JP2008021448A - Fuel cell system and fuel cell control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To execute wet-state control of a fuel cell with high accuracy. <P>SOLUTION: A fuel cell system is provided with the fuel cell, including a plurality of single cells, a first wet-state detection means, a second wet-state detection means, a comparison means, and a control means. The first wet-state detection means detects the wet state of a first single cell, including at least one single cell among a plurality of the single cells, and the second wet-state detection means detects the wet state of a second single cell, including at least one single cell, that is different from that of the first single cell among a plurality of the single cells. The comparison means compares the wet state of the first single cell with that of the second single cell. The control means controls the wet state of the fuel cell, on the basis of the comparison results. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell system and a fuel cell control method, and more particularly to control of a wet state of a fuel cell.

  In a fuel cell, for example, when a solid polymer membrane is used as an electrolyte membrane, it is desirable to manage the wet state inside the fuel cell in order to generate power efficiently. For example, when the electrolyte membrane of a polymer electrolyte fuel cell is dried, the ion permeability deteriorates, resulting in a decrease in the output of the fuel cell. On the other hand, if excessive water is present in the fuel cell, water is condensed on the electrode to inhibit the diffusion of the reaction gas, resulting in a decrease in the output of the fuel cell. Further, if excessive water remains in the fuel cell when the fuel cell is not operating, the inside of the fuel cell freezes at a low temperature, which may hinder the next start of the fuel cell.

  In such a fuel system that handles a fuel cell, there is a technique for diagnosing the wet state of a fuel cell by measuring the current flowing through a portion that easily dries inside a single cell of the fuel cell and a portion where moisture tends to be excessive. Known (for example, Patent Document 1).

JP 2005-1000095 A2 Japanese Patent Laid-Open No. 2004-199988 JP 2002-367650 A

  However, the above technique does not consider the variation in wet state between single cells in a fuel cell including a plurality of single cells. For this reason, there is a possibility that control of the wet state of the entire fuel cell cannot be performed with high accuracy.

  The present invention has been made to solve the above-described problems, and an object thereof is to improve the accuracy of control of the wet state of a fuel cell.

  In order to achieve the above object, a first aspect of the present invention provides a fuel cell system. A fuel cell system according to a first aspect of the present invention includes a fuel cell including a plurality of single cells, a first wet state detection unit, a second wet state detection unit, a comparison unit, a control unit, Is provided. The first wet state detecting means detects a wet state of a first single cell portion including at least one single cell among the plurality of single cells. The second wet state detecting means detects a wet state of a second single cell part including at least one single cell different from the first single cell part among the plurality of single cells. The comparison means compares the wet state of the first single cell part and the second single cell part. The control means controls the wet state of the fuel cell based on the comparison result.

  According to the fuel cell system of the first aspect of the present invention, the wet state in the first single cell part and the second single cell part among the plurality of single cells is compared, and the fuel is based on the comparison result. Control the wet state of the battery. As a result, the wet state of the entire fuel cell can be accurately controlled.

  In the fuel cell system according to the first aspect of the present invention, the control means is configured to start the current operation of the fuel cell based on the comparison result of the wet state at the end of the previous operation of the fuel cell. The wet state of the fuel cell may be controlled. In this way, since the wet state of the fuel cell is controlled at the start of the current operation based on the comparison result of the wet state at the end of the previous operation, the wet state of the fuel cell is quickly determined from the start of the current operation. It can be controlled with high accuracy.

  In the fuel cell system according to the first aspect of the present invention, the first single cell portion may be a single cell that is more easily wetted than the second single cell portion. In this way, the wet state of the fuel cell can be accurately grasped by comparing the single cells having different wetness levels.

  In the fuel cell system according to the first state of the present invention, the plurality of single cells have a stack structure, and the first single cell portion is an end of the stack structure among the plurality of single cells. A single cell located at a position may be included. Further, the second single cell portion may be all of the plurality of single cells.

  In the fuel cell system according to the first aspect of the present invention, the first wet state detecting means is means for measuring the resistance of the first single cell part, and the second wet state detecting means is A means for measuring the resistance of the second single cell portion may be used. In this way, the wet state of the first single cell part and the second single cell part can be detected by measuring the resistance.

  In the fuel cell system according to the first aspect of the present invention, the control means humidifies the fuel cell when the second single cell portion is dried by a predetermined level or more than the first single cell portion. Humidification means for performing control may be included. In this way, it is possible to prevent the second single cell part that is easier to dry than the first single cell part from being excessively dried, and to prevent a decrease in the output of the fuel cell.

  The fuel cell system according to the first aspect of the present invention further includes a drying unit that dries the fuel cell based on a wet state of the first single cell portion when the operation of the fuel cell is finished, and the humidification The means is means for performing control to humidify the fuel cell when the second single cell unit is dried at a predetermined level or more from the first single cell unit at the start of the next operation of the fuel cell. May be. In this way, by drying the fuel cell based on the first single cell portion that tends to get wet at the end of the operation, the fuel cell can be prevented from freezing during the stop, and at the start of the operation, the first cell It is possible to prevent the second single cell part that is easier to dry than the single cell part from being excessively dried, and to prevent a decrease in the output of the fuel cell.

  The present invention can be realized in various aspects other than the first aspect, and can be realized as a method invention such as a control method for a fuel cell including a plurality of single cells.

  Next, embodiments of the present invention will be described based on examples with reference to the drawings.

A. Example:
・ Fuel cell system configuration:
With reference to FIG. 1 and FIG. 2, the structure of the fuel cell system based on an Example is demonstrated. FIG. 1 is an explanatory diagram illustrating a schematic configuration of a fuel cell system according to an embodiment. FIG. 2 is an explanatory diagram showing a schematic configuration of the fuel cell.

  As shown in FIG. 1, the fuel cell system 1000 includes a fuel cell 100, a hydrogen tank 200, an air compressor 300, and a cooling medium supply unit 500.

  The fuel cell 100 receives supply of air as an oxidizing gas and hydrogen as a fuel gas, and generates electric power through an electrochemical reaction using these gases. As shown in FIG. 2, the fuel cell 100 has a stack structure in which single cells 101 and separators 102 are alternately stacked. The single cell 101 is disposed on a solid polymer electrolyte membrane showing good proton conductivity in a wet state, an anode disposed on one surface of the solid polymer electrolyte membrane, and the other surface of the solid polymer electrolyte membrane. And a cathode (not shown). The separator 102 has a function of electrically connecting the stacked unit cells 101 and separating the reaction gas (oxidizing gas and fuel gas) supplied to each unit cell 101 for each unit cell 101. Although not shown in FIG. 2, the separator 102 is formed with a fuel gas flow path 25 for distributing fuel gas to each single cell 101 and an oxidizing gas flow path 35 for distributing oxidizing gas. A cooling medium flow path 55 for flowing the cooling medium therein is formed.

  In the fuel cell 100, current collectors 103 are disposed at both ends of the stack structure. The current collector 103 is connected to a wiring 61 for outputting the electromotive force of the fuel cell 100. On the wiring 61, a current sensor 110 for measuring a current flowing through the stack of the fuel cell 100 is disposed. Further, in the fuel cell 100, the voltage of one single cell (hereinafter referred to as an end cell) 101 located at one end of the stack structure among the single cells 101 constituting the stack structure of the fuel cell 100. A first voltage sensor 121 is provided for measuring. Further, the fuel cell 100 is provided with a second voltage sensor 122 for measuring the voltage of the entire single cell 101 constituting the stack structure of the fuel cell 100.

  Returning to FIG. 1, the description will be continued. The hydrogen tank 200 is a tank that stores hydrogen as a fuel gas. For example, the hydrogen tank 200 is a hydrogen cylinder that stores high-pressure hydrogen or a tank that stores hydrogen by being stored in a hydrogen storage alloy. The hydrogen tank 200 is connected to one end of the fuel gas passage 25 of the fuel cell 100 via the fuel gas supply passage 24. A pressure adjustment valve 220 and a fuel gas humidifier 210 are arranged on the fuel gas supply path 24. The fuel gas humidifier 210 humidifies the fuel gas by vaporizing water pumped from a water tank (not shown) and mixing it with the fuel gas. The fuel gas humidifier 210 can change the humidification amount under the control of the control unit 400 described later. The other end of the fuel gas passage 25 is connected to the fuel gas discharge passage 26. A discharge valve 240 is disposed on the fuel gas discharge path. One end of the circulation passage 28 is connected to the upstream side of the discharge valve 240 of the fuel gas discharge passage 26. The other end of the circulation flow path 28 is connected to the downstream side of the pressure adjustment valve 220 of the fuel gas supply path 24. A fuel gas pump 250 is disposed on the circulation channel 28.

  The hydrogen gas stored in the hydrogen tank 200 is discharged to the fuel gas supply path 24, adjusted (depressurized) to a predetermined pressure by the pressure adjustment valve 220, humidified by the fuel gas humidifier 210, and then fuel gas Is supplied to the fuel gas passage 25 of the fuel cell 100. The fuel gas discharged from the other end of the fuel gas passage 25 of the fuel cell 100 is caused to flow through the fuel gas discharge passage 26 and the circulation passage 28 by the fuel gas pump 250 and flows into the fuel gas supply passage 24 again. In this way, the remaining hydrogen in the fuel gas discharged from the fuel cell is a path comprising a part of the fuel gas supply path 24, a fuel gas flow path 25, a part of the fuel gas discharge path 26, and a circulation flow path 28. And is supplied to the fuel cell 100 again. Further, by opening the discharge valve 240, a part of the fuel gas containing moisture and impurities is discharged from the fuel gas discharge path 26 to the outside.

  The air compressor 300 takes in air as an oxidizing gas from the atmosphere. The air compressor 300 is connected to one end of the oxidizing gas passage 35 of the fuel cell 100 via the oxidizing gas supply passage 34. An oxidizing gas humidifier 310 is disposed on the oxidizing gas supply path 34. Similar to the fuel gas humidifier 210, the oxidizing gas humidifier 310 humidifies the oxidizing gas by evaporating the water pumped from a water tank (not shown) and mixing it with the oxidizing gas. Similar to the fuel gas humidifier 210, the oxidizing gas humidifier 310 can change the humidification amount under the control of the control unit 400 described later. An oxidant gas discharge path 36 is connected to the other end of the oxidant gas path 35. A pressure adjustment valve 320 is disposed in the oxidizing gas discharge path 36.

  The air compressor 300 supplies pressurized air to the oxidizing gas supply path 34 as oxidizing gas. The air supplied to the oxidizing gas supply path 34 is humidified by the oxidizing gas humidifier 310 and supplied to one end of the oxidizing gas flow path 35 of the fuel cell 100 as the oxidizing gas. The oxidizing gas discharged from the other end of the oxidizing gas channel 35 is released into the atmosphere through the oxidizing gas discharge channel 36. The pressure and flow rate of the oxidizing gas flowing through the oxidizing gas passage 35 are adjusted by controlling the pressure adjusting valve 320 and the opening degree on the oxidizing gas discharge passage 36 and the output of the air compressor 300.

  The fuel cell system 1000 further includes a cooling medium supply unit 500. The cooling medium supply unit 500 is a system for circulating the cooling medium to the cooling medium flow path 55 of the fuel cell 100, and includes a circulation pump and a radiator (not shown). As the cooling medium, for example, antifreeze water such as ethylene glycol is used. The cooling medium supply unit 500 is connected to one end of the cooling medium flow path 55 via the cooling medium supply path 54, and is connected to the other end of the cooling medium flow path 55 via the cooling medium discharge path 56.

  The fuel cell system 1000 further includes a load 610 and a converter 630 connected in parallel to the wiring 61 connected to the current collector 103 of the fuel cell 100 described above. The load 610 is a component that consumes the electric power output from the fuel cell 100, and is controlled by, for example, an inverter that converts the direct-current three-phase alternating current output from the fuel cell and a three-phase alternating current output from the inverter. Motor. Converter 630 is a DC / DC converter connected to secondary battery 620, and controls the voltage and current between two current collectors 103 of fuel cell 100 by setting the voltage of wiring 61. For example, the converter 630 can apply a minute alternating current component having a predetermined frequency to the current flowing between the two current collectors 103 of the fuel cell 100 by changing the voltage of the wiring 61 in a predetermined cycle.

  The fuel cell system 1000 further includes a control unit 400. For example, the control unit is configured using a known computer including a CPU, a ROM, a RAM, an input / output port, and the like, and controls the entire fuel cell system 1000. The control unit 400 is connected to each unit of the fuel cell system 1000, for example, the air compressor 300, the cooling medium supply unit 500, the converter 630, the pressure adjustment valve 320, and the discharge valve 240 so as to exchange control signals. Moreover, the control part 400 is connected so that information can be collected from various sensors (for example, the current sensor 110 and the voltage sensors 121 and 122). The control unit 400 includes various functions for controlling the entire fuel cell system 1000, including a function for collecting information from various sensors and a function for controlling the operation of each unit of the fuel cell system 1000. In FIG. FIG. 6 selectively illustrates functional units necessary for the description of the present embodiment, and in the present specification, the functional units are selectively described. The control unit 400 includes a resistance measurement unit 410, a resistance comparison unit 420, a drying control unit 430, and a humidification control unit 440 as functional units. The resistance measurement unit 410 measures the resistance value of the end cell described above based on the current and voltage acquired from the current sensor 110 and the first voltage sensor 121. In addition, the resistance measurement unit 410 measures the resistance values of the plurality of single cells 101 as a whole based on the current and voltage acquired from the current sensor 110 and the second voltage sensor 122. The resistance comparison unit 420 compares the resistance value of the end cell with the resistance values of the plurality of single cells 101 as a whole. The drying control unit 430 performs control for drying the fuel cell 100 based on the resistance value of the end cell. The humidification control unit 440 performs control to humidify the fuel cell 100 based on the comparison result of the resistance value by the resistance comparison unit 420. Each of these functional units will be described later.

・ Operation of the fuel cell system:
The operation of the fuel cell system 1000 will be described with reference to FIGS. FIG. 3 is a flowchart showing the operation steps of the operation end operation. FIG. 4 is a flowchart showing the operation steps of the operation start operation. FIG. 5 is a graph showing the relationship between the resistance value and the wet state in a single cell.

  First, an operation when the operation of the fuel cell 100 is ended (operation end operation) will be described. The operation end operation is started when the operation of the fuel cell 100 is ended, for example, when the fuel cell 100 is used as power for the automobile, the operation of the automobile is stopped and the key is returned to the off position. The When the operation end operation is started, the drying control unit 430 of the control unit 400 starts drying control of the fuel cell 100 (step S110). When the fuel cell 100 is in operation, the inside of the fuel cell 100 is controlled to contain a lot of moisture in order to keep the solid polymer electrolyte membrane moist. If the fuel cell 100 is stopped in a state where a lot of moisture is contained in the fuel cell 100, when the temperature of the fuel cell 100 is decreased, moisture is condensed inside the fuel cell 100, and the inside of the fuel cell 100 is There is a risk of freezing. For this reason, it is necessary to dry the inside of the fuel cell 100 in the operation end operation of the fuel cell. In the drying control, for example, the operation of the fuel gas humidifier 210 and the oxidizing gas humidifier 310 is stopped and the air compressor 300 is operated to cause the dried air to flow into the oxidizing gas flow path 35 of the fuel cell 100. Control. As a result, the water inside the fuel cell 100 is vaporized and taken out together with the dried air via the oxidizing gas discharge path 36, so that the inside of the fuel cell 100, for example, the electrolyte membrane of the single cell 101 is dried. Can do.

  When the drying control is started, the resistance measuring unit 410 of the control unit 400 acquires the above-described end cell resistance value (end resistance) Re (step S120). Specifically, the resistance measurement unit 410 controls the converter 630 to apply an AC component having a predetermined frequency to the current between the current collectors 103 at both ends of the fuel cell 100. The resistance measurement unit 410 acquires the current between the current collectors 103 from the current sensor 110 and acquires the voltage of the end cell from the first voltage sensor 121. The resistance measurement unit 410 calculates the end resistance Re based on the phase difference between the AC component of the acquired current and the AC component of the acquired voltage, and the frequency of the AC component.

  The resistance of the single cell 101 is determined mainly by the resistance of the components of the single cell 101 and the contact resistance between the components. Among these, the resistance (membrane resistance) of the solid polymer electrolyte membrane, which is a main component of the single cell 101, varies depending on the wet state of the solid polymer electrolyte membrane. Therefore, the wet state of the single cell 101 can be detected by measuring the resistance value of the single cell 101.

  As indicated by a solid line L in FIG. 5, when the single cell 101 is in a state of being wetter than the predetermined wet level Th, the resistance value of the single cell 101 is substantially constant. On the other hand, when the single cell 101 is in a state of being dried from a predetermined wet level Th, the resistance value of the single cell 101 increases as the single cell 101 is dried.

  When the end resistance Re is acquired, the drying control unit 430 of the control unit 400 determines whether or not the end resistance Re is greater than the threshold value C1 (step S130). The threshold value C1 is a value empirically determined in advance by experiments or the like, and is a resistance value of the single cell 101 corresponding to a state in which the single cell 101 is dried to such an extent that freezing does not occur at low temperatures (FIG. 5). During the operation of the fuel cell 100, since the resistance value of the single cell 101 is preferably low, the wet state of the single cell 101 is wetter than a predetermined level Th. When the drying control is started in the operation end operation, the end cell is gradually dried, and the resistance value of the end cell increases with drying. As a result, when the end cell is dried to such an extent that freezing at a low temperature does not occur, the end resistance Re becomes larger than the threshold C1.

  If the drying control unit 430 determines that the end resistance Re is smaller than the threshold value C1 (step S130: NO), the drying control is continued, and the process returns to step S120. When the drying control unit 430 determines that the end resistance Re is larger than the threshold (step S130: YES), the drying control ends (step S140). That is, the entire fuel cell 100 is dried until the above-described end cell of the plurality of single cells 101 is in a wet state corresponding to the resistance value C1. Here, the reason why the drying process is performed on the basis of the end cells is that the end cells are the cells that are most likely to be wet among the plurality of single cells 101. If the end cells that are most likely to be wetted are dried to such an extent that freezing does not occur, the single cells 101 other than the end cells are in a dry state than the end cells. Can be prevented. The reason why the end cell is most likely to be wet is that the end cell is close to the outside air, so that the temperature is lower than the other single cells 101. For this reason, since the generated water generated inside the fuel cell 100 is more agglomerated in the end cells, the end cells tend to be wet.

  When the drying control is completed, the resistance measuring unit 410 of the control unit 400 acquires and stores the end resistance Re and the total resistance Rt when the drying control is completed (step S150). The overall resistance Rt is the overall resistance value of the plurality of single cells 101. The method for obtaining the end portion resistance Re is as described above. The total resistance Rt is obtained from the current value acquired from the current sensor 110 and the voltage values of the plurality of single cells 101 acquired from the second voltage sensor 122 in the same manner as the calculation of the end resistance Re. Calculated. When the end resistance Re and the total resistance Rt at the end of the drying control are stored, the operation end operation is ended.

  Next, with reference to FIG. 4, an operation at the time of starting operation of the fuel cell 100 (operation start operation) will be described. The operation start operation is started when the fuel cell 100 is started, for example, when the fuel cell 100 is used as power for the automobile, and when the key is put in the ON position prior to the operation of the automobile. . When the operation start operation is started, the control unit 400 is activated (step S210). When the control unit 400 is activated, the control unit 400 acquires the end resistance Re and the total resistance Rt stored in step S150 (FIG. 3) of the operation end operation at the previous operation (step S220). When the end resistance Re and the total resistance Rt are acquired, the resistance comparison unit 420 of the control unit 400 determines the difference ΔR between the average resistance of the plurality of single cells 101 and the end resistance Re = (total resistance Rt / number of single cells− It is determined whether or not the end resistance Re) is greater than a predetermined threshold C2 (step S230).

  The wet state can be compared between the end cells and the single cells 101 other than the end cells depending on the magnitude of the difference ΔR. When the difference ΔR is larger than the predetermined threshold C2, the single cell 101 other than the end cell, for example, the single cell 101 in the central portion of the stack structure is too dry compared to the end cell. I can judge. On the contrary, when the difference ΔR is smaller than the predetermined threshold C2, it can be determined that there is not much difference in the degree of drying between the single cells 101 other than the end cells and the end cells. Such a difference in the degree of drying between the single cells 101 and the end cells other than the end cells is due to variations in the residual water distribution at the end of the previous operation. In the operation end operation after the end of the previous operation, since the drying control is performed with reference to the end cell (FIG. 3), for example, the residual water of the other single cell 101 is compared with the residual water of the end cell. In the case where the number of the cells is small, if the drying control is performed to such an extent that the end cells can be prevented from freezing, the other single cells 101 are excessively dried. On the other hand, when there is not much difference in the amount of water between the residual water of the end cell and the residual water of the other single cell 101, there is not much difference in the degree of drying between the end cell and the other single cell 101. Will disappear.

  When it is determined that the difference ΔR is smaller than the predetermined threshold C2 (step S230: NO), the control unit 400 starts up the fuel cell 100 by normal control (step S250). On the other hand, when it is determined that the difference ΔR is larger than the predetermined threshold C2 (step S230: YES), the control unit 400 starts the fuel cell 100 by humidification control (step S240). The humidification control is control for increasing the amount of humidification inside the fuel cell 100 as compared with the normal control. Specifically, the humidification control is executed by controlling the fuel gas humidifier 210 and the oxidizing gas humidifier 310, and increasing the humidification amount of the fuel gas and the oxidizing gas supplied to the fuel cell 100 from the normal control. The

  According to the fuel cell system 1000 according to the present embodiment described above, the drying control is executed at the end of the operation of the fuel cell 100 based on the wet state of the end cells that are likely to get wet. Can be prevented more reliably.

  At the start of operation of the fuel cell 100, the wet state of the end cell and the wet state of the single cell 101 other than the end cell are compared, and the fuel cell such as humidification control is based on the comparison result. Since the control for managing the wet state of 100 is performed, the control accuracy of the wet state of the fuel cell 100 can be improved. Specifically, as compared with the end cell, when the unit cell 101 other than the end cell is too dry, it recognizes that and starts up while increasing the amount of humidification. The inside of the battery 100 can be quickly brought into an appropriate humidified state.

  Further, the wet state of the end cells and other cells at the start of the operation of the fuel cell 100 is determined using the end resistance Re and the total resistance Rt at the end of the previous operation, so that the end resistance at the start of the operation is determined. It is not necessary to measure Re and the total resistance Rt, and the inside of the fuel cell 100 can be brought into an appropriately humidified state more quickly.

B. Variation:
・ First modification:
In the above embodiment, in the operation start operation, the control is performed based on the comparison result of the wet state between the end cell and the other cells, but instead, the control is performed in the normal operation operation. You can go. FIG. 6 is a flowchart showing the operation steps of the normal operation. The normal operation is performed while the vehicle is running, for example, when the fuel cell 100 is used as power for the vehicle, when the fuel cell 100 is being operated.

  During the normal operation, the resistance measuring unit 410 of the control unit 400 periodically acquires the end resistance Re and the total resistance Rt (step S310). When the end resistance Re and the total resistance Rt are acquired, the resistance comparison unit 420 of the control unit 400 calculates ΔR in the same manner as in the embodiment, and determines whether ΔR is greater than a predetermined threshold C3 (step). S320). If it is determined that ΔR is smaller than the predetermined threshold C3 (step S320: NO), the control unit 400 operates the fuel cell 100 under normal control. On the other hand, if it is determined that ΔR is larger than the predetermined threshold C3 (step S320: YES), the control unit 400 operates the fuel cell 100 by humidification control. In the operation by the normal control, for example, the fuel cell 100 generates power while controlling the wet state of the fuel cell 100 based on the value of the end resistance Re, that is, based on the wet state of the end cell. On the other hand, in the operation by the humidification control, as in the above-described embodiment, the amount of humidification is increased compared to the normal control, and the power generation of the fuel cell 100 is performed.

  According to the first modification, normally, the flooding of the fuel cell 100 can be suppressed by performing the operation while managing the wet state of the fuel cell 100 with reference to the end cells that are likely to get wet. Furthermore, when the unit cells 101 other than the end cells are too dry compared to the end cells, the fuel cell 100 is dried because the operation is performed with an increased amount of humidification. Therefore, it is possible to suppress an increase in internal resistance. That is, according to the first modification, it is possible to accurately manage the wet state of the fuel cell 100 during normal operation, and to suppress a decrease in the output of the fuel cell 100 due to flooding or excessive drying.

・ Second modification:
In the fuel cell system 1000 according to the above embodiment, the fuel gas humidifier 210 and the oxidizing gas humidifier 310 are provided, but the fuel gas humidifier 210 and the oxidizing gas humidifier 310 may not be provided. FIG. 7 is an explanatory diagram illustrating a schematic configuration of a fuel cell system according to a second modification. The fuel cell system 1000A according to the second modification differs from the fuel cell system 1000 according to the embodiment in that the oxidizing gas humidifier 310 is not provided on the oxidizing gas supply path 34 and the fuel is supplied on the fuel gas supply path 24. The gas humidifier 210 is not provided. Since the other configuration of the fuel cell system 1000A according to the second modification is the same as the configuration of the fuel cell system 1000 according to the embodiment described with reference to FIG. 1, the same configuration is illustrated in FIG. The same reference numerals are used and the description thereof is omitted.

  The change of the humidification amount in the second modified example is as follows. 1. Change of ratio of supply amount of oxidizing gas (air) to supply amount of fuel gas (hydrogen) 2. change of temperature of the fuel cell 100; It is executed by all or part of the change of the gas pressure of the oxidizing gas (air). An example of humidification control in the embodiment (FIG. 4: step S240), that is, an example in which the humidification amount is increased as compared with the normal control will be described in detail.

  When the humidification amount is increased, the air compressor 300 is controlled so that the ratio of the supply amount of the oxidizing gas to the supply amount of the fuel gas is smaller than that in the normal control. As a result, since the amount of residual water taken away by the oxidizing gas decreases with respect to the amount of generated water, the amount of residual water inside the fuel cell 100 increases and the amount of humidification of the fuel cell 100 increases.

  Further, when the amount of humidification is increased, the temperature of the fuel cell 100 is lowered by controlling the cooling medium supply unit 500 to circulate a large amount of cooling water through the cooling medium flow channel 55 as compared with the case of normal control. As a result, the saturated water vapor pressure inside the fuel cell 100 is lowered and the amount of moisture condensed inside the fuel cell 100 is increased, so that the amount of residual water carried away by the oxidizing gas is reduced. Therefore, the amount of residual water inside the fuel cell 100 increases and the amount of humidification of the fuel cell 100 increases.

  Further, when the humidification amount is increased, the air compressor 300 and the pressure adjustment valve 320 are controlled so that the gas pressure of the oxidizing gas flowing through the oxidizing gas passage 35 of the fuel cell 100 is made larger than that in the normal control. As a result, the amount of moisture condensed in the oxidizing gas and condensed in the fuel cell 100 increases, so that the amount of residual water taken away by the oxidizing gas decreases. Therefore, the amount of residual water inside the fuel cell 100 increases and the amount of humidification of the fuel cell 100 increases.

  By the control as described above, humidification control can be performed even in the fuel cell system 1000A without the fuel gas humidifier 210 and the oxidizing gas humidifier 310. Further, when the humidification control is performed, the output of the fuel cell 100 may be limited. This is because when the part of the fuel cell 100 is so dry that humidification control is necessary, the internal resistance of the fuel cell 100 is increased, and the output of the fuel cell 100 must be reduced.

  By performing the control as described above, in the fuel cell system 1000A according to the second modified example, it is possible to realize the same operation and effect as the fuel cell system 1000 according to the embodiment.

・ Third modification:
In the above embodiment, humidification control is performed by comparing the wet state of the end cells and the wet state of the plurality of single cells 101 as a whole, but the detection location of the wet state is not limited to this. For example, the wet state of the end cell may be compared with the wet state of one single cell 101 located near the center of the stack structure, or the wet state of the single cell 101 adjacent to the end cell and the end cell may be compared. The wet state of the two single cells 101 located near the center of the stack structure may be compared. That is, generally, the wet state of at least one single cell A of the plurality of single cells 101 and at least one single cell B (including a single cell different from the single cell A among the plurality of single cells 101 ( Comparing the wet state (including all of them), the variation in the wet state inside the fuel cell 100 can be estimated. However, it is preferable that one single cell A includes a portion that easily wets (for example, an end cell), and the other single cell B has a portion that is less likely to wet than one single cell A (for example, a cell near the center). ) Is preferably included. This is because variations in the wet state inside the fuel cell 100 can be accurately recognized.

Fourth embodiment:
In the above embodiment, the wet state of the single cell 101 is detected by calculating the resistance value of the single cell 101 to be detected as described above, but the wet state detection method is not limited to this. For example, the wet state of the single cell 101 may be detected by providing a water vapor partial pressure sensor inside the single cell 101. However, if the wet state of the single cell 101 is detected based on the resistance value of the single cell 101 as in the embodiment, the wet state of the single cell 101 can be detected relatively easily and accurately.

  As mentioned above, although this invention was demonstrated based on the Example and the modification, Embodiment mentioned above is for making an understanding of this invention easy, and does not limit this invention. The present invention can be changed and improved without departing from the spirit and scope of the claims, and equivalents thereof are included in the present invention.

It is explanatory drawing showing the schematic structure of the fuel cell system which concerns on an Example. It is explanatory drawing showing schematic structure of a fuel cell. It is a flowchart which shows the operation | movement step of driving | operation completion | finish operation | movement. It is a flowchart which shows the operation | movement step of driving | operation start operation | movement. It is a graph which shows the relationship between the resistance value in a single cell, and a wet state. It is a flowchart which shows the operation | movement step of normal driving | operation operation | movement. It is explanatory drawing showing schematic structure of the fuel cell system which concerns on a 2nd modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 24 ... Fuel gas supply path 25 ... Fuel gas flow path 26 ... Fuel gas discharge path 28 ... Circulation flow path 34 ... Oxidation gas supply path 35 ... Oxidation gas flow path 36 ... Oxidation gas discharge path 54 ... Cooling medium supply path 55 ... Cooling Medium flow path 56 ... Cooling medium discharge path 61 ... Wiring 100 ... Fuel cell 101 ... Single cell 102 ... Separator 103 ... Current collector 110 ... Current sensor 121 ... First voltage sensor 122 ... Second voltage sensor 200 ... Hydrogen tank DESCRIPTION OF SYMBOLS 210 ... Fuel gas humidifier 220 ... Pressure adjustment valve 240 ... Discharge valve 250 ... Fuel gas pump 300 ... Air compressor 310 ... Oxidizing gas humidifier 320 ... Pressure adjustment valve 400 ... Control part 410 ... Resistance measurement part 420 ... Resistance comparison part 430 ... Drying control unit 440 ... Humidification control unit 500 ... Cooling medium supply unit 610 ... Load 620 ... Secondary battery 630 ... CON Barter 1000, 1000A ... Fuel cell system

Claims (9)

A fuel cell system,
A fuel cell comprising a plurality of single cells;
A first wet state detecting means for detecting a wet state of a first single cell portion including at least one single cell among the plurality of single cells;
A second wet state detection means for detecting a wet state of a second single cell part including at least one single cell different from the first single cell part among the plurality of single cells;
A comparison means for comparing the wet state of the first single cell part and the second single cell part;
Control means for controlling the wet state of the fuel cell based on the result of the comparison;
A fuel cell system comprising: The fuel cell system according to claim 1, wherein
The control means controls the wet state of the fuel cell at the start of the current operation of the fuel cell based on the result of the comparison of the wet state at the end of the previous operation of the fuel cell. . The fuel cell system according to claim 1 or 2,
The fuel cell system, wherein the first unit cell part is a unit cell that is more easily wetted than the second unit cell part. The fuel cell system according to claim 3, wherein
The plurality of single cells have a stack structure,
The first single cell part includes a single cell located at an end of the stack structure among the plurality of single cells. In the fuel cell system according to claim 3 or 4,
The fuel cell system, wherein the second single cell portion is all of the plurality of single cells. The fuel cell system according to any one of claims 1 to 5,
The first wet state detecting means is means for measuring the resistance of the first single cell portion,
The fuel cell system, wherein the second wet state detecting means is means for measuring the resistance of the second single cell portion. The fuel cell system according to any one of claims 3 to 6,
The fuel cell system, wherein the control means includes a humidifying means for performing control to humidify the fuel cell when the second single cell part is dried by a predetermined level or more than the first single cell part. The fuel cell system according to claim 7, further comprising:
A drying unit that dries the fuel cell based on a wet state of the first single cell unit at the end of the operation of the fuel cell;
The humidifying means controls the humidification of the fuel cell when the second single cell part is dried at a predetermined level or more than the first single cell part at the next start of operation of the fuel cell. A fuel cell system. A method for controlling a fuel cell including a plurality of single cells,
Detecting a wet state of a first unit cell part including at least one unit cell among the plurality of unit cells;
Detecting a wet state of a second single cell part including at least one single cell different from the first single cell part among the plurality of single cells;
Compare the wet state of the first single cell part and the second single cell part,
A control method for controlling a wet state of the fuel cell based on the result of the comparison.

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