Calculation method of automobile water pump and fan control strategy based on threshold value

Abstract

The invention provides a calculation method for an automobile water pump and fan control strategy based on a threshold value. The calculation method comprises the following steps that S1, high-environment-temperature cooling heat loads are calculated; s2, the highest cooling grade opening threshold value at the high temperature is calculated, and cooling intervals are divided; s3, starting threshold calculation and division of other high-temperature cooling grades; and S4, low-temperature cooling grade calculation. According to the calculation method for the automobile water pump and fan control strategy based on the threshold value, the whole automobile can meet the cooling performance requirement, the energy consumption of the whole automobile can be reduced under the common working condition of a user, the NVH performance of the whole automobile is improved, and the calibration workload can be reduced to the maximum extent.

Description

Technical Field

[0001] The invention relates to the field of automobile technology, and in particular to a calculation method for an automobile water pump fan control strategy based on a threshold value. Background Art

[0002] The current automotive market is highly competitive, especially in terms of economy and NVH. For thermal management accessories, the operation strategy of water pumps and fans must not only ensure the cooling performance of the vehicle, but also play an important role in the energy consumption and NVH of the vehicle. Most of the current operation strategies for water pumps and fans in the industry are based on threshold value strategies. Under this strategy, the initial strategy threshold is determined only by experience: evenly divided according to the temperature limit of the components, for example, the motor temperature is 170℃, and there are 3 cooling levels, then the first level cooling is 50℃, the second level cooling is 100℃, and the third level cooling is 150℃; plus the later experimental calibration to determine the various thresholds in the control strategy: each cooling level threshold of each component needs to be calibrated, the calibration workload is large and may not cover all user conditions, because the calibration is basically carried out under several fixed conditions.

[0003] This strategy is widely used due to its simplicity and reliability. However, in the early stage, the thresholds for opening and closing different cooling levels of components are determined only through empirical values, without relevant theoretical or calculation basis. The opening thresholds of different cooling levels established in the early stage all need to be calibrated in later experiments. There are many calibration values. Especially when the strategy includes ambient temperature compensation and vehicle speed compensation, road test calibration often has limitations and cannot cover all user operating conditions well, resulting in high energy consumption for users in some operating conditions or abnormal operation of the water pump fan. Summary of the invention

[0004] In view of the defects in the prior art, the purpose of the present invention is to provide an accurate and effective method for formulating automobile water pump and fan control strategies, which can not only meet the cooling performance requirements of the entire vehicle, but also reduce the energy consumption of the entire vehicle under the user's common operating conditions, improve the NVH performance of the entire vehicle, and minimize the calibration workload.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] A calculation method for a threshold-based automobile water pump and fan control strategy comprises the following steps:

[0007] S1. Calculation of heat load for high ambient temperature cooling, including:

[0008] a. Definition of thermal management conditions: define the thermal management design conditions of the whole vehicle;

[0009] b. Heat dissipation calculation: Calculate the heat dissipation of cooling circuit components according to the defined thermal management conditions;

[0010] S2. Calculation of the threshold value for opening the highest cooling level at high temperature and division of cooling intervals, specifically including:

[0011] a. Determination of thermal protection threshold: The thermal protection threshold is determined by setting a preset amount according to the temperature protection threshold of each component, and the preset amount is a calibrable amount;

[0012] b. Determination of operating temperature: The operating temperature refers to the temperature range of components that start cooling. The operating temperature is lower than the thermal protection threshold and is determined by considering the degree of temperature fluctuation and the impact of cooling system aging on component life;

[0013] c. Flow and air volume design: preliminarily determine the inlet and outlet temperature difference, and calculate the required water flow and air volume based on the heat exchange;

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

[0015] Method 1 specifically includes:

[0016] a. Divide the heat range and temperature range at the same time;

[0017] b. Flow and air volume design: compare and optimize the divided heat range and temperature range, and calculate the required water flow and air volume;

[0018] Method 2 specifically includes:

[0019] a. Divide the temperature range;

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

[0021] S4. Calculation of low temperature cooling level, including:

[0022] a. Ambient temperature compensation: the temperature interval and / or heat interval divided by step S3 is corrected by ambient temperature; or the final fan and water pump duty cycle is corrected directly according to the ambient temperature;

[0023] b. Flow and air volume design: Calculate the required water flow and air volume based on the aforementioned ambient temperature corrected data.

[0024] Preferably, in step a of step S1, the defined thermal management conditions include ambient temperature, vehicle speed, and slope; in step b of step S1, when the cooling circuit is an electric drive cooling circuit, the heat dissipation is calculated as follows:

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

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

[0027] MCU heat dissipation: There are two methods: theoretical calculation and efficiency calculation. In the theoretical calculation method: Q MCU = conduction loss + switching loss, efficiency calculation method: Q MCU = Motor power * controller average efficiency.

[0028] Preferably, in step a of step S2, the preset amount is 5°C; in step b of step S2, taking into account the impact of temperature fluctuations on the life of components, for the MCU of the electric drive cooling circuit, taking into account its temperature transientness, faster temperature rise characteristics at high temperatures, and smoothing its internal junction temperature fluctuations, its initial cooling temperature is increased by the preset value.

[0029] Preferably, in step b of step S2, the influence of the aging of the heat dissipation system on the temperature of the components is taken into consideration, and based on the consideration of the aging of the heat dissipation system, a preset margin is matched to the cooling system.

[0030] Preferably, in step c of step S2, for the electric drive cooling circuit, after determining the heat of the power three-in-one and the MCU, determine the inlet and outlet temperature difference of the radiator or each component, and the inlet water temperature is based on the maximum inlet water temperature required by the component. = The coolant flow rate 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] Thermal interval division: According to the cooling level divided by the strategy, the thermal interval of the three-in-one power supply is evenly distributed according to the total cooling level to obtain the thermal intervals under different cooling levels with the same value; because the MCU needs to smooth the internal junction temperature fluctuation, the heat in the thermal intervals with high cooling levels is close, while the heat in the thermal intervals with low cooling levels is dispersed;

[0033] Temperature range division: Based on the consideration of reducing the energy consumption of the servo system, the cooling level of each component that requires cooling in the electric drive system is set with a temperature range with a larger temperature span before the fan is turned on. Within the cooling level after the fan is turned on, the three-in-one power supply and the motor are set with a linear temperature range. Since the MCU has a faster temperature rise at high temperatures, the temperature range is gradually reduced from low to high in whole or in part.

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

[0035] After the temperature range and heat range are divided, first take the components as the calculation object, and calculate the required system flow according to the lower limit of the temperature range set by the components. For the three-in-one power supply or MCU, first calculate the inlet and outlet water temperatures of the components according to the heat exchange calculation formula: ; The inlet and outlet temperature difference value taken when calculating the system flow is the same as the highest cooling level; after calculating the inlet and outlet water temperatures of the radiator, the system flow is calculated based on the heat dissipation, and finally the required air volume is calculated based on the calculated system flow combined with the inlet and outlet temperature difference of the radiator on the wind side;

[0036] According to the heat range, take the radiator as the calculation object, according to Calculate the radiator water flow, and then calculate the air volume, according to The radiator inlet and outlet water temperatures can be calculated, and the component body temperature can be further calculated.

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

[0038] After the temperature range is divided, define the inlet and outlet temperature difference and assume the inlet and outlet temperature values; calculate the heat exchange of components based on the inlet and outlet temperature values ​​and the temperature range; calculate the system flow based on the heat exchange and the inlet and outlet temperature difference; calculate the radiator inlet and outlet water temperature based on the calculated system flow and heat exchange; compare the radiator inlet and outlet water temperatures with the assumed component inlet and outlet temperature values. If they are different, assume the component inlet and outlet temperature values ​​again and repeat the steps until the difference between the two calculated temperature values ​​is within the set value; then calculate the required air volume based on the designed flow value and heat exchange with the radiator as the object.

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

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

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

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

[0043] Figure 1A flow chart of a calculation method for a threshold-based automobile water pump fan control strategy according to an embodiment;

[0044] Figure 2 A situation diagram that defines the thermal management conditions for a PHEV model. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments.

[0046] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0047] This embodiment provides a calculation method for a threshold-based automobile water pump and fan control strategy, which is applicable to cooling circuits of all types of automobiles using electronic water pumps, including:

[0048] 1. HEV (Hybrid Electrical Vehicle) various hybrid models, including PHEV (Plug-in HEV) / FHVE (Full HEV) / REEV (Range Extended EV), the corresponding cooling circuits include:

[0049] ① High-voltage electric drive cooling circuit (generally including three-in-one power supply (DCDC (DC-DC Converter) + OBC (On-Board Charger) + PDU (Power Distribution Unit)), MCU (Motor Control Unit));

[0050] ②Engine high temperature cooling circuit;

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

[0052] 2. Pure electric models:

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

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

[0055] The present embodiment provides a method for calculating the threshold-based automobile water pump and fan control strategy, such as Figure 1 As shown, the following steps are included:

[0056] S1. Calculation of heat load for cooling at high ambient temperature;

[0057] S2. Calculation of the threshold value for opening the highest cooling level at high temperature and division of cooling intervals;

[0058] S3, calculation and division of thresholds for opening other cooling levels at high temperature;

[0059] S4. Low temperature cooling level calculation (i.e. ambient temperature compensation strategy).

[0060] The method of this embodiment is described in detail below by taking the electric drive cooling circuit as an example:

[0061] 1. Regarding step S1, i.e., the calculation of the high ambient temperature cooling heat load, the so-called high ambient temperature is generally the average maximum temperature in summer for the R&D vehicle model in its target sales market. In contrast to the low ambient temperature, the high ambient temperature and the low ambient temperature are generally defined by the vehicle companies themselves. For convenience, the following are referred to as "high temperature" and "low temperature" to represent the high ambient temperature and the low ambient temperature; the so-called heat load refers to the heat generated by components due to efficiency loss, of which the part of the heat that needs to be taken away by the outside world. Generally, when thermal equilibrium is reached, the heat generated is equal to the heat dissipation. At this time, the heat generated is equal to the heat load. Basically, the design and calculation of the cooling system regard the heat generated as the heat dissipation, i.e., the heat load.

[0062] Step S1, namely, high ambient temperature cooling heat load calculation, specifically includes the following steps:

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

[0064] b. Heat dissipation calculation: Calculate the heat dissipation of cooling circuit components according to the defined thermal management conditions, 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: There are two calculation methods: theoretical calculation and efficiency calculation. The theoretical calculation method can be calculated by conduction loss + switching loss, and the efficiency calculation is calculated by motor power * controller average efficiency;

[0068] 2. Step S2, i.e., calculating the threshold value for opening the highest cooling level at high temperature and dividing the cooling interval, specifically includes the following steps:

[0069] a. Determination of thermal protection threshold: According to the preset amount of the temperature protection threshold of each component, such as 5°C (calibrable quantity), the thermal protection threshold is used as the thermal protection threshold. For example, if the motor temperature protection threshold is 155°C, it is reduced by 5°C, that is, 150°C, as the actual calculated thermal protection threshold as a safety margin;

[0070] b. Determination of operating temperature: The operating temperature is the temperature range of the components that start cooling. It is not only necessary to consider that the components do not exceed the aforementioned thermal protection threshold, but also to consider the impact of temperature fluctuation on the life of the components, including the impact of the aging of the cooling system on the temperature of the components. Based on the consideration of the aging of the cooling system, a certain margin is generally matched to the cooling system, but considering the impact of the degree of temperature fluctuation on the life of the components, it is necessary to give preference in strategy formulation, such as MCU (based on engineering experience, the initial cooling temperature value is the ambient temperature + 10℃~20℃. This consideration is because the radiator needs a suitable heat exchange temperature difference relative to the environment. If the temperature difference is too large, the cooling will be delayed, and if it is too small, the heat exchange efficiency will be poor. For example, if the design ambient temperature is 40℃, the initial cooling temperature of the motor is when the motor winding temperature reaches 60℃ and cooling begins. Because of the transient temperature of the MCU, the characteristics of faster heating at high temperature, and the consideration of smoothing its internal junction temperature fluctuations, the initial cooling temperature needs to be increased as much as possible. For example, if its threshold is 150℃, cooling starts at 100℃).

[0071] c. Flow and air volume design: Preliminarily determine the inlet and outlet temperature difference, and calculate the required water flow and air volume based on the heat exchange. Flow design cannot avoid the matching selection of the radiator, so the matching selection of the radiator is briefly described first. The so-called radiator matching selection: After determining the heat of the three-in-one power supply and the MCU, determine the inlet and outlet temperature difference of the radiator or each component. For example, the inlet and outlet temperature difference of the three-in-one power supply 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 is generally combined with two aspects: one is the experience value; the other is to consider the efficiency or effectiveness of the radiator. The temperature difference of the sum of the two is selected in the range of 4~7°C. Assuming the heat dissipation balance, that is, the heat generated by the heat source is equal to the heat dissipation of the radiator, then this temperature difference range is equal to the inlet and outlet temperature difference range of the radiator. If the radiator has a strong heat dissipation capacity, the temperature difference is small, otherwise the temperature difference is large, that is, the matched radiator can meet the heat dissipation requirements without excess capacity or low efficiency), the inlet water temperature is based on the highest inlet water temperature required by the component, such as 65°C, according to = Calculate the coolant flow rate. The air temperature difference passing through the radiator is generally 10~15℃ (the reason is the same as the temperature difference mentioned above). The same heat exchange formula is used to calculate the required cooling air volume (the calculation of the radiator's windward area, thickness, etc. will not be repeated).

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

[0073] 3. Regarding step S3, i.e., the calculation and division of the thresholds for opening other cooling levels at high temperatures, there are two main methods. One is to divide the heat interval and the temperature interval at the same time, compare and optimize the two divided intervals, and then obtain the final system water flow and air volume; the other is to divide the heat interval or the temperature interval first, and then calculate the required cooling water flow and air volume in different intervals using different methods. The essential difference between the two methods is that the second method has only one constraint, while the first method can be considered to have two constraints, because the division of both the heat interval and the temperature interval is based on experience. The following are stated separately:

[0074] The first method: divide the heat range and temperature range at the same time

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

[0076] ② Temperature range: In order to reduce the energy consumption of the servo system, the components of the electric drive system that require cooling can set a temperature range with a larger temperature span in the cooling level before the fan is turned on. In the cooling level after the fan is turned on, the power three-in-one and the motor can set a linear temperature range. However, because the MCU heats up faster at high temperatures, when the highest cooling level is level 5, the temperature range can be gradually narrowed from cooling level 3 to 5.

[0077] ③Flow and air volume design: After the temperature range and heat range are divided, first take the components as the calculation object, and calculate the required system flow according to the lower limit of the temperature range set by the components:

[0078] For a three-in-one power supply or MCU (since the heat of a three-in-one power supply is small, the heat of the three-in-one power supply can be added to the MCU for calculation. When dividing the temperature range and the heat range, the MCU is the main factor. The three-in-one power supply can be used as a check. Of course, it can also be done separately. Then the duty cycle of the water pump and the fan is their respective values. If they are combined, the duty cycle of the water pump and the fan takes the larger value), first, according to the heat exchange calculation formula, the inlet and outlet water temperature of the component can be calculated: , △T is the equivalent average temperature difference, and the KA value can be calculated according to the same formula based on the highest cooling level, i.e., cooling level 5, and the change of the KA value with the system flow rate is ignored. The inlet and outlet temperature difference value taken when calculating the system flow rate is the same as the highest cooling level, i.e., cooling level 5 (which can meet the cooling demand within the current cooling level without causing excessive energy consumption of the water pump). After calculating the inlet and outlet water temperatures of the radiator, the system flow rate is calculated based on the heat dissipation (or directly calculated based on the heat range, the calculated system flow rate will be different). Finally, the required air volume is calculated based on the calculated system flow rate combined with the inlet and outlet temperature difference on the wind side of the radiator.

[0079] It should be noted that according to the heat range, the radiator is taken as the calculation object. Calculate the water flow of the radiator (the inlet and outlet temperature difference is based on the empirical value, which is the same as the temperature difference selection method for radiator matching selection), and then calculate the air volume. The water temperature values ​​at the inlet and outlet of the radiator can be calculated, and then the temperature value of the component body can be calculated. Therefore, the division of heat intervals and the division of temperature intervals need to refer to and be corrected with each other to make the strategy more reasonable.

[0080] The second method: Calculate the required cooling water flow and air volume after dividing the temperature range

[0081] Since heat ranges are not easy to divide based on experience, but temperature ranges are relatively easy to divide and relatively reasonable, you can refer to this method to formulate strategies.

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

[0083] ②Flow design: After the temperature range is divided, define the inlet and outlet temperature difference and assume the inlet and outlet temperature values; calculate the heat exchange of components based on the inlet and outlet temperature values ​​and the temperature range; calculate the system flow based on the heat exchange and the inlet and outlet temperature difference; calculate the radiator inlet and outlet water temperature based on the calculated system flow and heat exchange; compare the radiator inlet and outlet water temperatures with the assumed inlet and outlet temperature values ​​of components. If they are different, assume the inlet and outlet temperature values ​​of components again and repeat the steps until the calculated temperature values ​​are within 0.5℃.

[0084] ③ Air volume design: Calculate the required air volume based on the designed flow value and heat exchange capacity with the radiator as the object.

[0085] 4. There are two methods for step S4, i.e., calculation and classification of other cooling levels:

[0086] The first method: According to the temperature interval and heat interval calculated in step S3 above, i.e., high temperature and other cooling levels, through ambient temperature correction, i.e., heat interval ambient temperature compensation and temperature interval ambient temperature compensation, the two intervals can be compensated accordingly according to the ambient temperature. For example, the highest cooling level execution interval of DCDC in the sales market with a design maximum temperature of 40°C is [70°C, 75°C) (i.e., 75°C>DCDC body temperature ≥ 75°C), then if the ambient temperature is 20°C, the temperature can be increased to [75°C, 80°C); the heat interval division is similar, and the heat exchange capacity of each interval can be increased. For example, the division comparison at 40°C and 20°C is shown in Table 1:

[0087] Table 1

[0088]

[0089] The second method is to directly modify the final fan and water pump duty cycle according to the ambient temperature, such as the low-temperature cooling strategy and high-temperature cooling strategy shown in Table 2 below:

[0090] Table 2

[0091]

[0092] Perform flow design and air volume design: Use the calculation method for flow design and air volume design in step S3 above to calculate the flow rate and air volume based on the data corrected by the ambient temperature.

[0093] Furthermore, the low ambient temperature cooling strategy in step S4, that is, the ambient temperature compensation strategy, also refers to the vehicle speed compensation strategy, and its calculation method is the same as the above ambient temperature compensation strategy method. Taking method 2 as an example (directly correcting the final fan and water pump duty cycle according to the vehicle speed), as shown in Table 3 below:

[0094] Table 3

[0095]

[0096] The calculation method of the automobile water pump and fan control strategy based on threshold values ​​provided in this embodiment calculates each threshold value in the water pump and fan control strategy through the heat exchange correlation theory. The threshold value obtained through theoretical calculation is much more accurate and the subsequent calibration workload is small. Often, the initial calibration value can be used to determine the subsequent high-level threshold value using the above theoretical calculation method.

[0097] The above describes the specific embodiments of the present invention. Through the above description, relevant personnel can make various changes and modifications without departing from the technical idea of ​​the present invention. Similar theoretical calculations or simulations also fall into this category.

Claims

1. A calculation method for a threshold-based automobile water pump and fan control strategy, characterized in that: The steps include: S1. Calculation of heat load for high ambient temperature cooling, including: a. Definition of thermal management conditions: define the thermal management design conditions of the whole vehicle; b. Heat dissipation calculation: Calculate the heat dissipation of cooling circuit components according to the defined thermal management conditions; S2. Calculation of the threshold value for opening the highest cooling level at high temperature and division of cooling intervals, specifically including: a. Determination of thermal protection threshold: The thermal protection threshold is determined by setting a preset amount according to the temperature protection threshold of each component, and the preset amount is a calibrable amount; b. Determination of operating temperature: The operating temperature refers to the temperature range of components that start cooling. The operating temperature is lower than the thermal protection threshold and is determined by considering the degree of temperature fluctuation and the impact of cooling system aging on component life; c. Flow and air volume design: preliminarily determine the inlet and outlet temperature difference, and calculate the required water flow and air volume based on the heat exchange; S3, high temperature other cooling level opening threshold calculation and division, including two methods: Method 1 specifically includes: a. Divide the heat range and temperature range at the same time; b. Flow and air volume design: compare and optimize the divided heat range and temperature range, and calculate the required water flow and air volume; Method 2 specifically includes: a. Divide the temperature range; b. Calculate the required water flow and air volume based on the divided temperature ranges; S4. Calculation of low temperature cooling level, including: a. Ambient temperature compensation: the temperature interval and / or heat interval divided by step S3 is corrected by ambient temperature; or the final fan and water pump duty cycle is corrected directly according to the ambient temperature; b. Flow and air volume design: Calculate the required water flow and air volume based on the aforementioned ambient temperature corrected data.

2. The calculation method of the threshold-based automobile water pump and fan control strategy according to claim 1 is characterized in that: In step a of step S1, the defined thermal management conditions include ambient temperature, vehicle speed, and slope; in step b of step S1, when the cooling circuit is an electric drive cooling circuit, the heat dissipation is calculated as follows: OBC heat dissipation: Q OBC =Charging power*average efficiency; DCDC heat dissipation: Q DCDC = maximum power * average efficiency; MCU heat dissipation: There are two methods: theoretical calculation and efficiency calculation. In the theoretical calculation method: Q MCU = conduction loss + switching loss, efficiency calculation method: Q MCU = Motor power * controller average efficiency.

3. The calculation method of the threshold-based automobile water pump and fan control strategy according to claim 1 is characterized in that: In step a of step S2, the preset value is 5°C; in step b of step S2, considering the impact of temperature fluctuation on the life of components, for the MCU of the electric drive cooling circuit, considering its temperature transientness, faster temperature rise at high temperature, and considering smoothing its internal junction temperature fluctuations, its initial cooling temperature is increased by the preset value.

4. The calculation method of the threshold-based automobile water pump and fan control strategy according to claim 1 is characterized in that: In step b of step S2, the influence of the aging of the heat dissipation system on the temperature of the components is taken into consideration, and based on the consideration of the aging of the heat dissipation system, a preset margin is matched to the cooling system.

5. The calculation method of the threshold-based automobile water pump and fan control strategy according to claim 1 is characterized in that: In step c of step S2, for the electric drive cooling circuit, after determining the heat of the power three-in-one and the MCU, determine the inlet and outlet temperature difference of the radiator or each component, and the inlet water temperature is based on the maximum inlet water temperature required by the component. = The coolant flow rate is calculated and the cooling air requirement is calculated based on the same heat exchange formula.

6. The calculation method of the threshold-based automobile water pump and fan control strategy according to claim 1 is characterized in that: In step S3, for the electric drive cooling circuit: Thermal interval division: According to the cooling level divided by the strategy, the thermal interval of the three-in-one power supply is evenly distributed according to the total cooling level to obtain the thermal intervals under different cooling levels with the same value; because the MCU needs to smooth the internal junction temperature fluctuation, the heat in the thermal intervals with high cooling levels is close, while the heat in the thermal intervals with low cooling levels is dispersed; Temperature range division: Based on the consideration of reducing the energy consumption of the servo system, the cooling level of each component that requires cooling in the electric drive system is set with a temperature range with a larger temperature span before the fan is turned on. Within the cooling level after the fan is turned on, the three-in-one power supply and the motor are set with a linear temperature range. Since the MCU has a faster temperature rise at high temperatures, the temperature range is gradually reduced from low to high in whole or in part.

7. The calculation method of the threshold-based automobile water pump and fan control strategy according to claim 1 is characterized in that: In step b of the first method of step S3, for the electric drive cooling circuit: After the temperature range and heat range are divided, first take the components as the calculation object, and calculate the required system flow according to the lower limit of the temperature range set by the components. For the three-in-one power supply or MCU, first calculate the inlet and outlet water temperatures of the components according to the heat exchange calculation formula: ; When calculating the system flow, the inlet and outlet temperature difference value is the same as the highest cooling level; after calculating the inlet and outlet water temperatures of the radiator, the system flow is calculated based on the heat dissipation, and finally the required air volume is calculated based on the calculated system flow combined with the inlet and outlet temperature difference of the radiator on the wind side; According to the heat range, take the radiator as the calculation object, according to Calculate the radiator water flow, and then calculate the air volume, according to The inlet and outlet water temperatures of the radiator can be calculated, and the temperature of the component body can be further calculated.

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

9. The calculation method of the threshold-based automobile water pump and fan control strategy according to claim 1, characterized in that: In step a of step S4, the vehicle speed may also be compensated, that is, the temperature interval and / or heat interval divided in step S3 may be corrected by the vehicle speed; or the final fan and water pump duty cycle may be corrected directly according to the vehicle speed.

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