JP5741922B2 - Fuel cell drying control method - Google Patents

Description

  The present invention relates to a method for suppressing drying of a fuel cell.

  During high-temperature operation of the fuel cell, the performance deteriorates due to the negative voltage due to dry-up due to the air inlet drying, or the drivability (so-called drivability) deteriorates due to the decrease in output.

  As one of the techniques for suppressing such drying, there is a method of increasing the water content of the electrolyte membrane by increasing the generated water by increasing the operating current of the fuel cell in the case of water shortage. (For example, refer to Patent Document 1).

  In addition, there is a method of controlling the temperature, the humidification amount, and the pressure so that the local current in the portion that is easily dried in the cell falls within a predetermined range (see, for example, Patent Document 2).

  Further, there is a method of controlling the water content of the membrane by increasing the air pressure if the temperature is equal to or higher than a predetermined value (for example, see Patent Document 3).

JP 2004-265862 A JP 2005-190997 A JP 2008-130471 A

  However, in the case of Patent Document 1, since power generation is performed with a current that is equal to or greater than the current for supplying the power necessary for running the fuel cell vehicle, the fuel consumption deteriorates. In addition, by increasing the current, the secondary battery must be charged to the secondary battery, and cannot be performed when the secondary battery has a high SOC (State of Charge) (increasing the current). Can not).

  In the case of Patent Document 2, the temperature cannot be controlled when the outside air temperature is high and the cooling capacity of the radiator is insufficient. Furthermore, in order to increase the humidification amount, a separate component for humidification is required, resulting in high costs. Further, when the pressure is increased, the power consumption of the air compressor is increased and the fuel consumption is deteriorated.

  Further, in the case of Patent Document 3, when the pressure is increased, the power consumption of the air compressor is increased and the fuel consumption is deteriorated.

  An object of the present invention is to provide a method for suppressing the drying of a fuel cell that can increase the amount of water produced in a dry portion without increasing the total current.

  In order to solve this problem, the present inventor has made various studies. In the case of the above-mentioned Patent Document 1, it is not necessary to increase the current in the portion that is not dried, but since the means for increasing the total current is taken, the current in the portion that is not dried is also increased. This is the reason for the above problem. In addition, in the case of Patent Document 2, the control depends on the cooling capacity, the control depends on the humidification from the outside, and the amount of steam carried away is not increased as the drying suppression means, but the generated water is not increased. This is the reason for the above problems. Furthermore, in the case of Patent Document 3, the reason for the above problem is that the amount of steam carried away is reduced as the drying suppression means, not the increase in generated water. The present inventor who has focused on these has come to obtain knowledge that leads to the solution of the problem.

  The present invention is based on such knowledge, and is a method for suppressing the drying of a fuel cell, in which the air that tends to dry in the fuel cell is reduced by reducing the air stoichiometric ratio or reducing the fuel cell voltage in the fuel cell. When power generation is biased at the inlet, drying is suppressed with the water generated when the dry part is generated, and when the fuel cell voltage is lowered, the durability and heat generation increase by lowering the fuel cell voltage In consideration of this, the amount of decrease in the fuel cell voltage is controlled according to the dryness.

  According to the present invention, it is possible to increase the amount of water produced in the dried portion without increasing the total current.

It is a flowchart which shows one Embodiment of this invention. It is a graph which shows the relationship between the current density and cell voltage in a fuel cell. It is a graph which shows the relationship between the capacity | capacitance component and voltage in a fuel cell. It is a flowchart which shows other embodiment of this invention.

  Hereinafter, the configuration of the present invention will be described in detail based on an example of an embodiment shown in the drawings. Hereinafter, as an example, a case where the present invention is applied to a fuel cell (or a fuel cell system including the fuel cell) scheduled to be mounted on a fuel cell vehicle will be described as an example. It is not limited to examples.

  Here, the fuel cell system to which the present invention is applied includes a fuel cell, means for controlling the air stoichiometric ratio, means for controlling the fuel cell (FC) voltage, means for estimating the dryness (the capacity component of the fuel cell). Measurement or means for measuring the FC temperature).

  In this embodiment, drying of the fuel cell is suppressed by the control device. Hereinafter, the drying suppression method is exemplified (see FIG. 1).

  In the present embodiment, after the start of the drying suppression control process (step SP1), first, it is confirmed whether or not the IG (ignition) of the fuel cell vehicle is ON (step SP2). If NO, the series of drying suppression control is terminated (step SP8). If YES, the process proceeds to step SP3.

  In step SP3, the capacity component of the fuel cell when the voltage drops as shown in FIG. 2 is calculated. Note that the smaller the capacity component of the fuel cell, the more dry the cell. In addition, the air inlet of the fuel cell tends to dry. FIG. 2 shows the dryness of the air inlet in the fuel cell.

  Next, it is determined whether the calculated capacitance component is equal to or less than a predetermined value (step SP4). Thereby, it can be judged whether dryness is more than fixed. If NO, normal power generation is performed (step SP7). If YES, drying suppression processing is performed in step SP5.

  In step SP5, it is determined that drying suppression is necessary because the fuel cell is dry, and processing such as reducing the air stoichiometric ratio or reducing the FC (fuel cell) voltage is performed according to the capacity component (step SP5). ). If the capacity component is small, the air inlet has a high degree of dryness. Therefore, in order to increase the amount of water generated at the air inlet (= biasing power generation toward the air inlet), the air stoichiometric ratio is reduced and the FC voltage is lowered. Moreover, since it is desired to reduce the fluctuation of the voltage in order to prevent platinum elution, it is preferable to decrease the FC voltage decrease width as the dryness is smaller (see FIG. 3). If the air stoichiometric ratio is 1, it can be seen that the air outlet does not generate power, and that power is generated at the air inlet or the center. Here, when the FC voltage is further lowered, power generation is biased toward the air inlet side.

  Next, after the above process (step SP5), it is determined whether or not a predetermined time has elapsed, or whether or not the remeasured capacity component is equal to or greater than a predetermined value (step SP6). In short, it is judged here whether or not drying can be suppressed.

  If NO in step SP6, step SP5 is repeated. If YES in step SP6, normal power generation is performed (step SP7), and the process returns to step SP2.

  According to the drying suppression method of the present embodiment described so far, the current density of the non-dried portion in the cell is reduced, and the current density of the dried portion is increased, thereby increasing the total current without increasing the total current. The amount of water produced can be increased.

  Moreover, since the drying suppression method of this embodiment is a method which does not depend on cooling capacity, it can be implemented even when the outside air temperature is high and the cooling capacity is insufficient.

  Moreover, since the drying suppression method of this embodiment does not require an external humidifier, it does not cause an increase in cost.

  Furthermore, since the drying suppression method of this embodiment does not require an increase in pressure, it does not cause an increase in power consumption of the air compressor.

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the scope of the present invention. Below, an example of the drying suppression process which used FC temperature as a parameter is shown (refer FIG. 4).

  After the start of the drying suppression control process (step SP11), first, it is confirmed whether or not the IG (ignition) of the fuel cell vehicle is ON (step SP12). If NO, the series of drying suppression control is terminated (step SP18). If YES, the process proceeds to step SP13.

  In step SP13, it is determined whether the FC temperature is equal to or higher than a predetermined value (step SP13). Thereby, it can be judged whether dryness is more than fixed. If NO, the process returns to step SP12, but if YES (if the FC temperature is equal to or higher than a predetermined value), it is determined that it is dry and the process proceeds to step SP14.

  In step SP14, it is determined whether or not a predetermined time has elapsed since the last drying suppression control. If NO, the process returns to step SP12, but if YES (after a certain period of time has elapsed), it is determined that it has been dried again, and the process proceeds to step SP15.

  In step SP15, a drying suppression process is performed according to the FC temperature. Specifically, the air stoichiometry is reduced or the FC voltage is lowered. Here, the higher the FC temperature, the more the air inlet is determined to be dry, and the higher the FC temperature is, the more power is biased toward the air inlet to increase the amount of generated water at the air inlet.

  Next, after the above process (step SP15), it is determined whether a predetermined time has elapsed (step SP16). If the predetermined time has not passed, the process returns to step SP15. If the predetermined time has passed, it is determined that drying could be suppressed (YES in step SP16), the normal power generation is restored (step SP17), and then the process returns to step SP12.

  The present invention is suitable for application to a fuel cell such as a fuel cell vehicle.

Claims (1)

A method of suppressing drying of a fuel cell,
When the fuel cell voltage drop occurs, calculate the capacity component of the fuel cell,
If the calculated capacity component is below a predetermined value, by a Turkey down the air stoichiometric ratio in the fuel cell, to bias the power generation tends to occur air inlet drying in the fuel cell, when was generated the dryer section Suppresses drying with generated water,
In addition, when the fuel cell voltage is reduced, the fuel cell voltage is controlled to decrease in accordance with the degree of dryness, taking into account the durability and heat generation increase caused by reducing the fuel cell voltage. Method.

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