JP2005085531A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of properly humidifying a stack. <P>SOLUTION: This fuel cell system is provided with the stack 1 formed by laminating a plurality of unit cells 10 each having high polymer films and electrically connecting them in series. The fuel cell system has a flow adjusting means to adjust a gas flow so that the gas flow to be supplied to end unit cells 10b positioned at both end parts of the stack 1 in its laminated direction becomes larger than the gas flow to be supplied to the center unit cells 10a positioned in the vicinity of the center part in the laminated direction. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel cell system including a solid polymer electrolyte fuel cell that is configured by stacking fuel cells using a polymer membrane as an electrolyte. In particular, the present invention relates to a configuration that optimizes the supply of reaction gas to each unit battery that contributes to power generation characteristics.

  One type of fuel cell is a solid polymer electrolyte fuel cell using a solid polymer membrane as an electrolyte. In this solid polymer membrane, water molecules present in the membrane are closely related to ionic conductivity, and if the membrane does not contain sufficient water, it does not function as an ionic conductor. Therefore, in the solid polymer electrolyte fuel cell, an operation such as humidifying the reaction gas to be supplied in advance is required. At this time, if the amount of humidification is excessive, water accumulates in the reaction gas flow path, the gas diffusion layer portion, etc., and the diffusion of the reaction gas may be hindered, resulting in a significant decrease in battery voltage. In particular, at the time of low temperature startup or during warm-up operation, the temperature of the unit cells arranged at the end in the stacking direction is unlikely to increase due to heat radiation from the end plate and the influence of heat capacity. As a result, the amount of condensed water increases and the battery voltage tends to decrease as described above.

Therefore, when a unit cell whose output voltage value V deviates from the normal range is first found in the fuel cell stack, it is determined whether or not the unit cell corresponds to the two cell portions at both ends of the fuel cell stack. A fuel cell system for discrimination has been proposed. When it is determined that the unit cell whose output voltage value V is out of the normal range is located at each of the two cell portions at both ends of the fuel cell stack, the humidification amount of the fuel gas and the oxidizing gas is reduced because the fuel cell stack is excessively humidified. I am letting. On the other hand, when it is determined that the unit cell is located inside the fuel cell stack excluding the two cells at both ends, it is determined that the fuel cell stack is insufficiently humidified. (For example, refer to Patent Document 1).
JP 2002-184438 A

  In the conventional technology described above, when a voltage drop occurs at the end of the fuel cell stack, the humidification amount of the fuel gas and the oxidizing gas supplied to the fuel cell stack is reduced. Thus, by reducing the humidity of the fuel gas and the oxidizing gas supplied to the entire fuel cell stack, the electrolyte membrane may be dried at the center of the fuel cell stack. As a result, the power generation efficiency in the fuel cell stack may be reduced.

  In view of the above problems, an object of the present invention is to provide a fuel cell system capable of appropriately humidifying a fuel cell stack.

  The present invention includes a fuel cell stack in which a plurality of unit cells each having a polymer film are stacked and electrically connected in series. Selectively so that the gas flow rate supplied to the end unit cells located at both ends of the fuel cell stack in the stacking direction is greater than the gas flow rate supplied to the center unit cells positioned near the center in the stacking direction. It has a flow rate adjusting means that can be adjusted.

  In this way, by selectively adjusting the gas flow rate supplied to the end unit cell to be larger than the gas flow rate supplied to the center unit cell, the water vapor flow rate discharged from the end unit cell can be reduced. Can be increased. As a result, flooding in the end unit cell can be suppressed, and the fuel cell stack can be appropriately humidified.

  A first embodiment will be described. The configuration of the fuel cell system used here is shown in FIG. Here, a fuel cell system used as a vehicle drive source will be described.

  A fuel cell stack (hereinafter referred to as a stack) 1 configured by stacking unit cells 10 to be described later is provided. As will be described later, the stack 1 includes a step motor 5 for changing the cross-sectional area of the supply manifold 11 that distributes the oxidant gas to the unit cells 10.

  Further, a fuel gas supply device 2 that supplies fuel gas to a fuel electrode (not shown) of the stack 1 is provided. For example, the fuel gas supply device 2 takes out hydrogen from a hydrogen tank (not shown) that stores high-pressure hydrogen gas, adjusts the pressure, and supplies the hydrogen to the fuel electrode of the stack 1 via the fuel gas supply path 7. Electric power is generated using fuel gas at the fuel electrode. The fuel gas not consumed at this time is supplied again to the fuel electrode of the stack 1 through a circulation path (not shown).

  In addition, an oxidant gas supply pump 3 that pumps oxidant gas supplied to an oxidant electrode (not shown) of the stack 1 is provided. Furthermore, the humidifier 4 which humidifies the oxidant gas pumped by the oxidant gas supply pump 3 is provided. The flow rate is adjusted by the oxidant gas supply pump 3, and the oxidant gas whose humidity is adjusted by the humidifier 4 is supplied to the oxidant electrode of the stack 1 through the oxidant gas supply path 8. Electric power is generated using the oxidant gas at the oxidant electrode, and the oxidant gas that has not been consumed at this time is discharged to the outside through the oxidant gas discharge path 9. For example, air is used as the oxidizing agent.

  Furthermore, a controller 6 for controlling such a fuel cell system is provided. The controller 6 adjusts the flow rate of the fuel gas supplied to the stack 1 in the fuel gas supply device 2 and the flow rate of the oxidant gas pumped to the stack 1 by the oxidant gas supply pump 3. Further, the flow rate of the reaction gas supplied to the unit cell 10 is adjusted by controlling the step motor 5 provided in the stack 1.

  Next, the configuration of the stack 1 will be described with reference to FIG.

  The stack 1 is configured by stacking a plurality of unit cells 10. The unit cell 10 includes an electrolyte membrane made of a solid polymer membrane, a fuel electrode and an oxidizer electrode disposed on both sides of the electrolyte membrane so as to sandwich the electrolyte membrane, and a separator that forms a partition between cells. It is constituted by doing. The electrolyte membrane is formed as a proton conductive membrane from a solid polymer material such as a fluorine resin. The two electrodes disposed on both sides of the membrane are made of platinum or a carbon cloth or carbon paper containing a catalyst made of platinum and other metals, and the surface on which the catalyst exists is in contact with the electrolyte membrane. Formed as follows. The separator is made of a dense carbon material that is impermeable to gas, and a large number of ribs are formed on one side or both sides to ensure the flow path of fuel gas, oxidant gas, or cooling medium.

  The oxidant gas is supplied to the supply manifold 11 that distributes the oxidant gas to the unit cells 10 through the oxidant gas supply path 8. The oxidant gas distributed from the supply manifold 11 to the unit cell 10 is used for the power generation reaction at the oxidant electrode. The oxidant gas that has not been used for power generation is recovered from the unit cell 10 to the discharge manifold 12 and discharged to the outside through the oxidant gas discharge path 9. The fuel electrode is similarly provided with a supply manifold and a discharge manifold (not shown), and is configured to distribute and collect the fuel gas to each unit cell 10.

  A movable portion 13 is provided in the supply manifold 11. Further, a step motor 5 for setting the position of the movable portion 13 in the supply manifold 11 is provided. By moving the movable part 13, the flow path cross section of the supply manifold 11 is changed. Here, the height h of the supply manifold 11 is changed by moving the movable portion 13. Here, the height h of the supply manifold 11 corresponds to the distance from the unit battery 10 in the space in the supply manifold 11. As described above, the flow path of the oxidizing gas flowing from the supply manifold 11 to the unit cell 10 is maintained, and the flow path cross-sectional area of the supply manifold 11 can be changed.

  When the power generation state of the stacked unit cells 10 is substantially uniform, the voltages of the central unit cell 10a disposed at the central portion in the stacking direction and the end unit cells 10b disposed at the end portions in the stacking direction are substantially equal. Will be equal. In such a case, the state of the stack 1 is set as shown in FIG. This is referred to as mode A. In the case of mode A, the position of the movable portion 13 is set so that the height h of the supply manifold 11 becomes a relatively large value. Thereby, as shown in FIG. 4, an oxidant gas having a substantially uniform flow rate can be supplied to the unit cells 10 constituting the stack 1.

  On the other hand, heat may be released from the end unit battery 10b to the outside air, and the temperature may be lower than that of the central unit battery 10a. At this time, the amount of water vapor that the exhaust gas can carry away from the stack 1 is suppressed as compared with the central unit battery 10a. As a result, flooding may occur in the end unit battery 10b, leading to a decrease in voltage. In such a case, the state of the stack 1 is set as shown in FIG. This is referred to as mode B. In the case of mode B, the position of the movable portion 13 is set so that the height h of the supply manifold 11 becomes a relatively small value. As a result, the flow velocity of the gas from the vicinity of the central portion in the stacking direction toward the end in the supply manifold 11 increases. That is, in the supply manifold 11, the static pressure at the end in the stacking direction is relatively higher than that at the center, so that the end unit battery 10 b is more than the center unit battery 10 a as shown in FIG. 4. The oxidant gas is supplied. Thereby, since more exhaust gas is discharged | emitted from the edge unit battery 10b, water vapor | steam discharge | emission amount can increase and the flooding in the edge unit battery 10b can be suppressed and prevented.

  Next, switching control between modes A and B will be described with reference to the flowchart of FIG. This flow starts when the activation switch that instructs the start of power generation of the stack 1 is turned on.

  In step S1, the count S of a timer (not shown) provided in the controller 6 is reset to an initial value (S = 0). In step S2, it is determined whether or not the stack 1 is generating power. When the power generation is not in progress, this flow ends. On the other hand, if it is determined in step S2 that power generation is in progress, the process proceeds to step S3 to determine whether one second has elapsed. That is, step S3 is repeated until it is determined that 1 second has elapsed since the timer was counted last time, and when it is determined that 1 second has elapsed, the process proceeds to step S4. In step S4, a timer is counted (S = S + 1).

  Next, in step S5, it is determined whether or not the count S is smaller than a predetermined value So. Here, the predetermined value So is the time that the entire stack 1 has to rise to the normal operating temperature. Or, it is the time until the start-up operation or warm-up operation ends. In the initial stage of startup, the temperature of the stack 1 is low, and particularly in the end unit battery 10b, the temperature is hardly increased due to the influence of outside air. As a result, flooding is likely to occur in the end unit battery 10b, and the voltage may decrease. Therefore, a time until the temperature of the stack 1, particularly the temperature of the end unit battery 10 b reaches a predetermined operating temperature is obtained in advance as a predetermined value So, and control for suppressing flooding of the end unit battery 10 b is performed during this time.

  That is, when the count S is smaller than the predetermined value So, flooding may occur particularly in the end unit battery 10b. Therefore, the process proceeds to step S7 and mode B is set. That is, the flow passage cross section of the supply manifold 11 is set so that the flow rate of the oxidant gas supplied to the end unit cell 10b is larger than that of the central unit cell 10a. Here, the height h of the supply manifold 11 is set to be relatively small by controlling the step motor 5.

  On the other hand, when the count S reaches the predetermined value So or more, it is determined that the power generation states of the central unit battery 10a and the end unit battery 10b are substantially the same, and the mode A is set in step S6. That is, the flow path cross section of the supply manifold 11 is set so that the flow rates of the oxidizing gas supplied to the central unit cell 10a and the end unit cell 10b are approximately the same. Here, the height h of the supply manifold 11 is set to be relatively large by controlling the step motor 5.

  When the mode is set in steps S6 and S7 as described above, the process returns to step S2, and steps S2 to S7 are repeated while power generation is continued. As described above, in the present embodiment, it is assumed that flooding is likely to occur particularly in the end unit battery 10b at the time of start-up, and mode B for suppressing flooding at the stacking direction end is set, and when a predetermined time (So) has elapsed, Mode A is set.

  Next, the effect of this embodiment will be described.

  A plurality of unit cells 10 having a polymer film are stacked, and a stack 1 is provided that is electrically connected in series. The gas flow rate supplied to the end unit cells 10b located at both ends of the stack 1 in the stacking direction is selectively adjusted to be larger than the gas flow rate supplied to the center unit cell 10a positioned near the center in the stacking direction. A flow rate adjusting means capable of Thereby, since the amount of drainage can be increased only in the end unit battery 10b, the power generation efficiency of the entire unit battery 10 can be improved without drying the polymer membrane. As a result, a fuel cell system that can appropriately humidify the stack 1 can be provided.

  Further, a supply manifold 11 is provided that extends in the stacking direction of the stack 1 and supplies gas to the unit cells 10. The flow rate adjusting means is configured to increase the flow velocity of the gas flowing in the supply manifold 11 toward the end in the stacking direction. As a result, the static pressure in the vicinity of the end portion can be largely adjusted in the supply manifold 11 as compared with the vicinity in the center in the stacking direction, so that the gas flow rate supplied to the end unit battery 10b can be increased.

  Further, a gas introduction flow path 8 for supplying gas to the supply manifold 11 from a position corresponding to the vicinity of the central portion in the stacking direction of the stack 1 is provided. The flow rate adjusting means is configured to change the flow rate of the gas by changing the cross-sectional area of the supply manifold 11. As described above, by supplying gas from the vicinity of the central portion in the axial direction of the supply manifold 11 and changing the flow path cross section of the supply manifold 11, the flow rate of the gas toward the end in the stacking direction can be adjusted. Can do. As a result, the flow rate of the gas supplied to the end unit battery 10b can be adjusted, and moisture removal of the end unit battery 10b can be selectively increased.

  Further, the flow rate adjusting means is a means for changing the distance from the unit cell 10 in the space inside the supply manifold 11. Here, the movable part 13 in the supply manifold 11 and the step motor 5 for setting the position of the movable part 13 are used. Thereby, the flow path cross-sectional area in the supply manifold 11 can be reduced without changing the flow path cross section when the gas moves from the supply manifold 11 to the unit cell 10. As a result, the gas can be smoothly moved from the supply manifold 11 to the unit cell 10, and it is possible to avoid a shortage of gas supply.

  In addition, there is provided means for determining whether flooding occurs in the end unit battery 10b. Here, in step S5, determination is made based on the elapsed time from the start of power generation. Until a predetermined time (So) elapses from the start of power generation, a larger amount of gas is supplied to the end unit cell 10b than to the central unit cell 10a. Here, a large amount of gas is supplied to the end unit battery 10b during the warm-up operation or the start-up operation. As a result, the amount of water vapor removed from the end unit cell 10b can be increased and the flooding can be suppressed especially at the initial stage of power generation where the temperature of the end unit cell 10b is low compared to the center unit cell 10a and flooding is likely to occur. be able to. When a predetermined time (So) has elapsed, approximately the same amount of gas is supplied to the center unit battery 10a and the end unit battery 10b. Thereby, if the temperature of the stack 1 rises, efficient power generation can be performed by supplying the same amount of gas to the central portion and the end portion in the stacking direction.

  Next, a second embodiment will be described. The configuration of the fuel cell system is shown in FIG. Hereinafter, a description will be given centering on differences from the first embodiment.

  A battery temperature sensor 21 for detecting the temperature of the stack 1 is provided. Here, the battery temperature sensor 21 is arranged so as to detect the temperature of the end unit battery 10b, but this is not restrictive. For example, in the small stack 1, the temperature of the central battery 10a may be detected. Other configurations are the same as those of the first embodiment.

  Such switching control between modes A and B of the fuel cell system will be described with reference to the flowchart of FIG. This flow starts when the activation switch that instructs the start of power generation of the stack 1 is turned on.

  In step S11, it is determined whether the stack 1 is generating power. If the power generation is not in progress, this flow ends. If it is determined that power is being generated, the process proceeds to step S12. In step S12, the battery temperature Tc is detected using the battery temperature sensor 21. In step S13, the detected battery temperature Tc is compared with a predetermined value To. Here, the predetermined value To is the normal operating temperature of the stack 1.

  When the battery temperature Tc is smaller than the predetermined value To, the process proceeds to step S15, and the mode B is set and the flow rate of the oxidant gas supplied to the end unit battery 10b is relatively increased to suppress / prevent flooding. To do. On the other hand, when the battery temperature Tc is equal to or higher than the predetermined value To, the process proceeds to step S14, mode A is set, and the oxidant gas is supplied to the stack 1 substantially evenly.

  Thus, if the mode is set in steps S14 and S15, the process returns to step S11 and this flow is repeated until power generation is stopped. In the present embodiment, it is determined from the temperature of the stack 1 whether or not flooding is likely to occur at the end, and modes A and B are selected.

  Instead of the battery temperature sensor 21, a cooling water temperature sensor that detects the cooling water temperature of the stack 1 may be provided, and the control in this embodiment may be executed by estimating the battery temperature Tc from the cooling water temperature.

  Alternatively, the amount of heat generated in the stack 1 and the amount of heat removed from the stack 1 may be calculated, the battery temperature Tc of the stack 1 may be calculated therefrom, and the control in this embodiment may be executed accordingly. For example, a means for detecting the output voltage and output current of the stack 1 is provided, the battery heat generation amount from the start of power generation is estimated based on the output voltage and output current, and the temperature Tc of the stack 1 is estimated according to this battery power generation amount May be. As described above, the battery temperature Tc is directly detected by the battery temperature sensor 21 in this case. However, the theoretical heat generation amount and transmission are determined from the environmental conditions such as the ambient temperature, the control information such as the stack 1 heat capacity, and the operation conditions. An estimated value calculated based on the thermal model may be used.

  Next, the effect of this embodiment will be described. Only the effects different from those of the first embodiment will be described below.

  In addition, there is provided means for determining whether flooding occurs in the end unit battery 10b. Here, a means for detecting or estimating the temperature of the unit battery 10 is provided, and in step S13, whether or not flooding occurs in the end unit battery 10b is determined based on the battery temperature Tc of the unit battery 10. Here, a battery temperature sensor 21 is provided as means for detecting the temperature of the unit battery 10. When the temperature of the unit cell 10 is lower than the predetermined temperature (To), a larger amount of gas is supplied to the end unit cell 10b than to the central unit cell 10a. As a result, even when the battery temperature Tc is low and the performance of the unit cells 10 at both ends in the stacking direction may be degraded, the entire unit cells 10 constituting the stack 1 can be operated in a good state. Become. Further, when the temperature of the unit battery 10 becomes equal to or higher than a predetermined temperature (To), substantially the same amount of gas is supplied to the central unit battery 10a and the end unit battery 10b. Thereby, efficient electric power generation can be performed. For example, even when the temperature of the end unit battery 10b is lowered and flooding occurs due to the influence of outside air during normal operation, the flooding of the end unit battery 10b can be reduced.

  Further, the temperature of the unit battery 10 is estimated based on the ambient temperature at the start of power generation, the estimated value of the battery heat generation from the start of power generation, and the heat capacity of the battery. For example, the output voltage of the stack 1 and output current detection means are provided, and the amount of heat generated by the battery from the start of power generation is estimated based on the output voltage and output current. Alternatively, the temperature of the unit battery 10 is estimated from the temperature of the cooling water. Thus, even when the battery temperature sensor 21 cannot be installed, the temperature of the unit battery 10 can be estimated.

  Next, a third embodiment will be described. The configuration of the fuel cell system is shown in FIG. Hereinafter, a description will be given centering on differences from the second embodiment.

  A battery temperature sensor for detecting the battery temperature of the stack 1 is provided. Here, a central part temperature sensor 22 that detects the temperature of the central part of the stack 1 in the stacking direction and end temperature sensors 23a and 23b that detect the temperatures of both ends of the stacking direction are provided. The temperature detected by the central temperature sensor 22 is the central temperature Tcc, the temperature detected by the end temperature sensor 23a is the end temperature Tca, and the temperature detected by the end temperature sensor 23b is the end temperature Tcb. Other configurations are the same as those of the first embodiment.

  Such switching control between modes A and B of the fuel cell system will be described with reference to the flowchart of FIG. This flow starts when the activation switch that instructs the start of power generation of the stack 1 is turned on.

  In step S21, it is determined whether or not the stack 1 is generating power. If the power generation is not in progress, this flow is terminated. If the power generation is in progress, the process proceeds to step S22. In step S22, the battery temperature Tcc, Tca, Tcb is detected using the center temperature sensor 22 and the end temperature sensors 23a, 23b.

  In step S23, a temperature difference ΔT (= Tcc− (Tca + Tcb) / 2) between the central portion and the end portion in the stacking direction is obtained, and this is compared with a predetermined value ΔTo. Here, the predetermined value ΔTo is a value at which it is possible to determine that the possibility of flooding at the end in the stacking direction is small when the temperature difference ΔT is equal to or less than the predetermined value ΔTo.

  If the temperature difference ΔT is larger than the predetermined value ΔTo in step S23, the process proceeds to step S25 and mode B is set. Accordingly, a relatively large amount of oxidant gas is supplied to the end unit battery 10b to suppress flooding. On the other hand, if the temperature difference ΔT is less than or equal to the predetermined value ΔTo, the process proceeds to step S24, where mode A is set, and approximately the same amount of oxidant gas is supplied to the center and the end in the stacking direction.

  If a mode is set in step S24, S25, it will return to step S21 and will repeat this flow until it stops electric power generation. Thus, in the present embodiment, it is determined from the temperature difference ΔT between the center portion in the stacking direction and the end portion whether or not the end portion is likely to be flooded, and the modes A and B are selected.

  Note that, as in the second embodiment, the battery temperatures Tcc, Tca, and Tcb may be estimated from the cooling water temperature and the heat generation amount. For example, at least one of the end temperature Tca, Tcb or the center temperature Tcc is estimated based on the ambient temperature at the start of power generation, the estimated value of the battery heat generation from the start of power generation, and the heat capacity of the stack 1. However, since the temperatures of the central part and the end part in the stacking direction are detected here, the battery temperature is estimated from the cooling water temperature or the calorific value at each part.

  Next, the effect of this embodiment will be described. Hereinafter, only effects different from those of the second embodiment will be described.

  Whether or not flooding occurs in the end unit battery 10b is determined based on the temperature difference ΔT between the central portion and the end portion of the stack 1. Means for detecting or estimating the temperature of the end unit battery 10b at both ends in the stacking direction, here, end temperature sensors 23a and 23b are provided. Further, a means for detecting or estimating the temperature of the central unit battery 10a, here, a central temperature sensor 22 is provided. When the temperature difference ΔT between the central portion and the end portion in the stacking direction is larger than the predetermined value ΔTo, a larger amount of gas is supplied to the end unit cell 10b than to the central unit cell 10a. As described above, even when the end temperatures Tca and Tcb are lower than the center temperature Tcc and the performance of the end unit battery 10b may be degraded, the entire unit battery 10 constituting the stack 1 is in a good state. It is possible to drive with. When the temperature difference ΔT is equal to or less than the predetermined value To, approximately the same amount of gas is supplied to the center unit battery 10a and the end unit battery 10b. Thereby, efficient electric power generation can be performed.

  Next, a fourth embodiment will be described. The configuration of the fuel cell system is shown in FIG. Hereinafter, a description will be given centering on differences from the first embodiment.

  A water temperature sensor 24 for detecting the temperature of the cooling water flowing in the stack 1 is provided. Here, for example, the water temperature sensor 24 is arranged so as to detect the temperature of the cooling water just before being discharged from the stack 1. Other configurations are the same as those of the first embodiment.

  Such switching control between modes A and B of the fuel cell system will be described with reference to the flowchart of FIG. This flow starts when the activation switch that instructs the start of power generation of the stack 1 is turned on.

  In step S31, the coolant temperature Tw of the stack 1 at the time of startup is detected by the water temperature sensor 24. In step S32, a predetermined value So (Tw) for the coolant temperature Tw at the time of activation is set. Here, the predetermined value So (Tw) is a time during which a state in which flooding is likely to occur particularly continues at the stacking direction end of the stack 1 when the cooling water temperature at the time of startup is Tw. That is, this is the time required for the temperature of the end unit battery 10b to rise sufficiently in the stack 1. Here, a control data table of Tw-So is stored in advance, and a predetermined value So (Tw) is set using this. The predetermined value So (Tw), which is the time required for the end to warm up, is set larger as the cooling water temperature Tw at the time of startup is lower.

  Next, in step S33, the timer count of the controller 10 is reset (S = 0). Thereafter, in steps S34 to S39, the same control as in steps S2 to S7 is performed. When the mode is set in steps S38 and S39, the process returns to step S34, and this flow is repeated until power generation is stopped.

  Thus, in this embodiment, the time (predetermined value So (Tw)) required for the temperature of the end unit battery 10b to rise to a temperature at which flooding can be suppressed is set according to the cooling water temperature Tw at the time of startup. If it is within that time, mode B is set, and thereafter normal mode A is set.

  Here, the predetermined value So (Tw) is set according to the cooling water temperature Tw at the start, but may be set according to the outside air temperature or the stack temperature at the start.

  Next, the effect of this embodiment will be described. Hereinafter, only effects different from those of the second embodiment will be described.

  The predetermined time (So (Tw)) is set according to the ambient temperature at the time of startup, the cooling water temperature, or the battery temperature. Hereinafter, similarly to the first embodiment, the mode B is continued until a predetermined time elapses. When the predetermined time has elapsed, the mode A is set. Thereby, it is possible to prevent an unnecessary increase in the flow rate of the supply gas to the end unit battery 10b, and it is possible to suppress the load on the means for sending the supply gas, here the oxidant gas supply pump 3. , Efficient operation can be performed.

  Next, a fifth embodiment will be described. The configuration of the fuel cell system is shown in FIG. Hereinafter, a description will be given centering on differences from the first embodiment.

  The stack 1 includes voltage detection means. Here, a central voltage sensor 25 that detects the voltage of the central unit battery 10a and end voltage sensors 26a and 26b that detect the voltages of the end unit batteries 10b at both ends are provided. The center voltage detected by the center voltage sensor 25 is Vc, the end voltage detected by the end voltage sensor 26a is Va, and the end voltage detected by the end voltage sensor 26b is Vb. Other configurations are the same as those of the first embodiment.

  Such switching control between modes A and B of the fuel cell system will be described with reference to the flowchart of FIG. This flow starts when the activation switch that instructs the start of power generation of the stack 1 is turned on.

  In step S41, it is determined whether or not the stack 1 is generating power. If the stack 1 is not generating power, this flow is terminated. If it is generating power, the process proceeds to step S42. In step S42, the battery voltage Vc, Va, Vb is detected by the center voltage sensor 25 and the end voltage sensors 26a, 26b.

  Next, in step S43, a voltage difference ΔV (= Vc− (Va + Vb) / 2) between the central unit battery 10a and the end unit battery 10b is calculated and compared with a predetermined value ΔVo. Here, the predetermined value ΔVo is a value that is determined to be a voltage drop in the end unit battery 10b when the voltage difference ΔV is larger than the predetermined value ΔVo. That is, the maximum value of the voltage difference between the center unit battery 10a and the end unit battery 10b when flooding is not generated and the oxidant gas is sufficiently supplied is obtained in advance by experiments or the like as the predetermined value ΔVo. .

  In step S43, if the voltage difference ΔV is larger than the predetermined value ΔVo, it is determined that the voltage of the end unit battery 10b has dropped, and the process proceeds to step S45 to set mode B. On the other hand, if it is determined in step S43 that the voltage difference ΔV is equal to or smaller than the predetermined value ΔVo, it can be determined that there is no local flooding in the end unit battery 10b, so the process proceeds to step S44 and mode A is set. To do.

  If a mode is set in step S43, S44, it will return to step S41 and this flow is repeated until electric power generation is stopped. As described above, in this embodiment, the mode is set by determining whether flooding occurs from the voltage difference between the central portion and the end portion in the stacking direction.

  Next, the effect in this embodiment is demonstrated. Only the effects different from those of the first embodiment will be described below.

  Whether or not flooding occurs in the end unit battery 10b is determined based on the voltage difference ΔV between the center and the end. A central voltage sensor 25 for detecting the voltage of the central unit battery 10a is provided. Further, end voltage sensors 26a and 26b for detecting the voltages of the end unit batteries 10b are provided. When the end voltages Va and Vb are lower than the center voltage Vc and the voltage difference ΔV is larger than a predetermined value ΔVo, a larger amount of gas is supplied to the end unit battery 10b than the center unit battery 10a. Thereby, when the voltage of the end unit battery 10b decreases, flooding can be eliminated, and the entire unit battery 10 constituting the stack 1 can be in a good state. Further, since the frequency of supplying a large amount of gas to the end unit battery 10b is limited to the case where the end voltages Va and Vb are decreased, the power consumed by the gas supply means, here, the oxidant gas supply pump 3 is reduced. Can do. For example, during normal operation, even when the end unit battery 10b is flooded due to the influence of outside air and the voltage is lowered, the flooding of the end unit battery 10b can be reduced to restore the voltage.

  Next, a sixth embodiment will be described. The configuration of the fuel cell system is shown in FIG. Hereinafter, a description will be given centering on differences from the fifth embodiment.

  In addition to the center voltage sensor 25 and the end voltage sensors 26a and 26b, the stack 1 includes current detection means for detecting the battery current I, in this case, a current sensor 27. The current sensor 27 may be provided in an electric circuit that supplies power from the stack 1 to a load (not shown). Other configurations are the same as those of the fifth embodiment.

  Such switching control between modes A and B of the fuel cell system will be described with reference to the flowchart of FIG. This flow starts when the activation switch for instructing the activation start of the stack 1 is turned on.

  In step S51, it is determined whether or not the stack 1 is generating power. If the power generation is not in progress, this flow is terminated. If the power generation is in progress, the flow proceeds to step S52. In step S52, the battery voltage Vc, Va, Vb is read from the center voltage sensor 25 and the end voltage sensors 26a, 26b, and the battery current I is read from the current sensor 27.

  In step S53, a normal voltage range Vco in the central unit battery 10a and normal voltage ranges Vao and Vbo in the end unit battery 10b are set for the battery current I. Next, in step S54, it is determined whether or not the center voltage Vc is within the normal range Vco. If it is determined that the center voltage Vc is not normal, the process proceeds to step S55. In step S55, an abnormality process is performed. The processing control at the time of abnormality is performed according to a known method and is omitted here. If the battery voltage in the stack 1 returns to normal due to the abnormal time process, the process returns to step S51 and this flow is repeated.

  On the other hand, when the central end pressure Vc is within the normal range Vco in step S54, the process proceeds to step S56. In step S56, it is determined whether or not the detected end voltages Va and Vb are in the normal ranges Vao and Vbo. If it is in the normal range Vao, Vbo, the process proceeds to step S57. Here, if at least one of the end voltages Va and Vb deviates from the normal range, it is determined that it is not normal.

  When it is determined that the end voltages Va and Vb are normal, that is, when it is determined that all the battery voltages Vc, Va and Vb are normal, the process proceeds to step S57. In step S57, mode A is set, and the oxidant gas is supplied to the unit battery 10 substantially uniformly.

  On the other hand, if it is determined that the end voltages Va and Vb are abnormal, that is, if the center voltage Vc is normal and the end voltages Va and Vb are determined to be abnormal, the process proceeds to step S58. . In step S58, mode B is set, and flooding in the end unit cell 10b is reduced / prevented by supplying more oxidant gas to the end unit cell 10b than in the central unit cell 10a. Thereby, the voltage drop of the end unit battery 10b is recovered.

  If a mode is set in step S57, S58, it will return to step S51 and this flow is repeated as long as electric power generation is continuing. Thus, the normal ranges Vao, Vbo, Vco of the battery voltages Va, Vb, Vc are set according to the battery current I, and when the battery voltage becomes abnormal only at the end, flooding is performed in the end unit battery 10b. Mode B is set as it may have occurred.

  Next, the effect of this embodiment will be described. Only the effects different from those of the fifth embodiment will be described below.

  Whether or not flooding occurs in the end unit battery 10b is determined based on whether or not the battery voltage is in a normal range. A current sensor 27 for detecting the battery current I is provided. Normal ranges Vao, Vbo, Vco of battery voltages Va, Vb, Vc corresponding to the battery current I are set. When the central voltage Vc is in the normal range Vco and the end voltages Va and Vb are not in the normal ranges Vao and Vbo, a larger amount of gas is supplied to the end unit cell 10b than to the central unit cell 10a. Thereby, when flooding occurs only in the end unit battery 10b and the voltage value becomes abnormal, the flooding can be reduced. Thus, it is possible to prevent an unnecessary increase in the gas flow rate supplied to the end unit battery 10b, and to reduce the power consumed by the oxidant gas supply pump 3.

  Next, a seventh embodiment will be described. The configuration of the fuel cell system is shown in FIG. 1 as in the first embodiment. The configuration of the stack 1 is shown in FIG. Hereinafter, a description will be given centering on differences from the first embodiment.

  A plurality of paths for supplying the oxidant gas from the gas supply path 8 to the supply manifold 11 are provided. Here, the gas supply path 8 is branched into three paths 8 a, 8 b and 8 c, and the ends of the respective paths 8 are connected to the supply manifold 11. The path 8a is connected to the vicinity of the center of the supply manifold 11 in the axial direction. In other words, the path 8a is connected to a position corresponding to the vicinity of the central portion of the stack 1 in the stacking direction. The paths 8b and 8c are connected to portions that are shifted to the end side to some extent from the center of the supply manifold 11, and the paths 8b and 8c are provided with gas flow rate adjusting valves 14b and 14c, respectively. The channel cross section of the path 8a is formed larger than the channel cross sections of the paths 8b and 8c.

  Thus, in this embodiment, instead of the movable part 13 and the step motor 5, at least one other than the path 8a that branches the gas supply path 8 into the paths 8a to 8c and is connected to the vicinity of the center in the stacking direction of the stack 1. A gas flow rate adjusting valve 14 is provided in the path (8b, 8c). Thereby, as described above, the modes A and B are switched by changing the ratio of the oxidant gas flow rate supplied to the end unit battery 10b.

  When it is determined that no flooding occurs in the end unit battery 10b, the mode A is set. In this case, the gas flow rate adjusting valves 14b and 14c are opened. In this way, by supplying the oxidant gas to the supply manifold 11 while being dispersed in the stacking direction, the amount of the oxidant gas supplied to all the unit cells 10 is made uniform.

  On the other hand, when it is determined that flooding may occur in the end unit battery 10b, the mode B is set. In this case, the gas flow rate adjusting valves 14b and 14c are closed. As a result, the oxidizing gas is supplied to the supply manifold 11 from the vicinity of the central portion in the stacking direction via the path 8a. In this case, since the static pressure at the end in the stacking direction is increased in the supply manifold 11, the supply flow rate of the oxidant gas to the end unit cell 10b is larger than that in the central unit cell 10a. As a result, flooding in the end unit battery 10b can be reduced / removed.

  In addition, although applied to the fuel cell system demonstrated in 1st Embodiment here, you may apply to any of the fuel cell system demonstrated in 1st-6th embodiment.

  Next, the effect of this embodiment will be described. Only the effects different from those of the first embodiment will be described below.

  A plurality of paths 8a, 8b, and 8c for supplying gas to the supply manifold 11 from a position corresponding to the vicinity of the central portion of the stack 1 in the stacking direction and a plurality of positions corresponding to the end side thereof are provided. The flow rate adjusting means is configured to selectively stop the gas supply from at least one of a plurality of positions corresponding to the end side. Here, the paths 8a, 8b and 8c and the gas flow rate adjusting valves 14b and 14c are used. As a result, the supply path of the oxidant gas to the supply manifold 11 can be changed, so that the oxidant gas supplied to the end unit cell 10b is increased when the end unit cell 10b is likely to be flooded. can do. Further, when all the unit cells 10 are under substantially uniform operating conditions, substantially the same amount of oxidant gas can be supplied to all the unit cells 10.

  Next, an eighth embodiment will be described. The configuration of the fuel cell system is shown in FIG. 1 as in the first embodiment. The configuration of the stack 1 is shown in FIG. Hereinafter, a description will be given centering on differences from the first embodiment.

  Here, a plurality of paths for supplying the oxidant gas from the gas supply path 8 to the supply manifold 11 are provided. Here, the gas supply path 8 is branched into three paths 8 a, 8 d, and 8 e, and the ends of the respective paths 8 are connected to the supply manifold 11. The path 8a is connected to the vicinity of the center of the supply manifold 11 in the axial direction. In other words, the path 8a is connected to a position corresponding to the vicinity of the central portion of the stack 1 in the stacking direction. The paths 8d and 8e are connected to the end of the supply manifold 11, and the paths 8d and 8e are provided with gas flow rate adjusting valves 14d and 14e, respectively. The flow path cross section of the path 8a is designed to be larger than the flow path cross sections of the paths 8d and 8e.

  As described above, in this embodiment, instead of the movable portion 13 and the step motor 5, at least the gas supply path 8 branches to the paths 8a, 8d, and 8e and is connected to the vicinity of the center of the stack 1 in the stacking direction. The gas flow rate adjusting valve 14 is provided in one path (8d, 8e). Thereby, as described above, the ratio of the oxidant gas flow rate supplied to the end unit battery 10b is adjusted, and the modes A and B are switched.

  When it is determined that no flooding occurs in the end unit battery 10b, the mode A is set. In this case, the gas flow rate adjusting valves 14d and 14e are opened. Thus, the amount of the oxidant gas supplied to all the unit cells 10 is made uniform by supplying the oxidant gas also from the end in the stacking direction.

  On the other hand, when it is determined that flooding may occur in the end unit battery 10b, the mode B is set. In this case, the gas flow rate adjusting valves 14d and 14e are closed. As a result, the oxidant gas is supplied from the path 8a to the vicinity of the central portion of the supply manifold 11 in the stacking direction. In this case, since the static pressure is increased at the end in the stacking direction in the supply manifold 11, the amount of oxidant gas supplied to the end unit cell 10b is larger than that in the central unit cell 10a. Thereby, the flooding in the end unit battery 10b can be reduced or eliminated.

  In addition, although applied to the fuel cell system demonstrated in 1st Embodiment here, you may apply to any of the fuel cell system demonstrated in 1st-6th embodiment.

  Next, the effect of this embodiment will be described. Only the effects different from those of the first embodiment will be described below.

  Thus, the plurality of paths 8a, 8d, and 8e for supplying gas to the supply manifold 11 from the position corresponding to the vicinity of the central portion in the stacking direction of the stack 1 and the plurality of positions corresponding to the end side are provided. The flow rate adjusting means is configured to selectively stop the gas supply from at least one of a plurality of positions corresponding to the end side. Here, the paths 8a, 8d, and 8e and the gas flow rate adjusting valves 14d and 14e are used. As described above, the oxidant gas is supplied to the supply manifold 11 from a plurality of positions corresponding to the end side, so that the oxidant gas can be supplied uniformly in the stacking direction in the mode A.

  Here, when the flooding is likely to occur in the end unit battery 10b, the flow rate supplied to the end unit battery 10b is increased only for the oxidant gas, but this is not restrictive. In the case where flooding may occur in the fuel electrode, the fuel gas flow path can be similarly configured and controlled.

  As described above, the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims.

  The present invention can be applied to a fuel cell that requires water management, such as a polymer electrolyte fuel cell. Further, the present invention can be applied to a fuel cell that requires a change in the flow rate distribution of the reaction gas.

It is a schematic block diagram of the fuel cell system used for 1st Embodiment. It is a state diagram when the stack used in the first embodiment is set to mode A. It is a state diagram when the stack used in the first embodiment is set to mode B. It is a figure which shows the oxidizing gas flow rate of the stack | stuck in 1st Embodiment. It is a flowchart which shows the switching method of mode A and B in 1st Embodiment. It is a schematic block diagram of the fuel cell system used for 2nd Embodiment. It is a flowchart which shows the switching method of mode A and B in 2nd Embodiment. It is a schematic block diagram of the fuel cell system used for 3rd Embodiment. It is a flowchart which shows the switching method of mode A and B in 3rd Embodiment. It is a schematic block diagram of the fuel cell system used for 4th Embodiment. It is a flowchart which shows the switching method of the modes A and B in 4th Embodiment. It is a schematic block diagram of the fuel cell system used for 5th Embodiment. It is a flowchart which shows the switching method of mode A and B in 5th Embodiment. It is a schematic block diagram of the fuel cell system used for 6th Embodiment. It is a flowchart which shows the switching method of the modes A and B in 6th Embodiment. It is a schematic block diagram of the stack used for 7th Embodiment. It is a schematic block diagram of the stack used for 8th Embodiment.

Explanation of symbols

1 stack (fuel cell stack)
5 Step motor (flow rate adjusting means)
8 Gas supply route (gas introduction channel)
8a-e route (gas introduction flow path)
10 unit battery 10a central unit battery 10b end unit battery 11 supply manifold 13 movable part (flow rate adjusting means)
14 Gas flow control valve (flow control means)
h Height (distance from the unit battery)

Claims (5)

A plurality of unit cells having a polymer film are stacked, and a fuel cell stack is provided that is electrically connected in series,
Selectively so that the gas flow rate supplied to the end unit cells located at both ends of the fuel cell stack in the stacking direction is greater than the gas flow rate supplied to the center unit cells positioned near the center in the stacking direction. A fuel cell system comprising flow rate adjusting means capable of adjusting. A supply manifold that extends in the stacking direction of the fuel cell stack and supplies gas to each of the unit cells;
2. The fuel cell system according to claim 1, wherein the flow rate adjusting unit is configured to increase a flow rate of a gas flowing in the supply manifold toward an end portion in a stacking direction. A gas introduction flow path for supplying gas to the supply manifold from a position corresponding to the vicinity of the central portion in the stacking direction of the fuel cell stack;
3. The fuel cell system according to claim 2, wherein the flow rate adjusting means is configured to change a flow velocity of the gas by changing a flow path cross-sectional area of the supply manifold.   4. The fuel cell system according to claim 3, wherein the flow rate adjusting unit is configured to change a flow path cross section of the manifold by changing a distance from the unit cell with respect to a space inside the supply manifold. A plurality of gas introduction passages for supplying gas to the supply manifold from a position corresponding to the vicinity of the central portion in the stacking direction of the fuel cell stack and a plurality of positions corresponding to the end side from the position;
2. The fuel cell system according to claim 1, wherein the flow rate adjusting unit is configured to selectively stop gas supply from at least one of a plurality of positions corresponding to the end portion side.

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