JP2010015933A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system, can prevent leakage of liquid ion and cross leakage in a fuel cell. <P>SOLUTION: The system includes a fuel cell including a matrix impregnated with ion liquid, an air electrode provided oppositely to a fuel electrode through the matrix, and a reservoir for supplying the ion liquid to the matrix through the air electrode; detection means 301, 302, 303 and 313 which detect a quantity of the ion liquid in the reservoir or a quantity of a mixture of the ion liquid and condensed water generated in the fuel cell; and a control means 313 which controls, based on the results detected by the detection means, the quantity of the ion liquid in the reservoir or the quantity of the mixture into a predetermined setting range. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel cell system, and more particularly to a fuel cell system for preventing leakage and cross leak of an ionic liquid.

  In recent years, fuel cells have attracted attention in response to social demands and trends against the background of environmental problems. In particular, as a fuel cell for an automobile, a fuel cell using an ionic liquid capable of generating power from a low temperature of 0 ° C. or lower to a high temperature of 100 ° C. or higher as an electrolyte has attracted attention.

  However, in a state where SR (Stoich Ratio: excess rate with respect to the air flow rate determined from the amount of oxygen necessary for the required current) is low, water generated by an electrochemical reaction at the air electrode is condensed. Even if SR is increased, the saturated water vapor pressure decreases in a low temperature state, and therefore the relative water vapor pressure (ratio of water vapor partial pressure to saturated water vapor pressure) increases. In such a state, condensed water may be mixed into the ionic liquid, and the ionic liquid may leak from the reservoir together with the water. In particular, when a fuel cell using an ionic liquid is used in an automobile that always starts from a low temperature, such a problem can frequently occur. In addition, when the ionic liquid is insufficient due to leakage, a phenomenon called cross leak occurs in which hydrogen in the fuel electrode and oxygen in the air electrode are directly mixed, thereby degrading the characteristics of the fuel cell.

As a method for monitoring the electrolyte content in the reservoir, there is one disclosed in Patent Document 1 below, but a method for preventing the electrolyte from leaking from the reservoir is not disclosed.
JP-A-6-288980

  The present invention has been made to solve such a problem, and detects the amount of ionic liquid in a reservoir or a mixed liquid amount of ionic liquid and water, and keeps the mixed liquid amount within a predetermined range. By controlling, leakage of the ionic liquid is prevented and cross leakage of the fuel cell is prevented.

  In order to solve the above problems, a fuel cell system according to the present invention includes a matrix impregnated with an ionic liquid, an air electrode provided opposite to the fuel electrode through the matrix, and replenishing the matrix with the ionic liquid through the air electrode. A fuel cell including the reservoir, a detection unit that detects the amount of the ionic liquid in the reservoir or the amount of the mixed liquid in which the ionic liquid and the condensed water generated in the fuel cell are mixed, and the detection unit detects And control means for controlling the amount of the ionic liquid in the reservoir or the amount of the mixed solution within a predetermined setting range based on the result.

  According to the fuel cell system of the present invention, it is possible to prevent the leakage of the ionic liquid and the cross leak of the fuel cell.

  Hereinafter, a control method for a fuel cell according to the present invention will be described in detail with reference to the drawings, divided into first to fourth embodiments.

  Before describing these embodiments, the overall configuration of the fuel cell stack will be briefly described in order to facilitate understanding of the present invention. FIG. 1 is a perspective view showing the overall configuration of the fuel cell stack, and FIG. 2 is an explanatory diagram for explaining the cross-sectional structure of the fuel cell constituting the fuel cell stack.

  As shown in FIG. 1, the fuel cell stack 1 includes a unit battery cell (hereinafter referred to as “fuel cell”) that generates an electromotive force by a reaction between an anode reaction gas (hydrogen in this specification) and a cathode reaction gas (oxygen in this specification). A predetermined number of cells 2) are laminated to form a laminated body 3. A current collector plate 4, an insulating plate 5, and an end plate 6 are disposed at both ends of the laminated body 3, and penetrates into the laminated body 3. The tie rod 7 is passed through the through hole (not shown), and a nut (not shown) is screwed to the end of the tie rod 7.

  In this fuel cell stack 1, an anode reaction gas, a cathode reaction gas, and a liquid medium (specifically, cooling water or warm water) are respectively circulated in flow channel grooves formed in each fuel cell 2. A gas supply port 8, an anode reaction gas discharge port 9, a cathode reaction gas supply port 10, a cathode reaction gas discharge port 11, a medium supply port 12 and a medium discharge port 13 are formed in one end plate 6.

  The anode reaction gas is supplied from the anode reaction gas supply port 8, flows through the anode reaction gas supply channel groove formed in each fuel cell 2, and is discharged from the anode reaction gas discharge port 9. The cathode reaction gas is supplied from the cathode reaction gas supply port 10, flows in the cathode reaction gas supply channel groove formed in each fuel cell 2, and is discharged from the cathode reaction gas discharge port 11. The liquid medium is supplied from the medium supply port 12, flows through a medium supply channel groove formed in each fuel cell 2, and is discharged from the medium discharge port 13.

  As shown in FIG. 2, the fuel battery cell 2 includes a matrix (electrolyte) 230, an air electrode 200 and a fuel electrode 240 disposed on both sides of the matrix, and a reservoir 210 for supplying an ionic liquid to the matrix through the air electrode 200. It is comprised including.

  The matrix 230 is configured by, for example, impregnating an insulating porous body of SiC with an ionic liquid that is a liquid. The ionic liquid has high heat resistance, does not require water as a proton conduction medium, and has excellent characteristics as an electrolyte for a high-temperature fuel cell that has a very low vapor pressure. Further, some ionic liquids are liquid at 0 ° C. or lower, and by using such ionic liquids, it is possible to generate power from 0 ° C. or lower.

  The air electrode 200 includes a cathode catalyst layer as a catalyst metal that is an electrode catalyst and a gas diffusion layer.

  The fuel electrode 240 includes an anode catalyst layer and a gas diffusion layer.

  The reservoir 210 adjusts the amount of the ionic liquid in the matrix 230 to an appropriate amount by supplying the ionic liquid to the matrix 230 through the air electrode 200. The reservoir 210 is made of, for example, a porous carbon material, and is provided with a plurality of parallel air flow paths 220 for passing air as a reaction gas. The reservoir 210 holds an ionic liquid or a mixture of ionic liquid and water, and supplies the ionic liquid to the matrix 230 by capillary action.

  In a fuel cell using an ionic liquid, the electrolyte is liquid. Therefore, for stable operation, it is necessary to preliminarily mix the produced water with the ionic liquid and keep the amount of the ionic liquid or the mixed liquid of the ionic liquid and water in the matrix 230 appropriately. For example, when the ionic liquid in the matrix 230 or the mixed liquid of the ionic liquid and water is insufficient, a phenomenon called cross leak occurs in which hydrogen in the fuel electrode 240 and oxygen in the air electrode 200 are directly mixed. On the other hand, when the ionic liquid or the mixed liquid of the ionic liquid and water in the matrix 230 exceeds the allowable amount, the ionic liquid or the mixed liquid of the ionic liquid and water flows out to the air flow path 220, and the ionic liquid leaks to the outside. In addition, since the ionic liquid leaking from the matrix 230 or the mixed liquid of ionic liquid and water hinders the movement of air as a reaction gas to the three-phase interface, a phenomenon called flooding occurs and the performance of the fuel cell is degraded.

  When hydrogen is passed through the fuel flow path 250 and oxygen is passed through the air flow path 220, the hydrogen is converted into hydrogen ions by the catalytic action of the anode catalyst layer and discharges electrons. The hydrogen ions that have released the electrons pass through the matrix 230. In the cathode catalyst layer, hydrogen that has passed through the matrix 230 and electrons that have passed through an external channel (not shown) react with oxygen to produce water. By this action, the fuel electrode 240 becomes negative and the air electrode 200 becomes positive, and a DC voltage is generated between the fuel electrode 240 and the air electrode 200.

Hereinafter, the fuel cell control method and the control apparatus according to the present invention will be described in detail by dividing the first embodiment to the fourth embodiment.
[First Embodiment]
FIG. 3 is a block diagram showing the configuration of the fuel cell system according to the first embodiment of the present invention.

  As shown in FIG. 3, the fuel cell system according to the first embodiment includes a fuel cell stack 300 in which fuel cells are stacked, and a temperature sensor 301 that is provided on the air electrode side of each fuel cell and measures the cell temperature. Similarly, the ion conductivity sensor 302 provided on the air electrode side for measuring the ion conductivity of the reservoir on the air electrode side, and the water vapor pressure at the air electrode side air outlet provided on the downstream portion of the air flow path of each fuel cell. It has a water vapor pressure sensor 303 for measurement. Further, a compressor 305 for supplying external air to the air electrode of the fuel cell via the first heat exchanger 304, a first heat exchanger 304 (and a first radiator fan 304a) for adjusting the temperature of the discharge air of the compressor 305, Have Also, a hydrogen tank 306 that stores hydrogen to be supplied to the fuel electrode, a pressure regulator 307 that reduces high-pressure hydrogen supplied from the hydrogen tank to a pressure at which the fuel cell stack 300 can be supplied, a second heat exchanger 308 that raises the temperature of hydrogen, Have The third heat exchanger 310 (and the second radiator fan 310a) that adjusts the temperature of the fuel cell by adjusting the temperature of the cooling water that passes through the fuel cell, and the fuel cell by adjusting the flow rate of the cooling water. A cooling water pump 309 for adjusting the temperature of the cell is provided. Also, the power obtained from the secondary battery 311, the fuel cell stack 300 or the secondary battery 311 that is charged / discharged when there is a difference between the required output to the fuel cell system and the output of the fuel cell stack is converted into a voltage according to the application. Inverter 312. The control unit 313 includes an arithmetic / control device, a storage device, and an input / output device that control each component of the fuel cell system.

  Furthermore, the fuel cell system according to the first embodiment controls the air that flows through the air bypass channel 314 and the air bypass channel 314 that is connected in the middle of the air channel of the fuel cell and flows air into the air channel. An air bypass flow path control valve 315, a cooling water bypass flow path 316 connected in the middle of the cooling water flow path of the fuel battery cell, which flows out from the cooling water flow path and then flows into the cooling water path (that is, recirculates), cooling water A cooling water bypass channel control valve 317 is provided for controlling the cooling water flowing through the bypass channel 316. By opening the air bypass flow path control valve 315, the air flowing through the air bypass flow path 314 merges with the air flow path, so that the air flow rate downstream of the air flow path can be increased. By opening the cooling water bypass flow path control valve 317, the cooling water flowing through the cooling water flow path flows out of the cooling water bypass flow path 316. Therefore, the flow rate of the cooling water downstream of the cooling water flow path is reduced, and the fuel cells around the downstream The temperature of the cell can be raised. The number of cooling water bypass channels connected in the middle of the cooling water channel is not limited to one, and by connecting a plurality of cooling water bypass channels to any location of the cooling water channel, the cooling water is circulated at each location. sell.

  FIG. 4 is an explanatory view showing a cross section of the internal structure of the fuel battery cell. As shown in FIG. 4, the fuel cell includes a matrix 400 impregnated with an ionic liquid, a fuel electrode 410 and an air electrode 420 attached to both surfaces of the matrix 400 so as to face each other, and a fuel electrode 410 and an air electrode 420 on the outside. And a reservoir 430 sandwiched therebetween. The reservoir 430 is provided with an air flow path 430a and a fuel flow path 430b, which form air and hydrogen flow paths, respectively.

  FIG. 5 is an explanatory view showing the structure of the portion where the air flow path 500 of the reservoir is formed. The air channel 500 is provided with an air inlet 501, an air bypass inlet 502, and an air outlet 503. The air flowing in from the air inlet 501 flows through the air flow path 500 and flows out from the air outlet 503. An air bypass channel is connected to the air bypass inlet 502, and air flowing through the air bypass channel flows in. The reservoir includes a cooling water inlet 504 for supplying cooling water to a cooling plate through which cooling water flows, a cooling water outlet 505 for discharging cooling water flowing through the cooling plate, and a cooling water bypass, which will be described later. A cooling water bypass outlet 506 to which the flow path is connected is provided. In addition, a fuel inlet 507 through which hydrogen as fuel is introduced and a fuel outlet 508 through which hydrogen flows out are provided.

  FIG. 6 is an explanatory view showing the structure of the cooling plate. A cooling water channel 600 is provided in the cooling plate. The cooling water channel 600 is provided with a cooling water inlet 604, a cooling water bypass outlet 606, and a cooling water outlet 605. The cooling water that flows in from the cooling water inlet 604 flows through the cooling water flow path 600 and flows out from the cooling water outlet 605. A cooling water bypass channel is connected to the cooling water bypass outlet 606, and the cooling water flowing through the cooling water bypass channel flows out. The cooling water flowing out from the cooling water bypass outlet 606 flows through the cooling water bypass flow path through the bypass flow path control valve, and then reflows from the cooling water inlet 604 to return to the cooling water bypass flow path and the cooling water flow path 600. To do. Since the cooling plate is inserted as a part of the stacked structure in units of fuel cells constituting the fuel cell stack, an air inlet 601, an air outlet 603, an air bypass inlet 602, a fuel inlet 607, and a fuel outlet 608 are provided. It is done. The cooling plate is inserted in units of fuel cells constituting the fuel cell stack. However, the cooling plate is not limited to this, and may be inserted in any location of the fuel cell stack structure in the fuel cell stack.

  FIG. 7 is a flowchart for implementing the fuel cell system according to the first embodiment. Hereinafter, the flowchart shown in FIG. 7 will be described step by step.

[S700]
Start the compressor and start raising the temperature of the fuel cell stack.

The compressed hot air of about 180 ° C. is discharged from the compressor. Since the fuel cell stack has a normal operation temperature of 100 ° C. to 180 ° C. (hereinafter referred to as “steady operation temperature T ₀ ”), air is brought to this range by the first heat exchanger (and the first radiator fan). The air is supplied to the fuel cell stack at a reduced temperature. The fuel cell stack is warmed up by the heat of air supplied from the first heat exchanger.

[S710]
Start power generation of the fuel cell stack.

The temperature of the entire fuel cell stack immediately after the start of power generation by the fuel cell stack is equal to the ambient temperature. Therefore, until the temperature of the fuel cell stack reaches a steady operating temperature T _0, the maximum output of the fuel cell stack is in a state of being smaller than the maximum output in the steady operation temperature T _0.

[S720]
Measure the filling rate of the mixture of ionic liquid and water in the air electrode side reservoir.

  As described above, liquid water (hereinafter referred to as “condensed water”) is generated by condensation in a state where SR is low or in a state where SR is high but low. A part of the generated condensed water is mixed with the ionic liquid, and the liquid in which the condensed water and the ionic liquid are mixed (hereinafter referred to as “mixed liquid”) moves to the reservoir on the air electrode side by capillary attraction. As a result, the liquid mixture is stored in the reservoir together with the ionic liquid that originally occupied 60% of the holes in the reservoir. Here, the ratio of the vacancies in the reservoir occupied by the ionic liquid or the mixed liquid is defined as a filling rate F.

  In this step, the filling rate F is measured by a filling rate deriving subroutine for the air electrode side reservoir shown in FIG.

[S800]
The water vapor partial pressure _Pv downstream of the air flow path is measured.

  FIG. 9 is an explanatory diagram showing the positions of the water vapor pressure sensor 910, the ion conductivity sensor 920, and the cell temperature sensor 930 installed on the air electrode 900 side of the fuel cell. As shown in FIG. 9, the water vapor pressure sensor 910 is installed near the downstream side of the air flow path 940 of the air electrode 900.

  As the water vapor pressure sensor 910, for example, a capacitance-type water vapor pressure gauge can be used. Normally, it is difficult for this type of vapor pressure gauge to measure the water vapor pressure in a gas containing two or more components of vapor, but the water vapor pressure can be measured because the ionic liquid has the feature of being hardly volatile.

[S810]
Measuring the temperature _{T FC} of the fuel cell.

As shown in FIG. 9, for measuring the temperature _{T FC} of the fuel cell 950 by placing the cell temperature sensor 930 to the air electrode 900 of the fuel cell 950. A thermocouple can be used for the cell temperature sensor 930.

[S820]
To derive the water concentration C _w in the reservoir. Here, the water concentration _Cw refers to the ratio of the number of moles of water to the number of moles of ionic liquid. That is, the water concentration of the mixed liquid having the same number of moles of ionic liquid and water is 100 mol%.

FIG. 10 is a diagram showing a vapor pressure curve of the mixed liquid. As shown in FIG. 10, the relative water vapor pressure P _v / P ₀ and the water concentration C _w have a certain relationship. Here, the relative water vapor pressure refers to a value (P _v / P ₀ ) obtained by dividing the water vapor pressure P _v by the saturated water vapor pressure P ₀ . A curve indicating the relationship between the relative water vapor pressure P _v / P ₀ and the water concentration C _w is referred to as a vapor pressure curve. The relative water vapor pressure P _v / P ₀ can be calculated from the water vapor pressure P _v measured in step S800 and the saturated water vapor pressure P ₀ calculated from the temperature T _FC of the fuel cell measured in step S810. Here, the saturated water vapor pressure P ₀ is stored in advance in the storage device of the control unit in which the relationship between the temperature T _FC of the fuel cell and the saturated water vapor pressure P ₀ is compared with the measured temperature T _FC of the fuel cell. Can be calculated.

The vapor pressure curve varies depending on the ionic liquid. In this step, the vapor pressure curve of the ionic liquid to be used is measured in advance and stored in the storage device of the control unit. The vapor pressure curve of the ionic liquid is measured at several points within the range of the temperature T _FC of the fuel cell that is actually assumed according to the application. Relative water vapor pressure P _{v /} P ₀ calculated above, it is possible to calculate the water concentration C _w in the air electrode side reservoir by comparing the vapor pressure curve which had been stored.

Here, without deriving a filling factor F of the reservoir by the following steps S830～S840, may water concentration C _w in the reservoir derived in this step to derive the filling factor F of the reservoir. That is, the amount of water (number of moles) in the mixed liquid can be calculated from the initial value (number of moles) of the ionic liquid in the reservoir and the water concentration _Cw . Then, since the volume of water in the liquid mixture can be calculated, the filling rate F of the reservoir can be calculated from the sum of the volume of the known ionic liquid and the volume of water in the liquid mixture and the known pore volume of the reservoir as the design value. Can be derived.

[S830]
The conductivity σ of the mixed solution is derived.

  According to this step and the following step S840, the reservoir filling rate F can be derived more accurately.

In general, the ionic conductivity of the mixture increases as the amount of water mixed increases. This is because there is a correlation between the viscosity of the liquid and the ionic conductivity, and the viscosity of water is generally lower than that of the ionic liquid. In this step, pre plurality of water concentrations by measuring the temperature dependence of the ionic conductivity may be stored in the storage device, before the derived water concentration C _w and the ion conductivity temperature dependence obtained by the storage in step S820 Is calculated to calculate the ionic conductivity σ of the mixed solution.

FIG. 11 is a graph showing the temperature dependence of ion conductivity measured and stored for a mixed solution of water concentrations C ₁ , C ₂ , C ₃ (C ₁ > C ₂ > C ₃ ). The ionic conductivity σ of the mixture can be calculated by comparing the derived water concentration C _w and temperature dependencies fuel cell temperature T _FC and step S820 measured in step S810.

  On the other hand, the conductivity σ of the mixed solution can be derived by the following method. That is, the conductivity σ of the mixed solution can be directly obtained by the ion conductivity sensor.

  FIG. 12 is an explanatory diagram showing a configuration of an ion conductivity sensor used in the present embodiment. FIG. 12 is a cross-sectional view of the reservoir, and the ion conductivity sensor is provided inside the reservoir. The ion conductivity sensor includes an ion conductivity measuring unit 1200 having a porosity similar to that of a reservoir and made of an insulating material, and electrode terminals 1210 and 2 made of two pairs of platinum wires penetrating through the ion conductivity measuring unit. And an AC ohmmeter 1220 connected to a pair of platinum wires. By providing ion conductivity sensors at multiple locations such as air bypass channel inlet, air channel inlet, air channel outlet, and air channel middle, the accuracy of measurement of the ionic conductivity of the mixed liquid can be improved, and the filling rate control It becomes possible to improve the accuracy. For example, the accuracy of filling rate control can be improved by providing at least one temperature sensor and one ion conductivity sensor on the upstream side and the downstream side of the air bypass channel inlet.

  The resistance R between electrode terminals can be measured by an alternating current impedance method using an ion conductivity sensor. Then, the conductivity σ of the mixed liquid can be obtained by the following formula (1). In measuring the resistance R between the electrode terminals, it is necessary to fill the entire ion conductivity measuring unit 1200 with the mixed solution, and therefore, this needs to be considered in the design of the ion conductivity measuring unit 1200.

  Here, l is the distance between the electrodes of the platinum electrode, A is the area between the electrodes of the ion conductivity measuring unit, and these values are known because they are design values.

  By substituting the resistance R between the electrode terminals into the equation (1), the conductivity σ of the mixed liquid can be calculated.

[S840]
The filling rate F of the reservoir on the air electrode side is derived.

FIG. 13 is a graph of the relationship between the ratio of the conductivity σ of the liquid mixture to σ ₀ which is the conductivity of the ionic liquid (hereinafter referred to as “ion conductivity ratio σ / σ ₀ ”) and the filling rate F of the reservoir. FIG. The conductivity σ ₀ of the ionic liquid is unique to each ionic liquid and is known. The relationship between the ionic conductivity ratio σ / σ ₀ and the filling rate F is stored in advance in the storage device of the control unit, and the ionic conductivity ratio σ / σ ₀ is calculated from the conductivity σ of the liquid mixture derived in the previous step S830. The filling rate F of the reservoir can be derived by obtaining and comparing with the relationship between the ion conductivity ratio σ / σ ₀ and the filling rate F stored in advance.

  Hereinafter, returning to FIG. 7, the steps after step S730 are performed.

[S730]
It is determined whether or not the filling rate F of the reservoir is smaller than a predetermined filling rate upper limit threshold _Fmax .

When it is determined that the filling rate F of the reservoir is not smaller than the filling rate upper limit threshold _Fmax , it is determined that the ionic liquid may leak to the outside, and the process proceeds to step S740.

When it is determined that the filling rate F of the reservoir is smaller than the filling rate upper limit threshold _Fmax , it is determined that there is no possibility that the ionic liquid leaks to the outside, and the process proceeds to step S750.

Here, the value of the filling rate upper limit threshold F _{max is the same as} the value of the filling rate lower limit threshold F _min described later, the size of the air flow path, the volume of the reservoir on the air electrode side, the porosity of the reservoir, the reservoir It can be changed according to conditions such as the material of the catalyst, the material of the catalyst, the operation output, and the safety factor set for the electrolyte leakage and gas leakage. In the present embodiment, F _max = 80% and F _min = 40%.

First, a case where it is determined that the filling rate F is not smaller than the filling rate upper limit threshold F _max will be described. If it is determined that the filling rate F is not smaller than the filling rate upper limit threshold _Fmax even at one place, the process proceeds to step S740, and the first filling rate lowering subroutine including the following steps S1400 to S1420 is performed. FIG. 14 is a diagram illustrating a first filling rate lowering subroutine.

[S1400]
Charge state S of the secondary battery is judged whether or larger than the threshold S _0.

  The charging state S of the secondary battery is generally detected by the open-circuit voltage of the secondary battery, but is not limited to this.

If the state of charge S of the secondary battery is determined to be greater than the threshold value S _0, it is determined that the secondary battery is in the charge state of only withstand temporary discharge, the process proceeds to step S1410.

If the state of charge S of the secondary battery is determined not to be larger than the threshold S _0, it has become a state of charge of only secondary batteries make up for the difference between the power generation amount of required power and fuel cell stack of the fuel cell system Otherwise, the process proceeds to the second filling rate lowering subroutine of step S1420.

[S1410]
The power generation amount of the fuel cell stack is reduced while keeping the air flow rate supplied to the air electrode constant.

Reducing the amount of power generation of the fuel cell stack air flow as a constant water vapor pressure P _v decreases the amount of water produced by the electrochemical reaction is decreased, the relative vapor pressure P _{v /} P ₀ is decreased. According to the vapor pressure curve shown in FIG. 10, when the relative water vapor pressure P _v / P ₀ decreases, the water concentration C _w decreases. That is, the filling rate F of the reservoir on the air electrode side can be reduced.

The first filling rate lowering subroutine is executed until the filling rate F becomes smaller than the filling rate upper limit threshold _Fmax .

[S1420]
If the state of charge S of the secondary battery is determined not to be larger than the threshold S _0, the process proceeds to the second filling ratio decreases subroutine consisting of steps S1500. FIG. 15 is a diagram showing a second filling rate lowering subroutine.

[S1500]
Reduce the amount of fuel cell cooling water.

  In the fuel cell system according to this embodiment shown in FIG. 3, the temperature of the fuel cell is controlled by the cooling water pump 309 to control the amount of cooling water passing through the fuel cell, the first radiator fan 304a or the second radiator fan 310a. It can be controlled by adjusting the temperature of the air or the temperature of the cooling water by adjusting the rotational speed. In this step, the temperature of the fuel cell is raised by reducing the amount of cooling water that passes through the fuel cell. By increasing the temperature of the fuel cell, the rate at which liquid water evaporates from the reservoir on the air electrode side can be increased, and the filling rate F of the reservoir on the air electrode side can be decreased.

At the same time, the cooling water bypass passage control valve is opened. Then, since the cooling water flows out to the cooling water bypass channel connected in the middle of the cooling water channel, the amount of cooling water flowing downstream of the cooling water channel decreases, and the vicinity of the downstream of the air channel close to the downstream of the cooling water channel The reservoir temperature can be increased. Then, the saturated water vapor pressure P _{0 in} the reservoir near the air flow path increases and the relative water vapor pressure P _v / P ₀ decreases, so that the filling rate of the reservoir near the air flow path can be reduced, and the air The filling rate in the entire reservoir on the pole side can be made uniform. Further, making the filling rate of the reservoir uniform leads to prevention of local leakage of the ionic liquid.

On the other hand, when the air bypass channel control valve is opened, air flows in from the air bypass channel connected in the middle of the air channel, so that the air flow rate downstream of the air channel increases. Then, the water vapor pressure _Pv of the reservoir near the air flow path decreases and the relative water vapor pressure P _v / P ₀ decreases, so that the filling rate of the reservoir near the air flow path can be reduced, A more uniform filling rate can be achieved in the direction of the air flow path. Further, making the filling rate of the reservoir uniform leads to prevention of local leakage of the ionic liquid.

The second filling rate lowering subroutine is executed until the filling rate F becomes smaller than the filling rate upper limit threshold _Fmax .

Next, returning to FIG. 7, a case where it is determined that the filling rate F is smaller than the filling rate upper limit threshold F _max will be described. In this case, the process proceeds to step S750.

[S750]
It is determined whether the filling rate F is smaller than a predetermined filling rate lower limit threshold _Fmin .

When it is determined that the filling rate F is smaller than the filling rate lower limit threshold F _min, it is determined that the supply of the ionic liquid as the electrolyte from the air electrode side to the matrix is insufficient and a cross leak may occur. The process proceeds to step S760.

When it is determined that the filling rate F is not smaller than the filling rate lower limit threshold _Fmin , it is determined that the supply of the ionic liquid as the electrolyte from the air electrode side to the matrix is sufficient, and the process proceeds to step S770.

First, the case where it is determined that the filling rate F is smaller than the filling rate lower limit threshold F _min will be described. In this case, the process proceeds to step S760, and the first filling rate increasing subroutine including the following steps S1600 to S1620 is performed. FIG. 16 is a diagram showing a first filling rate increase subroutine.

[S1600]
Charge state S of the secondary battery is judged whether the threshold value S _e smaller.

  The charging state S of the secondary battery is generally detected by the open-circuit voltage of the secondary battery, but is not limited to this.

If the state of charge S of the secondary battery is determined to the threshold value S _e is smaller than, the secondary battery is judged that the temporarily in chargeable charge state, the process proceeds to step S1610.

If the charging state S is determined to not smaller than the upper threshold value S _e, we have an empty capacity to the secondary battery absorbs a difference between the generated amount of required power and fuel cell stack of the fuel cell system If not, the process proceeds to the second filling rate increase subroutine of step S1620.

[S1610]
The power generation amount of the fuel cell stack is increased while the air flow rate supplied to the air electrode is kept constant.

Increasing the amount of power generated by the fuel cell stack air flow as a constant water vapor pressure P _v increases the amount of water produced by the electrochemical reaction increases, the relative vapor pressure P _{v /} P ₀ is increased. According to the vapor pressure curve shown in FIG. 7, when the relative water vapor pressure P _v / P ₀ increases, the water concentration C _w increases. That is, the filling rate F of the reservoir on the air electrode side can be increased.

The first filling rate increasing subroutine is executed until the filling rate F becomes larger than the filling rate lower limit threshold _Fmin .

[S1620]
If the state of charge S of the secondary battery is judged to be not smaller than the threshold value S _e, the process proceeds to the second filling rate increase subroutine consisting of steps S1700. FIG. 17 is a diagram showing a second filling rate increase subroutine.

[S1700]
Increase fuel cell coolant flow.

As described above, in the fuel cell system according to this embodiment shown in FIG. 3, the temperature of the fuel cell is adjusted by adjusting the amount of cooling water passing through the fuel cell by the cooling water pump 309, the first radiator fan 304a or the first It can be controlled by adjusting the rotational speed of the two radiator fan 310a. In this step, the temperature of the fuel cell is lowered by increasing the amount of cooling water that passes through the fuel cell. According to the vapor pressure curve shown in FIG. 10, by decreasing the temperature of the fuel cell, the saturated water vapor pressure P ₀ is decreased and the relative water vapor pressure P _v / P ₀ is increased, so that the water concentration C _w is increased. . That is, the filling rate F of the reservoir on the air electrode side can be increased.

At the same time, the cooling water bypass passage control valve is opened. Then, the cooling water flows out from the cooling water channel to the cooling water bypass channel connected in the middle of the cooling water channel, so the amount of cooling water flowing downstream of the cooling water channel decreases, and the air close to the downstream of the cooling water channel The temperature of the reservoir near the downstream of the flow path can be raised. Then, the saturated water vapor pressure P _{0 in} the reservoir near the downstream of the air flow path increases and the relative water vapor pressure P _v / P ₀ decreases, so that the filling rate of the reservoir near the downstream of the air flow path is adjusted to decrease. And the filling rate in the entire reservoir on the air electrode side can be made uniform. Further, making the filling rate of the reservoir uniform leads to prevention of local leakage of the ionic liquid.

On the other hand, when the air bypass flow path control valve is opened, air flows from the air bypass flow path connected in the middle of the air flow path to the air flow path, so that the air flow rate downstream of the air flow path increases. Then, the water vapor pressure _Pv of the reservoir near the air flow path decreases and the relative water vapor pressure P _v / P ₀ decreases, so that the filling rate of the reservoir near the air flow path can be reduced, A more uniform filling rate can be achieved in the direction of the air flow path. Further, making the filling rate of the reservoir uniform leads to prevention of local leakage of the ionic liquid.

The second filling rate raising subroutine is executed until the filling rate F becomes smaller than the filling rate lower limit threshold _Fmin .

Next, returning to FIG. 7, the case where it is determined that the filling rate F is not smaller than the filling rate upper limit threshold F _min will be described. At this time, as described above, it is determined that the supply of the ionic liquid as the electric field from the air electrode side to the matrix is sufficient, and the process proceeds to step S770.

[S770]
It is determined whether or not the average temperature T _FCave of all the fuel cells has reached the steady operation temperature T _FC0 .

By performing steps S720 to S750 described above, the temperature of the fuel cell is raised while maintaining the filling rate F of the reservoir on the air electrode side within an appropriate range between the filling rate lower limit threshold value _Fmin and the filling rate upper limit threshold value _Fmax . . Then, it is determined whether or not the average temperature T _FCave of all the fuel cells has reached the steady operation temperature T _FC0 as the specification.

When the average temperature T _FCave of all the fuel cells _reaches the specified steady operation temperature T _FC0 , the start operation of the fuel cell stack is finished.

  In addition, the flow after step S720 in the flowchart for implementing the fuel cell system according to the first embodiment shown in FIG. 7 can be carried out continuously and continuously even during operation of the fuel cell stack.

  Here, the compressor, the first heat exchanger, the air bypass passage, and the air bypass passage control valve are added to the air supply means of the present invention, the third heat exchanger, the cooling water bypass passage, and the cooling water bypass passage control valve. Corresponds to a cooling means. The temperature sensor, water vapor pressure sensor, ion conductivity sensor, and control unit correspond to detection means, and the control unit corresponds to control means.

The effects of the fuel cell system according to the first embodiment of the present invention will be described below.
-It is possible to prevent leakage of the ionic liquid from the fuel cell and to prevent cross leakage of the fuel cell.
-The filling rate of the mixed liquid of ionic liquid and water in the reservoir can be made uniform.
・ Reservoir filling rate can be adjusted easily without the need for new equipment.
The temperature of the fuel cell can be adjusted without changing the supply amount of air and hydrogen.
[Second Embodiment]
FIG. 18 is a block diagram showing a configuration of a fuel cell system according to the second embodiment of the present invention. Since the configuration of the fuel cell system according to the second embodiment is the same as that of the first embodiment except for the configuration described below, redundant description is omitted.

  Unlike the first embodiment, in the second embodiment, the temperature of the air flowing through the air bypass flow path 1814 is adjusted independently by the independent fifth heat exchanger 1840 (and the fourth radiator fan 1840a). The cooling water channel includes a first independent cooling water channel 1820 and a second independent cooling water channel 1830 which are two cooling water channels independent of each other.

  The air bypass flow path 1814 is connected to an intermediate point of the air flow path, and air can be introduced from the intermediate point of the air flow path by opening the air bypass flow path control valve 1815. The temperature of the air bypass channel can be adjusted independently by changing the rotational speed of the radiator fan 1840a of the fifth heat exchanger 1840. That is, it is possible to adjust the temperature downstream of the air flow path with a higher degree of freedom than in the first embodiment. Thereby, a more uniform filling rate can be achieved in the direction of the air flow path of the reservoir. Further, making the filling rate of the reservoir uniform leads to prevention of local leakage of the ionic liquid.

  The first independent cooling water channel 1820 and the second independent cooling water channel 1830 that constitute the cooling water channel can be arranged at positions where the temperature of different regions of the fuel cell can be adjusted. That is, the first independent cooling water channel 1820 can be arranged at a position where the temperature upstream of the air channel can be adjusted, and the second independent cooling water channel 1830 can be arranged at a position where the temperature downstream of the air channel can be adjusted.

  The temperature of the cooling water flowing through the first independent cooling water flow path 1820 can be adjusted independently by changing the number of revolutions of the radiator fan 1821a of the third heat exchanger 1821, and the amount of cooling water is uniquely controlled by the first cooling water pump 1822. It can be adjusted. The temperature of the cooling water flowing through the second independent cooling water flow path 1830 can be adjusted independently by changing the rotation speed of the radiator fan 1831a of the fourth heat exchanger 1831. The amount of cooling water can be adjusted by the second cooling water pump 1832. It can be adjusted independently. Therefore, since independent temperature adjustment is possible with the two independent cooling water channels, two temperature regions can be set inside the fuel cell, and the temperature variation inside the fuel cell is further reduced, and the entire reservoir on the air electrode side is reduced. The filling rate can be made more uniform. Further, making the filling rate of the reservoir uniform leads to prevention of local leakage of the ionic liquid.

  FIG. 19 is an explanatory diagram showing the structure of the portion of the reservoir where the air flow path is formed. The reservoir includes a first cooling water inlet 1904 for supplying cooling water to the first independent cooling water channel of the cooling plate, and a first cooling water outlet 1906a for discharging cooling water flowing through the first independent cooling water channel. Is provided. Further, a second cooling water inlet 1906b for supplying cooling water to the second independent cooling water flow path and a second cooling water outlet 1905 for discharging the cooling water flowing through the second independent cooling water flow path are provided.

  FIG. 20 is an explanatory view showing the structure of the cooling plate. The cooling plate is provided with a cooling water flow path including a first independent cooling water flow path 2010 and a second independent cooling water flow path 2020. The first independent cooling water channel 2010 is provided with a first cooling water inlet 2004 and a first cooling water outlet 2006a. The second independent cooling water channel 2020 is provided with a second cooling water inlet 2006b and a second cooling water outlet 2005. The cooling water flowing in from the first cooling water inlet 2004 flows through the first independent cooling water flow path 2010 and flows out from the first cooling water outlet 2006a. The cooling water flowing in from the second cooling water inlet 2006b flows through the second independent cooling water flow path 2020 and flows out from the second cooling water outlet 2005. The cooling water flowing out from the cooling water outlet of each independent cooling water flow path is adjusted for the cooling water flow rate and the cooling water temperature by passing through a heat exchanger and a cooling water pump provided individually, and the respective cooling water inlets. It recirculates through the cooling water flow path by re-inflowing from.

  Here, the temperature may be adjusted independently by two independent cooling water flow paths by flowing warm water through the cooling plate. Two temperature regions can be set inside the fuel cell, so that the temperature variation inside the fuel cell can be further reduced and the filling rate in the entire reservoir on the air electrode side can be made more uniform. Further, making the filling rate of the reservoir uniform leads to prevention of local leakage of the ionic liquid.

  Moreover, although a cooling plate is installed for every fuel cell, it is not limited to this. That is, you may insert in the arbitrary locations of the fuel cell laminated structure in a fuel cell stack. Thereby, a plurality of temperature regions can be provided in the fuel cell stack, the filling rate of the reservoir of the fuel cell constituting the fuel cell stack can be made uniform, and leakage of the ionic liquid can be prevented.

  Here, the compressor, the first heat exchanger, the air bypass passage, the air bypass passage control valve, and the fifth heat exchanger are the air supply means of the present invention, the third heat exchanger, the fourth heat exchanger, The first cooling water pump and the second cooling water pump correspond to cooling means. The temperature sensor, water vapor pressure sensor, ion conductivity sensor, and control unit correspond to detection means, and the control unit corresponds to control means.

The fuel cell operating method according to the second embodiment of the present invention has the following effects in addition to the effects of the first embodiment.
-The degree of freedom in adjusting the filling rate of the reservoir can be further expanded.
A more uniform filling rate can be achieved in the air flow direction of the reservoir.
[Third Embodiment]
FIG. 21 is a block diagram showing a configuration of a fuel cell system according to the third embodiment of the present invention. The difference from the second embodiment is that the third embodiment further includes a humidification system that adjusts the humidity of the air flowing through the air bypass flow path. A duplicate description with the first and second embodiments is omitted.

  The humidification system 2150 includes a humidifier that humidifies air by water spray, a pump that supplies water to the humidifier, and a water tank that stores water to be supplied to the pump, but is not limited thereto. The humidification system 2150 is installed in the air bypass channel 2114 and humidifies the air flowing through the air bypass channel to increase the humidity. The air bypass flow path 1814 is connected to an intermediate point of the air flow path, and by opening the air bypass flow path control valve 2115, air humidified by the humidification system 2150 can be introduced from the intermediate point of the air flow path. . The temperature of the air bypass channel can be adjusted independently by changing the rotational speed of the radiator fan 2140a of the fifth heat exchanger 2140.

  FIG. 22 is a diagram showing a third filling rate increase subroutine. The third filling rate increase subroutine corresponds to the second filling rate increase subroutine of step S1320 described in the first embodiment. That is, the third filling rate increase subroutine can be executed in place of the second filling rate increase subroutine.

  Hereinafter, the third filling rate increase subroutine will be described.

[S2200]
Humidify the air in the air bypass channel.

By humidifying the air in the air bypass passage, the water vapor pressure P _v of the reservoir in the vicinity of the downstream air passage is increased, since the relative vapor pressure P _{v /} P ₀ is increased, the filling of the reservoir in the vicinity of the downstream air channel The rate can be adjusted to increase, and the filling rate in the entire reservoir on the air electrode side can be made uniform. In other words, a more uniform filling rate in the direction of the air flow path is eliminated by eliminating the variation factor that the amount of water condensing in the vicinity of the air flow path downstream is less than the amount of water condensing near the air flow path upstream. Can be achieved. Further, making the filling rate of the reservoir uniform leads to prevention of local leakage of the ionic liquid.

  Here, the compressor, the first heat exchanger, the air bypass passage, the air bypass passage control valve, and the fifth heat exchanger are the air supply means of the present invention, the third heat exchanger, the fourth heat exchanger, The first cooling water pump and the second cooling water pump correspond to cooling means. The temperature sensor, water vapor pressure sensor, ion conductivity sensor, and control unit correspond to detection means, and the control unit and humidification system correspond to control means.

The fuel cell operating method according to the third embodiment of the present invention has the following effects in addition to the effects of the first and second embodiments.
-Since the filling rate of the reservoir is increased by humidifying the air, the filling rate can be increased with high responsiveness.
[Fourth Embodiment]
FIG. 23 is a block diagram showing a configuration of a fuel cell system according to the fourth embodiment of the present invention. The difference from the first embodiment is that the fourth embodiment further includes four valves 2360 to 2363 for reversing the air flow direction in the air flow path.

  Of the four valves 2360 to 2363 in FIG. 23, the first direction conversion valve and the fourth direction conversion valve shown in black are closed valves, and the second direction conversion valve and the fourth direction conversion valve shown in white are shown in white. Is an open valve. That is, FIG. 23 shows a state where the air flow direction in the air flow path is reversed.

  For example, by reversing the direction of air flow in the air flow path at regular intervals, the amount of water that condenses downstream and in the vicinity of the air flow path can be averaged, so a more uniform filling rate in the air flow path direction Can be achieved. Further, making the filling rate of the reservoir uniform leads to prevention of local leakage of the ionic liquid.

  Here, the compressor, the first heat exchanger, the air bypass passage, and the air bypass passage control valve are added to the air supply means of the present invention, the third heat exchanger, the cooling water bypass passage, and the cooling water bypass passage control valve. Corresponds to a cooling means. The temperature sensor, water vapor pressure sensor, ion conductivity sensor, and control unit correspond to detection means, and the control unit and the first to fourth direction change valves correspond to control means.

The fuel cell operating method according to the fourth embodiment of the present invention has the following effects in addition to the effects of the first embodiment.
A more uniform filling rate can be achieved in the air flow path direction of the reservoir.

It is a perspective view which shows the whole structure of a fuel cell stack. It is explanatory drawing for demonstrating the cross-section of the fuel cell which comprises a fuel cell stack. 1 is a block diagram showing a configuration of a fuel cell system according to a first embodiment of the present invention. It is explanatory drawing which shows the cross section of the internal structure of a fuel cell. It is explanatory drawing which shows the structure of the part in which the air flow path of the reservoir | reserver of the fuel cell system which concerns on 1st Embodiment of this invention was formed. It is explanatory drawing which shows the structure of the cooling plate of the fuel cell system which concerns on 1st Embodiment of this invention. It is a flowchart for implementing the fuel cell system which concerns on 1st Embodiment of this invention. It is a figure which shows the filling rate derivation | leading-out subroutine of an air electrode side reservoir | reserver. It is explanatory drawing for showing the position of the water vapor pressure sensor, ion conductivity sensor, and cell temperature sensor which were installed in the air electrode side of the fuel cell of the fuel cell system concerning a 1st embodiment of the present invention. It is a figure which shows the vapor pressure curve of a liquid mixture. Water concentration C _1, a C _2, a graph showing the temperature dependence of ionic conductivity which is stored measured for a mixture of C _3. It is explanatory drawing which shows the structure of the ion conductivity sensor of the fuel cell system which concerns on 1st Embodiment of this invention. It is a figure which shows the graph of the relationship between ionic conductivity ratio and the filling rate of a reservoir. It is a figure which shows a 1st filling rate fall subroutine. It is a figure which shows the 2nd filling rate fall subroutine. It is a figure which shows a 1st filling rate raise subroutine. It is a figure which shows the 2nd filling rate raise subroutine. It is a block diagram which shows the structure of the fuel cell system which concerns on 2nd Embodiment of this invention. It is explanatory drawing which shows the structure of the part in which the air flow path of the reservoir | reserver of the fuel cell system which concerns on 2nd Embodiment of this invention was formed. It is explanatory drawing which shows the structure of the cooling plate of the fuel cell system which concerns on 2nd Embodiment of this invention. It is a block diagram which shows the structure of the fuel cell system which concerns on 3rd Embodiment of this invention. It is a figure which shows the 3rd filling rate raise subroutine. It is a block diagram which shows the structure of the fuel cell system which concerns on 4th Embodiment of this invention.

Explanation of symbols

1 Fuel cell stack,
2 fuel cells,
200 air electrode,
210 reservoir,
220 air flow path,
230 matrix,
240 fuel electrode,
250 fuel flow path,
300 fuel cell stack,
301 temperature sensor (detection means),
302 ion conductivity sensor (detection means),
303 water vapor pressure sensor (detection means),
304 first heat exchanger (air supply means),
304a First radiator fan,
305 compressor (air supply means),
306 hydrogen tank,
307 pressure regulator,
308 second heat exchanger,
309 cooling water pump,
310 third heat exchanger (cooling means),
310a second registrar fan,
311 secondary battery,
312 inverter,
313 control unit (detection means, control means),
314 air bypass flow path (air supply means),
315 Air bypass flow path control valve (air supply means),
316 Cooling water bypass channel (cooling means),
317 Cooling water bypass flow control valve (cooling means).

Claims (9)

A fuel battery cell comprising: a matrix impregnated with an ionic liquid; an air electrode provided facing the fuel electrode through the matrix; and a reservoir for replenishing the matrix with the ionic liquid through the air electrode;
Detecting means for detecting the amount of the ionic liquid in the reservoir or the amount of the mixed liquid in which the ionic liquid and the condensed water generated in the fuel cell are mixed;
Control means for controlling the amount of the ionic liquid in the reservoir or the amount of the mixed liquid within a predetermined setting range based on the result detected by the detection means;
A fuel cell system comprising: The fuel battery cell is further provided with air supply means for supplying air through an air flow path provided in the fuel battery cell,
The air supply means has at least one air bypass flow path that is connected to an air flow path in the fuel cell and capable of flowing the air,
The said control means has a bypass air flow rate adjustment means which adjusts the flow volume of the said air which flows into the said air bypass flow path, and controls the quantity of the ionic liquid in the said reservoir | reserver, or the quantity of the said liquid mixture. 2. The fuel cell system according to 1. The fuel battery cell is further provided with air supply means for supplying air through an air flow path provided in the fuel battery cell,
The air supply means has at least one air bypass flow path that is connected to an air flow path in the fuel cell and capable of flowing the air,
The said control means has a bypass air temperature adjustment means which adjusts the temperature of the air of the said air bypass flow path independently, and controls the quantity of the ionic liquid in the said reservoir | reserver, or the quantity of the said liquid mixture. 2. The fuel cell system according to 1. The fuel cell further includes cooling means for cooling the fuel cell by flowing cooling water through a cooling water flow path in the fuel cell,
The cooling means has at least one cooling water bypass flow path connected to the cooling water flow path and capable of returning the cooling water,
The control means includes a bypass cooling water flow rate adjusting means for adjusting a flow rate of the cooling water flowing through the cooling water bypass flow path and controlling an amount of the ionic liquid or the mixed liquid in the reservoir. The fuel cell system according to claim 1. The fuel cell further includes cooling means for cooling the fuel cell by flowing cooling water through a cooling water flow path in the fuel cell,
The cooling means has at least one cooling water bypass flow path connected to the cooling water flow path and capable of returning the cooling water,
The control means includes bypass cooling water temperature adjusting means for independently adjusting the temperature of the cooling water flowing in the cooling water bypass flow path and controlling the amount of the ionic liquid in the reservoir or the amount of the mixed liquid. The fuel cell system according to claim 1. The fuel cell further includes cooling means for cooling the fuel cell by flowing cooling water through a cooling water flow path in the fuel cell.
The cooling water flow path comprises a plurality of independent cooling water flow paths independent of each other,
The control means includes independent cooling water temperature adjusting means for independently adjusting the temperature of the cooling water flowing through the independent cooling water flow path and controlling the amount of ionic liquid or the amount of the mixed liquid in the reservoir. The fuel cell system according to claim 1. The fuel battery cell is further provided with air supply means for supplying air through an air flow path provided in the fuel battery cell,
The air supply means has at least one air bypass flow path that is connected to an air flow path in the fuel cell and capable of flowing the air,
The said control means has an air humidity adjustment means which adjusts the humidity of the said air which flows into the said air bypass flow path independently, and controls the quantity of the ionic liquid in the said reservoir | reserver, or the quantity of the said liquid mixture. Item 4. The fuel cell system according to Item 1.   The control means sets at least two temperature regions in the fuel cell or a fuel cell stack in which the fuel cells are stacked, and controls the amount of ionic liquid or the amount of the mixed solution in the reservoir. The fuel cell system according to claim 1, comprising:   2. The air flow direction reversing means for controlling the amount of the ionic liquid or the amount of the mixed liquid in the reservoir by reversing the flow direction of the air in the air flow path. The fuel cell system described in 1.

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