Battery System

Abstract

The objective of this invention is to determine with high precision whether thermally conductive material peeling has occurred. The ECU performs a process including the following steps: if the execution condition is met ("Yes" in S100), acquiring the battery temperature and inlet temperature (S102); acquiring the heat exchange rate in the refrigerator (S104); acquiring the heat generated by the battery (S106); acquiring the heat exchange rate in the heat exchanger (S108); calculating the thermal resistance k (S110); and if it is determined that the thermal resistance k is greater than the threshold k (0) ("Yes" in S112), determining that thermally conductive material peeling has occurred (S114).

Description

Technical Field

[0001] This invention relates to a battery system. Background Technology

[0002] Japanese Patent Application Publication No. 2021-064488 (Patent Document 1) discloses a technology in which an abnormality is determined to have occurred in the refrigerant system of the cooling device when no abnormality is detected in the air conditioning unit and the temperature sensor reading is higher than a specified value.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2021-064488 Summary of the Invention

[0004] Battery systems, for example, include batteries and heat exchange components. When a thermally conductive material is provided between the battery and the heat exchange components, it can sometimes peel off due to poor coating or external impacts from driving on rough roads. If peeling occurs within the thermally conductive material, the battery cannot be adjusted to an appropriate temperature. Since the condition of the thermally conductive material cannot be observed from outside the battery system, high-precision determination of whether peeling has occurred within the thermally conductive material is required.

[0005] The present invention was made to solve the above-mentioned problems, and its purpose is to provide a battery system that can accurately determine whether thermally conductive material has peeled off.

[0006] One aspect of the present invention relates to a battery system comprising: an energy storage device; a heat exchanger that exchanges heat with the energy storage device using a refrigerant; a thermally conductive material disposed between the energy storage device and the heat exchanger; a first detection device that detects a first temperature, which is the temperature of the refrigerant flowing into the heat exchanger; a second detection device that detects a second temperature, which is the temperature of the energy storage device; and a control device that calculates the thermal resistance between the heat exchanger and the energy storage device by dividing the value obtained by subtracting the second temperature from the first temperature by the amount of heat exchange in the heat exchanger. If the calculated thermal resistance is greater than a threshold, the control device determines that the thermally conductive material is in an abnormal state.

[0007] Therefore, if the thermally conductive material peels off, heat exchange between the energy storage device and the heat exchanger cannot proceed effectively. The temperature of the energy storage device rises, and the amount of heat exchanged in the heat exchanger decreases. Consequently, the thermal resistance increases. Therefore, the abnormal state of the thermally conductive material can be determined with high precision using thermal resistance.

[0008] In one embodiment, the heat exchanger is connected to a refrigerator. The control device calculates the heat exchange rate in the heat exchanger using a predetermined relationship between the heat generated by the energy storage device, the heat exchange rate in the refrigerator, and the heat exchange rate in the heat exchanger.

[0009] In this way, the amount of heat exchanged in the heat exchanger can be calculated with high accuracy using the mapping diagram.

[0010] In another embodiment, if the thermal resistance is greater than a threshold, the control device determines the state in which the thermally conductive material is stripped from at least one of the heat exchanger and the energy storage device as an abnormal state.

[0011] In this way, thermal resistance can be used to determine with high precision whether thermally conductive material peeling has occurred.

[0012] Invention Effects

[0013] According to the present invention, a battery system is provided that can determine with high precision whether thermally conductive material peeling has occurred. Attached Figure Description

[0014] Figure 1 This is a diagram illustrating an example of the structure of a vehicle equipped with a battery system according to an embodiment of the present invention.

[0015] Figure 2 This is a flowchart illustrating an example of a process performed by the ECU.

[0016] Figure 3 This is an example diagram illustrating the relationship between the heat generated by the battery, the heat exchange capacity of the refrigerator, and the heat exchange capacity in the heat exchanger. Detailed Implementation

[0017] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Furthermore, identical or corresponding parts in the drawings will be labeled with the same symbols, and their descriptions will not be repeated.

[0018] Figure 1 This is a diagram illustrating an example of the structure of a vehicle 200 equipped with the battery system 100 according to an embodiment of the present invention.

[0019] Vehicle 200 is electrically connected to power station 300 via cable 310, enabling it to exchange (charge and discharge) power with power station 300. AC power is exchanged between vehicle 200 and connector 311 located at the end of cable 310. Additionally, power station 300 exchanges power with the power system PG.

[0020] The vehicle 200 is equipped with a battery system 100, a charging port 210, a motor generator (MG) 220, and a charger 230.

[0021] Vehicle 200 is configured to operate using electricity stored in battery 40 of battery system 100. Vehicle 200 is, for example, a pure electric vehicle (BEV) without an engine (internal combustion engine). However, it is not limited to this; vehicle 200 can be a PHEV (plug-in hybrid electric vehicle) with an internal combustion engine, or other electric vehicles (xEV).

[0022] The charging port 210 is located on an exterior part of the vehicle 200 and has a shape that can be fitted with the connector 311. The exterior part includes a cover that, when the charging port 210 is not in use, covers the charging port 210 by closing the cover to prevent it from being exposed to the outside.

[0023] MG220 is, for example, a three-phase AC rotary motor. MG220 functions as the driving motor for vehicle 200. MG220 is driven by AC power from battery system 100, causing the drive wheels of vehicle 200 to rotate. Furthermore, MG220 regenerates electricity and outputs the generated AC power to battery system 100. Additionally, the number of driving motors in vehicle 200 is not particularly limited to one; it can be two or more.

[0024] The charger 230 is connected to both the charging port 210 and the battery system 100 (specifically, the relay 60). The charger 230 performs power conversion during power transfer with the power station 300. For example, the charger 230 converts AC power supplied from the power station 300 to DC power for supply to the battery system 100, or converts DC power supplied from the battery system 100 to AC power for supply to the power station 300. The charger 230 includes a power conversion circuit (e.g., an inverter and converter) configured to adjust the charging or discharging current.

[0025] The battery system 100 includes an electronic control unit (ECU) 10, a power control unit (PCU) 20, a battery 40, a system main relay (SMR) 50, and a relay 60.

[0026] ECU 10 is a control device including a processor 11, random access memory (RAM) 12, and a storage device 13. The storage device 13 is configured to store stored information. In addition to the program, the storage device 13 also stores information used in the program (e.g., mappings, formulas, and various parameters). In this embodiment, the processor 11 executes the program stored in the storage device 13, performing various processes based on ECU 10. However, these processes can also be executed solely through hardware (electronic circuits) without using software. ECU 10, for example, controls the operation of PCU 20, SMR 50, relay 60, and charger 230.

[0027] A voltage sensor 43, a current sensor 44, a battery temperature sensor 45, and an inlet temperature sensor 46 are connected to the ECU 10. The voltage sensor 43 detects the voltage Vb of the battery 40 and outputs a signal indicating the detection result to the ECU 10. The current sensor 44 detects the current Ib flowing through the battery 40 and outputs a signal indicating the detection result to the ECU 10. Furthermore, the battery temperature sensor 45 detects the temperature Tb of the battery 40 and outputs a signal indicating the detection result to the ECU 10. Finally, the inlet temperature sensor 46 detects the temperature Tw of the refrigerant flowing into the heat exchanger 240 and outputs a signal indicating the detection result to the ECU 10.

[0028] The battery 40 includes multiple energy storage units. These energy storage units are arranged in a predetermined number, for example, along the thickness direction of the energy storage units. The predetermined number is not particularly limited. The energy storage units are secondary batteries, typically lithium-ion secondary batteries. Lithium-ion secondary batteries are batteries that use lithium as the charge carrier; besides lithium-ion secondary batteries with a liquid electrolyte, all-solid-state batteries using a solid electrolyte can also be included. Furthermore, the battery 40 can be any energy storage device; for example, a large-capacity capacitor can be used instead of the battery 40.

[0029] SMR50 switches the connection / disconnection of the power line from battery 40 to PCU20 based on the control signal received from ECU10. When vehicle 200 is in motion, SMR50 is in a closed state (connected state). Furthermore, SMR50 is also in a closed state when power is exchanged between battery 40 and charging port 210 (and consequently, power station 300). Moreover, SMR50 is also in a closed state when performing temperature control based on ripple current, as described later.

[0030] Relay 60 is located between charger 230 and battery 40. Relay 60 switches the connection / disconnection of the power line (charge / discharge line) from charging port 210 to battery 40 according to the control signal received from ECU 10.

[0031] In this embodiment, the charging / discharging line, via the charging port 210, the charger / discharger 230, and the relay 60, is connected to the power line connecting the SMR50 and the PCU20. That is, the charging / discharging line is connected in parallel with respect to the SMR50 and the PCU20. However, this is not a limitation; the charging / discharging line can also be connected to the power line connecting the battery 40 and the SMR50. That is, the charging / discharging line can also be connected in parallel with respect to the battery 40 and the SMR50.

[0032] In the plugged-in vehicle 200, external charging (i.e., charging the battery 40 from the power station 300) and external discharging (i.e., discharging the battery 40 back to the power station 300) are both possible. Alternatively, the vehicle 200 may only be capable of external charging. When external charging or discharging is performed, the relay 60 is controlled to be in a closed state (connected state); when neither external charging nor discharging is performed, the relay 60 is controlled to be in an open state (disconnected state).

[0033] PCU20 includes a circuit (e.g., an inverter and converter) that uses power supplied from battery 40 to drive MG220. The inverter and converter are configured, for example, by combining multiple switching elements, and perform switching operations such as power conversion or voltage boosting based on control signals received from ECU10.

[0034] The vehicle 200 is also equipped with a cooling device for cooling the battery 40. The cooling device includes refrigerant circuits C1 and C2 and a refrigeration unit 270. The refrigerant circuit C1 includes a heat exchanger 240, a liquid receiver (R / T) 250, and a pump 260.

[0035] A heat exchanger 240 is disposed below the battery 40, and a thermally conductive material 42 is disposed between the battery 40 and the heat exchanger 240. The thermally conductive material 42 is, for example, composed of a silicone-based adhesive. The thermally conductive material 42 can be, for example, a thermally conductive gel, grease, paste, or sheet that can be bonded to the battery 40 or the heat exchanger 240.

[0036] Pump 260 circulates refrigerant in refrigerant circuit C1. The refrigerant flowing through refrigerant circuit C1 cools battery 40 as its temperature rises. The refrigerant includes, for example, coolant. Additionally, when the temperature of battery 40 is low due to weather or location (e.g., cold regions), the refrigerant flowing into heat exchanger 240 adjacent to battery 40 can be heated by a heater (not shown), thereby raising the temperature of battery 40. Refrigerant circuit C2 includes a refrigeration cycle device 280. Refrigeration cycle device 280 includes various (not shown) devices (e.g., compressor, condenser, expansion valve, and evaporator) for temperature adjustment via a refrigeration cycle (e.g., evaporation cycle, compression cycle, condensation cycle, and expansion cycle). The refrigeration circuit of an air conditioning system (not shown) mounted on vehicle 200 can constitute refrigeration cycle device 280. The refrigerant flowing through refrigerant circuit C2 is cooled by refrigeration cycle device 280. The refrigeration unit 270 is connected to refrigerant circuits C1 and C2, and heat exchange occurs between the refrigerant circulating in refrigerant circuit C1 and the refrigerant circulating in refrigerant circuit C2.

[0037] In the vehicle 200 with the structure described above, a thermally conductive material 42 is provided between the battery 40 and the heat exchanger 240. Sometimes, due to poor coating of the thermally conductive material 42, external impacts caused by driving on rough roads can cause the thermally conductive material 42 to peel off. If the thermally conductive material bonded to at least one of the battery 40 and the heat exchanger 240 peels off, it is impossible to adjust the battery 40 to an appropriate temperature. Since the condition of the thermally conductive material 42 cannot be confirmed from outside the battery system 100, it is required to determine with high accuracy whether peeling has occurred in the thermally conductive material 42.

[0038] Therefore, in this embodiment, the following is set up: ECU 10 uses the temperature Tw (first temperature) of the refrigerant flowing into heat exchanger 240, the temperature Tb (second temperature) of battery 40, and the heat exchange rate Q in heat exchanger 240 to calculate the thermal resistance k between heat exchanger and battery 40. If the calculated thermal resistance k is greater than the threshold k (0), it is determined that the thermally conductive material 42 is in an abnormal state. In addition, ECU 10 calculates the thermal resistance k, for example, by dividing the value obtained by subtracting temperature Tb from temperature Tw by the heat exchange rate Q in heat exchanger 240. More specifically, ECU 10 uses the formula k = (Tw - Tb) / Q to calculate the thermal resistance k.

[0039] Thus, if the thermally conductive material 42 peels off, heat exchange between the battery 40 and the heat exchanger 240 cannot proceed effectively, resulting in a decrease in the amount of heat exchanged Q in the heat exchanger 240 and an increase in the thermal resistance k. Therefore, by determining that the thermally conductive material 42 has peeled off if the thermal resistance k is greater than the threshold k (0), the abnormal state (i.e., the state in which the thermally conductive material 42 has peeled off) can be determined with high accuracy.

[0040] The following is for reference. Figure 2 An example of the processing performed by ECU10 will be explained. Figure 2 This is a flowchart illustrating an example of a process performed by ECU10.

[0041] In step (hereinafter referred to as step S) 100, ECU 10 determines whether the execution condition is met. The execution condition may include, for example, the formation of... Figure 1 The conditions for the refrigerant circuit C1 shown are those for charging or discharging. ECU 10, for example, forms conditions including those arising from the operation of a switching valve (not shown). Figure 1 In the case of the refrigerant circuit of the heat exchanger 240, R / T 250, pump 260, and refrigerator 270, it can be determined that a refrigerant circuit C1 has been formed. Furthermore, if the ECU 10 is not at zero current, it can be determined that charging or discharging is in progress. If the execution condition is determined to be met ("Yes" in S100), the process proceeds to S102.

[0042] In S102, ECU10 acquires temperatures Tb and Tw. ECU10 uses battery temperature sensor 45 and inlet temperature sensor 46 to acquire temperatures Tb and Tw. Then, processing proceeds to S104.

[0043] In S104, ECU10 acquires the amount of heat exchange in the refrigerator 270 within a predetermined period. The predetermined period is, for example, a period suitable for calculation based on the accuracy of the thermal resistance k through experiments, etc. The amount of heat exchange in the refrigerator 270 is acquired based on the operating state of the refrigeration cycle device 280 (e.g., the operating rate of the compressor in the refrigeration cycle device 280, the temperature of the refrigerant flowing into the condenser, the temperature of the refrigerant flowing out of the evaporator of the refrigerator 270, etc.). ECU10 can acquire the amount of heat exchange in the refrigerator 270, for example, using a mapping diagram or formula representing the relationship between the operating state of the refrigeration cycle device 280 and the amount of heat exchange in the refrigerator 270. Then, the process proceeds to S106.

[0044] In S106, ECU10 acquires the heat generated by battery 40 within a predetermined period. This predetermined period is the same as the predetermined period in S104, and therefore will not be described in detail again. ECU10 acquires the heat generated by battery 40, for example, using the Joule heat generated and the heat absorbed and released during chemical changes within the predetermined period. ECU10 calculates the Joule heat generated and the heat absorbed and released during chemical changes, for example, using the detection results from voltage sensor 43, current sensor 44, and battery temperature sensor 45. The calculation methods for Joule heat generated and the heat absorbed and released during chemical changes can use known techniques, and therefore will not be described in detail. The process then proceeds to S108.

[0045] In S108, ECU10 obtains the heat exchange quantity Q in heat exchanger 240. Specifically, ECU10 uses, for example, Figure 3 The table and mapping diagram shown indicate that the heat exchange quantity Q in the heat exchanger 240 is obtained based on the heat exchange quantity (heat exchange quantity of the refrigerator) obtained in S104 and the heat exchange quantity (heat generation of the battery) obtained in S106 in the battery 40.

[0046] Figure 3 This is a diagram illustrating an example of the relationship between battery heat generation, refrigerator heat exchange capacity, and heat exchange capacity Q in heat exchanger 240. Figure 3 The table shows that when the heat exchange capacity of the refrigerator is 1kW, the heat exchange capacity in the heat exchanger 240 is 4kW, 3kW, 2kW and 1kW when the heat output of the battery is 1kW, 2kW, 3kW and 4kW respectively.

[0047] Moreover, in Figure 3 The table shows that when the heat exchange capacity of the refrigerator is 2kW, the heat exchange capacity in the heat exchanger 240 is 5kW, 4kW, 3kW and 2kW when the heat output of the battery is 1kW, 2kW, 3kW and 4kW respectively.

[0048] Moreover, in Figure 3 The table shows that when the heat exchange capacity of the refrigerator is 3kW, the heat exchange capacity in the heat exchanger 240 is 5kW, 5kW, 4kW and 3kW when the heat output of the battery is 1kW, 2kW, 3kW and 4kW respectively.

[0049] Moreover, in Figure 3 The table shows that when the heat exchange capacity of the refrigerator is 4kW, the heat exchange capacity in the heat exchanger 240 is 5kW, 5kW, 5kW and 4kW when the heat output of the battery is 1kW, 2kW, 3kW and 4kW respectively.

[0050] For example, if the heat exchange capacity of the refrigerator obtained in S104 is 2kW, the relationship between the battery heat generation and the heat exchange capacity Q in the heat exchanger 240 becomes: Figure 3 The relationship shown in the thick-lined frame of the table becomes Figure 3 The linear relationship shown by LN1 of (A). Figure 3 The vertical axis of (A) represents the heat exchange quantity Q in the heat exchanger. Figure 3 The horizontal axis of (A) represents the battery's heat generation. For example... Figure 3 As shown in LN1, for example, when the heat exchange capacity of the refrigerator is 2kW and the heat generation of the battery is 4kW, the heat exchange capacity Q in the heat exchanger 240 is calculated to be 2kW. Then, the process moves to S110.

[0051] In S110, ECU10 calculates the thermal resistance k. That is, ECU10 uses the above formula k=(Tw-Tb) / Q to calculate the thermal resistance k. Then, the process moves to S112.

[0052] In S112, ECU10 determines whether the thermal resistance k is greater than the threshold k(0). The threshold is a value that can determine whether delamination has occurred in the heat-conducting material 42, and is a suitable value determined through experiments, etc. The threshold k(0) can be a predetermined value, or it can be set based on the driving period of the vehicle 200, the total driving distance, the historical record of the external temperature, the type of material used in the heat-conducting material 42, etc. Then, the process moves to S114.

[0053] In S114, ECU10 determines that the thermal conductive material 42 has peeled off. ECU10 may, for example, set the diagnostic flag indicating that the thermal conductive material 42 has peeled off to the on state, illuminate a specified warning light, or notify the user that peeling has occurred. Then, the process ends. Alternatively, if it is determined that the execution condition is not met ("No" in S100) or if it is determined that the thermal resistance k is below the threshold k(0) ("No" in S112), then the process ends.

[0054] The operation of ECU10 based on the structure and flowchart described above will be explained. For example, when it is determined that the conditions for charging battery 40 and forming a refrigerant circuit C1 including heat exchanger 240, R / T 250, pump 260 and refrigerator 270 are met, the execution condition is met ("Yes" in S100). Therefore, the battery temperature and inlet temperature are obtained (S102). Then, the refrigerator heat exchange quantity is obtained (S104), and the battery heat generation is obtained (S106). Using the obtained refrigerator heat exchange quantity, battery heat generation and... Figure 3The heat exchange rate Q in heat exchanger 240 is obtained from the table (S108). Then, the thermal resistance k is calculated using the formula k = (Tw - Tb) / Q (S110). If it is determined that the calculated thermal resistance k is greater than the threshold k (0) ("Yes" in S112), it is determined that the thermally conductive material 42 has peeled off (S114). On the other hand, if it is determined that the thermal resistance k is less than the threshold k (0) ("No" in S112), then the execution condition is waited for to be met.

[0055] As described above, in the battery system 100 according to this embodiment, if the thermally conductive material 42 peels off, heat exchange between the battery 40 and the heat exchanger 240 cannot be carried out effectively, the value of the heat exchange quantity Q in the heat exchanger 240 decreases, and therefore the value of the thermal resistance k increases. Therefore, by determining that the thermally conductive material 42 has peeled off if the thermal resistance k is greater than the threshold k (0), the abnormal state (i.e., the state in which the thermally conductive material 42 has peeled off) can be determined with high accuracy. Therefore, a battery system that can determine with high accuracy whether the thermally conductive material peeling off has occurred can be provided.

[0056] Furthermore, by using a mapping diagram representing the relationship between the heat generated by the battery 40, the heat exchange quantity in the refrigerator 270, and the heat exchange quantity Q in the heat exchanger 240, the heat exchange quantity in the heat exchanger can be calculated with high accuracy.

[0057] Furthermore, by using the formula k=(Tw-Tb) / Q to calculate the thermal resistance k, it is possible to determine with high accuracy whether the heat exchange between the battery 40 and the heat exchanger 240 is proceeding properly.

[0058] The following describes some variations.

[0059] In the above embodiment, the abnormal state in which the thermally conductive material 42 peels off is described, for example, assuming that the entire surface of the thermally conductive material 42 peels off from at least one of the battery 40 and the heat exchanger 240 (unbonded state). However, for example, multiple threshold values ​​of thermal resistance k corresponding to the abnormal state of partial peeling can be set to divide the abnormal state into multiple stages for determination.

[0060] Furthermore, in the above embodiment, the battery temperature sensor 45 was described as a sensor disposed within the battery 40. However, for example, the ECU 10 can correct the detection result of the battery temperature sensor 45 based on the location of the battery temperature sensor 45 within the battery 40. For instance, the ECU 10 can correct the detection result of the battery temperature sensor 45 to the temperature of the portion of the battery 40 that is close to the contact surface with the thermally conductive material 42. In this way, the heat generated by the battery can be calculated with high accuracy, and therefore the thermal resistance k can be determined with high accuracy. As a result, it is possible to determine with high accuracy whether the thermally conductive material 42 has peeled off.

[0061] Furthermore, in the above embodiment, the formula k=(Tw-Tb) / Q was used to calculate the thermal resistance k. However, the thermal resistance k can also be calculated by dividing the temperature difference between Tw and Tb by the amount of heat exchange in the heat exchanger 240. Alternatively, the thermal resistance k can be calculated when the inlet water temperature is greater than the battery temperature.

[0062] Furthermore, in the above embodiment, it was explained that the thermal conductive material 42 was peeled off when the thermal resistance k was greater than the threshold k (0). However, for example, it may also be determined that the thermal conductive material 42 was not peeled off from either the heat exchanger 240 or the battery 40 when the thermal resistance k was less than the threshold k (0).

[0063] Furthermore, the above-mentioned variations can be implemented by combining all or part of them appropriately.

[0064] It should be considered that the embodiments disclosed herein are illustrative in all respects and not restrictive. The scope of the invention is not shown in the foregoing description, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0065] Symbol Explanation

[0066] 10-ECU, 11-Processor, 12-RAM, 13-Storage device, 20-PCU, 40-Battery, 42-Thermal conductive material, 43-Voltage sensor, 44-Current sensor, 45-Battery temperature sensor, 46-Inlet temperature sensor, 50-SMR, 60-Relay, 100-Battery system, 200-Vehicle, 210-Charging port, 230-Charger / discharger, 240-Heat exchanger, 250-Reservoir (R / T), 260-Pump, 270-Refrigeration unit, 280-Refrigeration cycle unit, 300-Power station, 310-Cable, 311-Connector, PG-Power system.

Claims

1. A battery system, characterized in that, have: Energy storage devices; A heat exchanger that uses a refrigerant to exchange heat with the energy storage device; A thermally conductive material is disposed between the energy storage device and the heat exchanger; The first detection device detects a first temperature, which is the temperature of the refrigerant flowing into the heat exchanger; The second detection device detects a second temperature, which is the temperature of the energy storage device. and The control device calculates the thermal resistance between the heat exchanger and the energy storage device by dividing the value obtained by subtracting the second temperature from the first temperature by the amount of heat exchange in the heat exchanger. If the calculated thermal resistance is greater than the threshold, the control device determines that the thermally conductive material is in an abnormal state.

2. The battery system according to claim 1, characterized in that, The heat exchanger is connected to the refrigeration unit. The control device uses a predetermined relationship between the heat generated by the energy storage device, the heat exchange rate in the refrigerator, and the heat exchange rate in the heat exchanger to calculate the heat exchange rate in the heat exchanger.

3. The battery system according to claim 1 or 2, characterized in that, If the thermal resistance is greater than the threshold, the control device determines the state in which the thermally conductive material is detached from at least one of the heat exchanger and the energy storage device as the abnormal state.

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