Battery temperature control apparatus

Abstract

To suppress an increase of an inner electrical resistance caused by density unevenness of an electrolytic solution in adjusting the temperature of a battery by means of heat exchange.SOLUTION: A battery temperature control apparatus 10 according to the embodiment includes a temperature acquisition part which acquires temperature information of a cell within a battery pack in charging or discharging, a temperature adjustment part which adjusts the temperature of a battery pack by causing a coolant to flow, and a control part which acquires a coolant flow rate according to the temperature information by using a map in which a relation between a battery temperature and a coolant flow rate is defined, and controls an operation of the temperature adjustment part to cause the coolant to flow in a pulsing manner.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a battery temperature regulator. [Background technology]

[0002] Patent Document 1 discloses a battery temperature regulator that regulates the temperature of a battery by utilizing heat exchange with outside air such as a radiator. This battery temperature regulator is provided with a flow rate regulating valve that regulates the flow rate of the heat medium in a first path through which the heat medium flows via an outside air heat exchanger and in a second path through which the heat medium flows bypassing the outside air heat exchanger. When the outside air temperature is in a low-temperature environment lower than a predetermined reference outside air temperature, the operation of the flow rate regulating valve is controlled to regulate the flow rate ratio between the flow rate of the heat medium in the first path and the flow rate of the medium in the second path so that the battery temperature becomes the predetermined reference temperature. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2021-163670 A Summary of the Invention [Problem to be solved by the invention]

[0004] Generally, when the battery temperature is higher than the target temperature and the required cooling capacity of the temperature adjustment device is high, the temperature difference between the cells of the battery becomes large. However, even if the temperature is within the allowable range where the battery output does not decrease, the battery performance may decrease if the battery is continuously energized for a long time.

[0005] This is because the internal resistance increases due to uneven electrolyte concentration caused by the increase in current density associated with the increase in capacity of secondary batteries and the increase in continuous current-carrying time. In particular, the lower the cell temperature of the battery, the more likely the internal resistance increases. Furthermore, if the temperature difference between the cells of the battery from the inlet to the outlet of the heat medium increases due to cooling, the battery performance decreases due to the increase in loss and the decrease in cell voltage caused by the increase in internal resistance under conditions of long continuous current-carrying time.

[0006] The present invention has been made in consideration of such problems, and an object of the present invention is to provide a battery temperature control device that can suppress an increase in internal resistance caused by uneven electrolyte concentration when controlling the temperature of a battery using heat exchange. [Means for solving the problem]

[0007] A battery temperature control device according to one embodiment of the present invention includes a temperature acquisition unit that acquires temperature information of cells within a battery pack during charging and discharging, a temperature adjustment unit that adjusts the temperature of the battery pack by flowing a refrigerant, and a control unit that determines a refrigerant flow rate corresponding to the temperature information using a map that defines the relationship between battery temperature and refrigerant flow rate, and controls the operation of the temperature adjustment unit so as to flow the refrigerant in a pulsating manner. Effect of the Invention

[0008] According to the present invention, when adjusting the temperature of a battery by utilizing heat exchange, it is possible to suppress an increase in internal resistance caused by uneven concentration of the electrolyte. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic diagram showing a configuration of a battery temperature regulator according to a first embodiment. [Diagram 2] 2 is a flow chart illustrating a process flow of the battery temperature regulator of FIG. 1. [Diagram 3] FIG. 6 is a schematic diagram showing the configuration of a battery temperature regulating device according to a second embodiment. [Figure 4] 4 is a flow chart illustrating a process flow of the battery temperature regulator of FIG. 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. For clarity of explanation, the following description and drawings are omitted and simplified as appropriate. In addition, in each drawing, the same elements are given the same reference numerals, and duplicate explanations are omitted as necessary.

[0011] The present disclosure relates to a battery temperature regulator applicable to temperature regulation of a battery pack mounted on an electric vehicle such as a BEV (Battery Electric Vehicle) or a PHEV (Plug-in Hybrid Electric Vehicle). The performance required of such battery packs is increasing, and the amount of heat generated increases with an increase in load. For this reason, the required cooling capacity of the battery temperature regulator is increasing. On the other hand, it is predicted that if the cooling capacity of the battery temperature regulator is improved, the temperature difference between cells will increase, and some cells will become cold, resulting in a decrease in battery performance.

[0012] In addition, one of the characteristics of the way batteries are used in electric vehicles is that they are continuously energized for long periods of time. When energized for long periods of time, i.e., when only charging or discharging continues, the internal resistance of the cell increases due to uneven ion concentration in the electrolyte, and the performance of the battery is significantly reduced. Therefore, the present inventors have devised the following configuration.

[0013] Embodiment 1. Fig. 1 is a diagram showing the configuration of a battery temperature regulating device 10 according to a first embodiment. As shown in Fig. 1, the battery temperature regulating device 10 is applied to, for example, regulating the temperature of a battery pack 20 that supplies power to a motor of an electric vehicle or the like. The battery pack 20 generates power through an electrochemical reaction between air (oxidant gas) and hydrogen (fuel gas). The battery pack 20 has a stack structure in which a plurality of cells that generate power by receiving a supply of air and hydrogen are stacked.

[0014] The battery temperature regulating device 10 includes a temperature adjustment unit 1, a temperature sensor 2, a heater 3, and a controller 4. The temperature adjustment unit 1 includes a coolant flow path 11, a coolant pump 12, a three-way valve 13, a radiator 14, a fan 15, and a sub-radiator 16. The coolant flow path 11 circulates and supplies coolant (coolant) to the battery pack 20. The coolant flow path 11 is provided with a coolant pump 12 for circulating the coolant. The coolant pump 12 includes a counter (not shown) and can measure the ON time for circulating the coolant and the OFF time for stopping the circulation of the coolant when the coolant is caused to flow pulsatively.

[0015] A radiator 14 is provided in the cooling water flow path 11. The radiator 14 is a heat exchanger that exchanges heat between the cooling water heated to a high temperature by the battery pack 20 and the outside air blown by a fan 15, and releases heat generated in the battery pack 20 to the outside of the system. A sub-radiator 16 may be provided in parallel with the radiator 14 in the cooling water flow path 11. The sub-radiator 16 is a heat exchanger that exchanges heat between the cooling water and the atmosphere, and is used as an auxiliary when the cooling capacity of the radiator 14 alone is insufficient, such as when the battery pack 20 is under high load.

[0016] The cooling water flow path 11 is provided with a bypass flow path 17 for circulating the cooling water bypassing the radiator 14. The bypass flow path 17 is provided in parallel with the radiator 14. A three-way valve 13 is provided at a branch point of the cooling water flow path 11 and the bypass flow path 17. The three-way valve 13 switches the flow path for circulating the cooling water between the cooling water flow path 11 and the bypass flow path 17.

[0017] The battery pack 20 is provided with a temperature sensor 2 (temperature acquisition unit) that acquires temperature information of cells in the battery pack 20 during charging and discharging. In general, the maximum temperature of a cell affects the life of the battery pack 20, and the minimum temperature of a cell affects output performance. For this reason, the temperature sensor 2 acquires maximum temperature information of the cell with the highest temperature and minimum temperature information of the cell with the lowest temperature among the multiple cells of the battery pack 20. The acquired temperature information is input to the controller 4. The heater 3 maintains the cooling water, the temperature of which has increased, within a predetermined temperature range. The heater 3 may be provided, for example, on the cooling water inlet side of the battery pack 20.

[0018] The controller 4 is a control unit that uses a map that defines the relationship between the battery temperature and the flow rate of the cooling water (coolant) to determine the flow rate of the cooling water according to the temperature information acquired by the temperature sensor 2, and controls the operation of the temperature adjustment unit 1 to make the cooling water flow in a pulsating manner. Specifically, the controller 4 controls the operation (rotation speed) of the cooling water pump 12 to make the cooling water flow in a pulsating manner without reducing the flow rate of the cooling water circulating in the battery pack 20. In other words, the cooling water flows intermittently in the battery pack 20.

[0019] Here, the flow of processing by the battery temperature adjustment device of Fig. 1 will be described with reference to Fig. 2. In Fig. 2, threshold A is a temperature threshold of the battery pack 20 at which cooling of the battery pack 20 is started with priority in order to prevent overheating of the battery pack 20, for example. Threshold B is a temperature threshold of the battery pack 20 that is lower than threshold A and is set, for example, in order to extend the life of the battery pack 20. Threshold C is a lower temperature threshold of the battery pack 20 that is lower than threshold B and can satisfy the performance required of the battery.

[0020] As shown in FIG. 2, first, the controller 4 judges whether the maximum temperature of the cells in the battery pack 20 is higher than the threshold A (S11). If the maximum temperature of the cells is equal to or lower than the threshold A (S11 NO), the controller 4 judges whether the maximum temperature is higher than the threshold B (S12). If the maximum temperature is higher than the threshold B (S12 YES), a normal cooling operation of the battery pack 20 is performed. That is, the controller 4 uses a map that defines the relationship between the battery temperature and the cooling water flow rate (refrigerant flow rate) to obtain a cooling water flow rate corresponding to the maximum temperature information, and controls the cooling water pump 12 to circulate the cooling water so as to satisfy the cooling water flow rate (S13, cooling water circulation control). On the other hand, if the maximum temperature of the cells is equal to or lower than the threshold B (S12 NO), the controller 4 stops the cooling water pump 12 and sets the cooling water flow rate to 0 (S14, circulation stop control).

[0021] In S11, if the maximum cell temperature is higher than the threshold A (S11 YES), the controller 4 uses a map that defines the relationship between the battery temperature and the coolant flow rate to determine the flow rate of the coolant corresponding to the maximum temperature, and operates the coolant pump 12 intermittently without lowering the coolant flow rate. Specifically, the controller 4 first calculates the pump operation time (S15). The pump operation time refers to the ON time during which the coolant pump 12 is operated intermittently and the coolant is circulated at the coolant flow rate calculated by the controller 4. The controller 4 can set the ON time and OFF time of the coolant pump 12 according to, for example, the calculated coolant flow rate and the internal resistance index of the battery. Here, the internal resistance index of the battery is expressed by the formula of current integrated value x temperature coefficient. The temperature coefficient is, for example, a value set so that the lower the temperature, the larger the temperature, assuming that the temperature of the battery is 1 when the temperature of the coolant is 25°C.

[0022] The ON time of the intermittent control of the cooling water pump 12 can be set using a map that defines the relationship between the battery current value, the battery temperature, and the time during which the diffusion reaction of the battery does not start in advance. The OFF time of the intermittent control of the cooling water pump 12 can be set using a map that defines the relationship between the temperature difference between the maximum and minimum temperatures of the battery cell, and the battery current value in advance.

[0023] Then, it is determined whether the pump operation time is longer than the ON time (counter value) measured by the counter of the cooling water pump 12 and whether the minimum temperature is greater than a threshold value C (S16). If S16 is YES, the controller 4 operates the cooling water pump 12 to circulate the cooling water in a pulsating or intermittent manner (S17). If S16 is NO, the controller 4 stops the cooling water pump 12 and sets the flow rate of the cooling water to 0 (S18, circulation stop control).

[0024] Thus, according to the first embodiment, it is possible to reduce an increase in internal resistance due to a bias in the ion concentration of the electrolyte by intermittently operating the cooling water pump 12 without reducing the flow rate of the cooling water when there is a demand to cool the battery pack 20. Furthermore, when the battery pack 20 is cooled by the radiator 14, even in a low-temperature environment where the outside air temperature is lower than a predetermined reference outside air temperature, it is possible to suppress an increase in the internal resistance of the cells by performing intermittent control without reducing the flow rate of the cooling water.

[0025] Embodiment 2. Fig. 3 is a schematic diagram showing the configuration of a battery temperature adjustment device according to embodiment 2. In Fig. 3, the same components as those in Fig. 1 are given the same reference numerals, and the description thereof will be omitted as appropriate. The battery temperature adjustment device 10 shown in Fig. 3 includes a temperature adjustment unit 1, a temperature sensor 2, a heater 3, a controller 4, and a refrigerant circuit 30. For example, the temperature adjustment unit 1 can adjust the temperature of an in-vehicle battery pack 20, and the refrigerant circuit 30 can adjust the temperature of the vehicle interior.

[0026] In addition, the refrigerant circuit 30 can adjust the temperature of the coolant circulating through the coolant flow path 11. The refrigerant circuit 30 includes, for example, a refrigerant flow path 31, an evaporator 32, a compressor 33, a condenser 34, a first expansion valve 35, and a second expansion valve 36. The compressor 33 compresses the gas-phase refrigerant circulating through the refrigerant flow path 31. The gas-phase refrigerant compressed by the compressor 33 to have a high temperature and high pressure is sent to the condenser 34.

[0027] The condenser 34 condenses the gas phase refrigerant into a liquid phase refrigerant by releasing heat from the gas phase refrigerant that has been compressed by the compressor 33 to a high temperature and high pressure. The first expansion valve 35 reduces the pressure of the liquid phase refrigerant by expanding the high pressure liquid phase refrigerant compressed by the condenser 34. The liquid phase refrigerant reduced in pressure by the first expansion valve 35 is sent to the evaporator 32. The evaporator 32 cools the passenger compartment by exchanging heat between the surrounding air and the liquid refrigerant. The liquid refrigerant absorbs heat from the surrounding air and vaporizes to change into a gas phase refrigerant. This gas phase refrigerant returns to the compressor 33.

[0028] Similar to the first expansion valve 35, the second expansion valve 36 reduces the pressure of the liquid-phase refrigerant by expanding the high-pressure liquid-phase refrigerant compressed by the condenser 34. The liquid-phase refrigerant reduced in pressure by the second expansion valve 36 is sent to the chiller 40. The chiller 40 exchanges heat between the refrigerant circulating through the refrigerant flow path 31 and the cooling liquid circulating through the cooling water flow path 11.

[0029] Here, referring to FIG. 4, the flow of processing by the battery temperature regulator of FIG. 3 will be described. As shown in FIG. 4, first, the controller 4 judges whether or not the maximum temperature of the cells in the battery pack 20 is higher than the threshold A (S21). If the maximum temperature of the cells is equal to or lower than the threshold A (S21 NO), the controller 4 judges whether or not the maximum temperature is higher than the threshold B (S22). If the maximum temperature is higher than the threshold B (S22 YES), the controller 4 adjusts the compressor 33 to perform the cooling operation of the battery pack 20 with priority (S23). At this time, the controller 4 uses a map that specifies the relationship between the battery temperature and the cooling water flow rate to obtain the cooling water flow rate according to the maximum temperature information, and controls the cooling water pump 12 to circulate the cooling water so as to satisfy the cooling water flow rate. On the other hand, if the maximum temperature of the cells is equal to or lower than the threshold B (S22 NO), the controller 4 turns off the battery cooling (S24).

[0030] In S21, if the maximum cell temperature is higher than the threshold A (S21 YES), the controller 4 determines whether or not there is an air conditioning request (S25). If there is an air conditioning request (S25 YES), the controller 4 balances the intermittent operation of the refrigerant circuit 30 and the cooling water pump 12 with air conditioning by the evaporator 32 (S26). Note that for the intermittent operation of the cooling water pump 12, the ON time and the OFF time can be set as in the first embodiment. If there is no air conditioning request (S25 NO), the controller 4 determines whether or not the outlet pressure of the compressor 33 is higher than a predetermined threshold (S27).

[0031] If the answer is YES in S27, the cooling capacity of the refrigerant circuit 30 for the battery pack 20 will be high, which may increase the temperature difference between the cells of the battery. In this case, the controller 4 operates the refrigerant circuit 30 and the cooling water pump 12 intermittently to adjust the amount of cooling (S28). On the other hand, if the answer is NO in S27, the controller 4 adjusts the compressor 33 to perform a normal cooling operation for the battery pack 20 (S29). In this case, the required cooling capacity for the refrigerant circuit 30 is lower than that of the battery-priority cooling in S23. At this time, the controller 4 uses a map that defines the relationship between the battery temperature and the cooling water flow rate to determine the cooling water flow rate corresponding to the maximum temperature information, and controls the cooling water pump 12 to circulate the cooling water so as to satisfy the determined cooling water flow rate.

[0032] Thus, according to the second embodiment, even if there is a request for air conditioning when cooling of the battery pack 20 is required, it is possible to reduce an increase in internal resistance due to a bias in the ion concentration of the electrolyte by intermittently operating the refrigerant circuit 30 and the cooling water pump 12 without reducing the flow rate of the cooling water. Also, even if the outlet pressure of the compressor 33 is high, it is possible to suppress an increase in the internal resistance of the cells by performing intermittent control without reducing the flow rate of the cooling water.

[0033] The present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0034] 1 Temperature adjustment section 2 Temperature Sensor 3 Heater 4. Controller 10 Battery temperature controller 11 Cooling water flow path 12 Cooling water pump 13 Three-way valve 14 Radiator 15 Fan 16 Sub-radiator 17 Bypass flow path 20 Battery Pack 30 Refrigerant circuit 31 Coolant flow path 32 Evaporator 33 Compressor 34 Capacitor 35 First expansion valve 36 Second expansion valve 40 Chiller

Claims

[Claim 1] a temperature acquisition unit that acquires temperature information of cells in the battery pack during charging and discharging; a temperature adjusting unit that adjusts the temperature of the battery pack by flowing a coolant; a control unit that uses a map that defines a relationship between a battery temperature and a coolant flow rate to determine a coolant flow rate corresponding to the temperature information, and controls the operation of the temperature adjustment unit to cause the coolant to flow in a pulsating manner; Equipped with Battery temperature control device.

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