Electric vehicle thermal management system based on thick-film resistance water heater and control method

Abstract

The invention discloses an electric vehicle thermal management system based on a thick-film resistance water heater and a control method, the electric vehicle thermal management system comprises a heater, an electronic water pump, an electromagnetic valve, a sensor assembly and a control unit, the heater is internally provided with a heat-conducting fluid and at least three thick-film resistance units which are used for heating the heat-conducting fluid and are connected in parallel; the electromagnetic valve is connected with a water inlet of the whole vehicle waterway and a water outlet of the heater; the sensor assembly is used for detecting the temperature value of the heater, the flow value of the heater outlet and the pressure values of the heater inlet and the water pump outlet. The control unit is electrically connected with the thick-film resistor unit, the electronic water pump, the electromagnetic valve and the sensor assembly. The control unit adjusts operation parameters of the thick film resistor unit, the electromagnetic valve and the electronic water pump according to the temperature value, the flow value and the pressure value. By actively detecting the running state of the system and adjusting the working parameters in real time, the system is effectively protected, and the safety of the system is improved.

Description

Technical Field

[0001] The present invention relates to a thermal management system and a control method for an electric vehicle based on a thick film resistor water heater, belonging to the technical field of thermal management of new energy vehicles. Background Art

[0002] Currently, electric vehicles primarily use WPTC (positive temperature coefficient thermistor) heaters, which rely on the principle that resistance increases with temperature, thus achieving self-current limiting. However, this technology has the following drawbacks: Slow thermal response: The WPTC resistor material has large thermal inertia, and it takes more than 30 seconds from startup to stable output, which cannot meet the rapid heating requirements in low-temperature environments (such as -30°C cold start); Low energy efficiency: WPTC needs to operate at full power for a long time at low temperatures. The measured energy consumption is 40% to 50% higher than that of thick-film resistor solutions, which seriously shortens the vehicle's driving range. Strong dependence on antifreeze circulation: If there is air in the pipeline or the antifreeze is not full, the temperature of the local area of ​​WPTC will rise sharply (>200℃) due to poor heat dissipation, posing a risk of burning; Short lifespan: Frequent start-stop and temperature shock can easily cause cracking of the PTC ceramic piece, and the average lifespan is only 5 years.

[0003] Therefore, in some cases, thick-film resistor water heaters are used as a solution. Although thick-film resistors offer excellent performance, their safety is highly dependent on the circulation of antifreeze fluid. If there is air in the pipe or the fluid level is insufficient, localized areas of the ceramic tube may instantly heat up to over 500°C due to dry heating, causing them to burst. Existing technologies lack active detection and protection mechanisms, a key issue hindering their commercial application. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art and provide an electric vehicle thermal management system and control method based on a thick film resistor water heater, aiming to achieve effective protection of the system by actively detecting the operating status of the system and adjusting the operating parameters in real time.

[0005] To achieve the above object, the present invention is implemented by adopting the following technical solutions: In a first aspect, the present invention provides an electric vehicle thermal management system based on a thick film resistor water heater, comprising: A heater having a built-in heat transfer fluid and at least three thick film resistor units connected in parallel for heating the heat transfer fluid; An electronic water pump, which is respectively connected to the water inlet of the heater and the water outlet of the entire water circuit of the electric vehicle; Solenoid valves, which are respectively connected to the water inlet of the vehicle water circuit and the water outlet of the heater; A sensor assembly for detecting actual operating parameters of the heater and the water pump; a control unit electrically connected to the thick film resistor unit, the electronic water pump, the solenoid valve, and the sensor assembly; The control unit adjusts the set operating parameters of the thick film resistor unit, the solenoid valve and the electronic water pump according to the actual operating parameters and the preset trigger conditions.

[0006] Furthermore, the sensor assembly includes temperature sensors arranged axially at intervals along the thick film resistor unit and respectively used to detect the temperature values ​​of the upper section, middle section, and lower section of the heater, a flow sensor for detecting the flow value of the heater outlet, and a pressure sensor for detecting the heater inlet pressure value, heater outlet pressure value, and water pump outlet pressure value.

[0007] Furthermore, the upper temperature value, the middle temperature value, and the lower temperature value are represented by T1, T2, and T3 respectively; The axial temperature difference ΔT_axial is calculated using the following formula: ΔT_axial = T_max – T_min; Where, T_max represents the highest value among T1, T2, and T3, and T_min represents the lowest value among T1, T2, and T3; The control unit adjusts the operating parameters of the thick film resistor unit, the solenoid valve and the electronic water pump according to the axial temperature difference, the upper temperature value, the middle temperature value and the lower temperature value and the preset trigger conditions.

[0008] Furthermore, the control unit adjusts the operating parameters of the thick film resistor unit, the solenoid valve, and the electronic water pump according to the axial temperature difference, the upper temperature value, the middle temperature value, the lower temperature value, and the preset trigger condition value, including: Level 1 alarm: If ΔT_axial>3°C and lasts for 5 seconds, the control unit controls the thick film resistor unit to reduce the power by 10%; Level 2 alarm: If ΔT_axial>5°C or single-point temperature>95°C, the control unit controls the thick film resistor unit to reduce power by 30% and increases the water pump speed to 80% of the full speed; Emergency stop: If ΔT_axial>10℃ or T_max>105℃, the control unit immediately cuts off the power supply of all thick film resistor units and increases the water pump speed to full speed.

[0009] Furthermore, when the electric vehicle thermal management system is powered on for the first time, the control unit sends a command to close the solenoid valve and start the electronic water pump to run at a preset minimum speed for 5 seconds.

[0010] Furthermore, after the control unit sends a command to close the solenoid valve and start the electronic water pump to run at a preset minimum speed for 5 seconds, the control unit turns on the first thick film resistor unit to heat at a 10% PWM duty cycle for 30 seconds; Record the flow rate Q1 and temperature gradient ΔT1 at the heater outlet, and ΔT1 = T1 - T3; Among them, when Q1<0.3 L / min and ΔT1>5℃, it is determined that there is air resistance in the pipeline and the control unit enters the exhaust mode.

[0011] Furthermore, the exhaust mode includes: The control unit turns off the first thick film resistor unit, increases the speed of the water pump and performs exhaust.

[0012] Furthermore, when the flow rate value Q1 at the heater outlet is ≥0.5 L / min or ΔT1 ≤ 2° C., the control unit turns on the first thick film resistor unit, the second thick film resistor unit, and the third thick film resistor unit, and increases the total power to 30%.

[0013] Furthermore, the control unit collects the pressure fluctuation ΔP and the temperature rise rate ΔT / Δt of each section of the upper section, middle section, and lower section; Where ΔP = P_in - P_out, P_in represents the heater inlet pressure, P_out represents the heater outlet pressure, and ΔT represents the temperature change of the upper, middle, or lower section within a preset time period Δt. When ΔP continues to decrease and ΔT / Δt>5℃ / s, the control unit determines that the antifreeze fluid is insufficient and cuts off the power.

[0014] In a second aspect, the present invention provides a control method for an electric vehicle thermal management system based on a thick film resistor water heater, which is applicable to any of the above-mentioned electric vehicle thermal management systems based on a thick film resistor water heater; the method comprises the following steps: Detecting actual operating parameters of the heater and water pump through the sensor assembly; The control unit adjusts the set operating parameters of the thick film resistor unit, the solenoid valve and the electronic water pump according to the actual operating parameters and the preset trigger conditions.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides an electric vehicle thermal management system and control method based on a thick-film resistor water heater. By providing a heater with a built-in heat-conducting fluid and at least three parallel thick-film resistor units for heating the heat-conducting fluid, based on the excellent performance of the thick-film resistor units, thermal efficiency improvement and precise temperature control can be achieved.

[0016] The present invention also detects the actual operating parameters of the heater and water pump, and uses a control unit to adjust the set operating parameters of the thick film resistor unit, solenoid valve and electronic water pump according to the actual operating parameters and pre-set trigger conditions, thereby actively detecting the operating status of the system and adjusting the operating parameters in real time to achieve effective protection of the system and improve the safety of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a system architecture diagram of an electric vehicle thermal management system based on a thick film resistor water heater provided by an embodiment of the present invention; Figure 2 is a flow chart of antifreeze fluid status detection in an embodiment of the present invention (including low, medium and high power stage determination logic); Figure 3 is a timing diagram of ceramic tube axial temperature monitoring and power reduction control in an embodiment of the present invention; Figure 4 is a logic block diagram of waste heat recovery in an embodiment of the present invention; Figure 5 This is a logic block diagram of the SOC linkage control in an embodiment of the present invention. DETAILED DESCRIPTION

[0018] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0019] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0020] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances. Example

[0021] See also Figure 1 This embodiment introduces an electric vehicle thermal management system based on a thick film resistor water heater, including: a heater, an electronic water pump, a solenoid valve, a sensor assembly and a control unit.

[0022] Specifically, the heater contains a heat transfer fluid and four parallel thick-film resistor units (units 1, 2, 3, and 4) for heating the fluid. An electronic water pump is connected to the heater's water inlet and the electric vehicle's water system outlet. A solenoid valve is connected to the vehicle's water system inlet and the heater's water outlet. A sensor assembly detects the heater's temperature, the flow rate at the heater's outlet, and the pressures at the heater's inlet and the water pump's outlet. A control unit is electrically connected to the thick-film resistor units, the electronic water pump, the solenoid valve, and the sensor assembly. The control unit adjusts the operating parameters of the thick-film resistor units, the solenoid valve, and the electronic water pump based on the detected temperature, flow rate, and pressure.

[0023] In the above solution, based on the excellent performance of the thick-film resistor unit, it is possible to achieve improved thermal efficiency and precise temperature control. It also actively detects the operating status of the system and adjusts the operating parameters in real time to achieve effective protection of the system and improve system safety.

[0024] More specifically, the heat transfer fluid is antifreeze. The sensor assembly includes three temperature sensors spaced axially along the thick-film resistor unit, respectively detecting the temperatures of the upper, middle, and lower sections of the heater; a flow sensor located at the heater outlet for detecting the outlet flow rate; and a pressure sensor located at the water pump outlet and the heater inlet for detecting the water pump outlet pressure. The upper, middle, and lower section temperatures are denoted by T1, T2, and T3, respectively.

[0025] In this embodiment, the temperature sensor uses a PT1000 platinum resistor, with the three temperature sensors spaced 50 mm apart. The flowmeter is an electromagnetic flowmeter (accuracy ±0.1 L / min). The pressure sensor is a piezoresistive sensor (range 0-5 bar). The maximum flow rate of the electronic water pump is 10 L / min. The proportional solenoid valve has an adjustable opening from 0 to 100%.

[0026] See also Figure 2 This embodiment provides an electric vehicle thermal management system based on a thick film resistor water heater, and its operation process specifically involves the following steps: 1. Initialization phase: After the system is powered on, the control unit sends a command to close the solenoid valve and start the electronic water pump to run at the lowest speed (10% PWM duty cycle) for 5 seconds to establish the basic circulation pressure with a target pressure of 1.2 Bar.

[0027] If the pressure sensor detects that the pressure is continuously lower than 0.8 Bar, it determines that the system is leaking, triggers a shutdown and reports the fault code F01.

[0028] 2. Low power test stage (500 W, 10% rated power): The first thick film resistor unit was turned on and heated at 10% PWM duty cycle (corresponding to 500 W) for 30 seconds.

[0029] The following parameters are monitored: The flow value Q1 at the heater outlet, i.e. the flow meter reading Q1: the normal value is Q1 ≥ 0.5 L / min; Temperature gradient ΔT1, and ΔT1 = T1 - T3, normally ΔT1 ≤ 2℃.

[0030] Then make an exception judgment: If Q1 < 0.3 L / min and ΔT1 > 5°C, it is determined that there is air resistance in the pipeline and the system enters the exhaust mode: The exhaust mode is as follows: turn off the first thick film resistor unit, increase the water pump speed to 50% PWM, and last for 10 seconds; open the solenoid valve (opening 80%) to exhaust for 5 seconds, and repeat 3 times.

[0031] If the abnormality persists after exhausting, report fault code F02 (air not completely exhausted).

[0032] 3. Medium power verification stage (1500 W, 30% rated power): The first thick film resistor unit, the second thick film resistor unit, and the third thick film resistor unit are turned on, and the total power is increased to 30% (1500 W) for 60 seconds.

[0033] Monitoring parameters: Pressure fluctuation ΔP = P_in - P_out, normal range 0.3~0.5 Bar; P_in represents the pressure value at the heater inlet, and P_out represents the pressure value at the heater outlet; Temperature rise rate ΔT / Δt: Normal ≤3°C / s; ΔT represents the temperature change value of the upper, middle or lower section within the preset time period Δt.

[0034] Abnormal determination: If ΔP continues to decrease and ΔT / Δt>5℃ / s, it is determined that the antifreeze is insufficient, the power is cut off and F03 (low liquid level) is reported.

[0035] 4. Full power operation stage (5000 W, 100% rated power): After confirming that there are no abnormalities, turn on all units and gradually increase the PWM duty cycle from 30% to 90% (increase by 10% every 10 seconds); Use PID algorithm to dynamically adjust power and maintain target water temperature (set value T_set, default 85℃): PWM_output = Kp*(T_set - T_actual) + Ki*∫(T_set - T_actual)dt + Kd*d(T_actual) / dt; In the formula, PWM_output represents the pulse-width modulation output, used to adjust the heater's heating power. T_actual represents the actual temperature. d(T_actual) / dt is the time derivative of the actual water temperature, representing the instantaneous rate of change of the actual temperature T_actual over time. Kp and Ki are coefficients, ranging from Kp = 2 to 5, Ki = 0.1 to 0.5, and Kd = 0.05 to 0.2. By calculating the error between the set temperature and the actual temperature, T_set - T_actual, and combining the current value of this error (P), the historical accumulated value (I), and the rate of change of the actual temperature (D), a PWM output signal (PWM_output) is generated to adjust the power of the heating or cooling device. The ultimate goal is to ensure that the actual temperature T_actual reaches and maintains the set temperature T_set as quickly, smoothly, and accurately as possible.

[0036] Please note that Figure 3 This embodiment also provides a ceramic tube axial temperature layered protection strategy for detecting local overheating and triggering hierarchical protection by monitoring the axial temperature distribution of the ceramic tube, including the following steps: 1. Real-time temperature monitoring: T1, T2, and T3 are collected every 200 ms, and the axial temperature difference ΔT_axial is calculated, which is expressed as: ΔT_axial = T_max – T_min; Where, T_max represents the highest value among T1, T2, and T3, and T_min represents the lowest value among T1, T2, and T3; Calculate the temperature rise rate for each segment: dT / dt = (T_current - T_previous) / 0.2, where T_current represents the current water temperature and T_previous represents the previous water temperature. dT / dt estimates the average rate of change of temperature T within a 0.2-second interval.

[0037] 2. Adaptive power reduction control, the preset conditions for triggering alarms are as follows: Level 1 alarm: If ΔT_axial>3°C and lasts for 5 seconds, reduce the total power by 10%; Level 2 alarm: If ΔT_axial>5°C or single-point temperature>95°C, reduce power by 30% and increase pump speed to 80%; Emergency stop: If ΔT_axial>10℃ or T_max>105℃, immediately cut off the power supply of all units and start the water pump at full speed to dissipate heat.

[0038] 3. Historical data learning: The control unit records the operating conditions (ambient temperature, pump speed, power level) at each alarm and optimizes the power reduction threshold through machine learning algorithms (such as random forest) to reduce false triggering.

[0039] Specifically, in this embodiment, by collecting historical operating condition data with "real alarm" / "false trigger" labels and applying machine learning algorithms such as random forests to train a classification model, the core of the model is to learn the complex operating condition combination patterns that lead to false triggers. Using this learned knowledge, the classification model can generate dynamic power reduction threshold rules based on parameters such as ambient temperature, pump speed, and power level, allowing the model to directly participate in real-time decision-making. The ultimate effect is to significantly reduce unnecessary power reduction actions (false triggers), improve the stability and efficiency of system operation, and strictly guarantee the necessary safety protection capabilities. This optimization method based on historical data learning enables the control strategy to adapt to the complexity and variability of the actual operating environment.

[0040] In addition, please refer to Figure 4 and Figure 5 In order to improve the environmental protection effect, this embodiment also provides a waste heat recovery and energy optimization strategy based on integrating the waste heat of the motor and electric drive system and reducing the thick film resistor load, including the following steps: 1. Determination of waste heat priority: If the motor coolant temperature T_motor>50℃, the high-temperature coolant is preferentially introduced into the passenger compartment heating circuit through the three-way valve; When T_motor ≥ 70℃, the thick film resistor heating is turned off and the system relies entirely on waste heat.

[0041] 2. SOC linkage control: Dynamically adjust the upper limit of the heating power according to the battery SOC, including the following steps: 1. When the battery level is lower than 20%, the maximum output power is limited to 50% of the rated power 2. When the battery level is between 20% and 50%, the maximum output power is 80% of the rated power.

[0042] 3. When the battery level is above 50%, it is allowed to output 100% of the rated power. At the same time, in the charging state (CC / CV stage), it switches to the grid power supply mode to avoid battery discharge. Example

[0043] This embodiment provides a control method for an electric vehicle thermal management system based on a thick film resistor water heater, which is applicable to the electric vehicle thermal management system based on a thick film resistor water heater provided in the above embodiment 1, and includes the following steps: S100 , detecting the temperature value of the heater, the flow value of the heater outlet, and the pressure values ​​of the heater inlet and the water pump outlet through the sensor assembly.

[0044] S200 , the control unit adjusts the operating parameters of the thick film resistor unit, the solenoid valve, and the electronic water pump according to the temperature value, the flow value, and the pressure value. Example

[0045] This embodiment, based on the electric vehicle thermal management system based on a thick film resistor water heater provided in Example 1, provides a specific implementation process for detecting and eliminating antifreeze liquid vapor resistance, including the following steps: 1. After the vehicle is started, the control unit detects an ambient temperature of -15°C and requests heating. 2. Perform a low-power test (500 W). The flow meter shows Q1 = 0.2 L / min and ΔT1 = 7°C. 3. Trigger the exhaust procedure: the water pump speed is increased to 50% PWM, the solenoid valve is opened intermittently 3 times, and after exhaust, Q1 returns to 0.6L / min; 4. Enter full power operation and control the water temperature to be stable at 85±1℃. Example

[0046] This embodiment, based on the electric vehicle thermal management system based on a thick film resistor water heater provided in Example 1, provides a specific implementation process of power limitation under low battery SOC, including the following steps: 1. The electric vehicle battery management system (BMS) reports a remaining capacity (SOC) of 18%, and the control unit sets the maximum power (P_max) to 2500 W. 2. Prioritize Units 1 and 2 (total 2000 W), reserving Unit 3 for redundancy. 3. When SOC rises to 25%, P_max is automatically restored to 5000 W.

[0047] Example 3: This embodiment provides a computer-readable storage medium on which a computer program is stored. When the program is executed by a processor, the steps of any one of the methods described in Example 1 are implemented.

[0048] Embodiment 4: This embodiment provides a computer device, including: Memory, used to store computer programs / instructions; A processor, configured to execute the computer program / instructions to implement the steps of any one of the methods described in Example 2.

[0049] Example 5. This embodiment provides a computer program product, including a computer program / instruction, which implements the steps of any one of the methods described in Example 2 when executed by a processor.

[0050] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

[0051] Those skilled in the art will appreciate that embodiments of the present disclosure may be provided as methods, systems, or computer program products. Thus, the present disclosure may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present disclosure may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROMs, optical storage, etc.) containing computer-usable program code.

[0052] The present disclosure is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present disclosure. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0053] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0054] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 The steps for the function specified in one or more boxes.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present disclosure and are not intended to limit its scope of protection. Although the present disclosure has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that after reading the present disclosure, those skilled in the art can still make various changes, modifications or equivalent substitutions to the specific implementation methods of the invention, but these changes, modifications or equivalent substitutions are all within the scope of protection of the disclosed claims to be approved.

Claims

1. An electric vehicle thermal management system based on a thick film resistor water heater, characterized in that: include: A heater having a built-in heat transfer fluid and at least three thick film resistor units connected in parallel for heating the heat transfer fluid; An electronic water pump, which is respectively connected to the water inlet of the heater and the water outlet of the entire water circuit of the electric vehicle; Solenoid valves, which are respectively connected to the water inlet of the vehicle water circuit and the water outlet of the heater; A sensor assembly for detecting operating parameters of the heater and the water pump; a control unit electrically connected to the thick film resistor unit, the electronic water pump, the solenoid valve, and the sensor assembly; The control unit adjusts the set operating parameters of the thick film resistor unit, the solenoid valve and the electronic water pump according to the actual operating parameters and the preset trigger conditions.

2. The electric vehicle thermal management system based on thick film resistor water heater according to claim 1, characterized in that: The sensor assembly includes temperature sensors arranged axially at intervals along the thick film resistor unit and respectively used to detect the temperature values ​​of the upper section, middle section and lower section of the heater, a flow sensor for detecting the flow value of the heater outlet, and a pressure sensor for detecting the heater inlet pressure value, heater outlet pressure value and water pump outlet pressure value.

3. The electric vehicle thermal management system based on thick film resistor water heater according to claim 2, characterized in that: The upper temperature value, middle temperature value and lower temperature value are represented by T1, T2 and T3 respectively; The axial temperature difference ΔT_axial is calculated using the following formula: ΔT_axial = T_max – T_min; Where, T_max represents the highest value among T1, T2, and T3, and T_min represents the lowest value among T1, T2, and T3; The control unit adjusts the operating parameters of the thick film resistor unit, the solenoid valve and the electronic water pump according to the axial temperature difference, the upper temperature value, the middle temperature value and the lower temperature value and the preset trigger conditions.

4. The electric vehicle thermal management system based on thick film resistor water heater according to claim 3, characterized in that: The control unit adjusts the set operating parameters of the thick film resistor unit, the solenoid valve, and the electronic water pump according to the axial temperature difference, the upper temperature value, the middle temperature value, the lower temperature value, and the preset trigger condition value, including: Level 1 alarm: If ΔT_axial > 3°C and lasts for 5 seconds, the control unit controls the thick film resistor unit to reduce the power by 10%; Level 2 alarm: If ΔT_axial > 5°C or a single-point temperature > 95°C, the control unit controls the thick-film resistor unit to reduce power by 30% and increases the water pump speed to 80% of the full speed; Emergency stop: If ΔT_axial > 10°C or T_max > 105°C, the control unit immediately cuts off the power supply to all thick film resistor units and increases the water pump speed to full speed.

5. The electric vehicle thermal management system based on thick film resistor water heater according to claim 3, characterized in that: When the electric vehicle thermal management system is powered on for the first time, the control unit sends a command to close the solenoid valve and start the electronic water pump to run at the preset minimum speed for 5 seconds.

6. The electric vehicle thermal management system based on thick film resistor water heater according to claim 5, characterized in that: After the control unit sends a command to close the solenoid valve and start the electronic water pump to run at the preset minimum speed for 5 seconds, the control unit turns on the first thick film resistor unit and heats it at a 10% PWM duty cycle for 30 seconds; Record the flow rate Q1 and temperature gradient ΔT1 at the heater outlet, and ΔT1 = T1 - T3; When Q1 < 0.3 L / min and ΔT1 > 5°C, it is determined that there is air resistance in the pipeline and the control unit enters the exhaust mode.

7. The electric vehicle thermal management system based on thick film resistor water heater according to claim 6, characterized in that: The exhaust modes include: The control unit turns off the first thick film resistor unit, increases the speed of the water pump and performs exhaust.

8. The electric vehicle thermal management system based on thick film resistor water heater according to claim 6, characterized in that: When the flow rate value Q1 at the heater outlet is ≥0.5 L / min or ΔT1 ≤ 2°C, the control unit turns on the first thick film resistor unit, the second thick film resistor unit, and the third thick film resistor unit, and increases the total power to 30%.

9. The electric vehicle thermal management system based on thick film resistor water heater according to claim 8, characterized in that: The control unit collects the pressure fluctuation ΔP and the temperature rise rate ΔT / Δt of each section of the upper, middle and lower sections; Where ΔP = P_in - P_out, P_in represents the heater inlet pressure, P_out represents the heater outlet pressure, and ΔT represents the temperature change of the upper, middle, or lower section within a preset time period Δt. When ΔP continues to decrease and ΔT / Δt > 5°C / s, the control unit determines that the antifreeze fluid is insufficient and cuts off the power.

10. A control method for an electric vehicle thermal management system based on a thick film resistor water heater, characterized in that: The electric vehicle thermal management system based on the thick film resistor water heater according to any one of claims 1 to 9 comprises the following steps: Detecting actual operating parameters of the heater and water pump through the sensor assembly; The control unit adjusts the set operating parameters of the thick film resistor unit, the solenoid valve and the electronic water pump according to the actual operating parameters and the preset trigger conditions.

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