Electric vehicles

Abstract

To provide an electric vehicle in which temperature control and cooling control are less likely to interfere with each other. [Solution] The electric vehicle comprises a battery, a temperature control circuit, and a control device. The temperature control circuit heats or cools the battery by circulating a heat transfer medium through the battery. The control device controls the temperature control circuit to perform either a heating control, which heats the battery with a high-temperature heat transfer medium, or a cooling control, which cools the battery with a low-temperature heat transfer medium. The control device starts the heating control when the temperature of the low-temperature unit having the lowest temperature among the plurality of battery units is below the heating start temperature, and when the temperature of the high-temperature unit having the highest temperature rises to or above the cooling start temperature during the heating control, it lowers the temperature of the heat transfer medium to below the temperature at the start of the heating control and continues the heating control.

Description

Technical Field

[0001] The present invention relates to an electric vehicle that adjusts the temperature of a battery by circulating a heat medium.

Background Art

[0002] Patent Document 1 discloses a battery temperature adjustment cycle for adjusting the temperature of a battery. The battery temperature adjustment cycle is a temperature adjustment circuit that circulates a heat medium for heating or cooling the battery. The battery temperature adjustment cycle is controlled by a control device. The control device switches between a temperature increase control for heating the battery with a high-temperature heat medium and a cooling control for cooling the battery with a low-temperature heat medium to adjust the temperature of the battery.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] A battery includes a plurality of battery units. Each battery unit includes at least one battery cell. Due to aging deterioration or the like, variations occur in the performance of each battery unit within the battery, and variations may also occur in the temperature of each battery unit during the operation of the battery. In that case, a specific battery unit within the battery may require temperature increase, and another battery unit may require cooling. The heat medium for adjusting the temperature of the battery is not supplied to each battery unit individually, but is supplied to the entire battery. Therefore, if there are variations in the temperature of each battery unit within the battery, there is a possibility that the heating control and the cooling control may interfere with each other.

[0005] One object of the present invention is to provide an electric vehicle in which the cooling control and the heating control are less likely to interfere with each other.

Means for Solving the Problems

[0006] The inventors investigated a mechanism in which temperature rise control and cooling control interfere with each other. For example, the control device starts temperature rise control when the temperature of the low-temperature unit, which has the lowest temperature among multiple battery units, is below the temperature rise start temperature (e.g., 15°C), and stops temperature rise control when the temperature of the low-temperature unit reaches or exceeds the temperature rise end temperature (e.g., 25°C). The control device also starts cooling control when the temperature of the high-temperature unit, which has the highest temperature among multiple battery units, is above the cooling start temperature (e.g., 35°C), and stops cooling control when the temperature of the high-temperature unit reaches or falls below the cooling end temperature (e.g., 30°C). For example, if the temperature of the high-temperature unit reaches or exceeds the cooling start temperature (e.g., 35°C) while temperature rise control is being performed, temperature rise control is stopped to ensure battery safety. In this case, some battery units may not be sufficiently heated, potentially leading to a decrease in battery output. Also, if the temperature of a low-temperature unit falls below the temperature rise start temperature (e.g., 15°C) while cooling control is being performed, the output of that low-temperature unit decreases. Considering battery safety, cooling control to cool the battery continues, which may lead to a decrease in battery output.

[0007] <1> An electric vehicle according to one aspect of the present invention includes a battery containing a plurality of battery units, a temperature control circuit that raises or cools the battery by circulating a heat transfer medium through the battery, and a control device that controls the temperature control circuit to perform a temperature-raising control to raise the battery with a high-temperature heat transfer medium, or a cooling control to cool the battery with a low-temperature heat transfer medium. The control device starts the temperature-raising control when the temperature of the low-temperature unit having the lowest temperature among the plurality of battery units is below the temperature-raising start temperature, stops the temperature-raising control when the temperature of the low-temperature unit reaches or exceeds the temperature-raising end temperature, starts the cooling control when the temperature of the high-temperature unit having the highest temperature among the plurality of battery units is above the cooling start temperature, stops the cooling control when the temperature of the high-temperature unit reaches or exceeds the cooling end temperature, and continues the temperature-raising control when the temperature of the high-temperature unit reaches or exceeds the cooling start temperature during the implementation of the temperature-raising control by lowering the temperature of the heat transfer medium to a temperature lower than the temperature at the start of the temperature-raising control.

[0008] <2> An electric vehicle according to another aspect of the present invention includes a battery comprising a plurality of battery units, a temperature control circuit for raising or cooling the battery by circulating a heat transfer medium through the battery, and a control device for controlling the temperature control circuit to perform a temperature-raising control to raise the battery with a high-temperature heat transfer medium, or a cooling control to cool the battery with a low-temperature heat transfer medium. The control device starts the temperature-raising control when the temperature of the low-temperature unit having the lowest temperature among the plurality of battery units is below the temperature-raising start temperature, stops the temperature-raising control when the temperature of the low-temperature unit reaches or exceeds the temperature-raising end temperature, starts the cooling control when the temperature of the high-temperature unit having the highest temperature among the plurality of battery units is above the cooling start temperature, stops the cooling control when the temperature of the high-temperature unit reaches or exceeds the cooling end temperature, and continues the cooling control when the temperature of the low-temperature unit falls below the temperature-raising start temperature during the implementation of the cooling control by raising the temperature of the heat transfer medium above the temperature at the start of the cooling control. [Effects of the Invention]

[0009] the above <1> In this electric vehicle, if the temperature of a high-temperature unit exceeds the cooling start temperature during the temperature rise control process, the temperature of the heat transfer medium is lowered to below the temperature at the start of the temperature rise control process, and the temperature rise control continues. As a result, the multiple battery units in the battery are easily heated to a sufficient temperature.

[0010] the above <2> In this electric vehicle, when the temperature of the low-temperature unit falls below the temperature at which the cooling control started during the operation, the temperature of the heat transfer medium is raised above the temperature at which the cooling control started in order to continue the cooling control. As a result, the multiple battery units in the battery are easily cooled sufficiently. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a schematic diagram of an electric vehicle according to an embodiment. [Figure 2] Figure 2 is a schematic diagram of the battery configuration of an electric vehicle according to this embodiment. [Figure 3] Figure 3 is a flowchart showing the control procedure for temperature rise control according to the embodiment. [Figure 4] Figure 4 is a flowchart showing the control procedure for the cooling control according to the embodiment. [Modes for carrying out the invention]

[0012] An example of an embodiment of the electric vehicle according to the present invention will be described below with reference to the drawings. The sizes of the components shown in each drawing are represented for the purpose of clarifying the explanation and do not necessarily represent the actual dimensions. The present invention is not limited to the following examples and is included in the claims, with all modifications within the meaning and scope equivalent to the claims.

[0013] <Embodiment> The electric vehicle 1 of this embodiment is a BEV (Battery Electric Vehicle) or hybrid vehicle equipped with a drive motor (not shown). The electric vehicle 1 of this example includes a battery 5 that supplies power to the drive motor, a temperature control circuit 6 that adjusts the temperature of the battery 5 by circulating a heat transfer medium, and a control device 4 that controls the temperature control circuit 6. The electric vehicle 1 of this example further includes a heat pump circuit 2 that cools or heats the air inside the vehicle, and a heater-type heating circuit 3 for heating the air inside the vehicle. One of the features of the electric vehicle 1 of this embodiment is that it is configured so that the temperature rise control and cooling control performed by the control device 4 do not interfere with each other. The various components of the electric vehicle 1 of this example will be described in order below, followed by a description of the temperature rise control and cooling control.

[0014] ≪Battery≫ Battery 5 is a secondary battery that supplies power to a drive motor (not shown) that drives the electric vehicle 1. Power from battery 5 may also be supplied to devices other than the drive motor. In the electric vehicle 1 of this example, power from battery 5 is also supplied to the electric compressor of the heat pump circuit 2, which will be described later.

[0015] Battery 5 is, for example, a lithium-ion battery. Lithium-ion batteries pose a risk of fire due to thermal runaway. Therefore, UN ECE R100-02, Part 2 stipulates that if the temperature of the lithium-ion battery rises above a specified value, a warning must be issued to the crew, and sufficient time must be provided for the crew to evacuate.

[0016] As shown in Figure 2, the battery 5 comprises multiple battery units 50. Each battery unit 50 is a single unit containing multiple battery cells. Each battery unit 50 is equipped with a temperature sensor 40 for measuring the temperature of the battery unit 50. The measurement results from the temperature sensor 40 are input to the control device 4 and used to regulate the temperature of the battery 5.

[0017] ≪Temperature control circuit≫ As shown in FIG. 1, the temperature control circuit 6 is a circulation circuit that circulates a heat medium for adjusting the temperature of the battery 5. By maintaining the temperature of the battery 5 within an appropriate range by the temperature control circuit 6, the performance of the battery 5 is fully exhibited. When the temperature of the battery 5 is low, the temperature control circuit 6 warms the battery 5. When the temperature of the battery 5 is high, the temperature control circuit 6 cools the battery 5.

[0018] The temperature control circuit 6 of this example has a circulation path 60, a pump 61, and a chiller 62. The chiller 62 is not an essential component. The battery 5 is disposed in the middle of the circulation path 60. The circulation path 60 is arranged, for example, so as to contact the battery 5.

[0019] The pump 61 is configured to pump the heat medium in the circulation path 60. The pump 61 operates with power from an auxiliary battery (not shown). Starting from the pump 61, the heat medium circulates in the circulation path 60. In FIG. 1, the flow direction of the heat medium is indicated by a white arrow. The heat medium circulates through the circulation path 60 in the order of pump 61 → battery 5 → chiller 62 → circuit switching valve 7 → pump 61. The heat medium is, for example, an antifreeze such as a long-life coolant (LLC). The pump 61 is an electric pump. The pump 61 is provided upstream of the battery 5 and downstream of the circuit switching valve 7 described later. A first liquid temperature sensor 41 is disposed between the battery 5 and the pump 61. The temperature of the heat medium supplied to the battery 5 can be measured by the first liquid temperature sensor 41 disposed upstream of the battery 5. The measurement result of the first liquid temperature sensor 41 is input to the control device 4 and used to adjust the temperature of the battery 5.

[0020] The chiller 62 is disposed downstream of the battery 5. The chiller 62 is provided so as to contact the chiller 22 of the heat pump circuit 2 described later. As will be described later, a low-temperature heat medium flows through the chiller 22. Therefore, the heat of the heat medium of the temperature control circuit 6 that has passed through the battery 5 is cooled by the chiller 22.

[0021] <<Heat pump circuit>> The heat pump circuit 2 is a circulation circuit in which a heat medium different from the heat medium flowing through the temperature control circuit 6 circulates. A known configuration, for example, the configuration described in Japanese Patent Application Laid-Open No. 2015-93561, can be used for the heat pump circuit 2. The heat medium of the heat pump circuit 2 is, for example, a hydrofluorocarbon such as R134a. The heat pump circuit 2 is configured to perform heat exchange between the outside of the vehicle and the inside of the vehicle by circulating the heat medium, and constitutes a part of an air conditioner that warms or cools the inside of the vehicle. In FIG. 1, only a part of the heat pump circuit 2 is shown by a broken line. Although not shown, the heat pump circuit 2 includes a compressor that compresses the heat medium and an electromagnetic expansion valve that expands and diffuses the heat medium. The circulation of the heat medium in the heat pump circuit 2 is carried out by the compressor. A large amount of power is required for the operation of the compressor, and that power is supplied from the battery 5. The temperature of the heat medium compressed by the compressor becomes high. The heat medium expanded and diffused by the electromagnetic expansion valve becomes low temperature. In a hybrid vehicle, the compressor may be operated by the engine.

[0022] The heat pump circuit 2 includes an evaporator 20 and a condenser 21 which are heat exchangers for temperature adjustment inside the vehicle. The heat pump circuit 2 of this example further includes a chiller 22. The chiller 22 is not essential, and when the above-described temperature control circuit 6 does not have a chiller 62, the chiller 22 is not necessary. A high-temperature heat medium flows through the condenser 21. On the other hand, a low-temperature heat medium flows through the evaporator 20 and the chiller 22. The evaporator 20 is disposed inside an air conditioning unit 2A described later.

[0023] ≪Heating Circuit≫ The heater-type heating circuit 3 is a circulation circuit for circulating a heat medium that warms the inside of the vehicle. The heating circuit 3 includes a circulation path 30, a pump 31, a condenser 32, a heater 33, a heater core 34, and a reserve tank 35.

[0024] Pump 31 is configured to pump the heat transfer medium within the circulation path 30. The heat transfer medium circulates within the circulation path 30 starting from pump 31. In Figure 1, the direction of flow of the heat transfer medium is indicated by white arrows. The heat transfer medium circulates through the circulation path 30 in the following order: pump 31 → condenser 32 → heater 33 → heater core 34 → circuit switching valve 7 → pump 31. The heat transfer medium is, for example, an antifreeze such as LLC. Pump 31 is an electric pump.

[0025] The condenser 32, located downstream of the pump 31, is positioned to be in contact with the condenser 21 of the heat pump circuit 2. Heat from the condenser 21 of the heat pump circuit 2 is transferred to the condenser 32 of the heating circuit 3, thereby heating the heat transfer medium of the heating circuit 3 as it passes through the condenser 32.

[0026] A heater 33 located downstream of the capacitor 32 heats the heat transfer medium according to the heating temperature setting requirements. The heater 33 is, for example, a high-voltage heater (HVH).

[0027] The heater core 34, located inside the air conditioning unit 2A downstream of the heater 33, heats the air through heat exchange between the heat transfer medium and the air passing through the heater core 34. The air conditioning unit 2A is also known as HVAC (Heating, Ventilation, and Air Conditioning). In addition to the heater core 34, the air conditioning unit 2A includes a blower 2F, an evaporator 20, and an air mix door 2D. The blower 2F draws air from outside the vehicle into the air conditioning unit 2A through the intake port 2B and discharges the air from inside the air conditioning unit 2A into the vehicle interior through the outlet port 2C. The evaporator 20 is located downstream of the blower 2F and upstream of the heater core 34. The air mix door 2D is pivotably or slidably positioned between the evaporator 20 and the heater core 34. The air mix door 2D adjusts the mixing ratio of cold air from the evaporator 20 and hot air from the heater core 34 depending on the degree to which it is opened.

[0028] A second liquid temperature sensor 42 and a third liquid temperature sensor 43 are positioned between the heater 33 and the heater core 34, and between the heater core 34 and the circuit switching valve 7 in the heating circuit 3. The second liquid temperature sensor 42 measures the temperature of the heat transfer medium flowing into the heater core 34. The measurement result of the second liquid temperature sensor 42 is used as an indicator to adjust the output of the heater 33. The third liquid temperature sensor 43 measures the temperature of the heat transfer medium flowing into the circuit switching valve 7. The measurement result of the third liquid temperature sensor 43 is used as an indicator to adjust the opening degree of the circuit switching valve 7. The reserve tank 35 temporarily stores the heat transfer medium circulating in the heating circuit 3.

[0029] Circuit switching valve The circuit switching valve 7 switches the connection state between the heating circuit 3 and the temperature control circuit 6. The circuit switching valve 7 connects the part of the circulation path 30 of the heating circuit 3 that connects the heater core 34 and the reserve tank 35, and the part of the circulation path 60 of the temperature control circuit 6 that is upstream of the pump 61. By adjusting the opening degree of the circuit switching valve 7, the heating circuit 3 and the temperature control circuit 6 can be switched to one of the following: (1) a parallel circuit independent of each other, (2) a series circuit connected in a line, or (3) a mixed circuit where the heat transfer medium is mixed at the position of the circuit switching valve 7. The circuit switching valve 7 in this example is a four-way valve that can branch the flow path in four directions. A known four-way valve (for example, Japanese Patent Publication No. 2013-238310, Japanese Patent Publication No. 2020-200902) can be used. The circuit switching valve 7 is not limited to a four-way valve, but can be any valve that can branch the flow path in four or more directions, for example, a five-way valve or a six-way valve. The circuit switching valve 7 is operated by power from the auxiliary battery.

[0030] By changing the opening of the circuit switching valve 7, the temperature of the heat transfer medium flowing through the temperature control circuit 6 can be changed. When the heat transfer medium from the heating circuit 3 flows into the temperature control circuit 6, the temperature of the heat transfer medium flowing through the temperature control circuit 6 increases. The more heat transfer medium flows in from the heating circuit 3, the higher the temperature of the heat transfer medium in the temperature control circuit 6. Even if the amount of heat transfer medium flowing in from the heating circuit 3 remains the same, the temperature of the heat transfer medium in the temperature control circuit 6 can be increased by increasing the output of the heater 33. On the other hand, the less heat transfer medium flows in from the heating circuit 3, the lower the temperature of the heat transfer medium in the temperature control circuit 6. The temperature of the heat transfer medium in the temperature control circuit 6 can also be lowered by increasing the output of the compressor in the heat pump circuit 2 and lowering the temperature of the chiller 22.

[0031] ≪Control device≫ In this example, the control device 4 controls the heat pump circuit 2, the heating circuit 3, the temperature control circuit 6, and the circuit switching valve 7. Regarding the heat pump circuit 2, the control device 4 controls the operation of the electric compressor and the expansion valve. Regarding the heating circuit 3, the control device 4 controls the operation of the pump 31 and the heater 33. Regarding the temperature control circuit 6, the control device 4 controls the pump 61. Regarding the circuit switching valve 7, the control device 4 controls the opening degree of the circuit switching valve 7. In this example, the part of the control device 4 that controls the pump 61 is called the pump unit 46, and the part that controls the circuit switching valve 7 is called the valve control unit 47.

[0032] The control device 4 is comprised of an electronic control unit (ECU). An ECU typically includes a processor and memory. The processor is, for example, a CPU. The memory stores control programs and various data for the processor to execute. The control device 4 operates when the control programs stored in memory are executed by the processor. Furthermore, the control device 4 performs necessary calculations and decision-making processes based on the control programs stored in memory.

[0033] ≪Temperature Control≫ In this example, the temperature rise control performed by control device 4 is configured to suppress the intervention of cooling control. The temperature rise control is mainly performed during the winter when temperatures are low. The specific control procedure for the temperature rise control will be explained based on the flowchart in Figure 3.

[0034] The control device 4 determines whether the temperature Tbmin of the low-temperature unit with the lowest temperature among the multiple battery units 50 is below the temperature at which the heating starts (e.g., 15°C) (step S1). If the result of the determination in step S1 is Yes, the control device 4 starts heating control (step S2). The situation in which heating control is started is not particularly limited, and heating control can be started when the battery 5 is being charged, when the electric vehicle 1 is being started, or when the electric vehicle 1 is running. If the result of the determination in step S1 is No, the control device 4 returns to the process of step S1. In other words, the process of step S1 is repeated until it becomes necessary to heat up the battery 5.

[0035] In step S2, the temperature rise control is performed by a high-temperature heat transfer medium circulating through the temperature control circuit 6, which raises the temperature of the battery 5. The temperature of the heat transfer medium is a predetermined temperature Tmh (for example, 40°C). Temperature Tmh is a temperature determined in advance through preliminary tests or the like. Here, temperature Tmh refers to the temperature of the heat transfer medium just before it flows into the battery 5, that is, the temperature of the heat transfer medium measured by the first liquid temperature sensor 41 located upstream of the battery 5. As the high-temperature heat transfer medium circulates through the temperature control circuit 6, the battery 5 is heated, that is, each battery unit 50 within the battery 5 is heated. In the temperature rise control, for example, the opening of the circuit switching valve 7 changes, and high-temperature heat transfer medium flows from the heating circuit 3 into the temperature control circuit 6, thereby adjusting the temperature Tmh of the heat transfer medium in the temperature control circuit 6 to 40°C. At that time, the output of the heater 33 may be increased to raise the temperature of the heat transfer medium flowing through the heating circuit 3.

[0036] After step S2, the control device 4 determines whether the temperature Tbmax of the high-temperature unit having the highest temperature among the multiple battery units 50 is below the cooling start temperature (e.g., 35°C) (step S3).

[0037] If the result of step S3 is Yes, the control device 4 determines whether the temperature Tbmin of the low-temperature unit is above the heating completion temperature (e.g., 25°C) (step S4). If the result of step S4 is No, the control device 4 determines that the low-temperature unit has not yet been sufficiently heated, so it continues the heating control and returns to the determination in step S3. On the other hand, if the result of step S4 is Yes, all the battery units 50 in the battery 5 have been properly heated, so the control device 4 terminates the heating control. Terminating the heating control means that the control device 4 will not take any action to actively raise the temperature of the battery 5. For example, the control device 4 may stop the pump 60 of the temperature control circuit 6, reduce the output of the heater 33, or change the opening degree of the circuit switching valve 7.

[0038] If the result of the judgment in step S3 is No, that is, if the temperature Tbmax of the high-temperature unit exceeds the cooling start temperature (e.g., 35°C), conventionally, the problem of interference arises as to whether to continue the heating control or switch to cooling control. In practice, considering the safety of the battery 5, it is advisable to switch to cooling control. In this example, the control device 4 lowers the temperature Tmh of the heat transfer medium circulating through the temperature control circuit 6 and continues the heating control (step S5). The changed temperature Tmh of the heat transfer medium is above the cooling start temperature (e.g., 35°C) and below the temperature of the heat transfer medium before the change (e.g., 40°C). From the viewpoint of preventing the temperature Tbmax of the high-temperature unit from rising, in this example, the temperature Tmh is changed to 35°C, which is the cooling start temperature. The temperature Tmh may also be changed to the same temperature as the temperature Tbmax of the high-temperature unit at the time of step S3.

[0039] After step S5, the control device 4 determines whether or not the rise in the temperature Tbmax of the high-temperature unit is being suppressed (step S6). Specifically, it determines whether or not the temperature Tbmax is being suppressed based on the change in temperature Tbmax. For example, if the temperature Tbmax becomes higher than the temperature Tmh by a predetermined temperature (e.g., 3°C) or more, it can be determined that the rise in temperature Tbmax is not being suppressed. Also, for example, if the state in which the temperature Tbmax is higher than the temperature Tmh continues for a predetermined time (e.g., 30 seconds), it can be determined that the rise in temperature Tbmax is not being suppressed. These examples show the criteria for the determination result in step S6 to be No.

[0040] If the result of step S6 is Yes, that is, if the rise in the high-temperature unit is suppressed, the control device 4 determines whether the temperature Tbmin of the low-temperature unit is above the heating completion temperature (e.g., 25°C) (step S7).

[0041] If the result of step S7 is No, there are still battery units 50 in the battery 5 that have not yet been sufficiently heated, so the control device 4 continues the heating control and returns to the decision in step S6. On the other hand, if the result of step S7 is Yes, all battery units 50 in the battery 5 have been properly heated, so the control device 4 terminates the heating control.

[0042] If the temperature Tbmax of the high-temperature unit continues to rise after step S5, the high-temperature unit may experience thermal runaway. Therefore, if the result of the judgment in step S6 is No, the control device 4 switches from heating control to cooling control (step S8) to prevent the temperature Tbmax of the high-temperature unit from rising any further. In cooling control, a low-temperature heat transfer medium is circulated through the temperature control circuit 6. The temperature Tmc of this low-temperature heat transfer medium is, for example, 10°C. In cooling control, for example, the opening degree of the circuit switching valve 7 is changed, reducing the amount of high-temperature heat transfer medium flowing from the heating circuit 3 into the temperature control circuit 6, or stopping the flow to the temperature control circuit 6, thereby adjusting the temperature Tmc of the heat transfer medium in the temperature control circuit 6 to 10°C.

[0043] In cooling control, the control device 4 determines whether the temperature Tbmax of the high-temperature unit is below the cooling completion temperature (e.g., 30°C) (step S9). If the result of the determination in step S9 is Yes, it can be determined that the high-temperature unit has been cooled and the possibility of thermal runaway of the high-temperature unit has been reduced, so the control device 4 returns to the determination in step S1 and determines whether or not to restart the temperature rise control. On the other hand, if the result of the determination in step S9 is No, it can be determined that the cooling of the high-temperature unit is insufficient, so the control device 4 continues the cooling control and returns to the determination in step S9.

[0044] According to the above temperature control, even if there are temperature variations among the battery units 50 within the battery 5, each battery unit 50 can be raised to an appropriate temperature. As a result, sufficient output can be obtained from the battery 5. Furthermore, since the possibility of thermal runaway of the battery units 50 is reduced with the above temperature control, the battery 5 is safer.

[0045] Cooling control In this example, the cooling control performed by control device 4 is configured to suppress the intervention of temperature rise control. Cooling control is mainly performed during the summer when temperatures are high. The specific control procedure for cooling control will be explained based on the flowchart in Figure 4.

[0046] The control device 4 determines whether the temperature Tbmax of the high-temperature unit with the highest temperature among the multiple battery units 50 is below the cooling start temperature (e.g., 35°C) (step S10). If the result of the determination in step S10 is Yes, the control device 4 starts cooling control (step S11). The situation in which cooling control is started is not particularly limited, and cooling control may be started when the battery 5 is being charged, when the electric vehicle 1 is being started, or when the electric vehicle 1 is running. If the result of the determination in step S10 is No, the control device 4 returns to the process of step S10. In other words, the process of step S10 is repeated until it becomes necessary to cool the battery 5.

[0047] In the cooling control of step S11, the battery 5 is cooled by a low-temperature heat transfer medium circulating in the temperature control circuit 6. The temperature of the heat transfer medium is a predetermined temperature Tmc (for example, 10°C). Here, temperature Tmc is the temperature of the heat transfer medium just before it flows into the battery 5, that is, the temperature of the heat transfer medium measured by the first liquid temperature sensor 41 located upstream of the battery 5. The battery 5 is cooled, that is, each battery unit 50 within the battery 5 is cooled, by the circulation of the low-temperature heat transfer medium in the temperature control circuit 6. In the cooling control, for example, the opening of the circuit switching valve 7 is changed to reduce the amount of high-temperature heat transfer medium flowing from the heating circuit 3 into the temperature control circuit 6, or to stop the flow into the temperature control circuit 6, thereby adjusting the temperature Tmc of the heat transfer medium in the temperature control circuit 6 to 10°C. At that time, the output of the compressor may be increased to lower the temperature of the chiller 22 that cools the heat transfer medium in the temperature control circuit 6.

[0048] After step S11, the control device 4 determines whether the temperature Tbmin of the low-temperature unit is above the heating start temperature (e.g., 15°C) (step S12). If the result of the determination in step S12 is Yes, that is, if the low-temperature unit is not too cold, the control device 4 determines whether the temperature Tbmax of the high-temperature unit is below the cooling end temperature (e.g., 30°C) (step S13).

[0049] If the result of step S13 is Yes, the control device 4 determines that all battery units 50 in the battery 5 have been cooled to an appropriate temperature, and terminates the process. On the other hand, if the result of step S13 is No, the control device 4 continues the cooling control and returns to the decision in step S12.

[0050] If the result of the judgment in step S12 is No, that is, if the temperature Tbmin of the low-temperature unit exceeds the heating start temperature (e.g., 15°C), conventionally, the problem of interference arises as to whether to continue cooling control or switch to heating control. In practice, considering the safety of the battery 5, it is conceivable to continue cooling control, but this can result in an extremely overcooled battery unit 50, causing a decrease in the output of the battery 5. In this example, the control device 4 increases the temperature Tmc of the heat transfer medium circulating through the temperature control circuit 6 and continues cooling control (step S14). The changed temperature Tmc is higher than the temperature before the change (e.g., 10°C) and lower than or equal to the heating start temperature (e.g., 15°C). In this example, the temperature Tmc is changed to 15°C, which is the heating start temperature, from the viewpoint of preventing a decrease in the output of the low-temperature unit due to a decrease in the temperature Tbmin of the low-temperature unit. The temperature Tmc may also be changed to the same temperature as the temperature Tbmin of the low-temperature unit at the time of step S12.

[0051] After step S14, the control device 4 determines whether the temperature Tbmax of the high-temperature unit is below the cooling completion temperature (30°C) (step S15). If the result of the determination in step S15 is Yes, the control device 4 determines that all battery units 50 in the battery 5 have been properly cooled, and terminates the process. On the other hand, if the result of the determination in step S15 is No, the control device 4 determines that the cooling of the high-temperature unit is insufficient, and continues the cooling control, returning to the determination in step S15.

[0052] According to the above cooling control, even if there are temperature variations among the battery units 50 within the battery 5, each battery unit 50 can be cooled to an appropriate temperature. As a result, sufficient output can be obtained from the battery 5. Furthermore, in the above cooling control, the temperature Tmc of the heat transfer medium is increased to prevent the low-temperature unit from becoming too cold, so the temperature difference between the low-temperature unit's temperature Tbmin and the high-temperature unit's temperature Tbmax does not widen easily, and degradation of the battery unit 50 due to temperature differences is prevented. [Explanation of Symbols]

[0053] 1. Electric Vehicle 2. Heat pump circuit 2A Air conditioning unit, 2B Air intake, 2C Air outlet 2D Air Mix Door, 2F Blower 20 Evaporator, 21 Capacitor, 22 Chiller 3. Heating circuit 30 Circulation path, 31 Pump, 32 Condenser, 33 Heater, 34 Heater core 35 Reserve Tank 4. Control device 40 Temperature Sensors 41 First liquid temperature sensor, 42 Second liquid temperature sensor, 43 Third liquid temperature sensor 46 Pump control unit, 47 Valve control unit 5 batteries 50 battery units 6 Temperature control circuit 60 Circulation line, 61 Pump, 62 Chiller 7 Circuit changeover valve

Claims

1. A battery containing multiple battery units, A temperature control circuit that circulates a heat transfer medium through the battery to raise or cool the battery, The control device includes a temperature control circuit that controls the temperature control circuit to perform either a temperature rise control to raise the temperature of the battery using a high-temperature heat transfer medium, or a cooling control to cool the battery using a low-temperature heat transfer medium. The control device is The heating control is started when the temperature of the low-temperature unit having the lowest temperature among the plurality of battery units is below the heating start temperature, and the heating control is stopped when the temperature of the low-temperature unit reaches or exceeds the heating end temperature. The cooling control is started when the temperature of the high-temperature unit having the highest temperature among the plurality of battery units is equal to or above the cooling start temperature, and the cooling control is stopped when the temperature of the high-temperature unit falls below the cooling end temperature. If the temperature of the high-temperature unit rises to or above the cooling start temperature during the execution of the temperature-raising control, the temperature of the heat transfer medium is lowered to a temperature lower than the temperature at the start of the temperature-raising control, and the temperature-raising control is continued. Electric vehicle.

2. A battery containing multiple battery units, A temperature control circuit that circulates a heat transfer medium through the battery to raise or cool the battery, The control device includes a temperature control circuit that controls the temperature control circuit to perform either a temperature rise control to raise the temperature of the battery using a high-temperature heat transfer medium, or a cooling control to cool the battery using a low-temperature heat transfer medium. The control device is The heating control is started when the temperature of the low-temperature unit having the lowest temperature among the plurality of battery units is below the heating start temperature, and the heating control is stopped when the temperature of the low-temperature unit reaches or exceeds the heating end temperature. The cooling control is started when the temperature of the high-temperature unit having the highest temperature among the plurality of battery units is equal to or above the cooling start temperature, and the cooling control is stopped when the temperature of the high-temperature unit falls below the cooling end temperature. If the temperature of the low-temperature unit falls below the temperature at which the heating started during the execution of the cooling control, the temperature of the heat transfer medium is raised above the temperature at which the cooling control started, and the cooling control is continued. Electric vehicle.

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