Engine coolant temperature control method and apparatus

Abstract

The application discloses an engine coolant temperature control method and device, the method comprises the following steps: first-order low-pass filtering processing is carried out on the actual coolant temperature to obtain the filtered actual coolant temperature; it is judged whether the actual coolant temperature switching condition is satisfied or not, if yes, the actual temperature adopts the filtered actual coolant temperature, otherwise, the actual temperature continues to adopt the actual coolant temperature; in the two temperature switching processes, the absolute value of the change rate does not exceed the preset change rate value; the target coolant temperature is obtained as the original target temperature, dynamic optimization is carried out to obtain the final target temperature, and closed-loop PID control is carried out on the engine coolant temperature according to the final target temperature and the actual temperature; including: original target temperature reset, original target temperature transition, original target temperature decrement and other conditions, and the priority is lower and lower. The application solves the problems of low closed-loop control precision and poor robustness when the target coolant temperature changes greatly.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of engine control, and particularly relates to an engine coolant temperature control method and device. BACKGROUND

[0002] An engine is a power source for converting chemical energy into mechanical energy through combustion, and a large amount of heat energy is generated in the process; and from the perspectives of power performance, economy and emission performance, the engine is best operated at an optimal temperature, so a suitable cooling system needs to be equipped. The setting of the target coolant temperature of the engine is very important for the power performance, economy and service life of the engine. However, when the target coolant temperature changes greatly, the closed-loop control precision is not high, and the robustness is poor. Based on this, an engine coolant temperature control method and device are provided. SUMMARY

[0003] The application aims to provide an engine coolant temperature control method and device, and solve the problem of low closed-loop control precision and poor robustness when the target coolant temperature changes greatly.

[0004] The technical scheme adopted by the application is as follows:

[0005] An engine coolant temperature control method comprises the following steps:

[0006] The actual coolant temperature is subjected to first-order low-pass filtering to obtain filtered actual coolant temperature; it is judged whether the actual coolant temperature switching condition is met, if yes, the actual temperature adopts the filtered actual coolant temperature, otherwise, the actual temperature continues to adopt the actual coolant temperature; and in the switching process of the two temperatures, the absolute value of the change rate of the actual temperature does not exceed a preset change rate value;

[0007] The target coolant temperature is obtained as an original target temperature, the original target temperature is dynamically optimized to obtain a final target temperature, and the engine coolant temperature is subjected to closed-loop PID control according to the final target temperature and the actual temperature; including the following cases:

[0008] After the original target temperature reset condition is met, the final target temperature is the original target temperature;

[0009] After the original target temperature transition condition is met, the final target temperature transitions to the original target temperature at a preset change rate;

[0010] After the original target temperature reduction condition is met, the target temperature reduction is calculated according to the original target temperature, the intake temperature, the vehicle speed and the atmospheric temperature, the original target temperature is reduced to obtain the final target temperature, and the I term in the closed-loop PID control of the engine coolant temperature is adjusted after the I term adjustment condition is met.

[0011] In other cases, the original target temperature is filtered, and the final target temperature is the filtered original target temperature.

[0012] The priority of the above cases is from high to low.

[0013] Further, the actual cooling liquid temperature is first-order low-pass filtered, including:

[0014] T CoolantAct (N) = C1 × [T CoolantActRaw (N) - T CoolantAct (N-1)] + T CoolantAct (N-1)

[0015] In the formula, T CoolantAct (N) is the filtered actual cooling liquid temperature at time N, T CoolantAct (N-1) is the filtered actual cooling liquid temperature at time N-1, T CoolantActRaw (N) is the actual cooling liquid temperature at time N, C1 is the filter coefficient, N = 1, 2, 3, … and the time difference between adjacent times is a fixed update period ΔT.

[0016] Further, the actual cooling liquid temperature switching condition includes:

[0017] (1) The difference between the original target cooling liquid temperature and the actual cooling liquid temperature is not more than a first preset difference;

[0018] (2) |T CoolantAct (N) - T CoolantActRaw (N)| is greater than a second preset difference;

[0019] If the above two conditions are met at the same time, the actual cooling liquid temperature switching condition is met.

[0020] Further, the original target temperature reset condition includes:

[0021] (1) The high-speed fan opening time exceeds a first preset time;

[0022] (2) The low-speed fan opening time exceeds a second preset time;

[0023] (3) The engine stop time exceeds a third preset time;

[0024] (4) The engine knockback angle exceeds a fourth preset time and the knockback angle exceeds a preset angle; the fourth preset time depends on the atmospheric temperature and the intake temperature, the higher the atmospheric temperature and the intake temperature, the shorter the fourth preset time;

[0025] (5) The ratio of the engine request firing path torque to the engine maximum torque exceeds a preset torque ratio.

[0026] If any of the above conditions is met, the original target temperature reset condition is met.

[0027] Further, the original target temperature transition condition comprises:

[0028] (1) the absolute value of the difference between the original target temperature and the actual temperature does not exceed a third preset difference value;

[0029] (2) the absolute value of the difference between the original target temperature and the final target temperature at the previous moment does not exceed a fourth preset difference value;

[0030] If the above two conditions are met at the same time and the meeting time exceeds a fifth preset time, the original target temperature transition condition is met.

[0031] Further, after the original target temperature reduction condition is met, the target temperature reduction is calculated according to the original target temperature, the intake temperature, the vehicle speed and the atmospheric temperature, the original target temperature is reduced to obtain the final target temperature, and the I term in the closed-loop PID control of the engine coolant temperature is adjusted after the I term adjustment condition is met, including:

[0032] (1) when the high-speed fan is turned on, the final target temperature is obtained as follows:

[0033]

[0034] In the formula, T CoolantDsrdFinal (N) is the final target temperature at the Nth moment, T CoolantDsrdRaw (N) is the original target temperature at the Nth moment; T CoolantErr (N-1) is equal to T CoolantDsrdFinal (N-1)-T CoolantActCal (N), T CoolantDsrdFinal (N-1) is the final target temperature at the (N-1)th moment, T CoolantActCal (N) is the actual temperature at the Nth moment, T MAT (N) is the intake temperature at the Nth moment, T CoolantErr (N-1) absolute value is greater, T MAT (N) is greater, then f1(T CoolantErr (N-1), T MAT (N)) is greater; v(N) is the vehicle speed at the Nth moment, T Amb (N) is the atmospheric temperature at the Nth moment, the greater the vehicle speed v(N) is, the smaller T Amb (N) is, then k1(v(N), T Amb (N)) is greater; t1 is the first maximum time length for reducing the original target temperature, and the time difference between adjacent moments is a fixed update period ΔT;

[0035] If the actual temperature TCoolantActCal Subtract the original target temperature T CoolantDsrdRaw If the first temperature preset value is exceeded, the I term in the engine coolant temperature closed-loop PID control is cleared at the high-speed fan start time or exit time; further, if the high-speed fan start time exceeds the first time preset value, the entire I term is cleared.

[0036] (2) At the low-speed fan start time, the final target temperature is obtained as follows:

[0037]

[0038] In the formula, T CoolantDsrdFinal (N) is the final target temperature at the Nth time, T CoolantDsrdRaw (N) is the original target temperature at the Nth time; T CoolantErr (N-1) is equal to T CoolantDsrdFinal (N-1)-T CoolantActCal (N), T CoolantDsrdFinal (N-1) is the final target temperature at the (N-1)th time, T CoolantActCal (N) is the actual temperature at the Nth time, T MAT (N) is the intake air temperature at the Nth time, T CoolantErr (N-1) is the absolute value, T MAT (N) is the absolute value, T CoolantErr (N-1), T MAT (N)) is greater; v(N) is the vehicle speed at the Nth time, T Amb (N) is the atmospheric temperature at the Nth time, the greater the vehicle speed v(N) is, the smaller T Amb (N) is, the greater k2(v(N), T Amb (N)) is; t2 is the second maximum length of reducing the original target temperature;

[0039] If the actual temperature T CoolantActCal Subtract the original target temperature T CoolantDsrdRaw If the second temperature preset value is exceeded, the I term in the engine coolant temperature closed-loop PID control is cleared at the low-speed fan start time or exit time; further, if the low-speed fan start time exceeds the second time preset value, the entire I term is cleared.

[0040] Further, f2(T CoolantErr (N-1), T MAT (N)) is not greater than f1(T CoolantErr (N-1), T MAT (N)), k2(v(N), T Amb (N)) is not greater than k1(v(N), T Amb (N)).

[0041] Further, the filtering processing of the original target temperature comprises:

[0042] T CoolantDsrdFinal (N) = C2 x [T CoolantDsrdRaw (N) - T CoolantDsrdFinal (N-1)] + T CoolantDsrdFinal (N-1)

[0043] In the formula, T CoolantDsrdFinal (N) is the filtered original target temperature at time N, T CoolantDsrdFinal (N-1) is the filtered original target temperature at time N-1, T CoolantDsrdRaw (N) is the original target temperature at time N, and C2 is a filtering coefficient.

[0044] Further, the filtering coefficients C1 and C2 are updated by self-learning, comprising:

[0045] (1) the difference between the filtered original target temperature and the filtered actual coolant temperature does not exceed a first preset range all the time when the fan is not started;

[0046] (2) the difference between the filtered original target temperature and the filtered actual coolant temperature does not exceed a second preset range all the time after the high-speed fan is started;

[0047] After the above two conditions are met at the same time, the accumulated number CNT1 in the current driving cycle is increased by 1, if CNT1 reaches a first preset number, the filtering coefficient C1 is a first multiple before updating, and the filtering coefficient C2 is a second multiple before updating; the first multiple and the second multiple are greater than 1; after the current updating is completed, CNT1 is cleared, and the filtering coefficients C1 and C2 are updated and then stored after being powered off when the two conditions are met again in the next driving cycle;

[0048] (1) the difference between the filtered original target temperature and the filtered actual coolant temperature exceeds a third preset range all the time when the fan is not started;

[0049] (2) the difference between the filtered original target temperature and the filtered actual coolant temperature exceeds a fourth preset range all the time after the high-speed fan is started;

[0050] After the above two conditions are met at the same time, the accumulated number CNT2 in the current driving cycle is increased by 1, if CNT2 reaches a second preset number, the filtering coefficient C1 is a third multiple before updating, and the filtering coefficient C2 is a fourth multiple before updating; the third multiple and the fourth multiple are less than 1; after the current updating is completed, CNT2 is cleared, and the filtering coefficients C1 and C2 are updated and then stored after being powered off when the two conditions are met again in the next driving cycle.

[0051] An engine coolant temperature control device for implementing the engine coolant temperature control method of any one of the above, comprising:

[0052] An engine outlet water temperature sensor for detecting an actual coolant temperature;

[0053] An intake air temperature sensor for detecting an engine intake air temperature;

[0054] An atmospheric temperature sensor for detecting an atmospheric temperature;

[0055] A vehicle speed sensor for detecting a vehicle speed;

[0056] A water pump for controlling an engine coolant flow rate and controlling an engine coolant circulation flow;

[0057] A cooling fan having two rotation speeds, i.e., a low speed and a high speed, for cooling the coolant flowing through a radiator;

[0058] A thermostat or a thermal management module for performing closed-loop PID control on the engine coolant temperature according to a final target temperature and an actual temperature, and controlling the engine coolant temperature by controlling the engine coolant flow rate through the water pump.

[0059] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0060] The present application proposes a target coolant temperature control method from the aspects of engine protection, fuel economy and control precision improvement, and solves the problems of low control precision and poor robustness when the target coolant temperature changes greatly. BRIEF DESCRIPTION OF DRAWINGS

[0061] Figure 1 The engine coolant temperature control method flowchart of the present application embodiment. DETAILED DESCRIPTION

[0062] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0063] The application provides an engine coolant temperature control method and device, and the key points are as follows: (1) a working condition judgment method for resetting the final target water temperature to the original target water temperature; (2) a working condition judgment and execution method for gradually transitioning the final target water temperature to the original target water temperature; (3) a working condition judgment and execution method for adjusting the final target water temperature reduction; (4) a working condition judgment and execution method for filtering the original target water temperature; and (5) a filtering coefficient updating method for the actual water temperature and the target water temperature.

[0064] The common engine water cooling system comprises an engine outlet water temperature sensor, an intake temperature sensor, an atmospheric temperature sensor (or an atmospheric temperature signal), a vehicle speed sensor (or a vehicle speed signal), a water pump, a thermostat (a thermal management module) and a cooling fan.

[0065] The engine outlet water temperature sensor is used for detecting the engine outlet cooling water temperature.

[0066] The intake temperature sensor is used for detecting the engine intake temperature.

[0067] The atmospheric temperature sensor or the atmospheric temperature signal, the engine cooling system is hard-wired connected with the atmospheric temperature sensor, or receives the atmospheric temperature signal through network CAN communication.

[0068] The vehicle speed sensor or the vehicle speed signal, the engine cooling system is hard-wired connected with the vehicle speed sensor, or receives the vehicle speed signal through network CAN communication.

[0069] The water pump is used for controlling the circulation of the cooling water.

[0070] The thermostat (or the thermal management module), the thermostat is opened or the thermal management module is opened, which indicates that part of the cooling water is returned to the engine inlet after being cooled by the radiator, and the thermostat (or the thermal management module) performs closed-loop PID control according to the difference between the target water temperature and the actual water temperature, so that the actual water temperature follows the target water temperature by controlling the water pump to control the engine coolant flow rate, and the known technology can be seen.

[0071] The cooling fan has only two levels, i.e., two rotating speeds, low speed and high speed, and is used for cooling the cooling water flowing through the radiator.

[0072] The design purpose of the application is that, in the actual development process, if the target coolant temperature changes too fast, and since the cooling fan has only two rotating speeds, the problem of large temperature fluctuation in the temperature control process occurs.

[0073] As shown in Figure 1 , first, the actual coolant temperature read by the sensor is subjected to first-order low-pass filtering processing:

[0074] T CoolantAct (N) = C1 x [T CoolantActRaw(N) - T CoolantAct (N-1) + T CoolantAct (N-1), where N = 1, 2, 3...

[0075] T CoolantAct (N-1) is the filtered actual coolant temperature at time N-1; T CoolantAct (N) is the filtered actual coolant temperature at time N; the time difference between time N-1 and time N is a fixed update period ΔT (10 ms in this example); T CoolantActRaw (N) is the raw actual coolant temperature collected by the coolant temperature sensor at time N. In particular, T CoolantAct (0) is the filtered actual coolant temperature equal to the raw actual coolant temperature collected by the coolant temperature sensor when the vehicle is first powered on. C1 is the filter coefficient. The smaller the filter coefficient C1, the smoother the actual coolant temperature after filtering, and C1 is within the range of greater than 0 and less than 1. In this example, C1 is initially taken as 0.2, and will be updated and learned subsequently.

[0076] If the following conditions are met at the same time:

[0077] 1. If the difference between the raw target coolant temperature and the actual coolant temperature read by the sensor is not more than a first preset difference (8°C in this example);

[0078] 2. |T CoolantAct (N) - T CoolantActRaw (N)| is greater than a second preset difference (the second preset difference in this example is 2°C), i.e., the actual coolant temperature fluctuates greatly.

[0079] When the above two conditions are met at the same time, the actual coolant temperature switching condition is met. Then the actual coolant temperature T CoolantActCal (i.e., the actual coolant temperature) used in subsequent target coolant temperature (i.e., target water temperature) control adopts the filtered actual coolant temperature T CoolantAct , otherwise, the actual coolant temperature T CoolantActRaw read by the sensor is continued to be used. However, it is noted that in the switching process of the two temperatures, the absolute value of the change rate of the actual coolant temperature does not exceed 0.5°C.10ms, and after the transition is completed, the corresponding two temperatures are adopted. In the subsequent description, the actual coolant temperature used in the coolant temperature control will be referred to as the actual temperature.

[0080] Next, there are known methods for obtaining the target water temperature, and the target water temperature in the known art is referred to as the raw target water temperature T CoolantDsrdRaw In this application, the target water temperature is dynamically optimized, including:

[0081] 1) high-speed fan on time (the on time is cleared after the fan is turned off, and the timing will start again after it is turned on again) exceeds the first preset time T1 (3s in this example), or low-speed fan on time (the on time is cleared after the fan is turned off, and the timing will start again after it is turned on again) exceeds the second preset time T2 (2.5s in this example), or engine stop time exceeds the third preset time T3 (5h in this example), or engine knock retard angle (i.e. knock occurs after requesting to delay the ignition angle) exceeds the preset angle (6° in this example) and exceeds the fourth preset time T4 (the fourth preset time T4 in this example depends on the atmospheric temperature and the intake temperature: the higher the atmospheric temperature, the shorter the preset time to avoid knock, and when knock occurs, the final target water temperature needs to be set as close to the original target water temperature as soon as possible; the intake temperature refers to the temperature of the gas entering the cylinder, and the higher the intake temperature, the greater the possibility of engine knock, and similarly, to avoid knock, the final target water temperature needs to be set as close to the original target water temperature as soon as possible), or the ratio of engine requested torque to engine maximum torque exceeds the preset torque ratio (the engine requested torque is large, and the original target water temperature needs to be reached as soon as possible to achieve better engine combustion efficiency and thus achieve torque, and the preset value in this example is 0.98), then the final target water temperature is immediately set to the original target water temperature. In this example, the value of the fourth preset time T4 is shown in Table 1.

[0082] Table 1: Value table of the fourth preset time T4

[0083]

[0084] The original target water temperature takes into account the influence of engine knock protection, engine fuel economy, etc., so when the water temperature control system is relatively stable, or when the power demand is large or knock occurs, the final target water temperature T CoolantDsrdFinal needs to be controlled as soon as possible to equal the original target water temperature T CoolantDsrdRaw .

[0085] 2) The absolute value of the difference between the original target water temperature T CoolantDsrdRaw and the actual water temperature T CoolantActCal does not exceed the third preset difference (2°C in this example), and the absolute value of the difference between the original target water temperature T CoolantDsrdRaw and the final target water temperature T CoolantDsrdFinal at the previous time does not exceed the fourth preset difference, and the time when both conditions are met exceeds the fifth preset time T5 (0.5s in this example), then the final target water temperature T CoolantDsrdFinal is controlled to transition to the original target water temperature T CoolantDsrdRaw at a preset rate of change (the preset rate of change in this example is ±0.1°C.10ms). This gradual transition is because it is not as high as the first one in terms of engine protection or performance requirements, but is set to ensure the stability of the water temperature control.

[0086] 3) If actual water temperature T CoolantActCal Subtract the original target water temperature T CoolantDsrdRaw If the first temperature preset value (6℃ in this example) is exceeded, the I term in the PID control of the thermostat thermal management module closed loop control is cleared at the high speed fan opening time or exit time, that is, the I term is not updated at the high speed fan opening time or exit time; further, if the high speed fan opening time exceeds the first time preset value (5s in this example), the entire I term is cleared, that is, the entire I term is 0, to avoid integral saturation.

[0087] To avoid frequent fan opening, the final target water temperature T CoolantDsrdFinal The target water temperature reduction depends on the original target water temperature, intake temperature, vehicle speed and atmospheric temperature. The final target water temperature is obtained as follows:

[0088]

[0089] Wherein, T CoolantDsrdFinal (N) is the Nth moment final target water temperature, T CoolantDsrdFinal (N-1) is the N-1th moment final target water temperature, T CoolantDsrdRaw (N) is the Nth moment original target water temperature, T MAT (N) is the Nth moment intake temperature, v(N) is the Nth moment vehicle speed, T Amb (N) is the Nth moment atmospheric temperature, t1 is the maximum time length of reducing the target water temperature (2s in this example), T CoolantErr (N-1) is equal to T CoolantDsrdFinal (N-1)-T CoolantActCal (N), wherein T CoolantActCal (N) is the Nth moment actual water temperature, which has been introduced above, the time difference between time N-1 and time N is a fixed update period ΔT (10ms in this example). Wherein, when the absolute value of T CoolantErr (N-1) is larger, to avoid the problem of temperature closed loop control accuracy caused by large temperature difference, then f1(T CoolantErr (N-1), T MAT (N)) is larger; T MAT (N) is larger to avoid the occurrence of knock, and f1(T CoolantErr (N-1), T MAT (N)) is also larger. In this example, f1(T CoolantErr (N-1), T MAT (N)) is shown in Table 2.

[0090] Table 2 f1(T CoolantErr (N-1), T MAT(N)) value table

[0091]

[0092] The greater the vehicle speed v(N) or the smaller the T Amb (N), the stronger the engine heat dissipation capability, and the greater k1(v(N), T Amb (N) can be set to avoid temperature difference from causing temperature closed-loop control accuracy problems. In this example, k1(v(N), T Amb (N) values are shown in Table 3.

[0093] Table 3 k1(v(N), T Amb (N)) value table

[0094]

[0095] 4) If the actual water temperature T CoolantActCal (N) minus the original target water temperature T CoolantDsrdRaw (N) exceeds the second temperature preset value (4°C in this example), the low-speed fan is turned on or off, i.e., the sampling period in which the low-speed fan is turned on or off, and the I term of the thermostat thermal management module PID is cleared. If the low-speed fan is turned on for more than a preset value, the entire I term is cleared to avoid integral saturation.

[0096] To avoid frequent fan turning on, the target water temperature is reduced when the low-speed fan is turned on, and the final target water temperature is obtained as follows:

[0097]

[0098] wherein T CoolantDsrdFinal (N) is the final target water temperature at the Nth moment, T CoolantDsrdFinal (N-1) is the final target water temperature at the (N-1)th moment, T CoolantDsrdRaw (N) is the original target water temperature at the Nth moment, T MAT (N) is the intake air temperature at the Nth moment, v(N) is the vehicle speed at the Nth moment, T Amb (N) is the atmospheric temperature at the Nth moment, and t2 is the maximum time length for reducing the target water temperature (2s in this example). T CoolantErr (N-1) is equal to T CoolantDsrdFinal (N-1)-T CoolantActCal (N), wherein T CoolantActCal (N) is the actual water temperature at the Nth moment, and the time difference between the (N-1)th moment and the Nth moment is a fixed update period ΔT (10ms in this example). When the absolute value of T CoolantErr (N-1) is greater, f2(T CoolantErr(N-1), T MAT (N) is larger; T MAT (N) is larger. In order to avoid the occurrence of knock, f2(T CoolantErr (N-1), T MAT (N) is larger. It should be noted that f2(T CoolantErr (N-1), T MAT (N) is not larger than f1(T CoolantErr (N-1), T MAT (N), because the high-speed fan opening and closing process is more likely to cause water temperature oscillation, and the low-speed fan opening and closing process is relatively not easy to cause water temperature oscillation, and is set based on this. The f2(T CoolantErr (N-1), T MAT (N) value is shown in Table 4.

[0099] Table 4 f2(T CoolantErr (N-1), T MAT (N) value table

[0100]

[0101] In the case of larger vehicle speed v(N) or smaller T Amb (N), the engine heat dissipation ability is stronger, and then in order to avoid the problem of temperature closed-loop control precision caused by large temperature difference, k2(v(N), T Amb (N) can be set to be larger. It should be noted that k2(v(N), T Amb (N) is not larger than k1(v(N), T Amb (N), because the high-speed fan opening and closing process is more likely to cause water temperature oscillation, and the low-speed fan opening and closing process is relatively not easy to cause water temperature oscillation, and is set based on this. The k2(v(N), T Amb (N) value in this example is shown in Table 5.

[0102] Table 5 k2(v(N), T Amb (N) value table

[0103]

[0104] 5. In other cases, the target water temperature is filtered to avoid sudden changes in target water temperature, thereby affecting the water temperature control precision.

[0105] T CoolantDsrdFinal (N) = C2 × [T CoolantDsrdRaw (N) - T CoolantDsrdFinal (N-1)] + T CoolantDsrdFinal (N-1)

[0106] Wherein N=1,2,3..., C2 is a filter coefficient. The smaller the filter coefficient C2 is, the smoother the target water temperature is after filtering. C2 is within the range of greater than 0 and less than 1, and C2 is initially taken as 0.8 in the present example and will be updated subsequently.

[0107] Finally, the engine coolant temperature is closed-loop PID controlled according to the final target water temperature and the actual water temperature.

[0108] The priority of the above five conditions is lower and lower. Only when the condition of the previous priority is not met, the condition of the lower priority will be adopted.

[0109] As an optional implementation, the filter coefficients C1 and C2 of the actual water temperature and the target water temperature are self-learned and updated.

[0110] The specific updating method is as follows:

[0111] 1. When the fan is not started, and the difference between the final target water temperature (after filtering) and the actual water temperature (after filtering) is always not more than a preset value (±2°C in the present example);

[0112] 2. After the high-speed fan is started, and the difference between the final target water temperature (after filtering) and the actual water temperature (after filtering) is always not more than a preset value (±3.5°C in the present example)

[0113] After the above two conditions are met, the cumulative number CNT1 in the current driving cycle is increased by 1. If CNT1 reaches a first preset number (500 in the present example), the filter coefficient C1 is 1.002 times the previous update, and the filter coefficient C2 is 1.01 times the previous update. After the current update, CNT1 is cleared, and the accumulation is restarted when the two conditions are met again after the next driving cycle. The filter coefficients C1 and C2 are stored after being powered off after being updated.

[0114] 1. When the fan is not started, and the difference between the final target water temperature (after filtering) and the actual water temperature (after filtering) is always more than a preset value (±4°C in the present example);

[0115] 2. After the high-speed fan is started, and the difference between the final target water temperature (after filtering) and the actual water temperature (after filtering) is always more than a preset value (±6°C in the present example)

[0116] After the above two conditions are met, the cumulative number CNT2 in the current driving cycle is increased by 1. If CNT2 reaches a second preset number (1000 in the present example), the filter coefficient C1 is 0.985 times the previous update, and the filter coefficient C2 is 0.99 times the previous update. After the current update, CNT2 is cleared, and the accumulation is restarted when the two conditions are met again after the next driving cycle. The filter coefficients C1 and C2 are stored after being powered off after being updated.

[0117] The above completes the description of the coolant water temperature control method.

[0118] It should be noted that the size of the serial number of each step in the above embodiments does not mean the order of execution, and the execution order of each process should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0119] It should be noted that according to the needs of implementation, each step and component described in the present application can be split into more steps and components, or two or more steps and components or part of the operation of the step and component can be combined into a new step and component to achieve the purpose of the present application.

[0120] Those skilled in the art will readily understand that the above is only a preferred embodiment of the present application and is not intended to limit the present application, and any modifications, equivalent replacements and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. An engine coolant temperature control method characterized by, The method comprises the following steps: The actual cooling liquid temperature is subjected to first-order low-pass filtering to obtain filtered actual cooling liquid temperature; It is judged whether the actual cooling liquid temperature switching condition is met. If yes, the actual temperature adopts the filtered actual cooling liquid temperature; otherwise, the actual temperature continues to adopt the actual cooling liquid temperature; during the temperature switching process, the absolute value of the change rate of the actual temperature does not exceed a preset change rate value; The target cooling liquid temperature is obtained as an original target temperature, the original target temperature is dynamically optimized to obtain a final target temperature, and the engine cooling liquid temperature is subjected to closed-loop PID control according to the final target temperature and the actual temperature; The following cases are included: After the original target temperature reset condition is met, the final target temperature is the original target temperature; After the original target temperature transition condition is met, the final target temperature transitions to the original target temperature at a preset change rate; After the original target temperature reduction condition is met, the target temperature reduction is calculated according to the original target temperature, the intake temperature, the vehicle speed and the atmospheric temperature, the original target temperature is reduced to obtain the final target temperature, and the I term in the closed-loop PID control of the engine cooling liquid temperature is adjusted after the I term adjustment condition is met; In other cases, the original target temperature is subjected to filtering to obtain the final target temperature as the filtered original target temperature; The priority of the above cases is from high to low.

2. The engine coolant temperature control method according to claim 1, characterized by, The first-order low-pass filtering of the actual cooling liquid temperature comprises: In the formula, is filtered actual coolant temperature at the moment, is filtered actual coolant temperature at the moment, is actual coolant temperature at the moment, and C1 is a filter coefficient, and the time difference between adjacent moments is a fixed update period .

3. The engine coolant temperature control method according to claim 2, characterized by, The actual cooling liquid temperature switching condition comprises: (1) the difference between the original target cooling liquid temperature and the actual cooling liquid temperature does not exceed a first preset difference value; (2) greater than the second preset difference value; When the above two conditions are met at the same time, the actual cooling liquid temperature switching condition is met.

4. The engine coolant temperature control method according to claim 1, characterized by, The original target temperature reset condition comprises: (1) the high-speed fan opening time exceeds a first preset time; (2) the low-speed fan opening time exceeds a second preset time; (3) the engine stop time exceeds a third preset time; (4) the engine knockback angle exceeds a fourth preset time and the knockback angle exceeds a preset angle; the fourth preset time depends on the atmospheric temperature and the intake temperature, the higher the atmospheric temperature and the intake temperature, the shorter the fourth preset time; (5) the ratio of the engine request torque to the engine maximum torque exceeds a preset torque ratio value; When any of the above conditions is met, the original target temperature reset condition is met.

5. The engine coolant temperature control method according to claim 1, characterized by, The original target temperature transition condition comprises: (1) the absolute value of the difference between the original target temperature and the actual temperature does not exceed a third preset difference value; (2) the absolute value of the difference between the original target temperature and the final target temperature at the previous moment does not exceed a fourth preset difference value; When the above two conditions are met at the same time and the meeting time exceeds a fifth preset time, the original target temperature transition condition is met.

6. The engine coolant temperature control method according to claim 1, characterized by, After the original target temperature reduction condition is met, the target temperature reduction is calculated according to the original target temperature, the intake temperature, the vehicle speed and the atmospheric temperature, the original target temperature is reduced to obtain the final target temperature, and the I term in the closed-loop PID control of the engine cooling liquid temperature is adjusted after the I term adjustment condition is met, which comprises: (1) when the high-speed fan is opened, the final target temperature is obtained as follows: In the formula, is the final target temperature at the Nth moment, is the original target temperature at the Nth moment; is equal to , is the final target temperature at the (N-1)th moment, is the actual temperature at the Nth moment, is the intake air temperature at the Nth moment, the greater the absolute value, the greater, the greater; is the vehicle speed at the Nth moment, is the atmospheric temperature and vehicle speed at the Nth moment, the greater, the smaller, the greater, is the first maximum duration for reducing the original target temperature, and the time difference between adjacent moments is a fixed update period ; If the actual temperature Subtract the original target temperature If the first temperature preset value is exceeded, the I term in the engine coolant temperature closed-loop PID control is cleared at the high-speed fan start time or exit time; further, if the high-speed fan start time exceeds the first time preset value, the entire I term is cleared. (2) when the low-speed fan is opened, the final target temperature is obtained as follows: In the formula, is the final target temperature at the Nth moment, is the original target temperature at the Nth moment; is equal to , is the final target temperature at the (N-1)th moment, is the actual temperature at the Nth moment, is the intake air temperature at the Nth moment, the greater the absolute value, the greater, then the greater; is the vehicle speed at the Nth moment, is the atmospheric temperature at the Nth moment, vehicle speed the greater, the smaller, then the greater; is the second maximum length for reducing the original target temperature; If the actual temperature Subtract the original target temperature If the engine coolant temperature exceeds the second temperature preset value, the I term accumulation in the engine coolant temperature closed-loop PID control is cleared at the low-speed fan start time or the exit time. Further, if the low-speed fan start time exceeds the second time preset value, the entire I term is cleared.

7. The engine coolant temperature control method according to claim 6, characterized by, not greater than , not greater than .

8. The engine coolant temperature control method according to claim 2, characterized by, The filtering processing on the original target temperature comprises: wherein is the filtered original target temperature at the time instant, is the filtered original target temperature at the time instant, is the original target temperature at the time instant, C2 is a filter coefficient.

9. The engine coolant temperature control method according to claim 8, characterized by, The self-learning updating of the filtering coefficients C1 and C2 comprises: (1) the fan is not started, and the difference between the filtered original target temperature and the filtered actual coolant temperature is always not more than a first preset range; (2) the high-speed fan is started, and the difference between the filtered original target temperature and the filtered actual coolant temperature is always not more than a second preset range; After the above two conditions are met, the cumulative number CNT1 in the current driving cycle is increased by 1, if CNT1 reaches a first preset number, the filtering coefficient C1 is a first multiple of the previous one, and the filtering coefficient C2 is a second multiple of the previous one; the first multiple and the second multiple are greater than 1; after the current updating is completed, CNT1 is cleared, and the filtering coefficients C1 and C2 are stored after being powered off after being updated again when the two conditions are met in the next driving cycle; (1) the fan is not started, and the difference between the filtered original target temperature and the filtered actual coolant temperature is always more than a third preset range; (2) the high-speed fan is started, and the difference between the filtered original target temperature and the filtered actual coolant temperature is always more than a fourth preset range; After the above two conditions are met, the cumulative number CNT2 in the current driving cycle is increased by 1, if CNT2 reaches a second preset number, the filtering coefficient C1 is a third multiple of the previous one, and the filtering coefficient C2 is a fourth multiple of the previous one; the third multiple and the fourth multiple are less than 1; after the current updating is completed, CNT2 is cleared, and the filtering coefficients C1 and C2 are stored after being powered off after being updated again when the two conditions are met in the next driving cycle; Wherein, the first preset range is less than the third preset range, and the second preset range is less than the fourth preset range.

10. An engine coolant temperature control device for implementing the engine coolant temperature control method according to any one of claims 1 to 9, characterized by Comprise: An engine water outlet temperature sensor for detecting the actual coolant temperature; An intake temperature sensor for detecting the engine intake temperature; An atmospheric temperature sensor for detecting the atmospheric temperature; A vehicle speed sensor for detecting the vehicle speed; A water pump for controlling the engine coolant flow rate and controlling the engine coolant circulation flow; A cooling fan with two speeds: low speed and high speed, for cooling the coolant flowing through the radiator; A thermostat or thermal management module for closed-loop PID control of the engine coolant temperature according to the final target temperature and the actual temperature, and controlling the engine coolant temperature by controlling the water pump to control the engine coolant flow rate.

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