Fuel cell system

Abstract

To provide a fuel cell system capable of warming up a fuel cell by efficiently utilizing heat of a secondary battery.SOLUTION: There is provided a fuel cell system for vehicles which includes a fuel cell and a secondary battery. The fuel cell system includes: a first cooling passage where a coolant to cool the fuel cell flows; a second cooling passage where a coolant to cool the secondary battery flows; a connection passage connecting between the first cooling passage and the second cooling passage; an on-off valve opening / closing the connection passage; and a control unit controlling the on-off valve. The control unit obtains temperature of the fuel cell, and when the temperature is equal to or less than a predetermined temperature, opens the on-off valve and supplies a coolant from the second cooling passage to the first cooling passage.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a fuel cell system.

Background Art

[0002] Conventionally, fuel cell systems mounted on vehicles have been known (see, for example, Patent Document 1). In such a fuel cell system, it is necessary to control the temperature of the fuel cell so that the fuel cell system can operate efficiently. In the fuel cell system of Patent Document 1, the fuel cell is disposed on a circulation path through which a refrigerant passes, and the temperature of the fuel cell is controlled by controlling the temperature of the refrigerant.

[0003] In addition, in such a fuel cell system, when the temperature of the fuel cell drops, for example, the fuel cell is heated by a heater for warming the fuel cell or by a warm-up operation of the fuel cell. In the fuel cell system of Patent Document 1, a bypass passage through which the refrigerant flows is provided in the secondary battery, and by flowing the refrigerant through this bypass passage, the temperature of the secondary battery is used to suppress a drop in the temperature of the fuel cell. As a result, the opportunity for the warm-up operation of the fuel cell and the operation of the heater are suppressed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the fuel cell system of Patent Document 1, the refrigerant flowing through the bypass passage circulates only when the bypass valve is opened. Therefore, it takes time until the heat of the secondary battery is transferred to the refrigerant. As a result, the heat of the secondary battery cannot be efficiently utilized.

[0006] The objective of this disclosure is to provide a fuel cell system that can efficiently utilize the heat from a secondary battery to warm up the fuel cell. [Means for solving the problem]

[0007] The fuel cell system according to this disclosure is a fuel cell system for a vehicle having a fuel cell and a secondary battery, comprising: a first cooling passage through which a refrigerant for cooling the fuel cell flows; a second cooling passage through which a refrigerant for cooling the secondary battery flows; a connecting passage connecting the first cooling passage and the second cooling passage; an on-off valve for opening and closing the connecting passage; and a control unit for controlling the on-off valve, wherein the control unit obtains the temperature of the fuel cell, and if the temperature is below a predetermined temperature, opens the on-off valve and supplies refrigerant from the second cooling passage to the first cooling passage.

[0008] In this configuration, when the shut-off valve opens, the refrigerant flowing through the second cooling passage that cools the secondary battery flows through the first cooling passage that cools the fuel cell. As a result, the refrigerant that has already been heated by the secondary battery flows through the first cooling passage. Consequently, the heat from the secondary battery can be efficiently utilized to warm up the fuel cell. [Effects of the Invention]

[0009] According to this disclosure, it is possible to provide a fuel cell system that can efficiently utilize the heat of a secondary battery to warm up the fuel cell. [Brief explanation of the drawing]

[0010] [Figure 1] A system diagram of a fuel cell system according to one embodiment of the present disclosure. [Figure 2] A flowchart illustrating a control procedure performed by a control unit according to one embodiment of the present disclosure. [Modes for carrying out the invention]

[0011] Hereinafter, one embodiment of this disclosure will be described with reference to the drawings.

[0012] As shown in Figure 1, the fuel cell system 1 is a fuel cell system 1 for a vehicle C having a fuel cell (FC in Figure 1) 2 and a secondary battery (B in Figure 1) 4. The fuel cell system 1 includes a first cooling passage 10 through which a refrigerant for cooling the fuel cell 2 flows, a second cooling passage 12 through which a refrigerant for cooling the drive battery (an example of a secondary battery) 4 flows, a connecting passage 14 connecting the first cooling passage 10 and the second cooling passage 12, an on-off valve 16 for opening and closing the connecting passage 14, and a control device (an example of a control unit) 18 for controlling the on-off valve 16. The fuel cell system 1 may also include an electric compressor 20 for pressurizing an oxidizing gas (air in this embodiment), a tank 22 for storing fuel gas (hydrogen in this embodiment), and a heater 24 for heating the fuel cell 2. The on-off valve 16, electric compressor 20, tank 22, and heater 24 are each electrically connected to the control device 18.

[0013] The fuel cell system 1 of this embodiment is mounted on a vehicle C, such as a range-extender type plug-in fuel cell vehicle (PFCV) capable of external charging or external power supply. A motor generator (MG in Figure 1) 8 that drives the wheels 6 of vehicle C is electrically connected to the fuel cell 2 and the drive battery 4 via an inverter (not shown). The fuel cell system 1 is mainly started when charging of the drive battery 4 is required, and supplies the power generated by the fuel cell 2 to the drive battery 4 after the voltage is converted by a DC-DC converter (not shown). In addition, if the output from the drive battery 4 to the motor generator 8 is insufficient, power is temporarily supplied from the fuel cell 2 to the motor generator 8.

[0014] Fuel cell 2 is a device that generates electricity when fuel gas and oxidizing gas are supplied. In this embodiment, fuel cell 2 is a hydrogen fuel cell that generates water and electrical energy by combining hydrogen (fuel gas) and oxygen (oxidizing gas). Fuel cell 2 can be any general hydrogen fuel cell, and a detailed explanation is omitted. Fuel cell 2 has a temperature sensor 2a that can obtain the temperature of the fuel cell. The temperature sensor 2a is electrically connected to the control device 18. The amount of electricity generated by fuel cell 2 is controlled by the control device 18 controlling the amount of air supplied by the electric compressor 20 and the amount of hydrogen supplied from the tank 22.

[0015] The drive battery 4 is a device that stores the electricity generated by the fuel cell 2 and can supply the stored electricity to the motor generator 8. In this embodiment, the drive battery 4 is composed of a secondary battery such as a lithium-ion battery and has a battery module (not shown) which is composed of multiple battery cells. The drive battery 4 includes a temperature sensor that can acquire the temperature of the battery module (an example of battery temperature) and has a battery control unit 4a that can calculate the state of charge (SOC) from the voltage of the battery module. The drive battery 4 is electrically connected to the control device 18 via the battery control unit.

[0016] The first cooling passage 10 includes a first pump 10a and a first radiator 10b. The first cooling passage 10 cools the fuel cell 2 by allowing refrigerant to pass through it and circulating between the inside of the fuel cell 2 and the first radiator 10b. In this embodiment, the first pump 10a is an electric pump that pumps the refrigerant. The first pump 10a is connected to a control device 18 and its operation is controlled by the control device 18. The first radiator 10b is a heat exchanger that includes a first fan 10c and a heat exchange section (not shown). The first radiator 10b cools the refrigerant by exchanging heat between the refrigerant and air. The first fan 10c promotes the cooling of the refrigerant by increasing the airflow rate during heat exchange. In this embodiment, the refrigerant leaves the fuel cell 2 and enters the first radiator 10b. The refrigerant that leaves the first radiator 10b is pumped to the first pump 10a and enters the fuel cell 2 again. In other words, in this embodiment, the refrigerant flows clockwise in Figure 1. Therefore, the left side of the fuel cell 2 in Figure 1 is the outlet side of the first cooling passage 10, and the right side is the inlet side of the first cooling passage 10.

[0017] The second cooling passage 12 includes a second pump 12a and a second radiator 12b. The second cooling passage 12 allows refrigerant to pass through it, and the refrigerant circulates between the inside of the drive battery 4 and the second radiator 12b, thereby cooling the drive battery 4. In this embodiment, the second pump 12a is an electric pump that pumps the refrigerant. The second pump 12a is connected to a control device 18 and its operation is controlled by the control device 18. The second radiator 12b is a heat exchanger that includes a second fan 12c and a heat exchange section (not shown). The second radiator 12b cools the refrigerant by exchanging heat between the refrigerant and air. The second fan 12c promotes the cooling of the refrigerant by increasing the airflow rate during heat exchange. In this embodiment, the refrigerant leaves the drive battery 4 and enters the second radiator 12b. The refrigerant that leaves the second radiator 12b is pumped to the second pump 12a and enters the drive battery 4 again. In other words, in this embodiment, the refrigerant flows clockwise in Figure 1. Therefore, the left side of the drive battery 4 in Figure 1 is the outlet side of the second cooling passage 12, and the right side is the inlet side of the second cooling passage 12.

[0018] The connecting passage 14 is a passage that connects the first cooling passage 10 and the second cooling passage 12, thereby enabling the refrigerant that cools the fuel cell 2 and the refrigerant that cools the drive battery 4 to merge. In this way, the merging of the refrigerant that cools the fuel cell 2 and the refrigerant that cools the drive battery 4 enables heat exchange between the two refrigerants. In this embodiment, the connecting passage 14 has an outlet-side connecting passage 14a that connects the outlet sides of the first cooling passage 10 and the second cooling passage 12, and an inlet-side connecting passage 14b that connects the inlet sides of the first cooling passage 10 and the second cooling passage 12.

[0019] The on-off valve 16 controls the flow of refrigerant between the first cooling passage 10 and the second cooling passage 12 by opening and closing the connection passage 14. In this embodiment, one on-off valve 16 is provided for each of the outlet-side connection passage 14a and the inlet-side connection passage 14b. Each of the two on-off valves 16 is controlled by the control device 18. When the control device 18 opens the on-off valve 16 of the outlet-side connection passage 14a, refrigerant is supplied from the second cooling passage 12 to the first cooling passage 10 via the outlet-side connection passage 14a. On the other hand, when the control device 18 opens the on-off valve 16 of the inlet-side connection passage 14b, refrigerant is supplied from the first cooling passage 10 to the second cooling passage 12 via the inlet-side connection passage 14b. By opening the on-off valves 16 in this way, the control device 18 merges the refrigerant flowing through the second cooling passage 12 with the refrigerant flowing through the first cooling passage 10.

[0020] The control device 18 is an ECU (Electronic Control Unit) that controls the fuel cell system 1 to reach a desired operating state based on signals from various sensors and devices, as well as software including maps and programs stored in memory. In practice, the control device 18 consists of a microcomputer including an arithmetic unit, memory, and input / output buffers. It should be noted that various controls are not limited to software processing; they can also be processed by dedicated hardware (electronic circuits).

[0021] Next, the control procedure executed by the control device 18 will be described with reference to FIG. 2. The control device 18 starts the control procedure when an ignition switch (not shown) is turned on.

[0022] In step S1, the control device 18 determines whether charging of the drive battery 4 is necessary. The control device 18 may determine whether charging of the drive battery 4 is necessary based on whether the state of charge SOC is less than or equal to a predetermined state of charge SOCt. The predetermined state of charge SOCt may be, for example, the minimum state of charge SOC required when the vehicle C is driven by the drive battery 4. If the control device 18 determines that charging of the drive battery 4 is necessary (step S1 YES), the process proceeds to step S2.

[0023] In step S2, the control device 18 determines whether warm-up operation is necessary. In order to operate the fuel cell 2 most efficiently, it is preferable that the fuel cell temperature FCT, which is the temperature of the fuel cell 2, is about 60 degrees Celsius to 80 degrees Celsius. For this reason, the control device 18 acquires the fuel cell temperature FCT from the temperature sensor 2a, and determines that warm-up is necessary when the fuel cell temperature FCT is less than or equal to a predetermined temperature (for example, 60 degrees Celsius). If the control device 18 determines that warm-up is necessary (step S2 YES), the process proceeds to step S3.

[0024] In step S3, the control device 18 acquires the battery temperature BT, which is the temperature of the drive battery, and determines whether the battery temperature BT is higher than the fuel cell temperature FCT. When the battery temperature BT is less than or equal to the fuel cell temperature FCT, the fuel cell 2 cannot be warmed up using the heat of the drive battery 4. For this reason, if the control device 18 determines that the battery temperature BT is higher than the fuel cell temperature FCT (step S3 YES), the process proceeds to step S4.

[0025] In step S4, the control device 18 opens the on-off valve 16 and supplies and merges the refrigerant in the second cooling passage 12 to the first cooling passage 10. Thereby, the heat of the drive battery 4 is transmitted to the fuel cell 2 via the refrigerant. When the control device 18 opens the on-off valve 16, the process proceeds to step S5.

[0026] In step S5, the control device 18 determines whether the fuel cell temperature FCT is equal to or greater than the battery temperature BT. As described above, the fuel cell 2 cannot be warmed up unless the battery temperature BT is higher than the fuel cell temperature FCT. Therefore, if the battery temperature BT is less than or equal to the fuel cell temperature FCT (step S5 YES), the control device 18 proceeds to step S6 and closes the on-off valve 16. After closing the on-off valve 16, the control device 18 proceeds to step S8.

[0027] In step S7, the control device 18 determines whether or not the warm-up is complete. The control device 18 may determine that the warm-up is complete, for example, when the fuel cell temperature FCT reaches a temperature higher than a predetermined temperature (for example, 60 degrees Celsius). If the control device 18 determines that the warm-up is complete (step S7 YES), it proceeds to step S8 and starts the fuel cell 2 (FC-ON). Once the fuel cell 2 is started, the control device 18 proceeds to step S9.

[0028] In step S9, the control device 18 obtains the battery temperature BT again and determines whether the battery temperature BT has risen above the battery temperature BT before closing the on-off valve 16. If the battery temperature BT continues to rise despite the on-off valve 16 being closed, it is possible that the drive battery 4 is receiving heat from the fuel cell 2 due to a malfunction of the on-off valve 16. Therefore, if the control device 18 determines that the battery temperature BT has not risen (step S9 NO), it proceeds to step S10.

[0029] In step S10, the control device 18 determines whether charging is complete. The control device 18 may determine that charging is complete, for example, when the charge level (SOC) reaches a second predetermined charge level (SOCt2). The second predetermined charge level (SOCt2) should be a charge level (SOC) that allows the vehicle C to run sufficiently using the drive battery 4 as a power source (for example, a charge level (SOC) of 80% or higher). If the control device 18 determines that charging is complete (step S10 YES), it proceeds to step S11, stops the fuel cell 2 (FC-OFF), and stops charging the drive battery 4. After stopping the fuel cell 2, the control device 18 returns to step S1.

[0030] In step S1, if the control device 18 determines that charging is not necessary (step S1 NO), the control device 18 proceeds to step S12, transitions to a mode where it waits until charging becomes necessary, and returns to step S1.

[0031] In step S2, if the control device 18 determines that warming up is not necessary (step S2 NO), the control device 18 proceeds to step S8 and starts the fuel cell 2.

[0032] In step S3, if the control device 18 determines that the battery temperature BT is below the fuel cell temperature FCT, the control device 18 proceeds to step S13 and performs forced warm-up operation. Forced warm-up operation is a mode in which the fuel cell 2 is operated while performing either or both of the following: a temperature rise control that heats the fuel cell 2 with the heater 24, and a temperature rise control that heats the fuel cell 2 by increasing the amount of air supplied and hydrogen supplied by rotating the electric compressor 20 at high speed to increase the reaction amount of the fuel cell 2. After performing forced warm-up operation, the control device 18 proceeds to step S7.

[0033] In step S5, if the control device 18 determines that the battery temperature BT is higher than the fuel cell temperature FCT (step S5 NO), the control device 18 proceeds to step S4, maintains the open state of the on-off valve 16, and continues warming up the fuel cell 2 using the temperature of the drive battery 4.

[0034] If the control device 18 determines in step S7 that warm-up is not complete (step S7 NO), the control device 18 proceeds to step S3 and continues the above flow until warm-up is complete.

[0035] In step S9, if the control device 18 determines that the battery temperature BT is rising (step S9 YES), the control device 18 proceeds to step S14. Also, in step S10, if the control device 18 determines that charging is not complete (step S10 NO), the process proceeds to step S9, and the fuel cell 2 is operated to charge the drive battery 4 until charging is complete.

[0036] In step S14, the control device 18 determines whether the on-off valve 16 is malfunctioning. That is, if the battery temperature BT continues to rise despite the on-off valve 16 being closed as described above, there is a possibility that the on-off valve 16 is malfunctioning. The control device 18 may obtain the opening degree of the on-off valve 16 and, if the opening degree is not zero despite being instructed to close the valve, execute a fault determination control to determine that the on-off valve 16 is stuck open. If the control device 18 determines that the on-off valve 16 is malfunctioning (step S14 YES), it proceeds to step S15.

[0037] In step S15, the control device 18 increases the output of the second pump 12a to increase the pumping flow rate. In addition, the control device 18 may also increase the rotation of the second fan 12c to enhance the cooling of the refrigerant entering the second radiator 12b. The control device 18 performs the process of step S16 in parallel with the process of step S15.

[0038] In step S16, the control device 18 reduces the output of the first pump 10a and decreases the pumping flow rate.

[0039] Thus, when the on-off valve 16 is in an open fault state, the control device 18 increases the output of the second pump 12a to increase the circulation amount of refrigerant flowing through the second cooling passage 12, while simultaneously decreasing the output of the first pump 10a to reduce the circulation amount of refrigerant flowing through the first cooling passage 10, thereby performing fault cooling control. This prevents the refrigerant in the high-temperature first cooling passage 10 from flowing into the second cooling passage 12. In addition, the control device 18 increases the rotation of the second fan 12c to lower the refrigerant temperature that rises due to the refrigerant in the high-temperature first cooling passage 10 flowing into the second cooling passage 12. In this way, the control device 18 suppresses the temperature rise of the refrigerant flowing through the second cooling passage 12 and suppresses the temperature rise of the drive battery 4. This maintains the performance of the drive battery 4. After completing the process in step S16, the control device 18 proceeds to step S17.

[0040] In step S17, the control device 18 determines whether the battery temperature BT is still rising. In other words, the control device 18 determines whether the battery temperature BT has decreased due to the execution of fault cooling control. If the control device 18 determines that the battery temperature BT is rising (step S17 YES), it proceeds to step S18 and reduces the output of the fuel cell 2. In other words, if the battery temperature BT has not decreased since the execution of fault cooling control, the control device 18 reduces the output of the fuel cell 2. This reduces the temperature of the fuel cell 2. After reducing the output of the fuel cell 2, the control device 18 proceeds to step S10.

[0041] In step S14, if the control device 18 determines that the on-off valve 16 is not malfunctioning (step S14 NO), the control device 18 proceeds to step S10 and continues operating the fuel cell 2.

[0042] In step S17, if the control device 18 determines that the battery temperature BT has not risen (step S17 NO), the process proceeds to step S15 and the fault cooling control continues.

[0043] As explained above, this disclosure provides a fuel cell system that can efficiently utilize the heat from a secondary battery to warm up the fuel cell.

[0044] <Other Embodiments> Although embodiments of the present disclosure have been described above, the present disclosure is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention. In particular, the various modifications described herein can be combined as needed.

[0045] In the above embodiment, the battery temperature BT is obtained by a temperature sensor provided in the battery control unit 4a of the drive battery 4, but the disclosure is not limited thereto. For example, a temperature sensor may be provided in the second cooling passage 12, and the temperature of the refrigerant flowing through the second cooling passage 12 may be obtained and used as the battery temperature BT.

[0046] Furthermore, in the above embodiment, the fuel cell temperature FCT is obtained by a temperature sensor 2a provided in the fuel cell 2, but this disclosure is not limited thereto. For example, a temperature sensor may be provided in the first cooling passage 10 to obtain the temperature of the refrigerant flowing through the first cooling passage 10, and this may be used as the fuel cell temperature FCT. [Explanation of symbols]

[0047] 1: Fuel cell system 2:Fuel cell 4: Power battery 10: 1st cooling passage 12:Second cooling passage 14: Connecting passage 16: Shut-off valve 18: Control device BT:Battery temperature BTt: Predetermined battery temperature FCT: Fuel cell temperature

Claims

1. A fuel cell system for a vehicle having a fuel cell and a secondary battery, A first cooling passage through which a refrigerant for cooling the fuel cell flows, A second cooling passage through which a refrigerant for cooling the secondary battery flows, A connecting passage that connects the first cooling passage and the second cooling passage, A valve for opening and closing the aforementioned connecting passage, A control unit that controls the on / off valve, Equipped with, The control unit obtains the temperature of the fuel cell, and if the temperature is below a predetermined temperature, it opens the on / off valve and supplies refrigerant from the second cooling passage to the first cooling passage. The control unit acquires the battery temperature of the secondary battery, If, after closing the aforementioned valve, the battery temperature rises above the temperature before closing the valve, a fault detection control is executed to determine if the valve has opened. Fuel cell system.

2. A first pump is positioned on the first cooling passage and pumps the refrigerant flowing through the first cooling passage, A second pump is positioned on the second cooling passage and pumps the refrigerant flowing through the second cooling passage, Furthermore, When the control unit determines an open fault in the fault determination control, The system performs fault-to-failure cooling control by reducing the output of the first pump and increasing the output of the second pump. The fuel cell system according to claim 1.

3. If the temperature of the secondary battery does not decrease after the failure cooling control is executed, the control unit suppresses the output of the fuel cell. The fuel cell system according to claim 2.

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