JP7679766B2 - Battery cooling system and method for controlling battery cooling system - Google Patents

Description

The present invention relates to a battery cooling system and a method for controlling a battery cooling system.

In recent years, a technology has been known in which a heater is provided in the passage through which the cooling oil that cools the object to be cooled passes, and when moisture gets mixed into the oil, the oil is heated and the moisture in the oil is evaporated (see, for example, Patent Document 1). One example of the object to be cooled is a medical X-ray tube device.

JP 2004-311170 A

In the technology of Patent Document 1, a heater is provided in front of the object to be cooled, so when the control to evaporate the moisture is performed, high-temperature cooling oil reaches the object to be cooled. In addition to medical X-ray tube devices, possible objects to be cooled include batteries used in electric vehicles. If the object to be cooled is something with low heat resistance like a battery, there is a possibility that it will be thermally deteriorated by the high-temperature cooling oil.

The object of the present invention is to provide a battery cooling system that suppresses thermal degradation of a battery, and a method for controlling the battery cooling system.

In order to solve the above problems, the battery cooling system of the present invention includes a battery, a heater for heating cooling oil that cools the battery, a reserve tank capable of separating the cooling oil into gas and liquid, a heat exchanger for exchanging heat between the cooling oil and a predetermined fluid, and a control device for controlling the heater and the heat exchanger.
In the battery cooling system having the above-mentioned, the cooling oil flows through the heater, the reserve tank, the heat exchanger, and the battery in that order, and the control device controls the heater to heat the cooling oil to a first temperature at which moisture in the cooling oil evaporates, and controls the heat exchanger to cool the cooling oil to a second temperature lower than the first temperature.

Cooling oil heated by the heater flows into the battery via the reserve tank and heat exchanger. The water in the heated cooling oil evaporates in the reserve tank, and the oil is cooled by the heat exchanger. This allows cooled cooling oil to flow into the battery, preventing the battery from thermally deteriorating when the water evaporates and hot cooling oil flows into the battery.

Preferably, the control device changes the second temperature based on the temperature of the battery.

By changing the second temperature based on the battery temperature, it is possible to manage the battery temperature while preventing high-temperature cooling oil from flowing into the battery.

Preferably, when the battery temperature is lower than the third temperature, the second temperature is set higher than when the battery temperature is higher than the third temperature.

By setting the second temperature high when the battery temperature is lower than the third temperature, the battery can be warmed up while preventing high-temperature cooling oil from flowing into the battery. In addition, costs can be reduced by using a single heater to both evaporate the moisture in the cooling oil and warm up the battery.

Preferably, in a vehicle equipped with the above-mentioned battery cooling system and capable of charging the battery externally, at least one of the heater, heat exchanger, and control device is supplied with power from the battery, and the control device controls the heater to heat the cooling oil to a first temperature at which moisture in the cooling oil evaporates, and the heat exchanger to cool the cooling oil to a second temperature lower than the first temperature, when the vehicle is being charged.

By controlling the evaporation of moisture from the cooling oil while the vehicle is being charged, it is possible to prevent the increase in battery power consumption caused by the evaporation control and the resulting deterioration of the vehicle's driving performance.

The present invention provides a battery cooling system that suppresses thermal degradation of a battery, and a method for controlling the battery cooling system.

1 is a diagram showing a vehicle equipped with a battery cooling system according to an embodiment; 1 is a diagram illustrating a schematic configuration of a battery cooling system according to an embodiment. 3 is a flowchart showing a control for evaporating moisture in the control device of FIG. 2 . FIG. 4 is a diagram showing the relationship between the amount of water evaporation from cooling oil; 3 is a flowchart showing a control for warming up the battery in the control device of FIG. 2 .

<Embodiment>
1 is a diagram that shows a schematic diagram of a vehicle equipped with a battery cooling system 1 according to an embodiment. The battery cooling system 1 is equipped, for example, in an electric vehicle A that includes a motor (not shown) for driving the vehicle and a battery 10 (not shown) that supplies power to the motor, and the cooling system 1 cools the battery 10. The electric vehicle A refers to, for example, a hybrid electric vehicle (HEV), an electric vehicle (BEV), or a fuel cell electric vehicle (FCEV), etc.

Figure 2 is a diagram showing a schematic configuration of a battery cooling system 1 according to an embodiment. The battery cooling system 1 includes a cooling circuit 50 and a control device 21. The cooling circuit 50 includes a battery 10, a heater 11, a reserve tank 12, a heat exchanger 13, an oil pump, a first flow path 31, a second flow path 32, a third flow path 33, a fourth flow path 34, a fifth flow path 35, a first temperature sensor 41, a second temperature sensor 42, a third temperature sensor 43, and a fourth temperature sensor 44.

The cooling circuit 50 circulates the cooling oil in the following order: electric pump 14, first flow path 31, battery 10, second flow path 32, heater 11, third flow path 33, reserve tank 12, fourth flow path 34, heat exchanger 13, and fifth flow path 35. Therefore, the heat exchanger 13 is disposed between the heater 11 and the battery 10. Also, in FIG. 2, the arrows of the first flow path 31, second flow path 32, third flow path 33, fourth flow path 34, and fifth flow path 35 indicate the direction in which the cooling oil flows. The cooling oil may be a known oil, for example, an oil with high electrical insulation properties. Specifically, the cooling oil may be mineral oil, synthetic oil, silicone oil, fluorine oil, etc.

The electric pump 14 is driven by power supplied from the battery 10, draws in cooling oil from an intake port, and discharges the cooling oil from an exhaust port. The exhaust port of the electric pump 14 is connected to the first flow path 31. The cooling oil discharged from the electric pump 14 to the first flow path 31 is pumped toward the downstream side of the cooling circuit 50 by the discharge pressure of the electric pump 14. The battery 10 is connected to the downstream side of the first flow path 3120.

Battery 10 is a storage device capable of charging power, and corresponds to a "battery". Battery 10 is configured to have, for example, a battery case and a battery module (not shown). The battery module is configured, for example, from a lithium ion battery. The battery cells are not particularly limited as long as they are secondary batteries capable of charging and discharging power, and may be, for example, nickel-metal hydride batteries. Here, the downstream side of the first flow path 31 is connected to the inlet of the battery case of battery 10. Cooling oil flows into the inside of the battery case from the first flow path 31, and if the temperature of the cooling oil that has flowed in is lower than the temperature of the battery module, the heat of the battery module is transferred to the cooling oil, and the battery module can be cooled by the cooling oil. The cooling oil that flows out of battery 10 is supplied to heater 11 through the second flow path 32.

The heater 11 is driven by power supplied from the battery 10 and corresponds to a "heater" that warms up the battery 10. The warming up of the battery 10 is performed, for example, in a situation where the temperature of the battery 10 is low, such as in winter when the air temperature is low. Here, the downstream side of the second flow path 32 is connected to the inlet of the heater 11, and the cooling oil is supplied to the reserve tank 12 through the third flow path 33 connected to the outlet of the heater 11. In the above-mentioned warming up, the heater 11 is driven to heat the cooling oil flowing into the heater 11, and the heated cooling oil moves to the battery module to heat the battery 10. The heater 11 also has the role of evaporating the moisture in the cooling oil by heating the cooling oil, which will be described later.

The reserve tank 12 absorbs the volume expansion caused by the rise in temperature of the cooling oil to keep the amount of cooling oil circulating through the cooling circuit 50 constant, and also removes residual air contained in the cooling oil (gas-liquid separation). Here, the downstream side of the third flow path 33 is connected to the inlet of the reserve tank 12, and the cooling oil is supplied to the heat exchanger 13 through the fourth flow path 34 connected to the outlet of the reserve tank 12.

The heat exchanger 13 corresponds to a "heat exchanger" that exchanges heat between the supplied cooling oil and a predetermined fluid. The heat exchanger 13 exhausts heat from the battery 10 and discharges the cooling oil after heat exchange. The predetermined fluid is, for example, a cooling liquid in a refrigeration cycle, and the cooling liquid is supplied to the heat exchanger 13 by a cooling liquid supply pump 51. The refrigeration cycle is, for example, included in the air conditioner of the electric vehicle A, and by using the cooling liquid in the refrigeration cycle, the temperature of the cooling oil can be lowered more than when air is used as the predetermined fluid. Here, the downstream side of the fourth flow path 34 is connected to the inlet of the heat exchanger 13, and the fifth flow path 35 is connected to the outlet of the heat exchanger 13. The cooling oil discharged from the heat exchanger 13 is supplied to the battery 10 through the fifth flow path 35, the electric pump 14, and the first flow path 31. The cooling oil is cooled by the heat exchanger 13, and, for example, cooling oil at about room temperature flows into the battery 10. The temperature of the cooling oil flowing out of the heat exchanger 13 may be any temperature that the battery 10 can tolerate. The heat exchanger 13 is also capable of changing the strength of cooling. Specifically, a control valve 15 is provided that is driven by power supplied from the battery 10 and can adjust the amount of coolant in the refrigeration cycle that flows into the heat exchanger 13. By controlling the control valve 15 in the opening direction, the amount of coolant inflow increases, accelerating cooling.

The first temperature sensor 41 is disposed downstream in the battery case of the battery 10, detects the temperature Tbat of the battery 10, and outputs a signal indicating the detected value to the control device 21.

The second temperature sensor 42 is disposed downstream in the first flow path 31, near the inlet of the cooling oil of the battery 10. The second temperature sensor 42 detects the temperature Tflow1 of the cooling oil passing through the first flow path 31, and outputs a signal indicating the detected value to the control device 21.

The third temperature sensor 43 is disposed downstream in the reserve tank 12, detects the temperature Tres of the cooling oil stored in the reserve tank 12, and outputs a signal indicating the detected value to the control device 21.

The fourth temperature sensor 44 is located in the fifth flow path 35 near the outlet of the heat exchanger 13. The fourth temperature sensor 44 detects the temperature Tflow5 of the cooling oil passing through the fifth flow path 35 and outputs a signal indicating the detected value to the control device 21.

The control device 21 has a control unit 22 and corresponds to a "control device" that drives the heater 11, heat exchanger 13, and electric pump 14 at a predetermined timing. The heater 11 is driven to evaporate and remove moisture contained in the cooling oil, and the control unit 22 of the control device 21 opens the control valve 15 of the heat exchanger 13 at the same time as driving the heater 11. Driving the heater 11 increases the temperature of the cooling oil flowing into the heater 11. This increase in the temperature of the cooling oil vaporizes the moisture in the cooling oil, and the vaporized moisture passes through the third flow path 33 and is separated into gas and liquid in the reserve tank 12. In addition, by opening the control valve 15 of the heat exchanger 13 at the same time as driving the heater 11, the heated cooling oil is cooled by heat exchange with the desired liquid, and the cooling oil flowing out of the heat exchanger 13 drops to, for example, about room temperature. This allows moisture contained in the cooling oil to evaporate, preventing deterioration of the cooling oil, and increasing the withstand voltage of the electrical insulation, while preventing high-temperature cooling oil from flowing into the battery 10. Here, the control unit 22 controls the driving of the heater 11 and the driving and stopping of the control valve of the heat exchanger 13 based on the detected cooling oil temperatures Tres and Tflow5. Specifically, the control device 21 drives the heater 11 so that Tres becomes a predetermined temperature, and drives the control valve 15 of the heat exchanger 13 so that Tflow5 becomes approximately room temperature.

The configuration of the control device 21 can be realized by a combination of hardware and software resources, or by hardware resources alone. Analog elements, microcomputers, DSPs, ROMs, RAMs, ASICs, FPGAs, and other LSIs can be used as hardware resources. Programs such as firmware can be used as software resources.

Figure 3 is a flow chart showing the control of evaporating moisture by the control device 21 of Figure 2. The process of Figure 3 is periodically repeated by the control device 21. In this embodiment, "periodically" refers to a time interval at which not much moisture accumulates in the cooling oil, and is a predetermined interval determined in advance by experiments, etc.

First, the control unit 22 of the control device 21 drives the electric pump 14 and drives the control valve 15 of the heat exchanger 13 in the open direction (S100). The driving of the electric pump 14 causes the cooling oil to circulate in the cooling circuit 50.

Next, the control unit 22 of the control device 21 drives the heater 11 when the cooling oil is circulating in the cooling circuit 50 (S101). By driving the heater 11, the cooling oil flowing into the heater 11 from the third flow path 33 is heated, and the temperature of the cooling oil increases.

Next, the control valve 15 is controlled so that the temperature Tflow1 of the cooling oil passing through the first flow path 31 and the temperature Tflow5 of the cooling oil passing through the fifth flow path 35 are less than the second predetermined value Tp2 (S102). Here, the second predetermined value Tp2 is a temperature that corresponds to the "second temperature" and can be tolerated by the battery 10, and is set within a range of, for example, 30°C to 35°C. The control unit 22 of the control device 21 controls the opening degree of the control valve 15 so that the output value Tflow1 of the first temperature sensor 42 located in the first flow path 31 and near the cooling oil inlet of the heater 11 and the output value Tflow5 of the fourth temperature sensor 44 located in the fifth flow path 35 and near the outlet of the heat exchanger 13 are less than Tp2. In this embodiment, both Tflow1 and Tflow5 are controlled to be less than the second predetermined value Tp2, but either one of them may be controlled to be less than the second predetermined value Tp2.

Next, the control device 21 determines whether the temperature Tres of the cooling oil in the reserve tank 12 is equal to or greater than a first predetermined value Tp1 (S103). Specifically, the control unit 22 of the control device 21 determines whether the output value Tres of the third temperature sensor 43 disposed downstream in the reserve tank 12 is equal to or greater than Tp1. When the output value Tres of the third temperature sensor 43 is less than the first predetermined value (No in S103), the process returns to S101. As will be described later, Tp1 corresponds to the "first temperature", for example, 50°C, and may be any temperature at which the moisture in the cooling oil evaporates to a predetermined amount or more. Preferably, by controlling the temperature to be between 50°C or more and less than 80°C, thermal deterioration of the cooling circuit 50 of the reserve tank or the like, which has low heat resistance, can be suppressed.

When it is determined that the temperature Tres of the cooling oil in the reserve tank 12 is equal to or higher than Tp1 (Yes in S103), the control unit 22 of the control device 21 determines whether a predetermined time or more has elapsed since the temperature Tres of the cooling oil became equal to or higher than Tp1 (S104). When the predetermined time or more has not elapsed (No in S104), the process returns to S101. Here, the amount of water evaporation in the cooling oil depends on the heating time and the temperature of the cooling oil. That is, in order to achieve a predetermined amount of water evaporation, it is necessary to satisfy the relationship shown in FIG. 4. Specifically, when the cooling oil temperature is T1, water can be evaporated by heating for t1 hours, but when the cooling oil temperature is T2 (<T1), it is necessary to heat for t2 (>t1) hours or more. There is such a relationship in the evaporation of water in the cooling oil, and the predetermined time in this embodiment may be a time that the cooling oil is sufficiently heated by the heater 11 to evaporate water. Here, the predetermined amount of water evaporation in this embodiment is determined based on the heating temperature of the heater 11.

When it is determined that a predetermined time has elapsed since the temperature Tres of the cooling oil in the reserve tank 12 became equal to or higher than Tp1 (Yes in S104), the control unit 22 of the control device 21 stops driving the heater 11 (S105).

Next, the control device 21 determines whether the temperature Tres of the cooling oil in the reserve tank 12 is less than a second predetermined value Tp3 (S106). Specifically, the control unit 22 of the control device 21 is disposed downstream in the reserve tank 12 and determines whether the temperature Tres of the cooling oil stored in the reserve tank 12 is less than Tp2 or more.

When it is determined that the output value Tres of the third temperature sensor 43 is equal to or greater than Tp2 (Yes in S106), the control unit 22 of the control device 21 stops the electric pump 14, drives the control valve 15 of the heat exchanger 13 in the closing direction, and ends the process (S107). Here, in this embodiment, the electric pump 14 is stopped and the control valve 15 of the heat exchanger 13 is driven in the closing direction, but this may be done stepwise as long as the drive is limited. Also, the drive of only one of the electric pump 14 and the control valve 15 of the heat exchanger 13 may be stopped or limited. In this case, the limit of the electric pump 14 means reducing the intake and discharge amounts by the electric pump 14, and the limit of the heat exchanger 13 means reducing the inflow amount of the coolant in the refrigeration cycle by controlling the opening and closing of the control valve 15 described above.

According to the embodiment, the heater 11 is periodically driven to raise the temperature of the cooling oil, and the moisture in the cooling oil is evaporated in the reserve tank 12. Here, in this embodiment, the control valve 15 of the heat exchanger 13 is driven in the open direction along with the driving of the heater 11. The cooling oil heated by the heater 11 flows into the battery 10 via the reserve tank 12 and the heat exchanger 13. As a result, cooled cooling oil flows into the battery 10, and when the moisture evaporates, high-temperature cooling oil flows into the battery 10, which can prevent thermal deterioration of the battery 10.

Here, the control method for operating the heater 11 to warm up the battery 10 will be explained using the flowchart in Figure 5.

Figure 5 is a flowchart showing the control of warming up the battery 10 in the control device 21, and this control is started based on the temperature of the battery 10.

The control device 21 determines whether the temperature Tbat of the battery 10 is less than the third predetermined value Tp3 (S200). Specifically, the control unit 22 of the control device 21 determines whether the output value Tbat of the first temperature sensor 41 arranged downstream in the battery case of the battery 10 is less than Tp3.

Next, when the temperature Tbat of the battery 10 is less than Tp4 (Yes in S200), it is determined whether the cooling oil temperature Tflow1 is less than a fourth predetermined value Tp3. Specifically, the control unit 22 of the control device 21 determines whether the output value Tflow1 of the second temperature sensor 42, which is located downstream in the first flow path 31 and near the cooling oil inlet of the battery 10, is less than Tp4 (S201). Here, Tp4 is a temperature higher than Tp3 and lower than Tp2; for example, Tp3 is 0°C and Tp4 is 25°C.

When the temperature of the cooling oil in the first cooling path is less than Tp4 (Yes in S201), the heater 11 is driven (S202) and the process returns to S200. At this time, the control valve 15 of the heat exchanger 13 is driven in the closing direction, or the opening and closing of the control valve 15 is controlled to limit the cooling by the heat exchanger 13, thereby maintaining a temperature at which the battery 10 can be warmed up. As a result, the heat generated by the heater 11 is transferred to the battery 10 via the cooling oil, thereby warming up the battery 10. Also, if the heater 11 was already driven, it is allowed to continue to be driven.

When the temperature Tbat of the battery 10 is equal to or higher than Tp3, or the temperature Tflow1 of the cooling oil is equal to or higher than Tp4 (No in S200, No in S201), the control unit 22 of the control device 21 does not drive the heater 11, but drives the control valve of the heat exchanger 13 in the opening direction (S203). At this time, if the control valve 15 of the heat exchanger 13 is already being controlled in the opening direction, the control in the opening direction is continued, and room temperature cooling oil is allowed to flow into the battery 10.

In this manner, in the embodiment, the operation of the heater 11 and the control valve 15 of the heat exchanger 13 is switched depending on the evaporation of water in the cooling oil and the warming up of the battery 10. This allows one heater 11 to be used for both evaporating water from the cooling oil and warming up the battery 10, thereby reducing costs.

<Modification>
In the control for evaporating water in the above embodiment, the second predetermined value Tp2 may be changed based on the temperature of the battery 10. Specifically, it is set based on the output value of the first temperature sensor 41 arranged downstream in the battery case of the battery 10. For example, when the temperature of the battery 10 corresponds to the "third temperature" below freezing, Tp2 is set to a high value so that cooling oil at a temperature that allows the battery 10 to be warmed up is introduced. This causes the cooling by the heat exchanger 13 to be stopped or limited early, and the cooling of the cooling oil is suppressed, making it possible to warm up the battery 10, and the evaporation of water from the cooling oil and the warming up of the battery 10 can be performed simultaneously.

In the above embodiment, the control of evaporating moisture in FIG. 3 is described as being performed periodically, but it may be performed when the temperature of the cooling oil is low and evaporation of moisture in the cooling oil is not expected. Specifically, control of evaporating moisture is performed when the temperature Tbat of the battery 10 or the output value Tres of the third temperature sensor 43 is 50° C. or lower, which is a temperature at which evaporation of moisture in the cooling oil is not expected. In the above situation, when the moisture in the cooling oil is unlikely to evaporate and there is a high possibility that moisture remains in the cooling oil, the moisture in the cooling oil can be efficiently reduced by heating the cooling oil with the heater 11.

The amount of heat applied by the heater 11 may be different for removing moisture from the cooling oil and for warming up the battery. Specifically, the amount of heat applied to remove moisture from the cooling oil is greater than the amount of heat applied to warm up the battery. A large amount of heat is required to evaporate the moisture in the cooling oil, but a temperature that ensures the output of the battery is sufficient to warm up the battery, for example, about 20 to 25°C in winter. Even if the heater 11 heats the cooling oil to a temperature that can evaporate the moisture in the cooling oil to warm up the battery 11, the heat exchanger 13 cools the oil to a temperature that the battery can tolerate, resulting in unnecessary heating. By setting the amount of heat as described above, unnecessary heating can be suppressed and the consumption of the battery 10 can be reduced.

In the modified example, one heater 11 was used for both evaporating water from the cooling oil and warming up the battery 10, but a heater for evaporating water from the cooling oil and a heater for warming up the battery 10 may be provided separately. In that case, the heater for evaporating water from the cooling oil may be placed at the position of the heater 11, and the heater for warming up the battery 10 may be placed on the first flow path 31. Also, only one of the first temperature sensor 41 and the fourth temperature sensor 44 may be used.

The control for evaporating the moisture in the cooling oil may be performed when the electric vehicle A is being charged. By performing the control at this timing, it is possible to suppress a decrease in the output of the battery 10 that would be caused by performing the control while the vehicle is running. As another timing, the control may be performed when the electric vehicle A is stopped and the ignition is turned off. Performing the control at such a timing can also achieve the above-mentioned effects.

In addition, in the embodiment and modified example, the strength of the cooling of the heat exchanger is adjusted by the control valve 15, but the strength of the cooling of the heat exchanger may also be adjusted by controlling the flow rate of the coolant supply pump 51 of the refrigeration cycle.

The present invention has been described above based on the embodiments. The embodiments are merely examples, and it will be understood by those skilled in the art that multiple variations are possible in the combination of each component and each processing process, and that such variations are also within the scope of the present invention.

Reference Signs List 1 Battery cooling system 10 Battery 11 Heater 12 Reserve tank 13 Heat exchanger 14 Electric pump 21 Control device 22 Control unit 51 Coolant supply pump A Electric vehicle

Claims (7)

A battery;
a heater for heating a cooling oil for cooling the battery;
a reserve tank capable of separating the cooling oil into gas and liquid;
a heat exchanger for exchanging heat between the cooling oil and a predetermined fluid;
A control device for controlling the heater and the heat exchanger;
A battery cooling system comprising:
The cooling oil flows through the heater, the reserve tank, the heat exchanger, and the battery in this order.
The control device controls the heater to heat the cooling oil to a first temperature at which moisture in the cooling oil evaporates, and controls the heat exchanger to cool the cooling oil to a second temperature lower than the first temperature. The battery cooling system of claim 1, wherein the control device changes the second temperature based on the temperature of the battery. The battery cooling system according to claim 1 or 2, characterized in that the control device sets the second temperature higher when the temperature of the battery is lower than the third temperature compared to when the temperature of the battery is higher than the third temperature. At least one of the heater, the control device, and a control valve that controls the amount of coolant flowing into the heat exchanger is supplied with power from the battery;
4. The battery cooling system according to claim 1, wherein the control device controls the heater to heat the cooling oil to a first temperature at which moisture in the cooling oil evaporates, and the heat exchanger to cool the cooling oil to a second temperature lower than the first temperature, when the vehicle is being charged. A method for controlling a battery cooling system that cools a battery by cooling oil, comprising:
a heating step of heating the cooling oil to a first temperature at which moisture in the cooling oil evaporates;
a cooling step of cooling the cooling oil to a second temperature lower than the first temperature before the cooling oil reaches the battery after being heated;
A method for controlling a battery cooling system comprising: The method for controlling a battery cooling system according to claim 5, characterized in that the second temperature is changed based on the temperature of the battery. The method for controlling a battery cooling system according to claim 5 or 6, characterized in that when the temperature of the battery is lower than a third temperature, the second temperature is set higher than when the temperature of the battery is higher than the third temperature.

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