JP7207350B2 - Boiling cooling device and temperature control method - Google Patents

Description

TECHNICAL FIELD The present invention relates to an ebullient cooling device and a temperature control method.

Patent Document 1 discloses an evaporator that evaporates a liquid-phase working fluid by the heat of a device to be cooled, a condenser that is arranged above the evaporator and condenses the vapor-phase working fluid, and an evaporator that evaporates the liquid-phase working fluid. a vapor passage through which the gas-phase working fluid liquefied in the condenser flows to the condenser; a liquid passage through which the liquid-phase working fluid liquefied in the condenser flows to the evaporator; and a heater provided in the liquid passage. A cooling device is disclosed.

WO2018/047539

By the way, the ebullient cooling device is mounted on a vehicle and can cool a battery module composed of a plurality of battery cells. In the ebullient cooling device mounted on the vehicle, for example, a liquid passage is provided with a liquid surface so that the liquid level of the refrigerant in the evaporator (the liquid level of the liquid-phase working fluid) in contact with the battery cell has a contact area greater than or equal to a predetermined level. By controlling the circulation state of the working fluid using the on-off valve, it is possible to maintain the refrigerant liquid level in the evaporator and suppress temperature variations among the battery cells. This is expected to improve the life performance of the battery module.

However, the boiling cooling device mounted on the vehicle may not be able to control the circulation state of the working fluid in an environment where the outside air temperature is low. In addition, when the vehicle is tilted to the left or right, such as when the vehicle is stopped on the shoulder, the liquid level of the refrigerant in the evaporator does not contact all the battery cells. Variation occurs. Therefore, when the ambient temperature is low and the vehicle body is tilted, variations in the temperature of the battery cells increase.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an ebullient cooling device capable of suppressing large variations in the temperature of battery cells even when the outside air is cold and the vehicle body is tilted. and to provide a temperature control method.

The present invention includes an evaporator that absorbs heat from a battery cell to evaporate a liquid-phase working fluid, and a condenser that is disposed above the evaporator and condenses the vapor-phase working fluid that has been vaporized by the evaporator. a vapor passage for circulating the vapor-phase working fluid vaporized in the evaporator to the condenser; and a liquid passage for circulating the liquid-phase working fluid liquefied in the condenser to the evaporator. A boiling cooling device for cooling a battery module comprising a plurality of the battery cells mounted on a vehicle and circulating a working fluid between the evaporator and the condenser, wherein the The liquid passage includes a lower passage located below a connection port with the evaporator when the vehicle body of the vehicle is tilted, is provided in the lower passage, and is supplied with electric power to generate heat to generate the lower liquid passage. an on-off valve provided between the connection port and the temperature-increasing portion in the liquid passage; opening and closing of the on-off valve based on the temperature of the battery cell; a control unit that controls the temperature raising unit, wherein the control unit controls the on-off valve when the vehicle body is tilted and the temperature of the battery cell is higher than the outside air temperature of the vehicle. is closed to heat and evaporate the liquid-phase working fluid in the lower passage by the temperature raising unit.

The present invention includes an evaporator that absorbs heat from a battery cell to evaporate a liquid-phase working fluid, and a condenser that is disposed above the evaporator and condenses the vapor-phase working fluid that has been vaporized by the evaporator. a vapor passage for circulating the vapor-phase working fluid vaporized in the evaporator to the condenser; and a liquid passage for circulating the liquid-phase working fluid liquefied in the condenser to the evaporator. An ebullient cooling device comprising a loop-type thermosiphon, cooling a battery module composed of a plurality of the battery cells mounted on a vehicle, and circulating a working fluid between the evaporator and the condenser. In the temperature control method, when the body of the vehicle is tilted and the temperature of the battery cell is higher than the outside air temperature of the vehicle, the liquid passage is maintained in the state where the body is tilted. A temperature raising section heats and evaporates a liquid-phase working fluid in a lower passage located below a connection port with the evaporator, and opens and closes the liquid passage between the connection port and the temperature raising section. and closing with a valve.

In the present invention, when the outside air is cold and the vehicle body is tilted, the on-off valve provided in the liquid passage is closed to stop the circulation of the working fluid, and in addition, the working fluid in the lower passage is heated by the temperature raising section. It is possible to evaporate the liquid-phase working fluid in the lower passage and cause an increase in the pressure of the vapor-phase working fluid as the temperature of the working fluid rises. As a result, the liquid-phase working fluid that has accumulated in the lower passage due to the inclination of the vehicle body can be returned to the evaporator side. Therefore, even when the outside air is cold and the vehicle body is tilted, the liquid level of the liquid-phase working fluid in the evaporator can be brought into contact with all the battery cells, thereby suppressing the temperature variation of the battery cells. be able to.

FIG. 1 is a schematic diagram showing a schematic configuration of an ebullient cooling device according to an embodiment. FIG. 2 is a schematic diagram showing a normal cooling state in which the working fluid circulates inside the loop thermosiphon. FIG. 3 is a block diagram showing functional blocks of the electronic control unit. FIG. 4 is a flow chart showing a temperature control flow. FIG. 5 is a schematic diagram showing a case where the liquid phase side solenoid valve is closed and the heater is turned on. FIG. 6 is a schematic diagram showing a state in which the liquid-phase working fluid flows into the vapor passage from the state shown in FIG. FIG. 7 is a schematic diagram showing a transition from the state shown in FIG. 6 to a state in which the liquid-phase working fluid is returned to the evaporator. FIG. 8 is a schematic diagram showing the relationship between the liquid level of the liquid-phase working fluid in the evaporator and the battery cell when variation suppression temperature control is performed. FIG. 9 is a graph showing the temperature of the battery cells when variation suppression temperature control is performed. FIG. 10 is a schematic diagram showing the relationship between the liquid level of the liquid-phase working fluid in the evaporator and the battery cell in the comparative example. FIG. 11 is a graph showing temperatures of battery cells when normal cooling is continued as a comparative example. FIG. 12 is a graph showing the battery cell temperature when the gas phase side solenoid valve and the liquid phase side solenoid valve are kept closed as a comparative example.

Hereinafter, a boiling cooling device and a temperature control method according to embodiments of the present invention will be specifically described with reference to the drawings. In addition, this invention is not limited to embodiment described below.

FIG. 1 is a schematic diagram showing a schematic configuration of an ebullient cooling device according to an embodiment. FIG. 2 is a schematic diagram showing a normal cooling state in which the working fluid circulates inside the loop thermosiphon. In FIG. 2, arrows indicate the flow of the working fluid when it circulates.

The ebullient cooling device 1 cools a battery module 3 composed of a plurality of battery cells 2 . This ebullient cooling device 1 includes a loop-type thermosiphon 10 that transports heat using a working fluid that changes phases between a liquid phase and a gas phase. A working fluid is a heat transport medium, and absorbs or releases heat using latent heat when changing from gas to liquid.

The battery cell 2 is configured in a rectangular shape. The battery module 3 has a structure in which a plurality of battery cells 2 are arranged to be stacked. Moreover, the battery module 3 has a rectangular side surface (heat radiation surface) extending in the stacking direction of the battery cells 2 . A plurality of battery modules 3 are provided in the battery pack 4 . That is, the battery pack 4 contains a plurality of battery cells 2, including battery cells 2 arranged near the outside and battery cells 2 arranged inside near the center.

For example, the battery pack 4 is an in-vehicle battery mounted in an electric vehicle (EV) or a plug-in hybrid vehicle (PHV). In this case, the battery pack 4 stores electric power to be supplied to the driving motor. When the vehicle runs, the battery pack 4 supplies electric power to the running motor. Further, when charging from an external power source such as a charging stand, power is supplied from the external power source to the battery pack 4 mounted on the vehicle. In this manner, heat is generated in each battery cell 2 of the battery module 3 as the power is supplied during discharging and charging. The heat of the battery cell 2 is transported and dissipated by the loop thermosiphon 10 .

The loop-type thermosiphon 10 includes an evaporator 11, a condenser 12, a vapor passage 13 through which a vapor-phase working fluid flows, and a liquid passage 14 through which a liquid-phase working fluid flows. A working fluid is sealed in a closed loop circuit in the loop type thermosiphon 10 , and the working fluid can be circulated between the evaporator 11 and the condenser 12 . A steam passage 13 is arranged to connect the steam outlet of the evaporator 11 and the steam inlet of the condenser 12 . A liquid passage 14 is arranged to connect the liquid outlet of the condenser 12 and the liquid inlet of the evaporator 11 . Note that the steam outlet, steam inlet, liquid outlet, and liquid inlet described here are expressions in the direction in which the working fluid circulates during normal cooling.

The evaporator 11 absorbs the heat generated in the battery cell 2 to evaporate the liquid-phase working fluid. A liquid-phase working fluid is supplied to the interior of the evaporator 11 . The outer surface of evaporator 11 is in contact with the surface of battery cell 2 . As shown in FIG. 1 , the loop thermosiphon 10 is provided with an evaporator 11 for each battery module 3 . A plurality of evaporators 11 constitute a cooling circuit connected in parallel. Each evaporator 11 is arranged in contact with the side surface of each battery module 3 . The evaporator 11 extends along the stacking direction of the battery cells 2 and is in surface contact with the surface of the battery cells 2 over the entire vertical direction. A heat-receiving surface of the evaporator 11 is a plane along the vertical direction.

The liquid-phase working fluid supplied to the inside of the evaporator 11 receives the heat of the battery cells 2 and evaporates. When the liquid-phase working fluid evaporates in the evaporator 11 , heat is transferred from the battery cell 2 to the evaporator 11 due to transfer of latent heat associated with the evaporation. The evaporator 11 functions as a cooler that absorbs heat from the battery cells 2 and cools the battery cells 2 .

The liquid inlet of the evaporator 11 is provided vertically downward. A vapor outlet of the evaporator 11 is provided on the upper side in the vertical direction. In a direction perpendicular to the vertical direction (horizontal direction), the liquid inlet and vapor outlet of the evaporator 11 are arranged on opposite sides. As a result, the liquid-phase working fluid supplied to the evaporator 11 receives the heat of the battery cells 2 and evaporates. The steam vaporized inside the evaporator 11 flows upward in the vertical direction and flows out from the steam outlet to the steam passage 13 . Then, the heat generated in the battery cell 2 is transported to the condenser 12 by the gas-phase working fluid. The heat of the battery cells 2 is radiated by the condenser 12 .

The condenser 12 is arranged above the evaporator 11 and condenses the vapor-phase working fluid vaporized by the evaporator 11 . Since condenser 12 is arranged outside battery pack 4 , the piping (vapor passage 13 and liquid passage 14 ) near condenser 12 is also arranged outside battery pack 4 . Since it is outside the battery pack 4, the condenser 12 and the pipes in the vicinity thereof are in an environment where heat can easily be exchanged with the outside air. This condenser 12 is a heat exchanger that exchanges heat between the working fluid and the outside. For example, the condenser 12 is configured by a radiator that is an air-cooled radiator. A condenser 12 consisting of a radiator exchanges heat between the gaseous working fluid and the outside air of the vehicle. For example, when the vehicle is running, the radiator is exposed to wind, so the gas-phase working fluid can be dissipated.

Further, the condenser 12 has a function of absorbing heat from the outside and raising the temperature of the working fluid in the condenser 12 . For example, exhaust heat from a vehicle can be used, the exhaust heat can be absorbed by the condenser 12 , and the heat can be transferred to the working fluid in the condenser 12 . As an example, the condenser 12 is configured by a condenser that performs heat exchange between the refrigerant circulating in the vehicle air conditioner and the working fluid of the loop thermosiphon 10 . That is, the condenser 12 is composed of a heat exchanger that has both the function of a radiator and the function of a condenser described above, and can radiate the heat of the working fluid to the outside, and the heat of the refrigerant of the air conditioner ( (which may be waste heat from the vehicle) can be absorbed.

The vapor passage 13 and the liquid passage 14 are annularly formed as refrigerant passages. The steam passage 13 is a steam pipe that circulates the vapor-phase working fluid vaporized in the evaporator 11 to the condenser 12 . The liquid passage 14 is a liquid pipe that circulates the liquid-phase working fluid liquefied in the condenser 12 to the evaporator 11 .

The steam passage 13 is connected to the steam outlet of each evaporator 11 at its lower end. The vapor passage 13 has a structure in which a plurality of inlets are provided so that the vapor-phase working fluid vaporized in each evaporator 11 joins. In the steam passage 13, the piping portion after the steam joins extends upward in the vertical direction. The upper end of the steam passage 13 is connected to the steam inlet of the condenser 12 . The vapor-phase working fluid flowing through the steam passage 13 toward the condenser 12 reaches the condenser 12 after flowing upward in the vertical direction.

The liquid passage 14 is connected at its upper end to the liquid outlet of the condenser 12 . The liquid passage 14 extends vertically downward from the upper end so that the liquid-phase working fluid liquefied in the condenser 12 flows vertically downward under its own weight. Also, the lower end of the liquid passage 14 is connected to the liquid inlet of each evaporator 11 . The liquid passage 14 has a plurality of connection ports in its lower portion on the evaporator 11 side. The liquid-phase working fluid that has flowed vertically downward in the liquid passage 14 due to its own weight flows into the evaporator 11 through each connection port.

In this liquid passage 14, a lower passage 14a, which is a portion piped inside the battery pack 4, is provided. The lower passage 14a is located at the same vertical position as the liquid inlet of the evaporator 11 when the vehicle body is horizontal. That is, the lower passage 14a includes a portion provided with a connection port with the evaporator 11 .

Further, the steam passage 13 is provided with a gas phase side solenoid valve 15 for opening and closing the steam passage 13 . A liquid phase side solenoid valve 16 for opening and closing the liquid passage 14 is provided in the liquid passage 14 . Furthermore, the liquid passage 14 is provided with a heater 17 that heats the working fluid in the liquid passage 14 . The gas phase side solenoid valve 15 , the liquid phase side solenoid valve 16 and the heater 17 are all controlled by an electronic control unit (hereinafter referred to as ECU) 20 . A configuration of the ECU 20 will be described later with reference to FIG.

The gas phase side solenoid valve 15 is an on-off valve that switches between an open state and a closed state. As shown in FIG. 1 , the gas phase side solenoid valve 15 is provided inside the battery pack 4 . That is, the gas phase side solenoid valve 15 is arranged in a portion of the steam passage 13 that is piped inside the battery pack 4 . For example, the vapor phase side solenoid valve 15 is arranged in the vapor passage 13 near the outlet of the battery pack 4 where the vapor phase working fluid vaporized in each evaporator 11 joins. When the gas phase side solenoid valve 15 is open, the working fluid can flow between the vapor outlet of the evaporator 11 and the vapor inlet of the condenser 12 . On the other hand, when the gas phase side solenoid valve 15 is closed, the working fluid cannot flow between the steam outlet of the evaporator 11 and the steam inlet of the condenser 12 .

The liquid phase side solenoid valve 16 is an on-off valve that switches between an open state and a closed state. As shown in FIG. 1, the liquid phase side solenoid valve 16 is provided inside the battery pack 4 . That is, the liquid phase side solenoid valve 16 is arranged in a portion of the liquid passage 14 that is piped inside the battery pack 4 . For example, the liquid phase side solenoid valve 16 can be arranged in the liquid passage 14 near the inlet of the battery pack 4 . Furthermore, the liquid phase side solenoid valve 16 is arranged in a passage between the liquid inlet of the evaporator 11 and the installation location of the heater 17 in the liquid passage 14 in the battery pack 4 . When the liquid phase side solenoid valve 16 is open, the working fluid can flow between the vapor outlet of the evaporator 11 and the vapor inlet of the condenser 12 . On the other hand, when the liquid phase side solenoid valve 16 is closed, the working fluid cannot be circulated between the evaporator 11 and the condenser 12 .

The heater 17 generates heat by being supplied with power to heat the working fluid in the liquid passage 14 . This heater 17 is a temperature raising section that raises the temperature of the working fluid in the liquid passage 14 . As shown in FIG. 1 , the heater 17 is arranged inside the battery pack 4 and provided in the lower passage 14 a of the liquid passage 14 .

The lower passage 14a is, as shown in FIG. Further, the lower passage 14a is a passage located vertically below the liquid inlet of the evaporator 11 when the vehicle body is tilted left and right with respect to the horizontal direction. Therefore, the heater 17 provided in the lower passage 14a can raise the temperature of the liquid-phase working fluid staying in the lower passage 14a.

For example, when the ECU 20 performs temperature control, the heater 17 can boil the liquid-phase working fluid present in the liquid passage 14 . Alternatively, when there is a warm-up request for the battery cell 2, the ECU 20 can warm the battery cell 2 by raising the temperature of the liquid-phase working fluid present in the liquid passage 14 using the heater 17. .

The ECU 20 includes a CPU, a storage section storing data such as various programs, and an arithmetic processing section that performs various calculations for controlling the temperature of the battery cells 2 . The ECU 20 has a temperature control section 21 as an arithmetic processing section. Signals from various sensors are input to the ECU 20 . The temperature control unit 21 performs temperature control based on input signals from various sensors. In addition, in this description, the temperature of the battery cell 2 may be described as "battery temperature."

As shown in FIG. 3, the ECU 20 includes an acceleration sensor (G sensor) 31 that detects the longitudinal and lateral tilt of the vehicle body, a battery temperature sensor 32 that detects the temperature of the battery cell 2, and an outside air temperature sensor 33 that detects the outside air temperature. etc. are input. The battery temperature sensor 32 is attached to the surface of the battery cell 2 and detects battery temperature.

Based on the acceleration detected by the acceleration sensor 31, the ECU 20 can determine whether the vehicle body is tilted forward or backward or left or right. The ECU 20 detects the inclination of the vehicle body based on the signal input from the acceleration sensor 31, and determines whether or not the inclination angle of the vehicle body is within the allowable inclination angle range. The amount of working fluid (refrigerant amount) enclosed in the loop-type thermosiphon 10 is such that it can cool all the battery cells 2 of the battery module 3 even when the pipes are filled with vapor-phase working fluid in a cooled state. amount is set.

The temperature control unit 21 controls opening and closing of the gas phase side solenoid valve 15 and the liquid phase side solenoid valve 16 based on the temperature of the battery cell 2 detected by the battery temperature sensor 32 and the outside temperature detected by the outside temperature sensor 33. to adjust the temperature of the battery cell 2. Moreover, the temperature control unit 21 turns on the heater 17 to adjust the temperature of the battery cell 2 when a predetermined condition is satisfied. Thus, the temperature control unit 21 performs temperature control to adjust the temperature of the battery cell 2 to the optimum temperature by the loop thermosiphon 10 . The temperature control includes control (variation suppression temperature control) to suppress temperature variations among the plurality of battery cells 2 in the battery module 3 by closing the liquid phase side solenoid valve 16 and turning on the heater 17 . .

The ECU 20 controls the circulation state of the working fluid by the loop-type thermosiphon 10 by switching the opening/closing states of the gas-phase side solenoid valve 15 and the liquid-phase side solenoid valve 16 , thereby reducing temperature variations among the plurality of battery cells 2 . suppress In the loop-type thermosiphon 10, if there is a temperature difference between the condenser 12 on the heat radiation side and the evaporator 11 on the heat absorption side, the liquid-phase working fluid is vaporized in the evaporator 11, allowing the working fluid to circulate naturally. can be done. Further, even when the gas phase side solenoid valve 15 and the liquid phase side solenoid valve 16 are closed to stop the circulation, the vaporization of the working fluid progresses in the high temperature part of the evaporator 11, and the temperature variation can be converged. can. Furthermore, by switching the ON/OFF state of the heater 17, it is possible to switch between execution and non-execution of the variation suppression temperature control.

Further, the ECU 20 is configured to be able to determine that the battery module 3 is soaking, based on determination results such as whether the ignition switch is turned on or off or when the battery pack 4 is being charged or discharged. When the battery module 3 soaks, it means that the battery cells 2 are in a state of being discharged for the vehicle to run, and that the battery is not in a state of being charged from the external power source while the vehicle is stopped. In other words, a state in which the battery cell 2 does not receive or transmit electric power can be expressed as the soak time of the battery module 3 .

FIG. 4 is a flow chart showing a temperature control flow. The control shown in FIG. 4 is repeatedly executed by the ECU 20 .

The ECU 20 determines whether or not the vehicle body is tilted (step S1). In step S1, based on the signal from the acceleration sensor 31, it is determined whether the vehicle body is tilted leftward or rightward. The ECU 20 detects the orientation of the evaporator 11 and the inclination in the direction in which the temperature of the battery cells 2 varies by the determination process in step S1.

If the vehicle body is tilted (step S1: Yes), the ECU 20 determines whether the soak determination is ON (step S2). The soak determination means that the vehicle speed is equal to or less than the threshold value, the battery heat generation amount is low, and the condenser 12 is not required to cool. The battery heat generation amount is, for example, the heat generation amount of three battery modules. The heat generation amount of the battery module 3 is high during charging and discharging, and the heat generation amount of the battery module 3 is low during soaking. Further, the ECU 20 can detect the vehicle speed based on the input signal from the vehicle speed sensor and the input signal from the wheel speed sensor. The cooling request for the condenser 12 is a request for radiating the heat of the working fluid in the condenser 12 . In this step S2, for example, it is determined whether or not the vehicle is stopped and the battery cells 2 are not being charged or discharged. Therefore, when the determination in step S2 is affirmative, the case where the amount of heat generated by the battery module 3 is low while the vehicle is stopped with the vehicle body tilted to the left or right is included.

When the soak determination is ON (step S2: Yes), the ECU 20 determines whether or not the temperature of the battery cell 2 is higher than the sum of the outside air temperature and the temperature of the hysteresis (step S3). The temperature for hiss used in step S3 is a preset value. For example, it is possible to set a temperature difference as the temperature for the hysteresis such that the temperature variation of the battery cells 2 cannot be suppressed by the circulation stop control that only closes the gas phase side solenoid valve 15 and the liquid phase side solenoid valve 16. . In step S3, for example, the maximum temperature determined from among all the battery cells 2 included in the battery pack 4 is compared with the sum (comparison value) of the outside air temperature and the temperature of the hysteresis. If the determination in step S3 is affirmative, it is expected that the temperature difference of the battery cells 2 due to the tilting of the vehicle body, that is, the variation in the temperature of the battery cells 2 in the battery module 3 will increase. be.

When the temperature of the battery cell 2 is higher than the sum of the outside air temperature and the hysteresis temperature (step S3: Yes), the ECU 20 determines whether or not to end the variation suppression temperature control (step S4). Since the control flow shown in FIG. 4 is repeatedly executed, a negative determination is made in step S4 if the variation suppression temperature control control has not been started. Then, in step S4, it is determined whether a sufficient amount of refrigerant has been returned to the evaporator 11 or not. That is, in this step S4, it is determined whether or not the temperature variation is eliminated in the battery modules 3 as a whole.

If the variation suppression temperature control is not to be ended (step S4: No), the ECU 20 executes the variation suppression temperature control (step S5). If the variation suppression temperature regulation control has not been started, the control is started in step S5. On the other hand, if the variation suppression temperature regulation control has been started, the control is continued in step S5.

In this step S5, when starting the variation suppression control, first, the liquid phase side solenoid valve 16 is closed (step S5a), and the flow of the working fluid returned from the condenser 12 to the evaporator 11 via the liquid passage 14 is stopped. stop. After closing the liquid phase side solenoid valve 16, the heater 17 is turned on (step S5b). When the heater 17 is turned on with the liquid phase side solenoid valve 16 closed, the liquid phase working fluid existing in the liquid passage 14 can be boiled (see FIG. 5).

Specifically, when the vehicle body is tilted, liquid-phase working fluid that cannot be returned to the evaporator 11 and remains therein exists in the lower passage 14a located below the liquid inlet of the evaporator 11. . In step S5b, the liquid-phase working fluid present in the lower passage 14a is heated by the heater 17 to boil. When step S5b is performed, the liquid-phase working fluid in the lower passage 14a evaporates, the temperature of the vapor-phase working fluid rises in the vicinity of the heater 17, and the vapor-phase in the lower passage 14a operates. Fluid pressure increases. At this time, since the liquid phase side solenoid valve 16 is closed, the pressure increase in the liquid passage 14 does not occur on the side of the evaporator 11 rather than the liquid side side solenoid valve 16. also expands to the passage on the condenser 12 side.

Also, the temperature control of the condenser 12 is turned ON (step S5c). In step 5c, heat is absorbed from the outside and transferred to the working fluid in the condenser 12 . After that, the gas phase side solenoid valve 15 is closed (step S5d). Since the range in which the gas-phase working fluid exists in the liquid passage 14 expands to the vicinity of the condenser 12 after step S5c is performed and before step S5d is performed, the liquid phase in the condenser 12 The working fluid can flow out of the vapor inlet of the condenser 12 into the vapor passage 13 in liquid phase (see FIG. 6). Since the vapor passage 13 extends downward from the vapor inlet of the condenser 12 , the liquid-phase working fluid flowing out from the vapor inlet flows downward from the vapor passage 13 toward the evaporator 11 . Since the gas-phase side solenoid valve 15 is open, the liquid-phase working fluid in the vapor passage 13 flows into the evaporator 11 from the vapor outlet of the evaporator 11 .

Thus, in step S5, the liquid phase working fluid can be returned from the liquid passage 14 to the evaporator 11 via the condenser 12 and the vapor passage 13. FIG. Control is continued until a sufficient amount of working fluid is returned to the evaporator 11 . After this step S5 is carried out, this control routine ends. Note that the temperature control of the heater 17 and the condenser 12 can be turned on at the same time. In this case, the temperature of the heater 17 is set higher than that of the condenser 12 .

On the other hand, when ending the variation suppression temperature control (step S4: Yes), the ECU 20 turns off the heater 17 and the temperature control of the condenser 12 as end processing (step S6). In step S6, the heater 17 is switched from ON to OFF, and the capacitor temperature control is switched from ON to OFF. After this step S6 is carried out, this control routine ends.

When the temperature of the battery cell 2 is not higher than the sum of the outside air temperature and the temperature of the hysteresis (step S3: No), the ECU 20 determines whether the temperature of the battery cell 2 is higher than the outside air temperature (step S7). In step S7, it is determined whether or not the temperature of the battery cell 2 is higher than the outside air temperature, but the temperature difference is small.

When the temperature of the battery cell 2 is higher than the outside air temperature (step S7: Yes), the ECU 20 closes both the gas phase side solenoid valve 15 and the liquid phase side solenoid valve 16 (step S8). In step S8, control is executed to close the gas phase side solenoid valve 15 and the liquid phase side solenoid valve 16 to stop circulation of the working fluid between the evaporator 11 and the condenser 12. FIG. In the loop-type thermosyphon 10, even if the circulation is stopped, the vaporization of the working fluid proceeds from the high-temperature part of the evaporator 11, and the temperature of the high-temperature cells can be lowered. can converge. Therefore, even if the battery temperature is higher than the outside air temperature, if the temperature difference is small, it can be determined that it is sufficient to stop the circulation of the working fluid because the temperature change is small. Therefore, the variation in battery temperature can be suppressed by cooling control that only closes the gas phase side solenoid valve 15 and the liquid phase side solenoid valve 16 . As a result, it is possible to lower the temperature of locally existing high-temperature cells during soaking of the battery module 3 . After this step S8 is carried out, this control routine ends.

If the vehicle body is not tilted (step S1: No), the ECU 20 opens both the gas phase side solenoid valve 15 and the liquid phase side solenoid valve 16 (step S9). In step S9, control is performed to open the gas phase side solenoid valve 15 and the liquid phase side solenoid valve 16, and normal cooling control (during discharge and cooling control performed during charging). If the soak determination is not ON (step S2: No) or if the temperature of the battery cell 2 is not higher than the outside air temperature (step S7: No), the control routine proceeds to step S9. After step S9 is performed, this control routine ends.

Here, with reference to FIGS. 5 to 7, changes in the state of the loop type thermosiphon 10 when the variation suppression temperature control in step S5 described above is executed will be described. FIG. 5 is a schematic diagram showing a case where the liquid phase side solenoid valve is closed and the heater is turned on. FIG. 6 is a schematic diagram showing a state in which the liquid-phase working fluid flows into the vapor passage from the state shown in FIG. FIG. 7 is a schematic diagram showing a transition from the state shown in FIG. 6 to a state in which the liquid-phase working fluid is returned to the evaporator.

As shown in FIG. 5, the variation suppression temperature control is started, the liquid phase side solenoid valve 16 is closed, and the heater 17 is turned on while the circulation of the working fluid is stopped. The heater 17 boils the liquid-phase working fluid staying in the lower passage 14a. This boiling generates a vapor-phase working fluid in the lower passage 14a.

As shown in FIG. 6, if the variation suppression temperature control is continued, the temperature of the vapor-phase working fluid generated in the lower passage 14a by the heater 17 rises. Further, since the liquid-phase side solenoid valve 16 is closed, the pressure in the lower passage 14a rises due to the temperature rise of the gas-phase working fluid using the heater 17 . The pressure rise expands inside the liquid passage 14 from the portion on the side of the lower passage 14 a to the portion on the side of the condenser 12 . Therefore, the liquid-phase working fluid liquefied by heat dissipation in the condenser 12 becomes difficult to flow downward through the liquid passage 14 and is stored in the condenser 12 .

Then, if the variation suppression temperature control is further continued, as shown in FIG. flows downward inside the Further, since the vapor phase side solenoid valve 15 is open, the liquid phase working fluid flowing through the vapor passage 13 flows into the vapor outlet of the evaporator 11 from the vapor passage 13 . That is, the liquid-phase working fluid can be returned to the inside of the evaporator 11 .

Then, as shown in FIG. 7, by closing the gas phase side solenoid valve 15, circulation of the working fluid is stopped, and heat exchange between the working fluid and the outside air can be suppressed. At that time, the liquid level of the liquid-phase working fluid in the evaporator 11 is a liquid level that can come into contact with all the battery cells 2 . For example, as shown in FIG. 8, the amount of liquid-phase working fluid is such that it can contact all the battery cells. In this case, as shown in FIG. 9, the temperature variations among the battery cells are suppressed.

As described above, according to the embodiment, the liquid phase side solenoid valve 16 provided in the liquid passage 14 is closed to stop the circulation of the working fluid even when the vehicle body is tilted in an environment where the outside air temperature is low. In addition, by heating the working fluid in the lower passage 14a by the heater 17, the liquid-phase working fluid is evaporated in the lower passage 14a and the pressure rise of the vapor-phase working fluid accompanying the temperature rise of the working fluid is suppressed. can be generated. As a result, the liquid-phase working fluid temporarily retained in the lower passage 14 a due to the tilt of the vehicle body can be returned to the evaporator 11 via the liquid passage 14 , the condenser 12 , and the vapor passage 13 . Therefore, even when the outside air is cold and the vehicle body is tilted, the liquid level of the liquid-phase working fluid in the evaporator 11 can be brought into contact with all the battery cells 2, and the temperature variation of the battery cells 2 can be reduced. can be suppressed. As a result, deterioration of the battery cells 2 can be suppressed, and battery life can be extended.

Further, according to the embodiment, when the outside air is cold and the vehicle body is tilted, normal cooling control and control of only closing the gas phase side solenoid valve 15 and the liquid phase side solenoid valve 16 are executed (comparative example). Also, variations in the temperature of the battery cells 2 can be suppressed. 10 to 12 illustrate comparative examples.

As a comparative example, as shown in FIG. 10, when variation suppression temperature control is not executed, the amount of liquid-phase working fluid in the evaporator 11 is insufficient, and the liquid surface cannot contact all the battery cells. becomes. For example, when normal cooling control is performed when the outside air is cold and the vehicle body is tilted (comparative example), the liquid surface state shown in FIG. Large temperature variations occur between cells. As another comparative example, when the air temperature is low and the vehicle body is tilted, if cooling control is executed by simply closing the gas phase side solenoid valve 15 and the liquid phase side solenoid valve 16, the circulation of the working fluid is stopped. As a result, the heat exchange between the working fluid and the outside air is suppressed, but the liquid level state shown in FIG. 10 described above occurs, and as shown in FIG. Temperature variation occurs. In contrast to these comparative examples, according to the above-described embodiments, it is possible to suppress variations in the temperature of the battery cells 2 .

As a modification of the above-described embodiment, the condenser 12 is not limited to a condenser that exchanges heat with the refrigerant of an air conditioner. It may be configured by a heat exchanger that exchanges heat between. In this case, in the condenser 12, heat is exchanged between the working fluid and the cooling liquid, and the working fluid is condensed by transferring heat to the cooling liquid. Furthermore, a signal from a temperature sensor that detects the temperature of the coolant is input to the ECU 20 .

1 boiling cooling device 2 battery cell 3 battery module 4 battery pack 10 loop type thermosiphon 11 evaporator 12 condenser 13 steam passage 14 liquid passage 14a lower passage 15 vapor side solenoid valve 16 liquid side solenoid valve 20 electronic control device ( ECU)
21 temperature control unit 31 acceleration sensor 32 battery temperature sensor 33 outside air temperature sensor

Claims (2)

an evaporator that absorbs heat from the battery cell and evaporates the liquid-phase working fluid;
a condenser disposed above the evaporator for condensing the vapor-phase working fluid vaporized by the evaporator;
a vapor passage for circulating the vapor-phase working fluid vaporized by the evaporator to the condenser;
a liquid passage for circulating the liquid-phase working fluid liquefied in the condenser to the evaporator;
A boiling cooling device for cooling a battery module made up of a plurality of the battery cells mounted on a vehicle and circulating a working fluid between the evaporator and the condenser,
The liquid passage includes a lower passage located below a connection port with the evaporator when the vehicle body of the vehicle is tilted,
a temperature raising unit provided in the lower passage and configured to heat the working fluid in the lower passage by generating heat when supplied with electric power;
an on-off valve provided between the connection port and the temperature raising section in the liquid passage;
a control unit that controls opening and closing of the on-off valve and the temperature raising unit based on the temperature of the battery cell;
with
When the vehicle body is tilted and the temperature of the battery cell is higher than the outside air temperature of the vehicle, the control unit closes the on-off valve to increase the temperature of the lower passage by the temperature raising unit. An ebullient cooling device characterized by executing control to heat and evaporate a liquid-phase working fluid. an evaporator that absorbs heat from the battery cell to evaporate a liquid-phase working fluid; a condenser that is disposed above the evaporator and condenses the vapor-phase working fluid that has been vaporized by the evaporator; A loop type thermostat having a vapor passage for circulating a vapor-phase working fluid vaporized in an evaporator to the condenser, and a liquid passage for circulating a liquid-phase working fluid liquefied by the condenser to the evaporator. A method for controlling the temperature of the battery cells in an ebullient cooling device having a siphon and cooling a battery module comprising a plurality of the battery cells mounted on a vehicle and circulating a working fluid between the evaporator and the condenser. There is
When the body of the vehicle is tilted and the temperature of the battery cell is higher than the outside air temperature of the vehicle, the liquid passage is connected to the evaporator when the body is tilted. a step of heating and evaporating a liquid-phase working fluid in a lower passage located below the lower passage by a temperature raising section, and closing the liquid passage between the connection port and the temperature raising section by an on-off valve. A temperature control method characterized by:

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