JP2007027149A - Control device of fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve drainage efficiency of water retained in a fuel cell. <P>SOLUTION: When a fuel cell stack is made to generate electricity by a control unit (step S1), a cell voltage of the fuel cell stack is monitored by a cell voltage sensor (step S2), and when the cell voltage is judged to be lower than a predetermined value (step S3), a hydrogen gas supply regulator is controlled so as to raise fuel gas pressure (step S4), and then, a purge opening and closing valve is controlled to switch from a closed state to an open state (step S5). With this, a dynamic pressure of hydrogen gas pressure is generated to make an anode electrode side drain. Then, when the cell voltage of the fuel cell stack is judged to be higher than the predetermined value (step S6), the purge opening and closing valve 6 is controlled to switch from an open state to a closed state (step S7). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is used, for example, as a drive source for automobiles and the like, and is a fuel cell system having a purge valve for generating power by supplying hydrogen gas as fuel gas and air as oxidant gas and performing a purge operation in the hydrogen circulation path The present invention relates to a control device for a fuel cell system that controls the fuel.

  As a conventional fuel cell system, for example, one disclosed in Japanese Patent Application Laid-Open No. 7-235324 is known. When this fuel cell system detects that water has accumulated in the fuel cell stack by operating the fuel cell stack, the cathode side gas flow rate of the fuel cell stack is increased, and the accumulated water is generated by the dynamic pressure of oxygen gas. It was working to blow away.

  By the way, in the conventional fuel cell system, when adjusting the fuel gas pressure supplied from the fuel gas tank to the fuel cell stack, the fuel gas pressure is adjusted while supplying the fuel gas to the fuel cell stack. is not. On the other hand, conventionally, a fuel cell system having a fuel gas circulation channel for circulating the remaining fuel gas discharged from the fuel gas outlet of the fuel cell stack to the fuel gas inlet of the fuel cell stack has been proposed.

  In such a fuel cell system, it is conceivable that the technology for discharging the accumulated water in the fuel cell stack is also applied to the anode electrode side to improve the discharge efficiency of the accumulated water. However, if there is no circulation pump in the fuel gas circulation flow path, the fuel gas supply amount cannot be increased even if the fuel gas pressure is increased unless the fuel gas consumption of the fuel cell stack changes. is there. That is, with the fuel gas pressure kept constant in accordance with the operating conditions of the fuel cell stack, it is impossible to make the fuel gas supply amount more than the amount of fuel gas consumed in the fuel cell stack. When water clogging occurs, the fuel gas flow rate cannot be increased easily.

  On the other hand, when the occurrence of water clogging is detected, the purge valve is opened, and the fuel gas supply flow rate is the sum of the fuel gas amount consumed by the fuel cell stack and the exhaust gas amount from the purge valve. Thereby, in the fuel cell system, the amount of exhaust gas from the purge valve can be increased to supply the fuel gas to the fuel cell stack, and the fuel gas supply flow rate on the anode electrode side has been increased. However, the fuel consumption is reduced by releasing the fuel gas to the outside.

  In addition, as a method for removing the accumulated water in the fuel cell stack, there is a method for reducing the power output of the fuel cell stack by reducing the fuel gas pressure to recover the cell voltage. There is a problem that an unobtainable period occurs. This problem is particularly important in a fuel cell system not equipped with a secondary battery.

  Therefore, the present invention has been proposed in view of the above-described circumstances, and provides a control device for a fuel cell system that can improve the drainage efficiency of water accumulated in the fuel cell.

  According to a first aspect of the present invention, there is provided a control device for a fuel cell system in which a plurality of cell structures each having an electrolyte membrane sandwiched between an oxidant electrode and a fuel electrode are stacked, and an oxidant gas is supplied to the oxidant electrode side. And a fuel cell for generating power by supplying fuel gas to the fuel electrode side, a gas supply means for supplying oxidant gas and fuel gas to the fuel cell, and a fuel gas outlet and a fuel gas inlet of the fuel cell. The fuel cell system includes a fuel circulation path to be inserted and a purge valve provided in the fuel circulation path and releasing a part of the gas in the fuel circulation path to the outside.

  When it is determined that the cell voltage of the fuel cell is smaller than a predetermined value, the control device of the fuel cell system controls the gas supply means so as to increase the fuel gas pressure and then closes the purge valve. When the control is performed to open the fuel cell, and the cell voltage of the fuel cell is determined to be larger than a predetermined value, the purge valve is controlled to be closed from the open state.

  According to a second aspect of the present invention, there is provided a control device for a fuel cell system in which a plurality of cell structures each having an electrolyte membrane sandwiched between an oxidant electrode and a fuel electrode are stacked, and an oxidant gas is supplied to the oxidant electrode side. And a fuel cell for generating power by supplying fuel gas to the fuel electrode side, a gas supply means for supplying oxidant gas and fuel gas to the fuel cell, and a fuel gas outlet and a fuel gas inlet of the fuel cell. The fuel cell system includes a fuel circulation path to be inserted and a purge valve provided in the fuel circulation path and releasing a part of the gas in the fuel circulation path to the outside.

  The control device of the fuel cell system periodically opens and closes the purge valve when it is determined that the cell voltage of the fuel cell is smaller than a predetermined value, and the cell voltage of the fuel cell is larger than a predetermined value. If it is determined that the purge valve is closed, control is performed to close the purge valve.

  According to a third aspect of the present invention, there is provided a control device for a fuel cell system, wherein a plurality of cell structures each having an electrolyte membrane sandwiched between an oxidant electrode and a fuel electrode are stacked, and an oxidant gas is supplied to the oxidant electrode side. And a fuel cell for generating power by supplying fuel gas to the fuel electrode side, a gas supply means for supplying oxidant gas and fuel gas to the fuel cell, and a fuel gas outlet and a fuel gas inlet of the fuel cell. The fuel cell system includes a fuel circulation path to be inserted and a purge valve provided in the fuel circulation path and releasing a part of the gas in the fuel circulation path to the outside.

  The control device of the fuel cell system periodically controls the purge valve after controlling the gas supply means to increase the fuel gas pressure when it is determined that the cell voltage of the fuel cell is smaller than a predetermined value. Open / close control is performed, and when the cell voltage of the fuel cell is determined to be larger than a predetermined value, the purge valve is controlled to be closed.

  The fuel cell system control device according to claim 4 is the fuel cell system control device according to any one of claims 1 to 3, wherein the cell voltage of the fuel cell is determined to be smaller than a predetermined value. When at least one purge valve is controlled to open, and when it is determined that the cell voltage of the fuel cell is lower than a predetermined value after a predetermined period has elapsed since the one purge valve was opened. Control is performed to open the other purge valve, and control is performed to close the purge valve that is opened when it is determined that the cell voltage of the fuel cell is greater than a predetermined value.

  The fuel cell system control device according to claim 5 is the fuel cell system control device according to claim 1 or 3, wherein the cell voltage of the fuel cell is determined to be smaller than a predetermined value. The gas supply means is controlled to increase the fuel gas pressure stepwise.

  The fuel cell system control device according to claim 6 is the fuel cell system control device according to claim 1, 3 or 5, wherein the cell voltage of the fuel cell is smaller than a predetermined value. When the determination is made, the fuel gas pressure is increased, and the gas supply means is controlled to maintain the oxidant gas flow rate at the oxidant electrode.

  According to the control device of the fuel cell system according to claim 1, when the cell voltage of the fuel cell is smaller than the predetermined value, the purge valve is closed from the closed state after controlling the gas supply means to increase the fuel gas pressure. Since the control for opening is performed, the dynamic pressure of the fuel gas pressure immediately after the purge valve is opened can be increased. Therefore, according to the control device for this fuel cell system, the period for opening the purge valve can be shortened, the amount of fuel gas discharged by opening the purge valve can be reduced, and drainage efficiency can be reduced. Can be improved.

  According to the control device for a fuel cell system according to claim 2, when the cell voltage of the fuel cell is smaller than a predetermined value, the purge valve is periodically controlled to open and close, so that the number of fluctuations in the fuel gas pressure is increased. Can do. Therefore, according to the control device of this fuel cell system, the number of times of dynamic pressure generation of the fuel gas pressure can be increased, and the drainage efficiency can be further improved.

  According to the control device for a fuel cell system according to claim 3, when the cell voltage of the fuel cell is smaller than a predetermined value, the purge valve is periodically operated after controlling the gas supply means so as to increase the fuel gas pressure. Since the opening / closing control is performed, the synergistic effect of the increase in the dynamic pressure by increasing the fuel gas pressure and the increase in the number of occurrences of the dynamic pressure by periodically controlling the opening / closing of the purge valve can be exhibited. Even if the total amount of hydrogen gas discharged is small, it can be drained efficiently.

  According to the control device for a fuel cell system according to claim 4, when the cell voltage of the fuel cell is smaller than a predetermined value, at least one purge valve is controlled to be opened, and one purge valve is opened. If the cell voltage of the fuel cell is determined to be lower than the predetermined value after a predetermined period has elapsed, the other purge valve is controlled to open, so the total gas discharge flow rate in the fuel circulation channel is further increased. The dynamic pressure can be further increased.

  According to the control device for a fuel cell system according to claim 5, since the fuel gas pressure is increased stepwise when the cell voltage of the fuel cell is smaller than a predetermined value, the dynamic pressure can be further increased. Efficiency can be further improved.

  According to the control device for a fuel cell system according to claim 6, when the cell voltage of the fuel cell is smaller than a predetermined value, the fuel gas pressure is increased and the oxidant gas flow rate at the oxidant electrode is maintained. Even when the gas pressure is increased and the oxidant gas pressure is increased to reduce the oxidant gas flow rate, the oxidant gas flow rate can be prevented from decreasing and the drainage efficiency can be prevented from decreasing. Can be maintained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  The present invention is applied to, for example, the fuel cell system according to the first embodiment configured as shown in FIG. 1 and the fuel cell system according to the second embodiment configured as shown in FIG.

[Configuration of Fuel Cell System According to First Embodiment]
The fuel cell stack 1 provided in the fuel cell system according to the first embodiment includes a cell structure configured by sandwiching a solid polymer electrolyte membrane between an oxidant electrode (cathode electrode) and a fuel electrode (anode electrode). It has a stack structure in which a plurality of layers are stacked via separators. In addition, the fuel cell stack 1 is provided with an oxidant gas passage for allowing the oxidant gas to pass therethrough, a fuel gas passage for allowing the fuel gas to pass, and a cooling water passage for allowing the coolant to pass. The fuel cell stack 1 is supplied with air as an oxidant gas on the oxidant electrode side and with hydrogen gas as a fuel gas on the fuel electrode side. As a result, the fuel cell stack 1 generates electricity by moving and contacting each ion in the membrane using moisture as a medium.

  In this fuel cell system, a hydrogen tank 2 storing hydrogen, a hydrogen gas supply pressure regulating valve 3, a hydrogen circulation device 4 and a humidifier 5 are inserted through a hydrogen gas supply flow path L1, and a hydrogen gas inlet of the fuel cell stack 1 is inserted. 1a, a hydrogen gas system in which a hydrogen gas outlet 1b, a hydrogen gas inlet 1a, and a purge opening / closing valve 6 of the fuel cell stack 1 are inserted through a hydrogen gas circulation passage L2.

  The hydrogen gas supply pressure regulating valve 3 and the purge opening / closing valve 6 are connected to an actuator (not shown), and the opening / closing operation and the opening degree are controlled by driving the actuator according to a control signal from the control unit 17. The purge on / off valve 6 is controlled to open and close in accordance with a control signal from the control unit 17 and is opened to discharge the hydrogen gas in the fuel gas circulation passage L2 and in the fuel cell stack 1 to the outside.

  In this fuel cell system, when the fuel cell stack 1 is operated, the hydrogen stored in the hydrogen tank 2 in a high-pressure state is regulated by the control unit 17 by the hydrogen gas supply pressure regulating valve 3 and is supplied via the hydrogen gas supply flow path L1. The hydrogen circulator 4 is supplied. Thereby, the hydrogen gas pressure on the anode electrode side of the fuel cell stack 1 is adjusted. The hydrogen circulation device 4 supplies the humidifier 5 with the hydrogen gas supplied from the hydrogen gas supply pressure regulating valve 3 and the hydrogen gas supplied through the hydrogen gas circulation flow path L2. The humidifier 5 has a semipermeable membrane inside, and adjoins pure water and hydrogen gas through the semipermeable membrane, thereby allowing water molecules to pass through the semipermeable membrane to humidify the hydrogen gas. To the fuel cell stack 1.

  In this fuel cell system, the compressor 7 is inserted into the air supply flow path L3 and connected to the air inlet 1c of the fuel cell stack 1, and the air outlet 1d and the air pressure regulating valve 8 of the fuel cell stack 1 are connected to the air discharge flow path L4. An oxidant gas system inserted through the oxidant gas system is provided. The compressor 7 is driven with its rotation speed controlled in accordance with a control signal from the control unit 17, and adjusts and supplies the air flow rate to the fuel cell stack 1. The air pressure regulating valve 8 operates in accordance with a control signal from the control unit 17 and its opening degree is adjusted.

  In this fuel cell system, when the fuel cell stack 1 is operated, the compressor 7 is driven by the control unit 17 to supply air to the humidifier 5. In the humidifier 5, air is humidified in the same manner as hydrogen gas and supplied to the fuel cell stack 1. At this time, in the fuel cell system, the air pressure in the fuel cell stack 1, the air supply flow path L3, and the air discharge flow path L4 is adjusted by adjusting the opening of the air pressure regulating valve 8 by the control unit 17. .

  Furthermore, this fuel cell system has a water circulation system in which a water tank 9, a water pump 10, a radiator 11, a fuel cell stack 1, and a humidifier 5 are inserted through a water circulation channel L5. Further, the water circulation system in this fuel cell system includes a radiator fan 12 that cools water passing through the radiator 11.

  In such a fuel cell system, the water in the water tank 9 is supplied to the radiator 11 by the water pump 10 and the driving amount of the radiator fan 12 is controlled to control the water temperature and supply it to the fuel cell stack 1. As a result, the fuel cell stack 1 is cooled to adjust the temperature. And the water which cooled the fuel cell stack 1 is supplied to the humidifier 5, and a part is used for humidification in the humidifier 5, and it accumulate | stores in the water tank 9 again.

  Furthermore, this fuel cell system includes a hydrogen gas pressure sensor 13 for detecting the hydrogen gas pressure in the hydrogen gas supply channel L1 between the humidifier 5 and the fuel cell stack 1, the humidifier 5 and the fuel cell stack 1. The air pressure sensor 14 for detecting the air pressure of the air supply flow path L3 between the air flow sensor 15 and the air flow rate sensor 15 for detecting the air flow rate taken into the compressor 7 are provided. These hydrogen gas pressure sensor 13, air pressure sensor 14, and air flow rate sensor 15 are arranged as shown in FIG. 1 to detect the hydrogen gas pressure, air pressure, and air flow rate in fuel cell stack 1. . Furthermore, the fuel cell system includes a cell voltage sensor 16 that detects a cell voltage of each cell constituting the fuel cell stack 1. These sensors output the detected value to the control unit 17 as a sensor signal.

  The control unit 17 controls each part configured as described above. When an instruction to start driving the fuel cell stack 1 is input from the outside, the control unit 17 controls the hydrogen gas supply pressure regulating valve 3 so as to supply the hydrogen gas to the fuel cell stack 1 and also controls the fuel cell stack 1 The compressor 7 and the air pressure regulating valve 8 are controlled so as to supply air. Further, the control unit 17 outputs control signals to the water pump 10 and the radiator fan 12 to circulate water in the fuel cell stack 1 and the humidifier 5. Thereby, the control unit 17 starts the power generation of the fuel cell stack 1.

  Further, the control unit 17 recognizes the amount of power generated by the fuel cell stack 1 according to a signal indicating the accelerator opening from the outside, and recognizes necessary operating conditions such as hydrogen gas pressure and air pressure. Then, the control unit 17 controls the hydrogen gas supply pressure regulating valve 3 so as to adjust the hydrogen gas pressure so as to realize the operating condition, and controls the compressor 7 and the air pressure regulating valve 8 so as to adjust the air pressure. The water pump 10 and the radiator fan 12 are controlled so as to adjust the temperature of the fuel cell stack 1. Here, the control unit 17 refers to sensor signals from the hydrogen gas pressure sensor 13, the air pressure sensor 14, and the air flow rate sensor 15 so that the hydrogen gas pressure and the air pressure are set to substantially the same pressure value.

  Further, when the fuel cell stack 1 is in operation, the control unit 17 inputs a sensor signal from the cell voltage sensor 16, monitors the cell voltage of the fuel cell stack 1, and controls the anode electrode and the fuel cell stack 1. Detects cell voltage drop due to cathode clogging.

  Specifically, the control unit 17 compares the detected cell voltage with a preset allowable lower limit value. The control unit 17 determines whether or not the detected cell voltage is equal to or lower than the allowable lower limit value. When the detected cell voltage is smaller than the allowable lower limit value, each cell due to water staying in the fuel cell stack 1 is determined. Therefore, it is determined that water discharge is necessary, and water discharge processing is performed to control the operation of the purge on-off valve 6.

  Here, when hydrogen gas is supplied to the fuel cell stack 1, the purge on-off valve 6 is operated from the closed state to the open state, or from the open state to the closed state, as shown in FIG. A dynamic pressure at which the hydrogen gas pressure (hydrogen gas pressure in the fuel cell stack 1) detected by the gas pressure sensor 13 changes is generated. This dynamic pressure is generated by changing the hydrogen gas flow rate in the hydrogen gas supply flow path L1 and the anode electrode of the fuel cell stack 1 by opening and closing the purge on-off valve 6.

  That is, as shown in FIG. 2B, when the purge on-off valve 6 is changed from the closed state to the open state at time t1, the hydrogen gas flow velocity in the hydrogen gas supply flow path L1 temporarily rises, As shown in 2 (a), the hydrogen gas pressure temporarily decreases. Then, when the purge on-off valve 6 is opened during time t1 to time t2 (purge period), the hydrogen gas flow rate gradually decreases, so that the hydrogen gas pressure gradually returns to the original pressure value. Further, when the purge on-off valve 6 is changed from the open state to the closed state at time t2, the hydrogen gas flow velocity in the hydrogen gas supply flow path L1 is temporarily reduced, and the hydrogen gas pressure is temporarily increased.

  The control unit 17 performs a water discharge process using the dynamic pressure of the hydrogen gas pressure according to the operation of the purge on-off valve 6. The detailed processing contents of the control unit 17 when performing this water discharge processing will be described later.

  Further, the control unit 17 sets the hydrogen gas pressure according to the operating conditions of the fuel cell stack 1, the cell voltage reduction margin, etc. before controlling the open / close state of the purge open / close valve 6 when performing the water discharge process. The hydrogen gas supply pressure regulating valve 3 is controlled so as to increase to the predetermined pressure value.

[Operation of Fuel Cell System According to First Embodiment]
Next, the operation of the fuel cell system according to the first embodiment will be described with reference to the flowchart of FIG.

  According to this flowchart, first, in the state where the control unit 17 inputs a signal indicating the amount of power generated to generate the fuel cell stack 1 and the hydrogen gas pressure is adjusted under target operating conditions, for example, The water discharge process after step S1 is performed for every period. In this state, the purge on-off valve 6 is closed.

  First, in step S1, the current hydrogen gas supply pressure is detected by the control unit 17 from the sensor signal from the hydrogen gas pressure sensor 13, and the process proceeds to step S2 with the hydrogen gas pressure set as the reference hydrogen gas pressure.

  In step S2, the control unit 17 detects the cell voltage at the reference hydrogen gas pressure in step S1 based on the sensor signal from the cell voltage sensor 16, and proceeds to step S3.

  In step S3, the control unit 17 determines whether or not the cell voltage detected in step S2 is smaller than the allowable lower limit value. The allowable lower limit value is set in advance as a voltage value when the fuel cell stack 1 is clogged with water and the cell voltage decreases. The allowable lower limit value may be varied according to the generated power required for the fuel cell stack 1.

  When the control unit 17 determines that the cell voltage is smaller than the allowable lower limit value, it is determined that water clogging has occurred at the anode electrode, and the process proceeds to step S4. Then, it is determined that the cell voltage drop due to water clogging has not occurred, and the process returns to step S1.

  In step S4, the hydrogen gas supply pressure regulating valve 3 is controlled by the control unit 17 so as to increase the hydrogen gas pressure to a predetermined pressure value. That is, the pressure sum of the hydrogen gas pressure supplied to the fuel cell stack 1 by the control unit 17 in step S1 and the purge correction pressure corresponding to the pressure to be increased to increase the pressure to a predetermined pressure value, To control. Here, the predetermined pressure value is set according to the operating conditions of the fuel cell stack 1, the cell voltage reduction margin according to the cell voltage detected in step S2, and the like.

  When it is detected from the sensor signal from the hydrogen gas pressure sensor 13 that the hydrogen gas pressure has reached a predetermined pressure value by the operation of step S4, the process proceeds to step S5, and the control valve 17 closes the purge on-off valve 6. The control is advanced to the open state, and the process proceeds to step S6.

  In step S6, the control unit 17 detects the cell voltage after the purge on-off valve 6 is opened, and determines whether or not the cell voltage is smaller than the allowable lower limit value, thereby eliminating the water clogging. Determine whether or not. When the control unit 17 determines that the cell voltage is smaller than the allowable lower limit value and the clogging is not eliminated, the process proceeds to step S8. On the other hand, when it is determined that the cell voltage is larger than the allowable lower limit value and the water clogging has been eliminated, the process proceeds to step S7, the purge on-off valve 6 is closed, and the process returns to step S1.

  In step S8, the control unit 17 compares the purge valve opening time, which is an elapsed time from the time when the purge opening / closing valve 6 is opened in step S5, with the set time, and the purge valve opening time is shorter than the set time. Determine whether it is long or not. This set time is a time set in order to suppress a decrease in the function of the fuel cell stack 1 due to water clogging.

  When it is determined by the control unit 17 that the purge valve opening time is longer than the set time, the process proceeds to step S9 to stop the power generation of the fuel cell stack 1 in order to suppress the deterioration of the function of the fuel cell stack 1. The hydrogen gas supply pressure regulating valve 3 is closed and the operation of the compressor 7 is stopped. On the other hand, when it is determined that the purge valve opening time is not longer than the set time, the process returns to step S6.

  FIG. 4 shows changes in the cell voltage, the hydrogen gas supply flow rate, the hydrogen gas pressure, and the opening / closing state of the purge opening / closing valve 6 due to the fuel cell system performing such an operation.

  When the control unit 17 detects that the cell voltage has dropped and the cell voltage has become lower than the allowable lower limit at time A (FIG. 4 (a), step S3), hydrogen gas is supplied so as to obtain a predetermined pressure value. The pressure regulating valve 3 is controlled.

  When the hydrogen gas pressure is increased to a predetermined pressure value at time B (FIG. 4 (c), step S4), the purge opening / closing valve 6 is opened (FIG. 4 (d), step S5). At this time, since the hydrogen gas pressure is increased above the reference hydrogen gas pressure in step S1, a dynamic pressure is generated in which the hydrogen gas pressure further decreases from time B to time C (FIG. 4C). Thus, the hydrogen gas supply flow rate increases from time B to time C (FIG. 4B), and the hydrogen gas flow velocity in the anode electrode increases. By operating in this way, it is easy to blow off the water retained in the anode electrode. As a result, when the cell voltage is increased after time B and it is detected that the cell voltage has become larger than the allowable lower limit value, the purge on-off valve 6 is closed at time D (FIG. 4 (d), Step S7).

  In the example shown in FIG. 4, the hydrogen gas pressure drop from time B to time C occurs because the supply amount of hydrogen gas becomes insufficient when the purge on-off valve 6 is opened. Further, the increase in the hydrogen gas pressure after time D is a delay in the period required for the hydrogen gas supply pressure regulating valve 3 to return from the predetermined pressure value to the normal pressure value with respect to the period required for closing the purge on-off valve 6. Caused by.

  In order to eliminate the condensation of water vapor in the humidified air on the cathode electrode side and the clogging due to the generated water, for example, the dynamic pressure of the air is generated by increasing the flow rate of the compressor 7.

[Effect of the fuel cell system according to the first embodiment]
As described above in detail, according to the fuel cell system according to the first embodiment, water clogging generated at the anode electrode of the fuel cell stack 1 due to condensation of water vapor in the hydrogen gas humidified by the humidifier 5 is eliminated. To do.

  Further, in the fuel cell system according to the first embodiment, in order to increase the dynamic pressure immediately after opening the purge on-off valve 6, the purge on-off valve is increased after the hydrogen gas pressure is increased to a predetermined pressure value. 6 is in an open state, the dynamic pressure can be increased to increase the hydrogen gas flow rate, and drainage at the anode electrode can be performed efficiently. That is, according to this fuel cell system, the purge on-off valve is compared with the operation in which the hydrogen gas pressure is adjusted by the generated power required for the fuel cell stack 1 and the purge on-off valve 6 is simply opened. It is possible to increase the dynamic pressure immediately after opening 6.

  Therefore, according to this fuel cell system, the period during which the purge on-off valve 6 is open can be shortened, so that the amount of hydrogen gas discharged by opening the purge on-off valve 6 can be reduced. Thus, drainage on the anode electrode side can be performed efficiently. As described above, according to the fuel cell system, by efficiently draining water, it is possible to improve the fuel efficiency of hydrogen gas, reduce the air pressure and hydrogen gas pressure to reduce drainage time, and reduce the power generation output. Further, it is possible to improve drainage efficiency while maintaining the power generation output without affecting the power generation output without having to reduce the generated gas by power generation.

[Configuration of Fuel Cell System According to Second Embodiment]
Next, a fuel cell system according to a second embodiment will be described with reference to FIG. The same parts as those of the fuel cell system according to the first embodiment described above are denoted by the same reference numerals, and detailed description thereof is omitted.

  The fuel cell system according to the second embodiment shown in FIG. 5 is the fuel according to the first embodiment in that the first purge on-off valve 18 and the second purge on-off valve 19 are provided in the hydrogen gas circulation passage L2. Different from battery system.

  In such a fuel cell system, as in the first embodiment, the control unit 17 detects a drop in the cell voltage of the fuel cell stack 1 from the sensor signal from the cell voltage sensor 16, and the first purge on-off valve 18 and // A water discharge process for opening the second purge on-off valve 19 is performed.

[Operation of Fuel Cell System According to Second Embodiment]
Next, the operation of the fuel cell system according to the second embodiment will be described with reference to the flowchart of FIG.

  According to FIG. 6, in step S <b> 11 next to the processing in step S <b> 4, the control unit 17 controls to open only the first purge on / off valve 18. If it is determined in step S6 that the cell voltage has become larger than the allowable lower limit value, the first purge on / off valve 18 is closed in step S12, and the process is terminated.

  When it is determined in step S6 that the cell voltage is smaller than the allowable lower limit value, the process proceeds to step S8, and the control unit 17 performs the elapsed time from the time when the first purge opening / closing valve 18 is opened in step S11. It is determined whether or not a certain purge open time is longer than the first set time. If it is determined that the purge open time is longer than the first set time, the process proceeds to step S13.

  In step S13, the control unit 17 controls the second purge on-off valve 19 to be opened. As a result, both the first purge on-off valve 18 and the second purge on-off valve 19 are opened, and the gas in the hydrogen gas circulation flow path L2 from the first purge on-off valve 18 and the second purge on-off valve 19 is opened. Is in a state of discharging.

  In step S14, the control unit 17 determines whether or not the cell voltage has become smaller than the allowable lower limit value by opening the first purge on-off valve 18 and the second purge on-off valve 19. When it is determined that the cell voltage is not smaller than the allowable lower limit value, the process proceeds to step S15, the second purge on / off valve 19 is closed by the control unit 17, and the first purge on / off valve 18 is further closed in step S12. Close.

  On the other hand, when it is determined that the cell voltage is smaller than the allowable lower limit value, the process proceeds to step S16, and the purge open time from the time when the second purge on-off valve 19 is opened in step S13 is less than the second set time. It is determined whether or not it has become longer. If the purge opening time is longer than the second set time, the process proceeds to step S9. If not, the process returns to step S14 to open both the first purge on-off valve 18 and the second purge on-off valve 19. Keep the state that is in the state.

  The first set time and the second set time may be set so that the sum thereof becomes the set time in the first embodiment, or may be a time obtained by equally dividing the set time in the first embodiment.

[Effect of the fuel cell system according to the second embodiment]
As described above in detail, according to the fuel cell system according to the second embodiment, the cell voltage does not become larger than the allowable lower limit value even if the first purge on-off valve 18 is opened in step S11. In step S13, since the second purge on-off valve 19 is also opened, the total gas discharge flow rate in the hydrogen gas circulation passage L2 can be further increased as compared with the first embodiment. Further, the dynamic pressure can be increased. Therefore, according to this fuel cell system, when a certain period of time is required for the cell voltage to recover to the allowable lower limit value, water can be discharged in a short time, and water can be discharged effectively. .

  In the fuel cell system described below, the case where the two first purge opening / closing valves 18 and the second purge opening / closing valve 19 are provided has been described. However, the present invention is not limited to this, and more purge opening / closing valves are provided. Of course, the same effect can be obtained even if a valve is provided.

[Other examples of fuel cell system operation]
Next, a first operation example, a second operation example, and a third operation example will be described as other operation examples in the fuel cell system according to the first embodiment and the fuel cell system according to the second embodiment. In the operation example described below, the detailed description is omitted by attaching the reference numerals used in the first embodiment, but the fuel cell system according to the second embodiment is also applicable. .

"First operation example"
In the first operation example, when the cell voltage does not recover even when the purge on-off valve 6 is opened, an operation of increasing the hydrogen gas pressure stepwise is performed.

  That is, as shown in FIG. 7, even if the purge opening / closing valve 6 is opened in step S5, the cell voltage is smaller than the predetermined lower limit (step S6), and the purge opening / closing valve 6 is opened. When the elapsed time from the time is shorter than the set time (step S8), the process proceeds to step S21.

  In step S21, the hydrogen gas pressure currently supplied to the fuel cell stack 1 is obtained from the sensor signal from the hydrogen gas pressure sensor 13 by the control unit 17, and the current hydrogen gas pressure and a preset allowable upper limit pressure are obtained. Compare This allowable upper limit pressure is set to a pressure value that does not cause a deterioration in the function of the fuel cell stack 1 from the relationship with the air pressure in the fuel cell stack 1, for example.

  When it is determined that the current hydrogen gas pressure is not greater than the allowable upper limit pressure, the process proceeds to step S22, and the hydrogen gas pressure supplied to the fuel cell stack 1 is increased so as to increase by a predetermined increase pressure (α). The gas supply pressure regulating valve 3 is controlled, and the process returns to step S6. Accordingly, the hydrogen gas pressure supplied to the fuel cell stack 1 is set to the sum of the reference hydrogen gas pressure, the purge correction pressure, and the predetermined increase pressure (α) in step S4.

  In this fuel cell system, after the purge on-off valve 6 is opened, the cell voltage is at the allowable lower limit value, the purge open time is shorter than the set time, and the hydrogen gas pressure is lower than the allowable upper limit pressure. The hydrogen gas pressure is increased stepwise by repeatedly performing the processes of step S6, step S8, step S21, and step S22. On the other hand, when the hydrogen gas pressure becomes larger than the allowable upper limit pressure in step S21, the control unit 17 advances the process to step S9 to perform control to stop the power generation of the fuel cell stack 1.

  According to the fuel cell system performing such an operation, by increasing the hydrogen gas pressure in stages, the dynamic pressure can be further increased, and drainage at the anode electrode can be performed more efficiently.

"Second operation example"
In the second operation example, it is determined that the cell voltage is smaller than the allowable lower limit value, and the purge on-off valve 6 is opened from the closed state to the open state, and then the purge on-off valve 6 is periodically opened and closed within the purge open time. .

  That is, as shown in FIG. 8B, during the purge opening time from time t11 to time t12, the control unit 17 performs the purge during the period from time t11 to time t13, time t14 to time t15, and time t16 to time t12. The purge on-off valve 6 is opened, and the purge on-off valve 6 is closed during the period from time t13 to time t14 and from time t15 to time t16, so that the purge on-off valve 6 is periodically opened and closed. Switch operation with. The cycle for controlling the opening / closing of the purge on / off valve 6 in this way is determined by the operating conditions, the degree of recovery of the cell voltage, and the like, and is controlled by the control unit 17.

  By performing such an operation, the number of fluctuations of the hydrogen gas pressure can be increased as shown in FIG. Therefore, according to this fuel cell system, the number of occurrences of the dynamic pressure of the hydrogen gas pressure can be increased, and drainage at the anode electrode can be performed more efficiently.

  Further, according to this fuel cell system, the synergistic effect of increasing the dynamic pressure and increasing the number of occurrences of the dynamic pressure is exhibited by periodically controlling the opening / closing of the purge on-off valve 6 after the process of step S4. Therefore, even if the total hydrogen gas discharge amount from the purge on-off valve 6 during the purge opening time is small, the drainage can be efficiently performed.

  In the second operation example, the case where the hydrogen gas pressure is increased in step S4 has been described. However, even if the purge on-off valve 6 is controlled to open and close without increasing the hydrogen gas pressure, Drainage at the anode electrode can be efficiently performed by increasing the number of times of dynamic pressure generation of the hydrogen gas pressure.

"Third operation example"
In the third operation example, in step S4, the pressure of the hydrogen gas is increased and the air pressure is also increased so that the differential pressure between the anode and the cathode is less than a specified value, and the air pressure of the cathode is further increased. The air flow rate is increased so as to maintain the air flow rate before the air flow.

  That is, as shown in FIG. 9, in response to the decrease in the cell voltage (FIG. 9A), the hydrogen gas pressure and the hydrogen gas flow rate are increased in step S4 (FIGS. 9C and 9B). By increasing the air pressure (FIG. 9E), the air supply flow rate is increased (FIG. 9F). Thereafter, the purge on-off valve 6 is opened to generate a dynamic pressure of hydrogen gas pressure (FIG. 9D). At this time, the control unit 17 controls the air pressure control valve 8 so as to increase the air pressure with reference to the sensor signal from the air pressure sensor 14, and the compressor 7 while referring to the sensor signal from the air flow rate sensor 15. Is controlled to increase the air flow rate to a target air flow rate.

  By making such an operation, if the air flow rate when the air pressure is increased without changing the power generation output from the fuel cell stack 1 is constant, the air flow rate decreases due to the increase in air pressure, It can be prevented that the air flow rate at the cathode electrode decreases and the drainage efficiency decreases. Therefore, according to this fuel cell system, even when the air pressure is increased, the air flow rate can be maintained and the drainage efficiency can be maintained.

  The above-described embodiment is an example of the present invention. For this reason, the present invention is not limited to the above-described embodiment, and various modifications can be made depending on the design and the like as long as the technical idea according to the present invention is not deviated from this embodiment. Of course, it is possible to change.

It is a block diagram which shows the structure of the fuel cell system which concerns on 1st Embodiment to which this invention is applied. It is a figure for demonstrating the change of hydrogen gas pressure when changing the purge on-off valve from a closed state to an open state, and making it a closed state after a purge period, (a) shows a time change of hydrogen gas pressure, (b ) Shows the time change of the open / close state of the purge on-off valve. It is a flowchart which shows the operation | movement procedure of the water discharge process by the fuel cell system which concerns on 1st Embodiment to which this invention is applied. It is a figure which shows the relationship between the cell voltage, hydrogen gas flow rate, hydrogen gas pressure, and the opening / closing state of the purge on-off valve when water discharge processing is performed, (a) shows the time change of the cell voltage, (b) The change in the hydrogen gas flow rate over time is shown, (c) shows the change in hydrogen gas pressure, and (d) shows the change over time in the open / close state of the purge on-off valve. It is a block diagram which shows the structure of the fuel cell system which concerns on 2nd Embodiment to which this invention is applied. It is a flowchart which shows the operation | movement procedure of the water discharge process by the fuel cell system which concerns on 2nd Embodiment to which this invention is applied. It is a flowchart which shows the process sequence in the 1st operation example of the fuel cell system to which this invention is applied. It is a figure for demonstrating the 2nd example of operation | movement of the fuel cell system to which this invention is applied, (a) shows the time change of hydrogen gas pressure, (b) shows the time change of the opening-closing state of the purge on-off valve. Show. It is a figure for demonstrating the 3rd operation example of the fuel cell system to which this invention is applied, (a) shows the time change of a cell voltage, (b) shows the time change of a hydrogen gas flow rate, (c) Represents a change in hydrogen gas pressure, (d) a time change in the open / close state of the purge on-off valve, (e) a time change in air pressure, and (f) a time change in air flow rate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell stack 2 Hydrogen tank 3 Hydrogen gas supply pressure regulating valve 4 Hydrogen circulation device 5 Humidifier 6 Purge open / close valve 7 Compressor 8 Air pressure regulating valve 9 Water tank 10 Water pump 11 Radiator 12 Radiator fan 13 Hydrogen gas pressure sensor 14 Air pressure Sensor 15 Air flow sensor 16 Cell voltage sensor 17 Control unit L1 Hydrogen gas supply flow path L2 Hydrogen gas circulation flow path L3 Air supply flow path L4 Air discharge flow path L5 Water circulation flow path

Claims (6)

A plurality of cell structures each having an electrolyte membrane sandwiched between an oxidant electrode and a fuel electrode are stacked, an oxidant gas is supplied to the oxidant electrode side, and a fuel gas is supplied to the fuel electrode side. A fuel cell for generating electricity; a gas supply means for supplying an oxidant gas and a fuel gas to the fuel cell; a fuel circulation path through which the fuel gas outlet and the fuel gas inlet of the fuel cell are inserted; and a fuel circulation path provided in the fuel circulation path A control device for a fuel cell system that controls a fuel cell system having a purge valve that discharges part of the gas in the fuel circulation path to the outside,
When it is determined that the cell voltage of the fuel cell is smaller than a predetermined value, the purge valve is controlled from a closed state to an open state after controlling the gas supply means to increase the fuel gas pressure, and A control apparatus for a fuel cell system, wherein when the cell voltage of the fuel cell is determined to be greater than a predetermined value, the purge valve is controlled to be closed from an open state. A plurality of cell structures each having an electrolyte membrane sandwiched between an oxidant electrode and a fuel electrode are stacked, an oxidant gas is supplied to the oxidant electrode side, and a fuel gas is supplied to the fuel electrode side. A fuel cell for generating electricity; a gas supply means for supplying an oxidant gas and a fuel gas to the fuel cell; a fuel circulation path through which the fuel gas outlet and the fuel gas inlet of the fuel cell are inserted; and a fuel circulation path provided in the fuel circulation path A control device for a fuel cell system that controls a fuel cell system having a purge valve that discharges part of the gas in the fuel circulation path to the outside,
When the cell voltage of the fuel cell is determined to be lower than a predetermined value, the purge valve is periodically controlled to open and close, and when the cell voltage of the fuel cell is determined to be higher than the predetermined value, the purge valve is A control device for a fuel cell system, wherein the control is performed to close the fuel cell system. A plurality of cell structures each having an electrolyte membrane sandwiched between an oxidant electrode and a fuel electrode are stacked, an oxidant gas is supplied to the oxidant electrode side, and a fuel gas is supplied to the fuel electrode side. A fuel cell for generating electricity; a gas supply means for supplying an oxidant gas and a fuel gas to the fuel cell; a fuel circulation path through which the fuel gas outlet and the fuel gas inlet of the fuel cell are inserted; and a fuel circulation path provided in the fuel circulation path A control device for a fuel cell system that controls a fuel cell system having a purge valve that discharges part of the gas in the fuel circulation path to the outside,
When the cell voltage of the fuel cell is determined to be lower than a predetermined value, the purge valve is periodically opened and closed after controlling the gas supply means so as to increase the fuel gas pressure, and the cell of the fuel cell A control apparatus for a fuel cell system, wherein when the voltage is determined to be greater than a predetermined value, the purge valve is controlled to be closed. The fuel cell system has a plurality of purge valves in the fuel circulation path,
When it is determined that the cell voltage of the fuel cell is lower than a predetermined value, at least one purge valve is controlled to open, and the fuel cell is operated after a predetermined period has elapsed since the one purge valve was opened. The purge valve is controlled to open another purge valve when it is determined that the cell voltage of the fuel cell is lower than a predetermined value, and is opened when it is determined that the cell voltage of the fuel cell is higher than the predetermined value. The control device for a fuel cell system according to any one of claims 1 to 3, wherein the control is performed to close the fuel cell.   The gas supply means is controlled to increase the fuel gas pressure stepwise when it is determined that the cell voltage of the fuel cell is smaller than a predetermined value. Fuel cell system control device.   When it is determined that the cell voltage of the fuel cell is smaller than a predetermined value, the fuel gas pressure is increased, and the gas supply means is controlled to maintain the oxidant gas flow rate at the oxidant electrode. The control device for a fuel cell system according to claim 1, 3 or 5.