Fuel cell system and method for controlling a fuel cell system

Abstract

A fuel cell system (100) mounted on a vehicle (101), the fuel cell system (100) comprising: a fuel cell (10) configured to generate power by receiving a fuel gas and an oxidizing gas; a fuel gas supply unit (30) configured to supply the fuel gas to the fuel cell (10); a leakage sensor (25) configured to detect leakage of the fuel gas; a speed detector (22) configured to determine a speed of the vehicle (101); and a control device (20) configured to control the fuel gas supply unit (30), wherein the control device (20) is configured to perform leakage detection processing including: in a case where the speed of the vehicle (101) is greater than a predetermined threshold speed, stopping a supply of fuel gas to the fuel cell (10) or reducing a supply amount of the fuel gas to the fuel cell (10) if the leakage of the fuel gas is continuously detected during a predetermined first detection period; and in a case where the speed of the vehicle (101) is equal to or less than the threshold speed, stopping the supply of the fuel gas to the fuel cell (10) or reducing the supply amount of the fuel gas to the fuel cell (10) when the leakage of the fuel gas is continuously detected during a predetermined second detection period, wherein the second detection period is shorter than the first detection period.

Description

Background of the invention 1. Field of the invention

[0001] The present invention relates to a fuel cell system and a method for controlling the fuel cell system. 2. Description of the state of the art

[0002] For example, JP 2004-139842 A discloses a fuel cell system mounted in a vehicle that detects a leak of hydrogen supplied to the fuel cell as a fuel gas. DE 10 2019 117 852 A1 discloses a fuel gas supply control device, a fuel gas supply control method, and a method for starting a fuel cell vehicle.Here, a control unit is configured to determine a temporary anomaly and deactivate an electric valve when a signal input from a fuel gas sensor exhibits behavior that approaches a predetermined determination threshold before the predetermined unstable period elapses, and is configured to abort the determination of the temporary anomaly and open the electric valve when the signal from the fuel gas sensor is lower than a predetermined determination value within a predetermined period after the electric valve has been deactivated. A method for determining a fuel gas leak in a fuel cell system is also the subject of WO 2007 / 018 132 A1. Summary of the invention

[0003] When a fuel cell is installed in a vehicle, for example, in a state where airflow is unlikely to occur inside the vehicle, such as when the vehicle is stopped, the leaked fuel gas is likely to remain inside the vehicle. If detection of a fuel gas leak is delayed in such a state where airflow is unlikely to occur, the hydrogen leaked into the vehicle can remain in the vehicle for a shorter period of time than when the vehicle is traveling at high speed.

[0004] A technology of the present invention can be implemented with the aspects described below.

[0005] A first aspect of the present invention is a fuel cell system mounted on a vehicle. The fuel cell system includes a fuel cell configured to generate power by receiving a fuel gas and an oxidizing gas, a fuel gas supply unit configured to supply the fuel gas to the fuel cell, a leakage sensor configured to detect leakage of the fuel gas, a speed detector configured to detect the speed of the vehicle, and a control device configured to control the fuel gas supply unit.The control device is configured to perform leakage detection processing that includes stopping a supply of the fuel gas to the fuel cell or reducing a supply amount of the fuel gas to the fuel cell when the fuel gas leakage is continuously detected during a predetermined first detection period, in a case where the speed of the vehicle is greater than the predetermined threshold speed, and stopping the supply of the fuel gas to the fuel cell or reducing the supply amount of the fuel gas to the fuel cell when the fuel gas leakage is continuously detected during a predetermined second detection period, in a case where the speed of the vehicle is equal to or less than the threshold speed. The second detection period is shorter than the first detection period.

[0006] According to the fuel cell system of the above-described aspect, in a situation where the vehicle speed is low and the fuel gas leaked into the vehicle is likely to remain, based on a short-term determination using the second detection period, as a countermeasure against the fuel gas leakage, the fuel gas supply can be stopped at an earlier time or the supply amount of the fuel gas can be reduced at an earlier time. Thus, it is possible to contain the hydrogen leaked into the vehicle.

[0007] In a case where the fuel gas leakage is not detected before the period during which the fuel gas leakage is continuously detected exceeds a predetermined third detection period, the control device may resume the supply of the fuel gas to the fuel cell after stopping the supply of the fuel gas to the fuel cell if the vehicle speed is equal to or lower than the threshold speed and the fuel gas leakage is continuously detected during the second detection period. The third detection period is longer than the second detection period.

[0008] According to the fuel cell system of the above-described aspect, in a case where the leakage is not detected for a short period not exceeding the third detection period, the fuel gas supply is resumed even if the fuel gas leakage is erroneously detected and the fuel gas supply is stopped based on the short-term determination using the second detection period. Thus, the inconvenience to the user when the fuel gas supply is stopped due to such erroneous leakage detection is reduced.

[0009] The fuel cell system may further include a notification device configured to notify the user of the occurrence of fuel gas leakage. The control device may perform leakage countermeasure processing, which includes the processing of causing the notification device to notify the occurrence of fuel gas leakage in a case where the period during which the fuel gas leakage is continuously detected exceeds the third detection period, after the supply of fuel gas to the fuel cell is stopped when the speed of the vehicle is equal to or lower than the threshold speed and the fuel gas leakage is continuously detected during the second detection period.

[0010] According to the fuel cell system of the above-described aspect, as long as the period during which the fuel gas leakage is continuously detected does not exceed the third detection period, even if the fuel gas leakage is erroneously detected based on the short-term determination using the second detection period, the notification to the user is not performed. Thus, it is possible to curb a situation in which the occurrence of the fuel gas leakage is erroneously notified to the user.

[0011] The leakage countermeasure processing may include processing of terminating an operation of the fuel cell system.

[0012] According to the fuel cell system of the above-described aspect, it is possible to restrain a continuous operation of the fuel cell system while detecting the fuel gas leakage.

[0013] The fuel cell system may further include a secondary battery configured to store a portion of the power generated by the fuel cell. The control device may detect an acceleration operation of the vehicle by the user, perform an operation control for supplying the power of at least one of the fuel cell and the secondary battery to a drive power source of the vehicle in response to the acceleration operation, perform the leakage detection processing repeatedly in a predetermined control cycle while performing the operation control, and after the supply of the fuel gas to the fuel cell is stopped when the speed of the vehicle is equal to or lower than the threshold speed and the leakage of the fuel gas is continuously detected during the second detection period, the fuel gas supply to the fuel cell in a case,in which the acceleration process is detected before the period during which the leakage of the fuel gas is continuously detected exceeds the third detection period, to supply the power to the drive power source in response to the acceleration process and to accelerate the vehicle.

[0014] According to the fuel cell system of the above-described aspect, even if the fuel gas supply is stopped based on the short-term determination using the second detection period when the vehicle speed is low after the vehicle is accelerated by the user's acceleration operation, the fuel gas leakage is detected again under a determination condition according to the vehicle speed. Thus, it is possible to determine the fuel gas leakage by appropriately changing the determination condition according to the change in the vehicle speed. In addition, even after the gas supply is stopped, the fuel gas supply can be promptly resumed in response to the user's acceleration operation, so that the fuel cell promptly returns to a normal power generation state.This reduces the driving time that depends solely on the power output of the secondary battery, allowing the vehicle to accelerate smoothly.

[0015] The fuel gas supply unit includes a tank that stores the fuel gas, a main cutoff valve that controls an outflow of the fuel gas from the tank, and a supply device that adjusts the supply amount of the fuel gas to the fuel cell. The supply device is arranged on a downstream side of the main cutoff valve. The control device can, when the speed of the vehicle is greater than the threshold speed and the leakage of the fuel gas is continuously detected during the first detection period, stop the supply of the fuel gas to the fuel cell by closing the main cutoff valve, and, when the speed of the vehicle is equal to or less than the threshold speed and the leakage of the fuel gas is continuously detected during the second detection period, stop the supply of the fuel gas to the fuel cell by stopping the operation of the supply device without closing the main cutoff valve.

[0016] According to the fuel cell system of the above-described aspect, after the fuel gas supply is stopped, the fuel gas supply can be promptly and easily resumed by resuming the operation of the supply device when resumption of the fuel gas supply is determined. Furthermore, when the stoppage of the fuel gas supply is determined, the main cut valve is closed based on a higher-precision determination using the first detection period or the third detection period. Thus, the occurrence of a malfunction caused by fuel gas leakage can be further curbed.

[0017] A state where the speed of the vehicle is equal to or less than the threshold speed may be a state where the vehicle is stopped, and a state where the speed of the vehicle is greater than the threshold speed may be a state where the vehicle is traveling.

[0018] According to the fuel cell system of the above-described aspect, it is possible to take a countermeasure against the fuel gas leakage at an earlier time while stopping the vehicle and the leaked gas is more likely to remain in the vehicle.

[0019] A second aspect of the present invention is a method for controlling a fuel cell system. The fuel cell system is mounted in a vehicle and includes a fuel cell configured to generate power by receiving a fuel gas and an oxidizing gas, a leakage sensor configured to detect leakage of the fuel gas, a speed detector configured to detect the speed of a vehicle, and a control device configured to control the supply of the fuel gas to the fuel cell. The method includes a step of determining the speed of the vehicle by the speed detector, a step of detecting leakage of the fuel gas by the leakage sensor in a case where the speed of the vehicle is greater than a predetermined threshold speed,a step of stopping the supply of the fuel gas to the fuel cell or reducing a supply amount of the fuel gas to the fuel cell by the control device if the fuel gas leakage is continuously detected during a predetermined first detection period; and in a case where the speed of the vehicle is equal to or less than the threshold speed, a step of stopping the supply of the fuel gas to the fuel cell or reducing the supply amount of the fuel gas to the fuel cell by the control device if the fuel gas leakage is continuously detected during a predetermined second detection period. The second detection period is shorter than the first detection period.

[0020] The technology of the present invention can be implemented in various forms in addition to the fuel cell system and the method for controlling the fuel cell system. For example, the technology can be implemented in forms such as a vehicle equipped with a fuel cell system, a method for controlling a fuel gas supply unit, a countermeasure method when fuel gas leakage is detected, a control device or a computer program for implementing such methods, and a permanent recording medium that records such a computer program. Short description of the drawings

[0021] The features and advantages as well as the technical and economic significance of exemplary embodiments of the invention are described below with reference to the accompanying drawings in which like reference numerals designate like elements and in which: Fig. Figure 1 is a schematic diagram of a fuel cell system mounted in a vehicle; Fig. 2 is a schematic diagram showing an installation location of a leak detection unit in a vehicle; Fig. 3 is a flowchart explaining a flow of leakage detection processing according to a first embodiment; Fig. 4 is a flowchart explaining a flow of leakage detection processing according to a second embodiment; and Fig. 5 is a flowchart explaining a flow of leakage detection processing according to a third embodiment. Detailed description of the embodimentsFirst embodiment

[0022] Fig. 1 is a schematic diagram showing a configuration of a fuel cell system 100 according to a first embodiment. The fuel cell system 100 according to the first embodiment is mounted in a vehicle 101. The fuel cell system 100 includes a fuel cell 10 that generates power by receiving a fuel gas and an oxidizing gas, and supplies the power generated by the fuel cell 10 to a load device 110 mounted in the vehicle 101. The load device 110 includes, for example, a drive motor that is a drive power source, an electrical component, an auxiliary machine, or a connector used for power supply from outside the vehicle 101.

[0023] In the first embodiment, the fuel cell 10 is a solid polymer fuel cell that generates power through an electrochemical reaction between hydrogen as a fuel gas and oxygen as a fuel gas. The fuel cell 10 has a stacked structure in which a plurality of single cells 11 are stacked. Each of the single cells 11 is a power generation element capable of generating power even independently, and includes a membrane electrode assembly, which is a power generation body in which electrodes are arranged on both surfaces of an electrolyte membrane, and two separators that sandwich the membrane electrode assembly. The electrolyte membrane includes a thin solid polymer film that has good proton conductivity in a wet state where the electrolyte membrane contains moisture inside. An illustration of each component of the single cell 11 described above is omitted.Furthermore, the fuel cell 10 is not limited to a solid polymer electrolyte fuel cell, and various other types of fuel cells may be used. In other embodiments, for example, a solid oxide fuel cell may be used as the fuel cell 10.

[0024] The fuel cell system 100 includes a control unit 20 that controls operation of the vehicle 101 and power generation of the fuel cell 10. The control unit 20 includes an electronic control unit (ECU) that includes at least a processor and a primary storage device. A processor executes a program or instruction read from the primary storage device. Thus, the control unit 20 performs various functions for controlling power generation of the fuel cell 10. Additionally, at least part of the function of the control unit 20 may include a hardware circuit. In the first embodiment, the control unit 20 includes a storage unit 21 that stores information used for control in a non-volatile manner.

[0025] The control unit 20 performs operation control that detects an acceleration operation by a user using an accelerator pedal and the like (not shown), and, in response to the acceleration operation, supplies the power of at least one of the fuel cell 10 and a secondary battery 86, described below, to the drive motor included in the load device 110. Furthermore, the control unit 20 performs leakage detection processing that detects the leakage and takes countermeasures against the leakage of the fuel gas inside the vehicle 101. The leakage detection processing is described below.

[0026] The fuel cell system 100 further includes a speed detection unit 22, a leak detection unit 25, and a notification unit 28. The speed detection unit 22 detects the current speed of the vehicle 101 and outputs the current speed to the control unit 20. As described below, the control unit 20 uses a detection result of the speed of the vehicle 101 in the leak detection processing.

[0027] The leak detection unit 25 detects the fuel gas leakage inside the vehicle 101. In the first embodiment, the leak detection unit 25 includes, for example, an oxygen detector. The leak detection unit 25 determines the concentration of the fuel gas in the atmosphere inside the vehicle 101 and outputs the concentration to the control unit 20. If the concentration is higher than a predetermined threshold, the control unit 20 detects an occurrence of the fuel gas leakage. When the occurrence of the fuel gas leakage is detected, the control unit 20 measures the period during which the fuel gas leakage is continuously detected by the leak detection unit 25. In the leak detection processing, the control unit 20 determines whether the detected fuel gas leakage requires countermeasure based on the measured period. In the first embodiment, the leak detection unit 25 is installed at a plurality of locations inside the vehicle 101.An installation location of the leak detection unit 25 is described below.

[0028] Under the control of the control unit 20, the notification unit 28 notifies the user of the vehicle 101 that a fuel gas leak has been detected. The notification unit 28 includes, for example, a display unit, such as a display or indicator, arranged on the dashboard of the vehicle 101. The notification unit 28 may include a speaker that emits a warning sound or warning tone.

[0029] The fuel cell system 100 includes a fuel gas supply unit 30, a fuel gas circulation and discharge unit 40, and an oxidizing gas supply and discharge unit 50 as components that control the supply of reaction gas to the fuel cell 10. The fuel gas supply unit 30 supplies the fuel gas to the anode of the fuel cell 10. The fuel gas supply unit 30 includes a tank 31 that stores high-pressure fuel gas, a fuel gas pipe 32 that connects the tank 31 to the anode inlet of the fuel cell 10, a main shutoff valve 33, a regulator 34, and a supply device 35. The main shutoff valve 33, the regulator 34, and the supply device 35 are arranged in order from the upstream side, which is the side with the tank 31, on the fuel gas pipe 32.

[0030] The main shutoff valve 33 is formed with an electromagnetic valve that opens and closes under the control of the control unit 20. The main shutoff valve 33 controls the outflow of fuel gas from the tank 31. The regulator 34 is a pressure relief valve and, under the control of the control unit 20, adjusts the pressure inside the fuel gas pipe 32 on the upstream side of the supply device 35. The supply device 35 opens and closes regularly and sends fuel gas to the fuel cell 10. The supply device 35 includes, for example, an injector, which is an electromagnetically driven on-off valve that opens and closes at a set drive cycle. The control unit 20 adjusts the supply amount of fuel gas to the fuel cell 10 by controlling the drive cycle of the supply device 35.

[0031] The fuel gas circulation and discharge unit 40 circulates the fuel gas contained in the exhaust gas discharged from the anode of the fuel cell 10 to the fuel cell 10 and discharges waste water contained in the exhaust gas to the outside of the vehicle 101. The fuel gas circulation and discharge unit 40 includes an exhaust pipe 41, a gas / liquid separation unit 42, a circulation pipe 43, a circulation pump 44, a waste pipe 45, and a waste valve 46. The exhaust pipe 41 is connected to the anode outlet of the fuel cell 10 and the gas / liquid separation unit 42, and sends the exhaust gas, which includes the fuel gas that has not been used to generate power at the anode, and the waste water, to the gas / liquid separation unit 42 on the anode side.

[0032] The gas / liquid separation unit 42 separates a gas component and a liquid component from the exhaust gas flowing through the exhaust pipe 41 and stores the liquid component in a liquid state as the wastewater. The gas / liquid separation unit 42 is connected to the circulation pipe 43. The circulation pipe 43 connects the gas / liquid separation unit 42 and a portion downstream of the supply device 35 of the fuel gas pipe 32. The circulation pipe 43 further includes a circulation pump 44. The gas / liquid separation unit 42 sends the gas component separated from the exhaust gas to the circulation pipe 43. The circulation pump 44 sends the gas component containing the fuel gas sent to the circulation pipe 43 to the fuel gas pipe 32.

[0033] The wastewater pipe 45 is connected to a storage unit in which the wastewater from the gas / liquid separation unit 42 is stored. The wastewater pipe 45 has a wastewater valve 46 that opens and closes under the control of the control unit 20. The control unit 20 closes the wastewater valve 46 and normally opens the wastewater valve 46 at a predetermined time, so that the wastewater stored in the gas / liquid separation unit 42 is discharged to the outside of the vehicle 101 through the wastewater pipe 45.

[0034] The oxidizing gas supply and discharge unit 50 supplies oxygen contained in the air admitted into the interior of the vehicle 101 as an oxidizing gas to the fuel cell 10 through the radiator grille of the vehicle 101. The oxidizing gas supply and discharge unit 50 includes a supply pipe 51, a compressor 52, and an on-off valve 53. The supply pipe 51 is connected to the cathode inlet of the fuel cell 10. The compressor 52 and the on-off valve 53 are arranged in the supply pipe 51. The compressor 52 sends compressed gas obtained by compressing the air taken in from outside the vehicle 101 to the cathode of the fuel cell 10 through the supply pipe 51. The on-off valve 53 is normally in a closed state and is opened by compressing the compressed gas sent from the compressor 52, so that the compressed gas is allowed to flow into the fuel cell 10.

[0035] The oxidizing gas supply and discharge unit 50 discharges exhaust gas discharged from the cathode of the fuel cell 10 to the outside of the vehicle 101. The oxidizing gas supply and discharge unit 50 includes an exhaust pipe 56 and a pressure regulating valve 58. The exhaust pipe 56 is connected to the cathode outlet and discharges the exhaust gas discharged from the cathode of the fuel cell 10 to the outside of the vehicle 101. The pressure regulating valve 58 is arranged in the exhaust pipe 56 and adjusts the recompression on the cathode side of the fuel cell 10 under the control of the control unit 20.

[0036] The fuel cell system 100 includes a first converter 81, an inverter 83, a second converter 85, and the secondary battery 86 as components that control the power supplied to the load device 110. The fuel cell 10 is connected to an input terminal of the first converter 81 via a first DC conductor L1. The first converter 81 amplifies an output voltage of the fuel cell 10 under the control of the control unit 20.

[0037] An output terminal of the first converter 81 is connected to a DC terminal of the inverter 83 via a second DC conductor L2. The above-described load device 110 is connected to an AC terminal of the inverter 83. The inverter 83 performs a conversion between direct current and alternating current. The secondary battery 86 is connected to the second DC conductor L2 via the second converter 85. The secondary battery 86 includes, for example, a lithium-ion battery. The secondary battery 86 accumulates a portion of the power generated by the fuel cell 10 or regenerative power generated by the load device 110. Together with the fuel cell 10, the secondary battery 86 functions as a power source of the fuel cell system 100 under the control of the control unit 20.The control unit 20 controls an output current of the fuel cell 10 and the charging and discharging of the secondary battery 86 by means of the two converters 81, 85. Furthermore, the control unit 20 controls the frequency and voltage of a three-phase alternating current supplied to the load device 110 by means of the inverter 83.

[0038] Fig. 2 is a schematic diagram showing the installation location of the leak detection unit 25 in the vehicle 101. The interior of the vehicle 101 is divided into a vehicle cabin 102 in which the user sits, a front area 103 in front of the vehicle cabin 102, and a rear area 104 behind the vehicle cabin 102. In the first embodiment, the front area 103 includes the fuel cell 10 and the supply device 35 of the fuel supply unit 30. Furthermore, the rear area 104 includes a tank 31 of the fuel gas supply unit 30. The leak detection unit 25 is arranged in both the front area 103 and the rear area 104. The control unit 20 detects the fuel gas leakage near the supply device 35 through the leakage detection unit 25 of the front section 103 and detects the fuel gas leakage near the tank 31 through the leakage detection unit 25 in the rear section 104.Additionally, in another embodiment, the leak detection unit 25 may be arranged only in the front region 103 or in the rear region 104. The leak detection unit 25 may be arranged only in an installation region of the tank 31 or may be arranged only in an installation region of the fuel cell 10 or an installation region of the supply device 35.

[0039] Fig. 3 is a flowchart illustrating a flow of leak detection processing according to the first embodiment. When the user activates or starts the vehicle 101 and the fuel cell system 100 through an activation operation or a startup operation, the control unit 20 repeatedly executes the leak detection processing at a predetermined control cycle. When the user terminates the vehicle 101 and the fuel cell system 100 through a termination operation, the leak detection processing is repeated until the operation of the vehicle 101 and the fuel cell system 100 is stopped.

[0040] In step S10, the control unit 20 performs a vehicle speed determination to determine whether the vehicle 101 is currently in a low-speed state. The control unit 20 learns the current speed of the vehicle 101 from the speed determination unit 22 and compares the learned speed of the vehicle 101 with a predetermined threshold speed. The control unit 20 determines that the vehicle 101 is in a low-speed state when the speed of the vehicle 101 is equal to or less than the threshold speed, and determines that the vehicle 101 is not in the low-speed state when the speed of the vehicle 101 is greater than the threshold speed.

[0041] In addition, the low-speed state of the vehicle 101 in the present specification includes a state where the vehicle 101 is stopped at a speed of approximately 0 km / h. In the present specification, the term "approximately" means that speed A is substantially equal to speed B, and an error range between them is, for example, approximately 0 to 5%. Furthermore, the "state where the vehicle 101 is stopped" refers to a state where the vehicle 101 can travel by releasing the brake without the user's starting operation of the vehicle 101. The state where the vehicle 101 is stopped does not include a state where the travel of the vehicle 101 is stopped by the user's stopping operation, so that the vehicle 101 is completely stopped.In the first embodiment, the threshold speed is 0 km / h, and the control unit 20 determines that the vehicle 101 is in the low-speed state when the vehicle 101 is stopped. Furthermore, in another embodiment, the threshold speed may not be 0 km / h and may be set to a value of 0 km / h or higher and 20 km / h or lower, for example.

[0042] When the vehicle 101 is not in the low-speed state, the control unit 20 determines in step S20 whether the fuel gas leakage is continuously detected by the leakage detection unit 25 during a predetermined first detection period. The first detection period may be, for example, approximately 1 to 5 seconds. As described above, in the first embodiment, when the leakage detection unit 25 detects that the fuel gas concentration is greater than the predetermined threshold, the fuel gas leakage is detected, and the control unit 20 measures the period during which the fuel gas leakage is continuously detected. In step S20, if the fuel gas leakage is continuously detected during the first detection period, the control unit 20 determines that the fuel gas leakage requires countermeasure and performs the countermeasure processing in steps S50 and S60.Moreover, in the first embodiment, the control unit 20 performs the processing of steps S50 and S60 when the fuel gas leakage is continuously detected in at least one of a plurality of leakage detection units 25 during the first detection period.

[0043] In step S50, the control unit 20 stops the fuel gas supply to the fuel cell 10 through the fuel gas supply unit 30. In the first embodiment, the fuel gas supply is stopped by closing the main cutoff valve 33. Thus, an inflow of the fuel gas from the tank 31 to the fuel gas pipe 32 is blocked, and the progress of the fuel gas leakage is thus contained. Further, in another embodiment, the fuel gas supply may be stopped by stopping the power supply to the supply device 35, so that the driving of the supply device 35 is stopped. Moreover, the fuel gas supply may be stopped by closing the main cutoff valve 33 and stopping the driving of the supply device 35. In addition, even after the fuel gas supply is stopped, the vehicle 101 can be maintained in a state where it can travel using the power of the secondary battery 86.

[0044] As the countermeasure processing against the fuel gas leakage, the control unit 20 performs the leakage countermeasure processing in step S60 in addition to the processing of stopping the fuel gas supply in step S50. As the leakage countermeasure processing, the control unit 20 performs notification processing in which the user is notified of the occurrence of the fuel gas leakage by means of the notification unit 28. Further, the control unit 20 performs recording processing in which the occurrence of the fuel gas leakage requiring countermeasure is recorded as error information in a non-volatile manner in the storage unit 21 as the leakage countermeasure processing. In addition, the control unit 20 performs the processing in which the operation of the fuel cell system 100 is terminated or processing that prohibits the vehicle 101 from driving as the leakage countermeasure processing.After performing the leakage countermeasure processing, the control unit 20 ends the leakage detection processing of the current cycle.

[0045] In step S20, if the fuel gas leakage is not detected by the leakage detection unit 25 or if the period during which the fuel gas leakage is continuously detected is shorter than the first detection period, the control unit 20 ends the leakage detection processing of the current cycle as it is. Then, the control unit 20 starts the leakage detection processing of the next cycle.

[0046] If it is determined in step S10 that the vehicle 101 is in the low-speed state, the control unit 20 determines in step S30 whether the fuel gas leak is continuously detected during a second detection period. The second detection period is shorter than the first detection period. The second detection period may be approximately 200 to 800 milliseconds, for example.

[0047] In step S30, if the fuel gas leakage is continuously detected during the second detection period, the control unit 20 determines that the fuel gas leakage requiring countermeasure has occurred and performs the processing of steps S50 and S60 in a manner similar to the above description. Meanwhile, if the fuel gas leakage is not detected or if the period during which the fuel gas leakage is continuously detected is shorter than the second detection period, the control unit 20 ends the leakage detection processing of the current cycle and starts the leakage detection processing of the next cycle.

[0048] As described above, in the leakage detection processing of the first embodiment, when the vehicle 101 is in the low-speed state, it is determined whether the fuel gas leakage is serious in a short period of time using the second detection period, which is shorter than the first detection period, as the determination condition. When the vehicle 101 is in the low-speed state, there is less airflow generated by running in the vehicle 101, and the leaked fuel gas is likely to remain in the vehicle 101 than when the vehicle 101 is not in the low-speed state. After the leakage detection processing of the first embodiment, the countermeasure against the fuel gas leakage is performed at an earlier timing in a situation where the leaked fuel gas is likely to remain. Thus, an occurrence of a malfunction caused by the leaked fuel gas remaining is restrained.Specifically, in the first embodiment, the countermeasure against the fuel gas leakage is performed at an early stage in a situation where the vehicle 101 is stopped and the leaked fuel gas is more likely to remain. Thus, a better effect can be achieved. Second embodiment

[0049] Fig. Fig. 4 is a flowchart explaining a flow of the leak detection processing according to the second embodiment. The leak detection processing according to the second embodiment is implemented in the fuel cell system 100 shown in Fig. 1, which has the same configuration as the fuel cell system 100 described in the first embodiment. The leak detection processing according to the second embodiment is substantially the same as the leak detection processing according to the first embodiment, except that steps S32, S40, and S42 are added. The processing after it is determined in step S10 that the vehicle 101 is not in the low-speed state is substantially the same as the processing according to the first embodiment.

[0050] If it is determined in step S10 that the vehicle 101 is in the low-speed state, and the fuel gas leakage is continuously detected in step S30 during the second detection period, the control unit 20 causes the fuel gas supply unit 30 to stop the fuel gas supply to the fuel cell 10 in step S32. In the second embodiment, the control unit 20 stops the fuel gas supply to the fuel cell 10 by stopping the power supply to the supply device 35 without closing the main cut valve 33. Thus, the progress of the fuel gas leakage caused by the malfunction of the control of the supply device 35 and the like is contained. In addition, the processing in which the fuel gas supply is stopped is temporarily performed at this time as an emergency measure in anticipation of a possibility that the fuel gas supply to the fuel cell 10 will resume.This is because the fuel gas leakage detected at this time may be erroneously detected due to, for example, a noise signal from the leakage detection unit 25, or may be recovered a short time later. In addition, the vehicle 101 can travel using the power of the secondary battery 86 even after the fuel gas supply is stopped.

[0051] After stopping the fuel gas supply in step S32, the control unit 20 determines in the subsequent step S40 whether the period during which the fuel gas leakage is continuously detected after the leakage is detected by the leakage detection unit 25 exceeds a predetermined third detection period. The third detection period is longer than the second detection period, which is the determination condition in step S30. The third detection period may be equal to or shorter than the first detection period, which is the determination condition in step S20. The third detection period may be, for example, 1 to 5 seconds. In the second embodiment, the third detection period is equal to the first detection period.In step S40, when the period during which the fuel gas leakage is continuously detected by the leakage detection unit 25 exceeds the third detection period, the control unit 20 determines that the fuel gas leakage requiring the countermeasure is occurring and performs the processing of step S50. In step S50, the control unit 20 stops the fuel gas supply to the fuel cell 10 by closing the main shutoff valve 33. Thus, the flow of the fuel gas from the tank 31 to the fuel gas pipe 32 is blocked, thus further restraining the progress of the fuel gas leakage. The control unit 20 further performs the leakage countermeasure processing of step S60 described in the first embodiment.

[0052] If the fuel gas leakage is not detected in step S40 before the period during which the fuel gas leakage is continuously detected exceeds the third detection period, the control unit 20 causes the fuel gas supply unit 30 to resume the fuel gas supply to the fuel cell 10 in step S42. This is because the fuel gas leakage detected in step S30 is deemed to have been erroneously detected as described above or to have been resolved after detection. At this time, the fuel gas supply to the fuel cell 10 is stopped simply by stopping the power supply to the supply device 35. Thus, the fuel gas supply to the fuel cell 10 can be resumed by resuming the power supply to the supply device 35 in a simple, easy, and prompt manner.Thus, the fuel cell 10 can return to a normal power generation state, and the vehicle 101 can be driven normally using the power generated by the fuel cell 10 and the power of the secondary battery 86. After the above-described processing, the control unit 20 ends the leakage countermeasure processing of the current cycle.

[0053] As described above, in the leakage detection processing according to the second embodiment, determinations are made in two stages in steps S30 and S40 when the vehicle 101 is in the low-speed state. After the leakage detection processing according to the second embodiment, a countermeasure against the fuel gas leakage can be taken at an early time based on the short-term determination using the second detection period in step S30 as the determination condition. In addition, even if, for example, an erroneous determination caused by the noise occurring in the leakage detection unit 25 occurs in step S30, the occurrence of the fuel gas leakage is determined again based on the determination using the third detection period in the subsequent step S40.Thus, the reliability of the fuel gas leakage determination in the leakage detection processing is optimized. Furthermore, in the leakage detection processing according to the second embodiment, if the fuel gas leakage is not detected after the fuel gas supply is stopped, the fuel gas supply is resumed even if the fuel gas supply is stopped based on the short-term determination using the first detection period. Therefore, a period during which a drive torque of the vehicle 101 is insufficient and a driving performance of the vehicle 101 is reduced, resulting from the insufficient power from the fuel cell 10 due to the fuel gas supply to the fuel cell 10 being stopped, is shortened. Thus, inconvenience to the user is reduced.Furthermore, in the leakage detection processing according to the second embodiment, since the fuel gas supply to the fuel cell 10 can be resumed by resuming the power supply to the supply device 35 in step S42, it is possible for the vehicle 101 to return to a normal running state in a simple, easy, and prompt manner. Thus, the period of time during which the running performance of the vehicle 101 is reduced as described above is further reduced. In addition, in the leakage detection processing according to the second embodiment, when it is determined that the fuel gas leakage is occurring for a longer period based on the determination using the third detection period in step S40, the processing of a countermeasure against the fuel gas leakage is appropriately performed in steps S50 and S60. Thus, the progress of the malfunction caused by the fuel gas leakage can be contained.In addition, with the fuel cell system 100 and a method thereof according to the second embodiment, various functions and effects similar to those described in the first embodiment can be achieved. Third embodiment

[0054] Fig. Fig. 5 is a flowchart explaining a flow of leak detection processing according to a third embodiment. The leak detection processing according to the third embodiment is implemented in the fuel cell system 100 shown in Fig. 1, which has the same configuration as the fuel cell system 100 described in the first embodiment. The leak detection processing according to the third embodiment is substantially the same as the leak detection processing according to the second embodiment, except that steps S35 and S36 are added after step S32.

[0055] In the leakage detection processing according to the third embodiment, when the acceleration operation of the vehicle 101 is determined as described below, the fuel gas supply to the fuel cell 10 is resumed even after the fuel gas supply is stopped in step S32 and before the determination of step S40 is performed. If the acceleration operation of the vehicle 101 is determined by the user in step S35 before the period during which the fuel gas leakage is continuously detected by the leakage detection unit 25, the control unit 20 starts accelerating the vehicle 101 using the power of the secondary battery 86 in step S36. Then, in step S42, the control unit 20 resumes the power supply to the supply device 35 to resume the fuel gas supply to the fuel cell 10, in a manner similar to the manner described in the second embodiment.Thus, the power generated by the fuel cell 10 can be used in addition to the power of the secondary battery 86 for accelerating the vehicle 101. Thus, the period during which the drive torque is insufficient and the driving performance of the vehicle 101 is thus reduced.

[0056] When the fuel gas supply resumes, the control unit 20 begins the leakage detection processing of the next cycle. Thus, if the fuel gas leakage is still continuously detected even after the acceleration of the vehicle 101, it is determined that the fuel gas leakage is occurring for a longer period exceeding the first detection period or the third detection period in the leakage detection processing of the next cycle. In this case, appropriate countermeasures against the fuel gas leakage are performed in steps S50 and S60.

[0057] As described above, with the leak detection processing according to the third embodiment, the vehicle 101 can return to its normal running state in a shorter period of time when the fuel gas supply stoppage in step S32 is caused by erroneous detection by the leak detection unit 25 or a minor fuel gas leak. In addition, with the fuel cell system 100 and a method thereof according to the third embodiment, various functions and effects similar to those described in the first embodiment and the second embodiment can be obtained. Other embodiments

[0058] The various configurations described in the preceding embodiments can be modified, for example, as below. Similar to each of the preceding embodiments, all other embodiments described below are examples of aspects for implementing the technology of the present invention. Other embodiment 1

[0059] The installation location of the leak detection unit 25 is not limited to the location described in the above embodiment. For example, the leak detection unit 25 may be installed at a location where there is a connection point to the fuel gas pipe 32. The leak detection unit 25 may be arranged only at a location in the vehicle 101. Unlike the method of detecting the concentration of the fuel gas, the leak detection unit 25 may monitor the occurrence of fuel gas leakage. For example, the leak detection unit 25 may detect the occurrence of fuel gas leakage from the fuel gas pipe 32 by monitoring a change in the pressure in the fuel gas pipe 32. Other embodiment 2

[0060] In each of the embodiments described above, the vehicle 101 does not need to use the power generated by the fuel cell 10 for driving. In other words, the load device 110 to which the power generated by the fuel cell 10 is supplied does not need to include the driving power source of the vehicle 101. Other embodiment 3

[0061] In each of the embodiments described above, the supply amount of the fuel gas may be reduced in the processing in which the fuel gas supply is stopped in steps S32 and S50, instead of stopping the fuel gas supply to the fuel cell 10. In the leakage detection processing according to the second embodiment and the third embodiment, the processing in which the fuel gas supply is stopped in step S50 may be omitted after step S40. In this case, the leakage countermeasure processing in step S60 is performed while the fuel gas supply is stopped by stopping the drive of the supply device 35. Further, in the leakage detection processing according to the second embodiment and the third embodiment, the control unit 20 may stop the fuel gas supply to the fuel cell 10 by closing the main cut valve 33 in step S32. Other embodiment 4

[0062] In the leakage detection processing according to each of the above-described embodiments, the control unit 20 may change the method for stopping the gas supply depending on the location where the fuel gas leakage is detected, as a countermeasure against the detected fuel gas leakage when the fuel gas supply is stopped. For example, when the fuel gas leakage is detected by the leakage detection unit 25 arranged near the supply device 35, the control unit 20 may stop the fuel gas supply by stopping the operation of the supply device 35, and when the fuel gas leakage is detected by the leakage detection unit 25 arranged near the tank 31, the control unit 20 may stop the fuel gas supply by closing the main shutoff valve 33. Other embodiment 5

[0063] In each of the embodiments described above, the vehicle 101 may include a higher-level control unit that controls the operation of the vehicle 101 separately from the control unit 20 that performs the leakage detection processing. Other embodiment 6

[0064] In each of the embodiments described above, the leakage countermeasure processing in step S60 may be omitted. Furthermore, only the notification processing by the notification unit 28 may be performed as the leakage countermeasure processing, or at least one of the processing in which the operation of the fuel cell system 100 is terminated without performing the notification processing by the notification unit 28 and the processing in which the vehicle 101 is prohibited from traveling may be performed. In a case where the notification processing is not performed, the notification unit 28 may be omitted. Other

[0065] In the embodiments described above, parts or all of the functions and processes implemented by software may be implemented by hardware. In addition, parts or all of the functions and processes implemented by hardware may be implemented by software. For example, various circuits, such as an integrated circuit, a discrete circuit, or a circuit module combined from the same, may be used as the hardware.

[0066] The technology of the present invention is not limited to the foregoing embodiments, examples, and modifications, and can be implemented in various configurations within a range that does not deviate from the scope of the present invention. For example, the technical features in the embodiments, examples, and modifications can be appropriately replaced or combined according to the technical features of each aspect described in the summary of the invention. Furthermore, the technical features can be appropriately deleted both in a case where they are not described as essential in this specification and in a case where they are described as inessential in this specification.

Claims

[1] A fuel cell system (100) mounted on a vehicle (101), the fuel cell system (100) comprising: a fuel cell (10) configured to generate power by receiving a fuel gas and an oxidizing gas; a fuel gas supply unit (30) configured to supply the fuel gas to the fuel cell (10); a leakage sensor (25) configured to detect leakage of the fuel gas; a speed detector (22) configured to determine a speed of the vehicle (101); and a control device (20) configured to control the fuel gas supply unit (30), wherein the control device (20) is configured to perform leakage detection processing including: in a case where the speed of the vehicle (101) is greater than a predetermined threshold speed, stopping a supply of fuel gas to the fuel cell (10) or reducing a supply amount of the fuel gas to the fuel cell (10) if the leakage of the fuel gas is continuously detected during a predetermined first detection period; and in a case where the speed of the vehicle (101) is equal to or less than the threshold speed, stopping the supply of the fuel gas to the fuel cell (10) or reducing the supply amount of the fuel gas to the fuel cell (10) when the leakage of the fuel gas is continuously detected during a predetermined second detection period, wherein the second detection period is shorter than the first detection period. [2] The fuel cell system (100) according to claim 1, wherein the control device (20) is configured to resume the supply of the fuel gas to the fuel cell (10) in a case where the leakage of the fuel gas is not detected before the period during which the leakage of the fuel gas is continuously detected exceeds a predetermined third detection period, after the supply of the fuel gas to the fuel cell (10) is stopped, when the speed of the vehicle (101) is equal to or lower than the threshold speed and the leakage of the fuel gas is continuously detected during the second detection period, wherein the third detection period is longer than the second detection period. [3] The fuel cell system (100) according to claim 2, further comprising a notification device (28) configured to notify a user of an occurrence of fuel gas leakage, wherein the control device (20) is configured to perform leakage countermeasure processing including the processing of causing the notification device (28) to notify the occurrence of fuel gas leakage in a case where the period during which the fuel gas leakage is continuously detected exceeds the third detection period, after the supply of the fuel gas to the fuel cell (10) is stopped when the speed of the vehicle (101) is equal to or lower than the threshold speed and the fuel gas leakage is continuously detected during the second detection period. [4] The fuel cell system (100) according to claim 3, wherein the leakage countermeasure processing includes the processing in which an operation of the fuel cell system (100) is terminated. [5] Fuel cell system (100) according to one of claims 2 to 4, further comprising a secondary battery (86) configured to store a portion of the power generated by the fuel cell (10), wherein the control device (20) is designed to: to determine an acceleration process of the vehicle (101) by a user; in response to the acceleration operation, perform an operation control for supplying the power of at least one of the fuel cell (10) and the secondary battery (86) to a drive power source of the vehicle (101); to perform the leakage detection processing repeatedly in a predetermined control cycle while performing the operation control; and after the supply of the fuel gas to the fuel cell (10) is stopped when the speed of the vehicle (101) is equal to or lower than the threshold speed and the leakage of the fuel gas is continuously detected during the second detection period, to resume the supply of the fuel gas to the fuel cell (10) in a case where the acceleration operation is detected before the period during which the leakage of the fuel gas is continuously detected exceeds the third detection period, to supply the power to the drive power source in response to the acceleration operation and to accelerate the vehicle (101). [6] Fuel cell system (100) according to one of claims 2 to 5, wherein: the fuel gas supply unit (30) includes a tank (31) that stores the fuel gas, a main shut-off valve (33) that controls an outflow of the fuel gas from the tank (31), and a supply device (35) that adjusts the supply amount of the fuel gas to the fuel cell (10), wherein the supply device (35) is arranged on a downstream side of the main shut-off valve (33); the control device (20) is designed to: if the speed of the vehicle (101) is greater than the threshold speed and the leakage of the fuel gas is continuously detected during the first detection period, to stop the supply of the fuel gas to the fuel cell (10) by closing the main shut-off valve (33); and when the speed of the vehicle (101) is equal to or less than the threshold speed and the leakage of the fuel gas is continuously detected during the second detection period, to stop the supply of the fuel gas to the fuel cell (10) by stopping the operation of the supply device (35) without closing the main shutoff valve (33). [7] The fuel cell system (100) according to any one of claims 1 to 6, wherein a state in which the speed of the vehicle (101) is equal to or less than the threshold speed is a state in which the vehicle is stopped, and a state in which the speed of the vehicle is greater than the threshold speed is a state in which the vehicle is traveling. [8] A method for controlling a fuel cell system (100), wherein the fuel cell system (100) is mounted on a vehicle (101) and includes a fuel cell (10) configured to generate power by receiving a fuel gas and an oxidizing gas, a leakage sensor (25) configured to detect leakage of the fuel gas, a speed detector (22) configured to determine a speed of a vehicle (101), and a control device (20) configured to control the supply of the fuel gas to the fuel cell (10), the method comprising: Determining the speed of the vehicle (101) by the speed detector (22); Detecting the leakage of the fuel gas by the leakage sensor (25); in a case where the speed of the vehicle (101) is greater than a predetermined threshold speed, stopping the supply of the fuel gas to the fuel cell (10) or reducing a supply amount of the fuel gas to the fuel cell (10) by the control device (20) if the leakage of the fuel gas is continuously detected during a predetermined first detection period; and in a case where the speed of the vehicle (101) is equal to or less than the threshold speed, stopping the supply of the fuel gas to the fuel cell (10) or reducing the supply amount of the fuel gas to the fuel cell (10) by the control device (20) when the leakage of the fuel gas is continuously detected during a predetermined second detection period, wherein the second detection period is shorter than the first detection period.

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