Fuel battery system

Abstract

To provide a technique capable of efficiently warming up a fuel battery system at the time of cold start while suppressing the occurrence of pressure loss.SOLUTION: A fuel battery system includes: a first flow path provided with a fuel battery and a first cooling pump; a second flow path provided with a radiator; a first connection part connecting a first end of the first flow path and a first end of the second flow path; a second connection part connecting a second end of the first flow path and a second end of the second flow path; a third flow path connecting the first connection part and the second connection part; a three-way valve that is provided in the first connection part and can change a flow dividing ratio that is a ratio of a flow rate of a coolant flowing out to the second flow path with respect to the flow rate of the coolant flowing in from the first flow path; a fourth flow path in which a power consumption unit and a second cooling pump are provided; and a control part. The fourth flow path is provided between the three-way valve and the radiator, or between the radiator and the second connection part, and the control part sets the flow dividing ratio to 0% at the time of cold start and drives the first cooling pump.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses a cooling structure of a vehicle in which a first flow path provided with a fuel cell and a first cooling pump for cooling the fuel cell and a second flow path provided with a brake resistor and a second cooling pump for cooling the brake resistor are provided in parallel with each other. A first check valve for preventing backflow of the fluid after cooling the fuel cell is provided in the first flow path, and a second check valve for preventing backflow of the fluid after cooling the brake resistor is provided in the second flow path.

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 in which a check valve is provided in a flow path through which a refrigerant for cooling a fuel cell flows or in a flow path through which a refrigerant for cooling a brake resistor flows, a pressure loss occurs. A technique that can efficiently warm up the fuel cell system during cold start while suppressing the occurrence of pressure loss is desired.

Means for Solving the Problems

[0005] The present disclosure can be realized in the following forms.

[0006] (1) According to one aspect of the present disclosure, a fuel cell system is provided. This fuel cell system includes a first flow path provided with a fuel cell and a first cooling pump for cooling the fuel cell, a second flow path provided with a radiator, a first connection portion connecting a first end of the first flow path and a first end of the second flow path, a second connection portion connecting a second end of the first flow path and a second end of the second flow path, a third flow path connecting the first connection portion and the second connection portion, a three-way valve provided in the first connection portion, enabling the passage of refrigerant from the first flow path to the second flow path and from the first flow path to the third flow path, and capable of changing a flow ratio, which is the ratio of the flow rate of the refrigerant flowing out to the second flow path to the flow rate of the refrigerant flowing into the first flow path; a fourth flow path provided with a power consumption unit and a second cooling pump for cooling the power consumption unit; and a control unit for controlling the first cooling pump, the second cooling pump, and the flow ratio. The fourth flow path is provided between the three-way valve and the radiator or between the radiator and the second connection portion. The control unit sets the flow ratio to 0% at cold start and drives the first cooling pump. According to the fuel cell system of this aspect, since a check valve is not provided in the flow path through which the refrigerant flows, it is possible to suppress the occurrence of pressure loss. Also, at cold start of the fuel cell system, the refrigerant circulates only in the first flow path and the third flow path, and does not flow in the second flow path and the fourth flow path, so warm-up can be performed efficiently. (2) In the fuel cell system of the above aspect, when the flow ratio is a value greater than 0% and the second cooling pump is driven, the control unit may drive the first cooling pump so that the flow rate of the refrigerant flowing through the first flow path is equal to or greater than the flow rate of the refrigerant flowing into the second connection portion from the second flow path. According to the fuel cell system of this aspect, the refrigerant flowing into the second connection portion from the second flow path flows out to the first flow path. Therefore, it is possible to suppress the flow of the refrigerant from the second connection portion to the first connection portion through the third flow path. (3) In the fuel cell system of the above-described embodiment, when the temperature of the power consumption unit is equal to or higher than an upper limit temperature that is a predetermined temperature, the control unit sets a lower limit value of the flow rate distribution ratio to a first value that is a predetermined value greater than 0%, drives the second cooling pump, and drives the first cooling pump so that the flow rate of the refrigerant flowing through the first flow path is equal to or greater than the flow rate of the refrigerant flowing from the second flow path into the second connection portion. According to the fuel cell system of this embodiment, when the temperature of the power consumption unit is equal to or higher than the upper limit temperature, the power consumption unit can be cooled. (4) In the fuel cell system of the above-described embodiment, the power consumption unit is a brake resistor, and when the brake resistor is used and the temperature of the brake resistor is equal to or higher than the upper limit temperature, the control unit sets the lower limit value of the flow rate distribution ratio to the first value, drives the second cooling pump, and drives the first cooling pump so that the flow rate of the refrigerant flowing through the first flow path is equal to or greater than the flow rate of the refrigerant flowing from the second flow path into the second connection portion. According to the fuel cell system of this embodiment, when the brake resistor is used and the temperature of the brake resistor is equal to or higher than the upper limit temperature, the brake resistor can be cooled.

Brief Description of Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0008] A. First Embodiment: FIG. 1 is a block diagram showing a schematic configuration of a fuel cell system 100 in the first embodiment. The fuel cell system 100 is mounted, for example, on a fuel cell electric vehicle (FCEV) having a fuel cell as a drive source. The fuel cell system 100 includes a first flow path L1, a second flow path L2, a first connection part P1, a second connection part P2, a third flow path L3, a three-way valve 3, a fourth flow path L4, and a control part 10. The first flow path L1, the second flow path L2, the third flow path L3, and the fourth flow path L4 are flow paths through which a refrigerant flows inside. As the refrigerant, an antifreeze such as ethylene glycol, water, a mixed liquid of antifreeze and water, or the like is used. The fuel cell module 20 is constituted by the first flow path L1, the first connection part P1, the three-way valve 3, the third flow path L3, and the second connection part P2.

[0009] In the first flow path L1, a fuel cell 1 and a first cooling pump 2 are provided. The fuel cell 1 generates electricity by an electrochemical reaction between a cathode gas and an anode gas. The cathode gas is, for example, oxygen, and the anode gas is, for example, hydrogen. The fuel cell 1 supplies electric power to a traveling motor that is a drive power source of the vehicle on which the fuel cell system 100 is mounted. The first cooling pump 2 is a pump that cools the fuel cell 1 by supplying a refrigerant to the fuel cell 1.

[0010] In the second flow path L2, a radiator 4 is provided. The radiator 4 cools the refrigerant flowing through the second flow path L2 by heat exchange with the outside air.

[0011] The first connection part P1 connects the first end of the first flow path L1 and the first end of the second flow path L2. The second connection part P2 connects the second end of the first flow path L1 and the second end of the second flow path L2. The second end of the first flow path L1 is an end portion located on the side opposite to the first end of the first flow path L1 with the fuel cell 1 and the first cooling pump 2 interposed therebetween. The second end of the second flow path L2 is an end portion located on the side opposite to the first end of the second flow path L2 with the radiator 4 interposed therebetween.

[0012] The third flow path L3 connects the first connection part P1 and the second connection part P2.

[0013] The three-way valve 3 is provided at the first connection part P1. The three-way valve 3 enables the passage of the refrigerant from the first flow path L1 to the second flow path L2 and the passage of the refrigerant from the first flow path L1 to the third flow path L3. The three-way valve 3 is provided so that the flow rate ratio (diversion ratio), which is the ratio of the flow rate of the refrigerant flowing out to the second flow path L2 to the flow rate of the refrigerant flowing into the first flow path L1, can be changed. The diversion ratio is controlled by the control unit 10. When the diversion ratio is 0%, all of the refrigerant flowing into the first flow path L1 flows out to the third flow path L3. When the diversion ratio is 100%, all of the refrigerant flowing into the first flow path L1 flows out to the second flow path L2. When the diversion ratio is 50%, half of the refrigerant flowing into the first flow path L1 flows out to the second flow path L2 and the other half flows out to the third flow path L3. In this specification, the state where the diversion ratio is 0% is also referred to as "the state where the three-way valve 3 is closed", and the state where the diversion ratio is not 0% is also referred to as "the state where the three-way valve 3 is open". Also, the diversion ratio is also referred to as the opening degree of the three-way valve 3. The three-way valve 3 is also called a rotary valve.

[0014] The fourth flow path L4 is provided in parallel with the second flow path L2 between the radiator 4 and the second connection portion P2. In other words, the fourth flow path L4 is provided so as to bypass a part of the second flow path L2. The fourth flow path L4 is provided with a brake resistor 5 and a second cooling pump 6. The brake resistor 5 converts electric power generated by regeneration into heat energy and consumes it when the regenerative brake is used in a state where the charging rate of the battery of the vehicle equipped with the fuel cell system 100 exceeds a predetermined value. When the brake resistor 5 is used, the brake resistor 5 generates heat. The above-described battery stores the electric power generated by the fuel cell 1 and the electric power generated by the regeneration of the driving motor. The second cooling pump 6 is a pump that cools the brake resistor 5 by supplying a refrigerant to the brake resistor 5.

[0015] The control unit 10 controls the first cooling pump 2, the second cooling pump 6, and the flow rate ratio of the three-way valve 3. Specifically, the control unit 10 controls the flow rate of the refrigerant supplied to the fuel cell 1 by controlling the rotation speed of the first cooling pump 2, and controls the flow rate of the refrigerant supplied to the brake resistor 5 by controlling the rotation speed of the second cooling pump 6. Hereinafter, the flow rate of the refrigerant discharged from the first cooling pump 2 is referred to as the "flow rate of the first cooling pump 2", and the flow rate of the refrigerant discharged from the second cooling pump 6 is referred to as the "flow rate of the second cooling pump 6". The control unit 10 is composed of, for example, one or two or more ECUs (Electronic Control Unit).

[0016] When cooling the fuel cell 1, the control unit 10 drives the first cooling pump 2 and opens the three-way valve 3. As a result, the refrigerant circulates in the order of the first cooling pump 2, the fuel cell 1, the first connection part P1, the radiator 4, the second connection part P2, and the first cooling pump 2. When cooling the brake resistor 5, the control unit 10 drives the first cooling pump 2 and the second cooling pump 6 and opens the three-way valve 3. As a result, the refrigerant circulates in the order of the second cooling pump 6, the brake resistor 5, the second connection part P2, the first cooling pump 2, the fuel cell 1, the first connection part P1, the radiator 4, and the second cooling pump 6. When the flow split ratio is not 100%, a part of the refrigerant flows from the first connection part P1 to the second connection part P2 through the third flow path L3.

[0017] Figure 2 is a process diagram of the control process in the first embodiment. The control process starts when the fuel cell system 100 is started. The start of the fuel cell system 100 is, for example, when the switch for starting the vehicle on which the fuel cell system 100 is mounted is turned on.

[0018] In step S10, the control unit 10 determines whether the start of the fuel cell system 100 is a cold start. The control unit 10 determines that it is a cold start, for example, when the temperature of the fuel cell 1 is below the freezing point. If it is determined that it is a cold start, step S20 is executed. If it is determined that it is not a cold start, step S30 is executed.

[0019] In step S20, the control unit 10 sets the flow split ratio to 0% and drives the first cooling pump 2. At this time, the refrigerant circulates through the first flow path L1 and the third flow path L3 in the order of the first cooling pump 2, the fuel cell 1, the first connection part P1, the second connection part P2, and the first cooling pump 2. That is, the refrigerant circulates inside the fuel cell module 20. Also, in step S20, the control unit 10 operates the fuel cell 1. When the fuel cell 1 operates, the temperature of the fuel cell 1 rises. Since the refrigerant passing through the fuel cell 1 does not pass through the radiator 4, the fuel cell 1 is not cooled. As a result, the warm-up of the fuel cell system 100 is promoted.

[0020] Step S30 is executed after the warm-up of the fuel cell system 100 is completed. In step S30, the control unit 10 determines whether the flow split ratio is greater than 0% and whether the second cooling pump 6 is driven. When the flow split ratio is greater than 0% and the second cooling pump 6 is driven, step S40 is executed. When the flow split ratio is 0% or the second cooling pump 6 is not driven, step S50 is executed. The case where the flow split ratio is greater than 0% and the second cooling pump 6 is driven is, for example, the case where the brake resistor 5 is being cooled because the temperature of the brake resistor 5 has exceeded a predetermined temperature.

[0021] In step S40, the control unit 10 drives the first cooling pump 2 so that the flow rate of the refrigerant flowing through the first flow path L1 is equal to or greater than the flow rate of the refrigerant flowing into the second connection portion P2 from the second flow path L2. In other words, the control unit 10 sets the flow rate of the first cooling pump 2 to a value equal to or greater than the flow rate of the refrigerant flowing into the second connection portion P2 from the second flow path L2. When the flow split ratio is greater than 0% and within the range of less than 100%, the second flow path L2 and the third flow path L3 communicate with each other at the first connection portion P1. In this state, when the second cooling pump 6 is driven and the flow rate of the first cooling pump 2 is small, the refrigerant flowing into the second connection portion P2 from the second flow path L2 flows out to the third flow path L3 and flows backward through the third flow path L3. On the other hand, when the second cooling pump 6 and the first cooling pump 2 are driven as described above, the refrigerant flowing into the second connection portion P2 from the second flow path L2 flows out to the first flow path L1, so that the refrigerant can be prevented from flowing backward through the third flow path L3. The control unit 10 preferably drives the first cooling pump 2 when the flow split ratio is close to 50% and the second cooling pump 6 is driven.

[0022] In step S50, the control unit 10 determines whether or not the fuel cell system 100 has stopped. If the fuel cell system 100 has stopped, the control unit 10 ends the control process. If the fuel cell system 100 has not stopped, the control unit 10 returns the process to step S30. Here, the case where the fuel cell system 100 has stopped is, for example, the case where the switch for starting the vehicle on which the fuel cell system 100 is mounted is turned off.

[0023] According to the fuel cell system 100 in the first embodiment described above, since check valves are not provided in the flow path through which the refrigerant that cools the fuel cell 1 flows and the flow path through which the refrigerant that cools the brake resistor 5 flows, it is possible to suppress the occurrence of pressure loss.

[0024] FIG. 3 is a block diagram showing an example of a fuel cell system 200 in which a fourth flow path L4 is provided in parallel with the first flow path L1 between the second connection part P2 and the first cooling pump 2. In the fuel cell system 200, when the fuel cell system 200 is cold-started and the flow rate ratio is set to 0% and the first cooling pump 2 and the second cooling pump 6 are driven, the refrigerant circulates through the first flow path L1, the third flow path L3, and the fourth flow path L4 in this order: the fuel cell 1, the first connection part P1, the second connection part P2, the second cooling pump 6, the brake resistor 5, the first cooling pump 2, and the fuel cell 1. On the other hand, in the fuel cell system 100 of the present embodiment shown in FIG. 1, the control unit 10 sets the flow rate ratio to 0% and drives the first cooling pump 2 when the fuel cell system 100 is cold-started. In this case, the refrigerant circulates inside the fuel cell module 20 in this order: the first cooling pump 2, the fuel cell 1, the first connection part P1, the second connection part P2, and the first cooling pump 2. Therefore, unlike the fuel cell system 200, the refrigerant passing through the fuel cell 1 does not pass through the second cooling pump 6 and the brake resistor 5. As described above, in the fuel cell system 100 of the present embodiment, the refrigerant circulates only through the first flow path L1 and the third flow path L3, and does not flow through the second flow path L2 and the fourth flow path L4, so the fuel cell 1 can be efficiently heated during cold start. That is, warm-up can be efficiently performed during cold start.

[0025] Further, in the present embodiment, when the control unit 10 has a split ratio greater than 0% and the second cooling pump 6 is driven, the control unit 10 drives the first cooling pump 2 so that the flow rate of the refrigerant flowing through the first flow path L1 is equal to or greater than the flow rate of the refrigerant flowing into the second connection portion P2 from the second flow path L2. Therefore, the refrigerant flowing into the second connection portion P2 from the second flow path L2 flows out to the first flow path L1 and does not flow out to the third flow path L3. Thus, it is possible to suppress the refrigerant from flowing backward through the third flow path L3.

[0026] B. Second Embodiment: In the second embodiment, the content of the control process is different from that of the first embodiment. The configuration of each part of the fuel cell system 100 in the second embodiment is the same as that in the first embodiment.

[0027] FIG. 4 is a process diagram of the control process in the second embodiment. In FIG. 4, for the steps in which the same processes as those in FIG. 2 are executed, the same reference numerals as those in FIG. 2 are attached and the description thereof is omitted.

[0028] Step S110 is executed after the warm-up of the fuel cell system 100 is completed. In step S110, the control unit 10 determines whether or not the temperature of the brake register 5 is equal to or higher than a preset upper limit temperature. If the temperature of the brake register 5 is equal to or higher than the upper limit temperature, step S120 is executed. If the temperature of the brake register 5 is lower than the upper limit temperature, step S50 is executed.

[0029] In step S120, the control unit 10 opens the three-way valve 3 and drives the first cooling pump 2 and the second cooling pump 6. Specifically, the control unit 10 sets the split ratio to a value equal to or greater than a first value. Here, the first value is the lower limit value of the split ratio and is a preset value greater than 0%. Further, the control unit 10 drives the first cooling pump 2 so that the flow rate of the refrigerant flowing through the first flow path L1 is equal to or greater than the flow rate of the refrigerant flowing into the second connection portion P2 from the second flow path L2. As a result, the refrigerant circulates in the order of the second cooling pump 6, the brake register 5, the second connection portion P2, the first cooling pump 2, the fuel cell 1, the first connection portion P1, the radiator 4, and the second cooling pump 6, so that the brake register 5 is cooled.

[0030] In step S50, when it is determined that the fuel cell system 100 is not stopped, the control unit 10 returns the process to step S110.

[0031] According to the fuel cell system 100 in the second embodiment described above, when the temperature of the brake resistor 5 is equal to or higher than the upper limit temperature, the brake resistor 5 is cooled. Further, since the flow rate of the refrigerant flowing through the first flow path L1 is equal to or greater than the flow rate of the refrigerant flowing from the second flow path L2 into the second connection portion P2, it is possible to suppress the reverse flow of the refrigerant through the third flow path L3 in the process of cooling the brake resistor 5.

[0032] C. Third Embodiment: In the third embodiment, the content of the control process is different from that of the first embodiment. Also, in the third embodiment, the control unit 10 switches the operating state of the brake resistor 5 and controls the flow rate ratio and the flow rate of the first cooling pump 2 according to the operating state of the brake resistor 5. The configuration of each part of the fuel cell system 100 in the third embodiment is the same as that in the first embodiment.

[0033] FIG. 5 is a diagram for explaining the refrigerant flow rate and the flow division ratio in each operating state of the brake register 5. The operating states of the brake register 5 are four states: "when BR stops", "when BR pre-cools", "when BR operates", and "when BR post-cools". In this specification, BR means the brake register. "When BR stops" is a state where the brake register 5 is not in use. "When BR pre-cools" is a state where the temperature of the brake register 5 is being stabilized before it is used. "When BR operates" is a state where the brake register 5 is in use. "When BR post-cools" is a state where the temperature of the brake register 5 is being decreased after its use. FIG. 5 shows graphs of the flow rate of the first cooling pump 2, the flow rate of the second cooling pump 6, and the flow division ratio in each operating state of the brake register 5. In FIG. 5, the lower limit value of the flow rate of the first cooling pump 2 is shown by a solid line, and the actual flow rate of the first cooling pump 2 is shown by a dashed line. The flow rate of the second cooling pump 6 shown in FIG. 5 is the actual flow rate of the second cooling pump 6, and the flow division ratio shown in FIG. 5 is the lower limit value of the flow division ratio. Note that the actual flow rate of the first cooling pump 2 shown in FIG. 5, the lower limit value of the flow rate of the first cooling pump 2, the actual flow rate of the second cooling pump 6, and the value of the flow division ratio are examples.

[0034] FIG. 6 is a diagram for explaining the switching of the operating state of the brake register 5. The operating state of the brake register 5 is switched by the control unit 10. FIG. 6 shows examples of the lower limit value of the flow rate of the first cooling pump 2 and the lower limit value of the flow division ratio in each operating state of the brake register 5.

[0035] When the operating state of the brake register 5 is in the state of "when BR stops" and the charge rate of the battery of the vehicle equipped with the fuel cell system 100 exceeds the upper limit charge rate which is a predetermined value, the control unit 10 determines that there is a possibility of using the brake register 5, and switches the operating state of the brake register 5 from "when BR stops" to "when BR pre-cools".

[0036] When the operating state of the brake register 5 is in the "BR pre-cooling" state and the brake register 5 is used, the control unit 10 switches the operating state of the brake register 5 from "BR pre-cooling" to "BR operating". When the operating state of the brake register 5 is in the "BR pre-cooling" state, the brake register 5 is not used, and the charging rate of the battery is lower than the upper limit charging rate, the control unit 10 switches the operating state of the brake register 5 from "BR pre-cooling" to "BR stopped". The charging rate of the battery decreases, for example, when the vehicle runs using the power stored in the battery.

[0037] When the operating state of the brake register 5 is in the "BR operating" state and the use of the brake register 5 is completed, the control unit 10 switches the operating state of the brake register 5 from "BR operating" to "BR post-cooling".

[0038] When the operating state of the brake register 5 is in the "BR post-cooling" state and the temperature of the brake register 5 is lower than a predetermined temperature, the control unit 10 switches the operating state of the brake register 5 from "BR post-cooling" to "BR stopped". When the operating state of the brake register 5 is in the "BR post-cooling" state and the charging rate of the battery exceeds the upper limit charging rate, the control unit 10 switches the operating state of the brake register 5 from "BR post-cooling" to "BR pre-cooling". Note that the conditions for switching the operating state of the brake register 5 described above are just an example, and the control unit 10 may switch the operating state of the brake register 5 under conditions different from the above-described conditions.

[0039] Figure 7 is a process diagram of the control process in the third embodiment. In Figure 7, for the processes in which the same processes as those in Figure 4 are executed, the same reference numerals as those in Figure 4 are added, and the description is omitted.

[0040] Step S210 is executed after the warm-up of the fuel cell system 100 is completed. In step S210, the control unit 10 determines whether the brake resistor 5 has been used. In other words, the control unit 10 determines whether the operating state of the brake resistor 5 is "when BR is operating". If the brake resistor 5 has been used, step S110 is executed. If the brake resistor 5 has not been used, step S50 is executed.

[0041] In step S110, if it is determined that the temperature of the brake resistor 5 is equal to or higher than the upper limit temperature, step S120 is executed. If it is determined that the temperature of the brake resistor 5 is lower than the upper limit temperature, step S220 is executed.

[0042] In step S120, the control unit 10 opens the three-way valve 3 and drives the first cooling pump 2 and the second cooling pump 6. In other words, when the operating state of the brake resistor 5 is "when BR is operating" and the temperature of the brake resistor 5 is equal to or higher than the upper limit temperature, the control unit 10 opens the three-way valve 3 and drives the first cooling pump 2 and the second cooling pump 6. Specifically, the control unit 10 sets the flow rate ratio to a value equal to or higher than the first value, and drives the first cooling pump 2 so that the flow rate of the refrigerant flowing through the first flow path L1 is equal to or higher than the flow rate of the refrigerant flowing from the second flow path L2 into the second connection portion P2. In the examples shown in FIGS. 5 and 6, the first value is 10%, and the flow rate of the first cooling pump 2 is 120 L / min. Thereby, the brake resistor 5 is cooled.

[0043] In step S220, the control unit 10 sets the flow division ratio to 0% and drives the first cooling pump 2 and the second cooling pump 6. In other words, when the operating state of the brake resistor 5 is "when BR is operating" and the temperature of the brake resistor 5 is less than the upper limit temperature, the control unit 10 sets the flow division ratio to 0% and drives the first cooling pump 2 and the second cooling pump 6. In this case, the refrigerant passing through the fuel cell 1 circulates in the fuel cell module 20 in the order of the fuel cell 1, the first connection part P1, the second connection part P2, the first cooling pump 2, and the fuel cell 1. The refrigerant passing through the brake resistor 5 circulates through a part of the fourth flow path L4 and the second flow path L2 in the order of the brake resistor 5, the second cooling pump 6, and the brake resistor 5. Therefore, the fuel cell 1 and the brake resistor 5 are not cooled. Note that in step S220, the control unit 10 may stop the first cooling pump 2.

[0044] In step S50, when it is determined that the fuel cell system 100 is not stopped, the control unit 10 returns the process to step S210.

[0045] According to the fuel cell system 100 in the third embodiment described above, when the brake resistor 5 is used and the temperature of the brake resistor 5 is equal to or higher than the upper limit temperature, the control unit 10 sets the flow division ratio to a value equal to or higher than the first value, drives the second cooling pump 6, and drives the first cooling pump 2 so that the flow rate of the refrigerant flowing through the first flow path L1 is equal to or higher than the flow rate of the refrigerant flowing into the second connection part P2 from the second flow path L2. Therefore, when the brake resistor 5 is used and the temperature of the brake resistor 5 is equal to or higher than the upper limit temperature, the brake resistor 5 can be cooled. In addition, it is possible to suppress the reverse flow of the refrigerant in the third flow path L3.

[0046] Further, in the present embodiment, when the brake resistor 5 is used and the temperature of the brake resistor 5 is less than the upper limit temperature, the control unit 10 sets the flow division ratio to 0% and drives the first cooling pump 2 and the second cooling pump 6. In this case, since the low-temperature refrigerant that has passed through the brake resistor 5 does not pass through the fuel cell 1, it is possible to suppress the fuel cell 1 from being cooled and deteriorated.

[0047] D. Other Embodiments: (D-1) In the above embodiment, the fuel cell system 100 includes one fuel cell 1 and one brake resistor 5 each. In contrast, the fuel cell system may include a plurality of fuel cells 1 or a plurality of brake resistors 5. FIG. 8 is a block diagram showing an example of a fuel cell system 100b that includes two fuel cells 1 and two brake resistors 5 each. The fuel cell system 100b includes two fuel cell modules 20. The two fuel cell modules 20 are provided in parallel. Also, two brake resistors 5 are provided in parallel in the fourth flow path L4.

[0048] (D-2) In the above embodiment, the fourth flow path L4 is provided in parallel with the second flow path L2 between the radiator 4 and the second connection portion P2. In contrast, the fourth flow path L4 may be provided in parallel with the second flow path L2 between the first connection portion P1 and the radiator 4.

[0049] (D-3) In the above embodiment, the brake resistor 5 is provided in the fourth flow path L4. In contrast, a device that generates heat by consuming power, such as an ECU, may be provided in the fourth flow path L4 instead of the brake resistor 5. In this specification, a device that generates heat by consuming power, including the brake resistor 5, is called a power consumption unit. That is, a power consumption unit other than the brake resistor 5 may be provided in the fourth flow path L4 instead of the brake resistor 5.

[0050] (D-4) In the first embodiment, in the control process shown in FIG. 2, when the flow rate ratio is greater than 0% and the second cooling pump 6 is driven, the control unit 10 drives the first cooling pump 2 so that the flow rate of the refrigerant flowing through the first flow path L1 is equal to or greater than the flow rate of the refrigerant flowing into the second connection portion P2 from the second flow path L2. In contrast, the control unit 10 may not drive the first cooling pump 2 when the flow rate ratio is greater than 0% and the second cooling pump 6 is driven. That is, steps S30 to S50 of the control process shown in FIG. 2 may not be executed.

[0051] The present disclosure is not limited to the above-described embodiments, and can be implemented in various configurations without departing from the gist thereof. For example, the technical features in the embodiments corresponding to the technical features in each of the forms described in the summary of the invention can be appropriately replaced or combined in order to solve some or all of the above-described problems, or to achieve some or all of the above-described effects. Further, if the technical feature is not described as essential in this specification, it can be appropriately deleted.

Explanation of Reference Numerals

[0052] 1... fuel cell, 2... first cooling pump, 3... three-way valve, 4... radiator, 5... brake resistor, 6... second cooling pump, 10... control unit, 20... fuel cell module, 100, 100b, 200... fuel cell system, L1... first flow path, L2... second flow path, L3... third flow path, L4... fourth flow path, P1... first connection portion, P2... second connection portion

Claims

1. A fuel cell system, comprising: a first flow path provided with a fuel cell and a first cooling pump for cooling the fuel cell; a second flow path provided with a radiator; a first connection part connecting a first end of the first flow path and a first end of the second flow path; a second connection part connecting a second end of the first flow path and a second end of the second flow path; a third flow path connecting the first connection part and the second connection part; a three-way valve provided at the first connection part, allowing the refrigerant to pass from the first flow path to the second flow path and from the first flow path to the third flow path, and capable of changing a flow rate ratio, which is a ratio of the flow rate of the refrigerant flowing out to the second flow path to the flow rate of the refrigerant flowing into the first flow path; a fourth flow path provided with a power consumption unit and a second cooling pump for cooling the power consumption unit; a control unit for controlling the first cooling pump, the second cooling pump, and the flow rate ratio; the fourth flow path is provided between the three-way valve and the radiator or between the radiator and the second connection part; the control unit sets the flow rate ratio to 0% at cold start and drives the first cooling pump; a fuel cell system.

2. The fuel cell system according to claim 1, wherein when the flow rate ratio is greater than 0% and the second cooling pump is driven, the control unit drives the first cooling pump so that the flow rate of the refrigerant flowing through the first flow path is equal to or greater than the flow rate of the refrigerant flowing into the second connection part from the second flow path; a fuel cell system.

3. The fuel cell system according to claim 1, wherein when the temperature of the power consumption unit is equal to or higher than a preset upper limit temperature, the control unit sets a lower limit value of the flow rate ratio to a first value, which is a preset value greater than 0%, drives the second cooling pump, and drives the first cooling pump so that the flow rate of the refrigerant flowing through the first flow path is equal to or greater than the flow rate of the refrigerant flowing into the second connection part from the second flow path; a fuel cell system.

4. The fuel cell system according to claim 3, wherein the power consumption unit is a brake resistor, and when the brake resistor is in use and the temperature of the brake resistor is equal to or higher than the upper limit temperature, the control unit sets the lower limit value of the flow rate ratio to the first value, drives the second cooling pump, Drive the first cooling pump so that the flow rate of the refrigerant flowing through the first flow path is equal to or greater than the flow rate of the refrigerant flowing into the second connection portion from the second flow path. Fuel cell system.

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