Fuel Cell Systems

Abstract

To prevent degradation in power generation performance of a fuel cell stack.SOLUTION: A fuel cell system comprises a fuel cell stack, an anode gas supply part, a sealing valve, and a control device. The fuel cell stack has an anode passage and a cathode passage. The anode gas supply part supplies an anode gas to the fuel cell stack. The sealing valve seals the cathode passage. The sealing valve is a sealing valve whose opening can be adjusted. When the fuel cell stack is not generating power, the control device causes the anode gas supply part to fill the anode passage with the anode gas. The control device performs minimum opening control in which the opening of the sealing valve becomes a minimum opening that is smaller than the opening when the fuel cell stack is generating power. The control device performs full closure control in which the cathode passage is sealed by fully closing the sealing valve after the minimum opening control.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to fuel cell systems. [Background technology]

[0002] The fuel cell system disclosed in Patent Document 1 includes a fuel cell stack, a control device, and a sealing valve. The fuel cell stack includes fuel cells. The fuel cell stack generates electricity by a reaction between an anode gas and a cathode gas. The sealing valve is provided in a passage through which the cathode gas flows and in a passage through which the anode gas flows. When the fuel cell system is stopped, the control device maintains the sealing valve at an intermediate opening for a predetermined period of time and then fully closes the sealing valve. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2008-218242 A Summary of the Invention [Problem to be solved by the invention]

[0004] If power generation by the fuel cell stack is stopped while cathode gas remains in the cathode flow path of the fuel cell stack and anode gas remains in the anode flow path of the fuel cell stack, cross leakage may occur. Cross leakage is the permeation of cathode gas from the cathode flow path to the anode flow path, and anode gas from the anode flow path to the cathode flow path. If cross leakage occurs, the fuel cell is oxidized due to the permeation of the cathode gas into the anode flow path. This may result in a deterioration in the power generation performance of the fuel cell stack. [Means for solving the problem]

[0005] A fuel cell system that solves the above problem includes a fuel cell stack that generates electricity by reaction between an anode gas and a cathode gas, an anode gas supply unit that supplies the anode gas to the fuel cell stack, and a control device, wherein the fuel cell stack includes an anode flow path to which the anode gas is supplied, and a cathode flow path to which the cathode gas is supplied, and the fuel cell system includes a sealing valve that seals the cathode flow path and has an adjustable opening, and the control device, when the fuel cell stack is in a state where power generation is stopped, fills the anode flow path with the anode gas using the anode gas supply unit, and when the fuel cell stack is in a state where power generation is stopped, performs extremely small opening control to set the opening of the sealing valve to an extremely small opening that is smaller than the opening when the fuel cell stack is in a power generation state, and when the fuel cell stack is in a power generation stopped state, performs fully closed control to seal the cathode flow path by fully closing the sealing valve after the extremely small opening control.

[0006] When the fuel cell stack is in a power generation stopped state, the anode gas is filled into the anode flow path by the anode gas supply unit. The opening of the sealing valve is set to a minimum opening, so that the cathode gas does not easily flow into the cathode flow path. When the sealing valve is fully closed, the amount of cathode gas remaining in the cathode flow path can be reduced. After the sealing valve is fully closed, the anode gas remaining in the anode flow path reacts with the cathode gas remaining in the cathode flow path. Since the anode gas is filled into the anode flow path, the cathode gas can be consumed by the anode gas. That is, the cathode gas can be consumed so that cross leakage does not occur due to the anode gas filled into the anode flow path. This makes it possible to suppress deterioration of the power generation performance of the fuel cell stack.

[0007] For the above fuel cell system, the control device may place the fuel cell stack in the power generation stopped state when a power generation stop command is received for the fuel cell system, place the fuel cell stack in the power generation state when a power generation command is received for the fuel cell system, perform the full closure control if the power generation command is not received within a predetermined time after receiving the power generation stop command, and place the fuel cell stack in the power generation state without performing the full closure control if the power generation command is received within the predetermined time after receiving the power generation stop command.

[0008] In the above fuel cell system, the sealing valve may include a gear, a valve body that moves due to rotation of the gear, and a gear stopper that regulates the rotation of the gear, and the control device may not bring the gear and the gear stopper into contact with each other in the extremely small opening control, and may bring the gear and the gear stopper into contact with each other in the fully closed control. Effect of the Invention

[0009] According to the present invention, deterioration of the power generation performance of the fuel cell stack can be suppressed. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of a fuel cell system. [Diagram 2] FIG. 2 is a cross-sectional view showing a schematic structure of a sealing valve. [Diagram 3] 4 is a flowchart showing a sealing control performed by a control device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] An embodiment of a fuel cell system will now be described. 1, the industrial vehicle 10 includes a load 11, a power conversion unit 12, a key switch 13, a cooling system 70, and a fuel cell system 20. The industrial vehicle 10 is, for example, a forklift or a towing tractor.

[0012] The load 11 is a device that is driven by electricity. For example, the load 11 is an electric motor that is driven by electricity. The industrial vehicle 10 travels by being driven by this electric motor. The power conversion unit 12 converts the input power and outputs the converted power. The power conversion unit 12 includes a DC / DC converter and an inverter. The power output from the power conversion unit 12 is supplied to the load 11. The load 11 is driven by the power conversion unit 12.

[0013] The key switch 13 is operated by a user of the industrial vehicle 10. The key switch 13 is switched between on and off by the user's operation. In the following description, turning on the key switch 13 may be referred to as "key on," and turning off the key switch 13 may be referred to as "key off."

[0014] The fuel cell system 20 includes a fuel cell stack 21 , a cathode system 30 , an anode system 60 , a diluter 69 , and a controller 80 . The fuel cell stack 21 is, for example, a solid polymer fuel cell. The fuel cell stack 21 includes a plurality of fuel cell units 22. Each fuel cell unit 22 includes an anode electrode to which an anode gas is supplied, a cathode electrode to which a cathode gas is supplied, and an electrolyte membrane disposed between the anode electrode and the cathode electrode. The fuel cell units 22 are sandwiched between separators.

[0015] The fuel cell stack 21 includes a cathode flow path 23 and an anode flow path 26. A cathode gas flows through the cathode flow path 23. The cathode flow path 23 is provided, for example, in a separator facing the cathode electrode. Anode gas flows through the anode flow path 26. The anode flow path 26 is provided, for example, in a separator facing the anode electrode. The cathode flow path 23 includes an inlet 24 and an outlet 25. The cathode gas flows into the cathode flow path 23 from the inlet 24 and flows out from the outlet 25. The anode flow path 26 includes an inlet 27 and an outlet 28. The anode gas flows into the anode flow path 26 from the inlet 27 and flows out from the outlet 28. The fuel cell stack 21 generates power by a reaction between the anode gas and the cathode gas. The cathode gas is an oxidizing gas. An example of the oxidizing gas is oxygen in the air. The anode gas is a fuel gas, such as hydrogen gas.

[0016] The cathode system 30 includes a cathode gas inlet 31, an electric compressor 32, an intercooler 33, a cathode supply passage 34, a cathode discharge passage 37, and two sealing valves 40 and 41.

[0017] The cathode gas inlet 31 is an inlet for sucking a cathode gas into the fuel cell system 20. When oxygen in the air is used as the cathode gas, the cathode gas inlet 31 may be open to the atmosphere. The cathode gas inlet 31 may be connected to a gas cylinder that stores the cathode gas.

[0018] The electric compressor 32 is driven by an electric motor. The electric compressor 32 supplies cathode gas to the fuel cell stack 21. In detail, the electric compressor 32 compresses the cathode gas supplied from the cathode gas inlet 31 and supplies the compressed cathode gas to the fuel cell stack 21. The cathode gas supplied from the electric compressor 32 to the fuel cell stack 21 flows through the cathode flow path 23.

[0019] The intercooler 33 is supplied with the cathode gas discharged from the electric compressor 32. The intercooler 33 cools the cathode gas supplied from the electric compressor 32. The cathode gas supplied to the fuel cell stack 21 is the cathode gas after being cooled by the intercooler 33.

[0020] The cathode supply path 34 connects the electric compressor 32 and the cathode flow path 23. More specifically, the cathode supply path 34 connects the electric compressor 32 and the inlet 24 of the cathode flow path 23. The cathode supply path 34 includes a first supply path 35 and a second supply path 36. The first supply path 35 connects the electric compressor 32 and the intercooler 33. The second supply path 36 connects the intercooler 33 and the cathode flow path 23.

[0021] The cathode exhaust channel 37 connects the cathode flow path 23 and the diluter 69. More specifically, the cathode exhaust channel 37 connects the outlet 25 of the cathode flow path 23 and the diluter 69. The cathode exhaust channel 37 is a passage through which the cathode exhaust gas flows. The cathode exhaust gas is cathode gas discharged from the fuel cell stack 21 and contains generated water. The generated water is water generated by power generation in the fuel cell stack 21.

[0022] The two sealing valves 40, 41 include a first sealing valve 40 and a second sealing valve 41. The first sealing valve 40 is provided in the cathode supply passage 34. In this embodiment, the first sealing valve 40 is provided in the second supply passage 36, i.e., between the intercooler 33 and the cathode flow passage 23. The first sealing valve 40 may be provided in the first supply passage 35, i.e., between the intercooler 33 and the electric compressor 32. The second sealing valve 41 is provided in the cathode discharge passage 37.

[0023] 2, the sealing valves 40 and 41 are butterfly valves. The sealing valves 40 and 41 include a body 42, a seal member 44, a valve body 48, a rotating shaft 51, a reduction gear mechanism 52, a motor 54, and a gear stopper 55.

[0024] The body 42 has a flow passage 43 penetrating the body 42. That is, the body 42 is cylindrical. The seal member 44 is provided in the flow path 43. The seal member 44 is made of, for example, rubber. The seal member 44 is annular. The seal member 44 includes a tapered portion 45. The tapered portion 45 is a portion in which the inner diameter becomes smaller from a first end 46 to a second end 47 in the axial direction of the seal member 44. The seal member 44 is provided along the inner circumferential surface of the body 42.

[0025] The valve body 48 is provided in the flow path 43. The valve body 48 includes a main body 49 and a connecting portion 50. The main body 49 is disk-shaped. The diameter of the main body 49 is smaller than the maximum inner diameter of the tapered portion 45 and is larger than the minimum inner diameter of the tapered portion 45.

[0026] The rotating shaft 51 is provided on the connecting portion 50. The valve body 48 moves with the rotation of the rotating shaft 51. The opening degree of the sealing valves 40, 41 is adjusted by the movement of the valve body 48 with the rotation of the rotating shaft 51. The opening degree when the sealing valves 40, 41 are fully closed is, for example, 0.5°. When the sealing valves 40, 41 are fully closed, the valve body 48 is in close contact with the seal member 44. This seals the flow path 43.

[0027] The reduction mechanism 52 includes a gear 53. The gear 53 is one of a plurality of gears included in the reduction mechanism 52. The reduction mechanism 52 transmits the driving force of the motor 54 to the rotating shaft 51 via a plurality of gears including the gear 53. This causes the rotating shaft 51 to rotate. The sealing valves 40, 41 include a spring that biases the valve body 48 in a direction in which the valve body 48 closes. The valve body 48 is held at a position where the force applied from the motor 54 to the rotating shaft 51 and the force from the spring are balanced. It can be said that the opening degree of the sealing valves 40, 41 can be adjusted by controlling the motor 54.

[0028] The gear stopper 55 restricts the rotation of the gear 53. When the rotating shaft 51 is rotated in the direction in which the valve body 48 closes, the gear 53 comes into contact with the gear stopper 55. The contact between the gear 53 and the gear stopper 55 also restricts the rotation of the rotating shaft 51. That is, the rotation of the rotating shaft 51 in the direction in which the valve body 48 closes is restricted at the position where the gear 53 comes into contact with the gear stopper 55. The fully closed state of the sealing valves 40, 41 is a state in which the gear 53 comes into contact with the gear stopper 55. The fully closed state of both of the two sealing valves 40, 41 seals the cathode flow path 23.

[0029] As shown in FIG. 1, the anode system 60 includes a tank 61 , an anode gas supply unit 62 , a supply path 63 , a circulation path 64 , a gas-liquid separator 65 , a circulation pump 66 , an exhaust / drain valve 67 , and a pressure sensor 68 .

[0030] The tank 61 stores the anode gas. Anode gas is supplied to the anode gas supply unit 62 from the tank 61. The anode gas supply unit 62 is a member for adjusting the amount of anode gas supplied to the fuel cell stack 21. The amount of anode gas supplied to the fuel cell stack 21 can be adjusted by controlling the anode gas supply unit 62. As the anode gas supply unit 62, for example, a solenoid valve such as an injector can be used.

[0031] The supply path 63 connects the anode gas supply unit 62 and the anode flow path 26. More specifically, the supply path 63 connects the anode gas supply unit 62 and the inlet 27 of the anode flow path 26. The anode gas injected from the anode gas supply unit 62 is supplied to the fuel cell stack 21 through the supply path 63.

[0032] The circulation path 64 connects the anode flow path 26 and the supply path 63. More specifically, the circulation path 64 connects the outlet 28 of the anode flow path 26 and the supply path 63. The anode exhaust gas flows through the circulation path 64. The anode exhaust gas contains unreacted anode gas and generated water. The circulation path 64 is a passage for returning the unreacted anode gas contained in the anode exhaust gas to the supply path 63.

[0033] The gas-liquid separator 65 is provided in the circulation path 64. The gas-liquid separator 65 separates the anode exhaust gas into anode gas and produced water. The produced water separated from the anode exhaust gas is stored in the gas-liquid separator 65.

[0034] The circulation pump 66 is provided in the circulation path 64. The circulation pump 66 supplies the anode gas separated from the anode exhaust gas by the gas-liquid separator 65 to the supply path 63. This causes the anode gas to circulate.

[0035] The exhaust drain valve 67 is connected to the gas-liquid separator 65. The exhaust drain valve 67 can be switched between an open state and a closed state. When the exhaust drain valve 67 is in an open state, the generated water is discharged from the gas-liquid separator 65. When the exhaust drain valve 67 is in a closed state, the generated water cannot be discharged from the gas-liquid separator 65. That is, when the exhaust drain valve 67 is in a closed state, the generated water is stored in the gas-liquid separator 65. The exhaust drain valve 67 may be switched from a closed state to an open state when the amount of generated water stored in the gas-liquid separator 65 exceeds a threshold value. The exhaust drain valve 67 may be switched from a closed state to an open state at predetermined time intervals.

[0036] The gas-liquid separator 65 is connected to a diluter 69. When the exhaust drain valve 67 is opened, the produced water stored in the gas-liquid separator 65 and the anode exhaust gas are supplied to the diluter 69. The diluter 69 dilutes the anode exhaust gas with the cathode exhaust gas and discharges it into the atmosphere.

[0037] The pressure sensor 68 is provided in the supply path 63. The pressure sensor 68 detects the pressure in the supply path 63. The supply path 63, the anode flow path 26, and the circulation path 64 are connected to each other. For this reason, the supply path 63, the anode flow path 26, and the circulation path 64 can be considered to have the same pressure.

[0038] The cooling system 70 includes a refrigerant circulation path 72, a heat exchanger 73, a fan 74, a refrigerant pump 75, and a temperature measuring unit 76. The coolant circulation path 72 connects the fuel cell stack 21 and a heat exchanger 73. The heat exchanger 73 is, for example, a radiator. A coolant circulates through the coolant circulation path 72. For example, water, antifreeze, or air is used as the coolant.

[0039] The fan 74 blows air toward the heat exchanger 73. The air blown from the fan 74 cools the refrigerant inside the heat exchanger 73. The coolant pump 75 circulates the coolant through the coolant circulation path 72. The coolant cooled in the heat exchanger 73 is supplied to the fuel cell stack 21 through the coolant circulation path 72, whereby the fuel cell stack 21 is cooled.

[0040] The temperature measurement unit 76 measures the temperature of the coolant. The temperature measurement unit 76 may be provided to measure the temperature of the coolant before heat exchange with the fuel cell stack 21, or may be provided to measure the temperature of the coolant after heat exchange with the fuel cell stack 21.

[0041] The control device 80 includes a processor 81 and a storage unit 82. The storage unit 82 includes a random access memory (RAM) and a read only memory (ROM). The storage unit 82 stores program codes or instructions configured to cause the processor 81 to execute processes. The storage unit 82, i.e., the computer-readable medium, includes any available medium accessible by a general-purpose or special-purpose computer. The control device 80 may be configured by a hardware circuit such as an ASIC or an FPGA. The control device 80, which is a processing circuit, may include one or more processors that operate according to a computer program, one or more hardware circuits such as an ASIC or an FPGA, or a combination thereof.

[0042] The control device 80 controls the fuel cell system 20. The control device 80 can adjust the opening degrees of the sealing valves 40, 41. More specifically, the control device 80 can adjust the opening degrees of the sealing valves 40, 41 by driving the motor 54. The control device 80 can switch the exhaust / drain valve 67 between an open state and a closed state.

[0043] The control device 80 can determine whether the key switch 13 is on or off. For example, when the key switch 13 is turned on, the vehicle control device mounted on the industrial vehicle 10 notifies the control device 80 that the key switch 13 is turned on. Similarly, when the key switch 13 is turned off, the vehicle control device mounted on the industrial vehicle 10 notifies the control device 80 that the key switch 13 is turned off. This allows the control device 80 to determine whether the key switch 13 is on or off.

[0044] The control device 80 switches between a power generation state of the fuel cell stack 21 and a power generation stop state of the fuel cell stack 21 depending on the state of the key switch 13. When the key switch 13 is on, the control device 80 puts the fuel cell stack 21 into a power generation state. When the key switch 13 is off, the control device 80 puts the fuel cell stack 21 into a power generation stop state. Turning the key switch 13 on is a power generation command to the fuel cell system 20. Turning the key switch 13 off is a power generation stop command to the fuel cell system 20.

[0045] When the fuel cell stack 21 is in a power generating state, the control device 80 controls the power generation of the fuel cell stack 21. The control device 80 sets a target value for the amount of power generation of the fuel cell stack 21, i.e., a target value for the output of the fuel cell stack 21. The control device 80 can adjust the amount of cathode gas supplied to the fuel cell stack 21 by controlling the electric compressor 32. The control device 80 can adjust the amount of anode gas supplied to the fuel cell stack 21 by controlling the anode gas supply unit 62. The control device 80 controls so that the amount of power generation of the fuel cell stack 21 follows the target value. When the fuel cell stack 21 is in a power generating state, the opening degree of the sealing valves 40, 41 is, for example, 5° or more and less than 15°. The opening degree of the sealing valves 40, 41 is adjusted according to the flow rate of the cathode gas required for power generation in the fuel cell stack 21. In this case, the gear 53 and the gear stopper 55 are not in contact with each other.

[0046] Next, there will be described the sealing control performed by the control device 80. The sealing control is performed when the fuel cell stack 21 is in a power generating state. As shown in Fig. 3, in step S1, the control device 80 determines whether or not the industrial vehicle 10 has been keyed off. In other words, the control device 80 determines whether or not a power generation stop command has been received. If the determination result in step S1 is negative, the control device 80 performs the process of step S1 again. If the determination result in step S1 is positive, the control device 80 performs the process of step S2.

[0047] In step S2, the control device 80 brings the fuel cell stack 21 into a power generation stop state. The control device 80 stops the electric compressor 32 so that the cathode gas is not supplied to the fuel cell stack 21. Even when the fuel cell stack 21 is in a power generation stop state, power generation can be performed by the cathode gas remaining in the cathode flow path 23 and the anode gas remaining in the anode flow path 26. The power generation stop state refers to a state in which power generation by the fuel cell stack 21 is not intended. Therefore, power generation by reaction between the cathode gas remaining in the cathode flow path 23 and the anode gas remaining in the anode flow path 26 is permitted.

[0048] Next, in step S3, the control device 80 fills the anode gas into the anode flow passage 26 by controlling the anode gas supply unit 62. For example, the control device 80 fills the anode gas into the anode flow passage 26 until the pressure in the anode flow passage 26 detected by the pressure sensor 68 reaches a predetermined pressure.

[0049] Next, in step S4, the control device 80 seals the anode flow passage 26. The sealing of the anode flow passage 26 is performed by maintaining the exhaust / drain valve 67 in a closed state. By sealing the anode flow passage 26, the anode flow passage 26 is maintained in a state filled with anode gas. The process of step S4 may be performed before the process of step S3.

[0050] Next, in step S5, the control device 80 sets the sealing valves 40, 41 to the minimum opening. The minimum opening is an opening smaller than the opening when the fuel cell stack 21 is in a power generating state. More specifically, the minimum opening is smaller than the minimum value of the opening that the sealing valves 40, 41 can have when the fuel cell stack 21 is in a power generating state. The minimum opening is, for example, 1° or more and less than 5°. The control device 80 may control the motor 54 so that the sealing valves 40, 41 are at the minimum opening. The control device 80 may stop the motor 54 so that the sealing valves 40, 41 are at the minimum opening. When the motor 54 is stopped, no force is applied to the rotating shaft 51, and the opening of the sealing valves 40, 41 is reduced by the spring. This allows the sealing valves 40, 41 to be at the minimum opening. When the sealing valves 40, 41 are at the minimum opening, the gear 53 and the gear stopper 55 do not come into contact with each other. The minimum opening is set so that the gear 53 and the gear stopper 55 do not come into contact with each other. When the sealing valves 40, 41 are at the minimum opening, the cathode gas is permitted to flow through the flow path 43. Therefore, the cathode gas flows into the cathode flow path 23. When the sealing valves 40, 41 are at the minimum opening, the valve body 48 and the seal member 44 come into contact with each other depending on the opening, but the degree of contact between the valve body 48 and the seal member 44 is lower than the degree of contact when the sealing valves 40, 41 are fully closed. The process of step S5 is the minimum opening control.

[0051] Next, in step S6, the control device 80 measures the key-off time during which the key switch 13 is maintained off. In other words, the control device 80 measures the time since receiving a power generation stop command.

[0052] Next, in step S7, the control device 80 judges whether or not the key is turned on. If the judgment result of step S7 is positive, the control device 80 performs the process of step S11. If the judgment result of step S7 is negative, the control device 80 performs the judgment of step S8.

[0053] In step S8, the control device 80 judges whether the key-off time has elapsed a predetermined time. It can also be said that the control device 80 judges whether the predetermined time has elapsed since receiving a power generation stop command. The predetermined time may be arbitrarily set by the user, or may be determined according to the object on which the fuel cell system 20 is mounted. In the industrial vehicle 10, the key may be turned off and on repeatedly in a short period of time. For example, in the case of a forklift, the key may be turned off and on for each of various tasks, such as loading, unloading, checking the state of the load, and checking the surroundings. In this way, assuming a situation in which the key is turned off and on in a short period of time, the predetermined time may be set so that the judgment result of step S8 is not positive in a situation in which the key is turned off and on in a short period of time. The predetermined time can be arbitrarily set between 30 seconds and 5 minutes, for example. If the judgment result of step S8 is negative, the control device 80 returns to the processing of step S6. If the judgment result of step S8 is positive, the control device 80 performs the processing of step S9.

[0054] In step S9, the control device 80 fully closes the sealing valves 40, 41. The full closure of the sealing valves 40, 41 is performed by controlling the motor 54. The full closure of the sealing valves 40, 41 is performed by bringing the gear 53 into contact with the gear stopper 55 to forcibly stop the valve body 48. The process of step S9 is the full closure control. It can be said that the control device 80 performs the full closure control when it does not receive a power generation command within a predetermined time after receiving a power generation stop command.

[0055] Next, in step S10, the control device 80 stops the fuel cell system 20. Stopping the fuel cell system 20 means, for example, putting the control device 80 into a sleep state. In the sleep state, the functions of the control device 80 are reduced to a minimum. After completing the process of step S10, the control device 80 ends the sealing control.

[0056] In step S11, the control device 80 starts power generation in the fuel cell stack 21 by putting the fuel cell stack 21 into a power generation state. If the key is turned on before the key-off time has elapsed for a predetermined time, the control device 80 returns the fuel cell stack 21 to the power generation state. If the control device 80 receives a power generation command before the predetermined time has elapsed since receiving a power generation stop command, it can be said that the control device 80 puts the fuel cell stack 21 into the power generation state without performing full-closure control. After completing the processing of step S11, the control device 80 ends the sealing control.

[0057] The operation of this embodiment will be described. When the fuel cell stack 21 is brought into a power generation stop state by key-off, the anode gas is supplied from the anode gas supply unit 62 to fill the anode flow path 26 with anode gas. For example, the control device 80 fills the anode flow path 26 with anode gas until the pressure of the anode flow path 26 detected by the pressure sensor 68 reaches a predetermined pressure. This predetermined pressure is set so that the cathode gas can be consumed to an extent that no cross leakage occurs after the sealing valves 40, 41 are fully closed, even if a predetermined time has elapsed with the sealing valves 40, 41 in a state of minimal opening. The control device 80 sets the opening degree of the sealing valves 40, 41 to the minimal opening degree. When the sealing valves 40, 41 are at the minimal opening degree, the cathode gas is less likely to flow into the cathode flow path 23 than when the fuel cell stack 21 is in a power generation state. When the sealing valves 40, 41 are fully closed, the amount of cathode gas remaining in the cathode flow path 23 can be reduced. After the sealing valves 40, 41 are fully closed, the anode gas remaining in the anode flow path 26 reacts with the cathode gas remaining in the cathode flow path 23. Since the anode gas is filled in the anode flow path 26, the cathode gas can be consumed by the anode gas. In detail, when the anode gas is filled, the anode gas is filled so that the cathode gas can be consumed to an extent that does not cause cross leakage, based on the flow rate of the cathode gas flowing into the cathode flow path 23 during a predetermined time. In this way, the cathode gas remaining in the cathode flow path 23 after the sealing valves 40, 41 are fully closed can be consumed.

[0058] The effects of this embodiment will be described. (1) When the power generation of the fuel cell stack 21 is stopped, the anode gas is filled into the anode flow passage 26. The anode gas filled into the anode flow passage 26 can consume the cathode gas without causing cross leakage. This makes it possible to suppress deterioration of the power generation performance of the fuel cell stack 21.

[0059] Furthermore, since the full-closing control is performed after the minimum opening control, if the power generation of the fuel cell stack 21 starts between the minimum opening control and the full-closing control, the sealing valves 40, 41 are not fully closed. The full-closing of the sealing valves 40, 41 is performed by bringing the valve body 48 or a member required to move the valve body 48 into contact with another member. In the case of the sealing valves 40, 41 described in the embodiment, the full-closing is performed by bringing the gear 53 into contact with the gear stopper 55. Thus, since the full-closing of the sealing valves 40, 41 involves the contact between the valve body 48 or a member required to move the valve body 48 and another member, if the sealing valves 40, 41 are fully closed frequently, this causes the sealing valves 40, 41 to deteriorate. By performing the full-closing control after the minimum opening control, the frequency of the full-closing of the sealing valves 40, 41 can be reduced. This makes it possible to suppress deterioration of the sealing valves 40, 41.

[0060] (2) The control device 80 performs full-close control if the key is not turned on within a predetermined time after the key is turned off. If the key is turned on within the predetermined time, the control device 80 does not perform full-close control of the sealing valves 40, 41. This makes it possible to suppress deterioration of the sealing valves 40, 41.

[0061] In particular, when the fuel cell system 20 is mounted on an industrial vehicle 10, there are cases where key-off and key-on are repeated within a short period of time. By assuming such a situation where key-off and key-on are repeated within a short period of time and setting a predetermined time such that full-close control is not performed in such a situation, deterioration of the sealing valves 40, 41 can be appropriately suppressed.

[0062] (3) The sealing valves 40, 41 have low accuracy in opening and closing operations. For this reason, when the sealing valves 40, 41 are fully closed, the gear 53 is brought into contact with the gear stopper 55, which is achieved by this. In the minimum opening control, the gear 53 does not come into contact with the gear stopper 55. By performing the minimum opening control followed by the full closing control, the frequency with which the gear 53 comes into contact with the gear stopper 55 can be reduced. This makes it possible to suppress deterioration of the sealing valves 40, 41.

[0063] The embodiment can be modified as follows: The embodiment and the following modified examples can be combined with each other to the extent that there is no technical contradiction. Valves other than butterfly valves may be used as the sealing valves 40 and 41. For example, globe valves or gate valves may be used as the sealing valves 40 and 41.

[0064] The control device 80 may perform the full-closing control when the pressure of the anode flow path 26 drops by a predetermined value or more after the anode gas is filled into the anode flow path 26. Since the sealing valves 40 and 41 are opened to a minimum extent, the cathode gas flows into the cathode flow path 23. Therefore, even after the anode gas is filled into the anode flow path 26, the anode gas is consumed by reaction with the cathode gas. The pressure of the anode flow path 26 decreases over time. By performing the full-closing control when the pressure of the anode flow path 26 drops by a predetermined value or more after the anode gas is filled into the anode flow path 26, the same effect as in the embodiment can be obtained. The predetermined value is set to a value at which the cathode gas remaining in the cathode flow path 23 can be consumed to such an extent that no cross leak occurs when the sealing valves 40 and 41 are fully closed.

[0065] The control device 80 may perform full-close control when the temperature of the coolant drops by a predetermined temperature or more after the key-off is performed. During power generation in the fuel cell stack 21, the temperature of the coolant becomes higher than the outside air temperature. Therefore, when the fuel cell stack 21 stops generating power as a result of the key-off, the temperature of the coolant drops over time. By performing full-close control when the temperature of the coolant drops by a predetermined temperature or more after the key-off is performed, the same effect as in the embodiment can be obtained. The predetermined temperature is set to a value at which the cathode gas remaining in the cathode flow path 23 can be consumed to such an extent that no cross leak occurs when the sealing valves 40, 41 are fully closed.

[0066] The control device 80 may control the sealing valves 40, 41 to the minimum opening degree and then fill the anode gas into the anode flow passage 26. That is, the process of step S5 may be performed before the process of step S3.

[0067] The fuel cell system 20 may be installed in a passenger vehicle, a ship, a train, or the like. The fuel cell system 20 may be used as a stationary power generation device. The power generation stop command to the control device 80 can be issued by any operation of the user, not limited to turning off the key. For example, the power generation stop command may be input to the control device 80 by operating a lever, switch, push button, touch panel, or the like provided on the fuel cell system 20. The power generation stop command may be input to the control device 80 by operating the terminal carried by the user by connecting the control device 80 to a terminal carried by the user so as to be capable of communicating with each other by wire or wirelessly. Similarly, the power generation command to the control device 80 can be issued by any operation of the user. [Explanation of symbols]

[0068] 20 fuel cell system, 21 fuel cell stack, 23 cathode flow path, 26 anode flow path, 40, 41 sealing valve, 48 valve body, 53 gear, 55 gear stopper, 62 anode gas supply unit, 80 control device.

Claims

1. a fuel cell stack that generates electricity by a reaction between an anode gas and a cathode gas; an anode gas supply unit that supplies the anode gas to the fuel cell stack; A fuel cell system including a control device, The fuel cell stack comprises: an anode flow path to which the anode gas is supplied; a cathode flow path to which the cathode gas is supplied, The fuel cell system includes: a sealing valve that seals the cathode flow path and has an adjustable opening degree; The control device includes: filling the anode gas into the anode flow path by the anode gas supply unit when the power generation of the fuel cell stack is stopped; performing an extremely small opening control for setting the opening degree of the sealing valve to an extremely small opening degree that is smaller than the opening degree when the fuel cell stack is in a power generation stopped state; a full closure control for sealing off the cathode flow path by fully closing the sealing valve after the minimum opening control in the power generation stopped state of the fuel cell stack.

2. The control device includes: When a power generation stop command is received for the fuel cell system, the fuel cell stack is put into the power generation stop state; When a power generation command for the fuel cell system is received, the fuel cell stack is put into the power generation state; When the power generation command is not received within a predetermined time after the power generation stop command is received, the full-close control is performed.

2. The fuel cell system according to claim 1, wherein if the power generation command is received before the predetermined time has elapsed since the power generation stop command was received, the fuel cell stack is brought into the power generation state without performing the full closing control.

3. The sealing valve is Gears and A valve body that moves due to rotation of the gear; A gear stopper that restricts rotation of the gear, The control device includes: In the extremely small opening control, the gear and the gear stopper are not brought into contact with each other, 3. The fuel cell system according to claim 1, wherein in the full closing control, the gear is brought into contact with the gear stopper.

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