Electric vehicle

Abstract

To provide an electric vehicle which can secure, with a simple structure, a time for allowing occupants to escape when thermal runaway of a battery occurs.SOLUTION: An electric vehicle includes: a battery which supplies electric power to a drive motor; a pump which circulates a heat medium for adjusting a temperature of the battery; and a pump control unit which controls the pump. The pump control unit operates the pump on full power when abnormal heat generation occurs in the battery.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electric vehicle in which the temperature of a battery is adjusted by circulating a heat medium. [Background technology]

[0002] Patent Document 1 discloses a thermal management system for an electric vehicle. The thermal management system includes a battery-side coolant circuit. The battery-side coolant circuit circulates coolant that regulates the temperature of the battery. The battery-side coolant circuit includes a chiller and a battery. The chiller cools the coolant by heat exchange between a low-pressure refrigerant and the coolant. The battery supplies charged electricity to electric on-board devices such as a traction electric motor.

[0003] Batteries in electric vehicles are susceptible to thermal runaway. UN ECE R100-02 Part 2, a United Nations regulation, stipulates that a grace period be secured for occupants to evacuate from a dangerous environment triggered by thermal runaway of the battery. For example, Patent Document 2 discloses a technology that, when thermal runaway of a battery module constituting a battery is detected, flows cooling water stored in a water tank into the battery module to secure a grace period for occupants to evacuate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-119369 [Patent Document 2] Special Publication No. 2022-550824 Summary of the Invention [Problem to be solved by the invention]

[0005] Water tanks, which are used to prevent thermal runaway in batteries, take up space for installing equipment inside electric vehicles. Small electric vehicles have limited installation space, making it difficult to install large-capacity water tanks. Furthermore, installing a water tank is complicated, reducing the productivity of electric vehicles.

[0006] An object of the present invention is to provide an electric vehicle that has a simple configuration and that can ensure a grace period for occupants to evacuate in the event of thermal runaway of the battery. [Means for solving the problem]

[0007] An electric vehicle according to one aspect of the present invention includes a battery that supplies power to a drive motor, a pump that circulates a heat transfer medium that adjusts the temperature of the battery, and a pump control unit that controls the pump, wherein the pump control unit operates the pump at maximum output when the battery becomes abnormally hot. [Effects of the Invention]

[0008] The electric vehicle described above utilizes a pump that circulates a heat medium that regulates the battery temperature to slow the rate at which the battery temperature rises when the battery abnormally heats up, and therefore, with the electric vehicle described above, a grace period for occupants to evacuate can be secured with a simple configuration in the event of thermal runaway of the battery. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram of an electric vehicle according to an embodiment. [Figure 2] FIG. 2 is a schematic diagram of a battery provided in the electric vehicle according to the embodiment. [Figure 3] FIG. 3 is a flowchart showing a first control procedure for the electric vehicle according to the embodiment. [Figure 4] FIG. 4 is a flowchart showing a second control procedure for the electric vehicle according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] An example of an embodiment of an electric vehicle according to the present invention will be described below with reference to the drawings. The dimensions of components shown in the drawings are for the purpose of clarity of explanation and do not necessarily represent actual dimensions. The present invention is not limited to the following examples, but is defined by the claims, and includes all modifications within the meaning and scope of the claims.

[0011] <Embodiment> The electric vehicle 1 of the embodiment is a BEV (Battery Electric Vehicle) equipped with a drive motor (not shown), or a hybrid vehicle. The electric vehicle 1 of this example includes a battery 5 that supplies power to the drive motor, a temperature regulation circuit 6 that regulates the temperature of the battery 5 by circulating a heat medium, and a control unit 4 that controls the temperature regulation circuit 6. One of the features of the electric vehicle 1 of the embodiment is that the temperature regulation circuit 6 and the control unit 4 are configured to slow down the rate at which the temperature of the battery 5 rises when the battery 5 abnormally heats up.

[0012] The electric vehicle 1 of this example further includes a heat pump circuit 2 that cools and heats the air inside the vehicle, a heater-type heating circuit 3 that heats the air inside the vehicle, and an alarm device 9 that alerts the occupants to thermal runaway of the battery 5. Below, each component of the electric vehicle 1 of this example will be explained in order, and then the control for slowing down the rate of temperature rise of the battery 5 will be explained.

[0013] Battery The battery 5 is a secondary battery that supplies power to a drive motor (not shown) that drives the electric vehicle 1. The power from the battery 5 may be supplied to a device other than the drive motor. In the electric vehicle 1 of this example, the power from the battery 5 is also supplied to an electric compressor of the heat pump circuit 2, which will be described later.

[0014] The battery 5 is, for example, a lithium-ion battery. Lithium-ion batteries have the risk of catching fire due to thermal runaway. Therefore, UN ECE R100-02, Part 2 stipulates that if the temperature of a lithium-ion battery rises above a predetermined value, a warning must be issued to the occupants and a grace period must be given for the occupants to escape.

[0015] As shown in FIG. 2, the battery 5 includes a plurality of battery modules 50. Each battery module 50 is formed by assembling a plurality of battery cells. A temperature sensor 40 is disposed in each battery module 50 to measure the temperature of the battery module 50. The measurement results of the temperature sensor 40 are input to the control unit 4 and used to adjust the temperature of the battery 5.

[0016] ≪Temperature control circuit≫ As shown in FIG. 1, the temperature control circuit 6 is a circulation circuit that circulates a heat medium to regulate the temperature of the battery 5. The temperature control circuit 6 maintains the temperature of the battery 5 within an appropriate range, allowing the battery 5 to perform to its full potential. 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.

[0017] 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. A battery 5 is disposed midway along the circulation path 60. The circulation path 60 is disposed so as to come into contact with the battery 5, for example.

[0018] The pump 61 is configured to pump the heat medium in the circulation path 60. The pump 61 is powered by power from an auxiliary battery (not shown). The heat medium circulates through the circulation path 60, starting from the pump 61. In FIG. 1 , the flow direction of the heat medium is indicated by an outline arrow. The heat medium circulates through the circulation path 60 in the following order: pump 61 → battery 5 → chiller 62 → circuit switching valve 7 → pump 61. The heat medium is, for example, an antifreeze solution such as long-life coolant (LLC). The pump 61 is an electric pump. The pump 61 is disposed 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 first liquid temperature sensor 41, disposed upstream of the battery 5, can measure the temperature of the heat medium supplied to the battery 5. The measurement result of the first liquid temperature sensor 41 is input to the control unit 4 and used to adjust the temperature of the battery 5.

[0019] The chiller 62 is disposed downstream of the battery 5. The chiller 62 is provided so as to be in contact with a chiller 22 of the heat pump circuit 2, which will be 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 adjustment circuit 6 that has passed through the battery 5 is cooled by the chiller 22.

[0020] <Heat pump circuit> The heat pump circuit 2 is a circulation circuit through which a heat medium separate from the heat medium flowing through the temperature control circuit 6 is circulated. The heat pump circuit 2 can have a known configuration, such as the configuration described in JP 2015-93561 A. The heat pump circuit 2 uses a hydrofluorocarbon such as R134a. The heat pump circuit 2 exchanges heat between the vehicle interior and exterior by circulating the heat medium, and constitutes part of an air conditioner that heats and cools the vehicle interior. In FIG. 1 , only a portion of the heat pump circuit 2 is indicated by a dashed line. Although not shown, the heat pump circuit 2 includes an electric compressor that compresses the heat medium and an electromagnetic expansion valve that diffuses and expands the heat medium. The electric compressor is responsible for circulating the heat medium in the heat pump circuit 2. The electric compressor requires a large amount of power to operate, which is supplied from the battery 5. The temperature of the heat medium compressed by the electric compressor is high. The temperature of the heat medium diffused and expanded by the electromagnetic expansion valve is low.

[0021] The heat pump circuit 2 includes an evaporator 20 and a condenser 21, which are heat exchangers for adjusting the temperature inside the vehicle. In this example, the heat pump circuit 2 further includes a chiller 22. The chiller 22 is not essential, and if the temperature adjustment circuit 6 does not include the 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, which will be described later.

[0022] <Heating circuit> The heater-type heating circuit 3 is a circulation circuit for circulating a heat medium to heat the interior 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.

[0023] The pump 31 is configured to pump the heat medium in the circulation path 30. The heat medium circulates in the circulation path 30 starting from the pump 31. In FIG. 1, the flow direction of the heat medium is indicated by an outline arrow. The heat medium circulates in the circulation path 30 in the order of the pump 31 → condenser 32 → heater 33 → heater core 34 → circuit switching valve 7 → pump 31. The heat medium is, for example, an antifreeze liquid such as LLC. The pump 31 is an electric pump.

[0024] The condenser 32, which is arranged downstream of the pump 31, is arranged so as 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 medium of the heating circuit 3 passing through the condenser 32.

[0025] The heater 33 disposed downstream of the condenser 32 heats the heat medium in accordance with a request for setting the heating temperature. The heater 33 is, for example, a high voltage heater (HVH).

[0026] A heater core 34, located inside the air conditioning unit 2A downstream of the heater 33, heats the air by heat exchange between the heat medium passing through the heater core 34 and the air. The air conditioning unit 2A is also referred to as an HVAC (Heating, Ventilation, and Air Conditioning) unit. 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 compartment into the air conditioning unit 2A through an intake port 2B and discharges the air from the air conditioning unit 2A into the vehicle compartment through an 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 located between the evaporator 20 and the heater core 34 so as to be able to swing or slide freely. The air mix door 2D adjusts the mixing ratio of the cool air from the evaporator 20 and the hot air from the heater core 34 depending on the opening degree thereof.

[0027] A second liquid temperature sensor 42 and a third liquid temperature sensor 43 are arranged in the heating circuit 3 between the heater 33 and the heater core 34, and between the heater core 34 and the circuit switching valve 7. The second liquid temperature sensor 42 measures the temperature of the heat medium flowing into the heater core 34. The measurement result of the second liquid temperature sensor 42 is used as an index for adjusting the output of the heater 33. The third liquid temperature sensor 43 measures the temperature of the heat medium flowing into the circuit switching valve 7. The measurement result of the third liquid temperature sensor 43 is used as an index for adjusting the opening of the circuit switching valve 7. The reserve tank 35 temporarily stores the heat medium circulating through the heating circuit 3.

[0028] <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 portion of the circulation path 30 of the heating circuit 3 that connects the heater core 34 and the reserve tank 35 with the portion of the circulation path 60 of the temperature control circuit 6 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 series; or (3) a mixed circuit in which 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 into four directions. A known four-way valve (e.g., JP 2013-238310 A, JP 2020-200902 A) can be used as the four-way valve. The circuit switching valve 7 is not limited to a four-way valve, and any valve that can branch the flow path into four or more directions, such as a five-way valve or a six-way valve, can be used. The circuit switching valve 7 is operated by power from the auxiliary battery.

[0029] <Control Unit> In this example, the control unit 4 controls the heat pump circuit 2, the heating circuit 3, the temperature adjustment circuit 6, the circuit switching valve 7, and the alarm device 9. With respect to the heat pump circuit 2, the control unit 4 controls the operation of the electric compressor and the expansion valve. With respect to the heating circuit 3, the control unit 4 controls the operation of the pump 31 and the heater 33. With respect to the temperature adjustment circuit 6, the control unit 4 controls the pump 61. With respect to the circuit switching valve 7, the control unit 4 controls the opening degree of the circuit switching valve 7. In this example, of the control unit 4, the part that controls the pump 61 is called the pump control unit 46, the part that controls the circuit switching valve 7 is called the valve control unit 47, and the part that controls the alarm device 9 is called the alarm control unit 49.

[0030] The control unit 4 is configured by an electronic control unit (ECU). The ECU typically includes a processor and a memory. The processor is, for example, a CPU. The memory stores control programs to be executed by the processor and various data. The control unit 4 is operated by the processor executing the control programs stored in the memory. The control unit 4 also performs the necessary calculation processing and determination processing according to the control programs stored in the memory.

[0031] ≪Alarm device≫ The warning device 9 is a component that warns the occupants that the temperature of the battery 5 has exceeded a threshold. The warning device 9 may be a display device that displays at least one of a warning message and a warning symbol, or a speaker that emits at least one of a warning sound and a warning message. The warning device 9 may also be a combination of a display device and a speaker.

[0032] <First control procedure> As described at the beginning of the embodiment, in the electric vehicle 1 of this example, the temperature adjustment circuit 6 and the control unit 4 are configured to slow down the rate of temperature rise of the battery 5 when the battery 5 is abnormally heated. A specific control procedure when the battery 5 is abnormally heated will be described with reference to the flowchart in FIG.

[0033] When the ignition of the electric vehicle 1 is on, power is supplied to the drive motor from the battery 5. When the air conditioner is in cooling mode, power from the battery 5 is also supplied to the electric compressor of the heat pump circuit 2. Information about the temperature of each battery module 50 shown in Fig. 2 is input to the control unit 4 from the temperature sensor 40 at predetermined intervals.

[0034] The control unit 4 determines whether the temperature T of each battery module 50 exceeds a threshold value T0 (step S1). The threshold value T0 is a temperature that serves as an index for determining whether the battery 5 is abnormally overheating. If even one of the multiple battery modules 50 included in the battery 5 exceeds the threshold value T0, the battery 5 is determined to be abnormally overheating. This is because if one battery module 50 abnormally overheats, that heat may spread to the other battery modules 50, causing the other battery modules 50 to quickly overheat as well. The threshold value T0 is, for example, 60°C.

[0035] If the determination result in step S1 is "No", the control unit 4 determines that the battery 5 is not abnormally hot, and returns to the processing of step S1. On the other hand, if the determination result in step S1 is "Yes", the alarm control unit 49 of the control unit 4 activates the alarm device 9 (step S2).

[0036] Furthermore, the pump control unit 46 of the control unit 4 operates the pump 61 at the maximum rotation speed (step S3). If the pump 61 is stopped, the pump control unit 46 starts the pump 61 and operates it at the maximum rotation speed. By operating the pump 61 at the maximum rotation speed, the flow rate per unit time of the heat medium in the circulation path 60 of the temperature adjustment circuit 6 can be increased. As a result, heat is removed from the battery 5 by the heat medium, and the rate at which the temperature of the battery 5 rises slows. The slower rate at which the temperature of the battery 5 rises increases the grace period for the occupant to evacuate from the electric vehicle 1.

[0037] After step S3, the control unit 4 determines whether the liquid temperature in the temperature adjustment circuit 6 is equal to or higher than the liquid temperature in the heating circuit 3 (step S4). The liquid temperature in the temperature adjustment circuit 6 is the temperature of the heat medium in the temperature adjustment circuit 6 measured by the first liquid temperature sensor 41. The liquid temperature in the heating circuit 3 is the temperature of the heat medium in the heating circuit 3 measured by the third liquid temperature sensor 43. In an environment with high outside temperatures, such as in summer, the heating circuit 3 is not operating, and it is possible that the liquid temperature in the heating circuit 3 is lower than the liquid temperature in the temperature adjustment circuit 6.

[0038] If the determination result in step S4 is "No," the control unit 4 ends the process. On the other hand, if the determination result in step S4 is "Yes," the control unit 4 turns on the bypass from the temperature adjustment circuit 6 to the heating circuit 3 (step S5). Specifically, the valve control unit 47 of the control unit 4 changes the opening of the circuit switching valve 7, changing the temperature adjustment circuit 6 and the heating circuit 3 to a series circuit in which they are connected in series. Step S5 causes the heat medium at a temperature equal to or lower than the liquid temperature of the temperature adjustment circuit 6 to flow from the heating circuit 3 to the temperature adjustment circuit 6, slowing down the rate at which the temperature of the battery 5 rises. Furthermore, step S5 increases the total amount of heat medium used to cool the battery 5, increasing the heat capacity of the heat medium. Therefore, the temperature of the heat medium is less likely to rise due to the heat of the battery 5, and the effect of slowing down the rate at which the temperature of the battery 5 rises is likely to last longer.

[0039] Here, steps S4 and S5 are not performed if the electric vehicle 1 does not have the circuit switching valve 7. That is, the control unit 4 ends the process after step S3.

[0040] According to the first control procedure described above, by utilizing the existing temperature regulation circuit 6, it is possible to lengthen the grace period for occupants to evacuate without requiring any additional configuration.

[0041] <<Second control procedure>> In the second control procedure, a procedure for seamlessly shifting from temperature control of the battery 5 in normal times to control when the battery 5 is abnormally heated will be described with reference to FIG.

[0042] The performance of the battery 5 will not be fully achieved if the temperature of the battery 5 is too high or too low. When the electric vehicle 1 is running, the temperature of the battery 5 is maintained within an appropriate range by the temperature regulation circuit 6 so that the temperature of the battery 5 does not become too high. When the electric vehicle 1 is running, the battery 5 is operating, so the temperature of the battery 5 tends to rise. Therefore, under normal circumstances, the control unit 4 determines whether the temperature of the battery 5 exceeds a first threshold value T1 (step S10). The first threshold value T1 is a temperature that serves as an index for determining that the temperature of the battery 5 exceeds the appropriate range, and is, for example, 40°C.

[0043] If the determination result in step S10 is "No", it can be determined that the temperature of the battery 5 is within the appropriate range. If the temperature adjustment circuit 6 is operating, it can be determined that the current settings of the temperature adjustment circuit 6, the fluid temperature and the rotation speed of the pump 61, etc. are effective for adjusting the temperature of the battery 5. The control unit 4 returns to the processing of step S10.

[0044] If the determination result in step S10 is "Yes", the temperature adjustment circuit 6 cools the battery 5 (step S11). If the temperature adjustment circuit 6 is not operating, the temperature adjustment circuit 6 is operated. If the temperature adjustment circuit 6 is already operating, the cooling performance of the temperature adjustment circuit 6 is increased. For example, the control unit 4 controls the heat pump circuit 2 so that the temperature of the chiller 22 is lowered. The electric compressor provided in the heat pump circuit 2 operates using power from the battery 5. Additionally, the control unit 4 may increase the rotation speed of the pump 61. The pump 61 operates using power from the auxiliary battery.

[0045] After step S11, the control unit 4 determines whether the temperature of the battery 5 exceeds a second threshold value T2 (step S12). The second threshold value T2 is a temperature that serves as an index for determining that the battery 5 may generate abnormal heat, and is, for example, 50°C.

[0046] If the determination result in step S12 is "No", it can be determined that there is currently little possibility of abnormal heat generation in the battery 5. The control unit 4 returns to the processing of step S10.

[0047] On the other hand, if the determination result in step S12 is "Yes," it can be determined that there is a possibility that the battery 5 will generate abnormal heat. Therefore, the control unit 4 limits the output of the battery 5 (step S13). By limiting the output of the battery 5, the load on the battery 5 can be reduced, and the temperature rise of the battery 5 can be suppressed. When limiting the output of the battery 5, the electric compressor of the heat pump circuit 2 is first stopped. When the electric compressor stops, the flow of low-temperature heat medium in the chiller 22 of the heat pump circuit 2 stops. In this case, the cooling effect of the chiller 22 of the heat pump circuit 2 on the chiller 62 of the temperature control circuit 6 is significantly reduced. Therefore, in conjunction with the stopping of the electric compressor, the control unit 4 also stops the pump 61 of the temperature control circuit 6 to reduce power consumption of the auxiliary battery. Stopping the temperature control circuit 6 also temporarily suspends cooling of the battery. The control unit 4 further reduces the power supply to the drive motor to decelerate and ultimately stop the electric vehicle 1.

[0048] After limiting the output of the battery 5, the control unit 4 determines whether the temperature of the battery 5 exceeds a threshold value T0 (step S14). The threshold value T0 in the second control procedure is the same as the threshold value T0 in the first control procedure. That is, in step S14, it is determined whether the battery 5 is abnormally hot.

[0049] If the determination result in step S14 is "No," it can be determined that the battery 5 is not yet abnormally hot, and the control unit 4 returns to the processing of step S12. If the determination result in step S14 is "Yes," the control unit 4 proceeds to the processing of step S15. The processing of steps S15 to S18 after step S14 is the same as steps S2 to S5 in the first control procedure.

[0050] According to the second control procedure, it is possible to seamlessly shift from temperature control of the battery 5 under normal conditions to control when the battery 5 is overheating abnormally, and it is possible to ensure a grace period for occupants to evacuate when the battery 5 is overheating abnormally. [Explanation of symbols]

[0051] 1 Electric vehicles 2 Heat pump circuit 2A air conditioning unit, 2B intake, 2C outlet, 2D air mix door, 2F blower 20 evaporator, 21 condenser, 22 chiller 3 Heating circuit 30 circulation path, 31 pump, 32 condenser, 33 heater, 34 heater core 35 reserve tank 4. Control Unit 40 Temperature Sensor 41 first liquid temperature sensor, 42 second liquid temperature sensor, 43 third liquid temperature sensor 46 pump control section, 47 valve control section, 49 alarm control section 5 Battery 50 Battery Module 6 Temperature control circuit 60 circulation path, 61 pump, 62 chiller 7 Circuit switching valve 9 Alarm device

Claims

[Claim 1] a battery that supplies power to the drive motor; a pump that circulates a heat medium for adjusting the temperature of the battery; a pump control unit that controls the pump, the pump control unit operates the pump at maximum output when the battery generates abnormal heat. Electric vehicle.

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