JP2006114458A - Cooling device for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily start a fuel cell and reduce the electric power consumption of a cooling medium pump when starting the fuel cell or stopping the driving thereof. <P>SOLUTION: When stopping the driving of the fuel cell 1, the air communication hole of an air vent valve 4 is closed to discharge a cooling medium from the fuel cell 1 to a storage tank 9 using a supply and drain pump 8. The temperature of the inside of the fuel cell 1 is still relatively high so that the cooling medium is discharge into the storage tank 9 while the vapor pressure of the cooling medium is still high. If the temperature is lowered when starting, the vapor pressure of the cooling medium in the fuel cell 1 is lowered, so that the electric power consumption of the supply and drain pump 8 is reduced when the cooling medium is supplied from the storage tank 9 to the fuel cell 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell cooling apparatus.

  In a fuel cell, a fuel gas such as hydrogen gas and an oxidizing gas containing oxygen are electrochemically reacted through an electrolyte, and electric energy is directly taken out between electrodes provided on both surfaces of the electrolyte. In particular, a polymer electrolyte fuel cell using a polymer electrolyte has attracted attention as a power source for electric vehicles because of its low operating temperature and easy handling. That is, a fuel cell vehicle is equipped with a hydrogen storage device such as a high-pressure hydrogen tank, a liquid hydrogen tank, or a hydrogen storage alloy tank in the vehicle, and reacts by supplying hydrogen supplied therefrom and air containing oxygen to the fuel cell. This is the ultimate clean vehicle that drives the motor connected to the drive wheels with the electric energy extracted from the fuel cell, and the only exhaust material is water.

  In polymer electrolyte fuel cells, water is generated from hydrogen and oxygen by the electrochemical reaction of power generation, so water left inside the fuel cell freezes and closes the gas flow path when left under freezing after shutdown. And restarting becomes difficult.

As a countermeasure, it is conceivable to melt the ice by reducing the heat capacity of the fuel cell and by increasing the temperature of the fuel cell at the time of start-up. As specific measures, as disclosed in Patent Document 1 and Patent Document 2, the coolant is discharged to the outside of the fuel cell during the stop operation of the fuel cell, and the refrigerant is stored in a tank outside the fuel cell during the stop. There is a method of supplying the refrigerant into the fuel cell after the fuel cell is started. Normally, a liquid having a specific heat higher than that of carbon, metal, or the like constituting the fuel cell is generally used as a refrigerant. Therefore, according to this method, the heat capacity of the activated fuel cell can be reduced. .
Japanese Patent Publication No. 07-099698 (page 3, Fig. 1) JP 2003-331894 A (page 4, FIG. 1)

  However, in the above-described conventional fuel cell system, it is necessary to pump the refrigerant with a pump or the like when the refrigerant is discharged or supplied from the fuel cell, and in the process of starting or stopping the fuel cell where sufficient power cannot be taken out from the fuel cell. Auxiliary machinery load increases. Therefore, even if a secondary battery or the like is provided to supplement the power from the fuel cell, it is difficult to supply power from the secondary battery or the like at a low temperature. There was a problem that a case occurred.

  Further, if the refrigerant passage in the fuel cell is uneven, a portion where air remains in the refrigerant passage when the refrigerant is supplied into the fuel cell. If air remains in the refrigerant pipe, the amount of heat transfer is reduced and it becomes difficult to cool the fuel cell, which causes a problem of deterioration of the fuel cell due to heat.

  In order to solve the above-mentioned problems, the present invention provides a fuel cell device comprising means for discharging refrigerant from the fuel cell and supplying the refrigerant into the fuel cell, and an opening / closing mechanism for communicating the refrigerant with the atmosphere. A cooling device that discharges the refrigerant from the fuel cell and supplies the refrigerant into the fuel cell with the opening and closing mechanism closed; and supplies the refrigerant into the fuel cell at a temperature of the fuel cell. The fuel cell cooling apparatus is characterized in that the cooling is performed in a state lower than the temperature of the fuel cell when the refrigerant is discharged.

  According to the present invention, when the refrigerant is supplied to the refrigerant pipe of the fuel cell, the refrigerant pipe has a negative pressure, so that the load on the refrigerant supply means is reduced and the residual air in the refrigerant pipe is suppressed. There is an effect that can be.

  Next, embodiments of the present invention will be described in detail with reference to the drawings. In addition, although each Example described below is not specifically limited, it is an Example suitable for a fuel cell vehicle.

  FIG. 1 is a schematic configuration diagram illustrating a configuration of a first embodiment of a cooling device for a fuel cell according to the present invention. In FIG. 1, a fuel cell 1 is a fuel cell to be cooled, for example, a solid polymer electrolyte fuel cell. A refrigerant flow path (not shown) is provided inside the fuel cell 1 so that reaction heat accompanying power generation and Joule heat due to internal resistance of the fuel cell 1 can be cooled by the refrigerant flowing through the refrigerant flow path.

  This refrigerant is a refrigerant that does not freeze even below freezing point. For example, it is obtained by adding a freezing temperature reducing agent such as ethylene glycol to purified water. By adjusting the ethylene glycol concentration of the refrigerant, the lower limit temperature that can be used as the refrigerant can be controlled.

  A gas supply system that supplies fuel gas and oxidant gas to the fuel cell 1 is not directly related to the gist of the present invention, and is not shown.

  The radiator 2 is a heat exchanger that dissipates heat of the refrigerant outside the system, and a radiator fan (not shown) may be provided. The refrigerant circulation pump 3 is a pump that circulates the refrigerant between the fuel cell 1 and the radiator 2. The air vent valve 4 is a valve for venting air from the refrigerant circulation path, and is a valve for sealing the refrigerant circulation path when the refrigerant is withdrawn from the fuel cell 1. The circulation path valve 5 is a valve that opens and closes the refrigerant circulation path. The temperature sensor 6 is a sensor for measuring the temperature of the fuel cell. The supply / discharge passage valve 7 is a valve that discharges the refrigerant from the fuel cell 1 or supplies the refrigerant to the fuel cell 1. The supply / discharge pump 8 is a pump for supplying and discharging refrigerant. The storage tank 9 is a tank for storing the refrigerant discharged from the fuel cell 1. The refrigerant amount sensor 10 is a sensor that measures the amount of refrigerant in the storage tank 9.

  The controller 20 controls the circulation pump 3, the supply / discharge pump 8, the air vent valve 4, the circulation path valve 5, and the supply / discharge path valve 7 based on the detection value of the temperature sensor 6 and the detection value of the refrigerant amount sensor 10. Thus, the control device controls the discharge of the refrigerant from the fuel cell 1, the supply of the refrigerant to the fuel cell 1, and the circulation of the refrigerant.

  Although not particularly limited, in this embodiment, the controller 20 is composed of a CPU, a program ROM, a working RAM, and a microprocessor having an input / output interface.

  FIG. 2A is a flowchart showing the refrigerant process during the fuel cell operation stop process. The initial state when this flowchart starts is a state in which the supply of fuel gas and oxidant gas to the fuel cell 1 is stopped and power generation is stopped. The circulation pump 3 is in operation and the supply / discharge pump 8 is stopped. It is assumed that the air vent valve 4 blocks the outside air and the refrigerant flow path and opens the refrigerant circulation path in the left-right direction in the drawing. Further, the circulation path valve 5 is in an open state, and the supply / discharge path valve 7 is in a closed state.

  In the refrigerant processing in the stop process of FIG. 2A, first, in step (hereinafter, step is abbreviated as S) 10, the fuel cell temperature detected by the temperature sensor 6 is a predetermined cooling end temperature (for example, 70 [° C. ]) Or less is determined. If the fuel cell temperature is equal to or higher than the cooling end temperature, the process returns to S10 and waits for cooling.

  If it is determined in S10 that the fuel cell temperature has fallen below the predetermined cooling end temperature, the process proceeds to S12 and the circulation pump 3 is stopped. The cooling stop temperature is a temperature at which the temperature of the polymer electrolyte membrane due to the residual heat inside the fuel cell 1 does not exceed the heat resistance temperature even if the circulation of the refrigerant is stopped. It shall be remembered. Next, in S14, the air vent valve 4 on the refrigerant circuit is closed in three directions, and the circuit valve 5 is closed.

  Thereafter, the supply / discharge passage valve 7 is opened in S16, and the operation of the supply / discharge pump 8 for supplying and discharging the refrigerant is started in S18. At this time, the supply / discharge pump 8 is operated in a direction to send the refrigerant from the fuel cell 1 to the storage tank 9. During operation of the supply / discharge pump 8, the amount of refrigerant in the storage tank 9 is monitored by the refrigerant amount sensor 10 in the storage tank 9.

  Next, when the amount of refrigerant in the storage tank 9 reaches a predetermined amount at which it is determined in S20 that almost all of the refrigerant in the fuel cell 1 has been discharged, the process proceeds to S22, the supply / discharge passage valve 7 is closed, and in S24 The supply / discharge pump 8 is stopped, and the refrigerant process in the stop process is ended.

  FIG. 2B is a flowchart showing the refrigerant processing during the fuel cell startup process. The initial state when this flowchart starts is that the circulation pump 3 and the supply / discharge pump 8 are stopped, the air vent valve 4 is closed in three directions, and the circulation path valve 5 and the supply / discharge path valve 7 are closed. The fuel cell 1 is in a state where fuel gas and oxidant gas are supplied, power generation is started, and the temperature of the fuel cell 1 is starting to rise due to reaction heat.

  In the refrigerant process during the startup process in FIG. 2B, first, in S30, it is determined whether or not the fuel cell temperature detected by the temperature sensor 6 is equal to or higher than a predetermined cooling start temperature (for example, 20 [° C.]). This cooling start temperature is lower than the cooling end temperature (for example, 70 [° C.]) in S10 of FIG. 2A, and is a temperature at which it is determined that the fuel cell 1 can continuously generate power. Is experimentally determined and stored in the controller 20.

  If it is determined in S30 that the fuel cell temperature is lower than the cooling start temperature, the process returns to S30. If it is determined in S30 that the fuel cell temperature is equal to or higher than the cooling start temperature, the process proceeds to S32 and the supply / discharge path valve 7 is opened. Next, in S <b> 34, the supply / discharge pump 8 is operated to supply the refrigerant from the storage tank 9 to the fuel cell 1. The operation direction of the supply / discharge pump 8 at this time is a direction in which the refrigerant is sent from the storage tank 9 to the fuel cell 1. During the operation of the supply / discharge pump 8, the refrigerant amount in the storage tank 9 is monitored by the refrigerant amount sensor 10.

  Next, when the refrigerant amount in the storage tank 9 detected by the refrigerant amount sensor 10 reaches a predetermined amount (minimum amount) that is determined that the fuel cell 1 is almost filled with the refrigerant in S36, the supply / exhaust passage valve in S38. 7 is closed and the supply / discharge pump 8 is stopped in S40. Thereafter, the circulation path valve 4 and the air vent valve 5 are opened in S42, and the operation of the circulation pump 3 is started in S44.

  From the start of the operation of discharging the refrigerant from the fuel cell 1 until the fuel cell is stopped and until the supply of the refrigerant from the storage tank 9 to the fuel cell 1 is completed, the air vent valve 4 on the refrigerant circuit is connected to the atmosphere. Keep the refrigerant sealed. However, the degree of sealing need not be complete although the effect of the present embodiment is reduced.

  As described above, according to the present embodiment, when the refrigerant is supplied to the refrigerant flow path inside the fuel cell, the temperature of the refrigerant flow path in the fuel cell is lower than when the refrigerant is discharged, that is, the vapor pressure of the refrigerant is reduced. Therefore, the pressure inside the refrigerant flow path becomes negative, reducing the load on the supply / discharge pump that supplies the refrigerant from the storage tank to the fuel cell, reducing its power consumption, and reducing the air remaining in the refrigerant flow path. There is an effect that it can be suppressed.

  Next, Embodiment 2 of the fuel cell cooling apparatus according to the present invention will be described. The configuration of the second embodiment is the same as that of the first embodiment shown in FIG. Further, the refrigerant processing control during the start-up process of the fuel cell in the second embodiment is the same as that in the first embodiment shown in FIG.

  In the refrigerant processing control during the stop process in FIG. 2A of the first embodiment, the power generation of the fuel cell is stopped in advance, but in this embodiment, the power generation of the fuel cell 1 is performed in the stop process of the fuel cell. First, the operation to reduce the power generation amount is performed. Thereafter, the same operation as in the first embodiment is performed. Finally, after the supply / discharge pump 8 that discharges the refrigerant from the fuel cell 1 is stopped, the power generation of the fuel cell 1 is stopped.

  FIG. 3 is a refrigerant process control flowchart in the fuel cell stop process according to the second embodiment. The initial state when this flow chart is started is that the circulation pump 3 is in operation, the supply / discharge pump 8 is stopped, the air vent valve 4 shuts off the outside air and the refrigerant flow path, and the refrigerant circulation path in the left-right direction in the figure. It shall be open. Further, the circulation path valve 5 is in an open state, and the supply / discharge path valve 7 is in a closed state.

  First, in S50 of FIG. 3, the power generation amount of the fuel cell is reduced. For this purpose, the pressure and flow rate of the fuel gas and oxidant gas supplied to the fuel cell 1 are reduced. The degree of this reduction is, for example, such that the power necessary for driving the circulation pump 3 or the supply / discharge pump 8 can be covered by the generated power of the fuel cell 1.

  Next, in S52, it is determined whether or not the fuel cell temperature detected by the temperature sensor 6 has fallen below a predetermined cooling end temperature. If the fuel cell temperature is equal to or higher than the cooling end temperature, the process returns to S52 to wait for cooling.

  If it is determined in S52 that the fuel cell temperature has fallen below the predetermined cooling end temperature, the process proceeds to S54 and the circulation pump 3 is stopped. The cooling stop temperature is a temperature at which the temperature of the polymer electrolyte membrane due to the residual heat inside the fuel cell 1 does not exceed the heat resistance temperature even if the circulation of the refrigerant is stopped. It shall be remembered. Next, in S56, the air vent valve 4 on the refrigerant circuit is closed in three directions, and the circuit valve 5 is closed.

  Thereafter, the supply / discharge passage valve 7 is opened in S58, and the operation of the supply / discharge pump 8 for supplying / discharging the refrigerant is started in S60. At this time, the supply / discharge pump 8 is operated in a direction to send the refrigerant from the fuel cell 1 to the storage tank 9. During operation of the supply / discharge pump 8, the amount of refrigerant in the storage tank 9 is monitored by the refrigerant amount sensor 10 in the storage tank 9.

  Next, in S62, when the amount of refrigerant in the storage tank 9 reaches a predetermined amount determined that almost all of the refrigerant in the fuel cell 1 has been discharged, the process proceeds to S64, the supply / discharge path valve 7 is closed, and in S66. The supply / discharge pump 8 is stopped. Finally, supply of fuel gas and oxidant gas to the fuel cell 1 and power generation are stopped in S68, and the stop process is terminated.

  As described above, according to the present embodiment, in addition to the effects of the first embodiment, the refrigerant is discharged from the refrigerant flow path of the fuel cell while the temperature of the fuel cell is high to some extent. Since the refrigerant can be discharged in a state where the vapor pressure is high, there is an effect that it is possible to reduce the load on the refrigerant discharge means when discharging the refrigerant from the refrigerant flow path of the fuel cell.

  Next, a third embodiment of the fuel cell cooling device according to the present invention will be described. FIG. 4 is a schematic configuration diagram illustrating the configuration of the fuel cell cooling device according to the third embodiment, and FIG. 5 is a control flowchart of the refrigerant processing during the fuel cell activation process according to the third embodiment. The refrigerant processing during the fuel cell stop process is the same as that of the first embodiment shown in FIG.

  In the third embodiment, in addition to the configuration of the first embodiment, a manifold cooling device 11 and a manifold cooling device 12 are provided as cooling means on the refrigerant circulation path. The manifold cooling device 11 cools the refrigerant discharge manifold between the fuel cell 1 and the air vent valve 4, and the manifold cooling device 12 cools the refrigerant introduction manifold between the fuel cell 1 and the circulation path valve 5. Is. As the manifold cooling devices 11 and 12, an electronic cooling device applying a Peltier effect, a combination of heat radiation fins and a cooling fan, or the like can be used.

  In this embodiment, before starting the supply of the refrigerant to the fuel cell 1 in the fuel cell startup process, the manifold cooling device 11 and the manifold cooling device 12 are operated to cool the refrigerant manifold. Thereafter, the same operation as in the first embodiment is performed, and finally the operation of the circulation pump 3 is started, and then the operations of the manifold cooling device 11 and the manifold cooling device 12 are stopped.

  The initial state when the refrigerant processing in the fuel cell start-up process in the embodiment of FIG. 5 starts is that the circulation pump 3 and the supply / discharge pump 8 are stopped, the air vent valve 4 is closed in three directions, and the circulation path The valve 5 and the supply / discharge path valve 7 are closed. The fuel cell 1 is in a state where fuel gas and oxidant gas are supplied, power generation is started, and the temperature of the fuel cell 1 is starting to rise due to reaction heat.

  In the refrigerant processing during the startup process of FIG. 5, first, in S70, it is determined whether or not the fuel cell temperature detected by the temperature sensor 6 is equal to or higher than a predetermined cooling start temperature. This cooling start temperature is a temperature at which it is determined that the fuel cell 1 can continuously generate power, and is experimentally determined by an actual device and stored in the controller 20.

  If it is determined in S70 that the fuel cell temperature is lower than the cooling start temperature, the process returns to S70. If it is determined in S70 that the fuel cell temperature is equal to or higher than the cooling start temperature, the process proceeds to S72 to operate the manifold cooling devices 11 and 12 to cool the refrigerant manifold.

  Next, in S74, the supply / discharge passage valve 7 is opened. Next, the supply / discharge pump 8 is operated in S <b> 76 to supply the refrigerant from the storage tank 9 to the fuel cell 1. The operation direction of the supply / discharge pump 8 at this time is a direction in which the refrigerant is sent from the storage tank 9 to the fuel cell 1. During the operation of the supply / discharge pump 8, the refrigerant amount in the storage tank 9 is monitored by the refrigerant amount sensor 10.

  Next, in S78, when the refrigerant amount in the storage tank 9 detected by the refrigerant amount sensor 10 reaches a predetermined amount (minimum amount) in which it is determined that the fuel cell 1 is almost filled with the refrigerant, the supply / exhaust passage valve in S80. 7 is closed and the supply / discharge pump 8 is stopped in S82. Thereafter, the circulation path valve 4 and the air vent valve 5 are opened in S84, and the operation of the circulation pump 3 is started in S86. Finally, the manifold cooling devices 11 and 12 are stopped in S88, and the refrigerant process in the starting process is ended.

  As described above, according to the present embodiment, in addition to the effects of the first embodiment, the temperature of the refrigerant piping outside the fuel cell is prevented from being raised by the refrigerant that has been heated by the reaction heat by passing through the inside of the fuel cell. Therefore, when supplying the refrigerant to the refrigerant pipe, there is an effect that it is possible to particularly suppress the residual air in the refrigerant pipe outside the fuel cell.

  Next, a fourth embodiment of the fuel cell cooling apparatus according to the present invention will be described. The configuration of the fourth embodiment includes an outside air temperature predicting unit that predicts the minimum value of the outside air temperature during power generation stop of the fuel cell, in addition to the configuration of the first embodiment of FIG.

  The outside air temperature predicting means is, for example, a method of obtaining a predicted minimum low temperature in a stop area by connecting to a weather forecast site from a mobile phone or mobile communication device provided in the vehicle, or a minimum temperature from a stop time and the outside air temperature at that time. There is a way to predict.

  In this embodiment, in the process of stopping the operation of the fuel cell, first, the outside air temperature predicting means is operated to predict the minimum value of the outside air temperature after the fuel cell is stopped. Next, the predicted minimum value of the outside air temperature is compared with the freezing temperature at which it is determined that freezing occurs in the fuel cell. Then, when the lowest predicted outside air temperature is lower than the freezing temperature, the refrigerant is discharged from the fuel cell 1. Here, the freezing temperature is 0 [° C.] or a certain amount of temperature (1) from 0 [° C.] in consideration of the error in the outside air temperature predicting means and the fact that the fuel cell vehicle temperature is lower than the outside air temperature due to radiation cooling. ˜2 [° C.]) High value. The starting process of the fuel cell is the same as that of the first embodiment shown in FIG.

  Next, with reference to FIG. 6, the refrigerant process during the fuel cell stop process in the present embodiment will be described. First, in S90, the outside air temperature (Ta) while the vehicle is stopped is predicted by the outside air temperature predicting means. Next, in S92, it is determined whether or not the lowest outside temperature predicted value (Ta lowest value) is equal to or lower than the freezing temperature. If it is determined in S92 that the Ta minimum value is equal to or lower than the freezing temperature, the refrigerant discharge process in S94 is executed. If it is determined in S92 that the Ta minimum value exceeds the freezing temperature, the process is terminated without doing anything. The refrigerant discharge process in S94 is the same as the processes from S10 to S24 in FIG.

  As described above, according to the present embodiment, in addition to the effects of the first embodiment, the minimum value of the outside temperature is predicted when the fuel cell is stopped, and the minimum value of the predicted outside temperature indicates the possibility of freezing of the fuel cell. The refrigerant is discharged and supplied only in the case, and the number of times the refrigerant is discharged and supplied is reduced. Therefore, it is possible to shorten the start-stop time of the fuel cell and improve the efficiency of the fuel cell during the start-stop operation. There is an effect that can be done.

It is a schematic block diagram explaining the structure of Example 1 of the cooling device for fuel cells which concerns on this invention. 3 is a control flowchart of a controller according to the first embodiment. 6 is a control flowchart of a controller in Embodiment 2. It is a schematic block diagram explaining the structure of Example 3 of the cooling device for fuel cells which concerns on this invention. 10 is a control flowchart of a controller in Embodiment 3. 10 is a control flowchart of a controller in Embodiment 4.

Explanation of symbols

1: Fuel cell 2: Radiator 3: Circulation pump 4: Air vent valve 5: Circulation valve 6: Temperature sensor 7: Supply / exhaust passage valve 8: Supply / exhaust pump 9: Storage tank 10: Refrigerant amount sensor 20: Controller

Claims (4)

A cooling device for a fuel cell comprising means for discharging the refrigerant from the fuel cell and supplying the refrigerant into the fuel cell, and an opening / closing mechanism for communicating the refrigerant with the atmosphere,
The refrigerant is discharged from the fuel cell and the refrigerant is supplied into the fuel cell with the opening / closing mechanism closed, and the refrigerant is supplied to the fuel cell when the temperature of the fuel cell discharges the refrigerant. A cooling apparatus for a fuel cell, which is performed in a state lower than a temperature of the battery. 2. The cooling device for a fuel cell according to claim 1, wherein the operation of discharging the refrigerant from the inside of the fuel cell is performed while the fuel cell is generating electric power. Means for cooling the refrigerant piping outside the fuel cell;
2. The fuel cell cooling device according to claim 1, wherein the refrigerant pipe outside the fuel cell is cooled during the operation of supplying the refrigerant into the fuel cell. 3. An outside temperature predicting means for predicting the outside temperature is provided,
2. The fuel cell according to claim 1, wherein during the fuel cell stop operation, the refrigerant is discharged from the fuel cell when the minimum temperature predicted by the outside air temperature predicting means is lower than a predetermined temperature. Cooling system.

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