Fuel cell system

Abstract

To provide a fuel cell system that allows for precise control of the fuel cell's output current, even in systems where the fuel cell's output current depends on the battery voltage. [Solution] One aspect of the present disclosure is a fuel cell system 1 having an FC stack 11 that generates electricity by receiving hydrogen gas and air, a battery 12 that charges the electricity generated by the FC stack 11, a fan 63 that supplies air to the FC stack 11, and a control unit 16 that performs various controls, wherein the FC current depends on the battery voltage, and the control unit 16 controls the FC current by controlling the rotation speed of the fan 63.

Description

Technical Field

[0001] The present disclosure relates to a fuel cell system having a fuel cell that generates electricity by receiving supplies of a fuel gas and an oxidant gas.

Background Art

[0002] Patent Document 1 discloses a fuel cell system having a fuel cell that generates electricity by receiving supplies of a fuel gas from a fuel gas system and an oxidant gas from an oxidant gas system.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a fuel cell system without a DC-DC converter (specifically, as will be described later), the output current of the fuel cell depends on the voltage of the battery. Therefore, the output current of the fuel cell is controlled to a value during normal power generation (i.e., a value corresponding to the voltage of the battery during normal power generation) and a value during intermittent stop (i.e., a value corresponding to the voltage of the battery during intermittent stop). However, if the output current of the fuel cell can be finely controlled between the value during normal power generation and the value during intermittent stop, the responsiveness of the fuel cell system mounted on a fuel cell vehicle to the required output is improved. Here, Patent Document 1 does not disclose anything regarding the control of the output current of the fuel cell in such a fuel cell system without a DC-DC converter.

[0005] Therefore, the present disclosure has been made to solve the above-described problems, and an object thereof is to provide a fuel cell system that can finely control the output current of a fuel cell even in a system in which the output current of the fuel cell depends on the voltage of the battery. [[ID=[Means for solving the problem]

[0006] One embodiment of the present disclosure made to solve the above problems is a fuel cell system comprising a fuel cell that generates electricity by receiving a fuel gas and an oxidizer gas, a battery that charges the electricity generated by the fuel cell, an oxidizer gas supply device that supplies the oxidizer gas to the fuel cell, and a control unit that performs various controls, wherein the output current of the fuel cell depends on the voltage of the battery, and the control unit controls the output current of the fuel cell by controlling the amount of drive of the oxidizer gas supply device.

[0007] According to this embodiment, the amount of oxidizer gas supplied to the fuel cell is adjusted by controlling the drive amount of the oxidizer gas supply device, thereby controlling the output current of the fuel cell. In this way, even in a system where the output current of the fuel cell depends on the battery voltage, the output current of the fuel cell can be precisely controlled between the value during continuous power generation and the value during intermittent shutdown.

[0008] In the above embodiment, it is preferable that the control unit has a voltage measuring unit for measuring the voltage of the battery, or an SOC measuring unit for measuring the SOC of the battery, and that the control unit calculates a target current value for the fuel cell based on the measured value of the voltage measuring unit or the measured value of the SOC measuring unit and the accelerator opening of the fuel cell vehicle on which the fuel cell is installed.

[0009] According to this embodiment, a target value for the fuel cell's output current can be set in accordance with the battery state and the accelerator opening of the fuel cell vehicle. Therefore, the fuel cell's output current can be controlled according to the fuel cell vehicle's required output.

[0010] In the above embodiment, it is preferable that the control unit calculates the lower limit drive amount of the oxidizer gas supply device based on the target current value.

[0011] According to this embodiment, by controlling the drive amount of the oxidizer gas supply device to be above a set lower limit drive amount, it is possible to suppress the inability to generate power due to insufficient supply of oxidizer gas to the fuel cell. Therefore, the output current of the fuel cell can be controlled to a target value, and the output current of the fuel cell can be controlled according to the required output of the fuel cell vehicle.

[0012] In the above embodiment, it is preferable that the fuel cell system is an open cathode system in which the flow path for the oxidizer gas supplied to the fuel cell and the flow path for the gas that cools the fuel cell are shared, and the fuel cell is arranged in a manner that allows it to be exposed to the outside air, and the control unit corrects the lower limit drive amount based on the speed of the fuel cell vehicle.

[0013] In this embodiment, since the fuel cell is positioned to be exposed to the outside air, the supply of oxidizer gas to the fuel cell can be supplemented by the outside air. The amount of oxidizer gas that can be supplemented by the outside air changes depending on the speed of the fuel cell vehicle. Therefore, by correcting the lower limit drive amount of the oxidizer gas supply device based on the speed of the fuel cell vehicle, it is possible to suppress the generation of noise and power consumption caused by the operation of the oxidizer gas supply device.

[0014] For example, when a fuel cell vehicle is traveling at a high speed, the amount of oxidizer gas supplied to the fuel cell by outside air increases. Therefore, by correcting the lower limit of the drive amount of the oxidizer gas supply device to a lower value and reducing the drive amount of the oxidizer gas supply device, it is possible to suppress noise generation and power consumption caused by the operation of the oxidizer gas supply device.

[0015] In the above embodiment, it is preferable that the fuel cell has a temperature measuring unit for measuring the temperature of the fuel cell, and the control unit calculates a target drive amount for the oxidizer gas supply device based on the measurement value of the temperature measuring unit, and controls the drive amount of the oxidizer gas supply device to the lower limit drive amount if the calculated target drive amount is less than the lower limit drive amount.

[0016] In this embodiment, in an open cathode system, if the target drive amount of the oxidizer gas supply device calculated according to the fuel cell temperature is less than the lower limit drive amount for cooling the fuel cell with oxidizer gas, the drive amount of the oxidizer gas supply device is controlled to the lower limit drive amount. By maintaining the drive amount of the oxidizer gas supply device above the lower limit drive amount in this way, the output current of the fuel cell can be reliably secured. In other words, power generation by supplying oxidizer gas is prioritized over cooling the fuel cell by supplying oxidizer gas, thereby securing the fuel cell output current that corresponds to the required output of the fuel cell vehicle.

[0017] In the above embodiment, it is preferable that the fuel cell has a current measuring unit for measuring the output current, and the control unit calculates a target drive amount for the oxidizer gas supply device based on the deviation between the target current value and the measurement value of the current measuring unit, and controls the drive amount of the oxidizer gas supply device to the target drive amount.

[0018] According to this embodiment, the output current of the fuel cell can be controlled to a target current value by controlling the drive amount of the oxidizer gas supply device to a target drive amount. Therefore, the output current of the fuel cell can be controlled according to the required output of the fuel cell vehicle.

[0019] In the above embodiment, it is preferable that the system has a voltage measuring unit for measuring the voltage of the battery, or an SOC measuring unit for measuring the SOC of the battery, and that the control unit calculates a lower limit drive amount for the oxidizer gas supply device based on the measured value of the voltage measuring unit or the measured value of the SOC measuring unit and the accelerator opening of the fuel cell vehicle on which the fuel cell is installed, and controls the drive amount of the oxidizer gas supply device to be equal to or greater than the lower limit drive amount.

[0020] According to this embodiment, the output current of the fuel cell can be secured in accordance with the state of the battery and the accelerator opening of the fuel cell vehicle. [Effects of the Invention]

[0021] According to the fuel cell system of the present disclosure, even in a system where the output current of the fuel cell depends on the voltage of the battery, the output current of the fuel cell can be finely controlled.

Brief Description of the Drawings

[0022] [Figure 1] It is a configuration diagram of a fuel cell system (open cathode system) of the first embodiment. [Figure 2] (A) is a characteristic diagram of FC current and FC voltage, and (B) is a characteristic diagram of battery current and battery voltage. [Figure 3] It is a diagram showing the relationship between the rotational speed of the fan and the FC current. [Figure 4] It is a flowchart showing the content of the control performed in the first example of the first embodiment. [Figure 5] It is a diagram showing an example of a map defining the relationship between SOC and the estimated battery voltage. [Figure 6] It is a diagram showing an example of a map defining the relationship between the accelerator opening and the required output. [Figure 7] It is a diagram showing an example of a map defining the relationship between the target current value and the lower limit FAN rotational speed. [Figure 8] It is a diagram showing an example of a map defining the relationship between the vehicle speed and the correction coefficient. [Figure 9] It is a diagram showing an example of a map defining the relationship between the FC temperature and the target FAN rotational speed. [Figure 10] It is a flowchart showing the content of the control performed in the second example of the first embodiment. [[ID=3,7]] [Figure 11] It is a flowchart showing the content of the control performed in the third example of the first embodiment. [Figure 12] It is a diagram showing an example of a map defining the relationship between the required output, the battery voltage, and the lower limit FAN rotational speed (or the lower limit compressor rotational speed). [Figure 13] It is a configuration diagram of a fuel cell system (closed cathode system) of the second embodiment. [Figure 14]This is a flowchart illustrating the control procedures performed in the first embodiment of the second embodiment. [Figure 15] This figure shows an example of a map that defines the relationship between the target current value and the lower limit compressor rotation speed. [Figure 16] This is a flowchart illustrating the control procedures performed in the second embodiment of the second embodiment. [Figure 17] This is a flowchart illustrating the control procedures performed in the third embodiment of the second embodiment. [Figure 18] This is a diagram showing the configuration of a fuel cell vehicle equipped with the fuel cell systems of the first and second embodiments. [Modes for carrying out the invention]

[0023] Embodiments of the fuel cell system described herein will be explained.

[0024] [First Embodiment] First, the fuel cell system 1 of the first embodiment will be described.

[0025] (Fuel cell system configuration) As shown in Figure 1, the fuel cell system 1 of this embodiment includes an FC stack 11 (air-cooled FC stack), a battery 12, a hydrogen system 21, and an air-cooling system 22. The FC stack 11 is an example of a "fuel cell" as disclosed herein.

[0026] The FC stack 11 generates electricity by receiving a supply of fuel gas and oxidizer gas. In this embodiment, the fuel gas is hydrogen gas and the oxidizer gas is air. That is, the FC stack 11 generates electricity by receiving hydrogen gas from the hydrogen system 21 and air from the air system / cooling system 22. The electricity generated by the FC stack 11 is then supplied to the battery 12 and the motor 301 (or inverter) of the fuel cell vehicle 300 (see Figure 18).

[0027] The battery 12 is connected to the FC stack 11 and charges with the power generated by the FC stack 11. This battery 12 also supplies power to the motor 301. The fuel cell system 1 is also equipped with a battery voltage sensor 13 for measuring the voltage of the battery 12 (hereinafter referred to as "battery voltage") and an SOC (State of Charge) measurement unit 14 for measuring the SOC of the battery 12. The battery voltage sensor 13 is an example of the "voltage measurement unit" described herein.

[0028] Furthermore, the fuel cell system 1 is equipped with an FC stack current sensor 15. This FC stack current sensor 15 is a sensor that measures the output current of the FC stack 11 (i.e., the current of the power generated by the FC stack 11, hereinafter referred to as "FC current"). Note that the FC stack current sensor 15 is an example of the "current measuring unit" in this disclosure.

[0029] The hydrogen system 21 is located on the anode side of the FC stack 11. This hydrogen system 21 includes a hydrogen gas supply passage 31 and a hydrogen off-gas discharge passage 32.

[0030] The hydrogen gas supply passage 31 is a passage for supplying hydrogen gas from the hydrogen tank 41 (described later) to the FC stack 11. The hydrogen off-gas discharge passage 32 is a passage for discharging hydrogen gas (i.e., hydrogen off-gas) discharged from the FC stack 11.

[0031] Furthermore, the hydrogen system 21 includes a hydrogen tank 41 and an injector 42 in the hydrogen gas supply passage 31.

[0032] The hydrogen tank 41 is a container in which hydrogen gas is stored. The injector 42 is a device that injects hydrogen gas supplied from the hydrogen tank 41 into the downstream FC stack 11.

[0033] Furthermore, the hydrogen system 21 is equipped with an exhaust drain valve 51 in the hydrogen off-gas discharge passage 32 that controls the switching between discharging hydrogen off-gas and moisture to the outside and blocking it.

[0034] On the other hand, the air and cooling system 22 is located on the cathode side of the FC stack 11. This air and cooling system 22 includes an air supply passage 61, an air-off gas discharge passage 62, and a fan 63. The fan 63 is an example of the "oxidizer gas supply device" described herein.

[0035] The air supply passage 61 is a passage for supplying air from outside the fuel cell system 1 to the FC stack 11. The air-off gas discharge passage 62 is a passage for discharging air (i.e., air-off gas) discharged from the FC stack 11.

[0036] The fan 63 supplies air to the FC stack 11 via the air supply passage 61 and discharges air-off gas from the FC stack 11 via the air-off gas discharge passage 62.

[0037] In this embodiment, the fan 63 not only serves to generate electricity using the air supplied to the FC stack 11 via the air supply passage 61, but also serves to cool the FC stack 11. Thus, the fuel cell system 1 shown in Figure 1 is an open cathode system in which the air supply passage for the FC stack 11 and the air supply passage for cooling the FC stack 11 are shared, and the FC stack 11 is positioned so that it can be exposed to the outside air.

[0038] In other words, in the fuel cell system 1, the air supplied to the FC stack 11 by the fan 63 is used as a cooling gas for the FC stack 11. Furthermore, since the FC stack 11 is positioned to be exposed to the outside air, outside air can be supplied to the FC stack 11 as oxidizer gas air.

[0039] Furthermore, the fuel cell system 1 includes an FC stack temperature sensor T1 for measuring the temperature of the FC stack 11 (hereinafter referred to as "FC temperature") and a battery temperature sensor T2 for measuring the temperature of the battery 12 (hereinafter referred to as "battery temperature"). The FC stack temperature sensor T1 is an example of the "temperature measurement unit" in this disclosure.

[0040] Furthermore, the fuel cell system 1 has a control unit 16. The control unit 16 is a device that includes, for example, an arithmetic processing unit such as a CPU, a storage unit such as a ROM that stores control programs and control data processed by the CPU, and a RAM used as various work areas for control processing, and an input / output interface unit. The control unit 16 then performs various controls on the fuel cell system 1 according to the control program stored in the storage unit.

[0041] In this embodiment, the control unit 16 performs various controls of the fuel cell system 1, including controlling the injector 42, exhaust and drain valve 51, and fan 63, as well as performing various calculations.

[0042] Furthermore, the control unit 16 acquires the battery voltage measurement value from the battery voltage sensor 13, the state of charge (SOC) measurement value of the battery 12 from the SOC measurement unit 14, and the FC current measurement value from the FC stack current sensor 15. In addition, the control unit 16 acquires the FC temperature measurement value from the FC stack temperature sensor T1 and the battery temperature measurement value from the battery temperature sensor T2.

[0043] (Fuel cell system operation) In the fuel cell system 1 configured as described above, the hydrogen gas supplied to the FC stack 11 from the hydrogen gas supply passage 31 is used for power generation in the FC stack 11, and then discharged from the FC stack 11 as hydrogen off-gas to the outside of the fuel cell system 1 via the hydrogen off-gas discharge passage 32. Similarly, the air supplied to the FC stack 11 from the air supply passage 61 is used for power generation in the FC stack 11, and then discharged from the FC stack 11 as air off-gas to the outside of the fuel cell system 1 via the air off-gas discharge passage 62.

[0044] Furthermore, the electricity generated by the FC stack 11 is supplied to the battery 12 to charge it, or supplied to the motor 301 to drive it. The motor 301 is also supplied with power from the battery 12.

[0045] (A system without a DC-DC converter) As shown in Figure 1, the fuel cell system 1 of this embodiment is a so-called DC-DC converter-less system, in which a DC-DC converter is not placed between the FC stack 11 and the battery 12. Therefore, in the fuel cell system 1, as shown in Figure 2, the FC voltage is equal to (or approximately equal to) the battery voltage, and the FC current depends on the battery voltage. In other words, the fuel cell system 1 supplies the power generated by the FC stack 11 to the battery 12 and motor 301 without converting the FC voltage.

[0046] In the fuel cell system 1, since the FC voltage becomes equal to the battery voltage, the FC stack 11 generates power in accordance with the battery voltage during power generation, as shown in Figure 2. When the State of Charge (SOC) of the battery 12 becomes high, the FC stack 11 intermittently stops power generation (low-current mode power generation).

[0047] (Controlling FC current by adjusting the amount of air supplied to the FC stack) In the DC-DC converter-less fuel cell system 1, the FC current depends on the battery voltage. Therefore, as shown in Figure 2, the FC current is controlled to a value during continuous power generation (i.e., a value corresponding to the battery voltage during continuous power generation) and a value during intermittent shutdown (i.e., a value corresponding to the battery voltage during intermittent shutdown).

[0048] However, if the FC current can be precisely controlled (i.e., partially controlled) between the value during continuous power generation and the value during intermittent shutdown, in accordance with the required output of the fuel cell vehicle 300 on which the fuel cell system 1 is installed, the responsiveness of the fuel cell vehicle 300 to the required output will be improved.

[0049] Therefore, in this embodiment, an FC stack 11 is used which has the characteristic of linearly changing FC current with respect to the rotational speed of the fan 63 (indicated as "FAN rotational speed" in the figure), as shown in Figure 3, and the amount of air supplied to the FC stack 11 is adjusted by controlling the rotational speed of the fan 63. As a result, as shown in Figure 2(A), the FC current is finely controlled (i.e., partially controlled) between the value during continuous power generation and the value during intermittent shutdown. Note that the rotational speed is an example of the "drive amount" in this disclosure.

[0050] <First Example> Specifically, in this embodiment, the control unit 16 performs the control shown in Figure 4. As shown in Figure 4, the control unit 16 determines whether or not there is an intermittent stop request (low current mode request) (step S1). Here, an "intermittent stop request" is a request to intermittently stop the power generation of the FC stack 11.

[0051] Then, if there is no intermittent stop request (Step S1: YES), the control unit 16 calculates the target FC current using the following formula based on the actual battery voltage (or actual SOC) and the request output (Step S2). [Mathematics 1] Required power [W] / Battery voltage [V] = Target FC current [A]

[0052] If an actual SOC is used instead of the actual battery voltage, the battery voltage is estimated using the map in Figure 5 based on the actual SOC, and the target FC current is calculated using the formula in Equation 1 above with this estimated battery voltage.

[0053] Here, "actual battery voltage" refers to the measurement value of the battery voltage sensor 13, that is, the battery voltage measured by the battery voltage sensor 13. Also, "actual SOC" refers to the measurement value of the SOC measurement unit 14, that is, the SOC of the battery 12 measured by the SOC measurement unit 14.

[0054] Furthermore, "requested output" refers to the output required by the fuel cell vehicle 300 (see Figure 18) on which the FC stack 11 is installed. This requested output is calculated using the map in Figure 6, based on the measurement value from the accelerator opening sensor 302 (i.e., accelerator opening measurement unit, see Figure 18) of the fuel cell vehicle 300, i.e., the accelerator opening measured by the accelerator opening sensor 302. In addition, "target FC current" is the target value of the FC current and is an example of the "target current value" in this disclosure.

[0055] Next, as shown in Figure 4, the control unit 16 calculates the lower limit FAN rotation speed using the map in Figure 7 based on the target FC current calculated in step S2 (step S3). Here, "lower limit FAN rotation speed" is the lower limit of the rotation speed of the fan 63 provided in the air system / cooling system 22, and is an example of the "lower limit drive amount" in this disclosure.

[0056] Next, the control unit 16 calculates a correction coefficient using the map in Figure 8 according to the speed [km / h] of the fuel cell vehicle 300 (indicated as "vehicle speed" in Figure 4), and multiplies this correction coefficient by the lower limit FAN rotation calculated in step S3 (step S4). The vehicle speed of the fuel cell vehicle 300 is measured by the speed sensor 303 (i.e., speed measurement unit, see Figure 18) provided on the fuel cell vehicle 300.

[0057] Next, the control unit 16 controls the FC current while cooling the FC stack 11 with air. Based on the FC temperature, it calculates the target fan speed using the map in Figure 9, sets this as the final fan speed (i.e., the final fan speed of 63), and controls the fan speed of 63 to the target fan speed. However, the target fan speed must be greater than or equal to the lower limit fan speed (step S5). The "target fan speed" is the target value for the fan speed of 63 and is an example of the "target drive amount" in this disclosure.

[0058] By controlling the rotation speed of fan 63 to the target fan speed in this way, the amount of air supplied to the FC stack 11 can be adjusted to cool the FC stack 11 while controlling the FC current. If the calculated target fan speed is less than the lower limit fan speed, the control unit 16 controls the rotation speed of fan 63 to the lower limit fan speed.

[0059] Furthermore, if an intermittent stop request is received in step S1 (step S1: NO), the control unit 16 stops the fan 63 (step S6).

[0060] As described above, according to this embodiment, the control unit 16 controls the FC current by controlling the rotation speed of the fan 63.

[0061] In this way, the control unit 16 controls the amount of air supplied to the FC stack 11 by controlling the rotation speed of the fan 63, thereby controlling the FC current. In this manner, even in a DC-DC converter-less system where the FC current depends on the battery voltage, the FC current can be finely controlled between the value during continuous power generation and the value during intermittent shutdown, according to the output requirements of the fuel cell vehicle 300 on which the fuel cell system 1 is installed. As a result, the responsiveness to the output requirements of the fuel cell vehicle 300 is improved. This makes it possible to make the fuel cell vehicle 300, for example, a parallel hybrid vehicle with a small battery capacity 12.

[0062] Furthermore, the control unit 16 calculates the target FC current based on the measured value from the battery voltage sensor 13 or the SOC measurement unit 14 and the accelerator opening of the fuel cell vehicle 300.

[0063] In this way, a target value for the FC current can be set in accordance with the state of the battery 12 and the accelerator opening (i.e., the requested output) of the fuel cell vehicle 300. Therefore, the FC current can be controlled according to the requested output of the fuel cell vehicle 300.

[0064] Furthermore, the control unit 16 calculates the lower limit of the fan speed based on the target FC current.

[0065] In this way, by controlling the rotation speed of the fan 63 to a level higher than the calculated lower limit fan rotation speed, it is possible to suppress the inability to generate power due to insufficient air supply to the FC stack 11. Therefore, the FC current can be controlled to a target value, and the FC current can be controlled according to the required output of the fuel cell vehicle 300.

[0066] Furthermore, the control unit 16 corrects the lower limit of the FAN rotation speed based on the speed of the fuel cell vehicle 300.

[0067] In this embodiment, the FC stack 11 is positioned so that it can be exposed to the outside air, and the supply of air to the FC stack 11 can be supplemented by the outside air. The amount of air that can be supplemented by the outside air to the FC stack 11 changes depending on the speed of the fuel cell vehicle 300. Therefore, by correcting the lower limit of the fan speed of the fan 63 based on the speed of the fuel cell vehicle 300, it is possible to suppress the generation of noise and power consumption caused by the rotation of the fan 63.

[0068] For example, when the fuel cell vehicle 300 is moving at a high speed, the amount of outside air that can supplement the supply of air to the FC stack 11 increases. Therefore, by correcting the lower limit of the fan rotation speed of the fan 63 to a lower value and suppressing the rotation speed of the fan 63, the generation of noise and power consumption caused by the rotation of the fan 63 can be reduced.

[0069] Furthermore, if the target FAN rotation speed calculated based on the measurement value of the FC stack temperature sensor T1 is less than the lower limit FAN rotation speed, the control unit 16 controls the rotation speed of the fan 63 to the lower limit FAN rotation speed.

[0070] Thus, in an open cathode system, if the target rotational speed of the fan 63 calculated according to the FC temperature for cooling the FC stack 11 with air is below the lower limit fan speed, the rotational speed of the fan 63 is controlled to the lower limit fan speed. By maintaining the rotational speed of the fan 63 above the lower limit fan speed in this way, the FC current can be reliably secured. In other words, power generation by the FC stack 11 through air supply is prioritized over cooling the FC stack 11 through air supply, thereby securing the FC current that corresponds to the required output of the fuel cell vehicle 300.

[0071] <Second Example> In this embodiment, as shown in Figure 10, the control unit 16 differs from the first embodiment in that it calculates the target fan speed by applying feedback from the deviation between the target FC current calculated in step S12 and the actual FC current (step S13). Then, the control unit 16 controls the rotation speed of the fan 63 to the target fan speed calculated in step S13 (step S14). The "actual FC current" is the measurement value of the FC stack current sensor 15, i.e., the FC current measured by the FC stack current sensor 15. The "fan speed" is the rotation speed of the fan 63.

[0072] As described above, according to this embodiment, the control unit 16 calculates the target fan speed based on the deviation between the target FC current and the measurement value of the FC stack current sensor 15, and controls the rotation speed of the fan 63 to the target fan speed.

[0073] In this way, by controlling the rotational speed of fan 63 to the target fan speed, the FC current can be controlled to the target FC current. Therefore, the FC current can be controlled according to the required output of the fuel cell vehicle 300.

[0074] <Third Example> In this embodiment, as shown in Figure 11, the control unit 16 differs from the first and second embodiments in that it calculates the lower limit FAN rotation speed using the two-dimensional map shown in Figure 12, based on the actual battery voltage (or actual SOC) and the requested output (step S22).

[0075] As described above, according to this embodiment, the control unit 16 calculates a lower limit FAN rotation speed based on the measured value of the battery voltage sensor 13 or the measured value of the SOC measurement unit 14 and the accelerator opening of the fuel cell vehicle 300, and controls the rotation speed of the fan 63 to be equal to or greater than the lower limit FAN rotation speed.

[0076] This allows the FC current to be secured in accordance with the state of the battery 12 and the accelerator opening of the fuel cell vehicle 300 (i.e., the required output).

[0077] [Second Embodiment] Next, we will describe the fuel cell system 2 of the second embodiment, explaining the differences from the fuel cell system 1 of the first embodiment, and omitting the explanation of the points that are common to both fuel cell systems 1 and 2.

[0078] (Fuel cell system configuration) Fuel cell system 2 is a closed-cathode system and differs from fuel cell system 1 in that, as shown in Figure 13, it has an air system 122 and a cooling system 123.

[0079] The air system 122 is located on the cathode side of the FC stack 11. This air system 122 includes an air supply passage 161 and an air-off gas discharge passage 162.

[0080] The air supply passage 161 is a passage for supplying air to the FC stack 11 from outside the fuel cell system 2. The air-off gas discharge passage 162 is a passage through which air-off gas, which is air not used for power generation, is discharged from the FC stack 11.

[0081] The air system 122 includes an air compressor 171 and an inlet air valve 172 in the air supply passage 161. The air compressor 171 is a device that supplies air to the FC stack 11. The inlet air valve 172 is located downstream of the air compressor 171 in the airflow and is a valve that controls the flow rate of air supplied to the FC stack 11. The air compressor 171 is an example of the "oxidant gas supply device" of this disclosure.

[0082] Furthermore, the air system 122 includes an outlet air valve 173 in the air-off gas discharge passage 162. The outlet air valve 173 is a valve that controls the flow rate of air-off gas discharged from the FC stack 11 to the air-off gas discharge passage 162.

[0083] The cooling system 123 is a system for cooling the FC stack 11 and includes a cooling water passage 201 and a cooling fan 202. The cooling water passage 201 is a passage through which cooling water flows. The cooling fan 202 is a device that cools the cooling water flowing through the cooling water passage 201.

[0084] In such a fuel cell system 2, the control unit 16 controls the air compressor 171, the inlet air valve 172, the outlet air valve 173, the cooling fan 202, and the like.

[0085] (Fuel cell system operation) In the fuel cell system 2 configured as described above, in the air system 122, the air supplied to the FC stack 11 from the air supply passage 161 is used for power generation in the FC stack 11, and then discharged to the outside as air-off gas from the FC stack 11 via the air-off gas discharge passage 162.

[0086] (Controlling FC current by adjusting the amount of air supplied to the FC stack) In this embodiment, the control unit 16 controls the FC current by adjusting the amount of air supplied to the FC stack 11, as described below.

[0087] <First Example> In this embodiment, the control unit 16 performs the control shown in Figure 14. As shown in Figure 14, the control unit 16 determines whether or not there is an intermittent stop request (low current mode) (step S31).

[0088] Then, if there is no intermittent stop request (step S31: YES), the control unit 16 calculates the target FC current using the formula in Equation 1 based on the actual battery voltage (or actual SOC) and the request output (step S32).

[0089] Next, the control unit 16 calculates the lower limit compressor rotation speed using the map in Figure 15 based on the target FC current calculated in step S32 (step S33). Here, "lower limit compressor rotation speed" is the lower limit of the rotation speed of the air compressor 171 provided in the air system 122.

[0090] Next, the control unit 16 calculates the target compressor rotation speed according to the FC current value, sets this as the final compressor rotation speed (i.e., the final rotation speed of the air compressor 171), and controls the rotation speed of the air compressor 171 to the target compressor rotation speed. However, the target compressor rotation speed shall be equal to or greater than the lower limit compressor rotation speed (step S34). Note that the "target compressor rotation speed" is the target value of the rotation speed of the air compressor 171 and is an example of the "target drive amount" in this disclosure.

[0091] Furthermore, in step S31, if there is a request for intermittent stop (step S31: NO), the control unit 16 stops the air compressor 171 (step S35). Also, in step S35, the control unit 16 simultaneously closes the inlet air valve 172.

[0092] As described above, according to this embodiment, the control unit 16 controls the FC current by controlling the rotational speed of the air compressor 171.

[0093] In this way, the control unit 16 controls the amount of air supplied to the FC stack 11 by controlling the rotational speed of the air compressor 171, thereby controlling the FC current. In this manner, even in a DC-DC converter-less system where the FC current depends on the battery voltage, the FC current can be finely controlled between the value during continuous power generation and the value during intermittent shutdown, according to the output requirements of the fuel cell vehicle 300 on which the fuel cell system 1 is installed. As a result, the responsiveness to the output requirements of the fuel cell vehicle 300 is improved.

[0094] Furthermore, the control unit 16 calculates the lower limit compressor rotation speed based on the target FC current.

[0095] In this way, by controlling the rotation speed of the air compressor 171 to a level higher than the calculated lower limit compressor rotation speed, it is possible to suppress the inability to generate power due to insufficient air supply to the FC stack 11. Therefore, the FC current can be controlled to a target value and controlled according to the required output of the fuel cell vehicle 300.

[0096] Furthermore, if the target compressor rotation speed is less than the lower limit compressor rotation speed, the control unit 16 controls the rotation speed of the air compressor 171 to the lower limit compressor rotation speed.

[0097] In this way, by maintaining the rotational speed of the air compressor 171 above the lower limit compressor rotational speed, the FC current can be reliably secured.

[0098] <Second Example> In this embodiment, as shown in Figure 16, the control unit 16 differs from the first embodiment in that it calculates the target compressor rotation speed by applying feedback from the difference between the target FC current calculated in step S42 and the actual FC current (step S43).

[0099] Next, the control unit 16 controls the rotational speed of the air compressor 171 to the target compressor rotational speed (step S44).

[0100] As described above, according to this embodiment, the control unit 16 calculates the target compressor rotation speed based on the deviation between the target FC current and the measured value of the FC stack current sensor 15, and controls the rotation speed of the air compressor 171 to the target compressor rotation speed.

[0101] In this way, by controlling the rotational speed of the air compressor 171 to the target compressor rotational speed, the FC current can be controlled to the target FC current. Therefore, the FC current can be controlled according to the required output of the fuel cell vehicle 300.

[0102] <Third Example> In this embodiment, as shown in Figure 17, the control unit 16 differs from the first and second embodiments in that it calculates the lower limit compressor rotation speed using the two-dimensional map shown in Figure 12 based on the actual battery voltage (or actual SOC) and the requested output (step S52).

[0103] As described above, according to this embodiment, the control unit 16 calculates a lower limit compressor rotation speed based on the measured value of the battery voltage sensor 13 or the measured value of the SOC measurement unit 14 and the accelerator opening of the fuel cell vehicle 300, and controls the rotation speed of the air compressor 171 to be equal to or greater than the lower limit compressor rotation speed.

[0104] This allows the FC current to be secured in accordance with the state of the battery 12 and the accelerator opening of the fuel cell vehicle 300 (i.e., the required output).

[0105] It should be noted that the embodiments described above are merely illustrative examples and do not limit this disclosure in any way. Various improvements and modifications are possible without departing from the gist of the disclosure.

[0106] For example, the accelerator opening sensor 302 and the speed sensor 303 may be provided in the fuel cell system 1 or the fuel cell system 2. [Explanation of Symbols]

[0107] 1. Fuel cell system 2. Fuel cell system 11 FC stack 12 batteries 13. Battery voltage sensor 14 SOC measurement section 15 FC Stacked Current Sensor 16 Control Unit 21 Hydrogen-based systems 22 Air and Cooling Systems 61 Air supply passage 63 Fans 122 Air System 123 Cooling System 161 Air supply passage 171 Air Compressor 300 fuel cell vehicles 301 Motor 302 Accelerator position sensor 303 Speed ​​Sensor T1 FC Stack Temperature Sensor T2 Battery Temperature Sensor

Claims

1. A fuel cell that generates electricity by receiving fuel gas and oxidizer gas, A battery for charging the electricity generated by the aforementioned fuel cell, An oxidizer gas supply device that supplies the oxidizer gas to the fuel cell, A control unit that performs various controls, It has, In a fuel cell system in which the output current of the fuel cell depends on the voltage of the battery, The control unit controls the output current of the fuel cell by controlling the drive amount of the oxidizer gas supply device. A fuel cell system characterized by the following.

2. In the fuel cell system of claim 1, The battery has a voltage measuring unit for measuring the voltage of the battery, or an SOC measuring unit for measuring the SOC of the battery. The control unit, The measured value from the voltage measuring unit or the measured value from the SOC measuring unit, The accelerator opening of the fuel cell vehicle on which the aforementioned fuel cell is installed, Based on, To calculate the target current value of the fuel cell, A fuel cell system characterized by the following.

3. In the fuel cell system of claim 2, The control unit calculates the lower limit drive amount of the oxidizer gas supply device based on the target current value. A fuel cell system characterized by the following.

4. In the fuel cell system of claim 3, The fuel cell system is an open-cathode system in which the flow path for the oxidizer gas supplied to the fuel cell and the flow path for the gas that cools the fuel cell are shared, and the fuel cell is arranged in a manner that allows it to be exposed to the outside air. The control unit corrects the lower limit of the drive amount based on the speed of the fuel cell vehicle. A fuel cell system characterized by the following.

5. In the fuel cell system of claim 3, The fuel cell has a temperature measuring unit for measuring the temperature of the fuel cell, The control unit, Based on the measurement values ​​from the temperature measuring unit, the target drive amount of the oxidizer gas supply device is calculated. If the calculated target drive amount is less than the lower limit drive amount, the drive amount of the oxidizer gas supply device is controlled to the lower limit drive amount. A fuel cell system characterized by the following.

6. In the fuel cell system of claim 2, The fuel cell has a current measuring unit for measuring the output current, The control unit, Based on the deviation between the target current value and the measurement value of the current measuring unit, the target drive amount of the oxidizer gas supply device is calculated. Controlling the drive amount of the oxidizer gas supply device to the target drive amount, A fuel cell system characterized by the following.

7. In the fuel cell system of claim 1, The battery has a voltage measuring unit for measuring the voltage of the battery, or an SOC measuring unit for measuring the SOC of the battery. The control unit, The measured value from the voltage measuring unit, or the measured value from the SOC measuring unit, The accelerator opening of the fuel cell vehicle on which the aforementioned fuel cell is installed, Based on, The lower limit drive amount of the oxidizer gas supply device is calculated, The amount of drive of the oxidizer gas supply device is controlled to be greater than or equal to the lower limit of drive. A fuel cell system characterized by the following.

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