system A of the present invention in which the degree of activation treatment is changed according to the amount of cationic impurities will be described in detail.

  First, the relationship between the amount of cationic impurities contained in the electrolyte membrane 5e in the fuel cell single cell 2 and the activation treatment will be described.

FIG. 3 is a graph showing the relationship between the output voltage and the output current of the fuel cell single cell 2 when the electrolyte membrane 5e does not contain cationic impurities, that is, the IV characteristics. FIG. 4 is a graph showing the IV characteristics of the single fuel cell 2 when the electrolyte membrane 5e contains a cationic impurity. In both figures, the horizontal axis indicates the output current density, and the vertical axis indicates the output voltage. In the present embodiment, as an example of an index representing the amount of cationic impurities in the electrolyte membrane 5e, a ratio in which the sulfonic acid groups in the electrolyte membrane 5e are substituted with cationic impurities, that is, a sulfonic acid group substitution ratio is used. The sulfonic acid group substitution ratio in the case of FIG. 3 is 0%, and the sulfonic acid group substitution ratio in the case of FIG. 4 is 30%. Also, 1 cm ² cell is used as the single fuel cell 2, H ₂ / Air (1 L / min) is used as the fuel gas / oxidant gas, and the temperature of the single fuel cell 2 is 83 ° C. (relative humidity 30%). ).

  3 and 4, curves EI01 and EI02 show the case where the cathode potential of the single fuel cell 2 is continuously held at 0V for 30 minutes immediately before measuring the IV characteristics. However, in this embodiment, the cathode potential held immediately before is referred to as the pre-holding potential, and therefore the pre-holding potential in this case is 0V. On the other hand, in FIG. 3 and FIG. 4, curve EI11 and curve EI12 are obtained when the cathode potential of the single fuel cell 2 is continuously held at 0.6V for 30 minutes immediately before measuring the IV characteristics, The case where the holding potential is 0.6V is shown.

  In other words, the curve EI01 and the curve EI02 show that the flow rate of the oxidant gas on the cathode electrode 5c side is not reduced, but the actual potential is 0 V and the duration is 30 minutes with respect to the single fuel cell 2. The IV characteristic after performing the activation process and improving the performance of the fuel cell single cell 2 is shown. Similarly, in the curves EI11 and EI12, the flow rate of the oxidant gas on the cathode electrode 5c side is not reduced, but substantially, the ultimate potential is 0.6V and the duration is 30 minutes with respect to the single fuel cell 2. The IV characteristic after performing the activation process which is and improving the performance of the fuel cell single cell 2 is shown.

  As shown in FIG. 3 above, the curve EI01 and the curve EI11 substantially overlap. Therefore, in the case of a single fuel cell 2 that is not contaminated with cationic impurities, the degree of improvement in performance (IV characteristics) does not change even if the ultimate potential of the activation process is set to 0V or 0.6V. There was found. In other words, the effect of the activation process of the fuel cell single cell 2 is almost the same regardless of the ultimate potential of the activation process, and therefore, when not contaminated with cationic impurities, even if the degree of the activation process is low ( Example: 0.6V), it was found that the performance of the single fuel cell 2 was improved.

  On the other hand, as shown in FIG. 4 described above, the curve EI12 is significantly lower than the curve EI02. Therefore, in the case of the single unit fuel cell 2 that is contaminated with cation impurities, if the ultimate potential of the activation process is 0.6V, the degree of improvement in performance (IV characteristics) compared to 0V. Turned out to be low. In other words, the effect of the activation process of the fuel cell single cell 2 varies greatly depending on the ultimate potential of the activation process. Therefore, when the fuel cell unit cell 2 is contaminated with a cationic impurity, the higher the degree of the activation process (example: 0V) It has been found that the performance of the single fuel cell 2 is improved.

FIG. 5 to FIG. 7 summarize the experimental results as shown in FIG. 3 and FIG.
FIG. 5 is a graph showing the relationship between the output current density and the pre-holding voltage at a predetermined output voltage of the fuel cell single cell 2 when the sulfonic acid group substitution ratio of the electrolyte membrane 5e in the fuel cell single cell 2 is 0%. is there. The horizontal axis represents the previous holding potential, and the vertical axis represents the output current density. Curves A01, A02, and A03 in FIG. 5 are the cases where the oxygen concentration in the oxidant gas supplied to the cathode electrode 5c is 16%, 5%, and 1%, respectively. It shows that it is going once. Curves A01, A02, and A03 shown in FIG. 5 measure the IV characteristics after the cathode potential of the fuel cell unit 2 is continuously held at the previous holding potential for 30 minutes, and the output current density at a predetermined output voltage. And the pre-holding potential. In addition, the IV characteristic is substantially the performance of the fuel cell single cell 2 by executing an activation process in which the arrival potential is the previous holding potential and the duration is 30 minutes. It is IV characteristic after improving.

  As shown in FIG. 5, when the sulfonic acid group substitution ratio of the electrolyte membrane 5e in the fuel cell single cell 2 is 0%, that is, when it is not contaminated with cationic impurities, the output current density is almost independent of the pre-holding potential. It is constant. Therefore, the degree of improvement in the performance of the single fuel cell 2 is substantially constant without depending on the ultimate potential of the activation process. Therefore, when not contaminated with cationic impurities, it can be considered that even if the degree of activation treatment is relatively low, the performance of the fuel cell unit cell 2 is sufficient. This is the same even if the oxygen concentration is different, that is, the output current density is different.

  On the other hand, FIG. 6 and FIG. 7 show the output current density and the pre-holding at the predetermined output voltage of the fuel cell single cell 2 when the sulfonic acid group substitution ratio of the electrolyte membrane 5e in the fuel cell single cell 2 is 30% and 70%. It is a graph which shows the relationship with a voltage. In each figure, the horizontal axis, the vertical axis, the curves A11, A12 and A13, and the curves A21, A22 and A23 are the same as those in FIG.

  As shown in FIG. 6 and FIG. 7, when the sulfonic acid group substitution ratio of the electrolyte membrane 5e in the fuel cell single cell 2 is 30% or 70%, that is, when it is contaminated with cationic impurities, the output current is the same even at the same output voltage. The density changes depending on the previous holding potential, and the smaller the previous holding potential, the higher the output current density. Therefore, the degree of improvement in the performance of the fuel cell single cell 2 changes depending on the arrival potential of the activation process, and the performance improves as the arrival potential decreases. And this tendency becomes so high that there are many amounts of cationic impurities. Therefore, when contaminated with cationic impurities, when the amount of cationic impurities is large, the degree of activation treatment is increased as compared with when the amount of cationic impurities is small, so that the performance of the fuel cell single cell 2 is improved. It can be considered that the improvement of the above can be appropriately performed. This is the same even if the oxygen concentration is different, that is, the output current density is different.

The mechanism of the phenomenon shown in FIGS. 5 to 7 can be considered as follows, for example. FIG. 8 is a diagram for explaining the reason for the phenomenon shown in FIGS. FIG. 8A shows a case where the pre-holding potential is set to a low potential, that is, a case where the degree of the activation process is increased, and FIG. 8B shows a case where the pre-holding potential is set to a high potential, that is, the activation process is performed. In the case of weakening, M ⁺ represents a cation, and H ⁺ represents a proton (hydrogen ion). The phenomenon shown in FIGS. 5 to 7 cannot be explained only by removing the oxide film of the electrode catalyst, but is considered as follows. In normal operation, since the cathode potential is relatively high, for example, as shown in FIG. 8B, the cation is in a biased state. However, when the activation treatment is performed at a higher level, the anode 5a and the cathode It is considered that the potential difference with respect to 5c becomes small, the cations are not biased toward the cathode, and the cation is dispersed as shown in FIG. 8A. On the other hand, when the activation process is performed at a low level, the potential difference between the anode 5a and the cathode 5c does not become small, so that the cation remains biased toward the cathode and remains in the state of FIG. 8B. It seems that it does not change much. Therefore, immediately after the activation processing, the state becomes as shown in FIG. 8A when the degree is high, and the state becomes as shown in FIG. 8B when the degree is low, and the IV characteristics are examined in these states. It is considered that the characteristics are as shown in FIGS.

  Further, as described above, maintaining the cathode potential at a low potential by the activation treatment eliminates the uneven distribution of cations on the cathode electrode side of the electrolyte membrane 5e (FIG. 8A). Therefore, in addition to the effect of removing the oxide film of the electrode catalyst of the cathode electrode, the activation treatment has the effect of correcting the unevenness of the cation impurities in the electrolyte membrane 5e and uniformly distributing the cation impurities. Conceivable. In other words, it is considered that the cause of the performance deterioration of the single fuel cell 2 is not only the oxide film of the electrode catalyst but also the bias of the cation impurities in the electrolyte membrane 5e. However, the activation treatment of this embodiment not only removes the oxide film of the electrode catalyst, but also allows the cation impurities in the electrolyte membrane 5e to be uniformly distributed, so that the performance of the fuel cell single cell 2 can be further improved. Can be improved.

  From the above results, in the present embodiment, a novel activation process is performed in which the degree is changed according to the amount of cationic impurities, instead of the conventional activation process in which the cathode potential is simply lowered to a predetermined ultimate potential. . That is, when the amount of cation impurities in the electrolyte membrane 5e is zero or very small, the activation treatment may be performed mainly by removing the oxide film of the electrode catalyst. To lower. In this case, it is not necessary to eliminate the bias of cation impurities. As a result, the performance of the electrode catalyst is improved, whereby the performance of the fuel cell single cell 2 is improved. On the other hand, when the amount of cation impurities in the electrolyte membrane 5e is large, as the activation process, the oxide film of the electrode catalyst needs to be removed and the unevenness of the cation impurities needs to be eliminated. Is relatively high. As a result, the performance of the electrode catalyst is improved and the unevenness of cationic impurities is eliminated, thereby improving the performance of the fuel cell single cell 2. As described above, the degree of activation treatment is increased when the amount of cationic impurities in the electrolyte membrane 5e is large, and the degree of activation treatment is decreased when the amount of cationic impurities is small. The amount of metal eluted from the electrode catalyst can be suppressed.

  Here, the degree of the activation process is represented by the height of the cathode potential reaching potential, the length of the duration of the cathode potential reaching potential, or the frequency of the activation process. The change in the degree of the activation process may be made by changing one of them or by combining some of them. Here, in the case where the height of the ultimate potential of the cathode potential is used, the ultimate potential is determined to be low when the degree of activation processing is increased. In addition, when the length of the duration of the arrival potential of the cathode potential is used, the duration is determined to be long when the degree of the activation process is increased. In addition, when the frequency of the activation process is used, the frequency of the activation process is frequently determined when the degree of the activation process is increased. This is because the movement speed of the cationic impurities is slow when the potential is changed, but it is considered that the bias of the cationic impurities to the cathode electrode can be corrected by increasing the duration. Further, if the frequency is increased, the integration time for holding at a low potential becomes longer, so that it is considered that the same effect as that of increasing the duration can be obtained.

  In this embodiment, as the degree of the activation process, the height of the cathode potential reaching potential, the length of the duration of the cathode potential reaching potential, and the frequency of the activation process are used in combination. As the range of the ultimate potential, for example, 0.6V to 0.05V can be mentioned. Examples of the duration range include 1 second to continuous. Examples of the interval representing the frequency of the activation process include every minute to continuous. An example of the combination of the degree of activation processing in the present embodiment is shown in Table 1 below.

  In Table 1, the degree of activation treatment is divided into four stages. In the case of L4 with the lowest degree of activation processing, the ultimate potential is 0.6 V, the duration is 1 second, and the frequency is every 10 minutes. In the case of L3, which has the second lowest activation level, the ultimate potential is 0.4 V, the duration is 5 seconds, and the frequency is every 5 minutes. In the case of L2 where the degree of activation processing is the second highest, the ultimate potential is 0.2V, the duration is 10 seconds, and the frequency is every minute. In the case of L1 having the highest degree of activation treatment, the ultimate potential is 0.05V, the duration is during the condition satisfaction period, and the frequency is continuous. The data shown in Table 1 is stored in the ROM 62 of the electronic control unit 60, for example.

  As an index for determining the degree of the activation treatment, not only the amount of the cation impurities of the electrolyte membrane 5e described above but also other factors such as the temperature of the fuel cell stack 10 and the history of operation output may be used.

For example, the temperature of the fuel cell stack 10 corresponds to the relative humidity of the electrolyte membrane 5e, that is, the moisture concentration (water content) per unit volume, and the temperature of the fuel cell stack 10 and the relative humidity of the electrolyte membrane 5e are correlated. There is. When the temperature of the fuel cell stack 10 is relatively high, the relative humidity (moisture concentration) of the electrolyte membrane 5e is low, so that the influence of cation impurities in the electrolyte membrane 5e becomes large. This is clear from the data shown in FIG. FIG. 9 is a graph showing an example of the relationship between the membrane resistance of the electrolyte membrane and the amount of cationic impurities. However, the vertical axis represents the membrane resistance of the electrolyte membrane 5e, that is, the migration resistance of protons (H ⁺ ) in the electrolyte membrane 5e, and the horizontal axis represents the sulfonic acid group substitution ratio. Curve B1 shows the case where the relative humidity of the electrolyte membrane 5e is 30%, and curve B2 shows the case where the relative humidity of the electrolyte membrane 5e is 80%. As shown in the figure, the lower the relative humidity (curve B1), the higher the membrane resistance, that is, the battery performance tends to decrease (the proton transfer resistance correlates with the power generation performance (there is a negative correlation)). In addition, the higher the sulfonic acid group substitution ratio (cation impurity amount), the stronger the tendency. Therefore, it can be seen that, under the conditions where the relative humidity of the electrolyte membrane 5e is low, that is, the temperature of the fuel cell stack 10 is high, the battery performance is greatly reduced even with the same amount of cationic impurities, and the effect of the activation treatment is increased. . Therefore, even when the amount of cation impurities is the same, when the relative humidity of the electrolyte membrane 5e is low, that is, when the temperature of the fuel cell stack 10 is relatively high, the relative humidity of the electrolyte membrane 5e is high, that is, the fuel cell stack 10 The degree of activation treatment is made higher than when the temperature is low. For example, in terms of the temperature of the fuel cell stack 10, a method is conceivable in which a threshold temperature (example: 80 ° C.) is set, and the degree of activation processing is changed depending on whether the temperature is equal to or higher than the threshold temperature. In this case, threshold temperature data is stored in the ROM 62 of the electronic control unit 60, for example.

  FIG. 10 is a graph for determining the degree of the activation process. This graph shows the relationship between the cation impurity amount of the electrolyte membrane 5e, the temperature of the fuel cell stack 10, and the four levels L1 to L4 in Table 1 above, which are the degree of activation treatment. Here, the horizontal axis indicates the amount of cationic impurities, and the vertical axis indicates the degree of activation treatment. A straight line T01 is a graph when the temperature indicated by the temperature sensor 18 is 80 ° C. or higher, and a straight line T02 is a graph when the temperature indicated by the temperature sensor 18 is less than 80 ° C. The graph is partitioned into an R1 region, an R2 region, an R3 region, and an R4 region in order from the highest degree of activation. The data shown in FIG. 10 is stored in the ROM 62 of the electronic control unit 60, for example.

  The degree of activation treatment is determined by the degree of activation treatment indicated by a point on the straight line T01 or straight line T02 determined according to the estimated amount of cationic impurities and the measured temperature of the fuel cell stack 10 in the R1 region and the R2 region. , R3 region and R4 region are determined. When the degree of activation processing indicated by a point on the straight line is in the R1 region, the degree of activation processing is determined as L1. When the degree of the activation process indicated by the point on the straight line is in the R2 region, the degree of the activation process is determined as L2. When the degree of the activation process indicated by the point on the straight line is in the R3 region, the degree of the activation process is determined as L3. When the degree of the activation process indicated by the point on the straight line is in the R4 region, the degree of the activation process is determined as L4. For example, when the amount of cationic impurities is estimated to be CAC1, and the temperature of the fuel cell single cell 2 is less than 80 ° C., the point Q2 on the straight line T02 is specified, and the point Q2 is in the region R3, so L3 is selected. Further, for example, when the amount of cationic impurities is estimated to be CAC1, and the temperature of the single fuel cell 2 is 80 ° C. or higher, the point Q1 of the straight line T01 is specified, and the point Q1 is in the region R1, so the degree of activation processing L1 is selected as

  Based on the above, in the fuel cell system A, when the performance of the fuel cell unit cell 2 should be improved during operation of the fuel cell system A, the performance of the fuel cell unit cell 2 is improved using the following activation process. Perform performance improvement control.

  FIG. 11 is a diagram illustrating a method for improving the performance of a single fuel cell. The left vertical axis represents the output voltage VOUT of the single fuel cell 2, the right vertical axis represents the output current IOUT (indicated by current density) of the single fuel cell 2, and the horizontal axis represents time. The solid curve indicates the output voltage VOUT of the single fuel cell 2, and the broken curve indicates the output current IOUT of the single fuel cell 2. Since the anode potential is 0 V, the output voltage VOUT can be said to be a cathode potential. Further, the fuel cell system A allows the anode 5a and the cathode to flow by supplying a constant minute output current, i.e., idle output current, to the fuel cell stack 10 even when the fuel cell system A is in a no-load state, i.e., idle operation. The open-circuit voltage is not applied between the electrode 5c and the anode electrode catalyst layer 5as and the cathode electrode catalyst layer 5cs. The output voltage VOUT at that time is an idle output voltage.

  In the embodiment shown in FIG. 11, when the fuel cell system A is idling with the idle output current IA0 and the idle output voltage VA0, the performance improvement control of the single fuel cell 2 is suitably performed. The reason for this is that in the activation process performed in the method for improving the performance of a single fuel cell, the output of the fuel cell is reduced by narrowing the supply of oxidant gas, but the required output for the fuel cell is low during idle operation, This is because the vehicle behavior such as acceleration performance is hardly affected. In the present embodiment, when the ignition switch is in the P (parking) range and the ignition switch is on, the idle operation is performed. Therefore, the idle operation is performed by determining whether or not the engine is in the P range. It can be determined whether or not. In another embodiment (not shown), the electronic control unit 60 (CPU 64) determines whether the fuel cell stack 10 is idling in the P range based on the output signal from the output sensor 17. Further, in this embodiment, the method for improving the performance of the single fuel cell is performed during idle operation when the transmission is in the P range. The reason for this is that during idle operation when the transmission is in the D (drive) range, there is a case where the idle operation immediately shifts to normal operation that operates at an output current and output voltage corresponding to the load, and the oxidant gas is activated during the activation process. This is because if the supply of is restricted, the normal operation may be hindered. Alternatively, it is necessary to interrupt the activation process. On the other hand, when it is in the P range, it can be expected to be idle for a longer time than when it is in the D range. Therefore, the idle output current IA0 is the target current value of the fuel cell stack 10 during the idling operation in the P range where the performance improvement control of the single fuel cell 2 is not performed.

  Referring to FIG. 11, at time ta <b> 1, first, the electronic control unit 60 (CPU 64) receives an output signal indicating the transmission range from the transmission range sensor 19. When the transmission is not in the P range, the performance improvement control of the single fuel cell 2 is terminated and normal operation is performed. In normal operation, the fuel cell stack 10 is operated with an output current and an output voltage corresponding to a load request from the vehicle.

  When the transmission is in the P range, the amount of cation impurities in the electrolyte membrane 5e is estimated when the degree of the activation process related to the activation process control of the fuel cell single cell 2 to be executed is not set. The That is, at time ta1 to ta2, the electronic control unit 60 (CPU 64) executes the cation impurity amount estimation control. However, cationic impurity amount estimation control will be described later. As a result, at time ta2, the amount of cationic impurities in the electrolyte membrane 5e, that is, the sulfonic acid group substitution ratio in this embodiment is estimated. On the other hand, when the degree of the activation process has been set, activation process control for executing the activation process is performed. The activation process control will be described later.

  Subsequently, the electronic control unit 60 (CPU 64) executes activation process degree determination control. First, the temperature of the fuel cell stack 10 is measured. That is, at time ta2, the electronic control unit 60 (CPU 64) acquires the temperature of the fuel cell stack 10 from the temperature sensor 18. The temperature sensor 18 can be regarded as a temperature measurement unit configured to measure the temperature of the fuel cell stack 10. Furthermore, as described above, the temperature of the fuel cell stack 10 has a correlation with the relative humidity of the electrolyte membrane 5e. For example, when the temperature of the fuel cell stack 10 is relatively high, the relative humidity of the electrolyte membrane 5e is low. Therefore, the temperature sensor 18 can be regarded as a correlation parameter measurement unit that measures a parameter value correlated with the relative humidity of the electrolyte membrane 5e.

  Then, the electronic control unit 60 (CPU 64) uses the cation impurity amount of the electrolyte membrane 5e and the temperature of the fuel cell stack 10 to store the data shown in the graph of FIG. Referring to FIG. 4, the degree of activation processing is determined from among L1 to L4. In the example of this figure, the degree of the activation process is determined as the reached potential VA1, the process frequency Δtai, and the duration Δtap. The electronic control unit 60 (CPU 64) can be regarded as a processing degree determination unit configured to determine the degree of activation processing based on the amount of cationic impurities and the like.

  Thereafter, the electronic control unit 60 (CPU 64) executes activation process control based on the determined degree of activation process. That is, while the supply of the oxidant gas to the cathode electrode 5c is reduced to a predetermined flow rate by the turbo compressor 44, the output voltage VOUT, that is, the cathode potential is maintained at the ultimate potential VA1 for the duration Δtap for each processing frequency Δtai. The activation process is executed. That is, from time ta2 to time ta3, based on the command value from the electronic control unit 60, the DC / DC converter 11 maintains the output voltage VOUT at the idle output voltage VA0 and the output current IOUT at the idle output current IA0. To do. Thereafter, during the period from time ta3 to time ta4, based on the command value from the electronic control unit 60, the DC / DC converter 11 changes the output voltage VOUT to the ultimate potential VA1, thereby performing the activation process. The electronic control unit 60 (CPU 64), the turbo compressor 44, and the DC / DC converter 11 execute an activation process in which the cathode potential in the fuel cell single cell is temporarily reduced to the ultimate potential over a continuous time with a processing frequency. It can be seen as a processing unit configured to do this.

  Thereafter, the operation is performed in the same manner. For example, from time ta4 to time ta5, the output voltage VOUT is maintained at the idle output voltage VA0 and the output current IOUT is maintained at the idle output current IA0. Thereafter, during the period from time ta5 to time ta6, the output voltage VOUT is changed to the arrival potential VA1, and the output current IOUT is changed to the arrival current IA1, thereby performing the activation process. When the processing frequency is “continuous”, the period Δtax during which the output voltage VOUT in FIG. 11 is held at the idle output voltage VA0 is 0 (zero).

  After that, for example, at time ta7, the activation processing of the electrode catalyst of the cathode electrode should not be executed. For example, when the vehicle transmission is moved to the D (drive) range, the electronic control unit 60 (CPU 64) is activated. Disabling process is prohibited.

  Although the cationic impurity amount estimation control of the above embodiment is performed during idle operation, in another embodiment (not shown), cationic impurity control is performed when the idle operation is not performed.

  Further, in the activation processing degree determination control in the above embodiment, the amount of cation impurities in the electrolyte membrane 5e and the temperature of the fuel cell stack 10 are referred to. In another embodiment (not shown), the cation in the electrolyte membrane 5e is referred to. Only the amount of impurities is referred to, or at least one of the temperature of the fuel cell stack 10 and the operation output of the fuel cell stack 10 and the amount of cationic impurities in the electrolyte membrane 5e are referred to.

  In the above embodiment, the temperature of the fuel cell stack 10 is referred to as a parameter correlating with the relative humidity in the activation process degree determination control, but in another embodiment (not shown), the temperature of the fuel cell stack 10 is substituted. In addition, another parameter that can estimate the relative humidity of the electrolyte membrane 5e of the fuel cell single cell 2 is used. Other parameters that correlate with the relative humidity include, for example, the impedance of the single fuel cell 2, the humidity of the gas in the vicinity of the electrolyte membrane 5 e of the single fuel cell 2, and the single fuel cell of the cooling water supply pipe 51 in the fuel cell stack 10. The temperature in the vicinity of the cell 2 can be mentioned. For example, when the impedance is high, it is presumed that the moisture in the electrolyte membrane 5e is low and the conductivity is low, so that the relative humidity is low. When the humidity of the gas in the vicinity of the electrolyte membrane 5e is low, it can be said that the relative humidity is low because the moisture is estimated to be reduced by evaporation from the electrolyte membrane 5e. When the temperature in the vicinity of the single fuel cell 2 of the cooling water supply pipe 51 is high, it is estimated that the moisture in the electrolyte membrane 5e is evaporated and decreased, and therefore it can be said that the relative humidity is low.

  Next, a method for estimating the amount of cationic impurities in the electrolyte membrane 5e of the single fuel cell 2 of the fuel cell stack 10 will be described. As a method for estimating the amount of cationic impurities, the following method developed by the inventors of the present invention can be used. That is, this is a method of measuring the behavior of the output voltage of the single fuel cell 2 when the output current of the single fuel cell 2 is increased and held in steps during the operation of the fuel cell system A. This is because the inventor of the present invention discovered the behavior of the output voltage of the fuel cell unit cell 2 when the output current of the fuel cell unit cell 2 was increased and held in steps during the operation of the fuel cell system A. This is based on the fact that the amount of cationic impurities in the electrolyte membrane 5e has a correlation. Hereinafter, it will be described in detail with reference to the drawings.

  FIG. 12 is a diagram illustrating a method for estimating the amount of cationic impurities. This figure schematically shows the behavior of the output voltage VOUT when the output current IOUT is increased stepwise in the single fuel cell 2. However, the left vertical axis is the output voltage VOUT of the fuel cell single cell 2, the right vertical axis is the output current IOUT of the fuel cell single cell 2 (indicated by current density), and the horizontal axis is time. The solid curve indicates the output voltage VOUT of the single fuel cell 2, and the broken curve indicates the output current IOUT of the single fuel cell 2.

  FIG. 12 shows a case in which the amount of cationic impurities is estimated by controlling the output current of a single fuel cell according to a predetermined pattern. That is, when the fuel cell stack 10 is operated (operated) at the base output current IB and the base output voltage VB at time t0, the output current IOUT of the single fuel cell 2 is determined in advance from the base output current IB at time t1. The increase current IG is increased stepwise, and the increase current IG is maintained over the increase time Δt0 up to time t3. Here, the base output current IB is a target current value of the fuel cell stack 10 during normal operation in which the method for estimating the amount of cationic impurities is not performed. FIG. 12 shows a case where the base output current IB is lower than a predetermined threshold current, for example, the output current IOUT of the fuel cell stack 10 in a no-load state. When this method for estimating the amount of cationic impurities (FIG. 12) is applied to the above performance improvement control (FIG. 11), the base output current IB corresponds to the idle output current IA0, and the base output voltage VB is the idle output voltage. Corresponds to VA0.

  In this case, the output voltage VOUT decreases in a stepwise manner from the base output voltage VB to the minimum voltage VM at time t1, then starts to increase, and the steady voltage VC lower than the base output voltage VB by time t3 after the increase time Δt0. To increase. However, in the example shown in FIG. 12, the increase time Δt0 is a stabilization time that is sufficient for the output voltage VOUT to become a steady voltage, and after the increase time Δt0 has elapsed, the output current IOUT is changed to the original base output current IB. It shall be returned. At this time, at least the following three values related to the behavior of the output voltage VOUT and the amount of cationic impurities in the electrolyte membrane 5e have a correlation. That is, (1) a voltage drop amount ΔV that is a difference between the minimum voltage VM and the output voltage VE when the output voltage VOUT at a time t2 after a predetermined set time Δt1 from the time t1 is VE, and (2) a base output A minimum value drop amount ΔVm which is a difference between the minimum voltage VM and the voltage VB, and (3) a required time Δt2 from when the output current IOUT is increased to the increased current IG until a time t22 when the output voltage VOUT reaches the steady voltage VC, It is. As the amount of cationic impurities in the electrolyte membrane 5e increases, the voltage drop amount ΔV increases in (1), the minimum drop amount ΔVm increases in (2), and the required time Δt2 increases in (3). Become. In the present embodiment, the above (1) is used.

  Regarding (1) above, FIG. 13 shows the difference between the output voltage VOUTn when the amount of cationic impurities in the electrolyte membrane 5e is small and the output voltage VOUTc when the amount of impurities is large, and FIG. 14 shows a partially enlarged view thereof. . The left and right vertical and horizontal axes are the same as in FIG. When the fuel cell stack 10 is operated (operated) at the base output current IB and the base output voltage VB at time t0, the output current IOUT of the single fuel cell 2 indicated by the broken line at time t1 is preliminarily determined from the base output current IB. It is increased stepwise to a predetermined increase current IG. Then, the increased current IG is held over the increase time Δt0 up to time t3. Here, the output voltage VOUTn when the amount of the cation impurity in the electrolyte membrane 5e is small decreases in a step-like manner from the base output voltage VB to the minimum voltage VMn as shown by a one-dot chain line in FIG. At time t21 after time t2, the voltage increases to a steady voltage VCn lower than the base output voltage VB. On the other hand, the output voltage VOUTc when the amount of the cation impurity in the electrolyte membrane 5e is large decreases from the base output voltage VB to the minimum voltage VMc in a stepwise manner as shown by the solid line in FIG. At time t22 after t2, the voltage increases to a steady voltage VCc lower than the base output voltage VB.

  At this time, as the amount of cationic impurities in the electrolyte membrane 5e increases, the voltage drop amount ΔV, which is the difference between the minimum voltage VM and the output voltage VE at time t2 after the set time Δt1 from time t1, increases. However, the set time Δt1 is an arbitrary value smaller than the increase time Δt0. For example, as shown in FIG. 14, the voltage drop amount ΔVc, which is the difference between the minimum voltage VMc and the output voltage VEc when the amount of cationic impurities in the electrolyte membrane 5e is large, is the amount of cationic impurities in the electrolyte membrane 5e. The voltage drop amount ΔVn, which is the difference between the minimum voltage VMn and the output voltage VEn when the amount is small, is larger.

  An example of the relationship between the amount of cationic impurities and the amount of voltage drop ΔV is shown in FIG. The horizontal axis indicates the ratio of sulfonic acid groups in the electrolyte membrane 5e being replaced by cationic impurities. The vertical axis represents the voltage drop amount ΔV. This substitution ratio is an example of a value indicating the amount of cationic impurities. As shown by the curve CL, the voltage drop amount ΔV increases as the ratio of the sulfonic acid groups in the electrolyte membrane 5e replaced by cationic impurities increases, and the sulfonic acid groups are replaced by cations. The ratio is correlated with the voltage drop amount ΔV. Therefore, if the data shown in FIG. 15 is measured in advance for the predetermined increase current IG and increase time Δt0, the voltage drop amount ΔV is measured, and the data is referred to to replace the sulfonic acid group. The ratio, that is, the amount of cationic impurities can be estimated. Here, data indicating the graph of FIG. 15 for estimating the amount of cationic impurities is obtained in advance and stored in the ROM 62 in advance.

The reason why the relationship between the amount of cationic impurities and the amount of voltage drop ΔV is as shown in FIG. 15 is not necessarily clear, but is considered as follows. First, when the output current IOUT of the fuel cell stack 10 is increased in steps from the predetermined base output current IB to the increased current IG, the output voltage VOUT decreases rapidly and becomes VM due to the influence of accompanying water. This is considered to be because the anode 5a is dried and the movement of the cation impurities is slow and is delayed from the accompanying water, so that the internal resistance temporarily increases. Thereafter, the output voltage VOUT gradually recovers and becomes VE because the movement of the cation impurities is slow, and immediately after the increase of the output current IOUT, the cation impurities are also present on the anode 5a side of the electrolyte membrane 5e. However, it is considered that the output voltage VOUT is gradually recovered by gradually stabilizing the cation impurity Q toward the cathode electrode 5c and stabilizing it so that the conduction of H ⁺ ions is not hindered. Thus, since VM and VE are affected by cationic impurities, it is considered that the relationship between the amount of cationic impurities and the amount of voltage drop ΔV (= ME−VM) is as shown in FIG.

  However, in measuring the voltage drop amount ΔV, it is preferable to set the increased current IG and the base output current IB so that the voltage drop amount ΔV is increased in order to facilitate the measurement. For this purpose, it is conceivable to set the increase current IG and the base output current IB so that the voltage drop amount ΔV becomes very large when the base output current IB increases to the increase current IG stepwise. For example, the increase current IG is set to the output current IOUT when the load state of the fuel cell system A is the full load state. In this case, the output current IOUT becomes very large, and the output voltage VOUT becomes very small correspondingly, so that the voltage drop amount ΔV can also be made very large. Alternatively, when the base output current IB is smaller than a predetermined threshold current, the output current IOUT is increased stepwise from the base output current IB to the increased current IG. In that case, since the base output voltage VB serving as a reference increases in response to the base output current IB being small, the voltage drop amount ΔV can be greatly increased.

  In the present embodiment, the above (1) is used, but in another embodiment, the above (2) or (3) is used. FIG. 16 shows an example of the relationship between the amount of cationic impurities and the minimum value drop amount ΔVm for (2). The horizontal axis represents the sulfonic acid group substitution ratio in the electrolyte membrane 5e. The vertical axis represents the minimum value drop amount ΔVm. Therefore, the amount of cationic impurities can be determined by measuring the minimum value drop amount ΔVm and referring to FIG. On the other hand, FIG. 17 shows an example of the relationship between the amount of cationic impurities and the required time Δt2 for (3). The horizontal axis represents the sulfonic acid group substitution ratio in the electrolyte membrane 5e. The vertical axis represents the required time Δt2. Therefore, the amount of cationic impurities can be obtained by measuring the required time Δt2 and referring to FIG.

  Based on the above fact, in the fuel cell system A, when the amount of cationic impurities in the electrolyte membrane 5e of the fuel cell system A in the performance improvement control (FIG. 11) should be estimated (time ta1), the above (1) The following cationic impurity amount estimation control using the method is performed. However, in this embodiment, the base output current IB is the same as the idle output current IA0, and the base output voltage VB is the same as the idle output voltage VA.

  That is, based on the command value (instruction) from the electronic control unit 60, the DC / DC converter 11 increases the output current IOUT output from the fuel cell stack 10 (single fuel cell 2) from the predetermined base output current IB. Increasing to IG in a stepwise manner, the increased current IG is held for a predetermined increase time Δt0. Thereafter, the output current IOUT is returned to the base output current IB. Here, the DC / DC converter 11 can be regarded as a control unit that controls the current of the single fuel cell 2.

  At this time, the output sensor 17 decreases in a stepwise manner from the base output voltage VB to the minimum voltage VM with respect to the output voltage VOUT of the fuel cell single cell 2, and then increases, and after the increase time Δt0, the output voltage VOUT is lower than the base output voltage VB. The behavior of increasing to voltage VC is measured. Here, the output sensor 17 can be regarded as a measurement unit that measures the output voltage VOUT of the single fuel cell 2. The behavior of the measured output voltage VOUT is stored in the RAM 63, for example.

  Subsequently, the electronic control unit 60 calculates a voltage drop amount ΔV after a predetermined set time Δt1 from when the output current IOUT is increased to the increased current IG based on the data of the output voltage VOUT stored in the RAM 63. To do. Subsequently, based on the voltage drop amount ΔV, the substitution ratio of the sulfonic acid group is estimated as the amount of cationic impurities in the electrolyte membrane 5 e with reference to the data shown in the graph of FIG. 15 stored in advance in the ROM 62. Here, the electronic control unit 60 can be regarded as an estimation unit that estimates the amount of cationic impurities based on the measured output voltage VOUT of the fuel cell single cell 2.

  By performing the above cationic impurity amount estimation control, the fuel cell system A can estimate the cationic impurity amount in the electrolyte membrane 5e of the fuel cell single cell 2 during the operation of the fuel cell system A. In this embodiment, the cation impurity amount estimation control is performed during the idle operation, but may be performed when the idle operation is not performed. In this case, the cationic impurity amount estimation control is performed separately from the performance improvement control.

  In addition, the fuel cell system A includes a DC / DC converter 11 as a control unit, an output sensor 17 as a measurement unit, and an electronic control unit 60 as an estimation unit. Therefore, the fuel cell system A includes a control unit, a measurement unit, and an estimation unit, and includes a cationic impurity amount estimation unit configured to estimate the amount of cationic impurities contained in the electrolyte membrane of the fuel cell single cell. You can see that it is equipped.

  FIG. 18 shows a routine for performance improvement control of the single fuel cell 2 in the fuel cell system A of FIG. This routine is executed by interruption at regular intervals. Referring to FIG. 18, it is determined in step 100 whether or not the transmission has been moved to the P range. If the transmission is set to the P range, it is determined in step 101 whether or not the degree of the activation process of the activation process control has been determined. If the degree of activation processing of the activation processing control has been determined, the process proceeds to step 104. Immediately after switching from the D range to the P range, the degree of activation processing has not been determined, so the process proceeds to step 102, and in step 102, cation impurity amount control for estimating the amount of cation impurities in the electrolyte membrane 5e is performed. Executed. Next, in step 103, activation processing degree determination control is executed to determine the degree of activation processing based on the amount of cationic impurities estimated in step 102. Subsequently, in step 104, activation processing control is executed based on the degree of activation processing determined in step 103. When the transmission is not set to the P range in step 100, normal operation is performed in the fuel cell system A in step 105. In normal operation, the fuel cell stack 10 is operated with an output current and an output voltage corresponding to the load.

  FIG. 19 shows a control routine for estimating the amount of cationic impurities in the fuel cell system A of FIG. This routine is executed in step 102 of the performance improvement control routine of FIG. However, in this embodiment, the base output current IB is the idle output current IA0, and the base output voltage VB is the idle output voltage VA0. Referring to FIG. 19, in step 200, the output current IOUT of the fuel cell stack 10 is increased stepwise from the base output current IB to the increased current IG. The increase current IG is held for the increase time Δt0. In the subsequent step 201, the behavior of the output voltage VOUT that increases to the steady voltage VC lower than the base output voltage VB after being stepped from the base output voltage VB to the minimum voltage VM is measured. Next, at step 202, the output current IOUT is reduced to the base output current IB after the increase time Δt0 has elapsed since the output current IOUT was increased stepwise to the increase current IG. Next, at step 203, based on the measured behavior of the output voltage VOUT, the voltage drop amount ΔV after the set time Δt1 from the time when the output current IOUT is increased stepwise to the increased current IG is calculated. Then, based on the voltage drop amount ΔV, the data shown in the graph of FIG. 15 is referred to, and the amount of cationic impurities in the electrolyte membrane 5e is estimated.

  FIG. 20 shows a routine of activation processing degree determination control in the fuel cell system A of FIG. This routine is executed in step 103 of the performance improvement control routine of FIG. Referring to FIG. 20, in step 300, the temperature of the fuel cell stack 10 is measured. Subsequently, in step 301, based on the amount of cationic impurities in the electrolyte membrane 5e estimated in step 102 and the temperature of the fuel cell stack 10 measured in step 301, the data of FIG. Referring to the degree of activation processing (arrival potential VA1, processing frequency Δtai, and duration Δtap) is determined.

  FIG. 21 shows an activation process control routine in the fuel cell system A of FIG. This routine is repeatedly executed in step 104 of the performance improvement control routine of FIG. Referring to FIG. 21, in step 400, it is determined whether or not the output voltage VOUT has decreased to the ultimate potential VA1. If the output voltage VOUT has decreased to the ultimate potential VA1, it is determined in step 401 whether or not the duration Δtap has elapsed. When the duration Δtap has elapsed, the output voltage VOUT is returned to the original potential, that is, the idle output voltage VA0 in the subsequent step 402. On the other hand, if the duration Δtap has not elapsed, the process ends. On the other hand, if the output voltage VOUT has not decreased to the ultimate potential VA1 in step 400, it is determined in step 403 whether the processing frequency Δtai, that is, whether the interval has elapsed. When the interval has elapsed, in step 404, the output voltage VOUT is lowered to the ultimate potential VA1. On the other hand, if the interval has not elapsed, the process ends.

  Next, another embodiment of the fuel cell system A will be described. In this embodiment, the history of the operation output (= output voltage × output current) of the fuel cell stack 10 is referred to determine the degree of the activation process. The history of operation output is stored in the RAM 63, for example. The driving output of the fuel cell stack 10 is, for example, the driving output within a predetermined time (for example, 5 minutes) most recently of the fuel cell stack 10 and corresponds to the road conditions around the vehicle. If the driving output within the most recent predetermined time is relatively small, it can be estimated that the vehicle was traveling on a road where the driving output is small, such as a road in a traffic jam. Therefore, since it can be predicted that the performance recovery effect by performing the activation process is small, the activation process is not performed or the degree of the activation process is lowered. Conversely, when the driving output within the most recent predetermined time is relatively large, it can be estimated that the vehicle was traveling on a road where the driving output must be large, such as an expressway. Accordingly, it can be predicted that the performance recovery effect by performing the activation process is large, and therefore the degree of the activation process is increased. At this time, the history of the driving output can be acquired from the RAM 63 storing the driving history. The RAM 63 can be regarded as a latest history storage unit that stores a history of operation outputs within a predetermined time period immediately before the fuel cell stack 10.

  Next, another embodiment of the fuel cell system A will be described. In this other embodiment, the method for estimating the amount of cationic impurities in the electrolyte membrane 5e of the fuel cell single cell 2 is different from the above embodiment. Hereinafter, a method for estimating the amount of cationic impurities will be described.

  FIG. 22 is a diagram for explaining a method of estimating the amount of cationic impurities, and shows the IV characteristics of the single fuel cell 2. The horizontal axis indicates the output current density, and the vertical axis indicates the output voltage. The curve ExI1 and the curve ExI2 are obtained when the cathode potential of the fuel cell single cell 2 is continuously held at a predetermined voltage (example: 0.6V) for a predetermined time (example: 1 minute) immediately before measuring the IV characteristic. Indicates. However, the curve ExI1 shows the case where the electrolyte membrane 5e does not contain cationic impurities, that is, the case where the sulfonic acid group substitution ratio is 0%. A curve ExI2 shows a case where the electrolyte membrane 5e contains a cationic impurity, that is, a case where the sulfonic acid group substitution ratio exceeds a predetermined amount (eg, 30%) exceeding zero. In the example of this figure, when the sulfonic acid group substitution ratio is 0% (curve ExI1) with respect to the predetermined output voltage Ex, the output current density is Ixb, but the sulfonic acid group substitution ratio is a predetermined amount. The output current density is Ixa. Therefore, if the relationship between the output current density at the predetermined output voltage Ex and the sulfonic acid group substitution ratio is obtained in advance through experiments or the like, the sulfonic acid group substitution ratio can be determined from the output current density. Specifically, after the cathode potential of the single fuel cell 2 is continuously held at a predetermined voltage for a predetermined time, the output current density when the predetermined output voltage Ex is obtained is obtained, and the predetermined output voltage Ex obtained in advance is obtained. The relationship between the output current density and the sulfonic acid group substitution ratio may be referred to. A table as shown in FIG. 23 showing the relationship between the output current density Ix at the predetermined output voltage Ex and the sulfonic acid group substitution ratio SR is stored in the ROM 62 in advance.

  Alternatively, the output voltage and the output current density may be reversed. FIG. 24 is a diagram for explaining a method for estimating the amount of cationic impurities, and shows the IV characteristics of the fuel cell single cell 2. The horizontal axis, vertical axis, curve ExI1 and curve ExI2 are the same as those in FIG. In the example of this figure, when the sulfonic acid group substitution ratio is 0% (curve ExI1) for a predetermined output current density Ix, the output voltage becomes Exb, but the sulfonic acid group substitution ratio is a predetermined amount (example) : 30%), the output voltage becomes Exa. Therefore, if the relationship between the output voltage at the predetermined output current density Ix and the sulfonic acid group substitution ratio is obtained in advance by experiments or the like, the sulfonic acid group substitution ratio can be grasped from the output voltage. Specifically, after the cathode potential of the single fuel cell 2 is continuously held at a predetermined voltage (for example, 0.6 V) for a predetermined time (for example, 1 minute), an output when a predetermined output current density Ix is obtained. What is necessary is just to obtain | require voltage and refer to the relationship between the output voltage in the predetermined | prescribed output current density Ix calculated | required previously, and a sulfonic acid group substitution ratio. A table as shown in FIG. 25 showing the relationship between the output voltage Ex at the predetermined output current density Ix and the sulfonic acid group substitution ratio SR is stored in the ROM 62 in advance.

  Alternatively, the output voltage and the output current density may be combined. That is, if a table as shown in FIG. 26 showing the relationship between the output current density Ix and output voltage Ex and the sulfonic acid group substitution ratio SR is obtained in advance by experiment, the output voltage Ex at a certain arbitrary output current density Ix. Or by measuring the output current density Ix at a certain arbitrary output voltage Ex, the sulfonic acid group substitution ratio SR can be grasped by referring to the table. A table as shown in FIG. 26 is stored in the ROM 62 in advance.

  Next, still another embodiment of the fuel cell system A will be described. In this other embodiment, the method for estimating the amount of cationic impurities in the electrolyte membrane 5e of the fuel cell single cell 2 is different from the above embodiment. As described above, the cationic impurities may be Ca, Na, etc. contained in the snow melting agent, and Fe, Mo, Cr, Al, etc. contained in the parts of the fuel cell system A. Therefore, it is considered that the cation impurities increase as the operation time of the fuel cell stack 10 becomes longer. Therefore, if the relationship between the operating time of the fuel cell stack 10 and the amount of cation impurities (sulfonic acid group substitution ratio) in the electrolyte membrane 5e is obtained in advance through experiments or the like, the total operating time up to the present time of the fuel cell stack 10 is obtained. By doing so, the amount of cationic impurities (sulfonic acid group substitution ratio) can be grasped. A table as shown in FIG. 27 showing the relationship between the total operation time td of the fuel cell stack 10 and the amount of cationic impurities (sulfonic acid group substitution ratio) SR of the electrolyte membrane 5 e is stored in the ROM 62 in advance. At this time, the total operation time up to the present time of the fuel cell stack 10 can be acquired from the RAM 63 storing the operation history. Note that the parameter for estimating the amount of cationic impurities is not limited to the total operation time of the fuel cell stack 10 described above. For example, it may be the total travel distance of the vehicle on which the fuel cell stack 10 is mounted, the total power generation amount of the fuel cell stack 10 (that is, a value obtained by integrating the power with time), and the total current amount of the fuel cell stack 10 (that is, the current with time). It may be a parameter indicating an operation result such as a function value obtained by combining the current value and / or voltage value of the fuel cell stack 10 and the operation time, such as an integrated value). Further, when the cation impurities accumulated in the fuel cell stack 10 are washed and removed by a known method, the operation results such as the operation time after the washing and removal are used instead of the total operation time of the fuel cell stack 10. May be. The values of these parameters are stored in the RAM 63. Thus, the RAM 63 can be regarded as an operation result storage unit that stores parameters indicating the operation results of the fuel cell stack 10.

  Next, still another embodiment of the fuel cell system A will be described. In each of the above embodiments, first, (A) the cation impurity estimation unit measures the electrical characteristics and the operation time (hereinafter referred to as “electrical characteristics”) of the fuel cell single cell 2. Next, (B) the cation impurity estimation unit estimates the amount of cation impurities by referring to the relationship between the electrical characteristics acquired in advance and the amount of cation impurities based on the measured electrical characteristics and the like. Then, (C) the activation process determining unit determines the degree of the activation process based on the estimated amount of the cation impurity with reference to the relationship between the preset cation impurity quantity and the level of the activation process. . However, the present invention is not limited to this example.

  In the present embodiment, among the above (A) to (C), the process (B) is omitted, and first, (A) the cation impurity estimation unit measures the electrical characteristics and the like of the single fuel cell 2. . Then, (C ′) the activation process determination unit refers to the degree of the activation process with reference to the relationship between the preset electrical characteristics and the degree of the activation process based on the measured electrical characteristics and the like. To decide.

  For example, first, (A) when the fuel cell system A is operated with the base output current IB and the base output voltage VB, the output current IOUT of the single fuel cell 2 is increased from the base output current IB by a predetermined amount. The current IG is increased stepwise and held for an increase time Δt0. Then, the output voltage VOUT of the fuel cell single cell 2 at the increase time Δt0 is measured. At this time, a difference (minimum voltage drop) ΔV in the minimum voltage VM from the output voltage VE after a predetermined set time Δt1 after the output current IOUT is increased to the increased current IG, and a difference in the minimum voltage VM from the base output voltage VB. (Minimum value drop amount) ΔVm, or the required time Δt2 from when the output current IOUT is increased to the increased current IG until the output voltage VOUT reaches the steady voltage VC, is acquired as electrical characteristics or the like.

  Thereafter, (C ′) the voltage drop amount ΔV, the minimum value drop amount ΔVm, or the required time set in advance based on the measured voltage drop amount ΔV, the minimum value drop amount ΔVm, or the required time Δt2. The degree of the activation process is determined with reference to the relationship between Δt2 and the degree of the activation process. For example, as the voltage drop amount ΔV is increased, the minimum value drop amount ΔVm is increased, or the required time Δt2 is increased, the activation processing condition is lowered, and the duration is increased. And by increasing the frequency of processing, or by combining at least two of them, the degree of activation processing is determined to be high.

  Here, the relationship between the preset voltage drop amount ΔV, the minimum value drop amount ΔVm, or the required time Δt2 and the degree of activation processing is, for example, the graph of FIG. 15, the graph of FIG. 16, or the graph of FIG. And the graph of FIG. 10 can be easily obtained.

  Alternatively, for example, (A) after the output voltage VOUT of the single fuel cell 2 is held at a predetermined voltage value for a predetermined time, the output current Ix at the predetermined output voltage Ex or the predetermined output current Ix To obtain the output voltage Ex. Thereafter, (C ′) based on the measured output current Ix or output voltage Ex, the relationship between the preset output current Ix or output voltage Ex and the degree of activation processing is referred to. Determine the degree. For example, when the output current Ix or the output voltage Ex is relatively small, the activation processing conditions are set to lower the ultimate potential, the duration is increased, and the processing frequency compared to when the output current Ix or the output voltage Ex is relatively large. The degree of the activation treatment is determined to be high by combining any one of these or at least two of them.

  Here, the relationship between the preset output current Ix or output voltage Ex and the degree of activation processing is, for example, the graph of FIG. 22 and the table of FIG. 23, or the graph of FIG. 24 and the table of FIG. It can be easily obtained by combining the graph of FIG.

  In these cases, the same effects as those of the embodiment described with reference to FIGS.

  Next, still another embodiment of the fuel cell system A will be described with reference to FIG. This embodiment is different from the embodiment shown in FIG. 1 in that the fuel cell system A is a hydrogen gas non-circulating fuel cell system. The differences will be mainly described below.

  In the fuel cell system A shown in FIG. 1, the outlet of the fuel gas passage 30 and the fuel gas supply pipe 31 are connected by the anode offgas pipe 36 and the fuel gas circulation pipe 81, and the anode offgas containing the fuel gas is the fuel gas supply pipe. 31 is a system that circulates to 31, that is, a fuel gas circulation type fuel cell system. On the other hand, the fuel cell system A shown in FIG. 28 excludes the fuel gas circulation pipe 81 and the fuel gas circulation pump 39. That is, the fuel cell system A shown in FIG. 28 is a system in which the outlet of the fuel gas passage 30 and the fuel gas supply pipe 31 are separated, and the anode off gas containing the fuel gas is not circulated to the fuel gas supply pipe 31, This is a circulation type fuel cell system.

  Also in this case, the same effect as the fuel cell system A shown in FIG. 1 can be obtained.

A Fuel cell system 2 Fuel cell single cell 5e Electrolyte membrane IA Idle output current IOUT Output current VA Idle output voltage VOUT Output voltage

Claims (12)

When the fuel cell system is idling, an activation process is performed in which the cathode potential of at least one fuel cell single cell of the fuel cell system is temporarily reduced to the ultimate potential over the duration with a processing frequency. A processing unit configured to:
A cationic impurity amount estimation unit configured to estimate the amount of cationic impurities contained in the electrolyte membrane of the fuel cell single cell;
When the amount of the cation impurity is large, the activation treatment condition is set lower than the time when the amount of the cation impurity is small, the reaching potential is lowered, the duration is increased, and the treatment frequency is A processing degree determining unit that determines to increase the degree of the activation processing by combining any one of or at least two of them;
With
The processing unit executes the activation processing with the degree determined by the processing degree determination unit.
Fuel cell system. The cationic impurity amount estimation unit is
When the fuel cell system is operating with a base output current and a base output voltage,
Increasing the output current of the single fuel cell from the base output current in a stepwise manner to a predetermined increase current, and maintaining the increase time,
Measure the output voltage of the fuel cell single cell in the increased time,
Based on the measured output voltage, configured to estimate the amount of cationic impurities,
The fuel cell system according to claim 1. When the output current is increased and held stepwise up to the increased current, the output voltage decreases stepwise from the base output voltage to a minimum voltage and then increases toward a steady voltage lower than the base output voltage. Is supposed to
The cationic impurity estimator is
Estimating the amount of cationic impurities so that the difference between the minimum voltage and the output voltage after a predetermined set time shorter than the increase time after the output current is increased to the increase current increases as the difference increases. The amount of the cation impurity is estimated so as to increase as the difference between the minimum voltage and the base output voltage increases, or the output voltage is increased to the increased current and the output voltage is increased to the steady voltage. Is configured to estimate the amount of cationic impurities so as to increase as the time required to reach
The fuel cell system according to claim 2. The increased current is the output current when the load of the fuel cell system is full load.
The fuel cell system according to claim 2 or 3. When the base output current of the fuel cell single cell is smaller than a threshold current, the cation impurity amount estimation unit increases the output current of the fuel cell single cell stepwise to the increased current, and the measurement is performed at this time. Configured to estimate the amount of cationic impurities based on the output voltage
The fuel cell system according to any one of claims 2 to 4. The cation impurity estimation unit holds an output voltage at a predetermined output voltage and / or an output voltage at a predetermined output current after holding the output voltage of the single fuel cell at a predetermined voltage value for a predetermined time. Is configured to estimate the amount of cationic impurities based on
The fuel cell system according to claim 1. An operation result storage unit configured to store an operation result of the fuel cell stack;
The cation impurity amount estimation unit is configured to estimate the cation impurity amount based on the operation results of the fuel cell stack with reference to the operation result storage unit.
The fuel cell system according to claim 1. A correlation parameter measurement unit that measures a value of a parameter correlated with the relative humidity of the electrolyte membrane in the fuel cell stack;
The processing degree determination unit determines, based on the measured value of the parameter, that when the relative humidity is low, the degree of the activation process is increased compared to when the relative humidity is high.
The fuel cell system according to any one of claims 1 to 7. The parameter is the temperature, impedance, or humidity of gas near the electrolyte membrane in or near the fuel cell stack,
The fuel cell system according to claim 8. A latest history storage unit configured to store a history of output within a predetermined time period closest to the fuel cell stack;
The processing degree determination unit is configured to determine the degree of the activation process higher when the output within the most recent predetermined time is high compared to when the output is low.
The fuel cell system according to any one of claims 1 to 9. When the fuel cell system is idling, an activation process is performed in which the cathode potential of at least one fuel cell single cell of the fuel cell system is temporarily reduced to the ultimate potential over the duration with a processing frequency. A processing unit configured to:
When the fuel cell system is operated with the base output current and the base output voltage, the output current of the single fuel cell is increased stepwise from the base output current to a predetermined increase current to increase the time. Hold over,
Measure the output voltage of the fuel cell single cell in the increased time,
When the output current is increased and held stepwise up to the increased current, the output voltage decreases stepwise from the base output voltage to a minimum voltage and then increases toward a steady voltage lower than the base output voltage. When the difference in the minimum voltage with respect to the output voltage after a predetermined set time shorter than the increase time after the output current is increased to the increase current is increased, the base As the difference between the minimum voltage and the output voltage increases, or as the time required for the output voltage to reach the steady voltage after the output current is increased to the increased current, the activation process increases. The condition is any one of decreasing the arrival potential, increasing the duration, and increasing the processing frequency. Other by combining at least two of them, the processing order determining unit that determines to increase the extent of the activation treatment,
With
The processing unit executes the activation processing with the degree determined by the processing degree determination unit.
Fuel cell system. When the fuel cell system is idling, an activation process is performed in which the cathode potential of at least one fuel cell single cell of the fuel cell system is temporarily reduced to the ultimate potential over the duration with a processing frequency. A processing unit configured to:
After the output voltage of the single fuel cell is held at a predetermined voltage value for a predetermined time, an output current at a predetermined output voltage and / or an output voltage at a predetermined output current is acquired, and the predetermined output When the value of the output current in voltage and / or the value of the output voltage in the predetermined output current is relatively small, the activation process condition is set to the ultimate potential compared to when the value is relatively large. , Increase the duration, and increase the processing frequency, or by combining at least two of them, the degree of the activation processing is determined to be increased A processing degree determination unit to perform,
With
The processing degree processing unit executes the activation processing with the degree determined by the determining unit.
Fuel cell system.

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