Cooling system

Abstract

To properly cool a fuel cell stack.SOLUTION: A cooling system S includes: a first pump 13 that is provided in a cooling flow path 1 downstream of a radiator 10 and upstream of an FC stack 11 and transfers cooling water; a control valve 14 that is provided at a first junction in the cooling flow path 1 and adjusts a first flow rate of the cooling water flowing from the radiator 10 to the first pump 13 and a second flow rate of the cooling water flowing from a first branch flow path 2 to the first pump 13; a second pump 23 that is provided in a second branch flow path 3 upstream of a braking resistor 21 and transfers cooling water; and a control device 30 that determines a first transfer rate of the first pump 13 on the basis of an adjustment degree of the first flow rate and the second flow rate of the adjustment valve and a temperature of the FC stack 11, and determines a second transfer rate of the second pump 23 on the basis of the adjustment degree and the first transfer rate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cooling system. [Background technology]

[0002] The cooling system of Patent Document 1 adjusts a first flow rate of cooling water flowing through a first flow path provided for cooling a fuel cell stack based on a second flow rate of cooling water flowing through a second flow path provided for cooling a braking resistor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-12332 Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional cooling systems, the cooling flow path branches into a first flow path and a second flow path at a branching point downstream of the radiator, the first flow path and the second flow path merge at a junction point downstream of the pumps provided in the first flow path and the second flow path, and the cooling water circulates by returning to the radiator downstream of the junction point. However, if the second flow rate of the cooling water flowing through the second flow path is greater than the first flow rate of the cooling water flowing through the first flow path, the cooling water flowing through the second flow path may flow back into the first flow path, which may prevent the fuel cell stack from being properly cooled.

[0005] The present invention has been made in view of these points, and has as its object to appropriately cool a fuel cell stack. [Means for solving the problem]

[0006] A cooling system according to an aspect of the present invention includes a cooling flow path that circulates cooling water between a radiator and a fuel cell stack; a first pump that is provided in the cooling flow path downstream of the radiator and upstream of the fuel cell stack and that transports the cooling water; a first branch flow path that branches off from the cooling flow path downstream of the fuel cell stack, bypasses the radiator, and merges at a first junction upstream of the first pump; and a second branch flow path that is provided in the cooling flow path at the first junction and that controls a first flow rate of the cooling water flowing from the radiator to the first pump and a second flow rate of the cooling water flowing from the first branch flow path to the first pump. a second branch flow path that branches off from a branch point upstream of the adjustment valve in the cooling flow path and joins the cooling flow path at a second joining point downstream of the fuel cell stack; a braking resistor provided in the second branch flow path; a second pump that is provided in the second branch flow path upstream of the braking resistor and transports the cooling water; and a control device that determines a first transfer amount of the first pump based on an adjustment degree of the first flow rate and the second flow rate of the adjustment valve and a temperature of the fuel cell stack, and determines a second transfer amount of the second pump based on the adjustment degree and the first transfer amount.

[0007] The cooling system may further include a first check valve provided downstream of a branch point between the cooling channel and the first branch channel in the cooling channel and upstream of the second junction point in the cooling channel.

[0008] The hydraulic system may further include a second check valve provided in the second branch flow path downstream of the braking resistor and upstream of the second junction in the second branch flow path.

[0009] The cooling system may further include a three-way valve provided at the second junction to prevent backflow of the cooling water between the cooling flow path and the second branch flow path.

[0010] The adjustment valve may increase the first flow rate and decrease the second flow rate as the temperature of the cooling water at the first junction increases.

[0011] The control device may increase the first transfer amount as the first flow rate corresponding to the adjustment degree increases.

[0012] The control device may increase the first transfer amount as the temperature of the fuel cell stack increases.

[0013] The control device may determine the second feed amount based on the determined first feed amount, the adjustment degree, and the temperature of the braking resistor.

[0014] The control device may be configured to increase the second transport amount as the temperature of the braking resistor increases while the braking resistor is in an activated state.

[0015] The control device may determine the second feed amount to be greater than 0 and smaller than the first feed amount when the braking resistor is not activated.

[0016] The control device may determine the first transfer amount and the second transfer amount by referring to a transfer amount map stored in a memory unit, the transfer amount map indicating the first transfer amount corresponding to the adjustment degree, the state of whether the braking resistor is activated or not, and the temperature of the fuel cell stack, and the second transfer amount corresponding to the first transfer amount. [Effects of the Invention]

[0017] The present invention provides the effect of appropriately cooling the fuel cell stack. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a diagram schematically illustrating the configuration of a cooling system S according to the present embodiment. [Figure 2] 1 is a diagram showing a schematic configuration of a cooling system S provided with a check valve. [Figure 3] 1 is a diagram showing a schematic configuration of a cooling system S provided with a three-way valve. [Figure 4] 4 is a diagram showing an example of a processing sequence in the control device 30. FIG. [Figure 5] FIG. 10 is a diagram showing an example of a transfer amount map stored in a storage unit. DETAILED DESCRIPTION OF THE INVENTION

[0019] <Configuration of Cooling System S> Fig. 1 is a diagram schematically illustrating the configuration of a cooling system S according to this embodiment. The cooling system S illustrated in Fig. 1 includes a cooling flow path 1, a first branch flow path 2, a second branch flow path 3, a radiator 10, a fuel cell stack 11, a first temperature sensor 12, a first pump 13, a control valve 14, a braking resistor 21, a second temperature sensor 22, a second pump 23, and a control device 30.

[0020] The cooling system S is mounted on the vehicle and has the function of cooling the fuel cell stack 11 and the braking resistor 21 by exchanging heat between the fuel cell stack 11 and the braking resistor 21 and the cooling water. First, each flow path through which the cooling water flows will be described.

[0021] The cooling flow path 1 is a flow path provided to cool the fuel cell stack 11, and circulates cooling water between the radiator 10 and the fuel cell stack 11. The cooling flow path 1 is provided with the radiator 10, a control valve 14, a first pump 13, and the fuel cell stack 11 along the cooling water circulation direction D1.

[0022] As shown by the dashed line in Fig. 1, the first branch flow path 2 is a flow path that branches off from a first branch point 4 downstream of the fuel cell stack 11 in the cooling flow path 1, bypasses the radiator 10, and merges at a first junction point (not shown) upstream of the first pump 13. As shown in Fig. 1, a control valve 14 is provided at the first junction point. Also, direction D2 shown in Fig. 1 is the direction in which the coolant flows in the first branch flow path 2. By providing the first branch flow path 2 in this manner, the cooling system S can flow the coolant that has not exchanged heat with the radiator 10 to the fuel cell stack 11 when the fuel cell stack 11 is not being cooled.

[0023] The second branch flow path 3 is provided to cool the braking resistor 21. As shown by the dashed dotted line in Fig. 1 , the second branch flow path 3 branches off from a second branch point 5 upstream of the control valve 14 in the cooling flow path 1 and merges with the cooling flow path 1 at a second junction point 6 downstream of the fuel cell stack 11. A second pump 23 and the braking resistor 21 are provided in the second branch flow path 3 along the cooling water flow direction D3. Next, each device provided in each flow path will be described.

[0024] The radiator 10 is provided upstream of the regulator valve 14 in the cooling flow path 1, and cools the coolant that has passed through at least one of the fuel cell stack 11 and the braking resistor 21. The radiator 10 cools the coolant, for example, by exchanging heat between the coolant and wind (driving wind) flowing from the front of the vehicle equipped with the cooling system S. The radiator 10 may be provided with a fan for promoting the inflow of wind from the front of the vehicle.

[0025] The fuel cell stack 11 is a module in which a plurality of fuel cells are stacked, and is provided downstream of the first pump 13 in the cooling flow path 1. The fuel cell stack 11 generates electricity through a chemical reaction between a fuel gas such as hydrogen gas and an oxidant gas such as oxygen in the air, and supplies the generated electricity to a drive source (for example, a motor) provided in a vehicle equipped with the cooling system S. In the following description, the fuel cell stack 11 will be referred to as an FC stack 11.

[0026] The first temperature sensor 12 is a sensor for detecting the temperature of the FC stack 11 and outputs the detected temperature to the control device 30. The first pump 13 is provided in the cooling flow path 1 downstream of the radiator 10 and upstream of the FC stack 11, and transfers the cooling water. The first pump 13 has, for example, a rotor, and rotates the rotor at a first rotation speed corresponding to a first transfer amount obtained from the control device 30 to suck in the cooling water, and discharges the sucked in cooling water to the FC stack 11. The first transfer amount is the amount of cooling water discharged by the first pump 13 to the FC stack 11 per unit time.

[0027] The control valve 14 is provided at the first junction in the cooling flow path 1 and adjusts a first flow rate of the coolant flowing from the radiator 10 to the first pump 13 and a second flow rate of the coolant flowing from the first branch flow path 2 to the first pump 13. The control valve 14 is, for example, a thermostat and has a first valve for adjusting the first flow rate, a second valve for adjusting the second flow rate, and a thermistor for detecting the temperature of the coolant at the first junction. The first and second valves are adjusted so that the larger the opening of one valve is, the smaller the opening of the other valve is. The thermistor is provided, for example, at the discharge port of the control valve 14.

[0028] The control valve 14 adjusts the ratio between the first flow rate and the second flow rate of the cooling water flowing to the first pump 13 by determining the valve apertures of the first valve and the second valve based on, for example, the temperature detected by the thermistor. Specifically, the higher the temperature of the cooling water at the first junction, the larger the first flow rate and the smaller the second flow rate. That is, the higher the temperature detected by the thermistor, the larger the valve aperture of the first valve and the smaller the valve aperture of the second valve. On the other hand, the lower the temperature detected by the thermistor, the smaller the valve aperture of the first valve and the larger the valve aperture of the second valve. The control valve 14 outputs an adjustment degree indicating the determined valve apertures of the first valve and the second valve (i.e., the ratio between the first flow rate and the second flow rate) to the control device 30.

[0029] By operating the adjustment valve 14 as described above, the cooling system S increases the first flow rate the higher the temperature of the cooling water downstream of the adjustment valve 14, thereby making it easier to exchange heat between the cooling water that has been cooled through heat exchange with the radiator 10 and the FC stack 11. On the other hand, the cooling system S increases the second flow rate the lower the temperature of the cooling water downstream of the adjustment valve 14, thereby allowing cooling water that has not exchanged heat with the radiator 10 to flow into the FC stack 11, thereby preventing the FC stack 11 from being overcooled.

[0030] Furthermore, in the cooling system S, the larger the second flow rate (the smaller the first flow rate), the larger the third flow rate of the coolant flowing from the radiator 10 to the second pump 23, which makes it easier to exchange heat between the coolant cooled by heat exchange with the radiator 10 and the braking resistor 21. The larger the third flow rate, the larger the flow rate of the coolant flowing from the second branch flow path 3 at the second junction 6, which makes it easier for the coolant to stagnate upstream of the second junction 6 and downstream of the first branch point 4. As a result, at the first branch point 4, the larger the third flow rate, the larger the second flow rate of the coolant branching into the first branch flow path 2.

[0031] The braking resistor 21 is, for example, a brake such as a retarder, and is provided in the second branch flow path 3. When the braking resistor 21 receives instruction information indicating an instruction to brake the vehicle from the control device 30, the braking resistor 21 brakes the vehicle. The second temperature sensor 22 is a sensor for detecting the temperature of the braking resistor 21, and outputs the detected temperature to the control device 30.

[0032] The second pump 23 is provided upstream of the braking resistor 21 in the second branch flow path 3 and transfers the cooling water. The second pump 23 has, for example, a rotor and rotates the rotor at a second rotation speed corresponding to a second transfer amount obtained from the control device 30 to suck in the cooling water and discharge the sucked cooling water to the braking resistor 21. The second transfer amount is the amount of cooling water discharged by the second pump 23 to the braking resistor 21 per unit time.

[0033] The control device 30 is a device that includes, for example, one or more processors such as a CPU (Central Processing Unit) or an ECU (Electronic Control Unit). The control device 30 executes processes such as receiving an operation from the driver of the vehicle to decelerate or stop the vehicle and causing the braking resistor 21 to brake the vehicle, and determining a first transfer amount and a second transfer amount to cool the FC stack 11 and the braking resistor 21. The control device 30 may have a housing that contains electronic components, or may be a printed circuit board on which electronic components are mounted.

[0034] Incidentally, a conventional control device 30 determines a first transfer amount corresponding to a subtraction value obtained by subtracting a target temperature of the FC stack 11 from the temperature detected by the first temperature sensor 12, and outputs a first rotation speed of the rotor corresponding to the first transfer amount to the first pump 13. Then, the control device 30 determines a second rotation speed of the rotor corresponding to a second transfer amount based on the first rotation speed of the rotor, and outputs the second rotation speed to the second pump 23.

[0035] In the above-described conventional operation, when the control valve 14 reduces the first flow rate and the control device 30 increases the second rotation speed, the flow rate of the cooling water flowing from the second branch flow path 3 to the second junction 6 may be greater than the flow rate of the cooling water flowing from the first branch point 4 to the second junction 6. In this case, if the flow rate of the cooling water flowing from the first branch point 4 to the second junction 6 is extremely small, the cooling water flowing from the second branch flow path 3 to the second junction 6 may not flow in direction D4 from the second junction 6, but may flow back from the second junction 6 to the first branch point 4. Therefore, the control device 30 determines the first transfer rate of the first pump 13 based on the adjustment degree of the first and second flow rates of the control valve 14 and the temperature of the FC stack 11, and determines the second transfer rate of the second pump 23 based on the adjustment degree and the first transfer rate.

[0036] For example, the control device 30 increases the first transfer amount as the first flow rate corresponding to the adjustment degree acquired from the adjustment valve 14 increases. Furthermore, for example, the control device 30 increases the first transfer amount as the temperature of the FC stack 11 detected by the first temperature sensor 12 increases. Next, for example, the control device 30 determines a first relative ratio of the second transfer amount to the first transfer amount based on the adjustment degree, and determines the second transfer amount as the multiplied value obtained by multiplying the first transfer amount by the first relative ratio. When expressed as a percentage, the first relative ratio indicates a value greater than 0 and less than 100. For example, the control device 30 decreases the first relative ratio as the valve opening degree of the first valve included in the adjustment degree increases.

[0037] Then, the control device 30 outputs a first rotation speed corresponding to the determined first transfer amount to the first pump 13, and outputs a second rotation speed corresponding to the determined second transfer amount to the second pump 23. By operating as described above, the control device 30 can make the second transfer amount smaller than the first transfer amount, and therefore can make the flow rate of the cooling water flowing from the second branch flow path 3 to the second junction 6 smaller than the flow rate of the cooling water flowing from the first branch point 4 to the second junction 6. As a result, the control device 30 can prevent the cooling water from flowing back from the second junction 6 to the first branch point 4, and the cooling system S can appropriately cool the FC stack 11.

[0038] If the drive source of a vehicle equipped with cooling system S includes a motor, when the vehicle accelerates, FC stack 11, which generates electricity to supply to the motor, generates heat, but braking resistor 21 does not. On the other hand, when the vehicle decelerates or stops, braking resistor 21, which operates to brake the vehicle, generates heat, but FC stack 11 does not. In other words, when the vehicle is running, if one of FC stack 11 or braking resistor 21 operates and generates heat, the other does not operate and does not generate heat.

[0039] Therefore, the control device 30 may determine the first transfer amount and the second transfer amount based on whether the braking resistor 21 is operating. For example, when the braking resistor 21 is not operating, the control device 30 determines the first transfer amount based on the adjustment degree of the control valve 14 and the temperature of the FC stack 11. Then, the control device 30 determines the second transfer amount that is greater than 0 and smaller than the first transfer amount, for example, by multiplying the determined first transfer amount by a first relative ratio that corresponds to the adjustment degree. By operating the control device 30 in this manner, the cooling system S can flow coolant to the FC stack 11 and also flow coolant from the second branch flow path 3 to the radiator 10, thereby appropriately cooling the FC stack 11 and cooling the coolant.

[0040] For example, when the braking resistor 21 is operating, the control device 30 determines a first transfer amount based on the adjustment degree and the temperature of the FC stack 11, and then determines a second transfer amount based on the determined first transfer amount, the adjustment degree, and the temperature of the braking resistor 21. For example, the control device 30 increases the second transfer amount as the second flow rate corresponding to the adjustment degree increases, and increases the second transfer amount as the temperature of the braking resistor 21 increases.

[0041] For example, when braking resistor 21 is activated, control device 30 determines a second relative ratio of the second transfer amount to the first transfer amount based on the adjustment degree, and determines the second transfer amount as the multiplied value obtained by multiplying the first transfer amount by the second relative ratio. When expressed as a percentage, the second relative ratio indicates a value of 100 or more. For example, control device 30 increases the second relative ratio as the valve opening degree of the second valve included in the adjustment degree increases, and increases the second relative ratio as the temperature of braking resistor 21 detected by second temperature sensor 22 increases.

[0042] By operating the control device 30 as described above, the control device 30 can make the second transfer amount greater than the first transfer amount when the braking resistor 21 is in an operating state. As a result, the cooling system S can appropriately cool the FC stack 11 that is not generating power without overcooling it, and can also appropriately cool the braking resistor 21 that is in an operating state.

[0043] However, even if the cooling system S can cool the FC stack 11 and braking resistor 21 by operating the control device 30 as described above, there are cases in which the second transfer amount is greater than the first transfer amount. For example, when the braking resistor 21 is operating, the FC stack 11 does not generate electricity, so the temperature of the FC stack 11 drops and the temperature of the braking resistor 21 rises, which can cause the second transfer amount to be greater than the first transfer amount. As a result, in the cooling system S, there is a risk that the cooling water will flow back from the second junction 6 to the first branch point 4. To address this, the cooling system S may be provided with a check valve to prevent backflow.

[0044] Fig. 2 is a diagram schematically showing the configuration of a cooling system S provided with a check valve. The cooling system S shown in Fig. 2 differs from the cooling system S shown in Fig. 1 in that it includes a first check valve 31 and a second check valve 32, but is otherwise the same. As shown in Fig. 2, the first check valve 31 is provided downstream of a first branch point 4 between the cooling channel 1 and the first branch channel 2 in the cooling channel 1, and upstream of a second junction 6 in the cooling channel 1.

[0045] By providing the first check valve 31 in this manner, the cooling system S can prevent the coolant from flowing back from the second junction 6 to the first branch point 4, even when the second transfer rate is greater than the first transfer rate. Furthermore, by preventing backflow, the cooling system S allows the coolant to flow appropriately to the radiator 10, thereby allowing the FC stack 11 and braking resistor 21 to be cooled appropriately.

[0046] 2, the cooling system S may further include a second check valve 32 downstream of the braking resistor 21 in the second branch flow path 3 and upstream of the second junction 6 in the second branch flow path 3. By providing the second check valve 32 in this manner, the cooling system S can prevent the cooling water that has passed through the first check valve 31 from flowing back into the second branch flow path 3 when the second transfer rate is much smaller than the first transfer rate.

[0047] Furthermore, the cooling system S may include a three-way valve instead of the first check valve 31 and the second check valve. FIG. 3 is a diagram schematically illustrating the configuration of the cooling system S including a three-way valve. The cooling system S illustrated in FIG. 3 differs from the cooling system S illustrated in FIG. 1 in that it includes a three-way valve 33, but is otherwise the same. The three-way valve 33 is provided at the second junction 6 and prevents backflow of the cooling water between the cooling flow path 1 and the second branch flow path 3. Specifically, the three-way valve 33 directs the cooling water flowing from the first branch point 4 and the braking resistor 21 to the three-way valve 33 downstream of the three-way valve 33 in the cooling flow path 1, thereby preventing the cooling water from flowing (backflowing) from the three-way valve 33 to the first branch point 4 and the braking resistor 21.

[0048] <Processing sequence in the control device 30> Fig. 4 is a diagram showing an example of a processing sequence in the control device 30. The processing sequence shown in Fig. 4 is a sequence showing the operation of the control device 30 to output the rotor rotation speeds to the first pump 13 and the second pump 23. The control device 30 repeats the processing sequence shown in Fig. 4 at a predetermined control period (for example, 1 second).

[0049] The control device 30 acquires the adjustment degree of the adjustment valve 14 from the adjustment valve 14 (S11), and acquires the temperature of the FC stack 11 from the first temperature sensor 12 (S12). The control device 30 determines a first transfer amount of the first pump 13 based on the adjustment degree and the temperature of the FC stack 11 (S13), and outputs a first rotation speed of the rotor corresponding to the first transfer amount to the first pump 13 (S14).

[0050] The control device 30 determines the state of the braking resistor 21, which indicates whether the braking resistor 21 is operating, based on whether an operation to decelerate or stop the vehicle has been received from the driver of the vehicle (S15). If the braking resistor 21 is operating (YES in S16), the control device 30 obtains the temperature of the braking resistor 21 from the second temperature sensor 22 (S17), and determines the second transfer rate of the second pump 23 based on the temperature, the first transfer rate, and the adjustment degree (S18).

[0051] On the other hand, if the braking resistor 21 is not activated (NO in S16), the control device 30 determines the second transfer amount of the second pump 23 based on the first transfer amount and the adjustment degree (S18). The control device 30 outputs the second rotation speed of the rotor corresponding to the determined second transfer amount to the second pump 23 (S19).

[0052] <Modification> In the above explanation, an example has been given of the operation in which the control device 30 determines the first transfer amount and the second transfer amount based on parameters such as the adjustment degree, the temperature of the FC stack 11, and the state of the braking resistor 21 each time the control device 30 acquires the parameters at a predetermined control cycle, but the present invention is not limited to this. The control device 30 may determine the first transfer amount and the second transfer amount by referencing a transfer amount map stored in a memory unit of the control device 30. The transfer amount map is a map that indicates the first transfer amount corresponding to the adjustment degree, the state of whether the braking resistor 21 is activated, and the temperature of the FC stack 11, and the second transfer amount corresponding to the first transfer amount.

[0053] Fig. 5 is a diagram showing an example of a transfer amount map stored in a storage unit. For ease of explanation, Fig. 5 shows transfer amount maps M1, M2, and M3 out of multiple transfer amount maps M corresponding to each adjustment degree of the regulator valve 14. Each transfer amount map M shows a "first transfer amount (or first rotation speed)" and a "second transfer amount (or second rotation speed)" corresponding to the "braking resistor 21," "FC stack 11 temperature," and "braking resistor 21 temperature."

[0054] "Braking resistor 21" indicates whether the braking resistor 21 is operating. "FC stack 11 temperature" indicates a range that includes the temperature detected by the first temperature sensor 12. "Braking resistor 21 temperature" indicates a range that includes the temperature detected by the second temperature sensor 22. "First transfer amount (or first rotation speed)" is a setting value for setting a first rotation speed for the first pump 13, corresponding to the first transfer amount or first rotation speed. "Second transfer amount (or second rotation speed)" is a setting value for setting a second rotation speed for the second pump 23, corresponding to the second transfer amount or second rotation speed.

[0055] The control device 30, for example, identifies a transfer amount map M from among a plurality of transfer amount maps M that corresponds to the adjustment degree acquired from the adjustment valve 14. For example, when the braking resistor 21 is operating, the control device 30 identifies a first range that includes the temperature detected by the first temperature sensor 12 and a second range that includes the temperature detected by the second temperature sensor 22. The control device 30 determines the first transfer amount and the second transfer amount by identifying the setting values to be set for the first pump 13 and the second pump 23 that correspond to the identified first and second ranges.

[0056] On the other hand, for example, when braking resistor 21 is not operating, control device 30 determines the first transfer rate and the second transfer rate by identifying a first range that includes the temperature detected by first temperature sensor 12 and identifying the set values to be set for first pump 13 and second pump 23 that correspond to the first range. By operating control device 30 as described above, control device 30 can reduce the amount of processing required to determine the first transfer rate and the second transfer rate.

[0057] In FIG. 5 , the “first feed amount (or first rotation speed)” may indicate the first feed amount or the first rotation speed, and the “second feed amount (or second rotation speed)” may indicate a relative ratio to the first feed amount or the first rotation speed. As an example, the “first feed amount (or first rotation speed)” may indicate the first rotation speed, and the “second feed amount (or second rotation speed)” may indicate a relative ratio. In this case, when the braking resistor 21 is not activated, the control device 30 identifies the first rotation speed and relative ratio corresponding to the identified first range, and determines the second rotation speed as a multiplied value obtained by multiplying the first rotation speed by the relative ratio. Furthermore, when the braking resistor 21 is activated, the control device 30 identifies the first rotation speed and relative ratio corresponding to the identified first and second ranges, and determines the second rotation speed as a multiplied value obtained by multiplying the first rotation speed by the relative ratio.

[0058] <Effects of Cooling System S> As described above, the cooling system S comprises: a first pump 13 that is provided in the cooling flow path 1 downstream of the radiator 10 and upstream of the FC stack 11 and that transfers cooling water; a control valve 14 that is provided at the first junction in the cooling flow path 1 and that adjusts a first flow rate of the cooling water flowing from the radiator 10 to the first pump 13 and a second flow rate of the cooling water flowing from the first branch flow path 2 to the first pump 13; a second pump 23 that is provided in the second branch flow path 3 upstream of the braking resistor 21 and that transfers cooling water; and a control device 30 that determines a first transfer amount of the first pump 13 based on the adjustment degree of the first flow rate and second flow rate of the adjustment valve 14 and the temperature of the FC stack 11, and determines a second transfer amount of the second pump 23 based on the adjustment degree and the first transfer amount.

[0059] By configuring the cooling system S in this manner, the control device 30 can determine the first transfer amount at which the first pump 13 transfers cooling water to the FC stack 11 based on the first flow rate that corresponds to the adjustment degree of the control valve 14, and can therefore determine an appropriate first transfer amount that corresponds to the adjustment degree. Furthermore, the control device 30 can determine a second transfer amount that is smaller than the first transfer amount based on the adjustment degree and the first transfer amount, and can therefore prevent the cooling water flowing through the second branch flow path 3 from flowing back at the second junction 6. As a result, in the cooling system S, the cooling water flows appropriately through each flow path, and the FC stack 11 can be cooled appropriately.

[0060] The present invention has been described above using embodiments, but the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. For example, all or part of the device can be configured by functionally or physically distributing or integrating any unit. Furthermore, new embodiments resulting from any combination of multiple embodiments are also included in the embodiments of the present invention. The effects of the new embodiments resulting from the combination also have the effects of the original embodiments. [Explanation of symbols]

[0061] S Cooling System 1 Cooling Channel 2 First branch channel 3 Second branch channel 4 First Branch Point 5 Second Branching Point 6 Second confluence point 10 Radiator 11 Fuel cell stack 11 FC stack 12 First temperature sensor 13 First Pump 14 Control valve 21 Braking resistor 22 Second temperature sensor 23 Second Pump 30 Control device 31 First check valve 32 Second check valve 33 Three-way valve

Claims

1. a cooling flow path for circulating cooling water between the radiator and the fuel cell stack; a first pump that is provided in the cooling flow path downstream of the radiator and upstream of the fuel cell stack and that transports the cooling water; a first branch flow path that branches off from the cooling flow path downstream of the fuel cell stack, bypasses the radiator, and joins at a first joining point upstream of the first pump; an adjustment valve provided at the first junction in the cooling flow path, which adjusts a first flow rate of the cooling water flowing from the radiator to the first pump and a second flow rate of the cooling water flowing from the first branch flow path to the first pump; a second branch flow path that branches off from a branch point upstream of the adjustment valve in the cooling flow path and merges with the cooling flow path at a second merging point downstream of the fuel cell stack; a braking resistor provided in the second branch flow path; a second pump provided in the second branch flow path upstream of the braking resistor and configured to transport the cooling water; a control device that determines a first transfer amount of the first pump based on an adjustment degree of the first flow rate and the second flow rate of the adjustment valve and a temperature of the fuel cell stack, and that determines a second transfer amount of the second pump based on the adjustment degree and the first transfer amount; A cooling system having:

2. a first check valve provided in the cooling flow path downstream of a branch point between the cooling flow path and the first branch flow path and upstream of the second junction point in the cooling flow path; The cooling system of claim 1 .

3. a second check valve provided in the second branch flow path downstream of the braking resistor and upstream of the second junction point in the second branch flow path; The cooling system of claim 2 .

4. a three-way valve provided at the second junction to prevent backflow of the cooling water in the cooling flow path and the second branch flow path; The cooling system of claim 1 .

5. the adjusting valve increases the first flow rate and decreases the second flow rate as the temperature of the cooling water at the first junction increases. The cooling system of claim 1 .

6. the control device increases the first transfer amount as the first flow rate corresponding to the adjustment degree increases, The cooling system of claim 1 .

7. the control device increases the first transfer amount as the temperature of the fuel cell stack increases; The cooling system of claim 1 .

8. The control device determines the second feed amount based on the determined first feed amount, the adjustment degree, and the temperature of the braking resistor. The cooling system of claim 1 .

9. the control device increases the second feed amount as the temperature of the braking resistor increases while the braking resistor is in operation; The cooling system of claim 8.

10. The control device determines the second transfer amount to be greater than 0 and smaller than the first transfer amount when the braking resistor is not activated.

10. The cooling system according to claim 8 or 9.

11. the control device determines the first transfer amount and the second transfer amount by referring to a transfer amount map stored in a memory unit, the transfer amount map indicating the first transfer amount corresponding to the adjustment degree, a state of whether the braking resistor is activated, and a temperature of the fuel cell stack, and the second transfer amount corresponding to the first transfer amount; The cooling system of claim 1 .

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