A threshold-based computing method for a control strategy of an automobile water pump and fan

Abstract

The application provides a calculation method of a threshold-based automobile water pump and fan control strategy, comprising the following steps: S1, cooling heat load calculation under high ambient temperature; S2, calculation of the highest cooling level opening threshold under high temperature and cooling interval division; S3, calculation of the opening threshold of other cooling levels under high temperature and division; and S4, calculation of the cooling level under low temperature. The calculation method of the threshold-based automobile water pump and fan control strategy can not only meet the cooling performance requirements of the whole vehicle, but also reduce the energy consumption of the whole vehicle under the common working conditions of users, improve the NVH performance of the whole vehicle, and minimize the calibration workload.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of automobile technology, in particular, to a calculation method of a vehicle water pump and fan control strategy based on a threshold value. BACKGROUND

[0002] The current automobile market is highly competitive, especially in terms of economic and NVH performance. For thermal management accessories, the operation strategy of the water pump and fan plays an important role in ensuring the cooling performance of the vehicle, while also affecting the energy consumption and NVH performance of the vehicle. Currently, most of the operation strategies for water pumps and fans in the industry are based on threshold values. In this strategy, the threshold values for different cooling levels of the components are determined based on experience: according to the temperature tolerance of the components, the temperature tolerance is divided into three cooling levels, for example, the temperature tolerance of the motor is 170℃, the first cooling level is 50℃, the second cooling level is 100℃, and the third cooling level is 150℃. In addition, the threshold values in the control strategy are determined through later experimental calibration: each cooling level threshold of each component needs to be calibrated, which is time-consuming and may not cover all user conditions, as the calibration is usually performed under a few fixed conditions.

[0003] This strategy is widely used due to its simplicity and reliability. However, the threshold values for different cooling levels of the components in the early stage are determined based on experience, without any theoretical or computational basis. The threshold values for different cooling levels determined in the early stage need to be calibrated in the later stage, which is time-consuming, especially when the strategy includes environmental temperature compensation and vehicle speed compensation. Road testing calibration may not cover all user conditions, resulting in higher energy consumption or abnormal operation of the water pump and fan in some conditions. SUMMARY

[0004] To overcome the shortcomings of the prior art, the present application provides an accurate and effective method for developing a vehicle water pump and fan control strategy. This method can not only meet the cooling performance requirements of the vehicle, but also reduce the energy consumption of the vehicle in common user conditions, improve the NVH performance of the vehicle, and minimize the calibration workload.

[0005] To achieve the above-mentioned application purposes, the present application provides the following technical solutions:

[0006] A calculation method for a vehicle water pump and fan control strategy based on a threshold value, comprising the following steps:

[0007] S1, high environmental temperature cooling heat load calculation, specifically including:

[0008] a. Thermal management condition definition: define the thermal management design condition of the vehicle;

[0009] b. Heat dissipation calculation: calculate the heat dissipation of the cooling loop components based on the defined thermal management condition;

[0010] S2, maximum cooling level opening threshold calculation at high temperature and cooling interval division, specifically comprising:

[0011] a. Thermal protection threshold determination: the temperature protection threshold of each component is reduced by a preset amount as the thermal protection threshold, and the preset amount is a calibratable amount;

[0012] b. Working temperature determination: the working temperature refers to the component temperature range for starting cooling, the working temperature is lower than the thermal protection threshold, and the temperature fluctuation degree and the influence of heat dissipation system aging on component life are considered to determine;

[0013] c. Flow and air volume design: the inlet and outlet temperature difference is preliminarily determined, and the required water flow and air volume are calculated according to the heat exchange amount;

[0014] S3, high temperature other cooling level opening threshold calculation and division, including two ways:

[0015] Way one, specifically comprising:

[0016] a. Dividing heat interval and temperature interval at the same time;

[0017] b. Flow and air volume design: comparing and optimizing the divided heat interval and temperature interval, calculating the required water flow and air volume;

[0018] Way two, specifically comprising:

[0019] a. Dividing temperature interval;

[0020] b. Calculating the required water flow and air volume based on the divided temperature interval;

[0021] S4, low temperature cooling level calculation, specifically comprising:

[0022] a. Ambient temperature compensation: through the temperature interval and / or heat interval divided in step S3, through ambient temperature correction; or directly according to ambient temperature correction final fan and pump duty ratio;

[0023] b. Flow and air volume design: according to the data corrected by the foregoing ambient temperature, calculating the required water flow and air volume.

[0024] Preferably, in step S1, the defined thermal management working condition includes ambient temperature, vehicle speed and slope; in step S1, when the cooling circuit is an electric drive cooling circuit, the calculation method of heat dissipation is:

[0025] OBC heat dissipation: Q OBC = charging power * average efficiency;

[0026] DCDC heat dissipation: Q DCDC = maximum power * average efficiency;

[0027] MCU heat dissipation: with two ways of theoretical calculation and efficiency calculation, in the theoretical calculation way: Q MCU = on-state loss + switching loss, in the efficiency calculation way: Q MCU = motor power * controller average efficiency.

[0028] Preferably, in the a step of step S2, the preset amount is 5℃; in the b step of step S2, considering the influence of temperature fluctuation degree on the service life of parts, for the MCU of the electric drive cooling circuit, the transient nature of its temperature, the faster temperature rise at high temperature, and the smoothing of its internal junction temperature fluctuation are considered, and the initial cooling temperature is increased by a preset value.

[0029] Preferably, in the b step of step S2, the influence of heat dissipation system aging on the temperature of parts is considered, and based on the consideration of heat dissipation system aging, a preset allowance is matched for the cooling system.

[0030] Preferably, in the c step of step S2, for the electric drive cooling circuit, after determining the heat of the power three-in-one and the MCU, the temperature difference of the radiator or each part inlet and outlet is determined, the inlet water temperature is according to the highest inlet water temperature required by the parts, and = The cooling liquid flow is calculated, and the cooling air requirement is calculated based on the same heat exchange formula.

[0031] Preferably, in step S3, for the electric drive cooling circuit:

[0032] Heat interval division: according to the cooling level divided by the strategy, the heat interval of the power three-in-one is evenly distributed according to the total cooling level to obtain a unified value of the heat interval under different cooling levels; because the MCU needs to smooth the internal junction temperature fluctuation, the heat interval is close at high cooling level, and the heat interval is dispersed at low cooling level;

[0033] Temperature interval division: based on the consideration of reducing the energy consumption of the servo system, each part requiring cooling in the electric drive system is set to a large temperature interval before the fan is turned on, and the power three-in-one and the motor are set to a linear temperature interval after the fan is turned on. Because the MCU has a faster temperature rise at high temperature, the temperature interval is gradually reduced from low to high.

[0034] Preferably, in the b step of the first way of step S3, for the electric drive cooling circuit:

[0035] After the temperature interval and the heat interval are divided, first, taking the component as the calculation object, the system flow required by the lower limit value of the temperature interval set by the component is calculated, and for the power three-in-one or MCU, the inlet and outlet water temperatures of the component are calculated according to the heat exchange amount calculation formula: When the system flow is calculated, the inlet and outlet temperature difference value is the same as the highest cooling level; after the inlet and outlet water temperatures of the radiator are calculated, the system flow is calculated according to the heat dissipation amount, and finally, the required air volume is calculated according to the calculated system flow and the inlet and outlet temperature difference of the air side of the radiator;

[0036] According to the heat interval, taking the radiator as the calculation object, the radiator water flow is calculated according to The air volume is calculated, and the inlet and outlet water temperature values of the radiator are calculated according to The component body temperature value is further calculated.

[0037] Preferably, in the b step of the second mode of step S3, for the electric drive cooling circuit:

[0038] After the temperature interval is divided, the inlet and outlet temperature difference is defined and the inlet and outlet temperature values are assumed; the component heat exchange amount is calculated according to the inlet and outlet temperature values and the temperature interval; the system flow is calculated according to the heat exchange amount and the inlet and outlet temperature difference; the inlet and outlet water temperatures of the radiator are calculated according to the calculated system flow and the heat exchange amount; the inlet and outlet water temperatures of the radiator and the assumed inlet and outlet temperature values of the component are compared, if different, the inlet and outlet temperature values of the component are assumed again and the steps are repeated until the calculated temperature values are within the set value; and then the required air volume is calculated according to the designed flow value and the heat exchange amount with the radiator as the object.

[0039] Preferably, in the a step of step S4, the vehicle speed can also be compensated, that is, the temperature interval and / or the heat interval divided by step S3 are corrected by the vehicle speed; or the final fan and water pump duty ratio is directly corrected according to the vehicle speed.

[0040] Compared with the prior art, the present application has the following beneficial effects:

[0041] The calculation method of the automobile water pump and fan control strategy based on the threshold value provided by the present application can not only meet the cooling performance requirements of the whole vehicle, but also reduce the energy consumption of the whole vehicle under the user's common working conditions, improve the NVH performance of the whole vehicle, and can greatly reduce the calibration workload. BRIEF DESCRIPTION OF DRAWINGS

[0042] Other features, objects and advantages of the present application will become more apparent from the following detailed description of non-limiting embodiments, made with reference to the accompanying drawings:

[0043] Figure 1Flow chart of the calculation method of the threshold-based automobile water pump and fan control strategy described in the embodiment;

[0044] Figure 2 Define the situation diagram for the thermal management working condition of a PHEV vehicle. DETAILED DESCRIPTION

[0045] To make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments of the present application.

[0046] Therefore, the detailed description of the embodiments of the present application provided below in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by a person of ordinary skill in the art without making creative efforts based on the embodiments in the present application are within the scope of protection of the present application.

[0047] The present embodiment provides a calculation method of a threshold-based automobile water pump and fan control strategy, and the application scope includes: cooling circuits of all types of automobiles applying electronic water pumps, including:

[0048] 1. HEV (Hybrid Electrical Vehicle) various types of hybrid vehicles, including PHEV (Plug-in HEV plug-in hybrid) / FHVE (Full HEV light hybrid) / REEV (Range Extended EV extended-range hybrid), and the corresponding cooling circuits include:

[0049] ① High-voltage electric drive cooling circuit (generally containing power three-in-one (DCD (DC-DC Converter) + OBC (On-Board Charger vehicle-mounted charger) + PDU (Power Distribution Unit power distribution unit)), MCU (Motor Control Unit motor controller));

[0050] ② Engine high-temperature cooling circuit;

[0051] ③ Battery cooling circuit (water-cooled battery pack vehicle);

[0052] 2. Pure electric vehicle:

[0053] ① High-voltage electric drive cooling circuit: same as above

[0054] ② Battery cooling circuit (water-cooled battery pack vehicle): same as above.

[0055] The threshold-based automobile water pump and fan control strategy calculation method provided by the embodiment, as shown in Figure 1 includes the following steps:

[0056] S1, cooling heat load calculation under high ambient temperature;

[0057] S2, calculation of the highest cooling level opening threshold under high temperature and division of the cooling interval;

[0058] S3, calculation of the opening threshold of other cooling levels under high temperature and division;

[0059] S4, calculation of the cooling level under low temperature (i.e. ambient temperature compensation strategy).

[0060] The method of the embodiment is specifically described as follows in combination with an electric drive cooling circuit as an example:

[0061] 1. For step S1, i.e. cooling heat load calculation under high ambient temperature, the so-called high ambient temperature is generally the average maximum temperature of the target sales market of the development vehicle in summer, which is opposite to the low ambient temperature, and the high ambient temperature and the low ambient temperature are generally defined by the vehicle enterprise itself. For convenience, the high ambient temperature and the low ambient temperature are referred to as "high temperature" and "low temperature" hereinafter. The so-called heat load refers to the heat generated by components due to efficiency loss, among which the part of heat that needs to be taken away by the outside world is generally equal to the heat dissipation when thermal equilibrium is reached. At this time, the heat generation is equal to the heat load. Basically, the cooling system design and calculation take the heat generation as the heat dissipation, i.e. the heat load.

[0062] Step S1, i.e. cooling heat load calculation under high ambient temperature, specifically includes the following steps:

[0063] a. Thermal management working condition definition: define the thermal management design working condition of the vehicle, including ambient temperature, vehicle speed, slope, etc. Figure 2 The thermal management working condition definition of a certain PHEV vehicle is shown;

[0064] b. Heat dissipation calculation: calculate the heat dissipation of the cooling circuit components according to the defined thermal management working condition. Taking the electric drive circuit as an example:

[0065] OBC heat dissipation: Q OBC = charging power * average efficiency;

[0066] DCDC heat dissipation: Q DCDC = maximum power * average efficiency;

[0067] MCU heat dissipation: has two calculation methods, i.e. theoretical calculation and efficiency calculation. The theoretical calculation method may be, for example, calculation through on-state loss + switching loss, and the efficiency calculation is calculated through motor power * controller average efficiency;

[0068] 2. For step S2, i.e., the calculation of the maximum cooling level opening threshold at high temperature and the division of the cooling interval, the following steps are included:

[0069] a. Thermal protection threshold determination: The thermal protection threshold is determined by subtracting a preset amount, such as 5°C (which can be calibrated), from the temperature protection threshold of each component. For example, if the temperature protection threshold of the motor is 155°C, then the actual calculation of the thermal protection threshold is 150°C, which is 5°C lower than the original value, serving as a safety margin.

[0070] b. Working temperature determination: The working temperature, i.e., the temperature range of the component that starts cooling, not only considers keeping the component working below the aforementioned thermal protection threshold, but also considers the impact of temperature fluctuations on the component's lifespan, including the impact of the aging of the heat dissipation system on the component's temperature. Based on the consideration of the aging of the heat dissipation system, a certain amount of surplus is generally given to the cooling system. However, considering the impact of temperature fluctuations on the component's lifespan, the strategy needs to be inclined, such as the MCU (according to engineering experience, the initial cooling temperature is the ambient temperature + 10°C~20°C, which is considered because the heat exchanger needs a suitable temperature difference relative to the environment. A large temperature difference will delay cooling, and a small temperature difference will result in poor heat exchange efficiency. For example, if the design ambient temperature is 40°C, the initial cooling temperature of the motor is 60°C, and cooling starts. The MCU needs to be cooled as soon as possible due to its temperature transience, high temperature rise, and the need to smooth its internal junction temperature fluctuations, so the initial cooling temperature needs to be as high as possible. For example, if the threshold is 150°C, then the cooling starts at 100°C).

[0071] c. Flow and air volume design: The inlet and outlet temperature difference is preliminarily determined, and the required water flow and air volume are calculated based on the heat exchange amount. The flow design cannot avoid the matching selection of the heat sink, so the matching selection of the heat sink is briefly described. The so-called heat sink matching selection: after determining the heat of the power three-in-one and the MCU, the inlet and outlet temperature difference of the heat sink or each component is determined. For example, the inlet and outlet temperature difference of the power three-in-one is generally within 1°C, and the inlet and outlet temperature difference of the MCU is generally 3~6°C (the selection of the two inlet and outlet temperature differences generally considers two aspects: one is the experience value; one is to consider the efficiency or effectiveness of the heat sink, and the temperature difference selected in the range of 4~7°C is the sum of the two, assuming that the heat balance, i.e., the heat generated by the heat source is equal to the heat dissipated by the heat sink, then the temperature difference in this range is equal to the inlet and outlet temperature difference of the heat sink. If the heat dissipation capacity of the heat sink is strong, the temperature difference will be small, and vice versa, i.e., the matching heat sink can meet the heat dissipation demand and will not be overcapacity or have a small effectiveness). The inlet water temperature is determined according to the maximum inlet water temperature required by the component, such as 65°C, and the required water flow and air volume are calculated based on the heat exchange amount. = The cooling liquid flow rate is calculated, and the air temperature difference through the radiator is generally 10-15℃ (for the same reason as the above temperature difference). The same heat exchange formula is used to calculate the cooling air requirement (radiator windward area, thickness, etc.).

[0072] The flow rate and air volume design for the highest cooling level (in practice, cooling level 5) in a high temperature environment is actually a check of the thermal management design condition, at which the fan speed is the highest and the system flow rate is the largest.

[0073] 3. For the high-temperature other cooling level opening threshold calculation and division in step S3, there are mainly two methods. One is to divide the heat interval and temperature interval simultaneously, compare and optimize the two intervals, and then obtain the final system water flow rate and air volume. The other is to divide the heat interval or temperature interval first, and then calculate the required cooling water flow rate and air volume in different intervals. The essential difference between the two methods is that the second method has only one constraint condition, while the first method can be considered to have two constraint conditions, because the division of the heat interval or the temperature interval is mainly based on experience. The following will be stated respectively:

[0074] First: simultaneous division of heat interval and temperature interval

[0075] ① Heat interval: According to the cooling level divided by the strategy, the heat interval of the power three-in-one can be divided according to the total cooling level to obtain a uniform value of the heat interval under different cooling levels. The MCU needs to smooth the internal junction temperature fluctuations, so the heat interval is close at high cooling levels, and the heat interval is dispersed at low cooling levels. For example, the total heat of the highest cooling level, i.e., cooling level 5, is 2kW, and the initial heat calculation interval of each cooling level is: Level 0-0.2kW; Level 1 - 0.3kW; Level 2 - 0.7kW; Level 3 - 1.3kW; Level 4 - 1.7kW.

[0076] ② Temperature interval: In order to reduce the energy consumption of the servo system, the temperature interval of each cooling component in the electric drive system can be set to a larger temperature interval before the fan is turned on, and the power three-in-one and the motor can be set to a linear temperature interval after the fan is turned on. However, the MCU has a faster temperature rise at high temperatures, so the temperature interval can be gradually reduced from cooling level 3 to 5 when the highest cooling level is level 5.

[0077] ③ Flow rate and air volume design: After the temperature interval and heat interval are divided, the system flow rate required by the component is first calculated according to the lower limit value of the temperature interval set by the component:

[0078] For power three-in-one or MCU (since the power three-in-one is small in heat, the power three-in-one heat can be added to the MCU for calculation, and in the division of temperature interval and heat interval, the MCU is mainly taken as the standard, and the power three-in-one can be used as a check, of course, it can also be divided separately, then the duty cycle of the water pump and the fan is the respective value, if they are combined together, the duty cycle of the water pump and the fan takes the larger value), first, the inlet and outlet water temperatures of the components can be calculated according to the heat exchange calculation formula: ,△T is the equivalent average temperature difference, KA value can be calculated according to the highest cooling level, i.e. cooling level 5, according to the same formula, and the change of KA value with system flow is ignored. When calculating the system flow, the inlet and outlet temperature difference value and the highest cooling level, i.e. cooling level 5, are taken as the same (that is, the cooling demand in the current cooling level is met and the water pump energy consumption is not too large). After the inlet and outlet water temperatures of the radiator are calculated, the system flow is calculated according to the heat dissipation (or directly calculated according to the heat interval, the calculated system flow will be different), and finally the required air volume is calculated according to the calculated system flow and the inlet and outlet temperature difference of the radiator air side.

[0079] It should be noted that according to the heat interval, the radiator is taken as the calculation object, and the heat dissipation is calculated according to The water flow of the radiator is calculated (the inlet and outlet temperature difference is taken as the empirical value, and the temperature difference selection method for matching the radiator is the same), and then the air volume is calculated, which can be calculated according to The inlet and outlet water temperature values of the radiator can be calculated, and then the component body temperature values can be calculated, so the division of the heat interval and the temperature interval needs to be referred to and corrected, and the strategy needs to be made more reasonable.

[0080] The second kind: after dividing the temperature interval, the required cooling water flow and air volume are calculated

[0081] Since the heat interval is not good to divide according to experience, and the temperature interval is relatively easy to divide and relatively reasonable, this method can be referred to for formulating the strategy.

[0082] ① Division of temperature interval: same as the first method.

[0083] ② Flow design: after the temperature interval is divided, the inlet and outlet temperature difference is defined and the inlet and outlet temperature values are assumed; the component heat exchange is calculated according to the inlet and outlet temperature values and the temperature interval; the system flow is calculated according to the heat exchange and the inlet and outlet temperature difference; the inlet and outlet water temperatures of the radiator are calculated according to the calculated system flow and heat exchange; the calculated temperature values of the radiator inlet and outlet are compared with the assumed component inlet and outlet temperature values, if they are different, the component inlet and outlet temperature values are assumed again and the steps are repeated until the difference between the two calculated temperature values is within 0.5℃.

[0084] ③ Air volume design: the required air volume is calculated according to the designed flow value and heat exchange, taking the radiator as the object.

[0085] 4. For step S4, i.e. other cooling level calculation and division, there are two methods:

[0086] The first method: according to the temperature interval and heat interval calculated in step S3, i.e. high-temperature other cooling level calculation, the two intervals can be compensated according to the ambient temperature through ambient temperature correction, i.e. heat interval ambient temperature compensation and temperature interval ambient temperature compensation. For example, the execution interval of the highest cooling level of the DCDC in the market with the highest temperature of 40℃ is [70℃, 75℃) (i.e. 75℃ > DCDC body temperature ≥ 75℃). If the ambient temperature is 20℃, the temperature can be raised to [75℃, 80℃). The heat interval division is the same, and the heat exchange of each interval can be increased, as shown in the following table 1:

[0087] Table 1

[0088]

[0089] The second method: directly correct the final fan and water pump duty ratio according to the ambient temperature, for example, the low-temperature cooling strategy and high-temperature cooling strategy shown in the following table 2:

[0090] Table 2

[0091]

[0092] Flow design and air volume design: based on the corrected data of the ambient temperature, the flow and air volume are calculated by using the calculation method of the flow design and air volume design in step S3.

[0093] Further, the low-ambient-temperature cooling strategy in step S4, i.e. the ambient temperature compensation strategy, also includes the vehicle speed compensation strategy, and the calculation method is the same as the ambient temperature compensation strategy method. For example, the second method (directly correct the final fan and water pump duty ratio according to the vehicle speed) is shown in the following table 3:

[0094] Table 3

[0095]

[0096] The calculation method of the automobile water pump and fan control strategy based on the threshold value provided in the embodiment calculates each threshold value in the water pump and fan control strategy through the heat exchange correlation formula. The threshold value obtained by theoretical calculation has high accuracy, and the later calibration workload is small. The initial value obtained by calibration can be used to determine the subsequent high-level threshold value by using the theoretical calculation method.

[0097] The above describes the specific embodiments of the present application, and through the above description, relevant personnel can make various changes and modifications without deviating from the technical idea of the present application, and similar theoretical calculations or simulations belong to this category.

Claims

1. A calculation method for a threshold-based control strategy for automotive water pumps and fans, characterized in that, Includes the following steps: S1. Calculation of cooling heat load at high ambient temperature, specifically including: a. Definition of Thermal Management Operating Conditions: Defines the design operating conditions for the vehicle's thermal management; b. Heat dissipation calculation: Calculate the heat dissipation of cooling circuit components based on the defined thermal management conditions; S2. Calculation of the highest cooling level activation threshold and cooling zone division at high temperatures, specifically including: a. Determination of thermal protection threshold: The thermal protection threshold is determined by a preset amount based on the temperature protection threshold of each component, and the preset amount is a calibrable quantity; b. Determination of operating temperature: The operating temperature refers to the temperature range of the component when cooling is started. The operating temperature is lower than the thermal protection threshold and is determined by taking into account the degree of temperature fluctuation and the impact of heat dissipation system aging on the life of components. c. Flow rate and air volume design: Initially determine the inlet and outlet temperature difference, and calculate the required water flow rate and air volume based on the heat exchange capacity; S3, Calculation and classification of activation thresholds for other high-temperature cooling levels, including two methods: Method 1 specifically includes: a. Simultaneously divide the heat range and the temperature range; b. Flow and air volume design: Compare and optimize the divided heat and temperature zones, and calculate the required water flow and air volume; Method two specifically includes: a. Divide the temperature range; b. Calculate the required water flow rate and air volume based on the defined temperature ranges; S4. Low-temperature cooling rating calculation, specifically including: a. Ambient temperature compensation: Based on the temperature range and / or heat range defined in step S3, the ambient temperature is corrected; or the final fan and water pump duty cycle is directly corrected based on the ambient temperature. b. Flow rate and air volume design: Calculate the required water flow rate and air volume based on the aforementioned ambient temperature correction data.

2. The calculation method for the automotive water pump and fan control strategy based on threshold values ​​according to claim 1, characterized in that, In step S2, step a, the preset value is 5°C; in step S2, step b, considering the impact of temperature fluctuation on the lifespan of components, for the MCU of the electric drive cooling circuit, considering its temperature transients, faster high-temperature heating characteristics, and considering smoothing its internal junction temperature fluctuations, its initial cooling temperature is increased by the preset value.

3. The calculation method for the threshold-based automotive water pump and fan control strategy according to claim 1, characterized in that, In step b of step S2, the impact of heat dissipation system aging on component temperature is considered, and based on the consideration of heat dissipation system aging, a preset margin is matched to the cooling system.

4. The calculation method for the automotive water pump and fan control strategy based on threshold values ​​according to claim 1, characterized in that, In step S3, regarding the electric drive cooling circuit: Heat range division: Based on the cooling level division strategy, the heat range of the power supply three-in-one is evenly distributed according to the total cooling level to obtain heat ranges under different cooling levels with a uniform value; because the MCU needs to smooth out internal junction temperature fluctuations, the heat in the heat range of the high cooling level is close, while the heat in the heat range of the low cooling level is dispersed. Temperature range division: Based on the consideration of reducing the energy consumption of the servo system, the cooling levels of the various components of the electric drive system that require cooling are set with a large temperature range before the fan is turned on. After the fan is turned on, the power supply unit and the motor are set with a linear temperature range. As the MCU heats up faster at high temperatures, its temperature range gradually narrows from low to high, either entirely or partially.

5. The calculation method for the automotive water pump and fan control strategy based on threshold values ​​according to claim 1, characterized in that, In step b of the second method of step S3, regarding the electric drive cooling circuit: After the temperature range is defined, the inlet and outlet temperature difference is defined and the inlet and outlet temperature values ​​are assumed; the heat exchange of the components is calculated based on the inlet and outlet temperature values ​​and the temperature range; the system flow rate is calculated based on the heat exchange and the inlet and outlet temperature difference; the inlet and outlet water temperatures of the radiator are calculated based on the calculated system flow rate and heat exchange. Compare the inlet and outlet water temperatures of the radiator with the assumed inlet and outlet temperatures of the components. If they are different, assume the inlet and outlet temperatures of the components again and repeat the steps until the temperature values ​​calculated by the two are within the set value. Then, calculate the required air volume based on the designed flow rate and heat exchange rate, taking the radiator as the object.

6. The calculation method for the automotive water pump and fan control strategy based on threshold values ​​according to claim 1, characterized in that, In step a of step S4, vehicle speed can also be used for compensation, that is, the temperature range and / or heat range divided in step S3 can be corrected by vehicle speed; or the final fan and water pump duty cycle can be directly corrected based on vehicle speed.

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