JP2004265862A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system controlling the water content in the fuel cell by regulating an generated current, which is restrained from giving influence on the driving of a vehicle in the case of being applied to a fuel cell vehicle. <P>SOLUTION: In the case that the moisture content in the fuel cell 10 is insufficient, the water generation is increased by increasing the driving current of the fuel cell 10 and water content of an electrolyte film is increased. On the other hand, in the case that the moisture content in the fuel cell 10 is excessive, the water generation is decreased by decreasing the driving current of the fuel cell 10 and the inside of the fuel cell is dried. Thus, the state of water in the fuel cell is controlled by utilizing the increase/decrease of the amount of the generated water corresponding to the current generated by the fuel cell. Furthermore, the excess/deficiency of the generated power against an required electric power is compensated by charging and discharging of a secondary battery 12. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a fuel cell system including a fuel cell that generates electric power by a chemical reaction between hydrogen and oxygen, and is suitable for a mobile generator such as a vehicle, a ship, and a portable generator, or a small household generator. is there.

  When the fuel cell is operated, if the water content of the solid electrolyte membrane inside the fuel cell is insufficient, the conductivity of the solid electrolyte membrane decreases, the electric resistance of the solid electrolyte membrane increases, and the battery output decreases. On the other hand, if excess water is present on the anode / cathode electrode, the electrochemical reaction on the electrode surface is hindered, and the battery output decreases. Therefore, it is necessary to appropriately maintain the water content on the anode / cathode electrode while maintaining the water content in the electrolyte membrane optimally.

On the other hand, there has been proposed a fuel cell system in which the amount of water generated in the fuel cell is controlled by controlling the power generation current of the fuel cell to control the amount of water inside the fuel cell (for example, see Patent Document 1).
JP 2001-256988 A

  According to the control method described in Patent Document 1, the power generation current is increased when the inside of the fuel cell is short of moisture, and conversely, the power generation current is decreased when the inside of the fuel cell is excessively water. Is controlled so that the water content of the sample becomes an appropriate value. However, when this control method is applied to an actual fuel cell vehicle, the power generated by the fuel cell is insufficient for the power required for traveling by controlling the power generated by the fuel cell according to the moisture state. In some cases, there are cases where the excess occurs. As a result, there is a problem in that an attempt to control the generated current during traveling affects the traveling.

  In view of the above, the present invention controls a generated current to control the amount of water in a fuel cell and, when applied to a fuel cell vehicle, can suppress the influence on the running of the fuel cell. The purpose is to provide a system.

  In order to achieve the above object, in the invention according to claim 1, a fuel cell (10) that generates electric power by a chemical reaction between a fuel gas containing hydrogen and an oxidizing gas containing oxygen, and Current control means (40) for controlling the generated current, fuel supply means (31) for supplying fuel gas to the fuel cell, oxidizing gas supply means (21) for supplying oxidizing gas to the fuel cell, and electric energy Power storage means (12) for storing power, and charge / discharge control means (40) for controlling charging / discharging of the power storage means (12). The current control means (40) is provided with the fuel cell (10). ) To control the amount of water in the fuel cell (10) by controlling the generated current of the fuel cell (10), and the charge / discharge control means (40) Controlled by Based on the difference between the generated power of the fuel cell (10) in the power generation current of the fuel cell (10) it is characterized by controlling the charging and discharging of the power storage means (12).

  As described above, by controlling the amount of water inside the fuel cell (10) using the fact that the amount of generated water increases or decreases according to the generated current of the fuel cell (10), the state of water inside the fuel cell 10 is optimized. It becomes possible to control. In addition, a power storage means (12) for storing electric energy is provided, and the excess or deficiency between the power generated by the fuel cell (10) and the required power is adjusted by charging and discharging the power storage means (12). When the fuel cell system is applied to a fuel cell vehicle, it is possible to suppress the influence on the vehicle running.

  Specifically, as in the second aspect of the present invention, the fuel cell system further includes a diagnosis unit (40) for diagnosing a water state inside the fuel cell (10), and the control unit (40) is controlled by the diagnosis unit (40). The power generation current of the fuel cell (10) can be controlled according to the result of the water state diagnosis.

  More specifically, when the diagnosing means (40) diagnoses that the water content inside the fuel cell (10) is insufficient, the control means (40). Increases the power generation current of the fuel cell (10), and when the diagnostic means (40) determines that the amount of water in the fuel cell (10) is excessive, as in the invention according to claim 4, The control means (40) can reduce the generated current of the fuel cell (10).

  As described above, by controlling the amount of water inside the fuel cell using the fact that the amount of generated water increases or decreases according to the generated current of the fuel cell, it is possible to optimally control the state of water inside the fuel cell. In addition, a humidifier for humidifying the fuel gas or the oxidizing gas can be omitted.

  The invention according to claim 5 is characterized in that the fuel cell is divided into a plurality of power generation areas (10A, 10B), and the control means (40) individually controls the generation current in each power generation area.

  By the way, if the generated current is controlled for controlling the moisture state of the fuel cell, the generated power of the fuel cell may be excessive or insufficient with respect to the required power. On the other hand, according to the invention described in claim 5, by individually controlling the generated current in each power generation region, it is possible to adjust the excess or deficiency of the generated power while controlling the moisture state of the fuel cell. . For example, if the fuel cell dries and the generated current needs to be increased in order to increase the water content of the electrolyte membrane, power generation is performed only in a small number of power generation regions to adjust the generated power to be excessive. On the other hand, when the water content in the fuel cell becomes excessive, the power generation current in some power generation areas is reduced to lower the water content, while the power generation current in other power generation areas is increased to reduce the insufficient power. adjust.

  In the invention described in claim 8, a hydrogen path (30) for leading the fuel gas to the plurality of power generation areas (10A, 10B) and an air path (20) for leading the oxidizing gas to the plurality of power generation areas (10A, 10B). And a diagnostic means (40) for individually diagnosing the water status of the plurality of power generation areas (10A, 10B). The plurality of power generation areas (10A, 10B) are provided with a hydrogen path (30) and an air path (20). The control means (40) is arranged in series with at least one of the power generation areas (10A), and the control means (40) generates power in the upstream power generation area (10A) in accordance with the result of the diagnosis of the moisture state of the downstream power generation area (10B) by the diagnosis means (40). It is characterized by controlling the current.

  According to this, the water generated in the power generation area on the upstream side can be used as humidification water in the power generation area on the downstream side. At this time, the power generation area on the downstream side can be controlled by controlling the power generation current in the power generation area on the upstream side. By controlling the amount of water supplied to the power generation unit, the water condition in the downstream power generation area can be optimally controlled.

  By the way, when the diagnosing means (40) diagnoses that the water content of the downstream power generation area (10B) is insufficient, the control means (40) controls the upstream means. The power generation current of the power generation area (10A) on the side is increased.

  In addition, the code | symbol in the parenthesis of each said means shows the correspondence with the concrete means described in embodiment mentioned later.

(1st Embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. The fuel cell system according to the present embodiment is applied to an electric vehicle (fuel cell vehicle) that runs using a fuel cell as a power source.

FIG. 1 shows the overall configuration of the fuel cell system of the present embodiment. As shown in FIG. 1, the fuel cell system according to the present embodiment includes a fuel cell 10. The fuel cell (FC stack) 10 generates electric power using an electrochemical reaction between hydrogen and oxygen. In this embodiment, a solid polymer electrolyte fuel cell is used as the fuel cell 10, and a plurality of cells serving as basic units are stacked. Each cell has a configuration in which an electrolyte membrane is sandwiched between a pair of electrodes. In the fuel cell 10, the supply of hydrogen and air (oxygen) causes the following electrochemical reaction between hydrogen and oxygen to generate electric energy.
(Hydrogen electrode ^{_{side) H 2 → 2H + + 2e}} -
(Oxygen electrode side) 2H ⁺ + 1 / 2O ₂ + 2e ⁻ → H ₂ O
The electric power generated by the fuel cell 10 is supplied to an electric load 11 that consumes electric energy and a secondary battery 12 that stores electric energy. The charge / discharge amount of the secondary battery 12 is controlled by the power distribution controller 13. Incidentally, in the case of an electric vehicle, an electric motor as a vehicle driving source corresponds to the electric load 11. Further, the secondary battery 12 corresponds to a power storage unit of the present invention. Note that a capacitor or the like can be used as the power storage unit instead of the secondary battery 12.

  In the fuel cell system, an air path (oxygen path) 20 for supplying air (oxygen) to the oxygen electrode (positive electrode) side of the fuel cell 10 and hydrogen is supplied to a hydrogen electrode (negative electrode) side of the fuel cell 10. Hydrogen path 30 is provided.

  An electric compressor 21 for pumping air is provided at the most upstream portion of the air path 20. The compressor 21 can adjust the air supply amount (oxygen supply amount) to the fuel cell 10 by changing the rotation speed.

  A hydrogen cylinder 31 filled with high-pressure hydrogen is provided at the most upstream part of the hydrogen path 30. Between the hydrogen cylinder 31 and the fuel cell 10 in the hydrogen path 30, a flow control valve 32 for adjusting the amount of hydrogen supplied to the fuel cell 10 is provided. Instead of the hydrogen cylinder 31, for example, a reformer that generates hydrogen by a reforming reaction or a hydrogen tank that stores a pure hydrogen by incorporating a hydrogen storage material such as a hydrogen storage alloy can be used.

  The fuel cell system includes a water content sensor 50 for detecting the water content inside the fuel cell 10, and the water content sensor 50 is arranged at an air outlet of the fuel cell 10.

  The fuel cell system is provided with a control unit 40 for performing various controls. The control unit 40 is configured to receive each sensor signal from the moisture amount sensor 50, an accelerator opening sensor (not shown), and the like. The control unit 40 is configured to output a control signal to the power distribution controller 13, the compressor 21, the flow control valve 32, and the like. The control unit 40 corresponds to the current control unit, the charge / discharge control unit, and the diagnosis unit of the present invention.

  Next, water content control in the fuel cell system of the present embodiment will be described with reference to FIG. FIG. 2 is a flowchart showing the procedure of moisture control. The following moisture control is repeatedly performed at a predetermined control interval.

  First, the power required for running the vehicle is calculated from the accelerator opening and the like, and the required power of the fuel cell 10 is determined (S101). Subsequently, the power that can charge and discharge the secondary battery 12 is measured (S102). Subsequently, the moisture content at the outlet of the fuel cell 10 is measured by the moisture content sensor 50 (S103).

  Next, it is determined whether or not the water content measured in S103 is below the lower limit (S104). The lower limit is a value set in advance for diagnosing a shortage of water. When it is determined that the measured water content is lower than the lower limit value, that is, when the water content is insufficient, the correction current value is calculated by the correction current value = K1 × (target water content−measured water content) ( S105). K1 is a coefficient having a positive value when obtaining the correction current value. Since the measured moisture content is smaller than the target moisture content which is an appropriate value, (target moisture content-measured moisture content) becomes a positive value. , The correction current value becomes a positive value. As a result, the operating current of the fuel cell 10 can be increased to increase the generated water, and the amount of water inside the fuel cell 10 can be increased.

  On the other hand, if it is determined that the measured water content is not below the lower limit, it is determined whether the water content measured in S103 is above the upper limit (S106). The upper limit is a value set in advance for diagnosing excess water. When it is determined that the measured water content is higher than the upper limit value, that is, when the water content is excessive, a correction current value is obtained by correction current value = K2 × (target water content−measured water content) (S107). ). K2 is a coefficient having a negative value when obtaining the correction current value. Since the measured moisture content is larger than the target moisture content, which is an appropriate value, (target moisture content-measured moisture content) is a negative value. As a result, the correction current value becomes a negative value. As a result, the operating current of the fuel cell 10 can be reduced to reduce the generated water, and the water content inside the fuel cell 10 can be reduced.

  Next, when it is determined in S104 that the measured water content is lower than the lower limit value, and when it is determined in S106 that the measured water content is higher than the upper limit value, the fuel cell target power generation amount and the secondary The battery charge / discharge amount is determined (S108). The process for determining the fuel cell target power generation amount and the secondary battery charge / discharge amount will be described later in detail.

  On the other hand, if it is determined in S106 that the measured moisture content does not exceed the upper limit value, that is, if the moisture content is appropriate, there is no need to perform moisture control, so the correction current value is set to 0 (S109). . In this case, the required power is set as the fuel cell target power generation amount, and the charge / discharge amount of the secondary battery is set to 0 (S110).

  Next, based on the fuel cell target power generation amounts obtained in S108 and S110, the number of rotations of the compressor 21 is adjusted to control the amount of air supplied to the fuel cell 10, and the flow rate adjustment valve 32 is used to control the amount of air supplied to the fuel cell 10. The power supply amount of the fuel cell 10 is controlled by controlling the hydrogen supply amount (S111). Next, the charge / discharge amount of the secondary battery 12 is controlled by the power distributor 13 based on the charge / discharge amount of the secondary battery obtained in S108 (S112).

  Next, a fuel cell target power generation amount / secondary battery charge / discharge amount determination process in the fuel cell system of the present embodiment will be described with reference to FIGS. FIG. 3 is a flowchart showing the procedure for determining the fuel cell target power generation amount / secondary battery charge / discharge amount, and corresponds to the subroutine of S108 in FIG. 4 and 5 are characteristic diagrams showing the relationship between the current I and the electric power P of the fuel cell 10. FIG. 4 shows a case where the water content is insufficient, and FIG. 5 shows a case where the water content is excessive. The IP characteristic maps shown in FIGS. 4 and 5 are stored in a storage device such as a ROM of the control unit 40.

  First, the IP characteristics shown in FIGS. 4 and 5 are read (S201), and a required current required to output the required power obtained in S101 is calculated from the IP characteristics (S202). Next, a corrected power generation amount of the fuel cell 10 is calculated (S203). Specifically, the target current value is calculated by adding the correction current value obtained in S105 and S107 to the required current obtained in S202, and the fuel cell target power generation amount when generating power at the target current value from the IP characteristic is calculated. The difference between the required power generation amount and the fuel cell target power generation amount is defined as the corrected power generation amount. When the water content is insufficient, the corrected power generation amount becomes a positive value, and when the water content is excessive, the corrected power generation amount becomes a negative value.

  Next, it is determined whether or not the corrected power generation amount is positive (S204). When it is determined that the corrected power generation amount is positive, that is, when the water content is insufficient, it is determined whether the chargeable power of the secondary battery 12 calculated in S102 exceeds the corrected power generation amount. (S205). When the rechargeable power of the secondary battery does not exceed the corrected power generation amount, that is, when the corrected power generation amount, which is the surplus power generation amount, cannot be absorbed by charging the secondary battery 12, the corrected power generation amount can be charged to the secondary battery. The power is set (S206).

  Next, the target power generation amount of the fuel cell is set to a value obtained by adding the corrected power generation amount to the required power generation amount (S207), and the charge amount of the secondary battery 12 is set to the corrected power generation amount (S208).

  If it is determined in S204 that the corrected power generation amount is not positive, that is, if the water content is excessive, it is determined whether the dischargeable power of the secondary battery 12 calculated in S102 exceeds the absolute value of the corrected power generation amount. Is determined (S209). If the dischargeable power of the secondary battery does not exceed the absolute value of the corrected power generation amount, that is, if the corrected power generation amount that is insufficient power generation cannot be compensated for by the discharge of the secondary battery 12, the absolute value of the corrected power generation amount is reduced by two. The next battery dischargeable power is set (S210).

  Next, the target power generation amount of the fuel cell is set to a value obtained by subtracting the absolute value of the corrected power generation amount from the required power generation amount (S211), and the discharge amount of the secondary battery 12 is set to the absolute value of the corrected power generation amount (S212).

  As described above, by controlling the amount of water inside the fuel cell 10 using the fact that the amount of generated water increases or decreases according to the generated current of the fuel cell 10 as in the present embodiment, the water state inside the fuel cell 10 is optimized. And the need for a humidifier for humidifying the fuel gas and the oxidizing gas can be eliminated.

  Further, when the generated current is controlled for controlling the moisture state of the fuel cell 10, the generated power of the fuel cell 10 may be excessive or insufficient with respect to the required power. On the other hand, in the present embodiment, the secondary battery 12 is charged when the power generation of the fuel cell 10 is excessive with respect to the required power, and when the power generation of the fuel cell 10 is insufficient with respect to the required power. Insufficient power is supplied from the secondary battery 12 to the electric load 11.

  As described above, the secondary power is calculated based on the difference between the required power for the fuel cell 10 and the generated power (target power generation) of the fuel cell 10 at the current value (target current value) controlled for adjusting the moisture state. By controlling the charging and discharging of the battery 12, it is possible to absorb the excess or deficiency of the power generated by the fuel cell 10 while optimally controlling the moisture state inside the fuel cell 10. Thus, when the fuel cell system is applied to a fuel cell vehicle, when the fuel cell system is applied to a fuel cell vehicle, it is possible to prevent the traveling of the vehicle from being affected.

(2nd Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIGS. The same or equivalent parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

  FIG. 6 shows the overall configuration of the fuel cell system of the present embodiment. As shown in FIG. 6, the fuel cell system according to the present embodiment includes first and second fuel cells 10A and 10B, and the generated current of each of the fuel cells 10A and 10B can be individually controlled. Each of the fuel cells 10A and 10B corresponds to a power generation region of the present invention.

  The air path is branched into two at the downstream side of the compressor 21, air is supplied to the first fuel cell 10A via the first air path 20A, and is supplied to the second fuel cell 10B via the second air path 20B. Air is supplied. An air distribution adjusting valve 22 that adjusts a distribution ratio between air supplied to the first fuel cell 10A and air supplied to the second fuel cell 10B is disposed in the second air path 20B.

  The hydrogen path is branched into two at the downstream side of the hydrogen cylinder 31, hydrogen is supplied to the first fuel cell 10A via the first hydrogen path 30A, and the second fuel cell 10B is supplied via the second hydrogen path 30B. Is supplied with hydrogen. A hydrogen distribution adjusting valve 33 that adjusts the distribution ratio of hydrogen supplied to the first fuel cell 10A and hydrogen supplied to the second fuel cell 10B is disposed in the second hydrogen path 30B.

  At the air outlets of the fuel cells 10A and 10B, first and second moisture content sensors 50A and 50B for detecting the moisture content inside the fuel cells 10A and 10B are arranged. In the present embodiment, the power distribution controller 13 controls the power generation ratio between the power generation amount of the first fuel cell 10A and the power generation amount of the second fuel cell 10B.

  The control unit 40 is configured to receive each sensor signal from both the moisture content sensors 50A and 50B, an accelerator opening sensor (not shown), and the like. The control unit 40 is configured to output a control signal to the power distribution controller 13, the compressor 21, the air distribution adjustment valve 22, the hydrogen distribution adjustment valve 33, and the like.

  Next, water content control in the fuel cell system of the present embodiment will be described with reference to FIG. FIG. 7 is a flowchart showing the procedure of moisture control. The following moisture control is repeatedly performed at a predetermined control interval.

  First, the power required for running the vehicle is calculated from the accelerator opening and the like, and the total power of both fuel cells 10A and 10B is determined (S301).

  Next, the moisture content of the first fuel cell 10A is measured by the first moisture content sensor 50A (S302), and the moisture content of the second fuel cell 10B is measured by the second moisture content sensor 50B (S303), and S302 and S303. Based on the measurement results in the above, the water content of the first fuel cell 10A is compared with the water content of the second fuel cell 10B, and it is determined which water content is higher or lower (S304).

  Next, a diagnosis is made as to whether the amount of water inside the fuel cells 10A, 10B is excessive or deficient, and predetermined control is performed according to the diagnosis result.

  First, it is determined whether or not the water content of the fuel cell having a small water content is insufficient (S305). If the water content is insufficient, the operating current of the fuel cell having the small water content is increased and the total generated power is excessive. Then, the operation current of the fuel cell having the higher water content is reduced to prevent the occurrence of (S306). As a result, in a fuel cell having a shortage of water, the generated water increases due to an increase in the operating current, so that the water content of the electrolyte membrane can be increased.

  If the fuel cell with the smaller water content is not short of water (NO in S305), it is determined whether or not the fuel cell with the larger water content is excessive (S307). In addition to decreasing the operating current of the fuel cell having the larger amount of water, the operating current of the fuel cell having the smaller amount of water is increased in order to prevent shortage of the total generated power (S308). Thereby, in the fuel cell with excess water, the generated water decreases due to the decrease in the operating current, and therefore the inside can be dried.

  If the water content is appropriate (NO in both S305 and S307), the operating currents of both fuel cells 10A and 10B are made equal (S309).

  Next, an air supply amount and a hydrogen supply amount to each of the fuel cells 10A and 10B are determined based on the operating current set in S306, S308 and S309 (S310), and air distribution adjustment is performed based on the determined values. The distribution ratio is adjusted by the valve 22 and the hydrogen distribution adjusting valve 33 to control the air supply amount and the hydrogen supply amount to each of the fuel cells 10A and 10B (S311).

  As in the present embodiment, by controlling the amount of water inside each of the fuel cells 10A and 10B by utilizing the fact that the amount of generated water increases and decreases in accordance with the power generation current of each of the fuel cells 10A and 10B, 10B can be optimally controlled, and a humidifier for humidifying the fuel gas and the oxidizing gas can be omitted.

  Further, by individually controlling the power generation current of each of the fuel cells 10A and 10B, the water content inside each of the fuel cells 10A and 10B is optimally controlled, and the excess and deficiency of the total power generation of both fuel cells 10A and 10B. Can be absorbed.

(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIGS. The same or equivalent parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

  FIG. 8 shows the overall configuration of the fuel cell system of the present embodiment. As shown in FIG. 8, the fuel cell system according to the present embodiment includes first and second fuel cells 10A and 10B, and the generated current of each of the fuel cells 10A and 10B can be individually controlled. Each of the fuel cells 10A and 10B corresponds to a power generation region of the present invention.

  Both fuel cells 10A and 10B are arranged in series in the air path 20 and the hydrogen path 30. Specifically, the first fuel cell 10A is located upstream of the second fuel cell 10B, so that air and hydrogen are first supplied to the first fuel cell 10A and pass through the first fuel cell 10A. Later, it is supplied to the second fuel cell 10B.

  At the air outlets of the fuel cells 10A and 10B, first and second moisture content sensors 50A and 50B for detecting the moisture content inside the fuel cells 10A and 10B are arranged. In the present embodiment, the power distribution controller 13 controls the power generation ratio between the power generation amount of the first fuel cell 10A and the power generation amount of the second fuel cell 10B.

  The control unit 40 is configured to receive each sensor signal from both the moisture content sensors 50A and 50B, an accelerator opening sensor (not shown), and the like. The control unit 40 is configured to output a control signal to the power distribution controller 13, the compressor 21, the flow control valve 32, and the like.

  Next, water content control in the fuel cell system of the present embodiment will be described with reference to FIG. FIG. 9 is a flowchart showing the procedure of moisture control. The following moisture control is repeatedly performed at a predetermined control interval.

  First, the electric power required for running the vehicle is calculated from the accelerator opening and the like, and the total electric power of both fuel cells 10A and 10B is determined (S401). Next, the water content of the first fuel cell 10A is measured by the first water content sensor 50A (S402), and the water content of the second fuel cell 10B is measured by the second water content sensor 50B (S403).

  Next, based on the measurement results in S402 and S403, an excess or deficiency of the water content in both fuel cells 10A and 10B is diagnosed, and predetermined control is performed according to the diagnosis result.

  First, when the water content of the second fuel cell 10B is insufficient (S404: YES) and the water content of the first fuel cell 10A is excessive (S405: YES), the operating current of the first fuel cell 10A is reduced. By reducing the amount of water, the water generated by the first fuel cell 10A is reduced to dry the inside of the first fuel cell 10A (S406), and the operating current of the second fuel cell 10B is increased to increase the second fuel cell 10B. The water content of the electrolyte membrane of the second fuel cell 10B is increased by increasing the generated water of 10B (S407).

  If the water content of the second fuel cell 10B is insufficient (S404: YES) and the water content of the first fuel cell 10A is not excessive (S405: NO), the operating current of the first fuel cell 10A is increased. At the same time (S408), the operating current of the second fuel cell 10B is reduced (S409).

  Here, since both fuel cells 10A and 10B are arranged in series in the air path 20 and the hydrogen path 30, the water generated by the first fuel cell 10A can be used as humidifying water for the second fuel cell 10B. . Therefore, the water content of the electrolyte membrane of the second fuel cell 10B increases by increasing the operating current of the first fuel cell 10A and increasing the water generated by the first fuel cell 10A as in S408. Further, by using excess water inside the first fuel cell as humidifying water as in S406, the water content of the electrolyte membrane of the second fuel cell 10B can be increased.

  When the water content of the second fuel cell 10B is excessive (S404: NO, S410: YES), the operating current of the second fuel cell 10B is reduced to reduce the water generated by the second fuel cell 10B. The inside of the second fuel cell 10B is dried, and the operating current value of the first fuel cell 10A is increased in order to adjust the decrease in the operating current of the second fuel cell 10B. (S411, S411 ').

  If the water content of the second fuel cell 10B is excessive (S404: NO, S410: YES) and the first fuel cell 10A is too watery (S412: YES), the air supply amount is increased by the air compressor. Then, the fuel cell 10A is dried. (S413).

  If the water content of the second fuel cell 10B is excessive (S404: NO, S410: YES), and if the water content of the first fuel cell 10A is not excessive (S412: NO), the second fuel cell 10B in S411 The operation of increasing the operating current of the first fuel cell 10A in S411 ′ is continued as it is in order to adjust the decrease in the operating current of FIG.

  If the water content of the second fuel cell 10B is appropriate (NO in both S404 and S410) and the water content of the first fuel cell 10A is excessive (YES in S415), the operating current of the first fuel cell 10A is reduced. In order to reduce the amount of water generated by the first fuel cell 10A to dry the inside of the first fuel cell 10A (S416), and to adjust the decrease in the operating current of the first fuel cell 10A in S416, The operating current of the second fuel cell 10B is increased (S417).

  By arranging both fuel cells 10A and 10B in series in the air path 20 and the hydrogen path 30 as in the present embodiment, water generated by the first fuel cell 10A is used as humidifying water for the second fuel cell 10B. be able to. Therefore, when the amount of water in the second fuel cell 10B is insufficient, the water state of the second fuel cell 10B can be optimally controlled by increasing the amount of water generated by the first fuel cell 10A.

  Further, by individually controlling the power generation current of each of the fuel cells 10A and 10B, the water content inside each of the fuel cells 10A and 10B is optimally controlled, and the excess and deficiency of the total power generation of both fuel cells 10A and 10B. Can be absorbed.

(Other embodiments)
In the second and third embodiments, two fuel cells 10A and 10B are used, but three or more fuel cells may be used.

  In the third embodiment, both fuel cells 10A and 10B are arranged in series with respect to the air path 20 and the hydrogen path 30. However, both fuel cells 10A and 10B are connected to one of the air path 20 and the hydrogen path 30. And the air path 20 and the hydrogen path 30 may be arranged in parallel with each other.

  In the first, second, and third embodiments, the moisture content sensor is installed at the air path outlet of the fuel cell, but may be installed at the hydrogen path outlet of the fuel cell.

  In the first, second, and third embodiments, the water content in the fuel cell is measured by the water content. However, the water content may be indirectly estimated from the voltage variation of each cell constituting the fuel cell stack.

FIG. 1 is a conceptual diagram of a fuel cell system according to a first embodiment. It is a flowchart which shows moisture control of 1st Embodiment. 6 is a flowchart illustrating a procedure for determining a target fuel cell power generation amount and a secondary battery charge / discharge amount. FIG. 4 is a characteristic diagram illustrating a relationship between a current I and a power P of a fuel cell. FIG. 4 is a characteristic diagram illustrating a relationship between a current I and a power P of a fuel cell. It is a conceptual diagram of a fuel cell system of a second embodiment. It is a flow chart which shows moisture control of a 2nd embodiment. It is a conceptual diagram of a fuel cell system of a third embodiment. It is a flow chart which shows moisture control of a 3rd embodiment.

Explanation of reference numerals

  10, 10A, 10B: fuel cell, 40: control unit (control means, diagnostic means).

Claims (9)

A fuel cell (10) that generates electric power by a chemical reaction between a fuel gas containing hydrogen and an oxidizing gas containing oxygen;
Current control means (40) for controlling the generated current of the fuel cell (10);
Fuel supply means (31) for supplying a fuel gas to the fuel cell;
Oxidizing gas supply means (21) for supplying an oxidizing gas to the fuel cell;
Power storage means (12) for storing electrical energy;
Charge / discharge control means (40) for controlling charge / discharge of the power storage means (12),
The current control means (40) controls the amount of water inside the fuel cell (10) by controlling the generated current of the fuel cell (10),
The charge / discharge control means (40) is configured to generate power required for the fuel cell (10) and to generate power of the fuel cell (10) at a power generation current of the fuel cell (10) controlled by the current control means. A charge / discharge of the power storage means (12) based on a difference between the power storage means (12) and the power storage means (12). Diagnostic means (40) for diagnosing the water condition inside the fuel cell (10);
The fuel cell system according to claim 1, wherein the current control means (40) controls a generated current of the fuel cell (10) in accordance with a result of the water condition diagnosis by the diagnosis means (40). . When the diagnosing means (40) diagnoses that the water content inside the fuel cell (10) is insufficient, the current control means (40) increases the power generation current of the fuel cell (10). The fuel cell system according to claim 2, wherein: When the diagnosis means (40) diagnoses that the water content inside the fuel cell (10) is excessive, the current control means (40) reduces the power generation current of the fuel cell (10). The fuel cell system according to claim 2, wherein: The fuel cell is divided into a plurality of power generation areas (10A, 10B), and the current control means (40) individually controls the power generation current in each power generation area. The fuel cell system according to any one of the first to third aspects. Diagnostic means (40) for dividing into a plurality of power generation areas (10A, 10B) and individually diagnosing the water status of the plurality of power generation areas;
If it is diagnosed that the water content of the power generation area that has been diagnosed as having the lowest moisture content is insufficient, it is necessary to increase the current until the power generation area that has the lowest moisture content has the appropriate moisture content. The fuel cell system according to claim 5, wherein: Diagnostic means (40) for dividing into a plurality of power generation areas (10A, 10B) and individually diagnosing the water status of the plurality of power generation areas;
When the power generation region diagnosed as having the highest moisture content is diagnosed as having an excessive amount of water, the current is reduced until the power generation region having the highest moisture content has an appropriate moisture amount. The fuel cell system according to claim 5. A hydrogen path (30) for guiding the fuel gas to the plurality of power generation areas (10A, 10B), an air path (20) for guiding the oxidizing gas to the plurality of power generation areas (10A, 10B), and the plurality of power generation areas Diagnostic means (40) for individually diagnosing the water status of the regions (10A, 10B);
The plurality of power generation areas (10A, 10B) are arranged in series with at least one of the hydrogen path (30) and the air path (20),
The current control means (40) controls a generated current of the upstream power generation area (10A) according to a result of the diagnosis of the water status of the downstream power generation area (10B) by the diagnosis means (40). The fuel cell system according to claim 5, wherein: When the diagnosing means (40) diagnoses that the water content of the downstream power generation area (10B) is insufficient, the current control means (40) controls the power generation area (10A) of the upstream side. The fuel cell system according to claim 8, wherein the generated current is increased.

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