JP2015204253A - Control method of fuel battery system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control method of a fuel battery system for improving a discharge performance by resolving a dried state of a fuel battery.SOLUTION: This method of controlling a fuel battery system is to control the fuel battery system including a fuel cell assembly formed by a plurality of fuel battery cells, a fuel gas passage for supplying a fuel gas to an anode electrode, a fuel gas pressure adjusting device disposed on the fuel gas passage for pulsating the pressure of the fuel gas, and a resistance measuring apparatus for measuring the resistance value of either one of the fuel battery cell and the fuel cell assembly, and carrying ouf no circulation of the fuel gass. The pulsation width of the fuel gas is set at a prescribed value ΔPby the fuel gas pressure adjusting device and the fuel battery assembly is operated, and during operation, when the resistance value of at least either one of the fuel battery cell and the fuel battery assembly, that is measured by the resistance measuring device, is higher than a prescribed reference value, the pulsation width of the fuel gas pressure is increased from ΔP, and when the resistance value is not more than the reference value R, the operation of the fuel battery system is continued.

Description

  The present invention relates to a control method for a fuel cell system that eliminates the dry state of the fuel cell and improves discharge performance.

  The technology of the fuel cell system for controlling the dry and wet state in the gas flow path has been known so far. Patent Document 1 discloses a fuel cell system provided with an increase / decrease difference setting means for reducing an increase / decrease difference set according to a required output to the fuel cell when the amount of liquid water in the anode flow path is small.

JP 2013-191370 A

In the invention of Patent Document 1, the aim is to increase the amount of liquid water in the anode flow path by reducing the pressure increase / decrease difference. However, as a result of the study by the present inventors, it has been clarified that the dry state in the gas flow path may advance by reducing the pressure increase / decrease difference.
The present invention has been accomplished in view of the above circumstances, and an object of the present invention is to provide a control method of a fuel cell system that eliminates the dry state of the fuel cell and improves the discharge performance.

A control method for a fuel cell system according to the present invention is a fuel cell assembly in which a plurality of fuel cell cells each including a membrane / electrode assembly including an anode electrode on one surface side and a cathode electrode on the other surface side are assembled. A fuel gas passage disposed on one side of the membrane-electrode assembly and supplying fuel gas to the anode electrode, and a fuel gas pressure disposed on the fuel gas passage and pulsating the pressure of the fuel gas A method for controlling a fuel cell system, comprising: an adjustment device; and a resistance measurement device that measures a resistance value of at least one of a fuel cell and a fuel cell assembly, and does not circulate fuel gas. , pulsation width of the fuel gas pressure to operate the fuel cell assembly as the predetermined value [Delta] P ₀ by the fuel gas pressure regulating device, in the operation, fuel cell and the fuel collector by the resistance measuring device A first resistance value of at least one of the assemblies is measured, when the first resistance value is higher than a predetermined reference value R _0, the fuel gas pressure regulating device, the pulsation width of the fuel gas pressure The pulsation width ΔP ₀ is increased, and when the first resistance value is equal to or less than the reference value R ₀ , the operation of the fuel cell system is continued.

In the present invention, the fuel cell system includes a resistance change rate measuring device that measures a change rate with respect to time of the resistance value of at least one of the fuel cell and the fuel cell assembly, and the pulsation width of the fuel gas pressure When the resistance change rate after increasing the pulsation width is measured by the resistance change rate measuring device and the resistance change rate after increasing the pulsation width is less than a predetermined reference value α ₀ (<0). The pulsation width of the fuel gas pressure is maintained for a predetermined time, and the pulsation width of the fuel gas pressure is further increased by the fuel gas pressure adjustment device when the resistance change rate after the pulsation width increase is not less than the reference value α ₀ and less than 0. When the resistance change rate after increasing and increasing the pulsation width is 0 or more, it is preferable to reduce the pulsation width of the fuel gas pressure below the ΔP ₀ .

In the present invention, the pulsation width of the fuel gas pressure is maintained for a predetermined time based on the measured value of the resistance change rate after the increase of the pulsation width, and at least one of the fuel cell and the fuel cell assembly is obtained by the resistance measurement device. One of the second resistance values is measured, and when the second resistance value is higher than the reference value _R0 , the resistance change rate is measured again by the resistance change rate measuring device, and the second resistance value is measured. When the value is less than or equal to the reference value R _0, it is preferable to continue the operation of the fuel cell system.

In the present invention, when the pulsation width of the fuel gas pressure is reduced, the resistance change rate after the reduction of the pulsation width is measured by the resistance change rate measuring device, and the resistance change rate after the reduction of the pulsation width is the reference value α. _When it is less than _0, the pulsation width of the fuel gas pressure is maintained for a predetermined time, and when the resistance change rate after the pulsation width is reduced is equal to or more than the reference value α ₀ and less than 0, the fuel gas pressure is adjusted by the fuel gas pressure adjusting device. It is preferable to continue the operation of the fuel cell system when the pulsation width is further reduced and the resistance change rate after the pulsation width reduction is 0 or more.

In the present invention, when the pulsation width of the fuel gas pressure is maintained for a predetermined time based on the measured value of the resistance change rate after the pulsation width is reduced, at least one of the fuel cell and the fuel cell assembly is obtained by the resistance measurement device. One of the third resistance values is measured, and when the third resistance value is higher than the reference value R ₀ , the resistance change rate is measured again by the resistance change rate measuring device, and the third resistance value is measured. When the value is less than or equal to the reference value R _0, it is preferable to continue the operation of the fuel cell system.

  In the present invention, the fuel cell system further includes an oxidant gas channel disposed on the other surface side of the membrane-electrode assembly and supplying an oxidant gas to the cathode electrode, and the fuel gas channel and Preferably, the oxidant gas flow path is disposed so that the flow direction of the fuel gas and the flow direction of the oxidant gas face each other, and the fuel cell system does not perform humidification control.

  According to the present invention, by increasing the pulsation width of the fuel gas pressure, the dry state can be eliminated and the discharge characteristics of the fuel cell system can be improved.

It is a figure which shows an example of the fuel cell used for this invention, Comprising: It is the figure which showed typically the cross section cut | disconnected in the lamination direction. It is a schematic diagram of a circuit showing an example of a fuel cell system controlled in the present invention. It is a graph which shows the relationship between a hydrogen pressure pulsation width and a fuel cell voltage. In the control method of this invention, the fuel gas pressure, the pulsation width | variety of fuel gas pressure, the time change rate of resistance, and four graphs showing each time change of resistance typically were shown side by side. It is a flowchart which shows 1st Embodiment of the control method of this invention. It is a flowchart which shows 2nd Embodiment of the control method of this invention. It is a flowchart which shows 3rd Embodiment of the control method of this invention. It is a flowchart which shows a part of 4th Embodiment of the control method of this invention. It is a flowchart which shows a part of 5th Embodiment of the control method of this invention.

A control method for a fuel cell system according to the present invention is a fuel cell assembly in which a plurality of fuel cell cells each including a membrane / electrode assembly including an anode electrode on one surface side and a cathode electrode on the other surface side are assembled. A fuel gas passage disposed on one side of the membrane-electrode assembly and supplying fuel gas to the anode electrode, and a fuel gas pressure disposed on the fuel gas passage and pulsating the pressure of the fuel gas A method for controlling a fuel cell system, comprising: an adjustment device; and a resistance measurement device that measures a resistance value of at least one of a fuel cell and a fuel cell assembly, and does not circulate fuel gas. , pulsation width of the fuel gas pressure to operate the fuel cell assembly as the predetermined value [Delta] P ₀ by the fuel gas pressure regulating device, in the operation, fuel cell and the fuel collector by the resistance measuring device A first resistance value of at least one of the assemblies is measured, when the first resistance value is higher than a predetermined reference value R _0, the fuel gas pressure regulating device, the pulsation width of the fuel gas pressure The pulsation width ΔP ₀ is increased, and when the first resistance value is equal to or less than the reference value R ₀ , the operation of the fuel cell system is continued.

The discharge state of the fuel cell depends greatly on the water content in the cell. In particular, during a high temperature operation of 70 ° C. or higher, a voltage drop due to drying tends to occur. In a so-called circulation-less system in which the supply gas is not circulated, the counterflow effect is reduced, so that a voltage drop due to drying may occur even at a temperature of about 60 ° C. or at a low load.
As a method for mitigating the reduction of the counterflow effect, a technique of pulsating the pressure of the fuel gas with a constant amplitude is known. By pulsating the pressure of the fuel gas and instantaneously increasing the fuel gas flow rate, the fuel gas can be spread over the entire fuel gas flow path, and as a result of the electrode reaction proceeding evenly inside the fuel cell, water generated As a result, the entire fuel gas channel can be sufficiently moistened, and drying can be suppressed. Further, since the supply amount of the fuel gas can be suppressed as compared with the case where the pressure of the fuel gas is always high, the fuel consumption can be saved in the circulation-less system in which the fuel gas is not reused.

As described above, the present inventors have found that in a fuel cell that pulsates the pressure of fuel gas, the dry state further proceeds by reducing the width of the pulsation. FIG. 3 is a graph showing the relationship between the hydrogen pressure pulsation width and the fuel cell voltage. This graph was obtained under a temperature condition of 60 ° C. and a current density condition of 0.2 A / cm ² . As can be seen from FIG. 3, when the pulsation width exceeds 30 kPa, the cell voltage gradually decreases. However, when the pulsation width is smaller than 20 kPa, the cell voltage rapidly decreases. That is, it can be seen that if the pulsation width is reduced from a certain pulsation width, the possibility that the cell voltage is greatly reduced is higher. Under these temperature and current density conditions, the cell voltage can be maintained high by setting the pulsation width to 20 kPa or more and 30 kPa or less, and if the pulsation width is out of the range, a high cell voltage cannot be expected. It becomes. As described above, the pulsation width of the fuel gas has an optimum value or optimum range in which the cell voltage can be kept high.

  As a result of diligent efforts, the present inventors have maintained the optimum value or optimum range of the pulsation width on the basis of a map showing the relationship between the pulsation width of the fuel gas pressure and the cell voltage. It was possible to suppress the voltage reduction and to further improve the fuel consumption, and the present invention was completed.

  FIG. 1 is a view showing an example of a fuel cell used in the present invention, and is a view schematically showing a cross section cut in the stacking direction. The membrane / electrode assembly 8 includes a polymer electrolyte membrane (hereinafter sometimes simply referred to as an electrolyte membrane) 1 having hydrogen ion conductivity, and a pair of cathode electrode 6 and anode electrode 7 sandwiching the electrolyte membrane 1. . The fuel cell (single cell) 100 includes a membrane / electrode assembly 8 and a pair of separators 9 and 10 that sandwich the membrane / electrode assembly 8 from the outside of the electrode. An oxidant gas passage 11 and a fuel gas passage 12 are secured at the boundary between the separator and the electrode. Usually, a laminated body of a catalyst layer and a gas diffusion layer is used as an electrode in order from the electrolyte membrane side. That is, the cathode electrode 6 includes a stacked body of the cathode catalyst layer 2 and the gas diffusion layer 4, and the anode electrode 7 includes a stacked body of the anode catalyst layer 3 and the gas diffusion layer 5.

  The polymer electrolyte membrane is a polymer electrolyte membrane used in a fuel cell, and is a fluorine polymer electrolyte membrane containing a fluorine polymer electrolyte such as perfluorocarbon sulfonic acid resin represented by Nafion (trade name). In addition, sulfonic acid groups are used in hydrocarbon polymers such as engineering plastics such as polyether ether ketone, polyether ketone, polyether sulfone, polyphenylene sulfide, polyphenylene ether, and polyparaphenylene, and general-purpose plastics such as polyethylene, polypropylene, and polystyrene. And a hydrocarbon polymer electrolyte membrane including a hydrocarbon polymer electrolyte into which a protonic acid group (proton conductive group) such as a carboxylic acid group, a phosphoric acid group, or a boronic acid group is introduced.

The electrode preferably includes a catalyst layer and a gas diffusion layer.
Both the anode catalyst layer and the cathode catalyst layer can be formed using a catalyst ink containing a catalyst, a conductive material, and a polymer electrolyte.
As the polymer electrolyte, the same material as the polymer electrolyte membrane described above can be used.
As the catalyst, usually, a catalyst component supported on conductive particles is used. The catalyst component is not particularly limited as long as it has catalytic activity for the oxidation reaction of the fuel supplied to the anode electrode or the reduction reaction of the oxidant supplied to the cathode electrode. What is generally used for the fuel cell can be used. For example, platinum or an alloy of platinum and a metal such as ruthenium, iron, nickel, manganese, cobalt, and copper can be used. As the conductive particles as the catalyst carrier, carbon particles such as carbon black, conductive carbon materials such as carbon fibers, and metal materials such as metal particles and metal fibers can also be used. The conductive material also plays a role of imparting conductivity to the catalyst layer.

  The method for forming the catalyst layer is not particularly limited. For example, the catalyst layer may be formed on the surface of the gas diffusion sheet by applying catalyst ink to the surface of the gas diffusion sheet and drying, or the polymer electrolyte membrane. A catalyst layer may be formed on the surface of the polymer electrolyte membrane by applying a catalyst ink on the surface and drying. Alternatively, a transfer sheet is prepared by applying a catalyst ink to the surface of the transfer substrate and drying, and the transfer sheet is bonded to the polymer electrolyte membrane or the gas diffusion sheet by thermocompression bonding or the like. A catalyst layer may be formed on the surface of the polymer electrolyte membrane or a catalyst layer may be formed on the surface of the gas diffusion sheet by a method of peeling the material film.

  The catalyst ink is obtained by dispersing the above catalyst, electrode electrolyte, and the like in a solvent. The solvent of the catalyst ink may be appropriately selected. For example, alcohols such as methanol, ethanol and propanol, organic solvents such as N-methyl-2-pyrrolidone (NMP) and dimethyl sulfoxide (DMSO), or organic solvents such as these Mixtures and mixtures of these organic solvents and water can be used. In addition to the catalyst and the electrolyte, the catalyst ink may contain other components such as a binder and a water repellent resin as necessary.

  The method for applying the catalyst ink, the drying method, and the like can be selected as appropriate. For example, examples of the coating method include a spray method, a screen printing method, a doctor blade method, a gravure printing method, a die coating method, and the like. Examples of the drying method include reduced pressure drying, heat drying, and reduced pressure heat drying. There is no restriction | limiting in the specific conditions in reduced pressure drying and heat drying, What is necessary is just to set suitably. The thickness of the catalyst layer is not particularly limited, but may be about 1 to 50 μm.

  As the gas diffusion sheet for forming the gas diffusion layer, a gas diffusion property capable of efficiently supplying fuel to the catalyst layer, conductivity, and a strength required as a material constituting the gas diffusion layer, for example, Carbonaceous porous bodies such as carbon paper, carbon cloth, carbon felt, titanium, aluminum and alloys thereof, nickel, nickel-chromium alloy, copper and alloys thereof, silver, zinc alloy, lead alloy, niobium, tantalum, iron, Examples thereof include a metal mesh composed of a metal such as stainless steel, gold or platinum, or a conductive porous material such as a metal porous material. The thickness of the conductive porous body is preferably about 50 to 500 μm.

The gas diffusion sheet may be composed of a single layer of the conductive porous material, but a water repellent layer may be provided on the side facing the catalyst layer. The water-repellent layer usually has a porous structure containing conductive particles such as carbon particles and carbon fibers, water-repellent resin such as polytetrafluoroethylene (PTFE), and the like. The water-repellent layer is not always necessary, but it can improve the drainage of the gas diffusion layer while maintaining an appropriate amount of liquid water in the catalyst layer and the polymer electrolyte membrane. There is an advantage that the electrical contact between the layers can be improved.
The polymer electrolyte membrane and the gas diffusion sheet on which the catalyst layer is formed by the above-described method are appropriately overlapped and subjected to thermocompression bonding or the like, and bonded together to obtain a membrane / electrode assembly.

  The produced membrane / electrode assembly is preferably held by a separator having a reaction gas flow path to form a single cell. The separator has conductivity and gas sealing properties, and can function as a current collector and gas sealing body, for example, a carbon separator containing a high concentration of carbon fiber and made of a composite material with resin, metal A metal separator using a material can be used. Examples of the metal separator include those made of a metal material excellent in corrosion resistance, and those coated with a coating that enhances the corrosion resistance by coating the surface with carbon or a metal material excellent in corrosion resistance. . The reaction gas flow path described above can be formed by appropriately compression molding or cutting such a separator.

FIG. 2 is a schematic diagram of a circuit showing an example of a fuel cell system controlled in the present invention. The arrows in FIG. 2 indicate both the gas flow path and the gas flow direction in the flow path. Moreover, the double wavy line in FIG.
The fuel cell assembly in FIG. 2 indicates, for example, a fuel cell stack when a flat cell as shown in FIG. 1 is adopted as the fuel cell. Further, when a hollow fiber cell is adopted as the fuel cell, the fuel cell assembly refers to a bundle of the hollow fiber cells twisted together.

  The oxidant gas flow path 11 and the fuel gas flow path 12 in FIG. 2 correspond to the oxidant gas flow path 11 or the fuel gas flow path 12 shown in FIG. As shown in FIG. 2, the oxidant gas flow path 11 and the fuel gas flow path 12 are preferably arranged so that the flow direction of the oxidant gas and the flow direction of the fuel gas face each other. By facing the gas flow directions in this way (so-called counter flow), water generated near the outlet of the oxidant gas flow path can be transported to the vicinity of the fuel gas flow path through the electrolyte membrane. The entire gas flow path can be appropriately moistened. Therefore, when adopting the counter flow configuration, it is not necessary to perform the humidification control of the fuel cell assembly.

The resistance measuring device 21 in FIG. 2 is a device that measures the resistance value of at least one of the fuel cell assembly and the fuel cells constituting the assembly. The resistance measuring device 21 may be provided outside the fuel cell assembly as shown in FIG. 2 or may be incorporated in the fuel cell assembly. The resistance measured by the resistance measuring device is an index indicating whether or not the fuel cell is operating well, specifically, whether or not the inside of the fuel cell is wet or dry.
Specific examples of the resistance measuring device include an ohmmeter and an impedance measuring device.
The fuel cell system according to the present invention may include a resistance change rate measuring device. The resistance change rate measured by the measuring device refers to the change rate with respect to time of the resistance value of at least one of the fuel cell assembly and the fuel cell constituting the assembly.
The resistance measuring device and the resistance change rate measuring device may be the same device or different devices. Further, the resistance change rate measuring device may be a device that calculates a resistance change rate based on a resistance value measured by the resistance measuring device.

  In the fuel cell system controlled in the present invention, a so-called fuel gas circulation-less system that does not circulate the fuel gas is employed. In the fuel gas circulation-less system, the frequency of the fuel cell is exposed to drying to reduce the counter flow effect due to the decrease in the fuel gas flow rate. Therefore, the control for drying suppression is particularly effective in the fuel gas circulation-less system.

The fuel gas pressure adjusting device in FIG. 2 is a device that is arranged on the fuel gas flow path and pulsates the pressure of the fuel gas supplied to the fuel cell assembly.
In the present invention, “pulsating the pressure of the fuel gas” means that the pressure of the fuel gas is periodically increased and decreased within a certain width. The period of pulsation is approximately in the range of 1 to 10 Hz, although it varies depending on the scale of the fuel cell assembly.
The fuel gas pressure adjusting device used in the present invention may be the fuel gas supply device itself, a device attached to the fuel gas supply device, or a device different from the fuel gas supply device. May be. Specific examples of the fuel gas pressure adjusting device include an injector.
The fuel gas used for this invention will not be specifically limited if it is normally used for a fuel cell, For example, hydrogen gas etc. are mentioned.

The fuel cell system preferably has in advance a map of the relationship between the pulsation width of the fuel gas pressure and the fuel cell voltage as shown in FIG. The map in this case varies depending on the structure of the fuel battery cell, and changes one by one depending on operating conditions such as current and temperature.
A map showing the relationship between the pulsation width of the fuel gas pressure and the fuel cell voltage may be stored in advance in the storage means. In this case, an optimal map can be selected from the storage means depending on the operating environment of the fuel cell.
Note that the storage unit may newly read a pulsation width considered to be optimum fed back from each step of control described later as a map. By updating the map one by one in this way, it is possible to acquire fuel cell aging data.
Specific examples of the storage means for storing the map include a semiconductor storage device such as a memory and a magnetic storage device such as a hard disk.

The fuel cell system is basically operated according to the above map while selecting the optimum pulsation width of the fuel gas pressure on the map. However, when the fuel cell system is put to practical use (for example, in the case of a so-called ON board), such as when the fuel cell system is mounted on a car, an increase in the resistance value of the fuel cell and / or the fuel cell assembly is detected. In addition, it is desirable to optimize the pulsation width of the fuel gas pressure based on a control method independent of the map. This is because the fuel cell system installed in the vehicle can be operated more efficiently by adjusting the pulsation width in a flexible manner according to the control method described later according to environmental changes such as road conditions. It is to become.
When the resistance value of the fuel cell and / or the fuel cell assembly is sufficiently lowered and the normal operation is resumed, the control according to the present invention is terminated and the map is called again to select the pulsation width of the fuel gas pressure. The operation of the fuel cell system may be continued.

An outline of control using the fuel cell system described above will be described with reference to FIG. FIG. 4 shows four graphs schematically showing the fuel gas pressure, the pulsation width of the fuel gas pressure, the time change rate of the resistance, and each time change of the resistance in the control method of the present invention. . From the upper graph of FIG. 4, a graph showing the time change of the fuel gas pressure, a graph showing the time change of the pulsation width of the fuel gas pressure, a graph showing the relationship between the time change rate of resistance and time, and the resistance and time It is a graph which shows the relationship.
In FIG. 4, the fuel gas pressure and its pulsation width are so-called inputs to the fuel cell system, whereas the resistance and its rate of change with time correspond to the output of the fuel cell system.

In FIG. 4, from time 0 to t ₁ , the fuel cell assembly is operated with the pulsation width of the fuel gas pressure as the initial value ΔP ₀ . The initial value ΔP ₀ is a value that matches the map as described above. However, in FIG. 4, the resistance value R ₁ of the fuel cell is higher than a desired resistance value R _0. Therefore, in order to reduce the resistance value, control for adjusting the pulsation width is performed independently of the map.
At time t ₁ , the pulsation width of the fuel gas pressure is slightly increased from the initial value ΔP ₀ . Thus, the instantaneous stoichiometric ratio of the fuel gas can be increased by increasing the pulsation width of the fuel gas pressure. As a result, compared also with its state prior to time t _1, the entire fuel gas flow field can be spread to the fuel gas, so that the fuel gas flow path slightly wet. The resistance value R is an indicator of the wet state. At the time t _{1 when} the pulsation width of the fuel gas pressure is increased, the resistance value starts to decrease, but becomes constant with the passage of time and does not reach the target resistance value R ₀ .

Therefore, by increasing more the pulsation width of the fuel gas pressure at the time t _2, further increase the instantaneous stoichiometric ratio of the fuel gas. As a result, compared to the prior time t ₂ state, further it can supply fuel gas to the entire fuel gas flow path, so that the fuel gas flow passage is sufficiently wetted. The wet state of the fuel gas channel can be confirmed from the resistance value. At time t ₂ with increased pulsation width of the fuel gas pressure, the resistance value begins further down, after a set time has elapsed, the resistance value is less than R _0. From this result, it was increased pulsation width of the fuel gas constant pressure or more at time t _2, it can be seen effective to correct the dryness of the fuel gas passage.
Thus, after the resistance value becomes less than the target R ₀ , the pulsation width of the fuel gas pressure is controlled along the map, and the operation of the fuel cell system is continued.

The wet state of the fuel gas channel can also be estimated from the time rate of change of resistance (dR / dt). Fixed time from the time t ₁ with increased pulsation width of the fuel gas pressure, the time rate of change of resistance is less than 0. Since the resistance value becomes constant over time, the time change rate of resistance returns to zero.
When increasing the pulse width of the fuel gas pressure, when the time rate of change of resistance is less than the predetermined value alpha _0, the resistance itself may be determined that sufficient Decreased. For example, as shown in FIG. 4, when the pulsation width of the fuel gas pressure is increased at time t ₁ , the resistance time change rate exceeds a predetermined value α ₀ , and therefore the resistance reduction is still insufficient. I can judge. On the other hand, the time change rate of the resistance is less than the predetermined value α _{0 for a} certain time from time t _{2 when} the pulsation width of the fuel gas pressure is further increased. From this result, by increasing the pulse width of the fuel gas pressure at the time t _2, it may be determined that the resistance is sufficiently lowered.

The initial value ΔP ₀ of the pulsation width of the fuel gas pressure is obtained by mapping the relationship between the fuel gas pulsation width and the cell voltage as shown in FIG. 3 under a predetermined temperature and current density. It is preferable to use it as a constant. Further, since the initial value ΔP ₀ varies depending on the structure of the fuel cell, it is more preferable to map it for each structure of the fuel cell.

FIG. 5 is a flowchart showing the first embodiment of the control method of the present invention. Hereinafter, the first embodiment will be described with reference to FIGS. 2 and 5.
First, the fuel cell assembly is operated by the fuel gas pressure adjusting device with the pulsation width of the fuel gas pressure set to a predetermined value ΔP ₀ (S1). Next, during operation, the resistance value R ₁ (first resistance value) of the fuel cell and / or the fuel cell assembly is measured by the resistance measurement device (S2, S3). Resistance R ₁ is in the case of less than the reference value R ₀ is completed the control, to continue the operation of the fuel cell system. On the other hand, when the resistance value R ₁ is greater than the reference value R ₀ is the fuel gas pressure regulating device, the pulsation width of the fuel gas pressure, increased to greater [Delta] P ₁ than the [Delta] P ₀ (S4), and ends the control Continue the operation of the fuel cell system.
The number of increases in the pulsation width of the fuel gas pressure may be two as shown in FIG. 4 or more.

FIG. 6 is a flowchart showing a second embodiment of the control method of the present invention. Hereinafter, the second embodiment will be described with reference to FIGS. 2 and 6. In the second to fifth embodiments, the fuel cell system further includes the resistance change rate measuring device.
Steps S11 to S14 are the same as S1 to S4 of the first embodiment described above. However, in the second embodiment, after increasing the pulsation width of the fuel gas pressure to ΔP ₁ (S14), the resistance change rate is measured by the resistance change rate measuring device (S15). Hereinafter, the resistance change rate measured after increasing the pulsation width may be referred to as the resistance change rate after increasing the pulsation width.
When the resistance change rate after the pulsation width increase is less than the predetermined reference value α ₀ (<0) (S16), the pulsation width of the fuel gas pressure is maintained for a predetermined time (S17), and the control is terminated. On the other hand, when the rate of change in resistance after increasing the pulsation width is greater than or equal to the reference value α ₀ and less than 0 (S18), the pulsation width of the fuel gas pressure is further increased to ΔP ₂ (> ΔP ₁ ) by the fuel gas pressure adjusting device. (S19), the control is terminated. When the resistance change rate after the pulsation width increase is 0 or more, the pulsation width of the fuel gas pressure is set to ΔP ₃ smaller than ΔP ₀ (S20), and the control is terminated.

FIG. 7 is a flowchart showing a third embodiment of the control method of the present invention. Hereinafter, the third embodiment will be described with reference to FIGS. 2 and 7. The three-point reader in FIG. 7 means that the flowchart is omitted.
S31 to S40 are the same as S11 to S20 of the second embodiment described above. However, in the third embodiment, after maintaining the pulsation width of the fuel gas pressure for a predetermined time (S37), the resistance value R ₂ of the fuel cell and / or fuel cell assembly is measured by the resistance measurement device (second Resistance value) is measured (S41). Resistance R ₂ is in the case of less than the reference value R ₀ is completed the control, to continue the operation of the fuel cell system. On the other hand, when the resistance value R ₂ is higher than the reference value R ₀ is the resistance variation rate measuring device measures the resistance change rate again (S35), by comparing the said rate of change in resistance and the reference value alpha ₀ Fuel The pulsation width of the gas pressure is determined again (S36 to S40).

In the third embodiment, when the pulsation width of the fuel gas pressure is increased to ΔP ₂ (> ΔP ₁ ) (S39), the resistance change rate is measured again by the resistance change rate measuring device (S35 ′). Then, the resistance change rate is compared with the reference value α ₀ to determine the pulsation width of the fuel gas pressure again (S36 ′). S35 ′ and S36 ′ correspond to S35 and S36. Further, in the omitted portion shown in the three-point reader, S37 ′ to S42 ′ similar to S37 to S42 are performed. In this way, after increasing the pulsation width of the fuel gas pressure, the resistance change rate is measured, and the resistance change rate is compared with the reference value α ₀ to repeatedly determine the pulsation width of the fuel gas pressure. You can also.

FIG. 8 is a flowchart showing a part of the fourth embodiment of the control method of the present invention (the second half of the fourth embodiment). The first half of the fourth embodiment is the same as the second and third embodiments. S20 of the second embodiment and S40 of the third embodiment correspond to S50 of the fourth embodiment. Hereinafter, the second half of the fourth embodiment will be described with reference to FIGS. 2 and 8.
In the fourth embodiment, after reducing the pulsation width of the fuel gas pressure from ΔP ₁ to ΔP ₃ (S50), the resistance change rate is measured by the resistance change rate measuring device (S51). Hereinafter, the resistance change rate measured after reducing the pulsation width may be referred to as the resistance change rate after the pulsation width reduction.
When the resistance change rate after the pulsation width reduction is less than the reference value α ₀ (<0) (S52), the pulsation width of the fuel gas pressure is maintained for a predetermined time (S53), and the control is terminated. On the other hand, when the rate of change in resistance after the reduction of the pulsation width is greater than or equal to the reference value α ₀ and less than 0 (S54), the pulsation width of the fuel gas pressure is further reduced to ΔP ₄ (<ΔP ₃ ) by the fuel gas pressure regulator. (S55), the control is terminated. If the rate of change in resistance after increasing the pulsation width is 0 or more, it is considered that at least the pulsation width is not the cause of the decrease in resistance.

FIG. 9 is a flowchart showing a part of the fifth embodiment of the control method of the present invention (the second half of the fifth embodiment). Note that the first half of the fifth embodiment is the same as the second and third embodiments. S20 of the second embodiment and S40 of the third embodiment correspond to S60 of the fifth embodiment. Hereinafter, the second half of the fifth embodiment will be described with reference to FIGS. 2 and 9. The three-point reader in FIG. 9 means that the flowchart is omitted.
S60 to S65 are the same as S50 to S55 of the fourth embodiment described above. However, in the fifth embodiment, after maintaining the pulsation width of the fuel gas pressure for a predetermined time (S63), the resistance value R ₃ (third value of the fuel cell assembly and / or the fuel cell assembly is measured by the resistance measurement device. Resistance value) is measured (S66). The resistance value R ₃ in the case of less than the reference value R ₀ is completed the control, to continue the operation of the fuel cell system. On the other hand, when the resistance value R ₃ greater than the reference value R ₀ is the resistance variation rate measuring device measures the resistance change rate again (S61), by comparing the said rate of change in resistance and the reference value alpha ₀ Fuel The pulsation width of the gas pressure is determined again (S62 to S65).

In the fifth embodiment, when the pulsation width of the fuel gas pressure is reduced to ΔP ₄ (<ΔP ₃ ) (S65), the resistance change rate is measured again by the resistance change rate measuring device (S61 ′). Then, the resistance change rate is compared with the reference value α ₀ to determine the pulsation width of the fuel gas pressure again (S62 ′). S61 ′ and S62 ′ correspond to S61 and S62. Further, in the omitted portion shown in the three-point reader, S63 ′ to S67 ′ similar to S63 to S67 are performed. In this way, after reducing the pulsation width of the fuel gas pressure, the resistance change rate is measured, and the resistance change rate and the reference value α ₀ are compared to determine the pulsation width of the fuel gas pressure repeatedly. You can also.
In addition, the control method of this invention is not necessarily limited only to the said 1st-5th embodiment.

DESCRIPTION OF SYMBOLS 1 Polymer electrolyte membrane 2 Cathode catalyst layer 3 Anode catalyst layer 4, 5 Gas diffusion layer 6 Cathode electrode 7 Anode electrode 8 Membrane / electrode assembly 9, 10 Separator 11 Oxidant gas flow channel 12 Fuel gas flow channel 21 Resistance measuring device 100 Fuel cell single cell

Claims (6)

A fuel cell assembly comprising a plurality of fuel cell units each including a membrane / electrode assembly including an anode electrode on one side of the electrolyte membrane and a cathode electrode on the other side;
A fuel gas flow path disposed on one side of the membrane-electrode assembly and supplying fuel gas to the anode electrode;
A fuel gas pressure adjusting device disposed on the fuel gas flow path and pulsating the pressure of the fuel gas;
A resistance measuring device that measures the resistance value of at least one of the fuel cell and the fuel cell assembly, and
A method of controlling a fuel cell system that does not circulate fuel gas,
The fuel cell assembly is operated with the pulsation width of the fuel gas pressure set to a predetermined value ΔP ₀ by the fuel gas pressure adjusting device,
During the operation, the resistance measuring device measures a first resistance value of at least one of the fuel cell and the fuel cell assembly,
When the first resistance value is higher than a predetermined reference value R ₀ , the pulsation width of the fuel gas pressure is increased from the pulsation width ΔP ₀ by the fuel gas pressure adjusting device,
The method of controlling a fuel cell system, wherein the operation of the fuel cell system is continued when the first resistance value is equal to or less than the reference value _R0 . The fuel cell system includes a resistance change rate measuring device that measures a change rate with respect to time of the resistance value of at least one of the fuel cell and the fuel cell assembly, and
When the pulsation width of the fuel gas pressure is increased,
Measure the resistance change rate after the pulsation width increase by the resistance change rate measuring device,
When the resistance change rate after the pulsation width increase is less than a predetermined reference value α ₀ (<0), the pulsation width of the fuel gas pressure is maintained for a predetermined time,
When the rate of change in resistance after increasing the pulsation width is not less than the reference value α ₀ and less than 0, the pulsation width of the fuel gas pressure is further increased by the fuel gas pressure adjusting device,
2. The method of controlling a fuel cell system according to claim 1, wherein the pulsation width of the fuel gas pressure is reduced from the ΔP ₀ when the resistance change rate after the pulsation width increase is 0 or more. When the pulsation width of the fuel gas pressure is maintained for a predetermined time based on the measured value of the resistance change rate after the pulsation width increase,
Measuring the second resistance value of at least one of the fuel cell and the fuel cell assembly by the resistance measuring device;
When the second resistance value is higher than the reference value _R0 , the resistance change rate is measured again by the resistance change rate measuring device,
The control method of a fuel cell system according to claim 2, wherein the operation of the fuel cell system is continued when the second resistance value is equal to or less than the reference value _R0 . When the pulsation width of the fuel gas pressure is reduced,
Measure the rate of resistance change after pulsation width reduction by the resistance change rate measuring device,
When the resistance change rate after the pulsation width reduction is less than the reference value α ₀ , the pulsation width of the fuel gas pressure is maintained for a predetermined time,
When the resistance change rate after the pulsation width reduction is not less than the reference value α ₀ and less than 0, the pulsation width of the fuel gas pressure is further reduced by the fuel gas pressure adjusting device,
The method for controlling a fuel cell system according to claim 2 or 3, wherein the operation of the fuel cell system is continued when the rate of change in resistance after the reduction of the pulsation width is 0 or more. When the pulsation width of the fuel gas pressure is maintained for a predetermined time based on the measured value of the rate of change in resistance after the pulsation width reduction,
A third resistance value of at least one of the fuel cell and the fuel cell assembly is measured by the resistance measuring device;
When the third resistance value is higher than the reference value R ₀ , the resistance change rate is measured again by the resistance change rate measuring device,
The method of controlling a fuel cell system according to claim 4, wherein the operation of the fuel cell system is continued when the third resistance value is equal to or less than the reference value _R0 . The fuel cell system further includes an oxidant gas channel disposed on the other surface side of the membrane-electrode assembly and supplying an oxidant gas to the cathode electrode,
The fuel gas flow path and the oxidant gas flow path are respectively arranged such that the flow direction of the fuel gas and the flow direction of the oxidant gas face each other,
Furthermore, the fuel cell system control method according to any one of claims 1 to 5, wherein the fuel cell system does not perform humidification control.