JP5803445B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system.

  As a conventional fuel cell system, when the fuel cell system is stopped, the operation of the fuel cell is continued and stopped after confirming that the fuel cell has risen to a predetermined temperature (see Patent Document 1). .

JP 2003-151601 A

  The temperature increase rate of the fuel cell increases because the heat loss increases as the power generated by the fuel cell increases. However, since the electrical parts that can be energized after the fuel cell system is stopped are limited to the minimum auxiliary equipment necessary to continue the operation of the fuel cell, they generate more power than the power consumed by the auxiliary equipment. I couldn't. Therefore, there has been a problem that the time required for raising the fuel cell to a predetermined temperature after the fuel cell system is stopped becomes long.

  The present invention has been made paying attention to such a conventional problem, and aims to increase the temperature rise rate of the fuel cell by increasing the generated power of the fuel cell after the fuel cell system is stopped. To do.

  The present invention is a fuel cell system in which an anode gas and a cathode gas are supplied to a fuel cell to generate power and the vehicle is driven by the generated power. When the fuel cell system is instructed to stop the fuel cell system when the fuel cell is warmed up, the fuel cell system continues to generate power from the fuel cell until the warm-up is completed, and the generated power is supplied to the battery. And a charging permission means for permitting charging of the battery even when a normal upper limit charging rate set during vehicle travel is exceeded during warm-up operation after stopping.

  According to the present invention, during warm-up after stop, charging to the battery is permitted even if the normal upper limit charging rate set during vehicle travel is exceeded, so the power generated by the fuel cell during warm-up after stop is increased. Can be made. Thereby, the temperature increase rate of the fuel cell during the warm-up operation after the stop can be improved.

1 is a schematic view of a fuel cell system according to an embodiment of the present invention. It is a flowchart explaining stop control of the fuel cell system by one Embodiment of this invention. It is a flowchart explaining a dry operation time calculation process. It is a map which calculates the estimated amount of generated water balance until the temperature of the fuel cell stack reaches the warm-up completion temperature based on the required heat amount and the average cell voltage. It is a table which calculates the rotational speed of the cathode compressor driven at the time of drying operation based on outside temperature. 6 is a map for calculating the drying operation time based on the amount of moisture in the electrolyte membrane when the warm-up operation is completed after the stop and the rotation speed of the cathode compressor driven during the drying operation. It is a flowchart explaining an allowable upper limit charging rate calculation process. It is a flowchart explaining a target charging power calculation process. It is a flowchart explaining a temporary target charging power process. It is a flowchart explaining a 1st limited charging power calculation process. It is a table which calculates the temperature rise of an inverter based on an electric power integrated value. It is a map which calculates 1st limited charging power based on the implementation time of warm-up operation after a stop, battery temperature, and battery charge rate. It is a flowchart explaining a 2nd limited charging power calculation process. It is a table which calculates minimum discharge electric energy based on the minimum reduction charge rate. It is a map which calculates the 2nd restriction charge power based on the minimum amount of discharge electric power and battery temperature. It is a flowchart explaining a drying driving | operation process. It is a time chart explaining the operation | movement of stop control of the fuel cell system by one Embodiment of this invention. It is a time chart explaining the operation | movement of stop control of the fuel cell system by one Embodiment of this invention.

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

  In a fuel cell, an electrolyte membrane is sandwiched between an anode electrode (fuel electrode) and a cathode electrode (oxidant electrode), an anode gas containing hydrogen in the anode electrode (fuel gas), and a cathode gas containing oxygen in the cathode electrode (oxidant) Electricity is generated by supplying gas. The electrode reaction that proceeds in both the anode electrode and the cathode electrode is as follows.

Anode electrode: 2H ₂ → 4H ⁺ + 4e ⁻ (1)
Cathode electrode: 4H ⁺ + 4e ⁻ + O ₂ → 2H ₂ O (2)

  The fuel cell generates an electromotive force of about 1 volt by the electrode reactions (1) and (2).

  When a fuel cell is used as a power source for automobiles, a large amount of electric power is required. Therefore, the fuel cell is used as a fuel cell stack in which several hundred fuel cells are stacked. Then, a fuel cell system that supplies anode gas and cathode gas to the fuel cell stack is configured, and electric power for driving the vehicle is taken out.

  FIG. 1 is a schematic diagram of a fuel cell system 100 according to an embodiment of the present invention.

  The fuel cell system 100 includes a fuel cell stack 1, a cathode gas supply / discharge device 2, an anode gas supply / discharge device 3, a stack cooling device 4, a power system 5, and a controller 6.

  The fuel cell stack 1 is formed by stacking several hundred fuel cells, and receives the supply of anode gas and cathode gas to generate electric power necessary for driving the vehicle. The fuel cell stack 1 includes an anode electrode side output terminal 11 and a cathode electrode side output terminal 12 as terminals for taking out electric power.

  The cathode gas supply / discharge device 2 is a device that supplies cathode gas to the fuel cell stack 1 and discharges cathode off-gas discharged from the fuel cell stack 1 to the outside air. The cathode gas supply / discharge device 2 includes a cathode gas supply passage 21, a filter 22, a cathode compressor 23, and a cathode gas discharge passage 24.

  The cathode gas supply passage 21 is a passage through which the cathode gas supplied to the fuel cell stack 1 flows. The cathode gas supply passage 21 has one end connected to the filter 22 and the other end connected to the cathode gas inlet hole of the fuel cell stack 1.

  The filter 22 removes foreign matters in the cathode gas taken into the cathode gas supply passage 21.

  The cathode compressor 23 is provided in the cathode gas supply passage 21. The cathode compressor 23 takes in air (outside air) as cathode gas through the filter 22 into the cathode gas supply passage 21 and supplies it to the fuel cell stack 1.

  The cathode gas discharge passage 24 is a passage through which the cathode off gas discharged from the fuel cell stack 1 flows. One end of the cathode gas discharge passage 24 is connected to the cathode gas outlet hole of the fuel cell stack 1, and the other end is an open end.

  The anode gas supply / discharge device 3 is a device that supplies anode gas to the fuel cell stack 1 and discharges anode off-gas discharged from the fuel cell stack 1 to the cathode gas discharge passage 24. The anode gas supply / discharge device 3 includes a high-pressure tank 31, an anode gas supply passage 32, a pressure reducing valve 33, an anode gas discharge passage 34, and a purge valve 35.

  The high pressure tank 31 stores the anode gas supplied to the fuel cell stack 1 in a high pressure state.

  The anode gas supply passage 32 is a passage for supplying the anode gas discharged from the high-pressure tank 31 to the fuel cell stack 1. The anode gas supply passage 32 has one end connected to the high pressure tank 31 and the other end connected to the anode gas inlet hole of the fuel cell stack 1.

  The pressure regulating valve 33 is provided in the anode gas supply passage 32. The pressure regulating valve 33 is controlled to be opened and closed by the controller 6 and adjusts the pressure of the anode gas flowing out from the high-pressure tank 31 to the anode gas supply passage 32 to a desired pressure.

  The anode gas discharge passage 34 is a passage through which the anode off gas discharged from the fuel cell stack 1 flows. The anode gas discharge passage 34 has one end connected to the anode gas outlet hole of the fuel cell stack 1 and the other end connected to the cathode gas discharge passage 24.

  The purge valve 35 is provided in the anode gas discharge passage 34. The purge valve 35 is controlled to be opened and closed by the controller 6 and controls the flow rate of the anode off gas discharged from the anode gas discharge passage 34 to the cathode gas discharge passage 24.

  The stack cooling device 4 is a device that cools the fuel cell stack 1 and maintains the fuel cell stack 1 at a temperature suitable for power generation. The stack cooling device 4 includes a cooling water circulation passage 41, a radiator 42, a bypass passage 43, a three-way valve 44, a circulation pump 45, a PTC heater 46, and a water temperature sensor 47.

  The cooling water circulation passage 41 is a passage through which cooling water for cooling the fuel cell stack 1 circulates.

  The radiator 42 is provided in the cooling water circulation passage 41. The radiator 42 cools the cooling water discharged from the fuel cell stack 1.

  The bypass passage 43 has one end connected to the coolant circulation passage 41 and the other end connected to the three-way valve 44 so that the coolant can be circulated by bypassing the radiator 42.

  The three-way valve 44 is provided in the cooling water circulation passage 41 on the downstream side of the radiator 42. The three-way valve 44 switches the cooling water circulation path according to the temperature of the cooling water. Specifically, when the temperature of the cooling water is relatively high, the cooling water circulation path is such that the cooling water discharged from the fuel cell stack 1 is supplied again to the fuel cell stack 1 via the radiator 42. Switch. On the contrary, when the temperature of the cooling water is relatively low, the cooling water discharged from the cooling water discharged from the fuel cell stack 1 flows through the bypass passage 43 without passing through the radiator 42 and is again returned to the fuel cell stack 1. The cooling water circulation path is switched so as to be supplied.

  The circulation pump 45 is provided in the cooling water circulation passage 41 on the downstream side of the three-way valve 44 and circulates the cooling water.

  The PTC heater 46 is provided in the cooling water circulation passage 41 between the three-way valve 44 and the circulation pump 45. The PTC heater 46 is energized when the fuel cell stack 1 is warmed up to raise the temperature of the cooling water.

  The water temperature sensor 47 is provided in the cooling water circulation passage 41 on the upstream side of the radiator 42. The water temperature sensor 47 detects the temperature of the cooling water discharged from the fuel cell stack 1 (hereinafter referred to as “stack cooling water temperature”). In the present embodiment, the stack cooling water temperature is used as the temperature of the fuel cell stack 1.

  The power system 5 includes a current sensor 51, a voltage sensor 52, a drive motor 53, an inverter 54, a battery 55, and a DC / DC converter 56.

  The current sensor 51 detects a current taken out from the fuel cell stack 1 (hereinafter referred to as “output current”).

  The voltage sensor 52 detects an inter-terminal voltage (hereinafter referred to as “output voltage”) between the anode electrode side output terminal 11 and the cathode electrode side output terminal 12.

  The drive motor 53 is a three-phase AC synchronous motor in which a permanent magnet is embedded in a rotor and a stator coil is wound around a stator. The drive motor 53 functions as an electric motor that is driven to rotate by receiving electric power supplied from the fuel cell stack 1 and the battery 55, and power generation that generates electromotive force at both ends of the stator coil during deceleration of the vehicle in which the rotor is rotated by external force. Function as a machine.

  The inverter 54 includes a plurality of semiconductor switches such as IGBTs (Insulated Gate Bipolar Transistors). The semiconductor switch of the inverter 54 is controlled to be opened / closed by the controller 6, whereby DC power is converted into AC power or AC power is converted into DC power. When the drive motor 53 functions as an electric motor, the inverter 54 converts the combined DC power of the generated power of the fuel cell stack 1 and the output power of the battery 55 into three-phase AC power and supplies the three-phase AC power to the drive motor 53. On the other hand, when the drive motor 53 functions as a generator, the regenerative power (three-phase AC power) of the drive motor 53 is converted into DC power and supplied to the battery 55.

  The battery 55 charges the surplus power generated by the fuel cell stack 1 (output current × output voltage) and the regenerative power of the drive motor 53. The electric power charged in the battery 55 is supplied to auxiliary equipment such as the cathode compressor 23 and the PTC heater 46 and the drive motor 53 as necessary.

  The DC / DC converter 56 is a bidirectional voltage converter that raises and lowers the output voltage of the fuel cell stack 1. By controlling the output voltage of the fuel cell stack 1 by the DC / DC converter 56, the output current of the fuel cell stack 1, and thus the generated power, is controlled.

  The controller 6 includes a microcomputer having a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface). In addition to the water temperature sensor 47, the current sensor 51, and the voltage sensor 52, the controller 6 includes an outside air temperature sensor 61 that detects the outside air temperature, and a start request for the fuel cell system based on on / off of the start key. A key sensor 62 that detects a stop request, an accelerator stroke sensor 63 that detects the amount of depression of an accelerator pedal, an SOC (State Of Charge) sensor 64 that detects a charging rate of the battery 55 (hereinafter referred to as “battery charging rate”), and a battery 55 Signals from various sensors necessary for controlling the fuel cell system 100 such as the battery temperature sensor 65 for detecting the temperature of the battery are input.

  The controller 6 controls the fuel cell system 100 based on these input signals.

  Here, when the fuel cell system 100 is mounted on a vehicle as in this embodiment, it is required to be able to start quickly even in a low temperature environment where the outside air temperature is below 0 ° C. Therefore, it is necessary to suppress a decrease in power generation performance at the next start due to freezing of water generated by an electrode reaction during power generation (hereinafter referred to as “product water”). Therefore, after the start key is turned off, it is desirable to perform a drying operation in which the cathode compressor 23 is driven to discharge moisture in the fuel cell stack 1 to the outside and dry the electrolyte membrane in preparation for the next start.

  After the fuel cell system 100 is started, a warm-up operation is performed to increase the temperature in the fuel cell stack using heat generated by the electrode reaction up to a temperature at which stable power generation can be performed. However, if the start key is turned off during the warm-up operation, the warm-up is not yet completed and the stack temperature is relatively low. There is a possibility that the electrolyte membrane cannot be dried. Also, when the stack temperature is low, the time required for drying the electrolyte membrane is longer than when the stack temperature is high.

  Therefore, when the start key is turned off during the warm-up operation, it is desirable to continue the warm-up operation and perform the dry operation after the warm-up is completed. Hereinafter, the warm-up operation that is subsequently performed after the start key is turned off during the warm-up operation is referred to as “warm-up operation after stop”.

  However, since the warm-up operation after the stop is performed after the start key is turned off, if the time for the warm-up operation after the stop becomes long, the fuel cell system 100 is completely stopped after the start key is turned off. It takes longer to be done. If so, some drivers may feel uncomfortable, so we want to shorten the warm-up time after stopping as much as possible.

  The temperature increase rate of the fuel cell stack 1 increases as the generated power of the fuel cell stack 1 increases, because the amount of heat energy released to the outside as a loss increases. Therefore, in order to shorten the time for the warm-up operation after the stop, it is effective to increase the generated power during the warm-up operation after the stop.

  The supply destination of the generated power during the warm-up operation after the stop is auxiliary equipment (cathode compressor 23, PTC heater 46 and cooling water circulation pump 45) that needs to be driven to continue the power generation and promote the warm-up, and the battery. Limited to 55. At this time, since the power that can be supplied to the auxiliary machines is generally determined, the only way to increase the power generated during the warm-up operation after stopping is to increase the power supplied to the battery 55.

  Here, conventionally, a battery charging rate (hereinafter referred to as an “upper limit charging rate”) that prohibits charging of the battery 55 is received for regenerative power from the drive motor 53 during vehicle travel, and a high potential state is maintained for a long time. In consideration of the deterioration of the battery 55 due to this, the battery charge rate is set to a relatively low value of about 70% (hereinafter referred to as “normal upper limit charge rate”).

  However, since the warm-up operation after the stop is performed after the start key is turned off, it is not necessary to limit the battery charge rate to the normal upper limit charge rate in order to accept the regenerative power from the drive motor 53. Further, for the deterioration of the battery 55 due to the high potential state being maintained for a long time, the cathode compressor 23 is driven by consuming the power of the battery 55 during the drying operation performed after the warm-up operation after the stop, What is necessary is just to reduce a battery charge rate to a normal upper limit charge rate.

  Therefore, in the present embodiment, the upper limit charging rate is set to be higher than the normal upper limit charging rate during the warm-up operation after the stop. As a result, the power generated during the warm-up operation after the stop can be increased, so that the time from when the start key is turned off until the fuel cell system 100 is completely stopped can be shortened. Hereinafter, stop control of the fuel cell system 100 according to this embodiment will be described.

  FIG. 2 is a flowchart illustrating stop control of the fuel cell system 100 according to the present embodiment.

  In step S1, the controller 6 determines whether or not the start key of the fuel cell system 100 is off. If the start key of the fuel cell system 100 is off, the controller 6 performs the process of step S2. On the other hand, if the start key of the fuel cell system 100 is on, the current process is terminated.

  In step S2, the controller 6 determines whether or not the fuel cell stack 1 has been warmed up. Specifically, it is determined whether or not the stack cooling water temperature is equal to or higher than a predetermined warm-up completion temperature. When the controller 6 determines that the stack cooling water temperature is lower than the warm-up completion temperature and the warm-up of the fuel cell stack 1 has not been completed, the controller 6 performs the process of step S3. On the other hand, when it is determined that the stack cooling water temperature is equal to or higher than the warm-up completion temperature and the fuel cell stack 1 has been warmed up, the process of step S7 is performed.

  In step S <b> 3, the controller 6 performs a calculation process of the duration of the drying operation (hereinafter referred to as “drying operation time”) that is performed after the end of the warm-up operation after the stop. The drying operation time calculation process will be described later with reference to FIG.

  In step S <b> 4, the controller 6 performs a calculation process of an upper limit charging rate (hereinafter referred to as “allowable upper limit charging rate”) during the warm-up operation after stopping. The allowable upper limit charging rate calculation process will be described later with reference to FIG.

  In step S5, the controller 6 calculates a target value (hereinafter referred to as “target charging power”) of power supplied to the battery 55 during the warm-up operation after stopping. The target charging power calculation process will be described later with reference to FIG.

  In step S <b> 6, the controller 6 supplies the target charging power to the battery 55 and charges the battery 55.

  In step S7, the controller 6 performs a drying operation process. The drying operation process will be described later with reference to FIG.

  Hereinafter, the drying operation time calculation process will be described with reference to FIGS. 3 to 6. In the drying operation time calculation process, the amount of moisture in the electrolyte membrane when the stack cooling water temperature is raised to the warm-up completion temperature is estimated, and the electrolyte membrane is determined according to the rotational speed of the cathode compressor 23 driven during the drying operation. Calculate the time required to dry the.

  FIG. 3 is a flowchart illustrating the drying operation time calculation process.

  In step S31, the controller 6 multiplies the temperature difference between the warm-up completion temperature and the stack cooling water temperature when the start key is turned off by the heat capacity of the fuel cell stack 1 obtained in advance through experiments or the like, The amount of heat necessary to bring the temperature of the battery stack 1 to the warm-up completion temperature (hereinafter referred to as “necessary amount of heat”) is calculated.

  In step S <b> 32, the controller 6 divides the output voltage detected by the voltage sensor 52 by the number of fuel cells in the fuel cell stack 1, thereby obtaining an average value of the voltages of the fuel cells (hereinafter referred to as “average cell voltage”). calculate.

  In step S33, the controller 6 refers to a map shown in FIG. 4 to be described later, and the balance of generated water in the fuel cell stack until the stack cooling water temperature reaches the warm-up completion temperature based on the required heat amount and the average cell voltage. The amount (hereinafter referred to as “estimated generated water balance”) is estimated. The estimated amount of generated water balance is considered to be obtained by subtracting the amount of generated water discharged outside the fuel cell stack 1 as water vapor by the cathode gas from the amount of generated water generated until the stack cooling water temperature reaches the warm-up completion temperature. Can do.

  In step S34, the controller 6 adds the estimated amount of generated water balance and the amount of water in the membrane of the electrolyte membrane when the start key is turned off, so that the electrolyte membrane at the end of the warm-up operation after stoppage is added. Estimate the amount of water in the membrane. The amount of water in the membrane of the electrolyte membrane can be calculated based on the internal resistance of the fuel cell stack 1 calculated by, for example, the AC impedance method. It is known that there is a correlation between the amount of water in the membrane of the electrolyte membrane and the internal resistance of the fuel cell stack 1, and the amount of moisture in the membrane of the electrolyte membrane is small and the electrolyte membrane is in a dry state. From time to time, the internal resistance of the fuel cell stack 11 increases.

  In step S35, the controller 6 refers to a table in FIG. 5 to be described later, and estimates the rotational speed of the cathode compressor 23 that is driven during the drying operation based on the outside air temperature detected by the outside air temperature sensor 61.

  In step S36, the controller 6 refers to the map of FIG. 6 described later, and determines the amount of water in the electrolyte membrane when the warm-up operation is completed after the stop and the rotational speed of the cathode compressor 23 driven during the drying operation. Based on this, the drying operation time is calculated.

  FIG. 4 is a map for calculating the estimated generated water balance until the temperature of the fuel cell stack 1 reaches the warm-up completion temperature based on the necessary heat amount and the average cell voltage.

  As shown in FIG. 4, the generated water balance increases as the calorific value increases and the average cell voltage increases.

  FIG. 5 is a table for calculating the rotational speed of the cathode compressor 23 driven during the drying operation based on the outside air temperature.

  As shown in FIG. 5, the rotational speed of the cathode compressor 23 driven during the drying operation is set to the maximum rotational speed until the outside air temperature exceeds a predetermined temperature. However, when the cathode compressor 23 is driven at the maximum rotational speed, the discharge temperature may exceed the upper limit temperature defined in the specification depending on the outside air temperature. Therefore, when the outside air temperature becomes higher than the predetermined temperature, the rotational speed of the cathode compressor 23 is decreased as the outside air temperature increases.

  FIG. 6 is a map for calculating the drying operation time based on the amount of moisture in the electrolyte membrane when the warm-up operation after the stop is completed and the rotational speed of the cathode compressor 23 driven during the drying operation.

  As shown in FIG. 6, the drying operation time becomes longer as the amount of water in the electrolyte membrane at the completion of the warm-up operation after the stop increases, and as the rotational speed of the cathode compressor 23 during the drying operation decreases.

  Next, the allowable upper limit charging rate calculation process will be described with reference to FIG. In the allowable upper limit charging rate calculation process, the allowable upper limit charging rate during the warm-up operation after stop is calculated according to the power consumption when the cathode compressor 23 is driven for the drying operation time. This is performed after the end of warm-up operation after stop even if the battery charge rate is increased by more than the normal upper limit charge rate by the charge rate corresponding to the power consumption during dry operation during warm-up operation after stop. This is because the charge rate can be reduced during the drying operation.

  FIG. 7 is a flowchart illustrating the allowable upper limit charging rate calculation process.

  In step S41, the controller 6 calculates the power consumption of the cathode compressor 23 during the drying operation based on the rotational speed of the cathode compressor 23 driven during the drying operation.

  In step S42, the controller 6 multiplies the drying operation time by the power consumption of the cathode compressor 23 during the drying operation, and calculates the power consumption during the drying operation. In other words, the power consumption during the drying operation is the amount of power that can be charged to the battery 55 during the warm-up operation.

  In step S43, the controller 6 divides the power consumption during the dry operation by the battery capacity, thereby charging the power consumption during the dry operation, that is, the power [kW] that can be charged to the battery 55 during the warm-up operation. Convert to rate [%]. Hereinafter, the increase amount of the battery charge rate that can be allowed during the warm-up operation is referred to as “allowable increase charge rate”.

  In step S44, the controller 6 calculates the provisional allowable upper limit charging rate by adding the allowable increase charging rate to the battery charging rate when the start key is turned off.

  In step S45, the controller 6 compares the provisional allowable upper limit charge rate and the limit upper limit charge rate, and calculates the smaller one as the allowable upper limit charge rate. The limit upper limit charging rate is a charging rate determined by the standard of the battery 55, and is set to 85% in the present embodiment.

  Next, the target charging power calculation process will be described with reference to FIGS. In the target charging power calculation process, the charging power of the battery 55 is basically calculated so that the battery charging rate becomes the allowable upper limit charging rate at the end of the warm-up operation after stopping. However, the charging power of the battery 55 is limited by the power input characteristics of the battery 55. In addition, it is necessary to charge the battery 55 so that the temperature does not exceed the management upper limit temperature predetermined for each battery 55. Therefore, in this embodiment, the target charging power of the battery 55 is calculated in consideration of the power input characteristics and temperature of the battery 55.

  FIG. 8 is a flowchart for explaining the target charging power calculation process.

  In step S51, the controller 6 performs a calculation process of charging power (hereinafter referred to as “provisional target charging power”) necessary for setting the battery charging rate to the allowable upper limit charging rate at the end of the warm-up operation after the stop. The provisional target charging power calculation process will be described later with reference to FIG.

  In step S <b> 52, the controller 6 performs a calculation process of the upper limit charging power of the battery 55 that is limited by the power input characteristic of the battery 55 (hereinafter referred to as “first limited charging power”). The first limited charging power calculation process will be described later with reference to FIG.

  In step S <b> 53, the controller 6 performs a calculation process of the upper limit charging power of the battery 55 that is limited by the temperature of the battery 55 (hereinafter referred to as “second limited charging power”). The second limited charging power will be described later with reference to FIG.

  In step S <b> 54, the controller 6 calculates the smallest of the temporary target charging power, the first limited charging power, and the second limited charging power as the target charging power for the battery 55.

  FIG. 9 is a flowchart for explaining the provisional target charging power processing.

  In step S511, the controller 6 multiplies the battery capacity obtained by subtracting the battery charge rate detected by the SOC sensor 64 from the allowable upper limit charge rate, and charges the battery 55 to make the battery charge rate the allowable upper limit charge rate. The amount of electric power that needs to be calculated (hereinafter referred to as “provisional target charging electric energy”) is calculated.

  In step S512, the controller 6 calculates the temporary target charging power by dividing the temporary target charging power amount by the drying operation time.

  FIG. 10 is a flowchart illustrating the first limited charging power calculation process.

  In step S521, the controller 6 refers to the map of FIG. 11 and calculates the heat generation amount of the fuel cell stack 1 per unit time based on the generated power of the fuel cell stack 1 and the average cell voltage.

  In step S522, the controller 6 divides the necessary heat amount by the calorific value of the fuel cell stack 1, thereby performing the warm-up operation time after the stop, that is, the time required for the stack cooling water temperature to reach the warm-up completion temperature. Is calculated.

  In step S523, the controller 6 refers to the map of FIG. 12, and calculates the first limited charging power based on the execution time of the post-stop warm-up operation, the battery temperature, and the battery charge rate.

  FIG. 11 is a map for calculating the calorific value of the fuel cell stack 1 per unit time based on the generated power of the fuel cell stack 1 and the average cell voltage.

  As shown in FIG. 11, the heat generation amount of the fuel cell stack 1 increases as the generated power of the fuel cell stack 1 increases and the average cell voltage decreases.

  FIG. 12 is a map for calculating the first limited charging power based on the execution time of the warm-up operation after stop, the battery temperature, and the battery charging rate.

  As shown in FIG. 12, the higher the battery charge rate and the lower the battery temperature, the smaller the first limited charging power. On the other hand, as the execution time of the warm-up operation after the stop becomes shorter, the first limited charging power increases as shown by the broken line in the figure.

  FIG. 13 is a flowchart illustrating the second limited charging power calculation process.

  In step S531, the controller 6 subtracts the normal upper limit charging rate from the battery charging rate detected by the SOC sensor 64 to reduce the battery charging rate (hereinafter referred to as “minimum reduced charging rate”) that must be reduced at the minimum during the drying operation. calculate.

  In step S532, the controller 6 refers to the table of FIG. 14 and does not discharge at the minimum in order to reduce the battery charge rate to the normal upper limit charge rate when the fuel cell system 100 is stopped based on the minimum decrease charge rate. The amount of power that should not be calculated (hereinafter referred to as “minimum discharge power amount”) is calculated.

  In step S533, the controller 6 refers to the map of FIG. 15 and calculates the second limited charging power based on the minimum discharge power amount and the battery temperature.

  FIG. 14 is a table for calculating the minimum discharge electric energy based on the minimum decrease charging rate.

  As shown in FIG. 14, when the minimum decrease charging rate is a negative value, the minimum discharge power amount is zero. On the other hand, when the minimum reduction charge rate is a positive value, the minimum discharge power amount increases as the minimum charge rate increases.

  FIG. 15 is a map for calculating the second limited charge power based on the minimum discharge power amount and the battery temperature.

  As shown in FIG. 15, the second limited charge power increases as the minimum discharge power increases and the battery temperature decreases.

  Next, the drying operation process will be described with reference to FIG. In the drying operation process, the cathode compressor 23 and other auxiliary devices are driven so that the battery charging rate is normally equal to or lower than the upper limit charging rate at the end of the drying operation, that is, when the fuel cell system 100 is completely stopped. .

  FIG. 16 is a flowchart illustrating the drying operation process.

  In step S71, the controller 6 calculates the minimum discharge power amount by multiplying the battery charge rate detected by the SOC sensor 64 minus the normal upper limit charge rate by the battery capacity.

  In step S72, the controller 6 calculates the minimum discharge power of the battery 55 by dividing the minimum discharge power amount by the drying operation time.

  In step S <b> 73, the controller 6 compares the minimum discharge power of the battery 55 with the power consumption of the cathode compressor 23. When the minimum discharge power of the battery 55 is greater than or equal to the power consumption of the cathode compressor 23, the controller 6 performs the process of step S74. On the other hand, when the minimum discharge power of the battery 55 is less than the power consumption of the cathode compressor 23, the process of step S75 is performed.

  In step S74, the controller 6 drives the cathode compressor 23 with the electric power of the battery 55 and also supplies the battery 55 to the auxiliary equipment other than the cathode compressor 23 so that the discharge power of the battery 55 becomes equal to or higher than the minimum discharge power. Supply power. In this case, the power generation of the fuel cell stack 1 is stopped.

  In step S <b> 75, the controller 6 drives the cathode compressor 23 with the power of the battery 55 and the generated power of the fuel cell stack 1.

  In step S76, the controller 6 determines whether or not the drying operation time has elapsed since the drying operation was started. If the drying operation time has not elapsed, the controller 6 ends the current process. On the other hand, if the drying operation time has elapsed, the process of step S77 is performed.

  In step S77, the controller 6 stops the power supply to the cathode compressor 23 and stops the fuel cell system 100 completely.

  FIG. 17 is a time chart illustrating the stop control operation of the fuel cell system 100 according to the present embodiment. This time chart is a time chart when the target temporary charging power is set as the target charging power in the target charging power calculation process. In order to facilitate understanding of the invention, a time chart when the upper limit charging rate during the warm-up operation after stopping is limited to the normal upper limit charging rate is shown as a comparative example.

  If the start switch is turned off during the warm-up operation at time t1, the warm-up operation is started after the stop.

  Here, in the case of the comparative example, since the upper limit charging rate during the warm-up operation after the stop is limited to the normal upper limit charging rate, when the battery charging rate reaches the normal upper limit charging rate at time t2, the battery 55 is charged. The power becomes zero. Therefore, after time t2, the generated power of the fuel cell stack 1 decreases and the temperature increase rate of the fuel cell stack 1 decreases.

  On the other hand, in the case of the present embodiment, the upper limit charging rate during the warm-up operation after the stop is set to a large allowable upper limit charging rate that is higher than the normal upper limit charging rate. Even after reaching the rate, charging of the battery 55 is continued.

  Therefore, since the generated power of the fuel cell stack 1 does not decrease after the time t2, the temperature increase rate of the fuel cell stack 1 becomes faster than that of the comparative example. As a result, the time at which the stack cooling water temperature reaches the warm-up completion temperature is time t6 in the comparative example, but at time t4 in this embodiment, the stack cooling water temperature reaches the warm-up completion temperature in this embodiment. The time is earlier than the comparative example.

  When the stack coolant temperature reaches the warm-up completion temperature at time t3, the warm-up operation is stopped after the stop and the drying operation is performed. When the drying operation is started, the electric power of the battery 55 is supplied to the cathode compressor 23 so that the battery charging rate is reduced to the normal upper power receiving rate. As a result, the cathode compressor 23 is driven to dry the electrolyte membrane.

  When the time from the start of the drying operation reaches the drying operation time at time 4, the drying operation is terminated.

  FIG. 18 is a time chart illustrating the stop control operation of the fuel cell system 100 according to the present embodiment. This time chart is a time chart when the second limited charging power is set as the target charging power in the charging power calculation process.

  When the start switch is turned off during the warm-up operation at time t11, the warm-up operation is started after the stop.

  During the warm-up operation after the stop, the generated power of the fuel cell stack 1 is supplied to the battery 55, and the charging rate and battery temperature of the battery 55 are increased accordingly. At this time, as shown in the map of FIG. 15 described above, the second limited charging power decreases as the battery temperature increases.

  Therefore, when the second limited charging power becomes smaller than the provisional target charging power at time t12, the charging power is limited to the second limiting charging power. After time t12, the charging power of the battery 55 also increases as the battery temperature increases. Decrease. A decrease in battery 55 charging power suppresses an increase in battery temperature.

  When the stack cooling water temperature reaches the warm-up completion temperature at time t13, the warm-up operation is stopped after the stop and the drying operation is performed. When the drying operation is started, the electric power of the battery 55 is supplied to the cathode compressor 23 so that the battery charging rate is reduced to the normal upper power receiving rate. At this time, the temperature of the battery 55 is increased by supplying the power of the battery 55 to the cathode compressor 23. However, since the charging power is limited during the warm-up operation after the stop and the increase in the battery temperature is suppressed, the battery 55 is dried. It is possible to suppress the battery temperature from becoming higher than the upper limit temperature during operation.

  According to the present embodiment described above, when the start key is turned off during the warm-up operation, the drying operation is performed after the warm-up operation after the stop. In the warm-up operation after the stop, charging to the battery 55 is permitted even if the battery charge rate exceeds the normal upper limit charge rate set during vehicle travel.

  As a result, during warm-up operation after stopping, the generated power of the fuel cell stack 1 can be supplied to the battery 55 even after the battery charge rate exceeds the normal upper limit charge rate. it can. Thereby, the fall of the temperature increase rate of the fuel cell stack 1 during the warm-up operation after the stop can be suppressed, and the time from when the start key is turned off until the drying operation is started can be shortened.

  Further, according to the present embodiment, during the drying operation, the cathode compressor 23 is driven by consuming the electric power of the battery 55 so that the charging rate of the battery 55 is reduced to at least the normal upper limit charging rate, and the electrolyte membrane is dried. I made it.

  Thereby, since the battery charge rate is always equal to or lower than the normal upper limit charge rate at the end of the drying operation, the high potential state is not maintained for a long time even if the period becomes longer until the next start. Therefore, deterioration of the battery 55 can be suppressed.

  Further, according to the present embodiment, the power supplied to the battery 55 during the warm-up operation after the stop is limited according to the power input characteristics of the battery 55.

  Thereby, the optimal charge according to the characteristic of the battery 55 can be performed.

  Further, according to the present embodiment, the power supplied to the battery 55 during the warm-up operation after the stop is limited according to the battery temperature so that the battery temperature does not exceed the management upper limit temperature at the end of the drying operation.

  Thereby, it can suppress that battery temperature becomes higher than management upper limit temperature, and can suppress deterioration of the battery 55. FIG.

  Further, according to the present embodiment, the power consumption of the battery during the drying operation is reduced as the difference between the normal upper limit charging rate and the battery charging rate is reduced.

  As a result, the battery charge rate can be prevented from becoming too low at the next start, and the electric power necessary to start the fuel cell system can be reliably ensured.

  Note that the present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

1 Fuel cell stack (fuel cell)
55 Battery 100 Fuel cell system S3 to S6 Warm-up operation means after stop S4 Charging permission means S7 Drying operation means S34 Water content estimating means S36 Drying operation time estimating means S42 Power consumption calculating means S45 Upper limit charging rate calculating means S74, S75 Discharge means

Claims (8)

A fuel cell system in which an anode gas and a cathode gas are supplied to a fuel cell to generate power, and the vehicle is driven by the generated power,
When a stop command for the fuel cell system is issued when the fuel cell is warmed up, the power generation of the fuel cell is continued until the warm-up is completed, and the post-stop warm-up operation means for supplying the generated power to the battery;
Charging permission means for permitting charging to the battery even when exceeding a normal upper limit charging rate set during vehicle travel during warm-up operation after stopping;
A fuel cell system comprising: A drying operation means for reducing the amount of water in the fuel cell after completion of the warm-up operation after stopping;
Discharging means that consumes power of the battery during the drying operation, and at least reduces the charging rate of the battery to the normal upper limit charging rate;
The fuel cell system according to claim 1, comprising: The charging permission means includes
A moisture amount estimating means for estimating a moisture amount in the fuel cell when the temperature of the fuel cell is raised to a warm-up completion temperature;
A drying operation time estimating means for estimating the duration of the drying operation based on the amount of water in the fuel cell;
Based on the duration of the drying operation, power consumption estimation means for estimating the power consumption during the drying operation;
Based on the power consumption during the dry operation, an upper limit charge rate calculating means for calculating the upper limit charge rate of the battery during the warm-up operation after stopping;
With
Permit charging the battery until the charge rate of the battery reaches the upper limit charge rate;
The fuel cell system according to claim 2. The warm-up operation means after the stop is
Calculating the maximum supply power to the battery based on the difference between the upper limit charge rate and the battery charge rate so that the charge rate of the battery becomes the upper limit charge rate at the end of the warm-up operation after the stop; Supplying the battery with its maximum supply power,
The fuel cell system according to claim 3. The warm-up operation means after the stop is
Based on the power input characteristics of the battery, calculate the available power that can be supplied to the battery,
When the maximum supply power is larger than the suppliable power, the suppliable power is supplied to the battery.
The fuel cell system according to claim 4. The warm-up operation means after the stop is
Based on the temperature of the battery, the supplyable power that can be supplied to the battery is calculated so that the temperature of the battery does not exceed a predetermined upper limit temperature at the end of the drying operation,
When the maximum supply power is larger than the suppliable power, the suppliable power is supplied to the battery.
The fuel cell system according to claim 4. The warm-up operation means after the stop is
The higher the temperature of the battery, the smaller the power that can be supplied to the battery,
The fuel cell system according to claim 6. The discharging means includes
When the difference between the charging rate of the battery during the drying operation and the normal upper limit charging rate is larger, the power consumption of the battery is increased, and the charging rate of the battery is reduced to the normal upper limit charging rate .
The fuel cell system according to any one of claims 2 to 7, characterized in that:

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