Fuel cell cooling system

Abstract

The present application relates to a fuel cell cooling system mounted on a vehicle, having: a flow path of a refrigerant; a cooler that cools the refrigerant in the cooler flow path; a fuel cell that is cooled by heat exchange with the refrigerant in the fuel cell flow path; a heat generating body that is cooled by heat exchange with the refrigerant in the heat generating body flow path; a first pump and a second pump that send out the refrigerant in the fuel cell flow path and the refrigerant in the heat generating body flow path, respectively; and a control circuit. When the vehicle is started, the control circuit implements a first process and a second process, the first process is a process of operating the first pump in a state where the second pump is stopped, and the second process is a process of operating the second pump in addition to the first pump if the temperature of the refrigerant in the fuel cell flow path or the cooler flow path exceeds a first reference value in the first process.

Description

Technical Field

[0001] The technology disclosed in this specification relates to fuel cell cooling systems. Background Technology

[0002] Japanese Patent Application Publication No. 2008-126911 discloses a fuel cell cooling system for cooling a fuel cell mounted in a vehicle. This fuel cell cooling system includes a refrigerant flow path for refrigerant to flow within it. A cooler for cooling the refrigerant within the refrigerant flow path and a fuel cell that is cooled through heat exchange with the refrigerant within the refrigerant flow path are provided within the refrigerant flow path. The fuel cell is cooled by supplying the refrigerant cooled by the cooler to the fuel cell. Summary of the Invention

[0003] There are cases where a flow path for cooling other heat-generating elements is arranged parallel to the flow path where the fuel cell is located. Hereinafter, the flow path where the fuel cell is located will be referred to as the fuel cell flow path, and the flow path where the heat-generating element is located will be referred to as the heat-generating element flow path. Furthermore, the flow path where the cooler is located will be referred to as the cooler flow path. Sometimes, refrigerant is circulated in the fuel cell flow path and the cooler flow path without refrigerant flowing into the heat-generating element flow path. In this state, the temperature of the refrigerant in the fuel cell flow path and the cooler flow path becomes higher than the temperature of the refrigerant in the heat-generating element flow path. Then, if refrigerant is flowed into the heat-generating element flow path, the low-temperature refrigerant in the heat-generating element flow path flows into the fuel cell flow path. As a result, the fuel cell is rapidly cooled, placing a heat load on the fuel cell. In this specification, a technique for reducing the heat load placed on the fuel cell is proposed.

[0004] A first fuel cell cooling system according to one embodiment of this specification is mounted in a vehicle. This fuel cell cooling system includes a refrigerant flow path for refrigerant to flow internally. The refrigerant flow path includes a cooler flow path, a fuel cell flow path, and a heating element flow path. The upstream ends of the fuel cell flow path and the upstream ends of the heating element flow path are connected to a branch provided at the downstream end of the cooler flow path. The downstream ends of the fuel cell flow path and the downstream ends of the heating element flow path are connected to a confluence portion provided at the upstream end of the cooler flow path. The aforementioned fuel cell cooling system further comprises: a cooler configured to cool the refrigerant within the cooler's flow path; a fuel cell configured to be cooled by heat exchange with the refrigerant within the fuel cell's flow path; a heating element configured to generate heat during operation and be cooled by heat exchange with the refrigerant within the heating element's flow path; a first pump configured to deliver the refrigerant within the fuel cell's flow path downstream; a second pump configured to deliver the refrigerant within the heating element's flow path downstream; and a control circuit configured to control the fuel cell, the first pump, and the second pump. The control circuit is configured to operate the fuel cell and the first pump during vehicle operation. The control circuit is configured to operate the second pump during the operation of the heating element. When the vehicle is started, the control circuit is configured to perform a first step and a second step. The first step is to operate the first pump when the second pump is stopped. The second step is to operate the second pump in addition to the first pump if the temperature of the refrigerant in the fuel cell flow path or the cooler flow path exceeds a first reference value during the first step.

[0005] In the first fuel cell cooling system described above, when the vehicle is started, the control circuit performs a step of activating the first pump while the second pump is stopped. Therefore, in the first step, the refrigerant circulates in the fuel cell flow path and the cooler flow path, while remaining stationary in the heating element flow path. The refrigerant circulating in the fuel cell and cooler flow paths is heated by the fuel cell. By circulating the refrigerant in the fuel cell and cooler flow paths without it flowing in the heating element flow path, the temperature of the circulating refrigerant can rise more quickly. This allows the fuel cell temperature to rise more rapidly. Therefore, the fuel cell's power generation efficiency increases rapidly after the vehicle starts. Furthermore, if the temperature of the refrigerant in the fuel cell or cooler flow path exceeds a first reference value in the first step, the control circuit performs a second step of activating the second pump in addition to the first pump. In the second step, the refrigerant circulates in a circulation path consisting of the fuel cell flow path, the heating element flow path, and the cooler flow path. That is, the refrigerant in the heating element flow path circulates together with the refrigerant in the fuel cell and cooler flow paths. Therefore, the temperature of the refrigerant in the heating element flow path rises. After the vehicle starts, the control circuit performs normal control. In normal control, the control circuit operates the fuel cell and the first pump while the vehicle is in motion, and operates the second pump when the heating element is operating. Therefore, if the heating element is operating, the refrigerant in the heating element flow path flows into the fuel cell flow path due to the operation of the second pump. At this time, because the refrigerant in the heating element flow path is preheated, it is difficult for a sharp temperature change to occur in the fuel cell. Therefore, the heat load applied to the fuel cell can be reduced.

[0006] A second fuel cell cooling system, as disclosed in this specification, is mounted in a vehicle. This fuel cell cooling system includes a refrigerant flow path for refrigerant to flow internally. The refrigerant flow path includes a cooler flow path, a fuel cell flow path, and a heating element flow path. The upstream ends of the fuel cell flow path and the upstream ends of the heating element flow path are connected to a branch provided at the downstream end of the cooler flow path. The downstream ends of the fuel cell flow path and the downstream ends of the heating element flow path are connected to a confluence portion provided at the upstream end of the cooler flow path. The aforementioned fuel cell cooling system further comprises: a cooler configured to cool the refrigerant within the cooler's flow path; a fuel cell configured to be cooled by heat exchange with the refrigerant within the fuel cell's flow path; a heating element configured to generate heat during operation and be cooled by heat exchange with the refrigerant within the heating element's flow path; a first pump configured to deliver the refrigerant within the fuel cell's flow path downstream; a second pump configured to deliver the refrigerant within the heating element's flow path downstream; and a control circuit configured to control the fuel cell, the first pump, and the second pump. The control circuit is configured to operate the fuel cell and the first pump while the vehicle is in motion. The control circuit is configured to operate the second pump while the heating element is operating. The control circuit is configured to perform a first step of operating the first pump and the second pump when the vehicle is started.

[0007] In the second fuel cell cooling system described above, the control circuit performs a first step of activating the first and second pumps upon vehicle startup. Therefore, in this first step, the refrigerant circulates in a loop consisting of the fuel cell flow path, the heating element flow path, and the cooler flow path, causing the temperature of the refrigerant in the heating element flow path to rise. After vehicle startup is complete, the control circuit performs normal control. In normal control, the control circuit activates the fuel cell and the first pump while the vehicle is in motion, and activates the second pump when the heating element is operating. Therefore, if the heating element is operating, the refrigerant in the heating element flow path flows into the fuel cell flow path due to the operation of the second pump. At this time, because the refrigerant in the heating element flow path is preheated, rapid temperature changes are less likely to occur in the fuel cell. Therefore, the heat load applied to the fuel cell can be reduced.

[0008] A third fuel cell cooling system, as disclosed in this specification, is installed in a vehicle. This fuel cell cooling system includes a refrigerant flow path for refrigerant to flow internally. The refrigerant flow path includes a cooler flow path, a fuel cell flow path, and a heating element flow path. The upstream ends of the fuel cell flow path and the upstream ends of the heating element flow path are connected to a branch provided at the downstream end of the cooler flow path. The downstream ends of the fuel cell flow path and the downstream ends of the heating element flow path are connected to a confluence portion provided at the upstream end of the cooler flow path. The aforementioned fuel cell cooling system further comprises: a cooler configured to cool the refrigerant within the cooler flow path; a fuel cell configured to be cooled by heat exchange with the refrigerant within the fuel cell flow path; a heating element configured to generate heat during operation and be cooled by heat exchange with the refrigerant within the heating element flow path; a first pump configured to deliver the refrigerant within the fuel cell flow path downstream; a second pump configured to deliver the refrigerant within the heating element flow path downstream; and a control circuit configured to control the fuel cell, the first pump, and the second pump. The control circuit is configured to operate the fuel cell and the first pump while the vehicle is in motion. The control circuit is configured to operate the second pump while the heating element is in operation. The control circuit is configured to, while the vehicle is in motion and the heating element is not in operation, if the temperature difference between the refrigerant within the fuel cell flow path and the refrigerant within the heating element flow path exceeds a first reference value, then perform a first step of operating the second pump.

[0009] In the third fuel cell cooling system described above, the control circuit operates the fuel cell and the first pump while the vehicle is in motion, and operates the second pump while the heating element is operating. When the heating element and the second pump are not operating, the refrigerant circulates in the fuel cell flow path and the cooler flow path, while the refrigerant in the heating element flow path does not flow. If the heat generated in the fuel cell is high, the temperature of the refrigerant circulating in the fuel cell flow path and the cooler flow path rises. On the other hand, since the refrigerant in the heating element flow path does not flow, its temperature does not rise. When the vehicle is in motion and the heating element is not operating, if the temperature difference between the refrigerant in the fuel cell flow path and the refrigerant in the heating element flow path exceeds a reference value, the control circuit performs the first step of operating the second pump. That is, in the first step, both the first and second pumps operate. Therefore, the refrigerant circulates in the circulation path formed by the fuel cell flow path, the heating element flow path, and the cooler flow path, and the temperature difference of the refrigerant in this circulation path decreases. This prevents the temperature difference between the refrigerant in the fuel cell flow path and the refrigerant in the heating element flow path from becoming excessively large. Therefore, even if refrigerant flows from the heating element flow path into the fuel cell flow path due to the operation of the heating element and the second pump, it is difficult for a drastic temperature change to occur in the fuel cell. Thus, the heat load applied to the fuel cell can be reduced. Attached Figure Description

[0010] Hereinafter, the features, advantages, technical and industrial importance of exemplary embodiments of the present invention will be described with reference to the accompanying drawings, in which the same reference numerals denote the same constituent elements, wherein:

[0011] Figure 1 This is a refrigerant circuit diagram representing the structure of a fuel cell cooling system.

[0012] Figure 2 This is a flowchart illustrating the preparatory actions of Example 1.

[0013] Figure 3 This is a flowchart illustrating the preparatory actions of Example 2.

[0014] Figure 4 This is a flowchart illustrating the preparatory actions of Example 3.

[0015] Figure 5 This is a flowchart illustrating the preparatory actions of Example 4. Detailed Implementation

[0016] In one example of the first fuel cell cooling system described above, the control circuit may be configured to execute a third step of stopping the second pump if the temperature of the refrigerant in the refrigerant flow path exceeds a second reference value during the second step.

[0017] In this structure, when the temperature difference of the refrigerant decreases, the second pump can be stopped to suppress power consumption.

[0018] In one example of the first fuel cell cooling system described above, the control circuit may be configured to operate the second pump at a minimum speed during the second process described above.

[0019] In this specification, the minimum speed is the minimum usable speed determined by the pump's specifications.

[0020] In the second step, the second pump is activated to combine the refrigerant in the heating element flow path with the refrigerant in the fuel cell flow path and the cooler flow path. By operating the second pump at its lowest speed, the refrigerant in the heating element flow path mixes slowly with the refrigerant in the fuel cell flow path and the cooler flow path. Therefore, rapid temperature changes in the fuel cell can be suppressed in the second step.

[0021] In one example of the second fuel cell cooling system described above, the control circuit may be configured to execute a second step to stop the second pump if the temperature of the refrigerant in the refrigerant flow path exceeds a reference value during the first step.

[0022] In this structure, when the temperature difference of the refrigerant decreases, the second pump can be stopped to suppress power consumption.

[0023] In one example of the second fuel cell cooling system described above, the control circuit may be configured to operate the second pump at a minimum speed during the first process described above.

[0024] In one example of the third fuel cell cooling system described above, the control circuit may be configured to perform a second step of stopping the second pump if the difference between the temperature of the refrigerant in the fuel cell flow path and the temperature of the refrigerant in the heating element flow path is lower than a second reference value during the first step.

[0025] In this structure, when the temperature difference of the refrigerant decreases, the second pump can be stopped to suppress power consumption.

[0026] In one example of the third fuel cell cooling system described above, the heating element may be configured to operate during the first step described above.

[0027] This structure allows for a reduction in the refrigerant temperature difference in a shorter time.

[0028] In one example of the third fuel cell cooling system described above, the control circuit may be configured to operate the second pump at a minimum speed during the first process described above.

[0029] Figure 1The fuel cell cooling system 10 of the illustrated embodiment is mounted in a vehicle. The fuel cell cooling system 10 has a fuel cell 12 (FC). The fuel cell 12 supplies power to the vehicle's motor. The fuel cell cooling system 10 cools the fuel cell 12.

[0030] The fuel cell cooling system 10 has a refrigerant flow path 50 for internal circulation of refrigerant. The refrigerant flow path 50 includes a cooler flow path 52, a fuel cell flow path 54, a heating element flow path 56, and a bypass flow path 58.

[0031] The cooler flow path 52 extends from the confluence section 60 to the branch section 62. The cooler flow path 52 has an upstream flow path 52a, a branch flow path 52b, a branch flow path 52c, and a downstream flow path 52d. The upstream end of the upstream flow path 52a is connected to the confluence section 60, which is the upstream end of the cooler flow path 52. The branch flow paths 52b and 52c branch into two flow paths on the downstream side of the upstream flow path 52a. The downstream ends of the branch flow paths 52b and 52c are connected to the upstream end of the downstream flow path 52d. The downstream end of the downstream flow path 52d is connected to the branch section 62, which is the downstream end of the cooler flow path 52. The refrigerant in the cooler flow path 52 flows from the confluence section 60 (upstream end) through the upstream flow path 52a, branch flow paths 52b and 52c, and downstream flow path 52d to the branch section 62 (downstream end). In branch flow paths 52b and 52c, the refrigerant is separated and flows in branch flow paths 52b and 52c. A radiator 14 is provided in branch flow path 52b. The radiator 14 cools the refrigerant flowing in branch flow path 52b by exchanging heat with the outside air. A radiator 16 is provided in branch flow path 52c. The radiator 16 cools the refrigerant flowing in branch flow path 52c by exchanging heat with the outside air.

[0032] The upstream end of the bypass flow path 58 is connected to the middle of the upstream side flow path 52a of the cooler flow path 52. The downstream end of the bypass flow path 58 is connected to the middle of the downstream side flow path 52d of the cooler flow path 52. A rotary valve 20 is provided at the connection between the bypass flow path 58 and the upstream side flow path 52a. Hereinafter, the portion of the upstream side flow path 52a upstream of the rotary valve 20 will be referred to as the first part 52a-1, and the portion downstream of the rotary valve 20 will be referred to as the second part 52a-2. The rotary valve 20 changes the flow rate of refrigerant flowing from the first part 52a-1 to the bypass flow path 58 and the flow rate of refrigerant flowing from the first part 52a-1 to the second part 52a-2. When the opening degree S of the rotary valve 20 is 100%, all the refrigerant flowing in the first part 52a-1 flows to the second part 52a-2. When the rotary valve 20 is open at 50%, half of the refrigerant flowing in the first section 52a-1 flows to the second section 52a-2, and the remaining half of the refrigerant flowing in the first section 52a-1 flows to the bypass path 58. When the rotary valve 20 is open at 0%, all the refrigerant flowing in the first section 52a-1 flows to the bypass path 58. An ion exchanger 18 is provided in the bypass path 58. The ion exchanger 18 removes ions from the refrigerant flowing in the bypass path 58. Ions dissolve into the refrigerant from the piping or other components constituting the refrigerant flow path 50. By allowing the refrigerant to flow in the bypass path 58 (i.e., the ion exchanger 18), the ion concentration in the refrigerant can be reduced.

[0033] The upstream ends of the fuel cell flow path 54 and the heating element flow path 56 are connected to the downstream end of the cooler flow path 52 at the branch 62. The downstream ends of the fuel cell flow path 54 and the heating element flow path 56 are connected to the upstream end of the cooler flow path 52 at the confluence 60.

[0034] A pump 21 is installed in the fuel cell flow path 54. Pump 21 delivers refrigerant from the fuel cell flow path 54 downstream. Downstream of pump 21, the fuel cell flow path 54 branches into branch flow path 54a and branch flow path 54b. A fuel cell 12 and a temperature sensor 42 are disposed in branch flow path 54a. The fuel cell 12 is cooled by heat exchange with the refrigerant flowing in branch flow path 54a. The temperature sensor 42 is disposed downstream of the fuel cell 12. The temperature sensor 42 detects the temperature T1 of the refrigerant after passing through the fuel cell 12. An intercooler 24 is disposed in branch flow path 54b. The intercooler 24 is cooled by heat exchange with the refrigerant flowing in branch flow path 54b.

[0035] A pump 22, a brake resistor 28, a temperature sensor 44, and a check valve 30 are provided in the heating element flow path 56. Pump 22 delivers refrigerant downstream from the heating element flow path 56. The brake resistor 28 is located downstream of pump 22. The brake resistor 28 is sometimes referred to as an excess power heater or electric heater. When the vehicle's motor performs regenerative braking with a fully charged battery, the brake resistor 28 converts the excess power generated during regenerative braking into heat energy for consumption. The brake resistor 28 is cooled through heat exchange with the refrigerant in the heating element flow path 56. The temperature sensor 44 is located downstream of the brake resistor 28. The temperature sensor 44 detects the temperature T2 of the refrigerant after passing through the brake resistor 28. The check valve 30 is located downstream of the temperature sensor 44. The check valve 30 prevents refrigerant from flowing back into the heating element flow path 56.

[0036] The fuel cell cooling system 10 has an integrated ECU 70 (Integrated Electronic Control Unit) and an EV-ECU 72 (Electric Vehicle-Electronic Control Unit) as control circuits. The EV-ECU 72 controls the braking resistor 28, etc. The integrated ECU 70 controls pumps 21 and 22, fuel cell 12, etc.

[0037] Next, the operation of the fuel cell cooling system 10 will be explained. The integrated ECU 70 generates electricity by activating the fuel cell 12. The vehicle uses the electricity generated by the fuel cell 12 for driving. While the vehicle is in motion, the integrated ECU 70 keeps the fuel cell 12 continuously operating. Additionally, if the vehicle starts, the integrated ECU 70 activates the pump 21. While the vehicle is in motion, the integrated ECU 70 keeps the pump 21 operational. When the pump 21 is operational, refrigerant flows in a circulation path formed by the fuel cell flow path 54 and the cooler flow path 52. The refrigerant flowing in this circulation path is cooled by the radiators 14 and 16. Therefore, the refrigerant cooled by the radiators 14 and 16 flows into the fuel cell flow path 54 (particularly the branch flow path 54a), cooling the fuel cell 12. This prevents the fuel cell 12 from becoming excessively hot. Furthermore, when the pump 21 is operating while the pump 22 is stopped, the check valve 30 is closed to prevent refrigerant from flowing from the downstream end of the fuel cell flow path 54 into the heat source flow path 56. That is, by closing the check valve 30, the backflow of refrigerant in the heating element flow path 56 can be prevented.

[0038] When the refrigerant circulates in the circulation path formed by the fuel cell flow path 54 and the cooler flow path 52, the integrated ECU 70 controls the opening S of the rotary valve 20 to allow some or all of the refrigerant that has passed through the first part 52a-1 of the cooler flow path 52 to flow into the bypass flow path 58. As a result, the integrated ECU 70 performs an ion removal process, removing ions from the refrigerant via the ion exchanger 18. The integrated ECU 70 performs the ion removal process when the ion concentration in the refrigerant increases.

[0039] If the vehicle's motor performs regenerative braking while the battery is fully charged, the EV-ECU 72 activates the braking resistor 28. Excess power generated by the motor is then consumed by the braking resistor 28. When the braking resistor 28 is activated, it generates heat. The EV-ECU 72 sends this information to the integrated ECU 70. If the braking resistor 28 is activated, the integrated ECU 70 activates the pump 22. When the pump 22 is activated, the check valve 30 opens, and the refrigerant in the heating element flow path 56 flows downstream. Therefore, the refrigerant flowing to the branch 62 in the cooler flow path 52 flows into the fuel cell flow path 54 and the branch of the heating element flow path 56. The refrigerant that has passed through the fuel cell flow path 54 and the refrigerant that has passed through the heating element flow path 56 merges at the confluence 60 and flows into the cooler flow path 52. If the refrigerant flows within the heating element flow path 56, the braking resistor 28 is cooled by the refrigerant within it. This prevents the braking resistor 28 from becoming excessively hot.

[0040] Next, the preparatory actions for implementing the integrated ECU 70 will be explained. The preparatory actions for Examples 1 to 4 will be explained below.

[0041] [Example 1]

[0042] Figure 2 This illustrates the preparatory actions for Example 1. For example... Figure 2As shown, the preparatory actions of Embodiment 1 are performed immediately after the ignition device is turned on or just after the vehicle is ready-on (i.e., vehicle startup). Before vehicle startup, the temperature of the fuel cell 12 and the temperature of the refrigerant in the refrigerant flow path 50 are low. Immediately after the ignition device is turned on, the integrated ECU 70 performs step S2. In step S2, the integrated ECU 70 operates the fuel cell 12 and the pump 21 while the pump 22 is stopped. Power is generated by the operation of the fuel cell 12. The operation of the pump 21 causes the refrigerant to circulate in the circulation path formed by the fuel cell flow path 54 and the cooler flow path 52. In addition, since the pump 22 is stopped in step S2, the refrigerant in the heating element flow path 56 does not flow. In addition, the radiators 14 and 16 are operated in step S2. Therefore, the refrigerant circulating in the circulation path formed by the fuel cell flow path 54 and the cooler flow path 52 is heated by the fuel cell 12 and cooled by the radiators 14 and 16. The integrated ECU 70 repeatedly performs step S4 during the execution of step S2. In step S4, the integrated ECU 70 determines whether the temperature T1 detected by the temperature sensor 42 (i.e., the temperature of the refrigerant immediately after passing through the fuel cell 12) is above the reference temperature Ta (e.g., 30°C). The integrated ECU 70 continues step S2 until it determines in step S4 that the temperature T1 is above the reference temperature Ta.

[0043] Immediately after the start of step S2, the fuel cell 12 has a low power generation efficiency due to its low temperature. The temperature of the fuel cell 12 rises as it operates. However, the refrigerant circulating in the circulation path formed by the fuel cell flow path 54 and the cooler flow path 52 cools the fuel cell 12, thus preventing a sharp rise in temperature. The temperature of the fuel cell 12 rises steadily over time. Furthermore, the temperature of the circulating refrigerant gradually rises due to the heating effect of the fuel cell 12. At this time, since the refrigerant in the heating element flow path 56 is not flowing, the amount of circulating refrigerant is relatively small. Therefore, the temperature of the circulating refrigerant rises relatively quickly. Consequently, the temperature of the fuel cell 12 also rises relatively quickly. Thus, in step S2, by circulating the refrigerant in the circulation path formed by the fuel cell flow path 54 and the cooler flow path 52 while the refrigerant in the heating element flow path 56 is stopped, the temperature of the fuel cell 12 can rise relatively quickly. Therefore, during the execution of step S2, the power generation efficiency of the fuel cell 12 can increase at a relatively rapid rate. If the temperature T1 of the refrigerant in the fuel cell flow path 54 reaches the temperature Ta, the integrated ECU 70 executes step S6.

[0044] In step S4 described above, a determination is made as to whether the temperature of the circulating refrigerant has risen to a predetermined value. Therefore, in step S4, the determination of whether the temperature of the refrigerant in the cooler flow path 52 has reached a reference value can be performed instead of the determination of whether the temperature of the refrigerant in the fuel cell flow path 54 has reached a reference value.

[0045] In step S6, the integrated ECU 70 operates pump 22 at its lowest speed. That is, in step S6, the integrated ECU 70 maintains the operation of fuel cell 12 and pump 21 while operating pump 22 at its lowest speed. Furthermore, in step S6, even when braking resistor 28 is stopped, the integrated ECU 70 keeps pump 22 running. The integrated ECU 70 repeatedly executes step S8 during the execution of step S6. In step S8, the integrated ECU 70 determines whether the stop condition for pump 22 is met. The integrated ECU 70 continues step S6 until the stop condition for pump 22 is met. If the determination in step S8 is "yes" (i.e., the stop condition for pump 22 is met), the integrated ECU 70 stops pump 22 in step S9.

[0046] In step S6, the refrigerant flows within the heating element flow path 56 due to the operation of pump 22. That is, in step S6, the refrigerant circulates within the circulation path formed by the fuel cell flow path 54, the heating element flow path 56, and the cooler flow path 52. Since the flow of refrigerant in the heating element flow path 56 stopped during the execution of step S2, the temperature of the refrigerant in the heating element flow path 56 is low at the beginning of step S6. On the other hand, during the execution of step S2, the temperature of the refrigerant in the fuel cell flow path 54 and the cooler flow path 52 rises to a relatively high temperature. During the implementation of step S2, the temperature of the refrigerant in the heating element flow path 56 rises because the refrigerant mixes between the fuel cell flow path 54, the cooler flow path 52, and the heating element flow path 56.

[0047] In step S6, by rotating pump 22 at its lowest speed, the thermal load on fuel cell 12 can be suppressed. For example, if pump 22 is rotated at a high speed in step S6, the low-temperature refrigerant in the heating element flow path 56 will rapidly flow into the fuel cell flow path 54 via the cooler flow path 52. As a result, the low-temperature refrigerant will rapidly flow into the fuel cell 12, whose temperature has risen to a relatively high temperature, causing a sharp drop in the temperature of the fuel cell 12. Therefore, a temperature shock is applied to the fuel cell 12, placing a thermal load on it. In contrast, in the actual step S6, because pump 22 is rotated at its lowest speed, the low-temperature refrigerant in the heating element flow path 56 slowly merges with the refrigerant in the fuel cell flow path 54 and the cooler flow path 52. Therefore, the sharp temperature drop of the fuel cell 12 can be suppressed. Furthermore, since step S6 begins when the temperature of the circulating refrigerant reaches a reference value (i.e., when it is determined to be "yes" in step S4), the temperature difference between the circulating refrigerant (i.e., the refrigerant in the fuel cell flow path 54 and the cooler flow path 52) and the refrigerant in the heating element flow path 56 is not so large at the beginning of step S6. Therefore, a sharp temperature drop in the fuel cell 12 can be suppressed during the implementation of step S6. Thus, the application of heat load to the fuel cell 12 can be suppressed. In addition, since step S6 is implemented with the aim of merging the refrigerant in the heating element flow path 56 with the refrigerant in the fuel cell flow path 54 and the cooler flow path 52, there is no problem even if the pump 22 is rotated at the lowest speed. Furthermore, by rotating the pump 22 at the lowest speed, power consumption in the pump 22 can also be suppressed.

[0048] As described above, if the stop condition for pump 22 is determined to be met in step S8, the integrated ECU 70 stops pump 22 in step S9. The stop condition for pump 22 can be a condition that indicates the temperature of the refrigerant in the heat-generating flow path 56 has risen sufficiently.

[0049] For example, a predetermined time elapsed since the start of step S6 can be used as a stopping condition for pump 22. If a predetermined time has elapsed since the start of step S6, it can be determined that the temperature of the refrigerant in the heating element flow path 56 has risen above a certain value. Therefore, when a predetermined time has elapsed since the start of step S6, if the determination is "yes" in step S8, pump 22 can be stopped in step S9.

[0050] Additionally, for example, the temperature of the refrigerant in the refrigerant flow path 50 can be set as a stop condition for pump 22 if it is above a reference temperature. For example, the temperature T1 detected by temperature sensor 42 can be set as a stop condition for pump 22 if it is above a reference temperature Tb. Here, the reference temperature Tb used in step S8 is a temperature higher than the reference temperature Ta used in step S4. Since the temperature T1 of the refrigerant after passing through fuel cell 12 is correlated with the temperature of the refrigerant in the heating element flow path 56, if the temperature T1 is above the reference temperature Tb, it can be determined that the temperature of the refrigerant in the heating element flow path 56 has risen above a certain value. Therefore, when the temperature T1 rises above the reference temperature Tb, it is determined as "yes" in step S8, and pump 22 can be stopped in step S9. Additionally, for example, the temperature T2 detected by temperature sensor 44 can be set as a stop condition for pump 22 if it is above a reference temperature Tc. Temperature T2 is the temperature of the refrigerant in the heating element flow path 56. Therefore, this stop condition becomes a condition for directly determining the temperature of the refrigerant in the heating element flow path 56. Therefore, when the temperature T2 rises above the reference temperature Tc, it is determined as "yes" in step S8, and pump 22 can be stopped in step S9. Alternatively, the temperature of the refrigerant in the cooler flow path 52 can be set to be above a predetermined temperature as the stopping condition for pump 22.

[0051] After pump 22 is stopped in step S9, the integrated ECU 70 performs normal vehicle operation control. In normal control, the integrated ECU 70 keeps fuel cell 12 and the first pump 21 operating continuously. Additionally, the integrated ECU 70 stops pump 22 when braking resistor 28 is stopped. Therefore, when braking resistor 28 is stopped, refrigerant does not flow in heating element flow path 56. Conversely, if braking resistor 28 is activated, the integrated ECU 70 activates pump 22. At this time, the integrated ECU 70 operates pump 22 at a high speed corresponding to the temperature of braking resistor 28. Therefore, the refrigerant stagnating in heating element flow path 56 rapidly merges with the refrigerant in fuel cell flow path 54 and cooler flow path 52. Since the refrigerant in heating element flow path 56 was heated in the previously implemented step S6, even though the refrigerant in heating element flow path 56 rapidly merges with the refrigerant in fuel cell flow path 54 and cooler flow path 52, no drastic temperature change occurs in fuel cell 12. Thus, the thermal load on fuel cell 12 can be suppressed. In this way, by heating the refrigerant in the heat source flow path 56 through a preparatory action performed immediately after the vehicle is started, the situation of applying a heat load to the fuel cell 12 can be suppressed even if the refrigerant in the heat source flow path 56 quickly flows into the fuel cell flow path 54 due to the operation of the braking resistor 28.

[0052] The reference temperature Ta in Example 1 is an example of a first reference value in the first fuel cell cooling system. The reference temperature Tb in Example 1 is an example of a second reference value in the first fuel cell cooling system.

[0053] [Example 2]

[0054] Figure 3 This illustrates the preparatory actions for Example 2. For example... Figure 3 As shown, the preparatory actions of Embodiment 2 are performed immediately after the ignition device is turned on or just ready-on (i.e., vehicle start-up). Immediately after the ignition device is turned on, the integrated ECU 70 performs step S16. In step S16, the integrated ECU 70 operates the fuel cell 12 and pump 21, and operates pump 22 at its lowest speed. That is, unlike Embodiment 1, in Embodiment 2, not only pump 21 but also pump 22 is operated immediately after the ignition device is turned on. The operation of pumps 21 and 22 causes the refrigerant to circulate in the circulation path formed by the fuel cell flow path 54, the heating element flow path 56, and the cooler flow path 52. Therefore, the refrigerant circulating in the circulation path formed by the fuel cell flow path 54, the heating element flow path 56, and the cooler flow path 52 is heated by the fuel cell 12 and cooled by the radiators 14 and 16. During the implementation of step S16, the temperature of the circulating refrigerant gradually rises due to the heating of the fuel cell 12. Therefore, during the implementation of step S16, the temperature of the refrigerant in the heating element flow path 56 gradually increases. In step S16, since the pump 22 is operated to merge the refrigerant in the heating element flow path 56 with the refrigerant in the fuel cell flow path 54 and the cooler flow path 52, there is no problem even if the pump 22 rotates at its lowest speed. Furthermore, by rotating the pump 22 at its lowest speed, power consumption in the pump 22 can be suppressed. During the implementation of step S16, the integrated ECU 70 repeatedly performs the determination in step S18 (determination of whether the pump 22's stop condition is met). The stop condition for the pump 22 is equivalent to the stop condition described in Example 1. For example, the temperature T1 detected by the temperature sensor 42 can be taken as a reference temperature Tb or higher as the stop condition for the pump 22. If the determination in step S18 is "yes", the integrated ECU 70 stops the pump 22 in step S19.

[0055] After pump 22 is stopped in step S19, the integrated ECU 70 performs normal vehicle control. In normal control, the integrated ECU 70 keeps fuel cell 12 and first pump 21 operating continuously. Additionally, the integrated ECU 70 stops pump 22 when braking resistor 28 is stopped, and starts pump 22 when braking resistor 28 is active. If pump 22 is active due to the operation of braking resistor 28, the refrigerant stagnating in the heating element flow path 56 rapidly merges with the refrigerant in fuel cell flow path 54 and cooler flow path 52. However, since the refrigerant in heating element flow path 56 is heated in the previously implemented step S18, no abrupt temperature change occurs in fuel cell 12. Therefore, the thermal load on fuel cell 12 is suppressed.

[0056] The reference temperature Tb in Example 2 is an example of a reference value in the second fuel cell cooling system.

[0057] [Example 3]

[0058] Figure 4 This describes the preparatory actions for Embodiment 3. The preparatory actions of Embodiment 3 are performed while the vehicle is in motion and the braking resistor 28 is stopped. However, if the braking resistor 28 operates while the vehicle is in motion, the cooling action for the braking resistor 28 is performed before the preparatory actions of Embodiment 3.

[0059] As described above, this is performed while the vehicle is in motion and the braking resistor 28 is stopped. Figure 4 The preparatory action. Therefore, in Figure 4 At the start of the preparatory action, fuel cell 12 and pump 21 are operating, while pump 22 is stopped. In step S24, the integrated ECU 70 determines whether the difference between the temperature T1 of the refrigerant in the fuel cell flow path 54 and the temperature T2 of the refrigerant in the heating element flow path 56 is greater than a reference value Tth. As long as T1 - T2 > Tth1 is not satisfied, the integrated ECU 70 repeatedly executes the determination in step S24.

[0060] exist Figure 4In the initial state before the start of the preparatory operation (i.e., the fuel cell 12 and pump 21 are working, and pump 22 is stopped), the refrigerant circulates in the circulation path formed by the fuel cell flow path 54 and the cooler flow path 52, while the refrigerant in the heating element flow path 56 does not flow. Since the circulating refrigerant is heated by the fuel cell 12, it has a temperature above a certain level. On the other hand, since the refrigerant in the heating element flow path 56 is stagnant, its temperature is low. If the temperature T1 of the refrigerant in the fuel cell flow path 54 rises due to the heating of the fuel cell 12, and the temperature T2 of the refrigerant in the heating element flow path 56 decreases over time, then the difference between temperature T1 and temperature T2 is greater than the reference value Tth1. In this case, the integrated ECU 70 determines "yes" in step S24 and executes step S26.

[0061] In step S26, the integrated ECU 70 operates the pump 22. That is, the integrated ECU 70 maintains the fuel cell 12 and pump 21 in operation while simultaneously operating the pump 22. In step S26, the integrated ECU 70 rotates the pump 22 at its lowest speed. The operation of the pump 22 causes the refrigerant to flow within the heating element flow path 56. Specifically, in step S26, the refrigerant circulates within the circulation path formed by the fuel cell flow path 54, the heating element flow path 56, and the cooler flow path 52. In other words, in step S26, the temperature of the refrigerant in the heating element flow path 56 is increased by mixing the refrigerant with the lower temperature in the fuel cell flow path 54 and the cooler flow path 52. In step S26, because the pump 22 rotates at its lowest speed, the lower temperature refrigerant in the heating element flow path 56 slowly merges with the refrigerant in the fuel cell flow path 54 and the cooler flow path 52. Therefore, a rapid temperature drop in the fuel cell 12 can be suppressed. Therefore, the thermal load applied to the fuel cell 12 can be suppressed. Furthermore, since step S26 is performed to combine the refrigerant in the heating element flow path 56 with the refrigerant in the fuel cell flow path 54 and the cooler flow path 52, no problem occurs even when the pump 22 is rotated at its lowest speed. Additionally, by rotating the pump 22 at its lowest speed, power consumption in the pump 22 can be suppressed.

[0062] As described above, since the refrigerant in the heating element flow path 56 mixes with the refrigerant in the fuel cell flow path 54 during step S26, the temperature difference between the refrigerant in the fuel cell flow path 54 (T1) and the refrigerant in the heating element flow path 56 (T2) decreases during step S26. The integrated ECU 70 repeatedly performs the determination in step S28 during the implementation of step S26. In step S28, the integrated ECU 70 determines whether the difference between temperature T1 and temperature T2 is below a reference value Tth2. The reference value Tth2 is a value below the reference value Tth1. If the difference between temperature T1 and temperature T2 is below the reference value Tth2, the integrated ECU 70 determines "yes" in step S28 and stops the pump 22 in step S29. That is, if the temperature difference between temperature T1 and temperature T2 decreases to below the reference value Tth2 due to the implementation of step S26, the integrated ECU 70 determines "yes" in step S28 and stops the pump 22 in step S29. After pump 22 is stopped in step S29, integrated ECU 70 performs normal control of the vehicle during driving.

[0063] Thus, in Embodiment 3, the difference between temperature T1 and temperature T2 is monitored by repeatedly performing step S24 while the vehicle is in motion. Furthermore, if the difference between temperature T1 and temperature T2 exceeds a reference value Tth1, step S26 is implemented to reduce the difference between temperature T1 and temperature T2 to a value below the reference value Tth2. Therefore, in Embodiment 3, the difference between temperature T1 and temperature T2 can be prevented from becoming excessively large while the vehicle is in motion.

[0064] In normal control, the integrated ECU 70 keeps the fuel cell 12 and the first pump 21 operating continuously. Additionally, the integrated ECU 70 stops the pump 22 when the braking resistor 28 is stopped, and starts the pump 22 when the braking resistor 28 is in operation. If the pump 22 operates due to the operation of the braking resistor 28, the refrigerant stagnating in the heating element flow path 56 rapidly merges with the refrigerant in the fuel cell flow path 54 and the cooler flow path 52. However, since the preparatory action of Embodiment 3 prevents the temperature difference between temperature T1 and temperature T2 from becoming extremely large during vehicle operation, even if the pump 22 operates due to the operation of the braking resistor 28 (i.e., even if the refrigerant in the heating element flow path 56 merges with the refrigerant in the fuel cell flow path 54 and the cooler flow path 52), no drastic temperature change occurs in the fuel cell 12. Therefore, the application of heat load to the fuel cell 12 can be suppressed.

[0065] The reference value Tth1 in Example 3 is an example of the first reference value in the third fuel cell cooling system. The reference value Tth2 in Example 3 is an example of the second reference value in the third fuel cell cooling system.

[0066] [Example 4]

[0067] Figure 5 The difference between the preparatory action of Embodiment 4 and that of Embodiment 3 is that, in step S26, the braking resistor 28 and the pump 22 are operated together, and in step S29, the braking resistor 28 and the pump 22 are stopped together. The other structures of the preparatory action of Embodiment 4 are the same as those of Embodiment 3.

[0068] In step S26 of Embodiment 4, the integrated ECU 70 operates the braking resistor 28 together with the pump 22. That is, in step S26, the integrated ECU 70 operates the braking resistor 28 even if no excess power is generated by the motor. In step S26 of Embodiment 4, since the braking resistor 28 is operated, the refrigerant in the heating element flow path 56 is heated by the braking resistor 28. Therefore, in step S26 of Embodiment 4, the difference between temperature T1 and temperature T2 can be reduced faster than in step S26 of Embodiment 3. In step S29 of Embodiment 4, the integrated ECU 70 returns to normal control by stopping the braking resistor 28 and the pump 22 together.

[0069] Furthermore, in the above embodiments, the heating element disposed in the heating element flow path 56 is a braking resistor 28, but other heating elements may also be disposed in the heating element flow path 56.

[0070] Furthermore, in the above embodiment, pump 21 is configured upstream of fuel cell 12 in fuel cell flow path 54, but pump 21 may also be configured downstream of fuel cell 12. Additionally, in the above embodiment, these devices are configured in heating element flow path 56 in the order of pump 22, braking resistor 28, and check valve 30 from the upstream side, but the order of these devices may be different.

[0071] The embodiments have been described in detail above, but these are merely illustrative and do not limit the technical solutions. The technology described in the technical solutions includes technologies derived from various modifications and alterations of the specific examples described above. The technical elements described in this specification or drawings exert their technical usefulness individually or in various combinations, and are not limited to the combinations described in the technical solutions at the time of application. Furthermore, the technology illustrated in this specification or drawings achieves multiple objectives simultaneously, and achieving even one objective is itself technically useful.

Claims

1. A fuel cell cooling system, installed in a vehicle, characterized in that, include: A refrigerant flow path is provided for the refrigerant to flow inside. The refrigerant flow path includes a cooler flow path, a fuel cell flow path, and a heating element flow path. The upstream ends of the fuel cell flow path and the upstream ends of the heating element flow path are connected to a branch provided at the downstream end of the cooler flow path. The downstream ends of the fuel cell flow path and the downstream ends of the heating element flow path are connected to a confluence provided at the upstream end of the cooler flow path. A cooler configured to cool the refrigerant within the cooler flow path; A fuel cell is configured to be cooled by heat exchange with the refrigerant within the fuel cell flow path; The heating element is configured to generate heat during operation and is cooled by heat exchange with the refrigerant within the flow path of the heating element; The first pump is configured to deliver the refrigerant in the fuel cell flow path to the downstream side; The second pump is configured to deliver the refrigerant in the flow path of the heating element to the downstream side; as well as The control circuit is configured to control the fuel cell, the first pump, and the second pump. The control circuit is configured to operate the fuel cell and the first pump while the vehicle is in motion. The control circuit is configured to activate the second pump during the operation of the heating element. When the vehicle is started, the control circuit is configured to perform a first step and a second step. The first step is to activate the first pump when the second pump is stopped. The second step is to activate the second pump in addition to the first pump if the temperature of the refrigerant in the fuel cell flow path or the cooler flow path exceeds a first reference value during the first step. The control circuit is configured to execute a third step that stops the second pump if the temperature of the refrigerant in the refrigerant flow path exceeds a second reference value during the second step.

2. The fuel cell cooling system according to claim 1, characterized in that, The control circuit is configured to operate the second pump at the lowest possible speed during the second process.

3. A fuel cell cooling system, installed in a vehicle, characterized in that, include: A refrigerant flow path is provided for the refrigerant to flow inside. The refrigerant flow path includes a cooler flow path, a fuel cell flow path, and a heating element flow path. The upstream ends of the fuel cell flow path and the upstream ends of the heating element flow path are connected to a branch provided at the downstream end of the cooler flow path. The downstream ends of the fuel cell flow path and the downstream ends of the heating element flow path are connected to a confluence provided at the upstream end of the cooler flow path. A cooler configured to cool the refrigerant within the cooler flow path; A fuel cell is configured to be cooled by heat exchange with the refrigerant within the fuel cell flow path; The heating element is configured to generate heat during operation and is cooled by heat exchange with the refrigerant within the flow path of the heating element; The first pump is configured to deliver the refrigerant in the fuel cell flow path to the downstream side; The second pump is configured to deliver the refrigerant in the flow path of the heating element to the downstream side; as well as The control circuit is configured to control the fuel cell, the first pump, and the second pump. The control circuit is configured to operate the fuel cell and the first pump while the vehicle is in motion. The control circuit is configured to activate the second pump during the operation of the heating element. When the vehicle is started, the control circuit is configured to perform a first step of activating the first pump and the second pump. The control circuit is configured to execute a second step that stops the second pump if the temperature of the refrigerant in the refrigerant flow path exceeds a reference value during the first step.

4. The fuel cell cooling system according to claim 3, characterized in that, The control circuit is configured to operate the second pump at the lowest possible speed during the first process.

5. A fuel cell cooling system, installed in a vehicle, characterized in that, include: A refrigerant flow path is provided for the refrigerant to flow inside. The refrigerant flow path includes a cooler flow path, a fuel cell flow path, and a heating element flow path. The upstream ends of the fuel cell flow path and the upstream ends of the heating element flow path are connected to a branch provided at the downstream end of the cooler flow path. The downstream ends of the fuel cell flow path and the downstream ends of the heating element flow path are connected to a confluence provided at the upstream end of the cooler flow path. A cooler configured to cool the refrigerant within the cooler flow path; A fuel cell is configured to be cooled by heat exchange with the refrigerant within the fuel cell flow path; The heating element is configured to generate heat during operation and is cooled by heat exchange with the refrigerant within the flow path of the heating element; The first pump is configured to deliver the refrigerant in the fuel cell flow path to the downstream side; The second pump is configured to deliver the refrigerant in the flow path of the heating element to the downstream side; as well as The control circuit is configured to control the fuel cell, the first pump, and the second pump. The control circuit is configured to operate the fuel cell and the first pump while the vehicle is in motion. The control circuit is configured to activate the second pump during the operation of the heating element. The control circuit is configured such that, while the vehicle is in motion and the heating element is not operating, if the temperature difference between the refrigerant in the fuel cell flow path and the refrigerant in the heating element flow path exceeds a first reference value, then the first step of activating the second pump is executed. The control circuit is configured to perform a second step of stopping the second pump if the difference between the temperature of the refrigerant in the fuel cell flow path and the temperature of the refrigerant in the heating element flow path is lower than a second reference value in the first step.

6. The fuel cell cooling system according to claim 5, characterized in that, The heating element is configured to operate in the first step.

7. The fuel cell cooling system according to claim 5 or 6, characterized in that, The control circuit is configured to operate the second pump at the lowest possible speed during the first process.

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