Electric vehicles

Abstract

To provide an electric vehicle that can reduce the increase in the conductivity of the heat transfer medium that occurs when using an electric vehicle. [Solution] An electric vehicle equipped with a battery that supplies power to a drive motor includes a heating circuit that circulates a heat transfer medium to a heater core that heats air conditioning air, a temperature control circuit that circulates the heat transfer medium to raise or cool the battery, a circuit switching valve that switches the connection state between the heating circuit and the temperature control circuit, and a control device that controls the heating circuit, the temperature control circuit and the circuit switching valve. The control device obtains an estimated value by estimating the conductivity of the heat transfer medium based on the thermal history of the heat transfer medium, and if the estimated value exceeds a threshold, after the power switch of the electric vehicle is turned OFF, it controls the circuit switching valve to connect the heating circuit and the temperature control circuit and circulate the heat transfer medium.

Description

Technical Field

[0001] The present invention relates to an electric vehicle including a battery that supplies electric power to a drive motor.

Background Art

[0002] Patent Document 1 discloses an electric vehicle including a heating-side cooling water circuit, a battery-side cooling water circuit, and a circuit connection part. The heating-side cooling water circuit is a heating circuit that circulates cooling water, which is a heat medium for heating air blown into the vehicle interior in a heating mode. The battery-side cooling water circuit is a temperature adjustment circuit that circulates cooling water, which is a heat medium for adjusting the temperature of the battery. The battery supplies electric power to electric in-vehicle devices such as a traveling drive motor.

[0003] The circuit connection part is a configuration for connecting the heating-side cooling water circuit and the battery-side cooling water circuit as needed. By the circuit connection part, the heat medium of the heating circuit and the heat medium of the temperature adjustment circuit are circulated independently, or the heat medium of the heating circuit and the heat medium of the temperature adjustment circuit flow into each other's circuits. That is, the heat medium flowing through the heating circuit and the heat medium flowing through the temperature adjustment circuit are common heat media.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When a heating circuit is operating, heat is applied to the heat transfer medium flowing through it. If the temperature of the heat transfer medium remains high for an extended period, the medium may deteriorate, or ions may leak into the heat transfer medium from the circulation path, including the piping. As a result, the conductivity of the heat transfer medium may gradually increase. If a highly conductive heat transfer medium leaks from the circulation path and comes into contact with the battery, it may adversely affect the battery. To solve these problems, it is necessary to replace the heat transfer medium, use a heat transfer medium that does not easily become highly conductive, or construct the flow path with materials that do not easily release ions. All of these measures reduce the productivity of electric vehicles, including costs, and increase maintenance effort.

[0006] One of the objectives of the present invention is to provide an electric vehicle that can reduce the increase in the conductivity of the heat transfer medium that occurs when using an electric vehicle. [Means for solving the problem]

[0007] <1> An electric vehicle according to one aspect of the present invention is an electric vehicle equipped with a battery that supplies power to a drive motor, comprising: a heating circuit that circulates a heat transfer medium to a heater core that heats air conditioning air; a temperature control circuit that circulates the heat transfer medium to raise or cool the battery; a circuit switching valve that switches the connection state between the heating circuit and the temperature control circuit; and a control device that controls the heating circuit, the temperature control circuit and the circuit switching valve. The control device obtains an estimated value by estimating the conductivity of the heat transfer medium based on the thermal history of the heat transfer medium, and if the estimated value exceeds a threshold, after the power switch of the electric vehicle is turned OFF, it controls the circuit switching valve to connect the heating circuit and the temperature control circuit and circulate the heat transfer medium.

[0008] <2> the above <1> In the electric vehicle described above, if the estimated value exceeds a threshold while the electric vehicle is running, the control device may control the heating circuit by changing the first set temperature of the heat transfer medium, which corresponds to the temperature of the air conditioning air set by the occupant, to a second set temperature that is lower than the first set temperature. [Effects of the Invention]

[0009] the above <1> In this electric vehicle, if the estimated conductivity of the heat transfer medium exceeds a threshold, the heating circuit and temperature control circuit are connected and the heat transfer medium is circulated after the electric vehicle's power switch is turned OFF. When the heating circuit is in use, the temperature of the heat transfer medium flowing through the temperature control circuit is usually lower than the temperature of the heat transfer medium flowing through the heating circuit. Therefore, by circulating the heat transfer medium with the heating circuit and temperature control circuit connected, the temperature of the heat transfer medium in the heating circuit can be rapidly reduced. As a result, deterioration of the heat transfer medium and leakage of ions from the circulation path into the heat transfer medium are reduced, and the increase in the conductivity of the heat transfer medium is reduced.

[0010] the above <2> In electric vehicles, if the estimated conductivity of the heat transfer medium exceeds a threshold while the electric vehicle is running, the first set temperature of the heat transfer medium in the heating circuit is lowered. As a result, the heat history applied to the heat transfer medium from the heating circuit can be reduced, thus reducing the increase in the conductivity of the heat transfer medium. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a schematic diagram of the electric vehicle according to Embodiment 1. [Figure 2] Figure 2 is a flowchart showing the control procedure for reducing the increase in conductivity of the heat transfer medium according to Embodiment 1. [Figure 3] Figure 3 is a flowchart showing the control procedure for reducing the increase in conductivity of the heat transfer medium according to Embodiment 2. [Figure 4] Figure 4 is a flowchart showing the control procedure for reducing the increase in conductivity of the heat transfer medium according to Embodiment 3. [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) and a battery 5 that supplies power to the drive motor. The electric vehicle 1 of this example, equipped with the battery 5, includes a heating circuit 3 for warming the air inside the vehicle, a temperature control circuit 6 for adjusting the temperature of the battery 5, a circuit switching valve 7 for switching the connection state between the heating circuit 3 and the temperature control circuit 6, and a control device 4 for controlling these. The electric vehicle 1 of this example further includes a heat pump circuit 2 for cooling or heating the air inside the vehicle. A common heat transfer medium 8 is circulated between the heating circuit 3 and the temperature control circuit 6. A heat transfer medium different from the heat transfer medium 8 is circulated between the heat pump circuit 2. One of the features of the electric vehicle 1 of this embodiment is that it is configured so that the increase in the conductivity of the heat transfer medium 8 associated with the use of the electric vehicle 1 can be reduced by control by the control device 4. 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. Battery 5 is, for example, a lithium-ion battery. 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 compressor 23 of the heat pump circuit 2, which will be described later.

[0015] If a conductive liquid comes into contact with a point in the battery 5 where current flows, it may cause a malfunction in the battery 5. For example, heat transfer fluid 8 may leak from the heating circuit 3 or the temperature control circuit 6 due to some factor and come into contact with the battery 5. In this case, if the conductivity of the heat transfer fluid 8 is high, it may cause a malfunction in the battery 5. In particular, the piping of the heat transfer fluid 8 in the temperature control circuit 6 is close to the battery 5, so heat transfer fluid 8 leaking from the temperature control circuit 6 is likely to come into contact with the battery 5.

[0016] ≪Heating Circuit≫ The heating circuit 3 is a circulation circuit for circulating the heat transfer medium 8 that warms the interior of the vehicle. The heating circuit 3 comprises a circulation path 30, a pump 31, a condenser 32, a heater 33, a heater core 34, and a reserve tank 35.

[0017] Pump 31 is a component that pumps the heat transfer medium 8 within the circulation path 30. The heat transfer medium 8 circulates within the circulation path 30 starting from pump 31. In Figure 1, the direction of flow of the heat transfer medium 8 is indicated by hatched arrows. The heat transfer medium 8 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 an antifreeze such as long-life coolant (LLC). Pump 31 is an electrically operated pump.

[0018] A 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 8 of the heating circuit 3 as it passes through the condenser 32. A heater 33 located downstream of the condenser 32 heats the heat transfer medium 8 according to the heating temperature setting requirements. The heater 33 is, for example, a high-voltage heater.

[0019] The heater core 34 disposed inside the air conditioning unit 2A downstream of the heater 33 heats the air by heat exchange between the heat medium 8 passing through the heater core 34 and the air. The air conditioning unit 2A is also referred to as, for example, 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 sucks air from outside the vehicle compartment into the air conditioning unit 2A through the intake port 2B and discharges the air from the air conditioning unit 2A into the vehicle compartment through the outlet port 2C. The evaporator 20 is a member constituting a part of the heat pump circuit 2 described above, and is provided downstream of the blower 2F and upstream of the heater core 34. The air mix door 2D is disposed between the evaporator 20 and the heater core 34 so as to be swingable or slidable. The air mix door 2D adjusts the mixing ratio of the cold air from the evaporator 20 and the hot air from the heater core 34 according to its opening degree.

[0020] A liquid temperature sensor 42 and a liquid temperature sensor 43 are disposed between the heater 33 and the heater core 34 in the heating circuit 3, and between the heater core 34 and the circuit switching valve 7. The liquid temperature sensor 42 measures the temperature of the heat medium 8 flowing into the heater core 34. The measurement result of the liquid temperature sensor 42 is used as an index for adjusting the output of the heater 33. The liquid temperature sensor 43 measures the temperature of the heat medium 8 flowing into the circuit switching valve 7. The measurement result of the liquid temperature sensor 43 is used as an index for adjusting the opening degree of the circuit switching valve 7. The reserve tank 35 temporarily stores the heat medium 8 circulating in the heating circuit 3.

[0021] ≪Temperature control circuit≫ As shown in FIG. 1, the temperature control circuit 6 is a circulation circuit that circulates a heat medium 8 for adjusting the temperature of the battery 5. As will be described later, the heat medium 8 of the temperature control circuit 6 may be mixed with the heat medium 8 of the heating circuit 3. That is, the heat medium 8 of the temperature control circuit 6 and the heat medium 8 of the heating circuit 3 are the same heat medium 8. By maintaining the temperature of the battery 5 within an appropriate range by this 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.

[0022] 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.

[0023] The pump 61 is configured to pump the heat medium 8 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 8 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 8 circulates through the circulation path 60 in the order of pump 61 → battery 5 → chiller 62 → circuit switching valve 7 → pump 61. The pump 61 is an electric pump. The pump 61 is provided downstream of a circuit switching valve 7 (to be described later) and upstream of the battery 5. A 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 liquid temperature sensor 41 disposed upstream of the battery 5. The measurement result of the liquid temperature sensor 41 is input to the control device 4 and used to adjust the temperature of the battery 5.

[0024] 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 (to 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 control circuit 6 that has passed through the battery 5 is cooled by the chiller 22.

[0025] 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.

[0026] By changing the opening of the circuit switching valve 7, the temperature of the heat transfer medium 8 flowing through the temperature control circuit 6 can be changed. When the heat transfer medium 8 from the heating circuit 3 flows into the temperature control circuit 6, the temperature of the heat transfer medium 8 flowing through the temperature control circuit 6 increases. The more heat transfer medium 8 flows in from the heating circuit 3, the higher the temperature of the heat transfer medium 8 in the temperature control circuit 6. Even if the amount of heat transfer medium 8 flowing in from the heating circuit 3 remains the same, the temperature of the heat transfer medium 8 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 8 flows in from the heating circuit 3, the lower the temperature of the heat transfer medium 8 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 23 of the heat pump circuit 2, which will be described later, and lowering the temperature of the chiller 22.

[0027] ≪Heat pump circuit≫ The heat pump circuit 2 is a circulating circuit through which a heat transfer medium separate from the heat transfer medium 8 flowing through the heating circuit 3 and the temperature control circuit 6 is circulated. Known configurations, such as those described in Japanese Patent Application Publication No. 2015-93561, can be used for the heat pump circuit 2. The heat transfer medium in the heat pump circuit 2 is, for example, a hydrofluorocarbon such as R134a. The heat pump circuit 2 is configured to exchange heat between the outside and inside of the vehicle by circulating the heat transfer medium, and constitutes part of the air conditioning system that heats or cools the inside of the vehicle. In Figure 1, only a portion of the heat pump circuit 2 is shown by a dashed line. The heat pump circuit 2 includes a compressor 23 that compresses the heat transfer medium and an electromagnetic expansion valve (not shown) that diffuses and expands the heat transfer medium. The compressor 23 operates using power from, for example, a battery 5. The circulation of the heat transfer medium in the heat pump circuit 2 is handled by the compressor 23. The operation of the compressor 23 requires a large amount of power, which is supplied from the battery 5. The temperature of the heat transfer medium compressed by the compressor 23 becomes high. The heat transfer medium, expanded by the electromagnetic expansion valve, becomes cold. In a hybrid vehicle, the compressor 23 may be operated by the engine.

[0028] The heat pump circuit 2 includes an evaporator 20 and a condenser 21, which are heat exchangers for regulating the temperature inside the vehicle. In this example, the heat pump circuit 2 further includes a chiller 22. The chiller 22 is not essential; if the temperature control circuit 6 described above does not have a chiller 62, then the chiller 22 is not necessary. A high-temperature heat transfer medium flows through the condenser 21. On the other hand, a low-temperature heat transfer medium flows through the evaporator 20 and the chiller 22.

[0029] ≪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 compressor 23 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.

[0030] 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.

[0031] ≪Control to reduce the increase in conductivity of the heat transfer medium≫ As the temperature of the heat transfer medium 8 increases, the conductivity of the heat transfer medium 8 tends to increase due to degradation of the heat transfer medium 8. Therefore, the control device 4 in this example implements control to reduce the increase in the conductivity of the heat transfer medium 8. The timing at which this control is implemented is mainly when the power to the electric vehicle 1, which was used while heating was on, is turned off. The control procedure in this example will be explained below based on the flowchart in Figure 2.

[0032] The control device 4 determines whether the power to the electric vehicle 1 has been turned off (step S1). This determination is made, for example, based on a signal output to the control device 4 when an occupant presses the power switch installed on the instrument panel. If the result of the determination in step S1 is No, the control device 4 returns to the process of step S1.

[0033] If the result of step S1 is Yes, the control device 4 determines whether the estimated conductivity of the heat transfer medium 8 exceeds the first threshold (step S2). If the result is No, the conductivity of the heat transfer medium 8 is considered not to be high enough to cause serious malfunction in the battery 5 even if the heat transfer medium 8 comes into contact with the battery 5. Therefore, the control device 4 terminates the process and terminates the operation of each component of the electric vehicle 1 in the procedure normally performed when turning off the power to the electric vehicle 1.

[0034] The estimated conductivity of the heat transfer medium 8 used in the decision in step S2 is calculated based on the thermal history of the heat transfer medium 8. The calculation of the estimated value is performed independently of the control in this example. The thermal history is, for example, the product of the temperature of the heat transfer medium 8 and the time it was maintained at that temperature. The estimated value can be calculated by multiplying this product by a predetermined coefficient. The coefficient varies depending on the temperature. The coefficient also changes depending on the type of heat transfer medium 8, the material of the flow path of the heat transfer medium 8, etc. The coefficient is a value obtained by preliminary testing. If the temperature of the heat transfer medium 8 changes during one use of the electric vehicle 1, the estimated conductivity of the heat transfer medium 8 can be obtained by adding up the individual estimated values ​​obtained for each thermal history. For example, if, during one use of electric vehicle 1, the heat transfer medium in heating circuit 3 is subjected to a heat history of 300 seconds at 75°C, 100 seconds at 70°C, and 10 seconds at 65°C, the estimated conductivity of the heat transfer medium 8 in heating circuit 3 is 75 × 300 × α1 + 70 × 100 × α2 + 65 × 10 × α3. α1, α2, and α3 are coefficients at 75°C, 70°C, and 65°C, respectively. If the temperature of the heat transfer medium 8 is below a predetermined value, for example, below 40°C, the summation of the individual estimates does not need to be performed. The estimated values ​​are not reset unless the heat transfer medium 8 is replaced.

[0035] When the estimated conductivity of the heat transfer medium 8 in the heating circuit 3 is Y1 and the estimated conductivity of the heat transfer medium 8 in the temperature control circuit 6 is Y2, the estimated conductivity of the entire heat transfer medium 8 can be calculated by adding them together as follows. For example, if the capacity of the heat transfer medium 8 in the heating circuit 3 is L1 liters and the capacity of the heat transfer medium 8 in the temperature control circuit 6 is L2 liters, the estimated conductivity of the entire heat transfer medium 8 can be calculated by (L1 × Y1 + L2 × Y2) / (L1 + L2).

[0036] If the result of step S2 is Yes, that is, if the calculated estimated conductivity of the heat transfer medium 8 exceeds the first threshold, the control device 4 determines whether the temperature obtained by subtracting the temperature Tb of the heat transfer medium 8 in the temperature control circuit 6 from the temperature Th of the heat transfer medium 8 in the heating circuit 3 exceeds the second threshold (step S3). Temperature Th is, for example, a value obtained by the liquid temperature sensor 42 in Figure 1. Liquid temperature sensor 42 is a liquid temperature sensor placed in the heating circuit 3 at a position where the heat transfer medium 8 is likely to show the highest temperature. Temperature Tb is, for example, a value obtained by the liquid temperature sensor 41. Liquid temperature sensor 41 is a liquid temperature sensor placed in the temperature control circuit 6 at a position where the heat transfer medium 8 is likely to show a relatively low temperature. When the heating circuit 3 is in use, it can be assumed that the temperature of the heat transfer medium 8 in the heating circuit 3 is higher than the temperature of the heat transfer medium 8 in the temperature control circuit 6.

[0037] In step S3, the device determines whether it is necessary to use electricity to mix the heat transfer medium 8 of the heating circuit 3 with the heat transfer medium 8 of the temperature control circuit 6. The second threshold is, for example, 10°C. If the result of the determination in step S3 is No, the control device 4 terminates the process.

[0038] If the result of step S3 is Yes, the control device 4 connects the heating circuit 3 and the temperature control circuit 6 and circulates the heat transfer medium 8 (step S4). Here, "connecting" means controlling the circuit switching valve 7 to make the heating circuit 3 and the temperature control circuit 6 a single fluid circuit. The circulation of the heat transfer medium 8 is preferably performed by operating at least one of the pump 31 of the heating circuit 3 and the temperature control circuit 6. The operation in step S4 mixes the high-temperature (e.g., 80°C) heat transfer medium 8 in the heating circuit 3 with the low-temperature (e.g., 40°C) heat transfer medium 8 in the temperature control circuit 6, and the temperature of the heat transfer medium 8 in the heating circuit 3 decreases rapidly. As already mentioned, the higher the temperature of the heat transfer medium 8, the higher its conductivity tends to be, so the rapid decrease in the temperature of the heat transfer medium 8 in the heating circuit 3 suppresses the increase in the conductivity of the heat transfer medium 8.

[0039] After step S4, the control device 4 determines whether the temperature Th of the heat transfer medium 8 in the heating circuit 3 is below a third threshold (step S5). The third threshold is, for example, 50°C. If the result of the determination in step S5 is No, the control device 4 returns to the process of step S5. That is, the connection between the heating circuit 3 and the temperature control circuit 6, and the operation of the pump 61 continue.

[0040] If the result of the judgment in step S5 is Yes, that is, if the temperature Th of the heat transfer medium 8 in the heating circuit 3 has dropped sufficiently, the control device 4 stops the circulation of the heat transfer medium 8 by stopping the pumps 31 and 61 (step S6), and the process ends. In step S6, the control device 4 may also operate the circuit switching valve 7 to make the heating circuit 3 and the temperature control circuit 6 into independent fluid circuits.

[0041] According to the control procedure described above, it is possible to suppress the further increase in the conductivity of the heat transfer medium 8 after its conductivity exceeds a predetermined value. Therefore, even if the heat transfer medium 8 leaks from the heating circuit 3 or the temperature control circuit 6 and adheres to the battery 5, it is less likely that the battery 5 will malfunction. In addition, because the conductivity of the heat transfer medium 8 does not increase easily, the frequency of replacing the heat transfer medium 8 when using the electric vehicle 1 decreases, and the running costs of the electric vehicle 1 decrease.

[0042] In the control described above, pumps 31, 61, etc., are not operated after the power to the electric vehicle 1 is turned off until the conductivity of the heat transfer medium 8 exceeds a predetermined value. Therefore, compared to a configuration in which the heat transfer medium 8 is mixed each time the power to the electric vehicle 1 is turned off, power required to operate pumps 31, 61 can be saved, and the load on pumps 31, 61 can be reduced.

[0043] The control described above is performed based on information from existing liquid temperature sensors 41 and 42. In other words, the control described above does not require a sensor to measure the conductivity of the heat transfer medium 8 and can be performed by updating the software of the control device 4.

[0044] <Embodiment 2> In Embodiment 2, the procedure for implementing control to reduce the increase in conductivity of the heat transfer medium 8 during charging of the electric vehicle 1 will be described based on the flowchart in Figure 3. In the flowchart in Figure 3, the same reference numerals are used for the same operations as in the flowchart in Figure 2. For example, step S1 in Figure 3 is the same as step S1 in Figure 2.

[0045] In step S1, the control device 4 determines that the power has been turned off, and in step S2, if it determines that the estimated conductivity of the heat transfer medium 8 exceeds the first threshold, it determines whether or not it is charging (step S7). If the determination result is No, i.e., it is not charging, the control device 4 performs the processing from step S3 to step S6. The processing from step S3 to step S6 is the same as in Embodiment 1, as already described.

[0046] If the result of step S7 is Yes, i.e., charging is in progress, then power is always available from the charging connector. At this point, the control device 4 determines whether the temperature Th of the heat transfer medium 8 in the heating circuit 3 exceeds a third threshold (step S8). This third threshold is the same as the third threshold in step S5. In other words, in step S8, it is determined whether the temperature Th of the heat transfer medium 8 in the heating circuit 3 is high enough to potentially increase the conductivity of the heat transfer medium 8. If the result of step S8 is No, the control device 4 terminates the process.

[0047] If the result of step S8 is Yes, the control device 4 connects the heating circuit 3 and the temperature control circuit 6 and turns on battery cooling (step S9). Turning on battery cooling here means operating the compressor 23 of the heat pump circuit 2 shown in Figure 1 to flow a low-temperature heat transfer medium to the chiller 22, and operating the pump 61 of the temperature control circuit 6. As a result, the heat transfer medium 8 of the temperature control circuit 6 is cooled by heat exchange between the chiller 22 of the heat pump circuit 2 and the chiller 62 of the temperature control circuit 6. Because the heat transfer medium 8 of the temperature control circuit 6 is forcibly cooled, the temperature of the heat transfer medium 8 of the heating circuit 3 drops rapidly. Since the power to operate the compressor 23 is supplied from the charging connector, the battery 5 is not loaded to operate the compressor 23.

[0048] After step S9, the control device 4 determines whether the temperature Th of the heat transfer medium 8 in the heating circuit 3 exceeds the third threshold (step S10). If the result of the determination in step S10 is No, the control device 4 returns to the determination in step S10.

[0049] If the result of step S10 is Yes, that is, if it is determined that the temperature Th of the heat transfer medium 8 in the heating circuit 3 is sufficiently low, the control device 4 turns off the battery cooling (step S11) and terminates the control.

[0050] According to the control described above, the increase in the conductivity of the heat transfer medium 8 can be effectively suppressed without placing a load on the battery 5.

[0051] <Embodiment 3> In Embodiment 3, in addition to the control in Embodiment 1 or Embodiment 2, a procedure for implementing control to reduce the increase in the conductivity of the heat transfer medium during use of the electric vehicle 1 will be described based on the flowchart in Figure 4.

[0052] When the electric vehicle 1 is in use, the control device 4 determines whether the heating is turned ON or not (step S12). If the result of the determination in step S12 is No, the control device 4 returns to the determination in step S12.

[0053] If the result of step S12 is Yes, the control device 4 determines whether the estimated conductivity of the heat transfer medium 8 in the heating circuit 3 exceeds the first threshold (step S13). If the result of step S13 is No, the control device 4 returns to the determination in step S12.

[0054] If the result of step S13 is Yes, the control device 4 lowers the temperature Th of the heat transfer medium 8 in the heating circuit 3 (step S14). The temperature Th before step S14 is the first set temperature corresponding to the temperature of the air conditioning set by the occupants. In step S14, the temperature Th is changed to a second set temperature that is lower than this first set temperature. Specifically, for example, the control device 4 lowers the temperature Th by lowering the output of the heater 33 in Figure 1 or by lowering the output of the compressor 23 of the heat pump circuit 2. As a result, the heat supplied to the heat transfer medium 8 in the heating circuit 3 is reduced, and the decrease in the conductivity of the heat transfer medium 8 is suppressed.

[0055] When step S14 is performed, the amount of heat introduced into the air conditioning air from the heater core 34 in Figure 1 decreases. This means that the heating efficiency may decrease, potentially reducing the comfort level inside the vehicle. Therefore, the control device 4 controls various parts of the electric vehicle 1 to maintain comfort inside the vehicle (step S15). Specifically, for example, the control device 4 adjusts the opening of the air mix door 2D so that more of the air conditioning air from the air conditioning unit 2A passes through the heater core 34. In addition, the control device 4 increases the rotation speed of the blower 2F so that more warm air is introduced into the cabin. By implementing such control, even if the temperature Th of the heat transfer medium 8 in the heating circuit 3 decreases, the comfort level inside the vehicle is less likely to be compromised. [Explanation of Symbols]

[0056] 1. Electric Vehicle 2. Heat pump circuit, 3. Heating circuit, 4. Control device, 5. Battery, 6. Temperature control circuit 7. Circuit switching valve, 8. Heat transfer medium 2A Air conditioning unit, 2B Air intake, 2C Air outlet 2D Air Mix Door, 2F Blower 20 Evaporator, 21 Capacitor, 22 Chiller 30 Circulation path, 31 Pump, 32 Condenser, 33 Heater 34 Heater core, 35 Reserve tank 41, 42, 43 Liquid temperature sensor 60 Circulation line, 61 Pump, 62 Chiller

Claims

1. An electric vehicle equipped with a battery that supplies power to the drive motor, A heating circuit that circulates a heat transfer medium to a heater core that heats the air conditioning air, A temperature control circuit that circulates the heat transfer medium for raising or cooling the battery, A circuit switching valve that switches the connection state between the heating circuit and the temperature control circuit, The system includes a control device that controls the heating circuit, the temperature control circuit, and the circuit switching valve, The control device is Based on the thermal history of the heat transfer medium, an estimated value is obtained by estimating the conductivity of the heat transfer medium. If the estimated value exceeds the threshold, after the power switch of the electric vehicle is turned OFF, the circuit switching valve is controlled to connect the heating circuit and the temperature control circuit and to circulate the heat transfer medium. Electric vehicle.

2. The electric vehicle according to claim 1, wherein the control device controls the heating circuit by changing the first set temperature of the heat transfer medium, which corresponds to the temperature of the air conditioning air set by the occupant, to a second set temperature lower than the first set temperature, when the estimated value exceeds a threshold while the electric vehicle is in motion.

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