Liquid cooling system of new energy automobile and control method of liquid cooling system

Abstract

The invention relates to the technical field of new energy automobiles, and discloses a liquid cooling system of a new energy automobile and a control method thereof.The liquid cooling system of the new energy automobile comprises a physical structure unit, a fluid power unit and a sensing and control unit, and the physical structure unit comprises a heat dissipation and bearing integrated lower shell integrated with an internal cooling flow channel; the heat dissipation and bearing integrated lower shell and the side wall capillary network form a three-dimensional composite heat dissipation structure, the fluid power unit comprises an active liquid cooling loop and a passive siphon loop which are connected in parallel, and the sensing and control unit comprises a three-level distributed sensing network and a control center. The heat exchange area is increased through the three-dimensional composite heat dissipation structure, working condition self-adaptive switching and zero-energy-consumption safety redundancy are achieved through the dual-mode fluid loop, and the energy density, the heat dissipation efficiency and the system operation safety of the battery pack are improved by combining model prediction with a proportional integral differential control algorithm.

Description

Technical Field

[0001] This invention relates to the field of new energy vehicle technology, specifically to a liquid cooling system for new energy vehicles and its control method. Background Technology

[0002] With the advancement of global science and technology and economic development, global energy and environmental issues are becoming increasingly prominent, and the transition from gasoline-powered vehicles to new energy vehicles has become the mainstream trend in the automotive industry. The surge in the number of new energy vehicles and the rapid development of science and technology have driven the transformation of power battery cells towards higher discharge and charge rates. Under high-rate charging and discharging conditions, complex and intertwined chemical reactions occur within the power battery cells, generating a large amount of heat. If thermal management intervention is not implemented at these high exothermic temperatures, the continuous high-temperature state of the power battery cells will accelerate their aging process, thereby reducing their lifespan. In severe cases, it can even lead to thermal runaway, causing damage to the entire new energy vehicle and resulting in injuries or fatalities.

[0003] Currently, power battery cooling technologies mainly include heat pipe cooling, phase change cooling, liquid cooling, and air cooling. Among these, heat pipe cooling and phase change cooling are still in the research stage and have not yet been widely applied in practical industries. While air cooling technology has advantages such as simple structure, environmental friendliness, low cost, and ease of maintenance, it also suffers from drawbacks such as low heat transfer coefficient, slow cooling speed, low heat exchange efficiency, and high operating noise. In an era where power batteries require fast charging and discharging, air cooling technology cannot meet the heat dissipation needs of most new energy vehicles.

[0004] Therefore, liquid cooling technology and composite refrigeration technology have become key research and application technologies in contemporary times. However, traditional refrigeration technology is essentially one-dimensional surface cooling. In traditional liquid cooling solutions, the liquid cooling plate only contacts one side of the power battery cell, resulting in a limited heat dissipation area. The heat generated in the upper part of the power battery cell needs to be conducted through the cell's own interior to the bottom before being carried away by the liquid cooling plate. This results in a long heat transfer path, high thermal resistance, and low heat exchange efficiency, making it difficult to solve the problem of large overall temperature differences within the power battery cell.

[0005] Furthermore, existing liquid cooling circuits are limited in their fluid drive capabilities, relying on electric water pumps. If the electric water pump or controller fails, the entire power battery cooling system immediately collapses, resulting in low system redundancy and an inability to handle emergency failure conditions.

[0006] In terms of battery pack structure design, existing battery packs generally adopt a stacked design, with battery pack structural components, independent liquid cooling plates, power battery cells, and module bracket components stacked layer by layer. The stacked design results in a complex battery pack system structure, large overall weight, and low internal space utilization, which in turn limits the energy density of new energy vehicle battery packs and increases the weight of new energy vehicle bodies. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a liquid cooling system and its control method for new energy vehicles, which solves the limitations of existing battery thermal management systems in terms of heat dissipation performance, structural integration, safety redundancy, and control accuracy, especially addressing the contradiction between high heat load and low energy consumption requirements.

[0008] To achieve the above objectives, the present invention provides a liquid cooling system for new energy vehicles, comprising: a physical structural unit, a fluid power unit, and a sensing and control unit.

[0009] The physical structural unit includes an integrated heat dissipation and load-bearing lower shell and a three-dimensional composite heat dissipation structure, reflecting a deep integration of structure and heat dissipation function. The integrated heat dissipation and load-bearing lower shell is made of high-strength aluminum alloy and adopts a double-layer hollow structure, integrating the coolant flow channels between the upper and lower layers. The flow channels are arranged in a honeycomb array and adopt a human vein-inspired flow channel design. The design ensures high strength load-bearing capacity while improving temperature uniformity and heat exchange efficiency. The flow channels serve as coolant channels and also as structural reinforcing ribs of the lower shell, enhancing the mechanical load-bearing capacity of the lower shell. The integrated heat dissipation and load-bearing lower shell integrates a coolant inlet, a coolant outlet, and threaded interfaces for installing pressure and temperature sensors, reducing the risk of external pipeline connections and leaks.

[0010] The three-dimensional composite heat dissipation structure is composed of the upper inner wall of the lower shell and the side capillary network set on the side of the cell. The side capillary network is composed of multiple microchannel copper tubes. Through the thermal interface material, it is in close contact with the side of the cell. The coolant flows through the bottom and side of the cell simultaneously, realizing three-dimensional surround heat dissipation of the cell. This increases the heat exchange area, reduces thermal resistance, and adopts an integrated design to directly replace the traditional module side plate, module end plate and module bracket in the battery pack. This simplifies the battery pack structure and achieves lightweighting and improved energy density.

[0011] The fluid power unit constructs an active liquid cooling circuit and a passive siphon circuit connected in parallel, forming a dual-mode redundant fluid transport network. The active liquid cooling circuit includes an electric water pump, a solenoid valve, and an external radiator, using a mixed solution of ethylene glycol and deionized water as the working fluid to cope with forced circulation cooling under high heat load conditions such as fast charging or high-speed driving. The active liquid cooling circuit integrates a positive temperature coefficient heater to achieve rapid preheating in low-temperature environments and can be coupled to a refrigerator. By requesting the air conditioning system to intervene through the control center, deep cooling can be achieved. The solenoid valve is a direct-acting proportional solenoid valve used to achieve zoned flow regulation.

[0012] The passive siphon circuit includes a siphon generator and a condenser, and is filled with a low-boiling-point phase change medium as the working fluid. Under low-load conditions, the passive siphon circuit utilizes the heat-driven natural circulation principle of the working fluid absorbing heat and evaporating in the capillary network on the side wall and condensing and refluxing in the condenser to achieve zero-energy temperature maintenance. As a key safety redundancy guarantee, the passive siphon circuit can forcibly take over when the active circuit fails, ensuring the safety of the battery system. The active liquid cooling circuit and the passive siphon circuit are connected and isolated through parallel valves.

[0013] The sensing and control unit includes a three-level distributed sensing network and a control center, realizing refined sensing and intelligent control. The three-level distributed sensing network includes a cell-level sensing layer, a module-level sensing layer, and a system-level sensing layer, comprehensively collecting key operating data such as temperature, flow rate, pressure, and battery state of charge. The cell-level sensing layer obtains temperature data of key nodes of a single cell through negative temperature coefficient thermistors.

[0014] The control center operates on an automotive-grade microcontroller. Its hardware architecture includes a signal acquisition input terminal, a core processing unit, and an actuator drive output terminal. The actuator drive output terminal is equipped with a full-bridge drive circuit and a pulse width modulation generator, and has the ability to send request signals to the vehicle controller via the controller area network bus. Under high-load conditions, the control center calls model predictive control algorithms and machine learning prediction algorithms to generate initial control outputs. The model predictive control algorithm, based on a battery thermodynamic model, calculates the optimal control input by optimizing the objective function, balancing temperature control accuracy and system energy consumption. The control center has a zoned targeted cooling function, capable of adjusting the opening of corresponding branch solenoid valves using proportional-integral-derivative (PID) control logic based on local hotspot determination criteria. PID calculates the sum of the basic opening, proportional adjustment term, integral adjustment term, and derivative adjustment term as the real-time opening adjustment target value for the solenoid valve. The derivative adjustment term is calculated based on the rate of change of temperature deviation over time, achieving predictive adjustment of temperature changes.

[0015] A liquid cooling control method for new energy vehicles includes the following steps: S1: After the liquid cooling system is powered on or woken up, the control center performs a self-test to check the working status of the active liquid cooling circuit components and the three-level distributed sensing network sensors.

[0016] S2: After the self-test is completed, the three-level distributed sensing network continuously collects temperature baseline detection data and state variable data. The state variable data includes battery temperature, charging and discharging current and ambient temperature. The liquid cooling system reads the battery state of charge and obtains the temperature distribution through a negative temperature coefficient thermistor.

[0017] S3: The control center determines the current vehicle operating condition based on the collected data. The current vehicle operating condition includes low load condition, high load condition, and whether local hot spots are detected.

[0018] S4: The current vehicle operating condition control center selects the cooling path based on the operating condition judgment result. Under low load, the passive siphon circuit is activated, and under high load, the active liquid cooling circuit is activated. When a local hot spot is detected during the operation of the active liquid cooling circuit, the zone-enhanced cooling logic is entered.

[0019] S5: When the active liquid cooling circuit is activated, the control center calls the model predictive control algorithm and the machine learning predictive algorithm to generate an initial control output. The initial control output includes the flow rate setting of the cooling medium and the adjustment command of the cooling fan speed.

[0020] S6: When a fault is detected in the active liquid cooling circuit, the control center triggers a safety redundancy strategy, immediately forces a switch to passive siphon circuit operation, and sends a power limiting request to the vehicle controller to limit the battery charging and discharging power to ensure that the vehicle enters a safe limp mode.

[0021] S7: During the execution of the cooling path, the control center continuously calculates the error value between the temperature data and the set threshold data, and uses the proportional-integral-derivative feedback adjustment algorithm to dynamically adjust the control output according to the error value, so as to realize the real-time closed-loop adjustment of the liquid cooling system.

[0022] This invention provides a liquid cooling system and its control method for new energy vehicles. It has the following beneficial effects: 1. This invention achieves three-dimensional surround heat dissipation of the bottom and sides of the battery cell by using a three-dimensional composite heat dissipation structure composed of an integrated heat dissipation and load-bearing lower shell and a capillary network on the side wall. This increases the heat exchange area and reduces the thermal resistance of the heat transfer path. At the same time, the three-dimensional composite heat dissipation structure uses heat dissipation channels as structural reinforcing ribs, replacing the module side plates and brackets in traditional battery packs. This reduces the number of unnecessary components inside the battery pack, improves the structural strength of the battery pack, reduces the weight of the battery pack, and increases the volumetric energy density of the battery pack.

[0023] 2. This invention constructs a dual-mode redundant thermal management mechanism by forming a fluid power unit consisting of an active liquid cooling circuit and a passive siphon circuit connected in parallel. The active liquid cooling circuit can provide powerful cooling under high-load conditions such as fast charging or high-speed driving, while the passive siphon circuit can achieve zero-energy consumption natural circulation heat dissipation by utilizing the latent heat of phase change of the working fluid under low-load or parking conditions. In addition, when the active liquid cooling circuit fails, the passive siphon circuit can automatically intervene as a safety redundancy to prevent battery thermal runaway and improve the operational reliability and safety of the liquid cooling system of new energy vehicles.

[0024] 3. This invention achieves monitoring and proactive management of battery thermal state through a three-level distributed sensing network combined with model predictive control and machine learning algorithms. By collecting multi-dimensional data at the cell, module, and system levels, the control center can identify local hot spots and independently adjust the opening of the solenoid valves in the corresponding areas using a PID algorithm to achieve zoned targeted cooling. At the same time, the model predictive control algorithm can predict future temperature trends based on the current state and adjust actuator actions in advance, avoiding the lag effect of temperature regulation, ensuring temperature consistency within the battery module, and reducing system operating energy consumption. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall structure of the liquid cooling system of the present invention; Figure 2 This is a schematic diagram of the active liquid cooling circuit principle of the present invention; Figure 3 This is a schematic diagram of the passive siphon circuit principle of the present invention; Figure 4 This is a schematic diagram of the integrated heat dissipation and load-bearing lower shell structure of the present invention. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] See attached document Figure 1 The present invention provides a liquid cooling system for a new energy vehicle, comprising: a physical structural unit, a fluid power unit, and a sensing and control unit.

[0028] The physical structural unit includes an integrated heat dissipation and load-bearing lower housing and a three-dimensional composite heat dissipation structure. The integrated heat dissipation and load-bearing lower housing supports the battery module and integrates internal cooling channels. The three-dimensional composite heat dissipation structure consists of the integrated heat dissipation and load-bearing lower housing and a capillary network on the sidewalls of the battery cells, used for surrounding heat dissipation of the cells. The design of the three-dimensional composite heat dissipation structure adopts an integrated design concept, directly replacing the module side plates, module end plates, and module brackets in traditional battery packs. The deep integration of the three-dimensional composite heat dissipation structure eliminates a large number of unnecessary parts, simplifies the battery pack structure, reduces the battery pack weight, increases the energy density of the battery pack, and reduces the vehicle weight.

[0029] The fluid power unit comprises two parallel cooling loops: an active liquid cooling loop and a passive siphon loop. The active liquid cooling loop includes an electric water pump, solenoid valves, and an external radiator, used for forced circulation cooling under high load conditions. The passive siphon loop includes a siphon generator and a condenser, used to achieve autonomous circulation of coolant under low load conditions or when the active loop fails, utilizing phase change and gravity. The active liquid cooling loop and the passive siphon loop are physically connected and isolated by parallel valves, ensuring that the two modes can operate independently and seamlessly switch between them under specific fault conditions, forming a dual-mode redundant fluid transport network.

[0030] The sensing and control unit comprises a three-level distributed sensing network and a control center (e.g., a battery management system, BMS). The three-level distributed sensing network monitors key parameters such as temperature, pressure, and flow rate within the system (including cell-level, module-level, and system-level). The control center receives the sensing data, executes control algorithms, and sends control commands to actuators (such as electric water pumps and solenoid valves) in the active liquid cooling loop.

[0031] See attached document Figure 4 The integrated heat dissipation and load-bearing lower shell is made of high-strength aluminum alloy, specifically 6061-T6 aluminum alloy, and undergoes solution treatment followed by artificial aging. According to material performance testing, the selected 6061-T6 aluminum alloy has a tensile strength of 310 MPa, a yield strength of 276 MPa, an elongation of 12% to 17%, and a density of 2.7 g / cm³. 3 The 6061-T6 aluminum alloy has a thermal conductivity of 180 W / m·K and high reliability, meeting the 15-year service life requirement. The integrated heat dissipation and load-bearing lower shell is manufactured using vacuum brazing or 3D printing technology to ensure its structural strength and heat dissipation performance. The integrated heat dissipation and load-bearing lower shell features a double-layered hollow structure.

[0032] The upper layer of the integrated heat dissipation and load-bearing lower shell is in direct contact with the battery cell module, while the lower layer is isolated from the external environment. The cooling channel is located in the middle of the integrated heat dissipation and load-bearing lower shell. The internal channels of the double-layer hollow structure are arranged in a honeycomb array and feature a human vein-inspired flow channel design. This human vein-inspired flow channel design significantly increases temperature uniformity, reduces flow resistance, and improves heat exchange efficiency. The pore size of the honeycomb structure ranges from 8 mm to 12 mm (diameter of the inscribed circle of a regular hexagon), with 10 mm being the preferred value. A 10 mm pore size was chosen because it provides a compressive strength of 3 to 5 MPa in aluminum alloy materials while maintaining a relative density of approximately 0.08, achieving a balance between lightweight and high strength. The cross-sectional shape of the flow channel is rectangular. The cross-sectional area and channel length of the rectangular flow channel need to be designed based on the actual conditions of different vehicle applications, optimizing for structural strength and heat dissipation requirements. The pore size and channel height are matched to form multiple microchannels, increasing the heat exchange area while maintaining reasonable flow resistance. The flow channel serves as both a coolant passage and a structural reinforcing rib of the integrated heat dissipation and load-bearing lower shell, enhancing its mechanical load-bearing capacity and improving its resistance to bending, torsion, and impact.

[0033] To improve heat exchange efficiency, turbulence fins are installed inside the flow channel. The thickness of the turbulence fins is 0.3 mm to 0.5 mm, and the spacing is 1.5 mm to 2.0 mm, which is used to enhance the turbulence effect of the coolant.

[0034] The integrated heat dissipation and load-bearing lower housing incorporates both a coolant inlet and outlet. This integration reduces the need for external piping connections and lowers the risk of leakage. Furthermore, the integrated heat dissipation and load-bearing lower housing features threaded interfaces for mounting pressure and temperature sensors. These sensors are integrated within the flow channels for real-time monitoring of the cooling system's status. Fluororubber sealing rings are used at the interfaces to ensure the integrity of the fluid system's seal. The connection between the integrated heat dissipation and load-bearing lower housing and the new energy vehicle chassis employs a multi-point distributed fixing strategy. The integrated heat dissipation and load-bearing lower housing is connected to the chassis through multiple mounting points located in areas of high structural strength, such as flow channel intersections.

[0035] See attached document Figure 1The three-dimensional composite heat dissipation structure combines bottom cooling and side cooling. The bottom cooling section is formed by the upper inner wall of the integrated heat dissipation and support lower shell, which functions as a bottom cold plate. The side cooling section consists of a capillary network located on the side of the battery cell. A dense network of sidewall capillary tubes is arranged on the side of the battery cell, embedded in the heat dissipation framework of the battery module. The sidewall capillary tubes are small-diameter pipes, closely arranged between the battery cells, and in direct contact with the side of the battery cells. The bottom cold plate and the sidewall capillary network are interconnected, forming a unified coolant circulation system.

[0036] The sidewall capillary network consists of multiple microchannel copper tubes. Based on fluid dynamics and heat transfer optimization, the inner diameter of the microchannel copper tubes is selected between 1.5 mm and 3 mm to provide a large specific surface area while ensuring sufficient flow rate. The inner diameter of the microchannel copper tubes is 2 mm, and the outer diameter is 3 mm. The arrangement density of the sidewall capillary network on the side of the cell is one capillary tube every 10 mm to 20 mm along the height direction of the cell's side. For a standard cell with a height of 100 mm, 5 to 10 capillary tubes are arranged.

[0037] The sidewall capillary network contacts the battery cell via a thermally conductive interface material (TIM) to ensure minimal thermal resistance. Specifically, thermally conductive silicone grease or adhesive is filled between the battery cell side and the microchannel copper tube, with the thickness controlled between 0.1 mm and 0.2 mm. The microchannel copper tube is fixed using mechanical clamping or bonding to ensure a contact pressure between 0.5 MPa and 1 MPa to reduce contact thermal resistance.

[0038] The coolant flows through the integrated lower casing channel and the side capillary network simultaneously over the bottom and sides of the battery cell. This three-dimensional composite heat dissipation structure achieves three-dimensional, enveloping heat dissipation for the battery cell. The coolant enters the bottom cold plate from the coolant inlet, flows within the cold plate, and absorbs heat from the bottom of the battery cell. Then, the coolant is distributed to the side capillary networks on each side, where it exchanges heat with the sides of the battery cell, further absorbing heat. Finally, the coolant flows from the side capillary networks to the coolant outlet, completing one cycle.

[0039] When this invention is applied to different vehicle platforms, such as from a sedan platform to an SUV platform, the overall size of the battery pack changes. The sidewall capillary network adopts a modular splicing method, increasing the number of parallel capillary modules to accommodate changes in battery pack length. During modular adjustments, the hydraulic diameter of a single capillary remains unchanged, ensuring that the flow resistance and heat transfer characteristics of the coolant within the capillary are consistent across different vehicle models, reducing the complexity of recalibrating control parameters.

[0040] See attached document Figure 2The active liquid cooling circuit is used to handle high heat load conditions, such as when the battery is fast charging or the vehicle is traveling at high speed. The circuit uses a mixed solution of ethylene glycol and deionized water as the circulating working fluid, with a volume ratio of 50:50. The freezing point of the mixed solution is below -35 degrees Celsius, and the boiling point is above 108 degrees Celsius.

[0041] To adapt to special scenarios, a PTC (Positive Temperature Coefficient) heater is integrated into the active liquid cooling circuit. The PTC heater is integrated within the battery pack and combined with the coolant circuit, placing the PTC heater in the coolant. When the battery temperature falls below a set threshold (e.g., 5 degrees Celsius), the control center activates the PTC heater to heat the coolant until the battery temperature reaches above 10 degrees Celsius, at which point heating stops. The PTC heater preheats the battery in low-temperature environments, raising its temperature and placing it in a suitable operating environment, effectively improving charge / discharge efficiency and performance, and extending battery life.

[0042] The active liquid cooling circuit circulates coolant via an electronic water pump. The process is as follows: coolant enters through the main inlet, flows through the integrated heat dissipation and load-bearing lower casing for basic cooling, and is then distributed via a solenoid valve and pumped through a quick-connect connector into the capillary network on the side walls of the three-dimensional heat dissipation frame. This network surrounds the battery cells from the side, and after sufficient heat absorption, the coolant collects at the main outlet and flows out, completing the circulation. At the external radiator, a cooling fan is connected to the control center. Based on the difference between the coolant outlet temperature and the ambient temperature, the control center linearly adjusts the cooling fan speed via a PWM signal. When the coolant temperature is high, the cooling fan speed increases to enhance heat dissipation; when the coolant temperature is low, the cooling fan speed decreases or shuts off.

[0043] The active liquid cooling circuit features zoned control, enabling targeted cooling of localized hotspots. The Battery Management System (BMS) identifies localized hotspots based on sensing data. Specific criteria are: first, the temperature of a single cell exceeds the average temperature by 5 degrees Celsius; second, the temperature gradient in a certain area exceeds 3 degrees Celsius per centimeter; third, the temperature change rate of a certain cell exceeds 2 degrees Celsius per minute. If any of these conditions are met, the detected area is determined to be a hotspot area.

[0044] For hotspot areas, the control center outputs control signals to adjust the opening degree of the corresponding branch solenoid valves. The solenoid valve opening adjustment ratio is controlled by PID based on the temperature deviation. The adjustment logic is as follows: ; Where: opening degree represents the real-time opening degree adjustment target value of the solenoid valve; base opening degree represents the default opening degree value of the solenoid valve in the non-adjustment state, which is usually set to 50% to maintain the basic cooling flow. This represents the proportional adjustment coefficient, used for real-time adjustment based on the current temperature deviation. This represents the integral adjustment coefficient, used to eliminate steady-state temperature errors in the system. This represents the differential adjustment coefficient, used to make advance adjustments based on the rate of change of temperature deviation; This represents the difference between the current detected temperature of the hotspot area and the system's set target temperature. Represents a time variable; Represents the time infinitesimal element, and represents the difference. The variable to be integrated is the variable into which the error is accumulated over time; Indicates the difference Over time The rate of change of temperature, i.e., the speed at which temperature changes.

[0045] When the calculated opening ratio is positive, the solenoid valve opening ratio increases, reaching a maximum opening of 100%. When the calculated opening ratio is negative, the solenoid valve opening ratio decreases, reaching a minimum opening of 10%, to prevent insufficient cooling due to complete closure. The solenoid valve is a direct-acting proportional solenoid valve with a full-stroke response time of less than or equal to 50 milliseconds and a maximum operating pressure of 3.5 bar. For extreme high-temperature or ultra-fast charging conditions, the active liquid cooling circuit is also coupled with a chiller. When the external radiator cannot meet the cooling requirements, the control center requests the air conditioning system to intervene, controlling the start of the air conditioning compressor and adjusting the electronic expansion valve and compressor speed to control the cooling capacity. The chiller forcibly lowers the coolant temperature, achieving deep cooling.

[0046] See attached document Figure 3 The passive siphon circuit is used in low-load conditions or to provide safety redundancy when the active liquid cooling circuit fails. When the heat load is low, the system will prioritize the use of the passive siphon circuit to maintain temperature balance in a zero-energy manner, thereby improving the energy utilization efficiency of the whole vehicle. The operation of the passive siphon circuit does not consume external electrical energy.

[0047] The working medium in the passive siphon circuit is a low-boiling-point phase change medium. Specifically, HFE-7100 was chosen as the working medium, with a boiling point of 61 degrees Celsius. This boiling point falls within the upper limit of the battery's operating temperature range. When the battery temperature reaches 50 to 60 degrees Celsius, the working medium begins to boil, generating vapor to drive the cycle.

[0048] The working principle of the passive siphon circuit is based on heat-driven natural circulation. The natural circulation process includes the following physical stages: The first stage is heat absorption and evaporation. The heat generated by the battery cell is transferred to the capillary network on the side wall, causing the liquid working fluid in contact with the heat source to absorb latent heat and boil and vaporize. The working fluid expands in volume and decreases in density, forming a vapor-liquid two-phase mixture. The second stage is gas-liquid separation and rising. The mixture of the vaporized working fluid and the unevaporated liquid working fluid flows upward into the siphon generator under the action of buoyancy due to the density difference. Gas-liquid separation is completed in the siphon generator, and the gas working fluid continues to rise. The third stage is condensation and reflux. The gas working fluid flows to the condenser located at a higher position under the drive of the pressure difference. In the condenser, it releases heat to the external environment and condenses into a liquid phase. The liquid working fluid returns to the heat source side of the battery cell along the reflux pipeline under the action of gravity, completing the closed-loop circulation. The circulation process has self-regulating characteristics. The higher the battery cell temperature, the more intense the evaporation of the working fluid, the greater the driving pressure difference, the faster the circulation flow rate, and the enhanced heat dissipation capacity.

[0049] The activation condition of the passive siphon circuit is based on a temperature difference threshold. When the temperature difference between the sidewall capillary network and the condenser is greater than or equal to 5 degrees Celsius, the passive siphon circuit enters a self-sustaining cycle state.

[0050] See attached document Figure 1 A three-level distributed sensing network is used to monitor the operating status of the battery system in real time and provide data input to the control center (BMS).

[0051] The first layer of the three-level distributed sensing network is the cell-level sensing layer, which deploys four temperature sensors in each cell. This layer monitors the temperature of key nodes within a single cell using multiple temperature sensors: at the root of the positive terminal, it monitors the heat generated by the contact resistance at the connection point; at the root of the negative terminal, it monitors the temperature at the current output point; at the center of the side of the cell, it monitors the core temperature; and at the center of the bottom, it monitors a reference temperature for cooling effectiveness. Additionally, the cell-level sensing layer also monitors the cell's voltage.

[0052] The second layer of the three-level distributed sensing network is the module-level sensing layer. The module-level sensing layer monitors the temperature gradient by placing one temperature sensor at each of the four corners of the module and one temperature sensor at the center of the module, forming a five-point temperature field monitoring network. At the same time, the module-level sensing layer also monitors the total voltage of the battery module, including sampling the positive and negative voltages of each cell and monitoring the total voltage of the module.

[0053] The third layer of the three-tier distributed sensing network is the system-level sensing layer. This layer monitors the operating parameters of the cooling system, including coolant inlet temperature sensors, coolant outlet temperature sensors, main circuit flow sensors, flow sensors for each zone branch, a system pressure sensor array, and leak detection acoustic sensors. The system-level sensing layer also monitors environmental parameters, such as internal and external ambient temperature sensors for the battery pack, and internal humidity sensors. Furthermore, the overall electrical parameters of the battery pack, such as the total current sensor, total voltage sampling circuit, and insulation resistance monitoring, are also monitored by the system-level sensing layer.

[0054] The Business Management System (BMS), as the core of the perception and control unit, receives and processes all data collected by the three-level distributed perception network. The BMS employs an automotive-grade 32-bit multi-core microcontroller with a clock frequency of at least 300 MHz and a floating-point unit (FPU). The hardware architecture of the BMS includes signal acquisition inputs, a core processing unit, and actuator drive outputs. The signal acquisition inputs are equipped with multiple analog-to-digital converters (ADCs) and communication interfaces to receive analog temperature signals from NTC thermistors, voltage signals from pressure and flow sensors, and current signals from current Hall effect sensors. The core processing unit runs control algorithms. The actuator drive outputs are equipped with an H-bridge drive circuit and a PWM generator to send adjustable duty cycle PWM control signals to the electric water pump, on / off or proportional adjustment signals to the solenoid valve, and speed control signals to the external cooling fan. It also has the ability to send request signals to the vehicle control unit (VCU) and air conditioning control unit (ACU) via the CAN bus, forming a complete closed-loop hardware control link.

[0055] Under high-load conditions, the Battery Management System (BMS) employs a Model Predictive Control (MPC) strategy. Based on a thermodynamic model of the battery, MPC predicts future temperature changes and formulates optimal control actions. A key aspect of the MPC algorithm is constructing an accurate battery temperature prediction model and updating its parameters in real-time to adapt to environmental changes. The goal of MPC is to find an optimal balance between maintaining the desired battery temperature and reducing energy consumption. The BMS calculates future control inputs using an optimization algorithm, and the MPC algorithm optimizes the battery's temperature response and system energy efficiency by adjusting the control inputs in real-time. The objective function of the MPC strategy is shown below: ; in: The predicted battery temperature is represented by time t; Indicates the desired battery temperature; Indicates control inputs (such as the flow rate of the cooling medium or the fan speed); and It serves as a weighting factor, used to balance the accuracy of temperature control with energy consumption.

[0056] Machine learning predictive models are used to improve the adaptability of control strategies to complex operating conditions. The system's real-time data-driven decision-making further enhances the intelligence level of the temperature management system. By integrating sensor data, historical maintenance records, and environmental information, it can assess the battery's thermal risk and performance status in real time. Utilizing big data analytics and machine learning techniques, key influencing factors for temperature management can be extracted from the data, and control strategies can be adjusted in real time. The machine learning predictive model uses a set of real-time collected state variables... As input. State variables. This includes the battery's current temperature, charging / discharging current, terminal voltage, and ambient temperature.

[0057] Machine learning prediction models use a pre-trained function and a set of model parameters For state variables The process involves processing the data to output a predicted control value. Specifically, a random forest or neural network model is used to predict the battery's temperature response and dynamically adjust the control parameters. The model's prediction function is expressed as follows: ; in: The predictive control output of the model is used for feedforward control of the actuators in the active liquid cooling loop or as a reference for subsequent closed-loop regulation. The machine learning predictive model can not only react according to the current state, but also predict and prevent potential thermal problems, thereby achieving more proactive and precise temperature control.

[0058] During the real-time execution phase, the Battery Management System (BMS) uses a PID algorithm to perform closed-loop regulation of the actuators. The goal of the PID algorithm is to maintain the battery temperature within the desired range. During operation, the battery temperature and coolant temperature are continuously monitored and compared with the target temperature. The BMS adjusts the actuator's actions in real time using the PID control algorithm. The BMS first calculates the set threshold data. Temperature data detected by a three-level distributed sensing network Error value between The formula for calculating the error value is as follows: ; in, It sets a threshold data. The temperature data is detected by the temperature baseline, and then the control center uses the error value... Calculate output quantity Output It is used to adjust the speed of the electric water pump or the opening of the solenoid valve in the active liquid cooling circuit, and to control and regulate the battery thermal management unit, motor thermal management unit, and vehicle electronic equipment thermal management unit. The controller output calculation formula is as follows: ; Among them: here, This is the proportional gain, used for real-time adjustment based on the current error; The integral gain is used to eliminate the long-term steady-state error of the system, where For error in time up to the current time The cumulative integral; This is the differential gain, used for predictive adjustment based on the rate of change of the error; In time Error value at time; For the controller in time Output at any given moment; This is a differential operator that takes the derivative with respect to time. Simultaneously, the system monitors the coolant flow rate and pressure to ensure the circuit operates normally. If an anomaly is detected, such as insufficient flow, the system increases the water pump speed or issues an alarm.

[0059] See attached document Figure 1 When a new energy vehicle is charged at room temperature, the liquid cooling system is activated. The Business Management System (BMS) first performs a system self-test to confirm that the electronic water pump, solenoid valves, and sensors in the active liquid cooling circuit are functioning correctly. The system self-test includes: checking whether the electronic water pump, solenoid valves, fans, and sensors are functioning correctly; checking whether the coolant level and pressure are within the normal range; and checking whether the circuit communication is normal. If the self-test passes, the system enters standby mode; otherwise, it reports a fault and takes appropriate safety measures.

[0060] After self-testing, the three-level distributed sensing network begins real-time collection of key operational data such as temperature, voltage, and current at each level (cell, module, system) within the battery pack. The Battery Management System (BMS) receives this key operational data and, based on charging current and battery heat generation rate information, determines the current charging condition as a high-load condition. The BMS, based on this key operational data and thermal management strategies, determines the current operating condition, such as normal driving, fast charging, or rapid acceleration. Simultaneously, the BMS sets a target temperature based on the battery charging characteristics. Under fast charging conditions, stronger cooling is required, with a target temperature set at 25℃. Under normal driving conditions, the target temperature is set at 30℃. The cooling requirement calculation takes into account the current battery temperature, temperature rise rate, and temperature difference.

[0061] For high-load conditions, the Battery Management System (BMS) activates the active liquid cooling loop. The electric water pump starts running, driving the coolant to circulate in the loop. The coolant first flows through the internal channels of the integrated heat dissipation and heat-bearing lower casing, transferring heat to the bottom of the battery module. Subsequently, the coolant absorbs heat from the sides of the battery cell through the capillary network on the side walls of the three-dimensional composite heat dissipation structure, achieving three-dimensional surround heat dissipation for the battery cell.

[0062] The Business Management System (BMS) invokes Model Predictive Control (MPC) and Machine Learning (ML) prediction algorithms, combined with the current system state. Based on the predictive model, initial control commands for the electric water pump speed and solenoid valve opening are generated. Solenoid valve opening control command The aim is to bring the battery temperature close to the target temperature. And optimize energy consumption.

[0063] During charging, a three-level distributed sensing network continuously monitors the cell temperature. When the battery management system (BMS) detects that the temperature rise rate of a local cell is too rapid or exceeds a preset threshold, it is identified as a local hotspot. The BMS then adjusts the opening of the solenoid valve in the corresponding hotspot branch to increase the coolant flow and enhance cooling of the local hotspot. Simultaneously, the BMS uses real-time temperature data... With the set target temperature Error between The control command is adjusted through a PID feedback control algorithm. Dynamic adjustments are made to ensure that the battery temperature remains stable within the optimal operating range.

[0064] See attached document Figure 1 When a new energy vehicle is operating under low load, such as constant speed cruising or long-term parking standby, the heat generated by the battery system is relatively low. At this time, the control center (BMS) determines, based on the temperature data collected by the three-level distributed sensing network, that the battery module temperature is within an acceptable range and the heat load has not reached the activation threshold of the active liquid cooling circuit.

[0065] Under such low heat load conditions, in order to reduce energy consumption and ensure basic battery temperature management, the battery management system (BMS) decides to activate the passive siphon circuit. The passive siphon circuit does not require external power to drive it and operates based on the thermally driven natural circulation.

[0066] Specifically, the small amount of heat generated by the battery cell is absorbed by the liquid working fluid in the passive siphon circuit, causing the liquid working fluid to evaporate at the contact point with the heat source. The vaporized working fluid has a lower density than the liquid working fluid, creating a driving pressure difference in the siphon generator. This driving pressure difference drives the vaporized working fluid to flow to the condenser. In the condenser, the vaporized working fluid releases heat to the external environment and condenses into a liquid phase. Subsequently, the liquid working fluid flows back to the heat source side of the battery cell by gravity, completing the cooling cycle and thus achieving energy-free heat dissipation of the battery system.

[0067] When the Battery Management System (BMS) detects a temperature difference of 5 degrees Celsius or greater between the sidewall capillary network and the condenser via a three-level distributed sensing network, it indicates that the passive siphon circuit has entered a self-sustaining cycle. The passive siphon circuit continuously transfers heat, effectively managing battery temperature without consuming additional energy, reducing overall system energy consumption, and providing safety redundancy for the active liquid cooling circuit.

[0068] See attached document Figure 1 This invention also provides a method for controlling a liquid cooling system in a new energy vehicle, specifically including: Step S1: After the liquid cooling system of the new energy vehicle is powered on or woken up, the Business Management System (BMS) first performs a system self-test to check whether the electronic water pump, solenoid valve, and sensors of the three-level distributed sensing network in the active liquid cooling circuit are working properly. The self-test process also includes consistency verification of sensor signals to eliminate the risk of sensor drift or failure. In addition, the self-test program covers the verification of the cooling fan function to confirm whether the cooling fan can respond normally to the speed control command; at the same time, it reads the system pressure sensor data to determine whether the coolant level and pressure are within the normal operating range, and performs a handshake test on the circuit communication link between the BMS and each actuator to ensure the real-time and accuracy of control command transmission.

[0069] Step S2: After the self-test is completed, the three-level distributed sensing network begins to continuously collect system data, including temperature baseline detection data. and as state variables The data collected includes real-time temperature distribution of each cell in the battery pack obtained through NTC thermistors, as well as fluid dynamic parameters obtained through flow meters and pressure sensors. In addition, the system also reads the battery state of charge (SOC) and the external ambient temperature as key inputs for assessing the current thermal load potential of the battery.

[0070] Step S3: The Battery Management System (BMS) receives sensing data in real time and determines the current vehicle operating condition based on the data. The determination logic includes: determining whether the vehicle is under low load, determining whether it is under high load, and determining whether localized hot spots are detected. The determination is based on a combination of battery charging / discharging current, battery temperature rise rate, and vehicle driving status. Simultaneously, the BMS calculates the desired battery temperature based on the operating conditions. The process of determining the operating conditions takes into account both the rate of temperature rise and the temperature difference data between the cells, thereby identifying rapid acceleration and transient high load scenarios.

[0071] Step S4: The control center selects the cooling path based on the operating condition determination result. If the determination result is a low-load condition, the control center issues a command to shut down the electric water pump, open the passive loop valve, and decide to activate the passive siphon loop. If the determination result is a high-load condition, the control center issues a command to start the electric water pump and decides to activate the active liquid cooling loop. If a local hot spot is detected during the operation of the active liquid cooling loop, the zone-enhanced cooling logic is entered; otherwise, the uniform cooling logic is maintained.

[0072] Step S5: When the active liquid cooling loop is activated, the control center invokes the Model Predictive Control (MPC) algorithm and the Machine Learning (ML) predictive algorithm to generate the initial control output. Initial control output It covers the setting of the cooling medium flow rate and the adjustment command of the cooling fan speed. The model predictive control algorithm constructs an accurate battery temperature prediction model and updates the model parameters in real time. Under the premise of meeting the temperature control accuracy, it calculates the optimal combination of control inputs, thereby optimizing the battery's temperature response characteristics and improving the overall energy efficiency ratio of the system.

[0073] Step S6: When the control center detects a fault in the active liquid cooling circuit (e.g., electric water pump failure, coolant leakage causing a sudden pressure drop or abnormal flow), the control center triggers a safety redundancy strategy. If the main pump fails, the backup pump is started or the battery power is reduced to decrease the heat load. If there is a coolant leak, the solenoid valve is closed, the leak area is isolated, and an alarm is triggered. If the temperature is too high, the battery power is limited, and the cooling system is activated to the maximum extent. If the active circulation is confirmed to have completely failed, the electric water pump power is immediately cut off, the passive siphon circuit is opened, and a forced switch to passive siphon circuit operation is initiated. A power limiting request is sent to the vehicle controller to limit the battery charging and discharging power to reduce heat generation, putting the vehicle into a safe limp mode to ensure safe driving in fault mode until a safe stop. In addition, the system also has thermal runaway warning and suppression functions. When an abnormal increase in the temperature of a battery cell is detected, and thermal runaway is determined to have occurred, the system will increase the coolant flow to the cooling circuit where the cell is located, activate the emergency cooling mode, and simultaneously cut off the battery charging circuit.

[0074] Step S7: During the execution of the cooling path, the control center continuously collects temperature data. and compare it with the set threshold data. Comparison, using the error calculation formula The error value is obtained. Subsequently, the control center uses a PID feedback adjustment algorithm to adjust the control based on the error value. Dynamically adjust control output This enables real-time closed-loop regulation of the cooling system. The closed-loop regulation process is a continuous cycle that continues until the vehicle is powered off or enters a dormant state.

Claims

1. A liquid cooling system for a new energy vehicle, characterized in that, include: A physical structural unit, a fluid dynamics unit, and a sensing and control unit; The physical structure unit includes a heat dissipation and load-bearing integrated lower shell and a three-dimensional composite heat dissipation structure. The heat dissipation and load-bearing integrated lower shell is used to support the battery module and integrates internal cooling channels. The three-dimensional composite heat dissipation structure is composed of the heat dissipation and load-bearing integrated lower shell and the side wall capillary network disposed on the side of the battery cell, which is used to surround the battery cell for heat dissipation. The fluid power unit includes an active liquid cooling circuit and a passive siphon circuit connected in parallel. The active liquid cooling circuit includes an electric water pump, a solenoid valve, and an external radiator for forced circulation cooling. The passive siphon circuit includes a siphon generator and a condenser for autonomous circulation of coolant using phase change and gravity. The active liquid cooling circuit and the passive siphon circuit are connected and isolated by parallel valves. The sensing and control unit includes a three-level distributed sensing network and a control center. The three-level distributed sensing network is used to monitor temperature, pressure and flow parameters within the system. The control center is used to receive sensing data and send control commands to the actuators in the active liquid cooling circuit.

2. The liquid cooling system for a new energy vehicle according to claim 1, characterized in that, The integrated heat dissipation and load-bearing lower housing adopts a double-layer hollow structure design. The upper layer of the double-layer hollow structure is in contact with the battery cell module, while the lower layer is isolated from the external environment. The middle layer is the internal cooling channel, which is arranged in a honeycomb array. Turbulence fins are provided inside the channel. The integrated heat dissipation and load-bearing lower housing also integrates a coolant inlet, a coolant outlet, and threaded interfaces for installing pressure sensors and temperature sensors.

3. The liquid cooling system for a new energy vehicle according to claim 1, characterized in that, The sidewall capillary network is embedded in the heat dissipation skeleton of the battery module and is closely arranged between the cells. The sidewall capillary network is composed of multiple microchannel copper tubes. The microchannel copper tubes are in contact with the side of the cell through a thermally conductive interface material. The three-dimensional composite heat dissipation structure forms a bottom cold plate through the upper inner wall of the integrated heat dissipation and support lower shell. The coolant enters the bottom cold plate through the coolant inlet, then flows into the sidewall capillary network, and finally converges to the coolant outlet, forming a three-dimensional surround heat dissipation for the bottom and sides of the cell.

4. The liquid cooling system for a new energy vehicle according to claim 1, characterized in that, The active liquid cooling circuit integrates a positive temperature coefficient heater, which is combined with the coolant circuit. The active liquid cooling circuit uses a mixed solution of ethylene glycol and deionized water as the circulating working fluid. The control center adjusts the speed of the cooling fan at the external radiator through a pulse width modulation signal based on the difference between the coolant outlet temperature and the ambient temperature.

5. The liquid cooling system for a new energy vehicle according to claim 1, characterized in that, The control center is configured to adjust the opening of the corresponding branch solenoid valve for local hot spots. The adjustment logic adopts proportional-integral-derivative control. The real-time opening adjustment target value of the solenoid valve is the sum of the basic opening, proportional adjustment, integral adjustment and derivative adjustment. The proportional adjustment is calculated based on the current temperature deviation, the integral adjustment is calculated based on the accumulation of temperature deviation over time, and the derivative adjustment is calculated based on the rate of change of temperature deviation over time. The temperature deviation is the difference between the detected temperature of the hot spot area at the current moment and the system set target temperature.

6. The liquid cooling system for a new energy vehicle according to claim 5, characterized in that, The active liquid cooling circuit is also coupled with a cooler. When the external radiator cannot meet the cooling requirements, the control center requests the air conditioning system to intervene, controls the air conditioning compressor to start and adjusts the electronic expansion valve, and lowers the coolant temperature through the cooler. The solenoid valve is a direct-acting proportional solenoid valve.

7. The liquid cooling system for a new energy vehicle according to claim 1, characterized in that, The passive siphon circuit is filled with a low-boiling-point phase change medium as the working fluid. The working principle of the passive siphon circuit is as follows: the heat generated by the battery cell is transferred to the capillary network on the side wall, causing the liquid working fluid to absorb heat and evaporate, forming a gas-liquid two-phase mixed fluid. Under the action of density difference buoyancy, the mixed fluid enters the siphon generator for gas-liquid separation. The gas phase working fluid rises and flows to the condenser. After the gas phase working fluid is condensed into a liquid phase in the condenser, it returns to the heat source side of the battery cell along the return pipeline under the action of gravity.

8. The liquid cooling system for a new energy vehicle according to claim 1, characterized in that, The three-level distributed sensing network includes a cell-level sensing layer, a module-level sensing layer, and a system-level sensing layer. The cell-level sensing layer is used to monitor the temperature at the root of the positive electrode post, the root of the negative electrode post, the center of the side, and the center of the bottom of a single cell. The module-level sensing layer is used to monitor the temperature field distribution at the four corners and the center of the battery module. The system-level sensing layer is used to monitor the inlet and outlet temperatures and flow rate of the coolant, system pressure, leak detection acoustic waves, ambient temperature, and overall electrical parameters of the battery pack.

9. A liquid cooling system for a new energy vehicle according to claim 1, characterized in that, The hardware architecture of the control center includes a signal acquisition input terminal, a core processing unit, and an actuator drive output terminal. The signal acquisition input terminal is equipped with an analog-to-digital converter and a communication interface. The actuator drive output terminal is equipped with a full-bridge drive circuit and a pulse width modulation generator for controlling the electronic water pump, the solenoid valve, and the cooling fan. The control center is also configured to send request signals to the vehicle controller via the controller local area network bus.

10. A liquid cooling control method for a new energy vehicle, applied to the liquid cooling system of a new energy vehicle as described in any one of claims 1-9, characterized in that, Includes the following steps: S1: After the system is powered on or woken up, the control center performs a system self-test to check the working status of the active liquid cooling circuit components and the three-level distributed sensing network sensors. S2: After the self-test is completed, the three-level distributed sensing network collects temperature baseline detection data and state variable data, including battery temperature, charging and discharging current and ambient temperature. S3: The control center determines the current vehicle operating condition based on the collected data. The operating condition includes low load condition, high load condition, and whether local hot spots are detected. S4: The control center selects the cooling path based on the operating condition judgment result: if it is a low load condition, the passive siphon circuit is activated; if it is a high load condition, the active liquid cooling circuit is activated; if a local hot spot is detected during the operation of the active liquid cooling circuit, the zoned enhanced cooling logic is entered. S5: When the active liquid cooling loop is activated, the control center calls the model predictive control algorithm and the machine learning predictive algorithm to generate the initial control output; S6: When a fault is detected in the active liquid cooling circuit, the control center triggers a safety redundancy strategy, switches to passive siphon circuit operation, and limits battery power; S7: During the execution of the cooling path, the control center continuously calculates the error value between the temperature data and the set threshold data, and uses the proportional-integral-derivative feedback adjustment algorithm to dynamically adjust the control output according to the error value.

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