JP2016139515A - Estimation method for cation impurity amount and estimation device for cation impurity amount in fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To estimate a cation impurity amount in a cation exchange membrane during an operation of a fuel cell system while suppressing a rise in manufacturing cost.SOLUTION: An estimation method for a cation impurity amount is the one for estimating the cation impurity amount included in an electrolytic material in a membrane electrode gas diffusion layer junction body 5 of at least one fuel cell single cell 2 of a fuel cell system when the fuel cell system A is operated at a base output current IB and a base output voltage VB. The estimation method includes steps of: increasing an output current IOUT of the fuel cell single cell in a step manner from the base output current to a predetermined increased current IG and maintaining that for an increase time Δt0; measuring an output voltage VOUT of the fuel cell single cell in the increase time; and estimating the cation impurity amount on the basis of the measured output voltage of the fuel cell single cell.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method for estimating the amount of cationic impurities and a device for estimating the amount of cationic impurities in a fuel cell system.

  A method for measuring a concentration of conductive impurities such as metal ions eluted in an anode off-gas and a cathode off-gas of a fuel cell stack of a fuel cell system when the fuel cell system is operated, the concentration of the conductive impurities It is determined whether or not the conditions suitable for the measurement are satisfied, and when the conditions are satisfied, the condensed water is generated from the moisture contained in each off-gas by the condenser, and the generated condensed water is electrically conductive. A method for measuring the concentration of conductive impurities is known in which the conductivity is detected by a conductivity sensor, and the concentration of the conductive impurities is calculated from the detected conductivity (see, for example, Patent Document 1).

JP 2007-059265 A

In the fuel cell system, metal cations (cations) may enter the fuel cell single cell of the fuel cell stack by being accompanied by air supplied to the fuel cell stack during the operation of the fuel cell system. is there. Examples of the metal cation entering the single fuel cell include Ca and Na contained in the snow melting agent and Fe, Mo, Cr and Al contained in the fuel cell system components. Here, the cation exchange membrane illustrated by Nafion (trademark) is used for the fuel cell single cell as an electrolyte membrane. Therefore, when a metal cation enters the fuel cell unit cell, it enters the cation exchange membrane and stays in the membrane as it is, thereby replacing the sulfonic acid group in the membrane. Therefore, when the amount of metal cation in the membrane increases, the sulfonic acid group involved in H ⁺ ion conduction decreases in the cation exchange membrane, making it difficult for H ⁺ ions to move, ie, proton conductivity. The battery performance deteriorates due to the decrease. Thus, the amount of cation impurities in the cation exchange membrane is closely related to the degree of deterioration of battery performance. Therefore, knowing the amount of cation impurities in the cation exchange membrane during operation of the fuel cell system estimates the degree of deterioration of the fuel cell stack and single fuel cell during operation, and is appropriate for the degree of deterioration. It is very important to take corrective actions. However, in Patent Document 1, the concentration of conductive impurities in the anode off-gas and cathode off-gas is measured, but the amount of cation impurities in the cation exchange membrane is not measured. Even if the amount of cation impurities in the cation exchange membrane can be estimated from the concentration of the conductive impurities in the anode off-gas and cathode off-gas, additional equipment such as a condenser and a conductivity sensor is required, resulting in production costs. Cause an increase. A technique capable of estimating the amount of cation impurities in the cation exchange membrane during operation of the fuel cell system while suppressing an increase in manufacturing cost is desired.

  According to one aspect of the present invention, when a fuel cell system is operated with a base output current and a base output voltage, the membrane electrode gas diffusion layer assembly of at least one fuel cell single cell of the fuel cell system. A method for estimating the amount of cationic impurities contained in an electrolyte material, wherein the output current of the fuel cell single cell is increased stepwise from the base output current to a predetermined increased current and held for an increased time Measuring the output voltage of the fuel cell unit cell during the increased time, and estimating the amount of cationic impurities based on the measured output voltage of the fuel cell unit cell. A method for estimating the amount of cationic impurities in a fuel cell system is provided.

  According to another aspect of the present invention, when the fuel cell system is operated with the base output current and the base output voltage, the membrane electrode gas diffusion layer assembly of at least one fuel cell unit of the fuel cell system. An apparatus for estimating the amount of cationic impurities contained in the electrolyte material of the fuel cell, wherein the output current of the fuel cell single cell is increased stepwise from the base output current to a predetermined increase current and held for an increase time A current control unit that performs measurement, a measurement unit that measures the output voltage of the single fuel cell during the increase time, and an estimation unit that estimates the amount of the cationic impurities based on the measured output voltage of the single fuel cell An apparatus for estimating the amount of cationic impurities in a fuel cell system is provided.

  The amount of cation impurities in the cation exchange membrane can be estimated during operation of the fuel cell system while suppressing an increase in manufacturing cost.

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 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 typically the relation between the amount of cation impurities, and the amount of voltage drop. It is a figure which illustrates typically the mechanism of the behavior of the output voltage of a fuel cell single cell. It is a flowchart which shows the cationic impurity amount estimation control routine of a fuel cell system. It is a graph which shows an example of the experiment of the output voltage of a fuel cell single cell. 10 is an enlarged graph showing a part of FIG. 9. 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 figure explaining the method to estimate the amount of cationic impurities of another Example. It is a graph which shows typically the relation between the amount of cation impurities, the minimum voltage, and the amount of minimum value drop. It is a graph which shows an example of the experiment of the output voltage of the fuel cell single cell of another Example. It is a figure explaining the method to estimate the amount of cationic impurities of another Example. It is a graph which shows typically the relationship between the amount of cation impurities, and required time. It is a graph which shows an example of the experiment of the output voltage of the fuel cell single cell of another Example. 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 turbo compressor 44 in the oxidant gas supply pipe 41 and to the turbo compressor in the oxidant gas supply pipe 41. When the downstream side oxidant gas supply pipe 41 </ b> D downstream of 44 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 supply pipe 51. 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 which are 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, and Output signals of a pressure sensor and a temperature sensor (not shown) in the fuel cell system A are input to the input port 65 via the corresponding AD converter 67. 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 material of the anode electrode catalyst layer 5as and the cathode electrode catalyst layer 5cs include catalyst-supported carbon that supports a catalyst such as 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. 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, as described above, in the fuel cell system A, during the operation of the fuel cell system A, the Ca, Na, Fe in the electrolyte material of the single fuel cell 2 of the fuel cell stack 10, for example, in the electrolyte membrane 5e. In some cases, cation impurities such as Mo, Cr and Al may enter. In that case, the cation impurities remain in the electrolyte membrane 5e, and the sulfonic acid group in the membrane is replaced. As a result, the proton conductivity of the electrolyte membrane 5e decreases, and the battery performance deteriorates. Therefore, knowing the amount of cation impurities in the electrolyte membrane 5e during the operation of the fuel cell system A estimates the degree of deterioration of the fuel cell stack and the single fuel cell 2 and takes appropriate measures according to the degree of deterioration. Is very important to do.

  Accordingly, the inventors of the present invention have conducted extensive studies to know the amount of cationic impurities in the electrolyte membrane 5e, and as a result, have newly found the following facts. That is, during operation of the fuel cell system A, 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 stepwise, and the cation impurities in the electrolyte membrane 5e The fact is that the quantity has a correlation. Therefore, by 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, the amount of cationic impurities is determined. Can be estimated. Hereinafter, it will be described in detail with reference to the drawings.

  FIG. 3 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. In addition, even when the fuel cell system A is in a no-load state during operation, an open voltage is generated between the anode electrode 5a and the cathode electrode 5c by causing a certain minute output current to flow through the fuel cell stack 10. The anode electrode catalyst layer 5as and the cathode electrode catalyst layer 5cs are prevented from being deteriorated so as not to be applied. In the embodiment shown in FIG. 3, when the output current IOUT of the single fuel cell 2 is such a constant minute current, that is, when the fuel cell system A is in a no-load state, the estimation of the amount of cationic impurities is preferably performed. Is called.

  FIG. 3 shows that 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 fuel cell single cell 2 from the base output current IB at time t1. It shows a case where the increase current IG is increased stepwise to a predetermined increase current IG, and the increase current IG is maintained over an 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. 3 also 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. 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. 3, the increase time Δt0 is a steady 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, the fact that 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 is newly found this time. That is, (1) When the output voltage VOUT at time t2 after a predetermined set time Δt1 after time t1 is VE, the voltage drop amount ΔV that is the difference between the minimum voltage VM with respect to the output voltage VE, (2) 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 the output voltage VOUT reaches the steady voltage VC t22. 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 this embodiment, (1) will be further described.

  Regarding the above (1), FIG. 4 shows the difference between the output voltage VOUTn when the amount of cationic impurities in the electrolyte membrane 5e is small, for example, zero, and the output voltage VOUTc when the amount of impurities is large. Is shown in FIG. 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 a 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, as shown by a solid line in FIG. 4, decreases in a stepped manner from the base output voltage VB to the minimum voltage VMc, and then increases. 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. 5, 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.

  FIG. 6 schematically shows the relationship between the amount of cationic impurities and the amount of voltage drop ΔV. 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 an index of 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. 6 is measured in advance, the substitution rate of the sulfonic acid group, that is, the amount of cationic impurities can be estimated by measuring the voltage drop amount ΔV and referring to the data. . Here, data indicating the graph of FIG. 6 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. 6 is not necessarily clear, but is considered as follows. FIG. 7 is a diagram schematically illustrating the mechanism of the behavior of the output voltage VOUT of the single fuel cell 2. However, the upper diagram shows FIG. 3 reprinted, the middle diagram shows the behavior of moisture W in the electrolyte membrane 5e, and the lower diagram shows the behavior of the cation impurity Q in the electrolyte membrane 5e.

  P1 in the upper diagram is a state at time t0 when the output current IOUT and the output voltage VOUT of the fuel cell stack 10 are the constant base output current IB and the base output voltage VB. At that time, as shown in the middle diagram, the water W in the electrolyte membrane 5e is in a steady state and is present almost uniformly in the membrane. Further, as shown in the lower diagram, the cation impurities Q in the electrolyte membrane 5e are also in a steady state and are present almost uniformly in the membrane.

P2 in the upper diagram indicates that the output current IOUT of the fuel cell stack 10 is increased from the base output current IB in a stepped manner to increase current IG, and the output voltage VOUT is decreased in a stepped manner from the base output voltage VB to the minimum voltage VM. It is in the state. At that time, as shown in the middle figure, H ⁺ ions move in the electrolyte membrane 5e from the anode electrode 5a to the cathode electrode 5c (not shown), so that the water W in the electrolyte membrane 5e becomes H ⁺ ions. Accordingly, since it is biased toward the cathode electrode 5c, the anode electrode 5a side of the electrolyte membrane 5e is dried. Here, as shown in the lower figure, since the diffusion coefficient of the cation impurity Q in the electrolyte membrane 5e is small, the cation impurity Q cannot move as fast as H ⁺ ions, that is, the output current IOUT increases. Immediately after the movement, it hardly moves and remains almost uniformly in the film. Therefore, in the vicinity of the anode 5a of the electrolyte membrane 5e, the proportion of moisture W is relatively small due to the effect of accompanying water, and the proportion of the cationic impurities Q that inhibit the conduction of H ⁺ ions is relatively high. The internal resistance increases and the output voltage OUT decreases rapidly. The degree of this decrease, that is, the voltage drop amount ΔV, is considered to increase as the proportion of ions that inhibit H ⁺ ion conduction, that is, the cation impurity Q increases.

P3 in the upper diagram is a state in which the output current IOUT is increased stepwise to the increase current IG for a while, that is, the output voltage VOUT is higher than the minimum voltage VM. At that time, as shown in the middle diagram, as an action to alleviate the unevenness of the moisture W in the electrolyte membrane 5e, reverse diffusion occurs in which the moisture W moves in the electrolyte membrane 5e from the cathode electrode 5c side to the anode electrode 5a side. At the same time, moisture is generated by an electrochemical reaction at the cathode electrode 5c, and part of the moisture diffuses into the electrolyte membrane 5e from the cathode electrode 5c side. Further, as shown in the lower diagram, the cation impurity Q in the electrolyte membrane 5e gradually moves to the cathode 5c side. Accordingly, in the vicinity of the anode electrode 5a of the electrolyte membrane 5e, the ratio of moisture W that conducts H ⁺ ions increases and the ratio of cations that inhibit H ⁺ ion conduction decreases, so that the internal resistance is low. Thus, the output voltage OUT rises.

  P4 in the upper diagram is a state immediately before reaching the time t3 after the output current IOUT is increased to the increased current IG, that is, the state where the output voltage VOUT is the steady voltage VC. At that time, as shown in the middle figure, the unevenness of the moisture W in the electrolyte membrane 5e is almost eliminated, that is, the moisture W is substantially uniform from the cathode 5c side to the anode 5a side, and a steady state is obtained. However, since the output current IOUT is large and the amount of generated water is large compared to the case of P1 in the upper diagram, the amount of moisture W is large. Further, as shown in the lower diagram, the cation impurity Q in the electrolyte membrane 5e is stabilized in a state of being biased toward the cathode electrode 5c and becomes a steady state.

As described above, when the output current IOUT of the fuel cell stack 10 is increased in a stepped manner from the predetermined base output current IB to the increased current IG, the output voltage VOUT rapidly decreases and becomes VM. This is considered to be because the anode 5a is dried due to the influence of the above, and the movement of the cation impurity Q is slow and delayed from the accompanying water, so that the internal resistance temporarily increases. Since the movement of the cation impurity Q is slow, there is a large amount of the cation impurity Q on the anode electrode 5a side of the electrolyte membrane 5e immediately after the increase of the output current IOUT. It is considered that the output voltage VOUT gradually recovers by moving toward the cathode 5c side, stabilizing and not hindering the conduction of H ⁺ ions.

  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.

  Based on the above fact, in the fuel cell system A, when the amount of cationic impurities in the electrolyte membrane 5e should be estimated during operation of the fuel cell system A, the following cationic impurity amount estimation control is performed. Below, the case where the amount of cationic impurities in the electrolyte membrane 5e is estimated about the fuel cell single cell 2 is demonstrated.

  First, it is determined whether or not the amount of cationic impurities in the electrolyte membrane 5e of the fuel cell system A should be estimated based on the vehicle travel distance, a predetermined schedule, and the like. Specifically, for example, it is determined that the cation impurity amount should be estimated every time the vehicle travel distance reaches a predetermined set distance, and otherwise, it is determined that it is not time to estimate the cation impurity amount. . When the amount of cationic impurities is to be estimated, it is determined whether or not the base output current IB is less than or equal to a preset threshold current Ith. When the base output current IB is less than or equal to the threshold current Ith, the process proceeds to the following process for estimating the amount of cationic impurities.

  That is, based on the command value from the electronic control unit 60, the DC / DC converter 11 steps the output current IOUT output from the fuel cell stack 10 (single fuel cell 2) from the predetermined base output current IB to the increased current IG. The increase current IG is maintained 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 current 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 single fuel cell 2, then starts to increase, and after the increase time Δt 0, it 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 the amount of voltage drop 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. 6 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.

  As described above, the above cation impurity amount estimation control can be performed by existing devices (eg, the DC / DC converter 11, the output sensor 17, and the electronic control unit 60). Therefore, it is possible to estimate the amount of cation impurities in the cation exchange membrane during operation of the fuel cell system A while suppressing an increase in manufacturing cost.

  The base output current IB is a target current value. In the above cation impurity amount estimation control, the target current value is temporarily changed to the increased current IG and the output voltage VOUT is measured. Therefore, the increase time Δt0 is preferably short in order to quickly return the output current IOUT to the target current value.

  In the above embodiment, the increase current IG is allowed to flow for the increase time Δt0 even after the set time Δt1. In another embodiment (not shown), after the output voltage VOUT is measured until the set time Δt1, that is, after the set time Δt1 has elapsed, the increased current IG is reduced to the base output current IB. In this case, the increase time Δt0 is not the steady time described above but the set time Δt1.

  In the above embodiment, the target of the cation impurity amount estimation control is one single fuel cell 2. In yet another embodiment (not shown), the target of the cationic impurity amount estimation control is the fuel cell stack 10. In that case, the output current IOUT and the output voltage VOUT are measured by the output sensor 16, and parameters such as the output voltage VOUT and the voltage drop amount ΔV are changed to those for the fuel cell stack 10, and the cation impurity amount estimation control is performed. To implement.

  In the above embodiment, the cation impurity amount estimation control is performed during the operation of the fuel cell system A. In yet another embodiment (not shown), the cation impurity amount estimation control is performed when the fuel cell system A is stopped. In this case, the fuel cell system A is started based on a preset schedule or the like, and the base output current IB is supplied to the fuel cell stack 10 to execute the cation impurity amount estimation control. After the cationic impurity amount estimation control is completed, the fuel cell system A is stopped.

  Further, the fuel cell system A includes the DC / DC converter 11 as a current control unit, the output sensor 17 as a measurement unit, and the electronic control unit 60 as an estimation unit. It can be seen that the apparatus includes an estimation device for the amount of cationic impurities provided with a part and an estimation part.

  FIG. 8 shows a cationic impurity amount estimation control routine in the fuel cell system A of FIG. This routine is executed by interruption at regular intervals. Referring to FIG. 8, in step 100, it is determined whether or not it is time to estimate the amount of cationic impurities in the electrolyte membrane 5e of the fuel cell system A. When the amount of cation impurities is to be estimated, it is determined in subsequent step 101 whether or not the base output current IB is equal to or less than the threshold current Ith. When the base output current IB is less than or equal to the threshold current Ith, in the subsequent step 102, 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 following step 103, the behavior of the output voltage VOUT that increases to the steady voltage VC lower than the base output voltage VB after decreasing in a stepwise manner from the base output voltage VB to the minimum voltage VM is measured. Next, at step 104, 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 105, 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. 6 is referred to, and the amount of cationic impurities in the electrolyte membrane 5e is estimated. On the other hand, when it is not time to estimate the amount of cationic impurities in step 100 and when the base output current IB is larger than the threshold current Ith in step 101, a process of estimating the amount of cationic impurities (steps 102 to 105). ) Is not executed.

  FIG. 9 is a graph showing an example of an experiment of the output voltage VOUT when the output current IOUT is increased stepwise in the single fuel cell 2, and FIG. 10 is a graph showing an enlarged part of FIG. . However, the left vertical axis indicates the output voltage VOUT (V) of the single fuel cell 2 indicated by a solid line and a one-dot chain line, the right vertical axis indicates the output current IOUT of the single fuel cell 2 indicated by a broken line, and the horizontal axis indicates time (seconds). ).

  In this experimental example, at time t1 = 900 seconds, the output current IOUT of the fuel cell single cell 2 is increased from the base output current IB to a predetermined increase current IG in a stepwise manner, and the increase time up to time t3 = 1200 seconds. The increased current IG is held for Δt0 = 300 seconds. At that time, the output voltage VOUTn when the amount of cation impurities is substantially zero is from the base output voltage VB = 0.89 V at time t1 = 900 seconds to the minimum voltage VMn = 0. After decreasing to 59V in a stepped manner, it starts to increase and increases to a steady voltage VCn = 0.64V lower than the base output voltage VB = 0.89V by time t3 = 1200 seconds after the increase time Δt0 = 300 seconds. To do. On the way, at t2 = 910 seconds after the set time Δt1 = 10 seconds, the output voltage VOUTn = VEn = 0.62V, and the voltage drop amount ΔVn which is the difference between the minimum voltage VMn = 0.59V with respect to the output voltage VEn is 0. It is obtained as 03V. On the other hand, the output voltage VOUTc when there is a cation impurity amount decreases in a stepped manner from the base output voltage VB = 0.89V at time t1 = 900 seconds to the minimal voltage VMc = 0.35V in 901 seconds after one second. After that, the output starts increasing and increases to a steady voltage VCc = 0.61V lower than the base output voltage VB = 0.89V by time t3 = 1200 seconds after the increase time Δt0 = 300 seconds. In the middle of this, the output voltage VOUTc = VEc = 0.52V at t2 = 910 seconds after the set time Δt1 = 10 seconds has elapsed, and the voltage drop amount ΔVc, which is the difference between the minimum voltage VMc = 0.35V and the output voltage VEc, is 0. 17V is obtained.

  By carrying out the above experimental examples in the fuel cell single cell 2 having various known cation impurity amounts, that is, the sulfonic acid group substitution ratio, a voltage drop as shown in FIG. 11 is shown as an example of the graph shown in FIG. A curve CL indicating the relationship between the amount and the amount of cationic impurities is obtained. Conversely, if the curve CL indicating the relationship between the voltage drop amount and the cation impurity amount as shown in FIG. 11 is known, the above measurement is performed in the fuel cell single cell 2 with the unknown cation impurity amount. Based on the obtained voltage drop amount ΔV, the amount of cationic impurities can be estimated by referring to the curve CL as shown in FIG.

  Next, another embodiment of the fuel cell system A will be described with reference to FIG. In this other embodiment, the value relating to the behavior of the output voltage VOUT used when estimating the amount of cationic impurities is different from the embodiment shown in FIG. Specifically, (2) the minimum value drop amount ΔVm, which is the difference between the base output voltage VB and the minimum voltage VM, described in FIG. 3 is used as a value related to the behavior of the output voltage VOUT. The differences will be mainly described below.

  FIG. 12 is a diagram for explaining a method for estimating the amount of cationic impurities according to another embodiment. FIG. 12 is a graph showing the behavior of the output voltage VOUT when the output current IOUT is increased stepwise in the single fuel cell 2 shown in FIG. In another embodiment shown in FIG. 12, the minimum drop amount ΔVm is used as a value related to the behavior of the output voltage VOUT used when estimating the amount of cationic impurities. The reason for this is that, in the mechanism described in FIG. 7, in P2 in the upper diagram, the amount of the minimum value drop ΔVm of the output voltage VOUT increases as the proportion of the cation impurity Q increases. At this time, the amount of cation impurities is estimated so that the amount of cation impurities increases as the minimum value drop amount ΔVm increases.

  FIG. 13 schematically shows the relationship between the amount of cationic impurities and the minimum value drop amount ΔVm. 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 minimum value drop amount ΔVm. As indicated by a solid curve CL1, the minimum value drop amount ΔVm increases as the ratio of the sulfonic acid groups in the electrolyte membrane 5e replaced by cationic impurities increases. Therefore, if the data shown in FIG. 13 is measured in advance, the substitution rate of the sulfonic acid group, that is, the amount of cationic impurities can be estimated by measuring the minimum value drop ΔVm and referring to the data. it can.

  FIG. 14 is a graph showing an example of an experiment of the output voltage VOUT when the output current IOUT is increased stepwise in the fuel cell single cell 2, and the output current IOUT, the output voltages VOUTn, and VOUTc are shown again in FIG. . In the embodiment of FIG. 14, the output current IOUT of the fuel cell single cell 2 is increased from the base output current IB to the predetermined increase current IG in a stepped manner at time t1 = 900 seconds until time t3 = 1200 seconds. The increased current IG is held for the increased time Δt0 = 300 seconds. At that time, the output voltage VOUTn when the amount of cation impurities is substantially zero is the minimum voltage from the base output voltage VB = 0.89 V at time t1 = 900 seconds, and at time t11 = 901 seconds after Δtm = 1 second. After decreasing stepwise to VMn = 0.59V, it starts to increase. That is, the minimum voltage VMn is determined to be 0.59V, and the minimum value drop amount ΔVmn is determined to be 0.30V. On the other hand, the output voltage VOUTc when the amount of cationic impurities is present is from the base output voltage VB = 0.89V at time t1 = 900 seconds, to the minimum voltage VMc = 0.35V at time t11 = 901 seconds after Δtm = 1 second. After decreasing to stepwise, it starts to increase. That is, the minimum voltage VMc is obtained as 0.35V, and the minimum value drop amount ΔVmc is obtained as 0.54V.

  If the minimum voltage VM is obtained, it is not necessary to cause the increase current IG to flow over the increase time Δt0 up to the time t3. In yet another embodiment (not shown), when the minimum voltage VM is obtained, the increase current IG Is reduced to the base output current IB. In this case, the increase time Δt0 is not the above-described stabilization time, but is a time when the output voltage VOUT starts to increase from the minimum voltage VM, that is, a time slightly longer than Δtm.

  By carrying out the above experimental examples in various fuel cell single cells with known amounts of cationic impurities, that is, sulfonate group substitution ratios, the minimum value drop amount ΔVm and the amount of cationic impurities as shown in FIG. A curve CL1 indicating the relationship is obtained. On the other hand, if the curve CL1 indicating the relationship between the minimum value drop amount ΔVm and the amount of cationic impurities as shown in FIG. 13 is known, the above measurement is performed for the unit cell 2 of which the amount of cationic impurities is unknown. The amount of cationic impurities can be estimated by referring to the curve CL1 based on the obtained minimum value drop amount ΔVm.

  Also in this case, the same effect as the fuel cell system A shown in FIG. 1 can be obtained. In addition, since the time until acquisition of the minimum voltage VM is short, quick estimation is possible. Furthermore, since it takes only a short time until the minimum voltage VM is acquired, it is not necessary to hold the increased current IG over the increase time Δt0 until time t3, and energy consumption can be reduced if it is not held.

  Next, still another embodiment of the fuel cell system A will be described with reference to FIG. In this further embodiment, the value relating to the behavior of the output voltage VOUT used when estimating the amount of cationic impurities is different from the embodiment shown in FIG. Specifically, (3) required time Δt2 described in FIG. 3 is used. The differences will be mainly described below.

  FIG. 15 is a diagram illustrating a method for estimating the amount of cationic impurities according to still another embodiment. FIG. 15 is a graph showing the behavior of the output voltage VOUT when the output current IOUT is increased stepwise in the single fuel cell 2 shown in FIG. In yet another embodiment shown in FIG. 15, the required time Δt2 is used as a value related to the behavior of the output voltage VOUT used when estimating the amount of cationic impurities. The reason for this is that, in the mechanism described in FIG. 7, in P2 in the upper diagram, the higher the proportion of the cation impurity Q, the greater the degree to which the output voltage VOUT decreases (minimum value drop amount ΔVm). This is because it takes a long time Δt2 for VOUT to return to the steady voltage VC. At that time, the amount of cationic impurities is estimated so that the amount of cationic impurities increases as the required time Δt2 becomes longer. Here, the steady voltage VC is, for example, the output voltage VOUT when the output voltage VOUT does not change during a preset time (eg, several tens of seconds). However, “not changing” means that the rate of change of the output voltage VOUT is within a preset rate of change (example: 1%).

  FIG. 16 schematically shows the relationship between the amount of cationic impurities and the required time Δt2. 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 required time Δt2. As indicated by the solid curve CL2, the required time Δt2 increases as the proportion of the sulfonic acid groups in the electrolyte membrane 5e replaced with cationic impurities increases. Therefore, if the data shown in FIG. 16 is measured in advance, the substitution time of the sulfonic acid group, that is, the amount of cationic impurities can be estimated by measuring the required time Δt2 and referring to the data.

  FIG. 17 is a graph showing an example of an experiment of the output voltage VOUT when the output current IOUT is increased stepwise in the fuel cell single cell 2, and the output current IOUT, the output voltages VOUTn, and VOUTc are shown again in FIG. . In the embodiment of FIG. 17, the output current IOUT of the fuel cell single cell 2 is increased from the base output current IB to the predetermined increase current IG in a stepped manner at time t1 = 900 seconds until time t3 = 1200 seconds. The increased current IG is held for the increased time Δt0 = 300 seconds. At that time, the output voltage VOUTn when the amount of cation impurities is substantially zero is the base output voltage VB = 0.89 V at time t1 = 900 seconds, and the minimum voltage VMn = 0.59 V in 901 seconds after 1 second. Then, the voltage starts to increase and reaches a steady voltage VCn = 0.64 V at time t21 = 990 seconds. That is, the required time Δt2n is obtained as 90 seconds. On the other hand, the output voltage VOUTc when there is a cation impurity amount decreases in a stepped manner from the base output voltage VB = 0.89V at time t1 = 900 seconds to the minimal voltage VMc = 0.35V in 901 seconds after one second. After that, it starts to increase and reaches a steady voltage VCc = 0.60 V at time t22 = 1129 seconds. That is, the required time Δt2c is obtained as 229 seconds.

  When the output voltage VOUT becomes the steady voltage VC, it is not necessary to flow the increased current IG over the increase time Δt0 until the time t3. Therefore, in yet another embodiment (not shown), the output voltage VOUT becomes the steady voltage VC. At the time, the increased current IG is reduced to the base output current IB. In this case, the increase time Δt0 is not the steady time described above but the required time Δt2.

  By carrying out the above experimental examples in various fuel cell single cells with known amounts of cationic impurities, that is, sulfonic acid group substitution ratios, a curve CL2 showing the relationship between the required time Δt2 and the amount of cationic impurities can be obtained. On the contrary, if the curve CL2 indicating the relationship between the required time Δt2 and the amount of cationic impurities is known, the measurement as described above is performed in the fuel cell single cell 2 where the amount of cationic impurities is unknown, and the required time obtained. Based on Δt2, the amount of cationic impurities can be estimated by referring to the curve CL2.

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

  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. 18 excludes the fuel gas circulation pipe 81 and the fuel gas circulation pump 39. That is, the fuel cell system A shown in FIG. 18 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 5 Membrane electrode gas diffusion layer assembly IB Base output current IOUT Output current IG Increase current VB Base output voltage VOUT Output voltage Δt0 Increase time

Claims (12)

Cationic impurities contained in the electrolyte material in the membrane electrode gas diffusion layer assembly of at least one fuel cell single cell of the fuel cell system when the fuel cell system is operated with the base output current and the base output voltage A method for estimating quantity,
Increasing the output current of the fuel cell single cell from the base output current in a stepwise manner to a predetermined increased current and holding it for an increased time; and
Measuring the output voltage of the single fuel cell in the increase time;
Estimating the amount of cationic impurities based on the measured output voltage of the single fuel cell;
Comprising
A method for estimating the amount of cationic impurities in a fuel cell system. 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 amount of cationic impurities is estimated so as to increase as the difference in the minimum voltage with respect to the output voltage after a predetermined set time after the output current is increased to the increased current increases.
The method for estimating the amount of cationic impurities 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 amount of cationic impurities is estimated so as to increase as the difference between the minimum voltage and the base output voltage increases.
The method for estimating the amount of cationic impurities 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 amount of the cation impurity is estimated so as to increase as the time required for the output voltage to reach the steady voltage after the output current is increased to the increased current increases.
The method for estimating the amount of cationic impurities according to claim 1. The increased current is the output current when the load of the fuel cell system is full load.
The estimation method of the amount of cationic impurities as described in any one of Claims 1 thru | or 4. 6. When the base output current of the single fuel cell is smaller than a threshold current, the amount of cationic impurities is estimated by increasing the output current of the single fuel cell to the increased current stepwise. The estimation method of the amount of cationic impurities as described in any one of these. Cationic impurities contained in the electrolyte material in the membrane electrode gas diffusion layer assembly of at least one fuel cell single cell of the fuel cell system when the fuel cell system is operated with the base output current and the base output voltage A device for estimating the quantity,
A current control unit configured to increase the output current of the fuel cell single cell from the base output current to a predetermined increase current in a stepwise manner and hold it for an increase time;
A measurement unit for measuring the output voltage of the single fuel cell in the increase time;
Based on the measured output voltage of the fuel cell single cell, an estimation unit for estimating the amount of the cationic impurities,
Comprising
An apparatus for estimating the amount of cationic impurities in a fuel cell system. 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 estimation unit estimates the amount of cationic impurities so that the difference between the minimum voltage and the output voltage after a predetermined set time after the output current is increased to the increased current increases as the difference increases. ,
The cation impurity amount estimation apparatus according to claim 7. 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 estimation unit estimates the amount of cationic impurities so that the difference between the minimum voltage and the base output voltage increases as the difference increases.
The cation impurity amount estimation apparatus according to claim 7. 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 estimation unit estimates the amount of cationic impurities so that the time required for the output voltage to reach the steady voltage increases as the output current increases to the increased current,
The estimation method of the amount of cationic impurities of Claim 7. The increased current is the output current when the load of the fuel cell system is full load.
The estimation apparatus of the amount of cationic impurities as described in any one of Claims 7 thru | or 10. When the base output current of the single fuel cell is smaller than a threshold current, the current control unit increases the output current of the single fuel cell to the increased current stepwise, thereby the estimation unit The estimation apparatus of the amount of cation impurities as described in any one of Claims 7 thru | or 11 which estimates the amount of cation impurities.

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