JP2005174600A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system in which the starting performance of a fuel cell is improved, and of which efficient power generation is possible. <P>SOLUTION: This is a fuel cell system having a fuel cell stack 100 constituted of a laminated structure 200 in which a plurality of fuel cells (6, 7) to generate electric power by receiving supply of a fuel gas and an oxidizer gas are laminated in juxtaposition, an end plate 3 arranged respectively at both ends parts in the laminated direction of the laminated structure 200, and a main current collection board 5 which is arranged respectively between the end plate 3 and the laminated structure body 200 and takes out the electric power generated by the laminated structure 200. This includes a resistor 8 arranged between the main current collection board 5 of at least one end part and the end plate 3 among both ends parts in the laminated layer direction of the laminated structure 200, an auxiliary current collection plate 9 arranged between the resistor 8 and the end plate 3, and a switch means 10 to switch the taking-out of the electric power generated by the laminated structure 200 between the main current collection board 3 of one end part and the auxiliary current collection plate 9. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel cell system, and more particularly to a fuel cell system that improves the startability of the fuel cell and enables efficient power generation.

  Separator for sandwiching a membrane electrode assembly in which two gas diffusion electrodes corresponding to a fuel electrode and an oxidant electrode are arranged on both sides of an electrolyte membrane and supplying fuel gas and oxidant gas to the fuel electrode and oxidant electrode, respectively In a fuel cell stack in which unit cells (cells) composed of the above are stacked and stacked, when each cell is supplied with fuel and an oxidant to generate power, heat equivalent to the amount of power generated is generated. .

  In the fuel cell stack, the unit cells arranged in the middle of the stacking method include cells that are adjacent on both sides. On the other hand, the unit cell (hereinafter referred to as “end cell”) arranged at the end in the stacking direction has only one side of the adjacent cell, and the other side is the current collector plate. A metal member or the like having a high thermal conductivity is adjacent to each other. Since the end cell is radiated to the outside through the metal member, a temperature drop is likely to be caused as compared with the unit cell disposed in the middle. Due to this temperature decrease, the power generation performance of the end cell may be reduced, and condensation is generated and the discharge of generated water is reduced, and in particular, the cell voltage is reduced on the high current side. . As the difference between the temperature inside the fuel cell stack and the outside air temperature increases, the temperature drop of the end cells becomes particularly significant. Furthermore, at the time of start-up in a sub-freezing atmosphere, generated water is generated in the end cells simultaneously with power generation, and when the end cells are cooled to below sub-freezing, the generated water freezes and the reaction gas flow path (oxidant gas flow path). And / or the fuel gas flow path) or the porous carbon of the electrolyte membrane may be clogged. Therefore, there is a problem that the voltage of the end cell is lowered due to the reaction gas shortage due to the blocking of the reaction gas channel or the porous carbon, and the entire fuel cell stack cannot be started smoothly.

  In order to solve this problem, the current collector plate is heated by the current output from the solid polymer electrolyte fuel cell at the portion of the current collector plate that is in contact with the outer surface of the separator located at at least both ends of the unit fuel cell stack. There is disclosed a solid polymer electrolyte fuel cell in which an exothermic body is formed, which can prevent the end cells from being overcooled (see, for example, Patent Document 1). However, the heating element is provided between the current collector plate and the unit cell (unit cell), and the electric power output from the solid polymer electrolyte fuel cell is always consumed via this heating element. Therefore, even when the end cells are not required to be heated as in the steady state operation, power is wasted, and the power generation efficiency of the entire fuel cell stack is reduced.

Therefore, in order to solve this problem, a heating element provided with a power extraction terminal is arranged outside at least one of the anode-side current collector plate and the cathode-side current collector plate provided at both ends of the unit cell in the stacking direction. When the temperature of the unit cell disposed on the end side in the stacking direction is reduced, the solid polymer that generates heat by taking out power from the heating element An electrolyte fuel cell is disclosed (for example, see Patent Document 2). In this case, when the fuel cell stack is in a steady operation state, the electric power is not taken out from the heating element, so that the electric power consumption by the heating element is prevented and efficient power generation can be reliably performed.
JP-A-8-167424 JP 2003-45462 A

  In the configuration of the invention disclosed in Patent Document 2, a low-conductivity heating element provided with a power extraction terminal is disposed outside a highly conductive current collector plate. The heating element cannot flow evenly, and most of the current is concentrated in the vicinity of the portion of the heating element where the power extraction terminal is provided. Therefore, since the heat generating portion of the heat generating element is localized, the heating to the end cell is also localized, and there is a problem in the reliability and performance of the end cell itself and by extension, the entire fuel cell stack.

  The present invention has been made to solve such a problem. The end unit cell is heated more uniformly with a simple configuration and operation method, and the power generation performance of each unit cell is improved. An object of the present invention is to provide a fuel cell system capable of improving the startability of the battery and capable of generating power efficiently.

  The present invention relates to a fuel cell system including a fuel cell stack, a resistor disposed between a main current collecting plate and an end plate at least one of the both ends in the stacking direction of the stacked structure, and a resistor An auxiliary current collecting plate disposed between the body and the end plate, and switching means for switching the extraction of the electric power generated by the laminated structure between the main current collecting plate and the auxiliary current collecting plate at one end. Have.

  When the switching means switches the extraction of electric power from the fuel cell stack to the auxiliary current collector plate, heat is generated in the resistor due to the current flowing through the resistor. Since the heat generated by the resistor heats the end cell, the temperature rise of the end cell is promoted, and efficient power generation can be performed.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram showing the configuration of the fuel cell system according to the first embodiment of the present invention.

  The fuel cell unit 100 receives fuel gas (for example, hydrogen), oxidant gas (for example, air), and the like from an oxidant gas unit, a fuel gas unit, and a cooling water unit (not shown) according to instructions from the control unit 300. , Generate electricity by receiving cooling water supply.

  This fuel cell unit 100 sandwiches a membrane electrode assembly in which two gas diffusion electrodes corresponding to a fuel electrode and an oxidant electrode are arranged on both sides of an electrolyte membrane, and a fuel gas and an oxidant are respectively placed on the fuel electrode and the oxidant electrode. A laminated structure in which unit batteries (cells) each composed of a separator for supplying gas are arranged and stacked is sandwiched between end plates 3. At the end of this laminated structure, there is a main current collecting plate 5 for taking out the electric power generated by each cell. In order to raise the temperature by flowing current, the resistor 8 and the resistor 8 are made to conduct current. In addition, an auxiliary current collecting plate 9 and an insulating plate 4 for taking out the generated electric power are provided. The main current collecting plate 5, the resistor 8 and the auxiliary current collecting plate 9 are each formed in a plate shape, and are arranged in close contact with each other in the stacking direction of the stacked structure. These parts are fastened in the stacking direction by the fastening parts 2, and the fuel cell stack 200 is configured by each part.

  The fuel cell stack 200 is housed in the fuel cell stack mounting box 1. The fuel cell stack mounting box 1 is configured to cover the periphery of the fuel cell stack 200, in particular, the periphery of the main current collector plate 5, the resistor 8, and the auxiliary current collector plate with an electrically insulating heat insulating material.

  The main current collecting plates 5a and 5b and the auxiliary current collecting plates 9a and 9b of the fuel cell unit 100 are connected to changeover switches 10a and 10b, respectively, which are electric switching means. By switching the changeover switches 10a and 10b, it is possible to select whether the electric power generated by the fuel cell unit 100 is taken out from the main current collecting plates 5a and 5b or from the auxiliary current collecting plates 9a and 9b.

  A load such as a motor is connected between the changeover switches 10a and 10b, and consumes electric power generated by the fuel cell unit 100 according to an instruction from the control unit 300. In addition, a voltmeter is provided between the changeover switches 10a and 10b, and the voltage value output from the fuel cell unit 100 can be acquired.

  Next, the operation of the fuel cell system according to the first embodiment of the present invention will be described.

  FIG. 2 is a flowchart of the operation of the startup process of the fuel cell system performed by the control unit 300.

  First, when the fuel cell system starts a startup process, the control unit 300 includes an oxidant gas supply unit and an oxidant gas discharge unit, a fuel gas supply unit and a fuel gas discharge unit, a cooling water supply unit and a cooling water discharge unit. Signals are respectively sent to supply reaction gas (hydrogen and oxygen) and cooling water to the fuel cell stack 200 (step 1001). In response to the supply of the reaction gas, the fuel cell stack 200 starts power generation.

  Next, a signal is sent to the changeover switches 10a and 10b for taking out electric power, and the changeover switches 10a and 10b are connected to the auxiliary current collecting plates 9a and 9b (step 1002). By doing so, the fuel cell unit 100 and the load are electrically connected, and the load starts to operate in the constant load mode (step 1003).

  At this time, the fuel cell stack 200 generates electric power and generates heat. Moreover, since electric power is taken out from the auxiliary current collecting plates 9a and 9b, when the current flows through the resistors 8a and 8b, the resistors generate heat, and the temperature around the end cell 7 is increased. Then, the voltage on both sides of the fuel cell stack 200 and the current flowing to the load are increased, and it is determined whether or not the voltage of the fuel cell stack 200 is stable (or whether or not the current flowing to the load is stable) ( Step 1004). If it is determined that the voltage across the fuel cell stack 200 is stable, the start-up process is determined to be successful, and the control unit 300 sends a signal to the power take-out changeover switches 10a and 10b, and the changeover switches 10a and 10b are connected to the main current collecting plate 5a. And 5b side (step 1005). By switching to the main current collecting plates 5a and 5b, no current flows through the resistors 8a and 8b, and the resistors 8a and 8b do not generate heat.

  This completes the startup process.

  In the conventional fuel cell stack 200, the end cell is in contact with a current collector plate or end plate having a high thermal conductivity, and thus heat radiation to the outside is larger than that in the intermediate cell. Slower than cell. Therefore, immediately after the fuel cell is started, the temperature of the end cell becomes lower than the temperature set in the fuel cell stack 200, and the performance of the end cell tends to be lowered (see FIG. 3).

  FIG. 4 is a graph showing the temperature change of the end cell 7 when the load is connected to the main current collector plate 5 and when the load is switched to the auxiliary current collector plate 9 and the current is passed through the resistor 8. is there. As shown in FIG. 4, when the current is passed through the resistor 8 by switching to the auxiliary current collector plate 9, the temperature of the end cell 7 shifts to the set temperature more quickly.

  According to the fuel cell system of the first embodiment of the present invention, when the fuel cell stack 200 is activated, the current collecting plate for taking out the electric power generated by the fuel cell stack 200 is switched to the auxiliary current collecting plate 9; The resistor is heated by passing a current through the resistor 8. Since the heat generated by the resistor heats the end cell 7, the temperature increase of the end cell 7 whose temperature rise is slower than that of the intermediate cell 6 is promoted, and the overall startability of the fuel cell stack 200 is improved.

  The fuel cell stack mounting box 1 is configured so that the main current collecting plate 5, the resistor 8, and the auxiliary current collecting plate 9 of the fuel cell stack 200 are covered with an electrically insulating heat insulating material. The heat radiation from the part to the atmosphere can be reduced, the heat generated by the resistor 8 is efficiently transmitted to the end cell 7, and the power generation efficiency of the fuel cell system is improved.

  During the starting process, power is taken directly from the auxiliary current collector plate 9 instead of from the resistor 8, so that the potential difference on both sides of the resistor 8 is reduced, and the in-plane distribution of the current flowing through the resistor 8 is more uniform. become. Therefore, the heat (hot spot) generated locally in the resistor can be suppressed, and the performance and durability of the stack are improved.

  Moreover, since the electrical resistance of the main current collecting plate 5 and the auxiliary current collecting plate 9 is low, the potential difference in the plate surface of the current collecting plate is small even when a current is passed. Therefore, the current passing in the thickness direction of the resistor 8 sandwiched between the main current collecting plate 5 and the auxiliary current collecting plate 9 has a more uniform distribution in the in-plane direction. Accordingly, it is possible to improve the disadvantage that the heat generated by the current passage at the start-up is concentrated only in the vicinity of the power lead-out line, the heating to the end cell 7 becomes more uniform, and the performance and durability of the stack are improved. Will be improved.

  Next, a second embodiment of the present invention will be described.

  FIG. 5 is a block diagram showing the configuration of the fuel cell system according to the second embodiment of the present invention. The second embodiment is different from the first embodiment in that temperature sensors (21a and 21b) are provided in the end cells 7 located at (at least one of) both ends of the fuel cell stack 200. In addition, the same code | symbol is attached | subjected to the structure which performs the same effect | action as 1st Embodiment, and the description is abbreviate | omitted.

  FIG. 6 is a flowchart of the operation of the starting process of the fuel cell system performed by the control unit 300 according to the second embodiment.

  Steps 2001 and 2002 are the same as the start-up process (steps 1001 and 1002 in FIG. 1) of the first embodiment, and the description thereof is omitted.

  After successfully starting the fuel cell system, the temperature of the fuel cell stack 200 rises, and the difference between the preset temperature preset in the fuel cell stack 200 and the temperature of the end cell 7 measured by the temperature sensor 21 is a predetermined value. It is determined whether or not it is less than (ΔT1) (step 2003). When the temperature difference between the set temperature and the end cell 7 is lower than ΔT1, that is, when the difference between the temperature of the end cell 7 and the set temperature is less than ΔT1, the temperature of the end cell 7 is The start-up process is judged to be successful because it is close enough to the set temperature. The control unit 300 sends a signal to the power take-out changeover switches 10a and 10b to connect the changeover switches 10a and 10b to the main current collecting plates 5a and 5b (step 2004). By switching to the main current collecting plates 5a and 5b, no current flows through the resistors 8a and 8b, and the resistors 8a and 10b do not generate heat.

  This completes the startup process.

  FIG. 7 is a graph showing a temperature change during the startup process according to the second embodiment.

  When the fuel cell system starts to start, the temperature of the fuel cell stack 200 starts to gradually increase. When the difference between the value of the temperature sensor 21 of the end cell 7 and the set temperature falls below ΔT1, it is determined that the startup process is successful. Depending on the heating rate of the resistor 8, the temperature rise of the end cell 7 may be faster or slower than the temperature rise of the intermediate cell 6, so it is necessary to select the resistor 8 having an appropriate heating rate. is there.

  FIG. 8 is a flowchart illustrating an operation during operation performed by the control unit 300 according to the second embodiment.

  After the fuel cell system is activated by the process of FIG. 6, first, it is determined whether or not the difference between the preset temperature preset in the fuel cell system and the temperature of the end cell 7 exceeds ΔT2 (step 3001). When the difference between the set temperature and the temperature of the end cell 7 exceeds ΔT2, that is, when the temperature of the end cell 7 departs from the set temperature and the difference becomes ΔT2, the process proceeds to step 3002. If not, repeat this process and wait.

  In step 3002, a signal is sent to the power take-out changeover switches 10a and 10b, and the changeover switches 10a and 10b are connected to the auxiliary current collecting plates 9a and 9b (step 3002). By doing so, current flows through the resistors 8a and 8b, and the resistors generate heat, and the temperature around the end cell 7 is increased.

  Next, it is determined whether or not the difference between the set temperature and the temperature of the end cell 7 is less than ΔT1 (step 3003). When the difference between the set temperature and the temperature of the end cell 7 is less than ΔT1, that is, when the temperature of the end cell 7 approaches the set temperature and the difference becomes ΔT1, the process proceeds to step 3004. If not, repeat this process and wait.

  In step 3004, the changeover switches 10a and 10b are connected to the main current collecting plates 5a and 5b. By switching to the main current collecting plates 5a and 5b, no current flows through the resistors 8a and 8b, and the resistors 8a and 10b do not generate heat.

  FIG. 9 is a graph showing a change in the temperature of the end cell 7 in the process of FIG.

  When the temperature of the end cell 7 is lower than the installation temperature and the difference exceeds ΔT2, the resistor 8 generates heat by switching to the auxiliary current collecting plate 9, and the temperature of the end cell 7 is increased. Thereafter, when the temperature of the end cell rises and the difference between the temperature of the end cell 7 and the set temperature falls below ΔT1, the resistor is switched by switching from the auxiliary current collecting plate 9 to the main current collecting plate 5. 8 stops heating and the temperature of the end cell 7 is not increased.

  According to the fuel cell system of the second embodiment of the present invention, the end cell detected by the temperature sensor (21a and 21b) provided in the end cell 7 located at least one of the both ends of the fuel cell stack 200. When the temperature of 7 becomes lower than the set temperature, the power extraction is switched to the auxiliary current collector plates (9a, 9b) and the resistor 8 is energized, whereby the resistor 8 generates heat and heats the end cells 7. Further, when the temperature of the end cell 7 becomes higher than the set temperature, the power extraction is switched to the main current collector plate (8a, 8b), the energization of the resistor 8 is stopped, and the heat generation of the resistor 8 is stopped. To do. Thus, when the difference between the temperature of the end cell 7 and the preset temperature of the fuel cell stack 200 is reduced when the fuel cell system is activated or during the operation after the activation, the power extraction is performed as an auxiliary collection. When switching to the electric plate 9 and the difference between the temperature of the end cell 7 and the set temperature is increased, the power extraction can be controlled to be switched to the main current collecting plate 5. In this way, not only the start-up time of the fuel cell can be shortened, but also control can be performed to ensure that the temperature of the end cell 7 is close to the set temperature during start-up and during operation.

  Next, a fuel cell system according to a third embodiment of the present invention will be described.

  The third embodiment is different from the first and second embodiments in that a temperature sensor is provided in the intermediate cell 6 in addition to the end cell 7. In addition, the same code | symbol is attached | subjected to the structure which performs the effect | action same as 1st and 2nd embodiment, and the description is abbreviate | omitted.

  FIG. 10 is a flowchart of the operation of the startup process of the fuel cell system performed by the control unit 300 according to the third embodiment.

  Step 4001 and step 4002 are the same as the start-up process (steps 1001 and 1002 in FIG. 1) of the first embodiment, and the description thereof is omitted.

  Next, it is determined whether or not the difference between the temperature of the end cell 7 and the temperature of the intermediate cell 6 is higher than ΔT3 (step 4003). When the difference between the temperature of the end cell 7 and the temperature of the intermediate cell 6 is higher than ΔT3, that is, the temperature of the end cell 7 is separated from the temperature of the intermediate cell 6 and the difference becomes ΔT3. If so, the process proceeds to step 4006. If not, the process proceeds to step 4004.

  In step 4004, it is determined whether or not the difference between the temperature of the end cell 7 and the set temperature is lower than ΔT1. When the difference between the temperature of the end cell 7 and the set temperature is lower than ΔT1, that is, when the temperature of the end cell 7 approaches the set temperature and the difference becomes ΔT1, the start process is successful. The process proceeds to step 4005. If not, the process returns to step 4003.

  In step 4005, the changeover switches 10a and 10b are connected to the main current collecting plates 5a and 5b. By switching to the main current collecting plates 5a and 5b, no current flows through the resistors 8a and 8b, and the resistors 8a and 10b do not generate heat.

  This completes the startup process.

  On the other hand, in step 4006, the changeover switches 10a and 10b are connected to the main current collecting plates 5a and 5b. By switching to the main current collecting plates 5a and 5b, no current flows through the resistors 8a and 8b, and the resistors 8a and 10b do not generate heat.

  Next, it is determined whether or not the difference between the temperature of the end cell 7 and the temperature of the intermediate cell 6 is lower than ΔT3 (step 4007). When the difference between the temperature of the end cell 7 and the temperature of the intermediate cell 6 is higher than ΔT3, that is, the temperature of the end cell 7 is separated from the temperature of the intermediate cell 6 and the difference becomes ΔT3. If so, the process proceeds to step 4002, and if not, the process proceeds to step 4008.

  In step 4008, it is determined whether or not the difference between the temperature of the end cell 7 and the set temperature is lower than ΔT1. When the difference between the temperature of the end cell 7 and the set temperature is lower than ΔT1, that is, when the temperature of the end cell 7 approaches the set temperature and the difference becomes ΔT1, the start process is successful. Judgment is completed and the startup process is completed. If not, the process returns to step 4007.

  FIG. 11 is a graph showing temperature changes during the startup process of FIG.

  The fuel cell system is activated and the temperature of the fuel cell stack 200 rises. At this time, when the temperature of the end cell 7 becomes higher than the temperature of the intermediate cell 6 due to the heat of the resistor 8, and the difference between the temperature of the end cell 7 and the temperature of the intermediate cell 6 exceeds ΔT3. Then, the changeover switch 10 is switched to take out power from the main current collecting plate 5 and no current flows through the resistor 8. By doing so, the resistor does not emit heat, and the temperature rise of the end cell 7 is delayed. When the temperature of the end cell 7 is lower than the temperature of the intermediate cell 6 and the difference between the temperature of the end cell 7 and the temperature of the intermediate cell 6 exceeds ΔT3, the changeover switch 10 is switched. Electric power is taken out from the auxiliary current collector plate 9 and a current is passed through the resistor 8. By doing so, the resistor 8 generates heat, and the temperature rise of the end cell 7 is accelerated.

  By repeating this, the fuel cell stack 200 is controlled in a range where the difference between the temperature of the end cell 7 and the temperature of the intermediate cell 6 does not exceed ΔT3. When the difference between the temperature of the end cell 7 and the set temperature finally falls below ΔT1, it is determined that the startup process has been successful.

  In the fuel cell system of the third embodiment, the end cell 7 and the intermediate cell 6 are provided with temperature sensors, and the main current collector plate 5 or the auxiliary current collector plate 9 is switched depending on the comparison result of the respective temperatures. Since it is determined whether or not the resistor 8 generates heat, the temperature difference between the end cell 7 and the intermediate cell 6 can be reduced.

  In particular, as shown in FIG. 8, depending on the heating rate of the resistor 8, the temperature rise rate of the end cell 7 may be faster or slower than the temperature rise rate of the intermediate cell 6. If the temperature difference between the cells occurring at startup is too large, the degree of expansion of the components that make up the cells will change, and in the worst case, it will adversely affect the reliability and durability of the fuel cell, such as gas leakage and component damage. There is a risk of bringing. According to the control method of the third embodiment, it is possible to suppress a temperature difference between cells generated at the time of activation, and to improve the reliability and durability of the fuel cell.

  In particular, when the fuel cell system is started up, the extraction of electric power is switched to the auxiliary current collector plate 9, and when the temperature indicated by the temperature sensor 21 becomes too higher than the temperature sensor 21, the electric power is extracted to the main current collector plate 5. Switch. When the temperatures indicated by the two sensors approach, the power extraction is switched to the auxiliary current collector plate 9 again. This process is repeated until the fuel cell stack 200 is completely activated. By doing so, it is possible to suppress an extreme overshoot that may occur in the process of increasing the temperature of the end cell 7 at the time of startup, and to improve the durability and reliability of the fuel cell.

  Next, a fuel cell system according to a fourth embodiment of the present invention will be described.

  In the fourth embodiment, a plurality of resistors (8b, 31, 32) and a plurality of auxiliary current collector plates (9b, 32, 34) for taking out electric power while passing a current through each resistor are arranged. Yes. In addition, the same code | symbol is attached | subjected to the structure which performs the effect | action same as 1st thru | or 3rd Embodiment, and the description is abbreviate | omitted.

  FIG. 12 is a block diagram showing the configuration of the fuel cell system according to the fourth embodiment of the present invention.

  The changeover switch 10c is connected to the main current collector plate 5b and each auxiliary current collector plate (9b, 32, 34). By switching the changeover switch 10c, (1) no current flows through the resistor, (2 It is possible to select any one of (1) flowing current only through the resistor 9b, (3) flowing current through the resistors 9b and 32, and (4) flowing current through all the resistors 9b, 32, and 34.

  According to the fourth embodiment of the present invention, the amount of heat generated from the resistor is proportional to the resistance value. Therefore, when starting the fuel cell system, the number of resistors to be energized according to the level of the outside air temperature. Therefore, the starting speed of the fuel cell stack 200 can be adjusted. In particular, when the outside air temperature is low, a larger amount of heat generation can be obtained by energizing more resistors, and the fuel cell stack 200 can be started more quickly.

  Next, a fuel cell system according to a fifth embodiment of the present invention will be described.

  In the fifth embodiment, the heat generated by the resistor is used to suppress the occurrence of flooding. In addition, the same code | symbol is attached | subjected to the structure which performs the same effect | action as 1st thru | or 4th Embodiment, and the description is abbreviate | omitted.

  FIG. 13 is an explanatory diagram showing details of an end portion of the fuel cell stack 200 in the fuel cell system according to the fifth embodiment.

  An oxidant gas flow path 36 is formed in the separator 37 which is the end face of the end cell 7 of the fuel cell stack, and as shown in the figure, the oxidant gas flows in the direction of the chain line arrow. The end plate 43 is provided with an oxidant gas discharge port (not shown). The resistors (39, 40) are provided separately, and one resistor 40 is provided on the outlet side of the oxidant gas flow path. The auxiliary current collecting plates (41, 42) are divided in the same manner as the resistor, and one auxiliary current collecting plate 42 is provided on the oxidant gas discharge port side. The resistors 39 and 40 and the auxiliary current collectors 41 and 42 are electrically insulated by insulating means, respectively. For example, the insulators are separated during the division of the resistors 39 and 40 and the auxiliary current collectors 41 and 42. Is arranged.

  The end self-learning detection means 400 is installed in the end cell 7, and is constituted by, for example, a pressure loss detection sensor of the oxidant gas flow path, a voltage sensor of the end cell 7, etc., and the operating conditions are constant. If the pressure loss or cell voltage fluctuation increases, flooding is determined and the information is sent to the control unit 300. Further, the fuel cell system operation state detection means 500 detects the state of the fuel cell system, for example, whether the system is starting up or in steady operation, and sends the information to the control unit 300.

  The changeover switch S1 can select whether or not to extract power from the main current collector plate 38 by turning the switch ON / OFF. The changeover switch S2 can select whether or not power is taken out from the auxiliary current collecting plate 42 by turning the switch ON / OFF. The changeover switch S3 can select whether or not power is taken out from the auxiliary current collecting plate 41 by ON / OFF of the switch. That is, when the changeover switch S2 is turned on, electric power is taken out from the auxiliary current collecting plate 42, and current flows through the resistor 40, so that the resistor 40 generates heat. Similarly, when the changeover switch S3 is turned on, electric power is taken out from the auxiliary current collecting plate 41, and current flows through the resistor 39, so that the resistor 40 generates heat.

  FIG. 14 is a table showing the state of each changeover switch when the fuel cell system is started, during normal operation, and when flooding occurs.

  When starting the fuel cell system, as in the first to fourth embodiments described above, when the end cell temperature is low, the changeover switch S1 is opened and the changeover switches S2 and S3 are closed. Then, the end cell is heated by taking out the electric power from the auxiliary current collecting plates 41 and 42 and causing the current to flow through the resistors 39 and 40. After the system startup process is completed, during normal operation, the changeover switch S1 is closed, the changeover switches S2 and S3 are opened, and electric power is taken out from the main current collector plate 38.

  Further, when the end self-learning detection means determines that flooding has occurred in the oxidant gas flow path 36 of the end cell, the control unit 300 opens the change-over switches S1 and S3, and switches them. Only switch S2 is closed. In this case, since electric power is taken out from the auxiliary current collecting plate 42, heat is generated from the resistor 40 by passing a current through the resistor 40. This heat can evaporate liquid water accumulated in the flow path and the gas diffusion layer, thereby suppressing flooding.

In the fifth embodiment of the present invention, when the end self-learning detection means determines that flooding has occurred in the oxidant gas flow path 36 of the end cell, only the changeover switch S2 is closed. Since the heat generated in the resistor 40 heats the place where flooding is likely to occur, that is, the downstream side of the oxidant gas flow path, the heat generated by the resistor is transferred to the oxidant gas flow path and the gas diffusion layer. It can be used effectively to evaporate the accumulated liquid water, and the generation of flooding can be suppressed with less energy loss. Also, by dividing the resistor and the auxiliary current collector, the flow path Since only the resistor that needs to evaporate the liquid water accumulated in the gas diffusion layer can generate heat, only the appropriate part can generate heat with less energy loss. It is possible to suppress the occurrence of flooding in a place where flooding is more likely to occur.

  Next, a fuel cell system according to a sixth embodiment of the present invention will be described.

  The sixth embodiment differs from the first to fifth fuel cell systems in the configuration of the current collector plate and the resistor. In addition, the same code | symbol is attached | subjected to the structure which performs the effect | action same as 1st thru | or 5th Embodiment, and the description is abbreviate | omitted.

  FIG. 15 is an explanatory diagram showing a detailed configuration of the main current collector plate, the resistor, and the auxiliary current collector plate of the fuel system according to the sixth embodiment. 15A is a side view, FIG. 15B is an enlarged view around the resistor 53, and FIG. 15C is a cross-sectional view taken along line AA in FIG. 15A.

  An insulator 55 is provided on the surface of the main current collector 52 adjacent to the end cell 51, and the main current collector 52 is in contact with the auxiliary current collector 54 via the insulator 55. The main current collecting plate 52 is provided with a plurality of concave holes, which are parts for fitting the resistor 53, and the resistor 53 is fitted into the concave hole so as to be electrically conductive. Is done. The resistor 53 is also in contact with the auxiliary current collector 54 so as to be electrically conductive.

  In the sixth embodiment of the present invention, the end of the fuel cell stack 200 is not a three-layer structure as in the configuration example (FIG. 1) of the first embodiment, and the resistor 53 is the main current collector plate. 52, the main current collecting plate 52 and the auxiliary current collecting plate 54 have a two-layer structure. Therefore, the volume of the fuel cell stack 200 can be reduced, and the output density of the fuel cell stack 200 can be improved. .

  In the embodiment of the present invention described above, the control performed by calculating the difference between the set value and the current value is exemplified, but this is controlled by another method (for example, the PID method). However, the essence of the present invention does not change.

It is a block diagram which shows the structure of the fuel cell system of the 1st Embodiment of this invention. It is a flowchart of operation | movement of the starting process of the fuel cell system of the 1st Embodiment of this invention. It is a graph which shows the temperature change at the time of starting of the conventional fuel cell system. It is a graph which shows the temperature change of the edge part cell 7 of the 1st Embodiment of this invention. It is a block diagram which shows the structure of the fuel cell system of the 2nd Embodiment of this invention. It is a flowchart of operation | movement of the starting process of the fuel cell system of the 2nd Embodiment of this invention. It is a graph which shows the temperature change at the time of the starting process of the 2nd Embodiment of this invention. It is a flowchart which shows the operation | movement in driving | operation of the fuel cell system of the 2nd Embodiment of this invention. It is a graph which shows the temperature change during driving | operation of the 2nd Embodiment of this invention. It is a flowchart of operation | movement of the starting process of the fuel cell system of the 3rd Embodiment of this invention. It is a graph which shows the change of the temperature at the time of a starting process of the 3rd Embodiment of this invention. It is a block diagram which shows the structure of the fuel cell system of the 4th Embodiment of this invention. It is explanatory drawing which shows the detail of the fuel cell stack 200 edge part of the 5th Embodiment of this invention. It is a table | surface which shows the state of each changeover switch of the 5th Embodiment of this invention. It is explanatory drawing which shows the detailed structure of the main collector plate, a resistor, and an auxiliary collector plate of the fuel system of the 6th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mounting box 2 Fastening part 3 End plate 4 Insulation plate 5a, 5b Main current collection plate 6 Intermediate part cell 7 End part cell 8a, 8b, 31, 33 Resistor 9a, 9b, 32, 34 Auxiliary current collection plate 10a, 10b 10c changeover switch 21a, 21b Temperature sensor 36 Oxidant flow path 37 Separator 38 Main current collector plate 39, 40 Resistor 41, 42 Auxiliary current collector plate 43 End plate S1, S2, S3 Changeover switch 51 End cell 52 Main collector Electrical plate 53 Resistor 54 Auxiliary current collector 55 Insulator 100 Fuel cell unit 200 Fuel cell stack 300 Control unit 400 End self-learning detection means 500 Fuel cell system operation state detection means

Claims (10)

A laminated structure in which a plurality of fuel cells that generate power by receiving supply of fuel gas and oxidant gas are arranged in parallel; and
End plates respectively disposed at both ends in the stacking direction of the stacked structure;
A main current collector plate disposed between the end plate and the laminated structure, and for extracting power generated by the laminated structure;
In a fuel cell system having a fuel cell stack constituted by:
A resistor disposed between the main current collector plate and the end plate at at least one of the both ends in the stacking direction of the stacked structure,
An auxiliary current collector disposed between the resistor and the end plate;
A fuel cell system comprising switching means for switching extraction of electric power generated by the laminated structure between the main current collecting plate and the auxiliary current collecting plate at the one end. The one end has a plurality of resistors and an auxiliary current collector,
2. The fuel cell according to claim 1, wherein the switching unit switches the extraction of electric power generated by the fuel cell stack from any one of the main current collecting plate and the plurality of auxiliary current collecting plates. system. The laminated structure has a temperature sensor,
The fuel cell system according to claim 1, wherein the switching unit is switched in accordance with an output of the temperature sensor. The resistor and the auxiliary current collector have a divided structure, and insulating means for insulating between the one divided resistor and the auxiliary current collector and the other divided resistor and auxiliary current collector is disposed. And
The switching means is capable of switching between taking out the electric power generated by the fuel cell stack from the main current collecting plate or one of the divided auxiliary current collecting plates. The fuel cell system according to claim 1.   5. The fuel cell system according to claim 4, wherein at least one of the divided resistor and the auxiliary current collector plate is disposed in the vicinity of the flow path of the oxidant gas.   5. The fuel cell system according to claim 4, wherein at least one of the divided resistor and the auxiliary current collecting plate is disposed in the vicinity of the downstream side of the flow path of the oxidant gas. The resistor is fitted into a fitting portion provided on the surface of the main current collector plate,
On the surface of the main current collector plate, an insulating portion that insulates between the surface of the main current collector plate and the surface of the auxiliary current collector plate is disposed except for a portion where the resistor is in contact with the auxiliary current collector plate. The fuel cell system according to claim 1, wherein   The fuel cell system according to claim 1, wherein the main current collecting plate, the resistor, and the auxiliary current collecting plate are covered with an electrically insulating heat insulating material.   2. The fuel cell system according to claim 1, wherein the switching unit extracts electric power from the auxiliary current collecting plate when the stacked structure is started. 3.   4. The fuel cell system according to claim 3, wherein the switching unit extracts electric power from the auxiliary current collecting plate when a detection value of the temperature sensor is lower than a predetermined value. 5.

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